The next step in nanotechnology_365bet线上网投

2.B.解析:段落中尚无明确的段落主旨句,

可是段子中冒出了大气反映非凡细节信息的辞藻:20microwatts(微瓦),200

nanometers(皮米),hundredsoftimessmallerthanthewidthofahuman

hair,100milliontimesmorepowerful,225horsepower(马力),

那么些细节音信贯穿全段,从质量上它们各自用于描述功率和尺寸大小,

因此可直接判断B(描述了皮米引擎的功率和尺寸大小)是答案。

Tostart,ajetenginerequirespneumaticrotationoftheturbine,

AC-electricalfuelpumps,andanAC-electricalflashthatignitesthe

fuel。

Astheturbine(behindthecombustionchamber)isalready

rotating,thefrontinletfansarealsorotating。

Aftertheignition,

bothfansandturbinespeeduptheirrotation。

Ascombustionstabilizes,

theenginethereafteronlyneedsthefueltorunatidle。

Thestarted

enginecannowreplacetheAPUwhenstartingupfurtherengines。

During

flighttheAPUanditsgeneratorarenotneeded。

Letsimagineasculptorbuildingastatue,justchippingawaywithhis

chisel。

Michelangelohadthiselegantwayofdescribingitwhenhesaid,

Everyblockofstonehasastatueinsideofit,anditsthetaskof

thesculptortodiscoverit。

Butwhatifheworkedintheopposite

direction?

Notfromasolidblockofstone,butfromapileofdust,

somehowgluingmillionsoftheseparticlestogethertoformastatue。

Theauxiliaryfuelpumpprovidesfuelunderpressuretothefuel/air

controlunitforenginestartingand/oremergencyuse。

Afterstarting,

theengine-drivenfuelpumpprovidesfuelunderpressurefromthefuel

tanktothefuel/aircontrolunit。

Thiscontrolunit,whichessentially

replacesthecarburetor,metersfuelbasedonthemixturecontrol

setting,andsendsittothefuelmanifoldvalveataratecontrolledby

thethrottle。

Afterreachingthefuelmanifoldvalve,thefuelis

distributedtotheindividualfueldischargenozzles。

Thedischarge

nozzles,whicharelocatedineachcylinderhead,injectthefuel/air

mixturedirectlyintoeachcylinderintakeport。

AAnintroductionofaToyota’s225horsepowerV6engine。

Now,computingisjustoneexample。

ItstheonethatIminterestedin,

thatmygroupisreallyinvestedin,butthereareothersinrenewable

energy,inmedicine,instructuralmaterials,wherethescienceisgoing

totellyoutomovetowardsthenano。

Thatswherethebiggestbenefit

is。

Butifweregoingtodothat,thescientistsoftodayandtomorrow

aregoingtoneednewtoolstoolsjustliketheonesIdescribed。

And

theywillneedchemistry。

Thatsthepoint。

Thebeautyofscienceis

thatonceyoudevelopthesenewtools,theyreoutthere。

Theyreout

thereforever,andanyoneanywherecanpickthemupandusethem,and

helptodeliveronthepromiseofnanotechnology。

Inafuelinjectionsystem,thefuelisinjectedeitherdirectlyinto

thecylinders,orjustaheadoftheintakevalve。

Afuelinjection

systemisconsideredtobelesssusceptibletoicingthanthecarburetor

system。

Impacticingontheairintake,however,isapossibilityin

eithersystem。

Impacticingoccurswheniceformsontheexteriorofthe

airplane,andblocksopeningssuchastheairintakefortheinjection

system。

假设段落中有众所周知的“细节音信词”,

可以考虑拔取那一个细节新闻所展示的主题内容来确认段落主题。

APUsarealsousedtorunaccessorieswhiletheenginesareshutdown。

Thisallowsthecabintobecomfortablewhilethepassengersare

boardingbeforetheaircraftsenginesarestarted。

Electricalpoweris

usedtorunsystemsforpreflightchecks。

SomeAPUsarealsoconnected

toahydraulicpump,allowingcrewstooperatehydraulicequipment(such

asflightcontrolsorflaps)priortoenginestart。

Thisfunctioncan

alsobeused,onsomeaircraft,asabackupinflightincaseofengine

orhydraulicfailure。

Iknowthatsanabsurdnotion。

Itsprobablyimpossible。

Theonlyway

yougetastatuefromapileofdustisifthestatuebuiltitselfif

somehowwecouldcompelmillionsoftheseparticlestocometogetherto

formthestatue。

Figure4:Relationshipoftraveldistanceandspeedofvariousportions

ofpropellerblade。

ETheworkingprincipleofthenanomotor。

APUsprovidingelectricityat400Hzaresmallerandlighterthantheir

50/60Hzcounterparts,butarecostlier;thedrawbackbeingthatsuch

highfrequencysystemssufferfromvoltagedrops。

Butthatwas15yearsago,andfantasticsciencewasdone,really

importantwork。

Wevelearnedalot。

Wewereneverabletotranslate

thatscienceintonewtechnologiesintotechnologiesthatcould

actuallyimpactpeople。

Andthereasonis,thesenanomaterials

theyrelikeadouble-edgedsword。

Thesamethingthatmakesthemso

interestingtheirsmallsizealsomakesthemimpossibletowork

with。

Itsliterallyliketryingtobuildastatueoutofapileof

dust。

Andwejustdonthavethetoolsthataresmallenoughtowork

withthem。

Butevenifwedid,itwouldntreallymatter,becausewe

couldntonebyoneplacemillionsofparticlestogethertobuilda

technology。

Sobecauseofthat,allofthepromiseandallofthe

excitementhasremainedjustthat:promiseandexcitement。

Wedonthave

anydisease-fightingnanobots,theresnoelevatorstospace,andthe

thingthatImmostinterestedin,nonewtypesofcomputing。

Figure2:Thearrowsinthisillustrationindicatethedirectionof

motionofthecrankshaftandpistonduringthefour-strokecycle。

Paragraph4____。

Althoughtheamountofenergy(能量)producedissmall20

microwatts(百卓殊之一瓦)itisquiteimpressive(给人回忆深入的)in

relationto(与比较)thetinyscaleofthemotor。

Thewholesetupis

lessthan200nanometers(飞米)onaside,orhundredsoftimessmaller

thanthewidth(宽度)ofahumanhair。

Ifitcouldbescaleduptothe

sizeofanautomobileengine,itwouldbe100milliontimesmore

powerful(强大的)thana丰田Camry’s225horsepower(马力)V6

engine。

IftheAPUfailsbeforeenginestart,theenginescannotbestarted

withoutanexternalstartcarttoprovideasourceofbleedair。

If

theAPUfailsmid-flight,therewillbenoimmediateeffect。

Even

withouttheAPU,therearetwoadditionalwaystorestartanaircraft

engineinflight:

Now,asitturnsout,thisisnotthatalienofaproblem。

Wejustdont

buildanythingthisway。

Peopledontbuildanythingthisway。

Butif

youlookaroundandtheresexampleseverywhereMotherNature

buildseverythingthisway。

Everythingisbuiltfromthebottomup。

You

cangotothebeach,youllfindthesesimpleorganismsthatuse

proteinsbasicallymoleculestotemplatewhatisessentiallysand,

justpluckingitfromtheseaandbuildingtheseextraordinary

architectureswithextremediversity。

Andnaturesnotcrudelikeus,

justhackingaway。

Sheselegantandsmart,buildingwithwhats

available,moleculebymolecule,makingstructureswithacomplexityand

adiversitythatwecantevenapproach。

Andshesalreadyatthenano。

Shesbeenthereforhundredsofmillionsofyears。

Weretheonesthat

arelatetotheparty。

Theairplaneengineandpropeller,oftenreferredtoastheaircraft

powerplant,workincombinationtoproducethrust。

Thepowerplant

propelstheairplaneanddrivesthevarioussystemsthatsupportthe

operationofanairplane。

Paragraph2

Paragraph4

Paragraph5

Paragraph6

TheAPUisasmalljetenginethatisusedtostartthelargerjet

engines。

Inairlinersitsusuallyattheveryrearoftheaircraft,

belowthetail。

Largeenginesareheavyandrequirealotoftorqueto

spinup,morethanastarterbatterycangenerate。

So,thebatteryspins

upamuchsmallerAPUjetengine。

High-speedbleedairfromtheAPUis

usedtospinupthemainengine。

Asanexample:ifItooktheroom-sizedcomputerthatsentthreemento

themoonandbackandsomehowcompresseditcompressedtheworlds

greatestcomputerofitsday,soitwasthesamesizeasyoursmartphone

youractualsmartphone,thatthingyouspent300bucksonandjust

tossouteverytwoyears,wouldblowthisthingaway。

Youwouldnotbe

impressed。

Itcouldntdoanythingthatyoursmartphonedoes。

Itwould

beslow,youcouldntputanyofyourstuffonit,youcouldpossibly

getthroughthefirsttwominutesofaWalkingDeadepisodeifyoure

lucky

Reciprocatingengines活塞发动机

FPossiblefieldsofapplicationinthefuture。

APUsfittedto***extended-rangetwin-engineoperations(ETOPS)

***aircraftareacriticalsafetydevice,astheysupplybackup

electricityandcompressedairinplaceofthedeadengineorfailed

mainenginegenerator。

WhilesomeAPUsmaynotbestartableinflight,

ETOPS-compliantAPUsmustbeflight-startableataltitudesuptothe

aircraftserviceceiling。

Recentapplicationshavespecifiedstartingup

to43,000ft(13,000m)fromacompletecold-soakconditionsuchasthe

HamiltonSundstrandAPS5000fortheBoeing787Dreamliner。

IftheAPUor

itselectricalgeneratorisnotavailable,theaircraftcannotbe

releasedforETOPSflightandisforcedtotakealongernon-ETOPS

route。

Sowedecidedthatweregoingtousethesametoolthatnatureuses,

andthatschemistry。

Chemistryisthemissingtool。

Andchemistryworks

inthiscasebecausethesenanoscaleobjectsareaboutthesamesizeas

molecules,sowecanusethemtosteertheseobjectsaround,muchlikea

tool。

Thatsexactlywhatwevedoneinourlab。

Wevedeveloped

chemistrythatgoesintothepileofdust,intothepileof

nanoparticles,andpullsoutexactlytheonesweneed。

Thenwecanuse

chemistrytoarrangeliterallybillionsoftheseparticlesintothe

patternweneedtobuildcircuits。

Andbecausewecandothat,wecan

buildcircuitsthataremanytimesfasterthanwhatanyonesbeenable

tomakeusingnanomaterialsbefore。

Chemistrysthemissingtool,and

everydayourtoolgetssharperandgetsmoreprecise。

Andeventually

andwehopethisiswithinahandfulofyearswecandeliveronone

ofthoseoriginalpromises。

Figure7:Float-typecarburetor。

DPreviousinventionsofnanoscale(皮米级的)products。

APICAPS3200APUforAirbusA320family。

TheprimarypurposeofanaircraftAPUistoprovidepowertostartthe

mainengines。

Turbineenginesmustbeacceleratedtoahighrotational

speedtoprovidesufficientaircompressionforself-sustaining

operation。

Smallerjetenginesareusuallystartedbyanelectricmotor,

whilelargerenginesareusuallystartedbyanairturbinemotor。

Before

theenginesaretobeturned,theAPUisstarted,generallybyabattery

orhydraulicaccumulator。

OncetheAPUisrunning,itprovidespower

(electric,pneumatic,orhydraulic,dependingonthedesign)tostart

theaircraftsmainengines。

(Laughter)

Reductioninevaporativeicing。

Betterfuelflow。

Fasterthrottleresponse。

Precisecontrolofmixture。

Betterfueldistribution。

Easiercoldweatherstarts。

提示:

Itprovidescabinairandelectricpowerbeforetheenginesare

started(savingbatterypower)。

Itprovidesanemergencysourceofelectricpowerintheeventof

enginefailure。

Itcanstarttheaircraftenginesmid-flightinanemergency。

best365官网,Thepointistheprogressitsnotgradual。

Theprogressis

relentless。

Itsexponential。

Itcompoundsonitselfyearafteryear,to

thepointwhereifyoucompareatechnologyfromonegenerationtothe

next,theyrealmostunrecognizable。

Andweoweittoourselvestokeep

thisprogressgoing。

Wewanttosaythesamething10,20,30yearsfrom

now:lookwhatwevedoneoverthelast30years。

Yetweknowthis

progressmaynotlastforever。

Infact,thepartyskindofwinding

down。

Itslikelastcallforalcohol,right?

Ifyoulookunderthe

covers,bymanymetricslikespeedandperformance,theprogresshas

alreadyslowedtoahalt。

Soifwewanttokeepthispartygoing,we

havetodowhatwevealwaysbeenabletodo,andthatistoinnovate。

Mixturecontrol

BAdescriptionofthenanomotorintermsofpowerandsize。

TheAPUisnormallyleftoffinflight,butmaybeturnedonforcertain

long-hauloverwaterflightsasanextraprecaution。

Soourgroupsroleandourgroupsmissionistoinnovatebyemploying

carbonnanotubes,becausewethinkthattheycanprovideapathto

continuethispace。

Theyarejustliketheysound。

Theyretiny,hollow

tubesofcarbonatoms,andtheirnanoscalesize,thatsmallsize,gives

risetothesejustoutstandingelectronicproperties。

Andthescience

tellsusifwecouldemploythemincomputing,wecouldseeuptoaten

timesimprovementinperformance。

Itslikeskippingthroughseveral

technologygenerationsinjustonestep。

TheTiniestElectricMotorintheWorld

across-bleedstart,wherebleedairfromaworkingengineisused

tostartadeadengine,or

awindmillstart,wheretheaircraftdivesandattainsenoughspeed

thatramairspinstheturbinefastenoughtoallowarelight。

(Laughter)

Theinductionsystembringsinairfromtheoutside,mixesitwithfuel,

anddeliversthefuel/airmixturetothecylinderwherecombustion

occurs。

Outsideairenterstheinductionsystemthroughanintakeport

onthefrontoftheenginecowling。

Thisportnormallycontainsanair

filterthatinhibitstheentryofdustandotherforeignobjects。

Since

thefiltermayoccasionallybecomeclogged,analternatesourceofair

mustbeavailable。

Usually,thealternateaircomesfrominsidethe

enginecowling,whereitbypassesacloggedairfilter。

Somealternate

airsourcesfunctionautomatically,whileothersoperatemanually。

二零零六年教材上增产了大约17篇小说,词汇选项,阅读判断,概括大意落成句子,

阅读精晓,补全短文,完型填空各种题型上都有新增小说。

理工类和卫生类新增的稿子更展现专业性。

新增小说的语言难度和难点考点设置处境在自然水准上显示了08年考题的出题趋势。

AircraftwithAPUscanalsoacceptelectricalandpneumaticpowerfrom

groundequipmentwhenanAPUhasfailedorisnottobeused。

Some

airportsreducetheuseofAPUsduetonoiseandpollution,andground

powerisusedwhenpossible。

Sotherewehaveit。

Wehavethisreallyimportantproblemandwehave

whatisbasicallytheidealsolution。

Thescienceisscreamingatus,

Thisiswhatyoushouldbedoingtosolveyourproblem。

So,allright,

letsgetstarted,letsdothis。

Butyoujustrunrightbackintothat

double-edgedsword。

Thisidealsolutioncontainsamaterialthats

impossibletoworkwith。

Idhavetoarrangebillionsofthemjustto

makeonesinglecomputerchip。

Itsthatsameconundrum,itslikethis

undyingproblem。

Onastandarddayatsealevelwiththeengineshutdown,themanifold

pressuregaugewillindicatetheambientabsoluteairpressureof29。

92

in。

Hg。

Becauseatmosphericpressuredecreasesapproximately1in。

Hg

per1,000feetofaltitudeincrease,themanifoldpressuregaugewill

indicateapproximately24。

92in。

Hgatanairportthatis5,000feet

abovesealevelwithstandarddayconditions。

二〇〇八年课题预测分析

Oncetheenginesarestarted,theAPUisnolongerrequired,butitdoes

provideacoupleofsecondaryfunctions:

WhenIwasagraduatestudent,itwasoneofthemostexcitingtimesto

beworkinginnanotechnology。

Therewerescientificbreakthroughs

happeningallthetime。

Theconferenceswerebuzzing,therewastonsof

moneypouringinfromfundingagencies。

Andthereasoniswhenobjects

getreallysmall,theyregovernedbyadifferentsetofphysicsthat

governordinaryobjects,liketheonesweinteractwith。

Wecallthis

physicsquantummechanics。

Andwhatittellsyouisthatyoucan

preciselytunetheirbehaviorjustbymakingseeminglysmallchangesto

them,likeaddingorremovingahandfulofatoms,ortwistingthe

material。

Itslikethisultimatetoolkit。

Youreallyfeltempowered;

youfeltlikeyoucouldmakeanything。

Atagivenaltitude,thehigherthetachometerreading,thehigherthe

poweroutputoftheengine。

ETheworkingprincipleofthenanomotor。

AndweweredoingitandbyweImeanmywholegenerationofgraduate

students。

Weweretryingtomakeblazingfastcomputersusing

nanomaterials。

Wewereconstructingquantumdotsthatcouldonedaygo

inyourbodyandfindandfightdisease。

Therewereevengroupstrying

tomakeanelevatortospaceusingcarbonnanotubes。

Youcanlookthat

up,thatstrue。

Anyways,wethoughtitwasgoingtoaffectallpartsof

scienceandtechnology,fromcomputingtomedicine。

AndIhavetoadmit,

IdrankalloftheKool-Aid。

Imean,everylastdrop。

bycylinderarrangementwithrespecttothecrankshaft—radial,

in-line,v-typeoropposed,or

bythemethodofcooling—liquidorair-cooled。

365娱乐场体育投注,指定的多个段落都未曾分明的段落大旨句(二〇〇七年理工类A/B级概括大意题中三个指定段落都尚未明了段落宗旨句),考生方可因此通读指定段落的不经意来概括出段落主旨,

或倚靠一些实用的答题技巧肯定段落大旨。

以确认段落第4段的段落主旨为例分析答题技巧:

延伸阅读:

Anauxiliarypowerunit(APU)isadeviceonavehiclethatprovides

energyforfunctionsotherthanpropulsion。

Theyarecommonlyfoundon

largeaircraftandnavalshipsaswellassomelargelandvehicles。

AircraftAPUsgenerallyproduce115Valternatingcurrent(AC)at400Hz

(ratherthan50/60Hzinmainssupply),toruntheelectricalsystemsof

theaircraft;otherscanproduce28Vdirectcurrent(DC)。

APUscan

providepowerthroughsingle-orthree-phasesystems。

APUFunction

Nowthatlastone,thatsareallyimportantone。

Wejusthavecometo

expectthepaceofcomputingadvancementstogoonindefinitely。

Weve

builtentireeconomiesonthisidea。

Andthispaceexistsbecauseofour

abilitytopackmoreandmoredevicesontoacomputerchip。

Andasthose

devicesgetsmaller,theygetfaster,theyconsumelesspowerandthey

getcheaper。

Anditsthisconvergencethatgivesusthisincredible

pace。

Therefore,atanoutsideairtemperatureof100°F,atemperaturedropof

70°Fresultsinanairtemperatureinthecarburetorof30°F。

C[u]Surfacetension[/u](表面张力)。

ButMichaelheputsitoff。

Fine,Igetit。

Theirmothersstill

alive,itwouldmakeherupset。

Wejustsaid,WhatstheFredoinour

problem?

Whatarewenotdealingwith?

Whatarewenotdoing,butneeds

tobedonetomakethisasuccess?

Andtheansweristhatthestatue

hastobuilditself。

Wehavetofindaway,somehow,tocompel,to

convincebillionsoftheseparticlestoassemblethemselvesintothe

technology。

Wecantdoitforthem。

Theyhavetodoitforthemselves。

Anditsthehardway,andthisisnottrivial,butinthiscase,its

theonlyway。

Someairplanesareequippedwithacarburetorairtemperaturegauge,

whichisusefulindetectingpotentialicingconditions。

Usually,the

faceofthegaugeiscalibratedindegreesCelsius(°C),withayellow

arcindicatingthecarburetorairtemperatureswhereicingmayoccur。

Thisyellowarctypicallyrangesbetween-15°Cand+5°C(5°Fand41°F)。

Iftheairtemperatureandmoisturecontentoftheairaresuchthat

carburetoricingisimprobable,theenginecanbeoperatedwiththe

indicatorintheyellowrangewithnoadverseeffects。

However,ifthe

atmosphericconditionsareconducivetocarburetoricing,theindicator

mustbekeptoutsidetheyellowarcbyapplicationofcarburetorheat。

(难度B/A级/二零零六年理工类教材新增文章)

Atthispoint,wesaid,Letsjuststop。

Letsnotgodownthatsame

road。

Letsjustfigureoutwhatsmissing。

Whatarewenotdealing

with?

Whatarewenotdoingthatneedstobedone?

ItslikeinThe

Godfather,right?

WhenFredobetrayshisbrotherMichael,weallknow

whatneedstobedone。

Fredosgottogo。

Mostairplanesalsoareequippedwithanoutsideairtemperature(OAT)

gaugecalibratedinbothdegreesCelsiusandFahrenheit。

Itprovidesthe

outsideorambientairtemperatureforcalculatingtrueairspeed,and

alsoisusefulindetectingpotentialicingconditions。

BAdescriptionofthenanomotorintermsofpowerandsize。

Thankyousomuchforyourtime。

Iappreciateit。

Thefuel/airmixtureisthendrawnthroughtheintakemanifoldandinto

thecombustionchambers,whereitisignited。

The“float-type

carburetor”acquiresitsnamefromafloat,whichrestsonfuelwithin

thefloatchamber。

Aneedleattachedtothefloatopensandclosesan

openingatthebottomofthecarburetorbowl。

Scientistsrecentlymadepublicthetiniestelectricmotorever

built。

Youcouldstuffhundredsofthemintotheperiodattheendof

thissentence。

Onedayasimilarenginemightpoweratinymechanical

doctorthatwouldtravelthroughyourbodytoremoveyourdisease。

Themotorworksbyshuffling(来回运动)atoms(原子)betweentwo

moltenmetaldroplets(小滴)inacarbonnanotube(纳米管)。

One

dropletisevensmallerthantheother。

Whenasmallelectriccurrentis

appliedtothedroplets,atomsslowlygetoutofthelargerdropletand

jointhesmallerone。

Thesmalldropletgrows–butnevergetsasbigas

theotherdroplet–andeventuallybumpsintothelargedroplet。

Asthey

touch,thelargedropletrapidlysopsup(吸入)theatomsithad

previouslylost。

Thisquickshiftinenergyproducesapower

stroke(动力行程)。

Thetechniqueexploitsthefactthatsurfacetensionthetendency

ofatomsormoleculestoresistseparatingbecomesmoreimportantat

smallscales。

Surfacetensionisthesamethingthatallowssomeinsects

towalkonwater。

Althoughtheamountofenergyproducedissmall20

microwatts(百相当之一瓦)itisquiteimpressive(给人记念深切的)

inrelationto(与相比较)thetinyscaleofthemotor。

Thewholesetup

islessthan200nanometersonaside,orhundredsoftimessmallerthan

thewidthofahumanhair。

Ifitcouldbescaleduptothesizeofan

automobileengine,itwouldbe100milliontimesmorepowerfulthana

丰田Camry’s225horsepowerV6engine。

In1988,ProfessorRichardMullerandcolleaguesmadethefirst

operating(工作的,运行的)micromotor(微型发动机),whichwas100

microns(微米)across,oraboutthethicknessofahumanhair。

In2003,

Zettlsgroupcreatedthefirstnanoscalemotor。

In2006,theybuilta

nanoconveyor(皮米传送带),whichmovestinyparticlesalonglikecars

inafactory。

Nanotechnology(微米技术)engineerstrytomimicnature,building

thingsatom-by-atom。

Amongotherthings,nanomotorscouldbeusedin

opticalcircuitstoredirectlight,aprocesscalledopticalswitching。

Futuristsenvision(预想)adaywhennanomachines(微米机器),powered

bynanomotors(微米引擎),travelinsideyourbodytofinddiseaseand

repairdamagedcells。

Now,asoddasthatsounds,thatisalmostexactlytheproblemIworkon

inmylab。

Idontbuildwithstone,Ibuildwithnanomaterials。

Theyre

thesejustimpossiblysmall,fascinatinglittleobjects。

Theyreso

smallthatifthiscontrollerwasananoparticle,ahumanhairwouldbe

thesizeofthisentireroom。

Andtheyreattheheartofafieldwe

callnanotechnology,whichImsureweveallheardabout,andweveall

heardhowitisgoingtochangeeverything。

Althoughsomeolderadjustable-pitchpropellerscouldonlybeadjusted

ontheground,mostmodernadjustable-pitchpropellersaredesignedso

thatyoucanchangethepropellerpitchinflight。

Thefirst

adjustable-pitchpropellersystemsprovidedonlytwopitchsettingsa

low-pitchsettingandahigh-pitchsetting。

Today,however,nearlyall

adjustable-pitchpropellersystemsarecapableofarangeofpitch

settings。

C[u]Surfacetension[/u](表面张力)。

Thismetersthecorrectamountoffuelintothecarburetor,depending

uponthepositionofthefloat,whichiscontrolledbytheleveloffuel

inthefloatchamber。

Whenthelevelofthefuelforcesthefloatto

rise,theneedlevalveclosesthefuelopeningandshutsoffthefuel

flowtothecarburetor。

Theneedlevalveopensagainwhentheengine

requiresadditionalfuel。

AAnintroductionofaToyota’s225horsepowerV6engine。

Thereasonforthetwististoproduceuniformliftfromthehubtothe

tip。

Asthebladerotates,thereisadifferenceintheactualspeedof

thevariousportionsoftheblade。

Thetipofthebladetravelsfaster

thanthatpartnearthehub,becausethetiptravelsagreaterdistance

thanthehubinthesamelengthoftime。

DPreviousinventionsofnanoscale(微米级的)products。

Whentheairflowsthroughtheventuri,alow-pressureareaiscreated,

whichforcesthefueltoflowthroughamainfueljetlocatedatthe

throat。

Thefuelthenflowsintotheairstream,whereitismixedwith

theflowingair。

从二零零七年考题的出题情形和二〇〇八年教材的编写景况来看,二零零六年职称拉脱维亚语考试如故将可能从教材中摘选一部分试题直接作为考题。

二零零六年考题难度应该与二零零七年考题难度相当。

Thepropellerisarotatingairfoil,subjecttoinduceddrag,stalls,

andotheraerodynamicprinciplesthatapplytoanyairfoil。

Itprovides

thenecessarythrusttopull,orinsomecasespush,theairplane

throughtheair。

练习:

Theaircraftpowerplantpart

2/2

FPossiblefieldsofapplicationinthefuture。

Theclimbpropellerhasalowerpitch,thereforelessdrag。

Lessdrag

resultsinhigherr。

p。

m。

andmorehorsepowercapability,whichincreases

performanceduringtakeoffsandclimbs,butdecreasesperformanceduring

cruisingflight。

Thecruisepropellerhasahigherpitch,thereforemoredrag。

Moredrag

resultsinlowerr。

p。

m。

andlesshorsepowercapability,whichdecreases

performanceduringtakeoffsandclimbs,butincreasesefficiencyduring

cruisingflight。

Thepropellerisusuallymountedonashaft,whichmaybeanextension

oftheenginecrankshaft。

Inthiscase,ther。

p。

m。

ofthepropeller

wouldbethesameasthecrankshaftr。

p。

m。

Onsomeengines,the

propellerismountedonashaftgearedtotheenginecrankshaft。

Inthis

type,ther。

p。

m。

ofthepropellerisdifferentthanthatoftheengine。

Inafixed-pitchpropeller,thetachometeristheindicatorofengine

power。

Therevolutionsperminuteareregulatedbythethrottle,whichcontrols

thefuel/airflowtotheengine。

Carburetorairtemperaturegauge

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