(SoE) School of Engineering

<p>Shiv Nadar University is a comprehensive, multidisciplinary, research-focused, and student-centric University offering a full range of academic programs at the undergraduate, postgraduate and doctoral level. With state-of-the-art infrastructure, the University comprises of academic wings, sophisticated labs, international standard sports facilities, amphitheaters, auditorium, conference rooms and smart classrooms. The University&rsquo;s goal is to become internationally recognized for the quality of its research and creative endeavors and their applicability to improving quality of life, generating new insights and expanding the boundaries of human knowledge creativity. Committed to excellence in teaching, research and service, the University aims to serve the higher education needs of India and the world beyond.</p>

Shiv Nadar University

In this paper, we investigate the potential of Support Vector Machines (SVMs) for power quality data mining in electrical power systems. Modified wavelet transform, known as S-transform, has been used to extract unique features of the various power quality disturbances. Feature vectors from S-transform analysis are used to train the SVM classifier. Various multi-class SVM algorithms have been applied on the power quality data under study and the Directed Acyclic Graph (DAGSVM) algorithm is found to be performing well. A comparison between the DAGSVM method and the one based on Artificial Neural Network demonstrates the efficiency of the SVM method in classifying PQ disturbances. © 2006 IEEE.

World University root node

Electrical Engineering

Proceedings - Third International Conference onInformation Technology: New Generations, ITNG 2006

Knowledge discovery in power quality data using Support Vector Machine and S-transform

Fuzzy decision trees are powerful, top-down, hierarchical search methodology to extract human interpretable classification rules. However, they are often criticized to result in poor learning accuracy. In this paper, we propose Neuro-Fuzzy Decision Trees (N-FDTs); a fuzzy decision tree structure with neural like parameter adaptation strategy. In the forward cycle, we construct fuzzy decision trees using any of the standard induction algorithms like fuzzy ID3. In the feedback cycle, parameters of fuzzy decision trees have been adapted using stochastic gradient descent algorithm by traversing back from leaf to root nodes. With this strategy, during the parameter adaptation stage, we keep the hierarchical structure of fuzzy decision trees intact. The proposed approach of applying backpropagation algorithm directly on the structure of fuzzy decision trees improves its learning accuracy without compromising the comprehensibility (interpretability). The proposed methodology has been validated using computational experiments on real-world datasets. © World Scientific Publishing Company.

International Journal of Neural Systems

Neuro-Fuzzy decision trees

Let G = (V, E) be an undirected graph on n vertices, and let Δ(u, v) denote the distance in G between two vertices u and v. Thorup and Zwick showed that for any positive integer t, the graph G can be preprocessed to build a data structure that can efficiently report t-approximate distance between any pair of vertices. That is, for any u, v V, the distance reported is at least Δ(u, v) and at most tΔ(u, v). The remarkable feature of this data structure is that, for t3, it occupies subquadratic space, that is, it does not store all-pairs distances explicitly, and still it can answer any t-approximate distance query in constant time. They named the data structure approximate distance oracle because of this feature. Furthermore, the trade-off between the stretch t and the size of the data structure is essentially optimal.In this article, we show that we can actually construct approximate distance oracles in expected O(n2) time if the graph is unweighted. One of the new ideas used in the improved algorithm also leads to the first expected linear-time algorithm for computing an optimal size (2, 1)-spanner of an unweighted graph. A (2, 1) spanner of an undirected unweighted graph G = (V, E) is a subgraph (V, ), E, such that for any two vertices u and v in the graph, their distance in the subgraph is at most 2Δ(u, v) + 1. © 2006 ACM.

ACM Transactions on Algorithms

Approximate distance oracles for unweighted graphs in expected O(n 2) time

We present alternate reductions of the nearest neighbor searching problem to Point Location in Balls that reduces the space bound of Sariel Har-Peled's [S. Har-Peled, A replacement for Voronoi diagrams of near linear size, in: Proc. of IEEE FOCS, 2001, pp. 94-103, full version available from http://www.uiuc.edu/~sariel/papers] recent result on Approximate Voronoi Diagrams to linear while maintaining the logarithmic search time. We do this by simplifying the construction of [S. Har-Peled, A replacement for Voronoi diagrams of near linear size, in: Proc. of IEEE FOCS, 2001, pp. 94-103, full version available from http://www.uiuc.edu/~sariel/papers] that reduces the number of balls generated by algorithm by a logarithmic factor to O (n log n). We further reduce the number of balls by a new hierarchical decomposition scheme and a generalization of PLEBs to achieve linear space decomposition for nearest neighbor searching. The construction of our data structures takes O (n log n) time. © 2006 Elsevier Inc. All rights reserved.

Fulltext

Journal of Computer and System Sciences

Nearest neighbors search using point location in balls with applications to approximate Voronoi decompositions

Civil Engineering

Proceedings of the American Society for Composites 2006 - Twenty First {\ldots}

Durability of Recycled Cellulose Fiber-Polymer Composites

Effects of MgO deposition on SiSi O2 system and charge carrier trapping and recombination in SiSi O2 MgO structures are studied using second-harmonic generation (SHG). An ultrafast 800 nm laser was used both for multi-photon induced electron injection through the Si O2 into a potential well in the MgO, and for monitoring the time-dependent SHG signal, which is sensitive to the electric field at the SiSi O2 interface. Our results indicate that the MgO deposition introduces new trap states, and electrons trapped in the MgO transport more readily through the Si O2 than those in traps on the surface of Si O2. We attribute this to differences in trap energy levels and/or differences in process damage-induced defect densities in the Si O2. © 2006 American Institute of Physics.

Applied Physics Letters

Studies of charge carrier trapping and recombination processes in Si/SiO 2/MgO structures using second-harmonic generation

This paper describes design and implementation of a single axis dc attraction type electromagnetic suspension system where an electromagnet of 2.6 kg mass is levitated over a large gap under a fixed ferromagnetic guide-way. The electromagnet exhibits nonlinear force-current-distance characteristics, and if controllers are to be designed by using linear analysis, the air-gap is restricted to a small region around the chosen nominal operating point. In this work, an attempt has been made to increase the operating range of an electromagnetic suspension system by using the concept of piecewise linear control where the nonlinear force-current-airgap relationships of the magnetic suspension system have been successively linearized at several operating points with a suitable controller designed for each operating point. A novel analog switching scheme has been designed and implemented to automatically switch to the relevant controller depending on the actual air-gap. © 2006 ISA - The Instrumentation, Systems, and Automation Society.

ISA Transactions

Large gap control in electromagnetic levitation

The present work reports on the little explored correlation of electrical properties in conjunction with morphology of RF sputtered aluminum nitride (AlN) films at different substrate temperatures (100 °C -400 °C). Electrical properties, especially insulator charge density (Qin) and interface state density (Dit) were studied by using Al/AlN/Si (MIS) as a test vehicle. X-ray diffraction, FTIR spectroscopy, AFM and SEM techniques were studied for crystal orientation, bond formation, surface roughness and grain size of AlN film, respectively. Relatively highly c-axis (0 0 2) oriented films were found in between 200 °C and 300 °C with FTIR absorption peak at 682 cm-1. Decrease in Qin from 7.9 × 1011 cm-2 to 1.0 × 1011 cm-2 found to be associated with increase in surface roughness and grain size, with temperature. There is no significant change in interface state density with deposition temperature. It is found that better crystallinity results in a good dielectric constant. © 2005 Elsevier B.V. All rights reserved.

Current Applied Physics

Correlation of electrical and morphological properties of sputtered aluminum nitride films with deposition temperature

An attempt to correlate deposition-induced effects and the morphological properties with the electrical properties of the aluminum nitride (AlN) films have been made. The AlN film was sputter deposited on silicon while increasing the pressure in steps from 2×10-3 to 8×10-3 mbar. An X-ray diffractogram revealed that the intensity of (0 0 2) orientation increased till 6×10-3 mbar pressure, but it changed to (1 0 0) orientation of the AlN film at 8×10-3 mbar. The FTIR spectra of the absorption band of the films were observed around 682 cm-1 and became prominent at 6×10-3 mbar. A decrease in the grain size was seen by SEM images at 8×10-3 mbar. The AFM measurements revealed that the surface roughness varied from 1.56 to 3.24 nm with pressure. It was found that the insulator charge density (Qin) increased from 1.4×1011 cm-2 to 1.3×1012 cm-2 with increase in pressure. On the other hand, the interface state density (Dit) was found minimum (7.3×1011 eV-1 cm-2) at 6×10-3 mbar. It is found that presence of the Qin and Dit are primarily governed by the sputtering pressure of the AlN film. © 2006 Elsevier Ltd. All rights reserved.

Vacuum

A study on the interface and bulk charge density of AlN films with sputtering pressure

Power amplifier plays most important part of the electromagnetic suspension system. The recent advances in the technology of attraction type magnetic levitation are attributable almost entirely to the development of solid state electronic and power semiconductor devices. The amplifier should have properties like fast dynamics, wide bandwidth, ability to handle large payload, energy efficient, high reliability and should be cost-effective. Both linear and switching mode power amplifiers have been used in the field of DC electromagnetic suspension system. In this paper different possible switched mode power circuits for single magnet based electromagnetic levitation system have been discussed and a comparative study has been made of the different topologies of power amplifiers based on their structure and some experimental results. In the actual work design, fabrication and testing of an electromagnetic levitation scheme has been made as a complete project. But in this paper the emphasis is given on power amplifier portion due to limitation of space. A new single switch based switched mode power amplifier for electromagnetic levitation has been introduced. This circuit is simpler in topology and has some definite advantages over mostly reported asymmetrical H-bridge converter [10].