Influence of wheel and rail profile shape on the initiation of rolling contact fatigue cracks at high axle loads

The influence of wheel and rail profile shape features on the initiation of rolling contact fatigue (RCF) cracks is evaluated based on the results of multi-body vehicle dynamics simulations. The damage index and surface fatigue index are used as two damage parameters to assess the influence of the different features. The damage parameters showed good agreement to one another and to in-field observations. The wheel and rail profile shape features showed a correlation to the predicted RCF damage. The RCF damage proved to be most sensitive to the position of hollow wear and thus bogie tracking. RCF initiation and crack growth can be reduced by eliminating unwanted shape features through maintenance and design and by improving bogie tracking.     

A Practical Model for Deformation Prediction of Highway Subgrade Soils

This paper reports a practical constitutive relation for highway subgrade soils. The proposed model is derived based on the laboratory repeated-load testing of four subgrade soils. Statistical parameters generally used in the power model of subgrade permanent strain are expanded into material constants with engineering significance. The constitutional relation reported in this paper can be used in the mechanistic-based pavement design of highway flexible pavements and railroad tracks.     

The public administrator: Regulating for maritime transport efficiency

One role often fulfilled by public administrators is to regulate private enterprise in the public interest. The academic literature has not developed this area fully because public administration is not always tasked with this function. Nevertheless, when regulation forms a part of the responsibilities of the public administrator, it is among the most important. An essential foundation for effective regulation is a complete understanding of the implications and impact of regulatory action. In the absence of regulation, entrepreneurial awareness is applied in the private sector exclusively to satisfying consumer wants. In a regulated market, the entrepreneur’s focus is shifted toward regulatory imperatives. Regulation offers non-market opportunities for entrepreneurial innovation, as well as imposing new market constraints. This paper examines regulation of the maritime industry by the US federal government as an example.     

An Analysis of the Impact of the Internet on Coastal Management

The role of the Internet in coastal management practice is analyzed through the Internet's communication and information access capacity. Primary and secondary impacts of the Internet in coastal management are assessed. A broad research framework is employed, including background on the development and spread of the Internet worldwide; analysis of emerging literature on the societal impact of the Internet; limited existing research on the use of the Internet by environmental management professionals generally and coastal managers in particular; and personal experience of the authors in the development of coastal management Internet sites. This analytical framework is supplemented by the first survey of integrated coastal management (ICM) Internet websites by www.coastalmanagement.com and a case study of the Internet Center for Coastal Management (ICCM) Internet-based communication platform based at the University of Washington. The survey of ICM websites found a total of 77 websites worldwide, with a dominance of sites in English located in the developed world. Assessment of the first year of operation of the ICCM project to facilitate discussion between coastal management practitioners and students in the United States and the Philippines demonstrates the enormous potential of the Internet as a communications tool in coastal management and also reveals the many practical technological and cultural constraints of using the Internet, especially in working on a project between the developed and developing world. Three groups of scenarios of the future use of the Internet in coastal management with decreasing levels of forecast certainty, namely, "probable," and "possible," and "potential for" are presented and discussed. Finally, the potential for the Internet to fundamentally transform the practice of coastal management is analyzed. It is concluded that while such a potential exists, there remain significant research questions requiring further analysis before the full transformative potential, and the possible impacts of such a transformation on coastal management, can be fully assessed. This article aims to provide a benchmark against which such future assessments can be made.     

A railway capacity determination model and rail access charging methodologies

This article discusses approaches to the determination of railway capacity and the significance of the following factors on capacity: mix of trains, length and weight of trains, direction of train travel, acceleration and deceleration, stopping protocols of trains, location and length of crossing loops, location of signals, length of sections, dwell times and sectional running times. A more accurate method to calculate railway capacity is developed using previously unaddressed aspects for capacity determination. Capacity and pricing are two key issues for organizations involved with open track access regimes. A train access charging methodology is therefore developed and incorporated into a railway capacity determination model.     

The impact of weather conditions on bikeshare trips in Washington,DC

Bicycle usage can be affected by colder weather, precipitation, and excessive heat. The research presented here analyzes the effect of weather on the use of the Washington, DC, bikeshare system, exploiting a dataset of all trips made on the system. Hourly weather data, including temperature, rainfall, snow, wind, fog, and humidity levels are linked to hourly usage data. Statistical models linking both number of users and duration of use are estimated. Further, we evaluate trips from bikeshare stations within one quarter mile of Metro (subway) stations at times when Metro is operating. This allows us to determine whether Metro serves as a back-up option when weather conditions are unfavorable for bicycling. Results show that cold temperatures, rain, and high humidity levels reduce both the likelihood of using bikeshare and the duration of trips. Trips taken from bikeshare stations proximate to Metro stations are affected more by rain than trips not proximate to Metro stations and less likely when it is dark. This information is useful for understanding bicycling behavior and also for those planning bikeshare systems in other cities.     

温拌技术的发展与现状

该文介绍了温拌沥青技术的发展与现状,有关经验可供专业人员参考。     

Lagrangian flow in the California Undercurrent, an observation and model comparison

During the period 1992–1998, 38 isobaric RAFOS floats were deployed to sample the subsurface flow of the California Undercurrent. The deployments, released over the California continental slope west of San Francisco, have sampled robust year-round poleward subsurface flow associated with the Undercurrent most seasons and the combined inshore current and Undercurrent in winter. Two other types of flow have been seen: a region of weak flow with little net displacement just west of the California Undercurrent, and an active westward propagating eddy field. This eddy field appears to be the primary mechanism for moving floats from the Undercurrent into the ocean interior. The observations and statistics from the RAFOS floats are compared with Lagrangian estimates of particles tracked in a global high resolution ocean simulation in order to evaluate the fidelity of the model along an eastern boundary. The results show that the model reproduces the general character of the flow reasonably well, but underestimates both the mean and eddy energies by a substantial amount.