In this paper, we propose the modeling of a real-case problem where a farmer has to optimize the use of his/her land by selecting the best mix of crops to cultivate. Complexity of the problem is due to the several fac...
详细信息
In this paper, we propose the modeling of a real-case problem where a farmer has to optimize the use of his/her land by selecting the best mix of crops to cultivate. Complexity of the problem is due to the several factors that have to be considered simultaneously. These include the market prices variability of harvested products, the specific resource requests for each crop, the restrictions caused by limited machines availability, and the timing of operations required to complete each crop cultivation. We provide two different mathematical formulations for the analyzed problem. The first one represents a natural integerprogramming formulation looking for the crop-mix that maximizes the farmer's expected profit measured as the difference between revenues obtained by selling the harvested products and the production costs. Since the revenue of each crop depends on the price as quoted at the exchange market and the yield per hectare of harvested product, we define it as a random variable. Then, the second model uses the maximization of the Conditional Value-at-Risk (CVaR) as objective function and looks for the crop-mix that allows to maximize the average expected profit under a predefined quantile of worst realizations. To test and compare the proposed models with the cultivation choice made by the farmer, we use Italian historical data represented by monthly returns of different crops over a time period of 16 years. Computational results emphasize the advantage of using the CVaR model for a risk-averse farmer and provide interesting insights for farmers involved in similar problems. (C) 2016 Elsevier Ltd. All rights reserved.
Due to the acceleration of technological developments and shortening of product life cycles, product recovery has gained great importance in recent years. Disassembly line balancing (DLB) problem is one of the most im...
详细信息
Due to the acceleration of technological developments and shortening of product life cycles, product recovery has gained great importance in recent years. Disassembly line balancing (DLB) problem is one of the most important problems encountered during disassembly operations in product recovery. In this study, a single model and complete DLB problem with balancing issues, hazardousness of parts, demand quantities and direction changes is considered. Majority of DLB studies in the literature solve this problem using heuristics or metaheuristics which do not guarantee the optimality. Although a few studies present mathematical formulations for some variants of this problem, they prefer to solve the problem by using heuristics or metaheuristics due to the non-linear structure and combinatorial nature of the problem. In this study, a generic mixed integer linear programming (MILP) model is developed for the investigated problem and its performance is tested through a series of benchmark instances. The computational results demonstrate that the proposed MILP model is able to solve test instances with up to 30 tasks. Hence, it can effectively be utilized to evaluate the optimality performance of DLB approaches. Moreover, several extensions on the MILP model regarding to line balancing, hazardousness and demand of parts and direction changes are proposed and their effects are analyzed through computational studies. (c) 2019 Elsevier Ltd. All rights reserved.
The analysis of the Quality of Service (QoS) level in a Cloud Computing environment becomes an attractive research domain as the utilization rate is daily higher and higher. Its management has a huge impact on the per...
详细信息
The analysis of the Quality of Service (QoS) level in a Cloud Computing environment becomes an attractive research domain as the utilization rate is daily higher and higher. Its management has a huge impact on the performance of both services and global Cloud infrastructures. Thus, in order to find a good trade-off, a Cloud provider has to take into account many QoS objectives, and also the manner to optimize them during the virtual machines allocation process. To tackle this complex challenge, this article proposed a multiobjective optimization of four relevant Cloud QoS objectives, using two different optimization methods: a Genetic Algorithm (GA) and a mixed integer linear programming (MILP) approach. The complexity of the virtual machine allocation problem is increased by the modeling of Dynamic Voltage and Frequency Scaling (DVFS) for energy saving on hosts. A global mixed-integer non linearprogramming formulation is presented and a MILP formulation is derived by linearization. A heuristic decomposition method, which uses the MILP to optimize intermediate objectives, is proposed. Numerous experimental results show the complementarity of the two heuristics to obtain various trade-offs between the different QoS objectives. (C) 2017 Elsevier B.V. All rights reserved.
The scheduling literature is extensive, but much of this work is theoretical and does not capture the complexity of real world systems. Capital goods companies produce products with deep and complex product structures...
详细信息
The scheduling literature is extensive, but much of this work is theoretical and does not capture the complexity of real world systems. Capital goods companies produce products with deep and complex product structures, each of which requires the coordination of jobbing, batch, flow and assembly processes. Many components require numerous operations on multiple machines. Integrated scheduling problems simultaneously consider two or more simultaneous decisions. Previous production scheduling research in the capital goods industry has neglected maintenance scheduling and used metaheuristics with stochastic search that cannot guarantee an optimal solution. This paper presents a novel mixed integer linear programming model for simultaneously solving the integrated production and preventive maintenance scheduling problem in the capital goods industry, which was tested using data from a collaborating company. The objective was to minimise total costs including: tardiness and earliness penalty costs;component and assembly holding costs;preventive maintenance costs;and set-up, production, transfer and production idle time costs. Thus, the objective function and problem formulation were more extensive than previous research. The tool was successfully tested using data obtained from a collaborating company. It was found that the company's total cost could be reduced by up to 63.5%.
The problem of ranking efficient decision making units (DMUs) is of interest from both theoretical and practical points of view. In this paper, we propose an integrated data envelopment analysis and mixedinteger non-...
详细信息
The problem of ranking efficient decision making units (DMUs) is of interest from both theoretical and practical points of view. In this paper, we propose an integrated data envelopment analysis and mixedinteger non-linearprogramming (MINLP) model to find the most efficient DMU using a common set of weights. We linearize the MINLP model to an equivalent mixed integer linear programming (MILP) model by eliminating the non-linear constraints in which the products of variables are incorporated. The formulated MILP model is simpler and computationally more efficient. In addition, we introduce a model for finding the value of epsilon, since the improper choice of the non-Archimedean epsilon may result in infeasible conditions. We use a real-life facility layout problem to demonstrate the applicability and exhibit the efficacy of the proposed model.
The use of distributed energy system (DES), such as combined heat and power (CHP) and district heating and cooling system, is spreading. DES is also indispensable for introducing renewable energy. Although introductio...
详细信息
ISBN:
(纸本)9781538653265
The use of distributed energy system (DES), such as combined heat and power (CHP) and district heating and cooling system, is spreading. DES is also indispensable for introducing renewable energy. Although introduction cost of renewable energy is high, the generation cost is low. Hence, there is a possibility that marginal fuel cost will be affected an electricity charge. Some external factors can influence on the capacity planning of DES. Therefore, we developed the model to optimize equipment capacities and long-term operations of DES. This planning approach is used two methods, using particle swarm optimization (PSO) and mixed integer linear programming (MILP). The long-term optimization results show that there are changes in the installed capacity and operation.
This paper extends our previous work in I and [2] on optimal scheduling of autonomous vehicle arrivals at intersections, from one to a grid of intersections. A scalable distributed mixedintegerlinear Program (MILP) ...
详细信息
ISBN:
(纸本)9781538654286
This paper extends our previous work in I and [2] on optimal scheduling of autonomous vehicle arrivals at intersections, from one to a grid of intersections. A scalable distributed mixedintegerlinear Program (MILP) is devised that solves the scheduling problem for a grid of intersections. A computational control node is allocated to each intersection and regularly receives position and velocity information from subscribed vehicles. Each node assigns an intersection access time to every subscribed vehicle by solving a local MILP. Neighboring intersections will coordinate with each other in real-time by sharing their solutions for vehicles' access times with each other. Our proposed approach is applied to a grid of intersections and its positive impact on traffic flow and vehicles' fuel economy is demonstrated in comparison to conventional intersection control scenarios.
The intelligence algorithm used in the backbone grid search is unrobust and has uncertain results. To tackle the drawback, this paper proposes a mixed integer linear programming (MILP) model for generating the power s...
详细信息
ISBN:
(数字)9781728116754
ISBN:
(纸本)9781728116761
The intelligence algorithm used in the backbone grid search is unrobust and has uncertain results. To tackle the drawback, this paper proposes a mixed integer linear programming (MILP) model for generating the power system backbone grid. Based on the graph theory, this model considers the connectivity of the backbone grid as linear constraints with integer variables. Constrains of line power in the model are elicited by the derivation from Kirchhoff's current law. Since the expressions in this model are analytical and linear, with the help of developed MILP algorithm, the proposed model can fully solve the problem of absence of robustness in existing method. The simulations of IEEE 39-bus system and IEEE 118-bus system show that the proposed model is effective and reliable, which provides a new idea for the development in this research.
In this paper, we propose a home energy management (HEM) scheme in the residential area for electricity cost and peak to average ratio (PAR) reduction. Furthermore, reduction in imported electricity from the external ...
详细信息
ISBN:
(纸本)9781538620700
In this paper, we propose a home energy management (HEM) scheme in the residential area for electricity cost and peak to average ratio (PAR) reduction. Furthermore, reduction in imported electricity from the external grid is also the objective of this study. Our proposed scheme schedules smart appliances as well as electrical vehicles (EVs) charging/discharging optimally according to the consumer preferences. Each consumer has its own grid-connected microgrid for electricity generation;which consists of wind turbine, solar panel, micro gas turbine (MGT) and energy storage system (ESS). Furthermore, the scheduling problem is mathematically formulated and solved by mixed integer linear programming (MILP). We also provide the comparison of the optimal solutions, while considering EVs with and without discharging capabilities. Findings from simulations affirm our proposed scheme in terms of above-mentioned objectives.
In this paper, we consider the problem of localizing the subsequence in time series which contains the dynamic pattern of interest. This is motivated by brain computer interface application where we need to analyze th...
详细信息
ISBN:
(纸本)9781538637883
In this paper, we consider the problem of localizing the subsequence in time series which contains the dynamic pattern of interest. This is motivated by brain computer interface application where we need to analyze the dynamic pattern of brain signals in response to external stimulus. We treat the localization as a binary label assignment problem and formalize a mixed integer linear programming (MILP) problem. The optimal solution is obtained by minimizing a cost function associated with label assignment subject to empirical constraints induced by data acquisition process. We first experiment with synthetic data to evaluate the effectiveness of the proposed MILP formulation and achieve 10.8 % improvement on F-1-score. We then experiment with electrocorticographic (ECoG) data for a classification task and achieve 8.8 % improvement on accuracy using subsequences localized by our method compared to other methods.
暂无评论