arXiv subjects

Przemysław Gawroński

Publications and source records attributed to Przemysław Gawroński.

5 recordsLinked to original sources

arXiv2022

Instability of oscillations in the Rosenzweig-MacArthur model of one consumer and two resources

The system of two resources $R_1$, $R_2$ and one consumer $C$ is investigated within the Rosenzweig-MacArthur model with Holling type II functional response. The rates $β_i$ of consumption of resources $i=1,2$ are coupled by the condition $β_1+β_2=1$. The dynamic switching is introduced by a maximization of $C$: $dβ_1/dt=(1/τ) dC/dβ_1$, where the characteristic time $τ$ is large but finite. The space of parameters where both resources coexist is explored numerically. The results indicate that oscillations of $C$ and mutually synchronized $R_i$ which appear at $β_i=0.5$ are destabilized for $β_i$ larger or smaller. Then, the system is driven to one of fixed points where either $β_1>0.5$ and $R_1<R_2$ or the opposite. This behaviour is explained as an inability of the consumer to change the preferred resource, once it is chosen.

physics.soc-ph↗

arXiv2016

Gain and loss of esteem, direct reciprocity and Heider balance

The effect of gain and loss of esteem is introduced into the equations of time evolution of social relations, hostile or friendly, in a group of actors. The equations allow for asymmetric relations. We prove that in the presence of this asymmetry, the majority of stable solutions are jammed states, i.e. the Heider balance is not attained there. A phase diagram is constructed with three phases: the jammed phase, the balanced phase with two mutually hostile groups, and the phase of so-called paradise, where all relations are friendly.

physics.soc-ph↗

arXiv2015

Simulated hysteresis loop of a bent Fe-rich glass-covered wire

We present new micromagnetic simulations, where an influence of the wire shape on the spatial distribution of internal magnetoelastic stress is taken into account. Local magnetoelastic anisotropy is approximated to be uniaxial, with spatial dependence due to the stress distribution. The hysteresis loop is calculated with the $mumax^3$ software for the wire volume and separately for selected parts of the wire, including the surface. The bistability of the calculated surface hysteresis loops depends on the behaviour of the neighboring part of the inner core, most close to the surface element where the surface loop is measured.

cond-mat.mtrl-sci↗

arXiv2011

Remagnetization process of Fe-Rich Amorphous Wire under Time Dependent Tensile Stress

An influence of a time dependent external tensile stress on the remagnetization process of a bistable wire is investigated experimentally and numerically. The dependence of the magnetization on the frequency of the tensile stress is analyzed in terms of the magnetic domain structure of Fe-rich wires. The dependence of the switching field on the phase of the tensile stress is presented and reproduced by a straightforward numerical simulation of the remagnetization process in a bistable wire. There, the input is the experimental static dependences of the switching field and of the magnetization of the wire on an external tensile stress. The presented dependences of the switching field and the magnetization on the periodic tensile stress allow to tune the shape of the hysteresis loop, what can be useful in constructing a phase sensor.

cond-mat.mtrl-sci↗

arXiv2010

Crowd dynamics - being stuck

We consider a crowd of N persons trying to exit some area trough a small exit. The probability is calculated that an individual is able to withdraw from the crowd under one's own steam. The problem is simulated within the generalized force model (D. Helbing et al., Nature 407 (2000) 487), and all model parameters are taken from this paper. The results indicate, that in a crowd of 150 persons, this probability is not greater than ten percent. We also evaluate the number of helpers necessary to get the above probability of fifty percent.

physics.soc-ph↗