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1
Content available Properties of an α-clique approach to obtaining the hub and spoke structure in optimization of transportation systems
Mazbic-Kulma B., Owsinski J. W., Barski A., Sęp K., Stańczak J.
Control and Cybernetics
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2018
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Vol. 47, no. 2
173--189
EN
The paper is devoted to the analysis of a graph transformation, pertinent for the transport and logistic systems and their planning and management. Namely, we consider, for a given graph, representing some existing transport or logistic system, its transformation to a (non-equivalent) so-called ”hub-and-spoke” structure, known from both literature and practice of transportation and logistics. This structure is supposed to bring benefits in terms of functioning and economic performance of the respective systems. The transformation into the ”hub-and-spoke” is not only non-equivalent (regarding the original graph of the system), but is also, in general, non unique. The structure sought is composed of two kinds of elements - nodes of the graph (stations, airports, havens, etc.), namely: the subgraph of hubs, which, in principle, ought to constitute a complete sub-graph (a clique), and the ”spokes”, i.e. the subsets of nodes, each of which is connected in the ultimate structure only with one of the hubs. The paper proposes a relaxation of the hub-and-spoke structure by allowing the hub subgraph not to be complete, but at least connected, with a definite ”degree of completeness” (alpha), from where the name of ”alpha-clique”. It is shown how such structures can be obtained and what are the resulting benefits for various assumptions, regarding such structures. The benefits are measured here with travel times. The desired structures are sought with an evolutionary algorithm. It is shown on an academic example how the results vary and how the conclusions, relevant for practical purposes, can be drawn from such analyses, done with the methods here presented.
2
Content available Modeling of dynamic market of energy with local energy clusters
Stańczak J., Radziszewska W.
Control and Cybernetics
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2018
|
Vol. 47, no. 2
157--171
EN
Clusters of energy are a new mechanism, meant to support development of modern power grids in Poland. In this article, we experimentally check the influence of a hypothetical presence of clusters on energy markets. We present a two level real time power market, where the power first is balanced within a cluster and then an inter-cluster trading is performed, in which the country power grid is a participant in the market. We show that it can be beneficial for all parties to maintain such a schema and that it is also a possible direction for further research.
3
Content available The airport gate assignment problem – multi-objective optimization versus evolutionary multi-objective optimization
Kaliszewski I., Miroforidis J., Stańczak J.
Computer Science
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2017
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Vol. 18 (1)
41--52
EN
In this paper, we approach the Airport Gate Assignment Problem by Multi-objective Optimization as well as Evolutionary Multi-objective Optimization. We solve a bi-criteria formulation of this problem by the commercial mixed-integer programming solver CPLEX and a dedicated Evolutionary Multi-objective Optimization algorithm. To deal with multiple objectives, we apply a methodology that we developed earlier to capture decision-maker preferences in multi-objective environments. We present the results of numerical tests for these two approaches.
4
Content available Wyzwania naukowe informatyzacji uczelni publicznej
Zawiła-Niedźwiecki J., Kamińska A., Stańczak J., Zajkowski A.
Studia Informatica Pomerania
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2016
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Nr 4 (42)
97--108
PL
Uczelnia publiczna jest podmiotem o szczególnej roli społecznej, funkcjonuje równocześnie w kontekście wielowiekowej tradycji akademickiej i uniwersyteckiej, jaki w ramach bieżących uwarunkowań podmiotów publicznych oraz na konkurencyjnych rynkach edukacyjnym, naukowym i doradczym. Powoduje to potrzebę poszukiwania modelu organizacyjno-funkcjonalnego odpowiedniego dla specyficznej korporacji, jaką jest taka uczelnia. Jest to nie tylko wyzwanie z zakresu praktyki zarządzania, ale i naukowe, dotyczące poszczególnych aspektów funkcjonowania organizacyjnego i zarządzania (Woźnicki, 2007). Celem artykułu jest przedstawienie koncepcji metodycznego podejścia do procesu informatyzacji uczelni publicznej oraz badań, które temu służą. Podjęto tylko te z tych wyzwań, które są związane z prowadzeniem polityki informacyjnej oraz systematyczną informatyzacją uczelni publicznej. Nie wyczerpuje to potencjału wyzwań naukowych nowego organizowania uczelni publicznych w Polsce i zarządzania nimi.
EN
The public university is a entity of a particular social role, functioning simultaneously in the context of the centuries-old tradition of academic and university, as well as under the current conditions of public entities and competitive markets, educational, scientific and advisory capacity. This results in the need to find a model of organizational and functional suitable for a specific corporation which is the university. This is not only a challenge in the field of management practices, but research concerning various aspects of the organization and management. The article only ones with these challenges, which are related to the conduct of information policy and systematic computerization of public university. However, this does not close the potential of the scientific challenges of the new organization and management of public universities in Poland.
5
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
|
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.
6
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.
7
Content available remote Agent-based evolutionary method of simulation the CO2 emission permits market
Stańczak J.
Foundations of Computing and Decision Sciences
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2013
|
Vol. 38, No. 4
251--265
EN
This article describes the problem of simulation of the CO2 emission permits market. First, it introduces a CO2 permission market model with transactions and purchase prices, in particular with a separate goal function for each party, transactions with price negotiations between regions and - as a consequence of introducing prices for permits – the possibility of investigating the influence of purchase/sale prices on the market. The behavior of such market model is simulated using a method, which is based on a specialized evolutionary method but introduces independent agents with their own transaction preferences.
8
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
|
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.
9
Wieloagentowa metodyka zarządzania niedoborami i nadmiarami enegii w sieciach dystrybucyjnych
Nahorski Z., Pałka P., Stańczak J., Radziszewska W.
Rynek Energii
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2011
|
nr 1
22-27
PL
W artykule opisano projekt komputerowego systemu wieloagentowego, którego zadaniem będzie bilansowanie na bieżąco różnic między aktualnym zapotrzebowaniem na energię a planem długoterminowym w warunkach rozproszonej lokalnej generacji energii, w tym ze źródeł odnawialnych. Powstałe różnice wynikają z braku możliwości dokładnego przewidzenia poziomu generacji przez niesterowalne źródła energii oraz poboru przez odbiorniki. Zaprojektowany system będzie dążyć do zrównoważenia bilansu zapotrzebowania i produkcji energii w krótkich przedziałach czasu, rzędu jednej minuty, tak aby nadążyć za zmieniającymi się w czasie rzeczywistym parametrami pracy urządzeń generujących energię. System ten używa autonomicznych agentów, będących elementami oprogramowania. Agenty te posiadają własne cele i komunikując się ze sobą, wyprowadzają system z nieplanowanych niedoborów i nadmiarów produkowanej energii.
EN
The paper presents an idea of the computer multi-agent system for managing the unbalanced energy in a distribution low voltage networks with distributed generations including renewable sources. The main goal of the system application is control and minimization of the differences between the current energy demand and the long-time plan. These differences are caused by unpredictable level of electric power generation by uncontrolled sources (like wind turbine) or randomness of power utilization. The planned system will tend to balance these differences on-line in short time intervals (about one minute) to follow-up the varying level of power generation by local power sources. The system uses autonomous software agents. Every agent has its own goal and communicates with others in order to reduce (minimize) the unplanned shortages or surpluses of energy.
10
Content available Evolutionary approach to obtain graph covering by densely connected subgraphs
Stańczak J., Potrzebowski H., Sęp K.
Control and Cybernetics
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2011
|
Vol. 40, no 3
849-875
EN
This article describes two evolutionary methods for dividing a graph into densely connected structures. The first method deals with the clustering problem, where the element order plays an important role. This formulation is very useful for a wide range of Decision Support System (DSS) applications. The proposed clustering method consists of two stages. The first is the stage of data matrix reorganization, using a specialized evolutionary algorithm. The second stage is the final clustering step and is performed using a simple clustering method (SCM). The second described method deals with a completely new partitioning algorithm, based on the subgraph structure we call α-clique. The α-clique is a generalization of the clique concept with the introduction of parameter α, which imposes for all vertices of the subgraph the minimal percentage (α*100%) of vertices of this subgraph that must be connected with vertices of this α-clique. Traditional clique is an instance of α-clique with α = 1. Application of this parameter makes it possible to control the degree (or strength) of connections among vertices (nodes) of this subgraph structure. The evolutionary approach is proposed as a method that enables finding separate α-cliques that cover the set of graph vertices.
11
Content available Finding structure kernel and shell with predetermined cardinality of kernel set, using evolutionary algorithm
Mażbic-Kulma B., Stańczak J., Sęp K.
Total Logistic Management
|
2010
|
no. 3
53-64
EN
The theory of logistic transportation systems deals with models of phenomena connected with movement of goods and persons. The developed model of the transportation system is expected to simulate a real system, but also should help us to solve given transportation tasks. In order to describe transportation system (rail, bus or air), as a routine a connection graph would be used. Vertices of the graph can be train stations, bus stops etc. The edges show direct connections between vertices. Its direct application 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 its particular instance the α-clique structured graphs of connections. In the present approach, we use a predetermined number of communication hubs with the possibility of direct determining which nodes should become hubs or selecting them by the solving method. This structure allows to concentrate and order the transport of goods/persons among vertices and enables to reduce the number of analyzed vertices as well as arcs/edges of the graph. To obtain the desired structure, an evolutionary algorithm (EA) was applied.
PL
Teoria logistycznych systemów transportowych zajmuje się zagadnieniem połączeń w przewozach ludzi i towarów. Od modelu systemu transportowego oczekuje się symulowania rzeczywistego systemu w celu rozwiązywania problemów transportowych. Do opisania systemów transportowych (kolejowych, drogowych czy lotniczych) przydatne mogą się okazać grafy. Wierzchołki grafu mogą odpowiadać węzłom logistycznym, takim jak: stacje kolejowe, przystanki autobusowe, lotniska itd., a krawędzie - bezpośrednim połączeniom pomiędzy węzłami. Dokładny model trudno byłoby analizować lub optymalizować, dlatego jako przydatny model proponujemy strukturę kernel and shell oraz jej szczególny przypadek - strukturę α-klikową jako graf odwzorowujący strukturę połączeń. Struktury te umożliwiają koncentrację i zarządzanie transportem pomiędzy węzłami. W celu uzyskania tej struktury stosujemy specjalizowany algorytm ewolucyjny (EA).
12
Content available remote Evolutionary approach to find kernel and shell structure of a connection graph
Mażbic-Kulma B., Potrzebowski H., Stańczak J., Sęp K.
Total Logistic Management
|
2009
|
no. 2
37-50
EN
The theory of logistic transportation systems deals with models of phenomena connected with movement of goods and persons. The developed model of the transportation system is expected to simulate a real system, but also should help us to solve given transportation tasks. In order to describe transportation system (rail, bus or air), as a routine a connection graph would be used. Vertices of the graph can be train stations, bus stops etc.. The edges show direct connections between vertices. Its direct application 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 its particular instances: hub-and-spoke and α-clique structured graphs of connections. These structures enable to concentrate and order the transport of goods/persons among vertices. To obtain these desired structures an evolutionary algorithm (EA) was applied. This method enables to reduce the number of analyzed vertices as well as arcs/edges of the graph.
PL
Reguły gospodarki rynkowej i coraz ostrzejsza konkurencja zmuszają przedsiębiorstwa do poszukiwania sposobów obniżenia kosztów działalnosci gospodarczej. Konieczność redukcji kosztów dotyczy m.in. gospodarki transportowej. Znaczenie optymalizacji rozwiązań w sferze transportu w aspekcie kosztowym jest szczegolnie istotne, jeżeli weźmie się pod uwagę znaczny udział kosztów transportu w kosztach logistycznych przedsiebiorstwa. Oczywisty staje się fakt, iż nie jest możliwe funkcjonowanie firm działających na współczesnych globalnych rynkach bez transportu. Zdecydowana większość przedsiębiorstw znajduje się w pewnej odległości od swoich źrodeł zaopatrzenia, co sprawia, że są one zależne od transportu łączącego źrodlo zaopatrzenia z miejscem konsumpcji. Specjalizacja pracy, masowa konsumpcja i ekonomia skali produkcji powodują, że miejsca wytwarzania produktów nie pokrywają się z miejscem, gdzie zgłaszany jest na nie popyt. Stąd też transport staje się niezbędnym narzędziem łączącym nabywców i sprzedawców. W niniejszym artykule przedstawiono narzędzie wspomagające modelowanie systemu transportowego. Jak wiadomo, dokładny model systemu transportowego przedsiębiorstwa trudno jest analizować czy też optymalizować jego działanie. Dlatego jako model sieci transportowej proponujemy strukturę kernel and shell i jej szczególne przypadki: strukturę hub and spoke oraz strukturę α-klikową. Struktury te umożliwiają koncentrację i zarządzanie transportem pomiędzy węzłami. W celu uzyskania tych struktur z wejściowego grafu połączeń stosujemy opracowane przez nas specjalizowane algorytmy ewolucyjne (EA).
13
Evolutionary algorithm for market simulations
Stańczak J.
Prace Naukowe Politechniki Warszawskiej. Elektronika
|
2009
|
z. 169
163-172
EN
Evolutionary algorithms (EA) have recently become not only tools for efficient optimization of very difficult problems, but also are applied to simulate behavior of different kinds of systems, among them also games, economic systems and markets. This new domain of EA applications is known as Agent-Based Computational Economics (ACE). This article describes two applications of EA to simple market simulations. The main aim of EA in this approach is to find (sub-) optimal strategies of behavior for the participants of that market game. The first example is a simple market with only several participants and one product, well known as an instance of Cournot oligopoly game. The second example is more complicated and describes a market of permits for CO2 emission, created by the Kyoto Protocol and introduces to the simple Walrasian model the influence of calculated on-line permits prices.
14
Evolutionary approach to solve hub-and-spoke problem using α-cliques
Mażbic-Kulma B., Potrzebowski H., Stańczak J., Sęp K.
Prace Naukowe Politechniki Warszawskiej. Elektronika
|
2008
|
z. 165
121-130
EN
The theory of transportation systems deals with models of phenomena connected with movement of goods and persons. The model of the transportation system should simulate a real system, but should also be a tool that enables to solve given transportation tasks. In order to describe transportation system (rail, bus or air), as a routine a connection graph would be used. Vertices of the graph can be train stations, bus stops or in case of air transport - airports. The edges of the graph show direct connections between vertices. It can be noticed that such a graph can have many vertices as well as many edges. Its direct application 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 a graph was introduced, using the hub-and-spoke structured graph of connections. This structure enables to concentrate and order the transport of goods/persons among vertices. To obtain the hub-and-spoke structure an evolutionary algorithm (EA) was applied. EA divides the connection graph into α-cliques (a generalization of the notion of a clique, which groups into sub-graphs highly connected vertices) and then in each α-clique a vertex with a maximum degree in this sub-graph and a maximal number of connections among other selected hubs is chosen. The α-clique with chosen vertex constitutes a "hub" with point-to-point connections - "spokes". This method enables reducing the number of analyzed vertices as well as arcs of the graph. Examples visualizing functioning of the described algorithms are presented later in this paper.
15
Non-stationary optimization with multi-population evolutionary algorithm
Stańczak J., Trojanowski K.
Prace Naukowe Politechniki Warszawskiej. Elektronika
|
2007
|
z. 160
251-259
EN
Non-stationary optimization of randomly changing environments is a subject of unfading interest.In this paper we study application of multipopulation evolutionary algorithm to this problem. Presented algorithm works with a set of sub-populations managed by the mechanism of exclusion coming from the multiswarm version of particle swarm approach. The results show significant improvement of the efficiency of the new algorithm in comparison with a single population approach.
16
Evolutionary algorithm to find graph covering subsets using α-cliques
Potrzebowski H., Stańczak J., Sęp K.
Prace Naukowe Politechniki Warszawskiej. Elektronika
|
2006
|
z. 156
351-358
EN
The article describes a new evolutionary based method to divide graph into strongly connected structures we called α-cliques. The α-clique is a generalization of a clique concept with the introduction of parameter a. Using this parameter it is possible to control the degree (or strength) of connections among vertices (nodes) of this sub-graph structure. The evolutionary approach is proposed as a method that enables to find separate a-cliques that cover the set of graph vertices.
17
Content available remote Optimal control of multistage deterministic, stochastic and fuzzy processes in the fuzzy environment via an evolutionary algorithm
Stańczak J.
Control and Cybernetics
|
2005
|
Vol. 34, no 2
525-552
EN
This paper deals with the problem of control of deterministic, stochastic and fuzzy systems with a fixed termination time and fuzzy constraints imposed on controls and states. Constrains imposed on the system are given as membership functions of particular fuzzy sets. Transition functions for controlled systems are given as a matrix of transitions between states for a deterministic object, a matrix of probabilities of transitions for a stochastic object and a matrix of membership functions of transitions for a fuzzy system. An optimal (or sub-optimal) control is obtained using a specialized evolutionary algorithm (EA), which is a development over the previously used methods based on simple genetic algorithm. The specialized EA seems to be a very effective tool for solving such a class of optimization problems, comparing advantageously with the traditional simple genetic algorithm approach and with the previously used solutions like dynamic programming or branch and bound. The specialization of the applied EA is obtained using dedicated problem encoding, the method of ranking of genetic operators and the controlled selection of population members.
18
Content available Biologically inspired methods for control of evolutionary algorithms
Stańczak J.
Control and Cybernetics
|
2003
|
Vol. 32, no 2
411-433
EN
In this paper two methods for evolutionary algorithm control are proposed. The first one is a new method of tuning tlie probabilities of genetic operators. It is assumed in the presented approach that every member of the optimized population conducts his own ranking of genetic operators' qualities. This ranking enables computing the probabilities of execution of genetic operators. This set of probabilities is a basis of experience of every individual and according to this basis the individual chooses the operator in every iteration of the algorithm. Due to this experience one can maximize the chances of his offspring to survive. The second part of the paper deals with a self-adapting method of selection of individuals to a subsequent generation. Methods of selection applied in the evolutionary algorithms are usually inspired by nature and prefer solutions where the main role is played by randomness, competition and struggle among individuals. In the case of evolutionary algorithms, where populations of individuals are usually small, this causes a premature convergence to local minima. In order to avoid this drawback I propose to apply an approach based rather on an agricultural technique. Two new methods of object selection are proposed: a histogram selection and a mixed selection. The methods described were tested using examples based on scheduling and TSP.
19
Perspektywy polskich firm w aplikacji systemów automatyki w energetyce
Stańczak J.
Zeszyty Naukowe. Elektryka / Politechnika Opolska
|
2000
|
nr 255, z. 49
395-400
20
Eksploatacyjny system do bieżącego wyznaczania strat rozruchowych bloku 360 MW Elektrowni Opole
Kabza Z., Stańczak J.
Zeszyty Naukowe. Elektryka / Politechnika Opolska
|
2000
|
nr 255, z. 49
158-172
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