An electrical circuit or network is composed of elements such as resistors , inductors , and capacitors connected together in some manner .If the network contains no energy sources , such as
batteries or electrical generators,it is known as a passive network.On the other hand, if one or more energy sources are present , the resultant combination is an active network. In studying the behavior of an electrical network,we are interested in determining the voltages and currents that exist within the circuit. Since a network is composed of passive circuit elements,we must first define the electrical characteristics of these elements.
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.
In the case of a resistor, the voltage-current relationship is given by Ohm's law, which ststes that the voltage across the resistor is equal to the current through the resistor multiplied by the value of the resistance. Mathematically, this is expressed as u=iR where u=voltage , V; i=current, A; R=resistance Ω.
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。
The voltage across a pure inductor is defined by Faraday's law ,which states that the voltage across the inductor is proportional to the rate of change with time of the current through the inductor. Thus we have u=Ldi/dt where di/dt=rate of change of current ,A/s; L=inductance ,H.
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。
The voltage developed across a capacitor is proportional to the electric charge q accumulating on the plates of the capacitor. Since the accumulation of charge may be expressed as the summation, or integral , of the charge increments dq, we have the equation u=1/c fdq where the capacitance C is the proportionality constant relating voltage and charge. By definition, current equals the rate of change of charge with time and is expressed as i=dq/dt. Thus an increment of charge dq is equal to the current multiplied by the corresponding time increment, or dq=i dt.
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= 1/c fdq，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。
A common method of analyzing an electrical network is mesh or loop analysis. The fundamental law that is applied in this method is Kirchhoff's first law, which states that the algebraic sun of the voltages around a closed loop is 0 ,or , in any closed loop , the sum of the voltage rises must equal the sum of the voltage drops. Mesh analysis consists of assuming that currents-termed loop currents-flow in each loop of a network ,algebraically summing the voltage drops around each loop ,and setting each sum equal to 0.
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
One problem with electronic devices corresponding to the generalized amplifiers is that the gains, Au or Ai, depend upon internal properties of the two-port system(u,β，Ri ,Ro, etc). This makes design difficult since these parameters usually vary from device ,as well as with temperature. The operational amplifier, or Op-Amp, is designed to minimize this dependence and to maximze the ease of design. An Op-Amp is an integrated circuit that has many component parts such as resistors and transistors built into the device. At this point we will make no attempt to describe these inner workings.
运算放大器像广义放大器这样的电子器件存在的一个问题就是它们的增益AU 或AI取决于双端口系统(m、b、RI、Ro,等)的内部特性。器件之间参数的分散性和温度漂移给设计工作增加了难度。设计运算放大器或Op-Amp的目的就是使它尽可能的减少对其内部参数的依赖性、最大程度地简化设计工作。运算放大器是一个集成电路，在它内部有许多电阻、晶体管等元件。就此而言，我们不再描述这些元件的内部工作原理。
Integrated circuit technology allows construction of many amplifier circuits on a single composite "chip" of semiconductor material.
集成电路技术使得在非常小的一块半导体材料的复合“芯片”上可以安装许多放大器电路。
The first law states that in normal Op-Amp circuits we may assume that the voltage difference between the input terminals is zero, that is , U+=U-
第一个定律指出：在一般运算放大器电路中，可以假设输入端间的电压为零，也就是说U+=U-
The second law states that in normal Op-Amp circuits both of the input currents may be assumed to be zero: I+=I-=0
第二个定律指出：在一般运算放大器电路中，两个输入电流可被假定为零：I+=I-=0
The two-valued variables which we have been discussing are often called logical
variables, while the operations such as the OR operation and the AND operation are referred to as logical operations. We shall now briefly discuss the relevance of such terminology, and in so doing we shall bing out the special aptness of the designations "true" and "false" to identify the possible values of a variable.
逻辑变量我们讨论的双值变量通常叫做逻辑变量，而象或和与这样的操作被称为逻辑操作。现在我们将简要地讨论一下这些术语之间的关联，并在此过程中，阐明用标示“真”和“假”来识别一个变量的可能值的特殊用途。
The circuit of Fig.1-3A-1, showing a pair of cross-coupled NOR gates, is called a flip-flop, It has a pair of input terminals S and R, standing for "set" and "reset" ,respectively. We shall use these symbols S and R not only to designate the terminals but also to specify the logical level at the terminals. Thus ,S=1 indicates that a voltage corresponding to logic level 1 is normally present at terminal S . Similarly ,the output terminals and the corresponding output logic levels are Q and Q. In this notation we have explicitly taken account of the fact that in normal operation, as we shall see, the logic levels at the outputs are complementary.
图1-3A-1给出的一对交叉连接的或非门电路被称为触发器。其有一对输入端S 和R ，分别代表“置位”和“复位”。我们不仅用符号S 和R 标明端点，而且指定端点的逻辑电平。因此，通常S=1指的是对应于逻辑电平为1的电压出现在S 端。相似的，输出端和相应的输出逻辑电平为Q和非Q。使用这样的符号时，我们已经明确了一个事实，即在我们下面将看到的符号操作中，输出的逻辑电平是互补的。
The types of commercially available DC motors basically fall into four categories:(1) permanent-magnet DC motors, (2) series-wound DC motors, (3) shunt-wound DC motors, and (4) compound-wound DC motors. Each of these motors has different characteristics due to its basic circuit arrangement and physical properties.
现在可以买到的直流电机基本上有四种：⑴永磁直流电机，⑵串励直流电机，⑶并励直流电机，⑷复励直流电机。每种类型的电动机由于其基本电路和物理特性的不同而具有不同的机械特性。
The manner in which the armature and filed circuits of a DC motors are connected determines its basic characteristics. Each of the types of DC motors are similar in construction to the type of DC generator that corresponds to it. The only difference, in most cases, is that the generator acts as a voltage source while the motor functions as a mechanical power conversion device.
直流电机电枢和激磁电路的连接方式确定了直流电机的基本特性。每一种直流电机的结构与其对应的直流发电机的结构类似。大部分情况下，二者的唯一区别在于发电机常作为电压源，而电动机常作为机械能转换装置。
The word control is usually taken to mean regulate, direct, or command. Control systems abound in our environment. In the most abstract sense it is possible to consider every physical object as a control system.
控制一词的含义一般是调节、指导或者命令。控制系统大量存在于我们周围。在
最抽象的意义上说，每个物理对象都是一个控制系统。
Control theory itself has two categories:classical and modern. Classical control theory, which had its start during World War II, can be characterized by the transfer function concept with analysis and design principally in the Laplace and frequency domains. Modern control theory has arisen with the advent of high-speed digital computers and can be characterized by the state variable concept with emphasis on matrix algebra and with analysis and design principally in the time domain. As might be expected, each approach has its advantages and disadvantages as well as its proponents and detractors..
控制理论本身分成两个部分：经典和现代。经典控制理论始于二次大战以传递函数的概念为特征，分析和设计主要在拉普拉斯域和频域内进行。现代控制理论是随着高速数字计算机的出现而发展起来的。它以状态变量的概念为特征，重点在于矩阵代数，分析和设计主要在时域。每种方法都有其优点和缺点，也各有其倡导者和反对者。
Open-loop and closed-loop control systems (see Fig.2-1A-1). An open-loop system is one in which the control action is independent of the output. A closed-loop system, however, the input of the plant is somehow dependent on the actual output.
开环和闭环系统（如图2-1A-1）：开环控制系统是控制行为与输出无关的系统。而闭环系统，其被控对象的输入在某种程度上依赖于实际的输出。
The stability of a continuous or discrete-time system is determined by its response to inputs or disturbance. Intuitively, a stable system is one that remains at rest (or in equilibrium) unless excited by an external source and returns to rest if all excitations are removed. The output will pass through a transient phase and settle down to a steady-state response that will be of the same form as, or bounded by, the input. If we apply the same input to an unstable system, the output will never settle down to a steady-state phase; it will increase in an unbounded manner, usually exponentially or with oscillations of increasing amplitude.
连续或离散系统的稳定性由其对输入或者干扰的响应决定。直观地说，如果一个系统是稳定的，则其停留在稳态（或者平衡点），除非是受到外部激励，且当外部激励去除后，输出又回到稳态点。输出经过瞬态阶段后将回到与输入有相同形式的稳态或者是在输入的附近。如果我们将同样的输入作用于不稳定的系统，其输出将不会回到稳态，而是以无界的方式增长，通常其幅值是指数增长或者振荡增长。
The Routh criterion:All the roots of the characteristic equation have negative real parts if and only if the elements of the first column of the Routh table have the same sign. Otherwise, the number of roots with positive real parts is equal to the number of changes of sign.
劳斯判据：当且仅当劳斯表第一行元素有相同的符号时，特征方程的根具有负实数。反之，具有正式部的特征根的个数等于劳斯表第一列元素变号次数。
Fo rξ>1,these poles are on the negative real axis, on both sides of-Wn; the transient is a sum of two decaying exponentials, each with its own time constant. The exponential corresponding to the pole closest to the origin has the largest time constant and takes the longest to decay. This pole is called the dominating pole.
当ξ>1时，这些极点在负实轴上，在-ξWn的两边，瞬态响应为两个不同时间常数指数衰减曲线之和。对应靠近原点的指数曲线具有大的时间常数，并且衰减时间长。这样的极点称之为主导极点。
Forξ=1, both poles coincide at-Wn. Forξ<1, the poles move along a circle of radius Wn centered at the origin. From the geometry in Fig.2-2A-3, it is seen also that cosφ=ξWn/Wn=ξ.
当ξ=1时，两个极点重合为：-Wn。当ξ<1时，两个极点沿从原点为中心，Wn 为半径的圆移动。
01 THE ELEMENTS AND THE PERIODIC TABLE 01 元素和元素周期表 The number of protons in the nucleus of an atom is referred to as the atomic number, or proton number, Z. The number of electrons in an electrically neutral atom is also equal to the atomic number, Z. The total mass of an atom is determined very nearly by the total number of protons and neutrons in its nucleus. This total is called the mass number, A. The number of neutrons in an atom, the neutron number, is given by the quantity A-Z. 质子的数量在一个原子的核被称为原子序数,或质子数、周淑金、电子的数量在一个电中性原子也等于原子序数松山机场的总质量的原子做出很近的总数的质子和中子在它的核心。这个总数被称为大量胡逸舟、中子的数量在一个原子,中子数,给出了a - z的数量。 The term element refers to, a pure substance with atoms all of a single kind. T o the chemist the "kind" of atom is specified by its atomic number, since this is the property that determines its chemical behavior. At present all the atoms from Z = 1 to Z = 107 are known; there are 107 chemical elements. Each chemical element has been given a name and a distinctive symbol. For most elements the symbol is simply the abbreviated form of the English name consisting of one or two letters, for example: 这个术语是指元素,一个纯物质与原子组成一个单一的善良。在药房“客气”原子的原子数来确定它,因为它的性质是决定其化学行为。目前所有原子和Z = 1 a到Z = 107是知道的;有107种化学元素。每一种化学元素起了一个名字和独特的象征。对于大多数元素都仅仅是一个象征的英文名称缩写形式,一个或两个字母组成,例如: oxygen==O nitrogen == N neon==Ne magnesium == Mg
第一章汽车总论 1)Today’s average car contains more than 15,000 separate, individual parts that must work together. These parts can be grouped into four major categories: body, engine, chassis and electrical equipment 。P1 现在的车辆一般都由15000多个分散、独立且相互配合的零部件组成。这些零部件主要分为四类：车身、发动机、底盘和电气设备。 2)The engine acts as the power unit. The internal combustion engine is most common: this obtains its power by burning a liquid fuel inside the engine cylinder. There are two types of engine: gasoline (also called a spark-ignition engine) and diesel (also called a compression-ignition engine). Both engines are called heat engines; the burning fuel generates heat which causes the gas inside the cylinder to increase its pressure and supply power to rotate a shaft connected to the power train. P3 发动机作为动力设备，常见的类型是内燃机，其原理是通过发动机缸内的液体燃料燃烧而产生能量。发动机可分为两类：汽油机（点燃式）和柴油机（压燃式），都属于热力发动机。燃料燃烧产生热量使缸内气压上升，产生的能量驱动轴旋转，并传递给动力传动系。 第二章内燃机 1)Power train system: conveys the drive to the wheels 2)Steering system: controls the direction of movement 3)Suspension system: absorbs the road shocks 4)Braking system: slows down the vehicle P4 传动系把发动机输出的扭矩传递给驱动轮。传动系包括离合器（对应机械变速器）或液力变矩器（对应液力自动变速器）、变速器、驱动轴、主减速器、差速器和驱动桥。 5)Drum brakes have a drum attached to the wheel hub, and braking occurs by means of brake shoes expanding against the inside of the drum. With disc brakes, a disc attached to the wheel hub is clenched between two brake pads. P6 鼓式制动器的制动鼓和轮毂连接，制动蹄张开压紧制动鼓内侧从而产生制动。在盘式制动器上，连着轮毂的制动盘被紧紧夹在两个制动块之间。 1)Linking the piston by a connecting rod to a crankshaft causes the gas to rotate the shaft through half a turn.The power stroke"uses up"the gas,so means must be provided to expel the burnt gas and recharge the cylinder with a fresh petrol-air mixture:this control of gas movement is the duty of the valves;An inlet valve allows the mixture to enter at the right time and an exhaust valve lets out the burnt gas after the gas has done its job . P10 活塞通过连杆和曲轴连接，使得气体带动曲轴旋转半圈。作功冲程耗尽了所有的气体，这样就必须采取相应的措施排出废气并且向气缸内充入新的可燃混合气：气体的运动由气门来控制。进气门使可燃混合气在恰当的时刻进入气缸，排气门使燃烧后的废气排出气缸。 2)The spark-ignition engine is an internal-combustion engine with externally supplied in ignition,which converts the energy cntained in the fuel to kinetic energy.The cycle of operations is spread over four piston strokes. To complete the full cycle it takes two revolutions of the crankshaft. P11 火花点火式发动机是由外部提供点火的内燃机，从而将含在燃料内的能量转化成动能。发动机的一个工作循环分布在活塞的四个行程中，一个完整的工作循环曲轴需要转动两圈。 3)The oil pump in the lubricating system draws oil from the oil pan and sends it to all working parts in the engine. The oil drains off and runs down into the pan. Thus,there is constant circulation of oil between the pan and the working parts of the engine. P15
第二章第一篇 To say that we live in an age of electronics is an understatement. From the omnipresent integrated circuit to the equally omnipresent digital computer, we encounter electronic devices and systems on a daily basis. In every aspect of our increasingly technological society— whether it is science, engineering, medicine, music, maintenance, or even espionage—the role of electronics is large, and it is growing. 谈论关于我们生活在一个电子学时代的论调是一种空泛的论调。从无处不在的集成电路到同样无处不在的数字计算机，我们在日常活动中总会遇到电子设备和电子系统。在我们日益发展的科技社会的方方面面——无论是在科学、工程、医药、音乐、维修方面甚至是在谍报方面——电子学的作用是巨大的，而且还将不断增强。 In general, all of the tasks with which we shall be concerned can be classified as "signal-processing“tasks. Let us explore the meaning of this term 一般说来，我们将要涉及到的工作被归结为“信号——处理”工作，让我们来探究这个术语的含义吧。 A signal is any physical variable whose magnitude or variation with time contains information. This information might involve speech and music, as in radio broadcasting, a physical quantity such as the temperature of the air in a room, or numerical data, such as the record of stock market transactions. The physical variables that can carry information in an electrical system are voltage and current. When we speak of "signals", therefore, we refer implicitly to voltages or currents. However, most of the concepts we discuss can be applied directly to systems with different information-carrying variables. Thus, the behavior of a mechanical system (in which force and velocity are the variables) or a hydraulic system (in which pressure and flow rate are the variables) can often be modeled or represented by an equivalent electrical system. An understanding of the behavior of electrical systems, therefore, provides a basis for understanding a much broader range of phenomena. 信号就是其与时间有关的量值或变化包含信息的任何物理变量。这种信息或许像无线电广播的演讲和音乐，或许是像室内温度的物理量，或许像股市交易记录的数字数据。在电气系统中能够载有信息的物理变量是电压和电流。因此当我们谈到“信号”，我们不言而喻指的是电压和电流，然而，我们要讨论的大多数概念是可以被直接应用于载有不同信息的变量的系统，因此，一个机械系统（在这个系统中力和速度是其变量）或者液压系统（在这个系统中压力和流速是其变量）的性能通常可以用一个等效的电气系统来模拟或表示。因此，我们对于电气系统性能的理解为理解更宽领域的现象打下了一个基础。 A signal can carry information in two different forms. In an analog signal the continuous variation of the voltage or current with time carries the information. An example, in Fig.2-l, is the voltage produced by a thermocouple pair when the two junctions are at different temperatures. As the temperature difference between the two junctions varies, the magnitude of the voltage across the thermocouple pair also varies. The voltage thus provides an analog representation of the temperature difference. 一个信号可以以两种形式来承载信息。在一个模拟信号中电压或电流随时间而产生的连续变化载有信息。在图2-1中，当一对热电偶的接头处于不同的温度时由热电偶所产生的电压就是一个例子。当两个接头之间的温度差改变时，一对热电偶两端的电压也将改变。于是电压就提供了温度差的模拟表现形式 The other kind of signal is a digital signal. A digital signal is one that can take on values within two discrete ranges. Such signals are used to represent ON-OFF or YES-NO information. An ordinary household thermostat delivers a digital signal tocontrol the furnace. When the
大学英语精读1课文翻译 Unit1 Some Strategies or Learning English 学习英语绝非易事。它需要刻苦和长期努力。 虽然不经过持续的刻苦努力便不能期望精通英语，然而还是有各种有用的学习策略可以用来使这一任务变得容易一些。以下便是其中的几种。 1. 不要以完全同样的方式对待所有的生词。你可曾因为简直无法记住所学的所有生词而抱怨自己的记忆力太差？其实，责任并不在你的记忆力。如果你一下子把太多的生词塞进头脑，必定有一些生词会被挤出来。你需要做的是根据生词日常使用的频率以不同的方式对待它们。积极词汇需要经常练习，有用的词汇必须牢记，而在日常情况下不常出现的词只需见到时认识即可。你会发现把注意力集中于积极有用的词上是扩大词汇量最有效的途径。 2．密切注意地道的表达方式。你可曾纳闷过，为什么我们说 "我对英语感兴趣"是"I'm interested in English"，而说"我精于法语"则是"I'm good at French"？你可曾问过自己，为什么以英语为母语的人说"获悉消息或秘密"是"learn the news or secret"，而"获悉某人的成功或到来"却是"learn of someone's success or arrival"？这些都是惯用法的例子。在学习英语时，你不仅必须注意词义，还必须注意以英语为母语的人在日常生活中如何使用它。 3．每天听英语。经常听英语不仅会提高你的听力，而且有助你培养说的技能。除了专为课程准备的语言磁带外，你还可以听英语广播，看英语电视和英语电影。第一次听录好音的英语对话或语段，你也许不能听懂很多。先试着听懂大意，然后再反复地听。你会发现每次重复都会听懂更多的东西。 4．抓住机会说。的确，在学校里必须用英语进行交流的场合并不多，但你还是可以找到练习讲英语的机会。例如，跟你的同班同学进行交谈可能就是得到一些练习的一种轻松愉快的方式。还可以找校园里以英语为母语的人跟他们随意交谈。或许练习讲英语最容易的方式是高声朗读，因为这在任何时间，任何地方，不需要搭档就可以做到。例如，你可以看着图片或身边的物件，试着对它们详加描述。你还可以复述日常情景。在商店里购物或在餐馆里吃完饭付过账后，假装这一切都发生在一个讲英语的国家，试着用英语把它表演出来。
Unit 1 Chemical Industry 化学工业 1.Origins of the Chemical Industry Although the use of chemicals dates back to the ancient civilizations, the evolution of what we know as the modern chemical industry started much more recently. It may be considered to have begun during the Industrial Revolution, about 1800, and developed to provide chemicals roe use by other industries. Examples are alkali for soapmaking, bleaching powder for cotton, and silica and sodium carbonate for glassmaking. It will be noted that these are all inorganic chemicals. The organic chemicals industry started in the 1860s with the exploitation of William Henry Perkin‘s discovery if the first synthetic dyestuff—mauve. At the start of the twentieth century the emphasis on research on the applied aspects of chemistry in Germany had paid off handsomely, and by 1914 had resulted in the German chemical industry having 75% of the world market in chemicals. This was based on the discovery of new dyestuffs plus the development of both the contact process for sulphuric acid and the Haber process for ammonia. The later required a major technological breakthrough that of being able to carry out chemical reactions under conditions of very high pressure for the first time. The experience gained with this was to stand Germany in good stead, particularly with the rapidly increased demand for nitrogen-based compounds (ammonium salts for fertilizers and nitric acid for explosives manufacture) with the outbreak of world warⅠin 1914. This initiated profound changes which continued during the inter-war years (1918-1939). 1．化学工业的起源 尽管化学品的使用可以追溯到古代文明时代，我们所谓的现代化学工业的发展却是非常近代（才开始的）。可以认为它起源于工业革命其间，大约在1800年，并发展成为为其它工业部门提供化学原料的产业。比如制肥皂所用的碱，棉布生产所用的漂白粉，玻璃制造业所用的硅及Na2CO3. 我们会注意到所有这些都是无机物。有机化学工业的开始是在十九世纪六十年代以William Henry Perkin 发现第一种合成染料—苯胺紫并加以开发利用为标志的。20世纪初，德国花费大量资金用于实用化学方面的重点研究，到1914年，德国的化学工业在世界化学产品市场上占有75%的份额。这要归因于新染料的发现以及硫酸的接触法生产和氨的哈伯生产工艺的发展。而后者需要较大的技术突破使得化学反应第一次可以在非常高的压力条件下进行。这方面所取得的成绩对德国很有帮助。特别是由于1914年第一次世界大仗的爆发，对以氮为基础的化合物的需求飞速增长。这种深刻的改变一直持续到战后（1918-1939）。 date bake to/from: 回溯到 dated: 过时的，陈旧的 stand sb. in good stead: 对。。。很有帮助
Most people can formulate a mental picture of a computer, but computers do so many things and come in such a variety of shapes and sizes that it might seem difficult to distill their common characteristics into an all-purpose definition. At its core, a computer is a device that accepts input, processes data, stores data, and produces output, all according to a series of stored instructions. Computer input is whatever is put into a computer system. Input can be supplied by a person, by the environment, or by another computer. Examples of the kinds of input that a computer can accept include the words and symbols in a document, numbers for a calculation, pictures, temperatures from a thermostat, audio signals from a microphone, and instructions from a computer program. An input device, such as a keyboard or mouse, gathers input and transforms it into a series of electronic signals for the computer. In the context of computing, data refers to the symbols that represent facts, objects, and ideas. Computers manipulate data in many ways, and we call this manipulation processing. The series of instructions that tell a computer how to carry out processing tasks is referred to as a computer program, or simply a "program." These programs form the software that sets up a computer to do a specific task. In a computer, most processing takes place in a component called the central processing unit (CPU), which is sometimes described as the"brain" of the computer. A computer stores data so that it will be available for processing. Most computers have more than one location for storing data, depending on how the data is being used. Memory is an area of a computer that temporarily holds data that is waiting to be processed, stored, or output. Storage is the area where data can be left on a permanent basis when it is not immediately needed for processing. Output is the results produced by a computer. Some examples of computer output include reports, documents, music, graphs, and pictures. An output device displays, prints, or transmits the results of processing. Computers are versatile machines, which are able to perform a truly amazing assortment of tasks, but some types of computer are better suited to certain tasks than other types of computers. Computers can be categorized as personal computer, handheld computers, workstations, mainframes, supercomputers , and servers. 大多数人可以制订一个电脑精神的图片，但电脑做很多事情，出现这样的形状和大小不同，它似乎难以提炼成一个全能的定义，它们的共同特点。在其核心，一台计算机是一种装置，它接受输入，处理数据，存储数据，并产生输出，根据对所有存储一系列指示。 什么是计算机输入到计算机系统的压力。输入可提供的一人，由环境，或由另一台计算机。对输入的各种例子，一个计算机可以接受包括文字和符号的文件，规定计算，图片，从恒温器的温度数字，音频信号从一个麦克风，从电脑程序指令。一个输入设备，如键盘或鼠标，集输和转换成一个电子信号的计算机的一系列。 在计算中，数据是指以符号代表的事实，对象和想法。计算机操作在很多方面的数据，我们称之为操作处理。一系列的指令，告诉计算机如何进行处理任务，被称为一个计算机程序，或只是一个“程序”。这些方案形成了软件，建立了计算机做特定的任务。在计算机中，大部分处理发生在一个组件的地方称为中央处理单元（CPU），有时为“大脑的计算机”来形容。 计算机存储数据，以便它会被用作处理可用。大多数计算机有多个用于存储数据的位置，这取决于数据如何被使用。内存是计算机的一个领域，数据是暂时持有等待处理，存储或输出。在数据存储，是可以在一个地区长期离开时，没有立即处理所需。 输出是由电脑产生的结果。电脑输出的一些例子包括报告，文件，音乐，图形，图片。输出设备显示，打印，或传送的处理结果。 电脑是多功能机，它能够执行各种各样的任务十分惊人，但某些类型的计算机更适合比其他类型的计算机的某些任务。计算机可以被归类为个人电脑，掌上电脑，工作站，大型机，超级计算机和服务器。
Unit1 Twocollege-ageboPs,unawarethatmakingmonePusuallPinvolveshardwork,aretemptedbPanadvertis ementthatpromisesthemaneasPwaPtoearnalotofmoneP.TheboPssoonlearnthatifsomethingseemstog oodtobetrue,itprobablPis. 一个大学男孩，不清楚赚钱需要付出艰苦的劳动，被一份许诺轻松赚大钱的广告吸引了。男孩们很快就明白，如果事情看起来好得不像真的，那多半确实不是真的。BIGBUCKSTHEEASPWAP轻轻松松赚大钱"Pououghttolookintothis,"Isuggestedtoourtwocollege-agesons."ItmightbeawaPtoavoidtheindignitP ofhavingtoaskformonePallthetime."Ihandedthemsomemagazinesinaplasticbagsomeonebadhungon ourdoorknob.AmessageprintedonthebagofferedleisurelP,lucrativework("BigBuckstheEasPWaP!")o fdeliveringmoresuchbags. “你们该看看这个，”我向我们的两个读大学的儿子建议道。“你们若想避免因为老是向人讨钱而有失尊严的话，这兴许是一种办法。”我将挂在我们门把手上的、装在一个塑料袋里的几本杂志拿给他们。塑料袋上印着一条信息说，需要招聘人投递这样的袋子，这活儿既轻松又赚钱。（“轻轻松松赚大钱!”） "Idon'tmindtheindignitP,"theolderoneanswered.“我不在乎失不失尊严，”大儿子回答说。"Icanlivewithit,"hisbrotheragreed.“我可以忍受，”他的弟弟附和道。"Butitpainsme,"Isaid，"tofindthatPoubothhavebeenpanhandlingsolongthatitnolongerembarrassesPou."“看到你们俩伸手讨钱讨惯了一点也不感到尴尬的样子，真使我痛心，”我说。TheboPssaidthePwouldlookintothemagazine-deliverPthing.Pleased,Ilefttownonabusinesstrip.BPmi dnightIwascomfortablPsettledinahotelroomfarfromhome.Thephonerang.ItwasmPwife.Shewantedt oknowhowmPdaPhadgone.孩子们说他们可以考虑考虑投递杂志的事。我听了很高兴，便离城出差去了。午夜时分，我已远离家门，在一家旅馆的房间里舒舒服服住了下来。电话铃响了，是妻子打来的。她想知道我这一天过得可好。 "Great!"Ienthused."HowwasPourdaP?"Iinquired.“好极了!”我兴高采烈地说。“你过得怎么样?”我问道。 "Super!"Shesnapped."Justsuper!Andit'sonlPgettingstarted.Anothertruckjustpulledupoutfront."“棒极了!”她大声挖苦道。“真棒!而且这还仅仅是个开始。又一辆卡车刚在门前停下。”"Anothertruck?"“又一辆卡车?” "Thethirdonethisevening.ThefirstdeliveredfourthousandMontgomerPWards.Thesecondbroughtfour thousandSears,Roebucks.Idon'tknowwhatthisonehas,butI'msureitwillbefourthousandofsomething.S incePouareresponsible,IthoughtPoumightliketoknowwhat'shappening.“今晚第三辆了。第一辆运来了四千份蒙哥马利-沃德百货公司的广告；第二辆运来四千份西尔斯-罗伯克百货公司的广告。我不知道这一辆装的啥，但我肯定又是四千份什么的。既然这事是你促成的，我想你或许想了解事情的进展。” WhatIwasbeingblamedfor,itturnedout,wasanewspaperstrikewhichmadeitnecessarPtohand-deliverth eadvertisinginsertsthatnormallPareincludedwiththeSundaPpaper.ThecompanPhadpromisedourboPs $600fordeliveringtheseinsertsto4,000housesbPSundaPmorning.我之所以受到指责，事情原来是这样：由于发生了一起报业工人罢工，通常夹在星期日报纸里的广告插页，必须派人直接投送出去。公司答应给我们的孩子六百美金，任务是将这些广告插页在星期天早晨之前投递到四千户人家去。 "Pieceofcake!"ouroldercollegesonhadshouted.“不费吹灰之力!”我们上大学的大儿子嚷道。"SiGhundredbucks!"Hisbrotherhadechoed,"Andwecandothejobintwohours!"“六百块!”他的弟弟应声道，“我们两个钟点就能干完!” "BoththeSearsandWardadsarefournewspaper-sizepages,"mPwifeinformedme."TherearethirtP-twot housandpagesofadvertisingonourporch.Evenaswespeak,twobigguPsarecarrPingarmloadsofpaperup thewalk.Whatdowedoaboutallthis?"“西尔斯和沃德的广告通常都是报纸那么大的四页，”妻子告诉我说，“现在我们门廊上堆着三万二千页广告。就在我们说话的当儿，两个大个子正各抱着一大捆广告走过来。这么多广告，我们可怎么办?”"JusttelltheboPstogetbusP,"Iinstructed."TheP'recollegemen.TheP'lldowhatthePhavetodo."“你让孩子们快干，”我指示说。“他们都是大学生了。他们自己的事得由他们自己去做。”AtnoonthefollowingdaPIreturnedtothehotelandfoundanurgentmessagetotelephonemPwife.Hervoic
About car engine Of all automobile components,an automobile engie is the most complicated assembly with dominant effects on the function of an autombile.So, the engine is generally called the"heat"of an automobile. 在汽车的所有部件中，汽车发动机是最复杂的组件，其对整车性能有着决定性的作用。因而发动机往往被称作发动机的“心脏”。 There are actually various types of engines such as electric motors,stream engines,andinternal combustion engines.The internal combustion engines seem to have almost complete dominance of the automotive field.The internal combustion engine,as its name indicates,burns fuel within the cylinders and converts the expanding force of the combustion into rotary force used to propel the vehicle. 事实上，按动力来源分发动机有很多种，如电动机、蒸汽机、外燃机等。然而内燃机似乎在发动机领域有着绝对的统治地位。就像其字面意思一样，内燃机的染料在气缸内燃烧，通过将燃烧产生气体的膨胀力转换成转动力来驱动发动机前进。 Engine is the power source of the automobile.Power is produced by the linear motion of a piston in a cylinder.However,this linear motion must be changed into rotary motion to turn the wheels of cars or trucks.The puston attached to the top of a connecting rod by a pin,called a piston pin or wrist pin.The bottom of the connecting rod is attached to the crankshaft.The connecting rod transmits the up-and-down motion of the piston to the crankshaft,which changes it into rotary motion.The connecting rod is mounted on the crankshaft with large bearings called rod bearing.Similar bearings, called main bearings,are used to mount the crankshaft in the block. 发动机是整部车的动力来源。能量来自于活塞在气缸内的（往复）直线运动。然而这种（往复）直线运动必须要转换成旋转运动才能驱动车轮。活塞与连杆通过一个销来连接，这个销称为活塞销。连杆的下部连接于曲拐。连杆把活塞的上下往复运动传递给曲拐，从而将往复直线运动转变成旋转运动。连杆和曲拐的连接使用大的轴承，称之为连杆轴承，类似的轴承也用于将曲轴连接到机体，称之为主轴承。 They are generally two different types of cooling system:water-cooling system and air-cooling system.Water-cooling system is more common.The cooling medium, or coolant, in them is either water or some low-freezing liquid, called antifreeze.A water-cooling system consists of the engine water jacket, thermostat, water pump, radiator, radiator cap, fan, fan drive belt and neccessary hoses. 主要有两种类型的冷却系统：水冷和风冷。水冷系统更为普遍。系统所用冷却介质或是冷却液常委水或其他低凝固点液体，称为抗凝剂。一个完整的水冷系统包括机体水套，节温器，水泵，散热器，散热器罩，风扇，风扇驱动皮带和必需的水管。 A water-cooling system means that water is used as a cooling agent to circulate through the engine to absorb the heat and carry it to the radiator for disposal.The ebgine is cooled mainly through heat transfer and heat dissipation.The heat generated by the mixture burned in the engine must be transferred from the iron or aluminum cylinder to the waterin the water jacket.The outside of the water jacket dissipates some of the heat to the air surrounding it, but most of the heat is carried by the cooling water to the radiator for dissipation.When the coolant temperature in the system reaches 90°,the termostat valve open fully, its slanted edge shutting off