水产养殖专业英语讲义

专业外语讲义 (14)

pistons 活塞 The piston with its rings, seals the cylinder and transmits the gas pressure to the connecting rod. It absorbs heat from the gas, and this heat must be carried away if the metal temperature is to be held within safe limits. The constant reversal of the piston travel sets up inertia forces, which increase both with the weight of the piston and with its speed. For this reason designers try to keep piston weight low, particularly in high-speed engines. 活塞，连同活塞环密封汽缸，并把气体的压力传递给连杆。活塞从气体吸收热量。假如要使金属的温度保持在安全限度以内，就必须散热。活塞行程的不断往复产生惯性力，此力随活塞的重量和及其速度而增大。为此，设计者设法使活塞造得轻些，特别是高速发动机。 In “uncooled” pistons, the heat absorbed by the piston top travels through the piston side-walls, then through the rings into the cylinder walls and finally to the jacket water surrounding the cylinder. In highly loaded engines, additional means of heat removal are necessary; this is accomplished by a liquid, generally oil. These are termed “cooled” pistons. 在无冷却的活塞中，活塞顶部吸收的热量通过活塞侧壁，再通过活塞环，传入汽缸壁，最后，传向包在汽缸周围的水套中的水里。在那些高负荷的发动机中，散热的附加措施是必要的。采用液体通常是油液进行冷却。这种活塞被称为“冷却”活塞。 The top section of a piston is called the crown and the lower section the skirt. . The shape of the top of the crown depends largely on the design of the combustion chamber. The crown section is usually thick, in order to withstand the gas pressure without distorting and to provide a good path for the heat flow from the upper surface of the crown to the rings. When running the piston diameter increases because of the increase in temperature. To take care of the greater expansion in the high-temperature zone, the crown is machined on a slight taper, the diameter being greatest where the crown meets the skirt and becoming less toward the top. 活塞的顶端部分称为活塞顶，下面部分称为活塞裙。顶部的形状主要取决于燃烧室的设计。为了承受气体压力而不变形，并让热流从活塞顶表面传向活塞环提供良好通道，活塞顶部通常很厚。在运行中，因为温度升高，活塞直径增大。考虑到高温区热膨胀较大，活塞顶部加工成低小锥形，即活塞顶部和活塞裙部交接处直径最大，愈向顶部直径愈小。 The crown carries the upper set of rings, which are the “compression”, or “power rings”. In most uncooled pistons, a division plate above the wristpin prevents lubricating oil from splashing against the hot under-surface of the crown. The amount of splashed oil would be insufficient to cool the piston; consequently, the oil would overheat and carbon deposits would form. 活塞顶部装有一组上活塞环，是压缩环或动力环。在多数不冷却活塞中，活塞销上的隔板防止机油飞溅到活塞顶下部的热表面。飞溅的机油量不足以冷却活塞，因此，机油就因过热而形成积碳。 The skirt of a trunk piston takes the side-thrust of the connecting rod and prevents the piston from rocking from side to side; it also carries the lower set of rings, which are the “oil-control” rings. Below the upper ring band, where heavy wall thickness is needed to carry the heat flow, the piston skirt becomes much thinner. The running clearance between the skirt and the cylinder wall must be small; therefore, it is important that the thin skirt should stay truly round. For this reason, interior ribs are used to stiffen the skirts of cast pistons. 筒状活塞的裙部承受连杆的侧向推力，并防止活塞从一侧向另一侧摆动，裙部也装有一组下活塞环，为机油控制环（油环）。活塞的上环带的下面，必须有足够的壁厚，以防止传热（携带热流），而活塞的裙部可薄一些（变得更薄。）活塞的裙部和汽缸壁之间的运行间隙很小，

讲义专业英语1

专业英语讲义 教材：电气信息类专业英语 王群主编 适用专业：电气工程 主讲教师：邓秋玲

一主讲内容 第１章专业英语的文体特点（１学时） 第２章专业英语翻译（１学时） 第３章专业英语文献及其检索和阅读（１学时） 第４章专业英语论文组织和写作（１学时） 第５章专业英语阅读材料（２０学时） 二参考教材 １电气工程及其自动化专业英语戴文进主编者电子工业出版社２电气自动化专业英语李久胜主编．哈尔滨工业大学出版社３科技英语保清主编．中国农业机械出版社．１９８６

Chapter one Literary Feature of Specialized English 1.1 Introduction 1 Purpose: To study specialized English aims at training students’comprehension and application ablity to specialized English, and letting them to grasp some requisite specialized terms for speciality reading.basic skill and knowledges. thereby they can acquire the newest specialized knowledge(expertise) for science and technology. information data and other information relative to speciality by means of English, and positively take part in international interflow course of science and technology. 2 The definition of specialized English [1]:I n general speaking, English can be divided into two classes,one is common English or general English or ordinary English and English for science and technology,the other Specialized English or English for special [2]The relation of English for science and technology and specialized English 1.2 lexical characteristic As the developing of English,old vocabularies eliminate gradually while new ones spring up constantly. 1.2.1lexical classification 1 special technical words such as diode,substation. 2 special sub-technical words special sub-technical words are words used in common by many specialities and subjects while they have different meanings/connotations in different specialities and subjects such as power, condenser. 3 non-technical words used in common English.

化学化工专业英语(课本内容)

第二章科技英语构词法 词是构成句子的要素，对词意理解的好坏直接关系到翻译的质量。 所谓构词法即词的构成方法，即词在结构上的规律。科技英语构词特点是外来语多（很多来自希腊语和拉丁语）；第二个特点是构词方法多，除了非科技英语中常用的三种构词法—转化、派生及合成法外，还普遍采用压缩法、混成法、符号法和字母象形法。 2.1转化法（Conversion） 由一种词类转化成另一种词类，叫转化法。例如： water(n.水)→water(v.浇水) charge(n.电荷) →charge(v.充电) yield(n.产率) →yield(v.生成) dry(a.干的) →dry（v.烘干） slow(a.慢的) →slow(v.减慢) back(ad.在后、向后) →back（v.使后退、倒车） square(n.正方形) →square(a.正方形的) 2.2派生法（Derivation） 通过加前、后缀构成一新词。派生法是化工类科技英语中最常用的构词法。 例如“烷烃”就是用前缀（如拉丁或希腊前缀）表示分子中碳原子数再加上“-ane”作词尾构成的。若将词尾变成“-ane”、“-yne”、“-ol”、“-al”、“-yl”，则分别表示“烯”、“炔”、“醇”、“醛”、“基”、等。依此类推，从而构成千成种化学物质名词。常遇到这样的情况，许多化学化工名词在字典上查不到，全若掌握这种构词法，能过其前、后缀分别代表的意思，合在一起即是该词的意义。下面通过表1举例说明。需要注意的是，表中物质的数目词头除前四个另有名称外，其它均为表上的数目词头。 本书附录为化学化工专业常用词根及前后缀。此外还可参阅《英汉化学化工词汇》（第三版）附录中的“英汉对照有机基名表”、“西文化学名词中常用的数止词头”及“英汉对照有机词尾表”。 据估计，知道一个前缀可帮助人们认识450个英语单词。一名科技工作者至少要知道近50个前缀和30个后缀。这对扩大科技词汇量，增强自由阅读能力，提高翻译质量和加快翻译速度都是大有裨益的。 2．3合成法（Composition） 由两个或更多的词合成一个词，叫合成法。有时需加连字符。 如副词+过去分词well-known 著名的 名词+名词carbon steel 碳钢 rust-resistance 防锈 名词+过去分词computer-oriented 研制计算机的 介词+名词by-product 副产物 动词+副词makeup 化妆品 check-up 检查 形容词+名词atomic weight 原子量 periodic table 周期表 动词+代词+副词pick-me-up 兴奋剂 副词+介词+名词out-of-door 户外 2．4压缩法（Shortening） (1)只取词头字母 这种方法在科技英语中较常用。

《自动化专业英语》中英文翻译-中文部分

第二部分 控制理论 第1章 1.1控制系统的引入 人类控制自然力量的设计促进人类历史的发展,我们已经广泛的能利用这种量进行在人类本身力量之外的物理进程?在充满活力的20世纪中,控制系统工程的发展已经使得很多梦想成为了现实?控制系统工程队我们取得的成就贡献巨大?回首过去,控制系统工程主要的贡献在机器人,航天驾驶系统包括成功的实现航天器的软着陆,航空飞机自动驾驶与自动控制,船舶与潜水艇控制系统,水翼船?气垫船?高速铁路自动控制系统,现代铁路控制系统? 以上这些类型的控制控制系统和日常生活联系紧密,控制系统是一系列相关的原件在系统运行的基础上相互关联的构成的,此外控制系统存在无人状态下的运行,如飞机自控驾驶,汽车的巡航控制系统?对于控制系统,特别是工业控制系统,我们通常面对的是一系列的器件,自动控制是一个复合型的学科?控制工程师的工作需要具有力学,电子学,机械电子,流体力学,结构学,无料的各方面的知识?计算机在控制策略的执行中具有广泛的应用,并且控制工程的需求带动了信息技术的与软件工程的发展? 通常控制系统的范畴包括开环控制系统与闭环控制系统,两种系统的区别在于是否在系统中加入了闭环反馈装置? 开环控制系统 开环控制系统控制硬件形式很简单,图2.1描述了一个单容液位控制系统, 图2.1单容液位控制系统 我们的控制目标是保持容器的液位h 在水流出流量V 1变化的情况下保持在一定 可接受的范围内,可以通过调节入口流量V 2实现?这个系统不是精确的系统,本系 统无法精确地检测输出流量V 2,输入流量V 1以及容器液位高度?图2.2描述了这 个系统存在的输入(期望的液位)与输出(实际液位)之间的简单关系, 图2.2液位控制系统框图 这种信号流之间的物理关系的描述称为框图?箭头用来描述输入进入系统,以及

生物工程专业英语翻译(第二章)

Lesson Two Photosynthesis 内容： Photosynthesis occurs only in the chlorophyllchlorophyll叶绿素-containing cells of green plants, algae藻, and certain protists 原生生物and bacteria. Overall, it is a process that converts light energy into chemical energy that is stored in the molecular bonds. From the point of view of chemistry and energetics, it is the opposite of cellular respiration. Whereas 然而 cellular细胞的 respiration 呼吸is highly exergonic吸收能量的and releases energy, photosynthesis光合作用requires energy and is highly endergonic. 光合作用只发生在含有叶绿素的绿色植物细胞，海藻，某些原生动物和细菌之中。总体来说，这是一个将光能转化成化学能，并将能量贮存在分子键中，从化学和动能学角度来看，它是细胞呼吸作用的对立面。细胞呼吸作用是高度放能的，光合作用是需要能量并高吸能的过程。Photosynthesis starts with CO2 and H2O as raw materials and proceeds through two sets of partial reactions. In the first set, called the light-dependent reactions, water molecules are split裂开 (oxidized), 02 is released, and ATP and NADPH are formed. These reactions must take place in the presence of 在面前 light energy. In the second set, called light-independent reactions, CO2 is reduced (via the addition of H atoms) to carbohydrate. These chemical events rely on the electron carrier NADPH and ATP generated by the first set of reactions. 光合作用以二氧化碳和水为原材料并经历两步化学反应。第一步，称光反应，水分子分解，氧分子释放，ATP和NADPH形成。此反应需要光能的存在。第二步，称暗反应，二氧化碳被还原成碳水化合物，这步反应依赖电子载体NADPH以及第一步反应产生的ATP。 Both sets of reactions take place in chloroplasts. Most of the enzymes and pigments 色素for the lightdependent reactions are embedded 深入的内含的in the thylakoid 类囊体 membrane膜隔膜 of chloroplasts 叶绿体. The dark reactions take place in the stroma.基质 两步反应都发生在叶绿体中。光反应需要的大部分酶和色素包埋在叶绿体的类囊体膜上。暗反应发生在基质中。 How Light Energy Reaches Photosynthetic Cells（光合细胞如何吸收光能的） The energy in light photons in the visible part of the spectrum can be captured by biological molecules to do constructive work. The pigment chlorophyll in plant cells absorbs photons within a particular absorption spectrums statement of the amount of light absorbed by chlorophyll at different wavelengths. When light is absorbed it alters the arrangement of electrons in the absorbing molecule. The added energy of the photon boosts the energy condition of the molecule from a stable state to a less-stable excited state. During the light-dependent reactions of photosynthesis, as the absorbing molecule returns to the ground state, the "excess" excitation energy is transmitted to other molecules and stored as chemical energy. 生物分子能捕获可见光谱中的光能。植物细胞中叶绿素在不同光波下吸收部分吸收光谱。在吸收分子中，光的作用使分子中的电子发生重排。光子的能量激活了分子的能量状态，使其

自动化专业英语复习资料

element n、元件，成分node n、节点branch n、分支loop n、回路resistor n、电阻器impedance n、阻抗analog n、模拟digital adj、数字的pulse n、脉冲interface n、接触面，界面decoder n、解码器 transformer n、变压器single-phase 单相pulsate vi、脉动three-phase power三相电源three-phase circuit 三相电路 wye connection 星形连接delta connection 三角形连接phase voltage 相电压line voltage 线电压voltmeter n、电压表ammeter n、电流表clamp-on ammeter钳式安培表 solid-state adj、固态的valve n、真空管，活栓semiconductor n、半导体switching n、开关diode n、二极管inverter n、反向换流器(逆变器) thyristor n、硅可控整流器inverter thyristor 晶闸管逆变器transistor n、晶体管substantial adj、牢固的fluorescent lamp ballast 荧光灯镇流器HVDC transmission system 高压直流输电系统 induction motor 感应电动机rectifier n、整流器 thyratron n、闸流管ignitron n、引燃管，放电管cycloconverter n、循环变流器spectrum n、光谱 wafer n、圆片，晶片chopper n、斩波器polarity n、极性silicon-controlled rectifiers (SCR) n、可控硅整流器 gate turn-off thyristors (GTO) n、门极可关断晶闸管 MOS Controlled Thyristor (MCT) n、MOS控制晶闸管

农林牧渔业英文

农林牧渔业英文 【篇一：水产常用英文】 aquaculture 水产养殖 aquaculture activity 水产养殖活动aquaculture farm 水产养殖场 aquaculture production 水产养殖生产 aquaculture site 水产养殖地点 aquaculturist 从事水产养殖业的人士 aquatic biota 水生生物 aquatic community 水生?落aquatic ecosystem 水生生态系统 aquatic environment 水生环境aquatic life 水生生物 aquatic organism 水生生物 aquatic system 水体 aqueous waste 含水废物 水产：aquaculture 水产业：fishery 淡水养殖：fresh water aquaculture 海水养殖：mariculture 溶解氧：do（dissolved oxygen） 总氨氮：tan（total ammonia nitrogen） 亚硝酸：nitrite 硝酸：nitrate 盐度：salinity 碱度：alkaninity 硬度：hardness 增氧机：areator 增氧：aeration 亲鱼：brood stock 子鱼：offspring 鱼苗：fry 虾苗：pl（post larvae） 石灰：agriculture lime 生石灰：slaked 熟石灰：hydrate lime 南美白对虾：pacific white shrimp 斑节对虾：tiger shrimp 拟穴青蟹：mud crab 淡水小龙虾：cray fish 蛤：clam

生物工程生物技术专业英语翻译(二)

第二章生长与代谢的生物化学 2.1 前言 一个微生物以生产另一个微生物为目的。在某些情况下，利用微生物的生物学家们希望这样的情况能够快速频繁的发生。在另外一些产物不是生物体自身的情况下，生物学家必须对它进行操纵使微生物的目标发生变化，这样以来，微生物就要努力的挣脱对它们繁殖能力的限制，生产出生物学家希望得到的产物。生物体的生长过程及其生产出的各种产物与微生物代谢的本质特点是密不可分的。 代谢过程是两种互相紧密联系又以相反方向进行的活动过程。合成代谢过程主要是细胞物质的生成，不仅包括构成细胞的主要组成物质（蛋白质、核酸、脂质、碳水化合物等等），同时也包括它们的前提物质——氨基酸、嘌呤与嘧啶、脂肪酸、各种糖与糖苷。合成代谢不是自发进行的，必须由能量所推动，对大多数微生物来说，是通过一系列的产能分解代谢过程来供给能量。碳水化合物分解为CO2和水的过程是最为常见的分解代谢反应，然而微生物以这样的方式还能够利用更大范围的还原性含碳化合物。分解代谢与合成代谢所有微生物生物化学的基础，可以从两者的平衡关系或者分别对它们进行讨论。 实际中，我们要有效的区分那些需要空气中的氧进行需氧代谢的生物与那些进行厌氧代谢的生物。还原性含碳化合物与O2反应生成水和CO2，这是一个高效的放热反应过程。因此，一个进行需氧代谢的生物要使用一小部分底物进行分解代谢以维持某一水平的合成代谢，即成长过程。对于厌氧型生物，其底物的转化的过程基本上是一个不匀称的反应（氧化还原反应），产生很少的能量，因此，大部分底物都要被分解从而

维持一定水平的合成代谢。 在生物体中这种差别能够明显的体现出来，比如酵母，它属于兼性厌氧生物，即它可在有氧条件下生长也可在无氧环境下生存。需氧酵母使糖以同样的速度转化为CO 2和水，相对产生高产量的新酵母。而厌氧条件下，酵母菌生长缓慢，此时酵母被有效的转化为酒精和CO 2。 2.2 代谢与能量 分解代谢与合成代谢间的有效联系在于，各种分解代谢过程促进少量反应物的合成，而后又被用来促进全面的合成代谢反应。在这种重要的中间产物中，其中最为重要的是ATP ，其含有生物学家所说的“高能键”。在ATP 分子中，酐与焦磷酸残基相联。高能键在水解过程中所产生的热量就被用来克服在其形成过程中需要摄入的能量。像ATP 这类分子，为细胞提供了流通能量，当将ATP 用于生物合成反应时，其水解产物为ADP （腺苷二磷酸）或者某些时候为AMP （腺苷一磷酸）：（反应式） 仍含有一个高能键的ADP 通过腺苷酸激酶反应也可生成ATP ：（反应式）。 磷酸化作用是生物体中普遍的反应，通常由ATP 作用而发生。 经过磷酸化生成的物质通常比最初的化合物更具有反应活性，用无机磷酸进行磷酸化反应是无法进行的，因为，平衡反应式的相反方向生成大量的水（55M ）。 细胞的“能量状态”认为是由占有优势的组分：ATP 、ADP 、AMP 作用形成的。为了给出一个量值，Daniel Atksirson 提出了“能荷”这个概念，定义一个细胞的能荷为： 在“满荷”细胞中，仅含有ATP 一种腺嘌呤核苷酸，它的能荷值定义为 1.0。如果三种核苷酸的量相等，即ATP=ADP=AMP ，则细胞的能荷为ATP+0.5 ADP ATP+ ADP+AMP

专业英语复习资料

1.Types of Business Organization: 1)Sole Proprietorship :an unincorporated business owned by one person 2)Partnership :owned by two or more individuals (called partners) a)Limited partnership——general partners,limited partners 3)Corporation :a legal entity separate from its owners 2、Separation of Ownership and Control (pros and cons)： Pros(赞成的理由): Specialization，Efficiency，Diversify，Going concern Cons(反对的理由)：Four major downsides：agency problem,free-riding problem,increased costs of information https://www.360docs.net/doc/08306049.html,rmation asymmetry 3.Overview of Financial Statements balance sheet; income statement;statement of cash flows;statement of retained earnings 4. Statement of Retained Earnings,it shows: the retained earnings balance at the start of the period;how much the firm earned (net income); how much dividends the firm paid;how much net income was reinvested back into the firm (retained earnings);any repurchases of the firm’s stock;any new issues of the firm’s stock; andthe retained earnings balance at the close of the period. 4. Statement of Cash Flow:Operating Cash Flows ，Investing Cash Flows ，Financing Cash Flows 5.Analyzing Financial Ratios Financial ratios are not standardized. Analyzing a single financial ratio for a given year may not be very useful. Some of a firm’s financial accounting practices or choices will affect its financial statements and, finally, its financial ratios. Financial ratios do not provide analysts with all of th e answers about a firm’s condition. 7. Uses and Limitations of Financial Ratio Analysis：while ratio analysis can provide useful information concerning a company’s operations and financial condition, it does have limitations that necessitate care and judgment 1.Risk-return tradeoff Investors will take on additional risk only if they anticipate high return. 2.Time value of money A dollar available today is worth more than a dollar available at a future date. This is because a dollar today can be invested to earn a return. 3.Types of value Going-concern value,Liquidation value ,Book value ,Market value ，ntrinsic value 4.Valuation Approaches discounted cash flow (DCF) valuation，relative valuation，contingent claim valuation，option-pricing models 7.Contractual Provisions of a Typical Bond Par Value,and Coupon Rate,Maturity,Call Provisions,Sinking Fund Provisions,Conversion Rights ,Put Provisions,Indenture,Trustee,Collateral,Bond Rating 1.Introduction to Risk and Return All financial assets are expected to produce cash flows, and the risk of an asset is judged by the risk of its cash flows. Here are two assumptions about risk and return: Assumption (1): The returns from investments are normally distributed.Assumption (2): Investors are risk-averse. The risk of an asset can be considered in two ways: (1) on a stand-alone basis (2) in a portfolio context. In a portfolio context, an asset’s risk can be divided into two components: a,diversifiable risk ;b. market risk.An asset with a high degree of relevant (market) risk must provide a relatively high expected rate of return to attract investors. 4.Efficient Market Hypothesis (EMH) Assumption 1:The returns from investments are normally distributed.Assumption 2: Investors are risk-averse.Assumption3:Investorsare rational.Assumption4:Investors are price takers.Assumption 5: The Efficient Market Hypothesis (EMH) holds. 5. Three types of financial market efficiency: allocationally efficient, operationally efficient,informationally efficient 6. Three main factors associated with informational market efficiency The type of information to which the market price reacts,The speed at which the market price reacts to information,The degree to which market participants over-or under-react to information 8. Characteristics of an Informationally Efficient Market Price changes cannot be predicted. The price of the asset is equal to its fundamental (unobserved but true) value.Prices change due to the inflow of new information, and information flows randomly to the market.Therefore, price changes should be random and unpredictable. 10. Modern portfolio theory —Markowitz’s Mean-variance Framework ,Efficient portfolios are those that have: the lowest risk for an expected rate of return; or the highest expected rate of return for a given level of risk.The assets that meet these criteria make up the efficient frontier.

《化学工程与工艺专业英语》课文翻译Unit 21 Chemical Industry and Environment

Unit 21 Chemical Industry and Environment 化学工业与环境 How can we reduce the amount of waste that is produced? And how we close the loop by redirecting spent materials and products into programs of recycling? All of these questions must be answered through careful research in the coming years as we strive to keep civilization in balance with nature. 我们怎样才能减少产生废物的数量？我们怎样才能使废弃物质和商品纳入循环使用的程序？所有这些问题必须要在未来的几年里通过仔细的研究得到解决，这样我们才能保持文明与自然的平衡。 1.Atmospheric Chemistry Coal-burning power plants, as well as some natural processes, deliver sulfur compounds to the stratosphere, where oxidation produces sulfuric acid particles that reflect away some of the incoming visible solar radiation. In the troposphere, nitrogen oxides produced by the combustion of fossil fuels combine with many organic molecules under the influence of sunlight to produce urban smog. The volatile hydrocarbon isoprene, well known as a building block of synthetic rubber, is also produced naturally in forests. And the chlorofluorocarbons, better known as CFCs, are inert in automobile air conditioners and home refrigerators but come apart under ultraviolet bombardment in the mid-stratosphere with devastating effect on the earth’s stratospheric ozone layer. The globally averaged atmospheric concentration of stratospheric ozone itself is only 3 parts in 10 million, but it has played a crucial protective role in the development of all biological life through its absorption of potentially harmful shout-wavelength solar ultraviolet radiation. 1．大气化学 燃煤发电厂像一些自然过程一样，也会释放硫化合物到大气层中，在那里氧化作用产生硫酸颗粒能反射入射进来的可见太阳辐射。在对流层，化石燃料燃烧所产生的氮氧化物在阳光的影响下与许多有机物分子结合产生都市烟雾。挥发的碳氢化合物异戊二烯，也就是众所周知的合成橡胶的结构单元，可以在森林中天然产生含氯氟烃。我们所熟悉的CFCs，在汽车空调和家用冰箱里是惰性的，但在中平流层内在紫外线的照射下回发生分解从而对地球大气臭氧层造成破坏，全球大气层中臭氧的平均浓度只有3ppm，但它对所有生命体的生长发育都起了关键的保护作用，因为是它吸收了太阳光线中有害的短波紫外辐射。 During the past 20 years, public attention has been focused on ways that mankind has caused changes in the atmosphere: acid rain, stratospheric zone depletion, greenhouse warming, and the increased oxidizing capacity of the atmosphere. We have known for generations that human activity has affected the nearby surroundings, but only gradually have we noticed such effects as acid rain on a regional then on an intercontinental scale. With the problem of ozone depletion and concerns about global warming, we have now truly entered an era of global change, but the underlying scientific facts have not yet been fully established. 在过去的二十年中，公众的注意力集中在人类对大气层的改变：酸雨、平流层臭氧空洞、温室现象，以及大气的氧化能力增强，前几代人已经知道，人类的活动会对邻近的环境造成影响，但意识到像酸雨这样的效应将由局部扩展到洲际范围则是慢慢发现的。随着臭氧空洞问题的出现，考虑到对全球的威胁，我们已真正进入到全球话改变的时代，但是基本的