Electrical Engineering

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Shiv Nadar University

In this paper, a Hamilton-Jacobi-Bellman (HJB) equation based optimal control algorithm for robust controller design is proposed for a nonlinear system. Utilising the Lyapunov direct method, the controller is shown to be optimal with respect to a cost functional, which includes penalty on the control effort, the maximum bound on system uncertainty and cross-coupling between system state and control. The controllers are continuous and require the knowledge of the upper bound of system uncertainty. In the present algorithm, neural network is used to approximate value function to find approximate solution of HJB equation using least squares method. Proposed algorithm has been applied on a nonlinear system with matched uncertainties. It is also applied to the system having uncertainties in input matrix. Results are validated through simulation studies. Copyright © 2009, Inderscience Publishers.

World University root node

(SoE) School of Engineering

International Journal of Automation and Control

Robust control of nonlinear systems using neural network based HJB solution

The present work explores the possibility of employing non-destructive testing (NDT) technique of thermal wave imaging, using infrared radiations, to study the interface between bamboo and glue, and gaps in glue application therein. This is a relatively unexplored area as regards bamboo, and thus a novelty, though thermal imaging of detecting glue deficiency in laminated wood has been reported. Active thermography technique using Frequency Modulated Thermal Wave Imaging (FMTWI) has been used to identify frequencies which would give good images of the glue deficiencies.Glue bands and gaps up to 5 mm, could be imaged using lock-in thermography through slivers of 2 mm thickness. The inspection time ranged from 65 s to 350 s depending on the glue type. These findings point to the possibility of using thermal NDT for applications of bamboo and its composites/laminates. © KFRI 2009.

Journal of Bamboo and Rattan

Bamboo-glue interface thermography for non-destructive testing

Piezoelectric films, such as aluminium nitride (AlN), are of great interest for the fabrication of thin film bulk/surface acoustic resonators, where the growth parameters and the substrate material influence the morphological properties. Herein, AlN films were deposited using RF reactive sputtering on Si, SiO2, metal (Al, Cu, Cr and Au) coated silicon, GaAs and InP substrates. C-axis (002) oriented AlN films were observed on most of the substrates, where the surface morphologies of the films grown on the 1.5 mm thick SiO2 layer and GaAs substrate were found to be non-uniform. Moreover, AlN films deposited on the Cr electrode exhibit well textured film with fairly uniform grains, while the films deposited on other metal electrodes exhibit a granular type of structure with mixed small and large grains. After optimisation of growth parameters, silicon micromachining was performed by the wet chemical etching method. Suspended Cr-AlN-Cr-SiO2 cantilevers of 20 μm in width were fabricated for futuristic microelectromechanical systems (MEMS) applications. © 2009 Institute of Materials, Minerals and Mining.

Surface Engineering

Morphological investigation of aluminium nitride films on various substrates for MEMS applications

AlN films were grown on silicon substrates by RF reactive magnetron sputtering. At high sputtering powers, (002) preferred orientation as well as Al-N absorption band becomes prominent. The surface roughness and grain size of sputtered films were found to increase with RF power. Surface acoustic wave (SAW) device has been made on the grown (002) oriented piezoelectric AlN film with interdigital transducer (IDT) electrodes spacing corresponding to a wavelength of 60 μm. The centre frequency of the SAW filter was found to be 84.304 MHz, which gives a phase velocity of 5058 m/s with an electromechanical coupling coefficient (K 2) of 0.34%. Low etch rate of AlN films were observed in doped TMAH solution. Threedimensional suspended Cr/AlN/Cr/SiO 2 microstructures were also fabricated by wet chemical etching. © ASM International.

Journal of Materials Engineering and Performance

Growth of AlN films and its process development for the fabrication of acoustic devices and micromachined structures

Solid-state electronics

A CAD-compatible closed form approximation for the inversion charge areal density in double-gate MOSFETs

IEEE transactions on electron devices

An Improvement to the Numerical Robustness of the Surface Potential Approximation for Double-Gate MOSFETs

Text Categorization (TC) remains as a potential application area for linear support vector machines (SVMs). Among the numerous linear SVM formulations, we bring forward linear PSVM together with recently proposed distributional clustering (DC) of words to realize its potential in TC realm. DC has been presented as an efficient alternative to conventionally used feature selection in TC. It has been shown that, DC together with linear SVM drastically brings down the dimensionality of text documents without any compromise in classification performance. In this paper we use linear PSVM and its extension Fuzzy PSVM (FPSVM) together with DC for TC. We present experimental results comparing PSVM/FPSVM with linear SVMlight and SVMlin on popular WebKB text corpus. Through numerous experiments on subsets of WebKB, we reveal the merits of PSVM and FPSVM over other linear SVMs. © Springer-Verlag Berlin Heidelberg 2009.

Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)

Text categorization using fuzzy proximal svm and distributional clustering of words

One of the main issues of orthogonal frequency division multiplexing (OFDM) is the high peak-to-average power ratio (PAPR) of the transmitted signal which adversely affects the complexity of power amplifiers. The selected mapping (SLM) technique is one of the promising PAPR reduction techniques for OFDM. In this reported work, rows of normalised Riemann matrices are selected as phase sequence vectors for the SLM technique. MATLAB simulations show PAPR reduction of around 2.3dB using the proposed method compared with methods reported in the literature. © 2009 The Institution of Engineering and Technology.

Electronics Letters

SLM based PAPR reduction of OFDM signal using new phase sequence

Effect of laser flux density on the structural quality and optical properties of Zn0.6Cd0.4S thin films synthesized by ultraviolet pulsed laser deposition have been studied. The stoichiometric composition of this alloy was estimated using lattice constant calculated via XRD data. Surface morphology of the samples was examined using AFM. Optical properties were studied at room temperature by transmittance, absorbance, and photoluminescence measurements. Studies revealed that there is an improvement in the structural quality with increasing the laser flux density in some range. However, too high laser flux density could lead to the degradation in structural quality of thin film. It was observed from the PL data that with increase in laser flux density there is a decrease in the band gap. Transmission data shows a transmittance of more than 70% in the visible region. TEM investigation of the samples reveals that the particles are spherical in shape with average diameter of 15 nm. © 2009 Elsevier B.V. All rights reserved.

Thin Solid Films

Effect of laser flux density on ZnCdS thin films

C axis oriented AlN films were deposited on silicon substrate by radio frequency reactive magnetron sputtering. Subsequently the films were annealed in a horizontal furnace at temperatures ranging from 400 to 800°C for 30 min in nitrogen ambient. The change in the morphological properties with annealing temperatures was investigated using X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy and atomic force microscopy techniques. Morphological studies revealed that the annealing increased surface roughness and grain size. In addition, Al-N bond density along with the crystallinity of the deposited films was improved with annealing. The electrical properties, namely the insulator charge density (Qin) and the interface electronic state density (Dit), were estimated by the capacitance-voltage (C-V) measurements. It was found that the Qin increased, but the Dit decreased with annealing temperature. Lower leakage current with improved resistivity and dielectric behaviour was also observed with annealing. © 2009 Institute of Materials, Minerals and Mining.