Ljupco KocarevMacedonian Academy of Sciences and Arts | MANU
Ljupco Kocarev
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Publications (444)
The magnitude of the coronavirus disease (COVID-19) pandemic has an enormous impact on the social life and the economic activities in almost every country in the world. Besides the biological and epidemiological factors, a multitude of social and economic criteria also govern the extent of the coronavirus disease spread in the population. Consequen...
The research on core-periphery structure of global trade from a complex-network perspective has shown that the world system is hierarchically organized into blocks and that countries play different roles in the world economy. Yet, little attention has been paid to investigating whether the sectoral international trade networks conform to a core-per...
Aims
Citizens’ perceived values play a decisive role in shaping a responsive society, driving social and political attitudes and behaviors. Understanding these values, influenced by cultural, historical, and personal experiences, is essential for comprehending public perspectives on social, economic, and ecological aspects crucial for sustainable s...
Following the relevant literature on higher education services, the objective of this study explores how the higher education perceived value outlines students’ satisfaction with the service and their migration intentions. Data from1,150 university students in Macedonia was collected and analyzed using Partial Least Squares Structural Equation Mode...
With the ever increasing interconnectedness among countries and industries, globalization has empowered economies and promoted international trade, capital flow and labor mobility, leading to improved products and services. However, the growing interdependence has also propelled an inherent reliance on joint cooperation which has considerably influ...
Detailed knowledge of individual income dynamics is one essential ingredient for investigating the existence of the American dream, pertinent to the question Are we able to improve our income status during our working life? This key question simply boils down to observing individual status and how it moves between two thresholds: the current income...
The Ornstein–Uhlenbeck (O-U) process with resetting is considered as the anomalous transport taking place on a three-dimensional comb. The three-dimensional comb is a comb inside a comb structure, consisting of backbones and fingers in the following geometrical correspondence x–backbone →y–fingers–backbone →z–fingers. Realisation of the O-U process...
The Ornstein-Uhlenbeck process is interpreted as Brownian motion in a harmonic potential. This Gaussian Markov process has a bounded variance and admits a stationary probability distribution, in contrast to the standard Brownian motion. It also tends to a drift towards its mean function, and such a process is called mean-reverting. Two examples of...
The problem with waste generation and waste treatment that countries worldwide are facing, even after the implementation of measures, raises the question of the adequacy and viability of the regulations. The waste sector has been shown to contribute to a most notable increase in greenhouse gas (GHG) emissions in many countries worldwide, mainly com...
Higher education research has claimed that the successful future of the educational service is highly dependent on the competencies and observations of the participants in the system, where service quality, employee satisfaction and engagement play an essential role in organizational competitiveness. Therefore, to contribute to the scarce investiga...
Air pollution remains a severe concern in European countries, especially in Western Balkan, where the air monitoring data point to harmful ambient pollution. The public concern with this issue becomes particularly critical during the fall and winter months, when the contamination is more visible, provoking a series of reactions directed principally...
The Ornstein-Uhlenbeck (O-U) process is a generalised diffusion process, introduced as a model for the velocity of a particle undergoing a Brownian motion confined in harmonic potential. The process is a stationary, meaning that over time, it tends to drift towards its long-time mean function: such a process is called mean-reverting. Here, we inves...
We analyze different stochastic processes with multiplicative noise under resetting in non-homogeneous media. We use the subordination approach, which is a powerful technique for solving various diffusion and Fokker-Planck equations, to analyze the probability density functions and the mean squared displacements. Additionally, we show that such sys...
We consider the rotational diffusion equation with a generalised memory kernel in the context of dielectric relaxation processes in a medium composed of polar molecules. We give an overview of existing models on non-exponential relaxation and introduce an exponential resetting dynamic in the corresponding process, providing a detailed analysis of t...
The Ornstein-Uhlenbeck (O-U) process can be interpreted as a Brownian motion in a harmonic potential. The process is an established Gauss-Markov process that has a bounded variance and admits a stationary probability distribution, in contrast to the standard Brownian motion. Over time, the process tends to drift towards its mean function: such a pr...
Despite the molecular evidence that a nearly linear steady-state current-voltage relationship in mammalian astrocytes reflects a total current resulting from more than one differentially regulated K+ conductance, detailed ordinary differential equation (ODE) models of membrane voltage Vm are still lacking. Various experimental results reporting alt...
We introduce a refined way to diffusely explore complex networks with stochastic resetting where the resetting site is derived from node centrality measures. This approach differs from previous ones, since it not only allows the random walker with a certain probability to jump from the current node to a deliberately chosen resetting node, rather it...
The Ornstein-Uhlenbeck process is interpreted as Brownian motion in a harmonic potential. This Gaussian Markov process has a bounded variance and admits a stationary probability distribution, in contrast to the standard Brownian motion. It also tends to a drift towards its mean function, and such a process is called mean-reverting. Two examples of...
Contextualized language models are becoming omnipresent in the field of Natural Language Processing (NLP). Their learning representation capabilities show dominant results in almost all downstream NLP tasks. The main challenge that low-resource languages face is the lack of language-specific language models since their pre-training process requires...
Detailed knowledge of individual income dynamics is crucial for investigating the existence of the American dream: Are we able to improve our income status during our working life? This key question simply boils down to observing individual status and how it moves between two thresholds: the current income and the desired income. Yet, our knowledge...
Detailed knowledge of individual income dynamics is crucial for investigating the existence of the American dream: Are we able to improve our income status during our working life? This key question simply boils down to observing individual status and how it moves between two thresholds: the current income and the desired income. Yet, our knowledge...
Intramolecular vibrational dynamics of CCOH torsions and OH stretching vibrations in 1-naphthol were followed by Fourier transform infrared (FTIR) spectroscopy and quantum-theoretical computations. The possibility of unintentional trans → cis transformation induced by broad- and narrowband incident IR radiation during the standard IR experiment was...
We analyze diffusion processes with finite propagation speed in a non-homogeneous medium in terms of the heterogeneous telegrapher's equation. In the diffusion limit of infinite-velocity propagation we recover the results for the heterogeneous diffusion process. The heterogeneous telegrapher's process exhibits a rich variety of diffusion regimes in...
We analyze diffusion processes with finite propagation speed in a non-homogeneous medium in terms of the heterogeneous telegrapher's equation. In the diffusion limit of infinite-velocity propagation we recover the results for the heterogeneous diffusion process. The heterogeneous telegrapher's process exhibits a rich variety of diffusion regimes in...
We consider one-dimensional Brownian search in presence of trapping. The diffusion equation of the particle is represented by a memory kernel which enters the general waiting time probability density function. We find the general form of the first arrival time density, search reliability and efficiency and analyze several special cases of the memor...
In this paper, an event-triggered Reinforcement Learning (RL) method is proposed for the optimal attitude consensus of multiple rigid body networks with unknown dynamics. Firstly, the consensus error is constructed through the attitude dynamics. According to the Bellman optimality principle, the implicit form of the optimal controller and the corre...
Despite the molecular evidence that the nearly linear steady-state current-voltage relationship in mammalian astrocytes reflects a total current resulting from more than one differently regulated K ⁺ conductances, detailed ODE models of membrane voltage V m are still lacking. Repeated experimental results of deregulated expressions of major K ⁺ cha...
We introduce non-Markovian SIR epidemic spreading model inspired by the characteristics of the COVID-19, by considering discrete- and continuous-time versions. The distributions of infection intensity and recovery period may take an arbitrary form. By taking corresponding choice of these functions, it is shown that the model reduces to the classica...
The COVID-19 pandemic resulted in great discrepancies in both infection and mortality rates between countries. Besides the biological and epidemiological factors, a multitude of social and economic criteria also influenced the extent to which these discrepancies appeared. Consequently, there is an active debate regarding the critical socio-economic...
Objective
To investigate the impact of atrial flutter (Afl) in the atrial arrhythmias classification task. We additionally advocate the use of a subject-based split for future studies in the field in order to avoid within-subject correlation which may lead to over-optimistic inferences. Finally, we demonstrate the effectiveness of the classifiers o...
We explore the role of non-ergodicity in the relationship between income inequality, the extent of concentration in the income distribution, and income mobility, the feasibility of an individual to change their position in the income rankings. For this purpose, we use
the properties of an established model for income growth that includes “resetting...
Diffusion with stochastic resetting is a paradigm of resetting processes. Standard renewal or master equation approach are typically used to study steady state and other transport properties such as average, mean squared displacement etc. What remains less explored is the two time point correlation functions whose evaluation is often daunting since...
The application of the fractional calculus in the mathematical modelling of relaxation processes in complex heterogeneous media has attracted a considerable amount of interest lately. The reason for this is the successful implementation of fractional stochastic and kinetic equations in the studies of non-Debye relaxation. In this work, we consider...
In this paper, an event-triggered Reinforcement Learning (RL) method is proposed for the optimal attitude consensus of multiple rigid body networks with unknown dynamics. Firstly, the consensus error is constructed through the attitude dynamics. According to the Bellman optimality principle, the implicit form of the optimal controller and the corre...
We study a heterogeneous diffusion process with position-dependent diffusion coefficient and Poissonian stochastic resetting. We find exact results for the mean squared displacement and the probability density function. The nonequilibrium steady state reached in the long time limit is studied. We also analyze the transition to the nonequilibrium st...
This paper addresses ontology and ethics of an AI agent called digital me. We define digital me as an autonomous, decision-making, and learning agent, representing an individual and having practically immortal life. It is assumed that digital me is equipped with the big-five personality model, ensuring that it provides a model of some aspects of a...
We explore the role of non-ergodicity in the relationship between income inequality, the extent of concentration in the income distribution, and mobility, the feasibility of an individual to change their position in the income distribution. For this purpose, we explore the properties of an established model for income growth that includes "resettin...
Substantial research has been dedicated to describing remote work, yet the understanding of working from home since the Covid-19 pandemic remains rather limited. While recognising the necessity for exploring employees' perceptions and interaction with technology as the ultimate requirement for a functional work-from-home, this study observes the fa...
Diffusion with stochastic resetting is a paradigm of resetting processes. Standard renewal or master equation approach are typically used to study steady state and other transport properties such as average, mean squared displacement etc. What remains less explored is the two time point correlation functions whose evaluation is often daunting since...
We study the effects of stochastic resetting on geometric Brownian motion with drift (GBM), a canonical stochastic multiplicative process for nonstationary and nonergodic dynamics. Resetting is a sudden interruption of a process, which consecutively renews its dynamics. We show that, although resetting renders GBM stationary, the resulting process...
We introduce non-Markovian SIR epidemic spreading model inspired by the characteristics of the COVID-19, by considering discrete- and continuous-time versions. The incubation period, delayed infectiousness and the distribution of the recovery period are modeled with general functions. By taking corresponding choice of these functions, it is shown t...
Purpose
As part of the COVID-19 preventive measures that have entirely impacted individuals' lives worldwide, remote work has been indicated as one of the most challenging aspects that have passed through great adaptation in the past months, highlighting the need for its better understanding. Following the fundamental theoretical frameworks of moti...
We study the effects of stochastic resetting on geometric Brownian motion (GBM), a canonical stochastic multiplicative process for non-stationary and non-ergodic dynamics. Resetting is a sudden interruption of a process such that the dynamics is renewed intermittently. Quite surprisingly, although resetting renders GBM stationary, the resulting pro...
In this work we consider the first encounter problems between a fixed and/or mobile target A and a moving trap B on Bethe Lattices and Cayley trees. The survival probabilities (SPs) of the target A on the both kinds of structures are considered analytically and compared. On Bethe Lattices, the results show that the fixed target will still prolong i...
Fluctuating environments are situations where the spatio-temporal stochasticity plays a significant role in the evolutionary dynamics. The study of the evolution of cooperation in these environments typically assumes a homogeneous, well mixed population, whose constituents are endowed with identical capabilities. In this paper, we generalize these...
This review addresses issues of various drift-diffusion and inhomogeneous advection problems with and without resetting on comb like structures. Both the Brownian diffusion search with a drift and the inhomogeneous advection search on the comb structures are analyzed. The analytical results are verified by numerical simulations in terms of coupled...
This paper addresses ontology and ethics of an AI agent called digital me. We define digital me as autonomous, decision-making, and learning agent, representing an individual and having practically immortal own life. It is assumed that digital me is equipped with the big-five personality model, ensuring that it provides a model of some aspects of a...
Classical option pricing schemes assume that the value of a financial asset follows a geometric Brownian motion (GBM). However, a growing body of studies suggest that a simple GBM trajectory is not an adequate representation for asset dynamics due to irregularities found when comparing its properties with empirical distributions. As a solution, we...
Myelin plays a crucial role in how well information travels between brain regions. Complementing the structural connectome, obtained with diffusion MRI tractography, with a myelin-sensitive measure could result in a more complete model of structural brain connectivity and give better insight into white-matter myeloarchitecture. In this work we weig...
Во текот на подолг временски период наназад, општествениот и политичкиот либерализам е прифатен како посакувана основа за социетална организација. Економската теорија се обиде да се приспособи на оваа ситуација и да развие софистицирани модели за да го оправда тврдењето дека индивидуите се самоорганизираат во општествено посакувана состојба. Сепак,...
In this paper, the resilient control for linear discrete-time multi-agent networks subjected to unconfined cyber-attacks is investigated based on a data-driven method. Firstly, according to the evolution of the original network dynamics, a distributed data-driven estimation algorithm is presented. On this basis, a switching control law is proposed...
Classical option pricing schemes assume that the value of a financial asset follows a geometric Brownian motion (GBM). However, a growing body of studies suggest that a simple GBM trajectory is not an adequate representation for asset dynamics due to irregularities found when comparing its properties with empirical distributions. As a solution, we...
We study random walks on complex networks with transition probabilities which depend on the current and previously visited nodes. By using an absorbing Markov chain we derive an exact expression for the mean first passage time between pairs of nodes, for a random walk with a memory of one step. We have analyzed one particular model of random walk,...
We study a distribution of times of the first arrivals to absorbing targets in turbulent diffusion, which is due to a multiplicative noise. Two examples of dynamical systems with a multiplicative noise are studied. The first one is a random process according to inhomogeneous diffusion, which is also known as a geometric Brownian motion in the Black...
Во текот на подолг временски период наназад, општествениот и политичкиот либерализам е прифатен како посакувана основа за социетална организација. Економската теорија се обиде да се прилагоди на оваа ситуација и да развие софистицирани модели за да го оправда тврдењето дека индивидуите се самоорганизираат во општествено посакувана состојба. Сепак,...
In this work we consider the first encounter problems between a fixed and/or mobile target A and a moving trap B on Bethe Lattices and Cayley trees. The survival probability (SP) of the target A on the both kinds of structures are analyzed analytically and compared. On Bethe Lattices, the results show that the fixed target will still prolong its su...
Myelin plays a crucial role in how well information travels between brain regions. Many neurological diseases affect the myelin in the white matter, making myelin-sensitive metrics derived from quantitative MRI of potential interest for early detection and prognosis of those conditions. Complementing the structural connectome, obtained with diffusi...
An amendment to this paper has been published and can be accessed via a link at the top of the paper.
We study a diffusion process on a three-dimensional comb under stochastic resetting. We consider three different types of resetting: global resetting from any point in the comb to the initial position, resetting from a finger to the corresponding backbone and resetting from secondary fingers to the main fingers. The transient dynamics along the bac...
We study two types of biased random walk over complex networks, which are based on local information. In the first approach, the transitions towards neighboring nodes with smaller degrees are favored. We show analytically that for well connected networks, biasing the random walk based on inverse of nodes' degrees leads to a uniform distribution of...
We call upon the research community to standardize efforts to use daily self-reported data about COVID-19 symptoms in the response to the pandemic and to form a collaborative consortium to maximize global gain while protecting participant privacy.
We present an analytical treatment of anomalous diffusion in a three-dimensional comb (xyz-comb) by using the Green's function approach. We derive exact analytical solutions for the propagators for an instantaneous point injection and natural boundary conditions. The marginal distributions for all three directions are obtained and the corresponding...
We study a diffusion process on a three-dimensional comb under stochastic resetting. We consider three different types of resetting: global resetting from any point in the comb to the initial position, resetting from a finger to the corresponding backbone and resetting from secondary fingers to the main fingers. The transient dynamics along the bac...
The expansion of global production networks has raised many important questions about the interdependence among countries and how future changes in the world economy are likely to affect the countries’ positioning in global value chains. We are approaching the structure and lengths of value chains from a completely different perspective than has be...
Diffusion on a three dimensional xyz-comb is analyzed. Three different types of resetting are considered. These are: (i) global resetting to the initial position, (ii) resetting to the x-backbone, and (iii) resetting to the main y-fingers. Analyzing the probability density functions, their stationary distributions and the mean squared displacements...
We analyze diffusion processes with finite propagation speed in heterogeneous media in terms of the telegrapher's or Cattaneo equation with position-dependent diffusion coefficient. In the diffusion limit of infinite-velocity propagation we recover the results for diffusion equations with position-dependent diffusivity. We observe various diffusive...
The expansion of global production networks has raised many important questions about the interdependence among countries and how future changes in the world economy are likely to affect the countries' positioning in global value chains. We are approaching the structure and lengths of value chains from a completely different perspective than has be...