A kinetic and equilibrium studyof competitive adsorption b

高一物理力学原理英语阅读理解25题1<背景文章>Newton's three laws of motion are fundamental principles in physics that have had a profound impact on our understanding of the physical world.The first law, also known as the law of inertia, states that an object at rest will stay at rest, and an object in motion will stay in motion with the same speed and in the same direction unless acted upon by an unbalanced force. For example, a book lying on a table will remain there until someone pushes or pulls it. This law was revolutionary as it challenged the then - existing ideas about motion. Newton discovered this law through his careful observations and experiments.The second law of motion is expressed as F = ma, where F is the net force acting on an object, m is the mass of the object, and a is the acceleration. This law explains how the force applied to an object is related to its mass and acceleration. In real - life applications, when you push a shopping cart, the harder you push (greater force), the faster it will accelerate, given that the mass of the cart remains the same.The third law states that for every action, there is an equal and opposite reaction. A classic example is when a rocket launches. The rocket expels gas downward (action), and in return, the gas exerts an equal andopposite force on the rocket, propelling it upward (reaction). Newton's discovery of these laws was a milestone in the history of science and has been used in various fields such as engineering, astronomy, and transportation.1. <问题1>A. According to Newton's first law, if an object is moving in a straight line at a constant speed, what will happen if no unbalanced force acts on it?A. It will gradually slow down.B. It will keep moving at the same speed and in the same direction.C. It will suddenly change direction.D. It will stop immediately.答案：B。

高三英语学术论文的阅读单选题40题1.The author's argument is cogent, but some critics find it controversial. The word "cogent" means _____.A.weakB.persuasiveC.confusingD.boring答案：B。

“cogent”的意思是“有说服力的”。

选项A“weak”表示“弱的”；选项C“confusing”表示“令人困惑的”；选项D“boring”表示“无聊的”。

在学术语境中，“cogent”常用来形容论证、观点等具有说服力。

2.The study presents a comprehensive analysis of the problem. The word "comprehensive" means _____.A.narrowB.partialC.thoroughD.superficial答案：C。

“comprehensive”的意思是“全面的、彻底的”。

选项A“narrow”表示“狭窄的”；选项B“partial”表示“部分的”；选项D“superficial”表示“表面的”。

在学术语境中，“comprehensive”常用来形容对某一问题的分析很全面。

3.The researcher's hypothesis is tenable. The word "tenable" means _____.A.impossibleB.doubtfulC.reasonableD.absurd答案：C。

“tenable”的意思是“站得住脚的、合理的”。

选项A“impossible”表示“不可能的”；选项B“doubtful”表示“可疑的”；选项D“absurd”表示“荒谬的”。

在学术语境中，“tenable”常用来形容假设、观点等合理。

equilibrium英文解释Equilibrium is a fundamental concept in physics, chemistry, economics, and other fields, referring to a state of balance or stability where opposing forces or influences are balanced, resulting in no net change or motion. In other words, it is a state where the system is at rest or in a constant state of motion, with no tendency to change.In physics, equilibrium is often described as the state where a system is in a state of dynamic balance, with all forces acting on it canceled out by opposing forces. This can be seen in mechanical systems, where objects are atrest or moving with constant velocity, or in thermodynamic systems, where the system is in a state of thermal balance, with no net heat flow.In chemistry, equilibrium is typically referred to as a state where a chemical reaction proceeds in both directions at the same rate, resulting in no net change in theconcentrations of the reactants and products. This state is known as chemical equilibrium, and it is described by the law of mass action, which states that the rate of a chemical reaction is proportional to the product of the concentrations of the reactants.In economics, equilibrium is often described as a state where the supply and demand for a particular good or service are balanced, resulting in a stable price. This state is known as market equilibrium, and it is described by the law of supply and demand, which states that the price of a good or service will adjust to balance the quantity supplied with the quantity demanded.In all these fields, equilibrium is an important concept because it represents a state of stability and predictability. When a system is in equilibrium, it is generally easier to understand and predict its behavior than when it is in a state of flux or change. Additionally, equilibrium states often correspond to optimal or most efficient conditions, making them important targets for engineering, economic policy, and other applications.However, it is important to note that equilibrium is not always a static or unchanging state. In many systems, equilibrium is a dynamic state, with small fluctuations or perturbations constantly occurring. These fluctuations can be caused by external influences, internal fluctuations in the system, or random events. In these cases, the system will continually adjust to maintain the balance orstability of the equilibrium state.Additionally, it is worth noting that achieving or maintaining an equilibrium state can often be challenging. In many cases, it requires careful control or management of the system, as well as an understanding of the interactions and dependencies within the system. For example, in economic systems, maintaining market equilibrium often requires government intervention or regulation to prevent market failures or excesses. In physical systems, achieving equilibrium may require precise control of external conditions or the manipulation of system parameters.In conclusion, equilibrium is a fundamental conceptthat describes a state of balance or stability in various fields. It represents a state where opposing forces or influences are balanced, resulting in no net change or motion. While equilibrium may be seen as a static or unchanging state in some cases, it is often a dynamic state that requires careful management and control to maintain. Understanding and manipulating equilibrium states iscrucial in many fields, including physics, chemistry, economics, and engineering, and has important applications in real-world scenarios.。

2022年考研考博-考博英语-西北大学考试全真模拟易错、难点剖析AB卷（带答案）一.综合题(共15题)1.单选题Tom wasn't happy about the delay, and （）.问题1选项A.I was neitherB.I wasn't neitherC.neither was ID.either was I【答案】C【解析】句意：汤姆对耽搁很不高兴，我也是。

根据句意可知，前后表示同样的情况，肯定用So+助动词+主语，否定用Neither+ 助动词+主语，所以选项C正确。

2.单选题George Gallup, Jr ., the man who makes and（）his reputation （）knowing what Americans think, has brought all his polling strategies together to identify and analyze what he calls future forces.问题1选项A.challenges...onB.stakes...onC.hazards...toD.bets...to【答案】B【解析】challenge…on在……方面挑战；stake…on把赌注押在……上面；hazard...to 对……有危险；bet不与to搭配。

句意：George Gallup，Jr .这个把自己的名誉押在知晓美国人想法上的人，将所有的投票策略集中到一起，以确定和分析他所说的未来力量。

选项B符合句意。

3.单选题In a world that aims to eliminate hunger and disparities in wealth, globe equilibrium is vital.问题1选项A.equityB.balanceC.inequalityD.discretion【答案】C【解析】根据句意可知，这里是消除贫富差距。

彭桓武留欧期间的科学贡献刘金岩【摘要】彭桓武,中国著名理论物理学家,"两弹一星"功勋奖章获得者.1938年至1947年,彭桓武先后在英国爱丁堡大学、爱尔兰都柏林研究院理论物理所学习工作.彭桓武回国后曾参与组织中华人民共和国核武器理论设计工作并注重培养理论物理人才.基于档案、书信以及手稿等资料,介绍彭桓武留欧期间与玻恩、薛定谔、海特勒等物理学家的交往.此外,尝试评述彭桓武早期在固体物理、介子理论和量子场论等方面的研究工作.从而,有助于理解彭桓武回国后在中国核武器理论设计和理论物理发展方面的贡献.%Huan-wu Peng ( 1915 ~2007 ) was a famous Chinese theoretical physicist. From 1938 to 1947 , he successively studied and worked in the University of Edinburgh and Dublin Institu-te for Advanced Studies in Ireland. After he came back China in 1947, Peng committed himself to the theoretical designs of nuclear weapons and cultivating young talents. Based on primary and other historical materials, this article makes a special inquiry into Peng's association with M. Born, E.Schr?dinger and W. H. Heitler. Moreover, it also attempts to make a preliminary comments on Peng's work on solid state physics, Meson theory and quantum field theory. All of the above men-tioned could be helpful to understand Peng's contributions to the theoretical design of nuclear weapon and theoretical physics' development in China.【期刊名称】《自然科学史研究》【年(卷),期】2018(037)001【总页数】17页(P87-103)【关键词】彭桓武;玻恩;薛定谔;介子理论;量子场论【作者】刘金岩【作者单位】中国科学院自然科学史研究所,北京 100190【正文语种】中文【中图分类】N092;K826.1彭桓武(1915～2007)是新中国核武器理论设计和理论物理研究的奠基者之一。

sat物理知识点总结SAT Physics is a subject test designed to assess students' knowledge and understanding of various physics concepts and principles. It covers a wide range of topics, including mechanics, electricity and magnetism, waves, optics, heat and thermodynamics, and modern physics. This knowledge summary will provide an overview of the key concepts and principles tested on the SAT Physics exam.MechanicsMechanics is the branch of physics that deals with the motion of objects and the forces that cause or influence that motion. It is a fundamental topic in physics and is tested extensively on the SAT Physics exam. Some of the key concepts and principles in mechanics include:1. Kinematics: Kinematics is the study of motion without considering the forces that cause it. It includes concepts such as displacement, velocity, acceleration, and equations of motion.2. Newton's laws of motion: Newton's laws of motion are fundamental principles that describe the behavior of objects in response to forces. They include the first law (inertia), the second law (F = ma), and the third law (action and reaction).3. Work, energy, and power: These concepts are related to the transfer and transformation of energy in mechanical systems. They include the work-energy theorem, kinetic and potential energy, and power.4. Linear momentum and collisions: Linear momentum is the product of an object's mass and velocity, and it is conserved in isolated systems. Collisions between objects involve the transfer of momentum and kinetic energy.5. Circular motion and gravitation: Circular motion is the motion of an object along a curved path, and it involves centripetal acceleration and centripetal force. Gravitation is the force of attraction between objects with mass, and it is described by the law of universal gravitation. Electricity and MagnetismElectricity and magnetism are closely related phenomena that are fundamental to many aspects of modern technology. The SAT Physics exam covers a range of topics related to electricity and magnetism, including:1. Electric fields and forces: Electric fields are regions of space around charged objects where electric forces are exerted on other charged objects. The strength and direction of the electric field can be calculated using Coulomb's law.2. Electric potential and capacitance: Electric potential is a measure of the potential energy per unit charge in an electric field. Capacitance is a measure of an object's ability to store electric charge.3. Electric circuits: Electric circuits are systems of conductors and components through which electric current can flow. They can be analyzed using principles such as Ohm's law and Kirchhoff's laws.4. Magnetic fields and forces: Magnetic fields are regions of space around magnets or current-carrying conductors where magnetic forces are exerted on other magnetic or current-carrying objects. The strength and direction of the magnetic field can be calculated using the right-hand rule.5. Electromagnetic induction: Electromagnetic induction is the process by which a changing magnetic field induces an electric current in a conductor. It is the principle behind generators and transformers.Waves and OpticsWaves and optics are important topics in physics that describe the behavior of light and other types of waves. The SAT Physics exam covers a range of topics related to waves and optics, including:1. Wave properties: Waves are disturbances that propagate through a medium or space, and they can be described in terms of properties such as wavelength, frequency, amplitude, and speed.2. Interference and diffraction: Interference is the interaction of two or more waves, leading to the reinforcement or cancellation of their amplitudes. Diffraction is the bending of waves around obstacles and through apertures.3. Ray optics: Ray optics describes the behavior of light as it interacts with lenses, mirrors, and other optical components. It can be used to understand phenomena such as reflection, refraction, and image formation.4. Wave optics: Wave optics describes the behavior of light as a wave, including phenomena such as interference, diffraction, and polarization.Heat and ThermodynamicsHeat and thermodynamics are important topics in physics that describe the behavior of thermal energy and the principles underlying processes such as heat transfer and thermodynamic cycles. The SAT Physics exam covers a range of topics related to heat and thermodynamics, including:1. Temperature and thermal equilibrium: Temperature is a measure of the average kinetic energy of the particles in a substance, and thermal equilibrium is the condition in which two objects have the same temperature.2. Heat transfer: Heat can be transferred between objects through conduction, convection, and radiation. These processes depend on factors such as temperature difference, material properties, and surface area.3. Laws of thermodynamics: The laws of thermodynamics describe the behavior of energy in thermodynamic systems, including principles such as conservation of energy, entropy, and the second law of thermodynamics.4. Ideal gases and the ideal gas law: Ideal gases are theoretical gases that obey the ideal gas law, which relates the pressure, volume, and temperature of a gas.Modern PhysicsModern physics is a branch of physics that deals with phenomena that cannot be explained by classical physics, including topics such as quantum mechanics and relativity. The SAT Physics exam covers a range of topics related to modern physics, including:1. Quantum mechanics: Quantum mechanics is the branch of physics that describes the behavior of matter and energy at the atomic and subatomic scales. It includes concepts such as quantization, wave-particle duality, and the uncertainty principle.2. Atomic and nuclear physics: Atomic and nuclear physics describe the behavior of atoms and atomic nuclei, including topics such as atomic structure, radioactivity, and nuclear reactions.3. Special relativity: Special relativity is a theory describing the behavior of objects moving at high speeds, including principles such as time dilation, length contraction, and the equivalence of mass and energy.4. Particle physics: Particle physics is the study of the fundamental particles and forces that make up the universe, including topics such as elementary particles, the standard model, and the properties of forces and interactions.In addition to these key topics, the SAT Physics exam also covers a range of practical skills related to experimental design, data analysis, and mathematical problem-solving. It is important for students to develop a strong understanding of the fundamental concepts and principles of physics, as well as the ability to apply this knowledge in various contexts. By mastering the key topics and skills tested on the SAT Physics exam, students can improve their performance and achieve success on the test.。

A Comprehensive Modeling Study of Hydrogen OxidationMARCUS´O CONAIRE,1HENRY J.CURRAN,2JOHN M.SIMMIE,1WILLIAM J.PITZ,3 CHARLES K.WESTBROOK31National University of Ireland,Galway,Ireland2Galway-Mayo Institute of Technology,Galway,Ireland3Lawrence Livermore National Laboratory,Livermore,CA94551Received19November2003;accepted28May2004DOI10.1002/kin.20036Published online in Wiley InterScience().ABSTRACT:A detailed kinetic mechanism has been developed to simulate the combustion ofH2/O2mixtures,over a wide range of temperatures,pressures,and equivalence ratios.Over theseries of experiments numerically investigated,the temperature ranged from298to2700K,thepressure from0.05to87atm,and the equivalence ratios from0.2to6.Ignition delay times,flame speeds,and species composition data provide for a stringent testof the chemical kinetic mechanism,all of which are simulated in the current study with varyingsuccess.A sensitivity analysis was carried out to determine which reactions were dominatingthe H2/O2system at particular conditions of pressure,temperature,and fuel/oxygen/diluentratios.Overall,good agreement was observed between the model and the wide range of exper-iments simulated.C 2004Wiley Periodicals,Inc.Int J Chem Kinet36:603–622,2004INTRODUCTIONThe prospect of a hydrogen-based economy has prompted increased interest in the use of hydrogen as a fuel given its high chemical energy per unit mass and cleanliness.It appears that most of the technologi-cal problems in using hydrogen in spark-ignited inter-nal combustion engines,including NO x emissions[1], have now been solved;vehicular on-board storage is probably the one remaining difficulty[2,3].There is also continued interest in developing a bet-ter understanding of the oxidation of hydrocarbon fu-Correspondence to:Henry J.Curran;e-mail:henry.curran@ nuigalway.ie.Contract grant sponsor:Higher Education Authority of Ireland.Contract grant number:PRTLI-II.c 2004Wiley Periodicals,Inc.els[4]over a wide range of operating conditions in order to increase efficiency and to reduce the emis-sion of pollutant species.All,or almost all petrochem-ical,fuels are hydrocarbons which burn to form carbon dioxide and water.Thus,the development of a detailed kinetic mechanism for hydrocarbon oxidation neces-sarily begins with a hydrogen/oxygen submechanism, followed by the addition of CO chemistry.In recent years,many kinetic studies of hydrogen oxidation have concentrated on a single set of experi-mental results obtained either in shock tubes,or inflow reactors or inflames;these have been simulated using a detailed kinetic mechanism.This procedure has been criticized recently by Smith[5]who asserts that uncer-tainty limits on individual reaction rate constants pro-duce a parameter space of possible mechanisms still too imprecise for accurate prediction of combustion properties such asflame speed or ignition delay,thus604´O CONAIRE ET AL.requiring additional system data.Smith adds that low pressure and counterflowflames,mixtures in shock tubes,andflow or well-stirred reactors are examples of such experimental environments.It is the aim of this study to apply a hydrogen kinetic mechanism to as broad a range of combustion environments as possible.There have been a very large number of measure-ments made on the reaction between hydrogen and oxy-gen.These includeflame speed measurements,burner-stabilizedflames in which species profiles are recorded, shock tube ignition delay times,and concentration pro-files inflow reactor studies.This study aims to simu-late these experiments using a detailed chemical kinetic mechanism which takes its origin from Mueller et al.[6]in their study of hydrogen oxidation in aflow re-actor.Mueller and coworkers validated their mecha-nism using only theirflow reactor data over the tem-perature range850–1040K,at equivalence ratios of 0.3≤φ≤1.0,pressures of0.3to15.7atm and resi-dence times of0.004to1.5s.We have exercised their mechanism against shock-tube data,burner-stabilized flame experiments,andflame speed data and have made modifications to some of the kinetic parameters in or-der to achieve better overall agreement between mecha-nism simulations and this broader range of experimen-tal results.Previously,Marinov et al.[7]had also devel-oped a detailed H2/O2kinetic mechanism to simulate shock tube,flame speed,and burner-stabilizedflame experiments with good agreement between model and experiment but a large body of data sets have become available since then.Therefore,this study presents a new detailed chemical kinetic mechanism for hydro-gen oxidation but with increased attention paid to ex-periments conducted at high pressures since internal combustion engines operate at elevated pressures.Davis et al.[8]have recently presented a re-examination of a H2/CO combustion mechanism in which they simulated some of the experimental data included in this study.Their work was motivated by new kinetic parameters for the important reaction ˙H+O2+M=H˙O2+M and by new thermodynamic data for˙OH,and had the objective of optimizing their H2/CO model against experiment.IGNITION DELAYS IN SHOCK WAVESSchott and Kinsey[9]measured ignition delay times of two H2/O2/Ar fuel mixtures behind incident shock waves over a wide range of reactant densities in the temperature range1085–2700K and at1atm. Skinner and Ringrose[10]measured the ignition de-lays of an H2/O2/Ar mixture in the temperature range 965–1076K and at a reflected shock pressure of 5atm.Asaba et al.[11]performed experiments inthe temperature range1500–2700K,at reflected shockpressures of178–288Torr,at an equivalence ratio,φ,of0.5and with98%argon dilution.Fujimoto and Sujiki[12]measured ignition delay times of stoichiometricH2/O2/Ar fuel mixtures in the reflected shock pressurerange1.3–5atm and in the temperature range700–1300K.Hasegawa and Asaba[13]measured ignitiondelays in the temperature range920–1650K,at a re-flected shock pressure of5.5atm,withφ=0.25at94%argon dilution.Bhaskaran et al.[14]reported ignitiondelay times for a29.59%H2,14.79%O2,55.62%N2mixture in the temperature range1030–1330K and ata constant reflected shock pressure of2.5atm.More recently,Slack[15]studied stoichiometrichydrogen–air mixtures in a shock tube and measuredinduction times near the second explosion limit.Theexperiments were performed at a reflected shock pres-sure of2atm in the temperature range980–1176K.Cheng and Oppenheim[16]reported ignition delaytimes for a6.67%H2,3.33%O2,and90%Ar mixture inthe temperature range1012–1427K and at a reflectedshock pressure,P5 1.9atm.Koike[17]measured ignition delay times for two hydrogen/oxygen/argonfuel mixtures of incident shock pressure20Torr in thetemperature range1000–1040K.In a methane shock-tube study,Hidaka et al.[18]carried out some measurements of a H2/O2/Ar mix-ture at1250–1650K and at reflected shock pressuresof1.6–2.8bar.Petersen et al.[19]measured high-pressure(33–87atm)H2/O2/Ar reflected shock igni-tion delays at1189–1876K and at an equivalence ratioof1.0in every case for six mixtures.Petersen et al.[20]measured reflected ignition delay times in threehighly dilute H2/O2/Ar mixtures at temperatures of1010–1750K,equivalence ratio range1.0≤φ≤1.47and around atmospheric pressure.Finally,Wang et al.[21]carried out reflected shock measurements in vari-ous H2/air/steam mixtures at954–1332K and pressuresof3.36–16.63atm.Hydrogen concentration was15%of air throughout.FLAME MEASUREMENTSAtmospheric Flame Speed Measurements Very many hydrogen/airflame speed studies have been performed at atmospheric pressure,over various ranges of equivalence ratio.Koroll et al.[22]reported data in the equivalence ratio range0.15≤φ≤5.5, Iijima and Takeno[23]in the range0.5≤φ≤3.9,and Takahashi et al.[24]in the range1≤φ≤4.How-ever,these data did not account for the effects of flame stretch.A COMPREHENSIVE MODELING STUDY OF HYDROGEN OXIDATION 605The earliest stretch-corrected atmospheric hydro-gen/air flame speed experiments were performed by Wu and Law [25]in the range 0.6≤φ≤6.Since then,stretch-corrected flame speeds,all of which were per-formed at 1atm,have been reported at various equiva-lence ratio ranges:Egolfopoulos and Law [26](0.25≤φ≤1.5),Law [27](0.4≤φ≤1.5),Vagelopoulos et al.[28](0.3≤φ≤0.55),Dowdy et al.[29](0.3≤φ≤5),and Aung [30](0.3≤φ≤5)and Tse et al.[31](0.4≤φ≤4),Fig.1.The measurements of Takahashi et al.[24]are con-siderably faster than the rest of the data and 10%faster than the intermediate values of Tse et al.and Dowdy et al.at an equivalence ratio of 1.75.The slowest flame speeds are those of Aung et al.[30]that have a maxi-mum flame speed of 2.6m s −1at φ=1.65.The authors point to possible greater stretch effects than accounted for to explain the relative slowness of their data.The Koroll et al.values [22],on the other hand,are much faster than any other between 1.0≤φ≤2.5.The re-cent flame speed measurements of Dowdy et al.[29]and Tse et al.[31]probably are the most representa-tive of the entire data set;they have a maximum flame speed of 2.85m s −1at φ=1.75.Lamoureux et al.[32]very recently measured the speeds of freely propagating flames in a spherical bomb for five H 2/air mixtures using a diluent consisting of CO 2+He to mimic the effect of water vapor on flame speed.The mixtures were composed of as follows:x (40%He +60%CO 2)+(1−x )(H 2+air),wherexFigure 1Atmospheric H 2/O 2/air flame speeds versus equivalence ratio,T i =298K. Koroll et al.[22], +Iijima and Takeno [23], Takahashi et al.[24];stretch corrected: ×Wu and Law [25]×Egolfopoulos and Law [26],•Law [27],⊕Vagelopoulos et al.[28], Dowdy et al.[29],+Aung et al.[30],and Tse et al.[31].ranged from 0.0to 0.4,and with synthetic air of com-position O 2:N 2=20:80.High-Pressure Flame SpeedsIn addition to their atmospheric flame speed measure-ments,Tse et al.[31]also measured mass burning velocities for H 2/O 2/He mixtures in the equivalence ratio range 0.5≤φ≤3.5and between 1and 20atm at an initial temperature of 298K.It was reported that flames became increasingly unstable at elevated pres-sures.For this reason,true stretch-free flame speeds become more diffcult to measure.Experimentally,in the case of the 10–20atm data,the oxygen to fuel ratio was reduced to suppress diffusional-thermal instabil-ity and delay hydrodynamic ing helium as the diluent also helped minimize instability up to 20atm by reducing the Lewis number of the flame and retarding the formation of flame cells.Stretch-free flame speeds have only been available up to a few at-mospheres.The oxygen to helium ratio at 1to 5atm was 1:7(12%dilution)and at elevated pressures,this ratio was 1:11.5(8%dilution).Burner-Stabilized FlameIn their investigation of a rich 18.83%hydrogen,4.6%oxygen,and 76.57%nitrogen flame at atmospheric pressure,Dixon-Lewis and Sutton [33]measured the temperature pro file and the concentration pro files of the stable species in the flame,above and below the burner.Flame structure measurements had been car-ried out by Kohse-H ¨Oinghaus et al.[34]who measured˙Hand ˙OH radical concentrations versus distance in a H 2/O 2/Ar flame,at a pressure of 95mbar,in the equiva-lence ratio range 0.6≤φ≤1.4and in the temperature range 1100–1350K.Vandooren and Bian [35]investi-gated the structure of a rich H 2/O 2/Ar flame over a flat burner at a pressure of 35.5Torr and at an equivalenceratio of 1.91.They reported H 2,O 2,H 2O,˙H,˙O,and ˙OH species mole fractions versus distance above the burner.Flow ReactorsMueller et al.[6]measured H 2,O 2,and H 2O pro files over the temperature range 850to 1040K,at equiva-lence ratios of 0.3≤φ≤1.0in the pressure range from 0.3to 15.7atm and over a range of residence times of 0.004to 1.5s.Previously,Yetter et al.[36]reported atmospheric H 2,O 2,and H 2O pro files at 910K,and at an equivalence ratio of 0.3.606´O CONAIRE ET AL.Experiments SimulatedA representative selection of recent experimental work has been chosen to validate the H2–O2combustion mechanism.The chosen experiments were1.the ignition delay times measured by Schott andKinsey[9],Skinner and Ringrose[10],Fujimotoand Suzuki[12],Bhaskaran and Gupta[14],Slack[15],Cheng and Oppenheim[16],Petersenet al.[19],Hidaka et al.[18],Petersen et al.[20],and Wang et al.[21].Simulations of the dataof Asaba et al.[11],Hasegawa and Asaba[13],and Koike[17]were not attempted in this studybecause of a lack of sufficient information.2.theflame speed measurements of Dowdy et al.[29].Theseflame speeds not only span a widerange of equivalence ratio but are in agreementwith the more recent values of Tse et al.[31].Dowdy and coworkers also measured the tem-perature profiles,thus making their data moreamenable to simulation.3.the high-pressureflame speed measurements ofTse et al.[31].This data is the only set wherehydrogenflame speeds have been measured atpressures greater than5atm.4.the very lean H2/air and H2/air/CO2/Heflamespeed measurements of Lamoureux et al.[32].5.the burner-stabilizedflame profiles of Vandoorenand Brian[35]in which reactant and intermedi-ate species concentrations were measured as afunction of height above the burner surface.Alsoincluded are the species profiles of Dixon-Lewisand Sutton[33].6.the comprehensiveflow reactor data of Muelleret al.[6]along with a single data set from Yetteret al.[36].CHEMICAL KINETIC MODELINGThe chemical kinetic mechanism was developed and simulations performed using the HCT program[37]. Initially,ignition delay times measured by Slack[15], Fig.8,and Hidaka et al.[18],Fig.7,and theflow re-actor experiments of Mueller et al.[6],Fig.25,were simulated with very good agreement observed between experiment and model.The mechanism was then con-verted into Chemkin3.6[38]format and the simula-tions repeated in order to compare results from both codes,which were in very good agreement as expected. Thereafter,all other experiments including theflame speeds and the burner-stabilizedflame profiles were simulated using only the Chemkin applications.Thermodynamic and Transport Properties The H2/O2reaction mechanism consists of19reversible elementary reactions,Table I,togetherwith the thermochemical data,Table II.Reverse rateconstants were computed by microscopic reversibility.The thermochemical data for each species consideredin the mechanism are from the Chemkin thermody-namic database[51]with the exception of two:1. H f(H˙O2,298K)of3.0kcal mol−1,from Hillsand Howard[52]which is in good agreementwith the recent reappraisal by Ramond et al.[53]of3.2±0.5kcal mol−1.2. H f(˙OH,298K)of8.91kcal mol−1which isbased on recommendations by Ruscic et al.[54]and Herbon et al.[55].The Chemkin database of transport parameters wasused without modification.As in the study of Tseet al.[31],the kinetic parameters of helium were as-sumed equal to those of argon in order to simulateflame propagation where helium is the diluent.As Tseet al.noted,using the third-body efficiency of argon formonatomic helium is a useful starting estimate;ther-molecular reactions such as˙H+O2+M=H˙O2+M become significant at elevated pressures and so the un-certainties in these values can create considerable dif-ferences in theflame speeds.Mechanism FormulationThe kinetic mechanism referred to in this study as thisstudy or the revised mechanism has its origins in the CO/H2/O2reaction mechanism of Yetter et al.[56], which was updated later by Kim et al.[57]and is,for the most part,taken from the more recent work of Mueller et al.[6].We found it necessary to modify some of the kineticparameters of Mueller et al.in order to achieve an over-all improvement with all the experimental data sim-ulated here.This altered version of the mechanism,Table I,the revised mechanism,reproduces the se-lected experimental datasets more accurately than thatpublished by Mueller and coworkers.The entire data set has also been simulated using rel-evant portions from Leeds1.5[58],Konnov[59,60]andGRI-Mech3.0[61]which are all primarily methane ox-idation mechanisms.The reason for using both Konnovmechanisms is that the shock tube data presented inFigs.4–6was used to validate version0.3,while themore recent version0.5was used to simulate the re-maining data.A select set of experiments is repro-duced here using GRI-Mech,Leeds,and Konnov asA COMPREHENSIVE MODELING STUDY OF HYDROGEN OXIDATION607Table I Revised H2/O2Reaction Mechanism(units:cm3,mol,s,kcal,K)Reaction A n E a Ref.H2/O2chain reactions1˙H+O2=˙O+˙OH1.91×10140.0016.44[39]2˙O+H2=˙H+˙OH5.08×104 2.67 6.292[40]3˙OH+H2=˙H+H2O2.16×108 1.51 3.43[41]4˙O+H2O=˙OH+˙OH2.97×106 2.0213.4[42]H2/O2dissociation/recombination reactions5a H2+M=˙H+˙H+M4.57×1019−1.40105.1[43]6b˙O+˙O+M=O2+M6.17×1015−0.500.00[43]7c˙O+˙H+M=O˙H+M4.72×1018−1.000.00[43]8d,e˙H+˙OH+M=H2O+M4.50×1022−2.000.00[43]×2.0Formation and consumption of H˙O29f,g˙H+O2+M=H˙O2+M3.48×1016−0.41−1.12[44]˙H+O2=H˙O21.48×10120.600.00[45] 10H˙O2+˙H=H2+O21.66×10130.000.82[6]11H˙O2+˙H=˙OH+˙OH7.08×10130.000.30[6]12H˙O2+˙O=˙OH+O23.25×10130.000.00[46] 13H˙O2+˙OH=H2O+O22.89×10130.00−0.50[46]Formation and consumption of H2O214h H˙O2+H˙O2=H2O2+O24.2×10140.0011.98[47] H˙O2+H˙O2=H2O2+O21.3×10110.00−1.629[47] 15i,f H2O2+M=˙OH+O˙H+M1.27×10170.0045.5[48] H2O2=˙OH+O˙H2.95×10140.0048.4[49] 16H2O2+˙H=H2O+˙OH2.41×10130.00 3.97[43] 17H2O2+˙H=H2+H˙O26.03×10130.007.95[43]×1.25 18H2O2+˙O=˙OH+H˙O29.55×1006 2.00 3.97[43] 19h H2O2+˙OH=H2O+H˙O21.0×10120.000.00[50] H2O2+˙OH=H2O+H˙O25.8×10140.009.56[50]a Efficiency factors are H2O=12.0;H2=2.5.b Efficiency factors are H2O=12;H2=2.5;Ar=0.83;He=0.83.c Efficiency factors are H2O=12;H2=2.5;Ar=0.75;He=0.75.d Original pre-exponential A factor is multiplied by2here.e Efficiency factors are H2O=12;H2=0.73;Ar=0.38;He=0.38.f Troe parameters:reaction9,a=0.5,T∗∗∗=1.0×−30,T∗=1.0×10+30,T∗∗=1.0×10+100;reaction15,a=0.5,T∗∗∗=1.0×−30, T∗=1.0×10+30.g Efficiency factors are H2=1.3;H2O=14;Ar=0.67;He=0.67.h Reactions14and19are expressed as the sum of the two rate expressions.i Efficiency factors are H2O=12;H2=2.5;Ar=0.45;He=0.45;Table II H f(298.15K)kcal mol−1,S(300K)and C p(T)in cal mol−1K−1Specific heat capacity,C pSpecies H298KS300K300K400K500K800K1000K1500K f˙H52.09827.422 4.968 4.968 4.968 4.968 4.968 4.968˙O59.5638.500 5.232 5.139 5.080 5.016 4.999 4.982˙OH8.9143.933 6.947 6.9927.0367.1997.3417.827 H20.0031.256 6.902 6.960 6.9977.0707.2097.733 O20.0049.0507.0107.2207.4378.0688.3508.721 H2O−57.7745.1548.0008.2318.4469.2239.87511.258 H˙O2 3.0054.8098.3498.8869.46510.77211.38012.484 H2O2−32.5355.72410.41611.44612.34614.29415.21316.851 N20.0045.900 6.8207.1107.5207.7708.2808.620 Ar0.0037.000 4.900 4.900 4.900 4.900 4.900 4.900 He0.0030.120 4.970 4.970 4.970 4.970 4.970 4.970608´O CONAIRE ET AL.an indication of their performance but they have not been comprehensively tested.A comparison shows that these mechanisms are quite different,Table III;not only does the total num-ber of reactions differ but so do the rate constant expressions.Reaction KineticsIt will be clarified later why we made the modifications we did but for now let us look at those that have been made.One of the rate expressions that we modified was˙H+˙OH+M=H2O+M.Figure2illustrates a selection of experimental and review kinetic recommendations for this reaction from Tsang and Hampson[43],Gay and Pratt[62],Baulch et al.[63],Troe[64],Zellner et al.[65],and Bulewicz and Sugdan[66].Between1250and2000K,there is at least a100-fold range in reported experimental and review data.The revised rate constant,see Table I,is twice the recommendation of Tsang and Hampson. Most of the data for the reaction:H2O2+˙H= H2+H˙O2lies between700and1100K.The data plot-ted alongside our revised rate constant for this reac-tion,Fig.3,include the experimental data of Baldwin et al.[67]in addition to the review data of Baulch et al.[63],Tsang and Hampson[43],Lee and Hochgreb[68], Baldwin and Walker[69],and Gorse and V olman[70].In a recent study,Michael et al.[71]measured the rate constant of the reaction˙H+O2+M=H˙O2+M. The measured rate constants for the collision partners nitrogen and argon are in good agreement with our es-timates and so it was decided to adhere to the estimated rate constants and efficiencies.Simulating Experimental Conditions Senkin[72]or Aurora[73]compute the time evolution of a homogeneous reacting gas mixture in a closed sys-tem.This includes predicting the chemical behavior be-hind incident and reflected shock waves in a shock tubeTable III A comparison of the mechanisms testedListed Duplicate Actual Mechanism Reactions Reactions Reactions This study21419 Mueller et al.29427 GRI-Mech3.030627 Leeds1.523222 Konnov0.324223 Konnov0.529427Figure2˙H+˙OH+M=H2O+M.◦this study,⊗Tsang and Hampson[43](used by Mueller and coworkers),•Gay and Pratt[62], Baulch et al.[63], Troe[64], Zellner et al.[65], Bulewicz and Sugden[66], Baulch et al.[63].and species evolution in a laminarflow reactor.A limit-ing case,frequently applied when simulating reactions in shock waves and also used in this study,assumes a constant volume(density)boundary which we used to simulate reflected shock ignition delay times.The Shock code[74]was used to simulate ignition delay times behind incident shocks.We used the application Premix[75]to model time-independent,adiabatic freely propagating(expanding spherical)flame speeds in addition to speciesandFigure3H2O2+˙H=H˙O2+H2.◦this study,⊗Tsang and Hampson[43](used by Mueller and coworkers), Baulch et al.[63], Baldwin and Jackson[67], Lee and Hochgreb[68], Baldwin and Walker[69]and Gorse and V olman[70].A COMPREHENSIVE MODELING STUDY OF HYDROGEN OXIDATION 609intermediate concentration pro files in a burner-stabilized flame.In order to allow for changes in the structure of the flame with time,a re-gridding strat-egy is included which involves the computation of the optimum grid as part of the time-dependent solution.We used the standard Chemkin transport package,with thermal diffusion included and increased the number of grid-points until the flame speed converged.Mixture-averaged transport properties were employed.Some modeling workgroups such as Resources Research In-stitute,University of Leeds prefer to use the multi-component transport wrence Livermore Na-tional Laboratories use the mixture-averaged transport properties as we do.Shock TubeKonnov [59,60]used the experiments of Schott and Kinsey along with those of Skinner and Ringrose,to validate version 0.3of his mechanism at temperatures of 965–2700K.In both studies,ignition delays be-low 1200K correspond to the time of maximum [˙OH];above 1200K they correspond to the time at which [˙OH]=10−6mol dm −3.In addition,both studies plot-ted the experimental data as the concentration of molec-ular oxygen multiplied by the ignition delay time versus temperature.Figures 4–6depict both sets of experimen-tal results with Konnov ’s mechanism predictions in ad-dition to those of our current mechanism and those of Mueller et al.Both our predictions and those of Mueller et al.are identical except for Skinner et al.and are in overall good agreement with the experimental data.The ignition delay times,␶,measured by Hidaka and coworkers correspond to the tangent totheFigure 4␶×[O 2]versus 1/T Skinner and Ringrose [10]8%H 2+2%O 2+balance Ar,at 1atm.——this study ,–-–-Mueller et al.,···Konnov 0.1–0.3,[59].Figure 5␶×[O 2]versus 1/T Schott and Kinsey [9]1%H 2+2%O 2+balance Ar,at 1atm.——this study and Mueller et al.,···Konnov 0.1–0.3,[59].maximum rate of increase in water concentration,(d[H 2O]/d t )max =␶,and were thus calculated in our simulations with very good agreement between our model (the Mueller mechanism gives identical results)and experiment,Fig.7.Slack [15]measured ignition delay times in stoi-chiometric hydrogen/air mixtures at a re flected shock pressure of two atmospheres.The revised mecha-nism performed very well over the entire tempera-ture range in simulating the experimental data,Fig.8.The Mueller et al.mechanism,on the other hand,pre-dicts slower ignition times,particularly at temperatures below 1025K.Figure 6␶×[O 2]versus 1/T Schott and Kinsey [9]4%H 2+2%O 2+balance Ar,at 1atm.——this study and Mueller et al.,···Konnov 0.1–0.3,[59].610´OCONAIRE ETAL.Figure 7Ignition delay measurements 1.0%H 2+1.0%O 2,balance Ar,at 3bar;Hidaka et al.[18] ;model predictions ——this study and Mueller et al.,---Leeds 1.5,···GRI-Mech 3.0,–--Konnov 0.5.The mechanism is in good agreement with theignition delays of Fujimoto and Suzuki [12],partic-ularly between 900and 1100K,Fig.9,although the mechanism is too slow at temperatures below 950K.The results of Petersen et al.[19]along with model predictions are shown in Fig.10.Three sets of data from the same study,in the pressure range 33–64atm and in the temperature range 1650–1930K,have also been simulated with good agreement,but are not shown here.The ignition delays were measured as the tangent of the pressure pro file versus time.Figure 11illustratesFigure 8Ignition delay times of stoichiometric H 2/air,at 2atm,from Slack [15]: ;model predictions ——this study ,–-–-Mueller et al.and Mueller et al.with ⑀(H 2)=1.3for˙H+O 2+M =H ˙O 2+M,---Leeds 1.5,···GRI-Mech 3.0and Konnov0.5.Figure 9Ignition delay times for stoichiometric H 2/air,from Fujimoto and Suzuki [12]: light emission,◦pressure;——this study ,---Mueller et al.the difference between the ignition delay time mea-sured from the onset of temperature rise and the ignition time measured by the tangent of the pressure pro file.The more recent atmospheric shock tube measurements of Petersen et al.[20],Figs.11and 12,are also re-produced with reasonable success by our mechanism although the experiments shown in Fig.12are con-siderably faster than those predicted by this study and Mueller et al.For this set of data,the ignition delay time could not be determined from the simulated pressure or temperature pro files at high temperatures,simply because the pressure and temperature did not give an unambiguous ignition delay time as the mixtureswereFigure 10Ignition delay times for stoichiometric H 2/O 2/Ar [19]; 0.5%H 2+0.25%O 2,64–87atm;•2.0%H 2+1.0%O 2,33atm; 0.1%H 2+0.05%O 2,64atm;model predictions:——this study and Mueller et al.,–-,---Leeds 0.5,···GRI-Mech 3.0,–--Konnov 0.5.A COMPREHENSIVE MODELING STUDY OF HYDROGEN OXIDATION611Figure 11Ignition delay times [20]: 1.03%H 2+0.5%O 2,balance Ar,at 1atm;model predictions ——based on pressure-rise,---based on temperature-rise.very dilute;so,the ignition delay time was re-de fined,in this case only,as the time corresponding to a maxi-mum in the product of the concentrations of ˙OHand ˙O,that is [˙O]×[˙OH].Two additional sets of data from thatstudy,in the temperature range 1100–1520K and at 1atm were simulated with good agreement but are not shown here.The measurements of Cheng et al.[16]and Bhaskaran et al.[14]are replicated well in this study ,Figs.13and 14.The experiments of Wang et al.[21]are well reproduced although only one data set is shown here,Fig.15.The only signi ficant discrepancies arise for the 0%and 15%steam mixtures,where the mea-sured ignition delay times are a lot faster thanthoseFigure 12Ignition delay measurements [20]: 1.03%H 2+0.5%O 2,balance Ar,at 1atm;model predictions ——this study and Mueller etal.Figure 13Ignition delay times from Cheng and Oppenheim [16]: 6.67%H 2+3.33%O 2,balance Ar,at 1.9atm;model predictions ——this study ,–-–-Mueller et al.,---Leeds 0.5,···GRI-Mech 3.0,–--Konnov 0.5.predicted by the models below 1010and 1090K,respectively.Rotational relaxation of N 2was not taken into consideration.Given that atomic species substantially decrease the vibrational relaxation rate [76,77],this is probably a reasonable assumption for Figs.8,14,and 15.The improved predictions are a result of choosing athird-body ef ficiency of 1.3for H 2in the reaction ˙H+O 2+M =H ˙O2+M,whereas Mueller et al.adopted a value of 2.5.This has resulted in the improvements seen in the simulation of the ignition delays of Slack,Fig.8,and those of Fujimoto et al.,Fig.9.Figure 14Ignition delay measurements from Bhaskaran et al.[14]: 22.59%H 2+14.79%O 2,balance N 2,at 2.5atm;model predictions ——this study ,–-–-Mueller et al.,---Leeds 0.5,···GRI-Mech 3.0,–--Konnov 0.5.。

关于冰块实验的作文英语Title: The Ice Cube Experiment: Unveiling the Secrets of Science。

Introduction:Science, with its endless mysteries and intriguing phenomena, often beckons us to explore and unravel its secrets. Among the many fascinating experiments that captivate both young minds and seasoned scientists alike is the timeless ice cube experiment. This experiment, seemingly simple yet profoundly insightful, unveils the principles of physics, chemistry, and thermodynamics. In this essay, we delve into the intricacies of the ice cube experiment, exploring its underlying principles, applications, and significance in scientific inquiry.Understanding the Experiment:At its core, the ice cube experiment involves observingthe process of ice melting in various environmental conditions. It serves as a practical demonstration of concepts such as heat transfer, phase transitions, and equilibrium. By subjecting ice cubes to different temperatures, pressures, and mediums, researchers can investigate the factors influencing the rate of melting and the final equilibrium state.Key Concepts:1. Heat Transfer: Heat transfer plays a central role in the ice cube experiment. When an ice cube is exposed to a warmer environment, such as room temperature air or water, heat energy flows from the surroundings to the ice cube. This influx of heat causes the ice cube to absorb thermal energy, leading to a rise in temperature and ultimately melting.2. Phase Transitions: The transition of water from a solid (ice) to a liquid state exemplifies a phase transition. As heat is absorbed by the ice cube, thekinetic energy of its molecules increases, eventuallysurpassing the threshold for maintaining a solid structure. Consequently, the bonds holding the water molecules in a rigid lattice break, resulting in the formation of liquid water.3. Equilibrium: Throughout the melting process, the system strives to reach equilibrium, where the rate of ice melting equals the rate of heat absorption. At equilibrium, the temperature remains constant, and the ice-water mixture coexists in a delicate balance. Understanding the concept of equilibrium is crucial for interpreting experimental results and predicting the behavior of complex systems.Experimental Variations:The versatility of the ice cube experiment allows for a myriad of variations, each offering unique insights into physical phenomena. Some common variations include:1. Temperature Variation: Altering the temperature of the surroundings can significantly impact the rate of ice melting. By placing ice cubes in environments of differenttemperatures, researchers can observe how heat transfer influences the melting process.2. Pressure Variation: Pressure also affects the melting point of ice, albeit to a lesser extent than temperature. High-pressure environments, such as those found deep underwater or in pressurized containers, can lower the melting point of ice, causing it to melt more rapidly.3. Medium Variation: The medium surrounding the ice cube, whether air, water, or another substance, can influence the rate of melting. For instance, ice melts more slowly in cold water than in warm water due to differences in thermal conductivity.Significance and Applications:Beyond its educational value, the ice cube experiment has practical applications in various fields:1. Climate Science: Studying the melting behavior ofice cubes provides insights into the processes driving glacial melting and sea-level rise, crucial considerations in climate change research.2. Engineering: Understanding heat transfer and phase transitions is essential for designing efficient cooling systems, refrigeration units, and thermal insulation materials.3. Food Science: Food preservation techniques oftenrely on controlling temperature and phase transitions to extend the shelf life of perishable goods.Conclusion:In conclusion, the ice cube experiment serves as a gateway to understanding fundamental principles of physics and chemistry. Its simplicity belies the depth of knowledge it offers, making it a timeless educational tool and a cornerstone of scientific inquiry. By unraveling the mysteries hidden within the humble ice cube, we gain valuable insights into the workings of the natural worldand pave the way for technological advancements that benefit society as a whole.。