TUSHAR JAIN

Design/methodology/approach – The hybridization is carried out in two phases; first, the diversity in searching the optimal solution is increased using selection, crossover, and mutation operators. Second, the search direction vector is optimized using PSO to enhance the ...

234 Int. J. Automation and Control, Vol. 4, No. 2, 2010 ... Hybrid bacterial foraging and particle swarm optimisation for fuzzy precompensated control of flexible manipulator ... Department of Electronics and Computer Engineering, Caledonian College of Engineering, Muscat 111, ...

We have performed transition state searches on the potential energy landscape for bulk and freestanding film polymer glasses and identified connected minima. An analysis of the displacements between minima shows that the sites that undergo the greatest displacement are highly localized in space for both the bulk and the thin-film systems studied. In the case of the thin film, the clusters originate at the surface and penetrate into the center of the film thereby coupling the relaxation in the center of the film to the mobile surface layer. Furthermore, the energy barriers between minima are lower in the thin film than in the bulk system. These findings can rationalize the experimentally observed depression of the glass transition temperature in freestanding polymer films.

Molecular simulations of a model, deeply quenched polymeric glass show that the elastic moduli become strongly inhomogeneous at length scales comprising several tens of monomers; these calculations reveal a broad distribution of local moduli, with regions of negative moduli coexisting within a matrix of positive moduli. It is shown that local moduli have the same physical meaning as that traditionally ascribed to moduli obtained from direct measurements of local constitutive behaviors of macroscopic samples.

A newly proposed Monte Carlo formalism has been used to simulate a glass-forming liquid above and below the glass transition temperature. The heat capacity exhibits a sharp peak at a temperature lower than that reported from extensive molecular dynamics simulations. Its height is larger than that reported earlier. At temperatures below mode coupling, the average inherent-structure energy of the configurations generated in this work is significantly lower than that reported in the literature. The entropy of the supercooled liquid is calculated directly from our simulations and that of a disordered solid is calculated by a normal-mode analysis. We find that at low temperatures these two entropy curves become essentially parallel. They do not intersect each other, raising questions about the existence of a Kauzmann temperature in this glass-forming mixture.