Diffraction-limited CCD imaging with faint reference stars

By selecting short exposure images taken using a CCD with negligible readout noise we obtained essentially diffraction-limited 810 nm images of faint objects using nearby reference stars brighter than I=16 at a 2.56 m telescope. The FWHM of the isoplanatic patch for the technique is found to be 50 arcseconds, providing ~20% sky coverage around suitable reference stars.Comment: 4 page letter accepted for publication in Astronomy and Astrophysic

Economic and demographic issues related to deployment of the Satellite Power System (SPS)

Growth in energy consumption stimulated interest in exploitation of renewable sources of electric energy. One technology that was proposed is the Satellite Power System (SPS). Before committing the U.S. to such a large program, the Department of Energy and the National Aeronautics and Space Administration are jointly participating in an SPS Concept Development and Evaluation Program. This white paper on industrial and population relocation is part of the FY 78 preliminary evaluation of related socio-economic issues. Results of four preliminary assessment activities are documented

Functional design for operational earth resources ground data processing

The author has identified the following significant results. Study emphasis was on developing a unified concept for the required ground system, capable of handling data from all viable acquisition platforms and sensor groupings envisaged as supporting operational earth survey programs. The platforms considered include both manned and unmanned spacecraft in near earth orbit, and continued use of low and high altitude aircraft. The sensor systems include both imaging and nonimaging devices, operated both passively and actively, from the ultraviolet to the microwave regions of the electromagnetic spectrum

Mixing effectiveness in the Apollo oxygen tanks of spin-up and rotation-reversal maneuvers

Two-dimensional simulations of stratified flows in the Apollo oxygen tanks have been used to estimate the mixing effectiveness of spin-up and rotation-reversal maneuvers. Calculations have been made for square and circular cylindrical tank geometries. Differences arising from heater position on the tank wall or near the center of the tank have been investigated. In the event of a prolonged period without normal maneuvers, the potential pressure decay (drop in pressure that would result from adiabatic mixing) can be suppressed by more than a factor of two through the use of spin-up and rotation-reversal maneuvers. Changes in rotation rate of order three revolutions per hour or greater are sufficient for this purpose

A review of modular strategies and architecture within manufacturing operations

This paper reviews existing modularity and modularization literature within manufacturing operations. Its purpose is to examine the tools, techniques, and concepts relating to modular production, to draw together key issues currently dominating the literature, to assess managerial implications associated with the emerging modular paradigm, and to present an agenda for future research directions. The review is based on journal papers included in the ABI/Inform electronic database and other noteworthy research published as part of significant research programmes. The research methodology concerns reviewing existing literature to identify key modular concepts, to determine modular developments, and to present a review of significant contributions to the field. The findings indicate that the modular paradigm is being adopted in a number of manufacturing organizations. As a result a range of conceptual tools, techniques, and frameworks has emerged and the field of modular enquiry is in the process of codifying the modular lexicon and developing appropriate modular strategies commensurate with the needs of manufacturers. Modular strategies and modular architecture were identified as two key issues currently dominating the modular landscape. Based on this review, the present authors suggest that future research areas need to focus on the development and subsequent standardization of interface protocols, cross-brand module use, supply chain power, transparency, and trust. This is the first review of the modular landscape and as such provides insights into, first, the development of modularization and, second, issues relating to designing modular products and modular supply chains

Economic Consequences of a Nitrate Ban on U.S. and Ohio Hog Farmers

Exact date of working paper unknown.Because of potential health hazards, the USDA may ban nitrite use in the meat processing industry. A nitrite ban without an alternative substitute may cause disequilibrium within the meat industry. Farmers and meat processors will sustain increased costs as they transfer resources from one enterprise to another

Low frequency m=1 normal mode oscillations of a self-gravitating disc

A continuous system such as a galactic disc is shown to be well approximated by an N-ring differentially rotating self-gravitating system. Lowest order (m=1) non-axisymmetric features such as lopsidedness and warps are global in nature and quite common in the discs of spiral galaxies. Apparently these two features of the galactic discs have been treated like two completely disjoint phenomena. The present analysis based on an eigenvalue approach brings out clearly that these two features are fundamentally similar in nature and they are shown to be very Low frequency Normal Mode (LNM) oscillations manifested in different symmetry planes of the galactic disc. Our analysis also show that these features are actually long-lived oscillating pattern of the N-ring self-gravitating system.Comment: 5 figures. Accepted for publication in MNRAS Letter

Self-Consistent Response of a Galactic Disk to an Elliptical Perturbation Halo Potential

We calculate the self-consistent response of an axisymmetric galactic disk perturbed by an elliptical halo potential of harmonic number m = 2, and obtain the net disk ellipticity. Such a potential is commonly expected to arise due to a galactic tidal encounter and also during the galaxy formation process. The self-gravitational potential corresponding to the self-consistent, non-axisymmetric density response of the disk is obtained by inversion of Poisson equation for a thin disk. This response potential is shown to oppose the perturbation potential, because physically the disk self-gravity resists the imposed potential. This results in a reduction in the net ellipticity of the perturbation halo potential in the disk plane. The reduction factor denoting this decrease is independent of the strength of the perturbation potential, and has a typical minimum value of 0.75 - 0.9 for a wide range of galaxy parameters. The reduction is negligible at all radii for higher harmonics (m > or = 3) of the halo potential. (abridged).Comment: 26 pages (LaTex- aastex style), 3 .eps figures. To appear in the Astrophysical Journal, Vol. 542, Oct. 20, 200