46 research outputs found

    Computing Limiting Average Availability of a Repairable System through Discretization

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    Formulas for limiting average availability of a repairable system exist only for some special cases: (1) either the lifetime or the repair time is exponential; or (2) there is one spare unit and one repair facility. We consider a more general setting involving several spare units and several repair facilities; and we allow arbitrary life- and repair time distributions. Under periodic monitoring, which essentially discretizes the time variable, we compute the limiting average availability. The discretization approach closely approximates the existing results in the special cases; and increases the limiting average availability as we include additional spare unit or additional repair facility

    Applications of delay time theory to maintenance practice of complex plant

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    This thesis is concerned with investigating and understanding the role andconsequence of different modelling options and parameter estimation options formodelling a complex plant. As systems become more complicated and required newtechnologies and methodologies, more sophisticated maintenance models and controlpolicies are need to solve the maintenance problems. The initial chapter introduces thereview of previous work on a single component system and multi-component system.Although in recent years there has been a shift in the maintenance literature fromconsideration of single items to systems composed of several components, so far only afew papers have tackled the modelling of actual multi-component plant. In the thirdchapter, delay time concept and analysis technique have been presented. Ofparticularly importance are parameter estimation methods, namely the objective methodand the subjective methods. In the fourth chapter the component PM model and thesystem PM model for downtimes and costs based upon various PM policies arediscussed. The key options within maintenance modelling are to determine regularMinspection periods for the system modelled as a whole, and to determine the periodsfor the plant as a set of separate component models. An extension to the downtimemodel is presented for the case when the downtime due to failures within system is notsmall, and impacts upon the estimate of the number of failures arising over a specifiedtime zone. In the following chapter, we address parameter estimation methods usingsimulated data, and assess the ability of estimation techniques to capture the trueparameter values. Particular attention is paid to the problem arising during theparameter estimating process because of the inadequate recording of PM data andimplied correlation between model parameters. Finally, a case study is presented ofmaintenance modelling of production plant in a local company with view to improvingcurrent practice. The model developed is based upon the delay time concept wherebecause of an absence of PM data, using the results of earlier chapters, the processparameters and the delay time distribution were estimated from failure data only using the method of maximum likelihood. The modelling was repeated based uponsubjective assessmentosf parameter,a nd considerablec onsistencyw ith the objectivelybased case obtained. For the plant study, modelling indicated the current PMinspection program was ineffective. A snap-shot approach is then applied to assessother ways of reducing the downtime, and the possibility of improving the PMinspection practice. This leads to readily adapted improvements

    Safety and Reliability - Safe Societies in a Changing World

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    The contributions cover a wide range of methodologies and application areas for safety and reliability that contribute to safe societies in a changing world. These methodologies and applications include: - foundations of risk and reliability assessment and management - mathematical methods in reliability and safety - risk assessment - risk management - system reliability - uncertainty analysis - digitalization and big data - prognostics and system health management - occupational safety - accident and incident modeling - maintenance modeling and applications - simulation for safety and reliability analysis - dynamic risk and barrier management - organizational factors and safety culture - human factors and human reliability - resilience engineering - structural reliability - natural hazards - security - economic analysis in risk managemen

    Aeronautical Engineering: A continuing bibliography (supplement 158)

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    This bibliography lists 499 reports, articles and other documents introduced into the NASA scientific and technical information system in January 1983

    Efficient Decision Support Systems

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    This series is directed to diverse managerial professionals who are leading the transformation of individual domains by using expert information and domain knowledge to drive decision support systems (DSSs). The series offers a broad range of subjects addressed in specific areas such as health care, business management, banking, agriculture, environmental improvement, natural resource and spatial management, aviation administration, and hybrid applications of information technology aimed to interdisciplinary issues. This book series is composed of three volumes: Volume 1 consists of general concepts and methodology of DSSs; Volume 2 consists of applications of DSSs in the biomedical domain; Volume 3 consists of hybrid applications of DSSs in multidisciplinary domains. The book is shaped upon decision support strategies in the new infrastructure that assists the readers in full use of the creative technology to manipulate input data and to transform information into useful decisions for decision makers

    Control, guidance, and navigation for advanced manned missions. Volume 3 - Radiation sensor systems Final report

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    Development of radiation sensor subsystems for advanced manned space mission

    An evaluation of the challenges of Multilingualism in Data Warehouse development

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    In this paper we discuss Business Intelligence and define what is meant by support for Multilingualism in a Business Intelligence reporting context. We identify support for Multilingualism as a challenging issue which has implications for data warehouse design and reporting performance. Data warehouses are a core component of most Business Intelligence systems and the star schema is the approach most widely used to develop data warehouses and dimensional Data Marts. We discuss the way in which Multilingualism can be supported in the Star Schema and identify that current approaches have serious limitations which include data redundancy and data manipulation, performance and maintenance issues. We propose a new approach to enable the optimal application of multilingualism in Business Intelligence. The proposed approach was found to produce satisfactory results when used in a proof-of-concept environment. Future work will include testing the approach in an enterprise environmen

    Lightning protection of aircraft

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    The current knowledge concerning potential lightning effects on aircraft and the means that are available to designers and operators to protect against these effects are summarized. The increased use of nonmetallic materials in the structure of aircraft and the constant trend toward using electronic equipment to handle flight-critical control and navigation functions have served as impetus for this study
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