学科分类
/ 12
230 个结果
  • 简介:Theground-stateandthermodynamicpropertiesofquantummixed-spinchainsof1/2-1/2-1-1and3/2-3/2-1-1areinvestigatedbyaquantumMonteCarlosimulationwiththeloop-clusteralgorithm.For1/2-1/2-1-1chain,wefindithastwophasesseparatedbyanenergy-gapvanishingpointintheground-state.For3/2-3/2-1-1chain,thenumericalresultsshowtwoenergy-gapvanishingpointsisolatedbydifferentphasesinitsground-state.Ourcalculationsindicatethatallthesegroundstatephasescanbeunderstoodbymeansofvalence-bond-solidpicture,andthethermodynamicbehavioratfinitetemperaturesiscontinuousasafunctionofparameterα=J2/J1.

  • 标签: 蒙特卡罗模拟 混合自旋链 铁磁性 基态 热力学性质 能隙
  • 简介:Thedipole-length,velocityandaecelerationabsorptionoscillatorstrengthsforthe1s^22p-ls^2nd(3_2=11to20arecalculatedusingtheenergiesandthemulticonfiguratloninteractionwavefunctionsobtainedfromafullcorepluscorrelationmethod.Theagreementbetweenthef-valuescalculatedfromthelength,velocityandaccelerationformulaeisexcellent.Ourresultsagreecloselywiththeexperimentaldataavailableintheliterature.Combiningthesediscreteoscillatorstrengthswiththesingle-channelquantumdefecttheory,thediscreteoscillatorstrengthsforthetransitionsfrom1s^22pstatetohighlyexcitedstates(n_>10)andtheoscillatorstrengthdensitiescorrespondingtothebound-freetransitionsareobtained.

  • 标签: 类锂系统 振荡器 量子缺陷 电离化原子系统 原子物理学
  • 简介:ConsideringthatKBe2BO3F2(KBBF)isanoutstandingdeepultravioletcrystalwhichcangeneratetheshortestwavelengthsinsecondharmonicgenerationandsum-frequencygeneration,wereportthedeterminationofthenonlinearopticalcoefficientsoftheKBBFcrystal.Thed11coefficientwasdeterminedtobe0.49pm/VbytheMakerfringesmethodatthewavelength1064nm,whichisinagreementwellwiththetheoreticalvalue.

  • 标签: 非线性光学 KBe2BO3F2晶体 测量
  • 简介:Asimplemethodisappliedtocalculatingtheisotopeshifts(ISs)on5S1/2→4D3/2,5/2transitionsof87,88Sr+.FirstwehavecalculatedtheISsoflowertransitionsonaseriesofalkali-likesystemssuchasB2+,Ca+andBa+,whichareinagreementwithotherworks.ThentheISson5S1/2→4D3/2,5/2transitionsof87,88Sr+,whichareusefultostudytheSr+opticalfrequencystandard,areevaluated.

  • 标签: 原子物理 同位素位移 5S1/2→4D3/2 5/2 精细结构
  • 简介:HL-2AisthefirsttokamakwithdivertorinChina.TheobjectivesofHL-2Aaretoproducemoreadaptabledivertorconfigurationstostudyenergyexhaustandimpuritycontrol,andtostudyenhancedcoreplasmaconfinementbyprofilecontrolandmoderateplasmashaping.HL-2Ahaswelloptimizedoperationalflexibilityandexcellentaccessi-bilityforthediagnosticsystemstofacilitatevariousplasmaexperiments.

  • 标签: HL-2A 托卡马克装置 结构设计 等离子体物理学 涡轮分子泵
  • 简介:近代科学进入中国之回顾与前瞻──诺贝尔奖获得者杨振宁博士199418日在南宁的演讲有机会同大家讨论近代科学进入中国之回顾与前瞻,我很高兴。今天我要谈的是,近代科学如何发源于西方,随后又怎样进入中国的经过。了解这个过程以后,我们就能够对今天中华民...

  • 标签: 近代科学 回顾与前瞻 诺贝尔奖获得者 杨振宁 1994年8月 《几何原本》
  • 简介:Weperformfirst-principlecalculationsforthestudyoftheorthorhombicRb2Cd2(SO4)3structure.Electronicenergybands,totalandpartialdensitiesofstatesarereportedandanalysed.Itisfoundthatoxygenatomic2pelectronsstronglyhybridizewithRb/orCd4dandS2pstates,resultingintwo-typeionicgroupswithweakcouplings.Itisshownthatmacroscopicdomainwallsoriginatefromsuchweak-couplingionicgroups,arisingatthecellboundaries.Theasymmetriccationbonds(Rb-OandCd-O)andthesubsequentrotationsoftheS04tetrahedracanleadtothedrivingforceoftheferroelectricbehaviour.Thepredictedpyroelectriccurrenteffectsareobservedexperimentallyintheferroelectricphase.

  • 标签: 轨道杂交 斜方晶结构 氧原子 电子状态 铁电物质 畴壁能量
  • 简介:研究了YBaCu3O6~7超导催化剂上CO的加氢制醇反应。考察了温度、压力和空速等条件对催化剂反应性能的影响。反应的主要产物是甲醇、CO和少量甲醚。利用XPS、XRD和AFM等技术对催化剂的结构、铜的存在状态和反应活性位进行表征发现,在反应过程中,YBaCu3O6~7由orthombic相转变为tetragonal相。反应活性位可能是Cu(I)物种。反应后催化剂颗粒的分散程度明显提高

  • 标签: CO2加氢 YBa2Cu3O6~7超导催化剂 结构 活性位
  • 简介:HL-2AisanewdivertortokamakunderconstructionatSouthwesternInstituteofPhysics(SWIP),Chengdu,China,basedontheexperiencefromHL-1andHL-1M.HListheshorttermofaChinesewordthatmeans"ToroidalCurrentDevice".ThemainobjectivesofHL-2Aaretoproducemoreadaptabledivertorconfigurationstostudyenergyexhaustandimpuritycontrol(thefirstdivertortokamakplasmainChina),andtostudyenhancedplasmaconfinementbyprofilecontrolandmoderateplasmashaping.

  • 标签: HL-2A工程 环流工程 离子加速器 中国 成都市
  • 简介:Atokamakplasmadischargeinvolvesaseriesofcomplexandconcertedactionsconductedbyitscontrolsystem.TheHL-2Acontrolsystemcanbedividedintotwopartst,themachinecontrolsystemandthedischargecontrolsystem.Themachinecontrolsystem,whichconsistsofindustrialPC(IPC),configuresandoperatesthetokamak'svarioustechnicalsubsystems.Timingsys-temisintegratedintomachinecontrolsystemgivingabsolutetimeforallsubsystems.Thedischargecontrolsystem,

  • 标签: 等离子体 受控核反应装置 HL-2A 环流离子加速器 程序编辑
  • 简介:Run2atFermilabbeganinMarch,2001,CDFwillcollectdataatamaximumrateof20MByte/secduringtherun.Theofflinereconstructionofthisdatamustkeepupwiththedatatakingrate.ThisreconstructionoccursonalargePCfarm,whichmusthavethecapacityforquasi-realtimedatareconstruction,forreprocessingofsomedataandforgenerationandprocessingofMonteCarlosamples.Inthispaerwewillgivethedesignrequirementsofrthefarm,describethehardwareandsoftwaredesignusedtomeetthoserequirements,describetheearlyexperienceswithRun2dataprocessing,anddiscussfutureprospectsforthefarm,includingsomeideasaboutRun2bprocessing.

  • 标签: 脱机计算机 多量计算系统 软件开发