2,425 research outputs found
Concept development of a tendon arm manipulator and anthropomorphic robotic hand
AMETEK/ORED inhouse research and development efforts leading toward a next-generation robotic manipulator arm and end-effector technology is summarized. Manipulator arm development has been directed toward a multiple-degree-of-freedom, flexible, tendon-driven concept referred to here as a Tendon Arm Manipulator (TAM). End-effector development has been directed toward a three-fingered, dextrous, tendon-driven, anthropomorphic configuration which is referred to as an Anthropomorphic Robotic Hand (ARH). Key technology issues are identified for both concepts
Gravitational Radiation from a Naked Singularity -- Odd-Parity Perturbation --
It has been suggested that a naked singularity may be a good candidate for a
strong gravitational wave burster. The naked singularity occurs in the generic
collapse of an inhomogeneous dust ball. We study odd-parity mode of
gravitational waves from a naked singularity of the Lema\^{\i}tre-Tolman-Bondi
space-time. The wave equation for gravitational waves are solved by numerical
integration using the single null coordinate. The result is that the naked
singularity is not a strong source of the odd-parity gravitational radiation
although the metric perturbation grows in the central region. Therefore, the
Cauchy horizon in this space-time would be marginally stable against odd-parity
perturbations.Comment: 14 pages, 7 figures, to be published in Prog. Theor. Phys. Final
version, with minor changes. Reference 13 adde
Gravitational Radiation from a Naked Singularity. II - Even-Parity Perturbation -
A naked singularity occurs in the generic collapse of an inhomogeneous dust
ball. We study the even-parity mode of gravitational waves from a naked
singularity of the Lema\^{\i}tre-Tolman-Bondi spacetime. The wave equations for
gravitational waves are solved by numerical integration using the single null
coordinate. The result implies that the metric perturbation grows when it
approaches the Cauchy horizon and diverges there, although the naked
singularity is not a strong source of even-parity gravitational radiation.
Therefore, the Cauchy horizon in this spacetime should be unstable with respect
to linear even-parity perturbations.Comment: 16 pages, 5 figures, errors and typos corrected, final versio
Physical Processes in Naked Singularity Formation
Gravitational collapse is one of the most fruitful subjects in gravitational
physics. It is well known that singularity formation is inevitable in complete
gravitational collapse. It was conjectured that such a singularity should be
hidden by horizons if it is formed from generic initial data with physically
reasonable matter fields. Many possible counterexamples to this conjecture have
been proposed over the past three decades, although none of them has proved to
be sufficiently generic. In these examples, there appears a singularity that is
not hidden by horizons. This singularity is called a `naked singularity.' The
appearance of a naked singularity represents the formation of an observable
high-curvature, strong-gravity region. In this paper we review examples of
naked singularity formation and recent progress in research of observable
physical processes - gravitational radiation and quantum particle creation -
from a forming naked singularity.Comment: 76 pages, 25 figure file
Relativistic gyratons in asymptotically AdS spacetime
We study the gravitational field of a spinning radiation beam-pulse (a
gyraton) in a D-dimensional asymptotically AdS spacetime. It is shown that the
Einstein equations for such a system reduce to a set of two linear equations in
a (D-2)-dimensional space. By solving these equations we obtain a metric which
is an exact solution of gravitational equations with the (negative)
cosmological constant. The explicit metrics for 4D and 5D gyratons in
asymptotically AdS spacetime are given and their properties are discussed.Comment: 10 page
The spherical symmetry Black hole collapse in expanding universe
The spherical symmetry Black holes are considered in expanding background.
The singularity line and the marginally trapped tube surface behavior are
discussed. In particular, we address the conditions whether dynamical horizon
forms for these cosmological black holes. We also discuss about the
cosmological constant effect on these black hole and the redshift of the light
which comes from the marginally trapped tube surface.Comment: 7 pages, 3 figures. Accepted for publication in International Journal
of Modern Physics D (IJMPD). arXiv admin note: text overlap with
arXiv:gr-qc/0308033 and arXiv:gr-qc/030611
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