ON COMPUTING A BUY/COPY POLICY USING THE PITT-KRAFT MODEL

The Pitt-Kraft model of buying versus photocopying results in a small, but complex, nonlinear program. This paper identifies a Kuhn-Tucker point and demonstrates that for certain parameter values it is not optimal. A policy generation procedure is presented; the purpose is to prevent convergence of a primal algorithm to this inferior policy, which satisfies the Kuhn-Tucker optimality conditions

Quadratic Binary Programming Models in Computational Biology

In this paper we formulate four problems in computational molecular biology as 0-1 quadratic programs. These problems are all NP-hard and the current solution methods used in practice consist of heuristics or approximation algorithms tailored to each problem. Using test problems from scientific databases, we address the question, “Can a general-purpose solver obtain good answers in reasonable time?” In addition, we use the latest heuristics as incumbent solutions to address the question, “Can a general-purpose solver confirm optimality or find an improved solution in reasonable time?” Our computational experiments compare four different reformulation methods: three forms of linearization and one form of quadratic convexification

CONVERGENCE OF COLUMN GENERATION FOR SEMI-INFINITE PROGRAMS IN THE PRESENCE OF EQUALITY CONSTRAINTS

A convergence theorem is presented for the standard column generation algorithm which embodies GLM. The primary extension of earlier published theorems is the allowance of equality constraints. A related stability theorem is introduced to demonstrate robustness

AN EXACT UPDATE FOR HARRIS' TREAD

The purpose of this note is to show how Harris' TREAD value can be computed without approximation

SEARCHING ONE MULTIPLIER IN GLM

A unified approach is developed for one-dimensional GLM. The major result is a convergence theorem for interval reduction. Comparative analysis of bisection, linear interpolation and tangential approximation reveals the relative advantages of tangential approximation

GLM Versus Continuous Approximation for Convex Integer Programs

GLM is compared to continuous approximation for convex, integer programs. After noting the stronger bound provided by GLM, Lagrangian duality and a gap closing heuristic is used to demonstrate how GLM may provide a better feasible policy as well

Inverting graphs of rectangular matrices

AbstractThis paper addresses the question of determining the class of rectangular matrices having a given graph as a row or column graph. We also determine equivalent conditions on a given pair of graphs in order for them to be the row and column graphs of some rectangular matrix. In connection with these graph inversion problems we discuss the concept of minimal inverses. This concept turns out to have two different forms in the case of one-graph inversion. For the two-graph case we present a method of determining when an inverse is minimal. Finally we apply the two-graph theorem to a class of energy related matrices

Dynamical Color Correlations in a SU(2)cSU(2)_c Quark Exchange Model of Nuclear Matter

The quark exchange model is a simple realization of an adiabatic approximation to the strong-coupling limit of Quantum Chromodynamics (QCD): the quarks always coalesce into the lowest energy set of flux tubes. Nuclear matter is thus modeled in terms of its quarks. We wish to study the correlations imposed by total wavefunction antisymmetry when color degrees of freedom are included. To begin with, we have considered one-dimensional matter with a $SU(2)$ color internal degree of freedom only. We proceed by constructing a totally antisymmetric, color singlet {\it Ansatz} characterized by a variational parameter $\lambda$ (which describes the length scale over which two quarks in the system are clustered into hadrons) and by performing a variational Monte Carlo calculation of the energy to optimize $\lambda$ for a fixed density. We calculate the $q-q$ correlation function as well, and discuss the qualitative differences between the system at low and high density.Comment: 32 pages in REVTeX, IU/NTC 93-28, FSU-SCRI-93-161. The postscript file, including 12 figures, is available via anonymous ftp from ftp.scri.fsu.edu in /pub/jorgep/magic.p

Occult purulent pericarditis detected by indium-111 leukocyte imaging.

Leukocyte imaging with indium-111 is a relatively new technique which, to this point in time, has been discussed almost exclusively in the radiologic literature. Although this procedure has been used mainly to detect intra-abdominal infection, the thorax is routinely imaged along with the abdomen, and therefore detection of cardiac disease may be feasible. This case report is of a young woman after liver transplantation who developed occult purulent pericarditis initially detected by a leukocyte scan with indium-111. This case demonstrates that striking pericardial uptake on a whole-body indium-111 leukocyte scan can occur with purulent pericarditis, and it reemphasizes how insidiously purulent pericarditis may present in an immunosuppressed patient