On a Method for Estimating Power Spectra

In many engineering problems, the power spectra of random signals have to be measured. In this paper, a method for estimating the unknown parameters in the power spectral density functions of discrete random processes is presented. The spectral density functions are represented by a ratio of two real polynomials in z. It is assumed that only a finite record of the random process is observed and no knowledge about its probability distribution is required. An estimation procedure is developed. It is shown that the denominator parameter estimates can be first obtained. Then the numerator parameters are estimated by filtering the poles from the spectrum. A four parameter example is given to demonstrate the method.     

On the Power of Precedence Life Tests

Eilbott and Nadler [3] study precedence life tests and obtaini closed form expressions for the small sample and asymptotic power under the assumption that the underlying distributions are exponential. In the present paper it is shown that their expressions are in fact valid for a large class of distributions which includes the exponential as well as some other parametric families important in life testing, reliability testing and related fields.     

巴西大停电的思考

2018年3月21日15：48,巴西发生了大停电事故,巴西北部和东北部电力系统与主网解列,切除负荷19760 MW,约占电网总负荷的25%,85%的州受到影响,造成巨大的经济损失。为避免大面积停电事故的发生,介绍了历史上历次大停电事故的主要过程及危害,总结了大停电事故的经验教训。从自然因素、设备故障、事故处理不当、策略失误等方面,分析了大停电事故的主要原因并提出了相应的改进对策。结合新能源接入、交直流混合电力系统、能源互联网、信息物理电力系统、人工智能等当前电网发展和研究的热点,提出应对大停电事故的主要研究方向。     

Hands‐On,Minds‐On Electric Power Education*

ABET Engineering Criteria 2000 has encouraged changes in engineering education. The deregulation of the electric power industry is also causing changes in the types of jobs power engineers take upon graduation. This paper describes efforts by power faculty at Kansas State University to provide students more hands‐on active learning experience with power systems and machinery. A summary of the power curriculum is provided. The courses affected include an energy conversion course required of all electrical engineering students, and a new power laboratory course required of students taking the electric power option. Examples of student assignments are provided. Observations and discussion of the in‐class experiences are provided. The paper describes work done and in progress to convert the traditional power courses into studio‐type courses in which instruction can flow from lecture to laboratory to computer demonstration formats with ease. Future plans for the project are also discussed.     

On the Measurement of Power via a Superheterodyne Spectrum Analyzer

The measurement of power via a superheterodyne spectrum analyzer is investigated. In particular, the performances of two common measurement techniques, in which one is based on a “channel-power” approach and the other on the use of the analyzer in a “zero-span” mode, are assessed. The purpose is both to show advantages and drawbacks of these techniques and to provide useful hints for improving the measurement accuracy and repeatability. To this aim, an original theoretical approach, which is suitably supported by meaningful experimental examples, is proposed in this paper. The experiments also show how to compensate some typical measurement errors due to the analyzer video-filter effects by a simple calibration procedure.     

基于面向对象的隔振系统功率流求解方法

针对复杂隔振系统———单层隔振和多层隔振的混合式系统的求解策略进行了详细的理论分析,给出了 深度优先的结构化建模方法。在此基础上,将隔振系统的结构化分析方法和软件设计中的OO(Object Oriented)思想相 结合,提出了复杂柔性隔振系统面向对象的功率流求解策略。     

基于HMM的核动力旋转机械故障诊断的研究

隐Markov模型(HMM)已经证明是学习动态时间序列的概率模型的最广泛应用的工具之一,它可以使用一个隐变量来模拟系统的动态行为的变化。核动力旋转机械升速过程具有信息量大、信号非平稳、重复再现性不佳等特点,HMM很适合处理此类信号。将HMM引人到核动力旋转机械的故障诊断中,提出了一种基于HMM的故障诊断方法。     

On the Power Handling Properties of High Temperature Superconducting Microwave Contiguous Duplexer

The power handling properties of a high temperature superconducting (HTS) microwave contiguous duplexer are measured in this letter. The HTS contiguous duplexer was fabricated using YBa₂Cu₃O₇ (YBCO) thin films on a 0.5-mm-thick LaA1O₃ substrate, operation frequencies of which are centered at 3.25 GHz and 3.75 GHz with 500-MHz-wide channels. The tested frequency response of power handling property of the HTS contiguous duplexer shows that there is a decreased power handling property on the crossover region; however, this microwave nonlinearity does not affect the engineering application of HTS contiguous duplexers and multiplexers.     

BSJG22功率型衰减器微波参数测试电路研究

本文介绍一种用于测量BSJG22功率型衰减器微波参数如电压驻波比、衰减量的测试电路,并在实验中得到验证,其参数检测值达到厂家指标要求。     

基于马斯洛需求层次理论电动轮椅创新设计探析

从马斯洛的 "需要层次论"出发用户分析了iBOT智能轮椅相对于普通电动轮椅的创新性和优势.并结合国内外电动轮椅的产品研发现状,提出电动轮椅创新设计的需求整合理论,倡导基于满足用户生理和心理需求的电动轮椅创新设计理念.这对我国医疗器械创新设计也有一定参考价值.     

On Advanced Control Methods toward Power Capture and Load Mitigation in Wind Turbines

This article provides a survey of recently emerged methods for wind turbine control. Multivariate control approaches to the optimization of power capture and the reduction of loads in components under time-varying turbulent wind fields have been under extensive investigation in recent years. We divide the related research activities into three categories: modeling and dynamics of wind turbines, active control of wind turbines, and passive control of wind turbines. Regarding turbine dynamics, we discuss the physical fundamentals and present the aeroelastic analysis tools. Regarding active control, we review pitch control, torque control, and yaw control strategies encompassing mathematical formulations as well as their applications toward different objectives. Our survey mostly focuses on blade pitch control, which is considered one of the key elements in facilitating load reduction while maintaining power capture performance. Regarding passive control, we review techniques such as tuned mass dampers, smart rotors, and microtabs. Possible future directions are suggested.     

对建筑施工企业人力资源管理的探讨

随着我国加入WTO、建筑企业资质的重新定位,建筑企业经营的内外环境正发生着一系列的深刻变化,人力资源管理作为企业的轴心管理,对提升企业管理水平和企业长远发展都具有深远的价值。本文对建筑施工企业的人力资源管理如何适应形势的需要作探讨。     

光伏发电系统发电功率预测

为解决光伏发电系统发电功率在不同条件下误差较大问题,提出光伏发电系统发电功率预测新方法。通过分析光伏发电系统结构,研究光伏发电系统发电功率影响因素;以季节和天气类型作为历史样本选取样本源,针对气象部门提供的预测日分时气象数据在历史数据库中寻找相似数据点作为历史样本;依据历史样本构建离线参数寻优数据总集,使用核函数极限学习机算法构建发电系统发电功率预测模型,通过粒子群算法优化模型参数。实验结果表明：所提方法在不同条件下预测太阳能光伏发电系统发电功率的平均绝对百分比误差分别为1.47%和6.39%,光伏组件在综合异常条件下发电功率预测误差相对变化均低于1%,证明所提方法满足实际预测要求。     

浅谈电流互感器二次绕组错误接线对电能计量的影响

电力系统要安全经济运行,必须装设一些测量仪表,以测量电路中各种电气量,如电压、电流、功率、电能等。电流互感器作为测量电能的直接工具之一。它的准确、公平、公正直接关系到厂网双方的经济利益,因此分析电流互感器二次绕组错误接线就显得十分有必要。在工程实践中,通过对某变电站的一条35kV线路的线损分析,提出了电流互感器在实际安装中应该把握的重要环节和注意事项。     

试论人因工程学应用于核电建设全过程

国内外已公布了许多用于核电厂的人因工程学标准或导则，但用于核电建设项目全过程的导则则尚未见到。经过全面调研，作者草拟了《人因工程学用于核电厂建设项目的实施导则（初稿）》。文章扼要论述了该导则的主要思想和内容，强调应将人因工程学渗透进核电建设全过程，阐明编制并实施“人因工程学应用大纲”的方法及各阶段实施要点，说明应当在各级工作组织中设置人因工程学专业小组或人因工程师负责有关具体工作等     

On Improving the Celebrated Paris’ Power Law for Fatigue,by Using Moving Least Squares

In this study, we propose to approximate the a－n relation as well as the da/dn－∆K relation, in fatigue crack propagation, by using the Moving Least Squares (MLS) method. This simple approach can avoid the internal inconsistencies caused by the celebrated Paris’ power law approximation of the da/dn－∆K relation, as well as the error caused by a simple numerical differentiation of the noisy data for a－n measurements in standard fatigue tests. Efficient, accurate and automatic simulations of fatigue crack propagation can, in general, be realized by using the currently developed MLS law as the “fatigue engine” [da/dn versus ∆K], and using a high-performance “fracture engine” [computing the K-factors] such as the Finite Element Alternating Method.
In the present paper, the “fatigue engine” based on the present MLS law, and the “fracture engine” based on the SafeFlaw computer program developed earlier by the authors, in conjunction with the COTS software ANSYS, were used for predicting the total life of arbitrarily cracked structures.
By comparing the numerical simulations with experimental tests, it is demonstrated that the current approach can give excellent predictions of the total fatigue life of a cracked structure, while the celebrated Paris’ Power Law may miscalculate the total fatigue life by a very large amount.     

Power Measurement in DVB-T Systems: On the Suitability of Parametric Spectral Estimation in DSP-Based Meters

Performance assessment and large-scale monitoring of terrestrial digital video broadcasting (DVB-T) transmission apparatuses are currently a pressing need due to the rapid growth of related broadcasting networks in many countries. Power measurements, in particular, play a very important role since RF and IF signal power, RF channel power, RF and IF power spectrum, noise (or unwanted) power, and power efficiency are relevant parameters to be measured as accurately as possible. Although modern spectrum analyzers and high-performance vector signal analyzers exhibit satisfying accuracy and repeatability, their cost, weight, and size make them unsuitable for the purpose. This paper is focused on the design and realization of a digital signal processing-based meter for power measurement in DVB-T systems that is capable of granting good accuracy, satisfying repeatability, reduced measurement time, and cost effectiveness. This paper deals with the digital signal processing algorithm to be implemented in the meter, paying attention to parametric power spectral density (PSD) estimators for their reduced memory requirement and potentially limited computational burden. In particular, a parametric estimation algorithm that is capable of assuring a fast measurement rate is implemented and made operative. The simulation and emulation stages are properly designed to regulate the most relevant parameters of the adopted PSD estimators according to the specific features of the signals involved; a number of experiments on actual DVB-T signals are conducted, the results of which are compared to those provided by competitive measurement solutions.      

论技术权力与政治权力的关联性

权力始终贯穿于人类社会的发展过程中，将其引入到社会科学的多种领域，就成为人们分析该领域内事物相互作用的普遍性工具。技术权力与政治权力既相互区别又相互联系，即两者的本质目的是一致的，两者互为前提，相互促进，相互制约，并相互转化。政治权力具有显著的续惯性与继承性，在很长时期之内都表现为强者恒强；与之相较，技术权力的续惯性与继承性较弱；但技术权力具有能动性与活跃性。技术权力与政治权力有序合理的作用是增强综合国力的重要路径。     

用输入输出法在线测量强功率整流设备运行效率

整流效率是大型整流设备的主要技术指标之一。本文介绍了用输入—输出法现场实时在线测量大型整流设备运行效率的原理、设备及操作要点，重点介绍了云南省计量测试研究所研制的９００型效率仪的原理、结构、性能指标、应用情况及技术改进。