Absolute parametric instability in a nonuniform plane plasma waveguide

The paper reports an analysis of the effect of spatial plasma nonuniformity on absolute parametric instability (API) of electrostatic waves in magnetized plane waveguides subjected to an intense high-frequency (HF) electric field using the separation method. In this case the effect of strong static magnetic field is considered. The problem of strong magnetic field is solved in 1D nonuniform plane plasma waveguide. The equation describing the spatial part of the electric potential is obtained. Also, the growth rates and conditions of the parametric instability for periodic and aperiodic cases are obtained. It is found that the spatial nonuniformity of the plasma exerts a stabilizing effect on the API. It is shown that the growth rates of periodic and aperiodic API in nonuniform plasma are less compared to that of uniform plasma.     

Optical characteristics of transparent samarium oxide thin films deposited by the radio-frequency sputtering technique

Transparent metal oxide thin films of samarium oxide (Sm₂O₃) were prepared on pre-cleaned fused optically flat quartz substrates by radio-frequency (RF) sputtering technique. The as-deposited thin films were annealed at different temperatures (873, 973 and 1073 K) for 4 h in air under normal atmospheric pressure. The topological morphology of the film surface was characterized by using atomic force microscopy (AFM). The optical properties of the as-prepared and annealed thin films were studied using their reflectance and transmittance spectra at nearly normal incident light. The estimated direct optical band gap energy (\(E_{\mathrm {g}}^{\mathrm {d}}\)) values were found to increase by increasing the annealing temperatures. The dispersion curves of the refractive index of Sm₂O₃ thin films were found to obey the single oscillator model.     

Step index fibre using laser interferometer

A model is suggested to describe the fringe shift which occurs due to the phase variations of cladded glass fibre introduced between the two plates of the liquid wedge interferometer illuminated with a He–Ne laser. The fringe shift of the phase object which appears in the denominator of the Airy distribution formula of the multiple beam interference is represented in the harmonic term. An experiment is conducted using liquid wedge interferometer where the step index glass fibre of a nearly quadratic thickness variation is introduced between the two plates of the interferometer. The obtained fringe shift shows a good agreement with the proposed quadratic model. The Matlab code is written to plot the interferometer fringes comprising the shift of the step index fibre. Secondly, recognition of elliptical fibres is outlined using tomographic imaging. Finally, results and concluding remarks are given.     

Improving methane storage on wet activated carbons at various amounts of water

Different mesoporous activated carbons were prepared by both chemical and physical activation processes and were examined for methane uptake in the presence of water.Methane isotherms were obtained at ...     

Vectorized Directional Sweep Based Parallelization Method for Factored Alternating Direction Implicit (ADI) Schemes

A new parallelization method is proposed for factored alternating direction implicit (ADI) schemes based on the vectorized global domain directional sweep. This approach, when combined with multi-partitioning domain decomposition, significantly reduces the frequency of necessary communication calls and minimizes processor idling during the sweeping processes. The present parallelization approach is applied to a number of vectorized two-dimensional compressible Navier-Stokes solvers. The codes vary in complexity from laminar to algebraic turbulence closure model and finally the strongly coupled Navier-Stokes and K-e equations. Implementation is conducted using PVM (Parallel Virtual Machine) message passing tool on the Cray T3D massively parallel processing (MPP) machine. The implemented parallel codes are assessed in terms of accuracy and parallel performance.