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991.
992.
Current and projected system requirements for inertial reference assemblies emphasize high accuracy, long life, and low power. An inertial reference assembly ( IRA) which embodies the aforementioned characteristics was developed recently. Pulse rebalanced gas-bearing gyroscopes were used to attain high accuracy and long life. Temperature compensation of gyroscope parameters (in lieu of temperature control) and dual voltage spinmotor operation helped achieve low-power operation. The latter two items represent an advancement in the state of the art and form the subject of this paper. These techniques were used in the construction of a three-axis IRA with an operating power less than 50 watts. It has achieved 0.1 percent scale factor accuracy over a 60°F range. 相似文献
993.
H.E. Hinteregger 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1981,1(12):39-52
The development of significantly improved representations of solar EUV inputs for computer-aided investigations of the terrestrial thermosphere and ionosphere has become attractive particularly for the present solar cycle which has been covered by reasonably complete and continuous EUV observations from the AE-E Satellite. These representations try to satisfy some rather incongruous , regarding (a) the strong wavelength-dependence in the atmospheric cross sections of the various types of EUV photon interactions, (b) the great differences in the relative amplitudes of the various types of variations in the full-disk fluxes of emissions at different wavelengths, and (c) the persisting desire to use only a as actual input variables for computational models supposed to cover the entire EUV wavelength range (remembering the great success of empirical thermospheric models using only two indices). These general physical and specific aeronomical demands indeed outline a very difficult task. The present study, based mainly on AE-E satellite observations during 1976–1979, represents an exploratory step, only clarifying some important developmental aspects, without recommending any specific formulations for immediately practicable adoption in aeronomical modelling at this time. 相似文献
994.
E.R. Mustel 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1981,1(3):15-23
The author's finding that active regions are sources of relatively slow and approximately radial quasistationary corpuscular streams is confirmed by using the fact that active regions are closely connected with coronal holes. Furthermore, attention is paid to numerous papers according to which the active regions characterized by enhanced and prolonged chromospheric (flare) activity are also sources of quasistationary corpuscular streams. Velocities of gases in these streams are higher than velocities of gases in streams from “quiet” active regions.On the basis of all these studies it is suggested that the origin of outflow of plasma from “quiet” active regions and from active regions with enhanced flare activity is the same and is due to some continuous non-stationary processes in the active regions. The velocity of gases in all these streams grows with increasing continuous flare activity in the active regions.It is concluded that quasistationary corpuscular streams from active regions with enhanced flare activity are important sources of cosmic rays from the sun. 相似文献
995.
Pecht M.G. Fink J. Hakim E. Wyler J. 《Aerospace and Electronic Systems Magazine, IEEE》1997,12(7):39-42
The Qualified Manufacturer List (QML) approach, detailed in MIL-I-38535, General Specification for Integrated Circuits (Microcircuit) Manufacturing, embraces many of the commercial practices employed by high volume microcircuit suppliers. Nevertheless, with the availability of highly reliable and lower cost commercial parts, the QML approach becomes unnecessary and undesirable. In this paper we attempt to show why US government support of the QML program is leading the military and government to unaffordable access to out-dated technologies, damaging our country's military and avionics position. We will present information to show why we support the retraction of MIL-PRF-38535 and any other documents which imply that QML parts are superior to commercial parts, including those of QPL, MIL-STD-454, and MIL-HDBK-217 (now prohibited from use in all new Army programs) 相似文献
996.
E. Illés A. Horváth 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1981,1(8):49-52
L-grooves are the consequence of layered structure of Phobos, which are made up of parallel layers of different composition or hardness. 相似文献
997.
A. H. Gabriel E. Antonucci K. J. H. Phillips 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1981,1(13):267-273
The X-Ray Polychromator experiment has been in operation on the SMM satellite for over three months. It is observing flares and active regions in the wavelength range 1Å to 23Å using a number of different modes. These include polychromatic imaging, high resolution line profiles, high dispersion spectra, and light curves with high time-resolution. Data are described together with some of the preliminary analysis and interpretation. 相似文献
998.
999.
Taylor H.P. Haroules G.G. Brown W.E. 《IEEE transactions on aerospace and electronic systems》1969,(4):581-588
In angle tracking antenna applications, the angle sensing boresight accuracy capabilities are important. The ability of an antenna to precisely determine the bearing angle to a point source is determined by the slope of the control function pattern at boresight. In the presence of extraneous interference, the magnitudes of the sidelobe and backlobe responses are important. Control pattern slope (angular sensitivity) is primarily a function of aperture illumination. It can be described by a current distribution in intensity and phase at every point. Once distribution is defined, lobe structure is defined by the associated transform. When more than one feed is used, the distribution will be a vector sum of the individual feed distributions. The resulting secondary pattern can be defined in terms of the amplitude distribution and the phase center locations of the contributing feeds. With a four-horn monopulse configuration, the feed phase centers are displaced from the boresight axis. Placing the phase centers on the boresight axis by rotating the feeds through 45 degrees results in a different set of intensity and phase values. A quite different secondary pattern results. The control function obtained by the subtraction of the powers from a paired set of on-axis feeds results in a lower sidelobe level than that obtained with a conventional monopulse combiner for a given feed taper. 相似文献
1000.
If accurate first-order corrections for ionospheric delay are applied to VHF ranging signals, the second-order terms become dominant. Only with abnormally large values of ionospheric electron content do the second-order terms lead to serious errors, however. Since these terms can be estimated to within 10 percent, further correction can lead to very small position errors. 相似文献