A study on the evaluation of usefulness depending on the image reconstruction method in bone SPECT scan

The recent advances in image-processing techniques have led to the development of many methods to reduce the scan time without degrading the image quality. In particular, tomography has improved image reconstruction methods with the concomitant improvement of high-quality images. In this study, PRECEDENCE 16 was used to reconstruct images using the filtered back projection method, which is generally used, and the Astonish method and three-dimensional ordered-subsets expectation maximization method, which are based on repetition techniques. In qualitative and quantitative analysis of the reconstructed images, a comparison was made between images with different acquisition times and between images with the same acquisition time, which aimed at determining the optimal method for reconstructing high-quality images. A blind test for qualitative analysis confirmed almost no difference in image quality depending on the image acquisition time. Furthermore, in quantitative analysis, there was no significant difference in image quality depending on the image acquisition time. On the other hand, the results of the analysis in the image reconstruction method with the same acquisition time demonstrated a significant difference. The images reconstructed by the Astonish method, which uses a repetition technique, are believed to be excellent because they have high resolution and provide clinical diagnostic information. This study confirmed that the reconstruction method with a repetition technique could be used to improve image quality and reduce the scan time, despite not being in general use until recently due to the lengthy time needed for image reconstruction and lack of storage space.     

不同介质中超声波传播速度测量方法之比较

基于共振干涉法、相位法和反射回波法测量了空气和水中超声波的传播速度,比较了三种方法的优缺点,共振干涉法和相位法可测量气体和液体中的声速,反射回波法可测量液体和固体中的声速;相位法误差最小,共振干涉法误差相对较大。共振干涉法研究了示波器接收的交变电压随传播距离的变化规律,计算得空气和水中超声波的损耗系数分别为0.01381、0.01829,超声波在水中的损耗较大。使用Origin软件直线拟合,对实验结果进行分析和评价。     

原子光谱分析中的间接测定法

本文对近年来原子光谱分析间接测定法的进展及应用进行了综述,内容包括:方法原理、AAS间接法、ICP-AES间接法和FIA-AAS间接法。附参考文献57篇。     

“0.618”法、Fibonacci法、抛物线法搜寻复摆周期极值点

在实验室条件下,用"0.618"法、Fibonacci法和抛物线法来搜寻钟摆复摆周期极值点位置.通过实验发现,Fibonacci法在搜索精度上比"0.618"法高,但在搜寻速度上不占优势,而抛物线法在搜寻速度和精度上比"0.618"法和Fibonacci法都好.     

反射法和自准法测三棱镜顶角的比较

通过对反射法和自准法测量三棱镜顶角的比较,从测量的准确程度以及实验过程中操作容易程度来看,自准法更适合测量三棱镜顶角。     

介质光波导的数值计算及近似方法

综述介质光波导中模式分析方法的最新进展。着重分析严格的数值分析方法及近似方法最近的研究进展。依据方法的计算精确度、计算效率和计算复杂度等因素．对有限元法和有限差分法这两种数值分析方法以及有效指数法和频谱指数法等近似方法进行讨论。论述磁光波导的分析方法。     

齐次平衡法、Weiss-Tabor-Carnevale法及Clarkson-Kruskal约化法之间的联系

扩充齐次平衡法的应用范围,用于寻找非线性数学物理方程的Bcklund变换和相似约化,其结果分别等同于Weiss-Tabor-Carnevale (WTC) 法及Clarkson-Kruskal (CK) 法结果,并从理论上进一步说明三种方法之间的密切联系. 关键词： 齐次平衡法 WTC法 CK约化法     

一种新的格状波分复用光网络保护方法

在P圈法和哈密顿环保护法的基础上,提出了一种新的适用于格状波分复用光网络的基于资源的环保护方法,我们称之为RP圈法.与其他基于环的格状光网络保护方法相比,RP圈法具有配置方式简单、与业务模型不相关以及圈具有长度限制等许多特点.文中给出了RP圈法的一种启发式算法,仿真结果表明此算法具有较高的容量效率,是一种可适用于动态业务的实用化光网络保护方法.     

Explicit multi-symplectic method for the Zakharov—Kuznetsov equation

We propose an explicit multi-symplectic method to solve the two-dimensional Zakharov-Kuznetsov equation. The method combines the multi-symplectic Fourier pseudospectral method for spatial discretization and the Euler method for temporal discretization. It is verified that the proposed method has corresponding discrete multi-symplectic conservation laws. Numerical simulations indicate that the proposed scheme is characterized by excellent conservation.     

光纤化学传感同步吸收-荧光法的建立

建立一种光纤化学传感同步测定吸收光谱和荧光光谱的新方法。自制同步吸收-荧光比色皿,结合光纤化学传感技术,建立同步吸收-荧光光谱法检测仪器,分别测定罗丹明B,维生素B₂,维生素B₆等溶液的同步吸收-荧光光谱,且与传统的紫外-可见吸光光度法和荧光法进行对比。同步吸收-荧光光谱法测得罗丹明B,维生素B₂,维生素B₆与传统吸光光度法和荧光光谱法检测的吸收光谱图和荧光光谱的图谱大体一致。最大荧光强度波长与传统的荧光方法比较准确度高,但最大吸收波长略有偏差。同步吸收-荧光光谱法等同于同步测定荧光物质的吸收光谱和荧光光谱,实现二光谱合二为一,测定最大发射波长时准确度高,但最大吸收波长略有偏差,值得深一步研究。     

A study of fringe pattern trace and analysis

In this paper,the gometric center and centroid method are suggested to tracecenter location of a close fringe pattern.The fringe pattern of the interferogram is analysed byusing the general Fourier method.The analytic accuracy is controlled by using P-test methodof statistics.The analytic accuracy and sampling speed of the fringe pattern depend on thequality of the interferogram and the numbers of the sampling points.     

光场空间相干性的测量方法及比较

本文归纳了基于分波前干涉原理的具有代表性的干涉测量方法——杨氏双孔干涉法、逆波前杨氏干涉法和非冗余孔径阵列干涉测量法,以及基于分振幅干涉原理的干涉测量方法——自参考干涉测量法;介绍了各种测量方法的工作原理、实验配置;比较了4种测量方法的优缺点,并给出每种方法的最佳应用领域。本文结论可为根据对空间相干性测量的不同要求,选择合适的测量方法提供初步参考。     

基于MOF界面重构的多物质ALE方法

提出一种基于MOF(Moment-of-Fluid)界面重构的多物质ALE(Arbitrary Lagrangian-Eulerian)方法.流体力学方程组采用相容有限元方法进行空间离散.提出一种新的二维子网格力学模型,用来计算混合网格中的物理量经过一个拉氏步后发生的变化,混合网格内的界面重构采用MOF方法.提出一种精确积分守恒重映方法.给出数值算例,如空气和水的Riemann问题,Dukowicz问题,水中强激波与空气泡相互作用问题等.结果表明,方法具有较高的精度,能够处理物质界面和网格的大变形问题.     

An improved interpolating element-free Galerkin method with a nonsingular weight function for two-dimensional potential problems

In this paper, an improved interpolating moving least-square (IIMLS) method is presented. The shape function of the IIMLS method satisfies the property of the Kronecker δ function. The weight function used in the IIMLS method is nonsingular. Then the IIMLS method can overcome the difficulties caused by the singularity of the weight function in the IMLS method. The number of unknown coefficients in the trial function of the IIMLS method is less than that of the moving least-square (MLS) approximation. Then by combining the IIMLS method with the Galerkin weak form of the potential problem, the improved interpolating element-free Galerkin (IIEFG) method for two-dimensional potential problems is presented. Compared with the conventional element-free Galerkin (EFG) method, the IIEFG method can directly use the essential boundary conditions. Then the IIEFG method has higher accuracy. For demonstration, three numerical examples are solved using the IIEFG method.     

An improved interpolating element-free Galerkin method with nonsingular weight function for two-dimensional potential problems

In this paper, an improved interpolating moving least-square (IIMLS) method is presented. The shape function of the IIMLS method satisfies the property of Kronecker δ function. The weight function used in the IIMLS method is nonsingular. Then the IIMLS method can overcome the difficulties caused by the singularity of the weight function in the IMLS method. And the number of unknown coefficients in the trial function of the IIMLS method is less than that of the moving least-square (MLS) approximation. Then by combining the IIMLS method with the Galerkin weak form of the potential problem, the improved interpolating element-free Galerkin (IIEFG) method for two-dimensional potential problems is presented. Compared with the conventional element-free Galerkin (EFG) method, the IIEFG method can directly use the essential boundary conditions. Then the IIEFG method has a higher accuracy. For demonstration, three numerical examples are solved using the IIEFG method.     

测量电池电动势和内阻中不确定度评定方法比较

本文介绍了用板式电势差计测量电池电动势和内阻中直线拟合参数的不确定度的评定方法,并用图解法和最小二乘法求得的结果进行比较,得出评定方法的可行性与优缺点.     

基于交互模式的柔性体接触碰撞动力学建模方法

目前对于任意形状的柔性体接触碰撞问题,一般采用有限元离散,通用的建模方法有两类:罚函数法和附加约束法.罚函数法将接触作用视为弹簧阻尼力元,无需求解约束方程,但依赖于碰撞力参数的选取;附加约束法可严格满足接触约束条件,但数值求解更为复杂.针对两类接触模型各自的优缺点,提出基于交互模式的建模方法.该方法将整个模型分为局部静力学模块和主体动力学模块,在每个积分步内,局部静力学模块求解接触力,主体动力学模块求解运动学变量,两个模型之间进行位移和力的交互.该方法综合了附加约束法和罚函数法各自的优点,既无需人为选取碰撞参数,又满足局部区域互不嵌入的约束条件,同时数值求解方便.通过杆-板碰撞的实验算例及滑块-滑槽多点碰撞的数值算例,验证了该方法的有效性.     

冲击动力学中离散元与有限元相结合的计算方法研究

 阐述了一种离散元与有限元法相结合的计算方法,编制了可应用于细观模拟的二维程序,对受冲击载荷作用的均匀材料和非均匀材料的响应特征进行了计算,并对数值模拟进行了验证。计算结果与理论值较吻合,验证了方法的可行性。     

基于Monte Carlo的热脉冲法数据分析

热脉冲法是测量聚合物介质薄膜空间电荷分布的有效方法之一, 其数据的分析涉及第一类Fredholm积分方程, 只能采用合适的数值计算方法进行求解, 而Monte Carlo法是近年来提出的数值求解该方程的方法之一. 本文尝试使用Monte Carlo法在频域内实现热脉冲数据的分析, 通过一系列模拟计算讨论Monte Carlo法的分析效果. 计算结果表明: Monte Carlo法可实现对热脉冲法实验数据的有效分析, 提取被测薄膜内的电场分布, 而且计算的电场分布在整个样品厚度上都与真实分布较好地符合, 可有效地弥补尺度变换法只在样品表面附近获得较高准确度的缺陷. 该方法的局限性在于计算结果存在一定的振荡, 且在噪声和数据误差的影响下, 其准确性很大程度上依赖于奇异值分解过程中容差的选择, 在应用的方便程度方面还有待进一步提升.     

离散元与有限元结合的多尺度方法及其应用

在深入研究复杂结构和非均质材料冲击响应和破坏机理的过程中,往往遇到多尺度计算问题.提出并建立起离散元与有限元结合的多尺度方法,该方法采用离散元对感兴趣的局部进行细观尺度的模拟,利用有限元进行宏观的模拟,从而节约了计算时间.采用一种特殊的过渡层衔接离散元区和有限元区.将这一方法应用于激光辐照下预应力铝板的破坏响应,并将得到的模拟结果与实验进行了比较.