新型并联电容器保护方案优化设计

对目前并联电容器的常见故障现象与原因进行了总结,针对这些故障提出了一种基于功率平衡的并联电容器保护算法和并联电容器保护处置方案.该保护算法利用在并联电容器发生故障时有功功率绝对值之和大于定值实现了对并联电容器的不平衡保护,通过仿真与实际运行情况对该保护算法进行了验证,结合现场运行情况对并联电容器的不同故障类型的保护与处...     

MIPS系统异常现场分析工具的设计与实现

众所周知,嵌入式系统中CPU的应用快速增长,快速推出新产品并推向市场也变得越来越重要。但是开发和完成一个稳定的产品很困难,特别是复杂的嵌入式系统。在所有的负面影响因素中,嵌入式系统死机是最不能接受的。本文将讨论一种专门用于在一些特定现场解决系统死机问题的有用分析工具。本文通过对为嵌入式应用设计的CPU的异常现场检测机理进行分析,对一种程序运行堆栈分析方法进行介绍。该方法可追溯引起系统异常的代码所在及列出其调用栈清单。为了验证分析有效性并理解导致嵌入式系统异常的原因,该工具可以列出函数/子程序调用树状图,而不用修改正常使用的嵌入式系统产品生成版本。本文介绍的工具已经在MIPS芯片嵌入式系统配置平台MSTAR-7821上进行测试和验证。     

基于多轴电液伺服转向系统的重型车辆操纵稳定性研究

车辆的操纵稳定性是影响车辆行驶安全性的关键因素,操纵稳定性分析通常基于经典线性二自由度车辆动力学模型。该模型忽略了转向系统的影响,直接以前轮转角为输入,无法充分描述车辆的操纵稳定性。以多轴电液助力式转向车辆为研究对象,在二自由度动力学模型的基础上进一步考虑了电液伺服转向系统对车辆操纵稳定性的影响,建立以转向盘转角为输入的多轴电液助力式转向车辆二自由度动力学模型并进行仿真分析。结果表明,电液伺服转向系统模型的加入显著增加了多轴车辆到达稳态转向的时间,且在小转角转向时车辆瞬态质心侧偏角峰值降低,车辆操纵稳定性有所改善。因此,考虑电液伺服转向系统部分的模型可有效提升重型多轴车辆转向性能分析的准确度。     

Systems thinking applied to safety during manual handling tasks in the transport and storage industry

Injuries resulting from manual handling tasks represent an on-going problem for the transport and storage industry. This article describes an application of a systems theory-based approach, Rasmussen's (1997. Safety Science 27, 183), risk management framework, to the analysis of the factors influencing safety during manual handling activities in a freight handling organisation. Observations of manual handling activities, cognitive decision method interviews with workers (n = 27) and interviews with managers (n = 35) were used to gather information about three manual handling activities. Hierarchical task analysis and thematic analysis were used to identify potential risk factors and performance shaping factors across the levels of Rasmussen's framework. These different data sources were then integrated using Rasmussen's Accimap technique to provide an overall analysis of the factors influencing safety during manual handling activities in this context. The findings demonstrate how a systems theory-based approach can be applied to this domain, and suggest that policy-orientated, rather than worker-orientated, changes are required to prevent future manual handling injuries.     

Partial factors for imposed loads in areas for storage and industrial use

The procedures for reliability verification of new or existing buildings are calibrated to account for uncertainties and variability of resistance and load parameters. However, present standards often provide a single approach to specification of design values of all imposed loads on buildings without particular distinction between loads associated with considerable uncertainties and well-defined loads. While the former are represented by common loads in office and residential buildings, the latter, including loads due to storage of materials, material handling equipment, machinery or tanks, require different approaches for estimating design values. This contribution identifies the characteristics of well-defined imposed loads and proposes a methodology for calibrating partial factors. Key steps of the methodology consist of assessing static load effect, dynamic amplification if relevant, model uncertainty, sensitivity factors and target reliability. Careful consideration of these influences then yields partial factors that reflect reduced uncertainties in estimating the effects of well-defined imposed loads. It appears that the commonly accepted partial factor of 1.5 in Eurocodes may be reduced. When multiple crossings are considered, the partial factor can be taken independent of the number of crossings while the characteristic value is adjusted. Further studies should be particularly focused on advanced probabilistic modelling of dynamic amplification and of model uncertainties.     

Dairy cow handling facilities and the perception of Beef Quality Assurance on Colorado dairies

A survey was conducted on Colorado dairies to assess attitudes and practices regarding Dairy Beef Quality Assurance (DBQA). The objectives were to (1) assess the need for a new handling facility that would allow all injections to be administered via DBQA standards; (2) establish if Colorado dairy producers are concerned with DBQA; and (3) assess differences in responses between dairy owners and herdsmen. Of the 95 dairies contacted, 20 (21%) agreed to participate, with a median herd size of 1,178. When asked to rank the following 7 traits—efficiency, animal safety, human safety, ease of animal handling, ease of operation, inject per Beef Quality Assurance (BQA) procedures, and cost—in order of priority when designing a new handling facility, human and animal safety were ranked highest in priority (first or second) by the majority of participants, with ease of animal handling and efficiency ranked next. Interestingly, the administration of injections per BQA standards was ranked sixth or seventh by most participants. Respondents estimated the average annual income from the sale of cull cows to be 4.6% of all dairy income, with 50% receiving at least one carcass discount or condemnation in the past 12 mo. Although almost all of the participating dairy farmers stated that the preferred injection site for medications was the neck region, a significant number admitted to using alternate injection sites. In contrast, no difference was found between responses regarding the preferred and actual location for intravenous injections. Although most participating producers are aware of BQA injection guidelines, they perceive efficiency as more important, which could result in injections being administered in locations not promoted by BQA. Dairy owners and herdsmen disagreed in whether or not workers had been injured in the animal handling area in the last 12 mo. Handling facilities that allow for an efficient and safe way to administer drugs according to BQA guidelines and educational opportunities that highlight the effect of improved DBQA on profitability could prove useful. Dairy producers play a key role in ensuring that dairy beef is safe and high quality, and just as they are committed to producing safe and nutritious milk for their customers, they should be committed to producing the best quality beef.     

Scheduling of short-term hydrothermal energy system by parallel multi-objective differential evolution

With the growing concerns on energy and environment, the short-term hydrothermal scheduling (SHTS) which minimizes the fuel cost and pollutant emission simultaneously is playing an increasing important role in the modern electric power system. Due to the complicated operation constraints and objectives, SHTS is classified as a multi-objective optimization problem. Thus, to efficiently resolve this problem, this paper develops a novel parallel multi-objective differential evolution (PMODE) combining the merits of parallel technology and multi-objective differential evolution. In PMODE, the population with larger size is first divided into several smaller subtasks to be concurrently executed in different computing units, and then the main thread collects the results of each subpopulation to form the final Pareto solutions set for the SHTS problem. During the evolutionary process of each subpopulation, the mutation crossover and selection operators are modified to enhance the performance of population. Besides, an external archive set is used to conserve the Pareto solutions and provide multiple evolutionary directions for individuals, while the constraint handling method is introduced to address the complicated operational constraints. The results from a mature hydrothermal system indicate that when compared with several existing methods, PMODE can obtain satisfactory solutions in both fuel cost and environmental pollutant, which is an effective tool to generate trade-off schemes for the hydrothermal scheduling problem.     

Constrained multi-objective optimization using constrained non-dominated sorting combined with an improved hybrid multi-objective evolutionary algorithm

Constrained multi-objective optimization problems (cMOPs) are complex because the optimizer should balance not only between exploration and exploitation, but also between feasibility and optimality. This article suggests a parameter-free constraint handling approach called constrained non-dominated sorting (CNS). In CNS, each solution in a population is assigned a constrained non-dominated rank based on its constraint violation degree and Pareto rank. An improved hybrid multi-objective optimization algorithm called cMOEA/H for solving cMOPs is proposed. Additionally, a dynamic resource allocation mechanism is adopted by cMOEA/H to spare more computational efforts for those relatively hard sub-problems. cMOEA/H is first compared with the baseline algorithm using an existing constraint handling mechanism, verifying the advantages of the proposed constraint handling mechanism. Then cMOEA/H is compared with some classic constrained multi-objective optimizers, experimental results indicating that cMOEA/H could be a competitive alternative for solving cMOPs. Finally, the characteristics of cMOEA/H are studied.     

Study of ITER equatorial port plug handling system and vacuum sealing interface

In the field of the ITER port plug engineering and integration task, CEA has contributed to define proposals concerning the port plugs vacuum sealing interface with the vessel flange and the equatorial plug handling.The 2001 baseline vacuum flange sealing consisted of TIG welding of a 316L strip plate on to U shapes. This arrangement presented some issues like welding access, implementation of tools, lip consumption, complex local leak test, continuous leak checking. Therefore, an alternate sealing solution based on the use of metallic gaskets is proposed. The different technical aspects are discussed to explain how this design can simplify the maintenance and deal with safety and vacuum requirements.The design of the mechanical attachment and vacuum sealing of the plug has constantly evolved, but the associated remote handling equipment was not systematically reviewed. An update of the cask and maintenance procedure was studied in order to design it in accordance with the last generic plug flange design. This includes a concept of a gripping system that uses the plug flange bolting area and, to help the remote handling process, a cantilever assisting system is suggested to increase the reliability of the transfer operation between vacuum vessel and cask.     

Water hydraulic manipulator for fail safe and fault tolerant remote handling operations at ITER

Department of Intelligent Hydraulics and Automation (IHA) of Tampere University of Technology has been involved in the European Fusion program since 1994 within the ITER reactor maintenance activities. In this paper we discuss the design and development of a six degrees of freedom water hydraulic manipulator with a force feedback for teleoperation tasks. The manipulator is planned to be delivered to Divertor Test Platform 2 (DTP2) during year 2008. The paper also discusses the possibility to improve the fail safe and redundant operation of the manipulator. During the design of the water hydraulic manipulator, special provisions have been made in order to meet the safety requirements such as servo valve block for redundant operation and safety vane brakes for fail safe operation.