6,207 research outputs found
Resource design in constrained networks for network lifetime increase
As constrained "things" become increasingly integrated with the Internet and accessible for interactive communication, energy efficient ways to collect, aggregate, and share data over such constrained networks are needed. In this paper, we propose the use of constrained RESTful environments interfaces to build resource collections having a network lifetime increase in mind. More specifically, based on existing atomic resources, collections are created/designed to become available as new resources, which can be observed. Such resource design should not only match client's interests, but also increase network lifetime as much as possible. For this to happen, energy consumption should be balanced/fair among nodes so that node depletion is delayed. When compared with previous approaches, results show that energy efficiency and network lifetime can be increased while reducing control/registration messages, which are used to set up or change observations
Boundary-induced phase transitions in traffic flow
Boundary-induced phase transitions are one of the surprising phenomena
appearing in nonequilibrium systems. These transitions have been found in
driven systems, especially the asymmetric simple exclusion process. However, so
far no direct observations of this phenomenon in real systems exists. Here we
present evidence for the appearance of such a nonequilibrium phase transition
in traffic flow occurring on highways in the vicinity of on- and off-ramps.
Measurements on a German motorway close to Cologne show a first-order
nonequilibrium phase transition between a free-flow phase and a congested
phase. It is induced by the interplay of density waves (caused by an on-ramp)
and a shock wave moving on the motorway. The full phase diagram, including the
effect of off-ramps, is explored using computer simulations and suggests means
to optimize the capacity of a traffic network.Comment: 5 figures, revte
Removing non-stationary, non-harmonic external interference from gravitational wave interferometer data
We describe a procedure to identify and remove a class of non-stationary and
non-harmonic interference lines from gravitational wave interferometer data.
These lines appear to be associated with the external electricity main
supply, but their amplitudes are non-stationary and they do not appear at
harmonics of the fundamental supply frequency. We find an empirical model able
to represent coherently all the non-harmonic lines we have found in the power
spectrum, in terms of an assumed reference signal of the primary supply input
signal. If this signal is not available then it can be reconstructed from the
same data by making use of the coherent line removal algorithm that we have
described elsewhere. All these lines are broadened by frequency changes of the
supply signal, and they corrupt significant frequency ranges of the power
spectrum. The physical process that generates this interference is so far
unknown, but it is highly non-linear and non-stationary. Using our model, we
cancel the interference in the time domain by an adaptive procedure that should
work regardless of the source of the primary interference. We have applied the
method to laser interferometer data from the Glasgow prototype detector, where
all the features we describe in this paper were observed. The algorithm has
been tuned in such a way that the entire series of wide lines corresponding to
the electrical interference are removed, leaving the spectrum clean enough to
detect signals previously masked by them. Single-line signals buried in the
interference can be recovered with at least 75 % of their original signal
amplitude.Comment: 14 pages, 5 figures, Revtex, psfi
Duality and exact correlations for a model of heat conduction
We study a model of heat conduction with stochastic diffusion of energy. We
obtain a dual particle process which describes the evolution of all the
correlation functions. An exact expression for the covariance of the energy
exhibits long-range correlations in the presence of a current. We discuss the
formal connection of this model with the simple symmetric exclusion process.Comment: 19 page
Vacuum entanglement enhancement by a weak gravitational field
Separate regions in space are generally entangled, even in the vacuum state.
It is known that this entanglement can be swapped to separated Unruh-DeWitt
detectors, i.e., that the vacuum can serve as a source of entanglement. Here,
we demonstrate that, in the presence of curvature, the amount of entanglement
that Unruh-DeWitt detectors can extract from the vacuum can be increased.Comment: 6 pages, 1 figur
Coherent Line Removal: Filtering out harmonically related line interference from experimental data, with application to gravitational wave detectors
We describe a new technique for removing troublesome interference from
external coherent signals present in the gravitational wave spectrum. The
method works when the interference is present in many harmonics, as long as
they remain coherent with one another. The method can remove interference even
when the frequency changes. We apply the method to the data produced by the
Glasgow laser interferometer in 1996 and the entire series of wide lines
corresponding to the electricity supply frequency and its harmonics are
removed, leaving the spectrum clean enough to detect possible signals
previously masked by them. We also study the effects of the line removal on the
statistics of the noise in the time domain. We find that this technique seems
to reduce the level of non-Gaussian noise present in the interferometer and
therefore, it can raise the sensitivity and duty cycle of the detectors.Comment: 14 pages, 8 figures, Revtex, psfig. To appear in Phys. Rev.
A new numerical method to construct binary neutron star initial data
We present a new numerical method for the generation of binary neutron star
initial data using a method along the lines of the the Wilson-Mathews or the
closely related conformal thin sandwich approach. Our method uses six different
computational domains, which include spatial infinity. Each domain has its own
coordinates which are chosen such that the star surfaces always coincide with
domain boundaries. These properties facilitate the imposition of boundary
conditions. Since all our fields are smooth inside each domain, we are able to
use an efficient pseudospectral method to solve the elliptic equations
associated with the conformal thin sandwich approach. Currently we have
implemented corotating configurations with arbitrary mass ratios, but an
extension to arbitrary spins is possible. The main purpose of this paper is to
introduce our new method and to test our code for several different
configurations.Comment: 18 pages, 8 figures, 1 tabl
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