5外文翻译原文
桥梁毕业设计外文翻译5
附录附录A 外文翻译第一部分英文原文4.2.2 Model that Failed in Punching ShearIt was realized that complete restraint in both the longitudinal and transversedirections is necessary for the development of the internal arching system in the deck slab. With this realization,another half-scale model of a two-girder bridge was built. This model also had a deck slab reinforced only by polypropylene fibres, and was very similar to the previous one, the main difference being that the top flangesof the girders were now interconnected by transverse steel straps lying outside the deck slab. A view of the steel work of this model can be seen in Fig. 4.7.These straps were provided so as to serve as transverse ties to the internal arch in the slab.The 100 mm thick slab of the model with transverse straps failed under a central load of 418 kN in a punching-shear failure mode. As can be seen in Fig. 4.8, the damaged area of the slab was highly localized. It can be appreciated that with such a high failure load, the thin deck slab of the half-scale model could have easily withstood the weights of even the heaviest wheel load of commercial vehicles.The model tests described above and in sub-section 4.2.1 clearly demonstrate that an internal arching action will indeed develop in a deck slab, but only if it is suitably restrained.4.2.3 Edge StiffeningA further appreciation of the deck slab arching action is provided by tests on a scale model of a skew slab-on-girder bridge. As will be discussed in sub-section 4.4.2, one transverse free edge of the deck slab of this model was stiffened by a composite steel channel with its web in the vertical plane. The other free edge was stiffened by a steel channel diaphragm with its web horizontal and connected to the deck slab through shear connectors. The deck slab near the former transverse edge failed in a mode that was a hybrid between punching shear and flexure. Tests near the composite diaphragm led to failure at a much higher load in punching shear (Bakht and Agarwal, 1993).The above tests confirmed yet again that the presence of the internal arching action in deck slabs induces high in-plane force effects which in turn demand stiffer restraint in the plane of the deck than in the out-of-plane direction.4.3 INTERNALLY RESTRAINED DECK SLABSDeck slabs which require embedded reinforcement for strength will now be referred to as internally restrained deck slabs. The state-of-art up to 1986 relating to the quantification and utilization of the beneficial internal arching action in deck slabs with steel reinforcement has been provided by Bakht and Markovic (1986). Their conclusions complemented with up-to-date information are presented in this chapter in a generally chronological order which, however, cannot be adhered to rigidlybecause of the simultaneous occurrence of some developments.4.3.1 Static Tests on Scale ModelsAbout three decades ago, the Structures Research Office of the Ministry of Transportation of Ontario (MTO), Canada, sponsored an extensive laboratory-based research program into the load carrying capacity of deck slabs; this research program was carried out at Queen's University, Kingston, Ontario. Most of this research was conducted through static tests on scale models of slab-on-girder bridges. This pioneering work is reported by Hewitt and Batchelor (1975) and later by Batchelor et al. (1985), and is summarized in the following.The inability of the concrete to sustain tensile strains, which leads to cracking, has been shown to be the main attribute which causes the compressive membrane forces to develop. This phenomenon is illustrated in Fig. 4.9 (a) which shows the part cross-section of slab-on-girder bridge under the action of a concentrated load.The cracking of the concrete, as shown in the figure, results in a net compressive force near the bottom face of the slab at each of the two girder locations. Midway between the girders, the net compressive force moves towards the top of the slab. It can be readily visualized that the transition of the net compressive force from near the top in the middle region, to near the bottom at the supports corresponds to the familiar arching action. Because of this internal arching action, the failure mode of a deck slab under a concentrated load becomes that of punching shear.If the material of the deck slab has the same stress-strain characteristics in both tension and compression, the slab will not crack and, as shown in Fig. 4.9 (b), will not develop the net compressive force and hence the arching action.In the punching shear type of failure, a frustum separates from the rest of the slab, as shown in schematically in Fig. 4.10. It is noted that in most failure tests, the diameter of the lower end of the frustrum extends to the vicinity of the girders.From analytical and confirmatory laboratory studies, it was established that the most significant factor influencing the failure load of a concrete deck slab is the confinement of the panel under consideration. It was concluded that this confinement is provided by the expanse of the slab beyond the loaded area; its degree was founddifficult to assess analytically. A restraint factor, η, was used as an empirical measure of the confinement; its value is equal to zero for the case of no confinement and 1.0 for full confinement.The effect of various parameters on the failure load can be seen in Table 4.1, which lists the theoretical failure loads for various cases. It can be seen that an increase of the restraint factor from 0.0 to 0.5 results in a very large increase in the failure load. The table also emphasizes the fact that neglect of the restraint factor causes a gross underestimation of the failure load.It was concluded that design for flexure leads to the inclusion of large amounts of unnecessary steel reinforcement in the deck slabs, and that even the minimum amount of steel required for crack control against volumetric changes in concrete is adequate to sustain modern-day, and even future, highway vehicles of North America.It was recommended that for new construction, the reinforcement in a deck slab should be in two layers, with each layer consisting of an orthogonal mesh having the same area of reinforcement in each direction. The area of steel reinforcement in each direction of a mesh was suggested to be 0.2% of the effective area of cross-section of the slab. This empirical method of design was recommended for deck slabs with certain constraints.4.3.2 Pulsating Load Tests on Scale ModelsTo study the fatigue strength of deck slabs with reduced reinforcement, five small scale models with different reinforcement ratios in different panels were tested at the Queen's University at Kingston. Details of this study are reported by Batchelor et al. (1978).Experimental investigation confirmed that for loads normally encountered in North America deck slabs with both conventional and recommended reducedreinforcement have large reserve strengths against failure by fatigue. It was confirmed that the reinforcement in the deck slab should be as noted in sub-section 4.3.1. It is recalled that the 0.2% reinforcement requires that the deck slab must have a minimum restraint factor of 0.5.The work of Okada, et al. (1978) also deals with fatigue tests on full scale models of deck slabs and segments of severely cracked slab removed from eight to ten year old bridges. The application of these test results to deck slabs of actual bridges is open to question because test specimens were removed from the original structures in such a way that they did not retain the confinement necessary for the development of the arching action.4.3.3 Field TestingAlong with the studies described in the preceding sub-section, a program of field testing of the deck slabs of in-service bridges was undertaken by the Structures Research Office of the MTO. The testing consisted of subjecting deck slabs to single concentrated loads, simulating wheel loads, and monitoring the load-deflection characteristics of the slab. The testing is reported by Csagoly et al. (1978) and details of the testing equipment are given by Bakht and Csagoly (1979).Values of the restraint factor, η, were back-calculated from measured deflections.A summary of test results, given in Table 4.2, shows that the average value of η in composite bridges is greater than 0.75, while that for non-composite bridges is 0.42. It was concluded that for new construction, the restraint factor, η, can be assumed to have a minimum value of 0.5.Bakht (1981) reports that after the first application of a test load of high magnitude on deck slabs of existing bridges, a small residual deflection was observed in most cases. Subsequent applications of the same load did not result in further residual deflections. It is postulated that the residual deflections are caused by cracking of the concrete which, as discussed earlier, accompanies the development of the internal arching action. The residual deflections after the first cycle of loading suggest that either the slab was never subjected to loads high enough to cause cracking, or the cracks have 'healed' with time.第二部分汉语翻译4.2.2 在冲切剪应力下的实效模型我们已经知道在桥面板内部拱形系统的形成中，不仅纵向而且横向也被完全约束限制是完全必要的。
中国的对外贸易外文翻译及原文
外文翻译原文Foreign T rade o f ChinaMaterial Source:W anfang Database Author:Hitomi Iizaka1.IntroductionOn December11,2001,China officially joined the World T rade Organization(WTO)and be c a me its143rd member.China’s presence in the worl d economy will continue to grow and deepen.The foreign trade sector plays an important andmultifaceted role in China’s economic development.At the same time, China’s expanded role in the world economy is beneficial t o all its trading partners. Regions that trade with China benefit from cheaper and mor e varieties of imported consumer goods,raw materials and intermediate products.China is also a large and growing export market.While the entry of any major trading nation in the global trading system can create a process of adjustment,the o u t c o me is fundamentally a win-win situation.In this p aper we would like t o provide a survey of the various institutions,laws and characteristics of China’s trade.Among some of the findings, we can highlight thefollowing:•In2001,total trade to gross domestic pr oduct(GDP)ratio in China is44%•In2001,47%of Chinese trade is processed trade1•In2001,51%of Chinese trade is conduct ed by foreign firms in China2•In2001,36%of Chinese exports originate from Gu an gdon g province•In2001,39%of China’s exports go through Hong Kong to be re-exported elsewhere2.Evolution of China’s Trade RegimeEqually remarkable are the changes in the commodity composition of China’s exports and imports.Table2a shows China’s annu al export volumes of primary goods and manufactured goods over time.In1980,primary goods accounted for 50.3%of China’s exports and manufactured goods accounted for49.7%.Although the share of primary good declines slightly during the first half of1980’s,it remains at50.6%in1985.Since then,exports of manufactured goods have grown at a muchfaster rate than exports of primary goods.As a result,the share of manufactur ed goods increased t o90.1%,and that of primary good decr eased to9.9%by2001.Also shown in those tables are five subgr oups for manufactur ed goods and primary goods.China’s export was highly dependent on its exports of coal, petroleum,and petr oleum products until mid-80s.The large export volume of petr oleum was also support ed by a sharp rise in oil prices during the period.In1985, the share of mineral fuels is26.1%.In1986,the su d d en decline in the share of primary goods in total exports occurs,which is largely associated with the decline in the export volume of mineral fuels.The price reforms coupled with the declined world petr oleum price areattributable t o the decline.Domestic agriculture production expanded during the1980’s in response to the higher prices thr ough the price reforms and mo r e opportunities given t o the producers to market their products.Although the share of food and live animals in total exports has declined over time,China has become a net exporter of such products since1984.T urning to the manufactur ed goods,the large increase in the share of the manufactur ed goods in the total exports since mid-80s is largely accounted for by the increase in the export in the textile category and the miscellaneous products category.These two gr oups include labor-intensive products such as textiles,apparel, footwear,and toys and sporting goods.During the1990s,the category that exhibited the mos t significant surge in exports is machinery and transport equipment.Its share exp anded from9.0%in1990t o35.7%in2001.3.China’s Processing Trade and Trade by For eign Invested FirmsChina established the legal framework for processing and assembly arrangements in1979.Since then,China has built up considerable strengths in assembling and processing of industrial parts and components.It covers a wide range of industries such as electric machinery,automobile,aerospace,and shipbuilding.T able3a and T able3b demonstrate the amount of processing exports and imports and the importance of stateowned enterprises(SOEs)and foreign-invested enterprises(FIEs)in such forms of trade for1995-2001. Throughout the period from1995to2001,the shares of these two types of processing exports exceed more than half of China’s total exports.In2001，processing exports account for55.4%of the total exports.As is seen in T able3a, process&assembling was dominat ed by SOEs in1995.However,the tr end has been changing.The share of SOEs in process&assembling has been steadilydeclining over the years from84%in1995to62%in2001.The other type of trade, process with imported materials was largely conducted by FIEs and their shares have been gradually increasing from81%in1995to88%in2001.In China’s imports(see T able3b),processing trade is relatively small comp a r ed to exports. After it peak ed at49%in1997,processed imports decline to39%in2001.The decreasing importance of SOEs can be seen in China’s imports as well.Shares by SOEs decr eased from81%in1995t o58%in2001for process&assembling,and from18%to7%for process with imported materials.The decr eased role for SOEs in processing trade may reflect the inefficiency in conducting their business.Since 1997,the Chinese government decided t o implement the shareholding system and t o sell a large numbe r of medium-and small-sized SOEs to the private sector.A n u mbe r of larger enterprise gr oups will be established in various industries thr ough mergers,acquisitions,and leasing and contracting.The restructuring of SOEs is intended to increase profits and to improve their competitive edge.4.China’s Tr ade by Provinces and RegionsA regional breakdown of exports and imports reveals important characteristics of the foreign trade in China.In1997,89.1%of the total exports came from the Eastern region of China(Beijing,Tianjin,Heibei,Lioaning,Guangxi,Shanghai, Jiangsu,Zhejiang,Fujian,Shangdong,Guandong and Hainan).Within the East,the Southeast region accounts for76.3%of China's exports in1997.4Gu ang dong alone pr oduces41.6%of the total exports for the sa me year.Such regional imbalances in exporting activities persist to the present day.In2001,Guandong's share of the national exports is36.0%.For the Southeast and the East,the shares are respectively 79.0%and91.1%.This imbalance of the regional growth in foreign trade may partially be attributed t o the various geographic-specific and sequential o pen-d oo r policies China has exercised thr oughout the last twenty years.The strong growth of th e export sector in the coastal area has been support ed by the massive use of foreign direct investment(FDI).FDI was first attracted by the creation of the Special Economic Zones(SEZ).FDI was concentrated in the provinces of the Southeast coast,namely,Guandong and Fujian.The multinational enterprises that are export-oriented or use adv anced technologies are able to enjoy various preferential policies in the SEZs,such as r educed or ex empt e d corporate income tax,exemption from import tariffs on imported equipment and raw materials.In1984,fourteen coastal cities were opened and were grant ed similar policies as SEZs.Out of thosefourteen cities,ten are located in the Southeast coast regions and four are in the rest of the Eastern regions.Furthermore in1985,similar preferential policies were grant ed t o other coastal economic regions,Pearl River Delta,Y angtze River Delta and Minnan Delta which is t o the south of Fujian.In1990,Pu d o n g in Shanghai was opened and was grant ed extensive preferential policies.Since1984,the Chinese government established thirty-two national-level Economic and T echnological Development Zones(ETDZs).The share of exports in The Y angtze River Delta,the home of Shanghai and two provinces,Jiangsu and Zhejiang has grown steadily during the period1997to 2001.The share of those three regions grew to10.1%,11.0%,and9.1%in2001 from8.1%,7.9%and5.9%in1997,respectively.As the role of high-tech industry beco mes mo r e significant in China’s output and China’s comparative advantage in skilled-labor and capital-intensive industries beco mes higher,the Y angtze River Delta be co mes a new magnet for investment by foreign enterprises.These foreign investments in turn lead to mo r e export and trade.5.Foreign T rade by Major World RegionsUsing China’s official statistics,Table4a and4b highlight merchandise export s and imports t o and from major world regions for1993-2001:Asia,Africa,Europe, Latin America,North America and Oceania.As we see from Table4a,China’s most important export region has always been Asia,which absorbs53%of China’s exports in2001.However,their share of absorption declines from almost62%,their peak level of1995.The importance of North America and Europe in China’s exports, however,has been increasing since1998.In2001,North America takes in mo r e than22%of exports and Europe takes in mo r e than18%.6.China’s Merchandise Exports and Imports by Major Trading PartnersTable5a and Table5b document China’s merchandise exports to and imports from its major trading partners,using China’s official statistics.According to Tabl e 5a,the major exports markets for China in2001are:the United States(20.4%), Hong Kong(17.5%),Japan(16.9%)and the European Union(15.4%).It is well-known that a large proportion of Chinese exports to Hong Kong are re-exported elsewhere so that the true size of the Hong Kong export market has t o be estimated. T o save space for this paper,we will just rely on the official Chinese figures.6Even without adjusting for re-exports,the United States in2001is the largest export market for China.Thus,from an international trade perspective alone,the most important bilateral trade relationship for China is the relationship with the UnitedStates.T ogether t he United States,Hong Kong,Japan and the European Union take in70.2%of China’s exports in2001.Within ASEAN(Association of Southeast Asian Nations),Singapore has been the largest export market for China.In2001, 31.5%of China’s total exports to ASEAN is destined for Singapore.Within the European Union(EU),Germany is the largest market with23.8%of the total Chinese exports going to the EU.9.ConclusionIn the future,we see that there are at least two challenges facing China in the area of international trade.First,with China’s competitiveness growing,many countries will perceive that their producers will no t be able to c o mpe t e with the Chinese exports,either in the third market or in their own domestic market.The backlash will take the form of an increased use of anti-dumping duties and safeguards.W e have already seen the use of such trade instruments against China from a variety of countries,including Japan,the European Union and the United States.A relatively new development is that even developing countries such as India and Mexico are using anti-dumping measur es against Chinese exports to their countries.The difficulty with anti-dumping duties is that they are generally WT O-consistent.Thus joining the WTO d o es no t mean that other countries will reduce their use of anti-dumping duties against China.A second challenge facing China is how t o manage its trade relationship with the United States.The United States is the largest economy on earth.The United States is China’s largest export market.It is also a critical source of technology.A stable and healthy relationship with the United States is important for China’s economic development.It is always a difficult adjustment process for countries to accept a newly e mer gen t economic power.The United States as well as other countries may perceive China as a potential economic threat.Judging from the experience of the relationship betw een the United States and a rising Japan in the 1970s and the1980s,it will n o t be too har d to imagine that there will be difficulties in the trade relationship betw een the United States and China.Managing and smoothing such a relationship should be an important goal for China.译文中国的对外贸易资料来源:万方数据库作者：Hitomi Iizaka1、简介2001年12月11日，中国正式加入世界贸易组织（WTO），成为其第143个成员，中国在世界经济中的作用将继续增强和深化。
(完整版)外文翻译
外文文献原稿和译文原稿logistics distribution center location factors:(1) the goods distribution and quantity. This is the distribution center and distribution of the object, such as goods source and the future of distribution, history and current and future forecast and development, etc. Distribution center should as far as possible and producer form in the area and distribution short optimization. The quantity of goods is along with the growth of the size distribution and constant growth. Goods higher growth rate, the more demand distribution center location is reasonable and reducing conveying process unnecessary waste.(2) transportation conditions. The location of logistics distribution center should be close to the transportation hub, and to form the logistics distribution center in the process of a proper nodes. In the conditional, distribution center should be as close to the railway station, port and highway.(3) land conditions. Logistics distribution center covers an area of land in increasingly expensive problem today is more and more important. Is the use of the existing land or land again? Land price? Whether to conform to the requirements of the plan for the government, and so on, in the construction distribution center have considered.(4) commodities flow. Enterprise production of consumer goods as the population shift and change, should according to enterprise's better distribution system positioning. Meanwhile, industrial products market will transfer change, in order to determine the raw materials and semi-finished products of commodities such as change of flow in the location of logistics distribution center should be considered when the flow of the specific conditions of the relevant goods.(5) other factors. Such as labor, transportation and service convenience degree, investment restrictions, etc.How to reduce logistics cost，enhance the adaptive capacity and strain capacity of distribution center is a key research question of agricultural product logistics distribution center．At present，most of the research on logistics cost concentrates off theoretical analysis of direct factors of logistics cost, and solves the problem of over-high logistics Cost mainly by direct channel solution．This research stresses on the view of how to loeate distribution center, analyzes the influence of locating distribution center on logistics cost．and finds one kind of simple and easy location method by carrying on the location analysis of distribution center through computer modeling and the application of Exeel．So the location of agricultural product logistics distribution center can be achieved scientifically and reasonably, which will attain the goal of reducing logistics cost, and have a decision．making support function to the logisties facilities and planning of agricultural product．The agricultural product logistics distribution center deals with dozens and even hundreds of clients every day, and transactions are made in high-frequency. If the distribution center is far away from other distribution points，the moving and transporting of materials and the collecting of operational data is inconvenient and costly. costly．The modernization of agricultural product logistics s distribution center is a complex engineering system，not only involves logistics technology, information technology, but also logistics management ideas and its methods，in particular the specifying of strategic location and business model is essential for the constructing of distribution center. How to reduce logistics cost，enhance the adaptive capacity and strain capacity of distribution center is a key research question of agricultural product logistics distribution center. The so—called logistics costs refers to the expenditure summation of manpower, material and financial resources in the moving process of the goods．such as loading and unloading，conveying，transport，storage，circulating，processing, information processing and other segments. In a word。
电气工程及其自动化专业外文文献英文文献外文翻译方面
1、 外文原文（复印件）A: Fundamentals of Single-chip MicrocomputerT h e sin gle -ch ip mi c ro co m p u t e r is t h e cu lm in at io n of b ot h t h e d e ve lo p me nt of t h e d ig ita l co m p u t e r a n d t h e i nte g rated c ircu it a rgu ab l y t h e to w mo st s ign if i cant i nve nt i o n s of t h e 20t h c e nt u ry [1].T h ese to w t yp e s of arch ite ct u re are fo u n d in s in gle -ch ip m i cro co m p u te r. S o m e e mp l oy t h e sp l it p ro gra m /d at a m e m o r y of t h e H a r va rd arch ite ct u re , s h o wn in -5A , ot h e rs fo l lo w t h e p h i lo so p hy, wid e l y ad a p ted fo r ge n e ral -p u rp o se co m p u te rs an d m i cro p ro ce ss o rs , of m a kin g n o l o g i ca l d i st in ct i o n b et we e n p ro gra m an d d ata m e m o r y as in t h e P rin c eto n a rch ite ct u re , sh o wn in -5A.In ge n e ra l te r m s a s in g le -ch ip m ic ro co m p u t e r is ch a ra cte r ized b y t h e in co r p o rat io n of all t h e u n its of a co mp u te r into a s in gle d e vi ce , as s h o w n in F i g3-5A-3.-5A-1A Harvard type-5A. A conventional Princeton computerProgrammemory Datamemory CPU Input& Output unitmemoryCPU Input& Output unitResetInterruptsPowerFig3-5A-3. Principal features of a microcomputerRead only memory (ROM).RO M is u su a l l y fo r t h e p e r m an e nt , n o n -vo lat i le sto rage of an ap p l i cat io n s p ro g ram .M a ny m i c ro co m p u te rs a n d m i cro co nt ro l le rs are inte n d ed fo r h i gh -vo lu m e ap p l i cat io n s a n d h e n ce t h e e co n o m i cal man u fa c t u re of t h e d e vi ces re q u ires t h at t h e co nt e nts of t h e p ro gra m me mo r y b e co mm i ed p e r m a n e nt l y d u r in g t h e m a n u fa ct u re of c h ip s . C lea rl y, t h i s imp l ies a r i go ro u s ap p ro a ch to ROM co d e d e ve lo p m e nt s in ce ch an ges can n o t b e mad e af te r m an u fa ct u re .T h i s d e ve l o p m e nt p ro ces s m ay i nvo l ve e mu l at i o n u sin g a so p h ist icated d e ve lo p m e nt syste m wit h a h ard wa re e mu l at i o n capab i l it y as we ll as t h e u s e of p o we rf u l sof t war e to o l s.So m e m an u fa ct u re rs p ro vi d e ad d it i o n a l ROM o p t io n s b y in clu d in g in t h e i r ran ge d e v ic es w it h (o r inte n d ed fo r u s e wit h ) u se r p ro g ram m a b le m e mo r y. T h e s im p lest of t h e se i s u su a l l y d e v i ce wh i ch can o p e rat e in a m i cro p ro ce s so r mo d e b y u s in g s o m e of t h e in p u t /o u t p u t l in es as an ad d res s a n d d ata b u s fo r a cc es sin g exte rn a l m e m o r y. T h is t yp e o f d e vi ce can b e h ave f u n ct i o n al l y as t h e s in gle ch ip m i cro co m p u t e r f ro m wh i ch it i s d e ri ved a lb e it wit h re st r icted I/O an d a m o d if ied exte rn a l c ircu it. T h e u s e of t h e se RO M le ss d e vi ces i s co mmo n e ve n in p ro d u ct io n circu i ts wh e re t h e vo lu m e d o e s n ot ju st if y t h e d e ve lo p m e nt co sts of cu sto m o n -ch ip ROM [2];t h e re ca n st i ll b e a si gn if i cant sav in g in I/O an d o t h e r ch ip s co m pared to a External Timing components System clock Timer/ Counter Serial I/O Prarallel I/O RAM ROMCPUco nve nt io n al m i c ro p ro ces so r b ased circ u it. M o re exa ct re p l a ce m e nt fo rRO M d e v ice s can b e o b tain ed in t h e fo rm of va ria nts w it h 'p i g g y-b a c k'E P ROM(E rasab le p ro gramm ab le ROM )s o cket s o r d e v ice s w it h E P ROMin stead of ROM 。
5G无线通信网络中英文对照外文翻译文献
5G无线通信网络中英文对照外文翻译文献(文档含英文原文和中文翻译)翻译：5G无线通信网络的蜂窝结构和关键技术摘要第四代无线通信系统已经或者即将在许多国家部署。
然而，随着无线移动设备和服务的激增，仍然有一些挑战尤其是4G所不能容纳的，例如像频谱危机和高能量消耗。
无线系统设计师们面临着满足新型无线应用对高数据速率和机动性要求的持续性增长的需求，因此他们已经开始研究被期望于2020年后就能部署的第五代无线系统。
在这篇文章里面，我们提出一个有内门和外门情景之分的潜在的蜂窝结构，并且讨论了多种可行性关于5G无线通信系统的技术，比如大量的MIMO技术，节能通信，认知的广播网络和可见光通信。
面临潜在技术的未知挑战也被讨论了。
介绍信息通信技术（ICT）创新合理的使用对世界经济的提高变得越来越重要。
无线通信网络在全球ICT战略中也许是最挑剔的元素，并且支撑着很多其他的行业，它是世界上成长最快最有活力的行业之一。
欧洲移动天文台（EMO）报道2010年移动通信业总计税收1740亿欧元,从而超过了航空航天业和制药业。
无线技术的发展大大提高了人们在商业运作和社交功能方面通信和生活的能力无线移动通信的显著成就表现在技术创新的快速步伐。
从1991年二代移动通信系统(2G)的初次登场到2001年三代系统（3G）的首次起飞，无线移动网络已经实现了从一个纯粹的技术系统到一个能承载大量多媒体内容网络的转变。
4G无线系统被设计出来用来满足IMT-A技术使用IP面向所有服务的需求。
在4G系统中，先进的无线接口被用于正交频分复用技术（OFDM），多输入多输出系统（MIMO）和链路自适应技术。
4G无线网络可支持数据速率可达1Gb/s的低流度，比如流动局域无线访问，还有速率高达100M/s的高流速，例如像移动访问。
LTE系统和它的延伸系统LTE-A，作为实用的4G系统已经在全球于最近期或不久的将来部署。
然而，每年仍然有戏剧性增长数量的用户支持移动宽频带系统。
外文文献翻译译稿和原文【范本模板】
外文文献翻译译稿1卡尔曼滤波的一个典型实例是从一组有限的，包含噪声的，通过对物体位置的观察序列(可能有偏差）预测出物体的位置的坐标及速度。
在很多工程应用（如雷达、计算机视觉）中都可以找到它的身影。
同时，卡尔曼滤波也是控制理论以及控制系统工程中的一个重要课题。
例如，对于雷达来说，人们感兴趣的是其能够跟踪目标.但目标的位置、速度、加速度的测量值往往在任何时候都有噪声。
卡尔曼滤波利用目标的动态信息，设法去掉噪声的影响，得到一个关于目标位置的好的估计.这个估计可以是对当前目标位置的估计(滤波),也可以是对于将来位置的估计（预测），也可以是对过去位置的估计（插值或平滑).命名[编辑]这种滤波方法以它的发明者鲁道夫。
E。
卡尔曼(Rudolph E. Kalman）命名，但是根据文献可知实际上Peter Swerling在更早之前就提出了一种类似的算法。
斯坦利。
施密特（Stanley Schmidt)首次实现了卡尔曼滤波器。
卡尔曼在NASA埃姆斯研究中心访问时,发现他的方法对于解决阿波罗计划的轨道预测很有用，后来阿波罗飞船的导航电脑便使用了这种滤波器。
关于这种滤波器的论文由Swerling（1958）、Kalman (1960)与Kalman and Bucy（1961）发表。
目前,卡尔曼滤波已经有很多不同的实现.卡尔曼最初提出的形式现在一般称为简单卡尔曼滤波器。
除此以外，还有施密特扩展滤波器、信息滤波器以及很多Bierman, Thornton开发的平方根滤波器的变种.也许最常见的卡尔曼滤波器是锁相环，它在收音机、计算机和几乎任何视频或通讯设备中广泛存在。
以下的讨论需要线性代数以及概率论的一般知识。
卡尔曼滤波建立在线性代数和隐马尔可夫模型(hidden Markov model）上.其基本动态系统可以用一个马尔可夫链表示，该马尔可夫链建立在一个被高斯噪声（即正态分布的噪声）干扰的线性算子上的。
系统的状态可以用一个元素为实数的向量表示.随着离散时间的每一个增加，这个线性算子就会作用在当前状态上，产生一个新的状态,并也会带入一些噪声,同时系统的一些已知的控制器的控制信息也会被加入。
外文翻译原文
Stability of hybrid system limit cycles: application to the compass gait biped RobotIan A. Hiskens'Department of Electrical and Computer EngineeringUniversity of Illinois at Urbana-ChampaignUrbana IL 61801 USAAbstractLimit cycles are common in hybrid systems. However the non-smooth dynamics of such systems makes stability analysis difficult. This paper uses recent extensions of trajectory sensitivity analysis to obtain the characteristic multipliers of non-smooth limit cycles. The stability of a limit cycle is determined by its characteristic multipliers. The concepts are illustrated using a compass gait biped robot example.1 IntroductionHybrid system are characterized by interactions between continuous (smooth) dynamics and discrete events. Such systems are common across a diverse range of application areas. Examples include power systems [l], robotics [2, 3], manufacturing [4] and air-traffic control [5]. In fact, any system where saturation limits are routinely encountered can be thought of as a hybrid system. The limits introduce discrete events which (often) have a significant influence on overall behaviour.Many hybrid systems exhibit periodic behaviour. Discrete events, such as saturation limits, can act to trap the evolving system state within a constrained region of state space. Therefore even when the underlying continuous dynamics are unstable, discrete events may induce a stable limit set. Limit cycles (periodic behaviour) are often created in this way. Other systems, such as robot motion, are naturally periodic.Limit cycles can be stable (attracting), unstable (repelling) or non-stable (saddle). The stability of periodic behaviour is determined by characteristic (or Floquet) multipliers. A periodic solution corresponds to a fixed point of a Poincare map. Stability of the periodic solution is equivalent to stability of the fixed point. The characteristic multipliers are the eigenvalues of the Poincare map linearized about the fixed point. Section 4 reviews the connection between this linearized map and trajectory sensitivities.Poincare maps have been used to analyse the stability of limit cycles in various forms of hybrid systems. However calculation of the underlying trajectory sensitivities has relied upon particular system structures, see for example [7, 8], or numerical differencing, for example [6]. This paper uses a recent generalization of trajectory sensitivity analysis [9] to efficiently detemine the stability of limit cycles in hybrid systems.A hybrid system model is given in Section 2. Section 3 develops the associated variational equations. This is followed in Section 4 by a review of stability analysis of limit cycles. Conclusions and extensions are presented in Section 5.2 ModelDeterministic hybrid systems can be represented by a model that is adapted from a differential-algebraic (DAE) structure. Events are incorporated via impulsive action and switching of algebraic equations, giving the Impulsive Switched (DAIS) modelwheren x R ∈ are dynamic states and my R ∈ are algebraic states;(.)δ is the Dirac delta;(.)u is the unit-step function;,:n mnj f h RR +→；(0)(),:i n mng gR R ±+→; some elements of each(.)gwill usually be identicallyzero, but no elements of the composite g should be identically zero; the()i g± aredefined with the same form as g in (2), resulting in a recursive structure for g;,dey yare selected elements of y that trigger algebraic switching and state reset(impulsive) events respectively;dyandeymay share common elements.The impulse and unit-step terms of the DAIS model can be expressed in alternative forms:Each impulse term of the summation in (1) can be expressed in the state reset formwhere the notation x+denotes the value of x just after the reset event, whilstx-andy-refer to the values of x and y just prior to the event.The contribution of each()i g± in (2) can be expressed aswith (2) becomingThis form is often more intuitive than (2).It can be convenient to establish the partitionswherex -are the continuous dynamic states, for example generator angles, velocities andfluxes;z are discrete dynamic states, such as transformer tap positions and protection relay logic states;λ are parameters such as generator reactances, controller gains and switching times. The partitioning of the differential equations f ensures that away from events,x -evolves according to .(,)x y f x --=, whilst z and λ remain constant. Similarly,the partitioning of the reset equationsjhensures thatx -and λ remain constantat reset events, but the dynamic states z are reset to new values given by(,)jh y x z--+=-. The model can capture complex behaviour, from hysteresis and non-windup limits through to rule-based systems [l]. A more extensive presentation of this model is given in [9].Away from events, system dynamics evolve smoothly according to the familiardifferential-algebraic modelwhere g is composed of(0)gtogether with appropriate choices of()i g- or()i g+ ,depending on the signs of the corresponding elements of yd. At switching events (2),some component equations of g change. To satisfy the new g = 0 equation, algebraic variables y may undergo a step change. Reset events (3) force a discrete change in elements of x. Algebraic variables may also step at a reset event to ensure g= 0 is satisfied with the altered values of x. The flows of and y are defined respectively aswhere x(t) and y(t) satisfy (l),(2), along with initial conditions,3 'Ikajectory SensitivitiesSensitivity of the flowsxφandyφto initial conditionsxare obtained bylinearizing (8),(9) about the nominal trajectory,The time-varying partial derivative matrices given in (12),(13) are known as trajectory sensitiuities, and can be expressed in the alternative formsThe formxx ,xy provides clearer insights into the development of thevariational equations describing the evolution of the sensitivities. The alternative form 0(,)x t x φ, 0(,)yt x φ highlights the connection between the sensitivities and the associated flows. It is shown in Section 4 that these sensitivities underlie the linearization of the Poincare map, and so play a major role in determining the stability of periodic solutions.Away from events, where system dynamics evolve smoothly, trajectory sensitivities 0xx andxy are obtained by differentiating (6),(7) withrespect to 0x.This giveswhere/xf x f≡∂∂, and likewise for the other Jacobian matrices. Note that,,,xyxyf fg gare evaluated along the trajectory, and hence are time varyingmatrices. It is shown in 19, 101 that the numerical solution of this(potentially high order) DAE system can be obtained as a by-product of numerically integrating the original DAE system (6),(7). The extra computational cost is minimal. Initial conditions forxx are obtained from (10) aswhere I is the identity matrix. Initial conditions for 0zy follow directly from(17),Equations (16),(17) describe the evolution of the sensitivitiesxx andxybetween events. However at an event, the sensitivities are generally discontinuous. It is necessary to calculate jump conditions describing the step change inxx andxy . For clarity, consider a single switching/reset event, so the model (1),(2) reduces(effectively) to the formLet （(),()x y ττ） be the point where the trajectory encounters the triggering hypersurface s(x,y) = 0, i.e., the point where an event is initiated. This point is called the junction point and r is the junction time. It is assumed the encounter is transversal.Just prior to event triggering, at time τ-, we haveSimilarly,,y x++are defined for time τ+, just after the event has occurred. It isshown in [9] that the jump conditions for the sensitivitiesxx are given byThe assumption that the trajectory and triggering hypersurface meet transversally ensures a non-zero denominator for 0x τ The sensitivitiesxy . immediatelyafter the event are given byFollowing the event, i.e., for t τ+>, calculation of the sensitivities proceeds according to (16),(17) until the next event is encountered. The jump conditions provide the initial conditions for the post-event calculations.4 Limit Cycle AnalysisStability of limit cycles can be determined using Poincare maps [11, 12]. This section provides a brief review of these concepts, and establishes the connection with trajectory sensitivities.A Poincark map effectively samples the flow of a periodic system once every period. The concept is illustrated in Figure 1. If the limit cycle is stable, oscillations approach the limit cycle over time. The samples provided by the corresponding Poincare map approach a fixed point. A non-stable limit cycle results in divergent oscillations. For such a case the samples of the Poincare map diverge.To define a Poincare map, consider the limit cycle Γshown in Figure 1. Let ∑ be a hyperplane transversal to Γ at*x. The trajectory emanating from*xwill again encounter ∑ at*xafter T seconds, where T is the minimum period of the limit cycle. Due to the continuity of the flowxφwith respect to initial conditions, trajectories starting on ∑ in a neighbourhood of*x. will, in approximately T seconds, intersect ∑ in the vicinity of*x. Hencexφand ∑define a mappingwhere()kT x ττ≈ is the time taken for the trajectory to return to ∑. Complete details can hefound in [11,12]. Stability of the Paincare map (22) is determined by linearizing P at the fixed point*x, i.e.,From the definition of P(z) given by (22), it follows that DP(*x) is closely related to thetrajectory sensitivities***(,)(,)xxT T x x xφφ∂≡∂. In fact, it is shown in [11] thatwhereσ is a vector normal to ∑.The matrix*(,)xT x φis exactly the trajectory sensitivity matrix after one period of the limitcycle, i.e., starting from*xand returning to*x. This matrix is called the Monodromymatrix .It is shown in [11] that for an autonomous system, one eigenvalue of *(,)xT x φ isalways 1, and the corresponding eigenvector lies along **(,)f y x The remaining eigenvalues*(,)xT x φof coincide with the eigenvalues of DP(*x ), and are known as the characteristicmultipliers mi of the periodic solution. The characteristic multipliers are independent of the choice of cross-section ∑ . Therefore, for hybrid systems, it is often convenient to choose ∑ as a triggering hypersurface corresponding to a switching or reset event that occurs along the periodic solution.Because the characteristic multipliers mi are the eigenvalues of the linear map DP(x*), they determine the stability of the Poincarb map P(kx), and hence the stability of the periodic solution.Three cases are of importance: 1. Alli m lie within the unit circle, i.e., 1im<,i ∀.The map is stable, so the periodicsolution is stable. 2. Allim lie outside the unit circle. The periodic solution is unstable.3. Someim lie outside the unit circle. The periodic solution is non-stable.Interestingly, there exists a particular cross-section*∑, such thatwhere *ς∈∑.This cross-section*∑is the hyperplane spanned by the n - 1 eigenvectors of*(,)xT x φthat are not aligned with **(,)f y x . Therefore the vector *σthat is normal to*∑ is the left eigenvector of *(,)xT x φ corresponding to the eigenvalue 1. The hyperplane*∑is invariant under*(,)xT x φ, i.e., **(,)f y x maps vectors *ς∈∑back into*∑.5 ConclusionsHybrid systems frequently exhibit periodic behaviour. However the non-smooth nature of such systems complicates stability analysis. Those complications have been addressed in this paper throughapplication of a generalization of trajectory sensitivity analysis. Deterministic hybrid systems can be represented by a set ofdifferential-algebraic equations, modified to incorporate impulse (state reset) action and constraint switching. The associated variational equations establish jump conditions that describe the evolution of sensitivities through events. These equations provide insights into expansion/contraction effects at events. This is a focus of future research.Standard Poincar6 map results extend naturally to hybrid systems. The Monodromy matrix is obtained by evaluating trajectory sensitivities over one period of the (possibly non-smooth) cyclical behaviour. One eigenvalue of this matrix is always unity. The remaining eigenvalues are the characteristic multipliers of the periodic solution. Stability is ensured if all multipliers lieReferences[l] LA. Hiskens and M.A. Pai, “Hybrid systems view of power system modelling,” in Proceedings of the IEEE International Symposium on Circuits and Systems, Geneva, Switzerland, May 2000.[2] M.H. Raibert, Legged Robots That Balance, MIT Press, Cambridge, MA, 1986.[3] A. Goswami, B. Thuilot, and B. Espiau, “A study of the passive gait of a compass-like biped ro bot: symmetry and chaos,’’ International Journal of Robotics Research, vol. 17, no. 15, 1998.[4] S. Pettersson, “Analysis and design of hybrid systems,” Ph.D. Thesis, Department of Signals and Systems, Chalmers University of Technology, Goteborg, Sweden, 1999.[5] C. Tomlin, G. Pappas, and S. Sastry, “Conflict resolution for air traffic management:A study in multiagent hybrid systems,” IEEE Transactions on Automatic Control, vol. 43, no. 4, pp. 509-521, April 1998.[6] A. Goswami, B. Espiau, and A. Keramane, “Limit cycles in a passive compass gait biped and passivity-mimicking contr ol laws,” Journal of Au tonomous Robots, vol. 4, no. 3, 1997. 171 B.K.H. Wong, H.S.H. Chung, and S.T.S. Lee, ‘Computation of the cycle state-variable sensitivity matrix of PWM DC/DC converters and its applica tion,” IEEE Transactions on Circuit s and Systems I, vol. 47, no. 10, pp. 1542-1548, October 2000.[8] M. Rubensson, B. Lennartsson, and S. Petters son, “Convergence to limit cycles in hybrid systems - an example,” in Prepri nts of 8th International Federation of Automatic Control Symposium on Large Scale Systems: Theo y d Applications, Rio Patras, Greece, 1998, pp. 704-709.[9] I.A. Hiskens and M.A. Pai, “Trajectory sensitivity analysis of hyhrid systems,” IEEE Transactions on Circuits and Systems I, vol. 47, no. 2, pp. 204-220, February 2000.[10]D. Chaniotis, M.A. Pai, and LA. Hiskens, “Sen sitivity analysis of differential-algebraic systems using the GMRES method - Ap plication to power systems,” in Proceedings of the IEEE International Symposium on Circuits and Systems, Sydney, Australia, May 2001.[11]T.S Parker and L.O. Chua, Practical Numerical Algorithms for Chaotic Systems, Springer-Verlag, New York, NY, 1989.[12]R. Seydel, Practical Bifurcation and Stability Analysis, Springer-Verlag. New York, 2nd edition, 1994.。
物流专业外文翻译5
1. The Definition of LogisticsAfter completing a commercial transaction, logistics will execute the transfer of goods from the supplier( seller) to the customer( buyer) in the most cost-effective manner. This is the definition of logistics. During the transfer process, hardware such as logistics facilities and equipment( logistics carriers) are needed, as well as information control and standardization. In addition, supports from the government and logistics association should be in place.Three major functions of logistics(1) Creating time value: same goods can be valued different at different times. Goods often stop during the transfer process, which is professionally called the storage of logistics. It creates the time value for goods.(2) Creating location value: same goods can be valued differently at different locations. The value added during the transfer process is the location value of logistics.(3) Distribution processing value: sometimes logistics create distribution processing value, which changes the length, thickness and packages of the goods. Like popular saying, “ cutting into smaller parts” is the most commonly seen distribution processing within logistics create added value for goods.2. Logistics is a new commercial area, developing from the traditional stage to a modern one. The main differences between these two stage include:(1) Modern logistics adopts containerization techniques. The goods transfer process starts with packaging, followed by transportation, storage and distribution. The whole process is operated under logistics standards. Based on the logistics base module of 600×400mm, from the logistics module of 1,200×1,000mm, and enlarge to the size of2,591×2,438mm-the size of high×wide of the container. It can be adjusted to the standard sizes of containers for trains, trucks and ships.(2) Information technologies are most important for modern logistics. Bar Code, POS, EDI and GPS systems dramatically improve the efficiency and accuracy of the logistics activities. Internet further assists the market development, operation and management of the logistics industry.3.International LogisticsAn increasing number of companies are involving in international markets through exporting, licensing, joins ventures, and ownership. This trend should continue. With such expansion there is a need to develop worldwide logistics networks. Integrated logistics management and cost analysis will be more complex and difficult to manage.There are some future trends in internationalization:(1) More logistics executives with international responsibilities(2) Expansion of the number and size of foreign trade zones.(3) Reduction in the amount of international paperwork and documentation(4) More foreign warehousing is owned and controlled by the exporting firm(5) Increasing number of smaller firm(6) Foreign ownership of logistics service firms, e. g., public warehousing and transportation carriers.(7) Increasing multiple distribution channelsThe international transport and the international logistics are same things in some way. So, when the international trading involved, the firm must establish international logistics systems to provide the products and service demanded. The most significant development in international logistics will be the increasing sophistication information system adopted and independent departments to operate.4.Packaging.Packaging performs two basic functions–marketing and logistics. In marketing the packaging acts promotion and advertising. Its size, weight, color, and printed information attract customers and convey knowledge of the product. When firms are involved in international marketing, packaging becomes even more important. Products sold to foreign countries travel greater distances and undergo more handling operations. The logistics package is to protect the products during the process of logistics.Scrap disposal. The logistics process must effectively and quickly handle, transport, and store waste products. If they can be reused or recycled, logistics company should arrange and move them to the re–production and re–processing locations.Return goods handling. The handling of return goods is often called reverse distribution. Buyers may return items to the seller for a number of reasons. Most logistics systems are not good enough to handle such cases. In many industries, consumers return products for warranty repair, replacement, or recycling, reverse distribution costs may be very high. Reverse distribution will become more important as customers demand more flexible and favorable return policies.5.Third Part Logistics ( TPL)Third Part Logistics provides all the logistics services. They act as a bridge or facilitator between the first part( supplier or producer) and the second part( buyer or customer). The primary objectives of third part logistics providers are to lower the total cost of logistics for the supplier and improve the service level to the customer.Third Part Logistics have been growing rapidly. Cost reduction and demands for batter and cheaper services are the main drives behind the growth. A third part logistics provider will be in a position to consolidate business from several companies and offer frequent pick–ups and deliveries, whereas in–house transportation cannot. Other reasons are as follows:* The company does not specialize in logistics;* The company does not have sufficient resources;* Eager to implement better logistics operation or does not have time to develop the required capabilities in–house;* The company is venturing into a new business with totally different logistics requirements;* Merger or acquisition may make outsourcing logistics operations more attractive than to integrate logistics operations.6.Global LogisticsDeveloped countries often deal with globalization in two ways: to be more cost competitive with third world countries, and to look for new partners in other countries to manufacture components, subassemblies and even the final products. The second approach forces most developed countrie s to get into a new area called “ global logistics”.Benefits of global operations include cheap raw materials and end products, lower labor cost, better quality, increased internal competition and better customer service. Some of the disadvantages are unreliable delivery, poor communication and longer time from design to finish production. Challenges are often cultural and linguistic differences, legal requirements, logistics suppliers or manufacturers, exchange rates.There are three major flows involved in global logistics: material flow, document flow and cash flow.7.Logistics into the FutureLogistics is changing at a rapid and acceleration rate. There are two reasons are its rapid growth:Firstly, pressure to change by the development of the system itself(1) High–speed computing and data transmission can instantly transmit and react to user demand(2) More flexible and accurate logistic planning and control through computers and data processing(3) Flexible computer facilities help problem solving and increase decisions accuracy(4) Awareness of total cost measurement and management accountingSecondly, pressures for changes from the wider economy.(1) Be flexible in handling markets of different sizes for better competition(2) There is increasing specialization in markets and growth in retailing.(3) Life cycles for products are shortening. Logistics systems need to be more efficient, faster and more flexible(4) Move from mass production towards flexible manufacturing system( FMS). These systems enable a company to switch production quickly from one product to another (5) Competitive pressures lead to more efforts to improve customer service.8.The process of logistical integration can be divided into four stages:Stage 1. Began in the early 1960s in the USA and involved the integration of all activities associated with distribution. Separate distribution departments were to coordinate the management of all processes within physical distributionmanagement( PDM).Stage 2. PDM was applied to the inbound movement of materials, components, and subassemblies, generally known as “ materials management”. By the late 1970s, many firms had established “ logistics department” with overall responsibility for the movement, storage, and handling of products upstream and downstream of the production operation.Stage 3. Logistics plays an important coordinating role, as it interfaces with most other functions. With the emergence of business process re–engineering( BPR) in the early 1990s, the relationship between logistics and related functions was redefined.“ System integration” occurred. Cross–functional integration should achieve greater results.物流的定义在完成商业交易之后,物流将以最低成本和最高效益的方式执行将商品从供应商(卖方)流转到顾客(买方)的过程。
外文翻译原文
IntroductionLatvian legislation for forest protection belts Latvian legislation demands that forest protection belts are established around all cities and towns. The concept of protection belts originates from the Soviet Era and is maintained in Latvian legislation despite the radical changes to the political system after regaining indepen-dence in 1991. The legal background for the establish-ment of protection belts is as follows:•Law on Protection Belts (1997, 2002)•Forest Law (2000)•Law on Planning of Territorial Development (1998).Designating a greenbelt around the city of Riga, LatviaJanis DonisLatvian State Forestry Research Institute ‘Silava’, Salaspils, LatviaAbstract: Latvian legislation demands that forest protection belts are established around all cities and towns. The main goal of a protection belt is to provide suitable opportuni-ties for recreation to urban dwellers and to minimise any negative impacts caused by urban areas on the surrounding environment. Legislation states the main principles to be adopted, which include the maximum area of protection belts, their integration in terri-torial development plans and restrictions placed on forest management activities. The largest part of the forest area around Riga is owned by the municipality of Riga, which, as a result, has two competing interests: to satisfy the recreational needs of the inhabitants of Riga, and to maximise the income from its property. In order to compile sufficient background information to solve this problem, the Board of Forests of Riga Municipality initiated the preparation of a proposal for the designation of a new protection belt.The proposal was based on the development and application of a theoretical framework developed during the 1980s. The analysis of the recreational value of the forest (5 class-es of attractiveness) was carried out based on categories of forest type, dominant tree species, dominant age, stand density, distance from urban areas and the presence of at-tractive objects. Information was derived from forest inventory databases, digital forest maps and topographic maps. Additional information was digitised and processed using ArcView GIS 3.2. Local foresters were asked about the recreation factors unique to differ-ent locations, such as the number of visitors and the main recreation activities. From a recreational point of view and taking into account legal restrictions and development plans for the Riga region, it was proposed to create three types of zones in the forest: a protection belt, visually sensitive areas and non-restricted areas.Key words:greenbelt forest, recreational value, GIS, zoningThe Law on Protection Belts states that protection belts around cities (with forests as part of a green zone)have to be established (a) to provide suitable conditions for recreation and the improvement of the health of urban dwellers, and (b) to minimise the negative im-pact of urban areas on the surrounding environment.Urban For.Urban Green.2 (2003):031–0391618-8667/03/02/01-031 $ 15.00/0Address for correspondence:Latvian State Forestry Re-search Institute ‘Silava’, Rı¯gas iela 111, Salaspils, LV-2169,Latvia. E-mail: donis@silava.lv© Urban & Fischer Verlaghttp://www.urbanfischer.de/journals/ufugRegulation nr 263 (19.06.2001) on the ‘Methodology for the establishment of forest protection belts around towns’issued by the Cabinet of Ministers (CM) states: (a) The area of a protection belt depends on the numberof inhabitants in the town: towns with up to 10,000 inhabitants should have a maximum of 100 ha of protection belt, those with between 10,000 and 100,000 inhabitants a maximum of 1,500 ha, and towns with more than 100,000 inhabitants a maxi-mum of 15,000 ha;(b) the borders of protection belts have to be able to beidentifiable on the ground, using features such as roads, ditches, power lines, and so forth;(c) protection belts have to be recorded in the territorialplans of regions adjacent to the town or city; and (d) establishment of protection belts has to be agreedupon by local municipalities.According to law, protection belts should be man-aged using adapted silvicultural measures. Clear-cut-ting, for example, is prohibited in a protection belt to mitigate any negative impacts of the city on the sur-rounding environment. The Forest Law of 2000 and subsequent regulations including the Regulation on Cutting of Trees, and the Regulation on Nature Conser-vation in Forestry define clear-cuts as felled areas larg-er than 0.1 ha where the basal area is reduced below a critical level in one year. These regulations also state the permitted intensity and periodicity of selective cut-ting (30–50%, at least 5 years between entries).The third element of the legal framework relevant for protection belts in Latvia is the Law on Planning of Territorial Development (1998). It defines:(a) Principles and responsibilities of the different or-ganisations involved;(b) the contents of territorial plans;(c) the procedures for public hearing; and(d) the procedures for the acceptance of plans.The law also states that protection belts around towns have to be designated in territorial plans. Thus, the legislation gives very detailed descriptions of the restrictions to maximum area, activities and guidelines for delineation and so forth, while there are no ‘rules’for the choice of what areas are to be included in pro-tection belts. It is up to territorial planners to propose what areas to include and for negotiation among mu-nicipalities to approve the selection.Protection belt for the city of RigaRiga and the Riga region are situated in the Coastal Lowland of Latvia within the Gulf of Riga. The main landform types are the Baltic Ice Lake plain, the Litto-rina Sea plain and the Limnoglacial plain and bog plain. The total area of the administrative area of the City of Riga covers 307.2 km2, and that of the Riga re-gion 3,059 km2. In 2000 the city of Riga had 815,000 inhabitants, while an additional 145,000 people resided in the greater Riga region. During the last decade the number of inhabitants in Riga decreased by 10.5%and in Riga region by 5.3%. In the mid-1990s the main types of industry in Riga were food processing, timber and wood processing, metal fabricating and engineer-ing, while in the region agriculture and forestry, wood processing, pharmaceuticals, and the power industry were the main activities. Due to reduced industrial ac-tivities today, the main sources of pollution in Riga re-gion are road transport and households.The greater part of the Riga region is covered by for-est, i.e. 1,642 km2or 53%. About 26% of the land is used for agriculture, 4% is covered by bogs, and 4% by water. The Riga region also has a coastal dune zone of some 30 km along the Gulf of Riga. The main tree species to be found in the Riga region are Scots pine (Pinus sylvestris L.),birch (Betula spp.) and Norway spruce (Picea abies (L.) Karsten) (see Table 1). In the administrative area of the city of Riga, 57 km2 or about 19% of the land area is forest. Scots pine is the domi-nant species, covering approx. 46.9 km2(i.e. 88% of the total forest area).According to the legislation described before, a pro-tection belt around Riga city, with a maximum size of 15,000 ha, could be designated. Moreover, any propos-al has to be agreed upon among 24 local municipalities. The Riga region is divided into 24 administrative units: 7 towns and 17 pagasts or ‘parishes’.Riga municipality currently owns more than 55,600 ha of forests. Most are situated in the vicinity of Riga. Four forest administrative districts lie completely with-in Riga region and close to Riga city (see Fig. 1). The total area of these districts is 44,158 ha out of which forest stands cover 36,064 ha (82%). Thus the Riga municipality forests of those 4 districts cover only 17% of the total forest area of the Region. The dominant tree species in the municipally owned forests are Scots32J.Donis:Designating a greenbelt around the city of Riga,LatviaUrban For.Urban Green.2 (2003)Table 1.Tree species composition in the Riga region Dominant tree Area covered, ha Average age, years species––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––Total Municipa-Total Municipa-lity*lity* Scots pine95,27627,3718581 Norway spruce20,8493,0175139Birch30,5585,1246056 Other10,438552––Total157,12136,0647369*Data only for the 4 forest districts of the Riga city munici-pality that are entirely situated within the Riga region.pine, birch and Norway spruce. These cover 76%, re-spectively 14% and 8% of the forest area. Other species cover less than 2% of the area.Until the re-establishment of Latvian independence almost all forestland was owned by the state but since then many areas have been returned to their former owners and are now privately owned. Current regula-tions state that until the designation of new boundaries for protection belts has been agreed upon, all forests of the previously existing and protected green zone have to remain protected whatever their functional role or ownership status. Consequently almost all forests of the Riga municipality located in the Riga region have management restrictions placed on them, and the same can be said for forests of other owners within the previ-ously existing green zone. Currently, therefore, on the one hand significant recreation opportunities for urban dwellers are provided, while on the other hand forest owners’rights to obtain income from timber harvest in the suburban areas continue to be restricted. Suburban municipalities also lose income because of reduced land taxes from land with management restrictions.The board of Forests of the Municipality of Riga there-fore initiated the preparation of a proposal to designate a new protection belt.Study to support protection belt designation The main objective of the study presented here has been to obtain background information in preparation for further discussions with local municipalities. Stud-ies in Latvia as well as elsewhere have revealed that recreational values of forests depend mainly on forest characteristics, location and level of pollution (Emsis et al. 1979; Emsis 1989; Holgen et al. 2000; Lindhagen & Hörnsten 2000; Rieps ˇas 1994; Su ¯na 1973, 1979). A very important aspect is the distance to the forest from places where people live (e.g. Rieps ˇas 1994). The abil-ity of a forest stand to purify the air by filtering or ab-sorbing dust, micro-organisms, and noxious gases de-pends on tree and shrub species composition, age, tree size and stand density (Emsis 1989). Stands purify the air most effectively at the time of maximum current an-nual volume increment, usually between 30 to 60 years of age in Latvian conditions, depending on species.Recreational value, on the other hand, increases with age (and tree size) and reaches its maximum consider-ably later. Taking into account the peculiarities of the dispersal of pollution as described by Laivin ‚s ˇ et al.(1993) and Za ¯lı¯tis (1993), selective cutting is prefer-able in the vicinity of a pollution source, especially ifJ.Donis:Designating a greenbelt around the city of Riga,Latvia 33Urban For.Urban Green.2 (2003)Fig. 1.Location ofthe Riga municipali-ty forests in the Riga region.the forest consists of a narrow strip between the pollu-tion source and housing. If the distance between a pol-lution source and housing exceeds several kilometres, a patch clear-cut system with stands of different ages is sufficient to provide a reduction in the negative impact of urban areas. Taking into account the fact that closer to residential areas it is more important to consider the visual qualities of the forest (e.g. Tyrväinen et al. 2003), this purification ability can generally be ignored when planning protection belts.MethodsThis study to support the designating of the Riga pro-tection belt used the following data sources for analysis (see Fig. 2): forest inventory databases, digital forest maps of the Riga municipal forests which are situated outside the administrative borders of the city (55,600 ha of which 44,158 ha located in the Riga region) (see Fig. 1), and corresponding topographic maps.The study and its developed proposal are based on an application of a theoretical approach developed during the 1980s by the Latvian State Forestry Research Insti-tute ‘Silava’(Emsis 1989) and the Lithuanian Forestry Research Institute (Riepsˇas 1994). According to the methodology developed by Emsis (1989), the first step in the process is to evaluate the recreational potential of the forest stands. This is carried out by analysing the following factors:• The tolerance of the forest ecosystem to different lev-els of anthropogenic (recreation) loading;• the status of forest ecosystems in terms of the damage or degradation as a result of recreational use;•the suitability of the landscape for non-utilitarian recreation (recreational value); and• the existing and potential levels of recreational loads.The second step involves evaluating the existing andexpected functional roles of the forest.The tolerance of the forest ecosystem to different levels of anthropogenic impact or loading is evaluated using a framework based on a combination of forest type, dominant tree species, dominant age group, soil type and relief, according to the stability of ecosystem. All stands are classified into one of five tolerance classes. The highest score is given to mature deciduous forests on mesotrophic and mesic soils on flat topogra-phy, while the lowest score is given to young pine stands on oligotrophic soils on steep slopes (forests on dunes).In this study ecosystem tolerance could not be evalu-ated, as it was primarily a desk using existing databas-es, and topographic relief maps were not available in digital form. The status of the forest ecosystem in rela-tion to damage or degradation was evaluated in terms of the degree of change in vegetation cover, under-growth, tree root exposure of the and level of littering, classified into three classes.Assessment of the recreational value of the forest stands was calculated using a formula developed by Riepsˇas (1994):Recreational value VR= (VS*kW*kS+VA)*kPWhere VSis stand suitability based on key internal at-tributes of the stand, such as species, age, stand densityand forest type. VSvalues range from 0 for young, high-density grey alder (Alnus incana L.) on wet peat soils, to 100 for average density mature pine stands ondry mineral soils. kwis a coefficient depending on the distance of the stand from watercourses, ranging from0.1 for stands further than 2 km from watercourses to1.0 for stands up to 500 m from watercourses. kSis a coefficient depending on the distance of the stand from urban areas, ranging from 0.1 for stands further than34J.Donis:Designating a greenbelt around the city of Riga,LatviaUrban For.Urban Green.2 (2003)Fig. 2.Structure of data sources used in data ana-lysis.80 km from Riga to 1.0 for stands within 30 km ofRiga. VA is an additional value depending on the pres-ence of attractive features, for example, 25 for forest stands up to 500 m from settlements, including summer cottages, or for areas intensively used for recreation ac-cording to information of local foresters. kP is a coeffi-cient depending on the level of environmental pollu-tion. Its value is 0 if the actual pollution level exceeds limit values, 0.5 if the level of environment pollution is between 50% and 100% of limit values, and 1 if the level of actual pollution is less than 50% of the limit values. In this study a coefficient of 1.0 was used, be-cause SO2and O3concentrations measured by Rigabackground measuring stations did not exceed 50% of the limit values (Fammler et al. 2000).The division of stands into classes of stand suitabili-ty is based on studies of visitors’preferences. Coeffi-cients kw, ksand VAare based on visitors’spatial distri-bution and show the ratio of the number of visitors in different zones. The evaluation of existing and expect-ed recreational loads was carried out by local foresters. They marked existing and potential recreation places on forest maps, including:•Small areas or sites for activities such as swimming, barbecuing, and so forth.•Recreation territories, defined as areas of 20 ha or more where people stay longer periods for walking, jogging, skiing or other forms of both active and pas-sive recreation.•Traditionally popular places for the collection of berries and mushrooms.•Recreational routes, including routes from public transport stops to recreation sites or recreation terri-tories, and between recreation sites and territories. For each recreation site and recreation territory data on the main seasons of use, the periods of use (week-days, weekends), and the average number of people in ‘rush-hours’during good weather conditions was col-lected or estimated.Data processing was carried out using ArcView GIS3.2a, Visual Fox pro and Microsoft Excel. VS values foreach stand were calculated from information in the for-est database using Visual Fox pro. Information collect-ed at a later stage from local foresters was digitised using separate themes (layers) in ArcView GIS 3.2a. Buffer zones along watercourses and water bodies, as well as residential areas, recreation sites and territoriesand recreation routes were created to get kW ,kSand VAvalues for each stand. Then VR values were calculatedfor each stand.A selection of recreation sites and territories was vis-ited by members of the project team in order to evalu-ate the state of the ecosystem with respect to wear and tear arising from different levels of recreational use. An evaluation of the existing functional role of each forest stand was carried out using the existing categories offorest protection. The anticipated future functional role was evaluated by annalysing the recreational value of stands, known expectations in terms of territorial de-velopment, and existing legal restrictions in order to find a compromise between recreation possibilities and other services of the forest. Next, a first draft of the protection belt was drawn according to experts’judge-ment. This draft included forests with high recreational value adjacent to residential areas and summer cot-tages, and larger tracts intensively used for recreation with medium to high recreational value.ResultsAccording to the original forest classification 65% of the total forest land area was designated as a commer-cial greenbelt forest, for which the main management goals are timber production and environmental consid-erations. The remaining 35% were designated as pro-tected (see Table 2). With regards to protected areas in Latvia: the main management goals of nature parks are nature conservation and recreation, including some ed-ucation. The goal for nature reserves is nature conser-vation, while that of the protected greenbelt forests is recreation.While interviewing local foresters it was revealed that they find it difficult to evaluate dispersed recreation loads (for example collection of berries, mushrooms). The assessments of foresters varied greatly and were considered to be unreliable. It was therefore decided to map only the places important for recreation, but not to use the inaccurate estimates of visitor numbers.In Latvia, special investigations have to be carried out in order to develop management objectives and principles for protected forests as part of the preparation of management plans. Pilot studies and visits to some of the recreation areas have revealed that the evaluation of the state of the forest ecosystem is useful only when de-veloping the detailed management plan. Even then, this is only the case for places identified by local foresters as recreation sites or territories, because otherwise it is too time consuming to carry out fieldwork which provides little useful additional information.Calculated VSvalues show that on average the forests studied have a medium suitability value for recreation (average score 47) (see Table 2). There are considerable differences between districts, with aver-age value ranging from 32 points in Olaine to 66 points in the Garkalne district. This indicates that the average stands in the Garkalne district are more suitable for recreation than those in other districts. If other aspects are taken into account, such as distance from wherepeople live, and VRvalues are calculated it can be seenJ.Donis:Designating a greenbelt around the city of Riga,Latvia35Urban For.Urban Green.2 (2003)that the districts are still ranked as follows: Garkalne,Jugla, Tireli and Olaine.Only 10% of the forest owned by Riga municipality within the Riga region were evaluated as having a high or very high recreational value. 12% had medium recreational value, while large areas used for the col-lection of berries and mushrooms were evaluated as having low or very low recreational value (60% of the total forest area) (see Table 3).More than 16% of the area is covered by bogs, for which according to the used methodology, recreational value was not evaluated at all. Some areas were recorded by the local foresters as important places for the collec-tion of berries. However, more valuable from a recre-ational point of view were those forests situated east and north-east of the city (Garkalne and Jugla districts),while the forests to the south (Olaine and Tireli districts)were found to have a lower recreational value (V R ).36J.Donis:Designating a greenbelt around the city of Riga,LatviaUrban For.Urban Green.2 (2003)Table 2.Distribution of forest by forest categories according to the original functional role Forest districtDataFormer forest category Total–––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––Commercial Nature Nature Protected greenbelt forests parks reserves greenbelt forestsGarkalneArea, ha521.27,698.78,219.9Average of V S *61.966.566.2Average of V R **59.350.751.4JuglaArea, ha 8,376.74,098.812,475.4Average of V S 45.656.949.1Average of V R 22.034.025.7OlaineArea, ha 11,765.4707.512,473.0Average of V S 31.941.032.6Average of V R 8.527.410.0TireliArea, ha 8,689.5257.91,025.01,016.910,989.3Average of V S 40.666.710.059.342.3Average of V R 17.055.3 1.044.920.6TotalArea, ha 28,831.6779.11,025.013,522.044,157.6Average of V S 39.863.510.061.647.1Average of V R16.357.91.043.725.9* V S Suitability value – based on stand parameters (0–100 points).** V R Recreation value (0–125 points) based on stand parameters, distance to the residential areas, water and other attractive objects.Table 3.Distribution of forest areas by classes of attractiveness and by designated functional role Designated zoneDataClass of attractiveness Total –––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––n.a.Very low Low Medium High Very high 0<2525,1–5051–7575–100100<Protection belt Area, ha76.7560.12,266.42,222.7850.5743.66719.9Average of V R *0.012.036.063.390.0125.053.4Visually sensitive Area, ha 447.64,150.54,157.7853.4847.1179.810636.1Average of V R 0.07.837.460.996.7125.028.5Non-restricted Area, ha 6,664.715,389.12,548.61,090.5874.8234.026801.7Average of V R 0.0 5.234.761.197.2125.015.8TotalArea, ha 7,189.020,099.88,972.74,166.52,572.31,157.344157.6Average of V R0.06.236.362.294.6125.025.9*V R Recreation value (0–125 points) based on stand parameters, distance to the residential areas, water and other attractive objects.Areas along main roads and railways are known to be visually sensitive, because of the large number of peo-ple who can see them during travel. The same is true for forest in the vicinity of small villages. Taking into ac-count the fact that legislation prohibits clear-cuts in pro-tection belts – which is not always necessary in order to maintain the visual quality of the landscape – it was proposed, as part of the zoning strategy, to create so called visually sensitive areas. In these areas the forest owner (Riga municipality) is recommended to use more detailed landscape-planning techniques and to pay more attention to visual aspects during management.As a result of the study, seen from a recreational point of view and taking into account legal restrictions and so forth, it has been proposed to create three zoning categories: (1) protection belts, (2) visually-sensitive areas, and (3) non-restricted areas (see Fig. 3). The protection belt should include:• Forest with high recreational value adjacent to residen-tial areas and summer cottages, to form a 200–500 m wide belt.• Larger tracts of forestland intensively used for recre-ation.The zone of visually-sensitive areas should include:• Forests within the administrative borders of Riga mu-nicipality and in the vicinity of villages (up to 200–500 m distance).• Forests along roads of national and regional impor-tance, railways, watercourses and streams as a protec-tion belt of 100–300 m wide.• Places used for mushroom and berry collection in the original restricted protection belt.• Places that could become important for recreation in the near future.J.Donis:Designating a greenbelt around the city of Riga,Latvia 37Urban For.Urban Green.2 (2003)Table 4.Proposed distribution of forest categories in designated zones (in hectares)Designated zoneFormer forest category Grand Total––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––Commercial Nature Nature Protected greenbelt forests parks reserves greenbelt forests Protection belt355.2779.15,585.76,719.9Visually sensitive areas 3,503.97,132.110,636.1Non-restricted areas 24,972.51,025.0*804.226,801.7Total 28,831.6779.11,025.013,522.044,157.6*Forests within nature reserves are not intended for recreation; their primary management goal is nature conservation.Fig. 3.Proposal for zon-ing of the Riga municipalforests in Riga region.The remaining areas should consequently be classi-fied as non-restricted areas.A revision of the first draft plan was made taking into account the known prospective development plans of Riga and Riga region. As a result, for forests owned by Riga municipality and located in Riga region the pro-posal is to include 6,720 ha in the protection belt (see Table 3). Moreover, it has been suggested to designate 10,636 ha as visually-sensitive areas, but to omit the re-maining 26,802 ha from zoning, as these do not need special management from a recreation point of view. Average recreational values of stands in this area range from 53 (medium), through 28 (low) to 15 points (very low) respectively.As a result, the major part of the forest remains in the same functional category as in the original allocation (see Table 4). As was mentioned above, the classifica-tion described here is only based on recreational as-pects, thus forests in nature reserves are misleadingly shown as non-restricted forests. Only 5,586 ha out of the 13,500 thousand ha of the originally protected greenbelt forests are proposed to be included in the protection belt, while 355 ha of the previous commer-cial greenbelt forests are proposed to be placed under stronger protection.DiscussionForests owned by Riga municipality within the Riga re-gion are divided over 13 rural municipalities. Accord-ing to legislation, revised draft proposals for zoning Riga city forests have to be accepted by Riga munici-pality, while the final decision is up to Riga and the sur-rounding municipalities. The study presented here has provided a tentative estimate of the recreational value and suitability of the forests for recreation and can be used as a starting point for political discussions. At the very beginning the intention was to divide the forests in two categories: the protection belt and the remainder of the forest. During the study it was concluded, however, that a third category would be needed, that of visually sensitive areas. Within this category more attention would have to be paid to the amenity of the landscape, but there would be no need to drastically restrict com-mercial forest management. As nature parks are also designated for recreation, it has been proposed to in-clude all forests of nature parks in the protection belt. It has to be noted that all the forests within the adminis-trative borders of cities, and as such not included in this study, are designated as protected. As a consequence, the forest area available for recreation to the inhabi-tants of Riga would increase to 12,500 ha.Unlike many other European cities, where timber ex-traction is of small importance (Konijnendijk 1999),Riga municipal forests have a considerable economic role. It is estimated that the allowable annual cut in suburban forests amounts to 169,800 m3or 81% of the annual increment (Dubrovskis et al. 2002). It should be kept in mind that income from logging is used for for-est regeneration and tending, forest fire protection and maintenance of recreation facilities.The objective of this study was not to evaluate the precision of the method nor possible errors occurring when applying it. This study revealed, however, the in-completeness of the methodology used. Bogs, which are very sensitive to recreation loads, are ascribed quite a high level of attractiveness from a recreation point of view (for the collection of wild berries), but according to the methodology they are not evaluated at all. All watercourses were assumed to be attractive sites, while the preliminary evaluation of recreation loads showed this not to be true. The use of watercourses is very vari-able and obviously depends on water quality and vege-tation structure of the edges or banks. Another aspect which was not taken into account was that amenity of a forest is not simply the sum of the amenity values of forest stands (Pukkala et al. 1995).It seems that the evaluation based on dominant species is appropriate for screening areas, but for more detailed management plans, species mixture, the number of forest layers, and principles of landscape architecture also have to be taken into account (Bell 1999; Bell & Nikodemus 2000). Various studies have shown that people prefer uneven-aged forests (e.g. Melluma et al. 1982) and uneven-aged stands (e.g. Riepsˇas 1994). The impacts of the screening effect show that there are, even in the visually-sensitive and commercial zones, considerable areas with high and very high recreational value. This is mainly because delineation of zonal boundaries is carried out using easily distinguishable natural lines, and often it is not worth including single stands of high recreational value in the protection belt if, as a consequence, re-strictions on management would be placed over whole compartments of 50 ha.For the preparation of specific management guide-lines detailed field inventories have to be carried out. This has not been done in this study, where more re-liance was placed on the experience of local foresters and existing databases. Detailed economical calcula-tions have yet to be carried out in order to evaluate the direct and indirect value of the forest. These will also assist in obtaining more background information to be used as part of a holistic approach and for development of a decision support system to resolve contradictions between different interest groups.After acceptance of the draft plan by the municipali-ty of Riga, the process of negotiation between Riga and its surrounding municipalities is currently ongoing.38J.Donis:Designating a greenbelt around the city of Riga,Latvia Urban For.Urban Green.2 (2003)。
英文翻译 附原文
本科毕业设计(论文) 外文翻译（附外文原文）系 ( 院 )：资源与环境工程系课题名称：英文翻译专业(方向)：环境工程班级：2004-1班学生：3040106119指导教师：刘辉利副教授日期：2008年4月20使用褐煤（一种低成本吸附剂）从酸性矿物废水中去除和回收金属离子a. 美国, 大学公园, PA 16802, 宾夕法尼亚州立大学, 能源部和Geo 环境工程学.b. 印度第80号邮箱, Mahatma Gandhi ・Marg, Lucknow 226001, 工业毒素学研究中心, 环境化学分部,于2006 年5月6 日网上获得，2006 年4月24 日接受，2006 年3月19 日;校正，2006 年2月15 日接收。
摘要酸性矿物废水(AMD), 是一个长期的重大环境问题，起因于钢硫铁矿的微生物在水和空气氧化作用, 买得起包含毒性金属离子的一种酸性解答。
这项研究的主要宗旨是通过使用褐煤（一种低成本吸附剂）从酸性矿水(AMD)中去除和回收金属离子。
褐煤已被用于酸性矿水排水AMD 的处理。
经研究其能吸附亚铁, 铁, 锰、锌和钙在multi-component 含水系统中。
研究通过在不同的酸碱度里进行以找出最适宜的酸碱度。
模拟工业条件进行酸性矿物废水处理, 所有研究被进行通过单一的并且设定多专栏流动模式。
空的床接触时间(EBCT) 模型被使用为了使吸附剂用量减到最小。
金属离子的回收并且吸附剂的再生成功地达到了使用0.1 M 硝酸不用分解塔器。
关键词:吸附; 重金属; 吸附; 褐煤; 酸性矿物废水处理; 固体废料再利用; 亚铁; 铁; 锰。
文章概述1. 介绍2. 材料和方法2.1. 化学制品、材料和设备3. 吸附步骤3.1. 酸碱度最佳化3.2. 固定床研究3.2.1 单一栏3.2.2 多栏4. 结果和讨论4.1. ZPC 和渗析特征4.2 酸碱度的影响4.3. Multi-component 固定吸附床4.3.1 褐煤使用率4.4. 吸附机制4.5. 解吸附作用研究5. 结论1. 介绍酸性矿物废水(AMD) 是一个严重的环境问题起因于硫化物矿物风化, 譬如硫铁矿(FeS2) 和它的同素异形体矿物(α-FeS) 。
5、外文文献翻译(附原文)产业集群,区域品牌,Industrial cluster ,Regional brand
外文文献翻译（附原文）外文译文一：产业集群的竞争优势——以中国大连软件工业园为例Weilin Zhao,Chihiro Watanabe，Charla-Griffy-Brown[J]. Marketing Science,2009(2):123-125.摘要：本文本着为促进工业的发展的初衷探讨了中国软件公园的竞争优势。
产业集群深植于当地的制度系统，因此拥有特殊的竞争优势。
根据波特的“钻石”模型、SWOT模型的测试结果对中国大连软件园的案例进行了定性的分析。
产业集群是包括一系列在指定地理上集聚的公司，它扎根于当地政府、行业和学术的当地制度系统，以此获得大量的资源，从而获得产业经济发展的竞争优势。
为了成功驾驭中国经济范式从批量生产到开发新产品的转换，持续加强产业集群的竞争优势,促进工业和区域的经济发展是非常有必要的。
关键词：竞争优势；产业集群；当地制度系统；大连软件工业园；中国；科技园区；创新；区域发展产业集群产业集群是波特[1]也推而广之的一个经济发展的前沿概念。
作为一个在全球经济战略公认的专家,他指出了产业集群在促进区域经济发展中的作用。
他写道：集群的概念,“或出现在特定的地理位置与产业相关联的公司、供应商和机构，已成为了公司和政府思考和评估当地竞争优势和制定公共决策的一种新的要素。
但是，他至今也没有对产业集群做出准确的定义。
最近根据德瑞克、泰克拉[2]和李维[3]检查的关于产业集群和识别为“地理浓度的行业优势的文献取得了进展”。
“地理集中”定义了产业集群的一个关键而鲜明的基本性质。
产业由地区上特定的众多公司集聚而成,他们通常有共同市场、,有着共同的供应商,交易对象,教育机构和其它像知识及信息一样无形的东西，同样地,他们也面临相似的机会和威胁。
在全球产业集群有许多种发展模式。
比如美国加州的硅谷和马萨诸塞州的128鲁特都是知名的产业集群。
前者以微电子、生物技术、和风险资本市场而闻名,而后者则是以软件、计算机和通讯硬件享誉天下[4]。
外文翻译原文.
e c o l o g i c a l e n g i n e e r i n g 28(2006124–130a v a i l ab l e a t w w w.sc i e n c ed i re c t.c omj o u r n a l h o m e p a g e :w w w.e l s e v i e r.c o m /l o c a t e /e c o l e n gPlant-biofilm oxidation ditch for in situ treatm ent of polluted watersQi-Tang Wu a ,∗,Ting Gao a ,Shucai Zeng a ,Hong Chua ba College of Natural Resources and Environment,South China Agricultural University,Guangzhou 510642,ChinabDepartment of Civil and Structural Engineering,Hong Kong Polytechnic University,Hung Hom,Kowloon,Hong Kong SAR,Chinaa r t i c l ei n f o Article history:Received 17December 2005Received in revised form 16May 2006Accepted 18May 2006Keywords:Plant-biofilm oxidation ditch (PBFODIn situWastewater treatmenta b s t r a c tEutrophication of surface water bodies is a problem of increasing environmental and ecolog-ical concern worldwide and is particularly serious in China.In the present study,oxidation ditches were connected to a lake receiving municipal sewage sludges.T wo 24m 2(width 2m,length 12mparallel plastic oxidation ditches material were installed on a lake near the inlet of the municipal sewage.Zizania caduciflora and Canna generalis were grown in the ditches with plastic floating supporters for the removal of N and P from the sewage.The experiment was conducted firstly with municipal sewage in autumn–winter seasons for about 150daysunder the following conditions:2m 3/h influent flow,0.75kW jet-flow aerator(air/water of 5,18h HRT (hydrological retention timeand a return ratio of 10.Then it was run with the polluted lake water in summer–autumn for about 160days with an aerator of 1.25kW and an influent of 6m 3/h (air/water 3.3,HRT 6h.The performance was quite stable during the experimental period for the municipal sewage treatment.The average removal rates of COD (chemical oxygen demand,SS (suspended solids,TP (total phosphorus,NH 4+-N and inorganic-N were 70.6,75.8,72.6,52.1and50.3%,respectively.For the polluted lake water treatment,the average concentrations of COD,NH 4+-N and TP were 42.7,13.1and 1.09mg/L,respectively,in the influent and were 25.1,6.4and 0.38mg/L,respectively,in the effluent.The capacity of the plants to remove N and P by direct uptake was limited,but the indi-rect mechanisms also occurred.The proposed process,transforming the natural lake into a wastewater treatment plant,could evidently reduce the costs of the sewage collection,the land space requirement and the construction compared with conventional sewage treat-ment plants,and is especially suited to conditions in south China and south-east Asia.©2006Elsevier B.V .All rights reserved.1.IntroductionMany water bodies are subject to eutrophication due to eco-nomic constraints in reducing point sources of nutrients and/or to a high proportion of diffuse sources,and the prob-lem is particularly common in China because the proportion of treated municipal sewage is still low due to the relatively high capital investmentrequired.Accordingly,43.5%of 130investi-gated major lakes in China were found to be highly eutrophied∗Corresponding author .Tel.:+862085280296;fax:+862085288326.E-mail address:qitangwu@ (Q.-T.Wu.and 45%were of intermediate status (Li et al.,2000.These pol-luted lakes were mainly located in economically developed regions and especially around cities where large amounts of municipal sewage are discharged without appropriate treat-ment.Increasingly,natural or constructed wetlands,including buffer zones(Correll,2005,are being used for removal of pol-lutants from wastewater or for treatment of stormwater runoff from agricultural land and other non-point sources (Mitsch ete c o l o g i c a l e n g i n e e r i n g28(2006124–130125Table1–COD and BOD5of the study lake sampled at three points for5days inMay2003COD(mg/LBOD5(mg/LBOD5/COD13May89.5135.700.4083.3334.500.4189.5136.600.4114May55.5624.800.4589.5135.200.3949.3820.900.4227May105.1141.300.3981.0832.300.40111.1141.000.3728May60.0026.830.4563.3327.700.4463.3327.000.4329May90.0035.700.4093.3337.000.40117.9949.400.42al.,2000;Coveney et al.,2002;Belmont et al.,2004.However, this method requires a large land area in addition to the lake in question.For in situ treatment of hypereutrophic water bodies where the transparency of the water does not allow regrowth of submerged macrophytes,phosphorus precipitation in eutrophic lakes by iron application(Deppe and Benndorf, 2002or by additions of lime(Walpersdorf et al.,2004has been reported.Aeration of river water has been employed to remediate polluted rivers since the1970s(Wang et al.,1999. Increasing oxygen transfer inflow by stones placed in rivers was studied by Cokgor and Kucukali(2004.Growingfloating aquatic macrophytes(Sooknah and Wilkie,2004or terrestrial green plants usingfloating supports(Li and Wu,1997,physical ecological engineering(PEEN(Pu et al.,1998,and biotic addi-tives have also been applied(Chen,2003.However,these sim-ple designs do not constitute a real water treatment system and the efficiencies of these treatments are unsatisfactory.Activated sludge systems have been proved efficient treat-ing municipal sewage since the1960s(Ray,1995.However, this type of system has not been used for in situ remediation of polluted lakes or rivers.In the present study,the oxidation ditch technique was adopted on a lake receiving municipal sewage sludge.Floating green plants and the biofilms com-prisingfloating materials and plant roots were also added to enhance N and P removal.A pilot scale experiment was set up to test the feasibility and performance of the plant-enhanced oxidation ditch for in situ treatment ofboth the municipal sewage and the polluted lake water.2.Experimental2.1.Site descriptionThe study lake was situated at South China Agricultural Uni-versity,Guangzhou,China.The area of the lake was about 10000m2and the depth0.5–3m.This lake received the munic-ipal sewage from the residential area around the university.Fig.1–Surface arrangement of the plant-biofilm oxidation ditch and the waterflows.(1Wall of nylon tissue;(2nets of5mm;(3nets of0.25mm;(4oxidation ditch;(5jet-flow aerator;(6water pump;(7floating green plants;(8sewage entry.2.2.Establishment of the plant-biofilm oxidationditchesT wo24m2(width2m,length12mparallel oxidation ditches made of plastic materials were installed along the lake bank near the sewage inlet.The inner ditch was made of cement and the outer ditch was isolated with nylon tissues andfix-ing PVC(polyvinyl chloridetubes.Fig.1showsthe surface arrangement and the waterflow path.The coarse suspended solids in the influent werefiltered by two pl astic nets,one with a pore size of5mm and the other with a pore size of0.25mm,whereas the suspended solids in the effluent werefiltered by a plastic net with a pore size of 0.25mm.Zizania caduciflora and Canna generalis were grown in the ditch with theplast icfloating supporters which held the plants in position.Thefloating supporters were made of closed126e c o l o g i c a l e n g i n e e r i n g28(2006124–130PVC tubes and nylon nets and each was3.6m2.Zizania caduci-flora was grown on twofloating supporters an d Canna gener-alis on another two supporters.The plants were planted in four columns andfive lines.The twofloating supporters with Canna generalis were near the influent and the two with Zizania caduciflora were near the effluent.The entire disposal system is shown in Photo1.2.3.Conduct of the experimentsAn experiment was conductedfirstly on municipal sewage in autumn–winter seasons of2003–2004for about150days. The aeration of the oxidation ditch was achieved using a jet-flow aerator of0.75kW(Aqua Co.,Italy;air generation10m3/h, water jet rate22–28m3/h.The water sampling started on18 September2003and endedon12February2004.The influent was2m3/h created by a water pump of0.37kW.With the jet-flow aerator of0.75kW the theoretical air/water ratio was5, HRT was18h and the return ratio was10–13.The system was then run with the polluted lake water in summer and autumn2004for about160days with an aerator of1.25kW and with an influent of6m3/h(air/water3.3,HRT 6h.The influent was not created by water pump but by the driving fo rce of the jet-flow aerator.The water sampling for the second run started on15May2004and endedon15October 2004.2.4.Sampling and analysisThe influent and effluent were sampled every3–5days at 08:00–09:00a.m.andat17:00–18:00p.m.,each with three sam-pling re plicates for thefirst run.For the second run,the influ-ent and effluent were sampled1day a week.The water sam-pler took0–30cm surface water.The samples were analyzed for COD Cr,BOD5,SS,TP,NO3−-N,NH4+-N and pH according to standard methods(APHA,1995.The plant s were transplanted ontofloating supporters two weeks before water sampling and thefirst harvest was carried out60days later and at the termination of thefirst run for the municipal sewage.The plant biomass and N and P con-tents were measured according to the methods proposed by the Soil and Agro-Chemical Analysis Committee of China(Lu, 2000.The total uptakes of N and P were calculated and com-pared with the total removal of these elements calculated by the cumulative removal each day following measurement of a water sample.Total N removal=(average N in influent−average N in effluent×48×D iwhere48was the treated water volume per day in m3/day;D i was the number of days following the water sampling and before the next sampling.3.Results and discussionTable2shows the removal of COD Cr and SS by plant-biofilm oxidation ditch for the treatment of the municipal sewage in autumn–winter seasons of2003–2004.The removal of COD Cr varied from60to79%with an average of70%for the influent COD Cr ranging from100to200mg/L,a nd resulted in effluent COD Cr valuesfrom30to55mg/L(Table2,Fig.2.The average removal percentage was about75%for SS and variedfrom68to82%(Table2.The effluent SS was about 30mg/L which is the effluent limit value of the second grade for the sewage treatment plants in China(GB18918,2002 (Fig.3,for the influents varying from60to240mg/L.The average NH4+-N removal from influent was52%,which was lower in winter than in autumn(Table3.This may be due to lower bacterial activity in winter,but theinfluent NH4+-NTable2–Removal of COD and SS by the plant-biofilm oxidation ditch for the in situ treatment of municipal sewage each month in autumn–winter seasons of2003–2004Period Sampled days Water temperature(◦CInfluent(mg/LEffluent(mg/LRemoval(%COD Cr18–30September528.0118.54(3.01a34.34(7.8367.74 3–28October826.1123.91(4.0333.51(4.2672.661–7November326.0153.94(2.7337.60(3.8175.4918–28November423.1170.22(4.2835.45(5.3778.711–15December419.3180.36(8.2039.24(7.0677.6511–31January314.5128.46(3.6652.04(5.2359.504–12February216.8178.35(4.1662.86(5.8362.47Average150.54(4.3042.15(5.6370.60SS18–30September528.0160.4041.6074.18 3–28October826.1144.3826.2581.171–7November326.0116.0033.3370.7918–28November423.1111.7521.5080.981–15December419.390.5028.5068.4211–31January314.5104.0017.3382.384–12February216.8120.5033.0072.57Average121.0828.7975.78e c o l o g i c a l e n g i n e e r i n g28(2006124–130127Fig.2–COD in the influent and effluent of the plant-biofilm oxidation ditch for the in situ treatment of municipal sewage in autumn–winter seasons of2003–2004.was also higher in winter(Fig.4probably because of lower water consumption in the cold season.The total inorganic-N removal was similar to that for NH4+-N(Table3.NO3−-N concentrations were rather similar in the influent and the effluent.The total P removal varied from63to78%and was higher and more regular than N removal(Table3.The P concentra-tion in treated effluent was about1mg/L(Fig.5and conformed to the Chinese municipal sewage treatment standard which is set to3mg/L for second grade regions and1.5forfirst grade regions(GB18918,2002.Fig.6shows typical changes in the water quality param-eters for the sampling points from inlet to outlet.Thisindi-Fig.3–Suspended solids concentration in the influent and effluent of the p lant-biofilm oxidation ditch for the in situ treatment of municipal sewage in autumn–winter seasons of2003–2004.cates that COD and SS decreased gradually,but NH4+-N and TP dropped substantially following the mixing with the return water by the aerator and then decreased slowly,while NO3−-N and pH of the water remained virtually unchanged.The water DO increased dramatically following the aeration,decreased slowly thereafter and remained rather high even in the efflu-ent(about5.5mg/L.For the second run treating the polluted lake water on-site,the average influent COD Cr was42.7mg/L and the effluent 25.1mg/L for about160days during summer–autumn seasons (Fig.7.The removal of NH4+-N was about50%from about13.1 to6.4mg/L.Total-P in the effluents was rather stable,bei ngTable3–The removal of N and P by the plant-biofilm oxidation ditch for the in situ treatment of municipal sewage for each month in autumn–winter seasons of2003–2004Period Sampled days Water temperature(◦CInfluent(mg/LEffluent(mg/LRemoval(%NH4+-N18–30September528.020.60(0.30a7.16(0.2264.72 3–28October826.126.55(0.2310.15(0.2061.671–7November326.030.00(0.4113.67(0.2254.5118–28November423.135.15(0.7915.95(0.2653.991–15December419.335.89(0.3515.93(0.2755.1511–31January314.530.57(0.6918.59(0.2236.634–12February216.835.23(0.0521.61(0.0637.72Average30.57(0.4014.72(0.2152.06NH4+-N+NO3−-N18–30September528.023.06(0.159.24(0.1159.94 3–28October826.128.31(0.1212.01(0.1457.571–7November326.031.42(0.2114.58(0.1153.5918–28November423.136.32(0.4016.81(0.1353.721–15December419.337.41(0.1917.54(0.1453.1111–31January314.531.96(0.3720.07(0.1337.204–12February216.837.11(0.0323.35(0.0337.08Average32.23(0.2116.23(0.1150.32TP18–30September528.0 3.56(0.070.81(0.0475.56 3–28October826.1 4.01(0.140.87(0.0478.241–7November326.0 4.37(0.13 1.20(0.0472.5618–28November423.1 4.89(0.16 1.13(0.0776.661–15December319.5 4.86(0.80 1.38(0.2371.07 11–31January314.5 3.75(0.45 1.35(0.0363.32 4–12February216.8 4.75(0.10 1.51(0.0566.20 Average 4.31(0.16 1.16(0.0471.89128e c o l o g i c a l e n g i n e e r i n g 28(2006 124–130Fig.4–NH 4+-N concentration in the influent and effluent of the plant-biofilm oxidation ditch for the in situ treatment of municipal sewage in autumn–winter seasons of2003–2004.Fig.5–Total-P concentration in the influent and effluent of the plant-biofilm oxidation ditch for the in situ treatment of municipal sewage in autumn–winter seasons of2003–2004.Fig.6–T ypical changes in the pollutants in theplant-biofilm oxidation ditch during the in situ treatment ofFig.7–The influent and effluent concentrations of COD (up,NH 4+-N (medianand total-P (bottomin theplant-biofilm oxidation ditch treating polluted lake water.about 0.38mg/L from an average of 1.09mg/L in the influents.The removal of COD Cr ,NH 4+-N and Total-P was then quite sat-isfactory both for the municipal sewage and the polluted lake water.The removal of N and P was somewhat higher than con-ventional oxidation ditches,perhaps due to the existence of the plant-biofilm in the studiedsystem.However,the direct uptake rates of N and P by green plants were almost negligi-ble compared to the total removal of these elements by the whole system (Table4.However,the plants may have cre-ated localized anaerobic conditions by their root exudates and dead biomass and enhance the denitrification of N by micro-organisms as occurs in constructed wetlands (Hone,2000.Besides the green plants,the proposed system also con-tains biofilm coated to the plastic materials.The high velocity of return-fluent was different to the conventional oxidation ditch.Kugaprasatham et al.(1982showed that the increase of the fluent velocity could increase the density of the biofilm if the nutrient conditions were suitable for bacteria growth.Simultaneous nitrification/denitrification (SND(Van Mun ch etal.,1996may also occur in the system.Concerning the P removal of the system,biological phos-phate removal processes may occur but were not significant because there was no sludge removal and very little sludge precipitation after the run for treatment of municipal sewage.This may partly due to the existence of some ferric chains which were added to precipitate and fix the nylon tissue to the lake bottom,with formation of precipitates of ferric phos-e c o l o g i c a l e n g i n e e r i n g 2 8 ( 2 0 0 6 124–130 129 Table 4 – Proportions of N and P uptake by plants and total removal in the plant-biofilm oxidation ditch treating municipal sewage Date Days ZCa Harvested fresh biomass (g CG ZC 5 September–4 November 5 November–6 January Total or average a Plant uptake (g N CG 5.30 13.03 System removal (kg N CG P Percent of plant uptake N (% P (% P ZC 0.88 0.24 2.79 60 63 123 2200 625 9725 2750 4150 4.85 1.20 24.38 0.72 0.95 37.63 65.45 103.1 7.13 12.78 19.91 0.03 0.02 0.02 0.02 0.01 0.01 ZC: Zizania caduciflo ra; CG: Canna generalis. tained for at least 1 year. The actual mechanisms still remain to be identified. The oxidation ditch has been used for many years worldwide as an economical and efficient wastewater treatment technology that can remove COD, nitrogen and a fraction of the phosphorusefficiently. Anaerobic tanks (Liu et al., 2002 and phased isolation ditch systems with intra-channel clarifier (Hong et al., 2003 were added to the system to increase the TP removal efficiency. The proposed process takes an artificial process in combination with natural purification, transforming the natural lake into the wastewater treatment plant, and could evidently reduce the costs of sewage collection, the landspace requirement and the construction costs compared with the conventional sewage treatment plants. This process could be especially suitable to subtropical regions and to many water bodies in south China and southeast Asia where sewage treatment facilities are not well established. China. The authors are grateful to Dr. P. Christie, Department of Agricultural and Environmental Science, Queen’s University Belfast, UK, and Dr. Y. Ouyang, Department of Water Resources, St. Johns River Water Management District, Palatka, FL, USA, for their valuable suggestions and language corrections. references 4. Conclusions The present study adapted the oxidation ditch on the lake surface for in situ treatment of municipal sewage or polluted lake water in combination with plant biofilms for performing N and P removal, and running experiments at pilot scale for about 1.5 years resulted in the following observations: (1 The system was quite satisfactory and stable for treatment of municipal sewage and polluted lake water in removing COD, NH4 + -N and P. (2 The direct uptake of N and P by plants was negligible in comparison with the totalremoval by the system, but indirect mechanisms via plant root exudates and biofilms merit further studies. (3 The proposed process could dramatically reduce the costs of sewage collection, the land-space requirement and the construction costs compared with conventional sewage treatment plants; might be suitable for treatment of both municipal sewage and polluted lake water; and could lead to the promotion of wastewater treatment in many developing countries. Acknowledgements This study was funded by Department of Science and Technology of Guangdong Province (Grant no. 2004B33301007, American Public Health Association (APHA, 1995. Standards Methods for the Examination of Water and Wastewater, 19th ed. American Public Health Association, Washington, DC. Belmont, M.A., Cantellano, E., Thompson, S., Williamson, M.,S’anchez, A., Metcalfe, C.D., 2004. Treatment of domestic wastewater in a pilot-scale natural treatment system in central Mexico. Ecol. Eng. 23, 299–311. Chen, Y.C., 2003. Bioremediation Engineering of Polluted Environment. Chemical Industry Press, Beijing, p. 304 (in Chinese. Cokgor, S., Kucukali, S., 2004. Oxygen transfer in flow around and over stones placed in a laboratory flume. Ecol. Eng. 23, 205–219. Correll, D.L., 2005. Principles of planning and establishment of buffer zones. Ecol. Eng. 24, 433–439. Coveney, M.F., Stites, D.L., Lowe, E.F., Battoe, L.E., Conrow, R., 2002. Nutrient removal from eutrophic lake water by wetland filtration. Ecol. Eng. 19, 141–159. Deppe, T., Benndorf, J., 2002. Phosphorus reduction in a shallow hypereutrophic reservoir by in-lake dosage of ferrous iron. Water Res. 36, 4525–4534. Hone, A.J., 2000. Phytoremediation by constructed wetlands. In: Terry, N., Banuelos, G. (Eds., Phytoremediation of Contaminated Soil and Water. Lewis Publishers, pp. 13–40. Hong, K.H., Chang, D., Hur, J.M., Han, S.B., 2003. Novel phased isolation ditch system for enhanced nutrient removal and its optimal operating strategy. J. Environ. Sci. Health Part A 38, 2179–2189. Kugaprasatham, S., Nagaoka, H., Ohgaki, S., 1982. Effect of turbulence on nitrifying biofilms at non-limiting substrate conditions. Water Res. 26, 1629–1638. Li, F.X., Xin, Y., Chen, W., 2000. Assessment of eutrophication level of lakes. Chongqing Environ. Sci. 22, 10–11 (in Chinese. Li, F.B., Wu, Q.T., 1997.Domestic wastewater treatment with means of soilless cultivated plants. Chin. J. Appl. Ecol. 8, 88–92 (in Chinese. Liu, J.X., Wang, B.Z., van Groenestijn, J.W., Doddema, H.J., 2002. Addition of anaerobic tanks to an oxidation ditch system to enhance removal of phosphorus from wastewater. J. Environ. Sci. 14, 245–249.130 e c o l o g i c a l e n g i n e e r i n g 2 8 ( 2 0 0 6 124–130 Lu, R.K., 2000. Soil and Agricultural Chemistry Analysis. China Agriculture Press, Beijing (in Chinese. Mitsch, W.J., Horne, A.J., Nairn, R.W., 2000. Nitrogen and phosphorus retention in wetlands—ecological approaches to solving excess nutrient problems. Ecol. Eng. 14, 1–7. Pu, P., Hu, W., Yan, J., Wang, G., Hu, C., 1998. A physico-ecological engineering experiment for water treatment in a hypertrophic lake in China. Ecol. Eng. 10, 179–190. Ray, B.T., 1995. Environmental Engineering. PWS Publishing Company, New York, pp. 299–341. Sooknah, R.D., Wilkie, A.C., 2004. Nutrient removal by floating aquatic macrophytes cultured in anaerobically digested flushed dairy manure wastewater. Ecol. Eng. 22, 27–42. Van Munch, E.P., Land, P., Keller, J., 1996. Simultaneous nitrification and denitrification in bench-scale sequencing batch reactors. Water Sci. Technol. 20,277–284. Wang, C.X., Lin, H., Shi, K.H., 1999. Restoration of polluted river by pure oxygen aeration. Shanghai Environ. Sci. 18, 411–413 (in Chinese. Walpersdorf, E., Neumann, T., Stuben, D., 2004. Efficiency of natural calcite precipitation compared to lake marl application used for water quality improvement in an eutrophic lake. Appl. Geochem. 19, 1687–1698.。
外文翻译资料原文
Nt
t t
B
+
4
C
Figure 1. GraphicalAnalysis of Square Wave Spectrum
*
4
' ,SPECTRALCANCELLATION In figure 1, wave A is a square wave moving between the
A
t
values +I and -1. Wave B is a sinusoidal wave with the same fundamental frequency. Multiplying the waves generates wave C, a function that is always positive. Fourier analysis will show that the square wave, A, has spectral power at the frequency of the sine wave, B, because the average value of this product function, C, is non-zero. Figure 2 shows a similar set of waves, except that wave A is a square wave inverted every third cycle. Wave B is the same sinusoid as before, and wave C is the product of the two waves. Wave C is the argument of the Fourier integral. Note that the average value of wave C is exactly zero. Modified square wave A has no spectral power at the frequency of sine wave B. Repeated inversion has suppressedthis frequency.
外文翻译--外文原文
外文翻译--外文原文MCU DescriptionSCM is also known as micro-controller (Microcontroller Unit), commonly used letters of the acronym MCU MCU that it was first used in industrial control. Only a single chip by the CPU chip developed from a dedicated processor. The first design is by a large number of peripherals and CPU on a chip in the computer system, smaller, more easily integrated into a complex and demanding on the volume control device which. INTEL's Z80 is the first designed in accordance with this idea processor, then on the development of microcontroller and dedicated processors have parted ways.Are 8-bit microcontroller early or 4 bits. One of the most successful is the INTEL 8031, for a simple, reliable and good performance was a lot of praise. Then developed in 8031 out of MCS51 MCU Systems. SCM systems based on this system until now is still widely used. With the increased requirements of industrial control field, began a 16-bit microcontroller, because the cost is not satisfactory but have not been very widely used. After 90 years with the great development of consumer electronics, microcontroller technology has been a huge increase. With INTEL i960 series, especially the later series of widely used ARM, 32-bit microcontroller quickly replace high-end 16-bit MCU status and enter the mainstream market. The traditional 8-bit microcontroller performance have been the rapid increase capacity increase compared to 80 the number of times. Currently, high-end 32-bit microcontroller clocked over 300MHz, the performance catching the mid-90's dedicated processor, while the average model prices fall to one U.S. dollars, the most high-end [1] model only 10 dollars. Modern SCM systems are no longer only in the development and use of bare metal environment, a large number of proprietary embedded operating system is widely used in the full range of SCM. The handheld computers and cell phones as the core processing of high-end microcontroller can even use a dedicated Windows and Linux operating systems.SCM is more suitable than the specific processor used in embedded systems, so it was up to the application. In fact the number of SCM is the world's largest computer. Modern human life used in almost every piece of electronic and mechanical products will be integrated single chip. Phone, telephone, calculator, home appliances, electronic toys, handheld computers and computer accessories such as a mouse with a 1-2 in both the Department of SCM. Personal computer will have a large number ofSCM in the work. General car with more than 40 SCM, complex industrial control systems may even have hundreds of SCM in the same time work! SCM is not only far exceeds the number of PC and other computing the sum, or even more than the number of human beingsSingle chip, also known as single-chip microcontroller, it is not complete a certain logic chips, but to a computer system integrated into a chip. Equivalent to a micro-computer, and computer than just the lack of a microcontroller I / O devices. General talk: a chip becomes a computer. Its small size, light weight, cheap, for the study, application and development of facilities provided. At the same time, learning to use the MCU is to understand the principle and structure of the computer the best choice.SCM and the computer functions internally with similar modules, such as CPU, memory, parallel bus, the same effect as well, and hard disk memory devices, and different is its performance of these components were relatively weak many of our home computer, but the price is low , usually not more than 10 yuan you can do with it ...... some control for a class is not very complicated electrical work is enough of. We are using automatic drum washing machine, smoke hood, VCD and so on appliances which could see its shadow! ...... It is primarily as a control section of the core componentsIt is an online real-time control computer, control-line is that the scene is needed is a stronger anti-jamming ability, low cost, and this is, and off-line computer (such as home PC), the main difference.Single chipMCU is through running, and can be modified. Through different procedures to achieve different functions, in particular special unique features, this is another device much effort needs to be done, some great efforts are very difficult to do. A not very complex functions if the 50's with the United States developed 74 series, or the 60's CD4000 series of these pure hardware buttoned, then the circuit must be a large PCB board! But if the United States if the 70's with a series of successful SCM market, the result will be a drastic change! Just because you are prepared by microcomputer programs can achieve high intelligence, high efficiency and high reliability!As the microcontroller on the cost-sensitive, so now the dominant software or the lowest level assembly language, which is the lowest level in addition to more than binary machine code language, and as so low why is the use? Many high-levellanguage has reached the level of visual programming Why is not it? The reason is simply that there is no home computer as a single chip CPU, not as hard as a mass storage device. A visualization of small high-level language program which even if only one button, will reach tens of K of size! For the home PC's hard drive in terms of nothing, but in terms of the MCU is not acceptable. SCM in the utilization of hardware resources to be very high for the job so although the original is still in the compilation of a lot of use. The same token, if the giant computer operating system and applications run up to get home PC, home PC, also can not afford to.Can be said that the twentieth century across the three "power" era, that is, the age of electricity, the electronic age and has entered into the computer age. However, this computer, usually refers to the personal computer, referred to as PC. It consists of the host, keyboard, monitor and other components. Another type of computer, most people do not know how. This computer is to give all kinds of intelligent machines single chip (also known as micro-controller). As the name suggests, this computer system took only a minimal integrated circuit, can be a simple operation and control. Because it is small, usually hidden in the charged mechanical "stomach" in. It is in the device, like the human brain plays a role, it goes wrong, the whole plant was paralyzed. Now, this microcontroller has a very broad field of use, such as smart meters, real-time industrial control, communications equipment, navigation systems, and household appliances. Once all kinds of products were using SCM, can serve to upgrade the effectiveness of products, often in the product name preceded by the adjective - "intelligent," such as intelligent washing machines. Now some technical personnel of factories or other amateur electronics developers to engage in out of certain products, not the circuit is too complicated, that function is too simple and can easily be copied. The reason may be stuck in the product did not use a microcontroller or other programmable logic device.SCM historySCM was born in the late 20th century, 70, experienced SCM, MCU, SoC three stages.First model1.SCM the single chip microcomputer (Single Chip Microcomputer) stage, mainly seeking the best of the best single form of embedded systems architecture. "Innovation model" success, laying the SCM and general computer completely different path of development. In the open road of independent development ofembedded systems, Intel Corporation contributed.2.MCU the micro-controller (Micro Controller Unit) stage, the main direction of technology development: expanding to meet the embedded applications, the target system requirements for the various peripheral circuits and interface circuits, highlight the object of intelligent control. It involves the areas associated with the object system, therefore, the development of MCU's responsibility inevitably falls on electrical, electronics manufacturers. From this point of view, Intel faded MCU development has its objective factors. In the development of MCU, the most famous manufacturers as the number of Philips Corporation.Philips company in embedded applications, its great advantage, the MCS-51 single-chip micro-computer from the rapid development of the micro-controller. Therefore, when we look back at the path of development of embedded systems, do not forget Intel and Philips in History.Embedded SystemsEmbedded system microcontroller is an independent development path, the MCU important factor in the development stage, is seeking applications to maximize the solution on the chip; Therefore, the development of dedicated single chip SoC trend of the natural form. As the microelectronics, IC design, EDA tools development, application system based on MCU SoC design have greater development. Therefore, the understanding of the microcontroller chip microcomputer can be, extended to the single-chip micro-controller applications.MCU applicationsSCM now permeate all areas of our lives, which is almost difficult to find traces of the field without SCM. Missile navigation equipment, aircraft, all types of instrument control, computer network communications and data transmission, industrial automation, real-time process control and data processing, extensive use of various smart IC card, civilian luxury car security system, video recorder, camera, fully automatic washing machine control, and program-controlled toys, electronic pet, etc., which are inseparable from the microcontroller. Not to mention the area of robot control, intelligent instruments, medical equipment was. Therefore, the MCU learning, development and application of the large number of computer applications and intelligent control of the scientists, engineers.SCM is widely used in instruments and meters, household appliances, medical equipment, aerospace, specialized equipment, intelligent management and processcontrol fields, roughly divided into the following several areas:1. In the application of Intelligent InstrumentsSCM has a small size, low power consumption, controlling function, expansion flexibility, the advantages of miniaturization and ease of use, widely used instrument, combining different types of sensors can be realized Zhuru voltage, power, frequency, humidity, temperature, flow, speed, thickness, angle, length, hardness, elemental, physical pressure measurement. SCM makes use of digital instruments, intelligence, miniaturization, and functionality than electronic or digital circuits more powerful. Such as precision measuring equipment (power meter, oscilloscope, various analytical instrument).2. In the industrial control applicationWith the MCU can constitute a variety of control systems, data acquisition system. Such as factory assembly line of intelligent control3. In Household AppliancesCan be said that the appliances are basically using SCM, praise from the electric rice, washing machines, refrigerators, air conditioners, color TV, and other audio video equipment, to the electronic weighing equipment, varied, and omnipresent.4. In the field of computer networks and communications applicationsMCU general with modern communication interface, can be easy with the computer data communication, networking and communications in computer applications between devices had excellent material conditions, are basically all communication equipment to achieve a controlled by MCU from mobile phone, telephone, mini-program-controlled switchboards, building automated communications call system, train radio communication, to the daily work can be seen everywhere in the mobile phones, trunked mobile radio, walkie-talkies, etc.5. Microcomputer in the field of medical device applicationsSCM in the use of medical devices is also quite extensive, such as medical respirator, the various analyzers, monitors, ultrasound diagnostic equipment and hospital beds, etc. call system.6. In a variety of major appliances in the modular applicationsDesigned to achieve some special single specific function to be modular in a variety of circuit applications, without requiring the use of personnel to understand its internal structure. If music integrated single chip, seemingly simple function, miniature electronic chip in the net (the principle is different from the tape machine),you need a computer similar to the principle of the complex. Such as: music signal to digital form stored in memory (like ROM), read by the microcontroller, analog music into electrical signals (similar to the sound card).In large circuits, modular applications that greatly reduce the volume, simplifies the circuit and reduce the damage, error rate, but also easy to replace.7. Microcontroller in the application field of automotive equipmentSCM in automotive electronics is widely used, such as a vehicle engine controller, CAN bus-based Intelligent Electronic Control Engine, GPS navigation system, abs anti-lock braking system, brake system, etc..In addition, the MCU in business, finance, research, education, national defense, aerospace and other fields has a very wide range of applications.Application of six important part of learningMCU learning an important part of the six applications1, Bus:We know that a circuit is always made by the devices connected by wires, in analog circuits, the connection does not become a problem because the device is a serial relationship between the general, the device is not much connection between the , but the computer is not the same circuit, it is a microprocessor core, the device must be connected with the microprocessor, the device must be coordination between, so they need to connect on a lot, as if still analog circuit like the microprocessor and devices in the connection between the individual, the number of lines will be a little more surprising, therefore the introduction of the microprocessor bus Zhong Each device Gongtong access connections, all devices 8 Shuju line all received eight public online, that is the equivalent of all devices together in parallel, but only this does not work, if there are two devices send data at the same time, a 0, a 1, then, whether the receiver received what is it? This situation is not allowed, so to be controlled by controlling the line, time-sharing the device to work at any time only one device to send data (which can have multiple devices to receive both). Device's data connection is known as the data bus, the device is called line of control all the control bus. Internal or external memory in the microcontroller and other devices have memory cells, the memory cell to be assigned addresses, you can use, distribution, of course, to address given in the form of electrical signals, and as more memory cells, so, for the address allocation The line is also more of these lines is called the address bus.Second, data, address, command:The reason why these three together because of the nature of these three are the same - the number, or are a string of '0 'and '1' form the sequence. In other words, addresses, instructions are also data. Instruction: from single chip designer provides a number of commonly used instructions with mnemonic we have a strict correspondence between the developer can not be changed by the MCU. Address: the search for MCU internal, external storage units, input and output port based on the address of the internal unit value provided by the chip designer is good, can not be changed, the external unit can be single chip developers to decide, but there are a number of address units is a must (see procedures for the implementation of the process).Third, P0 port, P2 and P3 of the second function I use:Beginners often on the P0 port, P2 and P3 port I use the second function puzzled that the second function and have a switch between the original function of the process, or have a directive, in fact, the port The second feature is automatic, do not need instructions to convert. Such as P3.6, P3.7 respectively WR, RD signal, when the microchip processing machines external RAM or external I / O port, they are used as a second function, not as a general-purpose I / O port used, so long as a A microprocessor implementation of the MOVX instruction, there will be a corresponding signal sent from the P3.6 or P3.7, no prior use of commands. In fact 'not as a general-purpose I / O port use' is also not a 'no' but (user) 'not' as a general-purpose I / O port to use. You can arrange the order of a SETB P3.7's instructions, and when the MCU execution to the instruction, the also make P3.7 into a high, but users will not do so because this is usually will cause the system to collapse.Fourth, the program's implementation:Reduction in power after the 8051 microcontroller within the program counter (PC) in the value of 0000 ', the process is always from the 0000' units started, that is: the system must exist in ROM 0000 'this unit , and in 0000 'unit must be stored in a single instruction.5, the stack:Stack is a region, is used to store data, there is no special about the region itself is a part of internal RAM, special access to its data storage and the way that the so-called 'advanced post out backward first out ', and the stack has a special data transmission instructions that' PUSH 'and' POP ', has a special expertise in its servicesunit, that is, the stack pointer SP, whenever a PUSH instruction execution, SP on (in the Based on the original value) automatically add 1, whenever the implementation of a POP instruction, SP will (on the basis of the original value) automatically by 1. As the SP values can be changed with the instructions, so long as the beginning of the process to change the value of the SP, you can set the stack memory unit required, such as the program begins, with an MOV SP, # 5FH instructions When set on the stack starting from the memory unit 60H unit. There is always the beginning of the general procedure with such a directive to set the stack pointer, because boot, SP initial value of 07H, 08H This unit from the beginning to stack next, and 08H to 1FH 8031 is the second in the region, three or four working register area, often used, this will lead to confusion of data. Different authors when writing programs, initialize the stack is not exactly the same directive, which is the author's habit. When set up the stack zone, does not mean that the region become a special memory, it can still use the same memory region as normal, but generally the programmer does not regard it as an ordinary memory used.From the world of radio in the world to a single chipModern computer technology, industrial revolution, the world economy from the capital into the economy to knowledge economy. Field in the electronic world, from the 20th century into the era of radio to computer technology in the 21st century as the center of the intelligent modern era of electronic systems. The basic core of modern electronic systems are embedded computer systems (referred to as embedded systems), while the microcontroller is the most typical and most extensive and most popular embedded systems.First, radio has created generations of excellence in the worldFifties and sixties in the 20th century, the most representative of the advanced electronic technology is wireless technology, including radio broadcasting, radio, wireless communications (telegraph), Amateur Radio, radio positioning, navigation and other telemetry, remote control, remote technology. Early that these electronic technology led many young people into the wonderful digital world, radio show was a wonderful life, the prospects for science and technology. Electronics began to form a new discipline. Radio electronics, wireless communications began e-world journey. Radio technology not only as a representative of advanced science and technology at that time, but also from popular to professional fields of science, attracting the young people and enable them to find a lot of fun. Ore from the bedside to thesuperheterodyne radio radio; report issued from the radio amateur radio stations; from the telephone, electric bell to the radio control model. Became popular youth radio technology, science and technology education is the most popular and most extensive content. So far, many of the older generation of engineers, experts, Professor of the year are radio enthusiasts. Fun radio technology, radio technology, comprehensive training, from basic principles of electronics, electronic components to the radio-based remote control, telemetry, remote electronic systems, has trained several generations of technological excellence.Second, from the popularity of the radio era to era of electronic technologyThe early radio technology to promote the development of electronic technology, most notably electronic vacuum tube technology to semiconductor electronic technology. Semiconductor technology to realize the active device miniaturization and low cost, so more popular with radio technology and innovation, and to greatly broaden the number of non-radio-control areas.The development of semiconductor technology lead to the production of integrated circuit, forming the modern electronic technology leap from discrete electronics into the era of era of integrated circuits. Electronic design engineers no longer use the discrete electronic components designed circuit modules, and direct selection of integrated circuit components constitute a single system. They freed the design of the circuit unit dedicated to system design, greatly liberating the productive forces of science and technology, promote the wider spread of electronic systems.Semiconductor integrated circuits in the basic digital logic circuits first breakthrough.A large number of digital logic circuits, such as gates, counters, timers, shift registers, and analog switches, comparators, etc., for the electronic digital control provides excellent conditions for the traditional mechanical control to electronic control. Power electronic devices and sensor technology to make the original to the radio as the center of electronic technology turned to mechanical engineering in the field of digital control systems, testing in the field of information collection, movement of electrical mechanical servo drive control object.Semiconductor and integrated circuit technology will bring us a universal age of electronic technology, wireless technology as the field of electronic technology a part of.70 years into the 20th century, large scale integrated circuit appeared to promotethe conventional electronic circuit unit-specific electronic systems development. Many electronic systems unit into a dedicated integrated devices such as radios, electronic clocks, calculators, electronic engineers in these areas from the circuit, the system designed to debug into the device selection, peripheral device adapter work. Electronic technology, and electronic products enriched, electronic engineers to reduce the difficulty, but at the same time, radio technology, electronic technology has weakened the charm. The development of semiconductor integrated circuits classical electronic systems are maturing, remain in the large scale integrated circuit other than the shrinking of electronic technology, electronic technology is not the old days of radio fun times and comprehensive engineering training.Third, from the classic era of electronic technology to modern electronic technology of the times80 years into the 20th century, the century of economic change is the most important revolution in the computer. The computer revolution in the most important sign is the birth of the computer embedded applications. Modern computer numerical requirements should be born. A long period of time, is to develop the massive computer numerical duty. But the computer shows the logic operation, processing, control, attracting experts in the field of electronic control, they want development to meet the control object requirements of embedded applications, computer systems. If you meet the massive data-processing computer system known as general-purpose computer system, then the system can be the embedded object (such as ships, aircraft, motorcycles, etc.) in a computer system called the embedded computer. Clearly, both the direction of technology development are different. The former requires massive data storage, handling, processing and analysis of high-speed data transmission; while the latter requires reliable operation in the target environment, the external physical parameters on high-speed acquisition, analysis and processing logic and the rapid control of external objects. It will add an early general-purpose computer data acquisition unit, the output driver circuit reluctance to form a heat treatment furnace temperature control system. This general-purpose computer system is not possible for most of the electronic system used, and to make general-purpose computer system meets the requirements of embedded applications, will inevitably affect the development of high-speed numeric processing. In order to solve the contradiction between the development of computer technology, in the 20th century 70s, semiconductor experts another way, in full accordance with the electronic systemembedded computer application requirements, a micro-computer's basic system on a chip, the formation of the early SCM (Single Chip Microcomputer). After the advent of single chip in the computer industry began to appear in the general-purpose computer systems and embedded systems the two branches. Since then, both the embedded system, or general-purpose computer systems have been developed rapidly.Although the early general-purpose computer converted the embedded computer systems, and real embedded system began in the emergence of SCM. Because the microcontroller is designed specifically for embedded applications, the MCU can only achieve embedded applications. MCU embedded applications that best meet environmental requirements, for example, chip-level physical space, large-scale integrated circuits low-cost, good peripheral interface bus and outstanding control of instruction.A computer system microcontroller core, embedded electronic systems, intelligent electronic systems for the foundation. Therefore, the current single chip electronic system in widespread use of electronic systems to enable rapid transition to the classical modern intelligent electronic systems.4, single chip to create the modern era of electronic systemsA microcontroller and embedded systemsEmbedded computer systems from embedded applications, embedded systems for early general-purpose computer adapted to the object system embedded in a variety of electronic systems, such as the ship's autopilot, engine monitoring systems. Embedded system is primarily a computer system, followed by it being embedded into the object system, objects in the object system to achieve required data collection, processing, status display, the output control functions, as embedded in the object system, embedded system computer does not have an independent form and function of the computer. SCM is entirely in accordance with the requirements of embedded system design, so SCM is the most typical embedded systems. SCM is the early application of technical requirements in accordance with the design of embedded computer chip integration, hence the name single chip. Subsequently, the MCU embedded applications to meet the growing demands of its control functions and peripheral interface functions, in particular, highlight the control function, so has international name the single chip microcontroller (MCU, Microcontroller Unit).2 MCU modern electronic systems consisting of electronic systems will become mainstream。
汽车专业外文翻译5
英文翻译Motor Cars1. How the Engine WorksAn engine that converts heat energy into mechanical energy is called a heat engine ,and the car engine is one type of heat engine. It derives heat from the burning or 'combustion', of a fuel and converts this heat into useful work for driving the car.The fuel used in the vast majority of car engines is petrol, which is one of the many products obtained from crude oil found in the earth. Petrol, when mixed with the right amount of air, will burn when a flame or spark is applied to it.In the car engine, air mixed with petrol is taken into a confined space and compressed. The mixture is then ignited and it burns. In burning it heats the air, which expands, and the force of expansion is then converted into a rotary movement to drive the wheels of the car.To be able to use this energy effectively we have to control the burning or combustion process and the force of expansion. Firstly, we need a tube, or 'cylinder', closed at one end, in which to compress and burn the petrol and air mixture. Then we need a piston which can slide freely in the cylinder, and which can be driven outwards by theforce of expansion. To convert the outward movement of the piston into a rotary movement we must join it by a connecting rods to a crankshaft. We need one passage for the entry of the mixture into the cylinder and another to let out the used gases. To control the entry of the mixture and the exhaust of the gases we need valves, and these are called the inlet and exhaust valves. Finally, we need some means of igniting the mixture in the top of the cylinder, the part called the combustion chamber; and for this we use a sparking plug.By timing the opening and closing of the valves and by timing the arrival of the spark we can control the whole sequence of events and make the piston move in and out over and over again.THE CYLINDERSMotor-car engines may have four, six, or eight cylinders. Look at figure 1.These cylinders are usually mounted in a cylinder block on top of the engine. Beneath the cylinder block is the crankcase, which contains two shafts, the crankshaft and the camshaft. As you have read, the crankshaft is revolved by the outward movement ofthe pistons in the cylinders. This rotary movement of the crankshaft transmits the power developed by the engine through the gearbox to the driving wheels and sets the car in motion.When the crankshaft rotates it also causes the rotation of the camshaft, which lies alongside it in the crankcase. As the camshaft rotates, it pushes up rods alongside each cylinder to open and shut the valves at the top of the cylinder.There are two valves to each cylinder. The inlet valve lets air and petrol into the combustion chamber of the cylinder when it is opened. When the exhaust valve is opened the gases formed after the combustion in the chamber are allowed to escape . These gases are led away from the car through an exhaust pipe.Let us examine the action of one of the cylinders in more detail. Look at figure 2.In (a) the piston is near the top of the cylinder with the inlet valve open and the exhaust valve closed, If the crankshaft is turned, either by hand or by the starter motor ,the piston is drawn down by the connecting rod and a charge of petrol-air mixture rushes in. When the piston reaches the bottom of its stroke the inlet valve is closed by the action of a spring. This stroke is called the induction stroke.In (b) both valves are closed and the crankshaft forces the piston up to compress the mixture in the top of the cylinder. This, then, is called the 'compression' stroke. Towards the end of the compression stroke a spark from the sparking plug causes the mixture to ignite.In (c) we see that the heat of combustion has caused a rapid rise in pressure in the combustion chamber and this has forced the piston down. Through the connecting rod the piston causes the crankshaft to continue to rotate. This stroke is called the'expansion' or 'power' stroke, and we can say now that the engine has 'fired'. At the end ofthis stroke, as the crankshaft rotates, causing the camshaft alongside it to continue to rotate, one of the cams on the camshaft pushes up the rod, which causes the exhaust valve to open, allowing the exhaust gases to escape.In (d) we see the fourth and final stroke, the 'exhaust' stroke. The exhaust valve has been forced open by the rotation of the camshaft, and the crankshaft, continuing to rotate, drives the piston back up the cylinder, forcing out the exhaust gases. At the end of this stroke the exhaust valve is closed by the action of a spring, and the camshaft, continuing to rotate, pushes up a second rod to force the inlet valve open. Now the cylinder will receive another charge of petrol-air mixture, and the sequence of four strokes, 'induction', 'compression', 'expansion' or 'power', and 'exhaust', will startagain.Because there is a four-stroke sequence, or 'cycle', in this type of internal combustion engine it is called a four-stroke engine. There are also two一stroke engines used, for example, for motor scooters, and for some motor cycles.Let us think of a car with four cylinders. Remember that it is only on the expansion stroke that power is transmitted to make the crankshaft rotate. Let us number the cylinders, 1,2,3,4. They may transmit power in this order. 1,2,4,3. This means that when number 1 cylinder is on the expansion stroke, number 2 is on the compression stroke, number 4 is on the induction stroke, and number 3 cylinder is on the exhaust stroke. The four pistons, moving up and down inside their cylinders in this order, push down rods connected to the crankshaft at different times and at different points along its shaft. This keeps the crankshaft revolving and the crankshaft, when the gears are engaged, keeps the car moving.2. The Fuel and Ignition SystemsThe fuel system includes a fuel tank, a fuel pump, and a carburetor.The fuel pump may be operated either mechanically from the engine camshaft or electrically. Its function is to pump petrol from the petrol tank and deliver it to the carburetor. It contains a fine filler to exclude particles of dust or dirt which may have found their way into the tank.The carburetor is mounted on the inlet pipe, or inlet 'manifold', which leads to the inlet valves of each cylinder. Its function is to 'carburet', or mix, the required amounts of petrol and air for combustion in the cylinders. It regulates automatically the proportions of petrol and air and also allows the driver to control the rate of delivery of the mixture, and so vary the speed of the engine.See figure 3. This is a simple type of carburetor. It makes use of a fuel reservoir or "float chamber" to which petrol is pumped by the petrol pump. The level of the petrol in. the chamber is kept constant by the action of a float which, as it rises with the petrol, closes a needle valve when the correct level is reached. The petrol from the float chamber flows to a small jet situated in a narrow tube called the choke tube. When the engine is running, i.e. when the pistons are moving up and down in the cylinders, air is drawn in and passes through the choke tube. Here it mixes with the petrol and passes out into the inlet manifold of the engine. The amount of mixture allowed to pass is controlled by a butterfly valve, or ’throttle', situated in the carburetor outlet. This valve is operated by the accelerator pedal. An air cleaner may be connected to the air inlet to remove dust from the air and prevent it getting into thecylinders and down into the engine lubricating oil, where it can cause increased engine wear.The proportion of air and petrol required at varying engine speeds is controlled automatically. When starting a cold engine a much richer mixture, one with a higher proportion of petrol to air, is required. This is obtained by restricting the amount of air entering the carburetor. In most cars the driver does this by pulling out a knob called the choke and this partly closes the tube carrying air to the cylinders. The driver must remember to push the choke in again as soon as possible after starting to avoid damage to the engine and waste of fuel.THE IGNITION SYSTEMThe function of the ignition system is to provide the spark in the combustion chamber to ignite the mixture of petrol and air at the right instant. The system nor many comprises a coil, a distributor, and sparking plugs.The coil produces the high-voltage impulse required to make the spark at the sparking plugs. It really consists of two coils of insulated wire wound one around the other so that the number of turns in the inner, 'secondary', coil is much greater than that in the outer, 'primary', coil.A low voltage is supplied to the primary coil and suddenly interrupted. At that moment an impulse at very much higher voltage is induced in the secondary coil.V oltages of 6 or 12 volts supplied to the primary, low一tension, coil result in voltages of 10,000 volts or more being obtained from the secondary, high tension, coil. When the car is started the low-tension supply is provided by the car's battery.Remember that the low-tension supply must be broken suddenly to produce the high-tension supply from the secondary coil. This is done in an instrument called the distributor. The distributor is placed between the coil and the sparking plugs.Inside the distributor are contact points. The contact between them is broken by a revolving cam, which forces them apart. Then they are forced together again by a spring pressing against the arm holding one contact. It is when the contact points are forced apart that the low一tension supply, going through a lead to the coil, is suddenly interrupted.A second lead, going from the coil back to the distributor, conveys the high-tension (H.T.) supply to the distributor head. From there other leads distribute the H. T. supply to each of the sparking plugs in turn.You will remember that each cylinder of the car has a sparking plug. The metal part of the sparking plug is screwed into the combustion chamber of the cylinder. Theplug contains two electrodes with a small gap between them. When the plug receives a high-tension impulse from the distributor a spark is caused as the impulse jumps the gap between the two electrodes. This spark ignites the petrol-air mixture in the combustion chamber.3. Cooling and Lubricating the EngineThe combustion of the mixture in the engine naturally makes a great deal of heat and the engine must not be allowed to become overheated. The function of the cooling system is to control this heat.The engine may be either water or air cooled, but the vast majority is water cooled. Water in the water jacket surrounding the cylinders picks up the surplus heat from the engine and the heated water rises. It then circulates through the radiator, where it is cooled by the passage of air past the radiator tubes, and returns to the bottom of the water jacket. A fan, which is driven from the engine crankshaft, assists cooling by increasing the draught through the radiator at low speeds. A pump may be used to help in circulating the water.The engine must also be prevented from running too cool and therefore the temperature of the water is normally controlled within certain limits by the action of a device known as a thermostat. This has the effect of varying the circulation of the water so that, for instance, when the engine is first started less water is allowed to circulate and the engine warms up quickly.The cooling system can, of course, freeze up in very cold weather, and this can cause considerable damage. For this reason it is advisable to add good antifreeze solution, on that can be left in throughout the summer, which will prevent freezing in winter and protect the system from corrosion all the year round.THE LUBRICATION SYSTEMLubrication is necessary for two main reasons to reduce friction and wear in the engine, and to help carry away was to heat from the bearings, in which the crankshaft and camshaft revolve inside the crankcase, from the pistons, and from the other working parts. In addition, it helps the piston rings to seal in the combustion gases, to prevent them escaping down into the cylinders. (These piston rings are rings fitted into grooves around the top of each piston.)The majority of engines have what is known as a 'force feed', or pressure, lubricating system. The bottom of the crankcase is enclosed by a sheet-metal pan, or 'sump'. This holds the engine lubricating oil and has a drain plug through which used oil may be drained off. A pump draws oil from the sump and pumps it through a filterand then through channels, called 'oil ways', to the bearings of the crankshaft and camshaft, and also to the valve gear. At the same time, oil flowing from the bearings forms an oil mist in the crankcase and this mist lubricates the cylinder walls.A warning light or oil gauge, controlled by the pressure of the oil in the system, is usually provided so that the driver will know when the system is not functioning and the oil is not circulating properly. If the system is not functioning properly the working parts may seize up and cause serious damage to the car engine. It is, therefore, essential for the driver to stop the engine as soon as he sees his warning light come on.4. The BrakesThe brakes function by absorbing in friction the energy possessed by the moving car. In so doing they convert the energy into heat.There are two types of brakes, the drum brake and the disc brake. Either or both types may be fitted, but where both types are used it is usual for the disc brakes to be fitted to the front wheels.DRUM BRAKESThe drum brake consists of a pair of semicircular brake shoes mounted on a fixed back plate and situated inside a drum. This drum is fixed to the road wheel and rotates with it. One end of each shoe is on a pivot and a spring holds the other end in contact with the piston of a hydraulic cylinder. (In front brakes it is usual to use two hydraulic cylinders in order to equalize the pressures exerted by the shoes. See figure 4.) Each shoe is faced with material, known as brake lining, which produces high, frictional resistance.The hydraulic system comprises a master cylinder and the slave cylinders, which are the cylinders on the road wheels. The slave cylinders are connected to the master cylinder by tubing and the whole system is filled with hydraulic fluid. A piston in the master cylinder is connected to the brake pedal, so that when the driver depresses. The pedal the fluid is forced out to each slave cylinder and operates their pistons. The fluid pushes the pistons out of their cylinders. They, in turn, push against the inner ends of the brake shoes and force them against the brake drums in each wheel. We say that the brakes are on. This friction of the shoes against the drums, which are fixed to the road wheels, slows down or stops the car. As the brake pedal is allowed to come up, the hydraulic fluid returns to its original position, the pistons retract, and a spring attached to each brake shoe returns it also to its original position, free of the brake drum. Now we say that the brakes are off.The brakes may also be operated by mechanical linkages from the foot pedal and handbrake lever. Common practice is to operate both from and rear brakes hydraulically with a secondary mechanical system operating the rear brakes only from the hand lever. One of the great advantages of hydraulic operation is that the system is self-balancing, which means that the same pressure is automatically produced at all four brakes, whereas mechanical linkages have to be very carefully adjusted for balance. Of course, if more pressure is put on one of the brakes than on the others there-is a danger that the car will skid.The mechanical linkage operating on the rear brakes is a system of rods or cables connecting the handbrake lever to the brake-shoe mechanisms, which work entirely Independently of the hydraulic system.Drum brakes are prone to a reduction in the braking effort, known as 'fade', caused by the overheating of the linings and the drum. Fade can affect all or only some of the brakes at a time, but it is not permanent, and full efficiency returns as soon as the brakes have cooled down. However, fading is unlikely to occur except after the brakes have been used repeatedly in slowing the car from a high speed or after braking continuously down a steep hill. Descending such a hill, it would have been preferable to use engine braking by changing down into a lower gear. Drum brakes can be made less prone to fade by improving the cooling arrangements, by arranging for more air to be deflected over them, for example.DISC BRAKESThe disc brake consists of a steel disc with friction pads operated by slave hydraulic cylinders. The steel disc is attached to the road wheel and rotates with it. Part of this steel disc is enclosed in a caliper. (See figure 5) This caliper contains two friction pads, one on each side of the disc, and two hydraulic cylinders, one outside each pad. The pads are normally held apart by a spring, but when the driver depresses the brake pedal, pistons from the hydraulic cylinders force the pads against the sides of the disc. Because the disc is not enclosed all the way round, the heat generated when the brakes are applied is dissipated very much more quickly than it is from brake shoes which are entirely enclosed inside a drum. This means that disc brakes are less prone to fade than drum brakes.汽车1. 发动机如何工作一个把热能源转换成机械的能源的发动机叫做一个热发动机，而且汽车发动机是热发动机的一个类型。
5 中英文翻译
外文参考文献全文及译文英文原文4.1 DefinitionA durable lining is one that performs satisfactorily in the working environment during its anticipated service life. The material used should be such as to maintain its integrity and, if applicable, to protect other embedded materials.4.2 Design lifeSpecifying the required life of a lining (see Section 2.3.4) is signifi-cant in the design, not only in terms of the predicted loadings but also with respect to long-term durability. Currently there is no guide on how to design a material to meet a specified design life, although the new European Code for Concrete (British Standards Institution, 2003) addresses this problem. This code goes some way to recommending various mix proportions and reinforcement cover for design lives of 50 and 100 years. It can be argued that linings that receive annular grouting between the excavated bore and the extrados of the lining, or are protected by primary linings, for example sprayed concrete, may have increased resistance to any external aggressive agents. Normally, these elements of a lining system are considered to be redundant in terms of design life. This is because reliably assessing whether annulus grouting is complete or assessing the properties or the quality of fast set sprayed concrete with time is generally difficult.Other issues that need to be considered in relation to design life include the watertightness of a structure and fire-life safety. Both of these will influence the design of any permanent lining.4.3 Considerations of durability related to tunnel useLinings may be exposed to many and varied aggressive environments. Durability issues to be addressed will be very dependent not only on the site location and hence the geological environment but also on the use of the tunnel/shaft (see Fig. 4.1).The standards of material, design and detailing needed to satisfy durability requirements will differ and sometimes conflict. In these cases a compromise must be made to provide the best solution possible based on the available practical technology.4.4 Considerations of durability related to tunnel4.4.1 Steel/cast-iron liningsUnprotected steel will corrode at a rate that depends upon the temperature, presence of water with reactive ions (from salts and acids) and availability of oxygen. Typically corrosion rates can reach about 0.1 mm/year. If the availability of oxygen is limited, for example at the extrados of a segmental lining, pitting corrosion is likely to occur for which corrosion rates are more difficult to ascertain.Grey cast-iron segments have been employed as tunnel linings for over a hundred years, with little evidence as yet of serious corrosion. This is because this type of iron contains flakes of carbon that become bound together with the corrosion product to prevent water and, in ventilated tunnels, oxygen from reaching the mass of the metal. Corrosion is therefore stifled. This material is rarely if ever used in modern construction due to the higher strength capacities allowed with SGI linings.Spheroidal-Graphite cast iron (SGI) contains free carbon in nodules rather than flakes, and although some opinion has it that this will reduce the self-stifling action found in grey irons, one particular observation suggests that this is not necessarily so. A 250 m length of service tunnel was built in 1975 for the Channel Tunnel, and SGI segments were installed at the intersection with the tunnel constructed in 1880. The tunnel was mainly unventilated for the next ten years, by which time saline groundwater had caused corrosion and the intrados appeared dreadfully corroded. The application of some vigorous wire brushing revealed that the depth of corrosion was in reality minimal.4.4.2 Concrete liningsIn situ concrete was first used in the UK at the turn of the century. Precast concrete was introduced at a similar time but it was not used extensively until the 1930s. There is therefore only 70 to 100 years of knowledge of concrete behaviour on which to base the durability design of a concrete lining.The detailed design, concrete production and placing, applied curing and post curing exposure, and operating environment of the lining all impact upon its durability. Furthermore, concrete is an inherently variable material. In order to specify and design to satisfy durability requirements, assumptions have to be made about the severity of exposure in relation to deleterious agents, as well as the likely variability in performance of the lining material itself. The factors that generally influence the durability of the con-crete and those that should be considered in the design and detailing of a tunnel lining include:1.operational environment2.shape and bulk of the concrete3.cover to the embedded steel4.type of cement5.type of aggregate6.type and dosage of admixture7.cement content and free water/cement ratio8.workmanship, for example compaction’ finishing, curing9.permeability, porosity and dijfusivity of the final concrete.The geometric shape and bulk of the lining section is important because concrete linings generally have relatively thin walls and are possibly subject to a significant external hydraulic head. Both of these will increase the ingress of aggressive agents into the concrete.4.5 Design and specification for durabilityIt has to be accepted that all linings will be subject to some level of corrosion and attack by both the internal and external environment around a tunnel. They will also be affected by fire. Designing for durability is dependent not only on material specification but also on detailing and design of the lining.4.5.1 Metal liningsOccasionally segments are fabricated from steel, and these should be protected by the application of a protective system. Liner plates formed from pressing sheet steel usually act as a temporary support while an in situ concrete permanent lining is constructed. They are rarely protected from corrosion, but if they are to form a structural part of the lining system they should also be protected by the application of a protective system. Steel sections are often employed as frames for openings and to create small structures such as sumps. In these situations they should be encased in con-crete with suitable cover and anti-crack reinforcement. In addition, as the quality of the surrounding concrete might not be of a high order consideration should be given to the application of a protec-tive treatment to such steelwork.Spheroidal-Graphite cast iron segmental tunnel linings are usually coated internally and externally with a protective paint system. They require the radial joint mating surfaces, and the circumferential joint surfaces, to be machined to ensure good load transfer across thejoints and for the formation of caulking and sealing grooves. It is usual to apply a thin coat of protective paint to avoid corrosion between fabrication and erection, but long-term protective coatings are unnecessary as corrosion in such joints is likely to be stifled.It is suggested that for SGI segmental linings the minimum design thicknesses of the skin and outer flanges should be increased by one millimetre to allow for some corrosion (see Channel Tunnel case history in Chapter 10). If routine inspections give rise to a concern about corrosion it is possible to take action, by means of a cathodic protection system or otherwise, to restrain further deterioration. The chance of having to do this over the normal design lifetime is small.(1)Protective systemsCast iron segmental linings are easily protected with a coating of bitumen, but this material presents a fire hazard, which is now unacceptable on the interior of the tunnel. A thin layer, up to 200 um in thickness, of specially formulated paint is now employed; to get the paint to adhere it is necessary to specify the surface preparation. Grit blasting is now normally specified, however, care should be taken in the application of these coatings. The problem of coatings for cast iron is that grit blasting leavesbehind a surface layer of small carbon particles, which prevents the adhesion of materials, originally designed for steelwork, and which is difficult to remove. It is recommended that the designer take advice from specialist materials suppliers who have a proven track record.Whether steel or cast iron segments are being used, consideration of the ease with which pre-applied coatings can be damaged during handling, erection and subsequent construction activities in the tunnel is needed.(2) Fire resistanceExperiences of serious fires in modern tunnels suggest that temperatures at the lining normally average 600-700 °C, but can reach 1300 °C (see Section 4.5.3). It is arguable that fire protection is not needed except where there is a risk of a high-temperature (generally hydrocarbon) fire. It can be difficult to find an acceptable economic solution, but intumescent paint can be employed. This is not very effective in undersea applications. As an alternative an internal lining of polypropylene fibre reinforced concrete might be considered effective. 4.5.2 Concrete liningsAll aspects of a lining’s behaviour during its design life, both under load and within theenvironment, should be considered in order to achieve durability. The principle factors that should be considered in the design and detailing are:1.Material(s)2.production method3.application method (e.g. sprayed concrete)4.geological conditions5.design life6.required performance criteria.(1) CorrosionThe three main aspects of attack that affect the durability of concrete linings are:corrosion of metalschloride-induced corrosion of embedded metalscarbonation-induced corrosion of embedded metals.Corrosion of metalsUnprotected steel will corrode at a rate that depends upon temperature, presence of water and availability of oxygen. Exposed metal fittings, either cast in (i.e. a bolt- or grout-socket), or loose (e.g. a bolt), will corrode (see Section 4.5.4). It is impractical to provide a comprehensive protection system to these items and it is now standard practice to eliminate ferrous cast in fittings totally by the use of plastics. Loose fixings such as bolts should always be specified with a coating such as zinc.Chloride-induced corrosionCorrosion of reinforcement continues to represent the single largest cause of deterioration of reinforced concrete structures. Whenever there are chloride ions in concrete containing embedded metal there is a risk of corrosion. All constituents of concrete may contain some chlorides and the concrete may be contaminated by other external sources, for example de-icing salts and seawater.Damage to concrete due to reinforcement corrosion will only normally occur when chloride ions, water and oxygen are all present.Chlorides attack the reinforcement by breaking down the passive layer around the reinforcement. This layer is formed on the surface of the steel as a result of the highly alkaline environment formed by the hydrated cement. The result is the corrosion of the steel, whichcan take the form of pitting or general corrosion. Pitting corrosion reduces the size of the bar, while general corrosion will result in cracking and spalling of the concrete.Although chloride ions have no significant effect on the per-formance of the concrete material itself, certain types of concrete are more vulnerable to attack because the chloride ions then find it easier to penetrate the concrete. The removal of calcium alumi- nate in sulphate-resistant cement (the component that reacts with external sulphates), results in the final concrete being less resistant to the ingress of chlorides. To reduce the penetration of chloride ions, a dense impermeable concrete is required. The use of corrosion inhibitors does not slow down chloride migration but does enable the steel to tolerate high levels of chloride before corrosion starts.Current code and standard recommendations to reduce chloride attack are based on the combination of concrete grade (defined by cement content and type, water/cement ratio and strength, that is indirectly related to permeability) and cover to the reinforcement. The grade and cover selected is dependent on the exposure condition. There are also limits set on the total chlorides content of the concrete mix.Carbonation-induced corrosionIn practice, carbonation-induced corrosion is regarded as a minor problem compared with chloride- induced corrosion. Even if carbonation occurs it is chloride-induced corrosion that will generally determine the life of the lining. Carbonated concrete is of lower strength but as carbonation is lim-ited to the extreme outer layer the reduced strength of the concrete section is rarely significant.Damage to concrete will only normally occur when carbon dioxide, water, oxygen and hydroxides are all present. Carbonation is unlikely to occur on the external faces of tunnels that are constantly under water, whereas some carbonation will occur on the internal faces of tunnels that are generally dry. Carbonation-induced corrosion, how-ever, is unlikely in this situation due to lack of water. Linings that are cyclically wet and dry are the most vulnerable.When carbon dioxide from the atmosphere diffuses into the concrete, it combines with water forming carbonic acid. This then reacts with the alkali hydroxides forming carbonates. In the presence of free water, calcium carbonate is deposited in the pores. The pH of the pore fluid drops from a value of about 12.6 in the uncarbonated region to 8 in the carbonated region. If this reduction in alkalinity occurs close to the steel, it can cause depassivation. Inthe presence of water and oxygen corrosion of the reinforcement will then occur.To reduce the rate of carbonation a dense impermeable concrete is required.As with chloride-induced corrosion, current code and standard recommendations to reduce carbonation attack are based on the combination of concrete grade and reinforcement cover.Other chemical attackChemical attack is by direct attack either on the lining material or on any embedded materials, caused by aggressive agents being part of the contents within the tunnel or in the ground in the vicinity of the tunnel. Damage to the material will depend on a number of factors including the concentration and type of chemical in question, and the movement of the ground-water, that is the ease with which the chemicals can be replenished at the surface of the concrete. In this respect static water is generally defined as occurring in ground having a mass permeability of <10-6m/s and mobile water >10-6 m/s. The following types of exchange reactions may occur between aggressive fluids and components of the lining material:●sulphate attack●acid attack●alkali-silica reaction (ASR).Sulphates (conventional and thaumasite reaction)In soil and natural groundwater, sulphates of sodium, potassium, magnesium and calcium are common. Sulphates can also be formed by the oxi-dation of sulphides, such as pyrite，as a result of natural processes or with the aid of construction process activities. The geological strata most likely to have a substantial sulphate concentration are ancient sedimentary clays. In most other geological deposits only the weathered zone (generally 2m to 10m deep) is likely to have a significant quantity of sulphates present. By the same processes, sulphates can be present in contaminated ground. Internal corro-sion in concrete sewers will be, in large measure, due to the presence of sulphides and sulphates at certain horizons dependent on the level of sewer utilisation. Elevated temperatures will contribute to this corrosion.Ammonium sulphate is known to be one of the salts most aggressive to concrete. However, there is no evidence that harmful concentrations occur in natural soils.Sulphate ions primarily attack the concrete material and not the embedded metals. They are transported into the concrete in water or in unsaturated ground, by diffusion. The attackcan sometimes result in expansion and/or loss of strength. Two forms of sulphate attack are known; the conventional type leading to the formation of gypsum and ettringite, and a more recently identified type produ-cing thaumasite. Both may occur together.Constituents of concrete may contain some sulphates and the concrete may be contaminated by external sources present in the ground in the vicinity of the tunnel or within the tunnel.Damage to concrete from conventional sulphate reaction will only normally occur when water, sulphates or sulphides are all present. For a thaumasite-producing sulphate reaction, in addition to water and sulphate or sulphides, calcium silicate hydrate needs to be present in the cement matrix, together with calcium carbonate. In addition, the temperature has to be relatively low (generally less than 15 °C).Conventional sulphate attack occurs when sulphate ions react with calcium hydroxide to form gypsum (calcium sulphate), which in turn reacts with calcium aluminate to form ettringite. Sulphate resisting cements have a low level of calcium aluminate so reducing the extent of the reaction. The formation of gypsum and ettringite results in expansion and disruption of the concrete.Sulphate attack, which results in the mineral thaumasite, is a reaction between the calcium silicate hydrate, carbonate and sulphate ions. Calcium silicate hydrate forms the main binding agent in Portland cement, so this form of attack weakens the con-crete and, in advanced cases, the cement paste matrix is eventually reduced to a mushy, incohesive white mass. Sulphate resisting cements are still vulnerable to this type of attack.Current code and standard recommendations to reduce sulphate attack are based on the combination of concrete grade. Future code requirements will also consider aggregate type. There are also limits set on the total sulphate content of the concrete mix but, at present, not on aggregates, the recommendations of BRE Digest 363 1996 should be followed for any design.AcidsAcid attack can come from external sources, that are present in the ground in the vicinity of the tunnel, or from within the tunnel. Groundwater may be acidic due to the presence of humic acid (which results from the decay of organic matter), carbonic acid or sulphuric acid. The first two will not produce a pH below 3.5. Residual pockets of sulphuric (natural andpollution), hydrochloric or nitric acid may be found on some sites, particularly those used for industrial waste. All can produce pH values below 3.5. Carbonic acid will also be formed when carbon dioxide dissolves in water.Concrete subject to the action of highly mobile acidic water is vulnerable to rapid deterioration. Acidic ground waters that are not mobile appear to have little effect on buried concrete.Acid attack will affect both the lining material and other embedded metals. The action of acids on concrete is to dissolve the cement hydrates and, also in the case of aggregate with high calcium carbonate content, much of the aggregate. In the case of concrete with siliceous gravel, granite or basalt aggregate the sur-face attack will produce an exposed aggregate finish. Limestone aggregates give a smoother finish. The rate of attack depends more on the rate of movement of the water over the surface and the quality of the concrete, than on the type of cement or aggregate.Only a very high density, relatively impermeable concrete will be resistant for any period of time without surface protection. Damage to concrete will only normally occur when mobile water conditions are present.Current code and standard recommendations to reduce acid attack are based on the concrete grade (defined by cement content and type, water/cement ratio and strength). As cement type is not significant in resisting acid attack, future code requirements will put no restrictions on the type used.(2) Alkali Silica Reaction (ASR)Some aggregates contain particular forms of silica that may be susceptible to attack by alkalis originat-ing from the cement or other sources.There are limits to the reactive alkali content of the concrete mix, and also to using a combination of aggregates likely to be unreactive. Damage to concrete will only normally occur when there is a high moisture level within the concrete, there is a high reactivity alkali concrete content or another source of reactive alkali, and the aggregate contains an alkali-reactive constituent. Current code and standard recommendations to reduce ASR are based on limiting the reactive alkali content of the concrete mix, the recommendations of BRE 330 1999 should be followed for any design.(3) Physical processesVarious mechanical processes including freeze-thaw action, impact, abrasion and cracking can cause concrete damage.Freeze-thawConcretes that receive the most severe exposure to freezing and thawing are those which are saturated during freezing weather, such as tunnel portals and shafts.Deterioration may occur due to ice formation in saturated con-crete. In order for internal stresses to be induced by ice formation, about 90% or more by volume of pores must be filled with water. This is because the increase in volume when water turns to ice is about 8% by volume.Air entrainment in concrete can enable concrete to adequately resist certain types of freezing and thawing deterioration, provided that a high quality paste matrix and a frost-resistant aggregate are used.Current code and standard recommendations to reduce freeze- thaw attack are based on introducing an air entrainment agent when the concrete is below a certain grade. It should be noted that the inclusion of air will reduce the compressive strength of the concrete.ImpactAdequate behaviour under impact load can generally be achieved by specifying concrete cube compressive strengths together with section size, reinforcement and/or fibre content. Tensile capacity may also be important, particularly for concrete without reinforcement.AbrasionThe effects of abrasion depend on the exact cause of the wear. When specifying concrete for hydraulic abrasion in hydraulic applications, the cube compressive strength of the concrete is the principal controlling factor.CrackingThe control of cracks is a function of the strength of concrete, the cover, the spacing, size and position of reinforce-ment, and the type and frequency of the induced stress. When specifying concrete cover there is a trade-off between additional protection from external chloride attack to the reinforcement, and reduction in overall strength of the lining.4.5.3 Protective systemsAdequate behaviour within the environment is achieved by specify-ing concrete to thebest of current practice in workmanship and materials. Protection of concrete surfaces is recommended in codes and standards when the level of aggression from chemicals exceeds a maximum specified limit. Various types of surface protection include coatings, waterproof barriers and a sacrificial layer.(1) CoatingsCoatings have changed over the years, with tar and cut-back bitumens being less popular, and replaced by rubberised bitumen emulsions and epoxy resins. The fire hazard associated with bituminous coatings has limited their use to the extrados of the lining in recent times. The risk of damage to coat-ings during construction operations should be considered.(2) Waterproof barriersThe requirements for waterproof barriers are similar to those of coatings. Sheet materials are commonly used, including plastic and bituminous membranes. Again, the use of bituminous materials should be limited to the extrados.(3) Sacrificial layerThis involves increasing the thickness of the concrete to absorb all the aggressive chemicals in the sacrificial outer layer. However, use of this measure may not be appropriate in circumstances where the surface of the concrete must remain sound, for example joint surfaces in segmental linings.(4) Detailing of precast concrete segmentsThe detailing of the ring plays an important role in the success of the design and performance of the lining throughout its design life. The ring details should be designed with consideration given to casting methods and behaviour in place. Some of the more important considerations are as follows.4.5.5 Codes and standardsBuilding Research Establishment (BRE) Digest 330: 1999 (Building Research Establishment, 1999), Building Research Establishment (BRE) Digest 363: 1996 (Building Research Establishment, 1996)，BRE Special Digest 1 (Building Research Establishment, 2003) and British Standard BSEN 206-1: 2000 (British Standards Institution, 2003) are the definitive reference points for designing concrete mixes which are supplemented by BS8110 (British Standards Institution, 1997) and BS 8007 (British Standards Institution, 1987). BSEN 206-1 also references Eurocode 2: Design of Concrete Structures (European Commission,1992).(1) European standardsEN206 Concrete - Performance, Production and Conformity, and DD ENV 1992-1-1 {Eurocode 2: Design of Concrete Structures Part 1) (British Standards Institution, 2003 and European Commission，1992).Within the new European standard EN 206 Concrete - Perfor-mance, Production and Conformity，durability of concrete will rely on prescriptive specification of minimum grade, minimum binder content and maximum water/binder ratio for a series of defined environmental classes. This standard includes indicative values of specification parameters as it is necessary to cover the wide range of environments and cements used in the EU member states.Cover to reinforcement is specified in DD ENV 1992-1 -1 (Eurocode 2: Design of Concrete Structures Part 1 - European Commission, 1992).(2) BRE 330:1999This UK Building Research Establishment code (Building Research Establishment, 1999) gives the back-ground to ASR as well as detailed guidance for minimising the risks of ASR and examples of the methods to be used in new construction.(3) Reinforcement BRE 363: 1996This UK Building Research Establishment code (Building Research Establishment, 1996) discusses the factors responsible for sulphate and acid attack on concrete below ground level and recommends the type of cement and quality of concrete to provide resistance to attack. (4) BRE Special Digest 1This special digest (Building Research Establishment, 2003) was published following the recent research into the effects of thaumasite on concrete. It replaces BRE Digest 363: 2001. Part 4 is of specific reference to precast concrete tunnel linings.(5) BS 8110/BS 8007Guidance is given on minimum grade, minimum cement and maximum w/c ratio for different conditions of exposure. Exposure classes are mild, moderate, severe, very severe, most severe and abrasive related to chloride attack, carbonation and freeze-thaw. The relationship between cover of the reinforcement and concrete quality is also given together with crack width (British Standards Institution, 1987a and 1997a).(6) OthersChemically aggressive environments are classified in specialist standards. For information on industrial acids and made up ground, reference may be made to a specialist producer of acid resistant finishes or BS 8204-2 (British Standards Institu-tion, 1999). For silage attack, reference should be made to the UK Ministry of Agriculture, Fisheries and Food.中文翻译4.1 定义耐用的衬砌指的是在衬砌的预期服务寿命内提供令人满意的工作环境。
外文文献翻译原文+译文
外文文献翻译原文Analysis of Con tin uous Prestressed Concrete BeamsChris BurgoyneMarch 26, 20051、IntroductionThis conference is devoted to the development of structural analysis rather than the strength of materials, but the effective use of prestressed concrete relies on an appropriate combination of structural analysis techniques with knowledge of the material behaviour. Design of prestressed concrete structures is usually left to specialists; the unwary will either make mistakes or spend inordinate time trying to extract a solution from the various equations.There are a number of fundamental differences between the behaviour of prestressed concrete and that of other materials. Structures are not unstressed when unloaded; the design space of feasible solutions is totally bounded；in hyperstatic structures, various states of self-stress can be induced by altering the cable profile, and all of these factors get influenced by creep and thermal effects. How were these problems recognised and how have they been tackled?Ever since the development of reinforced concrete by Hennebique at the end of the 19th century (Cusack 1984), it was recognised that steel and concrete could be more effectively combined if the steel was pretensioned, putting the concrete into compression. Cracking could be reduced, if not prevented altogether, which would increase stiffness and improve durability. Early attempts all failed because the initial prestress soon vanished, leaving the structure to be- have as though it was reinforced; good descriptions of these attempts are given by Leonhardt (1964) and Abeles (1964).It was Freyssineti’s observations of the sagging of the shallow arches on three bridges that he had just completed in 1927 over the River Allier near Vichy which led directly to prestressed concrete (Freyssinet 1956). Only the bridge at Boutiron survived WWII (Fig 1). Hitherto, it had been assumed that concrete had a Young’s modulus which remained fixed, but he recognised that the de- ferred strains due to creep explained why the prestress had been lost in the early trials. Freyssinet (Fig. 2) also correctly reasoned that high tensile steel had to be used, so that some prestress would remain after the creep had occurred, and alsothat high quality concrete should be used, since this minimised the total amount of creep. The history of Freyssineti’s early prestressed concrete work is written elsewhereFigure1:Boutiron Bridge,Vic h yFigure 2: Eugen FreyssinetAt about the same time work was underway on creep at the BRE laboratory in England ((Glanville 1930) and (1933)). It is debatable which man should be given credit for the discovery of creep but Freyssinet clearly gets the credit for successfully using the knowledge to prestress concrete.There are still problems associated with understanding how prestressed concrete works, partly because there is more than one way of thinking about it. These different philosophies are to some extent contradictory, and certainly confusing to the young engineer. It is also reflected, to a certain extent, in the various codes of practice.Permissible stress design philosophy sees prestressed concrete as a way of avoiding cracking by eliminating tensile stresses; the objective is for sufficient compression to remain after creep losses. Untensionedreinforcement, which attracts prestress due to creep, is anathema. This philosophy derives directly from Freyssinet’s logic and is primarily a working stress concept.Ultimate strength philosophy sees prestressing as a way of utilising high tensile steel as reinforcement. High strength steels have high elastic strain capacity, which could not be utilised when used as reinforcement; if the steel is pretensioned, much of that strain capacity is taken out before bonding the steel to the concrete. Structures designed this way are normally designed to be in compression everywhere under permanent loads, but allowed to crack under high live load. The idea derives directly from the work of Dischinger (1936) and his work on the bridge at Aue in 1939 (Schonberg and Fichter 1939), as well as that of Finsterwalder (1939). It is primarily an ultimate load concept. The idea of partial prestressing derives from these ideas.The Load-Balancing philosophy, introduced by T.Y. Lin, uses prestressing to counter the effect of the permanent loads (Lin 1963). The sag of the cables causes an upward force on the beam, which counteracts the load on the beam. Clearly, only one load can be balanced, but if this is taken as the total dead weight, then under that load the beam will perceive only the net axial prestress and will have no tendency to creep up or down.These three philosophies all have their champions, and heated debates take place between them as to which is the most fundamental.2、Section designFrom the outset it was recognised that prestressed concrete has to be checked at both the working load and the ultimate load. For steel structures, and those made from reinforced concrete, there is a fairly direct relationship between the load capacity under an allowable stress design, and that at the ultimate load under an ultimate strength design. Older codes were based on permissible stresses at the working load; new codes use moment capacities at the ultimate load. Different load factors are used in the two codes, but a structure which passes one code is likely to be acceptable under the other.For prestressed concrete, those ideas do not hold, since the structure is highly stressed, even when unloaded. A small increase of load can cause some stress limits to be breached, while a large increase in load might be needed to cross other limits. The designer has considerable freedom to vary both the working load and ultimate load capacities independently; both need to be checked.A designer normally has to check the tensile and compressive stresses, in both the top and bottom fibre of the section, for every load case. The critical sections are normally, but not always, the mid-span and the sections over piers but other sections may become critical ，when the cable profile has to be determined.The stresses at any position are made up of three components, one of which normally has a different sign from the other two; consistency of sign convention is essential.If P is the prestressing force and e its eccentricity, A and Z are the area of the cross-section and its elastic section modulus, while M is the applied moment, then where ft and fc are the permissible stresses in tension and compression.c e t f ZM Z P A P f ≤-+≤Thus, for any combination of P and M , the designer already has four in- equalities to deal with.The prestressing force differs over time, due to creep losses, and a designer isusually faced with at least three combinations of prestressing force and moment;• the applied moment at the time the prestress is first applied, before creep losses occur,• the maximum applied moment after creep losses, and• the minimum applied moment after creep losses.Figure 4: Gustave MagnelOther combinations may be needed in more complex cases. There are at least twelve inequalities that have to be satisfied at any cross-section, but since an I-section can be defined by six variables, and two are needed to define the prestress, the problem is over-specified and it is not immediately obvious which conditions are superfluous. In the hands of inexperienced engineers, the design process can be very long-winded. However, it is possible to separate out the design of the cross-section from the design of the prestress. By considering pairs of stress limits on the same fibre, but for different load cases, the effects of the prestress can be eliminated, leaving expressions of the form:rangestress e Perm issibl Range Mom entZ These inequalities, which can be evaluated exhaustively with little difficulty, allow the minimum size of the cross-section to be determined.Once a suitable cross-section has been found, the prestress can be designed using a construction due to Magnel (Fig.4). The stress limits can all be rearranged into the form:()M fZ PA Z e ++-≤1 By plotting these on a diagram of eccentricity versus the reciprocal of the prestressing force, a series of bound lines will be formed. Provided the inequalities (2) are satisfied, these bound lines will always leave a zone showing all feasible combinations of P and e. The most economical design, using the minimum prestress, usually lies on the right hand side of the diagram, where the design is limited by the permissible tensile stresses.Plotting the eccentricity on the vertical axis allows direct comparison with the crosssection, as shown in Fig. 5. Inequalities (3) make no reference to the physical dimensions of the structure, but these practical cover limits can be shown as wellA good designer knows how changes to the design and the loadings alter the Magnel diagram. Changing both the maximum andminimum bending moments, but keeping the range the same, raises and lowers the feasible region. If the moments become more sagging the feasible region gets lower in the beam.In general, as spans increase, the dead load moments increase in proportion to the live load. A stage will be reached where the economic point (A on Fig.5) moves outside the physical limits of the beam; Guyon (1951a) denoted the limiting condition as the critical span. Shorter spans will be governed by tensile stresses in the two extreme fibres, while longer spans will be governed by the limiting eccentricity and tensile stresses in the bottom fibre. However, it does not take a large increase in moment ，at which point compressive stresses will govern in the bottom fibre under maximum moment.Only when much longer spans are required, and the feasible region moves as far down as possible, does the structure become governed by compressive stresses in both fibres.3、Continuous beamsThe design of statically determinate beams is relatively straightforward; the engineer can work on the basis of the design of individual cross-sections, as outlined above. A number of complications arise when the structure is indeterminate which means that the designer has to consider, not only a critical section,but also the behaviour of the beam as a whole. These are due to the interaction of a number of factors, such as Creep, Temperature effects and Construction Sequence effects. It is the development of these ideas whichforms the core of this paper. The problems of continuity were addressed at a conference in London (Andrew and Witt 1951). The basic principles, and nomenclature, were already in use, but to modern eyes concentration on hand analysis techniques was unusual, and one of the principle concerns seems to have been the difficulty of estimating losses of prestressing force.3.1 Secondary MomentsA prestressing cable in a beam causes the structure to deflect. Unlike the statically determinate beam, where this motion is unrestrained, the movement causes a redistribution of the support reactions which in turn induces additional moments. These are often termed Secondary Moments, but they are not always small, or Parasitic Moments, but they are not always bad.Freyssinet’s bridge across the Marne at Luzancy, started in 1941 but not completed until 1946, is often thought of as a simply supported beam, but it was actually built as a two-hinged arch (Harris 1986), with support reactions adjusted by means of flat jacks and wedges which were later grouted-in (Fig.6). The same principles were applied in the later and larger beams built over the same river.Magnel built the first indeterminate beam bridge at Sclayn, in Belgium (Fig.7) in 1946. The cables are virtually straight, but he adjusted the deck profile so that the cables were close to the soffit near mid-span. Even with straight cables the sagging secondary momentsare large; about 50% of the hogging moment at the central support caused by dead and live load.The secondary moments cannot be found until the profile is known but the cablecannot be designed until the secondary moments are known. Guyon (1951b) introduced the concept of the concordant profile, which is a profile that causes no secondary moments; es and ep thus coincide. Any line of thrust is itself a concordant profile.The designer is then faced with a slightly simpler problem; a cable profile has to be chosen which not only satisfies the eccentricity limits (3) but is also concordant. That in itself is not a trivial operation, but is helped by the fact that the bending moment diagram that results from any load applied to a beam will itself be a concordant profile for a cable of constant force. Such loads are termed notional loads to distinguish them from the real loads on the structure. Superposition can be used to progressively build up a set of notional loads whose bending moment diagram gives the desired concordant profile.3.2 Temperature effectsTemperature variations apply to all structures but the effect on prestressed concrete beams can be more pronounced than in other structures. The temperature profile through the depth of a beam (Emerson 1973) can be split into three components for the purposes of calculation (Hambly 1991). The first causes a longitudinal expansion, which is normally released by the articulation of the structure; the second causes curvature which leads to deflection in all beams and reactant moments in continuous beams, while the third causes a set of self-equilibrating set of stresses across the cross-section.The reactant moments can be calculated and allowed-for, but it is the self- equilibrating stresses that cause the main problems for prestressed concrete beams. These beams normally have high thermal mass which means that daily temperature variations do not penetrate to the core of the structure. The result is a very non-uniform temperature distribution across the depth which in turn leads to significant self-equilibrating stresses. If the core of the structure is warm, while the surface is cool, such as at night, then quite large tensile stresses can be developed on the top and bottom surfaces. However, they only penetrate a very short distance into the concrete and the potential crack width is very small. It can be very expensive to overcome the tensile stress by changing the section or the prestress。
机械类外文文献翻译(中英文翻译)
机械类外文文献翻译(中英文翻译)英文原文Mechanical Design and Manufacturing ProcessesMechanical design is the application of science and technology to devise new or improved products for the purpose of satisfying human needs. It is a vast field of engineering technology which not only concerns itself with the original conception of the product in terms of its size, shape and construction details, but also considers the various factors involved in the manufacture, marketing and use of the product.People who perform the various functions of mechanical design are typically called designers, or design engineers. Mechanical design is basically a creative activity. However, in addition to being innovative, a design engineer must also have a solid background in the areas of mechanical drawing, kinematics, dynamics, materials engineering, strength of materials and manufacturing processes.As stated previously, the purpose of mechanical design is to produce a product which will serve a need for man. Inventions, discoveries and scientific knowledge by themselves do not necessarily benefit people; only if they are incorporated into a designed product will a benefit be derived. It should be recognized, therefore, that a human need must be identified before a particular product is designed.Mechanical design should be considered to be an opportunity to use innovative talents to envision a design of a product, to analyze the systemand then make sound judgments on how the product is to be manufactured. It is important to understand the fundamentals of engineering rather than memorize mere facts and equations. There are no facts or equations which alone can be used to provide all the correct decisions required to produce a good design.On the other hand, any calculations made must be done with the utmost care and precision. For example, if a decimal point is misplaced, an otherwise acceptable design may not function.Good designs require trying new ideas and being willing to take a certain amount of risk, knowing that if the new idea does not work the existing method can be reinstated. Thus a designer must have patience, since there is no assurance of success for the time and effort expended. Creating a completely new design generally requires that many old and well-established methods be thrust aside. This is not easy since many people cling to familiar ideas, techniques and attitudes. A design engineer should constantly search for ways to improve an existing product and must decide what old, proven concepts should be used and what new, untried ideas should be incorporated.New designs generally have "bugs" or unforeseen problems which must be worked out before the superior characteristics of the new designs can be enjoyed. Thus there is a chance for a superior product, but only at higher risk. It should be emphasized that, if a design does not warrant radical new methods, such methods should not be applied merely for the sake of change.During the beginning stages of design, creativity should be allowedto flourish without a great number of constraints. Even though many impractical ideas may arise, it is usually easy to eliminate them in the early stages of design before firm details are required by manufacturing. In this way, innovative ideas are not inhibited. Quite often, more than one design is developed, up to the point where they can be compared against each other. It is entirely possible that the design which is ultimately accepted will use ideas existing in one of the rejected designs that did not show as much overall promise.Psychologists frequently talk about trying to fit people to the machines they operate. It is essentially the responsibility of the design engineer to strive to fit machines to people. This is not an easy task, since there is really no average person for which certain operating dimensions and procedures are optimum.Another important point which should be recognized is that a design engineer must be able to communicate ideas to other people if they are to be incorporated. Communicating the design to others is the final, vital step in the design process. Undoubtedly many great designs, inventions, and creative works have been lost to mankind simply because the originators were unable or unwilling to explain their accomplishments to others. Presentation is a selling job. The engineer, when presenting a new solution to administrative, management, or supervisory persons, is attempting to sell or to prove to them that this solution is a better one. Unless this can be done successfully, the time and effort spent on obtaining the solution have been largely wasted.Basically, there are only three means of communication available tous. These are the written, the oral, and the graphical forms. Therefore the successful engineer will be technically competent and versatile in all three forms of communication. A technically competent person who lacks ability in any one of these forms is severely handicapped. If ability in all three forms is lacking, no one will ever know how competent that person is!The competent engineer should not be afraid of the possibility of not succeeding in a presentation. In fact, occasional failure should be expected because failure or criticism seems to accompany every really creative idea. There is a great deal to be learned from a failure, and the greatest gains are obtained by those willing to risk defeat. In the final analysis, the real failure would lie in deciding not to make the presentation at all. To communicate effectively, the following questions must be answered:(1) Does the design really serve a human need?(2) Will it be competitive with existing products of rival companies?(3) Is it economical to produce?(4) Can it be readily maintained?(5) Will it sell and make a profit?Only time will provide the true answers to the preceding questions, but the product should be designed, manufactured and marketed only with initial affirmative answers. The design engineer also must communicate the finalized design to manufacturing through the use of detail and assembly drawings.Quite often, a problem will occur during the manufacturing cycle [3].It may be that a change is required in the dimensioning or tolerancing of a part so that it can be more readily produced. This fails in the category of engineering changes which must be approved by the design engineer so that the product function will not be adversely affected. In other cases, a deficiency in the design may appear during assembly or testing just prior to shipping. These realities simply bear out the fact that design is a living process. There is always a better way to do it and the designer should constantly strive towards finding that better way.Designing starts with a need, real or imagined. Existing apparatus may need improvements in durability, efficiently, weight, speed, or cost. New apparatus may be needed to perform a function previously done by men, such as computation, assembly, or servicing. With the objective wholly or partly defined, the next step in design is the conception of mechanisms and their arrangements that will perform the needed functions.For this, freehand sketching is of great value, not only as a record of one's thoughts and as an aid in discussion with others, but particularly for communication with one's own mind, as a stimulant for creative ideas.When the general shape and a few dimensions of the several components become apparent, analysis can begin in earnest. The analysis will have as its objective satisfactory or superior performance, plus safety and durability with minimum weight, and a competitive east. Optimum proportions and dimensions will be sought for each critically loaded section, together with a balance between the strength of the several components. Materials and their treatment will be chosen. These important objectives can be attained only by analysis based upon the principles ofmechanics, such as those of statics for reaction forces and for the optimumutilization of friction; of dynamics for inertia, acceleration, and energy; of elasticity and strength of materials for stress。
外文翻译原文
Project Management ProcessDurgesh BurdeAbstract:There are the rules of project management. Project management skills are indispensable for project managers, and other managers who control intricate actions and responsibilities, because intricate responsibilities are projects. Project management skills are necessary for any intricate responsibility, where diverse results are feasible, requiring plan and assess alternatives, and organizing actions and assets to deliver an outcome. Projects arrive in all forms and dimensions, from the little and simple to extremely big and highly intricate. Project management may be concerned with everything such as:- public, products, finance, buildings and premises, acquisition, services, purchasing, resources, construction, plant and equipment, training, culture, divestment, storage, distribution, logistics, IT and communications, staffing and management, administration, sales, selling, marketing, human resources, etc. Project management, for projects large or small, should follow the simple process:Project management process1.Detailed requirement for the project.2.Plan the project - time, team, activities, resources, and financials.3.Correspond the project plan to the project group.4.Consent and allot project actions.5.Control, encourage, notify, promote, and facilitate the project team.6.Verify, assess, evaluate project development; regulate project procedure, andnotify the project members and others.7.Finish project; evaluation and report on project performance; Admire and thanksto the project members.1. Detailed requirement for the projectFrequently called the project 'terms of reference', the project requirement should be an exact depiction of what the project aspires to accomplish, and the criteria and flexibilities concerned, its factors, scope, range, outputs, sources, participants, budgets and timescales.The project manager must discuss with others and then consent the project requirement with superiors, or with relevant authorities. The requirement may engage several drafts before it is agreed. A project requirement is essential in that it creates a measurable accountability for anyone wishing at any time to assess how the project is going, or its success on completion. Project terms of reference also provide an essential discipline and framework to keep the project on track, and concerned with the original agreed aims and parameters. A properly formulated and agreed project requirement also protects the project manager from being held to account for issues that are outside the original scope of the project or beyond the project manager's control.This is the step to agree special circumstances or exceptions with those in authority. Once you have published the terms of reference you have created a very firm set of expectations by which you will be judged. So if you have any concerns, or want to renegotiate, now's the time to do it.The largest projects can require several weeks to produce and agree project terms of reference. Most normal business projects however require a few days thinking and consulting to produce a suitable project requirement. Establishing and agreeing a project requirement is an important process even if your task is simple one.An outline for a project requirement:1.Describe purpose, aims and deliverables.2.State factors (timescales, budgets, range, scope, territory, authority).3.State people involved and the way the team will work (frequency of meetings,decision-making process).4.Establish 'break-points' at which to review and check progress, and how progressand results will be measured.2. Plan the project - time, team, activities, resources, and financials.Plan the various steps and tasks of the project. A valuable tip is to work backwards from the end aim, identifying all the things that need to be put in place and done, in reverse order. First, idea generation will help to gather most of the points and issues. For complex projects, or when you lack experience of the issues, involve others in the idea generation process. Thereafter it is a question of putting the issues in the right order, and establishing relationships and links between each issue. Complex projects will have a number of tasks running in parallel. Some parts of the project will need other parts of the project to be completed before they can begin or progress. Some projects will require a feasibility step before the completion of a detailed plan.a) Project timescalesMost projects come in late - that is just the way it is - so do not plan a timescale that is over-ambitious. Preferably, plan for some adversaries. If you have been given a fixed deadline, plan to meet it earlier, and work back from that earlier date. Build some slippage or leeway into each phase of the project. Err on the side of caution where you can. Otherwise, you will be making a rod for your own back.b) The project teamAnother important part of the planning stage is picking your team. Take great care, especially if you have team-members imposed on you by the project brief. Selecting and gaining commitment from the best team members - whether directly employed, freelance, contractors, suppliers, consultants or other partners - is crucial to the quality of the project, and the ease with which you are able to manage it. Generally try to establish yourteam as soon as possible. Identifying or appointing one or two people even during the terms of reference stage is possible sometimes. Appointing the team early maximizes their ownership and buy-in to the project, and maximizes what they can contribute. But be very cautious of appointing people before you are sure how good they are, and not until they have committed themselves to the project upon terms that are clearly understood and acceptable. Do not imagine that teams need to be full of paid and official project team members. Some of the most valuable team members are informal advisors, mentors, helpers, who want nothing other than to be involved and a few words of thanks. Project management on a tight budget can be a lonely business - get some help from good people you can trust, whatever the budget.To plan and manage large complex projects with various parallel and dependent tasks you will need to put together a 'Critical Path Analysis' and a spreadsheet on MS Excel or equivalent. Critical Path Analysis will show you the order in which tasks must be performed, and the relative importance of tasks. Some tasks can appear small and insignificant when they might actually be hugely influential in enabling much bigger activities to proceed or give best results. A Gantt chart is a useful way of showing blocks of activities over time, at a given cost, and for managing the project and its costs along the way.Various project management software is available, much of which is useful, but before trying it, you should understand and concentrate on developing the pure project management skills, which are described in this process. The best software in the world will not help you if you cannot do the key things.c) The project 'critical path analysis''Critical Path Analysis' sounds very complicated, but it's a very logical and effective method for planning and managing complex projects. This is how to create a critical path analysis. As an example, the project is a simple one - making a fried breakfast.First note down all the issues (resources and activities in a rough order):Assemble crockery and utensils, assemble ingredients, prepare equipment, make toast, fry sausages and eggs, grill bacon and tomatoes, lay table, warm plates, serve.Note that some of these activities must happen in parallel. That is to say, if you tried to make a fried breakfast by doing one task at a time, and one after the other, things would go wrong. Certain tasks must be started before others, and certain tasks must be completed in order for others to begin. The plates need to be warming while other activities are going on. The toast needs to be toasting while the sausages are frying, and at the same time the bacon and sausages are under the grill. The eggs need to be fried last. A critical path analysis is a diagrammatical representation of what needs done and when. Timescales and costs can be applied to each activity and resource. Here's the critical path analysis for making a fried breakfast:This critical path analysis example below shows just a few activities over a few minutes. Normal business projects would see the analysis extending several times wider than this example, and the time line would be based on weeks or months. It is possible to use MS Excel or a similar spreadsheet to create a critical path analysis, which allows financial totals and time totals to be planned and tracked. Various specialized project management software enable the same thing. Beware however of spending weeks on the intricacies of computer modeling, when in the early stages especially, a carefully hand drawn diagram - which requires no computer training at all - can put 90% of the thinking and structure in place.d) Gantt chartsGantt Charts are extremely useful project management tools. You can construct a Gantt Chart using MSExcel or a similar spreadsheet. Every activity has a separate line. Create a time-line for the duration of the project (the breakfast example shows minutes, but normally you would use weeks, or for very big long-term projects, months). You can colour code the time blocks to denote type of activity (e.g. intense, watching brief, directly managed, delegated and left to run, etc.) You can schedule review and break points. At the end of each line you can show as many cost columns for the activities as you need. The breakfast example shows just the capital cost of the consumable items and a revenue cost for labour and fuel. A Gantt chart like this can be used to keep track of progress for each activity and how the costs are running. You can move the time blocks around to report on actuals versus planned, and to re-schedule, and to create new plan updates. Costs columns can show plan and actuals and variances, and calculate whatever totals, averages, ratios, etc you need. Gantt Charts are the most flexible and useful of all project management tools, but remember they do not show the importance and inter-dependence of related parallel activities, and they will not show the necessity to complete one task before another can begin, as a critical path analysis will do, so you need both tools, especially at the planning stage.e) Project financial planning and reportingFor projects, involving more than petty cash you will need a spreadsheet to plan and report planned and actual expenditure. Use MSExcel or similar. If you do not know how to put together a basic financial plan, get some help from someone who knows. Make sure you bring a good friendly, flexible financial person into your team - it is a key function of project management, and if you cannot manage the financial processes your self, you need to be able to rely completely on whoever does it for you. The spreadsheet must enable you to plan, administer and report the detailed finances of your project. Create a cost line for main expenditure activity, and break this down into individual elements. Create a system for allocating incoming invoices to the correct activities (your bought-ledger people will not know unless you tell them), and showing when the costs hit the project account. Establish clear payment terms with all suppliers and stick to them. Projects develop problems when team members get dissatisfied; rest assured, non- or late-payment is a primary cause of dissatisfaction.Remember to set some budget aside for 'contingencies' - you will need it.f) Project contingency planningPlanning for and anticipating the unforeseen, or the possibility that things may not go as expected, is called 'contingency planning'. Contingency planning is vital in any task when results and outcomes cannot be absolutely guaranteed. Often a contingency budget needs to be planned, as there are usually costs associated. Contingency planning is about preparing fallback actions, and making sure that leeway for time, activity and resource exists to rectify or replace first-choice plans. A simple contingency plan for the fried breakfast would be to plan for the possibility of breaking the yolk of an egg, in which case spare resource (eggs) should be budgeted for and available if needed. Another might be to prepare some hash browns and mushrooms in the event that any of the diners are vegetarian. It may be difficult to anticipate precisely what contingency to plan for in complex long-term projects, in which case simply a contingency budget is provided, to be allocated later when and if required.3. Correspond the project plan to the project group.This serves two purposes: it informs people what is happening, and it obtains essential support, agreement and commitment. If your project is complex and involves a team, then you should involve the team in the planning process to maximize buy-in, ownership, and thereby accountability. Your project will also benefit from input and consultation from relevant people at an early stage.4. Consent and allot project actions.Your plan will have identified those responsible for each activity. Activities need to be very clearly described, including all relevant parameters, timescales, costs, and deliverables. When delegated tasks fail this is typically because they have not been explained clearly, agreed with the other person, or supported and checked while in progress. So publish the full plan to all in the team, but do not issue all the tasks unless the recipients are capable of their own forward planning. Long-term complex projects need to be planned in more detail and great care must be taken in delegating and supporting them. Do not delegate anything unless it makes sure for perfection.5. Control, encourage, notify, promote, and facilitate the project team.Manage the team and activities by meeting, communicating, supporting, and helping with decisions. Admire vociferously; charge quietly. One of the big challenges for a project manager is deciding how much freedom to give for each delegated activity. Tight parameters and lots of checking are necessary for inexperienced people who like clear instructions, but this approach is the kiss of death to experienced, entrepreneurial and creative people. They need a wider brief, more freedom, and less checking. Manage these people by the results they get - not how they get them. Look out for differences in personality and working styles in your team. They can get in the way of understandingand cooperation. Your role here is to enable and translate. Face to face meetings, when you can bring team members together, are generally the best way to avoid issues and relationships becoming personalized and emotional. Communicate progress and successes regularly to everyone. Give the people in your team the applause, particularly when someone high up expresses satisfaction - You must take the blame for anything that goes wrong - never dump on anyone in your team.6. Verify, assess, evaluate project development; regulate project procedure, and notify the project members and others.Check the progress of activities against the plan. Review performance regularly and at the stipulated review points, and confirm the validity and relevance of the remainder of the plan. Adjust the plan if necessary in light of performance, changing circumstances, and new information, but remain on track and within the original terms of reference. Be sure to use transparent, pre-agreed measurements when judging performance. Identify, agree and delegate new actions as appropriate. Inform team members and those in authority about developments, clearly, concisely and in writing. Plan team review meetings. Stick to the monitoring systems you established. Probe the apparent situations to get at the real facts. Examine causes and learn from mistakes. Identify reliable advisors and experts in the team and use them. Keep talking to people, and make yourself available to all.7. Finish project; evaluation and report on project performance; Admire and thanks to the project members.At the end of your successful project, hold a review with the team. Ensure you understand what happened and why. Replicate on any failures and mistakes positively, objectively, and without allocating personal blame. Reflect on successes gratefully and realistically. Write a review report, and make observations and recommendations about follow up issues and priorities - there will be plenty.As project manager, to be at the end of a project and to report that the project plan has been fully met, on time and on budget, is a significant achievement, whatever the project size and complexity. The mix of skills required is such that good project managers can manage anything.Conclusions:Businesses sometimes use formal systems development processes. These help assure that systems are developed successfully. A formal process is more effective in creating strong controls, and auditors should review this process to confirm that it is well designed and is followed in practice. A good formal systems development plan outlines: • A strategy to align development with the organization’s broader objectives•Standards for new systems•Project management policies for timing and budgeting•Procedures describing the processRegardless of the methodology used, the project development process will have the same above major stages: requirement for the project, Plan the project, project group, project actions, project team, evaluate project development, regulate project procedure and finish project; evaluation and report on project performance; Admire and thanks to the project members.References:1.Project Management Guidebook2.How to Manage Projects, Priorites and Deadlines3.Project Manager Today, January 2008.4.The Big Project, July 2008.<><><><><><><><><><><><><><><><>><><><><><><>><><><><><><><><> © Durgesh Burde. The author can be reached at durgesh19@ . The author is freelance writer and his area of research is project management and human development.。
新概念英语第三册课文及翻译5
新概念英语第三册课文及翻译5课文内容新概念英语第三册课文及翻译5是一篇约800字的文章，内容如下："In the wild north-west of Canada, there are no roads. Here separate towns and villages are hundreds of miles apart. Travellers cross the wide rivers and lakes by canoe or 'plane, but between the settlements, the simplest and quickest way to get about is on foot. A journey made on foot through this wilderness is called a 'hike'.One bright summer's morning I began a hike which was to take me through a vast forest to some distant lakes. I carried a rucksack with clothes, a light tent, and some tinned food. In the early morning the weather was fine, but by noon it was extremely hot, for there was no shade where the tall trees grew close together. In the afternoon I came to a wide swift river. It had been raining in the mountains and the river was swollen. A bridge had been built across it, but the water had risen aboveit and it was almost covered by the swift current. I had no wish to risk my life, so I unpacked my inflatable rubber boat and inflated it with my foot-pump. I tied my rucksack to the front of the boat and then swam and paddled my way to the other side."翻译"在加拿大的荒野西北部，没有公路。
- 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)。
Contents lists available at ScienceDirect , 2015, 528: 17-24.半正定矩阵的乘积Jianlian Cui , Chi-Kwong Li , Nung-Sing SzeDepartment of Mathematics, Tsinghua University, Beijing 100084, PR China Department of Mathematics, College of William and Mary, Williamsburg,VA 23187, USA Department of Applied Mathematics, The Hong Kong Polytechnic University,Hong Kong摘 要 已知每个具有非负性决定因子的复方阵是正半定矩阵的乘积.在乘积中存在需要两个或五个半正定矩阵的矩阵的表征.然而，缺少乘积中需要三个或四个半正定矩阵的矩阵的表征. 在本文中，我们给出了这两种类型矩阵的完整表征.有了这些结果，我们给了一个确定方阵是否可以表示为k 半正定矩阵的乘积的算法,k = 1,2,3,4,5. 关键词 半正定矩阵，数值范围1 介绍令n M 为n n ⨯个复数矩阵的集合.在[3]中，作者表明，具有非负决定因子的n M 中的矩阵总是可以写成五个或更少的半正定矩阵的乘积.这是对[1]的结果的延伸，n M 中具有的决定因素的每个矩阵都是五个或更少正定矩阵的乘积.类似于[1]中的分析，[3]的作者研究那些可以表示为两个，三个或四个半正定矩阵的乘积.特别地，对于矩阵可以表示为两个半正定矩阵的乘积，也有人表示不是zI 形式的任何矩阵，其中z 不是非负数，可以写成四个半正定矩阵的乘积.此外，[3，定理3.3] 已被证明.如果应用单一相似性来改变方阵形式12*0n T T M T ⎡⎤=∈⎢⎥⎣⎦，使得1T 是可逆的，2T 是零矩阵，并且如果1T 是三个正定矩阵的乘积，则T 可以表示为三个半正定矩阵的乘积.反之并不如此.以下示例显然不是这样.例题1.1让9900T --⎡⎤=⎢⎥⎣⎦,那么9313151132151811T -⎡⎤⎡⎤⎡⎤=⎢⎥⎢⎥⎢⎥-⎣⎦⎣⎦⎣⎦是三个半正定矩阵的乘积. 然而1[9]T =-不是它的乘积三个正定矩阵，因为1det()0T <.当然，可以强制1det()0T >这个明显必要条件推测是否符合额外的假设. 然而，通过修改示例1.12221222322299()()()00II T I A I A I A I --⎡⎤⊗==⊗⊗⊗⎢⎥⎣⎦, 使用因式分解123T A A A =.在修改示例中，我们有129T I =-和220T =.由[1，定理4]，129,T I =-是不小于5的正数的乘积确定矩阵.在下一节中，我们将给出可以写为三个半正定矩阵的乘积的矩阵的完整表征，此外，我们添加一个必要和足够的可逆矩阵的条件，可以写成三个正定矩阵的乘积. 通过这些结果，可以使用给定矩阵的Jordan 形式及其数值范围来决定是否可以表示为二，三，四或五个半正定矩阵的乘积.2 三个半正定矩阵的乘积我们将证明以下内容.定理2.1.假设120T R T T ⎡⎤=⎢⎥⎣⎦使得1T 是可逆的. 那么T 是三个半正定矩阵的乘积，当且仅当满足以下条件：2()00.a R T ≠≠或2()0,0,b R T ≠=1T 是三个正定矩阵的乘积. 我们通过一些引理来证明定理2.1引理2.2 令,n A S M ∈，使得S 是可逆的.那么当且仅当 * S AS 是时，A 是奇数个半正定矩阵的乘积.在下一个引理中，我们需要矩阵n A M ∈的数值范围的概念被定义为{}()*:,*1.n W A x Ax x C x x =∈=数值范围是研究矩阵的有用工具. 可以看到[2，第1章]为数值范围的基本属性.引理2.3 假设100p T R T ⎡⎤=⎢⎥⎣⎦使得1m T M ∈是可逆的，并且R 是非零的.那么T 是三个半正定矩阵的乘积.证明：首先，我们表明存在一个p m ⨯矩阵S ，使得1T RS +是三个正定矩阵的乘积.如果1m =，则存在p S C ∈，使得10T RS +>.假设1m >并且R 具有奇异值分解**111k k kR s x y s x y =++，其中1,...,k s s 是非零奇异的R 和1,...,m k x x C ∈和1,..,p k y y C ∈是相应的右和左单位奇异向量. 让{}1,...,m e e 是m C 的标准基.取一个U ，使11Ux e =. 由于1T 是可逆的，所以*11ˆT UTU =也是可逆的. 假设*1ˆt 是1T 的第一行. 令12ˆv t e ε=+，并且1ˆ()T ε是通过用*v 替换其第一行而从1T 获得的m m ⨯矩阵. 取足够小0ε>，使得v 不是1e 的倍数，矩阵1ˆ()T ε仍然是可逆的. 令1*11i S s re y v U θ-=且0r >，[0,2)θπ∈.且****1111ˆ().i U T RS U UTU URSU T re e v θ+=+=+ 由于v 不是1e 的倍数，所以矩阵*1e v 的秩不正常，因此*1()W e v 是具有焦点0和1v0>，其中1v 是v 的第一个条目; 例如，见[2，定理1.3.6]. 由于图()XW X 是连续的，对于足够大的0r >，*11ˆ(/)i W e v e T r θ-+ 仍然包含0作为任何[0,2)θπ∈的内点.那么令**1111ˆˆ()().i i i e W T re e v re W e v T rθθθ-+=+ 此外，可以选择值r 使得11ˆˆdet()/det(())r T T ε>. 现在由行列式相对于第一行的线性度，**111111ˆˆˆdet()det(())det()det()det(())i i T RS U T RS U T re e v T re T θθε+=+=+=+ 因为11ˆˆdet()det(())i T re T θε<，存在[0,2)θπ∈，使得1det()0T RS +>.通过[1，定理3](另见命题2.4)，1T RS +是三个正定矩阵的乘积.最后，请注意*1000000mmp p p p T R I T RSR I S T S I I +⎡⎤⎡⎤⎡⎤⎡⎤==⎢⎥⎢⎥⎢⎥⎢⎥⎢⎥⎣⎦⎣⎦⎣⎦⎣⎦ 由[3，定理3.3]，T 是三个半正定矩阵的乘积，T 也是引理2.2.定理证明2.1，假设T 是三个半正定矩阵的乘积.如果0R ≠或20T ≠，那么我们完成了.否则，10p T T =⊕是三个半正定矩阵的乘积.由[3，命题3.5]，1T 是三个正定矩阵的乘积.为了证明相反，我们考虑以下三种情况.情况1：假设0R ≠我们使用p 上的感应，2T 的大小.如果1p =，则结果从引理2.3得到：2[0]T =. 假设2T 的大小最大为1p -的结果.由于2T 是无效的，不失一般性，我们可以假设2T 是上三角矩阵，2122200T T T ⎡⎤=⎢⎥⎣⎦，其中211p T M -∈. 写12[]R R R =其中1R 是(1)m p ⨯-. 如果10R ≠，矩阵11210T R T ⎡⎤⎢⎥⎣⎦是一种三个半正定矩阵的乘积，例如123PP P . 此外，通过[3，定理2.2](另见命题3.1)，我们可以假设12P P 和都是可逆的.令222(1) 1.R X m p T ⎡⎤=+-⨯⎢⎥⎣⎦对于任意的U ，0>ε11312321111*10000000()1P P PP P P P X T P X εεεε----⎡⎤⎡⎤⎡⎤⎡⎤==⎢⎥⎢⎥⎢⎥⎢⎥⎣⎦⎣⎦⎣⎦⎣⎦ 显然，11[0]Q P =⊕和133[]Q P ε-=⊕是半正定矩阵.现在可以选择一个足够小，使0ε>,12121*1()1P P X Q P X εε--⎡⎤=⎢⎥⎣⎦ 也是半正定. 因此，T 是三个半正定矩阵123QQ Q 的乘积.现在假设10R =，那么T 的第() 1m +列是零列. 通过交换第() 1m +和最后一个索引，可以看到T 是排列相似于1212200000T RT T ⎡⎤⎢⎥⎢⎥⎢⎥⎣⎦,其中2122(1),(1)(1),11R m p T p p T p ⨯--⨯-⨯-是是是（）还要注意，R 非零，21T 是无效的. 通过归纳，1210T R T ⎡⎤⎢⎥⎣⎦是三个半正定矩阵123PP P 的乘积. 由[3，定理2.2]，我们可以进一步假定2P 和3P 都是可逆的. 令220Y T ⎡⎤=⎣⎦，那么任意0ε>，11*1312323211113220000()00000()100T RP P PP P P YP T YYP T εεεε----⎡⎤⎡⎤⎡⎤⎡⎤⎡⎤⎢⎥==⎢⎥⎢⎥⎢⎥⎢⎥⎢⎥⎣⎦⎣⎦⎣⎦⎣⎦⎢⎥⎣⎦再次，可以选择一个足够小的0ε>，使得上述方程左侧的所有三个矩阵都是半正定的. 因此，T 是排列相似的到三个半正定矩阵的乘积，因此T 也可以写成三个半正定矩阵的乘积.情况2：假设 0R =，2T 是非零. 在不失一般性的情况下，我们可以假设2T 是具有零对角线条目的上三角形，而2T 的第一行是非零的.令0mp I S ZI ⎡⎤=⎢⎥⎣⎦，那么 **1*122200000mmp p I T IZ T Z T S TS Z I T I T ⎡⎤⎡⎤⎡⎤⎡⎤==⎢⎥⎢⎥⎢⎥⎢⎥⎢⎥⎣⎦⎣⎦⎣⎦⎣⎦. 情况3：假设 0R =，20T =.如果1T 是三个正定矩阵的乘积，则10p T T =⊕是三个半正定矩阵的乘积.注意，定理2.1取决于检查可逆矩阵是三个正定矩阵的乘积. 这种条件在[1，定理3]中给出. 我们根据以下命题的数值范围重新得出结果，该方法基于[1，定理3和事实3.2]中的讨论.命题2.4 令n T M ∈使得() 0det T >.然后，当且仅当以下之一成立时，T 是三个正定矩阵的乘积.（a ）()W T 包含0作为内点.（b ）()W T 包含正数， T 的特征值的参数可以被排列成：11-...0nn j j πθθπθ=<≤≤<=∑使得.请注意，在[1，p. 88]，作者在条件(3.6b)条件(3.6b)中要求对应于我们的条件(b)，T 的所有实际特征值都是正的，这是通过我们假设所有j 的(,)j θππ∈-来保证的.3 确定因素的数量在本节中,我们描述了一种算法,用于确定乘积等于给定的n A M ∈与非负决定子的半正定矩阵的最小数量.我们首先提出以下定理,为矩阵A 的乘积提供一些简单的测试, 两个半正定矩阵满足条件(a),(b),(c)的等价性在[3，定理2.2]中给出.包括一个简短的证明.命题3.1 令A 为方阵. 以下是等同的. (a)A 是两个半正定矩阵的乘积.(b)=A BC ，其中,B C 是半正定矩阵，使得B 或C 是可逆的.(c)A 相似于非负对角矩阵.(d)A 与上部块三角矩阵整体相似，使得对角线块是对应于不同标量的标量矩阵. (e)A 的最小多项式只有简单的非负数. 证明：(c)(d)(e)已是显然.111**11**()():()()()()c b A S DS S S S DS S D S S S -----⇒===()()b a ⇒：显然.()()a c ⇒:假设=A BC ,其中,B C 是n n ⨯半正定. 令U 为酉矩阵，使*00k U BU B =⊕，其中0n k B M -∈为正定矩阵. 让1112*2122CC U CU C C ⎡⎤=⎢⎥⎣⎦. 假设V 是一个整数，使得对于正定矩阵*1100e V C V C =⊕. 我们可以用()U V I ⊕代替U ，并假设1100e C C =⊕.因为C 是半正定的，01*12200000e C C C C C ⎡⎤⎢⎥=⎢⎥⎢⎥⎣⎦,那么 010100**122000000000000000000e e k k k C C CC B B U AU C C ⎡⎤⎡⎤⎡⎤⎡⎤⎢⎥⎢⎥==⎢⎥⎢⎥⎢⎥⎢⎥⎣⎦⎣⎦⎢⎥⎢⎥⎣⎦⎣⎦,11110101012200112200000000000000000000000000000e k k k k k k k e E C C C C EC C B B B E E E E E E C B B ---⎡⎤⎡⎤-⎡⎤⎡⎤⎡⎤⎡⎤⎢⎥⎢⎥⎢⎥⎢⎥⎢⎥⎢⎥⎢⎥⎢⎥⎢⎥⎢⎥⎢⎥⎣⎦⎢⎥⎢⎥⎣⎦⎣⎦⎢⎥⎣⎦⎣⎦⎣⎦⎡⎤=⊕⎢⎥⎣⎦（）因此，A 相似于1122000000k e CB B ⎡⎤⊕⎢⎥⎣⎦（，它是半正定的，并且是相似于非负对角矩阵.现在，我们准备提出一个算法来检查具有det ()0,A ≥的矩阵n A M ∈是否可以被写为k 个正半矩阵的乘积，但1,2,3,4,5k ≠.算法3.2 令n A M ∈,det ()0,A ≥如果n A I α=，使得[0,)α∉+∞,则A 可以表示为五个半正定矩阵的乘积.否则,应用与A 的酉矩阵相似得到上三角矩阵120T R T T ⎡⎤=⎢⎥⎣⎦,使得1T 是可逆的,2T 是无效的.(1)如果T 是非负对角矩阵，那么T 本身就是一个半正定矩阵.(2)条件(1)不成立，A 满足命题3.1中的任何一个等效条件. 那么A 可以表示为两个半正定矩阵的乘积.(3)假设(1)和(2)不成立. 那么A 可以表示为三个半正定矩阵的乘积，但不限于以下任何一个.(3.a)R 或2T 不为零.(3.b)0R =和20T =，1T 是三个正定的乘积矩阵.在(3.b)中，如果以下之一成立，则可逆矩阵1T 是三个正定矩阵的乘积. (i)1det 0,T ≠，1()W T 包含0作为内部点，(ii)0不在1()W T 的内部，1()W T 包含正数，j θ∑，其中12k πθθθπ-<≤<⋅⋅⋅<<是1T 的特征值的参数.（4）假设条件(1),(2),(3)不成立，即1=0p T T ⊕，使得上三角矩阵1T 对于(i)和(ii)均不成立,那么A 可以表示为四个半正定矩阵的乘积.4 致谢作者要感谢裁判仔细阅读手稿，崔先生的研究得到了国家自然科学基金委的支持，是滑铁卢大学量子计算研究所的附属成员.他也是上海大学著名教授；他的研究由美国NSF 授权DMS 1331021，西蒙斯基金会赠款351047和中国11571220的NNSF 拨款支持.Sze 的研究得到了香港RGC 授予理大502512及理大中央研究资助G-UC25的支持.5 参考文献[1] C.S. Ballantine, Products of positive definite matrices. IV, Linear Algebra Appl. 3 (1970) 79–114.[2] Horn Johnson, Topics in Matrix Analysis, Cambridge University Press, Cambridge, 1991.[3] P.Y. Wu, Products of positive semidefinite matrices, Linear Algebra Appl. 111 (1988) 53–61.。