3,454 research outputs found
Zero Temperature Insulator-Metal Transition in Doped Manganites
We study the transition at T=0 from a ferromagnetic insulating to a
ferromagnetic metallic phase in manganites as a function of hole doping using
an effective low-energy model Hamiltonian proposed by us recently. The model
incorporates the quantum nature of the dynamic Jahn-Teller(JT) phonons strongly
coupled to orbitally degenerate electrons as well as strong Coulomb correlation
effects and leads naturally to the coexistence of localized (JT polaronic) and
band-like electronic states. We study the insulator-metal transition as a
function of doping as well as of the correlation strength U and JT gain in
energy E_{JT}, and find, for realistic values of parameters, a ground state
phase diagram in agreement with experiments. We also discuss how several other
features of manganites as well as differences in behaviour among manganites can
be understood in terms of our model.Comment: To be published in Europhysics Letter
Theory of Insulator Metal Transition and Colossal Magnetoresistance in Doped Manganites
The persistent proximity of insulating and metallic phases, a puzzling
characterestic of manganites, is argued to arise from the self organization of
the twofold degenerate e_g orbitals of Mn into localized Jahn-Teller(JT)
polaronic levels and broad band states due to the large electron - JT phonon
coupling present in them. We describe a new two band model with strong
correlations and a dynamical mean-field theory calculation of equilibrium and
transport properties. These explain the insulator metal transition and colossal
magnetoresistance quantitatively, as well as other consequences of two state
coexistence
Evaluation of Effectiveness of Wavelet Based Denoising Schemes Using ANN and SVM for Bearing Condition Classification
The wavelet based denoising has proven its ability to denoise the bearing vibration signals by improving the signal-to-noise ratio (SNR) and reducing the root-mean-square error (RMSE). In this paper seven wavelet based denoising schemes have been evaluated based on the performance of the Artificial Neural Network (ANN) and the Support Vector Machine (SVM), for the bearing condition classification. The work consists of two parts, the first part in which a synthetic signal simulating the defective bearing vibration signal with Gaussian noise was subjected to these denoising schemes. The best scheme based on the SNR and the RMSE was identified. In the second part, the vibration signals collected from a customized Rolling Element Bearing (REB) test rig for four bearing conditions were subjected to these denoising schemes. Several time and frequency domain features were extracted from the denoised signals, out of which a few sensitive features were selected using the Fisher’s Criterion (FC). Extracted features were used to train and test the ANN and the SVM. The best denoising scheme identified, based on the classification performances of the ANN and the SVM, was found to be the same as the one obtained using the synthetic signal
Stranding of spinner dolphin, Stenella longirostris (Gray, 1828) at Karwar, Karnataka
A spinner dolphin, Stenella longirostris , locally
called ‘handi meenu’ was noticed in dead condition
floating near the marine cage farm of CMFRI, Karwar,
approximately 600 m away, from sea shore of
Aligadda village in the evening hours on 31st August
2012. The specimen was an adult female of 175 cm
total length and 55 kg weight. The animal had a small
injury near its left eye probably as a result of getting
entangled in fishing nets or got injured in purse-seine
operation which resulted in its death
Whale shark landings in Uttar Kannada, Karnataka
The whale shark, Rhincodon typus Smith, 1828,
has a circumglobal distribution in tropical and warm
temperate seas. Since May 2003 it has been included
under Appendix II of CITES, making the trade of this
species regulated. The status of this species has
since then been upgraded from “Data deficient” in
1996 to “Vulnerable” in 2000 by the IUCN. Currently
it is protected under Schedule I Part II of the Wildlife
Protection Act of India, 1972
Modelling Deformations in Car Crash animation
In this paper, we present a prototype of a deformation engine to efficiently model and render the damaged structure of vehicles in crash scenarios. We introduce a novel system architecture to accelerate the computation, which is traditionally an extremely expensive task. We alter a rigid body simulator to predict trajectories of cars during a collision and formulate a correction procedure to estimate the deformations of the collapsed car structures within the contact area. Non-linear deformations are solved based on the principle of energy conservation. Large plastic deformations resulting from collisions are modelled as a weighted combination of deformation examples of beams which can be produced using classical mechanics
PepServe: a web server for peptide analysis, clustering and visualization
Peptides, either as protein fragments or as naturally occurring entities are characterized by their sequence and function features. Many times the researchers need to massively manage peptide lists concerning protein identification, biomarker discovery, bioactivity, immune response or other functionalities. We present a web server that manages peptide lists in terms of feature analysis as well as interactive clustering and visualization of the given peptides. PepServe is a useful tool in the understanding of the peptide feature distribution among a group of peptides. The PepServe web application is freely available at http://bioserver-1.bioacademy.gr/Bioserver/PepServe/
A single-molecule approach to ZnO defect studies: single photons and single defects
Investigations that probe defects one at a time offer a unique opportunity to
observe properties and dynamics that are washed out of ensemble measurements.
Here we present confocal fluorescence measurements of individual defects in
Al-doped ZnO nanoparticles and undoped ZnO sputtered films that are excited
with sub-bandgap energy light. Photon correlation measurements yield both
antibunching and bunching, indicative of single-photon emission from isolated
defects that possess a metastable shelving state. The single-photon emission is
in the range 560 - 720 nm and typically exhibits two broad spectral peaks
separated by approximately 150 meV. The excited state lifetimes range from 1 -
13 ns, consistent with the finite-size and surface effects of nanoparticles and
small grains. We also observe discrete jumps in the fluorescence intensity
between a bright state and a dark state. The dwell times in each state are
exponentially distributed and the average dwell time in the bright (dark) state
does (may) depend on the power of the exciting laser. Taken together, our
measurements demonstrate the utility of a single-molecule approach to
semiconductor defect studies and highlight ZnO as a potential host material for
single-defect based applications.Comment: 33 pages, 7 figure
Low-temperature far-infrared ellipsometry of convergent beam
Development of an ellipsometry to the case of a coherent far infrared
irradiation, low temperatures and small samples is described, including a
decision of the direct and inverse problems of the convergent beam ellipsometry
for an arbitrary wavelength, measurement technique and a compensating
orientation of cryostat windows. Experimental results are presented: for a gold
film and UBe13 single crystal at room temperature (lambda=119 um), temperature
dependencies of the complex dielectric function of SrTiO3 (lambda=119, 84 and
28 um) and of YBa2Cu3O7-delta ceramic (lambda=119 um).Comment: 14 pages, 6 figure
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