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Oppressed species can form a winning pair in a multi-species ecosystem
Attila Szolnoki, Matjaž Perc, 2023, original scientific article

Keywords: cyclic dominance, alliance, biodiversity
Published in DKUM: 15.04.2024; Views: 43; Downloads: 0
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Extended matrix norm method : applications to bimatrix games and convergence results
Burhaneddin İzgi, Murat Özkaya, Nazım Kemal Üre, Matjaž Perc, 2023, original scientific article

Abstract: In this paper, we extend and apply the Matrix Norm (MN) approach to the nonzero-sum bimatrix games. We present preliminary results regarding the convergence of the MN approaches. We provide a notation for expressing nonzero-sum bimatrix games in terms of two matrix games using the idea of separation of a bimatrix game into two different matrix games. Next, we prove theorems regarding boundaries of the game value depending on only norms of the payoff matrix for each player of the nonzero-sum bimatrix game. In addition to these, we refine the boundaries of the game value for the zero/nonzero sum matrix games. Therefore, we succeed to find an improved interval for the game value, which is a crucial improvement for both nonzero and zero-sum matrix games. As a consequence, we can solve a nonzero-sum bimatrix game for each player approximately without solving any equations. Moreover, we modify the inequalities for the extrema of the strategy set for the nonzero-sum bimatrix games. Furthermore, we adapt the min-max theorem of the MN approach for the nonzero-sum bimatrix games. Finally, we consider various bimatrix game examples from the literature, including the famous battle of sexes, to demonstrate the consistency of our approaches. We also show that the repeated applications of Extended Matrix Norm (EMN) methods work well to obtain a better-estimated game value in view of the obtained convergence results.
Keywords: game theory, nonzero sum game, bimatrix game, matrix norms, battle of sexes, convergence
Published in DKUM: 15.04.2024; Views: 33; Downloads: 0
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Time delays shape the eco‑evolutionary dynamics of cooperation
Sourav Roy, Sayantan Nag Chowdhury, Srilena Kundu, Gourab Kumar Sar, Jeet Banerjee, Biswambhar Rakshit, Prakash Chandra Mali, Matjaž Perc, Dibakar Ghosh, 2023, original scientific article

Abstract: We study the intricate interplay between ecological and evolutionary processes through the lens of the prisoner’s dilemma game. But while previous studies on cooperation amongst selfsh individuals often assume instantaneous interactions, we take into consideration delays to investigate how these might afect the causes underlying prosocial behavior. Through analytical calculations and numerical simulations, we demonstrate that delays can lead to oscillations, and by incorporating also the ecological variable of altruistic free space and the evolutionary strategy of punishment, we explore how these factors impact population and community dynamics. Depending on the parameter values and the initial fraction of each strategy, the studied eco-evolutionary model can mimic a cyclic dominance system and even exhibit chaotic behavior, thereby highlighting the importance of complex dynamics for the efective management and conservation of ecological communities. Our research thus contributes to the broader understanding of group decision-making and the emergence of moral behavior in multidimensional social systems.
Keywords: cooperation, time delay, evolutionary dynamics, social dilemma, social physics
Published in DKUM: 04.04.2024; Views: 46; Downloads: 4
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A conceptual model for a circular city : a case study of Maribor, Slovenia
Kristijan Brglez, Matjaž Perc, Rebeka Kovačič Lukman, 2024, original scientific article

Abstract: Cities play a crucial role in achieving sustainable development. Decision-makers require assistance in developing city transformation plans amidst the emergence of various city models. A content analysis using concept mapping was conducted to examine smart, circular, and green city models. The analysis, supported by Leximancer, revealed that city models are evolving by adopting benefcial solutions from competitors, refecting a strong focus on sustainable development. Additionally, twentyfour research areas essential for implementing a circular city were identifed and validated. Furthermore, a conceptual model for a circular city was developed, incorporating the Defne-Measure-Analyse-Improve-Control tool and a problem-solving system. Testing the model on Maribor highlighted challenges in monitoring the transition towards circularity. The study validates the established model but emphasises the need for further research and case studies to verify its practicality. This scientifc research enhances the understanding of city models and their evolution towards sustainability, providing valuable insights for decision-makers and urban planners.
Keywords: city models, conceptual model, content analysis, problem-solving structure
Published in DKUM: 29.03.2024; Views: 52; Downloads: 2
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The complexity and interconnectedness of circular cities and the circular economy for sustainability
Kristijan Brglez, Matjaž Perc, Rebeka Kovačič Lukman, 2023, original scientific article

Abstract: In our study, we are evaluating the dynamic interplay between circular cities and the circular economy, revealing connections shaped by new research insights, using Web of Science database. We have in depth analysed 671 publications from 1990 to mid- 2023, employing Leximancer and VOSviewer tools. Our analysis uncovered key themes, including buildings, waste management, value chains, and sustainable development, linking the circular cities concept and circular economy framework. Emerging research trends, such as urban metabolism, urban mining, governance models, the built environment, sustainability benchmarks, and value chain management, signify deliberate shifts towards higher circular development and implementation. These trajectories harmonise with overarching sustainable development goals. Contemporary research emphasises urban mining, circular indicators, adaptive resource reuse, and urban structure regeneration. This focus facilitates transitioning from linear models to heightened circularity within urban contexts. Research inclination is shifting from traditional economic and environmental concerns towards holistic urban configurations that prioritise social integration, communal well-being, and the dynamics of the social economy. Through this analytical expedition, we offer novel insights that enhance our understanding of the intricate symbiosis between circular cities and the circular economy. Our findings provide a scientific foundation for formulating targeted strategies by decision-makers and guiding urban landscapes towards transformative trajectories aligned with sustainable development objectives and sustainable cities.
Keywords: bibliometric analysis, circular city, circular economy, content analysis, Leximancer, sustainability, sustainable development goals
Published in DKUM: 29.03.2024; Views: 43; Downloads: 2
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Age and market capitalization drive large price variations of cryptocurrencies
Arthur A. B. Pessa, Matjaž Perc, Haroldo V. Ribeiro, 2023, original scientific article

Abstract: Cryptocurrencies are considered the latest innovation in finance with considerable impact across social, technological, and economic dimensions. This new class of financial assets has also motivated a myriad of scientific investigations focused on understanding their statistical properties, such as the distribution of price returns. However, research so far has only considered Bitcoin or at most a few cryptocurrencies, whilst ignoring that price returns might depend on cryptocurrency age or be influenced by market capitalization. Here, we therefore present a comprehensive investigation of large price variations for more than seven thousand digital currencies and explore whether price returns change with the coming-of-age and growth of the cryptocurrency market. We find that tail distributions of price returns follow power-law functions over the entire history of the considered cryptocurrency portfolio, with typical exponents implying the absence of characteristic scales for price variations in about half of them. Moreover, these tail distributions are asymmetric as positive returns more often display smaller exponents, indicating that large positive price variations are more likely than negative ones. Our results further reveal that changes in the tail exponents are very often simultaneously related to cryptocurrency age and market capitalization or only to age, with only a minority of cryptoassets being affected just by market capitalization or neither of the two quantities. Lastly, we find that the trends in power-law exponents usually point to mixed directions, and that large price variations are likely to become less frequent only in about 28% of the cryptocurrencies as they age and grow in market capitalization.
Keywords: cryptocurrency, price variation, market value, econophysics
Published in DKUM: 25.03.2024; Views: 91; Downloads: 7
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Analiza hidroloških zahtev za načrtovanje novega sistema odvajanja meteornih voda v Brežicah : magistrsko delo
Luka Papa, 2023, master's thesis

Abstract: V magistrskem delu je obravnavano področje odvodnjavanja urbanih površin, hidrotehnike in hidravlike. Obravnavan je aktualni problem preobremenjenosti mešanih odpadnih komunalnih sistemov in posledično čistilnih naprav, in sicer s pomočjo realnega primera izdelane dokumentacije idejne zasnove za pridobitev projektnih in drugih pogojev (IZP) pri podjetju PROINFRA, d. o. o., številka projekta 193: »Odvajanje meteornih voda za širše območje ob Cesti svobode«. Magistrsko delo zajema teoretične osnove in tehnične usmeritve različnih standardov in programske opreme za konkretni primer. Uporabljeni so bili nemški standardi DWA za inženirske objekte (cevovodi, razbremenilniki in zadrževalniki) in programsko orodje Urbano Canalis 11.
Keywords: gradbeništvo, nizke gradnje, hidrotehnika, dimenzioniranje meteorne kanalizacije
Published in DKUM: 19.12.2023; Views: 262; Downloads: 31
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Analiza primernosti dehidracije blata na ČN Celje : magistrsko delo
Rok Stojnšek, 2023, master's thesis

Abstract: Zadnja leta se v Sloveniji ter tudi na ČN Celje srečujemo s problemom končne dispozicije blata. Količina blata, s katero se srečujemo na ČN Celje na letni ravni je 6000 ton, Toplarna Celje pa lahko za sežig sprejme zgolj 4000 ton. V magistrski nalogi bomo najprej ovrednotili vse stroške, ki nastanejo pri trenutni obdelavi odpadnega blata. Preučili bomo različne možnosti uporabe blata. Blato nastaja dnevno in ga je potrebno dnevno odstranjevati iz sistema, zato se je pripravila analiza primernosti dehidracije. Ena izmed rešitev problematike odstranjevanja blata iz ČN Celje je, da se osredotočimo na ustrezno dehidracijo blata, druga pa, da dehidrirano blato dodatno sušimo in posledično zmanjšamo volumen ter težo. Pri obeh postopkih je treba upoštevati stroške v vseh fazah dehidracije, poleg stroškov investicije tudi stroške porabe energije in polimera, ter stroške odvoza ter sosežiga.
Keywords: gradbeništvo, odpadno blato, čistilna naprava, odpadne vode, komunala, centrifuga, stiskalna preša, sušenje blata, stroškovna analiza
Published in DKUM: 27.10.2023; Views: 272; Downloads: 26
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The benefits, costs and feasibility of a low incidence COVID-19 strategy
Thomas Czypionka, Emil Nafis Iftekhar, Barbara Prainsack, Viola Priesemann, Simon Bauer, André Calero Valdez, Sarah Cuschieri, Enrico Glaab, Eva Grill, Jenny Krutzinna, Christos Lionis, Helena Machado, Carlos Martins, George N Pavlakis, Matjaž Perc, Elena Petelos, Martyn Pickersgill, Alexander Skupin, Eva S. Schernhammer, Ewa Szczurek, Sotirios Tsiodras, Peter Willeit, Paul Wilmes, 2022, original scientific article

Abstract: In the summer of 2021, European governments removed most NPIs after experiencing prolonged second and third waves of the COVID-19 pandemic. Most countries failed to achieve immunization rates high enough to avoid resurgence of the virus. Public health strategies for autumn and winter 2021 have ranged from countries aiming at low incidence by re-introducing NPIs to accepting high incidence levels. However, such high incidence strategies almost certainly lead to the very consequences that they seek to avoid: restrictions that harm people and economies. At high incidence, the important pandemic containment measure ‘test-trace-isolate-support’ becomes inefficient. At that point, the spread of SARS-CoV-2 and its numerous harmful consequences can likely only be controlled through restrictions. We argue that all European countries need to pursue a low incidence strategy in a coordinated manner. Such an endeavour can only be successful if it is built on open communication and trust.
Keywords: disease dynamics, exponential growth, virality, strategy
Published in DKUM: 25.09.2023; Views: 438; Downloads: 32
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