Managing Potential Health Risks from Electric Powerlines: A Decision Analysis Caught in Controversy

Over the past 20 years, several epidemiological studies have found an association between exposure to electromagnetic fields (EMFs) and health effects, including childhood leukemia and adult brain cancer. However, experts strongly disagree about whether this association is causal and, if so, how strong it is. In this article, we examine several alternatives to reduce EMFs from sources of the California power grid, including undergrounding distribution and transmission lines and reconfiguring or rephasing lines. The alternatives were evaluated in terms of the potential health risk reduction, cost, impacts on service reliability, property values, and many other consequences. Because of the uncertainty about an EMF-health link, the main effort was to determine the sensitivity of the decisions to the probability and seriousness of an EMF hazard. User-friendly computer models were developed to allow stakeholders to change the model assumptions and parameters to analyze the impacts of their own assumptions and estimates on the decision. The analysis clearly demonstrated that only four of the many concerns raised by the stakeholders could make a difference in the decision: health risks, costs, service reliability, and property values. Whether undergrounding, moderate alternatives for EMF reduction, or no change was the best decision depended on a few key factors, including the probability that EMF exposure is a hazard, the severity of this hazard, how the EMF reduction measures are financed, and the impacts on property values. While the analysis did not resolve the EMF issues, it showed that even in the most controversial settings, a little analysis goes a long way to clarifying the issues and to focus the debate.     

非完全消化-火焰原子吸收光谱法测定指甲中的镁锌

建立了非完全消化-火焰原子吸收光谱法快速测定指甲中镁、锌的分析方法,在低温下用浓硝酸消解样品。可获得均匀、透明的样品溶液。以空白溶液为参比,用工作曲线法测定。对样品处理条件、化学干扰、硝酸的影响、试液与空白溶液粘度一致性、背景吸收干扰及检出限进行了考察。测定结果的相对标准偏差小于2.9％,测定结果为灰化法一致,相对误差小于±2.0％。方法简便、快速、准确。     

略论西方国家电力监管立法及其借鉴意义

在系统介绍西方国家电力监管立法的基础上,就西方国家在电力监管立法的基本意义、价值目标和基本模式、内容等进行了全面分析,从中总结出了电力监管立法要注意制定监管规则、保持监管之独立性,以及支持竞争保持中立等对我国具有重要借鉴意义的若干经验。     

偏振光的双光束与多光束干涉

本文通过时平面偏振光的双光束与多先束干涉现象的讨论，使对偏振光的干涉有进一步的认识，并计算出偏振光照明条件下，光栅的光强分布和分辨本领。     

相对论的建立与高层理论观念的能动作用

本文首先简述了相对论的理论构建过程，然后扼要地说明了在其理论构建过程中所涉及利的高层理论观念，最后探讨了高层理论观念在现代物理研究中的能动作用．     

几种传输线的场分布

求开放平板线、外正三角形內圆同轴线、外方內圆同轴线、外正六边形內圆同轴线的特性阻抗而建立的精确保角变换的基础上,本文进一步讨论了显式逆变换函数,从而求得了这几种传输线的场分布的闭合表达式。由于所用保角变换的精确性,所得的显式场分布在内导体和外导体的内接圆尺寸之比小于0.5in。基本上是准确的,在这个尺寸比稍大些时也可作为参考。这些场分布对于了解传输线的功率容量,计算衰减常数,考虑功率耦合,设计有关的有源器件等都是必不可少的。文中获得的几种传输线的场分布的显著特点是计算方便,在一般实用范围內有足够的精度。     

新型高压静电解冻柜设计

针对肉食品专营店和餐饮店对冷冻肉的解冻需求,设计研制了一台新型高压静电解冻柜。该解冻柜采用了高压静电解冻技术。设计了基于可编程逻辑控制器( PLC)的控制系统,可自动调控解冻柜温湿度和电场强度。根据设计性能参数,计算了解冻过程所需加热、制冷负荷和加湿蒸汽量。经解冻实验表明,该解冻柜能缩短解冻时间,降低汁液流失率,抑制微生物的繁殖,且解冻后肉样外观新鲜,肉色泽鲜红,具有实际应用价值。     

考虑消费者预期的电动汽车分时租赁市场价格竞争模型

分时租赁平台作为电动汽车推广的主要方式，其特征与打车软件类似，在风险资本的推动下极易引发价格战。各租车公司的市场需求量不仅与自己的定价有关，也与竞争对手的定价策略相关，目标都是各自利润的最大化。本文在考虑消费者预期的基础上，研究了需求函数为线性情形下的多人博弈，证明了此博弈是超模博弈以及Nash均衡的存在性和唯一性。并进一步揭示了降价幅度、交叉价格和价格敏感消费群体占比对均衡价格、均衡需求量和利润的影响关系，讨论了价格竞争过程中各租车公司的决策过程与利弊关系。结果表明：任意租车公司的降价行为都会引发整个市场的降价反应，且降价幅度随着博弈阶段的推进逐渐减小，最终收敛于均衡价格；动态定价博弈存在最优组合策略，市场竞争时应当把握好降价幅度，避免过度的价格竞争；均衡价格是关于消费者预期的单调减函数，价格敏感的消费群体占比越大，租车公司间价格竞争越激烈，降价幅度会越大，均衡价格越低；对于市场份额大的租车公司利润是关于价格敏感型消费者占比的单调增函数，但对中小租车公司而言则是单调减函数，价格敏感的消费者越多，对大公司有利，对中小公司不利。     

Topological Performance Measures as Surrogates for Physical Flow Models for Risk and Vulnerability Analysis for Electric Power Systems

Critical infrastructure systems must be both robust and resilient in order to ensure the functioning of society. To improve the performance of such systems, we often use risk and vulnerability analysis to find and address system weaknesses. A critical component of such analyses is the ability to accurately determine the negative consequences of various types of failures in the system. Numerous mathematical and simulation models exist that can be used to this end. However, there are relatively few studies comparing the implications of using different modeling approaches in the context of comprehensive risk analysis of critical infrastructures. In this article, we suggest a classification of these models, which span from simple topologically‐oriented models to advanced physical‐flow‐based models. Here, we focus on electric power systems and present a study aimed at understanding the tradeoffs between simplicity and fidelity in models used in the context of risk analysis. Specifically, the purpose of this article is to compare performance estimates achieved with a spectrum of approaches typically used for risk and vulnerability analysis of electric power systems and evaluate if more simplified topological measures can be combined using statistical methods to be used as a surrogate for physical flow models. The results of our work provide guidance as to appropriate models or combinations of models to use when analyzing large‐scale critical infrastructure systems, where simulation times quickly become insurmountable when using more advanced models, severely limiting the extent of analyses that can be performed.     

大功率回旋管双阳极电子枪计算机辅助设计

根据回旋管对电子枪的要求,采用综合法和分析法设计了该双阳极磁控注入电子枪。编制了一套大型的计算程序;利用计算机辅助设计,给出了电极形状、电子轨迹与电子注参量。计算表明,这种电子枪具有速度零散小、层流性好、体积小等特点。该电子枪更能适应大电流工作情况,已经用于制管实验中。由热测实验表明,它具有明显的优点。