# Search

Now showing items 11-20 of 29

#### Efficient Iterative Solution of the Three-Dimensional Helmholtz Equation

(1998-10-15)

We examine preconditioners for the discrete indefinite Helmholtz equation on a
three-dimensional box-shaped domain with Sommerfeld-like boundary conditions.
The preconditioners are of two types. The first is derived
by ...

#### Eigenanalysis of Some Preconditioned Helmholtz Problems

(1998-10-15)

In this work we calculate the eigenvalues obtained by
preconditioning the discrete Helmholtz operator with
Sommerfeld-like boundary conditions on a rectilinear domain, by
a related operator with boundary conditions
that ...

#### Text Summarization via Hidden Markov Models and Pivoted QR Matrix Decomposition

(2001-05-10)

A sentence extract summary of a document is a subset of the
document's sentences that contains the main ideas in the
document.
We present two approaches to generating such summaries.
The first uses a pivoted QR ...

#### Computation and Uses of the Semidiscrete Matrix Decomposition

(1999-04-06)

We derive algorithms for computing a semidiscrete approximation to a
matrix in the Frobenius and weighted norms. The approximation is formed
as a weighted sum of outer products of vectors whose elements are plus or
minus ...

#### Adaptive Use of Iterative Methods in Predictor-Corrector Interior Point Methods for Linear Programming

(1999-04-06)

In this work we devise efficient algorithms for finding the search
directions for interior point methods applied to linear programming
problems. There are two innovations. The first is the use of updating of
preconditioners ...

#### A Multigrid Method Enhanced by Krylov Subspace Iteration for Discrete Helmholtz Equations

(1999-08-27)

Standard multigrid algorithms have proven ineffective for the solution of
discretizations of Helmholtz equations. In this work we modify the standard
algorithm by adding GMRES iterations at coarse levels and as an outer ...

#### A Semi-Discrete Matrix Decomposition for Latent Semantic Indexing in Information Retrieval

(1998-10-15)

The vast amount of textual information available today is useless unless
it can be effectively and efficiently searched. In information
retrieval, we wish to match queries with relevant documents. Documents
can be ...

#### Large Latent Semantic Indexing via a Semi-Discrete Matrix Decomposition

(1998-10-15)

With the electronic storage of documents comes the possibility of
building search engines that can automatically choose documents relevant
to a given set of topics. In information retrieval, we wish to match
queries ...

#### Displaying Confidence Images

(2000-07-20)

Algorithms for computing images result in an estimate of an image.
The image may result from deblurring a measured image, from
deconvolving a set of measurements, or from computing an image
by modeling physical processes ...

#### Stagnation of GMRES

(2001-11-12)

We study problems for which the iterative method \gmr
for solving linear systems of equations makes no progress
in its initial iterations. Our tool for analysis is
a nonlinear system of equations, the stagnation ...