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Optimisation Problem (optimisation + problem)
Selected AbstractsComplexity of resilient network optimisation,EUROPEAN TRANSACTIONS ON TELECOMMUNICATIONS, Issue 7 2009Mateusz, otkiewicz Path restoration (PR) is one of the basic mechanisms for securing telecommunication networks against failures. In the paper, we discuss the complexity of certain variants of a multi-commodity flow network optimisation problem in directed graphs related to state-independent path restoration mechanisms. We demonstrate that most variants of the considered problem are -hard. Depending on the variant, we show how the problem can be reduced either from the partition problem or from the problem of finding an arc-disjoint pair of paths that connect two distinct pairs of nodes. We also demonstrate that at the same time the considered problem is difficult to approximate. The complexity results of the paper are important as they can help to devise proper algorithms for resilient network design tools. Copyright © 2009 John Wiley & Sons, Ltd. [source] Profit Margins, Adjustment Costs and the Business Cycle: An Application to Spanish Manufacturing Firms*OXFORD BULLETIN OF ECONOMICS & STATISTICS, Issue 1 2003José C. Fariñas The objective of this paper is to investigate the cyclical behaviour of mark-ups, using a panel of Spanish manufacturing firms over the period 1990,1998. Margins are estimated from the optimal conditions derived from the firm's optimisation problem, which assumes that labour inputs are subject to adjustment costs. A number of results emerge from the estimations. First, we find positive and asymmetric adjustment costs for permanent labour inputs. Second, price-cost margins are markedly procyclical. Our estimates suggest that labour adjustment costs more than double the variability of average margins with respect to Lerner indexes. Third, we find differences in the parameters of the adjustment technology across industries which make markups of intermediate and production good industries more cyclical than consumer good industries. Finally, industry-specific price-cost margins are higher in more concentrated industries. [source] A New Specification of Labour Supply in the MONASH Model with an Illustrative ApplicationTHE AUSTRALIAN ECONOMIC REVIEW, Issue 1 2003Peter B. Dixon MONASH is a dynamic general equilibrium model of the Australian economy. This article describes a new labour-market specification for MONASH in which people are allocated in year t to categories according to their labourmarket activities in year t , 1. People in each category plan their labour supplies by solving an optimisation problem. Via these problems, we introduce the assumption that people in employment categories supply labour more strongly to employment activities than do people in unemployment categories. Thus we find that employment-stimulating policies in t , 1 increase labour supply in t by shifting the composition of the labour force in t in favour of employment categories and away from unemployment categories. We illustrate this idea by using MONASH to simulate the Dawkins proposal to combine a freeze on award wage rates with tax credits for low-wage workers in low-income families. We find that the Dawkins policy would generate a significant short-run increase in employment. With the increase in employment generating an increase in labour supply, the employment benefits of the policy would persist over many years. However, in the long run, we would expect the effect of the policy on aggregate employment to be small and to depend on how the policy affected the ratio of real after-tax wage rates to unemployment benefits. [source] What Have you Done for me Lately?THE ECONOMIC JOURNAL, Issue 518 2007Release of Information, Strategic Manipulation of Memories How should a rational agent (politician/employee/advertiser) release information in order to manipulate the memory imperfections of his forgetful assessor (electorate/supervisor/consumer)? This article attempts to answer this question using a memory model based on the principles of recency, similarity and repetition. I show that the problem of a rational agent who releases information to a forgetful assessor can be modelled as a standard dynamic optimisation problem and we describe the properties of the optimal profile for releasing information. The theoretical results are applicable in a wide range of social and economic contexts, such as political campaigns, employee performance evaluations and advertising strategies. [source] Economic drought management index to evaluate water institutions' performance under uncertainty*AUSTRALIAN JOURNAL OF AGRICULTURAL & RESOURCE ECONOMICS, Issue 1 2007Eva Iglesias Reservoir management and intertemporal water allocation are critical issues in semiarid regions where agriculture has to confront highly variable rainfall patterns. In this paper, we derive and propose an economic drought management index (EDMI) to evaluate water institutions' performance to cope with drought risk. The EDMI is based on the optimal conditions of a stochastic dynamic optimisation problem that characterises reservoir management. The index's main advantages are its ease of interpretation and breadth of scope, as it incorporates information on hydrological processes, structural constraints, water institutions' rules, and the economic benefits of water use. An empirical application is developed to assess the institutional rules governing water allocation in two different supply systems in Andalusia (southern Spain). [source] Optimisation and the selection of conservation contracts*AUSTRALIAN JOURNAL OF AGRICULTURAL & RESOURCE ECONOMICS, Issue 1 2007Stefan Hajkowicz This paper explores alternative techniques for the selection of conservation contracts under competitive tendering programs. Under these programs, purchasing decisions are often based on the benefits score and cost for proposed projects. The optimisation problem is to maximise the aggregate benefits without exceeding the budget. Because the budget rarely permits all projects to be funded, there is a binary choice problem, known in the operations research published work as a knapsack problem. The decision-maker must choose which projects are funded and which are not. Under some circumstances, the knapsack problem can be unsolvable because computational complexity increases exponentially with the number of projects. This paper explores the use of several decision rules for solving the optimisation problem including the use of advanced meta-heuristics. It is shown that commonly applied techniques for project selection may not be providing the optimal solution. Improved algorithms can increase the environmental programs benefits and staying within budget. The comparison of algorithms is based on real data from the Western Australian Conservation Auction. [source] Ethics in operations research and sustainable developmentINTERNATIONAL TRANSACTIONS IN OPERATIONAL RESEARCH, Issue 4 2010Jean-Pierre Brans Abstract During the last 100 years, major social, economic, environmental and technical problems have arisen that today jeopardise mankind's very existence. The authors argue that operations research (OR) should be more strongly involved by developing models to face today's crucial challenges. OR should change drastically because it is traditionally involved mainly with optimisation problems, which are often counterproductive in the sense of ethical behaviour: new basic approaches are required. This paper provides some avenues on how to develop instruments for addressing mankind's sustainability problems, and for complying with ethical principles. It is proposed to have a mix of techniques, mainly: systems thinking, multi-criteria decision-making and dynamic control. A global framework, called ASMC (Adaptive, Systemic, Multi-criteria, Control procedure), is proposed for developing these ideas. Some sustainable development applications are presented. [source] | ||||||||||