Papers by Keyword: Constraints

Abstract: Much of the scheduling theory assumes that machines are always available to process jobs at any time during the scheduling horizon. However, machines may be unavailable for various reasons in realistic practices, such as unexpected failures or variable maintenance activities. This article discusses in depth the works published in the literature of joint scheduling of jobs and variable maintenance activities in the flowshop sequencing problems. Our literature review focuses first on the basic concepts of scheduling problems, and more specifically, the scheduling strategies of production and maintenance that have been identified in the literature. Subsequently, we focus our attention on the principal methods for solving scheduling problems, while presenting in the following the main published works for the aforementioned systems. Lastly, a comparative analysis is carried out to highlight the fundamental ideas leading to the adoption of an effective approach capable of producing an optimal solution in a reasonable calculation time.

Abstract: In general, planning and scheduling of production are treated separately under the hierarchical strategy. Then, over the time, the iterative strategy appeared which partially considers the scheduling constraints during planning, except that the latter remains unsatisfactory because there is no guarantee that these constraints are taken into account. For this, is born the integrated strategy which integrates planning and scheduling and aims to solve the problem and define a feasible production plan. Since capacity constraints don’t reflect reality in terms of resource availability, and they are not always considered, capacity becomes aggregated. To remedy this problem, it is necessary to integrate more precise constraints of scheduling at the planning level. Based on this observation, we propose in this article a new model that integrates planning and scheduling and considers the constraint of resource availability. In our model, the objective function optimizes the total cost of production for a mono-level job-shop problem. To solve this N-P difficult problem we use a stochastic approached method as genetic algorithm (GA).

Abstract: This article concerns the integration of planning and scheduling production system. Planning and scheduling are usually treated separately because of their complexity. Scheduling largely depends on the production quantities computed at the production planning level. However, ignoring scheduling constraints in the tactical level leads to inconsistent decisions. So, it is important to integrate planning and scheduling to efficiently manage operations and to determine a realistic production plan for a given sequence of jobs on each machine. In this paper, we present some approaches proposed to solve the problem and we realize a comparison between the two most interesting ones, using the standard solver CPLEX.

Abstract: Globalization has had a significant impact on company’s management, particularly in the supply chain (lead time, investment in production capacity and technology, organization & management ...). The sales and operations planning (S&OP) include all the processes that link the strategic objectives of the enterprise with the production plan. The impact of the S&OP on operational performance was consistently and significantly demonstrated in the operational aspects of production ; quality (conformity of production, product quality and reliability), delivery (the delivery agility, reliability of supply, manufacturing deadlines, lead times), stocks (reduction of inventory levels, inventory optimization) and flexibility (flexible volume and mix). Our objective in this paper is to present, in the first part, a literature overview of the sales and operations planning, and various research and models developed. In the second part, we will emphasize the transversal aspect of our research that involves both operational issues, tactical and strategic in a context subject to different constraints.

Abstract: This paper will relate initially to the scheduling characteristics of flexible manufacturing systems, and more specifically, the scheduling problems in flowshop and hybrid flowshop type systems representing interesting structures for the modeling of several problems resulting from the industrial world. Subsequently, we will focus our attention on the principal methods for solving scheduling problems, while presenting in the following the main published works for the aforementioned systems. Lastly, a comparative analysis will be carried out to highlight the fundamental ideas leading to the adoption of an effective approach capable of producing an optimal solution in a reasonable calculation time.

Abstract: Currently, the problem of energy crisis and environmental deterioration on the world is extremely urgent, so people now are trying to turn to many kinds of renewable energy to solve these problems. Of these renewable energies, because of its cleanness and availability, wind power has broadened prospect and in recent years, it is considered to connect wind power to the grid in large quantities to make full use of it. However, wind power possesses the shortcoming such as randomness so that when it is connected to the grid, it may have great impact to the grid and damage the balance of the power system. Based on the fluctuation regularity of load and the characteristics of volatility, intermittent and randomness of wind power, the operation characteristics when large-scale wind power is connected to the grid and active regulation characteristics of conventional power source such as fire power, the multi time-scale “source to source” active coordinated control technique is proposed.

Abstract: The design of data mining system in database is researched. Vast amounts of information contained in the database, and the data show the diversity of characteristics, resulting in lower efficiency of data mining in database, which database brought greater difficulties to information query. To avoid these shortcomings, database performance optimization method based on cloud computing is proposed. The model of cloud computing data relationship is established to describe the connection between related data inthe database, thus providing the basis for data query. The load state of data nodes is calculated to enable rapid information inquiryin the database. Experimental results show that using this algorithm to optimize data inquiry in database can improve the efficiency of informationinquiry indatabase effectively.