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Mathematical programming model of cost optimization for supply chain from perspective of logistics provider

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Sitek P. , Wikarek J.

tom Vol. 3, No. 2

49-61

The article presents the problem of optimizing the supply chain from the perspective of a logistics provider and includes a mathematical model of multilevel cost optimization for a supply chain in the form of MILP (Mixed Integer Linear Programming). The costs of production, transport and distribution were adopted as an optimization criterion. Timing, volume, capacity and mode of transport were also taken into account. The model was implemented in the environment of LINGO ver. 12 package. The implementation details, the basics of LINGO as well as the results of the numerical tests are presented and discussed. The numerical experiments were carried out using sample data to show the possibilities of practical decision support and optimization of the supply chain. In addition, the article presents the current state of logistics outsourcing.

Efficient exact A* algorithm for the single plant Hydro Unit Commitment problem

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Heintzmann A. , Artigues C. , Bendotti P. , Ngueveu S. U. , Rottner C.

Annals of Computer Science and Information Systems

2023

tom Vol. 35

533--543

The Hydro Unit Commitment problem (HUC) specific to hydroelectric plants is part of the electricity production planning problem, called Unit Commitment Problem (UCP). More specifically, the studied case is that of the HUC with a single plant, denoted 1-HUC. The plant is located between two reservoirs. The horizon is discretized in time periods. The plant operates at a finite number of points defined as pairs of the generated power and the corresponding water flow. Several constraints are considered. Each reservoir has an initial volume, as well as window resource constraints, defined by a minimum and maximum volume per time period. At each time period, there is an additional positive, negative or zero intake of water in the reservoirs. The case of a price-taker revenue maximization problem is considered. An efficient exact A* variant, so called HA*, is proposed to solve the 1-HUC accounting for window constraints, with a reduced search space and a dedicated optimistic heuristic. This variant is compared to a classical Resource Constrained Shortest Path Problem (RCSPP) algorithm and a Mixed Integer Linear Programming formulation solved with CPLEX. Results show that the proposed algorithm outperforms both concurrent alternatives in terms of computational time in average on a set of realistic instances, meaning that HA* exhibits a more stable behavior with a larger number of instances solved.