电力系统稳定器在某300MW火力发电机组上的应用及参数优化试验研究

随着全国联网工程的不断实施和快速励磁系统的广泛采用,电力系统的正阻尼变弱,致使电网中弱阻尼震荡时有发生。电力系统稳定器PSS对低频弱阻尼振荡有很好的抑制作用,在电力系统中得到了广泛的应用。文章主要介绍了南瑞继保公司的PCS9410A型电力系统稳定器在300MW火力发电机组上的应用,总结了现场PSS试验方法及流程。并根据现场试验数据,对现场PSS模型的相关参数进行了整定,同时验证了电力系统稳定器对电网弱阻尼振荡起到了良好的抑制作用。     

Sexual, physical, verbal/emotional abuse and unexplained chest pain

Objectives

Approximately one third of patients with non cardiac chest pain (NCCP) report a history of abuse, however no data exists on the prevalence of abuse among people with unexplained chest pain in the general population. We aimed to determine if there is a relationship between childhood sexual, physical, emotional abuse and unexplained chest pain, and to identify whether any potential relationship is being driven by an association with psychological distress.

Methods

Subjects were identified from 2 previous random population surveys that included people with irritable bowel syndrome (IBS) and/or functional dyspepsia (FD) and healthy controls. People in the unexplained chest pain group (n = 27) had chest pain in the past 12 months that was not heartburn or heart disease. People in the comparison group (n = 60) did not have chest pain for more than 12 months. Self-reported abuse and psychological variables were assessed using validated measures.

Results

Emotional/verbal abuse (20.8% versus 4.4%, P = 0.032) and physical abuse (16.7% versus 2.2%, P = 0.028) were significantly more common in people with unexplained chest pain versus the comparison group. Only a history of emotional/verbal abuse was a significant independent predictor of meeting criteria for unexplained chest pain (OR = 5.66; 95%CI 1.01–31.80, P = 0.049) even after controlling for IBS and/or FD (OR = 5.45; 95%CI 0.96–30.83, P = .05), but not when depression was controlled for (OR = 4.70; 95%CI 0.90–27.61), P = 0.08.

Conclusions

A history of childhood emotional/verbal abuse is a risk factor for having unexplained chest pain but the association may be moderated by psychological distress, specifically depression.     

用于WiMAX系统中LDPC译码器的改进型Benes网络结构

提出了一种性能优化的Benes网络结构作为开关网络用于WiMAX系统中的低密度奇偶校验码译码器．该网络结构在译码器的输入数目不是2的指数时,能获得最优化的性能．该网络结构是非阻塞的并且可以实现输入输出之间的任何排列组合,因此可以支持WiMAX系统中规定的19种模式．为了减少网络结构的硬件复杂度,提出一种用来产生该网络中所有2×2开关的控制信号的高效算法．同时,使用该高效算法可以减少整个网络的延时．结果表明,该控制信号的生成电路可以节省25．4％的芯片面积,并且总体网络的延时可以缩短36．2％．     

祛魅与救赎:教师身份的返魅

势利的教育造就了祛魅的教师,过度世俗化的教师角色使教师崇高的身份充满了危机。因此,教师角色必须返魅,教师必须勇敢地踏上自我救赎与自我超越之旅,体现崇高,体验良心,体悟智慧,召回并彰显师之魅。     

J458双升液管液面悬浮低压铸造机的研发与应用

分析了国内低压铸造装备及其工艺的落后现状,提出了双升液管液面悬浮低压铸造机方案,介绍了微机液面悬浮加压装置、四柱式主机、轨道辐射加热熔池式保温炉和保温炉传动机构的组成、工作原理和特点。     

低碳经济：县域发展的挑战、机遇和对策

低碳经济是以低耗能、低排放、低污染为基础的经济发展模式,是世界各国当前研究和发展的重点。我国县域发展低碳经济是必然选择,面临着许多挑战,同时又面临着许多机遇。本文在分述县城发展低碳经济的挑战和机遇时,提出了县域低碳经济发展政策建议。     

低噪声高增益LC谐振放大器设计与制作

为了放大微弱的高频信号,需要使用LC谐振放大器。以三极管等分立元件构建的单调谐放大器,具有功耗小,噪声低等优点。三级谐振放大器级联实现较大的增益,级间通过高频变压器互感耦合,便于调整谐振频率,并减少损耗。经测试,本LC谐振放大器放大中心谐振频率15．1MHz,偏差100kHz,-3dB带宽300kHz,实现80dB的放大倍数,功耗324mW。输入50μV微弱信号时,输出无明显失真。结果表明,该LC谐振放大器具有低噪声、低功耗、高增益等优点。     

“几近全人”的丫鬟——《红楼梦》中平儿形象分析

平儿是风流二爷贾琏的通房大丫头,口如蜜饯心似虎狼的凤辣子的贴身丫头。她身世凄苦,无父母兄弟,甚至连姓氏都无从考证,生存处境可见一斑。然而最终从容地行走于贾府上下左右。其生存艺术和悲剧结局,发人深思。     

低碳经济视域中的“节约”理念

低碳视域中的节约理念是对中华民族传统美德的继承和发展,有其鲜明的时代特征和极为丰富的思想内涵。低碳节约不仅仅做"减法"更是在做"加法";低碳节约使人们的生活更美好;是社会公德、企业道德、家庭美德和个人道德的主要内容,应在全社会予以提倡。     

高职学生低碳践行的调查与分析

通过调查发现,高职生对低碳生活有一定的认识,低碳意识清晰,低碳目的明确,但践行较弱。因此,应加大低碳环保知识的宣传教育,教育学生树立正确的低碳观,倡导低碳要注重实效,让低碳真正成为一种习惯。