Hydrodynamic modeling of mass loss from cataclysmic variable secondaries

Results of detailed computer simulations of mass loss from a cataclysmic variable secondary are presented. The calculations involve solution of the nonlinear hydrodynamical equations of stellar structure under varying degrees of approximation in an attempt to determine stability of the mass loss process. For comparison with previous theoretical studies dynamical sequences were computed assuming spherically symmetric mass loss from the secondary. The assumption of spherical symmetry is very poor since nearly all of the transferred material is lost within a small region about the inner Lagrangian point. Dynamical sequences treating only the region near the Lagrangian point were constructed in a manner consistent with the assumption of Roche geometry. Finally the effects of mass flow nonorthogonal to the Roche equipotential surfaces were treated in a very simple way. The last generalization produces stable mass loss in a model which was unstable for the less realistic approximation schemes. The finding of stable mass transfer implies that instability of the secondary star is not the mechanism leading to cataclysmic variable outbursts. This conclusion is consistent with published observations of dwarf novae made just prior to outburst.A detailed account of this study will be published elsewhere.Now at National Center for Atmospheric Research, P. O. Box 3000, Boulder, CO 80307     

The Impact of Integrated Electronics on Aerospace Avionic Subsystems

Integrated electronics or microelectronics is one of today's major technical frontiers. Possibilities offered to the designer of avionics subsystems, for aerospace vehicles, by these techniques, are almost limitless, from the point of view of performance capabilities as well as reliability and maintainability. Application will change current engineering practices in avionics design. Some changes will be easy; in others, problems will appear. This paper discusses these changes, indicating potential gains to be expected as well as potential problem areas. The rise in the application of integrated electronics is expected to be high for the next 10 to 15 years. By 1980, integrated circuitry will have largely replaced the use of discrete components, and the rate-of-increase-of-application curves will level off.     

Efficient wideband jammer ing when using stretch processing

Techniques are described for performing adaptive jammer ing over extremely wide bandwidths on radar systems which use linear frequency modulated (LFM) waveforms and stretch processing. It is assumed that the range uncertainty of the target is a small percentage of the equivalent range extent of the uncompressed pulse. The assumption allows the cancellation to take place following stretch processing in either the time domain using a narrowband sliding filter that keeps up with the chirp fate or in the frequency domain. The new approach supports ing performance over gigahertz of bandwidth comparable to that previously achieved over a few megahertz using approximately the same number of spatial degrees of freedom.     

The use of model-based test requirements throughout the productlife cycle

Test requirements, which are generally collected in multiple disparate formats throughout the life cycle of an electronic product, could be used in various applications that reduce test and development cycle times and increase the confidence in the final test program. Unfortunately, test requirements are seldom captured in a consistent format that may be processed by a computer, thus eliminating the possibility of using such requirements in an engineering application. Additionally, such an approach disallows test requirements captured in one segment of the product life cycle to be reused in subsequent life cycle stages. This paper describes a model-based methodology, specifically the Test Requirements Model (TeRM), which can be shown to facilitate the transfer of test-related product information between various stages of the life cycle. This transportability, in conjunction with an exchange format that can be processed by a computer, permits test requirement information to support value-added applications in the engineering process throughout the life cycle of a product     

Performance of 10- and 20-target MSE classifiers

MIT Lincoln Laboratory is responsible for developing the ATR (automatic target recognition) system for the DARPA-sponsored SAIP program; the baseline ATR system recognizes 10 GOB (ground order of battle) targets; the enhanced version of SAIP requires the ATR system to recognize 20 GOB targets. This paper presents ATR performance results for 10- and 20-target mean square error (MSE) classifiers using high-resolution SAR (synthetic aperture radar) imagery.     

Battery condition management: an important way to protect acritical asset

The efficacy of employing battery condition management equipment and procedures is demonstrated on the solid basis of field experience in which the host batteries were found either to be flawed or operated in ways that would compromise reliability. Examples found using such equipment and reported in this paper include a cell whose voltage vacillated daily while on float, post/strap joints whose accept/reject connection integrity was erratic with time, chargers whose voltages were improperly set (both high and low), and a battery room environment whose conditions were life-shortening to electrolytic cells     

An adventure in technology and marketing: a personal account. Tripto the Orient via the Moon

Early in the sixties when President Kennedy announced the goal to land a man on the Moon and return him safely to Earth, there was no way to gauge, accurately and reliably, the millions of pounds of fuel and oxidizer in the proposed rocket. Late in the sixties, when Phillips Petroleum and Marathon Oil contracted to provide large-scale, long term, ocean transport of Liquefied Natural Gas, no system existed to satisfactorily gauge this stream of high value cargoes for commercial transactions. The adventure in solving these related problems led to a worldwide market for LNG Custody Transfer Systems, a successful transfer of technology from a NASA program to commercial use     

Lunar Exploration Neutron Detector for the NASA Lunar Reconnaissance Orbiter

The design of the Lunar Exploration Neutron Detector (LEND) experiment is presented, which was optimized to address several of the primary measurement requirements of NASA’s Lunar Reconnaissance Orbiter (LRO): high spatial resolution hydrogen mapping of the Moon’s upper-most surface, identification of putative deposits of appreciable near-surface water ice in the Moon’s polar cold traps, and characterization of the human-relevant space radiation environment in lunar orbit. A comprehensive program of LEND instrument physical calibrations is discussed and the baseline scenario of LEND observations from the primary LRO lunar orbit is presented. LEND data products will be useful for determining the next stages of the emerging global lunar exploration program, and they will facilitate the study of the physics of hydrogen implantation and diffusion in the regolith, test the presence of water ice deposits in lunar cold polar traps, and investigate the role of neutrons within the radiation environment of the shallow lunar surface.     

Recent Advances in Understanding Particle Acceleration Processes in Solar Flares

We review basic theoretical concepts in particle acceleration, with particular emphasis on processes likely to occur in regions of magnetic reconnection. Several new developments are discussed, including detailed studies of reconnection in three-dimensional magnetic field configurations (e.g., current sheets, collapsing traps, separatrix regions) and stochastic acceleration in a turbulent environment. Fluid, test-particle, and particle-in-cell approaches are used and results compared. While these studies show considerable promise in accounting for the various observational manifestations of solar flares, they are limited by a number of factors, mostly relating to available computational power. Not the least of these issues is the need to explicitly incorporate the electrodynamic feedback of the accelerated particles themselves on the environment in which they are accelerated. A brief prognosis for future advancement is offered.