Effect of On-Axis Dip in Refractive-Index Profile on the Cutoff Frequency of Modes of Few Mode Fibers: A Numerical Approach

Abstract

The normalized cutoff frequencies of the linearly polarized (LP) modes of a graded-index few mode fiber have been calculated as a function of profile shape parameters using a simple numerical method. The effect of refractive-index dip on these cutoff frequencies and on the order of appearance of these modes has been investigated. The presence of dip causes an increase in the cutoff V values of all the modes, and the maximum shift in the cutoff V value is found to be even 20% for some modes. The order of appearance of some modes also gets drastically affected.     

Integration of barotropic vorticity equation over spherical geodesic grid using multilevel adaptive wavelet collocation method

In this paper, we present the multilevel adaptive wavelet collocation method for solving non-divergent barotropic vorticity equation over spherical geodesic grid. This method is based on multi-dimensional second generation wavelet over a spherical geodesic grid. The method is more useful in capturing, identifying, and analyzing local structure [1] than any other traditional methods (i.e. finite difference, spectral method), because those methods are either full or partial miss important phenomena such as trends, breakdown points, discontinuities in higher derivatives of the solution. Wavelet decomposition is used for interpolation and adaptive grid refinement on different levels.     

Strangeness enhancement in Cu-Cu and Au-Au collisions at √S(NN)=200 GeV

We report new STAR measurements of midrapidity yields for the Λ, Λ[over ˉ], K(S)(0), Ξ(-), Ξ[over ˉ](+), Ω(-), Ω[over ˉ](+) particles in Cu+Cu collisions at √S(NN)==200 GeV, and midrapidity yields for the Λ, Λ[over ˉ], K(S)(0) particles in Au+Au at √S(NN)==200 GeV. We show that, at a given number of participating nucleons, the production of strange hadrons is higher in Cu+Cu collisions than in Au+Au collisions at the same center-of-mass energy. We find that aspects of the enhancement factors for all particles can be described by a parametrization based on the fraction of participants that undergo multiple collisions.     

On Inverse Limits and Direct Limits for Fuzzy Topological Spaces

Li has introduced the concepts of inverse system and direct system for fuzzy topological spaces and studied inverse limits and direct limits on such spaces by presenting the explicit constructions of these limits.In this paper some important concepts of fuzzy topology,such as,product fuzzy topology,quotient fuzzy topology,fuzzy continuity etc.,are used for further study of inverse limits and direct limits for fuzzy topological spaces.     

Transetherification polycondensation: The roles of the catalyst,monomer structure,and polymerization conditions

A detailed study of the novel melt transetherification polycondensation process, which was recently developed in our laboratory, is presented. The efficacy of different catalysts, such as p‐toluenesulfonic acid (PTSA), camphorsulfonic acid, and their pyridinium salts, was examined. The pyridinium salts, especially pyridinium camphorsulfonate (PCS), outperformed PTSA both in terms of the polymer molecular weights (the polydispersity) and the extent of discoloration of the polymer. The evolution of the molecular weight with the polymerization time was monitored with two different catalysts, PTSA and PCS, and these studies demonstrated that, while PTSA yielded polymers with a broad molecular weight distribution, the use of PCS curtailed possible side reactions that led to this broadening. Model reactions suggested that one possible reason for this broadening could be the formation of macrocyclics facilitated by an ether–ether exchange reaction, which was shown to occur much more rapidly when PTSA was used. A further interesting and rather unprecedented feature, which became apparent while the effect of the acid–catalyst concentration was being examined, was the dual role played by the acid, which acted both beneficially as a catalyst and detrimentally, defunctionalizing the chain end and terminating polymer growth. This conclusion was based on the observed decrease in the molecular weight of the polymer at very high catalyst concentrations, which suggested that there existed an optimum catalyst concentration at which a balance was struck between the molecular weight of the polymer formed and the polymerization time. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 102–111, 2004     

ϒ′ (10.01) resonance parameters

On the basis of some exactly solvable models we suggest that the Rayleigh-Schrödinger perturbation series for the energy eigenvalue may have nothing to do with the corresponding exact value in case the vacuum expectation value of the system changes discontinuously, i.e. the system undergoes first-order phase transition.     

Effect of non-magnetic impurities on the observation of superconducting gap excitations by raman scattering

The effect of small concentrations of non-magnetic substitutional impurities (characterized by changes in mass, nearest neighbour force constants and local electron-phonon interaction) on the observability of superconducing (sc) gap excitations in 2H-NbSe₂ by Raman scattering is considered within the theoretical framework of Balseiro and Falicov (bf). The phonon self-energy when evaluated forq=0 using the Einstein oscillator model for the host phonons is seen to have a pole corresponding to the impurity mode besides the gap excitation one around 2Δ previously obtained bybf. A splitting of the impurity mode into two in thesc state is predicted. An enhancement occurs in the strength of thesc gap excitation peak whenever it is close to the impurity mode. The data from the experiments of Sooryakumar, Klein and Frindt on impure samples of 2H-NbSe₂ are discussed in the light of the present calculation. Preliminary results of this paper were presented by one of us (snb) at the International Conference on Phonon Physics at Indiana University, Bloomington, USA, in August-September 1981.