Directions: Write a letter to your cousin, who is going to take the College Entrance Examination and feels stressed, giving him some suggestions. Write your letter with no less than 100 words. Do not sign your name at the end of the letter. Use "Li Ming" instead. Do not write the address.

设总体X服从于正态分布Nμσ2σ＞0从该总体中抽取简单随机样本X1X2X2nn≥2其样本均值为求统计量Y=的数学期望EY

已知商品的需求量D和供给量S都是价格p的函数D=Dp=s=sp=bp其中a＞0b＞0为常数价格p是时间t的函数且满足方程k为正常数．①假设当t=0时价格为1．试求需求量等于供给时量时的均衡价格pe

设ABC是三个两两相互独立的事件且PABC=00＜PC＜1则一定有______．

设X1X2Xn是总体N01的简单随机样本记T=则ET的值为______

设AB为n阶对称矩阵下列结论不正确的是______

设n=12则下列级数中肯定收敛的是______

AB均是n阶矩阵且A2-2AB=E则秩rAB-BA+A=______．

设X1X2Xn为来自总体N0σ2的样本则样本二阶原点矩的方差为______

已知线性方程组AX=kβ1+β2有解其中A=则k等于______

设fx在-∞0]上连续且满足求fx及其极小值

设fx在ab内可微且fa=fb=0f’a＜0f’b＜0则方程f’x=0在ab内______．

设函数fx在x=2的某邻域内可导且f’2=0又=-2则f2______．

设随机变量ξ的分布密度为求系数A

设A=ijn×n是正交矩阵将A以行分块为A=α1α2αnT则方程组AX=bb=b1bnT的通解为______

已知随机变量X和Y相互独立则X～N11Y～N14又PaX+bY≤0=则a与b应满足关系式______

Donotsignyourownnameattheendoftheletter.UseDepartmentofChineseLanguageandLiteratureinstead. Donotwritetheaddress.

Chronicinsomniaisamajorpublichealthproblem.Andtoomanypeopleareusing1therapiesevenwhilethereareafewtreatmentsthatdowork.MillionsofAmericans2awakeatnightcountingsheeporhaveastiffdrinkor3anpillhopingitwillmakethemsleepy.4expertsagreeallthatself-medicatingisabadideaandthecausesofchronicinsomniaremain5.a Chronicinsomniaisamajorpublichealthproblem.Andtoomanypeopleareusing1therapiesevenwhilethereareafewtreatmentsthatdowork.MillionsofAmericans2awakeatnightcountingsheeporhaveastiffdrinkor3anpillhopingitwillmakethemsleepy.4expertsagreeallthatself-medicatingisabadideaandthecausesofchronicinsomniaremain5. Almostathirdofadultshavetroublesleepingandabout10percenthave6ofdaytimeimpairmentthatsignaltrueinsomnia.But7thecomplaintsscientistsknowsurprisinglylittleaboutwhatcauseschronicinsomniaitshealthconsequencesandhowbesttotreatitapanelofspecialists8togetherbytheNationalInstitutesofHealthconcludedWednesday.Thepanelcalled9abroadrangeofresearchintoinsomnia10thatifscientistsunderstoodits11causestheycoulddevelopbettertreatments. Mostbutnotallinsomniaisthoughtto12otherhealthproblemsfromarthritisanddepressiontocardiovasculardisease.Thequestionofteniswhethertheinsomniacamefirstorwasaresultoftheotherdiseasesandhowtroublesleepingin13complicatesthoseotherproblems.Otherdiseases14theriskofinsomniaseemstoincreasewithageandtobemore15amongwomenespeciallyaftertheir50s.Smokingcaffeineandnumerous16drugsalsoaffectsleep. TheNIHisspendingabout$200millionthisyearonsleep-relatedresearchsome17tospecificdisordersandothers18theunderlyingscientificlawsthatcontrolthenervoussystemofsleep.Theagencywas19thepane’sreviewbeforedecidingwhatadditionalworkshouldbe20atinsomnia. 15

设随机变量X的分布函数为对X独立观测3次则3次结果都不超过1的概率为______．

设fuv具有连续偏导数且f’uuv+f’vuv=sinu+veu+v求yx=e-2xfxx所满足的一阶微分方程并求其通解

二次型fx1x2x3=x12+4x22+4x32-4x1x2+4x1x3-8x2x3的规范型是______

若|f’x|＜g’xx≥a则当x＞a时必有______

设A是n阶正定矩阵E是n阶单位阵证明A+E的行列式大于1

方程=0在区间01内的实根个数为______

设X1X2Xn是取自总体X的简单随机样本X的概率密度为-∞＜x＜+∞λ＞0．试求λ的矩估计

设=5则=______．

设微分方程yx是方程Y+x-1Y’+x2y=ex满足y0=0y’0=1的解则______

Donotsignyourownnameattheendoftheletter.UseLiMinginstead. Donotwritetheaddress

用配方法化二次型fxyz=x2+2y2+5z2+2xy+6yz+2zx为标准形并求所用的可逆线性变换．

已知矩阵B满足BA*+2A-1=B其中A*是A的伴随矩阵则|B|=______．

已知f’x=arctanx-12f0=0则fxdx=______．

设随机变量X服从02上的均匀分布Y服从参数λ=2的指数分布且XY相互独立记随机变量Z=X+2Y.求Z的概率密度

假设一部机器在一天内发生故障的概率为0.2机器发生故障时全天停止工作若一周5个工作日里无故障可获利润10万元发生一次故障仍可获利润5万元发生二次故障所获利润为0元发生三次或三次以上故障就要亏损2万元求一周内期望利润是多少

设α1=1231Tα2=112-1Tα3=13a3Tα4=357-1Tβ=011bTⅠ当ab满足什么条件时β可由α1α2α3α4线性表示且表示式唯一Ⅱ当ab满足什么条件时β可由α1α2α3α4线性表示且表示式不唯一并求出β的表示式

Themythologyofaculturecanprovidesomevitalinsightsintothebeliefsandvaluesofthatculture.Byusingfantasticandsometimesincrediblestoriestocreateanoraltraditionbywhichtoexplainthewondersofthenaturalworldandteachlessonstoyoungergenerationsasocietyexposesthoseideasandconceptsheldmostimportant.Justasimportantasthefinallessontobegatheredfromthestorieshoweverarethecharactersandtherolestheyplayinconveyingthatmessage.PerhapstheepitomeofmythologyanditsuseasatooltopassonculturalvaluescanbefoundinAesop’sFablestoldandretoldduringtheeraoftheGreekEmpire.Aesopaslavewhowonthefavorofthecourtthroughhisimaginativeanddescriptivetalesalmostexclusivelyusedanimalstofilltherolesinhisshortstories.Humanswhenatallpresentalmostalwaysplayedthepartofbumblingfoolsstrugglingtolearnthelessonbeingpresented.ThischoiceofcharacterizationallowsustoseethattheGreeksplacedwisdomonalevelslightlybeyondhumansimplyingthatdeepwisdomandunderstandingisauniversalqualitysoughtbyratherthansteanningfromhumanbeings.Aesop’sfablesillustratedthecentralthemesofhumilityandself-reliancereflectingtheimportanceofthosetraitsinearlyGreeksociety.Thefollyofhumanswasusedtocontrastagainsttheultimategoalofattainingahigherlevelofunderstandingandawarenessoftruthsaboutnatureandhumanity.Forexampleonenotablefablefeaturesafoxrepeatedlytryingtoreachabunchofgrapesonaveryhighvine.Afterfailingatseveralattemptsthefoxgivesupmakingupitsmindthatthegrapeswereprobablysouranyway.Thefable’slessonthatweoftenplaydownthatwhichwecan’tachievesoastomakeourselvesfeelbetterteachesthereaderorlistenerinanentertainingwayaboutoneoftheweaknessesofthehumanpsyche.ThemythologyofotherculturesandsocietiesrevealtheunderlyingtraitsoftheirrespectiveculturesjustasAesop’sfablesdid.ThestoriesofRomangodsAztecghostsandEuropeanelvesallservedtotrainancientgenerationsthoselessonsconsideredmostimportanttotheircommunityandtodaytheyofferapowerfullookingglassbywhichtoevaluateandconsiderthecontextualenvironmentinwhichthosecultureexisted.Theauthorappearstoviewfablesas

设A=则A2011-2A2010=______

设随机变量XY相互独立X在区间[05]上服从均匀分布Y服从参数为1的指数分布令Z=maxXY.计算PX+Y＞1

矩阵A=与下面矩阵______相似．

A=Am×nRA．=rb为m维列向量则有______

函数fxy=在点00处______．

=______．

计算D是下图中的阴影区域．

Cyberspacedatasuperhighwaysmultimedia—forthosewhohaveseenthefuturethelinkingofcomputerstelevisionandtelephoneswillchangeourlivesforever.Yetforallthetalkofaforthcomingtechnologicalutopialittleattentionhasbeengiventotheimplicationsofthesedevelopmentsforthepoor.AswithallnewhightechnologywhiletheWestconcernsitselfwiththehowthequestionofforwhomisputasideonceagain.Economistsareonlynowrealizingthefullextenttowhichthecommunicationsrevolutionhasaffectedtheworldeconomy.Informationtechnologyallowstheextensionoftradeacrossgeographicalandindustrialboundariesandtransnationalcorporationstakefulladvantageofit.Termsoftradeexchangeandinterestratesandmoneymovementsaremoreimportantthantheproductionofgoods.Theelectroniceconomymadepossiblebyinformationtechnologyallowsthehavestoincreasetheircontrolonglobalmarkets—withdestructiveimpactonthehave-nots.Forthemtheresultisinstability.Developingcountrieswhichrelyontheproductionofasmallrangeofgoodsforexportaremadetofeellikesmallpartsintheinternationaleconomicmachine.Asfuturesaretradedoncomputerscreensdevelopingcountriessimplyhavelessandlesscontroloftheirdestinies.SowhataretheoptionsforregainingcontrolOnealternativeisfordevelopingcountriestobuyinthelatestcomputersandtelecommunicationsthemselves—socalleddevelopmentcommunicationsmodernization.Yetthisleadstolong-termdependencyandperhapspermanentconstraintsondevelopingcountries’economies.CommunicationstechnologyisgenerallyexportedfromtheU.S.EuropeorJapan;thepatentsskillsandabilitytomanufactureremaininthehandsofafewindustrializedcountries.Itisalsoexpensiveandimportedproductsandservicesmustthereforebeboughtoncredit—creditusuallyprovidedbytheverycountrieswhosecompaniesstandtogain.Furthermorewhennewtechnologyisintroducedthereisoftentoolowalevelofexpertisetoexploititfornativedevelopment.Thismeansthatwhilelocalelitesforeigncommunitiesandsubsidiariesoftransnationalcorporationsmaybenefitthosewhoselivesdependonaccesstotheinformationaredeniedit.Thedevelopmentofmodemcommunicationstechnologyindevelopingcountriesmay

设X服从正态分布N022而X1X2X15为来自总体X的简单随机样本则随机变量所服从的分布为______

已知三元二次型fx1x2x3=XTAX矩阵A的对角元素之和为3且AB+B=0其中B=求出此二次型

设函数y=yx由方程组所确定试求．

设二次型的正负惯性指数都是1则a=______

设向量组Ⅰα1α2αs的秩为r1向量组Ⅱβ1β2βs的秩为r2且向量组Ⅱ可由向量组Ⅰ线性表示则______

OneofthemostpressingchallengesthattheUnitedStates—andindeedtheworld—willfaceinthenextfewdecadesishowtoalleviatethegrowingstressthathumanactivitiesareplacingontheenvironment.Theconsequencesarejusttoogreattoignore.Wildlifehabitatsarebeingdegradedordisappearingaltogetherasnewdevelopmentstakeupmoreland.PlantandanimalspeciesarebecomingextinctatagreaterratenowthanatanytimeinEarth’shistory.Asmanyas30percentoftheworld’sfishstocksareoverexploited.Andthelistgoeson.Yetthereisreasontohavehopeforthefuture.Advancesincomputingpowerandmolecularbiologyareamongthetremendousincreasesinscientificcapabilitythatarehelpingresearchersgainabetterunderstandingoftheseproblems.Recentdevelopmentsinscienceandtechnologycouldprovidethebasisforsomemajorandtimelyactionsthatwouldimproveourunderstandingofhowhumanactivitiesaffecttheenvironment.Onepriorityforresearchisimprovinghydrologicalforecasting.Ithasbeenestimatedthattheworld’swaterusecouldtripleinthenexttwodecades.AlreadywidespreadwatershortageshaveoccurredinpartsofChinaIndiaNorthAfricaandtheArabianPeninsula.TheneedforwateralsoistakingitstollonfreshwaterecosystemsintheUnitedStates.Only2percentofthenation’sstreamsareconsideredingoodconditionandcloseto40percentofnativefishspeciesareraretoextinct.Usingavarietyofnewremotesensingtoolsscientistscanlearnmoreabouthowprecipitationaffectswaterlevelshowsurfacewaterisgeneratedandtransportedandhowchangesinthelandscapeaffectwatersupplies.Topreventoutbreaksofinfectiousdiseasesinplantsanimalsandhumansmorestudyisneededonhowpathogensparasitesanddisease-carryingspecies—aswellashumansandotherspeciestheyinfect—areaffectedbychangesintheenvironment.Theoveruseofantibioticsbothinhumansandinfarmanimalshascontributedtothegrowthofantibiotic-resistantmicroorganisms.Researcherscantakeadvantageofnewtechnologiesingeneticsandcomputingtobettermonitorandpredicttheeffectsthatenvironmentalchangesmighthaveondiseaseoutbreaks.HumanshavemadealterationstoEarth’ssurface—suchastropicaldeforestationreductionofsurfaceandgroundwaterandmassivedevelopment—sodramaticthattheyapproachthelevelsoftransformationthatoccurredduringglacialperiods.Suchalterationscausechangesinlocalandregionalclimateandwilldeterminethefutureofagriculture.Recentadvancesindatacollectionandanalysisshouldbeusedtodocumentandbetterunderstandthecausesandconsequencesofchangesinlandcoveranduse.ThepoorconditionofstreamsintheU.S.canbeattributedto

Upuntilafewdecadesagoourvisionsofthefuturewerelargely—thoughbynomeansuniformly—glowinglypositive.Scienceandtechnologywouldcurealltheillsofhumanityleadingtolivesoffulfillmentandopportunityforall.Nowutopiahasgrownunfashionableaswehavegainedadeeperappreciationoftherangeofthreatsfacingusfromasteroidstriketoepidemicflutoclimatechange.Youmightevenbetemptedtoassumethathumanityhaslittlefuturetolookforwardto.Butsuchgloominessismisplaced.Thefossilrecordshowsthatmanyspecieshaveenduredformillionsofyears—sowhyshouldn’tweTakeabroaderlookatourspecies’placeintheuniverseanditbecomesclearthatwehaveanexcellentchanceofsurvivingfortensifnothundredsofthousandsofyears.LookupHomosapiensintheRedListofthreatenedspeciesoftheInternationalUnionfortheConversationofNatureIUCNandyouwillread:ListedasLeastConcernasthespeciesisverywidelydistributedadaptablecurrentlyincreasingandtherearenomajorthreatsresultinginanoverallpopulationdecline.SowhatdoesourdeepfutureholdAgrowingnumberofresearchersandorganizationsarenowthinkingseriouslyaboutthatquestion.ForexampletheLongNowFoundationhasitsflagshipprojectamechanicalclockthatisdesignedtostillbemarkingtimethousandsofyearshence.Perhapswillfullyitmaybeeasiertothinkaboutsuchlengthytimescalesthanaboutthemoreimmediatefuture.Thepotentialevolutionoftoday’stechnologyanditssocialconsequencesisdazzlinglycomplicatedandit’sperhapsbestlefttosciencefictionwritersandfuturologiststoexplorethemanypossibilitieswecanenvisage.That’sonereasonwhywehavelaunchedArcanewpublicationdedicatedtothenearfuture.Buttakealongerviewandthereisasurprisingamountthatwecansaywithconsiderableassurance.Assooftenthepastholdsthekeytothefuture:wehavenowidentifiedenoughofthelong-termpatternsshapingthehistoryoftheplanetandourspeciestomakeevidence-basedforecastsaboutthesituationsinwhichourdescendantswillfindthemselves.Thislongperspectivemakesthepessimisticviewofourprospectsseemmorelikelytobeapassingfad.Tobesurethefutureisnotallrosy.Butwearenowknowledgeableenoughtoreducemanyoftherisksthatthreatenedtheexistenceofearlierhumansandtoimprovethelotofthosetocome.Ourvisionofthefutureusedtobeinspiredby

设fx在-∞+∞内是可导的奇函数则下列函数中是奇函数的是______

Collegegraduatesarenowleavingschoolwithnotonlyadiplomabutalsowithmoredebtthaninanyotherperiodinhistory.AccordingtotheCollegeBoardaveragefinancialaidperfulltimeequivalentstudentadjustedforinflationhasalmostdoubledinthelastdecade.Additionallynotonlyistheaveragestudentdebtloadhigherbutalsothenumberofloansoriginatedincreasedbynearlyfourfold.Thusstudentlendinghasincreasedinbreadthaswellasdepthdoublyimpactingthefinancialsituationsofthosestudentswhomustdependonstudentloanstofinancetheireducation.Furthermorethesefiguresnodoubtunderstatethetruelevelofindebtednessincurredbystudentsandtheirfamiliessincesomeundoubtedlyfinancepartoftheireducationandlivingexpensesthroughtheuseofconsumerloanshomeequityloansorcreditcards.Thusthealreadyhugeburdenofstudentloandebtincurredbystudentsandtheirfamiliesisexacerbatedbyfinancialobligationsfromothersources.Thissituationistheoutcomeofaprecariouscombinationofeasycreditthankstocardissuerswhoareeagertotapintothislucrativemarketfinancialnaivetéonthepartofstudentsandasenseonbothsidesthatifworsecomestoworsemommyanddaddywillstepinandsetthingsright.Allcombinetomakecreditatemptingluretostudentsstrappedforcash.Whilecreditstillremainavirtualelementforthefinancingofmanystudents’educationatexpensivecollegesitsimplicationsmustcarefullyweighedandconsideredlestthecash-poorstudentfindhimselfwithmorethathebargainedfor.MoststudentsintheUnitedStatesattendcollegeswhosetuitiondoesnotexceed$15000however.Neverthelessrisingpricescombinedwithstagnantincomegainsamonglow-andmoderate-incomefamilieshavemadeitdifficultifnotimpossibleforastudentfromafamilyofsuchanincomelevelastudentwhohasthemosttogainfromacollegeeducationtoattendcollegewithoutsignificantlyaddingtothefinancialburdenofhisorherfamily.Whilestudentloansstillremainavitalelementforthefinancingofmanystudents’educationatexpensivecollegesitsimplicationsmustbecarefullyweighedandconsideredlestthecash-poorstudentfindhimselfwithmorethanhebargainedfor.Theauthorviewsstudentloansas

=______

设n阶实对称矩阵A的秩为r且满足A2=A求Ⅰ二次型xTAx的标准形Ⅱ行列式|E+A+A2++An|的值其中E为单位矩阵

设ab为正常系数λ为非负常数微分方程Ⅰ求该方程的通解Ⅱ证明当λ=0时当λ＞0时

设且F可微证明

电话公司有300台分机每台分机有6%的时间处于与外线通话状态设每台分机是否处于通话状态相互独立用中心极限定理估计至少安装多少条外线才能保证每台分机使用外线不必等候的概率不低于0.95

积分的值等于______

______.

设随机变量ξ的分布密度为求Eξ和Dξ

设A为三阶矩阵α1α2α3为三维线性无关列向量组且有Aα1=α2+α3Aα2=α3+α1Aα3=α1+α2．求A的全部特征值

设fx在-∞+∞存在二阶导数且fx=-f-x当x＜0时有f’x＜0fx＞0则当x＞0时有______

Relativitytheoryhashadaprofoundinfluenceonourpictureofmatterbyforcingustomodifyourconceptofaparticleinanessentialway.46Inclassicalphysicsthemassofanobjecthadalwaysbeenassociatedwithanindestructiblematerialsubstancewithsomestuffofwhichallthingswerethoughttobemade.Relativitytheoryshowedthatmasshasnothingtodowithanysubstancebutisaformenergy.Energyhoweverisadynamicquantityassociatedwithactivityorwithprocesses.47Thefactthatthemassofaparticleisequivalenttoacertainofenergymeansthattheparticlecannolongerbeseenasastatic_objectbuthastobeconceivedasadynamicpatternaprocessinvolvingtheenergywhichmanifestitselfastheparticle’smass.48ThisnewviewofparticleswasinitiatedbyDiracwhenheformulatedarelativisticequationdescribingthebehaviorofelectrons.Dirac’stheorywasnotonlyextremelysuccessfulinaccountingforthefinedetailsofatomicstructurebutalsorevealedafundamentalsymmetrybetweenmatterandanti-matter.Itpredictedtheexistenceofananti-matterwiththesamemassastheelectronbutwithanoppositecharge.ThispositivelychargedparticlenowcalledthepositronwasindeeddiscoveredtwoyearsafterDirachadpredictedit.Thesymmetrybetweenmatterandanti-matterimpliesthatforeveryparticlethereexistsanantiparticleswithequalmassandoppositecharge.Pairsofparticlesandantiparticlescanbecreatedifenoughenergyisavailableandcanbemadetoturnintopureenergyinthereverseprocessofdestruction.49TheseprocessesofparticlecreationanddestructionhadbeenpredictedfromDirac’stheorybeforetheywereactuallydiscoveredinnatureandsincethentheyhavebeenobservedmillionsoftimes.Thecreationofmaterialparticlesfrompureenergyiscertainlythemostspectaculareffectofrelativitytheoryanditcanonlybeunderstoodintermsoftheviewofparticlesoutlinedabove.50Beforerelativisticparticlephysicstheconstituentsofmatterhadalwaysbeenconsideredasbeingeitherelementaryunitswhichwereindestructibleandunchangeableorascompositeobjectswhichcouldbebrokenupintotheirconstituentparts.Andthebasicquestionwaswhetheronecoulddividematteragainandagainorwhetheronewouldfinallyarriveatsomesmallestindivisibleunits.

=______

dxdx=______

若则f[φx]=______．

设A为三阶矩阵有三个不同特征值λ1λ2λ3对应的特征向量依次为α1α2α3令β=α1+α2+α3．βAβA2β线性无关

Chronicinsomniaisamajorpublichealthproblem.Andtoomanypeopleareusing1therapiesevenwhilethereareafewtreatmentsthatdowork.MillionsofAmericans2awakeatnightcountingsheeporhaveastiffdrinkor3anpillhopingitwillmakethemsleepy.4expertsagreeallthatself-medicatingisabadideaandthecausesofchronicinsomniaremain5. Almostathirdofadultshavetroublesleepingandabout10percenthave6ofdaytimeimpairmentthatsignaltrueinsomnia.But7thecomplaintsscientistsknowsurprisinglylittleaboutwhatcauseschronicinsomniaitshealthconsequencesandhowbesttotreatitapanelofspecialists8togetherbytheNationalInstitutesofHealthconcludedWednesday.Thepanelcalled9abroadrangeofresearchintoinsomnia10thatifscientistsunderstoodits11causestheycoulddevelopbettertreatments. Mostbutnotallinsomniaisthoughtto12otherhealthproblemsfromarthritisanddepressiontocardiovasculardisease.Thequestionofteniswhethertheinsomniacamefirstorwasaresultoftheotherdiseasesandhowtroublesleepingin13complicatesthoseotherproblems.Otherdiseases14theriskofinsomniaseemstoincreasewithageandtobemore15amongwomenespeciallyaftertheir50s.Smokingcaffeineandnumerous16drugsalsoaffectsleep. TheNIHisspendingabout$200millionthisyearonsleep-relatedresearchsome17tospecificdisordersandothers18theunderlyingscientificlawsthatcontrolthenervoussystemofsleep.Theagencywas19thepane’sreviewbeforedecidingwhatadditionalworkshouldbe20atinsomnia. 1

当x→0时fx=x-sinax与gx=x2ln1-bx是等价无穷小则______

已知在-∞+∞上存在原函数求常数A并求fx的原函数

Todaysome30%ofsmallbusinessownersdon’thaveaWebpresenceatallwhilethevastmajoritywhodoarewatchingtheirsitessitstalewaitingandwantingforbusiness.WheredidthingsgowrongTherearecommonprinciplesfollowedbythosewhosedreamsofonlinesuccesshavebecomereality.41Buildyoursitearoundyourcustomer:Thinkingofyoursiteasyouronlinestorefrontbuiltarounddeliveringthehighest-qualitycustomerexperiencefromthemomentyourcustomerstepsthroughthedoor.42Justbecauseyoubuiltitdoesn’tmeanthey’llcome:Ifyouaren’tseeingalargevolumeoftargetedtraffictoyoursiteit’stimetouptheante.43Integratecustomerloyaltyprogramsandpromotions:Methodscontaindiscountsnewsorfriendlyservicereminders.Usediscountpromotionalofferstostayintouchwithpastvisitorstoyoursite.44Justifyyourmonthlyspendingthroughproductbundling:Whilepay-per-clickInternetadvertisingismuchmorecost-effectivethantraditionalmediachannelsbundlingproductstogetherwillnotonlyincreaseyoursalesrevenuebutalsoenableyoutogetmoreoutofyourper-clickadrates.45Measureyourprogress:YoursitemaybelivebuthowisitperformingArmedwiththesesimplelessonsvowtomakeyourbusinessrealizethetruepromiseoftheInternet.A.Amanufacturingcompanyselling$50itemswashavingtroublejustifyingthecostofonlinekeywordads.Bybundlingproductstocreatepackagesof$100ormoreandadvertisingtowholesalecustomerslookingtobuyinbulkthemanufacturerdroppeditssalesrepresentativeagenciesandfocusedonlargevolumebuyerssuchasWal-MartandTarget.Needlesstosaythecompanyhadnotroubleexceedingitsyearlysalesquota.B.Oneofmypastclientshadawell-designedphysicalstorefrontsolidpricesandqualityofferings.Howeverhewasn’tabletodriveenoughstoretrafficdespitetargetedadvertisingeffortsinprintpublicationsandotherofflinevenues.Wedecidedtoshiftthoseaddollarstoanonlinepay-per-clickcampaign—inwhichtheadvertiserpayswheneversomeoneclicksonitsentrypostedduringthecourseofasitesearchbasedonkeywordsrelevanttohisbusiness.Theimmediateimpactwasstaggering.Onlinerevenuesoaredtenfoldto$1millionfrom$100000withinonlyafewmonths.C.Withtoday’stechnologyyourreturncanbeeasilymeasured.IfyourelyonyourWebsiteasasalestoolyoucan’taffordnottoinvestinsiteanalytics.MakesureyourWebsolutionincludesaneasy-to-usereportingtoolthatpresentsthisinformationinaclearconciseformat.AfterallwhilemetricsareacriticalpartoftheWebequationyoudon’thavethetimetospendhoursdiggingthroughreamsofdata.D.YearsagoIworkedwithawomanwhosoldpursesonlinethroughahome-builtsitethatlackedcriticale-commercecomponents.Afterasimpleredesignincludingproductdescriptionscomprehensivenavigationandasecureuser-friendlyorderingsystemherrevenueincreasedfivefold.Andshebeganreceivingravereviewsfromcustomersimpressedwiththeeaseandconvenienceoftheonlineshoppingexperience.E.Onlinesuccessdemandsmorethansimplepresence.YourInternetinvestmentshouldpayforitselfwithnewcustomersandincreasedsales.Findatrustedpartnerwhocanhelpyounavigatetoday’sandtomorrow’stechnologyandwhounderstandsthebottom-linerealitiesofyourbusiness.F.OnevillarentalcompanyhadaWebsitethatgeneratedveryfewcallsandonlinebookings.Ihelpedthecompanysetupalastminutedealsdistributionlist.Bysubscribingsitevisitorswouldreceiveweeklye-mailsoffering11th-hourdiscountsonvillarentals.Asaresultthecompanycapturedcontactinformationforthousandsofpossiblecustomersreduceditsunusedinventorytoalmostzeroandincreasedrevenuesignificantly.

Todaysome30%ofsmallbusinessownersdon’thaveaWebpresenceatallwhilethevastmajoritywhodoarewatchingtheirsitessitstalewaitingandwantingforbusiness.WheredidthingsgowrongTherearecommonprinciplesfollowedbythosewhosedreamsofonlinesuccesshavebecomereality.41Buildyoursitearoundyourcustomer:Thinkingofyoursiteasyouronlinestorefrontbuiltarounddeliveringthehighest-qualitycustomerexperiencefromthemomentyourcustomerstepsthroughthedoor.42Justbecauseyoubuiltitdoesn’tmeanthey’llcome:Ifyouaren’tseeingalargevolumeoftargetedtraffictoyoursiteit’stimetouptheante.43Integratecustomerloyaltyprogramsandpromotions:Methodscontaindiscountsnewsorfriendlyservicereminders.Usediscountpromotionalofferstostayintouchwithpastvisitorstoyoursite.44Justifyyourmonthlyspendingthroughproductbundling:Whilepay-per-clickInternetadvertisingismuchmorecost-effectivethantraditionalmediachannelsbundlingproductstogetherwillnotonlyincreaseyoursalesrevenuebutalsoenableyoutogetmoreoutofyourper-clickadrates.45Measureyourprogress:YoursitemaybelivebuthowisitperformingArmedwiththesesimplelessonsvowtomakeyourbusinessrealizethetruepromiseoftheInternet.A.Amanufacturingcompanyselling$50itemswashavingtroublejustifyingthecostofonlinekeywordads.Bybundlingproductstocreatepackagesof$100ormoreandadvertisingtowholesalecustomerslookingtobuyinbulkthemanufacturerdroppeditssalesrepresentativeagenciesandfocusedonlargevolumebuyerssuchasWal-MartandTarget.Needlesstosaythecompanyhadnotroubleexceedingitsyearlysalesquota.B.Oneofmypastclientshadawell-designedphysicalstorefrontsolidpricesandqualityofferings.Howeverhewasn’tabletodriveenoughstoretrafficdespitetargetedadvertisingeffortsinprintpublicationsandotherofflinevenues.Wedecidedtoshiftthoseaddollarstoanonlinepay-per-clickcampaign—inwhichtheadvertiserpayswheneversomeoneclicksonitsentrypostedduringthecourseofasitesearchbasedonkeywordsrelevanttohisbusiness.Theimmediateimpactwasstaggering.Onlinerevenuesoaredtenfoldto$1millionfrom$100000withinonlyafewmonths.C.Withtoday’stechnologyyourreturncanbeeasilymeasured.IfyourelyonyourWebsiteasasalestoolyoucan’taffordnottoinvestinsiteanalytics.MakesureyourWebsolutionincludesaneasy-to-usereportingtoolthatpresentsthisinformationinaclearconciseformat.AfterallwhilemetricsareacriticalpartoftheWebequationyoudon’thavethetimetospendhoursdiggingthroughreamsofdata.D.YearsagoIworkedwithawomanwhosoldpursesonlinethroughahome-builtsitethatlackedcriticale-commercecomponents.Afterasimpleredesignincludingproductdescriptionscomprehensivenavigationandasecureuser-friendlyorderingsystemherrevenueincreasedfivefold.Andshebeganreceivingravereviewsfromcustomersimpressedwiththeeaseandconvenienceoftheonlineshoppingexperience.E.Onlinesuccessdemandsmorethansimplepresence.YourInternetinvestmentshouldpayforitselfwithnewcustomersandincreasedsales.Findatrustedpartnerwhocanhelpyounavigatetoday’sandtomorrow’stechnologyandwhounderstandsthebottom-linerealitiesofyourbusiness.F.OnevillarentalcompanyhadaWebsitethatgeneratedveryfewcallsandonlinebookings.Ihelpedthecompanysetupalastminutedealsdistributionlist.Bysubscribingsitevisitorswouldreceiveweeklye-mailsoffering11th-hourdiscountsonvillarentals.Asaresultthecompanycapturedcontactinformationforthousandsofpossiblecustomersreduceditsunusedinventorytoalmostzeroandincreasedrevenuesignificantly.

如果

设方程x2=y2y确定y是x的函数则dy=______．

Themythologyofaculturecanprovidesomevitalinsightsintothebeliefsandvaluesofthatculture.Byusingfantasticandsometimesincrediblestoriestocreateanoraltraditionbywhichtoexplainthewondersofthenaturalworldandteachlessonstoyoungergenerationsasocietyexposesthoseideasandconceptsheldmostimportant.Justasimportantasthefinallessontobegatheredfromthestorieshoweverarethecharactersandtherolestheyplayinconveyingthatmessage.PerhapstheepitomeofmythologyanditsuseasatooltopassonculturalvaluescanbefoundinAesop’sFablestoldandretoldduringtheeraoftheGreekEmpire.Aesopaslavewhowonthefavorofthecourtthroughhisimaginativeanddescriptivetalesalmostexclusivelyusedanimalstofilltherolesinhisshortstories.Humanswhenatallpresentalmostalwaysplayedthepartofbumblingfoolsstrugglingtolearnthelessonbeingpresented.ThischoiceofcharacterizationallowsustoseethattheGreeksplacedwisdomonalevelslightlybeyondhumansimplyingthatdeepwisdomandunderstandingisauniversalqualitysoughtbyratherthansteanningfromhumanbeings.Aesop’sfablesillustratedthecentralthemesofhumilityandself-reliancereflectingtheimportanceofthosetraitsinearlyGreeksociety.Thefollyofhumanswasusedtocontrastagainsttheultimategoalofattainingahigherlevelofunderstandingandawarenessoftruthsaboutnatureandhumanity.Forexampleonenotablefablefeaturesafoxrepeatedlytryingtoreachabunchofgrapesonaveryhighvine.Afterfailingatseveralattemptsthefoxgivesupmakingupitsmindthatthegrapeswereprobablysouranyway.Thefable’slessonthatweoftenplaydownthatwhichwecan’tachievesoastomakeourselvesfeelbetterteachesthereaderorlistenerinanentertainingwayaboutoneoftheweaknessesofthehumanpsyche.ThemythologyofotherculturesandsocietiesrevealtheunderlyingtraitsoftheirrespectiveculturesjustasAesop’sfablesdid.ThestoriesofRomangodsAztecghostsandEuropeanelvesallservedtotrainancientgenerationsthoselessonsconsideredmostimportanttotheircommunityandtodaytheyofferapowerfullookingglassbywhichtoevaluateandconsiderthecontextualenvironmentinwhichthosecultureexisted.Themainpointofthistextis

若函数fx与gx在-∞+∞内可导且fx＜gx则必有______

Cyberspacedatasuperhighwaysmultimedia—forthosewhohaveseenthefuturethelinkingofcomputerstelevisionandtelephoneswillchangeourlivesforever.Yetforallthetalkofaforthcomingtechnologicalutopialittleattentionhasbeengiventotheimplicationsofthesedevelopmentsforthepoor.AswithallnewhightechnologywhiletheWestconcernsitselfwiththehowthequestionofforwhomisputasideonceagain.Economistsareonlynowrealizingthefullextenttowhichthecommunicationsrevolutionhasaffectedtheworldeconomy.Informationtechnologyallowstheextensionoftradeacrossgeographicalandindustrialboundariesandtransnationalcorporationstakefulladvantageofit.Termsoftradeexchangeandinterestratesandmoneymovementsaremoreimportantthantheproductionofgoods.Theelectroniceconomymadepossiblebyinformationtechnologyallowsthehavestoincreasetheircontrolonglobalmarkets—withdestructiveimpactonthehave-nots.Forthemtheresultisinstability.Developingcountrieswhichrelyontheproductionofasmallrangeofgoodsforexportaremadetofeellikesmallpartsintheinternationaleconomicmachine.Asfuturesaretradedoncomputerscreensdevelopingcountriessimplyhavelessandlesscontroloftheirdestinies.SowhataretheoptionsforregainingcontrolOnealternativeisfordevelopingcountriestobuyinthelatestcomputersandtelecommunicationsthemselves—socalleddevelopmentcommunicationsmodernization.Yetthisleadstolong-termdependencyandperhapspermanentconstraintsondevelopingcountries’economies.CommunicationstechnologyisgenerallyexportedfromtheU.S.EuropeorJapan;thepatentsskillsandabilitytomanufactureremaininthehandsofafewindustrializedcountries.Itisalsoexpensiveandimportedproductsandservicesmustthereforebeboughtoncredit—creditusuallyprovidedbytheverycountrieswhosecompaniesstandtogain.Furthermorewhennewtechnologyisintroducedthereisoftentoolowalevelofexpertisetoexploititfornativedevelopment.Thismeansthatwhilelocalelitesforeigncommunitiesandsubsidiariesoftransnationalcorporationsmaybenefitthosewhoselivesdependonaccesstotheinformationaredeniedit.Itcanbeinferredfromthepassagethat

已知某产品总产量的变化率为问在达到平均年产量最大时再生产3年求这3年的平均年产量．

设常数λ＞0且级数收敛则级数______

设A为三阶实对称矩阵且存在可逆矩阵使得又A的伴随矩阵A*有特征值λ0λ0所对应的特征向量为α=[25-1]T．计算A*-1

计算二重积分其中积分区域D由y轴与曲线y=y=围成

Collegegraduatesarenowleavingschoolwithnotonlyadiplomabutalsowithmoredebtthaninanyotherperiodinhistory.AccordingtotheCollegeBoardaveragefinancialaidperfulltimeequivalentstudentadjustedforinflationhasalmostdoubledinthelastdecade.Additionallynotonlyistheaveragestudentdebtloadhigherbutalsothenumberofloansoriginatedincreasedbynearlyfourfold.Thusstudentlendinghasincreasedinbreadthaswellasdepthdoublyimpactingthefinancialsituationsofthosestudentswhomustdependonstudentloanstofinancetheireducation.Furthermorethesefiguresnodoubtunderstatethetruelevelofindebtednessincurredbystudentsandtheirfamiliessincesomeundoubtedlyfinancepartoftheireducationandlivingexpensesthroughtheuseofconsumerloanshomeequityloansorcreditcards.Thusthealreadyhugeburdenofstudentloandebtincurredbystudentsandtheirfamiliesisexacerbatedbyfinancialobligationsfromothersources.Thissituationistheoutcomeofaprecariouscombinationofeasycreditthankstocardissuerswhoareeagertotapintothislucrativemarketfinancialnaivetéonthepartofstudentsandasenseonbothsidesthatifworsecomestoworsemommyanddaddywillstepinandsetthingsright.Allcombinetomakecreditatemptingluretostudentsstrappedforcash.Whilecreditstillremainavirtualelementforthefinancingofmanystudents’educationatexpensivecollegesitsimplicationsmustcarefullyweighedandconsideredlestthecash-poorstudentfindhimselfwithmorethathebargainedfor.MoststudentsintheUnitedStatesattendcollegeswhosetuitiondoesnotexceed$15000however.Neverthelessrisingpricescombinedwithstagnantincomegainsamonglow-andmoderate-incomefamilieshavemadeitdifficultifnotimpossibleforastudentfromafamilyofsuchanincomelevelastudentwhohasthemosttogainfromacollegeeducationtoattendcollegewithoutsignificantlyaddingtothefinancialburdenofhisorherfamily.Whilestudentloansstillremainavitalelementforthefinancingofmanystudents’educationatexpensivecollegesitsimplicationsmustbecarefullyweighedandconsideredlestthecash-poorstudentfindhimselfwithmorethanhebargainedfor.ThemainpointofParagraph4is

假设生产和销售某产品的收益R是产量的q二次函数经统计得知当产量q分别为024时总收入R分别为068万元试确定R与q之间的函数关系

求解差分方程yx+1+3yx=x·2x．

计算二重积分x2+ydσ其中D是由x2+y2=2y的上半圆直线x=-1x=1及x轴围成的区域．

幂级数的和函数为______

Sustainabledevelopmentisappliedtojustabouteverythingfromenergytocleanwaterandeconomicgrowthandasaresultithasbecomedifficulttoquestioneitherthebasicassumptionsbehinditorthewaytheconceptisputtouse.Thisisespeciallytrueinagriculturewheresustainabledevelopmentisoftentakenasthesolemeasureofprogresswithoutaproperappreciationofhistoricalandculturalperspectives.Tostartwithitisimportanttorememberthatthenatureofagriculturehaschangedmarkedlythroughouthistoryandwillcontinuetodoso.MedievalagricultureinnorthernEuropefedclothedandshelteredapredominantlyruralsocietywithamuchlowerpopulationdensitythanitistoday.Ithadminimaleffectonbiodiversityandanypollutionitcausedwastypicallylocalized.Intermsofenergyuseandthenutrientscapturedintheproductitwasrelativelyinefficient.Contrastthiswithfarmingsincethestartoftheindustrialrevolution.Competitionfromoverseasledfarmerstospecializeandincreaseyields.Throughoutthisperiodfoodbecamecheapersafeandmorereliable.Howeverthesechangeshavealsoledtohabitatlossandtodiminishingbiodiversity.What’smoredemandforanimalproductsindevelopingcountriesisgrowingsofastthatmeetingitwillrequireanextra300milliontonsofgrainayearby2050.Yetthegrowthofcitiesandindustryisreducingtheamountofwateravailableforagricultureinmanyregions.Allthismeansthatagricultureinthe21stcenturywillhavetobeverydifferentfromhowitwasinthe20th.Thiswillrequireradicalthinking.Forexampleweneedtomoveawayfromtheideathattraditionalpracticesareinevitablymoresustainablethannewones.Wealsoneedtoabandonthenotionthatagriculturecanbezeroimpact.Thekeywillbetoabandontherathersimpleandstaticmeasuresofsustainabilitywhichcentreontheneedtomaintainproductionwithoutincreasingdamage.Insteadweneedamoredynamicinterpretationonethatlooksattheprosandconsofallthevariouswaylandisused.Therearemanydifferentwaystomeasureagriculturalperformancebesidesfoodyield:energyuseenvironmentalcostswaterpuritycarbonfootprintandbiodiversity.ItisclearforexamplethatthecarbonoftransportingtomatoesfromSpaintotheUKislessthanthatofproducingthemintheUKwithadditionalheatingandlighting.Butwedonotknowwhetherlowercarbonfootprintswillalwaysbebetterforbiodiversity.Whatiscrucialisrecognizingthatsustainableagricultureisnotjustaboutsustainablefoodproduction.Specializationandtheefforttoincreaseyieldshaveresultedin

设λ1λ2是n阶矩阵A的特征值α1α2分别是A的属于λ1λ2的特征向量则______

Inapurelybiologicalsensefearbeginswiththebody’ssystemforreactingtothingsthatcanharmus—theso-calledfight-or-flightresponse.Ananimalthatcan’tdetectdangercan’tstayalivesaysJosephLeDoux.Likeanimalshumansevolvedwithanelaboratemechanismforprocessinginformationaboutpotentialthreats.Atitscoreisaclusterofneuronsdeepinthebrainknownastheamygdala. LeDouxstudiesthewayanimalsandhumansrespondtothreatstounderstandhowweformmemoriesofsignificanteventsinourlives.Theamygdalareceivesinputfrommanypartsofthebrainincludingregionsresponsibleforretrievingmemories.Usingthisinformationtheamygdalaappraisesasituation—Ithinkthischargingdogwantstobiteme—andtriggersaresponsebyradiatingnervesignalsthroughoutthebody.Thesesignalsproducethefamiliarsignsofdistress:tremblingperspirationandfast-movingfeetjusttonamethree. Thisfearmechanismiscriticaltothesurvivalofallanimalsbutnoonecansayforsurewhetherbeastsotherthanhumansknowthey’reafraid.ThatisasLeDouxsaysifyouputthatsystemintoabrainthathasconsciousnessthenyougetthefeelingoffear. HumanssaysEdwardM.Hallowellhavetheabilitytocallupimagesofbadthingsthathappenedinthepastandtoanticipatefutureevents.Combinethesehigherthoughtprocesseswithourhardwireddangerdetectionsystemsandyougetanear-universalhumanphenomenon:worry. That’snotnecessarilyabadthingsaysHallowell.Whenusedproperlyworryisanincredibledevicehesays.Afterallalittlehealthyworryingisokayifitleadstoconstructiveaction—likehavingadoctorlookatthatweirdspotonyourback. Hallowellinsiststhoughthatthere’sarightwaytoworry.Neverdoitalonegetthefactsandthenmakeaplan.Hesays.Mostofushavesurvivedarecessionsowe’refamiliarwiththebelt-tighteningstrategiesneededtosurviveaslump. Unfortunatelyfewofushavemuchexperiencedealingwiththethreatofterrorismsoit’sbeendifficulttogetfactabouthowweshouldrespond.That’swhyHallowellbelievesitwasokayforpeopletoindulgesomeextremeworrieslastfallbyaskingdoctorsforCiproandbuyinggasmasks. WhichofthefollowingisthebestwaytodealWithyourworriesaccordingtoHallowell

设fx+yxy=x2+y2+xy则dfxy=______．

设幂级数的收敛半径为2则级数a+1n的收敛区间为______

设函数fx连续则=______

Chronicinsomniaisamajorpublichealthproblem.Andtoomanypeopleareusing1therapiesevenwhilethereareafewtreatmentsthatdowork.MillionsofAmericans2awakeatnightcountingsheeporhaveastiffdrinkor3anpillhopingitwillmakethemsleepy.4expertsagreeallthatself-medicatingisabadideaandthecausesofchronicinsomniaremain5.a Chronicinsomniaisamajorpublichealthproblem.Andtoomanypeopleareusing1therapiesevenwhilethereareafewtreatmentsthatdowork.MillionsofAmericans2awakeatnightcountingsheeporhaveastiffdrinkor3anpillhopingitwillmakethemsleepy.4expertsagreeallthatself-medicatingisabadideaandthecausesofchronicinsomniaremain5. Almostathirdofadultshavetroublesleepingandabout10percenthave6ofdaytimeimpairmentthatsignaltrueinsomnia.But7thecomplaintsscientistsknowsurprisinglylittleaboutwhatcauseschronicinsomniaitshealthconsequencesandhowbesttotreatitapanelofspecialists8togetherbytheNationalInstitutesofHealthconcludedWednesday.Thepanelcalled9abroadrangeofresearchintoinsomnia10thatifscientistsunderstoodits11causestheycoulddevelopbettertreatments. Mostbutnotallinsomniaisthoughtto12otherhealthproblemsfromarthritisanddepressiontocardiovasculardisease.Thequestionofteniswhethertheinsomniacamefirstorwasaresultoftheotherdiseasesandhowtroublesleepingin13complicatesthoseotherproblems.Otherdiseases14theriskofinsomniaseemstoincreasewithageandtobemore15amongwomenespeciallyaftertheir50s.Smokingcaffeineandnumerous16drugsalsoaffectsleep. TheNIHisspendingabout$200millionthisyearonsleep-relatedresearchsome17tospecificdisordersandothers18theunderlyingscientificlawsthatcontrolthenervoussystemofsleep.Theagencywas19thepane’sreviewbeforedecidingwhatadditionalworkshouldbe20atinsomnia. 17

OneofthemostpressingchallengesthattheUnitedStates—andindeedtheworld—willfaceinthenextfewdecadesishowtoalleviatethegrowingstressthathumanactivitiesareplacingontheenvironment.Theconsequencesarejusttoogreattoignore.Wildlifehabitatsarebeingdegradedordisappearingaltogetherasnewdevelopmentstakeupmoreland.PlantandanimalspeciesarebecomingextinctatagreaterratenowthanatanytimeinEarth’shistory.Asmanyas30percentoftheworld’sfishstocksareoverexploited.Andthelistgoeson.Yetthereisreasontohavehopeforthefuture.Advancesincomputingpowerandmolecularbiologyareamongthetremendousincreasesinscientificcapabilitythatarehelpingresearchersgainabetterunderstandingoftheseproblems.Recentdevelopmentsinscienceandtechnologycouldprovidethebasisforsomemajorandtimelyactionsthatwouldimproveourunderstandingofhowhumanactivitiesaffecttheenvironment.Onepriorityforresearchisimprovinghydrologicalforecasting.Ithasbeenestimatedthattheworld’swaterusecouldtripleinthenexttwodecades.AlreadywidespreadwatershortageshaveoccurredinpartsofChinaIndiaNorthAfricaandtheArabianPeninsula.TheneedforwateralsoistakingitstollonfreshwaterecosystemsintheUnitedStates.Only2percentofthenation’sstreamsareconsideredingoodconditionandcloseto40percentofnativefishspeciesareraretoextinct.Usingavarietyofnewremotesensingtoolsscientistscanlearnmoreabouthowprecipitationaffectswaterlevelshowsurfacewaterisgeneratedandtransportedandhowchangesinthelandscapeaffectwatersupplies.Topreventoutbreaksofinfectiousdiseasesinplantsanimalsandhumansmorestudyisneededonhowpathogensparasitesanddisease-carryingspecies—aswellashumansandotherspeciestheyinfect—areaffectedbychangesintheenvironment.Theoveruseofantibioticsbothinhumansandinfarmanimalshascontributedtothegrowthofantibiotic-resistantmicroorganisms.Researcherscantakeadvantageofnewtechnologiesingeneticsandcomputingtobettermonitorandpredicttheeffectsthatenvironmentalchangesmighthaveondiseaseoutbreaks.HumanshavemadealterationstoEarth’ssurface—suchastropicaldeforestationreductionofsurfaceandgroundwaterandmassivedevelopment—sodramaticthattheyapproachthelevelsoftransformationthatoccurredduringglacialperiods.Suchalterationscausechangesinlocalandregionalclimateandwilldeterminethefutureofagriculture.Recentadvancesindatacollectionandanalysisshouldbeusedtodocumentandbetterunderstandthecausesandconsequencesofchangesinlandcoveranduse.Throughoutthetexttheauthormainlyemphasizes

Chronicinsomniaisamajorpublichealthproblem.Andtoomanypeopleareusing1therapiesevenwhilethereareafewtreatmentsthatdowork.MillionsofAmericans2awakeatnightcountingsheeporhaveastiffdrinkor3anpillhopingitwillmakethemsleepy.4expertsagreeallthatself-medicatingisabadideaandthecausesofchronicinsomniaremain5.a Chronicinsomniaisamajorpublichealthproblem.Andtoomanypeopleareusing1therapiesevenwhilethereareafewtreatmentsthatdowork.MillionsofAmericans2awakeatnightcountingsheeporhaveastiffdrinkor3anpillhopingitwillmakethemsleepy.4expertsagreeallthatself-medicatingisabadideaandthecausesofchronicinsomniaremain5. Almostathirdofadultshavetroublesleepingandabout10percenthave6ofdaytimeimpairmentthatsignaltrueinsomnia.But7thecomplaintsscientistsknowsurprisinglylittleaboutwhatcauseschronicinsomniaitshealthconsequencesandhowbesttotreatitapanelofspecialists8togetherbytheNationalInstitutesofHealthconcludedWednesday.Thepanelcalled9abroadrangeofresearchintoinsomnia10thatifscientistsunderstoodits11causestheycoulddevelopbettertreatments. Mostbutnotallinsomniaisthoughtto12otherhealthproblemsfromarthritisanddepressiontocardiovasculardisease.Thequestionofteniswhethertheinsomniacamefirstorwasaresultoftheotherdiseasesandhowtroublesleepingin13complicatesthoseotherproblems.Otherdiseases14theriskofinsomniaseemstoincreasewithageandtobemore15amongwomenespeciallyaftertheir50s.Smokingcaffeineandnumerous16drugsalsoaffectsleep. TheNIHisspendingabout$200millionthisyearonsleep-relatedresearchsome17tospecificdisordersandothers18theunderlyingscientificlawsthatcontrolthenervoussystemofsleep.Theagencywas19thepane’sreviewbeforedecidingwhatadditionalworkshouldbe20atinsomnia. 11

A是n阶矩阵且A3=0则______

设y=1+sinxx则=______

设二维随机变量XY在区域D://0＜x＜1|y|=x内服从均均分布求关于X的边缘概率密度函数及随机变量Z=2X+1的方差DZ

Rewardsandpunishmentsareusedindifferentwaysbydifferentcommunitiestomaintainsocialorderandpreserveculturalvalues.Inallculturesparentsmustteachtheirchildrentoavoiddangerandtoobservethecommunity’smoralprecepts.Adultsalsoconditioneachother’sobservanceofsocialnormsusingmethodsrangingfrommildformsofcensuresuchaslookingawaywhensomeonemakesaninappropriateremarktoimprisoningorexecutingindividualsforbehaviorconsidereddeviantordangerous.ThecaningofAmericanteenagerMichaelFayinSingaporeforvandalismin1994broughtwidemediaattentiontoculturaldifferencesintheapplicationofpunishment.FacedwithincreasingviolenceathomemanyAmericansendorsedSingapore’suseofcorporalpunishmenttomaintainsocialorder.WasFay’spunishmenteffectiveWhetherhesubsequentlyavoidsvandalismisunknownbutthepunishmentdidapparentlyleadtohisavoidanceofSingapore—whichheleftpromptly. Theoperanttechniquessocietiesusetomaintainsocialcontrolvaryinpartwiththedangersandthreatsthatconfrontthem.TheGusiiofKenyawithahistoryoftribalwarfarefacethreatsnotonlyfromoutsidersbutalsofromnaturalforcesincludingwildanimals.Gusiiparentstendtorelymoreonpunishmentandfearthanonrewardsinconditioningappropriatesocialbehaviorintheirchildren.Caningfooddeprivationandwithdrawingshelterandprotectionarecommonformsofpunishment. IncontrasttheMixtecansofJuxtlahuacaMexicoareahighlycohesivecommunitywithlittleinternalconflictandsocialnormsthatencouragecooperation.TheirsocialpatternsappearadaptivefortheMixtecansaredominatedbythenearbySpanishMexicanswhocontroltheofficialgovernmentandmanyeconomicresourcesintheirregion.TheMixtecansdonotgenerallyimposefinesorjailsentencesorusephysicalpunishmenttodeteraggressionineitheradultsorchildren.Rathertheytendtorelyonsoothingpersuasion.Socialostracismisthemostfearedpunishmentandsocialtieswithinthecommunityareverystrongsoresponsesthatreinforcethesetiesareeffectiveinmaintainingsocialorder. IntheUnitedStatesfearofsocialostracismorstigmawasonceamorepowerfulforceinmaintainingcontroloverantisocialbehaviorespeciallyinsmallcommunities.Todayevenimprisonmentdoesnotappeartobeanadequatedeterrenttomanyformsofcrimeespeciallyviolentcrime.Althoughonereasonistheinconsistentapplicationofpunishmentanothermaybethefactthatimprisonmentnolongercarriestheintensestigmaitoncehadsothatprisonisnolongerasaneffectivepunishment. ThewordstigmaPara.4mostprobablymeans

设fx为连续函数计算其中D是由y=x3y=1z=-1围成的区域

设A为n阶方阵A*为A的伴随矩阵且A11≠0证明方程组Ax=bb≠0有无穷多解的充要条件中b为A*X=0的解