焊轨机的发展前景

本文介绍了能够解决现代钢轨,包括电炉钢钢轨,在使用线路焊轨机进行焊接工作时发生焊接问题的新工艺、新技术和新装备。     

Corrosion of working chains continuously immersed in seawater

Chains used in the offshore industry typically are exposed to continued high rates of corrosion, in part due to the working of the chain not permitting a build up of protective rusts. Herein, a procedure is described for estimating the corrosion loss of low-alloy steel chain under continued immersion corrosion conditions. The procedure is based on extensive recent investigations of the effects of water temperature, salinity, water velocity, and surface roughness on steel corrosion under field conditions. Since the working of the chain does not allow corrosion products (rust) to build up on the critical contact surfaces, erosion due to wear and abrasion can be estimated separately. Two example applications are given.     

中国油轮安全和防污染管理制度

<正>中国是石油消费大国,也是进口大国,2009年石油进口量达到1.99亿吨,其中1.91亿吨通过海上油轮运输。油轮一旦发生事故,极易造成灾难性后果。为此,近年来,交通运输部加大了对油轮安全和防污染管理方面的力度。首先,加强源头管理。交通运输部制定了《船舶安全营运和防止污染管理规则》,并自2004年7月1日起对500总吨及以上的国内油船生效。2006年,颁布了《老旧运输     

乘员膝部碰撞台车试验与车身结构设计

介绍了Euro NCAP关于膝部碰撞试验要求和试验方法。依据该试验方法采用现有的台车试验系统对配有膝部气囊的某车型进行了典型膝部碰撞试验研究。在膝部碰撞伤害区域内选取驾驶员左膝侧、乘员左膝侧、乘员右膝侧和转向柱下护板4个位置作为碰撞试验点,通过分析大腿力和膝部滑移量碰撞试验结果可知,4个碰撞位置设计均符合要求。     

Fuel burn and environmental implications of airline hub networks

Hubs act as switching points for interactions and so are places through which flows are concentrated. This research uses the interactions between a system of cities as an experimental context for understanding selected environmental costs and benefits of concentrated flow. Whether hub based networks create additional environmental costs has been debated in the literature. In this paper, fuel burn is used as an indicator of environmental cost. The essential ideas are: (1) to examine fuel costs associated with larger aircraft; (2) to determine implications of higher loads on dense routes; and (3) to model the resulting implications for hub and gateway location. Variants of these questions apply to passenger and freight flows, and the paper will initially concentrate on passenger models.The paper shows that by modeling fuel burn and introducing a fixed charge (like a set up cost), a multiple allocation hub and spoke model can be adjusted to direct more or less flow onto the inter-facility connector. In other words, usage of multiple connections and direct links can be controlled and modeled as a function of the fixed charge. The resulting networks are characterized by quite different levels of passenger miles, aggregate fuel burn and fixed charges. The preferred network in terms of minimal fuel burn is found by subtracting the fixed set up charge, thereby focusing attention on the modeled fuel burn. The lowest cost set up is a network with a high degree of connectivity, and a pure single assignment hub network has the highest fuel cost (as a result of larger passenger miles needed by connecting paths). The data also allow a tabulation of total passenger miles, which, not surprisingly, track very closely with the fuel burn. In an interesting application of the ideas, it is shown that a fuel efficient network may require a large number of smaller regional jets, and in the interests of avoiding noise and congestion from so many extra airport operations, the carriers may choose to substitute a smaller number of larger planes, thereby slightly increasing fuel needs. This paper also provides a key ingredient for models of an international network where it is impossible to serve many long distance market pairs without consolidation.     

舰船典型舱室气流组织数值模拟

  目的  为比较不同送风方案对居住舱室空气环境的影响,  方法  采用计算流体力学技术对四人居住舱室内的空气环境舒适性进行数值研究。分析气流组织分布的评价指标,对夏季工况下舱室模型的风速、温度、相对湿度、PMV值和CO₂浓度进行模拟计算。通过对比不同送风方案的模拟结果,研究送风角度、送风温度和送风量对舱室内气流组织热舒适性及空气品质的影响。  结果  研究结果表明：送风角度分别取30°和45°时对模拟结果影响较小;降低送风温度并减小送风量虽然会导致舱室内空气湿度相对较小、CO₂浓度较高,但均可满足设计要求,且综合考虑气流组织的评价指标,研究的方案能提高舱室气流组织热舒适性。  结论  \t\t 研究结果对居住舱室送风口布置具有一定的指导意义。     

The impact of ride-hailing on vehicle miles traveled

Transportation - Ride-haling such as Uber and Lyft are changing the ways people travel. Despite widespread claims that these services help reduce driving, there is little research on this topic....     

Rural speed limit changes and safety

There is little information in the literature on the relation between rural speed and safety. The wide variation in rural speed limits that are applied in different countries tends to confirm that this relation is poorly understood. The changes in fatal, injury and all accidents that followed a change in the rural speed limit in seven countries were regressed against the change in vehicle mean speed. The results showed that speed significantly affects safety and that within certain limits the relation is linear. The regressions indicated that a 1 km/h reduction in speed will reduce all severities of accidents by between 4 and 5%. It is suggested that part of this reduction is due to a change in economic factors.     

Practical safety considerations for short headway automated transit systems

Continued interest in Personal Rapid Transit (PRT) systems as one solution to urban traffic congestion emphasizes the need for careful consideration of the safety of short headway automated transit systems. Current approaches to the determination of safe headways are reviewed. The reduction in headway which could be achieved by improved braking and signaling hardware is outlined. Improved design of emergency brakes is the most important single factor in the reduction of safe headways.

Very short headway systems are reviewed from a safety standpoint. Such systems might be safely operated if operation at intermediate headways (separations on the order of the stopping distance) can be avoided.     

Spin glass and the interactions of congestion and emissions: An exploratory step

This paper models traffic congestion formation on highways and roads by recognizing the centrality of dynamical systems and using concepts from complexity theory as imbedded in the spin glasses analogue. Further, it explores the concept of how an increase in air pollution caused by vehicle exhaust emission can be traced to traffic congestion, specifically to the acceleration/deceleration of vehicles on the roads. First, spin glass is introduced and then by applying the two-dimensional x − y Ising model and defining a Hamiltonian (based on Edwards-Anderson and Mattis models of spin glass systems) for a system of vehicles on the road, derivations are made of the specific friction of congestion and the bulk modulus of congestion using the Gibbs-Boltzmann statistic. Similarly using the interactions of vehicles with each other and the resulting accelerations and decelerations of vehicles as the basis for exhaust emissions, derivations are made of a specificity of exhaust emissions. These are analogues to the entropy models of thermodynamics. This series of derivations serves as an analytical model for detecting incidents of congestion and increase in air pollution due to exhaust emissions in transportation systems.