Optimal tank-trailer routing using the ILOG constraint programming – a Taiwan case study

Abstract

This paper investigates the routing of pressurized tank trailers and proposes a scheduling plan which ensures the practical delivery of industrial gases under the objective of reducing transportation costs. Using constraint programming, we solve a combinatorial optimization problem that incorporates both hard and soft constraints for routing and scheduling tank trailers. Hard constraints are resource and safety/regulation constraints, whereas soft constraints are utilization and efficiency constraints. This approach enables tank-trailer routing and scheduling management to consider different combinations of parameters and view the results in ‘real-time.’ The routing and scheduling results based on a case study in Taiwan fulfil the goals of avoiding risks associated with transporting industrial gases, and attaining efficient delivery while conforming to regulations and consistent with good business practice. The results also suggest that significant economies in distribution costs are possible.     

LNG船的燃气和蒸汽轮机推进器(英文)

Propulsion of liquefied natural gas (LNG) ships is undergoing significant change. The traditional steam plant is losing favor because of its low cycle efficiency. Medium-speed diesel-electric and slow-speed diesel-mechanical drive ships are in service, and more are being built. Another attractive alternative is combined gas and steam turbine (COGAS) drive. This approach offers significant advantages over steam and diesel propulsion. This paper presents the case for the COGAS cycle.     

A non-Hertzian method for solving wheel–rail normal contact problem taking into account the effect of yaw

A novel approach is proposed in this paper to deal with non-Hertzian normal contact in wheel–rail interface, extending the widely used Kik–Piotrowski method. The new approach is able to consider the effect of the yaw angle of the wheelset against the rail on the shape of the contact patch and on pressure distribution. Furthermore, the method considers the variation of profile curvature across the contact patch, enhancing the correspondence to CONTACT for highly non-Hertzian contact conditions. The simulation results show that the proposed method can provide more accurate estimation than the original algorithm compared to Kalker’s CONTACT, and that the influence of yaw on the contact results is significant under certain circumstances.     

Scaled vehicle tire characteristics: dimensionless analysis

This article demonstrates the use of dimensional analysis for scaled vehicle tires. The motivation for this approach is the understanding of realistic nonlinear tire behavior in scaled vehicle control studies. By examining the behavior of vehicle tires within a dimensionless framework, several key tire parameters are developed that allow for an appropriate relationship between full-sized tires and scaled tires. Introducing these scalings into vehicle dynamics studies allows for the development of scaled vehicles that have a high degree of dynamic similitude with full-sized vehicles, but are safer and more economical testbeds on which to develop experimental control strategies. Experimental data are used to compare the nonlinear characteristics for sets of scaled and full-sized tires. Finally, design of a scaled vehicle based on tire characteristics is demonstrated.     

Emergence of ‘new professionalism’ among Chinese seafarers: empirical evidence and policy implications

In this paper some of the factors that were influential in establishing a Canadian shipping policy position à proposissues raised by the UNCTAD V meeting are examined. The first of these issues was the question of early ratification and entry in force of the Conventin on a Code of Conduct for Liner Conferences. The second involved the relationship between flages of convenience and fleet expansion in the developing countries (LDCs). The third concerned LDC participation in the carriage of bulk cargoes. The author concludes that Canada's stance was determined by the fact that she was a major user of shipping withouta significant fleet of her own, and shows how she attempted to balance her sympathy with Third World aspirations with the demands of her own national interests.     

Impact of scale increase of container ships on the generalised chain cost

In recent years, an increase in the size of the container ships could be observed. The question is how these larger ships will influence the total generalised costs from a port of loading to a destination in the European hinterland. The second question is whether a scale increase of the container ships on other loops, such as a loop from the United States to Europe, has the same impact on the generalised chain costs as on the loop from Asia to Europe. A derived question is which element of the total chain has the highest importance, and whether this balance varies as the ship size changes. In this article, a model is developed that allows answering the above research questions. The model is designed to simulate the cost of a complete loop of a container ship and of a chain that uses that same loop. For the chain cost simulation, the maritime part is determined by the loop. From the ports of loading and unloading, the port container handling and the hinterland transportation costs are also integrated. The model also allows calculating the total chain cost from a point of origin (either a hinterland region or a port) to a destination point (also a port or a hinterland region). An actual container loop of a container shipping company can be introduced in the model. An application is made to two existing container loops, namely from Asia respectively the United States to Europe. It turns out that changing ship does indeed lead to economies of scale, but also that the impact is larger on the Asia–Europe connection than on the US–Europe connection. Furthermore, the maritime component has the biggest share in the total chain cost, but as ship size increases, the shares start getting closer to each other. This research contributes to the existing literature in two ways. First of all, it quantifies the impact of the scale increase of container ships throughout the total chain. Second, this is done from a bottom-up engineering modelling approach.     

Managing Traffic by Privatization of Road Capacity: A Property Rights Approach

Abstract

Road congestion remains a serious problem, despite all the efforts to limit road use and to manage growing road traffic volumes. Economic approaches (such as pricing) are introduced based on traditional welfare economic theory. Although they are sometimes very successful, the magnitude of traffic issues also requires alternative and unconventional approaches. Perhaps a more innovative perspective is needed. The paper discusses an alternative economic approach starting from property rights theory. It is translated in transport systems in concepts of infrastructure capacity slot management, where slots are dynamically priced and exclusively allocated to individual users. Debates and practices regarding this approach in air traffic and rail traffic are further developed than in the field of road traffic. The paper aims to explore the potential benefits and disadvantages of the property rights approach for road traffic. Attention is paid to major institutional and technical conditions. The conclusion is that the approach theoretically has clear advantages and seems technologically feasible. Nevertheless, serious political and institutional issues have to be solved first.