Investigation of the Imaging Polarization Effect Based on a Pixellated CdZnTe Detector

A pixel array CdZnTe imaging system, employing a 40 × 40× 5 mm^3 pixellated CdZnTe detector, is established. The imaging polarization effect in the CdZnTe pixellated detector for a collimated CS137 Gamma source is investigated in detail. The experimental results for different irradiated fluxes indicate that excessive irradiated flux indeed causes central pixels to be shut off completely. The imaging performance of the polarized detector is severely degraded. Polarized detector counts are simultaneously reduced to one-third of the non-polarized detector counts. A theoretical model of potential distribution is also proposed by solving the Poisson equation and, in turn, the electric potential distortion for high irradiated flux is discussed by comparison with the experimental results.     

一类非牛顿流体流动问题的变分原理和广义变分原理

本文将钱伟长教授[1]的不可压缩粘性流的最大功率消耗原理推广到一类特殊的非牛顿流体─-广义牛顿流体的流动问题,并采用识别的拉氏乘子法来解除变分约束条件,导出其广义变分原理。     

高效液相色谱法测定血浆中的乙酰螺旋霉素

乙酰螺旋霉素(Ac-SPM)是近年来广泛应用于临床的一种十六碳大环内酯类抗生素,其体内外抗菌活性均优于螺旋霉素。Ac-SPM是双乙酰螺旋霉素Ⅱ、Ⅲ和单乙酰螺旋霉素Ⅱ、Ⅲ四个组分的混合物。我们采用柱色谱法,在薄层色谱法(TLC)的监测下,分离制得Ac-SPM的各组分标准品,以此为     

运动导体中电磁场计算的迎风有限元法

运动导体中电磁场控制方程为一对流扩散型微分方程,为克服此类方程的Galerkin有限元解在网格Peclet数大于1时出现的伪振荡同时克服Heinrich迎风有限元法对扩散项处理的不合理性,提出了一种修正的Heinrich迎风有限元法,并应用于若干运动导体电磁场的有限元分析。     

高效液相色谱法用于右美沙芬缓释剂的研究

用高效液相色冷荧光检测技术研究了右美沙芬缓释剂在人体内的药代动力学,并与右美沙芬普通剂型相比较计算了右美沙芬缓释剂的相对生物利用度。     

VARIATIONAL PRINCIPLE AND GENERALIZED VARIATIONAL PRINCIPLE IN HYDRODYNAMICS OF A CLASS OF NON－NEWTONIAN FLUID

ＶＡＲＩＡＴＩＯＮＡＬＰＲＩＮＣＩＰＬＥＡＮＤＧＥＮＥＲＡＬＩＺＥＤＶＡＲＩＡＴＩＯＮＡＬＰＲＩＮＣＩＰＬＥＩＮＨＹＤＲＯＤＹＮＡＭＩＣＳＯＦＡＣＬＡＳＳＯＦＮＯＮ－ＮＥＷＴＯＮＩＡＮＦＬＵＩＤＳｈｅｎＭｉｎ（沈敏）,ＳｕｎＱｉ－ｒｅｎ（孙其仁）（Ｓ...     

液相色谱-质谱分析中的基质效应

介绍了液相色谱-质谱(LC-MS)分析中基质效应的产生机制、来源、评定方法和消除措施.基质效应由共流出的分析物和基质的竞争以及影响接口的离子化效率所致,主要来源于生物样品中的内源性组分和样品处理后引入的杂质.不同批次的生物样品,其基质效应存在差异,可通过柱后注射法和提取后添加法2种方法评定基质效应.实例介绍了基质效应、提取回收率和整个方法过程效率的具体计算方法.基质效应可能影响LC-MS方法的灵敏度、准确度和精密度,通过样品前处理、氘代内标的使用、色谱分离、质谱分析等过程的优化可有效消除基质效应.     

Copper Nanobelt Reorientation by Molecular Dynamics Simulation

Atomic simulations using embedded atom method （EAM） are performed for Cu （100） nanobelts to study the structural and mechanical behaviour. Cu （100） nanobelts are along[001] taken as the z-axis and have a rectangular cross section in the x - y plane, with [100] and [010] taken as x and y axes. The periodic boundary is used along the z-axis to simulate an infinitely long nanobelt, and other surfaces are free. The simulations are carried out under the mechanical loading with an elongation strain rate of 8.0×10^8 s^-1 along the z-axis. The results show that the nanobelt undergoes a transition from the initial structure with a （100） axis and {100} lateral surfaces to a new structure with the （112） as the z-axis and the lateral surfaces are {111} and {110} respectively, instead of the original {100} surfaces. The mechanism of the structural transition is ascribed to the dislocation propagation through the nanobelt under the external stresses.     

不同厚度像素CdZnTe探测器的性能测试和评估

碲锌镉材料(CdZnTe)是目前探测X射线和γ射线的最好材料之一。将241 Am和137 Cs辐射源作用于像素CdZnTe探测器,通过实验和仿真分别得到能量谱估计、能量分辨率和峰值效率。由实验和仿真结果得出:在662keV的高能量下,厚度较大的CdZnTe探测器可获得更高的能量分辨率和峰值效率,但在59.5keV低能处会出现拖尾升高和电荷损失的现象;厚度较薄的探测器在低能处的特性反而更好。     

不同厚度像素CdZnTe探测器的性能测试和评估

碲锌镉材料（CdZnTe）是目前探测X射线和射线的最好材料之一。将241Am和137Cs辐射源作用于像素CdZnTe探测器,通过实验和仿真分别得到能量谱估计、能量分辨率和峰值效率。由实验和仿真结果得出:在662 keV的高能量下,厚度较大的CdZnTe探测器可获得更高的能量分辨率和峰值效率,但在59.5 keV低能处会出现拖尾升高和电荷损失的现象; 厚度较薄的探测器在低能处的特性反而更好。