Calculation of Fourier coefficients of a function given at a set of arbitrary points

A numerical method is presented for the calculation of Fourier coefficients of a function which is given at a discrete set of arbitrary points. The function is approximated by a sum of Cheby?shev polynomials. This is performed by Clenshaw's method of curve fitting, which is a least-squares method. The Cheby?shev coefficients are then used to construct linear combinations of Bessel functions, which are very good approximations of the Fourier coefficients.     

A Stochastic Method of Allocation of Components to Maximize Reliability

The purpose of this paper is to present a method of implicit enumeration that can be used in reliability problems to maximize system reliability subject to cost constraints. The method is based on a stochastic approach in which probability distributions are attached to families of allocations. Probability distributions permit the experienced scheduler to apply his experience as well as factors which are not taken directly into account by the mathematical form of the problem. This feature together with getting near-optimal solutions are its principal features. When compared to other methods, speed is gained because the cost projection part of the method deals with functions of random variables rather than methods such as linear programming. The method is presented for systems in which all components are in series.     

多端口网络噪声系数测试方法

将多端口网络某端口噪声系数的定义推广到非等噪声输入情形,并提出了两种多端口网络噪声系数测试方法。第一种方法方便快捷,只需测量任意一个端口的噪声系数即可得到多端口网络噪声系数。第二种方法不包含系统误差,但测试工作量及计算量较大。分别给出了两种测试方法的测量实例,并对两者的结果进行了比较,两者结果在误差范围内完全一致。第二种方法关于输入噪声功率的计算结果表明,第一种方法的系统误差可以忽略。该测试方法不仅适用于等增益网络,也适用于非等增益网络,文中给出了非等增益网络的测量实例。该测试方法可广泛应用于相控阵雷达所用T/R组件等多端口网络噪声系数的测试。     

雷达辐射源信号识别效能评估的I2TOPSIS方法

针对雷达辐射源信号识别效能评估方法杂乱,指标模糊等问题,提出一种基于I2TOPSIS雷达辐射源信号识别效能评估方法。该方法主要在以下三点对传统区间TOPSIS方法进行改进:利用熵值计算指标权值;利用理论极值确定正负理想点;利用区间距离计算评估方案到正负理想点的距离,并将I2TOPSIS方法应用于雷达辐射源信号识别效能评估中得到一种新的雷达辐射源信号识别效能评估方法。最后通过与传统区间TOPSIS方法的评估对比实验证明新方法所得结果更合理、可行。      

Characteristics of Photorelaxation in Vascular Smooth Muscle: Evidence Supporting the Hypothesis of Drug-Receptor Equilibrium Disturbance

The affinity of norepinephrine for the ?-adrenergic receptor in rabbit thoracic aorta is determined by three different methods. The first method assumes that the effect is directly proportional to receptor occupancy from which affinity is computed from the A50. The second method is a null method and employs a prior partial blockade, assuming only that equal effects imply equal receptor occupancy without making the direct proportion assumption. The third method is a new ``relaxation' method in which the equilibrium is upset by a transient perturbation with UV radiation, and the kinetics of the restoration process are analyzed, from which not only affinity, but both forward and reverse rate constants are determined. Affinity constants determined by the ``null' and ``relaxation' methods are in agreement, while the affinity constant determined by A50 is low. The nature of the photo-induced relaxation is discussed along with the basis for extending the relaxation method to other drug-effector combinations.     

Approximate Time-Variable Coherence Analysis of Multichannel Signals

We present a new method for signal extraction from noisy multichannel epileptic seizure onset EEG signals. These signals are non-stationary which makes time-invariant filtering unsuitable. The new method assumes a signal model and performs denoising by filtering the signal of each channel using a time-variable filter which is an estimate of the Wiener filter. The approximate Wiener filters are obtained using the time-frequency coherence functions between all channel pairs, and a fix-point algorithm. We estimate the coherence functions using the multiple window method, after which the fix-point algorithm is applied. Simulations indicate that this method improves upon its restriction to assumed stationary signals for realistically non-stationary data, in terms of mean square error, and we show that it can also be used for time-frequency representation of noisy multichannel signals. The method was applied to two epileptic seizure onset signals, and it turned out that the most informative output of the method are the filters themselves studied in the time-frequency domain. They seem to reveal hidden features of the epileptic signal which are otherwise invisible. This algorithm can be used as preprocessing for seizure onset EEG signals prior to time-frequency representation and manual or algorithmic pattern classification.     

Content-Driven Progressive Transmission of Grey-Scale Images

A lossless progressive transmission method for grey-scale images which concentrates early transmission efforts on areas of greater image information content is described. The receiver does not have a priori knowledge of which image areas are to receive preferential treatment, and the preferential level of resolution is the pixel. The method makes use of simultaneous geometric and information content decompositions. The method is computationally simple with a complexity which grows linearly with the number of pixels. Compression achieved approaches that obtained by nonprogressive lossless methods, and is approximately the same as for homogeneous progressive lossless methods. Extensions of the method for progressive transmission with limited distortion and greater compression are also discussed.     

利用IDFT技术实现天线的时域近场测量

本文提出了一种利用离散付立叶反变换(IDFT)技术完成天线的时域近场测量的方法.首先依据付立叶变换理论论证了这种方法的可行性,用典型算例证明了该方法的有效性和正确性,同时对实现这种测试方法可能引入的误差进行了分析,随后提出了应用该方法完成测试时关键技术参数确定的原则,讨论了用该方法测试所获得的实验结果,得出了结论.     

分布参数系统辨识的小波谱方法

本文克服了用不完全可微的小波函数进行导数变换和乘积变换的困难,构造了用于处理分布参数系统问题的小波谱方法,该方法具有良好的收敛性和乘法自适应性.基于该谱方法,文中讨论了分布参数系统的辨识问题,提出了分布参数系统辨识的小波谱方法,算例分析表明了该方法的有效性.     

Minimax Optimization of Networks by Grazer Search

A new optimization method called grazer search has been developed. This method is suitable for nonlinear minimax optimization of network and system responses. A linear programming problem using gradient information of one or more highest ripples in the response error function to produce a downhill direction followed by a linear search to find a minimum in that direction is central to the algorithm. Unlike the razor search method due to Bandler and Macdonald, the present method overcomes the problem of discontinuous derivatives characteristic of minimax objectives without using random moves. It can fully exploit the advantages of the adjoint network method of evaluating partial derivatives of the response function with respect to the variable parameters. Sufficient details are given to enable the grazer search method to be readily programmed and used. Although the method is intended for the computer-aided solution of an extremely wide range of design problems, it is largely compared with other methods on microwave network design problems, for which the solutions are known. Its reliability and efficiency on more arbitrary problems, examples of which are also included, is thereby established.     

The secrets to the success of the rush-larsen method and its generalizations

One of the most popular methods for solving the ordinary differential equations (ODEs) that describe the dynamic behavior of myocardial cell models is known as the Rush-Larsen (RL) method. Its popularity stems from its improved stability over integrators such as the forward Euler (FE) method along with its easy implementation. The RL method partitions the ODEs into two sets: one for the gating variables, which are treated by an exponential integrator, and another for the remaining equations, which are treated by the FE method. The success of the RL method can be understood in terms of its relatively good stability when treating the gating variables. However, this feature would not be expected to be of benefit on cell models for which the stiffness is not captured by the gating equations. We demonstrate that this is indeed the case on a number of stiff cell models. We further propose a new partitioned method based on the combination of a first-order generalization of the RL method with the FE method. This new method leads to simulations of stiff cell models that are often one or two orders of magnitude faster than the original RL method.     

W波段交错双栅色散测量与比较

采用谐振法,基于小孔耦合设计了W波段矩形槽交错双栅色散测试方案。考虑了倒圆角带来的影响,采用精密计算机数控技术(CNC)工艺加工慢波结构进行测试,获得了辨识较高的谐振峰,得到了0-p 相移范围内所有对应的本征谐振点。基于小孔耦合谐振法的仿真值与严格谐振法、准周期法的仿真值相比最大偏差0.1%,证明了色散测试方案的合理性。基于小孔耦合谐振法的实测值与仿真值相比最大偏差0.3491%,充分说明慢波结构的加工精度满足工程应用需求,这些结果为深入开展下一步试验打下良好基础。     

Application of web-spline method in electromagnetics

The finite element method, which uses weighted extended basis splines (web-splines) for solving two-dimensional electromagnetic wave equations, has been studied. The web-spline method, which does not need any mesh generation, is implemented easily. The web-spline method is more accurate numerical technique than the standard finite-element method. This new approach is applied to two-dimensional wave equations. The approximated solutions are compared with the literature. Using web-splines, more accurate results are obtained with fewer nodes.     

蝶形微带天线的全波分析与宽带设计

介绍了蝶形微带贴片天线的一种全波分析方法－矩量法,与多端网络法相比,其适应范围更广。然后介绍了展宽天线频带的一种设计方法。通过不对称馈电方式,激励起两个相近频率的模式,从而使微带天线驻波比带宽获得明显展宽。测试结果与计算结果相当吻合,证实了数值分析与设计方法的有效性。     

Desegmentation Method for Analysis of Two-Dimensional Microwave Circuits

A new method for the analysis of two-dimensional planar circuits called the "desegmentation" method is proposed. This method is applicable to configurations which can be converted into regular shapes (for which Green's functions are known) by adding one or more regular shaped segments to them. Two examples of planar circuits, chosen such that the results could be verified by the previously known segmentation technique, illustrate the validity of the method.     

射频吸波材料波导测试法装置的仿真分析

射频吸波材料在电磁兼容(EMC)领域有着广泛的应用,密闭波导测试法是吸波材料性能测试的重要手段,适用于500MHz-1GHz频率范围,具有所需试样数目较少的优点.本文介绍了波导法的基本原理和实验室设计完成的波导法装置结构,并对影响波导法装置性能的因素进行仿真分析,在分析的基础上优化结构设计.     

A new hierarchical belief-rule-based method for reliability evaluation of wireless sensor network

With the wide applications of wireless sensor network (WSN), its reliability evaluation has been attracted more attention. The reliability of a WSN is affected mainly by internal and external factors, which include internal faults and external attacks. In this paper, a reliability evaluation method based on a hierarchical belief rule base (BRB) method is proposed for the reliability evaluation of the WSN. First, the factors affecting the reliability of a WSN are analysed, and the reliability evaluation process that considers the WSN fault evaluation and WSN security evaluation is described. Second, the reliability evaluation model is constructed based on the hierarchical BRB model. The qualitative knowledge is used by the BRB model to build initial belief rules, and the quantitative data are used to optimize the initial parameters of the BRB model, which can utilize various types of uncertainty information effectively. Therefore, the proposed method can be applied to the WSN reliability evaluation, which is a complex and uncertain problem. Finally, a simulation case study and an actual case study of wellhead blowout monitoring are conducted to verify the effectiveness of the proposed method. The reliability results of actual WSN are obtained by the standard testing method, where the loss and accuracy rates of the collected data are treated as the observation factors for obtaining the actual reliability values. The estimated results of hierarchical BRB model are very close to the actual reliability values, which shows that the proposed method can be used for evaluating the reliability of the actual WSN accurately.     

Surface integral equation method for the analysis of an obliquelystratified half-space

The radiation of a source in the presence of an obliquely stratified half-space is studied using the surface integral equation method. A generalized extinction theorem for the obliquely stratified half-space problem is derived, which gives eight surface integral equations for the fields. The Green's functions for the stratified media are found by a semianalytical method. These surface integral equations can be used to solve the rather complicated two-dimensional problem by the one-dimensional finite element method (FEM), which saves computer memory and computation time compared to the conventional two-dimensional FEM. for some special cases, the results obtained by this method are compared with those obtained by the numerical mode matching method and the Fourier integral technique. Excellent agreement has been observed between them. This method is general for any obliquely stratified half-space with arbitrarily many layers in each region     

基于模式识别进行模拟电路故障诊断的方法

本文运用故障树分析法对模拟电路进行分析，按照电路结构对其按树枝形逐级划分建立故障集；将模式识别理论中的隶属函数法以及近邻法推广到可以进行模拟电路的故障诊断．讨论了该方法的原理以及建立字典进行诊断的方法，并给出了仿真实例。     

一类密钥流生成器的相关分析

多输出逻辑函数是构造密码系统的重要工具,相关免疫性是设计安全逻辑函数的重要准则。该文利用一种较为简单的方法证明了多输出逻辑函数相关免疫性两种刻划的等价性。还对一类利用多输出逻辑函数相关免疫函数构造的密钥流生成器进行了相关性分析,证明了这种构造方法是不成立的,并不能达到构造者期望的相关免疫性,并且分别利用Walsh变换技术和线性序列电路逼近方法找出了这类密钥流生成器的漏洞,从而说明这类生成器在相关攻击下是脆弱的。