857,301 research outputs found

    Fuzzy uncertainty modelling for project planning; application to helicopter maintenance

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    Maintenance is an activity of growing interest specially for critical systems. Particularly, aircraft maintenance costs are becoming an important issue in the aeronautical industry. Managing an aircraft maintenance center is a complex activity. One of the difficulties comes from the numerous uncertainties that affect the activity and disturb the plans at short and medium term. Based on a helicopter maintenance planning and scheduling problem, we study in this paper the integration of uncertainties into tactical and operational multiresource, multi-project planning (respectively Rough Cut Capacity Planning and Resource Constraint Project Scheduling Problem). Our main contributions are in modelling the periodic workload on tactical level considering uncertainties in macro-tasks work contents, and modelling the continuous workload on operational level considering uncertainties in tasks durations. We model uncertainties by a fuzzy/possibilistic approach instead of a stochastic approach since very limited data are available. We refer to the problems as the Fuzzy RoughCut Capacity Problem (FRCCP) and the Fuzzy Resource Constraint Project Scheduling Problem (RCPSP).We apply our models to helicopter maintenance activity within the frame of the Helimaintenance project, an industrial project approved by the French Aerospace Valley cluster which aims at building a center for civil helicopter maintenance

    IWMI medium term plan 2010-2012

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    Research institutes / Strategy planning / Financial situation / Research priorities / Research projects / Project planning / Maintenance costs / Water resource management / Irrigated farming

    Inadequacies in the water reforms in the Kyrgyz Republic: an institutional analysis

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    Water resource management / Analysis / Irrigation management / Participatory management / Water users’ associations / Research methods / Agrarian reform / Irrigation programs / Operations / Maintenance / Conflict / Rivers / Kyrgyzstan

    The Temporal Logic of the Tower Chief System

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    The purpose is to describe the logic used in the reasoning scheme employed in the Tower Chief system, a runway configuration management system. First, a review of classical logic is given. Defensible logics, truth maintenance, default logic, temporally dependent propositions, and resource allocation and planning are discussed

    The Survival of the Conformist: Social Pressure and Renewable Resource Management

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    This paper examines the role of pro-social behavior as a mechanism for the establishment and maintenance of cooperation in resource use under variable social and environmental conditions. By coupling resource stock dynamics with social dynamics concerning compliance to a social norm prescribing non-excessive resource extraction in a common pool resource (CPR), we show that when reputational considerations matter and a sufficient level of social stigma affects the violators of a norm, sustainable outcomes are achieved. We find large parameter regions where norm-observing and norm-violating types coexist, and analyze to what extent such coexistence depends on the environment.Cooperation, Social Norm, Ostracism, Common Pool Resource, Evolutionary Game Theory, Replicator Equation, Agent-based Simulation, Coupled Socio-resource Dynamics

    Maintenance and Continued Development of the IISTPS Transportation Information System, TRANSWEB, MTI Report 99-01

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    The Norman Y. Mineta International Institute for Surface Transportation Policy Studies (IISTPS) at San José State University (SJSU) conducted this project to maintain and continue development of a transportation information system entitled TransWeb . The project elements included: 1) the maintenance and continued development of a World Wide Web site for IISTPS (TransWeb); 2) development and maintenance of a library resource database; and 3) a survey of transportation professionals, primarily in California, regarding their use of the Internet and TransWeb. Site statistics reported here show the extent to which the transportation community uses TransWeb. Standard maintenance procedures are employed, including a weekly review and update by student assistants. The report’s conclusions and recommendations focus on continued maintenance and updating of equipment, features and content to reflect the growing importance of World Wide Web for transportation professionals, researchers, and students

    Development of an Ant Colony Optimization Algorithm to improve Maintenance Process Efficiency

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    Efficient maintenance policies are of fundamental importance because of their fallbacks into the safety and economics of air traffic operations. Usually the optimization of maintenance process is limited to a resource optimization in position and number. But it should be considered that maintenance tasks are performed by man whose excessive workload has negative falls-out not only for workers well-being but also for process safety and efficiency. Thus, in maintenance process optimization it is necessary to take into account also ergonomic aspects of workplace. This gives rise to an optimization of the maintenance process by using an ergonomic approach. In this way, the result of the optimization could allow improvements in the quality of the work of maintenance, but also a greater efficiency of the whole maintenance system. An ant colony optimization algorithm has been developed in order to optimize the system efficiency. This kind of algorithm natively permits to improve man movements into the workplace; furthermore the optimization of the workplace ergonomics has been added. To do this, an objective function of efficiency levels has been determined, linked to any task performed by man. Some protocols have been created on the basis of a literature survey and experimental results. This paper illustrates an applied research in which a method for the optimization of the maintenance process efficiency has been developed in order to show the applicability of a tool offering benefits on both sides: the maintenance process and the related human factors

    Project scheduling under uncertainty using fuzzy modelling and solving techniques

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    In the real world, projects are subject to numerous uncertainties at different levels of planning. Fuzzy project scheduling is one of the approaches that deal with uncertainties in project scheduling problem. In this paper, we provide a new technique that keeps uncertainty at all steps of the modelling and solving procedure by considering a fuzzy modelling of the workload inspired from the fuzzy/possibilistic approach. Based on this modelling, two project scheduling techniques, Resource Constrained Scheduling and Resource Leveling, are considered and generalized to handle fuzzy parameters. We refer to these problems as the Fuzzy Resource Constrained Project Scheduling Problem (FRCPSP) and the Fuzzy Resource Leveling Problem (FRLP). A Greedy Algorithm and a Genetic Algorithm are provided to solve FRCPSP and FRLP respectively, and are applied to civil helicopter maintenance within the framework of a French industrial project called Helimaintenance
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