2,285 research outputs found
Collective decision making in cohesive flocks
Most of us must have been fascinated by the eye catching displays of
collectively moving animals. Schools of fish can move in a rather orderly
fashion and then change direction amazingly abruptly. There are a huge number
of further examples both from the living and the non-living world for phenomena
during which the many interacting, permanently moving units seem to arrive at a
common behavioural pattern taking place in a short time. As a paradigm of this
type of phenomena we consider the problem of how birds arrive at a decision
resulting in their synchronized landing. We introduce a simple model to
interpret this process. Collective motion prior to landing is modelled using a
simple self-propelled particle (SPP) system with a new kind of boundary
condition, while the tendency and the sudden propagation of the intention of
landing is introduced through rules analogous to the random field Ising model
in an external field. We show that our approach is capable of capturing the
most relevant features of collective decision making in a system of units with
a variance of individual intentions and being under an increasing level of
pressure to switch states. We find that as a function of the few parameters of
our model the collective switching from the flying to the landing state is
indeed much sharper than the distribution of the individual landing intentions.
The transition is accompanied by a number of interesting features discussed in
this report
HIV-pozitív én-elbeszélések. Metadiegetikus és extradiegetikus narratívák szerepe az identifikációban - (Szub)kultúra létrejötte az elbeszélésben/elbeszéltségben
Azonos című doktori értekezés tézisei
Signatures of fractal clustering of aerosols advected under gravity
Aerosols under chaotic advection often approach a strange attractor. They
move chaotically on this fractal set but, in the presence of gravity, they have
a net vertical motion downwards. In practical situations, observational data
may be available only at a given level, for example at the ground level. We
uncover two fractal signatures of chaotic advection of aerosols under the
action of gravity. Each one enables the computation of the fractal dimension
of the strange attractor governing the advection dynamics from data
obtained solely at a given level. We illustrate our theoretical findings with a
numerical experiment and discuss their possible relevance to meteorology.Comment: Accepted for publication in Phys. Rev. E (Rapid Communications
Az „Idegbizottság” szerepe a homoszexualitás magyarországi dekriminalizációjában
Tanulmányunkban a másként „megoldhatatlannak” tűnő társadalmi kérdések medikalizációjának menetét illusztráljuk egy 20. századi magyarországi történeti példán keresztül: a homoszexuális cselekmények 1961-es magyarországi dekriminalizációjának hátterét vizsgáljuk meg 1958-ból származó, korábban ismeretlen levéltári források fényében
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