1. Critical transitions in pancreatic isletsDean Korošak, Sandra Postić, Andraž Stožer, Boštjan Podobnik, Marjan Rupnik, 2025, izvirni znanstveni članek Opis: Calcium signals in pancreatic � cell collectives show a sharp transition from uncorrelated to correlated state resembling a phase transition as the slowly increasing glucose concentration crosses the tipping point. However, the exact nature or the order of this phase transition is not well understood. Using confocal microscopy to record the collective calcium activation of � cells in an intact islet under changing glucose concentration in an increasing and then decreasing way, we first show that in, addition to the sharp transition, the coordinated calcium response exhibits a hysteresis indicating a critical, first-order transition. A network model of � cells combining link selection and coordination mechanisms capture the observed hysteresis loop and the critical nature of the transition. Our results point towards an understanding of the role of islets as tipping elements in the pancreas that, interconnected by perfusion, diffusion, and innervation, cause the tipping dynamics and abrupt insulin release.
Ključne besede: cellular organization, physiology & dynamics, phase transitions in biological systems, complex networks, endocrine system, optical microscopy
Objavljeno v DKUM: 19.03.2025; Ogledov: 0; Prenosov: 2
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2. A system dynamics approach to decision-making tools in farm tourism developmentMaja Borlinič Gačnik, Črtomir Rozman, Andrej Škraba, Boris Prevolšek, 2020, izvirni znanstveni članek Opis: Background: Besides visiting the main tourist attractions in Slovenia, many tourists want to spend their free time in the countryside as well, but the number of farming establishments in Slovenia diminished distinctly in the last years.
Objectives: This paper aims to develop a system dynamics model, with the goal to analyse dynamics of the diversification of agricultural holdings into farm tourism activities in Slovenia.
Methods/Approach: A system dynamics methodology was chosen to model the diversification in farm tourism. First, we present a basic concept of a system dynamics model with a causal loop diagram. Further, a system dynamics model with different scenarios is presented.
Results: The main feedback loops were identified, and the simulation model was used to analyse different simulation scenarios of the transition of farming establishments into farm tourism facilities.
Conclusions: The model provides the answers to the strategic questions about the dynamics of transfer into tourist farms, using several simulation scenarios. The transition mainly relies on subsidies, promotion of diversification and the growth of rural tourism, which provides a relevant direction for the development of future incentives.
Ključne besede: farm tourism, rural tourism, modelling, system dynamics, causal loop diagram, simulation
Objavljeno v DKUM: 13.01.2025; Ogledov: 0; Prenosov: 3
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3. Developing a diversification strategy of non-agricultural activities on farms using system dynamics modelling : a case study of SloveniaMaja Borlinič Gačnik, Boris Prevolšek, Karmen Pažek, Črtomir Rozman, Andrej Škraba, 2022, izvirni znanstveni članek Opis: Purpose: This paper aims to analyse the main variables and causal relationships in the system structure of the diversification of non-agricultural activities on agricultural holdings using system dynamics (SD) modelling. The SD model aims to simulate depictions of the behaviour of the real system while testing the effects of alternative decisions over time.
Design/methodology/approach: An SD methodology was chosen to model diversification in farm tourism.
Findings: A system approach increases the authors’ understanding of the transition of agricultural holdings to farm tourism. The results indicate that the transition to farm tourism depends on the level of tourism development in a certain area. The system is influenced by subsidies allocated by authorities to expand primary agricultural activities. The model describes a situation in which the tourism and agricultural industries have been affected by the COVID-19 pandemic.
Research limitations/implications: The research is limited by the small set of available data due to the limited number of farms in Slovenia. One major problem is the difference in statistical data on the same activity collected from different institutions in Slovenia.
Practical implications: The paper includes implications for understanding the transition process to farm tourism, allowing policymakers to experiment with subsidies and promotion to explore the efficacy and efficiency of proposed policies.
Originality/value: This study provides a structured, systemic view of the diversification of non-agricultural activities on agricultural holdings, where the simulation results are a reliable reflection of the behaviour of the actual system being modelled.
Ključne besede: system dynamics, modelling, simulation, diversification, farm tourism, farm policy, Slovenia, simulation scenarious
Objavljeno v DKUM: 11.12.2024; Ogledov: 0; Prenosov: 5
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4. Diverse strategic identities induce dynamical states in evolutionary gamesIrene Sendiña-Nadal, Inmaculada Leyva, Matjaž Perc, David Papo, Marko Jusup, Zhen Wang, Juan A. Almendral, Pouya Manshour, Stefano Boccaletti, 2020, izvirni znanstveni članek Opis: Evolutionary games provide the theoretical backbone for many aspects of our social life: from cooperation to crime, from climate inaction to imperfect vaccination and epidemic spreading, from antibiotics overuse to biodiversity preservation. An important, and so far overlooked, aspect of reality is the diverse strategic identities of individuals. While applying the same strategy to all interaction partners may be an acceptable assumption for simpler forms of life, this fails to account for the behavior of more complex living beings. For instance, we humans act differently around different people. Here we show that allowing individuals to adopt different strategies with different partners yields a very rich evolutionary dynamics, including time-dependent coexistence of cooperation and defection, systemwide shifts in the dominant strategy, and maturation in individual choices. Our results are robust to variations in network type and size, and strategy updating rules. Accounting for diverse strategic identities thus has far-reaching implications in the mathematical modeling of social games.
Ključne besede: cooperation, evolutionary game theory, social physics, collective dynamics, complex system
Objavljeno v DKUM: 20.11.2024; Ogledov: 0; Prenosov: 6
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5. Strategically positioning cooperators can facilitate the contagion of cooperationGuoli Yang, Matteo Cavaliere, Cheng Zhu, Matjaž Perc, 2021, izvirni znanstveni članek Opis: The spreading of cooperation in structured population is a challenging problem which can be observed at diferent scales of social and biological organization. Generally, the problem is studied by evaluating the chances that few initial invading cooperators, randomly appearing in a network, can lead to the spreading of cooperation. In this paper we demonstrate that in many scenarios some cooperators are more infuential than others and their initial positions can facilitate the spreading of cooperation. We investigate six diferent ways to add initial cooperators in a network of cheaters, based on diferent network-based measurements. Our research reveals that strategically positioning the initial cooperators in a population of cheaters allows to decrease the number of initial cooperators necessary to successfully seed cooperation. The strategic positioning of initial cooperators can also help to shorten the time necessary for the restoration of cooperation. The optimal ways in which the initial cooperators should be placed is, however, non-trivial in that it depends on the degree of competition, the underlying game, and the network structure. Overall, our results show that, in structured populations, few cooperators, well positioned in strategically chosen places, can spread cooperation faster and easier than a large number of cooperators that are placed badly.
Ključne besede: cooperation, evolutionary game theory, social physics, collective dynamics, complex system
Objavljeno v DKUM: 22.10.2024; Ogledov: 0; Prenosov: 3
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7. 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: 179
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8. 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: 213
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9. 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: 158
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10. 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: 396
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