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  • 1.
    Baourakis, George
    et al.
    Department of Economic and Management Sciences, Mediterranean Agronomic Institute of Chania.
    Migdalas, Athanasios
    DSS Laboratory Department of Production and Industrial Engineering, Technical University of Crete.
    Kourgiantakis, M.
    Department of Production Engineering and Management, Technical University of Crete, Department of Economic and Management Sciences, Mediterranean Agronomic Institute of Chania.
    The impact of e-commerce on agro-food marketing: The case of agricultural cooperatives, firms and consumers in Crete2002Ingår i: British Food Journal, ISSN 0007-070X, E-ISSN 1758-4108, Vol. 104, nr 8Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper is concerned with the impact of e‐commerce on agro‐food marketing. First, a theoretical framework is specified for the Internet as a marketing tool with emphasis on the agro‐food and organic food sections. Subsequently we present the results of a survey that was conducted in order to investigate how Cretan agricultural cooperatives use or tend to use the business methodology of e‐commerce. Consumers and managers of cooperatives in Crete reveal their expectations from the new technology. From this survey valuable information is gained about the practical relations between e‐commerce and the agro‐food market on the island, and divergence from the theoretical framework is noticed.

  • 2. Barcelo, J.
    et al.
    Jornsten, A.
    Migdalas, Athanasios
    Department of Mathematics, Linköping Institute of Technology.
    The Resource Constrained Spanning Tree Problem: Alternative Modelling and Algorithmic Approaches1993Ingår i: Algorithms and model formulations in mathematical programming, Berlin: Encyclopedia of Global Archaeology/Springer Verlag, 1993, s. 142-143Kapitel i bok, del av antologi (Refereegranskat)
  • 3.
    Chinchuluun, Altannar
    et al.
    University of Florida.
    Karakitsiou, Athanasia
    Department of Production Engineering and Management, Technical University of Crete.
    Migdalas, Athanasios
    Department of Production Engineering and Management, Technical University of Crete.
    Mavrommati, Athanasia
    Department of Production Engineering and Management, Technical University of Crete.
    Game Theory Models and their Application in Inventory Management and Supply Chain2008Ingår i: Pareto Optimality, Game Theory And Equilibria, New York: Encyclopedia of Global Archaeology/Springer Verlag, 2008, s. 833-865Kapitel i bok, del av antologi (Refereegranskat)
    Abstract [en]

    Analysis of supply chain politics can benefit from applying game-theory concepts extensively. Game theory tries to enlighten the interactions between individuals or groups of people whose goals are opposed conflicting, or at least partially competing. In this chapter, we review classic game theoretical approaches to modeling and solving certain problems in supply chain management. Both noncooperative and cooperative models are discussed and solution procedures are presented in single-period and multiperiod settings. As used here, a “game” is a metaphor for any interaction among the decision makers in a supply chain.

  • 4.
    Chinchuluun, Altannar
    et al.
    Department of Industrial and Systems Engineering, Center for Applied Optimization, University of Florida.
    Pardalos, Panos M.Department of Industrial and Systems Engineering, Center for Applied Optimization, University of Florida.Migdalas, AthanasiosDepartment of Production Engineering and Management, Technical University of Crete.Pitsoulis, LeonidasDepartment of Production Engineering and Management, Aristotle University of Thessaloniki.
    Pareto Optimality, Game Theory and Equilibria2008Samlingsverk (redaktörskap) (Refereegranskat)
  • 5.
    Damberg, Olof
    et al.
    Division of Optimization, Department of Mathematics, Linköping Institute of Technology.
    Migdalas, Athanasios
    Department of Mathematics, Linköping Institute of Technology.
    A Data Parallel Space Dilation Algorithm for the Concentrator Location Problem'1995Ingår i: Parallel processing of discrete optimization problems: DIMACS workshop, April 28 - 29, 1994 / [ed] Panos M. Pardalos; Mauricio G.C. Resende; K.G. Ramakrishnan, Providence, RI: American Mathematical Society (AMS), 1995, s. 57-80Konferensbidrag (Refereegranskat)
  • 6.
    Damberg, Olof
    et al.
    Division of Optimization, Department of Mathematics, Linköping Institute of Technology.
    Migdalas, Athanasios
    Division of Optimization, Department of Mathematics, Linköping Institute of Technology.
    Distributed Disaggregate Simplicial Decomposition: A Parallel Algorithm for Traffic Assignment1997Ingår i: Network Optimization, Berlin: Encyclopedia of Global Archaeology/Springer Verlag, 1997, s. 172-193Kapitel i bok, del av antologi (Refereegranskat)
    Abstract [en]

    In this work we present a parallel algorithm for the user equilibrium traffic assignment problem. The algorithm is based on the concepts of simplicial decomposition, regularization and partial linearization. The parallel implementation is a synchronous, single program multiple data, algorithm using local load balancing. PVM is used for communication purposes. We present numerical results for two parallel platforms: a DEC Alpha cluster and a Parsytec GC/PowerPlus and for three real world traffic networks. The results show moderate speed-up with increasing efficiency for increasing OD-pair to link ratio

  • 7.
    Damberg, Olof
    et al.
    Division of Optimization, Department of Mathematics, Linköping Institute of Technology.
    Migdalas, Athanasios
    Department of Mathematics, Linköping University.
    Simulated annealing, local search and Lagrangean heuristics for concentrator location in centralised communication networks: a comparative study1994Rapport (Övrigt vetenskapligt)
  • 8.
    Damberg, Olof
    et al.
    Division of Optimization, Department of Mathematics, Linköping Institute of Technology.
    Migdalas, Athanasios
    Division of Optimization, Department of Mathematics, Linköping Institute of Technology.
    Narula, S.C.
    Location Problems and Parallel Programming: A Tutorial'1993Ingår i: Vol. 4, s. 87-92Artikel i tidskrift (Övrigt vetenskapligt)
  • 9.
    Damberg, Olof
    et al.
    Division of Optimization, Department of Mathematics, Linköping Institute of Technology.
    Migdalas, Athanasios
    Department of Mathematics, Institute of Technology, Linköping University.
    Storøy, Sverre
    Department of Informatics, University of Bergen.
    Parallel Algorithms for Network Problems1997Ingår i: Parallel Algorithms for Network Problems, Encyclopedia of Global Archaeology/Springer Verlag, 1997, s. 183-238Kapitel i bok, del av antologi (Refereegranskat)
    Abstract [en]

    In this chapter we review parallel algorithms for some linear network problems, with special emphasis on the bipartite assignment problem. The many-to-one assignment problem is considered, and a breadth-first-search algorithm for finding augmenting paths is exemplified. We also review parallel algorithms for single- and multicommodity network problems with convex objective functions. A simplicial decomposition approach to the traffic assignment problem is presented and an SPMD implementation is given.

  • 10. D'Apruzzo, Marco
    et al.
    Marino, Marina
    Migdalas, Athanasios
    Department of Production Engineering and Management, Technical University of Crete.
    Pardalos, Panos M.
    Department of Industrial and Systems Engineering, Center for Applied Optimization, University of Florida.
    Nonlinear Optimization: A Parallel Linear Algebra Standpoint2006Ingår i: Handbook of Parallel Computing and Statistics, Boca Raton, Fl: CRC Press, 2006, s. 259-281Kapitel i bok, del av antologi (Refereegranskat)
  • 11. D'Apruzzo, Marco
    et al.
    Marino, Marina
    Migdalas, Athanasios
    Department of Production Engineering and Management, Technical University of Crete.
    Pardalos, Panos M.
    Department of Industrial and Systems Engineering, Center for Applied Optimization, University of Florida.
    Toraldo, Geraldo
    Dipartimento di Ingegneria Agraria ed Agronomia, Universita di Napoli Federico II.
    Parallel computing in global optimization2006Ingår i: Handbook of Parallel Computing and Statistics, Boca Raton, Fl: CRC Press, 2006, s. 225-258Kapitel i bok, del av antologi (Refereegranskat)
  • 12.
    Eksioglu, B.
    et al.
    University of Florida.
    Migdalas, Athanasios
    Department of Production Engineering and Management, Technical University of Crete.
    Pardalos, Panos M.
    Department of Industrial and Systems Engineering, Center for Applied Optimization, University of Florida.
    Heuristic approaches to production-inventory-distribution problems in supply chains2003Ingår i: Optimization and industry :: new frontiers ; [International Conference Optimization and Industry, held in Australia in 2001] / [ed] Panos M. Pardalos, Dordrecht: Kluwer Academic Publishers, 2003, s. 15-37Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper we focus on global optimization issues in supply chains. We propose solution methods for production, inventory and distribution problems with fixed charge costs that arise in a supply chain. The production-inventory-distribution problem with fixed charges falls under the category of minimum concave cost network flow problems which are known to be NP-hard. We present two heuristic approaches; a dynamic slope scaling procedure (DSSP) and a greedy randomized adaptive search procedure (GRASP). DSSP and GRASP both have strong intuitive appeal and are straightforward to implement. We compare the two heuristic approaches by presenting a broad set of computational results.

  • 13.
    Ghannadan, Saied
    et al.
    Division of Optimization, Department of Mathematics, Linköping Institute of Technology.
    Migdalas, Athanasios
    Department of Mathematics, Linköping University.
    Tuy, Hoang
    Institute of Mathematics, Hanoi, Division of Optimization, Department of Mathematics, Linköping Institute of Technology.
    Värbrand, Peter
    Division of Optimization, Department of Mathematics, Linköping Institute of Technology.
    Heuristics based on Tabu search and lagrangean relaxation for the concave production-transportation problem1994Ingår i: Studies in Regional and Urban Planning, ISSN 1106-2606, Vol. 3, s. 127-140Artikel i tidskrift (Refereegranskat)
  • 14.
    Ghannadan, Saied
    et al.
    Division of Optimization, Department of Mathematics, Linköping Institute of Technology.
    Migdalas, Athanasios
    Division of Optimization, Department of Mathematics, Linköping Institute of Technology.
    Tuy, Hoang
    Institute of Mathematics, Hanoi, Division of Optimization, Department of Mathematics, Linköping Institute of Technology.
    Värbrand, Peter
    Division of Optimization, Department of Mathematics, Linköping Institute of Technology.
    Tabu Metaheuristic based on Local Search for the Concave Production-Transportation Problem'1996Ingår i: Studies in Locational Analysis, ISSN 1105-5162, Vol. 8, s. 33-47Artikel i tidskrift (Refereegranskat)
  • 15.
    Helgason, Thorkell
    et al.
    Science Institute, Department of Mathematics, University of Iceland.
    Jörnsten, Kurt O.
    Institute of Finance and Management Science, The Norwegian School of Economics and Buisiness Admistration.
    Migdalas, Athanasios
    Division of Optimization, Department of Mathematics, Linköping Institute of Technology.
    Maxmin Formulation of the Apportionments of Seats to a Parliament1995Ingår i: Minimax and Applications, New York: Encyclopedia of Global Archaeology/Springer Verlag, 1995, s. 109-118Kapitel i bok, del av antologi (Refereegranskat)
    Abstract [en]

    We consider the problem of apportioning a fixed number of seats in a national parliament to the candidates of different parties that are elected in constituencies so as to meet party and constituency constraints. We propose a maxmin formulation of the problem. The purpose is to obtain a fair apportionment of the parliament seats, in the sense that the minimum number of voters behind any possible parliament majority is maximum. We illustrate the concepts with some examples, including an example from the last Icelandic election

  • 16.
    Helgason, Thorkell
    et al.
    Science Institute, Department of Mathematics, University of Iceland.
    Jörnsten, Kurt O.
    Migdalas, Athanasios
    Department of Mathematics, Linköping University.
    Maxmin formulation of the apportionments of seats to a parliament1994Rapport (Övrigt vetenskapligt)
  • 17.
    Hellstrand, Johan
    et al.
    Linköping University.
    Larsson, Torbjörn
    Department of Mathematics, Institute of Technology, Linköping University.
    Migdalas, Athanasios
    Department of Mathematics, Linköping University.
    A characterization of the uncapacitated network design polytope1981Rapport (Övrigt vetenskapligt)
  • 18.
    Hellstrand, Johan
    et al.
    Department of Mathematics, University of Linköping.
    Larsson, Torbjörn
    Department of Mathematics, University of Linköping.
    Migdalas, Athanasios
    Department of Mathematics, University of Linköping.
    A characterization of the uncapacitated network design polytope1992Ingår i: Operations Research Letters, ISSN 0167-6377, E-ISSN 1872-7468, Vol. 12, nr 3, s. 159-163Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The uncapacitated network design problem is considered. We show that the feasible polytope of the continuous relaxation of this problem has the property that any path along the edges of the convex hull of its integer points is also a path along the edges of the polytope itself. This property may be of computational interest since it implies the possibility of solving the uncapacitated network design problem by a pivoting scheme. © 1992.

  • 19.
    Hellstrand, Johan
    et al.
    Linköping University.
    Migdalas, Athanasios
    Department of Mathematics, Linköping University.
    A network design problem solvable by the integral simplex method1989Rapport (Övrigt vetenskapligt)
  • 20. Holmqvist, K.
    et al.
    Migdalas, Athanasios
    Division of Optimization, Department of Mathematics, Linköping Institute of Technology.
    Pardalos, Panos M.
    Department of Industrial and Systems Engineering, Center for Applied Optimization, University of Florida.
    Parallelized Heuristics for Combinatorial Search1997Ingår i: Parallel Computing in Optimization, Encyclopedia of Global Archaeology/Springer Verlag, 1997, s. 269-294Kapitel i bok, del av antologi (Refereegranskat)
    Abstract [en]

    Combinatorial optimization problems of various kinds arise in different fields. Many of these problems are large, complicated problems that require huge computing powers and long execution times for the solving procedure. Therefore the use of massively parallel computer architectures presents an interesting opportunity. The difficulty in solving these problems can sometimes also necessitate the use of heuristic methods that do not necessarily find the global optimum. In this chapter, we give brief descriptions of the techniques and discuss different parallel implementations of the modern heuristic techniques Simulated Annealing, Tabu Search, Genetic Algorithms, and GRASP

  • 21.
    Holmqvist, Kristina
    et al.
    Division of Optimization, Department of Mathematics, Linköping Institute of Technology.
    Migdalas, Athanasios
    Division of Optimization, Department of Mathematics, Linköping Institute of Technology.
    A C++ Class Library for Interval Arithmetic in Global Optimization1996Ingår i: State of the Art in Global Optimization: Computational Methods and Applications, Encyclopedia of Global Archaeology/Springer Verlag, 1996, s. 213-226Kapitel i bok, del av antologi (Refereegranskat)
    Abstract [en]

    Global optimization methods based on interval arithmetic have potential to efficiently solve problems that standard nonlinear programming techniques cannot handle well. In interval arithmetic the machine arithmetic is performed by approximating a real number with an enclosing interval, rather than with a single floating point number. Hence, an automatic control over rounding errors is provided. To use interval arithmetic in practice either a language with built-in interval arithmetic or a suitable subroutine library is needed. Such a library can with advantage be implemented in C++, realizing intervals as objects with well defined interfaces. In this paper we report experience from implementing and using a C++ class library for global optimization using interval arithmetic. Measurements show that the use of object oriented programming and operator overloading does not affect performance negatively. In fact, our C++ implementation of interval arithmetic is actually faster than a comparable Fortran implementation.

  • 22.
    Holmqvist, Kristina
    et al.
    Division of Optimization, Department of Mathematics, Linköping Institute of Technology.
    Migdalas, Athanasios
    Division of Optimization, Department of Mathematics, Linköping Institute of Technology.
    Pardalos, Panos M.
    Department of Industrial and Systems Engineering, Center for Applied Optimization, University of Florida, Center for Applied Optimization and Department of Industrial and Systems Engineering, University of Florida, Gainesville.
    Greedy Randomized Adaptive Search for a Location Problem with Economies of Scale1997Ingår i: Developments in Global Optimization: [Third Workshop on Global Optimization, Szeged, Hungary, December 10 - 14, 1995] / [ed] Immanuel M. Bromze; Tibor Csendes ; Reiner Horst; PAnos M. Pardalos, Dordrecht: Kluwer Academic Publishers, 1997, s. 301-313Konferensbidrag (Refereegranskat)
    Abstract [en]

    We consider a heuristic approach for the solution of a location problem with economies of scale. The method chosen has a strong intuitive appeal, a prominent empirical track record, and is trivial to efficiently implement on parallel processors. We define the various components comprising this GRASP approach and perform a step-by-step development of such a heuristic for the location problem with concave costs. Computational results for problems of dimensions up to 100 × 1000 are reported.

  • 23.
    Holmqvist, Kristina
    et al.
    Division of Optimization, Department of Mathematics, Linköping Institute of Technology.
    Migdalas, Athanasios
    Division of Optimization, Department of Mathematics, Linköping Institute of Technology.
    Pardalos, Panos M.
    Department of Industrial and Systems Engineering, Center for Applied Optimization, University of Florida.
    Parallel Continuous Non-Convex Optimization1997Ingår i: Parallel Computing in Optimization, Encyclopedia of Global Archaeology/Springer Verlag, 1997, s. 471-527Kapitel i bok, del av antologi (Refereegranskat)
    Abstract [en]

    Parallel globed optimization is one very promising area of research since due to inherent difficulty of the problems it studies, only instances of limited dimension can be solved in reasonable computer time on conventional machines. However, the use of parallel and distributed processing can substantially increase the possibilities for the success of the global optimization approach in practice. In this chapter we are concerned with the development of parallel algorithms for solving certain classes of non-convex optimization problems. We present an introductory survey of exact parallel algorithms that have been used to solve structured (partially separable) problems and problems with simple constraints, and algorithms based on parallel local search and its deterministic or stochastic refinements for solving general non-convex problems. Indefinite quadratic programming, posynomial optimization, and the general global concave minimization problem can be solved using these approaches. In addition, the minimum concave cost network flow problem and location problems with economies of scale are used in illustrating these techniques for the solution of large-scale, structured problems.

  • 24.
    Holmqvist, Kristina
    et al.
    Division of Optimization, Department of Mathematics, Linköping Institute of Technology.
    Pardalos, Panos M.
    Department of Industrial and Systems Engineering, Center for Applied Optimization, University of Florida.
    Migdalas, Athanasios
    Department of Mathematics, Linköping Institute of Technology.
    A GRASP algorithm for the single source uncapacitated minimum concave-cost network flow problem1998Ingår i: Network Design: Connectivity and Facilities Location : Dimacs Workshop April 28-30, 1997, Providence, R.I: American Mathematical Society (AMS), 1998, s. 131-142Kapitel i bok, del av antologi (Refereegranskat)
  • 25.
    Jörnsten, K.O.
    et al.
    Chr. Michelsens Institute, Fantoft.
    Migdalas, Athanasios
    Department of Mathematics, Linköping Institute of Technology.
    Designing a minimal spanning tree network subject to a budget constraint1988Ingår i: Optimization, ISSN 0233-1934, E-ISSN 1029-4945, Vol. 19, nr 4, s. 475-484Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The problem of determining a minimal spanning tree, subject to side constraints, arises frequently in the design of computer communication networks and pipeline systems. In this paper, a specific case of the general problem, with only one side constraint of the knapsack type is considered. For its solution, a new Lagrangian relaxation, based on a reformulation of the problem through the utilization of duplication of variables, is developed. Theoretical and computational results, indicating the superiority of the new approach, over the straightforward Lagrangian relaxation, are presented. Finally, the possibility of adopting the approach for the solution of more general problems is demonstrated.

  • 26.
    Jörnsten, Kurt O.
    et al.
    Department of Mathematics, Linköping Institute of Technology.
    Larsson, Torbjörn
    Department of Mathematics, Institute of Technology, Linköping University.
    Lundgren, Jan T.
    Department of Mathematics, Linköping Institute of Technology.
    Migdalas, Athanasios
    Department of Mathematics, Linköping Institute of Technology.
    An entropy model with variable target1990Ingår i: Environment and planning A, ISSN 0308-518X, E-ISSN 1472-3409, Vol. 22, nr 4, s. 493-506Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper an entropy model with variable target is presented, in which target values are assumed to belong to a specified convex set, so that multiple base-year information and forecasts of future trends can be handled without prior aggregation of such information into one fixed target.Three solution methods for such a model are presented -- one cutting-plane and two search methods -- all of which utilize the fact that entropy models with fixed targets can be solved efficiently. Some comments on potential applications and reasonable target-set specifications are made and numerical examples are presented

  • 27.
    Karakitsiou, Athanasia
    et al.
    Department of Business Administration, Educational Technological Institute of Central Macedonia, Serres, Greece .
    Kourgiantakis, Markos
    Department of Business Administration, Technological Educational Institute of Crete, Heraklion, Greece.
    Mavrommati, Athanasia
    Department of Economics, University of Ioannina, Ioannina, Greece .
    Migdalas, Athanasios
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Industriell Ekonomi.
    Regional efficiency evaluation by input-oriented data envelopment analysis of hotel and restaurant sector2018Ingår i: Operational Research, ISSN 1109-2858, E-ISSN 1866-1505Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper analyses the efficiency of hotel and restaurant sector across all of the thirteen regions in Greece. For our purpose, DEA models were applied in order to evaluate the tourist efficiency and competitiveness of different regions in Greece. The application of this frontier method permits the calculation of efficiency scores based on a series of inputs (number of local units, number of employees and investments) and output (turnover). For the years, 2002–2013, with respectively constant and variable returns to scale models, the empirical analysis shows the differences in the efficiency performance of the Greek regions. More specifically, Attica and South Aegean can be regarded as “moving ahead” regions, whereas some other like, Thessaly, Central Macedonia, Central Greece and Epirus can be considered as “falling further” regions.

  • 28.
    Karakitsiou, Athanasia
    et al.
    DSS Laboratory Department of Production and Industrial Engineering, Technical University of Crete.
    Mavrommati, Athanasia
    Department of Production Engineering and Management, Technical University of Crete.
    Migdalas, Athanasios
    DSS Laboratory Department of Production and Industrial Engineering, Technical University of Crete.
    Efficient Minimization over Products of Simplices and its Application to Nonlinear Multicommodity Network Problems2005Ingår i: Operational Research, ISSN 1109-2858, E-ISSN 1866-1505, Vol. 4, nr 2, s. 99-118Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Many problems in portfolio selection, in traffic planning and in computer communicationnetworks can be formulated as nonlinear problems involving minimization of a nonlinearfunction over simplices. Based on the concepts of regularization and partial linearization, wepropose an efficient solution technique for such programs, prove its global convergence anddiscuss the possibilities for parallel implementation. We provide, as an application, analgorithm for traffic assignment which outperforms previous state-of-the-art codes

  • 29.
    Karakitsiou, Athanasia
    et al.
    Department of Mathematics, Linköping Institute of Technology.
    Mavrommati, Athanasia
    Department of Production Engineering and Management, Technical University of Crete.
    Migdalas, Athanasios
    Department of Mathematics, Linköping Institute of Technology.
    Measuring Production Efficiency in the Greek Food Sector2004Ingår i: Supply Chain and Finance, Singapore: World Scientific and Engineering Academy and Society, 2004, s. 138-150Kapitel i bok, del av antologi (Refereegranskat)
  • 30.
    Karakitsiou, Athanasia
    et al.
    Department of Production Engineering and Management, Technical University of Crete.
    Mavrommati, Athanasia
    Department of Production Engineering and Management, Technical University of Crete.
    Migdalas, Athanasios
    Department of Production Engineering and Management, Technical University of Crete.
    Tsiakali, Konstantina
    Department of Production Engineering and Management, Technical University of Crete.
    Customer Satisfaction Evaluation in the Tourism Industry: A case study of Chania2007Ingår i: Foundations of Computing and Decision Sciences, ISSN 0867-6356, Vol. 32, s. 111-123Artikel i tidskrift (Refereegranskat)
  • 31.
    Karakitsiou, Athanasia
    et al.
    Department of Production Engineering and Management, Technical University of Crete.
    Mavrommati, Athanasia
    Department of Production Engineering and Management, Technical University of Crete.
    Migdalas, Athanasios
    Department of Production Engineering and Management, Technical University of Crete.
    Tsiakali, Konstantina
    Department of Production Engineering and Management, Technical University of Crete.
    Effieciency Measurment and Evalution of the Greek Hotel Industry2007Ingår i: Journal of Travel and Tourism Reasearch, Vol. 7, s. 96-110Artikel i tidskrift (Refereegranskat)
  • 32.
    Karakitsiou, Athanasia
    et al.
    Department of Business Administration, Technological Educational Institute of Central Macedonia.
    Migdalas, Athanasios
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Industriell Ekonomi.
    Convex optimization problems in supply chain planning and their solution by a column generation method based on the Frank Wolfe method2016Ingår i: Operational Research, ISSN 1109-2858, E-ISSN 1866-1505, Vol. 16, nr 3, s. 401-421Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Many problems in supply chain optimization concern the minimization of a differentiable convex objective function subject to a set of linear constraints. The aim of this work is to present a number of such problems and to propose an efficient method for their solution. The proposed method is based on improvements of the well known Frank–Wolfe algorithm. The computational results of the proposed algorithm demonstrate its effectiveness and efficiency

  • 33.
    Karakitsiou, Athanasia
    et al.
    DSS Laboratory Department of Production and Industrial Engineering, Technical University of Crete.
    Migdalas, Athanasios
    DSS Laboratory Department of Production and Industrial Engineering, Technical University of Crete.
    Decentralized Coordination Mechanism for Integrated Production Transportation Inventory Problem in the Supply Chain using Lagragian Relaxation2008Ingår i: Operational Research, ISSN 1109-2858, E-ISSN 1866-1505, Vol. 8, nr 3, s. 257-278Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper is concerned with integrated production, inventory and transportation planning problems directly related to the supply chain management. We establish a Lagrangian based coordination mechanism within the context of the decentralized planning approach. In addition, we demonstrate that dual prices obtained by the described approach might provide enough accuracy in case of sudden changes, such as in a customer’s demand, and thus they could assist agents to find new solutions. Computational results show that the proposed mechanism is able to help organizations to facilitate collaboration, improve business agility and meet business goals

  • 34.
    Karakitsiou, Athanasia
    et al.
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Industriell Ekonomi.
    Migdalas, Athanasios
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Industriell Ekonomi.
    Discrete bi-level facility models with competing customers2015Konferensbidrag (Refereegranskat)
    Abstract [en]

    The research work dealing with the bi-level formulation of location problems is limited only to the competition among the locators, that is it is supposed that either both the locator and the allocator are the same or the customer (i.e., the user as a whole) knows the optimality criterion of the locator and agrees assively with it. Customers' preferences as well as externalities (such as roadcongestion, facility congestion, emissions etc) caused by the location decisions are either ignored or controlled by incorporating constraints in order to ensure the achievement of a predetermined target. However, this approach treats customers as irresolute beings. Thus, if, for example, the customers travel to the facilities to obtain the offered service, then there is no compulsion or intensive for them to attend the designated facility. This means that, once the facilities are open, what the locator wishes the customers to do may not coincide with their own wish and behavior. We suppose that the customers are involved in a Nash game in order to ensure what they conceive as the best level of services for themselves. In order to take into consideration the effects of such competition in the facilities location decisions we propose a bi-level programming approach to the problem.

  • 35.
    Karakitsiou, Athanasia
    et al.
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Industriell Ekonomi.
    Migdalas, Athanasios
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Industriell Ekonomi.
    Discrete compettitive facility location: Modelling and optimization approaches2014Konferensbidrag (Refereegranskat)
    Abstract [en]

    Competitive facility location problems are concerned with thefollowing situation: a firm wants to locate a predefined num-ber of facilities to serve customers locate in some region wherethere already exist (or will be) other firms offering the sameservice. Both new and existing firms compete for optimizingtheir market share of profit. A discrete version of such problemsarises when it is assumed that there is a ( rather small ) finitenumber of candidate locations and the markets consist of pointdemands. We review modelling and optimization approaches forthis type of problems and we emphasize and develop the bi-levelprogramming methodology.

  • 36.
    Karakitsiou, Athanasia
    et al.
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Industriell Ekonomi.
    Migdalas, Athanasios
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Industriell Ekonomi.
    Locating facilities in a competitive environment2017Ingår i: Optimization Letters, ISSN 1862-4472, E-ISSN 1862-4480, Vol. 11, nr 5, s. 929-945Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The research work dealing with the bi-level formulation of location problems is limited only to the competition among the locators, that is, it is supposed that either both the locator and the allocator are the same or the customer knows the optimality criterion of the locator and agrees passively with it. Customers’ preferences as well as externalities (such as road congestion, facility congestion, emissions etc) caused by the location decisions are either ignored or controlled by incorporating constraints in order to ensure the achievement of a predetermined target. However, this approach treats customers as irresolute beings. Thus, if, for example, the customers travel to the facilities to obtain the offered service, then there is no compulsion or intensive for them to attend the designated facility. This means that, once the facilities are open, what the locator wishes the customers to do may not coincide with their own wish and behavior. We suppose that the customers are involved in a Nash game in order to ensure what they conceive as the best level of services for themselves. In order to take into consideration the effects of such competition in the facilities location decisions we propose a bi-level programming approach to the problem.

  • 37.
    Karakitsiou, Athanasia
    et al.
    Department of Business Administration, Technological Educational Institute of Central Macedonia.
    Migdalas, Athanasios
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Industriell Ekonomi.
    Nash type games in competitive facilities location2016Ingår i: International Journal of Decision Support System Technology, ISSN 1941-6296, E-ISSN 1941-630X, Vol. 2, nr 1-3, s. 4-12Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In a non-cooperative game, a Nash equilibrium corresponds to a set of strategies, which ensure that none of the players are better off by unilaterally changing his strategy. This work focuses on the application of Nash Equilibrium to the competitive facility location. Its aim is to provide an up to date review of the literature concerning the discrete version of the problem

  • 38.
    Karakitsiou, Athanasia
    et al.
    Department of Production Engineering and Management, Technical University of Crete.
    Migdalas, Athanasios
    Department of Production Engineering and Management, Technical University of Crete.
    Optimization and Coordination for Linear Integrated Production, Inventory and Transportation Planning in Supply Chain by Decomposition Methods2006Ingår i: 18th National Conference on Planning: Information Retrieval and Knowledge Management / [ed] George Evagelidis ; L. Karamitopoulos; Dimitris Dervos, 2006, s. 673-687Konferensbidrag (Refereegranskat)
  • 39.
    Karakitsiou, Athanasia
    et al.
    DSS Laboratory Department of Production and Industrial Engineering, Technical University of Crete.
    Migdalas, Athanasios
    DSS Laboratory Department of Production and Industrial Engineering, Technical University of Crete.
    Quantitative Inventory Modelling and Future Trends in Supply Chain Management2002Ingår i: Financial Engineering, ECommerce and Supply Chain, Encyclopedia of Global Archaeology/Springer Verlag, 2002, s. 271-293Kapitel i bok, del av antologi (Refereegranskat)
    Abstract [en]

    There is a trend in coordinating all the firm’s activities as an integrated system called supply chain. However, the treatment of inventories remains of high interest in all enterprises within this framework. Inventory is a major investment in most companies and it influences their flexibility and success. Traditionally, a large number of research activities have been focused on finding the best answer to the two basic questions concerning inventory management, i.e., when and how much to order. The majority of those research works have used quantitative methods to find the optimal solution. However, in recent years, because of innovations in technology, changes in customer expectations, and availability of new methods of production, attention has been attracted to a philosophy, also known as the JIT method, which considers inventory as a waste. The purpose of this paper is to present a paradigm of classical mathematical inventory models, to give a short review of their evolution into more realistic representations of the inventory system, and to discuss new trends in and the future of inventory management in the era of globalization and networking

  • 40.
    Karakitsiou, Athanasia
    et al.
    Department of Business Administration, Technological Educational Institute of Central Macedonia, Serres, .
    Migdalas, AthanasiosLuleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Industriell Ekonomi.Rassia, Stamatina Th.INSEAD.Pardalos, Panos M.Department of Industrial and Systems Engineering, Center for Applied Optimization, University of Florida, Gainesville.
    City Networks: Collaboration and Planning for Health and Sustainability2017Samlingsverk (redaktörskap) (Refereegranskat)
  • 41.
    Kourgiantakis, M.
    et al.
    Department of Production Engineering and Management, Technical University of Crete.
    Mandalianos, I.
    Department of Production Engineering and Management, Technical University of Crete.
    Pardalos, Panos M.
    Department of Industrial and Systems Engineering, Center for Applied Optimization, University of Florida.
    Migdalas, Athanasios
    Department of Production Engineering and Management, Technical University of Crete.
    Optimization in E-Commerce2006Ingår i: Handbook of Optimization in Telecommunications, New York: Encyclopedia of Global Archaeology/Springer Verlag, 2006, s. 1017-1050Kapitel i bok, del av antologi (Refereegranskat)
  • 42.
    Larsson, Torbjörn
    et al.
    Department of Mathematics, Institute of Technology, Linköping University.
    Migdalas, Athanasios
    Department of Mathematics, Linköping Institute of Technology.
    An algorithm for nonlinear programs over Cartesian product sets1990Ingår i: Optimization, ISSN 0233-1934, E-ISSN 1029-4945, Vol. 21, nr 4, s. 535-542Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We describe a solution procedure for nonseparable nonlinear programming problems over Cartesian product sets. Problems of this type frequently arise in transportation planning and in the analysis and design of computer communication networks. The basic algorithmic concept is to induce separability by linearizing the nonseparable part of the objective function, This algorithm and the well-known Frank-Wolfe method have many similarities. It is illustrated by a small numerical example.

  • 43.
    Larsson, Torbjörn
    et al.
    Department of Mathematics, Institute of Technology, Linköping University.
    Migdalas, Athanasios
    Department of Mathematics, Institute of Technology, Linköping University.
    An algorithm for nonlinear programs over cartesian product sets1987Rapport (Övrigt vetenskapligt)
  • 44.
    Larsson, Torbjörn
    et al.
    Department of Mathematics, Institute of Technology, Linköping University.
    Migdalas, Athanasios
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Industriell Ekonomi.
    Michael, Patriksson
    Department of Mathematical Sciences, Chalmers University of Technology.
    A generic column generation principle: derivation and convergence analysis2015Ingår i: Operational Research, ISSN 1109-2858, E-ISSN 1866-1505, Vol. 15, nr 2, s. 163-198Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Given a non-empty, compact and convex set, and an a priori definedcondition which each element either satisfies or not, we want to find an elementbelonging to the former category. This is a fundamental problem of mathematicalprogramming which encompasses nonlinear programs, variational inequalities,saddle-point problems. We present a conceptual column generation scheme, whichalternates between solving a restriction of the original problem and a columngeneration phase which is used to augment the restricted problems. We establishgeneral applicability of the conceptual method, as well as to the three problemclasses mentioned. We also establish a version of the conceptual method in whichthe restricted and column generation problems are allowed to be solvedproximately, and of a version allowing for the dropping of columns. We showsome solution methods (e.g., Dantzig–Wolfe decomposition and simplicialcomposition) are special instances, and present new convergent column generationmethods in nonlinear programming, such as a sequential linear programming typemethod. Along the way, we also relate our quite general scheme in nonlinearprogramming presented in this paper with several other classic, and more recent,iterative methods in nonlinear optimization.

  • 45.
    Larsson, Torbjörn
    et al.
    Department of Mathematics, Institute of Technology, Linköping University.
    Migdalas, Athanasios
    Department of Mathematics, Linköping Institute of Technology.
    Michael, Patriksson
    Department of Mathematical Sciences, Chalmers University of Technology, Department of Mathematics, Linköping Institute of Technology.
    A partial linearization method for the traffic assignment problem1993Ingår i: Optimization, ISSN 0233-1934, E-ISSN 1029-4945, Vol. 28, nr 1, s. 47-61Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper presents a new solution technique for the traffic assignment problem. The approach is based on an iteratively improved nonlinear and separable approximation of the originally nonseparable objective function, and resembles the Frank-Wolfe algorithm in the sense that the subproblem separates with respect to commodities. Since the single-commodity subproblems are strictly convex, the new algorithm will not suffer from the poor convergence behaviour of the Frank-Wolfe algorithm, which is a consequence of the extreme solutions of its linear subproblems. The solution method is outlined along with convergence results, and a dual approach to the solution of the strictly convex subproblems is described. The performance of the algorithm is illustrated with two numerical examples

  • 46.
    Larsson, Torbjörn
    et al.
    Department of Mathematics, Institute of Technology, Linköping University.
    Migdalas, Athanasios
    Department of Mathematics, Institute of Technology, Linköping University.
    Rönnqvist, Mikael
    Department of Mathematics, Institute of Technology, Linköping University.
    A Lagrangean heuristic for the capacitated concave minimum cost network flow problem1994Ingår i: European Journal of Operational Research, ISSN 0377-2217, E-ISSN 1872-6860, Vol. 78, nr 1, s. 116-129Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We propose a heuristic solution technique for the capacitated concave minimum cost network flow problem based on a Lagrangean dualization of the problem. Despite its dual character the algorithm guarantees the generation of primal feasible solutions which are local optima and therefore candidates of being the global optimum. The Lagrangean dual is solved by a subgradient search procedure and provides a lower bound to the optimal value. The lower bound is, in general, stronger than the one obtained by a linear approximation of the original problem. It can be used as a judgement of the quality of the solution or in a branch and bound procedure. Computational results from randomly generated problems are presented

  • 47.
    Larsson, Torbjörn
    et al.
    Department of Mathematics, Institute of Technology, Linköping University.
    Migdalas, Athanasios
    Department of Mathematics, Institute of Technology, Linköping University.
    Rönnqvist, Mikael
    Department of Mathematics, Institute of Technology, Linköping University.
    A Lagrangean heuristic for the capacitated concave minimum cost network flow problem1989Rapport (Övrigt vetenskapligt)
  • 48.
    Mandalianos, I.
    et al.
    Department of Production Engineering and Management, Technical University of Crete.
    Kourgiantakis, M.
    Department of Production Engineering and Management, Technical University of Crete.
    Migdalas, Athanasios
    Department of Production Engineering and Management, Technical University of Crete.
    Prometheus: A web based system focusing on local E-government2005Ingår i: Management of Technological Changes / [ed] C. Rusu; Y. Philis, 2005, Vol. 1, s. 133-138Konferensbidrag (Refereegranskat)
    Abstract [en]

    Governments around the world attempt to modernize public administration through e-Government. Nevertheless, the evolution of e- government practices reveal a clear division in the use of IT between the developed and the developing countries, as well as between central administration and local administration authorities. Concerning the specific characteristics of local authorities, like municipalities, this paper presents a new, web-based, open source e-government system for such organizations. The design and specifications of system's components were based on the specific needs of some municipalities in Crete. Moreover, the pilot implementation and evaluation at the municipality of Souda revealed important aspects that are critical for the success of local e-government systems.

  • 49.
    Marinakis, Y.
    et al.
    Technical University of Crete, School of Production Engineering and Management, Chania, Greece.
    Marinaki, M.
    Technical University of Crete, School of Production Engineering and Management, Chania, Greece.
    Migdalas, Athanasios
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Industriell Ekonomi. Aristotle University of Thessalonike, Department of Civil Engineering, Thessalonike, Greece.
    A Multi-Adaptive Particle Swarm Optimization for the Vehicle Routing Problem with Time Windows2019Ingår i: Information Sciences, ISSN 0020-0255, E-ISSN 1872-6291, Vol. 481, s. 311-329Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper, a new variant of the Particle Swarm Optimization (PSO) algorithm is proposed for the solution of the Vehicle Routing Problem with Time Windows (VRPTW). Three different adaptive strategies are used in the proposed Multi-Adaptive Particle Swarm Optimization (MAPSO) algorithm. The first adaptive strategy concerns the use of a Greedy Randomized Adaptive Search Procedure (GRASP) that is applied when the initial solutions are produced and when a new solution is created during the iterations of the algorithm. The second adaptive strategy concerns the adaptiveness in the movement of the particles from one solution to another where a new adaptive strategy, the Adaptive Combinatorial Neighborhood Topology, is used. Finally, there is an adaptiveness in all parameters of the Particle Swarm Optimization algorithm. The algorithm starts with random values of the parameters and based on some conditions all parameters are adapted during the iterations. The algorithm was tested in the two classic sets of benchmark instances, the one that includes 56 instances with 100 nodes and the other that includes 300 instances with number of nodes varying between 200 and 1000. The algorithm was compared with other versions of PSO and with the best performing algorithms from the literature.

  • 50.
    Marinakis, Yannis
    et al.
    School of Production Engineering and Management, Technical University of Crete, Decision Support Systems Laboratory, Department of Production Engineering and Management, Technical University of Crete.
    Marinaki, Magdalene
    School of Production Engineering and Management, Technical University of Crete.
    Migdalas, Athanasios
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Industriell Ekonomi.
    A hybrid clonal selection algorithm for the location routing problem with stochastic demands2016Ingår i: Annals of Mathematics and Artificial Intelligence, ISSN 1012-2443, E-ISSN 1573-7470, Vol. 76, nr 1-2, s. 121-142Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper, a new formulation of the Location Routing Problem with Stochastic Demands is presented. The problem is treated as a two phase problem where in the first phase it is determined which depots will be opened and which customers will be assigned to them while in the second phase, for each of the open depots a Vehicle Routing Problem with Stochastic Demands is solved. For the solution of the problem a Hybrid Clonal Selection Algorithm is applied, where, in the two basic phases of the Clonal Selection Algorithm, a Variable Neighborhood Search algorithm and an Iterated Local Search algorithm respectively have been utilized. As there are no benchmark instances in the literature for this form of the problem, a number of new test instances have been created based on instances of the Capacitated Location Routing Problem. The algorithm is compared with both other variants of the Clonal Selection Algorithm and other evolutionary algorithms.

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