Siriphong Lawphongpanich

Optimizing Ship Berthing

Abstract : Ship berthing plans reserve a location for inbound U.S. Navy surface vessels prior to their port entrance, or reassign ships once in port to allow them to complete, in a timely manner, reprovisioning, repair, maintenance, training, and certification tests prior to redeploying for future operational commitments. Each ship requires different services when in port, such as shore power, crane, ordnance, and fuel. Unfortunately, not all services are offered at all piers, and berth shifting is disruptive and expensive: A port operations scheduler strives to reduce unnecessary berth shifts. We present an optimization model for berth planning and demonstrate it for Norfolk Naval Station, which exhibits all the richness of berthing problem:. the Navy faces.

Optimizing Submarine Berthing with a Persistence Incentive

Submarine berthing plans reserve mooring locations for inbound U.S. Navy nuclear submarines prior to their port entrance. Once in port, submarines may be shifted to different berthing locations to allow them to better receive services they require or to make way for other shifted vessels. However, submarine berth shifting is expensive, labor inten- sive, and potentially hazardous. This article presents an optimization model for submarine berth planning and demonstrates it with Naval Submarine Base, San Diego. After a berthing plan has been approved and published, changed requests for services, delays, and early arrival of inbound submarines are routine events, requiring frequent revisions. To encourage trust in the planning process, the effect on the solution of revisions in the input is kept small by incorporating a persistence incentive in the optimization model. q 1997 John Wiley & Sons, Inc. Naval Research Logistics 44: 301 - 318, 1997. Although the Cold War has ended, United States Navy submarines remain very capable and effective ships of war: A smaller number of submarines operated from fewer submarine bases will continue to play a significant role in national defense. The wise use of time and resources while submarines are in port will improve the state of readiness of a smaller fleet. While in port, a submarine completes preventive and corrective maintenance, replenishes stores, and conducts training and certification tests to maintain high material and personnel readiness. Ideally, a submarine in port should devote its time exclusively to these activities. However, submarines frequently spend time shifting berths. Some shifts are necessary and some are not. Services such as ordnance loading and the use of special maintenance equip- ment require that a submarine be moored at a specific location. During periodic maintenance upkeep, personnel from a submarine tender assist the submarine crew, and berthing near the tender is preferable. During training, inspection, and other periods, it is desirable to berth closer to shore, near squadron offices and training facilities. When conditions permit,

Mathematical and computational models for congestion charging

Although transportation economists have advocated the tolling of urban streets as a mechanism for controlling congestion and managing travel demands for over 50 years, it is only recently that this idea has become practical. When compared to the alternative of building more roads, congestion pricing - in particular via electronic tolling - is attractive and has been adopted in countries around the world. Recent implementations in London, Singapore, and various cities in Norway, as well as a number of projects in the United States, have been judged successful. This book presents rigorous treatments of issues related to congestion pricing. The chapters describe recent advances in areas such as mathematical and computational models for predicting traffic congestion, determining when, where, and how much to levy tolls, and analyzing the impact of tolls on transporation systems. The analyses and methodologies developed in this book provide: - Mechanisms that aid in determining and comparing congestion pricing schemes - Methodologies for evaluating the efficiency of existing and proposed congestion pricing schemes - A means to predict the impact of pricing on urban transporation systems - Information essential to the financial and political success of congestion pricing programs.

A DUAL ASCENT ALGORITHM FOR TRAFFIC ASSIGNMENT PROBLEMS

A dual decomposition algorithm is developed for large-scale traffic assignment problems. In contrast to standard methods, this algorithm does not require that the system or user optimal objective function be differentiable and it allows bounds on the arc flows. Iterates alternate between dual ascent steps and calculations of shortest paths as in the Frank-Wolfe method. Although a dual method, it produces feasible flow patterns at each iteration. Convergence of the method is proven and a computational example is given.

Allocation of tasks to specialized processors: A planning approach

Abstract This paper addresses the problem of scheduling randomly arriving tasks of different types at a diversified service system. Servers at such a system differ in that each may specialize in one task type, but can also perform others perhaps less rapidly and adequately than does a specialist. We consider the issue of how much redirection of tasks from specialists to non-specialists may be desirable in such a system and propose a static model in which tasks are randomly assigned to servers. Two scheduling strategies for individual servers are also considered: one in which each server performs the tasks assigned to him or her in order of their arrival and the second in which each server schedules his or her workload optimally. The problems for finding the best random assignment probabilities are formulated as mathematical programs. Results from a numerical example provide information that is both informative and useful in decision-making.

Benders decomposition for variational inequalities

The partitioning technique of J.F. Benders, which was generalized to nonlinear programming by Geoffrion, is further generalized to linearly constrained variational inequality problems. The conditions under which such a generalization is possible and appropriate are examined.An important area of application is the asymmetric traffic assignment problem for which the decomposition assumes a simple and effective form. A computational example demonstrates the algorithm.

The equivalence of transfer and generalized benders decomposition methods for traffic assignment

In prior work we have given an intuitive development of Transfer Decomposition, a decomposition of the traffic assignment problem into two traffic assignment problems. The intent of this paper is to provide a rigorous basis for this technique by establishing that it is a generalized Benders decomposition. As an illustration of the result, we give a decomposition algorithm that is based on the familiar Frank-Wolfe method.

Simplicial with truncated Dantzig-Wolfe decomposition for nonlinear multicommodity network flow problems with side constraints

The simplicial decomposition (SD) subproblem for a nonlinear multicommodity network flow problem is simply its linear approximation. Instead of solving the subproblem optimally, this paper demonstrates that performing one iteration of Dantzig-Wolfe decomposition is generally sufficient for SD to efficiently converge to an optimal solution.