Calculation of the wide-angle neutron spectra from the ~9Be(d,xn) reaction in a thick beryllium target

The multi-layer computing model is developed to calculate wide-angle neutron spectra, in the range from0° to 180° with a 5° step, produced by bombarding a thick beryllium target with deuterons. The double-differential cross-sections(DDCSs) for the ~9 Be(d, xn) reaction are calculated using the TALYS-1.8 code. They are in agreement with the experimental data, and are much better than the PHITS-JQMD/GEM results at 15°, 30°, 45° and 60° neutron emission angles for deuteron energy of 10.0 MeV. In the TALYS-1.8 code, neutron contributions from direct reactions(break-up, stripping and knock-out reactions) are controlled by adjustable parameters, which describe the basic characteristics of typical direct reactions and control the relative intensity and the position of the ridgy hillock at the tail of DDCSs. It is found that the typical calculated wide-angle neutron spectra for different neutron emission angles and neutron angular distributions agree quite well with the experimental data for 13.5 MeV deuterons. The multi-layer computing model can reproduce the experimental data reasonably well by optimizing the adjustable parameters in the TALYS-1.8 code. Given the good agreement with the experimental data, the multi-layer computing model could provide better predictions of wide-angle neutron energy spectra, neutron angular distributions and neutron yields for the ~9 Be(d, xn) reaction neutron source.     

吸气剂在高真空多层绝热LNG槽车内吸附性能研究

为了利用吸附等温线理论模型模拟高真空多层绝热LNG槽车内吸气剂的吸附过程,对在真空技术中常用的等温式进行了分析研究。通过实验获得吸气剂在室温下的吸氢等温线,同时利用实验数据得到考虑分子间作用力的BET模型中的参数值。将模型结果与实验数据进行对比分析,结果表明:考虑分子间作用力的BET模型不能用作高真空多层绝热LNG槽车真空夹层内吸气剂吸附量的计算。利用Temkin和Freundlich等温式分段对实验数据进行拟合,对于1#吸气剂,拟合方程式计算得出的吸附量与实验数据的相对误差仅为2.6%,表明拟合方程能够对吸气剂在室温下的吸氢量进行准确预测。     

关于复对称矩阵特征根的补注

This note investigates the relationship of eigenvalues of Hermitian matrices P and UPU+ with UU+ = Ik and k ≤ n. We present several equivalent conditions for λi(UPU+) = λi(P) (i ≤ k ≤ n).     

浅水长波近似方程组的拟小波解

以浅水长波近似方程组为例,提出了拟小波方法求解(1 1)维非线性偏微分方程组数值解,该方程用拟小波离散格式离散空间导数,得到关于时间的常微分方程组,用四阶Runge-K utta方法离散时间导数,并将其拟小波解与解析解进行比较和验证.     

广义正定矩阵的行列式不等式

研究了广义正定矩阵的行列式理论，给出了一些新的结果，推广了Ky Fan、Openheim、Minkowski、Ostrowski-Taussky等著名行列式不等式，削弱了华罗庚不等式的条件．     

探求数学课堂“化学反应”的“催化剂”

在教学实践中,笔者深刻感受到数学课堂添加“催化剂”能促进课堂发生“化学反应”.课堂的化学反应指通过教师的组织引导,学生实现全面发展.发展乃是质而不是量的变化,是让学生学会探究,激发学习的主动性和积极性,使学生学会、会学、乐学,不是一味地接受和存储知识.类比到数学课堂,催化剂指能加速课堂化学反应的策略方法.     

低温容器真空夹层中绝热材料放气特性实验研究

绝热材料放气是造成低温容器真空夹层真空失效、绝热性能恶化的主要原因。利用自建的材料放气速率实验装置,对绝热材料的放气特性、残余气体成分及影响因素进行了实验研究。实验结果表明：绝热材料的放气特性曲线符合非金属材料扩散放气模型,残余气体成分包括H₂O、N₂、O₂及CO₂,且主要成分为H₂O;真空夹层内的真空度越高,材料的放气速率越大;材料表面粗糙度越大,其放气速率越大;氮气置换空气的抽真空工艺亦可引起绝热材料的放气速率大幅度提升。     

一类非线性奇异椭圆方程的非平凡解

讨论一类非线性奇异椭圆方程边值问题,运用正则化方法,经过取两次极限,得到了这个问题的一个非平凡解.     

EXISTENCE AND ASYMPTOTIC BEHAVIOR OF SOLUTIONS TO A SINGULAR PARABOLIC EQUATION

In this paper,we study the initial-boundary value problem for a class of singular parabolic equations.Under some conditions,we obtain the existence and asymptotic behavior of solutions to the problem by parabolic regularization method and the sub-super solutions method.As a byproduct,we prove the existence of solutions to some problems with gradient terms,which blow up on the boundary.     

初中物理电流概念教学模型比较分析及启示

电流概念是初中电学最基本的概念之一,也是学生学习电学的基础.在相关研究的基础上,发现国内外物理教学研究工作者提出了4种类比模型——“水流类比模型”“自行车车链模型”“引力模型”“电子传输模型”并用其来进行电流概念的教学.现分析比较这4种电流类比模型,对使用物理模型进行电流概念教学作出讨论,希望对教科书内容的编写以及新时期的中学物理教学有所裨益.