teratogenic effects of ENU in the syrian Hamster.cancer research.Dipaolo

第23卷增刊II V ol. 23 Sup. II 工 程 力 学 2006年 12 月 Dec. 2006 ENGINEERING MECHANICS141——————————————————— 收稿日期：2006-07-30基金项目：山西省自然科学基金项目(2006011050)作者简介：*李 珠(1959)，男，河南开封人，教授，博士，博导，从事结构工程与力学研究(E-mail: lizhu9999@)； 张泽平(1964)，男，山西原平人，副教授，博士生，从事结构工程研究； 刘元珍(1974)，女，山西霍州市人，讲师，博士生，从事结构工程研究； 穆启华(1970)，男，山西应县人，学士，从事结构工程研究。

文章编号：1000-4750(2006)Sup.II-0141-09建筑节能的重要性及一项新技术李 珠1，张泽平1，刘元珍1，穆启华²(1. 太原理工大学建筑与土木工程学院，太原 030024；2. 太原思科达科技发展有限公司，太原 030006)摘 要：能源是社会发展的动力，有计划、有节制地利用能源是可持续发展的重要保证。

介绍了建筑节能的含义及范围，分析了我国目前的建设规模及能耗状况，并与经济发达国家能耗状况进行对比，反映建筑节能的重要性及紧迫性。

针对我国目前外墙保温的实际情况，提出一种新型外墙保温技术——玻化微珠保温系统，采用理论分析和试验相结合的方法进行研究开发。

试验及工程应用均表明该系统保温性能优异，同时绿色环保，具有良好的经济效益和社会效益，有着广阔的应用前景。

关键词：建筑节能；外墙；玻化微珠；保温系统；能耗状况 中图分类号：TU201.5 文献标识码：ATHE IMPORTANCE OF ENERGY EFFICIENCY IN BUILDINGS ANDINTRODUCTION OF A NEW TECHNIQUELI Zhu 1, ZHANG Ze-ping 1, LIU Yuan-zhen 1 , MU Qi-hua 2(1. College of Architecture & Civil Engineering of TUT, Taiyuan, Shanxi 030024, China; 2. Taiyuan Si keda Science Develop Limited Company, Taiyuan, Shanxi 030006, China)Abstract: As the power of society development, energy resources must be utilized designedly and abstemiously to meet the requirement of sustainable development. The definition and scope of energy efficiency in buildings are introduced firstly, and the status is presented on construction scale and energy consumption. Energy consuming level in Chinese buildings is compared with that in developed countries to represent the importance and urgency of energy efficiency in buildings in China. Based on the situation analysis on exterior wall insulation, a new technique, glazed hollow bead insulation system, was proposed for heat preservation and energy saving in exterior wall. Theoretical analysis was combined with experiments in the research. The experimental results and the practice in civil engineering both showed that the insulation system had excellent energy-conservation performance. The insulation system has no harmful effect on environment, additionally, it shows better economical and social benefits than other insulation techniques, therefore it can be used widely in civil engineering.Key words: energy efficiency in buildings; exterior wall; glazed hollow bead; insulation system; status ofenergy consumption随着生产力的急速发展，世界各国能源的消耗量越来越高，世界能源需求量以每年2%的比率增长，对世界能源消费的长期预测表明，2050年全世界总能源耗费将达到1975年的4倍[1]。

a r X i v :0803.1689v 1 [a s t r o -p h ] 12 M a r 2008The effect of turbulent intermittency on the deflagration todetonation transition in SN Ia explosionsLiubin Pan,J.Craig Wheeler and John ScaloAstronomy Department,University of Texas at Austinpanlb@ ABSTRACT We examine the effects of turbulent intermittency on the deflagration to det-onation transition (DDT)in Type Ia supernovae.The Zel’dovich mechanism for DDT requires the formation of a nearly isothermal region of mixed ash and fuel that is larger than a critical size.We primarily consider the hypothesis by Khokhlov et al.and Niemeyer and Woosley that the nearly isothermal,mixed region is produced when the flame makes the transition to the distributed regime.We use two models for the distribution of the turbulent velocity fluctuations to estimate the probability as a function of the density in the exploding white dwarf that a given region of critical size is in the distributed regime due to strong local turbulent stretching of the flame structure.We also estimate lower limits on the number of such regions as a function of density.We find that the distributed regime,and hence perhaps DDT,occurs in a local region of critical size at a density at least a factor of 2−3larger than predicted for mean conditions that neglect intermittency.This factor brings the transition density to be much larger than the empirical value from observations in most situations.We also consider the intermittency effect on the more stringent conditions for DDT by Lisewski et al.and Woosley.We find that a turbulent velocity of 108cm/s in a region of size 106cm,required by Lisewski et al.,is rare.We expect that intermittency givesa weaker effect on the Woosley model with stronger criterion.The predicted transition density from this criterion remains below 107g/cm 3after accounting for intermittency using our intermittency models.Subject headings:stars:interiors—supernovae:general—turbulence1.IntroductionA successful model for Type Ia Supernova (SNIa)explosions is required to produce a de-flagration to detonation transition (DDT)by observational constraints.A pure deflagrationmodel gives exploding kinetic energy lower than observed(Khokhlov1991;Gamezo et al. 2003;R¨o pke&Hillebrandt2005)and pure detonation leads to overproduction of iron group elements and too little intermediate elements(Branch et al.1982,1983).The densityρtr at which the transition occurs determines the amount of the nickel produced(H¨oflich1995; H¨oflich and Khokhlov1996;Dominguez,H¨oflich&Straniero2001).Therefore a prediction ofρtr,consistent with the observed nickel production,is essential to a DDT theory for SNe Ia.The mechanism by which the DDT occurs still remains a mystery.The most studied candidate is the Zel’dovich mechanism,which requires the existence of an almost isother-mal region of mixed ash and fuel that is larger than a critical size l c to drive a supersonic shock that is sufficiently strong to sweep over the entire star(Khokhlov et al.1997,here-after KOW;Niemeyer and Woosley1997,hereafter NW).One hypothesis is that a nearly isothermal region is produced by turbulent preconditioning.KOW argued that,to produce an almost isothermal mixture of ash and fuel,the laminarflame must be quenched by tur-bulent stretching,at least locally.This might allow the cold fuel to mix with the ash both thermally by electron conduction and chemically by diffusivity without being burned.They assumed that the criterion to quench aflame is that the turbulent velocity at the laminar flame thickness must be larger than the laminarflame speed.NW gave a similar argument based on the distributedflame burning regime in turbulent combustion.The criterion for a distributedflame is expressed in terms of the Gibson scale at which the turbulence velocity equals the laminarflame speed.If the Gibson scale is smaller than the laminarflame thick-ness,turbulent stretching can generate structures within theflame and theflame is in the distributed regime.NW speculated that in this regimeflames can be temporally quenched in some regions,which can host the detonation after being homogenized in temperature and composition by turbulent mixing.The criterion for the distributed regime is equivalent to that forflame quenching used by KOW.Both criteria give the same condition on the turbu-lence intensity for given laminarflame properties(see§2).As the density in the star drops due to the overall expansion,it is easier for turbulence to affect the laminarflame because of the decrease in theflame speed and the increase inflame thickness.With presumed tur-bulence parameters,the criterion for the turbulence intensity,determined by the robustness of laminarflames disturbed by turbulent motions,translates to a transition densityρtr for the DDT.Several uncertainties exist in the simple model given by these two early studies.First, it is not clear whether the criterion used by KOW,equivalent to that for a distributed regime(NW),is sufficient forflame breaking.How,or even if,flames are quenched is still an open question.Second,it is uncertain whether(local)flame quenching is indeed necessary to produce a nearly isothermal region.Finally,later studies by Lisewski,Hillebrandt andWoosley(2000)(hereafter Lisewski et al2000;see also Lisewski et al.2000b)and Woosley (2007)find that entering the distributed regime,while probably a necessary condition,is not sufficient for the DDT to occur.Based on a requirement for turbulent transport to be efficient at producing a shallow temperature and composition gradient around the laminar flame,Lisewski et al.(2000)find that the turbulent velocity at the scale106cm needed for a detonation is very large,∼108cm/s.Woosley(2007)claims that the DDT occurs only when the turbulentflame thickness exceeds a critical length scale.We show in§2that the two criteria,although arising from different physical considerations,are basically equivalent. The corresponding condition is more stringent than that assumed by KOW and NW.In this paper we examine the effect of turbulent intermittency on the onset of distributed burning that may relate to the DDT.Despite the uncertainties listed above,we will mainly consider the model by KOW and NW and use it to illustrate the potential importance of intermittency in SN Ia explosions.Our calculations can be applied to the criteria by Lisewski et al.(2000)and Woosley(2007)in a straightforward way.A quantitative analysis using their criteria requires data for laminarflame properties and critical length scales at densities below107g cm−3that are not immediately available(see§2).We give a qualitative discussion of the intermittency effect on their DDT models.Intermittency is an important concept in turbulence theory.It is characterized by intense local events,e.g.,strong stretching at small scales,which occur at a frequency much larger than predicted from a Gaussian distribution(see,e.g.,Frisch1995).The physical origin of intermittency in turbulentflows is the spatial inhomogeneity in the energy dissipation rate: most kinetic energy is viscously dissipated in thefinest structures,e.g.,vortex tubes,which occupy only a small volume fraction.These rare but intense dissipative structures give rise to a spatially inhomogeneous and intermittent distribution for the turbulent intensity and the stretching rate.Intermittency is shown as broad exponential tails in the probability distribution for the stretching rate or the dissipation rate at small scales(see§3).The tails get broader at smaller scales,meaning that the probability offinding an extreme turbulent stretching rate or intensity increases with decreasing scales.According to1D simulation results by KOW and NW,the critical size,l c,of the isother-mal region required for a DDT via the Zel’dovich mechanism is much smaller,especially at large densities,than the expected integral length scale for the buoyancy-driven turbulence in SN Ia explosions.This suggests that only a smallflame region with a sufficiently strong local turbulence intensity may be needed to trigger a detonation.Turbulent intermittency, which indicates the existence of regions of small sizes where the turbulent stretching is much larger than the average value over theflow,is therefore expected to have important conse-quences for DDT.The transition could happen earlier at a higher transition densityρtr thanpredicted by models using the average turbulent intensity.At higher densities,much larger turbulent intensity is required for the DDT,but the rapid decrease of l c with increasing den-sity makes an earlier DDT possible for two reasons.First,the probability is larger tofind regions of smaller sizes l c with extreme turbulent stretching rate or intensity.Second,there are more regions of smaller size available as candidates to host the detonation.Clearly,the intermittency effect accounts for the intuitive dependence ofρtr on l c:the smaller the critical size,the easier it may be for the transition to happen.To what degree the intermittency effect increasesρtr is the main question we investigate in this paper.In§2,we review the criteria for the DDT in models by KOW,NW,Lisewski et al. (2007)and Woosley(2007)and formulate a new criterion taking into account the effect of intermittency.We describe two intermittency models by Oboukhov(1962)and Kolmogorov (1962)and by She and Leveque(1994)in§ing the intermittency models,we evaluate the transition density from the new criteria in§4.Our results are summarized and discussed in§5.2.Criteria for the DDTThe criterion used in NW for judging whether aflame is in the distributed regime,which was also assumed to be the condition for the DDT,is to compare the Gibson scale l G with the laminarflame thickness l f.The Gibson scale is defined such thatδu(l G)=S l whereδu(l)is the amplitude of the velocityfluctuations at the scale l(or equivalently the velocity difference over a scale l,i.e.,δu(l)=u(l+x)−u(x))and S l is the laminarflame speed1.If l G∼>l f, the turbulence cannot internally disturb theflame and the turbulence in effect wrinkles the flame.This is called theflamelet regime.Only when l G∼<l f,can turbulence stretch the flame efficiently to generate structures within theflame and the turbulent combustion enters the distributed regime.The condition l G∼<l f is equivalent toδu(l f)∼>δu(l G)=S l since δu(l)is an increasing function of the scale l2.The latter,which means that the turbulentvelocityfluctuationδu(l f)at the scale of theflame thickness l f is larger than the laminar flame speed,is the criterion used in KOW forflame quenching and the DDT.Following KOW,we introduce a factor of K∼1in the criterion to account for the uncertainty in theflame breaking mechanism,i.e.,δu(l f)≥KS l.We will consider two values for K,i.e.,K=1and K=8(KOW;For K=8,to quench aflame,the Gibson scale has to be K3=512times smaller than theflame width).This criterion can also be written in terms of timescales.Noting that the turbulent stretching timescale,τt,at the flame thickness isτt(l f)=l f/δu(l f)and that the nuclear reaction timescale,τn,is related to theflame speedτn=l f/S l,the criterion is equivalent toτt(l f)<τn/K,i.e.,to break theflame the stretching timescale at theflame thickness must be smaller than the nuclear burning timescale(see Niemeyer and Kerstein1997).To apply this criterion,the Kolmogorov(1941)scalingδu(l)=¯ǫ1/3l1/3is usually used to calculateδu(l f)from the turbulent velocityfluctuations at large scales where¯ǫis the average dissipation rate in theflow.From this scaling,the criterion can be written as(KOW,NW),>KS l(1)¯ǫ1/3l1/3for¯ǫ>K3S3l/l f=K3ǫf(2) whereǫf is defined as S3l/l f.Although we use the convenient criterion(2)in terms of the dissipation rate in our calculations,the turbulent stretching is more fundamental and we will use the concept of theflame stretching in our discussions.The laminarflame speed and thickness depend on the chemical composition and the density(Timmes and Woosley1992,KOW).In Table1,we list theflame speed,theflame thickness as a function of density for a white dwarf with half carbon and half oxygen,mainly taken from Timmes and Woosley(1992).The laminar speed decreases and the thickness increases quickly with decreasing densityρ,thereforeǫf decreases rapidly with decreasing ρas shown in Table1.The average dissipation rate is estimated to be¯ǫ=U3/L where U and L are the characteristic velocity and length scales of the turbulence,normally set by motions on the large,driving scale.At large scales,the turbulence is driven by the Rayleigh-Taylor instability.The length scale L might be expected to be about the size,R f, of theflame region,L≃R f∼108cm and the velocity scale to be about the Rayleigh-Taylor velocity at this scale U∼0.5respectively,are not equivalent.scales larger than106cm freeze out due to the overall expansion of the star.In that case, L∼106−107cm and U∼107cm/s.We will take U and L as parameters.Note that the criterion eq(2)depends on U and L through the dissipation rate.Given the dissipation rate ¯ǫ,the critical density below which the inequality(eq2)is satisfied can be obtained using ǫf as a function ofρin Table1.For example,if U∼100km/s and L∼100km,¯ǫ∼1014 cm2/s3and wefind that,from interpolation in Table1,¯ǫis larger thanǫf at a density less than∼4×107g/cm3.Therefore criterion(2)predicts a transition densityρtr≃4×107 g/cm3for K=1(see KOW and NW).If K=8,the predicted transition density is smaller,ρtr∼1.5×107g/cm3.In the second line of Table2,we give the predictedρtr for different values of the parameters,which decreases with decreasing dissipation rate¯ǫ.The numbers in parenthesis correspond to K=8.When using the criterion eq(2),we need to keep in mind that the spatialfluctuations ofǫ(see§3)are completely neglected and the criterion only applies to the overall situation in the combustionflow.We will refer to this criterion as the mean criterion.When the mean criterion is met,the only implication is that the combustion is in the distributed regime in general.Considering the intermittency of turbulence,i.e.,the spatially inhomogeneous distribution of the stretching strength,there can be places where the stretching rate is much weaker than the average.These places could still be in theflamelet stage while most other places are in the distributed regime.Or conversely,even if the mean criterion(2)is not satisfied,one cannot exclude the possibility of there existing a region that experiences strong stretching and gets into the distributed regime when most of the structure is still in the flamelet regime.This latter fact is important for the deflagration to detonation transition. The fact that the DDT does not require the entire star to be in the distributed regime but instead only needs a region of size much smaller than the white dwarf radius(see below, KOW),coupled with the intrinsic intermittency,suggests that DDT could occur earlier than predicted by eq(2)and hence at a larger transition density.The detonation can be triggered locally when a region appears that is larger than the critical size and enters the distributed regime due to a strong local stretching.It is important to study the degree to which this intermittency effect increases the transition density,which is constrained by observations. Clearly the answer depends on the critical size,which we consider next.The question of how large the isothermal region with well-mixed ash and fuel has to be for a detonation was studied by KOW(see also NW).In their model,the DDT occurs via the Zel’dovich mechanism(Zel’dovich et al.1970)where the mixed region begins spontaneous ignition at the place with the minimum induction time,and theflame propagates with a phase speed equal to the inverse of the spatial gradient of the induction time,which is large for nearly isothermal and well-mixed regions and is not limited by the speed of sound.As the phase speed decreases below the Chapman-Jouget speed,a shock forms just ahead of theflame front.Whether this shock can explode the whole star depends on the strength of the shock when entering the pure fuel,which is determined by the size of the isothermal region. If the isothermal region is small and the shock is weak,theflame front and shock separate with theflame front lagging behind the shock and the shock cannot make the whole star explode.The critical strength of the shock corresponds to a critical size of the isothermal region,over which the shock can be ing1D simulations,KOW and NW obtained the critical size,l c,which depends on the density and the chemical composition. It is interesting to note that at early time when the density is large,the required size is much smaller than that at later times.We will show this has important consequences.The critical size is much smaller than what current numerical simulations can resolve,therefore the problem of the intermittent stretching at scale l c cannot be addressed by simulations.We need a local criterion to check whether a region of a given size l,in particular l c,is in the distributed regime or not.For that purpose,we use a local average dissipation rateǫl (see eq.8in§3for a definition)in a region of size l to replace¯ǫ.Following the same argument that leads to equation(2),the criterion for a region of size l being in the distributed regime isǫl>K3ǫf(3) where we have used the refined similarity hypothesis by Kolmogorov(1962)(see eq.9in §3).Due to the random nature of turbulentflows,ǫl is stochastic,and a statistical approachis necessary.We therefore ask the question:what is the probability that any region of size l is in the distributed regime?This is given by the cumulative probability P(ǫl>K3ǫf). To answer this question,we need the probability distribution P(ǫl)ofǫl.Fortunately,this distribution has been extensively studied in the intermittency models for turbulence,which we describe in§3.Although these models were originally proposed for homogeneous and isotropic turbulence,we will assume they apply to SNe Ia where the turbulence is stratified and may not arrive at isotropy even at very small scales.Once the distribution is specified, one can calculate the probability offinding that a region of given size l c is in the distributed regime,P(ǫlc >K3ǫf)=∞K3ǫfP(ǫlc)dǫlc(4)which depends on the density through l c andǫf.An immediate examination of eq(4)shows that,at larger density,the lower limit of the integral K3ǫf is larger because of the fastflame speed and the smallflame thickness.This tends to decrease the probability.However,at larger density,l c is smaller and the intermittency of turbulence tells us that the tail of the distribution P(ǫl)is broader for smaller l.This tends to counteract the decrease of the cumulative probability due to the larger lower integral limit at higher densities.Furthermore,for smaller l c ,there are more regions of size l c available in the star.This could make the transition occur significantly earlier with a transition density considerably larger than predicted by eq (2).We need to multiply the probability that a given region of size l c is in the distributed regime by the number,N l c ,of regions of size l c available in order to calculate the number of regions that are both larger than l c and in the distributed regime at any given density.We assume that the deflagration to detonation transition happens whenN l c ×P (ǫl c >K 3ǫf )=1.(5)Since we are concerned with the flame being stretched into the distributed regime,only locations around the flame front are of interest when calculating N l c .Therefore,we onlycount regions in the vicinity of the flame front.N l c depends on the size,R f ,of the flame region and the flame geometry.A typical value for R f is 108cm (Khokhlov 1995),which could be smaller at an earlier time.We will set R f ≃L in our calculations in order to decrease the number of parameters.Note that R f >L when the freezeout effect is considered and therefore the number N l c we use is a lower limit.If the flame region is a 2D spherical front,N l c ∼4πR 2f /l 2c .If the flame structure is highly convoluted,it may have a fractal dimension larger than 2.In that case,N l c is larger.The upper limit for N l c is ≃4πR 3f /3l 3c ,which applies if the flame geometry is close to 3D.Again,we take the lower limit N l c =4πR 2f/l 2c ,thus the transition density we will get is a lower limit.As discussed in the Introduction,Lisewski et al.(2000)and Woosley (2007)find that entering the distributed regime is not sufficient for the DDT to occur and give criteria stronger than that used in KOW and NW.Lisewski et al.(2000)considered how turbulent transport affects the temperature and composition profile around a laminar flame.They assumed that,at any point,turbulence translates the temperature and composition by a distance l t ,over which turbulence can transport during a local induction time τi .The distance l t is a function of position since τi depends on local temperature and composition.It is estimated by the length scale of a turbulent eddy with turnover time equal to τi ,i.e.,l t /δu (l t )=τi .Using the Kolmogorov (1941)scaling,we get l t =¯ǫ1/2τ3/2i .For given turbulence intensity,temperature and composition profiles around a laminar flame front can be calculated from the translation.Clearly,more efficient turbulent transport gives shallower temperature and composition profile,which is needed for detonation.By checking whether the resulting profiles,as initial conditions to solve the 1D hydrodynamic equations,can lead to a detonation,Lisewski et al.(2000),obtained a condition for the DDT on the turbulent intensity.They found that,for a successful detonation,the turbulent velocity has to be ∼108cm/s at the scale 106cm.This condition is stronger than just entering the distributedregime3.Since the expected turbulent velocity at scale106cm is106−107cm/s,Lisewski et al.(2000)concluded that a DDT via the Zel’dovich mechanism in SNe Ia is unlikely. However,considering the spatial inhomogeneity of turbulent intensity,i.e.,intermittency,it is possible for regions of size106cm with large enough turbulent velocity to arise.The result of Lisewski et al.(2000)motivated R¨o pke(2007)to study the probability of finding a region of size106cm with a turbulent rms velocity of∼108cm/ing data from 3D numerical simulations with a turbulent subgrid-scale method,R¨o pke(2007)analyzed the velocityfluctuations at the grid size(106cm)and obtained a fat exponential tail for large velocityfluctuations that extends up to108cm/s.The large velocityfluctuations seem likely to be located at the trailing edge of a bubble-like feature(R¨o pke2007).This confirms the intermittency in the turbulent combustionflow in SNe Ia;there exist grid cells where the turbulent intensity is much stronger than the average.From the probability offinding a grid cell with required turbulent intensity,R¨o pke concluded that the DDT triggered by a local cell with large velocityfluctuations is possible but probably rare.In our notations, the probability is given by P(ǫ106cm>1018cm2/s3)where1018cm2/s3corresponds to the dissipation rate in a region of size106cm with a rms velocity of108cm/s.We will calculate this probability and consider the availability of such regions using two intermittency models given in§3and compare with the results of R¨o pke(2007)in§4.Woosley(2007)proposed a new criterion for the DDT based on a calculation of the distributedflame width using an eddy diffusivity approximation.Making an analogy to the estimate of the laminarflame thickness,Woosley(2007)obtained the distributedflame widthλfrom the equationλ≃(D(λ)τn)1/2where D(λ)=δu(λ)λis the eddy diffusivity at scaleλandτn is the nuclear reaction ing the Kolmogorov(1941)scaling(note that this formula for forδu(λ),the distributedflame width is given byλ=¯ǫ1/2τ3/2nλis similar to l t in Lisewski et al.(2000)).Woosley(2007)assumed that the condition for detonation is that the minimum burning timescale in the distributedflame is smaller than the sound crossing time over the distributedflame widthλ,or equivalently,λ∼>r min sonic where r minis the sound crossing length over the minimum burning timescale in the distributed sonicflame.The minimum sound crossing length is thus the critical size of the distributedflame width for detonation.The criterionλ∼>r min sonic is equivalent to¯ǫ∼>(r min sonic)2/τ3n.Noting thatτn=l f/S l,the condition can be written as¯ǫ∼>(r min sonic/l f)2ǫf.Since r min sonic given in Table4of Woosley(2007)is close to l c listed in Table1in this paper,we will use l c instead of r minsonic for simplicity,i.e.,¯ǫ∼>(l c/l f)2ǫf.(6) which is much stronger than eq(2)because l c is much larger than the laminarflame thickness l f.This condition can be used to determine the transition densityρtr by the same calculation process as in the case of the criterion eq(2).Note that,except a factor of(τn/τi)3,this criterion is basically equivalent to that given in footnote(3)for the requirement by Lisewski et al.(2000).Wefind that,for the reasonable turbulence parameters listed in Table2,the criterion results in a transition density below107g cm−3and we cannot specify it due to the lack of data for l c,S l and l f at densities below107g cm−3.In his estimate forρtr,Woosley(2007)used U=108cm/s at scale L=106cm through-out the calculations,based on the result by R¨o pke(2007)on the possibility of the existence of regions of size106cm with a rms velocity of108cm/s.With these turbulence parameters he derivedρtr=107g cm−3.Clearly,in Woosley’s calculation,the intermittency effect implic-itly contributes to the transition density obtained because,as discussed earlier,a turbulent rms velocity of108cm/s at106cm can only arise from intermittency.The intermittency effect for the criterion of Woosley(2007)can be included more con-sistently in our formulation.Instead of considering a single special scale106cm,our model specifies intermittency over a continuous range of scales corresponding to critical sizes at different densities.Following the same steps that lead to eq(5),we incorporate the inter-mittency effect in the DDT model of Woosley(2007)and obtain a criterion,N lc×P(ǫl c>(l c/l f)2ǫf)=1.(7) which only differs from eq.5by the lower limit in the cumulative probability.We will discuss about this criterion in§4.We point out that the eddy diffusivity method used by Woosley(2007)to approximate the combined action of the turbulent advection and the microscopic diffusivity is an oversim-plification.This procedure implicitly assumes a smooth structure in the distributedflame and neglects thefluctuations of temperature and concentration,which may be important in determining the effective width of distributedflames.3.IntermittencyKolmogorov’s1941theory assumes that the energy transfer in the inertial range is equal to the average dissipation rate¯ǫin theflow and is the same throughout the inertial scalesdown to the viscous scale where the kinetic energy is removed.This assumption,together with the similarity hypothesis,predicts that the statistics of the velocity difference(or the velocityfluctuations)at any inertial scale is completely determined by the average dissipation rate¯ǫ.However,fluctuations in the dissipation rate clearly exist as can be seen from the formula for the local viscous dissipation rate,ǫ(x,t)=νǫ(x+x′,t)d x′.(8)4πl3|x′|<lClearly,the mean ofǫl is equal to¯ǫand thus is independent of l.This means that the average energyflux over all the inertial scales is constant.Theǫl distribution is essential to the intermittency models for turbulence.Note that this distribution is exactly what we need in our calculations for the transition of the turbulent combustion to the distributed regime by turbulent stretching and quenching described in§2,eqs(4)and(5).Intermittency in turbulence is usually expressed in terms of the scaling behavior of the structure functions δu(l)p ∼lζp whereδu(l)=u(x+l)−u(x)is the(longitudinal)velocity difference andζp is the scaling exponent for the p th-order structure function.Kolmogorov’s 1941theory predicts that the exponentζp goes with p asζp=p/3.However experimental data(e.g.,Anselmet et al.1984)have shown departure from this linear relation andζp increases significantly slower than p/3at large p.This“anomalous”scaling is referred to as intermittency.The data indicate broader and broader tails for the distribution ofδu(l)at smaller and smaller scales,e.g.,the kurtosis of the distribution, δu(l)4 / δu(l)2 2∝lζ4−2ζ2, increases with decreasing l becauseζ4<2ζ2.The distribution ofδu(l)is fatter for smaller l.The anomalous scaling is fundamentally caused by thefluctuations in the dissipation rateǫl.Applying the refined similarity argument for homogeneous and isotropic turbulence (Kolmogorov1962),the velocity difference over a separation l can be related to the dissipation rateǫl,l1/3.(9)δu(l)∼ǫ1/3l(note that the Kolmogorov’s1941theory uses¯ǫ.)The structure functions are then given by,δu(l)p ∝ ǫp/3l l p/3.(10)。

考试注意事项整个试卷共120题,听力部分有30道题,长度约25分钟,该部分结束后立即开始语法词汇部分,然后是填充部分和阅读部分。

这三部分时间统用,共80分钟。

听力录音长度约21分钟,共30题,其中10题有惩罚措施:做对得1分,做错扣0.5分。

因此建议:不要做没有把握的题。

阅读部分中第111-120题亦有惩罚措施:做对得1分;做错扣1分。

请先下载听力试题的声音文件(MP3格式。

按鼠标右键,用―目标另存为...‖将声音文件下载到硬盘上,然后用相关软件播放。

试题的标准答案附在最后。

请自己核对答案。

最终成绩的换算表:Part I Listening Comprehension (听力理解每个正确答案乘以 1Part II Grammar and Vocabulary (语法、词汇每个正确答案乘以 0.6Part III Cloze (填充每个正确答案乘以 0.8Part IV Reading Comprehension (阅读理解每个正确答案乘以 1四项换算后的成绩之和为总分。

满分为100分。

录取等级参考标准如下:高级班:65分以上中级班:50-64分准中级班:35-49分基础班:20-34分Part I Listening ComprehensionSection ADirections :In this section, you will hear 10 short statements. The statements will be spoken just once. They will not be written out for you, and you must listen carefully in order to understand what the speaker says.When you hear a statement, you will have a period of 15 to 20 seconds to read the four sentences in your test book and decide which one is closest in meaning to the statement you have heard. Then, on your answer sheet, find the number of the problem and mark your answer by drawing with a pencil a short bar across the corresponding letter in the brackets.Listen to the following example:You will hear:You will read:[A] He's been living in Beijing for a long time.[B] He used to live in Beijing.[C] He's gone to Beijing for a short visit.[D] He should stay longer in Beijing,Sentence [B] "He used to live in Beijing" is closest in meaning to the statement "He is no longer living in Beijing." Therefore you should choose answer [B].1. [A] Tom is riding a bike.[B] The bike is upside down.[C] Tom is repairing the bike.[D] Tom is cleaning his bike.2. [A] Professor Graff doesn't usually write on the blackboard.[B] Students are rarely bored in Professor Grafts class.[C] The professor uses graphs when she lectures.[D] Students in the graphic arts course don't take notes.3. [A] They are with them.[B] It is with them.[C] They are with her.[D] He is with her.4. [A] I passed the test because I studied hard.[B] I won't do well on the test if I don't study.[C] I failed the test because I didn't study enough.[D] I'll study hard so I can pass the test.5. [A] How long is the school term?[B] Why did you turn over the stool?[C] I wish I know how to get to the dormitory.[D] I want the term to end soon.6. [A] The boat owner must be rich.[B] This man must be the owner.[C] Those men are both rich.[D] The boat has a monkey on it.7. [A] Alice answered Jean's question.[B] Alice allowed Jean to respond.[C] Jean's response was questionable.[D] Alice accepted the answer.8.[A] Bob bought a new pair of sandals.[B] Bob's sandals were fixed.[C] The shoemaker only made sandals.[D] The shoemaker wore sandals.9.[A] We have to go to a party after work.[B] We are going to have a party when the house has been painted.[C] We went to a huge party after the house was painted.[D] We'll go to the party if the house is painted.10. [A] They read about the invention in the news report.[B] The inventor wrote an interesting news report.[C] A reporter asked the inventor some questions.[D] The reporter was watching the news.Section BDirections:In this section you will hear 10 short conversations between two speakers. At the end of each conversation, a question will be asked about what was said. You will hear the question only once. When you have heard the question, you will have a period of 15 to 20 seconds to read the four possible answers marked [A], [B], [C] and [D] and decide which is the best answer. Mark your answer on the answer sheet by drawing with a pencil a short bar across the corresponding letter in the brackets.Example :You will hear:'You will read:[A] At the office.[B] On his way to work.[C] Home in bed.[D] Away on vacation.From the conversation, we know that Bill is sick and will have to stay in bed until Monday. The best answer, then, is [C] "Home in bed." Therefore, you should choose answer [C].11. [A] On the steps.[B] By the window.[C] At s store.[D]In a bank.12. [A] It's almost time for lunch.[B] Only a few strawberries will be eaten at lunch.[C] There are just enough strawberries for lunch.[D] There won't be many people for lunch.13.[A] No one knows how Mary gets to work.[B] It's surprising that Mary could repair the record player.[C] She threw the old records away.[D] She doesn't think the record player works.14. [A] In a railroad station.[B] In a bus terminal.[C] In a restaurant.[D] In a hotel room.15. [A] At the information desk.[B] On the platform.[C] On the train.[D] Near the stairs.16. [A] Eighteen.[B] Nineteen.[C] Twenty.[D] Twenty-eight.17. [A] He gave homework.[B] He prepared a test.[C] He opened the book to page 20.[D] He went to the cinema.18. [A] He doesn't understand the question.[B] He will definitely not lend her the money.[C] He will lend her the money.[D] He might lend her the money.19. [A] She lost her money.[B] The price of postage went up.[C] She didn't know where the post office.[D] The post office was closed today.20. [A] Zero.[B] One.[C]Two.[D] Three.Section CDirections :In this section you will hear several brief talks and/or conversations. You will hear them once only. After each one, you will hear some questions. You will hear each question once only. After you hear the question, you will have 1 5 to 20 seconds to choose the best answer from the four choices given. Mark your answer on the answer sheet by drawing with a pencil a short bar across the corresponding letter in the brackets.21. [A] A person's character.[B] A person's voice characteristics.[C] A person's health.[D] A person's profession.22. [A] The strength of the speaker.[B] The force of air that comes from the lungs.[C] The weight of the speaker.[D] The height of the speaker.23. [A] The highness or lowness of sounds.[B] The loudness of sounds.[C] The force of sounds.[D] The speed of sounds.24. [A] The Student Activities Office will open.[B] Seniors will measure their heads.[C] Students will order new school hats.[D] Seniors will graduate.25. [A] All students[B] All seniors[C] All graduating seniors[D] All faculty26. [A] What kind of ceremony there will be[B] How to order the graduation outfit[C] How much to pay for the clothes[D] Where to go for graduation27. [A] Rent them[B] Buy them[C] Clean them[D] Measure them28. [A] Michael Jackson.[B] Muhammad Ali[C] A very famous actor.[D] A very famous and powerful president.29. [A] He was a gold medal winner in Olympics.[B] He is the younger brother of Michael Jackson.[C] He had some influence on the president of the U.S.[D] He is quite popular with the American young people today.30. [A] They usually don't live long.[B] They usually are quickly forgotten by the public.[C] They don't know where to hide themselves.[D] They are usually very fat.Part II Grammatical Structure and Vocabulary(30 minutesSection ADirections :There are 10 sentences in this section. Beneath each sentence there are 4 words or phrases marked [A], [B], [C] and [D]. Choose the one word or phrase that best completes the sentence. Mark your answer on the answer sheet by drawing with a pencil a short bar across the corresponding letter in the brackets.Example: I have been to the Great Wall three times ___ 1979.[A] from[B] after[C] for[D] sinceThe sentence should read, "I have been to the Great Wall three times since 1979." Therefore you should choose [D].31. Those foreign visitors look very ____.[A] smartly[B] wildly[C] like friends[D] friendly32.It ____ every day so far this month.[A] is raining[B] rains[C] has rained[D] rained33. James has just arrived, but I didn't know he ____ until yesterday.[A] will come[B] was coming[C] had been coming[D] came34. She ought to ___ my letter a week ago. But she was busy with her work.[A] have answered[B] answering[C] answer[D] be answered35. The house ____ windows are broken is unoccupied.[A] its[B] whose[C] which[D] those36. _____ of gold in California caused many people to travel west in hope of becoming rich.[A] The discovering[B] To discover[C] The discovery[D] On discovering37. _____ the Wright brothers successfully flew their airplane.[A] The century was beginning[B] It was the beginning of the century[C] At the beginning of the century[D] The beginning of the century38. After a brief visit to New Orleans,____.[A] returning to New York and beginning to write his greatest poetry did Walt . Whitman.[B] Walt Whitman returned to New York and began to write his greatest poetry.[C] Walt Whitman was writing his greatest poetry when he returned to New York.[D] having returned to New York Walt Whitman wrote his greatest poetry.39. We wish that you ____ such a lot of work , because we know that you would have enjoyed theparty.[A] hadn't had[B] hadn't[C] didn't have had[D] hadn't have40. Since your roommate is visiting her family this weekend, why_____ you have dinner with ustonight[A] will[B] won't[C]do[D] don'tSection BDirections :There are 10 sentences in this section. Each sentence has four parts underlined. The four underlined parts are marked [A], [B], [C] and [D]. Identify the one underlined part that is wrong. Mark your answer on the answer sheet by drawing with a pencil a short bar across the corresponding letter in the brackets.Example:A number of foreign visitors were taken to the industrial exhibition which they sawA B C Dmany new products.Answer [C] is wrong because the sentence should read, "A number of foreign visitors were taken to the industrial exhibition where they saw many new products." So you should choose[C].41. Thomas is most excellent in the family.A B C D42. By 1642 all towns in the colony of Massachusetts was required by law to have schools.A B C D43. Both moths and butterflies have a keen sense of sight, smell, and tasting.A B C D44.The plane took off after holding up for hours by fog.A B C D45. Smith sold most of his belongings. He has hardly nothing left in the house.A B C D46. The reason why I decided to come here is because this university has a goodA B CDepartment of English.D47.If he would have finished his paper a little sooner, he would have graduated this term.A B C D48. Most experts agree that there have never been such an exciting series ofA B Cbreakthroughs in the search for a cancer cure as we have seen recently.D49. If one does not have respect for himself, you cannot expect others to respect him.A B C D50. The South is mostly Democrat politically, when the North has both DemocratsA B C Dand Republicans.Section CDirections:There are 20 sentences in this section. Each sentence has a word or phrase underlined. There are four words or phrases beneath each sentence. Choose the one word or phrase which would best keep the meaning of the original sentence if it were substituted for the underlined part. Mark your choice on the answer sheet by drawing with a pencil a short bar across the corresponding letter in the brackets.Example: The initial step is often the most difficult.[A] quickest[B] longest[C] last[D] firstThe best answer is [D] because "first" has the same meaning as "initial" in the sentence. Therefore you should choose [D].51. The initial talks were the base of the later agreement.[A] first[B] quickest[C] last[D] longest52. She is quiet and pious at church in the morning but gossips all afternoon.[A]gentle[B] smiling[C]joyful[D] devout53. The weatherman said, "It will be chilly this afternoon."[A] wet[B] turbid[C] hot[D] cold54. He walked to his bedroom cautiously because he heard strange sounds in it.[A] happily[B] carefully[C] curiously[D] noisily55. Apparently she never got my letter after all.[A] Evidently[B] Disappointedly[C] Luckily[D] Anxiously56. Placing tags on ducks and geese as they migrate is one method of studying the behavior of birds.[A] sleep for winter[B] move from one place to another[C] flee their enemies[D] search for food57. In September, 1835, Darwin's vessel arrived at the Galapagos Islands.[A] assistant[B] cargo[C] ship[D] gun58. Movie studios often boost a new star with guest appearances on television talk shows.[A] attack[B] watch[C] denounce[D] promote59. When products advertise extensively on television, they are often ridiculously overpriced.[A] inexpensive[B] costly[C] valueless[D] overabundant60. John and his brother have entirely different temperaments.[A] likings[B] dispositions[C] tastes[D] objectives61. Seeds are contained in the center of fleshy fruit such as apples and pears.[A] core[B] focus[C] nucleus[D] median62. One of the responsibilities of a forest ranger is to drive slowly through the area in search of animals in distress.[A] cruise[B] tiptoe[C] skid[D] mare63. Mrs. Palmer was offended by the clerk's mean remark.[A] tasty[B] nasty[C] misty[D] musty64. Most recipients of the peace prize are given the award in person, but sometimes the award is givenposthumously.[A] when the person is out of the country[B] after the person has died[C] to political prisoners[D] by mail65. Seeing the Grand Canyon from the air is a sight to behold.[A] hold upon[B] remember[C] anticipate[D] gaze upon66: Mythical creatures have been a part of the folklore of many cultures throughout the centuries.[A] Appealing[B] Magical[C] Legendary[D] Fighting67. Everyone would like a panacea for health problems.[A] protection against[B] advice for[C] a cure-all for[D] a decrease in68. In the fall it is gratifying to see stalks of wheat ready for harvest.[A] terrifying[B] satisfying[C] surprising[D] relaxing69. A bad winter storm can paralyse an urban area.[A] immobilise[B] evacuate[C] isolate[D] stabilise70. Even though he was obese, Oliver Hardy gained fame as a comedian.[A] dying[B] crazy[C] unhappy[D]fatPart III ClozeDirections: For each blank in the following passage, choose the best answer from the choices in the column on the right. Then, on your answer sheet, find the number of the question and draw a short bar across the corresponding letter.There is a lot of luck in the drilling foroil. The [71] may just miss the oil although it is near;[72], it may strike oil at a fairly high[73]. When the drill goes down, itbrings [74] soil. The sample of soil from various depths areexamined for traces of [75]. If they are disappointed at one place, thedrillers go to [76]. Great sums ofmoney [77] spent, for example in the deserts of Egypt, in ‗prospecting‘ for oil. Sometimes[78] is found. When you buy a few gallons of petrol for our cars, we pay not only the [79] of the petrol, but also part of the cost if the search that 71.[A] time[B] man[C] drill[D] plan72. [A] at last[B] in the end[C] as a result[D] on the other hand73. [A] level[B] time[C] place[D] price74. [A] down[B] up[C] on[D] in75. [A] sand[B] water[C] oil[D] gas76. [A] another[B] the other[C] others[D] one another77. [A] are[B] is[C] has been[D] have been78. [A] a little[B] little[C] a few[D] few79. [A] amount[B] price[C] cost[D] drilling北京语言大学出国人员培训部/入学考试样题/2013is [ 80 ] going on.When the crude oil is obtained from the field, it is taken to the refineries.[ 81 ].The commonestform of treatment is [ 82 ]. When the oil is heated, the first vapours[ 83 ] are cooled and become the finest petrol. Petrol has a lowboiling[ 84 ]; if a little is poured into the hand, it soon vaporizes.Gas that comes off the [ 85 ] lateris condensed into paraffin. [ 86 ] the lubricating oils of variousgrades are produced. What [ 87 ] is heavy oil that is used as fuel.There are four main areas ofthe world [ 88 ] deposits of oil appear.The first is [ 89 ] of the Middle East.Another is thearea [ 90 ] North and South America, and the third, between Asia and Australia. The fourth area is the part near the North Pole. 80. [A] often[B] frequently[C] busily[D] always81. [A] to be treated[B] to treat[C] for treatment[D] for treating82. [A] heated[B] to be heated[C] to heat[D] heating83. [A] to rise[B] rises[C] rising[D] risen84. [A] level[B] place[C] point[D] degree85. [A] ground[B] air[C] oil[D] water86. [A] Then[B] Last of all[C] Afterwards[D] Lately87. [A] remains[B] remain[C] remained[D] remaining88. [A] there[B] which[C] that[D] where89. [A] the one[B] one[C] that[D] this90. [A] between[B] among[C] above[D] belowPart IV Reading Comprehension(40 minutesDirections:In this part there are passages followed by questions or unfinished statements, each with four suggested answers. Choose the one you think is the best answer. Mark your choice on the answer sheet by drawing with a pencil a short bar across the corresponding letter in the brackets. Questions 91-94 are based on the following passage:The fiddler crab is a living clock. It indicates the time of day by the color of its skin, which is dark by day and pale by night. The crab's changing skin color follows a regular 24-hour cycle that exactly matches the daily rhythm of the sun.Does the crab actually keep time, or does its skin simply respond to the sun's rays, changing color according to the amount of light that strikes it? To find out, biologists kept crabs in a dark room for two months. Even without daylight the crab's skin color continued to change precisely on schedule.This characteristic probably evolved in response to the rhythm of the sun, to help protect the crab from sunlight and enemies. After millions of years it has become completely regulated inside the living body of the crab.The biologists noticed that once each day the color of the fiddler crab is especially dark, and that each day this occurs fifty minutes later than on the day before. From this they discovered that each crab follows not only the rhythm of the sun but also that of the tides. The crab's period of greatest darkening is precisely the time of low tide on the beach where it was caught!91. The fiddler crab is like a clock because it changes color[A] in a regular 24-hour rhythm.[B] in response to the sun's rays.[C] at low tide.[D] every fifty minutes.92. The crab's changing color[A] tells the crab what time it is.[B] protects the crab from the sunlight and enemies.[C] keeps the crab warm.[D] is of no real use.93. When the fiddler crabs were kept in the dark, they[A] did not change color.[B] changed color more quickly.[C] changed color more slowly.[D] changed color on the same schedule.94. The best title for the passage is[A] The Rhythmic Cycles of the Sun and Tide[B] Discoveries in Biology[C] A Scientific Study[D] A living ClockThere is another example of the revolution in railway signaling and safety measures which can also be attributed to the widespread introduction of electricity in the last decade of the nineteenth century. The track circuit, patented by one William Robinson as far back as 1872, was based on a simple principle. A section of track is insulated at the rail joints from the adjoining sections, and an electrically-operated switch or relay is maintained in the closed position by a low-voltage current passing continually through the rails. The effect of the entry of a train on the insulated section is to short-circuit this current through its wheels and axles with the result that the switch opens. It will be appreciated that should the current fail or should an accidental short-circuit take place, the device will behave as if a train were on the section. However, it will obey the essential requirement of every safety device that in the event of failure the danger signal is given.95. What does the paragraph preceding this one probably discuss?[A] Another one of Robinson's inventions[B] A twentieth-century safety device[C] An electrically-operated safety device[D] Railroading in the mid-nineteenth century96. In the last sentence in the passage, what does the word "it" refer to?[A] An accidental short-circuit[B] A danger signal[C] A safety device[D] A train97. Which of the following statements is TRUE?[A] Railway signaling improved with the American Revolution.[B] The last century saw great progress in railway signaling device.[C] The track circuit is a simple application of a complex principle.[D] The widespread introduction of electricity took place around 1910.98. If a short-circuit takes place, what will happen to the section containing the safety device?[A] A fire will start.[B] A danger signal will be given.[C] A train will derail.[D] The electrically operated switch will close.99. What is the result when a train passed over a section with a low-voltage current?[A] It will derail.[B] A switch opens.[C] A danger signal is given.[D] It will shock the crew.100. What is the topic of this passage?[A] The development of electrical safety devices[B] The inventions of William Robinson[C] The danger of railroad accidents[D] The operation of an electrical safety device for trainsLife near the shore everywhere is affected by the tides, which come and go twice each day in a cycle of about twelve-and-a-half hours —just different enough from the daily cycle of the sun so that there can be no regular relationship between the shore being alternately wet and dry and alternately light and dark. The extent of the tides varies greatly, from as little as one foot in inland seas like the Mediterranean, to fifty feet or so in the Bay of Fundy in Nova Scotia. In some parts of the world, one of the two daily tides rises higher and falls lower than the other; and tides at the time of new moon and full moon are generally greater than at other times. The extent of the intertidal zone thus varies from day to day as well as from place to place.The kinds of organisms living in the region between the tidal limits depend very much on whether the shore is rocky, sandy, or muddy. Rocky shores have the most obviously rich faunas, because of the firm anchorage for both animals and plants, and because of the small pools left by the retreating seas. Sandy shores, especially when exposed to surf (as they usually are, have the fewest kinds of animals.101. Which of the following factors does not affect the extent of the tides?[A] Place[B] Time[C] The moon[D] The composition of the shore soil102. The time span between tides[A] varies as much as the extent of the tides.[B] is a more constant phenomenon than the extent of the tides.[C] is shorter in inland seas.[D] and the extent of tides depend upon each other.103. The two tides in a given day[A] may vary in extent.[B] never vary in extent.[C] always vary in extent.[D] only vary in extent at the time of a new moon or a full moon.104. The composition of the intertidal soil affect[A] the nature of tides.[B] the temperature of the water in that area.[C] the amount of animals and plants living in that area.[D] the level of pollution in that area.105. Muddy shores[A] have poorer faunas than do sandy shores.[B] have richer faunas than do rocky shores.[C] have poorer faunas than do rocky shores, but richer faunas than do sandy shores.[D] have no faunas at all.106. The smallest tides occur in[A] open seas.[B] inland.[C] bays.[D] deeper seas.Reading is the key to school success and, like any skill, it takes practice. A child learns to walk by practising until he no longer has to think about how to put one foot in front of the other. A great athlete practices until he can play quickly, accurately, without thinking. Tennis players call that "being in the zone." Educators call it "automaticity."A child learns to read by sounding out the letters and decoding the words. With practice, he stumbles less and less, reading by the phrase. With automaticity, he doesn't have to think about decoding the words, so he can concentrate on the meaning of the text.It can begin as early as first grade. In a recent study of children in Illinois schools, Alan Rossman of Northwestern University found automatic readers in the first grade who were reading almost three times as fast as the other children and scoring twice as high on comprehension tests. At fifth grade, the automatic readers were reading twice as fast as the others, and still outscoring them on accuracy, comprehension and vocabulary."It's not I.Q. but the amount of time a child spends reading that is the key to automaticity," according to Rossman. Any child who spends at least 3.5 to 4 hours a week reading books, magazines or newspapers will in all likelihood reach automaticity. At home, where the average child spends 25 hours a week watching television, it can happen by turning off the set just one night in favour of reading.You can test your child by giving him a paragraph or two to read aloud - something unfamiliar but appropriate to his age. If he reads aloud with expression, with a sense ofthe meaning of the sentences, he probably is an automatic reader. If he reads haltingly, one word at a time, without expression or meaning, he needs more practice.107. The first paragraph tells us____.[A] what automaticity is[B] how accuracy is acquired[C] how a child learns to walk[D] how an athlete is trained108. An automatic reader[A] sounds out the letters[B] concentrates on meaning[C] has a high I.Q.[D] pays much attention to the structures of sentences109. The Illinois study shows that the automatic reader's high speed[A] costs him a lot of work[B] affects his comprehension[C] leads to his future success[D] doesn't affect his comprehension110. A bright child[A] also needs practice to be an automatic reader[B] always achieves great success in comprehension tests[C] becomes an automatic reader after learning how to read[D] is a born automatic readerQuestions 111 - 116 are based on the following passage:The Triumph of Unreason?Neoclassical economics is built on the assumption that humans are rational beings who have a clear idea of their best interests and strive to extract maximum benefit (or―utility‖, in economist-speak from any situation. Neoclassical economics assumes that the process of decision-making is rational. But that contradicts growing evidence that decision-making draws on the emotions—even when reason is clearly involved.The role of emotions in decisions makes perfect sense. For situations met frequently in the past, such as obtaining food and mates, and confronting or fleeing from threats, the neural mechanisms required to weigh up the pros and cons will have been honed by evolution to produce an optimal outcome. Since emotion is the mechanism by which animals are prodded towards such outcomes, evolutionary and economic theory predict the same practical consequences for utility in these cases. But does this still apply when the ancestral machinery has to respond to the stimuli of urban modernity?One of the people who thinks that it does not is George Loewenstein, an economist at Carnegie Mellon University, in Pittsburgh. In particular, he suspects that modern shopping has subverted the decision-making machinery in a way that encourages people to run up debt. To prove the point he has teamed up with two psychologists, Brian Knutson of Stanford University and Drazen Prelec of the Massachusetts Institute of Technology, to look at what happens in the brain when it is deciding what to buy.。

a rXiv:h ep-ph/232v128Fe b22UCLA/02/TEP/5Future determination of the neutrino-nucleon cross section at extreme energies.a Alexander Kusenko Department of Physics and Astronomy,UCLA,Los Angeles,CA 90095-1547RIKEN BNL Research Center,Brookhaven National Laboratory,Upton,NY 11973Future detectors of cosmic rays,such as EUSO and OWL,can test the Standard Model predictions for the neutrino interactions at energies well beyond the reach of any terrestrial experiment.The relative rates of horizontal and upgoing air showers,combined with the angular distribution of upgoing air showers will allow one to measure the neutrino-nucleoncross section at √s =314GeV.(Thiscorresponds to a laboratory energy E ν=5.2×1013eV of an incident neutrino.)UHE neutrinos are expected to arise from pion and muon decays.The subsequent oscillations generate a roughly equal fraction of each neutrino flavor.Tau neutrinos interacting below the surface of the Earth can create an energetic τ-lepton,whose decay in the atmosphere produces an UAS.It is clear that,for smaller values of the cross section,the Earth is more transparent for neutrinos,so that more of them can interact just below the surface and produce a τthat can come out into the atmosphere.As long as the mean free path λνis smaller than the radius of the Earth,the rates of UAS increase with λν∝1/σνN .The rates of HAS,however,areproportionalFigure1:The air shower probability per incident tau neutrino as a function of the neutrino cross section.The incident neutrino energy is1020eV and the assumed energy threshold for detection of UAS is E th=1018eV forcurve1and1019eV for curve2.toσν;they decrease for a smaller cross section.The comparison of the two rates,shown in NFig.1,can allow a measurement of the cross section which is practically independent of the uncertainties in the incident neutrinoflux.In addition,the angular distribution of UAS alone can be used as an independent mea-surement of the cross section.The peak of the angular distribution of UAS occurs5when cosθpeak≈λν/2R⊕,which depends on the cross section.It is comforting to know that the program of UHE neutrino astronomy,which is one of the goals of EUSO and OWL,is not at risk,regardless of any theoretical uncertainties in the neutrino cross section.For a larger cross section,HAS are more frequent than HAS,while for a smaller value UAS dominate.Nevertheless,the total rates of combined events remain roughly,as shown in Fig.1.constant for a wide range ofσνNOn the other hand,some of the reported bounds on the neutrinoflux are directly affected by the uncertainties in the neutrino-nucleon cross section.For example,the reported bounds on the UHE neutrinoflux due to the non-observation of neutrino-initiated HAS14and of radio signals produced by neutrino interactions near the surface of the moon15are weaker if the cross section is smaller.To conclude,the future neutrino cosmic-ray experiments can determine the neutrino-nucleon cross section at energies as high as1011GeV,or higher,by comparing the rates of UAS with those of HAS;or by measuring the angular distribution of UAS events.Hence,there is an exciting opportunity do a particle physics experiment using a natural“beam”of cosmic UHE neutrinos in the near future.In addition,the overall prospects for UHE neutrino astronomy are not marred by possible theoretical uncertainties in the value of the neutrino-nucleon cross section:the total number of horizontal and upgoing events remains sufficient for a wide range .ofσνNAcknowledgmentsThis work was supported in part by the DOE grant DE-FG03-91ER40662.References1.J.L.Feng,P.Fisher,F.Wilczek and T.M.Yu,arXiv:hep-ph/0105067.2.X.Bertou,P.Billoir,O.Deligny, chaud and A.Letessier-Selvon,arXiv:astro-ph/0104452.3.G.Domokos and S.Kovesi-Domokos,arXiv:hep-ph/9805221.4.D.Fargion,arXiv:astro-ph/0002453.5.A.Kusenko and T.Weiler,arXiv:hep-ph/0106071.6.For reviews,see,e.g.,P.Bhattacharjee and G.Sigl,Phys.Rept.327,109(2000);M.Nagano and A.A.Watson,Rev.Mod.Phys.72,689(2000);T.J.Weiler,arXiv:hep-ph/0103023;P.Biermann and G.Sigl,arXiv:astro-ph/0202425.7.F.W.Stecker, C.Done,M.H.Salamon and P.Sommers,Given at High-energyNeutrino Astrophysics Workshop on Astrophysics of High-energy Neutrinos:Particle Physics,Sources,Production Mechanisms and Detection Prospects,Honolulu,Hawaii, 23-26Mar1992;K.Mannheim,Astropart.Phys.3,295(1995);R.J.Protheroe, arXiv:astro-ph/9607165;F.Halzen and E.Zas,Astrophys.J.488,669(1997)[arXiv:astro-ph/9702193].8.E.Waxman,Phys.Scripta T85,117(2000)[arXiv:astro-ph/9911395];Nucl.Phys.Proc.Suppl.87,345(2000)[arXiv:astro-ph/0002243].9.T.Weiler,Phys.Rev.Lett.49,234(1982);Astropart.Phys.11,303(1999);D.Fargion,B.Mele and A.Salis,Astrophys.J.517,725(1999).10.For a recent review,see,e.g.,E.Waxman,Nucl.Phys.Proc.Suppl.100,314(2001).11.R.J.Protheroe,astro-ph/9809144;G.Gelmini and A.Kusenko,Phys.Rev.Lett.82,5202(1999);Phys.Rev.Lett.84,1378(2000);S.Yoshida,G.Sigl and 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A.Kuzmin, D.V.Semikoz and G.Sigl,arXiv:hep-ph/0112351;G.Gelmini and G.Varieschi,hep-ph/0201273.13.G.M.Frichter,D.W.McKay and J.P.Ralston,Phys.Rev.Lett.74,1508(1995);Phys.Rev.Lett.77E,4107(1996);R.Gandhi,C.Quigg,M.H.Reno and I.Sarcevic,Astropart.Phys.5,81(1996);R.Gandhi,C.Quigg,M.H.Reno and I.Sarcevic,Phys.Rev.D58, 093009(1998)14.R.M.Baltrusaitis,et al.(Fly’s Eye Collaboration),Phys.Rev.D31,2192(1985).15.P.Gorham,K.Liewer,and C.Naudet,[astro-ph/9906504]and Proc.26th Int.CRConf.,Salt Lake City,Utah,Aug.1999;Alvarez-Muniz and E.Zas,astro-ph/0102173;P.W.Gorham,K.M.Liewer,C.J.Naudet,D.P.Saltzberg and D.R.Williams,astro-ph/0102435.。

This article appeared in a journal published by Elsevier.The attached copy is furnished to the author for internal non-commercial research and education use,including for instruction at the authors institutionand sharing with colleagues.Other uses,including reproduction and distribution,or selling or licensing copies,or posting to personal,institutional or third partywebsites are prohibited.In most cases authors are permitted to post their version of thearticle(e.g.in Word or Tex form)to their personal website orinstitutional repository.Authors requiring further informationregarding Elsevier’s archiving and manuscript policies areencouraged to visit:/authorsrightsStability and migration of charged oxygen interstitials in ThO 2andCeO 2H.Y.Xiao a ,⇑,Y.Zhang b ,a ,W.J.Weber a ,baDepartment of Materials Science &Engineering,University of Tennessee,Knoxville,TN 37996,USA bMaterials Science &Technology Division,Oak Ridge National Laboratory,Oak Ridge,TN 37831,USAReceived 27June 2013;received in revised form 9August 2013;accepted 4September 2013Available online 30September 2013AbstractDensity functional theory calculations have been carried out to study the stability and migration of charged oxygen interstitials in ThO 2and CeO 2.The calculations demonstrate that the oxygen interstitial is likely to lose electrons under p -type conditions and gainelectrons under n -type conditions.Neutral O 0split and singly positive O þsplit O–O h 110i split interstitials,and doubly negative octahe-dral (O 2Àocta :)oxygen interstitial are found to be the lowest-energy configurations within a certain Fermi energy range.In both oxides,the O 0split is the most mobile,and the migration energies of the split oxygen interstitials in ThO 2are lower than in CeO 2,indicating higher oxygen interstitial mobility in ThO 2than in CeO 2.Ó2013Acta Materialia Inc.Published by Elsevier Ltd.All rights reserved.Keywords:DFT;Charged defect;Oxygen interstitial;Stability and migration1.IntroductionFluorite-structured oxides such as UO 2,PuO 2and ThO 2are important nuclear fuels in fission reactors [1,2],where they are exposed to irradiation damage from neutrons,high-energy charged particles (e.g.fission products)and alpha decay.Such irradiation damage produces atomic point defects,as well as electrons and holes that can trap point defects.The point defects contribute to the micro-structural evolution in nuclear fuel,although many of these defects recombine directly at elevated temperatures [3].The mobility of these primary radiation defects plays an impor-tant role in the microstructural evolution,and secondary diffusion-controlled reactions between defects can result in the formation of defect clusters,dislocation loops and voids.For example,the so-called Willis cluster that is formed by oxygen interstitial aggregation has been observed in UO 2experimentally [4].Oxygen interstitial dis-location loops lying on the {111}plane have been observed by Yasunaga et al.[5]in CeO 2irradiated withan electron beam.The formation of such defects may ulti-mately lead to the degradation of thermal and mechanical properties of nuclear materials [6].In addition to nuclear applications,oxygen interstitial defects have been sug-gested to provide oxygen mobility that facilitates the oxy-gen storage capacity of CeO 2in catalytic converters [3,7].Also,in systems such as ThO 2+x ,the anion-to-cation ratio has a strong effect on the physical and chemical properties,e.g.thermal conductivity [8].Understanding the stability and migration of oxygen interstitials is thus of critical importance for the evaluation of material properties and performance.In the past few decades,extensive studies of oxygen interstitial formation and transport in UO 2have been car-ried out [1,9–13].ThO 2and CeO 2,on the other hand,have received relatively less attention [1,14,15].In these studies,the point defects were treated as neutral charge states.However,it is well known that point defects in semicon-ductors and ceramics may be electrically charged due to doping,impurities or nonstoichiometry.For example,the oxygen interstitial in PuO 2.25is found to be singly charged (O À)[16].Under irradiation,atomic defects are produced by displaced atoms and even greater numbers of electrons1359-6454/$36.00Ó2013Acta Materialia Inc.Published by Elsevier Ltd.All rights reserved./10.1016/j.actamat.2013.09.001⇑Corresponding author.E-mail address:hyxiao@ (H.Y.Xiao)./locate/actamatAvailable online at ScienceDirectActa Materialia 61(2013)7639–7645and holes are created by ionization.Thus,even if neutral defects are created under irradiation,the trapping of ioni-zation-induced electrons and holes can result in the forma-tion of charged defects,as in the case of yttria-stablized ZrO2[17].These charged defects can affect defect structure, trapping rates of electrons and holes,defect formation and migration energies[18],and the kinetics of microstructure evolution,as in the faster grain growth observed in nano-crystalline cubic ZrO2under irradiation at cryogenic tem-peratures compared to higher temperatures[19].In the case of ZnO,it has been shown that the diffusion mecha-nism for the oxygen interstitial is dependent on the defect charge state[20].Other important properties,such as the luminescence quenching rates,may also be influenced by the charge state.Recently,the charge states of defects influorite-struc-tured oxides have gained increasing interest[21–24],but these studies are mainly focused on the formation of charged defects.At present,the stability and migration of charged oxygen interstitials influorite-structured oxides, including the migration energies and pathways,has not yet been well studied.In this study,we investigate charged oxygen interstitial formation and migration in ThO2and CeO2.Here,CeO2is used as a surrogate material in place of PuO2for performance evaluation in harsh environments [25–27],because they share the same crystallographic struc-ture,and several thermophysical and chemical properties. Our main aims are:(i)to gain fundamental insight into charged oxygen interstitial behavior in ThO2and CeO2; (ii)to motivate experimental studies and provide support for their interpretation;and(iii)to provide physical param-eters(e.g.defect configurations and energetics)for higher-scale modeling offluorite-structured oxide fuels.putational detailsAll the calculations were carried out within the density functional theory(DFT)framework using the projector-augmented wave method,as implemented in the Vienna Ab Initio Simulation Package(VASP)[28].The exchange-correlation effects were treated by the local-den-sity approximation(LDA)in the Ceperley–Alder parame-trization[29],with spin-polarized effects considered. Structural optimizations were carried out at variable cell shape and volume,as well as under the condition that the Hellmann–Feynman force on each atom should be smaller than0.01eV A˚putations were based on a2Â2Â2 supercell consisting of96atoms,with a4Â4Â4k-point sampling in reciprocal space and a cutoffenergy of 550eV for the plane-wave basis set.Our previous work on oxygen vacancy formation and migration in CeO2has shown that the Hubbard U correction for the on-site Cou-lomb interaction must be taken into account due to the existence of Ce3+[30],which is consistent with other theo-retical studies on reduced ceria[31–33].In this study,plus U correction calculations were also performed to investi-gate if the Hubbard U correction for Th5f(or Ce4f)electrons is necessary for ThO2(or CeO2)containing anoxygen interstitial.In the LDA+U calculations,the method proposed by Dudarev et al.[34]was used,and effective U values of4eV for Th and6eV for Ce,obtained from our previous study[30],were employed.The mini-mum-energy pathways for oxygen interstitial migration in ThO2and CeO2were investigated by the climbing-image nudged elastic band method[35].3.BackgroundFor systems with charged defects,spurious electrostatic and elastic interactions between the defect and its periodic images can be large,and the system converges very slowly with respect to the supercell size.To correct the electro-static effects on the formation energies of charged defects, several approaches have been proposed[36–40].Here,the screened Madelung-like lattice energy of point defects pro-posed by Leslie and Gillan[39]is employed,i.e.E corr¼q2a M2e L, where L=XÀ1/3is the linear supercell dimension,X is the volume of the supercell,e is the dielectric constant and a M is the appropriate Madelung constant for the respective supercell geometry.Another correction for the charged sys-tem is the potential alignment,D V,which is used to esti-mate the valence band maximum(VBM)of the defective supercell.The D V value is obtained by the averaged differ-ence between the local potentials far from the defect in the defective supercell and the corresponding ones in the per-fect supercell[41].The defect formation energies are definedby E f¼E defÀE perfectþn i l Oþq E FþE bulkVBMþD VÀÁþE corr [42],where E def and E perfect are the total energies of the supercell with and without a defect,respectively,n i is the number of atoms being removed or added,and l O is the chemical potential of O.The value of l O is obtained under O-rich or M-rich(M=Th or Ce)conditions.Under O-rich conditions,the experimental chemical potential of O(l O) from the free O2molecule is employed[43];under M-rich conditions,l O is obtained by l MO2¼l Mþ2l O;wherelMO2and l M are calculated from the total energies of bulk MO2and M,respectively.The term in parentheses is the electronic chemical potential that represents the change in energy associated with charged defects.In this term,E F is the Fermi level in the bulk with reference to the VBM,which can vary within the band gap,E bulkVBMis the energy of the bulk VBM,and D V is the electrostatic potential alignment of the defective structure.The additional charge q is set by adding or removing electrons from the supercell. The last term,E corr,is thefirst-order Madelung correction energy.4.Results and discussionparison of LDA+U and LDA calculations for oxygen interstitial formationPulsed neutron diffraction experiments performed on a nanoscale powder of CeO2by Mamontov and Egami7640H.Y.Xiao et al./Acta Materialia61(2013)7639–7645revealed oxygen interstitial occupation at the octahedral site of the CeO2[3].Our ab initio molecular dynamics sim-ulation of low-energy recoil events in ThO2,CeO2and ZrO2also showed that,under low-energy irradiation,oxy-gen interstitials generally occupy the octahedral site(O octa.)[2].In addition to this octahedral site,the O–O h110i split interstitial(O split)is also a possible stable defect.These two oxygen interstitial(O int)configurations,as shown in Fig.1, are considered as the initial configurations in the present work to study charged oxygen interstitial incorporation and migration in ThO2and CeO2.To investigate the effect of considering the Hubbard U correction for Th5f and Ce4f electrons on the stability of oxygen interstitial in ThO2and CeO2,the formation energies for the octahedral oxygen interstitials with charge states varying from2Àto2+arefirst calculated by both LDA and LDA+U methods.The variation of the formation energies as a function of the Fermi level with different charge states in both oxides is shown in Fig.2. Under both O-rich and Th-rich conditions,it appears that consideration of the Hubbard U correction for the Th5f electrons has only a small influence on the interstitial formation energies in ThO2.In CeO2,the plus U correctionfor the Ce4f electrons affects the O2Àocta:interstitialformation under both O-and Ce-rich conditions,which narrows the stability region by$0.25eV.The density ofstate distribution for the O2Àocta:interstitial in CeO2andThO2obtained by both methods is further analyzed,as illustrated in Fig.3.It turns out that the standard LDA describes well the splitting of Ce4f and Th5f electrons into occupied and unoccupied states,and LDA+U only pushes the unoccupied states to a higher energy level.This is different from the case of oxygen vacancy formation in CeO2[30],for which the Hubbard U correction for the on-site Coulomb interaction is necessary to localize the Ce4f electrons.For the split oxygen interstitials in both oxides,the LDA+U and LDA methods also predict very similar formation energies,and the f electrons are well 4.2.Stability of oxygen interstitialsThe defect formation energies for octahedral and splitoxygen interstitials in ThO2and CeO2are presented in Fig.4a and b,respectively.Because oxygen interstitials are more favorable under O-rich conditions than Th-rich conditions,only the O-rich condition is considered here. In ThO2,it is found that the Oþsplit,O0split,OÀocta:and O2Àocta: are the lowest-energy configurations in the Fermi energy ranges0–0.32,0.32–1.35, 1.35–2.73and 2.73–4.04eV, respectively.The geometrical configurations for the Oþsplit,O0splitand O2Àocta:interstitials in ThO2are shown in Fig.5. Our calculations indicate that the stability of oxygen inter-stitial depends on the charge state,Fermi level and oxygen interstitial configuration.The stability of oxygen interstitial in ThO2is found to be different from that in UO2 [21,22,44],for which the O2-interstitial is more stable over most of the Fermi energy range.Such a discrepancy may be caused by the different interactions between the oxygen interstitial and its neighbors.In CeO2,the Oþsplit,O0splitand O2Àocta:interstitials are the low-est-energy configurations in the Fermi energy ranges0–0.39, 0.39–1.76and 1.76–2.17eV,respectively,as shown inFig.4b.Similar to the case of ThO2,the Oþsplitinterstitial is preferred under p-type conditions,where the Fermi level isvery close to the valence band maximum,and O2Àocta:is favored under n-type conditions,i.e.as the Fermi level approaches the conduction band minimum.These results suggest that,in both ThO2and CeO2,the oxygen interstitial is likely to lose electrons under p-type conditions and gain electrons under n-type conditions,behaving as a donor and acceptor defect,respectively.Erhart et al.[45]also sug-gested the donor-and acceptor-like characters of the oxygen interstitial atoms in ZnO.It should be pointed out that the singly positive split interstitials are only stable when the Fermi level is very close to the valence band maximum.Bad-er charge analysis shows that these singly positive split inter-stitials donate electrons to all of theirfirst-neighboring cations,resulting in a positive charge state of the interstitials. Anotherfinding is that the energy difference between the octahedral and split interstitials with a specific charge stateis much smaller in ThO2,and that OÀocta:is one of the low-est-energy configurations within the Fermi energy range in ThO2but not in CeO2.This suggests despite the fact that ThO2and CeO2have the samefluorite-type structure,the size and electronic configuration of the cations may signifi-cantly affect the oxygen interstitial stability.To study the effect of charge states on the interatomic structures,the structural properties for oxygen interstitials with different charge states in both oxides have been further analyzed,as summarized in Table1.For the octahedral interstitials,the distance between the oxygen interstitial and its neighboring lattice oxygens increases as q increases from2Àto2+.This is because in MO2the lattice O ions are negatively charged,and the introduction of negatively or positively charged O int will push the nearest lattice oxygens away due to the repulsive interaction,or pull theFig.1.Schematic view of(a)octahedral(O octa.)and(b)split(O splitoxygen interstitial in ThO2.H.Y.Xiao et al./Acta Materialia61(2013)7639–76457641of oxygen interstitial formation energies with Fermi level in(a and b)ThO2and(c and d)CeO2under O-and M-rich and dotted lines correspond to the results obtained from LDA+U and LDA calculations,respectively.Density of state for O2Àocta:interstitial in(a)CeO2and(b)ThO2by LDA and LDA+U calculations.The Fermi level is set at the the energy.Fig.4.Oxygen interstitial formation energies as a function of the energy in(a)ThO2and(b)CeO2.Solid and dashed lines octahedral and split interstitials,respectively.nearest lattice oxygens closer due to the attractive interac-tion,respectively.Consequently,positive oxygen intersti-tials cause volume compression,and neutral or negative oxygen interstitials cause volume expansion.In the case of split interstitials,the h O int –O int i distance increases as q varies from 2+to 2À;however,the distances between either O int of the split interstitials and their neighboring lat-tice oxygens do not exhibit a singular change.Further-more,the introduction of the O 2þsplit into the system causes volume compression,and the split interstitials with other charge states cause volume swelling.Obviously,the charge states have considerable effects on the geometrical struc-tures for both split and octahedral interstitials.For some split interstitials in ThO 2and CeO 2,it is noted that the h O int –O int i bond distance is close to that of a freeO 2molecule,i.e.1.21A˚.However,the O–O split interstitial interacts with its neighboring atoms,and does not form an O 2molecule.Fig.6shows the charge density distribution for the O þsplit interstitial in ThO 2.The h Th–O 1i and h Th–O 2i bond lengths are each 2.46A˚.Each O int in the split interstitial interacts with two lattice oxygens at bond dis-tances of 2.41and 3.38A˚,respectively.The average Bader charge of the two oxygens in the split interstitial is +0.58|e|,as compared with the charge of ±0.16|e|in a free O 2,suggesting that the two oxygens in the split interstitial do not form a free molecule.Our theoretical prediction of the structural and electronic properties of the O þsplit pro-vides fundamental information for the design and interpre-tation of planned low-temperature irradiation experiments in these fluorite-structured oxides.(a) O split +(b) O split 0(c) O octa.2-<O-O>:1.39 Å<O-O>:1.43 ÅFig.5.Schematic view of geometrical configuration for (a)O þsplit ,(b)O 0split and (c)O 2Àocta :in ThO Table 1Geometrical properties for oxygen interstitial in ThO 2and CeO 2:d h O int –O int i is the h O–O i bond length of the split interstitial;d h O int –O lat i is the distance between the interstitial and its neighboring lattice oxygens;and D V is the defect formation volume relative to the perfect volume (V 0).ThO 2CeO 2d h O int –O int i (A˚)d h O int –O lat i (A ˚)D V /V 0(%)d h O int –O int i (A ˚)d h O int –O lat i (A ˚)D V /V 0(%)O 2þsplit1.362.38À0.28 1.31 2.28À0.41O þsplit 1.38 2.410.22 1.35 2.350.20O 0split 1.43 2.470.74 1.39 2.410.93O Àsplit1.992.43 1.24 1.40 2.42 1.78O 2Àsplit 2.43 2.42 1.76 2.35 2.35 2.23O 2þocta :– 2.44À0.90– 2.36À1.12O þocta :– 2.45À0.39– 2.37À0.46O 0octa :– 2.470.14– 2.400.23O Àocta :– 2.510.69– 2.430.98O 2Àocta :–2.541.26–2.471.87ThO 1O 2O(a)O 1O 2Th(b)2.46 Å2.46 Å1.38 Å(c)O 1O 2O 2.41 Å3.38Å2.41 ÅO O split +O split +O split +distribution for O þsplit in ThO 2projected on planes (a)containing interstitials and their first neighboring their first neighboring cations and (c)containing interstitials and their first neighboring anions.H.Y.Xiao et al./Acta Materialia 61(2013)7639–764576434.3.Oxygen interstitial migrationThe calculated energy barriers for oxygen interstitial migration in ThO 2and CeO 2are given in Table 2.In both oxides,the O þsplit is the most mobile,with migration energies of 0.13and 0.56eV in ThO 2and CeO 2,respectively.The O 0split interstitials,which also have a high degree of stability,have only slightly higher migration energies.These results indicate that the oxygen split interstitial is more mobile in ThO 2than in CeO 2.The activation energy for oxygen self-diffusion in ThO 2,which occurs via oxygen vacancies,has been determined experimentally [1,14];however,direct experimental measurement of oxygen vacancy and intersti-tial migration energies have not been reported.As shown in Fig.7,the saddle-point for O þsplit migration corresponds to the oxygen interstitial occupying an octahe-dral site O þocta :ÀÁ,which was shown to be a metastable state in Fig.4.The distance between the O int and its neighboringTh atoms is 2.79A˚,which is 0.33A ˚larger than that in the migrating defect replaces one lattice atom,and the lattice atom then becomes the migrating species,have been con-sidered [46,48].Although different migration barrier values were obtained,these calculations suggested that the inter-stitialcy mechanism in UO 2is more energetically preferable than the direct interstitial mechanism.For ThO 2and CeO 2,the interstitialcy mechanism is also found to be more favor-able than the direct interstitial mechanism.The case of O 2Àocta :interstitial migration in ThO 2via the interstitialcy mechanism is illustrated in Fig.7,where the saddle-pointcorresponds to the O 2Àsplit configuration.However,the energy barrier is significantly higher than that for O þsplit interstitial migration.Our calculations suggest that oxygen interstitial migra-tion in ThO 2and CeO 2is influenced by the charge state,configuration of the oxygen interstitial,and the composi-tion of host material.In ZnO,Erhart and Albe [20]also found the O 2-interstitial migrates via a different mecha-nism than the O 0and O 2+interstitials.The fact that the migration barrier and pathway are strongly dependent on the charge state in some oxides suggests the possibility of using an applied electric field to affect the diffusion and to control defect concentrations [48].The migration behav-ior of the oxygen interstitial in ThO 2and CeO 2generally exhibit similar characteristics,whereas the size and elec-tronic configuration of the cations still influence the migra-tion barriers,resulting in lower oxygen interstitial mobility in CeO 2.It is expected that these results may provide some new insights for future theoretical and experimental studies of point defects behavior in fluorite-structured oxides.5.ConclusionsIn summary,an ab initio method based on DFT has been employed to study the stability and migration of charged oxygen interstitial in ThO 2and CeO 2.It is shown that the Fermi level has a significant influence on the stabil-ity of oxygen interstitial.In ThO 2,the O þsplit ,O 0split ,O Àocta :and O 2Àocta :are the lowest-energy configurations in the Fermi energy ranges 0–0.32,0.32–1.35, 1.35–2.73and 2.73–4.04eV,respectively.In the case of CeO 2,the O þsplit ,O 0splitand O 2Àocta :interstitials are the lowest-energy configurations in the Fermi energy ranges 0–0.39,0.39–1.76and 1.76–2.17eV,respectively.These results suggest that oxygen interstitials behave as donor-and acceptor-like defects under p -type and n -type conditions,respectively.Split and octahedral interstitials with different charge states can cause local volume compression or swelling.Although the h O–O i bond length of split interstitial is close to that of a free O 2,the two oxygens interact with their neighbors rather than forming a free O 2molecule.In both oxides,the O þsplit migration has the lowest migra-tion barrier,for which the saddle-point corresponds to the oxygen interstitial occupying an octahedral site.The lowest migration energies are determined to be 0.13eV in ThO 2and 0.56eV in CeO 2,indicative of a higher mobility for the oxygen interstitial in ThO 2.Our calculations suggestTable 2Energy barrier for oxygen interstitial migration in ThO 2and CeO 2.ThO 2CeO 2O þsplit 0.130.56O 0split 0.320.76O Àocta :0.98–O 2Àocta :1.040.80Fig.7.Migration pathway for O 0split and O 2Àocta :in ThO 2.7644H.Y.Xiao et al./Acta Materialia 61(2013)7639–7645that the oxygen interstitial behavior in ThO2and CeO2is influenced by the charge state,interstitial configuration and composition of the host material.The stability and migration of the oxygen interstitial in both oxides generally exhibit similar characteristics;however,the migration bar-riers are significantly affected by cation size and electronic configuration.AcknowledgementsThis work was supported as part of the Materials Sci-ence of Actinides,an Energy Frontier Research Center funded by the US Department of Energy,Office of Science, Office of Basic Energy Sciences.The theoretical calcula-tions were performed using the supercomputer resources at the Environmental Molecular Sciences Laboratory lo-cated at Pacific Northwest National Laboratory,and the National Energy Research Scientific Computing Center lo-cated at Lawrence Berkeley National Laboratory. 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周佳悦，候艳丽，王凡予，等. 超声辅助低共熔溶剂提取红松树皮原花青素及动力学研究[J]. 食品工业科技，2023，44（14）：229−236. doi: 10.13386/j.issn1002-0306.2022100070ZHOU Jiayue, HOU Yanli, WANG Fanyu, et al. Ultrasonic-Assisted Deep Eutectic Solvent Extraction of Proanthocyanidins from Korean Pine Bark and Its Kinetics[J]. Science and Technology of Food Industry, 2023, 44(14): 229−236. (in Chinese with English abstract). doi: 10.13386/j.issn1002-0306.2022100070· 工艺技术 ·超声辅助低共熔溶剂提取红松树皮原花青素及动力学研究周佳悦1，候艳丽1，王凡予1，郭庆启1,2,*（1.东北林业大学生命科学学院，黑龙江哈尔滨 150040；2.黑龙江省森林食品资源利用重点实验室，黑龙江哈尔滨 150040）摘　要：目的：对超声辅助低共熔溶剂法提取红松树皮原花青素的工艺条件进行优化，拟合提取动力学方程，旨在对红松树皮中原花青素的资源开发利用提供理论和技术参考。

方法：以原花青素得率为指标，筛选最佳低共熔溶剂体系，并进一步通过单因素结合响应面优化超声辅助低共熔溶剂提取红松树皮中原花青素的主要工艺参数。

通过提取过程中不同温度和不同时间条件下原花青素得率的变化，拟合出最佳的原花青素提取动力学模型并验证。

结果：氯化胆碱、丙三醇和水的摩尔比为1:1:4制备的低共熔溶剂为红松树皮原花青素的最佳提取溶剂；响应面法优化工艺参数条件为：液料比16 mL/g ，超声时间50 min ，超声温度55 ℃，超声功率480 W 时，红松树皮原花青素的提取效果最好，原花青素得率为4.11%；Boltzman 模型能够很好地拟合超声辅助低共熔溶剂提取原花青素动力学过程（R 2≥0.9768），模型验证值与预测值拟合度较高（R 2≥0.9442）。

Material Safety Data SheetMelamine MSDSSection 1: Chemical Product and Company IdentificationProduct Name: MelamineCatalog Codes: SLM3256CAS#: 108-78-1RTECS: OS0700000TSCA: TSCA 8(b) inventory: MelamineCI#: Not available.Synonym: 2,4,6-Triamino-s-Triazine; Isomelami;neChemical Name: MelamineChemical Formula: C3-H6-N6Section 2: Composition and Information on IngredientsComposition:NameCAS #% by WeightMelamine108-78-1100Toxicological Data on Ingredients: Melamine: ORAL (LD50): Acute: 3161 mg/kg [Rat]. 3296 mg/kg [Mouse]. DERMAL(LD50): Acute: &gt;1000 mg/kg [Rabbit].Section 3: Hazards IdentificationPotential Acute Health Effects: Hazardous in case of skin contact (irritant), of eye contact (irritant), of ingestion, of inhalation(lung irritant).Potential Chronic Health Effects:CARCINOGENIC EFFECTS: Classified 3 (Equivocal evidence.) by NTP. 3 (Not classifiable for human.) by IARC. MUTAGENIC EFFECTS: Mutagenic for bacteria and/or yeast. TERATOGENIC EFFECTS: Not available. DEVELOPMENTAL TOXICITY: Not available. Repeated or prolonged exposure is not known to aggravate medical condition.Section 4: First Aid MeasuresEye Contact:Check for and remove any contact lenses. In case of contact, immediately flush eyes with plenty of water for at least 15 minutes. Cold water may be used. Get medical attention.Skin Contact:In case of contact, immediately flush skin with plenty of water. Cover the irritated skin with an emollient. Remove contaminated clothing and shoes. Cold water may be used.Wash clothing before reuse. Thoroughly clean shoes before reuse. Get medical attention.Serious Skin Contact:Wash with a disinfectant soap and cover the contaminated skin with an anti-bacterial cream. Seek immediate medical attention.Inhalation:If inhaled, remove to fresh air. If not breathing, give artificial respiration. If breathing is difficult, give oxygen. Get medical attention.Serious Inhalation: Not available.Ingestion:Do NOT induce vomiting unless directed to do so by medical personnel. Never give anything by mouth to an unconscious person. Loosen tight clothing such as a collar, tie, belt or waistband. Get medical attention if symptoms appear.Serious Ingestion: Not available.Section 5: Fire and Explosion DataFlammability of the Product: May be combustible at high temperature.Auto-Ignition Temperature: Not available.Flash Points: CLOSED CUP: Higher than 93.3°C (200°F).Flammable Limits: Not available.Products of Combustion:These products are carbon oxides (CO, CO2), nitrogen oxides (NO, NO2...), cyanide fumes, irritating and toxic fumes and gases.Fire Hazards in Presence of Various Substances: Slightly flammable to flammable in presence of heat.Explosion Hazards in Presence of Various Substances:Risks of explosion of the product in presence of mechanical impact: Not available. Risks of explosion of the product in presence of static discharge: Not available.Fire Fighting Media and Instructions:SMALL FIRE: Use DRY chemical powder. LARGE FIRE: Use water spray, fog or foam. Do not use water jet.Special Remarks on Fire Hazards: Not available.Special Remarks on Explosion Hazards: Not available.Section 6: Accidental Release MeasuresSmall Spill:Use appropriate tools to put the spilled solid in a convenient waste disposal container. Finish cleaning by spreading water on the contaminated surface and dispose of according to local and regional authority requirements.Large Spill:Use a shovel to put the material into a convenient waste disposal container. Finish cleaning by spreading water on the contaminated surface and allow to evacuate through the sanitary system.Section 7: Handling and StoragePrecautions:Keep locked up.. Keep away from heat. Keep away from sources of ignition. Empty containers pose a fire risk, evaporate the residue under a fume hood. Ground all equipment containing material. Do not ingest. Do not breathe dust. Wear suitable protective clothing. In case of insufficient ventilation, wear suitable respiratory equipment. If ingested, seek medical advice immediately and show the container or the label. Avoid contact with skin and eyes. Keep away from incompatibles such as oxidizing agents, acids.Storage: Keep container tightly closed. Keep container in a cool, well-ventilated area. Do not store above 23°C (73.4°F).Section 8: Exposure Controls/Personal ProtectionEngineering Controls:Use process enclosures, local exhaust ventilation, or other engineering controls to keep airborne levels below recommended exposure limits. If user operations generate dust, fume or mist, use ventilation to keep exposure to airborne contaminants below the exposure limit.Personal Protection:Splash goggles. Lab coat. Dust respirator. Be sure to use an approved/certified respirator or equivalent. Gloves.Personal Protection in Case of a Large Spill:Splash goggles. Full suit. Dust respirator. Boots. Gloves. A self contained breathing apparatus should be used to avoid inhalation of the product. Suggested protective clothing might not be sufficient; consult a specialist BEFORE handling this product.Exposure Limits: Not available.Section 9: Physical and Chemical PropertiesPhysical state and appearance: Solid. (Crystalline solid.)Odor: Not available.Taste: Not available.Molecular Weight: 126.12 g/moleColor: White.pH (1% soln/water): Not available.Boiling Point: Not available.Melting Point: <250°C (482°F)Critical Temperature: Not available.Specific Gravity: 1.573 (Water = 1)Vapor Pressure: Not applicable.Vapor Density: 4.34 (Air = 1)Volatility: Not available.Odor Threshold: Not available.Water/Oil Dist. Coeff.: Not available.Ionicity (in Water): Not available.Dispersion Properties: See solubility in water.Solubility:Partially soluble in cold water. Insoluble in diethyl ether.Section 10: Stability and Reactivity DataStability: The product is stable.Instability Temperature: Not available.Conditions of Instability: Dust generation, excess heat, incompatible materials.Incompatibility with various substances: Reactive with oxidizing agents, acids.Corrosivity: Not available.Special Remarks on Reactivity: Not available.Special Remarks on Corrosivity: Not available.Polymerization: Will not occur.Section 11: Toxicological InformationRoutes of Entry: Inhalation. Ingestion.Toxicity to Animals:Acute oral toxicity (LD50): 3161 mg/kg [Rat]. Acute dermal toxicity (LD50): >1000 mg/kg [Rabbit].Chronic Effects on Humans:CARCINOGENIC EFFECTS: Classified 3 (Equivocal evidence.) by NTP. 3 (Not classifiable for human.) by IARC. MUTAGENIC EFFECTS: Mutagenic for bacteria and/or yeast.Other Toxic Effects on Humans: Hazardous in case of skin contact (irritant), of ingestion, of inhalation (lung irritant).Special Remarks on Toxicity to Animals: Not available.Special Remarks on Chronic Effects on Humans:May cause adverse reproductive effects (fertility, fetotoxicity), and may affect genetic material based on animal data. May also be tumorigenic (carcinogenic) based on animal data.Special Remarks on other Toxic Effects on Humans:Acute Potential Health Effects: Skin: May cause skin irritation. Eyes: May cause eye irritation. Inhalation: May cause irritation of the respiratory tract and affect respiration. May affect behavior and sense organs, liver and blood. Ingestion: May cause irritation of the digestive tract with nausea, vomiting and diarrhea. May affect the urinary system.Section 12: Ecological InformationEcotoxicity: Not available.BOD5 and COD: Not available.Products of Biodegradation:Possibly hazardous short term degradation products are not likely. However, long term degradation products may arise. Toxicity of the Products of Biodegradation: The products of degradation are less toxic than the product itself.Special Remarks on the Products of Biodegradation: Not available.Section 13: Disposal ConsiderationsWaste Disposal:Waste must be disposed of in accordance with federal, state and local environmental control regulations.Section 14: Transport InformationDOT Classification: Not a DOT controlled material (United States).Identification: Not applicable.Special Provisions for Transport: Not applicable.Section 15: Other Regulatory InformationFederal and State Regulations:Pennsylvania RTK: Melamine Massachusetts RTK: Melamine New Jersey: Melamine TSCA 8(b) inventory: MelamineOther Regulations: EINECS: This product is on the European Inventory of Existing Commercial Chemical Substances.Other Classifications:WHMIS (Canada): Not controlled under WHMIS (Canada).DSCL (EEC):R36/37/38- Irritating to eyes, respiratory system and skin. S24/25- Avoid contact with skin and eyes. S36/37/39- Wear suitable protective clothing, gloves and eye/face protection.HMIS (U.S.A.):Health Hazard: 2Fire Hazard: 1Reactivity: 0Personal Protection: ENational Fire Protection Association (U.S.A.):Health: 2Flammability: 1Reactivity: 0Specific hazard:Protective Equipment:Gloves. Lab coat. Dust respirator. Be sure to use an approved/certified respirator or equivalent. Splash goggles.Section 16: Other InformationReferences: Not available.Other Special Considerations: Not available.The information above is believed to be accurate and represents the best information currently available to us. However, wemake no warranty of merchantability or any other warranty, express or implied, with respect to such information, and we assumeno liability resulting from its use. Users should make their own investigations to determine the suitability of the information fortheir particular purposes.。

122大鲵粗提物延缓秀丽线虫衰老的研究黄正杰1,2，崔建云1,2*，任发政1,2,3，赵慧1,31.中国农业大学食品科学与营养工程学院；2.教育部—北京市共建功能乳品重点实验室；3.北京市高等学校畜产品工程研究中心（北京100083）摘要试验研究了人工养殖大鲵粗提物延缓秀丽线虫衰老的功能性质，从而为科学的认识大鲵的营养保健功能提供理论依据。

通过测定秀丽线虫寿命、后代数、虫体大小及线虫的急性热应激和急性氧应激能力，评价了大鲵粗提物的延寿抗衰老功效并探讨了大鲵粗提物延缓衰老作用机理。

试验结果表明，浓度50 mg/L的大鲵粗提物可以提高线虫寿命，对大鲵生殖能力没有影响。

关键词大鲵；粗提物；秀丽线虫；延缓衰老Study on Anti-aging Effects of Crude Extract of Giant Salamander onCaenorhabditis elegansHuang Zheng-jie1,2, Cui Jian-yun1,2*, Ren Fa-zheng1,2,3, Zhao Hui1,31.College of Food Science and Nutritional Engineering, China Agricultural University；2.Key Laboratory of Functional Dairy；3. Beijing Higher Institution Engineering Research Center of Animal Product (Beijing 100083) Abstract The functional properties of anti-aging effects of crude extract of Giant salamander on Caenorhabditis elegans was studied, so as to provide a theoretical basis for scientifi c understanding of the nutritional properties of giant salamander. The anti-aging effect and probed anti-aging mechanism of crude extract of Giant salamander on Caenorhabditis elegans have been evaluated by measuring the C. elegans life span, number of posterity, size and the ability of acute heat stress and the ability of acute oxidative stress. The results showed that a certain concentration crude extract of Giant salamander can increase life span of Caenorhabditis elegans and has no effects on the reproductive capacity of Caenorhabditis elegans. Keywords Giant salamander; crude extract; Caenorhabditis elegans; anti-aging中国大鲵俗称娃娃鱼，是我国特有的珍惜大型两栖动物，隶属两栖纲，有尾目，隐腮鲵科，大鲵属，具有很高的生理保健和食用营养价值。

2025年北师大版英语高考复习试题与参考答案一、听力第一节（本大题有5小题，每小题1.5分，共7.5分）1、Listen to the following dialogue between two students, and answer the question.Student A: Hey, are you planning to follow the exam schedule strictly? Student B: Yeah, I always try to stick to a routine. How about you?Student A: Well, I like to mix it up a bit. It keeps me motivated.Question: What does Student A prefer when it comes to following an exam schedule?A. To follow the routine strictly.B. To mix up the schedule to stay motivated.C. To follow the schedule only when it’s convenient.D. To avoid any schedule altogether.Answer: BExplanation: Student A indicates that they like to mix up the schedule to stay motivated, which is equivalent to choice B.2、 Listen to the following conversation about a school trip, and complete the following sentence with the correct information.Teacher: Ok, everyone, we’re going to have a field trip next week. It’s a science-themed trip to the museum downtown.Student A: That sounds amazing! What are we going to learn there, though?Teacher: Well, you’ll get a behind-the-scenes look at how exhibits are put together, and you’ll interact with some of the curators. Plus, there are interactive displays where you can try out different experiments.Question: What will the students be able to do during the trip to the museum?A. Simply observe the exhibits without participating.B. Work with the curators to put together new exhibits.C. Participate in interactive experiments and discussions.D. Finish the field trip without visiting the museum.Answer: CExplanation: The teacher mentions that the students will be able to participate in interactive experiments and discussions, which corresponds to choice C.3.What does the man suggest doing?A) Having a picnic.B) Going to the cinema.C) Visiting the museum.D) Playing tennis.Answer: A) Having a picnic.Explanation: The woman mentions that it’s a beautiful day and asks the man what he thinks they should do. The man responds by suggesting they take advantage of the weather and have a picnic in the park. Therefore, the correct answer isA) Having a picnic.4.Where are the speakers most likely?A) At home.B) In a restaurant.C) On a bus.D) In a bookstore.Answer: B) In a restaurant.Explanation: The dialogue involves one speaker asking for recommendations on dishes and commenting on the menu, while the other speaker provides suggestions and describes the specials. This context strongly suggests that the conversation is taking place in a restaurant, making B) In a restaurant the correct choice.5、 Listening Section AQuestion: How is the woman going to the airport?A) By bus.B) By taxi.C) By subway.Answer: BExplanation:In the recording, the man asks, “Are you going to the airport by bus or by taxi?” The woman replies, “I decide to take a taxi because it will be faster.” Therefore, the correct answer is B) By taxi.解析：录音中，男士问：“你要去机场是乘公交还是打车？”女士回答：“我决定打车去，因为会更快。