(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

Dilution has long been considered a solution to many problems of toxic/flammable material releases. It implies diluting to a concentration that is below physiologically dangerous levels for a toxic substance (generally below TLV), or to a level below LFL for a flammable material release, ensuring that the process adopted for dilution does not itself enhance the risks. In this paper, we discuss the dilution of a gaseous release by deliberate and cautious mixing with air to reduce its concentration to a harmless level. The idea bears its origin to the Bhopal Gas Tragedy where some families saved themselves by turning the ceiling fans on when MIC reached their bedrooms at the dead of very cold night on December 2-3, 1984. The air pushed in by the fans diluted the MIC to below the harm level. Some of the advantages of using air dilution are: no cost of air, no air storage needed, no need to treat the air after use as in case of water curtains; required equipment, its maintenance and staff training in its use are very likely to cost less than in other ways of handling a release. Air dilution may not be feasible in all cases, such as gaseous release within a congested equipment layout, release that forms a liquid pool, etc. The method needs to be evaluated for each case. © 2005 Elsevier Ltd. All rights reserved.

Chemical Engineering

Journal of Loss Prevention in the Process Industries

Dilution with air to minimise consequences of toxic/flammable gas releases

Matousek [Discrete Comput. Geom. 24 (1) (2000) 61-84] designed an O(nlogn) deterministic algorithm for the approximate 2-means clustering problem for points in fixed dimensional Euclidean space which had left open the possibility of a linear time algorithm. In this paper, we present a simple randomized algorithm to determine an approximate 2-means clustering of a given set of points in fixed dimensional Euclidean space, with constant probability, in linear time. We first approximate the mean of the larger cluster using random sampling. We then show that the problem can be reduced to a set of lines, on which it can be solved by carefully pruning away points of the larger cluster and randomly sampling on the remaining points to obtain an approximate to the mean of the smaller cluster. © 2005 Elsevier B.V.

World University root node

Fulltext

Computational Geometry: Theory and Applications

A linear time algorithm for approximate 2-means clustering

We generalize the k-means algorithm presented by the authors [14] and show that the resulting algorithm can solve a larger class of clustering problems that satisfy certain properties (existence of a random sampling procedure and tightness). We prove these properties for the k-median and the discrete k-means clustering problems, resulting in O(2(k/ε (1) dn) time (1 + ε)-approximation algorithms for these problems. These are the first algorithms for these problems linear in the size of the input (nd for n points in d dimensions), independent of dimensions in the exponent, assuming k and ε to be fixed. A key ingredient of the k-median result is a (1 + ε)-approximation algorithm for the 1-median problem which has running time O(2(1/ε) d). The previous best known algorithm for this problem had linear running time. © Springer-Verlag Berlin Heidelberg 2005.

Lecture Notes in Computer Science

Linear time algorithms for clustering problems in any dimensions

Civil Engineering

McMAT 2005, The 2005 Joint ASME/ASC/SES Conference on Mechanics and Materials

Evaluation of Nano Composite Constituent Properties Using Multiple Scale Models

Second breakdown phenomenon in advanced NMOS ESD protection devices has remained an enigma due to the complex electrical and thermal effects that are responsible for its triggering. For the first time, we present a critical study of the high current phenomenon in ultra short-time scale to understand the physics of instability in protection devices around the second breakdown region. It is demonstrated that for advanced protection devices, carrier heating in the high field drain region causes a fall in the saturation drift velocity, which increases the transit time of carriers through the depletion region. This in turn, causes greater impact ionization due to higher accumulation of avalanche-generated carriers; leading to the formation of a propagating ionizing wave front, which culminates in a regenerative avalanche injection induced second breakdown failure. © 2005 IEEE.

Electrical Engineering

Technical Digest - International Electron Devices Meeting, IEDM

New physical insight and modeling of second breakdown (It2) phenomenon in advanced ESP protection devices

The accident at Bhopal on the night of December 2-3, 1984 was the world's worst accident, resulting in the immediate death of approximately 4,000 and the subsequent death of over 16,000, with life long injuries suffered by over 200,000 followed by genetic mutations to affect several generations of offsprings. The pollution of water bodies is affecting several hundred thousand more. No other recorded accident anywhere in the world has produced even 10% of the above casualties and life-long effects. In this paper, we will briefly describe the accident and the significant effects it has had on regulations, process development and design, training, teaching, RD, etc., all impacting process safety. © 2004 IChemE.

Institution of Chemical Engineers Symposium Series

Bhopal and the global movement on process safety

Aluminum nitride films (AlN) were grown on silicon and quartz substrates by DC reactive magnetron sputtering. They were annealed at 600 and 800 °C for 30 min in the presence of nitrogen gas. Ellipsometry, FTIR spectroscopy, optical transmission spectrum and C-V measurements were carried out to study the optical, structural and electrical properties of AlN films. It was found that annealing enhances the optical transmittance and bandgap. Annealing also results in an increase in Al-N bond density and band broadening of AlN absorption band. XRD studies revealed that the films are amorphous in nature. The refractive index of the films did not change significantly, whereas dielectric constant decreased with an increase in annealing temperature. Positive insulator charge density (Qin) increased, whereas interface electronic state density (Dit) decreased as a result of annealing. © 2004 Elsevier B.V. All rights reserved.

Surface and Coatings Technology

Effect of annealing on DC sputtered aluminum nitride films

Aluminum nitride films were deposited, at 200 °C, on silicon substrates by RF sputtering. Effects of rapid thermal annealing on these films, at temperatures ranging from 400 to 1000 °C, have been studied. Fourier transform infrared spectroscopy (FTIR) revealed that the characteristic absorption band of Al-N, around 684 cm-1, became prominent with increased annealing temperature. X-ray diffraction (XRD) patterns exhibited a better, c-axis, (0 0 2) oriented AlN films at 800 °C. Significant rise in surface roughness, from 2.1 to 3.68 nm, was observed as annealing temperatures increased. Apart from these observations, micro-cracks were observed at 1000 °C. Insulator charge density increased from 2×1011 to 7.7×1011 cm-2 at higher temperatures, whereas, the interface charge density was found minimum, 3.2×1011 eV-1cm-2, at 600 °C. © 2006 Elsevier Ltd. All rights reserved.

Materials Science in Semiconductor Processing

Influence of rapid thermal annealing on morphological and electrical properties of RF sputtered AlN films

This paper exploits a resistance-capacitance (RC) model of transient heat conduction for estimation of defect depth, and more significantly of the defect area, from single point surface temperature evolutions over the defect and non-defect regions of material subjected to step heating. For the initial time behaviour of the surface temperature, a distributed RC model has been presented and analysed for estimation of defect depth and area. In contrast, a lumped RC model forms the basis for obtaining an analytical expression for defect area from the later part of the surface temperature evolution. The derived analytical expression estimates the defect area from the defect depth, the saturation value of the absolute thermal contrast and the slopes of the initial and final surface temperature evolution. The presented method does not require knowledge of material thermal properties or the value of the incident heat flux for estimation of defect parameters. The method has been validated by estimating the parameters of defects of various sizes and at different depths from experimental and simulated surface temperature evolutions. © 2004 Elsevier Ltd. All rights reserved.

NDT and E International

Electro-thermal modelling and analysis for estimation of defect parameters by stepped infrared thermography

This paper proposes novel techniques for thermal nondestructive testing based on frequency modulated thermal waves. A mild steel sample having discontinuities at different depths is taken as a test sample. The limited depth resolution of the lock in thermography due to the fixed driving frequency of the excited heat sources is overcome by the proposed new technique. A pulse compression approach is used to detect subsurface discontinuities using linear frequency modulated thermal wave imaging and digitized linear frequency modulated thermal wave imaging. In this way, the peak power for probing the specimen can be decreased markedly by increasing the average transmitted energy, which is proportional to the length of the modulated excitation signal. Comparison between the techniques based on the analog frequency modulated signal and its digital form are presented.