考研英语冲刺作文

考研英语冲刺作文

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具体内容：英语考试不管是不是考研，到了即将冲刺的时候，总是有那么

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Coal-firedpowerplantsTh...

英语考试不管是不是考研，到了即将冲刺的时候，总是有那么几篇英语

作文是我们要掌握的。下面是我给大家整理的，供大家参阅！

：Coal-firedpowerplants

TheinventionoftheincandescentlightbulbbyThomasA.Edison

in1879createdademandforacheap,readilyavailablefuelwith

whichtogeneratelargeamountsofelectricpower.Coalseemedto

fitthebill,anditfueledtheearliestpowerstations,(whichwere

setupattheendofthenineteenthcenturybyEdisonhimself).As

morepowerplantswereconstructedthroughoutthecountry,the

relianceoncoalincreasedthroughoutthecountry,therelianceon

coalincreased.SincetheFirstWorldWar,coal-firedpowerplants

hadacombinedintheUnitedStateseachyear.In1986suchplants

hadacombinedgeneratingcapacityof289,000megawattsandconsumed

83percentofthenearly900milliontonsofcoalminedinthecountry

thatyear.Giventheuncertaintyinthefuturegrowthofthenearly

900milliontonsofcoalminedinthecountrythatyear.Giventhe

uncertaintyinthefuturegrowthofnuclearpowerandinthesupply

ofoilandnaturalgas,coal-firedpowerplantscouldwellprovide

upto70percentoftheelectricpowerintheUnitedStatesbythe

endofthecentury.

Yet,inspiteofthefactthatcoalhaslongbeenasourceof

electricityandmayremainonformanyyears(coalrepresentsabout

80percentofUnitedStatesfossil-fuelreserves),ithasactually

neverbeenthemostdesirablefossilfuelforpowerplants.Coal

containslessenergyperunitofweightthanweightthannatural

gasoroil;itisdifficulttotransport,anditisassociatedwith

ahostofenvironmentalissues,amongthemacidrain.Sincethelate

1960sproblemsofemissioncontrolandwastedisposalhavesharply

reducedtheappealofcoal-firedpowerplants.Thecostof

amelioratingtheseenvironmentproblemsalongwiththerisingcost

ofbuildingafacilityaslargeandcomplexasacoal-firedpower

plant,havealsomadesuchplantslessattractivefromapurely

economicperspective.

Changesinthetechnologicalbaseofcoal-firedpowerplantscould

restoretheirattractiveness,however.Whereassomeofthese

changesareintendedmainlytoincreasetheproductivityofexisting

plants,completelynewtechnologiesforburningcoalcleanlyare

alsobeingdeveloped.

：ThesourceofEnergy

Asummaryofthephysicalandchemicalnatureoflifemustbegin,

notontheEarth,butintheSun;infact,attheSunsverycenter.

Itisherethatistobefoundthesourceoftheenergythatthe

Sunconstantlypoursoutintospaceaslightandheat.Thisenergy

islibratedatthecenteroftheSunasbillionsuponbillionsof

nucleiofhydrogenatomscollidewitheachotherandfusetogether

toformnucleiofhelium,andindoingso,releasesomeoftheenergy

thatisstoredinthenucleiofatoms.Theoutputoflightandheat

oftheSunrequiresthatsome600milliontonsofhydrogenbe

convertedintoheliumintheSuneverysecond.ThistheSunhasbeen

doingforseveralthousandsofmillionsofyear.

ThenuclearenergyisreleasedattheSunscenterashigh-energy

gammaradiation,aformofelectromagneticradiationlikelightand

radiowaves,onlyofverymuchshorterwavelength.Thisgamma

radiationisabsorbedbyatomsinsidetheSuntobereemittedat

slightlylongerwavelengths.Thisradiation,initsturnis

absorbedandreemitted.Astheenergyfiltersthroughthelayers

ofthesolarinterior,itpassesthroughtheX-raypartofthe

spectrumeventuallybecominglight.Atthisstage,ithasreached

whatwecallthesolarsurface,andcanescapeintospacewithout

beingabsorbedfurtherbysolaratoms.Averysmallfractionofthe

Sunslightandheatisemittedinsuchdirectionsthatafterpassing

unhinderedthroughinterplanetaryspace,ithitstheEarth.

：ObtainingFreshwaterfromicebergs

Theconceptofobtainingfreshwaterfromicebergsthataretowed

topopulatedareasandaridregionsoftheworldwasoncetreated

asajokemoreappropriatetocartoonsthanreallife.Butnowit

isbeingconsideredquiteseriouslybymanynations,especially

sincescientistshavewarnedthatthehumanracewilloutgrowits

freshwatersupplyfasterthanitrunsoutoffood.

Glaciersareapossiblesourceoffreshwaterthathasbeen

overlookeduntilrecently.Three-quartersoftheEarthsfreshwater

supplyisstilltiedupinglacialice,areservoirofuntappedfresh

watersoimmensethatitcouldsustainalltheriversoftheworld

for1,000years.Floatingontheoceanseveryyearare7,659trillion

metrictonsoficeencasedin10000icebergsthatbreakawayfrom

thepolaricecaps,morethanninetypercentofthemfromAntarctica.

Hugeglaciersthatstretchovertheshallowcontinentalshelfgive

birthtoicebergsthroughouttheyear.Icebergsarenotlikesea

ice,whichisformedwhentheseaitselffreezes,rather,theyare

formedentirelyonland,breakingoffwhenglaciersspreadoverthe

sea.Astheydriftawayfromthepolarregion,icebergssometimes

movemysteriouslyinadirectionoppositetothewind,pulledby

subsurfacecurrents.Becausetheymeltmoreslowlythansmaller

piecesofice,icebergshavebeenknowntodriftasfarnorthas

35degreessouthoftheequatorintheAtlanticOcean.Tocorral

themandsteerthemtopartsoftheworldwheretheyareneededwould

notbetoodifficult.

Thedifficultyarisesinothertechnicalmatters,suchasthe

preventionofrapidmeltinginwarmerclimatesandthefunneling

offreshwatertoshoreingreatvolume.Buteveniftheicebergs

losthalfoftheirvolumeintowing,thewatertheycouldprovide

wouldbefarcheaperthanthatproducedbydesalinization,or

removingsaltfromwatero

：FolkCultures

Afolkcultureisasmallisolated,cohesive,conservative,nearly

self-sufficientgroupthatishomogeneousincustomandracewith

astrongfamilyorclanstructureandhighlydevelopedrituals.

Orderismaintainedthroughsanctionsbasedinthereligionor

familyandinterpersonal.Relationshipsarestrong.Traditionis

paramount,andchangecomesinfrequentlyandslowly.Thereis

relativelylittledivisionoflaborintospecializedduties.Rather,

eachpersonisexpectedtoperformagreatvarietyoftasks,though

dutiesmaydifferbetweenthesexes.Mostgoodsarehandmadeand

subsistenceeconomyprevails.Individualismisweaklydevelopedin

folkculturesasaresocialclasses.Unalteredfolkculturesno

longerexistinindustrializedcountriessuchastheUnitedStates

andCanada.PerhapsthenearestmodernequivalentinAngloAmerica

istheAmish,aGermanAmericanfarmingsectthatlargelyrenounces

theproductsandlaborsavingdevicesoftheindustrialage.InAmish

areas,horsedrawnbuggiesstillserveasalocaltransportation

deviceandthefaithfularenotpermittedtoownautomobiles.The

AmishscentralreligiousconceptofDemut“humility”,clearly

reflectstheweaknessofindividualismandsocialclasssotypical

offolkculturesandthereisacorrespondingstrengthofAmishgroup

identity.RarelydotheAmishmarryoutsidetheirsect.