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961.
Cole S.N. Sjoberg E.S. Fanuele M.A. Rittenbach O.E. Olesch R.G. 《IEEE transactions on aerospace and electronic systems》1979,(5):594-599
The environment and radar operation simulator (EROS) is a hardware system whose function is to produce realistic synthetic radar backscatter, incorporating both target and clutter. The simulator is electrically connected to a subject radar and responds in real time to the radar's antenna scan angle by producing the correct composite video signal. 相似文献
962.
M.J. Hagyard R.L. Moore A.G. Emslie 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1984,4(7):71-80
We present observational results and their physical implications garnered from the deliberations of the FBS Magnetic Shear Study Group on magnetic field shear in relation to flares. The observed character of magnetic shear and its involvement in the buildup and release of flare energy are reviewed and illustrated with emphasis on recent results from the Marshall Space Flight Center vector magnetograph. It is pointed out that the magnetic field in active regions can become sheared by several processes, including shear flow in the photosphere, flux emergence, magnetic reconnection, and flux submergence. Modeling studies of the buildup of stored magnetic energy by shearing are reported which show ample energy storage for flares. Observational evidence is presented that flares are triggered when the field shear reaches a critical degree, in qualitative agreement with some theoretical analyses of sheared force-free fields. Finally, a scenario is outlined for the class of flares resulting from large-scale magnetic shear; the overall instability driving the energy release results from positive feedback between reconnection and eruption of the sheared field. 相似文献
963.
Ramachandra K.V. Srinivasan V.S. 《IEEE transactions on aerospace and electronic systems》1977,(4):419-423
An X, Y, Z Kalman tracking filter is described and its steady state characteristics are analytically determined when the radar sensor meaures range, bearing, and elevation (?, ?, ?) at uniform intervals of time, T seconds. The relationship between the quantities measured by the sensor (?, ?,?) and the Cartesian coordinate system (X, Y, Z) is explicitly considered. 相似文献
964.
G.E. Brueckner 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1981,1(9):101-115
The intensity of continua and emission lines which form the solar UV spectrum below 2100 Å is variable. Continua and emission lines originating from different layers in the solar atmosphere show a different degree of variability. Coronal emission lines at short wavelengths are much more variable than continua at longer wavelengths which originate in lower layers of the solar atmosphere. Typical time-scales of solar UV variability are minutes (flare induced), days (birth of active regions), 27 days (solar rotation), 11 years (solar cycle) and perhaps centuries, caused by long-term changes of the solar activity. UV intensity variations have been determined by either absolute irradiance measurements or by contrast measurements of plages vs. the quiet sun. Plages are the main contributor to the solar UV variability. Typical values for the solar UV variability over a solar cycle are: <1% at wavelengths longer than 2100 Å, 8% at 2080 Å (continuum), 20% at 1900 Å (continuum), 70% at H Lyα, 200% in certain emission lines 1200 < λ < 1800 Å and more than a factor of 4 in coronal lines λ < 1000 Å. Plage models predict the variable component of the solar UV radiation within ±50%. Absolute fluxes are known within ±30%. Several efforts are underway to monitor the solar UV irradiance with a precision better than a few percent over a solar activity cycle. 相似文献
965.
M.G. Kivelson K.W. Behannon T.E. Cravens I. de Pater T.V. Johnson D.L. Matson H. Masursky D.J. Southwood V.M. Vasyliunas 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1983,3(3):5-14
A was presented in conjunction with the Twenty-fourth Plenary Meeting of the Committee on Space Research. This paper summarizes the talks presented and places the remaining papers of this volume in context. 相似文献
966.
J Kiefer S Rase F Schopfer E Schneider K Weber G Kraft 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1983,3(8):115-125
The action of heavy ions (Ar to U) accelerated to specific energies up to about 10 MeV/u (u=atomic mass unit) on different functions of yeast cells was studied. Ribosomal-RNA synthesis is inhibited according to a single-hit mechanism. Inactivation cross-sections were linearly related to the ratio of the squares of the effective charge Z* and the velocity of the ions. It is concluded from the analysis that the range of the most energetic delta-electrons is larger than previously assumed. There is no such dependence for survival and induction of mutants. In both cases cross-sections increase with the ion's specific-energy indicating an important contribution of long-range delta-electrons. The analysis shows that diploid yeast is not killed by a single-hit mechanism even by very heavy ions if the track width is too small. The relative importance of the penumbral region is even more pronounced with the more sensitive strains. 相似文献
967.
G.G.C. Palumbo 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1982,2(9):51-57
In this paper IUE observations of two type II and three type I Supernovae (see Table I and Table II) are reviewed. The type II events were also observed by Einstein and SN 1980k was detected in the soft X-ray energy band. Combining UV spectra available of the same events one has the elements to construct a physical picture which accounts for all observations. For the type II events it appears that the progenitor star was a massive supergiant which underwent a severe mass loss before becoming Supernova. For the type I events there is neither X-ray nor, for the time being, radio detection. The high similarity of the optical and UV spectra for the three events indicates that type I Supernovae are the end products of one and the same phenomenon. 相似文献
968.
W.A. Gault G.G. Shepherd 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1982,2(7):111-114
A CCD imaging device has been designed which combines a spatial resolution of 0.1° with a spectral resolving power of 105, sufficient to measure Doppler shifts and line widths of individual atmospheric emission lines. It will be flown aboard Spacelab and will be used to study neutral winds and temperatures as functions of height, latitude and time of day. 相似文献
969.
J.M. Malherbe G. Simon P. Mein N. Mein B. Schmieder J.C. Vial 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1982,2(11):53-56
Disappearances of preflare filaments have been observed on June 22, 1980 (S07,W13) (flare at 13.04 U.T.) and September 3, 1980 (flare at 7.52 U.T.). The analysis of MSDP data (MEUDON) leads to the followings conclusions : - Disappearances begin a few minutes before the Hα impulsive phase. - The filaments can be seen again after the flares. - Upwards motions occur in several points, without disturbing significantly preëxisting downflows.Velocity maps suggest shears or velocity loops.The filament disappearance seems to be due to a heating mechanism beginning before the flare maximum. 相似文献
970.
The theoretical basis and methods of implementation of a moment algorithm for the range separation estimation of two closely spaced point targets are presented. Moment estimation and noise filtering techniques introduced here result in a considerable improvement over Baum's algorithm. The error bounds are established and it is shown that the spectral moment estimator exhibits optimum (zero bias, minimum variance) performance when the target separation normalized to the standard deviation of the Gaussian pulse is 2?1.5. Monte Carlo simulation is performed to verify the approximations made and to demonstrate the feasibility of the working models. 相似文献