7,444 research outputs found
Mechanism of magnetostructural transformation in multifunctional MnGaC
MnGaC undergoes a ferromagnetic to antiferromagnetic, volume
discontinuous cubic-cubic phase transition as a function of temperature,
pressure and magnetic field. Through a series of temperature dependent x-ray
absorption fine structure spectroscopy experiments at the Mn K and Ga K edge,
it is shown that the first order magnetic transformation in MnGaC is
entirely due to distortions in Mn sub-lattice and with a very little role for
Mn-C interactions. The distortion in Mn sub-lattice results in long and short
Mn-Mn bonds with the longer Mn-Mn bonds favoring ferromagnetic interactions and
the shorter Mn-Mn bonds favoring antiferromagnetic interactions. At the first
order transition, the shorter Mn-Mn bonds exhibit an abrupt decrease in their
length resulting in an antiferromagnetic ground state and a strained lattice.Comment: Accepted in J. Appl. Phys. Please contact authors for supplementary
informatio
Automated Classification of 2000 Bright IRAS Sources
An Artificial Neural Network (ANN) has been employed using a supervised
back-propagation scheme to classify 2000 bright sources from the Calgary
database of IRAS (Infrared Astronomy Satellite) spectra in the wavelength
region of 8-23 microns. The data base has been classified into 17
pre-determined classes based on spectral morphology. We have been able to
classify more than 80 percent of the 2000 sources correctly at the first
instance. The speed and robustness of the scheme will allow us to classify the
whole of LRS database, containing more than 50,000 sources in the future.Comment: 26 pages, To appear in ApJS after July 200
Quantitative Analysis of Hydrogenated DLC Films by Visible Raman Spectroscopy
The correlations between properties of hydrogenated diamond like carbon films
and their Raman spectra have been investigated. The films are prepared by
plasma deposition technique, keeping different hydrogen to methane ratio during
the growth process. The hydrogen concentration, sp content, hardness and
optical Tauc gap of the materials have been estimated from a detail analysis of
their Raman spectra. We have also measured the same parameters of the films by
using other commonly used techniques, like sp content in films by x-ray
photoelectron spectroscopy, their Tauc gap by ellipsometric measurements and
hardness by micro-hardness testing. The reasons for the mismatch between the
characteristics of the films, as obtained by Raman measurements and by the
above mentioned techniques, have been discussed. We emphasize on the importance
of the visible Raman spectroscopy in reliably predicting the above key
properties of DLC films.Comment: 19 pages, 8 figure
Growth Stress Induced Tunability of Dielectric Constant in Thin Films
It is demonstrated here that growth stress has a substantial effect on the
dielectric constant of zirconia thin films. The correct combination of
parameters - phase, texture and stress - is shown to yield films with high
dielectric constant and best reported equivalent oxide thickness of 0.8 nm. The
stress effect on dielectric constant is twofold, firstly, by the effect on
phase transitions and secondly by the effect on interatomic distances. We
discuss and explain the physical mechanisms involved in the interplay between
the stress, phase changes and the dielectric constant in detail.Comment: 11 pages, 5 figure
Color image encryption and decryption using Hill Cipher associated with Arnold transform
Image security over open network transmission is a big concern nowadays. This paper proposes another methodology for color image encoding and decoding using two stage Hill Cipher method which is connected with Arnold Transformation. The forgoing created a strategy for encryption and decryption of color image information and touched on just the premise of keys. In this plan, keys and the agreement of Hill Cipher (HC) are basic. Moreover, keys multiplication (pre or post) over an RGB image information framework is inevitable to know to effectively decrypt the first image information. We have given a machine simulation with a standard example and the result is given to support the stalwartness of the plan. This paper gives a detailed comparison between prior proposed methods and this methodology. The system has potential utilization in computerized RGB image transforming and security of image information
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