Workpiece positioning and clamping scheme
The workpiece positioning and benchmarks should be consistent with the design basis, and should be prevented with a workpiece positioning, and the best choice." "one-two sales as a positioning benchmarks in CNC machine tools, benchmarks, and the positioning is carefully to find.
On the CNC lathe workpiece positioning installed with basic principles of ordinary machine tools. The Install method workpiece workpiece impact the processing accuracy and efficiency in order to give full play to the characteristics of their work, and the CNC machine tools folder installed workpiece should take into account the following factors:
1. as far as possible common fixture, only when you must design and manufacture of special fixture;
2. structural design to meet the accuracy requirements;
3. ease of positioning and clamping;
4. cleanup for ease of cutting;
5. resist cutting forces by sufficient rigidity;
·Determine order passes and passes route
The cutting line is the index of controlled processing tool relative to the workpiece and the direction of the trajectory. Reasonable choice of processing route is very important, because it is part of the machining accuracy and surface quality are closely related. In determining the cutting line is the main consideration the following points: 1）E nsure that parts of the request processing accuracy.
2) convenient numerical computation, reduce the programming effort.
3) find the shortest route to reduce processing time in order to improve processing efficiency air knife.
4) minimize procedures paragraph number.
5) Ensure that workpiece contours of the surface roughness after processing the request should be final, ultimate contours go straight sword processing.
6) The dilemma knives knife (entry with all the routes have to seriously consider in order to minimize the contours on the cutting edge knife (elastic deformation caused by sudden changes) and left a knife marks, also need to avoid the contours on surface vertical cutter and workpiece scratch.
Processing arrangements should be based on parts of the structure of the order and stock status and orientation clamp needed to take into account, with a focus on the rigidity of the job is not compromised. Order should be carried out by the following principles:
( 1) the process of processing cannot affect next process among the positioning and Clamping, punctuated by a universal machine tool manufacturing processes should also be integrated into account.
( 2) First-shaped cavity in the process, and then shape processes.
( 3) In the same location, gripping manner or with a knife processing processes, with a view to reducing duplication best connect with positioning, number changer number number plates and sift.
( 4) At the same time that you install in the process, many road arrangements should be first-come-first-served basis to the workpiece rigid undermine small processes. ·Cutting sequence of arrangements:
① first rough after finishing first roughing, semi-finishing intermediate arrangements, final arrangements finishing and polishing.
② After hsien Chu at the first part of the Assembly base and work surfaces, and other major surface processing, arrangements such as keyways, after light and threaded holes for fastening and other minor surface processing. Due to minor surface processing workload small and often has a position with major surface accuracy requirements, it is generally placed after the main surface of the half-finished, done prior to finishing.
③ After the first hole for parts such as box, frame, link, base, machining end surface of the plane and hole used as a location, and then machining holes. This allows the positioning of workpiece clamping is stable and reliable, which guarantees the position accuracy of hole and plane, reducing tool wear and bring convenience to the hole.
④ base to serve as a precision base surface, would be the first to process. So, the first operation is usually positioned surface roughing and semi-finishing (sometimes including finishing), and then to finish the base of location machining other surfaces. For example, the top hole machining of shaft parts.
工件的定位与装夹方案：
工件的定位与基准应与设计基准保持一致，应防止过定位，对与箱体工件最好选择“一面两销”作为定位基准，定位基准在数控机床上要仔细找正。
在数控车床上工件定位安装的基本原则与普通机床相同。工件的装夹方法影响工件的加工精度和效率，为了充分发挥数控机床的工作特点，在装夹工件时，应考虑以下几种因素：
1.尽可能采用通用夹具，必须时才设计制造专用夹具；
2.结构设计要满足精度要求；
3.易于定位和装夹；
4.易于切削的清理；
5.抵抗切削力由足够的刚度；
3.确定走刀顺序及走刀路线：
走刀路线是指数控加工过程中刀具相对于被加工件的运动轨迹和方向。加工路线的合理选择是非常重要的，因为它与零件的加工精度和表面质量密却相关。在确定走刀路线是主要考虑下列几点:
1）保证零件的加工精度要求。
2）方便数值计算，减少编程工作量。
3）寻求最短加工路线，减少空刀时间以提高加工效率。
4）尽量减少程序段数。
5）保证工件轮廓表面加工后的粗糙度的要求，最终轮廓应安排最后一走刀连续加工出来。
6）刀具的进退刀（切入与切出）路线也要认真考虑，以尽量减少在轮廓处停刀（切削力突然变化造成弹性变形）而留下刀痕，也要避免在轮廓面上垂直下刀而划伤工件。
加工顺序的安排应根据零件的结构和毛坯状况，以及定位夹紧的需要来考虑，重点是工件的刚性不被破坏。顺序一般应按下列原则进行：
(1)上道工序的加工不能影响下道工序的定位与夹紧，中间穿插有通用机床加工工序的也要综合考虑。
(2)先进行内形内腔加工序，后进行外形加工工序。
(3)以相同定位、夹紧方式或同一把刀加工的工序最好连接进行，以减少重复定位次数，换刀次数与挪动压板次数。
(4)在同一次安装中进行的多道工序，应先安排对工件刚性破坏小的工序。
4.切削加工顺序的安排：
①先粗后精先安排粗加工，中间安排半精加工，最后安排精加工和光整加工。
②先主后次先安排零件的装配基面和工作表面等主要表面的加工，后安排如键槽、紧固用的光孔和螺纹孔等次要表面的加工。由于次要表面加工工作量小，又常与主要表面有位置精度要求，所以一般放在主要表面的半精加工之后，精加工之前进行。
③先面后孔对于箱体、支架、连杆、底座等零件，先加工用作定位的平面和孔的端面，然后再加工孔。这样可使工件定位夹紧稳定可靠，利于保证孔与平面的位置精度，减小刀具的磨损，同时也给孔加工带来方便。
④基面先行用作精基准的表面，要首先加工出来。所以，第一道工序一般是进行定位面的粗加工和半精加工(有时包括精加工)，然后再以精基面定位加工其它表面。例如，轴类零件顶尖孔的加工。
Workpiece positioning and clamping scheme
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Page1 Electrical Energy Transmission（电能输送） From reference 1 Growing populations and industrializing countries create huge needs for electrical energy. Unfortunately, electricity is not always used in the same place that it is produced, meaning long-distance transmission lines and distribution systems are necessary. But transmitting electricity over distance and via networks involves energy loss. So, with growing demand comes the need to minimize this loss to achieve two main goals: reduce resource consumption while delivering more power to users. Reducing consumption can be done in at least two ways: deliver electrical energy more efficiently and change consumer habits. Transmission and distribution of electrical energy require cables and power transformers, which create three types of energy loss: the Joule effect, where energy is lost as heat in the conductor (a copper wire, for example); magnetic losses, where energy dissipates into a magnetic field; the dielectric effect, where energy is absorbed in the insulating material. The Joule effect in transmission cables accounts for losses of about 2.5 % while the losses in transformers range between 1 % and 2 % (depending on the type and ratings of the transformer). So, saving just 1 % on the electrical energy produced by a power plant of 1 000 megawatts means transmitting 10 MW more to consumers, which is far from negligible: with the same energy we can supply 1 000 - 2 000 more homes. Changing consumer habits involves awareness-raising programmers, often undertaken by governments or activist groups. Simple things, such as turning off lights in unoccupied rooms, or switching off the television at night (not just putting it into standby mode), or setting tasks such as laundry for non-peak hours are but a few examples among the myriad of possibilities. On the energy production side, building more efficient transmission and
通信工程导论 论文题目 院系 专业 班级 学号 学生姓名 联系方式 年月 摘要 通信工程专业与信息的联系是密不可分的。信息是可以描述的客观现象，且具有一定物理含义的消息或知识，信息是可以用数值、文字、声音、图像等形式描述的状态，信息是用数据作为载体来描述和表达的客观现象，信息是对数据加工提炼的结果，是对人类有用的知识，信息是隐含在物理信号中具有一定含义的消息，信号处理的目的是为了从信号中获取有用的知识。信息技术的内涵包括传感，通信和计算机。主要分为两类：一类是管理信息系统；另一类是指面对自然科学领域的工程。 关键词：通信，技术，系统，光纤、数字微波、卫星、移动、3G、4G、CDMA 引言 在经过李老师的精彩讲解之后，我对通信工程专业有了更加清晰的认识，了解了通信专业的发展，我国目前通信产业的现状以及未来发展的方向。使我对自己未来大学四年的规划，目标更加明确。其中老师主要介绍了通信行业的发展趋势、通信系统的组成、通信工程专业的培养目标、通信工程专业的课程体系还有
与我们息息相关的生活方面的建议、简单说说毕业后的去向。在此表示衷心感谢！在科技发展如此迅速的今天，通信业在社会中占据着不可替代的地位，各种各样的信息每天都在变换着。何谓信息？不知道有多少人知道。从古老的结绳记事，烽火传烟，飞鸽传书，到当前的手机，网络，电话等等通信方式，人们的通信方式发生了翻天覆地的变化，变的更加方便，快捷，舒适，给人类的沟通带来了无与伦比的便捷，缩短了时空的距离，提高了沟通的效率，为经济发展全球化铺上了高速通道。可以说通信方式的发展促进了时代的进步，当然这离不开科技的发展，更重要的是离不开一门专业——通信工程的发展。合肥学院独具特色的第二课堂管理体系，使我校的办学能力不断的提升，下面将进行介绍。胡国华老师对我们通信工程专业的发展及就业方向、发展前景也进行了详细的介绍。下面我将给大家详细介绍。 目录 一、引子： (1) 二、通信工程的含义： (1) 三、通信工程专业的培养目标： (3) “平台+模块”形式的课程体系： (3) 四个平台+ 三个方向： (4) 四个平台 (4) （1）通识基础教育平台； (4) 三个方向 (4) 四、通信工程专业发展趋势和毕业生去向： (5) 光纤通信发展前景 (5) 无线通信发展前景 (5) 就业现状: (6) 就业前景: (6) 五、通信工程实验室建设背景： (7) 2、通信工程实训中心实验室建设内容 (7) 六、开设的实训项目 (7)
自动控制论文 作者洪劲松 专业电气工程及其自动化 学号120301628 指导教师赵国新
Automatic control is when no one is directly involved in the case, the use of additional equipment or control device, the machine, device, or a working state of the control object or parameters (charged) automatically according to the predetermined rules. The traditional industrial production process using dynamic control technology, can effectively improve the quality of the products and the enterprise economic benefit. In today's rapid development of science and technology, automatic control technology in the field of industrial and agricultural production, national defense and science and technology, has a very important role. In a short span of one hundred years, the development of automatic control theory has been surprising, has a huge impact on human society. Automatic control theory is the study of automatic control common law science and technology. It is both an ancient and has become a mature discipline, another door is developing, the strong vitality of the emerging disciplines. From 1868 maxwell J.C.M axwell low order system stability criterion is put forward to date more than one hundred years, the development of automatic control theory can be divided into four main stages: the first stage: the classical control theory (or) classical control theory of the formation, development and maturity; The second stage: the rise of modern control theory and development; The third stage: big system control the rise and development stage; The fourth stage: intelligent control stage of development. The basic characteristics of the first stage of the classical control theory is mainly used for linear time-invariant systems research, namely for describing the system of linear differential equation with constant coefficients of analysis and synthesis; It is used only for single input and single output feedback control system; Only discuss the relationship between the system input and output, and ignore the internal state of the system, is a method of external description of the system. The basic method used: root locus method, frequency method, PID regulator (frequency domain). Control theory in the early stage of development, the automatic adjustment principle is based on the feedback theory, mainly used in industrial control. Feedback theory for feedback control. Feedback control is one of the most basic is the most important control mode, after the introduction of feedback signal, system response to come from the external and internal interference become very dull, so as to improve the anti-interference ability and the control precision of the system. Feedback effects, meanwhile, brings the problem of system stability, which was once the system stability problem in people inspired people to conduct the thorough research to the feedback control system in the enthusiasm, promote the development of the theory of automatic control and improvement. So in a sense, the classical feedback control theory is accompanied by the emergence and development of control technology and gradually improve and mature. During the second world war, in order to design and manufacture of aircraft and Marine autopilot, artillery positioning system, radar tracking system based on feedback principle of military equipment, to further promote and perfect the development of automatic control theory. In 1868, maxwell (J.C.M axwell) lower order algebraic criterion of the stability of the system are put forward. In 1875 and 1896, mathematicians rous (Routh) and hull weitz (Hurwitz) respectively independently the stability criterion of high order system was put forward, namely the Routh Hurwitz criterion. During the second world war (1938-1945), Nyquist (H.N yquist) in 1948, proposed the theory of frequency
Building construction concrete crack of prevention and processing Abstract The crack problem of concrete is a widespread existence but again difficult in solve of engineering actual problem, this text carried on a study analysis to a little bit familiar crack problem in the concrete engineering, and aim at concrete the circumstance put forward some prevention, processing measure. Keyword: Concrete crack prevention processing Foreword Concrete's ising 1 kind is anticipate by the freestone bone, cement, water and other mixture but formation of the in addition material of quality brittleness not and all material.Because the concrete construction transform with oneself, control etc. a series problem, harden model of in the concrete existence numerous tiny hole, spirit cave and tiny crack, is exactly because these beginning start blemish of existence just make the concrete present one some not and all the characteristic of quality.The tiny crack is a kind of harmless crack and accept concrete heavy, defend Shen and
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Programmable designed for electro-pneumatic systems controller John F.Wakerly This project deals with the study of electro-pneumatic systems and the programmable controller that provides an effective and easy way to control the sequence of the pneumatic actuators movement and the states of pneumatic system. The project of a specific controller for pneumatic applications join the study of automation design and the control processing of pneumatic systems with the electronic design based on microcontrollers to implement the resources of the controller. 1. Introduction The automation systems that use electro-pneumatic technology are formed mainly by three kinds of elements: actuators or motors, sensors or buttons and control elements like valves. Nowadays, most of the control elements used to execute the logic of the system were substituted by the Programmable Logic Controller (PLC). Sensors and switches are plugged as inputs and the direct control valves for the actuators are plugged as outputs. An internal program executes all the logic necessary to the sequence of the movements, simulates other components like counter, timer and control the status of the system. With the use of the PLC, the project wins agility, because it is possible to create and simulate the system as many times as needed. Therefore, time can be saved, risk of mistakes reduced and complexity can be increased using the same elements. A conventional PLC, that is possible to find on the market from many companies, offers many resources to control not only pneumatic systems, but all kinds of system that uses electrical components. The PLC can be very versatile and robust to be applied in many kinds of application in the industry or even security system and automation of buildings.
The General Situation of AT89C51 The AT89C51 is a low-power, high-performance CMOS 8-bit microcomputer with 4K bytes of Flash Programmable and Erasable Read Only Memory (PEROM) and 128 bytes RAM. The device is manufactured using Atmel’s high density nonvolatile memory technology and is compatible with the industry standard MCS-51?instruction set and pin out. The chip combines a versatile 8-bit CPU with Flash on a monolithic chip; the Atmel AT89C51 is a powerful microcomputer which provides a highly flexible and cost effective solution to many embedded control applications. Features: ?Compatible with MCS-51?Products ?4K Bytes of In-System Reprogrammable Flash Memory ?Endurance: 1,000 Write/Erase Cycles ?Fully Static Operation: 0 Hz to 24 MHz ?Three-Level Program Memory Lock ?128 x 8-Bit Internal RAM ?32 Programmable I/O Lines ?Two 16-Bit Timer/Counters ?Six Interrupt Sources ?Programmable Serial Channel ?Low Power Idle and Power Down Modes The AT89C51 provides the following standard features: 4K bytes of Flash, 128 bytes of RAM, 32 I/O lines, two 16-bit timer/counters, a five vector two-level interrupt architecture, a full duplex serial port, on-chip oscillator and clock circuitry. In addition, the AT89C51 is designed with static logic for operation down to zero frequency and supports two software selectable power saving modes. The Idle
UNIT 1 A 电路 电路或电网络由以某种方式连接的电阻器、电感器和电容器等元件组成。如果网络不包含能源，如 电池或发电机，那么就被称作无源网络。换句话说，如果存在一个或多个能源，那么组合的结果为有源网络。在研究电网络的特性时，我们感兴趣的是确定电路中的电压和电流。因为网络由无源电路元件组成，所以必须首先定义这些元件的电特性. 就电阻来说，电压-电流的关系由欧姆定律给出，欧姆定律指出：电阻两端的电压等于电阻上流过的电流乘以电阻值。在数学上表达为: u=iR (1-1A-1)式中 u=电压，伏特；i =电流，安培；R = 电阻，欧姆。 纯电感电压由法拉第定律定义，法拉第定律指出：电感两端的电压正比于流过电感的电流随时间的 变化率。因此可得到：U=Ldi/dt 式中 di/dt = 电流变化率，安培/秒； L = 感应系数，享利。 电容两端建立的电压正比于电容两极板上积累的电荷q 。因为电荷的积累可表示为电荷增量dq的和或积分，因此得到的等式为 u= ，式中电容量C是与电压和电荷相关的比例常数。由定义可知，电流等于电荷随时间的变化率，可表示为i = dq/dt。因此电荷增量dq 等于电流乘以相应的时间增量，或dq = i dt，那么等式 (1-1A-3) 可写为式中 C = 电容量，法拉。 归纳式(1-1A-1)、(1-1A-2) 和 (1-1A-4)描述的三种无源电路元件如图1-1A-1所示。注意，图中电流的参考方向为惯用的参考方向，因此流过每一个元件的电流与电压降的方向一致。 有源电气元件涉及将其它能量转换为电能，例如，电池中的电能来自其储存的化学能，发电机的电能是旋转电枢机械能转换的结果。 有源电气元件存在两种基本形式：电压源和电流源。其理想状态为：电压源两端的电压恒定，与从 电压源中流出的电流无关。因为负载变化时电压基本恒定，所以上述电池和发电机被认为是电压源。另一方面，电流源产生电流，电流的大小与电源连接的负载无关。虽然电流源在实际中不常见，但其概念的确在表示借助于等值电路的放大器件，比如晶体管中具有广泛应用。电压源和电流源的符号表示如图1-1A-2所示。 分析电网络的一般方法是网孔分析法或回路分析法。应用于此方法的基本定律是基尔霍夫第一定律，基尔霍夫第一定律指出：一个闭合回路中的电压代数和为0，换句话说，任一闭合回路中的电压升等于电压降。网孔分析指的是：假设有一个电流——即所谓的回路电流——流过电路中的每一个回路，求每一个回路电压降的代数和，并令其为零。 考虑图1-1A-3a 所示的电路，其由串联到电压源上的电感和电阻组成，假设回路电流i ，那么回路总的电压降为因为在假定的电流方向上，输入电压代表电压升的方向，所以输电压在（1-1A-5）式中为负。因为电流方向是电压下降的方向，所以每一个无源元件的压降为正。利用电阻和电感压降公式，可得等式(1-1A-6)是电路电流的微分方程式。 或许在电路中，人们感兴趣的变量是电感电压而不是电感电流。正如图1-1A-1指出的用积分代替式(1-1A-6)中的i，可得1-1A-7 UNIT 3 A 逻辑变量与触发器
电厂蒸汽动力的基础和使用 1.1 为何需要了解蒸汽 对于目前为止最大的发电工业部门来说, 蒸汽动力是最为基础性的。 若没有蒸汽动力, 社会的样子将会变得和现在大为不同。我们将不得已的去依靠水力发电厂、风车、电池、太阳能蓄电池和燃料电池,这些方法只能为我们平日用电提供很小的一部分。 蒸汽是很重要的,产生和使用蒸汽的安全与效率取决于怎样控制和应用仪表,在术语中通常被简写成C&I(控制和仪表 。此书旨在在发电厂的工程规程和电子学、仪器仪表以 及控制工程之间架设一座桥梁。 作为开篇,我将在本章大体描述由水到蒸汽的形态变化,然后将叙述蒸汽产生和使用的基本原则的概述。这看似简单的课题实际上却极为复杂。这里, 我们有必要做一个概述:这本书不是内容详尽的论文,有的时候甚至会掩盖一些细节, 而这些细节将会使热力学家 和燃烧物理学家都为之一震。但我们应该了解,这本书的目的是为了使控制仪表工程师充 分理解这一课题,从而可以安全的处理实用控制系统设计、运作、维护等方面的问题。1.2沸腾:水到蒸汽的状态变化 当水被加热时,其温度变化能通过某种途径被察觉(例如用温度计 。通过这种方式 得到的热量因为在某时水开始沸腾时其效果可被察觉,因而被称为感热。 然而,我们还需要更深的了解。“沸腾”究竟是什么含义?在深入了解之前,我们必须考虑到物质的三种状态:固态,液态,气态。 (当气体中的原子被电离时所产生的等离子气体经常被认为是物质的第四种状态, 但在实际应用中, 只需考虑以上三种状态固态,
物质由分子通过分子间的吸引力紧紧地靠在一起。当物质吸收热量,分子的能量升级并且 使得分子之间的间隙增大。当越来越多的能量被吸收,这种效果就会加剧,粒子之间相互脱离。这种由固态到液态的状态变化通常被称之为熔化。 当液体吸收了更多的热量时,一些分子获得了足够多的能量而从表面脱离,这个过程 被称为蒸发(凭此洒在地面的水会逐渐的消失在蒸发的过程中,一些分子是在相当低的 温度下脱离的,然而随着温度的上升,分子更加迅速的脱离,并且在某一温度上液体内部 变得非常剧烈,大量的气泡向液体表面升起。在这时我们称液体开始沸腾。这个过程是变为蒸汽的过程,也就是液体处于汽化状态。 让我们试想大量的水装在一个敞开的容器内。液体表面的空气对液体施加了一定的压 力,随着液体温度的上升,便会有足够的能量使得表面的分子挣脱出去,水这时开始改变 自身的状态,变成蒸汽。在此条件下获得更多的热量将不会引起温度上的明显变化。所增 加的能量只是被用来改变液体的状态。它的效用不能用温度计测量出来,但是它仍然发生 着。正因为如此,它被称为是潜在的,而不是可认知的热量。使这一现象发生的温度被称为是沸点。在常温常压下,水的沸点为100摄氏度。 如果液体表面的压力上升, 需要更多的能量才可以使得水变为蒸汽的状态。 换句话说, 必须使得温度更高才可以使它沸腾。总而言之,如果大气压力比正常值升高百分之十,水必须被加热到一百零二度才可以使之沸腾。
一、前言 在全社会对节能的重视，在绿色新能源的发展现状，贵州的一些偏远山区，由于地理条件和经济落后，能源短缺等原因，电力供应和电力成本高，当地的电力短缺，没有电，人们对权力的渴望来解决用电问题迫在眉睫，他们始终坚持这样一来国家能够稳定发展与经济也可以很好的发展。今天我省能够使用电网和其他的发电机来发电。不然，对我我省的地势环境，历史，远程用户发送电路具有功耗小，途中损失比较严重。各种网络的使用是很难能维护的，难以保障连续供电。 该论文依向着节约能源和建设绿色环保新能源的想法贵州的风能和太阳能的偏远地区并不突出，电力资源短缺，使用更少的功率特性的用户建议的应用在贵州省，小风光互补电源的设计问题。复合材料结构的系统设计，对DC/DC变换器模块的设计选择，最大功率合理选择（M或T）跟踪模式，能够完成最大功率监督，改变其费用，简单结构，依赖专门用电直流电池组充电的同时思考，在DC/DC模块为基础的变化，设计PLC作为主要控制部件，控制器采集数据，电池端电压，电流。 本文针对绿色能源的发展，新的节能减排和发展国家目前所倡导的和谐的解释人和社会发展的需求的发展，人与自然；同时，本研究也为其它地区的独立发电有一定意义。 1.1 论文课题研究的背景和意义 能量是物质基础，中国经济的增长和人民生活的关键。然而人类在利用化石 燃料时，也引发了剧烈的生态系统与环境污染破损等问题。最近，每个列国渐渐了解到能源对我们的重要，更明白了普通的能源使用过程当中对生态系统与环境系统破损。许多国家都根据国情出发，治理了环境的恶化，以及开发和利用可再生，无污染的新能源作为可持续发展的一个重要组成部分。 风能和太阳能是取之不竭, 用之有余的可再生能源，风力发电和太阳能发电系统在我国取得了广泛的使用，他们的发电形式都有其长处。在现实生活中的主导力量，但由于客观条件，有些地方无法实现电力的发展与建设。 在移动通信基站的建设，电力设备被应用到传统的最近市电或者小的发电厂，电力，存在以下问题：1)电盲；2)电压波动；3)雷击损坏；4)基站电源线被人为
西南交通大学 毕业设计（英文翻译） 节能型机房温湿度远程控制系统测控节点设 计 年级: 学号: 姓名: 专业: 指导老师: 二零一一年六月
Mosix Mosix修改bsdi上的BSD/ OS来提供电脑上的跨网络的动态负载平衡组和先发制人进程迁移。这是不错的东西，不只是为并行处理，但对于通常使用一个集群很像一个可扩展的SMP。是否有Linux版本？详细信息，请看www.cs.huji.ac.il/mosix/。NOW (工作站网络) 伯克利工作站网络项目，https://www.doczj.com/doc/df14123784.html,/，已经极推广了并行计算中使用工作站网络，这里还有很多工作在进行中，都致力于“在未来几年展示一个实际的100处理器系统”。唉，他们不使用linux。 并行处理使用linux 并行处理使用Linux WWW站点，https://www.doczj.com/doc/df14123784.html,/LDP/,是这些指南和许多相关文件包括为全日制量身订造的在线幻灯片的家园。除了在报纸项目上，普渡大学电机与计算机工程系已经是并行处理的领先者，这个的设立是为了帮助别人申请并行处理的Linux电脑。 自从普渡大学的第一组Linux个人电脑在1994年2月组装以来，已经诞生了许多的Linux PC集群，有些还包括视频墙。然而这些集群使用386，486和奔腾系统（没有奔腾Pro系统），英特尔最近获得普渡大学的捐赠，将允许它的奔腾II系统构建多个大型集群（与单个群集计划多达165机）。并且这些集群都将有论文网，也具有最传统的网络。 奔腾Pro集群研讨会 1997年，4月10-11日，埃姆斯实验室在得梅因，爱荷华州举行了奔腾Pro集群研讨会。WWW在本次研讨会，https://www.doczj.com/doc/df14123784.html,/workshops/PPCworkshop.html，从云集的参加者中收集了很多丰富的PC集群信息。 TreadMarks帝斯曼(分布式共享存) 帝斯曼（分布式共享存）是一种技术，即一个消息传递系统可以出现的行为作为一个SMP。有不少这样的系统，其部分使用OS页故障触发消息传输机制。TreadMarks，https://www.doczj.com/doc/df14123784.html,/~willy/TreadMarks/overview.html，是这种系统更有效地之一，并在Linux集群上运行。坏消息是“TreadMarks”正在由一个小成本的大学和非盈利机构的分配。欲了解更多有关该软件，请联系https://www.doczj.com/doc/df14123784.html,信息。 U型网 (用户级网络接口架构) U型网（用户级网络接口架构）在康奈尔大学，
P1 二、复合难句： 1、Mining may well have been the second of humankind's earliest endeavors--granted that agriculture was the first. The two industries ranked together as the primary or basic industries of early civilization 如果说农业是人类最早的产业（文明）的话，那么采矿就理所当然地排在第二。这两种产业作为人类早期文明最原始或最基本的产业联系在了一起。 2、If we consider fishing and lumbering as part of agriculture and oil and gas production as part of mining , then agriculture and mining continue to supply all the basic resources used by modern civilization 如果我们把捕鱼业和伐木业作为农业的一部分，而石油和天然气产业作为采矿的一部分，那么农业和采矿业至今仍是现代文明所使用的基础资源的支柱 3、Here the term mining is used in its broadest context as encompassing the extraction of any naturally occurring mineral substances-solid , liquid , and gas-from the earth or other heavenly bodies for utilitarian purposes. 这里所说的采矿是指广义上的，因为它包括为实利目的而从地球或其他天体岩石中获取任何天然形成的固态、液态和气态矿物的开采 4、Mine：An excavation made in the earth to extract minerals 采矿：为了开采矿物而在地球上进行的一种挖掘 5、Mining: the activity , occupation , and industry concerned with the extraction of minerals 采矿业：一种与开采矿物有关的活动、职业和产业 6、Mining engineering: the practice of applying engineering principles to the development , planning , operation , closure and reclamation of mines. 采矿工程：运用工程原理生产、规划、运作和关闭（充填）以及对矿山再利用（复垦）的一种实践 7、Mineral：A naturally occurring inorganic element or compound having an orderly internal structure and a characteristic chemical composition , crystal form , and physical properties. 矿物：一种天然形成的无机元素或化合物（无机物），它有着有序的内部构造、特有的化学成分、结晶形式和物理性质。 8、Rock：Any naturally formed aggregate of one or more types of mineral particles
Page1 Generators and Motors From reference 1 1. Direct-current generators impress on the line a direct or continuous emf, one that is always in the same direction. Commercial dc generators have commutators, which distinguish them from ac generators. The function of a commutator and the elementary ideas of generation of emf and commutation are discussed in Div. 1. Additional information about commutation as applied to dc motors, which in general is true for dc generators, is given below. 2. Excitation of generator fields. To generate an emf, conductors must cut a magnetic field which in commercial machines must be relatively strong. A permanent magnet can be used for producing such a field in a generator of small output, such as a telephone magneto or the magneto of an insulation tester, but in generators for light and power the field is produced by electromagnets, which may be excited by the machine itself or be separately excited from another source.Self-excited machines may be of the series, shunt, or compound type, depending upon the manner of connecting the field winding to the armature. In the series type of machine,the field winding (the winding which produces the magnetic field) is connected in series with the armature winding. In the shunt type, the field winding is connected in parallel,shunt, with the armature winding. Compound machines have two field windings on each pole. One of these windings is connected in series with the armature winding, and the other is connected in parallel or shunt with the armature winding. 3. Armature winding of dc machines may be of the lap or the wave type. The difference in the two types is in the manner of connecting the armature coils to the commutator.A coil is the portion of the armature winding between successive connections to the commutator.In the lap type of winding (see Fig. 7.1) the two ends of a coil are connected to adjacent commutator segments. In the wave type of winding (see Fig. 7.2) the two ends of a coil are connected to commutator segments that are displaced from each other by approximately 360 electrical degrees.The type