Fracture analysis of local delaminations in laminated composites

A shear deformation model was developed to analyze local delaminations growing from transverse cracks in 90 degree plies located around the mid plane of symmetric laminates. The predictions of the model agree reasonably with experimental data from T300/934 graphite epoxy laminates. The predicted behavior is such that, in combination with an edge delamination model, the critical loads can be predicted accurately in the range of n from .5 to 8

Flux enhancement in the inner region of a geometrically and optically thick accretion disk

The surface flux (and the corresponding observed flux) of a geometrically thick ``funnel'' shaped disk is computed taking into account the radiation impinging on the surface from other parts of the disk. It is found that the ratio of the maximum apparent luminosity to the real luminosity of the disk is only a factor $\approx 5$ even when the opening angle of the disk is small ($\approx 15^o$). Thus, geometrically beamed emission from ``funnel'' shaped sub-Eddington disks around stellar mass black holes, cannot explain the Ultra-Luminous X-ray sources detected in nearby galaxies.Comment: accepted for publication in Ap

How Do Glassy Domains Grow?

We construct the equations for the growth kinetics of a structural glass within mode-coupling theory, through a non-stationary variant of the 3-density correlator defined in Phys. Rev. Lett. 97}, 195701 (2006). We solve a schematic form of the resulting equations to obtain the coarsening of the 3-point correlator $\chi_3(t,t_w)$ as a function of waiting time $t_w$. For a quench into the glass, we find that $\chi_3$ attains a peak value $\sim t_w^{0.5}$ at $t -t_w \sim t_w^{0.8}$, providing a theoretical basis for the numerical observations of Parisi [J. Phys. Chem. B 103, 4128 (1999)] and Kob and Barrat [Phys. Rev. Lett. 78, 4581 (1997)]. The aging is not "simple": the $t_w$ dependence cannot be attributed to an evolving effective temperature.Comment: 6 pages, 5 figure

The Hall Number, Optical Sum Rule and Carrier Density for the tt-t′t'-JJ model

We revisit the relationship between three classical measures of particle number, namely the chemical doping $x$, the Hall number $x_{hall}$ and the particle number inferred from the optical sum rule $x_{opt}$. We study the $t$-$t'$-$J$ model of correlations on a square lattice, as a minimal model for High $T_c$ systems, using numerical methods to evaluate the low temperature Kubo conductivites. These measures disagree significantly in this type of system, owing to Mott Hubbard correlations. The Hall constant has a complex behavior with several changes of sign as a function of filling $x$, depending upon the model parameters. Thus $x_{hall}$ depends sensitively on $t'$ and $J$, due to a kind of quantum interference.Comment: Typos removed,9 Figures, (Revised Figure.3 contains comparison with experiments

Spin-s wavefunctions with algebraic order

We generalize the Gutzwiller wavefunction for s = 1/2 spin chains to construct a family of wavefunctions for all s > 1/2. Through numerical simulations, we demonstrate that the spin spin correlation functions for all s decay as a power law with logarithmic corrections. This is done by mapping the model to a classical statistical mechanical model, which has coupled Ising spin chains with long range interactions. The power law exponents are those of the Wess Zumino Witten models with k = 2s. Thus these simple wavefunctions reproduce the spin correlations of the family of Hamiltonians obtained by the Algebraic Bethe Ansatz.Comment: 10 pages, 7 figure

INTEGRAL SOLUTIONS

We obtain the non-trival integral solutions for quartic Diaphoptine equations with two variables is presented. A few numerical examples are given

Performance Evaluation of Computation Intensive Tasks in Grid

Grid computing is a special type of parallel computing, which allows us to unite pools of servers, storage systems, and networks into a single large virtual super computer. Grid computing has the advantages of solving complex problems in a shorter time and also makes better use of the existing hardware. It can take advantage of underutilized resources to meet business requirements while minimizing additional costs. There are many Grid setup tools available. In this paper, Globus Toolkit, an open source tool for grid enabled applications, is considered. Initially grid is established between two systems running Linux, using Globus Toolkit. A simple matrix multiplication program, which is capable of running both in grid and stand alone systems, is developed. The application is executed in single system varying the order of the matrices. The same application is split into two sub jobs and run on two grid machines with different orders. Finally the results of the execution are compares and the results are presented in graphs. The work can be extended further to find the type of parallelizing suitable for the application developed. Similarly, FP tree algorithm is taken and the data sets are fed into different machine and in stand alone system. A suitable load balancing mechanism for grid application is discussed. The sections in the paper are arranged as following; Introduction to Grid, Grid setup using Globus toolkit, splitting of the matrix application, FP tree algorithm, performance results, future works, conclusion and references