简介:摘要目的探讨学习成绩与重度饮酒的可能关联,为相应干预措施的制定提供科学依据。方法采用调查问卷,调查7235名12-23岁学生。结果5个学习水平之间,男生重度饮酒率的差异有统计学意义(x2=31.740,P=0.000),女生也有统计学意义(x2=26.458,P=0.000)。女生,学习成绩差的(第五级)报告率明显高;男生,报告率明显低的是第二级(学习成绩中等偏下),学习成绩优良的报告率并不低。3类高中之间,男生重度饮酒率的差异有统计学意义(x2=24.083,P=0.000),女生也有统计学意义(x2=14.469,P=0.001)。不论性别,职业高中较高,普通高中略高于重点高中。结论学生重度饮酒率与“绝对”的学习成绩(高中类型)、“相对”的学习成绩(班级排位)都有着密切关联。
简介:Todevelopanewmagnesiumalloywithexcellentformabilityatroomtemperature,theeffectofY,Ce,andGdadditionontextureandstretchformabilityofMg–1.5Znalloyswascarriedout.TheresultshowsthatY,Ce,andGdadditioninMg–1.5Znalloyscaneffectivelyweakenandmodifythebasalplanetexture,characterizedbyTD-splittextureinwhichthepositionofbasalistitledfromnormaldirection(ND)towardtransversedirection(TD).WhenMg–1.5ZnalloywithGdadditionappearslowtextureintensityandTD-splittexture,wherethepositionofbasalpolesistiltedbyabout±35°fromNDtowardtoTD,thelargestErichsenvalueof7.0andtheelongationratereaches29.1%inTDdirection.However,YandCeadditioninMg–1.5Znalloyspromotealargenumberofsecondphaseparticles,whichcancelthecontributionoftheuniquebasaltexturetostretchformabilityandductility.
简介:采用粉末冶金方法制备含Y2O3的稀土钼合金,利用金相显微镜、扫描电子显微镜(SEM)、X射线衍射(XRD)、能谱分析(EDS)等手段对钼合金的断裂特征和组织结构进行对比分析,研究稀土氧化物Y2O3含量对钼合金组织和性能的影响。研究表明:添加Y2O3能细化晶粒、改善钼合金的晶粒均匀性和致密度、提高钼合金的性能;拉伸强度和屈服强度随Y2O3含量的增加呈现先增高后降低的趋势,在Y2O3含量为1%时,抗拉强度达511.43MPa,屈服强度456.99MPa,分别是纯钼材料的1.31倍和1.57倍,综合力学性能最佳;在烧结坯中,Y2O3颗粒分布均匀,主要以球形和等轴状形式存在于晶界上。
简介:摘要:工作面开采采用Y型通风系统,两进一回Y型通风方式是适合无煤柱开采技术要求的预防和治理工作面上隅角瓦斯积聚最有效的通风方式;大大降低了回采工作面上半段沿倾向的瓦斯浓度递增梯度和上隅角瓦斯浓度,能有效地防止工作面的瓦斯积聚,为工作面的高产高效提供了可靠保证。
简介:TheelectronicpropertiesandtopologicalphasesofThXY(X=Pb,Au,Pt,PdandY=Sb,Bi,Sn)compoundsinthepresenceofspin–orbitcoupling,usingdensityfunctionaltheoryareinvestigated.TheThPtSncompoundisstableintheferromagneticphaseandtheotherThXYcompoundsarestableinnonmagneticphases.Bandstructuresofthesecompoundsintopologicalphases(insulatorormetal)andnormalphaseswithingeneralizedgradientapproximation(GGA)andEngel–Voskogeneralizedgradientapproximation(GGAEV)arecompared.TheThPtSn,ThPtBi,ThPtSb,ThPdBi,andThAuBicompoundshavetopologicalphasesandtheotherThXYcompoundshavenormalphases.Bandinversionstrengthsandtopologicalphasesofthesecompoundsatdifferentpressurearestudied.Itisseenthatthebandinversionstrengthsofthesecompoundsaresensitivetopressureandforeachcompoundasecond-orderpolynomialfittedonthebandinversionstrengths–pressurecurves.
简介:ThemixturemodelofAl85Y4Nd4Ni7alloyinwhichapartiallycrystallizedamorphousalloyisregardedasananocompositeofanAlnanoparticleandaremainingamorphousmatrixispresented.Itsevolutionintheprocessofcrystallizationhasbeeninvestigatedbydifferentialscanningcalorimetry(DSC),X-raydiffraction(XRD),andtransmissionelectronmicroscopy(TEM).Mainlyamorphousstructurewithα-Alnanocrystalsembeddedintheamorphousmatrixhasbeenrevealedbymeltspiningthealloy.Crystallizationisshowedtooccurinthreestages:(1)crystallizationofamorphousalloyandformationofAlNiY,AlNdNiandunknowncrystallinephases,(2)formationofAl3YandAl3Nd,and(3)formationofAl3Ni.
简介:摘要目的探讨5类家庭类型与学生6种不健康饮食行为之间的可能关联。方法采用问卷调查喝软饮料、吃甜点、吃油炸食品、吃西式快餐、吃路边摊、偏食的报告率,共调查24735名12-23岁男、女生。结果5类家庭学生的报告率之间有统计学意义的不良饮食行为,男生有吃路边摊(x2=12.198,P=0.016)和吃西式快餐(x2=10.353,P=0.035),女生仅有吃路边摊(x2=10.998,P=0.027),都表现为稳定家庭较低,不稳定家庭较高。结论家庭类型与学生不健康饮食行为的关联不明显。