Comparative study of the tribological behavior

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比较文学研究

比较文学研究IntroductionComparative literature is a field of study that is concerned with the study of different literary works from various cultures, languages, and backgrounds. This field of study is essential because it expands our understanding and interpretation of literature, and also helps us appreciate the diversity and various complexities of human cultures and experiences.In this article, we will delve into the world of comparative literature research and explore some of the essential aspects of comparative literature research that make it a unique and important field of study. We will also explore the different categories into which comparative literature research can be categorized and how they contribute to the field's development.Categories of Comparative Literature ResearchComparative literature research can be divided into four broad categories: comparative literary history, comparative literary theory, comparative cultural studies, and comparative genre studies.1. Comparative Literary HistoryThis category of comparative literature research is concerned with analyzing literary works from different historical contexts and cultures. It seeks to understand the cultural, social, and political factors thatinfluenced the creation and development of literary works in different contexts. This category of comparative literature research aims to trace the evolution of literary genres, themes, and styles across different cultures and periods.For example, a comparative literary historian may compare the works of William Shakespeare and Miguel de Cervantes to understand how their literary works reflected the political and social contexts of Elizabethan England and 17th century Spain respectively.2. Comparative Literary TheoryThis category of comparative literature research is concerned with exploring different literary theories from different cultures and periods. It creates a framework for analyzing and interpreting literary works from different perspectives and helps scholars understand the differences and similarities in literary works across different cultures.For example, a comparative literary theorist may compare the works of Jacques Derrida and Mikhail Bakhtin to understand the different ways that philosophy and linguistics impact literary analysis.3. Comparative Cultural StudiesThis category of comparative literature research is concerned with understanding the ways in which different cultures express themselves through their literature. It explores aspects of cultural identity and how literary works reflect cultural values and beliefs.For example, a comparative cultural studies scholar may compare the works of Chinua Achebe and Ngugi wa Thiong'o to understand the ways in which African literature addresses issues of cultural identity, colonialism, and postcolonialism.4. Comparative Genre StudiesThis category of comparative literature research is concerned with analyzing the different literary genres across different cultures and periods. It seeks to identify the similarities and differences in literary genres and understand how they have evolved over time.For example, a comparative genre studies scholar may compare the works of Edgar Allan Poe and Arthur Conan Doyle to understand how their works contributed to the development of the detective fiction genre.ConclusionComparative literature research is an essential field of study that explores the ways in which literary works are connected across cultures, languages, and time periods. It is a dynamic field that offers many possibilities for comparative analysis and provides insight into the complexities of human culture and expression.By examining literary works from different perspectives, comparative literature research can help us better understand ourselves and our place in the world. It can also help us appreciate the diversity and beauty of human expression, contribute to improving cross-culturalcommunication, and foster greater empathy and understanding among people from different cultural backgrounds.。

比较文学英语

比较文学英语Comparative Literature: An In-Depth AnalysisComparative literature, as an interdisciplinary field, delves into the complexities and similarities of literary works across different cultures, epochs, and genres. It examines how these works reflect and shape the human experience, while also exploring the diverse literary traditions and aesthetics that have emerged throughout history.The study of comparative literature begins with a recognition of the vast array of literary expressions that exist. These range from ancient epics and classical poetryto modern novels and digital narratives. Each work is a unique product of its cultural and historical context, yet they also share common themes, motifs, and literary devices. By comparing these works, we can gain a deeperunderstanding of their individual qualities as well as the larger patterns and trends that unite them.One of the key aspects of comparative literature is the examination of how different cultures approach similarthemes or subjects. For instance, the concept of love has been explored in countless literary works across the globe. However, the way love is portrayed and understood varies significantly depending on the cultural background of the author. In some cultures, love is seen as a transcendental force that overcomes all obstacles, while in others it is a more practical and earthbound emotion. By comparing these different representations of love, we can gain insightsinto the values and beliefs that shape each culture's understanding of this fundamental human experience.Another important aspect of comparative literature is the analysis of literary genres and forms. Different cultures have developed unique literary traditions that are reflected in their choice of genres and the ways in which these genres are employed. For example, the epic poem is a genre that has a long history in many cultures, but its form and content vary significantly depending on the cultural context. By comparing these different versions of the epic, we can understand how genre conventions evolve and adapt to different cultural needs and tastes.Furthermore, comparative literature also explores the relationship between literature and other cultural expressions such as art, music, and philosophy. It examines how these different forms of expression influence and inform each other, creating a rich and complex tapestry of cultural expression. For instance, a literary work may be influenced by the visual art of its time, or it may draw inspiration from philosophical ideas that were prevalent during its creation. By tracing these connections, we can gain a more comprehensive understanding of the literary work itself as well as its place within the larger cultural landscape.In conclusion, comparative literature is a multifaceted and enriching field that offers insights into the diversity and interconnectedness of human experience. Through the comparative analysis of literary works, we can gain a deeper understanding of both individual works and thelarger cultural and historical forces that shape them. As such, it is a valuable tool for exploring the complexities of human expression and understanding the ways in which different cultures and epochs have interpreted and represented the world.。

氧化硅硬度

氧化硅硬度1. 简介氧化硅（Silicon Dioxide），化学式SiO2，是一种无机化合物，也是地壳中最丰富的化合物之一。

它是由硅和氧元素组成的，常见的形态有结晶态和非晶态。

氧化硅在自然界中广泛存在，是石英、玻璃等材料的主要成分。

氧化硅具有很高的硬度，是一种非常坚硬的材料。

本文将从氧化硅的硬度测试方法、硬度的影响因素、应用领域等方面进行详细介绍。

2. 氧化硅硬度测试方法2.1 莫氏硬度莫氏硬度是常用的硬度测试方法之一，它通过比较不同材料对硬度标准矿物的抗刮擦能力来确定硬度。

然而，由于氧化硅的硬度很高，超过了莫氏硬度测试所能测试的范围，因此莫氏硬度测试对于氧化硅并不适用。

2.2 维氏硬度维氏硬度是另一种常用的硬度测试方法，它通过在测试样品表面施加一定负荷，测量产生的压痕面积来确定硬度。

对于氧化硅的维氏硬度测试，常用的测试方法是维氏金刚石压头压入氧化硅样品表面，然后测量压痕面积来计算硬度值。

2.3 纳米硬度纳米硬度测试是一种用于测量材料表面硬度的高精度测试方法。

它利用纳米压头对材料表面进行压痕测试，并通过测量压痕的深度来计算硬度值。

纳米硬度测试可以提供更准确的硬度数据，并且对于硬度较高的材料如氧化硅来说更加适用。

3. 影响氧化硅硬度的因素3.1 结晶度氧化硅的结晶度对其硬度有着重要的影响。

结晶度高的氧化硅比非晶态氧化硅具有更高的硬度。

这是因为结晶态氧化硅具有更紧密的晶格结构，原子之间的结合更紧密，从而使得材料更加坚硬。

3.2 杂质含量氧化硅中杂质的含量也会影响其硬度。

杂质的存在会导致晶格结构的不完整，从而降低氧化硅的硬度。

因此，在制备氧化硅材料时，需要尽量控制杂质的含量，以提高氧化硅的硬度。

3.3 烧结温度烧结温度是指在制备氧化硅过程中，将材料加热至一定温度以促使粉末颗粒结合成块体的温度。

烧结温度的高低会对氧化硅的硬度产生影响。

一般来说，较高的烧结温度可以使氧化硅颗粒更好地结合，从而提高硬度。

4. 氧化硅的应用领域由于氧化硅具有优异的硬度和化学稳定性，它在许多领域中得到了广泛的应用。

DP590带钢屈服和抗拉强度的微磁定量预测

试验研究开损艏泖j DO I:10.11973/wsjc202011003DP590带钢屈服和抗拉强度的微磁定量预测王贤贤，何存富，刘秀成(北京工业大学机械工程与应用电子技术学院，北京100124)摘要：基于微磁检测方法对DP590带钢的屈服强度和抗拉强度进行无损定量预测。

采用两级退火工艺对10个试件进行处理，得到强度不同的拉伸试样。

利用多功能传感器同步检测试件表面的切向磁场强度和磁巴克豪森噪声信号.提取得到多项特征磁参量。

通过变异系数分析方法，评价检测装置对磁参量的重复检测性能。

对比分析了多元一次和多元二次模型对屈服强度和抗拉强度的定量预测精度，结果表明，多元二次方程对带钢强度指标的预测精度更高，其方程拟合确定系数大于0.97，预测平均误差小于3 %。

关键词：微磁检测；屈服强度;抗拉强度；多元线性回归；定量预测中图分类号：TH879; 0348.9; TG115.28 文献标志码：A 文章编号：1000-6656(2020) 11-0010-06 Micromagnetic quantitative prediction of yield and tensile strength of DP590 steel stripW A N G X ia n x i a n*H E C u n f u. L I U X iu c h e n g(School of Mechanical Engineering and Applied Electronics Technology, Beijing University of Technology,Beijing 100124, China)A b s t r a c t：The yield strength and the tensile strength of DP590 steel strip were nondestructively andquantitatively predicted based on the micromagnetic testing method. Ten specimens were prepared and two-stageannealing method was employed to change the yield and tensile strength of the specimens. A multi-functional sensorwas used to simultaneously detect the tangential magnetic field and magnetic Barkhausen noise in the surface of thetested specimens. Multiple feature parameters representing the magnetic properties of the tested material wereextracted from the obtained signals. The coefficient of variation analysis method was applied to evaluate therepeatability performance of the experimental set-up with respect to the measured magnetic parameters.Comparative studies were conducted to investigate the accuracy of multivariate linear and quadratic models inpredicting the yield and tensile strength of the specimens. The results show that the multivariate quadratic modelhas better performances than the multivariate linear model. The coefficient of determination of the multivariatequadratic model is higher than 0.97. The prediction errors of the multivariate quadratic model to both the yield andtensile strength are less than 3%.K e y w o r d s：micromagnetic testing；yield strength；tensile strength；multiple linear regression；quantitative predictionDP590双相钢（由铁素体和马氏体组成）具有低屈强比、高初始加工硬化率、良好的强度和延性配合等特点，在汽车车身结构件、加强件、防撞件的制收稿日期：2020-04-20基金项目：国家重点研发计划资助项目（2018YFF01012300)作者简介:王贤贤（1993 —），女，博士研究生，主要研究方向为力学性能的微磁无损检测通信作者:刘秀成，xiuchliu@10 2020年第42卷第11期造中得到广泛应用带钢性能（如屈服强度、抗拉强度等)是产品质量检验的重要内容。

不同亚铁矿物对As（Ⅲ）和As（Ⅴ）的表面吸附特征及机制比较研究

苏广权，鞠琳，郑翔宇，等.不同亚铁矿物对As （Ⅲ）和As （Ⅴ）的表面吸附特征及机制比较研究[J].农业环境科学学报,2023,42（7）：1495-1504.SU G Q,JU L,ZHENG X Y,et parative study on the surface adsorption characteristics of different ferrous minerals for As （Ⅲ）and As （Ⅴ）and their mechanisms[J].Journal of Agro-Environment Science ,2023,42（7）：1495-1504.不同亚铁矿物对As （Ⅲ）和As （Ⅴ）的表面吸附特征及机制比较研究苏广权1，鞠琳1，郑翔宇1，姚爱军1*，杨晶柳1，赵曼2，王诗忠2，汤叶涛2，仇荣亮2，3，4（1.中山大学地理科学与规划学院，广州510006；2.中山大学环境科学与工程学院，广东省环境污染控制与修复技术重点实验室，广州510006；3.岭南现代农业科学与技术广东省实验室，广州510642；4.华南农业大学资源环境学院，广东省农业农村污染治理与环境安全重点实验室，广州510642）Comparative study on the surface adsorption characteristics of different ferrous minerals for As （Ⅲ）andAs （Ⅴ）and their mechanismsSU Guangquan 1,JU Lin 1,ZHENG Xiangyu 1,YAO Aijun 1*,YANG Jingliu 1,ZHAO Man 2,WANG Shizhong 2,TANG Yetao 2,QIU Rongliang 2,3,4（1.School of Geography and Planning,Sun Yat-sen University,Guangzhou 510006,China;2.School of Environmental Science and Engineering,Guangdong Provincial Key Lab for Environmental Pollution Control and Remediation Technology,Sun Yat-sen University,Guangzhou 510006,China;3.Guangdong Laboratory for Lingnan Modern Agriculture,South China Agricultural University,Guangzhou 510642,China;4.Guangdong Provincial Key Laboratory of Agricultural &Rural Pollution Abatement and Environmental Safety,College of Natural Resources and Environment,South China Agricultural University,Guangzhou 510642,China ）收稿日期：2023-01-01录用日期：2023-03-29作者简介：苏广权（1998—），男，广东揭阳人，硕士研究生，研究方向为农田重金属污染修复。

摩擦磨损文献总结

表面呈现明显的犁沟,磨损机理以犁削磨损为主. 这是由于TiN薄膜硬度大大超过GCr15钢球硬度,且多弧镀TiN薄膜表面微观凸凹不平,在摩擦切向力作用下对钢球产生犁削磨损.这说明磨损主要发生在对磨钢球上,磨屑主要为Fe的氧化物,这层氧化物对TiN薄膜有一定的隔离保护作用经磨球反复挤压后与TiN表层有较好的黏着性,进而替代TiN薄膜,与磨球形成摩擦接触面. 随着稳定、均匀的转移层的逐渐形成,摩擦系数趋于稳定[ 6 ]摩擦切向力增大,容易使硬质TiN磨粒脱落,犁削作用和颗粒磨损的增强导致摩擦系数增大. 与此同时应力增大使接触面积变大,摩擦系数相应提高.高速下涂层有较好的减磨抗磨作用涂层磨损的原因为粘着磨损、氧化磨损及扩散磨损几类涂层在与Si3N4对磨时，只有TiN涂层未从基体上剥落以前的研究表明[19-20]，TiOx在摩擦过程中起到了润滑剂的作用；所以当温度到达400°时，在摩擦轨迹上形成的Ti的氧化物使得摩擦系数降低。

这是因为在摩擦轨迹上形成的Cr的氧化物减轻了摩擦表面光滑平整，相当于抛光磨损抛光磨损机制、破损和剥离是TiCN 图层的主要磨损机制从基体剥落涂层中的气孔摩擦层是由氧化铬摩擦碎片经挤压在摩擦轨迹上粘接形成在室温下，对磨面光滑，在TiN涂层轨迹上发现了含有Si和O的摩擦层，金相学观察表明在25°时涂层发生磨料磨损伴随着Si3N4的化学分解TiN涂层的表面粗糙，产生了很深的中央凹槽TiOx的形成起到了润滑的作用，因此摩擦系数下降高的接触面温度源于较高的滑动速度和载荷产生的摩擦热。

这种环境下引起的涂层和基体之间的热应力失配，界面应力的变化、基体的塑性流动都是涂层失效的原因在25°摩擦时，两摩擦表面平整光滑，涂层未发生破损。

在涂层的表面有很薄的一层转移层，经分析这是由于相对较软的Si3N4发生了摩擦化学分解后形成的。

Si3N4经化学分解后形成的氧化膜在摩擦的过程中会与氧和水继续反应。

丙酸杆菌代谢物与山梨酸钾抑菌作用比较研究

食品研究与开发F ood Research And Development圆园19年5月第40卷第10期DOI ：10.3969/j.issn.1005-6521.2019.10.004基金项目：常熟市科技发展计划（农业）项目（CN201614）作者简介：郑丽雪（1982—），女（汉），副教授，硕士，研究方向：食品生物技术。

*通信作者：齐斌（1965—），男（汉），教授，博士，研究方向：微生物资源与现代工业发酵技术。

丙酸杆菌代谢物与山梨酸钾抑菌作用比较研究郑丽雪1，2，黎英1，王家皓1，董苗苗1，陈倩倩1，齐斌1，*（1.常熟理工学院生物与食品工程学院，江苏常熟215500；2.苏州市食品生物技术重点实验室，江苏常熟215500）摘要：以一株费氏丙酸杆菌突变株为出发菌株，通过改变发酵培养基、接种量和初始培养pH 值3方面，研究其代谢产物对大肠杆菌和沙门氏菌的抑菌作用，并与山梨酸钾的抑菌作用进行对比。

结果表明：3种发酵培养基均对大肠杆菌和沙门氏菌均存在一定的抑制作用，其中以乳酸钠（sodium lactate broth ，SLB ）培养基发酵时，该菌株代谢产物的抑菌活性分别为25.3AU/mL 和18.3AU/mL ，结果要优于0.1%的山梨酸钾的抑菌活性（21.1AU/mL 和14.1AU/mL ）；对于接种量而言，对大肠杆菌和沙门氏菌的抑菌活性最佳的接种量分别为6%和5%，其抑菌活性分别为28.1AU/mL 和18.0AU/mL ，抑菌效果均优于0.1%的山梨酸钾；对于不同培养pH 值而言，对大肠杆菌和沙门氏菌的抑菌活性最适初始pH 值分别为6.5和6，抑菌活性分别为27.6AU/mL 和14.5AU/mL ，其抑菌效果也优于0.1%的山梨酸钾。

所以，选择在适宜条件下发酵所得的丙酸杆菌代谢物，对大肠杆菌和沙门氏菌的抑制效果要优于山梨酸钾。

对丙酸杆菌代谢物抑菌作用的研究将为新型天然防腐剂的开发提供依据与试验数据支撑。

埃克森美孚全面润滑解决方案应对非道路移动机械国四标准

ʌ３ɔＸＩＡＮＧＪ，ＺＨＡＮＧＺ．Ｓｌｉｄｉｎｇｗｅａｒｏｆｐｏｌｙｅｔｈｅｒｉｍｉｄｅｍａｔｒｉｘｃｏｍｐｏｓｉｔｅｓ［Ｊ］．Ｗｅａｒ，２００５，２５８（５／６）：７８３－７８８．ʌ４ɔＣＨＥＮＢＢ，ＷＡＮＧＪＺ，ＹＡＮＦＹ．ＣｏｍｐａｒａｔｉｖｅｉｎｖｅｓｔｉｇａｔｉｏｎｏｎｔｈｅｔｒｉｂｏｌｏｇｉｃａｌｂｅｈａｖｉｏｒｓｏｆＣＦ／ＰＥＥＫｃｏｍｐｏｓｉｔｅｓｕｎｄｅｒｓｅａｗａｔｅｒｌｕｂｒｉｃａｔｉｏｎ［Ｊ］．ＴｒｉｂｏｌｏｇｙＩｎｔｅｒｎａｔｉｏｎａｌ，２０１２，５２：１７０－１７７．ʌ５ɔ朱艳吉，陈晶，姜丽丽，等．组装改性碳纤维增强聚醚醚酮复合材料的摩擦学性能［Ｊ］．润滑与密封，２０１５，４０（８）：６１－６５．ＺＨＵＹＪ，ＣＨＥＮＪ，ＪＩＡＮＧＬＬ，ｅｔａｌ．ＴｈｅｔｒｉｂｏｌｏｇｉｃａｌｐｒｏｐｅｒｔｉｅｓｏｆＰＥＥＫｃｏｍｐｏｓｉｔｅｓｒｅｉｎｆｏｒｃｅｄｂｙａｓｓｅｍｂｌｅｄｍｏｄｉｆｉｃａｔｉｏｎｏｆｃａｒｂｏｎｆｉｂｅｒ［Ｊ］．ＬｕｂｒｉｃａｔｉｏｎＥｎｇｉｎｅｅｒｉｎｇ，２０１５，４０（８）：６１－６５．ʌ６ɔ张志毅，章明秋，曾汉民．ＣＦ／ＰＥＥＫ复合材料的摩擦磨损行为研究［Ｊ］．中山大学学报（自然科学版），１９９６，３５（６）：１５－１８．ＺＨＡＮＧＺＹ，ＺＨＡＮＧＭＱ，ＺＥＮＧＨＭ．ＴｈｅｆｒｉｃｔｉｏｎａｎｄｗｅａｒｂｅｈａｖｉｏｒｏｆＰＥＥＫｃｏｍｐｏｓｉｔｅｓｒｅｉｎｆｏｒｃｅｄｂｙｃａｒｂｏｎｆｉｂｅｒ［Ｊ］．ＡＣＴＡＳｃｉｅｎｔｉａｒｕｍＮａｔｕｒａｌｉｕｍＵｎｉｖｅｒｓｉｔａｔｉｓＳｕｎｙａｔｓｅｎｉ，１９９６，３５（６）：１５－１８．ʌ７ɔＦＲＩＥＤＲＩＣＨＫ，ＺＨＡＮＧＺ，ＳＣＨＬＡＲＢＡＫ．Ｅｆｆｅｃｔｓｏｆｖａｒｉｏｕｓｆｉｌｌｅｒｓｏｎｔｈｅｓｌｉｄｉｎｇｗｅａｒｏｆｐｏｌｙｍｅｒｃｏｍｐｏｓｉｔｅｓ［Ｊ］．ＣｏｍｐｏｓｉｔｅｓＳｃｉｅｎｃｅａｎｄＴｅｃｈｎｏｌｏｇｙ，２００５，６５（１５／１６）：２３２９－２３４３．ʌ８ɔＣＨＡＮＧＬ，ＦＲＩＥＤＲＩＣＨＫ．Ｅｎｈａｎｃｅｍｅｎｔｅｆｆｅｃｔｏｆｎａｎｏｐａｒｔｉｃｌｅｓｏｎｔｈｅｓｌｉｄｉｎｇｗｅａｒｏｆｓｈｏｒｔｆｉｂｅｒ⁃ｒｅｉｎｆｏｒｃｅｄｐｏｌｙｍｅｒｃｏｍｐｏｓ⁃ｉｔｅｓ：ａｃｒｉｔｉｃａｌｄｉｓｃｕｓｓｉｏｎｏｆｗｅａｒｍｅｃｈａｎｉｓｍｓ［Ｊ］．ＴｒｉｂｏｌｏｇｙＩｎ⁃ｔｅｒｎａｔｉｏｎａｌ，２０１０，４３（１２）：２３５５－２３６４．ʌ９ɔＪＩＡＮＧＺＹ，ＧＹＵＲＯＶＡＬＡ，ＳＣＨＬＡＲＢＡＫ，ｅｔａｌ．Ｓｔｕｄｙｏｎｆｒｉｃｔｉｏｎａｎｄｗｅａｒｂｅｈａｖｉｏｒｏｆｐｏｌｙｐｈｅｎｙｌｅｎｅｓｕｌｆｉｄｅｃｏｍｐｏｓｉｔｅｓｒｅｉｎｆｏｒｃｅｄｂｙｓｈｏｒｔｃａｒｂｏｎｆｉｂｅｒｓａｎｄｓｕｂ⁃ｍｉｃｒｏＴｉＯ２ｐａｒｔｉｃｌｅｓ［Ｊ］．ＣｏｍｐｏｓｉｔｅｓＳｃｉｅｎｃｅａｎｄＴｅｃｈｎｏｌｏｇｙ，２００８，６８（３／４）：７３４－７４２．ʌ１０ɔＬＩＮＧＭ，ＸＩＥＧＹ，ＳＵＩＧＸ，ｅｔａｌ．Ｈｙｂｒｉｄｅｆｆｅｃｔｏｆｎａｎｏｐａｒｔｉ⁃ｃｌｅｓｗｉｔｈｃａｒｂｏｎｆｉｂｅｒｓｏｎｔｈｅｍｅｃｈａｎｉｃａｌａｎｄｗｅａｒｐｒｏｐｅｒｔｉｅｓｏｆｐｏｌｙｍｅｒｃｏｍｐｏｓｉｔｅｓ［Ｊ］．ＣｏｍｐｏｓｉｔｅｓＰａｒｔＢ：Ｅｎｇｉｎｅｅｒｉｎｇ，２０１２，４３（１）：４４－４９．ʌ１１ɔＭＡＮ，ＬＩＮＧＭ，ＸＩＥＧＹ，ｅｔａｌ．Ｔｒｉｂｏｌｏｇｉｃａｌｂｅｈａｖｉｏｒｏｆｐｏｌｙ⁃ｅｔｈｅｒｅｔｈｅｒｋｅｔｏｎｅｃｏｍｐｏｓｉｔｅｓｃｏｎｔａｉｎｉｎｇｓｈｏｒｔｃａｒｂｏｎｆｉｂｅｒｓａｎｄｐｏｔａｓｓｉｕｍｔｉｔａｎａｔｅｗｈｉｓｋｅｒｓｉｎｄｒｙｓｌｉｄｉｎｇａｇａｉｎｓｔｓｔｅｅｌ［Ｊ］．ＪｏｕｒｎａｌｏｆＡｐｐｌｉｅｄＰｏｌｙｍｅｒＳｃｉｅｎｃｅ，２０１２，１２３（２）：７４０－７４８．ʌ１２ɔＧＵＯＱＢ，ＲＯＮＧＭＺ，ＪＩＡＧＬ，ｅｔａｌ．Ｓｌｉｄｉｎｇｗｅａｒｐｅｒｆｏｒｍａｎｃｅｏｆｎａｎｏ⁃ＳｉＯ２／ｓｈｏｒｔｃａｒｂｏｎｆｉｂｅｒ／ｅｐｏｘｙｈｙｂｒｉｄｃｏｍｐｏｓｉｔｅｓ［Ｊ］．Ｗｅａｒ，２００９，２６６（７／８）：６５８－６６５．ʌ１３ɔＷＡＮＧＱＨ，ＺＨＡＮＧＸＲ，ＰＥＩＸＱ．Ｓｔｕｄｙｏｎｔｈｅｓｙｎｅｒｇｉｓｔｉｃｅｆｆｅｃｔｏｆｃａｒｂｏｎｆｉｂｅｒａｎｄｇｒａｐｈｉｔｅａｎｄｎａｎｏｐａｒｔｉｃｌｅｏｎｔｈｅｆｒｉｃ⁃ｔｉｏｎａｎｄｗｅａｒｂｅｈａｖｉｏｒｏｆｐｏｌｙｉｍｉｄｅｃｏｍｐｏｓｉｔｅｓ［Ｊ］．Ｍａｔｅｒｉａｌｓ＆Ｄｅｓｉｇｎ，２０１０，３１（８）：３７６１－３７６８．ʌ１４ɔＣＨＥＮＢＢ，ＬＩＸＦ，ＹＡＮＧＪ，ｅｔａｌ．Ｅｎｈａｎｃｅｍｅｎｔｏｆｔｈｅｔｒｉｂｏ⁃ｌｏｇｉｃａｌｐｒｏｐｅｒｔｉｅｓｏｆｃａｒｂｏｎｆｉｂｅｒ／ｅｐｏｘｙｃｏｍｐｏｓｉｔｅｂｙｇｒａｆｔｉｎｇｃａｒｂｏｎｎａｎｏｔｕｂｅｓｏｎｔｏｆｉｂｅｒｓ［Ｊ］．ＲＳＣＡｄｖａｎｃｅｓ，２０１６，６（５５）：４９３８７－４９３９４．ʌ１５ɔＣＨＥＮＢＢ，ＬＩＸ，ＪＩＡＹＨ，ｅｔａｌ．ＭｏＳ２ｎａｎｏｓｈｅｅｔｓ⁃ｄｅｃｏｒａｔｅｄｃａｒｂｏｎｆｉｂｅｒｈｙｂｒｉｄｆｏｒｉｍｐｒｏｖｉｎｇｔｈｅｆｒｉｃｔｉｏｎａｎｄｗｅａｒｐｒｏｐｅｒ⁃ｔｉｅｓｏｆｐｏｌｙｉｍｉｄｅｃｏｍｐｏｓｉｔｅ［Ｊ］．ＣｏｍｐｏｓｉｔｅｓＰａｒｔＡ：ＡｐｐｌｉｅｄＳｃｉｅｎｃｅａｎｄＭａｎｕｆａｃｔｕｒｉｎｇ，２０１８，１０９：２３２－２３８．埃克森美孚全面润滑解决方案应对非道路移动机械国四标准由中国工程机械工业协会举办的非道路移动机械四阶段排放标准（工程机械行业）交流研讨会在无锡圆满举行㊂埃克森美孚作为协办单位，在研讨会上发表主旨演讲，解读国四排放标准对柴油发动机的影响，面对中国机械行业高质量发展的新时代新挑战，埃克森美孚的全面润滑解决方案将积极助力设备制造商及终端用户平稳度过国标更新的缓冲期，进一步实现节能减排，绿色发展㊂应国家生态环境部发布的‘＜非道路柴油移动机械污染物排放控制技术要求＞标准“要求，国四标准将于２０２２年１２月１日（５６０ｋＷ以下的发动机）正式开始实施㊂新国标的出台标志着行业对环保要求进一步收紧，节能减排在长远发展中的战略地位愈加重要㊂相比国三标准，国四标准最大的不同是３７５６０ｋＷ功率范围内的发动机都必须加装废气后处理设备㊂而润滑油中的硫㊁磷及硫酸盐灰分等成分会通过不同机制影响后处理系统的运作，影响排放㊂因此，行业需要更高标准的润滑油以提升和颗粒捕集器及催化剂的相容性㊂低ＳＡＰＳ（低硫㊁低磷㊁低灰分）将成为新标准颁布后非道路机械重要的选油标准㊂凭借１５０多年的专业积淀和行业洞察，埃克森美孚已率先推出了多款ＣＫ－４级别产品，构建出完善的产品线，为升级后的发动机及其尾气后处理系统提供更为优越的保护和杰出的性能，践行品牌对深耕中国市场的承诺㊂卓越的低温流动性㊁抗磨损及杰出的氧化稳定性能都帮助油品在多重严苛的工况下发挥出色，有效保护发动机的后处理系统，实现更长的换油周期㊂美孚黑霸王傲超５Ｗ－３０先进全合成润滑油在实际工况的节能测试中被证明相较原用油可节省油耗高达３０８％，同时可减少３０８％污染物排放量；美孚黑霸王合成级１０Ｗ－４０可在长达１０万公里的换油周期内提供卓越保护；美孚黑霸王超高级１５Ｗ－４０做到了抗磨性能的提升，其抗磨损保护性能比ＣＫ－４ＡＰＩ发动机测试要求高５０％㊂除了高质量的发动机润滑油，埃克森美孚也通过美孚优释达系列服务，为用户提供包括油品分析㊁换油服务等等的专业技术支持，帮助提升设备管理水平㊂同时，埃克森美孚还在液压油㊁润滑脂等领域为设备制造商及终端用户提供全方位润滑解决方案，为生产力添翼㊂９９２０２１年第４期㊀曹凤香等：纳米颗粒ＴｉＯ２和ＳｉＯ２对碳纤维／超高分子量聚乙烯复合材料力学和摩擦学性能的影响。

对比辩证英文作文题目

对比辩证英文作文题目Comparative and Dialectical EssayThe world we live in is a complex and multifaceted one, where different perspectives and ideas often collide. This is particularly true in the realm of language, where the nuances and complexities of expression can lead to a rich tapestry of understanding or a tangled web of misunderstanding. In this essay, we will explore the concepts of comparative and dialectical thinking, and how they can shape our approach to language and communication.Comparative thinking is the process of identifying and analyzing the similarities and differences between two or more entities. In the context of language, this might involve comparing the grammatical structures, vocabulary, or cultural influences of different languages. By examining the points of convergence and divergence, we can gain a deeper appreciation for the diversity of human expression and the ways in which language reflects the unique experiences and perspectives of different societies.One of the key benefits of comparative thinking is that it allows us to challenge our own assumptions and biases. When we are confrontedwith a language or culture that operates in a fundamentally different way from our own, it can force us to re-evaluate our preconceived notions and consider alternative ways of understanding the world. This can lead to a more nuanced and flexible approach to communication, where we are better equipped to navigate the complexities of cross-cultural exchange.Dialectical thinking, on the other hand, is a more dynamic and interactive process of exploring the tensions and contradictions inherent in a given topic or idea. In the realm of language, this might involve examining the ways in which different linguistic traditions or schools of thought engage in a kind of intellectual discourse, each offering a unique perspective or critique of the other.The power of dialectical thinking lies in its ability to uncover the underlying assumptions and biases that shape our understanding of language. By engaging in a back-and-forth dialogue, we can challenge our own preconceptions and gain a deeper appreciation for the multifaceted nature of human expression. This can be particularly useful in the context of language learning, where the ability to navigate the nuances and complexities of a new linguistic system can be a critical factor in achieving proficiency and fluency.One of the key differences between comparative and dialectical thinking is the degree of engagement and interaction. Whilecomparative thinking involves a more detached and analytical approach, dialectical thinking requires a more active and participatory stance. In the context of language, this might mean not only examining the structural and cultural differences between languages, but also engaging in discussions and debates that explore the underlying assumptions and biases that shape our understanding of language.Another important distinction is the role of synthesis. Comparative thinking often aims to identify the similarities and differences between two or more entities, with the goal of developing a more comprehensive understanding of the subject matter. Dialectical thinking, on the other hand, is more focused on the tension and conflict between different perspectives, with the ultimate goal of synthesizing a new, more nuanced understanding that transcends the individual viewpoints.In the end, both comparative and dialectical thinking are essential tools for navigating the complexities of language and communication. By combining these approaches, we can develop a more holistic and flexible understanding of the ways in which language shapes and is shaped by the human experience. Whether we are learning a new language, engaging in cross-cultural exchange, or simply exploring the rich tapestry of human expression, the abilityto think comparatively and dialectically can be a powerful asset in our quest for greater understanding and connection.。

A comparative study of adhesion test methods for hard coatings

Surface and Coatings Technology 113(1999)86–102A comparative study of adhesion test methods for hard coatingsH.Ollendorf 1,D.Schneider *Fraunhofer Institut fu ¨r Werksto ﬀ-und Strahltechnik,Winterbergstraße 28,01277Dresden,GermanyReceived 17July 1998;accepted 25November 1998AbstractThe feasibility of seven techniques for testing and evaluating the adhesion of thin ﬁlms was investigated:scratch test,four-pointbending test,Rockwell test,cavitation test,impact test,laser-acoustics and acoustic microscopy.The studies were performed with TiN ﬁlms (thickness 1.2–2.45m m)deposited on the annealed steel 42CrMo4.The adhesion of the TiN ﬁlms was varied by varying the time of pre-sputtering the steel substrate with argon ions before the ﬁlm deposition.Argon pre-sputtering for 15min is recommended to guarantee an optimal adhesion.The pre-sputtering time,t S,was reduced down to 0.5min to reduce the adhesion.The following test parameters were used to evaluate the adhesion:the friction work,acoustic emission activity and critical load of the scratch test,the critical strain and the defect density of the four-point bending test,the proportional damage area of cavitation test,the critical number of loading cycles of the impact test,and Young’s modulus of the ﬁlm measured with the laser-acoustic method.These test parameters were examined for any correlation with the pre-sputtering time,t S.The results aresummarized in a table that shows which test methods and test parameters yield corresponding and contradictory evaluations of the ﬁlm quality.The e ﬀect of defect density and residual stresses is ser-acoustics and acoustic microscopy are non-destructive methods.Young’s modulus,as measured by laser-acoustics,is sensitive to the density of micro-defects.This is expected to indicate their e ﬀect on the adhesion.©1999Elsevier Science S.A.All rights reserved.Keywords:Adhesion;Bending test;Cavitation test;Impact test;Laser-acoustics;Scratch test;TiN ﬁlms1.Introductionthe nature of the bonds between the atoms of both materials.The ‘‘practical adhesion’’does not only Testing the adhesion of thin ﬁlms is one of the most depend on the ‘‘basic adhesion’’.This refers to the important and di ﬃcult tasks of surface engineering.It failure of hard coatings for wear protection,which is already di ﬃcult to ﬁnd a generally acceptable deﬁni-depends on a complex combination of the elastic proper-tion of adhesion between ﬁlm and substrate that takes ties and fracture toughness of the ﬁlm and substrate,the complexity of the e ﬀects of the material microstruc-the size distribution of ﬂaws,pores and other lattice ture,the external loading and the environmental aspects defects,the loading conditions and the friction behavior into account.The terms ‘‘basic adhesion’’and ‘‘practical against impacting or scraping particles and components adhesion’’were introduced to distinguish between study-[3].Therefore,surface engineering is interested in evalu-ing the fundamental physical aspects of the adhesion ating the ‘‘practical adhesion’’.Several methods are phenomenon and developing practically relevant test used,such as the scratch test,bending test,impact test,procedures for classifying the quality of a coating [1,2].cavitation test,and Rockwell imprint test.However,‘‘Basic adhesion’’is understood to be the summation of sometimes they provide contradictory results.all interatomic interactions at the interface of the ﬁlm An extensive test program was performed with TiN and substrate.This can be quantiﬁed as the work ﬁlms on steel to study the feasibility of these test necessary for completely separating the ﬁlm and sub-methods.TiN ﬁlms with di ﬀerent levels of adhesion to strate along the interface,excluding all e ﬀects other thanthe steel surface were prepared by ion plating.The adhesion was varied by varying the pre-sputtering time with argon ions.It is known that pre-sputtering a steel *Corresponding author.Tel:+493512583451;Fax:+493512583310;surface for 15min guarantees a good adhesion of TiN e-mail:schneider@iws.fhg.de[4].Seven test series with a total of 130samples were 1Present address:White Oak Semiconductor,6000Technology Blvd.,Sandston,VA 23150,USA.prepared with pre-sputtering times from t S=0.5to0257-8972/99/$–see front matter ©1999Elsevier Science S.A.All rights reserved.PII S0257-8972(98)00827-587H.Ollendorf,D.Schneider /Surface and Coatings Technology 113(1999)86–10215min.The test parameters of the adhesion tests were 2.2.Varying the ﬁlm adhesionexamined for any correlation with the pre-sputtering time,t S.The parameters are plotted versus the logarithmTiN ﬁlms with a thickness of 1.2–2.4m m were depos-ited by ion plating on the surface of the 42CrMo4of t Ssince the e ﬀect of the pre-sputter process on theadhesion reduces with increasing time,t S.samples by ion plating.The adhesion was varied by using di ﬀerent pre-sput-The ﬁlm quality was additionally characterized by Auger spectroscopy,hardness measurements and X-ray tering times,t S,(with plasma gas:argon).A series ofsamples series with pre-sputtering times of t S=0.5,1,2,texture investigations.It is desirable to evaluate the ﬁlm adhesion non-3,5and 15min was prepared.The best ﬁlm adhesion was expected for t S=15min and the worst adhesion fordestructively.Acoustic microscopy has shown to be able to detect interface imperfections and microscopic ﬂaws t S=0.5min.Since the improvement in adhesion is known to saturate with pre-sputtering time,the [5]and was involved in the test program.Surface acoustic waves are a promising non-destruc-increment of t Swas increased.The greatest improvementin adhesion is expected for shorter pre-sputtering times,tive method for characterizing thin ﬁlms and near-surface regions.High-frequency elastic vibrations propa-t S,but the pre-sputtering e ﬀect reduces with increasing t S .A maximum time of t S =15min is recommended for gate along the surface and allow Young’s moduli of the thin ﬁlms and substrates to be measured.Young’s modu-the ion-plating process used.The technology for depositing TiN ﬁlms with di ﬀerent lus represents the sti ﬀness of the material,which in turn depends on the average bonding strength in the tested adhesion is shown schematically in Fig.1.Two reference specimens with t S=15min have been additionally pre-material volume.It is also inﬂuenced by the defect density.A certain amount of microscopic pores and pared in each deposition run to identify the variations in stoichiometry of the ﬁlm which could accompany the micro-cracks can drastically reduce the modulus [6].Surface acoustic waves of a suitable frequency range adhesion e ﬀect.This was done by covering the samples intended for poorer adhesion with an aluminum foil in penetrate through the ﬁlm and interface into the sub-strate and,therefore,can be expected to detect a reduced the ﬁrst-phase t Pof the pre-sputtering process.Therefore,only the surfaces of the two reference samples strength of the interface caused by defects and lattice imperfections [7].Defects in both the brittle ﬁlm and were cleaned by argon etching during t P.Afterwards,the aluminum foils were removed from the protected the interface can be origins of the failure of the ﬁlm–-substrate composite.The Young modulus of the TiN samples,and both the reference samples and the test samples were argon-sputtered.The pre-sputtering timeﬁlms was measured with a laser-acoustic technique that enables variations in ﬁlm modulus of less than ±2.5%to be detected [8].Empirical correlations of the ﬁlm modulus with the results of the adhesion tests wereinvestigated.These correlations enable the ﬁlms to be non-destructively tested and improve the interpretation of the adhesion tests.The results of all tests are summarized in Table 1to evaluate the feasibility of the methods and to show agreements and contrasts.A discussion of the e ﬀects of di ﬀerent aspects of the adhesion behavior on the test results closes the article.2.Test material,preparation and characterization 2.1.Substrate preparationThe steel 42CrMo4steel was used as a substrate material.The samples had dimensions of 6×8×60mm,which were determined by the requirements of the four-point bending test.Before the ﬁlm deposition,the steel samples were quenched and tempered to a hardness of 350HV.The surface was polished to a roughness,R a,Fig.1.Simultaneous deposition of TiN ﬁlms with poor and good adhe-of 0.05m m.Afterwards,the samples were annealed at sion (reference samples)with di ﬀerent times,t S,of pre-sputtering withargon ions.560°C in vacuum so as to become stress-free.88H.Ollendorf,D.Schneider /Surface and Coatings Technology 113(1999)86–102of the test samples is determined by t S =15min −t P.After ﬁnishing the pre-sputtering process,the TiN ﬁlms coating was deposited on all samples with the same process parameters.In this way,ﬁlms with a good and poor adhesion could be deposited simultaneously.The quality of the test series was checked by measuring the Young modulus of the reference sample coatings.2.3.Controlling the ﬁlm qualityIt is known that the Young modulus of TiN sensitively depends on the stoichiometry [9].Therefore,the laser-acoustic method was used to check the ﬁlm quality of the reference samples of each test series.This could not Fig.3.Data record of the Scratch test showing the friction force,F F,be carried out on test samples with a lower pre-sputtering and acoustic emission events with increasing load,L N,for a ﬁlm withtime,t S,since the reduced adhesion is expected tot S=1min.inﬂuence the Young modulus.An introductory test series prepared with t S=15mincontents have been found within the interface region of showed an elastic modulus of E =435±5GPa for samples with t S=0.5min,which did not occur in thesamples with a good adhesion and stoichiometric com-reference samples with t S=15min.This result impliesposition.Higher ﬁlm moduli were not measured.that the sputtering treatment has the expected inﬂuence Therefore,this value was used as the threshold.on adhesion.This procedure should ensure that no e ﬀects other The hardness of the ﬁlm material was measured by than varying the ﬁlm adhesion inﬂuenced the results of the micro-indentation method (Shimadzu DUH 202)the mechanical tests.with a load of 1g.The values of 2100±300DHV are in agreement with those given in the literature.2.4.Characterizing the ﬁlmsThe micro-indentation tests were not su ﬃciently sensi-tive to determine the quality of the di ﬀerent test series.The textures of 12TiN ﬁlms were investigated by The ﬁlm thickness was determined by the X-ray X-ray di ﬀraction.A weak [111]texture was found ﬂuorescence technique (Fischerscope X-Ray 1020).A (already known for TiN ﬁlms deposited with moderate measuring uncertainty of D d /d ≤±0.02was achieved by ion PVD processes like ion plating [10]).careful calibration and a counting time of 5min.Eleven samples with pre-sputtering times of t S=0.5,2,5and 15min were investigated by Auger spectroscopy.Examples of Auger depth proﬁles are shown in Fig.2 3.Results for two pre-sputtered samples (t S=0.5and 15min).They reveal that the TiN ﬁlms have a stoichiometric 3.1.Scratch testcomposition.Slightly enhanced carbon and oxygenThe tests were performed with a Rockwell-shaped diamond indentor continuously loaded with a normal force,FN,from 0to 70N [11].The transverse velocityof the sample to the diamond was 10mm min −1,and the loading rate,d F N/d x =10N mm −1.The scratcheswere 7mm long.The friction force,F F,and the acousticemission signals were recorded.A typical data record is shown in Fig.3.The following test parameters were deduced from the scratch test:$critical load deduced from microscopic evaluation of the crack pattern around the scratch;$friction work along the scratch;$total number of acoustic emission signals in the scratch test;$critical load deduced from the Weibull statistical distribution of the ﬁrst acoustic emission signals in a Fig.2.Auger depth proﬁles for two samples pre-sputtered for t S=0.5and 15min,respectively.series of 20scratch tests;89H.Ollendorf,D.Schneider /Surface and Coatings Technology 113(1999)86–102$critical load deduced from the Weibull statistical su ﬃciently sensitive to distinguish between the other adhesion states.No signiﬁcant correlation between criti-distribution of the acoustic emission signals in one scratch test.cal load and pre-sputtering time was found.3.1.1.E v aluating the crack pattern3.1.2.Friction workFig.4shows two micrographs of scratches on samples The friction of the Rockwell diamond against the with a pre-sputtering time of t S=0.5and 15min.Thesample increased during the scratch test when the dia-sample pre-sputtered for 0.5min shows typical cracks mond removed the TiN ﬁlm from the steel substrate.and detachments in the form of chipping [12,13].The Fig.5shows the friction force,F F,versus the normalcoating material was not chipped away for samples pre-load on the stylus,F N,for two samples under di ﬀerentsputtered for 15min.Here,cracks are visible on either pre-sputtering times,t S.As long as the Rockwell dia-side of the scratch trace.Detailed experiments showed mond scratches the TiN ﬁlm,the friction force F Fisthat these cracks occurred coincidentally with the acous-identical for both samples with t S=2and 15min.In thetic signals [14].range of the breakthrough of the ﬁlm,F Fincreases moreRaster electron microscopic investigations conﬁrmed for the sample with t S=2min.This suggests that thethat light microscopic observations allowed a reliable area under the curve should be used as a test parameter detection of the ﬁrst ﬁlm detachments around the scratch for the adhesion.It is deﬁned as the friction work:trace.The test criteria proposed by Burnett and Rickerby [15]were used to determine the critical load of the ﬁlm detachment.The method revealed the lower W F=P F F d x =PF F /d FN d x d F N .(1)adhesion of the test series with t S=0.5min,but was not(a)(b)Fig.4.Light microscopic micrographs of scratches on samples with di ﬀerent pre-sputtering:(a)t S =15min;(b)t S=0.5min.90H.Ollendorf,D.Schneider /Surface and Coatings Technology 113(1999)86–1023.1.3.Acoustic emission acti v ityThe acoustic emission signals detected during the scratch test were ascribed to brittle micro-fractures in the TiN ﬁlm or the interface.The frequency of these events seems to be related to the defect density.Therefore,the number of acoustic emission events,N AE,is used as a test parameter for the adhesion.Fig.7shows the correlations of N AEwith the pre-sputteringtime,t S,for the three di ﬀerent classes of ﬁlm thickness.The acoustic emission activity,N AE,reduces withincreasing pre-sputtering time,t S,and shows the samebehavior as the friction work,W F,in Fig.6.Thiscorresponds to the assumption that the defect density is lower in samples produced under a longer pre-sputtering time.Signiﬁcant correlation coe ﬃcients from R =−0.56to −0.62weredetermined.Fig.5.Friction force,F F ,versus normal load,L N,in the scratch test3.1.4.Statistical e v aluation of acoustic emissionfor samples with di ﬀerent pre-sputtering time,t S.The Weibull statistical distribution function is applied for evaluating the fracture strength of hard and brittle Fig.6shows the correlations of friction work,W F,withceramics and was also proposed for the scratch test of pre-sputtering time,t S,for three ranges of ﬁlm thickness:hard coatings [16].The fracture tests of a series of 1.2–1.6m m,1.6–2.0m m,2.0–2.4m m.W Fdecreases withsamples yield a distribution of strength values that can increasing pre-sputtering time,t S.The ﬁlms werebe described by the Weibull distribution ing detached at higher loads,and the diamond scratched this distribution function,F (L ),it is possible to deter-the ﬁlm more than the substrate along the scratch trace mine the critical load,L C,for the fracture with a givenof 7mm.The correlation coe ﬃcients of R =−0.57and probability and the parameter m depending on the shape −0.88are signiﬁcant.of the distribution [17]:It is emphasized that signiﬁcant correlations could only be found for limited ranges of ﬁlm thickness.This F (L )=1−exp C −A L L CB mD.(2)proved to be true for all other test parameters of the present studies and conﬁrms the well-known ﬁnding that the results of adhesion tests can be compared only for The statistical evaluation was applied to the acoustic emission detected during the scratch.To study the typessimilar ﬁlmthicknesses.Fig.6.Friction work,W F ,versus pre-sputtering time,t S,for three ranges of ﬁlm thickness,d .R is the correlation coe ﬃcient.91H.Ollendorf,D.Schneider /Surface and Coatings Technology 113(1999)86–102Fig.7.Total number of acoustic emission signals,N AE ,during the scratch test versus pre-sputtering time,t S,for three classes of ﬁlm thickness,d .R is the correlation coe ﬃcient.of failure indicated by the signals,some tests were Weibull statistical distribution function in the form:stopped after the ﬁrst acoustic emission event.Microscopic investigations revealed that these acoustic ln ln {1/[1−F (L )]} =m ln L −m ln L C.(3)emission signals were always correlated with detach-ments of the ﬁlm.Therefore,the Weibull statistical F (L )was deduced from the normalized number of the scratch tests having shown an acoustic emission at the distribution was applied to the ﬁrst acoustic emission event detected in the scratch test.Twenty scratch tests load L .The critical load,L C,can be determined fromEq.(3)for ln ln{1/[1−F (L )]} =0,which is illustrated were performed for one distribution,ﬁve tests on each one of four samples of a test series.The results were in Fig.8.This is the load,L ,where 63.2%of all scratch tests released an acoustic emission signal.The parameter,plotted in a double-logarithmic diagram as shown in Fig.8for two sample series with a pre-sputtering time m ,can be deduced from the slope of ln ln{1/[1−F (L )]} versus ln(L )in Eq.(3).From the almost linear depen-of t S=2and 15min,respectively.This represents theFig.8.Double-logarithmic Weibull diagram for the probability,F ,of the ﬁrst acoustic emission event in the scratch test at the load,L N,for twosample series with di ﬀerent pre-sputtering times,t S .The deduction of the critical load,L C1,is shown.92H.Ollendorf,D.Schneider /Surface and Coatings Technology 113(1999)86–102Fig.9.Correlations of the critical load,L C1,with the pre-sputtering time,t S,for three classes of ﬁlm thickness d .R is the correlation coe ﬃcient.dence in Fig.8,it can be concluded that the ﬁrst signalssignals emit the ﬁrst signal at higher loads than samples showing only few signals.This could be explained by of the acoustic emission are Weibull-distributed.The correlations between critical load,L C1,with pre-lower residual stresses in the ﬁlms with more defects.A high defect density could prevent high residual stresses sputtering time,t S,are shown for the three classes ofﬁlm thicknesses in Fig.9.Correlation coe ﬃcients from occurring in the ﬁlm.Higher external loads must be applied to trigger the ﬁrst micro-fracture.However,by R =−0.5344to −0.762were determined.This suggests that the pre-sputtering time,t S,inﬂuences the acousticusing X-ray di ﬀraction,signiﬁcant di ﬀerences in residual stresses could not be detected by X-ray di ﬀraction.emission.However,it is emphasized that L C1decreaseswith increasing t S.This means that ﬁlms with a better-Further investigations were carried out to determine whether the Weibull distribution could also be applied than-expected adhesion show their ﬁrst brittle micro-fracture at lower loads.Obviously,L C1does not reﬂectto the acoustic emission of a single scratch test.This seems doubtful for tests with a high frequency of acoustic the e ﬀect of the pre-sputtering process in the expected manner.emission signals,since the fracture events cannot be assumed to be independent from each other,required Taking into account the activity of the acoustic emis-sion characterized by N AE(Fig.7)reveals the surprisingfor a statistical evaluation.However,the acoustic emis-sion usually starts with single isolated events whoseresult that samples showing many acoustic emissionFig.10.Double-logarithmic Weibull diagram of the acoustic emission in a single scratch test.93H.Ollendorf,D.Schneider /Surface and Coatings Technology 113(1999)86–1023.2.Four-point bending testThe four-point bending test is shown schematically in Fig.13.The sample was ﬁxed in the jig in such a way that the TiN ﬁlm was loaded by compressive stress to make the results comparable to those of the scratch test.The end of the sample was connected to an acoustic emission transducer to detect micro-fractures during the bending test.The samples were not coated within the area near the loading stamps so as to avoid the detection of acoustic signals other than those generated by the homogenous bending of the ﬁlm.Further details of the test procedure are described elsewhere [18,19].The data record of the bending test (Fig.14)shows the stress,s ,versus the strain,e ,in the upper layer of the sample and Fig.11.Double-logarithmic Weibull diagram of the acoustic emissionthe cumulative number of acoustic emission signals.in the ﬁrst stage of scratch test for three samples with di ﬀerent pre-Two test parameters were determined.The critical sputtering times,t S.strain,e C,was determined as the strain where 10%ofthe total number of the acoustic emission signals had origins can be assumed not to interact.Fig.10shows a been detected.The crack density,D C,was obtained fromWeibull diagram for the acoustic emission of a single an optical micrograph of the coated area after the scratch test.It can be seen that in the ﬁrst stage,the bending test.The stress–strain diagram did not yield acoustic emission events show a linear realtionship of any information about the ﬁlm since the e ﬀect of the the Weibull distribution in the double-logarithmic repre-2-m m-thick ﬁlm is too small compared to the 8-mm-sentation.This section of the diagram can be statistically thick steel substrate.analyzed,as shown in Fig.11.The e ﬀect of the pre-The micrographs in Fig.15a and b show the ﬁlms of sputtering time,t S,on the Weibull plot can be seen.two samples of di ﬀerent pre-sputtering time,t S.The ﬁlmIncreasing t Sshifts the distribution function to loweron the sample with a lower pre-sputtering time loads.A critical load,denoted L C2,was derived and(t S=2min,Fig.15b)shows more and longer cracks in plotted against t S in Fig.12.This shows that L C2dependsthe ﬁlm.The visible cracks are perpendicular to the on t S as well as L C1(Fig.9),and decreases with increas-surface.No detachments of the ﬁlms were observed.ing pre-sputtering time,t S.This suggests that bothThe crack density,D C,is plotted versus the sputteringparameters L C1and L C2reveal the same mechanicaltime,t S ,in Fig.16a.D Cis signiﬁcantly lower forproperty of the TiN ﬁlms.However,they both yield results contrary to the expected adhesion behavior.t S =15min than for t S=2min.This behavior is inFig.12.Correlations of the critical load,L C2,with the pre-sputtering time,t S,for three classes of ﬁlm thickness,d .R is the correlation coe ﬃcient.94H.Ollendorf,D.Schneider /Surface and Coatings Technology 113(1999)86–102Fig.13.Schematic representation of the four-point bending test.Fig.14.Data record of a four-point bending test of a TiN-coated sample with t S=2min,showing the cumulative number of acoustic emissionevents,C AE ,and the stress,s ,versus strain,e .The deduction of the critical strain,e C,is shown.agreement with that observed for the friction work,dimension,the blisters collapse,accompanied by the formation of a microscopic water jet that hits the surface W F ,and the acoustic emission activity,N AE,of the scratch test (Figs.6and 7).However,the critical strain,with a high pressure,generating a mechanical pulse.Since many blisters develop and collapse permanently,e C,shows an unexpected behavior.It indicates a thresh-old of the micro-fractures.Fig.16b reveals that eCthis test acts like many local impact tests on a large area and with a high repetition rate.Fig.18a–c show the decreases with increasing t S.One-tenth of all micro-fractures occurred at a lower strain in ﬁlms whose REM micrographs of three samples with di ﬀerent pre-sputtering times.In the cavitation test,the surface is adhesion was expected to be better.This corresponds to the results obtained for the critical loads L C1and LC2attacked in many parts,and destruction and detachment of the ﬁlm material can result.The ﬁlm with of the scratch test (Figs.9and 12).It seems that the acoustic emission signals detected in bending and scratch t S=15min shows the least damage (Fig.18a).The damage increases with decreasing t S.Image processingtests reveal the same fracture mechanism.was applied to determine the proportional area of the damage,A D .Fig.19shows A Dversus the pre-sputter3.3.Ca v itation testtime t S .The damaged area,A D,reduces with increasingpre-sputtering time,t S.This is an expected result.TheThe cavitation test is performed in a water tank in which the sample surface is exposed to high-power cavitation test yields the same evaluation behavior of the adhesion of the TiN ﬁlms as the friction work,W F,ultrasound (Fig.17)[20].An ultrasonic transducer with a diameter of 16mm is arranged about 0.5mm above and the acoustic emission activity,N AE,of the scratchtest and the crack density,D F,of the four-point bend-the sample.The high-power ultrasound generates blisters on the surface of the sample.Having reached a critical ing test.95H.Ollendorf,D.Schneider /Surface and Coatings Technology 113(1999)86–102Fig.17.Schematic representation of the cavitation test.3.4.Impact testThe impact test allows the local fatigue strength of the ﬁlm–substrate compound to be tested [21].A sche-matic representation of the test apparatus is shown in Fig.20.The sample is cyclically loaded by a ball of cemented carbide that is repetitively pushed on the sample surface.The cyclical loading is applied by a device that consists of a spring and a magnetic coil.The impact frequency can be varied from 0to 50Hz,and the force of the impact can be varied from 0to 1500N.The impact force is controlled by a strain gauge.The damage of the sample is evaluated by an optical micro-scope.The test parameter is the critical number of loading cycles,N C,up to the point at which the surfaceshows no further damage.The result has the form of a Woehler diagram (Fig.21a).N C versus t Sispresented(a)(b)Fig.15.Micrographs of TiN ﬁlms with di ﬀerent pre-sputtering time,in Fig.21b,which shows that the critical number of t S ,after the four-point bending test:(a)t S =15min;(b)t S=2min.cycles,N C,decreases with increasing pre-sputtering time,t S.The impact test indicated that pre-sputtering makes the ﬁlm adhesion worse.This corresponds to the results of the critical loads,L C1and L C2,of the scratch test(Figs.9and 12)and the critical strain,e C,of the four-point bending test (Fig.16b).3.5.Rockwell testThe advantage of this method is that it is easy to use,even in an industrial environment.A conventional hard-ness Rockwell test is performed and the damage pattern of the hard coating around the imprint is evaluated microscopically at a magniﬁcation of 100×.Standard damage pictures serve to classify the adhesion into six classes HF1–HF6[13,22].The Rockwell test was not su ﬃciently sensitive to distinguish between TiN ﬁlms with di ﬀerentpre-sputter-ing times.Even for test samples with a pre-sputtering Fig.16.Results of four-point bending test.(a)Crack density,D C,intime of only t S=1min,the test indicated that thethe ﬁlm after the test versus the sputtering time,t S.(b)Critical strain,e C ,versus sputtering time,t S.adhesion was of a good quality.。

天麻最细粉和普通粉对帕金森病大鼠神经行为学、氧化应激反应和神经炎症反应的对比研究.doc

天麻最细粉天麻最细粉和普通粉和普通粉和普通粉对帕金森病大鼠对帕金森病大鼠对帕金森病大鼠神经行为学神经行为学神经行为学、、氧化应激反应和神经炎症反应的应的对比研究对比研究陈慧1，艾国2, 3 *，黄正明21. 解放军95810部队医院，北京1000552. 解放军302医院全军中药研究所，北京 1000393. 军事医学科学院放射与辐射医学研究所，北京 100850摘要目的目的：观察天麻最细粉和普通粉对帕金森病（PD ）大鼠神经行为学、氧化应激反应和神经炎症反应的影响，对比最细粉和普通粉的作用差别。

方法方法方法：采用脑内定位注射6-羟基多巴胺（6-OHDA ）建立PD 大鼠模型。

设立正常组，模型组，天麻普通粉低、中、高剂量组（0.45、0.9、1.8 g/kg ）和天麻最细粉低、中、高剂量组（0.45、0.9、1.8 g/kg ）。

观察PD 大鼠神经行为学、氧化应激反应和神经炎症反应的变化。

结果结果结果：经过天麻普通粉和最细粉的治疗后，PD 大鼠均有不同程度的神经行为学改善，丙二醛（MDA ）含量降低，谷胱甘肽（GSH ）含量升高，谷胱甘肽过氧化物酶（GSH-Px ）和超氧化物歧化酶（SOD ）活性增加，一氧化氮（NO ）和α-肿瘤坏死因子（TNF-α）含量亦降低，且最细粉的效果更佳。

结论结论结论：天麻普通粉和最细粉均对PD 大鼠的神经行为学、氧化应激反应和神经炎症反应有改善作用，而且天麻最细粉的作用更加明显，为天麻最细粉的临床使用提供了科学依据。

关键词天麻天麻；；最细粉最细粉；；普通粉普通粉；；帕金森病大鼠帕金森病大鼠；；对比研究Comparative study on the the neuroethology, oxidative stress and inflammatory responses in rats with Parkinson’s disease of superfine and common powder of Gastrodia elata Bl.CHEN Hui 1, AI Guo 2, 3 *, HUANG Zheng-ming 21. Hospital of army 95810, Beijing 100055, China2. Department of Pharmacy, 302 Hospital of PLA, Beijing 100039, China3. Institute of Radiation Medicine, Academy of Military Medical Sciences, Beijing 100850, ChinaAbstract Objective : To comparative study on the the neuroethology, oxidative stress and inflammatory responses in rats with Parkinson’s disease (PD) of superfineand common powder of Gastrodia elata Bl.Method: Model of PD rat was established with injection of 6-hydroxydopamine (6-OHDA) into the substantia nigra of right side brain. The mouse were divided into the normal group, model group, Gastrodia elata mon powder of low, medium and high dose groups (0.45, 0.9, 1.8 g/kg), and superfine powder of low, medium and high dose groups (0.45, 0.9, 1.8 g/kg). The changes of neuroethology, oxidative stress and inflammatory responses in PD rats after treatment with superfine and common powder of Gastrodia elata Bl.were observed. Result: The rats in PD model group after treatment with superfine and common powder of Gastrodia elata Bl. appeared different levels of improvement of neuroethology. After treatment, superfine and common powder of Gastrodia elata Bl. can decrease the levels of malondialdehyde (MDA), nitric oxide (NO) and tumor necrosis factor-α (TNF-α), increase the content of glutathione (GSH), and enhance the activity of glutathione-peroxidase (GSH-Px) and superoxide dismutase (SOD) different levels. Conclusion: Both the superfine and common powder of Gastrodia elata Bl.has the improvement effect on the neuroethology, oxidative stress and inflammatory responses in rats with PD. Furthermore, the superfine powder is more effective than the common powder in pharmacological action, which provided experimental references for the clinical study of superfine powder of Gastrodia elata Bl.Key Words Gastrodia elata Bl.;superfine powder; common powder; rats with Parkinson’s disease (PD);comparative study作者简介：陈慧，女，主管药师，研究方向为临床药理。

Chapter03 Introduction to Tribology 机械零件设计英文PPT全套教案

Life of fatigue wear should be treated statistically due to its so many influencing uncertainties.
Lubrication
The object of lubrication is to reduce friction, wear, and heating of machine parts which move relative to each other.
The film pressure is created by the moving surface itself pulling the lubricant into a wedge-shaped zone at a velocity sufficiently high to create the pressure necessary to separate the surfaces against the load on the bearing.
The coefficient of friction is the shear strength of the junctions divided by the yield pressure of the softer component.
Tribological Solutions
By using solid surface coatings with low resistance to transverse shear
The area of real contact between couples is proportional to the load; thus the frictional force should be proportional to the load.

逻辑和悖论英语作文

逻辑和悖论英语作文英文回答：Logic and paradox are two concepts that are often thought of as being in opposition to each other. Logic is the study of reasoning and argumentation, and it is based on the idea that there are certain rules that govern how we can draw conclusions from premises. Paradox, on the other hand, is a statement that seems to contradict itself. At first glance, it may seem like logic and paradox are incompatible, but upon closer examination, we can see that they are actually two sides of the same coin.One of the most famous examples of a paradox is theLiar Paradox. The Liar Paradox states that "this statement is false." If the statement is true, then it must be false, but if the statement is false, then it must be true. This paradox has been puzzling philosophers for centuries, and it has led to the development of a number of different theories about the nature of truth and falsehood.Another famous paradox is Zeno's Paradox of Motion. Zeno's Paradox states that it is impossible to travel from one place to another because in order to do so, you must first travel half the distance, and then half of the remaining distance, and so on. This process will never end, so it is impossible to actually reach your destination. Zeno's Paradox has been used to argue against the reality of motion, and it has also led to the development of a number of different theories about the nature of time and space.Logic and paradox are both essential to our understanding of the world. Logic provides us with thetools we need to reason about the world and to draw conclusions from our observations. Paradox, on the other hand, challenges our assumptions about the world and forces us to think more deeply about the nature of reality. Together, logic and paradox help us to understand the world around us and to make sense of our place in it.中文回答：逻辑和悖论是两个通常被认为相互对立的概念。

中药寒热药性研究方法综述

•990 •中华中医药杂志(原中W医药学报)2021〈丨:2)彳第36卷第2期CJTCMP, February 202丨，Vol.36, No.2•综述•中药寒热药性研究方法综述夏元枢\魏国辉王振国\付先军1^山东中阪药大学中医药经典理论教育部重点实验室，济南250355;2山东中医药大学智能与信息T.程学院，济南250355)摘要：以现代科技方法对中医药理论进行科学诠释，是•中医药发展、发扬和t小准化所亟耑的重要一步，对药性的研究是其中的重要一环中药四性理论是中药药性理论体系的核心，现代科技的不断发展为中药寒热药性研究提供了新的r•段与途径，推动其进入分子水平，除对其M性表征~物质基础的研究外，还汗始探寻其内在机制文章着重从屮药物象、基W组学、蛋闩组学和代谢组学等角度对中药寒热药性研究进展进彳r综述，以展承近年来中药寒热药性研究的不同思路与方法关键词：中药药性；寒热；研究方法；物象；基因组学；蛋白组学；代谢组学基金资助：国家重点基础研究发展计划（973计划）（N〇.2007(:B512600)，国家f t然科学基金项目(N o.81473369 )Review on research methods of cold and heat property of Chinese materia medicaX I A Y u a n-s h u1，W E I G u o-h u i12,W A N G Z h e n-g u o1，F U X i a n-j u n1('Key Laboratory for Classical Theory of Traditional Chinese Medicine of Education Ministry. Shangdong University ofTraditional Chinese Medicine, Jinan 250355, China; :College of Science and Technology,Shandong University of Traditional Chinese Medicine. Jinan 250355, China )Abstract: Ii is an urgent step for the development and standardization of traditional Chinese medicine to interpret its theory with modern scientific and technological methods, of which the research on the properties Chinese materia medica is thekey. The theory of four properties of Chinese materia medica is the core of the Chinese materia medica property theory. With thecontinuous development of modern science and technology, new means and approaches are provided for the study of the coldand heat of Chinese materia medica, which makes the research into the molecular level. In addition to the study of its attributerepresentation and material basis, it also begins to explore its internal mechanism. In this paper, the study of the cold and heat ofChinese materia medica is reviewed from the perspectives of the image of Chinese materia medica, genomics, proteomics andmetabonomics, trying to show different research ideas and methods in recent years.K e y W o r d s: Properties of Chinese materia medica; Cold and heat; Research methods; Image; Genomics; Proteomics;MetabonomicsF u n d i n g：National Key Basic Research Development Program (973 Program) (No.2(X)7CB512600). National NaturalScience Foundation of China (No.81473369)中药药性理论是构成中医理论体系的重要-环中药药性中的四性理论，报据其对人体阴阳、寒热产生作H i的方向和程度分为寒、热、温、凉m,四性理论是中药药性理论的核心内容121。

A Comparative Study on the Bug-Proneness of Different Types of Code Clones

A Comparative Study on the Bug-Proneness ofDifferent Types of Code ClonesManishankar Mondal Chanchal K.Roy Kevin A.SchneiderDepartment of Computer Science,University of Saskatchewan,Canada{mshankar.mondal,chanchal.roy,kevin.schneider}@usask.caAbstract—Code clones are deﬁned to be the exactly or nearly similar code fragments in a software system’s code-base.The existing clone related studies reveal that code clones are likely to introduce bugs and inconsistencies in the code-base.However, although there are different types of clones,it is still unknown which types of clones have a higher likeliness of introducing bugs to the software systems and so,should be considered more important for managing with techniques such as refactoring or tracking.With this focus,we performed a study that compared the bug-proneness of the major clone-types:Type1,Type2, and Type3.According to our experimental results on thousands of revisions of seven diverse subject systems,Type3clones exhibit the highest bug-proneness among the three clone-types. The bug-proneness of Type1clones is the lowest.Also,Type3 clones have the highest likeliness of being co-changed consistently while experiencing bug-ﬁxing changes.Moreover,the Type3 clones that experience bug-ﬁxes have a higher possibility of evolving following a Similarity Preserving Change Pattern(SPCP) compared to the bug-ﬁx clones of the other two clone-types.From the experimental results it is clear that Type3clones should be given a higher priority than the other two clone-types when making clone management decisions.We believe that our study provides useful implications for ranking clones for refactoring and tracking.I.I NTRODUCTIONCode cloning is a common yet controversial software en-gineering practice which is often employed by programmers during software development and maintenance for repeating common functionalities.Cloning refers to the task of copying a code fragment from one place of a code-base and pasting it to some other places with or without modiﬁcations[42].The original code fragment(i.e.,the code fragment from which the copies were made)and the pasted code fragments become clones of one another.Two exactly or nearly similar code fragments form a clone pair.A group of similar code fragments forms a clone class.Code clones are of great importance from the perspectives of software maintenance and evolution.A great many studies [1],[2],[9]–[11],[13],[15],[17],[19]–[22],[24],[25],[35], [36],[48],[50]have already been conducted on the impacts of clones on the evolution and maintenance of software systems. While some of these studies[1],[10],[11],[17],[19]–[21] identify some positive impacts of code clones,a number of studies[2],[9],[13],[15],[22],[24],[25],[35],[36],[48] have shown empirical evidence of strong negative impacts of code clones such as hidden bug propagation[22],late propagation[2],unintentional inconsistencies[2],[9],and high instability[36].Because of these negative impacts,code clones are considered to be the number one bad smell in a software system’s code-base.According to a number of studies[2],[4],[9],[12],[13], [22],[23],[48],[53],code clones are directly related to bugs and inconsistencies in a software system.However, although there are different types of code clones,none of the existing studies investigate the comparative bug-proneness of these different clone-types.Such an investigation is important because it can help us identify which type(s)of clones have the highest tendency of exhibiting bug-proneness and thus,should be considered to be the most important ones for management such as refactoring and tracking.Focusing on this issue in this research work we investigate the comparative bug-proneness of the major types of code clones:Type1,Type2,and Type3 (deﬁned in Section II).In particular,we answer four important research questions listed in Table I.According to our in-depth investigation on thousands of revisions of seven diverse subject systems written in two different programming languages(C and Java)we can state that:(1)Type3clones have a higher bug-proneness compared to Type1and Type2clones.The bug-proneness of Type1clones is the lowest among the three clone-types.Our statistical signiﬁcance tests show that Type3clones have a signiﬁcantly higher bug-proneness than Type1clones.(2)Type3clones have the highest likeliness of being co-changed(i.e.,getting changed together)consistently among the three clone-types when changed toﬁx a bug.(3)Type3bug-ﬁx clones have the highest possibility of evolving following a Similarity Preserving Change Pattern called SPCP.According to our previous studies[33],[34], SPCP clones(i.e.,clones that evolve following a Similarity Preserving Change Pattern)are the most important ones to consider for clone management.Our experimental results imply that Type3clones should be given a higher priority than the other two clone-types when making clone management decisions(such as clone refactor-ing,or tracking)and ourﬁndings(points2and3above)can be used to rank code clones during clone management.In our previous studies[33],[34]we detected and ranked SPCP clones for refactoring and tracking on the basis of their co-change tendencies.However,we should also consider their bug-proneness.Our implemented prototype tool is capable of automatically detecting SPCP clones that exhibited bug-proneness during evolution.Thus,it can help us rank clones considering their bug-proneness too.TABLE IR ESEARCH Q UESTIONSSL Research QuestionRQ1Which clone types have a higher possibility of experiencing bugﬁxing changes?RQ2Do the clone fragments from the same clone class co-change(i.e.,change together)consistently during a bug-ﬁx?RQ3What proportion of the clone fragments that experienced bug-ﬁxing changes are SPCP clones?The rest of the paper is organized is as follows:Section II describes the terminology,Section III discusses the exper-imental steps,Section IV answers the research questions by presenting and analyzing the experimental results,Section V mentions the possible threats to validity,Section VI discusses the related work,andﬁnally,Section VII concludes the paper by mentioning possible future work.II.T ERMINOLOGYTypes of clones.We conduct our experiment considering both exact(Type1)and near-miss clones(Type2and Type 3clones).As is deﬁned in the literature[42],[43],if two or more code fragments in a particular code-base are exactly the same disregarding the comments and indentations,these code fragments are called exact clones or Type1clones of one another.Type2clones are syntactically similar code fragments.In general,Type2clones are created from Type 1clones because of renaming identiﬁers or changing data types.Type3clones are mainly created because of additions, deletions,or modiﬁcations of lines in Type1or Type2clones. Similarity Preserving Change Pattern(SPCP).In our previous studies[33],[34]we showed that the code clones that evolve following a Similarity Preserving Change Pattern (SPCP)are the most important ones for refactoring or tracking.A Similarity Preserving Change Pattern consists of a Similar-ity Preserving Change and/or a Re-synchronizing Change. Similarity Preserving Change.Let us consider two code fragments that are clones of each other in a particular revision of a subject system.A commit operation was applied to this revision,and any one or both of these code fragments(i.e., clone fragments)received some changes.However,in the next revision(created because of the commit operation)if these two code fragments are again considered clones of each other(i.e., the code fragments preserve their similarity),then we say that the code fragments received a Similarity Preserving Change in the commit operation.Re-synchronizing Change.A re-synchronizing change con-sists of a diverging change followed by a converging change. Let us consider two code fragments that are clones of each other in a particular revision.A commit operation C i was applied to this revision,and any one or both of the fragments received some changes in such a way that the code fragments were not considered clones of each other in the next revision. We say that the code fragments experienced a diverging change.However,in a later commit operation C i+n(n>= 1)any one or both of the code fragments received some changes,and because of these changes the code fragments again became clones of each other.We say that the codeTABLE IIS UBJECT S YSTEMSSystems Lang.Domains LLR Revisions Ctags C Code Def.Generator33,270774 Camellia C Image Processing Library89,063170 BRL-Cad C3-D Modeling39,309735 jEdit Java Text Editor191,8044000 Freecol Java Game91,6261950 Carol Java Game25,0911700 Jabref Java Reference Management45,5151545 LLR=LOC in the Last Revisionfragments experienced a converging change in commit C i+n.A diverging change followed by a converging change is termed a re-synchronizing change.III.E XPERIMENTAL S TEPSWe perform our investigation on seven subject systems (Table II)downloaded from an on-line SVN repository[39].A.Preliminary StepsWe perform the following preliminary steps before an-alyzing bug-proneness:(1)Extraction of all revisions(as mentioned in Table II)of each of the subject systems from the online SVN repository;(2)Method detection and extraction from each of the revisions using CTAGS[6];(3)Detection and extraction of code clones from each revision by applying the NiCad[5]clone detector;(4)Detection of changes between every two consecutive revisions using diff;(5)Locating these changes to the already detected methods as well as clones of the corresponding revisions;(6)Locating the code clones detected from each revision to the methods of that revision;(7)Detection of method genealogies considering all revisions using the technique proposed by Lozano and Wermelinger [25];(8)Detection of clone genealogies by identifying the propagation of each clone fragment through a method geneal-ogy;and(9)Detection of SPCP clone fragments by analyzing clone change patterns.For completing these steps we use the tool SPCP-Miner[30].For the details of these steps we refer the interested readers to our earlier work[32].We use NiCad[5]for detecting clones because it can detect all major types(Type1,Type2,and Type3)of clones with high precision and recall[45],[46].Using NiCad we detect block clones including both exact(Type1)and near-miss (Type2,Type3)clones of a minimum size of10LOC with 20%dissimilarity threshold and blind renaming of identiﬁers. These settings are explained in detail in our earlier work[32]. For different settings of a clone detector the clone detection results can be different and thus,theﬁndings regarding the bug-proneness of code clones can also be different.Thus, selection of reasonable settings(i.e.,detection parameters)is important.We used the mentioned settings in our research, because in a recent study[49]Svajlenko and Roy show that these settings provide us with better clone detection results in terms of both precision and recall.Clone Genealogies of Different Clone-Types.SPCP-Miner [30]detects clone genealogies considering each clone-type (Type1,Type2,and Type3)separately.Considering aparticular clone-type itﬁrst detects all the clone fragments of that particular type from each of the revisions of the candidate system.Then,it performs origin analysis of these detected clone fragments and builds the genealogies.Thus,all the instances in a particular clone genealogy are of a particular clone-type.An instance is a snap-shot of a clone fragment in a particular revision.A detailed elaboration of the genealogy detection approach is presented in our previous study[33].As we obtain three separate sets of clone genealogies for three different clone-types,we can easily determine and compare the bug-proneness of these clone-types.Tackling Clone-Mutations.Xie et al.[53]found that mutations of the clone fragments(i.e.,a particular clone fragment may change its type)might occur during evolution. If a particular clone fragment is considered of a different clone-type during different periods of evolution,SPCP-Miner extracts a separate clone-genealogy for this fragment for each of these periods.Thus,even with the occurrences of clone-mutations,we can clearly distinguish which bugs were experienced by which clone-types.B.Bug-proneness Detection TechniqueFor a particular candidate system,weﬁrst retrieve the com-mit messages by applying the‘SVN log’command.A commit message describes the purpose of the corresponding commit operation.We automatically infer the commit messages using the heuristic proposed by Mockus and V otta[29]in order to identify those commits that occurred for the purpose ofﬁxing bugs.Then we identify which of these bug-ﬁx commits make changes to clone fragments.If one or more clone fragments are modiﬁed in a particular bug-ﬁx commit,then it is an implication that the modiﬁcation of those clone fragment(s) was necessary forﬁxing the corresponding bug.In other words,the clone fragment(s)are related to the bug.In this way we examine the commit operations of a candidate system, analyze the commit messages to retrieve the bug-ﬁx commits, and identify those clone fragments that are related to the bug-ﬁx.We also determine the number of changes that occurred to such a clone fragment in a bug-ﬁx commit using the UNIX diff command.For the details of change detection we refer the interested readers to our earlier work[32].The way we detect the bug-ﬁx commits was also previously followed by Barbour et al.[2].Barbour et al.[2]detected bug-ﬁx commits in order to investigate whether late propagation in clones is related to bugs.They atﬁrst identiﬁed the occurrences of late propagations and then analyzed whether the clone fragments that experienced late propagations are related to bug-ﬁx.In our study we detect bug-ﬁx commits in the same way as they detected,however,our study is not limited to the late propagation clones only.We investigate the bug-proneness of all clone fragments in a software system. Also,Barbour et al.[2]did not investigate Type3clones in their study.We consider Type3clones in our bug-proneness analysis.Moreover,we compare the bug-proneness of different types of code clones from different perspectives.None of the existing studies do such comparisons.IV.E XPERIMENTAL R ESULTS AND A NALYSISWe present and analyze our experimental results in the following subsections in order to answer the research questions mentioned in Table I.RQ1:Which clone types have a higher possibility of experi-encing bugﬁxing changes?Rationale.It is important to know which types of clones have a higher probability of experiencing bug-ﬁx changes compared to the others.The code clones exhibiting higher bug-proneness should be given higher priorities when making clone management decisions(such as refactoring and tracking). Refactoring or tracking of such clone fragments(i.e.,highly bug-prone clones)could help us minimize the probability of the occurrences of bugs or inconsistencies in these fragments in the future.In a previous study[36]we found Type1and Type2clones to be more unstable(i.e.,change-prone)than Type3clones.However,there is no empirical study on the correlation between change-proneness and bug-proneness of code clones.Thus,we should not infer the bug-proneness of clone types from their change-proneness.A comparative study on the bug-proneness of different types of code clones is important.We perform our investigations for answering RQ 1in the following two ways.•Investigation1:Investigation regarding the proportion of bug-ﬁx changes experienced by the code clones.•Investigation2:Investigation regarding the proportion of code clones experiencing bug-ﬁx changes. Investigation 1.Investigating what proportion of the changes that occurred to the clone fragments of different clone-types are related to a bug-ﬁx.Considering the code clones of a particular clone-type of a particular subject system,weﬁrst determine how many changes occurred to the code clones during the period of evolution(consisting of the revisions mentioned in Table II). Then we identify which of these changes were related to a bug-ﬁx.Finally,we calculate the percentage of changes related to a bug-ﬁx considering each clone-type of each of the candidate systems using the following equation.PCB=NBC∗100/TNC(1) TNC is the total number of changes that occurred to the code clones of a particular clone type of a particular subject system, NBC is the number of bug-ﬁx changes that occurred to those code clones,and lastly,PCB denotes the percentage of changes related to a bug-ﬁx with respect to all the changes(TNC)that occurred to those code clones.Table III shows the TNC and PCB for each clone-type of each of the subject systems.We also plot the percentages(PCB)in the graph of Fig.1to get a visual understanding regarding their comparison.From Fig.1we see that for six out of seven subject systems (i.e.,except Camellia)the percentage of bug-ﬁx changes is the lowest for the Type1case.For four systems(Ctags, Camellia,Freecol,and Carol)the percentage regarding the Type3case is the highest among the three cases(Type1, Type2,and Type3).For the remaining three systems,theTABLE IIIP ERCENTAGE OF CHANGES RELATED TO BUG -FIXType 1Type 2Type 3Systems TNC PCB TNC PCB TNC PCB Ctags 4010%8411.90%16114.29%Camellia 219.52%200%25914.67%BRL-Cad 3220.93%4119.51%2157.9%Freecol13420.89%12621.43%76630.42%jEdit 159425.91%14547.59%126543.08%Carol24514.69%27921.86%112323.15%Jabref 304 4.27%244 6.56%1164 6.44%PCB =Percentage of Changes related to a Bug-ﬁx.CtagsCamellia BRL-Cad FreecoljEditCarolJabrefOverallparison regarding the percentage of bug-ﬁx changes that occurred to the clone fragments.percentage regarding the Type 2case is the highest.The ﬁgure also shows the overall percentages (i.e.,measured over all the subject systems)for the three clone-types.We see that the percentage of bug-ﬁx changes is the highest in Type 3case.The overall percentages regarding the other two cases (Type 1,and Type 2)are almost the same.We calculate the overall percentages using the following equation.OP T ype i =100∗for all systems NBC T ype ifor all systems T NC T ype i (2)OP T ype i is the overall percentage of bug-ﬁx changes oc-curred to the T ype i clones.NBC T ype i is the number of bug-ﬁx changes to the T ype i clones of a particular subject system.T NC T ype i is the total number of changes that occurred to the T ype i clones of a subject system.Investigation 2.Investigating what proportion of the clone fragments in different clone-types are related to bug-ﬁx changes?We mentioned (in Section III)that we determine the ge-nealogies of the detected clone fragments.Considering each clone-type of each of the subject systems we determine how many clone genealogies were created during the evolution and how many of these experienced a bug-ﬁx.From these two values we determine the percentage of clone genealogies that experienced bug-ﬁxing changes using a similar equation to Eq.1.Table IV shows the total number of clone genealogies (the column TNCG )as well as the percentage of bug-ﬁx clone genealogies (the column PCGB )for each clone-type of each of the candidate systems.We also plot the percentages (PCGB )in the graph of Fig.2for easily understanding the comparison of bug-proneness among the three clone-types.The ﬁgure also shows the overall percentages of clone genealogies relatedTABLE IVP ERCENTAGE OF CLONES RELATED TO BUG -FIXType 1Type 2Type 3Systems TNCG PCGB TNCG PCGB TNCG PCGB Ctags 527.69%88 4.55%1559.03%Camellia 3000.67%480%177 6.21%BRL-Cad 136 2.2%287.14%1277.87%Freecol239 5.86%1627.41%75214.23%jEdit73980.99%399 5.01%2688 6.85%Carol4157.47%21115.17%68219.65%Jabref 483 1.66%228 6.14%1363 2.27%PCGB =Percentage of Clone Genealogies related to a Bug-ﬁx.5101520parison regarding the percentage of clone fragments that experi-enced bug-ﬁxing changes.bug-ﬁx for each clone-type.Overall percentages were calcu-lated using a similar equation to Eq.2.From Fig.2we see that for all of the subject systems except Jabref,the percentage of clones related to bug-ﬁx is the highest in the Type 3case.Also,the percentage of bug-ﬁx clones is the lowest in the Type 1case for most of the systems except Ctags,and Camellia.The overall percentages of the bug-ﬁx clones in the three clone-types provide such implications.Finally,the graph in Fig.2implies that Type 3clones generally have a much higher tendency of experiencing bug-ﬁxing changes compared to the clone fragments of the other two clone-types.Statistical Signiﬁcance Tests.We were also interested to investigate whether Type 3clones have a signiﬁcantly higher tendency of experiencing bug-ﬁxing changes compared to the clones of the other two types.We performed Mann-Whitney-Wilcoxon (MWW)tests [27]considering the percentages of the bug-ﬁx clone genealogies of the three cases (Type 1,Type 2,and Type 3)as recorded in Table IV.We ﬁrst determine whether the percentages regarding the Type 3case are signiﬁcantly higher than those of the Type 1case.Our MWW test result implies that the percentages regarding Type 3case are signiﬁcantly higher than the percentages regarding Type 1case with a p-value of 0.026(for two tailed test)which is less than 0.05.However,we observe that the percentages for the Type 3case are not signiﬁcantly higher than those of the Type 2case.The MWW test is non-parametric and does not require the samples to be normally distributed [26].This test can be applied to both small and large sample sizes [38].In our research,we perform this test considering a signiﬁcance level of 5%.Finally,it appears that the percentage of Type 3clones that experience bug-ﬁxing changes is signiﬁcantly higher than the percentage of bug-ﬁx clones in the Type 1case .Answer to RQ1.From our investigations we can state that while Type3clones have a higher bug-proneness compared to the other two clone-types in general,the bug-proneness of Type1clones is the lowest for most of our subject systems.Our statistical signiﬁcance test results indicate that Type3clones have a signiﬁcantly higher bug-proneness compared to Type 1clones.In general,the total number of Type3clones in a software system is higher compared to the other two clone-types as is evident in Table IV(except Camellia,jEdit,and BRL-Cad). Also,our investigation results indicate that Type3clones have the highest possibility of introducing bugs.Finally,our ﬁndings imply that possibly Type3clones should be managed (i.e.,refactored or tracked)with the highest priority.A possible reason behind why Type3clones exhibit the highest bug-proneness is that these are gapped clones(i.e., there are some non-clone lines in the Type3clone fragments). Thus,copy-pasting and consistently changing a Type3clone fragment is not as straight forward as in the cases of Type1 and Type2clones.Also,because of the gaps in the Type3 clones,refactoring of such clones might sometimes be difﬁcult, and it causes an increased number of Type3clones in the software systems(i.e.,as can be seen from our experimental results).Because of the existence of the gaps,possibly tracking is the best suitable management technique for Type3clones. RQ2:Do the clone fragments from the same clone class co-change(i.e.,change together)consistently during a bug-ﬁx? Rationale.From our answer to RQ1we understand that code clones of each clone-type have a tendency of experienc-ing bug-ﬁxing changes,and Type3clones have the highest tendency.However,it is also important to know whether two or more clone fragments from the same clone class co-changed (i.e.,changed together)consistently(i.e.,the clone fragments were modiﬁed in the same way)during bug-ﬁxes.Such clones are more important for clone management than those clones that did not experience consistent co-change during bug-ﬁxes for the following reasons.(1)If more than one clone fragments from the same clone class are changed together consistently during a bug-ﬁx,then it is an implication that those clone fragments contained the same bug andﬁxing of that bug required those clone fragments to be modiﬁed together consistently.Uniﬁcation of these clone frag-ments(i.e.,that co-changed consistently during bug-ﬁxes)into a single one through refactoring can possibly help usﬁx future bugs or inconsistencies with reduced effort,because in that case the bug-ﬁxing changes will require to be implemented in a single code fragment rather than implementing/propagating the same changes to multiple similar code fragments.(2)If only a single clone fragment from a particular clone class is modiﬁed forﬁxing a bug leaving the other fragments in that class as they are,then it is an implication that this particular clone fragment does not require to maintain consistency with the other clone fragments in its class,and it has a tendency of evolving independently.Such a fragment might not be regarded as a member of the class if it continues to evolve independently,and in that case it should not be considered for clone management.For this research question we investigate whether clone fragments from the same clone class have a tendency of co-changing consistently during a bug-ﬁx,and if so,how this tendency differs across the clone-types.The clone-type with a higher tendency should be given a higher priority when making clone management decisions.Methodology.In a previous study[33]we showed that if two or more clone fragments from the same clone class experience a similarity preserving co-change(we deﬁne it in the next paragraph)in a particular commit operation,then it is an implication that they co-changed consistently(i.e.,they were changed in the same way)in that commit.Considering this fact we answer this research question by automatically examining the bug-ﬁx commits and determining whether two or more clone fragments from the same clone class experi-enced similarity preserving co-change s in these commits.If such clone fragments really exist,then these should be given higher priorities for management as we have just discussed. Similarity Preserving Co-change.Let us consider that two code fragments CF1and CF2are clones of each other in revision R.A commit operation C was applied on this revision and both of these two code fragments were changed(i.e., the clone fragments were co-changed)in this commit.If in revision R+1(created because of the commit operation C) these two code fragments are again considered as clones of each other(i.e.,if they preserve their similarity),then we say that CF1and CF2experienced a similarity preserving co-change in the commit operation C.Considering each clone-type of each of the subject systems we determine which clone fragments experienced bug-ﬁx com-mits and which of these clone fragments received similarity preserving co-changes in the bug-ﬁx commits.Finally,we determine the percentage of clone fragments that received similarity preserving co-changes in the bug-ﬁx commits with respect to all clone fragments related to bug-ﬁx.Table V shows the total number of clones related to bug-ﬁx and the percentage of bug-ﬁx clones that experienced similarity preserving co-changes during bug-ﬁx commits.We also show these percentages in Fig.3to do a visual comparison of the percentages regarding different clone-types.From Fig.3we see that there are no vertical bars for Type 2and Type3cases of Ctags,and also,for Type2case of Camellia.The reason is that the number of bug-ﬁx clones that experienced similarity preserving co-changes is zero for each of these cases.This is also evident from Table V.From the overall percentages we see that bug-ﬁx clones of Type3 have the overall highest tendency of experiencing similarity preserving co-changes in the bug-ﬁx commits.The tendency for Type2case is also very near to that of the Type3 case.Bug-ﬁx clones of Type1have the lowest tendency of experiencing similarity preserving co-changes during bug-ﬁx. We also manually analyzed the similarity preserving co-changes that occurred to the bug-ﬁx clones of each clone-type of Freecol during the bug-ﬁx commits to see whether the clone。

从三价铬溶液电沉积非晶Cr-C镀层及其性能研究

从三价铬溶液电沉积非晶Cr-C镀层及其性能研究范文俊，崔红兵，王萌，王新东（北京科技大学物理化学系，北京100083）摘要：以316L不锈钢为基体，在不同沉积电流密度下制备了非晶Cr-C镀层，研究了沉积电流密度对镀层表面形貌、化学组成、耐腐蚀性以及表面疏水性的影响。

结果表明，随着电流密度增大，镀层C含量减少，表面缺陷增多，耐腐蚀性下降，疏水性降低。

在20A/dm2电流密度下制备的Cr-C镀层表面平整无缺陷，含碳量最高，耐腐蚀性最强，对应腐蚀电流密度为5×10-9A/dm2，表面疏水性也最强。

关键词：电镀；三价铬溶液；Cr-C镀层；耐腐蚀性中图分类号：TQ153.1文献标识码：APreparation and Performance Study of Amorphous Cr-C Coating Electrodeposited from Trivalent Chromium Solution FAN Wenjun，CUI Hongbing，WANG Meng，WANG Xindong（Department of Physical Chemistry，University of Science and Technology Beijing，Beijing100083，China）Abstract：The amorphous Cr-C coatings were prepared under different deposition current densities on the substrate of316L stainless steel，and the effects of deposition current density on the surface morphol⁃ogy，chemical composition，corrosion resistance and surface hydrophobicity of the coating were studied. The results showed that the C content of the coating decreased as the current density increased，as well as the surface defects increased，the corrosion resistance decreased，and the hydrophobicity decreased. The Cr-C coating prepared at a current density of20A/dm2showed a smooth surface without defects，the highest carbon content，the best corrosion resistance with the corrosion current density of5×10-9 A/dm2，and the strongest surface hydrophobicity.Keywords：electroplating；trivalent chromiun solution；Cr-C coating；corrosion resistance电镀铬层由于其良好的机械性能，在精密机械零件领域得到了普遍应用，如模具、医用手术器械等。

A comparative structural and electrochemical study of

A comparative structural and electrochemical study ofmonoclinic Li3Fe2(PO4)3and Li3V2(PO4)3Se´bastien Patoux a,Ca˘lin Wurm a,Mathieu Morcrette a,Gwenae¨lle Rousse b,Christian Masquelier a,*a Laboratoire de Re´activite´et de Chimie des Solides,CNRS UMR6007,Universite´de Picardie Jules Verne,33rue Saint-Leu,80039Amiens Cedex,Franceb Institut Laue Langevin,BP156,F-38042Grenoble Cedex9,FranceAbstractPure monoclinic Li3M2(PO4)3(M:Fe,V)powders(<1m m in diameter)were obtained by an original route that involved initial homogenization of precursors in aqueous solution followed by slow evaporation and annealing under controlled atmosphere at moderate temperatures.The crystal structure of Li3V2(PO4)3was determined for theﬁrst time through Rietveld reﬁnements of neutron diffraction data. As for Li3Fe2(PO4)3,Li is distributed within three crystallographic sites,fully occupied at room temperature.The values of the temperature factors on Li(2)and Li(3)sites(ﬁve-fold coordination)were found signiﬁcantly higher than that of Li(1)(four-fold coordination). Li3V2(PO4)3shows four reversible redox phenomena upon insertion of two Liþ(V3þ/V2þcouple),at1.98,1.88,1.73and1.70V vs. Li.By comparison,Li3Fe2(PO4)3shows two reversible redox phenomena upon insertion of two Liþ(Fe3þ/Fe2þcouple),at2.88and2.73V vs. Li.Experimental capacities close to the theoretical ones were obtained after optimal composite electrode preparation through ball-milling.In situ X-ray diffraction showed very minor changes from Li3M2(PO4)3to Li5M2(PO4)3.Additionally,Li is extracted from Li3V2(PO4)3towards V2(PO4)3(V4þ/V3þand V5þ/V4þcouples)through four redox phenomena at3.59,3.67,4.06and4.35V vs.Li.Despite all these phase transitions,the[M2(PO4)3]framework is remarkably stable on cycling,particularly for M:Fe,while partial vanadium dissolution into the electrolyte occurs either on deep reduction to1.5V or deep oxidation to4.6V vs.Li.#2003Elsevier Science B.V.All rights reserved.Keywords:Structural study;Monoclinic;Crystallographic1.IntroductionRecently,polyanion3-D structures built of PO4tetrahedra and FeO6octahedra have engendered much interest for their potential use as cheap positive electrodes for lithium rechargeable batteries[1].Efforts towards this relatively novel class of intercalation hosts for lithium have focused on systems such as the olivine Li1Àx FePO4[2,3]and NASICON compositions Li x Fe2(SO4)3[4]or Li3þx Fe2(PO4)3[5,6]into which reduction/oxidation of Fe3þ/Fe2þoccurs at potentials close to3.43,3.55and2.8V vs.Li/Liþ,respectively.For applications,the material of choice of the so-called poly-anionic structures is with no doubt the olivine LiFePO4that, since the pioneering discovery of Padhi et al.[2]has gained much interest[7–9].Recent optimization of LiFePO4has focused on:(i)increasing the electronic conductivity of composite electrodes through carbon coating on the active material particles[7,8];and(ii)lowering the synthesis temperature to$4008C with the use of strongly reactive iron oxalate under N2[9].LiFePO4stands as a serious candidate for the next generation of Li-based polymer or Li-ion batteries.Materials of general composition A x MM’(PO4)3(A:Li, Na,...;M and M0:transition metal element)adopt either the ‘‘A’’-form or‘‘B’’-form(NASICON)that differ in the3-D connectivity between MM0(PO4)3units.Among this very rich family of compositions and crystal structures,the NASICON Li3Fe2(PO4)3[5,6],LiTi2(PO4)3[10]and Li3V2(PO4)3[11,12]were shown to react electrochemically with lithium at2.8,2.5and3.7V vs.Liþ/Li,for the Fe3þ/2þ, Ti4þ/3þand V3þ/4þcouples,respectively.Delmas and co-workers were theﬁrst to demonstrate nice reversibility through a two-phase process between LiTi2(PO4)3and Li3Ti2(PO4)3(138mAh/g)[10]but the practical use of these materials was still under question,due to their low intrinsic electronic conductivity.We recently paid particular atten-tion to circumvent this handicap and reported[13,24]thatJournal of Power Sources119–121(2003)278–284*Corresponding author.E-mail address:christian.masquelier@sc.u-picardie.fr(C.Masquelier).0378-7753/03/$–see front matter#2003Elsevier Science B.V.All rights reserved.doi:10.1016/S0378-7753(03)00150-2energetic ball-milling of Fe(III)-containing phosphates with conductive carbon(carbon SP or acetylene black)resulted in a very signiﬁcant improvement of their electrochemical performances.Lithium extraction out of the monoclinic form of Li3V2(PO4)3(anti-NASICON)has been demonstrated by Barker and Saidi[14]and Sato et al.[15].More recently, promising behaviour was reported by Saı¨di et al.[16]and Nazar et al.[17–19]in the course of our study.Our study aims to compare the electrochemical and structural behaviour of isotypical iron and vanadium phosphates upon lithium inser-tion and/or extraction.We will show,after a detailed exam-ination of the crystal structures of monoclinic Li3Fe2(PO4)3 and Li3V2(PO4)3(determined from powder neutron diffrac-tion data)that,despite an impressive number of phase transi-tions,very minor structural changes occur over a wide range of lithium contents into the M2(PO4)3framework.While Fe(III)can only be reduced to Fe(II)(Li3þx Fe2(PO4)3), V(III)can be either oxidized to V(IV)(Li3Àx V2(PO4)3)or reduced to V(II)(Li3þx V2(PO4)3).Similar comparisons were recently reported[20]for Li1Æx MP2O7(M(III)¼Fe,V). 2.ExperimentalPure A-Li3M2(PO4)3(M:Fe,V)powders were obtained by an original route that involved initial homogenization of precursors in aqueous solution(1mol/l)followed by slow evaporation of H2O at1008C and volatile species at3008C under air and further annealing(400–8008C)of the resulting solid until crystallization.Stoichiometric amounts of Fe(NO3)3Á9H2O and LiH2PO4were mixed in the case of Li3Fe2(PO4)3.Stoichiometric amounts of NH4VO3(V(V)) and LiH2PO4were mixed in the case of Li3V2(PO4)3.In this case,the annealing was conducted up to7508C(12h)under a gasﬂow of N2/H2(10%)to achieve reduction of V(V)to V(III).Note that for both compounds,the initial mixing of precursors in solution was essential to favour lower synthesis temperatures that resulted in smaller particle sizes(spheri-cal,less than1m m in diameter)than by direct solid state synthesis(particle sizes>50m m).The crystal structure of A-Li3V2(PO4)3was solved from room temperature powder diffraction data recorded on the high resolution neutron powder diffractometer D1A (l¼1:9104A˚)at ILL-Grenoble(France).The crystal struc-ture of A-Li3Fe2(PO4)3was determined from room tem-perature powder diffraction data recorded on the neutron multicounters powder diffractometer G4.2(l¼2:3433A˚) at LLB of Saclay(France).Both structures were obtained from Rietveld reﬁnements[21]using the program Fullprof [22]from an initial set of atomic coordinates of Li3Fe2(PO4)3previously determined from single-crystal diffraction data[23].Differential scanning calorimetry mea-surements(DSC)were performed on a Mettler DSC25 device driven by the interface TC11,with a heating rate of 10K/min.The electrochemical tests were performed in standard Swagelok TM cells with a lithium foil at the negative elec-trode and A-Li3M2(PO4)3(M:Fe,V)/carbon composites at the positive electrode.A Whatman GF/D borosilicate glass ﬁber sheet saturated with a1M LiPF6electrolyte solution in 1:1(w/w)of dimethyl carbonate/ethylene carbonate con-stitutes the separator member.The active material powders were mechanically ball-milled with Super P carbon(SP, MMM Carbon,Belgium)in the proportions200/40mg (16.67%of carbon)in a stainless steel container using a SPEX8000mixer to generate sufﬁcient impacts/shocks [24].A MacPile automatic cycling/data recording system (Biologic SA,Claix,France)operating in galvanostatic mode at C/10regime,was used for the electrochemical data recording.For in situ X-ray diffraction,a modiﬁed Swage-lok-type was mounted,horizontally,on a D8Bruker dif-fractometer(Co K a radiation,y–y geometry,PSD counter) and monitored by a MacPile system in a galvanostatic intermittent titration technique(GITT)mode at C/20regime (1h)with open circuit(1h)to collect the X-ray data.3.Results and discussions3.1.Crystal structures at room temperatureFor both Li3Fe2(PO4)3and Li3V2(PO4)3,lithium order-ing at room temperature over three crystallographic sites generates a slight monoclinic distortion[23]that cannot be well spotted by standard X-ray diffraction nor low-resolu-tion neutron plementary synchrotron X-ray diffraction experiments were carried out at LURE (Orsay)to conﬁrm the purity of Li3Fe2(PO4)3[24]and Li3V2(PO4)3.Similarly to the iron counterpart[23], Li3V2(PO4)3presents a monoclinic distortion of the classic orthorhombic cell at room temperature(Fig.1).We con-ﬁrmed by differential scanning calorimetry and tempera-ture-controlled X-ray diffraction the sequences of a ðmonoclinicÞ$bðorthorhombicÞ$g(orthorhombic) phase transitions due to lithium disordering between room temperature and573K.Note that under air,Li3V2(PO4)3is not stable above800K,at which temperature oxidation of V(III)takes place.The Rietveld reﬁnements of the neutron diffraction patterns of A-Li3Fe2(PO4)3and A-Li3V2(PO4)3,recorded at room temperature(a-forms),are presented in Fig.2.The space group P21/n(ﬁrst setting,binary axis c)was preferred rather than P21/c(binary axis b)in order to keep the same setting as that of the original paper of Bykov[23].A-Li3Fe2(PO4)3 (a¼8:571(1)A˚,b¼12:017(1)A˚,c¼8:616(1)A˚,g¼90:52(1)8,V¼887(1)A˚3)and A-Li3V2(PO4)3(a¼8:605-(1)A˚,b¼12:038(1)A˚,c¼8:591(1)A˚,g¼90:60(1) V¼890(1)A˚3)are isostructural with the monoclinic form of Fe2(SO4)3with Z¼4[25].Satisfactory conventional R-factors were obtained R wp¼3:69%and R B¼3:76%for A-Li3Fe2(PO4)3,whereas R wp¼7:08%and R B¼7:97%S.Patoux et al./Journal of Power Sources119–121(2003)278–284279for A-Li 3V 2(PO 4)3.Hence,less accuracy was obtained for A-Li 3V 2(PO 4)3as vanadium is essentially transparent to neutron radiation.However,all the bond-strengths and polyhedra distortions for both compounds are in perfect accordance with the formula of Zachariasen [26,27].All the 20independent atoms of the unit cell are in general position 4e (Table 1).The transition element M (M:Fe or V)is distributed over two independent positions.At room temperature,lithium ions fully occupy three distinct sites,two of them being in ﬁve-fold coordination (Li(2)and Li(3)),whereas Li(1)is in four-fold coordination.The peculiar distribution of lithium ions within the framework is worth of consideration as they are located within (a ,c )‘‘conduction planes ’’(Fig.3)that generate strong anisotropy in ionic conduction.More interestingly,even is the fact that for both compounds,the re ﬁned temperature factors on Li(2)and Li(3)sites (ﬁve-fold coordination)are signi ﬁcantly higher than that of Li(1),which indicates that ionic con-duction is likely to occur mainly along [001].To further support this point,during the order –disorder a !b !g transitions,only the Li(2)and Li(3)sites are involved,their occupancy factors becoming fractionate.As discussed else-where [28],these observations are of importance for a good understanding of the complex phase transitions that occur during lithium extraction from Li 3V 2(PO 4)3.3.2.Insertion of lithium between 3.0and 1.0V vs.Li Lithium insertion is possible into both A-Li 3M 2(PO 4)3(M:Fe,V)compounds.Experimental galvanostaticandFig.1.X-ray diffraction pattern (exp.)of the room temperature form of A-Li 3V 2(PO 4)3recorded from a synchrotron radiation with l ¼0:9616A˚.The experimental pattern is compared with two simulated patterns (simul.)calculated in monoclinic P 21/n or orthorhombic Pcan spacegroup.Fig.2.Neutron diffraction Rietveld profiles of the experimental (circles)and calculated (full lines)patterns for (a)A-Li 3Fe 2(PO 4)3and (b)A-Li 3V 2(PO 4)3.The vertical lines indicate the possible Bragg positions.Differences between experimental and calculated patterns are also drawnbelow.Fig.3.Projection on the (a ,c )plane of the lithium ions distribution in A-Li 3M 2(PO 4)3(M:Fe,V).Segments are drawn between neighboring Li positions to indicate possible conduction pathways.280S.Patoux et al./Journal of Power Sources 119–121(2003)278–284derivative curves are plotted in plete lithium insertion leads to compositions close to Li5M2(PO4)3in which Fe or V are reduced to M(II).Both compounds show, atﬁrst sight,similar electrochemical behaviour on reduction with the existence of a well-deﬁned intermediate composi-tion Li4M2(PO4)3.It is remarkable to note that the1V difference between the average positions of Fe3þ/Fe2þand V3þ/V2þredox couples is the same as that observed for these two couples in Li1þx FeP2O7and Li1þx VP2O7[20] and also the same as that established in aqueous solution. From PITT measurements,we indicated recently[24] that lithium insertion within the two-phase domains Li3Fe2-(PO4)3–Li4Fe2(PO4)3(2.88V vs.Li)and Li4Fe2(PO4)3–Li5Fe2(PO4)3(2.73V vs.Li)was kinetically limited more by electron or ion transport within each phase rather than from phase front migration.The existence of an intermedi-ate phase Li4Fe2(PO4)3results probably from lithium inser-tion into a given new crystallographic site that generates local reduction of the nearest Fe positions.A close exam-ination of the relative positions of MO6octahedra within the structure besides the interstitial space available for Li insertion does not favour the M(1)nor the M(2)site to be reducedﬁrst between Li3Fe2(PO4)3and Li4Fe2(PO4)3. Hence,we believe that a new lithium distribution occurs within the interstitial space for Li4Fe2(PO4)3which does not necessarily generate Fe3þ/Fe2þcharge ordering.This is supported by the experimental data of Manthiram[29]on lithium insertion into monoclinic Fe2(SO4)3:there is,in this case,only one intercalation plateau(at 3.6V vs.Li) between Fe2(SO4)3and Li2Fe2(SO4)3,even though iron isTable1Atomic coordinates and isotropic displacement factors obtained by Rietveld refinements of neutron diffraction data for A-Li3Fe2(PO4)3(normal)and A-Li3V2(PO4)3(bold)Atoms Sites Wyckoff positions B iso(A˚2)Occupancy M1(Fe)4e0.2462(5)0.1079(3)0.4619(4)0.26(7)1M1(V)0.2461a0.1072a0.4606a0.61a1M2(Fe)4e0.7541(2)0.3950(3)0.4708(4)0.22(7)1M2(V)0.7534a0.3943a0.4703a0.59a1P14e0.1030(9)0.1484(5)0.1069(8)0.9(2)10.1068(9)0.1489(8)0.1014(11) 1.4(2)1P24e0.60393(9)0.3495(6)0.1160(8)0.6(1)10.6004(9)0.3493(7)0.1164(11) 1.5(2)1P34e0.0359(7)0.4932(6)0.2512(11) 1.0(1)10.0349(9)0.4924(7)0.2474(12) 1.1(2)1O14e0.4292(7)0.3309(5)0.0885(7)0.9(1)10.4257(9)0.3305(6)0.0915(9) 1.5(2)1O24e0.9237(7)0.1497(5)0.1151(7)0.6(1)10.9262(9)0.1471(6)0.1108(10) 1.3(2)1O34e0.3527(7)0.2620(5)0.4806(7)0.6(1)10.3547(8)0.2607(6)0.4799(8) 1.2(2)1O44e0.8022(7)0.2193(5)0.4972(64)0.3(2)10.8041(9)0.2185(7)0.4952(9) 1.5(2)1O54e0.1669(8)0.0389(5)0.0580(7) 1.4(1)10.1727(10)0.0394(7)0.0518(8) 1.6(2)1O64e0.6455(7)0.4713(5)0.0920(7)0.8(1)10.6435(9)0.4747(6)0.0883(9) 1.2(2)1O74e0.4507(7)0.0689(4)0.3678(8)0.4(1)10.4500(8)0.0667(5)0.3688(9)0.9(2)1O84e0.9273(8)0.4037(5)0.3132(7)0.6(1)10.9277(9)0.4033(6)0.3196(9) 1.0(2)1O94e0.1709(6)0.4317(4)0.1710(7)0.4(1)10.1697(9)0.4291(6)0.1697(9) 1.4(2)1O104e0.5979(7)0.0701(4)0.1273(8)0.6(1)10.6098(9)0.0750(6)0.1346(10) 1.6(2)1O114e0.1635(6)0.1868(5)0.2636(7)0.3(2)10.1660(9)0.1862(7)0.2670(9) 1.5(2)1O124e0.6374(7)0.3168(5)0.2868(8) 1.0(1)10.6399(9)0.3176(6)0.2868(9) 1.1(2)1Li14e0.288(2)0.320(2)0.275(2)0.1(4)10.292(3)0.328(2)0.298(2)0.5(4)1Li24e0.571(2)0.202(2)0.419(2) 1.4(5)10.571(3)0.195(2)0.421(3) 2.9(6)1Li34e0.901(3)0.243(2)0.291(3) 5.2(7)10.911(4)0.233(3)0.305(4) 4.7(8)1a Due to the‘‘transparency’’of vanadium in neutron diffraction,these parameters must be refined one by one,and cannot be incorporated in the final refinement.S.Patoux et al./Journal of Power Sources119–121(2003)278–284281distributed over two distinct crystallographic sites.Despite the phase transition at x ¼1,optimized electrodes of Li 3þx Fe 2(PO 4)3cycle remarkably well in the potential range 3.5–2.0V for 0 x 1:8(320Wh/kg for a mean voltage of 2.75V)as can be seen in Fig.5.In situ X-ray diffraction experiments [30]con ﬁrmed the existence of two two-phase domains and revealed only very minor,and reversible,changes in the framework over a whole dis-charge/charge cycle.As for A-Li 3Fe 2(PO 4)3,lithium may be inserted into A-Li 3V 2(PO 4)3according to,at ﬁrst sight,a similar mechan-ism:two main intercalation plateaus at 1.86and 1.73V vs.Li are distinguished.More careful experiments than those recently reported by Sato [31]reveal though that there are actually four distinct phenomena at 1.98,1.86,1.73and 1.70V vs.Li (Fig.4),each of them corresponding roughly to 0.5electrons exchanged per formula unit.The theore-tical capacity was achieved experimentally,with the com-plete reduction of the V 3þions into V 2þions.There is however a rapid capacity fade on cycling due to vanadium dissolution into the electrolyte,as already mentioned for LiVP 2O 7[20].In situ X-ray diffraction (Fig.5)shows a very similar behaviour for both compositions,the framework being maintained throughout the whole insertion range.As a number of diffraction peaks of the monoclinic P 21/n unit cell overlap,satisfactory re ﬁnement of the lattice para-meters of the intermediate composition Li 4M 2(PO 4)3and of the ﬁnal composition Li 5M 2(PO 4)3was dif ﬁcult.We found however very similar trends for both compounds between the two de ﬁnite compositions Li 3M 2(PO 4)3and Li 4M 2(PO 4)3:contraction along [100](À1.5%),Fig.4.Left part:charge-discharge and discharge –charge profiles of A-Li 3Fe 2(PO 4)3and A-Li 3V 2(PO 4)3recorded under galvanostatic conditions (C /10)in the 1.50–4.65V range vs.Li þ/Li.Right part:derivative curves of potentiodynamic intermitent titration technique (PITT)data (10mV steps for t max ¼1h,I min equivalent to C/20).Fig.5.In situ X-ray diffraction recorded during Li insertion in GITT mode into (a)Li 3Fe 2(PO 4)3and (b)Li 3V 2(PO 4)3.Diffractometer D8Bruker,Co K a ,y –y geometry,PSD counter.282S.Patoux et al./Journal of Power Sources 119–121(2003)278–284elongation along[010]and[001](þ1.6andþ1.5%, respectively)and increase of the monoclinic distortion to91.18.This represents only a minor global volume change and accounts for the nice reversibility of the system.3.3.Extraction of lithium between3.0and4.65V vs.LiIn this region of potentials,only Li3V2(PO4)3is of interest as Fe3þcannot be oxidized to Fe4þbelow5V vs.Liþ/Li. The oxidation of V3þto V4þby lithium extraction out of monoclinic Li3V2(PO4)3was reported by Nanjundaswamy [32]and Sato[33]and more recently by Barker[14,16]and Nazar[17].On the other hand,successful attempts to prepare the NASICON form of Li3V2(PO4)3by ion exchange from the sodium analogue Na3V2(PO4)3allowed to identify an interesting Li-extraction plateau at3.77V vs. Li for the V3þ/V4þredox couple[12].Contrary to Sato et al.[33],we found that there was no need to dope monoclinic Li3V2(PO4)3with zirconium to get nice reversibility of this material upon oxidation.Only careful electrode preparation(intimate mixing with conduc-tive carbon)is needed to fully oxidize V3þinto V4þfrom the pristine Li3V2(PO4)3to the Li-extracted LiV2(PO4)3(Fig.4) which corresponds to an energy density of$500Wh/g.Our results are extremely similar to those reported recently [16,17]:three reversible voltage plateaus at3.59,3.67and 4.06V vs.Li are clearly distinguished,stressing the exis-tence of Li2.5V2(PO4)3,Li2V2(PO4)3and LiV2(PO4)3com-positions as intermediate phases.Note that even under C/5 charge and discharge rates,very small polarization of the cell was observed.The nature of the intermediate phases has been addressed elsewhere by means of ex situ neutron diffraction[17]or in situ X-ray diffraction[28].As we mentioned earlier in this paper,the greater mobility of lithium on Li(3)sites(ﬁve-fold coordination)probably favors this site to be emptiedﬁrst during oxidation.If so, from the examination of Li–vanadium nearest environments(d Li(1)–V(1)¼ 2.95A˚,d Li(2)–V(2)¼ 2.90A˚,d Li(3)–V(2)¼2.73A˚)this would be associated with oxidation of vanadium on the V(2)siteﬁrst.In the same way,the very low mobility of lithium on Li(1)sites(four-fold coordination)is a good indication that this site is probably the remaining one occupied at the intermediate composition LiV2(PO4)3. Between Li3V2(PO4)3and LiV2(PO4)3,the volume of the monoclinic unit cell was found to decrease from890to 824A˚3as a result of oxidation of V3þto V4þ.It is interesting to note then that despite this rather big unit cell contraction (D V=V¼À7:4%)the overall Li3V2(PO4)3–LiV2(PO4)3is highly reversible as only13%of the capacity was lost after 100cycles at room temperature at C/10,between3.0and4.2V vs.Li(Fig.6).Additional cycling tests within nar-rower voltage windows(3.0–3.5V;ﬁrst two plateaus,1eÀexchanged and3.9–4.2V;third plateau,1eÀexchanged) lead to a similar stability.On increasing the upper cut-off voltage to4.65V vs.Li, LiV2(PO4)3may be further oxidized to$V2(PO4)3which leads to a speciﬁc capacity of197mAh/g.Fig.4shows a dissymmetry between the shapes of the charge and discharge galvanostatic curves.The fourth oxidation peak at4.35V (stronger polarization of the cell for this step)presents on discharge a large hysteresis that is hidden within theﬁrst broad reduction peak on discharge between4.0and3.8V. There is no structural irreversibility even on extracting lithium to V2(PO4)3as indicated by:(i)the four plateaus on charge are still observed on extensive cycling;and(ii)in situ X-ray diffraction[28]showed that the pattern of Li3V2(PO4)3after a full cycle is the same as that of the pristine compound.Fig.6shows however a more rapid decay of the capacity on cycling than when the upper voltage cut-off is limited to4.2V.As mentioned for Li1Àx VP2O7 [20],progressive dissolution of vanadium in the electrolyte and/or electrolyte decomposition at high voltage may be at the origin of this phenomenon.Note that upon oxidation from LiV2(PO4)3to V2(PO4)3,we observed a unit cell expansion from824to835A˚3.Chemical extraction of lithium(using NO2BF4in acet-onitrile for7days under stirring)out of monoclinic Li3V2(PO4)3allowed preparation of V2(PO4)3with no lithium residue(conﬁrmed by chemical analysis).A similar experiment had already been reported by Gopalakrishnan et al.[34]to prepare the NASICON form of V2(PO4)3by Fig.6.Evolution of specific capacities under a C/10cycling regime at ‘‘high’’potential(HP)for A-Li3V2(PO4)3,using different cut-off voltages, and at low potential(LP)for both A-Li3Fe2(PO4)3and A-Li3V2(PO4)3(full symbols:on discharge;opened symbols:on charge).S.Patoux et al./Journal of Power Sources119–121(2003)278–284283sodium extraction out of Na3V2(PO4)3(in this case,Cl2in CHCl3was used).The obtained V2(PO4)3was placed in an air-free cell for X-ray diffraction and indexed to a mono-clinic unit cell in the same space group(P21/n)as that of Li3V2(PO4)3.The overall unit cell contraction found is of D V=V¼À6%,with the in situ X-ray diffraction data (À6.2%)and in good agreement with the results of Nazar et al.(À6.6%)[17].4.ConclusionA-Li3V2(PO4)3and A-Li3Fe2(PO4)3are two interesting positive electrode materials for lithium and lithium-ion batteries.In A-Li x V2(PO4)3(0x5),we highlighted the presence of eight(4þ4)two-phase domains in the 1.0–4.65V vs.Liþ/Li range.The Li3V2(PO4)3–LiV2(PO4)3 reaction,which corresponds to the exchange of one electron per V and the complete oxidation of V3þinto V4þ,is nicely reversible with a good capacity retention($130mAh/g)in cycling,at a mean potential of3.86V thus giving an energy density of$500Wh/kg.Such a material,with a cheaper transition metal element,could almost approach the perfor-mances of LiCoO2.The use of the third electron,conducting to A-V2(PO4)3,would increase these numbers,but the cycling behaviour is not optimized yet.A-Li3Fe2(PO4)3, which is only active for lithium insertion,can reversibly exchange two electrons at$2.75V vs.Liþ/Li($350Wh/ kg)onto two distinct plateaus,both corresponding to the reduction of the Fe3þions into Fe2þfor A-Li5Fe2(PO4)3. 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