Increasing the reliability and the profit in a redundancy allocation problem

This paper proposes a new mathematical model for multi-objective redundancy allocation problem (RAP) without component mixing in each subsystem when the redundancy strategy can be chosen for individual subsystems. Majority of the mathematical model for the multi-objective redundancy allocation problems (MORAP) assume that the redundancy strategy for each subsystem is predetermined and fixed. In general, active redundancy has received more attention in the past. However, in practice both active and cold-standby redundancies may be used within a particular system design and the choice of the redundancy strategy becomes an additional decision variable. The proposed model for MORAP simultaneously maximizes the reliability and the net profit of the system. And finally, to clarify the proposed mathematical model a numerical example will be solved. Keywords: Redundancy Allocation Problem, Serial-Parallel System, Redundancy Strategies, MORAP

The reliability optimization of mechanical systems using metaheuristic approach

The multiobjective Ant Colony System (ACS) meta-heuristic has been developed successfully to provide a solution for the reliability optimization problems of series-parallel system and has been demonstrated its application to the reliability design of gearbox. The problems involve the selection of components with multiple choice and redundancy levels that produce maximum benefit, and are subject to the cost and weight constraints at the system level. These are very common and realistic problems involving conception design of engineering system and reliability engineering. It is becoming increasingly important to develop efficient solutions to these problems because many mechanical and electrical systems are becoming more complex, even as development schedules get shorter and reliability requirements become very stringent. The multiobjective Ant Colony System algorithm offers distinct advantages to these problems compared to alternative optimization methods, and can be applied to a more diverse problem domain with respect to the type or size of the problems. Through the combination of probabilistic search, multi-objective formulation of local moves and the dynamic penalty method, the multi-objective ACSRAP, which performs very well on the redundancy apportionment problems (RAP) of the series-parallel k-out-of-n : G subsystem and reliability design of gear box, allows us to obtain an optimal design solution very frequently and more quickly than with other heuristic approaches. Therefore, the use of these techniques to the reliability optimization problems of mechanical systems announces great potential and makes it possible to develop a powerful and economic tool for which the designers always seek

Decision support system for multi-objective forest management: a study in the Queen Elizabeth National Forest Park in Scotland

SIGLEAvailable from British Library Document Supply Centre- DSC:D91694 / BLDSC - British Library Document Supply CentreGBUnited Kingdo

Multiple Criteria Decision Support; Proceedings of an International Workshop, Helsinki, Finland, August 7-11, 1989

Multiple Criteria Decision Making has been an important and active research area for some 20 years. In the 1970's, research focused on the theory of multiple objective mathematical programming and on procedures for solving multiple objective mathematical programming problems. During the 1980's, a shift in emphasis towards multiple criteria decision support was observed. Accordingly, much research has focused on the user interface, the behavioral foundations of decision making, and on supporting the entire decision-making process from problem structuring to solution implementation. Because of the shift in research emphasis the authors decided to make "Multiple Criteria Decision Support" the theme for the International Workshop, which was held at Suomen Saeaestoepankkiopisto in Espoo, Finland. The Workshop was organized by the Helsinki School of Economics, and sponsored by the Helsinki School of Economics and IIASA, Austria. This volume provides an up-to-date coverage of the theory and practice of multiple criteria decision support. The authors trust that it will serve the research community as well as the previously published Conference Proceedings based on IIASA Workshops

Regional forestry sector modelling of options for industrial forest plantations in Indonesia

Regional resource planning and decision-making for industrial forest plantation development increasingly involves participation by members of the public. Motivation to maximise or minimise the degree to which groups with various interests can satisfy their individual objectives should recognise outcomes arrived at in a consensus decision-making environment. In this study, a planning framework is devised and adopted, which describes a regional planning system prepared in order to assist in the design and evaluation of strategic industrial forest plantation development in Indonesia. The central component of this planning system is interactive Multi-Objective Decision Making (MODM) modelling with linkages between optimisation and simulation models. The framework of the whole planning system demonstrates the capability and feasibility of resolving important and conflicting objectives through discussion and communicative decision processes that can be reinforced with modelling sensitivity outputs. In other words, a methodology is developed that allows strategic options for plantation planning to be analysed interactively. The MODM models here are MINMAX and MINSUM goal programming formulations. This model has various features that characterise industrial forest plantation development planning, including physical production, social, economic, environmental, and location aspects. This formulation, moreover, has several advantages such as capturing the essence of the multi-objective decision making problem, encompassing the entire range of feasible tradeoffs among all objectives through parametric programming in order to derive forestland allocations optimally, as well as serving important implementable and practical interests. A minimum economic size (MES) spreadsheet-based model is run to determine profitable plantation sizes by using financial criteria such as IRR and NPV. The MES model outputs are then incorporated within MODM models. A major part of the research reported here was to develop a way of transferring data between simulation and LP models directly through file transfers, and transferring LP derived solutions directly back to the simulation model. This linkage has several advantages: for example, theoretically optimal LP solutions are usually unrealistic in practical or implementational terms because of administrative, social, environmental and other similar problems facing forest management; whereas simulation allows one to explore the effects of deviations from "optimal" LP solutions, and to simulate both in more detail and in broader aggregations of things such as age classes, log types and locations. If measures, e.g. wood and financial flows, are unsatisfactory, some constraints are modified and formed for the relevant LP model utilising, for example, the future log assortment flow consequences and the tradeoffs among them. The automated linkage between optimisation and simulation models provides easy data and solution transfers so that decision makers and stakeholders may gain detailed insights before any consensus decisions need to be made. A geographic information system (GIS) is utilised to enhance pictorially the preferred solutions, information, and appearance. The whole planning system is demonstrated and tested in an indicative case study. The results display the major advantages of consistency, clarity and simplicity of the approach to regional forestland allocation. The framework and results at this stage are only preliminary, because some data are still incomplete and unrefined. This study is, therefore, an initial description and explanation of methodology and an indication of the nature of desirable results rather than a firm policy recommendation pertaining to the case study area. In principle, the framework could also become multi-temporal by creating each variable in a time-dependent fashion. The planning system developed has the ability to incorporate social, financial, environmental, and technical variables in a comprehensive participatory development process. The ultimate value of the quantitative information represented in this framework (or methodology) through a background case study analysis is its ability to facilitate policy formulation to satisfy decision-makers and stakeholders when making informed choices in fundamental management decisions

Optimization Models Using Fuzzy Sets and Possibility Theory

Optimization is of central concern to a number of disciplines. Operations Research and Decision Theory are often considered to be identical with optimization. But also in other areas such as engineering design, regional policy, logistics and many others, the search for optimal solutions is one of the prime goals. The methods and models which have been used over the last decades in these areas have primarily been "hard" or "crisp", i.e. the solutions were considered to be either feasible or unfeasible, either above a certain aspiration level or below. This dichotomous structure of methods very often forced the modeler to approximate real problem situations of the more-or-less type by yes-or-no-type models, the solutions of which might turn out not to be the solutions to the real problems. This is particularly true if the problem under consideration includes vaguely defined relationships, human evaluations, uncertainty due to inconsistent or incomplete evidence, if natural language has to be modeled or if state variables can only be described approximately. Until recently, everything which was not known with certainty, i.e. which was not known to be either true or false or which was not known to either happen with certainty or to be impossible to occur, was modeled by means of probabilities. This holds in particular for uncertainties concerning the occurrence of events. probability theory was used irrespective of whether its axioms (such as, for instance, the law of large numbers) were satisfied or not, or whether the "events" could really be described unequivocally and crisply. In the meantime one has become aware of the fact that uncertainties concerning the occurrence as well as concerning the description of events ought to be modeled in a much more differentiated way. New concepts and theories have been developed to do this: the theory of evidence, possibility theory, the theory of fuzzy sets have been advanced to a stage of remarkable maturity and have already been applied successfully in numerous cases and in many areas. Unluckily, the progress in these areas has been so fast in the last years that it has not been documented in a way which makes these results easily accessible and understandable for newcomers to these areas: text-books have not been able to keep up with the speed of new developments; edited volumes have been published which are very useful for specialists in these areas, but which are of very little use to nonspecialists because they assume too much of a background in fuzzy set theory. To a certain degree the same is true for the existing professional journals in the area of fuzzy set theory. Altogether this volume is a very important and appreciable contribution to the literature on fuzzy set theory

Proceedings of the NASA Conference on Space Telerobotics, volume 2

These proceedings contain papers presented at the NASA Conference on Space Telerobotics held in Pasadena, January 31 to February 2, 1989. The theme of the Conference was man-machine collaboration in space. The Conference provided a forum for researchers and engineers to exchange ideas on the research and development required for application of telerobotics technology to the space systems planned for the 1990s and beyond. The Conference: (1) provided a view of current NASA telerobotic research and development; (2) stimulated technical exchange on man-machine systems, manipulator control, machine sensing, machine intelligence, concurrent computation, and system architectures; and (3) identified important unsolved problems of current interest which can be dealt with by future research