A synthetic network using current conveyors of the open-circuit impedance matrix of a linear time-invariant multiport

Previous research appearing in the literature required that all the realizable z parameters of the open-circuit impedance matrix of a linear time-invariant multiport network must be real, rational, stable functions. Although different z parameters could be selected independently without necessarily to having common poles, this also required that all the z parameters be minimum phase. A synthetic network using second-generation current conveyors (CCIIs), third-generation current conveyors (CCIIIs) and differential difference current conveyors (DDCCs) is proposed here, with each transfer impedance parameter being either minimum or nonminimum phase. Additionally, it can be designed automatically by computers since the current conveyor circuits, the transfer functions and numerical methods are available.     

Excellent Field‐Emission Performances of Neodymium Hexaboride (NdB6) Nanoneedles with Ultra‐Low Work Functions

High‐quality NdB₆ nanostructures with a low work function are successfully synthesized via an one‐step catalyst‐free chemical vapor deposition process. Field emission properties of these nanostructures (curve nanowires, short‐straight nanorods, long‐straight nanowires, and nanoneedles) are systematically investigated and found to be strongly affected by the tip morphologies and temperatures. The nanoneedles with sharp tips demonstrate the lowest turn‐on (2.71 V/μm) and threshold (3.60 V/μm) electric fields, as well as a high current density (5.37 mA/cm²) at a field of 4.32 V/μm in comparision with other nanostructures. Furthermore, with an increase in temperature from room temperature to 623 K, the turn‐on field of the nanoneedles decreases from 2.71 to 1.76 V/μm, and the threshold field decreases from 3.60 to 2.57 V/μm. Such excellent performances make NdB₆ nanomaterials promising candidates for application in flat panel displays and nanoelectronics building blocks.     

电子式互感器在数字化变电站中的应用

本文就电子式互感器在数字化变电站中的应用进行了探讨,结合了具体的实例,通过对电子式互感器的工作原理进行分析,对比有源和无源两种类型的电子式互感器技术的优缺点,从而总结出有源电子式互感器优于无源电子式互感器,其具有较好的稳定性、抗震动以及受温度影响小等工程应用特性,还根据一些应用上的问题,提出了解决措施,以期能为电子式互感器更好地应用于数字化变电站中提供参考。     

Exponential l 2–l ∞ Control for Discrete-Time Switching Markov Jump Linear Systems

The problem of exponential l ₂–l _∞ control is considered in this paper for a class of discrete-time switching Markov jump linear systems. First, the definition of exponential l ₂–l _∞ mean square stability for discrete-time switching Markov jump linear systems is introduced. Then, by resorting to the average dwell time approach, the mean square exponential stability criteria are presented with an exponential l ₂–l _∞ performance index and a decay rate, and the corresponding controller is also designed. Finally, numerical and application examples are provided to demonstrate the effectiveness of the obtained results.     

分布式发电并网系统综述

随着分布式发电(Distributed Generation)应用的增加,越来越多的分布式发电正在接入电网,由此带来的并网问题日益重要:并网系统(包括硬件和软件)主要用来连接分布式发电和电网(通常是本地电网),本文主要讨论了分布式发电与电网之间的并网类型,并网系统的分类、功能、主要结构及采取的控制方法,并简要介绍了现有的分布式发电并网导则。     

P2P流量优化技术及标准化进展

文章综述了P2P流量优化的技术路线（P2P应用层优化和层间协同机制）,介绍了目前具有代表性的一些解决方案,如应用层优化方案IDMaps、Vivaldi、iPlan、OnO,层间协作方案P4P、Oracle、PPM和DDP,以及国内外标准化组织标准推进情况。     

On Vector Quasi-Equilibrium Problems with Set-Valued Maps

In this paper, we introduce a new class of vector quasi-equilibrium problems with set-valued maps. Almost all the vector equilibrium models of the Blum-Oettli type in the literature are special cases of our new class of equilibrium problems under consideration. Moreover, a number of C-diagonal quasiconvexity properties are proposed for set-valued maps, which are natural generalizations of the -diagonal quasiconvexity for real functions. Together with an application of continuous selection and fixed-point theorems, these conditions enable us to prove unified existence results of solutions for such vector equilibrium problems.     

An Algorithm to Construct <Emphasis Type="BoldItalic">k</Emphasis>-Regular <Emphasis Type="BoldItalic">k</Emphasis>-Connected Graphs with the Maximum <Emphasis Type="BoldItalic">k</Emphasis>-Diameter

 Let f(2m,k) be the Maximum k-diameter of k-regular k-connected graphs on 2m vertices. In this paper we give an algorithm and prove that we can construct k-regular k-connected graphs on 2m vertices with the maximum k-diameter using it. We also prove some known results about f(2m,k) and verify that we can get some unknown values of f(2m,k) by our algorithm. Received: December 1, 2000 Final version received: March 12, 2002 Acknowledgments. We thank the referee for many useful suggestions.     

ICI cancellation for OFDM communication systems in time-varying multipath fading channels

In orthogonal frequency division multiplexing (OFDM) systems, time-varying multipath fading leads to the loss of subcarrier orthogonality and the occurrence of intercarrier interference (ICI). In this study, an efficient ICI suppression with less noise enhancement for multicarrier equalization is presented by using a parallel canceling scheme via frequency-domain equalization techniques, with the assumption that the channel impulse response (CIR) varies linearly during a block period. In order to avoid performance deterioration due to unreliable initial estimations in the parallel cancellation scheme, a cost function with proper weighting factor is introduced to improve the performance of the proposed equalizer. The proposed equalizer consists of a set of prefilters and a set of ICI cancellation filters, with two stages to perform different functions to achieve minimum mean square error (MMSE) equalization. The prefilters compensate for the multiplicative distortion at the first stage, and the ICI cancellation filters remove the effects of ICI by a parallel cancellation scheme at the second stage. Finally, the performance of the proposed equalizer is analyzed and compared with that of other equalizers, indicating significant performance improvement.     

高校计算机公共机房管理研究

大学计算机实验室不仅是教育和实践的场所,还是学生学习知识的主要平台.为了提高教育质量,许多大学都建立了大型计算机实验室.由于规模大,它受硬件和软件故障或安全管理问题等多个因素的影响,并且发生的频率相对较高.良好的计算机实验室管理和维护可以为师生提供稳定的网络环境.文章旨在研究如何保持计算机在大学计算机实验室中运行,如何...