81,686 research outputs found
Teleprinter uses thermal printing technique
Alphameric/facsimile printer receives serial digital data in the form of a specified number of bits per group and prints it on thermally sensitive paper. A solid state shift-register memorizes the incoming serial digital data
Spectral properties of the tandem Jackson network, seen as a quasi-birth-and-death process
Quasi-birth-and-death (QBD) processes with infinite ``phase spaces'' can
exhibit unusual and interesting behavior. One of the simplest examples of such
a process is the two-node tandem Jackson network, with the ``phase'' giving the
state of the first queue and the ``level'' giving the state of the second
queue. In this paper, we undertake an extensive analysis of the properties of
this QBD. In particular, we investigate the spectral properties of Neuts's
R-matrix and show that the decay rate of the stationary distribution of the
``level'' process is not always equal to the convergence norm of R. In fact, we
show that we can obtain any decay rate from a certain range by controlling only
the transition structure at level zero, which is independent of R. We also
consider the sequence of tandem queues that is constructed by restricting the
waiting room of the first queue to some finite capacity, and then allowing this
capacity to increase to infinity. We show that the decay rates for the finite
truncations converge to a value, which is not necessarily the decay rate in the
infinite waiting room case. Finally, we show that the probability that the
process hits level n before level 0 given that it starts in level 1 decays at a
rate which is not necessarily the same as the decay rate for the stationary
distribution.Comment: Published at http://dx.doi.org/10.1214/105051604000000477 in the
Annals of Applied Probability (http://www.imstat.org/aap/) by the Institute
of Mathematical Statistics (http://www.imstat.org
The Angular Size and Proper Motion of the Afterglow of GRB 030329
The bright, nearby (z=0.1685) gamma-ray burst of 29 March 2003 has presented
us with the first opportunity to directly image the expansion of a GRB. This
burst reached flux density levels at centimeter wavelengths more than 50 times
brighter than any previously studied event. Here we present the results of a
VLBI campaign using the VLBA, VLA, Green Bank, Effelsberg, Arecibo, and
Westerbork telescopes that resolves the radio afterglow of GRB 030329 and
constrains its rate of expansion. The size of the afterglow is found to be
\~0.07 mas (0.2 pc) 25 days after the burst, and 0.17 mas (0.5 pc) 83 days
after the burst, indicating an average velocity of 3-5 c. This expansion is
consistent with expectations of the standard fireball model. We measure the
projected proper motion of GRB 030329 in the sky to <0.3 mas in the 80 days
following the burst. In observations taken 52 days after the burst we detect an
additional compact component at a distance from the main component of 0.28 +/-
0.05 mas (0.80 pc). The presence of this component is not expected from the
standard model.Comment: 12 pages including 2 figures, LaTeX. Accepted to ApJ Letters on May
14, 200
Technical management techniques for identification and control of industrial safety and pollution hazards
Constructive recommendations are suggested for pollution problems from offshore energy resources industries on outer continental shelf. Technical management techniques for pollution identification and control offer possible applications to space engineering and management
A Statistical Description of AGN Jet Evolution from the VLBA Imaging and Polarimetry Survey (VIPS)
A detailed analysis of the evolution of the properties of core-jet systems
within the VLBA Imaging and Polarimetry Survey (VIPS) is presented. We find a
power-law relationship between jet intensity and width that suggests for the
typical jet, little if any energy is lost as it moves away from its core. Using
VLA images at 1.5 GHz, we have found evidence that parsec-scale jets tend to be
aligned with the the direction of emission on kiloparsec scales. We also found
that this alignment improves as the jets move farther from their cores on
projected scales as small as ~50-100 pc. This suggests that realignment of jets
on these projected scales is relatively common. We typically find a modest
amount of bending (a change in jet position angle of ~5 deg.) on these scales,
suggesting that this realignment may typically occur relatively gradually.Comment: Accepted to ApJ, 20 pages, 8 figure
Effect of environment on biological burden during spacecraft assembly
Determining effects of environment on accumulation of biological burden on spacecraft during assembl
Gauge Invariant Effective Stress-Energy Tensors for Gravitational Waves
It is shown that if a generalized definition of gauge invariance is used,
gauge invariant effective stress-energy tensors for gravitational waves and
other gravitational perturbations can be defined in a much larger variety of
circumstances than has previously been possible. In particular it is no longer
necessary to average the stress-energy tensor over a region of spacetime which
is larger in scale than the wavelengths of the waves and it is no longer
necessary to restrict attention to high frequency gravitational waves.Comment: 11 pages, RevTe
Magnetic oscillations in planar systems with the Dirac-like spectrum of quasiparticle excitations II: transport properties
The quantum magnetic oscillations of electrical (Shubnikov de Haas effect)
and thermal conductivities are studied for graphene which represents a
distinctive example of planar systems with a linear, Dirac-like spectrum of
quasiparticle excitations. We show that if a utmost care was taken to separate
electron and phonon contributions in the thermal conductivity, the oscillations
of electron thermal conductivity, and the Lorenz number,
would be observable in the low field (less than a few Teslas) regime.Comment: 11 pages, RevTeX4, 6 EPS figures; 2 references, 1 figure and one more
section are added; final version published in PR
Quantum interface between an electrical circuit and a single atom
We show how to bridge the divide between atomic systems and electronic
devices by engineering a coupling between the motion of a single ion and the
quantized electric field of a resonant circuit. Our method can be used to
couple the internal state of an ion to the quantized circuit with the same
speed as the internal-state coupling between two ions. All the well-known
quantum information protocols linking ion internal and motional states can be
converted to protocols between circuit photons and ion internal states. Our
results enable quantum interfaces between solid state qubits, atomic qubits,
and light, and lay the groundwork for a direct quantum connection between
electrical and atomic metrology standards.Comment: Supplemental material available on reques
The Enigmatic Radio Afterglow of GRB 991216
We present wide-band radio observations spanning from 1.4 GHz to 350 GHz of
the afterglow of GRB 991216, taken from 1 to 80 days after the burst. The
optical and X-ray afterglow of this burst were fairly typical and are explained
by a jet fireball. In contrast, the radio light curve is unusual in two
respects: (a) the radio light curve does not show the usual rise to maximum
flux on timescales of weeks and instead appears to be declining already on day
1 and (b) the power law indices show significant steepening from the radio
through the X-ray bands. We show that the standard fireball model, in which the
afterglow is from a forward shock, is unable to account for (b) and we conclude
that the bulk of the radio emission must arise from a different source. We
consider two models, neither of which can be ruled out with the existing data.
In the first (conventional) model, the early radio emission is attributed to
emission from the reverse shock as in the case of GRB 990123. We predict that
the prompt optical emission would have been as bright (or brighter) than 8th
magnitude. In the second (exotic) model, the radio emission originates from the
forward shock of an isotropically energetic fireball (10^54 erg) expanding into
a tenuous medium (10^-4 cm^-3). The resulting fireball would remain
relativistic for months and is potentially resolvable with VLBI techniques.
Finally, we note that the near-IR bump of the afterglow is similar to that seen
in GRB 971214 and no fireball model can explain this bump.Comment: ApJ, submitte
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