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991.
Shapiro E.Y. Schenk F.L. Decarli H.E. 《IEEE transactions on aerospace and electronic systems》1979,(2):245-252
The feasibility of providing flight control systems with software-managed redundancy is investigated. It is shown that sufficient information can be extracted from aircraft attitude sensors to allow analytic reconstruction of the stability augmentation system (SAS) sensor signals in the event of SAS sensor failures. The sensor signal reconstruction is performed in a deterministic setting by using a Luenberger observer. A simple and efficient design procedure is presented based on Gopinath's [1] work. As an illustrative example, the proposed sensor signal reconstruction technique is exercised on the L-1011 aircraft lateral axis rigid body simulation. It is shown that with an accurate airframe model perfect reconstruction is feasible. In addition, it is also shown via simulation results that with imperfect knowledge of the airframe model (based on standard wind tunnel data), the proposed reconstruction is accurate enough to have a negligible impact on the overall aircraft performance. 相似文献
992.
Several advanced capacitor designs that might be used in high average power space applications are described. Each type is fundamentally limited by breakdown phenomena. All are intrinsically limited to maximum fields on the order of 1000 MV/m. None of these units has been space rated for energy storage applications. Several problems that must be solved before use in space are presented as well as the current state of the art and estimates of developmental potential 相似文献
993.
R.K. Crouch A.L. Fripp W.J. Debnam I.O. Clark P.G. Barber F.M. Carlson 《Acta Astronautica》1985,12(11):923-929
Lead-tin-telluride has been grown in a thermally stable mode (solutally unstable) and in a solutally stable (thermally unstable) mode in a Bridgman configuration. Significant differences in the crystal morphology and the compositional homogeneity have been found between the two configurations. In addition, for the solutally stable configuration, evidence has been found that the flow characteristics in the melt change drastically during the course of the run. 相似文献
994.
F. Creutzberg D.J. McEwen 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1982,2(10):85-88
Observations of auroral particles by rockets and satellites show the existence of structured “inverted V” type precipitation events with electron characteristic energies ranging up to several hundred eV in the post-noon dayside auroral region. Two station ground-based measurements from Cape Parry, NWT and Sachs Harbour, NWT, Canada from meridian scanners and auroral all-sky TV cameras are used in conjunction with rocket-borne electron measurements to study the temporal and spatial characteristics of the associated auroral emissions. The frequent occurrence of narrow, transient auroral arcs with lifetimes of 1–2 minutes, resulting from the inverted V events, is discussed. 相似文献
995.
The author examines a systems approach to automation that the printed circuit board (PCB) manufacturer can use in order to adapt today's technology for his or her individual needs. He begins with an overview of production functions. He then describes the subsystems approach, the steps leading to computerization, implementation, the bare board test system, and preprocessing 相似文献
996.
Dorr RF 《Aerospace America》2004,42(2):6-8
The Washington Watch column reports on President Bush's recently announced human space flight program, which includes new policies for returning the shuttle to flight, finishing the International Space Station by 2010, and developing a new space vehicle to return to the Moon; challenges in the airline industry; and selection of a helicopter for use by the President. 相似文献
997.
Grazing-incidence telescopes for X-ray astronomy 总被引:1,自引:0,他引:1
R. Giacconi W. P. Reidy G. S. Vaiana L. P. Van Speybroeck T. F. Zehnpfennig 《Space Science Reviews》1969,9(1):3-57
We review the progress made at our laboratory over the past several years in developing grazing-incidence imaging X-ray optics. Mirrors, detection systems and dispersion techniques are discussed and experimental results are given. We discuss the application of two telescope systems to a number of experimental observations in X-ray astronomy. 相似文献
998.
The tracking of synchronous satellites to provide propagation delays for the synchronization of clocks is described. The tracking is accomplished by range measurements to the satellite from three stations using signals transponded by the satellite. These same signals also functioned as the timing signals for the synchronization of other stations' clocks. Although the range measurements were of low resolution by usual standards, approximately 3000 meters, they provided the delays necessary to synchronize clocks to 40 microseconds or better. These results were obtained over a 4-month period using two satellites with measurements from five stations in the United States and South America. 相似文献
999.
The effect of geometric distortion on the local accuracy of the image registration algorithms using cross correlation is presented. Using a probabilistic model describing images as homogeneous random patterns, expressions for the mean and covariance of the local error vector in terms of image and noise autocorrelation functions, geometric distortion, and reference image area are derived. The geometric distortions considered are those represented by an affine transformation of image coordinates. It is shown that for a fixed geometric distortion there is an image size (integration area) that minimizes the local error. The optimum area decreases with increasing geometric distortion. 相似文献
1000.