14,069 research outputs found
Traffic Analysis in Random Delaunay Tessellations and Other Graphs
In this work we study the degree distribution, the maximum vertex and edge
flow in non-uniform random Delaunay triangulations when geodesic routing is
used. We also investigate the vertex and edge flow in Erd\"os-Renyi random
graphs, geometric random graphs, expanders and random -regular graphs.
Moreover we show that adding a random matching to the original graph can
considerably reduced the maximum vertex flow.Comment: Submitted to the Journal of Discrete Computational Geometr
Scalar Field Oscillations Contributing to Dark Energy
We use action-angle variables to describe the basic physics of coherent
scalar field oscillations in the expanding universe. These analytical mechanics
methods have some advantages, like the identification of adiabatic invariants.
As an application, we show some instances of potentials leading to equations of
state with , thus contributing to the dark energy that causes the
observed acceleration of the universe.Comment: 17 pages, 6 figures, Latex file. Sec.II reduced, discussion on sound
speed added in Sec.IV, new references added. Accepted for publication in
Physical Review
On simulation of local fluxes in molecular junctions
We present a pedagogical review of current density simulation in molecular
junction models indicating its advantages and deficiencies in analysis of local
junction transport characteristics. In particular, we argue that current
density is a universal tool which provides more information than traditionally
simulated bond currents, especially when discussing inelastic processes.
However, current density simulations are sensitive to choice of basis and
electronic structure method. We note that discussing local current conservation
in junctions one has to account for source term caused by open character of the
system and intra-molecular interactions. Our considerations are illustrated
with numerical simulations of a benzenedithiol molecular junction.Comment: 10 pages, 6 figure
High Resolution X-Ray Spectra of Capella: Initial Results from the Chandra High Energy Transmission Grating Spectrometer
High resolution spectra of the active binary Capella (G8 III + G1 III)
covering the energy range 0.4-8.0 keV (1.5-30 Angstroms) show a large number of
emission lines, demonstrating the performance of the HETGS. A preliminary
application of plasma diagnostics provides information on coronal temperatures
and densities. Lines arising from different elements in a range of ionization
states indicate that Capella has plasma with a broad range of temperatures,
from log T = 6.3 to 7.2, generally consistent with recent results from
observations with the Extreme Ultraviolet Explorer (EUVE) and the Advanced
Satellite for Cosmology and Astrophysics (ASCA). The electron density is
determined from He-like O VII lines, giving the value N_e=10^10 cm^-3 at
T_e=2*10^6 K; He-like lines formed at higher temperatures give only upper
limits to the electron density. The density and emission measure from O VII
lines together indicate that the coronal loops are significantly smaller than
the stellar radius.Comment: 9 pages, 3 figures (1 color) accepted for ApJ
Zonal asymmetries in middle atmospheric ozone and water vapour derived from Odin satellite data 2001â2010
Stationary wave patterns in middle atmospheric ozone (O<sub>3</sub>) and water vapour (H<sub>2</sub>O) are an important factor in the atmospheric circulation, but there is a strong gap in diagnosing and understanding their configuration and origin. Based on Odin satellite data from 2001 to 2010 we investigate the stationary wave patterns in O<sub>3</sub> and H<sub>2</sub>O as indicated by the seasonal long-term means of the zonally asymmetric components O<sub>3</sub>* = O<sub>3</sub>-[O<sub>3</sub>] and H<sub>2</sub>O* = H<sub>2</sub>O-[H<sub>2</sub>O] ([O<sub>3</sub>], [H<sub>2</sub>O]: zonal means). At mid- and polar latitudes we find a pronounced wave one pattern in both constituents. In the Northern Hemisphere, the wave patterns increase during autumn, maintain their strength during winter and decay during spring, with maximum amplitudes of about 10â20 % of the zonal mean values. During winter, the wave one in O<sub>3</sub>* shows a maximum over the North Pacific/Aleutians and a minimum over the North Atlantic/Northern Europe and a double-peak structure with enhanced amplitude in the lower and in the upper stratosphere. The wave one in H<sub>2</sub>O* extends from the lower stratosphere to the upper mesosphere with a westward shift in phase with increasing height including a jump in phase at upper stratosphere altitudes. In the Southern Hemisphere, similar wave patterns occur mainly during southern spring. By comparing the observed wave patterns in O<sub>3</sub>* and H<sub>2</sub>O* with a linear solution of a steady-state transport equation for a zonally asymmetric tracer component we find that these wave patterns are primarily due to zonally asymmetric transport by geostrophically balanced winds, which are derived from observed temperature profiles. In addition temperature-dependent photochemistry contributes substantially to the spatial structure of the wave pattern in O<sub>3</sub>* . Further influences, e.g., zonal asymmetries in eddy mixing processes, are discussed
Collective modes and correlations in one-component plasmas
The static and time-dependent potential and surface charge correlations in a
plasma with a boundary are computed for different shapes of the boundary. The
case of a spheroidal or spherical one-component plasma is studied in detail
because experimental results are available for such systems. Also, since there
is some knowlegde both experimental and theoretical about the electrostatic
collective modes of these plasmas, the time-dependent correlations are computed
using a method involving these modes.Comment: 20 pages, plain TeX, submitted to Phys. Rev.
User quality of experience of mulsemedia applications
User Quality of Experience (QoE) is of fundamental importance in multimedia applications and has been extensively studied for decades. However, user QoE in the context of the emerging multiple-sensorial media (mulsemedia) services, which involve different media components than the traditional multimedia applications, have not been comprehensively studied. This article presents the results of subjective tests which have investigated user perception of mulsemedia content. In particular, the impact of intensity of certain mulsemedia components including haptic and airflow on user-perceived experience are studied. Results demonstrate that by making use of mulsemedia the overall user enjoyment levels increased by up to 77%
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