Effect of FGM core

合集下载

Effect of the material-hardening mode on the springback

Effect of the material-hardening mode on the springbacksimulation accuracy of V-free bendingXuechun Li a,*,Yuying Yang a ,Yongzhi Wang a ,Jun Bao a ,Shunping Li baSchool of Material Science and Engineering,Harbin Institute of Technology,435,Hei Longjiang,Harbin 150001,ChinabNorthwestern Polytechnical University,Xi’an,Shanxi 710072,ChinaReceived 2January 2001AbstractLower springback simulation accuracy is a common problem for large complex sheet metal parts with FE software.The springback of V-free bending is studied in this paper by using a self-developed 2D elasto-plastic ﬁnite element program.A linear-hardening model and an elasto-plastic power-exponent hardening model of the material are adopted in this study.The change of the material’s Young’s modulus with plastic deformation is also considered.The results show that the material-hardening mode directly affects the springback simulation accuracy,and the greater the veracity of the hardening mode,the greater the springback accuracy.#2002Published by Elsevier Science B.V .Keywords:Springback simulation;Hardening model;Young’s modulus1.IntroductionSpringback is severe during the unloading phase of bending and greatly affects the forming accuracy of the bent parts.To exactly and effectively forecast the springback is the basis of achieving a steady and precise shape of the formed part.Springback is related to many factors such as tooling geometry,material properties,friction and so on.Springback is so complicated that it is hard to simulate ually very low precision can be found in ﬁnite element codes for springback simulation [1].Springback is caused by the release of internal stress during the unloading phase in sheet metal forming,so factors affecting the stress calculation accuracy will affect the springback calculation.It is indicated that the ﬁnite element dimensions and the material’s hardening model have greater effects on the stress calculation.The material’s hardening model,viz the material’s stress–strain relationship,expresses the basic properties of the material during plastic deformation.It is important to cor-rectly select and reasonably pre-digest the stress–strain curve to enhance the accuracy of the springback simulation of bending with FE codes [2,3].It is common knowledge that Young’s modulus is an important parameter in a plastic-hardening model.The lit-erature shows that the value of Young’s modulus of cold-rolled plate varies when it is undergoing plastic deformation,therefore,to consider the change of Young’s modulus of the material can increase the springback simulation accuracy [4–6].In this paper,the springback of V-free bending is studied with three materials:LY12(M),LF21(M)and SPCC,and the change of the material’s Young’s modulus with plastic deformation is considered in a self-developed 2D elasto-plastic ﬁnite element code to study the effects of the materi-al’s hardening mode on springback accuracy.2.Material-hardening modelGenerally,when a sheet metal begins to deform plasti-cally,the stress–strain relationship is very complicated and hard to express.For the convenience of actual application,some material-hardening models and relevant empirical equations have been put forward for different metal materi-als.Among them,the linear-hardening model and the elasto-plastic power-exponent hardening model are two frequently used models for simulation analysis.The linear-hardening model is as follows:s ¼E e ðe <e S Þs s þE T e ðe !e S Þ (1)where e S is the strain at the yield point,E the Young’s modulus (elastic modulus),E T the tangent modulus after yielding,s s the yield stress,s the true stress and e the truestrain.Journal of Materials Processing Technology 123(2002)209–211*Corresponding author.Tel.:þ86-451-6415776;fax:þ86-451-6415776.E-mail address:youlf@ (X.Li).0924-0136/02/$–see front matter #2002Published by Elsevier Science B.V .PII:S 0924-0136(02)00055-9The elasto-plastic power-exponent hardening model has the form:s ¼E e ðe <e S ÞK e n ðe !e S Þ(2)where K and n represents the hardening coef ﬁcient and the hardening exponent,respectively.The change of Young ’s modulus with plastic deforming can be expressed as [7]:E ¼E 0ð1þe p Þmwhere E 0is the initial Young ’s modulus and e p the equivalent plastic strain.Through the tensile test,the basic property parameters for three materials:LY12(M),LF21(M)and SPCC,were obtained,as shown in Table 1.And the Young ’s modulus –plastic strain relationships for the materials are shown in Fig.1.3.FEM for the springback simulation of V-free bending The static implicit algorithm is adopted in the FE code to simulate the V-free bending process.The counter node contact force at the end of forming phase is used as the initial acting force for springback calculation.Then an iteration algorithm begins until all the node contact forces becomes 0.The tooling dimensions for V-free bending are shown in Fig.2.In the developed FE code,an elasto-plastic algorithm is used in the loading phase and an elastic algo-rithm in springback,and the four nodes isoparametric plane element is adopted.Also,the change of Young ’s modulus with plastic deformation is considered.4.Results and analysisIn V-free bending simulation,different hardening modes result in different stress ﬁelds at the end of bending forming,viz the initial acting force for springback calculation will be different.In the simulation,the material ’s hardening mod-ulus H 0must be calculated to form a constitutive matrix,which can be expressed as:H 0¼d s d e p(3)or H 0¼EE T E ÀE T(4)where E T is the slope of the stress –strain curve after yielding,namely E T ¼d s d e(5)Table 1Basic property parameters Materials s (MPa)E 0(GPa)E T (MPa)K (MPa)n mLY12(M)91.4170.089386.668356.2250.206À0.0855LF21(M)60.0067.339148.15164.1170.183À0.1068SPCC 246.05159.048553.339551.6470.226À0.0351Fig.1.The change of Young ’s modulus with plasticdeformation.Fig.2.Tooling diagram:(1)punch;(2)blank;(3)die.Fig.3.Bending angle vs.springback angle for three materials without considering the change of Young ’s modulus with plastic deformation.BISO —linear-hardening model,MISO —elasto-plastic power-exponent hardening model.210X.Li et al./Journal of Materials Processing Technology 123(2002)209–211It is obvious that the stress obtained with the elasto-plastic power-exponent hardening model is more accurate than that with the linear-hardening model.As a result,the initial acting force for springback calculation is more accurate with the use of the elasto-plastic power-exponent hardening model.Fig.3is the relationship between the bending angle in the forming phase and the springback angle in the springback phase under the two material-hardening models.The bend-ing angle is the supplementary angle of the bent part ’s included angle.The ﬁgure shows that the springback calcu-lated with the elasto-plastic power-exponent hardening model is closer to the experiment results than that with the linear-hardening model.Figs.4–6show the relationships between the bending angle in the forming phase and the springback angle in the springback phase for the three materials,with the elasto-plastic power-exponent hardening model including the change of Young ’s modulus with plastic deformation.It has been proven by the experimental results that the value of Young ’s modulus changes along with plastic deformation,so considering the change of Young ’s modulus in the FE code can describe the deforming state of the material more truly,and the springback calculated is closer to the experiment value.5.Conclusions1.The material ’s hardening model directly affects the accuracy of springback calculation.The greater the veracity of the hardening model,the greater the springback accuracy.The springback calculated with the elasto-plastic power-exponent hardening model agrees better with experimental results than that calculated with the linear-hardening model.2.Young ’s modulus has a great effect on springback simulation ing the change of Young ’s modulus with plastic deformation can enhance the accuracy of springback simulation.References[1] D.B.Zhu,Newest progress on the springback ’s study of plate forming,J.Plas.Eng.1(2000)11–17.[2]Z.T.Zhang,D.Lee,Development of a new model for plane strainbending and springback analysis,J.Mater.Eng.Perform.4(3)(1995)291–300.[3]Z.T.Zhang,S.J.Hu,Stress and residual stress distributions in planestrain bending,Int.J.Mech.Sci.40(6)(1998)533–543.[4] A.Makinouchi,H.Ogawa,Use the ITAS-2D Program to Calculate theSpringback with Considering the Change in Young ’s Modulus due to Plastic Deformation,Unite Report Conference of Plastic Deformation,No.43,Tokyo,1992,pp.755–756.[5]L.J.Devin,A.H.Streppl,A process model for air bending,J.Mater.Process.Technol.57(1996)48–54.[6]S.Shima,M.Yang,A study of accuracy in an intelligent V-bendingprocess for sheet metals,Material 44(500)(1995)578–583.[7]X.C.Li,Y .Y .Yang,Discuss on the relationship between the Young ’smodulus and plastic deformation,J.Harbin Inst.Technol.32(5)(2000)54–56.Fig.4.Bending angle vs.springback angle for materialSPCC.Fig.5.Bending angle vs.springback angle for materialLY12(M).Fig.6.Bending angle vs.springback angle for material LF21(M).X.Li et al./Journal of Materials Processing Technology 123(2002)209–211211。

不同建筑固废再生骨料取代率下粗粒土填料永久变形特性及安定行为研究

第 55 卷第 3 期2024 年 3 月中南大学学报(自然科学版)Journal of Central South University (Science and Technology)V ol.55 No.3Mar. 2024不同建筑固废再生骨料取代率下粗粒土填料永久变形特性及安定行为研究肖源杰1, 2，王政1，AMINU Umar Faruk 1，王萌1，李昀博1，孔坤锋3，陈宇亮4，周震5，李志勇4(1. 中南大学土木工程学院，湖南长沙，410075；2. 重载铁路工程结构教育部重点实验室 (中南大学)，湖南长沙，410075；3. 中国铁道科学研究院集团有限公司铁道建筑研究所，北京，100081；4. 湖南省交通科学研究院有限公司，湖南长沙，410015；5. 广东省交通规划设计研究院集团股份有限公司，广东广州，510440)摘要：为探究城市建筑拆除固废再生骨料部分或全部取代天然骨料用于粗粒土路基填料的可行性，开展不同再生骨料取代率、含水率、围压和剪应力比等组合下的室内大型静动三轴试验，定量研究土性参数和应力状态对试样抗剪强度和累积塑性应变特性的影响规律。

基于半对数坐标下累积塑性应变发展的多阶段特征，分别考虑不同阶段塑性变形累积速率以及相邻两阶段的塑性变形累积速率的差异，提出适用于建筑固废再生骨料路基填料的新型安定行为判定准则。

研究结果表明：再生骨料路基填料试样的累积塑性应变随含水率和剪应力比的增大而增大，当再生骨料路基填料试样在剪应力比为0.3和0.5时，抗累积变形性能与天然骨料路基填料试验所得的抗累积变形性能接近，综合考虑抗剪强度和累积塑性变形特性的再生骨料路基填料最优取代率为85%；新安定行为判定准则具有较高的准确性，可为相似路基填料的长期路用性能评定提供理论依据。

关键词：道路工程；建筑固废；再生骨料；永久变形；安定行为中图分类号：TU43 文献标志码：A 文章编号：1672-7207（2024）03-1008-15Permanent deformation characteristics and shakedown behavior of coarse-grained fill materials incorporating different proportions ofaggregates recycled from building demolition wastes收稿日期： 2023 −06 −20；修回日期： 2023 −08 −20基金项目(Foundation item)：国家自然科学基金资助项目(52178443)；国家重点研发计划项目(2019YFC1904704)；交通运输部重点科技项目(2022-MS5-122)；中南大学研究生自主探索创新项目(2023ZZTS0019) (Project(52178443) supported by the National Natural Science Foundation of China; Project(2019YFC1904704) supported by the National Key Research & Development Program of China; Project(2022-MS5-122) supported by the Ministry of Transport Key Science & Technology Program of China; Project(2023ZZTS0019) supported by the Graduate Student Free Exploration Innovation Program of Central South University)通信作者：王萌，博士研究生，从事路基工程研究；E-mail ：**************.cnDOI: 10.11817/j.issn.1672-7207.2024.03.015引用格式：肖源杰, 王政, AMINU Umar Faruk, 等. 不同建筑固废再生骨料取代率下粗粒土填料永久变形特性及安定行为研究[J]. 中南大学学报(自然科学版), 2024, 55(3): 1008−1022.Citation: XIAO Yuanjie, WANG Zheng, AMINU Umar Faruk, et al. Permanent deformation characteristics and shakedown behavior of coarse-grained fill materials incorporating different proportions of aggregates recycled from building demolition wastes[J]. Journal of Central South University(Science and Technology), 2024, 55(3): 1008−1022.第 3 期肖源杰，等：不同建筑固废再生骨料取代率下粗粒土填料永久变形特性及安定行为研究XIAO　Yuanjie1, 2, WANG　Zheng1, AMINU　Umar Faruk1, WANG　Meng1, LI　Yunbo1, KONG　Kunfeng3,CHEN　Yuliang4, ZHOU　Zhen5, LI　Zhiyong4(1. School of Civil Engineering, Central South University, Changsha 410075, China;2. MOE Key Laboratory of Engineering Structure of Heavy Haul Railway(Central South University),Changsha 410075, China;3. Railway Engineering Research Institute, China Academy of Railway Sciences Corporation Limited,Beijing 100081, China;4. Hunan Communications Research Institute Co. Ltd., Changsha 410015, China;5. Guangdong Communication Planning & Design Institute Group Co. Ltd., Guangzhou 510440, China)Abstract:In order to address the feasibility of the mixed subgrade filling of natural aggregate and recycled aggregates from construction and demolition waste(RAW), laboratory static/dynamic triaxial tests under different conditions of recycled aggregate replacement rate, moisture content, confining pressure and shear stress ratio were carried out, and the effect of index properties and stress states on the shear strength and accumulative plastic strain characteristics of the specimen were explored. Based on the multi-stage characteristics of plastic strain development under semi-logarithmic coordinates, and considering the plastic deformation accumulation rate at different stages and the difference in plastic deformation accumulation rate in adjacent two stages, a new shakedown behavior determination criterion suitable for subgrade filling mixed with RAW was proposed. The results show that the accumulative plastic strain of the specimen increases with the increase of moisture content and shear stress ratio, and the specimens mixed with RAW show similar plastic deformation resistance ability compared to natural aggregate when the shear stress ratio is 0.3 and 0.5. After comprehensive comparative analysis of strength and deformation characteristics, it is recommended to use recycled aggregate subgrade filled with 85% replacement rate. The new shakedown behavior determination criterion has high accuracy and can provide a theoretical basis for the long-term pavement performance evaluation of similar subgrade fillings.Key words: road engineering; construction and demolition waste; recycled aggregates; permanent deformation;shakedown behavior随着中国城市化进程迅速发展，新建基础设施和老旧城区改造产生的建筑垃圾量急剧攀升[1]，但综合循环再生利用率距《“十四五”循环经济发展规划》提出的“到2025年，建筑垃圾综合利用率达到60%”这一目标仍存在差距。

铁粉芯和铁氧体材料--Magnetics

E CORES

Four permeabilities for Kool Mµ® E cores range from 26µ to 90µ and fourteen sizes are tooled ranging from the EF 12.6 to the Metric E80 size. Kool Mµ® E cores provide a higher energy storage than gapped ferrite E cores, resulting in a smaller core size.
Kool Mu and Ferrite Comparison
Soft Saturation
Powder Core Structure
Schematic Microscopic Views Uncompacted µ~1
Magnetic Alloy Non-magnetic insulating material
n
No Gap
Discrete Gaantages: 1. Higher Bsaturation 2. Softer Saturation 3. Full saturation at high temperature (not shown)

Kool Mu

®
Cores
Kool Mµ® powder cores offer a low cost option for applications that require reasonably low losses and reasonably high saturation. Kool Mµ® material is available as both toroids and E core geometries. Other shapes, such as U cores, are currently in development. Typical applications for Kool Mµ® powder cores are PFC Chokes, Boost/Buck Regulators, Inductors, Output Inductors and Flybacks.

功能梯度材料的发展及其在内燃机上的应用_孙志远

·新材料·功能梯度材料的发展及其在内燃机上的应用天津大学天津内燃机研究所　孙志远　李艳琳(天津　300072)摘要　本文对功能梯度材料的设计、制备、特性评价做了简单介绍,同时研究了金属陶瓷功能梯度材料在内燃机上的应用。

实验表明这种新型材料对发动机的动力性,燃油消耗率均有不同程度的改善。

初步分析表明,金属陶瓷功能梯度材料所具有的良好的减磨性对发动机功率、扭矩的提高,油耗的下降有重要作用。

关键词　金属陶瓷　功能梯度材料　特性评价　内燃机。

Development of Functionally Gradient Materials and TheirApplication to Internal Combustion EnginesTianjin Internal Combustion Engine Research Institute,Tianjin University　Sun Zhiyuan　Li Yanlin(Tianj in　300072)A bstract　This paper introduces the design,fabrication and evaluation of FGM(functionally Gradient Material).The important task is to research the influence of ceramic-metal F GM on perfor mances of internal combustion en-gines.The results show that the new material improves the power output,fuel consumption and durability.The further analysis verifies that the ceramic-metal FGM impr oves the po wer and torque and decreases the fuel-consumption be-cause it reduces the friction loss.Key words　Ceramic-metal,Functionally gradient material,E valuation of characteristics,Internal combustion engine1　前言自20世纪以来,科学技术发展突飞猛进,当今人类面临一场新的技术革命,需要愈来愈多、品种各异、性能独特的材料。

The effects of dust in simple environments Large Magellanic Cloud HII regions

ERIC F. BELL, KARL D. GORDON, ROBERT C. KENNICUTT, JR., & DENNIS ZARITSKY Steward Observatory, University of Arizona, Tucson, AZ 85721
TO APPEAR IN APJ: January 20 2002, vol. 565, no. 1
ies of different types, as a function of redshift, gives us direct in-
sight into where, when and how galaxies evolve (see e.g. Madau
et al. 1996; Blain et al. 1999; Steidel et al.ቤተ መጻሕፍቲ ባይዱ1999, for attempts to
ABSTRACT
We investigate the effects of dust on Large Magellanic Cloud (LMC) H II region spectral energy distributions using arcminute-resolution far-ultraviolet (FUV), Hα, far-infrared (FIR), and radio images. Widely-used indicators of the amount of light lost to dust (attenuation) at Hα and in the FUV correlate with each other, although often with substantial scatter. There are two interesting systematic discrepancies. First, Hα attenuations estimated from the Balmer decrement are lower than those estimated from the Hα-to-thermal radio luminosity ratio. Our data, at this stage, cannot unambiguously identify the source of this discrepancy. Second, the attenuation at 1500Å and UV spectral slope, β, correlate, although the slope and scatter are substantially different from the correlation ﬁrst derived for starbursting galaxies by Calzetti et al. Combining our result with those of Meurer et al. for ultra-luminous infrared galaxies and Calzetti et al. for starbursting galaxies, we conclude that no single relation between β and 1500Å attenuation is applicable to all star-forming systems.

Centing应用程序的效果应用程序对于应对肥胖区域的知识和态度的评估说明书

The Effectiveness of Sicenting Application Towards Knowledge and Attitude of Responding Stunting Regency in Singaparna District, TasikmalayaDistrict in 20191st Sinta FitrianiStikes Respati Tasikmalaya Tasikmalaya, Indonesia 2ndHariyani Sulistyoningsih Stikes Respati Tasikmalaya Tasikmalaya, IndonesiaAbstract —Background: To increase the capacity of cadres in early detection and prevention of stunting through the provision of health information, health promotion media are needed that can assist cadres in carrying out these activities. The Centing Application (Detection and Prevent Stunting) is a software for early detection of stunting events in toddlers as well as an Android-based stunting information media which is carried out by entering toddlers' data in the form of age, sex, weight and height. Objective: This is to determine the effectiveness of the Centing Application to the Knowledge and Attitudes of Posyandu Cadres in Singaparna District in 2019. Method: The type of research used is quantitative analytic design method Quasi Experiment One Group Pretest-Posttest approach. The population is 24 cadres of stunting response. The sampling technique is purposive sampling with the following criteria: willing to be a respondent, bring a smartphone. Instruments used: questionnaire and Si centing application. Results: there is the influence of the critical application in increasing the knowledge of stunting response cadres with a t value of 19.080> 2.068. While the attitude variable has a value asymp.sig (2tailed) = 0,000 <0.05 meaning that there is a difference between the value of the cadre's attitude before and after means that there is a positive influence on changes in the attitude of the cadre stunting response.Keywords —Sicenting Application, Knowledge, Attitude, StuntingI. INTRODUCTIONStunting is defined as a short or very short body state based on the Body Length index by Age (PB / U) or Body Height by Age (TB / U) with a threshold (z-score) between -3 SD up to <-2 elementary school. Stunting in children is a long-term result of chronic consumption of a low-quality diet combined with morbidity, infectious diseases and environmental problems [1].The incidence of stunting (short) under five is a major nutritional problem facing Indonesia. Based on Nutrition Status Monitoring data for the past three years, short hasthe highest prevalence compared to other nutritional problems such as malnutrition, thinness, and fat. The prevalence of short toddlers has increased from 2016 which is 27.5% to 29.6% in 2017. The prevalence of short toddlers in Indonesia tends to be static. The results of the Basic Health Research (Riskesdas) in 2007 showed the prevalence of short toddlers in Indonesia at 36.8%. In 2010, there was a slight decline to 35.6%. However, the prevalence of short toddlers increased again in 2013 to 37.2% [2].West Java Province in 2017 had a stunting prevalence of 29.2% [3]. Based on data from the Tasikmalaya District Health Office it was found that the Singapore District District was one of the areas with stunting prevalence in February 2019 of 136 infants with very short nutritional status and 444 infants with short status [4].Impacts that can arise from stunting can be divided into short-term and long-term impacts. Short-term impacts include an increase in morbidity and mortality; Cognitive, motor and verbal development in children is not optimal; and increasing health costs. Long-term Impacts That arise: Posture that is not optimal when mature (shorter than in general); Increased risk of obesity and other diseases; Decreased reproductive health; Less than optimal learning capacity and performance during school term; and Non-optimal work productivity and capacity [5].One of the efforts to detect and prevent stunting can be done at posyandu. Monitoring the growth of children under five in the posyandu is a very strategic effort to detect early growth disorders. Early prevention is one of the best ways to reduce the prevalence of stunting in West Java. The most important procedures for early prevention are routine screening and persistent follow-up for toddlers. The Posyandu program made by the government has been very good and has become a concrete solution to reach all levels of society. The better the service provided by the posyandu is proportional to the improvement intheProceedings of the 1st Paris Van Java International Seminar on Health, Economics,Social Science and Humanities (PVJ-ISHESSH 2020)Copyright © 2021 The Authors. Published by Atlantis Press SARL.quality of public health. The routine screening process for height / age should be a mandatory agenda in every activity carried out at the posyandu [6].To increase the capacity of cadres in early detection and prevention of stunting through the provision of health information, health promotion media are needed that can assist cadres in carrying out these activities. The Centing Application (Detection and Prevent Stunting) is a software for early detection of stunting events in toddlers as well as an Android-based stunting information media which is carried out by entering toddlers' data in the form of age, sex, weight and height. Determination of nutritional status will be processed quickly so that cadres can easily determine the nutritional status of the toddler. In addition Si Centing also provides a stunting information menu from the definition, causes, prevention and handling of stunting in the form of an attractive image so that it can be used as a media during counseling activities. Based on the background above, the author is interested in conducting research with the title "Effectiveness of the Centing Application to Knowledge and Attitudes of Stunting Response Cadres in Singapore District in 2019". The purpose of this study is to determine the Effectiveness of Centing Applications on Knowledge and Attitude of Stunting Response Cadres in Singapore District in Tahun 2019II.METHODType of research used is quantitative analytical method design Quasi Experiment One Group Pretest-Posttest approach. The population is 24 cadres of stunting response. The sampling technique is purposive sampling with the following criteria: willing to be a respondent, bring a smartphone. Instruments used: questionnaire and Si centing application. Analysis of research with t test when normally distributed and Wilcoxon test for data that is not normally distributed.III.RESULTSA.Characteristics of respondentsTABLE I. CHARACTERISTICS OF STUNTING RESPONSE CADRES SINGAPARNA DISTRICT, TASIKMALAYA REGENCY IN 2019response cadres are the majority aged> 50 years (37.5%), the majority of high school graduates are 11 people (45.8%), the majority of cadres do not work are 18 people years, 10 people (41.7%).B.Increased knowledge and attitudes of cadresAn increase in knowledge and attitudes of cadres with the following results:TABLE II. KNOWLEDGE OF CADRES BEFORE AND AFTER USING THEAPPLICATION SI CENTINGBased on table II it is found that the average cadre knowledge value before being given the centing application is 7.17 with a standard deviation of 1,606. while the average cadre knowledge after being given the centing application is 13.54 with a standard deviation of 0.884.Statistical test results obtained p value 0,000 means that there is a significant difference between cadre knowledge before and after the centing application is given. So it can be concluded that there is an influence given the critical application in increasing knowledge of stunting response cadres with a t value of 19.080> from t table 2.068.C.Attitude of cadres before and after using theapplicationAs for the attitude of cadres responding to stunting before and after the application of the centing is listed in the following table:TABLE III. THE ATTITUDE OF CADRES BEFORE AND AFTER USING THE APPLICATION SI CENTING IN THE SINGAPARNA DISTRICT OFBased on table III above, it is found that negative ranks are 0 meaning that there is no decrease in the value of attitude before and after the centing application is given. While positive ranks are 24, it means that all cadres experience an increase in the value of attitude before and after the centing application is given with a mean rank of 12.50 and a sum of rank of 300.00. The ties value in the attitude variable is 0 meaning that there is no similar attitude value between before and after the centing application is given.Based on the statistical test output, the value of asymp.sig (2 tailed) is 0,000 <0.05, which means that there is a significant difference between the cadre attitudes before and after using the Centing application, which means there is a significant and positive influence given by the centing application to changes stunting response cadre attitude.IV.DISCUSSIONThe Si Centing application is an Android-based health innovation designed to facilitate cadres in early detection of stunting events and become a media for health promotion when conducting counseling and counseling. The use of this application can increase the knowledge and attitude of cadres, this is in accordance with the results of research which states that the use of cellular technology in research conducted by Otu A, Ebenso B, Okuzu O and Dawodu EO shows that mHealth innovations can help alleviate some health system constraints such as lack of equipment to collect data, and limited access to training in health such as maternal and child health, and reproductive health. mHealth improves health system functions and knowledge by 11% from before and changes in attitudes towards disease [7].Of various forms of information and telecommunications technology, mobile phones are considered to be a very suitable tool to advance education in developing regions. The use of this smartphone is more effective than modules without applications [8]. This is consistent with the results of research conducted by Wahyuni T regarding the effect of smartphone applications on a person's knowledge and skills in stimulating growth and development of infants, indicating an increase in knowledge and skills. Therefore, the provision of information through attractive media tools will facilitate a person to do the stimulation independently [9].Media is a tool or material used as a tool to convey messages. The media functionsto further clarify the messages that will be delivered by the message giver to the recipient of the message. The use of media is very important to explain the messages or material delivered during counseling. The use of extension media should not lead to a double understanding. The extension media used must meet media requirements. These requirements include interesting, in accordance with the goals of counseling, easily captured, brief, clear, in accordance with the messages to be conveyed, and polite [10].Based on the results of the research above stated that android-based media has an influence in increasing knowledge. Android-based smartphone is a concrete manifestation of technological advances in the field of communication whose users around the world have reached 1.4 billion active users. Indonesia as one of the world's citizens has the effect of having an android smartphone with the number of android smartphone users in Indonesia has reached 47 million users. In the 2015 Hongko Pulung Seto study, where the android application-based learning media was able to increase the average value of EFI (Electronic Fuel Injection) learning material. That is allegedly because the android application-based learning media has mobile properties that can be used anywhere so that it is able to attract interest in learning. This has an impact on the effectiveness of the learning so that it can improve learning outcomes in the learning material.Based on the results of the study it was found that the average cadre knowledge value before being given the centing application was 7.17 with a standard deviation of 1,606. while the average cadre knowledge after being given the centing application is 13.54 with a standard deviation of 0.884. Statistical test results obtained p value 0,000 means that there is a significant difference between cadre knowledge before and after the centing application is given. So it can be concluded that there is an influence given the critical application in increasing knowledge of stunting response cadres with a t value of 19.080> from t table 2.068.Knowledge is the result of "knowing" and from this happens after a person senses a certain object. Sensing to an object occurs through the five human senses namely vision, hearing, smell, taste and touch with oneself. At the time of sensing to produce knowledge is strongly influenced by the intensity of the attention of theperception of the object. Most of human knowledge is obtained through the eyes and ears [11].There are several factors that influence a person's knowledge and attitude. According to Notoadmojo explained that knowledge is influenced by the level of education, age, and experience. Education provides an influence on one's level of knowledge, with higher education will affect higher mastery of the material that must be mastered. Age gives an influence where age can affect the memory or memory possessed by someone. The older a person eats the process of mental development will get better. Thus, the more mature a person's level of development affects the person's way of gaining knowledge. Another thing is the ease of information, because information can help speed up someone to obtain new knowledge [11].Applications The centing an android-based health innovations that are designed to facilitate early detection of cadres in the incidence of stunting and a media when carrying out health promotion and education counseling. The use of this application can increase the knowledge and attitudes of cadres, this is in accordance with the results of Handayani's research in 2019 in Garut Regency which states that there are significant differences between cadre knowledge before and after application application is free ofchildren stunting with p values <0.001. The results showed that the increase in cadre knowledge by 25.1%. explained that the use ofapplications smartphonethe haspotential to be used as a means of health promotion that can improve one's knowledge and attitudes [3, 12].To increase knowledge, innovative health promotion media is needed, one of which is a learning media based on Android application that has a mobile nature that can be used anywhere so that it is able to attract interest in receiving health information.Based on the statistical test output obtained asymp.sig value (2 tailed) is 0,000 <0.05 meaning that there is a significant difference between cadre attitudes before and after using the Si Centing application, which means there is an influence significant and positive application is given by the centing to the changing attitudes of stunting cadres.Attitude is a reaction or response that is still closed from someone to a stimulus or object. Attitude is not an action or activity but is a predisposition to the action of a behavior. That attitude is still a closed reaction, not an open reaction or open behavior. Attitude is a readiness to react to objects in a particular environment as an appreciation of the object [11,13].The results of this study are in accordance with the results of the study Handayani in 2019 in Garut Regency which states that there is a significant difference between knowledge before and after the application of stunting-free children is given the test results it is known that the value of p <0.001 can thus be stated that a significant difference in attitude before and after the provision of information through the application offree children stunting-. The average% increase in attitude before and after the provision of information through the application offree children stunting- 76.2%.Attitudes arise based on the evaluation process in individuals who give conclusions about the stimulus in the form of good value, negative, positive, pleasant not pleasant. The attitude structure consists of three mutually supporting components namely cognitive, affective, and conative components. The cognitive component is a representation that is believed by individuals to have an attitude, the affective component is a feeling that involves emotional aspects, and conative is an aspect of a certain tendency to behave in accordance with the attitudes of a person [14].Cadre attitude is a reflection of cadres' perceptions of the tasks they carry, including early detection of development. The better the attitude of the cadres, the cadres have a positive perception of their duties in the early detection of developments so that the cadres can implement it well [15].Android-based health promotion media make it easier for cadres to obtain information so as to increase positive perceptions within the cadre to be able to carry out their duties of early detection of stunting and disseminating health information about stunting prevention early on.V.CONCLUSIONSThere are the influence of the application of the centing application in increasing knowledge and attitudes of stunting response cadres in Singaparna Sub-district Tasikmalaya Regency in 2019.VI.SUGGESTIONSThe Centing application can be used by cadres in carrying out their duties of early detection of stunting and making media health promotion when conducting counseling or counseling in Integrated Healthcare Center activities so thatcan be early cases of stuntingdetected in infants andcan be done preventionearly.ACKNOWLEDGMENTSWe would like to thank the STIKES Respati, the Singaparna Public Health Center, the Cikunir Village Government and the stunting response cadres for their collaboration so that this research activity could be carried out in accordance with the targets set.REFERENCES[1] WHO, Nutrition Landscape Information System (NLIS) countryprofile indicators: interpretation guide. Switzerland, 2010. [2] The Indonesian Ministry of Health, Basic Health Research in2013. Jakarta: Indonesian Ministry of Health, 2014.[3] N. J. Handayani T, Tarawan V, “Increased Knowledge andAttitudes of Cadres About Stunting in Toddlers Age 12 - 36Months Through Application of Free Stunting (AbsChildren),”J. Midwifery, vol. 5, no. 4, pp. 357–363.[4] Tas ikmalaya District Health, “Profile of Tasikmalaya DistrictHealth Office,” Tasikmalaya.[5] RI Ministry of Health, “Bulletin of the health data andinformation window,” Jakarta, 2018.[6] A. Setyowati, M., & Retno, “Mapping the Status of ToddlerNutrition in Supporting the Achievement of the MillenniumDevelopment Goals (MDGs),” Public Health, vol. 10, no. 2, pp.10–21, 2015.[7] D. E. Otu A, Ebenso B, Okuzu O, “Using a mHealth tutorialapplication to change the knowledge and attitude of frontlinehealth workers to Ebola virus disease in Nigeria: a before andafter study,” Hum. Resour. Health, vol. 14, no. 5, 2016.[8] S. S. Barnett I, Befani B, “Designing an impact evaluation for amobile phone application for nutrition service delivery inIndonesia,” CDI Dev. Semin., 2014.[9] Wahyuni T, “The Effect of Mother Cares Application onIncreasing Parents’ Knowledge and Skills in StimulatingToddler Growth and Age 12-18 Months,” Med. Cendikia, vol. 4,no. 1, 2017.[10] S. I. Suiraoka I, Health Education Media. Graha knowledge.Yogyakarta, 2012.[11] S. Notoatmodjo, Health Promotion; Teori anda Application.Jakarta: Rineka Copyrighted, 2012. [12] S. S. Coughlin SS, Whitehead M, Sheats JQ, Mastromonico J,“A Review of Smartphone Applications for Promoting PhysicalAc tivity,” Jacobs J. Community Med., 2016.[13] Sinta Fitriani, Health Promotion. Yogyakarta: Graha Science,2011.[14] L. V. Adistie F, Maryam NNA, “Health Cadres Knowledgeabout Early Detection of Malnutrition in Toddlers.,” J. Sci.Technol. Appl. Community, 2017.[15] I. H. Pakasi AM, Korah BH, “Relationship of Health CadresKnowledge and Attitudes with Posyandu Services,” MidwifeSci. J., 2016.。

无导线起搏与传统起搏对三尖瓣反流短期影响的对比研究

㊃心脏电生理学专题㊃无导线起搏与传统起搏对三尖瓣反流短期影响的对比研究郭雨龙㊀付明鹏㊀刘晨㊀乔宇㊀郭金锐㊀刘可㊀郭涛650102昆明,云南省阜外心血管病医院心律失常中心通信作者:郭雨龙,电子信箱:kktury8859@DOI:10.3969/j.issn.1007-5410.2023.04.004㊀㊀ʌ摘要ɔ㊀目的㊀比较无导线起搏与传统起搏患者的短期三尖瓣反流变化情况,并分析三尖瓣反流的相关因素㊂㊀方法㊀回顾性纳入2020年1月至2022年11月在云南省阜外心血管病医院就诊的新植入起搏器94例患者,分为无导线起搏组(47例)和传统起搏组(47例),通过经胸超声心动图评估术前㊁术后6月内的三尖瓣反流程度及恶化情况,比较两组三尖瓣反流恶化的发生率㊂Logistic回归分析发生三尖瓣反流的相关因素㊂㊀结果㊀发生三尖瓣反流恶化者共29例(30.9%),无导线起搏组和传统起搏组的发生风险相似(14例比15例,29.8%比31.9%),差异无统计学意义(χ2=0.050,P=0.823)㊂二元logistic回归分析结果显示,单腔起搏器是发生三尖瓣中㊁大量反流的独立影响因素(χ2=10.031,P=0.010)㊂㊀结论㊀与传统起搏器相比,无导线起搏器可能并不减少术后短期发生三尖瓣反流的风险㊂ʌ关键词ɔ㊀无导线起搏;㊀心脏起搏;㊀三尖瓣反流;㊀三尖瓣瓣下复合体基金项目:云南省临床医学中心项目;云南省卫生健康委员会医学后备人才培养计划(H-2018037);云南省阜外心血管病医院院级科研基金项目(2019YFKT-04)Comparison of the short-term effects of leadless pacing and traditional pacing on tricuspidregurgitation㊀Guo Yulong,Fu Mingpeng,Liu Chen,Qiao Yu,Guo Jinrui,Liu Ke,Guo TaoDepartment of Arrhythmia,Fuwai Yunnan Cardiovascular Hospital,Kunming650102,ChinaCorresponding author:Guo Yulong,Email:kktury8859@.ʌAbstractɔ㊀Objective㊀To compare the short-term risk of tricuspid regurgitation in patients treatedwith leadless pacemaker or traditional pacemaker,and to determine its related factors.㊀Methods㊀A totalof94patients who were newly implanted leadless or traditional pacemakers in Fuwai Yunnan CardiovascularHospital from January2020to November2022were retrospectively enrolled.All were divided into theleadless pacemaker group(n=47)and the tranditional pacemaker group(n=47).The transthoracic echocardiography was used to evaluate the severity and deterioration of tricuspid regurgitation before and6months after operation.Logistic regression analyses was used to assess its related factors.㊀Results㊀A totalof29(30.9%)patients had tricuspid regurgitation deterioration.There was no significant difference in therisk of tricuspid regurgitation deterioration between the leadless and tranditional pacemaker groups(14casesvs.15cases,29.8%vs.31.9%,χ2=0.050,P=0.823).Binary logistic regression analyses resultindicated that single-chamber pacemaker was an independent factor of moderate to massive tricuspid regurgitation(χ2=10.031,P=0.010).㊀Conclusions㊀Compared with traditional pacemaker,leadless pacemaker probably cannot reduce the short-term risk of tricuspid regurgitation after operation.ʌKey wordsɔ㊀Leadless pacemaker;㊀Cardiac pacing;㊀Tricuspid regurgitation;㊀Tricuspid subvalvular apparatusFund program:Yunnan Provincial Clinical Medical Center Project;Yunnan Provincial Health Commission Medical Reserve Talent Training Plan(H-2018037);Yunnan Fuwai Cardiovascular DiseaseHospital Hospital-Level Research Fund Project(2019YFKT-04)㊀㊀心脏起搏是严重心动过缓最有效的治疗方式㊂传统心脏起搏器由脉冲发生器及相连接的电极导线构成,电极导线一般通过上腔静脉途径植入心腔内,右心室起搏电极导线跨过三尖瓣进入右室内固定㊂但是在以机械机制为主的多种机制介导下,传统心脏起搏会有加重恶化三尖瓣反流风险㊂无导线起搏是近年来最新的心脏起搏技术,与传统起搏器不同,无导线起搏器体积仅有胶囊大小,可通过特殊的输送装置,经下腔静脉途径植入右心室内,植入成功后输送装置可完全撤除,具有创伤小㊁恢复快,以及避免了囊袋并发症等特点㊂其心腔内留存的无导线起搏器仅在右心室内,不会遗留跨三尖瓣的电极导线㊂但是,无导线起搏对患者三尖瓣反流影响的临床研究数据较少,且尚无直接比较无导线起搏与传统起搏的报道㊂因此,我们通过纳入无导线起搏与匹配的传统起搏患者,在术前与术后短期通过经胸超声心动图评估三尖瓣反流情况,比较两组之间三尖瓣反流恶化的发生率,以此评估无导线起搏对三尖瓣反流的影响,希望能为无导线起搏的进一步推广应用提供有价值的临床信息㊂1㊀对象和方法1.1㊀研究对象回顾性队列研究㊂纳入2020年1月至2022年11月在云南省阜外心血管病医院新植入起搏器患者,分为无导线起搏组和传统起搏组㊂纳入标准: (1)无导线起搏组符合无导线起搏适应证,且成功完成无导线起搏器植入手术者;(2)传统起搏组按照年龄㊁性别进行1ʒ1匹配,纳入同期就诊的符合传统起搏适应证且成功完成植入者㊂排除标准: (1)因传统起搏感染㊁电极故障或电池耗竭而转用无导线起搏者;(2)仅植入心房电极单腔起搏器者;(3)原有起搏器更换或升级者㊂本研究符合医学研究伦理学要求(编号:2022-94)㊂所有患者均知情同意㊂1.2㊀方法1.2.1㊀无导线起搏器植入手术㊀采用美敦力无导线起搏器(型号Micra TM MC1VR01或Micra TM AV MC1AVR1),所有操作均在导管室血管造影机透视指导下完成㊂穿刺右股静脉,置入导引钢丝,逐级扩张;若右股静脉穿刺或置入导丝不顺则换用左股静脉,沿导引钢丝置入输送装置,应用输送装置将无导线起搏器送至右心室内;多体位投照(至少三个体位:右前斜30ʎ㊁左前斜45ʎ及正位)确认跨过三尖瓣到达右心室中下间隔部,造影确认与心肌贴靠情况满意后,施加一定压力推送输送系统,并释放无导线起搏器,稍微回退输送鞘管,通过牵拉试验证实无导线起搏器头端勾挂满意,且测试阈值㊁阻抗㊁感知等参数满意后方可剪断拉绳;若不满意,则回收后重新定位释放㊂整个手术过程中,静脉推注3000U肝素,输送鞘管持续肝素盐水冲洗,最后撤除输送装置㊁缝合伤口,最后加压包扎㊂1.2.2㊀传统起搏器植入手术㊀采用传统起搏器,所有操作均在导管室血管造影机透视指导下完成㊂穿刺左锁骨下静脉或腋静脉,置入导引钢丝,若穿刺或置入导丝不顺则改为右侧植入,沿锁骨下做4~ 5cm皮肤切口,逐层分离至深筋膜层,制作合适大小的皮下囊袋,应用可撕开鞘管置入起搏电极,右房电极定位固定至右心耳,右室电极定位固定至右室间隔部或心尖部(均使用主动固定电极),测试阈值㊁阻抗㊁感知等参数满意后,拔除可撕开鞘管,电极尾端连接脉冲发生器并埋置于囊袋内,充分止血㊁冲洗后逐层缝合,最后加压包扎㊂1.3㊀观察指标和随访所有患者在植入术前1周内及术后6个月内完成经胸超声心动图对三尖瓣反流情况进行评估㊂使用GE或飞利浦超声探头,在彩色血流多普勒下测量三尖瓣反流束面积与右心房面积比和(或)缩流颈宽度综合评估三尖瓣反流情况的变化㊂其中,面积比<10%为微量反流,10%~20%为少量或轻度反流,21%~40%为中量或中度反流,>40%为大量或重度反流;缩流颈宽度<3mm为少量或轻度反流,缩流颈宽度3~7mm为中量或中度反流,缩流颈宽度>7mm为大量或重度反流㊂此外,三尖瓣反流恶化定义为与术前相比,术后面积比增加超过5%和(或)缩流颈宽度增加超过1mm㊂1.4㊀统计学方法应用SPSS20.0软件进行统计分析㊂符合正态分布的计量资料用 xʃs表示,组间比较采用独立样本t检验;计数资料用百分构成比表示,组间比较采用χ2检验㊂Logistic回归分析影响术后新增三尖瓣中㊁大量反流的相关因素㊂P<0.05为差异有统计学意义㊂2㊀结果2.1㊀两组的基线临床资料比较如表1所示,两组的诊断差异有统计学意义,表现为无导线起搏组诊断为ȡⅡ度房室传导阻滞的比例显著低于传统起搏组,而诊断为心房颤动伴RR长间歇的比例显著高于传统起搏组(P= 0.005)㊂其余基线临床资料相似,差异均无统计学意义(均为P>0.05)㊂2.2㊀两组的起搏器植入术后即刻右室电极参数比较无导线起搏组中,38例(80.9%)使用Micra TM表1㊀两组的基线临床资料比较项目总体(94例)无导线起搏组(47例)传统起搏组(47例)t/χ2值P值年龄( xʃs,岁)78.9ʃ9.979.3ʃ9.978.4ʃ10.00.4390.688男性[例(%)]56(59.6)28(59.6)28(59.6)0.000 1.000诊断[例(%)]10.7810.005㊀窦房结功能障碍38(40.4)19(40.4)19(40.4)㊀ȡⅡ度房室传导阻滞34(36.2)11(23.4)23(48.9)㊀心房颤动伴RR长间歇22(23.4)17(36.2)5(10.6)心功能指标( xʃs)㊀左室射血分数(%)62.0ʃ7.262.7ʃ6.261.2ʃ8.10.9900.325㊀左室舒张末期内径(mm)46.6ʃ6.646.4ʃ6.846.9ʃ6.50.2950.769表2㊀两组起搏器植入术后即刻右室电极参数比较( xʃs)项目总体(94例)无导线起搏组(47例)传统起搏组(47例)t值P值右室电极阻抗(Ω)797.8ʃ214.0819.6ʃ196.8775.9ʃ230.00.9880.326右室电极阈值(V@0.4ms)0.70ʃ0.420.70ʃ0.490.71ʃ0.340.1310.896 R波感知振幅(mV)9.96ʃ4.759.28ʃ4.4010.64ʃ5.02 1.3980.166表3㊀两组术前和术后的三尖瓣反流情况比较[例(%)]项目总体(94例)无导线起搏组(47例)传统起搏组(47例)χ2值P值术前三尖瓣反流14.7960.002㊀无或微量32(34.0)10(21.3)22(46.8) 6.8230.009㊀少量/轻度43(45.7)21(44.7)22(46.8)0.0430.836㊀中量/中度11(11.7)8(17.0)3(6.4) 2.5740.109㊀大量/重度8(8.5)8(17.0)0(0.0)8.7440.003术后三尖瓣反流14.1480.003㊀无或微量28(29.8)7(14.9)21(44.7)9.9700.002㊀少量/轻度35(37.2)18(38.3)17(36.2)0.0460.831㊀中量/中度18(19.1)11(23.4)7(14.9) 1.0990.294㊀大量/重度13(13.8)11(23.4)2(4.3)7.2310.007MC1VR01(起搏模式VVI),9例(19.1%)使用Micra TM AV MC1AVR1(起搏模式VDD),所有无导线起搏器均位于右室中低位间隔部㊂传统起搏组中,9例(19.1%)使用单腔起搏器(模式VVI),38例(80.9%)使用双腔起搏器(模式DDD);右室电极导线在心尖部3例(6.4%),在间隔部44例(93.6%)㊂如表2所示,两组起搏器植入术后右室电极的即刻参数均相似,差异无统计学意义(均为P>0.05)㊂2.3㊀两组术前和术后的三尖瓣反流情况比较如表3所示,两组术前的三尖瓣反流情况差异有统计学意义(P=0.002),表现为无导线起搏组的无或微量三尖瓣反流率明显低于传统起搏组(P= 0.009),而大量/重度三尖瓣反流率明显高于传统起搏组(P=0.003)㊂两组术后的三尖瓣反流情况差异也有统计学意义(P=0.003),表现为无导线起搏组的无或微量三尖瓣反流率明显低于传统起搏组(P=0.002),而大量/重度三尖瓣反流率明显高于传统起搏组(P=0.007)㊂与术前比较,术后新增的有临床意义的三尖瓣中大量反流有12例,其中无导线起搏组6例(12.8%),传统起搏组6例(12.8%),组间比较差异无统计学意义(χ2=0.000,P=1.000)(图1)㊂三尖瓣反流恶化者共29例(30.9%),其中无导线起搏组14例(29.8%),传统起搏组15例(31.9%),组间比较差异无统计学意义(χ2=0.050, P=0.823)(图1)㊂图1㊀两组发生三尖瓣反流情况比较2.4㊀术前三尖瓣反流程度对术后发生三尖瓣反流恶化的影响进一步研究显示,术前三尖瓣无或微少量反流者在术后出现反流恶化的比例为29.3%(22/75),而术前三尖瓣中㊁大量反流者在术后出现反流恶化的比例为36.8%(7/19),两者之间比较差异无统计学意义(χ2=0.401,P=0.527)㊂2.5㊀Logistic回归分析结果采用二元logistic回归分析(Wald后退法),分析术后新增三尖瓣中㊁大量反流的影响因素,无导线起搏组纳入因素为年龄㊁性别㊁起搏适应证诊断㊁术前左室射血分数㊁舒张末期内径及术前三尖瓣反流情况,传统起搏器纳入因素除上述外,增加右室电极位置及起搏器类型(单腔或双腔)㊂最终在无导线起搏组中未发现影响术后新增三尖瓣中㊁大量反流的有统计学意义相关因素(均为P>0.05);而在传统起搏患者中,发现起搏器类型[Exp(B)= 35.589,P=0.01]是独立影响因素,其中单腔起搏器患者术后出现新增三尖瓣中㊁大量反流的比例远高于双腔起搏器患者[4例比2例,44.4%(4/9)比5.3%(2/38),χ2=10.031,P=0.002]㊂3　讨论本研究发现,无导线起搏器与传统起搏器相比,术后短期发生三尖瓣反流恶化及新发中㊁大量三尖瓣反流的比例无统计学差异,故无导线起搏可能并不能够减少对三尖瓣反流的负面影响㊂三尖瓣反流是右心室起搏的常见并发症㊂国外研究报道术后三尖瓣反流的发生率7%~21%,三尖瓣反流恶化或加重的比例为10%~45%[1]㊂一般认为,导致或加重三尖瓣反流的机制以机械损伤为主,机械机制主要包括植入过程中起搏电极导线直接损伤瓣叶导致穿孔或撕裂㊁导线嵌顿于瓣叶之间㊁导线与瓣叶粘连或与腱索缠绕等㊂与普通电极导线相比,更粗㊁更硬的除颤电极导线导致三尖瓣反流的概率更高;此外,长期高比例右室非生理性起搏㊁慢性右心扩大及三尖瓣环扩张也是远期三尖瓣反流发生及加重的因素㊂其中,术中电极导管对三尖瓣的直接机械损伤是短期发生三尖瓣反流的主要机制㊂使用的电极越硬㊁越粗或暴力操作等均是潜在的危险因素,而慢性电极导线粘连㊁高比例右室非生理起搏及右心扩大瓣环扩张则是远期发生三尖瓣反流的主要机制[1-3]㊂国内关于三尖瓣反流的报道的例数较少且还有争议,赵波等[4]发现长期右室心尖部起搏仅导致轻微反流,引起有临床意义的三尖瓣反流恶化的比例更低㊂邹宝明等[5]发现无论右室心尖部还是间隔部起搏都不会在短期内明显加重三尖瓣反流㊂无导线起搏是最新的心脏起搏技术,与传统右室起搏不同,无导线起搏在植入后并不会长期遗留跨三尖瓣的电极导线,因此其对三尖瓣的影响及机制可能会不同㊂目前国外关于无导线起搏对三尖瓣反流作用的研究报道有限,而国内尚无相关报道㊂2019年Beurskens等[6]报道无导线起搏术后1年三尖瓣反流加重的比例为43%㊂2022年一项关于无导线起搏器的真实世界研究,纳入植入心房感知㊁心室起搏的无导线起搏器患者,发现中度以上的三尖瓣反流发生率为48.8%(21/43)[7]㊂因此,无导线起搏器导致或加重三尖瓣反流的风险依然存在,甚至可能比传统起搏器高㊂此项研究发现,在起搏器植入术后短期内,总体三尖瓣反流恶化发生概率为30.9%,无导线起搏组为29.8%,传统起搏组为31.9%,考虑到本研究中我们为了更早地发现短期影响效果,所定义的三尖瓣反流恶化的超声心动图指标较为敏感,远比临床症状更早出现变化,因此该比例应该会高于真实世界中有临床症状的三尖瓣反流发病率㊂我们发现两组间差异无统计学意义,可认为无导线起搏并不能够减少对三尖瓣的负面影响㊂表1中两组间的入院诊断有统计学差异,无导线起搏组的心房颤动伴RR长间歇患者比例更高,这是其最早及最强的植入适应证,很可能对结果造成一定影响㊂由表3中可看出,本研究无导线起搏组术前的中㊁大量三尖瓣反流者更多,这是由于我们在开展无导线起搏器植入术初期误以为其对三尖瓣反流的影响较小,因此在病人选择上有了偏差,而后续统计分析发现术前反流程度并未影响其术后恶化情况,故这种差异并不影响本文的主要研究结论㊂而经过本研究之后,我们对无导线起搏与三尖瓣的相互作用又有了更多认识,将进一步优化及改善今后对患者的处理决策,希望能更好改善预后㊂从表面上看,由于无导线起搏器并不会长期遗留跨瓣导线,从理论上来说慢性三尖瓣粘连及腱索缠绕的发生率可能会低于传统起搏器,似乎避免了传统起搏引发三尖瓣反流的一些机制㊂但是,无导线起搏器植入须使用更粗㊁更硬的输送装置,操作中对三尖瓣的损伤可能会大于传统起搏,发生瓣膜穿孔的风险是否增加尚无报道㊂另外,国外有学者发现,无导线起搏器植入后对三尖瓣瓣下复合体的干扰较大,瓣下复合体是个解剖概念,主要指与瓣膜㊁腱索连接的乳头肌,三尖瓣下一般有三组乳头肌,前组在右室游离壁,下组及间隔组分别在下壁及右室间隔面,下组及后组乳头肌可能表现不完全而腱索就直接连接到间隔面或心室壁[8]㊂固定于间隔面的无导线起搏器虽然无跨瓣导线,但可能会显著影响间隔侧的三尖瓣瓣下复合体功能,由此加重三尖瓣反流㊂然而,目前对于无导线起搏器与三尖瓣相互作用的认识有限,还需要进一步的研究及临床实践来明确,尤其需要心脏外科及心脏结构专业与起搏电生理专业的合作㊂本研究有一些局限性㊂本研究仅为临床观察性研究,例数较少,并非严密设计的随机对照研究,而且三尖瓣反流的可能影响因素较多,本研究也未能完全排除无导线/传统起搏选择以外的其他可能干扰因素,结论的说服力有限㊂总之,与传统起搏器相比,无导线起搏器可能并不减少术后短期发生三尖瓣反流的风险㊂利益冲突:无参㊀考㊀文㊀献[1]Addetia K,Harb SC,Hahn RT,et al.Cardiac ImplantableElectronic Device Lead-Induced Tricuspid Regurgitation[J].JACC Cardiovasc Imaging,2019,12(4):622-636.DOI:10.1016/j.jcmg.2018.09.028.[2]郑晓琳,张澍,陈珂萍.心内膜导线相关的三尖瓣反流[J].中国心脏起搏与心电生理杂志,2014,28(5):443-445.DOI:10.13333/ki.cjcpe.2014.05.018.㊀Zheng XL,Zhang S,Chen KP.Tricuspid valve regurgitationassociated with Endocardium leads[J].Chin J Card PacingElectrophysiol,2014,28(5):443-445.DOI:10.1333/ki.cjcpe.2014.05.018.[3]Kim JB,Spevack DM,Tunick PA,et al.The effect oftransvenous pacemaker and implantable cardioverter defibrillatorlead placement on tricuspid valve function:an observational study[J].J Am Soc Echocardiogr,2008,21(3):284-287.DOI:10.1016/j.echo.2007.05.022.[4]赵波,宋建平,邹操.长期右室心尖部起搏对三尖瓣反流的影响[J].中国心脏起搏与心电生理杂志,2012,26(4):315-318.DOI:10.13333/ki.cjcpe.2012.04.014.㊀Zhao B,Song JP,Zou C.Effects of long-term permanent rightventricular apical pacing on tricuspid regurgitation[J].Chin JCard Pacing Electrophysiol,2012,26(4):315-318.DOI:10.13333/ki.cjcpe.2012.04.014.[5]邹宝明,王景武,孙克陆,等.围术期右室流入道间隔部起搏对三尖瓣反流的影响[J].中华全科医学,2015,13(6):896-898.DOI:10.16766/ki.issn.1674-4152.2015.06.019.㊀Zou BM,Wang JW,Sun KL,et al.Influence of right ventricularinlet septum pacing on tricuspid regurgitation during perioperativeperiod[J].Chin J Gen Pract,2015,13(6):896-898.DOI:10.16766/ki.issn.1674-4152.2015.06.019. [6]Beurskens NEG,Tjong FVY,de Bruin-Bon RHA,et al.Impactof Leadless Pacemaker Therapy on Cardiac and AtrioventricularValve Function Through12Months of Follow-Up[J].CircArrhythm Electrophysiol,2019,12(5):e007124.DOI:10.1161/CIRCEP.118.007124.[7]Kowlgi GN,Tseng AS,Tempel ND,et al.A real-worldexperience of atrioventricular synchronous pacing with leadlessventricular pacemakers[J].J Cardiovasc Electrophysiol,2022,33(5):982-993.DOI:10.1111/jce.15430.[8]Tadic M.Multimodality Evaluation of the Right Ventricle:AnUpdated Review[J].Clin Cardiol,2015,38(12):770-776.DOI:10.1002/clc.22443.(收稿日期:2023-01-31)(本文编辑:李鹏)㊃读者㊃作者㊃编者㊃GB/T7713.2 2022‘学术论文编写规则“已于2023年7月1日实施㊀㊀2022年12月30日,国家市场监督管理总局和国家标准化管理委员会联合发布了GB/T7713.2 2022‘学术论文编写规则“,并已于2023年7月1日实施㊂无论是学术论文㊁学位论文还是科技报告,其撰写和编排都需要遵循一定的规范,以利于信息系统的收集㊁存储㊁处理㊁加工㊁检索㊁利用㊁交流㊁传播㊂GB/T7713 1987‘科学技术报告㊁学位论文和学术论文的编写格式“,对学术论文㊁学位论文和科技报告的撰写要求及编排格式作了统一规定㊂鉴于三者的使用对象及使用目的不尽相同,撰写要求及编排格式差异较大,后来修订GB/T7713时,将其分为3个部分分别进行修订㊂第1部分:学位论文编写规则㊂目的在于规定了学位论文的撰写格式和要求㊂第2部分:学术论文编写规则(简称本规则 )㊂目的在于规定了学术论文的撰写要求和编排格式㊂第3部分:科技报告编写规则㊂目的在于规定了科技报告的编写㊁组织㊁编排等要求㊂本规则描述了撰写和编排学术论文的基本要求和格式规范㊂学术论文编写的标准化和规范化,是使其格式和体例规范化,语言㊁文字和符号规范化,技术和计量单位标准化,以便于学术论文的检索和传播,促进学术成果的交流和使用㊂本规则的适用范围,包括一切反映自然㊁社会和人文等的科学体系的学术论文㊂然而,由于学科门类㊁选定课题㊁研究工作方法㊁工作进行阶段㊁观测和调查等各方面的差异,采用本规则进行学术论文编写宜采取严肃性和灵活性相结合的原则㊂本规则对GB/T7713 1987中的学术论文编写内容进行了必要的检查㊁更新,进而形成单独的学术论文编写规则,代替GB/T7713 1987中的学术论文编写格式部分㊂现可登录国家标准化管理委员会网站或通过以下网址/bzgk/gb/showGb?type=online&hcno= 0B963916637B8F34B295FCF4A51A1BE5查询本规则全文㊂。

产品的五个层次

• 第四个层次，附加产品，即提供超过顾客期望的服务和利益，以便把公司的提供物与竞争者的提供物区别开来。如旅馆－－电视机，网络接口，鲜花，结帐快捷，美味的晚餐，优良服务等。获得惊奇和高兴 • 第五个层次是潜在产品，即该产品在将来最终可能会实现的全部附加部分和转换部分（产品将来的发展方向〕。如旅馆－－全套家庭式旅馆的出现
核心产品
பைடு நூலகம்
形式产品
大隆鞋机的售后服务：延伸产品(附加产
品)
电视机上网：潜在产品
1.著名的法国香水业有句名言：“设计精美的香水瓶是香水的最佳推销员。”法国香水的包装瓶根据香味类型使用统一的造型。如有种香味类似森林和木料的男用香水，它的包装瓶子被设计成细高如树的造型，又配上能让人联想到木板的本色细条纸盒外包装；另一叫“高山”的香水，包装瓶子被设计成旋转升天式。试分析这些造型别致、富于联想的包装的特点？ 2.根据我国《韩非子》中所记的买椟还珠的典故，讨论“货卖一张皮”的深刻寓意？
产品的五个层次
Five levels of overall product
Core Product
Physical Product
Expected Augmented Potential Product Product products
• 第一层次，核心产品，即顾客真正需要的基本服务或利益。如旅馆－－休息与睡眠 • 第二个层次，形式产品，实现核心利益所必须的基础产品，即产品的基本形式。如旅馆－－床，浴室，毛巾，衣柜，厕所等。 • 第三个层次，期望产品，即购买者在购买产品时通常期望或默认的一组属性和条件。如旅馆－－干净的床，新的毛巾，清洁的厕所，相对安静的环境。获得满意

物理学外文翻译

Effect of Quantum Confinement on Electrons and Phonons in Semiconductors We have studied the Gunn effect as an example of negative differential resistance(NDR).This effect is observed in semiconductors,such as GaAs,whose conduction band structure satisfies a special condition,namely,the existence of higher conduction minima separated from the band edge by about 0.2-0.4eV..As a way of achieving this condition in any semiconductor,Esaki and Tsu proposed in 1970 [9.1]the fabrication of an artificial periodic structure consisting of alternate layers of two dissimilar semiconductors with layer superlattice.They suggested that the artificial periodicity would fold the Brillouin zone into smaller Brillouin zones or “mini-zones”and therefore create higher conduction band minima with the requisite energies for Gunn oscillations.iWith the development of sophisticated growth techniques such as molecular beam epitaxy（MBE）and metal-organic chemical vapor deposition(MOCVD)discussed in Sect.1.2,it is now possible to fabricate the superlattices(to be abbreviated as SLs)envisioned by Esaki and Tsu[9.1].In fact,many other kinds of nanometer scale semiconductor structures(often abbreviated as nanostructures)have since been grown besides the SLs.A SL is only one example of a planar or two-dimensional nanostructure .Another example is the quantum well (often shortened to QW).These terms were introduced ｉｎＳｅｃｔｓ．１．２ａｎｄ７．１５ｂｕｔｈａｖｅｎｏｔｙｅｔｂｅｅｎｄｉｓｃｕｓｓｅｄｉｎｄｅｔｉａｌ．Ｔｈｅｐｒｏｐｏｓｅof this chapter is to study the electronic and vibrational properties of these two-dimensional nanostructures.Structures with even lower dimension than two have also been fabricated successfully and studied. For example,one-dimensional nanostructures are referred to as quantum wires.In the same spirit,nanometer-size crystallites are known as quantum dots.There are so many different kinds of nanostructures and ways to fabricate them that it is impossible to review them all in this introductory book. In some nanostructures strain may be introduced as a result of lattice mismatch between a substrate and its overlayer,giving rise to a so-called strained-layer superlattice.In this chapter we shall consider only the best-study nanostructures.Our purpose is to introduce readers to this fast growing field.One reason why nanostructures are of great interest is that their electronic and vibrational properties are modified as a result of their lower dimensions and symmetries.Thus nanostructures provide an excellent opportunity for applying the knowledge gained in the previous chapters to understand these new developments in the field of semiconductors physics.Due to limitations of space we shall consider in this chapter only the effects of spatial confinement on the electronic and vibrational properties of nanostructures and some related changers in their optical and transport properties.Our main emphasis will be on QWs,since at present they can be fabricated with much higher degrees of precision and perfection than all other structures.We shall start by defining the concept of quantum confinement and discuss its effect on the electrons and phonons in a crystal.This will be followed by a discussion of the interaction between confined electrons and phonons.Finally we shall conclude with a study of a device(known as a resonant tunneling device)based on confined electrons and the quantum Hall effect(QHE)in a two-dimensional electron gas.The latter phenomenon was discoveredby Klaus von Klitzing and coworkers in 1980 and its significance marked by the award of the 1985 Nobel Prize in physics to ｖｏｎ Klitzing for this discovery.Together with the fractional quantum Hall effect it is probably the most important development in semiconductor physics within the last two decades.Quantum Confinement and Density of StatesIn this book we have so far studied the properties of electrons ,phonons and excitons in either an infinite crystal or one with a periodic boundary condition(the cases of surface and interface states )In the absence of defects, these particles or excitations are described in terms of Bloch waves,which can propagate freely throughout the crystal.Suppose the crystal is finite and there are now two infinite barriers,separated by a distance L,which can reflect the Bloch waves along the z direction.These waves are then said to be spatially confined.A classical example of waves confined in one dimension by two impenetrable barriers is a vibrating string held fixed at two ends.It is well-known that the normal vibration modes of this string are standing waves whose wavelength λ takes on the discrete values given by Another classical example is a Fabry-Perot interferometer (which has been mentioned already in Set.7.2.6 in connection with Brillouin scattering).As a result of multiple reflections at the two end mirrors forming the cavity ，electromagnetic waves show maxima and minima in transmission through the interferometer at discrete wavelengths.If the space inside the cavity is filled with air,the condition for constructive interference is given by (9.1).At a transmission minimum the wave can be considered as “confined ”inside the interferometer.n λ=2L/n, n=1,2,3… .(9.1)For a free particle with effective mass *m confined in a crystal by impenetrablebarriers(i.e.,infinite potential energy)in the z direction,the allowed wavevectors z k of the Bloch waves are given byzn κ=2∏/n λ=n ∏/L, n=1,2,3… (9.2)And its ground state energy is increased by the amount E relative to the unconfined case:))(2(2222212Lm m k E z ∏==∆** (9.3)This increase in energy is referred to as the confinement energy of the particle.It is a consequence of the uncertainty principle in quantum mechanics. When the particle is confined within a distance L in space(along the z direction in this case)the uncertainty in the z component of its momentum increases by an amount of the order of /L.The corresponding increase in the particle ’s kinetic energy is then givenby(9.3).Hence this effect is known also as quantum confinement.In addition to increasing the minimum energy of the particle,confinement also causes its excited state energies to become quantized.We shall show later that for an infinite one-dimensional”square well”potential the excited state energies are given by n E∆2,where n=1,2,3…as in (9.2).It is important to make a distinction between confinement by barriers and localization via scattering with imperfections。

deep cryogenic heat treatment on the corrosion resistance and wear behavior of 1.2080 tool steel

Technical ReportEffects of applying an external magnetic ﬁeld during the deep cryogenic heat treatment on the corrosion resistance and wear behavior of 1.2080tool steelAmin Akhbarizadeh a ,⇑,Kamran Amini b ,Sirus Javadpour aa Department of Materials Science and Engineering,School of Engineering,Shiraz University,Zand Ave.,Shiraz,Fars,Iran bDepartment of Materials Engineering,Majlesi Branch,Islamic Azad University,Isfahan,Irana r t i c l e i n f o Article history:Received 3January 2012Accepted 23March 2012Available online 21April 2012a b s t r a c tThis work concerns with the effect of applying an external magnetic ﬁeld on the corrosion behavior,wear resistance and microstructure of 1.2080(D2)tool steel during the deep cryogenic heat treatment.These analyses were performed via scanning electron microscope (SEM),optical microscope (OM),transmission electron microscope (TEM)and X-ay diffraction (XRD)to study the microstructure,a pin-on-disk wear testing machine to study the wear behavior,and linear sweep voltammetry to study the corrosion behav-ior of the samples.It was shown that the deep cryogenic heat treatment eliminates retained austenite and makes a more uniform carbide distribution with higher percentage.It was also observed that the deep cryogenic heat treatment improves the wear behavior and corrosion resistance of 1.2080tool steel.In comparison between the magnetized and non-magnetized samples,the carbide percentage decreases and the carbide distribution weakened in the magnetized samples;subsequently,the wear behavior and corrosion resistance attenuated compared in the magnetized samples.Crown Copyright Ó2012Published by Elsevier Ltd.All rights reserved.1.IntroductionCryogenic heat treatment is a special kind of supplementary heat treatment that has been changed from black art since 1930to science in these decades [1].Tool and carburized steels are pre-dominantly hypereutectoid and ledeburitic steels [2]that their austenite is not transformed to martensite completely after con-ventional heat treatments [3–7].Cryogenic heat treatment is a common recommendation to eliminate or decrease retained aus-tenite via phase transformation to martensite in low temperatures [2].The cryogenic treatment can be performed in two different ap-proaches:(a)shallow cryogenic treatment performed at tempera-tures higher than À100°C and (b)deep cryogenic treatment that is performed at temperatures lower than À125°C and regularly in the liquid nitrogen temperature (À196°C)[8].The deep cryo-genic heat treatment decreases retained austenite in an isothermal transformation [9]due to lowering the temperature down the mar-tensite ﬁnish temperature (M f )[2].Beyond the elimination of re-tained austenite,some newly formed carbide are produced in the martensite matrix,increasing the carbide percentage and thereby making a more homogeneous carbide distribution compared to the non-cryogenically treated samples [10–14].These newly formed carbides are g ones instead of usual e carbides witch are smaller in size and more uniform in distribution [2].During thedeep cryogenic heat treatment,a high density of defects such as dislocations,twins and voids are produced due to high internal stresses induced by the transformation of austenite to martensite.Additionally,the different thermal expansion coefﬁcient of austen-ite and martensite increases the defects density.A high degree of distortion takes place in the martensite structure due to the aus-tenite–martensite transformation.The structure distortion,ther-modynamic instability and supersaturated martensite structure at low temperatures force carbon atoms to jump and segregate to nearby defects [15].These phenomena that lead to decomposi-tion of the martensite during the deep cryogenic treatment pro-duce some new carbides nuclei which act as future carbide nucleation sites in subsequent tempering [16].This accepted and common theory was challenged by Oppenkowski et al.[17],who claimed that the better carbide distribution is obtained due to a high degree of plastic deformation in the martensite structure dur-ing the deep cryogenic heat treatment.This plastic deformation which is a result of a high level of contraction in the structure makes the martensite dislocations mobile,and these dislocations draw out carbon atoms from the supersaturated structure.These extracted carbon atoms would be preferential sites for the carbide nucleation during prior tempering [17].Despite whole of these dif-ferences in theories,it was clearly showed that the deep cryogenic heat treatment improves the hardness and wear behavior of tool steels from some percentage to some hundred percentages.This improvement is a consequence of elimination the retained austen-ite as well as formation a more uniform carbide distribution with higher percentage [18–20].0261-3069/$-see front matter Crown Copyright Ó2012Published by Elsevier Ltd.All rights reserved./10.1016/j.matdes.2012.03.045Corresponding author.Tel.:+989171134163;fax:+987112307293.E-mail address:Akhbarizadeh@shirazu.ac.ir (A.Akhbarizadeh).It was shown that Martensitic transformation is accelerated in the existence of external magnetic ﬁelds.When an external magnetic ﬁeld is applied to an austenitic steel,some unusual martensitic transformation takes palace that is a consequence of a reduction in austenite–martensite transformation energy barrier [21].This phenomena increases the start and ﬁnish temperature of martensite transformation (M s and M f )due to the phase instability which is induced in the austenite [22,23].Different phases show different magnetic characteristics in Fe-based alloys.Magnetization of the ferromagnetic bcc phase (martensite)in Fe based alloys is much greater than the fcc para-magnetic phase (austenite).In the presence of an external mag-netic ﬁeld,different magnetic properties of austenite and martensite,change the transformation temperature for some de-grees [24].Moreover,some studies showed that magnetic ﬁeld re-duces the carbon atoms diffusivity due to its effect on the atoms jumping frequency in steels.In other words,the carbon atoms fre-quency reduces as a result of a magnetic ﬁeld [25,26].A lot of experimental studies were carried out to investigate the effect of the deep cryogenic heat treatment on tool steels,but none of them focused on the effect of the deep cryogenic heat treatment with the existence of an external magnetic ﬁeld.Additionally,this study spotlights the effect of a magnetic ﬁeld during the deep cryo-genic heat treatment on the corrosion behavior of 1.2080tool steel via linear sweep voltammetry.To explain this behavior,micro-structural changes were also studied by scanning electron micro-scope (SEM),optical microscope (OM),transmission electron microscope (TEM)and X-ray diffraction (XRD).In addition,the wear behavior of the samples was also studied via a pin-on-disk wear tester and SEM.2.Experimental detailsA 20mm bar of 1.2080tool steel was cut into disks with the height of 5mm.The nominal composition of the steel bar was (wt.%):2.2%C,0.6%Si,0.6%Mn,12%Cr,0.5V,0.4%W and 83.7%Fe.The samples were austenized at 950°C for 15min,and then oil quenched.After quenching,one group of samples was assumed as the conventionally treated ones (CHT)and the other samples were deep cryogenically treated.The samples which were cryogenicallyheat treated,were cooled down to À195°C gradually,held at that temperature for some hours and then warmed up to room temper-ature slowly to prohibit any severe temperature gradient (Fig.1).It should be mentioned that the deep cryogenic heat treatment was performed on the samples immediately after quenching to prohibit austenite aging at room temperature [27].Two groups of the sam-ples were deep cryogenically treated for 24and 48h and named DCT24and DCT48respectively.For the deep cryogenic treatment with the presence of an external magnetic ﬁeld,two other groups of the samples were connected to a magnet with a magnetic ﬂux density of 0.12T and then deep cryogenically treated for 24and 48h (Fig.2).These magnetized-deep cryogenically treated samples were named MDCT24and MDCT48respectively.All ﬁve groups of the samples were tempered at 150°C for 3h.The samples surface was then grounded up to the number 1000grinding paper to reach a uniform and smooth surface.The samples were examined by the XRD method with CuK a radiation to calculate the retained austenite percentage according to the ASTM E 975-00standard [28].To calculate the carbide per-centage,the samples were etched in a 100ml H 2O,10g K 3Fe(CN)6Fig.1.Schematic representation of the deep cryogenic heat treatment of 1.2080tool steel.Sample Magnet MagnetMagnet Steel coreSample2.Magnet assembly to the samples for the deep cryogenic heat treatment (MDCT).and10g NaOH etchant for6–10s.This etchant only affects the car-bide and help us to trace them in the structure.The surfaces micro-graphs were analyzed by Clemex Vision(version3.5.025)software to calculate the carbide percentage.Hardness tests were conducted by Rockwell C and microhard-ness test methods.The Rockwell C tests were conducted using a KOOPA UV1hardness tester with a pre-load of60kg and an ap-plied load of150kg.The microhardness testing was done via a KOOPA MH1micro-hardness tester equipped with a Vickers inden-ter under a load of500g and dwell time of15s.The Rockwell C and microhardness tests were done at least for5and15times respec-tively in each sample to reach a trustful average.The microstructure of the samples was examined using a scan-ning electron microscope(SEM Seron AIS-2100),to study the car-bide distribution and percentage.The samples were etched in a combination of100ml H2O,10g K3Fe(CN)6and10g NaOH–mixed acid(3ml HF,53ml H2NO3,2ml CH3COOH and42ml H20)and ni-tal4%(96ml ethanol and4ml HNO3)for2s and3–4times.This etchants distinguish the carbide for better observation during the SEM analysis.The samples microstructure was also studied by a transmission electron microscope(TEM,Philips CM200)to study the distribution of veryﬁne carbides.To do so,the samples were mechanically polished to1l m height,and then more thinning was continued by jet polishing and ion beam thinning.Finally, the samples were punched to a disk with the diameter of3mm.The corrosion resistance of the samples was determined using linear sweep voltammetry experiments.The polarization measure-ments were carried out with a sweep rate of5mV sÀ1using an Autolab potentiostat model type3,EcoChemie BV and a General Purpose electrochemical System4.9software.It was conducted in a5wt.%NaCl aqueous solution using a classic three-electrode cell with a platinum plate as the counter electrode and an Ag/AgCl electrode as the reference electrode.The samples were cleaned in acetone and then drawn in deionized water before the electro-chemical test.The samples were covered with lacquer so that only 1cm2area was exposed to the electrolyte.The specimens were im-mersed in the mentioned solution for20min at room temperature to reach a steady state Open Circuit Potential(OCP).Wear tests were conducted under loads of110and160N in three sliding speeds(0.05,0.1and0.15m/s)and at24±4°C via a pin-on-disk wear testing machine by steel pins with the hardness of65HRC.The wear rate was calculated usingWr¼D m=ðq LF NÞÂ106ð1Þwhere Wr is the wear rate in mm3/Nm;D m,the weight loss in mg, q,the steel density in g/cm3;L,the wear distance in meter and F N, the load in Newton.The worn out surface of the samples was studied using SEM to clarify the wear mechanism of the samples.3.Results and discussion3.1.MicrostructureThe XRD analysis of the samples shows that retained austenite vanishes during the deep cryogenic heat treatment(Fig.3).The re-tained austenite percentage decreases from8%in the CHT sample to lower than1%(the detection limit of the XRD technique).The optical microscope(OM)micrographs show that the carbide per-centage increases from18%in the CHT sample to26%and24%in the DCT48and DCT24respectively.In comparison between the magnetized and the non-magnetized samples,the carbide percent-age decreases for a few percent in the magnetized ones.It shows that the carbide percentage decreases to23%in the MDCT48sam-ple and22%in MDCT24samples(Fig.4and Table1).The hardness of the samples was evaluated using Rockwell C and microhardness methods(Table2).The results showed that the deep cryogenic heat treatment increases the hardness of the samples about4%with respect to the Rockwell C and16–20%with respect to the microhardness test.This improvement is lower in the magnetized samples and is about2%with respect to theRock-Fig.3.XRD pattern of1.2080tool steel.well C test and7–14%with respect to the microhardness test (Fig.5).The improvement percentage was calculated using Improvement percentage¼ððsample hardnessÞÀðCHT hardnessÞÞ=ðCHT hardnessÞÂ100ð2ÞWith increasing the holding time,the hardness of the samples increases,but in comparison between the magnetized and non-magnetized samples with the same holding durations,the hard-ness of the magnetized samples decreases for6–10%compared to the non-magnetized ones.The SEM micrographs of the samples show that the carbide dis-tribution becomes more homogeneous after the deep cryogenic heat treatment(Fig.6).During the deep cryogenic treatment,the structure was contracted and some new defects including disloca-tions,twins,etc.were created.These defects attract carbon atoms from the saturated and contracted martensite structure.These atoms would act as preferential sites for carbide nucleation during the former tempering,increase the carbide percentage and make a more homogenous distribution[15].In longer holding durations at the deep cryogenic temperature, further carbon atoms jump to nearby defects due to more dura-tions in which the sample endure a high degree of contraction and subsequently the carbide percentage increases in theseTable1Carbides percentage in 1.2080tool steel samples.Sample nomination Carbides percentageCHT18 DCT2424 MDCT2422 DCT4826 MDCT4823Table2Average hardness and microhardness of1.2080tool steel.Sample nomination Microhardness(MPa)Rockwell C hardness(HRC)CHT79563.2DCT2493865.5MDCT2485064.5DCT4896865.9MDCT4891065.2 micrograph of the samples at100Â:(a)CHT,(b)DCT24,(c)MDCT24,(d)DCT48,(e)MDCT48after etching in100ml H2O,10g K3Fe(CN)samples(Fig.6b and d).It was also shows that in comparison be-tween the magnetized and non-magnetized deep cryogenically treated samples,the magnetized samples present a weaker carbide distribution(Fig.6c and e).The TEM micrograph of the DCT48sam-ple also shows that some newly formed nano-sized carbides were precipitated during the deep cryogenic heat treatment.These nano-sized carbides were in the size of20–80nm and improve the hardness of the samples accompanied with other new mi-cron-sized carbides(Fig.7).Isothermal martensite transformation is an unusual time dependent formation of martensite at a constant temperature, which is a function of holding time at temperatures below the mar-tensitic start transformation temperature(M s).The isothermal martensite transformation seriously affected by external magnetic ﬁelds[9].Koch[24]showed that the isothermal martensite trans-formation obeys a C shape diagram,alike the diffusional transfor-mation,and the noise of the TTT curve is shifted to lower temperatures with less incubation time.This leads to a faster mar-tensite transformation due to a less incubation time.The martensite growth is fast and the isothermal martensite formation kinetics is completely controlled by the nucleation rate [29].The effective driving force for the nucleation is described by D G v¼D G chemvþD GstrainvþD Gmagvð3Þwhere D G chemv is the chemical potential of austenite and martensite phases.The driving force is controlled by the difference in the chemical potential of austenite and martensite phases in associa-tion of volume differences between phasesðD G strainvÞ.In the presence of an external magneticﬁeld,the change in the magnetic energyðD G magvÞchanges the energy barrier.Note that D Gchemv is a negativevalue and the strain energy chemical potential D G strainv is a positive value in Eq.(3).It can be shown thatD G magv¼À8:44lHð4Þwhere l0H is the applied magneticﬁeld and subsequently the valueof D G magv is always negative.Therefore,the effective driving force for the nucleation has more negative values in the presence of an exter-nal magneticﬁeld[30].The energy barrier for the nucleation of isothermal martensite can be described byD GÃ¼wD G n va j T0ðHÞÀT jÀnð5Þwhere w and n are constants and D G v a|T0(H)ÀT|Àn is the energy gain(per unit volume)of the nucleating phase which scaleswith Fig.5.Hardness improvement in the samples as compared to the CHT sample:(a)HRC and(b)microhardness test.undercooling with respect to the ﬁeld dependent transformation temperature (T 0(H )).In the presence of an external magnetic ﬁeld,the effective driving force for nucleation (D G v )increases and there-by the energy barrier deceases (Eq.(5))[29].In the existence of a magnetic ﬁeld,the activation energy of the austenite–martensite transformation decreases;in other words,M s increases [29].This in-crease facilitates the martensite formation during the isothermal martensite transformation.Easier transformations do not let the dislocations to attract the carbon atoms up to the prior value and subsequently the carbide percentage decreases in the magnetized samples compared to the non-magnetized ones.Additionally,some studies showed that magnetic ﬁeld reduces the carbon atoms diffu-sivity due to its effect on the atoms jumping frequency [25,26].In other words,the carbon atoms frequency reduces as a result of a magnetic ﬁeld.This reduction in frequency reduces the jumping en-ergy of the carbon atoms at the deep cryogenic temperatures and subsequently leads to lower the carbide percentage in future tem-pering.Simultaneous effect of these phenomena reduces the ﬁnal carbide percentage and reduces its homogenous distribution (Fig.6).3.2.Wear behaviorThe wear test of the samples was carried out at two different loads of 110and 160N at three different sliding speeds of 0.5,0.1and 0.15m/s.The results show that the deep cryogenic heat treatment improves the wear resistance of the sample for 60–80%(Fig.8).This improvement increases with increasing the hold-ing time in the deep cryogenic temperature.This improvement is a consequence of retained austenite elimination,better carbide dis-tribution and a more uniform carbide distribution.In comparison between the magnetized and non-magnetized samples,the magnetized samples show a weaker wear behavior due to their weaker carbide distribution and lower carbide per-centage.In the magnetized deep cryogenically treated samples (MDCT24and MDCT48)simultaneous effect of increasing the M s temperature and reduction in the jumping frequency of carbon atoms,decreases the carbide percentage and attenuate the carbide homogenous distribution.It also reveals that with increasing the sliding speed,the wear rate increases vividly (Fig.8a and b).Despite severe changesinof (a)CHT,(b)DCT24,(c)MDCT24,(d)DCT48and (e)MDCT48samples at 750Âafter etching in a combination of 100ml H 2O,nital 4%.Fig.7.TEM micrograph of the DCT48sample at(a)122,000Âand(b)162,000Â.of the samples versus sliding speed after1000m sliding distance under,(a)110N and(b)160the samples weight loss,the wear rate in different loads did not change obviously,because in Eq.(1),the normal force at the denominator of the equation neuters the weight loss in thenumerator.of the worn out surface of (a)CHT,(b)DCT24,(c)MDCT24,(d)DCT48and (e)MDCT48samples at 300Âafter 1000m sliding DCT48MDCT48DCT24MDCT24CHTFig.10.Polarization curve of the 1.2080tool steel samples in 5%NaCl aqueous solution.The worn out surface of the samples shows that the predomi-nant wear mechanism is adhesive(Fig.9).The worn out surface of the deep cryogenically treated samples shows smoother preface compared to the CHT sample.In comparison between the magne-tized and non-magnetized samples,the worn out surface of the magnetized samples shows a more rough appearance compared to the non-magnetized deep cryogenically treated samples in the same holding durations(Fig.9).The micrographs clearly show that the deep cryogenic heat treatment improves the worn out surface after wear test due to retained austenite elimination and a more uniform carbide distribution with higher percentage(Fig.9a and b).The worn out surface of the magnetized samples(MDCT24 and MDCT48)shows that the wear test,were harmed these sam-ples more intensively compared to the non-magnetized deep cryo-genically treated ones(Fig.9b–e).This severe damage is a consequence of lower carbide percentage and weaker carbide dis-tribution in the MDCT samples.3.3.Corrosion behaviorTo determine the corrosion behavior,linear sweep voltammetry was performed on the samples in5wt.%NaCl aqueous solution (Fig.10).Calculated electrochemical parameters of the samples are listed in Table3.The results showed that due to a more uniform carbide distribution in association with the higher carbide percent-age,corrosion behavior of the deep cryogenically treated samples were improved.Some studies showed that,chromium carbide and oxides improve the corrosion resistance of steels[30,31].Table3 shows that the DCT samples have a more positive E corr and lower I corr which is indicative of the better corrosion resistance.The corrosion resistance was improved in longer holding durations(DCT48)due to increasing the carbide percentage for3%(vol.%)and a more uni-form carbide distribution.In comparison between the magnetized and non-magnetized samples,the magnetized ones show a lower carbide percentage,and regarding the corrosion resistance of chro-mium carbide[30]the corrosion behavior of the MDCT samples des-cends compared to the DCT ones in the same holding durations. 4.ConclusionTo study the effect of applying a weak magneticﬁeld on the cor-rosion behavior,wear resistance and microstructure of1.2080tool steel during the deep cryogenic heat treatment,the heat treatment was performed with/without the external magneticﬁeld of0.12T. The obtained results are summarized as follows:1.The deep cryogenic heat treatment eliminated retained austen-ite,increased the carbide percentage and produced a more uni-form carbide distribution.It was also showed that the deep cryogenic heat treatment increased the hardness and improved the wear and corrosion resistance of1.2080tool steel.2.Applying a magneticﬁeld during the deep cryogenic heattreatment weakened the carbide distribution and decreased the carbide percentage due to its effect in easier martensitetransformation during the deep cryogenic treatment and reduc-ing the carbon atoms jumping frequency.Subsequently,apply-ing a magneticﬁeld during the deep cryogenic heat treatment decreased the hardness,weakened the corrosion resistance and increased the wear rate in comparison with the conven-tionally deep cryogenically treated samples.3.The magnetization during the deep cryogenic heat treatment isnot proposed owing to its destructive effect on the microstruc-ture and wear resistance of1.2080tool steel.4.The predominant wear mechanism in all the samples was adhe-sive wear.References[1]Wilkins C.Cryogenic processing;the big chill.EDM Today;1999.p.36–44.[2]Gill SS,Singh J,Singh R,Singh H.Metallurgical principles of cryogenicallytreated tool steels—a review on the current state of science.Int J Adv Manuf Technol2011;54:59–82.[3]Preciado M,Bravo PM,Alegre JM.Effect of low temperature tempering priorcryogenic treatment on carburized steels.J Mater Process Technol 2006;176(1–3):41–4.[4]Meng F,Tagashira K,Azuma R,Sohma H.Role of eta carbide precipitations inthe wear resistance improvements of Fe–12Cr–Mo–V–1.4C tool steel by cryogenic treatment.ISIJ Int1994;34:205–10.[5]Bensely A,Prabhakaran A,Mohan Lal D,Nagarajan G.Enhancing the wearresistance of case carburized steel(En353)by cryogenic treatment.Cryogenics 2005;45(12):747–54.[6]Mohan Lal D,Renganarayanan S,Kalanidhi A.Cryogenic treatment toaugment wear resistance of tool and die steels.Cryogenics2001;41(3): 149–55.[7]Yugandhar T,Krishnan PK.Cryogenic treatment and its effects on tool steel.In:Proceedings of6th international tooling conference,Karlstad University;September2002.p.671–84.[8]Akhbarizadeh A,Shafyei A,Golozar MA.Effects of cryogenic treatment on wearbehavior of D6tool steel.Mater Des2009;30:3259–64.[9]San Martin D,Van Dijk NH,Brück E,Van der Zwaag S.The isothermalmartensite formation in a maraging steel:a magnetic study.Mater Sci Eng A 2008;481–482:757–61.[10]Amini K,Nategh S,Shafyei A.Inﬂuence of different cryo treatments ontribological behavior of80CrMo125cold work tool steel.Mater Des 2010;31:4666–75.[11]Akhbarizadeh A,Golozar MA,Shafyei A,Kholghy M.Effects of austenizing timeon wear behavior of D6tool steel after deep cryogenic treatment.J Iron Steel Res2009;16:29–32.[12]Collins DN.Deep cryogenic treatment of tool steels—a review.Heat Treat Met1996;23(2):40–2.[13]Collins DN,Dormer J.Deep cryogenic treatment of a D2cold-worked tool steel.Heat Treat Met1997;3:71–4.[14]Yun D,Xiaoping L,Hongshen X.Deep cryogenic treatment of high-speed steeland its mechanism.Heat Treat Met1998;3:55–9.[15]Das D,Dutta AK,Ray KK.On the enhancement of wear resistance of tool steelsby cryogenic treatment.Philos Mag Lett2008;88:801–11.[16]Stratton PF.Optimising nano-carbide precipitation in tool Steels.Mater Sci EngA2007;449–451:809–12.[17]Oppenkowski A,Weber S,Theisen W.Evaluation of factors inﬂuencing deepcryogenic treatment that affect the properties of tool steels.J Mater Process Technol2010;210:1949–55.[18]Moore K,Collins DN.Cryogenic treatment of three heat treated tool steels.KeyEng Mater1993;86–87:47–54.[19]Babu PS,Rajendran P,Rao KN.Cryogenic treatment of M1,EN19,and H13toolsteels to improve wear resistance.J Inst Eng India MM2005;86:64–6. [20]Zurecki Z.Cryogenic quenching of steel revisited,ASM proceedings:heattreating.Pennsylvania:ASM;2006.p.106–13.[21]Kakeshita T,Saburi T,Shimizu K.Effects of hydrostatic pressure andmagneticﬁeld on martensitic transformations.Mater Sci Eng A2008;273–275:21–39.[22]Murase S,Kobatake S,Tanaka M,Tashiro I,Horigami O,Ogiwara H,et al.Effectsof a high magneticﬁeld on fracture toughness at4.2K for austenitic stainless steels.Fusion Eng Des1993;20:451–4.[23]Shimizu K,Kakeshita T.Effect of magneticﬁelds on martensitictransformations in ferrous alloys and steels.ISIJ Int1989;29:97–116.[24]Koch CC.Experimental evidence for magnetic or electricﬁeld effects on phasetransformations.Mater Sci Eng A2000;287:213–8.[25]Xia ZX,Zhang C,Lan H,Liu ZQ,Yan ZG.Effect of magneticﬁeld on interfacialenergy and precipitation behavior of carbides in reduced activation steels.Mater Lett2011;65:937–9.[26]Nakamichi S,Tsurekawa S,Morizono Y,Watanabe T,Nishida M,Chiba A.Diffusion of carbon and titanium in c-iron in a magneticﬁeld and a magnetic ﬁeld gradient.J Mater Sci2005;40:3191–8.[27]Gulyaev AP.Improved methods of heat treating high speed steels to improvethe cutting properties.Metallurgy1937;12:65–70.Table3Electrochemical parameters of1.2080tool steel in5wt.%NaCl aqueous solution.Samples nomination I corr a E corr bCHT 3.4Â10–5À0.56 DCT24 5.99Â10À7À0.5 MDCT24 2.01Â10À6À0.525 DCT48 4.84Â10À7À0.461 MDCT488.85Â10À7À0.48 a Icorrcorrosion current density.b Ecorr corrosion potential.122 A.Akhbarizadeh et al./Materials and Design41(2012)114–123。

Effects of Silica Fume and Rice Husk Ash on the Properties of Heavy Weight Concrete

Effects of Silica Fume and Rice Husk Ash on the Propertiesof Heavy Weight ConcreteK.Sakr1Abstract:Considerable efforts are being taken worldwide to utilize local natural waste and by-product materials in making concrete, such as silica fume͑SF͒or rice husk ash͑RHA͒as supplementary cementing materials to improve concrete properties͑durability, strength,etc.͒.The effect of using SF or RHA as a partial replacement for cement has been investigated.Ilmenite and baryte were used as heavy aggregates while gravel was used as a reference normal aggregate.Physical,mechanical,and shielding properties of different types of heavy weight concrete were studied.The durability of the studied concrete was investigated.The study was extended to investigate the microstructure,the infrared and thermal analysis,and the effect of absorbed gamma radiation of the studied concrete types. Results showed that ilmenite concrete mixed with15%SF had the highest density;compressive,tensile,ﬂexural,and bond strengths; modulus of elasticity;and attenuation coefﬁcient values.Concrete mixed with RHA had good resistance to sulfate attack,while concrete mixed with SF had better resistance to sulfate attack.There was no signiﬁcant effect for either SF or RHA on the concrete gamma attenuation coefﬁcient.Results showed that concrete mixed with RHA had higher mechanical and physical properties than that mixed without any additives but lower properties than that mixed with SF.DOI:10.1061/͑ASCE͒0899-1561͑2006͒18:3͑367͒CE Database subject headings:Concrete;Recycling;Ashes;Material properties.IntroductionImprovement of concrete durability and strength are of great con-cern,especially when the concrete is exposed to an aggressiveenvironment.A large amount of research has been carried out tostudy both the durability and strength of concrete to obtain highperformance concrete͑Aitcin and Neville1993͒.The basic as-pects of the production of high performance concrete are the useof a low water/cement͑W/C͒ratio and supplementary cementingmaterials͑Kaplan1989͒.Due to growing environmental concernsand the need to conserve energy and resources,considerable ef-forts have been made worldwide to utilize local natural waste andby-product materials in making concrete,e.g.,silica fume͑SF͓͒ACI Committee226͑1987͔͒and rice husk ash͑RHA͒,which, under controlled burning and with sufﬁcient grinding of the ricehusk,can be used as a supplementary cementing material͑Mahdy1999a͒.The heavy aggregates͑coarse andﬁne͒must not reactwith the cement or contain materials that may adversely affect thestrength of concrete made with those aggregates.The aim of this work is to determine the optimum percentage ͑0,5,10,15,or20%͒of SF or RHA as a partial replacement of cement for heavy weight concrete properties,and to compare the obtained results of the different types of heavy weight concrete with gravel͑ordinary͒concrete regarding physical and mechani-cal properties,microscopic scanning,infrared and thermal analy-sis,durability,radiation shielding properties,and the effect of gamma radiation doses on the properties of heavy weight concrete.Experimental WorkMaterialAggregatesThe aggregates used were special natural heavy weight mineral ores,mainly ilmenite and baryte.They were used as theﬁne and coarse aggregates for the heavy weight concrete.Gravel and sand were used as the coarse andﬁne aggregate for the gravel concrete. Ilmenite and baryte ore were supplied from the Red Sea region and from Aswan mining.Gravel and sand were obtained from Kattamya,Cairo,Egypt.The grading of the heavy aggregate was in compliance with ASTM C-637͑ASTM1984͒.Table1demon-strates that the physical and mechanical properties of the aggre-gates used were also in compliance with ASTM C-673-84͑El-Sadani2001͒.The chemical components of the aggregates used are given in Table2.Ordinary Portland CementOrdinary Portland cement was provided from Torah Factory, Egypt.The cement had a speciﬁc gravity of3.15and aﬁneness of 2.9ϫ105mm2/gm.The main chemical components of the cement used were62.5%CaO,21%SiO2,6.5%Al2O3,3.8%MgO,3% Fe2O3,and2.1%SO3͑El-Sadani2001͒.Silica FumeThe SF had a high content of amorphous silicon dioxide and consisted of spherical particles.The unite weight of the SF was1Hot Laboratory Center,Atomic Energy Authority,P.O.Box135759,Kalubiuah,Cairo,Egypt.E-mail:Khaledsakr555@Note.Associate Editor:Jason Weiss.Discussion open until November1,2006.Separate discussions must be submitted for individual papers.Toextend the closing date by one month,a written request must beﬁled withthe ASCE Managing Editor.The manuscript for this paper was submittedfor review and possible publication on April15,2003;approved on June29,2004.This paper is part of the Journal of Materials in Civil Engi-neering,V ol.18,No.3,June1,2006.©ASCE,ISSN0899-1561/2006/3-367–376/$25.00.JOURNAL OF MATERIALS IN CIVIL ENGINEERING©ASCE/MAY/JUNE2006/3672.3ϫ103kg/m3,and the speciﬁc surface area was 19ϫ106mm2/gm;the particles were spherical,at4.00␮m in size,and the bulk density was3.0ϫ103kg/m3.The chemical composition of the SF was95%SiO2,1.0%CaO,1.0%Al2O3, and1.5%Fe2O3.Rice Husk AshRice husk ash͑RHA͒was obtained by burning RH in a furnace with a controlled temperature in order to establish the optimum burning temperature and burning time.Grinding of RHA aims to achieve the best speciﬁc surface area.It was found that the most convenient and economical temperature required for conversion of the RH into ash was600°C for3h͑El-Karmouty2000͒. The RHA that was used had a speciﬁc surface area of 5.6ϫ106mm2/g,and the unite weight was2.06ϫ103kg/m3. The chemical composition of the RHA was87.0%SiO2,1.75% Al2O3,2.5%Fe2O3,2.5%CaO,2.3%MgO,and2.5%K2O.The silica content of the ash was derived from the amorphous silica present in the cellular structure of the husks.X-ray diffraction of the RHA showed that the RHA contained mainly amorphous ma-terials with a very small amount of crystallized quartz ͑El-Karmouty2000͒.Superplasticizer(High Range Water Reducing Admixture)Superplasticizer͑SP͒͑Sikament-163͒was used to maintain a con-stant workability,expressed as constant slump without any addi-tional amount of mixing water and without any direct effect on the compressive strength of the concrete.It was composed of sodium salt͑sulfonated naphthalene formaldhyde condensate͒. The superplasticizer complied with ASTM C-494Type F.The slump was controlled by adding a suitable dose of SP to have a slump of30–120mm for all types of tested concretes ͑El-Manaseer and Keil1992͒.Mix DesignSeveral trial mixes were prepared according to the absolute vol-ume method to obtain a maximum density.The mix designs aregiven in Table3.Sample PreparationCubes of150ϫ150ϫ150mm dimension were prepared for thecompressive strength test,while cylinders150mm in diameterand300mm in height were prepared for the tensile and bondingstrength tests.Three prismatic specimens of the different types ofconcrete in dimensions of200ϫ200ϫ120mm were prepared tobe used after28days of preparation for the permeability investi-gation.One face of the specimen was subjected to water pressureof1bar for48h,followed by3bars for24h,andﬁnally7barsfor24h.The specimen was then split open at its middle by ap-plying a compression load.The penetration depth of the waterwas measured and the average values were recorded.Three cy-lindrical slices of100mm diameter and50mm thickness wereoven dried until their weight became constant and then were leftin the open air for cooling.The samples were immersed in waterand reweighted every24h;then,the water absorption percentagefor different types of tested concrete was calculated accordingto ASTM C-642-90.For the sulfate resistance test,cubes ͑100ϫ100ϫ100mm͒were immersed in a5%MgSO4solution for different periods͑1,3,and6months͒and the loss in compres-sive strength due to sulfate attack was determined.Shielding testsfor gamma rays͑␥-rays͒were performed using cobalt-60andcesium-137point sources of3.7ϫ104Bq͑1␮Ci͒activity.Dif-ferent thicknesses of concrete specimens ranging from20to100mm cut from cubic specimens of150ϫ150ϫ150mmwere used.Tests were carried out using a4-in.-diameter NaITable1.Physical and Mechanical Properties of Aggregates Used͑El-Sadani2001͒Properties Speciﬁcation number Ilmenite Baryte Gravel Sand Speciﬁc gravity͑kg/m3͒ASTM C-12 4.2ϫ103 4.0ϫ103 2.7ϫ103 2.65ϫ103 Unite weight͑kg/m3͒ASTM C-29 2.80ϫ103 2.75ϫ103 1.72ϫ103 1.67ϫ103 Max-nominal size͑mm͒ASTM C-136202020—V oid ratio͑%͒—332737—Water absorption͑%͒ASTM C-1 2.2 1.70.8—Crushing value͑%͒ASTM C-131384316—Fineness modulus ASTM C-125 1.85 2.4— 2.65Table 2.Chemical Analysis Percent of Aggregates Used͑El-Sadani2001͒Chemical analysis percentAggregateIlmenite Baryte Gravel SandTiO238.50.35——Fe2O327.50.5 1.30.3 CaO0.120.7 1.50.8 FeO27.50.20.150.14 SiO2 2.4 3.8092.196.4 Al2O3 1.52 1.4 2.50.2 BaSO4—90.9——BaO0.720.90.20.1 LOI0.810.90 1.20 1.5Table3.Mix Proportions To Produce about1m3of Different Types of ConcreteCompositionConcrete typeGravelconcreteBaryteconcreteIlmeniteconcrete Fine aggregate͑kg/m3͒7701,1001,120 Coarse aggregate͑kg/m3͒1,2001,8101,950 Cement content͑kg/m3͒375SF/C0,5,10,15,and20%RHA/C0,5,10,15,and20%W/C40%Superplasticizer Suitable dose,maximum dose at15%,20%of SF or RHA in concreteSlump͑mm͒30–120368/JOURNAL OF MATERIALS IN CIVIL ENGINEERING©ASCE/MAY/JUNE2006͑sodium-iodied crystal͒detector connected to a computerized multichannel analyzer͑MCA͒for measuring the gamma counting behind the test specimens͑Fig.1͒.The average attenuation coef-ﬁcient values of the concrete type tested were calculated using the attenuation equation͑I=I o·e−␮x͒,where I,I o=intensity of gamma activity after and before the shield material,respectively;␮=attenuation coefﬁcient factor;and x=thickness of the tested sample͑Kaplan1989͒.To investigate the effect of absorbed gamma radiation on com-pressive strength,groups of cubes having50mm sides were pre-pared.After28days of preparation,the cubes were exposed to gamma rays emitted from a Co60irradiation cell for a period of50 and100h to have a gamma dose of50and100rad,then the compressive strength was determined.A dimension correction factor of the cubic samples was done to compare the results ob-tained in the comparative study͑Neville1981͒.All results ob-tained were statistically analyzed to determine their signiﬁcance by calculating the P-value.The P-value of a result indicates the probability of error that the result has a signiﬁcant effect on the measured parameter.A probability of error of0.05was used.If the P-value is equal to or less than0.05,the data are considered signiﬁcant͑Mahdy1999b͒.ResultsPhysical PropertiesThe slump of gravel concrete alone or mixed with different per-centages of SF or RHA ranged between60and120mm,using suitable doses of superplastizer͑SP͒,while that of baryte concrete was40–80mm,and that of amenite concrete was about 30–60mm.This may be attributed to sharp edges of the aggre-gate and to the difference in absorption percentage of the aggre-gates,which was2.2%for ilmenite,1.7%for baryte,and0.8%for gravel.The density of the ilmenite concrete͑3.35ϫ103kg/m3͒was higher than that of the gravel concrete͑2.3ϫ103kg/m3͒or baryte concrete͑3.2ϫ103kg/m3͒by45and5%,respectively. This can be attributed to the fact that the ilmenite aggregate had a density of4.2ϫ103kg/m3,which is higher than that of both the baryte aggregate͑4.0ϫ103kg/m3͒and the gravel aggregate ͑2.7ϫ103kg/m3͒.Mixing a different percentage of SF or RHA had no signiﬁcant effect on concrete density.The incorporation of SF with cement paste contributed to the hydration reactions by providing nucleation sites for Ca͑OH͒2and also by reacting with the alkali and Ca++.The calcium silicate hydrate formed by the reaction of SF with CH−may be slightly different from thatformed by hydration of the calcium silicate phases in cement ͑Detwiler and Metha1989͒.The permeability of the ilmenite concrete was lower than thatof the baryte or gravel concrete͑ilmenite concrete had a lowerpenetration depth of about18mm,while that of the for baryteconcrete was about22mm and that of the gravel concrete was27mm͒.Results showed that the ilmenite concrete mixed with15%of SF had the lowest permeability͑water penetration depthwas about12mm͒as compared to the baryte concrete͑waterpenetration depth was about15mm͒and the gravel concrete ͑water penetration depth was about20mm͒.Also,it was found that the ilmenite concrete mixed with15%of RHA had the lowestpermeability͑water penetration depth was about15mm͒as com-pared to the baryte concrete͑water penetration depth was about19mm͒and the gravel concrete͑water penetration depth wasabout22mm͒,but it was higher than the corresponding mixesincorporating SF.This can be attributed to the fact that the densityof the solidiﬁed SF was slightly higher than that of the hydratedcement,and so the higher density of the SF concretes producesthe lowest permeability͑Bayasi and Zhou1993͒.The water absorption of the ilmenite concrete͑2.5%͒was lowas compared to that of the gravel concrete͑3.7%͒and the baryteconcrete͑2.8%͒.The ilmenite concrete mixed with20%SF byweight of cement replaced showed a reduction in water absorp-tion of about11,7,4,and3%as compared to0,5,10,and15%of SF,respectively.For20%by weight of cement replaced ofRHA,the reduction was found to be13,9,7,and5%,as com-pared to0,5,10,and15%of RHA,respectively,so the absorp-tion decreased with increase of SF or RHA proportion in concrete.This is due to the pozzolanic behavior of SF or RHA,whichdensiﬁes the material structure and converts concrete pores tosmall and unconnected pores͑Dass1984͒.Mechanical PropertiesTable4shows the compressive strength͑f c͒͑MPa͒of different types of concrete mixed with different percentages of SF or RHA at different ages.Fig.2showed that the ilmenite concrete had the highest com-pressive strength when compared to the corresponding baryteconcrete or gravel concrete at different ages.This increase may beattributed to the shape,speciﬁc surface area,and hardness of theilmenite aggregates͑El-Sadani2001͒.It may also be due to theeffect of titanium oxide͑TiO2͒in ilmenite,which may be com-bined with water to form a gelatinous material thatﬁlls thevoids Fig.1.Diagram of shielding properties investigationJOURNAL OF MATERIALS IN CIVIL ENGINEERING©ASCE/MAY/JUNE2006/369in the cement matrix,consequently increasing bonding between the cement particles and thus increasing its compressive strength ͑El-Dakroury 1998͒.Fig.3showed that concrete mixed with SF had a higher compressive strength than that mixed with RHA,and concretes mixed with 15%SF had the highest compressive strength value.It is clear that,as the SF or RHA percent increases,the compressive strength increases up to 15%.Beyond 15%,the compressive strength starts to decrease as the SF or RHA percent increases.This may be due to the high speciﬁc surface areas of SF or RHA,which consume more water to have the same workability ͑Metha 1982͒.The compressive strength ͑f c 90͒of the ilmenite concrete mixed with 15%of SF was about 23%higher than that of 0%SF,while the compressive strength ͑f c 90͒of ilmenite con-crete mixed with 15%of RHA was about 21%higher than that of 0%RHA.This increase may be because the high dose of SF or RHA in the concrete liberated pozzolanic reaction with the cal-cium hydroxide existing in the cement.Microsilica particles could ﬁll the voids in the cement paste because of their small size andTable pressive Strength ͑f c ͒͑MPa ͒of Tested Concretes at Different AgesType of concrete Replacement percentageConcrete+percentage of SFConcrete+percentage of RHAf c 7͑MPa ͒f c 28͑MPa ͒f c 56͑MPa ͒f c 90͑MPa ͒f c 7͑MPa ͒f c 28͑MPa ͒f c 56͑MPa ͒f c 90͑MPa ͒Gravel03044.551.555.53044.551.555.5532.048.554.558.031.545.553.556.51034.55056.063.032.549.556.063.01537.054.06065.535.55059.564.02033.547.550.553.031.043.052.061.0Baryte032.545.048.056.032.545.048.056.0534.047.053.056.533.046.054.058.01036.052.055.057.535.052.053.058.0154054.057.06039.054.055.059.02038.051.553.054.036.052.053.055.0Ilmenite034.046.55057.034.046.55057.0535.048.555.061.036.047.054.059.01036.555.058.065.037.05059.063.01542.057.061.0704052.062.069.02038.053.056.064.038.051.055.061.0Fig.2.Relation between compressive strength ͑MPa ͒and concrete age ͑days ͒of tested concretes mixed with different percentage of SF orRHAFig.3.Relation between compressive strength ͑f c 90͒͑MPa ͒of tested concretes and different replacement percentage of SF or RHAspherical shape,leading to partial closure of these voids;this is the main reason for the improvement in concrete durability and strength͑Bayasi and Zhou1993͒.Table5shows the indirect tensile strength͑f t͒͑MPa͒,theﬂex-ural strength͑f t͒͑MPa͒,the bond strength͑f b͒͑MPa͒,and the static modulus of elasticity in compression͑E͒͑GPa͒of concrete mixed with different percentages of SF or RHA as a partial ce-ment replacement after28days of preparations.Fig.4showed that the highest value of indirect tensile strength͑4.7MPa͒was for the ilmenite concrete mixed with15%SF,at31and21% higher,respectively,than those of the corresponding gravel con-crete and baryte concrete mixed with15%SF.On the other hand, 15%of RHA mixed with baryte concrete showed a higher tensile strength when compared to gravel concrete but a lower tensile strength than ilmenite concrete mixed with15%of RHA.The ilmenite concrete exhibited the highestﬂexural strength,bond strength,and static modulus of elasticity in compression as com-pared to the baryte or gravel concrete.It can be seen that15%of SF mixed with ilmenite concrete increasedﬂexural strength,bond strength,and static modulus of elasticity in compression as com-pared to concrete mixed with15%of RHA͑Fig.5͒.Concrete types mixed with RHA showed higher values of mechanical prop-erties as compared with gravel concrete,but it had lower values than concrete mixed with SF.This can be attributed to the silicon dioxide in SF,which forms a calcium silicate compound in its hydrate gel state.The reaction of silicon dioxide with calcium hydroxide lowers the alkalinity of the pore solution caused by cement hydration,which reduces the amount of available calcium hydroxide.The increased calcium silicate hydrate gel and reduc-tion in capillary pores in the concrete paste are the main factors in its increased strength and impermeability͑Detwiler and Metha 1989͒.Table5.Mechanical Properties of Studied Concrete Types after28Days of PreparationType of concrete ReplacementpercentageConcrete+percentage of SF Concrete+percentage of RHAf t͑MPa͒f f͑MPa͒f b͑MPa͒E͑GPa͒f t͑MPa͒f f͑MPa͒f b͑MPa͒E͑GPa͒Gravel0 2.7 4.9 5.521.5 2.7 4.9 5.521.55 3.0 5.6 6.122.3 2.9 5.5 6.722.010 3.2 6.27.323.2 3.1 6.07.023.015 3.67.77.624.9 3.47.57.524.220 3.57.47.524.5 3.47.47.423.8 Baryte0 2.9 4.9 6.229.6 2.9 4.9 6.229.65 3.3 6.07.331.5 3.1 6.07.130.110 3.57.07.933.8 3.3 6.87.732.015 3.98.18.535.0 3.67.98.033.520 3.88.08.134.0 3.67.87.931.5 Ilmenite0 3.7 5.9 6.935.5 3.7 5.9 6.935.55 4.07.47.836.0 3.97.17.937.010 4.28.58.136.8 4.08.58.037.015 4.79.08.939.5 4.58.98.338.020 4.58.78.637.5 4.08.58.136.5Fig.4.Relation between indirect tensile strength͑f t28͒͑MPa͒of tested concretes and different replacement percentage of SF orRHA Fig.5.Relation between different mechanical properties of studied concretes mixed with15%of SF or RHAMicroscopic StudiesThe microstructure of three different types of concrete was exam-ined using a scanning electron microscope at 35ϫmagniﬁcation to study the inner structure of the tested concrete samples.Results are shown in Fig.6.It was observed that the ilmenite concrete ͓Fig.6͑a ͔͒is denser than both the baryte concrete ͓Fig.6͑b ͔͒and the gravel concrete ͓Fig.6͑c ͔͒.The capillary pores of gravel concrete ͓Fig.6͑c ͔͒,without SF or RHA,were found to have numerous continuous large pores,which could result in high per-meability of the gravel concrete ͑Van der Mass 1972͒.For the baryte concrete ͓Fig.6͑b ͔͒,capillary pores were observed,but they were less in size and distribution than those of the gravel concrete ͓Fig.6͑c ͔͒.Figs.6͑d–f ͒show the presence of SF in con-crete mixtures,and from Fig.6͑f ͒it can be observed that the pores formed in gravel concrete mixed with 15%SF were fewer and smaller than those found in concrete mixed without SF.Fig.6͑e ͒shows the interaction between the surface of SF particles and cement paste in baryte concrete mixed with 15%SF,while Fig.6͑d ͒shows the transition zone of the pozzolanic reaction between the SF particles and the ilmenite aggregate.Gravelconcrete,Fig.6.Microstructure investigation of tested concretes:͑a ͒ilmenite concrete;͑b ͒baryte concrete;͑c ͒gravel concrete;͑d ͒ilmenite concrete +15%SF;͑e ͒baryte concrete+15%SF;and ͑f ͒gravel concrete+15%SF372/JOURNAL OF MATERIALS IN CIVIL ENGINEERING ©ASCE /MAY/JUNE 2006baryte concrete,and ilmenite concrete mixed with15%SF or RHA showed a much denser microstructure as compared to that without SF or RHA.This can be attributed to the fact that the pozzolanic reactions of SF or RHA increase the concrete densiﬁ-cation and enhance conversion of concrete pores into small and unconnected pores͑Van der Mass1972͒.Infrared PropertiesInfrared͑IR͒spectroscopy was used to investigate additional in-formation for characterizing the chemical components of different types of tested concrete mixed with and without SF or RHA. Results are given in Fig.7.Characteristic bands at wave lengths equal to3,640,3,400,1,660,1,440,1,200,1,100,975,880,and 770cm−1were observed for all tested concrete types.The band at 3,640cm−1may be due to the presence of calcium hydroxide.The broad absorption band near3,400cm−1is mainly due to vibration of the hydrogen bond in the OH group present either as H–OH or as Si–OH.The absorption band at1,660cm−1may be due to free water molecules;the presence of such bands indicates that water molecules are free,either absorbed in cement pores or attached on the surface of calcium silicate hydrate͑C–S–H͒particles ͑Scrivener and Pratt1987͒.The band at1,440cm−1may be due to carbonate;the broad band in the region950–1,200cm−1detects the C–S–H structure͑this band and the bands at about3,450and 1,600cm−1are the most signiﬁcant bands to C–S–H͒.The band at 975cm−1may be due to the presence of Si–O,while the band at 1,100cm−1is due to sulfate presence.The band at880cm−1may be indicating the presence of calcite as a separate phase,and the band at770cm−1may be due to AL-O vibrations of the aluminate mineral components.In the case of ilmenite concrete,asharp Fig.7.Infrared spectra of raw used materials and different types of tested concretes mixed with15%of SF or RHAJOURNAL OF MATERIALS IN CIVIL ENGINEERING©ASCE/MAY/JUNE2006/373band occurs at 1,120cm −1,which may be due to a new band formed between the silicate hydrate and the gel formed from its oxides with water ͑Scrivener and Pratt 1987͒.There was no sig-niﬁcant effect due to increasing the presence of SF or RHA in concrete on the obtained IR spectra.Thermal InvestigationsThermogravimetrical analysis ͑TGA ͒of all concrete types was performed to investigate the total percent of weight loss ͑at 800°C with a heating rate of 10°C/min ͒due to evaporated free water found in pores of different types of concrete mixed with different percentages of SF or RHA.Fig.8showed that the weight loss percent decreased as the SF or RHA percent in-creased;this may be attributed to blockage of pores by the ﬁne particles of SF or RHA.Ilmenite concrete incorporating 20%SF showed the lowest value of total weight loss,followed by that incorporating 15%SF.The total weight loss value is nearly equally distributed through the different temperatures.From the obtained TGA and IR spectra,it can be stated that SF or RHA added to cement change the water content in the hydrated cement,including both the water attached to C–S–H and the free water in the pores of hydrated cement,and may react with cement products.Durability InvestigationThe durability of concrete is one of the main factors considered in the evaluation of concrete quality.The durability investigation included the sulfate resistance ͑Kilinckale 1997͒of different types of concrete incorporating 15%of SF or RHA as compared with that without SF or RHA.Fig.9shows the compressive strength ͑MPa ͒of different types of concrete mixed with 0and 15%of SF or RHA immersed in 5%MgSO 4͑sulfate ions ͒solution or in water for different periods after preparation.Results showed that the reductions in compressive strength of the gravel,baryte,and ilmenite concrete mixed without SF or RHA were 8.5,7.0,and 8.0%,respectively,after immersion in 5%MgSO 4for 28days,while the reductions after 90days of immersion were 16,14,and 14%,respectively.The reduction percentages of the compressivestrength of gravel,baryte and ilmenite concrete incorporating 15%of SF when immersed in a sulfate solution for 28days were 4,3.8,and 3.5%,respectively,while those for the studied con-crete types incorporating 15of RHA were 5,6,and 6%,respec-tively.Generally,the compressive strength of the ilmenite con-crete mixed with 15%of SF immersed in 5%MgSO 4solution showed the highest resistance to sulfate attack,and the effect of the presence of RHA in concrete was lower than that of SF in a sulfate environment.Moreover,the decrease rate of the effect of sulfate ions on compressive strength was generally increased as the immersion time in the sulfate solution increased.Shielding PropertiesThe attenuation coefﬁcient ͑␮͒͑cm −1͒and half-value layer thick-ness ͑HVL ͒͑mm ͒͑the thickness of absorber material needed to reduce the source intensity to its half value ͒of all types of con-crete studied using Co 60and Cs 137gamma point sources are given in Table 6.Fig.10showed that the addition of SF or RHA to the concrete mixture had no signiﬁcant effect on the attenuation coefﬁcient ͑␮͒.Results indicate that ilmenite concrete has the highest attenu-ation coefﬁcient ͑␮͒and lowest half-value thickness;this can be attributed to the fact that ilmenite concrete has the highest density as compared to other concrete types ͑Abdel-Azim et al.1995͒.Effect of Gamma Radiation Exposure on Compressive StrengthThe effects of different gamma ray doses on the compressive strength of gravel,baryte,and ilmenite concrete mixed with dif-ferent percentages of SF or RHA are shown in Fig.11.The me-chanical properties,durability,and chemical stability of the hy-drated cement paste were affected when the concrete was exposed to gamma ͑␥͒rays.The compressive strength decreases as the value of absorbed gamma ͑␥͒dose by sample increases due to the high frequency of ␥rays,which degrade the bonding strengthofFig.8.Relation between weight loss percent ͑WL%͒of tested concretes and cement replacement percentage of SF orRHAFig.9.Relation between compressive strength ͑f c ͒͑MPa ͒of studied concretes mixed with 15%of SF or RHA and different immersed periods ͑days ͒in 5%MgSO 4solution374/JOURNAL OF MATERIALS IN CIVIL ENGINEERING ©ASCE /MAY/JUNE 2006the hydrated cement particles͑Abdel-Azim et al.1995͒.It was found that the compressive strength of the gravel concrete͑0%of SF or RHA͒decreased by15and28%when exposed to doses of 50Mega rad͑rad is deﬁned as the unit of absorbed gamma dose and is equal to3.7ϫ10−10curie͒and100Mega rad,respectively, but the decrease in compressive strength of the baryte concrete was13and27.5%for the same doses,respectively,while the compressive strength of ilmenite concrete decreased by11and 24%when exposed to same absorbed gamma doses,respectively. Also,Fig.11indicates that,as the gamma absorbed dose in-creased,the compressive strength decreased in a nonlinear rela-tionship,and there was no signiﬁcant effect of the presence of SF or RHA on the compressive strength of different types of concrete exposed to different absorbed gamma doses.ConclusionsFrom the results obtained it can be concluded that:1.The aggregate type is the main element affecting the densityand strength of the concrete.The increase in densities of the ilmenite and baryte concrete with respect to the gravel con-crete was46and39%,respectively.Moreover,the ilmenite concretes showed higher compressive strength,indirect ten-sile strength,ﬂexural strength,bond strength,modulus of elasticity,and attenuation coefﬁcient values as compared to the baryte and gravel concretes.2.The microstructural investigation showed that using15%SFor15%RHA͑optimum dosage͒as a partial replacement of cement by weight in the case of ilmenite concrete led to an increase in concrete densiﬁcations and all properties.3.Concrete mixed with RHA has a lower compressive strengththan that mixed with SF.4.The RHA mixed with concrete had good resistance to sulfateattack,but SF mixed with concrete demonstrated better re-sistance to sulfate attack.5.There is no signiﬁcant effect due to the presence of SF orRHA on the concrete attenuation coefﬁcient for the concrete types studied.6.High gamma͑␥͒doses have a bad effect on the mechanicalproperties of all types of concrete,and there is no signiﬁcant effect of the presence of SF or RHA on the compressive strength of irradiated concrete.Table6.Attenuation Coefﬁcient͑␮͒͑cm−1͒and Half-Value Layer Thickness͑mm͒of Studied Concrete Samples Exposed to Co60and Cs137Gamma Point SourcesConcrete type ReplacementtypeReplacementpercentageAttenuation coefﬁcient͑␮͒͑cm−1͒Half-value layer thickness͑mm͒Co60Cs137Co60Cs1371,330KeV1,170KeV661KeV1,330KeV1,170KeV661KeVGravel SF011.511.67.157.059.098.5511.611.87.056.057.098.01012.112.27.153.056.098.51512.212.47.351.052.095.02012.412.37.25052.099.0 RHA011.511.67.157.059.098.5511.511.87.155.059.098.01011.912.17.153.056.098.51512.012.27.252.052.099.52012.112.37.35051.098.0 Baryte SF016.015.49.843.045.076.0516.115.69.841.044.074.01015.315.79.94043.0701516.316.010.341.042.567.52016.516.310.44043.076.0 RHA016.015.49.843.045.076.0516.115.69.741.044.072.01015.815.59.342.042.0701516.115.710.14041.0702016.016.010.24042.069.0 Ilmenite SF016.616.39.8541.042.070516.5 1.59.94041.071.01016.816.81041.041.5701517.417.110.438.04066.52017.517.210.539.042.068.0 RHA016.616.39.8541.042.070516.216.29.94041.0701016.716.59.741.04072.01517.016.91041.042.071.02016.817.09.942.041.068.0JOURNAL OF MATERIALS IN CIVIL ENGINEERING©ASCE/MAY/JUNE2006/375。

铁芯(磁芯)材质特性资料

19
2. Specifications of Ferrites
By (4) 200mT, N=10, f=10kHz
Gap=0mm Gap=1mm Gap=5mm Gap=10mm
20
2. Specifications of Ferrites
materials
420m T
P42
N5
Low Loss
P48
P41
250KW/m3
350KW/m3
P4
450KW/m3
700KHz
P5
1MHz P51
N4
5MHz P52
N42
P61 P62
N43
P46
DCBias
25℃~100 ℃
P47
25℃~120 P4℃5
High Freq.
Low ŋB
Temp. Tendency
ACME provides ferrite material in all applications: NiZn
EMI/EMC
HighBs
Low Permeability
• K05
WPC Low loss
• B25 NFC/RFID
Antenna
• L1
• K07 • K081
• B30 • H2
• L2
15
2. Specifications of Ferrites
Why there should not be gap in determining the ferrite properties?
Most magnetic field (so MMF)
drops across the air gap

001-Effect of aggregate gradation on properties of concrete

los 1.15 Table 1 Chemical compositions of sulphoaluminate cement/% SiO SO 3 K 2 O Na 2 0 TiO 2 11.41 27.87 2.59 43.86 1.2 9.59 0.45 0.15 1.27 P2O5 0.11
1. Introduction It is known that aggregate takes up 60%-90% of total volume of concrete which is the most widely used building materials in the world. Concrete properties such as mechanical and durability properties are highly affected by physical properties of aggregate such as aggregate gradation(Ioannis P., et al., 2013; Siddique, et al., 2012;W. B. Ashraf, et al., 2011; ErgulYasar, et al., 2004; Mucteba Uysal, et al., 2004; Rafat Ronnen Levinson, et al., 2002; D. Sari, et al., 2005; Yahia A, et al., 2002). Good aggregate gradation corresponds to high bulk density. Some research results about the effect of aggregate gradation on the properties of concrete have been established, however, the related researches are focused on Portland cement concrete (OPC)( Hui Zhao, et al., 2012; E. Yasar, et al., 2003; Medhat H Shehata, et al., 2000; M. Gillot, et al., 1993; E.J. Garboczi, et al., 1993), information about the effect of aggregate gradation on the properties of sulphoaluminate cement concrete(SACC) is less documented, therefore, the effect of aggregate gradation on the mechanical properties and durability properties of SACC needs more investigate. The most well-known methods of aggregate gradation contain: 1) using two different segments of aggregate (i.e. fine aggregates and coarse aggregates); 2) using total aggregate gradation that is combined aggregate gradation (W. B. Ashraf, et al., 2011). The latter attracts more interest in recent years. Among these methods, Fuller distribution, the maximum density

固定效应模型英文缩写

固定效应模型英文缩写In economics and related fields, the Fixed Effects Model is often referred to as FEM for brevity. It's a statistical technique that helps us understand how variables behave within specific groups or entities, while accounting for any inherent differences between them. FEM is particularly useful when dealing with panel data, where observations are made over time for multiple individuals or entities.When it comes to analyzing data, the Fixed Effects Model is a go-to choice for researchers. It allows us to isolate the effects of interest, stripping away any potential biases that might arise from inherent differences between groups. FEM is like a filter, helping us see through the noise and focus on what's really important.So, in simple terms, FEM is a way to peel back the layers and understand what's really driving changes in your data. It's a tool that helps you cut through the complexityand get to the heart of the matter. Whether you're a researcher, an economist, or a data analyst, FEM can be a valuable addition to your toolbox.Hey, you know what's handy? The Fixed Effects Model. Yeah, that FEM acronym stands for something pretty useful. Basically, it's a statistical model that lets us compare groups while taking into account their unique characteristics. So, if you're studying different countries or companies, FEM can help you figure out what's really driving the differences you see in your data. It's a great tool for getting insights into complex datasets.。

混合实验仪（Mixolab）评价筛选优质饺子粉

秦毛毛，王雯斐，刘艳喜，等. 混合实验仪（Mixolab ）评价筛选优质饺子粉[J]. 食品工业科技，2023，44（20）：257−264. doi:10.13386/j.issn1002-0306.2022110185QIN Maomao, WANG Wenfei, LIU Yanxi, et al. Evaluation and Screening of High-quality Dumpling Flour by Mixolab[J]. Science and Technology of Food Industry, 2023, 44(20): 257−264. (in Chinese with English abstract). doi: 10.13386/j.issn1002-0306.2022110185· 包装与机械 ·混合实验仪（Mixolab ）评价筛选优质饺子粉秦毛毛1，王雯斐1，刘艳喜1，常　阳1，周正富1，雷振生1,2，吴政卿1,*（1.河南省作物分子育种研究院，河南郑州 450002；2.河南省农业科学院小麦研究所/小麦国家工程实验室，河南郑州 450002）摘　要：利用混合实验仪对优质饺子粉进行评价筛选研究，旨在为达成饺子专用粉高效在线配粉提供理论支撑。

本研究以市场上现有的30种饺子粉为研究对象，通过分析面粉的白度、湿面筋含量、流变学特性、糊化特性等理化指标和饺子皮感官评分，比较不同饺子粉品质差异性，运用聚类分析将上述面粉进行等级分类。

结合混合实验仪软件的内置功能Chopin+标准协议对优类饺子粉进行测定并制作目标剖面图。

利用该剖面图实现了郑麦136、郑麦366和新麦26等3种基础粉的饺子皮配粉应用。

结果表明，30种饺子粉品质性状的变异系数大小依次为：形成时间>稳定时间>粉质质量指数>弱化度>面筋指数>衰减值>最低粘度>峰值粘度>湿面筋含量>糊化温度>吸水率>白度>峰值时间>感官评分，其中形成时间的变异系数最大，为68.59，感官评分变异系数最小，为0.11。

基于FGM(1,1)的中国瓦楞原纸产量预测

摘要：F G M(1,1)模型与G M(1,1)模型相比，对样本后期的预测精度较高，对我国瓦楞原纸产量进行了预测，结果显著。

利用F G M(1,1)模型对2022～2024年我国瓦楞原纸产量进行预测，结果显示：未来3年我国瓦楞原纸产量保持较高速度增长态势，通过分析表明这一预测结果有一定的可信度。

关键词：瓦楞原纸；产量；预测；FGM(1,1)模型Abstract: Compared with GM(1,1) model, FGM(1,1) model has higher prediction accuracy in the later period of samples. The output of corrugated paper in China was predicted using FGM(1,1) model, and the result is significant. The output of corrugated medium during 2022-2024 in China is predicted based on FGM(1,1) model. The results show that the output of corrugated medium in China remains at a high growth rate in the next three years, and the analysis shows that the prediction result is credible. Key words: corrugated medium; production; prediction; FGM (1,1) model基于FGM(1,1)的中国瓦楞原纸产量预测⊙ 舒服华（武汉理工大学继续教育学院，武汉 430070）Prediction of Production of Corrugated Medium in China Based on FGM(1,1)⊙ Shu Fuhua (School of Further Education of Wuhan University of Technology, Wuhan, Hubei 430070, China)□ 基金项目：湖北省自然科学基金项目（2020CFB232）：运筹学与统计技术研究。

Machine learning in prognosis of the femoral

The femur is the longest and the strongest bone in the human body. Its upper part, the femoral neck, is often subject to severe fractures, especially where older people are concerned. Intracapsular fractures of the femoral neck may considerably deteriorate the quality of their life. The speciﬁc structure and blood supply to the upper part of the femur contribute to complications, especially aseptic head necrosis and pseudoarthrosis (non-union), which frequently occur in the course of treatment. Such injuries should therefore be treated as urgent and the patient examined and treated as soon as possible. The system for predicting possible complications should serve as a tool in the process of treatment and in the follow-up period. It should therefore be beneﬁtial in two ways: 1. to point out the problematic patients and advise them to attend follow-up examinations frequently (at least for two years after the operation) to catch possible complications in time. 2. to help physicans choose the therapy which would minimize the risk of subsequent complications. In recent years many of machine learning algorithms have been developed that can be used as eﬃcient tools for the analysis of databases and for extracting the classiﬁcation knowledge that can be used to solve new problems in the given problem domain [6, 21, 22]. There have been many applications of machine learning to medical diagnostic problems [7, 8, 15, 17, 24, 27, 31]. As medical prognosis is a diﬃcult task for physicians due to large time delays (several years) in recognizing the correct prognosis [36], machine learning may be more useful for solving prognostic rather than diagnostic problems. Besides prediction accuracy, the explanation ability of the classiﬁer is also very important. To support the prognostic process in everyday practice, physicians need a classiﬁer that is able to explain its decisions. Such transparent decisions are much more acceptable for physicians. On the basis of the explanation he or she may accept or reject the proposed decision and eventually require additional tests to (dis)conﬁrm the hypothesis. In this paper we compare the performance and the explanation ability of several diﬀerent classiﬁers in the femoral neck fracture recovery problem. The algorithms are: the K-nearest neighbours algorithm, the semi-naive Bayesian classiﬁer, backpropagation with weight elimination learning of the multilayered feedforward neural networks, the LFC (lookahead feature construction) algorithm, and the Assistant-I and Assistant-R algorithms for top down induction of decision trees using information gain and RELIEFF as search heuristics, respectively. Section 2 brieﬂy describes the diﬀerent classiﬁers. Section 3 describes the data we used in our experiments. In Section 4 we compare the performance of the classiﬁers in terms of prediction accuracy and information score, and in Section 5 we compare the explanation ability of various classiﬁers. Section 6 gives the results for combinations of diﬀerent classiﬁers. Section 7 gives suggestions for applications of machine learning in medical diagnostic and prognostic problems.

女性生殖器割礼和产科结局:WHO在6个非洲国家协作的前瞻性研究

女性生殖器割礼和产科结局：WHO在6个非洲国家协作的前瞻性研究张旸【期刊名称】《世界核心医学期刊文摘：妇产科学分册》【年(卷),期】2006(0)10【摘要】Background: Reliable evidence about the effect of female genital mutilation(FGM) on obstetric outcome is scarce. This study examines the effect of different types of FGM on obstetric outcome. Methods: 28 393 women attending for singleton delivery between November, 2001, and March, 2003, at 28 obstetric centres in Burkina Faso, Ghana, Kenya, Nigeria, Senegal, and Sudan were examined before delivery to ascertain whether or not they had undergone FGM, and were classified according to the WHO system: FGM I, removal of the prepuce or clitoris, or both; FGM II, removal of clitoris and labia minora; and FGM III, removal of part or all of the external genitalia with stitching or narrowing of the vaginal opening. Prospective information on demographic, health, and reproductive factors was gathered. Participants and their infants were followed up until maternal discharge from hospital. Findings: Compared with women without FGM, the adjusted relative risks of certain obstetric complications were, in women with FGM I, II, and III, respectively: caesarean section1.03(95%CI 0.88-1.21), 1.29(1.09-1.52), 1.31(1.01-1.70); postpartum haemorrhage 1.03(0.87-1.21), 1.21(1.01-1.43), 1.69(1.34-2.12); extendedmaternal hospital stay 1.15(0.97-1.35), 1.51(1.29-1.76), 1.98(1.54-2.54); infant resuscitation 1.11(0.95-1.28), 1.28(1.10-1.49), 1.66(1.31-2.10), stillbirth or early neonatal death 1.15(0.94-1.41), 1.32(1.08-1.62), 1.55(1.12-2.16), and low birthweight 0.94(0.82-1.07), 1.03(0.89-1.18), 0.91(0.74-1.11). Parity did not significantly affect these relative risks. FGM is estimated to lead to an extra one to two perinatal deaths per 100 deliveries. Interpretation: Women with FGM are significantly more likely than those without FGM to have adverse obstetric outcomes. Risks seem to be greater with more extensive FGM.【总页数】1页(P1-1)【关键词】女性生殖器;WHO;非洲国家;阴蒂包皮;小阴唇;围生儿死亡;新生儿复苏;早期新生儿;产后出血;人口统【作者】张旸【作者单位】【正文语种】中文【中图分类】R714【相关文献】1.实用临床诊疗规范——妇产科:女性生殖器官损伤性疾病 [J], 尤志学2.女性生殖器结核对体外受精-胚胎移植妊娠结局的影响 [J], 郭丽娜;王旭平;吕翠婷;赵素英;乜照燕;张娜;甄秀丽3.人类生殖器疱疹病毒52和58型感染在台南女性妇产科医师中高发 [J], Moh J.-S.;C.-C.ChangChien;丁福4.女性和男性吸食大麻对体外受精及配子输卵管内移植结局影响的一项前瞻性研究[J], Klonoff;-;Cohen;H.;S.;Natarajan;L.;Victoria;Chen;R.5.女性生殖器割礼与尿结石 [J], Nour N.M.;朱亮因版权原因，仅展示原文概要，查看原文内容请购买。

Unit3 FoodFight ppt课件

❖ About Monsanto
❖ Monsanto was first established in 1901 and developed into a giant business enterprise over the past 100 years.
❖ In 2001 Monsanto announces that all of its U.S. seed production sites and its quality-assurance laboratory have received registration to the International Organization of Standardization (ISO) 9002 certification.
❖ Both genetic modification and traditional breeding involve altering the genetic make-up living organism so as to produce the desired traits. However, the two techniques have the following differences.
5.List the potential Benefits of GM Foods
6.What are the concerns over GM foods/ crops of green and code of DNA ( Deoxyribose Nucleic Acid). A gene is a unit of hereditary material, which carries the information to produce protein that determines the characteristics of an organism. Plants and animals from which foods are derived have thousands of genes in their cells.

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)。

Seyyed M. Hasheminejad*, Majid Rajabi
Acoustics Research Laboratory, Department of Mechanical Engineering, Iran University of Science and Technology, Narmak, Tehran 16844, Iran
a r t i c l e i n f o
Article history: Received 13 June 2007 Received in revised form 1 May 2008 Accepted 5 August 2008 Keywords: Buried FGM pipeline Dynamic stress concentrations Poroelastic medium
medium under conditions of plane strain. Gatmiri and Eslami [9] presented a complex functions approach to analyze scattering of harmonic waves by a circular cavity in an inﬁnite poroelastic medium. Xie et al. [10] used inverse Laplace transform in conjunction with Biot’s wave equation to investigate dynamic response of a circular tunnel with partially sealed liner subjected to axially symmetric transient radial traction and ﬂuid pressure in viscoelastic ﬂuid-saturated soil. Similarly, Liu et al. [11] used Biot’s theory along with the normal mode expansion technique to investigate scattering of an elastic wave by a permeable cylindrical shell embedded in poroelastic medium. Just recently, Hasheminejad and Avazmohammadi [12] used Biot theory of poroelasticity to study the dynamic stress concentrations due to the three-dimensional interaction of plane seismic waves with lined twin circular tunnels within a boundless ﬂuid-saturated poroelastic medium. In recent years, the study of functionally graded materials (FGMs) has attracted a lot of attention. FGMs are advanced composites, microscopically engineered to have a smooth spatial variation of material properties in order to improve overall performance. This is achieved by fabricating the composite material to have a gradual spatial variation in the constituent materials’ relative volume fractions and microstructure, thus tailoring its material composition based on functional performance requirements. FGMs offer great promise in applications where the operating conditions are severe, including heat exchanger tubes, fusion reactors, pressure vessels, and general wear and corrosion resistant coatings or for joining dissimilar materials in nuclear, chemical, and
International Journal of Pressure Vessels and Piping 85 (2008) 762–771
Contents lists available at ScienceDirect
International Journal of Pressure Vessels and Piping
* Corresponding author. E-mail address: hashemi@iust.ac.ir (S.M. Hasheminejad). 0308-0161/$ – see front matter Ó 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.ijpvp.2008.08.002
1. Introduction The study of the dynamic behavior of long underground or submarine structures, such as transportation pipelines or tunnels, subject to elastic waves is an important engineering problem in dynamic soil–structure interaction [1,2]. In particular, there exists a notable body of literature on seismic response of lined or unlined cylindrical cavities within a poroelastic formation. Only the most signiﬁcant recent works relevant to the present study shall be brieﬂy reviewed here. Senjuntichat and Rajapakse [3] employed Biot’s equations for poroelastodynamics in combination with the Laplace transform technique to investigate the transient response of a pressurized long cylindrical cavity in an inﬁnite poroelastic medium. Stamos et al. [4] used the method of Foda and Mei [5] to solve the problem of harmonic wave diffraction by tunnels in poroelastic Biot soil under conditions of plane strain. Hu et al. [6] used Biot’s theory to study scattering and refraction of plane strain waves by a cylindrical cavity in a ﬂuid-saturated soil. Yayuan et al. [7] obtained the solutions of the scattering by a poroelastic cylinder in a saturated soil. Kattis et al. [8] developed an efﬁcient and accurate (frequency domain) boundary elements method for solving problems of harmonic wave diffraction by unlined or lined cavities of an arbitrary geometry in an inﬁnite fully saturated poroelastic soil
journal homepage: /locate/ijpvp
Effect of FGM core on dynamic response of a buried sandwich cylindrical shell in poroelastic soil to harmonic body waves
a b s tLeabharlann r a c tThe two-dimensional dynamic interaction of progressive plane seismic waves with an arbitrarily thick, isotropic, and functionally graded cylindrical shell of inﬁnite extent embedded in a boundless ﬂuidsaturated porous elastic medium is investigated. The inhomogeneous shell is approximated by a laminate model, for which the solution is expected to gradually approach the exact one as the number of layers increases. Continuity of the displacement and stress components at the interfaces of neighboring layers is applied to form a system global transfer matrix, ultimately leading to determination of the modal scattering and transmission coefﬁcients. The analytical results are illustrated with numerical examples in which an air-ﬁlled steel–zirconia FGM shell, buried in a water-saturated Ridgeﬁeld Sandstone formation, is insoniﬁed by fast compressional or shear waves at normal incidence. The effects of material compositional gradient and FGM layer thickness on the basic dynamic ﬁeld quantities are evaluated and discussed. Limiting cases are considered and good agreements with the solutions available in the literature are obtained. Ó 2008 Elsevier Ltd. All rights reserved.