浅谈600MW火电机组逻辑优化方法

详细叙述了霍林河坑口电厂2×600MW机组AGC、一次调频优化逻辑优化方法。AGC优化主要是针对机组协调方式中存在的问题,改变其机组协调控制策略,并对控制子回路进行调整优化,以完善机组协调控制性能。一次调频优化主要是针对机组一次调频中存在的问题,优化控制逻辑和参数。本次优化可改进机组的AGC负荷适应能力和一次调频能力,提高机组主要运行参数的调节品质,使其具备安全、稳定、经济、长期运行的条件。     

200MW燃煤供热机组参与一次调频的技术解决方案

以北京热电分公司2号发电机组参与一次调频运行为基础,对热电机组实施一次调频的优化方案,以及优化后机组的参数设置及运行现状进行了介绍,分析了一次调频动作时对协调控制系统稳定性的影响,以及账行人员应采取的相关措施.     

汽轮机阀门流量特性优化

如果汽轮机阀门流量特性曲线与实际流量特性相差较大,在一次调频动作或变负荷时,容易造成负荷变化过大或不足;同时在阀门单、顺序阀切换时造成负荷波动较大,影响机组的稳定运行。DEH阀门流量特性试验就是通过试验的方式得到阀门流量特性曲线,以解决机组变负荷和一次调频时,可能出现负荷突变和调节缓慢以及单、顺序阀切换过程中出现的负荷摆动的现象,优化机组负荷控制精度,保证机组的安全运行。本文以某135MW机组为例,介绍了流量特性曲线的优化试验和计算方法。     

300MW机组一次调频动态分析

通过机组的一次调频试验,了解机组调速系统的静态特性和相关指标,定量认识调速系统相关环节的技术参数,检测机组在电网存在网频偏差情况下的快速补偿能力,验证机组DEH的一次调频逻辑和参数设置,考察机组参与电网的一次调频特性,从而保证机组一次调频的可靠性,提高东北电网的电能质量及频率的控制水平。     

大型灯泡贯流机组实现调频功能的探讨

通过对灯泡贯流式水电机组的调节以达到减少对电网频率变化幅度,介绍机组一次调频及二次调频的作用,为参与电网稳定运行做一次有益的探讨。     

发电机功率变送器故障导致机组停运原因分析及措施

在电力系统发展的过程中,发电机功率变送器是发电厂电力系统重要的控制设备,其直接影响发电机的运行状态。近期因发电机负荷变化或电气一次设备故障时,诱发发电机功率变送器发生故障,导致机组其他主要设备参数异常,直接引起机组给水流量低的保护动作,触发机组MFT保护机组解列。     

1000MW机组修后一次调频大扰动试验性能分析

发电机组的一次调频是汽轮机组的一个基本特性,随着电网内风电、光伏发电等清洁能源的占比增加,电网内火电机组的一次调频特性就显得更加重要。评价一次调频性能的技术指标还有快速性、稳定时间等,这些技术指标对机组和电网的稳定也是至关重要的,在大扰动发生时,虽然协调控制对机组一次调频性能有重要作用,但汽轮机做功能力对机组负荷响应有着决定性的影响。     

火电机组一次调频特性探讨

随着国家电网中大容量机组的数量不断增加,国内电网结构也不断改变,维护电网的稳定性具有重要的现实意义。电网频率是衡量电能质量的主要标准之一,是电网稳定的基础,在实际应用中,火电机组一次调频特性的优劣对维持电网频率的稳定具有重要作用。本文就是在介绍火电机组一次调频概念的基础上,对火电机组一次调频的参数和特性进行了分析。     

供热机组一次调频功能优化

介绍了神华国华北京热电分公司两台抽汽供热机组的控制基本结构及原一次调频设计方案中的不足之处,经过认真的分析和讨论,制定了机组的一次调频功能优化方案并施行,得到了预期的效果。     

国产超临界350MW机组孤网运行一次调频试验分析

通过对国产超临界350MW机组在孤网运行环境下,进行电源侧和负荷侧负荷突变的冲击试验,结合一次调频响应曲线分析,得出孤网总负荷200MW左右时,机组变动40MW以内负荷均在一次调频调节范围之内,满足孤网稳定运行要求,为今后孤网研究及生产运行提供参考。     

Students' Reactions to the Introduction of Videoconferencing for Classroom Instruction

This study examined how students who had no prior experience with videoconferencing would react to the use of videoconferencing as an instructional medium. Students enrolled in seven different courses completed a questionnaire at the beginning of the semester and again at the end of the semester. Students at the origination and remote sites did not differ in their reactions toward videoconferencing but there was a significant difference for gender. Women reacted less favorably to videoconferencing. Compared to the beginning of the semester, students reported significantly less positive attitudes toward taking a course through videoconferencing at the end of the semester. There were no significant differences in students' attitudes toward videoconferencing across courses at the beginning of the semester but there were significant differences across the courses at the end of the semester. The results suggest the need for better preparation for both students and instructors.     

Cooler temperatures inductive to locust outbreaks

Ajoint study by Prof. ZHANG Zhibin from the CAS Institute of Zoology and his co-workers from Norway, US and Swiss have indicated that historical outbreaks of migratory locusts in China were associated with cold spells, suggesting that China＇s projected climate warming could decrease the pest＇s numbers. The study was published in Proceedings of theNational Academy of Sciences on 17 September, 2007.     

Exploring Multiplexity: Social Network Structures in a Computer-Supported Distance Learning Class

A computer-mediated group is a complex entity whose members exchange many types of information via multiple means of communication in pursuit of goals specific to their environment. Over time, they coordinate technical features of media with locally enacted use to achieve a viable working arrangement. To explore this complex interaction, a case study is presented of the social networks of interactions and media use among members of a class of computer-supported distance learners. Results show how group structures associated with project teams dominated who communicated with whom, about what, and via which media over the term, and how media came to occupy their own communication niches: Webboard for diffuse class-wide communication; Internet Relay Chat more to named others but still for general communication across the class; and e-mail primarily for intrateam communication. Face-to-face interaction, occurring only during a short on-campus session, appears to have had a catalytic effect on social and emotional exchanges. Results suggest the need to structure exchanges to balance class-wide sharing of ideas with subgroup interactions that facilitate project completion, and to provide media that support these two modes of interaction.     

The Role of Intermediating Institutions in the Diffusion of Electronic Data Interchange (EDI): How Industry Associations Intervened in Denmark, Finland, and Hong Kong

Electronic data interchange (EDI) provides means for interorganizational communication, creates network externalities, requires an advanced information technology (IT) infrastructure, and relies on standards. In the diffusion of such innovations, institutional involvement is imperative. Such institutions contain governmental agencies, national and global standardization organizations, local government, and nonprofit private organizations like industry associations. The last type of organizations we call intermediating institutions. They intermediate or coordinate ("inscribe") the activities of a group of would-be adopters. Unfortunately, little is known of how these organizations shape the EDI diffusion trajectory. In this article we examine one specific type of intermediating organizations?industry associations?and how they advanced the EDI diffusion process in the grocery sectors of Hong Kong, Denmark and Finland. We identify six institutional measures, placed into a matrix formed by the mode of involvement (influence vs. regulation) and the type of diffusion force (supply push vs. demand pull), that can be mobilized to further the EDI diffusion. Industry associations were found to be active users of all these measures to varying degrees. Their role was critical especially in knowledge building, knowledge deployment, and standard setting. Furthermore, institutional involvement varied due to policy and cultural contingencies and power dependencies.     

Low doses of a red wine ingredient figh diabetes in mice

Aresearch group led by Prof. ZHAI Qiwei from the Institute for Nutritional Sciences under the CAS Shanghai Institutes for Biological Sciences has discovered that even relatively low doses of resveratrol--a chemical found in the skins of red grapes and in red wine--can improve the sensitivity of mice to the hormone insulin, according to a report in the October,2007 issue of Cell Metabolism. As insulin resistance is often characterized as the most critical factor contributing to the development of Type 2 diabetes, the findings“provide a potential new therapeutic approach for preventing or treating” both conditions, the researchers said.     

How Electronic Publishers are Protecting Against Piracy: Doubts About Technical Systems of Protection

The increasing prospects of digital piracy has prompted the perceived need by electronic publishers to adopt technical systems of protection, and governments to reform their copyright laws. This article is a preliminary study of the management of intellectual property by electronic publishers, defined as those involved in the production of online databases, and CD-ROMs. It focuses on three main issues: (1) how electronic publishers view the increasing threat of piracy; (2) the methods of protection employed to protect intellectual property in digital format; and (3) the importance of technological protection of intellectual property in electronic publications. The analysis is based on a sample of 23 UK electronic publishers. The interviews revealed an interesting assortment of protection methods and did not show that technological protection was a preferred way. Instead, the means of protection, in addition to copyright law, comprised niche markets, pricing, trust, bad publicity, and nontechnical and technical means.     

Rough Justice: A Statistical Assessment of ICANN's Uniform Dispute Resolution Policy

Long-standing conflict between domain name registrants and trademark holders prompted the Internet Corporation for Assigned Names and Numbers (ICANN) to create a global, mandatory arbitration procedure known as the Uniform Dispute Resolution Policy (UDRP). The UDRP has been used in 2166 cases involving 3938 domain names as of 1 November 2000. The policy gives the initiator of a complaint, generally a trademark holder, the right to choose which ICANN-accredited dispute resolution service provider (RSP) will handle the case. During the preparation of the UDRP,some feared that complainant selection would lead to "forum shopping" that might bias the results. This article performs a statistical assessment of the forum-shopping thesis and finds support for it. There are statistically significant differences in the various RSPs' propensity to take away names from defendants; there are also major differences in the number of cases brought to each RSP. RSPs who take away names have the larger share of cases. The study examines other variables that might explain differences in market share, such as price, the plaintiff's nationality, or the time taken to decide a case. It finds that nationality and time also are correlated with market share. The study concludes that shopping for a favorable outcome is an important factor in the UDRP.     

Prevalence of soft neurological signs in Chinese people

Prof. Raymond C.K. Chen, a neuropsychologist with the CAS Institute of Psychology, has made novel progress in his studies of schizophrenia. His work has been reported by a recent issue of Behavioural Neurology.     

Molecular motor assembly of a biomimetic system

Active biological molecules and functional structures can be fabricated into a bio-mimetic system by using molecular assembly method. Such materials can be used for the drug delivery, disease diagnosis and therapy, and new nanodevice construction.     

Monoculture Rubber Plantations Have Negative Ef ects on Controlling Splash Erosion

<正>In Xishuangbanna,one of China’s most biodiverse regions,landscape has changed dramatically during the past three decades due to the conversion of tropical rainforest to rubber plantations.In steep areas,terraces are often constructed before planting rubber trees,which causes two important changes in the soil:the destabilization of soil in the bench terraces and the increased vulnerability of unvegetated riser faces to erosion.Few studies have documented the nature and intensity of erosion on bench terraces.Prof.LIU Wenjie and his colleagues from the Xishuangbanna Tropical Botanical Garden(XTBG)conducted a study in Menglun County(21°5′39″N,101°15′55″E),Xishuangbanna to evaluate the influence