26,189 research outputs found

    Optimizing the number and location of warehouses in logistics networks considering the optimal delivery routes and set level of reserve stock

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    Forming the optimal structure of a warehouse network is one of the main strategic tasks in arranging an efficient logistics network. The suggested mathematical model and iterative method allow an optimal number and location of warehouses (in the area served by the logistics network) to be defined – with the minimum of total logistics costs for shipping of goods from suppliers through warehouses to customers. The focus is on optimal delivery routes and the optimal level to set for reserve stock contained in the storage network

    SLA Establishment with Guaranteed QoS in the Interdomain Network: A Stock Model

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    The new model that we present in this paper is introduced in the context of guaranteed QoS and resources management in the inter-domain routing framework. This model, called the stock model, is based on a reverse cascade approach and is applied in a distributed context. So transit providers have to learn the right capacities to buy and to stock and, therefore learning theory is applied through an iterative process. We show that transit providers manage to learn how to strategically choose their capacities on each route in order to maximize their benefits, despite the very incomplete information. Finally, we provide and analyse some simulation results given by the application of the model in a simple case where the model quickly converges to a stable state.Comment: 19 pages, 19 figures, IJCNC, http://airccse.org/journal/cnc/0711cnc13.pd

    Dynamic Collection Scheduling Using Remote Asset Monitoring: Case Study in the UK Charity Sector

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    Remote sensing technology is now coming onto the market in the waste collection sector. This technology allows waste and recycling receptacles to report their fill levels at regular intervals. This reporting enables collection schedules to be optimized dynamically to meet true servicing needs in a better way and so reduce transport costs and ensure that visits to clients are made in a timely fashion. This paper describes a real-life logistics problem faced by a leading UK charity that services its textile and book donation banks and its high street stores by using a common fleet of vehicles with various carrying capacities. Use of a common fleet gives rise to a vehicle routing problem in which visits to stores are on fixed days of the week with time window constraints and visits to banks (fitted with remote fill-monitoring technology) are made in a timely fashion so that the banks do not become full before collection. A tabu search algorithm was developed to provide vehicle routes for the next day of operation on the basis of the maximization of profit. A longer look-ahead period was not considered because donation rates to banks are highly variable. The algorithm included parameters that specified the minimum fill level (e.g., 50%) required to allow a visit to a bank and a penalty function used to encourage visits to banks that are becoming full. The results showed that the algorithm significantly reduced visits to banks and increased profit by up to 2.4%, with the best performance obtained when the donation rates were more variable

    Operations research in passenger railway transportation

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    In this paper, we give an overview of state-of-the-art OperationsResearch models and techniques used in passenger railwaytransportation. For each planning phase (strategic, tactical andoperational), we describe the planning problems arising there anddiscuss some models and algorithms to solve them. We do not onlyconsider classical, well-known topics such as timetabling, rollingstock scheduling and crew scheduling, but we also discuss somerecently developed topics as shunting and reliability oftimetables.Finally, we focus on several practical aspects for each of theseproblems at the largest Dutch railway operator, NS Reizigers.passenger railway transportation;operation research;planning problems

    Optimization models of rail transportation under the financial crisis

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    This paper proposes an analysis of the most used models to optimize the rail transportation. Are presented a series of optimization models of labor efficiency in this sector, but also elements that gives the information on the competitiveness of this mode of transport.railway, railway optimization, optimization models for railway

    A Study on Green Economy Indicators and Modeling: Russian Context

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    This article aims to assess and forecast the dynamics of a regional green economy. The research relevance is determined by the need to develop theoretical and methodological basis of the green economy for the transition period and to identify criteria basis for assessing the state and regional level of it. The authors applied the modern methods, which allowed to model criteria considering data uncertainty and both static and dynamic criteria. The research process involved the methods of scientific analysis, comparison and synthesis, the theory of fuzzy sets, and fuzzy modeling. The main principles and methodology of the criteria evaluation for a regional green economy are proposed. The principal methodological approach in this research combines the current state and dynamics of the green economy in evaluating and forecasting the conditions of data uncertainty. The research results form a theoretical, methodological, and practical basis for assessing the current state and level of a regional green economy development, determining the effectiveness of environmental and economic programs, optimizing financial management, conducting environmental monitoring, and developing state plans.The research was funded by the grant of the Ministry of Education and Science of the Russian Federation to Perm National Research Polytechnic University # 26.6884.2017/8.9 "Sustainable development of urban areas and the improvement of the human environment.

    A Study on Green Economy Indicators and Modeling: Russian Context

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    This article aims to assess and forecast the dynamics of a regional green economy. The research relevance is determined by the need to develop theoretical and methodological basis of the green economy for the transition period and to identify criteria basis for assessing the state and regional level of it. The authors applied the modern methods, which allowed to model criteria considering data uncertainty and both static and dynamic criteria. The research process involved the methods of scientific analysis, comparison and synthesis, the theory of fuzzy sets, and fuzzy modeling. The main principles and methodology of the criteria evaluation for a regional green economy are proposed. The principal methodological approach in this research combines the current state and dynamics of the green economy in evaluating and forecasting the conditions of data uncertainty. The research results form a theoretical, methodological, and practical basis for assessing the current state and level of a regional green economy development, determining the effectiveness of environmental and economic programs, optimizing financial management, conducting environmental monitoring, and developing state plans.The research was funded by the grant of the Ministry of Education and Science of the Russian Federation to Perm National Research Polytechnic University # 26.6884.2017/8.9 "Sustainable development of urban areas and the improvement of the human environment.

    Competition in network industries

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    A wave of privatization is sweeping the globe, affecting about 100 countries and adding up to an average of more than $60 billion a year in business in the past decade. The challenge is to ensure that privatization yields clear benefits. Empirical studies suggest that ownership change by itself will often yield results, especially when it reduces government interference. But the regulation required in areas of natural monopoly can become overly intrusive and undermine progress. Real competition is required to generate sizable and lasting welfare improvements. But in infrastructure sectors, the introduction of competition is complicated by the existence of complex transport and communications networks. Debate about whether and how to introduce competition in network industries is sometimes heated. Certain questions recur: Will continuing regulation be needed? Whether and at what terms will private finance be forthcoming? The author argues that policymakers need to understand how competitive forces can be brought to bear in network industries. He explains the following: 1) common principles that are often lost in"technical"debates about specific sectors; 2) various methods for introducing competition in network industries; 3) competition for the market, and bidding for franchises; 4) options for competition for existing networks; 5) options for expanding competitive systems by decentralizing investment in new network capacity; 6) the option of allowing competition among multiple networks; and 7) the implications of these options for the sectors and for financing industry expansion. In case of doubt, he contends, policymakers should not restrict the entry of competitive firms in such networks. If they do, entry restrictions should be subject to an automatic test after a set period, and reviewed for costs and benefits.Economic Theory&Research,Decentralization,Markets and Market Access,Environmental Economics&Policies,Labor Policies,Education for the Knowledge Economy,Economic Theory&Research,Access to Markets,Markets and Market Access,Environmental Economics&Policies
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