Investigation on the sensitive and insensitive zones of the rail support stiffness for the dynamic response of a vehicle system under low excitation frequencies

The variation of the rail support stiffness is an inherent issue of railway tracks. There is still no consensus on the influence of the rail support stiffness variation on the dynamic response of the vehicle–track system. One view indicates that changes of the support stiffness do not have considerable influence on the vehicle dynamic response. The main influence factor is the rail deflection. However, the opposite view presents that the influence of the support stiffness on the system dynamic response is obvious. Reasons that lead to the dispute of previous studies are the neglect of the influence of the excitation frequencies and a lack of understanding of stiffness sensitive zones. In this study a vehicle–track coupling model with equivalent overall support stiffness is employed to investigate the response of the vehicle to changes of the track stiffness and excitation frequencies. Results show that for each of frequencies (1–40?Hz) the dynamic response of the vehicle is only sensitive to a certain range of the support stiffness. A stiffness sensitive zone for each excitation frequency can be observed. In order to further study the influence of the subgrade on the vehicle system dynamic response a vehicle–track-subgrade model is utilised. The subgrade stiffness belonging to the stiffness sensitive zone has a significant influence on vehicle vibrations. For overall support stiffness of the rail higher than 20?kN/mm, the stiffness sensitive zones of low excitation frequencies can be avoided.     

佛山地铁三号线车站标准化和模块化设计探讨

地铁车站标准化和模块化设计有利于乘客使用和运营管理,为使佛山地铁三号线的标准车站布置标准化和模块化,汲取已有经验,并结合自身的理解和实践,提出佛山地铁三号线公共区(包括站台宽度、楼扶梯和票亭布置、站厅和站台高度、柱跨和公共卫生间布置)、设备区以及出入口、风亭和风道等的设计思路,给出标准车站标准化和模块化设计方案,并通过计算验算标准站的客流适应性。通过研究使佛山三号线地铁车站58%的公共区、19%的设备区和86%的风亭布置标准化,30%的设备区布置模块化,取得了一定的成果,可为其他轨道交通线路设计提供一定的参考。     

Stresses and Shear Fracture Zone of Jinshazhou Tunnel Surrounding Rock in Rich Water Region

Field evidence has shown that large-scale and unstable discontinuous planes in the rock mass surrounding tunnels in rich water region are probably generated after excavation. The tunnel surrounding rock was divided into three zones, including elastic zone, plastic damage zone and shear fracture zone fof assessing the stability of the tunnel surrounding rock. By local hydrogeology, the stresses of surrounding rock of Jinshazhou circular tunnel was analyzed and the stress solutions on the elastic and plastic damage zones were obtained by applying the theories of fluid-solid coupling and elasto-plastic damage mechanics. The shear fracture zone generated by joints was studied and its range was determined by using Mohr-Coulomb strength criterion. Finally, the correctness of the theoretical results was validated by comparing the scopes of shear fracture zones calculated in this paper with those from literature.     

大跨浅埋公路隧道CRD法施工围岩松动圈量测与分析

新奥法原理指导下的CRD分部开挖技术是目前大跨浅埋公路隧道施工的主要方法。鉴于大跨浅埋隧道不同施工工艺下围岩扰动影响差异较大,以宁常高速茅山隧道为例,采用多点电测锚杆和多点位移计对CRD法施工过程的围岩深层扰动区位移及应力进行监测与分析,得出围岩分步开挖的松动过程及松动圈主要分布特点,同时对锚杆设计支护深度的合理性进行验证,可为优化设计及指导施工提供技术根据。     

舰船环形区域配电结构及可靠性分析

舰船电网形式的选择直接关系到电力系统供电的可靠性,其重要性不亚于电站。在对舰船电网形式进行分析研究的基础上,利用基于可靠性框图的网络分析法,对几种典型的船舶电网进行了可靠性计算。通过分析对比四种船舶电网,得到环形区域双向供电方式的可靠性水平高于辐射网结构和电源环形网结构,是船舶电网结构发展的方向。     

A system for determining economic loss associated with estuary degradation

Abstract

This article suggests a method of estimating economic losses for estuary‐dependent faunal species under conditions whereby the impact of a given degrading development on a particular estuary has a significant degree of uncertainty associated with it. The approach draws on standard theories from a variety of disciplines to provide an operational procedure capable of joint application by biologists, economists, and other related disciplines with working responsibility in the subject area. Consideration is given to probability estimation of possible impacts, sensitivity to underlying assumptions, and decisional safety under conditions of uncertainty. Applied results are demonstrated in a simulation of a negative developmental impact on the estuary‐dependent salmon resources of the Fraser River in British Columbia.     

Watergate village: A case study of a permit application for a marina submitted to the U.S. army corps of engineers

Abstract

Abstract This case study, prepared by an interdisciplinary group of several scientists and planners and a lawyer, reviews the handling by the decision process of an application to the Baltimore District Corps of Engineers for permission to construct a marina. The study determines that while the project in question may not present a significant environmental threat, the project when considered in conjunction with other pending projects on the same subtributary would contribute to boat congestion and degradation of water quality. Changes in the decision process are suggested which would facilitate consideration of the cumulative impacts from a series of coastal alterations.     

Identification and assessment of aquatic resources for power plant sites on Maryland's Eastern shore

Abstract

A power plant siting procedure which accounts for the protection and preservation of aquatic resources, defined as sensitive life forms and life stages of economically valuable species of finfish and shellfish, is presented as it was executed on Maryland's Eastern Shore. Negative effects of power plant development and operation are generated principally by the cooling water intake and discharge system. The site‐selection procedure is thus presented as a two‐faceted process, termed regional screening, requiring the separate but simultaneous identification of land‐based sites and cooling systems. Criteria included in regional screening for cooling systems reflected life‐sustaining processes essential to the maintenance of aquatic resources. Major sources of effects of power plants on aquatic resources and siting principles as they affect aquatic resources are defined. Information‐gathering techniques included extensive interviews with key research scientists, state personnel, and numerous Chesapeake Bay watermen.     

高速公路中间带优化设计方法研究

针对高速公路中间带面临的行车安全、路基水害等问题,提出了中间带优化设计方法,以达到减少中间带占用空间,增加路面有效宽度,提高行车安全性,避免水害,提高道路通行能力,降低全寿命周期成本的目标。     

Tragedy of the San Francisco bay commons

Abstract

Although the early efforts to save San Francisco Bay in the 1960's provided the role model for protection of California's 1100 mile ocean coastline, neither Proposition 20 of 1972 nor the California Coastal Act of 1976 provided any benefits to San Francisco Bay. One result is that the Bay is locked into its urban, shoreline‐use dominated plan of 1969 while every other estuary and coastal wetland in California receives much stronger protection of its resources. Furthermore, due to the complexity of California's water laws, there is no instream flow protection for receiving waters such as San Francisco Bay. This is particularly critical considering that 70% of the Bay's freshwater inflow has been diverted. The Bay's present decline as the largest and most important estuary on the West Coast, as well as its possible death as an estuary, may be irreversible. The problem requires the immediate attention of engineering, scientific, economic and legal disciplines if San Francisco Bay is to be saved.