Browsing by Author "Chen, Chun-Hung"

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    Integrated Management of Highway Maintenance and Traffic
    (2003-12-05) Chen, Chun-Hung; Schonfeld, Paul M; Civil Engineering
    Highway maintenance, especially pavement rehabilitation or resurfacing, requires lane closures. This work develops an integrated model to help highway agencies in developing traffic control plans for maintenance activities and in efficiently managing traffic around highway work zones. Thus, the objective of this study is to develop methods for optimizing work zone characteristics in order to minimize the combined total costs for highway agencies and users. Work zone models are developed for three cases. For Case 1, with steady traffic inflows, four alternatives for two-lane highways and four alternatives for four-lane highways are proposed. Analytical solutions are found for optimized work zone lengths and diversion fractions based on minimizing the total cost. Guidelines for selecting the best alternative for different characteristics of traffic flows, road and maintenance processes are developed by deriving thresholds among alternatives. In Case 2, the models for two-lane highway and four-lane highway work zones for time-dependent inflows are developed. Two optimization methods, Powell's and Simulated Annealing, are adapted for this problem and compared. In numerical tests, a Simulated Annealing algorithm yields better solutions using less computer time than Powell's Method. The SAUASD (Simulated Annealing for Uniform Alternatives with a Single Detour) algorithm is developed to find the best single alternative within a maintenance project. The SAMASD (Simulated Annealing for Mixed Alternatives with a Single Detour) algorithm is developed to search through possible mixed alternatives and diverted fractions in order to further minimize total cost. Thus, traffic management plans with uniform alternatives or mixed alternatives within a maintenance project are developed. For Case 3, work zone optimization models for a road network with multiple detour paths and the SAMAMD (Simulated Annealing for Mixed Alternatives with Multiple Detour paths) algorithm are developed. Analyses based on the CORSIM simulation are used not only to estimate delay cost, but also to evaluate the effectiveness of optimization models. A comparison of the results from optimization and simulation models indicates that they are consistent. The optimization models do significantly reduce total cost, including user cost and maintenance cost, compared to the total cost of the current resurfacing policy in Maryland.
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    Online Appendix for “Gradient-Based Myopic Allocation Policy: An Efficient Sampling Procedure in a Low-Confidence Scenario”
    (2017) Peng, Yijie; Chen, Chun-Hung; Fu, Michael; Hu, Jian-Qiang
    This is the online appendix, which includes theoretical and numerical supplements containing some technical details and three additional numerical examples, which could not fit in the main body due to page limits by the journal for a technical note. The abstract for the main body is as follows: In this note, we study a simulation optimization problem of selecting the alternative with the best performance from a finite set, or a so-called ranking and selection problem, in a special low-confidence scenario. The most popular sampling allocation procedures in ranking and selection do not perform well in this scenario, because they all ignore certain induced correlations that significantly affect the probability of correct selection in this scenario. We propose a gradient-based myopic allocation policy (G-MAP) that takes the induced correlations into account, reflecting a trade-off between the induced correlation and the two factors (mean-variance) found in the optimal computing budget allocation formula. Numerical experiments substantiate the efficiency of the new procedure in the low-confidence scenario.
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    Online Appendix for “Ranking and Selection as Stochastic Control”
    (2017-04) Peng, Yijie; Chong, Edwin K. P.; Chen, Chun-Hung; Fu, Michael C.
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    Online Supplement to `Efficient Simulation Resource Sharing and Allocation for Selecting the Best'
    (2012) Peng, Yijie; Chen, Chun-Hung; Fu, Michael; Hu, Jian-Qiang
    This is the online supplement to the article by the same authors, "Efficient Simulation Resource Sharing and Allocation for Selecting the Best," published in the IEEE Transactions on Automatic Control.