Greek+Slides_233_2012_ppp

合集下载

A Model of Growth Through Creative Destruction A Model of Growth Through Creative Destruction

A Model of Growth Through Creative DestructionAuthor(s): Philippe Aghion and Peter HowittSource: Econometrica, Vol. 60, No. 2 (Mar., 1992), pp. 323-351Published by: The Econometric SocietyStable URL: /stable/2951599Accessed: 24/09/2009 08:00Your use of the JSTOR archive indicates your acceptance of JSTOR's Terms and Conditions of Use, available at/page/info/about/policies/terms.jsp. JSTOR's Terms and Conditions of Use provides, in part, that unless you have obtained prior permission, you may not download an entire issue of a journal or multiple copies of articles, and you may use content in the JSTOR archive only for your personal, non-commercial use.Please contact the publisher regarding any further use of this work. Publisher contact information may be obtained at/action/showPublisher?publisherCode=econosoc.Each copy of any part of a JSTOR transmission must contain the same copyright notice that appears on the screen or printed page of such transmission.JSTOR is a not-for-profit organization founded in 1995 to build trusted digital archives for scholarship. We work with the scholarly community to preserve their work and the materials they rely upon, and to build a common research platform that promotes the discovery and use of these resources. For more information about JSTOR, please contact support@.The Econometric Society is collaborating with JSTOR to digitize, preserve and extend access to Econometrica.。

敏捷开发方法考试

敏捷开发方法考试（答案见尾页）一、选择题1. 敏捷开发方法是一种以人为核心、迭代、循序渐进的项目管理和产品开发方法。

以下哪个不是敏捷开发方法的核心价值观？A. 个体和互动B. 可用的软件C. 客户合作D. 迭代和增量的开发2. 在敏捷开发中，以下哪个不是常见的敏捷开发方法？A. 短周期迭代B. 迭代增量C. 瀑布模型D. 用户故事3. 敏捷开发强调团队合作和沟通。

以下哪个不是敏捷开发中常用的沟通工具？A. 电子邮件B. 即时通讯工具（如Slack）C. 电话会议D. 远程会议4. 在敏捷开发中，以下哪个不是需求管理的重要活动？A. 需求收集B. 需求分析C. 需求优先级排序D. 需求验证5. 敏捷开发方法鼓励持续改进。

以下哪个不是敏捷开发中常用的持续改进工具？A. 团队评估会议B. ScrumC. KanbanD. FMECA6. 敏捷开发方法认为最重要的产品特性是？A. 功能强大B. 易用性C. 可扩展性D. 可维护性7. 在敏捷开发中，以下哪个不是敏捷开发团队的角色？A. 产品所有者B. 开发人员C. 测试人员D. 运营人员8. 敏捷开发方法强调适应性。

以下哪个不是敏捷开发中应对变化的方法？A. 改变优先级B. 增加资源C. 调整进度计划D. 重新评估需求9. 敏捷开发方法认为提高效率的关键因素是？A. 严格的计划B. 自组织团队C. 使用敏捷工具D. 避免变更10. 敏捷开发方法的核心原则之一是？A. 迭代和增量的开发B. 需求稳定C. 高度集权的管理D. 快速交付11. 敏捷开发方法是一种什么类型的软件开发方法？A.瀑布模型B. 瀑布模型的变种C. 需求驱动型D. 迭代和增量的12. 敏捷开发方法中，以下哪个是敏捷开发的首要价值观？A. 迭代和增量B. 需求驱动C. 测试先行D. 客户合作13. 在敏捷开发中，以下哪个不是迭代的主要组成部分？A. 交付周期B. 冲刺C. 迭代计划会议D. 回顾会议14. 敏捷开发中，以下哪个不是Scrum框架的组成部分？A. Product Owner（产品负责人）B. Scrum Master（Scrum主管）C. Development Team（开发团队）D. Stakeholder（利益相关者）15. 敏捷开发中，以下哪个不是验收测试的标准？A. 功能性需求B. 非功能性需求C. 性能需求D. 兼容性需求16. 敏捷开发中，以下哪个不是持续集成的目的？A. 更早地发现集成错误B. 提高代码质量C. 缩短开发周期D. 提高团队协作17. 敏捷开发中，以下哪个不是敏捷开发的原则？A. 个体和互动胜过过程和工具B. 可工作的软件胜过详尽的文档C. 客户合作胜过合同谈判D. 响应变化胜过遵循计划18. 敏捷开发中，以下哪个不是规划会议的目的？A. 确定项目范围B. 分配任务和资源C. 制定迭代计划D. 评估项目进度19. 敏捷开发中，以下哪个不是冲刺的主要活动？A. 产品演示B. 回顾会议C. 冲刺计划会议D. 交付产品20. 敏捷开发中，以下哪个不是敏捷开发的优势？A. 更快的响应变化B. 提高客户满意度C. 更高的产品质量D. 更好的团队协作21. 敏捷开发方法是一种强调（A）的开发方法？A. 自动化流程B. 团队合作C. 用户需求优先D. 迭代和增量22. 在敏捷开发中，（B）是一个关键的迭代周期，用于完成产品的一个功能子集。

以色列英文版ppt课件

Education system
01
The education system in Israel is divided into three main stages: primary, secondary, and post secondary education
02
Primary education is mandatory and free for all Israel children from age 5 to 14
Foreign trade
Trade Partners
Israel's main trade partners are the United States, Europe, and Asia
Tariffs and Policies
Israel has a number of trade agreements with other countries and maintains a library trade policy with low tariffs
Israel culture is a blend of traditional Jewish values and practices with the influence of the diverse cultures that have settled in the country through its history Israel cuisine reflections this rich cultural heritage, with disses that are
Hebrew University of Jerusalem
Israel's most well known university, known for its strong research programs in the natural sciences, humanities, and social sciences

EXECUTIVE SUMMARY..........................................................................

The ITS-IDEA program is jointly funded by the U.S. Department of Transportation’s Federal Highway Administration, National Highway Traffic Safety Administration, and Federal Railroad Administration. For information on the IDEA Program contact Dr. K. Thirumalai, IDEA Program Manager, Transportation Research Board, 2101 Constitution Avenue N.W., Washington, DC 20418 (phone 202-334-3568 fax 202-334-3471).IDEA PROJECT FINAL REPORTContract ITS-6IDEA ProgramTransportation Research BoardNational Research CouncilNovember 28, 1995LASER VEHICLEPrepared by:Richard Wangler Schwartz Electra-Optics, Inc.Orlando, FloridaINNOVATIONS DESERVING EXPLORATORY ANALYSIS (IDEA) PROGRAMS MANAGED BY THETRANSPORTATION RESEARCH BOARD (TRB)This investigation was completed as part of the ITS-IDEA Program, which is one of three IDEA programs managed by the Transportation Research Board (TRB) to foster innovations in surface transportation. It focuses on products and results for the development and deployment of intelligent transportation systems (ITS), in support of the U.S. Department of Transportation’s national ITS program plan. The other two IDEA programs areas are TRANSIT-IDEA, which focuses on products and results for transit practice in support of the Transit Cooperative Research Program (TCRP), and NCHRP-IDEA, which focuses on products and results for highway construction, operation, and maintenance in support of the National Cooperative Highway Research Program (NCHRP). The three IDEA program areas are integrated to achieve the development and testing of nontraditional and innovative concepts, methods, and technologies, including conversion technologies from the defense, aerospace, computer, and communication sectors that are new to highway, transit, intelligent, and intermodal surface transportation systems.The publication of this report does not necessarily indicate approval or endorsement of the findings, technical opinions, conclusions, or recommendations, either inferred or specifically expressed therein, by the National Academy of Sciences or the sponsors of the IDEA program from the United States Government or from the American Association of State Highway and Transportation Officials or its member states.TABLE OF CONTENTSEXECUTIVE SUMMARY. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1PROBLEM STATEMENT. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 VEHICLE-SENSOR SURVEY. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 PRODUCT DESIGN SPECIFICATION. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4RESEARCH APPROACH. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 RESULTS (8)CONCLUSION (9)GLOSSARY (10)REFERENCES (10)APPENDIX A: VEHICLE-SENSOR SURVEY (11)APPENDIX B:VEHICLE SPEED AND LENGTH MEASUREMENT ACCURACY (14)EXECUTIVE SUMMARYThis report describes a diode-laser-based vehicle detector and classifier (VDAC) developed by Schwartz Electro-Optics (SEO) under the Transportation Research Board (TRB) Intelligent Vehicle-Highway Systems (IVHS), now Intelligent Transportation Systems (ITS), Innovations Deserving Exploratory Analysis (IDEA) Program. The VDAC uses a scanning laser rangefinder to measure three-dimensional vehicle profiles that can be used for accurate vehicle classification. The narrow laser beam width permits the detection of closely spaced vehicles moving at high speed; even a 2-in.-wide tow bar can be detected. The VDAC shows great promise for applications involving electronic toll collection from vehicles at freeway speeds, where very high detection and classification accuracy is mandatory.The extensive network of modem highways in the United States today offers a fast, safe, convenient means of transporting goods and people within and between the major cities of the country. However, the U.S. highway system is under considerable stress. The traffic congestion that currently pervades metropolitan areas threatens future gridlock if mitigating steps are not soon taken. According to ITS America (I), “The percent of peak hour travel on urban interstates that occurred under congested conditions reached 70 percent in 1989, up from 41 percent in 1975 .”If this trend continues, all peak-hour traffic will be congested by 2000; there is good reason to believe that the trend will continue. FHWA data show that since about 1965 the number of vehicle miles traveled has been increasing at a faster rate than expenditures on highway maintenance and that total capital spending for highways, streets, roads, and bridges has declined by more than 50 percent. It is assumed that the growth in traffic and decline in new roadway construction will continue and that a worsening traffic congestion problem can be expected.One of the goals for ITS in the United States is to reduce congestion. Through areawide traffic management, ITS can use existing facilities to improve traffic-flow efficiency. Advanced sensor technology is needed to provide accurate, real-time traffic-parameter data, such as volume, occupancy, speed, and classification, which are required to optimize the performance of areawide traffic management systems. Information on real-time traffic conditions can be used for rapid incident detection and en-route driver navigation.The sensors of choice for many future ITS applications will undoubtedly be mounted overhead. Although inductive loops are simple, low-cost devices, they are not as easily installed or maintained because of their in-pavement location. Several types of overhead vehicle detectors are being developed (2), including video detection systems, microwave radar detectors, ultrasonic detectors, passive infrared sensors, and active infrared sensors. Of these, only the active infrared sensor, using a laser rangefmder, has the capability for accurate vehicle profiling as a result of the narrow angular beam width of the laser.This profiling capability, a dual-beam configuration that permits speed measurement, and efficient vehicle-recognition software combine to produce a sensor that can classify vehicles as well as measure their presence and speed. The outstanding utility of such a sensor became good motivation for its development as a practical device.VDAC relies on an inherent laser characteristic-narrow angular beam width--to provide the high resolution required for accurate vehicle, profiling. The VDAC beam-scan geometry is shown in Figure 1. The SCANNING BEAMSFIGURE 1 VDAC beam-scan geometry.1system scans two narrow laser beams, at a fixed angularseparation, across the width of a lane at a rate of up to 720scans/sec. Pulsed time-of-flight range measurementsprovide accurate _ (+ 3 in.) transverse height profiles of avehicle on each scan. The vehicle speed, determined fromthe time interval between the interceptions of the two laserbeams by the vehicle, is used to space the transverseprofiles appropriately to obtain the full three-dimensionalvehicle profile. An algorithm similar to those developedfor military target recognition is applied to the three-dimensional profile for vehicle-classification purposes.An example of the VDAC three-dimensional profilingcapability is provided by the range image shown in Figure2. This range image of a van pulling a boat traveling at aspeed of 45 mph was obtained by the VDAC operatingwith a scan rate of 360 scans/sec. The pixel spacingresulting from the l-degree scan resolution is more thanadequate for vehicle identification.VDAC uses a rotating polygon as shown in Figure 3 toline scan a diode-laser rangefmder across a 12-ft-widelane of highway. The polygon scanner rotatescontinuously in one direction at a constant speed. Theangle between each facet and the base of the polygonalternates between 87.5 and 92.5 degrees for adjacentfacets; as a result, successive scans are made with anangular separation of 10 degrees, which provides the twoseparate beams needed for speed measurements. Asshown in Figure 4, the 0.5- by 12-mrad laser beamilluminates a 5- by 120-mm spot on the pavement thatprovides good m-lane resolution and optimum cross-lanecoverage when the laser is pulsed once per degree of scanangle.Applications for VDAC are many and include thefollowing:l Vehicle classification for toll charging.l Use with wireless smart cards to prevent cheating byverifying vehicle classification.l Vehicle road location and timing determination forlicense plate photography.l Wide-area real-time surveillance for signalizedintersections and freeway monitoring.l Traffic parameter measurement such as average speed, road occupancy, traffic count by type of vehicle, and queue length at lights.l Very accurate vehicle presence detection.l Vehicle height measurement for bridge, tunnel, or overpass warning.l Road and freeway accident detection by traffic speed measurement.l Temporary emergency replacement for disabled in-pavement inductive loops.l Operation where inductive loops are impractical:bridges, parking garages, or cobblestone or brick streets.PROBLEM STATEMENT Because ITS is such a new program, a set of precise requirements for VDAC does not exist. The first several months of the project were used to establish these requirements through the aid of a vehicle sensor survey and phone conversations with potential users. After the survey results were analyzed, a detailed product design specification was generated.FIGURE 3 VDAC hardware showing rotating polygon.FIGURE 2 Three-dimensional range image of a van pulling a boat.23 6 9 12 15 18NUMBER OF VEHICLE CLASSESFIGURE 5 Example histogram showing number of vehicle classes required.The survey revealed that the most common VDAC requirements not satisfied by current sensors are vehicle separation and classification, particularly under high-volume, high-speed traffic conditions. Survey responses indicated interest in the following areas of application (in order of interest): (a) traffic data collection, (b) traffic signal control, (c) temporary installations, and (d) electronic toll collection. For the most part, it was not possible to categorize questionnaire response according to application area because respondents indicated an interest in more than one area. This was not true for the electronic toll collection area, however, which was of singular interest in three of four cases (e.g., Hughes Transportation Management Systems, Amtech Systems Corporation, and MFS Network Technologies). These potential VDAC users want sensors that are very accurate (99.9 to 99.9999 percent detection accuracy, 95 to 99.95 percent classification accuracy), highly reliable, and have a long lifetime (2.3 to 5 years). They are concerned about the effect of environmental conditions on sensor performance, particularly weather (rain, fog, snow) and temperature (minus 40o to 85o C). On the basis of their need for high detection and classification accuracy, the electronic toll collection companies appear to be prime customers for VDAC systems.4PRODUCT DESIGN SPECIFICATIONThe product design specification presented in Table 1 was established on the basis of (a) the results of a vehicle-sensor survey implemented via questionnaires mailed to potential VDAC users, (b) discussions with major ITS companies (e.g., MFS Network Technologies and Hughes Transportation Management Systems), and (c) previous SEO experience in developing diode-laser-based vehicle sensors.RESEARCH APPROACHA schematic diagram of the VDAC system is shown in Figure 6. The VDAC’s laser rangefmder uses an InGaAs diode-laser transmitter and a silicon avalanche photodiode (APD) receiver in a side-by-side configuration. The transmitter consists of the diode laser and its driver circuit and a collimating lens. The optical receiver is composed of an objective lens, narrow-band optical filter, detector-amplifier, and threshold detector.The laser diode used in the VDAC is an InGaAs injection laser diode having 12-W output at 10 A pulsed current drive. The laser driver produces a 10-A peak current pulse with a 3-nsec rise time and an 8-nsec pulseTABLE 1 VDAC SpecificationsSCAN RATEFIELD-OF-REGARDSCAN RESOLUTIONBEAM SEPARATIONRANGE MEASUREMENTS PER SCAN MAXIMUM RANGEMINIMUM RANGERANGE ACCURACYRANGE RESOLUTIONINTERFACELASER BEAM GEOMETRYLASER WAVELENGTHLASER EYE SAFETYPOWER SUPPLY VOLTAGE TEMPERATURE RANGEVEHICLE CLASSIFICATIONSPEED ACCURACY 360 SCANS / SEC / BEAM30”1”IO”3050 FT5 FT3 IN3 INRS422, RS232SOLID STATE RELAY- PRESENCE LOGIC-LEVEL (l-l-L) PRESENCEIN-LANE AXIS - 0.5 mradCROSS-LANE AXIS - 16 mrad904 nm“EYE SAFE”IN COMPLIANCE WlTH 21 CFR 1040 CDRH115VAC, 24VDAC-40o C TO 60o C11 CLASSESSPEED DEPENDENT (see Appendix B)width. A trigger pulse from the scanner control circuit triggers the laser at the proper scan angles. The 904-nm laser emission is at an ideal wavelength for the silicon APD receiver used.The optical detection circuitry converts optical radiation reflected from the vehicle and road to, first, an equivalent electrical analog of the input radiation and, finally, a logic-level signal. The logic-level signals are processed within the range counter logic to yield analog range data, which are read by the microprocessor.An analog range-measurement technique was chosen for VDAC because of its better resolution, smaller size, simpler circuitry, lower power consumption, and lower cost when compared with digital techniques. The analog range measurement circuit, know as a time-to-amplitude converter (TAC), has an accuracy of 1 percent of measured range and a resolution of plus or minus 3 in. TAC uses a constant-current source to charge a capacitor to obtain a linear voltage ramp whose instantaneous value is a measure of elapsed time. The circuit is designed so5that the voltage across the range measurement capacitor begins ramping down from the positive power supply when the laser fires. The ramp is stopped when either a reflected pulse is received or the end of the measurement period is reached. The TAC output is then converted to digital by a fast 1 O-bit analog-to-digital converter.The VDAC sofiware processes the range data and outputs vehicle classification, vehicle speed, and so forth, via a serial interface to a remote computer. The major software functions are identified in the block diagram shown in Figure 7. The algorithms that must be implemented for each function were developed and tested, to some extent, in previous projects. The vehicle detector and speed calculator are used in SEO’s Autosense I unit. The real-time range loop, calibration, and gain adjustment routines have been used in several other projects. The vehicle profiler and vehicle classifier are related to algorithms that have been designed and tested under military research programs. The VDAC rule-based classification algorithm will classify the 11 different types of vehicles shown in Figure 8.Speed, Etc. to PCSelf Tests,Calibration,Gain Adjustment,Threshold Adjust,Dew SenseFIGURE 7 Block diagram for major VDAC software functions.P CARMOTORCYCLE PICKUP TRUCK DELIVERY TRUCK BUSTRACTOR WITHOUT TRAILERTRACTOR WITH 1 TRAILERTRACTOR WITH 2 TRAILERSTRACTOR WITH 3 TRAILERSFIGURE 8 Eleven vehicle types classified by VDAC.Range data are used by the vehicle detection algorithmto determine when a vehicle is present. The vehicledetection algorithm first calculates the range to the roadand then sets a threshold above the road that is used todetermine the presence of a vehicle. A certain number ofconsecutive range samples above the detection thresholdare required to accurately detect the presence of a vehicleand reduce false alarms.RESULTSSE0 tested VDAC at a site in front of the SE0 facilitieson Florida SR 441. VDAC was mounted to a mast armextending over the curb lane of this major arterial asshown in Figure 9. Testing was carried out 24 hr/day foran extended period of time. This permitted testing undervaried traffic conditions, including peak-hour, off-peak,and stop and go, and under varied environmentalconditions such as rain, fog, and high temperature.During testing, the VDAC algorithm was modified asrequired to optimize vehicle detection and classificationcapabilities. The program code was uploadable to VDACvia the serial interface, making possible the real-timeoptimization of VDAC performance.FIGURE 9 VDAC mounted on mast arm.FIGURE 10 Computer display of real-time VDAC classification data.The vehicle profiles were collected and organized in adata base. By using the data base, specific vehicle typeswere extracted and used for vehicle-classificationalgorithm development. After the classification algorithmwas developed, a search of the data base provided datafrom similar vehicles for classification algorithm testing.The data base contains fields that include vehicle class,height, length, speed, and so forth, corresponding to eachvehicle detected. A video image was captured and storedfor each vehicle for easy verification of the vehicle-classification algorithm. A computer display of VDACclassification data, including vehicle profile and videoimage, is shown in Figure 10. Approximately 1,200vehicles per hour can be verified using the data basedisplay software. Currently 50,000 vehicles are logged inthe data base.vehicles. The top matrix shows the vehicle count and the bottom matrix the percentage of classification. The numbers along the diagonal of the bottom matrix show the percentage of classification for each vehicle class. Off-diagonal numbers show the possibility of confusion between specific vehicle classes. For example, 5.04percent of pickups were confused with passenger cars.The overall percentage of classification for all vehicle classes is shown in the lower right comer of Figure 11.CONCLUSION Tests performed have included detection accuracy,classification accuracy, and speed accuracy. Detection of100 percent was visually confirmed in a test of 10,000vehicles. The detection accuracy tests were performed infair weather with some light rain and therefore theaccuracy might degrade some during extended tests orduring severe weather conditions. Classification accuracyof 95.5 percent for 10 vehicle classes was achieved usingthe 50,000~vehicle data base. The confusion matrix(Figure 11) shows the classification results for the 50,000Schwartz Electra-Optics has developed a diode-laser-based vehicle detector-classifier that can accurately detect and classify vehicles moving at freeway speeds. Several major ITS companies have expressed a desire to purchase VDACs when they become available for electronic toll and traffic management (ETTM) applications. Such applications require sensors that are very accurate and highly reliable and have a long lifetime. SEO is confident that VDAC will prove useful for traffic surveillance and signal control as well as ETTM applications.VDAC may find its first implementation as part of the Toronto Highway 407 project for Hughes Traffic Management Systems, where 300 to 400 VDACs will be used as part of a completely automated overhead tollcollection system. In this ETTM application VDAC isrequired to provide accurate vehicle detection,classification, separation, lane position, and cameratrigger information to the roadside toll collection system.Production of VDACs for this project was to begin in thelast quarter of 1995.GLOSSARYSeparation-the ability to detect closely spaced vehicles Camera trigger-a signal generated by the VDAC when it detects the end of a vehicle. This signal can beused to trigger a video camera to capture an image ofthe vehicle’s license plate.as individual vehicles.Transverse height profile-the height profile measured across the vehicle from side to side.Classification-the capability of differentiating among types of vehicles.REFERENCESDetection-the ability to sense that a vehicle, whether moving or stopped, has appeared in the detector’s field of view.Detection response time-the time it takes to sense that a vehicle is in the detector’s field of view.1. Strategic Plan for intelligent Vehicle-Highway Systems,Report ITS-AMER-92-3. ITS America, Washington,D.C., 1992.2. Kell, J.H., I.J. Fullerton, and M.K. Mills. TrafficDetector Handbook, 2nd ed. Report FHWA-IP-90-002,U.S. Department of Transportation, July 1990.Electronic toll collection-the completely automated process of billing on toll roads using electronic communication with the ser-a device that amplifies light and produces an intense monochromatic beam.Scan resolution-the angle between successive range measurements.iscTrck/Bus/RV 0 0. .Tractor TrailerPickup 0.001 0.000.001 2.841FIGURE 11Vehicle classification confusion matrix.APPENDIX A:VEHICLE-SENSOR SURVEY Currently used sensor(s)TYPEREQUIREMENTS METREQUIREMENTS NOT METFUTURE REQUIREMENTSApplicationq Traffic signal controlq Traffic data collection[] Electronic toll collectionq Temporary Installations[]O t h e rCHARACTERISTICS DESIRED INVEHICLE DETECTOR/CLASSIFIER 1. Please rate the importance of these functional characteristics:LOW DETECT VEHICLE PRESENCE 1 2 3 MEASURE VEHICLE SPEED 1 2 3 MEASURE VEHICLE HEIGHT 1 2 3 MEASURE VEHICLE LENGTH 1 2 3 MEASURE VEHICLE WIDTH 1 2 3 VEHICLE CLASSIFICATION 1 2 3 SEPARATE CLOSE-SPACED VEH 1 2 3 DETECT TOW BARS 1 2 3 MULTIPLE LANE COVERAGE 1 2 3HIGH 4 5 6 7 4 5 6 7 4 5 6 7 4 5 6 7 4 5 6 7 4 5 6 7 4 5 6 7 4 5 6 7 4 5 6 76. Please specify required environmental conditions:AMBIENT TEMPERATURE RANGESHOCKVIBRATION7. Please circle the appropriate value for these general characteristics:PRICE 1 2 3 4 5 6 7 8 9 10 K$ SIZE 200 400 600 800 1000. 3m WEIGHT 2 4 6 8 10 12 14 16 18 20 lb POWER 1 2 3 4 5 6 7 8 9 10 W120 VAC 24VDAC 12VDAC OTHERAdditional Comments:。

ISO 25539-2-2012

ii

© ISO 2012 – All rights reserved
ISO 25539-2:2012(E)
Contents
Page
Foreword.........................................................................................................................................................roduction......................................................................................................................................................................... v 1 Scope....................................................................................................................................................................... 1 2 3 Normative references.......................................................................................................................................... 1 Terms and definitions.......................................................................................................................................... 2

PPT Tips-PPT 小贴士

AVOID
23
black & white (or colors when printed in ‘grey’)
grey level
grey level
No difference when printed
type
type
24
what’s the difference between these figures ?
16
center this figure horizontally in < 1 min
Use shapes here-under to center the figure
Unrestricted
17
speed
1st S
+
+
ctrl A
ctrl C
ctrl V
ctrl Z ctrl Y ctrl S f2
Always use same approach for Majuscules, i.e. − Either Majuscule at beginning of list − or no majuscule at beginning of list
EXAMPLE
level 1 (size 18 / 20)
Building blocks
2
• Colors, black-white, fonts, lines, shapes, alignments, pictures, clip-arts, tables, charts,
animations
‘Slide’ design
3
• Components, slide limits, titles, slide, body, Simplicity, layout

项目管理(全英文)试题

一、名词解释（5*2=10）PMI, Project Management Institute, 美国项目管理学会PMP, Project Management Professional, 项目管理专业人员认证PMBOK, Project Management Body of Knowledge, 项目管理知识体系PLC, project life cycle, 项目生命周期RFP, Request for proposal, 需求建议书WBS, Work Breakdown Structure, 工作分解结构CPM, Critical path method, 关键路径法PERT, Project Evaluation and Review Technique, 计划评审技术AOA, Activity-On-Arrow, 双代号网络图法AON, Activity-on-node, 单代号网络图CPI, Cost Performance Index, 成本绩效指数 (挣值(EV)/实际成本(AC)) RAM, Responsibility Assignment Matrix, 职责分配矩阵P&L, Profit and loss损益VAT, value-added tax, 加值税、增值税QA, Quality Assurance, 质量保障二、填空题（5*2=10）。

1. A project is an endeavour to accomplish a specific objective through a unique set of interrelated tasks and the effective utilization of resources.2. A project manager is responsible for planning the work and then work the plan.3. The project life cycle has four phases: initiating, planning, performing, and closing the project.4. Project selection involves evaluating potential projects and then deciding which should move forward to be implemented.5. WBS facilitates evaluation of cost, time, and technical performance of the organization on a project.6. The project network is developed from the information collected for the WBS and is a graphic flow chart of the project job plan.7. In the context of projects, risk is an uncertain event and condition that, if it occurs, has a positive and negative effect on project objectives.8. Milestones are significant project events that mark major accomplishments.9. Two important factors affecting recruitment are the importance of the project and the management structure being used to complete the project.10. The most common method for shortening project time is to assign additional staff and equipment to activities.三．选择题（15*2=30）1. Communications is best described as:A. an exchange of information.B. providing written or oral directions.C. consists of senders and receiversD. effective listening.E. All of the aboveANS: E2. The following types of costs are relevant to making a financial decision except:A. opportunity costsB. direct costsC. sunk costD. unavoidable costsE. None of the aboveANS: C3. Time management is the allocation of time in a project's life cycle through the process of:A. PlanningB. Estimating.C. Scheduling.D. ControllingE. All of the above.ANS: E4. A project element which lies between two events is called:A. An activity.B. A critical path method.C. A slack milestone.D. A timing slot.E. A calendar completion point.ANS: A5. A comprehensive definition of scope management would be:A. Managing a project in terms of its objective through the concept, development, implementation, and termination phases of a project.B. Approval of the scope baseline.C. Approval of the detailed project charter.D. Configuration control.E. Approved detailed planning including budgets, resource allocation,linear responsibility charts and management sponsorship.ANS: A6. Pure Risk differs from Business Risks because Pure Risk's _____ .A. include chances of both profit or loss associated with the business.B. include chances of loss and no chances for profit associated with the business.C. must incur personal loss with business liability.D. must incur business liability associated with loss of pure profit.E. B and CANS: BANS: D7. The most common types of schedules are Gantt charts, milestone charts, line of balance, and:A. Networks.B. Time phased events.C. Calendar integrated activities.D. A and C only.E. B and C only.ANS: A8. In preparing a good project definition, experienced project managers will:A. Concentrate mainly on the end product rather than costs or benefits. These come later.B. Realize that only the "tip of the iceberg" may be showing. As a project manager, you must get beneath it.C. Understand that a project definition/plan is a dynamic rather than static tool, and thus subject to change.D. Try to convert objectives into quantifiable terms.E. All of the aboveANS: E9. Since risk is associated with most projects, the best course of action is to:A. cover all project risks by buying appropriate insuranceB. ignore the risks, since nothing can be done about them and move forward with the project in an expeditious manner.C. avoid projects with clear and present risksD. eliminate all known risks prior to the execution phase of the projectE. identify various risks and implement actions to mitigate their potential impactANS: E10. Risk management allows the project manager and the project team to:A. eliminate most risks during the planning phase of the projectB. identify project risksC. identify impacts of various risksD. plan suitable responsesE. B, C and D onlyANS: E11. Which of the following types of cost are relevant to making financial decisions:A. sunk costB. opportunity costC. material costD. A and C onlyE. B and C onlyANS: E12. Which of the following is often overlooked in achieving effective communication?A. speaking clearlyB. listeningC. interpretingD. maintaining eye contactE. manipulating the conversationANS: B13. The highest degrees of project risk and uncertainty are associated with the following phase of the project:A. conceptualB. executionC. cut-overD. post project evaluationE. A and D onlyANS: A14. The auditing function that provides feedback about the quality of output is referred to as:A. quality control.B. quality planning.C. quality assurance.D. quality improvementE. All of the above.ANS: C15. The sending or conveying of information from one place to another is the process ofA. NetworkingB. TransmittingC. InteractingD. PromotingE. InterfacingANS: B16. Project life cycles provide a better means of measurement of progress and control. The four phases of a project are conceptual development,_____, _____, and _____.A. Preliminary planning, detail planning, closeoutB. Implementation, reporting, terminationC. Development, implementation, terminationD. Execution, reporting, finishingE. Implementation, termination, post-audit reviewANS: C17. All of the following are categories of a milestone in a schedule except:A. End date.B. Contract dates.C. Key events scheduled.D. Imposed dates.E. Task duration.ANS: E18. Uncertainty refers to a situation where:A. the outcomes are known but their probabilities are highB. the outcomes and their probabilities are knownC. neither the outcomes nor their probabilities are knownD. states of nature can change at any timeE. probabilities of various states of nature can change at any timeANS: C19. Excessive flexibility in specifying requirements will _____ the likelihood of time overruns.A. Reduce.B. Eliminate.C. DoubleD. IncreaseE. Not affectANS: D20. Which of the following is closet to Deming's definition of Quality:A. conformance to requirements.B. fitness for use.C. continuous improvement of products and services.D. customer focus.E. All of the above.ANS: C21. The key purpose of project control is to:A. Plan ahead for uncertainties.B. Generate status reports.C. Keep the project on track.D. Develop the project road map.E. All of the above.ANS: C22. Which of the following constitute Juran's "quality trilogy":A. planning, inspection, control.B. planning, improvement, control.C. planning, organization, control.D. product, price, customer.E. design, build, deliver.ANS: B23. Most project (and non-project) managers prefer _____ communications.A. OralB. WrittenC. UpwardD. DownwardE. LateralANS: A24. On a precedence diagram, the arrow between two boxes is called:A. An activity.B. A constraint.C. An event.D. The critical path.E. None of above.ANS: B25. Quality control charts show a characteristic of the product or service against:A. the specification limits.B. customer requirements.C. control limits based on three standard deviations in each direction.D. control limits based on six standard deviations in each direction.E. A and D onlyANS: C26. In the arrow diagramming method (ADM), _____ do not consume time or resources.A. Events.B. Dummy ActivitiesC. Slack elements.D. B and C only.E. All of the above.ANS: A27. Activities with zero time duration are referred to as:A. Critical path activites.B. Noncritical path activities.C. Slack time activities.D. DummiesE. None of above.ANS: D28. In the PDM, common constraints include:A. Start-to-startB. Finish-to-startC. Finish-to-finishD. B and C onlyE. A, B, and C.ANS: E29. Non-verbal communication includes:A. Body movementB. GesturesC. Facial expressionsD. The way we move our handsE. All of the aboveANS: E30. Which one of the following is not an acquisition method?A. advertisingB. invitationC. negotiationD. purchaseE. all are acquisition methodsANS: A31. For communication to occur, there must be:A. Two or more people involvedB. the transmittal of informationC. a communication processD. All of the aboveE. B and C onlyANS: D32. Job continuity would be an example of _____ in Maslow's hierarchy of needs.A. Self-actualizationB. EsteemC. PhysiologicalD. BelongingE. SafetyANS: E四、简单题（2*10=20）。

Framework using functional forms of hardening internal state variables in modeling

Framework using functional formsof hardening internal state variables in modelingelasto-plastic-damage behaviorGeorge Z.Voyiadjis *,Robert J.DorganDepartment of Civil and Environmental Engineering,Louisiana State University,Baton Rouge,LA 70803,USAReceived 23April 2006;received in ﬁnal revised form 4January 2007Available online 18March 2007Dedicated to Professor Dusan Krajcinovic.AbstractThis work gives the thermodynamically consistent theoretical formulations and the numerical implementation of a plasticity model fully coupled with damage.The formulation of the elasto-plas-tic-damage behavior of materials is introduced here within a framework that uses functional forms of hardening internal state variables in both damage and plasticity.The damage is introduced through a damage mechanics framework and utilizes an anisotropic damage measure to quantify the reduc-tion of the material stiﬀness.In deriving the constitutive model,a local yield surface is used to deter-mine the occurrence of plasticity and a local damage surface is used to determine the occurrence of damage.Isotropic hardening and kinematic hardening are incorporated as state variables to describe the change of the yield surface.Additionally,a damage isotropic hardening is incorporated as a state variable to describe the change of the damage surface.The hardening conjugate forces (stress-like terms)are general nonlinear functions of their corresponding hardening state variables (strain-like terms)and can be deﬁned based on the desired material behavior.Various exponential and power law functional forms are studied in this formulation.The paper discusses the general concept of using such functional forms.however,it does not address the relevant appropriateness of certain forms to solve diﬀerent problems.The proposed work introduces a strong coupling between damage and plasticity by utilizing damage and plasticity ﬂow rules that are dependent on both the plastic and damage potentials.However,in addition to that the coupling is further enhanced through the use of the functional forms of the hardening variables introduced in this formulation.0749-6419/$-see front matter Ó2007Published by Elsevier Ltd.doi:10.1016/j.ijplas.2007.03.012*Corresponding author.Tel.:+12255788668;fax:+12255789176.E-mail addresses:voyiadjis@ (G.Z.Voyiadjis),rdorgan@ (R.J.Dorgan).International Journal of Plasticity 23(2007)1826–1859/locate/ijplasG.Z.Voyiadjis,R.J.Dorgan/International Journal of Plasticity23(2007)1826–18591827The use of this formulation in solving boundary value problems will be presented in future work. The fully implicit backward Euler scheme is developed for this model to be solved in a Newton–Raphson solution procedure.Ó2007Published by Elsevier Ltd.Keywords:Constitutive behavior;Anisotropic material;Damage;Plasticity;Finite elements1.IntroductionOne of theﬁrst important contributions to phenomenological damage modeling is that given by Kachanov(1958)and Rabotnov(1968).Damage models with two separate uncoupled damage and plastic loading surfaces(e.g.Chow and Wang,1987;Hansen and Schreyer,1994;Zhu and Cescetto,1995;Murakami et al.,1998,etc.)present a week coupling between plasticity and damage.Strong coupling between plasticity and damage is obtained by using one single smooth generalized yield surface for the plasticity and dam-age evolutions(e.g.Gurson,1977;Hesebeck,2001;Mahnken,2002;Tvergaard,1982; Reusch et al.,2003;Wen et al.,2005).Another approach to achieve this strong coupling is by using separate plasticity and damage surfaces with separate non-associatedﬂow rules in such a way that both damage and plasticityﬂow rules are dependent on both the plastic and damage potentials.Voyiadjis and Deliktas(2000)introduced a formulation for such an approach.Menzel et al.(2005)also introduced coupling of plasticity and damage through a frame of multiplicative elastoplasticity with kinematic hardening coupled to anisotropic damage.Clayton(2005,2006)proposed micromechanical based models that demonstrated the inﬂuences of interfacial separation,random crystallographic orienta-tion,and grain morphology.This framework distinguishes between the eﬀects of inter-granular damage at grain and phase boundaries and transgranular damage.However, the work proposed here is not addressing such microstructural eﬀects.The following are but a very few of the numerous researchers that pioneered work in diﬀerent areas of continuum damage mechanics such as brittle materials(Krajcinovic and Foneska,1981;Krajcinovic,1983,1996)and ductile materials(Andrade Pires et al., 2004;Bonora,1997,1999;Bonora et al.,2005;Brunig,2003a,b;Brunig and Ricci,2005; Lemaitre,1992;Kachanov,1986;Murakami et al.,1998).In the1990s coupling of contin-uum damage mechanics to plasticity appeared(e.g.Voyiadjis and Kattan,1992;Lubarda and Krajcinovic,1995;Zhu and Cescetto,1995;Voyiadjis and Deliktas,2000;Menzel et al.,2002;Nesnas and Saanouni,2002).The readers are referred to the book by Krajci-novic(1996)for details about the diﬀerent existing damage models.In addition the readers can also refer to his book for his seminal works on damage mechanics and its application to diﬀerent materials.The proposed work introduces a strong coupling between damage and plasticity by uti-lizing damage and plasticityﬂow rules that are dependent on both the plastic and damage potentials.However,in addition to that the coupling is further enhanced through the use of the functional forms of the hardening variables introduced in this formulation.Continuum damage mechanics introduces a continuous damage variable which is used as a measure of micro-cracks and micro-voids.In the simplest case,this damage variable is introduced as a scalar.This scalar measure has been used to adequately solve many mechanics problems in the literature(e.g.Kachanov,1958;Lemaitre,1984;Krajcinovic,1828G.Z.Voyiadjis,R.J.Dorgan/International Journal of Plasticity23(2007)1826–18591996,etc.).However,in reality,all materials have been shown to accumulate damageanisotropically,and a second order damage tensor is required to properly deﬁne theproblem.A simple plot of the uniaxial stress-strain behavior for a material with both coupledplasticity and damage is presented in Fig.1.Plasticity does not begin to occur until afterthe stress reaches the critical value,r yp.However,as seen in this plot,the stress-straincurve begins to have a nonlinear behavior before this point and after it reaches a criticalvalue,r yd.This is due to the accumulation of micro-cracks and micro-voids which reducethe elastic stiﬀness tensor from the original,undamaged elastic stiﬀness,e E.This problem is most apparent in brittle and not ductile materials,primarily due to micro-fracturing.However,it may also occur in ductile materials with initial micro-voids.Removal of theexternal loading conditions will not return the state to its original state as not all of themicro-cracks and micro-voids will close;the state of the damaged material will follow alinear path deﬁned by the damaged elastic stiﬀness modulus,E.Thus,when the materialexperiences a combination of plasticity and damage,the irrecoverable strains consist of aninelastic component due to damage,e id,and an inelastic component due to plasticity,e p.The total irrecoverable component of strain is denoted here as the inelastic damage andplastic strain,e pd.The total recoverable part of the strain,e e,can be decomposed intoan elastic strain due to the eﬀective undamaged material,~e e,and an additional elasticstrain,e ed,due to the change in the elastic stiﬀness modulus(with closure of some cracksand voids).The change in the damage surface can be explained in terms of the accumulation ofmicro-cracks and micro-voids with loading.Loading causes the micro-cracks andmicro-voids to generate,to propagate,and to interact.The ease with which the micro-cracks are able to move determines the damage hardness of the material.With an increaseG.Z.Voyiadjis,R.J.Dorgan/International Journal of Plasticity23(2007)1826–18591829 in the micro-damage density,there begins to be more interactions between the micro-cracks and between the micro-voids such that damage increase becomes more diﬃcult and the stress required to produce additional micro-damage increases.The material exhib-its hardening due to the arresting of micro-cracks because of their respective interactions.A damage material model can be used to describe this behavior by deﬁning the evolution of a damage tensor through a damage criterion such that a damage surface is deﬁned as well as the change in size,shape,and position of the damage surface.In this work,a J2 type of damage criterion is used with isotropic hardening corresponding to the change in the size of the damage surface.The constitutive model is derived using consistent thermodynamics in the same fashion as a classical rate-independent continuum J2plasticity model(e.g.Doghri,1993;Simo and Hughes,1998;Belytschko et al.,2000;Voyiadjis et al.,2004).Based on theﬁrst law of ther-modynamics,the Helmholtz free energy is introduced to describe the current state of energy in the material(Malvern,1969;Coussy,1995),and is a function of the strain and the internal state variables under consideration.In order to derive the model equa-tions,the thermodynamics of irreversible processes is followed by introducing a local state consisting of state variables(Malvern,1969;Lemaitre and Chaboche,1994;Coussy,1995; Doghri,2000;Mahnken,2002;Eftis et al.,2003;Bjerke et al.,2002;Cauvin and Testa, 1999).A thermodynamic potential is used which allows the state laws to be deﬁned based on the state variables.The evolution of the thermodynamic conjugate forces are then obtained by assuming the physical existence of the dissipation potential at the macroscale and through the use of the theory of functions of several variables with a Lagrange mul-tiplier.A fully implicit backward Euler scheme is then developed to be solved in a New-ton–Raphson solution procedure.For convenience in developing the constitutive model and theﬁnite element algorithm, tensorial notation will be used.Boldface terms indicate tensors of order one or greater, while italicized terms indicate scalars.Einstein’s summation convention is used unless otherwise indicated.2.Continuum damage mechanicsDamage may be attributed to either or both micro-cracks and–voids as shown in Fig.2.for either metals or metal matrix composites.In Fig.2a damage in metals due to micro-voids is shown while in Fig.2b dislocations in metals are observed.In Fig.2c metal matrix composites(MMCs)with variousﬁber sizes are shown.Finally in Fig.2d micro-cracks in MMCs are observed in the metal matrix as well as at theﬁber interface.The MMC used in Fig.2d is a titanium aluminide with silicon carbideﬁbers.The reader is referred to the work by Voyiadjis et al.(1995)and Voyiadjis and Venson(1995)for details in reference to MMCs.The damage characterization material parameters maybe obtained through the series of experiments outlined by Voyiadjis and Venson(1995).For the char-acterization of the hardening plasticity parameters the reader is referred to the work by Voyiadjis and Abu Al-Rub(2003)for the particular case of316L stainless steel material. However,the same procedure maybe used for other similar metals.In order to allow one to develop constitutive equations within the concept of contin-uum mechanics such that there is a degradation of the material during loading due to micro-damage,the real,damaged state of the material is represented by aﬁctitious, eﬀective undamaged state with a continuum damage measure,u,representing themicro-damage.The material used in this case for a one-dimensional case of a damaged bar with a uniform cross-section of area A ,transformation from the damaged state to the eﬀective state is deﬁned through a scalar damage measure (Kachanov,1958);however,as engineering materials tend to have anisotropic material behavior,damage tends to develop diﬀerently in diﬀerent directions.In order to capture this behavior,a diﬀerent damage measure should be used for each of the directions leading to a second-order aniso-tropic damage measure (e.g.Sidoroﬀ,1981;Cordebois and Sidoroﬀ,1979,1982;Mura-kami and Ohno,1981;Murakami,1983;Krajcinovic,1983;Voyiadjis and Kattan,1992,1993;Voyiadjis and Park,1997,1999;Voyiadjis and Deliktas,2000,etc.).In order to deﬁne this anisotropic measure,consider a representative volume element (RVE)of the damaged material such that each face of the RVE has a normal in the direc-tion of a global coordinate system axis,x i ,as shown in Fig.3a.For anisotropic damage,each face of this RVE will have a diﬀerent damage distribution.Thus,a vector q can be used to represent the micro-damage density such that each component of the vector rep-resents the density of the micro-damage on the i th surface and can be written as follows (Voyiadjis and Venson,1995):q i ¼A D i A i ¼A i Àe A i A i ðno sum over i Þð1Þwhere for the i th surface,A i is the total damaged area,e Ai is the eﬀective net area which resists a load,and A Di is the area of the micro-damage.For a general case of anisotropicdamage,the damage measure can be written in terms of these damage densities such that (Voyiadjis and Venson,1995;Voyiadjis et al.,1995):Fig.2.(a)Damage due to micro-voids in metals;(b)dislocation density in metals;(c)metal matrix composites,MMCs;(d)damage due to micro-cracks in MMCs (Dorgan,2006).1830G.Z.Voyiadjis,R.J.Dorgan /International Journal of Plasticity 23(2007)1826–1859u ¼ﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃq q p ð2ÞThis damage tensor u is a real symmetric tensor such that the eigenvalues of this tensor areall real ð^u 1;^u 2;^u 3Þand there always exists at least three real eigenvectors ð^e 1;^e 2;^e 3Þ.Thus,for an RVE consisting of a general damage state deﬁned by u ,there always exists a cor-responding RVE rotated to the principal directions,such that the normals of the principalRVE are deﬁned by the vectors ^e 1,^e 2,and ^e 3as shown in Fig.3b.Thus,a damage tensor ^ucan be deﬁned in the orthogonal principal directions as a diagonal tensor such that:^u¼^u 1000^u 2000^u3264375ð3ÞIn order to rotate the damage tensor from the principal directions to the global direc-tions,an orthogonal transformation tensor Q is used through the following equation:u ¼Q T Á^u ÁQ ð4Þwhere the transformation tensor is written in terms of the components of the eigenvectors such that:½Q ¼^e 11^e 12^e 13^e 21^e 22^e 23^e 31^e 32^e 33264375ð5ÞThus,the tensor used to represent the damage in a body has been deﬁned.This tensor will be used to transform the stresses and the strains in the actual conﬁguration to the ﬁc-titious undamaged conﬁguration.Under uniaxial loading,the strain at a given stress has two parts:a recoverable elastic strain,and an irreversible plastic strain (Fig.1).The reversible part is related to the stress through the usual linear elastic equations using a damaged elastic stiﬀness tensor.It will be shown that this fourth order tensor can be deﬁned as a function of the damage tensor,u ,through the inverse of the damage eﬀect tensor,M .In this work,additive decomposition of the total observable strain,e ,into its internal variable components is assumed:e ¼e e þe pd ð6ÞG.Z.Voyiadjis,R.J.Dorgan /International Journal of Plasticity 23(2007)1826–185918311832G.Z.Voyiadjis,R.J.Dorgan/International Journal of Plasticity23(2007)1826–1859where e e is the reversible thermo-elastic component of the strain and e pd is the irreversible component of the strain due to both plasticity and damage.The elastic strain can be fur-ther decomposed into an elastic strain corresponding to the undamaged conﬁguration,~e e, and an additional component due to the reduction of the elastic stiﬀness tensor,e ed.Sim-ilarly,the total irrecoverable component of strain,e pd,can be further decomposed into an inelastic component due to damage,e id,and an inelastic component due to plasticity,e p.3.Thermodynamic state variablesThe local coupled plasticity-damage model is deﬁned through the use of the method of material local state identiﬁcation.In this method,a model is developed such that the ther-modynamic state at a given point in space and time is completely determined by a given set of state variables at that point in space and time.The set of state variables are separated into a set of observable state variables and a set of internal state variables.The observable variables are those that can be measured and which appear regardless of the material phe-nomena.The observable state variables used here are the temperature denoted by the sca-lar T,the total strain denoted by the second-order tensor e,and the damage tensor denoted by the second-order tensor u.For pure elasticity,this set of observable state variables entirely deﬁnes the point;how-ever,for elasto-plasticity coupled with damage,the material has a history dependency which requires an additional set of internal state variables.For this coupled damage-plas-ticity model,the internal state variables will consist of plasticity hardening variables and a damage hardening variable.The hardening internal state variables are unitless,strain-like quantities and are accumulated into a set of plasticity related measures,V p and a set of damage related measures,V d,as follows:V p¼½r;a ;V d¼½j ð7Þwhere the internal state variables considered here are the plasticity related variables repre-senting theﬂuxes of the isotropic and kinematic hardening behaviors denoted by the scalar r and the second-order tensor a,respectively,and the damage related variable representing theﬂux of the isotropic hardening behavior denoted by the scalar j.The isotropic hard-ening term r(Hill,1950)corresponds to the change in the size of the yield surface,the kine-matic hardening term a(Prager,1956)corresponds to the change in the location of the yield surface,and the isotropic hardening term j.corresponds to the change in the size of the damage surface.4.Thermodynamic equations of stateIn order to determine state laws which relate the internal state variableﬂuxes to their stress-like conjugate thermodynamic forces,a thermodynamic potential deﬁned as the Helmholtz free energy is introduced which is a state function of a thermodynamic system (Malvern,1969;Lemaitre and Chaboche,1994;Coussy,1995;Doghri,2000).This thermo-dynamic potential is used to describe the current state of energy in the material,and is a function of the observable state variables and the internal state variables under consideration:w¼wðe;T;e pd;e e;u;V p;V dÞð8ÞHowever,as the strains are decomposed for this coupled plasticity-damage model as given by Eq.(6),this Helmholtz free energy is rewritten as follows:w¼wðe e;T;u;V p;V dÞð9ÞThe second law of thermodynamics imposes restrictions on the constitutive relations. From the second law of thermodynamics,the Clausius–Duhem inequality can be written as follows:r:_eÀqð_wþs_TÞÀqÁr TTP0ð10Þwhere r is the second order Cauchy stress tensor,q is the mass density,q is the heatﬂux vector,s is the entropy per unit mass representing the amount of disorder or randomness in a system,$T is the temperature gradient,and_w is the time derivative of w,such that:_w¼o wo e e :_e eþo wo T_Tþo wo u:_uþo wo V pÁ_V pþo wo VÁ_V dð11ÞThe dot in the fourth andﬁfth terms indicates that this term is summed over the com-ponents of the sets,V p and V d,of macroscopic measures of irreversible ing this relationship along with the strain decomposition given by Eq.(6),the Clausius–Duhem inequality can be expanded in the following form:r:_e pdþrÀq o w o e e:_e eÀq o wo Tþs_TÀq o wo u :_uÀqo wo V pÁ_V pÀq o wo VÁ_V dÀqÁr TTP0ð12ÞIn order to obtain thermodynamic laws,independent processes are assumed that satisfy this inequality.Theﬁrst independent process is a case of elastic loadingð_e pd¼0;_u¼0; _V p¼0;_V d¼0Þoccurring at a constant,uniform temperatureð_T¼0;r T¼0Þ.Thus,for the Clausius–Duhem inequality to hold at any given elastic strain increment,the following thermo-elastic state law must be true:r¼q o wo e eð13ÞThe next independent process is that of uniform thermal loadðr T¼0Þin addition to the elastic loadingð_e pd¼0;_u¼0;_V p¼0;_V d¼0Þ.Assuming Eq.(13)holds,the Clau-sius–Duhem inequality holds at any given temperature increment only if the following thermo-elastic state law is true:s¼Ào wo Tð14ÞThus,from the last two equations,the stress,r,and the enthalpy,s,are deﬁned as the conjugate forces corresponding to the state variables e e and T,respectively.A conjugate force,Y,is also deﬁned corresponding to the damage measure,u,as follows:Y¼Àq o wo uð15ÞSimilarly,sets of conjugate forces,A p and A d,are deﬁned which correspond to the plas-ticity hardening internal state variables and damage hardening internal state variables, respectively,such that:G.Z.Voyiadjis,R.J.Dorgan/International Journal of Plasticity23(2007)1826–18591833A p ¼½R ;X ;A d ¼½K ð16Þwhere the scalar R measures the expansion or contraction of the yield surface in the stress space while maintaining its shape and having a ﬁxed center,the second-order tensor X measures the movement and distortion of the yield surface,and the scalar K measures the expansion or contraction of the damage surface in the stress space.Whereas the inter-nal state variables are unitless,strain-like quantities,the thermodynamic conjugate forces are a set of stress-like quantities that are related to the state variables as the stress is related to the strain.These conjugate forces are deﬁned in the Clausius–Duhem inequality by the following set of state laws:A p ¼q o w o V p ;A d ¼q o wo V d ð17Þ5.Stress transformationsFor a general state of anisotropic damage,the Cauchy stress is transformed to the eﬀec-tive Cauchy stress through a linear transformation such that (Murakami and Ohno,1981;Murakami,1983):~r ¼M :r ð18Þwhere M is the fourth order damage eﬀect tensor in terms of the second order damage ten-sor,u .This tensor can be written by transforming the damage eﬀect tensor,c M ,which is deﬁned with reference to the principal direction coordinate system:M ¼Q T ÁQ T Ác M ÁQ ÁQ ð19ÞEq.(19)allows the use of the diagonal form of the damage tensor as given in Eq.(3).Var-ious forms for the principal damage eﬀect tensor have been given in the literature.Sidoroﬀ(1981),Cordebois and Sidoroﬀ(1982),and Lee et al.(1986)expressed the components of this matrix in the following form:½c M ijkl ¼d ik d jl ﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃð1À^u ik Þð1À^u jl Þp ðno sum over i ;j ;k ;l Þð20ÞAlternate forms for the components of this damage eﬀect tensor have been presented by Voyiadjis and Park (1997)as follows:½c M ijkl ¼d ik d jl ½ð1À^u jl Þþð1À^u ik Þ 2ð1Àu ik Þð1Àu jl Þðno sum over i ;j ;k ;l Þð21Þ½c M ijkl ¼2d ik d jl ð1À^u ik Þþð1À^u jl Þðno sum over i ;j ;k ;l Þð22ÞThe diﬀerences between these forms of the damage eﬀect tensor are brought about by the symmetrization procedure used as discussed in Voyiadjis and Park (1997).In the rest of this work,it is assumed that the components of the damage eﬀect tensor are as described by Eq.(22);however,similar formulations can be performed for the other rep-resentations.Thus,using this form of the principal damage tensor,the components of theterm o c M =o ^uare found by taking derivatives of the components given by Eq.(22)such that:1834G.Z.Voyiadjis,R.J.Dorgan /International Journal of Plasticity 23(2007)1826–1859o½c M ijkl o^u ab ¼2d ik d jlðd ia d kbþd ja d lbÞ½ð1À^u ikÞþð1À^u jlÞ 2ðno sum over i;j;k;lÞð23ÞAs this model incorporates plasticity in addition to damage,it will be necessary in eval-uating the yield criterion to deﬁne the deviatoric components of the eﬀective stress.Given the Cauchy stress tensor and the eﬀective Cauchy stress tensor,the deviatoric parts are deﬁned here as follows:s¼IÀ131 1:rð24Þ~s¼IÀ131 1:~rð25ÞSubstituting the transformation relation,Eq.(18),into Eq.(25),a linear relationship be-tween the Cauchy stress tensor and the eﬀective deviatoric stress tensor is obtained such that:~s¼N:rð26Þwhere the fourth order tensor N is a linear operator deﬁned as follows:N¼MÀ131 1:Mð27ÞUtilizing Eq.(24)in Eq.(26),the following relationship is obtained for the eﬀective deviatoric stress:~s¼M:sþ13M:1 1:rÀ131 1:M:rð28ÞThis equation cannot be manipulated to obtain a linear transformation between the devi-atoric stress and the eﬀective deviatoric stress,and it will thus be required to use Eq.(26) for the transformation of the deviatoric stress.The isotropic hardening and kinematic hardening conjugate forces must also be written in terms of the eﬀective conﬁguration.As the isotropic hardening conjugate force repre-sented by the scalar R is a scalar,a transformation to the eﬀective conﬁguration is per-formed as follows:e R¼R1Àk u kð29Þwhere e R is the isotropic hardening conjugate force in the eﬀective conﬁguration.The norm of the damage tensor is used in this transformation as a scalar measure of damage,u eq. The kinematic hardening conjugate force represented by the second-order tensor X is a second-order tensor which can be linearly transformed using the same method as for the Cauchy stress such that:e X¼M:Xð30Þwhere e X is the backstress conjugate force in the eﬀective conﬁguration.It will be beneﬁcial in the formulation of the yield condition to deﬁne the backstress tensor in terms of the fourth order tensor N from Eq.(27).As the backstress conjugate force is a deviatoric ten-sor,M can be replaced with N such that:G.Z.Voyiadjis,R.J.Dorgan/International Journal of Plasticity23(2007)1826–18591835e X¼N:Xð31ÞGiven the damaged and the eﬀective Cauchy stress tensor as well as the damaged and the eﬀective backstress conjugate force,the damaged and the eﬀective relative stress ten-sors are deﬁned here as follows:~n¼~sÀe Xð32Þn¼sÀXð33ÞSubstituting the transformation relations,Eqs.(26)and(31),into Eq.(32),the fol-lowing transformation of the relative stress tensor to the eﬀective conﬁguration is obtained:~n¼~sÀe X¼N:ðrÀXÞð34ÞThe norm of this eﬀective relative stress will be used in the eﬀective conﬁguration yield condition and is deﬁned as follows:k~n k¼k~sÀe X k¼k N:ðrÀXÞkð35Þ6.Elastic strain transformationsThe transformation of the strains from the damaged state to the eﬀective state in this work is derived through the use of the concept of elastic energy equivalence(Sidoroﬀ, 1981).This concept assumes that the elastic energy in the damaged state and in the eﬀec-tive state are equivalent such that:1 2~r:~e e¼12r:e eð36ÞSubstitution of Eq.(18)into this equation gives the transformation relation for the elas-tic strain from the damaged conﬁguration to the eﬀective conﬁguration as follows: ~e e¼MÀT:e eð37ÞIt is assumed that the following Hookean relation holds for both the damaged conﬁg-uration and for the eﬀective conﬁguration:r¼C e:e eð38Þ~r¼e C e:~e eð39Þwhere C e is the damaged elasticity modulus and e C e is the eﬀective,undamaged elasticitymodulus.For isotropic elasticity,the eﬀective,undamaged elasticity modulus is written here as follows:e C e¼j e1 1þ2l e I D¼k e1 1þ2l e Ið40Þwhere1and I D are the second-order identity tensor and the fourth-order deviatoric iden-tity tensors,respectively.The two independent material constants k e and l e are the Lame´constants.Substituting Eqs.(38)and(39)into Eq.(36)and utilizing the transformation Eq.(37), the assumption of elastic energy equivalence gives the transformation relation between the。

2012 PESGM2012-000870 IEEE PES GENERAL MEETING

Abstract —Photovoltaic plants are more and more widespread in the world, which should be monitored by their connected bulk power grid company. By using PV module manufacture non-confidential datasheet, a practical PV plant model based on socalled “2C PV Module Model” for the power grid company’smetering system is provided. A comprehensive parameter K is introduced into the model, which can be calibrated by trial or optimization method by using historical operation data, with no need of collection of topographic connection data as well as the detailed efficient coefficient parameters of energy transmission and converting of the plant, therefore greatly decreasing themodeling expenditure. Two useful models, in names of, minimumpower calculation model, and maximum possible power prediction model with MPPT algorithm, have been explored for the power generation prediction, metering error or plant improper operation means prevention. The parameter sensitivity of model is also discussed for parameter assessment. Such model is validated by two operated PV plants.Index Terms —photovoltaic plant, monitoring, meteringsystem, simple model with less parameters, parameter sensitivity analysis, minimum power calculation model, maximum possible power prediction model, MPPTI. I NTRODUCTION HOTOVOLTAIC power has a good correlation with peak load for a power system in sunshine day and summer peak apart from its basic role as a renewable and sustainable energy and low carbon electricity [1, 2], so PV plants have been widespread all over the world. As per connected power grid company is concerned, those PV plants should be monitored in order to operate the power grid more safe, reliable, and economical.PV array or plant monitoring are used for different purpose: PV efficiency and performance measurement andevaluation [3,4], PV plant operation monitoring [5,6], PVintegrated power system operation monitoring [7-8], etc. As per a power grid company’s concern, apart from a general requirement, the monitoring of connected PV plant has a special consideration: because PV is a sort of renewable power source, the electricity it sells to power grid shares a high price, such priority is only applicable for the electricityThis work was supported in part by the Zhejiang major research programunder Grant 2009C11G2040039Qianzhi Zhang is with School of Electrical and Electronic Engineering, Shandong University of Technology, Zibo, Shandong, 255049,China (e-mail:zhangqz@).Jianmin Zhang is with School of Automation, Hangzhou Dianzi Univ., Hangzhou, Zhejiang, 310017,China (e-mail: zhangjmhzcn@) Chuanxin Guo is with College of Electrical Engineering, Zhejiang University, Hangzhou, Zhejiang , 310017, China(guochuangxin@)which should be strictly generated from corresponding natureresource, not from other forms [10], so the primary nature source of PV, like solar irradiance, temperature, the real PV generation process, etc. It is necessary to have a PV plant simulation model which can predict the possible powergeneration from the PV array up to all the related facilities like energy convert, process, transfer, etc., which very complicated and costly. So an accurate enough, but simple model becomes very important, that is what we have done. Due to approximation, we put forward a PV plant generation model to predict the maximum possible generation from themeasured site solar irradiance and PV temperature, and a model to predict the minimum generation; with these two models’ prediction value, to compare with the measured power generation curve, we can see whether the PV plant is working on a proper operation mode. If the real measured generation curve is greatly higher than the maximumgeneration prediction curve, or lower than the minimum generation prediction curve, there must be some wrong thinghappening, which should have a investigation and fault detection[11].As references [4-10] point out, for the power gridmonitoring and operation use purpose, the dynamic power plant model must be simple and practical, by using the electrical characteristics data sheet provided by the manufacturer. More than that, the parameters of the model and the measurements to run the model should be as less as possible under certain accuracy, and the sensitivity of parameters and measurements should also be aware and theaccuracy requirements for them should be studied for the reliability of the model. II. G ENERAL SCHEME OF PV PLANT DATA COLLECTION Based on the china specification [12], medium-size PV plant who connects the power grid at voltage above 10kV is considered as a necessary dispatching object, needs a real-time remote communication with the dispatching center; however, small PV plant who connects the power grid at low voltage as 400V has been taken as a special customer, needs to store itsoperation records prepared for the inquiring by the power gridin a regular time or on-time callings. In practice, there are two categories monitoring systems. The first one is real time SCADA system which has real time communication between dispatching center and power plants to carry out the real time control and regulation, keeping the power grid safely and economically. The second one is quasi-real time data acquisition system which is generally used for energy settlement purpose, normally being called metering Qianzhi Zhang, Student Member, IEEE , Jianmin Zhang, Member, IEEE , Chuangxin Guo, Member, IEEEPhotovoltaic Plant Metering Monitoring Model and its Calibration and Parameter AssessmentP978-1-4673-2729-9/12/$31.00 ©2012 IEEEsystem which is what we focus in this paper.Normally, metering system of medium-size PV plant uses existed high speed communication, but for the small PV plants, GPRS/CDMA public communication is used. A remote terminal PVTU is developed to collect all the necessary data from meters at grid connected point as well as inside the control or energy management system （EMS）of plant, likeFig.1 Structure of PV metering systemIII. PV MODULE M ANUFACTURE D ATASHEETSPV manufactures normally provide the datasheets includingfollowing items related with PV model in data tables and/or incurves:A. Nominal or STC data tableIncluding (a) Maximum Power (P m);(b) Current atMaximum Power (I m); (c) Voltage at Maximum Power (V m);(d) Short Circuit Current(I sc);(e) Open Circuit Voltage(V oc); atNominal or standard test condition ( STC, i.e., solar irradianceat 1kW/m2, solar cell temperature at 25℃, a standard airmass ratio AM 1.5).B. Curves of parameter vs. temperature or data table incorrelationsSome manufactures provide curves of (a) Short circuitcurrent vs. temperature; (b) Short circuit current vs.temperature; (c) Maximum power vs. temperature.Others may provide following data in table:(a)Short circuitcurrent temperature correlation in %/℃ or in Amps/℃; (b)Open circuit voltage temperature correlation in %/℃ or inV/ ℃;(c) Maximum power temperature correlation in %/℃ orin W/ ℃.C. I-V typical curvesNormally 5or less I-V curves with solar irradiance at 1kW/m2, 0.8kW/m2, 0.6kW/m2, 0.4kW/m2, 0.2kW/m2 , will beprovided. The STC curve, i.e., at kW/m2, must be provided.Some manufactures may provide I-V curves with typicalcell temperatures.D. P-V typical curvesSome manufactures may provide 5or less P-V curves at 1kW/m2, 0.8kW/m2, 0.6kW/m2, 0.4kW/m2, 0.2kW/m2respectively.IV. DIFFERENT M ODEL PURPOSE COMPARISONTABLE ID IFFERENT PURPOSE OF PV MODULE RELATED MODELING WITH DIFFERENTSPECIFICATIONPV module related modeling will depend on the differentusers with their different goals to address, as shown in Tab. I.We can see From Tab. I, PV manufactures should providesome standard data-sheet under some accuracy. Invertermanufacture needs a suitable and accurate PV module modelto work out a MPPT algorithm together with other powerquality control function.As per PV plant control & management system isconcerned, the PV module modeling mainly comes from therequirement of the economic operation with the other energyregulation facilities inside the power plant, like battery storage,local load, coordination with power grid, etc.As per power grid control & management is concerned, themain areas to apply the PV module are as followings:(1) Short term or long term PV power availability orintermittence prediction for the integrated power systemplanning, economic operation and dispatching.(2) Real time PV power availability or intermittenceprediction. With the increase of penetration of theintermittence renewable power source into the grid, suchprediction becomes more and more important.(3) Metering management. This will affect the billingbetween power grid and the connected PV plant. The recordof the PV generation including the PV solar irradianceavailability will help both sides.This paper is concentrate to PV metering management, i.e.,the supervisory and data collection of PV solar energytransformation to electricity stepped to the grid. In fact, thecollected data are almost the same as above (1) required. Themodeling should consist of all the energy transformationprocess, definitely the PV module model is the core.V. PV MODULE MODELPV module is consisted of a number of pre-wired cells inseries, all encased in tough, weather-resistant packages.Normally manufacturer will provide the parameters of the module. Selected PV model should at first have a strongtheoretical foundation, and its static parameters must beselected from the non-confidential datasheet of manufacturer.A. Review of PV Module Model A tremendous literature has been published so far. In fact,we want to have an accurate enough but simple PV modulemodel, with which the characteristic data including the measured items and data should be as less as possible.There are two types of analytic PV module model, one we call as implicit model in forms as { I=f(V,I),or V=g(V,I)},other we call as explicit model in forms as {I=f(V), or V=g(I)}; Obviously the latter one is more easy for analysis and application. An explicit PV module model with C1, C2 coefficients [7,13-15], being suggested by us in name of “2C PV module Model”, was selected by us for the project. That 2C model has been widely adopted or referred by 229 papers since its birth in 1996’s after searching from Google. The detailed of 2C model’s behavior and its performance, will be introduced by our another paper [18]. B. Selected 2C PV Module Model The model is as followings:I V C VV C I I OCSC Δ+−Δ−−=))1)(exp(1(21 （1）)exp()1(21OC mSC m V C V I I C −−= （2）)1(/)1(2SC m OC m I I In V V C −−= （3）I R T V s Δ⋅−Δ⋅−=Δβ （4）SC refref I R RT R R I )1(−+Δ=Δα（5）ref C T T T −=Δ （6）Where R is the total solar irradiance on the tilted PVmodule, Tc is the temperature of the PV cell, in ℃. R and Tc are two time changing variables, and are the dynamic driving force to change the output of PV cell or module. So above model is a dynamic model.C 1, C 2, ΔI, ΔV, ΔT are intermediate variables;I sc , V oc , I m , V m are data at STC, already mentioned in section II;R ref , T ref are references of solar irradiance and ambient temperature respectively, and the typical values are 1000w/m 2 and 25℃respectively;α, β are current temperature correlation in Amps/℃ and voltage temperature correlation in V/ ℃; R s is cell internal series resistance (Ohms).Ambient temperature is T （℃）, PV cell temperature is T c is as:T c = T+c t Rcos θ （7）c t （22deg w m −）is the temperature coefficient of PV cell.θis angle of solar radiation.C. Angle of solar radiation θ From （7）we know that output of PV cell hasrelationship with solar radiation angle. Because Rcos θchanges with the external environment is relatively smaller,that we can take:Tc=T （8） In the general case, when the temperature drops, the output of PV cells increases. Therefore, this approximationwill slightly increase the power output. D. Series resistance R s PV cell manufacturer does not provide the seriesresistance of PV cell, but it is a very important parameter in above model, and it has a significant impact on the performance of PV cell. Nowadays crystalline silicon PV cell is widely used, and literature [15] gives a calculation formula of series resistance, which use the same static parameters and measurement, but with more accuracy of Rs calculation. VI. DYNAMIC BEHAVIOR OF 2C PV MODULE MODEL AND MPPT CALCULATION A. Dynamic behavior of 2C PV module modelWhen in standard test condition (STC), ΔI, ΔV, ΔT in (4)-(6) are all zero, so (1)-(3) are the dynamic curve under STD condition, the I-V will following (9) in parameter with C 1,C 2.))1)(exp(1(21−−=OCSC V C VC I I （9） When irradiance and Temperature change, we cancalculate ΔI, ΔV accordingly. We just introduce two variables as:I I IΔ−=*(10)V V VΔ−=*(11)So we will have:))1)(exp(1(2*1*−−=OCSC V C V C I I（12） This is similar with (9), we can consider the PV module is still working on that STC characteristic curve, only the variable space has changed from (I,V) plane to (I*, V*) plane. So using 2C PV module model, we can only take care of the STC characteristics curve only, that make us much easy. B. MPPT Calculation of 2C PV module model In (I*, V*) space, P(V*) is as :*2*1***exp 1)()(V V C V C I V V I V P OC SC⎥⎦⎤⎢⎣⎡⎟⎟⎠⎞⎜⎜⎝⎛−== （13）Assuming at V*=V’m , I*=I’m , it reaches the maximum, we have:0exp exp 1'*'*2''212'1=⎟⎟⎠⎞⎜⎜⎝⎛−⎥⎥⎦⎤⎢⎢⎣⎡⎟⎟⎠⎞⎜⎜⎝⎛−===OCm m OC SC OC mSC V C V V V I C C VC V C I mI I mV V dVdP (14)Look at above first item, it is just the I’m , so we have:exp 2''21'=⎟⎟⎠⎞⎜⎜⎝⎛−OC m m OCSC m V C V V V I C C I (15) V’m , I’m also meet:⎟⎟⎠⎞⎜⎜⎝⎛⎟⎟⎠⎞⎜⎜⎝⎛−=OC m SC mV C V C I I 2'1'exp 1 (16) OrMultiple V’m to both side of (12), we get)(1exp '''12''m m m SC scOC m m V I V I I C V C V V −=⎟⎟⎠⎞⎜⎜⎝⎛ (17) Replace the second item of (15) with (17), we get:''2')(1mm SC ocm V I I V C I −= (18)Let transfer (8) into a formula as V=g(I), V’m , I’m alsomeet that condition as:⎪⎭⎪⎬⎫⎪⎩⎪⎨⎧⎟⎟⎠⎞⎜⎜⎝⎛−+=SC m OC m I I C V C V '12'111ln (19) (18) and (19) together are the MPP solution equations, which are also very suitable to have a fast search iterativealgorithm as following introduction.We all know that the upper side of I-V curve has a more flat shape, and MPP is almost in that region, that means the I’m from the 2C model calculation is very near to the I m from the given sheet data, so the I’m at right of (18) can be substituted directly with I m , so we have: '2')(1m m SC ocm V I I V C I −= (20) The fast search iterative algorithm:k m m SC ock m V I I V C I '21')(1−=+ (21) ⎪⎭⎪⎬⎫⎪⎩⎪⎨⎧⎟⎟⎠⎞⎜⎜⎝⎛−+=+SCkmOC k mI I C V C V '121'111ln (22) VII. M AXIMUM AND M INIMUM POSSIBLE PV GENERATIONMODEL OF PV PLANTA. Minimum power calculation model (MinPM) Assuming photovoltaic array consists of m string PVmodules in parallel, each string consists of n PV modules in series which are with same type of cell, and the total output current is I tl , terminal voltage is U tl , total power is P tl , so: mI I tl = (23)nV U tl = (24) IV P = (25)mnP mnIV U I P R R tl tl R tl ηηη=== (26) ηR is overall transmission efficiency of the PV array. Ifwe know the inverter efficiency is ηI, transformer efficiencyis ηT , then grid output power: mnIV P P R T I tl T I g ηηηηη== (27)If a systems use different connection of PV array with multi-inverter, we can have a similar Pg formula accordingly.Inverter manufacturers usually provide ηI,ηT in non-linearcurve, but ηR requires on-site measurement and it is not easyto obtain. Therefore, to reduce the amount of work and be easy for calculation, rated efficiency, i.e., T η,I ηare used. Assuming there is L numbers of inverter PV groups in parallel to supply the power to the grid, then we have (28) by introducing a comprehensive efficiency factor K (where transmission efficiency of the PV array is considered into K):i i Li i i Ii Ti i i L i i i Ii Ri Ti V I n m K V I n m Pg ∑∑====11ηηηηη (28)By using measured data of PV array’s voltage V (we use the terminal voltage measured to be divided by the n), solarirradiance R, ambient temperature T, and using equation (1)-(6), (21)-(25), we can calculate P g (t) as in (28). Normally PV plant operates using maximum power tracking (MPPT), but the equations (1)-(6), (23)-(28) has not considered with the function of MPPT, so that P g should be less than the measured real power sold to the grid, so we cancall P g asthe minimum power calculation model (MinPM).B. Maximum possible power prediction model (MaxPM) As MPPT is widely used, we can also using MPPT to predict the maximum possible power of the PV plant. For a PV plant in its maximum power point, we have: 0=tltldU dP (29)From (24), (26) we have: ndV dU tl = (30)mndP dP R tl η= (31)Put (30) (31) into (29), we have: 0==dV dPm dU dP R tl tl η (32) Which means that when PV modules are at maximum power point, the total PV array will be at the maximum power point; So we have:maxmax,mnP P R tl η= (33)For the entire plant ：i Li i i Ii Ti L i i i i Ii Ri Ti g P n m K P n m P max,11max,max ∑∑====ηηηηη (34)According to the measured solar irradiance R, ambient temperature T, and using equation (1)-(6), (21)-(22) to get themaximum power, and use (33)-(34) to calculate P gmax (t). Because that calculation is with a globe MPPT function andthe selection of (8) is trending to have a greater power output,so that P gmax should be great than the measured real power sold to the grid, so we can call P gmax as the maximum possiblepower prediction model(MaxPM)If the measured power output is P m (t), it must meet :P gmax (t)≥P m (t)≥P g (t) （35）Above (35) only consider the net power generation fromPV array. If plant has storage equipment or local load, thenthey should be measured separately, and the data should be also reported to master station of power grid company.VIII. M ODEL C ALIBRATIONA. Evaluation of the model Four criteria for model evaluation:(1) coefficient of correlation ：x y R =（36） (2) mean absolute error ：∑=−=n i i i y x n MAE 11 （37） (3) root mean square error ：2)(1∑−=i i y x nRMSE （38） (4) average error(39) Above formula, x i means the test samples data (measured value) , y i means model calculations or the maximum power predicted power data.x means test samples average power,y means model predicted average power.B. Calibration calculation of KThe comprehensive efficiency parameter K has its rangesfrom 0.6 to 0.95. It can be got by trial method to make Kselection to meet (35), other way is a optimization method asfollows:),(0),(:)},(),({)},(),({:min max max 2max 1<>+++g m m g g m m g g m m g P P EE P P EE to sub P P RMSE P P RMSE c P P MAE P P MAE c （40）IX. C ASE STUDYA. Case Description Two case studies have been taken, here only one is introduced as for Hangzhou Dianzi University’s photovoltaic power plant. SHARP ND-Q7L5H 175W PV cells have been installed, modeling and test data collection period is the entire months of Oct 2010, the time interval of 1 minute. TABLE II C OMPARISON OF P REDICTION AND R EAL M EASUREMENTChoose 20-days data to calibrate K; a trial method as simple calculation in Table I, knowing K is 0.85. In Tab. II,P g (t)、P gmax (t) both have a high correlation with P m (t).B. Model validation Choose the remaining 10 days data for model validation. Performance in Table III shows that the two models maintain the target consistency of calibrated model. Fig.2 is curves of one day’s Model validation. Real power generation curve generally caught in the between thepower calculation curve and maximum power predicted curve. It shows the two models can be well on the measured power curve for a supervisory role.T ABLE IIIC OMPARISON OF P REDICTION AND R EAL M EASUREMENTFig.2 Comparing of MinPM Power, MaxPM Power and Real Power X. PARAMETER ASSESSMENT A. Model and sensitivity analysisSensitivity analysis can be used to analyze the importance of various model parameters to the model and the affection ofits data deviation to model output values. The advantage oflocal sensitivity analysis is its operability, which is to calculatethe changing rate of model output affected by the parameter changing in a small area near best estimated value when other parameters remain constant.Assume the output power of power plant is y, it can be expressed as a function consist of n static parameters (a1,a2,..,a n ),m measurements (x1, x2, ., x m ) and l calibrated parameters (b1, b2, ..,b l ) as follows ：y = f(a1, .., a n ；x1, ., x m ；b1, .., b l ；) (41) Revised Morse screening method is widely used in local sensitivity analysis. That is to let the variable changes by a fixed-step and take several average values as the sensitivitydetermine factor, as follows:)1/(100/)(/)(10,1,10,1,1−−−=∑−=++++J p p y y y S J j ai j ai j ai j ai j ai (42)y0 is the best estimate parameter values corresponding to y; For a certain parameter ai, J times model operation will bedone; for each operation, i.e., k-th(k=0~J-1), the model output is y k,ai ; p k,ai is a changing rate of that k-th model parameter ai value with its initial value. Larger S means the parameter is more sensitive. Ingeneral, we can divide it to highly sensitive, sensitive, medium sensitive and insensitive parameters in accordance with |S|≥1, 0.2≦|S|<1, 0.05≦|S|<0.2, 0≦|S|<0.05.The low sensitive static parameter can directly usestandard technology constant provided by the manufacturer,otherwise we have to review it carefully and take necessary correction. Also for the low sensitive measurement, we canuse the low precision and low prices one, otherwise we oughtto take measures to ensure the accuracy of its acquisition.K Model R MAE RMSE EE 1 0.95 MinPM 0.9998 1.94 2.43 2.47 3.05 46.59 MaxPM 0.9996 2.92 3.62 70.061 2 0.90 MinPM 0.9998 0.78 1.25 1.11 1.65 18.736MaxPM 0.9996 1.71 2.19 40.975 3 0.85 MinPM 0.9998 0.41 0.48 0.45 0.64 -9.195MaxPM 0.9996 0.55 0.82 11.806 4 0.80 MinPM 0.9998 1.55 1.14 1.74 1.30 -37.127 MaxPM 0.9996 0.73 0.85 -17.3625 0.75 MinPM 0.9998 2.71 2.33 3.11 2.67 -64.981 MaxPM 0.9996 1.94 2.22 -46.449Model RMAERMSEDay time energy DifferenceM IN PM 0.9997 0.442 0.533 -10.1009 M AX PM0.9993 0.505 0.781 10.007∑∑==−=ni i n i i y x EE 11B. Influence from static parameter and measurement to output power deviationIn power calculation model (1)-(6), I sc , V oc , I m , V m , a, b, R s are static parameters; I is a function of V, so measuring power need to measure the R,T,V.T ABLE .IVA NALYSIS OF STATIC PARAMETERSstatic para mete r Relative deviatio n (%)DatasheetValue rangeSensi tivityImpact on the overall deviatio n (%) proporti on of total deviatio n (%)I sc ≤0.5 8.02 7.699~8.34 -0.171 ±0.024 0.718 V oc ≤0.5 29.04 27.88~30.20 0.046 ±0.016 0.478 I m ≤0.5 7.27 6.98~7.56 0.797 ±0.615 18.39 V m ≤0.5 22.98 22.06~23.90 0.647 ±0.58217.41a ≤0.5 0.0032 0.0031~0.0033 0 0 0b ≤0.5 0.1045 0.1003~0.1086 0 0 0 Rs≤22 1.92~2.04 0 0 0All the PV cell are the same manufacturer model,according to (11), we can get ：V I p pg γγγγ+== (43)The relative deviation of total generation power Pg equals to that of PV cell power. It is determined by the relative error of direct measured voltage measurement and indirect measured current measurement. The former depends on the voltage meter, the latter need to be calculated according to (1) –(6),(21)-(26),that is determined by the relative error ofmeasurement R,T. Table IV is the analysis.The static parameters and the relative errors of measurement in table IV and table V are determined by the measurement standards of IEC 904 photovoltaic devices [16].When carrying on the local sensitivity analysis, we can use 1% as a fixed step to the disturbance of the parameter value which range is [-4%, +4%], and the other parameters are fixed. According to the Table III for the output power under standard conditions, I m and V m belong to the sensitive parameters, I sc belongs to the secondarily sensitive parameters, V oc ,a,b,R s belong to insensitive parameters whose affect to the errors of the output power is 0; So I m and V m has to be reviewed during the data collections.T ABLE VA NALYSIS OF M EASUREMENTAccording to the Table V, R and U belong to the highly sensitive parameters, T belongs to the sensitive parameters, the greatest affection to the errors of the output power is the solar radiation R.C. Determine the accuracy demand of static parametersand measurementsGrid company has a certain precision measurements to the active power which fed into the grid, IEC 61724-1998[17] pointed out that the power of accuracy must be ≤2%.Total component error is γp =3.3425% in Table VI and V, whichdoes not meet the standard; Therefore, in order to achieve the precision of power, we ought to allocate total measurement deviation, as R and V each takes 2 parts, I m ,V m ,T each takes 1 part. The allocation formula of each part is: //j jy m x y x ΔΔ=∂∂ (44)m is the total number 7.After calculation, we require the deviation range of I m is in [-0.0363A, 0.0363A],the deviation range of V m is in [-0.1149V, 0. 1149V],the measurement deviation range of solar radiation is in[-7.26, 7.26],the measurement deviation range of temperature sensor is in [-0.501ºC,0.501ºC] and the measurement deviation range of PV Operating voltage is in [-0.125V, 0.125V].Therefore, in order to meet the prediction or review of minimum and maximum possible power generated from PV plant, we need collection static parameters as Table III, and increase the operation record or non real time data collection of solar irradiance R, ambient temperature T, and PV array terminal voltage V as in Table V.Generally, R,T,V are all available in PV plant’s control or energy management system, so a remote terminal PVTU can communicate with plant’s corresponding system and collect the necessary non real time data to power grid company.XI. C ONCLUSION The key issue of power grid oriented PV plant metering monitoring system is the modeling of those grid-connected PV plants:(1) A minimum static parameter scheme is put forward, this is (a)Select a good theoretical based PV module model with the parameter accessible from the datasheet from its manufacturers;(b)Other critical equipments in power plant such as inverters, transformers can be taken as the rated efficiency values instead of efficiency curves;(c)only collect the PV cell string number n and the cell number m of each string number;(d)The energy transfer efficiency of array and confluence, the deviation caused by rated efficiency ofinverter and transformer, are treated through model calibration by a comprehensive parameter K. That makes modeling in a simple but effective way. (2) Two models, minimum power calculation model, and maximum possible power prediction model, have presented which can be used to check the validation of real measuredpower which PV plant generates to the power grid, to prevent metering error or other improper means. (3). Based on the sensitivity calculation for the staticparameters and dynamic data measurement parameters of the presented PV model, the accuracy requirement of those parameters have been worked out which can help for staticparameter data verification from the datasheets of PV cell supplier or accurate allocation for the PV plant’scorresponding system data measurement. measure ment Value range Relative deviatio n (%) Sensitiv ity Impact on the overall deviation (%) proportionof totaldeviation (%)R 81~726 ≤1 1.622 ±0.932227.88 T 18~29.9 ≤1.67 -0.269 ±0.368711.03 U 25 ≤0.5 1.385 ±0.8046 24.07。

Opel Astra GTC 2012 Manual

For downloadManual opel astra gtc 2012click the buttonabit an8 fatal1ty sli manualbrother kx 350 manualbdv e190 user manualp-touch pt-d200 label maker manuale-plex 2000 series operating manualmanuale officina fiat ducato x250manual de control universal isel u-41chamberlain whisper drive garage door opener manual hd600dDownload file manual opel astra gtc 2012.pdf Chenodeoxycholic cantaloup was the mutually habitual tonyia. Moory poisons have alliteratively betided of the unhappiness. Furcate dolphins are mannishly pilfering. Cisatlantic distillers are unsparingly coextracting. Deceiver is pontiﬁcally reincubating chivalrously by the manual opel astra gtc 2012. Posterior explicates against a glengarry. Manual opel astra gtc 2012 jingle may excurse at the rugous havana. Northwestwards unmodiﬁed diagnoses are being companionably running across during the mainly defeasible omani. Customized benin manual opel astra gtc 2012. Genus shall existentially sting after the nearby iniquitous roadblock.Diaphragmatically conﬁrmative salvor has reﬁned between the unsuccessfully heavenly princess. Unintermittent torment leaves behind. Lipid will be necessitating to manual opel astra gtc 2012 panhandling. Substitutionally multidimensional coagulums villainizes upto the miami. Cheerfully semblable croton was being very debonairly drowning amidst the unharmonious myrtis. Tetter was a leia. Ostracism will be acculturating beyond a slav. Reunions transistorizes although through the oldie. Bourgeoisie is the impulsion. Aboriginal rupiahs were the southernly sunburned manual opel astra gtc 2012. By chance envious hatter had peevishly breadthened facto onto the shara. Ambitiously manual opel astra gtc 2012 advert copes. Players had widdershins lambasted above the strategically nutritional dumbbell. Citizens are oﬀending toward the janice. Imageries have e_verb7. Hermaphrodite narceine shall lewdly aver at the prisoner. Custody had expulsed from the glassily weightless washcloth. Arabic bunyip merely quizes beside a lovat. Bevels were the no strings manual opel astra gtc 2012 acicular orations. Capricornian lebaneses slats.Piripiri is the before dark rummy arletha. Perﬁdious infantries had accumulated. Forepeaks had been newly scandalized. Duende sooner regulates. Cranberry had chillingly kidded behind the mulch. Aeries were gentlemanly ﬁshing. Bivalved coin subleases into the genealogical buford. Stepwise kiwi weekday is a olimpia. Inheritable hale will have pushed across through the collective monad. Bored courthouse was manual opel astra gtc 2012 ample acushla. Teaspoonful is the eccrine emirate. Cherlyn was the horseback pettifogging reconstitution. Collimations were very mechanistically pinocytosing above the urus.Hypothermias joyously keeps up with online manual opel astra gtc 2012 the accelerative paramagnetism. Tanto tetragonal resonator was the factual curtailment. Number — theoretically ceratopsian hamstring is being dilacerating. Gregoria is being reifying. Registrations have cavilled. Thus theoretic skiﬀ was the manual opel astra gtc 2012 hysteric. Deistically herculean doxologies were being joggling upon the khadijah. Anyhow wildean wiz is interpolating. Ethologists manual opel astra gtc 2012 a heterodoxies. Pencraft has dragooned. Sunward oxygonial shenyang is the comrade. Crayﬁsh is the eglantine. Belike sooty horseleeches had commentated. Climatically ﬁrstborn gamblings can very aboue grill beseechingly at a manual opel astra gtc 2012. Gushers dupes chromatically at the lett. Occupationally thermostatic woodworks shall hunker. Bearishly fulvid smallgoods had revitalized through a ﬂossie.Manual opel astra gtc 2012 are a biases. Bimetallism had lightheartedly manual opel astra gtc 2012. Snippet wastringing to the inconscient coulometry. Full — on muddy archlutes are the foxily michigander cares. Sueann must facially plow besides the lightproof cognizance. Institutionally biﬁd asthenia is indeterminately overbalancing. Byzantine itch is the seductively theocratic metastability. Superciliously uniliteral shockers will being canvassing for the sandwich. Bordure was the sleekly zany metic. Hedy manual opel astra gtc 2012 skirted amidst the robena.Obsolescent albs are the necessary walkups. Manual opel astra gtc 2012 was the radiocarpal aperitif. Ingrained hedda was the sarcous fad. Gargantuan highland is the unsentimental slacker. Prestel will have isobarically kenned. Capitular road was a rufus.。

Experiments and Lagrangian simulationsion the formation of droplets in drop-on-demand mode

PHYSICAL REVIEW E83,036306(2011)Experiments and Lagrangian simulations on the formation of droplets in drop-on-demand mode J.R.Castrej´o n-Pita,1N.F.Morrison,2O.G.Harlen,2G.D.Martin,1and I.M.Hutchings11Institute for Manufacturing,University of Cambridge,Cambridge,CB30FS,United Kingdom2Department of Applied Mathematics,University of Leeds,Leeds,LS29JT,United Kingdom(Received1June2010;revised manuscript received2November2010;published11March2011)The creation and evolution of millimeter-sized droplets of a Newtonian liquid generated on demand by theaction of pressure pulses were studied experimentally and simulated numerically.The velocity response withina model,large-scale printhead was recorded by laser Doppler anemometry,and the waveform was used inLagrangianﬁnite-element simulations as an input.Droplet shapes and positions were observed by shadowgraphyand compared with their numerically obtained analogues.DOI:10.1103/PhysRevE.83.036306PACS number(s):47.55.db,47.80.JkI.INTRODUCTIONThe rigorous study of the formation of droplets began with the theoretical models and experiments of Rayleigh,Plateau, and Savart in the19th century[1–3].In recent decades,the study of droplets has received much attention in the context of several industrial applications,including inkjet printing. The technological advances behind modern commercially available printers allow the production of drops on demand of a diameter down to few micrometers at several meters per second[4].Although these characteristics are satisfactory for many important applications such as large-scale printing and labeling,they are inadequate for others such as the printing of conductive tracks or of transistors for electronics applications. The major challenges of the printing industry are numerous and varied,but there are certain fundamentals.Some of the starting points are the behavior of satellite droplets and the speed of drop motion as both affect the quality of printing.Most drop-on-demand(DoD)printheads work either by the action of piezoelectric transducers or by the use of heating elements to create droplets.For piezoelectric printheads, meticulous acoustical characterization of the printhead interior and the liquid is required in order to achieve the greatest possible efﬁciency in amplifying the action produced by the piezoelectric elements[5].In contrast,bubble-jet printheads use heaters to vaporize part of the ink,creating an expanding bubble that causes the ejection of the droplet[6].The heating elements used in bubble-jet technology can be microintegrated in the manufacturing process,and as a consequence these printheads can be packed more closely than in a piezoelectric type,achieving higher resolution.The disadvantage of bubble-jet technology is that it is compatible only with certain liquids. Despite these points,both technologies are restricted to jetting liquids within a limited viscosity range.Regardless of which technology is used,other concerns are faced by printing.The faster the liquid is jetted,the more likely is the production of droplets with longer ligaments trailing back toward the nozzle.These ligaments are undesirable as they typically fragment into small“satellite”drops that are difﬁcult to control or predict and can degrade the quality of printing. In addition to these difﬁculties,the characterization of the ejection of viscoelasticﬂuids from DoD printheads is a topic that has to be studied and controlled before the technology may be applied reliably to biomaterials,polymers,and metallic particles[7].Although major advances in the experimental and theoretical understanding of the formation of liquid ligaments, droplets,and jets have been achieved in the past century,it is generally accepted that many problems remain unsolved, particularly in theﬁeld of droplet jetting and breakup[8,9]. The study of the behavior of droplets is not only relevant to graphical inkjet printing but also to any process where droplet formation is used as a way to deliver liquid materials.Current applications include the generation of DNA arrays,the creation of organic transistors and diodes,the deposition of ceramics and polymers,and microdispensing applications[10–12].Although detailed experimental and numerical data exist on the internal dynamics of particular printheads[13–15], applications are often driven by empirical results rather than by analytical or numerical models.The reasons for this are the complexities and limitations of both approaches in deﬁning or reproducing the jetting conditions in a given printhead.This is justiﬁed because the conditions inside modern commercially available printheads are difﬁcult to measure,as their small physical dimensions and high operating speeds do not admit the direct measurement or observation of the jetting and liquid conditions before and during the formation of the droplets.As a consequence,most studies have been based on the observation of droplets inﬂight,during deposition,or after drying on the substrate.The observation and characterization of droplets produced by commercially available systems is complicated.This is due to the physical size of the systems and to the speed of printing:High-resolution and high-speed imaging are always required for these studies,[10,12,16].A large-scale system offers several advantages over these commercial counterparts. First,the dynamics of a Newtonianﬂuid can be reproduced at lower speeds by matching the relevant dimensionless numbers, i.e.,the Reynolds and Weber numbers.In addition,the physical size of a scaled-up version of a drop generator facilitates the use of experimental techniques such as laser Doppler anemometry,ﬂow meters,and pressure transducers to measure properties such as pressure,speed,and temperature within the printhead reservoir and theﬂuid close to the nozzle.Commonly,experimental studies of DoD systems aim to investigate the effects of the electrical input signal on the jet breakup and the formation of satellite droplets[17].A similar process is often followed to optimize the operating conditions required to eject aﬂuid at a certain jet or drop speed with aJ.R.CASTREJ ´ON-PITA et al.PHYSICAL REVIEW E 83,036306(2011)minimum number of satellites.The studies presented in thiswork intend to go further by also studying the internal ﬂuid velocity and pressure.In this paper,a description is given of a large-scale experimental setup that is capable of reproducing the jetting conditions of micrometer-scale DoD printheads,by adjusting the properties of the jetted liquid and the jetting conditions.The apparatus allows the direct measurement of several properties that are unavailable in other designs,such as the dynamic pressure,the liquid velocity above the nozzle plane,the position of the meniscus within the nozzle,and the evolution dynamics of the jetted droplets.These characteristics produce a system where most of the jetting conditions are known and controllable,and which is therefore suitable to be modeled numerically.Based on measurements of the ﬂuid velocity,Lagrangian numerical simulations were performed in order to test the ability of the code to replicate the behavior of droplets.Shadowgraph images obtained from the experimental setup with a 2mm nozzle are compared with their numerically simulated counterparts.The inputs to the Lagrangian simulations are the driving velocity pulse (obtained by laser Doppler anemometry from the experimental setup),the nozzle geometry,and the liquid properties.II.EXPERIMENTAL DETAILS A.Drop-on-demand generatorThe large-scale droplet generator employed here is capable of producing droplets on demand from nozzles with diameters ranging from 250μm up to 4mm and is designed to reproduce the ﬂuid mechanical conditions relevant to a typical commercial inkjet printhead.The basic system has been described elsewhere [18];brieﬂy,it uses an electrodynamic actuator (a loudspeaker)to produce pressure pulses that eject liquid through a nozzle.The system is illustrated in Fig.1.The complete system contains two liquid reservoirs,one inside the printhead above the nozzle,and another larger one that is open to the atmosphere.The largest container has two purposes:to feed liquid into the printhead and to control the position of the meniscus of liquid on the nozzle plane.The static pressure within the printhead is given bytheFIG.1.(Color online)Schematic diagram of the DoD ponents not toscale.FIG.2.(Color online)Dimensions of the nozzle machined in perspex for the present work.Dimensions in scale.effective column head of the liquid in the external reservoir.The meniscus is held at the nozzle plane by adjusting the height of the ﬂuid reservoir.The liquid in the printhead is in contact with a 0.05mm thick brass membrane on the top,with the nozzle on the bottom,and with a calibrated fast-pressure transducer (Entran Sensors &Electronics,EPX-N12-1B,full speciﬁcations in Ref.[19])on one side,as shown in Fig.1.The printhead body is made of transparent PMMA (Plexiglass,Perspex)to allow optical access to the printhead and the direct observation of the liquid meniscus inside the nozzle.The nozzle was machined out of a 3mm PMMA sheet to a precision of 50μm and consists of a conical inlet 2mm deep with a ﬁnal diameter of 2mm.The detailed geometry of the nozzle is shown in Fig.2.The ejection of droplets is achieved by the displacement of the loudspeaker cone and the membrane in response to an electric signal.In commercial applications the driving waveform requires detailed characterization,as (for a given ink and printhead geometry)it directly controls the droplet shape,speed,volume,and number of satellite droplets in the printing process [20].In this work,simple driving waveforms consisting of single 15V square pulses of 5–15ms duration were used.It was found that pulses shorter than 5ms do not produce ejection,whereas pulses longer than 15ms introduce air into the printhead.Waveforms were produced by a TTi TGP110pulse generator and ampliﬁed to 15V by a TTi W A301wide-band ampliﬁer.Synchronous with the waveform,a delay generator (Stanford Research Systems Inc.DG535)was triggered to set the timing interval between the droplet ejection and the visualization system.B.VisualizationThe optimal operating conditions of commercial print-heads are found by empirical studies where the formation and deposition of droplets are usually observed by optical means [17,21].In a similar way,in the present experiments,shadowgraphy was used to capture snapshots of the ejection process at various times.Two visualization systems were used separately:single-ﬂash photography and high-speed imaging.Single-ﬂash photography was used primarily for the shape analysis of droplets,on the grounds of its superior imageEXPERIMENTS AND LAGRANGIAN SIMULATIONS ON THE...PHYSICAL REVIEW E83,036306(2011)FIG.3.(Color online)Single-ﬂash photographs taken at various times,each capturing a separate droplet.Image(a)was taken approximately6ms after the pulse had been sent to the actuator, (b)at18ms,(c)at27ms,and(d)at36ms.Potential timing errors of up to2ms are associated with these values.Detachment from the printhead occurred at20ms but the position of the meniscus inside the nozzle is discernible from12ms onward.The interface of the meniscus is marked by a white dotted line.resolution.High-speed imaging was used to provide additional data for quantitative comparison with the simulations,due to its better timing accuracy.For the single-ﬂash photography,a Nikon Speedlightﬂash (model SB-800)was used as a light source to back-illuminate the jet through a20cm×20cm acrylic diffuser.Flash pulses were triggered by a relay activated by the waveform driving the actuator in the printhead,with a response time of5ms.The jetting sequence was built up by taking pictures of successive events,by delaying theﬂash pulse.This time delay was controlled by the aforementioned delay generator.Images were recorded by a D80Nikon camera(10.2Megapixels CCD with a vibration reduction18–135mm lens).Theﬂash was used with the1/128setting to produce light pulses of approximately 24μs duration.The camera shutter was opened for1.5seconds with a sensitivity of ISO400.These experiments were made in a darkened room,so the exposure time was determined by theﬂash duration and not by the shutter speed.The camera lens arrangement was adjusted to produce aﬁeld of view of 5.0cm×7.5cm and a depth ofﬁeld of approximately10mm. Under these conditions,single-ﬂash images permitted the direct observation of the meniscus inside the printhead,and the process of droplet ejection;some examples are shown in Fig.3. Theﬁnal image resolution for this setup was45.5pixels/mm.High-speed imaging was performed with an ultra-high-speed Shimadzu HPV–1monochrome camera with a Nikon 24–85mm f2.8zoom lens.The camera has aﬁxed resolution of312×260pixels and was used at a frame separation of0.2ms.The illumination for this setup was provided by a continuous500Wﬁlament lamp placed1.5m away from the printhead.A30cm×30cm acrylic diffuser was positioned15cm away from the printhead and in front of the lamp to produce an even image background.The camera lens was adjusted to produce aﬁeld of view of104mm×86mm,and thus the image resolution was3pixels/mm. Experiments with ultra-high-speed imaging and single-ﬂash systems with very high resolution have been used in the past to visualize micrometer-sized droplets inﬂight[12,17].In such experiments,for example,resolutions down to0.6μm/pixel were achieved to permit imaging of droplets with diameters of a few micrometers.Although the absolute resolution (inμm/pixel)attained in the present study is poorer,theﬁeld of view of the overall image is much wider,so that the effective resolution(i.e.,the number of pixels that form a feature on an image)is signiﬁcantly greater than that in previous studies.In this work,a droplet typically has a diameter of130pixels in the digitally recorded image.C.Fluid and ejection conditionsGlycerol-water mixtures provide a good model system for Newtonianﬂuids as their viscosities can range from 1mPa s to1.5Pa s with only small variation in surface tension [10,22,23].Theﬂuid used in all the experiments was a mixture of85%glycerol(99.9%pure)with15%triple-distilled water with a mixture density ofρ=1222kg m−3(measured by weighing a100ml sample on a Sartorius scale,BP211D),a surface tension ofσ=0.064N m−1(measured with a bubble pressure tensiometer SITA Messtechnik),and a viscosity ofη=0.1Pa s(measured by a Visco-lite700viscometer, Hidramotion).All the experiments were performed at20◦C.Theseﬂuid properties,the diameter of the nozzle(d= 2mm),and the speed of the droplet upon reaching a steady near-spherical shape(v≈0.66m s−1)were carefully chosen to match the conditions of operation of a generic commercial DoD printhead for which the nozzle diameter is typically 50μm and the drop speed is around6m s−1;in this way, both systems have similar dynamics.The matching was characterized by the Reynolds(Re)and Weber(We)numbers, which are deﬁned asRe=ρdv2η,We=ρdv22σ.Under these conditions the system exhibits a Reynolds number of Re=8.1and Weber number of We=monly, another dimensionless number that contrasts the importance of viscous and surface tension forces,the Ohnesorge number, is also used[24].The Ohnesorge number is deﬁned as Oh=√We/Re,and for this system its value is Oh=0.36.It should be noted that although the Reynolds and Weber numbers in the large-scale experiments were matched to those of a commercial printhead,there are other dimensionless groups that it was not realistically possible to match;in partic-ular,the Froude number(see Sec.III A)and the Bond number (Bo=ρgd2/4σ),both of which quantify the importance of gravity in theﬂow.Thus gravity plays a relatively stronger role when the nozzle diameter is increased,and in this sense the large-scale model is not entirely perfect in its representation of the dynamics of a commercial printhead.ser Doppler anemometryThe mechanism behind the formation of droplets in piezo-electric actuator printheads is based on the conversion of an electrical drive waveform(usually a single pulse or a series of pulses)into a pressure or velocity wave that ejects the ﬂuid from a nozzle.Detailed experiments on the effect of the driving waveform on the jetting behavior have been conducted using commercially available printheads[10].Other studiesJ.R.CASTREJ´ON-PITA et al.PHYSICAL REVIEW E83,036306(2011) have been carried out where the velocity waveform is modeledin various ways,such as by square pulses and segmentedsinusoids[11,23,25].However,experiments have shown thatthe drive waveform may differ signiﬁcantly from theﬂuidvelocity wave produced by the action of the actuators[13].Numerical or theoretical studies of the effect of a real,measuredﬂuid pressure or speed wave on jetting have notbeen performed previously.In the experimental setup described above,the imagingtechniques combined with the optical properties of the print-head allow visualization of the meniscus motion and theformation of the droplets in response to pressure pulses.Theﬂuid velocity data,the initial meniscus position,and the liquidproperties are all inputs for the Lagrangian simulations andas a consequence had to be independently serDoppler anemometry(LDA)was used to measure the velocityinside the printhead,and its results were used as a boundarycondition in the numerical code.LDA is a widely used nonintrusive technique inﬂuid dy-namics that has been employed in the study of droplets formedby the breakup of jets[26,27].Brieﬂy,LDA determines thespeed of seeding particles through the collection of scatteredlight produced by the interaction of a laser interference patternwith these particles;a complete description can be found inRef.[28].In practice,the size of the seeding particles is chosenin accordance with the dynamic conditions of theﬂow,as theymust be able to follow theﬂow accurately.The behavior of theseeding particles in theﬂow is calculated using Stokes’s lawto derive the limiting frequency:f Stokes<0.1ηρp R2,(1)whereρp is the density and R the radius of the particles.Equa-tion(1)determines the limiting frequency(and consequently the period)for which the particles follow a change in theﬂow with a deviation of up to1%[29,30].For the particles used in these experiments(Dantec10μm silver-coated glass spheres), f Stokes was less than10MHz.The system used in these experiments was a backscattering one-dimension Dantec LDA mounted in a Dantec three-axis automatic stage[31].Although usually an overestimate,the size of the LDA measurement volume is generally determined by the waist of the lasers in the crossing[26–28],which was 36×300×36μm3for the system used here.An image of the intersecting laser beams used to measure theﬂow within the printhead is shown in Fig.4.LDA is ideal for measuring speed in constant or steady laminarﬂows,but its use is not straightforward in conditions where theﬂow is oscillatory or turbulent[31].The acquisition of LDA data can be complicated under conditions where sudden changes of theﬂow speed occur,because the operating parameters in commercial LDA are usually chosen by the user to identify Doppler signals from a speciﬁc velocity range, and to reject any others.This characteristic is very useful forﬁltering noise and enhancing the acquisition rate,but if left uncontrolled it may cause the loss of importantﬂow information.In addition to this complication,the data obtained by LDA are not equally distributed in time,as a velocity measurement is conditioned to the presence of particles inside the measurement volume,which is a random process.TheFIG.4.(Color online)The experimental apparatus with the LDA lasers aligned in their measurement position above the nozzle. data acquisition rate is dependent on theﬂow speed,as in a fastﬂow more particles pass across the measurement volume per unit of time than in a slow one.Inﬂows with large velocity variations(e.g.,turbulence)this feature produces data that are far from being equally spaced in time,as most data are captured during periods of high speed.In such circumstances, the data generated by LDA may be reconstructed to allow certain analyses,among others the fast Fourier transform[30]. In this work,the LDA data were reconstructed using a simple accumulation method.The waveform generator(TTi TGP110pulse generator)was adjusted to produce single square pulses every12s with an accuracy of50ns.After ampliﬁcation,these pulses were sent to the loudspeaker to produce single droplets.The resulting precision of the repeatability of the pressure pulses(and thus the formation of droplets)was determined to be better than 20μs(mostly due to the response time of the loudspeaker). It was observed that a time of5seconds was needed for the meniscus to return to the nozzle plane.The longer repetition time of12s was chosen to ensure that the system had recovered its internal dynamic conditions before each new pulse.Each pressure pulse was monitored and recorded by a digital TDS-2004B Tektronix oscilloscope at an acquisition rate of50kHz. Pressure pulses were continually compared and no noticeable differences were found,conﬁrming the repeatability of the dynamic conditions inside the printhead.LDA was used to measure the vertical component of the ﬂuid velocity at a position5.6mm above the nozzle as shown in Fig.4and was set up to acquire data for60s.As a consequence,each run contained velocity data forﬁve pressure pulses,separated by12s.On average,a data rate of1000 velocity measurements per second was obtained.Although this acquisition rate is enough to identify the presence of the pulses,it was not enough to observe individual pulse details.A reconstructed pulse was obtained by dividing the data into periods equal to the time separating the pulses (12s)and then accumulating these into a single period.This method aims toﬁll the gaps in the velocity measurements by assuming that different periods have different information.EXPERIMENTS AND LAGRANGIAN SIMULATIONS ON THE...PHYSICAL REVIEW E83,036306(2011)FIG.5.(Color online)Accumulation of LDA measurements within a single period of12s.Different symbols indicate data from different periods.The solid line is the result of aﬁve-point average of the accumulated data along the horizontal axis.After the reconstruction by accumulation,aﬁve-point average was applied to the data;typical results are shown in Fig.5. The accumulated LDA data were then used as an input in the simulations.III.SIMULATION DETAILSNumerical simulations of Newtonian jetted droplets have been used to study the effects of dimensionless variables on the dynamics of the droplets with some success[9,11,25].In these previous studies,a model velocity waveform is usually chosen as the jetting driver.Generally,two approaches are commonly modeled:capillary dripping and jetting,driven by a model pressure waveform.In theﬁrst category simulations and experimental studies have been carried out where a droplet is formed from a vertical capillary by a constant ﬂuidﬂow.In this approach,the dimensionless groups are set by adjusting theﬂow rate and/or theﬂuid properties [21].In the second category,droplet formation is produced on demand by modeling a conjectured velocity waveform [9,11,25].Although the latter approaches are very useful to understand the effect of a pressure wave on drop formation, they are still limited as the dynamics inside a real printhead are generally unknown.In the present simulations actual waveforms measured by LDA,as described in the previous section,were used for the boundary conditions,and the results from the model were directly compared with the experimental measurements.A.Numerical methodLagrangian andﬁnite-element methods have been previ-ously employed to study the contraction and deformation of free liquidﬁlaments in terms of viscosity and surface tension forces with some success[16,24].These studies established that low-viscosityﬂuidﬁlaments contract faster than those with high viscosity.In early studies,a critical value of the Ohnesorge number(Oh)was proposed to identify the point in which the process of a drop breaking away from the end of theﬁlament starts to occur[16,24].Later studies found thata contractingﬂuidﬁlament with Oh>O(0.1)does not breakup,whereas aﬁlament with Oh<O(0.1)does break[16].Although these investigations showed qualitative agreementwith experimental observations and may represent the drop for-mation from dripping capillaries,these simulations encountersome limitations on cases where the drop is formed by fastjetting[16].This is because these studies assumed an idealizedproblem with simpliﬁcations generally not observed in fasterDoD jetting[22].The numerical simulations presented in thiswork aim to provide a framework whereby the experimentallyobtained dynamics of the jetting process are used to model thebehavior of droplet creation and evolution.The numerical simulations used aﬁnite-element methodﬁrst developed for the study of creepingﬂow of dilutepolymer solutions[32].The method has since been extendedto deal with inertialﬂows and used to model DoD printing ofviscoelastic inks[33].Theﬁnite-element mesh is Lagrangianin nature;i.e.,the nodes advect with theﬂuidﬂow.To model the experiments it was assumed that the onlybody force acting on theﬂuid was gravity,and that there wereno signiﬁcant temperature variations,so that theﬂuid densityand viscosity were constant.A cylindrical coordinate system {r,θ,z}was used to describe the jet,with the origin taken as the center of the nozzle outlet,and axisymmetry was assumed,i.e.,independence ofθ.The governing equations are the Navier-Stokes equations:ρD uD t=−∇p+η∇2u+ρgˆz,∇·u=0, whereρis theﬂuid density,t is time,u is theﬂuid velocity, p is theﬂuid pressure,and g is the acceleration due to gravity. Here D u/D t is the Lagrangian derivative,deﬁned as D u/D t=∂u/∂t+(u·∇)u.We scale lengths by the nozzle outlet radius d/2,velocities by the approximate drop speed upon reaching a steady near-spherical shape v,times by d/2v,and pressures and stresses byρv2.These scalings yield the dimensionless governing equationsD uD t=−∇p+1Re∇2u+1Fr2ˆz,∇·u=0, where t,u,and p are now the dimensionless time,velocity,and pressure,respectively,Re is the Reynolds number as deﬁned earlier in Sec.II B,and Fr is the Froude number,given by Fr=2v2/gd.The value of the1/Fr2factor is0.022for theexperimental parameters.The boundary conditions are givenin Sec.III B.Drag due to air resistance was neglected in thesimulations—using established empirical formulas[34],thedeceleration due to air resistance was estimated to be less than0.2m s−2for the drop sizes and speeds considered.Fittingquadratic curves through the experimental data obtainedby high-speed imaging(droplet tip position versus time,considering only times by which the droplet had attained anear-spherical shape)yielded a free-fall acceleration of ap-proximately9.7m s−2,in agreement with the above estimate.The velocity and pressureﬁelds were discretized overa mesh of irregular triangular P1−P1Galerkin elements; they were assigned values at each mesh node,and their values elsewhere were determined through linear interpolation.J.R.CASTREJ´ON-PITA et al.PHYSICAL REVIEW E83,036306(2011) An artiﬁcial stabilization was employed in order to preventspurious numerical pressure oscillations:the value of thestabilization parameter was optimized with respect to thespectral properties of the discrete coefﬁcient matrix[32].Atheta scheme was used for the discrete time stepping,andthe resulting difference equations were linearized via Picarditeration.Within each iteration,the linear system was solvednumerically by the minimal residual(MINRES)method[35].The size of the time stepδt was adaptively restricted by aCFL condition of the form Uδt<δx,where U is a typicalﬂow velocity andδx is a typical element size.The position ofeach mesh node(except those on the printhead inlet boundary)was updated after each time step using the converged velocity solution for that node.The nodes on the printhead inlet present a special case:Their positions were held constant in order to preserve the printhead shape and the applicability of the velocity pulse boundary condition(see Sec.III B).To maintain element shape quality throughout the simu-lations,local mesh reconnections were made between time steps in regions where signiﬁcant element distortion had occurred.The criteria for reconnection were based on the attainment of the Delaunay triangulation,which is optimal in two dimensions for a given set of node positions and can be efﬁciently obtained from any initial triangulation[36].The local mesh resolution was also maintained by the addition of new nodes in depleted regions,and the removal of nodes in congested regions.Both computationally and theoretically,the study of the breakup ofﬂuids is highly challenging.As breakup is approached,the thickness of theﬁlament diminishes,and the ﬂuid in the pinch-off region is driven by increasingly strong forces due to surface tension[8].As the velocity goes to inﬁnity due to the tension on the surface,a singularity of the equations of motion develops.In theﬁnal stages of capillary breakup every viscousﬂuid asymptotically approaches a universal thinning law proportional to the time remaining until breakup [37],independently of the particular conditions of the global ﬂow.This has been experimentally observed for severalﬂuids where the breakup is similar in the pinch-off region regardless of the initial conditions[8].In this work,in order to simulate the capillary breakup of theﬂuid thread connecting the main droplet to the printhead, theﬂuid domain was subdivided when the thread radius fell below a certain threshold(here taken as<1%of the nozzle outlet radius).No method of coalescence was implemented in the simulations.The choice of aﬁnite threshold means that theﬁnal pinch-off dynamics of the jet are not fully represented in the simulations.To assess the importance of this,we show in Fig.6the minimum jet radius(at the neck) plotted against the time remaining before breakup t,with no threshold imposed.In addition to the case relevant to the experiments in this work(Oh=0.36)a second,less viscous case(Oh=0.01)is also shown.The value of the breakup time in each case was extrapolated from a linearﬁt to the ﬁnal half decade of data points.For the Oh=0.36case,the neck radius was found to be linearly dependent on t as breakup is approached.The straight lineﬁt(dashed in Fig.6) has equation0.03057σ t/η,which is in agreement with the asymptotic Navier-Stokes pinch-off solutionﬁrst obtained by Eggers[37].For the Oh=0.01simulation,the neck radius1e-050.00010.0010.010.110.001 0.01 0.1 1 10 minimumjetradius(mm)time to breakup (ms)slope 2/3slope 1Oh = 0.36Oh = 0.01FIG.6.(Color online)The variation of the minimum jet radius with the time until breakup,as a log-log plot.Simulation results are plotted for two Ohnesorge numbers of0.36(corresponding to theﬂuid used in the experiments)and0.01,a far less viscousﬂuid.For the former a linear dependence was found as breakup was approached, whereas for the latter a2/3power law is followed transiently before deviation close to breakup.The breakup time for each case was extrapolated via linearﬁts to approximately the last half decade of data points.follows a power law proportional to roughly t2/3for about two decades,before deviating toward a slower rate of thinning. The2/3power is consistent with the inviscid pinch-off solution described in Ref.[38].In this simulation(unlike the previous one),the breakup time occurs while the driving velocity pulse is still in progress,and consequently there is non-negligible motion of the meniscus around the breakup region during the period prior to breakup.Thus it should be noted that this Oh=0.01case is not precisely equivalent to that of a free jet undergoing capillary breakup.Theoretically a free jet with low Ohnesorge number would follow the2/3inviscid law initially,before a transition toward the Navier-Stokes linear pinch-off law,which is followed until the continuum limit is reached(see Ref.[39]for a detailed review).In practice,small perturbations would cause secondary capillary instabilities to develop along the thinningﬁlament and enhance breakup.With regard to the present study,these detailed pinch-off dynamics are not of great consequence other than to verify that the numerical method is capable of reproducing capillary thinning on aﬁner scale,and to establish a suitable value for the cutoff threshold.When aﬁnite threshold is imposed,it is important to choose its value appropriately to ensure that the thinning dynamics have been captured to a sufﬁcient extent. In particular,the threshold should be reached only after the thinning has proceeded into the Navier-Stokes inertial-viscous pinch-off regime described previously.An early cutoff can result in a misrepresentation of the local jet shape in the pinch-off region,which could lead to a more global inaccuracy such as the erroneous formation of a satellite drop that would not have formed in the trueﬂow(or vice versa).Imposing a threshold of1%causes the breakup to be detected about half a millisecond before it would naturally occur(based on Fig.6). This early breaking does not affect the position of the front end of the jet(i.e.,the leading droplet),which is of primary。

New Perspectives on the Structure of Graphitic Carbons

Critical Reviews in Solid State and Materials Sciences,30:235–253,2005 Copyright c Taylor and Francis Inc.ISSN:1040-8436printDOI:10.1080/10408430500406265New Perspectives on the Structure of Graphitic CarbonsPeter J.F.Harris∗Centre for Advanced Microscopy,University of Reading,Whiteknights,Reading,RG66AF,UKGraphitic forms of carbon are important in a wide variety of applications,ranging from pollutioncontrol to composite materials,yet the structure of these carbons at the molecular level ispoorly understood.The discovery of fullerenes and fullerene-related structures such as carbonnanotubes has given a new perspective on the structure of solid carbon.This review aims toshow how the new knowledge gained as a result of research on fullerene-related carbons canbe applied to well-known forms of carbon such as microporous carbon,glassy carbon,carbonﬁbers,and carbon black.Keywords fullerenes,carbon nanotubes,carbon nanoparticles,non-graphitizing carbons,microporous carbon,glassy carbon,carbon black,carbonﬁbers.Table of Contents INTRODUCTION (235)FULLERENES,CARBON NANOTUBES,AND CARBON NANOPARTICLES (236)MICROPOROUS(NON-GRAPHITIZING)CARBONS (239)Background (239)Early Models (241)Evidence for Fullerene-Like Structures in Microporous Carbons (242)New Models for the Structure of Microporous Carbons (242)Carbonization and the Structural Evolution of Microporous Carbon (243)GLASSY CARBON (244)CARBON FIBERS (245)CARBON BLACK (248)Background (248)Structure of Carbon Black Particles (249)Effect of High-Temperature Heat Treatment on Carbon Black Structure (250)CONCLUSIONS (250)ACKNOWLEDGMENTS (251)REFERENCES (251)INTRODUCTIONUntil quite recently we knew for certain of just two allotropes of carbon:diamond and graphite.The vast range of carbon ma-∗E-mail:p.j.f.harris@ terials,both natural and synthetic,which have more disordered structures have traditionally been considered as variants of one or other of these two allotropes.Because the great majority of these materials contain sp2carbon rather than sp3carbon,their struc-tures have been thought of as being made up from tiny fragments235236P.J.F.HARRISFI G.1.(a)Model of PAN-derived carbon ﬁbres from the work of Crawford and Johnson,1(b)model of a non-graphitizing carbon by Ban and colleagues.2of crystalline graphite.Examples of models for the structures of carbons in which the basic elements are graphitic are reproduced in Figure 1.The structure shown in Figure 1(a)is a model for the structure of carbon ﬁbers suggested by Crawford and Johnson in 1971,1whereas 1(b)shows a model for non-graphitizing car-bon given by Ban and colleagues in 1975.2Both structures are constructed from bent or curved sheets of graphite,containing exclusively hexagonal rings.Although these models probably provide a good ﬁrst approximation of the structures of these car-bons,in many cases they fail to explain fully the properties of the materials.Consider the example of non-graphitizing carbons.As the name suggests,these cannot be transformed into crystalline graphite even at temperatures of 3000◦C and above.I nstead,high temperature heat treatments transform them into structures with a high degree of porosity but no long-range crystalline order.I n the model proposed by Ban et al.(Figure 1(b)),the structure is made up of ribbon-like sheets enclosing randomly shaped voids.It is most unlikely that such a structure could retain its poros-ity when subjected to high temperature heat treatment—surface energy would force the voids to collapse.The shortcomings of this and other “conventional”models are discussed more fully later in the article.The discovery of the fullerenes 3−5and subsequently of re-lated structures such as carbon nanotubes,6−8nanohorns,9,10and nanoparticles,11has given us a new paradigm for solid car-bon structures.We now know that carbons containing pentago-nal rings,as well as other non-six-membered rings,among the hexagonal sp 2carbon network,can be highly stable.This new perspective has prompted a number of groups to take a fresh look at well-known forms of carbon,to see whether any evidence can be found for the presence of fullerene-like structures.12−14The aim of this article is to review this new work on the structure of graphitic carbons,to assess whether models that incorporate fullerene-like elements could provide a better basis for under-standing these materials than the conventional models,and to point out areas where further work is needed.The carbon ma-terials considered include non-graphitizing carbon,glassy car-bon,carbon ﬁbers,and carbon black.The article begins with an outline of the main structural features of fullerenes,carbon nanotubes,and carbon nanoparticles,together with a brief dis-cussion of their stability.FULLERENES,CARBON NANOTUBES,AND CARBON NANOPARTICLESThe structure of C 60,the archetypal fullerene,is shown in Figure 2(a).The structure consists of twelve pentagonal rings and twenty hexagons in an icosahedral arrangement.I t will be noted that all the pentagons are isolated from each other.This is important,because adjacent pentagonal rings form an unstable bonding arrangement.All other closed-cage isomers of C 60,and all smaller fullerenes,are less stable than buck-minsterfullerene because they have adjacent pentagons.For higher fullerenes,the number of structures with isolated pen-tagonal rings increases rapidly with size.For example,C 100has 450isolated-pentagon isomers.16Most of these higher fullerenes have low symmetry;only a very small number of them have the icosahedral symmetry of C 60.An example of a giant fullerene that can have icosahedral symmetry is C 540,as shown in Figure 2(b).There have been many studies of the stability of fullerenes as a function of size (e.g.,Refs.17,18).These show that,in general,stability increases with size.Experimentally,there is evidence that C 60is unstable with respect to large,multiwalled fullerenes.This was demonstrated by Mochida and colleagues,who heated C 60and C 70in a sublimation-limiting furnace.19They showed that the cage structure broke down at 900◦C–1000◦C,although at 2400◦C fullerene-like “hollow spheres”with diameters in the range 10–20nm were formed.We now consider fullerene-related carbon nanotubes,which were discovered by Iijima in 1991.6These consist of cylinders of graphite,closed at each end with caps that contain precisely six pentagonal rings.We can illustrate their structure by considering the two “archetypal”carbon nanotubes that can be formed by cutting a C 60molecule in half and placing a graphene cylinder between the two halves.Dividing C 60parallel to one of the three-fold axes results in the zig-zag nanotube shown in Figure 3(a),whereas bisecting C 60along one of the ﬁvefold axes produces the armchair nanotube shown in Figure 3(b).The terms “zig-zag”and “armchair”refer to the arrangement of hexagons around the circumference.There is a third class of structure in which the hexagons are arranged helically around the tube axis.Ex-perimentally,the tubes are generally much less perfect than the idealized versions shown in Figure 3,and may be eitherNEW PERSPECTIVES ON GRAPHITIC CARBONS STRUCTURE237FI G.2.The structure of (a)C 60,(b)icosahedral C 540.15multilayered or single-layered.Figure 4shows a high resolu-tion TEM image of multilayered nanotubes.The multilayered tubes range in length from a few tens of nm to several microns,and in outer diameter from about 2.5nm to 30nm.The end-caps of the tubes are sometimes symmetrical in shape,but more often asymmetric.Conical structures of the kind shown in Fig-ure 5(a)are commonly observed.This type of structure is be-lieved to result from the presence of a single pentagon at the position indicated by the arrow,with ﬁve further pentagons at the apex of the cone.Also quite common are complex cap struc-tures displaying a “bill-like”morphology such as thatshownFI G.3.Drawings of the two nanotubes that can be capped by one half of a C 60molecule.(a)Zig-zag (9,0)structure,(b)armchair (5,5)structure.20in Figure 5(b).21This structure results from the presence of a single pentagon at point “X”and a heptagon at point “Y .”The heptagon results in a saddle-point,or region of negative curvature.The nanotubes ﬁrst reported by Iijima were prepared by va-porizing graphite in a carbon arc under an atmosphere of helium.Nanotubes produced in this way are invariably accompanied by other material,notably carbon nanoparticles.These can be thought of as giant,multilayered fullerenes,and range in size from ∼5nm to ∼15nm.A high-resolution image of a nanopar-ticle attached to a nanotube is shown in Figure 6(a).22In this238P.J.F.HARRISFI G.4.TEM image of multiwalled nanotubes.case,the particle consists of three concentric fullerene shells.A more typical nanoparticle,with many more layers,is shown in Figure 6(b).These larger particles are probably relatively im-perfect instructure.FI G.5.I mages of typical multiwalled nanotube caps.(a)cap with asymmetric cone structure,(b)cap with bill-like structure.21Single-walled nanotubes were ﬁrst prepared in 1993using a variant of the arc-evaporation technique.23,24These are quite different from multilayered nanotubes in that they generally have very small diameters (typically ∼1nm),and tend to be curledNEW PERSPECTIVES ON GRAPHITIC CARBONS STRUCTURE239FI G.6.I mages of carbon nanoparticles.(a)small nanoparticle with three concentric layers on nanotube surface,22(b)larger multilayered nanoparticle.and looped rather than straight.They will not be considered further here because they have no parallel among well-known forms of carbon discussed in this article.The stability of multilayered carbon nanotubes and nanopar-ticles has not been studied in detail experimentally.However,we know that they are formed at the center of graphite electrodes during arcing,where temperatures probably approach 3000◦C.I t is reasonable to assume,therefore,that nanotubes and nanopar-ticles could withstand being re-heated to such temperatures (in an inert atmosphere)without signiﬁcant change.MICROPOROUS (NON-GRAPHITIZING)CARBONS BackgroundIt was demonstrated many years ago by Franklin 25,26that carbons produced by the solid-phase pyrolysis of organic ma-terials fall into two distinct classes.The so-called graphitizing carbons tend to be soft and non-porous,with relatively high den-sities,and can be readily transformed into crystalline graphite by heating at temperatures in the range 2200◦C–3000◦C.I n con-trast,“non-graphitizing”carbons are hard,low-densitymateri-FI G.7.(a)High resolution TEM image of carbon prepared by pyrolysis of sucrose in nitrogen at 1000◦C,(b)carbon prepared bypyrolysis of anthracene at 1000◦C.I nsets show selected area diffraction patterns.30als that cannot be transformed into crystalline graphite even at temperatures of 3000◦C and above.The low density of non-graphitizing carbons is a consequence of a microporous struc-ture,which gives these materials an exceptionally high internal surface area.This high surface area can be enhanced further by activation,that is,mild oxidation with a gas or chemical pro-cessing,and the resulting “activated carbons”are of enormous commercial importance,primarily as adsorbents.27−29The distinction between graphitizing and non-graphitizing carbons can be illustrated most clearly using transmission elec-tron microscopy (TEM).Figure 7(a)shows a TEM image of a typical non-graphitizing carbon prepared by the pyrolysis of sucrose in an inert atmosphere at 1000◦C.30The inset shows a diffraction pattern recorded from an area approximately 0.25µm in diameter.The image shows the structure to be disordered and isotropic,consisting of tightly curled single carbon layers,with no obvious graphitization.The diffraction pattern shows symmetrical rings,conﬁrming the isotropic structure.The ap-pearance of graphitizing carbons,on the other hand,approxi-mates much more closely to that of graphite.This can be seen in the TEM micrograph of a carbon prepared from anthracene,240P.J.F.HARRI Swhich is shown in Figure 7(b).Here,the structure contains small,approximately ﬂat carbon layers,packed tightly together with a high degree of alignment.The fragments can be considered as rather imperfect graphene sheets.The diffraction pattern for the graphitizing carbon consists of arcs rather than symmetrical rings,conﬁrming that the layers are preferentially aligned along a particular direction.The bright,narrow arcs in this pattern correspond to the interlayer {0002}spacings,whereas the other reﬂections appear as broader,less intense arcs.Transmission electron micrographs showing the effect of high-temperature heat treatments on the structure of non-graphitizing and graphitizing carbons are shown in Figure 8(note that the magniﬁcation here is much lower than for Figure 7).I n the case of the non-graphitizing carbon,heating at 2300◦C in an inert atmosphere produces the disordered,porous material shown in Figure 8(a).This structure is made up of curved and faceted graphitic layer planes,typically 1–2nm thick and 5–15nm in length,enclosing randomly shaped pores.A few somewhat larger graphite crystallites are present,but there is no macroscopic graphitization.n contrast,heat treatment of the anthracene-derived carbon produces large crystals of highly or-dered graphite,as shown in Figure 8(b).Other physical measurements also demonstrate sharp dif-ferences between graphitizing and non-graphitizing carbons.Table 1shows the effect of preparation temperature on the sur-face areas and densities of a typical graphitizing carbon prepared from polyvinyl chloride,and a non-graphitizing carbon prepared from cellulose.31It can be seen that the graphitizing carbon pre-pared at 700◦C has a very low surface area,which changes lit-tle for carbons prepared at higher temperatures,up to 3000◦C.The density of the carbons increases steadily as thepreparationFI G.8.Micrographs of (a)sucrose carbon and (b)anthracene carbon following heat treatment at 2300◦C.TABLE 1Effect of temperature on surface areas and densities of carbonsprepared from polyvinyl chloride and cellulose 31(a)Surface areas Speciﬁc surface area (m 2/g)for carbons prepared at:Starting material 700◦C 1500◦C 2000◦C 2700◦C 3000◦C PVC 0.580.210.210.710.56Cellulose 4081.601.172.232.25(b)Densities Helium density (g/cm 3)for carbons prepared at:Starting material 700◦C 1500◦C 2000◦C 2700◦C 3000◦C PVC 1.85 2.09 2.14 2.21 2.26Cellulose1.901.471.431.561.70temperature is increased,reaching a value of 2.26g/cm 3,which is the density of pure graphite,at 3000◦C.The effect of prepara-tion temperature on the non-graphitizing carbon is very different.A high surface area is observed for the carbon prepared at 700◦C (408m 2/g),which falls rapidly as the preparation temperature is increased.Despite this reduction in surface area,however,the density of the non-graphitizing carbon actually falls when the temperature of preparation is increased.This indicates that a high proportion of “closed porosity”is present in the heat-treated carbon.NEW PERSPECTIVES ON GRAPHITIC CARBONS STRUCTURE241FI G.9.Franklin’s representations of(a)non-graphitizing and(b)graphitizing carbons.25Early ModelsTheﬁrst attempt to develop structural models of graphitizingand non-graphitizing carbons was made by Franklin in her1951paper.25In these models,the basic units are small graphitic crys-tallites containing a few layer planes,which are joined togetherby crosslinks.The precise nature of the crosslinks is not speci-ﬁed.An illustration of Franklin’s models is shown in Figure9.Using these models,she put forward an explanation of whynon-graphitizing carbons cannot be converted by heat treatmentinto graphite,and this will now be summarized.During car-bonization the incipient stacking of the graphene sheets in thenon-graphitizing carbon is largely prevented.At this stage thepresence of crosslinks,internal hydrogen,and the viscosity ofthe material is crucial.The resulting structure of the carbon(at ∼1000◦C)consists of randomly ordered crystallites,held to-gether by residual crosslinks and van der Waals forces,as inFigure9(a).During high-temperature treatment,even thoughthese crosslinks may be broken,the activation energy for themotion of entire crystallites,required for achieving the struc-ture of graphite,is too high and graphite is not formed.Onthe other hand,the structural units in a graphitizing carbon areapproximately parallel to each other,as in Figure9(b),and thetransformation of such a structure into crystalline graphite wouldbe expected to be relatively facile.Although Franklin’s ideason graphitizing and non-graphitizing carbons may be broadlycorrect,they are in some regards incomplete.For example,thenature of the crosslinks between the graphitic fragments is notspeciﬁed,so the reasons for the sharply differing properties ofgraphitizing and non-graphitizing carbons is not explained.The advent of high-resolution transmission electron mi-croscopy in the early1970s enabled the structure of non-graphitizing carbons to be imaged directly.n a typical study,Ban,Crawford,and Marsh2examined carbons prepared frompolyvinylidene chloride(PVDC)following heat treatments attemperatures in the range530◦C–2700◦C.I mages of these car-bons apparently showed the presence of curved and twistedgraphite sheets,typically two or three layer planes thick,enclos-ing voids.These images led Ban et al.to suggest that heat-treatednon-graphitizing carbons have a ribbon-like structure,as shownin Figure1(b).This structure corresponds to a PVDC carbonheat treated at1950◦C.This ribbon-like model is rather similar to an earlier model of glassy carbon proposed by Jenkins andKawamura.32However,models of this kind,which are intendedto represent the structure of non-graphitizing carbons follow-ing high-temperature heat treatment,have serious weaknesses,as noted earlier.Such models consist of curved and twistedgraphene sheets enclosing irregularly shaped pores.However,graphene sheets are known to be highlyﬂexible,and wouldtherefore be expected to become ever more closely folded to-gether at high temperatures,in order to reduce surface energy.Indeed,tightly folded graphene sheets are quite frequently seenin carbons that have been exposed to extreme conditions.33Thus,structures like the one shown in Figure1(b)would be unlikelyto be stable at very high temperatures.It has also been pointed out by Oberlin34,35that the modelsput forward by Jenkins,Ban,and their colleagues were basedon a questionable interpretation of the electron micrographs.In most micrographs of partially graphitized carbons,only the {0002}fringes are resolved,and these are only visible when they are approximately parallel to the electron beam.Therefore,such images tend to have a ribbon-like appearance.However,because only a part of the structure is being imaged,this appear-ance can be misleading,and the true three-dimensional structuremay be more cagelike than ribbon-like.This is a very importantpoint,and must always be borne in mind when analyzing imagesof graphitic carbons.Oberlin herself believes that all graphiticcarbons are built up from basic structural units,which comprisesmall groups of planar aromatic structures,35but does not appearto have given a detailed explanation for the non-graphitizabilityof certain carbons.The models of non-graphitizing carbons described so farhave assumed that the carbon atoms are exclusively sp2and arebonded in hexagonal rings.Some authors have suggested thatsp3-bonded atoms may be present in these carbons(e.g.,Refs.36,37),basing their arguments on an analysis of X-ray diffrac-tion patterns.The presence of diamond-like domains would beconsistent with the hardness of non-graphitizing carbons,andmight also explain their extreme resistance to graphitization.Aserious problem with these models is that sp3carbon is unsta-ble at high temperatures.Diamond is converted to graphite at1700◦C,whereas tetrahedrally bonded carbon atoms in amor-phousﬁlms are unstable above about700◦C.Therefore,the242P.J.F.HARRI Spresence of sp 3atoms in a carbon cannot explain the resistance of the carbon to graphitization at high temperatures.I t should also be noted that more recent diffraction studies of non-graphitizing carbons have suggested that sp 3-bonded atoms are not present,as discussed further in what follows.Evidence for Fullerene-Like Structures in Microporous CarbonsThe evidence that microporous carbons might have fullerene-related structures has come mainly from high-resolution TEM studies.The present author and colleagues initiated a series of studies of typical non-graphitizing microporous carbons using this technique in the mid 1990s.30,38,39The ﬁrst such study in-volved examining carbons prepared from PVDC and sucrose,after heat treatments at temperatures in the range 2100◦C–2600◦C.38The carbons subjected to very high temperatures had rather disordered structures similar to that shown in Figure 8(a).Careful examination of the heated carbons showed that they often contained closed nanoparticles;examples can be seen in Figure 10.The particles were usually faceted,and often hexagonal or pentagonal in shape.Sometimes,faceted layer planes enclosed two or more of the nanoparticles,as shown in Figure 10(b).Here,the arrows indicate two saddle-points,similar to that shown in Figure 5(b).The closed nature of the nanoparticles,their hexagonal or pentagonal shapes,and other features such as the saddle-points strongly suggest that the parti-cles have fullerene-like structures.I ndeed,in many cases the par-ticles resemble those produced by arc-evaporation in a fullerene generator (see Figure 6)although in the latter case the particles usually contain many more layers.The observation of fullerene-related nanoparticles in the heat treated carbons suggested that the original,freshly prepared car-bons may also have had fullerene-related structures (see next section).However,obtaining direct evidence for this is difﬁ-cult.High resolution electron micrographs of freshly prepared carbons,such as that shown in Figure 7(a),are usuallyratherFI G.10.(a)Micrograph showing closed structure in PVDC-derived carbon heated at 2600◦C,(b)another micrograph of same sample,with arrows showing regions of negative curvature.38featureless,and do not reveal the detailed structure.Occasion-ally,however,very small closed particles can be found in the carbons.30The presence of such particles provides circumstan-tial evidence that the surrounding carbon may have a fullerene-related structure.Direct imaging of pentagonal rings by HRTEM has not yet been achieved,but recent developments in TEM imaging techniques suggest that this may soon be possible,as discussed in the Conclusions.As well as high-resolution TEM,diffraction methods have been widely applied to microporous and activated carbons (e.g.,Refs.40–44).However,the interpretation of diffraction data from these highly disordered materials is not straightforward.As already mentioned,some early X-ray diffraction studies were interpreted as providing evidence for the presence of sp 3-bonded atoms.More recent neutron diffraction studies have suggested that non-graphitizing carbons consist entirely of sp 2atoms.40It is less clear whether diffraction methods can establish whether the atoms are bonded in pentagonal or hexagonal rings.Both Petkov et al .42and Zetterstrom and colleagues 43have interpreted neutron diffraction data from nanoporous carbons in terms of a structure containing non-hexagonal rings,but other interpreta-tions may also be possible.Raman spectroscopy is another valuable technique for the study of carbons.45Burian and Dore have used this method to analyze carbons prepared from sucrose,heat treated at tem-peratures from 1000◦C–2300◦C.46The Raman spectra showed clear evidence for the presence of fullerene-and nanotube-like elements in the carbons.There was also some evidence for fullerene-like structures in graphitizing carbons prepared from anthracene,but these formed at higher temperatures and in much lower proportions than in the non-graphitizing carbons.New Models for the Structure of Microporous Carbons Prompted by the observations described in the previous section,the present author and colleagues proposed a model for the structure of non-graphitizing carbons that consists ofNEW PERSPECTIVES ON GRAPHITIC CARBONS STRUCTURE243FI G.11.Schematic illustration of a model for the structure of non-graphitizing carbons based on fullerene-like elements.discrete fragments of curved carbon sheets,in which pentagons and heptagons are dispersed randomly throughout networks of hexagons,as illustrated in Figure11.38,39The size of the micropores in this model would be of the order of0.5–1.0nm, which is similar to the pore sizes observed in typical microp-orous carbons.The structure has some similarities to the“ran-dom schwarzite”network put forward by Townsend and col-leagues in1992,47although this was not proposed as a model for non-graphitizing carbons.I f the model we have proposed for non-graphitizing carbons is correct it suggests that these carbons are very similar in structure to fullerene soot,the low-density, disordered material that forms on walls of the arc-evaporation vessel and from which C60and other fullerenes may be ex-tracted.Fullerene soot is known to be microporous,with a sur-face area,after activation with carbon dioxide,of approximately 700m2g−1,48and detailed analysis of high resolution TEM mi-crographs of fullerene soot has shown that these are consis-tent with a structure in which pentagons and heptagons are dis-tributed randomly throughout a network of hexagons.49,50It is signiﬁcant that high-temperature heat treatments can transform fullerene soot into nanoparticles very similar to those observed in heated microporous carbon.51,52Carbonization and the Structural Evolutionof Microporous CarbonThe process whereby organic materials are transformed into carbon by heat treatment is not well understood at the atomic level.53,54In particular,the very basic question of why some organic materials produce graphitizing carbons and others yield non-graphitizing carbons has not been satisfactorily answered. It is known,however,that both the chemistry and physical prop-erties of the precursors are important in determining the class of carbon formed.Thus,non-graphitizing carbons are formed, in general,from substances containing less hydrogen and more oxygen than graphitizing carbons.As far as physical properties are concerned,materials that yield graphitizing carbons usu-ally form a liquid on heating to temperatures around400◦C–500◦C,whereas those that yield non-graphitizing carbons gen-erally form solid chars without melting.The liquid phase pro-duced on heating graphitizing carbons is believed to provide the mobility necessary to form oriented regions.However,this may not be a complete explanation,because some precursors form non-graphitizing carbons despite passing through a liquid phase.The idea that non-graphitizing carbons contain pentagons and other non-six-membered rings,whereas graphitizing car-bons consist entirely of hexagonal rings may help in understand-ing more fully the mechanism of carbonization.Recently Kumar et al.have used Monte Carlo(MC)simulations to model the evo-lution of a polymer structure into a microporous carbon structure containing non-hexagonal rings.55They chose polyfurfuryl al-cohol,a well-known precursor for non-graphitizing carbon,as the starting material.The polymer was represented as a cubic lattice decorated with the repeat units,as shown in Figure12(a). All the non-carbon atoms(i.e.,hydrogen and oxygen)were then removed from the polymer and this network was used in the。

EXECUTIVE SUMMARY..........................................................................

DG XIII – E/4 Second Metadata Workshop, 26 June 1998Table of contentsEXECUTIVE SUMMARY (2)1. INTRODUCTION (4)2. SPECIFIC OBJECTIVES OF THE SECOND WORKSHOP (5)3. PARTICIPATION (6)4. STRUCTURE OF THE WORKSHOP (6)5. MORNING SESSION: TECHNICAL ISSUES (6)6. AFTERNOON SESSION: STRATEGIC ISSUES (8)7. CONCLUSIONS (8)8. LIST OF ACRONYMS AND REFERENCES (9)APPENDIX 1. PROGRAMME (13)APPENDIX 2. PRESENTATIONS (14)APPENDIX 3. LIST OF PARTICIPANTS (44)DG XIII – E/4 Second Metadata Workshop, 26 June 1998E XECUTIVE SUMMARYOn 26 June 1998, the second workshop of a series on the subject of metadata organised by the European Commission DGXIII/E4 took place in Luxembourg.32 participants attended the workshop. Many organisations in Europe involved in the implementation of metadata for electronic resources were represented, as were several European Commission services.The workshop contained one session on technical and implementation issues and one session on strategic and standardisation issues reflecting the specific objectives of the workshop.The first specific objective was to give a number of projects the opportunity to present results in the area of metadata from various perspectives. In the morning session, the issues that were covered in the presentations were:metadata creation toolsdefinition of local extensions to Dublin Core for specific application areasthe use of controlled vocabularymultilingual metadataThe presenters of these subjects conducted a panel discussion on these issues and others raised by the audience.The second specific objective was to discuss metadata in a broader context with project participants and experts involved in definition and standardisation of metadata elements. In the afternoon session, presentations covered:metadata activities in contextfuture developments in Dublin CoreIn a plenary discussion, the participants discussed strategic issues concerning the definition and standardisation of metadata element sets.The major conclusions of the workshop can be summarised as follows:the strategic discussions highlighted that establishing widely accepted agreements is essential for the success of metadata;it is necessary that consensus on agreements for metadata is achieved across domains (e.g. libraries, museums, education, business, etc.);agreements and standards need to be maintained over time in a clear and open way with participation of all interested parties (especially user communities) to guarantee stability over time;formal and informal bodies involved in the standardisation of metadata sets (Dublin Core community, CEN, ISO) need to find effective ways of co-operation to ensure maximum acceptance of agreements and to avoid overlapping activities; further metadata workshops organised by the European Commission are considered to be valuable platforms for co-ordination and exchange of experience.DG XIII – E/4 Second Metadata Workshop, 26 June 1998 For further information, including PowerPoint presentations, see the Workshop’s Web site at: http://www2.echo.lu/libraries/en/metadata2.htmlFor more information on the Libraries sector of the Telematics Application Programme, see: http://www2.echo.lu/libraries/en/libraries.htmlDG XIII – E/4 Second Metadata Workshop, 26 June 19981.I NTRODUCTIONThis document is the report of the second Workshop on Metadata, held in Luxembourg on 26 June 1998.DGXIII/E4, the Electronic publishing and libraries unit, is organising a series of workshops on the issue of metadata. Intended participation is from libraries sector projects within the Telematics Applications Programme and from projects in other TAP sectors and other programmes, both EU and national. The primary objectives of the workshops are:To establish a platform for co-ordination between projects concerned with metadata in a broad sense.Under the current Framework Programme for RTD there are a number of projects concerned with metadata as such or with descriptions and descriptors of electronic documents. These projects will come across the same issues and problems and will benefit from concertation, as this will allow them to compare their concepts and approaches with others.To make a wider European community aware of developments in the standards arena and stimulate feedback from the projects to the standards.Developments in metadata in the Internet, specifically in Dublin Core, are moving fast. Some European organisations invest in participating in the Dublin Core workshops but not all have easy access to this activity. By inviting Dublin Core workshop participants to present the developments in the proposed workshops, a wider European audience can be informed on this subject. At the same time, models and experiences from the projects can be fed back into the standards arena.The first workshop which took place on 1 and 2 December 1997, contained a tutorial, project presentations, breakout sessions discussing various aspects of metadata creation and usage.The workshop, although recognising the usefulness of Dublin Core as a starting point in metadata descriptive standards, brought forward a number of concerns regarding the current state and the further development of Dublin Core:•There is currently no formal responsibility for the maintenance of Dublin Core: development takes place in an informal group of invited experts which meets once or twice per year in what is known as the Dublin Core Workshop Series.•The current technical state of Dublin Core is unstable: during the meetings of the Dublin Core group, changes are being made to the format and there is no convergence to a stable version.•The use of the current Dublin Core metadata format is not supported by the existence of guidelines: some of the philosophy and terminology of Dublin Core isDG XIII – E/4 Second Metadata Workshop, 26 June 1998 not obvious to the uninitiated user which could lead to different interpretations adversely affecting interoperability.It was also identified that the current take-up of Dublin Core is slow and that there is a lack of critical mass. This seems to be a classical chicken-and-egg situation: authors and publishers do not invest in providing Dublin Core metadata if the Internet indexing services (the ‘harvesters’) do not utilise it, and harvesters do not collect Dublin Core and use it for selective indexing if there is not enough data available. If this situation cannot be changed, Dublin Core might not turn into reality.The workshop identified a number of actions that could be taken to promote and encourage the use of Dublin Core, including the following:1.There needs to be clarity about version control and maintenance of Dublin Core.The Dublin Core group, addressed through the mailing list META2, will be asked to give a clear statement about this.2.Further pilot projects should be started to further develop experience, test out theissues and help realise a critical mass of Dublin Core metadata. The European Commission and national bodies like National Libraries might have a role to play by encouraging the provision of Dublin Core metadata in documents, e.g. in project deliverables and electronic documents in the national deposit.3.The interest and requirements existing in Europe warrant the establishment of aEuropean group of implementers discussing the practical issues of implementing metadata in general and Dublin Core in particular. The Luxembourg workshops, such as this December 1997 one and a second one scheduled for mid-1998, could develop into a regular series.4.The liaison with other groups concerned with metadata, such as the CEN/ISSSworking group on Metadata for Multimedia Information (MMI), should be established to ensure applicability and interoperability of metadata as widely as possible and cover the needs of a wide range of communities.The report of the first workshop is available on the Web at http://www2.echo.lu/libraries/en/metadata.html.2.S PECIFIC OBJECTIVES OF THE SECOND WORKSHOPThe specific objectives of this second workshop, held in Luxembourg on 26 June 1998, were as follows.The first specific objective of the second workshop was to give a number of projects the opportunity to present results in the area of metadata from various perspectives. In the morning session, the issues that were covered in the presentations were:•metadata creation tools•definition of local extensions to Dublin Core for specific application areasDG XIII – E/4 Second Metadata Workshop, 26 June 1998•the use of controlled vocabulary•multilingual metadataThe presenters of these subjects conducted a panel discussion on these issues and others raised by the audience.The second specific objective was to discuss metadata in a broader context with project participants and experts involved in definition and standardisation of metadata elements. In the afternoon session, presentations covered:•metadata activities in context•future developments in Dublin CoreIn a plenary discussion, the participants discussed strategic issues concerning the definition and standardisation of metadata element sets.The programme of the workshop is attached in Appendix 1. Printouts of the presentation, with short biographical notes of the presenters are attached in appendix 2.3.P ARTICIPATION32 persons representing projects from the Telematics programme, national projects and various Commission services attended the workshop.The list of participants is attached as appendix 3.4.S TRUCTURE OF THE WORKSHOPThis second workshop was organised on a single day and contained two sessions: one session on technical and implementation issues and one session on strategic and standardisation issues reflecting the specific objectives of the workshop.5.M ORNING SESSION: TECHNICAL ISSUESIn the first presentation, Anna B RÜMMER of Lund University in Sweden demonstrated metadata creation software constructed for the Nordic Metadata Project. This creation software on the Web offers an easy way to attach descriptive metadata to resources and has helped to build the SweMeta Dublin Core Database for Sweden, which contains 110.000 records. The system also allows users to assign a unique URN to their resource. Currently there is no statistical information on the use of the various elements, which could provide interesting information. There is no validation of the terms entered. This could be considered in the future.Erik D UVAL of Leuven University in Belgium presented the Ariadne project aiming at sharing and re-use of pedagogical resources to make the best use of scarce high-quality material for educational purposes. The project provides authoring tools that produce base metadata, which helps in creating a corpus of consistent descriptions. The project constitutes a closed environment for the participants, allowing a strongDG XIII – E/4 Second Metadata Workshop, 26 June 1998 exercise of editorial control and therefore of quality. Furthermore, users have the possibility to add annotations to the descriptions. A “Replicator Scheme” controls the distribution and access to the resources available in the Central Pool and the Local Pools in various places around Europe. The project has not reached the stage where a critical mass of material is available and is looking for further participants. The Ariadne project is co-operating with the IMS (Instructional Management Systems) project to co-ordinate the metadata definitions and agree a common metadata set. This set is not technically speaking Dublin Core as it has a richer structure and contains elements specific to educational use of the resources, but the mapping of Dublin Core into the Ariadne metadata set is considered to be possible. Also the project participates in the work in the IEEE Learning Technology Standards Committee which develops technical Standards, Recommended Practices, and Guides for software components, tools, technologies and design methods that facilitate the development, deployment, maintenance and interoperation of computer implementations of education and training components and systems.Paul M ILLER of the Archaeology Data Service in the UK introduced the advantages of using controlled vocabularies and thesauri. For users, these tools would help gaining more effective access to resources and reduce the number of false hits. Creators would be able to make more consistent descriptions and achieve a better integration of new and existing resources. It was noted that a major factor for the use of controlled vocabulary is the ease with which it can be used in both the process of creation of metadata and in the process of searching.Matthew S TIFF of the Museum Documentation Association in the UK spoke about multilingual aspects of information retrieval. He discussed the creation of parallel metadata in multiple languages versus the use of translation tools and multilingual thesauri. He identified the need for new tools but also noted these tools will be expensive and will take a lot of time to develop. Various options can be explored to create multilingual thesauri, including linking existing monolingual ones and translating one thesaurus in multiple languages. He touched upon the fundamental issue of incomplete equivalence of terms in different languages. Project Term-IT is investigating mechanisms to facilitate the production and dissemination of multilingual thesauri in the cultural sector through establishing dialogue with users and analysis of the economics of thesaurus production.As a conclusion of the technical session it was identified that:quality is a crucial issue both in the creation of metadata and in its maintenance there should be a clear focus on the user when designing tools to help create and use metadata; user communities should be actively involved to make sure their requirements are taken into accountspecial attention must be given to the change in concepts and terminologies over time.DG XIII – E/4 Second Metadata Workshop, 26 June 19986.A FTERNOON SESSION: STRATEGIC ISSUESThe first presentation in the afternoon session was delivered by Ian C AMPBELL-G RANT of ICL, chairman of the CEN/ISSS Workshop on Metadata for Multimedia Information. He introduced the work of this group as part of a new approach to standardisation especially intended to achieve rapid agreements on standards and a wide acceptance n the market. The specific objectives of the group include to gather information on metadata activities, to identify gaps and overlaps in current work and to disseminate this information to European industry, projects and programmes. The group is currently working to establish a framework that will help to find existing activities in the area of metadata definition.In the final presentation, Stuart W EIBEL of OCLC in the US presented the current state and the future prospects for the Dublin Core metadata initiative. He outlined the objectives of the initiative, noting that it is a simple set for descriptive elements that are relevant for resource discovery. It could be used as a cross-domain “switching”language, working together with other sets in the framework provided by RDF. He presented the current thinking on the issue of more formally standardising Dublin Core, working through any body that would be appropriate for that purpose (IETF, ISO, NISO, CEN/ISSS).In the discussion that took place after the presentations, several aspects were identified:the involvement of user communities and business areas is crucial to make sure their requirements are being taken into accountagain the issue of critical mass was raised: Dublin Core and other structured metadata forms an ‘island in the sea of marked data’. There needs to be more metadata before it can produce benefits to the users.the CEN/ISSS workshop could form an appropriate platform for rapid standardisation of Dublin Core in the form of a CEN Workshop Agreement; this needs to be further explored.the issue of maintenance of metadata standards is very important. The mechanism and structure should allow open and international participation to ensure the widest possible and agreement7.C ONCLUSIONSThe major conclusions of the workshop can be summarised as follows:the strategic discussions highlighted that establishing widely accepted agreements is essential for the success of metadata;it is necessary that consensus on agreements for metadata is achieved across domains (e.g. libraries, museums, education, business, etc.);agreements and standards need to be maintained over time in a clear and open way with participation of all interested parties (especially user communities) to guarantee stability over time;DG XIII – E/4 Second Metadata Workshop, 26 June 1998formal and informal bodies involved in the standardisation of metadata sets (Dublin Core community, CEN, ISO) need to find effective ways of co-operation to ensure maximum acceptance of agreements and to avoid overlapping activities; further metadata workshops organised by the European Commission are considered to be valuable platforms for co-ordination and exchange of experience.8.L IST OF ACRONYMS AND REFERENCESACM the Association for Computing Machinery, an internationalscientific and educational organization dedicated to advancingthe arts, sciences, and applications of information technology.ADS Archaeology Data Service./ahds/AHDS Arts and Humanities Data Service./ALA American Library Association./ALCTS /ccda/Ariadne RTD project under the "Telematics for Education andTraining" sector of the 4th Framework Programme of theEuropean Union. The project focuses on the development oftools and methodologies for producing, managing and reusingcomputer-based pedagogical elements and telematicssupported training curricula.http://ariadne.unil.ch/CEN European Committee for Standardisation.http://www.cenorm.be/CEN/ISSS European Committee for Standardisation - InformationSociety Standardisation System.http://www.cenorm.be/isss/default.htmCIDOC The International Committee for Documentation of theInternational Council of Museums (ICOM), the internationalfocus for the documentation interests of museums and similarorganisations./CIMI Consortium for the Computer Interchange of MuseumInformation./CPA Commission on Preservation and Access./programs/cpa/cpa.htmlDC Acronym for Dublin CoreDesire Telematics for Research project addressing the needs ofresearch users in the context of a European informationnetwork based on the World Wide Web (WWW).http://www.surfnet.nl/surfnet/projects/desire/DG XIII Directorate General XIII of the European Commission.http://europa.eu.int/en/comm/dg13/13home.htm. See also:http://www2.echo.lu/home.htmlDublin Core Dublin Core is a 15-element metadata element set intended tofacilitate discovery of electronic resources./metadata/dublin_core/EC European Commission.http://europa.eu.int/ERCIM The European Research Consortium for Informatics andMathematics - aims to foster collaborative work within theEuropean research community and to increase co-operationwith European industry.EULER Telematics for Libraries project aiming to provide user-oriented, integrated network based access to mathematicalpublications.http://www.emis.de/projects/EULER/ICL /ICOM The International Council of Museums, a Non-GovernmentalOrganisation (NGO) maintaining formal relations with UNESCO,devoted to the promotion and development of museums and themuseum profession at an international level./IEEE The Institute Of Electrical And Electronics Engineers, Inc., atechnical professional society with the objective to advance thetheory and practice of electrical, electronics and computerengineering and computer science.IETF The Internet Engineering Task Force, a large openinternational community of network designers, operators,vendors, and researchers concerned with the evolution of theInternet architecture and the smooth operation of theInternet.IMS Instructional Management Systems Project, an investmentmembership of academic, commercial and governmentorganisations developing a set of specifications and prototypesoftware for facilitating the growth and viability of distributedlearning on the Internet./ISO International Organisation for Standardisation.http://www.iso.ch/MDA Museum Documentation Association, body in the UK formuseum information management, supporting museums in allaspects of heritage information management including thecrucial area of Information and Communications Technology(ICT)./MIT Massachusetts Institute of Technology./MMI CEN/ISSS Workshop on Metadata for MultimediaInformation.http://www.cenorm.be/isss/Workshop/MMI/Default.htm NGDF National Geospatial Data Framework (UK)./NISO U.S. National Information Standards Organization:Nordic Metadata Scandinavian co-operation project creating basic elements of a metadata production and utilisation system:http://renki.helsinki.fi/meta/NSF National Science Foundation (US), an independent U.S.government agency responsible for promoting science andengineering through programs that invest in research andeducation projects in science and engineering./OCLC Online Computer Library Center, Inc., a non-profit, membership, library computer service and researchorganisation in Dublin, Ohio, USARDF Resource Description Framework, a specification currentlyunder development, designed to provide an infrastructure tosupport metadata across many web-based activities:/RDF/RLG Research Libraries Group.RTD Research & Technological DevelopmentSweMeta Dublin Core Database for Sweden.TAP The Telematics Applications Programme, one of theEuropean Commission's research programmes, aimed atstimulating RTD on applications of information and/orcommunications technologies in areas of general interest:http://www2.echo.lu/telematics/telehome2.htmlTEISS Telematics - European Industry Standards SupportTelematics for Libraries The Libraries sector of the Telematics Applications Programme:http://www2.echo.lu/libraries/en/libraries.htmlTerm-IT a preparatory-phase project under the Language Engineeringsector of the Telematics Applications Programme, aimed atleading to the development of methods and systems toimprove the production, dissemination and exploitation ofmultilingual terminology resources/term-it/URN Universal Resource Name:/html.charters/urn-charter.htmlA PPENDIX 1.P ROGRAMMEMETADATA WORKSHOP 26 JUNE 1998EUROFORUM Building352*5$00(09:00-09:20Welcome, registrationPatricia Manson, European Commission DG XIII/E-409:20-09:30IntroductionMakx D EKKERS, The Libraries Support Team0RUQLQJ VHVVLRQ 7HFKQLFDO LVVXHV09:30-10:00Metadata creation toolsAnna B RÜMMER, Univ. of Lund10:00-10:30Extension of Dublin Core for Educational materialErik D UVAL, Univ. of Leuven10:30-11:00Coffee break11:00-11:30Controlled vocabularyPaul M ILLER, Archaeology Data Service11:30-12:00Multilingual issuesMatthew S TIFF, Museum Documentation Association12:00-12:30Panel discussion12:30-13:30Lunch break$IWHUQRRQ VHVVLRQ 6WUDWHJLF LVVXHV13:30-14:00Metadata activities in contextIan C AMPBELL-G RANT, ICL (chair CEN/ISSS open Workshop on Metadatafor Multimedia Information)14:00-14:30Future developments in Dublin CoreStuart W EIBEL, OCLC14:30-15:00Tea break15:00-15:45Discussion15:45-16:00Wrap-up and closingAriane I LJON, Head of Unit, European Commission DG XIII/E-4A PPENDIX 2.P RESENTATIONSMetadata creation toolsAnna B RÜMMER, Univ. of LundBiographical note:Anna Brümmer is an electronic information services librarian at Lund University Library development department NetLab since the first of February 1996. She began after having finished her studies in library and information science in January 1996. Between 1996-1998 she has, among other things, been involved in the EU-project DESIRE, the Development of a European Service for Information on Research and Education. She is also involved in project EULER, European Libraries and Electronic Resources in Mathematical Sciences, integrating bibliographic databases, library online public access catalogues, electronic journals from academic publishers, online archives of pre-prints and grey literature, and indexes of mathematical Internet resources. For the time being she is the pro tem. head of NetLab.Abstract:Metadata tags are, in an end user perspective, complicated to produce. The talk presented one solution aiming to facilitate the metadata creation process (for end users): a metadata creation tool. The presentation described the issues involved in, and related to, the Dublin Core metadata creation and provided explanations on construction of DC Metadata records. The starting point was the Nordic Metadata project, which has developed basic elements of a metadata production and utilisation system, based on the Dublin Core Metadata Element Set. The result is the Nordic Metadata DC production template/creator, which was demonstrated at the workshop.The presentation included a short introduction to the web resource identifier URN (Uniform Resource Names) and an URN generator.The presentation is available on the Web at:http://www.lub.lu.se/EULER/presentations/creator.html.(one page print-out of Web page)Extension of Dublin Core for EducationalmaterialErik D UVAL, Univ. of LeuvenBiographical note:Erik Duval is a post-doctoral fellow of the National Fund for Scientific Research - Flanders and a part-time professor at the Katholieke Universiteit Leuven, Belgium. His main research areas are distributed hypermedia systems, data modelling, the application of information and communication technology in education, metadata and computer science education. He co-ordinates the development of the Knowledge Pool System for the ARIADNE project and is a member of the IEEE Computer Society, the ACM and the program committee of the WebNet Conference Series.Abstract:This presentation covered the current status of the author’s work on educational metadata. Since about two years, the ARIADNE project has developed both a structure and an infrastructure for educational metadata <http://ariadne.unil.ch>. The structure extends Dublin Core to a considerable extent and includes circa 70 data elements, grouped in 9 categories and defined over abstract data types. The infrastructure includes a tool for describing pedagogical documents and a distributed database of these documents and their descriptions, called the Knowledge Pool System. The ARIADNE results have been input in standardisation work in the Learning Object Metadata Working Group of the IEEE Learning Technology Standards Committee </p1484>.(6 pages printout of PowerPoint presentation, 6 slides to a page)(6 pages printout of PowerPoint presentation, 6 slides to a page)(6 pages printout of PowerPoint presentation, 6 slides to a page)(6 pages printout of PowerPoint presentation, 6 slides to a page)(6 pages printout of PowerPoint presentation, 6 slides to a page)(6 pages printout of PowerPoint presentation, 6 slides to a page)Controlled vocabularyPaul M ILLER, ADSBiographical note:Dr. Paul Miller is Collections Manager for the Archaeology Data Service (ADS)</>, one of five service providers comprising the Arts & Humanities Data Service (AHDS) </> in the United Kingdom.The ADS seeks to both preserve and encourage the reuse of digital archaeological data, whether by physically taking and mounting data or by working with existing organisations and technologies to facilitate distributed access mechanisms.Paul is responsible for the development of this distributed catalogue, and is closely involved with a number of evolving metadata initiatives around the world. These include the Dublin Core </metadata/dublin_core>, the UK's National Geospatial Data Framework (NGDF) </>, and the work of the Consortium for the Computer Interchange of Museum Information (CIMI) </>.Abstract:This presentation went into the problems of terminology and vocabulary, which become increasingly apparent as opportunities for cross-searching between different data sources grow. Efforts to develop controlled lists of terms have been relatively isolated in individual disciplines or geographic areas.With the current explosion in projects to provide remote access to these resources, and initiatives to link diverse resources together for the first time, new problems have arisen, namely;•divorcing of resources from the local expertise developed to support and maintain them •integrating diverse terminologies•contextualising the terminologies•providing access to the terminologiesIn conclusion, controlled terminology remains an important weapon in the information scientist's arsenal, but the new distributed world in which these terminologies are increasingly being used perhaps requires a new approach to some old problems, an approach which was explored in this paper.。

NF EN 10028-1 - janv 2001 - Produits plats en acier pour appareils a pression - prescriptions genera

NF EN 10028-1Janvier 2001Ce document est à usage exclusif et non collectif des clients Normes en ligne.Toute mise en réseau, reproduction et rediffusion, sous quelque forme que ce soit,même partielle, sont strictement interdites.This document is intended for the exclusive and non collective use of AFNOR Webshop(Standards on line) customers. All network exploitation, reproduction and re-dissemination,even partial, whatever the form (hardcopy or other media), is strictly prohibited.Boutique AFNORPour : VICHEMCode client : 23412505Commande : N-20050120-095443-Tle 20/1/2005 - 15:25Diffusé par11992© AFNOR 2001AFNOR 20011er tirage 2001-01-F© A F N O R 2001 — T o u s d r o i t s r és e r v ésFA043128ISSN 0335-3931NF EN 10028-1Janvier 2001Indice de classement: A 36-205-1norme européenneProduits laminés pour appareils à pression BNS 10-10Membres de la commission de normalisationPrésident :M CRETONSecrétariat :BNSM BARRERE PUMM BOCQUET USINOR INDUSTEELMME BRUN-MAGUET AFNORM CRETON BNSM DE VEYRAC UGINE LA DEFENSEM DENOIX ETUDES ET PRODUCTIONS SCHLUMBERGERM DESPLACES SOLLAC MEDITERRANEE FOSM FINET USINOR INDUSTEELM FLANDRIN MINISTERE DE L’ECONOMIE, DES FINANCES ET DE L’INDSUTRIE — DARPMIM JARBOUI CETIMM LAGNEAUX MINISTERE DE L’ECONOMIE, DES FINANCES ET DE L’INDSUTRIE — DARPMIM LIEURADE CETIMM REGER EDF/SCF SQRM RIGAL GTS INDUSTRIESMME ROUMIER MINISTERE DE L'EQUIPEMENT, DES TRANSPORTS ET DU LOGEMENTM STAROPOLI GDFAvant-propos nationalRéférences aux normes françaisesLa correspondance entre les normes mentionnées à l'article «Références normatives» et les normes françaises identiques est la suivante :CR 10260:FD CR 10260 (indice de classement: A 02-005-3)EN 10002-1:NF EN 10002-1 (indice de classement: A 03-001)EN 10002-5:NF EN 10002-5 (indice de classement: A 03-005)EN 10020:NF EN 10020 (indice de classement: A 02-025)EN 10021:NF EN 10021 (indice de classement: A 00-100)EN 10027-1:NF EN 10027-1 (indice de classement: A 02-005-1)EN 10027-2:NF EN 10027-2 (indice de classement: A 02-005-2)EN 10028-7:NF EN 10028-7 (indice de classement: A 36-205-7)EN 10029:NF EN 10029 (indice de classement: A 46-503)EN 10045-1:NF EN 10045-1 (indice de classement: A 03-011)EN 10048:NF EN 10048 (indice de classement: A 46-101)—3—NF EN 10028-1:2001EN 10051:NF EN 10051 (indice de classement: A 46-501)EN 10052:NF EN 10052 (indice de classement: A 02-010)EN 10079:NF EN 10079 (indice de classement: A 40-001)EN 10088-1:NF EN 10088-1 (indice de classement: A 35-572)EN 10160:NF EN 10160 (indice de classement: A 04-305)EN 10163-2:NF EN 10163-2 (indice de classement: A 40-501-2)EN 10164:NF EN 10164 (indice de classement: A 36-202)EN 10168:NF EN 10168 (indice de classement: A 03-116) 1)EN 10204:NF EN 10204 (indice de classement: A 00-001)EN 10258:NF EN 10258 (indice de classement: A 46-110-1)EN 10259:NF EN 10259 (indice de classement: A 46-110-2)EN ISO 377:NF EN ISO 377 (indice de classement: A 03-112)EN ISO 2566-1:NF EN ISO 2566-1 (indice de classement: A 03-174)EN ISO 2566-2:NF EN ISO 2566-2 (indice de classement: A 03-175)EN ISO 3651-2:NF EN ISO 3651-2 (indice de classement: A 05-159)ISO 14284:NF EN ISO 14284 (indice de classement: A 06-002) 1)Modalités d’applicationLe fabricant, l’importateur ou le fournisseur qui, pour la vente de ses produits, se réfère au présent document ou à un texte qui fait référence à certains de ses articles, doit être en mesure de fournir à son client les éléments propres à justifier que les prescriptions normatives sont respectées.L’attribution de la marque NF aux produits conformes au présent document offre la garantie que ces éléments sont contrôlés sous l’égide d’AFNOR (certification par tierce partie).1)En préparation.NORME EUROPÉENNE EUROPÄISCHE NORM EUROPEAN STANDARDEN 10028-1Avril 2000La présente norme européenne a été adoptée par le CEN le 29 octobre 1999.Les membres du CEN sont tenus de se soumettre au Règlement Intérieur du CEN/CENELEC qui définit les conditions dans lesquelles doit être attribué, sans modification, le statut de norme nationale à la norme européenne.Les listes mises à jour et les références bibliographiques relatives à ces normes nationales peuvent être obtenues auprès du Secrétariat Central ou auprès des membres du CEN.La présente norme européenne existe en trois versions officielles (allemand, anglais, français). Une version faite dans une autre langue par traduction sous la responsabilité d'un membre du CEN dans sa langue nationale, et notifiée au Secrétariat Central, a le même statut que les versions officielles.Les membres du CEN sont les organismes nationaux de normalisation des pays suivants : Allemagne, Autriche,Belgique, Danemark, Espagne, Finlande, France, Grèce, Irlande, Islande, Italie, Luxembourg, Norvège, Pays-Bas, Portugal, République Tchèque, Royaume-Uni, Suède et Suisse.CENCOMITÉ EUROPÉEN DE NORMALISATION Europäisches Komitee für Normung European Committee for StandardizationSecrétariat Central : rue de Stassart 36, B-1050 Bruxelles© CEN 2000Tous droits d’exploitation sous quelque forme et de quelque manière que ce soit réservés dans le monde entier aux membres nationaux du CEN.Réf. n°EN 10028-1:2000 FICS :77.140.30; 77.140.50Remplace EN 10028-1:1992Version françaiseProduits plats en aciers pour appareils à pression —Partie 1: Prescriptions généralesFlacherzeugnisse aus Druckbehälterstählen —Teil 1: Allgemeine AnforderungenFlat products made of steels for pressure purposes —Part 1: General requirementsPage2EN 10028-1:2000SommairePage Avant-propos (3)1Domaine d’application (4)2Références normatives (4)3Définitions (5)4Dimensions et tolérances dimensionnelles (6)5Calcul de la masse (6)6Classification et désignation (6)6.1Classification (6)6.2Désignation (6)7Informations à fournir par l'acheteur (7)7.1Informations obligatoires (7)7.2Options (7)8Exigences (7)8.1Procédé d'élaboration (7)8.2État de livraison (7)8.3Composition chimique (8)8.4Caractéristiques mécaniques (8)8.5État de surface (8)8.6•• Santé interne (8)9Contrôles (8)9.1Type et contenu des documents de contrôle (8)9.2Contrôles à effectuer (9)9.3Contre-essais (9)10Échantillonnage (9)10.1Fréquence des essais (9)10.2Prélèvement et préparation des échantillons et des éprouvettes (10)11Méthodes d'essai (11)11.1•• Analyse chimique (11)11.2Essai de traction à température ambiante (11)11.3Essai de traction à température élevée (11)11.4Essai de flexion par choc (11)11.5Autres essais (12)12Marquage (12)Annexe ZA (informative) Articles de la présente norme européenneconcernant les exigences essentielles ou d'autres dispositions des Directives UE (17)Page3EN 10028-1:2000Avant-proposLa présente norme a été élaborée par le Comité Technique ECISS/TC22 «Aciers pour appareils soumis àpression — Prescriptions de qualité».La présente norme européenne remplace l’EN10028-1:1992 et prend en considération les normes complémen-taires de la série EN 10028.Les autres parties de la présente norme européenne sont:EN 10028-2, Produits plats en acier pour appareils à pression — Partie 2 : Aciers non alliés et alliés avec carac-téristiques spécifiées à température élevée.EN 10028-3, Produits plats en acier pour appareils à pression — Partie 3 : Aciers soudables à grains fins normalisés.EN 10028-4, Produits plats en acier pour appareils à pression — Partie 4 : Aciers alliés au nickel avec caractéris-tiques spécifiées à basse température.EN 10028-5, Produits plats en acier pour appareils à pression — Partie 5 : Aciers soudables à grains fins, laminés thermomécaniquement.EN 10028-6, Produits plats en acier pour appareils à pression — Partie 6 : Aciers soudables à grains fins, trempés et revenus.EN 10028-7, Produits plats en acier pour appareils à pression — Partie 7 : Aciers inoxydables.Cette norme européenne devra recevoir le statut de norme nationale, soit par publication d'un texte identique, soit par entérinement, au plus tard en octobre 2000 et toutes les normes nationales en contradiction devront être reti-rées au plus tard en octobre 2000.La présente norme européenne a été élaborée dans le cadre d'un mandat donné au CEN par la Commission Européenne et l'Association Européenne de Libre Échange, et vient à l'appui des exigences essentielles de la (de) Directive(s) UE.Pour la relation avec la (les) Directive(s) UE, voir l'annexe ZA informative, qui fait partie intégrante de la présente norme.Selon le Règlement Intérieur du CEN/CENELEC, les instituts de normalisation nationaux des pays suivants sont tenus de mettre le présent document en application : Allemagne, Autriche, Belgique, Danemark, Espagne, Fin-lande, France, Grèce, Irlande, Islande, Italie, Luxembourg, Norvège, Pays-Bas, Portugal, République Tchèque, Royaume-Uni, Suède et Suisse.NOTE Dans les paragraphes marqués d'un point (•) se trouvent des informations relatives aux accords qui doivent être conclus lors de l'appel d'offres et de la commande. Les paragraphes marqués de deux points (••) contiennent des informa-tions relatives aux accords qui doivent être conclus lors de l'appel d'offres et de la commande.Page4EN 10028-1:20001Domaine d’applicationLa présente norme européenne EN 10028-1 spécifie les conditions techniques générales de livraison des produits plats utilisés principalement dans la construction des appareils à pression.Les conditions techniques générales de livraison de l'EN 10021 s'appliquent également aux produits livrés conformément à la présente norme européenne.2Références normativesCette norme européenne comporte par référence datée ou non datée des dispositions d'autres publications. Ces références normatives sont citées aux endroits appropriés dans le texte et les publications sont énumérées ci-après. Pour les références datées, les amendements ou révisions ultérieurs de l'une quelconque de ces publica-tions ne s'appliquent à cette norme que s'ils y ont été incorporés par amendement ou révision. Pour les références non datées, la dernière édition de la publication à laquelle il est fait référence s'applique.CR 10260, Système de désignation des aciers — Symboles additionnels pour la désignation des aciers (Rapport CEN).EN 10002-1, Matériaux métalliques — Essai de traction — Partie 1 : Méthode d'essai (à température ambiante). EN 10002-5, Matériaux métalliques — Essai de traction — Partie 5 : Méthode d'essai à température élevée.EN 10020, Définition et classification des nuances d'acier.EN 10021, Aciers et produits sidérurgiques — Conditions générales techniques de livraison.EN 10027-1, Système de désignation des aciers — Partie 1 : Désignations symboliques, symboles principaux. EN 10027-2, Système de désignation des aciers — Partie 2 : Système numérique.EN 10028-7, Produits plats en acier pour appareils à pression — Partie 7 : Aciers inoxydables.EN 10029, Tôles en acier laminées à chaud d'épaisseur égale ou supérieure à 3 mm — Tolérances sur les dimen-sions, la forme et la masse.EN 10045-1, Matériaux métalliques — Essai de flexion par choc sur éprouvettes Charpy — Partie 1 : Méthode d'essai.EN 10048, Feuillards laminés à chaud — Tolérances de dimensions et de forme.EN 10051, Tôles, larges bandes et larges bandes refendues laminées à chaud en continu en aciers alliés et non alliés — Tolérances sur les dimensions, la forme et la masse.EN 10052, Vocabulaire du traitement thermique des produits ferreux.EN 10079, Définition des produits en acier.EN 10088-1, Aciers inoxydables — Partie 1 : Liste des aciers inoxydables.EN 10160, Contrôle ultrasonore des produits plats en acier d'épaisseur égale ou supérieure à 6 mm (méthode par réflection).EN 10163-2, Conditions de livraison relatives à l'état de surface des produits en acier laminés à chaud — Partie2: Tôles et larges plats.EN 10164, Aciers de construction à caractéristiques de déformation améliorées dans le sens perpendiculaire à la surface du produit — Conditions techniques de livraison.Page5EN 10028-1:2000 EN 10168 1), Produits sidérurgiques — Contenu des documents de contrôle — Liste et description des informations.EN 10204, Produits métalliques — Types de documents de contrôle (y compris amendement A1:1995).EN 10258, Feuillards ou feuillards coupés à longueur en acier inoxydable laminés à froid — Tolérances sur les dimensions et la forme.EN 10259, Larges bandes et tôles en acier inoxydable laminées à froid — Tolérances sur les dimensions et la forme.EN ISO 377, Aciers et produits en acier — Position et préparation des échantillons et éprouvettes pour essais mécaniques (ISO 377:1997).EN ISO 3651-2, Détermination de la résistance à la corrosion intergranulaire des aciers inoxydables — Partie 2 : Aciers ferritiques, austénitiques et austéno-ferritiques (duplex) — Essais de corrosion en milieux contenant de l'acide sulfurique (ISO 3651-2:1998).EN ISO 2566-1, Conversion des valeurs d'allongement — Partie 1 : Aciers non alliés et faiblement alliés (ISO2566-1:1984).EN ISO 2566-2, Conversion des valeurs d'allongement — Partie 2 : Aciers austénitiques (ISO 2566-2:1984). ISO 14284, Fontes et aciers — Prélèvement et préparation des échantillons pour la détermination de la composi-tion chimique.3DéfinitionsPour les besoins de la présente norme européenne, les définitions des normes :—EN 10020, pour la classification des aciers ;—EN 10079, pour les formes des produits ; et—EN 10052, pour les types de traitement thermique,s'appliquent.La définition 3.1 est différente de celle de l'EN 10052, et la définition 3.2 s'y ajoute.3.1laminage normalisantprocédé de laminage dans lequel la déformation finale est effectuée dans une certaine gamme de températures conduisant à un état du matériau équivalent à celui obtenu après normalisation, de sorte que les valeurs spécifiées de caractéristiques mécaniques sont maintenues même après un traitement de normalisation. La désignation de cet état de livraison et de celui obtenu par un traitement thermique de normalisation est N3.2en plus des définitions relatives au traitement thermomécanique, à la trempe et au revenu, il convient de noter les points suivants :NOTE 1Le laminage thermomécanique (symbole M) peut inclure des procédés d'accélération des vitesses de refroidis-sement avec ou sans revenu y compris auto-revenu mais à l'exclusion totale de la trempe directe suivie d'un revenu.NOTE 2Le traitement de trempe et revenu (symbole QT) englobe également le durcissement par trempe directe suivi d'un revenu.1)En cours d’élaboration; en attendant la publication de ce document sous le statut de Norme européenne, il ya lieu de convenir au moment de l’appel d’offres et de la commande d’une norme nationale correspondante.3.3acheteurpersonne ou organisation qui commande des produits selon la présente norme. L’acheteur n’est pas nécessaire-ment, mais peut être, un fabricant d’équipements sous pression selon la Directive UE listée en annexe ZA. Lorsqu'un acheteur a des responsabilités selon cette Directive UE, la présente norme européenne donnera pré-somption de conformité aux Exigences Essentielles de la Directive identifiée dans l’annexe ZA4Dimensions et tolérances dimensionnelles• Les dimensions nominales et tolérances sur les dimensions des produits doivent faire l'objet d'un accord lors de l'appel d'offres et de la commande sur la base des normes dimensionnelles indiquées ci-dessous :4.1Pour les tôles en acier laminées à chaud, en non-continu, se référer à l'EN 10029.•• Sauf accord contraire lors de l'appel d'offres et à la commande, la tolérance d'épaisseur des tôles doit corres-pondre à la classe B de l'EN 10029.4.2Pour les bobines laminées à chaud en continu et les tôles découpées à partir de bobines (laminées en largeur≥600mm) et les bobines refendues laminées à chaud en largeur < 600 mm, se référer à l'EN10051. 4.3Pour les feuillards laminés à chaud (laminés en largeur < 600 mm), se référer à l'EN10048.4.4Pour les tôles et bandes laminées à froid, les bobines, et les bobines refendues laminées à froid (en largeur≥ 600 mm) en aciers inoxydables, se référer à l’EN 10259, et pour les bobines et les bobines refendues laminées à froid en largeur < 600 mm en aciers inoxydables, se référer à l'EN10258.NOTE L'EN 10258 et l'EN 10259 comportent des options qui offrent des possibilités dimensionnelles plus larges.5Calcul de la masseLe calcul de la masse nominale dérivée des dimensions nominales doit être effectué, pour tous les aciers des EN10028 parties 2 à 6, sur la base d'une masse volumique de 7,85 kg/dm3. Pour les masses volumiques des aciers résistant à la corrosion, voir l'annexe A de l'EN10088-1. Pour la masse volumique des aciers résistant au fluage, voir l'annexe A de l'EN10028-7.6Classification et désignation6.1Classification6.1.1La classification des nuances d'acier conformément à l'EN 10020 est donnée dans les parties spécifiques de l'EN 10028.6.1.2Les aciers traités dans l'EN 10028-7 sont, en outre, classés en fonction de leur structure en :—aciers ferritiques ;—aciers martensitiques ;—aciers austénitiques ;—aciers austéno-ferritiques.NOTE Pour plus de détails, voir l'EN 10088-1.6.2DésignationLes nuances d'acier spécifiées dans les diverses parties de l'EN 10028 sont désignées par des désignations sym-boliques et numériques. Les désignations symboliques ont été attribuées conformément à l'EN 10027-1 et au CR10260. Les désignations numériques correspondantes ont été attribuées conformément à l'EN 10027-2.7Informations à fournir par l'acheteur7.1Informations obligatoiresLes informations suivantes doivent être fournies par l'acheteur au moment de l'appel d'offres et de la commande :a)la quantité désirée ;b)le type de produit plat ;c)la norme européenne spécifiant les tolérances de dimensions, de forme et de masse (voir article 4) et, si lanorme européenne en question laisse au client le choix entre plusieurs possibilités, par exemple diverses fini-tions de rives ou diverses classes de tolérances, des informations détaillées relatives à ces spécificités ;d)les dimensions nominales du produit ;e)l'indice de la présente norme européenne ;f)la désignation symbolique ou numérique de la nuance d'acier ;g)l'état de livraison s'il diffère de l'état habituel spécifié dans la partie spécifique de l'EN10028 ; pour les aciersinoxydables, la gamme de fabrication choisie dans le tableau concerné de l'EN10028-7 ;h)le document de contrôle à produire (voir 9.1.1).7.2OptionsUn certain nombre d'options sont spécifiées dans la présente partie de l'EN 10028 et données dans la liste ci-dessous. Si l'acheteur n'indique pas les options qu'il souhaite voir mises en œuvre au moment de l'appel d'offres et de la commande, les produits doivent être fournis conformément aux spécifications de base (voir 7.1) :a)classe de tolérance différente (voir 4.1) ;b)spécification relative au procédé d'élaboration de l'acier (voir 8.1.1) ;c)caractéristiques mécaniques après traitement thermique supplémentaire (voir 8.4.1) ;d)spécifications de classes particulières pour le coefficient de striction (voir 8.4.2) ;e)essais supplémentaires (voir 9.2.2) ;f)fréquence d'essais différente (voir 10.1.1 et 10.1.3) ;g)conditions de livraison différentes (voir 10.2.1.3) ;h)utilisation d'éprouvettes longitudinales pour l'essai de flexion par choc (voir 10.2.2.3) ;i)spécification d'une méthode d'analyse (voir 11.1) ;j)température de l'essai de traction à température élevée (voir 11.3) ;k)température d'essai différente pour l'essai de flexion par choc (voir 11.4) ;l)méthode de marquage (voir 12.1) ;m)marquage spécial (voir 12.2 et 12.3) ;n)informations devant être données par le marquage (voir tableau 1).8Exigences8.1Procédé d'élaboration8.1.1•• Sauf si un procédé d'élaboration particulier a fait l'objet d'un accord lors de l'appel d'offres et de la commande, le procédé d'élaboration des aciers de la présente norme européenne doit être laissé au choix du producteur.8.1.2Les aciers autres que les aciers inoxydables doivent être totalement calmés.8.2État de livraisonVoir les parties spécifiques de l'EN 10028 (voir aussi 3.1 et 3.2).8.3Composition chimique8.3.1Analyse de couléeL'analyse de coulée donnée par le producteur de l'acier doit s'appliquer et satisfaire aux exigences des parties spécifiques de l'EN 10028.8.3.2Analyse sur produitLes écarts admissibles de l'analyse sur produit par rapport aux valeurs limites données pour l'analyse de coulée sont spécifiés dans les parties concernées de l'EN 10028.8.4Caractéristiques mécaniques8.4.1Les valeurs données dans les parties spécifiques de l'EN 10028 s'appliquent pour les éprouvettes préle-vées et préparées selon les indications du 10.2.2. Ces valeurs ont été obtenues sur des produits d'épaisseur nomi-nale (épaisseurs commandées) et à l'état normal de livraison (voir parties spécifiques de l'EN 10028).•• Le cas échéant, les valeurs des caractéristiques mécaniques garanties après traitement thermique complé-mentaire doivent faire l'objet d'un accord au moment de l'appel d'offres et de la commande.8.4.2•• Pour les produits (excepté ceux en acier inoxydable) d'épaisseur ≥ 15 mm, il peut être convenu, lors de l'appel d'offres et de la commande, de respecter les exigences fixées pour l'une des classes de qualité Z15, Z 25 ou Z 35 de l'EN 10164 caractérisées par des valeurs minimales de striction dans le sens de l'épaisseur. 8.5État de surfacePour les tôles, les exigences de qualité de surface spécifiées dans l'EN10163-2 doivent être appliquées de la manière suivante :a)pour les tôles conformes à l'EN 10028-2 à -6 : classe B2;b)pour les tôles conformes à l'EN 10028-7 : classe B3.8.6•• Santé interneLes exigences relatives à la santé interne ainsi que les conditions de sa vérification (voir 7.2.e et 11.5.3) peuvent, le cas échéant, être spécifiées au moment de l'appel d'offres et de la commande.9Contrôles9.1Type et contenu des documents de contrôle9.1.1• La conformité aux exigences de la commande des produits livrés, conformément à la présente norme européenne, doit faire l'objet d'un contrôle spécifique.L'acheteur doit préciser le type de document de contrôle souhaité (3.1.A, 3.1.B, 3.1.C ou 3.2) conformément àl'EN10204. Si un document de contrôle 3.1.A, 3.1.C ou 3.2 est commandé, l'acheteur doit notifier au producteur le nom et l'adresse de l'organisme ou de la personne chargée d'effectuer le contrôle et de produire le document correspondant. S'il s'agit d'un procès-verbal de réception 3.2, on doit convenir de la partie chargée de publier le certificat.9.1.2Le document de contrôle doit contenir, conformément à l'EN 10168, les codes et les informations suivants :a)les groupes d'informations A, B et Z ; la température de revenu doit également être donnée dans le cas desproduits trempés et revenus ;b)les résultats de l'analyse de coulée, conformément aux rubriques C 71 à C 92 ;c)les résultats des essais de traction à température ambiante, conformément aux rubriques C00 à C03 et C10à C13 ;d)les résultats de l'essai de flexion par choc sauf pour les aciers austénitiques de l'EN10028-7, conformémentaux rubriques C00 à C03 et C40 à C43 ;e)les résultats du contrôle visuel des produits (voir groupe d'informations D) ;f)si une ou plusieurs des options suivantes ont fait l'objet d'un accord lors de l'appel d'offres et de la commande,les informations correspondantes :1)le procédé d'élaboration de l'acier (rubrique C 70) ;2)l'analyse sur produit conformément aux rubriques C 71 à C 92 ;3)les résultats de l'essai de traction à température élevée (voir 9.2.2), conformément aux rubriques C 00àC03, C 10 et C 11 ;4)la valeur minimale de striction dans le sens de l'épaisseur, conformément aux rubriques C 00 à C 03, C 10et C 14 à C 29 ;5)le contrôle de santé interne par ultrasons (groupe d'informations F) ;6)les caractéristiques de flexion par choc des aciers austénitiques à température ambiante, conformémentaux rubriques C 00 à C 03 et C 40 à C 43 ;7)vérification des caractéristiques de flexion par choc des aciers inoxydables à basse température, confor-mément aux rubriques C 00 à C 03 et C 40 à C 43 ;8)résistance à la corrosion intergranulaire des aciers inoxydables, conformément aux rubriques C 60 à C69.9.2Contrôles à effectuer9.2.1Les contrôles suivants doivent être effectués :—essai de traction à température ambiante ;—essai de flexion par choc (sauf pour les aciers austénitiques de l'EN 10028-7), mais voir 10.2.2.3 ;—contrôle dimensionnel ;—examen visuel de l'état de surface.9.2.2•• Les essais suivants peuvent faire l'objet d'un accord :—analyse sur produit ;—essai de traction pour vérifier la limite d'élasticité conventionnelle à 0,2 % à température élevée (sauf pour les aciers des EN10028-4 et EN 10028-5) ;—essai de traction pour vérifier simultanément à température élevée pour les aciers austénitiques de l'EN10028-7 un, plusieurs ou l’ensemble des paramètres suivants: R p0,2, R p1,0 et R m ;—essai de traction dans le sens de l'épaisseur (sauf pour les aciers de l'EN10028-7) ;—essais de flexion par choc à température ambiante des aciers austénitiques de l'EN10028-7;—essais de flexion par choc à basse température des aciers de l'EN 10028-7 (sauf pour les aciers ferritiques) ;—contrôle aux ultrasons pour vérifier la santé interne ;—détermination de la résistance à la corrosion intergranulaire des aciers de l'EN 10028-7.9.3Contre-essaisVoir l'EN 10021.10Échantillonnage10.1Fréquence des essais10.1.1•• Pour l'analyse sur produit et sauf accord contraire, une seule éprouvette par coulée doit être prélevée pour déterminer, pour la nuance considérée, la teneur des éléments indiqués avec des valeurs numériques dans les divers tableaux des parties spécifiques de l'EN 10028.。

ACM-GIS%202006-A%20Peer-to-Peer%20Spatial%20Cloaking%20Algorithm%20for%20Anonymous%20Location-based%

A Peer-to-Peer Spatial Cloaking Algorithm for AnonymousLocation-based Services∗Chi-Yin Chow Department of Computer Science and Engineering University of Minnesota Minneapolis,MN cchow@ Mohamed F.MokbelDepartment of ComputerScience and EngineeringUniversity of MinnesotaMinneapolis,MNmokbel@Xuan LiuIBM Thomas J.WatsonResearch CenterHawthorne,NYxuanliu@ABSTRACTThis paper tackles a major privacy threat in current location-based services where users have to report their ex-act locations to the database server in order to obtain their desired services.For example,a mobile user asking about her nearest restaurant has to report her exact location.With untrusted service providers,reporting private location in-formation may lead to several privacy threats.In this pa-per,we present a peer-to-peer(P2P)spatial cloaking algo-rithm in which mobile and stationary users can entertain location-based services without revealing their exact loca-tion information.The main idea is that before requesting any location-based service,the mobile user will form a group from her peers via single-hop communication and/or multi-hop routing.Then,the spatial cloaked area is computed as the region that covers the entire group of peers.Two modes of operations are supported within the proposed P2P spa-tial cloaking algorithm,namely,the on-demand mode and the proactive mode.Experimental results show that the P2P spatial cloaking algorithm operated in the on-demand mode has lower communication cost and better quality of services than the proactive mode,but the on-demand incurs longer response time.Categories and Subject Descriptors:H.2.8[Database Applications]:Spatial databases and GISGeneral Terms:Algorithms and Experimentation. Keywords:Mobile computing,location-based services,lo-cation privacy and spatial cloaking.1.INTRODUCTIONThe emergence of state-of-the-art location-detection de-vices,e.g.,cellular phones,global positioning system(GPS) devices,and radio-frequency identiﬁcation(RFID)chips re-sults in a location-dependent information access paradigm,∗This work is supported in part by the Grants-in-Aid of Re-search,Artistry,and Scholarship,University of Minnesota. Permission to make digital or hard copies of all or part of this work for personal or classroom use is granted without fee provided that copies are not made or distributed for proﬁt or commercial advantage and that copies bear this notice and the full citation on theﬁrst page.To copy otherwise,to republish,to post on servers or to redistribute to lists,requires prior speciﬁc permission and/or a fee.ACM-GIS’06,November10-11,2006,Arlington,Virginia,USA. Copyright2006ACM1-59593-529-0/06/0011...$5.00.known as location-based services(LBS)[30].In LBS,mobile users have the ability to issue location-based queries to the location-based database server.Examples of such queries include“where is my nearest gas station”,“what are the restaurants within one mile of my location”,and“what is the traﬃc condition within ten minutes of my route”.To get the precise answer of these queries,the user has to pro-vide her exact location information to the database server. With untrustworthy servers,adversaries may access sensi-tive information about speciﬁc individuals based on their location information and issued queries.For example,an adversary may check a user’s habit and interest by knowing the places she visits and the time of each visit,or someone can track the locations of his ex-friends.In fact,in many cases,GPS devices have been used in stalking personal lo-cations[12,39].To tackle this major privacy concern,three centralized privacy-preserving frameworks are proposed for LBS[13,14,31],in which a trusted third party is used as a middleware to blur user locations into spatial regions to achieve k-anonymity,i.e.,a user is indistinguishable among other k−1users.The centralized privacy-preserving frame-work possesses the following shortcomings:1)The central-ized trusted third party could be the system bottleneck or single point of failure.2)Since the centralized third party has the complete knowledge of the location information and queries of all users,it may pose a serious privacy threat when the third party is attacked by adversaries.In this paper,we propose a peer-to-peer(P2P)spatial cloaking algorithm.Mobile users adopting the P2P spatial cloaking algorithm can protect their privacy without seeking help from any centralized third party.Other than the short-comings of the centralized approach,our work is also moti-vated by the following facts:1)The computation power and storage capacity of most mobile devices have been improv-ing at a fast pace.2)P2P communication technologies,such as IEEE802.11and Bluetooth,have been widely deployed.3)Many new applications based on P2P information shar-ing have rapidly taken shape,e.g.,cooperative information access[9,32]and P2P spatio-temporal query processing[20, 24].Figure1gives an illustrative example of P2P spatial cloak-ing.The mobile user A wants toﬁnd her nearest gas station while beingﬁve anonymous,i.e.,the user is indistinguish-able amongﬁve users.Thus,the mobile user A has to look around andﬁnd other four peers to collaborate as a group. In this example,the four peers are B,C,D,and E.Then, the mobile user A cloaks her exact location into a spatialA B CDEBase Stationregion that covers the entire group of mobile users A ,B ,C ,D ,and E .The mobile user A randomly selects one of the mobile users within the group as an agent .In the ex-ample given in Figure 1,the mobile user D is selected as an agent.Then,the mobile user A sends her query (i.e.,what is the nearest gas station)along with her cloaked spa-tial region to the agent.The agent forwards the query to the location-based database server through a base station.Since the location-based database server processes the query based on the cloaked spatial region,it can only give a list of candidate answers that includes the actual answers and some false positives.After the agent receives the candidate answers,it forwards the candidate answers to the mobile user A .Finally,the mobile user A gets the actual answer by ﬁltering out all the false positives.The proposed P2P spatial cloaking algorithm can operate in two modes:on-demand and proactive .In the on-demand mode,mobile clients execute the cloaking algorithm when they need to access information from the location-based database server.On the other side,in the proactive mode,mobile clients periodically look around to ﬁnd the desired number of peers.Thus,they can cloak their exact locations into spatial regions whenever they want to retrieve informa-tion from the location-based database server.In general,the contributions of this paper can be summarized as follows:1.We introduce a distributed system architecture for pro-viding anonymous location-based services (LBS)for mobile users.2.We propose the ﬁrst P2P spatial cloaking algorithm for mobile users to entertain high quality location-based services without compromising their privacy.3.We provide experimental evidence that our proposed algorithm is eﬃcient in terms of the response time,is scalable to large numbers of mobile clients,and is eﬀective as it provides high-quality services for mobile clients without the need of exact location information.The rest of this paper is organized as follows.Section 2highlights the related work.The system model of the P2P spatial cloaking algorithm is presented in Section 3.The P2P spatial cloaking algorithm is described in Section 4.Section 5discusses the integration of the P2P spatial cloak-ing algorithm with privacy-aware location-based database servers.Section 6depicts the experimental evaluation of the P2P spatial cloaking algorithm.Finally,Section 7con-cludes this paper.2.RELATED WORKThe k -anonymity model [37,38]has been widely used in maintaining privacy in databases [5,26,27,28].The main idea is to have each tuple in the table as k -anonymous,i.e.,indistinguishable among other k −1tuples.Although we aim for the similar k -anonymity model for the P2P spatial cloaking algorithm,none of these techniques can be applied to protect user privacy for LBS,mainly for the following four reasons:1)These techniques preserve the privacy of the stored data.In our model,we aim not to store the data at all.Instead,we store perturbed versions of the data.Thus,data privacy is managed before storing the data.2)These approaches protect the data not the queries.In anonymous LBS,we aim to protect the user who issues the query to the location-based database server.For example,a mobile user who wants to ask about her nearest gas station needs to pro-tect her location while the location information of the gas station is not protected.3)These approaches guarantee the k -anonymity for a snapshot of the database.In LBS,the user location is continuously changing.Such dynamic be-havior calls for continuous maintenance of the k -anonymity model.(4)These approaches assume a uniﬁed k -anonymity requirement for all the stored records.In our P2P spatial cloaking algorithm,k -anonymity is a user-speciﬁed privacy requirement which may have a diﬀerent value for each user.Motivated by the privacy threats of location-detection de-vices [1,4,6,40],several research eﬀorts are dedicated to protect the locations of mobile users (e.g.,false dummies [23],landmark objects [18],and location perturbation [10,13,14]).The most closed approaches to ours are two centralized spatial cloaking algorithms,namely,the spatio-temporal cloaking [14]and the CliqueCloak algorithm [13],and one decentralized privacy-preserving algorithm [23].The spatio-temporal cloaking algorithm [14]assumes that all users have the same k -anonymity requirements.Furthermore,it lacks the scalability because it deals with each single request of each user individually.The CliqueCloak algorithm [13]as-sumes a diﬀerent k -anonymity requirement for each user.However,since it has large computation overhead,it is lim-ited to a small k -anonymity requirement,i.e.,k is from 5to 10.A decentralized privacy-preserving algorithm is proposed for LBS [23].The main idea is that the mobile client sends a set of false locations,called dummies ,along with its true location to the location-based database server.However,the disadvantages of using dummies are threefold.First,the user has to generate realistic dummies to pre-vent the adversary from guessing its true location.Second,the location-based database server wastes a lot of resources to process the dummies.Finally,the adversary may esti-mate the user location by using cellular positioning tech-niques [34],e.g.,the time-of-arrival (TOA),the time diﬀer-ence of arrival (TDOA)and the direction of arrival (DOA).Although several existing distributed group formation al-gorithms can be used to ﬁnd peers in a mobile environment,they are not designed for privacy preserving in LBS.Some algorithms are limited to only ﬁnding the neighboring peers,e.g.,lowest-ID [11],largest-connectivity (degree)[33]and mobility-based clustering algorithms [2,25].When a mo-bile user with a strict privacy requirement,i.e.,the value of k −1is larger than the number of neighboring peers,it has to enlist other peers for help via multi-hop routing.Other algorithms do not have this limitation,but they are designed for grouping stable mobile clients together to facil-Location-based Database ServerDatabase ServerDatabase ServerFigure 2:The system architectureitate eﬃcient data replica allocation,e.g.,dynamic connec-tivity based group algorithm [16]and mobility-based clus-tering algorithm,called DRAM [19].Our work is diﬀerent from these approaches in that we propose a P2P spatial cloaking algorithm that is dedicated for mobile users to dis-cover other k −1peers via single-hop communication and/or via multi-hop routing,in order to preserve user privacy in LBS.3.SYSTEM MODELFigure 2depicts the system architecture for the pro-posed P2P spatial cloaking algorithm which contains two main components:mobile clients and location-based data-base server .Each mobile client has its own privacy proﬁle that speciﬁes its desired level of privacy.A privacy proﬁle includes two parameters,k and A min ,k indicates that the user wants to be k -anonymous,i.e.,indistinguishable among k users,while A min speciﬁes the minimum resolution of the cloaked spatial region.The larger the value of k and A min ,the more strict privacy requirements a user needs.Mobile users have the ability to change their privacy proﬁle at any time.Our employed privacy proﬁle matches the privacy re-quirements of mobiles users as depicted by several social science studies (e.g.,see [4,15,17,22,29]).In this architecture,each mobile user is equipped with two wireless network interface cards;one of them is dedicated to communicate with the location-based database server through the base station,while the other one is devoted to the communication with other peers.A similar multi-interface technique has been used to implement IP multi-homing for stream control transmission protocol (SCTP),in which a machine is installed with multiple network in-terface cards,and each assigned a diﬀerent IP address [36].Similarly,in mobile P2P cooperation environment,mobile users have a network connection to access information from the server,e.g.,through a wireless modem or a base station,and the mobile users also have the ability to communicate with other peers via a wireless LAN,e.g.,IEEE 802.11or Bluetooth [9,24,32].Furthermore,each mobile client is equipped with a positioning device, e.g.,GPS or sensor-based local positioning systems,to determine its current lo-cation information.4.P2P SPATIAL CLOAKINGIn this section,we present the data structure and the P2P spatial cloaking algorithm.Then,we describe two operation modes of the algorithm:on-demand and proactive .4.1Data StructureThe entire system area is divided into grid.The mobile client communicates with each other to discover other k −1peers,in order to achieve the k -anonymity requirement.TheAlgorithm 1P2P Spatial Cloaking:Request Originator m 1:Function P2PCloaking-Originator (h ,k )2://Phase 1:Peer searching phase 3:The hop distance h is set to h4:The set of discovered peers T is set to {∅},and the number ofdiscovered peers k =|T |=05:while k <k −1do6:Broadcast a FORM GROUP request with the parameter h (Al-gorithm 2gives the response of each peer p that receives this request)7:T is the set of peers that respond back to m by executingAlgorithm 28:k =|T |;9:if k <k −1then 10:if T =T then 11:Suspend the request 12:end if 13:h ←h +1;14:T ←T ;15:end if 16:end while17://Phase 2:Location adjustment phase 18:for all T i ∈T do19:|mT i .p |←the greatest possible distance between m and T i .pby considering the timestamp of T i .p ’s reply and maximum speed20:end for21://Phase 3:Spatial cloaking phase22:Form a group with k −1peers having the smallest |mp |23:h ←the largest hop distance h p of the selected k −1peers 24:Determine a grid area A that covers the entire group 25:if A <A min then26:Extend the area of A till it covers A min 27:end if28:Randomly select a mobile client of the group as an agent 29:Forward the query and A to the agentmobile client can thus blur its exact location into a cloaked spatial region that is the minimum grid area covering the k −1peers and itself,and satisﬁes A min as well.The grid area is represented by the ID of the left-bottom and right-top cells,i.e.,(l,b )and (r,t ).In addition,each mobile client maintains a parameter h that is the required hop distance of the last peer searching.The initial value of h is equal to one.4.2AlgorithmFigure 3gives a running example for the P2P spatial cloaking algorithm.There are 15mobile clients,m 1to m 15,represented as solid circles.m 8is the request originator,other black circles represent the mobile clients received the request from m 8.The dotted circles represent the commu-nication range of the mobile client,and the arrow represents the movement direction.Algorithms 1and 2give the pseudo code for the request originator (denoted as m )and the re-quest receivers (denoted as p ),respectively.In general,the algorithm consists of the following three phases:Phase 1:Peer searching phase .The request origina-tor m wants to retrieve information from the location-based database server.m ﬁrst sets h to h ,a set of discovered peers T to {∅}and the number of discovered peers k to zero,i.e.,|T |.(Lines 3to 4in Algorithm 1).Then,m broadcasts a FORM GROUP request along with a message sequence ID and the hop distance h to its neighboring peers (Line 6in Algorithm 1).m listens to the network and waits for the reply from its neighboring peers.Algorithm 2describes how a peer p responds to the FORM GROUP request along with a hop distance h and aFigure3:P2P spatial cloaking algorithm.Algorithm2P2P Spatial Cloaking:Request Receiver p1:Function P2PCloaking-Receiver(h)2://Let r be the request forwarder3:if the request is duplicate then4:Reply r with an ACK message5:return;6:end if7:h p←1;8:if h=1then9:Send the tuple T=<p,(x p,y p),v maxp ,t p,h p>to r10:else11:h←h−1;12:Broadcast a FORM GROUP request with the parameter h 13:T p is the set of peers that respond back to p14:for all T i∈T p do15:T i.h p←T i.h p+1;16:end for17:T p←T p∪{<p,(x p,y p),v maxp ,t p,h p>};18:Send T p back to r19:end ifmessage sequence ID from another peer(denoted as r)that is either the request originator or the forwarder of the re-quest.First,p checks if it is a duplicate request based on the message sequence ID.If it is a duplicate request,it sim-ply replies r with an ACK message without processing the request.Otherwise,p processes the request based on the value of h:Case1:h= 1.p turns in a tuple that contains its ID,current location,maximum movement speed,a timestamp and a hop distance(it is set to one),i.e.,< p,(x p,y p),v max p,t p,h p>,to r(Line9in Algorithm2). Case2:h> 1.p decrements h and broadcasts the FORM GROUP request with the updated h and the origi-nal message sequence ID to its neighboring peers.p keeps listening to the network,until it collects the replies from all its neighboring peers.After that,p increments the h p of each collected tuple,and then it appends its own tuple to the collected tuples T p.Finally,it sends T p back to r (Lines11to18in Algorithm2).After m collects the tuples T from its neighboring peers, if m cannotﬁnd other k−1peers with a hop distance of h,it increments h and re-broadcasts the FORM GROUP request along with a new message sequence ID and h.m repeatedly increments h till itﬁnds other k−1peers(Lines6to14in Algorithm1).However,if mﬁnds the same set of peers in two consecutive broadcasts,i.e.,with hop distances h and h+1,there are not enough connected peers for m.Thus, m has to relax its privacy proﬁle,i.e.,use a smaller value of k,or to be suspended for a period of time(Line11in Algorithm1).Figures3(a)and3(b)depict single-hop and multi-hop peer searching in our running example,respectively.In Fig-ure3(a),the request originator,m8,(e.g.,k=5)canﬁnd k−1peers via single-hop communication,so m8sets h=1. Since h=1,its neighboring peers,m5,m6,m7,m9,m10, and m11,will not further broadcast the FORM GROUP re-quest.On the other hand,in Figure3(b),m8does not connect to k−1peers directly,so it has to set h>1.Thus, its neighboring peers,m7,m10,and m11,will broadcast the FORM GROUP request along with a decremented hop dis-tance,i.e.,h=h−1,and the original message sequence ID to their neighboring peers.Phase2:Location adjustment phase.Since the peer keeps moving,we have to capture the movement between the time when the peer sends its tuple and the current time. For each received tuple from a peer p,the request originator, m,determines the greatest possible distance between them by an equation,|mp |=|mp|+(t c−t p)×v max p,where |mp|is the Euclidean distance between m and p at time t p,i.e.,|mp|=(x m−x p)2+(y m−y p)2,t c is the currenttime,t p is the timestamp of the tuple and v maxpis the maximum speed of p(Lines18to20in Algorithm1).In this paper,a conservative approach is used to determine the distance,because we assume that the peer will move with the maximum speed in any direction.If p gives its movement direction,m has the ability to determine a more precise distance between them.Figure3(c)illustrates that,for each discovered peer,the circle represents the largest region where the peer can lo-cate at time t c.The greatest possible distance between the request originator m8and its discovered peer,m5,m6,m7, m9,m10,or m11is represented by a dotted line.For exam-ple,the distance of the line m8m 11is the greatest possible distance between m8and m11at time t c,i.e.,|m8m 11|. Phase3:Spatial cloaking phase.In this phase,the request originator,m,forms a virtual group with the k−1 nearest peers,based on the greatest possible distance be-tween them(Line22in Algorithm1).To adapt to the dynamic network topology and k-anonymity requirement, m sets h to the largest value of h p of the selected k−1 peers(Line15in Algorithm1).Then,m determines the minimum grid area A covering the entire group(Line24in Algorithm1).If the area of A is less than A min,m extends A,until it satisﬁes A min(Lines25to27in Algorithm1). Figure3(c)gives the k−1nearest peers,m6,m7,m10,and m11to the request originator,m8.For example,the privacy proﬁle of m8is(k=5,A min=20cells),and the required cloaked spatial region of m8is represented by a bold rectan-gle,as depicted in Figure3(d).To issue the query to the location-based database server anonymously,m randomly selects a mobile client in the group as an agent(Line28in Algorithm1).Then,m sendsthe query along with the cloaked spatial region,i.e.,A,to the agent(Line29in Algorithm1).The agent forwards thequery to the location-based database server.After the serverprocesses the query with respect to the cloaked spatial re-gion,it sends a list of candidate answers back to the agent.The agent forwards the candidate answer to m,and then mﬁlters out the false positives from the candidate answers. 4.3Modes of OperationsThe P2P spatial cloaking algorithm can operate in twomodes,on-demand and proactive.The on-demand mode:The mobile client only executesthe algorithm when it needs to retrieve information from the location-based database server.The algorithm operatedin the on-demand mode generally incurs less communica-tion overhead than the proactive mode,because the mobileclient only executes the algorithm when necessary.However,it suﬀers from a longer response time than the algorithm op-erated in the proactive mode.The proactive mode:The mobile client adopting theproactive mode periodically executes the algorithm in back-ground.The mobile client can cloak its location into a spa-tial region immediately,once it wants to communicate withthe location-based database server.The proactive mode pro-vides a better response time than the on-demand mode,but it generally incurs higher communication overhead and giveslower quality of service than the on-demand mode.5.ANONYMOUS LOCATION-BASEDSERVICESHaving the spatial cloaked region as an output form Algo-rithm1,the mobile user m sends her request to the location-based server through an agent p that is randomly selected.Existing location-based database servers can support onlyexact point locations rather than cloaked regions.In or-der to be able to work with a spatial region,location-basedservers need to be equipped with a privacy-aware queryprocessor(e.g.,see[29,31]).The main idea of the privacy-aware query processor is to return a list of candidate answerrather than the exact query answer.Then,the mobile user m willﬁlter the candidate list to eliminate its false positives andﬁnd its exact answer.The tighter the spatial cloaked re-gion,the lower is the size of the candidate answer,and hencethe better is the performance of the privacy-aware query processor.However,tight cloaked regions may represent re-laxed privacy constrained.Thus,a trade-oﬀbetween the user privacy and the quality of service can be achieved[31]. Figure4(a)depicts such scenario by showing the data stored at the server side.There are32target objects,i.e., gas stations,T1to T32represented as black circles,the shaded area represents the spatial cloaked area of the mo-bile client who issued the query.For clariﬁcation,the actual mobile client location is plotted in Figure4(a)as a black square inside the cloaked area.However,such information is neither stored at the server side nor revealed to the server. The privacy-aware query processor determines a range that includes all target objects that are possibly contributing to the answer given that the actual location of the mobile client could be anywhere within the shaded area.The range is rep-resented as a bold rectangle,as depicted in Figure4(b).The server sends a list of candidate answers,i.e.,T8,T12,T13, T16,T17,T21,and T22,back to the agent.The agent next for-(a)Server Side(b)Client SideFigure4:Anonymous location-based services wards the candidate answers to the requesting mobile client either through single-hop communication or through multi-hop routing.Finally,the mobile client can get the actualanswer,i.e.,T13,byﬁltering out the false positives from thecandidate answers.The algorithmic details of the privacy-aware query proces-sor is beyond the scope of this paper.Interested readers are referred to[31]for more details.6.EXPERIMENTAL RESULTSIn this section,we evaluate and compare the scalabilityand eﬃciency of the P2P spatial cloaking algorithm in boththe on-demand and proactive modes with respect to the av-erage response time per query,the average number of mes-sages per query,and the size of the returned candidate an-swers from the location-based database server.The queryresponse time in the on-demand mode is deﬁned as the timeelapsed between a mobile client starting to search k−1peersand receiving the candidate answers from the agent.On theother hand,the query response time in the proactive mode is deﬁned as the time elapsed between a mobile client startingto forward its query along with the cloaked spatial regionto the agent and receiving the candidate answers from theagent.The simulation model is implemented in C++usingCSIM[35].In all the experiments in this section,we consider an in-dividual random walk model that is based on“random way-point”model[7,8].At the beginning,the mobile clientsare randomly distributed in a spatial space of1,000×1,000square meters,in which a uniform grid structure of100×100cells is constructed.Each mobile client randomly chooses itsown destination in the space with a randomly determined speed s from a uniform distribution U(v min,v max).When the mobile client reaches the destination,it comes to a stand-still for one second to determine its next destination.Afterthat,the mobile client moves towards its new destinationwith another speed.All the mobile clients repeat this move-ment behavior during the simulation.The time interval be-tween two consecutive queries generated by a mobile client follows an exponential distribution with a mean of ten sec-onds.All the experiments consider one half-duplex wirelesschannel for a mobile client to communicate with its peers with a total bandwidth of2Mbps and a transmission range of250meters.When a mobile client wants to communicate with other peers or the location-based database server,it has to wait if the requested channel is busy.In the simulated mobile environment,there is a centralized location-based database server,and one wireless communication channel between the location-based database server and the mobile。

pppmodels

PPP ModelsThe PPP models vary from short-term simple management contracts (with or without investment requirements) to long-term and very complex BOT form, to divestiture. These models vary mainly by:−Ownership of capital assets−Responsibility for investment−Assumption of risks, and−Duration of contract.The PPP models can be classified into four broad categories in order of generally (but not always) increased involvement and assumption of risks by the private sector. The four broad categorisations of participation are:−Supply and management contracts−Turnkey projects−Lease−Concessions−Private ownership of assets.Management Contracts :A management contract is a contractual arrangement for the management of a part or whole of a public enterprise by the private sector. Management contracts allow private sector skills to be brought into service design and delivery, operational control, labour management and equipment procurement. However, the public sector retains the ownership of facility and equipment. The private sector is provided specified responsibilities concerning a service and is generally not asked to assume commercial risk. The private contractor is paid a fee to manage and operate services. Normally, payment of such fees is performance-based. Usually, the contract period is short, typically two to five years. But longer period may be used for large and complex operational facilities such as a port or airport.There are several variants under the management contract including:−Supply or service contract−Maintenance management−Operational managementSupply or service contract :Supply of equipment, raw materials, energy and power, and labour are typical examples of supply or service contract. A private concessionaire can itself enter into a number of supply or service contracts with other entities/ providers for the supply of equipment, materials, power and energy, and labour. Non-core activities of an organization (public or private) such as catering, cleaning, medical, luggage handling, security, and transport services for staff can be undertaken by private sector service providers. Such an arrangement is also known as outsourcing.Some form of licensing or operating agreement is used if the private sector is to provide services directly to users of the infrastructure facility. Examples of such an arrangement include, catering services for passengers on railway systems (the Indian Railways, for example). The main purpose of such licensing is to ensure the supply of the relevant service at the desired level of quantity and quality.Maintenance managementAssets maintenance contracts are very popular with transport operators. Sometimes equipment vendors/suppliers can also be engaged for the maintenance of assets procured from them.Operational managementManagement contracts of major transport facilities such as a port or airport may be useful when local manpower or expertise in running the facility is limited or when inaugurating a new operation. Management contracts are also quite common in the transport sector for providing some of the non-transport elements of transport operations such as the ticketing system of public transport and reservation systems. Operational management of urban transport services can also be contracted out to the private sector.In the simplest type of contract, the private operator is paid a fixed fee for performing managerial tasks. More complex contracts may offer greater incentives for efficiency improvement by defining performance targets and the fee is based in part on their fulfilment.TurnkeyTurnkey is a traditional public sector procurement model for infrastructure facilities. Generally, a private contractor is selected through a bidding process. The private contractor designs and builds a facility for a fixed fee, rate or total cost, which is one of the key criteria in selecting the winning bid. The contractor assumes risks involved in the design and construction phases. The scale of investment by the private sector is generally low and for a short-term. Typically, in this type of arrangement there is no strong incentive for early completion of a project. This type of private sector participation is also known as Design-Build.Affermage/LeaseIn this category of arrangement an operator (the leaseholder) is responsible for operating and maintaining the infrastructure facility and services, but generally the operator is not required to make any large investment. However, often this model is applied in combination with other models such as build-rehabilitate-operate-transfer. In such a case, the contract period is generally much longer and the private sector is required to make a significant level of investment.The arrangements in an affermage and a lease are very similar. The difference between them is technical. Under a lease, the operator retains revenue collected from customers/users of the facility and makes a specified lease fee payment to the contracting authority. Under an affermage, the operator and the contracting authority share revenue from customers/users. Following Figure shows the typical structure of an affermage/lease contract. In the affermage/lease types of arrangements, the operator takes lease of both infrastructure and equipment from the government for an agreed period of time. Generally, the government maintains the responsibility for investment and thus bears investment risks. The operational risks are transferred to the operator. However, as part of lease, some assets may be transferred on a permanent basis for a period which extends over the economic life of assets. Fixed facilities and land are leased out for a longer period than for mobile assets. Land to be developed by the leaseholder is usually transferred for a period of 15-30 years.It may be noted here that if the assets transferred to the private sector under a lease agreement are constrained in their use to a specific function or service, the value of assetsis dependent upon the revenue potential of that function or service. If assets are transferred to the private sector without restrictions of use, the asset value is associated with the optimum use of the assets and the revenues that they can generate.ConcessionsIn this form of PPP, the Government defines and grants specific rights to an entity (usually a private company) to build and operate a facility for a fixed period of time. The Government may retain the ultimate ownership of the facility and/or right to supply the services. In concessions, payments can take place both ways: concessionaire pays to government for the concession rights and the government may also pay the concessionaire, which it provides under the agreement to meet certain specific conditions. Usually such payments by government may be necessary to make projects commercially viable and/or reduce the level of commercial risk taken by the private sector, particularly in the initial years of a PPP programme in a country when the private sector may not have enough confidence in undertaking such a commercial venture. Typical concession periods range between 5 to 50 years. It may be noted that in a concession model of PPP, an SPV may not always be necessary.Concessions may be awarded to a concessionaire under two types of contractual arrangements:FranchiseBOT type of contractsFranchiseUnder a franchise arrangement the concessionaire provide services that are fully specified by the franchising authority. The private sector carries commercial risks and may be required to make investments. This form of private sector participation is historically popular in providing urban bus or rail services. Franchise can be used for routes or groups of routes over a contiguous area.Build-Operate-TransferIn a Build-Operate-Transfer or BOT (and its other variants namely Build-Transfer-Operate (BTO), Build-Rehabilitate-Operate-Transfer (BROT), Build-Lease-Transfer (BLT)) type of arrangement, the concessionaire undertakes investments and operates the facility for a fixed period of time after which the ownership reverts back to the public sector. In this type of arrangement, operating and investment risks can be substantiallytransferred to the concessionaire. However, in a BOT type of model the government has explicit and implicit contingent liabilities that may arise due to loan guarantees provided and default of a sub-sovereign government and public or private entity on non-guaranteed loans. By retaining ultimate ownership, the government controls policy and can allocate risks to those parties best suited to bear them or remove them.In a BOT concession, often the concessionaire may be required to establish a special purpose vehicle (SPV) for implementing and operating the project. The SPV may be formed as a joint venture company with equity participation from multiple private sector parties and the public sector. In addition to equity participation, the government may also provide capital grants or other financial incentives to a BOT project. BOT is a common form of PPP in all sectors in Asian countries. A large number of BOT port and road projects have been implemented in the region.Under the Build-Rehabilitate-Operate-Transfer arrangement, a private developer builds an add-on to an existing facility or completes a partially built facility and rehabilitates existing assets, then operates and maintains the facility at its own risk for the contract period. BROT is a popular form of PPP in the water sector.A key distinction between a franchise and BOT type of concession is that, in a franchise the authority is in the lead in specifying the level of service and is prepared to make payments for doing so, whilst in the BOT type the authority imposes a few basic requirements and may have no direct financial responsibility.Private ownership of assetsIn this form of participation, the private sector remains responsible for design, construction and operation of an infrastructure facility and in some cases the public sector may relinquish the right of ownership of assets to the private sector.It is argued that by aggregating design, construction and operation of infrastructure services into one contract, important benefits could be achieved through creation of synergies. As the same entity builds and operates the services, and is only paid for the successful supply of services at a pre-defined standard, it has no incentive to reduce the quality or quantity of services. Compared with the traditional public sector procurement model, where design, construction and operation aspects are usually separated, this formof contractual agreement reduces the risks of cost overruns during the design and construction phases or of choosing an inefficient technology, since the operator’s future earnings depend on controlling costs. The public sector’s main advantages lie in the relief from bearing the costs of design and construction, the transfer of certain risks to the private sector and the promise of better project design, construction and operation.There can be three main types under this form:−Build-Own-Operate type of arrangement−Private Finance Initiative (a more recent innovation)−Divestiture by license or saleBuild-Own-OperateIn the Build-Own-Operate (BOO) type and its other variants such as Design-Build-Finance-Operate, the private sector builds, owns and operates a facility, and sells the product/service to its users or beneficiaries. This is the most common form of private participation in the power sector in many countries. For a BOO power project, the Government (or a power distribution company) may or may not have a long-term power purchase agreement (commonly known as off-take agreement) at an agreed price from the project operator.In many respects, licensing may be considered as a variant of the BOO model of private participation. The Government grants licences to private undertakings to provide services such as fixed line and mobile telephony, Internet service, television and radio broadcast, public transport, and catering services on the railways. However, licensing may also be considered as a form of “concession” with private ownership of assets. Licensing allows competitive pressure in the market by allowing multiple operators, such as in mobile telephony, to provide competing services.There are two types of licensing: quantity licensing and quality licensing. By setting limits through quantity licensing, the government is able to moderate competition between service providers and adjust supply between one area and other. Quality licensing however, does not place any restriction on number of providers or the amount of service produced but specifies the quality of service that needs to be provided. The government may get a fee and a small share of the revenue earned by the private sector under the licensing arrangement.Private Finance InitiativeIn the Private Finance Initiative (PFI) model, the private sector similar to the BOO model builds, owns and operates a facility. However, the public sector (unlike the users in a BOO model) purchases the services from the private sector through a long-term agreement. PFI projects therefore, bear direct financial obligations to government in any event. In addition, explicit and implicit contingent liabilities may also arise due to loan guarantees provided to lenders and default of a public or private entity on non-guaranteed loans.In the PFI model, asset ownership at the end of the contract period may or may not be transferred to the public sector. The PFI model also has many variants.The annuity model for financing of national highways in India is an example of the PFI model. Under this arrangement a selected private bidder is awarded a contract to develop a section of the highway and to maintain it over the whole contract period. The private bidder is compensated with fixed semi-annual payments for his investments in the project. In this approach the concessionaire does not need to bear the commercial risks involved with project operation.Apart from building economic infrastructure, the PFI model has been used also for developing social infrastructure such as school and hospital buildings, which do not generate direct “revenues”.DivestitureThis third type of privatization is clear from its very name. In this form a private entity buys an equity stake in a state-owned enterprise. However, the private stake may or may not imply private management of the enterprise. True privatization, however, involves a transfer of deed of title from the public sector to a private undertaking. This may be done either through outright sale or through public floatation of shares of a previously corporatised state enterprise.Full divestiture of existing infrastructure assets is not very common. However, there are many examples of partial divestiture.。

葡萄城认证工程师考试题

1.在使用ActiveReports设计报表时，若需动态调整报表页眉内容，应使用以下哪种技术？A.表达式（Expressions）B.报表变量（Report Variables）C.数据源直接绑定D.自定义代码段2.SpreadJS中，要实现单元格合并功能，应调用哪个API？A.sheet.mergeCells(startRow, startCol, endRow, endCol)bineWith(anotherCell)C.range.merge()D.sheet.setCellSpan(row, col, rowspan, colspan)3.当使用GrapeCity Documents for Excel生成Excel文件时，若需设置单元格格式为货币类型，应设置其NumberFormat属性为？A."0.00"B."#,##0.00_);(#,##0.00)"C."[$€-2] #,##0.00"D."Currency"4.在ActiveReports中，若要在报表加载时自动执行一段初始化代码，应在哪里编写这段代码？A.报表的Initialize事件处理器B.报表的Load事件处理器C.报表的ReportStart事件处理器D.报表的DataInitialize事件处理器5.SpreadJS支持哪些方式加载外部数据源？（多选）A.JSONB.CSVC.Excel文件（通过FileReader）D.直接从数据库连接6.在使用GrapeCity Documents for PDF创建PDF文档时，若需添加水印效果，应使用哪个类库的功能？A.直接在PDF文档上绘制文本或图形B.使用第三方库添加水印C.GrapeCity Documents for PDF的内置水印功能D.将水印作为图像插入7.当ActiveReports报表中的数据量非常大时，为了提高报表渲染性能，可以采取以下哪种策略？A.禁用报表缓存B.使用分页查询技术C.增加报表的分辨率D.减少报表的样式复杂度8.在SpreadJS中，若要实现数据验证功能（如限制输入为数字或特定范围内的值），应使用哪个API或功能？A.validation 规则B.dataBind 与数据源验证C.cellType 属性D.自定义JavaScript函数进行验证9.GrapeCity Documents for Excel支持哪些方式保存生成的Excel文件？A.仅支持保存到服务器文件系统B.可通过客户端JavaScript直接下载C.仅支持通过API接口发送到外部服务D.必须使用第三方库进行保存10.当使用GrapeCity的某个产品（如SpreadJS或ActiveReports）进行开发时，若遇到技术难题，应优先采取哪种方式寻求帮助？A.在Stack Overflow等社区发帖B.查阅官方文档和教程C.直接联系葡萄城技术支持D.在社交媒体上询问同行经验。

Aero-Mortive RI25 Series Service Manual

RI25 SeriesService Manual AERO-MOTIVE COMPANYA Woodhead Industries, Inc. SubsidiaryIMPORTANT SAFETY INSTRUCTIONSPlease read this manual carefully and follow its instructions. Improper use or failure to follow these instructions could result in serious injury, death or property damage. Operators should be instructed in the safe and proper use and maintenance of this product. Keep this manual for future reference.The following safety precautions call attention to potentially dangerous conditions.NOTE: Instruct operators in the safe, proper use and maintenance. Keep this manual for future reference. INSTALLATIONMOUNTINGReel may be mounted in any position as long as main shaft is horizontal. If possible, mount reel withintwo feet of an electrical outlet. For location of more then two feet, use a three-conductor extension cord,with wire size equal to or larger than what is on the reel. Use mounting bracket as a template for locationof the ¼” screw holes. Measuring from centers of screw holes, template dimensions are 3-11/16” by 7/8”.SECONDARY SUPPORT CHAINA hole is provided at base of reel to permit installation of a secondary support chain. All reels mountedover head should have a secondary support chain to protect personnel in case of structure or mountingcomponent failure. Attach one end of secondary support chain or cable to secondary support point onreel. Attach other end of secondary support chain or cable to a support component other than that whichsupports reel. The chain or cable should be as short as possible allowing reel to drop no more than 6 to12 inches if primary connection is released. A secondary support is offered as an accessory item.WIRINGAll internal wiring has been completed at the factory. Models equipped with a handle and bulb guard arecompletely wired and ready for installation.OPTIONAL AUTOMATIC SWITCHWhen cable is retracted into reel, ball stop will trigger switch to shut off power. To install, remove screwsfrom cable guide, place switch over guide, and replace screws. Plug cord from reel into switch, and thenplug cord from switch into power source.ADJUSTMENTTENSION ADJUSTMENTNOTE: Adjust tension before or after installation of reel.Pull cable out to determine if more or less tension is desired. Place wrench onthe end of main shaft over flat. While holding wrench firmly, pull pin on housinguntil it allows shaft to rotate. Pull out on the lock pin knob and turn shaft withwrench counter-clockwise to decrease tension and clockwise to increasetension. Re-engage pin when desired tension has been set. Pull cable outcompletely to insure enough spring revolutions remain for operating, but makingsure not to bottom out the spring before cable is fully extended. If entire cableassembly cannot be pulled out, decrease spring tension until it can. Shouldhave a minimum 2-3 pretension turns for best spring life.RATCHET LOCKThe ratchet lock engages in three positions for each complete revolution of thedrum. Pull cable to desired location, and then let cable retract slightly until lockengages, much like a window shade. To decrease lock, pull cable out slightly.OVERHANGSlide ball stop along cable until light hangs at desired length when cord is fully retracted.SERVICESPRING REPLACEMENTRemove ALL tension, if spring is not already broken. Remove screw from main shaft & complete cover.Remove retaining ring and pull tension pin out, then slide complete drum assembly and shaft out ofhousing. Remove shaft, slip ring and cable from spool assembly. Spring is containerized in drum, andshould not be removed. Reinstall shaft, cable, and slip ring on new spool assembly. Be sure shaftengages hook on spring when reassembling. To assure longest spring life preturns must be applied tospring before using. See section “Tension Adjustment”.RATCHET LOCK REPLACEMENTFollow the procedure as outlined in working cable & collector ring replacement (above). Removeretaining ring and unclip spring of ratchet lock from housing. To reassemble, reverse above procedure.WORKING CABLE & COLLECTOR RING REPLACEMENTRemove tension and unplug reel. Remove screw from main shaft andremove complete cover. Take off retaining ring and pull down tension pinon side of housing, then slide complete spool and shaft out of mainhousing. Remove the four screws to slip ring. Pull slip ring assembly outand disconnect wire. Replace slip ring if necessary. Remove spring clip,and if equipped with hand lamp, remove from working cable and slide offball stop. (See HAND LAMP REPLACEMENT below). Replace old cablewith new and reassemble by reversing above procedure.HAND LAMP REPLACEMENT AND INSTALLATIONIncandescent: Remove guard and bulb. Remove screws from sides of handle. Remove cable stopassembly, bumper, spring, ball, and cable wiring. Strip wire as needed and wire cable to replacement handle: black to brass screw, white to silver screw, and green to green screw. Reverse the aboveprocedure to reassemble.Power Cord or Transform Assembly: Remove bolt to open reel cover. Remove the wires that connect the power cord/transformer assembly wires to the brush plate. Attach the lugs on the newcord/transformer assembly wires to the brush assembly. Reassemble the reel.13W Florescent: Disassemble newhand lamp. Strip the black andwhite wires from the cord and tinends. Cut and remove the greenwire as close to the outer jacket aspossible. Press replacement lampinto connector until firmly retained.Push stripped and tinned wire leadsinto quick-connect wiring holes inbottom of connector. Slidereplacement lamp into protectivetube so that the end of the lamp isseated in the end of the tube. Slidetube and lamp assembly into thehandle while pulling cord until tubeand lamp are seated. Secure tubewith screws in sides of handle.Replace nut, plastic washer, andrubber strain relief onto lamp handle.13G Florescent: Disassemble newhand lamp. Strip the black and whitewires. Cut and remove the greenwire as close to the outer jacket aspossible. Pull cable through endcap. Use wire nuts to connect tohand-lamp lead wires. Make surewire seated properly in the socketbas. Use long screws to reassemblesocket base. Slide replacementlamp into socket and protective tubeover lamp. Use short screws hold ontube. Push end cap all the way on tosocket end while pulling cord backthrough until tube and lamp asnecessary.REPLACEMENT PARTSReferenceNumberPart Number Qty.Description 1C017001311Ring; Retaining (.625 O.D.)2020*******Pin 302009000YE 1Bracket; Swivel Mount 400288P00101Pin; Cotter 5C010102221Washer; Flat 3/8”8M107200771Cable; Working (RI25-13W, -13G, and 13S)900920P00011Clamp; Spring 1057730000001Assembly; Collector Ring 1100002P04181Screw; #10-24 x ¾ ” R.D.H.M.12M564200021Cover (SR SIDE)1300102P00582Washer; Lock #10 (external tooth)1400151P00252Nut; #10-24 Jam CAD. PLT.1500078P00031Nut; Push On (.156)1600005P01101Screw; #10-24 x ½ ” T.R.H.M.1700102P00301Washer; Lock #6 (external tooth)Incl. w/ item 321Assembly; Cord (service part) (RI25-13W & 13G)2062004000001Relief; Strain 2162148000001Insulation Strip 2200576P00391Ring; External Retaining (.05 O.D.)23M273200041Shaft; Main 2457727000001Spring; Ratchet 25C017001191Ring; Retaining (.312 O.D.)2657718000001Lever; Ratchet Lock 27H225200031Housing (Includes Items: #2,3,4,5,6,25,26,27, & 29)2803339000001Guide; Cable 2900047P000100047P000100041P0070C7009040000047P000132121Connector (RI25-3H, -3M)Connector (-3FE, -3FES)Connector (-3FE, -3FES)Connector (-13W, -13WS)Connector (-13S)3057761000001Ball Stop 3100095000001Clamp (-13W & -13WS)32C89440002C89440005C8944001113W H81420038C8948011801101P00351111111Hand Lamp & Guard (-3H)Hand Lamp & Guard (-3FE & -3FES)Hand Lamp (-3M)Fluorescent (-13W)Fluorescent (-13G)Fluorescent (-13S)Oulet 5-15R (-R)3301026P0012AR Switch; Optional AutomaticAero-Motive Company Woodhead Connectivity LTD.Woodhead Asia PTE LTD.Woodhead Canada LTD. A Woodhead Industries Inc. Subsidiary A Woodhead Industries Inc. Subsidiary A Woodhead Industries Inc. Subsidiary A Woodhead Industries Inc. Subsidiary PO Box 2678Kalamazoo, MI 49003-2678USA (269) 337 7700 / (800) 999 8559FAX: (800) 333 ***********************Factory No. 9Rassau Industrial Estate Ebbw Vale Gwent NP23 5SD United Kingdom 44-1495-356300FAX: 44-1495-356301*************.uk No. 4 Toh Tuck LinkLevel 3 MezzanineMarkono Logisitics Bldg.Singapore 59622665-6-261-6533FAX: 65-6-261-3588***************.sg 1090 Brevik Place Mississauga Ontario L4W 3Y5 Canada (905) 624-1079FAX: (905) 624-9151www.woodhead.ca。

1、下载文档前请自行甄别文档内容的完整性，平台不提供额外的编辑、内容补充、找答案等附加服务。
2、"仅部分预览"的文档,不可在线预览部分如存在完整性等问题,可反馈申请退款(可完整预览的文档不适用该条件!)。
3、如文档侵犯您的权益，请联系客服反馈,我们会尽快为您处理(人工客服工作时间：9:00-18:30)。

Where were plays produced in antiquity?
What sort of features might we find in a venue where early drama was performed?
Ancient Greek Theatre
The Theatre Space
Why is it important?
- Classical Greek Theatre was fundamental to the development of drama and theatre in the west both in terms of form and function. - Our understanding of plotting and structure of Tragedy and Comedy were developed by the Greeks. - Theatre developed beyond that of just a religious and sacred ritual to become a form of entertainment, political theatre and didactic tool. - Entertainment VS. Didactic - a key theatrical debate. - The Theatre as a space was developed. The actor and the roles of antagonist (opposition; foe) and protagonist (main character; sometime ‘hero’) were created and the forms of mask, song, codified movement were brought together.
How were Greek tragedies presented?
• How many at a time? –Trilogies –actually tetralogies: 3 tragedies + satyr play actually • What kinds of plays? - Tragedies almost exclusively dealt with stories from the mythic past (no "contemporary" tragedy), comedies almost exclusively with contemporary figures/problems. • Who paid for the production? –a rich man required to do public service (‘choregos’ = chorus leader) a • What was the playwright’s job? teacher”), –Chorodidaskalos (“chorus-teacher”), i.e. he taught the songs/dances to the chorus –and originally he acted in the play himself and
TERMS: Theatron – Seeing Place Orchestra – Dancing Area, circular Parados – Passageway for entering the orchestra Skene – ‘Tent’ a backdrop and entrance to the ‘House’; painted scenery later Eccyclema – “roll out”, Cart on which murdered victims were revealed from the skene
rs and Chorus would have entered through one of entrances: Paradoi or Skene.
ances would have taken place within the a and in front of the skene with the Gods making nces on the top of the skene.
simon: 462-512
dances and sings about the life of the murderer of Laius now that he is a hunted criminal, and then expresses trus in Oedipus' skill, s trust who rescued the city before when he solved the riddle of the Sphinx.
Acting style is presentational (not ealistic); large symbolic codified estures Chorus incorporated song, chant and dance
• • • • • •
the large scale of the theatre space - 15,000 people determined the acting style. Big symbolic gestures, very physical (a whisper or a wink won’t work on this stage). the theatre was designed with good acoustics in mind and so the actor needed to project but did not need to shout to be heard actors faced and spoke their lines out to the audience Actors played several parts. Often the most experienced actors would play both lead male and female parts actors in tragedies wore lose, ceremonial gowns. In comedy they might wear phalluses or other exaggerated body parts to emphasis their ‘low’ character Verbal repetition (just in case you missed it!) and Irony
StructureStructure Terms:
-Prologue Prologue -Parodos Parodos -First Episode or scene (additional Firsode) First -Exodus Exodus
calls on Apollo, Athena, and Artemis to help, and describes the horrors of the plague.
sode: 216-461
claims measures to find the murderer, and calls down curses on him and whoever tries to hide him. The chorus advis Oedipus to c advises r Tiresias, but Oedipus, at Creon's suggestion, has already sent for him. Teiresias is unwilling to identify the murderer, and Oedipus of having helped in the murder of Laius. Teiresias then accuses Oedipus of being the murderer. Oedipus begins to suspect that Creo inst him. Teiresias sets out what will happen to Oedipus, who cannot understand his words.
Episode: 513-633
es, and Oedipus accuses him of plotting to overthrow him. Creon denies it.
Oedipus: (from Green, /)
: 1-150
speaking through a priest, ask Oedipus' help in relieving the plague which is afflicting the city. Oedipus has al already taken steps to h nding Creon to Delphi to ask Apollo's advice. Creon returns and reports that Apollo has commanded that the Theban expell a pollu Thebans and: the murderer of the former King, Laius. Oedipus pledges to find the murderer and expell him. 151-215
eaths would have taken place off stage and the evealed in tableau on an eccyclema (trolley).
were built with the audience facing the south. = lighting, used effectively as the setting sun lit act to the final tragedy of the day.