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简述变频器的接线方法。

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Passage2

Questions6to10arebasedonthefollowingpassage:

Whenaluminumwasfirstproducedaboutahundredandfiftyyearsago,itwassodifficulttoseparateformtheoresinwhichitwasfoundthatitspricewashigherthanthatofgold.Thepriceremainedhighuntilanewprocesswasdiscoveredforrefiningthemetalwiththeaidofelectricityapproximatelythreequartersofacenturylater.Thenewmethodwassomuchcheaperthataluminumbecausepracticalformanypurposes,oneofwhichwasmakingpotsandpans.

Aluminumislightweight,rustproofandeasilyshapedintodifferentforms.Bymixingitwithothermetals,scientistshavebeenabletoproduceavarietyofalloys,someofwhichhavethestrengthofsteelbutweighonlyonethirdasmuch.

Today,theusesofaluminumareinnumerable.Perhapsitsmostimportantuseisintransportation.Aluminumisfoundintheengineofautomobiles,inthehullsofboats.Itisalsousedinmanypartsofairplanes.Infact,thehuge“airbus”planeswouldprobablyneverhavebeenproducedifaluminumdidnotexist.Bymakingvehicleslighterinweightaluminumhasgreatlyreducedtheamountoffuelneededtomovethem,Aluminumisalsobeingusedextensivelyinthebuildingindustryinsomecountries.

Sincealuminumissuchaversatile(多用的)metal,itisfortunatethatbauxite(铝土矿),whichisoneofitschiefsources,isalsooneoftheearth’smostplentifulsubstances.Asthesourceofaluminumisalmostinexhaustible,wecanexpectthatmoreandmoreuseswillbefoundforthisversatilemetal.

6.Thepriceofaluminumwassharplyreducedwhenpeoplediscoveredanewrefiningprocesswiththeaidof.

A.windB.solarenergyC.hydraulicpowerD.electricity

7.Aluminumis.

A.lightweight,rustproofbutnoteasilyshapedintodifferentforms

B.heavyweight,rustproofandeasilyshapedintodifferentforms

C.lightweight,rustproofandeasilyshapedintodifferentforms

D.lightweightandeasilyshapedintodifferentformsbutitiseasytobecomerusty

8.WhichofthefollowingisNOTtrue?

A.Aluminumiswidelyusedintransportation.

B.Aluminumisalsousedinmanypartsofairplanes.

C.Aluminumisbeingusedextensivelyinthebuildingindustry.

D.Aluminumisnotusedinitspureform.

9.Aluminumisfoundonearthmostlyintheformof.

A.puremetalB.bauxiteC.goldD.liquid

10.Whatisthepassagetalkingabout?

A.Thefeaturesofaluminumanditsfunctions.B.Theprocessofaluminum.

C.Thediscoveryofaluminum.D.Thepromisingfutureofaluminum.

Passage4

Questions16to20arebasedonthefollowingpassage:

Successfulinnovationshavedrivenmanyoldertechnologiestoextinctionandhaveresultedinhigherproductivity,greaterconsumptionofenergy,increaseddemandofrawmaterials,acceleratedflowofmaterialsthroughtheeconomyandincreasedquantitiesofmetalsandothersubstancesinuseeachperson.Thehistoryofindustrialdevelopmentaboundswithexamples.

In1870,horsesandmulesweretheprimesourceofpoweronU.S.farms.Onehorseormulewasrequiredtosupportfourhumanbeingsaratiothatremainedalmostconstantformanydecades.Atthattime,hadanationalcommissionbeenaskedtoforecastthepopulationfor1970,itsanswerprobablywouldhavedependedonwhetheritsconsultantswereofaneconomicortechnologicalturnofmind.Hadtheybeen“economists”,theywouldprobablyhaveprojectedthe1970horsesormulepopulationtobemorethan50million.Hadtheybeen“technologists”,theywouldhaverecognizedthatthepowerofsteamhadalreadybeenharnessedtoindustryandtolearnandoceantransport.Theywouldhaverecognizedfurtherthatitwouldbetheprimesourceofpoweronthefarm.Itwouldhavebeendifficultforthemtoavoidtheconclusionthatthehorseandmulepopulationwoulddeclinerapidly.

16.Accordingtothepassage,whatsuppliedmostofthepoweronU.S.farmsin1870?

A.AnimalsB.HumansC.EnginesD.Water

17.WhichofthefollowingisNOTmentionedbytheauthorasaconsequenceofnewtechnologicaldevelopments?

A.Oldertechnologiesdieaway.

B.ThequalityoflifeisImproved.

C.Overallproductivityincrease.

D.Morerawmaterialsbecomenecessary.

18.Itcanbeinferredfromthepassagethatby1870.

A.technologybegantobemoreeconomical

B.thesteamenginehadbeeninvented

C.theU.S.horsepopulationwasabout10million

D.anationalcommissionwasabout10million

19.Inthesecondparagraph,theauthorsuggeststhat“economists”would.

A.plantheeconomythroughyearlyforecasts

B.failtoconsidertheinfluenceoftechnologicalinnovation

C.valuetheeconomiccontributionoffarmanimals

D.consultthenationalcommissionontheeconomy

20.Whatistheauthor’sattitudetowardchangesbroughtonbytechnologicalinnovations?

A.Heisexcitedaboutthem.

B.Heacceptthemasnatural.

C.Heisdisturbedbythem.

D.Hequestionstheirusefulness.

Thissupermarketdevelopedrapidlyunderhis_____.

产程中胎心监护,下列哪项是错误的

Wecanbeginourdiscussionof“populationasglobalissue”withwhatmostpersonsmeanwhentheydiscuss“thepopulationproblem”:toomanypeopleonearthandatoorapidincreaseinthenumberaddedeachyear.Thefactsarenotindispute,Itwasquiterighttoemploytheanalogythatlikeneddemographicgrowthto“along,thinpowderfusethatburnssteadilyandhaltinglyuntilitfinallyreachesthechargeandexplodes.”

Tounderstandthecurrentsituation,whichischaracterizedbyrapidincreasesinpopulation,itisnecessarytounderstandthehistoryofpopulationtrends.Rapidgrowthisacomparativelyrecentphenomenon.Lookingbackatthe8,000yearsofdemographichistory,wefindthatpopulationshavebeenvirtuallystableorgrowingveryslightlyformostofhumanhistory.Formostofourancestors,lifewashard,oftennasty,andveryshort.Therewashighfertilityinmostplaces,butthiswasusuallybalancedbyhighmortality.Formostofhumanhistory,itwasseldomthecasethatoneintenpersonswouldlivepastforty,whileinfancyandchildhoodwereespeciallyriskyperiods.Often,societieswereincleardangerofextinctionbecausedeathratescouldexceedtheirbirthrates.Thus,thepopulationproblemthroughoutmostofhistorywashowtopreventextinctionofthehumanrace.

Thispatternisimportanttonotice.Notonlydoesitputthecurrentproblemsofdemographicgrowthintoahistoricalperspective,butitsuggeststhatthecauseofrapidincreaseinpopulationinrecentyearsisnotasuddenenthusiasmformorechildren,butanimprovementintheconditionsthattraditionallyhavecausedhighmortality.

Demographichistorycanbedividedintotwomajorperiods:atimeoflong,slowgrowthwhichextendedfromabout8,000BC.tillapproximatelyAD.1650.Inthefirstperiodofsome9600years,thepopulationincreasedfromsome8millionto500millionin1650.Between1650andthepresent,thepopulationhasincreasedfrom500milliontomorethan4billion.Anditisestimatedthatbytheyear2000therewillbe6.2billionpeoplethroughouttheworld.Onewaytoappreciatethisdramaticdifferenceinsuchabstractnumbersistoreducethetimeframetosomethingthatismoremanageable.Between8000BCand1650,anaverageofonly50,000personswasbeingaddedannuallytotheworld’spopulationeachyear.Atpresent,thisnumberisaddedeverysixhours.Theincreaseisabout80,000,000personsannually.

1.Whichofthefollowingdemographicgrowthpatternismostsuitableforthelongthinpowderfuseanalogy?

A.Avirtuallystableorslightlydecreasingperiodandthenasuddenexplosionofpopulation.

B.Aslowgrowthforalongtimeandthenaperiodofrapid,dramaticincrease.

C.Toomanypeopleonearthandafewrapidincreaseinthenumberaddedeachyear.

D.Alongperiodwhendeathratesexceedsbirthratesandthenashortperiodwithhigherfertilityandlowermortality.

2.Duringthefirstperiodofdemographichistory,societieswereoftenindangerofextinctionbecause___.

A.onlyoneintenpersonscouldlivepast40.

B.therewashighermortalitythanfertilityinmostplaces.

C.itwastoodangeroustohavebabiesduetothepoorconditions.

D.ourancestorshadlittleenthusiasmformorechildren.

3.Whichstatementistrueaboutpopulationincrease?

A.Theremightbeanincreaseof2.2billionpersonsfromnowtotheyear2000.

B.About50,000babiesareborneverysixhoursatpresent.

C.Between8000BCandthepresent,thepopulationincreaseisabout80,000,000personseachyear.

D.Thepopulationincreasedfasterbetween8000BCand1650thanbetween1650andthepresent.

4.Theauthorofthepassageintendsto___.

A.warnpeopleagainstthepopulationexplosioninthenearfuture.

B.comparethedemographicgrowthpatterninthepastwiththatafter1650.

C.findoutthecauseforrapidincreaseinpopulationinrecentyears.

D.presentusaclearandcompletepictureofthedemographicgrowth.

5.Theword“demographic”inthefirstparagraphmeans___.

A.statisticsofhuman.

B.surroundingsstudy.

C.accumulationofhuman.

D.developmentofhuman.

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