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The Global ETD Search service is a free service for researchers
to find electronic theses and dissertations. This service is
provided by the
Networked Digital Library of Theses and Dissertations.
Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
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An analysis of the Texas vehicle fleet and development of a vehicle operating cost model for use in transportation planningWelter, Dana 05 November 2012 (has links)
Vehicle operating costs are an invaluable tool to transportation engineers, who utilize them in applications such as cost-benefit analyses and utilization pricing. Many of the existing models in use, however, are significantly out-of-date with current technology.
Research was undertaken in partnership with the Texas Department of Transportation (TxDOT) to develop a new model of the operating costs associated with Texas vehicle fleets. A vehicle operating cost (Vcost) model was produced which estimates variable and fixed costs associated with both light-duty and heavy-duty vehicles. The model calculates both aggregate fleet costs and costs for individual representative vehicles. An analysis of Texas Vehicles, Titles, and Registration (VTR) records; Weigh-in-Motion data; vehicle counts; and national car sales data was used to generate the breakdown of the Texas fleet of vehicles and to determine representative vehicles. Operational costs for these vehicles fell into two main categories: fixed costs (depreciation, financing, insurance, and other) and variable costs (fuel and maintenance/repair). Relations were determined for each cost category for each representative vehicle over its entire operational age. In the case of heavy-duty vehicles, much of the operational costs information is proprietary and had to be gathered in survey work conducted with other members of a research team. A computer program was written that incorporates the cost relations for the representative vehicles as well as the Texas fleet characteristics in such a way that the user can examine the costs of both an individual vehicle and the aggregate costs associated with a fleet of vehicles. The user can also input a default fleet composition. The model allows users to alter key parameters (such as fuel price, financing rates, insurance costs, or vehicle fuel economies) for future adaptability to a changing economic and technological landscape. The model was developed in parallel with another researcher working on an advanced fuel consumption model, which would later be integrated into to the Vcost model. / text
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A fundamental approximation in MATLAB of the efficiency of an automotive differential in transmitting rotational kinetic energyVaughn, James Roy 30 July 2012 (has links)
The VCOST budgeting tool uses a drive cycle simulator to improve fuel economy predictions for vehicle fleets. This drive cycle simulator needs to predict the efficiency of various components of the vehicle's powertrain including any differentials. Existing differential efficiency models either lack accuracy over the operating conditions considered or require too great an investment. A fundamental model for differential efficiency is a cost-effective solution for predicting the odd behaviors unique to a differential. The differential efficiency model itself combines the torque balance equation and the Navier-Stokes equations with models for gear pair, bearing, and seal efficiencies under a set of appropriate assumptions. Comparison of the model with existing data has shown that observable trends in differential efficiency are reproducible in some cases to within 10% of the accepted efficiency value over a range of torques and speeds that represents the operating conditions of the differential. Though the model is generally an improvement over existing curve fits, the potential exists for further improvement to the accuracy of the model. When the model performs correctly, it represents an immense savings over collecting data with comparable accuracy. / text
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