近断层地震作用下SMA-滑移隔震结构的动力响应分析

基于形状记忆合金的超弹性效应,将形状记忆合金和滑移支座复合成一种新型的隔震支座:SMA-滑移支座.并应用在一隔震结构上.推导了地震激励下该支座隔震结构的运动方程,对滑移隔震结构进行了数值模拟分析.结果表明,支座具有良好的隔震性能,可有效的应用在隔震结构的振动控制上.     

石河子垦区农田土壤重金属含量与风险评价

在石河子垦区北泉镇和桃花镇采集农田土壤样品130个,测定土壤Cu、Zn、Cr、Cd、Pb、As和Hg7种重金属含量,系统分析了土壤重金属的分布特征,并对该地区土壤重金属的累积污染现状和潜在生态风险进行评价。结果表明：石河子垦区农田土壤Cu、Zn、Cr、Cd、Pb、As和Hg的平均含量分别为33．34、102．64、58．77、0．46、13．72、18．89和0．036mg／kg,均超过新疆土壤背景值,其中Cd、Hg、Pb和As最为显著。7种重金属平均含量均低于国家《土壤环境质量标准》二级标准,但Cd和As的超标率分别达到了16．92％和9．23％。土壤中Cu—Zn—As、Cr-Cd—Pb有较强的同源性,而Hg具有强烈的异源特征。北泉镇农田土壤Hg平均含量明显高于桃花镇,而Cd、Cr和Pb则低于桃花镇。不同土地利用类型农田土壤重金属的平均含量总体差异较小。7种重金属元素均存在不同程度的累积,Cd和Hg的单因子污染指数较大,重金属综合污染指数平均为0．71,属尚清洁（警戒限）。样点中重金属多因子综合潜在生态风险指数处于低潜在生态风险的占27％,中等潜在生态风险占50％,较高潜在生态风险占23％;其中,土壤Cd的潜在生态风险指数最大,其次是Hg。     

BiFeO3掺杂Pb（In1/2Nb1/2）O3-Pb（Mg1/3Nb2/3）O3-PbTiO3陶瓷的制备与磁电性能研究

以固相合成法制备了铁酸铋（BiFeO₃,简称BFO）掺杂的铌铟酸铅-铌镁酸铅-钛酸铅（Pb（In_1/2Nb_1/2）O₃-Pb（Mg_1/3Nb_2/3）O₃-PbTiO₃,简称PIN-PMN-PT）多铁性陶瓷材料,X射线衍射（XRD）测试结果表明：样品具有钙钛矿结构,电滞回线显示其铁电性良好,剩余极化值（P_r）可达18 μC·cm^-2.由于BiFeO₃掺杂后,样品电矩减小,氧空位增多,使其铁电畴翻转困难,样品的电性能略有下降,但是其磁性能随BiFeO₃掺入量的增加而逐渐增强,且样品居里温度（T_m）为200℃左右.该材料在电磁学领域有望成为具有应用前景的多铁性材料.     

Rapid directionally solidified microstructure characteristic and fracture behaviour of laser melting deposited Nb–Si–Ti alloy

Aiming at achieving fine and directionally-solidified microstructure of Nb-Si based alloy,Nb,Si and Ti powder particles were utilized as the raw materials,and laser melting deposition(LMD) experiments were conducted with1500 W and 2000 W laser power,respectively.The microstructure characteristic,micro-hardness,and indentation fracture toughness were examined by scanning electron microscope(SEM),X-ray energy dispersive spectrometer(XEDS) and X-ray diffraction(XRD).The results showed that the two kinds of as-deposited Nb-17 Si-23 Ti alloy samples were mainly composed of Nbss,(Nb,Ti)3 Si and Ti-rich Nbss,and the microstructure presents rapid directionally-solidified characteristic,in which the 100 crystallographic direction of Nbss and 110 crystallographic direction of(Nb,Ti)3 Si tend to be parallel to the LMD building direction.With the laser power increasing from 1500 W to 2000 W,the microstructure became more oriented and homogeneous.For the sample at 2000 W,the dendrite spacing was only about 1-2 μm,and Nbss and(Nb,Ti)3 Si couples grow alternately and they are parallel to the building direction strictly.In the meantime the micro-hardness and indentation fracture toughness reached 1075 HV and 20.3 MPa·m~(1/2),respectively,indicating significant improvement by the directional growth of fine Nbss and(Nb,Ti)3 Si phases,and the dimple fracture mode of the Nbss dendrites.