Assigning Orders to Suppliers with Linear Piecewise Concave Costs

Purpose: Once a set of suppliers has been determined, according to criteria of quality, price and reliability, among others, there remains the problem of assigning orders to the selected suppliers, in order to cover the needs at the lowest cost. We consider the case in which the needs of a component for a set of plants should be covered by suppliers with linear piecewise concave cost functions, a lower bound on the order size for the non-zero deliveries and a capacity constraint. The purpose is to design procedures for solving this problem. Design/methodology/approach: With the aim of providing practical tools to solve the problem of assigning orders to suppliers with linear piecewise concave costs, two mixed integer linear programs are proposed. Findings: The two MILP models are compared through an extensive computational experiment. This shows that both models, with a slight advantage for one of them, can be solved within a very short time, even when the dimensions of the instance largely exceed those that can occur in real cases. Originality/value: The paper proposes novel models that can be used to solve the problem to optimality in reasonable times and with standard optimization software.Peer Reviewe

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Depuración y autarquía (1939-1940)

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Los tres directores de la Escuela durante la guerra (1936-1939). (II) José Ballvé Martínez

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REALIDADE E ESPAÇO RURAL: ELEMENTOS PARA O SERVIÇO SOCIAL?

Resumo Trata-se sobre a abordagem da realidade na formação profissional, a partir da experiência do Serviço Social, com enfoque nas particularidades do campo e das expressões da questão social que se evidenciam no espaço rural sul-rio-grandense. Visa discutir como o espaço rural, reconhecido enquanto componente fundamental da realidade, com seus determinantes, vai sendo considerado como elemento para a formação profissional. Discorre-se sobre a realidade e a formação profissional em Serviço Social; o reconhecimento dos determinantes agrários da sociedade brasileira; e, por fim, um ensaio sobre a realidade rural sul-rio-grandense e sua relação com o Serviço Social