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1
Content available remote

Indifferents as an Interface between Contra and Pro

100%
Malarz K., Kułakowski K.
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issue 4
695-699
EN
In most sociophysical simulations on public opinion, only two opinions are allowed: Pro and Contra. However, in all political elections many people do not vote. Here we analyse two models of dynamics of public opinion, taking into account Indifferent voters: (i) the Sznajd model with symmetry Pro-Contra, (ii) the outflow one move voter model, where Contra's are converted to Indifferent by their Pro neighbours. Our results on the Sznajd model are in an overall agreement with the results of the mean field approach and with those known from the initial model formulation. The simulation on the voter model shows that an amount of Contra's who remain after convertion depends on the network topology.
2
Content available remote

The Sznajd Dynamics on a Directed Clustered Network

100%
Malarz K., Kułakowski K.
Acta Physica Polonica A
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2008
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vol. 114
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issue 3
581-588
EN
The Sznajd model is investigated in the directed ErdH os-Rényi network with the clusterization coefficient enhanced to 0.3 by the method of Holme and Kim. Within additional triangles, all six links are present. In this network, some nodes preserve the minority opinion. The time τof getting equilibrium is found to follow the log-normal distribution and it increases linearly with the system size. Its dependence on the initial opinion distribution is different from the analytical results for fully connected networks.
3
Content available remote

Bounded confidence model: addressed information maintain diversity of opinions

100%
Malarz K., Kułakowski K.
Acta Physica Polonica A
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2012
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vol. 121
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issue 2B
B-86-B-88
EN
A community of agents is subject to a stream of messages, which are represented as points on a plane of issues. Messages are sent by media and by agents themselves. Messages from media shape the public opinion. They are unbiased, i.e. positive and negative opinions on a given issue appear with equal frequencies. In our previous work, the only criterion to receive a message by an agent is if the distance between this message and the ones received earlier does not exceed the given value of the tolerance parameter. Here we introduce a possibility to address a message to a given neighbour. We show that this option reduces the unanimity effect, what improves the collective performance.
4
Content available remote

On a Combinatorial Aspect of Fashion

100%
Krawczyk M., Kułakowski K.
Acta Physica Polonica A
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2013
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vol. 123
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issue 3
560-563
EN
Simulations are performed according to the Axelrod model of culture dissemination, with modified mechanism of repulsion. Previously, repulsion was considered by Radillo-Diaz et al. as dependent on a predefined threshold. Here the probabilities of attraction and repulsion are calculated from the number of cells in the same states. We also investigate the influence of some homogeneity, introduced to the initial state. As the result of the probabilistic definition of repulsion, the ordered state vanishes. A small cluster of a few percent of population is retained only if in the initial state a set of agents is prepared in the same state. We conclude that the modelled imitation is successful only with respect to agents, and not only their features.
5
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Metastable Magnetic Structures in the Blume-Capel Model

81%
Kułakowski K., Antoniuk M., Del Moral A., Gawroński P.
Acta Physica Polonica A
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2000
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vol. 97
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issue 5
893-896
EN
We discuss a first-order phase transition from non-magnetic to magnetic phase at T=0. New results are presented on a spontaneously formed magnetic phase and its energy in the C15 atomic structure, in the presence of the antiferromagnetic interaction. A dynamic phase diagram is constructed for the phase transition. The results are discussed in the context of the pressure-driven phase transition, which was observed experimentally in YMn_{2}.
6
Content available remote

Opinion Formation in an Open System and the Spiral of Silence

81%
Gawroński P., Nawojczyk M., Kułakowski K.
Acta Physica Polonica A
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2015
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vol. 127
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issue 3A
A-45-A-50
EN
A new model is formulated of the sociological effect of the spiral of silence, introduced by Elisabeth Noelle-Neumann in 1974. The probability that a new opinion is openly expressed decreases with the difference between this new opinion and the perceived opinion of the majority. We also assume that the system is open, i.e. some people enter and some leave during the process of the opinion formation. An influence of a leader is simulated by a comparison of two runs of the simulation, where the leader has different opinion in each run. The difference of the mean expressed opinions in these two runs persists long after the leader's leave.
7
Content available remote

Evacuation in the Social Force Model is not Stationary

81%
Gawroński P., Kułakowski K., Kämpf M., Kantelhardt J.
Acta Physica Polonica A
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2012
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vol. 121
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issue 2B
B-77-B-81
EN
An evacuation process is simulated within the Social Force Model. Thousand pedestrians are leaving a room by one exit. We investigate the stationarity of the distribution of time lags between instants when two successive pedestrians cross the exit. The exponential tail of the distribution is shown to gradually vanish. Taking fluctuations apart, the time lags decrease in time till there are only about 50 pedestrians in the room, then they start to increase. This suggests that at the last stage the flow is laminar. In the first stage, clogging events slow the evacuation down. As they are more likely for larger crowds, the flow is not stationary. The data are investigated with detrended fluctuation analysis and return interval statistics, and no pattern transition is found between the stages of the process.
8
Content available remote

If Others Jump to the Queue Front, How Long I Will Wait?

81%
Krawczyk M., Gronek P., Nawojczyk M., Kułakowski K.
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EN
Two models of a queue are proposed: a human queue and two lines of vehicles before a narrowing. In both models, a queuer tries to evaluate his waiting time, taking into account the delay caused by intruders who jump to the queue front. As the collected statistics of such events is very limited, the evaluation can give very long times. The results provide an example, when direct observations should be supplemented by an inference from the context.
9
Content available remote

Magnetic Anisotropy and Magnetostriction of Atom Pairs

81%
Kułakowski K., Maksymowicz A., Magdoń M.
Acta Physica Polonica A
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1994
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vol. 85
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issue 5
869-873
EN
We calculated one-electron hopping contribution to two-ion magnetic anisotropy and shape magnetostriction in amorphous 3d-alloys. Calculations were performed in the narrow band limit and include spin-orbit coupling, the Zeeman orbital and spin magnetic moments terms with possible partial effective quenching of the orbital magnetic moments in metals. The parameters for numerical calculations are expected to correspond to pairs of Fe atoms with the spin-orbit coupling A= 0.03 eV and hopping integrals of about 3 eV. The magnetic anisotropy K changes its sign at some value Δ_{K} of effective magnetic splitting Δ proportional to the magnetization. Then the local easy axis which is parallel to the direction of the pair for small Δ switches to perpendicular easy plane case. K is nearly linear vs. Δ for small Δ and varies roughly as Δ^{3} for large splitting. The dependence of magnetostriction B on Δ is similar to that of magnetic anisotropy K(Δ). For small values of Δ the coefficient B is also linear. Magnetostriction changes its sign at Δ_{B} and becomes positive for Δ greater than Δ_{K}.
10
Content available remote

Exchange Magnetostriction in Disordered 2D Ising Ferromagnets

81%
Kawecka-Magiera B., Maksymowicz A., Kułakowski K., Lenda A.
Acta Physica Polonica A
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1997
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vol. 91
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issue 2
297-301
EN
We investigate volume and shape magnetoelastic strains of a 2D anisotropic Ising alloy with partial atomic order. Three possible origins of shape strain are distinguished: (i) anisotropy of elastic constants, (ii) anisotropy of magnetic bonds and (iii) anisotropy of the spatial derivatives of magnetic bonds. None of these mechanisms vanishes above the Curie temperature. Equilibrium strains are expressed in terms of anisotropic spin-spin nearest-neighbours correlation functions. These functions are calculated against temperature, both in ferromagnetic and paramagnetic phase. Shape strain decreases monotonously with temperature for the mechanisms (i) and (iii), and has a maximum near the Curie temperature for the case (ii). The results may be relevant for multilayer magnetic systems.
11
Content available remote

The Heaping Effect in the Survey Data on the Number of Friends

71%
Nawojczyk M., Stojkow M., Żuchowska-Skiba D., Krawczyk M., Kułakowski K.
Acta Physica Polonica A
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2018
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vol. 133
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issue 6
1417-1420
EN
The number of acquaintances is relevant for modeling social networks. Here we consider the data on the declared number of friends, as collected in 2000, 2007 and 2015 from Polish respondents above the age of 50. We demonstrate that the answers on the number of friends show sharp maxima at 10, 15, 20 and sometimes 30, which accompany a broader peak between 0 and 8. These results do not change qualitatively with sex and age of the respondents. The effect, known as data heaping, can be detected as a deviation from the Benford law.
12
Content available remote

Naming Boys after U.S. Presidents in 20th Century

62%
Kułakowski K., Kulczycki P., Misztal K., Dydejczyk A., Gronek P., Krawczyk M.
Acta Physica Polonica A
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2016
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vol. 129
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issue 5
1038-1044
EN
This paper deals with the popularity of given names in the United States, for the period 1885-2009. Based on the data obtained from the website of U.S. Social Security Administration, it was demonstrated that the fashion of naming babies after the incumbent American president passed away in the '60s. At the same time, however, examples were given, mainly concerning celebrities, after whom babies are still named. The above theses were strengthened with the aid of quantitative data analysis by constructing an index dedicated to the specifics of the task under investigation. The obtained results were discussed in the terms of the rally effect and of the Simmel theory of fashion.
13
Content available remote

Strategies in Crowd and Crowd Structure

52%
Gawroński P., Malarz K., Krawczyk M., Malinowski J., Kupczak A., Sikora W., Kułakowski K., Wąs J., Kantelhardt J.
Acta Physica Polonica A
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2013
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vol. 123
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issue 3
522-525
EN
In an emergency situation, imitation of strategies of neighbours can lead to an order-disorder phase transition, where spatial clusters of pedestrians adopt the same strategy. We assume that there are two strategies, cooperating and competitive, which correspond to a smaller or larger desired velocity. The results of our simulations within the Social Force Model indicate that the ordered phase can be detected as an increase of spatial order of positions of the pedestrians in the crowd.
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