4,225 research outputs found
Recommended from our members
New Women And New Negroes: Archetypal Womanhood In The 'Living Is Easy'
Englis
New Methods, Current Trends and Software Infrastructure for NLP
The increasing use of `new methods' in NLP, which the NeMLaP conference
series exemplifies, occurs in the context of a wider shift in the nature and
concerns of the discipline. This paper begins with a short review of this
context and significant trends in the field. The review motivates and leads to
a set of requirements for support software of general utility for NLP research
and development workers. A freely-available system designed to meet these
requirements is described (called GATE - a General Architecture for Text
Engineering). Information Extraction (IE), in the sense defined by the Message
Understanding Conferences (ARPA \cite{Arp95}), is an NLP application in which
many of the new methods have found a home (Hobbs \cite{Hob93}; Jacobs ed.
\cite{Jac92}). An IE system based on GATE is also available for research
purposes, and this is described. Lastly we review related work.Comment: 12 pages, LaTeX, uses nemlap.sty (included
Dipole Oscillations of a Bose-Einstein Condensate in Presence of Defects and Disorder
We consider dipole oscillations of a trapped dilute Bose-Einstein condensate
in the presence of a scattering potential consisting either in a localized
defect or in an extended disordered potential. In both cases the breaking of
superfluidity and the damping of the oscillations are shown to be related to
the appearance of a nonlinear dissipative flow. At supersonic velocities the
flow becomes asymptotically dissipationless.Comment: 4 pages, 4 figure
Persistent currents in a bosonic mixture in the ring geometry
In this paper we analyze the possibility of persistent currents of a
two-species bosonic mixture in the one-dimensional ring geometry. We extend the
arguments used by Bloch to obtain a criterion for the stability of persistent
currents for the two-species system. If the mass ratio of the two species is a
rational number, persistent currents can be stable at multiples of a certain
total angular momenta. We show that the Bloch criterion can also be viewed as a
Landau criterion involving the elementary excitations of the system. Our
analysis reveals that persistent currents at higher angular momenta are more
stable for the two-species system than previously thought.Comment: 20 pages and 7 figure
Mass flow through solid 4He induced by the fountain effect
Using an apparatus that allows superfluid liquid 4He to be in contact with
hcp solid \4he at pressures greater than the bulk melting pressure of the
solid, we have performed experiments that show evidence for 4He mass flux
through the solid and the likely presence of superfluid inside the solid. We
present results that show that a thermomechanical equilibrium in quantitative
agreement with the fountain effect exists between two liquid reservoirs
connected to each other through two superfluid-filled Vycor rods in series with
a chamber filled with solid 4He. We use the thermomechanical effect to induce
flow through the solid and measure the flow rate. On cooling, mass flux appears
near T = 600 mK and rises smoothly as the temperature is lowered. Near T = 75
mK a sharp drop in the flux is present. The flux increases as the temperature
is reduced below 75 mK. We comment on possible causes of this flux minimum.Comment: 20 pages, 22 figures, 7 table
The overlap parameter across an inverse first order phase transition in a 3D spin-glass
We investigate the thermodynamic phase transition taking place in the
Blume-Capel model in presence of quenched disorder in three dimensions (3D). In
particular, performing Exchange Montecarlo simulations, we study the behavior
of the order parameters accross the first order phase transition and its
related coexistence region. This transition is an Inverse Freezing.Comment: 9 pages, 6 figures, Contribution to the XII International Workshop on
Complex System
A Degenerate Bose-Fermi Mixture of Metastable Atoms
We report the observation of simultaneous quantum degeneracy in a dilute
gaseous Bose-Fermi mixture of metastable atoms. Sympathetic cooling of helium-3
(fermion) by helium-4 (boson), both in the lowest triplet state, allows us to
produce ensembles containing more than 10^6 atoms of each isotope at
temperatures below 1 micro-Kelvin, and achieve a fermionic degeneracy parameter
of T/Tf=0.45. Due to their high internal energy, the detection of individual
metastable atoms with sub-nanosecond time resolution is possible, permitting
the study of bosonic and fermionic quantum gases with unprecedented precision.
This may lead to metastable helium becoming the mainstay of quantum atom
optics.Comment: 4 pages, 3 figures submitted to PR
Intelligent multimedia indexing and retrieval through multi-source information extraction and merging
This paper reports work on automated meta-data\ud
creation for multimedia content. The approach results\ud
in the generation of a conceptual index of\ud
the content which may then be searched via semantic\ud
categories instead of keywords. The novelty\ud
of the work is to exploit multiple sources of\ud
information relating to video content (in this case\ud
the rich range of sources covering important sports\ud
events). News, commentaries and web reports covering\ud
international football games in multiple languages\ud
and multiple modalities is analysed and the\ud
resultant data merged. This merging process leads\ud
to increased accuracy relative to individual sources
The random Blume-Capel model on cubic lattice: first order inverse freezing in a 3D spin-glass system
We present a numerical study of the Blume-Capel model with quenched disorder
in 3D. The phase diagram is characterized by spin-glass/paramagnet phase
transitions of both first and second order in the thermodynamic sense.
Numerical simulations are performed using the Exchange-Monte Carlo algorithm,
providing clear evidence for inverse freezing. The main features at criticality
and in the phase coexistence region are investigated. The whole inverse
freezing transition appears to be first order. The second order transition
appears to be in the same universality class of the Edwards-Anderson model. The
nature of the spin-glass phase is analyzed by means of the finite size scaling
behavior of the overlap distribution functions and the four-spins real-space
correlation functions. Evidence for a replica symmetry breaking-like
organization of states is provided.Comment: 18 pages, 24 figures, 7 table
- …