中文2500字
本科毕业设计翻译
学生姓名：*****
班级：*****班
学号：*****
学院：材料科学与工程学院
专业：材料成型及控制工程
指导教师：***** 副教授
2011年3月25日
Section 4 – Die Design and Construction Guidelines for HSS Dies General Guidelines for Die Design and Construction
Draw Dies
Higher than normal binder pressure and press tonnage is necessary with H.S.S. in order to maintain process control and to minimize buckles on the binder. Dies must be designed for proper press type and size. In some cases, a double action press or hydraulic press cushion may be required toachieve the necessary binder forces and control. Air cushions or nitrogen cylinders may not provide the required force for setting of draw beads or maintaining binder closure if H.S.S. is of higher strength or thickness.
Draw beads for H.S.S. should not extend around corners of the draw die. This will result in locking out the metal flow and cause splitting in corners of stamping. D raw beads should “run out” at the tangent of the corner radius to minimize metal compression in corners, as shown in figure 16 on page 47. Better grades of die material may be necessary depending on the characteristics of the HSS, the severity of the part geometry, and the production volume. A draw die surface treatment, such as chrome plating, may be recommended for outer panel applications.
Form and Flange Dies
Part setup in form and flange dies must allow for proper overbend on all flanges for springback compensation. Springback allowance must be increased as material strength increases; 3 degrees for mild steels, but 6 degrees or more
for HSS.
Punch radii must be fairly sharp. 1t for lower strength steels. Higher strength steels may require larger radii, but keeping them as small as practical will reduce springback in the sidewalls.
Flange steel die clearance must be held to no more than one metal thickness clearance to reduce springback and sidewall curl.
Form and flange steels should be keyed or pocketed in the casting to avoid flexing.
Flange steels should be designed to wrap over and coin the flange break in order to set the break and reduce springback. See figure 17 on page 48.
Die strength must not be compromised with light-weight die construction. High strength steel will require a stiffer die to resist flexing and the resultant part distortions, especially for channel or “hat-section” parts. This type of part can also cause serious die damage if double blanks occur.
Cutting Dies
To reduce press tonnage requirements and extend die life, a minimum shear of four to six times metal thickness in twelve inches of trim steel length is recommended.
To reduce die maintenance, maximum trim angles should be about 5° to 10°less than those used for mild steel. Trim steels should be keyed or pocketed in casting to avoid flexing. Die clearance should be 7 to 10% of metal thickness.
Drawbead Types
Conventional Drawbeads Run-out Drawbeads For H.S.S.
Lock Beads for Stretch-Form Die
Figure 16
1. Providing a vertical step in the flange stiffens and straightens the flange, stopping sidewall curl as well as springback.
2. The addition of stiffening darts helps maintain a 90-degree flange.
3. By adding a horizontal step along the flange, the flange is stiffened, resulting in reduced springback.
4. Back relief on the upper flange steel allows for extra pressure to be applied futher out on the formed radius.
Section 5 – Die Tryout Guidelines for High Strength Steel Dies
General Guidelines for Die Tryout
Draw Dies
Higher draw die binder pressure and press tonnage will be necessary in order to maintain process control and draw parts without buckles. A double action press or a press with hydraulic cushion may be required in some cases to achieve the required binder forces.
HSS draw die operations will require sheet steel lubricants that are formulated for extreme pressures. Mill oils will not provide sufficient lubricity for most applications. Pre-lubes or dry film lubricants may be necessary for process control.
Die plan view punchline corner radii should be larger than with mild steels to avoid buckling in the corners of the binder.
Stretch Form Dies
Lock beads may require modification to avoid cracking or tearing with higher strength grades of HSS. Opening side walls of beads and enlarging corner radii will avoid cracking of high strength sheet steel. Lock beads should be continuous around the punchline for stretch form dies.
For large panels from stretch-form dies, such as a roof panel or hood outer, elastic recovery may result in a shrunken panel that does not fit well on the male die member of the trim or flange dies. This problem is corrected by adding a “plus” factor to the overall part dimensions of the draw die or stretc h
form die punch. This “plus” is usually no more than 2.5 mm at the center of the sides and the front, tapering to 0.0mm at the corners of the part profile on the punch. Finish part profile is defined, and plus is removed, in the main flange die.
Form and Flange Dies
The punch radius should be fairly sharp with 1 or 2t used for lower strength steel. HSS may require larger radii, but as small as practical to reduce springback of sidewalls.
The flange steel radius affects sidewall curl and springback on any offset flanges. This radius should also be small to reduce springback of side flanges. Overbend for springback compensation must be increased as tensile strength increases: 3 degrees is standard for mild steels, but 6 degrees or more will be required for HSS.
Flange steel die clearance should be tight, maintaining no more than one metal thickness clearance to reduce springback and sidewall curl.
Cutting Dies
To reduce press tonnage requirements and extend die life, a minimum shear of four to six times metal thickness in twelve inches of trim steel length is required.
Die clearance should be 7 to 10% of metal thickness for HSS.
To reduce trim steel maintenance, reduce maximum trim angles by about 5° to 10° from those used for mild steel. Trim steels should be keyed or pocketed in the casting to avoid flexing.
Die Tryout When Using Bake Hardenable Steel
In order to obtain the maximum benefits of BHS, tryout of the dies should be performed as follows: Circle grid analysis must be performed on a panel before any die rework is attempted. With the gridded panel as a reference, the die can be modified to provide a minimum biaxial stretch of 2.0%. Stretch-form or draw dies are best for this material.
For rough or functional tryout, it is possible to use mild steel with a 6% to 8% gauge increase to perform the normal process of die preparation. This alleviates complications when the BHS strengthens between each die being tried out. The reason for this is the time lag that normally occurs between a panel being formed and its use in the next operation.
When the entire line of dies is ready for approval, all dies must be set in line. Panels should be run through all the die operations consecutively. This will avoid some of the strengthening effects of time delays between stamping operations that can cause variation in panels. Dimensional approval of the panel will be most difficult if this procedure is not followed.
The strengthening reaction in the BHS can cause dimensional variation in flanges since springback will vary with time as the strength increases. This is why running the panel through all die operations consecutively is crucial to a successful buyoff.
Part Buyoff
To reduce the part buyoff time and eliminate many hours of tryout time, the benefits of functional build must be considered. This procedure has been
proven to save time and money by concentrating on an acceptable sub-assembly rather than making each stamping to part specifications. Those parts that are easiest to change are revised to suit the sub-assembly dimensional targets. Those parts that do not affect the sub-assembly quality are not changed, but the detail part specifications are revised. The functional build process will eliminate excessive tryout hours if used for part buyoff on HSS stampings.
In addition to saving tryout time and die rework costs with functional build, lower part variation can also be realized. Two dimensional challenges faced by the die maker when first trying out dies are to reduce the dimensional variation from nominal specifications, and to reduce the short term variation
from part to part. The typical priority is to first minimize part-to-part variation and later address nominal deviation. A strong argument for this strategy is that the deviation from nominal is not precisely known until a dimensionally consistent part can be evaluated. The results are a dimensionally consistent part even though a number of checkpoints may deviate from nominal, and perhaps even be out of tolerance. In many situations when dimensions on the die are reworked to shift them closer to nominal, they become less stable and result in higher part-to-part variation. The functional build philosophy evaluates the acceptability of the part after it becomes stable, and before minor dimensional shifts are made. Large deviant or critical dimensions may be identified for rework even with functional build. There are dimensions that can often be spared rework based on a functional build approach. In these cases, the part remains more stable and the die more robust because less rework occurs while attempting to shift dimensions.
For more information on functional build, refer to the Auto/Steel Partnership publication. “Event-Based Functional Build: An Integrated Approach to Body Development”.
第四节-高强度钢模具设计和制造指南
对模具设计和制造的一般准则
拉深模具
为了控制高强度钢的成形并减少板料边缘的弯曲，高强度钢成型时的压力和吨位高于一般情况是必要的。模具设计必须考虑适当的压力类型和尺寸。在某些情况下，为了达到需要的压边力和控制力可以用一种双动压力垫或液压垫。如果高强度钢有更高的强度和厚度，空气垫子或氮气缸可能提供不了固定拉深筋或保持边缘固定的力。
高强度钢拉深筋不应该在拉伸模具的转角处延长，这将会导致金属流动被锁定和在冲压件角落处产生开裂。拉深筋应该“远离”转角半径切线以减小金属在转角处压缩,如图16。
基于高强度钢的特性、重要部位的几何结构和生产量，选用好的材料制造模具是必要的。拉深模的表面处理,例如电镀，可推荐用于外板的应用。
胀形和翻边模
为了能补偿回弹量，用胀形和翻边模生产的零件必须允许适当的过度弯曲。回弹极限必须随材料强度增加而增加;3度适用于低度钢,但6度或以上适用于高强度钢。
冲床半径必须相当尖锐。低强度钢1吨位。高强度钢可以要求更大半径,但使保持和实际生产时一样小，可以降低侧壁的回弹。
翻边模具间隙必须不超过一个金属厚度间隙以降低回弹及侧壁发生
的卷曲。
胀形和翻边板材要固定在铸件里以避免发生挠曲。
翻边板材应设计时应包住和压住边缘断处以设置中断和减少回弹。见图17。
模具强度不能小于低强度模具结构的强度。高强度钢将会需要一个坚硬的模具来抵抗屈曲和相应部分的扭曲,尤其是对集中力处或冒形截面部分。这部分在成形多个毛坯时也会引起严重的模具损坏
剪切模具
为了降低吨位要求和延长模具寿命,十二英寸长的金属至少修剪四到六次。
为了减少模具的维修,最大修剪角应该在5°角到10°，应该低于使用低碳钢的角度。修剪钢材要固定在铸件中以避免铸件挠曲。模具间隙应该是7%到10%的金属厚度。
拉延筋的类型
传统的拉延筋高强度拉延筋
带压边圈拉延模具
1.提供一个垂直的台阶来强化和压制边缘,同时防止侧壁的卷曲以及回弹。
2.增加强化暗褶有助于维持一个90度边。
3.通过沿边缘添加一个横向的台阶、能强化边缘并减少回弹。
4.上边缘金属的补充使得额外的压力能够进一步应用于形成的半径上。
第五节高强钢模具的模具调试
对模具调试的一般准则
拉深模具
为了控制高强度钢成型控制并减少板料边缘的弯曲，在高强度钢成型时压力和吨位高于一般情况是必要的。在某些情况下，为了达到需要的压边力和控制力可以用一种双作用压力垫或液压垫。
高强度钢拉深模操作时需要用于制定极端的压力钢板润滑剂，机油对于大多数应用将不提供足够的润滑性。预先润滑或干膜润滑油对拉深过程控制有必要的作用。
拉伸成型
对于有高强度的高强度钢定位调整杆可能需要修改以避免断裂或撕裂。开放侧面转角半径的筋和扩大转角半径将避免高强度钢板的开裂。定位调整杆应连续围绕在延伸模的延伸方向上。
延伸模对于大型嵌板,如车顶或外罩，弹性的回复可能导致板面的收缩,以至于与凸模和翻边模不匹配。通过添加一个因素的来增大拉深模具或翻边部分尺寸来纠正这个问题。这个“添加的因素”是在该中心的侧面和前面增加不超过2.5毫米,冲头上转角处部分的锥度是0，在总的翻边模中，通过边界部分的剖面,增加的部分被移走。
胀形和翻边模
冲头半径应比较突出尖锐，低强度钢用1或2吨位。H.S.S.可能需要更大半径,但减小到使用时能减少侧壁回弹。
在任何平板翻边中翻边钢材会影响回弹和侧壁的卷曲。半径应该也小到可以减少边缘的回弹。
过度弯曲时回弹补偿必须随抗拉强度增加而增加:3度对于低强度钢是一种标准,但6度或以上将会被用于H.S.S。
翻边模模具间隙应该紧凑,保持间隙不超过一个金属厚度以减少回弹及侧壁的卷曲。
剪切模
降低吨位要求和延长模具寿命,十二英寸长的金属至少修剪四到六次。
对于高强度钢模具间隙应在7% - 10%的金属厚度。
减少模具的维修,最大修剪角应该在5°角到10°，应该低于对低碳钢的使用角度。修剪钢材要固定在铸件中以避免在铸件挠曲。
当使用加热可硬化钢材的模具试用
为了获得使用BHS的最大值,模具应进行如下:在行任何模具重新工作前都必须尝试分析圆网格。模具可作为一个参考网格板料、模具可修改提供的最小二轴的伸展2.0%。延伸模或拉伸模具最适合该材料。
粗糙度或功能调试,它可以用低碳钢增加6% -8%标准来来表现通常模具的准备过程。这能减轻在每个模具调试时BHS得到强化时的复杂情况。这一现象的原因可能是时间滞后,通常一个板料之间发生的形成及其用于下一个操作。
当整个系列的模具已准备就绪，所有的模具必须设置在一条线上。板
料能在所有的模具连续操作。这将避免一些加固效果的时间延迟操作,可以引起冲压件之间变化。如果这个过程是不被允许的那么尺寸的延伸将是最困难的。
BHS的变化会导致边缘尺寸的变化,因为随时间回弹将随强度的增加而增加。这就是为什么让板料能连续通过模具各部分，对一个成功的检查来说是至关重要的。
部分新产品引入
为了减少新产品引入时间和消除几个小时的调试时间,就要考虑功能建设所有的优势。这个应用程序被证明能节省时间和金钱通过专注于一个可接受的半成品,而不是迫使每个冲压分开进行。这些零件是最容易改变来适应半成品进行相应的修正尺寸的目标。这些部分并不足以影响半成品质量，但是细节部分规格被修改。如果将这种程序用于高强度钢冲压件新产品引入将会消耗过多时间。
在功能的建立中除了节省时间和模具调试成本,降低零件变化都有可能实现。模具制造商所面临两个尺寸上的挑战：当第一次尝试模具时相对于公称规格降低尺寸上的变化,降低了各部分间的短期尺寸变化。首要任务是要先减小零件间变化和偏差。这个策略一个强有力的论点认为偏离标称是被允许的直到零件尺寸上一致可以评估。尽管很多测试点偏离标准位置有的甚至超过偏差极限但在结果上它们尺寸上是一致的。在许多情况下当改变模具尺寸使它接近标准值,它们变得不稳定甚至导致部分间更大的变化。这功能建设理论评估零件变稳定后可接受程度,在小尺寸上的进行改变。即使功能的建立在模具重做时也会有大偏差或临界尺寸出现。基于功能性建设的方法重做时经常有些备用尺寸。在这些情况下,模具零件仍然更加稳定和模具具有更强的性能，因为在改变模具尺寸上有相对少的调
整。
更多的信息,请参阅功能建设汽车/钢合作出版。“基于事件的功能建设:一套综合的方法来发展部件”。
外文出处： 《Exploiting Software How to Break Code》By Greg Hoglund, Gary McGraw Publisher : Addison Wesley Pub Date : February 17, 2004 ISBN : 0-201-78695-8 译文标题： JDBC接口技术 译文： JDBC是一种可用于执行SQL语句的JavaAPI（ApplicationProgrammingInterface应用程序设计接口）。它由一些Java语言编写的类和界面组成。JDBC为数据库应用开发人员、数据库前台工具开发人员提供了一种标准的应用程序设计接口，使开发人员可以用纯Java语言编写完整的数据库应用程序。 一、ODBC到JDBC的发展历程 说到JDBC，很容易让人联想到另一个十分熟悉的字眼“ODBC”。它们之间有没有联系呢？如果有，那么它们之间又是怎样的关系呢？ ODBC是OpenDatabaseConnectivity的英文简写。它是一种用来在相关或不相关的数据库管理系统（DBMS）中存取数据的，用C语言实现的，标准应用程序数据接口。通过ODBCAPI，应用程序可以存取保存在多种不同数据库管理系统（DBMS）中的数据，而不论每个DBMS使用了何种数据存储格式和编程接口。 1．ODBC的结构模型 ODBC的结构包括四个主要部分：应用程序接口、驱动器管理器、数据库驱动器和数据源。应用程序接口：屏蔽不同的ODBC数据库驱动器之间函数调用的差别，为用户提供统一的SQL编程接口。 驱动器管理器：为应用程序装载数据库驱动器。 数据库驱动器：实现ODBC的函数调用，提供对特定数据源的SQL请求。如果需要，数据库驱动器将修改应用程序的请求，使得请求符合相关的DBMS所支持的文法。 数据源：由用户想要存取的数据以及与它相关的操作系统、DBMS和用于访问DBMS的网络平台组成。 虽然ODBC驱动器管理器的主要目的是加载数据库驱动器，以便ODBC函数调用，但是数据库驱动器本身也执行ODBC函数调用，并与数据库相互配合。因此当应用系统发出调用与数据源进行连接时，数据库驱动器能管理通信协议。当建立起与数据源的连接时，数据库驱动器便能处理应用系统向DBMS发出的请求，对分析或发自数据源的设计进行必要的翻译，并将结果返回给应用系统。 2．JDBC的诞生 自从Java语言于1995年5月正式公布以来，Java风靡全球。出现大量的用java语言编写的程序，其中也包括数据库应用程序。由于没有一个Java语言的API，编程人员不得不在Java程序中加入C语言的ODBC函数调用。这就使很多Java的优秀特性无法充分发挥，比如平台无关性、面向对象特性等。随着越来越多的编程人员对Java语言的日益喜爱，越来越多的公司在Java程序开发上投入的精力日益增加，对java语言接口的访问数据库的API 的要求越来越强烈。也由于ODBC的有其不足之处，比如它并不容易使用，没有面向对象的特性等等，SUN公司决定开发一Java语言为接口的数据库应用程序开发接口。在JDK1．x 版本中，JDBC只是一个可选部件，到了JDK1．1公布时，SQL类包（也就是JDBCAPI）
毕业设计说明书 英文文献及中文翻译 学院：专 2011年6月 电子与计算机科学技术软件工程
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Inventory management Inventory Control On the so-called "inventory control", many people will interpret it as a "storage management", which is actually a big distortion. The traditional narrow view, mainly for warehouse inventory control of materials for inventory, data processing, storage, distribution, etc., through the implementation of anti-corrosion, temperature and humidity control means, to make the custody of the physical inventory to maintain optimum purposes. This is just a form of inventory control, or can be defined as the physical inventory control. How, then, from a broad perspective to understand inventory control? Inventory control should be related to the company's financial and operational objectives, in particular operating cash flow by optimizing the entire demand and supply chain management processes (DSCM), a reasonable set of ERP control strategy, and supported by appropriate information processing tools, tools to achieved in ensuring the timely delivery of the premise, as far as possible to reduce inventory levels, reducing inventory and obsolescence, the risk of devaluation. In this sense, the physical inventory control to achieve financial goals is just a means to control the entire inventory or just a necessary part; from the perspective of organizational functions, physical inventory control, warehouse management is mainly the responsibility of The broad inventory control is the demand and supply chain management, and the whole company's responsibility. Why until now many people's understanding of inventory control, limited physical inventory control? The following two reasons can not be ignored: First, our enterprises do not attach importance to inventory control. Especially those who benefit relatively good business, as long as there is money on the few people to consider the problem of inventory turnover. Inventory control is simply interpreted as warehouse management, unless the time to spend money, it may have been to see the inventory problem, and see the results are often very simple procurement to buy more, or did not do warehouse departments . Second, ERP misleading. Invoicing software is simple audacity to call it ERP, companies on their so-called ERP can reduce the number of inventory, inventory control, seems to rely on their small software can get. Even as SAP, BAAN ERP world, the field of
Statistical hypothesis testing Adriana Albu，Loredana Ungureanu Politehnica University Timisoara,adrianaa@aut.utt.ro Politehnica University Timisoara,loredanau@aut.utt.ro Abstract In this article,we present a Bayesian statistical hypothesis testing inspection, testing theory and the process Mentioned hypothesis testing in the real world and the importance of, and successful test of the Notes. Key words Bayesian hypothesis testing; Bayesian inference;Test of significance Introduction A statistical hypothesis test is a method of making decisions using data, whether from a controlled experiment or an observational study (not controlled). In statistics, a result is called statistically significant if it is unlikely to have occurred by chance alone, according to a pre-determined threshold probability, the significance level. The phrase "test of significance" was coined by Ronald Fisher: "Critical tests of this kind may be called tests of significance, and when such tests are available we may discover whether a second sample is or is not significantly different from the first."[1] Hypothesis testing is sometimes called confirmatory data analysis, in contrast to exploratory data analysis. In frequency probability,these decisions are almost always made using null-hypothesis tests. These are tests that answer the question Assuming that the null hypothesis is true, what is the probability of observing a value for the test statistic that is at [] least as extreme as the value that was actually observed?) 2 More formally, they represent answers to the question, posed before undertaking an experiment,of what outcomes of the experiment would lead to rejection of the null hypothesis for a pre-specified probability of an incorrect rejection. One use of hypothesis testing is deciding whether experimental results contain enough information to cast doubt on conventional wisdom. Statistical hypothesis testing is a key technique of frequentist statistical inference. The Bayesian approach to hypothesis testing is to base rejection of the hypothesis on the posterior probability.[3][4]Other approaches to reaching a decision based on data are available via decision theory and optimal decisions. The critical region of a hypothesis test is the set of all outcomes which cause the null hypothesis to be rejected in favor of the alternative hypothesis. The critical region is usually denoted by the letter C. One-sample tests are appropriate when a sample is being compared to the population from a hypothesis. The population characteristics are known from theory or are calculated from the population.
软件工程专业BIOS资料外文翻译文献 What is the Basic Input Output System (BIOS)? BIOS is an acronym for Basic Input Output System. It is the program that stores configuration details about your computer hardware and enables your computer to boot up. Every time your computer is switched on the BIOS loads configuration data into main memory, performs a routine diagnostic test on your hardware, then loads the operating system. The BIOS resides in a ROM (Read-Only memory) chip, which is mounted on the motherboard, usually in a socket so it is removable. To the right is an example of what a BIOS chip may look like in your motherboard. This is a PLCC 32 pin type BIOS chip. It is a very common type. Every computer has BIOS. There are many types but the most common type of BIOS 's come from: AMI, Award and Phoenix. Motherboard manufacturers buy or lease the BIOS source code from these companies. The BIOS tells the operating system in your computer how to boot up, where to load everything, what to load, what memory and CPU are present and much more. A good comparison to further understand the
吉林化工学院理学院 毕业论文外文翻译English Title（Times New Roman ，三号） 学生学号：08810219 学生姓名：袁庚文 专业班级：信息与计算科学0802 指导教师：赵瑛 职称副教授 起止日期：2012.2.27～2012.3.14 吉林化工学院 Jilin Institute of Chemical Technology
1 外文翻译的基本内容 应选择与本课题密切相关的外文文献（学术期刊网上的），译成中文，与原文装订在一起并独立成册。在毕业答辩前，同论文一起上交。译文字数不应少于3000个汉字。 2 书写规范 2.1 外文翻译的正文格式 正文版心设置为：上边距：3.5厘米，下边距：2.5厘米，左边距：3.5厘米，右边距：2厘米，页眉：2.5厘米，页脚：2厘米。 中文部分正文选用模板中的样式所定义的“正文”，每段落首行缩进2字；或者手动设置成每段落首行缩进2字，字体：宋体，字号：小四，行距：多倍行距1.3，间距：前段、后段均为0行。 这部分工作模板中已经自动设置为缺省值。 2.2标题格式 特别注意：各级标题的具体形式可参照外文原文确定。 1．第一级标题（如：第1章绪论）选用模板中的样式所定义的“标题1”，居左；或者手动设置成字体：黑体，居左，字号：三号，1.5倍行距，段后11磅，段前为11磅。 2．第二级标题（如：1.2 摘要与关键词）选用模板中的样式所定义的“标题2”，居左；或者手动设置成字体：黑体，居左，字号：四号，1.5倍行距，段后为0，段前0.5行。 3．第三级标题（如：1.2.1 摘要）选用模板中的样式所定义的“标题3”，居左；或者手动设置成字体：黑体，居左，字号：小四，1.5倍行距，段后为0，段前0.5行。 标题和后面文字之间空一格（半角）。 3 图表及公式等的格式说明 图表、公式、参考文献等的格式详见《吉林化工学院本科学生毕业设计说明书（论文）撰写规范及标准模版》中相关的说明。
毕业设计（论文）外文文献翻译 文献、资料中文题目：软件开发概念和设计方法文献、资料英文题目： 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
外文资料原文 Software Development Concepts and Design Methodologies During the 1960s, ma inframes and higher level programming languages were applied to man y problems including human resource s yste ms,reservation s yste ms, and manufacturing s yste ms. Computers and software were seen as the cure all for man y bu siness issues were some times applied blindly. S yste ms sometimes failed to solve the problem for which the y were designed for man y reasons including: ?Inability to sufficiently understand complex problems ?Not sufficiently taking into account end-u ser needs, the organizational environ ment, and performance tradeoffs ?Inability to accurately estimate development time and operational costs ?Lack of framework for consistent and regular customer communications At this time, the concept of structured programming, top-down design, stepwise refinement，and modularity e merged. Structured programming is still the most dominant approach to software engineering and is still evo lving. These failures led to the concept of "software engineering" based upon the idea that an engineering-like discipl ine could be applied to software design and develop ment. Software design is a process where the software designer applies techniques and principles to produce a conceptual model that de scribes and defines a solution to a problem. In the beginning, this des ign process has not been well structured and the model does not alwa ys accurately represent the problem of software development. However,design methodologies have been evolving to accommo date changes in technolog y coupled with our increased understanding of development processes. Whereas early desig n methods addressed specific aspects of the
农村社会养老保险的现状、问题与对策研究社会保障对国家安定和经济发展具有重要作用，“城乡二元经济”现象日益凸现，农村社会保障问题客观上成为社会保障体系中极为重要的部分。建立和完善农村社会保障制度关系到农村乃至整个社会的经济发展，并且对我国和谐社会的构建至关重要。我国农村社会保障制度尚不完善，因此有必要加强对农村独立社会保障制度的构建，尤其对农村养老制度的改革，建立健全我国社会保障体系。从户籍制度上看，我国居民养老问题可分为城市居民养老和农村居民养老两部分。对于城市居民我国政府已有比较充足的政策与资金投人，使他们在物质和精神方面都能得到较好地照顾，基本实现了社会化养老。而农村居民的养老问题却日益突出，成为摆在我国政府面前的一个紧迫而又棘手的问题。 一、我国农村社会养老保险的现状 关于农村养老，许多地区还没有建立农村社会养老体系，已建立的地区也存在很多缺陷，运行中出现了很多问题，所以完善农村社会养老保险体系的必要性与紧迫性日益体现出来。 （一）人口老龄化加快 随着城市化步伐的加快和农村劳动力的输出，越来越多的农村青壮年人口进入城市，年龄结构出现“两头大，中间小”的局面。中国农村进入老龄社会的步伐日渐加快。第五次人口普查显示：中国65岁以上的人中农村为5938万，占老龄总人口的67.4%.在这种严峻的现实面前，农村社会养老保险的徘徊显得极其不协调。 （二）农村社会养老保险覆盖面太小 中国拥有世界上数量最多的老年人口，且大多在农村。据统计，未纳入社会保障的农村人口还很多，截止2000年底，全国7400多万农村居民参加了保险，占全部农村居民的11.18%，占成年农村居民的11.59%.另外，据国家统计局统计，我国进城务工者已从改革开放之初的不到200万人增加到2003年的1.14亿人。而基本方案中没有体现出对留在农村的农民和进城务工的农民给予区别对待。进城务工的农民既没被纳入到农村养老保险体系中，也没被纳入到城市养老保险体系中，处于法律保护的空白地带。所以很有必要考虑这个特殊群体的养老保险问题。
中英文对照外文翻译 (文档含英文原文和中文翻译) Application Fundamentals Android applications are written in the Java programming language. The compiled Java code — along with any data and resource files required by the application — is bundled by the aapt tool into an Android package, an archive file marked by an .apk suffix. This file is the vehicle for distributing the application and installing it on mobile devices; it's the file users download to their devices. All the code in a single .apk file is considered to be one application. In many ways, each Android application lives in its own world: 1. By default, every application runs in its own Linux process. Android starts the process when any of the application's code needs to be executed, and shuts down the process when it's no longer needed and system resources are required by other applications. 2. Each process has its own virtual machine (VM), so application code runs in isolation from the code of all other applications. 3. By default, each application is assigned a unique Linux user ID. Permissions are set so that the application's files are visible only to that user and only to the application itself — although there are ways to export them to other applications as well. It's possible to arrange for two applications to share the same user ID, in which case they will be able to see each other's files. To conserve system resources, applications with the same ID can also arrange to run in the same Linux process, sharing the same
软件专业毕业论文外文文献中英文翻译 Object landscapes and lifetimes Tech nically, OOP is just about abstract data typing, in herita nee, and polymorphism, but other issues can be at least as importa nt. The rema in der of this sect ion will cover these issues. One of the most importa nt factors is the way objects are created and destroyed. Where is the data for an object and how is the lifetime of the object con trolled? There are differe nt philosophies at work here. C++ takes the approach that con trol of efficie ncy is the most importa nt issue, so it gives the programmer a choice. For maximum run-time speed, the storage and lifetime can be determined while the program is being written, by placing the objects on the stack (these are sometimes called automatic or scoped variables) or in the static storage area. This places a priority on the speed of storage allocatio n and release, and con trol of these can be very valuable in some situati ons. However, you sacrifice flexibility because you must know the exact qua ntity, lifetime, and type of objects while you're writing the program. If you are trying to solve a more general problem such as computer-aided desig n, warehouse man ageme nt, or air-traffic con trol, this is too restrictive. The sec ond approach is to create objects dyn amically in a pool of memory called the heap. In this approach, you don't know un til run-time how many objects you n eed, what their lifetime is, or what their exact type is. Those are determined at the spur of the moment while the program is runnin g. If you n eed a new object, you simply make it on the heap at the point that you n eed it. Because the storage is man aged dyn amically, at run-time, the amount of time required to allocate storage on the heap is sig ni fica ntly Ion ger tha n the time to create storage on the stack. (Creat ing storage on the stack is ofte n a si ngle assembly in structio n to move the stack poin ter dow n, and ano ther to move it back up.) The dyn amic approach makes the gen erally logical assumpti on that objects tend to be complicated, so the extra overhead of finding storage and releas ing that storage will not have an importa nt impact on the creati on of an object .In additi on, the greater flexibility is esse ntial to solve the gen eral program ming problem. Java uses the sec ond approach, exclusive". Every time you want to create an object, you use the new keyword to build a dyn amic in sta nee of that object. There's ano ther issue, however, and that's the lifetime of an object. With Ian guages that allow objects to be created on the stack, the compiler determines how long the object lasts and can automatically destroy it. However, if you create it on the heap the compiler has no kno wledge of its lifetime. In a Ianguage like C++, you must determine programmatically when to destroy the
I / 11 本科毕业设计外文翻译 <2018届） 论文题目基于WEB 的J2EE 的信息系统的方法研究 作者姓名[单击此处输入姓名] 指导教师[单击此处输入姓名] 学科(专业 > 所在学院计算机科学与技术学院 提交日期[时间 ]
基于WEB的J2EE的信息系统的方法研究 摘要：本文介绍基于工程的Java开发框架背后的概念，并介绍它如何用于IT 工程开发。因为有许多相同设计和开发工作在不同的方式下重复，而且并不总是符合最佳实践，所以许多开发框架建立了。我们已经定义了共同关注的问题和应用模式，代表有效解决办法的工具。开发框架提供：<1）从用户界面到数据集成的应用程序开发堆栈；<2）一个架构，基本环境及他们的相关技术，这些技术用来使用其他一些框架。架构定义了一个开发方法，其目的是协助客户开发工程。 关键词：J2EE 框架WEB开发 一、引言 软件工具包用来进行复杂的空间动态系统的非线性分析越来越多地使用基于Web的网络平台，以实现他们的用户界面，科学分析，分布仿真结果和科学家之间的信息交流。对于许多应用系统基于Web访问的非线性分析模拟软件成为一个重要组成部分。网络硬件和软件方面的密集技术变革[1]提供了比过去更多的自由选择机会[2]。因此，WEB平台的合理选择和发展对整个地区的非线性分析及其众多的应用程序具有越来越重要的意义。现阶段的WEB发展的特点是出现了大量的开源框架。框架将Web开发提到一个更高的水平，使基本功能的重复使用成为可能和从而提高了开发的生产力。 在某些情况下，开源框架没有提供常见问题的一个解决方案。出于这个原因，开发在开源框架的基础上建立自己的工程发展框架。本文旨在描述是一个基于Java的框架，该框架利用了开源框架并有助于开发基于Web的应用。通过分析现有的开源框架，本文提出了新的架构，基本环境及他们用来提高和利用其他一些框架的相关技术。架构定义了自己开发方法，其目的是协助客户开发和事例工程。 应用程序设计应该关注在工程中的重复利用。即使有独特的功能要求，也