A survey of the Swiss public transport system and policy

This paper surveys Swiss public transport structure and policy. The regulatory regime is explained with the division between the two operators working under federal monopoly — the State railways (SBB) and the postbuses (PTT) — and the rest of the system. The rather complicated Swiss subsidy arrangements are described. The federal government's emphasis on introducing cheap public transport fares on environmental grounds through the federal transport measures (BTM) and the use of cheap fares in urban areas are discussed. The paper notes the Swiss people's rejection by a referendum of a federal commission's proposal for an integrated transport policy, though some of the solutions were introduced in their own right: the division of SBB into two parts, and the creation of the concept Rail 2000, later developed into Rail + Bus 2000. Finally, the paper reviews problems of the Swiss policy, including the future of cheap fares, making some comparisons with developments in Scandinavia.     

Biologically induced differences in erodibility and aggregation of subtidal and intertidal sediments: a possible cause for seasonal changes in sediment deposition

This study was carried out to describe the difference in erodibility and aggregation in a tidal basin including both subtidal and intertidal study sites and to use these results to explain the shifting erosion/deposition cycles at the sites. Erosion thresholds, erosion rates and settling velocities of the eroded material were measured at a mudflat transect and at sediment cores taken from a nearby tidal channel during surveys made in May 2000 and March 2002. Surface samples were analysed for grain-size, chl. a content, faecal pellet content, dry bulk density and organic content. Additionally, surface samples were taken at eight occasions in the period January 2002 to May 2003 from shallow tidal channels in the area. These samples were analysed for mud content and showed that major shifts in sediment distribution occurred in the period. The erodibility of the mudflat was generally high due to pelletization by the mudsnail Hydrobia ulvae but close to the salt marsh much lower erodibility was found, probably due to stabilisation by microphytobenthos. In contrast, the erodibility of the channel bed seemed to be very little influenced by biological activity and the relatively low erodibility found here was caused by physical characteristics of the sediment. The sediment eroded from the mudflat was generally strongly pelletized and showed high settling velocities whereas less aggregation and lower settling velocities were found for the channel bed sediments. Temporal variations of the mudflat stability and hydrodynamics resulted in temporal variations of deposition and erosion and the changing stability at the mudflat is likely to be one of the main reasons for a general transport of fine-grained sediment from the mudflat to the channel in the cold seasons and vice versa during the rest of the year.     

Service network design with asset management: Formulations and comparative analyses

In this paper, we address the service network design with asset management problem, which integrates asset management considerations into service network design models for consolidation-based freight carriers. We propose model formulations based on arc variables for both flow and design, as well as formulations with path flow variables and new cycle design variables. Problem instances reflecting actual planning problems are used in the computational study to analyze the strengths and weaknesses of the various model formulations and the impact of asset management considerations on the transportation plan and the computational effort. Experimental results indicate that formulations based on cycle variables outperform traditional arc-based formulations, and that considering asset management issues may significantly impact the outcome of service planning models.     

Hydro-elastic analysis and optimization of a composite marine propeller

The present paper addresses the design and optimization of a flexible composite marine propeller. The aim is to tailor the laminate to control the deformed shape of the blade and consequently the developed thrust. The development of a hydro-elastic model is presented, and the laminate lay-up which minimizes the fuel consumption for the cruising and maximum speed conditions is simultaneously determined. Results show a reduction of 1.25% in fuel consumption for the combined case corresponding to a decrease of 4.7% in the cruising speed condition. Finally, the strength of the optimal blade is analyzed using the Tsai-Wu strength index. After local tailoring of the laminate configuration throughout the propeller a maximum value of 0.7 is determined indicating no failure will occur under normal operation conditions. The results suggest that it is possible to design a medium-sized flexible composite marine propeller that will enable a reduction of the fuel consumption while withstanding the imposed loads