26,392 research outputs found
Research and development at ORNL/CESAR towards cooperating robotic systems for hazardous environments
One of the frontiers in intelligent machine research is the understanding of how constructive cooperation among multiple autonomous agents can be effected. The effort at the Center for Engineering Systems Advanced Research (CESAR) at the Oak Ridge National Laboratory (ORNL) focuses on two problem areas: (1) cooperation by multiple mobile robots in dynamic, incompletely known environments; and (2) cooperating robotic manipulators. Particular emphasis is placed on experimental evaluation of research and developments using the CESAR robot system testbeds, including three mobile robots, and a seven-axis, kinematically redundant mobile manipulator. This paper summarizes initial results of research addressing the decoupling of position and force control for two manipulators holding a common object, and the path planning for multiple robots in a common workspace
Bethe Ansatz for a Quantum Supercoset Sigma Model
We study an integrable conformal OSp(2m + 2|2m) supercoset model as an analog
to the AdS_5 X S^5 superstring world-sheet theory. Using the known S-matrix for
this system, we obtain integral equations for states of large particle density
in an SU(2) sector, which are exact in the sigma model coupling constant. As a
check, we derive as a limit the general classical Bethe equation of Kazakov,
Marshakov, Minahan, and Zarembo. There are two distinct quantum expansions
around the well-studied classical limit, the lambda^{-1/2} effects and the 1/J
effects. Our approach captures the first type, but not the second.Comment: 30 pages, 1 figure, v2: references adde
Hydrodynamics of Monolayer Domains at the Air-Water Interface
Molecules at the air-water interface often form inhomogeneous layers in which
domains of different densities are separated by sharp interfaces. Complex
interfacial pattern formation may occur through the competition of short- and
long-range forces acting within the monolayer. The overdamped hydrodynamics of
such interfacial motion is treated here in a general manner that accounts for
dissipation both within the monolayer and in the subfluid. Previous results on
the linear stability of interfaces are recovered and extended, and a
formulation applicable to the nonlinear regime is developed. A simplified
dynamical law valid when dissipation in the monolayer itself is negligible is
also proposed. Throughout the analysis, special attention is paid to the
dependence of the dynamical behavior on a characteristic length scale set by
the ratio of the viscosities in the monolayer and in the subphase.Comment: 12 pages, RevTeX, 4 ps figures, accepted in Physics of Fluids
Cold dark matter and primordial superheavy particles
The hypothesis that cold dark matter consists of primordial superheavy
particles, the decay of short lifetime component of which led to the observable
mass of matter while long living component survived up to modern times
manifesting its presence in high energetic cosmic rays particles is
investigated.Comment: LaTeX, 5 pages, no figure
Statistical Mechanics of Relativistic One-Dimensional Self-Gravitating Systems
We consider the statistical mechanics of a general relativistic
one-dimensional self-gravitating system. The system consists of -particles
coupled to lineal gravity and can be considered as a model of
relativistically interacting sheets of uniform mass. The partition function and
one-particle distitrubion functions are computed to leading order in
where is the speed of light; as results for the
non-relativistic one-dimensional self-gravitating system are recovered. We find
that relativistic effects generally cause both position and momentum
distribution functions to become more sharply peaked, and that the temperature
of a relativistic gas is smaller than its non-relativistic counterpart at the
same fixed energy. We consider the large-N limit of our results and compare
this to the non-relativistic case.Comment: latex, 60 pages, 22 figure
A model for fluctuating inflaton coupling: (s)neutrino induced adiabatic perturbations and non-thermal leptogenesis
We discuss an unique possibility of generating adiabatic density
perturbations and leptogenesis from the spatial fluctuations of the inflaton
decay rate. The key assumption is that the initial isocurvature perturbations
are created in the right handed sneutrino sector during inflation which is then
converted into adiabatic perturbations when the inflaton decays. We discuss
distinct imprints on the cosmic micro wave background radiation, which can
distinguish non-thermal versus thermal leptogenesis.Comment: 4 pages, version to be published in PR
A VLA Survey For Faint Compact Radio Sources in the Orion Nebula Cluster
We present Karl G. Janksy Very Large Array (VLA) 1.3 cm, 3.6 cm, and 6 cm
continuum maps of compact radio sources in the Orion Nebular Cluster. We
mosaicked 34 square arcminutes at 1.3 cm, 70 square arcminutes at 3.6 cm and
109 square arcminutes at 6 cm, containing 778 near-infrared detected YSOs and
190 HST-identified proplyds (with significant overlap between those
characterizations). We detected radio emission from 175 compact radio sources
in the ONC, including 26 sources that were detected for the first time at these
wavelengths. For each detected source we fit a simple free-free and dust
emission model to characterize the radio emission. We extrapolate the free-free
emission spectrum model for each source to ALMA bands to illustrate how these
measurements could be used to correctly measure protoplanetary disk dust masses
from sub-millimeter flux measurements. Finally, we compare the fluxes measured
in this survey with previously measured fluxes for our targets, as well as four
separate epochs of 1.3 cm data, to search for and quantify variability of our
sources.Comment: 13 pages, 6 figures, 4 tables, ApJ, in pres
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