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与研究生谈研究/学习方法陈小伟2009.03研究生的定位：本科生：掌握专业基础，被动学习；工作后，可能需较长时间具备初步的研究能力；硕士（bycourse,byresearch）在导师指导下，初步掌握研究方法和研究方向，师傅领进门，强调科研技能的训练；博士（byresearch）在导师指点下，较自主地在某一方向开展研究工作，已具备一定的研究能力；博士后，国外：临时工作，国内：考察后决定是否定岗研究生与导师的关系森林与兔子优秀的导师能预见到森林有无兔子、有多少兔子；在有兔子的森林中，优秀的学生凭己之力能抓到兔子，且抓到更多的兔子。论文的署名顺序、相互尊重Idea的归属与实际的劳动；国际惯例、国内高校、院内单位。研究生与导师双赢科研工作的步骤

1文献调研资料的完整、全方位认识；研究水平和研究进展；活跃的研究团体、密切相关的期刊和会议；直接决定申请课题的水平。2课题申请（立题）迫切需求、问题独特、方法新颖、思路清晰、研究实力科研工作的步骤

3课题分解负责人：研究能力和水平、组织协调、方向把握、深度认识、亲力亲为、能力资源的适配、其它；参加人：主观能动性、协同性、专业性、问题把握；明天的课题负责人4研究工作理论分析、实验研究、数值模拟5结题科技报告、论文、成果报奖对文献调研的认识重要性；但仅是科研工作的第一步；它服务于研究工作；不是研究工作的末态（强调）；工作中的误区中英文期刊的区别英文期刊，一般强调论文的完整性，论文篇幅较长，可达20页。信息量大，文章内容无跳跃，可重复推导。审稿严格，匿名制，国际性。专业期刊强调本专业的新动向，主编（公认权威）有引导性。中文期刊，论文篇幅短，一般不超过6页。相当于前者的TechnicalNote。文章内容大量删减，跳跃太多，正确与否很难判断。国内的一些情况，导致论文质量严重下降…建议：以外文期刊为主参考。美国“四大报告”

（AD、LANL、LLNL、Sandia)专业密切相关内容翔实、分类明晰时间前效性寻找研究方向信息中心：文献检索、平片报告GF报告的现状收录时间短、数据库不全研究水平良莠不齐处于较尴尬的发展期最新文献跟踪充分利用互联网

,,

，等等外文期刊文献预告（journalalerting)

，，，AIAA,IEEE,等等.中文文献库：万方系统最新文献跟踪论文摘要e-mail通知，期刊网址查阅期刊论文摘要和PDF文档。1~2月周期，图书馆重点查阅与本专业紧密相关的期刊电子版图书馆过往文献追溯专业细化，确立本专业紧密相关的期刊，一般而言，本专业的最好文章第一选择发表期刊。如冲击动力学，InternationalJournalofImpactEngineering按关键词查找数据库,INSPEC,,SCI,etc.；找寻最新的论文或综述文章,按引用文献追溯；阅读方法论文摘要(abstract)：论文工作的简介，重点在实验方法、理论模型、分析过程，文章的精华；引言(introduction)：文献综述，了解相关工作的动态，追踪前人工作；结论（conclusions)：与摘要不同，给出工作的创新点，在一般性的认识上有更独特的理解；讨论（discussions/remarks)：常给出作者对现有工作不足的分析、未来工作的建议，有启迪性；插图和公式（Figures&Formula):

可快速理解文章要旨；阅读方法确定论文有重要参考价值，才细读全文!!!论文阅读以理解为主，不需要逐字逐句翻译强调记录Word文档,重要段句，以备它用和遗忘。PDF文档。高效的阅读和Word记录文档有助于写作，如文献综述、句式借用等。词汇积累!!!关于“review:Non-idealprojectileimpactontargets”及其阅读GoldsmithW(1924-2003),加州伯克利教授，冲击动力学领域的最卓越教授之一。全文300余页，晚年生涯的又一显著贡献。该文献综述(专著)是开展非理想撞击/侵彻动力学研究的必读之书非力学专业，建议仅阅读PPT文档，专业词汇不作要求；力学专业（尤其从事冲击与穿甲动力学专业），建议阅读复印材料全文，并熟悉Notation的专业术语Thissurveysummarizesanalytical,numericalandexperimentalinvestigationsoftargetssubjectedtononstandardcollisions,penetrationandperforationofstrikers,definedasallcasesotherthannormalimpingementofapurelytranslatingimpactoronastationarytargetatnormalincidence.Thevastmajorityofballisticstudiesareconcernedwiththestandardconfigurationandconditionsindicated,butvirtuallyallfieldsituationsdeviatefromthisscenario.Thetopicstreatedhereinclude:obliqueimpact,yawimpact,impactwithyawandobliquity,impactonmovingtargets,rotatingpenetrators,impactoftumblingprojectiles,impingementofjetsorlongrodswithrelativetargetmotion,andricochet.Othertypesofnonidealprojectileimpactexist,buthavenotbeensufficientlyexploredtobedocumentedhere.Thesectionsaredivided

bystrikertype(whereapplicable)asspheres,projectilesandlongrods;byvelocityrange,andbythetypeofinvestigationperformed.Sufficienttechnicalinformationispresentedtoprovideareasonableassessmentofthecharacter,approachandresultsobtainedforthevariousstudies.Ifmoredetailedinformationconcerninganalyticalorexperimentalproceduresarerequired,thereadershouldconsulttheoriginalreferenceswhicharefullylisted.AbstractIntroductionThestudyoftheeffectsoftheimpactofprojectilesontargets

hasalonghistoryofnearlytwoandahalfcenturies;thefirst150yearsweredevotedalmostexclusivelytoempiricalstudies

ofthedegreeofpenetrationorachievementofperforationofinnumerabletargetsstruckunderavarietyofconditionsbyallmannerofmissilesovertheentirerangeofinitialvelocitiesv0achievableatanyparticulartime[1,2].ThefirstcollectionofrandomlyconductedtestresultswaspublishedbyHelie´[3];thisworkalsocontainedthefirstinformationonobliqueimpact,adeviationfromthestandardtestconfigurationsofnormalimpactofatranslatingpenetratoronastationarytarget.Theendofthe19thcentury

sawthebeginningofsimplesemi-empiricalorquasi-rationalrepresentationsofthistypeofimpact;thesehavebeensuccessivelyrefinedduringthe20thcenturytomorepreciselymodelvariousmechanismsmanifestedinthesecollisionsandthusprovideameasureofpredictivecapability.Furthermore,

thelastfourdecadeshaveseenthedevelopmentofmanynumericalproceduresinparallelwithanalyticaltoolstofurnishanalternativemethodforaquantitativedescriptionoftheimpactevent.Whenanalyticalrepresentationsprovedtobeintractableorinadequate,computationalresultsconstitutedthesolebasisofcomparisonwithmatchingexperimentaldata.Theseroutinesemploypointorspatialdiscretization,aconstitutiveequationforbothmechanicalandthermalbehavior,andcriteriafordeformationand/orfailurelimitsandphysicalseparationofinitiallyintegralcomponents.时间顺序的综述修饰词汇尽可能丰富，专业词汇要求准确BackgroundandscopeThevastmajorityoftheinvestigationsinthisdomainhaveinvolvedwhatwillbetermed‘‘idealcollisionconditions’’:thenormalimpactofapurelytranslatingprojectileagainstastationaryobject.Theenormousliteratureonthissubjectpassesahugevarietyofdifferenttargetmaterialsandthicknessesh(includingthelimitingsemi-infinitecase),aswellasahostofstrikergeometriesandavelocityrangefromabout5m/stothehypervelocitydomain,oftheorderof15km/s.Acomprehensivesurveyofthesubjectupto1977ispresentedinRef.[4],whichalsocontainsabriefreviewofearliersummaries.Thatreferencealsoprovidesaseriesofdefinitionsthatwillbecontinuedinthecurrentwork.Thisincludesthemeaningoftheall-inclusiveexpression‘‘striker’’andthemorerestrictedsignificanceof‘‘projectile’’and‘‘penetrator’’,characterizedbyatipshape,shankdiameterD,andlengthL.Italsoincludesthedefinitionoftarget,targetelementandbothtargetthickness(thin,h/D<1;intermediate,1<h/D<10;andsemi-infinite,h/D>10)andvelocityrangeclassifications(subordnance,v0<500m/s:ordnance,500<v0<1500m/s;ultraordnance,1.5<v0<3km/s,andhypervelocity,v0>3km/s).过渡和提出问题However,theseidealimpactsituationsonlyoccurinthelaboratory.Inreality,targetsurfacesdonotpresentthemselvesatnormalincidencetothetrajectoryofaprojectile;evenifthetrajectorywasdesignedforthestrikertoarriveinthisorientation,aerodynamicforcesandinstabilitieswillgeneratecollisionsatobliquityandwithyaw.Whilemanytargetsarestationary,otherswillbeinmotionand,further,theprojectilemaybefiredfromamobilesource,thateffectivelyproducesyawand/orobliquity.Manystrikersarelaunchedwitharotationalvelocityabouttheiraxesastheresultofbarrelrifling;thisspinalsorepresentsastabilizinginfluencefortheirintendedtrajectory.Perforationoforglancingcontactwithshieldsmayinducestrikertumbling,anotherfrequentlyobservedprojectilemotion.Thesedeviationsfromtheidealcollisionscenariowillbeexaminedinthesequel.给出论文的目标Thispresentation,consistingofanextensivesurvey(ratherthanacriticalreview)ofpublishedresearch,isintendedtoprovidethereaderwithanoverviewofthesubject,includingthedirectionandthrustoftheeffortsaswellassomemajorresults.Clearly,notalldetailsofthevariousinvestigationscanbeencapsulatedhere;rather,oneoftheobjectivesofthisworkistopermitthepractitionertodecidewhetherornotheneedstoconsultoriginalreferencesforfurtherinformation.Conversely,someimportantstudiesthatarenotreadilyavailableintheliteratureorwherethesubjecthasonlyreceivedlimitedattentionarepresentedinsomewhatgreaterdetail.However,thiscompendiumwillnotpassimpacts,albeitsatisfyingthenon-idealconditions,wherepenetrationand/orperforationisnotamajorobjective.Thus,variousinvestigationsinvolvingtheimpactofspheresonbeamsormassivestrata,suchasdiscussedinRefs.[20–28],willnotordinarilybepursuedhere.经验公式不能外推Asinmostcurrentdisciplinesinvolvingthephysicalsciences,studiesofthecollisioneventhavebeenundertakeneitherbyexperimentalmethods,analyticalornumericalmodeling,or,frequently,byacombinationofthesetechniques.Earlyexperimentationledtopurelyempiricalresultswhichfailedtoprovidelimitsontheirapplicabilityandhencecouldnotbeconfidentlyextrapolated.However,thereexistscurrentlyinthetradeasignificantlibraryofempiricalequationsusedbypractitionersfordesignpurposesandforpredictingballisticbehaviour.Thereasonfortheuseofsuchexpressions,whichdonothavearationalbasis,istheabsenceofsufficientlyaccuratemodelsforpredictingtheseevents.现象描述模型和计算模型倚赖于本构和失效准则，需要实验验证和判断；同行对数值分析的一些看法Conversely,phenomenologicalandcomputationalmodelingaddressdeformationanddamagepatterns;theyrelyheavilyonconstitutivebehavior,bothmechanicalandthermal,andonlimitingstatesexpressedintermsoffailurecriteria.Thus,theseapproachesrequirethebalanceoflaboratoryorfieldmeasurementstoassessthevalidityoftheassumptionsunderlyingthetheoreticaldevelopmentandtogagetherelativeimportanceofthevariousmechanismsconsidered.Onlybrieftreatmentsofpurelynumericalresultswillbegivenhere,asnumberssogeneratedcanbeoverwhelminganddonotaloneaidinanunderstandingofthephenomenon;furthermore,theymustberegardedverycarefullyintheabsenceofsupportingtestdataoranalyticalverification.Finally,althoughpartlyincludedhere,someoftheoldercoderesultsmaybeinerrororhavebeensupersededbymoreadvancedprograms.CharacteristicsofprojectileshavebeendetailedinRef.[4],dividedintomethodsoflaunchingandintendedeffect.Thestrikers,ofmassm,universallyemployedinthestudiescitedconsistedeitherofspheresorblunt,spherical,cylindro-conicalorogival-tippedcylinders(includingarmorpiercingshapes)withaspectratiosoffiveorless,andwithshankdiameterD.Alternatively,effectiveballisticperformancehasbeenachievedbyuseofkineticenergypenetratorscomprisedoflongrodsofcircularorsquarecrosssection,sometimessegmented[29,30],thatpresentaspectratiosof10ormore.Allofthesestrikersexhibitalongitudinalaxisofsymmetry(ornearsymmetry);spheres,ofcourse,featureaninfinitenumberofsuchsymmetryaxeswhichisoneoftheprincipalreasonsfortheiruseinballisticlaboratoryexperiments.Materialsfortheseimpactorsconsistofavarietyofmetalsincludingnumerousgradesofferroussubstancesrangingfrommildtothemostcomplextypeofalloysteel,withhardnessesupto

RC65.Inaddition,nearlypurealuminumandawholehostofaluminumalloys,magnesium,brass,copper,titanium,tantalum,tungstenandtungstencarbideandevendepleteduranium,aswellasavarietyofplasticsandceramics,suchaspolyethyleneandglass,havebeenutilizedforballisticpurposes.Thechoiceofmaterialisgovernedbytheintendedeffect:theprobabilityofperforationisenhancedifthestrikerhasahighdensityandkineticenergy,provided,itremainsintact;thisrequiresahighfailurestressanditanthardness,asachievedbyalloysteel.Large-scalecrateringattheimpactpositionrequiresamoredeformablematerial,butstillofsufficienthardnesstoproducesomepenetration,likesomegradesofaluminumalloy.Shatteringoftheimpactorisachievedwithelastic/brittlematerials,suchasglass,ceramicsorbrittlepolymers.Whentargetdeformationistheprimaryobjective,themass,presentedareaandvelocityofthestrikerplaytheprimaryrole.Targetmaterials,ingeneral,comprisevirtuallythewholegamutofmanufacturedand,incertaincases,naturalsubstances,thelatterbeingexemplifiedbyrocksandwood.However,thetargetsemployedintheinvestigationstobedescribedconsistalmostexclusivelyofseveralgradesofsteelandaluminum;exceptionsarerepresentedbystudiesinvolvingtitaniumandconcrete.Themetalsareconsideredtobemacroscopicallyhomogeneousandisotropic;theyarespecifiedbystandardterminologyandarecharacterizedforuniaxialtestsbyasetoftwostrain-rate-independentparametersintheelasticrange(usuallyYoung’smodulusEandPoisson’sratiov),ayieldstressY,astrain-hardeningrelationandanultimatestrength(orfailurestrain).Thisinformationiswelldocumentedinstandardreferencesinvolvingmaterialpropertiesandneednotbefurtherdiscussed.Concreteisacomplexmixturewhosematerialdescriptionisnotwellestablished.Themechanicalbehaviorofplasticsandcompositeshasbeenpresentedinanumberofjournalarticles,i.e.Refs.[31,32];althoughnonon-idealpenetrationdatahavebeenobtainedforthesesubstances,testsinvolvingsuchmaterials,similartothosedescribedhereforsteelandaluminum,willundoubtedlybeperformedinthenearfuture.Conclusions–Statusofnon-standardprojectileimpact

Thissurveyoftheimpactofprojectilesontargetunderconditionsotherthanthenormalcollisionoftranslatingstrikersonstationaryobjectswasintendedtosupplementanearliersurveyonnormalimpact[4],thatwassupplementedrecentlybymaterialsince1978[6].Theworkhasendeavoredtopassallaccessiblematerialonthesubject,includingthesomewhatextraneoustopicofjetpenetrationatobliquity,butwillinevitablyhavemissedsomeimportantcontributions.Inmanycases,sufficientinformationisprovidedsothatthereaderneednotconsulttheoriginalsources,butcompletepresentationsofcertainaspectsoftheinvestigations,notablyexperimentaldetails,arenotincluded.Itislikelythatanotherupdateonthesubjectisinorderinperhaps15–20years.Unfortunately,manyexcellentpapersarepublishedinobscureornon-archivaljournalsorelsecontainedinreportsbygovernmentagenciesanddefensefirms,andtheircirculationisthushighlyrestricted.Anendeavortoprintmajorresultsinwidelycirculatedpublicationswouldbeaeadditiontotheliterature.综述的时间性Thecontentsofthisworkmakeitclearthatcertaintopicshaveapparentlynotbeenexaminedatall,whileothershaveonlybeeninvestigatedbyafewresearchers.Thefirstcategorypasses,forexample,acombinationofyaw,obliquityandmovingtargetsand/orstrikerrotationforprojectiles,whilethesecondtopicisrepresentedbytheeffectsofrotationonpenetratorperformance.Mostofthetargetscitedareatleastmacroscopicallyhomogeneous;protectivebarriersarefrequentlycomposedofanumberofadjacentelementswhoseperformanceneedstobeinvestigated.Finally,exoticpenetratorssuchassegmentedrodshavenotbeenstudiedunderconditionsofnon-standardimpact;asignificantcontributioncanbemadeinthisareaaswell.作者对未来工作的意见Thephenomenadescribedaregenerallymorecomplexthanthoseproducedunder‘‘standard’’conditions,althoughthatstatecanbeausefulpointofdepartureformanyofthesituationsdescribedhere.Themethodologiesemployedintheinvestigationsinvolvethetechniquesofexperimentation,analyticaldescriptionsandnumericalmodeling;frequently,twoofthesethreeapproacheshavebeenappliedtoaparticularproblem,butseldomhaveallthreebeeninvoked.Testoperations,sometimescomputer-controlled,haveutilizedmodernmethodsofhigh-speedobservation,suchasflashand/orX-rayphotography,withpropulsiongeneratedeitherbystandardgunsorhighlyspecializedprojectiondevices,togetherwithahostofauxiliarymeasuringequipment.Analyseshavegenerallyutilizedtheprocedureofdynamicsofrigidbodies,strengthofmaterials,andvariousbranchesofcontinuummechanicssuchaselasticity,plasticity,viscoelasticityoracombination.Here,aswellasincomputercalculations,themostimportantdocumentationconcernsaproperdescriptionofthematerialbehavior,bothintermsofconstitutiverelationsandlimitingstrengths,particularlyundercombinedandrapidloading.Inthecontinuumdomain,thermaleffectshavegenerallybeenignored,althoughtheirpresencemusthaveastronginfluenceonmaterialproperties.However,sucheffectshavebeenincludedonanumberofoccasionsinequationsofstateusedinnumericalcalculations,althoughthebasisoftheserelationsarenotalwaysthoroughlydocumented.Whilemanyelementarymodelsbasedongrosslysimplifyingassumptionshavebeensuggested,onlyminimaleffortshavebeenexertedtoimprovethedescriptionofthephenomenonbysuccessiveadditionsofmorerigorousrepresentations.Furthermore,boththeoreticalandnumericaldescriptionshavebeendevotedalmostexclusivelytomacroscopicrepresentations,avoidingmaterialscienceconsiderationssuchasphasechanges,dislocationsandhardening.Itisinthesetwodomainsthatmuchusefulworkcanbedevelopedinthefuture.Majorinteresthasbeenshowninadescriptionoflimitingstatesofballisticbehavior,suchascriticalvelocitiesandanglesofobliquityforembedmentorricochet,andinvariousformsoffragmentationofthestrikers.Togetherwiththeconceptoftheballisticlimit,theseparametersareessentiallystructural/geometricalratherthancontinuummechanicalproperties.Theirspecificationisveryimportantfortheballistician,butonemustguardagainsttheuseofsuchvaluesoutsidethedomainwhereexperimentaldatahaveshownthemtobeapplicable.Sincegrossbehavioralchangescanbeexpectedwithcontinuousincreaseinimpactvelocity,thisprecautionshouldbeobvious.Ballisticphenomenaaresomeofthemostcomplicatedeventsthatcanbecreatedinthelaboratoryandinthefield,andtheintenseinterestofthecommunitytowanttounderstandtheseoccurrencesandtodescribethemproperlyisonlynatural.However,inadditiontoprovidingpracticalinformation,thatmaybevitalfornationalsecurity,projectileimpactalsoprovidesamechanismforstudyingfundamentalmechanicalprocessesandmaterialbehavior,andthisaspectofthescienceshouldnotbeoverlooked.阅读综述性期刊文献力学