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91.
This paper presents an investigation of self-focusing of Gaussian laser beam in collisionless plasma and its effect on stimulated Raman scattering process. The pump beam interacts with a pre-excited electron plasma wave thereby generating a back-scattered wave. On account of Gaussian intensity distribution of laser beam, the time independent component of the ponderomotive force along a direction perpendicular to the beam propagation becomes finite, which modifies the background plasma density profile in a direction transverse to pump beam axis. This modification in density affects the incident laser beam, electron plasma wave and back-scattered beam. We have set up the non-linear differential equations for the beam width parameters of the main beam, electron plasma wave, back-scattered wave and SRS-reflectivity by taking full non-linear part of the dielectric constant of collisionless plasma with the help of moment theory approach. It is observed from the analysis that focusing of waves greatly enhances the SRS reflectivity. 相似文献
92.
The present study focuses on the analysis of free vibrations of axisymmetric functionally graded hollow spheres. The material is assumed to be graded in radial di- rection with a simple power law. Matrix Frrbenious method of extended power series is employed to derive the analytical solutions for displacement, temperature, and stresses. The dispersion relations for the existence of various types of pos- sible modes of vibrations in the considered hollow sphere are derived in a compact form. In order to explore the character- istics of vibrations, the secular equations are further solved by using fixed point iteration numerical technique with the help of MATLAB software. The numerical results have been presented graphically for polymethyl methecrylate materials in respect of natural frequencies, frequency shift, inverse quality factor, displacement, temperature change, and radial stress. 相似文献
93.
We propose and describe an all-optical prefix tree adder with the help of a terahertz optical asymmetric demultiplexer (TOAD) using a set of optical switches. The prefix tree adder is useful in compound adder implementation. It is preferred over the ripple carry adder and the carry lookahead adder. We also describe the principle and possibilities of the all-optical prefix tree adder. The theoretical model is presented and verified through numerical simulation. The new method promises higher processing speed and accuracy. The model can be extended for studying more complex all-optical circuits of enhanced functionality in which the prefix tree adder is the basic building block. 相似文献
94.
Suvonil Sinha Ray Shovan Manna Anirban Ghosh Rajat K. Chaudhuri Sudip Chattopadhyay 《International journal of quantum chemistry》2019,119(4):e25776
IVO-SSMRPT is an affordable and accurate type of state-specific multireference perturbation (SSMRPT) theory that adds dynamic correlation energy to improved virtual orbital (IVO) complete active space configuration interaction (CASCI) wave functions using a single-root parametrization of multi-root Hilbert-space ansatz. We applied it to many chemically important di- and tri-radicals to analyze the geometries and electronic properties of spectroscopic interest for both closed- and open-shell singlet- and nonsinglet ground as well as excited states. We observed that IVO-SSMRPT identifies optimized geometries, splitting between multiplets and frequencies for several radicals that are similar to those displayed by current generation state-of-the-art methods but with admiringly decreased computational effort. This study illustrates the importance of having an accurate treatment of both nondynamical and dynamical correlation effects when examining multiradical species. Chemically and spectroscopically relevant answers can be obtained using our computationally tractable method. Our method will be a serviceable avenue for portraying open-shell interactions in other radicals. 相似文献
95.
AbstractA metal-, oxidant-, and additive-free conversion of hydroxamates to esters have been achieved using molecular iodine as the reagent using a novel but not-so-explored heron-type rearrangement. The reaction proceeds with almost equal facility with substrates having either electron-donating or electron-withdrawing substituent. Similarly, α,ß-unsaturated, and sterically hindered ortho-substituted hydroxamates also undergo the desired transformation smoothly. 相似文献
96.
An all-optical adder/subtractor (A/S) unit with the (TOAD) is proposed. The all-optical A/S unit with help of terahertz optical asymmetric demultiplexer a set of all-optical full-adders and optical exclusive- ORs (XORs), can be used to perform a fast central processor unit using optical hardware components. We try to exploit the advantages of TOAD-based optical switch to design an integrated all-optical circuit which can perform binary addition and subtraction. With computer simulation results confirming the described methods, conclusions are given. 相似文献
97.
Ayan Bhattacharya Rajat Subhra Hazra Parthanil Roy 《Stochastic Processes and their Applications》2018,128(1):182-210
Using the theory of regular variation, we give a sufficient condition for a point process to be in the superposition domain of attraction of a strictly stable point process. This sufficient condition is used to obtain the weak limit of a sequence of point processes induced by a branching random walk with jointly regularly varying displacements. Because of heavy tails of the step size distribution, we can invoke a one large jump principle at the level of point processes to give an explicit representation of the limiting point process. As a consequence, we extend the main result of Durrett (1983) and verify that two related predictions of Brunet and Derrida (2011) remain valid for this model. 相似文献
98.
Jasjit S. Walia Amrik S. Walia David C. Lankin Robert C. Petterson Janak Singh 《Journal of heterocyclic chemistry》1985,22(4):1117-1119
The synthesis of 4-amino-2,3-dihydro-1,5-benzothiazepine and its transformation to the new heterocycle Imidazo[2,1-d][1,5]benzothiazepine is described. 相似文献
99.
Flutter,Tumble and Vortex Induced Autorotation 总被引:1,自引:0,他引:1
Rajat Mittal Veeraraghavan Seshadri Holavanahalli S. Udaykumar 《Theoretical and Computational Fluid Dynamics》2004,17(3):165-170
The phenomenon of flutter and tumble of objects in free fall has been studied using two-dimensional numerical simulations of uniform flow past a plate which is free to rotate about a fixed axis through its centroid. Particular focus is on the effect of Reynolds number and plate thickness-to-length ratio on the flutter-to-tumble transition and on the observed frequency of the angular motions. Simulations indicate that the tendency to tumble increases with increasing Reynolds number and decreasing thickness ratio. A case is also made that the tumbling frequency for two-dimensional plates is governed by a Karman type vortex shedding process. These results for this pinned plate have also been verified by simulating a limited number of free-fall cases. 相似文献
100.
Relativistic state‐specific multireference perturbation theory incorporating improved virtual orbitals: Application to the ground state single‐bond dissociation 下载免费PDF全文