5,033 research outputs found
Modeling Spacing Distribution of Queuing Vehicles in Front of a Signalized Junction Using Random-Matrix Theory
Modeling of headway/spacing between two consecutive vehicles has many
applications in traffic flow theory and transport practice. Most known
approaches only study the vehicles running on freeways. In this paper, we
propose a model to explain the spacing distribution of queuing vehicles in
front of a signalized junction based on random-matrix theory. We show that the
recently measured spacing distribution data well fit the spacing distribution
of a Gaussian symplectic ensemble (GSE). These results are also compared with
the spacing distribution observed for car parking problem. Why
vehicle-stationary-queuing and vehicle-parking have different spacing
distributions (GSE vs GUE) seems to lie in the difference of driving patterns
Inter-vehicle gap statistics on signal-controlled crossroads
We investigate a microscopical structure in a chain of cars waiting at a red
signal on signal-controlled crossroads. Presented is an one-dimensional
space-continuous thermodynamical model leading to an excellent agreement with
the data measured.Moreover, we demonstrate that an inter-vehicle spacing
distribution disclosed in relevant traffic data agrees with the thermal-balance
distribution of particles in the thermodynamical traffic gas (discussed in [1])
with a high inverse temperature (corresponding to a strong traffic congestion).
Therefore, as we affirm, such a system of stationary cars can be understood as
a specific state of the traffic sample operating inside a congested traffic
stream.Comment: 6 pages, 4 figures, accepted for publication in J. Phys. A: Math.
Theo
Chemically specifi C multiscale modeling of clay-polymer nanocomposites reveals intercalation dynamics, tactoid self-assembly and emergent materials properties
A quantitative description is presented of the dynamical process of polymer intercalation into clay tactoids and the ensuing aggregation of polymerentangled tactoids into larger structures, obtaining various characteristics of these nanocomposites, including clay-layer spacings, out-of-plane clay-sheet bending energies, X-ray diffractograms, and materials properties. This model of clay-polymer interactions is based on a three-level approach, which uses quantum mechanical and atomistic descriptions to derive a coarse-grained yet chemically specifi c representation that can resolve processes on hitherto inaccessible length and time scales. The approach is applied to study collections of clay mineral tactoids interacting with two synthetic polymers, poly(ethylene glycol) and poly(vinyl alcohol). The controlled behavior of layered materials in a polymer matrix is centrally important for many engineering and manufacturing applications. This approach opens up a route to computing the properties of complex soft materials based on knowledge of their chemical composition, molecular structure, and processing conditions.This work was funded in part by the EU FP7 MAPPER project (grant number RI-261507) and the Qatar National Research Fund (grant number 09–260–1–048). Supercomputing time was provided by PRACE on JUGENE (project PRA044), the Hartree Centre (Daresbury Laboratory) on BlueJoule and BlueWonder via the CGCLAY project, and on HECToR and ARCHER, the UK national supercomputing facility at the University of Edinburgh, via EPSRC through grants EP/F00521/1, EP/E045111/1, EP/I017763/1 and the UK Consortium on Mesoscopic Engineering Sciences (EP/L00030X/1). The authors are grateful to Professor Julian Evans for stimulating discussions during the course of this project. Data-storage and management services were provided by EUDAT (grant number 283304)
Population mixing due to dipole-dipole interactions in a 1D array of multilevel atoms
We examine theoretically how dipole-dipole interactions arising from multiple
photon scattering lead to a modified distribution of ground state populations
in a driven, ordered 1D array of multilevel atoms. Specifically, we devise a
level configuration in which a ground-state population accumulated due solely
to dipole-dipole interactions can be up to 20\% in regimes accessible to
current experiments with neutral atom arrays. For much larger systems, the
steady state can consist of an equal distribution of population across the
ground state manifold. Our results illustrate how dipole-dipole interactions
can be accentuated through interference, and regulated by the geometry of
ordered atom arrays. More generally, control techniques for multilevel atoms
that can be degraded by multiple scattering, such as optical pumping, will
benefit from an improved understanding and control of dipole-dipole
interactions available in ordered arrays.Comment: paper is now identical to published versio
Random Matrices and Chaos in Nuclear Spectra
We speak of chaos in quantum systems if the statistical properties of the
eigenvalue spectrum coincide with predictions of random-matrix theory. Chaos is
a typical feature of atomic nuclei and other self-bound Fermi systems. How can
the existence of chaos be reconciled with the known dynamical features of
spherical nuclei? Such nuclei are described by the shell model (a mean-field
theory) plus a residual interaction. We approach the question by using a
statistical approach (the two-body random ensemble): The matrix elements of the
residual interaction are taken to be random variables. We show that chaos is a
generic feature of the ensemble and display some of its properties, emphasizing
those which differ from standard random-matrix theory. In particular, we
display the existence of correlations among spectra carrying different quantum
numbers. These are subject to experimental verification.Comment: 17 pages, 20 figures, colloquium article, submitted to Reviews of
Modern Physic
Analysis of nucleus-nucleus collisions at high energies and Random Matrix Theory
We propose a novel statistical approach to the analysis of experimental data
obtained in nucleus-nucleus collisions at high energies which borrows from
methods developed within the context of Random Matrix Theory. It is applied to
the detection of correlations in momentum distributions of emitted particles.
We find good agreement between the results obtained in this way and a standard
analysis based on the method of effective mass spectra and two-pair correlation
function often used in high energy physics. The method introduced here is free
from unwanted background contributions.Comment: 11 pages, 10 figure
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