基于WebGIS车辆定位系统的设计

探讨了如何利用WebGIS技术实现在Internet环境下车辆定位中的应用,包括系统的组成、工作原理、短消息和WebGIS架构等内容,该设计方法是在微软最新的开发环境.Net和Mapinfo公司的MapX控件基础上开发实现的,详细解释了WebGIS架构和介绍了车辆定位系统的主要功能。系统的实现使用户可以直接在Internet环境下完成查询指定车辆的位置等相关信息,为智能交通的实现奠定了基础。     

带整流负载同步发电机短路电流计算

该文对有阻尼绕组同步发电机整流系统和无阻尼绕组同步发电机整流系统直流侧短路时的最大短路电流进行了分析和计算,得出了随短路初始转子位置的不同,三相同步发电机整流系统直流侧短路电流峰值最大为交流侧最大短路电流,直流侧短路电流峰值最小可为交流侧量大短路电流值的0．933倍。     

Methodology for ro-ro ship and fleet sizing with application to short sea shipping

A novel methodology is developed for determining the characteristics of a cargo roll-on/roll-off (ro-ro) ship and the fleet size required for a given short sea shipping route. The ship and required fleet size to satisfy the transportation demand (for each pair of speed and freight rate) are determined using a database of existing cargo ro-ro ships to obtain the main technical characteristics of the most suitable ship. The time charter, voyage costs and revenue are then calculated considering the technical characteristics of each ship. Fuel costs are corrected for the actual ship speed and loading condition. A number of restrictions in the transportation problem are considered leading to the exclusion of unfeasible solutions. The maximum profit over the period of a year is identified among the feasible pairs of speed and freight rate. This general methodology is applied in a case study that considers the route between Leixões (Portugal) and Rotterdam (Netherlands). The study allows the identification of the most suitable ship and fleet sizes for different market penetration levels and quantifies the impact on shipping company profit of changes in parameters such as fuel costs, time charter costs, emission control area, installed propulsion power and stacking factor.     

船舶配电系统交流智能配电关键技术研究

本文首先论述了船舶交流配电系统的发展需求,然后重点研究了船舶配电系统交流智能配电的关键技术,包括限流判断控制策略、短路故障判断策略及冲击性负载引起限流后解除限流的判断策略,最后通过原理样机,验证了船舶配电系统交流智能配电关键技术解决途径的可行性。     

驼峰直流轨道电路短路故障点快速定位装置

本文介绍了一种驼峰直流轨道电路短路故障快速定位装置，此装置为作者在现场工作中长期探索并研制而成。该装置可使驼峰电子轨道电路短路所造成的设备故障点的查找更便捷准确，实践证明其安全、有效、实用。     

船用断路器短路分断能力的换算

断路器的额定短路分断能力是由制造厂提供的，该断路器在额定频率和规定的功率因素下的分断能力值。在船舶交流电力系统中，短路时的功率因数较低，一般COSφ为0．1-0．2，为此，在设计中选用断路器时，要进行其短路分断能力换算，本文介绍船用断路器短路电流分断能力的换算。     

Empirical analysis of short period traffic counts and their efficiency: the case of Indian traffic

Short period traffic counts (SPTCs) are conducted routinely to estimate the annual average daily traffic (AADT) at a particular site. This paper uses Indian traffic volume data to methodically and extensively study the effect of four aspects related to the design of SPTCs. These four aspects are: (i) for how long, (ii) on which days should SPTCs be carried out, (iii) how many times, and (iv) on which months should SPTCs be carried out? The analyses indicate that the best durations for conducting SPTCs are 3 days (starting with a Thursday) and 7 days, for total traffic and truck traffic, respectively. Further, these counts should be repeated twice a year keeping a separation of two months between the counts to obtain good estimates of AADT at minimal cost. An additional outcome of this study has been the determination of seasonal factor values for roads in developing economies, like India.     

舰船电力系统保护性能优化的自适应算法

为满足舰船电力系统保护在快速性和选择性方面的要求,提出保护性能优化模型,根据电力系统的运行方式、拓扑结构和故障类型的变化,实时在线计算并修改保护整定值的自适应保护方法。将快速性和选择性指标作为保护性能综合指标的基本元素,采用模拟退火粒子群算法进行优化,最终实现不同运行工况下保护性能最优的整定值自适应调整。并在PSCAD/EMTDC软件中建立包含自适应保护算法的舰船电力系统保护仿真模型,仿真结果证明所提方法可有效提高系统保护性能。     

Will a driving restriction policy reduce car trips?—The case study of Beijing,China

A driving restriction policy, as one of the control-and-command rationing measures, is a politically acceptable policy tool to address traffic congestion and air pollution in some countries and cities in the world. Beijing is the first city in China to implement this policy. A one-day-a-week driving restriction scheme was expected to take 20% of cars off the road every week day. Using household survey and travel diary data, we analyze the short-term effect of this driving restriction policy on individual travel mode choice. The data also allow us to identify which demographic groups are more likely to break the restriction rule. The estimates reveal that the restriction policy in Beijing does not have significant influence on individuals’ decisions to drive, as compared with the policy’s influence on public transit. The rule-breaking behavior is constant and pervasive. We found that 47.8% of the regulated car owners didn’t follow the restriction rules, and drove “illegally” to their destination places. On average, car owners who traveled during peak hours and/or for work trips, and whose destinations were farther away from the city center or subway stations, were more likely to break the driving restriction rules. Therefore, Beijing is probably in need of more comprehensive and palatable policy instruments (e.g., a combination of congestion tolls, parking fees, fuel taxes, and high-speed transit facilities) to effectively alleviate traffic congestion and air pollution.     

Breakthrough innovations in intermodal freight transport

Breakthrough innovations, whether technological, organizational or both, are a necessity if the market share of intermodal freight transport is to expand. The main growth potential lies in the markets for flows over short distances, for perishable and high-value commodities, for small consignments, and for flows that demand speed, reliability and flexibility. It will take radical innovations to produce a breakthrough in the modal split and allow these new markets to be conquered. This special issue is based on papers presented at an international conference on freight transport automation and multimodality, held in Delft in May 2002, that are illustrative of the direction of breakthrough research and development (R&D) aimed at increasing the market share for intermodal transport.