Comparison of the solutions from a novel variational method with numerical results for the study of beam propagation in a Kerr medium with nonlinear absorption

We present results from a novel variational method for the study of beam propagation in a Kerr medium with nonlinear absorption. This new method combines the variational method and a nonlinear absorption equation and gives a concise expression for the combination. The results obtained with this method show good quantitative agreement with numerical solutions obtained with the finite-difference method. It is shown that the variational method takes much less time than a numerical simulation with the finite-difference method for analysis of beam propagation in a thick medium with nonlinear absorption and nonlinear refraction. The new method makes detailed analysis of beam propagation in a Kerr medium with nonlinear absorption very simple and fast.     

Computational comparison of the conventional multislice method and the real space multislice method for simulating exit wavefunctions

The simulation of exit wavefunctions of a TEM sample is carried out by both the conventional multislice (C-MS) method and the real space multislice (RS–MS) method, with a series of different slice thicknesses. Surprisingly, the results calculated by the RS–MS method remain constant to seven significant figures when the slice thicknesses are changed within a wide range, while those calculated by the C-MS method change significantly. From the mathematical point of view, the C-MS method is only a first order approximation of the RS–MS method. Thus, the calculation precision of the RS–MS method is much higher than that of the C-MS method. Or to achieve the same precision, the slice thickness for the RS–MS method can be taken as two orders of magnitude larger than for the C-MS method in the simulation. As a result, the calculation speed for the RS–MS method may be even faster than that for the C-MS method in some cases. For the two advantages stated above, the RS–MS method may be more suitable for precise calculations.     

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。     

Quasi-geometrical optics methods in the theory of wave propagation through a randomly inhomogeneous layer

Some possibilities of using asymptotic methods, such as the Maslov method and the interference-integral method, in problems of wave propagation in randomly inhomogeneous media are considered. It is shown that using the Maslov method and the interference-integral method in a small-angle approximation, and neglecting amplitude fluctuations of partial waves, provides results of heuristic spectral methods that utilize expansions in terms of incoming or outgoing waves. The combined use of these asymptotic methods gives a third heuristic method, a mixed-integral representation obtained earlier by applying the method of two-scale expansions. It is pointed out that results of a mixed-integral representation change to those of the method of smooth disturbances and of the phase-screen method. Unlike the method of two-scale expansions, the proposed approach based on the combined use of asymptotic methods facilitates the process of taking into account the heterogeneity of a background medium.     

Full-Field Determination of Principal-Stress Directions Using Photoelasticity with Plane-Polarized RGB Lights

In this paper, we propose a new three-wavelength method for automatic measurement of principal-stress directions over an entire model on the basis of four-step phase shift method. This method uses four fringe patterns captured by a color charge-coupled devices (CCD) camera corresponding to four angular position arrangements of polaroids in a dark-field plane polariscope. The principal-stress directions can be determined by a single calculation. The method is applied to a circular disc under compression. The principal-stress direction distributions obtained from the proposed method are compared with those obtained from a conventional method and theory. It can be obviously seen that the proposed method accurately yields the principal-stress directions compared with the conventional method.     

HL-RBWO-冷腔特性的一种快速算法

 在传统谐振法基础上发展了一种计算慢性结构（SWS）冷腔参数的脉冲响应法，它的主要思想是利用有丰富谐波成分的窄脉冲作为激励源来代替实验系统中的扫频源，从而使得获取RBWO的色散曲线速度大大加快。这种方法使得脉冲响应法成为计算SWS冷腔参数的一种快速数值算法，更加适合于数值计算，并在研究HL-RBWO时得到有效的应用。     

光催化材料反应系数测量新方法

本文提出光催化材料反应系数测量新方法-Mass transfer based(MTB)方法,该方法不同于传统方法中忽略传质影响,而是通过CFD计算考虑传质影响,这种改进无需传统方法所需反应控制过程也可准确测量光催化材料反应系数。利用该方法测量了光催化材料降解甲醛的反应系数,实验验证了其可行性。     

一类延迟混沌系统沿主轴方向上Lyapunov指数的计算方法

提出了一种计算延迟混沌系统沿主轴方向上Lyapunov指数的方法：矩阵迭代法.给出了其计算方法的原理及推导过程;同时推导了一类泰勒展开法,介绍了已有的Wolf替代法计算延迟混沌系统的Lyapunov指数.分析了三种不同计算方法的优缺点,最后进行了数值模拟,验证方法的有效性. 关键词： Lyapunov指数 延迟混沌系统 矩阵迭代法 泰勒展开法     

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.     

一步法设计单色仪凹面全息光栅

凹面全息光栅是光谱分析仪器的核心器件之一,其成像质量直接决定了光谱分析仪器的分辨本领。利用光程函数理论设计凹面全息光栅是一个繁琐的求解非线性方程组的过程,该过程分两步进行,每步需要求解四个非线性方程。分两步求解不但过程麻烦,还不可避免地引入了取舍误差,降低了最优参数的精度。为了解决该问题,本文提出了一种设计单色仪凹面全息光栅的新方法——一步法,该方法不但可以简化求解过程、降低最优参数的误差,还可以方便地控制整体像差的变化趋势。采用有较强全局搜索能力的遗传算法求解该方法中非线性方程的极值问题,并与传统的方法对比验证了该方法的可行性和正确性,结果表明,一步法不但在方法上比两步法简便,其设计结果还优于两步法。     

蒙特卡洛模拟漫辐射时两种确定表面发射方向方法的比较

介绍一种有效的确定能束发射方向的方法——切球法.分析传统方法和切球法确定发射方向的原理及实施过程,说明切球法更为方便.采用2种方法对一简单的几何模型的角系数进行蒙特卡洛计算,所得结果与文献中积分结果进行比较,说明了切球法的可行性,计算精度能满足工程要求.同时对2种方法的计算耗时进行比较,切球法可以节省计算时间.将切球法应用到复杂系统中其优越性将会得到更加充分体现.     

基于相对微分计盒法的人造目标分形检测

对光电目标进行自动检测与识别是导弹末端智能制导的一项关键技术。基于图像分形维计算的相对微分计盒法,提出了一套实用的自然背景中人造目标的检测方法,给出了检测窗口与尺度选择的标准与参考值。大量实验证明,分形检测方法比传统的最大对比度检测方法稳定,是一种非常有前途的方法。     

复化辛普森法和傅里叶法在衍射计算上的比较

通过快速傅里叶变换(FFT)法和复化辛普森法对衍射的数值进行计算,可以看出快速傅里叶变换法是一种积分变换法,而复化辛普森法则是迭代相加的方法.通过计算得出了FFT法的计算速度高于复化辛普森法,计算精度则远低于复化辛普森法;复化辛普森法适合近距离菲涅尔衍射和近场衍射,而FFT法不适合.     

Calculation of group velocity dispersion of hybrid modes in Bragg fibers using a modified linear combination method

A calculation method is presented for the group velocity dispersion of hybrid modes in Bragg fibers. The method is obtained by extending a linear combination approximation of TE and TM modes in an asymptotic expansion method, and its equation can be solved using the Ferrari method. Numerical results were compared by those of a multilayer division method having higher accuracy than the present method. It was confirmed that both linear combination approximation and modified linear combination method can be precisely used above a cladding index difference of ≈1.0 for HE and EH modes.     

Vibro-acoustic analysis of complex systems

A general method is presented for predicting the ensemble average steady-state response of complex vibro-acoustic systems that contain subsystems with uncertain, or random, properties. The method combines deterministic and statistical techniques to produce a non-iterative hybrid method that incorporates equations of dynamic equilibrium and power balance. The method is derived explicitly without reference to statistical energy analysis (SEA); however, it is seen that the wave approach to SEA can be viewed as a special case of the proposed method. The proposed method provides a flexible way to account for necessary deterministic details in a vibro-acoustic analysis without requiring that an entire system be modeled deterministically. The method therefore provides a potential solution to the mid-frequency problem (in which a system is neither entirely deterministic nor entirely statistical). The application of the method is illustrated with a numerical validation example.     

微波器件微放电阈值计算的快速单粒子蒙特卡罗方法

为了计算微波器件的微放电阈值,提出了一种快速单粒子蒙特卡罗方法.该方法对二次电子出射能量、出射角度和相位等参数进行随机处理,结合四阶龙格库塔法和Furman模型模拟了电子运动和二次电子发射系数,并以多次连续碰撞的二次电子发射系数的算数平均值作为微放电效应发生的判据.以平板传输线横电磁模式为研究对象,分别采用快速单粒子蒙特卡罗方法、统计模型、传统蒙特卡罗方法以及粒子模拟方法计算其微放电阈值和敏感区域.计算结果表明,该方法不仅具有与统计模型和粒子模拟方法相当的计算精度,而且比统计模型方法的适应性更强,比传统蒙特卡罗方法的稳定性更好,比粒子模拟方法的计算效率高几十倍以上.     

罗替戈汀微球体外释放度的检查方法

分别采用摇床法和流通池法测定罗替戈汀微球的体外释放度,并通过与体内药动学曲线拟合进行选择.结果表明,摇床法和流通池法测定的体外释放度均与体内吸收具有明显相关性,相关系数r分别为0.9937和0.9978,且流通池法可检测到微球存在的较小突释.摇床法和流通池法均可用于罗替戈汀微球的体外释放度检查,流通池法作为一种新型溶出...     

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.     

泄漏波导法精确测量薄膜参数的理论和实验研究

对泄漏波导法测量薄膜折射率和厚度的实验方法做了介绍,基于四层介质结构的理论模型,通过严格的电磁场理论推导出了测量方法依据的本征色散方程,并使用了Newton-Raphson方法求解复传播常数,保证了测量的精确与快捷.以等离子增强化学气相沉积法生长的SiO2薄膜为例,对其折射率和厚度进行了测定.实验证明,本文方法与传统方法相比,不仅具有更高的测量精度,而且数据处理更加快捷,完成一片样品测试,仅花费机时60 ms.     

Eigenmode analysis of arbitrarily shaped two-dimensional cavities by the method of point-matching

In the proposed method, as in the boundary element method (BEM), a field problem is solved on its boundary along which nodes are distributed. The distinct feature of the proposed method is related to the fact that no interpolation functions between the nodes are required, so that the basic collocation method is employed to satisfy a given boundary condition. This approach reduces a large amount of numerical calculation induced due to the interpolation functions. Unlike the method of auxiliary sources (MAS), in the proposed method only the regular functions that have finite functional values everywhere including the origins are employed as basis functions. As a result, the proposed method does not need the auxiliary surface, the construction of which is a troublesome work because its form, dimension, shifting, etc. strongly influence the accuracy of the MAS. The eigenvalues calculated by the proposed method rapidly converge to the exact values thanks to the simplicity of the method. Moreover, the method gives mode shapes successfully without using the interpolation functions between the nodes. The efficiency and accuracy of the method are verified through several applications.