A comparison of Chinese,Japanese, and Korean shipyard production technology

This paper compares Chinese, Korean, and Japanese shipyard production technology. Development in the world shipbuilding over recent years has influenced focus areas related to shipyard manufacturing technologies and product performance. Software systems, information technology, production technology, and local challenges of shipyards are compared with shipbuilding outputs among these three countries. Various technologies developments, shipyard production and the problems in Chinese, Japanese, and Korean shipyards are discussed respectively. Finally, future areas of research are pointed out.     

汽车继电器触点瞬态接触传热特性数值模拟分析

继电器是车辆电器控制的重要控制元器件,其工作环境是瞬间大电流通过周期性闭合的触点,由于接触触点间接触电阻在闭合瞬间大电流的作用下产生焦耳热,导致触点极易发生熔焊的可能,严重影响继电器的使用性能,危害行车安全,据统计触点部分的故障率占到继电器故障率的90%以上。揭示汽车继电器触点瞬态接触传热特性,对改善继电器触点触点熔焊故障具有重要的现实意。本文采用分型接触理论建立接触电阻模型,综合考虑触点间接触力、接触面积及材料的比热容、导热系数等,建立了继电器触点闭合瞬间大电流作用下的有限元模型,模拟计算触点间的瞬态热场分布,为改善继电器触头熔焊现象提供理论支撑。     

可回转舵桨离合器国产化技术改造

阐述了全回转拖轮的可回转舵桨离合器的结构和工作原理,分析了立式铜鼓-钢圈滑擦型离合器存在的缺陷,提出了一种全新的国产化改造方案及其实施方法。该方案改造获得了良好的经济效益。     

基于PROFIBUS-DP的变频器在门机调速系统中的应用

当前港口门机变频调速系统中的调速指令,多采用从变频器的多功能端子输入,这种控制方法线缆繁多,走线复杂,故障率较高,给维护带来很多困难.本文介绍的是基于PROFIBUS-DP现场总线的变频器在门机交流调速系统中的应用.PROFI-BUS-DP现场总线是一种全数字化、双向、多站的通讯系统,用于分散外设的高速数据传输,其特点是最小化的响应时间和高抗干扰性.按照PROFI-BUS总线协议完成通讯功能,各站点之间只需一根RS-485双绞电缆连接,传输波特率为9.6～12000 kbit/s,传送距离长,能连接多个用户.基于PROFIBUS现场总线的变频器可以很方便地在PLC、各机构调速系统及工控机之间实现互联,可以完全实行数字化控制,同时二次控制回路设计简洁,可靠性大大提高.     

上海轨道交通1号线增扩编改造项目中的车轴齿轮箱组装工艺

介绍了上海轨道交通1号线增扩编项目中的齿轮箱结构特点及功能、组装工艺、轴承间隙的测量和调整方法,及驱动单元空转跑合试验。     

An analysis of bicycle route choice preferences in Texas,US

In the US, the rise in motorized vehicle travel has contributed to serious societal, environmental, economic, and public health problems. These problems have increased the interest in encouraging non-motorized modes of travel (walking and bicycling). The current study contributes toward this objective by identifying and evaluating the importance of attributes influencing bicyclists’ route choice preferences. Specifically, the paper examines a comprehensive set of attributes that influence bicycle route choice, including: (1) bicyclists’ characteristics, (2) on-street parking, (3) bicycle facility type and amenities, (4) roadway physical characteristics, (5) roadway functional characteristics, and (6) roadway operational characteristics. The data used in the analysis is drawn from a web-based stated preference survey of Texas bicyclists. The results of the study emphasize the importance of a comprehensive evaluation of both route-related attributes and bicyclists’ demographics in bicycle route choice decisions. The empirical results indicate that travel time (for commuters) and motorized traffic volume are the most important attributes in bicycle route choice. Other route attributes with a high impact include number of stop signs, red light, and cross-streets, speed limits, on-street parking characteristics, and whether there exists a continuous bicycle facility on the route.

A traffic analysis zone definition: a new methodology and algorithm

This paper develops a comprehensive approach to the definition of transportation analysis zones (TAZ), and therein, presents a new methodology and algorithm for the definition of TAZ embedded in geographic information systems software, improves the base algorithm with several local algorithms, and comprehensively analyses the obtained results. The results obtained are then compared to these presently used in the transportation analysis process of the Lisbon Metropolitan Area. The proposed algorithm presents a new methodology for TAZ design based on a smoothed density surface of geocoded travel demand data. The algorithm aims to minimise the loss of information when moving from a continuous representation of the origin and destination of each trip to their discrete representations through zones, and focuses on the trade-off between the statistical precision, geographical error, and the percentage of intra-zonal trips of the resulting OD matrix. The results for the Lisbon Metropolitan Area case study suggest a significant improvement in OD matrix estimates compared to current transportation analysis practises based on administrative units.

A copula-based joint multinomial discrete–continuous model of vehicle type choice and miles of travel

In this paper, a joint model of vehicle type choice and utilization is formulated and estimated on a data set of vehicles drawn from the 2000 San Francisco Bay Area Travel Survey. The joint discrete–continuous model system formulated in this study explicitly accounts for common unobserved factors that may affect the choice and utilization of a certain vehicle type (i.e., self-selection effects). A new copula-based methodology is adopted to facilitate model estimation without imposing restrictive distribution assumptions on the dependency structures between the errors in the discrete and continuous choice components. The copula-based methodology is found to provide statistically superior goodness-of-fit when compared with previous estimation approaches for joint discrete–continuous model systems. The model system, when applied to simulate the impacts of a doubling in fuel price, shows that individuals are more likely to shift vehicle type choices than vehicle usage patterns.

Traveled distance,stock and fuel efficiency of private vehicles in Canada: price elasticities and rebound effect

This paper presents estimates of the rebound effect and other elasticities for the Canadian light-duty vehicle fleet using panel data at the provincial level from 1990 to 2004. We estimate a simultaneous three-equation model of aggregate demand for vehicle kilometers traveled, vehicle stock and fuel efficiency. Price and income elasticities obtained are broadly consistent with those reported in the literature. Among other results, an increase in the fuel price of 10% would reduce driving by ~2% in the long term and by 1% the average fuel consumption rate. Estimates of the short- and long-term rebound effects are ~8 and 20%, respectively. We also find that an increase in the gross domestic product per capita of 10% would cause an increase in driving distance of 2–3% and an increase of up to 4% in vehicle stock per adult. In terms of policy implications, our results suggest that: (1) the effectiveness of new fuel efficiency standards will be somewhat mitigated by the rebound effect and (2) fuel price increases have limited impacts on gasoline demand.