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26 个结果
  • 简介:Background:RunningisbecominganincreasinglypopularactivityamongAmericanswithover50millionparticipants.Runningshoeresearchandtechnologyhascontinuedtoadvancewithnodecreaseinoverallrunninginjuryrates.Agrowinggroupofrunnersaremakingthechoicetotrytheminimalorbarefootrunningstylesofthepre-modemrunningshoeera.Thereissomeevidenceofdecreasedforcesandtorquesonthelowerextremitieswithbarefootrunning,butnocleardataregardinghowthiscorrespondswithinjuries.Thepurposeofthissurveystudywastoexaminefactorsrelatedtoperformanceandinjuryinrunnerswhohavetriedbarefootrunning.Methods:TheUniversityofVirginiaCenlcrforEnduranceSpor!createda10-questionsurveyregardingbarefootrunningthaiwa.spo.stedonavarietyofrunningblogsandFacebookpages.Percentageswerecalculatedforeachquestionacrossallsurveys.Fivehundredandnineparticipantsrespondedwithover93%ofthemincorporatingsometypeofbarefootrunningintotheirweeklymileage.Results:Amajorityoftheparticipants(53%)viewedbarefootrunningasatrainingtooltoimprovespecificaspectsoftheirrunning.However,closetohalf(46%)viewedbarefoottrainingasaviablealternativetoshoesforloggingtheirmiles.Alargeportionofrunnersinitiallytriedbarefootrunningduetothepromiseofimprovedefficiency(60%).anattempttogetpastinjury(53%)and/ortherecentmediahypearoundthepractice(52%).Alargemajority(68%)ofrunnersparticipatinginthestudyexperiencednonewinjuriesafterstartingbarefootrunning.Infact,mostrespondents(69%)actuallyhadtheirpreviousinjuriesgoawayafterstartingbarefootrunning.Runnersrespondedthattheirpreviousknee(46%),foot(19%),ankle(17%),hip(14%),andlowback(14%)injuriesallproceededtoimproveafterstartingbarefootrunning.Conclusion:Priorstudieshavefoundthatbarefootrunningoftenchangesbiomechanicscomparedtoshodrunningwithahypothesizedrelationshipofdecreasedinjuries.Thispaperreports

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  • 简介:Inphasefieldfracturemodelsthevalueoftheorderparameterdistinguishesbetweenbrokenandundamagedmaterial.Atcrackfacestheorderparameterinterpolatessmoothlybetweenthesetwostatesofthematerial,whichcanberegardedasphases.Thecrackevolutionfollowsimplicitlyfromthetimeintegrationofanevolutionequationoftheorderparameter,whichiscoupledtothemechanicalfieldequations.Amongotherphenomenaphasefieldfracturemodelsareabletoreproducecracknucleationininitiallysoundmaterials.Fora1Dsettingithasbeenshownthatcracknucleationistriggeredbythelossofstabilityoftheunfractured,spatiallyhomogeneoussolution,andthatthestabilitypointdependsonthesizeoftheconsideredstructure.Thisworknumericallyinvestigatestowhichextendsizeeffectsarereproducedbythe2Dphasefieldmodel.Exemplarily,afiniteelementstudyoftheholesizeeffectisperformedandthesimulationresultsarecomparedtoexperimentaldata.

  • 标签: 相场模型 规模效应 模型模拟 骨折 尺寸效应 演化方程
  • 简介:阶段地水晶(陆军)模型被用来模仿premelting脱臼运动对称当系统温度在时,在紧张行动下面倾斜谷物边界(STGB)远非,到融化的融化的点和结束分别地指。结果证明当premelting温度被接近到,本地premelting发生包围脱臼从在温度下面。STGB的premelting脱臼能在紧张行动下面滑行,并且premelting区域是为脱臼滑行的一个同伴。STGB腐烂的过程以二个高温度条件是很类似的。当premelting介绍,它减少为脱臼的滑行抵抗并且导致脱臼的一个更快的运动,并且也在STGB的腐烂过程期间引起系统的更多的精力减小。尽管有把紧张用于这些,premelting在STGB的整个腐烂过程取样,premelting脱臼区域显然不发展并且延长。这显示外部紧张行动不在高温度支持premelting,并且不能导致更多的premelting脱臼,它能在脱臼展览附近被欠到premelting阶段像液体的性质并且到容易滑行并且放松紧张精力的premelting脱臼;这与实验和分子的动力学的结果一致。

  • 标签: 位错反应 晶界 晶体 相场 温度条件 移动
  • 简介:Melt-spunribbonswhicharetheimportantrawmaterialforhot-deformedmagnetscanbepreparedbysingle-rollermelt-spinning.Inordertopreparewell-structuredribbons,themodeloftemperaturefieldforsingle-rollermelt-spinningprocesswasconstructedinthiswork.Theheatconductioninthisprocesswassimplifiedasonedimensionalheatconductionproblem.Itwasshownbymodelingthat,thetemperaturefieldinthemelt-spinningbeforesolidificationinthismodelcouldbedescribedasthisequationT(x,t)=Tmoexp[–k(x–x0)–k2αt]+T0.ThetemperatureT(x,t)ofthealloymeltsdecreasedwithincreasedpositionxandcoolingtimetexponentiallyfromthewheel-freesurfacetothewheel-sidesurface.TheconstantkdeterminedthedecreasespeedofalloytemperatureT(x,t),whichwasproportionaltotheinterfacialheattransfercoefficienthandtheinterfacialareaofheatconductionA0,butinverselyproportionaltothethermalconductivityK.x0wasthethicknessofthealloymelt.Withincreasedx0,thetemperaturedifferencebetweenwheel-freesurfaceandthewheel-sidesurfacebecamelarger,whichwouldleadtolargerdifferenceingrainsize.Inexperiments,theinfluenceofmelt-spinningprocessparametersonthetemperaturefieldmodelwasdiscussed,suchascoolingrollermaterials,wheelspeed,andsoon.Melt-spunribbonspreparedbysingle-rollermeltspinningatdifferentwheelspeedwereinvestigatedandmagneticpropertiesofdie-upsetmagnetsfrommelt-spunribbonsondifferentcoolingrollerwereanalyzed.Thevariationofgrainsizeinthedepthdirectionconsistedwithtemperaturefieldmodel.Thismodelprovideddirectionsforthepreparationofmelt-spunribbonswithuniformlydistributedfinegrains,whichwereverynecessaryforproducinghot-deformedmagnetswithhighmagneticperformance.

  • 标签: 温度场模型 制备工艺 钕铁硼粉末 熔纺 车轮速度 热传导问题
  • 简介:Thereciprocitymeasurementtheoryinanomalousreverberantsoundfieldswasinvestigated.AnimprovedmethodWasproposedduetotheinterrelatederrors.ThesourcevolumevelocityWascorrectedbyspatialaverageofmeasurementresultsandevaluationofthereverberantsoundfieldinfluenceonacousticenergydensity.Theresultwasvalidatedinunderwaterexperiment,correctedreciprocitymeasurementresultswerealmostthesameasdirectmeasurementresults.Itindicatesthatreverberantsoundfielddoesnotaffectthevaliditvoftheprinciple,butinfluencestheobtainmentofsourcevolumevelocity,theninfluencesthemeasurementoftransferfunctionswiththeprinciple.Theproposedmethodissimpleandeffectiveinanomalousreverberantsoundfields.Thestudymavbevaluablefortheapplicationswhicharebasedontheprinciple.

  • 标签: 混响声场 测量理论 传递函数 水下声学 互惠 应用
  • 简介:Toremovethescatteringeffectofthedisturbingsoundonthetargetsourcewhenimplementingnearfieldacousticholographyinanon-freefield,afreefieldrecoverytechniquebasedonthesphericalwavesuperpositionmethodisproposed.Inthemethod,thesoundfieldseparationtechniquebasedonthesphericalwavesuperpositionmethodisfirstusedtoseparatetheincomingandoutgoingfields,andafurtherstepforseparatingtheradiatedandscatteredfieldsisperformedbyutilizingthesurfaceadmittanceofthetargetsourceastheboundaryconc1ition.Thetechniquemakesitpossibletocorrectlyidentifynoisesourcesinanon-freesoundfeld.Thebasicprincipleofthetechniqueisdescribedfirstly,amethodforchoosingtheoptimalnumberofsphericalwaveexpansiontermsisgiven,andtwonumericalsimulationsareusedtodemonstratethevalidityofthistechnique.Itisshownthat,forthelowerfrequency,thescatteringeffectcanbeneglected,andtheradiatedfieldofthetargetsourcecanbeobtainedbythesoundfieldseparationtechnique,however,astheincreasingofthefrequcncy,thescatteringeffcctcannotbeneglected,andthefrecfieldrecoverytechniquehastobeusedtoobtaintheradiatedfieldofthetargetsource.

  • 标签: 球面波展开 自由场 叠加方法 回收率 恢复技术 分离技术
  • 简介:阶段地水晶(陆军)模型被雇用与格子失配和一个小倾斜角度在飞机凸的底层上模仿取向附生的层的生长的过程。系统的免费精力,取向附生的层的全部的原子序数,和弯曲和底层的角度的效果的变化被分析。结果证明当底层的表面是飞机时,免费精力随底层倾斜角度的增加增加,并且也,取向附生的层的全部的原子序数增加;当底层的表面是凸的时,免费精力随底层角度并且那么也的增加减少取向附生的层减少的全部的原子序数。这是取向附生的层的表面的边疆与增加凸的底层的倾斜角度从步bunching改变到hill-and-valley方面结构的原因。这些结果在对另外的方法结果的好同意。

  • 标签: 外延生长 模拟 晶体 相场 底物 倾斜角度
  • 简介:ToretrievewindfieldfromSARimages,thedevelopmentforsurfacewindfieldretrievalfromSARimagesbasedontheimprovementofnewinversionmodelispresent.GeophysicalModelFunctions(GMFs)havebeenwidelyappliedforwindfieldretrievalfromSARimages.AmongthemCMOD4hasagoodperformanceunderlowandmoderatewindconditions.AlthoughCMOD5isdevelopedrecentlywithamorefundamentalbasis,ithasambiguityofwindspeedandashapegradientofnormalizedradarcrosssectionunderlowwindspeedcondition.ThisstudyproposesamethodofwindfieldretrievalfromSARimagebycombiningCMOD5andCMOD4FiveVV-polarisationRADARSAT2SARimagesareimplementedforvalidationandtheretrievalresultsbyacombinationmethod(CMOD5andCMOD4)togetherwithCMOD4GMFarecomparedwithQuikSCATwinddata.Theroot-mean-squareerror(RMSE)ofwindspeedis0.75ms-1withcorrelationcoefficient0.84usingthecombinationmethodandtheRMSEofwindspeedis1.01ms-1withcorrelationcoefficient0.72usingCMOD4GMFaloneforthosecases.TheproposedmethodcanbeappliedtoSARimageforavoidingtheinternaldefectinCMOD5underlowwindspeedcondition.

  • 标签: SAR图像 风场反演 模式数 转基因食品 海面 图像检索
  • 简介:Energystorageplaysanincreasinglyimportantroleinmodernpowersystems.Itcanaddvaluetopowersystemsinvariousaspects.Thispaperdiscussespossibleenergystoragesystem(ESS)applicationsandtheirbenefitstopowersystems.Thesystemconfiguration,converterdesign,andrecentfieldinstallationsofanLVconverterbasedESSarepresented.

  • 标签: 现场安装 存储系统 转换器 配置 能源 低压
  • 简介:Regardforthefuzzinessandtherandomnessinsomeacousticfields,amethodforthenumericalanalysisofthe2DacousticfieldwithFuzzy-Randomparameterswasproposedbasedontheequivalentconversionofinformationentropy.Intheproposedmethod,afuzzyrandomacousticfieldwastreatedasapurefuzzyacousticfieldorapurerandomacousticfieldbytransformingallthevariablesintofuzzyvariablesorrandomvariables.Perturbationfiniteelementmethodsforanalyzingthetwo-dimensionalacousticfuzzyandrandomfieldarededuced.Thesoundpressureresponseofa2Dacoustictubeandthe2Dacousticcavityofacarwithfuzzy-randomparameterswereanalyzedbytheproposedmethodandtheMonteCarlomethod,theresultsshowthattheproposedmethodcanbewellappliedtothenumericalanalysisofthe2Dacousticfieldwithfuzzy-randomparameters,andhasgoodprospectofengineeringapplication.

  • 标签: 数值分析方法 随机参数 模糊性 声场 二维 蒙特卡罗方法
  • 简介:Inthisstudy,themainfactorsinfluencingthemeasurementsbymeansoftheoff-linelow-field1HNMRinthelabwerediscussedbaseonarobustcalibrationmodelestablishedbythePLSalgorithmusing255crudeoilsamples.Thepreheatingtemperaturehadagreatinfluenceontheviscosityofoilsamplesandtheresolutionofspectralanalysis.Therepeatabilityofspectralmeasurementswasimpactedbythemetalandwaxcontentoftheoilsamples.Forthecaseofhighwaxcontentoils,thewaxspeciesbegantocrystallizeinthecourseofdeterminationthatcouldaffecttherepeatabilityofspectralmeasurements.ThesefactorshaveevidencedwhythepreheatingdevicesandfilterunitarenecessarywhenlowfieldNMRsystemisusedintheonlineanalysisprocess.Theinvestigationisveryimportantfortheon-lineapplicationofthelowfieldNMR.

  • 标签: 低场核磁共振 原油分析 联机分析处理 核磁共振系统 可重复性 光谱测量
  • 简介:Foracompression-shearmixedmodeinterfacecrack,itisdifficulttosolvethestressandstrainfieldsconsideringthematerialviscosity,thecrack-tipsingularity,thefrictionaleffect,andthemixedloadinglevel.Inthispaper,amechanicalmodelofthedynamicpropagationinterfacecrackforthecompression-shearmixedmodeisproposedusinganelastic-viscoplasticconstitutivemodel.Thegoverningequationsofpropagationcrackinterfaceatthecrack-tiparegiven.Thenumericalanalysisisperformedfortheinterfacecrackofthecompression-shearmixedmodebyintroducingadisplacementfunctionandsomeboundaryconditions.Thedistributedregularitiesofstressfieldoftheinterfacecrack-tiparediscussedwithseveralspecialparameters.Thefinalresultsshowthattheviscosityeffectandthefrictionalcontacteffectonthecracksurfaceandthemixed-loadparameterareimportantfactorsinstudyingthemixedmodeinterfacecracktipfields.Thesefieldsarecontrolledbytheviscositycoefficient,theMachnumber,andthesingularityexponent.

  • 标签: compression-shear MIXED mode INTERFACE crack dynamic
  • 简介:在这份报纸,我们调查极端弱变化明确的表达的使用解决在近的地光学散布问题的一个波浪。以便捕获波浪的亚规模特征,我们和飞机波浪功能利用迅速凋落的波浪功能接近这块地的本地性质。我们分析全球集中并且给方法的一个错误评价。数字例子也被举表明策略的有效性。[从作者抽象]

  • 标签: 数值解法 散射问题 误差估计 近场 配方 模型
  • 简介:Thecreationandpropagationoflongitudinalacousticphonons(LAPs)inhighqualityhematitethinfilms(α-Fe2O3)epitaxiallygrownondifferentsubstrates(BaTiO3,SrTiO3,andLaAlO3)areinvestigatedusingthefemtosecondpump–probetechnique.Transientreflectionmeasurements(?R/R)indicatethephoto-excitedelectrondynamics,andtheinitialdecaylessthan1psandtheslowdecayof~500psareattributedtotheelectron-LOphononcouplingandelectron–holenonradiativerecombination,respectively.LAPsinα-Fe2O3filmcanbecreatedbyultrafastexcitationoftheligandfieldstate,suchastheligandfieldtransitionsunder800-nmexcitationaswellastheligandtometalcharge-transferwith400-nmexcitation.Thestrainmodulationsofthesoundvelocityandtheout-of-planeelasticpropertiesaredemonstratedinα-Fe2O3filmondifferentsubstrates.

  • 标签: 声学声子 赤铁矿 薄膜 位场转换 α-Fe2O3 电子动力学
  • 简介:这研究检验从一种蚊虫quinquefasciatus的一张领域人口在单个蚊子涉及permethrin抵抗的开发的基因变化和机制,HAmCqG0,并且与领域HAmCqG0紧张。六upregulated细胞色素P450基因,CYP9M10,CYP9J34,CYP6P14,CYP9J40,CYP6AA7,和CYP4C52v1,以前作为是在抵抗HAmCqG8蚊子在3紧张的幼虫被检验(易受影响的平板,父母HAmCqG0和选择permethrin的高度抵抗的HAmCqG8)和8HAmCqG0单个鸡蛋的木排殖民地,盖住危险性/抵抗的层次的一个范围到permethrin并且在t展出不同变化有到permethrin的最低忍耐的2根线并且从殖民地Cx_SERC5和Cx_SERC8,完全在钠隧道的L-to-Fkdr地点忍受易受影响的A等位基因显示出与平板紧张相比测试的所有6P450基因的更低或类似的层次,建议这2排队能在在HAmCq蚊子描绘杀虫药剂抵抗的未来研究被用作参考蚊子。这研究也提供在一张人口以内在个人涉及杀虫药剂抵抗的机制的详细调查:有到permethrin的抵抗的提高的层次的个人都显示了提高的抵抗机制任何一个在钠隧道,或两个P450基因表示,或L-to-F变化铺平的至少一个潜力。

  • 标签: 电阻变化 致倦库蚊 氯菊酯 参考线 细胞色素P450基因 蚊子
  • 简介:在一个挑出类型有弹性的基础上休息的稍微弄弯的围单人赛的碳nanotube(SWCNT)的非线性的震动的模型用非局部的Euler-Bernoulli有弹性的理论被开发。SWCNT被假定在外部泛音下面颤动电的力量地和一个分析答案被建议获得非线性的反响的频率。结果证明对数字模拟和获得的分析频率的好同意是完全与nanotube的弯曲有关。我们的模型预言尽管模型在自然是非线性的,弄弯的SWCNT能在弯曲的某个数量线性地表现,弄弯的SWCNT的这伪线性的震动的行为是基础的方面比率,非局部的参数,和僵硬的一个函数。

  • 标签: 单壁碳纳米管 非线性 弯曲度 动力场 性行为 振动模型