中文 外文文献翻译 毕业设计说明

金融体制、融资约束与投资——来自OECD的实证分析R．SemenovDepartment of Economics，University of Nijmegen，Nijmegen（荷兰内梅亨大学，经济学院）这篇论文考查了OECD的11个国家中现金流量对企业投资的影响.我们发现不同国家之间投资对企业内部可获取资金的敏感性具有显著差异,并且银企之间具有明显的紧密关系的国家的敏感性比银企之间具有公平关系的国家的低.同时，我们发现融资约束与整体金融发展指标不存在关系.我们的结论与资本市场信息和激励问题对企业投资具有重要作用这种观点一致，并且紧密的银企关系会减少这些问题从而增加企业获取外部融资的渠道。

一、引言各个国家的企业在显著不同的金融体制下运行。

金融发展水平的差别(例如，相对GDP的信用额度和相对GDP的相应股票市场的资本化程度），在所有者和管理者关系、企业和债权人的模式中，企业控制的市场活动水平可以很好地被记录.在完美资本市场,对于具有正的净现值投资机会的企业将一直获得资金。

然而，经济理论表明市场摩擦，诸如信息不对称和激励问题会使获得外部资本更加昂贵，并且具有盈利投资机会的企业不一定能够获取所需资本.这表明融资要素，例如内部产生资金数量、新债务和权益的可得性，共同决定了企业的投资决策.现今已经有大量考查外部资金可得性对投资决策的影响的实证资料（可参考，例如Fazzari（1998）、 Hoshi(1991)、 Chapman（1996）、Samuel(1998））.大多数研究结果表明金融变量例如现金流量有助于解释企业的投资水平。

这项研究结果解释表明企业投资受限于外部资金的可得性。

很多模型强调运行正常的金融中介和金融市场有助于改善信息不对称和交易成本，减缓不对称问题,从而促使储蓄资金投着长期和高回报的项目,并且提高资源的有效配置（参看Levine（1997)的评论文章）。

因而我们预期用于更加发达的金融体制的国家的企业将更容易获得外部融资.几位学者已经指出建立企业和金融中介机构可进一步缓解金融市场摩擦。

外文文献翻译的撰写说明
一、外文文献翻译的内容
通过外文文献查阅与翻译，进一步提高掌握使用外文的能力，熟悉本专业的主要的外文书刊，了解毕业设计（论文）课题的国内外信息与发展动向。

翻译的外文文献应主要选自学术期刊、学术会议的文章、有关著作及其他相关材料，应与毕业设计（论文）主题相关，并作为外文参考文献列入毕业设计（论文）的参考文献，中文译文后应附外文原文。

（一）标题应真实反映翻译外文的主体内容或原外文标题内容，一般控制在20个汉字以内。

可以用副标题对标题予以补充说明；
（二）标题下方正中为外文作者署名；
（三）外文翻译成中文的内容；
（四）外文著录。

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四、参考文献著录
参考文献著录按照GB7714-87文参考文献著录规则执行。

书写顺序为：序号.作者.论文名或著作名.杂志或会议名.卷号、期号或会议地点.出版社.页号.年。

毕业设计(论文）外文文献翻译院系：财务与会计学院年级专业：201＊级财务管理姓名:学号：132148*＊*附件: 财务风险管理【Abstract】Although financial risk has increased significantly in recent years risk and risk management are not contemporary issues。

The result of increasingly global markets is that risk may originate with events thousands of miles away that have nothing to do with the domestic market。

Information is available instantaneously which means that change and subsequent market reactions occur very quickly。

The economic climate and markets can be affected very quickly by changes in exchange rates interest rates and commodity prices。

Counterparties can rapidly become problematic。

As a result it is important to ensure financial risks are identified and managed appropriately. Preparation is a key component of risk management。

【Key Words】Financial risk，Risk management，YieldsI. Financial risks arising1.1What Is Risk1.1.1The concept of riskRisk provides the basis for opportunity. The terms risk and exposure have subtle differences in their meaning. Risk refers to the probability of loss while exposure is the possibility of loss although they are often used interchangeably。

建筑学Modern-Architecture现代建筑⼤学毕业论⽂外⽂⽂献翻译及原⽂毕业设计（论⽂）外⽂⽂献翻译⽂献、资料中⽂题⽬：现代建筑⽂献、资料英⽂题⽬：Modern Architecture⽂献、资料来源：⽂献、资料发表（出版）⽇期：院（部）：专业：班级：姓名：学号：指导教师：翻译⽇期： 2017.02.14建筑学毕业设计的外⽂⽂献及译⽂⽂献、资料题⽬：《Advanced Encryption Standard》⽂献、资料发表（出版）⽇期：2004.10.25外⽂⽂献：Modern ArchitectureModern architecture, not to be confused with 'contemporary architecture', is a term given to a number of building styles with similar characteristics, primarily the simplification of form and the elimination of ornament. While the style was conceived early in the 20th century and heavily promoted by a few architects, architectural educators and exhibits, very few Modern buildings were built in the first half of the century. For three decades after the Second World War, however, it became the dominant architectural style for institutional and corporate building.1. OriginsSome historians see the evolution of Modern architecture as a social matter, closely tied to the project of Modernity and hence to the Enlightenment, a result of social and political revolutions.Others see Modern architecture as primarily driven by technological and engineering developments, and it is true that the availability of new building materials such as iron, steel, concrete and glass drove the invention of new building techniques as part of the Industrial Revolution. In 1796, Shrewsbury mill owner Charles Bage first used his ‘fireproof’ design, which relied on cast iron and brick with flag stone floors. Such construction greatly strengthened the structure of mills, which enabled them to accommodate much bigger machines. Due to poor knowledge of iron's properties as a construction material, a number of early mills collapsed. It was not until the early 1830s that Eaton Hodgkinson introduced the section beam, leading to widespread use of iron construction, this kind of austere industrial architecture utterly transformed the landscape of northern Britain, leading to the description, "Dark satanic mills" of places like Manchester and parts of West Yorkshire. The Crystal Palace by Joseph Paxton at the Great Exhibition of 1851 was an early example of iron and glass construction; possibly the best example is the development of the tall steel skyscraper in Chicago around 1890 by William Le Baron Jenney and Louis Sullivan. Early structures to employ concrete as the chief means of architectural expression (rather than for purely utilitarian structure) include Frank Lloyd Wright's Unity Temple, built in 1906 near Chicago, and Rudolf Steiner's Second Goetheanum, built from1926 near Basel, Switzerland.Other historians regard Modernism as a matter of taste, a reaction against eclecticism and the lavish stylistic excesses of Victorian Era and Edwardian Art Nouveau.Whatever the cause, around 1900 a number of architects around the world began developing new architectural solutions to integrate traditional precedents (Gothic, for instance) with new technological possibilities. The work of Louis Sullivan and Frank Lloyd Wright in Chicago, Victor Horta in Brussels, Antoni Gaudi in Barcelona, Otto Wagner in Vienna and Charles Rennie Mackintosh in Glasgow, among many others, can be seen as a common struggle between old and new.2. Modernism as Dominant StyleBy the 1920s the most important figures in Modern architecture had established their reputations. The big three are commonly recognized as Le Corbusier in France, and Ludwig Mies van der Rohe and Walter Gropius in Germany. Mies van der Rohe and Gropius were both directors of the Bauhaus, one of a number of European schools and associations concerned with reconciling craft tradition and industrial technology.Frank Lloyd Wright's career parallels and influences the work of the European modernists, particularly via the Wasmuth Portfolio, but he refused to be categorized with them. Wright was a major influence on both Gropius and van der Rohe, however, as well as on the whole of organic architecture.In 1932 came the important MOMA exhibition, the International Exhibition of Modern Architecture, curated by Philip Johnson. Johnson and collaborator Henry-Russell Hitchcock drew together many distinct threads and trends, identified them as stylistically similar and having a common purpose, and consolidated them into the International Style.This was an important turning point. With World War II the important figures of the Bauhaus fled to the United States, to Chicago, to the Harvard Graduate School of Design, and to Black Mountain College. While Modern architectural design never became a dominant style in single-dwelling residential buildings, in institutional and commercial architecture Modernism became the pre-eminent, and in the schools (for leaders of the profession) the only acceptable, design solution from about 1932 to about 1984.Architects who worked in the international style wanted to break with architectural tradition and design simple, unornamented buildings. The most commonly used materials are glass for the facade, steel for exterior support, and concrete for the floors and interior supports; floor plans were functional and logical. The style became most evident in the design of skyscrapers. Perhaps its most famous manifestations include the United Nations headquarters (Le Corbusier, Oscar Niemeyer, Sir Howard Robertson), the Seagram Building (Ludwig Mies van der Rohe), and Lever House (Skidmore, Owings, and Merrill), all in New York. A prominent residential example is the Lovell House (Richard Neutra) in Los Angeles.Detractors of the international style claim that its stark, uncompromisingly rectangular geometry is dehumanising. Le Corbusier once described buildings as "machines for living", but people are not machines and it was suggested that they do not want to live in machines. Even Philip Johnson admitted he was "bored with the box." Since the early 1980s many architects have deliberately sought to move away from rectilinear designs, towards more eclectic styles. During the middle of the century, some architects began experimenting in organic forms that they felt were more human and accessible. Mid-century modernism, or organic modernism, was very popular, due to its democratic and playful nature. Alvar Aalto and Eero Saarinen were two of the most prolific architects and designers in this movement, which has influenced contemporary modernism.Although there is debate as to when and why the decline of the modern movement occurred, criticism of Modern architecture began in the 1960s on the grounds that it was universal, sterile, elitist and lacked meaning. Its approach had become ossified in a "style" that threatened to degenerate into a set of mannerisms. Siegfried Giedion in the 1961 introduction to his evolving text, Space, Time and Architecture (first written in 1941), could begin "At the moment a certain confusion exists in contemporary architecture, as in painting; a kind of pause, even a kind of exhaustion." At the Metropolitan Museum of Art, a 1961 symposium discussed the question "Modern Architecture: Death or Metamorphosis?" In New York, the coup d'état appeared to materialize in controversy around the Pan Am Building that loomed over Grand Central Station, taking advantage of the modernist real estate concept of "air rights",[1] In criticism by Ada Louise Huxtable and Douglas Haskell it was seen to "sever" the Park Avenue streetscape and "tarnish" the reputations of its consortium of architects: Walter Gropius, Pietro Belluschi and thebuilders Emery Roth & Sons. The rise of postmodernism was attributed to disenchantment with Modern architecture. By the 1980s, postmodern architecture appeared triumphant over modernism, including the temple of the Light of the World, a futuristic design for its time Guadalajara Jalisco La Luz del Mundo Sede International; however, postmodern aesthetics lacked traction and by the mid-1990s, a neo-modern (or hypermodern) architecture had once again established international pre-eminence. As part of this revival, much of the criticism of the modernists has been revisited, refuted, and re-evaluated; and a modernistic idiom once again dominates in institutional and commercial contemporary practice, but must now compete with the revival of traditional architectural design in commercial and institutional architecture; residential design continues to be dominated by a traditional aesthetic.中⽂译⽂：现代建筑现代建筑,不被混淆与'当代建筑' , 是⼀个词给了⼀些建筑风格有类似的特点, 主要的简化形式,消除装饰等. 虽然风格的设想早在20世纪,并⼤量造就了⼀些建筑师、建筑教育家和展品,很少有现代的建筑物,建于20世纪上半叶. 第⼆次⼤战后的三⼗年, 但最终却成为主导建筑风格的机构和公司建设.1起源⼀些历史学家认为进化的现代建筑作为⼀个社会问题, 息息相关的⼯程中的现代性,从⽽影响了启蒙运动,导致社会和政治⾰命.另⼀些⼈认为现代建筑主要是靠技术和⼯程学的发展, 那就是获得新的建筑材料,如钢铁, 混凝⼟和玻璃驱车发明新的建筑技术,它作为⼯业⾰命的⼀部分. 1796年, shrewsbury查尔斯bage⾸先⽤他的'⽕'的设计, 后者则依靠铸铁及砖与⽯材地板. 这些建设⼤⼤加强了结构,使它们能够容纳更⼤的机器. 由于作为建筑材料特性知识缺乏,⼀些早期建筑失败. 直到1830年初,伊顿Hodgkinson预计推出了型钢梁, 导致⼴泛使⽤钢架建设，⼯业结构完全改变了这种窘迫的⾯貌,英国北部领导的描述, "⿊暗魔⿁作坊"的地⽅如曼彻斯特和西约克郡. ⽔晶宫由约瑟夫paxton的重⼤展览, 1851年,是⼀个早期的例⼦,钢铁及玻璃施⼯; 可能是⼀个最好的例⼦,就是1890年由William乐男爵延长和路易沙利⽂在芝加哥附近发展的⾼层钢结构摩天楼. 早期结构采⽤混凝⼟作为⾏政⼿段的建筑表达(⽽⾮纯粹功利结构) ,包括建于1906年在芝加哥附近,劳埃德赖特的统⼀宫, 建于1926年瑞⼠巴塞尔附近的鲁道夫斯坦纳的第⼆哥特堂,.但⽆论原因为何, 约有1900多位建筑师,在世界各地开始制定新的建筑⽅法,将传统的先例(⽐如哥特式)与新的技术相结合的可能性.路易沙利⽂和赖特在芝加哥⼯作,维克多奥尔塔在布鲁塞尔,安东尼⾼迪在巴塞罗那, 奥托⽡格纳和查尔斯景mackintosh格拉斯哥在维也纳,其中之⼀可以看作是⼀个新与旧的共同⽃争.2现代主义风格由1920年代的最重要⼈物,在现代建筑⾥确⽴了⾃⼰的名声. 三个是公认的柯布西耶在法国, 密斯范德尔德罗和⽡尔特格罗⽪乌斯在德国. 密斯范德尔德罗和格罗⽪乌斯为董事的包豪斯, 其中欧洲有不少学校和有关团体学习调和⼯艺和传统⼯业技术.赖特的建筑⽣涯中,也影响了欧洲建筑的现代艺术,特别是通过⽡斯穆特组合但他拒绝被归类与他们. 赖特与格罗⽪乌斯和Van der德罗对整个有机体系有重⼤的影响.在1932年来到的重要moma展览,是现代建筑艺术的国际展览,艺术家菲利普约翰逊. 约翰逊和合作者亨利-罗素阁纠集许多鲜明的线索和趋势, 内容相似,有⼀个共同的⽬的,巩固了他们融⼊国际化风格这是⼀个重要的转折点. 在⼆战的时间包豪斯的代表⼈物逃到美国,芝加哥，到哈佛⼤学设计⿊⼭书院. 当现代建筑设计从未成为主导风格单⼀的住宅楼，在成为现代卓越的体制和商业建筑, 是学校(专业领导)的唯⼀可接受的, 设计解决⽅案,从约1932年⾄约1984年.那些从事国际风格的建筑师想要打破传统建筑和简单的没有装饰的建筑物。

山东建筑大学本科毕业设计说明书外文文献及翻译格式模版1附件3：（本科毕业论文）文献、资料题目：院（部）专班姓名：张三学号：指导教师：张九光翻译日期：2005.6.30，the National Institute of Standards and Technology (NIST) has been working to develop a new encryption standard to keep government information secure ．The organization is in the final stages of an open process of selecting one or more algorithms ，or data-scrambling formulas ，for the new Advanced Encryption Standard (AES) and plans to make adecision by late summer or early fall ．The standard is slated to go into effect next year ．AES is intended to be a stronger ，more efficient successor to Triple Data Encryption Standard (3DES)，which replaced the aging DES ，which was cracked in less than three days in July 1998．“Until we have the AES ，3DES will still offer protection for years to come ．So there is no need to immediately switch over ，”says Edward Roback ，acting chief of the computer security division at NIST and chairman of the AES selection committee ．“What AES will offer is a more efficient algorithm ．It will be a federal standard ，but it will be widely implemented in the IT community ．”According to Roback ，efficiency of the proposed algorithms is measured by how fast they can encrypt and decrypt information ，how fast they can present an encryption key and how much information they can encrypt ．The AES review committee is also looking at how much space the algorithm takes up on a chip and how much memory it requires ．Roback says the selection of a more efficient AES will also result in cost savings and better use of resources ．“DES w as designed for hardware implementations ，and we are now living in a world of much more efficient software ，and we have learned an awful lot about the design of algorithms ，”says Roback ．“When you start multiplying this with the billions of implementations done daily ，the saving on overhead on the networks will be enormous ．”……山东建筑大学毕业设计（或毕业论文，二选一）外文文献及译文- 1 -以确保政府的信息安全。

教育毕业设计说明范文As a student, the education graduation project holds a significant weight in my academic journey. 作为学生，教育毕业设计在我的学术之旅中扮演着重要的角色。

The education graduation project is not only a culmination of four years of hard work, but also a reflection of my passion and dedication to the field of education. 教育毕业设计不仅是四年努力的结晶，也是我对教育领域的热情和奉献的体现。

Through my education graduation project, I have the opportunity to delve deeper into a subject that interests me and make a meaningful contribution to the field. 通过我的教育毕业设计，我有机会更深入地研究我感兴趣的课题，并对该领域做出有意义的贡献。

One of the challenges I faced during my education graduation project was time management. 在我进行教育毕业设计期间面临的一个挑战是时间管理。

Balancing coursework, part-time work, and social commitments while working on my education graduation project required careful planning and organization. 在进行教育毕业设计的同时，平衡课程作业、兼职工作和社交活动需要细心的计划和组织。

广东工业大学华立学院本科毕业设计（论文）外文参考文献译文及原文系部经济学部专业经济学年级 2007级班级名称 07经济学6班学号 16020706001学生姓名张瑜琴指导教师陈锶2011 年05月目录1挑战：小额贷款中的进入和商业银行的长期承诺 (1)2什么商业银行带给小额贷款和什么把他们留在外 (2)3 商业银行的四个模型进入小额贷款之内 (4)3.1内在的单位 (4)3.2财务子公司 (5)3.3策略的同盟 (5)3.4服务公司模型 (6)4 合法的形式和操作的结构比较 (8)5 服务的个案研究公司模型：厄瓜多尔和Haiti5 (9)1 挑战：小额贷款中的进入和商业银行的长期承诺商业银行已经是逐渐重要的运动员在拉丁美洲中的小额贷款服务的发展2到小额贷款市场是小额贷款的好消息客户因为银行能提供他们一完整类型的财务的服务，包括信用，储蓄和以费用为基础的服务。

整体而言，它也对小额贷款重要，因为与他们广泛的身体、财务的和人类。

如果商业银行变成重的运动员在小额贷款，他们能提供非常强烈的竞争到传统的小额贷款机构。

资源，银行能廉宜地发射而且扩张小额贷款服务rela tively。

如果商业广告银行在小额贷款中成为严重的运动员，他们能提出非常强烈的竞争给传统的小额贷款机构。

然而，小额贷款社区里面有知觉哪一商业银行进入进入小额贷款将会是短命或浅的。

举例来说，有知觉哪一商业银行首先可能不搬进小额贷款因为时候建立小额贷款操作到一个有利润的水平超过银行的标准投资时间地平线。

或，在进入小额贷款，银行之后可能移动在－上面藉由增加贷款数量销售取利润最大值－或者更坏的事，退出如果他们是不满意与小额贷款的收益性的水平。

这些知觉已经被特性加燃料商业银行的情形进入小额贷款和后来的出口之内。

在最极端的，一些开业者已经甚至宣布，”降低尺度死！”而且抛弃了与主意合作的商业银行。

在最 signific 看得到的地方，蚂蚁利益商业银行可能带给小额贷款，国际的ACCION 发展发射而且扩张的和一些商业银行的关系小额贷款操作。

附件1（毕业设计一）材料科学与工程学院毕业实习环节外文翻译要求一、翻译论文的选择：1、与自己毕业设计相关的外文参考文献2、该译文可以作为设计论文中文献综述中的部分内容；3、原则上选取的英语原文不超过5页。

二、译文结构内容1、作者，英文原文题目，期刊名称，卷期号，年份，起止页码，2、文章题目，作者（保持英文，不需翻译），作者单位（英文不变）3、摘要，关键词4、正文部分：引言，试验过程，结果与讨论，结论，参考文献（保持原文状态）5、译文中的图标需要翻译，图可以复印后粘贴或扫描插入三、译文和原文统一装订在一起，独立与毕业论文一起上交四、几点附属说明1 文章所在期刊的期刊名及相关信息不要翻译。

2 文章的作者，作者的单位，地址，下注的通讯作者的情况，参考文献不要翻译。

3文章的题目，摘要，关键词，及正文都要按照原文的顺序来翻译。

4文章中图表翻译示例如下：此为翻译前的表格：此为翻译后的表格：表1 微波和常规方法加工的粉体金属样品的性能Table 1 Properties of microwave and conventionally processedpowdered metal samplesMW 代表微波烧结；conv代表常规方法。

大部分微波烧结的样品的断裂模量比常规方法烧结的要高。

许多微波烧结的样品的密度也是高于常规方法烧成的样品。

MW, microwave processed; conv., conventionally processed. Themodulus of rupture(MOR) of most microwave-processed samples ishigher than that of the conventional samples. The densities of manymicrowave-processed samples are also higher than those ofconventional samples.即表头和注释中英文都要。

毕业设计说明书英文文献及中文翻译学院：信息与通信工程专业：电子信息科学与技术2011年 6月外文文献原文Fundamentals of Time and Frequency IntroductionTime and frequency standards supply three basic types of information：time-of-day，time interval，and frequency. Time-of-day information is provided in hours，minutes，and seconds，but often also includes the date (month，day，and year). A device that displays or records time-of-day information is called a clock. If a clock is used to label when an event happened，this label is sometimes called a time tag or time stamp. Date and time-of-day can also be used to ensure that events are synchronized，or happen at the same time.Time interval is the duration or elapsed time between two events. The standard unit of time interval is the second(s). However，many engineering applications require the measurement of shorter time intervals，such as milliseconds (1 ms = 10 -3 s) ，microseconds (1 μs = 10 -6 s) ，nanoseconds (1 ns = 10 -9 s) ，and picoseconds (1 ps = 10 -12 s). Time is one of the seven base physical quantities，and the second is one of seven base units defined in the International System of Units (SI). The definitions of many other physical quantities rely upon the definition of the second. The second was once defined based on the earth‟s rotational rate or as a fraction of the tropical year. That changed in 1967 when the era of atomic time keeping formally began. The current definition of the SI second is the duration of 9，192，631，770 periods of the radiation corresponding to the transition between two hyperfine levels of the ground state of the cesium-133 atom.Frequency is the rate of a repetitive event. If T is the period of a repetitive event，then the frequency f is its reciprocal，1/T. Conversely，the period is the reciprocal of the frequency，T = 1/f. Since the period is a time interval expressed in seconds (s) ，it is easy to see the close relationship between time interval and frequency. Thestandard unit for frequency is the hertz (Hz) ，defined as events or cycles per second. The frequency of electrical signals is often measured in multiples of hertz，including kilohertz (kHz)，megahertz (MHz)，or gigahertz (GHz)，where 1 kHz equals one thousand (103) events per second，1 MHz equals one million (106) events per second，and 1 GHz equals one billion (109) events per second. A device that produces frequency is called an oscillator. The process of setting multiple oscillators to the same frequency is called synchronization.Of course，the three types of time and frequency information are closely related. As mentioned，the standard unit of time interval is the second. By counting seconds，we can determine the date and the time-of-day. And by counting events or cycles per second，we can measure frequency.Time interval and frequency can now be measured with less uncertainty and more resolution than any other physical quantity. Today，the best time and frequency standards can realize the SI second with uncertainties of ≈1×10-15.Physical realizations of the other base SI units have much larger uncertainties.Coordinated Universal Time (UTC)The world‟s major metrology laboratories routinely measure their time and frequency standards and send the measurement data to the Bureau International des Poids et Measures (BIPM) in Sevres，France. The BIPM averages data collected from more than 200 atomic time and frequency standards located at more than 40 laboratories，including the National Institute of Standards and Technology (NIST). As a result of this averaging，the BIPM generates two time scales，International Atomic Time (TAI)，and Coordinated Universal Time (UTC). These time scales realize the SI second as closely as possible.UTC runs at the same frequency as TAI. However，it differs from TAI by an integral number of seconds. This difference increases when leap seconds occur. Whennecessary，leap seconds are added to UTC on either June 30 or December 31. The purpose of adding leap seconds is to keep atomic time (UTC) within ±0.9 s of an older time scale called UT1，which is based on the rotational rate of the earth. Leap seconds have been added to UTC at a rate of slightly less than once per year，beginning in 1972.Keep in mind that the BIPM maintains TAI and UTC as ……paper‟‟ time scales. The major metrology laboratories use the published data from the BIPM to steer their clocks and oscillators and generate real-time versions of UTC. Many of these laboratories distribute their versions of UTC via radio signals which section 17.4 are discussed in.You can think of UTC as the ultimate standard for time-of-day，time interval，and frequency. Clocks synchronized to UTC display the same hour minute，and second all over the world (and remain within one second of UT1). Oscillators simonized to UTC generate signals that serve as reference standards for time interval and frequency.Time and Frequency MeasurementTime and frequency measurements follow the conventions used in other areas of metrology. The frequency standard or clock being measured is called the device under test (DUT). A measurement compares the DUT to a standard or reference. The standard should outperform the DUT by a specified ratio，called the test uncertainty ratio (TUR). Ideally，the TUR should be 10：1 or higher. The higher the ratio，the less averaging is required to get valid measurement results.The test signal for time measurements is usually a pulse that occurs once per second (1 ps). The pulse width and polarity varies from device to device，but TTL levels are commonly used. The test signal for frequency measurements is usually at a frequency of 1 MHz or higher，with 5 or 10 MHz being common. Frequency signalsare usually sine waves，but can also be pulses or square waves if the frequency signal is an oscillating sine wave. This signal produces one cycle (360∞or 2πradians of phase) in one period. The signal amplitude is expressed in volts，and must be compatible with the measuring instrument. If the amplitude is too small，it might not be able to drive the measuring instrument. If the amplitude is too large，the signal must be attenuated to prevent overdriving the measuring instrument.This section examines the two main specifications of time and frequency measurements—accuracy and stability. It also discusses some instruments used to measure time and frequency.AccuracyAccuracy is the degree of conformity of a measured or calculated value to its definition. Accuracy is related to the offset from an ideal value. For example，time offset is the difference between a measured on-time pulse and an ideal on-time pulse that coincides exactly with UTC. Frequency offset is the difference between a measured frequency and an ideal frequency with zero uncertainty. This ideal frequency is called the nominal frequency.Time offset is usually measured with a time interval counter (TIC). A TIC has inputs for two signals. One signal starts the counter and the other signal stops it. The time interval between the start and stop signals is measured by counting cycles from the time base oscillator. The resolution of a low cost TIC is limited to the period of its time base. For example，a TIC with a 10-MHz time base oscillator would have a resolution of 100 ns. More elaborate Tics use interpolation schemes to detect parts of a time base cycle and have much higher resolution—1 ns resolution is commonplace，and 20 ps resolution is available.Frequency offset can be measured in either the frequency domain or time domain.A simple frequency domain measurement involves directly counting and displaying thefrequency output of the DUT with a frequency counter. The reference for this measuremen t is either the counter‟s internal time base oscillator ， or an external time base. The counter‟s resolution ， or the number of digits it can display ， limits its ability to measure frequency offset. For example ， a 9-digit frequency counter can detect a frequency offset no smaller than 0.1 Hz at 10 MHz (1×10-8). The frequency offset is determined asmeasure nominal nominal(f -f )f= f Where f measur is the reading from the frequency counter ， and f nominal is the frequency labeled on the oscillator‟s nameplate ， or specified output frequency.Frequency offset measurements in the time domain involve a phase comparison between the DUT and the reference. A simple phase comparison can be made with an oscilloscope. The oscilloscope will display two sine waves. The top sine wave represents a signal from the DUT ， and the bottom sine wave represents a signal from the reference. If the two frequencies were exactly the same ， their phase relationship would not change and both would appear to be stationary on the oscilloscope display. Since the two frequencies are not exactly the same ， the reference appears to be stationary and the DUT signal moves. By measuring the rate of motion of the DUT signal we can determine its frequency offset. Vertical lines have been drawn through the points where each sine wave passes through zero. The bottom of the figure shows bars whose width represents the phase difference between the signals. In this case the phase difference is increasing ， indicating that the DUT is lower in frequency than the reference.Measuring high accuracy signals with an oscilloscope is impractical ， since the phase relationship between signals changes very slowly and the resolution of the oscilloscope display is limited. More precise phase comparisons can be made with a TIC. If the two input signals have the same frequency ， the time interval will notchange. If the two signals have different frequencies ， the time interval wills change ， and the rate of change is the frequency offset. The resolution of a TIC determines the smallest frequency change that it can detect without averaging. For example ， a low cost TIC with a single-shot resolution of 100 ns can detect frequency changes of 1 × 10 -7 in 1 s. The current limit for TIC resolution is about 20 ps ， which means that a frequency change of 2 ×10 -11 can be detected in 1 s. Averaging over longer intervals can improve the resolution to <1 ps in some units [6].Since standard frequencies like 5 or 10 MHz are not practical to measure with a TIC ， frequency dividers or frequency mixers are used to convert the test frequency to a lower frequency. Divider systems are simpler and more versatile ， since they can be easily built or programmed to accommodate different frequencies. Mixer systems are more expensive ， require more hardware including an additional reference oscillator ， and can often measure only one input frequency (e.g.， 10 MHz) ， but they have a higher signal-to-noise ratio than divider systems.If dividers are used ， measurements are made from the TIC ， but instead of using these measurements directly ， we determine the rate of change from reading to reading. This rate of change is called the phase deviation. We can estimate frequency offset as follows ：tf=T ∆Where △t is the amount of phase deviation ， and T is the measurement period. To illustrate ， consider a measurement of +1 μs of phase deviation over a measurement period of 24 h. The unit used for measurement period (h) must be converted to the unit used for phase deviation (μs). The equation becomes11t 1us f offset ===1.1610T 86400000000us -∆⨯（），，，As shown，a device that accumulates 1 μs of phase deviation/day has a frequency offset of 1.16 × 10 -11 with respect to the reference. This simple example requires only two time interval readings to be made，and △t is simply the difference between the two readings. Often，multiple readings are taken and the frequency offset is estimated by using least squares linear regression on the data set，and obtaining △t from the slope of the least squares line. This information is usually presented as a phase plot，as shown in Fig. 17.6. The device under test is high in frequency by exactly 1×10 -9，as indicated by a phase deviation of 1 ns/s.Dimensionless frequency offset values can be converted to units of frequency (Hz) if the nominal frequency is known. To illustrate this，consider an oscillator with a nominal frequency of 5 MHz and a frequency offset of +1.16 ′10 -11. To find the frequency offset in hertz，multiply the nominal frequency by the offset：(5 ×106) (+1.16×10 -11) = 5.80×10 -5 =+0.0000580 Hz Then，add the offset to the nominal frequency to get the actual frequency：5，000，000 Hz + 0.0000580 Hz = 5，000，000.0000580 HzStabilityStability indicates how well an oscillator can produce the same time or frequency offset over a given time interval. It doesn‟t indicate whether the time or frequency is “right” or “wrong，” but only whether it stays the same. In contrast，accuracy indicates how well an oscillator has been set on time or on frequency. To understand this difference，consider that a stable oscillator that needs adjustment might produce a frequency with a large offset. Or，an unstable oscillator that was just adjusted might temporarily produce a frequency near its nominal value. Figure 17.7 shows the relationship between accuracy and stability.Stability is defined as the statistical estimate of the frequency or time fluctuations of a signal over a given time interval. These fluctuations are measured with respect to a mean frequency or time offset.Short-term stability usually refers to fluctuations over intervals less than 100 s. Long-term stability can refer to measurement intervals greater than 100 s ， but usually refers to periods longer than 1 day.Stability estimates can be made in either the frequency domain or time domain ， and can be calculated from a set of either frequency offset or time interval measurements. In some fields of measurement ， stability is estimated by taking the standard deviation of the data set. However ， standard deviation only works with stationary data ， where the results are time independent ， and the noise is white ， meaning that it is evenly distributed across the frequency band of the measurement. Oscillator data is usually no stationary ， since it contains time dependent noise contributed by the frequency offset. With stationary data ， the mean and standard deviation will converge to particular values as more measurements are made. With no stationary data ， the mean and standard deviation never converge to any particular values. Instead ， there is a moving mean that changes each time we add a measurement. For these reasons ， a non-classical statistic is often used to estimate stability in the time domain. This statistic is sometimes called the Allan variance ， but since it is the square root of the variance ， its proper name is the Allan deviation. The equation for the Allan deviation (σy (τ)) is2y i+i y -y στ1（（） where y i is a set of frequency offset measurements containing y 1， y 2， y 3， and so on ， M is the number of values in the y i series ， and the data are equally spaced in segments τ seconds long. Or2x i+1i -2x +x στi+2（（x ） Where x i is a set of phase measurements in time units containing x 1， x 2， x 3，and so on，N is the number of values in the xi series，and the data are equally spaced in segments τ seconds long. Note that while standard deviation subtracts the mean from each measurement before squaring their summation，the Allan deviation subtracts the previous data point. This differencing of successive data points removes the time dependent noise contributed by the frequency offset. An Allan deviation graph is shown in Fig. 17.8. It shows the stability of the device improving as the averaging period (τ) gets longer，since some noise types can be removed by averaging. At some point，however，more averaging no longer improves the results. This point is called the noise floor，or the point where the remaining noise consists of no stationary processes such as flicker noise or random walk. The device measured in Fig. 17.8 has a noise floor of ~5 × 10 -11at τ = 100 s.Practically speaking，a frequency stability graph also tells us how long we need to average to get rid of the noise contributed by the reference and the measurement system. The noise floor provides some indication of the amount of averaging required to obtain a TUR high enough to show us the true frequency where xi is a set of phase measurements in time units containing x1，x2，x3，and so on is the number of values in the xi series，and the data are equally s paced in segments τ seconds long. Note that while standard deviation subtracts the mean from each measurement before squaring their summation，the Allan deviation subtracts the previous data point. This differencing of successive data points removes the time dependent noise contributed by the frequency offset. An Allan deviation graph is shown in Fig. 17.8. It shows the stability of the device improving as the averaging period (τ) gets longer，since some noise types can be removed by averaging. At some point，however，more averaging no longer improves the results. This point is called the noise floor or the point where the remaining noise consists of no stationary processes such as flicker noise or random walk. The device measured in Fig. 17.8 has a noise floor of ~5 × 10 -11at τ = 100 s.Practically speaking，a frequency stability graph also tells us how long we needto average to get rid of the noise contributed by the reference and the measurement system. The noise floor provides some indication of the amount of averaging required to obtain a TUR high enough to show us the true frequency offset of the DUT. If the DUT is an atomic oscillator (section 17.4) and the reference is a radio controlled transfer standard (section 17.5) we might have to average for 24 h or longer to have confidence in the measurement result. Five noise types are commonly discussed in the time and frequency literature：white phase，flicker phase，white frequency，flicker frequency，and random walk frequency. The slope of the Allan deviation line can help identify the amount of averaging needed to remove these noise types (Fig. 17.9). The first type of noise to be removed by averaging is phase noise，or the rapid，random fluctuations in the phase of the signal. Ideally，only the device under test would contribute phase noise to the measurement，but in practice，some phase noise from the measurement system and reference needs to be removed through averaging. Note that the Allan deviation does not distinguish between white phase noise and flicker phase noise. Table 17.2 shows several other statistics used to estimate stability and identify noise types for various applications.Identifying and eliminating sources of oscillator noise can be a complex subject，but plotting the first order differences of a set of time domain measurements can provide a basic understanding of how noise is removed by averaging. Figure 17.10 was made using a segment of the data from the stability graph in Fig. 17.8. It shows phase plots dominated by white phase noise (1 s averaging) ，white frequency noise (64 s averages) ，flicker frequency noise (256 s averages)，and random walk frequency (1024 s averages). Note that the white phase noise plot has a 2 ns scale，and the other plots use a 100 ps scale.外文文献中文翻译时间和频率的基本原理介绍时间和频率标准应用于三种基本信息类型：时间，时间间隔和频率.时间信息有小时，分，秒.通常还包括日期(年，月，日).用来显示和记录时间的器件叫做钟表，如果钟表标记了一件事的发生，那么这个标记叫做时间标签或时间印记.日期和时间能确保事情的同步或同时发生.时间间隔是两个事件持续或断续的时间，时间间隔的标准单位是秒，然而许多工程上应用要求更短的时间间隔，像毫秒，微秒，纳秒，和皮秒，时间是七个基本物理量之一，并且秒是国际单位体制制定七个基本单位之一.许多区其他物理量的定义是依靠秒而定义的.秒曾经定义根据地球回转率.原子时代正式开始在1967年目前SI定义秒为：秒是铯133原子(Cs133)基态的两个超精细能级之间跃迁所对应的辐射的9，192，631，770个周期所持续的时间。

毕业设计论文化学系毕业论文外文文献翻译中英文英文文献及翻译A chemical compound that is contained in the hands of the problemsfor exampleCatalytic asymmetric carbon-carbon bond formation is one of the most active research areas in organic synthesis In this field the application of chiral ligands in enantioselective addition of diethylzinc to aldehydes has attracted much attention lots of ligands such as chiral amino alcohols amino thiols piperazines quaternary ammonium salts 12-diols oxazaborolidines and transition metal complex with chiral ligands have been empolyed in the asymmetric addition of diethylzinc to aldehydes In this dissertation we report some new chiral ligands and their application in enantioselective addition of diethylzinc to aldehydes1 Synthesis and application of chiral ligands containing sulfur atomSeveral a-hydroxy acids were prepared using the literature method with modifications from the corresponding amino acids valine leucine and phenylalanine Improved yields were obtained by slowly simultaneous addition of three fold excess of sodium nitrite and 1 tnolL H2SO4 In the preparation of a-hydroxy acid methyl esters from a-hydroxy acids following the procedure described by Vigneron a low yield 45 was obtained It was found that much better results yield 82 couldbe obtained by esterifying a-hydroxy acids with methanol-thionyl chlorideThe first attempt to convert S -2-hydroxy-3-methylbutanoic acid methyl ester to the corresponding R-11-diphenyl-2-mercapto-3-methyl-l-butanol is as the following S-2-Hydroxy-3-methylbutanoic acid methyl ester was treated with excess of phenylmagnesium bromide to give S -11-diphenyl-3-methyl-12-butanediol which was then mesylated to obtain S -11-diphenyl-3-methyl-2-methanesulfonyloxy -l-butanol Unfortunately conversion of S-11-diphenyl-3-methyl-2- methanesulfonyloxy -l-butanol to the corresponding thioester by reacting with potassium thioacetate under Sn2 reaction conditions can be achieved neither in DMF at 20-60 nor in refluxing toluene in the presence of 18-crown-6 as catalyst When S -1ll-diphenyl-3-methyl-2- methane sulfonyloxy -l-butanol was refluxed with thioacetic acid in pyridine an optical active epoxide R-22-diphenyl -3-isopropyloxirane was obtained Then we tried to convert S -11-diphenyl-3-methyl-l2-butanediol to the thioester by reacting with PPh3 DEAD and thioacetic acid the Mitsunobu reaction but we failed either probably due to the steric hindrance around the reaction centerThe actually successful synthesis is as described below a-hydroxy acid methyl esters was mesylated and treated with KSCOCH3 in DMF to give thioester this was than treated with phenyl magnesium bromide to gave the target compound B-mercaptoalcohols The enantiomeric excesses ofp-mercaptoalcohols can be determined by 1H NMR as their S -mandeloyl derivatives S -2-amino-3-phenylpropane-l-thiol hydrochloride was synthesized from L-Phenylalanine L-Phenylalanine was reduced to the amino alcohol S -2-amino-3-phenylpropanol Protection of the amino group using tert-butyl pyrocarbonate gave S -2-tert-butoxycarbonylamino-3-phenylpropane-l-ol which was then O-mesylated to give S -2-tert-butoxycarbonylamino-3-phenylpropyl methanesulfonate The mesylate was treated with potassium thioacetate in DMF to give l-acetylthio-2-tert-butoxycarbonylamino-3-phenylpropane The acetyl group was then removed by treating with ammonia in alcohol to gave S -2-tert-butoxycarbonylamino-3-phenyl-propane-l-thiol which was then deprotected with hydrochloric acid to give the desired S-2-amino-3-phenylpropane-1-thiol hydrochlorideThe enantioselective addition of diethylzinc to aldehydes promoted by these sulfur containing chiral ligands produce secondary alcohols in 65-79 Synthesis and application of chiral aminophenolsThree substituted prolinols were prepared from the naturally-occurring L-proline using reported method with modifications And the chiral aminophenols were obtained by heating these prolinols with excess of salicylaldehyde in benzene at refluxThe results of enantioselective adBelow us an illustration forexampleN-Heterocyclic carbenes and L-Azetidine-2-carboxylicacidN-Heterocyclic carbenesN-Heterocyclic carbenes have becomeuniversal ligands in organometallic and inorganic coordination chemistry They not only bind to any transition metal with low or high oxidation states but also to main group elements such as beryllium sulfur and iodine Because of their specific coordination chemistry N-heterocyclic carbenes both stabilize and activate metal centers in quite different key catalytic steps of organic syntheses for example C-H activation C-C C-H C-O and C-N bond formation There is now ample evidence that in the new generation of organometallic catalysts the established ligand class of organophosphanes will be supplemented and in part replaced byN-heterocyclic carbenes Over the past few years this chemistry has become the field of vivid scientific competition and yielded previously unexpected successes in key areas of homogeneous catalysis From the work in numerous academic laboratories and in industry a revolutionary turningpoint in oraganometallic catalysis is emergingIn this thesis Palladium Ⅱ acetate and NN"-bis- 26-diisopropylphenyl dihydro- imidazolium chloride 1 2 mol were used to catalyze the carbonylative coupling of aryl diazonium tetrafluoroborate salts and aryl boronic acids to form aryl ketones Optimal conditions include carbon monoxide 1 atm in 14-dioxane at 100℃ for 5 h Yields for unsymmetrical aryl ketones ranged from 76 to 90 for isolated materials with only minor amounts of biaryl coupling product observed 2-12 THF as solvent gave mixtures of products 14-Dioxane proved to be the superior solvent giving higher yieldsof ketone product together with less biphenyl formation At room temperature and at 0℃ with 1 atm CO biphenyl became the major product Electron-rich diazonium ion substrates gave a reduced yield with increased production of biaryl product Electron-deficient diazonium ions were even better forming ketones in higher yields with less biaryl by-product formed 2-Naphthyldiazonium salt also proved to be an effective substrate givingketones in the excellent range Base on above palladium NHC catalysts aryl diazonium tetrafluoroborates have been coupled with arylboron compounds carbon monoxide and ammonia to give aryl amides in high yields A saturated yV-heterocyclic carbene NHC ligand H2lPr 1 was used with palladium II acetate to give the active catalyst The optimal conditions with 2mol palladium-NHC catalyst were applied with various organoboron compounds and three aryl diazonium tetrafluoroborates to give numerous aryl amides in high yield using pressurized CO in a THF solution saturated with ammonia Factors that affect the distribution of the reaction products have been identified and a mechanism is proposed for this novel four-component coupling reactionNHC-metal complexes are commonly formed from an imidazolium salt using strong base Deprotonation occurs at C2 to give a stable carbene that adds to form a a-complex with the metal Crystals were obtained from the reaction of imidazolium chloride with sodium t- butoxide Nal and palladium II acetate giving a dimeric palladium II iodide NHC complex The structure adopts a flat 4-memberedring u2 -bridged arrangement as seen in a related dehydro NHC complex formed with base We were pleased to find that chloride treated with palladium II acetate without adding base or halide in THF also produced suitable crystals for X-ray anaysis In contrast to the diiodide the palladium-carbenes are now twisted out of plane adopting a non-planar 4-ring core The borylation of aryldiazonium tetrafluoroborates with bis pinacolatoborane was optimized using various NHC ligand complexes formed in situ without adding base NN"-Bis 26-diisopropylphenyl-45-dihydroimidazolium 1 used with palladium acetate in THF proved optimal giving borylated product in 79 isolated yield without forming of bi-aryl side product With K2CO3 and ligand 1 a significant amount of biaryl product 24 was again seen The characterization of the palladium chloride complex by X-ray chrastallography deL-Azetidine-2-carboxylic acidL-Azetidine-2-carboxylic acid also named S -Azetidine-2-carboxylic acid commonly named L-Aze was first isolated in 1955 by Fowden from Convallaria majalis and was the first known example of naturally occurring azetidine As a constrained amino acid S -Azetidine-2-carboxylic acid has found many applications in the modification of peptides conformations and in the area of asymmetric synthesis which include its use in the asymmetric reduction of ketones Michael additions cyclopropanations and Diels-Alder reactions In this dissertation five ways for synthesize S-Azetidine-2-carboxylic acid were studied After comparing all methods theway using L-Aspartic acid as original material for synthesize S-Azetidine-2-carboxylic acid was considered more feasible All mechanisms of the way"s reaction have also been studied At last the application and foreground of S -Azetidine-2-carboxylic acid were viewed The structures of the synthetic products were characterized by ThermalGravity-Differential Thermal Analysis TG-DTA Infrared Spectroscopy IR Mass Spectra MS and 1H Nuclear Magnetic Resonance 1H-NMR Results showed that the structures and performances of the products conformed to the anticipation the yield of each reaction was more than 70 These can conclude that the way using L-Aspartie acid as original material for synthesize S -Azetidine-2-carboxylic acid is practical and effective杂环化合物生成中包含手性等问题如催化形成不对称碳碳键在有机合成中是一个非常活跃的领域在这个领域中利用手性配体诱导的二乙基锌和醛的不对称加成引起化学家的广泛关注许多手性配体如手性氨基醇手性氨基硫醇手性哌嗪手性四季铵盐手性二醇手性恶唑硼烷和过渡金属与手性配体的配合物等被应用于二乙基锌对醛的不对称加成中在本论文中我们报道了一些新型的手性配体的合成及它们应用于二乙基锌对醛的不对称加成的结果1含硫手性配体的合成和应用首先从氨基酸缬氨酸亮氨酸苯丙氨酸出发按照文献合成α-羟基酸并发现用三倍量的亚硝酸钠和稀硫酸同时滴加进行反应能适当提高反应的产率而根据Vigneron等人报道的的方法用浓盐酸催化从α-羟基酸合成α-羟基酸甲酯时只能获得较低的产率改用甲醇-二氯亚砜的酯化方法时能提高该步骤的产率从 S -3-甲基-2-羟基丁酸甲酯合成 R -3-甲基-11-二苯基-2-巯基-1-丁醇经过了以下的尝试 S -3-甲基-2-羟基丁酸甲酯和过量的格氏试剂反应得到 S -3-甲基-11-二苯基-12-丁二醇进行甲磺酰化时位阻较小的羟基被磺酰化生成 S -3-甲基-11-二苯基-2- 甲磺酰氧基 -1-丁醇但无论将 S -3-甲基-11-二苯基-2- 甲磺酰氧基 -1-丁醇和硫代乙酸钾在DMF中反应 20～60℃还是在甲苯中加入18-冠-6作为催化剂加热回流都不能得到目标产物当其与硫代乙酸在吡啶中回流时得到的不是目标产物而是手性环氧化合物 R -3-异丙基-22-二苯基氧杂环丙烷从化合物 S -3-甲基-11-二苯基-12-丁二醇通过Mitsunobu反应合成硫代酯也未获得成功这可能是由于在反应中心处的位阻较大造成的几奥斯塑手村犯体的合成裁其在不对称奋成中肠左用摘要成功合成疏基醇的合成路是将a-轻基酸甲酷甲磺酞化得到相应的磺酞化产物并进行与硫代乙酸钾的亲核取代反应得到硫酷进行格氏反应后得到目标分子p一疏基醇用p一疏基醇与 R 义一一甲氧基苯乙酞氯生成的非对映体经H侧NM吸测试其甲氧基峰面积的积分求得其ee值 3一苯基一氨基丙硫醇盐酸盐从苯丙氨酸合成斗3一苯基一氨基丙醇由L一苯丙氨酸还原制备氨基保护后得到习一3一苯基一2一叔丁氧拨基氨基一1一丙醇甲磺酞化后得到习一3一苯基一2一叔丁氧拨基氨基一1一丙醇甲磺酸酷用硫代乙酸钾取代后得匀一3-苯基一2一叔丁氧拨基氨基一1一丙硫醇乙酸酷氨解得习一3一苯基一2一叔丁氧拨基氨基一1一丙硫醇用盐酸脱保护后得到目标产物扔3一苯基屯一氨基丙硫醇盐酸盐手性含硫配体诱导下的二乙基锌与醛的加成所得产物的产率为65一79值为O井92手性氨基酚的合成和应用首先从天然的L一脯氨酸从文献报道的步骤合成了三种脯氨醇这些手性氨基醇与水杨醛在苯中回流反应得到手性氨基酚手性氨基酚配体诱导下的二乙基锌与醛的加成所得产物的产率为45一98值为0一90手性二茂铁甲基氨基醇的合成和应用首先从天然氨基酸绿氨酸亮氨酸苯丙氨酸和脯氨酸合成相应的氨基醇这些氨基醇与二茂铁甲醛反应生成的NO一缩醛经硼氢化钠还原得到手性二茂铁甲基氨基醇手性二茂铁甲基氨基醇配体诱导下的二乙基锌与醛的加成所得产物的产率为66一97下面我们举例说明一下例如含氮杂环卡宾和L-氮杂环丁烷-2-羧酸含氮杂环卡宾含氮杂环卡宾已广泛应用于有机金属化学和无机配合物化学领域中它们不仅可以很好地与任何氧化态的过渡金属络合还可以与主族元素铍硫等形成配合物由于含氮杂环卡宾不但使金属中心稳定而且还可以活化此金属中心使其在有机合成中例如C-H键的活化C-CC-HC-O和C-N键形成反应中有着十分重要的催化效能现有的证据充分表明在新一代有机金属催化剂中含氮杂环卡宾不但对有机膦类配体有良好的互补作用而且在有些方面取代有机膦配体成为主角近年来含氮杂环卡宾及其配合物已成为非常活跃的研究领域在均相催化这一重要学科中取得了难以想象的成功所以含氮杂环卡宾在均相有机金属催化领域的研究工作很有必要深入地进行下去本文研究了乙酸钯和NN双 26-二异丙基苯基 -45-二氢咪唑氯化物1作为催化剂催化芳基四氟硼酸重氮盐与芳基硼酸的羰基化反应合成了一系列二芳基酮并对反应条件进行了优化使反应在常温常压下进行一个大气压的一氧化碳14-二氧杂环己烷作溶剂100℃反应5h 不同芳基酮的收率达7690仅有微量的联芳烃付产物 212 反应选择性良好当采用四氢呋喃或甲苯作溶剂时得到含较多副产物的混合物由此可以证明14-二氧杂环己烷是该反应最适宜的溶剂在室温或0℃与一个大气压的一氧化碳反应联芳烃变成主产物含供电子取代基的芳基重氮盐常常给出较低收率的二芳基酮而含吸电子取代基的芳基重氮盐却给出更高收率的二芳基酮及较少量的联芳烃付产物实验证明2-萘基重氮盐具有很好的反应活性和选择性总是得到优异的反应结果在此基础上由不同的芳基四氟硼酸重氮盐与芳基硼酸一氧化碳和氨气协同作用以上述含氮杂环卡宾作配体与乙酸钯生成的高活性含氮杂环卡宾钯催化剂催化较高收率地得到了芳基酰胺优化的反应条件是使用2mol的钯-H_2IPr 1五个大气压的一氧化碳以氨气饱和的四氢呋喃作溶剂由不同的有机硼化合物与三种芳基重氮盐的四组份偶联反应同时不仅对生成的多种产物进行了定 L-氮杂环丁烷-2-羧酸L-氮杂环丁烷-2-羧酸又称 S -氮杂环丁烷-2-羧酸简称为L-Aze1955年由Fowden从植物铃兰 Convallaria majalis 中分离得到成为第一个被证实的植物中天然存在的氮杂环丁烷结构作为一种非典型的氨基酸已经发现 S -氮杂环丁烷-2-羧酸可广泛用于对多肽结构的修饰以及诸如不对称的羰基还原Michael 加成环丙烷化和Diels-Alder反应等不对称合成中的多个领域本文通过对 S -氮杂环丁烷-2-羧酸合成路线的研究综述了五种可行的合成路线及方法通过比较选用以L-天冬氨酸为初始原料合成 S -氮杂环丁烷-2-羧酸的路线即通过酯化反应活泼氢保护格氏反应内酰胺化反应还原反应氨基保护氧化反应脱保护等反应来合成 S -氮杂环丁烷-2-羧酸分析了每步反应的机理并对 S -氮杂环丁烷-2-羧酸的应用及前景给予展望通过热分析红外质谱核磁等分析手段对合成的化合物的结构进行表征结果表明所得的产物符合目标产物所合成的化合物的结构性能指标与设计的目标要求一致每步反应的收率都在70％以上可以判定以L-天冬氨酸为初始原料合成 S -氮杂环丁烷的路线方案切实可行。