2016届上海市松江区高三一模英语试题及答案

松江区2015学年度第一学期期末质量监测高三英语一模卷第I卷（共103分）I.ListeningComprehensionSectionA（10分）Directions:InsectionA,youwillheartenshortconversationsbetweentwospeakers.Attheendofeachconversation,aquestionwillbeaskedaboutwhatwassaid.Theconversationandthequestionwillbespokenonlyonce.Afteryouhearaconversationandthequestionaboutit,readthefourpossibleanswersonyourpaper,anddecidewhichoneisthebestanswertothequestionyouhaveheard.1.A.Ateacher. B.Anurse. C.Asecretary. D.Asaleswoman.2.A.$64. B.$40. C.$32. D.$80.3.A.Itmakesthewomanhomesick. B.Itisn’tfunandexciting.C.It’saboutthewoman’schildhood. D.Itwonagreataward.4.A.Shegotaticketfortheman. B.Shearrivedanhourearlierthantheman.C.Shemissedthemovie. D.Shewilltreatthemtosomefoodanddrinks.5.A.Hehasabadcough. B.Hehasaheadache.C.Hedoesn’tfeelverywell. D.Hehasatoothache.6.A.Pressclothes. B.Washdishes. C.Cleanthehouse. D.Cookdinner.7.A.Theset. B.Thesuits. C.Theactors. D.Theplot.8.A.Anassistant. B.Ateacher. C.Aninsuranceclerk. D.Alawyer.9.A.Gotothebeach. B.Gototheforestpark.C.Stayathome. D.Climbthemountain.10.A.Theywillhavebreakfasttogether. B.Theman’sworktimebeginsat9:05.C.Themanwillbelateforwork. D.Thewomandoesn’tneedtowork.SectionBDirections:InSectionB,youwillheartwoshortpassages,andyouwillbeaskedthreequestionsoneachofthepassages.Thepassageswillbereadtwice,butthequestionswillbespokenonlyonce.Whenyouhearaquestion,readthefourpossibleanswersonyourpaperanddecidewhichonewouldbethebestanswertothequestionyouhaveheard.Questions11through13arebasedonthefollowingpassage.11.A.MorethanUS$2trillion. B.MorethanUS$20million.C.MorethanUS$2million. D.MorethanUS$20trillion.12.A.Cooperationforstrongactionagainstclimatechange.B.Theconstructionofanoilpipelineacrossthecountry.C.Thecreationof100millionjobsforwomen.D.ThestrengtheningofAmericanworldwideleadership.13.A.Four. B.Three. C.Two. D.One.Questions14through16arebasedonthefollowingpassage.14.A.Persuadingcitizensnottobuythelatestproducts. B.Reusingsomeelectronicparts.C.Endinge-wasteinremoteareas. D.Sellinge-wastetoChinaandotherSoutheastAsiacountries. 15.A.Tosavemoneyforthegovernment. B.Toproducemoreprofits.C.Tosaveresources. D.Toprotecttheenvironment.16.A.Therapidupdateofphones. B.Companymarketingstrategies.C.Customerswantingadiscount. D.Consumerbehavior.SectionCDirections:InSectionC,youwillheartwolongerconversations.Theconversationswillbereadtwice.Afteryouheareachconversation,youarerequiredtofillinthenumberedblankswiththeinformationyouhaveheard.Writeyouranswersonyouranswersheet.Blanks17through20arebasedonthefollowingconversation.Completetheform.WriteONEWORDforeachanswer.LookingforaNewJobThewoman’ssituationHavingworkedinthecompanyfor___17___yearsNotbeinggivena(n)___18___yetHavinganinterviewtomorrowTheman’ssuggestionsNotbeingnervousasshehasthe___19___Showingthatsheis___20___andcangetalongwellwithothersBlanks21through24arebasedonthefollowingconversation.Completetheform.WriteNOMORETHANTHREEWORDSforeachanswer.Whyhasn’tthewomanseenthemanintheschoollibrary?He___21___foracoupleofdays.Whatdidthemandowhenhegotsick?Hehad___22___onastreetcorner.Whatisthewoman’sconclusionabouttheman’ssituation?Heate___23___,anditgavehimacold.Whataretheman’ssymptoms?Hehas___24___andacough,andbasicallyhefeelstired.II.GrammarandVocabularySectionA（16分）Directions:Afterreadingthepassagesbelow,fillintheblankstomakethepassagescoherentandgrammaticallycorrect.Fortheblankswithagivenword,fillineachblankwiththeproperformofthegivenword;fortheotherblanks,

useonewordthatbestfitseachblank.(A)Thehardlivesofagingmigrantworkershavecometonationalattentionlately.Themediahavereportedthatmanymigrantworkersovertheageof50saytheywanttosaveasmuchmoneyastheirbodyallowsthem(25)______(continue)earning.Theyhavenopensions,which(26)______(enjoy)byurbanworkers,andmanyarestillthechiefearnersoftheirfamilies.Theykeepuptheirenergyby(27)______(eat)moremeat,andconcealtheiragebydyingtheirhair.CommentatorChengZhenweiwritesonthatwhilethephysicalwell-beingofthesemigrantworkersisworrisome,(28)______conditionsoftheirfamiliesandtheirchildrenareabiggerconcern.Manyofthemigrantworkers’childrenarealsopoor,andhavelittlemeanstosupporttheirparents.Worsestill,(29)______theyoftendon’thavearethestomachandwillforhardworkandalsothelackofeducationorskillstofindbetter-payingjobs.(30)______(face)withtheirowndifficulteconomicsituation,thesemigrantworkersareshortofhopeandprospectofinheritedpovertyonthepartoftheirchildren,(31)______istheworstthingforthem,accordingtoCheng.(B)Weallknowthatregularphysicalexerciseisgoodforagirl’sbody,mind,andspirit.Recently,theWomen’sSportsFoundation(32)______(discover)thatsportsoffersomeextrabenefitsforgirls(33)__________________havingfunandgettingfit.Hereareafew:Girlswhoplaysportsdobetterinschool.Itisbelieved(34)______athleticswilltakeupalltheirstudytime.Butresearchshowsthatgirlswhoplaysportsdobetterinschoolandare(35)______(likely)tograduatethanthosewhodon’t.Exerciseimproveslearning,memory,andconcentration,whichcangiveactivegirlsanadvantagewhenitcomestotheclassroom.Girlswhoplaysportslearnteamworkandgoal-settingskills.Itisbyworkingwithcoachesandteammatestowingamesandmeetgoals(36)______theygetgreatpracticeforsuccesslaterinlife.Beingateamplayercanmakeiteasiertoworkwithothersandsolveproblems,(37)______itisonthefieldorintheworkplace.Sportshavehiddenhealthbenefits.Girlswhoplaysportsarelesslikelytosmokeandhaveareducedchanceofgettingbreastcancerlaterinlife.Sure,they(38)______getthesebenefitsfromanytypeofexercise.Butiftheyhavetroublegettingtothegym,theremaybemoreincentive(激励)toshowupandplayiftheyknowtheircoachesorteammatesdependonthem.Playingsportsbuildsself-confidence.Girlsinvolvedinathleticsfeelbetterabout(39)______,bothphysicallyandsocially.Ithelpstobuildconfidencewhentheyseetheirskillsimprovingandtheirgoals(40)______(become)reality.SectionB（10分）Directions:Completethefollowingpassagebyusingthewordsinthebox.Eachwordcanonlybeusedonce.Notethatthereisonewordmorethanyouneed.A.primarilyB.delayedC.interactD.equivalentE.identifiedF.intentionsG.acquisitionH.overwhelmingI.permanentlyJ.comparativek.necessityQuiteoften,educatorstellfamiliesofchildrenwhoarelearningEnglishasasecondlanguagetospeakonlyEnglish,andnottheirnativelanguage,athome.Althoughtheseeducatorsmayhavegood___41___,theiradvicetofamiliesismisguided,anditarisesfrommisunderstandingsabouttheprocessoflanguage___42___.Educatorsmayfearthatchildrenhearingtwolanguageswillbecome___43___confusedandthustheirlanguagedevelopmentwillbe___44___.Childrenarecapableoflearningmorethanonelanguage,whethersimultaneously(同时地)orsequentially(依次地).Infact,mostchildrenoutsideoftheUnitedStatesareexpectedtobecomebilingualoreven,inmanycases,multilingual.Globally,knowingmorethanonelanguageisviewedasanasset(资产)andevena___45___inmanyareas.ItisalsoofconcernthatthemisguidedadvicethatstudentsshouldspeakonlyEnglishisgiven___46___topoorfamilieswithlimitededucationalopportunities,nottowealthierfamilieswhohavemanyeducationaladvantages.Sincechildrenfrompoorfamiliesoftenare___47___asat-riskforacademicfailure,teachersbelievethatadvisingfamiliestospeakEnglishonlyisappropriate.Teachersconsiderlearningtwolanguagestobetoo___48___forchildrenfrompoorfamilies,believingthatthechildrenarealreadyburdenedbytheirhomesituations.IffamiliesdonotknowEnglishorhavelimitedEnglishskillsthemselves,howcantheycommunicateinEnglish?Advisingnon-English-speakingfamiliestospeakonlyEnglishis___49___totellingthemnottocommunicatewithor___50___withtheirchildren.Moreover,theunderlyingmessageisthatthefamily’snativelanguageisnotimportantorvalued.III.ReadingComprehensionSectionA（15分）Directions:ForeachblankinthefollowingpassagetherearefourwordsorphrasesmarkedA,B,CandD.Fillineachblankwiththewordorphrasethatbestfitsthecontext.Intheincreasinglybusierworldwhereproductivityisonthemindsofmany,insteadofdownloadingthelatesttimemanagementapp,orforcingyourselftostayatworkforhoursonend,istherea(n)___51___tobeingproductive?Thefirstthingweshouldknowisthatwillpowerisa(n)___52___sourcethatcanbeentirelyusedup.Soinsteadof___53___yourselftosimplytryharder,amoremethodicalapproachissuggested.Thefirststep:Getstarted!Itmayseem___54___butstudieshaveshownstartingaprojecttobethebiggestbarriertoproductivity.Beforestarting,ourbrainvisualizesthehardestpartstocome,andinsteadtriestosimulaterealworkbyfocusingonsmallmindlesstasks.___55___,there’sconstructofthemindknownastheZeigernikEffect(蔡格尼克效应),whichhelpshumanstofinishataskthatthey’vealreadystarted.TheZeigernikEffectshowsthatwhenwedon’tfinishatask,weexperience___56___andintrusivethoughtsaboutit.Sogetstarted.Nowwhatabouttimemanagement?Shockingly,whenwelookatmostoftheelitemusiciansintheworld,wefindthattheyaren’t___57___practicingmore.Instead,theyfocustheirenergyonthehardesttask.Thosemusicianshaveperiodsofintenseworkfollowedbybreaks.Notrelyingonwillpower,theyrelyontheir___58___anddisciplinedscheduling.Studieshavefoundthatmosteliteviolinistsgenerallyfollowa90minuteworkrulewitha15to20minutebreakafterwardseveryday.Buthowcanyoudevelopthedisciplinetofollowthis___59___?Onekeypointisgivingyourselfadeadline;writeitdown;markitinyourcalendar.Andyou’llbemuchmorelikelytocompleteyourtask.Ontopofthis,createsomethingcalledanaccountability(问责制)chartto___60___yourprogress.Inonecolumnwritethetimespan,andintheothertheactivitiesyouaccomplishedduringthistime,___61___thoseonadietwhorecordtheirfoodintake.Writingdownyourprogressallowsyouto___62___evaluateyourwork.Asopposedtoinaccuratelyassumingwhatyou’vedone,further___63___yourprogresstotheendhelpstoavoidsmallmindlesswork.Andfinally,stopmultitasking.Wellitmayfeellikeyou’reaccomplishingmore.Butactually,studiesshowthatmulti-taskersaremuchless___64___.Instead,tryandmakealistatnightofwhatyouwanttoaccomplishtomorrow.Withyouractionplan,you___65___theideaoftryingtocompletemultipleactivitiesatonce.Yourbrainwillfindtheselesschallenging.Anditwillmakethestartingprocesseasier.Withacleargoalandactionplaninmind,yourproductivitylevelscansoartonewheights. 51.A.room B.secret C.attitude D.origin52.A.outstanding B.inevitable C.exhaustible D.essential53.A.convincing B.resisting C.preventing D.discouraging54.A.difficult B.complicated C.obvious D.visible55.A.Generally B.Luckily C.Unfortunately D.Briefly56.A.division B.mission C.interruption D.discomfort57.A.necessarily B.hardly C.efficiently D.purposefully58.A.patience B.habit C.perseverance D.principle59.A.feature B.intention C.guidance D.routine60.A.prove B.influence C.document D.determine61.A.similarto B.relatedto C.availableto D.owingto62.A.rapidly B.desperately C.objectively D.relatively63.A.targeting B.tricking C.timing D.tracking64.A.promising B.productive C.practical D.plentiful65.A.stickto B.faceupto C.decideon D.getridofSectionB（24分）Directions:Readthefollowingthreepassages.EachpassageisFollowedbyseveralquestionsorunfinishedstatements.ForeachofthemtherearefourchoicesmarkedA,B,CandD.Choosetheonethatfitsbestaccordingtotheinformationgiveninthepassageyouhavejustread.(A)Technologicalchangeiseverywhereandaffectseveryaspectoflife,mostlyforthebetter.However,socialchangesbroughtaboutbynewtechnologyareoftenmistakenforachangeinattitudes.Anexampleathandistheinvolvementofparentsinthelivesoftheirchildrenwhoareattendingcollege.Surveysonthistopicsuggestthatparentstodaycontinuetobe“very”or“somewhat”overly-protectiveevenaftertheirchildrenmoveintocollegedormitories.Thesamesurveysalsoindicatethattherateofparentalinvolvementisgreatertodaythanitwasagenerationago.ThisisusuallyinterpretedasasignthatToday’sparentsaretryingtomanagetheirchildren’slivespastthepointwherethisbehaviorisappropriate.However,greaterparentalinvolvementdoesnotindicatethatparentsarefailingtoletgooftheir“adult”children.Inthecontextofthisdiscussion,itseemsvaluabletofirstfindoutthecauseofchangeinthecaseofparents’involvementwiththeirgrownchildren.Ifparentsofearliergenerationshadwantedtobeintouchwiththeircollege-agechildrenfrequently,wouldthishavebeenpossible?Probablynot.Ontheotherhand,doesthepossibilityoffrequentcommunicationtodaymeanthattheimpulsetodosowasn’tpresentagenerationago?Manystudiesshowthatolderparents--today’sgrandparents-wouldhavecalledtheirchildrenmoreoftenifthemeansandcostofdoingsohadnotbeenabarrier.Furthermore,studiesshowthatfinancesarethemostfrequentsubjectofcommunicationbetweenparentsandtheircollegechildren.Thefactthatcollegestudentsarefinanciallydependentontheirparentsisnothingnew;norarerequestsformoremoneytobesentfromhome.Thisphenomenonisneithergoodnorbad;itisafactofcollegelife,todayandinthepast.Thankstotheadvancedtechnology,weliveinanageofbetteredcommunication.Thishasmanyimplicationswellbeyondtherolethatparentsseemtoplayinthelivesoftheirchildrenwhohaveleftforcollege.Butitisusefultobearinmindthatallsuchchangescomefromthetechnologyandnotsomeimagineddesirebyparentstokeeptheirchildrenundertheirwings.66.Thesurveysinformusof____________.A.theconditionsofcollegedormitoriesB.thesignofparent’smanagementintheirownbehaviorsC.thedevelopmentofcommunicationtechnologyD.theparents’over-protectionoftheircollegechildren67.Whichofthefollowingstatementdoestheauthormostprobablyagreewith?A.Technologyexplainsgreaterparentalinvolvementwiththeirchildren.B.Parents’changedattitudesleadtocollegechildren’sdelayedindependence.C.Parentstodayarelessprotectivethanthoseinthepast.D.Thedisadvantagesofnewtechnologyoutweighitsadvantages.68.Whatisthemeaningoftheword“impulse”inthispassage?A.Desperation. B.Admiration. C.Urge. D.Depression.69.Whichofthefollowingwouldbethebesttitleforthepassage?A.DependenceorIndependence.B.TechnologyorAttitude.C.FamilyInfluenceorSocialChanges.D.CollegeManagementorCommunicationAdvancement.(B)Spanish-AmericanInstituteStudentCubNotesFreeandLowCostGyms,HealthClubsandPoolsNYCDepartmentofParksRecreationCentersRecreationCenters:The

NYCDepartmentofParkshasmanyRecreationCentersthroughout

NewYorkCity.RecreationCentersofferawiderangeof

free

and

membership

programsandservices.Somehaveindoorswimmingpools.Almostallhaveweightrooms,basketballcourts,dancestudios,boxingrings,artstudios,gamerooms,etc.

AllRecreationCentersofferawiderangeofprogramssuchasaerobics,dance,taichi,fencing,computerclasses,andart.

Manyprogramsarefreeandopentothegeneralpublicbutmanyrequiremembership.

Youdonotneedtobea

NewYorkCity

residenttousea

Recreation

Center.YoumayuseyourannualmembershipatanyandallCenters.UseoneneartheSpanish-AmericanInstituteandthenuseonenearyourhome.

Costs:Free

and

membership

programs.Standard

annual

membershipis

$50

forRecreationCentersand

$75

forRecreationCenterswithpools.(Doyouknowanyone55andolder?Theseniormembershipisonly

$10

ayear.)Standardannualmembershipprovidesscheduledaccesstothegym,pool,andalltheotherfacilities.Instructor-ledcoursessuchasaerobics,martialarts,music,oryoga

may

requireanadditionalfee.

MembershipandProgramInformation:Goto

the

homepage.Onthe“Facilities”menu,clickon“RecreationCenters.”Onthe“RecreationCenters”page,youwillfindinformationaboutmembershipandfees.YouwillalsoseelinkstoRecreationFacilitiesbyborough(Bronx,Brooklyn,

Manhattan,Queens,andStatenIsland).Onthe“Facilities”menu,youmayalsowanttocheckoutotherNYCDepartmentofParksfacilitiessuchasbeaches,iceskatingrinks,naturecenters,runningtracks,soccerfields,etc.RecreationCenters:ThereareseveralParksDepartmentRecreationCentersin

each

borough.Afteryougotothe“RecreationCenters”pageandclickonaborough,youwillfindalistofthecentersinthatboroughwiththeiraddresses,phonenumbers,andweblinks.Thelistwilllooklikethatfor

Manhattan

below.ClickonthelinkforaparticularCentertolearnmoreaboutitsservices,schedules,andprograms.70.WhatspecialbenefitscananannualmemberofRecreationCentersenjoy?A.Havingaccesstoallthefacilitiesallyear.B.Experiencingallprogramsandservicesfree.C.TakingfreeInstructor-ledcourses.D.Usingonlythecenternearyourhomefree.71.Ifyourparentsandgrandparents(bothoversixty)wanttogetthememberships,howmuchwilltheypay?A.Atleast$20. B.Atleast$120. C.Atleast$180. D.Atleast$220.72.Youwillprobablyfailtofind____________on

the

homepage.A.thecostforvariousmemberships B.thelocationsofrecreationscentersC.thestaffandprovidedservices D.thefacilities,phonesandweblinks(C) JusthowmuchdoestheConstitution（宪法）protectyourdigitaldata?TheSupremeCourtwillnowconsiderwhetherpolicecansearchthecontentsofamobilephonewithoutawarrant（授权令）ifthephoneisonoraroundapersonduringanarrest.Californiahasaskedthejusticestorestorethepracticethatthepolicemaysearchthroughthecontentsofsuspects’smartphonesatthetimeoftheirarrest.Itishard,thestatesays,forjudgestoassesstheimplicationsofnewandrapidlychangingtechnologies.ThejusticeswouldbecarelessiftheyfollowedCalifornia’sadvice.TheyshouldstartbyrejectingCalifornia’sweakargumentthatexploringthecontentsofasmartphoneissimilartosay,goingthroughasuspect’swallet.Thecourthasruledthatpolicedon’toffendagainsttheFourthAmendment（修正案）whentheygothroughthewallet,ofanarresteewithoutawarrant.Infact,exploringone’ssmartphoneismorelikeenteringhisorherhome.Asmartphonemaycontainanarrestee’sreadinghistory,financialhistory,medicalhistoryandcomprehensiverecordsofrecentcorrespondence.Americansshouldtakestepstoprotecttheirowndigitalprivacyandshouldavoidputtingimportantinformationinsmartphones.Butkeepingsensitiveinformationonthesedevicesisincreasinglyarequirementofnormallife.CitizensstillhavearighttoexpectprivatedocumentstoremainprivateandprotectedbytheConstitution’sprohibitiononunreasonablesearches.Inmanycases,itwouldnotbeverydifficultforauthoritiestoobtainawarranttosearchthroughphonecontents.Theycouldstilltrump（打出王牌）theFourthAmendmentprotectionswhenfacingsevereanddangerouscircumstances,suchasthethreatofimmediateharm,andtheycouldtakereasonablemeasurestoensurethatphonedataarenotdeletedoralteredwhileawarrantisontheway.Thejustices,though,maywanttoallowroomforpolicetocitesituationswheretheyareentitledtomoreflexibility.ButthejusticesshouldnotswallowCalifornia’sargumentwhole.NewtechnologysometimesdemandsfreshapplicationsoftheConstitution’sprotections.OrinKerr,alawprofessor,comparestheexplosionandaccessibilityofdigitalinformationinthe21stcenturywiththeestablishmentofautomobileuseasadigitalnecessityoflifeinthe20th.Atthattime,thejusticeshadtoexplainnewrulesforthenewpersonaldomain（领域）ofcars.Similarly,thejusticesmustsortouthowtheFourthAmendmentoftheConstitutionappliestodigitalinformationnow.73.TheSupremeCourtwillworkoutwhether,duringanarrest,itislegalto____________.A.searchforsuspects’mobilephoneswithoutawarrantB.checksuspects’phonecontentswithoutbeingauthorizedC.preventsuspectsfromdeletingtheirphonecontentsD.prohibitsuspectsfromusingtheirmobilephones74.Theauthor’sattitudetowardCalifornia’sargumentisoneof____________.A.tolerance B.indifference C.disapproval D.carefulness75.Theauthorbelievesthatexploringone’sphonecontentiscomparableto____________.A.gettingintoone’sresidenceB.handingone’shistoricalrecordsC.scanningone’scorrespondencesD.goingthroughone’swallet76.InParagraph4and5,theauthorshowshisconcernthat____________.A.principlesarehardtobeclearlyexpressedB.thecourtisgivingpolicelessroomforactionC.phonesareusedtostoresensitiveinformationD.citizens’privacyisnoteffectivelyprotected77.OrinKerr’scomparisonisquotedtoindicatethat____________.A.theConstitutionshouldbecarriedoutflexiblyB.NewtechnologyalsorequiresreinterpretationoftheConstitutionC.California’sargumentgoesagainstprinciplesoftheConstitutionD.PrinciplesoftheConstitutionshouldneverbealteredSectionC（8分）Directions:Readthepassagecarefully.Thenanswerthequestionsorcompletethestatementsinthefewestpossiblewords.Nooneshouldbeforcedtowearauniformunderanycircumstance.Uniformsaredemandingtothehumanspiritandtotallyunnecessaryinademocraticsociety.Uniformstelltheworldthatthepersonwhowearsonehasnovalueasanindividualbutonlylivestofunctionasapartofawhole.Theindividualinauniformlosesallself-worth.Therearethosewhosaythatwearingauniformgivesapersonasenseofidentificationwithalarger,moreimportantconcept.Whatcouldbemoreimportantthantheindividualhimself?Ifanorganizationissoweakthatitmustrelyonclothandbuttonstoinspireitsmembers,thatorganizationhasnorighttocontinueitsexistence.Otherssaythatthepracticeofmakingpersonswearuniforms,sayinaschool,eliminatesallenvyandcompetitioninthematterofdress,suchthatapoorpersonwhocannotaffordgood-qualityclothingisnottobebelittledbyawealthypersonwhowearsexpensivequalityclothing.Thosepersonsconvenientlyignoresuchconceptsasfreedomofchoiceandindividuality.Itisonlyashortstepfromforcingeveryonetodrivethesamecar,havethesametypeoffoods.Whenthishappens,allmotivationtoimproveone’slifeisremoved.Whywouldparentsbothertoworkhardsothattheirchildrencouldhaveabetterlifethantheyhadwhentheyknowthattheirchildrenaregoingtobeforcedtohaveexactlythesamelifethattheyhad?Uniformsalsohurttheeconomy.Rightnow,billionsofdollarsarespentonthefashionindustryyearly.Thousandsofpersonsareemployedindesigning,creatingandmarketingdifferenttypesofclothing.Ifeveryonewereforcedtowearuniforms,artisticpersonnelwouldbeunnecessary.Salespersonswouldbesuperf