电子枪发射系统的计算方法

提出一种混合计算方法,当电场精度较低时把电子的发射做为连续过程处理,当电场的精度较高时考虑电子发射的随机性.这种方法在保证计算准确性的前提下,较大程度地缩短了计算时间。     

混沌伪随机序列复杂度分析的符号动力学方法

通过将混沌伪随机序列看成一个符号序列，提出了用符号动力学的 方法来分析混沌伪随机序列的复杂度.以Logistic映射和耦合映射格子系统产生的混沌伪随 机序列为例，说明了该方法的应用，并将计算结果与近似熵ApEn法的计算结果作了比较.结 果表明，该方法可以有效地判断出不同的混沌伪随机序列的复杂程度，而且比近似熵法更为 优越. 关键词： 混沌 伪随机序列 符号动力学 熵     

非线性波动方程的新数值迭代方法

提出了一种新的求解非线性波动方程的数值迭代法,它是一种半解析的方法.与完全的数值计算方法扰法相比,它能够考虑各阶谐波的相互作用,且能够满足能量守恒定律.用它研究了非线性声波在液体中的传播性质,结果表明,在微扰法适用的声强范围内迭代法也适用,在微扰法不适用的一个较宽的声强范围内迭代法依然适用.     

非球面最适球面的确定方法——三点法

根据非球面生产的实际情况．指出非球面最适球面的确定方法．详细分析最适球面的计算方法．并对一抛物面进行了实例计算，通过与最小二乘法的计算结果比较．指出该方法具有计算简单、与加工工艺过程相符合等特点。     

An application of a transcorrelated procedure to the calculation of the energy of the hydrogen molecule

The ground-state energy of the hydrogen molecule is calculated using both the standard variational method and a new transcorrelated method. The value obtained with the new method compares favourably with that obtained by the standard method. If the method used in this paper can be extended to more complicated systems, it is expected that it will enable more accurate energies to be calculated for these systems than is possible using the standard variational method.     

An improved loopless mounting method for cryocrystallography

Based on a recent loopless mounting method, a simplified loopless and bufferless crystal mounting method is developed for macromolecular crystallography. This simplified crystal mounting system is composed of the following components: a home-made glass capillary, a brass seat for holding the glass capillary, a flow regulator, and a vacuum pump for evacuation. Compared with the currently prevalent loop mounting method, this simplified method has almost the same mounting procedure and thus is compatible with the current automated crystal mounting system. The advantages of this method include higher signal-to-noise ratio, more accurate measurement, more rapid flash cooling, less x-ray absorption and thus less radiation damage to the crystal. This method can be extended to the flash-freeing of a crystal without or with soaking it in a lower concentration of cryoprotectant, thus it may be the best option for data collection in the absence of suitable cryoprotectant. Therefore, it is suggested that this mounting method should be further improved and extensively applied to cryocrystallographic experiments.     

Large scale simulation of block copolymers with cell dynamics

Cell dynamics simulation (CDS) is a fast method to simulate kinetic processes in phase separating systems of large sizes. We review this method applied to block copolymer systems and illustrate it on a set of physical phenomena occurring in these systems. Achievements of CDS demonstrate, that the method can describe such complex phenomena rather well and therefore, is a complementary method to other more elaborate but slow techniques to which it can serve as a precursor.     

基于单曲面迭代计算的曲面透镜设计方法

为在平面上实现所需的照明,满足照明系统的要求,需要对光学系统进行二次设计。传统的设计方法往往用规则曲面指定透镜的一个表面,并以此为基础来设计另个一表面,这样会导致其表面形状复杂,不方便加工或装配。对此,提出了一种基于单曲面迭代计算的透镜曲面设计方法,即适当设计指定光线从透镜的一个表面到另一个表面的光路分布,再以此分别迭代计算透镜的各个表面。该设计方法采用两个自由曲面配合成曲面透镜,较以往的设计方法更加灵活、方便,设计得到的曲面镜头较以往更加简单光滑,便于加工和装配。结合一陈列灯镜头设计,给出了基于单曲面迭代计算的曲面透镜设计计算结果。     

Output functions and fractal dimensions in dynamical systems

We present a novel method for the calculation of the fractal dimension of boundaries in dynamical systems, which is in many cases many orders of magnitude more efficient than the uncertainty method. We call it the output function evaluation (OFE) method. We show analytically that the OFE method is much more efficient than the uncertainty method for boundaries with D<0.5, where D is the dimension of the intersection of the boundary with a one-dimensional manifold. We apply the OFE method to a scattering system, and compare it to the uncertainty method. We use the OFE method to study the behavior of the fractal dimension as the system's dynamics undergoes a topological transition.     

用图像数字化处理技术测试LED的光参数

由于LED的光比较微弱、体积小,所以在用常规的方法进行测试和使用较大的传感器时,容易产生较大的误差。为此,利用图像数字化处理技术及相应的装置对LED的配光曲线和光通量进行了测试,并介绍了它的基本原理和方法。     

机械刻划光栅的光线追迹方法

为了评价光栅的光谱质量,完成所设计光栅的光线追迹,针对机械刻划光栅的光线追迹提出了一种改进方法.在费马原理的基础上利用光程函数法得到入射光通过光栅后的光谱分布情况,再使用传输矩阵的计算方法构造出光谱的点列图.该方法适用于刻划在平面、球面和非球面基坯上的等间距和变间距光栅,光栅的光谱面可以为平面或者二次曲面. 通过刻划在非球面基坯上的凹面光栅验证了光线追迹方法的可靠性.     

采用相位法与极大值法测量超声波声速的准确度的研究

对极值法和相位法测量超声波声速的准确度问题进行了研究,实验与理论分析证明:相位法测量波长比极值法准确度要高.在与简谐运动有关的测量中,测量最大变化率点常常比测量最大值点的准确度要高,这在其他物理实验中也适用.     

利用强度周期性变化的光信号测量光速与介质的折射率

介绍了一种利用强度周期性变化的光信号来测量光速与介质折射率的方法,可以精确测量出光传播距离改变cm数量级时光传播时间的改变.如果在光路中放入介质,用这种方法可以很精确地测量出由此引入的光程差,并给出了一个测量介质折射率的新方法.     

“四色问题”研究

通过极大平面图的结构研究,提出了构造极大平面图的三种方法,即“加点法”、“删点法”与“任意法”.建立了一个理论系统,包括11个定义,12个命题及7个定理.采用“平行归纳法”证明了极大平面图可四着色,从而证明了“四色猜想”是对的.     

What is wrong with the projection operator method? removal of inconsistencies and a new self-consistent method for non-Markovian treatment of atom-field interactions

Summary In this paper it is pointed out, for the first time to the author's knowledge, that the application of the projection-operator method leads to the violation of a consistency condition if the so-called Born approximation is employed. Namely, the violation of this consistency condition causes the appearence of negative probabilities in the non-Markovian master equation and thus makes the applicability of the projection-operator method questionable. Further, it is shown that an additional Markov approximation re-establishes the applicability of the method. Moreover, a new self-consistent projection-operator method for treating non-Markovian time evolution in the case of interactions between atoms and field (reservoir) is developed. Finally, in the appendix it is shown that, if the usual non-self-consistent projection-operator method in the Born approximation is applied to the case of spontaneous emission from a two-level hydrogen atom, a negative probability for finding the atom in the excited state emerges. The author of this paper has agreed to not receive the proofs for correction.     

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.     

Estimating the amplitude of measurement noise present in chaotic time series

We propose a method for estimating the amplitude of measurement noise present in chaotic time series. This method is based on the evaluation of initial errors for a given time series and for a new one synthesized by adding an adequate amount of noise to the given one. The method is valid over a much wider range of noise levels than the previous methods are because it is not based on the detail of dynamical structure which generates the data. In addition, it is possible to check if the method is valid for the given data prior to its application. To confirm the effectiveness of the method we show the results of numerical experiments and apply the method to chaotic data obtained from an electrochemical experiment. (c) 1999 American Institute of Physics.     

改进的基于二维主分量分析的掌纹识别

主分量分析(PCA)是一种在众多生物特征识别中获得成功应用的特征提取技术,是一种基于二阶统计的在最小均方误差意义上的最优维数据压缩技术,它所提取的各特征分量之间是互不相关的。传统的PCA变换是对图像向量的分析,但向量维数一般都很高。二维主分量分析方法是最近兴起的针对图像矩阵的主分量分析方法,与一维主分量分析相比能更精确的计算原始数据的协方差矩阵。将其应用于掌纹识别,并在主分量的选取上加以改进,选取了更适合于分类的主分量。实验结果表明,该方法不仅有更高的识别率,而且维数更低。     

Stability Analysis and Order Improvement for Time Domain Differential Quadrature Method

The differential quadrature method has been widely used in scientific and engineering computation. However, for the basic characteristics of time domain differential quadrature method, such as numerical stability and calculation accuracy or order, it is still lack of systematic analysis conclusions. In this paper, according to the principle of differential quadrature method, it has been derived and proved that the weighting coefficients matrix of differential quadrature method meets the importantV-transformation feature. Through the equivalence of the differential quadrature method and the implicit Runge-Kutta method, it has been proved that the differential quadrature method is A-stable and $s$-stage $s$-order method. On this basis, in order to further improve the accuracy of the time domain differential quadrature method, a class of improved differential quadrature method of $s$-stage $2s$-order has been proposed by using undetermined coefficients method and Padéapproximations. The numerical results show that the proposed differential quadrature method is more precise than the traditional differential quadrature method.     

示波器测电容方法对比分析及数据处理

电容器的电容是电路的重要参数,如何精确测量是问题的关键。本文利用示波器测电容,通过几种方法对比分析及数据处理,给出最佳方案。