4,314 research outputs found
Properties of pedestrians walking in line: Stepping behavior
In human crowds, interactions among individuals give rise to a variety of
self-organized collective motions that help the group to effectively solve the
problem of coordination. However, it is still not known exactly how humans
adjust their behavior locally, nor what are the direct consequences on the
emergent organization. One of the underlying mechanisms of adjusting individual
motions is the stepping dynamics. In this paper, we present first quantitative
analysis on the stepping behavior in a one-dimensional pedestrian flow studied
under controlled laboratory conditions. We find that the step length is
proportional to the velocity of the pedestrian, and is directly related to the
space available in front of him, while the variations of the step duration are
much smaller. This is in contrast with locomotion studies performed on isolated
pedestrians and shows that the local density has a direct influence on the
stepping characteristics. Furthermore, we study the phenomena of
synchronization -walking in lockstep- and show its dependence on flow
densities. We show that the synchronization of steps is particularly important
at high densities, which has direct impact on the studies of optimizing
pedestrians flow in congested situations. However, small synchronization and
antisynchronization effects are found also at very low densities, for which no
steric constraints exist between successive pedestrians, showing the natural
tendency to synchronize according to perceived visual signals.Comment: 8 pages, 5 figure
Properties of pedestrians walking in line - Fundamental diagrams
We present experimental results obtained for a one-dimensional flow using
high precision motion capture. The full pedestrians' trajectories are obtained.
In this paper, we focus on the fundamental diagram, and on the relation between
the instantaneous velocity and spatial headway (distance to the predecessor).
While the latter was found to be linear in previous experiments, we show that
it is rather a piecewise linear behavior which is found if larger density
ranges are covered. Indeed, our data clearly exhibits three distinct regimes in
the behavior of pedestrians that follow each other. The transitions between
these regimes occur at spatial headways of about 1.1 and 3 m, respectively.
This finding could be useful for future modeling.Comment: 9 figures, 3 table
The experiences of women with polycystic ovary syndrome on a very low-calorie diet
The research was funded by an educational grant from LighterLife. Broom was the Medical Director for LighterLife at the time of the research. Johnson is the Head of Nutrition and Research at LighterLife. The authors report no other conflicts of interest in this work.Peer reviewedPublisher PD
Frozen shuffle update for an asymmetric exclusion process on a ring
We introduce a new rule of motion for a totally asymmetric exclusion process
(TASEP) representing pedestrian traffic on a lattice. Its characteristic
feature is that the positions of the pedestrians, modeled as hard-core
particles, are updated in a fixed predefined order, determined by a phase
attached to each of them. We investigate this model analytically and by Monte
Carlo simulation on a one-dimensional lattice with periodic boundary
conditions. At a critical value of the particle density a transition occurs
from a phase with `free flow' to one with `jammed flow'. We are able to
analytically predict the current-density diagram for the infinite system and to
find the scaling function that describes the finite size rounding at the
transition point.Comment: 16 page
Antibunched photons emitted by a dc-biased Josephson junction
We show experimentally that a dc biased Josephson junction in series with a high-enough-impedance microwave resonator emits antibunched photons. Our resonator is made of a simple microfabricated spiral coil that resonates at 4.4 GHz and reaches a 1.97kΩ characteristic impedance. The second order correlation function of the power leaking out of the resonator drops down to 0.3 at zero delay, which demonstrates the antibunching of the photons emitted by the circuit at a rate of 6Ă10^7 photons per second. Results are found in quantitative agreement with our theoretical predictions. This simple scheme could offer an efficient and bright single-photon source in the microwave domain
Inverse Compton Scenarios for the TeV Gamma-Ray Emission of the Galactic Centre
The intense Compton cooling of ultra-relativistic electrons in the
Klein-Nishina regime in radiation dominated environments, such as that found in
the Galactic Centre, may result in radically different electron spectra than
those produced by Synchrotron cooling. We explore these effects and their
impact on the X-ray and gamma-ray spectra produced in electron accelerators in
this region in comparison to elsewhere in our galaxy. We discuss the broad-band
emission expected from the newly discovered pulsar wind nebula G 359.95-0.04
and the possible relationship of this X-ray source to the central TeV gamma-ray
source HESS J1745-290. Finally we discuss the possible relationship of the
Galactic Centre INTEGRAL source IGR J1745.6-2901 to the TeV emission.Comment: 10 pages, 7 figures, to appear in ApJ 65
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