Use of SeaWiFS data for light availability and parameter estimation of a phytoplankton production model of the Bay of Biscay

Processing SeaWiFS (Sea-viewing Wide Field-of-view Sensor) data provides useful information for the observation and modelling of the phytoplankton production of the Bay of Biscay. Empirical algorithms allow the retrieval of chlorophyll a and non-living Suspended Particulate Matter (SPM) concentrations. These data are used to constrain a coupled 3D physical–biogeochemical model of the Bay of Biscay continental shelf. Two issues are investigated, depending on the variable used, to constrain the winter to spring phytoplankton production for the year 2001. First, SPM data is used as forcing data to correct the corresponding state variable of our model. This allows the realistic simulation of the light limited bloom at the end of February 2001, as observed with SeaWiFS chlorophyll a images and from the NUTRIGAS field cruise. Second, chlorophyll a data is used for parameter estimation of the biogeochemical model. The ability of assimilating these data is tested to improve the simulation of strong blooms observed in late May 2001 in the Loire and Gironde plumes. A global optimization method (Evolutive Strategies) is adapted to the complete 3-D coupled model, in order to find the best set of parameters. The hydrological conditions during the bloom can be validated with data from the PEL01 field cruise. After selection of the most sensitive parameters, the method is tested with twin experiments. Then, the use of real SeaWiFS data reduces the model/data misfit by a factor of two, improving the simulation of bloom intensities and extensions. The sets of parameters retrieved in each plume are discussed.     

让汽车与人们更安全——德尔福主动夜视系统

尽管这些年来汽车照明技术取得不小的进步,但夜间行车的风险仍比白天大得多.据美国国家公路交通安全管理局(NHTSA)的统计,虽然夜间行车在整个公路交通中只占1/4,发生的死亡事故却占了一半.     

Tradeoffs in incremental changes towards pedestrian-friendly environments: Physical activity and pollution exposure

A microsimulation of individuals’ activities is used in the context of a risk analysis framework to assess the impacts of hypothesized changes to the built environment on personal energy expenditure and on inhalation of air pollutants. Uncertainty is assessed using Monte Carlo simulations and sensitivity analyzes. We find both simulated individuals that augment and others that reduce their energy expenditure and inhalation dose of pollutants, with median increases displaying larger magnitudes than the decreases. Up to 75% of the population has significant increases in energy expenditure and pollutant inhalation. We also find, however, high uncertainty associated with the estimates. Results differ considerably depending on the travel mode choice model used in the simulation.     

Investigation of the impact of locomotive creep control on wear under changing contact conditions

This paper presents the locomotive traction controller performance with respect to the track wear under different operation conditions. In particular, an investigation into the dynamic response of a locomotive under changing wheel–rail friction conditions is performed with an aim to determine the effect of controller setting on track wear. Simulation using a full-scale longitudinal–vertical locomotive dynamic model shows that the appropriately designed creep threshold, controller, settings can effectively maintain a high tractive effort while avoiding excessive rail damage due to wear, especially during acceleration under low speed.     

Capitalization of BRT network expansions effects into prices of non-expansion areas

A before and after hedonic model is used to determine the property value impacts on properties already served by the transit system caused by extensions to Bogotá’s bus rapid transit system. Asking prices of residential properties belonging to an intervention area (N = 1407 before, 1570 after) or a control area (N = 267 before, 732 after) and offered for sale between 2001 and 2006 are used to determine capitalization of the enhanced regional access provided by the extension. Properties offered during the year the extension was inaugurated and in subsequent years have asking prices that are between 13% and 14% higher than prices for properties in the control area, after adjusting for structural, neighborhood and regional accessibility characteristics of each property. Furthermore, the appreciation is similar for properties within 500 m and properties between 500 m and 1 km of the BRT.     

ARTEMIS: French-German project for railway movements command and control

The development of railway transportation, especially through the gradual implementation of high-speed European network, is inciting railway companies to design railway movements command and control systems to enhance technical performance in terms of throughput and control of disturbances while simultaneously minimizing operational costs. The new command-control systems must be modular, adaptable and evolutive structures from both functional and geographical viewpoints if they are to satisfy all operational needs. Concurrent research into performance enhancement and cost reduction prescribes a system in which the majority of the “real time” components are aboards the locomotives. This is particularly true for those components used by the train to indicate its own position on the network as well as those enabling it to converse with operational control centers. The initial task is to design a global architecture of the command-control system that satisfies modularity and availability criteria followed by the development of numerous technical components including radar self-location systems and cellular radio transmission networks. The French (SNCF) and German (DB) national railways have implemented a vast program of co-operation aimed at providing valid, proven answers to these problems so as to allow their trains to travel freely on either network.     

A bus route evaluation model based on GIS and super-efficient data envelopment analysis

When compared to large cities in developed countries, the shares of public transportation in most Chinese cities are low. Increasing the competitiveness of urban public transportation remains an urgent problem. A capable evaluation method for public transportation is required to assist the development of urban transit systems. This paper focuses on the bus system. Being devoid of standard criteria, it is difficult to determine the efficiency of a transit system or any bus line using a single evaluation index. This paper proposes a comparative analysis to evaluate bus lines so as to filter out candidates for further optimization. From the viewpoints of transit planning, operation and quality of service, this paper establishes 10 subordinate evaluation indices and then uses geographical information system tools, global positioning system data and smart card data to assist the index definition and calculation. Super-efficient data envelopment analysis (DEA) method is adopted for the proposed single factor and comprehensive evaluation models. Finally, the bus system in Shenzhen, China is used as a case study. The comparable significant results validate the capability of the proposed model.     

Integrated fluid-thermal-structural numerical analysis for the quenching of metallic components

The quenching of a metal component with a channel section in a water tank is numerically simulated. Computational fluid dynamics (CFD) is used to model the multiphase flow and the heat transfer in film boiling, nucleate boiling and convective cooling processes to calculate the difference in heat transfer rate around the component and then combining with the thermal simulation and structure analysis of the component to study the effect of heat transfer rate on the distortion of the U-channel component. A model is also established to calculate the residual stress produced by quenching. The coupling fluid-thermal-structural simulation provides an insight into the deformation of the component and can be used to perform parameter analysis to reduce the distortion of the component.     

推力和横向压力作用下加筋板破坏分析的理想化结构单元法

理想化结构单元法(ISUM)已经成为评估结构系统中承受载荷能力的一个有效工具.本文给出了最新的ISUM板元公式,并考虑了双轴向推力和横向载荷对板元的加载.为了精确地模拟加筋板的性能,分别用梁-柱元和板元制作了肋材和板材的模型.与有限元分析(FEA)的比较表明该方法对解决加筋板在横向压力和推力载荷下的问题是适用的.对箱形桁材的四点弯曲试验的分析表明与试验数据吻合良好.