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Mixed Integer Linear Programming (mixed + integer_linear_programming)
Selected AbstractsThe Economics of Erosion and Sustainable Practices: The Case of the Saint-Esprit WatershedCANADIAN JOURNAL OF AGRICULTURAL ECONOMICS, Issue 2 2000Jean-Christophe Dissart This paper examines the economics of the adoption of sustainable production practices for soil erosion control. The research was conducted on three case farms within the Saint-Esprit watershed in Quebec using a two-stage process. The first stage involved the use of GIS (Geographical Information Systems) to record erosion characteristics (slope, etc.) for these farmers'fields. This erosion information was then included as input information in the second stage of the process. Mixed integer linear programming (MILP) was used to model both individual farms and the watershed. Increasing erosion constraints were applied to these models to investigate changes in crop production mixes for farms and the watershed. A comparison of the results (farms versus watershed) was used to investigate policy questions concerning an optimal erosion constraint for society. Results generated indicate that farms with higher net incomes would be advantaged by erosion constraints set at the watershed level, whereas farms with lower net revenues would be disadvantaged. Thus, trading of pollution permits could be encouraged. Cet article examine les aspects économiques de l'adoption de pratiques de production durables visant a réduire l'érosion du sol. La recherche fut effectuée sur trois fermes situées dans le has sin du Saint-Esprit au Québec, et impliqua un processus à deux étapes. Le premier étape consiste en l'utilisation du systéme d'informations géographiques " SIG " afin de noter les caractéristiques de l'érosion (pente, etc.) dans ces champs agricoles. Ces renseignements servirent de données au sein du deuxième étape. La méthode de programmation linéaire à nombres entiers mixtes fut employée afin de modéliser les fermes individuelles, ainsi que le bassin. Ensuite, les contraintes d,érosion furent appliquées sur ces modèles de manière croissante, et ce afin d'étudier les changements dans le melange des productions de cultures pour les fermes et le bassin. Une comparaison des résultats (fermes vs. bassin) fut accomplie pour examiner les questions de politiques pouvant mener à une contrainte d,érosion optimale pour la société. Les résultats obtenus démontrent que les fermes ayant des revenus nets élevés seraient avantagées par des contraintes d'érosion établies au niveau du bassin, tandis que les fermes aux revenus nets plus bas en seraient désavantagées. En conséquence, l'échange de permis de pollution est recommandé. [source] Modeling an industrial energy system: Perspectives on regional heat cooperationINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 9 2008S. Klugman Abstract Through energy efficiency measures, it is possible to reduce heat surplus in the pulp and paper industry. Yet pulp and paper mills situated in countries with a heat demand for residential and commercial buildings for the major part of the year are potential heat suppliers. However, striving to utilize the heat within the mills for efficient energy use could conflict with the delivery of excess heat to a district heating system. As part of a project to optimize a regional energy system, a sulfate pulp mill situated in central Sweden is analyzed, focusing on providing heat and electricity to the mill and its surrounding energy systems. An energy system optimization method based on mixed integer linear programming is used for studying energy system measures on an aggregated level. An extended system, where the mill is integrated in a regional heat market (HM), is evaluated in parallel with the present system. The use of either hot sewage or a heat pump for heat deliveries is analyzed along with process integration measures. The benefits of adding a condensing unit to the back-pressure steam turbine are also investigated. The results show that the use of hot sewage or a heat pump for heat deliveries is beneficial only in combination with extended heat deliveries to an HM. Process integration measures are beneficial and even increase the benefit of selling more heat for district heating. Adding a condensing turbine unit is most beneficial in combination with extended heat deliveries and process integration. Copyright © 2007 John Wiley & Sons, Ltd. [source] Quay crane scheduling at container terminals to minimize the maximum relative tardiness of vessel departuresNAVAL RESEARCH LOGISTICS: AN INTERNATIONAL JOURNAL, Issue 1 2006Jiyin Liu Abstract In this paper, we study the problem of scheduling quay cranes (QCs) at container terminals where incoming vessels have different ready times. The objective is to minimize the maximum relative tardiness of vessel departures. The problem can be formulated as a mixed integer linear programming (MILP) model of large size that is difficult to solve directly. We propose a heuristic decomposition approach to breakdown the problem into two smaller, linked models, the vessel-level and the berth-level models. With the same berth-level model, two heuristic methods are developed using different vessel-level models. Computational experiments show that the proposed approach is effective and efficient. © 2005 Wiley Periodicals, Inc. Naval Research Logistics, 2006 [source] Economic Lot Scheduling Problem with ReturnsPRODUCTION AND OPERATIONS MANAGEMENT, Issue 4 2006Ou Tang Motivated by a case study of a company that produces car parts, we study the multi-product economic lot scheduling problem for a hybrid production line with manufacturing of new products and remanufacturing of returned products. For this economic lot scheduling problem with returns (ELSPR), we consider policies with a common cycle time for all products, and with one manufacturing lot and one remanufacturing lot for each product during a cycle. For a given cycle time, the problem is formulated as a mixed integer linear programming (MIP) problem, which provides the basis for an exact solution. The application of this model for one of the core products of the case study company indicates a 16% reduction in cost compared to the current lot scheduling policy. [source] Optimal Synthesis of Protein Purification ProcessesBIOTECHNOLOGY PROGRESS, Issue 4 2001Elsa Vásquez-Alvarez There has been an increasing interest in the development of systematic methods for the synthesis of purification steps for biotechnological products, which are often the most difficult and costly stages in a biochemical process. Chromatographic processes are extensively used in the purification of multicomponent biotechnological systems. One of the main challenges in the synthesis of purification processes is the appropriate selection and sequencing of chromatographic steps that are capable of producing the desired product at an acceptable cost and quality. This paper describes mathematical models and solution strategies based on mixed integer linear programming (MILP) for the synthesis of multistep purification processes. First, an optimization model is proposed that uses physicochemical data on a protein mixture, which contains the desired product, to select a sequence of operations with the minimum number of steps from a set of candidate chromatographic techniques that must achieve a specified purity level. Since several sequences that have the minimum number of steps may satisfy the purity level, it is possible to obtain the one that maximizes final purity. Then, a second model that may use the total number of steps obtained in the first model generates a solution with the maximum purity of the product. Whenever the sequence does not affect the final purity or more generally does not impact the objective function, alternative models that are of smaller size are developed for the optimal selection of steps. The models are tested in several examples, containing up to 13 contaminants and a set of 22 candidate high-resolution steps, generating sequences of six operations, and are compared to the current synthesis approaches. [source] | ||||||||||