Derivative free method for computing modes of multilayer planar waveguide

A technique to solve generalized dispersion equation of multilayer planar waveguide has been demonstrated to obtain all the expected guided modes. The solution is based on the derivative free method for computing the zeros of an analytical function in complex plane. The derivative free method extracts the roots which are very close to actual zeros of the function. Roots are further refined using the robust iteration method to achieve the desired accuracy. Application of the proposed method has been verified by solving the modes of a variety of structures including lossless structure, leaky structure, quantum well waveguide, active waveguide, ARROW waveguide and metal clad waveguide. The method is efficient and computes all modes of planar waveguide with high accuracy.     

Effect of dopant and DC bias potential on dielectric properties of polyvinyl alcohol (PVA)/PbTiO3 - composite films

Composite films of Polyvinyl alcohol (PVA) mixed with Lead Titante Oxide (PbTiO₃) were prepared. Dopant incorporated and DC bias induced electrical parameters were disclosed with respect to pure PVA film. The results demonstrate dielectric polarization is not only directly proportional to PbTiO₃% of dopant but also external DC bias potential at 30 °C based on Maxwell Wagner theory. Hence these properties highly applicable as super-capacitor film and humidity sensor applications.     

A Multifunctional Microfluidic Platform for High-Throughput Experimentation of Electroorganic Chemistry

Electroorganic synthesis is a promising tool to design sustainable transformations and discover new reactivities. However, the added setup complexity caused by electrodes in the system impedes efficient screening of reaction conditions. Herein, we present a microfluidic platform that enables automated high-throughput experimentation (HTE) for electroorganic synthesis at a 15-microliter scale. Two HTE modules are demonstrated: 1) the rapid electrochemical reaction condition screening for a radical–radical cross-coupling reaction on micro-fabricated interdigitated electrodes, and 2) measurements of kinetics for mediated anodic oxidations using the microliter-scale cyclic voltammetry. The presented modular approach could be deployed for a range of other electroorganic chemistry applications beyond the demonstrated functionalities.     

Nondestructive evaluation of physico-mechanical properties of polypropylene copolymer by infra-red spectroscopy

We present a novel approach to nondestructive evaluation of various physico-mechanical properties of polypropylene copolymer (PPCP) by a single step measurement of infra-red spectrum followed by chemometric operation of the predetermined characteristic region of spectrum through an inbuilt software to obtain various properties/parameters i.e. average melt flow index (av. MFI), izod impact, and flexural modulus, required for quality evaluation of the copolymer. This method is simple, fast, and direct, involving only a single step measurement on the film (sample) as against the standard ASTM methods for the evaluation of these properties, which involve multi-steps and multi-instruments and are quite cumbersome. This method has been tested on a fairly large number of samples produced in a commercial plant, over a period of time and compared well with the corresponding values (properties) determined by the ASTM methods.     

Higher order approximations for tandem queueing networks

In this paper a higher order approximation for single server queues and tandem queueing networks is proposed and studied. Different from the most popular two-moment based approximations in the literature, the higher order approximation uses the higher moments of the interarrival and service distributions in evaluating the performance measures for queueing networks. It is built upon the MacLaurin series analysis, a method that is recently developed to analyze single-node queues, along with the idea of decomposition using higher orders of the moments matched to a distribution. The approximation is computationally flexible in that it can use as many moments of the interarrival and service distributions as desired and produce the corresponding moments for the waiting and interdeparture times. Therefore it can also be used to study several interesting issues that arise in the study of queueing network approximations, such as the effects of higher moments and correlations. Numerical results for single server queues and tandem queueing networks show that this approximation is better than the two-moment based approximations in most cases.     

Scattering of α-particles at medium energies

Elastic scattering of α-particles is treated within the context of high energy multiple diffraction theory. Terms up to fourth order in the expansion of the optical phase-shift function are retained (when necessary). The theoretical predictions are compared with the recent 5.05 and 4.30 GeV/c α-α measurements. The effects of short-range dynamical correlations are discussed.     

Measurement of true angular correlation in Fe57 in a single crystal of metallic cobalt

Unperturbed angular correlation in Fe⁵⁷ has been observed in a single crystal of metallic cobalt. The value of the angular correlation coefficient A₂=? 0·042±0·016 is obtained which gives the mixing ratioδ=? 0·17±0·03 for the 122 keV gamma-transition.     

Studies with scintillation coincidence spectrometer: Se75 and Sb125

Cascade relationships between gamma-transitions in the decay of Se⁷⁶ and Sb¹²⁵ have been investigated with the help of a scintillation coincidence spectrometer. A decay scheme for Se⁷⁵ has been proposed.     

Mössbauer studies in a-Fe76-xNixCr4B12Si8

Room temperature Mössbauer studies on a-Fe_76-xNi_xCr₄B₁₂Si₈ alloys (0≤x≤30) are reported. The average hyperfine field is observed to remain constant. P(H) shows a low hyperfine field component which is found to be nearly absent for 2≤x≤4 samples. An attempt has been made to understand the correlation of this to the low temperature resistivity behaviour of Cr containing Fe-based amorphous alloys.