Search results for " operations"

2016

Split-Delivery Capacitated Arc-Routing Problem: Lower Bound and Metaheuristic

2010

International audience; This paper proposes lower and upper bounds for the split-delivery capacitated arc-routing problem (SDCARP), a variant of the capacitated arc-routing problem in which an edge can be serviced by several vehicles. Recent papers on related problems in node routing have shown that this policy can bring significant savings. It is also more realistic in applications such as urban refuse collection, where a vehicle can become full in the middle of a street segment. This work presents the first lower bound for the SDCARP, computed with a cutting plane algorithm and an evolutionary local search reinforced by a multistart procedure and a variable neighborhood descent. Tests on …

Real-time weighting optimization in Chinese Postman Problem

2013

International audience; In this study, based on real-time constraint, an optimization method is proposed for solving the problem of the optimal tour. For that, we will construct a graph containing the real-time state of traffic. The collected data will be used to predict the future state traffic and to give an optimized cost of the tour. This optimization is tested in different sizes of the road networks. The results show that the proposed method is efficient and effective in solving the Chinese Postman Problem in real-time.

fuzzy approach to the robust facility layout in uncertain production environments

2001

The proposed method approaches the problem of the optimal facility layout using fuzzy theory. The optimal layout is a robust layout that minimizes the total material handling cost, when the product market demands are uncertain variables, which are defined as fuzzy numbers. Since each department has a limited production capacity, not all possible combinations, deriving from each product's market demand, are taken into account because some combination could exceed the overall department's productivity. Therefore, the optimal solution results by solving a 'constrained' fuzzy optimization problem, in which the fuzzy material handling costs corresponding to the layouts are evaluated, and a ranki…

Negotiation in Distributed Production Planning Environments

2006

Mass customization and global competition push enterprises to adopt proper business models able to capture all the opportunities arising from emerging competition rules. An increasing number of industrial enterprises distribute their production capacity world wide to achieve lower production costs, lower distribution costs (due to the closer proximity to customers), and deeper knowledge of customer needs. As a drawback, coordination of the different production plants and the balance among plants and enterprise goals represent a critical issue in the network management. In this context the paper looks at the production planning problem, adopting a traditional hierarchical time-based perspect…

A Fuzzy Discrete Event Simulator for Fuzzy Production Environment Analysis

1998

Abstract Discrete Event Simulation is a powerful tool to help production managers in planning manufacturing systems. The necessity to rapid react to market conditions is pushing production planners to process requirements and information affected by vagueness. Vagueness is related with event definition, therefore it is not manageable through statistical tools, but more properly by using fuzzy mathematics. Production situations where uncertainty takes body in term of vagueness are referred as Fuzzy Production Environments. Classical Discrete Event simulators are not suitable to deal with fuzzy variables, therefore they cannot be used to model Fuzzy Production Environments. This paper aims to…

An Object-Oriented Approach to Discrete-Event Simulation Applied to Underground Railway Systems

1999

This paper describes the implementation of an object-oriented simulator that supports the determination of timetables and the design of on-line control policies for underground rail way systems. The simulator has been developed on the basis of a new approach to object- oriented modelling. Such an approach has been used to design a development tool that supports the generation of simulation codes and is able to automatically define the skeleton of a code.

Risk Assessment of a compound feed process based on HAZOP analysis and linguistic terms

2016

[EN] The size and complexity of industrial plants, along with the characteristics of the products used, require a study, analysis and control of the existing risks in every industrial process. In this paper, a methodology for risk assessment in industrial plants, based on the combination of risks identification through the Hazard and Operability (HAZOP) analysis and the risks evaluation through linguistic variables and fuzzy numbers is applied to a case study consisting on a compound feed plant located in the town of Silla (Valencia, Spain). The results from this study show that the main risk in the compound feed production process is the formation of explosive atmospheres (ATEX). Therefore…

AGV-served assembly lines: influence of sequencing and launch policies on system performances

1990

SUMMARY The planning of an AGV-based flexible assembly line is studied. The conflicting objectives of the minimization of the AGVs wait along the line and of the maximization of the system productivity are investigated. To improve the system performances the late start policy to launch and transfer the AGVs is introduced and a heuristic sequencing algorithm is proposed. The developed computer-aided planning procedures make it possible to consider different AGV launch policies, buffer capacities and management goals; moreover, with the combined use of effective sequences a better utilization of the different resources is reached.

A GRASP algorithm for the container stowage slot planning problem

2016

This work presents a generalization of the Slot Planning Problem which raises when the liner shipping industry needs to plan the placement of containers within a vessel (stowage planning). State-of-the-art stowage planning relies on a heuristic decomposition where containers are first distributed in clusters along the vessel. For each of those clusters a specific position for each container must be found. Compared to previous studies, we have introduced two new features: the explicit handling of rolled out containers and the inclusion of separations rules for dangerous cargo. We present a novel integer programming formulation and a Greedy Randomized Adaptive Search Procedure (GRASP) to solv…