In this paper we consider two inverse problems in combinatorial optimization: inverse maximum flow (IMF) problem and inverse minimum cut (IMC) problem. IMF (or IMC) problem can be described as: how to change the capac...
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In this paper we consider two inverse problems in combinatorial optimization: inverse maximum flow (IMF) problem and inverse minimum cut (IMC) problem. IMF (or IMC) problem can be described as: how to change the capacity vector C of a network as little as possible so that a given flow (or cut) becomes a maximum flow (or minimum cut) in the network. After discussing some characteristics of these problems, we propose strongly polynormial algorithms for the two inverse problems.
Modeling the cost of road construction is a prerequisite for evaluation and planning of different alternatives for low-volume road networks included in a forest management plan. In this paper, a model for cost estimat...
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Modeling the cost of road construction is a prerequisite for evaluation and planning of different alternatives for low-volume road networks included in a forest management plan. In this paper, a model for cost estimation of forest roads is presented, based on the standard engineering properties of cross sections and the location-specific parameters of terrain slope and vegetation information. The model assumes six main cost elements of clearing operations, embankment, pavement, grading, culverts and ditch for total construction cost calculation. To validate the performance, the outputs of the model were compared with the experts' prediction for an existing forest road project in a mountain condition. The final result of the research showed that the model could estimate total cost of road construction in an accuracy range of perpendicular to 6.5%. The results of the validation process showed a 66.51% underestimate for clearing operation, 3.56% underestimate for embankment, 3.85% underestimate for surfacing, 3.32% underestimate for culverts, 20.54% underestimate for ditch excavation, and 22.33% overestimate for grading of the cut slope and travel way. According to the reasonable estimation for total cost, the model could be applied as an evaluation function in finding the optimized layout of a forest road network.
Blockage is a kind of phenomenon frequently occurred in a transport network, in which the human beings are the moving subjects. The minimum flow of a network defined in this paper means the maximum flow quantity throu...
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Blockage is a kind of phenomenon frequently occurred in a transport network, in which the human beings are the moving subjects. The minimum flow of a network defined in this paper means the maximum flow quantity through the network in the seriously blocked situation. It is an important parameter in designing and operating a transport network, especially in an emergency evacuation network. A branch and bound method is presented to solve the minimum flow problem on the basis of the blocking flow theory and the algorithm and its application are illustrated by examples.
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