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Shiv Nadar University

Center for Informatics

Linear and nonlinear regression problems are very common in different fields of science and engineering. A number of different methods to provide accurate input/output relationship have been proposed in the literature. Lazy learning is a recently introduced nonparametric regression technique that employs a memory based local learning approach. Employment of (i) local weighted regression for parametric identification and (ii) PRESS statistic to assess a local model for structural identification, are the two unique features of Lazy learning. The method attempts to fit the training data in a region around the location of the query point by locally interpolating the relevant neighboring points based on distance measure. This is particularly useful when limited number of input/output pairs are available and an accurate prediction is required. Being a memory based technique, it does not require separate training, which greatly enhances the speed of implementation. Moreover the method is less susceptible to noise contamination. All these features are illustrated with one benchmark multivariate statistical example and three important chemical engineering examples comprising boiling point prediction of aliphatic hydrocarbons using quantitative structural property relations, system identification for a continuous stirred tank reactor in which an exothermal irreversible reaction between sodium thiosulfate and hydrogen peroxide occurs and a fermentation process for polyol production. The performance of the proposed method is compared with some of the state-of-Art approaches. © 2003 by the authors. All rights reserved.

World University root node

International Journal of Chemical Reactor Engineering

Memory based local learning: Application to process engineering problems

The paper illustrates the application of the ant colony optimization algorithm to solve both continuous function and combinatorial optimization problems in reliability engineering. The ant algorithm is combined with the strength Pareto fitness assignment procedure to handle multiobjective problems. Further, a clustering procedure has been applied to prune the Pareto set and to maintain diversity. Benchmark case examples show the superiority of the ant algorithm to such problems. Copyright © 2002 John Wiley & Sons, Ltd.

Quality and Reliability Engineering International

Ant algorithm for single and multiobjective reliability optimization problems

Using ab initio total energy calculations we demonstrate that the recently found metal encapsulated silicon clusters Si12Be can be assembled to form hexagonal nanotubes of silicon. This is in contrast to undoped silicon structures that are distorted and have a tendency to agglomerate. The finite nanotubes have varying HOMO-LUMO gaps depending upon the length and amount of doping. However, infinite nanotubes are metallic, symmetric and stable, making metal encapsulation a useful route to generate metallic silicon nanowires for miniature devices.

Nano Letters

Cluster Assembled Metal Encapsulated Thin Nanotubes of Silicon

Physical Review

Magic behavior of Si 15 M and Si 16 M „ M{\"{A}}Cr , Mo and W {\ldots} clusters

Computer simulations have been playing an important role in understanding the evolution of structure, thermodynamic behaviour and other physicochemical properties of clusters. These studies have complemented experimental results and helped to develop basic concepts. In addition, it has become possible to do computer experiments to design new stable clusters with certain desired properties. Possibilities are being explored to ascertain whether certain magic clusters might be assembled to form solids. This could lead to the development of novel cluster-based materials. Here we review the progress in our understanding of the structural, electronic, magnetic and thermodynamic properties of clusters of metals and semiconductors, as well as mixed clusters. First principles approaches based on density functional theory have become central to such studies and a brief overview is given of widely used methods, such as those based upon a localized basis or a plane wave approach. Recent progress in transferable tight-binding parameter schemes is also discussed. Large metal clusters having up to several thousand atoms have been studied using simpler methods, such as the embedded-atom or the effective medium theory and results of some such studies are included.

Clusters and nanomaterials

Ab Initio Computer Simulations on Microclusters: Structures and Electronic Properties

Physica B: Condensed Matter

Electronic structure of single wall carbon nanotube bundles under compression as compared to graphite and hexagonal graphene stacking

of Silicon Singh, Abhishek Kumar; Kumar, Vijay; Briere, Tina M.; Kawazoe, Yoshiyuki

First-principles electronic structure calculations have been carried out on (formula presented) atoms using ultrasoft pseudopotentials, a plane wave basis and generalized gradient approximation for the exchange-correlation energy, to elucidate the growth behavior and the evolution of the electronic structure. Our results show that clusters with (formula presented) prefer high coordination structures with hexagonal antiprisms except for (formula presented) which has a distorted body centered cubic structure (bcc). Clusters with (formula presented) favor lowest spin configurations. Of particular importance is the finding that icosahedral growth is not favored in these clusters. There are large highest occupied-lowest unoccupied molecular orbital (HOMO-LUMO) gaps for clusters with 4, 6, 8, 10 and 16 atoms. These are in agreement with the observed low reactivities as well as the photoemission data of 6-, 8-, 10- and 16-atom clusters. Clusters with 4, 8, 10, 15 and 16 atoms are found to be magic, suggesting the importance of the atomically closed shell bcc structure of (formula presented) even though the HOMO-LUMO gap is small. However, (formula presented) is not magic. A dimerization behavior is obtained in (formula presented) and it is found to be even more prominent in the isoelectronic (formula presented) But, this tendency is absent in (formula presented) The calculated binding energies, electronic structures and fragmentation behavior are in good agreement with available experimental data. {\textcopyright} 2002 The American Physical Society.

Physical Review B - Condensed Matter and Materials Physics

Atomic and electronic structures of niobium clusters

Physical Review-Section B-Condensed Matter 65 (16), 161402R

{RAPID COMMUNICATIONS-Surface physics, low-dimensional systems and related topics-Symmetry-driven phase transformations in single-wall carbon-nanotube bundles under hydrostatic {\ldots}}

The structures and magnetic properties of Mn clusters containing 13, 15, 19 and 23 atoms have been predicted from ab initio electronic structure calculations. The lowest energy structures of the 13-, 19- and 23-atom clusters are icosahedral and have ordered spin configurations in which blocks of ferromagnetically coupled spins are antiferromagnetically coupled with each other. The 15-atom cluster is body-centered cubic with antiferromagnetic coupling. The net moments are small and lie in the range of (formula presented) however, the average local atomic moments have high values close to (formula presented) These results are discussed in light of recent Stern-Gerlach experiments. {\textcopyright} 2002 The American Physical Society.