Murphy's law

This paper deals with several identical turbine-generator sets, rated 13.8 kV, 29 MVA, for powering three separate floating offshore platforms. This article describes the generator sets testing program, the series of events leading up to the failure, a credible analysis of the failure, the steps taken to prevent future incidents, and conclusions regarding testing prior to acceptance of generator sets. A key lesson from this case is that even when electrical and mechanical equipment are being operated under the most controlled of environments, the element of risk is still present. Prior to conducting these types of tests on the vendor's test stands, the vendor should provide documentation that routine maintenance and testing has been performed.     

政策与法规

●外贸法将有重大修改,个人有望从事外贸经营据《报刊文摘》第1891期报道,已提请国家最高立法机关审议的对外贸易法草案,大部分内容将有所变动,其中很重要的一点是外贸经营者的范围将进一步扩大,享有外贸经营权的门槛再度降低。据有关人士透露,该修改案规定,自然人、法人和其它贸易组织依法登记后可从事货物和技术的进出口贸易。这意味着一旦修改案通过,普通百姓将可以以个人身份从事进出口贸易活动。今后我国从事外贸活动的经营主体将更加多样化。●我国将修改反倾销等3大条例在总结入世2年以来经验的基础上,我国将以修订完成的《外贸法》…     

政策与法规

●2003年度中小企业创新基金项目指南根据我国中小企业的特点和优势,2003年度新能源与高效节能领域将从以下3个方面重点支持科技型中小企业的技术创新:1.新型高效能量储存、转换技术及相关产品;2.可再生能源技术及产品;3.高效节能技术及产品。不支持:1.基于传统材料的普通铅酸蓄电池,普通氢镍电池和锂离子电池,尚未取得专利的一次电池及相关技术和产品;2.太阳能热水器等低温太阳能利用技术及相关产品。(一)新型高效能量储存及转换技术和相关产品1.动力电池及相关材料重点支持有研究开发工作基础,并可实现中试或产业化生产的动力电池相关材料…     

政策与法规

3月15日,国家质检总局公布了2004年度开展免检工作的产品类别目录。2004年拟对电池、建筑型材、床上用品、电视机、空凋器、电冰箱、水泥等26类产品开展免检。     

政策与法规

● 国家出台废电池污染防治技术政策 为贯彻《中华人民共和国固体废物污染环境防治法》,保护环境,保障人体健康,指导废电池污染防治工作,2003年10月9日,国家环境保护总局和国家发展与改革委员会、建设部、科技部、商务部联合发文给各省、自治区、直辖市环境保护局(厅)、计委、经贸委(经委)、建设厅、科技厅、外经贸委(厅),(环发[2003]163号)关于批准发布《废电池污染防治技术政策》。该技术政策作为指导性文件,自发布之日起实施。该技术     

Federal law and individual activities

The old federalism resulted in the establishment of basic rights that are protected from infringement by government. The new federalism results in extensions of both the scope of one's rights and the scope of their protection. The scope of natural rights protected is determined by the inalienability of such rights for all men. The scope of their protection depends on such issues as the points of overlap of the individual rights of the parties, the extent to which the parties engage the public in their transduction, etc. When do the rights of one party yield to the conflicting rights another? A logical standard is the extent to which each party has a claim based on a natural right or freedom. You may elect to constrain your right to free speech if you know I will exert my right to privacy and collect money damages from you if you tell a malicious lie about me     

Comparison of Ampere's circuital law (ACL) and the law ofBiot-Savart (LBS)

Ampere's circuital law (ACL) and the law of Biot-Savart (LBS) are applied to the computation of the magnetic flux density at the center of the square loop. The results are compared and some common misunderstandings of students are clarified. It is seen that LBS is general and applies to closed or open circuits. In the case of open circuits, care must be exercised in applying the ACL. Here, two choices present themselves; one is to use a modified form of ACL appropriate to the problem at hand and the second is to use ACL in its generalized form, which takes into account the inevitable charge accumulations     

防空导弹末段制导的最优导引律分析

随着导弹技术的不断发展,导弹末段制导中的比例导引律成为人们研究的重点。比例导引律实现简单,其通过调整导弹与目标之间的角速率就能达到制导的目的。但是比例导引律在设计的时候往往将导弹和目标看成质点,忽略了大气阻力等客观因素,这使得制导的精度并不高,以比例导引为基础,用最小脱靶量为设计原则,辅以直接侧向力从而提高制导精度。通过仿真表明以直接侧向力控制发动机可以很好的完成导弹对目标的打击。     

拦截机动目标的自适应模糊末制导律设计

为提高拦截大机动目标的制导性能,将模糊控制与变结构控制理论相结合,设计了一种模糊末制导律.将目标的机动加速度视为外界干扰,将制导系统的模糊控制规则多个输入变量转化为滑动曲面一个变量,并根据Lyapunov函数分析自适应模糊制导律参数的自适应律,保证了导弹与目标的视线角速率在较小的数值范围,提高制导系统的鲁棒性.仿真结果表明,在相同攻击时间内,对比于比例导引和一般模糊制导律,提出的自适应模糊末制导律减小了脱靶量和拦截时间.     

Generation scheduling and the switching curve law

The switching curve law is an analytic procedure derived from the dual of the Lagrangian relaxation approach to the static unit commitment (SUC) problem. It is argued here that this analytic result provides a new understanding of the general unit commitment problem not otherwise possible from numerical methods. Moreover, the SUC problem and the analytic results presented here have direct applications in the scheduling of hydro generation in power plants and in the interpretation of the pricing rules of the England and Wales Power Pool     

考虑不确定项的大气层内拦截弹制导律设计

针对一类建模过程中考虑不确定项的大气层内拦截弹,提出一种设计简单、高鲁棒性的拦截末段制导律。根据平面内拦截弹-目标的相对运动方程,引入拦截弹的一阶动力学模型,将系统建模误差和目标未知信息看作不确定项,建立下三角型非线性系统方程。应用自适应动态面控制方法设计新型制导律,解决系统输入与不确定项的非匹配问题,避免制导律中调整参数多、微分膨胀现象,且制导律阶数低,有利于工程化实现。稳定性分析说明控制器参数的合理选择满足系统稳定性要求。仿真结果说明该制导律具有缩短拦截时间、提高系统鲁棒性的特点。     

Does existing law fail to address nanotechnoscience?

The realm of nanotechnoscience (NTS) is vast and dense. A niche industry of nanocritics has arisen to address ethical principles that should govern the field, causal factors in that development, and the types of nanotechnological futures considered desirable. Although their visions of a nanotechnologized world vary considerably, commentators of many stripes share a concern about what they perceive as the same worrisome issue: a lack of appropriate ethical and legal principles and processes to guide nanotechnological R&D and commercialization.     

Georg Simon Ohm (of Ohm's law)

Georg Simon Ohm was a famous German scientist in the 19th century. His name was probably spoken more often than any other scientific name by electrical engineers during the Romantic Era of Electrical Engineering. This article gives a brief history of his life and his work that led to his discovery of what is known as Ohm's law.     

土与水工结构接触面模型研究

为了研究土与混凝土接触面的力学性质,对其剪切过程中应力应变曲线的数学模型进行分析。把接触面结构势能分为摩擦势能和粘聚势能两部分,从能量耗散的角度分析接触面剪切破坏机理。从数学特征方程的角度揭示传统双曲线模型的缺陷。根据能量耗散假定,建立接触面应力应变新模型,并给出实验数据的拟合参数。根据库伦准则,推导接触面剪切模量的表达式;根据土与混凝土接触面试验结果统计,建立各参数的确定方法,推荐初步的取值范围。算例模拟说明新模型的正确性。研究成果可供相关的工程设计参考。     

万安水库发电调度规律分析

本文根据万安水库电站目前的现状,利用已有的长系列入库径流资料,采用动态规划方法进行了长系列的发电优化调度计算和分析。本文的特点在于,一是考虑了主汛期和后汛期运行水位的不同组合对发电调度的影响;二是对优化计算结果进行了大量统计分析,分析得出了水库水位变化规律、水库汛末蓄满概率、发电调度规律等,并归纳出实用的发电调度函数(指导线)。     

A scaling law for membrane permeabilization with nanopulses

Experimental studies of plasma membrane permeabilization, caused by single, intense, submicrosecond square wave pulses, indicate that the product of electric field amplitude and pulse duration (the electrical impulse) can be considered a similarity or scaling factor. A model based on the hypothesis that the intensity of membrane permeabilization effects is linearly dependent on the electric charge transferred through the permeabilized membrane, provides results, which are consistent with the empirical observations. For multiple pulses, bioelectric effects caused by ultrashort pulses were found to scale with the square root of the pulse number. This square root dependence on the pulse number points to a statistical motion of cells between pulses with respect to the applied electric field, and can be explained using an extension of the random walk statistical results to random rotations. Besides membrane permeabilization, the scaling law has also been shown to hold for secondary bioelectric effects, which are caused by permeability changes in the plasma membrane or subcellular membranes.     

Engineering and the law: pillorying well-stocked scientists

Previously (ibid., March 1993, March 1994, May 1994) the authors discussed the conflict between headline-seeking reporters, and zealous scientists at the Office of Research Integrity seeking to convict high profile researchers of misconduct. The authors also discussed the rights of the researchers to a fair hearing on the charges against them. Here the following topics are discussed: responsibilities of the Director; responsibilities of the Policy and Education Division; responsibilities of the Research Investigations Division; misappropriation of NHS funds and the ALERT system; protecting whistleblowers; how to avoid trouble     

A fractional adaptation law for sliding mode control

This paper presents a novel parameter tuning law that forces the emergence of a sliding motion in the behavior of a multi‐input multi‐output nonlinear dynamic system. Adaptive linear elements are used as controllers. Standard approach to parameter adjustment employs integer order derivative or integration operators. In this paper, the use of fractional differentiation or integration operators for the performance improvement of adaptive sliding mode control systems is presented. Hitting in finite time is proved and the associated conditions with numerical justifications are given. The proposed technique has been assessed through a set of simulations considering the dynamic model of a two degrees of freedom direct drive robot. It is seen that the control system with the proposed adaptation scheme provides (i) better tracking performance, (ii) suppression of undesired drifts in parameter evolution, (iii) a very high degree of robustness and improved insensitivity to disturbances and (iv) removal of the controller initialization problem. Copyright © 2008 John Wiley & Sons, Ltd.