计及故障持续时间的电力系统暂态稳定分布式控制

针对电力系统故障持续时间会影响暂态稳定控制的问题, 本文提出了一种使系统在固定时间内恢复暂态稳定运行的策略. 该策略通过电力系统通信拓扑建模方法为每个发电机建立“邻居发电机”, 利用发电机本地信息和其邻居发电机的信息设计分布式控制器, 通过控制储能装置作用于受扰动后的系统, 使其在固定时间内恢复稳定运行. 其次, 此控制策略还解决了一些实际挑战, 如控制器的输入延时、外部的干扰、储能装置的容量限制等. 通过构建李雅普诺夫函数并利用图论知识对该策略展开了稳定性分析, 推导出了稳定系统的时间界限. 最后, 将控制器投入新英格兰39节点测试系统中, 并与其它控制器进行比较, 仿真结果验证了在低容量储能装置限制下和抗干扰性上控制器性能的优势.     

智能网容灾系统关键技术研究

随着电信业务的广泛应用,客户信息和业务处理的高度集中,促使电信运营商对电信业务支撑系统的容灾能力提出了越来越高的要求。叙述了容灾系统建设、基线建立、数据同步、灾难切换、业务恢复等若干重要环节,将容灾运用于生产实践中。     

On the robustness of median sampling in noisy evolutionary optimization

Evolutionary algorithms (EAs) are a sort of nature-inspired metaheuristics,which have wide applications in various practical optimization problems.In these prob...     

Ambient flash sintering of reduced graphene oxide/zirconia composites:Role of reduced graphene oxide

Fabrication of graphene/ceramic composites commonly requires a high-temperature sintering step with long times as well as a vacuum or inert atmosphere,which not only results in property degradation but also significant equipment complexity and manufacturing costs.In this work,the ambient flash sintering behavior of reduced graphene oxide/3 mol% yttria-stabilized ZrO₂(rGO/3 YSZ) composites utilizing rGO as both a composite component and a conductive additive is reported.When the sintering condition is carefully optimized,a dense and conductive composite can be achieved at room temperature and in the air within 20 s.The role of the rGO in the FS of the rGO/3 YSZ composites is elucidated,especially with the assistance of a separate investigation on the thermal runaway behavior of the rGO.The work suggests a promising fabrication route for rGO/ceramic composites where the vacuum and furnace are not needed,which is of interest in terms of simplifying the fabrication equipment for energy and cost savings.     

新型混合型限流断路器分析及试验

研究了一种基于高速斥力开关的交直流两用混合型限流断路器方案,该限流断路器在限流过程中先经过一个强迫换流过程,使得触头分离时高速斥力开关上电流减小到较小值,触头分离后再经历一个自然零电压换流过程,将斥力开关电流换流到二极管支路上.重点对限流断路器换流过程进行了理论分析及仿真,分析了其可能出现的4种分断情况.研制了400V/500A限流断路器样机,并进行了不同短路电流上升率的限流试验,验证了理论分析的正确性.     

新时期我国的政党外交与和谐世界构建

政党外交是国家总体外交的重要组成部分,是政府间外交的重要补充.倡导和谐世界建设,为中国共产党的对外交往活动注入了新的内涵.新时期,在继续坚持党际关系四项原则指导地位的同时,我国政党外交在理念和实践上都要适应和谐世界建设的需要,积极参与国际治理,为创造一个有利于我国和平发展的外部环境而不懈努力.     

Risk-based grouping for checked baggage screening systems

With millions of bags checked at over 7000 baggage screening locations in US daily, the checked baggage screening system may be exploited by the terrorists to do harm to the homeland security. Due to such a huge amount of luggage, how to improve the effectiveness and efficiency of the screening system becomes a challenging task. In this paper, we propose a risk-based cost-effectiveness model where checked bags are classified into several risk classes according to their risk characteristics. According to their risk levels, bags from different classes may go through different device combinations sequentially. For a multiple-device screening system, we determine the optimal sequence of the screening devices and the separate grouping strategies for bags from different risk classes with the objective of minimizing the expected cost per bag. Based on a detailed numerical study, we compare our model with three other cost-effectiveness models (the first model assumes that there is only one risk class, the second model assumes that there is only one group for each risk class, and the third model assumes that all devices in a device combination need to be gone through). Our major conclusions are that our proposed model is beneficial compared with other three models and moreover, the relative benefit becomes larger when the authority commands a stricter upper bound for the probability of false clear.     

Glossary

Editor's Note: In the history of city development, traditional Chinese cities as a whole had been for a long time a unique school in the world, because of their distinctive features in city form, cityscape, architecture,     

基于ISODATA算法的土地利用状况调查

针对现有利用遥感影像进行土地利用状况调查的需求,从统计模式识别的角度出发,在分析ISODATA算法基本原理的基础上,通过visual C＋＋语言编程实现,并将其运用于武汉市某地区的土地利用调查工作中,同时对照ER—DASIMAGINE软件处理结果对分类结果进行分析,提出了改进意见,证明了该方法的可行性与实用性。     

一种高电压输入的PFC电路的分析与实现

详细分析了一种适用于高电压输入的功率因数校正电路,它具有电压跟随型变换器Buck鄄Boost的特点,同时具有低电压应力、检流方便、效率高等优点。经仿真和实验结果验证,该电路与Buck鄄Boost变换器一样,在断续工作状态下自身具备完美的功率因数校正功能。