第一篇：专业英语翻译
8.Structural Steel Behaviour
土木0704乔荟07231104
静载下的力学性能 最重要的机械结构钢性能的静负荷是表示在理想化的拉伸应力应变Fig.8.1所示图。最初的刚才有一个线性的应力应变曲线的斜率是杨氏弹性模量。钢的弹性，同时保持在这个线性范围，完全恢复。该线弹性特性的限制，通常近似屈服应力约200000MPA，以及相应的范围内。超过这个限制塑性钢的流动没有任何压力，直到应变硬化应变的增加就达到了。这通常是塑料的范围相当大，以及对钢铁延性非常重视。
屈服应力或许是结构钢的最重要的强度特性，它随着钢材化学 不同发生显著的变化，最重要的成分是碳和锰，两者都会引起屈服应力的提高。屈服应力随着热处理方法和压制过程的工作量而变化，在同样的条件下压制次数多的薄板的屈服应力高于较厚的钢板。硬化也可以提高屈服应力，拉伸的速率影响屈服应力，高拉伸速率会提高前期屈服应力，也可以提高下屈服应力Fy.在试验中用到的用来确定特殊钢种屈服应力的拉伸速率比实际结构中经常遇到的几乎不变的速率要明显提高很多。根据设计目的，各个不同的钢级别要确定一个最小屈服应力，在澳大利亚和英格兰，是根据化学组成和热处理方法来分级的，而且各个级别的屈服应力随压制面最大厚度的增加而减小，另一方面，美国的惯例是在个级别内区分化学组成和热处理方法。所应用的屈服应力不随厚度而变化。每种钢材的最小屈服应力是根据一系列的标准拉伸试验的结果确定的。由于成分组成，热处理方法，压制次数，板厚和试验速率的小的变化，在这些试验结果中有种显著的分布，这种分布近似服从正态分布曲线。因此，某种钢材用在设计中的最小屈服应力通常是一个特征值，其在任何标准拉伸试验中会超过某个概率，因而一个独立的试验结果很可能明显高于我们引用的屈服应力。当然，这种区别会更明显的如果试验不再横截面最后的位置进行的话。通常认为，单向拉伸所确定的屈服应力对单向压缩也正确。
重复荷载下的疲劳破坏
结构钢经过多次的循环交变荷载后可能在低水平拉应力条件下发生破
坏。由重复荷载导致的局部损伤会引起这种高周疲劳破坏，它导致了微小裂缝的形成，疲劳裂缝的程度随着后来的重复荷载而逐渐增大，直到最终有效横截面积小以至发生突然破坏，高周疲劳只是当在结构物设计基准期可能出现大量的荷载循环时的一种设计的考虑。这通常是桥梁，起重机，和支撑机械的结构物的问题，而且风和波浪荷载也可能引起疲劳问题。显著影响疲劳强度的因素有荷载循环次数，荷载循环中的应力幅以及局部应力集中的大小。
通常，节点应当布置得使应力集中减少到最小，以使通过节点的‘应力流，尽可能平滑。
焊接细节也应考虑到这一决定，和不必要的'压力聚集者，应避免。它也将有利于限制，如可行，接头的地点，如在接近中性轴点，低应力区。
冲击荷载下的脆性破坏 结构钢不总表现出可塑的特性，在一些情况下可能发生突然破坏，即使名义拉应力很低。脆性破坏由局部高应力区域的微小裂缝的存在或形成而引发。一旦开始，裂纹就会稳定增长因为外力会提供撕裂钢材所需的能量。更严重的是快速不稳定传播的裂缝，因为储存在钢材中的固有的弹性应变能被释放并用来使钢材破坏。只要有足够的应变内能，这种裂缝是自扩展的并且将延伸至被扩展路径中的延性元件破裂。这种延性元件具有足够的变形能力吸收释放的内能。由于钢材的延性，在三向约束条件下，结构对脆性破坏的抵抗由局部应力集中的大小确定。高集中应力促进裂缝开展，所以由不良的几何形状和荷载布置引起的应力集中都很危险，而且材料的裂纹和缺陷也非常重要。不仅会增加局部应力而且有可能成为裂纹扩展区。结构钢的延性取决于钢材的组成，热处理方法和钢材的厚度，并且随温度和应变率的变化而变化。像发生在更厚或者更大颗粒元素的钢材中南，三向的几何约束也会促进脆性，这是因为有更高的局部应力，因为在开裂过程中的更大的能量释放和裂缝传播的减缓。
脆性破坏的危险可以由选择适合温度下延性的钢材类型来降低，或者通
过由减小应力集中和几何约束的观点来设计节点。装配技术应该尽量避免引进潜在的危险裂缝或缺陷。重要结构物的设计细节需要受目的在于探测严重缺陷的检查程序的影响。当然，设计者还必须适当考虑特种钢，制造技术，检测和修正程序的额外费用。
9.Earth Pressures
重力式传播的稳定条件
设计必须考虑的不是最终或使用极限状态，计算表明，必须有足够的经费是对发生不良极限状态有关一个特定类型的墙体了。在挡土墙的失效模式的数目可能对于检查外部稳定，重力墙被视为刚体（即没有内部收益或扭曲）。在某些类型的结构检验中，还需要有内部的稳定，例如钢筋混凝土墙，加固土墙。
上述给出的安全系数的运用是设计的传统方法，在1994年推荐的极限状态方法要求对强度代表值运用一个调节系数来获得设计值，例如，如果墙体位移量要求不超过0.5%的墙高，不排水强度下应用的M之应该小于1.5，承载能力计算时M应该在2到3之间，有效应力参数M应该小于1.2。结构内力和弯矩应该由设计土压力和水压力确定。为方便起见，重力墙壁取决于他们对外部的稳定和极限状态下自身的重量基本上应审查：力量作用在挡土墙中的垂直和水平分量计算。为了方便垂直力量包括墙壁的垂直载荷的重量和任何它可能携带，随土壤以上的L形和T形墙踵重量在一起。也可能是地球的压力造成的垂直分量的支持时，面对的不垂直，地面是倾斜的或在墙上摩擦是包括在内。
挡土墙的土压力
主动土压力对能够阻止土体塌落、滑移和蠕变为自然平衡状态的任何挡土结构施加水平向和竖直向荷载分量，这些结构在土压力的作用下会发生稍微的屈服。当挡土结构挤压墙后土体时，产生被动土压力。静止土压力是土
体施加给不屈服竖直挡土表面的水平压力。静止土压力表示介于主动和被动两种极限状态之间的情况。
每一种土压力都取决于土壤的物理特性以及土壤和结构的相对刚性。土最重要的性质看来是密度、砂土的内摩擦角、黏性土的黏聚力和超固结比。就任意土体材料来说，作用在常见挡土墙上的主动土压力水平分量可由针对墙背竖直、墙后填土面基本水平的一般土压力楔体理论很好地给出。
假定该墙体采用通常的施工方法进行回填，并且能够产生一小的转动（转动大小为0.001倍的墙体高度）引发回填土的内摩擦。该转角等价于土压力作用下20英尺墙体的上表面向外移动1/4英寸。
一般土压力楔体理论的公式（考虑了沿挡土墙墙面的摩擦）也可以用来计算墙体和填土面倾斜等其它所有情况下的水平分力。然而，和试验结果相比则表明计算结果对负超载情况有点偏小，对正超载情况有点偏大，但是相差不超过10%。如果考虑进关于实际坡度的条件的不确定性，将挡土墙简化为墙背垂直填土面水平的情况进行计算，也是足够精确的。
在所有情况下，侧向压力的竖直分量会使土压力合力与墙背的法线形成一个等于墙面摩擦角的角度。然而，该角度在任何情况下都不能超过墙后填土的内摩擦角。
有些土由于缺少排水及他们自身的性质，在任何情况下都可能变为流体（不管形成的流体材料是大面积的还是仅仅靠墙的一条窄层）；这些土的压力和与其具有同样密度的流体的静水压力相等。
浸没土的压力可由式(9.1)给出，只不过式中采用的材料容重会由于水的浮力和浸没条件下的内摩擦系数而降低；除此之外，也必须包括完全的静水压力。对于粒状材料来说，水下的浸没对内摩擦系数和墙面摩擦系数的影响非常小。
第二篇：专业英语翻译
Freeways,especially those built to Interstate standardsare the safest of the various classes of highways.高速公路,尤其是那些按照州际公路标准建造的是各种公路里面最安全的.While control of access, which limits vehicle conflicts(车辆冲突), isa primary factor in relatively low accident, injury,and fatality rates(事故,死亡率), other design features, such as wide medians and shoulders roadsides clear of obstructions, and the extensive use of protective barriers(护栏), are key factors as well.出入口控制减少车辆冲突，是获得较低的交通事故率和伤亡率的一个主 要因素。另外，其他的设计特性，如较宽的中央分隔带和较宽的路肩、路边无障碍物、大量采用防护栏等也是关键要素。
The higher design speeds(设计速度)used for freeways result in long sight distances(视距)due to long radiushorizontal curves and long vertical curves, and otherdesirable design features that create a safe drivingenvironment.高速公路采用较高的设计速度导致的长视距是由于大半径水平曲线和长的竖曲线，以及其他创造安全的驾驶环境的适宜的设计特性.Although most of the nation’s freeways enjoy this
relatively high level of design and safety, there are many opportunities for further enhancements.尽管全国绝大部分高速公路最喜欢这样的设计和安全性比较高的水平，但还是有很多地方需要进一步增强。
Safety improvements on freeways can also result in substantial savings in life and property(生命和财产)because freeways carry 25 percent of the nation’s total traffic.高速公路安全方面的改善，还会节约大量的生命财产资源，因为高速公路流量占了全国的总流量的25﹪。
Selecting the design speed for a freeway is an important safety element because most geometric criteria(准则，标准)related to or depend on it.选择高速公路的设计速度是一件重要的安全因素因为大部分的几何设计标准都是与它相关或者取决于它
In general, 110 kilometers per hour(km/h)should be the design speed for the mainline of a freeway , but it may need to be lower in areas of severe terrain or heavy development.一般来说，110千米每小时应该作为高速公路主干道的设计速度，但是在崎岖的地区或者施工难度大的地区可能需要降低。
For reconstruction, rehabilitation, and resurfacing(3R)
projects, the design speed should not be less than the original design speed or the current legal speed limit of that highway section.对于重建，恢复铺新路面工程，设计速度不应该低于平时设计速度或者那块交通干线区域的目前规定的速度限制。Design speeds for interchange ramps（立交匝道）depend on the type of ramp selected, for example , loop，diamond, or direct, and the low-volume（低交通量）, running speed（行驶速度）of the intersecting highway.立交匝道的设计速度取决于砸到的选择类型，例如，环形、菱形、直线型以及低交通量，相交交通干线的运行速度。Usually, the design speed is established by the most restrictive element of the ramp, typically, the sharpest curve（小半径曲线）.通常，这个设计速度被匝道的最限制的范围，典型的是小半径曲线。
Whatever design speed is selected, adequate transitions（转变、过渡）from the freeway proper and at the ramp terminal（末端、末尾）or merge point（合流点）should be developed.无论选择多大的设计速度，都应该发展来自高速公路本身的和在匝道末尾或者合流点的合适的过渡。
Safe and efficient traffic operations depend on adequate lane
and shoulder widths as outlined in A Police on Geometric Design of Highways and Streets.安全及高效的交通运作取决于按照《道路的几何尺寸的规定》设计的适当的行车线和路肩宽度。
The need to accommodate more traffic within existing or limited additional right-of-way on high-volume urban freeway has led some agencies to increase capacity by exchange full-lane or shoulder widths for additional travel lanes with reduced widths.在高交通量的城市高速公路上，在已有的或者额外有限的公路用地条件下，容纳更多的交通的需求，导致许多机构通过减小车道宽度或者路肩宽度来腾出额外的车道来提高通行能力。
Any proposed use of less-than-full-standard cross-section must be analyzed carefully on a site-by-site basis.Experience indicates that 3.3-m lane can operate safely if there are no other less-than-standard features;however, combined with shoulder-width reductions, substandard sight distance, and other features, 3.3-m lanes may not provide the same safe operation.任何少于全标准道路横截面的提议都必须建立在充分论证的基础上。经验表明，不考虑其他低于标准的因素，3.3
米得行车道宽足够保证安全。但是结合路肩宽度的减少，视距不足及其他因素，3.3米得行车道宽不能提供足够的安全度。Converting shoulder to travel lanes for additional capacity through a short bottleneck section has been shown to significantly reduce congestion-related accidents on some projects.Removing shoulders for several kilometers, however, has not had the same result.在某些项目中，在短程的瓶颈路段为了额外的通行能力，将路肩转变成行车道能显著减少由道路拥挤导致的交通事故。然而减少几公里长的路肩宽度，得不到同样的的结果。
Pavement marking, such as lane lines, edge lines, channelizing lines at interchanges and ramps, and word symbol markings, provide important information to the drivers.路面标记，像在立体交道和斜坡处的车道线，边缘线，通道线以及文字和符号标记，为驾驶员提供重要信息
Pavement markings define separate lanes of traffic traveling in the same direction, inform drivers of lane restrictions, and convey certain regulation and warnings that would not otherwise be clearly understand.路面标记定义了单独的车道交通朝同一方向行驶，告诉驾驶员该车道限速，以及传达某些规则和警告，否则，它们不会被驾驶员清楚的明白。
Pavement markings are particularly important at night and during inclement weather, and,therefore, must be retroreflective.While well-maintained painted pavement markings are acceptable, thicker, long-life markings ,such as thermoplastic or performed tapes ,may perform better in wet weather and heavy traffic.同时保养好的涂有油漆的路面标志是可以采用的，厚的，长寿命的标记，像热塑性塑料或预成行的条带，可以在潮湿的空气和交通繁忙时表现得更出色。
Some studies have been made regarding the benefits of wider edge line markings(150 to 200 mm versus the standard 100 mm width).The wider markings may particularly benefit older drivers.一些研究已经取得了有关更宽边缘线方面的好处（150到200毫米相对于100毫米的标准宽度）。更宽的标记对老司机尤为有利。
第三篇：专业英语翻译
桩筏基础的简化设计方法
摘要：在筏板基础本身并不能满足设计要求情况下，可通过在筏板下增加桩来提高其承载力。合理的布置一定量的桩，可以提高桩筏基础的承载力和减少总沉降和差异沉降。本文分析了简化计算方法的过程，对桩筏基础的初步设计提供了有用的依据。它包括两个阶段：
1.桩筏基础整体性能的评价；
2.单柱荷载作用下的性能评价。
第四篇：专业英语翻译
1)Electricity can be measured in amount and quality.电可以用数量和质量来度量。
2)Instrument transformers are installed on the high-voltage equipment.互感器安装在高压设备上。
3)Electric power is generated in power generating stations or plants.电能是在发电站或发电厂产生的。
4)The meters are calibrated and the scale is designed to read the value of the desired unit.这些仪表可以被校准并且设计了不同的量程，以便读出期望的数值。
5)Electrical energy can be stored in two metal plates separated by an insulation medium.Such a device is called a capacitor, and its ability to store electrical energy is termed capacitance.It is measured in Farads.电能可以储存在被一绝缘介质隔开的两块金属板中，这样的装置被称为电容器，它储存电能的能力就被称为电容。电容的测量单位是法拉。1)The signal should be filtered before it is amplified.The signal should be filtered before being amplified.放大信号前，应先对其进行滤波。
2)An object becomes hot.It is placed in the sun.Once being placed in the sun, an object becomes hot.物体放置在太阳下会变热。
3)We must do various experiments before a new electronic product is designed.Before designing a new electronic product we must do various experiments.在设计一个新的电子产品之前，我们必须做各种实验。
4)Changing resistance is a method for controlling the flow of the current.改变电阻是控制电流的一种方法。
5)Conducting electricity means the flow of electrons through an object.传导电流意味着电子在物体内的流动。
1)The power supply, which is shown in block-diagram in Fig.1, is a single-phase switch-mode inverter.The power supply shown in block-diagram in Fig.1 is a single-phase switch-mode inverter.图1中用框图表示的电源是一个单相开关逆变器。
2)A three-phase circuit, as it was pointed out above, is merely a combination of three single-phase circuits.A three-phase circuit, as pointed out above, is merely a combination of three single-phase circuits.正如上面所指出的那样，三相电路只不过是三个单相电路的组合。
3)The transistor, which is working with correctly polarities, can work as an amplifier.The transistor working with correctly polarities can work as an amplifier.工作于正确电源极性下的晶体管，作用就像放大器。
1）The capacity of individual generators is larger and larger so that the increasing demand of electric power is satisfied.The capacity of individual generators is larger and larger to satisfy the increasing demand of electric power.单台发电机的容量越来越大，目的就是满足不断增长的用电需求。2)What does a fuse do? It protects a circuit.The function of a fuse is to protect a circuit.保险的作用就是保护电路。1)If it is possible, the open-loop control approach should be used in this system.If possible, the open-loop control approach should be used in this system.可能的话，这个系统应该使用开环控制方法。
2)As illustrated in Fig.1, there is a feedback element in the closed-loop system.As in Fig.1, there is a feedback element in the closed-loop system.就像图1所示的那样，这个闭环系统中有一个反馈元件。
3)The device includes an instrument transformation and a relay system which has two circuits in it.The device includes an instrument transformation and a
relay system with two circuits in it.这个装置包括一个互感器和一个有两个电路的继电器系统。
1)It has been mentioned above that the electrons in a metal
are able to move freely through the metal, that their motion constitutes an electric current in the metal and that they play an important part in conduction of heat.前面已经提到：金属中电子能自由地通过金属，电子的移动在金属中形成了电流，电子在热传导中起着重要的作用。
2)The reluctance motor operates synchronously at a speed which is determined by the supply frequency and the number of poles for which the stator is wound.磁阻电动机以某一速率同步运转，该速率是由电源频率和定子绕制的级数决定的。
3)The testing of a cross-field generator will be described in this section with chief reference to the tests that are normally taken on every machine before it leaves the makers works.交磁发电机的试验将在本节中叙述，它主要涉及每台电机在离开制造厂前应进行的试验。1)All radiant energies have wavelike characteristics, which are analogous to those of waves moving through water.All radiant energies have wavelike characteristics analogous to those of waves moving through water.所有的辐射能都具有波的特性，与水中移动的波的特征相似。
2)The instruments present include some digital ones which are relative to DSPs.The instruments present include some digital ones relative to DSPs.到场的仪器中还有一些与DSP有关的数字仪器。
1.As the system expands and higher voltage levels become necessary for transmission, the older transmission lines are often relegated to subtransmission function.随着系统的扩大和更高的电压等级为输电所必需，旧的输电线路往往被移交给中压输电功能。
1.Roughly, the capability of lines of the same length varies at a rate somewhat greater than the square of the voltage.粗略的讲，长度相同的线路的容量，以比电压的平方略大的比率变化。
2.No definite capability can be specified for a line of a given voltage, however, because capability is dependent on the thermal limits of the conductor, allowable voltage drop, reliability, and requirements for maintaining synchronism between the machines of the system, which is known as stability.然而，无法为给定电压等级的线路指定确切的容量，这是因为容量取决于导线的发热极限、允许的电压降落、可靠性和维持系统中的发电机同步的要求（这被认为是稳定性）。
1.Capacitance exists between the conductors and is the charge on the conductors per unit of potential difference between them.电容存在于导体之间，等于导体上的电荷（电量）与导体间的电势差之比。或：电容存在于导体之间，等于导体之间单位电压对应的电量。“A per unit of B” 表示 “单位B上的A” 或者“A/B”。
2.Balance of the three phases can be restored by exchanging the positions of the conductors at regular intervals along the line so that each conductor occupies the original position of every other conductor over an equal distance, as shown in Fig.3.1.如图3.1所示，沿线路方向每隔一定间隔就交换导线位置，使每根导线都能占据具有相同输电距离的其他各导线的初始位置，以重建三相平衡。
Electrical energy can be stored in two metal plates separated by an insulating medium.Such a device is called capacitor or condenser.Its ability to store electrical energy is capacitance.It is measured in farads 电能可储存在由一绝缘介质隔开的两块金属极板内。这样的装置称之为电容器，其储存电能的能力称为电容。电容的测量单位是法拉。
1.Small industrial customers are supplied by primary feeders at this voltage level from the primary system, which also supplies the distribution transformers providing secondary voltages over single-phase three-wire circuits for residential and commercial customers at 120 V/240 V.小型工业用户由一次系统中此电压等级的一次馈线供电。一次系统也给经过单相三线电路为居民用电和商业用户提供120V/240V二次电压的配电变压器供电。
2.As illustrated in Fig.6.1, the aggregated load represented at a transmission substation(bus A)usually includes, in addition to the connected load devices, the effects of substation step-down transformers…
如图6.1所示，在输电变电站（母线A）所给出的集合负荷，除了所连接的负荷设备以外，通常还包括变电站降压变压器的影响……。
1.Roughly, loads are devices those consume electric energy or electric power consumed by customers mainly in distribution system.粗略的讲，负荷是主要在配电网中消耗电能的设备或者由用户消耗的功率。
2.The loads absorb electric energy from the power system and converts it into energy of other forms, which may be heat energy to heat water or to melt irons, or mechanical energy to drive a machine, etc.负荷从电力系统中吸收电能，并将其转换为其他形式的能量，可能是烧水或溶化钢铁的热能，或者是驱动机器的机械能等。
3.This kind of loads, especially those consume energy calculated by standard coals more over 10 thousands of tons per year, has a name of high energy consuming loads.这种负荷，尤其是那些年耗能万吨标准煤以上的负荷，被称为高耗能负荷。
1.The synchronous machine as an AC generator driven by a
turbine is the device which converts mechanical energy to electrical energy, in powers ranging up to 1500MW.作为由涡轮机驱动的交流发电机，同步电机是将机械能转化为电能的设备，其功率范围高达1500MW。
1.Hydropower plants can cause low dissolved oxygen levels in the water, a problem that is harmful to riverbank habitats.水电厂会导致水中的氧气溶解度降低——（这是）一个对岸边生存环境有害的问题。
2.For instance, in the United States, water power accounts for less than 20% of the total and that percentage will drop because most of the available sources of water power have been developed.例如，在美国，水电在全部电力中所占的比例不到20%，并且，因为大多数可用的水电资源已被开发，该百分数还会下降。
1.Most stations have ratings between 200 MW and 1500 MW so as to attain the high efficiency and economy of a large installation.大多数电站的额定值在200MW到1500MW之间，以实现大站的高效经济（运行）。
2.Thermal stations are usually located near a river or lake because large quantities of cooling water are needed to condense the steam as it exhausts from the turbines.热电厂通常位于河流或湖泊附近，这是因为需要大量的冷却水在蒸汽从汽轮机排出时将其冷凝。
1.Nuclear plants fueled by uranium account for a continually increasing share of the load, but their construction is slow and uncertain because of the difficulty of raising capital to meet the sharply rising cost of construction, constantly increasing safety requirements which cause redesign, public opposition to the operation of the plants, and delays in licensing.Flowing through a circuit, the current will lose part of it energy.当电流流过电路时，要损耗掉一部分能量。（现在分词短语作状语）
Doing experiment is of great help to us.做实验对我们的学习是很有帮助的。（动名词作主语）By changing the resistance，we can change the current.通过改变电阻，我们就能改变电流。（动名词作介宾）Mechanization is using machines instead of hand labor.机械化就是用机器来代替手工劳动。（动名词作表语）
When an electric current flow through a wire it meets some opposition.当电流流过导线时，它会遇到某种阻力。（状语从句）
Before one studies a system, it is necessary to define and discuss some important terms.在我们学习系统之前，必须定义并讨论一些重要的术语。（状语从句）It is possible that we use a computer to solve these complicated problem.我们可以用计算机来解这些复杂的题目。（表语从句）
You should determine which of the following functions is analytic.你应当确定下列函数中哪一个是解析式。（宾语从句）The fact is that radio waves travel as fast as light does.事实是无线电波的传播速度与光速一样快。（表语从句）The places where small computers can be used appear endless.可以使用小型计算机的场合似乎是无止境的。（定语从句）The instrument that we often use is very good in quality.我们经常使用的那台仪器质量很好。（定语从句）
The places where small computers can be used appear endless.可以使用小型计算机的场合似乎是无止境的。（定语从句）The instrument that we often use is very good in quality.我们经常使用的那台仪器质量很好。（定语从句）
Now we can determine where the slope is zero.现在我们可以求出何处斜率为零。（宾语从句）This is how a computer works.这就是计算机的工作原理。（宾语从句）Electrons always move toward where the potential is higher.电子总是朝向电位较高的地方移动。（介宾从句）
The fact that everything around us is matter is known to all.我们周围的一切东西均是物质这一事实是大家都知道的。（同位语从句）Section 2 Exercise 3
Section 3 Exercise3 必须强调的是线性电阻器是一个理想的电路元件；它是物理元件的数学模型。我们可以很容易地买到或制造电阻器，但很快我们发现这种物理元件只有当电流、电压或者功率处于特定范围时其电压——电流之比才是恒定的，并且这个比值也取决于温度以及其它环境因素。我们通常应当把线性电阻器仅仅称为电阻器。只有当需要强调元件性质的时候才使用更长的形式称呼它。
而对于任何非线性电阻器我们应当始终这么称呼它，非线性电阻器不应当必然地被视为不需要的元件。
Section 4 Exercise 3 如果一个电路有两个或多个独立源，求出具体变量值（电流或电压）的一种方法是使用节点分析法或网孔分析法。另一种方法是求出每个独立源对变量的作用然后把它们进行叠加。而这种方法被称为叠加法。叠加法原理表明线性电路某个元件两端的电压（或流过元件的电流）等于每个独立源单独作用时该元件两端的电压（或流过元件的电流）的代数和。Section 5 Exercise 3 相电压与相电流之比等于电路的阻抗，符号为字母Z，阻抗是一个具有量纲为欧姆的复数量。阻抗不是一个相量，因此不能通过把它乘以
并取其实部把它转换成时域形式。但是，我们把电感器看作是通过其电感量L表现为时域形式而通过其阻抗
表现为频域形式，电容在时域里为电容量C而在频域里为
，阻抗是某种程度上的频域变量而非时域变量。
Section 6 Exercise 3
第五篇：专业英语翻译
Forces of Interactions between Bare and Polymer-Coated Iron and Silica: Effect of pH, Ionic Strength, and Humic Acids The interactions between a silica substrate and iron particles were investigated using atomic force microscopy-based force spectroscopy(AFM).The micrometer-and nanosized iron particles employed were either bare or coated with carboxymethyl cellulose(CMC), a polymer utilized to stabilize iron particle suspensions.The effect of water chemistry on the forces of interaction was probed by varying ionic strength(with 100 mM NaCl and 100 mM CaCl2)or pH(4, 5.5, and 8)or by introducing 10 mg/L of humic acids(HA).When particles were uncoated, the forces upon approach between silica and iron were attractive at pH 4 and 5.5 and in 100 mM CaCl2 at pH 8, but they were negligible in 100 mM NaCl buffered to pH 8 and repulsive in water buffered to pH 8 and in HA solutions.HA produced electrosteric repulsion between iron particles and silica, likely due to its sorption to iron particles.HA sorption to silica was excluded on the basis of experiments conducted with a quartz-crystal microbalance with dissipation monitoring.Repulsion with CMC-coated iron was attributed to electrosteric forces, which were damped at high ionic strength.An extended DLVO model and a modified version of Ohshima’s theory were successfully utilized to model AFM data.PH、离子强度和腐殖酸对硅与裸露铁粒子和高分子聚合物包裹铁粒子之间相互作用的影响 利用以原子力显微镜为基础的光谱法研究石英基片和铁颗粒之间的相互作用。微米和纳米铁颗粒采用的都是赤裸的或羧甲基纤维素包裹的——一种用于稳定铁颗粒悬浮液的聚合物。通过不同离子强度（100mM氯化钠和100mM氯化钙）或PH值（4，5.5，和8）或通过引入10毫克/升的腐殖酸探讨水化学环境对这种相互作用力的影响。当粒子裸露时，硅和铁的相互接近的吸引力出现在PH值4和5.5。加100mM氯化钙时出现在PH值为8的时候。但在PH为8的100毫米氯化钠缓冲溶液中它们是可忽略的，在PH为8的水和腐殖酸溶液中表现为相互排斥。腐殖酸使铁颗粒和二氧化硅之间产生静电斥力，可能由于其吸附铁颗粒。通过进行了石英晶体微天平与耗散监测的实验，腐殖酸吸附硅胶的可能性被排除在外。与羧甲基纤维素包铁颗粒的斥力是由于静电力量，这种静电力在高离子强度会减弱。一个扩展的 DLVO模型和Ohshima理论修改后的版本成功地拟合了原子力显微镜得到的数据。
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