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1
Content available New developments in fuzzy clustering with emphasis on special types of tasks
Viattchenin D. A., Owsiński J. W., Kacprzyk J.
Control and Cybernetics
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2018
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Vol. 47, no. 2
115--130
EN
The paper is devoted to a survey of work done in fuzzy clustering, mainly during the first decade of the 21st century, and that with emphasis on various approachesto the problem, as well as various formulations of the very problem. That is why not only the classical formulations are treated, but several other problems, related to (the use of) clustering, like feature selection, inference systems, three-way clustering, and, on the other hand, such formulations of clustering as the possibilistic one or the one involving intuitionistic fuzzy sets. These are treated as the background for presentation of some specific ideas of the main author, concerning definite heuristic algorithms for effective solving of some of these problems.
2
Content available Identifying main center access hubs in a city using capacity and time criteria. The evolutionary approach
Owsiński J. W., Stańczak J., Barski A., Sęp K.
Control and Cybernetics
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2016
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Vol. 45, no. 2
207--223
EN
In this paper we consider the well known Hub and Spoke problem, analyzed in the context of Warsaw Public Transport System. Our method was designed for data preprocessing so as to allow using a timetable obtained from the public transport web site after conversion into the required data format. A dedicated evolutionary algorithm method that detects the hubs of almost all available transport means was also developed. The hubs identified are well connected to the center of the city and to other identified hubs (characterized by high capacity or short travel time). These hubs may become the skeleton of the public transport system and, in particular, good points for locating Park and Ride facilities.
3
Content available The kernel and shell structure as a tool for improving the graph of transportation connections
Mażbic-Kulma B., Owsiński J. W., Sęp K., Stańczak J.
Operations Research and Decisions
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2013
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Vol. 23, No. 2
91--105
EN
A model of a transportation system is expected to be useful in simulations of a real system to solve given transportation tasks. A connection graph is routinely used to describe a transportation system. Vertices can be train stations, bus stops, airports etc. The edges show direct connections between vertices. A direct approach can be difficult and computational problems can arise in attempts to organize or optimize such a transportation system. Therefore, a method for aggregating such graphs was introduced, using a general kernel and shell structure and its particular instances: α-clique structured graphs of connections and a hub and spoke transformation of the source graph. These structures enable the concentration and ordering of transport between vertices and reduction of the analyzed graph. To obtain the desired structures, several versions of a specialized evolutionary algorithm were developed and applied.
4
Content available Editorial : systems and operational research for modelling and decision making : a perspective from BOS conferences
Owsiński J. W.
Operations Research and Decisions
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2013
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Vol. 23, No. 2
5--9
5
Content available Evolutionary approach for obtaining the hub and spoke structure in the logistic network
Mażbic-Kulma B., Stańczak J., Owsiński J. W., Sęp K.
Total Logistic Management
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2011
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no. 4
89-105
EN
In order to describe transportation system, as a routine a connection graph would be used. Vertices of the graph can be train stations, bus stop, airports etc. The edges show direct connections between vertices. A direct application of such graph can be difficult and computational problems can occur while one would try to organize or optimize such a transportation system. Therefore, a method of aggregation of such graph was introduced, using the general kernel and shell structure and a hub and spoke transformation method of the source graph. These structures allow to concentrate and order the transport of goods/persons among vertices and enable to reduce the number of analyzed vertices as well as edges of the graph. In the presented paper we continue our work on kernel and shell and its instance hub and spoke methods of connection graph transformation. In this paper we develop model of the transportation system using the hub and spoke method with predetermined, minimum and indirectly described numbers of hub nodes. To obtain the desired structures, several versions of specialized evolutionary algorithm (EA) were developed and applied.
6
Content available remote Machine-part grouping and cluster analysis: similarities, distances and grouping criteria
Owsiński J.W.
Bulletin of the Polish Academy of Sciences. Technical Sciences
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2009
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Vol. 57, nr 3
217-228
EN
The paper considers the machine-part grouping problem, as equivalent to partitioning the set of machines and operations into subsets, corresponding to block diagonalisation with constraints. The attempts to solve the problem with clustering methods are outlined. The difficulties encountered are presented, related to (i) ambiguity of formulations; (ii) selection of criteria; and (iii) lack of effective algorithms. These are illustrated in more detail with a limited survey of similarity and distance definitions, and of criteria used, constituting the main body of the paper. The return is proposed to the basic paradigm of cluster analysis, as providing simple and fast algorithms, which, even if not yielding optimal solutions, can be controlled in a simple manner, and their solutions improved.
7
Content available remote Application of selected methods of graph theory and combinatorial heuristics to minimising the number of transits nodes in an air network
Mażbic-Kulma B., Owsiński J. W., Sęp K.
Total Logistic Management
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2008
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no. 1
111-123
EN
In the paper we present the notion of alpha-clique and some of its properties. Covering with alpha-cliques is a preprocessing method for an air network, described as a graph, in which vertices correspond to airports and edges correspond to air connections. Using the alpha-clique cover we obtain a hypergraph, in which we find the minimum transversal. The set of vertices thus obtained is the sought-for set of transits nodes, called hubs. Using the alpha-clique concept instead of proper cliques we can obtain the solution to the graph covering problem easier.
PL
W niniejszej pracy prezentujemy pojęcie alfa-kliki i pewne jej własności. Znalezienie pokrycia alfa-klikami traktujemy jako metodę preprocessingu dla sieci lotniczych opisanych jako graf, w którym węzły odpowiadają lotniskom, a krawędzie odpowiadają połączeniom lotniczym. Znajdując pokrycie alfa-klikami, uzyskujemy hipergraf, dla którego otrzymujemy minimalną transwersalę. W ten sposób uzyskujemy zbiór wierzchołków będących węzłami tranzytowymi czyli hubami. Stosując alfa-kliki zamiast odpowiednich klik, możemy uzyskać lepsze pokrycie grafu.
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