超高压GIS中快速暂态过电压产生机理及其防治

本文首先从VFTO产生及其产生机理等两个方面介绍了超高压GIS中的快速暂态过电压,随后对快速暂态过电压的危害进行了归纳与总结。进而提出了VFTO抑制措施,对于超高压GIS中的快速暂态过电压抑制有很好的指导意义。     

一起大电流雷击故障跳闸分析

本文针对一起大电流雷击故障跳闸事故的分析,在调研了现场情况的前提下,结合雷电定位系统数据,采用基于电磁暂态仿真分析程序的ATP-EMTP法,分别建立雷电电流波形和雷电通道波阻抗模型、输电线路模型、杆塔模型、绝缘子串闪络模型、接地电阻模型及感应电压模型,对其耐雷水平进行了计算,分析了跳闸原因,并针对本次事故的特点,提出了整改措施,预防类似事故再次发生,并为其线路的防雷提供经验。     

TCSC在500kV电网线路中的应用

采用可控串联补偿器(TCSC)可以提高长距离系统电网输送能力,抑制阻尼,提高系统暂态稳定性。该研究采用Matlab/Simulink软件建立500kV闭环电力系统,并加入TCSC模块进行动态仿真。结果表明,TCSC装置能够平滑、快速地进行阻抗调节,有效抑制阻尼,提高系统稳定性。     

智能电网中基于数据挖掘技术的可再生能源消费预测建模

传统电力系统逐渐步入智能电网时代后,数据量激增,传统的分析处理方法已捉襟见肘。数据挖掘正是解决这个难题的有力工具。本文分析了数据挖掘技术和智能电网各自的特点,揭示了二者之间的密切联系,并结合数据挖掘的相关理论,对该技术在智能电网中的应用给出了实例。本文最后还对数据挖掘技术在智能电网中的进一步推广进行了讨论。     

论武术与书法的异曲同工之妙

武术与书法是中国传统文化的两种表现形式,在各自发展的过程中形成了各自独立的内涵、法则和规律,但两者并非是相互独立的文化,而是彼此有交流、有沟通.文章运用了文献资料法、逻辑分析法和自身的实践体会,对两者进行系统的分析与探讨,旨在为更好地促进两者的发展提供借鉴、开拓思维,使其各自达到更高境界.     

谈谈暂态、静态和动态

近十几年来，悬坠钓法已被广大钓友接受并熟练掌握，因此而屡获佳绩者不胜枚举，不少人还成了高手和大师，但能说清其中力学原理并能清楚回答相关问题者却未见几人。前段时间，在国内几家垂钓刊物上发表的众多关于“剩余浮力”和如何调标的文章就是证明，很多文章让人看完之后一头雾水；还有些文章看似有些道理，但也经不住仔细推敲。之所以如此，是因为众钓友们混淆了“暂态”、     

基于FFT与db10小波变换的电网谐波综合分析

电力系统中引入各种非线性设备，使电网谐波越来越复杂，其中包含大量稳态部分和各种暂态突变部分。目前，比较经典的谐波检测方法就是快速傅里叶变换（FFT），它能快速且准确地计算出稳态谐波，但是对于非稳态谐波信号就无能为力了。小波分析（DWT）能有效地检测非稳态谐波信号，基于二者的优势提出了一种将FFT与DWT综合的谐波分析方法。通过在MATLAB上仿真表明这种方法既能准确检测非稳态信号，也能快速准确的计算稳态谐波的参数。     

大容量高压交流电动机软起动分析

随着国家经济的高速发展,各工业企业生产规模迅速扩大,企业用电设备数量、容量及单台电机最大容量也随之不断增大,用电状况十分复杂,对电网有较高要求。高压大电机直接起动,有诸多弊端,因而各种高压电气软起动装置应运而生。本文有两个主要目的,一是对各种现行高压软起动装置进行介绍,另一是结合工程实例,对电磁调压软起动装置的应用进行实例展示。     

我国城市化建设与社会体育发展的回顾与展望

文章通过对建国以来中国城市化建设以及社会体育发展历程的回顾,总结了城市化和社会体育各自的发展特征和相联系的地方,以及两者各自所呈现的诸多问题.在结合过往经验,结合相关研究的基础上对未来我国城市化进程中社会体育的发展谈了几点看法.     

基于贝叶斯网络和粗糙集的电网故障诊断方法

本文提出一种通过贝《斯网络和粗糙集对常用的电网故障情况进行诊断的方法。该方法可以灵活的表示不确定信息,并能进行不确定性推理。通过研究分析电网在各相短路故障时的电流和阻抗的变化,选用粗糙集理论对故障信息量进行约简,最后通过贝《斯网络对故障情况进行诊断。通过仿真实验,验证了该方法的正确性和有效性。     

Effects of material properties of cue on impact behaviour in follow and draw shots in billiards

The effective numerical method proposed by Shimamuraet al. (2007) is extended to predict the ball motion in a draw shot as well as a follow shot in billiards. The extended method is verified experimentally using a high speed camera. It is observed in the experiment that a ball rotates backwards with a lot of slip (between ball and table) at first and then rotates forwards in a draw shot. Such a ball motion is predicted quantitatively with the numerical method. Numerical simulations are performed to investigate the effects of material properties of a cue on ball behaviour in follow and draw shots and it is found that the impact force increases with increasing stiffness of the shaft in both follow and draw shots, while its duration time is shortened with increasing wave velocity in the shaft for both shots. It is also found that there is a certain shaft stiffness that gives the minimum ball centre velocity, the minimum angular velocity, the minimum slip velocity between ball and table and also the minimum time when the backward rotation changes to a forward one in a draw shot, while the ball centre velocity and the angular velocity increase with increasing shaft stiffness in a follow shot.     

Impact of touring,performance schedule,and definitions on 1-year injury rates in a modern dance company

There is ongoing debate about how to define injury in dance: the most encompassing one or a time-loss definition. We examined the relationship between touring, performance schedule and injury definition on injury rates in a professional modern dance company over one-year. In-house healthcare management tracked 35 dancers for work-related musculoskeletal injuries (WMSI), time-loss injuries (TLinj), complaints, and exposure. The year was divided into 6 segments to allow comparison of effects of performance, rehearsal, and touring. Injuries/segment were converted into injuries/1000-h dance exposure. We conducted negative binomial regression analysis to determine differences between segments, P ≤ 0.05. Twenty WMSI, 0.44 injuries/1000-h, were sustained over one-year. WMSI were 6 times more likely to occur in Segment-6, compared with other segments (incident rate ratio = 6.055, P = 0.031). The highest rate of TLinj and traumatic injuries also occurred in Segment-6, reflecting concentrated rehearsal, New York season and performances abroad. More overuse injuries occurred in Segment-2, an international tour, attributed to raked stages. Lack of methods to quantify performance other than injury may mask effects of touring on dancer’s well-being. Tracking complaints permits understanding of stressors to specific body regions and healthcare utilisation; however, TLinj remain the most important injuries to track because they impact other dancers and organisational costs.     

Are the Multidimensional Body Self-Relations Questionnaire Scales stable or transient?

Body image is an important concept when assessing mental health and, thus, a target for intervention work. The common approach to assess body image is via self-report and, consequently, it is important to assess stability and susceptibility of items to random change. Participants (N = 99, aged: 18–30 years) completed the 34-item Multidimensional Body Self-Relations Questionnaire-Appearance Scales (MBSRQ-AS) twice, separated by two weeks. Stability was quantified by calculating the test–retest differences for each item, with a stable item showing 90% of respondents’ differences within a criterion of ≤±1. This method was used in preference to correlation, which is a test of association rather than agreement. Analyses identified 29 stable items. Five items were found to be unstable including the entire “Appearance Evaluation” scale. One particular unstable question, Q9 = “Most people would consider me good-looking”, revealed strong associations with both gender and weight status. Forty-four per cent of “overweight” respondents changed their minds by more than ±1 compared with only 10% of “normal-weight” participants, suggesting that being overweight is associated with uncertainty and instability. We suggest that future research is needed to investigate why such factors as being overweight appear to be linked to instability in self-report measures of body image.     

Exercise-related transient abdominal pain secondary to median arcuate ligament syndrome: a case report

Exercise-related transient abdominal pain is a common entity in young athletes. An uncommon aetiology of this type of pain is median arcuate ligament syndrome. This article details an 18-year-old field hockey player who presented with a 1-year history of exercise-related transient abdominal pain. Despite a trial of preventative strategies, the patient’s pain persisted, prompting surgical intervention. Following a laparoscopic median arcuate ligament release, the patient’s symptoms resolved. Therefore, when exercise-related transient abdominal pain persists despite precautionary measures, median arcuate ligament syndrome should be considered.     

Carbohydrate ingestion improves endurance performance during a 1h simulated cycling time trial

This study examined the effect of carbohydrate ingestion on metabolic and performance-related responses during and after a simulated 1h cycling time trial. Eight trained male cyclists (VO 2 peak = 66.5ml kg -1 min -1 ) rode their own bicycles mounted on a windload simulator to imitate real riding conditions. At a self-selected maximal pace, the cyclists performed two 1h rides (separated by 7 days) and were fed either an 8% carbohydrate or placebo solution. The beverages were administered 25 min before (4.5ml kg -1 ) and at the end (4.5ml kg -1 ) of the ride. With carbohydrate feeding, plasma glucose tended (P = 0.21) to rise before the time trial. Compared with rest, the plasma glucose concentration decreased significantly (P < 0.05) at the end of both rides, with no statistically significant difference being observed between treatments. Thereafter, plasma glucose increased significantly (P < 0.05) at 15 and 30 min into recovery, and was significantly higher at 30 min during the carbohydrate trial compared with the placebo trial. No significant changes in plasma free fatty acids were observed during the ride. However, a significant increase (P < 0.05) in free fatty acids was found at 15 and 30 min into recovery, with no difference between trials. Mean power output was significantly (P < 0.05) greater during the carbohydrate compared with the placebo trial (mean - S.E.: 277-3 and 269-3W, respectively). The greater distance covered in the carbohydrate compared with the placebo trial (41.5-1.06 and 41.0–1.06km, respectively; P < 0.05) was equivalent to a 44s improvement. We conclude that pre-exercise carbohydrate ingestion significantly increases endurance performance in trained cyclists during a 1h simulated time trial. Although the mechanism for this enhancement in performance with carbohydrate ingestion cannot be surmised from the present results, it could be related to a higher rate of carbohydrate oxidation, or to favourable effects of carbohydrate ingestion on the central component of fatigue.     

Science and medicine of rowing: A review

The biology and medicine of rowing are briefly reviewed. Effort in a 2000 -m race is about 70% aerobic. Because the boat (and in some instances a cox) must be propelled, successful competitors are very tall, with a large lean mass and aerobic power. Large hearts may lead to erroneous diagnoses of a cardiomyopathy. Large respiratory minute volumes must be developed by chest muscles that are also involved in rowing. The vital capacity is typically large, and breathing becomes entrained. Expiration cannot be slowed relative to inspiration (as normally occurs at high rates of ventilation) and the limiting flow velocity may be reached, with the potential for airway collapse. Performance is strongly related to the power output at the ‘anaerobic threshold’, and lactate measures provide a guide to an appropriate intensity of endurance training. Peak blood lactate levels are higher in males (commonly 11–19 mmol·l -1 and occasionally as high as 25 mmol·l -1) than in females (9–11 mmol·l -1), probably because males have a greater muscle mass in relation to blood volume. The skeletal muscles are predominantly slow twitch in type, developing an unusual force and power at low contraction velocities. Many rowers have a suboptimal diet, eating excessive amounts of fat. Lightweight rowers also have problems of weight cycling. Aerobic power and muscle endurance often change by 10% over the season, but such fluctuations can be largely avoided by a well-designed winter training programme. Injuries include back and knee problems, tenosynovitis of the wrist and, since the introduction of large blades, fractures of the costae.     

我国体育市场管理法规研究

采用调查法和比较法对全国体育市场立法和管理现状进行调查,对部分较早出台并有一定代表性的省市的体育市场管理法规的立法和管理情况进行了研究,提出了体育市场管理立法和管理的原则、基本程序、措施及其一般模式,为规范全国体育市场管理提供参考依据。     

重新认识体育的社会关联

体育与政治之间存在一个悖论，体育的发展与经济实力之间没有直线相关，体育与教育部分重叠，体育与宗教最为近缘，体育可借用科学手段，体育的艺术禀性日益明显，体育与养生反映着两种人生观。     

上海社区体育竞赛参与者的特点探析

本文在专家访谈、问卷调查、数理统计和文献资料分析的基础上,探析了上海社区体育竞赛参与者的特点、参与者对社区体育赛事运作管理的看法等问题。在此基础上从引进社区体育赛事的志愿者、整合社区体育赛事的各种资源、开发社区体育竞赛的无形资产、组建非营利性的专业团队、规范社区体育赛事的服务管理等方面提出了进一步满足上海社区居民日益增长的体育竞赛参赛需求的对策与措施。