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Autapse-induced multiple coherence resonance in single neurons and neuronal networks
Ergin Yilmaz, Mahmut Ozer, Veli Baysal, Matjaž Perc, 2016, izvirni znanstveni članek

Opis: We study the effects of electrical and chemical autapse on the temporal coherence or firing regularity of single stochastic Hodgkin-Huxley neurons and scale-free neuronal networks. Also, we study the effects of chemical autapse on the occurrence of spatial synchronization in scale-free neuronal networks. Irrespective of the type of autapse, we observe autaptic time delay induced multiple coherence resonance for appropriately tuned autaptic conductance levels in single neurons. More precisely, we show that in the presence of an electrical autapse, there is an optimal intensity of channel noise inducing the multiple coherence resonance, whereas in the presence of chemical autapse the occurrence of multiple coherence resonance is less sensitive to the channel noise intensity. At the network level, we find autaptic time delay induced multiple coherence resonance and synchronization transitions, occurring at approximately the same delay lengths. We show that these two phenomena can arise only at a specific range of the coupling strength, and that they can be observed independently of the average degree of the network.
Ključne besede: neuronal dynamics, autapse, coherence resonance, scale-free network
Objavljeno: 23.06.2017; Ogledov: 26; Prenosov: 0
.pdf Polno besedilo (1,63 MB)

An evolutionary inspection game with labour unions on small-world networks
Matjaž Perc, Salahuddin M. Kamal, Yas Al-Hadeethi, Fouad A. Abolaban, Fahad M. Al-Marzouki, 2015, izvirni znanstveni članek

Opis: We study an evolutionary inspection game where agents can chose between working and shirking. The evolutionary process is staged on a small-world network, through which agents compare their incomes and, based on the outcome, decide which strategy to adopt. Moreover, we introduce union members that have certain privileges, of which the extent depends on the bargaining power of the union. We determine how the union affects the overall performance of the firm that employs the agents, and what are its influences on the employees. We find that, depending on its bargaining power, the union has significant leverage to deteriorate the productivity of a firm, and consequently also to lower the long-run benefits of the employees.
Ključne besede: cooperation, public goods, inspection, unions, physics of social systems
Objavljeno: 23.06.2017; Ogledov: 28; Prenosov: 1
.pdf Polno besedilo (568,84 KB)

A double-edged sword: benefits and pitfalls of heterogeneous punishment in evolutionary inspection games
Matjaž Perc, Attila Szolnoki, 2015, izvirni znanstveni članek

Opis: As a simple model for criminal behavior, the traditional two-strategy inspection game yields counterintuitive results that fail to describe empirical data. The latter shows that crime is often recurrent, and that crime rates do not respond linearly to mitigation attempts. A more apt model entails ordinary people who neither commit nor sanction crime as the third strategy besides the criminals and punishers. Since ordinary people free-ride on the sanctioning efforts of punishers, they may introduce cyclic dominance that enables the coexistence of all three competing strategies. In this setup ordinary individuals become the biggest impediment to crime abatement. We therefore also consider heterogeneous punisher strategies, which seek to reduce their investment into fighting crime in order to attain a more competitive payoff. We show that this diversity of punishment leads to an explosion of complexity in the system, where the benefits and pitfalls of criminal behavior are revealed in the most unexpected ways. Due to the raise and fall of different alliances no less than six consecutive phase transitions occur in dependence on solely the temptation to succumb to criminal behavior, leading the population from ordinary people-dominated across punisher-dominated to crime-dominated phases, yet always failing to abolish crime completely.
Ključne besede: crime, phase transition, social dilemma, physics of social systems
Objavljeno: 23.06.2017; Ogledov: 25; Prenosov: 0
.pdf Polno besedilo (1,62 MB)

The maximum entropy production principle and linear irreversible processes
Paško Županović, Domagoj Kuić, Željana Bonačić Lošić, Dražen Petrov, Davor Juretić, Milan Brumen, 2010, izvirni znanstveni članek

Opis: It is shown that Onsager’s principle of the least dissipation of energy is equivalent to the maximum entropy production principle. It is known that solutions of the linearized Boltzmann equation make extrema of entropy production. It is argued, in the case of stationary processes, that this extremum is a maximum rather than a minimum.
Ključne besede: entropy production, linear nonequilibrium thermodynamics, linearized Boltzmann equation
Objavljeno: 21.06.2017; Ogledov: 31; Prenosov: 0
.pdf Polno besedilo (107,41 KB)

Win-stay-lose-learn promotes cooperation in the spatial prisoner's dilemma game
Yongkui Liu, Xiaojie Chen, Lin Zhang, Long Wang, Matjaž Perc, 2012, izvirni znanstveni članek

Opis: Holding on to one's strategy is natural and common if the later warrants success and satisfaction. This goes against widespread simulation practices of evolutionary games, where players frequently consider changing their strategy even though their payoffs may be marginally different than those of the other players. Inspired by this observation, we introduce an aspiration-based win-stay-lose-learn strategy updating rule into the spatial prisoner's dilemma game. The rule is simple and intuitive, foreseeing strategy changes only by dissatisfied players, who then attempt to adopt the strategy of one of their nearest neighbors, while the strategies of satisfied players are not subject to change. We find that the proposed winstay-lose-learn rule promotes the evolution of cooperation, and it does so very robustly and independently of the initial conditions. In fact, we show that even a minute initial fraction of cooperators may be sufficient to eventually secure a highly cooperative final state. In addition to extensive simulation results that support our conclusions, we also present results obtained by means of the pair approximation of the studied game. Our findings continue the success story of related winstay strategy updating rules, and by doing so reveal new ways of resolving the prisoner's dilemma.
Ključne besede: social dilemmas, prisoner's dilemma, cooperation, networks
Objavljeno: 19.06.2017; Ogledov: 93; Prenosov: 0
.pdf Polno besedilo (390,56 KB)

Understanding recurrent crime as system-immanent collective behavior
Matjaž Perc, Karsten Donnay, Dirk Helbing, 2013, izvirni znanstveni članek

Opis: Containing the spreading of crime is a major challenge for society. Yet, since thousands of years, no effective strategy has been found to overcome crime. To the contrary, empirical evidence shows that crime is recurrent, a fact that is not captured well by rational choice theories of crime. According to these, strong enough punishment should prevent crime from happening. To gain a better understanding of the relationship between crime and punishment, we consider that the latter requires prior discovery of illicit behavior and study a spatial version of the inspection game. Simulations reveal the spontaneous emergence of cyclic dominance between criminals, inspectors, and ordinary people as a consequence of spatial interactions. Such cycles dominate the evolutionary process, in particular when the temptation to commit crime or the cost of inspection are low or moderate. Yet, there are also critical parameter values beyond which cycles cease to exist and the population is dominated either by a stable mixture of criminals and inspectors or one of these two strategies alone. Both continuous and discontinuous phase transitions to different final states are possible, indicating that successful strategies to contain crime can be very much counter-intuitive and complex. Our results demonstrate that spatial interactions are crucial for the evolutionary outcome of the inspection game, and they also reveal why criminal behavior is likely to be recurrent rather than evolving towards an equilibrium with monotonous parameter dependencies.
Ključne besede: crime, evolutionary games, collective phenomena, phase transitions, statistical physics
Objavljeno: 19.06.2017; Ogledov: 88; Prenosov: 0
.pdf Polno besedilo (433,51 KB)

Synchronous bursts on scale-free neuronal networks with attractive and repulsive coupling
Qingyun Wang, Guanrong Chen, Matjaž Perc, 2011, izvirni znanstveni članek

Opis: This paper investigates the dependence of synchronization transitions of bursting oscillations on the information transmission delay over scale-free neuronal networks with attractive and repulsive coupling. It is shown that for both types of coupling, the delay always plays a subtle role in either promoting or impairing synchronization. In particular, depending on the inherent oscillation period of individual neurons, regions of irregular and regular propagating excitatory fronts appear intermittently as the delay increases. These delay-induced synchronization transitions are manifested as well-expressed minima in the measure for spatiotemporal synchrony. For attractive coupling, the minima appear at every integer multiple of the average oscillation period, while for the repulsive coupling, they appear at every odd multiple of the half of the average oscillation period. The obtained results are robust to the variations of the dynamics of individual neurons, the system size, and the neuronal firing type. Hence, they can be used to characterize attractively or repulsively coupled scale-free neuronal networks with delays.
Ključne besede: synchronization, neuronal networks, noise, stochastic processes, scale-free networks, information transmission delay
Objavljeno: 19.06.2017; Ogledov: 60; Prenosov: 0
.pdf Polno besedilo (933,65 KB)

Resolution of the stochastic strategy spatial prisoner's dilemma by means of particle swarm optimization
Jianlei Zhang, Chunyan Zhang, Tianguang Chu, Matjaž Perc, 2011, izvirni znanstveni članek

Opis: We study the evolution of cooperation among selfish individuals in the stochastic strategy spatial prisoner's dilemma game. We equip players with the particle swarm optimization technique, and find that it may lead to highly cooperative states even if the temptations to defect are strong. The concept of particle swarm optimization was originally introduced within a simple model of social dynamics that can describe the formation of a swarm, i.e., analogous to a swarm of bees searching for a food source. Essentially, particle swarm optimization foresees changes in the velocity profile of each player, such that the best locations are targeted and eventually occupied. In our case, each player keeps track of the highest payoff attained within a local topological neighborhood and its individual highest payoff. Thus, players make use of their own memory that keeps score of the most profitable strategy in previous actions, as well as use of the knowledge gained by the swarm as a whole, to find the best available strategy for themselves and the society. Following extensive simulations of this setup, we find a significant increase in the level of cooperation for a wide range of parameters, and also a full resolution of the prisoner's dilemma. We also demonstrate extreme efficiency of the optimization algorithm when dealing with environments that strongly favor the proliferation of defection, which in turn suggests that swarming could be an important phenomenon by means of which cooperation can be sustained even under highly unfavorable conditions. We thus present an alternative way of understanding the evolution of cooperative behavior and its ubiquitous presence in nature, and we hope that this study will be inspirational for future efforts aimed in this direction.
Ključne besede: cooperation, prisoner's dilemma, particle swarm optimization, stochastic strategies
Objavljeno: 19.06.2017; Ogledov: 73; Prenosov: 0
.pdf Polno besedilo (627,24 KB)

Predictions of experimentally observed stochastic ground vibrations induced by blasting
Srđan Kostić, Matjaž Perc, Nebojša Vasović, Slobodan Trajković, 2013, izvirni znanstveni članek

Opis: In the present paper, we investigate the blast induced ground motion recorded at the limestone quarry “Suva Vrela” near Kosjerić, which is located in the western part of Serbia. We examine the recorded signals by means of surrogate data methods and a determinism test, in order to determine whether the recorded ground velocity is stochastic or deterministic in nature. Longitudinal, transversal and the vertical ground motion component are analyzed at three monitoring points that are located at different distances from the blasting source. The analysis reveals that the recordings belong to a class of stationary linear stochastic processes with Gaussian inputs, which could be distorted by a monotonic, instantaneous, time-independent nonlinear function. Low determinism factors obtained with the determinism test further confirm the stochastic nature of the recordings. Guided by the outcome of time series analysis, we propose an improved prediction model for the peak particle velocity based on a neural network. We show that, while conventional predictors fail to provide acceptable prediction accuracy, the neural network model with four main blast parameters as input, namely total charge, maximum charge per delay, distance from the blasting source to the measuring point, and hole depth, delivers significantly more accurate predictions that may be applicable on site. We also perform a sensitivity analysis, which reveals that the distance from the blasting source has the strongest influence on the final value of the peak particle velocity. This is in full agreement with previous observations and theory, thus additionally validating our methodology and main conclusions.
Ključne besede: blasting, vibrations, surrogate data, deterministic chaos, stochasticity
Objavljeno: 19.06.2017; Ogledov: 19; Prenosov: 0
.pdf Polno besedilo (1,45 MB)

Political systems affect mobile and sessile species diversity - a legacy from the post-WWII period
Sara Cousins, Mitja Kaligarič, Branko Bakan, Regina Lindborg, 2014, izvirni znanstveni članek

Opis: Political ideologies, policies and economy affect land use which in turn may affect biodiversity patterns and future conservation targets. However, few studies have investigated biodiversity in landscapes with similar physical properties but governed by different political systems. Here we investigate land use and biodiversity patterns, and number and composition of birds and plants, in the borderland of Austria, Slovenia and Hungary. It is a physically uniform landscape but managed differently during the last 70 years as a consequence of the political "map" of Europe after World War I and II. We used a historical map from 1910 and satellite data to delineate land use within three 10-kilometre transects starting from the point where the three countries meet. There was a clear difference between countries detectable in current biodiversity patterns, which relates to land use history. Mobile species richness was associated with current land use whereas diversity of sessile species was more associated with past land use. Heterogeneous landscapes were positively and forest cover was negatively correlated to bird species richness. Our results provide insights into why landscape history is important to understand present and future biodiversity patterns, which is crucial for designing policies and conservation strategies across the world.
Ključne besede: biology, plants, birds, political systems
Objavljeno: 19.06.2017; Ogledov: 15; Prenosov: 0
.pdf Polno besedilo (2,16 MB)

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