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161.
M. Poje B. Vuković M. Varga V. Radolić I. Miklavčić D. Faj J. Planinić 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2008
Cosmic radiation bombards us at high altitude with ionizing particles; the radiation has a galactic component, which is normally dominant, and a component of solar origin. Cosmic ray particles are the primary source of ionization in the atmosphere above 1 km; below 1 km radon is a dominant source of ionization in many areas. 相似文献
162.
B. Sylwester J. Sylwester K.J.H. Phillips E. Landi 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2008
We present the observations of He-like Ar triplet lines obtained by RESIK spectrometer aboard CORONAS-F. Interpretation of intensity ratios between triplet lines of lower Z elements is known to provide useful diagnostics of plasma conditions within the emitting source. Here, we investigate whether triplet line ratios are useful for interpretation of higher Z element spectra. A high sensitivity, low background and precise absolute calibration of RESIK allow to consider in addition also the continuum contribution. This provides a way to determine the Ar absolute abundance from the observed triplet component ratios. The method is presented and the results are shown for two selected flares. Derived values of Ar absolute abundance for these flares are found to be similar: 2.6 × 10−6 and 2.9 × 10−6. They fall in the range between presently accepted Ar photospheric and coronal abundances. 相似文献
163.
M. Amenomori S. Ayabe X.J. Bi D. Chen S.W. Cui Danzengluobu L.K. Ding X.H. Ding C.F. Feng Zhaoyang Feng Z.Y. Feng X.Y. Gao Q.X. Geng H.W. Guo H.H. He M. He K. Hibino N. Hotta Haibing Hu H.B. Hu J. Huang Q. Huang H.Y. Jia F. Kajino K. Kasahara Y. Katayose C. Kato K. Kawata Labaciren G.M. Le A.F. Li J.Y. Li Y.-Q. Lou H. Lu S.L. Lu X.R. Meng K. Mizutani J. Mu K. Munakata A. Nagai H. Nanjo M. Nishizawa M. Ohnishi I. Ohta H. Onuma T. Ouchi S. Ozawa J.R. Ren T. Saito T.Y. Saito 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2008
164.
B. Kirov K. Georgieva D. Batchvarov A. Boneva R. Krasteva G. Stainov S. Klimov T. Dachev 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2008
The main purposes of experiment “Obstanovka” (“Environment” in Russian) consisting of several instruments are to measure a set of electromagnetic and plasma phenomena characterizing the space weather conditions, and to evaluate how such a big and highly energy consuming body as the International Space Station disturbs the surrounding plasma, and how the station itself is charged due to the operation of so many instruments, solar batteries, life supporting devices, etc. Two identical Langmuir electrostatic probes are included in the experiment “Obstanovka”. In this paper the Langmuir probes for “Obstanovka” experiment are described, including the choice of geometry (spherical or cylindrical), a more reliable method for the sweep voltage generation, an adaptive algorithm for the probe’s operation. Special attention is paid to the possibility for remote upgrading of the instrument from the ground using the standard communication channels. 相似文献
165.
Vadher V.V. Smith I.R. Fanthome B.A. 《IEEE transactions on aerospace and electronic systems》1986,(1):64-70
Permanent magnet generators are often used as the pilot exciters of three-stage generating units to provide an efficient and reliable source of electrical power. No external power supply is then necessary, and the problems associated with brushwear and with arcing at the rubbing contacts are eliminated. A technique is presented here by which the performance of a permanent magnet generator, when combined with a rectifier-fed d.c. load at its output terminals, may be accurately and efficiently computed. The machine model takes into account the magnetization characteristic of the permanent magnet rotor and involves only parameters which can be determined from terminal measurements on the machine at standstill. Both computed and measured characteristics for an experimental machine are presented, and a comparison of these characteristics shows that the model can predict accurately all the major characteristics of the machine, as well as its detailed internal performance, when supplying a typical resistiveinductive load. 相似文献
166.
A numerical method is described for analyzing the performance of an acoustooptic receiver. The method provides output waveforms, probability density functions for samples of the output, and detection probabilities for output samples. The approach is general in that input pulse envelope shapes, pulse offset frequencies, and output rilter magnitude responses are arbitrary. The basic analysis is also independent of the shape of the optical beam and of the photodiode windows. 相似文献
167.
McCormick W.S. Tsui J.B.Y. Bakkie V.L. 《IEEE transactions on aerospace and electronic systems》1989,25(5):729-732
The instantaneous frequency measurement (IFM) receiver is capable of measuring the center frequency of single frequency pulses over a wide range (bandwidth) of center frequencies. Because of various constraints, the frequency resolution requirement results in long correlator delay times that reduce the single correlator bandwidth. A large bandwidth can be achieved only if two or more correlators are used. The problem of estimating frequency is then reduced to the simultaneous congruence problem of number theory. A design procedure is presented for solving the congruence problem for a given amount of noise protection, a stated frequency resolution, a minimum bandwidth, and a fixed level of precision (bits) in the IFM receiver 相似文献
168.
Application of digital cross-correlation spectroscopy to the spectra of the W Serpentis binaries SX Cas and RX Cas has allowed an accurate determination of the orbits and rotations of the (mass-losing) K-subgiant secondary components. The distortion of the primary radial-velocity curves due to the influence of the prominent accretion disks in these systems has been modelled to first order. This enables us to estimate k 1, and thereby the mass ratio q ≈ 0.30, to within ~ ± 20%. The absolute radii of the secondaries are derived independently from the observed rotations and periods, assuming synchronous rotation. They show that the stars fill their Roche lobes, or at least very nearly so. Rough fits to the available photometry shows both primaries to be unevolved mid-B stars; that in RX Cas appears completely obscured by the disk. Preliminary spectroscopic data for W Ser and W Cru show some promise for similar analyses of these systems. 相似文献
169.
F. M. Ipavich G. Gloeckler C. Y. Fan L. A. Fisk D. Hovestadt B. Klecker J. J. O'Gallagher M. Scholer 《Space Science Reviews》1979,23(1):93-101
We report initial measurements from the ULECA sensor of the Max-Planck-Institut/University of Maryland experiment on ISEE-1. ULECA is an electrostatic deflection — total energy sensor consisting of a collimator, deflection analyzer and an array of solid state detectors. The position of a given detector, which determines the energy per charge of an incident particle, together with the measured energy determine the particle's charge state. We find that a rich variety of phenomena are operative in the transthermal energy regime (10 keV/Q to 100 keV/Q) covered by ULECA. Specifically, we present observations of locally accelerated protons, alpha particles, and heavier ions in the magnetosheath and upstream of the Earth's bow shock. Preliminary analysis indicates that the behavior of these locally accelerated particles is most similar at the same energy per charge. 相似文献
170.
Trunk G.V. Cantrell B.H. Gordon W.B. 《IEEE transactions on aerospace and electronic systems》1979,(6):883-887
The Cramer-Rao bound for an unbiased estimate of the elevation angle of a target in the presence of multipath is calculated for the symmetric (target and image symmetric about the elevation symmetry plane of antenna) and nonsymmetric cases for an antenna consisting of 21 elements. These bounds are compared to the maximum likelihood estimates and it is found that the rms error of the maximum likelihood estimate (which has a bias) is below the Cramer-Rao bound for unbiased estimates. 相似文献