13C （α,n） 16O background in a liquid scintillator based neutrino experiment

α from natural radioactivity may interact with a nucleus and emit a neutron. The reaction introduces the background to the liquid scintillator （LS） based neutrino experiments. In the LS detector,α comes from 23Su, 232Th, and 210Po decay chains. For Gadolinium-doped LS （Gd-LS） detector, α also comes from 227Ac. The nucleus 13C is a natural component of Carbon which is rich in the LS. The background rate and spectrum should be subtracted carefully from the neutrino candidates. This paper describes the calculation of neutron yield and spectrum with uncertainty estimated. The results are relevant for many existing neutrino experiments and future LS or Gd-LS based experiments.     

杆杆型冲击拉伸试验装置的二维轴对称弹塑性有限元分析

对带有哑铃状圆柱形试件的杆杆型冲击拉伸试验装置,建立了含有多个物理和几何间断面的二维轴对称弹塑性有限元模型,采用动态增量非线性有限元程序ＡＤＩ－ＮＡ,进行了数值模拟模拟分析,揭示了应力波在试验系统中的传播规律,在弹性框架内初步论证了杆杆型冲击拉伸试验装置测试原理的有效性。     

具有竞争风险的步进应力加速寿命试验的最优设计和Bayes估计

讨论了渐进II型截尾数据中具有竞争风险的步进应力加速寿命试验的最优试验设计和参数估计.通过假定产品寿命服从Weibull分布,尺度参数对数是应力水平的线性函数基础上,利用KH模型采用极大似然方法和Bayes方法对模型参数进行了点估计和区间估计,而最优试验设计是使尺度参数对数的极大似然估计值在正常应力水平下的渐进方差达到最小.最后进行了仿真研究,结果显示提出的估计量具有良好的稳健性和有效性.