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International Journal of Pharmaceutics 222(2001)7–17Inﬂuence of hydrogel structure on the processes of waterpenetration and drug release from mixedhydroxypropylmethyl cellulose /thermally pregelatinized waxymaize starch hydrophilic matricesV.Michailova a,*,St.Titeva a ,R.Kotsilkova b ,E.Krusteva b ,E.Minkov aaDepartment of Pharmaceutical Technology ,Faculty of Pharmacy ,Medical Uni 6ersity ,2Duna 6Street ,Soﬁa 1000,BulgariabCentral Laboratory of Physicochemical Mechanics ,Bulgarian Academy of Sciences ,Acad .G .Bontche 6Street ,Soﬁa 1113,BulgariaReceived 12February 2001;accepted 23March 2001AbstractThe kinetics of water penetration and molsidomine release from both hydroxypropylmethyl cellulose (HPMC)and mixed HPMC /thermally pregelatinized waxy maize starch (SDWMT)hydrophilic matrices has been examined in 0.1mol dm −3HCl (pH 1.0)and 0.06mol dm −3Na 3PO 4/HCl buffer (pH 6.8).The rheological oscillatory test parameters of their gel layers obtained by swelling of the matrices in the two aqueous media have been observed.The kinetic swelling properties of mixed HPMC /SDWMT hydrogels (i.e.degree and velocity of both water penetration and swelling,transport mechanism which controls solvent sorption)directly inﬂuence the drug release behaviour and the structural features of the formed gel layer.Both diffusion processes are diffusion-controlled ones,their mechanisms being inﬂuenced insigniﬁcantly by the relaxation properties of the hydrated macromolecules.It has been established by means of comparative viscoelastic analysis,that mixed HPMC /SDWMT hydrogels demonstrate the typical behaviour of ‘ﬁlled’composite systems having poor adhesion between the surface of the elastic SDWMT ‘ﬁller’and the continuous HPMC phase.Due to the inter-phase relations between the swollen starch granules and the linear cellulose derivative as well as to the speciﬁc structure of amylopectin molecule,the pregelatinized waxy maize starch shows a stronger inﬂuence on the velocities of both water penetration and drug release from mixed HPMC /SDWMT matrices.©2001Published by Elsevier Science B.V.Keywords :Thermally pregelatinized waxy maize starch;Hydroxypropylmethyl cellulose;Mixed hydrophilic matrices;Water penetration;Rheology /locate /ijpharm1.IntroductionThermally pregelatinized starches prove to be very suitable for formulating of hydrophilic ma-*Corresponding author.Tel.:+359-2-9883142,ext.:225;fax:+359-2-9879874.E -mail addresses :vmihailova@mbox.pharmfac.acad.bg (V.Michailova),stiteva@mbox.pharmfac.acad.bg (S.Titeva).0378-5173/01/$-see front matter ©2001Published by Elsevier Science B.V.PII:S 0378-5173(01)00706-2V.Michailo6a et al./International Journal of Pharmaceutics222(2001)7–17 8trix systems(Mohile,1986;Herman and Remon, 1989;Sa´nchez et al.,1995)because their techno-logical and physicochemical properties are rather similar to those of the commonly used cellulose derivatives,i.e.hydroxypropylmethyl cellulose (HPMC),HPC,HEC.The native starch consists of two macromolecular structural analogues,i.e.a branched amylopectin and a linear amylose, whose content can vary between0and80%ac-cording to the starch genotype(Young,1984). Thermally pregelatinized starches are produced by gelatinization of the native starches followed by a process of thermal dehydration like extru-sion,drum-drying,roll-drying,spray-drying, freeze-drying(Snyder,1984;Sa´nchez et al., 1995).In vitro biopharmaceutical studies of pregelatinized starch hydrophilic matrices show that the main factors controlling their drug re-lease behaviour are the starch chemical composi-tion,i.e.amylose/amylopectin proportion,the degree of pregelatinization and the starch con-centration in the gel.It has been established that waxy maize starch(containing100%amy-lopectin)has the best potential for drug release retardation which progressively decreases with the increase of amylose content(Herman and Remon,1989).Like most unlimited swelling hy-drogels matrices,the drug release mechanism from these hydrogels is a diffusion-controlled one.It is determined by the structural character-istics of the gel layer(structural organization, diffusion capability,gel strength),and by the processes of both polymer swelling and gel layer erosion(Herman and Remon,1989).The structural characteristics of starch gels have been investigated extensively by means of the experimental and theoretical rheology meth-ods(Eliasson,1986;Doublier et al.,1987;Ellis et al.,1989).The rheological properties of starch pastes and gels are strongly dependent on the techniques of pregelatinization and especially on the temperatures and processing parameters,as well as on the amylose/amylopectin ratio,the swelling degree of starch granules and their con-centration in the gel(Bagley and Christianson, 1982;Doublier et al.,1987;Dintzis and Bagley, 1995).According to the modern view starch gels containing amylose are composite materials, consisting of an amylose network reinforced by the swollen starch granules(Ott and Hester, 1965;Carnali and Zhou,1996).Their swelling degree,their compressibility,and the adhesion between the continuous and dispersed phase control the rheological behaviour of the starch gels(Eliasson and Bohlin,1982;Ring and Stainsby,1982).The structural and rheological properties of pregelatinized waxy maize starch hydrogels(100%amylopectin)differ consider-ably from those of the highly elastic amylose containing gels.Their concentrated dispersions possess weaker gel structures,which depend on the concentration of whole or partially de-stroyed starch granules and on the dissolved amylopectin quantity(Bagley and Christianson, 1982;Evans and Lips,1990).In vivo the erosion of such a gel layer may accelerate the drug re-lease from pregelatinized waxy maize starch ma-trices(Herman and Remon,1989).Starch gel strength can be increased by means of chemical crosslinking(Gluck-Hirsh and Kokini,1997), enzymatic hydrolysis and retrogradation(Te Wierik et al.,1997),and addition of macro-molecular hydrophilic polymers(Sa´nchez et al., 1995)or complexing emulsiﬁers(Conde-Petit and Escher,1995).Some of these methods have been used for modifying the drug release kinet-ics from pregelatinized starch hydrogels (Sa´nchez et al.,1995;Te Wierik et al.,1997). For this reason we used HPMC,which is able to form elastic gels(Michailova et al.,1999),for developing of mixed matrix systems containing pregelatinized waxy maize starch.In this work,we evaluate the processes of both water penetration and molsidomine release from mixed hydrophilic HPMC/thermally prege-latinized waxy maize starch(SDWMT)matrices in0.1mol dm−3HCl(pH 1.0)and0.06mol dm−3Na3PO4/HCl buffer(pH6.8).A compara-tive rheological analysis of the mechanical spec-tra of the mixed hydrogels is made using a dynamic oscillatory viscoelastic test.The struc-tural features of the gel layer are related to the kinetics and mechanism of both water uptake and drug release.V.Michailo6a et al./International Journal of Pharmaceutics222(2001)7–1792.Materials and methods2.1.MaterialsHPMC(Methocel K15M Premium,Colorcon, UK)and HPMC/SDWMT mixtures of the fol-lowing ratios were used:80/20,60/40,40/60and 20/80.Methocel K15M has22%methoxy and 8.1%hydroxypropyl content;a2%w/v aqueous solution has a viscosity of:15000mPa s at 20°C(Doelker,1987).SDWMT consists of100% amylopectin;its14%w/v aqueous dispersion has a viscosity of287mPa s at20°C(Herman et al., 1989).The pregelatinized waxy maize starch was produced by spray-drying technique at the Phar-maceutical Technology Laboratory of the State University of Gent,Belgium.Molsidomine(N-ethoxycarbonyl-3-morpholinosydnonimine)was supplied by Sopharma Ltd.,Bulgaria.2.2.Preparation of hydrophilic matrix tabletsMatrix tablets containing8mg molsidomine and HPMC/SDWMT in the proportion ratios mentioned above were directly compressed on an eccentric tablet-press machine(Erweka,Germany) equipped with8mmﬂat punches at a pressure of 150MPa.The weight of each tablet was20091 mg.2.3.Liquid penetration studyThe process of liquid penetration into the hy-drophilic matrix tablets was examined gravimetri-cally by means of Stamberg and Sevcik method. The dry matrix tablet was weighed accurately in a tarred glass column consisting of a funnel of4 cm3volume,sinteredﬁlter and a tube taking the surplus of water away(Stamberg and Sevcik, 1966).The liquid penetration was studied using the following aqueous phase:(a)0.1mol dm−3 HCl solution(pH1.0),and(b)0.06mol dm−3 Na3PO4/HCl buffer(pH6.8).The Na3PO4/HCl buffer is prepared by mixing of800cm30.1mol dm−3HCl solution and100cm30.6mol dm−3 Na3PO4(Lehmann et al.,1999).The sample was soaked into the aqueous phase tested for a given period of time(1,2,3,4and5h)at a temperature of3790.5°C.Then the excess liquid was removed by centrifugation at2500min−1for10min and the swelled hydrogel was weighed again.For the weight of each swelled matrix,the mean value of six measurements was taken.The dynamics of the liquid uptake was expressed as a weight gain(w p) of the swelled matrix,in g penetrant/g dry poly-mer(Davidson and Peppas,1986),calculated as a ratio between the amount of the aqueous phase remaining in the swollen matrix for a given period of time and the initial weight of the dry matrix tablet.2.4.In6itro dissolution studyThe dissolution testing was performed using a USP XXIII rotating paddle apparatus(Erweka DT6)at a rotation speed of10091min−1and a temperature of3790.5°C.The dissolution medium(900cm3)was identical to that used in the liquid penetration studies,i.e.0.1mol dm−3 HCl solution(pH 1.0)and0.06mol dm−3 Na3PO4/HCl buffer(pH 6.8).The quantity of molsidomine released was measured spectropho-tometrically using a Hewlett Packard8452A ap-paratus at285and310nm for pH1.0and6.8, respectively.The mean value of three determina-tions is taken into account.The mean cumulative percentages of drug released were calculated(9 S.D.).2.5.Preparation of hydrogel systemsThe highly concentrated HPMC and mixed gels were obtained by swelling of the matrix tablets in the above mentioned aqueous phases,i.e.0.1mol dm−3HCl solution(pH1.0)and0.06mol dm−3 Na3PO4/HCl buffer(pH6.8),at a temperature of 3790.5°C for7h.The gel layer formed around the matrix was carefully separated from the unswollen core and then it was immediately tested rheologically.The swelling time(7h)was selected having in mind the in vitro evaluation of molsi-domine release processes from the hydrophilic matrices.The polymer concentration of the hy-drogels was between18and25%w/w.It was determined by means of DTA(Mettler TA3000, Switzerland)over a temperature range from35toV .Michailo 6a et al ./International Journal of Pharmaceutics 222(2001)7–1710170°C at a standard heating rate of 10°C per minute.2.6.Rheological studiesRheological studies of the hydrogel systems were performed with a Rheotron Brabender rheometer equipped with cone-plate systems (P8/B,P8/C).All measurements were carried out at a temperature of 3790.5°C.The storage (G %)and the loss (G %%)moduli,as well as the dynamic viscosity (p %)were obtained under the dynamic conditions of non-destructive oscillatory tests in a frequency range from 0.06to 31.95rad s −1.2.7.Data analysisThe kinetics of liquid penetration into the hy-drophilic matrices was analysed according to Eq.(1)(Michailova et al.,2000):w p =K p t n p ,(1)where w p is the weight gain of the swelled matrix;K p is the kinetic constant of water penetration;t is penetration time;n p is an exponent which depends on the water penetration mechanism.The evaluation of molsidomine release kinetics is based on Peppas ’equation (Peppas,1985):M t /M =kt n ,(2)where M t /M is the fraction of the drug released at time t ,k is the kinetic constant of drug release,and n is a release exponent whose values for a cylindrical geometry range between 0.45and 0.89depending on Fickian or anomalous release kinetics.The values of K p ,n p ,k and n for all tested hydrophilic matrices were calculated by regression analysis (values 995%con ﬁdence limits).3.Results and discussion3.1.E 6aluation of water penetration and drug release processes from mixed HPMC /SDWMT hydrogelsThe penetration pro ﬁles of 0.1mol dm −3HCl (pH 1.0)and 0.06mol dm −3Na 3PO 4/HCl buffer (pH 6.8)into pure HPMC and mixed HPMC /SD-WMT hydrophilic matrices are shown in Fig.1(a)and (b).The ionic strength of the aqueous phases and their pH values in ﬂuence the processes of water uptake into the hydrogels insigni ﬁcantly.For the media tested,the degree of water penetra-tion is the highest for the pure HPMC.It dimin-ishes with the increase of the pregelatinized starch quantity (20–60%),a slight minimum being ob-served with the system containing 40%SDWMT.With the 20/80HPMC /SDWMT matrices,the degree of water sorption greatly decreases.That dependence indicates the water-absorption and swelling capabilities of the two polymers (Gehrke,1992).In comparison with the cellulose derivative,Fig.1.Weight gain of HPMC and mixed hydrophilic matrices as a function of the swelling time.(a)0.1mol dm −3HCl medium;and (b)pH 6.8phosphate buffer.( )HPMC;and mixed HPMC /SDWMT matrices:( )80/20,( )60/40,( )40/60,(")20/80.V.Michailo6a et al./International Journal of Pharmaceutics222(2001)7–1711 Table1Values of kinetic parameters of both water penetration(K p and n p)and drug release(k and n)processes of HPMC and mixed HPMC/SDWMT hydrogels in0.1mol dm−3HClWater penetrationHPMC/SDWMT ratio Drug releasen p r k(h−n)K p(h−n)n r100/0 1.406590.02950.567890.01750.99860.230390.00390.536190.01380.99910.582990.01830.999380/200.277890.00261.334390.02470.549690.00640.99960.588990.01880.99860.365590.00481.294990.02310.468390.009360/400.99901.320190.040440/600.535490.03190.99810.399890.00460.429390.00760.99920.321390.02470.998020/800.464290.00321.091990.03460.386790.00440.9997Table2Values of kinetic parameters of both water penetration(K p and n p)and drug release(k and n)processes of HPMC and mixed HPMC/SDWMT hydrogels in Na3PO4/HCl buffer(pH6.8)HPMC/SDWMT ratio Drug releaseWater penetrationn p r k(h−n)n rK p(h−n)0.560190.00490.9999100/00.168290.00091.264690.00490.620690.00390.9999 80/20 1.228590.01010.565190.01020.99950.209690.00340.592290.01460.99830.582690.04040.99260.246890.00290.553790.00860.9994 60/40 1.118990.04310.552990.01510.99890.267890.00251.179690.01780.496290.009740/600.99900.356690.024120/800.99081.014090.04560.315190.00290.442390.00580.9996the pregelatinized starch hydrates to a consider-able lower degree although its swelling character-istics,such as swelling and water retention capacities,are enhanced as a consequence of the preliminarily physical modiﬁcation of the native waxy maize starch(Herman et al.,1989).The lower ability of SDWMT to swell may be ex-plained by the formation of intra-molecular hy-drogen bonds in the highly branched amylopectin (Hanselmann et al.,1996).Stabilizing andﬁxing the starch granules during the process of swelling, the bonds lead to preservation of their integrity and determine their high rigidity.The topological constraints exerted by the branches of the adja-cent molecules suppress the polymer segments’mobility and also diminish the degree of SDWMT hydration(Ferri and Lomellini,1999).Such inter-and intra-molecular relations of amylopectin molecules suggest a reduced gel layer diffusivity and a decreased drug release velocity from HPMC/SDWMT matrices containing higher pregelatinized starch quantity.The kinetic parameters of penetration,i.e.ki-netic penetration constant,K p,and penetration exponent,n p of0.1mol dm−3HCl and phosphate buffer into the pure HPMC and mixed HPMC/ SDWMT matrices are presented in Tables1and 2,respectively.With both solvents,the values of n p,ranging between0.53and0.59for all hy-drogels examined,determine a diffusion-con-trolled water sorption whose mechanism depending mainly on the hydrogel structure is inﬂuenced insigniﬁcantly by the relaxation proper-ties of hydrated macromolecules.As an exception, the HPMC/SDWMT20/80formulation displays a non-Fickian penetration behaviour(n p=0.32and 0.35for pH1.0and6.8,respectively).It is proba-bly due to the hydrogel structural characteristics, the lower swelling degree of pregelatinized starch and the slow erosion of the hydrated matrix. The molsidomine release proﬁles of the pure HPMC and mixed HPMC/SDWMT hydrogels in acid medium(pH1.0)and phosphate buffer(pH 6.8)are shown in Fig.2(a)and(b),respectively.V .Michailo 6a et al ./International Journal of Pharmaceutics 222(2001)7–1712In both dissolution media,the degree of drug release is the lowest with the HPMC matrices,the release rate being gradually enhanced with the increase of the pregelatinized starch fraction (Ta-bles 1and 2,respectively).An inverse proportion is observed between the velocities of both water penetration and drug release.The proportion sug-gests that the gel layers formed probably possess a heterogeneous microporous structure and a high diffusion capability.With all mixed HPMC /SD-WMT hydrogels,the values of the release expo-nent,n ,are close to 0.45(0.42–0.59)which is typical of a diffusion-controlled drug release pro-cess.The increase of the amount of pregelatinized starch in the tablets leads to a decrease in the values of n down to 0.45,which describes the systems rather as porous matrices.The usual kinetic swelling properties deter-mined for solvent-activated controlled-release sys-tems (i.e.degree and velocity of both water penetration and swelling,transport mechanism which controls solvent sorption)are directly re-lated to the drug release behaviour but they are insuf ﬁcient for prediction purposes regarding un-limited swelling hydrogels.The dependence be-tween the velocities of both water penetration and drug release processes as well as their identical mechanism show that the structural features of mixed HPMC /pregelatinized waxy maize starch hydrogels are the major factor controlling the drug release kinetics.To examine their inherent structure a comparative rheological analysis of hydrogel viscoelastic properties is used.3.2.Viscoelastic properties of mixed HPMC /SDWMT hydrogel systemsThe mechanical spectrum of both HPMC and mixed HPMC /SDWMT hydrogels in 0.1mol dm −3HCl obtained by means of a dynamic oscillation program are shown in Fig.3(a)–(e).The pure HPMC keeps its elastic character (G %\G %%),G %and G %%increasing as a function of fre-quency (Fig.3(a)),which determines the gel ’s ability to maintain a comparatively strong net-work structure (Michailova et al.,1999).Adding pregelatinized starch to the hydrogel changes the viscoelastic response.At low SDWMT percentage (20%)in the system,the elastic behaviour of the pure HPMC transforms into a viscoelastic one (G %:G %%)which is typical of weak structure hy-drogels in solid-to-liquid transition state (Fig.3(b)).With mixtures containing 40%starch,the relaxation spectrum suddenly changes its charac-ter (Fig.3(c));the system is in liquid-like state (G %B G %%)which is observed with concentrated polymer solutions under their critical gel concen-tration and with composite polymer systems ﬁlled with elastic ﬁllers at their maximum packing (Ferry,1980).The increase of pregelatinized starch quantity up to 60%reinforces the hydrogel structure modifying its liquid-like properties into viscoelastic ones (Fig.3(d)).With mixed hy-drogels containing 80%starch,the elastic be-haviour dominates throughout all the frequency ranges applied and there is a clearly expressedFig.2.Molsidomine release pro ﬁles of HPMC and mixed hydrophilic matrices.(a)0.1mol dm −3HCl medium;and (b)pH 6.8phosphate buffer.( )HPMC;and mixed HPMC /SDWMT matrices:( )80/20,( )60/40,( )40/60,(")20/80.V .Michailo 6a et al ./International Journal of Pharmaceutics 222(2001)7–1713Fig.3.Mechanical spectrum of HPMC and mixed HPMC /SDWMT hydrogels in 0.1mol dm −3HCl medium.(a)HPMC;and mixed HPMC /SDWMT hydrogels:(b)80/20;(c)60/40;(d)40/60;(e)20/80.G %( ),G %%( ),p %( ).plateau zone in the elastic modulus curve (Fig.3(e)).The mechanical spectrum obtained is typical of strong physical gels which is probably due to the highly-branched structure of the amylopectin molecule,its restricted mobility and low water-re-taining capacity (Hanselmann et al.,1996).In a phosphate buffer,the viscoelastic behaviour of the mixed HPMC /SDWMT hydrogels is similar to that of the acid medium (Fig.4(a)–(e)).The presence of 20–40%starch in the systems leads to weakening of the gel structure (Fig.4(a)–(c)).Its liquid-like properties (G %B G %%)change into vis-coelastic and elastic ones with the increase of the amount of SDWMT (60and 80%,respectively;Fig.4(d)and (e)).The rheograms of the hydrogel systems studied show that there is a sharply outlined boundary-line between the rheological behaviour of the hy-V .Michailo 6a et al ./International Journal of Pharmaceutics 222(2001)7–1714drogels containing up to 60%pregelatinized starch and the 20/80HPMC /SDWMT system.With hydrogels containing up to 60%SDWMT,the viscoelastic responses are situated in neigh-bouring,close-lying regions of the mechanical spectrum (i.e.in the beginning of the viscoelastic region,in the transition zone,and in the end of the terminal region),a fact which indicates swelled polymer systems having gel-like proper-ties.Their comparatively weak intra-molecular links facilitate the processes of both the aqueous penetration and the acceleration of the macro-molecular relaxation,which results in a higher hydration velocity of the mixed matrices.The weaker gel structure is probably a cause of the similarity in the water penetration rate constants because it gives one and the same relaxation opportunities to the molecules of the two poly-mers during the process of swelling.As different from the rheological response of the pure HPMCFig.4.Mechanical spectrum of HPMC and mixed HPMC /SDWMT hydrogels in pH 6.8phosphate buffer.(a)HPMC;and mixed HPMC /SDWMT hydrogels:(b)80/20;(c)60/40;(d)40/60;(e)20/80.G %( ),G %%( ),p %( ).V .Michailo 6a et al ./International Journal of Pharmaceutics 222(2001)7–1715parison of storage modulus (G %)curves of the gel systems as a function of the angular frequency in (a)0.1mol dm −3HCl medium and (b)pH 6.8phosphate buffer.( )HPMC;and mixed HPMC /SDWMT hydrogels:( )80/20,( )60/40,( )40/60,(")20/80.located at the beginning of the viscoelastic region,the one of the mixed hydrogel containing 80%SDWMT lies in the plateau zone of the mechani-cal spectrum which reveals an enhanced elasticity,a greater density of the network,and a stronger hydrogel structure.Such a highly elastic system resists the penetrant uptake to a signi ﬁcant degree (Gehrke,1992)and determines the considerably lower swelling extent of the hydrogel.Fig.5(a)and (b)represents the elastic moduli curves (G %)of the pure HPMC and mixed HPMC /SDWMT systems in acid medium and phosphate buffer,respectively,as a function of the angular frequency.Similar change of the gel strength is obtained in both media tested.Regardless of the quantitative proportion of the two polymer com-ponents,the shape of the G %curves of all mixed hydrogels and their slopes look the same but they differ from those of the pure HPMC considerably.This fact indicates that the rheological behaviour of the swelled starch grains determines both the elastic response and the gel strength of the mixed systems.The morphological analysis of mixed HPMC /SDWMT hydrogels and the dependence between their viscoelastic behaviour and polymers propor-tions characterize them as ‘ﬁlled ’composite sys-tems having poor adhesion between the surface of the elastic ‘ﬁller ’and the continuous phase (Schultz,1974).With such systems,the disperse phase of the elastic SDWMT ﬁller functions as asupporting structure,while the linear HPMC forms the disperse medium but it has no support-ing capability because of its weaker structure.For this reason,at low concentrations of the pregela-tinized starch,a common homogeneous HPMC network cannot be formed which suggests the existence of a porous gel structure and an in-creased diffusion capability.With the increase of the starch volume fraction (60–80%),a phase inversion occurs.The swelled starch particles form strong supporting structure whose compara-tively high rigidity causes the solid-like behaviour observed.The porous structure of the gel layer is probably preserved because the low mobility of amylopectin molecule con ﬁnes the formation of inter-penetrating network at the starch granule surfaces.Those features of the inherent hydrogel structure of mixed HPMC /SDWMT hydrophilic matrices explain the direct proportion between molsidomine release velocity and the pregela-tinized waxy maize starch content.4.ConclusionsThe kinetic swelling properties of both mixed HPMC /SDWMT hydrogels (i.e.degree and veloc-ity of both water penetration and swelling,trans-port mechanism which controls solvent sorption)directly in ﬂuence the drug release behaviour and the structural features of the formed gel layer.TheV.Michailo6a et al./International Journal of Pharmaceutics222(2001)7–17 16processes of both water penetration and drug release from the mixed hydrogels are diffusion-controlled ones,their mechanisms being inﬂu-enced insigniﬁcantly by the relaxation properties of the hydrated macromolecules.The speciﬁc structural dependence obtained for mixed HPMC/ SDWMT hydrogels deﬁnes them as‘ﬁlled’com-posite systems with poor adhesion between the surface of the elastic SDWMT‘ﬁller’and the continuous HPMC phase.Due to the inter-phase relations between the swollen starch granules and the linear cellulose derivative as well as to the speciﬁc structure of amylopectin molecule,the pregelatinized waxy maize starch shows a stronger inﬂuence on the velocities of both water penetra-tion and drug release from mixed HPMC/SD-WMT matrices.AcknowledgementsWe would like to thank Professor J.P.Remon (State University of Gent,Belgium)for his cour-tesy to provide the pregelatinized SDWMT starch for this research.ReferencesBagley,E.B.,Christianson,D.D.,1982.Swelling capacity of starch and its relationship to suspension viscosity–effect of cooking time,temperature,and concentration.J.Tex-ture Stud.13,115–126.Carnali,J.O.,Zhou,Y.,1996.An examination of the 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英语作文论题

1.The Impact of Technology on Modern Education Discuss how technological advancements have transformed the way we learn and teach.2.The Role of Social Media in Shaping Public Opinion Explore the influence of social media platforms on public perception and how it affects societal issues.3.Environmental Conservation:A Collective Responsibility Argue the importance of individual and collective efforts in preserving the environment.4.The Benefits of Bilingualism Elaborate on the cognitive,social,and professional advantages of being bilingual.5.The Ethics of Genetic Engineering Analyze the moral implications of genetic engineering and its potential impact on society.6.The Influence of Cultural Diversity on Global Business Discuss how cultural diversity can enhance or challenge international business practices.7.The Importance of Mental Health Awareness Advocate for the significance of mental health awareness in reducing stigma and improving wellbeing.8.The Effects of Globalization on Local Economies Examine the positive and negative economic impacts of globalization on local communities.9.The Role of Art in Society Reflect on how art can serve as a medium for expression, communication,and social change.10.The Challenges of Climate Change Discuss the scientific,political,and social challenges posed by climate change and potential solutions.11.The Evolution of Privacy in the Digital Age Consider how the concept of privacy has evolved with the rise of digital technology and its implications for individuals and society.12.The Impact of Urbanization on Rural Communities Analyze the effects of urbanization on rural areas,including migration,economic shifts,and cultural changes.13.The Significance of Education in Achieving Gender Equality Argue how education plays a crucial role in promoting gender equality and empowering women.14.The Role of Sports in Promoting National Identity Discuss how sports can foster asense of national pride and unity.15.The Ethics of Animal Testing Debate the ethical considerations surrounding the use of animals for scientific research and product testing.16.The Impact of Artificial Intelligence on Employment Consider the potential job displacement and creation due to advancements in AI and automation.17.The Importance of Sustainable Development Discuss the principles of sustainable development and its role in balancing economic growth with environmental protection.18.The Influence of Media on Body Image Explore how media representations of beauty can affect individuals selfesteem and body image.19.The Challenges of Refugee Crises Analyze the global refugee crisis,its causes,and the international communitys response.20.The Power of Volunteering Reflect on the personal and societal benefits of volunteering and its role in community development.。

东北黑土区耕地系统变化机理

第37卷第6期农业工程学报 V ol.37 No.62021年3月Transactions of the Chinese Society of Agricultural Engineering Mar. 2021 243东北黑土区耕地系统变化机理苏浩，吴次芳※（浙江大学公共管理学院，杭州，310058）摘要：耕地系统变化直接影响耕地生产能力和国家粮食安全。

该研究以东北黑土区典型地域克山县为研究区，重构耕地系统的科学内涵，运用GIS、RS手段和Matlab计算机编程，采用地理探测器模型，识别研究区1986年、2010年和2018年耕地系统变化关键影响因子，测算关键影响因子、各因子间交互作用对耕地系统变化的作用关系，揭示研究区耕地系统变化机理。

结果表明：1）耕地系统是具有长、宽、高的有机立体空间，在一定范围内是所有要素综合作用结果，同时它受周围环境影响与垂直方向、水平方向因子共同形成一个微生态环境。

2）1986年、2010年和2018年影响耕地系统变化的关键影响因子分别为5个、8个和6个。

1986—2018年不同时期耕地系统变化均受系统内部因子作用的影响，随着时间推移，水平方向作用因子对耕地系统变化的影响逐年加强，垂直方向作用因子的影响减弱，表现为影响耕地系统变化程度的关键影响因子由自然要素为主，转向自然与人类活动因素的双重影响。

其他因子影响相对较弱。

3）1986—2018年不同时期耕地系统内部影响因子与垂直和水平方向的其他因子交互作用对耕地系统变化的影响均为最大，水平方向与垂直方向的交互作用在研究期间影响的显著性显化程度不同。

与关键单一因子对耕地系统的影响相比，因子间交互作用后对研究区耕地系统变化空间分异的解释能力明显高于单一因子对其作用，具体表现为双因子增强或非线性增强的特征。

研究结果较好地反映了不同时期耕地系统变化空间分异的各因素单一和交互作用关系，为保护耕地和保障粮食安全提供了科学依据。

关键词：土地利用；遥感；耕地；东北黑土区；微生态环境；粮食安全；机理doi：10.11975/j.issn.1002-6819.2021.06.030中图分类号：F302.2 文献标志码：A 文章编号：1002-6819(2021)-06-0243-09苏浩，吴次芳. 东北黑土区耕地系统变化机理[J]. 农业工程学报，2021，37(6)：243-251. doi：10.11975/j.issn.1002-6819.2021.06.030 Su Hao, Wu Cifang. Mechanism of cultivated land system change in black soil areas of Northeast China[J]. Transactions of the Chinese Society of Agricultural Engineering (Transactions of the CSAE), 2021, 37(6): 243-251. (in Chinese with English abstract) doi：10.11975/j.issn.1002-6819.2021.06.030 0 引言耕地系统是粮食生产最基本的载体和生境条件，具有复杂性、自组织性、时空动态性、恢复性和非线性等耗散结构特征[1]。

水位变化对正倒锥体冰载荷影响的离散元分析

第51卷第1期力学学报V ol.51，No.1 2019年1月Chinese Journal of Theoretical and Applied Mechanics Jan.，2019颗粒材料计算力学专题水位变化对正倒锥体冰载荷影响的离散元分析1)龙雪∗刘社文†季顺迎∗,2)∗(大连理工大学工业装备结构分析国家重点实验室，大连116024)†(大连海事大学船舶与海洋工程学院，大连116026)摘要在海冰与锥体海洋结构的相互作用过程中，潮汐水位变化时海冰作用于锥体结构的位置改变对冰载荷具有显著影响.本文采用具有粘结破碎功能的离散元方法计算海冰与锥体作用的破坏过程.同时考虑海冰上下表面温度差异对海冰强度的影响，将离散元计算冰载荷及海冰破坏模式与渤海现场实测数据进行对比验证.离散元结果表明，海冰与正锥和倒锥碰撞时均发生弯曲破坏，且冰载荷均随水线处锥径的增大而增大.在水线处锥径相同的情况下，正锥冰载荷大于倒锥冰载荷，而正锥作用下海冰的断裂长度则较小.基于离散元计算结果和渤海现场观测资料分析了海冰与正锥、倒锥作用时冰载荷和断裂长度差异的主要原因.海冰与正倒锥交界线处作用时，一般发生弯曲破坏.当冰层中心高度与正倒锥交界线的高度相同时，海冰才会发生局部挤压破碎，但冰荷载并没有明显升高.由此可见，倒锥体结构可有效降低冰载荷从而具有较好的抗冰性能.以上研究表明离散元方法可确定海冰与锥体结构作用时的海冰破碎规律和冰载荷特性，为海洋工程结构的抗冰设计提供参考依据.关键词离散元方法，锥体结构，冰载荷，破坏模式，正倒锥体交界线中图分类号：P751,P731.15文献标识码：A doi：10.6052/0459-1879-18-342INFLUENCE OF WATER LEVEL ON ICE LOAD ON UPWARD-DOWNW ARD CONICALSTRUCTURE BASED ON DEM ANALYSIS1)Long Xue∗Liu Shewen†Ji Shunying∗,2)∗(State Key Laboratory of Structure Analysis of Industrial Equipment,Dalian University of Technology,Dalian116024,China)†(Nava Architecture and Engineering College,Dalian Maritime University,Dalian116026,China)Abstract During the interaction between the sea ice and the conical structure,the ice load is aﬀected by the position of the sea ice acting on the conical structure when the tidal water level changes.In this study,the discrete element method (DEM)with the bond and failure model is adopted to simulate the breaking process of sea ice acting on the conical structure.In DEM simulations,the inﬂuence of the ice temperature at the top and bottom surface of ice cover on the ice strength is considered.The ice load and the failure mode of ice cover simulated with DEM are compared well with theﬁeld data in the Bohai Sea.The DEM results indicate that the bending failure of ice cover occurs when it acts on the upward or downward cone.For both of the upward and downward cone,the ice load increases with the increase of the cone diameter at water level,but the ice load on upward cone is larger than that of downward cone.Meanwhile,the breaking length of ice cover on upward cone is smaller than that on the downward cone.The reasons for the diﬀerence2018–10–11收稿,2018–12–16录用,2018–12–17网络版发表.1)国家重点研发计划重点专项(2016YFC1401505,2016YFC1402706)和国家自然科学基金项目(51639004,41576179)资助.2)季顺迎，教授，主要研究方向：计算颗粒力学及工程应用.E-mail:jisy@引用格式：龙雪,刘社文,季顺迎.水位变化对正倒锥体冰载荷影响的离散元分析.力学学报,2019,51(1):74-84Long Xue,Liu Shewen,Ji Shunying.Inﬂuence of water level on ice load on upward-downward conical structure based on DEM analysis.Chinese Journal of Theoretical and Applied Mechanics,2019,51(1):74-84第1期龙雪等：水位变化对正倒锥体冰载荷影响的离散元分析75of ice load and breaking length between upward cone and downward cone are analyzed based on the DEM results and theﬁled observation in the Bohai Sea.Moreover,when the sea ice interacts with the interface of upward and downward cone,bending damage generally occurs.When the height of the ice cover center is very close to the height of the upward-downward cone interface,the local ice crushing occurs,but the ice load does not increase signiﬁcantly.Therefore,the downward conical structure has better performance of ice resistance with eﬀectively reducing the ice load.The DEM can be adopted to understand the mechanism of ice cover failure process,and provide reference for the anti-ice design of structures in cold ocean engineering.Key words discrete element method,conical structure,ice load,failure mode,interface of upward and downward cone引言在高纬度寒区海域，锥体平台结构因具有良好的抗冰性能而被广泛应用，如渤海的导管架平台、加拿大Confederation桥墩、芬兰Kemi-Ⅰ灯塔等[1-3].海冰与锥体结构作用时的主要破坏模式为弯曲破坏，且作用在锥体结构上的冰载荷具有明显的周期性[4-5].由于海冰的弯曲强度较小，且载荷作用周期较长，锥体结构在减小冰载荷和降低冰激振动方面具有显著优势[6-7].为保障寒区海域平台结构的安全运行，海冰的力学性质、锥体结构参数以及锥体结构冰载荷特性等相关研究受到较多关注[8-10].理论分析、现场测量、室内模型试验及数值模拟是海洋结构冰载荷研究的主要方法[11-13]，其中数值模拟具有成本低、周期短以及可重复性高等优点，成为工程海冰领域的重要研究途径.我国对锥体海洋平台结构的现场测量主要是在渤海JZ20-2和JZ9-3海域的导管架海洋平台上展开的，并基于大量实测数据建立了锥体结构的动冰力函数和冰力谱[14-15].Qu等[16]对实测冰载荷进行谱分析，研究锥体冰载荷的频率及冰激振动情况，为锥体冰载荷的研究提供了重要的现场数据.但由于现场实测结果受到复杂环境和测试误差等因素的影响，深入探究单一变量对冰载荷的影响具有较大难度.为研究锥体尺寸参数对其抗冰性能的影响，Xu 等[17]建立了渤海JZ20-2MUQ平台的等比例缩放模型，并在德国汉堡冰池(HSV A)进行了相关室内模型试验.该试验结果表明冰排与窄锥结构作用后呈楔型断裂，而与宽锥作用后呈板形断裂且冰载荷较大. Tian等[18]在冰池内的模型试验中发现，当锥径与冰厚比值小于30时冰载荷随锥径的增大而增大.以上研究均表明锥径大小是影响冰载荷和海冰破坏模式的重要因素.对于渤海锥体导管架海洋平台结构，潮汐变化会引起海冰作用位置处锥径的差异，并导致锥体冰载荷的显著变化.海冰与正锥作用将发生向上弯曲破坏，而与倒锥作用将发生向下弯曲破坏[19].当水线处的锥体直径相同时，正锥冰载荷要明显大于倒锥冰载荷[17].史庆增等[20]在试验中发现海冰与正倒锥交界处作用时发生挤压破碎的情况.但对于该挤压破碎发生机理的研究还不够完善，且海冰与锥体不同位置作用的冰载荷及破坏模式问题还需更深入研究.在冰载荷的现场测量和模型试验中，均较难测得海冰内部裂纹的发生和演化过程，而数值方法则可深入分析影响冰载荷变化的海冰断裂特征[21−22].采用有限元方法可对海冰与锥体作用过程中海冰的应力分布进行研究，但缺少对海冰断裂过程的分析[23].采用光滑粒子流体动力学方法可模拟海冰与船舶结构作用，但难以模拟海冰破碎后的动力学过程[24].另外，近场动力学等粒子方法也可对海冰的断裂过程进行模拟[25].但以上方法受到边界参数等影响较大，对海冰破碎过程的模拟具有一定的局限性.近年来，离散元方法(discrete element method, DEM)不仅可计算离散颗粒材料的力学性质[26-28]，在模拟海冰、岩石、石英玻璃等脆性材料中也有广泛应用，可更准确高效地用于描述脆性材料由连续体向散体转化的破碎特性[29-30].Hopkins[31]最早采用二维离散元模拟平整冰在斜面结构前的破碎堆积并形成冰脊的过程.Paavilainen等[32]采用二维有限元和离散元耦合方法(FEM-DEM)模拟了海冰在斜坡上的断裂堆积过程.为进一步提高离散元方法的准确性，Lau[33]采用三维块体离散元模型计算海冰的破碎过程，但计算规模难以满足工程应用需求.狄少丞等[34]将GPU高性能运算引入离散元方法中，并用于海冰与多桩腿结构作用的数值模拟，有效解决了工程尺度下离散元的计算效率问题.目前，离散76力学学报2019年第51卷元方法在海洋结构、船舶结构、核电站取水口等的结构设计及冰载荷计算中应用广泛，为具体的工程实践提供了有力的参考依据[35-36].本文采用具有粘结破碎功能的离散元方法模拟平整冰与正倒锥体结构的相互作用过程，研究海冰与锥体不同位置作用时海冰的破坏模式和冰载荷的变化规律，分析正倒锥交界处海冰破坏模式的变化情况，并揭示海冰与锥体结构不同位置作用时的破碎机理和冰载荷特性.1海冰与锥体结构作用的离散元方法1.1海冰颗粒单元的平行粘结模型采用离散元模拟海冰与锥体作用时，将海冰视为具有一定质量和大小的球形颗粒集合.按照六方最密堆积的方式将球形颗粒规则排列成平整冰.该排列方式具有对称性好，密集度高等特点[34].通过平行粘结模型将排列后的颗粒互相粘结，粘结颗粒间通过平行圆盘传递力和力矩，如图1所示[37].图1球体颗粒的平行粘结模型Fig.1Parallel bond method of spherical particles在平行粘结模型中，F n 和F s 分别为颗粒间的法向力和切向力，M n 和M s 分别为颗粒间的法向力矩和切向力矩.根据梁在横力作用下的弯曲理论，作用在粘结圆盘上的最大正应力和最大剪应力可分别表示为[37]σmax =F n A +sign(F n )|M s |IR ,τmax =|F s |A +|M n |JR (1)式中，A 为粘结圆盘的横截面积，J 为粘结圆盘的极惯性矩，I 为粘结圆盘的惯性矩，可分别表示为A =πR 2,I =14πR 4,J =12πR 4(2)式中，R 为粘结圆盘的半径，即球体颗粒的半径.1.2海冰粘结颗粒单元的失效准则为模拟海冰的断裂过程，这里考虑粘结颗粒单元间的粘结失效功能，其失效模式主要分为拉伸失效和剪切失效.图2中当粘结圆盘的最大正应力σmax >0时，则表示两个粘结颗粒处于压缩状态，其可发生剪切破坏；相反，当σmax <0时，则表示两个粘结颗粒处于拉伸状态，其可发生剪切或拉伸破坏.当粘结圆盘的最大正应力σmax 超过颗粒间的拉伸强度σt ，即σmax >σt ，粘结圆盘发生拉伸失效；当最大剪应力τmax 超过颗粒间的剪切强度τs ，即τmax >τs 时，粘结圆盘发生剪切失效.图2粘结颗粒的破坏失效准则Fig.2Failure criterion of bonded particles颗粒单元的拉伸破坏强度τt 和剪切破坏强度τs与颗粒间法向粘结强度σn b 和切向粘结强度σs b 密切相关.本文采用摩尔–库伦摩擦准则对剪切破坏强度进行确定[38]，即σt =σn b(3)τs =σs b +µb σmax(4)式中，µb 是海冰粘结颗粒之间的内摩擦系数，µb =tan ϕ，ϕ为粘结颗粒单元间的内摩擦角.粘结颗粒间法向和切向粘结强度的选取是影响离散元计算准确性的关键.它决定了海冰材料的压缩强度和弯曲强度等物理力学性质，也影响海冰与海洋结构作用时的破坏模式.此外，颗粒之间粘结失效可视为冰内裂纹的产生，粘结破坏的颗粒数量增加意味着冰内裂纹的扩展，宏观表现为海冰的断裂过程.当海冰与海洋结构相互作用发生破碎后，离散的海冰颗粒单元间的接触力采用赫兹接触模型进行计算，以确定碎冰的运动规律.1.3海冰强度与温盐分布的对应关系海冰强度与其温度、盐度均有密切关系.由于海水和空气温度不同，同时受海冰生消过程中冰内盐第1期龙雪等：水位变化对正倒锥体冰载荷影响的离散元分析77度的变化，海冰内部竖直剖面上的温度和盐度分布不是均匀的，由此导致海冰的强度分布也随之变化.渤海海冰的强度与温盐之间的关系可写作[4]v b =S i 0.532+49.185|T i |(5)σf =2.98e−5.06√v b(6)式中，T i 为海冰温度(°C)，−0.5°C T i −22.9°C ；S i 为海冰盐度(‰)；v b 为海冰的卤水体积(‰)；σf 为海冰的弯曲强度(MPa).当海冰与正锥体作用时，其下表面发生拉伸破坏，而与倒锥体作用时，则其上表面发生拉伸破坏.由于海冰上下表面及其内部的温度、盐度均有一定的差异，导致海冰内部强度的不同.本文在海冰的离散元计算中，将考虑其竖直剖面内强度的差异.为简化计算，这里忽略海冰剖面内盐度的变化，并假设海冰温度在竖直剖面内呈线性分布，从而将海冰强度设为海冰温度的线性函数.海冰的弯曲强度(σf )与颗粒单元的粘结强度(σb )紧密相关，可通过对海冰的三点弯曲试验确定海冰宏观强度与离散元微观参数之间的关系[39]σb =σf /(1.77−1.81e −h i /D p4.78)(7)式中，D p 为颗粒单元直径；h i 为海冰厚度.该关系式与渤海现场试验中测得的海冰弯曲强度对比验证结果良好[37]，可用于渤海海冰力学性质的模拟分析，是海冰离散元参数选取的重要依据.2海冰与正倒锥结构作用的离散元分析2.1海冰离散元参数的设定以渤海JZ20-2平台的锥体结构与海冰的相互作用为研究对象(如图3)，并参考渤海海冰的物理力学性质，建立海冰和锥体结构作用的离散元模型.为对比分析正锥和倒锥的冰载荷，在本文离散元模拟中设定正倒锥的倾斜角α均为60◦，锥体最大直径为4.0m ，最小直径为1.5m ，如图4(a)所示.当水位线高度(H )发生变化时，水线处的锥径(D )也随之变化.图4(b)为海冰的离散元模型，海冰不与结构碰撞的三个边界均采用弹簧边界进行弹性约束.该弹簧边界的刚度与颗粒间的接触刚度相同且在x 方向具有与海冰相同的运动速度.这样可采用有限尺寸的海冰区域近似模拟无限大平整冰与锥体结构的相互作用.同时，考虑海水对海冰单元的浮力和拖曳作用，并将海水流速设为常值[13].图3渤海JZ20-2正倒锥体导管架海洋平台Fig.3The JZ20-2jacket platform with upward-downwardcone in the BohaiSea图4海冰与锥体结构相互作用的离散元模型Fig.4DEM of the interaction between ice and conical structure这里的离散元计算参数由渤海海冰物理力学性质的现场和室内实测数据确定[4,16]，并列于表1中.首先根据式(5)和式(6)可推算海冰上下表面的弯曲强度，冰层上表面弯曲强度为1.91MPa ，下表面的弯曲强度为1.26MPa.再由式(7)对颗粒单元的粘结强度进行推算，上表面颗粒间的粘结强度为1.86MPa ，下表面颗粒间的粘结强度最小为1.22MPa ，并对中间颗粒的粘结强度进行线性插值.78力学学报2019年第51卷表1离散元计算的主要参数Table1Main parameters of DEM calculationDeﬁnition Symbol Valuedensity of sea waterρw1035.0kg/m3density of sea iceρi920.0kg/m3velocity of sea ice v i0.4m/sthickness of sea ice h i0.23mcalculation area size of sea ice l×w13.0m×13.0melastic modulus of sea ice E 1.0GPadiamete of particle cell D p0.054m total number of particle elements N p 2.9×105friction coeﬃcient ofµb0.2particle elementcoeﬃcient of friction betweenµs0.2sea ice and structuresalinity of sea ice S i 1.0‰upper and lower surfaceT i−7.0°C，−1.73°C temperatures of sea ice2.2正锥与倒锥上冰载荷的对比分析在渤海现场监测中，在正锥体上安装了压力传感器以测量结构冰载荷[1,16-17].这里采用该现场实测数据与离散元模拟结果进行对比验证.在对比分析海冰作用在正、倒锥体上的破坏模式时，均取结构水线处锥径为3.2m，其他计算参数相同.(1)正锥体上的冰载荷图5为不同时刻海冰作用在正锥体上的破碎过程，用不同颜色区分海冰弯曲破碎后的碎冰分布情况.冰排与正锥作用时，冰排内部产生径向裂纹及环向裂纹使冰排发生向上的弯曲破坏.破碎后的海冰多呈楔形块状分布在锥体周围，并在后续冰排的推动下沿锥面继续向上爬升并不断堆积.爬升的碎冰块在重力作用下将滑入水中，然后在海水的拖曳作用下向前继续漂移并从锥体两侧清除，由此形成一个完整的冰载荷周期.从冰块的破坏特性看，模拟结果与图6中渤海JZ20-2海洋平台的实测结果在规律上基本一致.图7(a)为渤海JZ20-2锥体平台上的冰载荷实测数据，图7(b)为本文离散元计算结果.该图表明离散元模拟的锥体冰载荷与实测结果在形式上均有明显的周期性特点.这是由于海冰与锥体作用时均发生弯曲破坏.在冰排和结构作用的加载和卸载过程中，冰排发生弯曲破碎时会形成较大的作用力.冰排破碎后，该作用力迅速减小直到后续冰排再次作用到锥体上.除考虑冰载荷的最大值外，还采用冰载荷时程中冰载荷峰值的均值作为对比分析的主要指标，以降低冰载荷时程的随机性影响.这里，渤海实测冰载荷峰值的最大值和均值分别为145.9kN和116.9kN，而本文离散元方法计算得的结果分别为166.5kN和128.5kN.可以看出，离散元的计算结果比实测结果略大.但考虑到离散元计算中的海冰参数与现场实测结果存在一定差异，该结果误差在可接受范围内.从图7(a)和图7(b)还可发现，在22s内的实测值和计算值均有9个明显的冰载荷峰值.这说明计算所得的冰载荷周期与实测结果较为接近.由此可见，从冰排的破坏模式、冰载荷的大小和周期上来看，离散元计算结果与渤海实测数据均比较一致，从而验证了该离散元方法及计算参数在锥体结构冰载荷模拟中的准确性.图5离散元模拟海冰与正锥体作用的破坏过程Fig.5Failure process of sea ice acting on upward cone simulated byDEM第1期龙雪等：水位变化对正倒锥体冰载荷影响的离散元分析79图6渤海JZ20-2平台海冰与正锥体作用Fig.6Interaction of sea ice and upward cone observed on the JZ20-2platform in the BohaiSea图7渤海实测冰载荷与离散元模拟结果对比Fig.7Comparison of ice loads on upward cone measured in the BohaiSea and simulated with DEM(2)倒锥体上的冰载荷潮汐会对海洋平台结构的水线高度造成影响，进而决定了海冰对锥体结构的作用位置.在较低水位时，海冰将作用于倒锥体上.图8为海冰与倒锥作用的离散元模拟结果.对于倒锥结构，海冰会发生向下的弯曲破坏，产生的碎块在海水的浮力和拖曳力作用下直接被清除.与正锥海冰的破坏过程相比，缺少碎冰沿结构表面堆积攀爬的过程.对比图5和图8中不同颜色的海冰碎块尺度，海冰与正锥作用后的海冰破碎尺寸明显小于倒锥的海冰碎块.海冰在倒锥体上破碎的实测现象如图9所示，其在冰块破碎规律上与本文离散元计算结果相一致.图8离散元模拟海冰与倒锥体作用的破坏过程Fig.8Breaking process of sea ice acting on downward cone simulatedwith DEM图10为离散元模拟的倒锥体上冰载荷变化情况，其最大值为81.9kN，峰值的均值为67.9kN.在以上正锥体和倒锥体的冰载荷计算中，海冰的计算参数包括锥径和流速等均相同.但正锥体上的冰载荷要明显大于倒锥体上的冰载荷，正锥体上的冰载荷周期也相应地小于倒锥体上的冰载荷周期.这主要是由于海冰在正锥体上会有破碎、爬升和清除过程，而在倒锥体上只有破碎和清除过程.碎冰块在正锥体的爬升过程中，上爬的碎冰块会对锥前冰盖在80力学学报2019年第51卷破碎前产生约束，从而提高了海冰发生弯曲破碎的作用力，即对锥体结构的作用力.然而，仅在冰排与倒锥体作用时，海冰在水面下受到的浮力稍大于重力，其不会在锥体前发生堆积，从而使海冰发生弯曲破坏的作用力也相对较小.图9渤海JZ20-2平台监测海冰与倒锥作用情况Fig.9Interaction of sea ice and downward cone observed the JZ20-2platform in the BohaiSea图10离散元模拟的倒锥体上冰载荷时程Fig.10Time series of ice loads on downward cone simulated by DEM2.3正锥与倒锥上海冰断裂长度的对比在海冰与锥体结构作用的弯曲破坏过程中，海冰的断裂长度决定了冰载荷的周期，同时也对冰载荷的大小有显著影响.这里定义无量纲海冰断裂长度λ=L b /h i ，式中L b 为断裂长度；h i 为海冰厚度.渤海JZ20-2锥体海洋平台上的场测量结果表明，λ均值在7.0左右[15].海冰的断裂长度不仅与其强度、密度、摩擦系数等因素有关，同时还受锥角、锥径及冰速等诸多因素的影响.下面采用离散元方法对海冰与正、倒锥作用的断裂长度进行对比分析.在计算海冰的断裂长度时，仅选取冰排在锥体结构前初次发生断裂时的径向长度，如图11所示.图12将以上DEM 计算得到的海冰与正锥、倒锥作用时的断裂长度进行对比，图中断裂长度值为对应时下刻锥体前所有断裂冰块尺寸的平均值.海冰作用在正、倒锥体上的无量纲断裂长度λ分别为6.9和10.8，即倒锥体上的断裂长度要明显大于正锥体.图11离散元模拟海冰的断裂长度Fig.11Breaking length of ice cover simulated withDEM图12正倒锥的海冰断裂长度Fig.12Breaking length of ice cover acting on upward anddownward cones3海冰与正倒锥作用位置对冰载荷的影响3.1锥径影响下正锥和倒锥体上的冰载荷随着潮汐水位的升降，海冰将分别作用于正锥体或倒锥体上，同时水线处锥径也会产生变化.下面通过离散元方法对正锥和倒锥上不同锥径下的冰载荷进行计算并对比分析.由于冰载荷时程具有显著的随机性，这里选取冰载荷时程曲线中所有载荷峰值点的平均值进行对比.图13(a)为正锥和倒锥上冰载荷随锥径的变化情况.从中可以看出，正锥与倒锥上冰载荷都随锥径的增大而增大，且倒锥体上的冰载荷明显低于倒锥体.图13(b)为正锥和倒锥上无量纲海冰断裂长度λ随锥径的变化情况.结果表明，锥径对海冰断裂长度的影响并不明显，但正锥体作用下的海冰断裂长度要明显小于倒锥体.下面分别从海冰的破碎过程、受力情况及海冰温度分布等三个方面分析正倒锥上冰载荷和断裂长度的差异.当海冰与正锥作用时，正锥水平方向的冰载荷可分为破碎力和攀爬力两部分.破碎力是在海冰发生弯曲破坏时产生的冰载荷；攀爬力则是碎冰块在锥体表面攀爬和堆积产生的.当海冰与倒锥作用时，海冰弯曲破坏时同样会产生破碎力，但碎冰块在重力和浮力共同作用下，很难在倒锥体表面爬升，其爬第1期龙雪等：水位变化对正倒锥体冰载荷影响的离散元分析81升力可以忽略不计.此外，当锥径越大时，海冰与锥体的等效接触面积也就越大，正锥体上的海冰堆积和攀爬作用也会增大，从而导致了冰载荷显著增大.图13锥径对冰载荷及断裂长度的影响Fig.13E ﬀect of cone diameter on ice load and breaking length当海冰作用于正锥体结构而向上发生弯曲破碎时，海冰向上翘起并沿结构表面攀爬.当海冰脱离水面后浮力消失，向下的重力作用会阻止海冰继续向上弯曲.然而，当海冰作用于倒锥体结构而向下发生弯曲破坏时，海冰始终处于水面下方，同时受重力和浮力的作用.该向上的合力同样会阻碍海冰向下弯曲，但该合力明显小于重力.因此，海冰向上弯曲时受到的结构阻力要大于向下弯曲时的阻力，从而使正锥体产生较大的冰载荷.此外，由于海冰的上、下表面分别与空气和海水接触，其上表面的温度一般要明显低于下表面，使海冰的上表面弯曲强度要大于下表面.为此，在本文离散元计算时也考虑了海冰温度的分布情况，并依此设定了相应的海冰单元间的粘结强度.当海冰作用于正锥体上而发生向上弯曲时，海冰的下表面发生拉伸破坏；而当作用于倒锥体上时，海冰则发生上表面的拉伸破坏.由于海冰上表面的强度要高于下表面强度，导致海冰向下弯曲时不易发生破碎，从而使海冰作用于倒锥体上时的断裂长度较大，且冰载荷周期也较大.以上情况同样影响到冰荷载的差异，即正锥体上的冰载荷降低，倒锥体上的冰载荷增大.但受以上海冰爬升模式、浮力作用等因素的影响，正锥体上的冰载荷依然相对较大.3.2正倒锥交界处的冰载荷随着潮汐水位高度的变化，海冰与正倒锥交界处相互作用时可能会发生由弯曲破坏向挤压破坏的转化.将海冰和正倒锥体交界处的作用按照作用位置分为三种类别，即：偏上接触、中心接触和偏下接触，如图14所示.其中冰层中线高度为H ic (虚线)，图14海冰与正倒锥交界处作用的三种模式Fig.14Three di ﬀerent contact modes between sea ice and the interfaceof upward-downward cone。

自然地理对中国发展的影响英语作文

自然地理对中国发展的影响英语作文The Land that Shaped My Home: How Nature Made ChinaHi there! My name is Xiao Ming and I'm going to tell you all about how the amazing lands of my country, China, have shaped our great nation over thousands of years. China is a vast place with incredibly diverse landscapes, from towering mountains to rolling plains to scorching deserts. The natural world has had a huge impact on where people settled, how they lived, and even the foods they ate. So let's take a journey across the geography of China and see how it molded the Middle Kingdom.First off, we have to talk about those majestic mountains! China is home to some of the highest peaks on our planet, like the Himalayas along the southwestern borders and the Kunlun range up in the northwest. These jagged, snow-capped giants made it really hard for ancient people to travel and settle in certain areas. But the mountain ranges also protected central China from invaders sweeping in from the north and west for centuries. That's how places like the Yellow River valley were able to develop thriving early farming settlements away from conflict.Speaking of the Yellow River, known as the "Mother River" and "Birthplace of Chinese Civilization", this twisting waterwayhas been a lifeline for people since ancient times. The fertile soil along its banks allowed villages to grow and agriculture to flourish thousands of years ago. Without the Yellow River's waters to drink and crops to eat, China may have never become one of the world's earliest civilizations!Then we have those sweeping deserts out west, like the Gobi and Taklamakan, that cover huge swaths of the country. Back in the day, merchants and traders had to brave these scorching, shifting sands on the legendary Silk Road trade routes connecting China to faraway lands. Pretty crazy to think about traveling across those vast deserts with just camels to carry your goods! It just goes to show how challenging China's terrain could be.Up in the northeast, we find the dense forests and rugged mountains of Manchuria. This area's climate of bitterly cold, snowy winters made it hard to live there when China was still a young nation. But the forests provided plenty of timber resources later on, which was very important as cities grew and construction ramped up across the country.It's also worth mentioning the mighty Yangtze River, which flows from Tibet all the way across southern and eastern China into the East China Sea. This vital waterway gave people accessto inner lands and allowed big cities like Wuhan and Nanjing to prosper as major trade hubs throughout history. Just picture those wooden riverboats loaded with precious cargo making their way along this vast river highway!So those are some of the major geographic features that shaped the development of my home country over the centuries. From fertile crop lands to imposing mountain barriers to critical river trade routes, the lands of China both aided and challenged our ancestors as they worked to build villages, cities, and eventually a great empire unified under one rule.But the influence of nature goes beyond just molding where people lived and how civilizations first formed. China's diverse environments also created distinct regional cuisines and cultural traditions that still make each area so unique today!Like down in tropical southern provinces such as Guangdong and Guangxi, where the warm, humid weather allowed crops like rice and fruit to easily grow. This abundance of vegetables and seafood from the nearby coasts made Cantonese cuisine so amazingly fresh and flavorful. The spicy hotpot dishes of Sichuan in the southwest can be traced back to people using tons of chilies as preservatives in the often damp, rainy climate there.Even the famed Peking Duck originated from the need to cure meats during Beijing's dry northern winters.Speaking of the north, the harshness of those long, freezing cold seasons created the thick, sturdy styles of clothing and architecture we see across regions like Inner Mongolia. Think about those heavy, insulated robes made from animal furs like sheep and camel hair - they were essential for braving the snow and icy winds that whipped across the northern plains each year. Adobe houses with tight, windowless designs also helped keep families warm when temperatures plunged way, way below freezing.So from what we eat to what we wear, the many gifts and challenges of China's environments stamped their mark on the diverse cultures we cherish across this spectacular land. The natural world truly shaped how the Chinese lived in the past and continues influencing daily life today.Pretty amazing when you stop to think about it, huh? A vast nation of over 1.4 billion people, yet our customs, foods, and even traditional clothes can often be so different just by traveling to the next province over. All because ofthe mountains, rivers, deserts, and other varied landscapes that make my home country such an incredible place.So the next time you bite into a juicy Sichuan peppercorn or bundle up in a cozy winter coat, remember - that's China's great geography at work, molding how we eat, dress, and thrive in this amazingly diverse land. Thanks for letting me share my nation's story with you!。

环境对建筑的影响英语作文

环境对建筑的影响英语作文英文回答：The environment has a profound influence on the design and construction of buildings. From the climate and geological conditions to the surrounding landscape and cultural context, the environment shapes the form, function, and sustainability of our built spaces.Climate and Geography.The climate of a region plays a significant role in determining the design of buildings. In hot and humid climates, buildings are often characterized by large overhangs, shaded windows, and open-air courtyards to promote natural ventilation and reduce solar heat gain. In cold and snowy climates, buildings typically feature thick insulation, double-glazed windows, and sloped roofs to withstand the elements.The geological conditions of a site also influence building design. Buildings located on unstable or sloping terrain may require special foundations and structural systems to ensure stability. In areas prone to earthquakes, buildings must be designed to withstand seismic forces.Landscape and Context.The surrounding landscape and cultural context can also shape the design of buildings. In urban areas, buildings are often influenced by the height and density of neighboring structures, as well as by the overall street grid and city plan. In rural areas, buildings may be designed to blend into the natural surroundings and complement the local vernacular architecture.Sustainability and Energy Efficiency.In recent years, there has been a growing emphasis on sustainability and energy efficiency in building design. Buildings are now being designed and constructed to minimize their environmental impact and reduce greenhousegas emissions. This can involve incorporating energy-efficient technologies such as solar panels, geothermal heating and cooling systems, and rainwater collection systems into building designs.中文回答：环境对建筑的影响。

周边环境对建筑的影响英语作文

周边环境对建筑的影响英语作文English: The surrounding environment plays a crucial role in influencing the design and construction of buildings. Factors such as climate, topography, natural resources, and cultural aspects all contribute to shaping the architectural style and functionality of a structure. For instance, buildings located in regions with extreme weather conditions, such as high temperatures or heavy rainfall, need to be designed with appropriate materials and ventilation systems to ensure comfort and durability. Topography, on the other hand, can impact the layout and orientation of a building to take advantage of natural light and views. Additionally, the availability of local materials and construction techniques can influence the aesthetics and sustainability of a building. Cultural aspects, including traditions, beliefs, and social norms, also play a significant role in architectural design, as buildings often reflect the values and identity of a community. In conclusion, the surrounding environment serves as a powerful source of inspiration and influence on the built environment, shaping buildings that respond sensitively to their context while meeting the needs of the inhabitants.中文翻译: 周边环境对建筑的设计和建设起着至关重要的影响。

周边环境对建筑的影响英语作文

The Impact of Surrounding Environment onArchitectureArchitecture, as a reflection of human civilization and culture, is not just a static structure but a dynamicentity that interacts and evolves with its surrounding environment. The influence of the environment on architecture is profound, shaping not only its design but also its function, sustainability, and even the way people perceive and interact with it.The physical characteristics of the environment play a crucial role in determining the architectural form. For instance, in areas prone to earthquakes, buildings are designed with reinforced concrete and other earthquake-resistant materials to ensure structural integrity. Similarly, in regions with extreme climatic conditions such as deserts or tundras, buildings are designed to withstand high temperatures, cold winds, and other environmental challenges.The natural landscape also has a significant impact on architecture. Architects often draw inspiration from the surrounding nature, integrating natural elements into theirdesigns. For example, in areas with beautiful mountain views, buildings may be designed to complement the natural landscape, using similar colors and materials, or even incorporating features like skylights or terraces to bring the outdoors in.Cultural and historical context also play a vital role in shaping architecture. Buildings in different regions reflect the unique traditions, values, and histories of their respective communities. For instance, the traditional architecture of China is characterized by its use of wooden frames and tiled roofs, while that of India is known forits intricate carvings and ornate facades. These architectural features not only reflect the aesthetic preferences of the people but also serve as symbols oftheir cultural identity.Moreover, the social and economic factors of the environment have a profound impact on architecture. The availability of resources, population density, and economic conditions all influence the type and quality of buildings constructed in a given area. For instance, in developing countries where resources are scarce, architects mayprioritize cost-effective and sustainable design solutions that utilize local materials and techniques. Conversely, in developed countries with abundant resources, architects may have more freedom to experiment with innovative andcutting-edge design ideas.In conclusion, the surrounding environment has a profound impact on architecture, shaping its design, function, and sustainability. Architects must consider the physical, natural, cultural, social, and economic factors of their environment when designing buildings to ensurethat they are not only aesthetically pleasing but also responsive to the unique challenges and opportunities presented by their context.**周边环境对建筑的影响**建筑作为人类文明和文化的反映，不仅仅是一个静态的结构，而是一个与其周边环境相互作用、不断演变的动态实体。

线练学校高三英语一轮 SBⅡ Units 阶段评估(八)

始驾州参艰市线练学校2011《亮剑》高三英语一轮复习测试题SBⅡUnits 9－12阶段评估第Ⅰ卷 (选择题，共95分)第一：英语知识运用(共三节，满分50分)第一节语音知识(共5小题；每小题1分，满分5分)1．swearA．heart B．research C．nearly D．bear2．recentlyA．restaurant B．secret C．prefer D．system3．commonA．company B．across C．bottom D．collar4．occurA．accept B．access C．according D．accident5．laughedA．noticed B．studied C．breathed D．learned第二节语法和词汇知识(共15小题；每小题1分，满分15分)6．—We each little thought the visiting team would win the match.—________，they got________score o f 4∶2.A．Not at all；the B．On the contrary；aC．Second to none；the D．By the way；a7．—Does________blood make you scared?—Yes！I faint________blood.A．the sight of；at the sight of B．a sight of；first sightC．the sight of；in sight of D．a sight of；in sight of8．________you are supposed to do________you don’t like a thing is changing it.Don’t complain.A．That；what B．When；that C．What；since D．What；when9．Not far from the club there was a garden，________owner seated in it playing bridge with his children every afternoon.A．whose B．its C．which D．that10．________he met with the terrible difficulty did he realize the importance of my advice.A．Even though B．Only beforeC．Never until D．Ever since11．He urged that we________him of what he would say on________the hall.A．reminded；setting foot on B．remind；setting foot inC．remind；setting foot on D．reminded；setting foot in12．Welltrained________the employees are，they are not so productive________expected under great pressure.A．although；as B．though；likeC．as；like D．as；as13．She recommended not only________to the evening party but also give a performance in English.A．should I go B．did I goC．I should go D．my going14．—Shall we go to the art exhibition right away?—________.It makes no difference whether I will go there or not.A．It’s your opinion B．I’m not sureC．It’s all up to you D．That’s your decision15．The view he________at the last sales meeting sounds a little reasonable.A．took down B．put forwardC．took off D．made up16．The scientist found animals sometimes try to hit or bite，especially________they are playing with a weaker partner.A．if B．before C．unless D．when17．________terrible weather we’ve been having these days!A．How a B．What a C．How D．What18．Considering my parents are very old，I decided to________two hours a day to keep them________.A．set out；a company B．set aside；companyC．set off；company D．set down；a company19．The letter to his son________，he hurried to the shop for some shopping.A．posting B．having postedC．posted D．had been posted20．As far as I know，she is seldom，________，absent from school.A．if ever B．if much C．if not D．if any第三节完形填空(共20小题；每小题1.5分，满分30分)Have you paid a visit to the town of Pressure and the town of Pleasure? The two towns were neighbours but had___21___in common.Residents built walls to__22__influence from the__23__town.In Pressure，everyone struggled to be the very best.When women__24__birth，they would compete to have the baby with the __25__cry.There was violent competition in every aspect of life.Because__26__was the index (指数) of success，people were always__27___making money，with no time for relaxation.Some young people couldn’t bear the intensity and resorted to drink or drugs to escape.___28___，over in Pleasure，the motto was “As long as you like it，do it.” People__29__without pressure and could do anything __30__liked.Children played computer games day and night.At school，teachers didn’t care__31__students showed up or not.Workers might sit around the office__32__sipping coffee and doing nothing.Thanks to the__33__of regulations，nobody worried about losing their jobs.It was pleasure that mattered.No one had the slightest thought of moving__34__，either for themselves or for the town.The computers they__35__were old models from Pressure.Some of the young were addicted (沉溺于) to__36__ because of the emptiness of their lives.Then，people in the two towns began asking themselves，“What is life__37__？” But，just before life in the two towns completely failed, there came a saint—Mr Reason.He went from door to door, __38__with people and giving advice.People in Pressure learnt to be content with what they had，while people in Pleasure began to make plans.They__39__the walls between them and built a road to connect the two.The townspeople__40__to realize the truth—there is no space between Pressure and Pleasure they don’t go to extremes.21. A．anything B．nothing C．everything D．something22．A.keep out B．look out C．work out D．give out23．A.another B．any C．every D．other24．A.gave B．took C．offered D．brought25. A．lower B．louder C．loudest D．lowest26．A.health B．joy C．wealth D．fun27．A.busy B．lazy C．easy D．hard28．A.Meanwhile B．At that timeC．At one time D．Once in a while29．A.got up B．grew up C．set up D．brought up30．A.we B．you C．they D．it31．A.what B．who C．where D．whether32. A．all way B．all night C．all way long D．all day long33．ck B．need C．pain D．voice34．A.backward B．forward C．upward D．downward35．A.made B．used C．borrowed D．repaired36．A.work B．money C．drugs D．books37．A.for B．at C．in D．to38．A.selling B．writing C．playing D．talking39．A.pulled down B．put down C．went down D．wrote down40．A.went B．returned C．happened D．came第二：阅读理解(共两节，满分45分)第一节(共20小题；每小题2分，满分40分)AWhen I was teaching in China，I certainly wanted my students to learn more，but I also really wanted them to enjoy classes.One of my favorite classes was teaching my students about music.I taught them about the many different styles of music and about the different cultures that had produced them.I played CDs in class to test my students’ increasing knowledge of music styles，but I decided that，although useful and fun，thi s just wasn’t memorable enough.As a student myself，I had learned to play classical and electric guitar.I decided that I would take my electric guitar into class，not only to further test my students，but also to givethem something memorable.During the lesson，I played various music styles，from country and western to blues，jazz and rock；after each piece，I would have my students，in groups，guess the style of music played.Their enthusiastic involvement told me all I needed to know about this class.It had been a great success.During a free talk about culture and music，I was delighted to hear their sensitive comments on the origins of rap，rock and blues music.Further to this，I set a class project，asking students to form their own band，choosing their own instruments，style of music and band name.The rest of the class would then interview each group about their group and their music.It was great for me to watch how their understanding of the subject had been so deeply rooted.And to help them learn more about music is my aim.I believe that making teaching memorable is the key not only to dynamic (动态的) learning for students，but also to pure enjoyment for teachers.If a teacher brings a range of different skills into the classroom，I am certain that the teacher will be in a great position to give his students unforgettable classes.After all，if students can see that a teacher loves teaching them，how can they fail to be inspired by such a teacher?41．The underlined word “them” in Paragraph 2 means________.A．classes B．studentsC．cultures D．different styles of music42．From the text，we know that the writer is very good at________.A．enjoying himself B．playing guitarC．a free talk about culture D．forming band43．The class band is built to help students________.A．interview each group B．watch how to play instrumentsC．learn more about music D．pure enjoyment for teachers44．Which of the following statements would the writer agree to?A．It is a good idea to have a band in a class.B．Teachers should talk to each of their students during music class.C．It is important for a teacher to have the right teaching for students.D．Understanding music can help students understand a teacher correctly.BGeoffrey Payne talked for the first time about the night when his wife was killed.The judgethought it was he who killed his wife.Now he wrote to a magazine from the prison about what had happened on the night of 13 October,2009.I had to stay late at the hospital that night to do an operation.I finally left at about 11 p．m..I drove home slowly because the weather was terrible—the wind was blowing and it was raining heavily.I was turning into our road when a man suddenly ran in front of my car.I almost hit him but I stopped just in time.I was frightened and the man looked frightened，too.I got out of the car but he ran away before I could ask if he was all right.It was strange.When I got home，the lights were on but it was very quiet.I called to my wife but there was no answer.Then I remembered that she was out at a concert.I was still very upset about what had happened on the road，so I made myself a drink.Then I went upstairs to have a bath.I saw that the window in the bedroom was open.This was strange because my wife always locked the doors and windows before she went out.She was afraid of burglars (夜盗者)．When I went to close the window，I found Ellen.She was lying on the floor.There was blood everywhere.I rushed over and felt her pulse but she was dead.I sat on the floor beside her body.I was too frightened to do anything.When I gained a bit of consciousness，the sky was getting light.I couldn’t remember a thing about that night.In the morning I phoned the police.They arrived about half an hour after I phoned them.But it seemed like hours.During that time I tried hard to recall what had happened the night before.I couldn’t stop thinking about the man on the road.What was he doing at that time of night in our quiet neighborhood? Why did he look so frightened? Why did he run away?45．Geoffrey Payne was a________.A．doctor B．policeman C．judge D．taxi driver46．When Payne got home，he found________.A．Ellen waiting for himB．the bedroom window closedC．a burglar in his houseD．Ellen lying on the floor，blood all over47．After he found Ellen dead，Payne________.A．called the police at onceB．tried to find out the murdererC．called out for helpD．was so scared that he could do nothing48．In this passage Payne tried to________.A．say something about his familyB．show he was very sorry for his wife’s deathC．make people believe the man in the road probably killed his wifeD．tell why his wife was killedCGeneral Airport TipsPlan to get to the airport at least an hour early，or two during holidays and other busy times；this will reduce the stress of the flight.If all goes well，you will have time to relax，shop for lastminute items，or have a meal before the flight.Flight DelaysFind out why your flight is delayed.Call the free call numbers.Find out if other airlines are experiencing similar delays.If you believe the delay is due to something other than weather or air traffic problems，then mention your suspicion (怀疑) and ask the airline agent to book you on the next available flight，either on the same airline or a competing one.This is called “Rule 240”，and all airlines are required to do e the lingo (行话) and ask“Can you 240 me？” when speaking with an agent.They will know what you mean.Flight Cancellations (取消)If your flight is canceled，then make a reservation on the next flight to your ually，airline personnel will try to book everyone on their next flight.Often they will put you on a competitor’s next flight only if you request it.If ontime arrival is important to you，when you check flights through our reservation system you can rate your choices based on their ontime ar rival records.Be sure to also check the weather conditions，as they often affect flight schedules.49．A person goes to the airport ahead of time mainly to________.A．buy what he wants in the airportB．have a good rest in the airplaneC．reduce the pressure of the flightD．get on the airplane immediately50．If a person calls “Rule 240”，he wants to________.A．change for the ticket to the next flightB．make sure the time for the next planeC．know if other flight delays happenD．ask the reason for the plane delay51．After a flight cancellation，a passenger can________.A．arrive at his destination on timeB．be arranged on a competing flightC．make sure the weather is quite fineD．reserve the next flight to his/her destination52．The purpose in writing this text is to________.A．show us how to get on a planeB．tell us what to do before and after a flightC．put forward suggestions for a flightD．teach us actions before an emergencyDOn this vivid planet，it appears colorful with many worldfamous buildings.Among these largest artificial articles in the world，many were designed by the same architect—Ieoh Ming Pei.Pei，the 1983 Laureate of the Pritzker，Architecture Prize，is a founding partner of I．M.Pei & Partners based in New York City.He was born in China in 1917，the son of a banker.He came to the United States in 1935 to study architecture at the Massachusetts Institute of Technology and the Harvard Graduate School of Design (M.Arch.1946)．From 1945 to 1948，Pei taught at Harvard.In 1948 he accepted the newly created post of director of Architecture at Webb & Knapp，Inc.，and this association resulted in major architectural and planning projects in big cities.In 1958，he formed the partnership of I．M.Pei & Associates，which became I．M.Pei & Partners in 1966.The partnership received the 1968 Architectural Firm Award of the American Institute of Architects.Pei has designed over forty projects in the world，twenty of which have been award winners.His outstanding projects have included the East Building of the National Gallery of Art，Washington，D.C.；the John Fitzgerald Kennedy Library near Boston and the Fragrant Hill Hotel near Beijing，China.Pei is now a member of the National Council on the Arts，and before served on the National Council on the Humanities.He is a fellow of the American Institute of Architects，a member of the Royal Institute of British Architects，and an elected member of the American Academy of Arts and Letters.He is a member of the Corporation of the Massachusetts Institute of Technology.As a student，he was awarded the MIT Traveling Fellowship，at Harvard.He later won a lot of honors.In 1982，the deans of the architectural schools of America chose I．M.Pei as the best designer of significant nonresidential (非住宅的) structures.53．________of Pei’s structures have won awards.A．More than forty B．Over twentyC．None D．Twenty54．When was I．M.Pei chosen as the best designer of significant nonresidential structures?A．In 1983. B．In 1982. C．In 1968. D．In 1948.55．Which of the following is true according to the text?A．Ieoh Ming Pei was born in America.B．Ieoh Ming Pei studied architecture at the Massachusetts Institute of Technology when he was young.C．Ieoh Ming Pei got a degree for architecture in 1948.D．Ieoh Ming Pei got a Harvard undergraduate degree in 1946.56．What would be the best title for the text?A．Ieoh Ming Pei’s Life and BackgroundB．A Famous Professor—Ieoh Ming PeiC．An Unusual Architect—Ieoh Ming PeiD．A Great Architect of Residential StructuresEEvery year，residents of Kunming，Yunnan Province welcome thousands of blackheaded gulls with food and happy laughter.The lovely white birds fly from Siberia to stay in the Dianchi area of the city in winter.But this year the white angels are no longer lovely in locals’eyes，due to their fear of bird flu.Although scientists have not found the deadly virus in the birds，few people will dare to risk their lives to feed the birds this year.Across the world，wild migratory birds seem to have become public enemy number one.Since the deadly H5N1 bird flu virus was discovered not only in Asia but also as far away as Europe and Africa，migratory birds were regarded as the carriers.Geographically speaking，the spread of bird flu appears to be following the migratory routes of wild birds.Bird flu is a common disease among wild migratory birds.But the virus may change itself when transferred to humans and animals.Since the World Health Organization warned last month that migratory birds could carry the deadly H5N1 virus that causes bird flu，many countries，like China，have started tracking migratory birds and cleaning up poultry markets (家禽市场)．China also didn’t allow all pigeon races last week.Scientists said that the migratory routes of wild birds are often far away from big cities.The risk of transferring the virus directly from wild birds to humans is very low.Scientists also warned that wild birds are shy creatures.They see you coming and fly away at once.But if a wild bird becomes easy to approach，people should be careful that it may be sick.57．Why are blackheaded gulls not welcomed in Kunming this year?A．Because residents there are too busy.B．Because the birds carry virus.C．Because the residents think more about their safety.D．Because they are advised not to approach the bird.58．According to the passage，H5N1 bird flu hasn’t been discovered in________so far.A．Africa B．Europe C．Asia D．America59．By mentioning what China has done，the author wants to show________.A．he doubts whether it is wise to do soB．the Chinese government paid great attention to the caseC．it is not easy to eat chicken in ChinaD．China will suffer a lot because of bird flu60．The purpose of writing the passage is to________.A．tell us bird flu has broke out in the worldB．advise people not to approach birdsC．emphasize the harm of bird fluD．say migrating birds may spread flu第二节(共5小题；每小题1分，满分5分)A：Some of our classmates are going to Japan for the summer vacation.Will you join them?B：__61__But I have to go back home to stay with my mother because she is badly ill in bed.A：Oh，that’s too bad!B：__62__A：Yes，my aunt in Hawaii has invited me to spend my vacation with her.B：Great！Hawaii is a wonderful place，isn’t it?A：Certainly，I suppose she’ll show me around some interesting places there.__63__B：As I know，Hawaii was discovered by Captain Cook in the 1770s and he got killed there the next year he discovered it.A：That’s right.__64__B：Sure，you’ll certainly enjoy yourself.But don’t forget to write to me，will you?A：__65__A．Of course，I will.B．B ut now it’s become a worldfamous scenic spot.C．I would go to，should I have the chance.D．Have you got a way to spend yours?E．No，never.F．And I’m going to read some books about its history as well.G．And I’ll go there as soon as the vacation starts.第Ⅱ卷(非选择题，共55分)第三：写作(共三节，满分55分)第一节单词拼写(共10小题；每小题1分，满分10分)66．On their________(到达) they began to look into the cause of the accident.67．The________(运输) of goods by air is very expensive.68．The first step is to________(废除) the existing system.69．He was glad to have________(克服) all the difficulties.70．We should pay more attention to our________(精神的) health.71．I________(保证) to be here tomorrow.72．He felt he needed to________(证明) his point.73．She________(禁止) them from mentioning the subject again.74．What kind of________(货币) do you want?75．Five people were________(逮捕) in connection with the robbery.第二节短文改错(共10小题；每小题1.5分，满分15分)As students，we have classes from early morningtill late afternoon.Therefore，take a tenminute break76.________Otherwise we may feel both physically or mentally78.________tired.During the break we usually did something79.________to get rid of tiredness.What we need is to have real rest，80.________rather than get even more tiring.So don’t do anything81.________which will make us too tired.My tenminute break is82.________pleasing.I often do some gentle exercise.Sometime I83.________第三节书面表达(满分30分)在英语课堂上，老师出示了下面一幅图画，请你回答“Which would you prefer，camping，hiking or biking？”这个问题。

周边环境对建筑的影响英语作文

周边环境对建筑的影响英语作文The surrounding environment plays a pivotal role in shaping the architecture of a building. It influences not only the aesthetic appeal but also the functionality and sustainability of the structure.Natural elements such as sunlight, wind, and rain dictate the orientation and design of buildings to optimize energy efficiency and comfort. For instance, windows are often placed to maximize natural light and cross-ventilation, reducing the need for artificial heating and cooling.Cultural and historical contexts also significantly impact architectural styles. Buildings in heritage areas often adopt traditional designs to blend in with the neighborhood, preserving the area's character and charm.Urban density and land availability are other factorsthat architects consider. In crowded cities, high-rise buildings are common to make the best use of limited space, while in rural areas, buildings tend to be more spread out.Moreover, the local availability of building materials can affect construction methods and costs. Using locally sourced materials not only supports the local economy but also reduces the environmental impact of transportation.The impact of the surrounding environment on architectureis a testament to the dynamic relationship between human-made structures and the natural world. It highlights the importance of designing buildings that are not only beautiful but also responsive to their surroundings.。

城市化对地理环境的影响英语作文

城市化对地理环境的影响英语作文Urbanization, the process of population concentration in cities, has profound impacts on the geographical environment. As cities expand and develop, they alter landscapes, ecosystems, and natural resources. This essay explores the various ways in which urbanization influences the geographical environment.One of the most evident impacts of urbanization is the transformation of land use patterns. As cities grow, they consume vast amounts of land for infrastructure, residential areas, and industrial zones. This leads to the conversion of natural habitats such as forests, wetlands, and agricultural land into built-up areas. Consequently, biodiversity is often reduced, and ecosystems are fragmented, affecting the overall balance of the environment.Moreover, urbanization affects water resources and hydrological systems. The increased demand for water in urban areas puts pressure on freshwater sources. Rivers are often dammed or diverted to meet the needs of growing populations, leading to changesin water flow patterns and altering aquatic ecosystems. Additionally, urbanization exacerbates issues such as water pollution and flooding due to inadequate wastewater treatment and impermeable surfaces that prevent natural infiltration.Air quality is another critical aspect influenced by urbanization. The concentration of industrial activities, transportation emissions, and energy consumption in cities contribute to air pollution. Pollutants such as particulate matter, nitrogen oxides, and volatile organic compounds have adverse effects on human health and the environment. Urban heat islands, where cities experience higher temperatures than surrounding rural areas, further exacerbate air quality issues and impact local climates.Furthermore, urbanization alters the natural landscape, leading to changes in soil composition and erosion patterns. The extensive paving and construction in cities reduce the amount of permeable surfaces, disrupting the water and nutrient cycles in soils. This can result in soil degradation, loss of fertility, and increased susceptibility to erosion during heavy rainfall events. Soil sealing also limits opportunities for vegetation growth, further impacting biodiversity and ecosystem services.Additionally, urbanization influences the energy dynamics of regions. Cities are major consumers of energy, primarily sourced from fossil fuels and electricity grids. The construction and operation of urban infrastructure, transportation networks, and buildings require significant energy inputs, contributing to greenhouse gas emissions and climate change. Moreover, the spatial concentration of energy demand in cities necessitates long-distance transportation of energy resources, leading to energy losses and environmental impacts associated with extraction and transport.In conclusion, urbanization profoundly shapes the geographical environment through changes in land use, water resources, air quality, soil dynamics, and energy consumption. While cities drive economic development and provide opportunities for social advancement, they also pose significant challenges for sustainable environmental management. Addressing the environmental impacts of urbanization requires holistic planning, innovative technologies, and proactive policies to ensure the long-term well-being of both urban residents and the surrounding ecosystems.。

影响房屋构造的因素英语作文

影响房屋构造的因素英语作文英文回答：Factors Affecting House Construction.The construction of a house is a complex process thatis influenced by a multitude of factors. These factors can be broadly categorized into three main groups:1. Site Factors: These factors relate to the specific location where the house will be built. They include:Terrain: The slope and topography of the land can significantly impact the design and construction of the house. Steeper slopes may require additional excavation and foundation work, while uneven terrain may necessitate special design considerations.Soil Conditions: The type of soil on the site plays a crucial role in determining the foundation type anddesign. Loose or unstable soils may require special measures, such as pilings or reinforced foundations, to ensure the stability of the structure.Environmental Conditions: Factors such as wind patterns, sun exposure, and precipitation levels can influence the design of the house. For example, homes in windy areas may require special roofing materials and structural reinforcements to withstand high winds, while homes in sunny climates may benefit from the use of passive solar design to reduce energy consumption.2. Architectural Factors: These factors relate to the design and aesthetics of the house. They include:Building Style: The architectural style chosen for the house will impact its overall appearance and functionality. Different styles, such as traditional, modern, or contemporary, have their own unique characteristics that influence the construction process.Materials: The selection of building materials, suchas wood, concrete, or brick, affects the durability, cost, and maintenance requirements of the house. Each material has its own strengths and weaknesses that must be considered during construction.Floor Plan: The layout and arrangement of rooms within the house have a major impact on the construction process. The size and shape of the rooms, as well as the placement of windows and doors, influence the structural design and the overall flow of the house.3. Economic Factors: These factors relate to the budget and financing available for the construction of the house. They include:Cost of Materials: The cost of building materials can vary significantly depending on the type and quality of materials used. The choice of materials will directly impact the overall construction costs.Labor Costs: The cost of labor for construction workers can also vary depending on the location, skilllevel, and availability of contractors. It is important to factor in labor costs when planning the budget for the project.Financing Options: The availability of financing options, such as mortgages or construction loans, can influence the feasibility and timing of the construction project. It is important to secure financing beforestarting construction to ensure that the project can be completed successfully.中文回答：影响房屋建造的因素有很多，主要有以下几方面：1. 场地因素：指房屋建造的具体地点，包括：地形，地表的坡度和地势起伏对房屋的设计和建造影响很大。

高楼对中国的影响英语作文

高楼对中国的影响英语作文The impact of high-rise buildings in China is undeniable. These towering structures have become symbols of modernity and economic prosperity, shaping the urban landscape and redefining the skyline.High-rise buildings have transformed the way peoplelive and work in China. With limited space in urban areas, these tall structures provide much-needed housing, office space, and commercial facilities. They have also contributed to the densification of cities, allowing for more efficient land use and better infrastructure planning.The construction and maintenance of high-rise buildings have created a demand for skilled labor and advanced technology in China. This has led to the development of a robust construction industry and the adoption of innovative building techniques, positioning China as a global leaderin skyscraper engineering and design.The presence of high-rise buildings has also had a profound impact on the environment in China. The increased energy consumption and carbon emissions associated with these structures have raised concerns about sustainability and urban air quality. However, efforts are being made to address these issues through the implementation of green building standards and the use of renewable energy sources.In addition to their practical functions, high-rise buildings have become cultural landmarks and tourist attractions in China. They have become symbols of progress and ambition, drawing visitors from around the world to marvel at their architectural grandeur and technological marvels.The proliferation of high-rise buildings has also sparked discussions about social inequality and urban development in China. While these structures represent economic growth and urbanization, they have also exacerbated the gap between the rich and the poor, leading to issues of housing affordability and social segregation.In conclusion, high-rise buildings have had a multifaceted impact on China, shaping its urban environment, economy, technology, and culture. While they have brought about significant changes, they have also raised important questions about sustainability, equality, and the future of urban development in the country.。

滑坡和崩塌英语作文

滑坡和崩塌英语作文Landslides and Rockfalls: Natural Phenomena with Significant Impacts.Landslides and rockfalls are two natural phenomena that can cause significant damage to human-built structures and environments. While they occur naturally due to geological and climatic factors, their frequency and severity can be exacerbated by anthropogenic activities. In this article,we will explore the causes, impacts, and mitigation strategies related to landslides and rockfalls.Landslides refer to the downward movement of soil, rock, or debris on a slope. They can be triggered by various factors such as heavy rainfall, earthquakes, snowmelt, and changes in地下水位. Landslides can occur on natural slopes as well as those modified by human activities such as road cuts, mining, and deforestation. When a landslide occurs,it can lead to the destruction of property, roads, and bridges, disrupting transportation and communicationnetworks. Additionally, landslides can pose a threat to human life, causing casualties and displacement.Rockfalls, on the other hand, involve the detachmentand fall of rocks from cliffs or slopes. They are often triggered by factors such as weathering, freeze-thaw cycles, and seismic activity. Rockfalls can also be influenced by human activities, such as mining, blasting, and deforestation. The impact of rockfalls can be devastating, causing damage to structures, roads, and bridges, and even leading to casualties.The impacts of landslides and rockfalls are not limited to the immediate area affected. They can have widespread economic and social consequences. For instance, the destruction of infrastructure can lead to decreased economic activity and increased costs for reconstruction. Additionally, the displacement of people due to landslides and rockfalls can lead to social and psychological issues.Mitigation strategies for landslides and rockfalls involve a combination of engineering measures and non-engineering approaches. Engineering measures may include slope stabilization techniques such as terracing, drainage systems, and soil nailing. Non-engineering approaches focus on land use planning, environmental conservation, andpublic education. For instance, limiting development in areas prone to landslides and rockfalls, promoting sustainable land use practices, and educating the public about the risks associated with these phenomena can help reduce their impact.In conclusion, landslides and rockfalls are natural phenomena that can have significant impacts on human-built structures and environments. While they are difficult to predict and control, effective mitigation strategies can help reduce their frequency and severity. A combination of engineering measures and non-engineering approaches is necessary to address the challenges posed by landslides and rockfalls and protect human life and property.。

周边环境对建筑的影响英语作文

周边环境对建筑的影响英语作文The surrounding environment plays a significant role in shaping the design and functionality of buildings. Architects often take into consideration various elements of the surrounding environment when planning and constructing structures.One of the key factors that influence architecture is the geographical location of the building. The climate, topography, and natural surroundings of a site can all impact the design choices, materials used, and energy efficiency of a building. For example, buildings in tropical regions may incorporate features like natural ventilation and shading to combat heat, while structures in colder climates might prioritize insulation and heating systems.Additionally, the cultural and historical context of an area can also influence architectural styles and building designs. Local traditions, customs, and materials often play a role in creating structures that blend harmoniously with the surrounding environment. Modern architects may draw inspiration from traditional elements to create contemporary buildings that reflect the localidentity and heritage.Furthermore, urban settings and the existing built environment can shape the form and function of new buildings. Factors such as zoning regulations, infrastructure, and neighboring structures can impact the height, layout, and aesthetic of a building. Architects must consider how their designs will interact with the surrounding urban fabric to create a cohesive and visually appealing environment.In conclusion, the surrounding environment has a profound impact on architecture, guiding architects in creating buildings that are not only functional and aesthetically pleasing but also responsive to the natural, cultural, and urban context in which they exist.中文翻译：周边环境在塑造建筑设计和功能方面起着重要作用。

介绍一个地质灾害英文作文

介绍一个地质灾害英文作文Geological disasters refer to natural events resulting from the Earth's geologic processes, causing severe destruction and loss of life and property. These catastrophic events include earthquakes, volcanoes, landslides, and tsunamis, among others. The devastating impact of geological disasters on human lives and infrastructure calls for comprehensive understanding and preparedness to minimizetheir consequences.Earthquakes are one of the most devastating geological disasters with the potential to cause widespread destruction. These sudden shaking or trembling of the Earth's surface occur due to the release of accumulated energy in the Earth's crust. The severity of an earthquake is measured using the Richter scale. When an earthquake strikes, buildings can collapse, roads can split open, and people may be trappedunder debris. Infrastructure damage and loss of life are common consequences.Landslides are another geological disaster that occurs when large amounts of rock, soil, or debris move down a slope. Heavy rainfall, earthquakes, volcanic activity, or human interactions can trigger landslides. These fast-moving masses can bury villages, roads, and buildings, leading tofatalities and rendering the affected areas inaccessible. Landslide-prone regions need proper mapping, monitoring, and early warning systems to mitigate the destructive impact.Volcanic eruptions represent an awe-inspiring yet highly dangerous geological phenomenon. When a volcano erupts,molten rock, ash, and gases are expelled from the Earth's crust, often resulting in destruction and environmental hazards. Lava flows destroy everything in their path,including farmland and forests, while ash clouds can impactair quality and disrupt air travel. Communities living nearvolcanoes must be educated about evacuation plans and have access to volcanic monitoring technology for timely warnings.Tsunamis, generated by underwater earthquakes, are giant ocean waves that can traverse thousands of kilometers with devastating force. Coastal areas are particularly vulnerable to tsunamis. When these waves reach the shore, they can cause massive flooding, destroy coastal structures, and claim numerous lives. Early detection and warning systems are crucial to provide adequate time for evacuation and save lives.To mitigate the impact of geological disasters, proper planning, infrastructure development, and public awareness are paramount. Governments and communities should work together to strengthen building codes and constructstructures capable of withstanding earthquakes and other natural hazards. Regular drills and education campaigns can enhance public preparedness and response during disasters.Monitoring systems, such as seismographs and satellite imaging, enable scientists to detect potential geological threats and issue timely warnings.In conclusion, geological disasters, including earthquakes, volcanoes, landslides, and tsunamis, are natural events that can cause immense destruction and loss of life. Understanding these phenomena, implementing preventive measures, and fostering preparedness can significantly reduce their impact on human lives and infrastructure. Byprioritizing safety and adopting appropriate strategies, we can strive to create a more resilient society in the face of geological disasters.。

科技对地形的影响英语作文

科技对地形的影响英语作文Technology has had a significant impact on the Earth's terrain. The development of advanced machinery and tools has allowed us to manipulate and shape the land in waysthat were previously unimaginable.One way technology has affected the terrain is through the construction of roads and highways. With the invention of heavy machinery such as bulldozers and excavators, we can now flatten and level the ground to create smooth surfaces for transportation. This has made it easier for people to travel and has opened up remote areas for development.In addition to roads, technology has also enabled us to build bridges across rivers and valleys. These structures not only provide a means of crossing but also alter the natural flow of water and change the landscape. The construction of bridges has allowed for the expansion of cities and the development of new communities.Furthermore, technology has revolutionized the mining industry. With the use of advanced drilling equipment and explosives, we can extract resources from deep within the Earth. This has led to the creation of vast open-pit mines and has significantly altered the natural topography. The excavation of minerals and metals has both positive and negative consequences for the environment.Another way technology has impacted the terrain is through the construction of dams. These structures harness the power of water to generate electricity and provide irrigation for agriculture. However, the creation of dams often requires flooding large areas of land, which can lead to the displacement of communities and the destruction of ecosystems.Moreover, technology has allowed us to reclaim land from the sea. Through the use of dikes and seawalls, we can protect coastal areas from erosion and flooding. Additionally, land reclamation projects have been undertaken to create new land for development, such as thefamous Palm Islands in Dubai. These artificial islands have transformed the coastal landscape and created new opportunities for tourism and real estate.Overall, technology has had a profound impact on the Earth's terrain. From the construction of roads and bridges to mining and land reclamation, our ability to shape and modify the land has been greatly enhanced. While these advancements have brought numerous benefits, they have also come with environmental and social consequences that we must carefully consider.。

地理因素的重要性英语作文

地理因素的重要性英语作文Geography plays a pivotal role in shaping the world we live in, influencing everything from culture and history topolitics and the economy. In this essay, we will explore the significance of geographical factors and how they impact various aspects of human life.Firstly, geographical factors determine the availability of natural resources, which in turn affects the economic development of a region. For instance, countries rich in oil, such as Saudi Arabia, have seen rapid economic growth due to the global demand for this resource. Conversely, regions with limited resources often struggle to achieve the same level of prosperity.Secondly, geography influences climate and weather patterns, which have a direct bearing on agriculture and food production. The fertile plains of the Nile River in Egypt,for example, have supported agriculture for millennia, contributing to the region's historical significance and development.Moreover, geographical location can impact a country's strategic importance and foreign relations. Nations with access to key shipping lanes, such as Singapore, often become hubs for international trade and diplomacy. This strategic positioning can lead to economic benefits and political alliances.Geography also shapes cultural identities and interactions. The isolation of certain regions, like islands or mountainous areas, can lead to the development of unique cultures and languages. At the same time, the proximity of different regions can foster cultural exchange and cooperation.Furthermore, geographical barriers can influence the spread of diseases and the development of public health strategies. The spread of the Black Death in the 14th century was significantly influenced by trade routes and population centers, highlighting the role of geography in public health crises.Lastly, an understanding of geographical factors is crucial for sustainable development and environmental conservation. The preservation of ecosystems, such as the Amazon rainforest or the Great Barrier Reef, requires knowledge of the geographical characteristics that make these areas unique and vulnerable.In conclusion, geographical factors are of paramount importance in understanding the complexities of our world. They influence economic development, cultural diversity, political dynamics, and environmental sustainability. Recognizing and respecting these factors is essential for the continued progress and well-being of societies around the globe.。

【2021年专升本备考】2015～2018年浙江专升本《英语》真题+参考答案

浙江省2015年选拔优秀高职高专毕业生进入本科学习统一考试英语请考生按规定用笔将所有试题的答案涂、写在答题纸上。

选择题部分注意事项：1.答题前，考生务必将自己的姓名、准考证用黑色字迹的签字笔或钢笔填写在答题纸规定的位置上。

2.每小题选出答案后，用2B铅笔把答题纸上对应题号的答案标号涂黑。

如需改动，用橡皮擦干净后，再选涂其他答案的标号。

不能答在试卷上。

第一部分：阅读理解（共20小题,每小题2分,满分40分）阅读下列材料,从每小题所给的四个选项（A、B、C和D)中,选出最佳选项。

AKaren Christiansen in Madison,Wisconsin,is licking stamps and addressing envelopes.Soon she and her fiance will be sending out invitations to their wedding.Meanwhile,Wei Yashung is at the hairdresser’s in Shanghai, China.She knows she will have a long wait.It’s May18,the most popular day to get married in China.The room is filled with brides preparing for their special day.“Everyone feels very emotional at this time.There are a lot of rituals and superstitions（迷信）at the wedding,”says Maxine Rowe,an anthropologist.Karen’s aunt and sisters help her check off the things she needs according to old customs.They recite the traditional verse,“Something old,something new,something borrowed,and something blue.”Friends and relatives gather around and contribute grandmother’s locket（纪念品盒）,a cousin’s wedding veil,or a blue garter to prepare for the ceremony.Many wedding traditions in western cultures began long ago and were designed to protect the couple from ad luck.“The wedding veil is a Greek custom intended to hide the bride from evil spirits,”says Maxine.“The Romans contributed the custom of bridesmaids to confuse the spirits.Wedding bouquets had strong-smelling herbs to scare witches and devils.”In China,thousands of couples choose May18for heir wedding day.“In the past,people consulted an almanac（历书）to find lucky days,”explains Maxine.“But in modern times a new tradition is being formed.”May 18sounds very close in Chinese to“wo yao fa,”or“I will get rich.”It is considered a good omen to get married on this day.Some people don’t think it’s a good idea for everyone to get married on the same day.“It’s silly and superstitious,”one reporter wrote.But hairdressers,florist,and owners of restaurants say it’s the best day.They can raise their prices and their services are fully booked.Maybe they are the ones who should be saying,“I will get rich.”1.The overall structure of this passage can be called______.[A]comparison and contrast[B]description of events in order of time[C]details leading to conclusion[D]generalization followed by details2.An anthropologist in Paragraph2probably studies______.[A]hairstyles[B]Jewels[C]Almanac[D]customs3.Why do Karen’s friends and relatives contribute a cousin’s wedding veil？[A]Because it is something old.[B]Because it is something new.[C]Because it is something borrowed.[D]Because it is something blue.4.The word“omen”in Paragraph5probably means______.[A]a sign of star[B]a sign of present[C]a sign of past[D]a sign of future5.What’s the writer’s tone in the last sentence“Maybe they are the ones who should be saying,‘I will get rich.’”?[A]Humorous.[B]Tolerant.[C]Matter-of-fact.[D]Furious.BThe easiest and least complicated way to motivate somebody is quite simply to pay them attention.What you say is not particularly important,nor necessarily is how long you spend saying it,as long as it’s something.“Nice weather”or“How are you?”will do.People just love attention,adults and children.Children love attention so much that they will do anything to get some.In fact,if children are not getting enough attention,they would rather be naughty and get told off than be“good”and be ignores.An interesting time in most households with young children is dinnertime—it’s the end of the day,everybody is tired,the house is in a mess and Johnny doesn’t like carrots and is refusing to eat his food. Again,the easy trap to fall into is to start getting cross with Johnny and getting into a big argument about his food. Again,he’s getting the attention he desires；even if it’s not the best sort of attention,it’s better than nothing.It’s fascinating if you’re able to stand back from the situation and instead focus attention and praise on Johnny’s brother who is eating his food—after all,he’s the one that is doing what you want him to do.After five or ten minutes or so of being ignores and deprived of the attention,it’s amazing how quickly（usually）Johnny sees sense and obeys.I’ve watched my own children in this situation go from screaming from behind the sofa that they won’t eat their food,to sheepishly crawling to the table saying that maybe they’ll have a little bit,to sitting in their chair wolfing the lot and saying,“Mummy,aren’t I doing good dinner eating?”—all without having one word spoken to them by their parents,who are busily paying attention to their brothers.This fundamental need for attention,and doing whatever it takes to get it,doesn’t disappear when we turn into adults.Sure,there are people who are“real attention seekers”in a loud and extravert（外向的）way,and there arethe shy,retiring types who don’t want attention in such a“sociable”way.But everybody still wants to be recognized and seen as worthwhile.5.What will children probably do to get parents’attention？[A]They will keep quiet for a long time.[B]They will ignore their parents.[C]They will behave naughtily.[D]They will get cross easily.5.What does the phrase“the easy trap to fall into”in Paragraph2probably mean？[A]A set-up situation parents are likely to go into.[B]The household work parents can not avoid.[C]Some tempting food children love to eat.[D]A bad habit children easily develop.6.An effective way to make children behave themselves may be to_____.[A]scold them severely[B]teach them what to do[C]give them total freedom[D]praise their sisters or brothers7.“Real attention seekers”in the last paragraph are probably those who_____.[A]motivate others to learn[B]associate with shy types[C]rely on negative attention[D]arouse others’attention openly8.What point does the author make by relating to children’s behavior？[A]Children’s upbringing needs parents’constant care.[B]Children are usually extravert while adults are sociable.[C]Both adults and children need to be seen as worthwhile.[D]The motivation of children differs greatly from that of adults.CNamed for the dense shade of their thick pines,the Black Hills of South Dakota have for centuries been considered holy by the Lakota Sioux,once the most powerful tribe in the West.Today,because of the passions of a few artists,the land itself has become holy in another way.It took the obsessed sculptor Gutzon Borglum,his son Lincoln,and four hundred workers fourteen years （1927-1941）to complete an artistic and engineering project so monumental that no one believed it possible: carving and blasting the six-story faces of George Washington,Thomas Jefferson,Teddy Roosevelt,and Abraham Lincoln out of stony Mount Rushmore.A little trivia:Washington’s eyes are11feet wide,and his nose is26feet long.Mr.Lincoln,for his part,sports a mole（痣）that measures16inches across.Just17miles away,the gigantic Crazy Horse Memorial is slowly taking shape.Also carved into granite（花岗岩）,this memorial,when completed somewhere around2050,after a century’s labor,will depict（刻画）Native America’s greatest warriors chief on his horse,dwarfing Mount Rushmore at563feet tall.The horse’s nostril（鼻孔）alone will be large enough to hold a five-room house.From Crazy Horse,head east on the beautiful14-miles Needles Highway,past billion-year-old granite hills, to Sylvan Lake and then north to Spearfish Canyon Scenic Byway,whose landscape you’ll easily recognize as the backdrops used in the film Dances with Wolves.Alternatively,you can park your bags in the pleasant Game Lodge that served as Calvin Coolidge’s Summer White House.Of the historic inn’s seven rooms,you can still book the room the thirtieth president and his wife occupied during the three months in1972.The lodge is one of three found within Custer State Park,whose18-miles Wildlife Loop Road runs through unfenced meadows where herds of 1,500buffalo roam.9.The word“sports”in Paragraph2most probably means_____.[A]is famous for[B]is characterized by[C]is decorated with[D]is accompanied by10.Of the four things mentioned in the passage,which one is the largest？[A]Washington’s eyes.[B]Washington’s nose.[C]Lincoln’s mole.[D]Crazy Horse’s nose.11.Which of the following projects is still in progress？[A]Lincoln’s face.[B]Crazy Horse.[C]Summer White House.[D]Wildlife Loop Road.12.What is NOT a feature that Mount Rushmore sculpture and Crazy Horse have in common？[A]They were very large.[B]They were carved out of granite.[C]They were located in the Black Hills.[D]They both depicted the Indian tribes.13.Who is the thirtieth president of the US？[A]Thomas Jefferson.[B]Teddy Roosevelt.[C]Abraham Lincoln.[D]Calvin Coolidge.D[A]A magazine.[B]A newspaper.[C]A government white paper.[D]A university journal.15.According to the passage,male managers tend to_______.[A]be more selfless in teamwork[B]ask more questions when surveyed[C]be considerate leaders in a company[D]claim the contribution made by their colleagues16.What can be found after comparing the findings in the UK and in the US ？[A]The findings are irrelevant.[B]The findings are contradictory.[C]The findings match each other.[D]The findings are not significant.17.What does the phrase“penny-pinching companies”in Paragraph 7probably mean ？Women are more efficient and trustworthy,have a better understanding of their workforce and are more generous with their praise.In short they make the best managers,and if men are to keep up they will have to start learning from their female counterparts,a report claims today.The survey of 1,000male and female middle and senior managers from across the UK is an indictment （谴责）of the ability of men to function as leaders in the modern workplace.A majority of those questioned believed women had a more modern outlook on their profession and were more open—minded and considerate.By way of contrast,a similar number believe male managers are self-centered and more likely to steal credit for work done by others.Management Today magazine,which conducted the research,said that after years of having to adopt a masculine identity and hide their emotions and natural behavior in the workplace,women have become role models for managers.The findings tally with a survey of female bosses carried out in the US.A five-year study of 2,500managers from 450firms found that many male bosses were rated by their staff of both sexes to be self-centered and autocratic （独裁的）.Women on the other hand leave men in the starting blocks when it comes to teamwork and communicating with staff.In Britain more than 61%of those surveyed said men did not make better bosses than women.Female managers use time more effectively,with many of those surveyed commenting that juggling （兼顾的）commitments is a familiar practice for women with a job and a family.Female managers also appear to make good financial sense for penny-pinching companies :most people,of either sex,would rather ask for a rise from a man.14.What is the source of the data mentioned in the passage ？[A]Companies that lack money.[B]Companies that are very generous.[C]Companies that earn a lot of money.[D]Companies that are unwilling to spend money.18.What is the main idea of the passage ？[A]Men are better managers than women.[B]Women are better managers than men.[C]Male managers are more willing to learn.[D]Men leaders and women leaders have different advantages.A.Focus on the conversation at hand.B.If you can’t look the interview in the eye,they won’t believe your answer.C.It is your real opportunity to get face to face with your potential employer.D.If the interviewers haven’t indicated when a decision will be reached,ask them.E.Explain in detail how a team atmosphere can improve your personal efficiency.F.Losers dwell on past losses whereas winners dwell on future success.第二部分：七选五阅读（共5小题,每小题2分,满分10分）文中有5个空格,每个空格为一题,要求考生根据文章的意思从所提供的7个选项中选出最合适的5个,分别填入空格处,其余2项为多余选项。

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