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Marcel G. Dagenais Marc J. I. Gaudry Tran Cong Liem 《Transportation Research Part B: Methodological》1987,21(6)
We develop an algorithm for solving regression models with Box-Cox transformations on both the dependent and independent variables, while simultaneously taking into account corrections for serial correlation of several orders and for heteroscedasticity. The latter correction is of a general form which contains as special cases most specifications of heteroscedasticity found in practice. We apply the procedure to three urban travel demand functions, two of which are currently used in their linear form by the Montreal Transit Authority, and analyze more than 100 specifications. Our results show that taking into account nonsphericalness of the residuals has a major impact on model parameter estimates, notably on those which determine the functional form of the model, and that, conversely, modifications of the functional form have strong implications for both the structure of autocorrelation and the importance of heteroscedasticity; moreover, we find interactions between autocorrelation and heteroscedasticity structures. We introduce a special measure of elasticity for variables which contain zero observations, particularly dummy variables. Moreover, we find that elasticities of demand and implicit values of time depend to a large extent on the stochastic specification of the model. 相似文献
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Marc Ulbrich 《天津汽车》2008,(8)
<天津汽车>:有人表示,传感器是汽车电子的关键元器件,电子自动控制工作依赖传感器的信息反馈,传感器在汽车中的成功应用开启了一个新的汽车时代. 相似文献
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We consider in this paper the problem of determining intermediate origin-destination matrices for composite mode trips that involve a trip by private car to a parking facility and the continuation of the trip to the destination either by walking or by a transit mode. The intermediate origin-destination matrices relate to each component of the composite mode trip: a matrix from the trip origins to intermediate destinations which are parking lots and a matrix from the parking lots to the final destinations. The approach that we propose to solve this problem is to modify the entropy based trip distribution models to consider inequality constraints related to parking lot capacities. Such models may be easily calibrated by using well known calibration methods or generalization of these methods and may be easily solved by applying a primal feasible direction method of nonlinear programming. 相似文献
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Griet De Backer Marc Vantorre Peter Frigaard Charlotte Beels Julien De Rouck 《Journal of Marine Science and Technology》2010,15(2):119-130
Oscillating point absorber buoys may rise out of the water and be subjected to bottom slamming upon re-entering the water.
Numerical simulations are performed to estimate the power absorption, the impact velocities and the corresponding slamming
forces for various slamming constraints. Three buoy shapes are considered: a hemisphere and two conical shapes with deadrise
angles of 30° and 45°, with a waterline diameter of 5 m. The simulations indicate that the risk of rising out of the water
is largely dependent on the buoy draft and sea state. Although associated with power losses, emergence occurrence probabilities
can be significantly reduced by adapting the control parameters. The magnitude of the slamming load is severely influenced
by the buoy shape. The ratio between the peak impact load on the hemisphere and that on the 45° cone is approximately 2, whereas
the power absorption is only 4–8% higher for the 45° cone. This work illustrates the need to include slamming considerations
aside from power absorption criteria in the buoy shape design process and the control strategy. 相似文献
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Marc J. Hershman 《Coastal management》2013,41(1):7-8
Abstract The economic and environmental consequences of a proposed Louisiana superport have been studied by researchers during the last three years. These studies provided technical information and management alternatives. Management alternatives included state control to avoid multiple superport developments, details for an Environmental Protection Plan, comparisons of onshore and offshore sites, and planning for ancillary development. Policy decisions which resulted include many of the recommendations of the research. It is suggested that environmental research can influence policy decisions and limit the options available to a decision maker provided some legal structure is created, quality control is implemented, and technological and environmental problems are recognized. Various analytical tools, such as energy cost accounting, group critique, and simulation models, have wide application for use in coastal zone management. 相似文献
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The second part of the state-of-the-art focuses on the development of the founders' double streams explaining single-outcome indicators (probability of accidents and fatalities, respectively) by fixed form regression, as outlined in the Part 1. Following Page (1997, pp. 67–122, 2001) and others, we use as turning point of the evolution of both aggregate and discrete approaches the DRAG-1 model of 1984, itself based on aggregate data, which introduced four key innovations in principle applicable to both streams. 相似文献