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831.
R.C. Butler E. Caroli O. Catani G. Di Cocco E. Morelli A. Rubini G. Spada A. Traci L. Barbareschi A. Igiuni M. Santini G. Villa A. Bazzano C. La Padula F. Polcaro P. Ubertini R.E. Baker J.N. Carter D. Ramsden 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1983,3(4):95-98
A large area (6000 cm2) actively shielded low energy gamma-ray telescope is going to be built by an Anglo-Italian collaboration. The telescope, named ZEBRA, will be capable of producing images of the X and gamma ray sky in the energy range 0.015–20 MeV with an intrinsic angular resolution of a few tenths of a degree. A prototype detector has been built in order to experimentally study the main characteristics of the detection plane. The preliminary results obtained during a balloon flight from Trapani, Sicily in July 1981 are presented. 相似文献
832.
L. Barbareschi C. La Padula M. Mastropietro F. Perotti G. Villa A. Bazzano L. Boccaccini R. Patriarca V.F. Polcaro P. Ubertini R.C. Butler G. Di Cocco G. Spada J.N. Carter P. Charalambous A.J. Dean J.B. Stephen 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1983,3(4):91-93
In order to improve the low energy capability (15 ÷ 150 KeV) of the balloon borne “ZEBRA” low energy gamma imaging telescope (150 KeV-20 MeV), a large area, high spectral resolution (5% at 60 KeV), low background detector has been designed and is now under development.It consists of two MultiWire Spectroscopic Proportional Counter (SPC), escape gated, that have a sensitive area of 6000 cm2, and are placed above the large area array of sodiumiodide position sensitive elements. 相似文献
833.
Lawrence C. Rowan Alexander F.H. Goetz Marguerite J. Kingston 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1983,3(2):125-132
The Shuttle Multispectral Infrared Radiometer (SMIRR) is a spectroradiometer covering the region from 0.5 to 2.5 μm in 10 channels that acquired data from spots 100 m in diameter along the subspacecraft ground track. It was flown aboard the second flight of the space shuttle Columbia, November 12–14, 1981. Data collected during orbit 16 over southern Egypt show that carbonate rocks, kaolinite, and possibly montmorillonite can be identified by their SMIRR spectral signatures and limited knowledge of the lithologic units present. Detailed analysis of SMIRR data for this area indicates that calcite, kaolinite, and montmorillonite rocks give rise to absorption features that result in characteristic 10 channel spectra. 相似文献
834.
An MHD converter using a mixture of metal in liquid and a metallic vapor should prove very efficient due to its high conductivity, and should function at relatively low temperatures. An experimental apparatus is being tested at the Grenoble Institute. 相似文献
835.
F.L. Scarf D.A. Gurnett W.S. Kurth R.L. Poynter 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1987,7(12):253-258
At Uranus, the Voyager 2 plasma wave investigation observed very significant phenomena related to radio emissions, dust impacts and magnetospheric wave-particle interactions. On January 19, 1986 (R= 270RU) the plasma wave investigation detected an intense radio burst at 31 and 56 kHz, and this provided the first indication that Uranus had a magnetosphere. During the encounter we observed more of these sporadic bursts, along with relatively continuous radio emissions extending down to 10 kHz, and a sporadic narrowband radio signal with f near 5 kHz. As Voyager passed through the ring plane, the plasma wave investigation recorded a large number of dust impacts. The dust ring was relatively diffuse (thickness of several thousand kilometers) and the peak impact rate was near 50 hits/second. The Voyager 2 plasma wave instrument also detected many strong electromagnetic and electrostatic plasma waves, with intensity peaks in the region within 12 Uranus adii. These waves have characteristics that can interact strongly with the local plasma and with the trapped energetic particles, leading to precipitation into the atmosphere, charged particle acceleration, and charged particle diffusion. In addition we detected strong wave activity in the region of the bow shock and moderate levels in the magnetic tail. 相似文献
836.
L.K. Harra-Murnion S.P. Plunkett S.F. Helsdon K.J.H. Phillips L. Van Driel-Gesztelyi B. Schmieder B. Rompolt M. Akioka 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1997,20(12):2333-2336
Yohkoh has observed many long duration events permitting a statistical study of the properties of these interesting events. We have selected ten flares for analysis which have durations between 5 and 20 hours, and size ranging from C to X GOES class. Employing the Soft X-ray Telescope, the Bragg Crystal Spectrometer, GOES spacecraft, and ground-based H data, we examine the morphology, temperature, emission measure, location of the hard X-ray source, non-thermal velocities and upflows of the plasma at different stages in the flare development. Our results are used to address the question of the energy source that maintains the hot plasma at temperatures of several million degrees for many hours. 相似文献
837.
A. Boelee C. de Jager A. Duijveman M. Galama R. Hoekstra P. Hoyng J. P. Imhof H. Lafleur H. V. A. M. Maseland W. A. Mels A. Schadee J. Schrijver Z. Svestka H. F. van Beek P. van Rens J. J. M. van der Laan W. van Tend F. Werkhoven G. Wiersma W. Zandee 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1981,1(13):255-266
We have selected four widely different flares from the early period of operations of the Hard X-Ray Imaging Spectrometer (HXIS) on SMM to illustrate the characteristic imaging properties of this experiment. For the small flare of April 4, 1980, we demonstrate the instrument's capability for locating a compact source. In the weak, but extensive, flare of April 6 we show how well the instrument can display spatial structure, and also the low level of the instrument background. In the 1B flare of April 7 we are able to locate positions of the X-ray emission in the soft and hard channels, and estimate the positional variations of the emission patches. Finally, in the IN flare of April 10, which produced the strongest hard X-ray burst we have seen so far, we repeat some of the studies made for the April 7 event, and also demonstrate the capability of the HXIS instrument to study the development, with high time resolution, of individual 8″ × 8″ elements of the flare. 相似文献
838.
A method is shown for suppressing the adaptive switching transient that arises in complex adaptive (LMS and stochastic approximation) algorithms due to signal normalization with controlled switched gains. The method involves rescaling of the adaptive weights with the normalizing gains just prior to the first adaptation with the new gains. In addition, an effective method of rescaling the adaptive gain factor based on the maximum eigenvalues of the respective covariance matrices is shown. 相似文献
839.
F Jamitzky M Scholer 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1997,19(12):1773-1776
Numerical simulations of magnetic reconnection with uniform resistivity show that the length of the current sheet increases for increasing magnetic Reynolds number. In order to prevent the current sheet from growing in general the resistivity is assumed to be localized. For uniform resistivity the reconnection proceeds much slower than for localized resistivity. In this paper analytical solutions of the hydromagnetic equation are presented for localized and uniform resistivity. It is shown that there exists an essential singularity in the behaviour of a solution of magnetic reconnection in the limit of large magnetic Reynolds number: For prescribed boundary conditions the solution for localized resistivity does not approach the solution for uniform resistivity in the limit of large magnetic Reynolds number. 相似文献
840.
S.R. Coriell W.J. Boettinger M.R. Cordes R.F. Sekerka 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1981,1(5):5-11
We investigate the role of gravity in a linear stability analysis of the onset of coupled convective and morphological instabilities during directional solidification at constant velocity of a dilute alloy of tin in lead. For solidification vertically upwards, the temperature gradient alone would cause a negative density gradient and the solute gradient alone would cause a positive density gradient. Two types of instability are found, a convective type that occurs for long wavelengths and a morphological type that occurs for short wavelengths. In general, these are coupled but the morphological instabilities are practically independent of gravity and thus correspond to the predictions of previous morphological stability theory in which density changes and convection are neglected. The convective instabilities depend strongly on gravity; for a growth velocity of V = 1 μm/s and a temperature gradient in the liquid of GL = 200 K/cm, the critical concentrations for convective instabilities are 3.1 × 10?4, 3.1 × 10?2 and 2.39 wt. % for ge = 980 cm/s2, 10?4 ge and 10?6 ge, respectively. For low velocities, the convective instabilities occur at much lower solute concentrations than the morphological instabilities whereas at high velocities, the reverse is true. At intermediate velocities where the changeover takes place, there are oscillitory instabilities of mixed character whose periods range from 60 s at ge to 6 × 104 s at 10?6 ge. 相似文献