12,721 research outputs found
Modeling the Behavior of the Surface to Liquid Interfaces in an Electrolytic Liquid
Understanding the mechanism for charge transfer between electrodes within an electrolyte dissolved in water is vital to better understanding the sources of electrical noise in the system. This research compares the electrical properties of liquid top gated graphene devices with the properties of two metal probes to model the system. By measuring the impedance of these systems at different frequencies, it is possible to develop a model of their electrical properties and to consider techniques to improve signal to noise at graphene interfaces
Spinodal Decomposition in High Temperature Gauge Theories
After a rapid increase in temperature across the deconfinement temperature , pure gauge theories exhibit unstable long wavelength fluctuations in
the approach to equilibrium. This phenomenon is analogous to spinodal
decomposition observed in condensed matter physics, and also seen in models of
disordered chiral condensate formation. At high temperature, the unstable modes
occur only in the range , where is on the order
of the Debye screening mass . Equilibration always occurs via spinodal
decomposition for at temperatures and for SU(3) for . For SU(3) at temperatures , nucleation may replace
spinodal decomposition as the dominant equilibration mechanism. Monte Carlo
simulations of SU(2) lattice gauge theory exhibit the predicted phenomena. The
observed value of is in reasonable agreement with a value predicted from
previous lattice measurements of .Comment: minor revisions, 16 pages, 6 figures, RevTe
Analytic Methods for Optimizing Realtime Crowdsourcing
Realtime crowdsourcing research has demonstrated that it is possible to
recruit paid crowds within seconds by managing a small, fast-reacting worker
pool. Realtime crowds enable crowd-powered systems that respond at interactive
speeds: for example, cameras, robots and instant opinion polls. So far, these
techniques have mainly been proof-of-concept prototypes: research has not yet
attempted to understand how they might work at large scale or optimize their
cost/performance trade-offs. In this paper, we use queueing theory to analyze
the retainer model for realtime crowdsourcing, in particular its expected wait
time and cost to requesters. We provide an algorithm that allows requesters to
minimize their cost subject to performance requirements. We then propose and
analyze three techniques to improve performance: push notifications, shared
retainer pools, and precruitment, which involves recalling retainer workers
before a task actually arrives. An experimental validation finds that
precruited workers begin a task 500 milliseconds after it is posted, delivering
results below the one-second cognitive threshold for an end-user to stay in
flow.Comment: Presented at Collective Intelligence conference, 201
A Phenomenological Treatment of Chiral Symmetry Restoration and Deconfinement
A phenomenological expression for the thermodynamic potential of gluons and
quarks is constructed which incorporates the features of deconfinement and
chiral symmetry restoration known from lattice simulations. The thermodynamic
potential is a function of the Polyakov loop and chiral condensate expectation
values. The gluonic sector uses a successful model for pure (SU(N_c)) gauge
theories in which the Polyakov loop eigenvalues are the fundamental order
parameters for deconfinement. The quark sector is given by a Nambu-Jona-Lasinio
model in which a constant background (A_0) field couples the chiral condensate
to the Polyakov loop. We consider the case of (N_f = 2) in detail. For two
massless quarks, we find a second order chiral phase transition. Confinement
effects push the transition to higher temperatures, but the entropy associated
with the gluonic sector acts in the opposite direction. For light mass quarks,
only a rapid crossover occurs. For sufficiently heavy quarks, a first order
deconfinement transition emerges. This simplest model has one adjustable
parameter, which can be set from the chiral transition temperature for light
quarks. It predicts all thermodynamic quantities as well as the behavior of the
chiral condensate and the Polyakov loop over a wide range of temperatures.Comment: 3 pages, 4 eps figures, Lattice 2002 conference contribution,
Lattice2002(nonzerot
Autonomic physiological data associated with simulator discomfort
The development of a physiological monitoring capability for the Army's advanced helicopter simulator facility is reported. Additionally, preliminary physiological data is presented. Our objective was to demonstrate the sensitivity of physiological measures in this simulator to self-reported simulator sickness. The data suggested that heart period, hypergastria, and skin conductance level were more sensitive to simulator sickness than were vagal tone and normal electrogastric activity
Characterization of low-noise quasi-optical SIS mixers for the submillimeter band
We report on the development of low-noise quasi-optical SIS mixers for the frequency range 400-850 GHz. The mixers utilize twin-slot antennas, two-junction tuning circuits, and Nb-trilayer junctions. Fourier-transform spectrometry has been used to verify that the frequency response of the devices is well predicted by computer simulations. The 400-850 GHz frequency band can be covered with four separate fixed-tuned mixers. We measure uncorrected double-sideband receiver noise temperatures around 5hν/kB to 700 GHz, and better than 540 K at 808 GHz. These results are among the best reported to date for broadband heterodyne receivers
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