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半导体一些术语的中英文对照

半导体一些术语的中英文对照离子注入机ion implanterLSS理论Lindhand Scharff and Schiott theory 又称“林汉德-斯卡夫—斯高特理论"。

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nominal rigidities and the dynamic effects of a shock to monetary policy

Nominal Rigidities and the Dynamic Eﬀects of a Shockto Monetary Policy∗Lawrence J.Christiano†Martin Eichenbaum‡Charles L.Evans§August27,2003AbstractWe present a model embodying moderate amounts of nominal rigidities that ac-counts for the observed inertia in inﬂation and persistence in output.The key featuresof our model are those that prevent a sharp rise in marginal costs after an expansion-ary shock to monetary policy.Of these features,the most important are staggeredwage contracts which have an average duration of three quarters,and variable capitalutilization.JEL:E3,E4,E5∗Theﬁrst two authors are grateful for theﬁnancial support of a National Science Foundation grant to the National Bureau of Economic Research.We would like to acknowledge helpful comments from Lars Hansen and Mark Watson.We particularly want to thank Levon Barseghyan for his superb research assistance,as well as his insightful comments on various drafts of the paper.This paper does not necessarily reﬂect the views of the Federal Reserve Bank of Chicago or the Federal Reserve System.†Northwestern University,National Bureau of Economic Research,and Federal Reserve Banks of Chicago and Cleveland.‡Northwestern University,National Bureau of Economic Research,and Federal Reserve Bank of Chicago.§Federal Reserve Bank of Chicago.1.IntroductionThis paper seeks to understand the observed inertial behavior of inﬂation and persistence in aggregate quantities.To this end,we formulate and estimate a dynamic,general equilibrium model that incorporates staggered wage and price contracts.We use our model to investigate what mix of frictions can account for the evidence of inertia and persistence.For this exercise to be well deﬁned,we must characterize inertia and persistence precisely.We do so using estimates of the dynamic response of inﬂation and aggregate variables to a monetary policy shock.With this characterization,the question that we ask reduces to:‘Can models with moderate degrees of nominal rigidities generate inertial inﬂation and persistent output movements in response to a monetary policy shock?’1Our answer to this question is,‘yes’.The model that we construct has two key features.First,it embeds Calvo style nominal price and wage contracts.Second,the real side of the model incorporates four departures from the standard textbook one sector dynamic stochastic growth model.These depar-tures are motivated by recent research on the determinants of consumption,asset prices, investment and productivity.The speciﬁc departures that we include are habit formation in preferences for consumption,adjustment costs in investment and variable capital utilization. In addition,we assume thatﬁrms must borrow working capital toﬁnance their wage bill.Our keyﬁndings are as follows.First,the average duration of price and wage contracts in the estimated model is roughly2and3quarters,respectively.Despite the modest nature of these nominal rigidities,the model does a very good job of accounting quantitatively for the estimated response of the US economy to a policy shock.In addition to reproducing the dynamic response of inﬂation and output,the model also accounts for the delayed,hump-shaped response in consumption,investment,proﬁts,productivity and the weak response of the real wage.2Second,the critical nominal friction in our model is wage contracts,not price contracts.A version of the model with only nominal wage rigidities does almost as well as the estimated model.In contrast,with only nominal price rigidities,the model performs very poorly.Consistent with existing results in the literature,this version of the model cannot generate persistent movements in output unless we assume price contracts of extremely long duration.The model with only nominal wage rigidities does not have this problem.Third,we document how inference about nominal rigidities varies across diﬀerent spec-iﬁcations of the real side of our model.3Estimated versions of the model that do not in-1This question that is the focus of a large and growing literature.See,for example,Chari,Kehoe and McGrattan(2000),Mankiw(2001),Rotemberg and Woodford(1999)and the references therein.2In related work,Sbordone(2000)argues that,taking as given aggregate real variables,a model with staggered wages and prices does well at accounting for the time series properties of wages and prices.See also Ambler,Guay and Phaneuf(1999)and Huang and Liu(2002)for interesting work on the role of wage contracts.3For early discussions about the impact of real frictions on the eﬀects of nominal rigidities,see Blanchardcorporate our departures from the standard growth model imply implausibly long price and wage contracts.Fourth,weﬁnd that if one only wants to generate inertia in inﬂation and persistence in output with moderate wage and price stickiness,then it is crucial to allow for variable capital utilization.To understand why this feature is so important,note that in our modelﬁrms set prices as a markup over marginal costs.The major components of marginal costs are wages and the rental rate of capital.By allowing the services of capital to increase after a positive monetary policy shock,variable capital utilization helps dampen the large rise in the rental rate of capital that would otherwise occur.This in turn dampens the rise in marginal costs and,hence,prices.The resulting inertia in inﬂation implies that the rise in nominal spending that occurs after a positive monetary policy shock produces a persistent rise in real output.Similar intuition explains why sticky wages play a critical role in allowing our model to explain inﬂation inertia and output persistence.It also explains why our assumption about working capital plays a useful role:other things equal,a decline in the interest rate lowers marginal cost.Fifth,although investment adjustment costs and habit formation do not play a central role with respect to inﬂation inertia and output persistence,they do play a critical role in accounting for the dynamics of other variables.Sixth,the major role played by the working capital channel is to reduce the model’s reliance on sticky prices.Speciﬁcally,if we estimate a version of the model that does not allow for this channel,the average duration of price contracts increases dramatically.Finally,weﬁnd that our model embodies strong internal propagation mechanisms.The impact of a monetary policy shock on aggregate activity continues to grow and persist even beyond the time when the typical contract in place at the time of the shock is reoptimized.In addition,the eﬀects persist well beyond the eﬀects of the shock on the interest rate and the growth rate of money.We pursue a particular limited information econometric strategy to estimate and evaluate our model.To implement this strategy weﬁrst estimate the impulse response of eight key macroeconomic variables to a monetary policy shock using an identiﬁed vector autoregres-sion(V AR).We then choose six model parameters to minimize the diﬀerence between the estimated impulse response functions and the analogous objects in our model.4 The remainder of this paper is organized as follows.In section2we brieﬂy describe our estimates of how the U.S.economy responds to a monetary policy shock.Section3 displays our economic model.In Section4we discuss our econometric methodology.Our empirical results are reported in Section5and analyzed in Section6.Concluding commentsand Fisher(1989),Ball and Romer(1990)and Romer(1996).For more recent quantitative discussions, see Chari,Kehoe and McGrattan(2000),Edge(2000),Fuhrer(2000),Kiley(1997),McCallum and Nelson (1998)and Sims(1998).4Christiano,Eichenbaum and Evans(1998),Edge(2000)and Rotemberg and Woodford(1997)have also applied this strategy in the context of monetary policy shocks.are contained in Section7.2.The Consequences of a Monetary Policy ShockThis section begins by describing how we estimate a monetary policy shock.We then re-port estimates of how major macroeconomic variables respond to a monetary policy shock. Finally,we report the fraction of the variance in these variables that is accounted for by monetary policy shocks.The starting point of our analysis is the following characterization of monetary policy:R t=f(Ωt)+εt.(2.1)Here,R t is the Federal Funds rate,f is a linear function,Ωt is an information set,andεt is the monetary policy shock.We assume that the Fed allows money growth to be whatever is necessary to guarantee that(2.1)holds.Our basic identifying assumption is thatεt is orthogonal to the elements inΩt.Below,we describe the variables inΩt and elaborate on the interpretation of this orthogonality assumption.We now discuss how we estimate the dynamic response of key macroecomomic variables to a monetary policy shock.Let Y t denote the vector of variables included in the analysis. We partition Y t as follows:Y t=[Y1t,R t,Y2t]0.The vector Y1t is composed of the variables whose time t elements are contained inΩt,and are assumed not to respond contemporaneously to a monetary policy shock.The vector Y2t consists of the time t values of all the other variables inΩt.The variables in Y1t are real GDP, real consumption,the GDP deﬂator,real investment,the real wage,and labor productivity. The variables in Y2t are real proﬁts and the growth rate of M2.All these variables,except money growth,have been logged.We measure the interest rate,R t,using the Federal Funds rate.The data sources are in an appendix,available from the authors.With one exception(the growth rate of money)all the variables in Y t are include in levels.Altig,Christiano,Eichenbaum and Linde(2003)adopt an alternative speciﬁcation of Y t,in which cointegrating relationships among the variables are imposed.For example,the growth rate of GDP and the log diﬀerence between labor productivity and the real wage are included.The key properties of the impulse responses to a monetary policy shock are insensitive to this alternative speciﬁcation.The ordering of the variables in Y t embodies two key identifying assumptions.First,the variables in Y1t do not respond contemporaneously to a monetary policy shock.Second,the time t information set of the monetary authority consists of current and lagged values of the variables in Y1t and only past values of the variables in Y2t.Our decision to include all variables,except for the growth rate of M2and real proﬁts in Y1t,reﬂects a long-standing view that macroeconomic variables do not respond instanta-neously to policy shocks(see Friedman(1968)).We refer the reader to Christiano,Eichen-baum and Evans(1999)for a discussion of sensitivity of inference to alternative assumptions about the variables included in Y1t.While our assumptions are certainly debatable,the anal-ysis is internally consistent in the sense that we make the same assumptions in our economic model.To maintain consistency with the model,we place proﬁts and the growth rate of money in Y2t.The V AR contains4lags of each variable and the sample period is1965Q3-1995Q3.5 Ignoring the constant term,the V AR can be written as follows:Y t=A1Y t−1+...+A4Y t−4+Cηt,(2.2)where C is a9×9lower triangular matrix with diagonal terms equal to unity,andηt is a9−dimensional vector of zero-mean,serially uncorrelated shocks with diagonal variance-covariance matrix.Since there are six variables in Y1t,the monetary policy shock,εt,is the7th element ofηt.A positive shock toεt corresponds to a contractionary monetary policy shock. We estimate the parameters-A i,i=1,...,4,C,and the variances of the elements ofηt-using standard least squares ing these estimates,we compute the dynamic path of Y t following a one-standard-deviation shock inεt,setting initial conditions to zero.This path, which corresponds to the coeﬃcients in the impulse response functions of interest,is invariant to the ordering of the variables within Y1t and within Y2t(see Christiano,Eichenbaum and Evans(1999).)The impulse response functions of all variables in Y t are displayed in Figure1.Lines marked‘+’correspond to the point estimates.The shaded areas indicate95%conﬁdence intervals about the point estimates.6The solid lines pertain to the properties of our structural model,which will be discussed in section3.The results suggest that after an expansionary monetary policy shock there is a:•hump-shaped response of output,consumption and investment,with the peak eﬀect occurring after about1.5years and returning to their pre-shock levels after about three years,•hump-shaped response in inﬂation,with a peak response after about2years,•fall in the interest rate for roughly one year,•rise in proﬁts,real wages and labor productivity,and5This sample period is the same as in Christiano,Eichenbaum and Evans(1999).6We use the method described in Sims and Zha(1999).•an immediate rise in the growth rate of money.Interestingly,these results are consistent with the claims in Friedman(1968).For example, Friedman argued that an exogenous increase in the money supply leads to a drop in the interest rate that lasts one to two years,and a rise in output and employment that lasts from two toﬁve years.Finally,the robustness of the qualitative features of ourﬁndings to alternative identifying assumptions and sample sub-periods,as well as the use of monthly data,is discussed in Christiano,Eichenbaum and Evans(1999).Our strategy for estimating the parameters of our model focuses on only a component of theﬂuctuations in the data,namely the portion that is due to a monetary policy shock. It is natural to ask how large that component is,since ultimately we are interested in a model that can account for the variation in the data.With this question in mind,the following table reports variance decompositions.In particular,it displays the percent of the variance of the k−step forecast error in the elements of Y t due to monetary policy shocks, for k=4,8and20.Numbers in parentheses are the boundaries of the associated95% conﬁdence interval.7Notice that policy shocks account for only a small fraction of inﬂation. At the same time,with the exception of real wages,monetary policy shocks account for a non-trivial fraction of the variation in the real variables.This last inference should be treated with caution.The conﬁdence intervals about the point estimates are rather large. Also,while the impulse response functions are robust to the various perturbations discussed in Christiano,Eichenbaum and Evans(1999)and Altig,Christiano,Eichenbaum and Linde (2003),the variance decompositions can be sensitive.For example,the analogous point estimates reported in Altig,Christiano,Eichenbaum and Linde(2003)are substantially smaller than those reported in Table1.3.The Model EconomyIn this section we describe our model economy and display the problems solved byﬁrms and households.In addition,we describe the behavior ofﬁnancial intermediaries and the monetary andﬁscal authorities.The only source of uncertainty in the model is a shock to monetary policy.7These conﬁdence intervals are computed based on bootstrap simulations of the estimated VAR.In each artiﬁcial data set we computed the variance decompositions corresponding to the ones in Table1.The lower and upper bounds of the conﬁdence intervals correspond to the2.5and97.5percentiles of simulated variance decompositions.3.1.Final Good FirmsAt time t,aﬁnal consumption good,Y t,is produced by a perfectly competitive,representative ﬁrm.Theﬁrm produces theﬁnal good by combining a continuum of intermediate goods, indexed by j∈[0,1],using the technologyY t=·Z10Y jt1f dj¸λf(3.1) where1≤λf<∞and Y jt denotes the time t input of intermediate good j.Theﬁrm takes its output price,P t,and its input prices,P jt,as given and beyond its control.Proﬁt maximization implies the Euler equationµP t jt¶λfλf−1=Y jt t.(3.2)Integrating(3.2)and imposing(3.1),we obtain the following relationship between the price of theﬁnal good and the price of the intermediate good:P t=·Z10P11−λf jt dj¸(1−λf).(3.3) 3.2.Intermediate Good FirmsIntermediate good j∈(0,1)is produced by a monopolist who uses the following technology:Y jt=½kαjt L1−αjt−φif kαjt L1−αjt≥φ0otherwise(3.4) where0<α<1.Here,L jt and k jt denote time t labor and capital services used to produce the j th intermediate good.Also,φ>0denotes theﬁxed cost of production.We rule out entry and exit into the production of intermediate good j.Intermediateﬁrms rent capital and labor in perfectly competitive factor markets.Proﬁts are distributed to households at the end of each time period.Let R k t and W t denote the nominal rental rate on capital services and the wage rate,respectively.Workers must be paid in advance of production.As a result,the j thﬁrm must borrow its wage bill,W t L jt, from theﬁnancial intermediary at the beginning of the period.Repayment occurs at the end of time period t at the gross interest rate,R t.Theﬁrm’s real marginal cost iss t=∂S t(Y)∂Y,where S t(Y)=mink,l©r k t k+w t R t l,Y given by(3.4)ª,where r k t=R k t/P t and w t=W t/P t.Given our functional forms,we haves t=µ1¶1−αµ1¶α¡r k t¢α(w t R t)1−α.(3.5)Apart fromﬁxed costs,theﬁrm’s time t proﬁts are:·P jt P t−s t¸P t Y jt,where P jt isﬁrm j’s price.We assume thatﬁrms set prices according to a variant of the mechanism spelled out in Calvo(1983).This model has been widely used to characterize price-setting frictions.A useful feature of the model is that it can be solved without explicitly tracking the distribution of prices acrossﬁrms.In each period,aﬁrm faces a constant probability,1−ξp,of being able to reoptimize its nominal price.The ability to reoptimize its price is independent across ﬁrms and time.If aﬁrm can reoptimize its price,it does so before the realization of the time t growth rate of money.Firms that cannot reoptimize their price simply index to lagged inﬂation:P jt=πt−1P j,t−1.(3.6) Here,πt=P t/P t−1.We refer to this price-setting rule as lagged inﬂation indexation.Let˜P t denote the value of P jt set by aﬁrm that can reoptimize at time t.Our notation does not allow˜P t to depend on j.We do this in anticipation of the well known result that, in models like ours,allﬁrms who can reoptimize their price at time t choose the same price (see Woodford,1996and Yun,1996).Theﬁrm chooses˜P t to maximize:∞X l=0¡βξp¢lυt+l h˜P t X tl−s t+l P t+l i Y j,t+l,(3.7)E t−1subject to(3.2),(3.5)and.(3.8)X tl=½πt×πt+1×···×πt+l−1for l≥11l=0In(3.7),υt is the marginal value of a dollar to the household,which is treated as exogenous by theﬁter,we show that the value of a dollar,in utility terms,is constant across households.Also,E t−1denotes the expectations operator conditioned on lagged growth rates of money,µt−l,l≥1.This speciﬁcation of the information set captures our assumption that theﬁrm chooses˜P t before the realization of the time t growth rate of money.To understand (3.7),note that˜P t inﬂuencesﬁrm j’s proﬁts only as long as it cannot reoptimize its price.The probability that this happens for l periods is¡ξp¢l,in which case P j,t+l=˜P t X tl.The presence of¡ξp¢l in(3.7)has the eﬀect of isolating future realizations of idiosyncratic uncertainty in which˜P t continues to aﬀect theﬁrm’s proﬁts.3.3.HouseholdsThere is a continuum of households,indexed by j∈(0,1).The j th household makes a sequence of decisions during each period.First,it makes its consumption decision,its capital accumulation decision,and it decides how many units of capital services to supply.Second, it purchases securities whose payoﬀs are contingent upon whether it can reoptimize its wage decision.Third,it sets its wage rate afterﬁnding out whether it can reoptimize or not. Fourth,it receives a lump-sum transfer from the monetary authority.Finally,it decides how much of itsﬁnancial assets to hold in the form of deposits with aﬁnancial intermediary and how much to hold in the form of cash.Since the uncertainty faced by the household over whether it can reoptimize its wage is idiosyncratic in nature,households work diﬀerent amounts and earn diﬀerent wage rates.So, in principle,they are also heterogeneous with respect to consumption and asset holdings.A straightforward extension of arguments in Erceg,Henderson and Levin(2000)and Woodford (1996)establish that the existence of state contingent securities ensures that,in equilibrium, households are homogeneous with respect to consumption and asset holdings.Reﬂecting this result,our notation assumes that households are homogeneous with respect to consumption and asset holdings but heterogeneous with respect to the wage rate that they earn and hours worked.The preferences of the j th household are given by:∞X l=0βl−t[u(c t+l−bc t+l−1)−z(h j,t+l)+v(q t+l)].(3.9)E j t−1Here,E j t−1is the expectation operator,conditional on aggregate and household j idiosyn-cratic information up to,and including,time t−1;c t denotes time t consumption;h jt denotes time t hours worked;q t≡Q t/P t denotes real cash balances;Q t denotes nominal cash balances.When b>0,(3.9)allows for habit formation in consumption preferences.The household’s asset evolution equation is given by:M t+1=R t[M t−Q t+(µt−1)M a t]+A j,t+Q t+W j,t h j,t(3.10)+R k t u t¯k t+D t−P t¡i t+c t+a(u t)¯k t¢.Here,M t is the household’s beginning of period t stock of money and W j,t h j,t is time t labor income.In addition,¯k t,D t and A j,t denote,respectively,the physical stock of capital,ﬁrm proﬁts and the net cash inﬂow from participating in state-contingent securities at time t. The variableµt represents the gross growth rate of the economy-wide per capita stock of money,M a t.The quantity(µt−1)M a t is a lump-sum payment made to households by the monetary authority.The quantity M t−P t q t+(µt−1)M a t,is deposited by the household with aﬁnancial intermediary where it earns the gross nominal rate of interest,R t.The remaining terms in(3.10),aside from P t c t,pertain to the stock of installed capital, which we assume is owned by the household.The household’s stock of physical capital,¯k t, evolves according to:¯k=(1−δ)¯k t+F(i t,i t−1).(3.11)t+1Here,δdenotes the physical rate of depreciation and i t denotes time t purchases of invest-ment goods.The function,F,summarizes the technology that transforms current and past investment into installed capital for use in the following period.We discuss the properties of F below.Capital services,k t,are related to the physical stock of capital byk t=u t¯k t.Here,u t denotes the utilization rate of capital,which we assume is set by the household.8 In(3.10),R k t u t¯k t represents the household’s earnings from supplying capital services.The increasing,convex function a(u t)¯k t denotes the cost,in units of consumption goods,of setting the utilization rate to u t.3.4.The W age DecisionAs in Erceg,Henderson and Levin(2000),we assume that the household is a monopoly sup-plier of a diﬀerentiated labor service,h jt.It sells this service to a representative,competitive ﬁrm that transforms it into an aggregate labor input,L t,using the following technology:L t=·Z10h1λjt dj¸λw.The demand curve for h jt is given by:h jt=µW t jt¶λwλw−1L t,1≤λw<∞.(3.12) Here,W t is the aggregate wage rate,i.e.,the price of L t.It is straightforward to show that W t is related to W jt via the relationship:W t=·Z10(W jt)11−λw dj¸1−λw.(3.13) The household takes L t and W t as given.8Our assumption that households make the capital accumulation and utilization decisions is a matter of convenience.At the cost of a more complicated notation,we could work with an alternative decentralization scheme in whichﬁrms make these decisions.Households set their wage rate according to a variant of the mechanism used to model price setting byﬁrms.In each period,a household faces a constant probability,1−ξw, of being able to reoptimize its nominal wage.The ability to reoptimize is independent across households and time.If a household cannot reoptimize its wage at time t,it sets W jt according to:W j,t=πt−1W j,t−1.(3.14) 3.5.Monetary and Fiscal PolicyWe assume that monetary policy is given by:µt=µ+θ0εt+θ1εt−1+θ2εt−2+...(3.15)Here,µdenotes the mean growth rate of money andθj is the response of E tµt+j to a time t monetary policy shock.We assume that the government has access to lump sum taxes and pursues a Ricardianﬁscal policy.Under this type of policy,the details of tax policy have no impact on inﬂation and other aggregate economic variables.As a result,we need not specify the details ofﬁscal policy.93.6.Loan Market Clearing,Final Goods Clearing and EquilibriumFinancial intermediaries receive M t−Q t from households and a transfer,(µt−1)M t from the monetary authority.Our notation here reﬂects the equilibrium condition,M a t=M t. Financial intermediaries lend all of their money to intermediate goodﬁrms,which use the funds to pay for L t.Loan market clearing requiresW t L t=µt M t−Q t.(3.16) The aggregate resource constraint isc t+i t+a(u t)≤Y t.We adopt a standard sequence-of-markets equilibrium concept.In the appendix we discuss our computational strategy for approximating that equilibrium.This strategy involves taking a linear approximation about the non-stochastic steady state of the economy and using the solution method discussed in Christiano(2003).For details,see the previous version of this paper,Christiano,Eichenbaum and Evans(2001).In principle,the non-negativity constraint on intermediate good output in(3.4)is a problem for this approximation.It turns out that the constraint is not binding for the experiments that we consider and so we ignore it.Finally, it is worth noting that since proﬁts are stochastic,the fact that they are zero,on average, 9See Sims(1994)or Woodford(1994)for a further discussion.implies that they are often negative.As a consequence,our assumption thatﬁrms cannot exit is binding.Allowing forﬁrm entry and exit dynamics would considerably complicate our analysis.3.7.Functional Form AssumptionsWe assume that the functions characterizing utility are given by:u(·)=log(·)z(·)=ψ0(·)2.(3.17)v(·)=ψq(·)1−σqqIn addition,investment adjustment costs are given by:F(i t,i t−1)=(1−Sµi t i t−1¶)i t.(3.18) We restrict the function S to satisfy the following properties:S(1)=S0(1)=0,andκ≡S00(1)>0.It is easy to verify that the steady state of the model does not depend on the adjustment cost parameter,κ.Of course,the dynamics of the model are inﬂuenced byκ. Given our solution procedure,no other features of the S function need to be speciﬁed for our analysis.We impose two restrictions on the capital utilization function,a(u t).First,we require that u t=1in steady state.Second,we assume a(1)=0.Under our assumptions,the steady state of the model is independent ofσa=a00(1)/a0(1).The dynamics do depend onσa.Given our solution procedure,we do not need to specify any other features of the function a. 4.Econometric MethodologyIn this section we discuss our methodology for estimating and evaluating our model.We partition the model parameters into three groups.Theﬁrst group is composed ofβ,φ,α,δ,ψ0,ψq,λw andµ.We setβ=1.03−0.25,which implies a steady state annualized real interest rate of3percent.We setα=0.36,which corresponds to a steady state share of capital income equal to roughly36percent.We setδ=0.025,which implies an annual rate of depreciation on capital equal to10percent.This value ofδis roughly equal to the estimate reported in Christiano and Eichenbaum(1992).The parameter,φ,is set to guarantee that proﬁts are zero in steady state.This value is consistent with Basu and Fernald(1994),Hall (1988),and Rotemberg and Woodford(1995),who argue that economic proﬁts are close to zero on average.Although there are well known problems with the measurement of proﬁts, we think that zero proﬁts is a reasonable benchmark.。

线粒体融合和裂变失衡英文

线粒体融合和裂变失衡英文Mitochondrial Fusion and Fission Imbalance.Mitochondria are dynamic organelles that undergo continuous fusion and fission events. These processes are essential for maintaining mitochondrial morphology, function, and quality control. Fusion allows mitochondria to exchange genetic material and proteins, thereby promoting complementation and repair. Fission, on the other hand, enables the segregation of damaged mitochondria for subsequent removal by mitophagy.An imbalance between mitochondrial fusion and fission can lead to various cellular abnormalities and diseases. Excessive fusion can result in the formation of hyperfused mitochondrial networks, which may impede mitochondrial motility and hinder the efficient distribution of mitochondria to subcellular compartments. Conversely, excessive fission can lead to mitochondrial fragmentation, which may compromise mitochondrial function and increasethe susceptibility to mitophagy.Causes of Mitochondrial Fusion and Fission Imbalance.Several factors can disrupt the balance between mitochondrial fusion and fission, including:Mutations in mitochondrial fusion and fission genes: Mutations in genes encoding mitochondrial fusion proteins (e.g., Mfn1, Mfn2, OPA1) or fission proteins (e.g., Drp1, Fis1) can impair their function and lead to an imbalance in fusion and fission events.Oxidative stress: Excessive reactive oxygen species (ROS) production can induce mitochondrial fission by activating Drp1 and inhibiting Mfn2.Calcium overload: Elevated intracellular calciumlevels can trigger mitochondrial fission by activating calcineurin, which dephosphorylates Drp1 and promotes its translocation to the mitochondria.Metabolic stress: Nutrient deprivation or hypoxia can induce mitochondrial fission to promote mitophagy and conserve energy.Viral infections: Certain viruses can interfere with mitochondrial fusion and fission processes, leading to mitochondrial dysfunction and cell death.Neurodegenerative diseases: Mitochondrial fusion and fission imbalances have been implicated in the pathogenesis of several neurodegenerative diseases, includingAlzheimer's disease, Parkinson's disease, and amyotrophic lateral sclerosis (ALS).Consequences of Mitochondrial Fusion and Fission Imbalance.Mitochondrial fusion and fission imbalance can have a range of consequences, including:Impaired mitochondrial function: Excessive fusion or fission can disrupt mitochondrial oxidative phosphorylation,ATP production, and calcium homeostasis.Increased susceptibility to apoptosis: Mitochondrial fragmentation can trigger the release of pro-apoptotic factors and promote cell death.Neurological dysfunction: Mitochondrial fusion and fission imbalances have been linked to cognitive decline, synaptic dysfunction, and neuroinflammation.Cardiovascular disease: Impaired mitochondrial fusion and fission can contribute to cardiac dysfunction and heart failure.Metabolic disorders: Mitochondrial fusion and fission imbalances have been implicated in obesity, insulin resistance, and type 2 diabetes.Therapeutic Strategies.Modulating mitochondrial fusion and fission processes holds therapeutic potential for treating a variety ofdiseases. Strategies aimed at restoring the balance between fusion and fission include:Pharmacological interventions: Small molecules that target mitochondrial fusion or fission proteins are being developed as potential therapeutic agents.Gene therapy: Gene therapy approaches aim to correct mutations in mitochondrial fusion and fission genes.Antioxidant therapies: Antioxidants can combat oxidative stress and protect mitochondria from excessive fission.Dietary interventions: Dietary modifications that promote mitochondrial biogenesis and reduce oxidative stress may improve mitochondrial fusion and fission dynamics.Conclusion.Mitochondrial fusion and fission are essentialprocesses for maintaining mitochondrial homeostasis and function. Imbalances between these processes can lead to cellular dysfunction and the development of various diseases. Understanding the mechanisms underlying mitochondrial fusion and fission imbalance and developing therapeutic strategies to restore balance hold promise for treating a range of pathological conditions.。

流体力学中英文词

气动中心 aerodynamic center
气动力 aerodynamic force
气动噪声 aerodynamic noise
气动加热 aerodynamic heating
离解 dissociation
地面效应 ground effect
气体动力学 gas dynamics
进口 entrance, inlet
出口 exit, outlet
扰动 disturbance, perturbation
分布 distribution
传播 propagation
色散 dispersion
弥散 dispersion
附加质量 added mass ,associated mass
库埃特流 Couette flow
单相流 single phase flow
单组份流 single-component flow
均匀流 uniform flow
非均匀流 nonuniform flow
二维流 two-dimensional flow
三维流 three-dimensional flow
马赫数 Mach number
平面流 plane flow
势 potential
势流 potential flow
速度势 velocity potential
复势 complex potential
复速度 complex velocity
流函数 stream function
源 source
有旋流 rotational flow
轴对称流 axisymmetric flow

半导体一些术语的中英文对照

半导体一些术语的中英文对照离子注入机ionimplanterLSS理论LindhandScharffandSchiotttheory 又称“林汉德-斯卡夫-斯高特理论”。

沟道效应channelingeffect射程分布rangedistribution深度分布depthdistribution投影射程projectedrange负性光刻胶negativephotoresist正性光刻胶positivephotoresist无机光刻胶inorganicresist多层光刻胶multilevelresist电子束光刻胶electronbeamresistX射线光刻胶X-rayresist刷洗scrubbing甩胶spinning涂胶photoresistcoating后烘postbaking光刻photolithographyX射线光刻X-raylithography电子束光刻electronbeamlithography离子束光刻ionbeamlithography深紫外光刻deep-UVlithography光刻机maskaligner投影光刻机projectionmaskaligner曝光exposure接触式曝光法contactexposuremethod接近式曝光法proximityexposuremethod光学投影曝光法opticalprojectionexposuremethod磷硅玻璃phosphorosilicateglass硼磷硅玻璃boron-phosphorosilicateglass钝化工艺passivationtechnology 多层介质钝化multilayerdielectricpassivation划片scribing电子束切片electronbeamslicing烧结sintering印压indentation热压焊thermocompressionbonding热超声焊thermosonicbonding冷焊coldwelding点焊spotwelding球焊ballbonding楔焊wedgebonding内引线焊接innerleadbonding外引线焊接outerleadbonding梁式引线beamlead装架工艺mountingtechnology附着adhesion封装packaging金属封装metallicpackagingAmbipolar双极的Ambienttemperature环境温度Amorphous无定形的，非晶体的Amplifier功放扩音器放大器Analogue(Analog)comparator模拟比较器Angstrom埃Anneal退火Anisotropic各向异性的Anode阳极Arsenic(AS)砷Auger俄歇Augerprocess俄歇过程Avalanche雪崩Avalanchebreakdown雪崩击穿Avalancheexcitation雪崩激发Backgroundcarrier本底载流子Backgrounddoping本底掺杂Backward反向Backwardbias反向偏置Ballastingresistor整流电阻Ballbond球形键合Band能带Bandgap能带间隙Barrier势垒Barrierlayer势垒层Barrierwidth势垒宽度Base基极Basecontact基区接触Basestretching基区扩展效应Basetransittime基区渡越时间Basetransportefficiency基区输运系数Base-widthmodulation基区宽度调制Basisvector基矢Bias偏置Bilateralswitch双向开关Binarycode二进制代码Binarycompoundsemiconductor二元化合物半导体Bipolar双极性的BipolarJunctionTransistor(BJT)双极晶体管Bloch布洛赫Blockingband阻挡能带Chargeconservation电荷守恒Chargeneutralitycondition电中性条件Chargedrive/exchange/sharing/transfer/storage电荷驱动/交换/共享/转移/存储Chemmicaletching化学腐蚀法Chemically-Polish化学抛光Chemmically-MechanicallyPolish(CMP)化学机械抛光Chip芯片Chipyield芯片成品率Clamped箝位Clampingdiode箝位二极管Cleavageplane解理面Clockrate时钟频率Clockgenerator时钟发生器Clockflip-flop时钟触发器Close-packedstructure密堆积结构Close-loopgain闭环增益Collector集电极Collision碰撞CompensatedOP-AMP补偿运放Common-base/collector/emitterconnection共基极/集电极/发射极连接Common-gate/drain/sourceconnection共栅/漏/源连接Common-modegain共模增益Common-modeinput共模输入Common-moderejectionratio(CMRR)共模抑制比Compatibility兼容性Compensation补偿Compensatedimpurities补偿杂质Compensatedsemiconductor补偿半导体ComplementaryDarlingtoncircuit互补达林顿电路ComplementaryMetal-Oxide-SemiconductorField-Effect-Transistor(CMOS)互补金属氧化物半导体场效应晶体管Complementaryerrorfunction余误差函数Computer-aideddesign(CAD)/test(CAT)/manufacture(CAM)计算机辅助设计/测试/制De.broglie德布洛意Decderate减速Decibel(dB)分贝Decode译码Deepacceptorlevel深受主能级Deepdonorlevel深施主能级Deepimpuritylevel深度杂质能级Deeptrap深陷阱Defeat缺陷Degeneratesemiconductor简并半导体Degeneracy简并度Degradation退化DegreeCelsius(centigrade)/Kelvin摄氏/开氏温度Delay延迟Density密度Densityofstates态密度Depletion耗尽Depletionapproximation耗尽近似Depletioncontact耗尽接触Depletiondepth耗尽深度Depletioneffect耗尽效应Depletionlayer耗尽层DepletionMOS耗尽MOSDepletionregion耗尽区Depositedfilm淀积薄膜Depositionprocess淀积工艺Designrules设计规则Die芯片（复数dice）Diode二极管Dielectric介电的Dielectricisolation介质隔离Difference-modeinput差模输入Differentialamplifier差分放大器Differentialcapacitance微分电容Diffusedjunction扩散结Diffusion扩散Diffusioncoefficient扩散系数Diffusionconstant扩散常数Diffusivity扩散率Diffusioncapacitance/barrier/current/furnace扩散电容/势垒/电流/炉Electrostatic静电的Element元素/元件/配件Elementalsemiconductor元素半导体Ellipse椭圆Ellipsoid椭球Emitter发射极Emitter-coupledlogic发射极耦合逻辑Emitter-coupledpair发射极耦合对Emitterfollower射随器Emptyband空带Emittercrowdingeffect发射极集边（拥挤）效应Endurancetest=lifetest寿命测试Energystate能态Energymomentumdiagram能量-动量(E-K)图Enhancementmode增强型模式EnhancementMOS增强性MOSEntefic(低)共溶的Environmentaltest环境测试Epitaxial外延的Epitaxiallayer外延层Epitaxialslice外延片Expitaxy外延Equivalentcurcuit等效电路Equilibriummajority/minoritycarriers平衡多数/少数载流子ErasableProgrammableROM(EPROM)可搽取（编程）存储器Errorfunctioncomplement余误差函数Etch刻蚀Etchant刻蚀剂Etchingmask抗蚀剂掩模Excesscarrier过剩载流子Excitationenergy激发能Excitedstate激发态Exciton激子Extrapolation外推法Extrinsic非本征的Extrinsicsemiconductor杂质半导体Face-centered面心立方Falltime下降时间Heatsink散热器、热沉Heavy/lightholeband重/轻空穴带Heavysaturation重掺杂Hell-effect霍尔效应Heterojunction异质结Heterojunctionstructure异质结结构HeterojunctionBipolarTransistor（HBT）异质结双极型晶体Highfieldproperty高场特性High-performanceMOS.(H-MOS)高性能MOS.Hormalized归一化Horizontalepitaxialreactor卧式外延反应器Hotcarrior热载流子Hybridintegration混合集成Image-force镜象力Impactionization碰撞电离Impedance阻抗Imperfectstructure不完整结构Implantationdose注入剂量Implantedion注入离子Impurity杂质Impurityscattering杂志散射Incrementalresistance电阻增量（微分电阻）In-contactmask接触式掩模Indiumtinoxide(ITO)铟锡氧化物Inducedchannel感应沟道Infrared红外的Injection注入Inputoffsetvoltage输入失调电压Insulator绝缘体InsulatedGateFET(IGFET)绝缘栅FETIntegratedinjectionlogic集成注入逻辑Integration集成、积分Interconnection互连Interconnectiontimedelay互连延时Interdigitatedstructure交互式结构Interface界面Interference干涉Internationalsystemofunions国际单位制Internallyscattering谷间散射Matching匹配Maxwell麦克斯韦Meanfreepath平均自由程Meanderedemitterjunction梳状发射极结Meantimebeforefailure(MTBF)平均工作时间Megeto-resistance磁阻Mesa台面MESFET-MetalSemiconductor金属半导体FETMetallization金属化Microelectronictechnique微电子技术Microelectronics微电子学Millenindices密勒指数Minoritycarrier少数载流子Misfit失配Mismatching失配Mobileions可动离子Mobility迁移率Module模块Modulate调制Molecularcrystal分子晶体MonolithicIC单片ICMOSFET金属氧化物半导体场效应晶体管Mos.Transistor(MOST)MOS.晶体管Multiplication倍增Modulator调制Multi-chipIC多芯片ICMulti-chipmodule(MCM)多芯片模块Multiplicationcoefficient倍增因子Nakedchip未封装的芯片（裸片）Negativefeedback负反馈Negativeresistance负阻Nesting套刻Negative-temperature-coefficient负温度系数Noisemargin噪声容限Nonequilibrium非平衡Nonrolatile非挥发（易失）性Normallyoff/on常闭/开Numericalanalysis数值分析Occupiedband满带Officienay功率Photoelectriccell光电池Photoelectriceffect光电效应Photoenicdevices光子器件Photolithographicprocess光刻工艺(photo)resist（光敏）抗腐蚀剂Pin管脚Pinchoff夹断PinningofFermilevel费米能级的钉扎（效应）Planarprocess平面工艺Planartransistor平面晶体管Plasma等离子体Plezoelectriceffect压电效应Poissonequation泊松方程Pointcontact点接触Polarity极性Polycrystal多晶Polymersemiconductor聚合物半导体Poly-silicon多晶硅Potential(电)势Potentialbarrier势垒Potentialwell势阱Powerdissipation功耗Powertransistor功率晶体管Preamplifier前置放大器Primaryflat主平面Principalaxes主轴Print-circuitboard(PCB)印制电路板Probability几率Probe探针Process工艺Propagationdelay传输延时Pseudopotentialmethod膺势发Punchthrough穿通Pulsetriggering/modulating脉冲触发/调制Pulse WidenModulator(PWM)脉冲宽度调制Punchthrough穿通Push-pullstage推挽级Qualityfactor品质因子Quantization量子化Schottkybarrier肖特基势垒Schottkycontact肖特基接触Schrodingen薛定厄Scribinggrid划片格Secondaryflat次平面Seedcrystal籽晶Segregation分凝Selectivity选择性Selfaligned自对准的Selfdiffusion自扩散Semiconductor半导体Semiconductor-controlledrectifier可控硅Sendsitivity灵敏度Serial串行/串联Seriesinductance串联电感Settletime建立时间Sheetresistance薄层电阻Shield屏蔽Shortcircuit短路Shotnoise散粒噪声Shunt分流Sidewallcapacitance边墙电容Signal信号Silicaglass石英玻璃Silicon硅Siliconcarbide碳化硅Silicondioxide(SiO2)二氧化硅SiliconNitride(Si3N4)氮化硅SiliconOnInsulator绝缘硅Siliverwhiskers银须Simplecubic简立方Singlecrystal单晶Sink沉Skineffect趋肤效应Snaptime急变时间Sneakpath潜行通路Sulethreshold亚阈的Solarbattery/cell太阳能电池Solidcircuit固体电路SolidSolubility固溶度Sonband子带Transistoraging(stress)晶体管老化Transittime渡越时间Transition跃迁Transition-metalsilica过度金属硅化物Transitionprobability跃迁几率Transitionregion过渡区Transport输运Transverse横向的Trap陷阱Trapping俘获Trappedcharge陷阱电荷Trianglegenerator三角波发生器Triboelectricity摩擦电Trigger触发Trim调配调整Triplediffusion三重扩散Truthtable真值表Tolerahce容差Tunnel(ing)隧道（穿）Tunnelcurrent隧道电流Turnover转折Turn-offtime关断时间Ultraviolet紫外的Unijunction单结的Unipolar单极的Unitcell原（元）胞Unity-gainfrequency单位增益频率Unilateral-switch单向开关Vacancy空位Vacuum真空Valence(value)band价带Valuebandedge价带顶Valencebond价键Vapourphase汽相Varactor变容管Varistor变阻器Vibration振动Voltage电压Wafer晶片Waveequation波动方程Waveguide波导Wavenumber波数CT:ContaminationThreshold??污染阀值Ctrl:Control控制；管理；抑制D:Die芯片DAC igitalAnalogConverter??数字转换器DSP igitalSignalProcessing数字信号处理EFO:ElevtronicFlame-Off电子打火系统FA:FaceAngle顶锥角（面锥角）FAB:FreeAirBall空气球FD:FloppyDisk软盘，软式磁碟片Frd:Forward??前进GEM:GenericHi:HightMagnification高倍率Hybd:Hybrid混合动力/混合式Impd:Impedence阻抗Ins:Inspection检查，检验L/F eadFrame框架Lo:LowMagnification低倍率PM reventiveMaintenance??PR atternRecognitionT/P:TopPlate??顶板UPH:UnitPerHour??每小时产量UTI:UltrasonicTransducerInterface超声波传感受器接口VLL:VisualLeadLocator导脚定位W/C:WireClamp??线夹W/H:WorkHolder??轨道W/S:WireSpool??线轴ESD:ElectroStaticDischarge静电释放EPa:ESDProtectedarea??静电防护区ESDS??????????????????????静电敏感设备BM:BreakdownMaintenance事后维修CM:CorrectiveMaintenance改良保养PVM:PreventiveMaintenance预防保养MP:MaintencePreventive保养预防PM:ProductionMaintenance生产保养BG：backgrinding??背部研磨DS：diesaw????将wafer切die DA：dieattach??=DB:diebond??装片WB：wirebond焊线????。

自动化专业英语词汇

inductionmachine感应式电机breakdowntorque极限转矩horseshoemagnet马蹄形磁铁breakawayforce起步阻力magneticfield磁场overhauling检修eddycurrent涡流wind-drivengenerator风动发电机right-handrule右手定则revolutionspersecond转/秒left-handrule左手定则numberofpoles极数slip转差率speed-torquecurve转速力矩特性曲线inductionmotor感应电动机plugging反向制动rotatingmagneticfield旋转磁场synchronousspeed同步转速winding绕组percentage百分数stator定子locked-rotortorque锁定转子转矩rotor转子full-loadtorque满载转矩inducedcurrent感生电流primemover原动机time-phase时间相位inrushcurrent涌流excitingvoltage励磁电压magnetizingreacance磁化电抗solt槽line-to-neutral线与中性点间的lamination叠片staorwinding定子绕组laminatedcore叠片铁芯leakagereactance漏磁电抗short-circuitingring短路环no-load空载squirrelcage鼠笼fullload满载rotorcore转子铁芯Polyphase多相(的)cast-aluminumrotor铸铝转子iron-loss铁损bronze青铜compleximpedance复数阻抗horsepower马力rotorresistance转子电阻random-wound散绕leakageflux漏磁通insulation绝缘locked-rotor锁定转子acmotor交流环电动机choppercircuit斩波电路endring端环separatelyexcited他励的alloy合金compounded复励coilwinding线圈绕组dcmotor直流电动机form-wound模绕demachine直流电机performancecharacteristic工作特性speedregulation速度调节frequency频率shunt并励revolutionsperminute转/分series串励motoring电动机驱动armaturecircuit电枢电路generating发电opticalfiber光纤per-unitvalue标么值interoffice局间的waveguide波导波导管operationalcalculus算符演算bandwidth带宽gain增益lightemittingdiode发光二极管pole极点silica硅石二氧化硅feedbacksignal反馈信号regeneration再生,后反馈放大dynamicresponse动态响应coaxial共轴的,同轴的voltagecontrolsystem电压控制系统high-performance高性能的mismatch失配carrier载波errordetector误差检测器mature成熟的excitationsystem励磁系统SingleSideBand(SSB)单边带fieldcurrent励磁电流couplingcapacitor结合电容transistor晶体管propagate传导传播high-gain高增益modulator调制器boost-buck升压去磁demodulator解调器feedbacksystem反馈系统linetrap限波器reactivepower无功功率shunt分路器feedbackloop反馈回路AmplitudeModulation(AM)调幅automaticVoltageregulator(AVR)自动电压FrequencyShiftKeying(FSK)移频键控调整器tuner调谐器referenceVoltage基准电压attenuate衰减magneticamplifier磁放大器incident入射的amplidyne微场扩流发电机two-wayconfiguration二线制self-exciting自励的generatorvoltage发电机电压limiter限幅器dcgenerator直流发电机manualcontrol手动控制polyphaserectifier多相整流器blockdiagram方框图boost增压linearzone线性区timeconstant时间常数potentialtransformer电压互感器forwardtransferfunction正向传递函数stabilizationnetwork稳定网络errorsignal误差信号stabilizer稳定器regulator调节器air-gapflux气隙磁通stabilizingtransformer稳定变压器saturationeffect饱和效应timedelay延时saturationcurve饱和曲线directaxistransienttimeconstant直轴瞬变fluxlinkage磁链时间常数perunitvalue标么值transientresponse瞬态响应shuntfield并励磁场solidstate固体magneticcircuit磁路buck补偿load-saturationcurve负载饱和曲线air-gapline气隙磁化线sinusoidaltimefunction正弦时间函数polyphaserectifier多相整流器complexnumber复数circuitcomponents电路元件Cartesiancoordinates笛卡儿坐标系circuitparameters电路参数modulus模electricaldevice电气设备realpart实部electricenergy电能imaginarypart虚部primarycell原生电池displacementcurrent位移电流energyconverter电能转换器trigonometrictransformations瞬时值conductor导体epochangle初相角heatingappliance电热器phasedisplacement相位差direct-current直流signalamplifier小信号放大器timeinvariant时不变的mid-frequencyband中频带self-inductor自感bipolarjunctiontransistor(BJT)双极性晶体mutual-inductor互感管thedielectric电介质fieldeffecttransistor(FET)场效应管storagebattery蓄电池electrode电极电焊条e.m.f=electromotivefore电动势polarity极性unidirectionalcurrent单方向性电流gain增益circuitdiagram电路图isolation隔离分离绝缘隔振loadcharacteristic负载特性emitter发射管放射器发射极terminalvoltage端电压collector集电极externalcharacteristic外特性base基极conductance电导self-biasresistor自偏置电阻volt-amperecharacteristics伏安特性triangularsymbol三角符号carbon-filamentlamp碳丝灯泡phasereversal反相idealsource理想电源infinitevoltagegain无穷大电压增益internalresistance内阻feedbackcomponent反馈元件active(passive)circuitelements有（无）源differentiation微分电路元件integration积分下限leakagecurrent漏电流impedance阻抗circuitbranch支路fidelity保真度P.D.=potentialdrop电压降summingcircuit总和线路反馈系统中的比potentialdistribution电位分布较环节r.m.svalues=rootmeansquarevalues均方Oscillation振荡根值inverse倒数effectivevalues有效值admittance导纳steadydirectcurrent恒稳直流电transformer变压器turnsratio变比匝比compoundgenerator复励发电机ampere-turns安匝(数)rheostat变阻器mutualflux交互(主)磁通self–excitationprocess自励过程vectorequation向(相)量方程commutationcondition换向状况c umulativelycompoundedmotor积复励电powerfrequency工频capacitanceeffect电容效应动机inductionmachine感应电机operatingcondition运行状态shuntexcited并励equivalentT–circuitT型等值电路seriesexcited串励rotor(stator)winding转子（定子绕组）耗separatelyexcited他励windingloss绕组（铜）损selfexcited自励primemotor原动机fieldwinding磁场绕组励磁绕组activecomponent有功分量speed-torquecharacteristic速度转矩特性reactivecomponent无功分量dynamic-stateoperation动态运行electromagnetictorque电磁转矩salientpoles凸极retardingtorque制动转矩excitedby励磁inductivecomponent感性（无功）分量fieldcoils励磁线圈a bscissaaxis横坐标air-gapfluxdistribution气隙磁通分布inductiongenerator感应发电机directaxis直轴s ynchronousgenerator同步发电机armaturecoil电枢线圈a utomaticstation无人值守电站rotatingcommutator旋转（整流子）换向器hydropowerstation水电站commutator-brushcombination换向器-电刷p rocessofself–excitation自励过程总线a uxiliarymotor辅助电动机mechanicalrectifier机械式整流器technicalspecifications技术条件波voltageacrosstheterminals端电压armaturem.m.f.wave电枢磁势Geometricalposition几何位置steady–statecondition瞬态暂态magnetictorque电磁转矩reactiveinrespectto相对⋯.性spatialwaveform空间波形a ctiveinrespectto相对⋯.呈阻性sinusoidal–densitywave正弦磁密度synchronouscondenser同步进相（调相）机externalarmaturecircuit电枢外电路c oincideinphasewith与⋯.同相instantaneouselectricpower瞬时电功率synchronousreactance同步电抗instantaneousmechanicalpower瞬时机械功algebraic代数的率algorithmic算法的应effectsofsaturation饱和效reluctance磁阻poweramplifier功率放大器1--masterelement主要元件，是指控制开关等元件。

民机高速风洞试验的阻力雷诺数效应修正

民机高速风洞试验的阻力雷诺数效应修正白峰;巴玉龙【摘要】It is important to get the accuracy aerodynamic character data for designers during the airplane design phase. The wind tunnel test with scaled model is one of the main ways. The wind tunnel’ s finite Re number limit the assessment of the transonic cruise drag, so we have to make the Re number effect correction for the drag of wind tunnel test. This article analyses the tolerance of wind tunnel drag measurement, and presents the wind tunnel test data basis for Re number effect correction. The constitution of transonic cruise drag is analyzed . The correct meth-od of the Min-Drag and Lift-Induced-Drag is discussed respectively, and the result is verified to get a reliable en-gineering method.%在飞机设计阶段，获得准确的气动特性数据对设计者是十分重要的，采用缩比模型的风洞试验是主要途径之一。

但是风洞条件限制了试验的Re数，从而影响了对跨音速巡航阻力的评估，因此需要对风洞试验结果的阻力进行Re数效应修正。

电磁助推翼段加速地面效应及稳定性分析

第９卷㊀第１期２０２４年１月气体物理ＰＨＹＳＩＣＳＯＦＧＡＳＥＳＶｏｌ.９㊀Ｎｏ.１Ｊａｎ.２０２４㊀㊀ＤＯＩ:１０.１９５２７/ｊ.ｃｎｋｉ.２０９６￣１６４２.１０８１电磁助推翼段加速地面效应及稳定性分析罗星东ꎬ㊀侯自豪ꎬ㊀李少伟ꎬ㊀薄靖龙ꎬ㊀翟茂春(中国航天科工飞航技术研究院磁电总体部ꎬ北京１０００７４)ＧｒｏｕｎｄＥｆｆｅｃｔｓａｎｄＳｔａｂｉｌｉｔｙＡｎａｌｙｓｉｓｏｆＡｉｒｆｏｉｌＡｃｃｅｌｅｒａｔｅｄｂｙＥｌｅｃｔｒｏｍａｇｎｅｔｉｃＰｒｏｐｕｌｓｉｏｎＬＵＯＸｉｎｇｄｏｎｇꎬ㊀ＨＯＵＺｉｈａｏꎬ㊀ＬＩＳｈａｏｗｅｉꎬ㊀ＢＯＪｉｎｇｌｏｎｇꎬ㊀ＺＨＡＩＭａｏｃｈｕｎ(ＩｎｓｔｉｔｕｔｅｏｆＭａｇｎｅｔｉｃＬｅｖｉｔａｔｉｏｎａｎｄＥｌｅｃｔｒｏｍａｇｎｅｔｉｃＰｒｏｐｕｌｓｉｏｎꎬＨＩＷＩＮＧＴｅｃｈｎｏｌｏｇｙＡｃａｄｅｍｙｏｆＣＡＳＩＣꎬＢｅｉｊｉｎｇ１０００７４ꎬＣｈｉｎａ)摘㊀要:电磁发射空天飞行器是未来可重复使用天地往返运输系统的重要发展方向之一ꎬ近地助推加速过程受电磁悬浮力影响ꎬ面临着复杂的地面效应与弹性稳定性问题ꎮ以ＮＡＣＡ００１２二维翼段为研究对象ꎬ建立了电磁力与气动力耦合的动力学模型ꎬ对翼段近地Ｍａ＝０~１.５加速过程中的流场特征㊁运行姿态和气动特性进行了数值模拟ꎮ结果表明ꎬ翼段加速诱导地面效应可分为４阶段ꎮ第１阶段ꎬ上下翼面为亚声速流动ꎬ翼段姿态和气动载荷基本无振荡ꎮ第２阶段ꎬ上翼面开始出现跨声速流动ꎬ下翼面流动以典型的变截面跨声速流动为主导ꎬ并伴随壅塞－通流模态转换ꎮ第３阶段ꎬ上翼面保持跨声速流动ꎬ下翼面流动壅塞再现ꎬ并呈现出完全膨胀的跨声速壅塞流动状态ꎮ在第２㊁３阶段ꎬ翼段姿态和气动载荷低频大幅振荡ꎮ第４阶段ꎬ上翼面发展为超声速流动ꎬ下翼面保持完全膨胀壅塞流动ꎬ翼段姿态和气动载荷高频小幅振荡ꎮ在此基础上ꎬ探究了悬浮高度㊁悬浮刚度㊁磁体间距对系统稳定性的影响ꎮ发现增加悬浮高度ꎬ有利于在一定程度上提高系统稳定性ꎻ适当增加悬浮刚度或悬浮磁体间距ꎬ同时限定电磁助推目标速度小于系统振荡发散临界Ｍａｃｈ数ꎬ有利于明显提高系统稳定性ꎮ关键词:电磁发射ꎻ地面效应ꎻ弹性系统ꎻ壅塞流动ꎻ稳定性㊀㊀㊀中图分类号:Ｖ２１１.５㊀㊀文献标志码:Ａ收稿日期:２０２３￣０８￣３１ꎻ修回日期:２０２３￣１０￣０９基金项目:国家自然科学基金(１２０７２０１４)第一作者简介:罗星东(１９９３ )㊀男ꎬ硕士ꎬ主要研究电磁发射地面效应㊁飞行器内外流ꎮＥ￣ｍａｉｌ:ｓｔａｒ＿ｅａｓｔ＠ｏｕｔｌｏｏｋ.ｃｏｍＡｂｓｔｒａｃｔ:Ａｅｒｏｓｐａｃｅｖｅｈｉｃｌｅｌａｕｎｃｈｅｄｂｙｅｌｅｃｔｒｏｍａｇｎｅｔｉｃｐｒｏｐｕｌｓｉｏｎｉｓａｐｏｔｅｎｔｉａｌｏｐｔｉｏｎｆｏｒｆｕｔｕｒｅｒｅｕｓａｂｌｅｓｐａｃｅｔｒａｎｓｐｏｒ￣ｔａｔｉｏｎｓｙｓｔｅｍｓ.Ｃｏｍｐｌｅｘｇｒｏｕｎｄｅｆｆｅｃｔｓａｎｄｓｔａｂｉｌｉｔｙｉｓｓｕｅｓａｒｅｉｎｄｕｃｅｄｇｅｎｅｒａｌｌｙｄｕｅｔｏｔｈｅｉｎｔｒｏｄｕｃｔｉｏｎｏｆｅｌｅｃｔｒｏｍａｇｎｅｔｉｃｌｅｖｉｔａｔｉｏｎｆｏｒｃｅ.Ａｄｙｎａｍｉｃｍｏｄｅｌｃｏｕｐｌｅｄｗｉｔｈｅｌｅｃｔｒｏｍａｇｎｅｔｉｃｆｏｒｃｅａｎｄａｅｒｏｄｙｎａｍｉｃｆｏｒｃｅｗａｓｅｓｔａｂｌｉｓｈｅｄｆｏｒｔｈｅｔｗｏ￣ｄｉ￣ｍｅｎｓｉｏｎａｌｗｉｎｇ(ＮＡＣＡ００１２).ＮｕｍｅｒｉｃａｌｓｉｍｕｌａｔｉｏｎｓｗｅｒｅｃｏｎｄｕｃｔｅｄｏｎｔｈｅｆｌｏｗｃｈａｒａｃｔｅｒｉｓｔｉｃｓꎬｏｐｅｒａｔｉｏｎａｌａｔｔｉｔｕｄｅꎬａｎｄａｅｒｏｄｙｎａｍｉｃｃｈａｒａｃｔｅｒｉｓｔｉｃｓｏｆｔｈｅｗｉｎｇｄｕｒｉｎｇｔｈｅＭａ＝０~１.５ａｃｃｅｌｅｒａｔｉｏｎｐｒｏｃｅｓｓ.Ｉｔｉｎｄｉｃａｔｅｓｔｈａｔｇｒｏｕｎｄｅｆｆｅｃｔｓｃａｎｂｅｄｉｖｉｄｅｄｉｎｔｏｆｏｕｒｓｔａｇｅｓ.Ｉｎｔｈｅｆｉｒｓｔｓｔａｇｅꎬｓｕｂｓｏｎｉｃｆｌｏｗｓａｒｅｐｒｅｓｅｎｔｅｄｏｎｂｏｔｈｔｈｅｕｐｐｅｒａｎｄｌｏｗｅｒｗｉｎｇｓｕｒｆａｃｅｓꎬａｎｄｔｈｅｒｅｉｓｂａｓｉｃａｌｌｙｎｏｏｓｃｉｌｌａｔｉｏｎｆｏｒｔｈｅａｔｔｉｔｕｄｅａｎｄａｅｒｏｄｙｎａｍｉｃｌｏａｄｓｏｆｔｈｅｗｉｎｇ.Ｉｎｔｈｅｓｅｃｏｎｄｓｔａｇｅꎬｔｒａｎｓｏｎｉｃｆｌｏｗｅｍｅｒ￣ｇｅｓｏｎｔｈｅｕｐｐｅｒｗｉｎｇｓｕｒｆａｃｅꎬｗｈｉｌｅｔｈｅｆｌｏｗｏｎｔｈｅｌｏｗｅｒｗｉｎｇｓｕｒｆａｃｅｉｓｄｏｍｉｎａｔｅｄｂｙａｔｙｐｉｃａｌｖａｒｉａｂｌｅｃｒｏｓｓ￣ｓｅｃｔｉｏｎｔｒａｎｓｏｎｉｃｆｌｏｗａｃｃｏｍｐａｎｉｅｄｂｙｔｈｅｔｒａｎｓｉｔｉｏｎｆｒｏｍｔｈｅｃｈｏｋｅｄｆｌｏｗｍｏｄｅｔｏｔｈｅｕｎｃｈｏｋｅｄｏｎｅ.Ｉｎｔｈｅｔｈｉｒｄｓｔａｇｅꎬｔｈｅｕｐｐｅｒｗｉｎｇｓｕｒｆａｃｅｍａｉｎｔａｉｎｓｔｒａｎｓｏｎｉｃｆｌｏｗｓꎬｗｈｉｌｅｔｈｅｌｏｗｅｒｗｉｎｇｓｕｒｆａｃｅｕｎｄｅｒｇｏｅｓｃｈｏｋｅｄｆｌｏｗｓｗｈｉｃｈａｒｅｆｕｌｌｙｅｘｐａｎｄｅｄ.Ｉｎｂｏｔｈｔｈｅｓｅｃｏｎｄａｎｄｔｈｉｒｄｓｔａｇｅｓꎬｔｈｅｗｉｎｇａｔｔｉｔｕｄｅａｎｄａｅｒｏｄｙｎａｍｉｃｌｏａｄｓｏｓｃｉｌｌａｔｅｓｉｇｎｉｆｉｃａｎｔｌｙａｔｌｏｗｆｒｅｑｕｅｎｃｉｅｓ.Ｉｎｔｈｅｆｏｕｒｔｈｓｔａｇｅꎬｔｈｅｕｐｐｅｒｗｉｎｇｓｕｒｆａｃｅｕｎｄｅｒｇｏｅｓｓｕｐｅｒｓｏｎｉｃｆｌｏｗｓꎬｗｈｉｌｅｔｈｅｌｏｗｅｒｗｉｎｇｓｕｒｆａｃｅｍａｉｎｔａｉｎｓｃｈｏｋｅｄｆｌｏｗｓ.Ｔｈｅｗｉｎｇａｔｔｉｔｕｄｅａｎｄａｅｒｏｄｙｎａｍｉｃｌｏａｄｓｏｓｃｉｌｌａｔｅｓｌｉｇｈｔｌｙａｔｈｉｇｈｆｒｅｑｕｅｎｃｉｅｓ.Ｏｎｔｈｉｓｂａｓｉｓꎬｔｈｅｅｆｆｅｃｔｓｏｆｓｕｓｐｅｎｓｉｏｎｈｅｉｇｈｔꎬｓｕｓｐｅｎｓｉｏｎｓｔｉｆｆｎｅｓｓａｎｄｓｐａｃｉｎｇｂｅｔｗｅｅｎｓｕｓｐｅｎｓｉｏｎｍａｇｎｅｔｓｏｎｔｈｅｓｙｓｔｅｍｓｔａｂｉｌｉｔｙｗｅｒｅｅｘｐｌｏｒｅｄ.Ｉｔｉｓｆｏｕｎｄｔｈａｔｉｎｃｒｅａ￣ｓｉｎｇｔｈｅｓｕｓｐｅｎｓｉｏｎｈｅｉｇｈｔｉｓｂｅｎｅｆｉｃｉａｌｆｏｒｉｍｐｒｏｖｉｎｇｓｙｓｔｅｍｓｔａｂｉｌｉｔｙ.Ｉｎｃｒｅａｓｉｎｇｔｈｅｓｕｓｐｅｎｓｉｏｎｓｔｉｆｆｎｅｓｓｏｒｓｐａｃｉｎｇｂｅｔｗｅｅｎｓｕｓｐｅｎｓｉｏｎｍａｇｎｅｔｓａｐｐｒｏｐｒｉａｔｅｌｙꎬｗｈｉｌｅｌｉｍｉｔｉｎｇｔｈｅｔａｒｇｅｔｓｐｅｅｄｏｆｅｌｅｃｔｒｏｍａｇｎｅｔｉｃｐｒｏｐｕｌｓｉｏｎｔｏｂｅｌｅｓｓｔｈａｎｔｈｅｃｒｉｔｉｃａｌ气体物理２０２４年㊀第９卷Ｍａｃｈｎｕｍｂｅｒｏｆｓｙｓｔｅｍｏｓｃｉｌｌａｔｉｏｎｄｉｖｅｒｇｅｎｃｅꎬｉｓｂｅｎｅｆｉｃｉａｌｆｏｒｓｉｇｎｉｆｉｃａｎｔｌｙｉｍｐｒｏｖｉｎｇｓｙｓｔｅｍｓｔａｂｉｌｉｔｙ.Ｋｅｙｗｏｒｄｓ:ｅｌｅｃｔｒｏｍａｇｎｅｔｉｃｌａｕｎｃｈꎻｇｒｏｕｎｄｅｆｆｅｃｔꎻｅｌａｓｔｉｃｓｙｓｔｅｍꎻｃｈｏｋｅｄｆｌｏｗꎻｓｔａｂｉｌｉｔｙ引㊀言新一代空天飞行器采用组合循环动力技术ꎬ可水平起降与重复使用ꎬ并可自由穿梭于低空㊁临近空间乃至近地轨道ꎬ是未来争夺太空经济和军事主动权的重要途径ꎮ由于飞行过程须跨越亚㊁跨㊁超㊁高超声速ꎬ所以需要兼顾飞行器在宽速域㊁大空域下的气动布局和组合动力效率等问题ꎬ这对系统设计提出了极大挑战[１]ꎮ涡波效应－乘波设计㊁机翼－乘波设计和变形/组合设计是目前发展宽速域飞行器的几种主要思路[２]ꎮ近年来ꎬ电磁发射技术逐渐成熟ꎬ为克服上述难题提供了另一种颇具潜力的解决方案[３]ꎮ利用电磁橇将飞行器在近地助推至超声速ꎬ能够有效规避低速起飞阶段ꎬ增加系统设计冗余度ꎮ国内外已对此开展了电磁助推发射方案验证和缩比模型试验验证[４]ꎮ不同于开域飞行ꎬ地面为近地流动营造了独特的半开放约束空间ꎬ通常诱发以复杂激波现象为主导的跨/超声速地面效应干扰ꎮ除空气动力学特性外ꎬ飞行器还处于电磁弹性力－气动力－结构弹性力多物理场耦合环境中ꎬ面临着复杂的气动弹性及稳定性问题ꎮ深入认知电磁助推加速地面效应并探索调控系统稳定性的手段是电磁发射技术开发的重要前提ꎮ依托地效飞行器[５ꎬ６]㊁航天器着陆[７ꎬ８]等研究背景ꎬ研究人员对低亚声速地面效应已建立起较丰富的认识[９￣１１]ꎮＭｏｒｒｏｗ等[１２]通过研究发现ꎬ与低亚声速地面效应不同ꎬ跨/超声速地面效应更为复杂ꎬ以激波及其反射现象为主要特征ꎮ罗世彬等[１３]综述了电磁助推发射的气动关键技术ꎬ认为飞行器－电磁橇在加速至超声速过程中ꎬ多体之间强烈的激波干扰会影响滑跑稳定性ꎮ研究人员对跨/超声速地面效应开展了必要讨论ꎮ在实验研究方面ꎬＤｏｉｇ等[１４￣１６]㊁Ｂａｒｂｅｒ等[１７]㊁Ｋｌｅｉｎｅ等[１８]㊁Ｓｈｅｒｉｄａｎ等[１９]采用镜像模型法ꎬ巧妙地消除了风洞中静止地面边界层的影响ꎬ对尖劈和子弹等简化构型在不同离地高度㊁来流速度下的超声速近地流场进行了实验ꎮ研究发现ꎬ当离地高度较小时ꎬ飞行器前缘上部呈现为脱体弓形激波ꎬ而下部因局部地面效应呈现为驻定正激波ꎮ除风洞实验外ꎬＰｕｒｄｏｎ等[２０]通过对比实弹射击和风洞实验结果ꎬ研究了静止地面对子弹超声速近地流场的影响ꎮ在数值模拟研究方面ꎬＯｌｉｖｉｕ等[２１]研究了圆柱体近地流动中的激波反射和尾涡结构ꎮＧａｏ等[２２]研究了跨声速地面效应下激波－边界层干扰导致的压力脉动和抖振现象ꎮ陈晓东等[２３]研究了磁悬浮助推发射装置的气动特性并进行了风洞缩比实验ꎮ肖虹等[２４]计算了Ｍａ＝０.１~２.０范围内某钝头体火箭橇实验中的地面效应干扰ꎮ王伟等[２５]针对细长体开展了Ｍａ＝２.５下不同攻角以及不同离地高度的地面效应研究ꎮＹｕ等[２６]进一步研究了乘波体构型在复杂地面构型下的地面效应流场和气动特性ꎮ与上述静态地面效应不同ꎬ助推加速引起的非定常地面效应更为复杂多变[２７]ꎬ常伴随流场结构非定常转变和气动载荷非线性时变ꎬ并出现双解问题和迟滞现象[２８￣３０]ꎮ针对非定常地面效应流动机理的研究尚处于起步阶段ꎬ仍待深入研究ꎮ气动弹性及稳定性问题在电磁发射中同样不可忽略ꎮ已有研究主要关注气动力－结构弹性力构成的经典弹性系统ꎮ例如ꎬＮｕｈａｉｔ等[３１]㊁Ｄｅｓｓｉ等[３２]研究了二维翼型在地面效应下的颤振特性ꎬ结果表明地面效应具有使翼型失稳的作用ꎮ张斌等[３３]通过涡诱导的圆柱自由振荡算例和二维颤振标模ꎬ研究了地面效应对气动弹性动态响应和颤振边界的影响ꎮ此外ꎬ电磁弹性力的引入将使得气动弹性问题更加突出㊁独特和复杂ꎮ为突出重点和分解难点ꎬ本文基于逐步解耦的思路ꎬ选取ＮＡＣＡ００１２典型二维翼段作为研究对象ꎬ对电磁弹性力－气动力耦合作用下的翼段加速地面效应进行研究ꎬ重点关注翼段加速过程中的流场㊁姿态和气动载荷的演变规律ꎬ同时考察弹性系统参数对电磁助推稳定性的影响ꎮ１㊀气动－电磁耦合模型和数值计算方法１.１㊀物理模型和控制方程图１为考察的二维ＮＡＣＡ００１２翼段示意图ꎮ坐标系原点Ｏ与翼段质心初始位置重合ꎬＸ轴沿水平方向ꎬ与电磁推进方向相反ꎻＹ轴沿铅垂方向ꎬ竖直向上ꎻＺ轴由右手法则确定ꎮ翼段上下型线对称ꎬ弦长ｌ为１.０ｍꎬ质心距离翼前缘０.４ｍꎬ俯仰角为体轴与Ｘ轴夹角ꎬ规定抬头为正ꎬ简记为θꎬ初始时刻θ＝θ０ꎮ单位展长翼段质量为８２.０ｋｇꎬ转６４第１期罗星东ꎬ等:电磁助推翼段加速地面效应及稳定性分析动惯量Ｉ为１１.４ｋｇｍ２ꎮ电磁悬浮系统的地面模组内置于地面ꎬ翼段通过预先布置于ＡꎬＢ两处的磁体与地面模组感应产生电磁悬浮力ꎬ从而悬浮于平面轨道上ꎮ质心离地悬浮高度为ｈꎬ初始时刻ｈ＝０.５ｍꎮ电磁悬浮力与悬浮高度相关ꎮ悬浮力可简化为位于翼段上ＡꎬＢ两点的弹簧振子 ꎮ弹簧刚度ｋ０与电磁悬浮刚度一致ꎬ为１５０ｋＮ/ｍꎮ翼段以加速度ａ＝１００ｍ/ｓ２向左匀加速运动ꎬ并保留沿Ｙ向平动和绕Ｚ轴转动ꎮ图１㊀电磁助推ＮＡＣＡ００１２翼段受力示意图Ｆｉｇ.１㊀ＳｃｈｅｍａｔｉｃｄｉａｇｒａｍｏｆｆｏｒｃｅａｎａｌｙｓｉｓｏｆｔｈｅＮＡＣＡ００１２ｗｉｎｇａｃｃｅｌｅｒａｔｅｄｂｙｅｌｅｃｔｒｏｍａｇｎｅｔｉｃｐｒｏｐｕｌｓｉｏｎ对于存在运动边界(即翼段)的非定常数值模拟ꎬ采用任意Ｌａｇｒａｎｇｅ￣Ｅｕｌｅｒ形式的流动控制方程求解ꎮ在控制体Ｖ内ꎬ积分形式的质量守恒㊁动量守恒和能量守恒方程通式为ｄｄｔʏＶρϕｄＶ＋ʏ∂Ｖρϕ(ｕ－ｕｓ) ｄＡ＝ʏ∂ＶΓ(Ñϕ) ｄＡ＋ʏＶＳϕｄＶ(１)式中ꎬρ是气体密度ꎻ∂Ｖ代表控制体边界ꎻＡ是网格面矢量ꎻϕ＝(１ꎬｕｉꎬＴ)是通用变量ꎬ其中ꎬｉ＝１ꎬ２ꎬ３ꎻｕ＝ｕｊ是速度矢量ꎬ其中ꎬｊ＝１ꎬ２ꎬ３ꎻｕｓ＝(ｕｓ１ꎬｕｓ２ꎬｕｓ３)是网格运动速度矢量ꎻΓ＝(０ꎬμꎬｋＴ/ｃｐ)是广义扩散系数ꎻＳϕ＝(０ꎬ∂ｐ/∂ｘｉ＋ＳｉꎬＳＴ)是广义源项ꎮ其中ꎬμ是动力黏度ꎬｋＴ是流体传热系数ꎬｃｐ是比热容ꎬｐ是静压ꎬＴ是温度ꎬＳｉ是动量方程源项ꎬＳＴ是能量方程黏性耗散项ꎮ为封闭上述方程ꎬ引入理想气体状态方程ｐ＝ρＲＴꎬ其中ꎬＲ是摩尔气体常数ꎮ上述方程中ꎬ位于运动物体表面的ｕｓ项须通过求解电磁弹性力－气动力耦合的动力学方程组获得ꎮ为建立动力学模型ꎬ以下对电磁弹性力进行建模ꎬ并给出电磁弹性力－气动力耦合受力模型ꎮ对图１中翼段进行简要受力分析ꎮ翼段受气动阻力Ｄ和气动升力Ｌ作用ꎬ二者对质心产生气动力矩Ｍａｉｒ＝－ＯＰˑ(Ｌ＋Ｄ)ꎬ其中Ｐ点为气动压心ꎮ此外ꎬ电磁悬浮力Ｆ１ꎬＦ２分别对质心产生电磁力矩Ｍ１ꎬＭ２ꎮ规定电磁悬浮力㊁气动力与ＸꎬＹ轴正方向一致为正ꎬ电磁力矩和气动力矩抬头为正ꎮ则有Ｆ１(ｔ)＝－ｋ(ｙＡ－ｙＡ０)＋Ｆ１ꎬｔ＝０(２)Ｆ２(ｔ)＝－ｋ(ｙＢ－ｙＢ０)＋Ｆ２ꎬｔ＝０(３)Ｍ１(ｔ)＝－ＯＡˑＦ１(４)Ｍ２(ｔ)＝－ＯＢˑＦ２(５)式中ꎬ等号第２项Ｆ１ꎬｔ＝０和Ｆ２ꎬｔ＝０表示求解初始时刻弹簧振子ＡꎬＢ具有的Ｙ向初始电磁悬浮力ꎮ因此ꎬ绕翼段质心的刚体动力学二自由度控制方程为ｍｙ㊆＝Ｌ＋Ｆ１＋Ｆ２－ｍｇ(６)Ｉθ㊆＝Ｍａｉｒ＋Ｍ１＋Ｍ２(７)式中ꎬｙ㊆是翼段质心垂向加速度ꎬθ㊆㊀是翼段绕质心的俯仰角加速度ꎮ对上述矢量方程进行标量化处理ꎬ则电磁悬浮力Ｆ１ꎬＦ２为Ｆ１＝－ｋ(ｙＡ－ｙＡ０)＋Ｆ１ꎬｔ＝０(８)Ｆ２＝－ｋ(ｙＢ－ｙＢ０)＋Ｆ２ꎬｔ＝０(９)式中ꎬｙＡꎬｙＢ分别是任意时刻ＡꎬＢ点的Ｙ向坐标ꎮ由刚体运动关系ꎬｙＡꎬｙＢ可由Ｏ点平动位移ｙ和相对Ｏ点的转动位移给定ꎮ以图１中Ｂ点为例χＢ＝ａｒｃｃｏｓＯＢｔ＝０ (１ꎬ０)ＯＢｔ＝０(１０)ｙＢ＝ｙ－ＯＢｓｉｎ(χＢ＋Δθ)(１１)式中ꎬχＢ是初始时刻由质心水平单位正矢量顺时针７４气体物理２０２４年㊀第９卷转动至与ＯＢ共线时的几何夹角ꎬ值域为[０ꎬp]ꎮDθ是相对于初始时刻的俯仰角变化量ꎮ同理χＡ＝ａｒｃｃｏｓＯＡｔ＝０ (１ꎬ０)ＯＡｔ＝０(１２)ｙＡ＝ｙ－ＯＡｓｉｎ(χＡ＋Δθ)(１３)进一步地ꎬ将式(８)~(１３)代入式(６)㊁(７)可得弹性系统控制方程的标量一般形式ｍｙ㊆＋ｋ[２ｙ－ｌＢｓｉｎ(χＢ＋Δθ)－ｌＡｓｉｎ(χＡ＋Δθ)－(ｙＡ０＋ｙＢ０)]＝Ｌ－ｍｇ＋(Ｆ１ꎬｔ＝０＋Ｆ２ꎬｔ＝０)(１４)Ｉθ㊆－ｌＡｃｏｓ(χＡ＋Δθ)ˑ{－ｋ[ｙ－ｌＡｓｉｎ(χＡ＋Δθ)－ｙＡ０]＋Ｆ１ꎬｔ＝０}＋ｌＢｃｏｓ(χＢ＋Δθ)ˑ{－ｋ[ｙ－ｌＢｓｉｎ(χＢ＋Δθ)－ｙＢ０]＋Ｆ２ꎬｔ＝０}＝Ｍａｉｒ(１５)式中ꎬｌＡ和ｌＢ表示ＡꎬＢ弹簧作用点与质心的距离ꎬ即ｌＡ＝ＯＡꎬｌＢ＝ＯＢꎮ本文考察相对理想化的初始状态ꎬ假定磁体ＡꎬＢ均位于体轴上ꎬｌＡ＝０.４ｍꎬｌＢ＝０.６ｍꎬ磁体间距ｌ０＝ｌＡ＋ｌＢ＝１.０ｍꎬ翼段初始俯仰角θ０＝０ꎬ则有ｙＡ０＝ｙＢ０＝０ꎬχＡ＝pꎬχＢ＝０ꎬDθ＝θꎻ同时假定弹簧初始处于松弛状态ꎬ则Ｆ１ꎬｔ＝０＝Ｆ２ꎬｔ＝０＝０ꎮ则式(１４)㊁(１５)可写为ｍｙ㊆＋ｋ(２ｙ－ｌＢｓｉｎθ＋ｌＡｓｉｎθ)＝Ｌ－ｍｇ(１６)Ｉθ㊆＋ｋ２(ｌ２Ｂ＋ｌ２Ａ)ｓｉｎ２θ＋ｋｙ(ｌＡ－ｌＢ)ｃｏｓθ＝Ｍａｉｒ(１７)对于以上弹性系统ꎬ图２给出了电磁弹性力－气动力－惯性力耦合作用下的翼段近地加速非定常分步求解策略ꎮ图２㊀翼段加速过程非定常求解策略Ｆｉｇ.２㊀Ｕｎｓｔｅａｄｙｓｏｌｕｔｉｏｎｓｔｒａｔｅｇｙｆｏｒｗｉｎｇａｃｃｅｌｅｒａｔｉｏｎ１.２　网格和计算方法翼段近地加速过程的计算域如图３所示ꎮ计算域的入口及出口均采用压力远场边界条件ꎬ并设置在远离翼段１０倍弦长距离以外ꎮ时变来流的Ｍａｃｈ数为Ｍａ＝０~１.５ꎬ压力为１ａｔｍ(１ａｔｍ＝１.０１３２５ˑ１０５Ｐａ)㊁温度为２８８.１５Ｋꎮ翼段和地面满足黏性无滑移绝热边界条件ꎬ地面速度与来流速度一致ꎮ图３㊀计算域及边界条件Ｆｉｇ.３㊀Ｃｏｍｐｕｔａｔｉｏｎａｌｄｏｍａｉｎａｎｄｂｏｕｎｄａｒｙｃｏｎｄｉｔｉｏｎｓ采用重叠网格法模拟翼段近地加速过程中的沉浮和俯仰运动ꎬ流向网格尺度约５ｍｍꎬ近壁面网格以增长率１.１８发展２５层ꎬ满足ｙ＋~１要求ꎮ图４展示了翼段邻域重叠网格ꎬ计算结果表明重叠交界面附近的网格匹配性较好ꎮ采用Ｆｌｕｅｎｔ密度基隐式求解器开展非定常数值模拟ꎬ湍流模型采用ｋ￣ωＳＳＴ模型ꎬ通量采用Ｒｏｅ￣ＦＤＳ格式ꎬ流场采用２阶迎风格式求解ꎬ采用ＣＦＬ＝１.５ꎮ在非定常计算中ꎬ时间迭代步长按照Δｔｓ＝ｍｉｎ(Δｘ/(ｕ＋ｃ)ꎬ２πｍ/ｋ)给定ꎬ其中Dｘ是流向网格尺度ꎬｕ是当地水平流动速度ꎬ本文计算统一取Δｔｓ＝５ˑ１０－５ｓꎮ图４㊀翼段邻域的重叠网格Ｆｉｇ.４㊀ＯｖｅｒｓｅｔｇｒｉｄｓａｒｏｕｎｄｔｈｅＮＡＣＡ００１２ｗｉｎｇ为了考察网格无关性ꎬ对来流Ｍａｃｈ数Ｍａ＝０.８条件下不同网格尺度下ＮＡＣＡ００１２翼段定常气动力进行了对比ꎮ其中ꎬ较稀疏网格数为１.４ˑ１０５(流向网格尺度１０ｍｍ)ꎬ中等尺度网格数为２.７ˑ１０５(流向网格尺度５ｍｍ)ꎬ较密集网格数为１.１２ˑ８４第１期罗星东ꎬ等:电磁助推翼段加速地面效应及稳定性分析１０６(流向网格尺度３ｍｍ)ꎮ结果表明ꎬ随着网格数量的增加ꎬ阻力㊁升力和力矩均趋于收敛ꎬ本文选取中等尺度网格开展研究ꎮ１.３㊀计算方法验证在跨/超声速阶段ꎬ激波干扰和激波－边界层干扰是典型的地面效应流动特征ꎮ采用Ｄｏｉｇ风洞实验结果[１１]ꎬ对本文数值方法模拟地效的有效性进行了验证ꎮ实验来流条件为Ｍａ＝２.４ꎬＲｅ＝３.０７´１０５ꎬα＝０ʎꎬ地面效应采用固定壁板方式模拟ꎮ在相同条件下开展了数值模拟ꎬ图５给出了数值纹影和子弹表面压力系数分布ꎮ为了更加直观地对比地面效应波系的位置及形态ꎬ这里将数值纹影与实验纹影对称放置ꎮ可见ꎬ数值与实验结果吻合较好ꎬ对激波捕捉的位置相近ꎮ(ａ)Ｓｃｈｌｉｅｒｅｎｐｈｏｔｏｇｒａｐｈ(ｂ)Ｓｕｒｆａｃｅｐｒｅｓｓｕｒｅｄｉｓｔｒｉｂｕｔｉｏｎ图５㊀超声速子弹地面效应的数值与实验对比ꎬＭａ＝２.４Ｆｉｇ.５㊀ＣｏｍｐａｒｉｓｏｎｏｆｇｒｏｕｎｄｅｆｆｅｃｔｓｏｆｔｈｅｓｕｐｅｒｓｏｎｉｃｐｒｏｊｅｃｔｉｌｅｂｅｔｗｅｅｎｎｕｍｅｒｉｃａｌａｎｄｅｘｐｅｒｉｍｅｎｔａｌｒｅｓｕｌｔｓꎬＭａ＝２.４进一步地ꎬ采用ＡＧＡＲＤ提供的ＮＡＣＡ００１２跨声速简谐振荡实验[２４]对非定常数值方法开展了验证ꎮ翼型的振荡形式如下α(ｔ)＝α０＋αｍｓｉｎ(ωｒｔ)(１８)式中ꎬα０为平均来流攻角ꎬαｍ为振荡幅值ꎬωｒ为角频率ꎮ图６给出了ＮＡＣＡ００１２跨声速简谐振荡抬头上仰α＝２.３４ʎ时刻的数值与实验压力系数分布对比结果ꎮ数值计算获得的压力分布与实验数据吻合良好ꎬ说明本文数值方法对含运动边界的动态俯仰模拟具有较高精度ꎮ图６㊀攻角α＝２.３４ʎ姿态时翼段压力系数分布Ｆｉｇ.６㊀Ｐｒｅｓｓｕｒｅｃｏｅｆｆｉｃｉｅｎｔｄｉｓｔｒｉｂｕｔｉｏｎｏｎｔｈｅｗｉｎｇｓｕｒｆａｃｅꎬα＝２.３４ʎ２㊀结果与讨论本节首先对二维ＮＡＣＡ００１２翼段在相对悬浮高度为ｈ/ｌ＝０.５下的典型加速地面效应进行研究ꎬ以厘清近地流场㊁翼段姿态和气动载荷的演变规律ꎬ而后考察翼段悬浮高度㊁悬浮刚度㊁悬浮磁体间距３个关键因素对电磁助推加速稳定性的影响ꎮ２.１㊀翼段加速地面效应及气动力特性翼段近地电磁悬浮推进过程中的典型时刻加速流场变化如图７所示ꎮ为了便于分辨各流场中翼段相对初始位置的沉浮位移和姿态ꎬ在图７中标识Ｏ点以显示初始时刻翼段质心位置ꎮ由于弹簧振子在初始时刻处于完全松弛状态ꎬ所以也可由沉浮位移判断电磁悬浮力的方向ꎮ同时ꎬ在图７中标识箭头位置和方向以表示压心位置和升力方向ꎬΔｘＯＰ/ｌ为质心指向压心的流向距离与弦长的比值ꎬ正值则表示压心在质心右方ꎮ图７表明ꎬ翼段在加速过程中的流场结构和受力特性复杂多变ꎬ根据速域可大致分为４个阶段ꎮ９４气体物理２０２４年㊀第９卷(ａ)Ｍａ＝０.４０㊀(ｂ)Ｍａ＝０.５０㊀(ｃ)Ｍａ＝０.６０(ｄ)Ｍａ＝０.７０㊀(ｅ)Ｍａ＝０.７６㊀(ｆ)Ｍａ＝０.８０(ｇ)Ｍａ＝０.８６㊀(ｈ)Ｍａ＝０.９０㊀(ｉ)Ｍａ＝１.００(ｊ)Ｍａ＝１.１０㊀(ｋ)Ｍａ＝１.３０㊀(ｌ)Ｍａ＝１.５０图７㊀ＮＡＣＡ００１２翼段近地助推加速典型Ｍａｃｈ数下流场压力系数云图Ｆｉｇ.７㊀ＰｒｅｓｓｕｒｅｃｏｅｆｆｉｃｉｅｎｔｄｉｓｔｒｉｂｕｔｉｏｎｏｆｔｈｅＮＡＣＡ００１２ｗｉｎｇａｔｒｅｐｒｅｓｅｎｔａｔｉｖｅＭａｃｈｎｕｍｂｅｒｓ第１阶段ꎬ当Ｍａɤ０.６０ꎬ上下翼面呈现亚声速流动ꎮ自由空间内上下翼面流动基本对称ꎬ压心位置近似与质心重合ꎬ翼段姿态相对稳定ꎮ而受地面效应影响ꎬ上下翼面流动逐渐出现差异ꎬ下翼面低压区迅速增大ꎬ出现局部超声速区域(图７(ｃ))ꎬ翼段压心前移(向左移动)并受到负升力ꎬ因此翼段下沉并低头ꎮ第２阶段ꎬ当０.６０<Ｍａɤ０.７６ꎬ上翼面前缘逐渐向跨声速流动过渡并形成局部超声速低压区域ꎻ而下翼面与地面所构造的约束空间类似收缩－扩张型喷管ꎬ当来流在下翼面建立起声速喉道(图７(ｄ))ꎬ流动产生壅塞并产生一系列压缩波向翼段前方传播ꎮ下翼面流动呈现为典型的变截面跨声速流动:亚声速－声速－超声速ꎬ但流动处于过膨胀状态ꎬ恢复激波Ｓ１位于翼段下方ꎮ但在电磁斥力及翼段前缘上方超声速低压持续作用下ꎬ翼段快速抬头并上升ꎬ喷管的收缩比减弱ꎬ下翼面流动伴随壅塞－通流状态快速转换(图７(ｅ))ꎮ因此ꎬ下翼面出现壅塞是第１阶段向第２阶段转变的明显判据ꎮ第３阶段ꎬ当０.７６ɤＭａ<０.９０ꎬ上翼面保持跨声速流动特点ꎬ以局部超声速低压膨胀区和其后的恢复激波Ｓ２为主要特征ꎬ随着来流速度增加ꎬＳ２逐渐后退ꎬ尾部斜激波Ｓ３形成ꎮ在电磁拉力作用下ꎬ翼段开始下降ꎬ下翼面重新建立起壅塞ꎬ与第２阶段壅塞流动不同的是ꎬ此时激波Ｓ１已完全退出下翼面ꎬ流动处于完全膨胀状态ꎮ因此壅塞再现是第２阶段向第３阶段转变的判据ꎮ综合第２和第３阶段来看ꎬ流动的非定常特性和壅塞－通流的交０５第１期罗星东ꎬ等:电磁助推翼段加速地面效应及稳定性分析替变换引起了翼段的升力方向㊁压心位置和悬浮姿态显著变化ꎬ对其运行稳定性影响明显ꎮ第４阶段ꎬ当０.９０ɤＭａ<１.５０ꎬ上翼面呈现出完全超声速流动ꎬ以此为标志流动开始进入第４阶段ꎻ下翼面持续保持壅塞ꎬ处于完全膨胀状态ꎮ当来流处于超声速速域时ꎬ翼段前方压缩波逐渐汇聚成为激波Ｓ４并向翼段靠近ꎬ下翼面壅塞流动以前缘脱体正激波为主要特征ꎬ翼段下半部多余流量从翼段前缘溢流口向翼段上半部泄流ꎮ该阶段ꎬ翼段受超声速地面效应影响ꎬ压心位置和悬浮姿态相对稳定ꎬ受到正升力和电磁拉力ꎬ翼段上浮ꎮ与流场分析相对应ꎬ图８给出了加速过程中的翼段质心垂向位移和俯仰角的演变曲线ꎮ可以看出ꎬ在第１阶段ꎬ质心垂向位移和俯仰角曲线较为顺滑ꎮ质心高度不断下降ꎬ最大位移量为－０.１ｍꎬ翼段连续低头ꎬ最小俯仰角约为－３.８ʎꎮ在第２ꎬ３阶段ꎬ由于气动压心后移－前移－后移和升力负－正的迅速转变ꎬ该阶段内的质心位移和俯仰角曲线出现明显振荡ꎮ特别地ꎬ对于第２阶段ꎬ在下翼面壅塞消失过程中ꎬ原本宽泛的低压区迅速缩小直至消失(图７(ｅ))ꎬ前缘压力得到恢复ꎬ同时前缘上表面局部超声速低压区开始显现ꎬ这一高一低造成翼段整体抬头趋势较明显ꎮ而当处于第３阶段ꎬ壅塞再现ꎬ随着上翼面恢复激波Ｓ２的后退和低压区的扩大ꎬ上下翼面流动特征趋近并相对稳定ꎬ压心始终位于质心附近ꎬ抬头趋势被抑制ꎬ俯仰角和质心位移整体保持平稳振荡ꎮ在第４阶段ꎬ质心位移和俯仰角的平均值先基本不变后略微降低ꎬ曲线的振幅明显减弱但频率明显升高ꎮ进一步地ꎬ对助推加速过程中的翼段气动力/力矩系数进行研究ꎬ其中参考面积为Ｓｒｅｆｆ＝１ｍ２ꎮ从图９可以看出ꎬ翼段气动载荷变化规律和图８中姿态变化规律相近ꎬ图８㊀翼段质心位移和俯仰角演变Ｆｉｇ.８㊀Ｅｖｏｌｕｔｉｏｎｏｆｃｅｎｔｒｏｉｄｄｉｓｐｌａｃｅｍｅｎｔａｎｄｐｉｔｃｈａｎｇｌｅｏｆｔｈｅｗｉｎｇ图９㊀翼段气动载荷系数演变Ｆｉｇ.９㊀Ｅｖｏｌｕｔｉｏｎｏｆａｅｒｏｄｙｎａｍｉｃｆｏｒｃｅｃｏｅｆｆｉｃｉｅｎｔｓｏｆｔｈｅｗｉｎｇ因此ꎬ亚声速地面效应对翼段运行姿态的影响特点可简要总结为基本无振荡ꎻ跨声速地面效应诱导翼段运行姿态低频大幅振荡ꎻ而超声速地面效应诱导翼段运行姿态高频小幅振荡ꎮ２.２㊀翼段稳定性分析２.２.１㊀气动－电磁弹性系统稳定性讨论通过前述分析发现ꎬ在跨/超声速运行阶段尤其是第２ꎬ３阶段ꎬ流场变化显著ꎬ翼段受到较强的非定常气动载荷冲击ꎬ表现出大幅度周期性振荡ꎬ容易产生稳定性问题ꎮ实际上ꎬ电磁悬浮力可认为是弹性力ꎬ这与传统的气动力－结构弹性力所构成的气动弹性问题类似ꎮ因此ꎬ本节从方程相似角度对悬浮加速运行稳定性进行分析ꎮ无外力干扰下的经典二元翼段弹性体颤振控制方程[３４]分别由质心动力学方程和绕动点刚心Ｅ的转动方程建立ꎬ可写为ｍ(ｙ㊆Ｅ－θ㊆Ｅｘａ＋ｇ)＋ＣｙＥｙ＋ＫｙＥｙ＝Ｌ＝ＱｙＥ(１９)ＩＥθ㊆Ｅ－ｍ(ｙ㊆Ｅ＋ｇ)ｘａ＋ＣθＥθＥ＋ＫθＥθ＝Ｍａｉｒ－Ｌｘａ＝ＱθＥ(２０)式中ꎬ广义坐标ｙＥ和θＥ分别是弹性体刚心的沉浮位移和绕刚心的俯仰角ꎻＩＥ表示绕刚心转动惯量ꎻｘａ为质心与刚心距离且质心位于刚心后方ꎻＣｙＥ和ＣθＥ分别为翼段弹性体刚心沉浮和俯仰阻尼系数ꎻＭａｉｒ是对质心的气动力矩ꎻＫｙＥ和ＫθＥ分别为翼段弹性体沉浮和俯仰刚度系数ꎻ两式等号右边ＱｙＥ和ＱθＥ分别对应刚心气动升力和刚心气动力矩ꎮ相较之下ꎬ虽然本文所考察的电磁弹性力－气动力系统(式(１６)~(１７))暂不考虑结构弹性和结构阻尼ꎬ即已略去与ｘａ和结构阻尼有关的量ꎬ但由于有电磁外部力的约束且不显含广义坐标θꎬ也具有一定复杂度ꎮ特别地ꎬ在小攻角振荡假设下ꎬ式１５气体物理２０２４年㊀第９卷(１６)~(１７)可改写为ｍ(ｙ㊆＋ｇ)＋２ｋｙ＋ｋ(ｌＡ－ｌＢ)θ＝Ｌ(２１)Ｉθ㊆＋ｋ(ｌ２Ａ＋ｌ２Ｂ)θ＝Ｍａｉｒ－ｋ(ｌＡ－ｌＢ)ｙ(２２)将式(１９)~(２０)与式(２１)~(２２)对比ꎬ不难发现ꎬ由电磁弹性力－气动力耦合模型推导出的弹性动力学控制方程与经典气动弹性控制方程形式类似ꎮ主导电磁悬浮近地加速系统的不稳定性因素主要存在３项ꎮ一是悬浮高度ｈꎬ该项直接影响地面效应和相关气动载荷ꎬ即方程等号右边的升力项Ｌ和力矩项Ｍａｉｒꎮ二是悬浮刚度ｋꎬ其直接影响了系统的刚度ꎮ三是悬浮磁体间距ꎬ由ｌＡ和ｌＢ决定ꎮ以下分别对悬浮高度㊁悬浮刚度和磁体间距对系统稳定性的影响开展研究ꎮ２.２.２㊀悬浮高度对系统稳定性的影响控制磁体间距和悬浮刚度不变ꎬ研究了不同初始相对悬浮高度ｈ/ｌ＝０.５ꎬ１.０ꎬ１.５对系统稳定性的影响ꎮ图１０给出了不同相对悬浮高度下翼段近地加速过程中质心位移和俯仰角演变曲线ꎮ可以看到ꎬ当增加悬浮高度ꎬ由于下翼面阻塞度减小ꎬ流动产生壅塞所需的Ｍａｃｈ数增加ꎬ地面效应减弱ꎬ因此第１阶段向第２阶段的转变Ｍａｃｈ数明显延后ꎬ但质心位移和俯仰角曲线的振荡幅度在不同悬浮高度下仍基本一致ꎮ此外ꎬ不同悬浮高度下ꎬ第３阶段向第４阶段转变的阈值基本不变ꎮ这主要是由于第３向第４阶段转变的标志是恢复激波Ｓ２退出上翼面ꎬ而不同离地悬浮高度下上翼面流动特征基本一致ꎮ(ａ)Ｃｅｎｔｒｏｉｄｄｉｓｐｌａｃｅｍｅｎｔ㊀㊀㊀(ｂ)Ｐｉｔｃｈａｎｇｌｅ图１０㊀不同悬浮高度下翼段加速质心位移和俯仰角演变Ｆｉｇ.１０㊀Ｅｖｏｌｕｔｉｏｎｏｆｃｅｎｔｒｏｉｄｄｉｓｐｌａｃｅｍｅｎｔａｎｄｐｉｔｃｈａｎｇｌｅｏｆｔｈｅｗｉｎｇａｔｄｉｆｆｅｒｅｎｔｓｕｓｐｅｎｓｉｏｎｈｅｉｇｈｔｓ上述结果表明ꎬ增加悬浮高度能够缩短跨/超声速地面效应气动激励的作用时间ꎮ并且ꎬ翼段在第４阶段的质心垂向高度下降更快ꎬ俯仰角曲线振荡的平均值基本趋于０ʎ攻角ꎬ但振幅略有增加ꎮ从系统稳定性来看ꎬ适当增加悬浮高度有利于减弱地面效应ꎬ从而提高系统稳定性ꎮ但考虑到工程可实现性ꎬ悬浮高度的可调节范围受诸多限制ꎬ对于实际工程应做进一步讨论ꎮ２.２.３㊀悬浮刚度对系统稳定性的影响控制悬浮高度和磁体间距不变ꎬ通过在悬浮刚度ｋ０基准上依次扩大１０倍和５０倍ꎬ研究不同悬浮刚度下的系统稳定性ꎮ图１１给出了悬浮刚度ｋ＝ｋ０ꎬ１０ｋ０ꎬ５０ｋ０下翼段近地加速过程中质心位移和俯仰角演变曲线ꎮ图１１表明ꎬ当增加悬浮刚度至１０ｋ０ꎬ５０ｋ０时ꎬ在加速前期阶段ꎬ翼段的质心沉浮位移和俯仰角的振荡幅度能够被有效抑制ꎬ位移振荡范围均限制在ʃ１０ｍｍ区间ꎮ但较大的悬浮刚度反而导致翼段更高频的振荡ꎬ直至发散ꎬ其中俯仰角最大值约４０ʎꎬ远远超过失速迎角ꎬ严重破坏了系统稳定性ꎮ并且ꎬ悬浮刚度５０ｋ０相比１０ｋ０工况的发散更加提前ꎬ出现在亚声速域ꎮ(ａ)Ｃｅｎｔｒｏｉｄｄｉｓｐｌａｃｅｍｅｎｔ２５第１期罗星东ꎬ等:电磁助推翼段加速地面效应及稳定性分析(ｂ)Ｐｉｔｃｈａｎｇｌｅ图１１㊀不同悬浮刚度下翼段加速质心位移和俯仰角演变Ｆｉｇ.１１㊀Ｅｖｏｌｕｔｉｏｎｏｆｃｅｎｔｒｏｉｄｄｉｓｐｌａｃｅｍｅｎｔａｎｄｐｉｔｃｈａｎｇｌｅｏｆｔｈｅｗｉｎｇａｔｄｉｆｆｅｒｅｎｔｓｕｓｐｅｎｓｉｏｎｓｔｉｆｆｎｅｓｓ为解释系统发散现象ꎬ进一步地ꎬ对不同悬浮刚度下翼段加速过程中的沉浮位移和俯仰角进行时频分析ꎮ图１２给出了加速过程中各频率翼段沉浮及俯仰运动随Ｍａｃｈ数变化的能量分布ꎮ其中ꎬ红色区域表征翼段运动能量集中频率ꎬ红色长虚线和短虚线分别表示无气动激励下翼段自由振荡的１阶及２阶固有频率ꎮ可见ꎬ当悬浮刚度为ｋ０时ꎬ翼段沉浮与俯仰运动的频率均偏离自由振荡系统固有频率ꎮ翼段的运动主要受到气动力/力矩周期性脉动激励ꎮ随着Ｍａｃｈ数增大ꎬ气动激励由亚声速阶段的简单低频激励(约１Ｈｚ)发展为跨声速阶段的复杂低频激励(１Ｈｚ与８Ｈｚ共存)ꎻ在超声速阶段ꎬ激励频率进一步升高ꎬ并引发系统以高于２阶固有频率的振动(２０Ｈｚ左右)ꎮ当悬浮刚度增大至１０ｋ０时系统悬浮刚度加强ꎬ悬浮力足以克服亚跨声速阶段的气动激励ꎬ但随着固有频率升高ꎬ气动激励与系统２阶模态发生耦合ꎬ加之悬浮系统阻尼不足ꎬ诱发系统以２阶特征频率发生颤振式的不稳定振动ꎮ当悬浮刚度增大至５０ｋ０时ꎬ系统１阶与２阶固有频率进一步升高并趋近ꎬ气动激励同时与１阶㊁２阶模态发生耦合ꎬ从而诱发系统提前在Ｍａ＝０.８时发生不稳定振动ꎮ从另一方面讲ꎬ若减小电磁助推加速的目标速度至系统发散前(如Ｍａ＝１.２)ꎬ限定系统悬浮刚度ｋ０<ｋ<１０ｋ０ꎬ则在该范围内增加悬浮刚度能够显著减弱系统振荡幅度ꎬ提高系统稳定性ꎮ２.２.４　悬浮磁体间距对系统稳定性的影响控制悬浮高度和悬浮刚度不变ꎬ进而研究不同悬浮磁体间距下(ｌｍ＝ｌＡ＋ｌＢ＝０.５ｌ０ꎬ１.０ｌ０ꎬ２.０ｌ０)的系统稳定性ꎮ式(１６)~(１７)表明ꎬ增加磁体的前后纵向间距ꎬ可以增大电磁悬浮力的力臂ꎬ从而增加系统的俯仰刚度ꎮ图１３给出了不同磁体间距下翼段近地加速过程中质心位移和俯仰角演变曲线ꎮ结果表明ꎬ增加悬浮磁体间距ꎬ能够大幅抑制加速过程中的质心沉浮位移和俯仰角的振荡幅度ꎬ但翼段在第４阶段的振荡频率略有升高ꎮ减小悬浮磁体间距ꎬ翼段出现明显沉浮和俯仰振荡的速域提前ꎬ并表现为低频大幅振荡ꎮ(ａ)ｋ＝ｋ０(ｂ)ｋ＝１０ｋ０３５。

自动化专业英语常用词汇及短语

一、自动化专业词汇英汉对照abscissa axis 横坐标ac motor 交流环电动机active (passive) circuit elements 有（无）源电路元件active component 有功分量active in respect to 相对….呈阻性admittance 导纳air-gap flux distribution 气隙磁通分布air-gap flux 气隙磁通air-gap line 气隙磁化线algebraic 代数的algorithmic 算法的alloy 合金ampere-turns 安匝(数)amplidyne 微场扩流发机电Amplitude Modulation(AM)调幅armature circuit 电枢电路armature coil 电枢线圈armature m.m.f. wave 电枢磁势波attenuate 衰减automatic station 无人值守电站automatic Voltage regulator(AVR)自动电压调整器auxiliary motor 辅助电动机bandwidth 带宽base 基极bipolar junction transistor (BJT)双极性晶体管block diagram 方框图boost 增压boost-buck 升压去磁breakaway force 起步阻力breakdown torque 极限转矩bronze 青铜buck 补偿capacitance effect 电容效应carbon-filament lamp 碳丝灯泡carrier 载波Cartesian coordinates 笛卡儿坐标系cast-aluminum rotor 铸铝转子chopper circuit 斩波电路circuit branch 支路circuit components 电路元件circuit diagram 电路图circuit parameters 电路参数coaxial 共轴的,同轴的coil winding 线圈绕组coincide in phase with 与….同相collector 集电极commutation condition 换向状况commutator-brush combination 换向器-电刷总线complex impedance 复数阻抗complex number 复数compound generator 复励发机电compounded 复励conductance 电导conductor 导体coupling capacitor 结合电容cumulatively compounded motor 积复励电动机dc generator 直流发机电dc motor 直流电动机de machine 直流机电demodulator 解调器differentiation 微分direct axis transient time constant 直轴瞬变时间常数direct axis 直轴direct-current 直流displacement current 位移电流dynamic response 动态响应dynamic-state operation 动态运行e.m.f = electromotive fore 电动势eddy current 涡流effective values 有效值effects of saturation 饱和效应electric energy 电能electrical device 电气设备electrode 电极电焊条electromagnetic torque 电磁转矩emitter 发射管放射器发射极end ring 端环energy converter 电能转换器epoch angle 初相角equivalent T –circuit T型等值电路error detector 误差检测器error signal 误差信号excitation system 励磁系统excited by 励磁exciting voltage 励磁电压external armature circuit 电枢外电路external characteristic 外特性feedback component 反馈元件feedback loop 反馈回路feedback signal 反馈信号feedback system 反馈系统fidelity 保真度field coils 励磁线圈field current 励磁电流field effect transistor (FET)场效应管field winding 磁场绕组励磁绕组flux linkage 磁链form-wound 模绕forward transfer function 正向传递函数Frequency Shift Keying(FSK)移频键控frequency 频率full load 满载full-load torque 满载转矩gain 增益gain 增益generating 发电generator voltage 发电机电压Geometrical position 几何位置heating appliance 电热器high-gain 高增益high-performance 高性能的horsepower 马力horseshoe magnet 马蹄形磁铁hydropower station 水电站ideal source 理想电源imaginary part 虚部impedance 阻抗incident 入射的induced current 感生电流induction generator 感应发机电induction machine 感应机电induction machine 感应式机电induction motor 感应电动机inductive component 感性（无功）分量infinite voltage gain 无穷大电压增益inrush current 涌流instantaneous electric power 瞬时电功率instantaneous mechanical power 瞬时机械功率insulation 绝缘integration 积分下限internal resistance 内阻interoffice 局间的inverse 倒数iron-loss 铁损isolation 隔离分离绝缘隔振laminated core 叠片铁芯lamination 叠片leakage current 漏电流leakage flux 漏磁通leakage reactance 漏磁电抗left-hand rule 左手定则light emitting diode 发光二极管limiter 限幅器line trap 限波器linear zone 线性区line-to-neutral 线与中性点间的load characteristic 负载特性load-saturation curve 负载饱和曲线locked-rotor torque 锁定转子转矩locked-rotor 锁定转子magnetic amplifier 磁放大器magnetic circuit 磁路magnetic field 磁场magnetic torque 电磁转矩magnetizing reacance 磁化电抗manual control 手动控制mature 成熟的mechanical rectifier 机械式整流器mid-frequency band 中频带mismatch 失配modulator 调制器modulus 模motoring 电动机驱动mutual flux 交互(主)磁通mutual-inductor 互感no-load 空载number of poles 极数operating condition 运行状态operational calculus 算符演算optical fiber 光纤Oscillation 振荡overhauling 检修P.D. = potential drop 电压降per unit value 标么值percentage 百分数performance characteristic 工作特性per-unit value 标么值phase displacement 相位差phase reversal 反相plugging 反向制动polarity 极性pole 极点polyphase rectifier 多相整流器polyphase rectifier 多相整流器Polyphase 多相(的)potential distribution 电位分布potential transformer 电压互感器power amplifier 功率放大器power frequency 工频primary cell 原生电池prime motor 原动机prime mover 原动机process of self –excitation 自励过程propagate 传导传播r.m.s values = root mean square values 均方根值random-wound 散绕reactive component 无功分量reactive in respect to 相对….性reactive power 无功功率real part 实部reference Voltage 基准电压regeneration 再生, 后反馈放大regulator 调节器reluctance 磁阻retarding torque 制动转矩revolutions per minute 转/分revolutions per second 转/秒rheostat 变阻器right-hand rule 右手定则rotating commutator 旋转（整流子）换向器rotating magnetic field 旋转磁场rotor (stator) winding 转子（定子绕组）rotor core 转子铁芯rotor resistance 转子电阻rotor 转子salient poles 凸极saturation curve 饱和曲线saturation effect 饱和效应self –excitation process 自励过程self excited 自励self-bias resistor 自偏置电阻self-exciting 自励的self-inductor 自感separately excited 他励separately excited 他励的series excited 串励series 串励short-circuiting ring 短路环shunt excited 并励shunt field 并励磁场shunt 并励shunt 分路器signal amplifier 小信号放大器silica 硅石二氧化硅Single Side Band(SSB) 单边带sinusoidal –density wave 正弦磁密度sinusoidal time function 正弦时间函数slip 转差率solid state 固体solt 槽spatial waveform 空间波形speed regulation 速度调节speed-torque characteristic 速度转矩特性speed-torque curve 转速力矩特性曲线squirrel cage 鼠笼stabilization network 稳定网络stabilizer 稳定器stabilizing transformer 稳定变压器staor winding 定子绕组stator 定子steady –state condition 瞬态暂态steady direct current 恒稳直流电storage battery 蓄电池summing circuit 总和路线反馈系统中的比较环节synchronous condenser 同步进相（调相）机synchronous generator 同步发机电synchronous reactance 同步电抗synchronous speed 同步转速technical specifications 技术条件terminal voltage 端电压the dielectric 电介质time constant 时间常数time delay 延时time invariant 时不变的time-phase 时间相位transformer 变压器transient response 瞬态响应transistor 晶体管triangular symbol 三角符号trigonometric transformations 瞬时值tuner 调谐器turns ratio 变比匝比two-way configuration 二线制unidirectional current 单方向性电流vector equation 向(相)量方程voltage across the terminals 端电压voltage control system 电压控制系统volt-ampere characteristics 伏安特性waveguide 波导波导管wind-driven generator 风动发机电winding loss 绕组（铜）损耗winding 绕组二、自动化专业短语1--master element主要元件，是指控制开关等元件。

Study on Dynamic Effects of Existing Tunnel Caused by Blasting Excavation of Undercross New Tunnel

Research Results
No.2 When the clear distance more than 15 meters, about 1.5 times the tunnel height, the location of blasting load has little influence on velocity and principal stress.
Study on Dynamic Effects of Existing Tunnel Caused by Blasting Excavation of Undercrossing New Tunnel
Xie Xiaofeng
School of Resources and Safety Engineering
Research Process
The layout of blast
Computational model
Research Process
Five kinds of clear distance
Research Process
Five kinds of footage
Research Results
No.3 When the clear distance less than 10 meters, the footage more than 2 meters, the distance between blasting position and cross-face within 1 time tunnel width, the velocity of existing tunnel will exceed the allowable value, damping measures should be taken to avoid devastating results. No.4 Displacement and maximum principal stress don’t work as main factors to existing tunnel safety.

如何在幻灯片中设置动的效果和速度

如何在幻灯片中设置动的效果和速度One of the essential features of a well-designed presentation is the use of dynamic effects to enhance visual appeal and engage the audience. In this article, we will explore how to set up motion effects and adjust their speed in PowerPoint slides.1. IntroductionThe use of dynamic effects in PowerPoint presentations can significantly elevate the impact of your message. They enable you to emphasize key points, transition between slides smoothly, and maintain the viewers' interest. In this article, we will delve into the process of setting up and adjusting motion effects, as well as optimizing their speed to create a captivating presentation.2. Adding Entrance EffectsEntrance effects are applied to individual objects or elements on a slide when they first appear. To add an entrance effect:- Select the object or text box you want to animate.- Navigate to the "Animations" tab on the PowerPoint ribbon.- Click on the "Add Animation" button to access the drop-down menu with various entrance effects.- Choose the desired effect, and PowerPoint will apply it to the selected object.3. Applying Exit EffectsExit effects determine how objects or elements on a slide disappear or exit the screen. This adds a touch of elegance to the presentation and helps in smoothly transitioning between slides. To apply an exit effect:- Select the object or text box you want to animate.- Go to the "Animations" tab.- Click on the "Add Animation" button and select an exit effect from the drop-down menu.- PowerPoint will apply the chosen exit effect to the selected object.4. Implementing emphasis effectsEmphasis effects allow you to highlight specific elements on a slide to draw the viewers' attention to critical information or key visuals. To add an emphasis effect:- Select the object or text box you want to animate.- Navigate to the "Animations" tab.- Click on the "Add Animation" button and select an emphasis effect from the drop-down menu.- PowerPoint will apply the selected emphasis effect to the chosen object.5. Adjusting Animation SpeedTiming is crucial when setting up motion effects, as the speed at which the animations occur can significantly impact the overall flow of the presentation. To adjust animation speed:- Select the animated object or text box.- Access the "Animations" tab.- Click on the "Effect Options" button and choose "Timing."- In the "Duration" field, enter the desired duration for the animation. Smaller values will speed up the animation, while larger values will slow it down. Experiment with different durations until you achieve the desired effect.6. Using Motion PathsMotion paths allow you to dictate the precise movement of an object on a slide. To apply a motion path:- Select the object you want to animate.- Go to the "Animations" tab and click on the "Add Animation" button.- Choose "More Motion Paths" to access a wide range of predefined paths.- Select the desired motion path, and PowerPoint will apply it to the selected object.7. Modifying Motion PathsOnce you have added a motion path to an object, you may want to make adjustments to suit your presentation's requirements. To modify a motion path:- Select the object with the assigned motion path.- Navigate to the "Animations" tab.- Click on the "Motion Path" button to access additional options.- Choose "Edit Points" to customize the path's control points manually.- Drag the control points to reshape the motion path as desired.8. ConclusionBy effectively utilizing dynamic effects and adjusting their speed, you can create visually appealing and engaging PowerPoint presentations. Whether it's adding entrance or exit effects, emphasis or motion paths, each animation should be carefully selected to complement your content and enhance the overall impact of your message. Remember to strike a balance between animation and content, keeping the focus on delivering your message effectively.。

微电子与固体电子学专业词汇

微电子学与固体电子学专业英语词汇Abrupt junction 突变结Accelerated testing 加速实验Acceptor 受主Acceptor atom 受主原子Accumulation 积累、堆积Accumulating contact 积累接触Accumulation region 积累区Accumulation layer 积累层Active region 有源区Active component 有源元Active device 有源器件Activation 激活Activation energy 激活能Active region 有源（放大）区Admittance 导纳Allowed band 允带Alloy-junction device合金结器件Aluminum（Aluminium）铝Aluminum - oxide 铝氧化物Aluminum passivation 铝钝化Ambipolar 双极的Ambient temperature 环境温度Amorphous 无定形的，非晶体的Amplifier 功放扩音器放大器Analogue（Analog）comparator 模拟比较器Angstrom 埃Anneal 退火Anisotropic 各向异性的Anode 阳极Arsenic （AS）砷Auger 俄歇Auger process 俄歇过程Avalanche 雪崩Avalanche breakdown 雪崩击穿Avalanche excitation雪崩激发Background carrier 本底载流子Background doping 本底掺杂Backward 反向Backward bias 反向偏置Ballasting resistor 整流电阻Ball bond 球形键合Band 能带Band gap 能带间隙Barrier 势垒Barrier layer 势垒层Barrier width 势垒宽度Base 基极Base contact 基区接触Base stretching 基区扩展效应Base transit time 基区渡越时间Base transport efficiency基区输运系数Base-width modulation基区宽度调制Basis vector 基矢Bias 偏置Bilateral switch 双向开关Binary code 二进制代码Binary compound semiconductor 二元化合物半导体Bipolar 双极性的Bipolar Junction Transistor （BJT）双极晶体管Bloch 布洛赫Blocking band 阻挡能带Blocking contact 阻挡接触Body - centered 体心立方Body-centred cubic structure 体立心结构Boltzmann 波尔兹曼Bond 键、键合Bonding electron 价电子Bonding pad 键合点Bootstrap circuit 自举电路Bootstrapped emitter follower 自举射极跟随器Boron 硼Borosilicate glass 硼硅玻璃Boundary condition 边界条件Bound electron 束缚电子Breadboard 模拟板、实验板Break down 击穿Break over 转折Brillouin 布里渊Brillouin zone 布里渊区Built-in 内建的Build-in electric field 内建电场Bulk 体/体内Bulk absorption 体吸收Bulk generation 体产生Bulk recombination 体复合Burn - in 老化Burn out 烧毁Buried channel 埋沟Buried diffusion region 隐埋扩散区Can 外壳Capacitance 电容Capture cross section 俘获截面Capture carrier 俘获载流子Carrier 载流子、载波Carry bit 进位位Carry-in bit 进位输入Carry-out bit 进位输出Cascade 级联Case 管壳Cathode 阴极Center 中心Ceramic 陶瓷（的）Channel 沟道Channel breakdown 沟道击穿Channel current 沟道电流Channel doping 沟道掺杂Channel shortening 沟道缩短Channel width 沟道宽度Characteristic impedance 特征阻抗Charge 电荷、充电Charge-compensation effects 电荷补偿效应Charge conservation 电荷守恒Charge neutrality condition 电中性条件Chargedrive/exchange/sharing/transfer/storage 电荷驱动/交换/共享/转移/存储Chemmical etching 化学腐蚀法Chemically-Polish 化学抛光Chemmically-Mechanically Polish （CMP）化学机械抛光Chip 芯片Chip yield 芯片成品率Clamped 箝位Clamping diode 箝位二极管Cleavage plane 解理面Clock rate 时钟频率Clock generator 时钟发生器Clock flip-flop 时钟触发器Close-packed structure 密堆积结构Close-loop gain 闭环增益Collector 集电极Collision 碰撞Compensated OP-AMP 补偿运放Common-base/collector/emitter connection 共基极/集电极/发射极连接Common-gate/drain/source connection 共栅/漏/源连接Common-mode gain 共模增益Common-mode input 共模输入Common-mode rejection ratio （CMRR）共模抑制比Compatibility 兼容性Compensation 补偿Compensated impurities 补偿杂质Compensated semiconductor 补偿半导体Complementary Darlington circuit 互补达林顿电路Complementary Metal-Oxide-Semiconductor Field-Effect-Transistor（CMOS）互补金属氧化物半导体场效应晶体管Complementary error function 余误差函数Computer-aided design （CAD）/test（CAT）/manufacture（CAM）计算机辅助设计/ 测试/制造Compound Semiconductor化合物半导体Conductance 电导Conduction band （edge）导带（底）Conduction level/state 导带态Conductor 导体Conductivity 电导率Configuration 组态Conlomb 库仑Conpled Configuration Devices 结构组态Constants 物理常数Constant energy surface 等能面Constant-source diffusion恒定源扩散Contact 接触Contamination 治污Continuity equation 连续性方程Contact hole 接触孔Contact potential 接触电势Continuity condition 连续性条件Contra doping 反掺杂Controlled 受控的Converter 转换器Conveyer 传输器Copper interconnection system 铜互连系统Couping 耦合Covalent 共阶的Crossover 跨交Critical 临界的Crossunder 穿交Crucible坩埚Crystal defect/face/orientation/lattice 晶体缺陷/晶面/晶向/晶格Current density 电流密度Curvature 曲率Cut off 截止Currentdrift/dirve/sharing 电流漂移/驱动/共享Current Sense 电流取样Curvature 弯曲Custom integrated circuit 定制集成电路Cylindrical 柱面的Czochralshicrystal 直立单晶Czochralski technique 切克劳斯基技术（Cz法直拉晶体J）Dangling bonds 悬挂键Dark current 暗电流Dead time 空载时间Debye length 德拜长度De.broglie 德布洛意Decderate 减速Decibel （dB）分贝Decode 译码Deep acceptor level 深受主能级Deep donor level 深施主能级Deep impurity level 深度杂质能级Deep trap 深陷阱Defeat 缺陷Degenerate semiconductor 简并半导体Degeneracy 简并度Degradation 退化Degree Celsius（centigrade）/Kelvin 摄氏/开氏温度Delay 延迟Density 密度Density of states 态密度Depletion 耗尽Depletion approximation 耗尽近似Depletion contact 耗尽接触Depletion depth 耗尽深度Depletion effect 耗尽效应Depletion layer 耗尽层Depletion MOS 耗尽MOS Depletion region 耗尽区Deposited film 淀积薄膜Deposition process 淀积工艺Design rules 设计规则Die 芯片（复数dice）Diode 二极管Dielectric 介电的Dielectric isolation 介质隔离Difference-mode input 差模输入Differential amplifier 差分放大器Differential capacitance 微分电容Diffused junction 扩散结Diffusion 扩散Diffusion coefficient 扩散系数Diffusion constant 扩散常数Diffusivity 扩散率Diffusion capacitance/barrier/current/furnace 扩散电容/势垒/电流/炉Digital circuit 数字电路Dipole domain 偶极畴Dipole layer 偶极层Direct-coupling 直接耦合Direct-gap semiconductor 直接带隙半导体Direct transition 直接跃迁Discharge 放电Discrete component 分立元件Dissipation 耗散Distribution 分布Distributed capacitance 分布电容Distributed model 分布模型Displacement 位移Dislocation 位错Domain 畴Donor 施主Donor exhaustion 施主耗尽Dopant 掺杂剂Doped semiconductor 掺杂半导体Doping concentration 掺杂浓度Double-diffusive MOS（DMOS）双扩散MOS.Drift 漂移Drift field 漂移电场Drift mobility 迁移率Dry etching 干法腐蚀Dry/wet oxidation 干/湿法氧化Dose 剂量Duty cycle 工作周期Dual-in-line package （DIP）双列直插式封装Dynamics 动态Dynamic characteristics 动态属性Dynamic impedance 动态阻抗Early effect 厄利效应Early failure 早期失效Effective mass 有效质量Einstein relation（ship）爱因斯坦关系Electric Erase Programmable Read Only Memory（E2PROM）一次性电可擦除只读存储器Electrode 电极Electrominggratim 电迁移Electron affinity 电子亲和势Electronic -grade 电子能Electron-beam photo-resist exposure 光致抗蚀剂的电子束曝光Electron gas 电子气Electron-grade water 电子级纯水Electron trapping center 电子俘获中心Electron Volt （eV）电子伏Electrostatic 静电的Element 元素/元件/配件Elemental semiconductor 元素半导体Ellipse 椭圆Ellipsoid 椭球Emitter 发射极Emitter-coupled logic 发射极耦合逻辑Emitter-coupled pair 发射极耦合对Emitter follower 射随器Empty band 空带Emitter crowding effect 发射极集边（拥挤）效应Endurance test =life test 寿命测试Energy state 能态Energy momentum diagram 能量-动量（E-K）图Enhancement mode 增强型模式Enhancement MOS 增强性MOS Entefic （低）共溶的Environmental test 环境测试Epitaxial 外延的Epitaxial layer 外延层Epitaxial slice 外延片Expitaxy 外延Equivalent curcuit 等效电路Equilibrium majority /minority carriers 平衡多数/少数载流子Erasable Programmable ROM （EPROM）可搽取（编程）存储器Error function complement （erfc）余误差函数Etch 刻蚀Etchant 刻蚀剂Etching mask 抗蚀剂掩模Excess carrier 过剩载流子Excitation energy 激发能Excited state 激发态Exciton 激子Extrapolation 外推法Extrinsic 非本征的Extrinsic semiconductor 杂质半导体Face - centered 面心立方Fall time 下降时间Fan-in 扇入Fan-out 扇出Fast recovery 快恢复Fast surface states 快界面态Feedback 反馈Fermi level 费米能级Fermi-Dirac Distribution 费米-狄拉克分布Femi potential 费米势Fick equation 菲克方程（扩散）Field effect transistor 场效应晶体管Field oxide 场氧化层Filled band 满带Film 薄膜Flash memory 闪烁存储器Flat band 平带Flat pack 扁平封装Flicker noise 闪烁（变）噪声Flip-flop toggle 触发器翻转Floating gate 浮栅Fluoride etch 氟化氢刻蚀Forbidden band 禁带Forward bias 正向偏置Forward blocking /conducting正向阻断/导通Frequency deviation noise频率漂移噪声Frequency response 频率响应Function 函数Gain 增益Gallium-Arsenide（GaAs）砷化钾Gamy ray r 射线Gate 门、栅、控制极Gate oxide 栅氧化层Gauss（ian）高斯Gaussian distribution profile 高斯掺杂分布Generation-recombination 产生-复合Geometries 几何尺寸Germanium（Ge）锗Graded 缓变的Graded （gradual）channel 缓变沟道Graded junction 缓变结Grain 晶粒Gradient 梯度Grown junction 生长结Guard ring 保护环Gummel-Poom model 葛谋-潘模型Gunn - effect 狄氏效应Hardened device 辐射加固器件Heat of formation 形成热Heat sink 散热器、热沉Heavy/light hole band 重/轻空穴带Heavy saturation 重掺杂Hell - effect 霍尔效应Heterojunction 异质结Heterojunction structure 异质结结构Heterojunction Bipolar Transistor（HBT）异质结双极型晶体High field property 高场特性High-performance MOS.（H-MOS）高性能MOS. Hormalized 归一化Horizontal epitaxial reactor 卧式外延反应器Hot carrior 热载流子Hybrid integration 混合集成Image - force 镜象力Impact ionization 碰撞电离Impedance 阻抗Imperfect structure 不完整结构Implantation dose 注入剂量Implanted ion 注入离子Impurity 杂质Impurity scattering 杂质散射Incremental resistance 电阻增量（微分电阻）In-contact mask 接触式掩模Indium tin oxide （ITO）铟锡氧化物Induced channel 感应沟道Infrared 红外的Injection 注入Input offset voltage 输入失调电压Insulator 绝缘体Insulated Gate FET（IGFET）绝缘栅FET Integrated injection logic集成注入逻辑Integration 集成、积分Interconnection 互连Interconnection time delay 互连延时Interdigitated structure 交互式结构Interface 界面Interference 干涉International system of unions国际单位制Internally scattering 谷间散射Interpolation 内插法Intrinsic 本征的Intrinsic semiconductor 本征半导体Inverse operation 反向工作Inversion 反型Inverter 倒相器Ion 离子Ion beam 离子束Ion etching 离子刻蚀Ion implantation 离子注入Ionization 电离Ionization energy 电离能Irradiation 辐照Isolation land 隔离岛Isotropic 各向同性Junction FET（JFET）结型场效应管Junction isolation 结隔离Junction spacing 结间距Junction side-wall 结侧壁Latch up 闭锁Lateral 横向的Lattice 晶格Layout 版图Lattice binding/cell/constant/defect/distortion 晶格结合力/晶胞/晶格/晶格常熟/晶格缺陷/晶格畸变Leakage current （泄）漏电流Level shifting 电平移动Life time 寿命linearity 线性度Linked bond 共价键Liquid Nitrogen 液氮Liquid－phase epitaxial growth technique 液相外延生长技术Lithography 光刻Light Emitting Diode（LED）发光二极管Load line or Variable 负载线Locating and Wiring 布局布线Longitudinal 纵向的Logic swing 逻辑摆幅Lorentz 洛沦兹Lumped model 集总模型Majority carrier 多数载流子Mask 掩膜板，光刻板Mask level 掩模序号Mask set 掩模组Mass - action law质量守恒定律Master-slave D flip-flop主从D触发器Matching 匹配Maxwell 麦克斯韦Mean free path 平均自由程Meandered emitter junction梳状发射极结Mean time before failure （MTBF）平均工作时间Megeto - resistance 磁阻Mesa 台面MESFET-Metal Semiconductor金属半导体FET Metallization 金属化Microelectronic technique 微电子技术Microelectronics 微电子学Millen indices 密勒指数Minority carrier 少数载流子Misfit 失配Mismatching 失配Mobile ions 可动离子Mobility 迁移率Module 模块Modulate 调制Molecular crystal分子晶体Monolithic IC 单片IC MOSFET金属氧化物半导体场效应晶体管Mos. Transistor（MOST ）MOS. 晶体管Multiplication 倍增Modulator 调制Multi-chip IC 多芯片IC Multi-chip module（MCM）多芯片模块Multiplication coefficient倍增因子Naked chip 未封装的芯片（裸片）Negative feedback 负反馈Negative resistance 负阻Nesting 套刻Negative-temperature-coefficient 负温度系数Noise margin 噪声容限Nonequilibrium 非平衡Nonrolatile 非挥发（易失）性Normally off/on 常闭/开Numerical analysis 数值分析Occupied band 满带Officienay 功率Offset 偏移、失调On standby 待命状态Ohmic contact 欧姆接触Open circuit 开路Operating point 工作点Operating bias 工作偏置Operational amplifier （OPAMP）运算放大器Optical photon =photon 光子Optical quenching光猝灭Optical transition 光跃迁Optical-coupled isolator光耦合隔离器Organic semiconductor有机半导体Orientation 晶向、定向Outline 外形Out-of-contact mask非接触式掩模Output characteristic 输出特性Output voltage swing 输出电压摆幅Overcompensation 过补偿Over-current protection 过流保护Over shoot 过冲Over-voltage protection 过压保护Overlap 交迭Overload 过载Oscillator 振荡器Oxide 氧化物Oxidation 氧化Oxidepassivation 氧化层钝化Package 封装Pad 压焊点Parameter 参数Parasitic effect 寄生效应Parasitic oscillation 寄生振荡Passination 钝化Passive component 无源元件Passive device 无源器件Passive surface 钝化界面Parasitic transistor 寄生晶体管Peak-point voltage 峰点电压Peak voltage 峰值电压Permanent-storage circuit 永久存储电路Period 周期Periodic table 周期表Permeable - base 可渗透基区Phase-lock loop 锁相环Phase drift 相移Phonon spectra 声子谱Photo conduction 光电导Photo diode 光电二极管Photoelectric cell 光电池Photoelectric effect 光电效应Photoenic devices 光子器件Photolithographic process 光刻工艺（photo）resist （光敏）抗腐蚀剂Pin 管脚Pinch off 夹断Pinning of Fermi level 费米能级的钉扎（效应）Planar process 平面工艺Planar transistor 平面晶体管Plasma 等离子体Plezoelectric effect 压电效应Poisson equation 泊松方程Point contact 点接触Polarity 极性Polycrystal 多晶Polymer semiconductor聚合物半导体Poly-silicon 多晶硅Potential （电）势Potential barrier 势垒Potential well 势阱Power dissipation 功耗Power transistor 功率晶体管Preamplifier 前置放大器Primary flat 主平面Principal axes 主轴Print-circuit board（PCB）印制电路板Probability 几率Probe 探针Process 工艺Propagation delay 传输延时Pseudopotential method 膺势发Punch through 穿通Pulse triggering/modulating 脉冲触发/调制Pulse Widen Modulator（PWM）脉冲宽度调制punchthrough 穿通Push-pull stage 推挽级Quality factor 品质因子Quantization 量子化Quantum 量子Quantum efficiency量子效应Quantum mechanics 量子力学Quasi - Fermi－level准费米能级Quartz 石英Radiation conductivity 辐射电导率Radiation damage 辐射损伤Radiation flux density 辐射通量密度Radiation hardening 辐射加固Radiation protection 辐射保护Radiative - recombination辐照复合Radioactive 放射性Reach through 穿通Reactive sputtering source 反应溅射源Read diode 里德二极管Recombination 复合Recovery diode 恢复二极管Reciprocal lattice 倒核子Recovery time 恢复时间Rectifier 整流器（管）Rectifying contact 整流接触Reference 基准点基准参考点Refractive index 折射率Register 寄存器Registration 对准Regulate 控制调整Relaxation lifetime 驰豫时间Reliability 可*性Resonance 谐振Resistance 电阻Resistor 电阻器Resistivity 电阻率Regulator 稳压管（器）Relaxation 驰豫Resonant frequency共射频率Response time 响应时间Reverse 反向的Reverse bias 反向偏置Sampling circuit 取样电路Sapphire 蓝宝石（Al2O3）Satellite valley 卫星谷Saturated current range 电流饱和区Saturation region 饱和区Saturation 饱和的Scaled down 按比例缩小Scattering 散射Schockley diode 肖克莱二极管Schottky 肖特基Schottky barrier 肖特基势垒Schottky contact 肖特基接触Schrodingen 薛定厄Scribing grid 划片格Secondary flat 次平面Seed crystal 籽晶Segregation 分凝Selectivity 选择性Self aligned 自对准的Self diffusion 自扩散Semiconductor 半导体Semiconductor-controlled rectifier 可控硅Sendsitivity 灵敏度Serial 串行/串联Series inductance 串联电感Settle time 建立时间Sheet resistance 薄层电阻Shield 屏蔽Short circuit 短路Shot noise 散粒噪声Shunt 分流Sidewall capacitance 边墙电容Signal 信号Silica glass 石英玻璃Silicon 硅Silicon carbide 碳化硅Silicon dioxide （SiO2）二氧化硅Silicon Nitride（Si3N4）氮化硅Silicon On Insulator 绝缘硅Siliver whiskers 银须Simple cubic 简立方Single crystal 单晶Sink 沉Skin effect 趋肤效应Snap time 急变时间Sneak path 潜行通路Sulethreshold 亚阈的Solar battery/cell 太阳能电池Solid circuit 固体电路Solid Solubility 固溶度Sonband 子带Source 源极Source follower 源随器Space charge 空间电荷Specific heat（PT）热Speed-power product 速度功耗乘积Spherical 球面的Spin 自旋Split 分裂Spontaneous emission 自发发射Spreading resistance 扩展电阻Sputter 溅射Stacking fault 层错Static characteristic 静态特性Stimulated emission 受激发射Stimulated recombination 受激复合Storage time 存储时间Stress 应力Straggle 偏差Sublimation 升华Substrate 衬底Substitutional 替位式的Superlattice 超晶格Supply 电源Surface 表面Surge capacity 浪涌能力Subscript 下标Switching time 开关时间Switch 开关Tailing 扩展Terminal 终端Tensor 张量Tensorial 张量的Thermal activation 热激发Thermal conductivity 热导率Thermal equilibrium 热平衡Thermal Oxidation 热氧化Thermal resistance 热阻Thermal sink 热沉Thermal velocity 热运动Thermoelectricpovoer 温差电动势率Thick-film technique 厚膜技术Thin-film hybrid IC薄膜混合集成电路Thin-Film Transistor（TFT）薄膜晶体Threshlod 阈值Thyistor 晶闸管Transconductance 跨导Transfer characteristic 转移特性Transfer electron 转移电子Transfer function 传输函数Transient 瞬态的Transistor aging（stress）晶体管老化Transit time 渡越时间Transition 跃迁Transition-metal silica 过度金属硅化物Transition probability 跃迁几率Transition region 过渡区Transport 输运Transverse 横向的Trap 陷阱Trapping 俘获Trapped charge 陷阱电荷Triangle generator 三角波发生器Triboelectricity 摩擦电Trigger 触发Trim 调配调整Triple diffusion 三重扩散Truth table 真值表Tolerahce 容差Tunnel （ing）隧道（穿）Tunnel current 隧道电流Turn over 转折Turn - off time 关断时间Ultraviolet 紫外的Unijunction 单结的Unipolar 单极的Unit cell 原（元）胞Unity-gain frequency 单位增益频率Unilateral-switch单向开关Vacancy 空位Vacuum 真空Valence（value）band 价带Value band edge 价带顶Valence bond 价键Vapour phase 汽相Varactor 变容管Varistor 变阻器Vibration 振动Voltage 电压Wafer 晶片Wave equation 波动方程Wave guide 波导Wave number 波数Wave-particle duality 波粒二相性Wear-out 烧毁Wire routing 布线Work function 功函数Worst-case device 最坏情况器件Yield 成品率Zener breakdown 齐纳击穿。

Investigations on the stability of dynamic avalanche in IGBTs

It is known that dynamic avalanche can be avoided by use of very high gate resistors t o keep the n-channel open until the load current decreases [3] (figure 2). The negative electron charge compensates the space charge resulting from the moving holes. This supression of dynamic avalanche, however, enhances the turn-off loss similarly and it is not clear from single cell simulation why this should be such a benefit for the device.
The electron current generated by dynamic avalanche can not much exceed the hole current which limits this “current gain” PAva[an&e close to one [SI. This is confirmed by our simulation results. In the IGBTs considered in this paper (as in most IGBTs), the pnpTransistor current gain is far below one, because of very shallow anode doping. Therefore, the regenerative feedback condition

自动化专业英语词汇

induction machine 感应式电机horseshoe magnet 马蹄形磁铁magnetic field 磁场eddy current 涡流right—hand rule 右手定则left-hand rule 左手定则slip 转差率induction motor 感应电动机rotating magnetic field 旋转磁场winding 绕组stator 定子rotor 转子induced current 感生电流time—phase 时间相位exciting voltage 励磁电压solt 槽lamination 叠片laminated core 叠片铁芯short—circuiting ring 短路环squirrel cage 鼠笼rotor core 转子铁芯cast—aluminum rotor 铸铝转子bronze 青铜horsepower 马力random—wound 散绕insulation 绝缘ac motor 交流环电动机end ring 端环alloy 合金coil winding 线圈绕组form—wound 模绕performance characteristic 工作特性frequency 频率revolutions per minute 转/分motoring 电动机驱动generating 发电per-unit value 标么值breakdown torque 极限转矩breakaway force 起步阻力overhauling 检修wind—driven generator 风动发电机revolutions per second 转/秒number of poles 极数speed—torque curve 转速力矩特性曲线plugging 反向制动synchronous speed 同步转速percentage 百分数locked—rotor torque 锁定转子转矩full—load torque 满载转矩prime mover 原动机inrush current 涌流magnetizing reacance 磁化电抗line—to—neutral 线与中性点间的staor winding 定子绕组leakage reactance 漏磁电抗no-load 空载full load 满载Polyphase 多相（的）iron-loss 铁损complex impedance 复数阻抗rotor resistance 转子电阻leakage flux 漏磁通locked-rotor 锁定转子chopper circuit 斩波电路separately excited 他励的compounded 复励dc motor 直流电动机de machine 直流电机speed regulation 速度调节shunt 并励series 串励armature circuit 电枢电路optical fiber 光纤interoffice 局间的waveguide 波导波导管bandwidth 带宽light emitting diode 发光二极管silica 硅石二氧化硅regeneration 再生，后反馈放大coaxial 共轴的,同轴的high-performance 高性能的carrier 载波mature 成熟的Single Side Band（SSB) 单边带coupling capacitor 结合电容propagate 传导传播modulator 调制器demodulator 解调器line trap 限波器shunt 分路器Amplitude Modulation（AM）调幅Frequency Shift Keying（FSK）移频键控tuner 调谐器attenuate 衰减incident 入射的two-way configuration 二线制generator voltage 发电机电压dc generator 直流发电机polyphase rectifier 多相整流器boost 增压time constant 时间常数forward transfer function 正向传递函数error signal 误差信号regulator 调节器stabilizing transformer 稳定变压器time delay 延时direct axis transient time constant 直轴瞬变时间常数transient response 瞬态响应solid state 固体buck 补偿operational calculus 算符演算gain 增益pole 极点feedback signal 反馈信号dynamic response 动态响应voltage control system 电压控制系统mismatch 失配error detector 误差检测器excitation system 励磁系统field current 励磁电流transistor 晶体管high—gain 高增益boost—buck 升压去磁feedback system 反馈系统reactive power 无功功率feedback loop 反馈回路automatic Voltage regulator（AVR)自动电压调整器reference Voltage 基准电压magnetic amplifier 磁放大器amplidyne 微场扩流发电机self-exciting 自励的limiter 限幅器manual control 手动控制block diagram 方框图linear zone 线性区potential transformer 电压互感器stabilization network 稳定网络stabilizer 稳定器air-gap flux 气隙磁通saturation effect 饱和效应saturation curve 饱和曲线flux linkage 磁链per unit value 标么值shunt field 并励磁场magnetic circuit 磁路load-saturation curve 负载饱和曲线air—gap line 气隙磁化线polyphase rectifier 多相整流器circuit components 电路元件circuit parameters 电路参数electrical device 电气设备electric energy 电能primary cell 原生电池energy converter 电能转换器conductor 导体heating appliance 电热器direct-current 直流time invariant 时不变的self-inductor 自感mutual-inductor 互感the dielectric 电介质storage battery 蓄电池e。

本科生以数值计算完成的SCI论文

本科生以数值计算完成的SCI论文说明：《计算物理基础》课程培养了学生的科学计算能力，在北师大本科毕业论文出现了一些用数值计算完成的SCI论文，以下是部分目录。

1. (SCI)Yan Zhou(周妍,2002届毕业生),Jing-dong Bao, Optimal Number of disperse states in the model of Brownian motors, Physical A 343(2004), 515-427;2. (SCI)Wei Wu(吴伟,2001届毕业生), Jing-Dong Bao, Coupling-induced transition of states in an asymmetrical double-well potential, Physical A, 388(2004) 417-427;3. (SCI)贾莹(2002届毕业生),刘玲,包景东,高温下复合核的热裂变速率,高能物理与核物理,27(2003)6104. (SCI)Jing-Dong Bao,`Ying Jia(2002届毕业生), Determination of fission rate by mean last passage time, Physical Review C, 69(2004)027602;5. (SCI)刘玲,吕坤(2003届届毕业生),包景东,重核熔合与裂变过程中的回流现象,高能物理与核物理,28(8),Aug(2004)854-858;6. (SCI)Jing-Dong Bao,`,Rong-wu Li, Wei Wu(2001届毕业生), Numerical Simulations of generalized Langgevin equations with deeply asymptotic parameters, Journal of Computational Physics 197(2004)241-252清华大学物理系01级计算物理课期末论文云天梁,蒋绍周: 星系碰撞. 98王莘泉: 双星系统与吸积92于洁: 电动力学实验室90薛小川: 随机行走与cahn-Hilliard方程92(无界面,看说明)祁永辉: 伊辛模型,孤子(mymodel) 95丁一伊辛模型95倪远,戚扬,周一帆,王怀仁,张磊95高斯光束,柱形波导,圆柱形波导,高亮: 最低能级上的粒子凝聚凝聚发生后玻色所的宏观性质95刘元: 磁聚集透镜92 吴恺,刘凌涛,刘未名, 转移矩阵(main)混沌(,orbit1,attractor(1)) 95秦岭孤立子90 葛峰俊群表计算95 杜昱运动镜面的反射(两个程序) 90 易震环高斯光束的立体演示87 陈佳高斯光束的研究88 张筠激光世界86 黄晶格林函数86 何清球形势阱85 赵益清,董耀旗回旋辐射,同步辐射90 范家骅,孙仲垚三维不同介质中的电场90 杨程稀,肖志虎数据转换画图, 测量原子激发态寿命82 许中杰用紧束缚近似计算晶体的能带85 李渭平行平面腔的叠代解87 于志浩测量原子激发态寿命85 田俊平,于玥,赵燕鹏匀速运动电子的电磁场83 刘佳流体力学84 苏国印匀速运动电子的电磁场83 王聪高斯光束75 代祥松天线辐射85张剑在正交电磁场中运动粒子80 区树清粒子运动辐射电磁场80 谢树泉,王锐任意静电磁场中带电粒子的运动80 潘红星静止与运动的粒子的场78 邵华,王首元康普顿散射83 赵通磁偶极子辐射88 赵瑞旋转磁偶极子辐射84 罗立波旋转磁偶极子辐射82 丁卓导体球的电场80 王鑫矩形波导中的电磁场80 黄华俊矩形波导中的电磁场86 王京阳几个程序63学生作业的图形界面举例。

爱护周围环境的英语作文

爱护周围环境的英语作文Protecting the environment around us is a responsibility that falls on the shoulders of every individual. Our planet Earth is the only home we have and it is our duty to ensure that it remains habitable for generations to come. The state of the environment directly impacts our quality of life and the well-being of all living beings on this planet. It is high time we recognize the gravity of the situation and take concrete actions to safeguard our environment.One of the most pressing environmental issues we face today is the problem of pollution. Air pollution, water pollution, and soil pollution are rampant in many parts of the world, posing serious threats to human health and the delicate balance of natural ecosystems. Vehicular emissions, industrial waste, and indiscriminate dumping of garbage are major contributors to this problem. We must find sustainable solutions to reduce our carbon footprint and minimize waste generation.Promoting the use of renewable energy sources such as solar power, wind power, and hydroelectric power can greatly help in reducing airpollution and greenhouse gas emissions. Governments and policymakers need to invest heavily in the development and implementation of clean energy technologies. Individuals can also do their part by making eco-friendly choices in their daily lives, such as using energy-efficient appliances, switching to hybrid or electric vehicles, and practicing proper waste management.Another critical aspect of environmental protection is the conservation of natural resources. Our natural resources, including freshwater, fossil fuels, and mineral deposits, are finite and must be used judiciously. Overexploitation and wasteful consumption of these resources can lead to depletion and environmental degradation. We need to adopt sustainable practices in agriculture, forestry, and mining to ensure that these resources are utilized in a responsible manner.Deforestation is another major concern that requires immediate attention. Forests play a crucial role in maintaining the ecological balance, regulating the climate, and providing habitats for countless species of flora and fauna. However, the relentless clearing of forests for agricultural land, urbanization, and industrial purposes has led to a significant loss of these valuable ecosystems. Reforestation efforts and the implementation of strict regulations on logging and land-use changes are essential to reverse this trend.The protection of biodiversity is also a crucial aspect of environmental conservation. The rich diversity of plant and animal life on our planet is facing unprecedented threats due to human activities such as habitat destruction, illegal poaching, and the introduction of invasive species. The loss of biodiversity not only diminishes the natural beauty of our world but also disrupts the delicate balance of ecosystems, with far-reaching consequences for the overall health of the environment. Efforts to establish protected areas, enforce wildlife conservation laws, and promote sustainable tourism can help in preserving the rich tapestry of life on Earth.Furthermore, the issue of climate change, driven by human-induced global warming, presents a serious challenge to the well-being of our planet. The burning of fossil fuels, deforestation, and unsustainable agricultural practices have led to a rapid increase in greenhouse gas emissions, which are trapping heat in the Earth's atmosphere and causing dramatic changes in weather patterns, rising sea levels, and the melting of glaciers. Mitigating the effects of climate change requires a global collaborative effort to transition towards a low-carbon economy, adopt sustainable land-use practices, and develop innovative technologies to capture and sequester carbon emissions.In addition to these major environmental concerns, there are numerous other threats to the health of our environment, such as the accumulation of plastic waste, the depletion of freshwaterresources, and the decline of pollinator populations. Addressing these issues requires a multifaceted approach that involves government policies, corporate responsibility, and individual actions.Governments play a crucial role in setting the right policies and regulations to protect the environment. They can implement strict emission standards, promote eco-friendly practices in industries, provide incentives for renewable energy adoption, and enforce laws against environmental destruction. International cooperation and global agreements, such as the Paris Climate Accord, are also essential in coordinating efforts to address transnational environmental challenges.Businesses and corporations also have a responsibility to minimize their environmental footprint and adopt sustainable practices. This can include the development of eco-friendly products, the implementation of green manufacturing processes, and the investment in renewable energy sources. Corporate social responsibility programs that focus on environmental conservation and community engagement can also contribute to the overall effort.Ultimately, the protection of the environment requires the active participation of every individual. Simple actions such as reducing waste, conserving water, and promoting sustainable transportation can have a significant collective impact. Education and awarenesscampaigns can empower people to make informed choices and become stewards of the environment. By fostering a sense of personal responsibility and a deep appreciation for the natural world, we can inspire individuals to take concrete steps to safeguard the environment and secure a sustainable future for our planet.In conclusion, the protection of the environment around us is a pressing and multifaceted challenge that requires the collective effort of governments, businesses, and individuals. By addressing issues such as pollution, resource depletion, deforestation, and climate change, we can work towards a more sustainable and resilient future for our planet and all its inhabitants. It is our duty as global citizens to take immediate and meaningful action to protect the environment and ensure that it remains a healthy and thriving home for generations to come.。

为什么野生动物濒临灭绝英语作文

为什么野生动物濒临灭绝英语作文全文共3篇示例，供读者参考篇1Why Wild Animals Are EndangeredThe beautiful diversity of life on our planet is one of the most precious gifts we have. From the towering grandeur of elephants to the vibrant colors of tropical frogs, the incredible variety of species inhabiting the Earth enriches our world and our lives immeasurably. However, this breathtaking biodiversity is under grave threat. All around the globe, wild animals are being pushed to the brink of extinction at an alarming rate. As a student deeply concerned about environmental issues, I feel it is crucial to understand why so many species are endangered and what we can do to protect them.One of the primary drivers behind the endangerment of wild animals is habitat loss. As the human population continues to grow exponentially, we are encroaching further and further into areas that were once untouched wilderness. Forests are cleared for urban expansion, agricultural land, logging, mining, and other human activities. This systematic destruction of naturalhabitats leaves numerous species without a home, food sources, or breeding grounds. Iconic animals like the Bengal tiger, whose numbers have plummeted from over 100,000 a century ago to as few as 3,500 today, are critically endangered due to widespread deforestation across their native ranges.The illegal wildlife trade is another major threat that has pushed many wild animals to the edge of oblivion. Driven by greed and a complete disregard for the welfare of other living beings, poachers mercilessly slaughter elephants for their ivory tusks, rhinos for their horns, and countless other creatures to fuel a lucrative black market. This senseless killing has brought some of the most majestic species on Earth perilously close to extinction in the wild. Pangolins, for instance, are now the most trafficked mammals globally due to misguided beliefs about the medicinal properties of their scales.Climate change, a consequence of human-induced global warming, is also taking a heavy toll on wild animal populations. Rising temperatures, shifting weather patterns, and increasingly frequent extreme weather events are disrupting the delicate balance of ecosystems around the world. Many species are unable to adapt quickly enough to these rapid changes, leading to dwindling numbers and, in some cases, outright extinction.Polar bears, whose very existence depends on Arctic sea ice for hunting and breeding, are facing an existential crisis as their icy habitats melt away.As if these threats were not dire enough, wild animals must also contend with pollution, overexploitation, introduced invasive species, and diseases transferred from humans and domestic animals. The cumulative effect of these multifaceted pressures is a biodiversity crisis of catastrophic proportions. Scientists estimate that we are currently experiencing the worst mass extinction event since the dinosaurs were wiped out 65 million years ago, with species disappearing at a rate hundreds of times higher than the natural background rate.The loss of these wild animals would be an incalculable tragedy, not just for the sake of the creatures themselves, but for the entire web of life on our planet. Each species, no matter how small or seemingly insignificant, plays a vital role in maintaining the delicate balance of the ecosystems they inhabit. Removing even a single strand from this intricate tapestry can havefar-reaching and unpredictable consequences. Beyond their ecological importance, wild animals also hold immense cultural, scientific, and economic value for humans. They inspire us withtheir majesty, offer insights into the mysteries of life, and sustain countless livelihoods through activities like ecotourism.Clearly, the urgency of protecting endangered wild animals cannot be overstated. But what can we, as students and citizens of this planet, do to help? The most impactful change we can make is to reshape our personal habits and choices to reduce our environmental footprint. This means adopting a more sustainable lifestyle by reducing consumption, minimizing waste, and embracing eco-friendly alternatives wherever possible. We can also support organizations working to protect habitats, combat poaching, and mitigate climate change through donations or volunteering.Perhaps most importantly, we must use our voices to raise awareness about this critical issue and advocate for stronger policies and stricter enforcement of existing laws to safeguard wild animals and their habitats. By writing to our elected representatives, participating in peaceful protests, and engaging our communities, we can generate the societal and political pressure needed to effect meaningful change.Ultimately, the fate of endangered wild animals rests in our hands. As the dominant species on this planet, we have an ethical obligation to be responsible stewards of the natural world and toensure that our actions do not come at the cost of driving other lifeforms into oblivion. The loss of biodiversity impoverishes us all and diminishes the vibrant tapestry of life that makes our Earth so remarkable. By taking concerted action now, we can preserve this precious inheritance for future generations and ensure that our children and grandchildren can experience the awe and wonder of our planet's wild animals for centuries to come.篇2Why Are Wildlife Species Becoming Endangered?The natural world is a wondrous place, teeming with an incredible diversity of plant and animal life. From the great baleen whales that roam the vast oceans to the vibrantly colored birds flitting through tropical rainforests, the sheer variety of life on our planet is nothing short of awe-inspiring. However, this rich tapestry of biodiversity is under grave threat, with more and more species being pushed to the brink of extinction each year. As a concerned student, I find this trend deeply troubling, and I believe it is crucial that we understand the driving forces behind this crisis in order to take meaningful action to protect our planet's precious wildlife.One of the primary culprits behind the declining populations of countless species is habitat loss. As human populations continue to grow, we have steadily encroached upon and destroyed the natural habitats that countless animals call home. Vast swaths of forests have been razed to make way for agricultural land, urban sprawl, and resource extraction projects like mining and logging operations. Pristine ecosystems have been fragmented, isolating once-contiguous populations and disrupting the delicate balance that allows species to thrive. This loss of habitat not only deprives animals of their homes but also disrupts their access to food, water, and breeding grounds, making it increasingly difficult for them to survive and reproduce.Closely tied to habitat loss is the issue of pollution and environmental degradation. Whether it's the release of toxic chemicals into the air, water, and soil, or the accumulation of plastic waste in our oceans, the rampant pollution caused by human activity is taking a devastating toll on wildlife populations. Contaminated ecosystems can directly poison animals, disrupt their reproductive cycles, and render entire habitats uninhabitable. The effects of pollution can also ripple through food chains, magnifying the impact on top predators and other species at higher trophic levels.Climate change, fueled by human-induced greenhouse gas emissions, is another major threat to wildlife. Rising temperatures, shifting weather patterns, and the increased frequency and intensity of extreme weather events like droughts, floods, and wildfires are all placing immense stress on delicate ecosystems and the species that inhabit them. For many animals, the rate of climate change is simply too rapid for them to adapt or migrate to more suitable environments, leaving them vulnerable to extinction.The illegal wildlife trade, driven by demand for products such as ivory, rhino horn, and exotic pets, is also a significant contributor to the decline of many species. Poaching and the capture of wild animals for the black market have decimated populations of elephants, rhinos, tigers, and countless other iconic species, often pushing them to the very edge of extinction. This illicit trade not only directly threatens the targeted species but also disrupts entire ecosystems, as the removal of keystone species can have cascading effects on the delicate ecological balance.While the challenges facing wildlife conservation are daunting, it is not too late to take decisive action to protect the incredible biodiversity of our planet. Governments, organizations,and individuals must work together to implement comprehensive conservation strategies that address the root causes of species decline.Firstly, we must prioritize the protection and restoration of natural habitats. This includes establishing and expanding protected areas, such as national parks and wildlife reserves, where ecosystems can thrive undisturbed. It also means implementing sustainable land-use practices that minimize habitat fragmentation and degradation, such as responsible urban planning, sustainable agriculture, and responsible resource extraction methods.Secondly, we must tackle the issue of pollution and environmental degradation head-on. This requires stricter regulations on industrial emissions, better waste management practices, and a concerted effort to transition towards cleaner, renewable sources of energy. Individuals can also play a role by reducing their personal consumption of single-use plastics and adopting more environmentally-friendly lifestyles.Thirdly, we must take urgent action to mitigate the impacts of climate change. This means enacting policies and initiatives that reduce greenhouse gas emissions and promote the development of sustainable, low-carbon technologies. It alsoinvolves investing in research and conservation efforts that help species adapt to changing climatic conditions, such as habitat corridors that facilitate migration and the development of climate-resilient ecosystems.Fourthly, we must combat the illegal wildlife trade through stronger law enforcement efforts, increased international cooperation, and public awareness campaigns that reduce demand for wildlife products. This includes cracking down on poaching operations, disrupting trafficking networks, and promoting alternative livelihoods for communities that have traditionally relied on the wildlife trade.Finally, we must prioritize education and public engagement to foster a deeper appreciation for the natural world and the importance of biodiversity conservation. By educating people, especially the younger generations, about the intrinsic value of wildlife and the vital roles that different species play in maintaining healthy ecosystems, we can cultivate a broader sense of stewardship and inspire individuals to take action to protect the planet's precious resources.Preserving the rich tapestry of life on Earth is not just a moral imperative; it is also crucial for ensuring the long-term sustainability of our planet and the well-being of humansocieties. The loss of biodiversity can have far-reaching consequences, disrupting delicate ecological balances, undermining ecosystem services upon which we rely, and depriving us of potential sources of food, medicine, and other valuable resources.As a student, I am deeply concerned about the future of our planet and the fate of the countless species that share this remarkable world with us. It is my hope that by raising awareness and advocating for meaningful action, we can stem the tide of extinctions and ensure that future generations can marvel at the incredible diversity of life on Earth, just as we have been fortunate enough to do. The task before us is daunting, but by working together and embracing a shared sense of responsibility for our planet, we can preserve the natural wonders that make our world so vibrant and extraordinary.篇3Why Wildlife Species are Facing ExtinctionAs a high school student, I've grown up learning about the incredible diversity of life on our planet. From the vast array of species in tropical rainforests to the mysteries of the deep ocean, the natural world is teeming with amazing creatures. However,it's becoming increasingly clear that human activities are pushing many wildlife species to the brink of extinction at an alarming rate. In this essay, I'll explore some of the major threats facing endangered species and why we need to take urgent action to protect them.One of the primary drivers of wildlife extinction is habitat loss and fragmentation. As the human population continues to grow, more and more land is being converted for urban development, agriculture, logging, mining, and other activities. This results in the destruction, degradation, and subdivision of the natural habitats that countless species depend on for food, shelter, and breeding grounds. Iconic species like tigers, elephants, and gorillas have seen their habitats shrink dramatically due to deforestation and encroaching human settlements.Another significant threat is overexploitation through activities like poaching, overfishing, and the illegal wildlife trade. Despite bans and regulations, the demand for products like ivory, rhino horn, exotic pets, and bush meat has driven many species to critically low population levels. Rhinos, for instance, are being aggressively poached for their horns, which are highly valued in some traditional medicines despite having no proven medicinalproperties. At the current rate of poaching, rhinos could be extinct in the wild within a couple of decades.The effects of climate change are also putting increasing strain on numerous species across the globe. Rising temperatures are altering weather patterns, causing droughts, wildfires, and other extreme events that disrupt ecosystems. Some species are being forced to migrate to find suitable habitats, while others are unable to adapt quickly enough to the rapidly changing conditions. Climate change is considered a key factor in the potential extinction of around one million species in the coming decades, according to a 2019 UN report.Other threats include invasive species that outcompete native wildlife, pollution that contaminates habitats, and diseases that can devastate vulnerable populations. The introduction of non-native species, whether intentionally or accidentally, has caused immense damage to local ecosystems, driving out indigenous species that had existed in balance for millennia.The loss of biodiversity due to extinction has far-reaching consequences, not just for the affected species, but for entire ecosystems and ultimately, for humanity itself. Many species play crucial roles in their environments, acting as pollinators, seed dispersers, or key components of the food web. Theirdisappearance can cause ecosystems to unravel, with ripple effects that are difficult to predict. Furthermore, the diversity of life on Earth provides invaluable resources, from potential medical cures to sources of food and materials. By allowing species to go extinct, we're essentially burning an irreplaceable library of biological knowledge that could prove vital for our own survival and well-being.On a personal level, the thought of living in a world without iconic animals like rhinos, elephants, tigers, and whales is deeply saddening to me. These creatures have existed alongside humanity for thousands of years, inspiring awe, respect, and a sense of wonder about the natural world. Losing them would be a profound tragedy, not just for the species themselves, but for the human experience and our connection to the planet we call home.So what can be done to prevent further extinctions? Firstly, we need to take immediate action to protect and restore habitats through measures like establishing and expanding protected areas, promoting sustainable agriculture and forestry practices, and controlling urban sprawl. Secondly, we must strictly enforce laws against poaching, wildlife trafficking, and other forms of overexploitation, while simultaneously addressing theunderlying economic and cultural factors that drive the demand for illegal wildlife products.Tackling climate change is also crucial for safeguarding biodiversity. This requires a global effort to transition away from fossil fuels and towards renewable energy sources, as well as implementing measures to reduce greenhouse gas emissions, protect carbon sinks like forests, and help species adapt to changing conditions.Importantly, we need to raise awareness and promote education about the value of biodiversity and the consequences of extinction. By fostering a deeper appreciation and understanding of the natural world, we can inspire people to take action and make more sustainable choices in their daily lives.Finally, we must support and fund conservation efforts, both locally and globally. This includes initiatives to protect threatened species, restore degraded habitats, and promote sustainable livelihoods for communities living in biodiversity hotspots. Governments, organizations, and individuals all have a role to play in providing the resources and support necessary to turn the tide on extinction.As a student, I feel a profound sense of responsibility to do my part in protecting the incredible diversity of life on our planet. We are the inheritors of this world, and it is up to our generation to ensure that future generations can experience and appreciate the wonders of nature, rather than living in an impoverished and diminished environment. By taking concrete actions and making sustainable choices, we can create a future where humans and wildlife can coexist in harmony, preserving the rich tapestry of life that makes our planet so remarkable.。

英语作文如何做好预算

英语作文如何做好预算The world we live in today is a complex and ever-evolving place. With the rapid advancements in technology, the globalization of economies, and the increasing interconnectedness of societies, we are faced with a multitude of challenges and opportunities. As we navigate this dynamic landscape, it is important to reflect on the role that each of us plays in shaping the future.One of the most pressing issues of our time is the urgent need to address the threat of climate change. The scientific consensus is clear – human-induced global warming is a real and pressing concern, with far-reaching implications for the environment, the economy, and human well-being. From rising sea levels and extreme weather events to the depletion of natural resources and the loss of biodiversity, the impacts of climate change are already being felt around the world.In order to mitigate the effects of climate change, we must take immediate and decisive action. This will require a concerted effort on the part of governments, businesses, and individual citizens. Governments must enact policies and regulations that incentivize the transition to renewable energy sources, promote energy efficiency,and protect vulnerable ecosystems. Businesses must adapt their practices to become more sustainable, investing in green technologies and reducing their carbon footprints. And as individuals, we must make changes to our daily lives, such as reducing our energy consumption, adopting more environmentally-friendly transportation options, and supporting eco-friendly products and services.Another pressing issue is the growing inequality and social disparities that exist both within and between countries. The gap between the wealthy and the poor is widening, and this has profound implications for social cohesion, economic stability, and the overall well-being of society. Addressing this challenge will require a multifaceted approach, including investments in education, healthcare, and social welfare programs, as well as policies that promote fair and equitable economic growth.In addition to these global challenges, we are also grappling with a range of complex social and political issues. The rise of populism and nationalism, the erosion of democratic institutions, and the increasing polarization of societies are all contributing to a sense of instability and uncertainty. To address these challenges, we must prioritize the values of tolerance, inclusivity, and respect for human rights. This will require a renewed commitment to the principles of democracy, a strengthening of civic institutions, and a willingness toengage in constructive dialogue and compromise.Despite the daunting nature of these challenges, there is also reason for hope. Around the world, we are seeing a groundswell of activism and civic engagement, as people of all ages and backgrounds come together to advocate for change. From the youth-led climate strikes to the global movements for racial justice and gender equality, there is a growing sense of collective power and a belief that we can create a better future.As we look ahead, it is clear that the challenges we face are complex and multifaceted. But by working together, drawing on our collective knowledge and resources, and staying committed to the values of justice, sustainability, and human dignity, we can overcome these challenges and build a more just, equitable, and resilient world. This will require us to think beyond our individual interests and to embrace a more holistic, systems-level approach to problem-solving. It will also require us to be open to new ideas, to embrace change, and to be willing to take risks in pursuit of a better future.Ultimately, the choices we make today will shape the world that our children and grandchildren inherit. It is our responsibility to ensure that we leave behind a more just, sustainable, and prosperous world – one that is better equipped to address the complex challenges of the future. By working together, drawing on our collective wisdomand resources, and staying committed to the values that define our shared humanity, we can create a better future for all.。

两种现象做比较的英语作文题目

两种现象做比较的英语作文题目Comparison of Two PhenomenaThe world we live in is a complex and multifaceted place, filled with a myriad of phenomena that captivate our attention and challenge our understanding. In this essay, we will explore and compare two distinct phenomena that have significant impacts on our lives and the broader societal landscape.The first phenomenon we will examine is the rapid advancements in technology and its transformative effects on our daily routines and the way we interact with the world around us. Over the past few decades, we have witnessed an unprecedented surge in technological innovations, from the ubiquitous smartphones that have become extensions of our very beings to the revolutionary breakthroughs in artificial intelligence and automation that are reshaping entire industries. The integration of technology into almost every aspect of our lives has brought about both remarkable conveniences and profound societal shifts.On one hand, the technological revolution has empowered us with unprecedented access to information, communication, andentertainment. With a few taps on our screens, we can instantly connect with loved ones across the globe, access a wealth of knowledge at our fingertips, and immerse ourselves in captivating digital experiences. This has led to a more interconnected world, where geographical boundaries have become increasingly blurred, and the exchange of ideas and cultural experiences has been greatly facilitated.Moreover, the advancements in technology have also transformed the way we work and conduct business. The rise of remote work, cloud-based collaboration, and intelligent automation has enabled greater flexibility, efficiency, and productivity in the workplace. Employees can now work from the comfort of their homes, collaborate seamlessly with teams dispersed across the world, and delegate mundane tasks to intelligent algorithms, freeing up time and resources for more strategic and creative endeavors.However, the ubiquity of technology has also brought about significant challenges and concerns. The constant bombardment of digital stimuli has led to increased levels of distraction, anxiety, and social isolation, as individuals struggle to maintain a healthy balance between their online and offline lives. The reliance on technology has also raised privacy and security concerns, as personal data and sensitive information become increasingly vulnerable to cyber threats and misuse.Furthermore, the rapid pace of technological change has disrupted traditional industries and business models, leading to job displacement and the need for workers to continuously upskill and adapt to new demands. The fear of automation and artificial intelligence replacing human labor has become a source of anxiety for many, as the long-term societal implications of these technological advancements remain uncertain.The second phenomenon we will examine is the growing awareness and concern for environmental sustainability and the urgent need to address the pressing challenges posed by climate change. In recent years, the global community has witnessed a surge in environmental activism, with individuals and organizations alike recognizing the grave consequences of human-induced environmental degradation and the imperative to adopt more sustainable practices.The effects of climate change, such as rising sea levels, extreme weather events, and the depletion of natural resources, have become increasingly evident and pose a significant threat to the well-being of our planet and its inhabitants. This has led to a heightened sense of responsibility and a call for collective action to mitigate the impact of our actions on the environment.One of the most notable manifestations of this environmentalconsciousness is the rise of renewable energy sources, such as solar, wind, and hydropower, as viable alternatives to fossil fuels. Governments, businesses, and individuals are increasingly investing in and adopting these clean energy solutions, driven by a desire to reduce carbon emissions and contribute to a more sustainable future.Additionally, there has been a growing emphasis on sustainable consumption and production practices, with consumers becoming more mindful of their purchasing decisions and the environmental impact of the goods and services they consume. This has led to the proliferation of eco-friendly products, the implementation of circular economy models, and the promotion of sustainable lifestyle choices, such as reducing waste, recycling, and adopting plant-based diets.However, the transition towards environmental sustainability is not without its challenges. The shift away from established industries and practices often faces resistance from vested interests and requires significant financial investments and political will to overcome. Furthermore, the uneven distribution of the impacts of climate change, with developing countries often bearing the brunt of the consequences, has raised questions of global equity and the need for collaborative international efforts to address these complex issues.In conclusion, the comparison of these two phenomena – the technological revolution and the growing environmentalconsciousness – reveals the multifaceted and interconnected nature of the challenges and opportunities we face as a global society. While the advancements in technology have brought about remarkable conveniences and transformative changes, they have also given rise to new concerns and societal disruptions. Similarly, the heightened awareness of environmental sustainability has catalyzed positive changes, but the path towards a truly sustainable future remains fraught with obstacles.As we navigate these complex landscapes, it is crucial that we strive to strike a delicate balance between technological progress and environmental stewardship, leveraging the power of innovation to address the pressing environmental challenges we face. By fostering collaborative efforts, embracing sustainable practices, and cultivating a deeper understanding of the intricate relationships between technology and the natural world, we can work towards a future that is both technologically advanced and environmentally responsible, ensuring the well-being of our planet and the generations to come.。

投稿信CoverLetter和Highlights

模板 1Dear Prof. XXXXX,Here within enclosed is our paper for consideration to be published on “(Journal name) ”. The further information about the paper is in the following:The Title: XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXThe Authors: XXXXXXXXXX XXXXXXXXXXXX and XXXXXXXXXXThe authors claim that none of the material in the paper hasbeen published or is under consideration for publication elsewhere.I am the corresponding author and my address and other information is as follows,？Address: Department of XXXXXXXXX,Tsinghua University,Beijing, 10084,E-mail:Tel: 86-Fax: 86-Thank you very much for consideration!Sincerely Yours,Dr. XXXXXXXXXXX模板 2Dear XX (Editor):Here is our paper submitted to "(XX Journal)".The Title: XXXXThe Authors: XXX XXX and XXXIn this paper, we ...The authors claim that none of the material in the paper has been published or is under consideration for publication elsewhere.The corresponding author is Dr. XXX and his address and other information is as following:Address: Department of XXX, XX University, ...,Tel: +86-xxx-xxxxxxxxFax: +86-xxx-xxxxxxxxThank you very much for consideration!Sincerely Yours,Dr. xxx模板 3Dear Mr. **We believe the paper may be of particular interest to the readersof your journal as it ........1.The work described has not been submitted elsewherefor publication, in whole or in part, and all the authors listed have approved the manuscript that is enclosed.2.I have read and have abided by the statement ofethical standards for manuscripts submitted to Neuroscience.kind regards.Your sincerely,通信作者Dear Prof. Gil:This is a manuscript by**and **entitled“.......”. It is submitted to be considered for publication as a“...” in your journal. This paper is new. Neither the entire paper nor any part ofits content has been published or has been accepted elsewhere. Itis not being submitted to any other journal.Correspondence should be addressed to **at the following address, phone and fax number, and email address:...Thanks very much for your attention to our paper.Sincerely yours,**投稿信模版四（实例）Case 1Dear Editor,We would like to submit the enclosed manuscript entitled "GDNF Acutely Modulates Neuronal Excitability and A-type Potassium Channels in Midbrain Dopaminergic Neurons", which we wish to be considered for publication in Nature Neuroscience.GDNF has long been thought to be a potent neurotrophic factor for the survival of midbrain dopaminergic neurons, which are degenerated in Parkinson ’s disease . In this paper, we report an unexpected, acute effect of GDNF on A-type potassium channels, leading to a potentiation of neuronal excitability, in the dopaminergic neurons in culture as well as in adult brain slices. Further, we show that GDNF regulates the K+ channels through a mechanism that involves activation of MAP kinase. Thus, this study has revealed, for thefirst time, an acute modulation of ion channels by GDNF. Our findings challenge the classic view of GDNF as a long-term survival factor for midbrain dopaminergic neurons, and suggest that the normal functionof GDNF is to regulate neuronal excitability, and consequently dopamine release. These results may also have implications in the treatment of Parkinson’s disease.Due to a direct competition and conflict of interest, we requestthat Drs. XXX of Harvard Univ., and YY of Yale Univ. not be considered as reviewers. With thanks for your consideration, I am Sincerely yours,case2Dear Editor,We would like to submit the enclosed manuscript entitled "Ca2+-binding protein frequenin mediates GDNF-induced potentiation of Ca2+ channels and transmitter release", which we wish to be considered for publication in Neuron.We believe that two aspects of this manuscript will make it interesting to general readers of Neuron. First, we report that GDNFhas a long-term regulatory effect on neurotransmitter release at the neuromuscular synapses. This provides the first physiologicalevidence for a role of this new family of neurotrophic factors in functional synaptic transmission. Second, we show that the GDNFeffect is mediated by enhancing the expression of the Ca2+-binding protein frequenin. Further, GDNF and frequenin facilitate synaptic transmission by enhancing Ca2+ channel activity, leading to an enhancement of Ca2+ influx. Thus, this study has identified, for thefirst time, a molecular target that mediates the long-term, synapticaction of a neurotrophic factor. Our findings may also have general implications in the cell biology of neurotransmitter release.HighlightsHighlights are a short collection of bullet points that convey the core findings and providereaders with a quick textual overview of the article. These three to five bullet pointsdescribe the essence of the research . results or conclusions) and highlight what isdistinctive about it.Highlights will be displayed in online search result lists, the contents list and in theonline article, but will not (yet) appear in the article PDF file or print.Author instructions:Highlights should be submitted as a separate file in EES by selecting "Highlights" from thedrop-down list when uploading files. Please adhere to the specifications below.Specifications:Include 3 to 5 highlights.There should be a maximum of85 characters , including spaces, per highlight.Only the core results of the paper should be covered.Examples ？？HighlightsWe model two hospitals which have regulated prices and compete on quality.We examine changes in the level of information about hospital quality.Increasing information will increase quality if hospital costs are similar.Increasing information will decrease quality if hospital costs are very different.Welfare effects depend on ex-ante or ex-post assumptions about quality information.？HighlightsHighly c -axis oriented ZnO nanowires were grown on glass using aqueous solutions.The growth temperature does not exceed 95°C in any step of the synthesis.The photocatalytic and wetting properties were studied upon UV irradiation.ZnO nanowires show superior photocatalytic activity.We report a reversible photo-induced transition from hydrophobic to super-hydrophilic.？HighlightsA conformational two-state mechanism for proton pumping complex I is proposed.The mechanism relies on stabilization changes of anionic ubiquinone intermediates.Electron-transfer and protonation should be strictly controlled during turnover.The mechanism explains the full reversibility of complex I.？HighlightsFading of a script alone does not foster domain-general strategy knowledge.Performance of the strategy declines during the fading of a script.Monitoring by a peer keeps performance of the strategy up during script fading.Performance of a strategy after fading fosters domain-general strategy knowledge.Fading and monitoring by a peer combined foster domain-general strategy knowledge.。

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/Langmuir ©2009American ChemicalSocietyDynamic Effects Induced Transition of Droplets on BiomimeticSuperhydrophobic SurfacesYong Chae Jung and Bharat Bhushan*Nanoprobe Laboratory for Bio-and Nanotechnology and Biomimetics (NLB 2),The Ohio State University,201West 19th Avenue,Columbus,Ohio 43210-1142Received March 3,2009.Revised Manuscript Received April 14,2009Superhydrophobic surfaces have considerable technological potential for various applications because of their extreme water-repellent properties.Dynamic effects,such as the bouncing and vibration of a droplet,can destroy the composite solid -air -liquid interface.The impact pressure of a bouncing droplet and the inertia force of a vibrating droplet affect the transition from a solid -air -liquid interface to a solid -liquid interface.Therefore,it is necessary to study the dynamic effect of droplets under various system parameters (impact velocity and frequency and amplitude of vibration).A new model for the prediction of the wetting and dewetting process during droplet vibration based on the relationship between the adhesion force and the inertia force of a droplet is proposed.To investigate whether micro-,nano-,and hierarchical structures can resist the destabilizing factors responsible for the transition,a study of bouncing and vibration of a water droplet is systematically conducted on various surfaces.The physics of wetting phenomena for water droplet studies is of fundamental importance in the geometrical design of superhydrophobic surfaces.1.IntroductionSuperhydrophobic and self-cleaning surfaces with a high static contact angle above 150°and low contact-angle hysteresis (the difference between the advancing and receding contact angles)play an important role in technical applications ranging from self-cleaning window glasses,paints,textiles,solar panels,and applica-tions requiring antifouling and include a reduction of drag for fluid flow to energy conservation.1-3At a low value of contact angle hysteresis,the droplets may roll in addition to slide,which faci-litates removal of contaminant particles.Surfaces with low contact-angle hysteresis have a low water roll-off (tilt)angle,which denotes the angle to which a surface must be tilted for roll off of water drops.Condensation of water vapor from the environment and/or process liquid film can form menisci,leading to high adhesion in devices requiring relative motion.4-6Superhydrophobic surfaces are needed to minimize adhesion between a surface and liquid.A model surface for superhydrophobicity and self-cleaning is provided by the leaves of the Lotus plant (Nelumbo nucifera ).7-11The leaf surface is very rough because of so-called papillose epidermal cells,which form asperities or papillae.In addition to the microscale roughness,the surface of the papillae is also rough with sub-micrometer-sized asperities composed of 3D epicuticu-lar waxes.The waxes of Lotus are tubules,but on other leaves,waxes also exist in the form of platelets or other morphologies.10,11Lotus leaves have hierarchical structures,which have been studied by Burton and Bhushan 8and Bhushan and Jung.9The water droplets on these surfaces readily sit on the apex of nanostructures because air bubbles fill in the valleys of the structure under the droplet.Therefore,these leaves exhibit considerable superhydro-phobicity.Water on such a surface forms a spherical droplet,and both the contact area and the adhesion to the surface are dramatically reduced.1,2,12A number of artificial roughness-induced hydrophobic sur-faces have been fabricated with hierarchical structures using electrodeposition,colloidal particles,photolithography,plasma treatment,self-assembly,and imprinting.13-20Molding is a low cost and reliable way of surface-structure replication and can provide a precision on the order of 10nm.21,22Bhushan et al.3,23,24and Koch et al.25developed a new method to fabricate hierarch-ical structured surfaces.Molding was used to replicate leaf and silicon microstructures,and self-assembly of wax was used to create nanostructures on top of the microstructures to realize hierarchical structures.This two-step process provides flexibility in the fabrication of a variety of hierarchical structures.*To whom correspondence should be addressed.E-mail:bhushan.2@.(1)Bhushan,B.;Jung,Y.C.J.Phys.:Condens.Matter 2008,20,225010.(2)Nosonovsky,M.;Bhushan,B.Multiscale Dissipative Mechanisms and Hierarchical Surfaces:Friction,Superhydrophobicity,and Biomimetics ;Springer-Verlag:Heidelberg,Germany,2008.(3)Bhushan,B.;Jung,Y.C.;Koch,K.Philos.Trans.R.Soc.,A 2009,367,1631.(4)Bhushan,B.Introduction to Tribology ;Wiley:New York,2002.(5)Bhushan,B.J.Vac.Sci.Technol.,B:Microelectron.Nanometer 2003,21,2262.(6)Bhushan,B.Nanotribology and Nanomechanics ;An Introduction ,2nd ed.;Springer-Verlag:Heidelberg,Germany,2008.(7)Barthlott,W.;Neinhuis,C.Planta 1997,202,1.(8)Burton,Z.;Bhushan,B.Ultramicroscopy 2006,106,709.(9)Bhushan,B.;Jung,Y.C.Nanotechnology 2006,17,2758.(10)Koch,K.;Bhushan,B.;Barthlott,W.Soft Matter 2008,4,1943.(11)Koch,K.;Bhushan,B.;Barthlott,W.Prog.Mater.Sci.2009,54,137.(12)Nosonovsky,M.;Bhushan,B.Mater.Sci.Eng.,R 2007,58,162.(13)Shirtcliffe,N.J.;McHale,G.;Newton,M.I.;Chabrol,G.;Perry,C.C.Adv.Mater.2004,16,1929.(14)Ming,W.;Wu,D.;van Benthem,R.;de With,G.Nano Lett.2005,5,2298.(15)Sun,M.;Luo,C.;Xu,L.;Ji,H.;Ouyang,Q.;Yu,D.;Chen,ngmuir 2005,21,8978.(16)Chong,M.A.S.;Zheng,Y.B.;Gao,H.;Tan,L.K.Appl.Phys.Lett.2006,89,233104.(17)del Campo,A.;Greiner,C.J.Micromech.Microeng.2007,17,R81.(18)Cortese,B.;Amone,S.D;Manca,M.;Viola,I.;Cingolani,R.;Gigli,ngmuir 2008,24,2712.(19)Zhao,Y.;Li,M.;Lu,Q.;Shi,ngmuir 2008,24,12651.(20)Kuan,C.Y.;Hon,M.H.;Chou,J.M.;Leu,I.C.J.Electrochem.Soc.2009,156,J32.(21)Madou,M.Fundamentals of Microfabrication ;CRC Press:Boca Raton,FL,1997.(22)Varadan,V.K.;Jiang,X.;Varadan,V.V.Microstereolithography and Other Fabrication Techniques for 3D MEMS ;Wiley:New York,2001.(23)Bhushan,B.;Koch,K.;Jung,Y.C.Soft Matter 2008,4,1799.(24)Bhushan,B.;Jung,Y.C.;Niemietz,A.;Koch,ngmuir 2009,25,1659.(25)Koch,K.;Bhushan,B.;Jung,Y.C.;Barthlott,W.Soft Matter 2009,5,1386.Jung and Bhushan ArticleIn practical applications of superhydrophobic surfaces,surfaces should maintain their ability to repel penetrating droplets under dynamic conditions.For example,bouncing droplet studies are of interest in rainwater and spray on surfaces,2and vibrating droplet studies are of interest in micro/nanofluidics and microelectronics.6These studies are of scientific interest in probing energy barriers responsible for contact-angle hysteresis.Recent studies have investigated wetting behavior during condensation 26and evapora-tion 27and the stability of the composite interface of artificial superhydrophobic surfaces and the transition from composite to homogeneous interface under pressure,28,29bouncing of drop-lets,30-33and vertical vibration.34Nosonovsky and Bhushan 2,12suggested that the destabilizing factors responsible for such a transition have different characteristic length scales,and thus multi-scale (hierarchical)roughness plays an important role in stabilizing the composite interface.Therefore,the effect of hierarchical struc-ture on wettability under dynamic conditions is needed.In our recent studies,artificial hierarchical surfaces,inspired by Lotus leaves,with higher static contact angles and lower contact angle hysteresis have been produced.3,23-25The data showed that a hierarchical structure is superior to flat,nano-,and microstruc-tured surfaces and show high static contact angle,low contact-angle hysteresis,and high self-cleaning efficiency,superior to that of the natural Lotus leaves.In the present study,to investigate whether micro-,nano-,and hierarchical structures can resist destabilizing factors,such as dynamic effects responsible for the transition,a study of bouncing and vibration of a water droplet are systematically conducted on various surfaces.A model for the prediction of phenomena on the wetting and dewetting process during vibration based on the relationship between the adhesion force and the inertia force of the droplet is proposed.2.Theoretical BackgroundA stable composite interface is essential for the successful design of superhydrophobic surfaces.However,the composite interface is fragile,and it may transform into a homogeneous interface.The dynamic effects,bouncing and vibration,affect the transition.The model for the bouncing was proposed by Jung and Bhushan.33They considered a water droplet hitting a surface consisting of a regular array of circular pillars with diameter D ,height H ,and pitch P .As the droplet hits the surface at velocity V I ,the liquid -air interface below the droplet is formed when the dynamic pressure is less than the Laplace pressure.However,if the maximum droop of the droplet is larger than the height of the pillar,the droplet contacts the bottom of the cavities between pillars.Determination of the critical velocity at which the droplet touches the bottom is obtained by equating the Laplace pressure to the dynamic pressure.To develop a composite interface,velocity should be smaller than the critical velocity,given asV I <ﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃ32γHF ðﬃﬃﬃ2p P -D Þs ð1Þwhere γis the surface tension of the liquid -air (vapor)interface and F is the mass density of the liquid droplet.Furthermore,in the case of large distances between the pillars,the liquid -air interface can easily be destabilized because of dynamic effects.This leads to the formation of the homogeneous solid -liquid interface.Next,we present a model for the vibration.In this model,we calculate expressions for adhesion force and inertia force as a function of droplet properties and operating conditions.Consider a small droplet of liquid deposited on a surface.The liquid and surface come together under equilibrium at a characteristic angle,called the static contact angle θ,as shown in Figure 1.When a droplet on a surface is vibrated,on the basis of Lamb,35a general expression for the resonance frequency f r of a free oscillating liquid droplet is given asf r ¼ﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃn ðn -1Þðn þ2Þγ3πF Vs ð2Þwhere V is the volume of the droplet and n represents the number of modes,with 2being the first mode,etc.For a spherical droplet with a radius R with the distance between the center of the droplet and the solid H ,the volume of droplet V is given byV ¼13πðR þH Þ2ð2R -H Þ¼13πR 3ð1-cos θÞ2ð2þcos θÞð3ÞRecent experimental studies were carried out by Noblin et al.36and Celestini and Kofman.37They showed that the frequency decreases with the volume of the droplet,and the trends are compared to a theoretical model.When liquid comes in contact with a surface,the energy gained for surfaces coming into contact is greater than the energy required for their separation (or the work of adhesion)by the quantity ΔW ,which constitutes the adhesion hysteresis.5For a surface,the difference between the two values of the interface energy (measured during loading and unloading)is given by ΔW .These two values are related to the advancing contact angle,θa ,and receding contact angle,θr ,of the surface.For example,a model based on Young’s equation has been used to calculate the work of adhesion from contact-angle hysteresis 2,38,39cos θa -cos θr ¼ΔW γð4ÞFigure 1.Droplet of the liquid in contact with a solid surface:contact angle θ,radius of droplet R ,and distance between the center of the droplet and the solid H .(26)Narhe,R.D.;Beysens,D.A.Europhys.Lett.2006,75,98.(27)Jung,Y.C.;Bhushan,B.J.Microsc.2008,229,127.(28)Yoshimitsu,Z.;Nakajima,A.;Watanabe,T.;Hashimoto,ngmuir 2002,18,5818.(29)Liu,B.;Lange,F.F.J.Colloid Interface Sci.2006,298,899.(30)Richard,D.;Clanet,C.;Quere,D.Nature 2002,417,811.(31)Bartolo,D.;Bouamrirene,F.;Verneuil,E.;Buguin,A.;Silberzan,P.;Moulinet,S.Europhys.Lett.2006,74,299.(32)Reyssat,M.;Pepin,A.;Marty,F.;Chen,Y.;Quere,D.Europhys.Lett.2006,74,306.(33)Jung,Y.C.;Bhushan,ngmuir 2008,24,6262.(34)Bormashenko,E.;Pogreb,Y.;Whyman,G.;Erlich,ngmuir 2007,23,6501.(35)Lamb,H.Hydrodynamics ;Cambridge University Press:Cambridge,U.K.,1932.(36)Noblin,X.;Buguin,A.;Brochard-Wyart,F.Eur.Phys.J.E 2004,14,395.(37)Celestini,F.;Kofman,R.Phys.Rev.E:Stat.,Nonlinear,Soft Matter Phys.2006,73,041602.(38)Good,R.J.J.Am.Chem.Soc.1952,74,5041.(39)Chen,Y.L.;Helm,C.A.;Israelachvili,J.N.J.Phys.Chem.1991,95,10736.Article Jung and Bhushan From eq4,the dominant force(adhesion force)responsible forthe separation between the droplet and surface is given by40,41F A¼Lγðcosθa-cosθrÞ¼2R sinθγðcosθa-cosθrÞð5Þwhere L is the length of the triple contact line,referred to as theline of contact of the solid,liquid,and air.The radius of aspherical droplet,R,depends upon the contact angle and can beobtained from eq3.It is known from experimental observations that the transitionfrom the composite to homogeneous interface is an irreversibleevent.Such a transition can be induced,for example,by applyingpressure or force to the droplet30-33,42and vibration.34Fromapplying vertical vibration of a droplet on a surface,the inertiaforce of droplet F I is given byF I¼F VAω2ð6Þwhere A andωare the amplitude and frequency of vibration, respectively.Bormeashenko et al.34showed that the transition occurred at a critical value of inertia force acting on the length of a triple line.However,if the inertia force of the droplet vibrated on the surface can overcome the adhesion force between the droplet and surface,in whichΔF is positive valueΔF¼F I-F Að7Þthe droplet can be vertically separated from the surface(bouncing off)before the composite solid-liquid-air interface is destroyed.3.Experimental Procedures3.1.Instrumentation.For the measurement of static contact angle,the droplet size should be smaller than the capillary length, but larger than the dimension of the structures present on the surfaces.Droplets of about5μL in volume(with radius of a spherical droplet about1mm)are gently deposited on the substrate using a microsyringe for the static contact angle.The image of the droplet is obtained by a digital camcorder(Sony, DCRSR100,Tokyo,Japan)with a10Âoptical and120Âdigital zoom.Images obtained were analyzed for the contact angle using Imagetool software(University of Texas Health Science Center). The process of the dynamic impact behavior was obtained with a high-speed camera(Kodak Ektapro HS Motion Analyezer, Model4540)operated at500frames/s for each experimental run and then measuring the dynamic impact behavior of the droplet as a function of time.The impact velocity was calculated by varying the droplet release height.33The size of the droplet was the same as that of a droplet for the static contact angle,as reported earlier. All measurements were made in a controlled environment at22( 1°C and45(5%relative humidity(RH).The process of dynamic behavior was obtained by a system producing vertical vibrations,as shown in Figure2.The system consists of an electrodynamic shaker(Labworks,Inc.,Model ET-126A/B)connected to a signal generator and power amplifier,a digital camcorder(Sony,DCRSR100,Tokyo,Japan)with an objective lens,and a lamp(Digital Instruments,Inc.,Model F0-50)for a light source.The specimen was placed on the top of the shaker,and a droplet was gently deposited using a microsyringe. The size of the droplet was the same as that of a droplet for the static contact angle,as reported earlier.The vibration frequency was controlled between0and300Hz at0.4mm amplitude for measurement of the resonance frequency of a droplet.For wetting behavior of a droplet on the surface,a frequency of30Hz,which was less than the resonance frequency,was chosen and the vibration amplitude was controlled between0and3mm.The vibration time applied to the droplet was1min for each experi-ment.All measurements were made in a controlled environment at22(1°C and45(5%RH.3.2.Samples.Microstructures were fabricated using Lotus leaves,after removing the original wax structures,and a micro-structured Si surface with pillars of14μm in diameter and30μm in height with a23μm pitch by soft lithography.3,23-25The replication is a two-step molding process,in which a negative replica of a template is generated using a polyvinylsiloxane dental wax and a positive replica is made with a liquid epoxy resin. Nanostructures were created by self-assembly of synthetic and plant waxes deposited by thermal evaporation.3,23-25The alkane n-hexatriacontane(C36H74)has been used for the development of platelet nanostructures.Tubule-forming waxes,which were iso-lated from leaves of Tropaeolum majus(L.)and Nelumbo nucifera, in the following referred to as T.majus and Lotus,were used to create tubule structures.The n-hexatriacontane,T.majus wax, and Lotus wax were deposited on the specimen surfaces by thermal evaporation.The amounts were0.12,0.2,and0.4μg/ mm2for n-hexatriacontane and0.8μg/mm2for T.majus and Lotus waxes,respectively.The specimens with T.majus and Lotus waxes were exposed to ethanol vapor for3days at50°C and then left in the oven at50°C in total for7days.The specimens with n-hexatriacontane were placed in a desiccator at room tempera-ture,and the n-hexatriacontane formed platelets within3days, without any treatment by temperature or solvents.Statistical parameters of nanostructures[root-mean-square(rms)height, peak-valley height,and summit density(η)]were calculated and are presented in Table1.Hierarchical structures were fabricated using a two-step fabri-cation process,including the production of microstructured surfaces by soft lithography and subsequent development of nanostructures on top by self-assembly of n-hexatriacontane and plant waxes,as described above.Flat epoxy resin and a micropatterned Si replica were covered with flat n-hexatriacon-tane and T.majus and Lotus waxes,and a microstructure in Lotus leaf replica were covered with flat Lotus waxes.Flat wax layers were made by melting the deposited waxes(3min at120°C)and subsequent rapid cooling of the specimen to5°C.Then,the specimens were stored for7days at21°C in a desiccator.The fast cooling of the wax prevents the formation of nanostructure roughness.Figure3shows the scanning electron microscope(SEM) micrographs of hierarchical structures.Hierarchical structures were found to be covered with a nanostructure of n-hexatriacon-tane platelets and T.majus and Lotus wax tubules.SEM micro-graphs show an overview(left column),a detail inhigher Figure2.Schematic of the vibration system consisting of an electrodynamic shaker with a signal generator and power amplifier,a digital camcorder with an objective lens,and a lamp.A droplet on a surface is vibrated vertically by a shaker.(40)Joanny,J.F.;de Gennes,P.G.J.Chem.Phys.1984,81,552.(41)Lee,S.-W.;Laibinis,P.E.J.Am.Chem.Soc.2000,122,5395.(42)Lafuma,A.;Qu e r e,D.Nat.Mater.2003,2,457.Jung and Bhushan Articlemagnification(middle column),and a large magnification of the created nanostructures with platelets and tubules(right column). All surfaces show a homogeneous distribution of the wax mass on the specimen.The nanostructure is formed by three-dimensional platelets of n-hexatriacontane,as shown in detail in Figure3.Platelets are flat crystals,grown perpendicular to the substrate surface.The plate-let thickness varied between50and100nm,and their length varied between500and1000nm.The recrystallized T.majus and Lotus waxes show tubular hollow structures with random orientation on the surfaces,as shown in Figure3.Their shapes and sizes show some variations.The tubular diameter varied between100and300nm for T.majus wax and between100and 150nm for Lotus wax,and the length varied between300and 1200nm for T.majus wax and between1500and2000nm for Lotus wax.4.Results and Discussion4.1.Wettability of Various Surfaces with Wax Platelets and Tubules.To study the effect of n-hexatriacontane platelets on various surfaces for superhydrophobicity,the static contact angle and contact-angle hysteresis were measured.3,23The values measured for various surfaces are summarized in Table2.For static contact angle and contact-angle hysteresis,droplets of about5μL in volume(with the diameter of a spherical droplet about2.1mm)were gently deposited on the surface using a microsyringe.For contact-angle hysteresis,the advancing and receding contact angles were measured at the front and back of the droplet,moving along the tilted surface,respectively.The static contact angle of a flat surface coated with a film of n-hexatriacontane was91°.As the mass of n-hexatriacontane for nanostructuring of flat surfaces increased,the static contact angle first increased followed by a decrease at a mass of0.2μg/ mm2.The highest static contact angle of a nanostructure was158°at a mass of0.2μg/mm2.For the specimen with a microstructure, the static contact angle was154°but increased to169°for the hierarchical surface structure.Contact-angle hysteresis for flat, micro-,and nanostructured surfaces show similar trends.The flat surface showed a contact-angle hysteresis of87°.The super-hydrophobic micro-and nanostructured surfaces showed a re-duction of contact-angle hysteresis of36°and23°,respectively. Only the hierarchical surface structure,with a static contact angle of169°and low contact-angle hysteresis of2°,exceeds the properties of well-known superhydrophobic and self-cleaning Lotus leaves.To study the effect of T.majus wax tubules on various surfaces for superhydrophobicity,the static contact angle and contact-angle hysteresis were measured.3,24The values measured for various surfaces are summarized in Table2.The data show that the static contact angle of a flat surface coated with a film of T. majus is112°but increased to164°when the wax formed a nanostructure of tubules.On the specimen with only a micro-structure,the static contact angle was154°but increased to171°for the hierarchical structure.Contact-angle hysteresis for flat, micro-,and nanostructured surfaces shows similar trends.The flat surface showed a contact-angle hysteresis of61°.The micro-structured surface shows a reduction of contact-angle hysteresis to27°.As tubules are formed on the flat and microstructured surfaces,the nanostructured and hierarchical structure surfaces have a low contact-angle hysteresis of5°and3°,respectively. To study the effect of Lotus wax tubules on various surfaces for superhydrophobicity,the static contact angle and contact-angle hysteresis were measured on flat,microstructured Lotus replica, micropatterned Si replica,and hierarchical surfaces.3,25The values measured for various surfaces are summarized in Table2.A static contact angle of80°was found for flat epoxy resin.Table1.Roughness Statistics for Nanostructure Surface Measured Using an AFM(Scan Size of10Â10μm)arms b height(nm)peak-valley height(nm)ηc(μm-2)n-Hexatriacontanenanostructure(0.12μg/mm2)465220.78 nanostructure(0.2μg/mm2)65663 1.39 nanostructure(0.4μg/mm2)82856 1.73T.majus Waxnanostructure(0.8μg/mm2)18015700.57Lotus Waxnanostructure(0.8μg/mm2)1871550 1.47a Nanostructures were fabricated with n-hexatriacontane,T.majus,and Lotus waxes.b rms=root mean square.cη=summitdensity.Figure3.SEM images taken at45°tilt angle(shown using three magnifications)of hierarchical structures using Lotus and micro-patterned Si replicas.Hierarchical structures were fabricated with 0.2μg/mm2mass of n-hexatriacontane after storage for3days at room temperature and0.8μg/mm2mass of T.majus and Lotus waxes after storage for7days at50°C with ethanol vapor.Article Jung and BhushanThe microstructured surfaces of the Lotus leaf replica and the microstructured Si replica(covered with a Lotus wax film)have static contact angles of158°and160°but show much higher contact angle hysteresis of29°and27°than found in hierarchical structures,respectively.Superhydrophobicity with a static con-tact angle of167°and a contact angle hysteresis of6°was also found in nanostructured surfaces.Melting of the wax led to a flat surface with a flat wax film,a much lower static contact angle of 139°,and higher contact angle hysteresis of49°.The data of a flat Lotus wax film on a flat replica show that the Lotus wax by itself is hydrophobic.For the hierarchical-structured Si replica,the high-est static contact angles of173°and lowest contact-angle hyster-esis of1°were found.The hierarchical-structured Lotus leaf replica showed a static contact angle of171°and a contact-angle hysteresis of2°.The recrystallized wax tubules are very similar to those of the original Lotus leaf but are0.5-1μm longer;the static contact angle is higher;and the contact-angle hysteresis is lower than reported for the original Lotus leaf(static contact angle of 164°and contact-angle hysteresis of3°).4.2.Observation of Transition during the Bouncing Droplet.To observe how the impact velocity influences the transition from the composite solid-air-liquid interface to the homogeneous solid-liquid interface during droplet impact,expe-riments with a droplet on various surfaces with n-hexatriacontane and T.majus and Lotus waxes were performed.Figure4shows snapshots of a droplet with1mm radius hitting various surfaces fabricated with0.2and0.4μm/mm2of n-hexatriacontane after storage at room temperature.The impact velocity was obtained just prior to the droplet hitting the surface.First,on the flat surface,it was found that the droplet did not bounce off,even though the impact velocity applied was up to1.5m/s.As shown in the images in the first row for each nano-,micro-,and hierarch-ical-structured surface,the droplet hitting the surface under an impact velocity of0.44m/s first deformed,then retracted,and bounced off the surface.Finally,the droplet sat on the surface and had a high contact angle,which suggests the formation of a solid-air-liquid interface.Next,we repeated the impact experiment by increasing the impact velocity.As shown in the second row of images for nanostructure(0.4μg/mm2)and microstructure, bounce off did not occur and the wetting of the surface(and possibly pinning of droplet)occurred at impact velocities of1.2 and0.77m/s,respectively,referred to as the critical impact velocity.This is because air pockets do not exist below the droplet as a result of droplet impalement by the structures,characterized by a smaller contact angle.These observations indicate the transition from the composite interface to the homogeneous interface.However,as shown in the second row of images for nanostructure(0.2μg/mm2)and hierarchical structure,during applying impact velocity of up to1.5m/s,the bounce off always occurred and the wetting of the surface did not occur.Figure5shows snapshots of a droplet with1mm radius hitting various surfaces fabricated with0.8μm/mm2of T.majus wax after storage at50°C with ethanol vapor.The trends are similar to the surfaces with n-hexatriacontane.As shown in the images in the first row for each nano-,micro-,and hierarchical-structured surface,the droplet hitting the surface under an impact velocity of0.44m/s always bounced off the surface.Finally,the droplet sat on the surface and had a high contact angle.For microstructure, the pinning of the droplet occurred at an impact velocity of0.94 m/s,as shown in the second row of images.For nanostructure and hierarchical structure,the droplet was always observed to bounce off the surfaces,during applying impact velocity of up to1.5m/s. Figure6shows snapshots of a droplet with1mm radius hitting flat,nanostructure,microstructure in Lotus replica,micropat-terned Si replica,and hierarchical structures using Lotus and micropatterned Si replicas,fabricated with0.8μm/mm2of LotusTable2.Summary of the Static Contact Angle and Contact-Angle Hysteresis for the Static Droplet,the Measured Resonance Frequency at the Fixed Amplitude Value of0.4mm,the Calculated Inertia Force of a Vibrated Droplet,and Adhesive Force between the Droplet and Surface on the Various Surfaces Fabricated with n-Hexatriacontane,T.majus,and Lotus Waxes aresonance frequency(Hz)static contact angle(deg)contact anglehysteresis(deg)first mode(n=2)second mode(n=3)F A(μN)F I(μN)at transitionor bouncing offΔF=F I-F A n-Hexatriacontaneflat91(2.087(1.9(141b,54c)103271260(3.7nanostructure(0.12μg/mm2)152(2.260(1.5(171b,111c)6316945(2.211-34(2.2(T)d nanostructure(0.2μg/mm2)158(2.423(1.3(165b,142c)5014710(1.6100(1.6(B)e nanostructure(0.4μg/mm2)156(2.326(1.3(165b,139c)5414913(2.011-2(2.0(B) microstructure154(1.936(1.6(167b,131c)8620821(1.79-12(1.7(T) hierarchical structure169(1.32(0.8(170b,168c)491440.2(0.06 3.6 3.4(0.06(B)T.majus Waxflat112(2.161(2.1(132b,71c)103261154(3.2nanostructure164(2.45(1.1(166b,161c)561661(0.4 5.4 4.4(0.4(B) microstructure154(1.927(1.5(165b,138c)7420115(1.810-5(1.8(T) hierarchical structure171(1.33(0.7(172b,169c)471390.2(0.06 2.9 2.7(0.06(B)Lotus Waxflat119(2.471(3.2(162b,91c)92243133(3.3nanostructure167(0.76(1.1(170b,164c)471380.8(0.08 3.2 2.4(0.08(B) microstructure(Lotus replica)158(2.729(2(165b,136c)6317914(1.811-3(1.8(T and B) microstructure(micropatterned Si replica)160(1.827(2.1(169b,142c)6618310(1.6100(1.6(B)hierarchical structure(Lotus replica)171(0.82(0.7(172b,170c)401390.1(0.04 3.6 3.5(0.04(B) hierarchical structure(micropatterned Si replica)173(0.81(0.6(174b,173c)381370.04(0.01 2.7 2.6(0.01(B)a A positive value ofΔF means that the droplet bounced off before the transition occurs.The variation represents(1standard deviation.b Advancing contact angle.c Receding contact angle.d T=transition.e B=bouncing off.。

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