Time Continuity in Discrete Time Models

Suerie, Christopher

doi:10.1007/b138843

Cited by 4 publications

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O problema integrado de dimensionamento e sequenciamento de lotes no processo de fabricação da cerveja: modelos e métodos de solução

Baldo¹

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This study deals with the multistage lot-sizing and scheduling problem in breweries.The brewing process can be divided into two main stages: preparation and filling of the liquid. The first stage occurs most of the time in fermentation and maturation tanks. The second stage occurs in the filling lines and it can start as soon as the liquid gets ready. The preparation time of the liquid takes several days, while in the carbonated beverage industries this time is at most a few hours. The purpose of this study is to obtain feasible production plans aimed at optimizing the decisions involved in these processes. Visits to brewery industries in Brazil and Portugal were held to a greater familiarity of the production process and data were collected. Mixed integer programming models have been developed to represent the problem, based on approaches for the CSLP (The Continuous Setup Lot-Sizing Problem), GLSP (General Lot Sizing and Scheduling Problem), SPL (Simple Plant Location Problem) and ATSP (Asymmetric Travelling Salesman Problem). The results show that the models are consistent and adequately represent the problem; however, they are difficult to be solved at optimality. This motivated the development of MIP-heuristic procedures, as well as a meta-heuristic GRASP (Greedy Randomized Adaptive Search Procedure). The obtained solutions by the heuristics are of good quality, when compared to the best lower bound found by solving the mathematical models. The tests were conducted using generated instances based on real data.

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O problema integrado de dimensionamento e sequenciamento de lotes no processo de fabricação da cerveja: modelos e métodos de solução

Baldo¹

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Modelling Multi-Period Set-up Times in the Proportional Lot-Sizing Problem

Kaczmarczyk

2009

dmms

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Abstract. This paper presents new mixed integer programming models for the Proportional Lot-Sizing Problem (PLSP) with set-up times longer than a period. Proposed models explicitly calculate the distribution of times amongst products in periods with a changeover and determine a final period for every set-up operation. Presented results prove that the proposed models are easier to solve using standard MIP methods than already known models.

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Practical Tips for Modelling Lot-Sizing and Scheduling Problems

Kaczmarczyk

2009

dmms

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Abstract. This paper presents some important alternatives for modelling Lot-Sizing and Scheduling Problems. First, the accuracy of models can improved by using short time buckets, which allow more detailed planning but lead to higher computational effort. Next, valid inequalities make the models tighter but increase their size. Sometimes it is possible to find a good balance between the size and tightness of a model by limiting a priori the number of valid inequalities. Finally, a special normalization of the variables simplifies the presentation of results and validation of models.

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Time Continuity in Discrete Time Models

Cited by 4 publications

References 0 publications

O problema integrado de dimensionamento e sequenciamento de lotes no processo de fabricação da cerveja: modelos e métodos de solução

O problema integrado de dimensionamento e sequenciamento de lotes no processo de fabricação da cerveja: modelos e métodos de solução

Modelling Multi-Period Set-up Times in the Proportional Lot-Sizing Problem

Practical Tips for Modelling Lot-Sizing and Scheduling Problems

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