27,242 research outputs found
Compact artificial hand
A relatively simple, compact artificial hand, is described which includes hooks pivotally mounted on first frame to move together and apart. The first frame is rotatably mounted on a second frame to enable "turning at the wrist" movement without limitation. The second frame is pivotally mounted on a third frame to permit 'flexing at the wrist' movement. A hook-driving motor is fixed to the second frame but has a shaft that drives a speed reducer on the first frame which, in turn, drives the hooks. A second motor mounted on the second frame, turns a gear on the first frame to rotate the first frame and the hooks thereon. A third motor mounted on the third frame, turns a gear on a second frame to pivot it
Governing dynamics by squeezing in a system of cold trapped ions
We consider a system of laser-cooled ions in a linear harmonic trap and study
the phenomenon of squeezing exchange between their internal and motional
degrees of freedom. An interesting relation between the quantum noise reduction
(squeezing) and the dynamical evolution is found when the internal and motional
subsystems are prepared in properly squeezed (intelligent) states.
Specifically, the evolution of the system is fully governed by the relative
strengths of spectroscopic and motional squeezing, including the phenomenon of
total cancellation of the interaction when the initial squeezing parameters are
equal.Comment: REVTeX, 5 pages, 2 figures, to appear in Phys. Rev.
P-V Criticality in Quasitopological Gravity
We investigate the thermodynamic behaviour of AdS quasitopological black hole
solutions in the context of extended thermodynamic phase space, in which the
cosmological constant induces a pressure with a conjugate volume. We find that
the third order exact quasitopological solution exhibits features consistent
with the third order Lovelock solutions for positive quasitopological coupling,
including multiple reentrant phase transitions and isolated critical points.
For negative coupling we find the first instances of both reentrant phase
transitions and thermodynamic singularities in five dimensions, along with
other modified thermodynamic behaviour compared to Einstein-AdS-Gauss Bonnet
gravity.Comment: 20 pages, 15 figures, REVTeX 4-1; updated to match published versio
Symmetry Breaking Using Value Precedence
We present a comprehensive study of the use of value precedence constraints
to break value symmetry. We first give a simple encoding of value precedence
into ternary constraints that is both efficient and effective at breaking
symmetry. We then extend value precedence to deal with a number of
generalizations like wreath value and partial interchangeability. We also show
that value precedence is closely related to lexicographical ordering. Finally,
we consider the interaction between value precedence and symmetry breaking
constraints for variable symmetries.Comment: 17th European Conference on Artificial Intelligenc
Recommended from our members
Dietary manipulation of broiler breeder growth through the feeding of conjugated linoleic acid
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
Quasiclassical Equations of Motion for Nonlinear Brownian Systems
Following the formalism of Gell-Mann and Hartle, phenomenological equations
of motion are derived from the decoherence functional formalism of quantum
mechanics, using a path-integral description. This is done explicitly for the
case of a system interacting with a ``bath'' of harmonic oscillators whose
individual motions are neglected. The results are compared to the equations
derived from the purely classical theory. The case of linear interactions is
treated exactly, and nonlinear interactions are compared using classical and
quantum perturbation theory.Comment: 24 pages, CALT-68-1848 (RevTeX 2.0 macros
On the Standard Approach to Renormalization Group Improvement
Two approaches to renormalization-group improvement are examined: the
substitution of the solutions of running couplings, masses and fields into
perturbatively computed quantities is compared with the systematic sum of all
the leading log (LL), next-to-leading log (NLL) etc. contributions to
radiatively corrected processes, with n-loop expressions for the running
quantities being responsible for summing N^{n}LL contributions. A detailed
comparison of these procedures is made in the context of the effective
potential V in the 4-dimensional O(4) massless model,
showing the distinction between these procedures at two-loop order when
considering the NLL contributions to the effective potential V.Comment: 6 page
- …