微电网的仿真与实验系统Ⅱ—建模仿真及实现

文中基于美国西部联合电网(Western Systems Coordinating Council,WSCC)3机9节点系统,建立了1个带有逆变并网接口的输电网模型,并利用逆变并网接口模型模拟了微电网与上级输电网的连接,对微电网对上级电网电压与频率的支持情况进行了数字仿真。仿真结果表明在上级输电网的有功与无功负荷发生突变时,微电网的接入使上级输电系统的有功与无功功率能够实现就地平衡,并保持系统频率与电压幅值的稳定。整个微电网系统仿真环境设定均按照实验室所能达到的低电压低容量条件下完成。文中所有仿真算法及结果均在PSCAD/EMTDC软件环境及动态模拟实验室中得到验证。     

微电网仿真与实验系统 Ⅰ.总体设计

从设计、数学建模、仿真等方面研究了微电网仿真与实验系统,在微电网模型基础上,采用美国西部联合电网(Western Systems Coordinating Council,WSCC)3机9节点系统作为标准输电网模型,结合硬件仿真实验平台,开发出微电网仿真与实验系统。该系统包括风力发电系统、光伏发电系统、并网接入系统、模拟输配电系统、负荷和仿真实验平台。研制的仿真及实验系统能够稳定可靠运行,实验证实了模型的正确性。应用表明,系统设计合理、功能完善,各方面性能能够满足微电网仿真和实验的要求。     

裘曰修涉胡中藻文字狱案考述

胡中藻文字狱案是乾隆前期文人因诗文遭祸的一宗大案,乾隆因此掀起了一场政治运动,江西籍官员裘曰修等人也受到牵连.裘曰修曾无意透露胡中藻诗集被查的消息,实际其与胡中藻并无交往,也没有刊刻、传播胡中藻诗集等直接行为.乾隆虽未将裘曰修治罪,但江西的其他涉案官员则遭到了相应的处罚.     

Sustainability in Australian schools: A cross-curriculum priority?

PROSPECTS - In light of Australian policy and curriculum initiatives aimed to prioritize Education for Sustainability (EfS) practices, this article discusses a study that evaluated a smart meter...     

青岛市服务外包实施追赶型发展战略的思考

青岛市服务外包发展起步晚,发展战略不强势,明显落后于国内同类城市,亟待采取追赶型战略加快发展.要把发展服务外包提高到更加突出的战略地位,作为优先扶持发展的重点产业,与青岛市促进产业优化和经济转型的大局相结合,采取有效措施,给予全力培育,使之成为全市以服务经济为主的产业结构的重要组成部分.     

Understanding divergent domestication traits from the whole-genome sequencing of swamp- and river-buffalo populations

Domesticated buffaloes have been integral to rice-paddy agro-ecosystems for millennia, yet relatively little is known about the buffalo genomics. Here, we sequenced and assembled reference genomes for both swamp and river buffaloes and we re-sequenced 230 individuals (132 swamp buffaloes and 98 river buffaloes) sampled from across Asia and Europe. Beyond the many actionable insights that our study revealed about the domestication, basic physiology and breeding of buffalo, we made the striking discovery that the divergent domestication traits between swamp and river buffaloes can be explained with recent selections of genes on social behavior, digestion metabolism, strengths and milk production.     

A comparison of students who delay kindergarten entry and those who are retained in grades K−5

Retention has been one way that school personnel have dealt with the problem of school failure. Some authors have proposed delayed school entry as an alternative to retention, especially since there are concerns about the effects of retention on students' self-esteem. It is unclear from the literature whether retention and delayed entry have differential outcomes on measures of school success. This study explored whether there were differences in IQ and achievement (at grades 2, 5, and 7) between students who delayed school entry and those who were retained in later elementary grades, as well as any interactions with gender. There was a significant 6-point difference in IQ, favoring the delayed-entry group. Furthermore, when the achievement test scores were analyzed using an ANCOVA with IQ as a covariate, no significant differences were identified for either group or gender. Implications for school practices are provided.     

Children born at risk: What's happening in kindergarten?

Many studies examine the development of infants born at risk for medical and developmental problems during the early years of life, but far fewer follow these children into their school years. This project compared high-risk vs. low-risk children in their performance on the WPPSI at pre- and postkindergarten levels. In general, both groups of children demonstrated increases in performance; however, their patterns of performance were different. The high-risk children showed increases predominantly in the Performance areas of the test, whereas the low-risk children demonstrated increases predominantly in the Verbal areas.