材料类外文文献翻译

本科毕业论文

外文文献及译文

文献、资料题目：The effects of heat treatment on

the microstructure and mechani-

cal property of laser melting dep-

ositionγ-TiAl intermetallic alloys 文献、资料来源：Materials and Design

文献、资料发表（出版）日期：2009.10.25

院（部）：材料科学与工程学院

专业：材料成型及控制工程

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翻译日期：2011.4.3

中文译文：

热处理对激光沉积γ-TiAl金属间化合物合金的组织与性能的影响摘要：

Ti-47Al-2.5V-1Cr 和Ti-40Al-2Cr (at.%)金属间化合物合金通过激光沉积（LMD）成形技术制造。显微组织的特征通过光学显微镜（OM）、扫描电子显微镜（SEM）、投射电子显微镜（TEM）、和X射线衍射仪（XRD）检测。沿轴向评估热处理后的沉积试样室温下的抗拉性能和维氏硬度。结果表明：由γ-TiAl 和α2-Ti3Al构成的γ-TiAl基体试样具有全密度柱状晶粒和细的层状显微组织。Ti-47Al-2.5V-1Cr基体合金和Ti-40Al-2Cr基体合金沿轴向的室温抗拉强度大约分别为650 MPa、600MPa，而最大延伸率大约为0.6% 。热处理后的Ti-47Al-2.5V-1Cr和Ti-40Al-2Cr合金可以得到不同的显微组织。应力应变曲线和次表面的拉伸断裂表明沉积和热处理后的试样的断裂方式是沿晶断裂。

1.简介

金属间化合物γ-TiAl合金由于其高熔点（﹥1450℃）、低密度（3g/cm3）、高弹性模量（160-180GPa）和高蠕变强度（直到900℃）成为很有前景的高温结构材料，一直受到广泛研究[1–4]。但是对于其结构应用来说，这种材料主要缺点之一是在室温下缺少延展性。此外，这种合金运用传统的制造工艺诸如锻压、轧制和焊接，加工起来比较困难[5]。

对于TiAl组份，传统的铸造技术不利条件是粗大的铸态组织导致室温下的机械性能变差。另一方面，在传统的缓慢冷却固结过程中诸如气孔和缩孔等金相缺陷是不可避免的。产品的形状和尺寸受热应力诱发结晶的制约，铸件的地延展性导致裂纹缺陷。虽然适当的组件可以通过传统的铸造工艺制造，但是这种方法相当昂贵、耗时。一些其他制造和加工方式如放电等离子烧结（SPS）[6,7]、混合粉末半固态成型[8]、烘托冶金反应[9]和激光工程粉末冶金零件近净成形(LENS) [10]一直受到广泛研究，以便制造出高质量的TiAl合金部件。然而，在此类金属的粉末冶金过程中不可避免的氮化和氧化的增强，进一步恶化了TiAl合金的延展性。

激光沉积（LMD）是一种利用电脑辅助设计（CAD）模型分层快速凝固材料添加剂为增效组分的制造技术。在LMD过程中，大功率激光束的运动有计算机数控（CNC）系统控制，而该系统由CAD模型发展而来。金属粉末注入激光聚焦带，然后从粉末输出喷嘴连续熔化。由于该方法冷却凝固速度高，连续层可堆积成全密度和极细小的快速凝固微观组织的近净成形零件。利用CAD文档的LMD添加剂分层制造的方式，可以得到任意复杂形状和尺寸的

近净成形零件。

在目前的研究中，激光沉积制造工艺成功制造出Ti–47Al–2.5V–1Cr和Ti–40Al–2Cr(at.%)金属间化合物合金零件。研究沉积试样热处理后的微观组织，并评估轴向维氏硬度和室温抗拉性能，表征拉伸断面和次表面的组织。

2.实验步骤

GS-TFL-8000 CO2激光器（最大输出功率8000W）和BSF-2粉末输出装置熔化和传送Ti–47Al–2.5V–1Cr 和 Ti–40Al–2Cr合金粉末，HNC-21M CNC数控装置控制工作台和激光束的运动。激光束和粉末喷嘴作为一个整体单元移动，以便合金粉末注入激光熔池。激光熔化沉积过程在一个特别设计的氩气清洗室中进行，恒压下，在氩气气氛中防止熔池氧化，清洗室中的氧含量小于万分之一。LMD加工过程中的参数：激光功率1500W，光束直径5mm，光束扫描速度5mm/s，单层沉积物厚度0.2-0.3mm，送粉速度4-5.5g/min。

在此研究中，Ti–47Al–2.5V–Cr和 Ti–40Al–2Cr合金粉末含氧量小于0.1(wt.%)，有真空熔化氩气等离子体雾化过程密封制造。Ti–6Al–2Zr–Mo–1V and Ti–47Al–2.5V–Cr铸态合金锭机械加工成直径10mm左右的细缆，然后通过特殊设计的喷嘴在等离子熔化炉中熔化。最后，喷嘴里的铸态合金在高速高纯度氩气流作用下形成球状粉，合金的粒度范围在70-75μm之间。另一方面，铸态Ti–6Al–2Zr–Mo–1V铸锭热滚到厚度为8–10 mm的薄墙型标本上作为基体材料（表1）。Ti–6Al–2Zr–1Mo–1V基体表面在激光熔化沉积之前预抛光，沉积试样密封在石英管中，然后在高温烘炉中热处理。

通过标准机械抛光法准备的金相试样用300 ml H2O、100 ml HNO3和100 ml HF混合溶液腐蚀。OL YMPUS BX51M光学显微镜、JEM-2100透射电镜和配备Lea-gue-2000 EDX 系统的KYKY-2800扫描电子显微镜表征微观组织、识别化学成分。使用HXZ-1000半自动硬度测试计测量梯度区的硬度，试验荷载200g，停留时间15s。拉伸试样（厚度1-1.5mm）

在MTS880测试系统上沿轴向测量试样的室温抗拉性能（图1）。

3.结果与讨论

3.1. 显微结构的分析

Ti–47Al–2.5V–1Cr 和Ti–40Al–2Cr合金薄板的几何尺寸都是40 m m×40 mm×6mm(图. 2a)。不同粒度组成的γ-TiAl和α2-Ti3Al相的沉积试样具有片状显微组织（FL）(图-2b 和c)，TiAl沉积试样中观察到细层的微观结构，可能是由于加工制造过程较高的凝固速率。γ-TiAl和α2-Ti3Al（图-3.b和c）有层状显微结构组成是固态相变的结果。含有46–49% (at.%)铝的TiAl合金在1125℃经历固态相变[12]：α→γ+α 2 。细化晶粒的尺寸是50–100 um ，超细层间距大约是0.2um。在激光熔化沉积过程中，沉积熔池下面的先前沉积层被扫描激光束连续不断的在加热至高温(>1500℃) [13]。熔池附近的热影响区必然发生前面提到的固态相变，最终导致片状显微组织的形成。该研究中，TiAl沉积试样中γ-TiAl (fcc)和α2-Ti3Al (hcp) 有一个方向关系(0 0 0 1) α2//(1 1 1)γ（图-3.e和f）。

图4显示了Ti–47Al–2.5V–1Cr 和Ti–40Al–2Cr沉积合金试样X射线衍射模型。沉积的Ti–47Al–2.5V–1Cr合金试样中可以清楚的观察Ti3Al-(2 0 0) 和Ti3Al-(2 0 1)峰值，但是，Ti–40Al–2Cr沉积合金试样的X射线衍射模型中却不显著。

不同加工方法得到的Ti–47Al–2.5V–1Cr 和Ti–40Al–2Cr合金试样热处理后的微观结构

不同（图5和图7）。同时，热处理后的TiAl合金试样中γ-TiAl和α2-Ti3Al片晶厚度见图6。EDS能谱仪分析结果显示试样的不同晶粒区（表2）的化学成分和腐蚀形态不同。这表明，经过1100℃和1125℃分别30分钟的热处理之后不能去掉材料的同质异性，而这可能是由于扩散速率低和热处理时间相对较短[14,15]。

3.2. 显微硬度

图8显示了热处理合金Ti–47Al–2.5V–1Cr 和Ti–40Al–2Cr沉积试样平均维氏硬度的变化。沉积Ti–47Al–2.5V–1Cr合金试样经1125℃退火30小时后水淬火，其维氏硬度从425HV 上升到455HV。另一方面沉积Ti–40Al–2Cr合金试样经1100℃退火30小时后空冷，其维氏硬度从400HV上升到450HV。这种变化可能是受长时间高温退火后不同肌理的细晶粒的形成引起微观组织变化的影响。

3.3. 室温抗拉性能

表3显示了沉积后热处理试样室温抗拉性能测试结果。十分明显，沉积试样Ti–47Al–2.5V–1Cr 和Ti–40Al–2Cr合金的极限抗拉强度（UTS）值与热加工试样相比低很多，这表明Ti–47Al–2.5V–1Cr和Ti–40Al–2Cr合金的室温抗拉性能受其微观结构的晶粒大小和层间隙的影响。图9所示的是热处理后Ti–47Al–2.5V–1Cr 和Ti–40Al–2C合金试样的室温拉伸应力—应变曲线，结果表明这种合金的延展性非常低。

热处理后的Ti–47Al–2.5V–1Cr 和Ti–40Al–2Cr合金试样的RT断裂表面和此表面沿纵向方向检测。沉积后热处理的Ti–47Al–2.5V–1Cr 和Ti–40Al–2Cr合金试样的断裂表面是平直且简单的。特别需要指出的是，韧性坑充分体现了层状显微结构的组织特征，这表明显微镜下可见的初始裂纹产生于单一晶粒，沿层界面生长，有时沿晶界处生长。

在本文中，激光沉积Ti–47Al–2.5V–1Cr 和Ti–40Al–2Cr合金成分沿纵向方向，有杰出的室温力学性能。沉积TiAl合金试样中观察到的细的层状显微结构可能是在LMD快速制造工艺中，由于凝固速率高产生的。与LMD加工工艺相

比，那些传统的铸造加工工艺，TiAl合金的凝固速率相对较低。相应的，那些缓慢冷却的加工工艺形成粗糙的等轴FL或者是复式（DP）显微组织。在这项研究中，在50-100um 范围的的显微结构沿纵向方向的室温拉伸强度能够达到550-650MPa。550-650MPa。然而，图6 b和c以及图7显示组织的层间隙几乎是在同一水平上，这说明相应的热处理时间不够长，还不足以使片层微观结构存

在明显的差异。与沉积合金试样相比较，热处理合金试样的极限抗拉强度的变化可以忽略不计。另一方面，与热处理试样0.6%的延展率相比，沉积Ti –47Al –2.5V –1Cr 和 Ti –40Al –2Cr 合金试样0.3%的延展率相对较低。图4是沉积后热处理的LMD 试样与传统加工TiAl 合金材料的室温抗拉特性的比较。许多研究表明，TiAl 合金的室温下的屈服强度和抗拉延性以及微观结构主要受晶粒大小和内部层间隙的影响[18–20]。通过各种固态热加工方法控制微观组织和细化晶粒可以改善激光熔覆沉积Ti –47Al –2.5V –1Cr 和 Ti –40Al –2Cr 合金的机械性能，这是因为机械性能对微观结构的敏感依赖性。

4. 结论

Ti–47Al–2.5V–1Cr 和Ti–40Al–2Cr (at.%) 金属间化合物合金通过激光沉积（LMD）制造工艺制造。由γ- TiAl和α2-Ti3Al构成的完全片状显微结构（FL）激光沉积形成γ-TiA l 样品。Ti–40Al–2Cr合金1100℃退火30分钟伴随无功电量可以获得晶粒度大小约为20um 的均匀的微观组织。Ti–47Al–2.5V–1Cr经过1125℃/30 min退火处理伴随无功电量，可获得晶粒大小约为100um微观组织。Ti–47Al–2.5V–1Cr合金伴随无功电量经1125℃/30min 退火处理后沿纵向方向，其室温抗拉强度高达650 MPa。Ti–40Al–2Cr合金经1100℃/30min 退火处理之后空冷，其室温抗拉强度沿纵向方向高达630 MPa。这种合金的延伸率至多为0.6%，这表明其延展性非常低。

鸣谢

本研究由国家基础研究项目(2006CB605206-2)和中国国家自然科学基金委员会(批准号No. 50625413)以及中国教育部长江学者创新研究小组资助研究。

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forced concrete structure reinforced with an overviewRein Since the reform and opening up, with the national economy's rapid and sustained development of a reinforced concrete structure built, reinforced with the development of technology has been great. Therefore, to promote the use of advanced technology reinforced connecting to improve project quality and speed up the pace of construction, improve labor productivity, reduce costs, and is of great significance. Reinforced steel bars connecting technologies can be divided into two broad categories linking welding machinery and steel. There are six types of welding steel welding methods, and some apply to the prefabricated plant, and some apply to the construction site, some of both apply. There are three types of machinery commonly used reinforcement linking method primarily applicable to the construction site. Ways has its own characteristics and different application, and in the continuous development and improvement. In actual production, should be based on specific conditions of work, working environment and technical requirements, the choice of suitable methods to achieve the best overall efficiency. 1、steel mechanical link 1.1 radial squeeze link Will be a steel sleeve in two sets to the highly-reinforced Department with superhigh pressure hydraulic equipment (squeeze tongs) along steel sleeve radial squeeze steel casing, in squeezing out tongs squeeze pressure role of a steel sleeve plasticity deformation closely integrated with reinforced through reinforced steel sleeve and Wang Liang's Position will be two solid steel bars linked Characteristic: Connect intensity to be high, performance reliable, can bear high stress draw and pigeonhole the load and tired load repeatedly.

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微软Visual Studio 1微软Visual Studio Visual Studio 是微软公司推出的开发环境，Visual Studio可以用来创建Windows平台下的Windows应用程序和网络应用程序，也可以用来创建网络服务、智能设备应用程序和Office 插件。Visual Studio是一个来自微软的集成开发环境IDE，它可以用来开发由微软视窗，视窗手机，Windows CE、.NET框架、.NET精简框架和微软的Silverlight支持的控制台和图形用户界面的应用程序以及Windows窗体应用程序，网站，Web应用程序和网络服务中的本地代码连同托管代码。 Visual Studio包含一个由智能感知和代码重构支持的代码编辑器。集成的调试工作既作为一个源代码级调试器又可以作为一台机器级调试器。其他内置工具包括一个窗体设计的GUI应用程序，网页设计师，类设计师，数据库架构设计师。它有几乎各个层面的插件增强功能，包括增加对支持源代码控制系统（如Subversion和Visual SourceSafe）并添加新的工具集设计和可视化编辑器，如特定于域的语言或用于其他方面的软件开发生命周期的工具（例如Team Foundation Server的客户端：团队资源管理器）。 Visual Studio支持不同的编程语言的服务方式的语言，它允许代码编辑器和调试器（在不同程度上）支持几乎所有的编程语言，提供了一个语言特定服务的存在。内置的语言中包括C/C + +中（通过Visual C++）,https://www.wendangku.net/doc/ad1840740.html,（通过Visual https://www.wendangku.net/doc/ad1840740.html,），C＃中（通过Visual C＃）和F＃（作为Visual Studio 2010），为支持其他语言，如M,Python,和Ruby等，可通过安装单独的语言服务。它也支持的 XML/XSLT,HTML/XHTML ,JavaScript和CSS.为特定用户提供服务的Visual Studio也是存在的：微软Visual Basic，Visual J＃、Visual C＃和Visual C++。 微软提供了“直通车”的Visual Studio 2010组件的Visual Basic和Visual C＃和Visual C + +，和Visual Web Developer版本，不需任何费用。Visual Studio 2010、2008年和2005专业版，以及Visual Studio 2005的特定语言版本（Visual Basic、C++、C＃、J＃），通过微软的下载DreamSpark计划，对学生免费。 2架构 Visual Studio不支持任何编程语言，解决方案或工具本质。相反，它允许插入各种功能。特定的功能是作为一个VS压缩包的代码。安装时，这个功能可以从服务器得到。IDE提供三项服务：SVsSolution，它提供了能够列举的项目和解决方案; SVsUIShell，它提供了窗口和用户界面功能（包括标签，工具栏和工具窗口）和SVsShell，它处理VS压缩包的注册。此外，IDE还可以负责协调和服务之间实现通信。所有的编辑器，设计器，项目类型和其他工具都是VS压缩包存在。Visual Studio 使用COM访问VSPackage。在Visual Studio SDK中还包括了管理软件包框架(MPF)，这是一套管理的允许在写的CLI兼容的语言的任何围绕COM的接口。然而，MPF并不提供所有的Visual Studio COM 功能。

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毕业设计（论文）外文参考文献及译文 英文题目Component-based Safety Computer of Railway Signal Interlocking System 中文题目模块化安全铁路信号计算机联锁系统 学院自动化与电气工程学院 专业自动控制 姓名葛彦宁 学号 200808746 指导教师贺清 2012年5月30日

Component-based Safety Computer of Railway Signal Interlocking System 1 Introduction Signal Interlocking System is the critical equipment which can guarantee traffic safety and enhance operational efficiency in railway transportation. For a long time, the core control computer adopts in interlocking system is the special customized high-grade safety computer, for example, the SIMIS of Siemens, the EI32 of Nippon Signal, and so on. Along with the rapid development of electronic technology, the customized safety computer is facing severe challenges, for instance, the high development costs, poor usability, weak expansibility and slow technology update. To overcome the flaws of the high-grade special customized computer, the U.S. Department of Defense has put forward the concept：we should adopt commercial standards to replace military norms and standards for meeting consumers’demand [1]. In the meantime, there are several explorations and practices about adopting open system architecture in avionics. The United Stated and Europe have do much research about utilizing cost-effective fault-tolerant computer to replace the dedicated computer in aerospace and other safety-critical fields. In recent years, it is gradually becoming a new trend that the utilization of standardized components in aerospace, industry, transportation and other safety-critical fields. 2 Railways signal interlocking system 2.1 Functions of signal interlocking system The basic function of signal interlocking system is to protect train safety by controlling signal equipments, such as switch points, signals and track units in a station, and it handles routes via a certain interlocking regulation. Since the birth of the railway transportation, signal interlocking system has gone through manual signal, mechanical signal, relay-based interlocking, and the modern computer-based Interlocking System. 2.2 Architecture of signal interlocking system Generally, the Interlocking System has a hierarchical structure. According to the function of equipments, the system can be divided to the function of equipments; the system

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附件1：外文资料翻译译文 抗侧向荷载的结构体系 常用的结构体系 若已测出荷载量达数千万磅重，那么在高层建筑设计中就没有多少可以进行极其复杂的构思余地了。确实，较好的高层建筑普遍具有构思简单、表现明晰的特点。 这并不是说没有进行宏观构思的余地。实际上，正是因为有了这种宏观的构思，新奇的高层建筑体系才得以发展，可能更重要的是：几年以前才出现的一些新概念在今天的技术中已经变得平常了。 如果忽略一些与建筑材料密切相关的概念不谈，高层建筑里最为常用的结构体系便可分为如下几类： 1.抗弯矩框架。 2.支撑框架，包括偏心支撑框架。 3.剪力墙，包括钢板剪力墙。 4.筒中框架。 5.筒中筒结构。 6.核心交互结构。 7. 框格体系或束筒体系。 特别是由于最近趋向于更复杂的建筑形式，同时也需要增加刚度以抵抗几力和地震力，大多数高层建筑都具有由框架、支撑构架、剪力墙和相关体系相结合而构成的体系。而且，就较高的建筑物而言，大多数都是由交互式构件组成三维陈列。 将这些构件结合起来的方法正是高层建筑设计方法的本质。其结合方式需要在考虑环境、功能和费用后再发展，以便提供促使建筑发展达到新高度的有效结构。这并

不是说富于想象力的结构设计就能够创造出伟大建筑。正相反，有许多例优美的建筑仅得到结构工程师适当的支持就被创造出来了，然而，如果没有天赋甚厚的建筑师的创造力的指导，那么，得以发展的就只能是好的结构，并非是伟大的建筑。无论如何，要想创造出高层建筑真正非凡的设计，两者都需要最好的。 虽然在文献中通常可以见到有关这七种体系的全面性讨论，但是在这里还值得进一步讨论。设计方法的本质贯穿于整个讨论。设计方法的本质贯穿于整个讨论中。 抗弯矩框架 抗弯矩框架也许是低，中高度的建筑中常用的体系，它具有线性水平构件和垂直构件在接头处基本刚接之特点。这种框架用作独立的体系，或者和其他体系结合起来使用，以便提供所需要水平荷载抵抗力。对于较高的高层建筑，可能会发现该本系不宜作为独立体系，这是因为在侧向力的作用下难以调动足够的刚度。 我们可以利用STRESS，STRUDL 或者其他大量合适的计算机程序进行结构分析。所谓的门架法分析或悬臂法分析在当今的技术中无一席之地，由于柱梁节点固有柔性，并且由于初步设计应该力求突出体系的弱点，所以在初析中使用框架的中心距尺寸设计是司空惯的。当然，在设计的后期阶段，实际地评价结点的变形很有必要。 支撑框架 支撑框架实际上刚度比抗弯矩框架强，在高层建筑中也得到更广泛的应用。这种体系以其结点处铰接或则接的线性水平构件、垂直构件和斜撑构件而具特色，它通常与其他体系共同用于较高的建筑，并且作为一种独立的体系用在低、中高度的建筑中。

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数据库外文参考文献及翻译 数据库外文参考文献及翻译数据库管理系统——实施数据完整性一个数据库，只有用户对它特别有信心的时候。这就是为什么服务器必须实施数据完整性规则和商业政策的原因。执行SQL Server的数据完整性的数据库本身，保证了复杂的业务政策得以遵循，以及强制性数据元素之间的关系得到遵守。因为SQL Server的客户机/服务器体系结构允许你使用各种不同的前端应用程序去操纵和从服务器上呈现同样的数据，这把一切必要的完整性约束，安全权限，业务规则编码成每个应用，是非常繁琐的。如果企业的所有政策都在前端应用程序中被编码，那么各种应用程序都将随着每一次业务的政策的改变而改变。即使您试图把业务规则编码为每个客户端应用程序，其应用程序失常的危险性也将依然存在。大多数应用程序都是不能完全信任的，只有当服务器可以作为最后仲裁者，并且服务器不能为一个很差的书面或恶意程序去破坏其完整性而提供一个后门。SQL Server使用了先进的数据完整性功能，如存储过程，声明引用完整性（DRI），数据类型，限制，规则，默认和触发器来执行数据的完整性。所有这些功能在数据库里都有各自的用途;通过这些完整性功能的结合，可以实现您的数据库的灵活性和易于管理，而且还安全。声明数据完整性声明数据完整原文请找腾讯3249114六,维-论'文.网 https://www.wendangku.net/doc/ad1840740.html, 定义一个表时指定构成的主键的列。这就是所谓的主键约束。SQL Server使用主键约束以保证所有值的唯一性在指定的列从未侵犯。通过确保这个表有一个主键来实现这个表的实体完整性。有时，在一个表中一个以上的列（或列的组合）可以唯一标志一行，例如，雇员表可能有员工编号（ emp_id ）列和社会安全号码（ soc_sec_num ）列，两者的值都被认为是唯一的。这种列经常被称为替代键或候选键。这些项也必须是唯一的。虽然一个表只能有一个主键，但是它可以有多个候选键。 SQL Server的支持多个候选键概念进入唯一性约束。当一列或列的组合被声明是唯一的， SQL Server 会阻止任何行因为违反这个唯一性而进行的添加或更新操作。在没有故指的或者合适的键存在时，指定一个任意的唯一的数字作为主键，往往是最有效的。例如，企业普遍使用的客户号码或账户号码作为唯一识别码或主键。通过允许一个表中的一个列拥有身份属性，SQL Server可以更容易有效地产生唯一数字。您使用的身份属性可以确保每个列中的值是唯一的，并且值将从你指定的起点开始，以你指定的数量进行递增（或递减）。（拥有特定属性的列通常也有一个主键或唯一约束，但这不是必需的。）第二种类型的数据完整性是参照完整性。 SQL Server实现了表和外键约束之间的逻辑关系。外键是一个表中的列或列的组合，连接着另一个表的主键（或着也可能是替代键）。这两个表之间的逻辑关系是关系模型的基础;参照完整性意味着这种关系是从来没有被违反的。例如，一个包括出版商表和标题表的简单的select例子。在标题表中，列title_id （标题编号）是主键。在出版商表，列pub_id （出版者ID ）是主键。 titles表还包括一个pub_id列，这不是主键，因为出版商可以发布多个标题。相反， pub_id是一个外键，它对应着出版商表的主键。如果你在定义表的时候声明了这个关系， SQL Server由双方执行它。首先，它确保标题不能进入titles表，或在titles表中现有的pub_id无法被修改，除非有效的出版商ID作为新pub_id出现在出版商表中。其次，它确保在不考虑titles表中对应值的情况下，出版商表中的pub_id的值不做任何改变。以下两种方法可

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Dashboard From Wikipedia, the free encyclopedia This article is about a control panel placed in the front of the car. For other uses, see Dashboard (disambiguation). The dashboard of a Bentley Continental GTC car A dashboard (also called dash, instrument panel (IP), or fascia) is a control panel located directly ahead of a vehicle's driver, displaying instrumentation and controls for the vehicle's operation. Contents 1.Etymology 2.Dashboard features 3.Padding and safety 4.Fashion in instrumentation 5.See also 6.References Etymology Horse-drawn carriage dashboard Originally, the word dashboard applied to a barrier of wood or leather fixed at the front of a horse-drawn carriage or sleigh to protect the driver from mud or other debris "dashed up" (thrown up) by the horses' hooves.[1] Commonly these boards did not perform any additional function other than providing a convenient handhold for ascending into the driver's seat, or a small clip with which to secure the reins when not in use. When the first "horseless carriages" were constructed in the late 19th century, with engines mounted beneath the driver such as the Daimler Stahlradwagen, the simple dashboard was retained to protect occupants from debris thrown up by the cars' front wheels. However, as car design evolved to position the motor in front of the driver, the dashboard became a panel that protected vehicle occupants from the heat and oil of the engine. With gradually increasing mechanical complexity, this panel formed a convenient location for the placement of gauges and minor controls, and from this evolved the modern instrument panel,

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PA VEMENT PROBLEMS CAUSED BY COLLAPSIBLE SUBGRADES By Sandra L. Houston,1 Associate Member, ASCE (Reviewed by the Highway Division) ABSTRACT: Problem subgrade materials consisting of collapsible soils are com- mon in arid environments, which have climatic conditions and depositional and weathering processes favorable to their formation. Included herein is a discussion of predictive techniques that use commonly available laboratory equipment and testing methods for obtaining reliable estimates of the volume change for these problem soils. A method for predicting relevant stresses and corresponding collapse strains for typical pavement subgrades is presented. Relatively simple methods of evaluating potential volume change, based on results of familiar laboratory tests, are used. INTRODUCTION When a soil is given free access to water, it may decrease in volume, increase in volume, or do nothing. A soil that increases in volume is called a swelling or expansive soil, and a soil that decreases in volume is called a collapsible soil. The amount of volume change that occurs depends on the soil type and structure, the initial soil density, the imposed stress state, and the degree and extent of wetting. Subgrade materials comprised of soils that change volume upon wetting have caused distress to highways since the be- ginning of the professional practice and have cost many millions of dollars in roadway repairs. The prediction of the volume changes that may occur in the field is the first step in making an economic decision for dealing with these problem subgrade materials. Each project will have different design considerations, economic con- straints, and risk factors that will have to be taken into account. However, with a reliable method for making volume change predictions, the best design relative to the subgrade soils becomes a matter of economic comparison, and a much more rational design approach may be made. For example, typical techniques for dealing with expansive clays include: (1) In situ treatments with substances such as lime, cement, or fly-ash; (2) seepage barriers and/ or drainage systems; or (3) a computing of the serviceability loss and a mod- ification of the design to "accept" the anticipated expansion. In order to make the most economical decision, the amount of volume change (especially non- uniform volume change) must be accurately estimated, and the degree of road roughness evaluated from these data. Similarly, alternative design techniques are available for any roadway problem. The emphasis here will be placed on presenting economical and simple methods for: (1) Determining whether the subgrade materials are collapsible; and (2) estimating the amount of volume change that is likely to occur in the 'Asst. Prof., Ctr. for Advanced Res. in Transp., Arizona State Univ., Tempe, AZ 85287. Note. Discussion open until April 1, 1989. To extend the closing date one month,

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Commercial Buildings Abstract: A guide and general reference on electrical design for commercial buildings is provided. It covers load characteristics; voltage considerations; power sources and distribution apparatus; controllers; services, vaults, and electrical equipment rooms; wiring systems; systems protection and coordination; lighting; electric space conditioning; transportation; communication systems planning; facility automation; expansion, modernization, and rehabilitation; special requirements by occupancy; and electrical energy management. Although directed to the power oriented engineer with limited commercial building experience, it can be an aid to all engineers responsible for the electrical design of commercial buildings. This recommended practice is not intended to be a complete handbook; however, it can direct the engineer to texts, periodicals, and references for commercial buildings and act as a guide through the myriad of codes, standards, and practices published by the IEEE, other professional associations, and governmental bodies. Keywords: Commercial buildings, electric power systems, load characteristics 1. Introduction 1.1 Scope This recommended practice will probably be of greatest value to the power oriented engineer with limited commercial building experience. It can also be an aid to all engineers responsible for the electrical design of commercial buildings. However, it is not intended as a replacement for the many excellent engineering texts and handbooks commonly in use, nor is it detailed enough to be a design manual. It should be considered a guide and general reference on electrical design for commercial buildings. 1.2 Commercial Buildings The term “commercial, residential, and institutional buildings”as used in this chapter, encompasses all buildings other than industrial buildings and private dwellings. It includes office and apartment buildings, hotels, schools, and churches, marine, air, railway, and bus terminals, department stores, retail shops, governmental buildings, hospitals, nursing homes, mental and correctional institutions, theaters, sports arenas, and other buildings serving the public directly. Buildings, or parts of buildings, within industrial complexes, which are used as offices or medical facilities or for similar nonindustrial purposes, fall within the scope of this recommended practice. Today’s commercial buildings, because of their increasing size and complexity, have become more and more dependent upon adequate and reliable electric systems. One can better understand the complex nature of modern commercial buildings by examining the systems, equipment, and facilities listed in 1.2.1. 1.2.2 Electrical Design Elements In spite of the wide variety of commercial, residential, and institutional buildings, some electrical design elements are common to all. These elements, listed below, will be discussed generally in this section and in detail in the remaining sections of this recommended practice. The principal design elements considered in the design of the power, lighting, and auxiliary systems include: 1) Magnitudes, quality, characteristics, demand, and coincidence or diversity of loads and load factors 2) Service, distribution, and utilization voltages and voltage regulation 3) Flexibility and provisions for expansion