BOKASUN a fast and precise numerical program to calculate the Master Integrals of the two-l

小学上册英语第2单元真题(含答案)英语试题一、综合题(本题有50小题，每小题1分，共100分.每小题不选、错误，均不给分)1 The __________ (社会结构) influences behavior.2 A ________ (植物遗传多样性保护) ensures survival.3 The chemical symbol for arsenic is ______.4 They are playing _______ (足球) in the yard.5 What do you call a story that is based on real events?A. FictionB. Non-fictionC. BiographyD. History答案: B6 I believe in the importance of empathy. Understanding how others feel helps us build strong connections. I practice empathy by __________ when talking to friends.7 She _____ (plays/plays) the piano well.8 The _____ (rainbow) has many colors.9 My mom is a __________ (心理咨询师).10 I saw a ______ in the yard.11 I can ______ (做到) my best in everything I try.12 Composting is a great way to recycle ______ matter for your garden. (堆肥是回收有机物质以供花园使用的好方法。

)13 A ______ can carry heavy loads.14 The _______ (Stonehenge) is a prehistoric monument in England.15 The _______ can help reduce stress.16 The Great Fire of London destroyed much of the city in ________.17 I enjoy playing ______ (足球) with my team on Saturdays.18 I can ______ (感谢) my teachers for their help.19 What do you call the process of growing plants?A. GardeningB. CookingC. CleaningD. Driving答案: A20 What is the name of the sweet food often eaten at birthday parties?A. PieB. CakeC. CookiesD. Ice Cream答案: B21 Many plants have ______ that attract bees and butterflies. (许多植物有吸引蜜蜂和蝴蝶的特征。

Optimization of the truss-type structuresusing the generalized perturbation-based Stochastic Finite Element Method Marcin Kamin´ski n,1,Marta SoleckaChair of Steel Structures,Department of Structural Mechanics,Faculty of Civil Engineering,Architecture and Environmental Engineering,Technical University of Lodz,Lodz,Poland a r t i c l e i n f oArticle history:Received28January2012Received in revised form27July2012Accepted7August2012Available online6October2012Keywords:Engineering optimizationStochastic Finite Element MethodResponse function methodStochastic perturbation techniqueReliability analysisa b s t r a c tThe main objective here is an engineering optimization of the truss-type structures using thegeneralized perturbation-based Stochastic Finite Element Method.This procedure is based on triplereliability analysis consisting of the limit states for the admissible eigenfrequencies,horizontaldisplacements and the reduced stresses;it obeys an application of the stainless steel as well as thealuminum as the structural materials.Such a reliability-based optimization follows strictly engineeringpractice,demands of the Eurocodes,cost minimization of the structures and future installations of thenew transmission equipment.The reliability analysis is based on the FORM approach,while computa-tional realization of the generalized SFEM guarantees reliable determination of thefirst fourprobabilistic moments of the structural response for any random dispersion in the design parameters.Numerical implementation has hybrid character and is based on interoperability of the FEM designsystem ROBOT and the computer algebra system MAPLE,where all probabilistic functions areprogrammed.&2012Elsevier B.V.All rights reserved.1.IntroductionTelecommunication towers undoubtedly belong to the class ofthe lightweight structures specifically exhibited to the stochasticinfluence of the wind blow and because of their reliability need tobe evaluated with respect to the strength,to maximum deflec-tions and rotations as well as to their eigenfrequencies[8].An uncertainty in the structural response of the towers and mastsin general follows the stochastic wind pressure andflattering,quasi-periodic and temporary ice covers increasing both mass andeffective surfaces of the structural elements.Temperaturesfluc-tuations leading to the significant thermal stresses not necessarilyuniformly influencing the entire structure(concerning dominat-ing southern exposure to the natural heating)play also importantrole[20].Geometrical imperfections in the connections(espe-cially in welds)and in the structural elements,consideringmaterial defects resulting from manufacturing stage,may bedecisive for an overall uncertainty magnitude.Because aluminumhas much more micro-compounds in its total volume thanstainless steel,randomization of the basic material properties iseven more justified here and random dispersion of these proper-ties should be significantly larger.Designing and manufacturing of truss-type structures(towers,masts and antennas)are still relatively new and very modern areafor the engineers and scientists.We notice continuous develop-ment of the telecommunication equipment and particularlymobile phones,which may demand the brand new structuralextensions in the nearest future.Therefore,an optimization of thesupporting structures’shape and the materials design is stillchallenging issue–an example is alternative usage of thealuminum and steel based supporting towers and other light-weight structures of the similar shape[11].It needs to beemphasized that since such structures are really some3D combi-nations of the beam and bar elements,classical mathematicalmethods for the shape or topology optimization(where optimalshape can be‘‘cutted off’’from some given volume subjected tothe specified boundary conditions)have no application here[2].An optimal shaping procedure is left rather to an engineeringintuition,experiments and practice as well as some kind of therobust optimization[4],where some small corrections are pro-vided a posteriori using the FEM reanalysis.Some optimizationconditions follow also technological demands on the telecommu-nication equipment efficiency,safety and maintenance,and thencannot be simply expressed in the structural mechanics language.On the other hand,the engineering reliability analysis is stillbeing developed[12,13],concerning at least demands of theEurocodes and acquisition of various stochastic methods inengineering practice.A necessity of structural reliability verifica-tion was introduced by Eurocode0(not only for the bridges’andskyscrapers’designing and maintenance[17]);our analysis isContents lists available at SciVerse ScienceDirectjournal homepage:/locate/finelFinite Elements in Analysis and Design0168-874X/$-see front matter&2012Elsevier B.V.All rights reserved./10.1016/j.finel.2012.08.002n Corresponding author.E-mail address:Marcin.Kaminski@p.lodz.pl(M.Kamin´ski).1Visiting Professor,Leibniz-Institut f¨ur Polymer Forschung Dresden e.V.,01069Dresden,Hohe Strasse6,Germany.Finite Elements in Analysis and Design63(2013)69–79focused on the towers initially designed according to the deter-ministic limit states.We are going to verify whether they have correct reliability indices or not and if they can be further optimized in this context.Rationally designed steel tower usually appears to automatically remain in the safe regime[8],while aluminum structures may need some additional stiffening of certain putational comparison provided here con-sists of a single steel and two aluminum structures being slightly below and above reliability limits.It is widely known,that the reliability measured with some indices must be computed not only for the load capacity and maximum deflections of some structures but also for their vibrations and fatigue under dynamic loads;it may demand more advanced stochastic computer methods[1,14,16,18,19].These are the main reasons to compare aluminum and steel manufactured telecommunication structures in the presence of uncertainty of material properties and to consider their optimization.We study randomfluctuations of the eigenfrequencies,stresses and deflec-tions for the same towers to discuss their reliability issues assuming that Young modulus of both materials is a truncated Gaussian random variable with the given expected value;the coefficient of variation is taken as the extra input parameter in this analysis.These towers have identical height and spatial distribution of the structural components and,naturally,different cross-sections of the particular members’groups.The generalized stochastic perturbation technique[6]is employed to achieve this goal because of the expected time savings(compared to the Monte-Carlo technique)and a capability to determine up to the fourth order probabilistic moments and coefficients[1,10,19]. Contrary to the previous models[6,8,10],now full tenth order stochastic expansions are used to recover all these moments, which significantly increases afinal accuracy of the probabilistic results.This stochastic technique is not supported by the Direct Differentiation Method(DDM);we employ the Response Function Method(RFM)[7],similar to the Response Surface Method(RSM) [15]explored in the reliability analysis.The major and very important difference is that the RFM uses higher order polyno-mial response relating a single input random variable with the structural output.The RSM is based rather on thefirst or second order approximations of this output with respect to multiple random structural parameters.An application of the RSM is impossible in current context because the second order trunca-tion for the response eliminates all higher order terms necessary for the reliable computations of the probabilistic structural behavior.Furthermore,RSM has some statistical aspects and issues[15],while the RFM has purely deterministic character and exhibits some errors typical for the mathematical approx-imation theory methods.A major novelty in this elaboration is an application of such a SFEM procedure for an optimization of large scale spatial struc-tures based on the reliability analysis.Wefind the set of mini-mum cross-sections in the given towers with randomized Young modulus,resulting in the set of minimum allowable reliability indices for displacements,stresses and pu-tational analysis shows that this optimization procedure is quite independent of the structural material and proceeds from the top to the bottom of the tower through the sections with different profiles.Computational procedure is provided using the Finite Element Method engineering system ROBOT(widely employed in civil engineering branch),where all eigenfrequencies,stresses and displacements are determined as the functions of Young modulus for all towers.Further computations of the response functions, their symbolic differentiation,probabilistic moments and the coefficients as well as their visualization are all provided with the use of computer algebra system MAPLE.This analysis is planned to be extended towards a full verification of the static and dynamic reliability,buckling fragility as well as including fatigue,ageing and corrosion phenomena[12]into the overall structure’s mathematical and computational models.It could be especially attractive using a fully extended version of some FEM systems implemented with the RFM and the stochastic reliability verification together with additional probabilistic visualization.2.Variational formulationLet us consider the following linear elasto-dynamic problem consisting of[3,9]equations of motion:D T rþ^f¼r€u,x A O,t A½t0,1Þð1Þconstitutive equations:r¼C e,x A O,t A½t0,1Þð2Þgeometric equations:e¼Du,x A O,t A½t0,1Þð3Þdisplacement boundary conditions:u¼^u,x A@O u,t A½t0,1Þð4Þstress boundary conditions:N r¼^t,x A@O s,t A½t0,1Þð5Þ initial conditions:u¼^u0,_u¼^_u0,t¼t0ð6ÞLet us consider the variation of uðx,tÞin some time moment t¼t denoted by d uðx,tÞ.Using the above equations one can show that ÀZOðD T rþ^fÀq€uÞT d u d OþZ@O sðN rÀ^tÞT d u dð@OÞ¼0ð7ÞAssuming further that uðx,t1Þ¼0,uðx,t2Þ¼0and that their variations also equal0,an integration by parts leads toZ t2t1d TÀZXr T d e d OþZX^f T d u d OþZ@X^t T d u dð@OÞ!d t¼0ð8ÞThe kinetic energy of the region O is of course defined asT¼12Zr_u T_u d Oð9ÞAssuming that the mass forces^f and the surface loadings^t are independent of the displacement vector u,one may modify Eq.(8) to the formdZ t2t1ðTÀJ pÞd t¼0ð10Þwhere J p is potential energy stored in OJ p¼UÀZX^f T u d OÀZ@X r^t T u dð@OÞ¼0ð11Þand where U is the elastic strain energyU¼12ZOe T C e d O:ð12ÞM.Kamin´ski,M.Solecka/Finite Elements in Analysis and Design63(2013)69–79 70Eq.(10)represents Hamilton principle widely used in struc-tural dynamics as the basis for the Finite Element Method implementation[3,5,9].putational implementationLet us consider a discretization of the displacementfield uðx,tÞusing the following form[3,9]:u aðx,tÞ¼/ðxÞq aðtÞ,ð13Þwhere q is a vector of the generalized coordinates of the discretized system.Contrary to the classical formulation of the perturbation-based Stochastic Finite Element Method,we intro-duce the additional index a¼1,y,M to distinguish between various solutions of the elasto-dynamic problem necessary to build up the response function.They are provided around the mean value of the input random parameter.Then,the strain tensor can be expressed ase aðx,tÞ¼BðxÞq aðtÞð14ÞThe discretized version of Hamilton principle is obtained asdZ t2t112q a T M a q aÀ12q a T K a q aÀÁd tþdZ t2t1ðQ a T q aÞd t¼0ð15ÞThe global mass matrix is defined asM a¼ZOr aðxÞB TðxÞBðxÞd Oð16Þso that all its partial derivatives with respect to random Young modulus equal0.The vector Q represents the external loadings acting on this structure.Finally,the global stiffness matrix equals to K a¼ZOB TC a B d Oð17ÞSince the3D bar and beam elements are used in further computa-tions,theirfirst partial derivatives with respect to random input parameter differ from0by only.Considering the assumptions that d qðt1Þ¼0,d qðt2Þ¼0ð18Þwefinally obtain the dynamic equilibrium systemM a q aþK a q a¼Q að19Þwhich represents equations of motion of the discretized system.We complete this equation usually with the component C a q a getting M a q aþC a q aþK a q a¼Q að20Þand we decompose the damping matrix asC a¼a0M aþa1K að21Þwhere the coefficients a0and a1are determined using the specific eigenfunctions for this problem.ThenM a q aþa0M a q aþa1K a q aþK a q a¼Q að22Þwhere no summation over the doubled indices a is applied here.As it is known[4],the case of undamped free vibrations leads to the following algebraic system:M a q aþK a q a¼0ð23Þand the solution q a¼A a sin o a t leads to the relationÀM a A a o2a sin o a tþK a A a sin o a t¼0ð24ÞSo that,for sin o a t a0and for A a a0there holdsÀM a o2aþK a¼0ð25ÞObviously,Eq.(20)for the time independent generalized coordinates returns the well known linear statics equilibrium systems for the RFM as follows[6,8]:K a q a¼Q að26Þ4.Stochastic perturbation-based equations4.1.Stochastic Taylor expansionLet us introduce the random variable b bðoÞand its prob-ability density function as p(b).The expected values and m th central probabilistic moments are defined as[6–8]E½b b0¼Zþ1À1bp bðxÞdxð27ÞmmðbÞ¼Zþ1À1ðbÀE½b Þm p bðxÞdxð28ÞA basic idea of the stochastic perturbation approach is to expand the state functions via Taylor series about their spatial expectations using some small parameter e40.In case of random quantity e¼e(b),the following expression is employed:e¼e0þX1n¼11n!e n@n e@b nðD bÞnð29Þwheree D b¼eðbÀb0Þð30Þis thefirst variation of b about b0,which is the expectation of b. Let us analyze further the expected values of any state function f(b)defined analogously to the formula(27)by its expansion via Taylor series as follows:E fðbÞÂüZþ1À1fðbÞp bðxÞdx¼Zþ1À1f0þX1n¼11n!e n fðnÞD b np bðxÞdxð31ÞFrom the numerical point of view,an expansion provided by the formula(31)is carried out over thefinite number of components to assure satisfactory accuracy.Let us focus on analytical derivation of the probabilistic moments for the struc-tural response.It is easy to prove that the general10th order expansion results for Gaussian variables in the following formula: E fðbÞÂüf0ðbÞb¼b0þ12e2m2ðbÞ@2f@b2b¼b0þÁÁÁþ1e10m10ðbÞ@10f@b b¼b0ð32ÞLet us mention that we multiply here by the relevant order probabilistic moments of the input random variables to get the algebraic formulas in symbolic computations.Therefore,this method in its generalized form is convenient for all the random distributions,where the above mentioned moments may be analytically derived(or at least computed for a specific combina-tion of the parameters).Finally,one may recover the kurtosis and the skewness from their well-known definitions askðfðbÞÞ¼m4ðfðbÞÞs4ðfðbÞÞÀ3bðfðbÞÞ¼m3ðfðbÞÞs3ðfðbÞÞð33ÞThe reliability index for the particular state functions equals RðfðbÞÞ¼E½^fÀf asð^fÀf aÞð34Þwhere the pairð^f;f aÞdenotes the admissible value of the given state function and its computed maximum value.Some civil engineering codes state for instance that this difference cannot be smaller than25%of the structural eigenfrequency,so thatM.Kamin´ski,M.Solecka/Finite Elements in Analysis and Design63(2013)69–7971Eq.(34)may serve for the straightforward estimation of thereliability for the structures subjected to the dynamic excitations.4.2.Structural response determination via the least squares techniqueThe Least Squares Method (LSM)is provided to determine an analytical polynomial interrelation between the state function (displacements,stresses and,independently,eigenvibrations fre-quencies)and the given input random parameter b .These poly-nomial approximations are inserted into the Taylor expansions as well as the formulas (32)and (A.1)–(A.3)to determine probabil-istic moments of the state functions provided that we have a single input random parameter.In case of multiple random variables we repeat this procedure for each input random variable separately and combine them through the cross-correlations.We consider a set of m data points ðb i ,u ði Þb Þfor b ¼1,y ,N ,somenonlinear continuous response function u b ¼f ðb Þand a curve(approximating polynomial)u b ¼f ðb ,^ub Þdepending on the para-meters ^uðj Þb ,j ¼1,y ,n ,where m Z n .The set of trial values is directly taken from the FEM experiments (Eqs.(23)or (26))forthe set of input parameters b 01,:::,b 0n that origin from equidistant partition of an interval ½b ÀD b ,b þD b .Usually a ratio D b =b is in a range of the few percents,which follows a specific type of this variable in a given boundary problem and its physical limitations.A recursive formula for b i holds true when we provide a partition of ½b ÀD b ,b þD b into n À1subintervals b i ¼b ÀD b þi2D b n À1ð35ÞFirst we define the residuals r i ðu b Þbetween the trial points andthe target function’s coefficientsr i ðu b Þ¼u ði Þb Àf ðb ,^u b Þð36Þto determine the components of the vector ^ub .It precedes using minimization of the functional S ðu b Þ¼X m i ¼1r 2i ðu b Þ:ð37ÞWe minimize it to find the coefficients in f ðb ,^u b Þ@S ðu b Þ@^uðj Þb ¼2X m i ¼1r i ðu b Þ@r i ðu b Þ@^uðj Þb ¼0;j ¼1,:::,n :ð38ÞSince the LHS derivatives combine the independent variable andthe coefficients,so that these gradient equations do not have a closed solution and some initial values must be adopted for the coefficients.It may be resolved via some iterative approximation as^u ðj Þb ffiðk þ1Þ^u ðj Þb ¼ðk Þ^u ðj Þb þD ^u ðj Þbð39Þwhere k denotes an iteration number and D ^uðj Þb stands for the so-called shift vector.The following Taylor linearization is applied at each iteration:f ðb i ,^u b Þffif b i ,ðk Þ^u b þX n j ¼1@f ðb i ,ðk Þ^u b Þ@^u b ð^u ðj Þb Àðk Þ^u ðj Þb Þð40ÞSince ð@r i =@^u ðj Þb Þ¼ÀJ b ij ,there holdsr i ðu b Þ¼D u ði Þb ÀX n s ¼1J b isD D sD u ði Þb ¼u ði Þb Àf ðb i ,ðk Þu b ÞD D s ¼^u ðs Þb Àðk Þ^u ðs Þbð41ÞSubstituting these expressions into the gradient equation (38),one obtainsÀ2X m i ¼1J b ij D u ði Þb ÀX n s ¼1J b is D D s !¼0ð42Þwhich effectively become a system of the linear equations:X m i ¼1X n s ¼1J b ij J bis D D s ¼X n i ¼1J b ij D u ði Þb ,j ¼1,:::,nð43ÞMatrix notation is introduced to get finally ðJ T J ÞD D ¼J T D uð44ÞFurther determination of the probabilistic moments and charac-teristics is based on determination of the partial derivatives of theresponse function with respect to the input random parameter [6–8]:@k f @b¼Yk i ¼1ðn Ài Þa n bn ÀkþY k i ¼2ðn Ài Þa n À1bn Àðk þ1ÞþÁÁÁþa n Àkð45ÞIt should be underlined that further time savings and effi-ciency increase may be obtained by an application of the weight-ing procedure into the least squares technique.Weighting procedure may enlarge an influence of the results close to the expectation of the input random variable on the resulting prob-abilistic moments.Then,probabilistic convergence of the pertur-bation method is apparently faster and approximating polynomial order may be reduced.5.Perturbation-based optimization procedureLet us consider a linear elastic spatial truss structure built up with n segments and two sets of discrete design variables A l i and A b i for i ¼1,y ,p .They simply denote the cross-section areas of the legs and braces belonging to the given segment indexed with i .These discrete variables are taken from the engineering tables,sothat A l i A l ij and A b i A bij ,where j ¼1,y ,r indices their all available discrete values,respectively.Let us assume that an increasing value of an index j is equivalent to the larger cross-section.Let us introduce further a random variable of the problem –that is Young modulus of the structural material denoted by e given uniquely by its expectation E [e ]and standard deviation s (e ).The design objective is minimization of the structural cross-sections A l i and A b i for i ¼1,..,p with respect to the boundary conditions given by Eqs.(4)and (5)and the constraints imposed on the displacements,stresses and eigenfrequencies of the tower.The first two of them are simply defined as b q ðA i ÞÀ^b q Z 0ð46Þb r ðA i ÞÀ^b rZ 0ð47Þwhere,according to Eurocode 0,we provide ^b q ¼^b r¼3.The indices in Eqs.(46)and (47)are computed using the First Order Reliability Method (FORM)as the ratio of expectation to the standard deviation of the limit function,which is simply a difference between allowable and maximum values for displace-ments and stresses.Further,the reliability index for eigenfre-quencies is calculated and we employ the following limit function for this purpose:g o ¼o f Ào w Z 1:25o w Ào w ¼0:25o wð48ÞM.Kamin´ski,M.Solecka /Finite Elements in Analysis and Design 63(2013)69–7972Both omegas in this formula denote the forced and eigenvi-bration frequencies.So that,the third constraint here is b x ðA i ÞÀ^b x¼E ½0:25o w s ð0:25o w ÞÀ^b xZ 0ð49Þsimilar to the previous case ^b x¼3.Reliability-based optimization process uses deterministically optimized tower structure and starts from the top segment,where the cross-sections of legs and braces A l i and A b i have minimum values for all i ¼1,y p ;according to the engineering intuition there holds A l i þ1Z A l i andA b i þ1Z A bi .Deterministic optimization deals with a structure sub-jected to the same boundary conditions,no input random vari-able,where the given constraints are replaced with the differences in-between allowable and maximum values of dis-placements,stresses and eigenvibration frequencies;they allmust be positive.A set of deterministically designed variables isa very good initial point in our procedure,because probabilistic case is a little bit more demanding.Of course,the maximum displacements are noticed at the top of the tower,whereas maximum stresses –in the lowestleg.We start our optimization procedure from the top section,where the tower is fragile at most and then,we continuesectionFig.1.Static scheme and photo of the telecommunication tower.Table 1Structural elements of the telecommunication tower.Segment no.Tower legs (mm)Tower braces (mm)Steel tower 1–2Ø219.1Â16.0Ø159.0Â12.53–4Ø219.1Â16.0Ø133.0Â10.05–6Ø193.7Â16.0Ø101.6Â11.07–8Ø139.7Â12.5Ø88.9Â10.09Ø139.7Â12.5Ø76.1Â8.010Ø88.9Â8.0Ø76.1Â8.0Aluminum tower no.11–2Ø323.9Â17.5Ø219.1Â12.53Ø323.9Â17.5Ø168.3Â17.54Ø193.7Â17.5Ø168.3Â17.55–6Ø193.7Â17.5Ø139.7Â11.07–8Ø139.7Â12.5Ø114.3Â12.59Ø139.7Â12.5Ø101.6Â8.010Ø108.0Â8.0Ø101.6Â8.0Aluminum tower no.21–2Ø457.0Â17.5Ø219.1Â12.53Ø323.9Â17.5Ø168.3Â17.54Ø193.7Â17.5Ø168.3Â17.55–6Ø193.7Â17.5Ø139.7Â11.07–8Ø139.7Â12.5Ø114.3Â12.59Ø139.7Â12.5Ø101.6Â8.010Ø108.0Â8.0Ø101.6Â8.0M.Kamin ´ski,M.Solecka /Finite Elements in Analysis and Design 63(2013)69–7973by section to its bottom according to the given flowchart.Weemploy the stress condition each time first,because it is almost always fulfilled,then we control the displacements,because they are more sensitive to the cross-sectional design.Finally,we check the condition imposed on the eigenfrequency based reliability index.We increase the legs cross sectional area and then,the rebars,if necessary.It needs to be mentioned that each change of the cross-sectional area results in sequential determination of the response function and the relevant probabilistic moments.That is why we start from the least sensitive condition and progress towards the most sensitive –to minimize the number of itera-tions with the LSM procedure.It is especially important to separate elastostatics from the eigenvibration FEM solutions,because the response function determination needs quite differ-ent algorithms and,probably,even various partitions.As it is proven by some SFEM tests,final verification of the eigenmodes does not demand frequently any further changes in cross-sections.6.Numerical illustrationsComputational analysis has been provided on the example of the telecommunication tower with the height equal to 60.0m discretized with 280two-noded linear elastic beams and bars with 150nodal points (see Fig.1–structural drawing,photo and static scheme).All geometrical data for the specific cross-sections are given in Table 1(round steel and aluminum pipes with the given diameters and thicknesses).The data collected in this table show that the optimization of aluminum tower is carried out by the proportional increasing of all the subgroups cross-sections in the steel tower,preserving the given reliability conditions.All towers consist of 10segments,each having 6.0m height,and are fully restrained at the bottom legs.The lower part is built up with nine segments exhibiting 5%geometrical convergence (7.90m distance of the legs at the very bottom),while the top segment has parallel legs (with the distance equal to 2.50m).The legs,according to their aerodynamic loadings and relatively large length,are designed as the full round cross-sections joined in-between the segments with bolts.The stiffening bars provided in the cross scheme are welded to the legs through the joining rectangular plates.The FEM analysis includes the dead load of the tower,its equipment together with the supporting structural elements,cables and exploitation installations as well as ice covers,static pressure from the wind blow and exploitation moving loads.We consider three design cases –(1)the steel tower designed fulfilling the traditional limit states and reliabilityconditions,(2)the aluminum version of this tower fulfilling the traditional limit states and the reliability condition on eigenfre-quencies as well as (3)the aluminum tower fulfilling both traditional limit states and all the reliability conditions also.By the aluminum version of the steel tower we further understand the tower having all connections and nodes in the same positions with slightly modified cross-sections but the external shape and cross-section type remains the same (steel versus aluminum round pipes and fully round cross-sections for the braces and the legs).As it is seen from a comparison of the detailed legs and braces’cross-sections,traditional designing procedures are deci-sively less restrictive than these based on the reliability indices.Aluminum tower no.2having almost the same cross-sections at the top needs about 30%larger elements at the bottom (mainly according to the horizontal deflection index)and it drastically influences the overall designing procedure.It is especially impor-tant because the exploitation and maintenance of such structures usually assumes some extra loads resulting from the new anten-nas and additional equipment,so that certain capacity reserves are always important in this case.Basic input random variable of the problem is Young modulus with the expected values for the steel members taken as E ½e s ¼210GPa,where E ½e a ¼70GPa is adopted for aluminum.This uncertainty follows the fact that this modulus is always determined experimentally with some statistical evidence,which shows that its standard deviation for aluminum is larger than for structural steels.Response functions of the eigenfrequencies as well as horizontal displacements are obtained in nine numerical FEM experiments consisting of E [e s ]¼241C 363GPa and E [e a ]¼50C 90GPa with equidistant partitions of these intervals.The response function for the steel tower eigenfrequencies was found using traditional polynomial interpolation,while the additional functions for the displacements –thanks to the sixth order approximants in the LSM.Analysis of both aluminum towers was entirely provided with the use of parabolic response functions;generally it is advised to apply the lowest possible order of the LSM approximation verified by the consistency with the given FEM data set (visually or by some fitness test).The results of computational modeling for horizontal displace-ments probabilistic moments and associated reliability indices are given in Figs.2–6,whereas analogous output data for the tower eigenfrequencies are given in Figs.7–11.In case of displacements we notice fluctuations of expected values,coefficients of variation,kurtosis,skewnesses and reliability indices all as the functions of vertical coordinate (related to the corresponding nodes in the mesh)and,at the same time,as the function of the input coefficientofFig.2.Expected values of the displacements for the steel and aluminum towers.M.Kamin´ski,M.Solecka /Finite Elements in Analysis and Design 63(2013)69–7974。

小学上册英语第4单元综合卷(有答案)英语试题一、综合题(本题有100小题，每小题1分，共100分.每小题不选、错误，均不给分)1.My sister loves to listen to __________ (音乐).2.iana Purchase doubled the size of the _______. (美国) The Magn3.My favorite fruit is ______ (苹果) because it is both sweet and ______ (健康). I eat one every day.4.My cat watches ______ (小鸟) from the window.5.He is _____ (playing/doing) video games.6.y of Ghent ended the War of ________ (1812). The Trea7.The Earth's surface features are influenced by various natural and ______ factors.8.How many hours are in a day?A. 12B. 24C. 36D. 48答案:B9.The _______ of an object can create tension in a rope.10.The _______ (猴子) plays with its friends.11.My uncle is a . (我叔叔是一位。

)12.The first successful heart-lung transplant was performed in _______. (1981年)13.The _______ of a spring can be determined by its compression.14.The chemical properties of an element are determined by its ______.15.The monkey is very ______ (聪明) and curious.16.He is a football player, ______ (他是一名足球运动员), and plays on a team.17.Which is the largest land animal?A. LionB. ElephantC. GiraffeD. Rhino答案:b18.My friend saw a ______ (企鹅) sliding on ice.19.The parrot's bright colors help it blend in with tropical ________________ (植物).20.What do we use to write?A. PaperB. PencilC. TableD. Chair答案: B21. A lion roars fiercely in the _______ as it prowls.22.In China, the _____ (8) River is one of the longest rivers.23.The capital of Russia is ________ (莫斯科).24.What is the capital city of Mongolia?A. UlaanbaatarB. ErdenetC. DarkhanD. Choibalsan答案: A25.听录音，标序号。

附录二：短文翻译练习英译汉：1. The History of April Fools’ DayHow do you think April Fools’ Day originated?Was there a historic epidemic of spring fever-tomfoolery in a tiny Finnish town in the early 1800s? Did a New Yorker in 1910 find a cockroach in his coffee cup and decide to recreate the experience for his officemate, thereby sparking a famous April 1st lawsuit?In a convincing testimonial to the saying that truth is stranger than fiction, we’ll tell you the story, or at least present the most viable theory of how April Fools’ Day came to be.Once upon a time, back in 16th-century France, before computers, people celebrated New Year’s Day on March25, the advent of spring. It was a festive time. They partied steadily until April 1. In1564, when the calendar reformed and became Gregorian（格里高利历，即阳历）, King Charles IX proclaimed, perhaps pompously, that New Year’s Day should be celebrated on January 1 instead of in the spring. Diehard conservatives resisted the change (or perhaps didn’t hear about it due to the absence of e-mail) and continued to celebrate New Year’s from March 25 to April 1. During this period of spring festivity, the more flexible French mocked the rigid revelers by sending them foolish gifts and invitations to non-existent parties. The victim of an April Fools’ Day prank was called a “poisson d’avril2”, or an “April fish”, because at that time of year, the sun was leaving the zodiacal sign of Pisces（双鱼座）.April Fools’ Day hit its stride in England in the 18th century, and was brought to colonial America by the English, Scottish, and French.......We may never learn the true origin of April Fools Day. However, the deeper question facing us today is, “What’s the best gag I can pull off?”42. The SphinxLaius, king of Thebes, was warned by an oracle that there was danger to his throne and life if his new-born son should be suffered to grow up. He therefore committed the child to the care of a herdsman with orders to destroy him; but the herdsman, moved with pity, yet not daring entirely to disobey, tied up the child by the feet and left him hanging to the branch of a tree. In this condition the infant was found by a peasant, who carried him to his master and mistress, by whom he was adopted and called Oedipus, or Swollen-foot.Many years afterwards Laius being on his way to Delphi, accompanied only by one attendant, met in a narrow road a young man also driving in a chariot. On his refusal to leave the may at their command the attendant killed one of his horses, and the stranger, filled with rage, slew both Laius and his attendant. The young man was Oedipus who thus unknowingly became the slayer of his own father.Shortly after this event the city of Thebes was afflicted with a monster which infested the highroad. It was called the Sphinx. It had the body of a lion and the upper part of a woman. It lay crouched on the top of a rock, and arrested all travelers who came that way, proposing to them a riddle, with the condition that those who could solve it should pass safe, but those who failed should be killed, Not one had yet succeeded in solving it, and all had been slain. Oedipus was not daunted by these alarming accounts, but boldly advanced to the trial. The Sphinx asked him, “What animal is that which in the morning goes on four feet, at noon on two, and in the evening upon three?” Oedipus replied, “Man, who in childhood creeps on hands and knees, in manhood walks erect, and in old age with the aid of a staff.” The Sphinx was so mortified at the solving of her riddle that she cast herself down from the rock and perished.The gratitude of the people for their deliverance was so great that they made Oedipus their king, giving him in marriage their queen Jocasta. Oedipus, ignorant of his parentage, had already become the slayer of his father; in marrying the queen he became the husband of his mother. These horrors remained undiscovered, till at length Thebes was afflicted with famine and pestilence, and the oracle being consulted, the double crime of Oedipus came to light. Jocasta put an end to her own life, and Oedipus, seized with madness, tore out his eyes and wandered away from Thebes, dreaded and abandoned by all except his daughters, who faithfully adhered to him, till after a tedious period of miserable wandering he found the termination of his wretched life.3. My FatherMy father lived in a small wooden house in western Canada, where he carved himself out a fruit orchard from the hillside and the forest. He had chosen it with one of the most beautiful view in the world, an open valley and a river winding, with mountains beyond, and the Kootenay lake just visible in the north and built himself a wide window, to look out on three sides. This window, and six Chippendale chairs which he had rescued in a farmer’s sale, and a few of his sketches on the walls, were all the luxury of the place. I spent two winters with him, and once brought him a pot of primulas while the snow still lay heavy all around; but he soon took occasion to say casually that he was not fond of forced plants: they took away something for him of the first rapture of the spring. His loves were very deep and gentle; they seemed not to be centered in islands of possession, like most human loves, but to be diffused among people and animals and plants, and even the shapes of things he saw; for he was a most sensitive artist. He lived among flowers and was first in his valley to send for bulbs from Holland and to fill his orchard with daffodils under the flowering trees. He was a good rider and a great walker and fond of the woodsmen and the hunters, and those who spend half the year away from their fellow men visiting traps in the mountain forests.Four years before his death, when he was seventy-two, a stroke took away from him the open-air life he loved; and though by the strength of his will he managed, step by step with the passing months, to walk a mile or so with a stick to lean on, most of his time came to be spent in the windows that looked out on his view. Here, he told me, the changing clouds and the light of the river would fill his mind withpleasantness for hours at a time and lead his thoughts into endless variation: and I believe this to be true, and that he was happy, for not only did he never complain, but his whole atmosphere was one of serenity and peaceful interest in all things as they came. And later, when I have thought of happiness and what it may be, I have always seen his gentle old head in the window, with the hillside full of tame pheasants and pigeons, and the valley and the mountains beyond, and have felt that the secret must have something in it of those older worlds which were as real to him as ours.4. Cultural Conflict“International communication” is communication between members of different cultures. This definition is simple. But the process is complex. Intercultural communication involves differing perceptions, attitudes, and interpretations. We know that even two people from the same culture can have communication problems. People can intentionally hurt each other by something they say or do. Isn’t it logical, then, that communication problems can be compounded among people who do not have the benefit of shared experiences (i.e. language and culture)?Cultures do not communicate; individuals do. Everyone has a unique style of communication. But cultures determine a general style for their members. The relationship of the individual to his culture is analogous to an actor and his director. The actor puts his own personality into his acting but is nevertheless influenced by the director. We are not always aware of the subtle influences of our culture. Likewise, we may not perceive that others are influenced by their cultures as well.Problems and misinterpretations do not result every time members from two cultures communicate. However, when cultural conflicts do arise, they may be perceived as personal rather than cultural. In the following example it is a cultural misunderstanding that creates negative feelings and confusion:A young woman from one culture is looking out of the window and sees a male acquaintance from another culture. He signals to her by puckering his lips. She quickly looks away from the window. Later she ignores him. He is confused and she is angry.The misunderstanding was due to the woman’s failure to understand the man’s nonverbal signal. In her culture, his gesture conveys a sexual advance. According to his culture, he was only saying (nonverbally), “Oh, there you are. I’ve been looking for you.” The woman’s misinterpretation resulted in her angry reaction and his confusion. If the two had known more about each other’s nonverbal cues, they could have avoided the cultural conflict.Some misunderstandings are insignificant and can be easily ignored or remedied. Other conflicts are more serious in that they can cause misunderstandings and create persistent negative attitudes toward foreigners.Difficulties in intercultural communication arise when there is little or no awareness of divergent cultural values and beliefs. In cross-cultural interaction, speakers sometimes assume that what they believe is right, because they have grown up thinking their way is the best. This ethnocentric assumption can result in negative judgments about other cultures. Another manifestation of ethnocentric attitudes is that people become critical of individuals from different cultures.Sometimes negative reactions do not result from actual interaction but rather from the fixed, preconceived beliefs we have about other people. These over-generalized beliefs or “stereotypes” frequently shape people’s perceptions of each other.Stereotypes originate and develop from numerous sources such as jokes, textbooks, movies, and television. Movies about cowboys and Indians portray cowboys as “civilized” and Indians as wild and “primitive.” A child who knows about the American Indian only through watching these movies will have a distorted and false image of this group of people. Stereotypes perpetuate inaccuracies about religious, racial, and cultural groups.Stereotyped beliefs prevent us from seeing people as individuals with unique characteristics. Negative stereotypes lead to prejudice, suspicion, intolerance, or hatred of other cultural groups.Cultural conflicts occur as a result of misinterpretations, ethnocentrism, stereotypes, and prejudice. Preventing these conflicts is possible with increased awareness of our own attitudes as well as sensitivity to cross cultural differences. Developing intercultural sensitivity does not mean that we need to lose our cultural identities—but rather that we recognize cultural influences within ourselves and within others.5. The Pleasures of ReadingAll the wisdom of the ages, all the stories that have delighted mankind for centuries, are easily and cheaply available to all of us within the covers of books—but we must know how to avail ourselves of the most unfortunate people are those who have never discovered how satisfying it is to read good books.If I am interested in people, in meeting them and finding out about them, some of the most remarkable people I’ve met existed only in a writer’s imagination, then on the pages of his book, and then, again, in my imagination. I’ve found in books new friends, new societies, new words.If I am interested in people, others are interested not so much in who as in how. Who in the books includes everybody from science-fiction superman two hundred centuries in the future all the way back to the first figures in history; How covers everything from the ingenious explanations of Sherlock Holmes to the discoveries of science and ways of teaching manners to children.Reading is a pleasure of the mind, which means that it is a little like a sport: your eagerness and knowledge and quickness make you a good reader. Reading is fun, not because the writer is telling you something, but because it makes your mind work...your own imagination works along with the author’s or even goes beyond his. Your experience, compared with his, brings you to the same or different conclusions, and your ideas develop as you understand his.Every book stands by itself, like a one-family house, but books in a library are like houses in a city. Although they are separate, together they all add up to something; they are connected with each other and with other cities, The same ideas, or related ones, turnup in different places; the human problems that repeat themselves in life repeat themselves in literature, but with different solutions according to different writings at different times. Books influence each other; they link the past, the present and the future and have their own generations, like families. Wherever you start reading you connect yourself with one of the families of ideas, and, in the long run, you not only find out about the world and the people in it; you find out about yourself, too.Reading can only be fun if you expect it to be. If you concentrate on books somebody tells you, you “ought” to read, you probably won’t have fun. If you put down a book you don’t like and try another till you find one that means something to you, and then relax with it, you will almost certainly have a good time to read, you probably won’t have fun. If you put down a book you don’t like and try another till you find one that means something to you, and then relax with it, you will almost certainly have a good time—and if you become, as a result of reading, better, wiser, kinder, or more gentle, you won’t have suffered during the process.6. COMPANIONSHIP OF BOOKS---Samuel SmilesA man may usually be known by the books he reads as well as by the company he keeps; for there is a companionship of books as well as of men; and one should always live in the best company, whether it be of books or of men.A good book may be among the best of friends. It is the same today that it always was, and it will never change. It is the most patient and cheerful of companions. It does not turn its back upon us in times of adversity or distress. It always receives us with the same kindness; amusing and instructing us in youth, and comforting and consoling us in age.Men often discover their affinity to each other by the love they have each for a book—just as two persons sometimes discover a friend by the admiration which both have for a third. There is an old proverb, “Love me, love my dog.” But there is more wisdom in this:“Love me, love my book.” The book is a truer and higher bond of union. Men can think, feel, and sympathize with each other through their favorite author. They live in him together, and he in them.“Books,” said Hazlitt, “wind into the heart; the poet’s verse slides in the current of our blood. We read them when young, we remember them when old. We feel that it has happened to ourselves. They are to be had very cheap and good. We breathe but the air of books.”A good book is often the best um of a life enshrining the best that life could think out; for the world of a man’s life is, for the most part, but the world of his thoughts. Thus the best books are treasuries of good words, the golden thoughts, which, remembered and cherished, become our constant companions and comforters. “They are never alone,” said Sir Philip Sidney, “that are accompanied by noble thoughts.”The good and true thought may in times of temptation be as an angel of mercy purifying andguarding the soul. It also enshrines the germs of action, for good words almost always inspire to good works.Books possess an essence of immortality. They are by far the most lasting products of human effort. Temples and statues decay, but books survive. Time is of no account with great thoughts, which are as fresh today as when they first passed through their author’s minds, ages ago. What was then said and thought still speaks to us as vividly as ever from the printed page. The only effect of time has been to sift out the bad products; for nothing in literature can long survive but what is really good.Books introduce us into the best society; they bring us into the presence of the greatest minds that have ever lived. We hear what they said and did; we see them as if they were really alive; we sympathize with them, enjoy with them, grieve with them; their experience becomes ours, and we feel as if we were in a measure actors with them in the scenes which they describe.The great and good do not die even in this world. Embalmed in books, their spirits walk abroad. The book is a living voice. It is an intellect to which one still listens. Hence we ever remain under the influence of the great men of old. The imperial intellects of the world are as much alive now as they were ages ago.7.Significance of Wildlife ProtectionWith rapid extinction of many wild species, more and more people come to realize the great significance of wildlife protection.We have to understand the problem in a new light that we protect ourselves through protecting wildlife. On the one hand, any species of widlife, as a critical joint of the ecological chain, helps to establish the ecological balance. If one species becomes extinct, it will disappear forever. What is more, it will inevitably result in the extinction of a chain of wildlife and the disruption of the ecological balance. Unpredictable disasters may occur. On the other hand, with the development of modern science and technology, man is just beginning to learn about wildlife. For example, if wild rubber trees had been extinct two centuries ago, there would be no auto industry today. Moreover, wildlife preserves unknown genetic codes, which may turn out to be of vital importance and free human beings from fatal diseases and natural disasters in the future.It is imperative for us to protect wildlife right now before it is too late, because man has already polluted the environment seriously and threatened the existence of many wild species. Let’ take actions to protect wildlife. Learning to live in harmony with all wildlife is part of modem civilization.8．COLNINGCLONING is suddenly in the news, thanks to revolutionary techniques developed by genetic engineers and other new breeds of biologists. The newspapers are full of stories describing how scientists can produce a clone, or an identical copy, of an organism from just a single cell. Biologistsnow have the ability to clone some plants and small animals. Can people be far behind?All of this seems frightening to many, not quite right to some, just plain startling to others. Perhaps the basic question is: how can cloning experiments contribute to future human welfare?WHAT IS A CLONE?A clone is an organism or a group of organisms created from a single parent. The process of cloning is really a from of asexual reproduction. You know that sexual reproduction involves the union of sex cells: the sperm from the male parent and the egg from the female parent. The nucleus of each sex cell-called a pronucleus-contains only one set of chromosomes with their genes and not the two sets that are found in the muclei of all other cells, called body cells, and which give each species its characteristic chromosome number. The union of sperm and egg in fertilization produces two full sets of chromosomes. It is the first step in the creation of a new and unique individual with traits and characteristics inherited from both parents.Cloning is asexual. There is only one parent. And the offspring has the hereditary traits of that single parent.The word “clone”comes from the ancient Greek root, klon, meaning a twig or slip. Taking a twig or cutting from a plant and growing it into another plant is actually cloning the plant.Today, however, the word “cloning”is used in a slightly different way. It has come to mean the production of an organism from just a single cell take from the body of a plant or animal. This single cell, being a body cell and not a sex cell, contains two sets of chromosomes—one set from its mother and one set from its father. It thus has all the genetic information necessary to produce a complete individual if it is stimulated to grow.9.Electronic Mail (E-mail)During the past few years, scientists the world over have suddenly found themselves productively engaged in a task they once spent their living avoiding writing, but particularly letter writing. Lured by electronic mail’s seductive blend of speed, convenience, skillfully, even cheerfully tapping out a great deal of correspondence.Electronic networks, woven into the fabric of scientific communication these days, are the route to colleagues in distant countries, shared data, bulletin boards and electronic journals. Anyone with a personal computers, a modem and the software to link computers over telephone lines can sign on. An estimated five million scientists have done so, with more joining every day, most of them communicating through a bundle of interconnected domestic and foreign routes known collectively as the internet, or net.E-mail is staring to edge out the fax, the telephone, overnight mail and, of course land mail. It shrinks time and distance between scientific collaborators, in part because it is conveniently asynchronous (writes can type while their colleagues across time zones sleep; their message will be waiting). If it is not yet speed discoveries, it is certainly accelerating disclosures.10.Other WorldsFrom what we know of our solar system, it appears unlikely that we wil find intelligent life as we know it on any of the other planets. Some microorganisms and plants might exist, but behings shaped like man or the fabled Martian monsters are not likely. Human life, according to scientists, developed on this planet because of the unique combination of many factors—the earth’s distance from the sun, the composition of our atmosphere, the structure of the earth’s surface the presence of certain organisms on the face of the plant. Yet many ask, are we the only ones in the universe?Although astronomers have never actually seen a planet outside of our solar system, they now recongnzie that other solar systems exist. With powerful radio telescopes, they have located these distant system. Astronomer Harlow Shapley has estimated that there may be life in the planetary system of one out of a million stars.Let’s take this million-to-one chance that astronomer Shapley believes and see what the chances really are! Our best scientific information tells us that there are over 100 billion stars in our own galaxy, and that there are about 100 million galaxies in the universe. They means that there are some 10 quintillion stars in the universe.Suppose that only one out of a million of these stars is a sun like our own sun. That would mean that there are some 10 trillion possible other suns in the universe. Again, let us use Shpley’s one-out-a-million chance to find how many of these suns could possibly have a planet like earth—a planet 93 million miles away, a planet with oxygen in the air for breathing , a planet on which man could live as he does on earth. There would be about 10 million other planets in the universe that could physically resemble the earth.Finally, suppose we use the one-in-a-million chance to find out how many of these have human life just as we have on earth. We would then find that there are 10 other “earths” with human life somewhere in this vast universe.Naturally, it would be quite a task to find these 10 out of the millions upon of stars and planets in the universe. But if we did, what would man be like? Would he still be in the cave-man stage? Or would he have developed a society far beyond ours? What would happen if we did meet a man from outer space?It is these unknowns and man’s unending thirst for knowledge that take us into space in search of other possible worlds like ours.11. Sunday Before the War--John CiardiOn Sunday, in a remote valley in the West of England, where the people are few and scattered and placid, there was no more sign among them than among the quiet hills of the anxiety that holds the world. They had no news and seemed to want none. The postmaster had been ordered to stay all day in his little post-office, and that was something unusual that interested them, but only because it affectedthe postmaster.It rained in the morning, but the afternoon was clear and glorious and shining, with all the distances revealed far into the heart of Wales and to the high ridges of the Welsh mountains. The cottages of that valley are not gathered into villages, but two or three together or lonely among their fruit-trees on the hillside; and the cottagers, who are always courteous and friendly, said a word or two as one went by, but just what they would have said on any other day and without any question about the war. Indeed, they seemed to know, or to wish to know, as little about that as the earth itself, which beautiful there at any time, seemed that afternoon to wear an extreme and pathetic beauty. The country, more than any other in England, has the secret of peace. It is not wild, though it looks into the wildness of Wales; but all its cultivation, its orchards and hopyards and fields of golden wheat, seem to have the beauty of time upon them, as if men there had long lived happily upon the earth with no desire for change nor fear of decay. It is not the sad beauty of a past cut off from the present, but a mellowness that the present inherits from the past; and in the mellowness all the hillside seems a garden to the spacious farmhouses and the little cottages; each led up to by its own narrow, flowery lane. There the meadows are all lawns with the lustrous green of spring even in August, and often over-shadowed by old fruit-trees—cherry, or apple, or pear; and on Sunday after the rain there was an April glory and freshness added to the quiet of the later summer.Nowhere and never in the world can there have been a deeper peace; and the bells from the little red church down by the river seemed to be the music of it, as the song of birds is the music of spring. There one saw how beautiful the life of man can be, and how men by the innocent labours of many generations can give to the earth a beauty it has never known in its wildness. And all this peace, one knew, was threatened; and the threat came into one’s mind as if it were a soundless message from over the great eastward plain; and with it the beauty seemed unsubstantial and strange, as if it were sinking away into the past, as if it were only a memory of childhood.So it is always when the mind is troubled among happy things, and then one almost wishes they could share one’s troubles and become more real with it. It seemed on that Sunday that a golden age had lasted till yesterday, and that the earth had still to learn the news of its ending. And this change had come, not by the will of God, not even by the will of man, but because some few men far away were afraid to be open and generous with each other. There was a power in their hands so great that it frightened them. There was a spring that they knew they must not touch, and , like mischievous and nervous children, they had touched it at last, and now all the world was to suffer for their mischief.So the next morning one saw a reservist in his uniform saying goodbye to his wife and children at his cottage-gate and then walking up the hill that leads out of the valley with a cheerful smile still on his face. There was the first open sign of trouble, a very little one, and he made the least of it; and, after all, this valley is very far from any possible war, and its harvest and its vintage of perry and cider will surely be gathered in peace.But what happiness can there be in that peace, or what security in the mind of man, when the madness of war is let loose in so many other valleys? Here there is a beauty inherited from the past,。

2024届山东中学联盟高三下学期5月预测热身卷英语试题+详细解析注意事项:1. 答卷前，考生务必将自己的姓名、考生号等填写在答题卡和试卷指定位置。

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3. 考试结束后，将本试卷和答题卡一并交回。

第一部分：阅读理解（共两节，满分50分）第一节（共15小题；每小题2.5分，满分37.5分）阅读下列短文，从每题所给的四个选项（A、B、C和D）中，选出最佳选项。

ASmall Ways You Can Donate Money To CharityThere are plenty of innovative ways that you can help people in need, even when money is tight. Here are just a few unique ways to give.Food Angel, Hong KongFood insecurity has become a global problem for families. In Hong Kong, the people behind the Food Angel program collect 45 tonnes of edible surplus food each week that grocery stores, restaurants and individuals would otherwise dispose of. That includes fresh fruits and vegetables and other perishables (易腐烂的食物) that aren’t normally accepted in food-donation boxes.The impact is significant: Volunteers make and serve around 20,000 meals and distribute more than 11,000 other meals and food packs every day.Frigos Solidaires, FranceImagine if those in need could help themselves to food with anonymity (匿名) and dignity. Frigos Solidaires, or Solidarity Fridges, was started with that aim by Dounia Mebtoul, a young restaurateur in Paris. Now, 130 fridges installed in front of places such as shops and schools offer free food to the hungry across France.Stuff A Bus, CanadaIn Edmonton, the transit service parks vehicles in front of supermarkets for its annual “Stuff a Bus” campaign each November. Volunteers collect food and cash donations from shoppers to fill buses bound for food banks. Since its start in 1995, the campaign has collected 553,000 kilograms of food and roughly half a million dollars.Rice Bucket Challenge, IndiaHeard of the Ice Bucket Challenge? You take a video of yourself dumping a bucket of ice water over your head, then nominate (指定) three more people to do the same. In some versions, the participant donates $100 if they don’t complete the challenge.“I thought it was an amazing way to raise awareness of ALS and raise funds,” recall s Manju Kalanidhi, a journalist in Hyderabad, India. But it didn’t make sense in her country, where water is too precious to waste, even for a good cause. Then in 2014, it hit her: Why not make it a Rice Bucket Challenge to fight hunger? “I gave a bucket o f rice to someone in need and clicked a photo. I shared it on Facebook and said, ‘This is a Rice Bucket Challenge.Why don’t you do it, too?’” Participants donate a bucket of rice to an individual or family —no, it’s not dumped — take a photo and post it on social media with a message encouraging others to do the same.1. Which one can help people in need get food without hurting their pride?A. Food Angel, Hong KongB. Frigos Solidaires, FranceC. Stuff A Bus, CanadaD. Rice Bucket Challenge, India2. What do you know about Rice Bucket Challenge in India?A. It is an amazing way to raise awareness of ALS.B. It was inspired by the Ice Bucket Challenge.C. A bucket of rice is given and dumped.D. A bucket of water is donated for a good cause.3. What’s the p urpose of the text?A. To explain how important to help people in need.B. To inspire readers to start a non-profit organization.C. To introduce some creative ways to give away.D. To appeal to readers to donate money to charity.【答案】1. B 2. B 3. C【解析】【导语】本文是一篇说明文。

小学上册英语第四单元寒假试卷(有答案)英语试题一、综合题(本题有100小题，每小题1分，共100分.每小题不选、错误，均不给分)1.My dad is very ________.2. A __________ (长期计划) can support sustainable gardening.3.My mom is a ________.4.The dog wagged its ______ (尾巴) when it saw me. It was very ______ (兴奋).5.I can create a _________ (玩具动物) out of clay.6.中国的________ (history) 充满了起伏与变迁。

7.She has a _____ (cat/dog) at home.8.The cake is ___ (frosted).9.The atmosphere is essential for ______ life on Earth.10.The ancient Chinese invented _____ paper.11.My sister sings in the ________ (合唱团).12. A _____ is a group of stars that is visible in the night sky.13.I like to ______ pictures. (draw)14. A tiny ___ (小龙) appears in stories.15.What do we call the primary color that mixes with blue to create violet?A. RedB. YellowC. GreenD. Orange答案:A16. A molecule that can donate protons is called an ______.17.The process of ______ involves the gradual breakdown of rocks.18.The ______ (水分) in soil is crucial for growth.19.My cousin is a great __________ (志愿者).20.I love reading mystery books. My favorite author is __________.21.The chemical symbol for chromium is __________.22.The flowers are _____ and colorful. (bright)23. A __________ is a mixture that can be separated by evaporation.24.The Sun is a medium-sized star in the ______ galaxy.25.The process of making glass involves heating sand to a high _____.26.The pufferfish can _________ itself. (膨胀)27.The __________ (历史的冲击) prompts reflection.28. A ____ is a friendly creature that enjoys company.29.What is the capital city of the Philippines?A. ManilaB. CebuC. DavaoD. Quezon City答案: A30.An alligator lives in _________ (沼泽地).31. A __________ (分子间力) influences the physical properties of a substance.32. A chemical reaction requires a change in ______.33.We can _____ (graft) plants to improve growth.34.The ice cream is _____ melting. (slowly)35.My dad tells _______ jokes.36.The __________ (地震) shook the buildings.37.The gecko can stick to _______ (墙壁).38.We need to ________ the house.39. A ________ (树枝) can break if it is too heavy.40.Certain plants can ______ (生存) in low-nutrient soils.41.I can ________ (lead) a team effectively.42.She is _______ (reading) a novel.43.The __________ (历史的跨文化交流) fosters understanding.44.What do we call a story that explains the origins of something?A. MythB. FableC. LegendD. Fairy tale答案: A45.The Age of Exploration began in the _______ century.46.The chemical process that occurs in our bodies to release energy is called ______.47.I see a _____ (bird/fish) in the tree.48.He is a mechanic, ______ (他是一名机械师), fixing cars.49.The _____ (枝条) can be pruned for better growth.50.The ostrich is the world's largest ______ (鸟).51.Burning wood produces __________.52.She is studying to be a ________.53.The playground is full of ______.54.My cousin is passionate about __________ (艺术).55.I see a _____ (caterpillar) on the leaf.56.I saw a _______ (小松鼠) eating an acorn.57.My __________ (玩具名) always makes me laugh when I __________ (动词).58. A ________ (植物采集) can be educational.59._______ are important for the environment.60.The chemical formula for ammonium sulfate is __________.61. Carta was signed in __________ (1215), limiting the power of the king. The Magn62.The goldfish swims gracefully in the _________ (水).63.The _____ (植物生物) is varied and complex.64.My cousin always visits us during ____.65.He has a pet ___ . (fish)66.My brother has a remote-controlled _____ (飞机).67.What is the main language spoken in the USA?A. SpanishB. EnglishC. FrenchD. Chinese答案: B68.The weather is _____ today. (nice)69.I like ________ (吃) ice cream.70.We have a ________ (meeting) after school.71.What do you call a group of wolves?A. PackB. HerdC. FlockD. Swarm答案: A72.I love to eat ___. (cake)73.I love learning new languages because it helps me understand different _______ (文化).74.Light from ancient stars provides clues about the early _______.75.My dad loves to ________ (烹饪).76.The _____ (fish/bird) is swimming.77.The ice cream truck is ______ (coming) down the street.78.Pandas mainly eat _________ (竹子).79.The hamster runs on its _______ every night.80.What is the name of the famous clock tower in London?A. Big BenB. Eiffel TowerC. Leaning Tower of PisaD. Statue of Liberty答案:A81.My uncle is a __________ (建筑师).82.I always _______ (帮助) my parents.83.My friend is a ______. He wants to be an astronaut.84.His favorite animal is a ________.85.The _____ (星星) twinkle at night.86.The teacher, ______ (老师), inspires us to dream big.87.In art class, we made ________ (手工艺品) using old toys. It was ________ (有趣的) to create something new!88.The rabbit has powerful _______ (后腿) for jumping.89.The police officer, ______ (警察), keeps the community safe.90. A lever can increase the ______ applied to an object.91.The _____ (ocean) is blue.92.The nurse provides care and support in _____ (医院).93.My mom enjoys doing ____ (puzzles).94.I enjoy _______ (看书) at the library.95.The __________ is cool and refreshing during the summer. (海洋)96.What is the name of the place where we go to watch movies?A. TheaterB. MuseumC. Concert HallD. Library答案: A97.What do we call the process of making food from sunlight, carbon dioxide, and water?A. PhotosynthesisB. RespirationC. FermentationD. Digestion答案: A. Photosynthesis98.Chemical reactions can be classified as ______ or physical changes.99. A mixture that is not uniform throughout is called a ______ mixture.100.My uncle is a skilled ____ (sculptor).。

疯狂英语 （新读写）A sun umbrella in space太空遮阳伞重庆　袁　泉1Scientists have floated the idea of using a giant space “umbrella ” as a solar shield (护罩) to protect the Earth from too much sunlight and help reduce global warming.2Istv n Szapudi, an astronomer at the Univer⁃sity of Hawaii Institute for Astronomy, had the bright idea of tying the huge shield to a captured asteroid (小行星) so it would have a counterweight (平衡物). This would prevent it from falling back to the Earth because of the forces of gravity or blowing away in space.3 He said studies using this approach could start now to create a workable design that could reduce climate change within decades. “In Hawaii, many use umbrellas to block the sunlight as they walk about during the day. I was thinking, could we do the same for the Earth and thereby reduce the approaching disasters of climate change?” Mr Szapudi said on the University of Hawaii s website.4 In his paper, published in the Proceedings of the National Academy of Sciences , Mr Szapudi explained that one of the simplest ways to lower the global temperature is to shadethe Earth from just a small part of the Sun s light.主题语境：科技发展 篇幅：347词 建议用时：7分钟科学家们认为，他们已经提出了一种缓解全球变暖的新方法：在太空中架起一把巨大的“伞”，保护地球免受过多的阳光照射。

小学上册英语第3单元真题试卷(有答案)英语试题一、综合题(本题有100小题，每小题1分，共100分.每小题不选、错误，均不给分)1.The _______ of an object can be tested by dropping it.2.The center of an atom is called the __________.3.Herbaceous plants are different from ______ (木本植物).4.The ______ (猴子) swings from tree to tree.5.Acids turn blue litmus paper ______.6.My ________ (玩具) makes a cool noise when I spin it.7.What do you call a person who studies rocks?A. BiologistB. GeologistC. MeteorologistD. Archaeologist答案:B8.The flowers are _______ (在盛开).9.The ________ (光合作用) process is vital.10.The ____ is a small animal that enjoys exploring its surroundings.11.My grandma loves to tell __________ (有趣的故事).12.Planting trees can combat ______ (气候变化).13.What do we call the process of photosynthesis?A. Conversion of light into energyB. Absorption of lightC. Dispersal of lightD. Reflection of light答案: A14.The sun is very _____ (热).15.The __________ (河流) flows into the ocean.16.Planting _____ (药用植物) can benefit health and wellness.17.The _____ (景观) can include many different plants.18.She has a red ______ (backpack).19.The invention of the printing press allowed for the mass production of _______.20.My dad is a __________ (飞行员) and travels a lot.21. A sloth spends most of its life hanging _______ ( upside down).22.What is the name of the famous ancient city in Italy?A. PompeiiB. RomeC. VeniceD. Florence答案:A.Pompeii23.An owl is a wise _______ that comes out at night.24.________ (植物资源利用) can enhance livelihoods.25.The _____ (computer/smartphone) is useful.26. A dog barks and a cat _______.27.The ancient Romans built ________ to transport water.28. A substance that increases the rate of a chemical reaction without undergoing permanent change is a _____ (catalyst).29.I have a toy _____ that can sing.30.The __________ is known for its vibrant nightlife.31. A ______ (植物的利用) can lead to innovative products.32. A ____ is known for its elaborate courtship dance.33.What is the first month of the year?A. FebruaryB. MarchC. JanuaryD. April答案: C34.She is _____ (playing) the flute.35.The ______ is important for clean air.36.What is the name of the fairy tale character who had long hair?A. CinderellaB. RapunzelC. Snow WhiteD. Belle答案: B37.I need to _____ (wash/clean) my room.38.The ____ has a cheerful song and is often heard in the morning.39.The __________ (历史的回响) resonates with humanity.40.The girl sings very ________.41.I have a _______ (subscription) to the magazine.42.I like to go to the ______ (电影院) to watch new movies. It’s always an exciting experience.43.The _____ (海豚) is known for its playful behavior.44. A ______ is a huge ball of ice and dust that orbits the sun.45.Let’s ________ a game after school.46.The __________ is where the Earth's crust is thinnest.47.My uncle is a _______ (职业). 他在 _______ (地点)工作.48.My friend is __________ (具有前瞻性).49.The kitten is ________ and soft.50.My dad is a ______. He enjoys woodworking.51. A _______ is a mixture that appears uniform throughout.52.I can sing songs with my musical ________ (玩具名称).53.The ________ (仙人掌) can survive in dry places with little water.54.The atmosphere contains gases that are essential for ______.55.My ________ (玩具名称) helps me learn about animals.56.My favorite game is ______ (Scrabble).57.Did you ever watch a _______ (小老虎) in the zoo?58.The owl hoots _______ (在夜间).59.What is the name of the famous American landmark known for its statue of a man on a horse?A. Mount RushmoreB. Lincoln MemorialC. Statue of LibertyD. Washington Monument答案: A. Mount Rushmore60.What animal barks?A. CatB. DogC. CowD. Sheep答案:b61.My ________ (弟弟) loves to draw pictures of animals.62.How many sides does a triangle have?A. 2B. 3C. 4D. 5答案:b63. A chemical reaction can produce heat, light, or _____.64. A rainy day means I can stay ______ (舒适).65.What do we call the small pieces of glass used for decoration?A. MarbleB. BeadsC. GemsD. Mosaic答案:D66.I have a _____ (collection) of postcards.67. A pelican has a large ________________ (喙).68.I often write emails to my ____.69.He likes to __________ books.70.My favorite color is ________ (blue).71.What is the capital of France?A. HamburgB. ParisC. RomeD. Madrid答案: B72.My uncle drives a ____ (bus) for the city.73.The hummingbird can hover in ______ (空中) thanks to its wings.74.The _______ can be found in many colors.75.What do we call the outer layer of the Earth?A. CrustB. MantleC. CoreD. Shell答案:A76.The capital of Italy is __________.77. A __________ is a type of bird known for its beautiful song.78.n Wall came down in ________ (1989). The Berl79.The boiling point of water is __________ degrees Fahrenheit.80. Carta was signed in __________ (1215). The Magn81. A displacement reaction involves one element replacing ______.82.The weather is _______ (很适合户外活动)。

托福阅读tpo54全套解析阅读-1 (2)原文 (2)译文 (4)题目 (5)答案 (9)背景知识 (10)阅读-2 (10)原文 (10)译文 (12)题目 (13)答案 (18)背景知识 (20)阅读-3 (25)原文 (26)译文 (27)题目 (28)答案 (33)背景知识 (35)阅读-1原文The Commercialization of Lumber①In nineteenth-century America, practically everything that was built involved wood.Pine was especially attractive for building purposes.It is durable and strong, yet soft enough to be easily worked with even the simplest of hand tools.It also floats nicely on water, which allowed it to be transported to distant markets across the nation.The central and northern reaches of the Great Lakes states—Michigan, Wisconsin, and Minnesota—all contained extensive pine forests as well as many large rivers for floating logs into the Great Lakes, from where they were transported nationwide.②By 1860, the settlement of the American West along with timber shortages in the East converged with ever-widening impact on the pine forests of the Great Lakes states. Over the next 30 years, lumbering became a full-fledged enterprise in Michigan, Wisconsin, and Minnesota. Newly formed lumbering corporations bought up huge tracts of pineland and set about systematically cutting the trees. Both the colonists and the later industrialists saw timber as a commodity, but the latter group adopted a far more thorough and calculating approach to removing trees. In this sense, what happened between 1860 and 1890 represented a significant break with the past. No longer were farmers in search of extra income the main source for shingles, firewood, and other wood products. By the 1870s, farmers and city dwellers alike purchased forest products from large manufacturingcompanies located in the Great Lakes states rather than chopping wood themselves or buying it locally.③The commercialization of lumbering was in part the product of technological change. The early, thick saw blades tended to waste a large quantity of wood, with perhaps as much as a third of the log left behind on the floor as sawdust or scrap. In the 1870s, however, the British-invented band saw, with its thinner blade, became standard issue in the Great Lakes states' lumber factories.Meanwhile, the rise of steam-powered mills streamlined production by allowing for the more efficient, centralized, and continuous cutting of lumber. Steam helped to automate a variety of tasks, from cutting to the carrying away of waste. Mills also employed steam to heat log ponds, preventing them from freezing and making possible year-round lumber production.④For industrial lumbering to succeed, a way had to be found to neutralize the effects of the seasons on production. Traditionally, cutting took place in the winter, when snow and ice made it easier to drag logs on sleds or sleighs to the banks of streams. Once the streams and lakes thawed, workers rafted the logs to mills, where they were cut into lumber in the summer. If nature did not cooperate—if the winter proved dry and warm, if the spring thaw was delayed—production would suffer. To counter the effects of climate on lumber production, loggers experimented with a variety of techniques for transporting trees out of the woods. In the 1870s, loggers in the Great Lakes states began sprinkling water on sleigh roads, giving them an artificial ice coating to facilitate travel. The ice reduced the friction and allowed workers to move larger and heavier loads.⑤But all the sprinkling in the world would not save a logger from the threat of a warm winter. Without snow the sleigh roads turned to mud. In the 1870s, a set of snowless winters left lumber companies to ponder ways of liberating themselves from the seasons. Railroads were one possibility.At first, the remoteness of the pine forests discouraged common carriers from laying track.But increasing lumber prices in the late 1870s combined with periodic warm, dry winters compelled loggers to turn to iron rails. By 1887, 89 logging railroads crisscrossed Michigan, transforming logging from a winter activity into a year-round one.⑥Once the logs arrived at a river, the trip downstream to a mill could be a long and tortuous one.Logjams (buildups of logs that prevent logs from moving downstream) were common—at times stretching for 10 miles—and became even more frequent as pressure on the northern Midwest pinelands increased in the 1860s. To help keep the logs moving efficiently, barriers called booms (essentially a chain of floating logs) were constructed to control the direction of the timber. By the 1870s, lumber companies existed in all the major logging areas of the northern Midwest.译文木材的商业化①在19世纪的美国，几乎所有建筑材料都含有木材。

2022-2023高三上英语期末模拟试卷注意事项:1．答题前，考生先将自己的姓名、准考证号码填写清楚，将条形码准确粘贴在条形码区域内。

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第一部分（共20小题，每小题1.5分，满分30分）1．The government officials met the workers and engineers working on the stadium, most____ were migrant workers．A．of which B．of who C．of whom D．of them2．––What did the doctor say about your injury?––She said I should avoid doing too much exercise ______ it feels better.A．until B．sinceC．if D．while3．Having pictures to color will keep children ______for hours.A．amused B．amusingC．amuse D．to amuse4．It's always a good idea to have a second key somewhere________ you lose the first one.A．in case B．now thatC．even though D．as long as5．Yet _______ in the process of development did they stop to consider the impact of their “progress” on nature.A．in no time B．at no pointC．as likely as not D．more often than not6．Every great accomplishment rests on the of what came before it; when you trace it back, you’ll see one small step that started it all.A．reputation B．expectationC．recreation D．foundation7．Every man has his faults. We should, therefore, lean to be ________ of others. A．ignorant B．responsibleC．reliable D．tolerant8．—Did you go to last night’s concert?— Y es. And the girl playing the violin at the concert _______ all the people present with her excellent ability.A. impressed B．compared C．conveyed D．observed9．It is going to rain today. Take an umbrella with you to ________ you from the rain. A．stop B．prevent C．keep D．protect10．According to the bank rules released recently, you have to pay a 25% ________ on each cheque you cash.A．admission B．pensionC．allowance D．commission11．The language in the c ompany’s statement is highly ________, thus making its staff confused.A．ambiguous B．apparentC．appropriate D．aggressive12．—Are you ready to leave?—Almost, I’ll be ready to go just as soon as I ________ putting the clean dishes away. A．get through B．give upC．carry out D．set about13．－Mike, our team will play against the Rockets this weekend. I am sure we will win. －________!A．Congratulations B．CheersC．Best wishes D．Good luck14．---I hear you’ll cancel all your plans and appointments. Why?---Th ey _____ my life. I just can’t stop.A．control B．controlledC．have controlled D．have been controlling15．I will give you some articles which you can when you write the report. A．refer to B．apply to C．lead to D．talk to16．—Why not talk with your parents about your willingness to attend 2017 Peking University Summer Camp?—I tried____ to get them to listen to me.A．in time B．in vainC．in need D．in case17．— Helen,are you going Io the airport to pick up Jack the day after tomorrow?— ________ tomorrow night.I would go.A．Were he to come back B．If he was about to come backC．Had he come back D．If he would come back18．________ in the last examination, she was more confident of another success in the coming one.A．To succeed B．To have succeeded C．Having succeeded D．succeeding 19．The online word “selfie” is gaining ______ and more and more people tend to use it nowadays.A．access B．admissionC．control D．currency20．—Sorry, I didn’t hear the door bell ring.—Your bell . Perhaps it needs repairing.A．never worked B．is never workingC．never works D．had never worked第二部分阅读理解（满分40分）阅读下列短文，从每题所给的A、B、C、D四个选项中，选出最佳选项。