scholarly journals Flocking behavior of the Cucker-Smale model under rooted leadership in a large coupling limit

2014 ◽  
Vol 72 (4) ◽  
pp. 689-701 ◽  
Author(s):  
Seung-Yeal Ha ◽  
Zhuchun Li ◽  
Marshall Slemrod ◽  
Xiaoping Xue
Keyword(s):  
Large Coupling ◽  
Flocking Behavior

scholarly journals Dipole radiation and beyond from axion stars in electromagnetic fields

2021 ◽  
Vol 2021 (6) ◽  
Author(s):  
Mustafa A. Amin ◽  
Andrew J. Long ◽  
Zong-Gang Mou ◽  
Paul M. Saffin
Keyword(s):  
Electromagnetic Fields ◽  
Parametric Resonance ◽  
Coupling Strength ◽  
Coupling Parameter ◽  
Strong Dependence ◽  
Dipole Radiation ◽  
Large Coupling ◽  
External Electromagnetic Fields ◽  
Order Of Magnitude ◽  
Dimensionless Coupling

Abstract We investigate the production of photons from coherently oscillating, spatially localized clumps of axionic fields (oscillons and axion stars) in the presence of external electromagnetic fields. We delineate different qualitative behaviour of the photon luminosity in terms of an effective dimensionless coupling parameter constructed out of the axion-photon coupling, and field amplitude, oscillation frequency and radius of the axion star. For small values of this dimensionless coupling, we provide a general analytic formula for the dipole radiation field and the photon luminosity per solid angle, including a strong dependence on the radius of the configuration. For moderate to large coupling, we report on a non-monotonic behavior of the luminosity with the coupling strength in the presence of external magnetic fields. After an initial rise in luminosity with the coupling strength, we see a suppression (by an order of magnitude or more compared to the dipole radiation approximation) at moderately large coupling. At sufficiently large coupling, we find a transition to a regime of exponential growth of the luminosity due to parametric resonance. We carry out 3+1 dimensional lattice simulations of axion electrodynamics, at small and large coupling, including non-perturbative effects of parametric resonance as well as backreaction effects when necessary. We also discuss medium (plasma) effects that lead to resonant axion to photon conversion, relevance of the coherence of the soliton, and implications of our results in astrophysical and cosmological settings.

scholarly journals Seasonal variability of SST fronts and winds on the southeastern continental shelf of Brazil

2019 ◽  
Vol 69 (11-12) ◽  
pp. 1387-1399 ◽  
Author(s):  
Huan-Huan Chen ◽  
Yiquan Qi ◽  
Yuntao Wang ◽  
Fei Chai
Keyword(s):  
Continental Shelf ◽  
Wind Stress ◽  
Seasonal Variability ◽  
Detection Algorithm ◽  
Coupling Coefficients ◽  
Seafloor Topography ◽  
Wind Stress Curl ◽  
Large Coupling ◽  
The Impact ◽  
Sst Fronts

Abstract Fourteen years (September 2002 to August 2016) of high-resolution satellite observations of sea surface temperature (SST) data are used to describe the frontal pattern and frontogenesis on the southeastern continental shelf of Brazil. The daily SST fronts are obtained using an edge-detection algorithm, and the monthly frontal probability (FP) is subsequently calculated. High SST FPs are mainly distributed along the coast and decrease with distance from the coastline. The results from empirical orthogonal function (EOF) decompositions reveal strong seasonal variability of the coastal SST FP with maximum (minimum) in the astral summer (winter). Wind plays an important role in driving the frontal activities, and high FPs are accompanied by strong alongshore wind stress and wind stress curl. This is particularly true during the summer, when the total transport induced by the alongshore component of upwelling-favorable winds and the wind stress curl reaches the annual maximum. The fronts are influenced by multiple factors other than wind forcing, such as the orientation of the coastline, the seafloor topography, and the meandering of the Brazil Current. As a result, there is a slight difference between the seasonality of the SST fronts and the wind, and their relationship was varying with spatial locations. The impact of the air-sea interaction is further investigated in the frontal zone, and large coupling coefficients are found between the crosswind (downwind) SST gradients and the wind stress curl (divergence). The analysis of the SST fronts and wind leads to a better understanding of the dynamics and frontogenesis off the southeastern continental shelf of Brazil, and the results can be used to further understand the air-sea coupling process at regional level.

scholarly journals On the effect of heterogeneity on flocking behavior and systemic risk

2017 ◽  
Vol 34 (3-4) ◽  
Author(s):  
Fei Fang ◽  
Yiwei Sun ◽  
Konstantinos Spiliopoulos
Keyword(s):  
Asymptotic Formula ◽  
Case Studies ◽  
Systemic Risk ◽  
Mean Field ◽  
Loss Probability ◽  
Loss Distribution ◽  
Interacting Diffusions ◽  
The Mean ◽  
Laplace Asymptotics ◽  
Flocking Behavior

AbstractThe goal of this paper is to study organized flocking behavior and systemic risk in heterogeneous mean-field interacting diffusions. We illustrate in a number of case studies the effect of heterogeneity in the behavior of systemic risk in the system, i.e., the risk that several agents default simultaneously as a result of interconnections. We also investigate the effect of heterogeneity on the “flocking behavior” of different agents, i.e., when agents with different dynamics end up following very similar paths and follow closely the mean behavior of the system. Using Laplace asymptotics, we derive an asymptotic formula for the tail of the loss distribution as the number of agents grows to infinity. This characterizes the tail of the loss distribution and the effect of the heterogeneity of the network on the tail loss probability.

Flocking Behavior of Shiny Cowbirds (Molothrus bonariensis) At Feeding Areas During the Daily Cycle

2016 ◽  
Vol 128 (2) ◽  
pp. 441-445 ◽  
Author(s):  
Gustavo H. Kattan ◽  
Anamaría Posada ◽  
Diego Fernando Arenas ◽  
José Luis Moreno ◽  
Ángela Barrera
Keyword(s):  
Daily Cycle ◽  
Molothrus Bonariensis ◽  
Flocking Behavior

Large coupling expansions for eigenenergies and Regge trajectories of the general even‐power potential with applications

1980 ◽  
Vol 21 (6) ◽  
pp. 1533-1538 ◽  
Author(s):  
L. K. Sharma ◽  
Jyoti Choubey ◽  
H. J. W. Müller‐Kirsten
Keyword(s):  
Large Coupling ◽  
Regge Trajectories

Enhanced Sensing and Activity Recognition System Using IoT for Healthcare

2021 ◽  
Vol 13 (2) ◽  
pp. 42-49
Author(s):  
Yamini G. ◽  
Gopinath Ganapathy
Keyword(s):  
Activity Recognition ◽  
Human Activity ◽  
Healthcare Services ◽  
Recognition System ◽  
Physical Activities ◽  
Video Data ◽  
Large Coupling ◽  
Sensing Technology ◽  
Medical Benefits ◽  
Primary Focus

Through the integration of advanced algorithms and smart sensing technology in healthcare services, huge medical benefits could be gained by the aged and sick people in determining their activity recognition. Human activity recognition (HAR) is still in the research for the past decades that promotes recognition of physical activities automatically. The main aim of HAR is to obtain and analyze the physical activities of a person, which could be promoted through several in-built sensors examined in the form of video data. Through this technique, necessary information could be obtained that also helps in preventing significant risks and also averts or alerts unfortunate events from happening. However, there is no particular categorization for human activity, and there is no description of the particular events to occur. The objective of this paper is to propose a healthcare information system based on IoT where enhancing activity recognition is the primary focus. Human activities are supposed to be diverse; it is necessary to choose appropriate sensors and the effective placement of those sensors in recognizing specific activities. One of the major challenges here is choosing the appropriate sensor for that particular instance and gathering data under particular circumstances. Due to the large coupling of sensors and their activity monitoring functionality, the solution to promote feasibility for the HAR predicament cannot be determined. A distinguishing feature of this paper is that it includes future users' perspectives.

scholarly journals Low-Amplitude Oscillations in the Inferior Olive: A Model Based on Electrical Coupling of Neurons With Heterogeneous Channel Densities

1997 ◽  
Vol 77 (5) ◽  
pp. 2736-2752 ◽  
Author(s):  
Yair Manor ◽  
John Rinzel ◽  
Idan Segev ◽  
Yosef Yarom
Keyword(s):  
Inferior Olive ◽  
Electrical Coupling ◽  
The Other ◽  
Sustained Oscillation ◽  
Large Coupling ◽  
Model Based ◽  
Subthreshold Oscillations ◽  
Coupling Current ◽  
Low Amplitude ◽  
Inferior Olivary

Manor, Yair, John Rinzel, Idan Segev, and Yosef Yarom. Low-amplitude oscillations in the inferior olive: a model based on electrical coupling of neurons with heterogeneous channel densities. J. Neurophysiol. 77: 2736–2752, 1997. The mechanism underlying subthreshold oscillations in inferior olivary cells is not known. To study this question, we developed a single-compartment, two-variable, Hodgkin-Huxley-like model for inferior olive neurons. The model consists of a leakage current and a low-threshold calcium current, whose kinetics were experimentally measured in slices. Depending on the maximal calcium and leak conductances, we found that a neuron model's response to current injection could be of four qualitatively different types: always stable, spontaneously oscillating, oscillating with injection of current, and bistable with injection of current. By the use of phase plane techniques, numerical integration, and bifurcation analysis, we subdivided the two-parameter space of channel densities into four regions corresponding to these behavioral types. We further developed, with the use of such techniques, an empirical rule of thumb that characterizes whether two cells when coupled electrically can generate sustained, synchronized oscillations like those observed in inferior olivary cells in slices, of low amplitude (0.1–10 mV) in the frequency range 4–10 Hz. We found that it is not necessary for either cell to be a spontaneous oscillator to obtain a sustained oscillation. On the other hand, two spontaneous oscillators always form an oscillating network when electrically coupled with any arbitrary coupling conductance. In the case of an oscillating pair of electrically coupled nonidentical cells, the coupling current varies periodically and is nonzero even for very large coupling values. The coupling current acts as an equalizing current to reconcile the differences between the two cells' ionic currents. It transiently depolarizes one cell and/or hyperpolarizes the other cell to obtain the regenerative response(s) required for the synchronized oscillation. We suggest that the subthreshold oscillations observed in the inferior olive can emerge from the electrical coupling between neurons with different channel densities, even if the inferior olive nucleus contains no or just a small proportion of spontaneously oscillating neurons.

FLOCKING STATES OF SELF-PROPELLING PARTICLES IN FREE SPACE

2007 ◽  
Vol 21 (23n24) ◽  
pp. 3954-3959 ◽  
Author(s):  
KWAN-TAI LEUNG ◽  
HSUAN-YI CHEN
Keyword(s):  
Continuum Model ◽  
Stationary Phases ◽  
Formation Flight ◽  
The Self ◽  
Particle Interactions ◽  
Simple Rules ◽  
Range Alignment ◽  
Steady State Solutions ◽  
Present Particle ◽  
Flocking Behavior

We present particle-based simulations for the flocking behavior of self-propelling particles. Built upon previous models, our models include realistic but simple rules for the self-propelling, drag, and inter-particle interactions. Depending on both the strength and range of the interactions, a host of stationary phases appear, including independent wandering, formation flight, swarm, and rotating vortex. Of particular interest, we determine that the rotating flock can only arise in the absence of long-range alignment. We also construct a phenomenological continuum model and obtain steady-state solutions for the rotating state.

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