9 research outputs found

    A simple and effective algorithm for the maximum happy vertices problem

    Get PDF
    In a recent paper, a solution approach to the Maximum Happy Vertices Problem has been proposed. The approach is based on a constructive heuristic improved by a matheuristic local search phase. We propose a new procedure able to outperform the previous solution algorithm both in terms of solution quality and computational time. Our approach is based on simple ingredients implying as starting solution gen- erator an approximation algorithm and as an improving phase a new matheuristic local search. The procedure is then extended to a multi-start configuration, able to further improve the solution quality at the cost of an acceptable increase in compu- tational time

    A Reference Point Method to Triple-Objective Assignment of Supporting Services in a Healthcare Institution

    Get PDF
    This paper presents an application of mixed integer programming model for op- timal allocation of workers among supporting services in a hospital. The services include logistics, inventory management, financial management, operations management, medical analysis, etc. The optimality criterion of the problem is to minimize operational costs of supporting services subject to some specific constraints. The constraints represent specific conditions for resource allocation in a hospital. The overall problem is formulated as a triple- objective assignment model, where the decision variables represent the assignment of people to various jobs. A reference point approach with the Chebyshev metric is applied for the problem solution. The results of computational experiments modeled on a real data from a hospital in Lesser Poland are reported

    An Incremental Approach for Storage and Delivery Planning Problems

    Get PDF
    We consider a logistic planning problem for simultaneous optimization of the storage and the delivery. This problem arises in the consolidate shipment using an intermediate storage in a supply chain, which is typically found in the automobile industry. The vehicles deliver the items from the origin to the destination, while the items can be stored at some warehousing facilities as the intermediate storage during the delivery. The delivery plan is made for each day separately, but the storage at a warehouse may last for more than one day. Therefore, the entire logistic plan should be considered over a certain period for the total optimization. We formulate the storage and delivery problem as a mixed integer programming. Then, we propose a relax-and-fix type heuristic method, which incrementally fixes decision variables until all the variables are fixed to obtain a complete solution. Moreover, a semiapproximate model is introduced to effectively fix the variables. Based on the formulation, the delivery plan can be solved for each day separately. This has the advantage especially in the dynamic situation, where the delivery request is modified from the original request before the actual delivery day. Numerical experiments show that the simultaneous optimization gives the effective storage plan to reduce the total logistic cost, and the proposed heuristics efficiently reduce the computational time and are robust against the dynamic situation

    A branch-and-cut algorithm for the Time Window Assignment Vehicle Routing Problem

    Get PDF
    This paper presents a branch-and-cut algorithm for the Time Window Assignment Vehicle Routing Problem (TWAVRP), the problem of assigning time windows for delivery before demand volume becomes known. A novel set of valid inequalities, the precedence inequalities, is introduced and multiple separation heuristics are presented. In our numerical experiments the branch-and-cut algorithm is 3.8 times faster when separating precedence inequalities. Furthermore, in our experiments, the branch-and-cut algorithm is 193.9 times faster than the best known algorithm in the literature. Finally, using our algorithm, instances of the TWAVRP are solved which are larger than the small scale instances previously presented in the literature

    Maximizaci贸n del valor actual neto en redes 贸pticas

    Get PDF
    En este trabajo se utilizan t茅cnicas de investigaci贸n operativa y estad铆stica para desarrollar una herramienta 煤til en la toma de decisiones en empresas de telecomunicaciones. Se comparan dos esquemas de particionamiento aplicables en redes 贸pticas, y se busca encontrar bajo qu茅 circunstancias, un esquema es mejor que otro. De la misma forma se define el dise帽o de red, que otorgue un mayor beneficio, dadas unas posibles ubicaciones que representan lugares demandantes de conexi贸n. La comparaci贸n entre ambos esquemas de particionamiento se realizar谩 en t茅rminos econ贸micos utilizando el Valor Actual Neto (VAN). Puesto que la expresi贸n del VAN es una funci贸n no lineal, se da soluci贸n mediante un modelo estad铆stico que explica la intensidad que ha de ser insertada en una red. Finalmente el problema OVALO (Optical network net present VALue Optimization) otorga como soluci贸n, un dise帽o de red que maximiza el beneficio total en valor actual de una inversi贸n a largo plazo.Postprint (published version

    Maximizaci贸n del valor actual neto en redes 贸pticas

    Get PDF
    En este trabajo se utilizan t茅cnicas de investigaci贸n operativa y estad铆stica para desarrollar una herramienta 煤til en la toma de decisiones en empresas de telecomunicaciones. Se comparan dos esquemas de particionamiento aplicables en redes 贸pticas, y se busca encontrar bajo qu茅 circunstancias, un esquema es mejor que otro. De la misma forma se define el dise帽o de red, que otorgue un mayor beneficio, dadas unas posibles ubicaciones que representan lugares demandantes de conexi贸n. La comparaci贸n entre ambos esquemas de particionamiento se realizar谩 en t茅rminos econ贸micos utilizando el Valor Actual Neto (VAN). Puesto que la expresi贸n del VAN es una funci贸n no lineal, se da soluci贸n mediante un modelo estad铆stico que explica la intensidad que ha de ser insertada en una red. Finalmente el problema OVALO (Optical network net present VALue Optimization) otorga como soluci贸n, un dise帽o de red que maximiza el beneficio total en valor actual de una inversi贸n a largo plazo

    A Reference Point Method to Triple-Objective Assignment of Supporting Services in a Healthcare Institution

    No full text
    Abstract. This paper presents an application of mixed integer programming model for optimal allocation of workers among supporting services in a hospital. The services include logistics, inventory management, financial management, operations management, medical analysis, etc. The optimality criterion of the problem is to minimize operational costs of supporting services subject to some specific constraints. The constraints represent specific conditions for resource allocation in a hospital. The overall problem is formulated as a tripleobjective assignment model, where the decision variables represent the assignment of people to various jobs. A reference point approach with the Chebyshev metric is applied for the problem solution. The results of computational experiments modeled on a real data from a hospital in Lesser Poland are reported. Keywords: reference point method, assignment problem, mixed integer programming, services operations management, healthcare planning. Mathematics Subject Classification: 90B50 -management decision making, 90B80 -discrete location and assignment, 90C11 -mixed integer programming, 90C90 -applications of mathematical programming
    corecore