ON SHOCK WAVE THEORY
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传播学经典理论英文版[中文批注]目录一、Opinion Leaders 意见领袖_____________________________________________ 2二、5W Box 5w 理论 _____________________________________________________ 2三、The Bias of Communication 传媒偏向论 __________________________________ 2四、The Spiral of Silence 沉默的螺旋 ________________________________________ 3五、Gatekeeper 把关人理论_______________________________________________ 4六、Selective exposure hypothesis 选择性接触假说 _____________________________ 4七、Knowledge Gap Theory 知识沟假说______________________________________ 5八、Agenda Setting Theory 议程设置理论____________________________________ 5九、Magic bullet theory 魔弹论 _____________________________________________ 5十、Information (Innovation)Diffusion Theory 信息(创新)扩散论____________ 6 十一、Uses and gratifications theory (UGT) 使用与满足理论______________________ 7 十二、Cultivation theory 教养理论 ____________________________________________ 8 十三、Limited-Effects Theory 有限效果论 ______________________________________ 8 十四、Marshall Mcluhan Media Theory 麦克卢汉的媒介理论_______________________ 9一、Opinion Leaders 意见领袖Active in information networks, have many information channels ,so they can often provide information and advice for others and can influence others.意见领袖是指在人际传播网络中经常为他人提供信息,同时对他人施加影响的“活跃分子”,他们在大众传播效果的形成过程中起着重要的中介或过滤的作用,由他们将信息扩散给受众,形成信息传递的两级传播。
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剑桥雅思阅读7原文(test3)READING PASSAGE 1You should spend about 20 minutes on Questions 1-13, which are based on Reading Passage 1 below.Ant IntelligenceWhen we think of intelligent members of the animal kingdom, the creatures that spring immediately to mind are apes and monkeys. But in fact the social lives of some members of the insect kingdom are sufficiently complex to suggest more than a hint of intelligence. Among these, the world of the ant has come in for considerable scrutiny lately, and the idea that ants demonstrate sparks of cognition has certainly not been rejected by those involved in these investigations.Ants store food, repel attackers and use chemical signals to contact one another in case of attack. Such chemical communication can be compared to the human use of visual and auditory channels (as in religious chants, advertising images and jingles, political slogans and martial music) to arouse and propagate moods and attitudes. The biologist Lewis Thomas wrote, ‘Ants are so much like human beings as to be an embarrassment. They farm fungi, raise aphids_as livestock, launch armies to war, use chemical sprays to alarm and confuse enemies, capture slaves, engage in child labour, exchange information ceaselessly. They do everything but watch television.’However, in ants there is no cultural transmission —everything must be encoded in the genes — whereas in humansthe opposite is true. Only basic instincts are carried in the genes of a newborn baby, other skills being learned from others in the community as the child grows up. It may seem that this cultural continuity gives us a huge advantage over ants. They have never mastered fire nor progressed. Their fungus farming and aphid herding crafts are sophisticated when compared to the agricultural skills of humans five thousand years ago but have been totally overtaken by modern human agribusiness.Or have they? The farming methods of ants are at least sustainable. They do not ruin environments or use enormous amounts of energy. Moreover, recent evidence suggests that the crop farming of ants may be more sophisticated and adaptable than was thought.Ants were farmers fifty million years before humans were. Ants can’t digest the cellulose in leaves — but some fungi can. The ants therefore cultivate these fungi in their nests, bringing them leaves to feed on, and then use them as a source of food. Farmer ants secrete antibiotics to control other fungi that might act as ‘weeds’, and spread waste to fertilise the crop.It was once thought that the fungus that ants cultivate was a single type that they had propagated, essentially unchanged from the distant past. Not so. Ulrich Mueller of Maryland and his colleagues genetically screened 862 different types of fungi taken from ants’ nests. These turned out to be highly diverse: it seems that ants are continually domesticating new species. Even more impressively, DNA analysis of the fungi suggests that the ants improve or modify the fungi by regularly swapping and sharing strains with neighbouring ant colonies.Whereas prehistoric man had no exposure to urban lifestyles — the forcing house of intelligence — the evidence suggests thatants have lived in urban settings for close on a hundred million years, developing and maintaining underground cities of specialised chambers and tunnels.When we survey Mexico City, Tokyo, Los Angeles, we are amazed at what has been accomplished by humans. Yet Hoelldobler and Wilson’s magnificent work for ant lovers, The Ants, describes a supercolony of the ant Formica yessensis on the Ishikari Coast of Hokkaido. This ‘megalopolis’ was reported to be composed of 360 million workers and a million queens living in 4,500 interconnected nests across a territory of 2.7 square kilometres.Such enduring and intricately meshed levels of technical achievement outstrip by far anything achieved by our distant ancestors. We hail as masterpieces the cave paintings in southern France and elsewhere, dating back some 20,000 years. Ant societies existed in something like their present form more than seventy million years ago. Beside this, prehistoric man looks technologically primitive. Is this then some kind of intelligence, albeit of a different kind?Research conducted at Oxford, Sussex and Zurich Universities has shown that when desert ants return from a foraging trip, they navigate by integrating bearings and distances, which they continuously update in their heads. They combine the evidence of visual landmarks with a mental library of local directions, all within a framework which is consulted and updated. So ants can learn too.And in a twelve-year programme of work, Ryabko and Reznikova have found evidence that ants can transmit very complex messages. Scouts who had located food in a maze returned to mobilise their foraging teams. They engaged incontact sessions, at the end of which the scout was removed in order to observe what her team might do. Often the foragers proceeded to the exact spot in the maze where the food had been. Elaborate precautions were taken to prevent the foraging team using odour clues. Discussion now centres on whether the route through the maze is communicated as a ‘left-right’ se quence of turns or as a ‘compass bearing and distance’ message.During the course of this exhaustive study, Reznikova has grown so attached to her laboratory ants that she feels she knows them as individuals — even without the paint spots used to mark them. It’s no surprise that Edward Wilson, in his essay, ‘In the company of ants’, advises readers who ask what to do with the ants in their kitchen to: ‘Watch where you step. Be careful of little lives.’Questions 1-6Do the following statements agree with the information given in Reading Passage 1?In boxes 1-6 on your answer sheet, writeTRUE if the statement agrees with the informationFALSE if the statement contradicts the informationNOT GIVEN if there is no information on this1 Ants use the same channels of communication as humans do.2 City life is one factor that encourages the development of intelligence.3 Ants can build large cities more quickly than humans do.4 Some ants can find their way by making calculations based on distance and position.5 In one experiment, foraging teams were able to use theirsense of smell to find food.6 The essay, ‘In the company of ants’, explores ant communication.Questions 7-13Complete the summary using the list of words, A-O, below.Write the correct letter, A-O, in boxes 7-13 on your answer sheet.Ants as farmersAnts have sophisticated methods of farming, including herding livestock and growing crops, which are in many ways similar to those used in human agriculture. The ants cultivate a large number of different species of edible fungi which convert 7..............into a form which they can digest. They use their own natural 8..............as weed-killers and also use unwanted materials as 9.............. . Genetic analysis shows they constantly upgrade these fungi by developing new species and by 10..............species with neighbouring ant colonies. In fact, the farming methods of ants could be said to be more advanced than human agribusiness, since they use 11..............methods, they do not affect the12..............and do not waste 13.............. .A aphidsB agriculturalC celluloseD exchangingE energyF fertilizersG foodH fungiI growing J interbreeding K natural L other specesM secretions N sustainable O environmentREADING PASSAGE 2You should spend about 20 minutes on Questions 14-26, which are based on Reading Passage 2 on the following pages.Questions 14-19Reading Passage 2 has seven sections, A-G.Choose the correct headings for sections A-F from the list ofheadings below.Write the correct number, i-x, in boxes 14-19 on your answer sheet.List of Headingsi The results of the research into blood-variantsii Dental evidenceiii Greenberg’s analysis of the dental and linguistic evidence iv Developments in the methods used to study early population movementsv Indian migration from Canada to the U.S.A.vi Further genetic evidence relating to the three-wave theory vii Long-standing questions about prehistoric migration to Americaviii Conflicting views of the three-wave theory, based on non-genetic evidenceix Questions about the causes of prehistoric migration to Americax How analysis of blood-variants measures the closeness of the relationship between different populations14 Section A15 Section B16 Section C17 Section D18 Section E19 Section FExample AnswerSection G viiiPopulation movements and geneticsA Study of the origins and distribution of human populations used to be based on archaeological and fossil evidence. Anumber of techniques developed since the 1950s, however, have placed the study of these subjects on a sounder and more objective footing. The best information on early population movements is now being obtained from the ‘archaeology of the living body’, the clues to be found in genetic material.B Recent work on the problem of when people first entered the Americas is an example of the value of these new techniques. North-east Asia and Siberia have long been accepted as the launching ground for the first human colonisers of the New World1. But was there one major wave of migration across the Bering Strait into the Americas, or several? And when did this event, or events, take place? In recent years, new clues have come from research into genetics, including the distribution of genetic markers in modern Native Americans2.C An important project, led by the biological anthropologist Robert Williams, focused on the variants (called Gm allotypes) of one particular protein — immunoglobin G — found in the fluid portion of human blood. All proteins ‘drift’, or produce variants, over the generations, and members of an interbreeding human population will share a set of such variants. Thus, by comparing the Gm allotypes of two different populations (e.g. two Indian tribes), one can establish their genetic ‘distance’, which itself can be calibrated to give an indication of the length of time since these populations last interbred.D Williams and his colleagues sampled the blood of over 5,000 American Indians in western North America during a twenty-year period. They found that their Gm allotypes could be divided into two groups, one of which also corresponded to the genetic typing of Central and South American Indians. Other tests showed that the Inuit (or Eskimo) and Aleut3 formed a thirdgroup. From this evidence it was deduced that there had been three major waves of migration across the Bering Strait. The first, Paleo-lndian, wave more than 15,000 years ago was ancestral to all Central and South American Indians. The second wave, about 14,000-12,000 years ago, brought Na-Dene hunters, ancestors of the Navajo and Apache (who only migrated south from Canada about 600 or 700 years ago). The third wave, perhaps 10,000 or 9,000 years ago, saw the migration from North-east Asia of groups ancestral to the modern Eskimo and Aleut.E How far does other research support these conclusion? Geneticist Douglas Wallace has studied mitochondrial DNA4 in blood samples from three widely separated Native American groups: Pima-Papago Indians in Arizona, Maya Indians on the Yucatan peninsula, Mexico, and Ticuna Indians in the Upper Amazon region of Brazil. As would have been predicted by Robert Williams’s work, all three groups appear to be descended from the same ancestral (Paleo-lndian) population.F There are two other kinds of research that have thrown some light on the origins of the Native American population; they involve the study of teeth and of languages. The biological anthropologist Christy Turner is an expert in the analysis of changing physical characteristics in human teeth. He argues that tooth crowns and roots5 have a high genetic component, minimally affected by environmental and other factors. Studies carried out by Turner of many thousands of New and Old World specimens, both ancient and modern, suggest that the majority of prehistoric Americans are linked to Northern Asian populations by crown and root traits such as incisor6 shoveling (a scooping out on one or both surfaces of the tooth), single-rooted upper first premolars6 and triple-rooted lower firstmolars6.According to Turner, this ties in with the idea of a single Paleo-lndian migration out of North Asia, which he sets at before 14,000 years ago by calibrating rates of dental micro-evolution. Tooth analyses also suggest that there were two later migrations of Na-Denes and Eskimo-Aleut.G The linguist Joseph Greenberg has, since the 1950s, argued that all Native American languages belong to a single ‘Amerind’ family, except for Na-Dene and Eskimo-Aleut — a view that gives credence to the idea of three main migrations. Greenberg is in a minority among fellow linguists, most of whom favour the notion of a great many waves of migration to account for the more than 1,000 languages spoken at one time by American Indians. But there is no doubt that the new genetic and dental evidence provides strong backing for Greenberg’s view. Dates given for the migrations should nevertheless be treated with caution, except where supported by hard archaeological evidence.1 New World: the American continent, as opposed to the so-called Old World of Europe, Asia and Africa2 modern Native American: an American descended from the groups that were native to America3 Inuit and Aleut: two of the ethnic groups native to the northern regions of North America (i.e. northern Canada and Greenland)4 DNA: the substance in which genetic information is stored5 crown/root: parts of the tooth6 incisor/premolar/molar: kinds of teethQuestions 20 and 21The discussion of Williams’s research indicates the periods at which early people are thought to have migrated along certainroutes. There are six routes, A-F, marked on map below.Complete the table below.Write the correct letter, A-F, in boxes 20 and 21 on your answer sheet.Route Period (number of years ago)20.................. 15,000 or more21.................. 600 to 700Early Population Movement to the AmericasQuestions 22-25Reading Passage 2 refers to the three-wave theory of early migration to the Americas. It also suggests in which of these three waves the ancestors of various groups of modern native Americans first reached the continent.Classify the groups named in the table below as originating fromA the first waveB the second waveC the third waveWrite the correct letter, A, B or C, in boxes 22-25 on your answer sheet.Name of group Wave numberInuit 22..................Apache 23..................Pima-Papago 24..................Ticuna 25..................Question 26Choose the correct letter, A, B, C or D.Write the correct letter in box 26 on your answer sheet.Christy Turn er’s research involved the examination ofA teeth from both prehistoric and modern Americans andAsians.B thousands of people who live in either the New or the Old World.C dental specimens from the majority of prehistoric Americans.D the eating habits of American and Asian populations.READING PASSAGE 3You should spend about 20 minutes on Questions 27-40, which are based on Reading Passage 3 below.Forests are one of the main elements of our natural heritage. The decline of Europe’s forests over the las t decade and a half has led to an increasing awareness and understanding of the serious imbalances which threaten them. European countries are becoming increasingly concerned by major threats to European forests, threats which know no frontiers other than those of geography or climate: air pollution, soil deterioration, the increasing number of forest fires and sometimes even the mismanagement of our woodland and forest heritage. There has been a growing awareness of the need for countries to get together to co-ordinate their policies. In December 1990, Strasbourg hosted the first Ministerial Conference on the protection of Europe’s forests. The conference brought together 31 countries from both Western and Eastern Europe. The topics discussed included the coordinated study of the destruction of forests, as well as how to combat forest fires and the extension of European research programs on the forest ecosystem. The preparatory work for the conference had been undertaken at two meetings of experts. Their initial task was to decide which of the many forest problems of concern to Europe involved the largest number of countries and might be thesubject of joint action. Those confined to particular geographical areas, such as countries bordering the Mediterranean or the Nordic countries therefore had to be discarded. However, this does not mean that in future they will be ignored.As a whole, European countries see forests as performing a triple function: biological, economic and recreational. The first is to act as a ‘green lung’ for our planet; by means of photosynthesis, forests produce oxygen through the transformation of solar energy, thus fulfilling what for humans is the essential role of an immense, non-polluting power plant. At the same time, forests provide raw materials for human activities through their constantly renewed production of wood. Finally, they offer those condemned to spend five days a week in an urban environment an unrivalled area of freedom to unwind and take part in a range of leisure activities, such as hunting, riding and hiking. The economic importance of forests has been understood since the dawn of man — wood was the first fuel. The other aspects have been recognised only for a few centuries but they are becoming more and more important. Hence, there is a real concern throughout Europe about the damage to the forest environment which threatens these three basic roles.The myth of the ‘natural’ forest has survived, yet there are effectively no remaining ‘primary’ forests in Europe. All European forests are artificial, having been adapted and exploited by man for thousands of years. This means that a forest policy is vital, that it must transcend national frontiers and generations of people, and that it must allow for the inevitable changes that take place in the forests, in needs, and hence in policy. The Strasbourg conference was one of the first events on such a scale to reach this conclusion. A general declaration wasmade that ‘a central place in any ecologically coherent forest policy must be given to continuity over time and to the possible effects of unforeseen events, to ensure that the full potential of these forests is maintained’.That general declaration was accompanied by six detailed resolutions to assist national policy-making. The first proposes the extension and systematisation of surveillance sites to monitor forest decline. Forest decline is still poorly understood but leads to the loss of a high proportion of a tree’s needles or leaves. The entire continent and the majority of species are now affected: between 30% and 50% of the tree population. The condition appears to result from the cumulative effect of a number of factors, with atmospheric pollutants the principal culprits. Compounds of nitrogen and sulphur dioxide should be particularly closely watched. However, their effects are probably accentuated by climatic factors, such as drought and hard winters, or soil imbalances such as soil acidification, which damages the roots. The second resolution concentrates on the need to preserve the genetic diversity of European forests. The aim is to reverse the decline in the number of tree species or at least to preserve the ‘genetic material’ of all of them. Although forest fires do not affect all of Europe to the same extent, the amount of damage caused the experts to propose as the third resolution that the Strasbourg conference consider the establishment of a European databank on the subject. All information used in the development of national preventative policies would become generally available. The subject of the fourth resolution discussed by the ministers was mountain forests. In Europe, it is undoubtedly the mountain ecosystem which has changed most rapidly and is most at risk. A thinly scattered permanentpopulation and development of leisure activities, particularly skiing, have resulted in significant long-term changes to the local ecosystems. Proposed developments include a preferential research program on mountain forests. The fifth resolution relaunched the European research network on the physiology of trees, called Eurosilva. Eurosilva should support joint European research on tree diseases and their physiological and biochemical aspects. Each country concerned could increase the number of scholarships and other financial support for doctoral theses and research projects in this area. Finally, the conference established the framework for a European research network on forest ecosystems. This would also involve harmonising activities in individual countries as well as identifying a number of priority research topics relating to the protection of forests. The Strasbourg conference’s main concern was to provide for the future. This was the initial motivation, one now shared by all 31 participants representing 31 European countries. Their final text commits them to on-going discussion between government representatives with responsibility for forests.Questions 27-33Do the following statements agree with the information given in Reading Passage 3?In boxes 27-33 on your answer sheet, writeTRUE if the statement agrees with the informationFALSE if the statement contradicts the informationNOT GIVEN if there is no information on this27 Forest problems of Mediterranean countries are to be discussed at the next meeting or experts.28 Problems in Nordic countries were excluded because they are outside the European Economic Community.29 Forests are a renewable source of raw material.30 The biological functions of forests were recognized only in the twentieth century.31 Natural forests still exist in parts of Europe.32 Forest policy should be limited by national boundaries.33 The Strasbourg conference decided that a forest policy must allow for the possibility of change.Questions 34-39Look at the following statements issued by the conference.Which six of the following statements, A-J, refer to the resolutions that were issued?Match the statements with the appropriate resolutions (Questions 34-39).Write the correct letter, A-J, in boxes 34-39 on your answer sheet.A All kinds of species of trees should be preserved.B Fragile mountain forests should be given priority in research programs.C The surviving natural forests of Europe de not need priority treatment.D Research is to be better co-ordinated throughout Europe.E Information on forest fires should be collected and shared.F Loss of leaves from trees should be more extensively and carefully monitored.G Resources should be allocated to research into tree diseases.H Skiing should be encouraged in thinly populated areas.I Soil imbalances such as acidification should be treated with compounds of nitrogen and sulphur.J Information is to be systematically gathered on any declinein the condition of forests.34 Resolution 135 Resolution 236 Resolution 337 Resolution 438 Resolution 539 Resolution 6Question 40Choose the correct letter, A, B, C or D.Write the correct letter in box 40 on your answer sheet.40 What is the best title for Reading Passage 3?A The biological, economic and recreational role of forestsB Plans to protect the forests of EuropeC The priority of European research into ecosystemsD Proposals for a world-wide policy on forest management剑桥雅思阅读7原文参考译文(test3)TEST 3 PASSAGE 1 参考译文:蚂蚁智能每当我们想到动物界的智能成员时,头脑中立刻出现的会是猿和猴子。
非理想爆轰波阵面传播的Level Set方法在爆轰驱动计算中的应用研究姜洋*,钟敏,孙承纬,李平,柏劲松(中国工程物理研究院流体物理研究所,四川绵阳 621900)摘要:基于爆轰冲击波动力学(DSD)理论,研究了计算二维贴体坐标系中非理想爆轰波阵面传播问题的Level Set方法。
根据Hamilton-Jacobi方程的Godunov差分格式,提出了非正交的贴体坐标系中Level Set函数方程的差分格式及其相应的数值方法。
将Level Set方法应用于自行研制的二维流体动力学程序TDY2D得到编码TDY_DSD,对爆轰波的传播及爆轰驱动的实验模型进行了数值模拟计算,所得的计算值均与实验值符合较好,具有较高精度。
关键词:爆炸力学;爆轰驱动;DSD理论;Level-Set方法;贴体坐标系;数值模拟中图分类号:O241;O382;O383文献标识码:AApplication of the Level Set method for propagation of non-ideal detonation to the numerical simulation for acceleration of metals by detonation waveAbstract:Based on the DSD (Detonation Shock Dynamics) theory, the Level Set method in body-fitted coordinate for propagation of non-ideal detonation is studied in this paper. According to the Hamilton-Jacobi formulation of the Godunov’s scheme, the finite difference method and algorithm for the propagation equation of non-ideal detonation in non-orthogonal body-fitted coordinate are studied. Then the Level Set method is incorporated into the 2D hydrodynamic code TDY2D to form a combination code TDY_DSD and it is used to compute some models about the propagation of detonation wave and the motion of flyers driven by explosive. The computation results are in good agreement with the experimental data and the precision in calculation is high.Key words: Mechanics of explosion; Acceleration by detonation products; DSD theory; Level set method; Body-fitted coordinate; Numerical simulation*作者简介:姜洋(1976-),女,助理研究员,博士生 从事计算流体力学、计算爆炸力学的理论和数值计算方法方面研究通信地址:四川绵阳919信箱105分箱 邮编621900电话:***********Email:**********************0引言对复杂几何形状炸药中爆轰波阵面传播过程的描述是炸药驱动装置设计中的一个重要课题,在军事及工程研究中具有重要的实际应用价值。
流体动力学 fluid dynamics连续介质力学 mechanics of continuous media介质 medium流体质点 fluid particle无粘性流体 nonviscous fluid, inviscid fluid连续介质假设continuous medium hypothesis流体运动学 fluid kinematics水静力学 hydrostatics液体静力学 hydrostatics支配方程 governing equation分步法 fractional step method伯努利定理 Bernonlli theorem毕奥-萨伐尔定律 Biot-Savart law欧拉方程 Euler equation亥姆霍兹定理 Helmholtz theorem开尔文定理 Kelvin theorem涡片 vortex sheet库塔-茹可夫斯基条件 Kutta-Zhoukowski condition布拉休斯解 Blasius solution达朗贝尔佯廖 d'Alembert paradox雷诺数 Reynolds number施特鲁哈尔数 Strouhal number随体导数 material derivative不可压缩流体 incompressible fluid质量守恒 conservation of mass动量守恒 conservation of momentum能量守恒 conservation of energy动量方程 momentum equation能量方程 energy equation控制体积 control volume液体静压 hydrostatic pressure涡量拟能 enstrophy压差 differential pressure流[动] flow流线 stream line流面 stream surface流管 stream tube迹线 path, path line流场 flow field流态 flow regime流动参量 flow parameter流量 flow rate, flow discharge涡旋vortex 涡量 vorticity涡丝 vortex filament涡线 vortex line涡面 vortex surface涡层 vortex layer涡环 vortex ring涡对 vortex pair涡管 vortex tube涡街 vortex street卡门涡街 Karman vortex street马蹄涡 horseshoe vortex对流涡胞 convective cell卷筒涡胞 roll cell涡 eddy涡粘性 eddy viscosity环流 circulation环量 circulation速度环量 velocity circulation偶极子 doublet, dipole驻点stagnation point总压[力] total pressure总压头 total head静压头 static head总焓 total enthalpy能量输运 energy transport速度剖面 velocity profile库埃特流 Couette flow单相流 single phase flow单组份流 single-component flow均匀流uniform flow非均匀流 nonuniform flow二维流 two-dimensional flow三维流 three-dimensional flow准定常流 quasi-steady flow非定常流 unsteady flow, non-steady flow 暂态流 transient flow周期流 periodic flow振荡流 oscillatory flow分层流 stratified flow无旋流 irrotational flow有旋流 rotational flow轴对称流 axisymmetric flow不可压缩性 incompressibility不可压缩流[动] incompressible flow浮体floating body定倾中心 metacenter阻力 drag, resistance减阻 drag reduction表面力 surface force表面张力 surface tension毛细[管]作用 capillarity来流 incoming flow自由流 free stream自由流线 free stream line外流 external flow进口 entrance, inlet出口 exit, outlet扰动 disturbance, perturbation分布 distribution传播 propagation色散 dispersion弥散 dispersion附加质量 added mass ,associated mass 收缩 contraction镜象法 image method无量纲参数dimensionless parameter几何相似 geometric similarity运动相似 kinematic similarity动力相似[性] dynamic similarity平面流 plane flow势 potential势流 potential flow速度势 velocity potential复势 complex potential复速度 complex velocity流函数 stream function源 source汇 sink速度[水]头 velocity head拐角流 corner flow空泡流 cavity flow超空泡 supercavity超空泡流 supercavity flow空气动力学 aerodynamics低速空气动力学 low-speed aerodynamics 高速空气动力学 high-speed aerodynamics 气动热力学 aerothermodynamics亚声速流[动] subsonic flow跨声速流[动] transonic flow超声速流[动] supersonic flow锥形流 conical flow楔流 wedge flow叶栅流 cascade flow非平衡流[动] non-equilibrium flow 细长体 slender body细长度 slenderness钝头体 bluff body钝体 blunt body翼型 airfoil翼弦 chord薄翼理论 thin-airfoil theory构型 configuration后缘 trailing edge迎角 angle of attack失速 stall脱体激波 detached shock wave波阻 wave drag诱导阻力 induced drag诱导速度 induced velocity临界雷诺数 critical Reynolds number前缘涡 leading edge vortex附着涡 bound vortex约束涡 confined vortex气动中心 aerodynamic center气动力 aerodynamic force气动噪声 aerodynamic noise气动加热 aerodynamic heating离解 dissociation地面效应 ground effect气体动力学 gas dynamics稀疏波 rarefaction wave热状态方程 thermal equation of state 喷管 Nozzle普朗特-迈耶流 Prandtl-Meyer flow瑞利流 Rayleigh flow可压缩流[动] compressible flow可压缩流体 compressible fluid绝热流 adiabatic flow非绝热流 diabatic flow未扰动流 undisturbed flow等熵流 isentropic flow匀熵流 homoentropic flow兰金-于戈尼奥条件Rankine-Hugoniot condition状态方程 equation of state量热状态方程 caloric equation of state 完全气体 perfect gas拉瓦尔喷管 Laval nozzle马赫角 Mach angle马赫锥 Mach cone马赫线 Mach line马赫数 Mach number马赫波 Mach wave当地马赫数 local Mach number冲击波shock wave激波 shock wave正激波 normal shock wave斜激波 oblique shock wave头波 bow wave附体激波 attached shock wave激波阵面 shock front激波层 shock layer压缩波 compression wave反射 reflection折射 refraction散射 scattering衍射 diffraction绕射 diffraction出口压力 exit pressure超压[强] over pressure反压 back pressure爆炸 explosion爆轰 detonation缓燃 deflagration水动力学 hydrodynamics液体动力学 hydrodynamics泰勒不稳定性 Taylor instability 盖斯特纳波 Gerstner wave斯托克斯波 Stokes wave瑞利数 Rayleigh number自由面 free surface波速 wave speed, wave velocity 波高 wave height波列 wave train波群 wave group波能 wave energy表面波 surface wave表面张力波 capillary wave规则波 regular wave不规则波 irregular wave浅水波 shallow water wave深水波 deep water wave重力波 gravity wave椭圆余弦波 cnoidal wave潮波 tidal wave涌波 surge wave破碎波 breaking wave船波 ship wave 非线性波 nonlinear wave孤立子 soliton水动[力]噪声 hydrodynamic noise水击 water hammer空化 cavitation空化数 cavitation number空蚀 cavitation damage超空化流 supercavitating flow水翼 hydrofoil水力学 hydraulics洪水波 flood wave涟漪 ripple消能 energy dissipation海洋水动力学 marine hydrodynamics谢齐公式 Chezy formula欧拉数 Euler number弗劳德数 Froude number水力半径 hydraulic radius水力坡度 hvdraulic slope高度水头 elevating head水头损失 head loss水位 water level水跃 hydraulic jump含水层 aquifer排水 drainage排放量 discharge壅水曲线 back water curve压[强水]头 pressure head过水断面 flow cross-section明槽流 open channel flow孔流 orifice flow无压流 free surface flow有压流 pressure flow缓流 subcritical flow急流 supercritical flow渐变流 gradually varied flow急变流 rapidly varied flow临界流 critical flow异重流 density current, gravity flow 堰流 weir flow掺气流 aerated flow含沙流 sediment-laden stream降水曲线 dropdown curve沉积物 sediment, deposit沉[降堆]积 sedimentation, deposition 沉降速度 settling velocity流动稳定性 flow stability不稳定性 instability奥尔-索末菲方程Orr-Sommerfeld equation涡量方程 vorticity equation泊肃叶流 Poiseuille flow奥辛流 Oseen flow剪切流 shear flow粘性流[动] viscous flow层流 laminar flow分离流 separated flow二次流 secondary flow近场流 near field flow远场流 far field flow滞止流 stagnation flow尾流 wake [flow]回流 back flow反流 reverse flow射流 jet自由射流 free jet管流 pipe flow, tube flow内流 internal flow拟序结构 coherent structure猝发过程 bursting process表观粘度 apparent viscosity运动粘性 kinematic viscosity动力粘性 dynamic viscosity泊 poise厘泊 centipoise厘沱 centistoke剪切层 shear layer次层 sublayer流动分离 flow separation层流分离 laminar separation湍流分离 turbulent separation分离点 separation point附着点 attachment point再附 reattachment再层流化 relaminarization起动涡 starting vortex驻涡 standing vortex涡旋破碎 vortex breakdown涡旋脱落 vortex shedding压[力]降 pressure drop压差阻力 pressure drag压力能 pressure energy型阻 profile drag滑移速度 slip velocity 无滑移条件 non-slip condition壁剪应力 skin friction, frictional drag 壁剪切速度 friction velocity磨擦损失 friction loss磨擦因子 friction factor耗散 dissipation滞后 lag相似性解 similar solution局域相似 local similarity气体润滑 gas lubrication液体动力润滑 hydrodynamic lubrication 浆体 slurry泰勒数 Taylor number纳维-斯托克斯方程Navier-Stokes equation牛顿流体 Newtonian fluid边界层理论 boundary later theory边界层方程 boundary layer equation边界层 boundary layer附面层 boundary layer层流边界层 laminar boundary layer湍流边界层 turbulent boundary layer温度边界层 thermal boundary layer边界层转捩 boundary layer transition 边界层分离 boundary layer separation 边界层厚度 boundary layer thickness位移厚度 displacement thickness动量厚度 momentum thickness能量厚度 energy thickness焓厚度 enthalpy thickness注入 injection吸出 suction泰勒涡 Taylor vortex速度亏损律 velocity defect law形状因子 shape factor测速法 anemometry粘度测定法 visco[si] metry流动显示 flow visualization油烟显示 oil smoke visualization孔板流量计 orifice meter频率响应 frequency response油膜显示 oil film visualization阴影法 shadow method纹影法 schlieren method烟丝法 smoke wire method丝线法 tuft method氢泡法 nydrogen bubble method相似理论 similarity theory相似律 similarity law部分相似 partial similarity定理 pi theorem, Buckingham theorem 静[态]校准 static calibration动态校准 dynamic calibration风洞 wind tunnel激波管 shock tube激波管风洞 shock tube wind tunnel水洞 water tunnel拖曳水池 towing tank旋臂水池 rotating arm basin扩散段 diffuser测压孔 pressure tap皮托管 pitot tube普雷斯顿管 preston tube斯坦顿管 Stanton tube文丘里管 Venturi tubeU形管 U-tube压强计 manometer微压计 micromanometer多管压强计 multiple manometer静压管 static [pressure]tube流速计 anemometer风速管 Pitot- static tube激光多普勒测速计laser Doppler anemometer,laser Doppler velocimeter热线流速计 hot-wire anemometer热膜流速计 hot- film anemometer流量计 flow meter粘度计 visco[si] meter涡量计 vorticity meter传感器 transducer, sensor压强传感器 pressure transducer热敏电阻 thermistor示踪物 tracer时间线 time line脉线 streak line尺度效应 scale effect壁效应 wall effect堵塞 blockage堵寒效应 blockage effect动态响应 dynamic response响应频率 response frequency底压 base pressure 菲克定律 Fick law巴塞特力 Basset force埃克特数 Eckert number格拉斯霍夫数 Grashof number努塞特数 Nusselt number普朗特数 prandtl number雷诺比拟 Reynolds analogy施密特数 schmidt number斯坦顿数 Stanton number对流 convection自由对流natural convection, free convec-tion强迫对流 forced convection热对流 heat convection质量传递 mass transfer传质系数 mass transfer coefficient热量传递 heat transfer传热系数 heat transfer coefficient对流传热 convective heat transfer辐射传热 radiative heat transfer动量交换 momentum transfer能量传递 energy transfer传导 conduction热传导 conductive heat transfer热交换 heat exchange临界热通量 critical heat flux浓度 concentration扩散 diffusion扩散性 diffusivity扩散率 diffusivity扩散速度 diffusion velocity分子扩散 molecular diffusion沸腾 boiling蒸发 evaporation气化 gasification凝结 condensation成核 nucleation计算流体力学computational fluid mechanics多重尺度问题 multiple scale problem伯格斯方程 Burgers equation对流扩散方程convection diffusion equationKDU方程 KDV equation修正微分方程modified differential equation拉克斯等价定理 Lax equivalence theorem数值模拟 numerical simulation大涡模拟 large eddy simulation数值粘性 numerical viscosity非线性不稳定性 nonlinear instability希尔特稳定性分析Hirt stability analysis相容条件 consistency conditionCFL条件Courant- Friedrichs- Lewy condition ,CFL condition狄里克雷边界条件Dirichlet boundarycondition熵条件 entropy condition远场边界条件far field boundary condition流入边界条件 inflow boundary condition 无反射边界条件nonreflecting boundary condition数值边界条件numerical boundary condition流出边界条件 outflow boundary condition 冯.诺伊曼条件 von Neumann condition近似因子分解法approximate factorization method人工压缩 artificial compression人工粘性 artificial viscosity边界元法 boundary element method配置方法 collocation method能量法 energy method有限体积法 finite volume method流体网格法 fluid in cell method, FLIC method通量校正传输法flux-corrected transport method通量矢量分解法 flux vector splitting method伽辽金法 Galerkin method积分方法 integral method标记网格法 marker and cell method, MAC method特征线法 method of characteristics直线法 method of lines矩量法 moment method多重网格法 multi- grid method板块法 panel method质点网格法particle in cell method, PIC method质点法 particle method 预估校正法 predictor-corrector method 投影法 projection method准谱法 pseudo-spectral method随机选取法 random choice method激波捕捉法 shock-capturing method激波拟合法 shock-fitting method谱方法 spectral method稀疏矩阵分解法 split coefficient matrix method不定常法 time-dependent method时间分步法 time splitting method变分法 variational method涡方法 vortex method隐格式 implicit scheme显格式 explicit scheme交替方向隐格式 alternating direction implicit scheme, ADI scheme反扩散差分格式anti-diffusion difference scheme紧差分格式 compact difference scheme 守恒差分格式 conservation difference scheme克兰克-尼科尔森格式Crank-Nicolson scheme杜福特-弗兰克尔格式Dufort-Frankel scheme指数格式 exponential scheme戈本诺夫格式 Godunov scheme高分辨率格式 high resolution scheme拉克斯-温德罗夫格式Lax-Wendroff scheme蛙跳格式 leap-frog scheme单调差分格式 monotone difference scheme 保单调差分格式 monotonicity preserving diffe-rence scheme穆曼-科尔格式 Murman-Cole scheme半隐格式 semi-implicit scheme斜迎风格式 skew-upstream scheme全变差下降格式total variation decreasing scheme TVD scheme迎风格式upstream scheme , upwind scheme计算区域 computational domain物理区域 physical domain影响域 domain of influence依赖域 domain of dependence区域分解 domain decomposition维数分解 dimensional split物理解 physical solution弱解 weak solution黎曼解算子 Riemann solver守恒型 conservation form弱守恒型 weak conservation form强守恒型 strong conservation form散度型 divergence form贴体曲线坐标 body- fitted curvilinear coordi-nates[自]适应网格 [self-] adaptive mesh适应网格生成 adaptive grid generation 自动网格生成 automatic grid generation 数值网格生成 numerical grid generation 交错网格 staggered mesh网格雷诺数 cell Reynolds number数植扩散 numerical diffusion数值耗散 numerical dissipation数值色散 numerical dispersion数值通量 numerical flux放大因子 amplification factor放大矩阵 amplification matrix阻尼误差 damping error离散涡 discrete vortex熵通量 entropy flux熵函数 entropy function伯努利方程 Bernoulli equation。
2017年同等学力英语真题答案及解析Part I Oral CommunicationSection ADialogue One1.本题选B解析:根据第1题空格下面一行Roger问“你现在住的地方有什么问题吗”可以推断Ann决定要换新的地方住了。
故本题选B.2.本题选A解析:第2题后面Ann回答“是的,但是它离学校有点远,每天往返太折腾人了”,这里的but转折后Ann是在说现在所住公寓不好的地方,那么可以推测转折前应该是在说好的地方,A项“我以为你喜欢那个公寓呢”符合语境,故本题选A.3.本题选C解析:根据第2题前面Roger说到“我知道拐角处有个公寓”以及后面Ann的回答“谢谢你”可推知Roger可能是要带Ann去看那个公寓,故本题选C.Dialogue Two4.本题选B解析:根据第4题后面Alice的回答“计划在10点进行”可知前面Kevin是在问时间,故本题选B 项.5.本题选A解析:根据第5题前面Alice说“弗兰克也打算对改进损益表底线提出一些建议(bottom line:最终赢利(或亏损);损益表底线)”以及第5题后面Kevin回答“他有敏锐的洞察力”可知这里Kevin 这里是在对于弗兰克提建议一事表示肯定,故本题选A.6.本题选C解析:根据第6题下面Alice的回答“不来,他马上要飞洛杉矶了,来不了”可知前面Kevin是在问某个人来不来参加会议,故本题选C.Section B7.本题选C解析:第7题前面主持人对希拉里进行了介绍后在空格后面说到“谢谢你能来”可知这是一段介绍嘉宾的开场白,C项“真的很荣幸你能来这里”符合语境,故本题选C.8.本题选B解析:由于前面主持人一直在介绍希拉里并对其能来参加节目表示荣幸和感谢,根据常识可推知希拉里接下来肯定也会回以同样的感谢,故本题选B.9.本题选A解析:第9题前面希拉里说到“我的整个团队来到我家,我们围坐在一起吃印度食物,喝酒”,可以推知她接下来是在对前面所做这些事进行一个强调,“这就是我们做的事”,故本题选A.10.本题选D解析:第10题前面主持人说到“就像是‘让我们只谈电视吧,不要谈刚才发生的事’?”,后面希拉里表示肯定“是的,是的”,可知后面就是在说“我们所有人一直在谈电视节目”。
流体力学专业英语词汇表流体动力学 fluid dynamics连续介质力学 mechanics of continuous media介质 medium流体质点 fluid particle无粘性流体 nonviscous fluid, inviscid fluid连续介质假设 continuous medium hypothesis流体运动学 fluid kinematics水静力学 hydrostatics液体静力学 hydrostatics支配方程 governing equation伯努利方程 Bernoulli equation伯努利定理 Bernonlli theorem毕奥-萨伐尔定律 Biot-Savart law欧拉方程 Euler equation亥姆霍兹定理 Helmholtz theorem开尔文定理 Kelvin theorem涡片 vortex sheet库塔-茹可夫斯基条件Kutta-Zhoukowski condition布拉休斯解 Blasius solution达朗贝尔佯廖 d'Alembert paradox雷诺数 Reynolds number施特鲁哈尔数 Strouhal number随体导数 material derivative不可压缩流体 incompressible fluid质量守恒 conservation of mass动量守恒 conservation of momentum能量守恒 conservation of energy动量方程 momentum equation能量方程 energy equation控制体积 control volume液体静压 hydrostatic pressure涡量拟能 enstrophy压差 differential pressure流[动] flow流线 stream line 流面 stream surface流管 stream tube迹线 path, path line流场 flow field流态 flow regime流动参量 flow parameter流量 flow rate, flow discharge 涡旋 vortex涡量 vorticity涡丝 vortex filament涡线 vortex line涡面 vortex surface涡层 vortex layer涡环 vortex ring涡对 vortex pair涡管 vortex tube涡街 vortex street卡门涡街 Karman vortex street 马蹄涡 horseshoe vortex对流涡胞 convective cell卷筒涡胞 roll cell涡 eddy涡粘性 eddy viscosity环流 circulation环量 circulation速度环量 velocity circulation 偶极子 doublet, dipole驻点 stagnation point总压[力] total pressure总压头 total head静压头 static head总焓 total enthalpy能量输运 energy transport速度剖面 velocity profile库埃特流 Couette flow单相流 single phase flow单组份流 single-component flow 均匀流 uniform flow非均匀流 nonuniform flow二维流 two-dimensional flow三维流 three-dimensional flow准定常流 quasi-steady flow非定常流 unsteady flow, non-steady flow暂态流 transient flow周期流 periodic flow振荡流 oscillatory flow分层流 stratified flow无旋流 irrotational flow有旋流 rotational flow轴对称流 axisymmetric flow不可压缩性 incompressibility不可压缩流[动] incompressible flow浮体 floating body定倾中心 metacenter阻力 drag, resistance减阻 drag reduction表面力 surface force表面张力 surface tension毛细[管]作用 capillarity来流 incoming flow自由流 free stream自由流线 free stream line外流 external flow进口 entrance, inlet出口 exit, outlet扰动 disturbance, perturbation分布 distribution传播 propagation色散 dispersion弥散 dispersion附加质量 added mass ,associated mass收缩 contraction镜象法 image method无量纲参数 dimensionless parameter几何相似 geometric similarity运动相似 kinematic similarity动力相似[性] dynamic similarity平面流 plane flow势 potential势流 potential flow速度势 velocity potential复势 complex potential复速度 complex velocity流函数 stream function源 source汇 sink速度[水]头 velocity head拐角流 corner flow空泡流 cavity flow超空泡 supercavity超空泡流 supercavity flow空气动力学 aerodynamics低速空气动力学 low-speed aerodynamics高速空气动力学 high-speed aerodynamics气动热力学 aerothermodynamics亚声速流[动] subsonic flow跨声速流[动] transonic flow超声速流[动] supersonic flow锥形流 conical flow楔流 wedge flow叶栅流 cascade flow非平衡流[动] non-equilibrium flow细长体 slender body细长度 slenderness钝头体 bluff body钝体 blunt body翼型 airfoil翼弦 chord薄翼理论 thin-airfoil theory构型 configuration后缘 trailing edge迎角 angle of attack失速 stall脱体激波 detached shock wave波阻 wave drag诱导阻力 induced drag诱导速度 induced velocity临界雷诺数 critical Reynoldsnumber前缘涡 leading edge vortex附着涡 bound vortex约束涡 confined vortex气动中心 aerodynamic center气动力 aerodynamic force气动噪声 aerodynamic noise气动加热 aerodynamic heating离解 dissociation地面效应 ground effect气体动力学 gas dynamics稀疏波 rarefaction wave热状态方程 thermal equation of state喷管 Nozzle普朗特-迈耶流 Prandtl-Meyer flow瑞利流 Rayleigh flow可压缩流[动] compressible flow可压缩流体 compressible fluid绝热流 adiabatic flow非绝热流 diabatic flow未扰动流 undisturbed flow等熵流 isentropic flow匀熵流 homoentropic flow兰金-于戈尼奥条件Rankine-Hugoniot condition状态方程 equation of state量热状态方程 caloric equation of state完全气体 perfect gas拉瓦尔喷管 Laval nozzle马赫角 Mach angle马赫锥 Mach cone马赫线 Mach line马赫数 Mach number马赫波 Mach wave当地马赫数 local Mach number冲击波 shock wave激波 shock wave正激波 normal shock wave斜激波 oblique shock wave 头波 bow wave附体激波 attached shock wave激波阵面 shock front激波层 shock layer压缩波 compression wave反射 reflection折射 refraction散射 scattering衍射 diffraction绕射 diffraction出口压力 exit pressure超压[强] over pressure反压 back pressure爆炸 explosion爆轰 detonation缓燃 deflagration水动力学 hydrodynamics液体动力学 hydrodynamics泰勒不稳定性 Taylor instability 盖斯特纳波 Gerstner wave斯托克斯波 Stokes wave瑞利数 Rayleigh number自由面 free surface波速 wave speed, wave velocity 波高 wave height波列 wave train波群 wave group波能 wave energy表面波 surface wave表面张力波 capillary wave规则波 regular wave不规则波 irregular wave浅水波 shallow water wave深水波 deep water wave重力波 gravity wave椭圆余弦波 cnoidal wave潮波 tidal wave涌波 surge wave破碎波 breaking wave船波 ship wave非线性波 nonlinear wave孤立子 soliton水动[力]噪声 hydrodynamic noise水击 water hammer空化 cavitation空化数 cavitation number空蚀 cavitation damage超空化流 supercavitating flow水翼 hydrofoil水力学 hydraulics洪水波 flood wave涟漪 ripple消能 energy dissipation海洋水动力学 marine hydrodynamics谢齐公式 Chezy formula欧拉数 Euler number弗劳德数 Froude number水力半径 hydraulic radius水力坡度 hvdraulic slope高度水头 elevating head水头损失 head loss水位 water level水跃 hydraulic jump含水层 aquifer排水 drainage排放量 discharge壅水曲线 back water curve压[强水]头 pressure head过水断面 flow cross-section明槽流 open channel flow孔流 orifice flow无压流 free surface flow有压流 pressure flow缓流 subcritical flow急流 supercritical flow渐变流 gradually varied flow急变流 rapidly varied flow临界流 critical flow异重流 density current, gravity flow堰流 weir flow掺气流 aerated flow含沙流 sediment-laden stream降水曲线 dropdown curve沉积物 sediment, deposit沉[降堆]积 sedimentation, deposition沉降速度 settling velocity流动稳定性 flow stability不稳定性 instability奥尔-索末菲方程 Orr-Sommerfeld equation涡量方程 vorticity equation泊肃叶流 Poiseuille flow奥辛流 Oseen flow剪切流 shear flow粘性流[动] viscous flow层流 laminar flow分离流 separated flow二次流 secondary flow近场流 near field flow远场流 far field flow滞止流 stagnation flow尾流 wake [flow]回流 back flow反流 reverse flow射流 jet自由射流 free jet管流 pipe flow, tube flow内流 internal flow拟序结构 coherent structure猝发过程 bursting process表观粘度 apparent viscosity运动粘性 kinematic viscosity动力粘性 dynamic viscosity泊 poise厘泊 centipoise厘沱 centistoke剪切层 shear layer次层 sublayer流动分离 flow separation层流分离 laminar separation湍流分离 turbulent separation分离点 separation point附着点 attachment point再附 reattachment再层流化 relaminarization起动涡 starting vortex驻涡 standing vortex涡旋破碎 vortex breakdown涡旋脱落 vortex shedding压[力]降 pressure drop压差阻力 pressure drag压力能 pressure energy型阻 profile drag滑移速度 slip velocity无滑移条件 non-slip condition壁剪应力 skin friction, frictional drag壁剪切速度 friction velocity磨擦损失 friction loss磨擦因子 friction factor耗散 dissipation滞后 lag相似性解 similar solution局域相似 local similarity气体润滑 gas lubrication液体动力润滑 hydrodynamic lubrication浆体 slurry泰勒数 Taylor number纳维-斯托克斯方程 Navier-Stokes equation牛顿流体 Newtonian fluid边界层理论 boundary later theory边界层方程 boundary layer equation边界层 boundary layer附面层 boundary layer层流边界层 laminar boundary layer湍流边界层 turbulent boundary layer温度边界层 thermal boundary layer边界层转捩 boundary layer transition边界层分离 boundary layer separation边界层厚度 boundary layer thickness位移厚度 displacement thickness动量厚度 momentum thickness能量厚度 energy thickness焓厚度 enthalpy thickness注入 injection吸出 suction泰勒涡 Taylor vortex速度亏损律 velocity defect law形状因子 shape factor测速法 anemometry粘度测定法 visco[si] metry流动显示 flow visualization油烟显示 oil smoke visualization孔板流量计 orifice meter频率响应 frequency response油膜显示 oil film visualization阴影法 shadow method纹影法 schlieren method烟丝法 smoke wire method丝线法 tuft method氢泡法 nydrogen bubble method相似理论 similarity theory相似律 similarity law部分相似 partial similarity定理 pi theorem, Buckingham theorem静[态]校准 static calibration动态校准 dynamic calibration风洞 wind tunnel激波管 shock tube激波管风洞 shock tube wind tunnel水洞 water tunnel拖曳水池 towing tank旋臂水池 rotating arm basin扩散段 diffuser测压孔 pressure tap皮托管 pitot tube普雷斯顿管 preston tube斯坦顿管 Stanton tube文丘里管 Venturi tubeU形管 U-tube压强计 manometer微压计 micromanometer多管压强计 multiple manometer静压管 static [pressure]tube流速计 anemometer风速管 Pitot- static tube激光多普勒测速计 laser Doppler anemometer,laser Doppler velocimeter热线流速计 hot-wire anemometer热膜流速计 hot- film anemometer流量计 flow meter粘度计 visco[si] meter涡量计 vorticity meter传感器 transducer, sensor压强传感器 pressure transducer热敏电阻 thermistor示踪物 tracer时间线 time line脉线 streak line尺度效应 scale effect壁效应 wall effect堵塞 blockage堵寒效应 blockage effect动态响应 dynamic response响应频率 response frequency底压 base pressure菲克定律 Fick law巴塞特力 Basset force埃克特数 Eckert number格拉斯霍夫数 Grashof number努塞特数 Nusselt number普朗特数 prandtl number雷诺比拟 Reynolds analogy施密特数 schmidt number斯坦顿数 Stanton number对流 convection自由对流 natural convection, free convec-tion强迫对流 forced convection热对流 heat convection质量传递 mass transfer传质系数 mass transfer coefficient热量传递 heat transfer传热系数 heat transfer coefficient对流传热 convective heat transfer辐射传热 radiative heat transfer动量交换 momentum transfer能量传递 energy transfer传导 conduction热传导 conductive heat transfer热交换 heat exchange临界热通量 critical heat flux浓度 concentration扩散 diffusion扩散性 diffusivity扩散率 diffusivity扩散速度 diffusion velocity分子扩散 molecular diffusion沸腾 boiling蒸发 evaporation气化 gasification凝结 condensation成核 nucleation计算流体力学 computational fluid mechanics多重尺度问题 multiple scale problem伯格斯方程 Burgers equation对流扩散方程 convection diffusion equationKDU方程 KDV equation修正微分方程 modifieddifferential equation拉克斯等价定理 Lax equivalence theorem数值模拟 numerical simulation大涡模拟 large eddy simulation数值粘性 numerical viscosity非线性不稳定性 nonlinear instability希尔特稳定性分析 Hirt stability analysis相容条件 consistency conditionCFL条件 Courant- Friedrichs- Lewy condition ,CFL condition狄里克雷边界条件 Dirichlet boundarycondition熵条件 entropy condition远场边界条件 far field boundary condition流入边界条件 inflow boundary condition无反射边界条件nonreflecting boundary condition数值边界条件 numerical boundary condition流出边界条件 outflow boundary condition冯.诺伊曼条件 von Neumann condition近似因子分解法 approximate factorization method人工压缩 artificial compression人工粘性 artificial viscosity边界元法 boundary element method配置方法 collocation method能量法 energy method有限体积法 finite volume method流体网格法 fluid in cell method, FLIC method通量校正传输法 flux-corrected transport method通量矢量分解法 flux vector splitting method伽辽金法 Galerkin method积分方法 integral method标记网格法 marker and cell method, MAC method特征线法 method of characteristics直线法 method of lines矩量法 moment method多重网格法 multi- grid method板块法 panel method质点网格法 particle in cell method, PIC method质点法 particle method预估校正法 predictor-corrector method投影法 projection method准谱法 pseudo-spectral method随机选取法 random choice method激波捕捉法 shock-capturing method激波拟合法 shock-fitting method谱方法 spectral method稀疏矩阵分解法 split coefficient matrix method不定常法 time-dependent method时间分步法 time splitting method变分法 variational method涡方法 vortex method隐格式 implicit scheme显格式 explicit scheme交替方向隐格式 alternating direction implicit scheme, ADI scheme 反扩散差分格式 anti-diffusion difference scheme紧差分格式 compact difference scheme守恒差分格式 conservation difference scheme克兰克-尼科尔森格式Crank-Nicolson scheme杜福特-弗兰克尔格式Dufort-Frankel scheme指数格式 exponential scheme戈本诺夫格式 Godunov scheme高分辨率格式 high resolution scheme拉克斯-温德罗夫格式 Lax-Wendroffscheme蛙跳格式 leap-frog scheme单调差分格式 monotone difference scheme保单调差分格式 monotonicity preserving diffe-rence scheme穆曼-科尔格式 Murman-Cole scheme半隐格式 semi-implicit scheme斜迎风格式 skew-upstream scheme全变差下降格式 total variation decreasing scheme TVD scheme迎风格式 upstream scheme , upwind scheme计算区域 computational domain物理区域 physical domain影响域 domain of influence依赖域 domain of dependence区域分解 domain decomposition维数分解 dimensional split物理解 physical solution弱解 weak solution黎曼解算子 Riemann solver守恒型 conservation form弱守恒型 weak conservation form强守恒型 strong conservation form散度型 divergence form贴体曲线坐标 body- fitted curvilinear coordi-nates[自]适应网格 [self-] adaptive mesh适应网格生成 adaptive grid generation自动网格生成 automatic grid generation数值网格生成 numerical grid generation交错网格 staggered mesh网格雷诺数 cell Reynolds number数植扩散 numerical diffusion数值耗散 numerical dissipation数值色散 numerical dispersion数值通量 numerical flux 放大因子 amplification factor 放大矩阵 amplification matrix 阻尼误差 damping error离散涡 discrete vortex熵通量 entropy flux熵函数 entropy function分步法 fractional step method。
TAIWANESE JOURNAL OF MATHEMATICSVol.4,No.1,pp.9-20,March2000ON SHOCK W A VE THEORYTai-Ping Liu∗Dedicated to Fon-Che Liu on his sixtieth birthday Abstract.We survey the qualitative shock wave theory.The survey ismeant to explain some of the key issues close to the interest of the authorand raise open questions.1.Hyperbolic Conservation LawsThe simplest equations to describe the shock waves are the hyperbolic conservation lawsu t+f(u)x=0.The theory started with the investigation of the Euler equations in the gas dynamicsρt+(ρv)x=0,(ρv)t+(ρv2+p)x=0,(ρE)t+(ρEv+pv)x=0.The book Courant-Friedrichs[11]gives the acount of the efforts on the equa-tions by many of the leading mathematicians before1948.Starting about the’40s,it was realized that it is possible to describe some of the key features of the shock behaviour by the scalar equation.The math-ematical theory of well-posedness for scalar equation,u∈R1,even for several space dimension x∈R n,is now well-understood;cf.Krushkov[21].The the-ory for scalar law has been generalized to Hamilton-Jacobi equation.One of the interesting properties of the solution operator is the compactness property.Received December27,1999.Communicated by P.Y.Wu.2000Mathematics Subject Classification:35L67,76L05,35L65,35L05.Key words and phrases:Shock wave,conservation law.∗Research supported in part by NSF Grant DMS-9803323.910Tai-Ping LiuFor instance,for convex law,f (u)=0,there are two time-invariants and that the oscillation of the initial data is immediately damped;x[24].This inviscid dissipation is still conjectured for the incompressibleflow and easily understood for scalar conservation law.It sets apart the shock wave theory from other nonlinear wave theories.Two important elements of the theory for hyperbolic conservation laws are the entropy condition for shock waves and the compactness property of the solution operator due to the nonlinearity of theflux function f(u).The study of the consequences of these,particularly on the qualitative behaviour of the solutions,is the goal of the theory for hyperbolic conservation laws.There is the notion of genuine nonlinearity and the entropy condition of Lax[23]which are the generalization of the convexity of the scalarflux f (u)=0and the compressibility of the shocks.For systems of conservation laws,u∈R n,n≥2,there are rich wave interaction phenomena.The classical works of Glimm[17],Glimm-Lax[18] study the nonlinear wave interactions and qualitative behavior of the solutions. There are several subsequent works:DiPerna[12,13],and Liu[28,29,31]on regularity and large-time behavior.There is the wave tracing technique(Liu [30]),which yields the more definite form of the principle of nonlinear super-position and is useful for the study of solution behaviour.For systems which are not necessarily genuinely nonlinear,there is the entropy condition of Liu[27].The qualitative behaviour of the solutions is richer and more complex;see Liu[31],Cheng[9]and Chern[10].There are recent important developments in the well-posedness theory. One theory is based on Bressan[1]on the L1-stability for infinitesimal variation of the initial data;cf.Bressan-Crasta-Picolli[2].The other is to construct a time-decreasing nonlinear functional which is equivalent to the L1-distance of two solutions(Liu-Yang[38,39]).One can formulate as an easy consequence of the well-posedness theory the function class for which the uniqueness theory holds;cf.[3].The well-posedness theory is based on Glimm’s construction of solutions and the study of nonlinear wave interactions(Glimm[17]).Through the wave tracing mechanism(Liu[31]),the construction of the nonlinear functional (Liu-Yang[39])is reduced to the study of the effects of wave coupling between the solutions on their L1-distance.Central to this study is the introduction of a generalized entropy functional(Liu-Yang[38]).The generalized entropy functional makes effective usage of the nonlinearity of theflux and is new even for the basic inviscid Burgers equation.The idea in Liu-Yang[39]comple-ments and is orthogonal to the classical work of Glimm[17]on nonlinear wave interactions in a given solution.On Shock Wave Theory11 So far there are two theories for hyperbolic conservation laws.There is the aforementioned qualitative theory originated with Glimm’s seminal works and followed up with the recent well-posedness theory.The other theory is the existence theory base on the theory of compensated compactness,starting with the work of Tartar[49].There have been intensive activities on the existence theory for two conservation laws and some works on large-time behaviors; cf.[7]and references therein.The solutions obtained by this approach of compensated compactness have not been shown to possess the nonlinear wave behavior.As a consequence,the aforementioned well-posedness theory is not applicable to these solutions.A fundamental open problem is to study the qualitative behavior of a general weak solution,not necessarily the one constructed by a particular method.So far,it is not known,for instance,if a weak solution satisfies such a basic property of hyperbolic equations as thefinite speed of propagation.In fact,the verification of this would lead to the understanding of the nonlinear wave interaction property.Ultimately,one hopes to study the wave behaviors, such as local regularity(cf.[13,31]),and large-time behavior([28,29])of the solutions.Sufficient regularity of the solutions would allow the application of the aforementioned well-posedness theory.The compactness theory of Glimm-Lax[18]applies to2×2systems.It says that solutions with small sup norm but infinite variation norm initial data become of local bounded variation for any positive time.This is easily seen for scalar equations;x[24].For2×2systems,wave interactions are of third order due to the existence of the coordinates of Riemann invariants. This makes it possible to generalize the scalar compactness result to2×2 systems.It is not known whether such a strong compactness result holds for more general systems,such as the full3×3gas dynamics equations.2.Viscous Conservation LawsThat the role of viscosity is important has been recognized since the time of Stokes.It is essential in the discussion of the entropy condition for shock waves.Consider the viscous conservation lawsu t+f(u)x=(B(u,ε)u x)x,where B(u,ε)is the viscosity matrix.An important example is the Navier-Stokes equations in gas dynamicsρt+(ρv)x=0,(ρv)t=(ρv2+p)x=(µv x)x,(ρE)t+(ρEv+pv)x=(µvv x+κT x)x. The dissipation parametersεhere are the viscosityµand the heat conductivity κ.When the dissipation parametersεare turned off,the inviscid system12Tai-Ping Liubecomes the hyperbolic conservation lawsB(u,0)=0.When the hyperbolic conservation law is strictly hyperbolic,such as the Euler equations,a shock(u−,u+)satisfies the entropy condition if and only if it is the limit of viscous traveling wavesu(x,t)=ϕ(x−st),ϕ(±∞)=u±.For non-strictly hyperbolic conservation laws,the situation is more com-plicated and interesting,as we will see later.We mention here that vacuum in the gasflow gives rise to singularities different from the shocks.In fact, shocks vanish upon hitting the vacuum[36].For the interesting and impor-tant studies of the question of vacuum,see the article of Tong Yang in this issue.There has been a substantial progress on the stability of viscous waves for systems with artificial viscosityu t+f(u)x=εu xx;cf.Liu[35],Yu[52],Zumbrun-Howard[55]and the references therein.The main technique is the pointwise estimate,which yields the solution behav-ior on and offcharacteristic directions.It originates from the study of the perturbation of a constant state;see Liu[33].The study of viscous contact continuities remains largely open,though there is the preliminary work of Liu-Xin[37].In a forthcoming paper,Yu and the author have succeeded in solving the Riemann problem(Liu-Yu[42]).For hyperbolic conservation laws,the Riemann problemu(x,0)=u ,x<0u r,x>0has the simple scaling and the solution is a function of x/t,u(x,t)=ϕ(x/t). The viscous conservation laws do not have such simple scaling.For small time,the scaling is that of linear parabolic equations.The intermediate time is characterized by the hyperbolic scaling.The large-time contains a subtle logarithmic scaling as the result of interaction of rarefaction and compres-sion waves.This simple problem thus yields rich wave phenomena.By simple scaling,the large-time behaviour of the Riemann solution is also the zero dissi-pation limit.The zero dissipation limit is an important problem and has been studied only for local time when the shocks are isolated(Goodman-Xin[19], Yu[52]).It is important to consider the solution of the viscous conservationOn Shock Wave Theory13 laws when the dissipationεis nonzero but small.The compensated compact-ness approach yields zero dissipation limit for particular2×2systems,though without qualitative understanding of the solutions.For physical systems,the viscosity matrix B(u,ε)is in general degenerate and the viscous conservation laws are not uniformly parabolic,but hyperbolic-parabolic.There is the basic energy method for the dissipation about a con-stant state(Kawashima[20]).One interesting consequence of the hyperbolic-parabolic nature of the system is that the Green function for the linearized system containsδ-functions.This and the pointwise study of the diffusion waves can be found in Liu-Zeng[43].Much remains to be done for the study of nonlinear waves for the physical viscous conservation laws.The situation becomes more complicated when the inviscid system is not strictly hyperbolic.An important case concerns the intermediate shocks for magneto-hydrodynamics;cf.Freistuhler-Liu[15].There is also the example of combustions.Waves which are more compressive than the classical gas dy-namics shocks are physical only as viscous waves and not as inviscid waves. Thus the intermediate shocks are stable only if the perturbation is small com-pared to the strength of the dissipations.Waves less compressive depend,in both thier existence and structure,sensitively on the form of dissipations.For instance,the weak detonations and deflagrations in the combustions cannot be described by the inviscid theory of Chapman-Jouget;cf.[11].For these nonclassical shocks,see Liu[34]and the references therein.So far these waves are studied only for simplified systems and their study for the whole physical systems remains to be done.3.Shock and Reaction-Diffusion WavesShock waves are one kind of nonlinear waves.Two other important classes of nonlinear waves are dispersion waves and reaction-diffusion waves.It is,of course,important to relate these distinct classes because a general physical situation often exhibits waves of mixed types.For the study of the limit of the dispersve equations to hyperbolic conservation laws,see Lax-Levermore-Venakidis[22].We now illustrate with an important physical situation of combustions,which relate the shock waves with reaction-diffusion waves.There are two classes of combustion waves in gas:the high-speed detona-tion waves and low-speed deflagration waves.The strong detonation wave is led by a gas dynamics shock,which raises the temperature beyond the ignition point,and is then followed by a reaction zone.Thus the strong detonation wave is dominated by the shock wave.The weak detonation wave is supersonic and precedes gas dynamics waves.Thus it is a reaction-diffusion wave.The slow-speed weak deflagration wave is usually studied by the reaction-diffusion14Tai-Ping Liuequations.This is done by assuming that the underlying gasflow is given and not affected by the reaction.To study the combustion waves in gas,there is the classical Chapman-Jouget inviscid theory(Courant-Friedrichs[11]).The theory is adequate for the strong detonations.To study the weak detonations and weak deflagra-tions,the role of diffusions becomes important.In fact,the existence of these waves depends sensitively on the dissipation parameters,a common feature of undercompression waves[34].There is analysis of weak detonations for a simple model of Rosales-Majda[46]in Liu-Yu[41].As indicated above,the analysis necessarily contains thinking of reaction-diffusion waves.The chemi-cal nonlinearity is more important than the gas dynamics nonlinearity for the stability analysis.The simplest realistic physical model for the gas combustions is the reactive Navier-Stokes equations.It would be interesting to study the stability of weak detonations and weak deflagrations for the reactive Navier-Stokes equations. Besides the reaction-diffusion nature of these waves,one needs also to consider the interactions with the gas dynamics waves as mentioned in the last section. The combustion waves for the reactive Navier-Stokes equations have been constructed in Gasser-Szmolyan[16].4.Conservation Laws and Dynamics SystemsThe rich theory for ODE,e.g.,KAM theory and chaos,has begun to have impact on nonlinear PDEs.There are,for instance,works on semilinear wave equations.For conservation laws,there are interesting works for scalar conser-vation laws using the ideas from dynamics systems,e.g.,[14,47].One property of the scalar equation,which is essential for these analyses,is the maximum principle.For systems,the maximum principle cannot hold due to nonlinear wave interactions.Clearly,rich phenomena await to be discovered for the sys-tem of conservation laws with sources.Possible topics include the study of time-periodic solutions,the KAM-type behavior and so forth.We mention here a recent work where the small divisor problem arises in the study of dis-crete traveling waves(Liu-Yu[40]).Consider the conservativefinite difference scheme for the hyperbolic conservation lawsu n+1−u n(x)∆t =F[u n](x+12∆x)−F[u n](x−12∆x)∆x,where u n(x)approximates u(n∆t,x)and the functional F[u]satisfies F[¯u]= f(¯u)for any constant function¯u.We have in mind the basic schemes such as the Lax-Friedrichs and Godunov schemes.It is well-known that discreteOn Shock Wave Theory15systems are harder than the corresponding continnum systems.To gain basic understanding,[40]considers the traveling waves for the difference schemes. For the continuous PDEs,the speed s of a wave can always be made zero through a change of independent variables x and t.For the discrete systems, however the C-F-L speed s∆t/∆x is an important variable.If it is rational, then the wave repeats itself afterfinite steps.For scalar equations,it has been shown that the traveling waves exist and behave similar to the viscous shocks.For systems,there is the striking dependence of the wave shape on the Diophantine property of the C-F-L speed.This is due to the interaction of waves of different characteristic families,which yields the small divisor prob-lem.In[40]it is shown that waves whose speeds are Diophantine exist and are nonlinear stable,but with tail behaviour different from viscous shocks.This singular behaviour is only begun to be understood and consistent with careful numerics.We don’t know what happens when the Diophantine property of the wave speed becomes weaker.Deeper understanding requires ideas from discrete dynamics systems.5.Multi-Dimensional Gas FlowsMuch of the deep works that have been done for systems of hyperbolic conservation laws are for one space dimension.There are studies of partic-ular solutions for the compressible Euler equations in more than one space dimensionsρt+mj=1(ρv j)xj(ρv i)+mj=1(ρv i v j)xj+p xi=0,i=1,2,...,m,(ρE)t+mj=1(ρEv j+pv j)xj=0.The classical book of Courant-Friedrichs[11]is still the good source for these. Self-similar solutions have been constructed;see also Zhang-Zheng[54].One characteristic of such a solution is that the gasflows around a solid bound-ary.The solid boundary,the obstacle,has simple geometrical property and defines theflow.The obstacle also helps to stablize theflow and allows for interesting global wave patterns.Examples include spherical waves pushed by an expanding piston and three-dimensionalflow around a cone.It would be interesting to study the nonlinear stability of these self-similarflows.For two-dimensional sursonic stationaryflows one may view one space dimension as time.The situation is then like one space dimension and methods such as the random choice method can be used for stablity study.16Tai-Ping LiuThere are two works on three-dimensionalflow around a cone.For straight cone,theflow is self-similar[11].There is the linearized approach for the study of theflow when the tip of the cone is perturbed(Chen[8]).The Euler equation is singular near the tip and there is delicate analysis of closure in the iterations. The global stability when the cone,away from the tip,is perurbed is done in Lien-Liu[26]using the locally self-similarflows as building blocks in the approximation.The approach is nonlinear and global because one chooses as building blocks the self-similarflows,which represents the farfield behaviour of theflow.There is the local existence of shock propagation based on the linear theory; cf.Majda[44].To mimic the one-dimensional theory and try to study the generalflow without the boundary may not be realistic.In particular,the multi-dimensional Riemann problem is hard,even though the solution is self-similar u(x,t)=φ(x/t),which reduces the dimension of independent variables by one(Li-Zhang-Yang[25]).The resulting Euler equations are then of mixed types. Nonlinear equations of mixed types are involved when one tries to resolve the so-called von Neumann paradox on the transition from regular reflection to Mach reflection in the gasflow around the ramp[11].So far the only analysis is about the algebraic studies of local wave patterns.Fully nonlinear PDE approach is needed for the resolution of the difficult transition problem.6.Microscopic ModelsShock waves are singular,stable occurring in compressible media.It is irreversible.These characteristics make it an interesting and necessary task for study,particularly when the model contains dissipation more general than the viscosity.This is so for the Boltzmann equation and various kinetic models. There are also the particle interacting models,where the dissipation usually comes from the randomness.One such model is the relaxation model.For a basic study of the simple model of a conservation law and a rate equationv t+f(v,w)x=0,w t+g(v,w)x=(W(v)−w)/ε,see Liu[32];see also Chen-Levermore-Liu[6]for more general systems.Many kinetic models are of relaxation type[5,51].Basic understandings are gained by comparing the relaxation model with the viscous conservation laws obtained through the Chapman-Enskog expansion([32,6],Zeng[53]).This approach has the shortcoming that the partial dispersive nature of the models is not considered.It would be nice to study the difference between the relaxationOn Shock Wave Theory17 model and the associated viscous conservation laws,such as the existence of subshocks in a smooth traveling wave[32,51].The Boltzmann equation is dissipative as seen from the Chapman-Enskog expansion relating it to the Navier-Stokes equations[5].However this is so only for large time when waves are sufficiently spreading out.There are works on the Boltzmann shocks,the traveling waves,based on the perturbation from the Navier-Stokes shocks.Such a perturbation method has been successful in dealing with dissipation waves in the time-asymptotic region(Nishida-Imai [45]).For strongly nonlinear soluitons such as the shocks,the method fails to obtain the physical shocks[4].One needs to come up with a fully nonlin-ear method for the Boltzmann equation,different from those effective for the viscous conservation laws.There are progresses in recent years on the macroscopic limits for the interacting particle systems with randomness;cf.Varadhan-Yau[50].The idea is the sophisticated central limit theorem that works for the situation when the macroscopic solutions,those of the compressible Euler equations, are smooth.It would be interesting to consider the situation when the Euler solutions contain shocks.Again,more nonlinear thinking is needed.References1. 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Department of Mathematics,Stanford UniversityStanford,CA94305,U.S.A.E-mail:liu@。