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简介：AsubsetofSofthevertexsetofagraphGiscalledacyclicifthesubgraphitinducesinGcontainsnocycles.SiscalledanacyclicdominatingsetofGifitisbothacyclicanddominating.Theminimumcardinalityofanacyclicdominatingset,denotedbyγα(G),iscalledtheacyclicdominationnumberofG.S.M.Hedetniemietal.on2000introducedtheconceptofacyclicdominationandposedthefollowingopenproblem:Isγα(G)≤δ(G)foranygraphwhosediameteristwo?Inthispaper,wegiveacounterexamplewhichdisprovestheproblem.

简介：that和which是较为活跃的关系代词，而不少同学用它们引导定语从句时常常不知道该用哪一个。现将它们的用法作一总结归纳并举例加以说明。

简介：Background:Ineconomicallyoptimalmanagement,treesthatareremovedinathinningtreatmentshouldbeselectedonthebasisoftheirvalue,relativevalueincrementandtheeffectofremovalonthegrowthofremainingtrees.Largevaluabletreeswithdecreasedvalueincrementshouldberemoved,especiallywhentheyovertopsmallertrees.Methods:Thisstudyoptimizedthetreeselectionruleinthethinningtreatmentsofcontinuouscovermanagementwhentheaimistomaximizetheprofitabilityofforestmanagement.Theweightsofthreecriteria(stemvalue,relativevalueincrementandeffectofremovalonthecompetitionofremainingtrees)wereoptimizedtogetherwiththinningintervals.Resultsandconclusions:Theresultsconfirmedthehypothesisthatoptimalthinninginvolvesremovingpredominantlylargetrees.Increasingstumpagevalue,decreasingrelativevalueincrement,andincreasingcompetitiveinfluenceincreasedthelikelihoodthatremovalisoptimaldecision.However,ifthespatialdistributionoftreesisirregular,itisoptimaltoleavelargetreesinsparseplacesandremovesomewhatsmallertreesfromdenseplaces.However,thebenefitofoptimalthinning,ascomparedtodiameterlimitcuttingisnotusuallylargeinpureone-speciesstands.Onthecontrary,removingthesmallesttreesfromthestandmayleadtosignificant(30-40%)reductionsinthenetpresentvalueofharvestincomes.

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简介：亲爱的朋友们，我们已经进入到了21世纪。但是你们知道本世纪哪些职业将消失吗?下面将告诉你们答案。原因是因为快速发展的因特网将在很多方面帮助我们并将代替许多工作。因此我们必须更加努力地学习以赶上时代的发展步伐，使我们的生活更精彩哦!

简介：前一讲,我们谈了“你是否天天读报”这个话题的几种回答的方式。其实,在实际谈话时,这个问题只是一个很通常的开头语,似投石问路。回答完这个问题之后,人们会很自然地将话题引向渎报的具体内容,如你所爱读的报纸和版面,构成一个完整的对话。由于所爱读的报纸和爱读的版面两者之间有许多相近之处

简介：Background:Forestecosystemsareincreasinglyseenasmulti-functionalproductionsystems,whichshouldprovide,besidestimberandeconomicbenefits,alsootherecosystemservicesrelatedtobiologicaldiversity,recreationalusesandenvironmentalfunctionsofforests.Thisstudyanalyzedtheperformanceofeven-agedrotationforestmanagement(RFM)continuouscoverforestry(CCF)andany-agedforestry(AAF)intheproductionofecosystemservices.AAFalowsbotheven-agedanduneven-agedmanagementschedules.Theecosystemservicesincludedintheanalyseswerenetpresentvalue,volumeofharvestedtimber,cowberryandbilberryyields,scenicvalueoftheforest,carbonbalanceandsuitabilityoftheforesttoSiberianjay.Methods:Dataenvelopmentanalysiswasusedtoderivenumericalefficiencyratiosforthethreemanagementsystems.Efficiencyratioisthesumofweightedoutputs(ecosystemservices)dividedbythesumofweightedinputs.ThelinearprogramingmodelproposedbyCharnes,CooperandRhodeswasusedtoderivetheweightsforcalculatingefficiencyscoresforthesilviculturalsystems.Resultsandconclusions:CCFprovidedmoreecosystemservicesthanRFM,andCCFwasmoreefficientthanRFMandAAFintheproductionofecosystemservices.Multi-objectivemanagementprovidedmoreecosystemservices(exceptharvestedtimber)thansingle-objectivemanagementthatmaximizedeconomicprofitability.Theuseoflowdiscountrate(resultinginlowcuttinglevelandhighgrowingstockvolume)ledtobettersupplyofmostecosystemsservicesthantheuseofhighdiscountrate.RFMwhereNPVwasmaximizedwithhighdiscountrateledtoparticularlypoorprovisionofmostecosystemservices.InCCFtheprovisionofecosystemserviceswaslesssensitivetochangesindiscountrateandmanagementobjectivethaninRFM.

简介：初一同学已学过了不少含what、which、who的句子，为了帮助大家加深印象，现归纳其用法如下：

简介：Criticalcardiogenicshockremainsaproblemwithstaggeringmortality,withthebesthopeofsurvivaldependingontimelyandaggressiveintervention.Thisoftenrequirestheuseofextracorporealmechanicalsupportinadditiontovasoactivemedicationstomanagepatientsthroughtheirinitialinsult.Thedecisiontousesuchsupportmustbemadeearlyintheclinicalpresentation,andisbestdoneinamultidisciplinaryfashion.Inthisarticle,wereviewtheliteratureandprovideanalgorithmforthetreatmentofcardiogenicshock.

简介：对每真实值的凸的功能在一个集合上上面围住的保证连续，集合应该怎么“厚”吗？为在Banach空间E的对称的集合A，这篇论文的答案是：如果并且仅当下列二个条件成立，在A上上面围住的每真实值的凸的功能在E上是连续的：我)跨度A有有限co-dimentions和ii)coA有非空的相对内部。这篇论文也证明子集A在E被包含令人满意如果，在A上上面围住的每真实值的凸的功能在E上是连续的(并且仅当)每真实值线性功能在A上上面跳了在E上是连续的，它也等价于那在A上围住的每真实值的凸的功能在E上是连续的。

简介：ＡＪ－ＣＯＮＶＥＸＳＵＢＳＥＴＷＨＩＣＨＩＳＮＯＴＰＳＨ－ＣＯＮＶＥＸＢｕＳｈａｎｇｑｕａｎ（步尚全）（Ｄｅｐａｒｔｍｅｎｔｏｆａｐｐｌｉｅｄｍａｔｈｅｍａｔｉｃｓ，ＴｓｉｎｇｈｕａＵｎｉｖｅｒｓｉｔｙ，Ｂｅｉｊｉｎｇ１０００８４，Ｃｈｉｎａ）Ａｂｓ...

简介：(本课选自仁爱版《英语》七年级下册第6单元第3话题sectionB.)一、教材分析本话题是以问路、指路为主,贯穿交通规则、交通标志、交通设施等内容,让学生学会遵守交通规则,学会助人为乐。其教学内容是循序渐进,环环紧

简介：Inrecentyears'stagedagger'typeshamneedlinghasbeenanticipatedtobeoneofthepossiblesolutionsformaskingpatientsinacupunctureresearch.Inordertoassessthevalidityofthistypeofneedling,weconductedtworandomized,single-blind,cross-overtrialswithacupuncture-experiencedsubjects.

简介：英语语法中，有一类是由“介词＋whioh／whom”引导的定语从句。本文分析它引导的非限定性定语从句，在从句中充当时间、地点或原因状语，引导定语从句需考虑的情况，引导定语从句错误透析。

简介：Forapolynomialp(z)ofdegreenwhichhasnozerosin|z|<1,Dewanetal.,(K.K.DewanandSunilHans,Generalizationofcertainwellknownpolynomialinequalities,J.Math.Anal.Appl.,363(2010),38–41)establishedzp′(z)+nβ2p(z)≤n2{(β2+1+β2)max|z|=1|p(z)|-(1+β2-β2)min|z|=1|p(z)|},foranycomplexnumberβwith|β|≤1and|z|=1.InthispaperweconsidertheoperatorB,whichcarriesapolynomialp(z)intoB[p(z)]:=λ0p(z)+λ1(nz2)p′(z)1!+λ2(nz2)2p′′(z)2!,whereλ0,λ1,andλ2aresuchthatallthezerosofu(z)=λ0+c(n,1)λ1z+c(n,2)λ2z2lieinthehalfplane|z|≤|z-n/2|.ByusingtheoperatorB,wepresentageneralizationofresultofDewan.Ourresultgeneralizescertainwell-knownpolynomialinequalities.

简介：一、which与as引导非限制性定语从句时的区别1.由as引导的非限制性定语从句可位于主句的句首,句中或句末,而which引导的非限制性定语从句只能放在主句的后面。例如:(1)Assherealized,hewasveryimportanttoher.(2)Water,aseveryoneknows,isaliquid.(3)Allthatglittersisnotgold,asweknow.(4)Theweatherforcastsaysitwillrainheavily,whichmakesusputoffthesportsmeet.2.在which引导的非限制性定语从句中,谓语动词若是am,are,is等系动词,则这些系动词不能省略;若是同样的情况,as后面可以省略am,are,is等系动词。例如:(1)HeisfromtheStates,as(is)clearfromhisaccent.他是美国人,他的口音清楚地说明了这一点。(is可省略)(2)Theweatherturnedoutfine,whichwaswh...

简介：1．关系词只能用that的情况A．先行词被序数词或形容词最高级所修饰，或本身是序数词、基数词、形容词最高级时，只能用that，而不用which。例如：

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