Computer-Simulation of the Dynamical Curving Behaviour of a Railway-Bogie

This paper describes the modelling of a two axle railway-bogie with variable design configurations and its application in the investigation of the behaviour in transitional and circular curves. Several results indicate possibilities to improve the curving properties and recommend the usage of forced-steering bogies, which show better performance in narrow curves without unbearable sacrifices to high-speed-behaviour on straight track.     

现代机车电传动仿真工具

现代机车动车是一个很复杂的系统,在开发过程中,机械、电子技术和调节技术的专家们必须密切合作.如果既要交换输入数据和结果,又要子系统模型相互直接连接,那么现代仿真工具能极有效地支持这种开发过程.     

Using a random displacement model to simulate turbulent particle motion in a baroclinic frontal zone: A new implementation scheme and model performance tests

Numerical artifacts can limit accurate simulation of turbulent particle motion when Lagrangian particle-tracking models are implemented in hydrodynamic models with stratified conditions like fronts. Yet, modeling of individual particle motion in frontal regions is critical for understanding sediment dynamics as well as the transport and retention of planktonic organisms. The objective of this research was to develop a numerical technique to accurately simulate turbulent particle motions in a particle-tracking model embedded within a hydrodynamic model of a frontal zone. A new interpolation scheme, the ‘water column profile’ scheme, was developed and used to implement a random displacement model for turbulent particle motions. A new interpolation scheme was necessary because linear interpolation schemes caused artificial aggregation of particles where abrupt changes in vertical diffusivity occurred. The new ‘water column profile’ scheme was used to fit a continuous function (a tension spline) to a smoothed profile of vertical diffusivities at the x–y particle location. The new implementation scheme was checked for artifacts and compared with a standard random walk model using (1) Well Mixed Condition tests, and (2) dye-release experiments. The Well Mixed Condition tests confirmed that the use of the ‘water column profile’ interpolation scheme for implementing the random displacement model significantly reduced numerical artifacts. In dye-release experiments, high concentrations of Eulerian tracer and Lagrangian particles were released at the same location up-estuary of the salt front and tracked for 4 days. After small differences in initial dispersal rates, tracer and particle distributions remained highly correlated (r = 0.84 to 0.99) when a random displacement model was implemented in the particle-tracking model. In contrast, correlation coefficients were substantially lower (r = 0.07 to 0.58) when a random walk model was implemented. In general, model performance tests indicated that the ‘water column interpolation’ scheme was an effective technique for implementing a random displacement model within a hydrodynamic model, and both could be used to accurately simulate diffusion in a highly baroclinic frontal region. The new implementation scheme has the potential to be a useful tool for investigating the influence of hydrodynamic variability on the transport of sediment particles and planktonic organisms in frontal zones.     

The coastal edge of the Northeast Water polynya in spring 1993

Multidisciplinary, marine ecological observations were conducted at the shallow water edge of the Northeast Water in June, 1993. Although variable in size and shape, a small polynya was constantly present at Eskimonaes, at the fast-ice edge of Ingolfsfjord. A shallow stratified layer developed at the water sufface at negative water and air temperatures—an effect of sea ice melting in cold water early in the season. Nutrients were recorded in considerable quantities, although by mid July NO₃ had become depleted. The chlorophyll and phytoplankton maxima at 8–12 m depth had peak values of 2 mg chl a m⁻³, typical for Arctic algal blooms. The phytoplankton included over 90 species and was dominated by the Fragillariopsis group. Zooplankton was poor in biomass and density, but over 23 taxa were found, with the copepods Oithona similis and Pseudocalanus acuspes being numerically dominant. Sedimentation was approximately 0.2 g dry weight m⁻² d⁻¹ and suspended matter concentrations ranged from 4 to 19 mg l⁻¹. The benthos was represented by hard bottom forms only, with a surprisingly dense cover of macrophytes. Juvenile sea urchins (Strongylocentrotus droebachiensis), brittle stars (Ophiocten sericeum) and amphipods were dominant. Higher trophic levels were represented by benthic feeders, such as eiders and walruses. The area observed was more similar to high Arctic fjord ecosystems than to the offshore central Northeast Water polynya.     

Hydrographic cruises off northwest Africa: the Canary Current and the Cape Ghir region

We present hydrographic data for several sections located along the African coastline and off Cape Ghir, carried out at times of weak surface winds (October 1995 and September 1997). The main sections are near the continental slope, at mean distances between 100 and 150 km from the coastline. North of Cape Ghir (31°N) the geostrophic transport (referenced to 650 m) of North Atlantic Central Water through these sections is 3.7 and 2.0 Sv for 1995 and 1997, respectively. This confirms that a major fraction of the water transport by the Canary Current flows east, into the continental slope off northwest Africa, at latitudes above Cape Ghir. Most of this flow continues south past Cape Ghir, along the coast and probably through the eastern passages of the Canary Archipelago. A significant fraction, however, may escape through surface Ekman transport (0.3–0.5 Sv during the early fall season) and by offshore flow at Cape Ghir (1.1 Sv in September 1997, referenced to 650 m). Despite the weak winds the Cape Ghir filament was clearly visible, characterized by localized coastal upwelling associated to a cyclonic shallow structure and cold (and fresh) waters stretching offshore as a very shallow feature (50–100 m deep). The satellite images show that the surface temperature field is highly variable, in rapid response to the surface winds, always with a core region of relatively cold water and commonly with one or two associated eddies. Our results support the existence of two recirculation cells in the area: a horizontal one that connects the interior eastern boundary currents with the coastal region and a vertical one related to both wind-induced and filament upwelling. The data also show a salinity subsurface maximum at the root of the filament, linked to water inflow from northern latitudes, and a subsurface anticyclonic eddy over the Agadir canyon, likely related to the poleward slope undercurrent.     

电气化动力总成——它会带来什么?

<正>德尔福公司与上海汽车集团股份有限公司(上海汽车)达成协议,将为上海汽车开发的中度混合动力车提供混合动力技术。这一协议的签署具有开创性的重要意义,它将目前中国市场最大的整车制造商上海汽车与德尔福公司的     

Quantifying uncertainty in high-resolution coupled hydrodynamic-ecosystem models

Marine ecosystem models are becoming increasingly complex and sophisticated, and are being used to estimate the effects of future changes in the earth system with a view to informing important policy decisions. Despite their potential importance, far too little attention has been, and is generally, paid to model errors and the extent to which model outputs actually relate to real-world processes. With the increasing complexity of the models themselves comes an increasing complexity among model results. If we are to develop useful modelling tools for the marine environment we need to be able to understand and quantify the uncertainties inherent in the simulations. Analysing errors within highly multivariate model outputs, and relating them to even more complex and multivariate observational data, are not trivial tasks. Here we describe the application of a series of techniques, including a 2-stage self-organising map (SOM), non-parametric multivariate analysis, and error statistics, to a complex spatio-temporal model run for the period 1988–1989 in the Southern North Sea, coinciding with the North Sea Project which collected a wealth of observational data. We use model output, large spatio-temporally resolved data sets and a combination of methodologies (SOM, MDS, uncertainty metrics) to simplify the problem and to provide tractable information on model performance. The use of a SOM as a clustering tool allows us to simplify the dimensions of the problem while the use of MDS on independent data grouped according to the SOM classification allows us to validate the SOM. The combination of classification and uncertainty metrics allows us to pinpoint the variables and associated processes which require attention in each region. We recommend the use of this combination of techniques for simplifying complex comparisons of model outputs with real data, and analysis of error distributions.     

MBS(R)--欧洲制动控制系统平台

克诺尔机车车辆制动公司开发了模块化的标准制动控制系统MBS,只需较少的费用就可适应欧洲铁路运输企业的各种不同要求.制动系统必须按用户的专门要求来开发.可适配的模块化MBS系统可用于欧洲各国的跨境运输,能满足欧洲不同的安全性规定.系统具有重量轻、所需安装位置小、寿命周期费用低、机车车辆使用率高的优点.Bombardier公司、德国铁路公司、瑞士和奥地利联邦铁路已从中获益.     

Application of NETSIM in modeling B‐signals

NETSIM is a powerful microscopic simulation model and has been applied to numerous traffic studies. However, it appears that there are few attempts to use it to study bus operations. One of the possible reasons may be the difficulty in modeling some of the unique characteristics in bus operations. A similar challenge was faced when a recent evaluation on bus operations involving priority signals (B‐signals) was undertaken in Singapore. This paper describes the difficulties faced when NETSIM was applied in modeling bus priority signals and the techniques adopted to overcome them. This study shows that, by incorporating innovative techniques, NETSIM can be effectively used to model bus operations along with other traffic in a network.