锡铁合金层不能超过一定的厚度,在一般情况下,厚度应该控制在0.4 ~0.8克/米2范围内。
1、正确正确
暂无解析
WhichofthefollowingitalicizedwordsDOESNOTcarrythemetaphoricalmeaning?
Theonlysoundsarebirdcallsandthesoftnoise________________(当水缓缓推动草时草所发出的)
Theauthortellsusinparagraph4________.
Recentresearchhasclaimedthatanexcessofpositiveionsintheaircanhaveanilleffectonpeople’sphysicalorpsychologicalhealth.Whatarepositiveions?Well,theairisfullofions,electricallychargedparticles,andgenerallythereisaroughbalancebetweenthepositiveandthenegativecharged.Butsometimesthisbalancebecomesdisturbedandalargerproportionofpositiveionsarefound.Thishappensnaturallybeforethunderstorm,earthquakeswhenwindssuchastheMistral,HamsinorSharavareblowingincertaincountries.Oritcanbecausedbyabuild-upofstaticelectricityindoorsfromcarpetsorclothingmadeofman-madefibres,orfromTVsets,duplicatorsorcomputerdisplayscreens.
Whenalargenumberofpositiveionsarepresentintheairmanypeopleexperienceunpleasanteffectssuchasheadaches,fatigue,irritability,andsomesensitivepeoplesuffernauseaorevenmentaldisturbance.Animalsarealsoaffected,particularlybeforeearthquakes,snakeshavebeenobservedtocomeoutofhibernation,ratstofleefromtheirburrows,dogshowlandcatsjumpaboutunaccountably.ThishasledtheUSGeographicalSurveytofundanetworkofvolunteerstowatchanimalsinanefforttoforeseesuchdisastersbeforetheyhitvulnerableareassuchasCalifornia.
Conversely,whenlargenumbersofnegativeionsarepresent,thenpeoplehaveafeelingofwell-being.Naturalconditionsthatproducetheselargeamountsarenearthesea,closetowaterfallsorfountains,orinanyplacewherewaterissprayed,orformsaspray.Thisprobablyaccountsforthebeneficialeffectofaholidaybythesea,orinthemountainswithtumblingstreamsorwaterfalls.
Toincreasethesupplyofnegativeionsindoors,somescientistsrecommendtheuseofionisers:smallportablemachines,whichgeneratenegativeions.Theyclaimthationisersnotonlycleanandrefreshtheairbutalsoimprovethehealthofpeoplesensitivetoexcesspositiveions.Ofcourse,therearethedetractors,otherscientists,whodismisssuchclaimsandareskepticalaboutnegative/positiveionresearch.Thereforepeoplecanonlymakeuptheirownmindsbyobservingtheeffectsonthemselves,oronothers,ofanegativerichorpoorenvironment.Afterallitisdebatablewhetherdependingonseismicreadingstoanticipateearthquakesismoreeffectivethanwatchingthecat.
1.Whateffectdoesexceedingpositiveionizationhaveonsomepeople?
A.Theythinktheyareinsane.
B.Theyfeelratherbad-temperedandshort-fussed.
C.Theybecomeviolentlysick.
D.Theyaretootiredtodoanything.
2.Inaccordancewiththepassage,staticelectricitycanbecausedby___.
A.usinghome-madeelectricalgoods.
B.wearingclothesmadeofnaturalmaterials.
C.walkingonartificialfloorcoverings.
D.copyingTVprogramsonacomputer.
3.Ahighnegativeioncountislikelytobefound___.
A.nearapoundwithawaterpump.
B.closetoaslow-flowingriver.
C.highinsomebarrenmountains.
D.byarotatingwatersprinkler.
4.Whatkindofmachinecangeneratenegativeionsindoors?
A.Ionisers.
B.Air-conditioners.
C.Exhaust-fans
D.Vacuumpumps.
5.Somescientistsbelievethat___.
A.watchinganimalstoanticipateearthquakesismoreeffectivethandependingonseismography.
B.theunusualbehaviorofanimalscannotbetrusted.
C.neitherwatchingnorusingseismographsisreliable.
D.earthquake
Thecountry’schiefexportsarecoal,carsandcottongoods,cars_____themostimportantofthese.