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581.
W Heinrich E V Benton B Wiegel G Rusch E Becker 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1994,14(10):969-977
Radiation effects of cosmic ray nuclei are generally described as a function of the particle LET. For a large number of space missions LET spectra have been measured and models have been developed to calculate these spectra that include the effects of geomagnetic shielding and shielding provided by material. In this paper we compare measured and calculated LET spectra. For low earth orbits events with high local energy deposition, i.e., short range secondaries, contribute significantly to the measured spectra. These events are produced by nuclear interactions, mainly induced by protons from the south atlantic anomaly. The technique to include these contributions in the models depends on the size of radiation sensitive volumes. For sizes comparable to or larger than the range of target secondaries it is essential to separate contributions by target interactions from those of cosmic rays. This separation is possible in experiments which use stacks of plastic nuclear track detectors. The yield of short range events generated by protons and measured in the detector can be calibrated from accelerator experimental data. We present first results for CR-39 detectors. 相似文献
582.
A major factor that will drive the definition and design of future avionics systems is affordability. Affordability is being addressed on numerous fronts such as hardware re-use, software re-use, COTS leveraging, and reduced cycle times. Each of these thrusts provide potential cost saving along with unique challenges. What is needed is a process that integrates these initiatives while ensuring the overall system objectives are achieved. An Open Systems-based process is key to integrating these initiatives and balancing affordability and system performance goals. Although Open Systems are being widely recognized as a key to affordability, most interpret Open Systems as a set of system attributes that need to be achieved. There are numerous claims of vendors saying they have an Open Systems architecture; or how their system will evolve to an Open Systems architecture. This emphasis is not on increasing affordability, but on attaching a politically-correct label to their product. In this paper, we focus on the Open Systems process as the key to affordability. An Open Systems process is based on Open Systems principles. This paper discusses the Open Systems principles and process in detail and shows how this process integrates numerous affordability initiatives 相似文献
583.
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
584.
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
585.
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
586.
587.
DARN/SuperDARN 总被引:1,自引:0,他引:1
588.
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
589.
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
590.
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