采用一种新的扩散法制备实用化的MgB_2超导体

利用一种新的Mg扩散方法,在常压下成功制备出致密的MgB2超导块材,样品密度最高达1.95g/cm3。结果表明:加热到900℃保温24h后炉冷,所得到的样品性能最佳。该样品在50Oe的外场下,超导转变温度(Tc)为38.1K,转变宽度仅0.9K;10K,20K,自场下临界电流密度(Jc)值分别达0.53,0.37MA/cm2。此外,通过添加少量纳米Pr6O11或者石墨,都能使MgB2的实用化性能得到显著改进。     

单缝密拼钢筋混凝土叠合板受弯性能试验研究

通过10块简支板的静力加载试验,对单缝密拼钢筋混凝土叠合板的破坏形态、刚度、裂缝和承载力进行了研究,并分析了桁架钢筋叠合板密拼缝的传力机理以及桁架钢筋与纵向受力钢筋的定量关系。结果表明:单缝密拼叠合板易在拼缝处发生沿叠合面的撕裂破坏,且其正截面受弯承载力和平均抗弯刚度均低于整浇板;在拼缝处设置桁架钢筋可以有效控制叠合面的撕裂破坏,并提高叠合板垂直于拼缝方向的刚度和承载力;桁架钢筋到拼缝距离等于板厚的试件,未发生拼缝处的叠合面撕裂破坏,其正截面受弯承载力比整浇板试件低6%,但比计算值大9%～18%。结合试验研究成果和国内外相关标准,提出了双向叠合板密拼拼缝的设计建议与构造要求。     

高强钢筋轻骨料混凝土梁短期裂缝试验研究

进行了10根配置400MPa和500MPa高强纵筋的陶粒轻骨料混凝土梁受弯性能试验,获得了10组裂缝间距和39组短期裂缝宽度数据,并收集了国内外27根高强钢筋轻骨料混凝土梁的裂缝试验数据。采用以上数据,分析了钢筋轻骨料混凝土梁的裂缝特征,并评估了JGJ 12—2006《轻骨料混凝土结构技术规程》中裂缝计算公式的适用性。结果表明,JGJ 12—2006的短期裂缝特征值计算方法仍适用于高强钢筋轻骨料混凝土梁,但按其公式计算的平均裂缝间距、平均裂缝宽度和最大裂缝宽度与试验值有一定偏差,二者之比的均值为0.992、1.276和1.037,因此建议对JGJ 12—2006中公式的部分参数进行修正。通过对试验数据的回归分析,得到了梁侧面受拉纵筋中心处裂缝宽度的修正计算式,以及梁侧面受拉钢筋中心处与受拉边缘裂缝宽度的换算关系式,建议公式计算得到的裂缝宽度和试验值吻合较好。     

CEFR中间热交换器一次侧数值模拟

应用CFX程序对中国实验快堆（CEFR）一回路中间热交换器（IHX）一次侧的1/6进行三维稳态模拟。计算获得IHX一次侧速度场、换热管束的温度分布及变化规律。结果表明,中间热交换器满足设计要求,能保证主热传输系统的正常工作。计算结果可为快堆调试及运行提供技术支持和理论依据。     

Effects of Annealing on the Structural and Photoluminescent Properties of Ag-Doped ZnO Nanowires Prepared by Ion Implantation

ZnO nanowires deposited on Si substrates were prepared by thermal evaporation of a mixture of ZnO and carbon powder. Ag ions with an energy of 63 keV and a dose of 5×1015 ions/cm-2 were implanted into the as-prepared ZnO nanowires. After ion implantation, the Ag-implanted ZnO nanowires were annealed in air at different temperatures from 600℃ to 1000℃. Effects of ion implantation and thermal annealing on the structural and photoluminescent (PL) properties of the ZnO nanowires were investigated by transmission electron microscopy (TEM), selected area energy dispersive X-ray spectroscopy (SAEDX), X-ray diffraction (XRD), and fluorescence spectrophotometry. TEM, HR-TEM, and SAEDX analyses demonstrated that efficient doping of Ag was achieved by ion implantation and the subsequent annealing process. XRD patterns revealed that the hexagonal wurtzite structure of ZnO nanowires was maintained after ion implantation. Photoluminescent emissions of ZnO nanowires were decreased significantly by Ag implantation but could be recovered by thermal annealing. The mechanism of the influence of ion implantation and annealing on the PL intensity was assessed.     

罗非鱼微冻保鲜过程中感官特性的研究

为探讨罗非鱼的保鲜方法,采用了罗非鱼微冻保鲜(-3~-5℃),对其贮藏过程中感官特性进行分析。结果表明,在微冻前9 d的总分在三级范围:色泽、气味、组织形态、肌肉弹性正常,食用安全;在10~19 d的总分在二级范围:色泽、气味、组织形态、肌肉弹性较正常;20d后的总分在一级范围:色泽、气味、组织形态、肌肉弹性不正常,腐败变质,不能食用。综上,鱼肉微冻保鲜21 d左右与正常冷藏保鲜相比较,从感官角度分析,保鲜时间明显延长。     

基于结构化保护的高安全级系统可信模型

In order to ensure the security of information systems, it's essential to make sure that system behav-iors are trusted. By analyzing threats that exist in execu-ting procedures, a trust model based on structured pro-tection is proposed. We consider that functional compo-nents, system actions and message flows between com-ponents are three key factors of information systems. Structured protection requirements on components, con-nections and action parameters are also provided. Four trusted properties of the model are deducted through formal analysis, and trusted system behavior is defined based on these properties. Furthermore, decision theo-rem of trusted system behavior is proved. The devel-oped prototype system indicates the model is practical. It is a general theory model built on logic deduction and independent on specific environment and the behaviors of the system designed and implemented following the model are trusted.     

长距离水平定向钻进技术在过江管施工中的应用

介绍了DN600过曹娥江管道施工采用的长距离水平定向钻进技术,阐述了长距离水平定向钻进DN600过江管施工的相关准备工作、关键施工工序以及在施工过程中碰到的问题及其解决方式,可为今后类似工程施工提供借鉴。     

TP347H奥氏体不锈钢高温过热器爆管原因分析

针对某电厂高温过热器爆管试样进行宏观形貌分析、金相分析、力学性能测试、晶间腐蚀试验,试验结果表明,爆管是由于TP 347H奥氏体不锈钢过热器管在弯制后未按规定进行固溶处理,材料在600℃运行时敏化,导致碳化铬在晶界上析出使晶界弱化,在腐蚀介质及各种应力共同作用下,发生晶间腐蚀爆管。