Self-assessmentix

1. Translatethearticleusingadictionary. Howmathscanimproveyourdrinkingwater Mathematicalmodellingcanhelpkeepthestuffthatcomesoutofyourtapscleanandfresh

InJuly,mywifeAvrilandIcelebratedour40thweddinganniversaryinBarbados.Wejokedwiththehotelwaiterthatweonlycameforthetapwater,whichisamazinglygood.Wefound

outwhywhenwevisitedHarrison’scave.Barbadosismostlyfossilisedcoral,whichactslikeagiantfilterforrainwater.Sothetapwaterisveryclean,withatangymineraltaste.

SeveralyearsagowewenttoSlovenia,andwereinvitedtojoinagroupofChinesekarstologistsvisitingthespectacularcavesthere.Karstisruggedlimestone,alljaggededgesandcollapsedholes.What’sallthisgeologygottodowithmaths?Well,Iwasidlyreadingamathematicsresearchjournalandcameacrossanarticleaboutkarst.

Greatstuffformathematiciansandgeologists,tobesure,butwhyshouldanybodyelsecareaboutkarst?

Theansweris:groundwater.Muchofthewaterwedrink,andthewaterthatindustriesuse,comesfromgroundwater.

Becausewerelyheavilyongroundwater,contaminationisaseriousproblem.Industrialwaste,excessfertiliserrunningofffields,landfillsitesforeverydayrubbish,anddozensofothersourcescancauseundesirablechemicalstogetintoourgroundwater.Tosomeextent,karstaquiferscancleanthemselves,giventime,butit’snotclearwhethertheycancopewiththelevelofcontaminationthatiscommontoday.Soscientistsneedtounderstandhowwaterflowsthroughtheporouskarstgeology.

Traditionally,theyusemathematicalmodelsoffluidflowthroughaporoussubstance.Theusualmodelsassumethattherockisequallyporouseverywhere,becauseuntilrecentlynooneknewhowtoincludemorerealisticeffects,suchascracksintherock,surfacesinkholes,andsprings.Thesumsweresimplytoodifficult,evenusingpowerfulcomputers.Butthosecracksaremoreimportantthantheporousrockwhenwewanttoknowhowcontaminantsmovefromplacetoplace.

That’swhereallthestuffaboutBeavers-Josephinterfacescomesin.It’showthemodellersdealwithholesandcracksinporousrock.Aftermanyyearsofeffort,themathematicianswhoworkinthisareahavediscoveredagoodwaytosetuprealisticmodelsinacomputer,andcalculatehoweffectivetherockisatfilteringoutchemicalnastiesandkeepingitselfclean.

TheEconomist

2. Writeanessaytosupportthefollowingstatement:“Mathematicsmakestheworldgoround”. Unitten

1. Scanthearticletostatethereasonsforawideruseofrenewablesourcesofenergy.

2. ReadthearticleagainandcompleteitwithasentenceA-e.Thereisonesentenceyoudon’tneed.

   1. Inordertoexploitrenewablesourcesofenergyitisoftennecessarytomakeaconsiderablecapitalinvestment.

   2. Geothermalenergyisalsobecomingmoreandmorewidelyusedinsomearrears.

   3. Thisairbornewaterultimatelyfallsasrain,creatingriverswhichmaybedammedtoproducehydroelectricpower.

   4. Thisestimate,however,doesnotallowforeconomicandenvironmentalconstraintsandisthereforesomewhatmisleading.

E.Indeed,itistheperceivednotionofsustainabilitythatisdrivinggovernmentsaroundtheworldtointroducelegislationpromotingtheuseofrenewableenergy.

RenewableEnergy

Climatechange,coupledwithconcernsabouthighoilandenergyprices,isdrivingaglobaltrendtowardstheincreaseduseofrenewableenergy.Unlikefossilfuelswhicharerapidlybeingdepleted,renewableenergysourcessuchassunlightandwindarenaturallyreplenishedandthereforesustainable.(1)_____________

Mostsourcesofrenewableenergyoriginateeitherdirectlyorindirectlyfromthesun.Forexample,bothwindandwavepowerderivetheirenergyindirectlyfromthesun.WhensolarradiationisabsorbedbytheEarthitisdissipatedaroundtheglobeintheformofwindsandoceancurrents.Thewindinteractswiththeoceansandtransfersmechanicalenergytowaterthuscreatingwaves.Inaddition,solarenergypromotesevaporationofwaterfromtheoceans.(2)_________________

Furthermore,solarenergydrivesthephotosynthesisnecessaryfortheplantsthatareusedtocreatebiofuels.Currently,onlyabout18%oftheworld’senergydemandissuppliedfromrenewableenergysources.However,thereisgreatpotentialtoincreasethiscontribution.Indeed,ithasbeenestimatedthatthetechnicalpotentialofrenewableenergyismorethan18timesthatofcurrentglobalprimaryenergydemand.(3)_________________________Owingtoconstraints,suchaseconomic

competitiveness,thepotentialthatislikelytoberealizedinpracticewillbeonlyafractionofthisvalue.

(4)_________________Thisisparticularlythecasewithlargeinfrastructureprojectssuchashydroelectricortidalbarrageschemes.Tobeeconomicallyviable,suchprojectsmustabsorblargecapitalcostsandstillbeabletocompeteonpricewithtraditionalsourcesofenergy–somethingwhichinmostcasesitisdifficulttodo.

PeggyDanielsBecker,AlternativeEnergy