Optimization Problems in k-out-of-n Systems

A k-out-of-n:G system is an important complex system and is used for mass transit and computer systems. This paper does not discuss the availability, but considers what is the most economical k-out-of-n system when the failure rate of each element is constant. We solve two problems to minimize the mean cost-rate; i) the optimal number of elements and ii) the optimal replacement time before system failure. A numerical example is given.     

On the Evaluation of the Reliability of k-out-of-n Systems

The paper provides some correcting remarks on several methods to determine the k-out-of-n:G system reliability - a problem that has taken more than its share in the literature. A Jain-Gopal paper presents two algorithms JG-1 and JG-2 to evaluate the reliability of a k-out-of-n System. The comparison of the computational costs of JG-1 with those of JG-2 and with other existing algorithms, especially Barlow-Heidtmann, need to be restated.     

改进的层式DCT在数字水印技术中的应用

数字水印问题研究中,DCT块效应是困扰版权保护的一大难点.结合小波特性,提出一种改进的层式DCT算法,并应用于数字水印.将DCT变换后所得子块的低中频系数分别抽样,然后将水印信息的变换域量值分别叠加到原始载体经改进的层式DCT变换后的低中频系数中,同时对改进的层式DCT变换的分层层数进行了研究.实验结果表明,水印方案具有很好的整体去方块效应,提高了水印的不可见性,对抗压缩、剪切等常规几何攻击具有较强的鲁棒性,并且两者之间达到了一个较好的平衡.进一步扩大了层式DCT的实际应用.     

OFDM系统中基于变换域信道估计方法的改进

在分析信道传输函数频谱特性的基础上,提出了一种改进的变换域信道估计方法,该方法通过改进低通滤波器的传输函数,有效地减小了符号间干扰和加性高斯白噪声对信道估计精确度的影响.仿真结果证明,在多普勒频移较大的情况下,该方法仍具有较小的误码率.     

一种改进的MIMO-OFDM系统注水功率分配算法

鉴于目前MIMO—OFDM系统中大多数比特功率分配算法需要多次迭代,复杂度较高,及系统比特分配离散性的特点,本文结合贪婪功率分配算法逐步优化的思想,提出了修正的二次注水功率比特分配算法。该算法首先利用注水功率分配方案得到连续速率最优的功率分配,接着针对实际数据速率量化的误差对不同特征模式下的功率进行微调,实验证明改进后的算法有效提高了系统的总体传输速率。     

OFDM系统中一种改进的抗频偏加窗法

该文提出了正交频分复用系统中一种改进的抗频偏接收端加窗的方法,接收端在去除发送端附加的循环前缀后重新进行循环扩展,然后进行奈奎斯特加窗, 并且窗函数不再限于具体的函数形式,是经过优化的数值解。数值计算结果表明,最优窗的抗频偏性能远好于其他窗函数。     

应用改进迭代物理光学方法分析电大尺寸开口腔体散射

为了克服用IPO法处理电大尺寸形状相对复杂的腔体散射时会出现迭代收敛慢甚至发散现象,本文引入松弛因子、异步迭代以及继承迭代等措施改进迭代的收敛性,所得结果与其它方法或实验结果符合很好。     

改进的谱减法在语音增强中的应用

提出了一种谱减法的改进形式,算法打破了噪声和语音是相互独立且噪声是零均值的高斯分布假设.实验表明这种改进型谱减算法有效提高了增强效果,更好地抑制了音乐噪声.     

改进的遗传算法在背包问题中的应用

介绍了一种最优保存遗传算法,针对该算法提出一种改进方案,一方面改变了保存最优个体的方法,另一方面对不满足约束条件的个体采用贪心策略进行改造,使其满足条件。最后通过一个具体的背包问题实例验证了改进算法的可行性和有效性。     

基于容斥原理与不交和公式的一个计算网络可靠性方法

这篇文章考虑了网络从源点ｓ到某些特定终点Ｋ的ＳＫＴ可靠性问题，文章基于容斥原理和不交和公式提出的一个新的拓扑公式，它比相应的Ｓａｔｙａｎａｒａｙａｎｎａ公式含有更少的项和算术运算，在此公式基础上，提出一个计算网络ＳＫＴ可靠性算法，它改进了相应的Ｓａｔｙａｎａｒａｙｍａｎｎａ算法，能产生更紧的可靠性表达式。     

Self-Organizing Migrating Strategies Applied to Reliability-Redundancy Optimization of Systems

The reliability-redundancy allocation problem is a mixed-integer programming problem. It has been solved by using optimization techniques such as dynamic programming, integer programming, mixed-integer non-linear programming, heuristics, and meta-heuristics. Meanwhile, the development of meta-heuristics has been an active research area in optimizing system reliability wherein the redundancy, the component reliability, or both are to be determined. In recent years, a broad class of stochastic algorithms, such as simulated annealing, evolutionary computation, and swarm intelligence algorithms, has been developed for reliability-redundancy optimization of systems. Recently, a new class of stochastic optimization algorithm called SOMA (Self-Organizing Migrating Algorithm) has emerged. SOMA works on a population of potential solutions called specimen, and is based on the self-organizing behavior of groups of individuals in a "social environment". This paper introduces a modified SOMA approach based on a Gaussian operator to solve reliability-redundancy optimization problems. In this context, three examples of mixed integer programming in reliability-redundancy design problems are evaluated. In this application domain, SOMA was found to outperform the previously best-known solutions available.     

一种改进的OFDM系统CFO的盲估计方法

OFDM系统的载波频偏导致相邻OFDM符号相同子载波上的信号功率产生了差异。基于这个思想,利用OFDM信号的4阶矩与频偏满足余弦函数关系的特点,提出一种载波频偏估计的改进方法,即子载波功率差分估计方法。该方法具有简单的闭式解,避免了迭代搜索过程,降低了计算量,同时也适用于慢时变的频率选择性衰落信道。仿真实验表明,与现有方法相比,改进后的方法在降低计算复杂度的同时也具有良好的估计性能。     

Self-Organization of Complex Networks Applied to Wireless World Systems

This paper provides a brief overview of the role that self-organization can play in the next generation wireless networks (S. Dixit, WWRF 8bis Meeting, February 26–27, Beijing, China). First, we present the definition, scope, and applicability of self-organization to wireless world systems. Then we briefly articulate the need for self-organization, and some recent breakthrough advances in this emerging area of research. This is followed by high-level system architecture for future communication systems and some early mechanisms for self-organization. The paper concludes with the challenges in this new field with key research issues.     

细导线精确算法在改进的减缩时域有限差分法中的应用

Riku M.M.等提出的FDTD的亚网格细导线精确算法,可以对给定直径的金属导线的电磁特性作精确计算.本文证明了由该算法格式计算的细线周围的电磁场分量,可以直接用于改进减缩时域有限差分(R-FDTD)法计算.用这种亚网格细线精确算法与改进R-FDTD结合计算了一个由细线源激励的矩形金属外壳的源输出功率,所得结果与文献报道的实验数据吻合.该算法与采用标准细线亚网格算法的计算结果相比,计算精度有明显提高.     

An Improved Simple Adaptive Control Applied to Power System Stabilizer

A conventional power system stabilizer (PSS) can improve the steady-state stability margin and increase the system positive damping, but it has some drawbacks, such as the time-consuming tuning and nonoptimal damping in the entire operating process. A proportional--integral (PI) adaptive control law in simple adaptive control (SAC) can overcome these drawbacks. However, it can only be applied to the plants with almost strict positive realness (ASPR), and the computation of adaptive control law is really complex. A new improved SAC (ISAC) based on quadratic performance index was proposed. A new PSS can be designed using the ISAC. The simulation and experimental results show that this stabilizer possesses good dynamic characteristics and regulation precision. They also show that the new PSS can improve the dynamic stability of the power system and suppress the low-frequency oscillation effectively.      

Method of Moments as Applied to Electromagnetic Problems

This paper reviews one of the most important general methods for solving electromagnetic-field problems, namely, the moment method. It begins with a brief mathematical foundation of the general method. Then, the various specializations are described, accompanied with relevant references to illustrate the pitfalls and shortcomings, as well as the advantages, as compared to other methods. Deterministic and eigenvalue problems are both discussed separately. Finally, two advanced techniques which have been found to be among the most efficient ones for solving matrix equations resulting from the moment method, namely, the coujugate gradient and the pseudo-inverse, are described. A version of their algorithm which is easily programmable on computer is also presented.     

频谱分析中的微分法与微分方程法

本文讨论了应用于傅里叶变换的微分性质的隐含假设,并叙述了信号不满足隐含假设时的修正方法。本文还给出了作为信号生成系统的微分方程描述,它使信号谱成为其生成系统的频率传递函数,指出了微分方程法的隐含假设。最后还给出了信号违反此假设时进行修正的方法。     

Digital Image Processing Applied to Scintillation Images from Biomedical Systems

Several nonlinear filtering methods have been developed for two-dimensional image signals obtained from an Anger Scintillation camera. The first method termed "pruning" is implemented in the frequency domain and filters out certain components of the two-dimensional amplitude spectrum. The other methods called "E-filtering" and "P-filtering" utilize a nonlinear transformation of the spatial coordinates which is proportional to the two-dimensional signal amplitude and energy spectrum, respectively. These nonlinear filtering techniques have been applied to phantom scintigrams as well as brain and heart scans of normal and abnormal patients. In addition, the detection of boundaries using the hexagonal Golay transform on filtered and unfiltered images is included. Finally, these filtering and edge detection techniques were for the first time applied to a new technique for the detection of acute myocardial infarcts.     

用于电力系统无线传感器网关的设计与实现

针对电力系统现场监测困难的问题,设计了一种基于ZigBee的无线自组网络通信方式,通过协调器来收集无线节点的信息,接近ARM连接的GPRS进行无线传输,以达到对监控点的准确监控。该设计在电力系统现场的试验中,较好地解决了远距离的监控问题。     

Improved Nyquist-I Pulses to Enhance the Performance of OFDM-Based Systems

Wireless Personal Communications - Pulse shaping is used in orthogonal frequency division multiplexing (OFDM) based systems to reduce inter-carrier interference (ICI) power and peak-to-average...