“电工学”课程的PBL教学模式初探

基于问题式学习PBL是一种以自主学习为特色的教学模式.本文详细论述了在"电工学"课程中进行PBL模式教学改革的实施方法与过程,并结合实践经验和学生的反馈意见,提出了发挥PBL教学模式特色的教学理论和实践框架.笔者还对PBL模式与国内传统教学模式的优势与不足进行比较,就如何使PBL模式适应中国教育体制和传统教育理念提出了建议.     

数字阵雷达天线波瓣图测试方法与试验验证

针对固定式相控阵雷达在中场法或远场法中不能实时得到天线波瓣图的问题,提出了采用扫描波瓣图替代天线波瓣图进行天线测试的方法。从理论上分别推导了和波束与差波束扫描波瓣图和天线波瓣图的解析式,研究了单元波瓣图对扫描波瓣图和天线波瓣图的影响,指出了在单元波瓣主瓣范围内扫描波瓣图和天线波瓣图近似等价。仿真和试验结果 均表明:扫描波瓣图和天线波瓣图在各项性能指标上都是等价的,可用于指导雷达总体依据扫描波瓣图对天线进行验收。     

Difference pattern synthesis in small planar phased arrays

A pattern synthesis technique for low sidelobe arbitrarily scanned difference beams in small planar phased arrays is presented. The approach is based on adaptive array theory and is the development of a technique used for radiation pattern synthesis in linear arrays. The method has been applied to measured element pattern data from a small planar array, which includes the effects of pattern corruption by mutual coupling. The successful synthesis of low sidelobe difference beams is demonstrated, with arbitrary difference plane and scan angle     

期望主瓣响应下任意阵方向图综合方法

为实现任意阵列天线的方向图综合,特别是考虑到不同空间指向对阵列方向图的影响,提出自适应原理与凸优化理论相结合的方向图综合法.该方法首先利用自适应原理综合法得到所需阵列方向图的旁瓣特性;而后,选择零度角的方向图主瓣作为期望主瓣;最后,在该期望主瓣响应下,将阵列方向图综合问题转化为二阶锥规划问题.采用凸优化循环迭代算法,完成对非凸优化问题的求解,从而保证方向图在满足期望主瓣响应的同时,使旁瓣特性与自适应方向图综合方法得到的结果最接近.理论分析与仿真结果表明,综合后阵列方向图在不同空间指向上具有与期望主瓣一致的主瓣特性,且其旁瓣也能够很好地保持对动态干扰的抑制特性.     

浅谈粗糙集理论及其应用进展

粗糙集理论是一种新型的处理模糊和不确定知识的数学工具。目前已在人工智能、知识与数据发现、模式识别与分类、故障检测等方面得到了广泛应用。首先描述了粗糙集的基本算法及其复杂度，包括等价关系，上下近似及约简算法；然后对粗糙集在一些领域中的应用进展情况进行了论述，例如模式识别与人工神经元网络等，最后给出了建议的研究方向。     

An aperture-matched compact range feed horn design

The moment method and the uniform geometrical theory of diffraction are used to obtain two separate solutions for theE-plane far field pattern of an aperture-matched horn antenna. This particular horn antenna consists of a standard pyramidal horn with the following modifications: a rolled edge section attached to the aperture edges and a curved throat section. The resulting geometry provides significantly better performance in terms of the pattern, impedance, and frequency characteristics than normally obtainable. The moment method is used to calculate theE-plane pattern and voltage standing-wave ratio (VSWR) of the antenna. However, at higher frequencies, the moment method requires large amounts of computation time. On the other hand, the uniform geometrical theory of diffraction provides a quick and efficient high frequency solution for theE-plane field pattern. In fact, the uniform geometrical theory of diffraction may be used to initially design the antenna; then the moment method may be applied to "fine tune" it. In both methods, a two-dimensionalE-plane model of the antenna is used, but these two-dimensional solutions yield excellent agreement with measured data of the actual three-dimensional antenna. This procedure has been successfully applied to design a compact range feed horn.     

Matrix feed designed from coupled dielectric waveguides

A periodic structure designed from unequal coupled dielectric waveguides is analyzed in the approximation of the theory of coupled waves. For an infinite periodic structure formed from infinite waveguides, a boundary-value problem for structure eigenmodes is formulated. The solution to the boundary-value problem is used to find eigenmode parameters and parameters used in the theory of coupled waves. A periodic structured formed from waveguides with a finite length, which are excited by the wave of one of these waveguides, is analyzed. The amplitude-and-phase distribution in the channels of the periodic array is determined and used for calculation (in the approximation of physical optics) of the structure’s radiation pattern. It is shown that, in the case of correct selection of the structure parameters, its radiation pattern may be close to a sector-shaped pattern.     

OFDM系统智能天线设计中的波束综合算法

基于自适应天线阵列理论。提出了一种新的可以应用于任意类型天线阵列的波束综合算法。根据与给定的参考波束的误差。引入虚拟干扰的概念，对目标波束图形状进行调整。应用本文提出的新算法，在主瓣和旁瓣位置都可以对波束进行有效的调节。最终获得阵列的最优权矢量，能够最小化目标波束图与参考波束图间的差异。理论分析与仿真结果表明与现有的同类算法相比，本算法能更有效地获得与参考波束基本相符的波束。在设计应用于OFDM智能天线系统时，通过对不同子载波频率上信号进行单独处理，利用该算法．进行波束综合，能够在整个有效频段，所有子载波上获得基本一致的阵列输出。     

具有领域独立性的通用模式识别方法的研究

统计方法是当前广泛采用的模式识别方法，但是这种方法的专业性较强，缺乏通用性。针对这种现状文章提出了基于结构模式识别理论的一种通用模式识别方法，该方法使用一系列结构检测子来提取信号特征．具有领域独立性。设计了对比实验，通过同传统的统计模式识别方法的比较验证了通用模式识别方法的有效性．通过两个不同领域的模式识别问题验证了该方法的领域独立性和有效性。     

一种基于模式的应用网关设计

分析了航空电信网(ATN)用于航空的数字通信网络以及协议CNS/ATM系统中通信网关的功能和应用,并简要介绍了网关及其模式化过程。在应用网关的设计中,引入模式设计的思想,给出了一种维护性、可靠性高的设计方式,提出了基于软件模式的应用以及网关的体系架构,并给出了几种关键模式的原理和具体应用,分析了应用的效果以及优点。     

Pattern recognition using a family of design algorithms based uponthe generalized probabilistic descent method

This paper provides a comprehensive introduction to a novel approach to pattern recognition which is based on the generalized probabilistic descent method (GPD) and its related design algorithms. The paper contains a survey of recent recognizer design techniques, the formulation of GPD, the concept of minimum classification error learning that is closely related to the GPD formalization, a relational analysis between GPD and other important design methods, and various embodiments of GPD-based design, including segmental-GPD, minimum spotting error training, discriminative utterance verification, and discriminative feature extraction. GPD development has its origins in basic pattern recognition and Bayes decision theory. It represents a simple but careful re-investigation of the classical theory and successfully leads to an innovative framework. For clarity of presentation, detailed discussions about its embodiments are provided for examples of speech pattern recognition tasks that use a distance-based classifier. Experimental results in speech pattern recognition tasks clearly demonstrate the remarkable utility of the family of GPD-based design algorithms     

Some Applications of Pattern Recognition to Oil And Gas Exploration

The application of pattern recognition to oil and gas prospection is very recent, and results are still sparse. This paper presents an introduction to pattern recognition, a summary of previous applications in seismic processing, and several new pattern recognition approaches. Topics discussed include impluse recognition, horizon correlation, determination of the boundaries and nature of a reservoir, and two-dimensional Fourier (f-k) filtering to attenuate ground roll. To conclude, we examine the outlook for pattern recognition and propose increased use of the theory of fuzzy sets for pattern recognition applications in oil and gas exploration.     

Second-Harmonic Effects in Tuned Reflectometers (Correspondence)

The theory of operation of the tuned microwave reflectometer has been well documented in the literature and its operating characteristics have been described in great detail. According to reflectometer theory, as a short slides in the output waveguide of a tuned reflectometer a pattern of detector response vs short displacement similar to that shown in Fig. 1 will be observed. The over-all slope of the pattern is due to attenuation in the output waveguide, while the regular variations are due to the less than ideal tuning of the reflectometer. In the practical operation of a reflectometer the pattern shown in Fig. 2 can be observed. Such a pattern obviously will result in errors in the determination of the magnitude and positions of maxima and minima. It is the purpose of this note to explain this pattern and the errors it can produce and to suggest a simple remedy.     

统计学习理论及支持向量机概述

针对传统统计模式识别理论中基于大数定理的假设，介绍了统计学习理论和以该理论为基础的支持向量机模式识别方法；指出了以结构风险最小化为原则的分类器设计方法。即同时兼顾分类能力最优化和经验风险最小化，支持向量机是统计学习理论的VC维理论和结构风险最小原理的具体实现。他通过非线性变换将输入空间变换到一个高维空间，然后在这个新空间中求取最优线性分类面。     

一种改进的支持向量机模式分类方法

支持向量机(Support Vector Machine,SVM)是在统计学习理论基础上发展起来的一种新的机器学习方法,已成为目前研究的热点,并在模式识别领域有了广泛的应用.首先分析了支持向量机原理,随后引入一种改进的径向基核函数,在此基础上,提出了一种改进核函数的SVM模式分类方法.与基于IRIS数据,进行了计算机仿真实验,与基干模糊k-近邻的模式分类仿真结果比较,结果表明改进的SVM方法分类性能比模糊k-近邻算法(Fuzzy k-Nearest Neighbor,FKNN)的分类性能更好,运算时间更短,更易于实时实现.     

汉字识别研究的回顾

本文回顾了汉字识别研究的历史。根据模仿人类视觉模型，基于文字图像的统计模式识别方法是文字识别取得瞩目进展的基础。模式识别信息熵理论揭示了模式分类的信息过程和理论极限，本文讨论了从汉字图像中提取特征以及文字识别分类器设计和学习的各种方法。介绍了文本识别必须解决的文字切分，版面分析、理解和重构，及提高识别性能等重点问题，最后，总结了文字识别研究的重要进展和对今后的展望。     

Further results on the information theory of deterministic functions and its application to pattern recognition

The author derived recently Shannon entropy and Renyi entropy for deterministic maps (different from the concepts which are utilized by physicists in the study of deterministic chaos) and his purpose herein is to extend the theory and to outline its prospects in pattern recognition. Entropies of random and of distributed functions are defined, and then entropic variance, divergence, mean square divergence and cross-entropic variance are obtained in quite a meaningful way. The results so obtained are used to derive identification criteria for pattern recognition, and an approach involving the local maximization of a multi-model landscape function is suggested. Basically, we are so dealing with an information theory without explicitly referring to probability.     

Out-of-Band Response of Reflector Antennas

The response of reflector antennas to out-of-band frequencies has been analyzed using physical optics. A simple approximate expression has been obtained for the effective aperture, and this expression yields both the receiving pattern and the frequency dependence of the on-axis gain. The theory has been compared with published out-of-band measurements, and the pattern agreement is good, but the measured gain falls below the theory. This discrepancy is caused by mismatch loss in the coax-to-waveguide adapter.     

阵列部分单元相位加权波瓣综合

从自适应信号处理的角度出发,描述了阵列天线部分单元仅相位加权波瓣综合方法,并通过计算实例验证了该方法的正确性。该方法可用在天线波瓣图中设置宽凹口以对付宽带宽角干扰,亦可用于机载雷达天线不对称波瓣赋形以抑制地海杂波等。部分单元相位加权波瓣综合方法比满阵单元相位加权波瓣综合方法更具有实现性和灵活性。     

Pattern synthesis in small phased arrays using adaptive arraytheory

A pattern synthesis technique for low sidelobe difference and scanned beams in small phased arrays is presented. The approach is based on adaptive array theory and is a development of a technique used for beam synthesis in an ideal, λ/2 spaced, isotropic array. The method has been applied to measured element pattern data from a five element linear array, which includes the effects of pattern corruption by mutual coupling. The successful synthesis of low sidelobe sum and difference beams are demonstrated, with the look direction on and scanned off boresight