回路电流矩阵方程的一种直观列写方法

给出一种直观列写电路回路电流矩阵方程的方法,通过直观建立独立源,受控源和控制变量等向量的KCL、KVL方程,使回路电流方程直观写出。该法可适用于含有各类受控源的电路,进行矩阵运算便可得到的回路电流解向量和任意输出解向量。     

电网络的回路岔集分析法

本文定义了描述网络图回路与节点关联状况的矩阵D,定义了回路岔集和回路岔集矩阵。提出并证明了回路节点矩阵与节点矩阵的乘积等于回路岔集矩阵的定理。定义了回路岔集导纳矩阵,假设回路岔集电压矢量作为中间计算量,导出了回路岔集方程,并提出了对电网络的回路岔集分析法。     

线性有源网络的导纳矩阵分析

本文用节点法分析了含理想电压源的网络,从网络的不含源导纳矩阵获得了含源网络的约束导纳矩阵以及节点短路电流源向量的公式。对于运算放大器,借助逆传输表示,统一了运算放大器网络的约束导纳矩阵规则。     

多线圈耦合电路的回路分析

本文从互感支路的伏安关系出发,导出了多线圈耦合网络具有理想电流源支路时的回路方程。方程的个数为独立回路数减去理想电流源支路数。建立方程的工作量与不具有互感电路情况大致相等。与一般节点法相比,在建立方程中不必求电感支路的电感逆矩阵;与改进节点法相比,一般情况下,方程的个数要少。本文建立的方程特别适用于具有大量多线圈偶合网络的分析。     

开关电容网络（SCN）广义节点方程的直接形成

本文提出一种形态含独立电压源、ＶＣＶＳ、零极子、开关、电容的多相周期性ＳＣＮ广义节点议程的有效算法，该算法利用ＳＣＮ每个相位定义的两个向量，直接形成具有最低维数的ＳＣＮ广义节点方程的矩阵，而不需在高阶矩阵求逆后形成ＳＣＮ节点方程，或利用矩阵行列运算形成ＳＣＮ广义节点方程，具有较低的时空复杂度。     

含受控源网络回路阻抗矩阵的建立

提出了一种含受控源网络回路阻抗矩阵简单直接的建立方法。该方法证明了回路阻抗矩阵Zl可以由不含受控源的回路阻抗矩阵Z′l和反映电路受控源与各回路电流之间关系的矩阵Z″l构成,从而可以避免建立回路阻抗矩阵时较为复杂的矩阵运算,以较为简单和直接的方式得到网络的回路阻抗矩阵。论文给出了直接建立Z″l矩阵的方法。     

电路分析中两种基本方法的比较

1 两种方法的基本情况 节点电压法和回路电流法是电路分析中的两种基本分析方法。两者对初接触电路的学生来说不分主次,因为在理论上,两者并无优劣之分,因而在讲授中历来同等对待。 在分析实际电路,特别是近二、三十年来应用计算机进行网络分析时,回路法受到冷遇,自改进节点提出后,人们更把注意力放在节点法和改进节点法上。这主要是因为回路方程的建立一般来说比较麻烦,而用节点法和改进节点法建立方程比较简易,特别是在某些特殊电路中,节点方程甚至可以根据网络的拓朴结构和元件参数直接建立。改进节点法更是放宽了网络的限制。这些问题好象用回路法无法解决,但实际上并非如此,只是人们还没有对回路法进行深入的研究罢了。权衡各类网络分析的整个过程,回路电流法在某些网络的分析中是有其优势的。下面就多线圈耦合网络的分析来作一探讨。     

节点法和回路法的实质与检验方法

电路理论中的节点法和回路法是分析电路最常用的方法，但是在列写相应的节点电压方程和回路电流方程时，自(互)导、自(互)阻及其符号容易忽视以致于漏写。本文对节点法和回路法的实质进行了分析，指出节点法的实质是各选取节点的KCL方程，回路法的实质是各选取回路的KVL方程，并根据其实质提出了一种检验电路方程的方法。节点法只需检验是否满足参考节点的KCL，回路法只需检验是否满足新回路的KVL，均只需检查一个方程，有助于快速而准确地解决电路问题，而且有利于利用数学建模的方法进行复杂电路仿真，并给出了基于Matlab的仿真实例。     

含源多端口网络源向量与参数矩阵间的关系

在电路课程中一端口网络的戴维南和诺顿定理为重点内容之一。从一端口扩展为多端口网络此两定理的表现,应予以关注。本文将给出含源多端口网络参数矩阵和源向量间的关系。以下为了叙述方便称含源的网络为含源网络,不含独立源的网络为非含独立源的网络,非含源网络仍可能是有源网络。非含源多端口网络可以用短路参数矩阵Y_0、开路参数矩阵Z_0或混合参数矩阵H表征。对含源多端口网络、全部端口开路情况下的各端口开路电压或全部端口短路情况下的各端口短路电流和部分端口开路,另一部分端口短路情况下的各端口电压和电流显然是不同的。为便于区分,以下对全部端口开路情况下的端口电压用V_(00?)表示,即,向量     

电路课程中含受控源电路教学的探讨

含受控源的电路在“电路”课程教学中既是难点又是重点。本文根据该课程的实际教学经验总结了含受控源电路的分析方法——基本分析方法（支路法、回路法、节点法和戴维南定理）和受控源等效变换法（受控源等效为电阻或电压源与电阻的串联组合）,结合一些具体实例对每一种方法做了详细的分析,总结了含受控源电路的教学特点,并对这两种分析法进行了比较,为含受控源电路的教学提供了有益的建议。     

一种OFDM中继系统的有限反馈预编码方法

基于正交频分复用的放大转发协作中继系统,为了减少系统误比特率、增加信道容量和增强实用性,该文提出一种实用的源节点预编码和中继节点预编码的联合优化有限比特反馈的预编码方法。利用3节点构成的两个下行链路,实现两跳协作通信方式;采用SVD分解和QR(orthogonal triangular)分解相结合设计预编码,其中源节点预编码每帧只要一个;优选量化码本,把预编码矩阵量化后反馈到发射端。仿真结果表明,该方案能提高平均和速率、降低误码率和改善中断概率特性,且反馈比特数较少具有更好的实用价值。     

Low dimensional adaptive texture feature vectors from class distance and class difference matrices

In many popular texture analysis methods, second or higher order statistics on the relation between pixel gray level values are stored in matrices. A high dimensional vector of predefined, nonadaptive features is then extracted from these matrices. Identifying a few consistently valuable features is important, as it improves classification reliability and enhances our understanding of the phenomena that we are modeling. Whatever sophisticated selection algorithm we use, there is a risk of selecting purely coincidental "good" feature sets, especially if we have a large number of features to choose from and the available data set is limited. In a unified approach to statistical texture feature extraction, we have used class distance and class difference matrices to obtain low dimensional adaptive feature vectors for texture classification. We have applied this approach to four relevant texture analysis methods. The new adaptive features outperformed the classical features when applied to the most difficult set of 45 Brodatz texture pairs. Class distance and difference matrices also clearly illustrated the difference in texture between cell nucleus images from two different prognostic classes of early ovarian cancer. For each of the texture analysis methods, one adaptive feature contained most of the discriminatory power of the method.     

Electromagnetic Scattering From Arbitrarily Shaped Dielectric Bodies Using Paired Pulse Vector Basis Functions and Method of Moments

A pair of orthogonal pulse vector basis functions is demonstrated for the calculation of electromagnetic scattering from arbitrarily-shaped material bodies. The basis functions are intended for use with triangular surface patch modeling applied to a method of moments (MoM) solution. For modeling the behavior of dielectric materials, several authors have used the same set of basis functions to represent equivalent electric and magnetic surface currents. This practice can result in zero-valued or very small diagonal terms in the moment matrix and an unstable numerical solution. To provide a more stable solution, we have developed orthogonally placed, pulse basis vectors: one for the electric surface current and one for the magnetic surface current. This combination ensures strongly diagonal moment matrices. The basis functions are suitable for electric field integral equation (EFIE), magnetic field integral equation (HFIE), and combined field formulations. In this work, we describe the implementations for EFIE and HFIE formulations and show example results for canonical figures.      

基于自适应加权Fisherface算法的人脸识别

提出了一种改进的Fisherface算法。算法首先利用Karhunen-Loeve（K-L）变换降维,在降维的子空间内,根据样本与同类样本间的距离赋予该样本一权值,再用加权后的样本求取类均值,以新的类均值重建类内散布矩阵和类间散布矩阵,从而改进Fisher判别函数。在ORL和Yale人脸库上的实验结果表明,该算法优于传统的主成分分析（PCA）方法和Fisherface方法,并能有效解决小样本情况下训练样本类均值偏离类中心的问题。     

Field Distribution Due to a Circular Current Loop Placed in an Arbitrary Position above a Conducting Plate

The calculation of eddy currents within a conducting slab when the excitation is a circular current loop in an arbitrary position above the slab is examined. The magnetic flux density in regions outside the slab is also determined. The diffusion equation of the magnetic vector potential is written in a coordinate system attached to the geometry of the configuration by using two Dirac functions. The field vectors are expressed as double Fourier integrals.     

Advanced control of induction motor based on load angle estimation

An advanced control system with load angle adjustment is introduced. The method is based on the action of a phase-locked loop, in which a position synchronization of two vectors to obtain a constant command angle between them is realized. In the system presented, the vectors are stator current and rotor flux. The load angle is kept constant by changing the position of stator current vector as a result of tuning its pulsation. Proportional-integral and fuzzy logic controllers are used to control the load angle. Because of using the load angle controller and simple relations for state variables, the proposed idea does not require exact speed measurement. The discussed control system is not sensitive to motor resistance variations. This idea is realized on a fixed-point digital signal processor and field-programmable gate arrays. Experimental results for the control system fed by a voltage-source inverter and controlled using a predictive current controller are presented.     

基于调频Z变换的均匀线阵波达方向估计

提出了一种基于调频Z变换(CZT)的宽带波达方向估计算法.由均匀线阵的理想聚焦条件,提出了其焦矩阵的波矢量域求解原理及计算方法:首先从聚焦频率处的聚焦矩阵中依次选取一行向量,用CZT分别计算其它带内,各聚焦矩阵中相应位置的行向量的波矢量谱,再由傅立叶反变换得到相应的行向鼍.该方法可选择信号频带围内的任意值作为聚焦频率,...     

Geometrically uniform frames

We introduce a new class of finite-dimensional frames with strong symmetry properties, called geometrically uniform (GU) frames, that are defined over a finite Abelian group of unitary matrices and are generated by a single generating vector. The notion of GU frames is then extended to compound GU (CGU) frames which are generated by a finite Abelian group of unitary matrices using multiple generating vectors. The dual frame vectors and canonical tight frame vectors associated with GU frames are shown to be GU and, therefore, also generated by a single generating vector, which can be computed very efficiently using a Fourier transform (FT) defined over the generating group of the frame. Similarly, the dual frame vectors and canonical tight frame vectors associated with CGU frames are shown to be CGU. The impact of removing single or multiple elements from a GU frame is considered. A systematic method for constructing optimal GU frames from a given set of frame vectors that are not GU is also developed. Finally, the Euclidean distance properties of GU frames are discussed and conditions are derived on the Abelian group of unitary matrices to yield GU frames with strictly positive distance spectrum irrespective of the generating vector.