Public transport demand: dynamic panel model analysis

This paper presents an original essay that explains the mobility behaviour towards the public transport supply in Tunisia. This research aims to determine the key variables affecting an individual’s decision to travel by public transport and explains how the use of these means fits the mobility strategies. The dynamic panel model is applied to twelve Tunisian Regional companies, where we aim to analyze the behaviours of Tunisian citizens in the regions where Regional Transport Companies ensure the total service supply of urban, interurban and suburban public transport of travellers. The results show that mobility behaviours are subject to various variables. In particular, service quality, mean price and active population are the most significant variables regarding public transport demand in Tunisia.     

法国的铁路电车会再掀起浪潮吗

在过去的25年间，人们将大部分资金投放在市中心区的交通（地铁、电车等）建设上， 而在新一届规划立法年度(2001-2007）之前，人们又对法国城市周边范围内的交通形式提 出新的问题。因为城市的范围虽然在不断地扩大，但周边城镇地区的交通状况如何却几乎没 有人去投资和关注。在将铁路改造成轻轨（由有轨电车转变而来）方面，德国、美国、英国 和瑞士的经验看上去十分诱人。目前，大量的工程建设还处在讨论阶段，但首项工程几乎 可以肯定将在2001-2007年期间完成。 　　欧洲的铁路电车 　　自从有了在卡尔斯鲁厄成功的经验之后，法国的城市中蓬勃兴起了许多项目，包括“电车线 路 间相互联运工程”、“铁道电车工程、“电车铁道工程”以及“地区间的电车线路工程”等 。越来越多的人到萨尔布吕肯和卡尔斯鲁厄地区（德国) 或者到瑞士、德国的其它线路网 上参观，他们可以看到许多电车线路远远地延伸到市区的外围。在1999年，SNFC（法国国家 铁路局）成立了一个周边城镇董事会，它的主要任务就是发展市郊的公共交通。在这种背 景下，缀尔豪斯市开始启动它的电车专线工程。许多其他法国城市也开始了类似的研究工作 ，一些工程项目被列入了巴黎地区和中央政府的计划合同当中。 　　这只是一时的现象吗？     

Small scale retentive structures and Dinophysis

Despite its rarity, Dinophysis acuminata is in terms of economic impact, the first toxic algal species along the coasts of Western Europe. It is observed at low levels (< 20 cell l^− 1) all the year round but toxic events occur mainly in late spring and summer. D. acuminata ecophysiology is largely unknown due to the inability to culture it. Therefore, standard biomass models based on inorganic nutrition are largely inadequate. Presently, any progress in describing the conditions of population growth of this species will be a step forward to prediction of harmful events at the coast. This species has been observed at increased, albeit low cell densities in retentive eddies located in pycnocline layers. A concentration build-up of one species results from the balance between growth and loss processes, one of the latter being dispersal. The scales of interest for a D. acuminata population are of the order of 10 nautical miles on the horizontal and duration of 10 days, for a reported achievable growth rate of 0.6 day^− 1. A three dimensional (3D) hydrodynamical model of the Bay of Biscay has been elaborated to reproduce hydrological structures over the last decade. We attempt here to relate the existence of retentive structures revealed from simulations under realistic forcing conditions and the toxic coastal events recorded in the 10-year time series of the French plankton monitoring network database. The eddies in the coastal area appear to be directly related with the Dinophysis coastal events and they may be a potential effective tool to predict those.     

Simulation and discussion on the decreasing flow stress scale effect

The miniaturization of products requires the mass production of microparts. The microforming can well meet this requirement. Due to the emergence of decreasing flow stress scale effect in the micro scale, the traditional forming process and theory may fail. Based on the crystal plasticity theory, upsetting tests of micro copper cylinders with different dimensions and grain sizes were simulated, and the decreasing flow stress scale effect was studied and discussed. Results show that with the decrease of billet dimensions, the flow stress is gradually decreased, and the decreasing flow stress scale effect is emerged; with the increase of grain size, the decreasing flow stress scale effect is more remarkable. It can also be seen that the decreasing flow stress scale effect can be well simulated with the crystal plasticity theory, and the necessary relevant information is provided for deeper understanding on this scale effect, as well as the design of processes and die structures in the microforming.