1,656 research outputs found
A robust braille recognition system
Braille is the most effective means of written communication between
visually-impaired and sighted people. This paper describes a new system
that recognizes Braille characters in scanned Braille document pages. Unlike
most other approaches, an inexpensive flatbed scanner is used and the system
requires minimal interaction with the user. A unique feature of this system is
the use of context at different levels (from the pre-processing of the image
through to the post-processing of the recognition results) to enhance robustness
and, consequently, recognition results. Braille dots composing characters are
identified on both single and double-sided documents of average quality with
over 99% accuracy, while Braille characters are also correctly recognised in
over 99% of documents of average quality (in both single and double-sided
documents)
Environment-induced dynamical chaos
We examine the interplay of nonlinearity of a dynamical system and thermal
fluctuation of its environment in the ``physical limit'' of small damping and
slow diffusion in a semiclassical context and show that the trajectories of
c-number variables exhibit dynamical chaos due to the thermal fluctuations of
the bath.Comment: Revtex, 4 pages and 4 figure
Fluctuation-dissipation relationship in chaotic dynamics
We consider a general N-degree-of-freedom dissipative system which admits of
chaotic behaviour. Based on a Fokker-Planck description associated with the
dynamics we establish that the drift and the diffusion coefficients can be
related through a set of stochastic parameters which characterize the steady
state of the dynamical system in a way similar to fluctuation-dissipation
relation in non-equilibrium statistical mechanics. The proposed relationship is
verified by numerical experiments on a driven double well system.Comment: Revtex, 23 pages, 2 figure
Probing structure-function relationships of serine hydrolases and proteases with carbamate and thiocarbamate inhibitors
Benzene-1,3-di-N-n-octylcarbamate (1), benzene-1-hydroxyl-3-N-n-octylcarbamate (2), benzene-1,3-di-N-n-ocztylthiocarbamate (3), and benzene-1-hydroxyl-3-N-n-octylthiocarbamate (4) are synthesized from 1,3-benzene-diol and are characterized as the pseudo-substrate inhibitors of acetylcholinesterase, butyrylcholinesterase, cholesterol esterase, lipase, trypsin, and chymotrypsin. For these six enzyme inhibitions by 1-4, the pK(i) values are linearly correlated with their log k(i) values - Bronsted plots. Therefore, 1-4 inhibit these enzymes through a common mechanism. Moreover, both pK(i) and log k(i) values for the inhibitions by 1,3, and 4 are linearly correlated with both pK(i) and log k(i) values for the inhibitions by 2, respectively. Thus, the pK(i) values for the inhibitions by 2 are defined as the nucleophilicity constants of these enzymes (n(enzyme)). The log k(2) values for the inhibitions by 1-4 are also linearly correlated with the n(enzyme) values. Therefore, the nucleophilicity for serine hydrolases and proteases toward 1-4 also applies the Swain-Scott correlations
BPS Electromagnetic Waves on Giant Gravitons
We find new 1/8-BPS giant graviton solutions in , carrying
three angular momenta along , and investigate their properties.
Especially, we show that nonzero worldvolume gauge fields are admitted
preserving supersymmetry. These gauge field modes can be viewed as
electromagnetic waves along the compact D3 brane, whose Poynting vector
contributes to the BPS angular momenta. We also analyze the (nearly-)spherical
giant gravitons with worldvolume gauge fields in detail. Expressing the
in Hopf fibration ( fibred over ), the wave propagates along the
fiber.Comment: 25 pages, no figures, v2: references adde
Predicted Infrared and Raman Spectra for Neutral Ti_8C_12 Isomers
Using a density-functional based algorithm, the full IR and Raman spectra are
calculated for the neutral Ti_8C_12 cluster assuming geometries of Th, Td, D2d
and C3v symmetry. The Th pentagonal dodecahedron is found to be dynamically
unstable. The calculated properties of the relaxed structure having C3v
symmetry are found to be in excellent agreement with experimental gas phase
infrared results, ionization potential and electron affinity measurements.
Consequently, the results presented may be used as a reference for further
experimental characterization using vibrational spectroscopy.Comment: 6 pages, 5 figures. Physical Review A, 2002 (in press
General 2 charge geometries
Two charge BPS horizon free supergravity geometries are important in
proposals for understanding black hole microstates. In this paper we construct
a new class of geometries in the NS1-P system, corresponding to solitonic
strings carrying fermionic as well as bosonic condensates. Such geometries are
required to account for the full microscopic entropy of the NS1-P system. We
then briefly discuss the properties of the corresponding geometries in the dual
D1-D5 system.Comment: 44 page
Polarimetric Properties of Flux-Ropes and Sheared Arcades in Coronal Prominence Cavities
The coronal magnetic field is the primary driver of solar dynamic events.
Linear and circular polarization signals of certain infrared coronal emission
lines contain information about the magnetic field, and to access this
information, either a forward or an inversion method must be used. We study
three coronal magnetic configurations that are applicable to polar-crown
filament cavities by doing forward calculations to produce synthetic
polarization data. We analyze these forward data to determine the
distinguishing characteristics of each model. We conclude that it is possible
to distinguish between cylindrical flux ropes, spheromak flux ropes, and
sheared arcades using coronal polarization measurements. If one of these models
is found to be consistent with observational measurements, it will mean
positive identification of the magnetic morphology that surrounds certain
quiescent filaments, which will lead to a greater understanding of how they
form and why they erupt.Comment: 22 pages, 8 figures, Solar Physics topical issue: Coronal Magnetis
Fermions from Half-BPS Supergravity
We discuss collective coordinate quantization of the half-BPS geometries of
Lin, Lunin and Maldacena (hep-th/0409174). The LLM geometries are parameterized
by a single function on a plane. We treat this function as a collective
coordinate. We arrive at the collective coordinate action as well as path
integral measure by considering D3 branes in an arbitrary LLM geometry. The
resulting functional integral is shown, using known methods (hep-th/9309028),
to be the classical limit of a functional integral for free fermions in a
harmonic oscillator. The function gets identified with the classical limit
of the Wigner phase space distribution of the fermion theory which satisfies u
* u = u. The calculation shows how configuration space of supergravity becomes
a phase space (hence noncommutative) in the half-BPS sector. Our method sheds
new light on counting supersymmetric configurations in supergravity.Comment: 28 pages, 2 figures, epsf;(v3) eq. (3.3) clarified and notationally
simplified; version to appear in JHE
1/16-BPS Black Holes and Giant Gravitons in the AdS_5 X S^5 Space
We explore 1/16-BPS objects of type IIB string theory in AdS_5 * S^5. First,
we consider supersymmetric AdS_5 black holes, which should be 1/16-BPS and have
a characteristic that not all physical charges are independent. We point out
that the Bekenstein-Hawking entropy of these black holes admits a remarkably
simple expression in terms of (dependent) physical charges, which suggests its
microscopic origin via certain Cardy or Hardy-Ramanujan formula. We also note
that there is an upper bound for the angular momenta given by the electric
charges. Second, we construct a class of 1/16-BPS giant graviton solutions in
AdS_5 * S^5 and explore their properties. The solutions are given by the
intersections of AdS_5 * S^5 and complex 3 dimensional holomorphic hyperspaces
in C^{1+5}, the latter being the zero loci of three holomorphic functions which
are homogeneous with suitable weights on coordinates. We investigate examples
of giant gravitons, including their degenerations to tensionless strings.Comment: 25 pages, no figures, v2: references added, comments added in the
conclusio
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