16,192 research outputs found
Radar shadow detection in SAR images using DEM and projections
Synthetic aperture radar (SAR) images are widely used in target recognition
tasks nowadays. In this letter, we propose an automatic approach for radar
shadow detection and extraction from SAR images utilizing geometric projections
along with the digital elevation model (DEM) which corresponds to the given
geo-referenced SAR image. First, the DEM is rotated into the radar geometry so
that each row would match that of a radar line of sight. Next, we extract the
shadow regions by processing row by row until the image is covered fully. We
test the proposed shadow detection approach on different DEMs and a simulated
1D signals and 2D hills and volleys modeled by various variance based Gaussian
functions. Experimental results indicate the proposed algorithm produces good
results in detecting shadows in SAR images with high resolution.Comment: 10 pages, 6 figure
Auslander Systems
The authors generalize the dynamical system constructed by J. Auslander in 1959, resulting in perhaps the simplest family of examples of minimal but not strictly ergodic systems. A characterization of unique ergodicity and mean-L-stability is given. The new systems are also shown to have zero topological entropy and fail to be weakly rigid. Some results on the set of idempotents in the enveloping semigroup are also achieved
Role of the cooling rate in the stability of the superconducting phase of (TMTSF)_2ClO_4
The noncentrosymmetric ClO anions of the organic superconductor
(TMTSF)ClO order below 24K. The size of domains where the anions are
ordered is substantially dependent on the cooling rate which is a key parameter
for the stability of the low temperature electronic ground states. We study the
effect of the cooling rate on the SC phase within a self consistent approach in
the framework of the time dependent Ginzburg-Landau theory taking into account
the superconducting fluctuations. We derive the superconducting transition
temperature which is found to decrease with increasing cooling rate in
agreement with recent experimental data.Comment: 5 pages including one figure. Published online in Europhysics Letter
Critical behavior of an Ising model with aperiodic interactions
We write exact renormalization-group recursion relations for a ferromagnetic
Ising model on the diamond hierarchical lattice with an aperiodic distribution
of exchange interactions according to a class of generalized two-letter
Fibonacci sequences. For small geometric fluctuations, the critical behavior is
unchanged with respect to the uniform case. For large fluctuations, the uniform
fixed point in the parameter space becomes fully unstable. We analyze some
limiting cases, and propose a heuristic criterion to check the relevance of the
fluctuations.Comment: latex file, 5 figures, accepted by Braz. Jour. Phy
Field behavior of an Ising model with aperiodic interactions
We derive exact renormalization-group recursion relations for an Ising model,
in the presence of external fields, with ferromagnetic nearest-neighbor
interactions on Migdal-Kadanoff hierarchical lattices. We consider layered
distributions of aperiodic exchange interactions, according to a class of
two-letter substitutional sequences. For irrelevant geometric fluctuations, the
recursion relations in parameter space display a nontrivial uniform fixed point
of hyperbolic character that governs the universal critical behavior. For
relevant fluctuations, in agreement with previous work, this fixed point
becomes fully unstable, and there appears a two-cycle attractor associated with
a new critical universality class.Comment: 9 pages, 1 figure (included). Accepted for publication in Int. J.
Mod. Phys.
ADO-Tutor: Intelligent Tutoring System for leaning ADO.NET
This paper describes an Intelligent Tutoring System for helping users with ADO.NET called ADO-Tutor. The Intelligent Tutoring System was designed and developed using (ITSB) authoring tool for building intelligent educational systems. The user learns through the intelligent tutoring system ADO.NET, the technology used by Microsoft.NET to connect to databases. The material includes lessons, examples, and questions. Through the feedback provided by the intelligent tutoring system, the user's understanding of the material is assessed, and accordingly can be guided to different difficulty level of exercises and/or the lessons. The Intelligent Tutoring System was evaluated by a group of users and the results were more than satisfactory in terms of the quality of the material and the design of the system
Magnetic field induced singlet - triplet phase transition in quasi one-dimensional organic superconductors
We propose a theoretical model of quasi-one-dimensional superconductors, with
attractive electron-electron interactions dominant in the singlet d-wave
channel and sub-dominant in the p-wave channel. We discuss, in the mean field
approximation, the effect of a magnetic field applied perpendicularly to the
direction of the lowest conductivity. The lowest free energy phase corresponds
to a singlet d-wave symmetry in low fields, but to a triplet symmetry in high
fields. A first order singlet-triplet phase transition is expected at moderate
applied fields of a few teslas. We propose to ascribe the recent critical field
and NMR experimental data, observed in superconducting (TMTSF)2ClO4 to such an
effect.Comment: 6 pages, 2 figures, accepted in EP
On dispersion and characteristic motions of temperature rate dependent materials
Three dimensional theory of thermomechanical material developed using techniques of continuum mechanics and law of thermodynamic
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