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Search Results: 1 - 10 of 325579 matches for " S. Mohit "
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Three octave spanning supercontinuum by red-shifted dispersive wave in photonic crystal fibers
Mohit Sharma,S. Konar
Physics , 2015,
Abstract: This paper presents a three layer index guided lead silicate (SF57) photonic crystal fiber which simultaneously promises to yield large effective optical nonlinear coefficient and low anomalous dispersion that makes it suitable for supercontinuum generation. At an operating wavelength 1550 nm, the typical optimized value of anomalous dispersion and effective nonlinear coefficient turns out to be ~4 ps/km/nm and ~1078 W^(-1) km^(-1), respectively. Through numerical simulation it is realized that the designed fiber promises to exhibit three octave spanning supercontinuum from 900 to 7200 nm by using 50 fs sech optical pulses of 5 kW peak power. Due to the cross-phase modulation and four-wave mixing processes, a long range of red-shifted dispersive wave generated, which assist to achieve such large broadening. In addition, we have investigated the compatibility of supercontinuum generation with input pulse peak power increment and briefly discussed the impact of nonlinear processes on supercontinuum generation.
A Priori Assessment of Algebraic Flame Surface Density Models in the Context of Large Eddy Simulation for Nonunity Lewis Number Flames in the Thin Reaction Zones Regime
Mohit Katragadda,Nilanjan Chakraborty,R. S. Cant
Journal of Combustion , 2012, DOI: 10.1155/2012/794671
Abstract: The performance of algebraic flame surface density (FSD) models has been assessed for flames with nonunity Lewis number (Le) in the thin reaction zones regime, using a direct numerical simulation (DNS) database of freely propagating turbulent premixed flames with Le ranging from 0.34 to 1.2. The focus is on algebraic FSD models based on a power-law approach, and the effects of Lewis number on the fractal dimension D and inner cut-off scale have been studied in detail. It has been found that D is strongly affected by Lewis number and increases significantly with decreasing Le. By contrast, remains close to the laminar flame thermal thickness for all values of Le considered here. A parameterisation of D is proposed such that the effects of Lewis number are explicitly accounted for. The new parameterisation is used to propose a new algebraic model for FSD. The performance of the new model is assessed with respect to results for the generalised FSD obtained from explicitly LES-filtered DNS data. It has been found that the performance of the most existing models deteriorates with decreasing Lewis number, while the newly proposed model is found to perform as well or better than the most existing algebraic models for FSD.
Alopecia-Areata Like Alopecia in Mycosis Fungoides, a Case Report
F. Farnaghi,Z. Safaee Naraghi,S. Mohit
Tehran University Medical Journal , 1998,
Abstract: Mycosis Fungoides (MF) is a cutaneous T-cell lymphoma (2,5). Alopecia is rarely seen in this disease, and the reported cases are in the form of follicular mucinosis (1,2,4). In this case report a patient is presented whose lesions all showed alopecia without mucinosis. Furthermore there was a patch of alopecia without any epidermal changes, which was clinicaly identical with alopecia areata, and histologically identical with MF. After six months of treatment there is regrowth of almost normal hair on all of the lesions
Effects of Turbulent Reynolds Number on the Performance of Algebraic Flame Surface Density Models for Large Eddy Simulation in the Thin Reaction Zones Regime: A Direct Numerical Simulation Analysis
Mohit Katragadda,Nilanjan Chakraborty,R. S. Cant
Journal of Combustion , 2012, DOI: 10.1155/2012/353257
Abstract: A direct numerical simulation (DNS) database of freely propagating statistically planar turbulent premixed flames with a range of different turbulent Reynolds numbers has been used to assess the performance of algebraic flame surface density (FSD) models based on a fractal representation of the flame wrinkling factor. The turbulent Reynolds number Ret has been varied by modifying the Karlovitz number Ka and the Damk?hler number Da independently of each other in such a way that the flames remain within the thin reaction zones regime. It has been found that the turbulent Reynolds number and the Karlovitz number both have a significant influence on the fractal dimension, which is found to increase with increasing Ret and Ka before reaching an asymptotic value for large values of Ret and Ka. A parameterisation of the fractal dimension is presented in which the effects of the Reynolds and the Karlovitz numbers are explicitly taken into account. By contrast, the inner cut-off scale normalised by the Zel’dovich flame thickness does not exhibit any significant dependence on Ret for the cases considered here. The performance of several algebraic FSD models has been assessed based on various criteria. Most of the algebraic models show a deterioration in performance with increasing the LES filter width. 1. Introduction Large eddy simulation (LES) is becoming increasingly popular for computational fluid dynamics (CFD) analysis of turbulent reacting flows due to the advancement and increased affordability of high-performance computing. The exponential temperature dependence of the chemical reaction rate poses one of the major challenges in LES modelling of turbulent reacting flows [1, 2]. Reaction rate closure models based on the concept of flame surface density (FSD) are well established in the context of the Reynolds averaged Navier Stokes simulations [3, 4] of turbulent premixed flames. However, the application of FSD-based modelling in LES is relatively recent [5–10]. The generalised FSD ( ) is defined as [5] where is the reaction progress variable. The overbar indicates the LES filtering operation in which the filtered value of a general quantity is evaluated as , where is a suitable filter function [5]. The combined contribution of the filtered reaction and molecular diffusion rates can be modelled using as , where is the fluid density, is the progress variable diffusivity, is the density-weighted surface-filtered displacement speed , and is the surface-filtered value of a general quantity . Often, is expressed in terms of the wrinkling factor , which is
Supercontinuum Generation in Photonic Crystal Fibers Possessing High Birefringence and Large Optical Nonlinearity
Mohit Sharma,Nitu Borgohain,S. Konar
Physics , 2015,
Abstract: This paper presents the design of an index guided highly birefringent photonic crystal fiber which promises to yield very large birefringence ~3.33 X 10^(-2) at 1550 nm and ~1.75 X 10^(-2) at 1064 nm as well as large effective nonlinearity ~80 W^(-1)km^(-1). Optical supercontinuum generation in the proposed fiber using a 1064 nm pump source with peak power of 1kW has been also presented. Finite difference time domain method (FDTD) has been employed to examine the optical properties such as fiber birefringence, mode field, V-parameter, walk-off and optical nonlinearity, while the Split-step Fourier method is used to solve the nonlinear Schrodinger equation felicitating the study of supercontinuum generation. Simulation results indicate that horizontal input pulse yields superior continuum in comparison to that of the vertically polarized input. However, the broadening of the continuum is about 1450 nm in case of horizontally polarized input light whereas it is approximately 2350 nm for vertically polarized.
Issues and Challenges in Node Connectivity in Mobile Ad Hoc Networks: A Holistic Review  [PDF]
Mohit Jain, Satish Chand
Wireless Engineering and Technology (WET) , 2016, DOI: 10.4236/wet.2016.71003
Abstract: One of the fundamental properties of an ad hoc network is its connectivity. Maintaining connectivity in wireless networks is extremely difficult due to dynamic changing topology of MANETs. There are several techniques to understand the connectivity level for a given network topology. In this paper, we examine the existing methods and discuss the issues and challenges that are still insurmountable in order to enhance the connectivity properties of wireless multi hop networks.
Effective Actions and Phase Fluctuations in d-wave Superconductors
Arun Paramekanti,Mohit Randeria,T. V. Ramakrishnan,S. S. Mandal
Physics , 2000, DOI: 10.1103/PhysRevB.62.6786
Abstract: We study effective actions for order parameter fluctuations at low temperature in layered d-wave superconductors such as the cuprates. The order parameter lives on the bonds of a square lattice and has two amplitude and two phase modes associated with it. The low frequency spectral weights for amplitude and relative phase fluctuations is determined and found to be subdominant to quasiparticle contributions. The Goldstone phase mode and its coupling to density fluctuations in charged systems is treated in a gauge-invariant manner. The Gaussian phase action is used to study both the $c$-axis Josephson plasmon and the more conventional in-plane plasmon in the cuprates. We go beyond the Gaussian theory by deriving a coarse-grained quantum XY model, which incorporates important cutoff effects overlooked in previous studies. A variational analysis of this effective model shows that in the cuprates, quantum effects of phase fluctuations are important in reducing the zero temperature superfluid stiffness, but thermal effects are small for $T << T_c$.
Golden Research Thoughts , 2013, DOI: 10.9780/22315063
Abstract: Present study was done in 30 anaemia patients against 30 controls . The tools used was SMMSE. Data were presented as mean and analyzed using students t test,Anemic had very highly significant cognitive dysfunction in the orientation, attention, language and construction domains of SMMSE and also on the total scores. Anaemic patients had significant circumscribed areas of cognitive dysfunctions compared to the control group but a clear relation between the severity of anaemia and the severity of cognitive dysfunction could not be established
Optimizing the Compression Ratio of Compression Ignition Engine Fuelled With Esters of Crude Rice Bran Oil
Mohit Vasudeva,Sumeet Sharma,S.K. Mohapatra,Krishnendu Kundu
International Journal on Theoretical and Applied Research in Mechanical Engineering , 2013,
Abstract: Experiments were carried out on a single cylinder four stroke variable compression ratio compression ignition engine with an attempt to figure out the optimum compression ratio fuelled with blend of methyl ester of crude rice bran oil with diesel. A 2-step transesterification reaction was carried out for the preparation of the methyl ester of crude rice bran oil. Experiments were carried out at different compression ratios ranging from 12 to 18. A B20 blend was used as fuel for conducting the experiments. At a compression ratio of 14 results showed significant improvement in the performance characteristics. Highest brake thermal efficiency along with lowest specific fuel consumption was observed at a compression ratio of 14. Compression ratio above and below 14 showed drop in the brake thermal efficiency and increase in specific fuel consumption.
Customised Zirconia Abutments Enhancing the Soft Tissue Restorative Interface
Mohit G Kheur,Tania Sethi,Shantanu S Jambhekar,Sumit Sethi
Indian Journal of Dental Advancements , 2011, DOI: 10.5866/3.4.681
Abstract: In the esthetic zone, proper preservation and contouring of the peri implant soft tissue is of utmost importance. Contouring of these soft tissues by use of customised healing abutments and provisional restorations is a commonly followed practice. However, after the soft tissue has been shaped, the use of a stock metallic abutment emerging out of the mucosa may not represent the best solution for long term desirable support of the soft tissue. Crowns placed with margins on such metallic abutments may lead to poor control of the margin geometry and location. Nowadays titanium abutments can have their per mucosal part customised using Zirconia. This represents a positive step in allowing good tissue contour, good control on the margins of the crown and use of a material that elicits a documented desirable tissue response.
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