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621.
Thursby M. Kisuck Yoo Grossman B. 《IEEE transactions on aerospace and electronic systems》1995,31(4):1341-1347
Smart electromagnetic structures (SEMS) are capable of interacting with the surrounding electromagnetic field and responding to it. A system is “smart” when it integrates sensing, processing, and control elements (e.g. antennas, neural networks, diodes) in an autonomous manner. A SEMS capable of tuning frequency autonomously is described. Data are presented showing that the system can extend the useable bandwidth of a microstrip patch antenna in a frequency hop environment to more than twice the static value 相似文献
622.
R. Z. Sagdeev G. A. Avanesov I. V. Barinov A. I. Debabov V. A. Kvasikov V. I. Moroz V. A. Shamis V. I. Tarnapolski D. A. Usikov Ya. L. Ziman B. S. Zhukov B. A. Smith S. Larson F. Szabo K. Szeg A. Kondor L. Vrhalmi E. Mernyi L. Szabo I. Toth P. Cruvellier A. Abergel J. -L. Bertaux J. E. Blamont M. Danz D. Mhlmann H. Stiller H. P. Zapfe 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1985,5(12):95-104
The VEGA-1 and VEGA-2 spacecraft made their closest approach to Comet Halley on 6 and 9 March, respectively. In this paper those results of the onboard imaging experiment which were obtained around closest approach are discussed. The nucleus of the comet was clearly identifiable as an irregularly shaped object, with overall dimensions of (16±1)×(8±1)×(8±1) km. The nucleus rotates in the prograde sense about an axis nearly perpendicular to the orbital plane with a period of 53±2 hours. Its albedo is only Many of the jet features observed during the second fly-by have been spatially reconstructed. Their sources form a quasi-linear structure on the surface. The dust above the surface is shown to be generally optically thin with the exception of certain specific dust jets. Brightness features on the surface are clearly seen. Correlating our data with other measurements, we conclude that the dirty snow-ball model will probably need to be revised. 相似文献
623.
Sanderson R.B. Tsui J.B.Y. Freese N.A. 《IEEE transactions on aerospace and electronic systems》1992,28(4):950-956
A method for digital determination of a single frequency from a sine wave sampled at less than the Nyquist rate is discussed. The method makes use of phase shift information to eliminate the aliasing ambiguity. Multiple sampled data are required to eliminate ambiguity completely. Computer modeling using simulated data corrupted by uncorrelated Gaussian noise was used to verify the approach. The results demonstrate that the frequency of an input sine wave can be correctly identified. This approach can be applied to electronic warfare (EW) receivers to increase their input bandwidth 相似文献
624.
625.
DARN/SuperDARN 总被引:1,自引:0,他引:1
626.
The quality of a delivered product or system is ultimately limited by the quality of its design and manufacturing process. Defects that escape the design, manufacturing, and test processes are delivered to customers. Process Potential Index (Cp) and Process Capability Index (Cpk) are now widely used to express design and manufacturing quality. Design quality may be estimated from product models, if they exist, or measured using parameter test data. The difficulty in using test data is not so much in the calculations, but in the recording, storing, and selection of the data to be used in the calculations. This paper defines the metrics of quality estimation and describes an implementation of a system for estimating defect levels and process capabilities. The implementation includes the definition of a standardized parametric data exchange language for test data and an analytical system to standardize product quality measurement 相似文献
627.
This article will look at the origins of the Cospas-Sarsat International cooperative space program and its transition in the mid-1980s from a technical demonstration to an operational program. It will then attempt to identify some of the reasons for its success, with a view toward determining their applicability to other joint space applications projects. 相似文献
628.
K.B. Serafimov 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1984,4(1):139-142
Methods were suggested in /1,2,3/ to find the maximum electron density NmF (or NmF2) and the) corresponding height hmF (hmF2) in the ionosphere through a combination of measurements on two airglow lines: the UV oxygen line at λ135.6 nm and the red oxygen line near λ630 nm. 相似文献
629.
B.J. Carr J. McDowell H. Sato 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1984,3(10-12)
We examine whether the IR background reported by Matsumoto (1983) could have been generated by stars or black holes in the pregalactic era, z=10100. 相似文献
630.
M.K. Goel B.C.N. Rao 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1984,4(1):111-117
In the present analysis, the mass spectrometer data from the ISS-b satellite, available in the form of contour plots at an average height of 1100 km for every alternate hour, is used. This analysis showed some interesting results in terms of the diurnal variation of the transition heights; at times dominance of He+ over the other ions, and the seasonal variations of different constituents. In the development of ion composition models, it is suggested that this type of result should be taken into consideration. 相似文献