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2. Understanding the structural complexity of induced travel demand in decision-making : a system dynamics approachJuan Angarita-Zapata, Jorge Parra-Valencia, Hugo Andrade-Sosa, 2016, izvirni znanstveni članek Opis: Background and purpose: Induced travel demand (ITD) is a phenomenon where road construction increases vehicles’ kilometers traveled. It has been approached with econometric models that use elasticities as measure to estimate how much travel demand can be induced by new roads. However, there is a lack of “white-box” models with causal hypotheses that explain the structural complexity underlying this phenomenon. We propose a system dynamics model based on a feedback mechanism to explain structurally ITD.
Methodology: A system dynamics methodology was selected to model and simulate ITD. First, a causal loop diagram is proposed to describe the ITD structure in terms of feedback loops. Then a stock-flows diagram is formulated to allow computer simulation. Finally, simulations are run to show the quantitative temporal evolution of the model built.
Results: The simulation results show how new roads in the short term induce more kilometers traveled by vehicles already in use; meanwhile, in the medium-term, new traffic is generated. These new car drivers appear when better flow conditions coming from new roads increase attractiveness of car use. More cars added to vehicles already in use produce new traffic congestion, and high travel speeds provided by roads built are absorbed by ITD effects.
Conclusion: We concluded that approaching ITD with a systemic perspective allows for identifying leverage points that contribute to design comprehensive policies aimed to cope with ITD. In this sense, the model supports decision- making processes in urban contexts wherein it is still necessary for road construction to guarantee connectivity, such as the case of developing countries.
Ključne besede: induced travel demand, system dynamics, decision-making, dynamic modeling
Objavljeno v DKUM: 23.01.2018; Ogledov: 1477; Prenosov: 167
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3. Systems approach to tourism : a methodology for defining complex tourism systemTadeja Jere Lazanski, 2017, izvirni znanstveni članek Opis: Background and Purpose: The complexity of the tourism system, as well as modelling in a frame of system dynamics, will be discussed in this paper. The phaenomenon of tourism, which possesses the typical properties of global and local organisations, will be presented as an open complex system with all its elements, and an optimal methodology to explain the relations among them. The approach we want to present is due to its transparency an excellent tool for searching systems solutions and serves also as a strategic decision-making assessment. We will present systems complexity and develop three models of a complex tourism system: the first one will present tourism as an open complex system with its elements, which operate inside of a tourism market area. The elements of this system present subsystems, which relations and interdependencies will be explained with two models: causal-loop diagram and a simulation model in frame of systems dynamics.
Design/methodology/approach: Systems methodology will be shown as the appropriate one, when we discuss complex systems challenges. For illustration, systems approach and systems methodology will be applied to tourism models. With building a qualitative causal-loop diagram we will describe the tourism system complexity in forms of system%s elements relations. Mutual influences among the elements will be presented with positive and negative loops, which forms circles of reinforcement and balance. This will help us to discuss the problem categorically. The final model will follow the causal-loop diagram. This will be a simulation model in a frame of system dynamics as an illustration of the discussed methodology.
Results: The methodology offers the solution of effective and holistic promotion of complex tourism system transformation, which has the potential to go beyond the myth of sustainable tourism and create significant shifts in the approach and acting of the participants (elements of the system) involved. Systems approach brings to tourism and the society, in general, broader dimensions of thinking, the awareness interdependency, interconnectivity, and responsibility for the behaviour of a system, which can be observed by feedback loops.
Conclusions: Findings about meaningfulness of systems thinking presented in the paper, are rarely presented to tourism society systemically and with the aim of designing sustainable complex tourism system. They show new approach, systems awareness and teaches thinking %out of the box%. Consequently, the sustainable behaviour is achieved: tourism supply and demand meet on responsible base and they connect to responsible stakeholders.
Ključne besede: systems approach, complexity, tourism system, modelling, system dynamics
Objavljeno v DKUM: 22.01.2018; Ogledov: 1144; Prenosov: 209
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4. Editorial : in memoriam professor emeritus D.Sc. Miroljub KljajićMirjana Kljajić Borštnar, Davorin Kofjač, Andrej Škraba, Gerhard-Wilhelm Weber, Andreja Pucihar, 2017, predgovor, uvodnik, spremna beseda Ključne besede: simulation, modeling, system dynamics, decision making
Objavljeno v DKUM: 29.11.2017; Ogledov: 1592; Prenosov: 151
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5. A system dynamics model for improving primary education enrollment in a developing countryChandra Sekhar Pedamallu, Linet Ozdamar, LS Ganesh, Gerhard-Wilhelm Weber, Erik Kropat, 2010, izvirni znanstveni članek Opis: The system dynamics approach is a holistic way of solving problems in real-time scenarios. This is a powerful methodology and computer simulation modeling technique for framing, analyzing, and discussing complex issues and problems. System dynamics modeling is often the background of a systemic thinking approach and has become a management and organizational development paradigm. This paper proposes a system dynamics approach for studying the importance of infrastructure facilities on the quality of primary education system in a developing nation. The model is built using the Cross Impact Analysis (CIA) method of relating entities and attributes relevant to the primary education system in any given community. The CIA model enables us to predict the effects of infrastructural facilities on the community's access of primary education. This may support policy makers to take more effective actions in campaigns that attempt to improve literacy.
Ključne besede: developing countries, system modeling, cross impact analysis, simulation, system dynamics, primary education
Objavljeno v DKUM: 28.11.2017; Ogledov: 1302; Prenosov: 374
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6. System dynamic models as decision-making tools in agritourismTadeja Jere Lazanski, 2016, izvirni znanstveni članek Opis: Agritourism as a type of niche tourism is a complex and softly defined phaenomenon. The demands for fast and integrated decision regarding agritourism and its interconnections with environment, economy (investments, traffic) and social factors (tourists) is urgent. Many different methodologies and methods master softly structured questions and dilemmas with global and local properties. Here we present methods of systems thinking and system dynamics, which were first brought into force in the educational and training area in the form of different computer simulations and later as tools for decision-making and organisational re-engineering. We develop system dynamics models in order to present accuracy of methodology. These models are essentially simple and can serve only as describers of the activity of basic mutual influences among variables. We will pay the attention to the methodology for parameter model values determination and the so-called mental model. This one is the basis of causal connections among model variables. At the end, we restore a connection between qualitative and quantitative models in frame of system dynamics.
Ključne besede: agritourism, multi-criteria decision-making, modelling, system dynamics
Objavljeno v DKUM: 14.11.2017; Ogledov: 1279; Prenosov: 199
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7. Validation of agent-based approach for simulating the conversion to organic farmingČrtomir Rozman, Andrej Škraba, Karmen Pažek, Davorin Kofjač, 2017, izvirni znanstveni članek Opis: Background and Purpose: The purpose of this study is to describe the principles of the development of parallel system-dynamics and agent-based models of organic farming for the case of Slovenia. The advantage of agent-based modeling is demonstrated by including geospatial information as an agent attribute. The models were compared by the validation, confirming the appropriate level of similarity.
Design/Methodology/Approach: Both system-dynamics and agent-based modeling approaches were applied. Statistical methods were used in the validation.
Results: The results of the validation confirm the appropriateness of the proposed agent-based model. Introducing additional attributes into the agent-based model provides an important advantage over the system-dynamics model, which serves as the paradigmatic example.
Conclusion: A thorough validation and comparison of the results of the system-dynamics and agent-based models indicates the proper approach to combining the methodologies. This approach is promising, because it enables the modeling of the entire agricultural sector, taking each particular farm into account.
Ključne besede: agent-based models, organic farming, system dynamics, validation, multimethod simulation
Objavljeno v DKUM: 01.09.2017; Ogledov: 1823; Prenosov: 410
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8. System dynamic model of measures for reducing the number of road accidents due to wrong-way movement on motorwaysDarja Topolšek, Martin Lipičnik, 2009, drugi znanstveni članki Opis: This paper provides a system dynamic model for reducing the number of motorway accidents due to wrong-way driving. Motorway accidents are often fatal due to high speeds. It is therefore necessary to carry out all the possible countermeasures in order to achieve adequate traffic management. One of the reasons for motorway accidents is driving in the wrong direction. Based on the analysis of the data on motorway accidents caused by driving in the wrong direction and based on the knowledge of individual project elements of junctions and slip roads, this paper will focus on this area. The possible countermeasures, presented here for preventing drivers from driving in the wrong direction on motorways drastically reduce the number of U-turn maneuvers that result in driving in the wrong direction and influence the level of safety on motorways. With the help of this model of system dynamics the countermeasures for reducing the number of such drivers will be confirmed and their effects will be shown.
Ključne besede: traffic safety, motorway, direction, road accidents, measures, system dynamics
Objavljeno v DKUM: 06.06.2017; Ogledov: 1421; Prenosov: 1588
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9. Alternative forecasting techniques that reduce the bullwhip effect in a supply chain : a simulation studyFrancisco Campuzano Bolarín, Antonio Guillamón Frutos, Ma Del Carmen Ruiz Abellón, Andrej Lisec, 2013, pregledni znanstveni članek Opis: The research of the Bullwhip effect has given rise to many papers, aimed at both analysing its causes and correcting it by means of various management strategies because it has been considered as one of the critical problems in a supply chain. This study is dealing with one of its principal causes, demand forecasting. Using different simulated demand patterns, alternative forecasting methods are proposed, that can reduce the Bullwhip effect in a supply chain in comparison to the traditional forecasting techniques (moving average, simple exponential smoothing, and ARMA processes). Our main findings show that kernel regression is a good alternative in order to improve important features in the supply chain, such as the Bullwhip, NSAmp, and FillRate.
Ključne besede: bullwhip effect, supply chain, kernel regression, system dynamics model
Objavljeno v DKUM: 31.05.2017; Ogledov: 1375; Prenosov: 210
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10. Web application for hierarchical organizational structure optimization : human resource management case studyDavorin Kofjač, Blaž Bavec, Andrej Škraba, 2015, izvirni znanstveni članek Opis: Background and Purpose: In a complex strictly hierarchical organizational structure, undesired oscillations may occur, which have not yet been adequately addressed. Therefore, parameter values, which define fluctuations and transitions from one state to another, need to be optimized to prevent oscillations and to keep parameter values between lower and upper bounds. The objective was to develop a simulation model of hierarchical organizational structure as a web application to help in solving the aforementioned problem.
Design/Methodology/Approach: The hierarchical structure was modeled according to the principles of System Dynamics. The problem of the undesired oscillatory behavior was addressed with deterministic finite automata, while the flow parameter values were optimized with genetic algorithms. These principles were implemented as a web application with JavaScript/ECMAScript.
Results: Genetic algorithms were tested against well-known instances of problems for which the optimal analytical values were found. Deterministic finite automata was verified and validated via a three-state hierarchical organizational model, successfully preventing the oscillatory behavior of the structure.
Conclusion: The results indicate that the hierarchical organizational model, genetic algorithms and deterministic finite automata have been successfully implemented with JavaScript as a web application that can be used on mobile devices. The objective of the paper was to optimize the flow parameter values in the hierarchical organizational model with genetic algorithms and finite automata. The web application was successfully used on a three-state hierarchical organizational structure, where the optimal flow parameter values were determined and undesired oscillatory behavior was prevented. Therefore, we have provided a decision support system for determination of quality restructuring strategies.
Ključne besede: hierarchical organizational structure, genetic algorithms, deterministic finite automata, system dynamics, optimization, human resources
Objavljeno v DKUM: 04.04.2017; Ogledov: 1917; Prenosov: 150
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