变电站直流高频开关电源的检测与验收

直流系统可靠与否直接关系到电网的安全,随着高频开关直流电源系统大量使用,该种电源系统的建成投运验收交接和运行检测、检查,已显得极为重要,从柜体、元器件外观的检查、整套系统电气技术参数检测都必须严格进行,并根据不同的目的进行相应项目的检查,运行中更应定期检查,及时发现存在的隐患,保证其在规定的参数下运行,以提高电池的服役年限。     

Multiple Temporalities of Policy Circulation: Gradual,Repetitive and Delayed Processes of BRT Adoption in South African Cities

In 2006, bus rapid transit (BRT) swept across South African cities. Within three years of learning of the Bogotá model of BRT, Johannesburg's Rea Vaya opened, followed shortly by Cape Town's MyCiTi, while several other cities are at various stages of planning and implementation. This article traces the circulation of BRT across the South African urban context to expose the multiple and varied temporalities through which BRT came to appear as the only available solution. These earlier encounters, which include the first published discussion of BRT in South Africa in a 1973 conference report, study visits to Curitiba in the 1990s and a failed attempt to implement a Bogotá‐style BRT system in Cape Town in 2003, were instrumental in creating a fertile ground for later adoption practices. While it may appear as if circulated policies shorten the gestation time from policy introduction to policy adoption, these repeated attempts to implement circulated innovations ensure that the turnover only seems accelerated. This article unravels the story of BRT adoption, departing from the theoretical discussions of the policy circulation process as a rapid phenomenon, instead demonstrating that it is gradual, repetitive and at times delayed.     

ROFIBUS现场总线在彩涂板生产线中的研究与实践

现今,我国的彩色涂层钢板的生产已经有了一定的发展,但是其生产水平还是比较低下,不能满足现代社会产业发展理念的需求,不能满足低碳发展、可持续发展的价值理念,PROFIBUS现场总线技术在生产中极大地满足了企业对彩涂板生产的需求。     

城市轨道交通直流牵引供电系统接触网残压

对于城市轨道交通来讲,在运行的过程中,直流牵引供电系统是使用最为主要的部件之一。在该系统应用的过程中,接触网残压问题是较为严重的问题,也是当前所出现问题当中比较普遍的一种。对于直流牵引供电系统来讲,当出现接触网残压问题时,可能会对人的生命安全造成严重威胁,同时也会使检修施工和接触网送电保护闭锁等相关工作受到影响,严重拖慢工作进度。因此,论文通过测试、仿真分析和模拟验证等方法,对城市轨道交通直流牵引供电系统接触网残压问题进行了研究与论述。     

Electrification of a city bus network—An optimization model for cost-effective placing of charging infrastructure and battery sizing of fast-charging electric bus systems

The deployment of battery-powered electric bus systems within the public transportation sector plays an important role in increasing energy efficiency and abating emissions. Rising attention is given to bus systems using fast charging technology. This concept requires a comprehensive infrastructure to equip bus routes with charging stations. The combination of charging infrastructure and bus batteries needs a reliable energy supply to maintain a stable bus operation even under demanding conditions. An efficient layout of the charging infrastructure and an appropriate dimensioning of battery capacity are crucial to minimize the total cost of ownership and to enable an energetically feasible bus operation. In this work, the central issue of jointly optimizing the charging infrastructure and battery capacity is described by a capacitated set covering problem. A mixed-integer linear optimization model is developed to determine the minimum number and location of required charging stations for a bus network as well as the adequate battery capacity for each bus line. The bus energy consumption for each route segment is determined based on individual route, bus type, traffic, and other information. Different scenarios are examined in order to assess the influence of charging power, climate, and changing operating conditions. The findings reveal significant differences in terms of required infrastructure. Moreover, the results highlight a trade-off between battery capacity and charging infrastructure under different operational and infrastructure conditions. This paper addresses upcoming challenges for transport authorities during the electrification process of the bus fleets and sharpens the focus on infrastructural issues related to the fast charging concept.     

基于成本分析的发车频率模型在广州BRT的应用

班车的发车频率对服务水平及成本控制都起着重要作用。发车频率低,可以降低成本,但是不能满足乘客需求,会引发一系列社会问题;发车频率高,虽然给乘客提供了更好的服务,但是却大大增加了运营成本。本文将在陈文进《大众运输路线服务模式构建之研究》中提出的基于成本的公交班车派发频率模型的基础上,增加环境因素的考虑对模型进行完善。再次本文将以LINGO为工具对模型进行简单求解,并将模型应用于广州快速公交对广州BRT的发车频率进行优化。     

谈直流发电机的基本工作原理、电枢反应及换向

直流发电机与直流电动机具有相同的结构,只是直流发电机是由原动机拖动旋转而发电。可见,它是把机械能变为电能的设备。文章以直流发电机为讨论对象,论述了直流发电机基本工作原理、结构、电路、磁路、运行原理、电枢反应及换向问题,指出了直流电机的最大弱点就是电流换向问题,并分析了影响换向的因素。     

电动轮自卸车电传动系统试验平台的可行性研究

文章依托科技部＂十五＂科研项目——＂交流驱动百吨级矿用自卸车的研制＂,介绍了电动轮自卸车的发展、原理和技术特点。为了满足电传动系统的试验需求,特别是对由柴油发动机、发电机、驱动电机及其测试和控制系统等构成的动力总成进行试验,建立了一个拥有不同驱动电机试验功能的试验平台。平台由变频异步电动机、交流同步发电机、驱动电机、测功机等机械设备和整流器、逆变器、励磁器等电气设备组成,采用CAN总线串行通信协议实现各电控单元之间的信息交换。通过发电机空载特性、外特性、驱动电机稳态运行性能等试验证明,该平台基本满足电动轮自卸车的各种试验条件,为驱动性能研究提供了良好的实验环境。     

基于功能组分解原理的高压配电网可靠性评估方法及其应用

基于功能组分解原理,提出了同时考虑变电站主接线形式和高压配电网结构的可靠性评估模型;建立了包括系统性指标和节点性指标的可靠性指标体系;基于潮流计算和最优理论,建立了反映系统故障行为和优化校正行为的可靠性评估算法。并将上述方法应用于某市2015年高压配电网结构方案的可靠性评估。研究表明,通过该方法得到的高压配电网可靠性评估结果真实可信,该方法具有良好的应用前景。     

现金余额型职业养老金计划及其对我国的启示

现金余额型养老金计划是美国职业养老金近年衍生出的创新模式之一,作为混合型计划的一种,其兼具确定给付型和确定缴费型养老金制度的特点。本文运用比较法分析了现金余额型养老金计划的运行机理,进而在分析我国目前职业养老金面,临的困境的基础上,指出现金余额型养老金计划对我国职业养老金建设的借鉴意义,具体包括：DC计划不是职业养老金...