Fixed-Rank Approximation of a Positive-Semidefinite Matrix from Streaming Data

Several important applications, such as streaming PCA and semidefinite programming, involve a large-scale positive-semidefinite (psd) matrix that is presented as a sequence of linear updates. Because of storage limitations, it may only be possible to retain a sketch of the psd matrix. This paper develops a new algorithm for fixed-rank psd approximation from a sketch. The approach combines the Nystrom approximation with a novel mechanism for rank truncation. Theoretical analysis establishes that the proposed method can achieve any prescribed relative error in the Schatten 1-norm and that it exploits the spectral decay of the input matrix. Computer experiments show that the proposed method dominates alternative techniques for fixed-rank psd matrix approximation across a wide range of examples

Practical sketching algorithms for low-rank matrix approximation

This paper describes a suite of algorithms for constructing low-rank approximations of an input matrix from a random linear image of the matrix, called a sketch. These methods can preserve structural properties of the input matrix, such as positive-semidefiniteness, and they can produce approximations with a user-specified rank. The algorithms are simple, accurate, numerically stable, and provably correct. Moreover, each method is accompanied by an informative error bound that allows users to select parameters a priori to achieve a given approximation quality. These claims are supported by numerical experiments with real and synthetic data

Local Chemical Environments and the Phonon Partial Densities of States of 57Fe in 57Fe3Al

Inelastic nuclear resonant scattering spectra were measured on alloys of Fe3Al that were chemically disordered, partially ordered, and D03 ordered. The features in the phonon partial density of states of 57Fe were found to change systematically with chemical short-range order in the alloy. Changes in the phonon partial density of states were modeled successfully by assigning vibrational spectra to 57Fe atoms in different first-nearest-neighbor chemical environments

Ant colony optimization for the single model U-type assembly line balancing problem

Cataloged from PDF version of article.An assembly line is a production line in which units move continuously through a sequence of stations. The assembly line balancing problem is defined as the allocation of tasks to an ordered sequence of stations subject to precedence constraints with the objective of optimizing a performance measure. In this paper, we propose ant colony algorithms to solve the single-model U-type assembly line balancing problem. We conduct an extensive experimental study in which the performance of the proposed algorithm is compared against best known algorithms reported in the literature. The results indicate that the proposed algorithms display very competitive performance against them. & 2009 Elsevier B.V. All rights reserved

PREDICATION AND COMPREHENSION OF RESERVOIR PARAMETERS OF WELL TESTING USING PAN SYSTEM SIMULATOR FOR INDIVIDUAL AND MULTIPLE WELLS

There are many softwares used to perform well test analysis, among which is Pan System. Many simulations have also been done to predicate reservoir parameters using well test analysis. This study aims to shed some light on the PREDICATION AND COMPREHENSION OF RESERVOIR PARAMETERS OF WELL TESTING USING PAN SYSTEM SIMULATOR FOR INDIVIDUAL AND MULTIPLE WELLS This study is a software simulation research which objective is to correlate pressure and time as a dependant variable in a well test analysis. This simulation will be using the Pan System Simulator which has been developed by Weatherford. The outcome of this simulation would be to demonstrate how well test analysis can be used to predicate reservoir parameters. Also, this study will demonstrate how a computer based well test analysis can be used to overcome the restrictions found on a manual well test analysis. The predicated parameters would then be used to study the effects of interfering wells on predicated parameters and also to classify and characterize the reservoir further. This document is a dissertation report which encompasses a background of the study, a problem statement, the objectives and scope of study, the relevancy and feasibility of study within the scope and time frame, the outline of the research methodology, the equipment involved, a Gantt chart depicting the study planning, the results obtained, discussion, conclusion and recommendation. The experiment was conducted on 7 individual wells where traditional and simulated well testing methods were conducted and also on 6 different cases of multiple well testing. Here, the results have helped comprehend the type of reservoir we are dealing with and what the parameters show. The reservoir dealt with follows a dual porosity flow regime reservoir and mostly parallel and single faulted boundaries. The criteria's of this reservoir together with the predicated parameters have aided in the understanding of the reservoir

Atom clusters and vibrational excitations in chemically-disordered Pt357Fe

Inelastic nuclear resonant scattering spectra of Fe-57 atoms were measured on crystalline alloys of Pt3Fe-57 that were chemically disordered, partially ordered, and L1(2) ordered. Phonon partial density of states curves for Fe-57 were obtained from these spectra. Upon disordering, about 10% of the spectral intensity underwent a distinct shift from 25 to 19 meV. This change in optical modes accounted for most of the change of the vibrational entropy of disordering contributed by Fe atoms, which was (+0.10 +/- 0.03) k(B) (Fe atom)(-1). Prospects for parametrizing the vibrational entropy with low-order cluster variables were assessed. To calculate the difference in vibrational entropy of the disordered and ordered alloys, the clusters must be large enough to account for the abundances of several of the atom configurations of the first-nearest-neighbor shell about the Fe-57 atoms