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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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A steady state model is derived for the full-bridge series-resonant power converter. Normalized parametric curves for various currents and voltages are then plotted versus the triggering angle of the switching devices. The calculations are compared with experimental measurements made on a 50 kHz converter and a discussion of certain operating problems is presented.
Objects detected at beam axis intersections. Group of light sources or detectors is mounted in box at focal plane of lens. Box can therefore illuminate or view several axes, each corresponding to source or detector of group. Proximity sensing system developed to trigger braking system of automatically controlled car.
Circuit requiring only four integrated circuits (IC's) measures both heart rate and breath rate. Phase-locked loops lock on heart-rate and respiration-rate input signals. Each loop IC contains two phase comparators. Positive-edge-triggered circuit used in making monitors insensitive to dutycycle variations.
Quick connect tapered joint used with minimum manipulation and force. Split ring retainer holds locking ring in place. Minimal force required to position male in female joint, at which time split-ring retainers are triggered to release split locking rings. Originally developed to assemble large space structures, joint is simple, compact, strong, lightweight, self alining, and has no loose parts.
Accidental turn-on prevented. PFET diverts load current around SCR to prevent false SCR triggering from current and voltage switching transients. New circuit used in all types of single phase and polyphase inverters and in buck-boost-, and flyback regulators.
A discharge process whose trigger conditions are a negative exposed metallic surface surrounded by a less negative dielectric, and a large voltage gradient at a dielectric/metal interface is proposed. Analysis of SCATHA data for a discharge substantiates the postulation. Surface discharges cause a small transient charge transfer to space which results in voltage transients. A method of computing these transients, based on the charge lost through the capacitance to space and a fraction of charge stored in the dielectric at the discharge source was developed. It gives an estimate of the discharge transients at the discharge site, which is used as input for coupling code analysis of structure/system response. The transient computations were applied to a three-axis stabilized, geosynchronous satellite for both sunlight and eclipse charging. The energy of the transient pulses are about 1 mJ for sunlight discharge and 8 mJ for eclipse. Changing of selected coatings on the satellite would relieve the stress.
Infrared photometry and maps from 2 to 100 microns are presented for three of the principal far infrared sources in NGC 6334. Each region is powered by two or more very young stars. The distribution of dust and ionized gas is probably strongly affected by the presence of the embedded stars; one of the sources is a blister H II region, another has a bipolar structure, and the third exhibits asymmetric temperature structure. The presence of protostellar objects throughout the region suggests that star formation has occurred nearly simultaneously in the whole molecular cloud rather than having been triggered sequentially from within.
Scoring and scuffing are defined as two distinct but related forms of failure of hardened ferrous components lubricated by liquids. Experimental observations of these phenomena are described, and criteria for scoring and scuffing are discussed. The mechanisms proposed by various authors to explain these observations are enumerated. The view presented here is that, under conditions yet to be defined, scoring is a gradual breakdown of the lubrication of interacting asperities, such lubrication being boundary or microelastohydrodynamic in nature, or a mixture of the two. The final scuffing stage represents a breakdown of the main elastohydrodynamic system, but this may be triggered by the deterioration in surface topography as a result of scoring. An extension of published theoretical treatment of elastohydrodynamic breakdown is proposed, and a critical experiment to assess the importance of edge effects in band contacts is suggested. The practical implications of the proposed mechanism are reviewed, and recommendations for further work are made. A possible thermal instability mechanism for the breakdown of boundary lubrication is outlined.
Cometary splitting is investigated from the dynamical and physical standpoints. A simple two-parameter model is proposed in which the rate of recession of the fragments is determined by the momentum from outgassing, so that the net differential force is of the same nature as the nongravitational perturbations detected in the motions of unsplit comets; the two parameters of the model are the differential radial acceleration and the time of splitting. It is shown that the model successfully represents the positional observations of nearly all the 21 known split comets. The following candidate triggering mechanisms for cometary splitting are considered: tidal forces, rotation, dust-mantle dumping, and radioactive heating. A model that fits the dynamical data and physical characteristics is presented which suggests that most fragments must be appreciably nonspherical and rapidly precessing.
A balloon-borne instrument has been used to detect cosmic-ray antiprotons. These are identified topologically by the appearance of annihilation prongs in a thick lead-plate spark chamber. The initial recording of the data is enriched in potential antimatter events by a selective trigger. After a small subtraction for background, 14 identified antiprotons yield a flux of 1.7 plus or minus 0.00005 antiproton/(sq m ster sec MeV) between 130 and 320 MeV at the top of the atmosphere. When combined with higher energy antiproton flux measurements, this result indicates that the antiprotons have a spectrum whose shape is the same as that of the protons, but with a magnitude reduced by a factor of 1/3000.
The results of a detailed investigation into the nature of the H I-rich quasi-stellar object 0351+026 are presented. An improved H I profile reveals the presence of two distinct components. A high-quality CCD image clearly shows the presence of two galaxies. The brighter galaxy hosts the QSO while the less luminous companion has a prominent, apparently stellar nucleus. Moreover, this image also shows streamers of nebulosity emanating from the two galaxies and has an overall morphology which is highly reminiscent of that seen in other strongly interacting galaxies. Optical spectroscopy of the system shows that the forbidden O III emission lies between the two nuclei and there is strong evidence of stellar absorption lines in both the host and companion galaxies. Overall, the data suggest that this system represents a violent encounter between two low-luminosity H I-rich galaxies. The possibility exists that this collision has triggered the QSO activity in the brighter galaxy.
A review is presented of the astrophysical reasoning that links supernovae to the origin of the solar system. Topics examined concerning the supernova connections include the abundances of the nuclides at the time the solar system formed, the collapse of a solar cloud by supernova triggering, the origins of isotopic anomalies in solar system samples, and the sputtering of interstellar dust with the attendant chemical and isotopic evolution of the interstellar medium. The controversies surrounding each of these topics are critically examined, focusing on the issues arising from the discovery of the isotopic anomalies in meteorites.
A study is presented of the processes occurring in the root cap of corn which are requisite for the formation of root cap inhibitor and which can be triggered or modulated by both light and gravity. The results of this study indicate the importance of protein synthesis for light-induced gravitropic bending in roots. Root caps in which protein synthesis is prevented are unable to induce downward bending. This suggests that light acts by stimulating proteins which are necessary for the translation of the gravitropic stimulus into a growth response (downward bending). The turnover of protein with time was also examined in order to determine whether light acts by stimulating the synthesis of unique proteins required for downward growth. It is found that auxin in combination with light allows for the translation of the gravitropic stimulus into a growth response at least in part through the modification of protein synthesis. It is concluded that unique proteins are stimulated by light and are involved in promoting the downward growth in roots which are responding to gravity.
Two recent observations have provided the basis for study of a relationship between solar activity and the formation of small particles in the earth's atmosphere; the discovery of annual increases of condensation nuclei (CN) at 30 km and the detection of sulfuric acid molecules in large negative ion clusters in the 25-35-km altitude region. These observations have led to formulation and testing of a model wherein CN are formed in a 'polar cloud chamber' supersaturated with sulfuric acid vapor and triggered by ionization associated with solar flare cosmic radiation. It is concluded that such a model provides a potential explanation of the observations.
An auroral substorm is a highly transient process which is triggered on auroral L shells and leads to an abrupt change of state in the nightside magnetosphere. Direct measurements of electric fields in the outer magnetosphere are of critical importance to understand the processes involved in sudden substorm enhancements. Shepard et al. (1980) reported direct measurements of electric fields from the GEOS 2 satellite at equatorial latitudes which showed 15 mV/m westward inductive electric fields in association with tail collapses. Similar direct electric field measurements of the westward inductive electric field at low latitudes from the ISEE 1 satellite during the onset phase of an auroral substorm are reported in the present investigation. The observations show a rapid inward magnetic field (westward electric field) motion near midnight at low or equatorial latitudes simultaneous with the sudden onset of auroral substorm enhancements near the foot of the satellite field line.
Observations have been made in conjunction with two active magnetospheric experiments (Araks and Trigger) in which an electron beam apparently stimulated the precipitation of high-energy electrons from the deep magnetosphere. In both experiments, the data were obtained from rocket-boosted, parachute-borne X-ray bremsstrahlung detectors which were initially deployed at an altitude of 80 km near the foot of the flux tubes affected by each experiment. The X-ray results from these experiments are discussed and compared in terms of beam physics. It is concluded that artificial electron beams injected from ionosphere can stimulate pitch angle scattering and precipitation of higher energy electrons in the magnetosphere via a particle-wave-particle interaction. This mechanism operates over at least one order of magnitude of injection energy.
The general theory of beam plasma discharge (BPD) is discussed in relation to space and laboratory beam injection situations. An important concept introduced is that even when beam plasma instabilities are excited, there are two regime of BPD with radically different observational properties. They are described here as BPD with either classical or anomalous energy depositions. For high pressures or low altitudes, the classical is expected to dominate. For high altitudes and laboratory experiments, where the axial system size is less than lambda sub en, no BPD will be triggered unless the unstable waves are near the ambient plasma frequency and their amplitudes at saturation are large enough to create suprathermal tails by collapsing.
Infrared photometry and maps from 2 to 100 microns are presented for three of the principal far infrared sources in NGC 6334. Each region is powered by two or more very young stars. The distribution of dust and ionized gas is probably strongly affected by the presence of the embedded stars; one of the sources is a blister H II region, another has a bipolar structure, and the third exhibits asymmetric temperature structure. The presence of protostellar objects throughout the region suggests that star formation has occurred nearly simultaneously in the whole molecular cloud rather than having been triggered sequentially from within. Previously announced in STAR as N83-16263