轮轨作用力计算分析及其校核

文章对文献[1]中的车辆-轨道的计算模型以及轮轨接触力迭代求解方法进行了改进。算例分析表明:改进后的数值计算结果与文献[2、3]给出的测试和仿真分析结果具有较好的一致性。此外,利用有限元分析软件ANSYS进行了建模、分析和验证。     

The dynamics of traffic assignment and traffic control: A theoretical study

The paper considers traffic assignment, with traffic controls, in an increasingly dynamic way. First, a natural way of introducing the responsive policy, P_o, into steady state traffic assignment is presented. Then it is shown that natural stability results follow within a dynamical version of this static equilibrium model (still with a constant demand). We are able to obtain similar stability results when queues are explicitly allowed for, provided demand is constant. Finally we allow demand to vary with time; we consider the dynamic assignment problem with signal-settings now fixed. Here we assume that vehicles are very short and that deterministic queueing theory applies, and show that the time-dependent queueing delay at the bottleneck at the end of a link is a monotone function of the time-dependent input profile to the bottleneck. We have been unable to obtain results when dynamic demand and responsive signal control are combined.     

A linear programming approach to conjoint measurment and trade-off analysis

There has been increasing attention placed on decomposition techniques such as conjoint measurement and trade-off analysis. Existing algorithms for both approaches use non-linear estimation techniques. In this paper, a linear integration rule is proposed along with a linear programming algorithm which is used to estimate part-utilities by minimizing the sum of the absolute deviations subject to monotonicity constraints. The algorithm was tested on simulated data and empirically. It was found that the algorithm performed well, especially when data are consistent with initial assumptions.     

LM331在内燃机车检测中的应用

本文给出一种应用于内燃机车水阻测试台的主电压检测电路,该电路使用廉价的单片V/F转换器,通过光电耦合方式,既保证了检测电压的精度,又可有效防止各种干扰串入计算机控制系统。     

Implementing green supply chain practices: an empirical investigation in the shipbuilding industry

ABSTRACT

Environmental concerns have become important in the shipbuilding industry. Governmental expectations about environmental and social performance are much higher than in the past. Public authorities penalize companies that do not comply with the rules. Shipbuilding companies face these challenges by introducing new technologies into their business processes. They do not only start initiatives to green their own business processes but also those of their supply chain partners. This form of environmental management is called Green Supply Chain Management (GrSCM) and its importance is increasingly recognized. Although GrSCM is growing, companies are experiencing difficulties engaging suppliers in environmental activities.

This empirical study analyses drivers for supply chain participation of suppliers in the shipbuilding industry. We explain the participations of suppliers in GrSCM practice by investigating influencing factors including governmental involvement in greening the supply chain, customer requirements towards green issues, feeling of social responsibility, competitive advantage by going green, and GrSCM readiness. Hypotheses are tested with partial least squares, using survey data of 93 suppliers of two leading shipbuilding companies. We found GrSCM readiness, competitive advantage, and social responsibility to be significant drivers in supplier participation. No significant support was found for governmental involvement and customer requirements.     

A non-geometrically similar model for predicting the wake field of full-scale ships

The scale effect leads to large discrepancies between the wake fields of model-scale and actual ships, and causes differences in cavitation performance and exciting forces tests in predicting the performance of actual ships. Therefore, when test data from ship models are directly applied to predict the performance of actual ships, test results must be subjected to empirical corrections. This study proposes a method for the reverse design of the hull model. Compared to a geometrically similar hull model, the wake field generated by the modified model is closer to that of an actual ship. A non- geometrically similar model of a Korean Research Institute of Ship and Ocean Engineering (KRISO)’s container ship (KCS) was designed. Numerical simulations were performed using this model, and its results were compared with full-scale calculation results. The deformation method of getting the wake field of full-scale ships by the non-geometrically similar model is applied to the KCS successfully.     

Intermodal Transit System Coordination

In urban areas where transit demand is widely spread, passengers may be served by an intermodal transit system, consisting of a rail transit line (or a bus rapid transit route) and a number of feeder routes connecting at different transfer stations. In such a system, passengers may need one or more transfers to complete their journey. Therefore, scheduling vehicles operating in the system with special attention to reduce transfer time can contribute significantly to service quality improvements. Schedule synchronization may significantly reduce transfer delays at transfer stations where various routes interconnect. Since vehicle arrivals are stochastic, slack time allowances in vehicle schedules may be desirable to reduce the probability of missed connections. An objective total cost function, including supplier and user costs, is formulated for optimizing the coordination of a general intermodal transit network. A four-stage procedure is developed for determining the optimal coordination status among routes at every transfer station. Considering stochastic feeder vehicle arrivals at transfer stations, the slack times of coordinated routes are optimized, by balancing the savings from transfer delays and additional cost from slack delays and operating costs. The model thus developed is used to optimize the coordination of an intermodal transit network, while the impact of a range of factors on coordination (e.g., demand, standard deviation of vehicle arrival times, etc) is examined.     

TTB or not TTB, that is the question: a review and analysis of the empirical literature on travel time (and money) budgets

This paper summarizes and analyses findings from more than two dozen aggregate and disaggregate studies of travel time (and sometimes money) expenditures, exploring the question of the existence of a constant travel time budget. We conclude (with prior researchers) that travel time expenditures are not constant except, perhaps, at the most aggregate level. Nevertheless, individuals’ travel time expenditures do show patterns that can be partly explained by measurable characteristics. Travel time expenditure is strongly related to individual and household characteristics (e.g., income level, gender, employment status, and car ownership), attributes of activities at the destination (e.g., activity group and activity duration), and characteristics of residential areas (e.g., density, spatial structure, and level of service). To the extent that travel time expenditures are constant at the aggregate level, the underlying mechanisms explaining that regularity are not well understood. Consequently, further research into explaining travel time and money expenditure patterns is justified.     

Witkar: Amsterdam's self-drive hire city car

A small electrically powered city car has been developed for self-drive hire in the centre of Amsterdam; 35 of these cars are now available to hire from 5 stations in the city centre. The. system has been designed for fully automatic control, including direct debit of hirers' accounts at the Amsterdam Savings Bank. The system, which was conceived in 1969 by an industrial designer and former city councillor to reduce traffic in central Amsterdam, failed to win the support of the City Council and has since been developed by a specially formed co-operative society. The co-operative managed to raise loans of US$ 250,000 for the first phase which has now been completed. This included the design and construction of the vehicles, the purchase of a mini-computer for the central control system, development of the control software and construction of the first five stations. A further 10 stations are scheduled for operation by the end of 1976, by which time the fleet should be extended to 100 vehicles. The ultimate target is 150 stations and 1000 vehicles.