衰减

This article is a review of different methods for attenuation correction in SPECT.

综述了常见的SPECT衰减校正方法，包括前、后校正法，本征法和迭代法。

Furthermore,the stability behavior and accuracy characteristics of the algorithmare proven by a spectral decomposition method.

在前人工作的基础上，提出了一种新的用于解决结构动力分析问题的时间积分方法——Taylor级数方法；建立了求解线性问题和非线性项可以表示为多元多项式形式的非线性问题的Taylor级数方法的理论，并给出递归求解通式；阐述了该方法的程序实施过程，给出了计算流程图，并在非线性有限元分析平台NFAP中嵌入了Taylor级数方法的计算模块；利用谱分解的方法分析了该方法的稳定性和精度特性，以封闭的解析形式给出了描述积分法特性的周期延长率和振幅衰减率的表达式；通过对该方法的理论分析和特性研究，阐述了该方法的可行性和高效性。

The following are the major work in this thesis which has been studied and still needs to be studied further in the future: 1 An improved adjoint variational method is developed, thus it can be applied to the LAGFD-WAM Wave Numerical Model for data assimilation; 2 A linear evolution equation of spectral perturbation is derived in order to analyze its increasing or decreasing mechanism.

本论文主要完成了以下几个方面的研究： 1）建立了推广形式的共轭变分同化方法，使之能够应用于LAGFD-WAM海浪数值模式； 2）导出了扰动谱线性演化方程，分析了扰动谱增长、衰减机制，考察了涌浪情况下扰动谱的持续时效问题及风浪情况下扰动的演变过程； 3）利用波谱共轭方程初步分析了同化模型中距离泛函的敏感性及敏感区域空间分布； 4）将推广的共轭变分方法应用于海浪谱能量平衡方程，建立了连续形式的海浪同化模型，特别是严格导出了风输入、破碎、底摩擦、波波非线性相互作用和波流相互作用各源函数的共轭源函数表示式； 5）分别进行了波谱层次上和有效波高层次上的同化试验，并对数值结果进行了分析。

X-ray tube spectrum model;spectrum reconstruction;attenuation data

X射线球管光谱模型；光谱重建；衰减数据

A physical meaningful seven-parameter X-ray tube spectrum model is firstly established. Then model parameters are calculated from attenuation data so that X-ray tube spectra can be reconstructed.

该方法首先建立一个具有物理意义的7参数球管光谱模型，再通过测量的光谱衰减数据求解模型参数，进而重建光谱。

Based on the research on the scattering of the Gaussian beam from single sphere, the intensity distributions of LGB beam in different propagation distance is analyzed. Without considering the relationship of scattering and phase shift, the beam coefficients is gained by the solution of scattering cross section, and the LGB is expanded in terms of the vector spherical harmonics as fundamental Gaussian beam. The scattering of the beam with orbital angular momentum from single sphere located on the propagation axis is studied.

在单体球粒子对高斯光束散射研究的基础上，分析了在自由空间不同传输距离LGB光束的光强分布情况，在不考虑散射和波束相移关系的情况下，将LGB作为入射高斯光束，通过对波束入射时的散射衰减截面求解得到波束因子，利用矢量球谐函数对入射高斯波束进行展开，从而研究了单球粒子在在轴条件下对具轨道角动量高斯波束入射的散射问题。

Finally, a design example of optical system used for smog attenuation testing system is given to illustrate the effect of spherical aberration on the image beam waist.

最后通过激光羽烟衰减测试系统中聚光光学系统的设计实例说明了球差对高斯光束像方束腰的影响。

With the theoretical model of spherical grain dynamics of sparse two-phase flow in single dimension, computing formulas of velocity′s attenuation and scattering distance were built for explosive residue grains in horizontal. Then, a simplified theoretical model on distribution of explosive residue was put forward on the basis of a spherical space with radius equalling to maximum horizontal scattering distance of explosive residue grains with certain diameter.

为了对残留物颗粒的飞散运动及分布规律进行理论分析，利用球形颗粒一维稀疏二相流动力学模型，研究得到炸药残留物颗粒的速度衰减及水平飞散距离计算公式；在此基础上，建立了以某粒径残留物颗粒水平运动极限距离为半径的炸药残留物颗粒球面空间分布简化理论模型。

Some methods to reduce capacity fade and the development of the spinel Li-Mn-0 are proposed.

提出了减少容量衰减的几种方法，并对尖晶石Li-Mn-O的发展作出展望。

Furthermore, the parameters of the pulse stacker, such as attenuation and time delay, etc, were worked out.

在此基础上，计算获得了脉冲堆积器的衰减系数、延时等控制参数。

On the other hand, the more important thing is because the urban housing is a kind of heterogeneity products.

另一方面，更重要的是由于城市住房是一种异质性产品。

Climate histogram is the fall that collects place measure calm value, cent serves as cross axle for a few equal interval, the area that the frequency that the value appears according to place is accumulated and becomes will be determined inside each interval, discharge the graph that rise with post, also be called histogram.

气候直方图是将所收集的降水量测定值，分为几个相等的区间作为横轴，并将各区间内所测定值依所出现的次数累积而成的面积，用柱子排起来的图形，也叫做柱状图。