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801.
T. Ono A. Kumamoto Y. Kasahara Y. Yamaguchi A. Yamaji T. Kobayashi S. Oshigami H. Nakagawa Y. Goto K. Hashimoto Y. Omura T. Imachi H. Matsumoto H. Oya 《Space Science Reviews》2010,154(1-4):145-192
The Lunar Radar Sounder (LRS) onboard the KAGUYA (SELENE) spacecraft has successfully performed radar sounder observations of the lunar subsurface structures and passive observations of natural radio and plasma waves from the lunar orbit. After the transfer of the spacecraft into the final lunar orbit and antenna deployment, the operation of LRS started on October 29, 2007. Through the operation until June 10, 2009, 2363 hours worth of radar sounder data and 8961 hours worth of natural radio and plasma wave data have been obtained. It was revealed through radar sounder observations that there are distinct reflectors at a depth of several hundred meters in the nearside maria, which are inferred to be buried regolith layers covered by a basalt layer with a thickness of several hundred meters. Radar sounder data were obtained not only in the nearside maria but also in other regions such as the farside highland region and polar region. LRS also performed passive observations of natural plasma waves associated with interaction processes between the solar wind plasma and the moon, and the natural waves from the Earth, the sun, and Jupiter. Natural radio waves such as auroral kilometric radiation (AKR) with interference patterns caused by the lunar surface reflections, and Jovian hectometric (HOM) emissions were detected. Intense electrostatic plasma waves around 20 kHz were almost always observed at local electron plasma frequency in the solar wind, and the electron density profile, including the lunar wake boundary, was derived along the spacecraft trajectory. Broadband noises below several kHz were frequently observed in the dayside and wake boundary of the moon and it was found that a portion of them consist of bipolar pulses. The datasets obtained by LRS will make contributions for studies on the lunar geology and physical processes of natural radio and plasma wave generation and propagation. 相似文献
802.
803.
804.
THE DIGITAL WAVE-PROCESSING EXPERIMENT ON CLUSTER 总被引:1,自引:0,他引:1
L. J. C. Woolliscroft H. St. C. Alleyne C. M. Dunford A. Sumner J. A. Thompson S. N. Walker K. H. Yearby A. Buckley S. Chapman M. P. Gough 《Space Science Reviews》1997,79(1-2):209-231
The wide variety of geophysical plasmas that will be investigated by the Cluster mission contain waves with a frequency range from DC to over 100 kHz with both magnetic and electric components. The characteristic duration of these waves extends from a few milliseconds to minutes and a dynamic range of over 90 dB is desired. All of these factors make it essential that the on-board control system for the Wave-Experiment Consortium (WEC) instruments be flexible so as to make effective use of the limited spacecraft resources of power and telemetry-information bandwidth. The Digital Wave Processing Experiment, (DWP), will be flown on Cluster satellites as a component of the WEC. DWP will coordinate WEC measurements as well as perform particle correlations in order to permit the direct study of wave/particle interactions. The DWP instrument employs a novel architecture based on the use of transputers with parallel processing and re-allocatable tasks to provide a high-reliability system. Members of the DWP team are also providing sophisticated electrical ground support equipment, for use during development and testing by the WEC. This is described further in Pedersen et al. (this issue). 相似文献
805.
Lohr D. A. Zanetti L. J. Anderson B. J. Potemra T. A. Hayes J. R. Gold R. E. Henshaw R. M. Mobley F. F. Holland D. B. Acuña M. H. Scheifele J. L. 《Space Science Reviews》1997,82(1-2):255-281
The primary objective of the investigation is the search for a body-wide magnetic field of the near Earth asteroid Eros. The Near Earth Asteroid Rendezvous (NEAR) 3-axis fluxgate magnetometer includes a sensor mounted on the high-gain antenna feed structure. The NEAR Magnetic Facility Instrument (MFI) is a joint hardware effort between GSFC and APL. The design and magnetics approach achieved by the NEAR MFI effort entailed low-cost, up-front attention to engineering solutions which did not impact the schedule. The goal of the magnetometer is reliable magnetic field measurements within 5 nT, which necessitates the use of an extensive spacecraft magnetic interference model but is achievable with the full year's orbital data set. Such a goal has been shown viable with recent in-flight calibration data and comparisons to the WIND magnetometer data. The NEAR MFI effort has succeeded in providing magnetic field measurements for the first flight in NASA's Discovery line. 相似文献
806.
Quantum field theory at finite temperature and density can be used for describing the physics of relativistic plasmas. Such systems are frequently encountered in astrophysical situations, such as the early universe, supernova explosions, and the interior of neutron stars. After a brief introduction to thermal field theory the usefulness of this approach in astrophysics will be exemplified in three different cases. First the interaction of neutrinos within a supernova plasma will be discussed. Then the possible presence of quark matter in a neutron star core and finally the interaction of light with the Cosmic Microwave Background will be considered. 相似文献
807.
高速切削在模具加工中的应用及发展趋势 总被引:9,自引:1,他引:9
叙述了高速切削技术的意义,并介绍了它在电极制造、淬硬材料型腔的直接加工及样件的快速成型中的应用及优点,并简要说明对高速铣床的要求. 相似文献
808.
Everett J.L. Bertolett A.D. Haak G.H. 《IEEE transactions on aerospace and electronic systems》1972,(4):498-504
Generating capacity additions planned for the 1970's and beyond include a high percentage of nuclear power plants. The light water reactor is the dominant type of commercial nuclear reactor being installed during the 1970's. Advancement to more efficient designs, such as the high-temperature gas-cooled reactor, is expected around 1980. Prospects for the breeder reactor and fusion energy systems dictate a major research and development effort. Attempts to control effluents from fossil-fired plants have resulted in a sharp increase in the use of low sulfur fuels. Research and development efforts are being intensified in an attempt to obtain a breakthrough in methods of stack emission control. 相似文献
809.
810.
G. Wibberenz H.V. Cane I.G. Richardson T.T. von Rosenvinge 《Space Science Reviews》2001,97(1-4):343-347
The maximum inclination of the heliospheric current sheet (the tilt angle) and the magnitude B of the heliospheric magnetic field are often used to characterize cosmic ray (CR) modulation. The relevance of B is likely to be the coupling of the interplanetary diffusion coefficients K to the field magnitude in a relation K∝B
−n. In this paper we study the coupled influence of tilt angle and magnetic field variations on the modulation of cosmic rays
at neutron monitor energies for the 1974 mini-cycle and for the onsets of solar cycles 21, 22, and 23. It is suggested that
for A>0 polarity epochs, the sensitivity of the CR response to variations in B is partly controlled by the size of the tilt angle, α. The onsets of cycles 21 and 23 exhibit differences, related to phase
differences in these parameters. A simple model is used to predict the CR response to variations in B.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献