The maximal downstroke of epicardial potentials as an index of electrical activity in mouse hearts

The maximal upstroke of transmembrane voltage (dV(m)/dt(max)) has been used as an indirect measure of sodium current I(Na) upon activation in cardiac myocytes. However, sodium influx generates not only the upstroke of V(m), but also the downstroke of the extracellular potentials V(e) including epicardial surface potentials V(es). The purpose of this study was to evaluate the magnitude of the maximal downstroke of V(es) (|dV(es)/dt (min)|) as a global index of electrical activation, based on the relationship of dV(m)/dt(max) to I(Na). To fulfill this purpose, we examined |dV(es)/dt(min)| experimentally using isolated perfused mouse hearts and computationally using a 3-D cardiac tissue bidomain model. In experimental studies, a custom-made cylindrical "cage" array with 64 electrodes was slipped over mouse hearts to measure V(es) during hyperkalemia, ischemia, and hypoxia, which are conditions that decrease I(Na). Values of |dV(es)/dt(min)| from each electrode were normalized (|dV(es)/dt (min)|(n)) and averaged (|dV(es)/dt(min)|(na)). Results showed that |dV(es)/dt(min)|(na) decreased during hyperkalemia by 28, 59, and 79% at 8, 10, and 12?mM [K(+)](o), respectively. |dV(es)/dt(min)| also decreased by 54 and 84% 20 min after the onset of ischemia and hypoxia, respectively. In computational studies, |dV(es)/dt(min)| was compared to dV(m)/dt(max) at different levels of the maximum sodium conductance G(Na), extracellular potassium ion concentration [K(+)](o), and intracellular sodium ion concentration [Na(+)](i), which all influence levels of I(Na). Changes in |dV(es)/dt(min)|(n) were similar to dV(m)/dt (max) during alterations of G(Na), [K(+)](o), and [Na(+)](i). Our results demonstrate that |dV(es)/dt(min)|(na) is a robust global index of electrical activation for use in mouse hearts and, similar to dV(m)/dt(max), can be used to probe electrophysiological alterations reliably. The index can be readily measured and evaluated, which makes it attractive for characterization of, for instance, genetically modified mouse hearts and drug effects on cardiac tissue.     

7× electrical pulse compression on an inhomogeneous nonlineartransmission line

A device which directly compresses electrical pulses using the concepts of soliton propagation along an inhomogeneous nonlinear transmission line is described. Numerical simulations on SPICE indicate that a 5 V input pulse with a FWHM of 66 ps can be compressed to a ⩾10 V output pulse with a FWHM ⩽5 ps. A compression factor of ⩾7 has been experimentally measured on a low frequency scale model compressor     

Teaching an automated agent to monitor the electrical power system of an orbital satellite

This paper illustrates an application of the Disciple knowledge acquisition methodology to build an intelligent adaptive agent for monitoring the electrical power system of an orbital satellite. This methodology is used by an expert to build and train an agent in much the same way that the expert would teach a human apprentice—by giving the agent specific examples of problems and solutions, explanations of these solutions, and supervising the agent as it solves new problems. During these interactions, the agent acquires general rules and concepts, continuously extending and improving its knowledge base. The agent learns by synergistically integrating the basic learning strategies: explanation-based learning, learning by analogy, and empirical inductive learning from examples. An important feature of Disciple-based agents is their ability to reason with incomplete and even partially incorrect information. The agent distinguishes between routine problems (problems it knows that it can solve correctly), innovative problems (problems to which it can recommend solutions, but for which it is not certain of the result), and creative problems (problems it is not able to solve). This allows the agent to solve a problem independently (for a routine problem), to ask confirmation of its solution (for an innovative problem), or simply to ask the expert to solve the problem (for a creative problem).     

Fuzzy logic control of an active power line conditioner

Fuzzy logic and active power line conditioners (APLC) are two tools that are being increasingly applied to power quality problems. In this paper, a switch-mode APLC that uses fuzzy logic to control the semiconductor switches is described. Frequency-domain analysis is used to determine the desired compensation current, and a rule-based piecewise-linear fuzzy proportional-integral controller (FPIC) provides the appropriate switching pattern of the APLC to generate the actual compensation current. MATLAB simulations and experimental measurements on a low-power (700 VA), digital signal processor-based, hardware prototype show that the APLC produces excellent results despite the use of a relatively low switching frequency, which is necessary to minimize semiconductor switching losses. The simulations and measurements are in good agreement and show that the APLC/FPIC system can significantly improve line current total harmonic distortion and power factor during both steady-state and transient operating conditions.     

大功率设备在电网波动下的研究对策

针对电网短暂波动或短时断电导致交流接触器脱扣的问题。设计一种在检测交流侧电压不正常情况下控制继电器切换到储能器件,避免交流接触器在电网波动情况的不正常工作的控制器;从而达到当电网波动出现时交流接触器维持吸合状态,实现在控制延迟的时间后断开。结果表明采用防电网波动控制器,能够有效解决交流接触器脱扣的问题,从而有效的避免电网波动事故的发生,使整个系统能够连续安全、可靠的运行。     

Measurements of the voltage induced on an overhead power line 20 mfrom triggered lightning

Voltages induced on a 448-m power distribution line by eleven return strokes in three lightning flashes artificially initiated 20 m from one end of the distribution line and the corresponding vertical electric fields at 500 m have been measured. Two types of induced-voltage waveforms were recorded: oscillatory and impulsive. The former exhibit peak values that range from tens of kilovolts to about 100 kV; the latter show peak voltages nearly an order of magnitude larger. Both types of induced voltage waveforms were observed to occur for different strokes within a single flash. Relatively successful modeling of the oscillatory voltage waveforms is presented. Modeling of the impulsive waveforms proved unsuccessful, probably due to those waveforms being in part associated with a failure, perhaps an unexpected flashover, in the measuring system     

Extraction of power line maps from millimeter-wave polarimetric SARimages

Radar backscatter of power lines has lower values than those of the surrounding ground clutter when the power line is oriented at an off-normal direction with respect to the radar line of sight. For power lines, the traditional detection algorithms that are commonly based on the statistics of the backscatter power of the clutter and target result in excessive false-alarm rates due to very low signal-to-clutter ratio. The application of a statistical polarimetric detection algorithm that significantly improves the signal-to-clutter ratio is demonstrated. The coherence between the co- and cross-polarized backscatter components is used as the detection parameter. This statistical detection parameter can be applied to any extended targets such as a suspended cable in clutter background. Detection criteria based on clutter backscattering coefficients, power line size, and aspect angle, as well as the number of independent samples are obtained. The performance of the algorithm for mapping power lines in SAR images is demonstrated using a number of low-grazing incidence polarimetric SAR images at 35 GHz     

浅谈发电厂的电气综合自动化系统

发电厂作为能源转换电能的工厂,随着我国科学技术不断的发展,发电也有效的利用了电气自动化技术,使其电气综合自动化系统,在满足人们用电需求的同时,降低了经营的成本,从而有效的促进我国经济的发展。对此本文就发电厂的电气综合自动化系统,结合其定义、发展以及功能改造进行分析,并提出相关的见解,希望对于我国电力系统的完善,有着积极促进的意义。     

基于电力线载波低压电缆防盗方案

电力电缆被盗对电力系统造成了严重的安全威胁和财产损失。本文设计了一套基于电力线载波通信的电缆防盗报警方案。载波通信通过扩频调制解调电路来实现。防盗报警系统由报警主站和线路探测终端组成,报警主站根据与各线路探测终端的载波通信成败或者所接收的终端状态信息数据来判断是否发生电力电缆被盗等异常信息,当异常状态出现时,报警主站通过GSM网络拨打电话和短信息发送向远端值班室人员传送警情。同时本文介绍了如何克服电力线上的噪声对载波的干扰,以及如何对断点进行定位的方案。     

电厂电气设备故障的解决措施剖析

对于电厂电气设备来说,在运行期间发生故障是在所难免的,如此一来,电力系统的正常运行便会受到影响,严重的甚至会引发安全事故,因此关键在于如何及时有效的解决故障问题。     

基于OFDM的电力线载波通信的研究

为了实现高压电力线的载波通信,提出利用正交频分复用(OFDM)技术实现高压电力线栽波通信的系统设计.在研究电力线栽波通信和OFDM调制解调技术基本原理的基础上,分析了OFDM技术应用于电力线通信的优缺点,并给出高压电力线栽波系统的硬件组成.     

基于OFDM的电力线载波通信的研究

为了实现高压电力线的载波通信,提出利用正交频分复用（OFDM）技术实现高压电力线载波通信的系统设计。在研究电力线载波通信和OFDM调制解调技术基本原理的基础上。分析了OFDM技术应用于电力线通信的优缺点,并给出高压电力线载波系统的硬件组成。     

基于电力线载波通信的智能用电管理系统设计

为了构建一个智能化小型电能网络,实现对用电设备的精确计量和远程控制,设计一套基于电力线载波通信的智能用电管理系统。系统整合了电能计量、电力线载波通信和继电器等模块,包含PLC插座,以S3C6410为智能网关核心,内嵌Web服务器,通过PC或移动终端可完成各种电器的远程监测和管理。测试结果表明,系统达到了设计要求,且结构简单,通信稳定,具有广泛的应用价值。     

Realization of an active inductance for a low power high bandwidth DC power line communication network transceiver

An active inductor based on an improved gyrator circuit is proposed. The active inductor is developed to be implemented in a high impedance transceiver for a wearable DC power line communication network where requirements such as low power consumption, high bandwidth and numerous nodes support are prioritized. A load isolation step is introduced to ensure the stability of the active inductance's size on different load currents. The proposed gyrator circuit is analyzed and optimized by means of theoretical calculations. The theoretical results are then verified by simulations and experiments in the frequency range up to 10 MHz.     

Radiation from the transmission line with an acute bend

The transmission and radiation characteristics at an acute bend of a transmission line are investigated analytically. First, in consideration of the strong coupling to the adjacent conductor, the current distributions are decomposed into even and odd modes. Applying the traveling-wave mode method to these modes, it is shown that transmission characteristics of the line with an acute bend can be easily obtained. The abrupt variation of the voltage near the bend is noted. Next, the discontinuities of the traveling wave currents are regarded as radiating sources and the radiation field from the bend in the transmission line is derived by the summation of fields created by each of the discontinuities. It is found that there exist the electric field component radiating strongly in the directions of propagation of the current and another electric field component radiating strongly into the intermediate direction. Finally, by comparing with the former method and experimental results, the validity of the method is confirmed     

浅谈电子电工技术在电力系统的应用

电子电工技术是一种综合性的新型技术,主要是将电子技术和电工技术有效结合在一起,是我国科学技术的产物,在全面性和智能性上表现出很大的优势。在电力系统中应用电子电工技术,提高了电能的利用效率,改善了传统电力系统中电力能力的弊端,是电力系统的改革和进步。本文就电子电工技术在电力系统中的应用进行探究,旨在与同行进行交流。     

含分布式电源配电网故障选线研究

当配电网发生单相接地短路故障时,短路电流中包含分布式电源提供的部分,造成对短路电流的整定和故障特征提取产生困难。为此,文中采用集合经验模态分解(EEMD)对故障零序电流进行分解以获得有限个本征模态函数分量,将处理获得的本征模态函数分量一阶差分的极性和模最大值相互对比,实现故障选线。EEMD过程主要使用加法和减法来处理信号,计算速度快。仿真分析表明,该方法简单、程序运行快、选线精度高,故障时间和过渡电阻等随机因素对选线结果影响小。     

Analysis of the harmful effects to buried oil pipeline from power line short-circuit fault

Based on the transmission line theory of the buried metallic structures,the concerned harmful effects to the buried oil and natural gas pipelines caused by the power line short-circuit fault are further discussed.A closed-form expression of the induced voltage caused by the short-circuit fault of the ultra-high voltage power(UHVAC) transmission line is given.The transmission line model of the buried pipeline is set up and a set of formulas for calculating induced voltage on the pipeline and the parameters of the buried pipeline in actual environment condition are given.At last,the characteristic of the harmful effects on the buried pipeline from the power line short-circuit fault are discussed.