橡胶减振系统的动力学冲击模拟和试验

橡胶减振装置在铁道运输系统中是必不可少的部件。基于将橡胶结构大变形和高阻尼特性考虑在内的自然频率域(NFR-Natural Frequency Region)方法,针对实际工业减振产品CUS单元在整个冲击过程中的动力响应测试,分别用2种模拟冲击质量体的有限元模型(点质量模型和实体模型)进行较详尽的分析,评估实体橡胶减振系统的时域冲击响应,所模拟的结果和测试数据吻合良好。可为有关工作提供参考,有助于更准确地模拟橡胶减振系统的动力响应,从而加快和优化设计过程。     

Web-Based Interactive VR-CAD System for Conceptual Design and Analysis

Introduction Exploring a large number of design variants in aconceptual design phase assists in identifying the mostcost-effective design. However, how to capture userintents is challenging[1]. Although the necessity andadvantages of integrating customers into the innova-tion process are widely recognized[2], customers havea passive role in this design involvement process. Thefirst reason is the complexity of modeling tools. Most3D product mockups are created using commercialCAD packages or …     

Challenges in Collaborative Governance for Coastal Restoration: Lessons from the Caernarvon River Diversion in Louisiana

In an effort to restore deteriorating coastal wetlands in Breton Sound, Louisiana, a diversion of Mississippi River water into the estuarine ecosystem has been operated at Caernarvon, Louisiana, since 1991. The diversion was implemented after a relatively long collaborative planning process beginning in the 1950s. The Caernarvon Interagency Advisory Committee, an official panel of stakeholders, considers scientific aspects of the freshwater inflow and stakeholder inputs in developing an operational plan, which internalizes stakeholder conflicts, while accomplishing goals of restoring the coastal ecosystem. Even though fishery representatives are committee members, local oyster fishers filed lawsuits in federal and state courts from 1994 through 2005, claiming damages to their oyster beds. These lawsuits were initially successful in state courts but were reversed by the Louisiana Supreme Court. The federal suits were unsuccessful. Following these lawsuits, voters in Louisiana in 2000 amended the State Constitution to protect coastal restoration projects against lawsuits reflecting increase in overall statewide support. Increasing scientific knowledge has contributed significantly to diversion operation. For better collaborative governance, efforts to increase common understanding among stakeholders will be needed, and a process to compensate interests of stakeholders suffering from impacts of restoration projects at an earlier stage should be institutionalized.     

The vehicle emissions and performance monitoring system: analysis of tailpipe emissions and vehicle performance

This paper describes tailpipe emission results generated by the Vehicle Performance and Emissions Monitoring system (VPEMS). VPEMS integrates on‐board emissions and vehicle/driver performance measurements with positioning and communications technologies, to transmit a coherent spatio‐temporally referenced dataset to a central base station in near real time. These results focus on relationships between tailpipe emissions of CO, CO₂, NO_x and speed and acceleration. Emissions produced by different driving modes are also presented. Results are generally as one would expect, showing variation between vehicle speed, vehicle acceleration and emissions. Data is based upon a test run in central London on urban streets with speeds not exceeding about 65 km/h. The results presented demonstrate the capabilities of the system. Various issues remain with regard to validation of the data and expansion of the system capability to obtain additional vehicle performance data.     

Local organization of transportation planning activities in the United States

This study provided an examination of the alternative means used by Metropolitan Planning Organizations (MPOs) to carry out transportation planning activities in different areas of the U.S.A. This has been done by first developing a general profile of the nature and functions of the MPOs in the 100 largest regions in the U.S. and by an in‐depth analysis of seven regions. The purpose of these activities was to examine similarities and differences between MPOs and to identify factors that appear to lead to the effectiveness or non‐effectiveness of MPOs in different areas. From the analysis, it is evident that there are wide differences between MPOs in their organization, function, and degree of effectiveness in carrying out transportation planning. These differences do not appear to be related to any structural characteristics of MPOs, but rather are the result of past history and the attitudes of people involved.     

Lessons from a Multi-Scale Historical Reconstruction of Newfoundland and Labrador Fisheries

In this article we use a multi-scale, multi-method historical reconstruction of post– World War II social-ecological interactions within fisheries in Newfoundland and Labrador to explore the dynamics of intensification, expansion, and resource degradation in managed fisheries. Our case study draws on landings statistics, other archival information, and the Local Ecological Knowledge (LEK) of fish harvesters to explore these linked dynamics at the macro, meso, and micro levels. By some measures we found large scale trends toward intensification of effort leading to over-harvesting at macro (province wide) levels. At the same time, at the local level (micro-scale) and across sectors and regions (the meso-scale), we found highly fluid fishing practices and a complex suite of stated motivations for change. As a basis for effective governance, an understanding of the dynamics of interactive restructuring in social ecological systems will require multi-scale analyses that are sensitive to this complexity.     

Prospects for computer aided railway scheduling: perspectives from users and parallels from mass transit

Railway scheduling faces new challenges as competition and, in many parts of the world, privatisation require ever better results, both in terms of minimising the resources used and maximising the performance achieved by those resources. It is therefore surprising that in practice railway scheduling tasks appear to be performed largely without the use of optimizing models. This paper takes two different perspectives, a case study of user needs from the UK railway industry and a comparative analysis with mass transit scheduling systems, to consider why this might be and assesses what the future prospects are for computer aided railway scheduling.

A number of conclusions are drawn: that optimization models need to be integrated with software packages that meet schedulers' data management needs; that researchers need to work with commercial developers to achieve this integration; that there needs to be an emphasis on extending models to cover more real‐life circumstances; and that solutions with international applicability should be sought.     

Do Public Transport Improvements Increase Agglomeration Economies? A Review of Literature and an Agenda for Research

Public transport improvements may increase economic productivity if they enable the growth and densification of cities, downtowns, or industrial clusters and thereby increase external agglomeration economies. It has been argued that the potential agglomeration benefits are large; if so, understanding them better would be useful in making funding decisions about public transport improvements. We reviewed theoretical and empirical literature on agglomeration as well as a small number of articles on transportation's role in agglomeration. The theoretical literature is useful in understanding possible avenues by which transportation improvements might affect agglomeration, although there is little discussion of public transport specifically. Relevant empirical studies tend to focus on metropolitan regions and use a generalized measure of transportation cost. But public transport impacts on agglomeration are likely to be different from road investment impacts. We identified several ways of conducting research building on this literature that would help evaluate the agglomeration impacts of public transport proposals: tracing the links between transport, agglomeration, and productivity; better motivating research using theories of agglomeration mechanisms; taking scale and redistribution into account; exploring the functional form of agglomeration economies; accounting for endogeneity in model structure; and considering development context.     

RANS simulation of a container ship using a single-phase level-set method with overset grids and the prognosis for extension to a self-propulsion simulator

Steady flow simulations for the Korean Research Institute for Ships and Ocean Engineering (KRISO) container ship (KCS) were performed for towing and self-propulsion. The main focus in the present article is on the evaluation of computational fluid dynamics (CFD) as a tool for hull form design along with application of state-of-the-art technology in the flow simulations. Two Reynolds-averaged Navier-Stokes (RANS) equation solvers were employed, namely CFDShip-Iowa version 4 and Flowpack version 2004e, for the towing and self-propulsion cases, respectively. The new features of CFDShip-Iowa version 4 include a single-phase level-set method to model the free surface and an overset gridding capability to increase resolution in the flow and wave fields. The new features of Flowpack version 2004e are related to a self-propulsion scheme in which the RANS solver is coupled with a propeller performance program based on the infinitely bladed propeller theory. The present work is based on a close interaction between IIHR-Hydroscience and Engineering of the University of Iowa and Osaka Prefecture University. In the following article, overviews are given of the present numerical methods and results are presented and discussed for the KCS in towing and self-propulsion modes, including comparison with available experimental fluid dynamics (EFD) data. Additional evaluation is provided through discussion of the recent CFD Workshop Tokyo 2005, where both methods appeared to yield very promising results.