1,963 research outputs found
Fast phonetic similarity search over large repositories
Analysis of unstructured data may be inefficient in the presence of spelling errors. Existing approaches use string similarity methods to search for valid words within a text, with a supporting dictionary. However, they are not rich enough to encode phonetic information to assist the search. In this paper, we present a novel approach for efficiently perform phonetic similarity search over large data sources, that uses a data structure called PhoneticMap to encode language-specific phonetic information. We validate our approach through an experiment over a data set using a Portuguese variant of a well-known repository, to automatically correct words with spelling errors
Hopping motion of lattice gases through nonsymmetric potentials under strong bias conditions
The hopping motion of lattice gases through potentials without
mirror-reflection symmetry is investigated under various bias conditions. The
model of 2 particles on a ring with 4 sites is solved explicitly; the resulting
current in a sawtooth potential is discussed. The current of lattice gases in
extended systems consisting of periodic repetitions of segments with sawtooth
potentials is studied for different concentrations and values of the bias.
Rectification effects are observed, similar to the single-particle case. A
mean-field approximation for the current in the case of strong bias acting
against the highest barriers in the system is made and compared with numerical
simulations. The particle-vacancy symmetry of the model is discussed.Comment: 8 pages (incl. 6 eps figures); RevTeX 3.
Extreme Ultra-Violet Spectroscopy of the Lower Solar Atmosphere During Solar Flares
The extreme ultraviolet portion of the solar spectrum contains a wealth of
diagnostic tools for probing the lower solar atmosphere in response to an
injection of energy, particularly during the impulsive phase of solar flares.
These include temperature and density sensitive line ratios, Doppler shifted
emission lines and nonthermal broadening, abundance measurements, differential
emission measure profiles, and continuum temperatures and energetics, among
others. In this paper I shall review some of the advances made in recent years
using these techniques, focusing primarily on studies that have utilized data
from Hinode/EIS and SDO/EVE, while also providing some historical background
and a summary of future spectroscopic instrumentation.Comment: 34 pages, 8 figures. Submitted to Solar Physics as part of the
Topical Issue on Solar and Stellar Flare
Quasi-continuous melting of model polymer monolayers prompts reinterpretation of polymer melting
Condensed matter textbooks teach us that melting cannot be continuous and indeed experience, including with polymers and other long-chain compounds, tells us that it is a strongly first-order transition. However, here we report nearly continuous melting of monolayers of ultralong n-alkane C390H782 on graphite, observed by AFM and reproduced by mean-field theory and MD simulation. On heating, the crystal-melt interface moves steadily and reversibly from chain ends inward. Remarkably, the final melting point is 80 K above that of the bulk, and equilibrium crystallinity decreases continuously from ~100% to <50% prior to final melting. We show that the similarity in melting behavior of polymers and non-polymers is coincidental. In the bulk, the intermediate melting stages of long-chain crystals are forbidden by steric overcrowding at the crystal-liquid interface. However, there is no crowding in a monolayer as chain segments can escape to the third dimension
The soft supersymmetry breaking in D=5 supergravity compactified on S_1/Z_2 orbifolds
We study the origin of the supersymmetry breaking induced by the mediation of
gravity and the radion multiplet from the hidden to the visible brane in the
context of the N=2, D=5 supergravity compactified on S_1/Z_2 orbifolds. The
soft supersymmetry breaking terms for scalar masses, trilinear scalar couplings
and gaugino masses are calculated to leading order in the five dimensional
Newton's constant k_5^2 and the gravitino mass m_{3/2}. These are finite and
non-vanishing, with the scalar soft masses be non-tachyonic, and are all
expressed in terms of the gravitino mass and the length scale R of the fifth
dimension. The soft supersymmetry breaking parameters are thus correlated and
the phenomenological implications are discussed.Comment: 16 pages, 3 figures, 1 Table, final version to appear in Physics
Letters B, slightly shortened, comments added, typos correcte
Statistical Theory for Incoherent Light Propagation in Nonlinear Media
A novel statistical approach based on the Wigner transform is proposed for
the description of partially incoherent optical wave dynamics in nonlinear
media. An evolution equation for the Wigner transform is derived from a
nonlinear Schrodinger equation with arbitrary nonlinearity. It is shown that
random phase fluctuations of an incoherent plane wave lead to a Landau-like
damping effect, which can stabilize the modulational instability. In the limit
of the geometrical optics approximation, incoherent, localized, and stationary
wave-fields are shown to exist for a wide class of nonlinear media.Comment: 4 pages, REVTeX4. Submitted to Physical Review E. Revised manuscrip
Exact solutions of the radial Schrodinger equation for some physical potentials
By using an ansatz for the eigenfunction, we have obtained the exact
analytical solutions of the radial Schrodinger equation for the pseudoharmonic
and Kratzer potentials in two dimensions. The energy levels of all the bound
states are easily calculated from this eigenfunction ansatz. The normalized
wavefunctions are also obtained.Comment: 13 page
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Use of Z-pinch radiation sources for high-pressure shock wave studies
The authors are developing a new shock wave diagnostic using Z pinch sources for high-pressure equation of state (EOS) measurements. Specifically, they are employing VISAR interferometry to measure the particle velocity of shocked materials and fiber optic probes to measure the shock speed. Combination of these measurements will allow absolute EOS data with Z accelerators. This report is a progress report on the development of this new approach to EOS measurements; however, preliminary data obtained with the diagnostics are encouraging. With further development of Z pinch sources, it is envisioned that a variety of EOS and constitutive property measurements can be made. Time-resolved wave profile measurements will then provide a variety of EOS and material property data, such as isentropic EOS, initial compressive strength and shock-induced compressive strength, dynamic tensile strength, kinetics of phase transitions, and surface stability studies
Quasars and their host galaxies
This review attempts to describe developments in the fields of quasar and
quasar host galaxies in the past five. In this time period, the Sloan and 2dF
quasar surveys have added several tens of thousands of quasars, with Sloan
quasars being found to z>6. Obscured, or partially obscured quasars have begun
to be found in significant numbers. Black hole mass estimates for quasars, and
our confidence in them, have improved significantly, allowing a start on
relating quasar properties such as radio jet power to fundamental parameters of
the quasar such as black hole mass and accretion rate. Quasar host galaxy
studies have allowed us to find and characterize the host galaxies of quasars
to z>2. Despite these developments, many questions remain unresolved, in
particular the origin of the close relationship between black hole mass and
galaxy bulge mass/velocity dispersion seen in local galaxies.Comment: Review article, to appear in Astrophysics Update
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