Projection Methods: Swiss Army Knives for Solving Feasibility and Best Approximation Problems with Halfspaces

We model a problem motivated by road design as a feasibility problem. Projections onto the constraint sets are obtained, and projection methods for solving the feasibility problem are studied. We present results of numerical experiments which demonstrate the efficacy of projection methods even for challenging nonconvex problems

A Proposal for a Comprehensive Restructuring of the Public Information System

After more than ten years of legislative, judicial and bureaucratic tinkering, the public information system created by the Freedom of Information Act (FOIA) is still far from satisfactory. The present public information system has not been successful because its drafters lacked imagination and failed to do the basic work necessary to create a sound foundation for such a comprehensive program. They failed to analyze the realistic goals of a public information system; they ignored the ultimate goals of improved government performance; they misrepresented the system\u27s costs, both in monetary expense to taxpayers and in diminished government performance. They considered neither alternative techniques nor the problem of designing the public information system as an integral part of the total governmental structure. Actual open government for the benefit of the general populace will be possible only if the basic weaknesses of the present system are explored in depth. This Article is an appeal to Congress to undertake the careful analysis necessary to construct a workable, useful public information system

State estimation and absolute image registration for geosynchronous satellites

Spacecraft state estimation and the absolute registration of Earth images acquired by cameras onboard geosynchronous satellites are described. The basic data type of the procedure consists of line and element numbers of image points called landmarks whose geodetic coordinates, relative to United States Geodetic Survey topographic maps, are known. A conventional least squares process is used to estimate navigational parameters and camera pointing biases from observed minus computed landmark line and element numbers. These estimated parameters along with orbit and attitude dynamic models are used to register images, using an automated grey level correlation technique, inside the span represented by the landmark data. In addition, the dynamic models can be employed to register images outside of the data span in a near real time mode. An important application of this mode is in support of meteorological studies where rapid data reduction is required for the rapid tracking and predicting of dynamic phenomena

Direct Investigation of Superparamagnetism in Co Nanoparticle Films

A direct probe of superparamagnetism was used to determine the complete anisotropy energy distribution of Co nanoparticle films. The films were composed of self-assembled lattices of uniform Co nanoparticles 3 nm or 5 nm in diameter, and a variable temperature scanning-SQUID microscope was used to measure temperature-induced spontaneous magnetic noise in the samples. Accurate measurements of anisotropy energy distributions of small volume samples will be critical to magnetic optimization of nanoparticle devices and media.Comment: 4 pages, 4 figures. Submitted to Physical Review Letter

The electron spectra in the synchrotron nebula of the supernova remnant G 29.7-0.3

EXOSAT results obtained with the imaging instrument (CMA) and the medium energy proportional counters (ME) are discussed. Assuming that the featureless power-law spectrum obtained in the 2 to 10 keV range is synchrotron radiation from relativistic electrons, one derives constraints on magnetic field strength and age of the nebula. The energy spectra of the electrons responsible for the emission in the radio and X-ray ranges are discussed. The great similarity of the physical properties of G 29.7-0.3 and of three synchrotron nebulae containing a compact object observed to pulse in X-rays makes G 29.7 - 0.3 a very promising candidate for further search for pulsed emission. Further observations at infrared wavelengths might reveal the break(s) in the emitted spectrum expected from the radio and X-ray power-law indices and give us more information on the production of the electron populations responsible for the emission of the nebula

Orbit/attitude estimation for the GOES spacecraft using VAS landmark data

A software system is described which provides for batch least squares estimation of spacecraft orbit, attitude, and camera bias parameters using image data from the Geostationary Operational Environmental Satellites (GOES). The image data are obtained by the Visible and Infrared Spin Scan Radiometer (VISSR) Atmospheric Sounder (VAS). The resulting estimated parameters are used for absolute image registration. Operating in the Digital Equipment Corporation (DEC) PDP-11/70 computer, the FORTRAN system also includes the capabilities of image display and manipulations. An overview of the system is presented as well as some numerical results obtained from observations taken by the SMS-2 satellite over a 3 day interval in August 1975

Calculation of the static and dynamical correlation energy of pseudo-one-dimensional beryllium systems via a many-body expansion

Low-dimensional beryllium systems constitute interesting case studies for the test of correlation methods because of the importance of both static and dynamical correlation in the formation of the bond. Aiming to describe the whole dissociation curve of extended Be systems we chose to apply the method of increments (MoI) in its multireference (MR) formalism. However, in order to do so an insight into the wave function was necessary. Therefore we started by focusing on the description of small Be chains via standard quantum chemical methods and gave a brief analysis of the main characteristics of their wave functions. We then applied the MoI to larger beryllium systems, starting from the Be6 ring. First, the complete active space formalism (CAS-MoI) was employed and the results were used as reference for local MR calculations of the whole dissociation curve. Despite this approach is well established for the calculation of systems with limited multireference character, its application to the description of whole dissociation curves still requires further testing. After discussing the role of the basis set, the method was finally applied to larger rings and extrapolated to an infinite chain