Modelling and validation of coupled high-speed maglev train-and-viaduct systems considering support flexibility

This study presents a more realistic modelling of the maglev-based high-speed railway line in Shanghai, China. Focus is placed on an accurate simulation of the two subsystems: the train subsystem including the magnets and the viaduct subsystem including the modular function units of the rails. The electromagnet force–air gap model with a proportional-derivative (PD) controller is adopted to simulate the interaction between the maglev train via its electromagnets and the viaduct via its modular function units. The flexibilities of the rails, girders, piers and associated elastic bearings are all considered in the modelling of the viaduct subsystem to investigate their effects on an interaction between the two subsystems. By applying the proposed model to the Shanghai maglev line, the essential characteristics of the coupled system can be duly captured. The accuracy and effectiveness of the proposed approach are then validated by comparing the computed dynamic responses and frequencies with the measurement results. It is confirmed that the proposed modelling with a detailed simulation of the magnets and modular function units can duly account for the dynamic interaction between the train and viaduct systems. Moreover, the effects of the inclusion of the flexibilities of the rails, girders and elastic supports to the response of the coupled system are respectively investigated, the results of which prove that their involvements are essential to the accurate prediction of the response of the coupled maglev train–viaduct system.     

应答器报文读取工具的运用

中国列车控制系统（CTCS）是保证行车安全，提高运输效率，实现列车运行控制自动化的主要技术装备。京津客运专线已经开通运行，其动车组控车模式完全依赖于地面应答器的数据，应答器是列车超速防护系统（ATP）的重要组成部分，其工作状态是否稳定直接影响到动车组的安全运行。根据中国列车控制系统基本规划，研究应答器报文的数据检测和读取是非常必要的。     

Short time-scale analysis of the NW Mediterranean ecosystem during summer–autumn transition: A 1D modelling approach

Modelling was used as a tool to better understand the physical and biological processes observed during the multidisciplinary cruise DYNAPROC 2 (DYNAmic of rapid PROCesses in the water column), which took place in the Ligurian Sea in September–October 2004. The aim of the cruise was to study the short time-scale physical and biological processes that occur when the ecosystem switches from summer oligotrophy to autumnal mesotrophy. In this study, we have tested two 1D physical–biological coupled models. The first was a classical model in which surface layer dynamics were obtained using the turbulent kinetic energy model of Gaspar [Gaspar et al., 1990]. The simulated food-web took into account ten state variables: three nutrients, three classes of phytoplankton, two classes of zooplankton and two types of detritus. The second model (called IDA, Isopycnals Depth Adjustment) was based on the initial one but it took into account the measured variations of isopycnals depths. The results showed that the IDA model most efficiently reproduced the observed ecosystem dynamics. We have therefore used the IDA model to show that physical processes observed during the cruise had a major effect on biological compartment, mainly on nano- and picophytoplankton.     

Determining the effects of scheduling on automated automobile guideway utilization

This paper develops an analytic approach for measuring the effect of vehicle scheduling and of metering methods required to balance entrance rates among stations on lane capacity utilization of automated automobile guideways. The scheduling process at each entrance is represented by a probabilistic model which generates a system of nonlinear equations. The solution of this system yields the maximum steady state input rates at the entrances to the guideway system. The method developed is applicable to network configurations in which a small number of merges must be scheduled for each vehicle before it enters the guideway. It is demonstrated by application to a corridor guideway serving a major activity center during peak inbound demand, and also it is shown how the approach may be extended to more complex networks.     

Hybrid modeling of seat-cab coupled system for truck

For the complex structure and vibration characteristics of the seat and cab system of truck, there is no reliable theoretical model for the suspensions design at present, which seriously restricts the improvement of ride comfort. In this paper, a 4 degree-of-freedom seat-cab coupled system model was presented; using the mechanism modeling method, its vibration equations were built; then, by the tested cab suspensions excitations and seat acceleration response, its parameters identification mathematical model was established. Combining the tested signals and a simulation model with the parameters identification mathematical model, a new method of hybrid modeling of seat-cab coupled system was presented. With a practical example of seat and cab system, the parameters values were identified and validated by simulation and test. The results show that the model and method proposed are correct and reliable, and lay a good foundation for the optimal design of seat suspension and cab suspensions to improve ride comfort.     

De l’intérêt de contrôler l’impact des hypothèses de composition du parc automobile sur l’estimation des émissions liées au trafic routier

Since the 1990s, transport project assessments take systematically pollutant emission estimations into account. This paper is about the methodological aspects of these calculations. It focuses more specifically on the car fleet hypothesis, which most often lays on national data, without consideration of local specificities. We use the last household travel survey from Lyon, 2006, and the SIMBAD model to compare the results of CO₂ and NO_x emissions estimated from the French national car fleet, the aggregated Lyon car fleet and the same fleet disaggregated by household location and income. We show that the error level varies, depending on the pollutant and the observation scale. The use of an aggregated local car fleet seems interesting and satisfactory for a global emission assessment. If the results are required at a more detailed spatial level, the use of this local fleet improves sharply the estimations in comparison of a national fleet; the fleet disaggregation refines the results for NO_x.     

基于多维平行六面体模型的动力总成悬置系统固有特性分析

工程实际中,汽车动力总成悬置系统不可避免地存在着一定的参数不确定性,且不确定参数间往往同时存在一定的相关性与独立性。本文中引入多维平行六面体模型处理系统参数相关性和独立性并存的情形,结合蒙特卡洛法提出了一种悬置系统固有特性的不确定性分析方法,并给出了方法的分析步骤。对某悬置系统的数值分析结果表明:该方法能有效处理系统不确定参数的相关性和独立性,与未考虑参数相关性的区间方法相比,该方法能获得更为合理的固有频率和解耦率区间范围;对于给定的研究模型,其左右悬置点的刚度相关性对系统固有特性的影响比较明显,在设计和研究过程中应给予重点关注。     

On the key role of nutrient data to constrain a coupled physical–biogeochemical assimilative model of the North Atlantic Ocean

A sequential assimilative system has been implemented into a coupled physical–biogeochemical model (CPBM) of the North Atlantic basin at eddy-permitting resolution (1/4°), with the long-term goal of estimating the basin scale patterns of the oceanic primary production and their seasonal variability. The assimilation system, which is based on the SEEK filter [Brasseur, P., Verron, J., 2006. The SEEK filter method for data assimilation in oceanography: a synthesis. Ocean Dynamics. doi: 10.1007/s10236-006-0080-3], has been adapted to this CPBM in order to control the physical and biogeochemical components of the coupled model separately or in combination. The assimilated data are the satellite Topex/Poseidon and ERS altimetric data, the AVHRR Sea Surface Temperature observations, and the Levitus climatology for salinity, temperature and nitrate.In the present study, different assimilation experiments are conducted to assess the relative usefulness of the assimilated data to improve the representation of the primary production by the CPBM. Consistently with the results obtained by Berline et al. [Berline, L., Brankart, J-M., Brasseur, P., Ourmières, Y., Verron, J., 2007. Improving the physics of a coupled physical–biogeochemical model of the North Atlantic through data assimilation: impact on the ecosystem. J. Mar. Syst. 64 (1–4), 153–172] with a comparable assimilative model, it is shown that the assimilation of physical data alone can improve the representation of the mixed layer depth, but the impact on the ecosystem is rather weak. In some situations, the physical data assimilation can even worsen the ecosystem response for areas where the prior nutrient distribution is significantly incorrect. However, these experiments also show that the combined assimilation of physical and nutrient data has a positive impact on the phytoplankton patterns by comparison with SeaWiFS ocean colour data, demonstrating the good complementarity between SST, altimetry and in situ nutrient data. These results suggest that more intensive in situ measurements of biogeochemical nutrients are urgently needed at basin scale to initiate a permanent monitoring of oceanic ecosystems.     

De la légitimité du transport en commun au Québec : un exemple simple de mesure de ses contributions au développement durable

While authorities consider transit as one of the solutions to enhance sustainable mobility, they do not provide a steady funding for its operation and growth. This inconsistency between political discourse and real intervention has motivated nine transit operators from six metropolitan areas of Quebec to conduct a study on the contribution of transit to sustainability. This article first presents the process of selecting indicators. For some of the indicators developed, the estimation method is detailed, which comprises of the following factors: resources, emission prevention, contribution to daily physical activity, accessibility to public transit and to activity locations, daily savings of using transit in comparison with car use, and the relative safety of transit use. Finally, the article explains the conceptual, methodological, and informational challenges that influenced the selection of indicators and their estimation methodologies.