简介:AgraphGiscalledchromatic-choosableifitschoicenumberisequaltoitschromaticnumber,namelych(G)=χ(G).Ohba’sconjecturestatesthateverygraphGwith2χ(G)+1orfewerverticesischromaticchoosable.ItisclearthatOhba’sconjectureistrueifandonlyifitistrueforcompletemultipartitegraphs.Recently,Kostochka,StiebitzandWoodallshowedthatOhba’sconjectureholdsforcompletemultipartitegraphswithpartitesizeatmostfive.Butthecompletemultipartitegraphswithnorestrictionontheirpartitesize,forwhichOhba’sconjecturehasbeenverifiedarenothingmorethanthegraphsKt+3,2*(k-t-1),1*tbyEnotomoetal.,andKt+2,3,2*(k-t-2),1*tfort≤4byShenetal..Inthispaper,usingtheconceptoff-choosable(orL0-size-choosable)ofgraphs,weshowthatOhba’sconjectureisalsotrueforthegraphsKt+2,3,2*(k-t-2),1*twhent≥5.Thus,Ohba’sconjectureistrueforgraphsKt+2,3,2*(k-t-2),1*tforallintegerst≥1.
简介:[摘要]JW电厂#4机组机组大修后,主机#2轴瓦在运行中出现瓦温偏高和轴振较大,瓦温高达107.7°(在开机运行30天后,通过运行曲线观察得知,轴瓦温度随时间有上升的趋势)。X方向轴振124μm,Y方向轴振107μm。严重的威胁机组的安全运行。本文着重介绍JW电厂超临界N600/24.2/566/566型机组#2轴承特征、轴瓦故障原因分析、轴瓦故障处理和故障处理后所取得的良好效果;希望能对同类型机组#2轴承振动故障的诊断、处理提供有益的参考和借鉴。
简介:老师在课堂上用实验演示了弹簧振子做简谐运动的周期T与振幅A无关,而取决于振子质量m和劲度系数k.为了便于记忆,老师给出了它的周期公式T=2πm/k~(1/2).这个公式是教材中没有的,老师也没有加以证明.我想,能否利用我所学的知识证明它呢?我头脑一下子兴奋起来了,课后就开始着手去证明了.在简谐运动过程中,弹簧的弹力是变化的,要
简介:摘要目的探讨MRI常规序列T2WI、T2WIFS、DWI及增强T1WIFS在肛瘘诊断中的价值对比。方法64例经手术病理证实为肛瘘的患者,比较分析横断位T2WI、T2WIFS、DWI及增强T1WIFS序列上肛瘘的显示价值。结果对于主瘘管的检出,四个序列手术病理符合率分别为T2WI89.06%、T2WIFS84.38%、DWI68.75%以及增强T1WIFS95.31%。结论肛瘘常规的四种MRI序列,增强T1WIFS序列诊断价值最大,DWI序列诊断价值最低。T2WI序列具有高的诊断价值,特别是对于主瘘管的显示,但对于炎性水肿的显示,还需要借助T2WIFS或增强T1WIFS序列。
简介:WehavesynthesizedandinvestigatedphysicalpropertiesoftwonewquaternarycompoundsGd2CoAl4T2(T=Si,Ge)singlecrystals,whichareisostructuraltoTb2NiAl4Ge2andEr2CoAl4Ge2.Themostimportantstructuralfeatureofthesematerialsistheanti-CaF2-typeCoAl4T2slabs.Thesematerialsshowmetallicbehaviorbelow300Kandthereisalong-rangeantiferromagnetic(AFM)transitionappearingat20and27KforGdCoAl4Ge2andGd2CoAl4Si2,respectively.ResistivityandheatcapacitymeasurementsalsoconfirmthesebulkAFMtransitions.Furtheranalysisindicatesthatthislong-rangeantiferromagnetismshouldresultfromthemagneticinteractionbetweenlocalmomentsofGd^3+ions.
简介:Objective:Toinvestigatetheeffectofbreast-conservationtherapyinearlystagebreastcancer.Methods:Atotalof234earlystagebreastcarcinomapatientsreceivedbreastconservingtreatmentinourhospital.Aftertheoperation,theyunderwentadjuvantchemotherapyandradiotherapy.Allofthesepatientsdesiredtopreservetheirbreasts.Results:Aftermedianfollow-upof29.46months(rangefrom3to100months),3caseshadlocalrelapseand8caseshaddistantmetastasis.Theoverallsurvivalrateof5yearwas96.7%,andthediseasefreesurvivalrateof5yearwas87.85%.Conclusion:Forearlystagebreastcarcinomapatients,classicquadrantectomy,axillarydissectionandpost-operativeadjuvantchemotherapyandradiotherapyleadtoexcellentlocalcontrolandgoodsurvival.
简介:目的:通过比较STTR、准T2W1、重T2W13种序列最优参数扫描磁共振脊髓成像图像质量优劣(扫描时间一定),寻找一种磁共振脊髓成像最优参数序列。方法:首先将60例病员或自愿者分成3组,其中STIR扫描20例,反转时间(TI)取80ms、100ms、120ms3种参数;准T2WI扫描20例,翻转角(FA)取15°、20°、25°3种参数;重T2W1扫描20例,回波时间(TE)取150ms、200ms、250ms3种参数(TR固定在6000ms),扫描后再行磁共振脊髓成像,选择出各序列中磁共振脊髓成像最优参数组合。然后将50例病员或自愿者,同时进行STIR、准T2WI、重T2WI各序列最优参数组合扫描,扫描出的图像由甲、乙、丙3位专业技术人员对3种序列磁共振脊髓成像质量进行双盲法审阅片,根据图像质量评价标准,评价3种序列扫描磁共振脊髓成像最优序列。结果:STIR、准T2WI、重T2WI3种扫描序列分别取参数TI=100ms、FA=20°、TE=200ms磁共振脊髓成像时以重T2WI为最优序列。结论:磁共振脊髓成像技术最优参数组合及最优序列为:TR:600ms、TE=200ms的自旋回波(SE)重T2WI序列。
简介:the Japanese manufacturers chose to focus on making products that Western manufacturersignored. Thus,weather and terrain become less important. The same logic applies to many other situations. For example,日本产品现在已经能和西方最强的对手一较高低
简介:the Japanese manufacturers chose to focus on making products that Western manufacturersignored. Thus,weather and terrain become less important. The same logic applies to many other situations. For example,日本产品现在已经能和西方最强的对手一较高低