简介:ThispaperreportsastudyofcomplexfocussingacousticfieldsofaconvexphasedarrayprobewidelyusedinultrasonicdiagnosticB-scanner.Thetimedelaynecessaryforelectronicfocussingandforgeometricfocussingofcomplexfocussingisgiven.BymeansofHelmholtz‘sintegralformula,theexpressionsofacousticfieldswereobtainedfortheelectronicfocussingandcomplexfocussing.Withsimpson‘snumericalintegral,agreatdealofcomputationswascarriedoutwithan86/330computer.Bymeansofusingdifferentparameters,anoptimumfocalrangeandbeamwidthofa4sequenceselectronicandcomplexfocussingacousticsystemwasselected.WithanEUB-40ultrasounddiagnosticB-scannerproducedbytheHitachicompany,thelateralfocussingacousticfieldandlateralresolutioninanechoictankwerephotographedbylatticingmethodandtheexperimentalresultiscon-sistentwiththetheory.
简介:Inthispaper,basedontheimplicitRunge-Kutta(IRK)methods,wederiveaclassofparallelschemethatcanbeimplementedontheparallelcomputerswithNs(Nisapositiveevennumber)processorsefficiently,anddiscusstheiterativelyB-convergenceoftheNewtoniterativeprocessforsolvingthealgebraicequationsofthescheme,secondlywepresentastrategyprovidinginitialvaluesparallellyfortheiterativeprocess.Finally,somenumericalresultsshowthatourparallelschemeishigherefficientasNisnotsolarge.
简介:指向nano探查基于的一个可被细菌破坏的肿瘤poly(?-caprolactone)-b-poly(ethylene乙二醇)有磁性的回声成像(MRI)的块共聚物(PCL-b-PEG)micellefunctionalized对比代理人diethylenetriaminepentaacetic酸金轧(DTPA-Gd3+)在壳上并且一在红外线附近(NIR)在为磁性的回声和光双形式的成像的核心的染料是准备。纵的relaxivity(r1)PCL-b-PEGDTPA-Gd3+,micelle是13.4(mmol/L)?1s?1,DTPA-Gd3+的三褶层,并且比有类似的结构的许多聚合对比代理人的高。在里面忍受xenografted胸肿瘤的一只裸体老鼠的光成像显示出的vivo双形式的micelle优先地经由folic在肿瘤积累了由提高的渗透和保留(EPR)效果的调停酸的活跃指向和被动累积。结果显示dualmodalitymicelle是为癌症察觉和诊断的有希望的nano探查。
简介:Anewapproachtodeterminealltheelectro-elasticconstantsofthepiezoelectriccrystalsinclass4mmhasbeenputforward.Asanexample,alltheconstantsofLithiumTetraborate(Li2B4O7)crystalhavebeenmeasuredbymeansoftheapproach.Theoutstandingadvantageoftheapproachisthatiton-lyneedstoemployinmeasurementthreecrystalplatesdifferentlyoriented.
简介:在laminar的非线性的传送对流的效果三维的Oldroyd-B液体流动被探讨。热转移现象被考虑非线性的热放射和热产生/吸收探索。边界层假设被考虑管理流动分析的数学模型。一些合适的类似变量被介绍把部分微分方程转变成平常的微分系统。有射击方法的Runge-Kutta-Fehlberg第四顺序、第五顺序的技术被用来获得无尺寸的速度和温度的答案。液体速度和温度上的各种各样的物理参数的效果被阴谋并且检验。比较与准确并且homotopy不安答案被做为粘滞液体大小写,和一根优秀火柴被注意。墙的数字价值砍在墙的压力和热转移率被公布并且调查。在德卜拉数字的价值的改进在液体速度上显示出反向的行为。当非线性的传送对流参数增加时,结果证明温度和热边界层被减少。Nusselt数字的价值比处于线性放射状况的那些处于非线性的放射状况是更高的。
简介:Thermoelectricityisatherrnorelatedpropertythatisofgreatimportanceinsingle-moleculejunctions.Theelectricalconductance(σ),electron-derivedthermalconductance(kel)andSeebeckcoefficient(S)ofBgo-basedsingle-moleculejunctionsareinvestigatedbyusingdensityfunctionaltheoryincombinationwithnon-equilibriumGreen'sfunction.Whenthedistancebetweentheleft/rightelectrodesis11.4A,therelationshipbetweenσandkelobeystheWiedemann-FranzlawverywellbecauseofthestronghybridizationbetweenB80molecularorbitalsandthesurfacestatesofAuelectrodes.Furthermore,thecalculatedLorenznumberisclosetothefamousvalueinmetalordegeneratesemiconductors.Inaddition,Sisonly—19.09μV/Kat300K,thusleadingtothesmallerelectron'sthermoelectriefigureofmerit(ZeiT=S^2σT/Kel).Interestingly,thestrainandchemicalpotentialcanmodulateB80-basedsingle-moleculejunctionsfromn-typetop-typewhenthecompressivestrainreaches—0.6Aorthechemicalpotentialshiftsto—0.16eV.ThismightbeattributedthatSreflectstheasymmetryintheelectricalconductancewithrespecttothechemicalpotentialandisproportionaltotheslopesofthetransmissionspectrum.
简介:HeteroatomM-ZSM-12zeolites(M=B,Al,Ge,Ga,Fe)arehydrothermallysynthesizedanditisprovedthattheheteroatomMisinvolvedintheframeworkofsynthesizedmolecularsievesbymeansofXRD,IRspectra.TheresultsofadsorptionanddiffusionexperimentsindicatethattheheteroatomMmodifiestheporevolume,specificsurfacearea,andthechannelofZSM-12molecularsieves.
简介:Lamellarcrystalsofdiblock,triblockandfour-armpoly(ethyleneglycol)-b-poly(ε-caprolactone)(PEG-b-PCL)crystalline-crystallinecopolymersweresuccessfullyobtainedfromtheirsolution.Morphologyandstructureoflamellarcrystalsofcrystalline-crystallinecopolymerswereinvestigatedusingtapping-modeatomicforcemicroscopy(AFM)andselectedareaelectrondiffraction(SAED).Allofthesesamplesshowedthetruncated-lozengemultilayerbasalshapeswithcentralscrewdislocationorcentralstack,whichwereallobtainedsimultaneouslyfromtheoilbath.ThediffractionpatternofPEGblocklamellarcrystalisattributedtothe(120)diffractingplanesandthepatternofPCLblocklamellarcrystalisattributedtothe(110)diffractingplanesand(200)diffractingplanesaccordingtotheSAEDresults.Four(110)crystalgrowthplanesandtwo(200)crystalgrowthplanesarediscoveredforthePCLblocks,butthe(120)crystalgrowthplanesofPEGblocksarehidedinthefigureofAFM.Thecrystallinestructureofthefour-armcopolymers(FA)ismoredisorderandconfusedthanthatofthediblock(DI)copolymerandthestriatedfoldsurfacestructuresoflamellarcrystalsoffour-armcopolymers(FA)aresmootherthantheseoflinearanalogues,owingtotheconfusedcrystallizationofblockscausedbythemutualrestrictionofblocksandthehindranceofthedendriticcores.Inaddition,theaspectratioofFAisgreaterthanthatoftheothers.Itishypothesizedthattherearetworeasonsforthechangeofaspectratios.First,the(200)diffractingplanesofPCLcrystalsgrewslowlycomparedtotheir(110)diffractingplanesbecauseofdifferenceintheenergybarrier.Secondly,edgedislocationsonthe(200)diffractingplanesarealsoresponsibleforthevariationoftheaspectratio.Consequently,thecrystallinedefectsareaugmentedbythecompetingblockscrystallizedsimultaneouslyandthehindranceofthedendriticcores.
简介:研究了吖啶橙(AO)与罗丹明B(RB)间发生能量转移的最佳条件,在pH=6.80的Britton-Robinson(B-R)缓冲溶液,十二烷基苯磺酸钠的介质中,AO-RB间发生有效能量转移,使RB荧光大大增强,叶酸(FA)的加入使能量转移体系的RB的荧光强度降低,即发生猝灭.以此建立了利用AO-RB能量转移荧光猝灭法测定叶酸的新方法.在优化的实验条件下,叶酸含量在2.0×10-6~8.0×10-5mol.L-1范围内与RB的荧光猝灭程度成良好的线性关系,相关系数0.9998,检出限为3.3×10-7mol.L-1.平行6次测定相对标准偏差为0.62%~0.94%,回收率为85.0%~105%,该方法稳定性好,选择性高,用于叶酸片中叶酸含量的测定,结果满意.
简介:Theoreticalmodelsofstellarevolutionpredictnegligiblequantitiesof6Li,9Be,and11Binthehydrogenburningphasesofastar’sevolution[1].TheprimordialBig-Bangnucleosynthesis(BBN)modelmightbemoregenerousinitsproductionoftheseelements[2].Theradiative-capturecrosssectionforprotoncaptureon11Bleadingto12CissmallatastrophysicallyinterestingenergiesbecauseofthelargeCoulombbarrier.
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简介:对赋Luxember范数或Orlicz范数的Orlicz型序列空间,诸如古典的、广义的及参数式的,本文总结、补充、比较列出了暴露点及暴露性的充分必要刻画,并对以往结果中的错误进行了修正,从而在序列空间方面系统地完成了有关暴露性的刻画。