Comment on “Implementation of a Web-Based Educational Tool for Digital Signal Processing Teaching Using the Technological Acceptance Model”

The author points out some errors in the paper by S. L. Toral Marin et al. (see ibid., vol.48, no.4, p.632-41, Nov. 2005)     

电磁筛控制系统的设计与实现

介绍一种基于PIC单片机和工控机的控制系统,用于筛选行业电磁筛的控制.给出了系统的主要硬件结构和软件设计流程,讨论了电路的工作原理和实现的功能.硬件核心采用PIC16F单片机,系统集成软件基于Windows2000,采用Client/Server结构,通过Modbus协议与和控制主板进行通讯,实现对高频电磁振动振网筛的控制和数据处理,生产现场实践证明该系统设计合理,功能完善,操作简单运行可靠.     

Discussion of “Using a static VAr compensator to balance adistribution system”

In the paper by J.-H. Chen et al. on `Using a static VAr compensator to balance a distribution system' (see ibid. vol.35, p.298-304, 1999), the authors have made a positive contribution to balancing an unbalanced system. However, the author makes several comments and shares his experience with compensators consisting of a thyristor switched inductor (TSI). The author discusses the harmonics and resonance of a TSI     

A Digital Signal Processing Teaching Methodology Using Concept-Mapping Techniques

The main goal of this study is to develop a scientific method for designing a teaching methodology used in a basic digital signal processing (DSP) course. The proposed method is based on concept-mapping techniques, which applies multivariate statistic analysis to summarize the experience and knowledge of teachers involved in basic DSP teaching. As a result, a set of teaching methodologies is obtained. This result, as well as other information obtained related to the relative importance of the concepts to be covered, has been used to program the course. Moreover, different teaching tools have been developed to implement the proposed teaching methodology. Finally, the reliability of the method has been compared with similar studies to validate the proposed methodology.     

基于软开关与磁集成技术的Cuk变换器

介绍了一种新型Cuk变换器,它同时应用了软开关与磁集成技术,实现输入、输出电感的电流零纹波,主开关管零电压开通,从而大大减少了高频开关电源的损耗和噪声,提高系统的整体效率和功率密度。描述了该变换器的拓扑结构、工作原理、参数设计方法,并对该变换器进行仿真,仿真结果证明了理论分析的正确性。     

Closure to discussion of “Using a static VAr compensator tobalance a distribution system”

The authors reply to a discussion by S.-M. Hsu (see ibid., vol.35, no.5, p.1174-6, 1999) of their original paper (see ibid., vol.35, p.298-304, 1999). The authors claim that Hsu provides technical details about the harmonic problems of the SVC, but has overlooked the main purpose of their paper. They point out that the point raised by Hsu on harmonics was dealt with in other papers that were referenced in the original paper     

浅谈安全用电的屏护和间距

主要讨论了安全用电的屏护和间距问题,用一系列数据使计量检定员懂得现场操作高低压设备的安全技术、最小安全距离等,工作中知己知彼,不出差错,从而达到事半功倍的效果.     

“Engineering” the wound-healing process

Our group is studying the modulation of fibroblast behavior by various wound-healing agents. 3-D collagen gels were used as an in vitro wound model to study human dermal fibroblast behavior. In this article, we hypothesize that efficient contraction of the in vitro wound model is associated with gap junction (GJ) formation between cells and, conversely, that inhibition of the in vitro wound-model contraction is associated with inhibition of GJ between cells. We used chitosan-collagen blends as the in vitro wound model, investigating the contractile behavior of fibroblasts and the effect of chitosan on wound contraction and GJ formation     

一种采用智能功率模块的调压调频高压电源

介绍了一种采用智能功率模块的调压调频高压电源 ,详述了其工作原理     

基于CS5460A设计三相电能表关键技术研究

介绍了使用CS5460A进行三相电能表应用设计方案,重点讨论了设计方案中需要注意的几个特殊技术问题,如:增益校准、角差校准、无功功率计算及其极性判别等。采用这种方案,已形成产品,并通过中国电科院形式试验,误差数据也很好。     

基于IEC61850报文模拟及分析技术的智能开关调测

智能化变电站的实现依赖于智能一次设备的广泛使用。智能一次设备实现了传感器及控制机构与一次设备本体的高度集成,并将测控信息通过网络以符合IEC 61850的信令方式集成到电网的管理过程中去。网络化及信令化的引入,使高压电器的测控发生了本质的改变,需要一种智能化的高效调测方法。文中分析了高压智能开关的相关测控信息特点,提出了基于IEC 61850报文模拟及分析技术的智能开关调测方法,描述了基于这种方法的系统实现,并介绍了如何利用这些方法,设计开关组合动作,实现重合闸的模拟及完成开关机械寿命试验。     

A New Approach to Economic Dispatching Using Load Bus Elimination Techniques

This paper presents a new technique to solving the economic dispatch problem based on a reduced order model of the original system. Loads are first modeled by their appropriate voltage-dependent models as load admittances. Load admittances are then added to the bus admittance matrix and their respective buses are eliminated. The obtained model is a reduced model of the original system. The admittance matrix is of the same order as the number of voltagecontrolled buses in the system. The variables of the reduced model are the voltage-controlled buses’ angles and active power generations. Newton Raphson method is used to calculate the angles and active generations of the reduced model while minimizing the operational cost. Load bus voltages and angles of the original system are then calculated by a direct method and load admittances are modified. The process is repeated until convergence is achieved. The simulation is carried out on IEEE 118 bus test system. A comparison between the new approach and the penalty factors method has been made. It is shown that operational cost is improved and solution time is significantly reduced when compared to the penalty factors method of economic dispatch.     

Comment on “Using the λ function to evaluate probemeasurements of charged dielectric surfaces” [and reply]

For original paper, see T.O. Rerup et al., ibid., vol. 3, pp. 770-777 (1996). Rerup et al. described the calibration of electrostatic probes used to measure the surface charge on dielectrics. This work showed that the use of the probe response theorem (the λ function), rather than the simple capacitative formula, leads to better experimental values. In this discussion, the commenter wishes to show that a more detailed interpretation can be extracted from the numerical results. In reply, Rerup et al. demonstrate that simple statistics cannot be used to extract, in a conclusive manner, a more detailed interpretation of the σ_λ,σ_D patterns. Moreover, with the limitations imposed by the axially symmetric λ function, there is little to be gained in pursuing the source of the discrepancies between σ_λ and σ_F. They agree with the commenter that a multi-point scanning procedure would be essential if the functional form of the surface charge distribution were unknown     

Implementation Issues in Voltage Zero Sequence-Based Encoderless Techniques

Recent articles demonstrate that sensorless drives for induction motors can operate at zero-electrical and mechanical frequencies with the aid of high-frequency signal injection techniques and processing the zero-sequence voltage signals. The paper presents some practical implementation issues affecting the performance of such a technique and shows how to improve the quality of the estimated angle. All the assessments are experimentally proved and have a general value that can be extended to other sensorless techniques injecting high-frequency signal.      

Chasing after “petty” computer crime

Non-violent crime has found a goldmine of opportunity in the computer world. What constitutes a crime and how it impacts people as a society and individually is very slowly being worked out. The next few years will surely bring changes and decisions that will affect everyone. The pace in which the legal system currently moves is slow. This is to try to ensure fairness to all the parties involved: the victim, the accused and society as a whole. Perhaps issues regarding computing will force it to accelerate, perhaps not. Time will only tell     

采用微控制器ST92141实现的高性能TPWM变频器

研制了用于家用电器交流异步电机调速的高性能低成本变频控制器。变频器输出波形由梯形波调制（TPWM）方法产生。微控制器（MCU）选用ST9系列8／16位单片机，功率放大部分由低价的单管IGBT及单桥驱动芯片L6386组成。该变频器系列能驱动0．1－2kW三相、双相、单相交流异步电机，已在变频洗衣机中获得成功应用。整机具有良好的稳定性和抗干扰性，通过了EMC脉冲传导干扰实验及国家家电安全标准检验。     

A Method for Reliability Optimization of Distributed Generation Using Meta-Heuristic and Probabilistic Techniques

Abstract—This article shows a method to optimize the reliability of an electric power system by the introduction of distributed generation. The reliability index of the system is determined as the failure probability of the system. A hybrid method that uses a binary shuffled frog-leaping algorithm and probabilistic load flow is proposed to search a large number of combinations for location and size of biomass power plants and photovoltaic units. The combination with the best performance minimizes the reliability index (probability of failure) of the system.     

磁传感器阵列测量大电流实验系统

电力系统中现有的大电流测量设备往往存在体积大、测量范围窄、绝缘困难等缺陷,故提出了使用磁传感器阵列测量交直流大电流的思路,该测量方法具有体积小、成本低、非接触测量、交直流通用、可数字化输出等优点。为了分析在实际系统中影响该方法测量精度的若干因素,利用基于离散傅里叶变换（DFT）的多相大电流测量算法,设计了大电流实验测量装置,并使用该装置进行了一系列不同母排形状的测量实验,并对各测量环节产生的误差来源进行了理论分析。实验结果验证了本测量方法的有效性。