关于用水问题的讨论——一个不可能性定理的证明

目前,我国的自来水平均价格城市为1.95元/立方米,农村为1.59元/立方米,处于偏低的水平。面对水资源浪费现象日益严重的现实,有人因此认为是自来水价格偏低而造成的,并且提出,利用提高税费来节约自来水的建议,但是,导致自来水浪费严重的根源却在于公共用水的实际免费使用,于是,这里出现了一个不可能性定理:在市场经济条件下,单纯利用水费改革,即价格杠杆来调节自来水的需求,是不可能达到节约的目的的。或无经济效率,或有失社会公平。进一步的分析发现,解决这一问题的最终途径却在于处理好经济效率与公平的关系。     

A multiobjective planning model for intercity train seat allocation

This paper presents a multiobjective planning model for generating optimal train seat allocation plans on an intercity rail line serving passengers with many‐to‐many origin‐destination pairs. Two planning objectives of the model are to maximise the operator's total passenger revenue and to minimise the passenger's total discomfort level. For a given set of travel demand, train capacity, and train stop‐schedules, the model is solved by fuzzy mathematical programming to generate a best‐compromise train seat allocation plan. The plan determines how many reserved and non‐reserved seats are to be allocated at each origin station for all subsequent destination stations on each train run operated within a specified operating period. An empirical study on the to‐be‐built Taiwan's high‐speed rail system is conducted to demonstrate the effectiveness of the model. The model can be used for any setting of travel demand and stop‐schedules with various train seating capacities.     

Real time traffic information and its impacts on route switching behavior of expressway drivers

Non‐quantifiable factors (e.g. perceived, attitudinal and preferential factors) have not been investigated fully in past transportation studies, which has raised questions on the predictive capabilities of the models. In this study, Structure Integration Models, with one of their sub‐models, Measurement Equation, are combined with latent variables, which are integrated with another sub‐model, Structural Equation. The estimated latent variables are used as explanatory variables in decision models. As a result, the explanatory and predictive capabilities of the models are enhanced. The models can then be used to describe the various behaviors of travelers of different types of transportation systems in a more accurate way. In this study, the Structure Integration Model was applied to study the impacts of real‐time traffic information on the route‐switching behavior of road users on the Sun Yat‐Sen expressway, Taiwan. At present, the real‐time traffic information provided on this expressway includes radio traffic reports and changeable message signs. The results of this study can facilitate the provision of traffic information on highways.     

公路工程建设项目合同管理系统总体设计

论述了工程项目合同的计算机辅助管理的可行性,提出了基于GIS和网络的合同管理系统的总体设计思路和系统的体系结构,并对其功能模块及系统的主要功能进行了描述.     

A macroscopic traffic model for highway work zones: Formulations and numerical results

This study presents a multilane model for analyzing the dynamic traffic properties of a highway segment under a lane‐closure operation that often incurs complex interactions between mandatory lane‐changing vehicles and traffic at unblocked lanes. The proposed traffic flow formulations employ the hyperbolic model used in the non‐Newtonian fluid dynamics, and assume the lane‐changing intensity between neighboring lanes as a function of their difference in density. The results of extensive simulation experiments indicate that the proposed model is capable of realistically replicating the impacts of lane‐changing maneuvers from the blocked lanes on the overall traffic conditions, including the interrelations between the approaching flow density, the resulting congestion level, and the exiting flow rate from the lane‐closure zone. Our extensive experimental analyses also confirm that traffic conditions will deteriorate dramatically and evolve to the state of traffic jam if the density has exceeded its critical level that varies with the type of lane‐closure operations. This study also provides a convenient way for computing such a critical density under various lane‐closure conditions, and offers a theoretical basis for understanding the formation as well as dissipation of traffic jam.     

新型接地刷在港口设备上的应用

神华黄骅港务公司堆取料机、装船机等设备上原有的接地刷(见图1)损坏严重,主要是其压缩弹簧变形或折断、支架扭曲变形等,其中任何一种损坏情况都严重影响接地效果:弹簧损坏后接地器和轨道将会压不实,或者根本起不到接地作用;支架扭曲变形会使接地器翘起或偏离轨道,减小与轨道的接触面积.     

铁路分局"客票发售和预订系统"的实施与应用

作者通过洛阳分局在同时建设6个车站“客票发售和预订系统”的实际过程中,对系统推广的规划设计,组织实施和应用管理进行了探讨和总结。     

西安黄土地区静力压入桩承载特性的试验研究

西安黄土地区采用静力压桩施工工艺完成以砂土层作为持力层的钢筋混凝土预制单桩竖向承载力试验,对其承载力特性及影响承载力的因素进行了分析。建议采用相关方程式确定静压桩单桩竖向承载力来作为工程设计的依据。     

航运市场呼唤中国的航运运价指数期货

随着全球一体化与世界经济的迅猛发展，世界范围内的贸易不断扩大，2000年海运物流量达到58．8亿t^[1]。由于航运价格受到许多因素的影响而变化，它的变化对货主、船东与雇船者带来许多不确定的风险，通过航运运价指数期货可以降低航运业的风险，从而保障航运市场的稳定持续发展。     

Effects of the 1988/89 climatic regime shift on the structure and function of the southwestern Japan/East Sea ecosystem

In this study we compared the structure of the ecosystem and the role of major species before and after 1988/89 climatic regime shift (CRS) in the southwestern Japan/East Sea. The 1988/89 CRS event changed the biomass and production of fisheries resources in the southwestern Japan/East Sea. Total biomass of all species groups in the ecosystem increased by 59% after the CRS. These results indicate that there were substantial changes in the function of major species in the southwestern Japan/East Sea ecosystem. The relative contribution of walleye pollock, at trophic level (TL) III, to the total flow of energy decreased drastically from 33.0% in the pre-CRS period to 4.3% in the post-CRS period, while that of common squid, at the same TL, doubled from 34.2% to 72.2% during the periods.