Characterization of Programmed-Waveform Pulsewidth Modulation

Programmed-waveform pulsewidth modulated (PWM) waveforms, applicable to ac-dc/dc-ac converters, are synthesized and analyzed in terms of several structural parameters. By invoking sensitivity studies and heuristics, optimal PWM structures are identified and contrasted. The results show total harmonic performance as a function of switching levels, waveform types, commutations per cycle, and filter bandpass.     

Cascaded neural network based small array synthesis with robustness to noise

A cascaded neural network approach has been presented in this paper to estimate the excitation for the desired field distribution using a radial basis function neural network (RBFNN). The article has employed an electromagnetic design example consisting of 5 × 5 and 6 × 6 planar antenna array of isotropic sources with inter element‐distance of 0.5λ to show the adaptation of the neural network model in estimating the desired output. A neural network is trained using a dataset of suitable excitation voltages and its corresponding radiation patterns, which proves to be efficient in predicting the excitation voltages required to generate the desired pattern. A set of techniques based on a cascaded neural network is adopted for pattern synthesis using magnitude and phase, magnitude only, and template‐based input data. The robustness of the method has also been tested by considering noise with different SNR levels. The results found in each case have a close fit with the desired pattern.     

Non linear dynamics of memristor based 3rd order oscillatory system

In this paper, we report for the first time the nonlinear dynamics of three memristor based phase shift oscillators, and consider them as a plausible solution for the realization of parametric oscillation as an autonomous linear time variant system. Sustained oscillation is reported through oscillating resistance while time dependent poles are present. The memristor based phase shift oscillator is explored further by varying the parameters so as to present the resistance of the memristor as a time varying parameter, thus potentially eliminating the need of external periodic forces in order for it to oscillate. Multi memristors, used simultaneously with similar and different parameters, are investigated in this paper. Mathematical formulas for analyzing such oscillators are verified with simulation results and are found to be in good agreement.     

TRANSIENT CONDUCTION AND RADIATION HEAT TRANSFER WITH VARIABLE THERMAL CONDUCTIVITY

The effect of variable thermal conductivity on transient conduction and radiation heat transfer in a planar medium is investigated. Thermal conductivity of the medium is assumed to vary linearly with temperature, while the other thermophysical properties and the optical properties are assumed constant. The radiative transfer equation is solved using the discrete transfer method, (DTM) and the nonlinear energy equation is solved using an implicit scheme. Transient as well as steady state results are found for an absorbing, emitting, and anisotropically scattering gray medium. Thermal conductivity has been found to have significant effects on both transient as well as steady state temperature and heat flux distributions. Some steady state results are compared with the results reported in the literature.     

Altruistic agents in uncertain dynamic games

The distributed operation of dynamic systems, such as traffic networks and the power grid, can be viewed as a dynamic game among their control agents. As the agents respond to one another’s decisions by resolving their problems, they trace a trajectory in decision space that, if convergent, arrives at a fixed point. Thus, two issues of concern are the convergence to attractors and their location relative to Pareto optimal solutions. This paper addresses these issues in games where each agent continually solves a problem from a family of unconstrained, but general optimization problems. Specifically, it delivers simple yet effective problem transformations to influence the convergence to and location of attractors—these transformations are referred to as altruistic factors and the agents that implement them are called altruistic agents. This paper proposes algorithms to draw attractors towards Pareto optimal solutions: for the case of quadratic functions, a thorough analysis of the rate of convergence is provided; for the case of general functions, a trust-region-based algorithm is proposed. An application of this game-theoretic framework is improvement of the quality of the solutions attained by distributed model predictive control, particularly in scenarios whose objective functions are quadratic and whose dynamics are linear. The text was submitted by the authors in English.     

Surface smoothening and characterization of silk fibers of Antheraea assamensis Helfer (muga) using some natural agents

Cocoons of Antheraea assamensis (muga) silkworm were treated with different classes of natural-acidic (Citrus limon and Dillenia indica) and alkaline (Musa balbisiana) materials with the aim to elucidate their effectiveness as degumming agents. The tensile strength of silk fibers increased significantly after bio-degumming compared to industrial degumming using sodium carbonate. Scanning electron microscopy of bio-degummed fibers appeared clean and even with clear individual fibroin filaments. FTIR studies confirmed that bio-degumming resulted in holding the innate nature of muga silk. Under the implemented experimental conditions, M. balbisiana and C. limon functioned as most efficient degumming agents, followed by D. indica. The findings of this study propose the use of such eco-friendly degumming practices over the usual harsh industrial treatments for obtaining applaudable quality of silk with robust strength necessary for both textile and biomaterial purpose, besides reducing the impact of chemical toxicity on the environment.     

A multi-agent technique for contingency constrained optimal powerflows

This paper does three things. First, it proposes that each critical contingency in a power system be represented by a “correction time” (the time required to eliminate the violations produced by the contingency), rather than by a set of hard constraints. Second, it adds these correction times to an optimal power flow and decomposes the resulting problem into a number of smaller optimization problems. Third, it proposes a multi-agent technique for solving the smaller problems in parallel. The agents encapsulate traditional optimization algorithms as well as a new algorithm, called the voyager, that generates starting points for the traditional algorithms. All the agents communicate asynchronously, meaning that they can work in parallel without ever interrupting or delaying one another. The resulting scheme has potential for handling power system contingencies and other difficult global optimization problems     

An ionic liquid as a potential multifunctional lubricating oil additive

Abstract

Homopolymer of decyl acrylate was synthesized and blended with phosphonium based ionic liquid and their characterisation was carried out by spectral method (NMR, IR), thermogravimetric analysis and gel permeation chromatography (GPC). Performance of these blends were evaluated by standard ASTM method in base oil which clearly indicates that the blend effectively act as anti-wear agent and also pour point depressants and viscosity modifiers. A comparison of their performances with homopolymer has also been evaluated and reported.