我的毕业设计是药店进销存管理系统 现在要一份外文翻译 求高手 发我邮箱 急急急急急_百度知道
我的毕业设计是药店进销存管理系统 现在要一份外文翻译 求高手 发我邮箱 急急急急急
进销存管理系统再大学生计算机论坛cccbbs的毕业设计范例有成品，你可以去搜索一下，
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我也想要外文翻译~我得题目也是药品~55555
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我们会通过消息、邮箱等方式尽快将举报结果通知您。请问你有云存储的外文翻译吗？能发我一份吗？谢谢！_百度知道
请问你有云存储的外文翻译吗？能发我一份吗？谢谢！
推荐个 存储基础 给你看看
谢谢~~待我研究一下^_^
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有，什么主题
你回答的好快呀~~基于云存储的隐私保护方案的研究与设计，只要与云存储和隐私保护有关即可
你做的毕业设计吗？怎么发给你？找了好久
是的，毕业设计，哎百度不让留邮箱，说可以发到“知道”里面？
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我们会通过消息、邮箱等方式尽快将举报结果通知您。测绘方面横断面纵断面外文翻译，邮箱。谢谢啦！_百度知道
测绘方面横断面纵断面外文翻译，邮箱。谢谢啦！
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什么东西，拿出来我给你解决。
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我们会通过消息、邮箱等方式尽快将举报结果通知您。哪位大哥大姐能给我一个有关于JSP的英文文献加翻译，毕业设计用的！这几天焦头烂额，发到我的邮箱里，谢谢_百度知道
哪位大哥大姐能给我一个有关于JSP的英文文献加翻译，毕业设计用的！这几天焦头烂额，发到我的邮箱里，谢谢
谁能发一个英文2到3页，有些深度的，用翻译软件翻译的就不用发了。liyangd420发的那个不行。
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我们会通过消息、邮箱等方式尽快将举报结果通知您。毕业设计英文翻译
毕业设计英文翻译
一 : 如何做毕业设计的外文翻译淮滨新闻网/ www.hb0376.net[毕业论文外文翻译]如何做毕业设计的外文翻译——简介毕设是一个大学生大学四年的最后阶段了，您是否准备好了呢？毕设一般需要调研报告和外文翻译已及论文等内容，今天小编就把自己做外文翻译的经验分享给大家[毕业论文外文翻译]如何做毕业设计的外文翻译——知识点EI论文检索网[毕业论文外文翻译]如何做毕业设计的外文翻译——详细知识[毕业论文外文翻译]如何做毕业设计的外文翻译 一如果您的英语不是很好，那么您可以使用百度翻译先把英文一段一段复制下来翻译，推荐不要太多一次，因为本身就不是正常语序的自动翻译是很乱的，少一点比较有逻辑，而且这个翻译一般导师是不会接受的，您需要自己重新调整语序和一些不正确的用词。还有一个提示是您最好使用百度翻译自带的复制按钮，而不是右键复制和Ctrl+C，否则不是有格式粘贴到word会有蓝色暗纹。[毕业论文外文翻译]如何做毕业设计的外文翻译 二文献选择，推荐您尽量选择PDF格式的外文文献，一般可以使用chrome内核浏览器打开，无需下载其他阅读器，其他格式文献可能不能复制文字，自己打是不可能的吧，除非您是自己直接翻译，而不使用百度翻译[毕业论文外文翻译]如何做毕业设计的外文翻译 三一般有的专业词汇百度自动翻译是词不对意的，所以您需要自己翻译这些单词，而且这些词汇是经常出现的，小编的技巧是先把不认识的专业单词复制到EI的文献检索中，搜索标题（不是主题），这样就会有中文的文献名字提到这个单词了，您只要对应到位置就可以，很有效果哦[毕业论文外文翻译]如何做毕业设计的外文翻译 四语序的调整是很复杂的，往往您怎么都看不懂机器翻译的是什么，这可能是知识积累还有欠缺，或者实在是语序复杂，您可以适当跳过这些内容或者按自己的理解翻译并询问您的导师。英语中的定语后置之类的语法也导致了机器翻译的语序问题，小编的经验是往往名词都有一句话来翻译，很长，不如分开用小句子，即使重复使用同样的词汇。[毕业论文外文翻译]如何做毕业设计的外文翻译 五一般导师还会要之前的英文文献的，所以要保留一份，而且如果英文文献很长，可以和导师协调，挑选一部分翻译。如果导师让您自己选文献，可以找找比较短的或者是日本人韩国人写的文章，比英语国家的好理解一点[毕业论文外文翻译]如何做毕业设计的外文翻译——注意事项图片来源网络二 : 机床刀具设计毕业论文中英文资料对照外文翻译文献综 10机床刀具设计中英文资料对照外文翻译文献综英语原文：Design Of Tool Machine PropResearch significanceThe original knife machine control procedures are designed individually, not used tool management system, features a single comparison, the knife only has to find the tool knife, knife positioning the shortest path, axis tool change, but does not support large-scale tool.Automatic knife in the knife election, in the computer memory knife-election on the basis of using the Siemens 840 D features, and the election procedures knife more concise, and complete the space Daotao View. ATC use the knife rapid completion of STEP-7 programming, and have been tested in practice. In the positioning of the knife, PLC controlled modular design method, which future production of similar machines will be very beneficial, it is easy to use its other machine. Automatic tool change systems will be faster growth, reduced tool change time, increase the positioning accuracy tool is an important means to help NC technology development. Tool and inventory components of modern production is an important link in the management, especially for large workshop management. The traditional way of account management, and low efficiency, high error rate, and not sharing information and data, tools and the use of state can not track the life cycle, are unable to meet the current information management needs. With actual production, we have to establish a workshop tool for the three-dimensional tool storage system to meet the knife workshop with auxiliary storage and management needs.The system uses optimization technology, a large number of computer storage inventory information, timely, accurate, and comprehensive tool to reflect the inventory situation. The entire system uses a graphical interface, man-machine dialogue tips from the Chinese menu, select various functions can be realized and the importation of all kinds of information. Management system using online help function. Through the workshop management, networkmanagement and sharing of information. Have automated inventory management, warehousing management tool, a tool for the management and statistical functions.1.System components and control structureThe entire system, including the structure and electrical machinery control systems.1.1.1Mechanical structure and working principleTool from the stent, drive, drive system, Turret, shielding, control system, and electrical components. Support from the column, beam, the upper and lower guide Central track, and track support component.1) Drive for the system chosen VVVF method. Cone used brake motors, with VVVF by Cycloid reducer through sprocket drive.2) Drag a variable frequency drive system and control technology. VVVF adopted, will speed drive shaft in the normal range adjustment to control the speed rotary turret to 5 ~ 30mm in, the drive shaft into two, two under through sprocket, the two profiled rollers Chain driven rotating shelves. Expansion chain adopted by the thread tight regulation swelling, swelling the regular way. - Conditioned, under the same chain-of-conditioning, so that the chain of uniform.3) Turret and shields the entire total of 14 independent Turret. 13 of them as a socket-Turret, as a drawer-Turret, each Turret back through the pin and, under the conveyor chain link chain plate, installed at the bottom roller, chain driven rotating turret rotation along the track. Outlet-Turret and BT50-BT40 Turret Turret two kinds of forms. To strengthen management, security,landscaping modeling, shelf peripherals and shields. Turret-drawer drawer placed at six other Des Voeux a knife, can be categorized with some of knife auxiliary equipment, such as bits, such as turning tools.1.1.2.Electrical Control SystemThis tool storage systems is the main electrical control their shelves for operational control and position control. Operational control equipment, including operation of the start of braking control. Position Control is the main location and address of the shelves for testing. Control system as shown in Figure 1.图 1 Tool Control System1) Electric Transmission horizontal rotary tool storage systems are the mechanical movements are repeated short-term work system. And the run-time system needs some speed, speed transmission needs, the system will use VVVF method can be used simple structure, reliable operation of the motor and frequency inverter.2) Control of the system is divided into two kinds of manual control and automatic control, manual control as a general reserve and debug ways to the system control computer (IPC) and the control unit (inverter contactor , etc.) consisting of a control system.3) location and positioning accuracy of the system automatically identify the site and location using a detection device as proximity switches, relays through the plate-point isolation and the number plate recorded close to the switching signal acquisition and operation of Hutchison with a Optimal Path addressable identify the current location and shelves of the purpose of the shelf location. In order to enable a more accurate positioning system, adopted two photoelectric switches, to detect the two shelves of the two films.1.2.The functions of the knifeknife The is the role of reserves a certain number of tools, machine tool spindle in hand to achieve the fungibility a disc cutter knife is the type of library, the chain knives, and other means, in the form of the knife and capacity according to the Machine Tool to determine the scope of the process.1.3.Common typesThe knife is a tool storage devices, the common knife mainly in the following forms:(1) the turret knifeIncluding the first level turret vertical turret and the first two, see Figure 2.6 a) and b):(2) the disc cutterDisc knife in the library with discoid knife, cutting tool along See how vertical arrangement (including radial and axial from knife from knife), along See how radial array into acute or arranged in the form of the knife. Simple, compact, more applications, but are ring-cutter, low utilization of space. Figure 2.7 a) to c). If the knife storage capacity must be increased toincrease the diameter of the knife, then the moment of inertia also increased correspondingly, the election campaign long knife. Tool number not more than 32 general. Cutter was multi-loop order of the space utilization knife, but inevitably given the knife from complex institutions, applicable to the restricted space Machine Tool storage capacity and more occasions. Two-disc structure is two smaller capacity knife on both sides of the sub-spindle place, more compactlayout, the number of certificates corresponding increase knife, apply to small and medium-sized processing center.(3) the chain knifeIncluding single-and multi-ring chain ring chain, chain link can take many forms change, see Figure 2.8 a) to c), thebasic structure shown inFigure 2. 8 doFeatures: knife apply tothe larger capacity of theoccasion, the space of thesmall number ofgenerally applicable tothe tool in the 30-120.Only increase the lengthof the chain tool will increase the number should not be increased circumferential speed of itsmoment of inertia of the knife does not increase the disc as large.(4) linear combination knife and the knife libraryThe linear knife simple structure in Figure 2.9, tool single order, the capacity of small knife,used for CNC lathe and drill press on. Because the location of fixed knife, ATC completed action by the spindle without manipulator. The cutter knife is generally the turret combination turret with a combination of the disc cutter knife and the chain combination. Every single knife the knife certificates of smaller, faster tool change. There are also some intensive drum wheel, and the lattice-type magazine for the knife, the knife-intensive though. Small footprint, but because of structural constraints, basically not used for single processing center, the concentration used for FMS for the knife system.机床刀具设计毕业论文中英文资料对照外文翻译文献综 10_毕业设计英文1.4 Tool storage capacityTool storage capacity of the first to consider the needs of processing, from the use of point of view, generally 10 to 40 knives, knife will be the utilization of the high, and the structure is compact.1.5 Tool options(1) choose to order processing tool according to the order, followed Add to the knife every knife in the Block. Each tool change, the order of rotation of a cutter knife on location, and remove the need knives, has been used by the cutter knife can be returned to the original Block, can also order Add Block, a knife. However, as the knife in the tool in different processes can not be repeated use of the knife must increase the capacity and lower utilization rate.(2) most of the arbitrary choice of the current system of using arbitrary NC election knives, divided into Daotao coding, coding and memory-cutter, three. Daotao coding tool code or knives or Daotao need to install the code used to identify, in accordance with the general principle of binary coding coding. Tool knife election coding method uses a special knife handle structure, and each of the coding tool. Each of the tool has its own code, thereby cutting tool can be in different processes repeatedly used, not to replace the tool back at the original knife, the knife capacity can be reduced accordingly. Memory-election this paper knife, in this way can knives and knife in the position corresponding to the Daotao memory of the PLC in the NC system, no matter which tool on the Inner knife, tool information is always there in mind, PLC . On the knife with position detection devices, will be the location of each Daotao. This tool can be removed and sent back to arbitrary. On the knife is also a mechanical origin, every election, the nearest knife selection.1.6. Control of the knife(1) the knife as a system to control the positioning axis. In the ladder diagram in accordance with the instructions for computing T code comparison of the output angle and speed of instructions to the knife the knife servo drive servo motor. Tool storage capacity, rotation speed,and / deceleration time, and other system parameters can be set in such a manner free from any outside influence positioning accurate and reliable but the cost is higher.(2) knife from the hydraulic motor drives, fast / slow the points, with proximity switches count and positioning. In comparison ladder diagram of the current storage system knife (knife spindle) and goals knife (pre-knife) and computing, then output rotation instructions, judging by the shortest path rotation in place. This approach requires sufficient hydraulic power and electromagnetic valve knife the rotational speed can be adjusted through the throttle. But over time may be oily hydraulic, oil temperature and environmental factors impact the change in velocity and accuracy. Not generally used in large and medium-sized machine tool change frequently.(3) the knife from AC asynchronous motor driven cam mechanism (Markov institutions), with proximity switches count, which means stable operation, and generally accurate and reliable positioning cam used in conjunction with a mechanical hand, ATC fast-positioning.2. ATC, the main types, characteristics, and the scope of application2.1 Auto Rotary ToolRotary Tool automatically onthe use of CNC machine tool is asimple installation of automatic toolchange, the Quartet and 47.60 TurretTool various forms, such as rotaryturret were installed on four, six ormore of the Tool , NC instructions byATC. Rotary Tool has two verticaland horizontal, relatively simplestructure, applicable to economicCNC lathe.Rotary Tool in the structure musthave good strength and stiffness,resistance to bear rough Cutting Toolin the cutting force and reduce therole of deformation and improveprocessing accuracy. Rotating Toolto choose reliable positioningprogramme structure and reasonable position, in order to ensure that each rotary turret toahigher position after repeated positioning accuracy (typically 0.001 to 0.005mm). Figure 2.1 shows the spiral movements of the Quartet Turret.Auto Rotary Tool in the simplest of ATC, is 180 o rotary ATC devices, as shown in Figure2.2 ATC instructions received, the machine control system put ATC spindle control to thedesignated location at the same time, the tool movement to the appropriate location, ATC, with the rotary axis and at the same time, the
drawbars from Spindle Cutting Tools rip, ATC, will be the tool from th ATC, 180 o rotary tool spindle and th ATC, the Rotary At the same time, the tool refocusing its position toaccept Spindle removed f Next, ATC, will be replaced with the cutter knives were unloaded into the spindle and tool: Finally, back to the original ATC, &standby& position. At this point, ATC completed procedures to continue to run. This ATC, the main advantage ofsimple structure, the less movement, fast tool change. The main disadvantage is that knives must be kept in parallel with the axis of the plane, and after the home side compared to the tool, chip and liquid-cutting knife into the folder, it is necessary to the tool plus protection. Cone knife folder on the chip will cause ATC error, or even damage knife folders, and the possibility of spindle. Some processing centre at the transfer, and the tool side. When the ATC command is called, the transfer-cutter knives will be removed, the machine go forward, and positioning with the ATC, in line with the position. 180 o &Rotary ATC devices can be used horizontal machine,can also be used for vertical machining centers.2. 2 ATC head-turret installedWith rotating CNC machine tool often used such ATC devices, with a few turret head spindle, each with a spindle on both knives, the first tower interim process can be automatic tool change-realization. The advantage is simple structure, tool change time is short, only about 2 s. However, due to spatial constraints, the number of spindle can not be too much, usually only apply to processes less, not to high precision machine tools, such as the NC drill, such as CNC milling machine. In recent years there has been a mechanical hand and the turret head with a knife for the automatic tool change ATC devices, as shown in Figure 2.3. It is in fact a turrethead ATC, and the knife-ATC device combination. The principle is as follows:5 turret on the first two tool spindle 3 and 4, when using the tool spindle 4 processing tool, the manipulator 2 will be the next step to the need for the tool does not work on the tool spindle 3 until after the completion of this process , the first rotary turret 180 o, ATC completed. ATC most of their time and processing time coincidence, the only real tool change time turret transposition of the first time, this approach mainly used for ATC and NC NC drilling file bed.2. 3.Daidao system for the automatic tool changeFigure 2.4 shows the knife and the whole machine tool CNC machine tools for the appearance of Fig.Figure 2.5 shows the knife and split-type machine to the appearance of CNC machine tool plans.At this point, knife storage capacity, a heavier tool can, and often additional transport unit to complete the knife between the spindle and cutting tool transport.Daidao the knife from the ATC, the election knives, automatic loading and unloading machine tool and tool exchange institutions (manipulator), composed of four parts, used widely.Tool Automatic Tool Change the manipulator system, the whole process more complicated ATC. We must first used in the processing of all installed in the standard tool on the knife handle in the machine outside the pre-size, according to a certain way Add to the knife. ATC, selected first in the knife knife, and then from ATC, from the knife from the knife or spindle, exchange, the new knife into the spindle, the old knife back into the knife.ATC, as the former two knives to accommodate a limited number can not be too many, can not meet the needs of complex parts machining, CNC machine tool Automatic Tool Change Daidao the use of the automatic tool change devices. The knife has more capacity, both installed in the spindle box side or above. As for the automatic tool change Daidao device CNC machine tool spindle box only a spindle, spindle components to high stiffness to meet the machining requirements. The number of establishments in larger knife, which can meet the more complex parts of the machining processes, significantly improving productivity. Daidao system for the automatic tool change applied to drilling centres and CNC machining centers. The comparisondrawn Daidao automatic tool change system is the most promising.机床刀具设计毕业论文中英文资料对照外文翻译文献综 10_毕业设计英文3.PLC control of the knife random mode of election3. 1Common methods of automatic election knifeAutomatic control of the knife CNC refers to the system after the implementation of user instructions on the knife library automation process, including the process to find knives and automatic tool change [(63,71]. CNC Machining Center device (CNC) directive issued by the election knife , a knife, the tool required to take the knife position, said the election automatic knife. automatically elected knife There are two ways: random sequence election knives and knife election method.3.1.1 order election knifeTool Selection order is the process tool according to the sequence of the insert knife, the use of knives in order to take place, used knives back at the original knife, can also order Add Block, a knife. In this way, no need Tool identification devices, and drive control is a relatively simple, reliable and can be used directly from the points of the knife machinery to achieve. But the knives in each of the tool in different processes can not be reused, if the tool is installed in accordance with the order of the knife, there will be serious consequences. The need to increase the number of knives and knife the capacity of the tool and reduce the utilization of the knife.3.1.2Random election knifeRandom election under the knife is arbitrary instructions to select the required tools, then there must be tool identification devices. Tool knife in the library do not have the processing in accordance with the order of the workpiece can be arbitrary storage. Each of the tool (or knifeblocks) are for a code, automatic tool change, the rotary cutter, every tool have been the &tool identification device& acceptable identification. When CNC tool code and the code in line with directives of the tool selected, the rotary cutter knives will be sent to the ATC position, waiting to grab manipulator. Random knife election is the advantage of the cutter knife in the order has nothing to do with the processing sequence, the same tool can be used repeatedly. Therefore, the relatively small number of knives, knife the corresponding smaller. Random elections knife on the tool must be coded to identify. There are three main coding.1. Tool coding. Adopt special knife handle structure coding, the drawbars on the knife handle back-end packages such as spacing of the coding part of the lock-nut fixed. Coding diameter ring diameter of a size two, respectively, said that binary &1& and &0& to the two rings are different, can be a series of code. For example, there are six small diameter of the ring can be made to distinguish between 63 (26-1 = 63) of the coding tool. All of 0 normally not allowed to use the code, to avoid the cutter knife Block did not confuse the situation.2. Knife Block coding. On the knife Block coding, coding tool, and tool into line with the number of knives in the Block. ATC knife when the rotation, so that each knife seats followed through knowledge knife, knife found blocks, knives stopped the rotation. At this time there is no knife handle encoding part of the knife handle simplified.3. Annex coding methods. This style of coding keys, coded cards, coding and coding-disc, which is the most widely used coding keys. First toknives are attached to a tool of the show wrapped coding keys, and when the cutter knife to the store at knife in, so put the number of keys to remember knife Block Road, will be inserted into key to the coding Block next to the key hole in the seat for the knife to the numbers.ConclusionFocused on in today's manufacturing environment tool storage and management of new models and methods, practical application of good results in systems integration and optimization, and other aspects of operations will be further explored, so that it has a higher theoretical and practical level.译文：机床刀具设计课题研究意义机床原来的刀库控制程序是单独设计的，没有采用刀具管理系统，功能也比较单一，只实现了刀库刀具的找刀、刀库最短路径定位、主轴换刀，而且不支持大型刀具。在刀库自动选刀方面，在计算机记忆式选刀的基础上采用了西门子840D特色功能，使选刀程序更简洁，并完成空刀套的查找。刀库快速换刀利用STEP-7完成编程，并在实际中得到验证。在刀库定位问题上，PLC程序控制采用模块化设计方法，这对今后生产类似机床将十分有利，很容易将其利用到其他机床上。自动换刀系统将以较快的速度增长，缩短换刀时间，提高刀具的定位精度是重要的手段，有利于数控技术的发展。刀具及其元件库存是现代生产管理中的重要环节, 特别是大型车间管理。传统的人工记帐管理方式, 效率低下, 错误率高, 且信息数据不能共享, 刀具的使用状态和寿命周期无法跟踪, 不能适应当前信息化管理需要。结合生产实际, 我们在车间刀具准备间建立刀具贮存立体库系统, 以满足车间刀辅具储存与管理的需要。该系统采用最优化技术, 利用计算机存储的大量库存信息, 能及时、准确、全面地反映刀具库的库存情况。整个系统采用图形界面, 人机对话由中文菜单提示, 可实现各种功能选择和各种信息的输入。管理系统采用在线帮助功能。可通过车间管理层、网络系统实现信息管理和共享。具有自动库存管理、刀具入库管理、刀具出库管理和统计查询功能。1.系统组成及其控制结构整个系统包括机械结构及电气控制系统。1.1.1 机械结构及工作原理刀具库由支架、驱动机构、传动系统、刀架、护罩、电气控制系统等部分组成。支架由立柱、横梁、上下导向环轨、支撑地轨组成。1)驱动机构 该系统选用了变频调速的方法。采用锥形制动电机, 带变频调速, 经摆线针轮减速器, 通过链轮传动。2)拖动与传动系统 采用变频控制技术。通过变频调速, 可使传动轴转速在正常范围内调节使刀架回转速度控制到 5～ 30mm in, 2 个传动轴各带上、下2 个链轮通过上、下2 条异形滚子链带动货架转动。链条胀紧机构采用螺纹调节胀紧, 为定期胀紧方式。调节时上、下链条松度调节一致, 使链条受力均匀。3)刀架与防护罩 整库共有14 列独立刀架。其中 13 列为插座式刀架, 1 列为抽屉式刀架, 每个刀架背部通过销轴与上、下输送链链板联接, 底部安装滚轮, 链条转动带动刀架沿地轨转动。插座式刀架分BT40 刀架和BT50 刀架 2 种形式。为加强管理, 保证安全, 美化造型, 货架外围加防护罩。抽屉式刀架分 6 个抽屉放置其他刀辅具, 可分类装存一些刀辅具, 如钻头、车刀等。1.1.2. 电气控制系统本刀具储存系统的电气控制主要是对其货架进行运行控制和位置控制。运行控制包括运行设备的启动、制动控制。位置控制主要是对货架位置和地址进行检测。控制系统框图如图 1 所示。图 1 刀具库控制系统图1)电气传动 水平旋转刀具储存系统各机械的动作都属于反复短时工作制。而且系统在运行时需要几种速度, 因此传动系统需要调速, 所以该系统选用了变频调速的方法, 可以采用结构简单、运行可靠的变频器和变频电动机。2)控制方式 该系统分为手动和自动控制2 种控制方式, 手动控制一般作为调试用和备用的工作方式; 自动控制方式为本系统计算机(IPC)和控制单元(变频器、接触器等)组成的一个自动控制系统。3)位置及定位精度检测 本系统中自动认址和位置检测采用了接近开关作为检测元器件, 通过光点隔离继电器板和记数板对接近开关采集的信号进行记数和运算处理, 采用最优路径寻址方式确定货架的当前位置和货架的目的位置。为了使系统定位更准确, 采用了 2 只光电开关, 分别检测2 个货架的2 只检测片。1.2.刀库的功能刀库的作用是储备一定数量的刀具，机械手实现主轴上刀具的互换}zs}a刀具的类型有盘式刀库、链式刀库等多种形式，刀库的形式和容量要根据机床的工艺范围来确定。1.3.常见类型刀库是存储刀具的装置，常见的刀库主要有以下几种形式:(1)转塔式刀库包括水平转塔头和垂直转塔头两种，见图2.6a)与b):(2)盘式刀库盘式刀库中刀库呈盘状,刀具沿盘面垂直排列(包括径向取刀和轴向取刀),沿盘面径向排列或成锐角排列的形式的刀库。结构简单、紧凑,应用较多,但刀具单环排列,空间利用率低。见图2.7a)~c)。若增加刀库容量必须使刀库的外径增大,那么转动惯量也相应增大,选刀运动时间长。刀具数量一般不多于32把。刀具呈多环排列的刀库的空间利用率高,但必然使得取刀机构复杂,适用于机床空间受限制而刀库容量又较大的场合。双盘式结构是两个较小容量的刀库分置于主轴两侧,布局较紧凑,储刀数量也相应增大,适用于中小型加工中心。(3)链式刀库包括单环链和多环链，链环形式可有多种变化，见图2.8a)~c)，基本结构见图2. 8do特点:适用于刀库容量较大的场合，所占的空间小，一般适用于刀具数在30-120把。仅增加链条长度即可增加刀具数，可以不增加圆周速度其转动惯量不像盘式刀库增加的那样大。机床刀具设计毕业论文中英文资料对照外文翻译文献综 10_毕业设计英文三 : 软件工程专业毕业设计外文文献翻译本科毕业设计外文文献翻译 （英文题目：Software Database An Object-Oriented Perspective. 中文题目：软件数据库的面向对象的视角 学生姓名：宋兰兰 学 院：信息工程学院 系 别：软件工程系 专 业：软件工程 班 级：软件09-1 指导教师：关玉欣 讲师二〇一三 年 六 月内蒙古工业大学本科毕业设计外文文献翻译内蒙古工业大学本科毕业设计外文文献翻译A HISTORICAL PERSPECTIVEFrom the earliest days of computers, storing and manipulating data have been a major application focus. The first general-purpose DBMS was designed by Charles Bachman at General Electric in the early 1960s and was called the Integrated Data Store. It formed the basis for the network data model, which was standardized by the Conference on Data Systems Languages (CODASYL) and strongly influenced database systems through the 1960s. Bachman was the first recipient of ACM’s Turing Award (the computer science equivalent of a Nobel prize) for work
he received the award in 1973. In the late 1960s, IBM developed the Information Management System (IMS) DBMS, used even today in many major installations. IMS formed the basis for an alternative data representation framework called the hierarchical data model. The SABRE system for making airline reservations was jointly developed by American Airlines and IBM around the same time, and it allowed several people to access the same data through computer network. Interestingly, today the same SABRE system is used to power popular Web-based travel services such as Travelocity!In 1970, Edgar Codd, at IBM’s San Jose Research Laboratory, proposed a new data representation framework called the relational data model. This proved to be a watershed in the development of database systems: it sparked rapid development of several DBMSs based on the relational model, along with a rich body of theoretical results that placed the field on a firm foundation. Codd won the 1981 Turing Award for his seminal work. Database systems matured as an academic discipline, and the popularity of relational DBMSs changed the commercial landscape. Their benefits were widely recognized, and the use of DBMSs for managing corporate data became standard practice.In the 1980s, the relational model consolidated its position as the dominant DBMS paradigm, and database systems continued to gain widespread use. The SQL query language for relational databases, developed as part of IBM’s System R project, is now the standard query language. SQL was standardized in the late 1980s, and the current standard, SQL-92, was adopted by the American National Standards Institute (ANSI) and1内蒙古工业大学本科毕业设计外文文献翻译International Standards Organization (ISO). Arguably, the most widely used form of concurrent programming is the concurrent execution of database programs (called transactions). Users write programs as if they are to be run by themselves, and the responsibility for running them concurrently is given to the DBMS. James Gray won the 1999 Turing award for his contributions to the field of transaction management in a DBMS.In the late 1980s and the 1990s, advances have been made in many areas of database systems. Considerable research has been carried out into more powerful query languages and richer data models, and there has been a big emphasis on supporting complex analysis of data from all parts of an enterprise. Several vendors (e.g., IBM’s DB2, Oracle 8, Informix UDS) have extended their systems with the ability to store new data types such as images and text, and with the ability to ask more complex queries. Specialized systems have been developed by numerous vendors for creating data warehouses, consolidating data from several databases, and for carrying out specialized analysis.An interesting phenomenon is the emergence of several enterprise resource planning(ERP) and management resource planning (MRP) packages, which add a substantial layer of application-oriented features on top of a DBMS. Widely used packages include systems from Baan, Oracle, PeopleSoft, SAP, and Siebel. These packages identify a set of common tasks (e.g., inventory management, human resources planning, financial analysis) encountered by a large number of organizations and provide a general application layer to carry out these tasks. The data is stored in a relational DBMS, and the application layer can be customized to different companies, leading to lower Introduction to Database Systems overall costs for the companies, compared to the cost of building the application layer from scratch. Most significantly, perhaps, DBMSs have entered the Internet Age. While the first generation of Web sites stored their data exclusively in operating systems files, the use of a DBMS to store data that is accessed through a Web browser is becoming widespread. Queries are generated through Web-accessible forms and answers are formatted using a markup language such as HTML, in order to be easily displayed in a browser. All the database vendors are adding features to their DBMS aimed at making it more suitable for deployment over the Internet. Database management continues to gain importance as more and more data is brought on-line, and made ever more accessible2内蒙古工业大学本科毕业设计外文文献翻译through computer networking. Today the field is being driven by exciting visions such as multimedia databases, interactive video, digital libraries, a host of scientific projects such as the human genome mapping effort and NASA’s Earth Observation System project, and the desire of companies to consolidate their decision-making processes and mine their data repositories for useful information about their businesses. Commercially, database manage- ment systems represent one of the largest and most vigorous market segments. Thusthes- tudy of database systems could prove to be richly rewarding in more ways than one!INTRODUCTION TO PHYSICAL DATABASE DESIGNLike all other aspects of database design, physical design must be guided by the nature of the data and its intended use. In particular, it is important to understand the typical workload that the d the workload consists of a mix of queries and updates. Users also have certain requirements about how fast certain queries or updates must run or how many transactions must be processed per second. The workload description and users’ performance requirements are the basis on which a number of decisions have to be made during physical database design.To create a good physical database design and to tune the system for performance in response to evolving user requirements, the designer needs to understand the workings of a DBMS, especially the indexing and query processing techniques supported by the DBMS. If the database is expected to be accessed concurrently by many users, or is a distributed database, the task becomes more complicated, and other features of a DBMS come into play.DATABASE WORKLOADSThe key to good physical design is arriving at an accurate description of the expected workload. A workload description includes the following elements:1. A list of queries and their frequencies, as a fraction of all queries and updates.2. A list of updates and their frequencies.3内蒙古工业大学本科毕业设计外文文献翻译3. Performance goals for each type of query and update.For each query in the workload, we must identify:Which relations are accessed.Which attributes are retained (in the SELECT clause).Which attributes have selection or join conditions expressed on them (in the WHERE clause) and how selective these conditions are likely to be. Similarly, for each update in the workload, we must identify:Which attributes have selection or join conditions expressed on them (in the WHERE clause) and how selective these conditions are likely to be.The type of update (INSERT, DELETE, or UPDATE) and the updated relation.For UPDATE commands, the fields that are modified by the update.Remember that queries and updates typically have parameters, for example, a debit or credit operation involves a particular account number. The values of these parameters determine selectivity of selection and join conditions.Updates have a query component that is used to find the target tuples. This component can benefit from a good physical design and the presence of indexes. On the other hand, updates typically require additional work to maintain indexes on the attributes that they modify. Thus, while queries can only benefit from the presence of an index, an index may either speed up or slow down a given update. Designers should keep this trade-offer in mind when creating indexes.NEED FOR DATABASE TUNINGAccurate, detailed workload information may be hard to come by while doing the initial design of the system. Consequently, tuning a database after it has been designed and deployed is important—we must refine the initial design in the light of actual usage patterns to obtain the best possible performance.The distinction between database design and database tuning is somewhat arbitrary. We could consider the design process to be over once an initial conceptual schema is designed and a set of indexing and clustering decisions is made. Any subsequent changes4内蒙古工业大学本科毕业设计外文文献翻译to the conceptual schema or the indexes, say, would then be regarded as a tuning activity. Alternatively, we could consider some refinement of the conceptual schema (and physical design decisions affected by this refinement) to be part of the physical design process.Where we draw the line between design and tuning is not very important.OVERVIEW OF DATABASE TUNINGAfter the initial phase of database design, actual use of the database provides a valuable source of detailed information that can be used to refine the initial design. Many of the original assumptions about the expected workload can be replaced by obs in general, some of the initial workload specification will be validated, and some of it will turn out to be wrong. Initial guesses about the size of data can be replaced with actual statistics from the system catalogs (although this information will keep changing as the system evolves). Careful monitoring of queries can reveal for example, the optimizer may not be using some indexes as intended to produce good plans.Continued database tuning is important to get the best possible performance.TUNING THE CONCEPTUAL SCHEMAIn the course of database design, we may realize that our current choice of relation schemas does not enable us meet our performance objectives for the given workload with any (feasible) set of physical design choices. If so, we may have to redesign our conceptual schema (and re-examine physical design decisions that are affected by the changes that we make).We may realize that a redesign is necessary during the initial design process or later, after the system has been in use for a while. Once a database has been designed and populated with data, changing the conceptual schema requires a significant effort in terms of mapping the contents of relations that are affected. Nonetheless, it may sometimes be necessary to revise the conceptual schema in light of experience with the system. We now5内蒙古工业大学本科毕业设计外文文献翻译consider the issues involved in conceptual schema (re)design from the point of view of performance.Several options must be considered while tuning the conceptual schema:We may decide to settle for a 3NF design instead of a BCNF design.If there are two ways to decompose a given schema into 3NF or BCNF, our choice should be guided by the workload.Sometimes we might decide to further decompose a relation that is already in BCNF. In other situations we might denormalize. That is, we might choose to replace a collection of relations obtained by a decomposition from a larger relation with the original (larger) relation, even though it suffers from some redundancy problems. Alternatively, we might choose to add some fields to certain relations to speed up some important queries, even if this leads to a redundant storage of some information (and consequently, a schema that is in neither 3NF nor BCNF).This discussion of normalization has concentrated on the technique of decomposition, which amounts to vertical partitioning of a relation. Another technique to consider is horizontal partitioning of a relation, which would lead to our having two relations with identical schemas. Note that we are not talking about physically partitioning the cuples
rather, we want to create two distinct relations (possibly with different constraints and indexes on each).Incidentally, when we redesign the conceptual schema, especially if we are tuning an existing database schema, it is worth considering whether we should create views to mask these changes from users for whom the original schema is more natural.TUNING QUERIES AND VIEWSIf we notice that a query is running much slower than we expected, we have to examine the query carefully to end the problem. Some rewriting of the query, perhaps in conjunction with some index tuning, can often ?x the problem. Similar tuning may be called for if queries on some view run slower than expected.When tuning a query, the first thing to verify is that the system is using the plan that 6内蒙古工业大学本科毕业设计外文文献翻译you expect it to use. It may be that the system is not finding the best plan for a variety of reasons. Some common situations that are not handled efficiently by many optimizers follow:A selection condition involving null values.Selection conditions involving arithmetic or string expressions or conditions using the or connective. For example, if we have a condition E.age = 2*D.age in the WHERE clause, the optimizer may correctly utilize an available index on E.age but fail to utilize an available index on D.age. Replacing the condition by E.age/2=D.age would reverse the situation.Inability to recognize a sophisticated plan such as an index-only scan for an aggregation query involving a GROUP BY clause.If the optimizer is not smart enough to and the best plan (using access methods and evaluation strategies supported by the DBMS), some systems allow users to guide the choice of a plan by providing hi for example, users might be able to force the use of a particular index or choose the join order and join method. A user who wishes to guide optimization in this manner should have a thorough understanding of both optimization and the capabilities of the given DBMS.(8)OTHER TOPICSMOBILE DATABASESThe availability of portable computers and wireless communications has created a new breed of nomadic database users. At one level these users are simply accessing a database through a network, which is similar to distributed DBMSs. At another level the network as well as data and user characteristics now have several novel properties, which affect basic assumptions in many components of a DBMS, including the query engine, transaction manager, and recovery manager.Users are connected through a wireless link whose bandwidth is ten times less than Ethernet and 100 times less than ATM networks. Communication costs are therefore significantly higher in proportion to I/O and CPU costs.Users’ locations are constantly changing, and mobile computers have a limited battery life. Therefore, the true communication costs is connection time and battery usage in addition to bytes transferred, and change constantly depending on location. Data is7内蒙古工业大学本科毕业设计外文文献翻译frequently replicated to minimize the cost of accessing it from different locations.As a user moves around, data could be accessed from multiple database servers within a single transaction. The likelihood of losing connections is also much greater than in a traditional network. Centralized transaction management may therefore be impractical, especially if some data is resident at the mobile computers. We may in fact have to give up on ACID transactions and develop alternative notions of consistency for user programs. MAIN MEMORY DATABASESThe price of main memory is now low enough that we can buy enough main memory to hold the entire database f with 64-bit addressing, modern CPUs also have very large address spaces. Some commercial systems now have several gigabytes of main memory. This shift prompts a reexamination of some basic DBMS design decisions, since disk accesses no longer dominate processing time for a memory-resident database:Main memory does not survive system crashes, and so we still have to implement logging and recovery to ensure transaction atomicity and durability. Log records must be written to stable storage at commit time, and this process could become a bottleneck. To minimize this problem, rather than commit each transaction as it completes, we can collect completed transactions and co this is called group commit. Recovery algorithms can also be optimized since pages rarely have to be written out to make room for other pages.The implementation of in-memory operations has to be optimized carefully since disk accesses are no longer the limiting factor for performance.A new criterion must be considered while optimizing queries, namely the amount of space required to execute a plan. It is important to minimize the space overhead because exceeding available physical memory would lead to swapping pages to disk (through the operating system’s virtual memory mechanisms), greatly slowing down execution.Page-oriented data structures become less important (since pages are no longer the unit of data retrieval), and clustering is not important (since the cost of accessing any region of main memory is uniform).8内蒙古工业大学本科毕业设计外文文献翻译（一）从历史的角度回顾从数据库的早期开始，存储和操纵数据就一直是主要的应用焦点。第一个通用的DBMS是由Charles Bechman于20世纪60年代早期在通用电器公司设计的，称为集成数据存储(Integrated Data Store).它奠定了网状数据模型的基础。网状数据模型由数据系统语言协会(CODASYL)标准化，并在整个20世纪60年代对数据库系统产生了巨大的影响。由于Bachman在数据库领域的贡献，他成为第一个ACM图灵奖（相当于计算机科学界的诺贝尔奖）的获得者，并于1973年接受了这一奖励。20世纪60年代末期，IBM成功开发了信息管理系统(IMS)DBMS。直至今天，它还在许多系统中使用。IMS奠定了另一个数据表达框架——层次数据模型的基础。同时，美国航空公司和IBM联合开发出用于飞机订票的SABRE系统，它允许多个用户通过计算机网络存取相同数据。有趣的是，今天SABRE系统被用于支持广为流行的基于Web的旅游服务，如Travelocity。1970年，Edgar Codd在IBM的San Jose研究实验室推出了一种新的，称为关系数据模型的数据表达框架。这后来被证明是数据库系统开发中的分水岭：它推进了几个基于关系模型的数据库管理系统的快速开发，并取得大量的理论成果，从而为数据库领域奠定了坚实的基础。Coff因为其杰出的工作而获得了1981年图灵奖。数据库系统作为学术学科已经成熟了，而且关系型DBMS的普及改变了商业应用前景。其益处被广泛认同，使用DBMS来管理公司数据变得很普遍。在20世纪80年代，关系模型巩固了它作为主导DBMS模式的地位，而数据库系统继续被广泛使用。作为IBM的 System R项目的一部分而开发的关系数据库SQL查询语言，现在成为了标准查询语言。SQL于20世纪80年代末期得到标准化，目前的标准SQL:1999被美国国家标准协会（ANSI）和国际标准组织（ISO）接受。并发编程使用最广的形式就是数据库程序（称为事务）的并发执行。用户编写程序时不用考虑其他程序的运行，并发执行操作由DBMS管理。James Gray因他对DBMS事务处理领域的贡献而获得了1999图灵奖。在20世纪80年代末期和90年代，数据库系统在很多方面得到发掌。相当多的研究侧重于功能强大的查询语言和更丰富的数据模型，其重点也放在了支持对企业各部分数据的复杂分析上。很多数据库提供商（如IBM的DB2,Oracle 8,Informix UDS）9内蒙古工业大学本科毕业设计外文文献翻译樱井扩展了它们的系统，使之具有存储诸如图像，文本等新数据类型的能力，以及回答更复杂查询的能力。大量的厂商已经为创建数据仓库，继承多个数据库的数据以及实现专业化分析而开发了专用系统。一个有趣的现象是随着一些企业资源规划（ERP）和管理自愿规划（MRP）软件包的出现，他们在DBMS之上增加了一层面向应用的特征。广泛使用的软件包有Baan,Oracle,PeopleSoft,SAP和Siebel等系统，它们先确定大多数组织机构所遇到的共同任务（例如，库存管理，人力资源规划，财务分析等），并提供一个通用的应用层以完成这些任务。数据存储在关系型DBMS中，可以为不同公司分别定制应用层。与从头开始创建应用层的开销相比，这样可以降低公司的总体开销。也许，在DBMS的发展中，最重要的事是DBMS已经进入了因特网时代。第一代Web站点是把数据存储在操作系统的文件中，而现在，使用DBMS存储数据并通过Web浏览器浏览数据已变得越来越普遍。通过Web可存取的表单界面来产生查询请求，并使用诸如HTML的标记语言将查询结果格式化，从而便于在浏览器中显示。所有数据库提供商都在增加它们的DBMS功能，使之更适于在因特网上部署。随着越来越多在线数据的产生，并且通过计算机网络越来越容易获得，数据库也变得更加重要了。今天，众多领域的发展需求，例如，多媒体数据库，互动视频，流数据，数字图书馆等精彩视频节目，人类基因图和NASA的地球观测系统等科学项目，以及公司对巩固它们的决策支持处理和有用信息挖掘的渴望，正推动着数据库领域的发展。在商业上，数据库管理系统代表着最大和最具活力的市场之一。所以，有关数据库系统的研究回报丰厚！（二）物理数据库设计简介与数据库设计的其他方面一样，我们要根据数据的性质和用途来进行物理数据库设计。特别是，我们必须了解数据库所必须支持的典型的工作负载，工作负载是查询和更新的混合体。用户有一些特定的要求，如，某些查询或更新的执行速度应该有多快，或者每秒钟必须处理多少个事务等。在物理数据库设计过程中，工作负载的描述和用户的需求是作出许多决策的基础。为了获得一个好的物理数据库设计，我们还要调整系统的性能以满足用户的需求。设计者需要明白DBMS工作的细节，特别是DBMS所支持的索引和查询处理技术。10内蒙古工业大学本科毕业设计外文文献翻译如果数据库允许多个用户并发访问，或者是分布式数据库，那么这是设计任务就变得更复杂了，还需要考虑DBMS的其他特点。（三）数据库负载一个好的数据库设计的关键是对所希望的负载有准确的描述。一个工作负载的描述包括以下几个部分：1.一个查询及其出现的频率的列表，一个查询的频率指该查询在所有的查询和更新中所占的比例。2.更新及其出现的频率列表。3.每一种查询和更新类型所对应的性能目标。对于在工作负载中的每个查询，我们必须确定：需要访问哪些关系。需要保留那些属性（在SELECT子句中）。在那些属性上有选择或连接条件（在WHERE子句中），以及这些条件具有多大的选择性。类似地，对工作负载中每个更新，我们必须确定：在哪些属性上有选择或连接条件（在WHERE语句中），以及有多大的选择性。 更新的类型（INSERT,DELETE,UPDATE）以及所要更新的关系。对于UPDATE命令，要更新哪些字段。典型的查询和更新都带有参数，例如，借款或存款操作都涉及某个特定的帐号。这些参数的值决定了选择和连接条件的选择性。更新中包括一个查询部分，用来找到目标元组。这个部分可以得益于一个好的物理设计和索引。另一方面，更新操作一般还要做一些额外的工作，以维护所修改的属性上的索引。这样，尽管查询总可以从索引受益，但是索引也可能使一个给定的更新加快或变慢。在生成索引时，设计者应该在头脑中进行一下权衡。（四）数据库调整的必要性准确地讲，在系统设计的初始阶段，我们很难得到工作负载的详细信息。所以在 11内蒙古工业大学本科毕业设计外文文献翻译系统设计完以后，对数据库的调整就变得很重要，我们必须按照实际的使用模式来对初始的设计进行求精，以便获得好的性能。对于如何区别数据库设计和数据库调整，人们有不同的看法。一种看法认为，一旦初始模式、索引和聚簇决策已经确定，那么设计过程也就结束了。接下去对概念模式或索引的任何改变，都被认为是对数据库进行调整的活动。另一种看法是，对于概念模式的进一步求精（和受这些改进影响的物理设计决策）也应该是物理设计过程的一部分。如何区分设计和调整并不是很重要的（五）数据库调整简介当数据库初始设计完成后，数据库的实际使用提供了一些有用的详细信息，它们可以用来对初始设计进行进一步求精。先前对工作负载的很多假设都可以用观察到的模式来代替；一般来讲，一些初始的关于工作负载的说明将得到验证，其中有一些可能是错误的。关于数据大小的初始猜测可以用实际的数据库的统计数字来代替（尽管这个信息会随着系统的不断进化而变化）。对于查询的仔细监测可龕发现一些预测不到的问题，例如，优化器可能不使用某些索引，尽管这些索引可以产生好的计划。为了获得可能的最好的性能，对数据库进行连续的调整是很重要的。（六）调整概念模式在数据库设计期间，我们也许会意识到，在给定工作负载和任何一组可行的物理设计选择的情况下，当前选择的关系模式并不能满足性能目标。如果是这样，我们也许必须重新设计概念模式（而且还要重新检查那些受到影响的物理设计决策）。在系统已经运行了一段时间后，我们也许会认识到在初始设计期间或之后重新设计的必要性。一旦数据库设计完成并且已经被装载数据了，如果要改变概念模式，就需要做出很大的努力去映射受到影响的关系的内容。然而，有时需要根据使用系统的经验来对概念模式进行修正。现在，我们从性能的角度来考虑概念模式（重新）设计中的一些问题。在对概念模式进行调整时我们必须考虑以下几点：12内蒙古工业大学本科毕业设计外文文献翻译我们也许应当采用3NF设计来代替BCNF设计。如果将一个关系分解为3NF或BCNF有两种方式，那么应该根据工作负载来进行选择。有时我们需要对一个应景是BCNF的关系进一步分解。在某些情况下可能进行反规范化。也就是，可能将一组由一个大关系分解而得到的关系用它们的原大关系代替，尽管这样会引起一些冗余的问题。而且，我们可能在特定的关系上加上一些字段来加速一些重要的查询，即使这样会导致对一些信息的冗余存储（从而使得模式既不是3NF也不是BCNF）。关于规范化的讨论集中在分解技术上，实际上就是对关系的垂直划分。另一个技术是对关系进行水平划分，这将导致两个具有相同模式的关系。这里需要注意的是，这里讨论的不是一个关系元组的物理划分；而是想创建两个不同的关系（可能具有不同的约束和索引）。另外，在重新设计概念模式时，特别是如果调整一个现存数据库的模式时，我们需要考虑是否定义视图来向用户隐藏这些改变，因为对于用户来说原始的模式可能更自然一些。（七）调整查询和视图如果一个查询比预计的要慢得多，那么我们就必须仔细检查并找出问题。通过对查询进行重写，并且进行一些索引的调整，常常能够解决问题。如果在视图上的一些查询运行得很慢，也可以进行类似的调整。当调整一个查询时，第一件事就是确定系统是否使用了你所希望的执行计划。由于一些原因，有时系统可能没有找到最好的执行计划。下面是很多优化器都不能有效处理的一些情况：含有空值的选择条件；选择条件含有算数或字符串表达式，或者使用OR进行条件连接。例如，如果在WHERE语句中有一个条件E.age=2*D.age，那么优化器可能会正确利用现有的在E.age上的索引，但是不能正确利用在D.age上的索引。当将条件变为E.age/2=D.age时，将会出现相反的情况。不能识别出一个复杂的执行计划，例如不能发现在GROUP BY语句中含有的 13内蒙古工业大学本科毕业设计外文文献翻译聚集操作的查询中的只读索引扫描计划。如果优化器不太聪明，不能发现最好的执行计划（使用DBMS支持的一些访问方法和执行策略），一些系统允许用户通过提供给优化器一些提示来指导计划的选择。例如，用户可能强迫系统使用特定的索引或连接的方法和顺序。如果一个用户希望以这种方式来指导优化，那么他应该对优化和给定的DBMS的能力有一个全面的理解。（八）其他专题移动数据库便携计算机和无线通信的应用创建了一批移动数据库用户。一方面，这些用户只是简单地通过网络来访问数据库，类似于分布式DBMS。另一方面，不论是网络，还是数据和用户，都有一些新的特性，这就影响了DBMS中的许多构件，包括查询引擎，事务管理程序和虎伏管理程序。通过无线连接的用户带宽是以太网的1/10左右，是ATM网的1/100左右。因此通信开销比I/O和CPU开销更高。用户的位置通常是变动的，而且移动计算机的电池寿命是有限的。因此，除内容传输开销以及因位置的频繁变动而产生的开销外，真正的通信开销体现在连接时间和电池的使用上。通常将数据生成多个副本，以使从不同位置的访问开销最小化。当一个用户移动的时候，一个事务可能需要从多个数据库服务器中访问数据，此时丢失连接的可能性比传统的网络要大。因此，集中式的事务管理也是不实际的，尤其是有些数据存储在移动计算机上更是这样。事实上，我们可能不得不放弃具有ACID特性的事务，而是为用户程序开发其他的一致性方法。主存数据库由于主存的价格已经很便宜了，许多应有可以购买足够的主存来保存整个数据库。而且，现代的CPU使用64位的寻址，有了很大的寻址空间。一些商用的数据库已有几个GB的主存。这促使重新考虑一些基本的DBMS设计决策，因为对于驻留内存的数据库，磁盘访问不再是主要的处理时间。主存也不能幸免于系统崩溃，所以仍然需要实现日志和恢复机制，以保证事务的原子性和持久性。在提交事务的时候，日志记录必须写到固定的存储中。这个处理可能会变成一个瓶颈。为了使该问题最小化，不是每完成一个事务就进行提交，而是收14内蒙古工业大学本科毕业设计外文文献翻译集已完成的事务，然后批量提交它们，这称为组提交。恢复算法同样也需要优化，因为很少这种情况：某页因需要为其他页省出空间而不得不被移出。应认真优化主存中的操作实现，因为磁盘存取不再是限制性能的要素。在优化查询时必须考虑新的标准，即执行一个计划时所需要的空间数量。最小化空间开销是很重要的，因为如果空间开销超出物理内存，会使交换页保存到磁盘（通过操作系统的虚拟存储机制），这将大大降低执行效率。基于页的数据结构不再重要了（因为页不再是数据检索的单位），同时，聚簇也不重要了（因为访问主存的任何区域的开销是一致的）。15四 : 商业街：商业街-英文翻译，商业街-设计与构思商业街是人流聚集的一个主要场所。采用东西方向排列，以入口为中轴对称布局，建筑立面多采用塔楼，骑楼，雨罩的元素使空间产生新的划分，室内空间既设置了集中商业，又有零散店铺，是西方现代MALL与中国传统商铺的有机组合。商业街以平面形式按照街的形式布置的单层或多层商业房地产形式。商业街_商业街 -英文翻译商业街 Business Street or Commercial Street商业街_商业街 -设计与构思设计图商业街指以平面形式按照街的形式布置的单层或多层商业房地产形式，其沿街两侧的铺面及商业楼里面的铺位都属于商业街商铺。商业街商铺与商业街的发展紧密联系，其经营情况完全依赖于整个商业街的经营状况以及人气，运营良好的商业街，其投资者大多数已经收益丰厚；运营不好的商业街，自然令投资商、商铺租户、商铺经营者都面临损失。1、要解决的问题解决商业街的繁华气氛于别墅的宁静气氛之间的冲突问题。解决商业街车行交通空间与步行交通空间的隔离的问题。解决商业街的平直单调，感觉很长，很枯燥的问题。解决商业街的历史人文记忆的缺乏。2、总体构思以景观意境为线索，遵循“以人为本”的原则，运用轴线对称布局，采用点，线，面成景的方式，参照所处位置及不同功能分割空间，营造1个多功能的，舒适的，令人愉悦的具有纯正法国浪漫气息的娱乐购物，文化休闲的街道环境。3、构思的基础1据心里进化论的观点，人类对大自然所作出的最表层，直接的，第一的反映是情感上的，不是认知上的，在情感反映的基础上，才有了思维与记忆、意识与行为。就像电影就是在创造1种场景感受，现代神经心理学也证明这一观点。方案的室外空间设计以传统江南古镇的模式来构筑整个商业街，从历史发展中形成小镇商业街和传统因素及其相互关系作了深入分析，如人流和街道的关系，河与街与住宅的关系，总结出1个空间的模式，运用到商业街中来。将1个古镇的街空间融合到商业街中来，使其不仅有现代商业街的时代气息，又蕴含原始的在几十年、甚至几百年间长出的空间，这些空间承载着政治、经济、文化以及人的生活方式的信息。街是随着人们交换产生与贸易的发展而逐渐生长的，它是由人们的生活需要而产生的1种商业形态，通过将街切割、打碎、重组再造的，运用以景观意境为出发点，寻找适宜的尺度，通过空间变化的重组，营造一条生长出来的街，通过各种元素，铺地、雕塑、喷泉、植物来解决商业街的标识性。街是人们行走，徜徉、休息、交流的开放空间，避免西单大街改造的那样的误区（人可以自由徜徉的街巷被大大拓宽成便利车行的大街，人群从街上被挤到过街天桥，或人们已被车流逼迫到某个区域，已不可自由徜徉，人的愉悦心情也就消大半，一条街道变成了一条车的河流，所以区分空间，使人与车的矛盾得到最大解决，）通过高差解决人车分流。4、景观的意境1远远的能听到时高时底，时缓时急的交响曲，迫不及待的走近观赏，法国凡尔赛宫式的水池上面跳跃着奏出欢快的乐曲，顿感精神倍增，两侧高耸的塔楼同样透露出法国的浪漫情调，中间高贵典雅的欧式拱券门诉说着你的不凡身份，走过林荫道，银铃般的笑声传来，穿过拱券门，旱喷泉广场上孩子们在玩耍嬉闹，走过嬉闹，开阔的草坪树木郁郁葱葱，人们无拘无束的躺在草坪上，三五成群的聊天，孩子在草地跑来跑去，临水栈道的长椅上，一对对情侣静静欣赏远处的晚霞。地铁商业街一、交通分析运动与通路：设计中充分考虑人的运动心理，把紧张的运动与放松的运动有机的结合起来，沿河散步道给人们提供1个可以曲折，延长的运动线路，放松休闲的观赏景观。采用坡道设计，提供带轮的步行交通，使设计更加人性化。确定适当距离的关键不仅是实际的自然距离，更重要的是感觉距离，通过景观节点的设置，景观设施来丰富人们的视觉感受，单调平直呆板的街道虽然很短，人的心理感受距离却很长。人车分流：通过竖向的变化，使行车道路与人行处于不同高差，人在商业街的购物会感觉安全，真正营造1个休闲，自由徜徉的街道环境。二、空间分析商业街的主要特点是因商业店铺的集中而形成了室外购物、休闲、餐饮等功能空间，基于商业街的店铺特色，决定了其设计的核心就是让空间有用而舒适。根据调查，一般商业街的尺度，都控制在8－12m左右，而这又是针对两侧都是店铺的商业街，在商业建筑前约19m宽的范围内，要满足停车，行车，还有步行的功能，所以商业街前面的步行街尺度定为5m宽，又考虑到车行对人流的影响，利用竖向高差的变化将其划分成2个不同的空间。在根据建筑的轴线在相关节点上设置种植坛形成景观序列，根据建筑的收放控制台阶的收放。1三、景观节点以景观意境为线索，按其所处位置的不同及功能的不同，大小设置3大景观区，它们既相互联系又具统一性，通过轴线的控制来实现。3大景观区为:入口广场与商业街区，旱喷泉广场区，邻水大草坪区,分别满足人们的购物娱乐，休闲的功能，动静分区的过渡功能，人们交流休息思考冥想的静态活动功能。四、色彩分析建筑的立面以梨黄（明亮）为主色调，门窗饰线，铁艺栏杆用白色或木色，建筑功能入口用骑楼来区别，色彩为红色砖墙（仿红色砖墙瓷砖），其整体为明亮的暖色调。设计的铺装，小品，附属设施等都采用暖色调设计，形成从色彩上达到统一的效果。五、停留区域与心理学边界效应理论边界效应理论指出：森林，海滩，树丛，林中空地，建筑广场的边缘，建筑的凹处，柱下等使人们喜爱停留的区域。我们在商业街设置休息的座椅，给人们提供驻足，停留，停下来与人交谈，停留一段时间的动作诱因。爱德华·霍尔在《隐匿的尺度》中指出处于边缘或背靠建筑物的立面有助于个人，团体与他人保持距离，是人们安全心理的需求所致。我们要紧两创造多层的边缘。人的活动是从内部和朝向公共空间的的中心的边界发展起来的，通过孩子们总是现在门前聚集一会，然后在开始游戏并占有整个空间。2弯曲的街道使步行变得更加有趣，且再见少风力干扰方面是由益处的。变换的接到空间，小型广场的穿插使步行网络的心理距离变短了。人在步行时都爱抄近道，人们走捷径的愿望是非常强烈的。哥本哈根的一处广场记录，每1个人都沿最短的线路穿过广场。开场空间中的步行线路，横穿空间中心是不舒服的，眼空间的边缘既可以体验到大空间的尺度，又能欣赏道街道或空间边界的细枝末节，令人赏心悦目。台阶是打断步行节奏的破坏元素，我们采用平缓的坡道替代。六、商业街入口广场避免目的地路程的一览无余，更要避免可见目的地而不得不绕行。可见目的的时要遵从简捷的原则。规划的直角使用功能是不方便的。这个聚集包括购物，娱乐休闲和享受生活！商业街的理想气氛应该是使人觉得亲切、放松、平易近人、有人情味，使人有愉悦的消费心情，而不是单纯的行走空间，人们在其中流连的过程本身也是1种体验和休闲！入口广场除了应该烘托建筑的特色与气势，更应该是1个适合人们停留的、开放的，水与绿地交融的公共休憩场所。商业街_商业街 -分类双莲商业街按照商业街经营的商品是专业类别，还是不加确定的复合形式，可将商业街分为专业商业街和复合商业街。专业商业街商铺往往集中经营某1类（种）商品，如建材商业街、汽车配件商业街、酒吧街、休闲娱乐街等；复合商业街商铺对经营的商品不加确定，经营者可以按照自己的设想去随意经营，如北京西单商业街，北京宣武区的大都市街等。宏观上讲，北京王府井商业街、上海南京路都属于商业街，但事实上，它们都是由多个规模不同的购物中心、百货大楼、体育用品商店、娱乐、餐饮等各类商业房地产组成；微观上讲，常见的商业街有建材、汽车配件、服装精品街、酒吧街、美容美发用品街等。上述以某类商品为经营内容的商业街，起步早的，大多数已经取得了成功。也有不少商业街采取各类商品混业经营的方式，商业街的命名只体现地点特征，这类商业街取得成功的难度比较大，除非像北京王府井大街，它经过长期的发展，已经成为中国人普遍了解、认同的商业概念，其成功才可以实现。按照商业街的建筑形式，也可将商业街分为单层商业街和多层商业街。单层商业街指采取单层建筑结构的商业街，多层商业街商铺自然指建筑形式为多层建筑的商业街。另外也可以按商业街商铺的形式划分为完全采取铺面形式的商业街，完全采取铺位形式的商业街和采取铺位、铺面结合形式的商业街等。1商业街_商业街 -设计理念商业街指以平面形式按照街的形式布置的单层或多层商业房地产形式，问题解决商业街的繁华气氛与别墅的宁静气氛之间的冲突问题。解决商业街车行交通空间与步行交通空间的隔离问题。解决商业街的平直单调，感觉很长，很枯燥的问题。解决商业街的历史人文记忆的缺乏。1构思以景观意境为线索，遵循“以人为本”的原则，运用轴线对称布局，采用点，线，面成景的方式，参照所处位置及不同功能分割空间，营造1个多功能的，舒适的，令人愉悦的具有纯正法国浪漫气息的娱乐购物，文化休闲的街道环境。基础据心里进化论的观点，人类对大自然所作出的最表层，直接的，第一的反映是情感上的，不是认知上的，在情感反映的基础上，才有了思维与记忆、意识与行为。就像电影就是在创造1种场景感受，现代神经心理学也证明这一观点。方案的室外空间设计以传统江南古镇的模式来构筑整个商业街，从历史发展中形成小镇商业街和传统因素及其相互关系作了深入分析，如人流和街道的关系，河与街与住宅的关系，总结出1个空间的模式，运用到商业街中来。将1个古镇的街空间融合到商业街中来，使其不仅有现代商业街的时代气息，又蕴含原始的在几十年、甚至几百年间长出的空间，这些空间承载着政治、经济、文化以及人的生活方式的信息。街是随着人们交换产生与贸易的发展而逐渐生长的，它是由人们的生活需要而产生的1种商业形态，通过将街切割、打碎、重组再造的，运用以景观意境为出发点，寻找适宜的尺度，通过空间变化的重组，营造一条生长出来的街，通过各种元素，铺地、雕塑、喷泉、植物来解决商业街的标识性。街是人们行走，徜徉、休息、交流的开放空间，避免西单大街改造的那样的误区（人可以自由徜徉的街巷被大大拓宽成便利车行的大街，人群从街上被挤到过街天桥，或人们已被车流逼迫到某个区域，已不可自由徜徉，人的愉悦心情也就消大半，一条街道变成了一条车的河流，所以区分空间，使人与车的矛盾得到最大解决，）通过高差解决人车分流。意境远远的能听到时高时低，时缓时急的交响曲，迫不及待的走近观赏，法国凡尔赛宫式的水池上面跳跃着奏出欢快的乐曲，顿感精神倍增，两侧高耸的塔楼同样透露出法国的浪漫情调，中间高贵典雅的欧式拱券门诉说着你的不凡身份，走过林荫道，银铃般的笑声传来，穿过拱券门，旱喷泉广场上孩子们在玩耍嬉闹，走过嬉闹，开阔的草坪树木郁郁葱葱，人们无拘无束的躺在草坪上，三五成群的聊天，孩子在草地跑来跑去，临水栈道的长椅上，一对对情侣静静欣赏远处的晚霞。交通分析运动与通路设计中充分考虑人的运动心理，把紧张的运动与放松的运动有机的结合起来，沿河散步道给人们提供1个可以曲折，延长的运动线路，放松休闲的观赏景观。采用坡道设计，提供带轮的步行交通，使设计更加人性化。确定适当距离的关键不仅是实际的自然距离，更重要的是感觉距离，通过景观节点的设置，景观设施来丰富人们的视觉感受，单调平直呆板的街道虽然很短，人的心理}