The Dynamics of a Railway Freight Wagon Wheelset With Dry Friction Damping

Summary We investigate the dynamics of a simple model of a wheelset that supports one end of a railway freight wagon by springs with linear characteristics and dry friction dampers. The wagon runs on an ideal, straight and level track with constant speed. The lateral dynamics in dependence on the speed is examined. We have included stick-slip and hysteresis in our model of the dry friction and assume that Coulomb's law holds during the slip phase. It is found that the action of dry friction completely changes the bifurcation diagram, and that the longitudinal component of the dry friction damping forces destabilizes the wagon.     

Microscopic activity sequence generation: a multiple correspondence analysis to explain travel behavior based on socio-demographic person attributes

Transportation - Activity sequencing is a crucial component of disaggregate modeling approaches. This paper presents a methodology to analyse and predict activity sequence patterns for persons...     

Cost-effectiveness assessment of CO2 reducing measures in shipping

International shipping is a significant contributor to global greenhouse gas (GHG) emissions, and is under mounting pressure to contribute to overall GHG emission reductions. There is an ongoing debate regarding how much the sector could be expected to reduce emissions and how the reduction could be achieved. This paper details a methodology for assessing the cost-effectiveness of technical and operational measures for reducing CO₂ emissions from shipping, through the development of an evaluation parameter called the Cost of Averting a Tonne of CO₂-eq Heating, CATCH, and decision criterion, against which the evaluation parameter should be evaluated. The methodology is in line with the Intergovernmental Panel on Climate Change (IPCC) and with regulatory work on safety and environmental protection issues at the International Maritime Organization (IMO).

The results of this study suggest that CATCH <50 $/tonne of CO₂-eq should be used as a decision criterion for investment in emission reduction measures for shipping. In total, 13 specific measures for reducing CO₂ emissions have been analysed for two selected case ships to illustrate the methodology. Results from this work shows that several measures are cost effective according to the proposed criterion. The results suggest that cost effective reductions for the fleet may well be in the order of 30% for technical measures, and above 50% when including speed reductions. The results of this study show that the cost effectiveness approach for the regulation of shipping emissions is viable and should be pursued in the ongoing regulatory process.     

Concept for a risk based Navigation Decision Assistant

A concept for a risk based decision support system for navigation of ships that face degrading weather conditions and dangers of damages to a ship at its cargo is outlined. Similar systems exist in various forms, mostly as prototypes, and are based on different ideas of how decision parameters should be communicated to a master as improved basis for decision making. The paper advocates that it is possible to develop a system that systematically is built on risk assessment approaches with the intention of being applicable for a specific ship with a specific loading situation in a real-time environment. The concept is based on modern reliability methodology and relies on state-of-the-art hydrodynamics software and information sources relating to the environment. Based on the various consequences that may occur, the study suggests a selection of limit states and shows how they can be integrated in the decision support system described. The paper presents the risk based concept only while testing of the concept is still in progress.     

Evidence of episodic changes in deep-sea mesozooplankton abundance and composition in the Levantine Sea (Eastern Mediterranean)

Mesozooplankton samples from the 4270-m deep Ierapetra Basin in the oligotrophic Levantine Sea have revealed a strong temporal variability in abundance and composition hitherto unknown for the deep sea pelagic zone. The phenomenon reflected by a survey in June 1993 as compared to January 1987 is assessed by (i) the increase of the mesozooplankton standing crop throughout the water column, (ii) the absence of a decline in mesozooplankton abundance with increasing depth below 1000 m, (iii) the outstanding dominance of two interzonal calanoid copepods at bathypelagic and abyssopelagic depths and (iv) a substantial faunal change due to the codominance of Calanus helgolandicus, which was found for the first time in the area. The underlying hydrographical factors are addressed in the light of the Eastern Mediterranean Transient (EMT). Apart from a possible long-term faunal change, the EMT may exaggerate episodic plankton blooms and surface-abyssopelagic coupling in space and time.     

On the morphological long-term development of dumped material in a low-energetic environment close to the German Baltic coast

The development of the bed bathymetry of an experimental dumping area was followed over three-and-a-half years by means of multibeam echosounder techniques. Two types of material were discharged in the bight of Mecklenburg in the Baltic Sea in approximately 20 m of water depth. One set of the discharges was 2900 m³ of glacial till and the other set was a 2400 m³ mixture of glacial till, sand and minor amounts of cohesive matter. Only approximately 2500 m³ (86%) of the glacial till and 1500 m³ (63%) of the mixed soil materials were deposited on the seabed. This means that already during the dumping process a considerable part of the sediment material drifted away. The glacial till formed crater-like rings of 30 m diameter with peaks up to 1.4 m above seabed, whereas the spatial structure of the mixed soil material was somewhat more diffuse, but with similar magnitudes in the peaks and troughs.The morphological changes were small and their quantification required a high measuring precision in the order of few cm in the vertical. The dominant processes of surface deformation was flattening of peaks and filling of troughs. The speed of this process decreased with horizontal scale: structures of less than 4 m horizontal extension had a trend to disappear within less than five years, whereas structures of larger than 8 m extension showed little change and are estimated to remain detectable for many decades. In contrast to the reworking of the matter inside the dumping structures, no net transport of material out of the dumping area could be detected. Extrapolating the observed morphological changes into the future it is estimated that without significant decrease in internal shear strength of the disposed till the structures will persist for at least 70 years. This can be attributed to the high internal stability of the dumped glacial till and the low hydrodynamic forces present at the seabed in this region.     

A model for national freight flows,distribution centers,empty trucks and urban truck movements

Trucks travel both short distances for local deliveries and long distances for transporting goods across the country. Often their travel behavior is tour-based, they run under tight schedules and under curfew on selected roads. Despite these differences from personal travel, in practice truck models largely follow person travel methods. To overcome this shortcoming, a two-layer truck model is developed for the Chicago Metropolitan Area. Long-distance trucks are driven by commodity flows, with distribution centers, rail yards, marine ports and airports being represented explicitly. Empty trucks are accounted for as well. For the short-distance truck model, a novel parameter estimation method makes use of limited data to derive region-specific parameters. The model is fully operational and validates reasonably well against traffic counts.     

豪华摆式列车ICE-T

介绍了开行新一代摆式列车ICE－T前的一些行之有效的准备工作，及该摆式列车的一些突出特点和对线路应该进行的改造措施，并阐述了该新型摆式列车投入运行后的情况和前2年的运行经验。     

瓦锡兰的服务工具箱中有什么

对这个问题的简单回答就是:服务可以保持瓦锡兰产品的高效工作能力-针对65,000 MW的2冲程发动机和70,000 MW的4冲程发动机-在每一年的每一天、每一小时都能够满足其所有者的需要。这就意味着我们必须能够随时随地提供必要的零件、人工和服务,用以保持产品最高的性能质量。