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Search Results: 1 - 10 of 2439 matches for " Kaushik Bhattacharya "
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Conversion from laparoscopic to open cholecystectomy
Bhattacharya Kaushik
Journal of Postgraduate Medicine , 2005,
Abstract:
Menetrier′s disease with gastrointestinal bleed
Bhattacharya Kaushik
Journal of Minimal Access Surgery , 2005,
Abstract:
Gastric diverticulum - ′Double pylorus appearance′
Bhattacharya Kaushik
Journal of Minimal Access Surgery , 2005,
Abstract:
Solution of the Dirac equation in presence of an uniform magnetic field
Kaushik Bhattacharya
Physics , 2007,
Abstract: In this work we discuss the properties of the solutions of the Dirac equation in presence of an uniform background magnetic field. In particular we focus on the nature of the solutions, their ortho-normality properties and how these solutions depend on the choice of the vector potential giving rise to the magnetic field. We explicitly calculate the spin-sum of the solutions and using it we calculate the propagator of the electron in presence of an uniform background magnetic field.
Neutrino absorption by W production in the presence of a magnetic field
Bhattacharya, Kaushik;Sahu, Sarira
High Energy Physics - Phenomenology , 2008, DOI: 10.1140/epjc/s10052-009-1052-9
Abstract: In this work we calculate the decay rate of the electron type neutrinos into $W$ bosons and electrons in presence of an external uniform magnetic field. The decay rate is calculated from the imaginary part of the $W$ exchange neutrino self-energy diagram but in the weak field limit and compare our result with the existing one.
Optimal Features Subset Selection and Classification for Iris Recognition
Kaushik Roy,Prabir Bhattacharya
EURASIP Journal on Image and Video Processing , 2008, DOI: 10.1155/2008/743103
Abstract: The selection of the optimal features subset and the classification have become an important issue in the field of iris recognition. We propose a feature selection scheme based on the multiobjectives genetic algorithm (MOGA) to improve the recognition accuracy and asymmetrical support vector machine for the classification of iris patterns. We also suggest a segmentation scheme based on the collarette area localization. The deterministic feature sequence is extracted from the iris images using the 1D log-Gabor wavelet technique, and the extracted feature sequence is used to train the support vector machine (SVM). The MOGA is applied to optimize the features sequence and to increase the overall performance based on the matching accuracy of the SVM. The parameters of SVM are optimized to improve the overall generalization performance, and the traditional SVM is modified to an asymmetrical SVM to treat the false accept and false reject cases differently and to handle the unbalanced data of a specific class with respect to the other classes. Our experimental results indicate that the performance of SVM as a classifier is better than the performance of the classifiers based on the feedforward neural network, the k-nearest neighbor, and the Hamming and the Mahalanobis distances. The proposed technique is computationally effective with recognition rates of 99.81% and 96.43% on CASIA and ICE datasets, respectively.
Optimal Features Subset Selection and Classification for Iris Recognition
Roy Kaushik,Bhattacharya Prabir
EURASIP Journal on Image and Video Processing , 2008,
Abstract: The selection of the optimal features subset and the classification have become an important issue in the field of iris recognition. We propose a feature selection scheme based on the multiobjectives genetic algorithm (MOGA) to improve the recognition accuracy and asymmetrical support vector machine for the classification of iris patterns. We also suggest a segmentation scheme based on the collarette area localization. The deterministic feature sequence is extracted from the iris images using the 1D log-Gabor wavelet technique, and the extracted feature sequence is used to train the support vector machine (SVM). The MOGA is applied to optimize the features sequence and to increase the overall performance based on the matching accuracy of the SVM. The parameters of SVM are optimized to improve the overall generalization performance, and the traditional SVM is modified to an asymmetrical SVM to treat the false accept and false reject cases differently and to handle the unbalanced data of a specific class with respect to the other classes. Our experimental results indicate that the performance of SVM as a classifier is better than the performance of the classifiers based on the feedforward neural network, the k-nearest neighbor, and the Hamming and the Mahalanobis distances. The proposed technique is computationally effective with recognition rates of 99.81% and 96.43% on CASIA and ICE datasets, respectively.
Gauge transformation through an accelerated frame of reference
Ashish Shukla,Kaushik Bhattacharya
Physics , 2009, DOI: 10.1119/1.3290866
Abstract: The Schr\"{o}dinger equation of a charged particle in a uniform electric field can be specified in either a time-independent or a time-dependent gauge. The wave-function solutions in these two gauges are related by a phase-factor reflecting the gauge symmetry of the problem. In this article we show that the effect of such a gauge transformation connecting the two wave-functions can be mimicked by the effect of two successive extended Galilean transformations connecting the two wave-function. An extended Galilean transformation connects two reference frames out of which one is accelerating with respect to the other.
Thermodynamics of the Lee-Wick partners: An alternative approach
Kaushik Bhattacharya,Suratna Das
Physics , 2011, DOI: 10.1103/PhysRevD.84.045023
Abstract: It was pointed out some time ago that there can be two variations in which the divergences of a quantum field theory can be tamed using the ideas presented by Lee and Wick. In one variation the Lee-Wick partners of the normal fields live in an indefinite metric Hilbert space but have positive energy and in the other variation the Lee-Wick partners can live in a normal Hilbert space but carry negative energy. Quantum mechanically the two variations mainly differ in the way the fields are quantized. In this article the second variation of Lee and Wick's idea is discussed. Using statistical mechanical methods the energy density, pressure and entropy density of the negative energy Lee-Wick fields have been calculated. The results exactly match with the thermodynamic results of the conventional, positive energy Lee-Wick fields. The result sheds some light on the second variation of Lee-Wick's idea. The result seems to say that the thermodynamics of the theories do not care about the way they are quantized.
A toy model based analysis on the effect of the Lee-Wick partners in the evolution of the early universe
Kaushik Bhattacharya,Suratna Das
Physics , 2012, DOI: 10.1103/PhysRevD.86.025009
Abstract: In the present article the thermodynamic results of the Lee-Wick partner infested universe have been applied in a toy model where there is one Lee-Wick partner to each of the standard model particle and more over the longitudinal degrees of freedom of the massive partners of the standard massless gauge bosons are neglected at high temperatures. For practical purposes, the chiral fermionic sector of Lee-wick theories requires two Lee-Wick partners per fermion which opens up the possibility for a negative energy density of the early universe. A toy Lee-Wick model with one fermionic partner relaxes such oddities and hence easy to deal with. In a similar way, the longitudinal degrees of freedom of the massive gauge boson partners also have the potential to yield negative energy densities and thus those will be neglected in a toy model study. In such a toy model one can analytically calculate the time-temperature relation in the very early radiation dominated universe which shows interesting new physics. The article also tries to point out how a Lee-Wick particle dominated early cosmology transforms into the standard cosmological model. Based on the results of this toy model analysis a brief discussion on the more realistic model, which can accommodate two Lee-Wick partners for each standard fermionic field and the longitudinal degree of freedom of partners of the gauge fields, is presented. It has been shown that such an universe is mostly very difficult to attain but there are certain conditions where one can indeed think of such an universe which can evolve into the standard cosmological universe in a short time duration.
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