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71.
概述了近年探则快中子的新技术,它们分别是:抑制γ射线、热中子和带电粒子的符合谱仪;高分辨、宽能量范围(0.1~15.0MeV)带正比计数器的3He夹心谱仪;含氢的纤维闪烁作用于抑制γ射线、中子位置分布和中子能谱测量,及合锂的纤维玻璃闪烁体用于长中子计数器测平均中子能量;中子的直接探测;用于中高能和重离子核物理的多元件阵列快中子探测器和极化仪;用于核核查的中子源影像探测器;高入射氚核能量和高能中子的伴随粒子技术等七个方面。它们对中子计量学的发展是重要的。 相似文献
72.
The compression creep deformation of the high volume fraction of SiC particles reinforced Al-Mg-Si composite fabricated by pressure-less infiltration was investigated. The experimental results show that the creep stress exponents are very high at temperatures of 673 K, 723 K and 773 K, and if taking the threshold stress into account, the true stress exponent of minimum creep strain rate is still approximately 5, although the volume fraction of reinforcements is very high. The creep strain rate in the high volume fraction rein- forced aluminum alloy matrix composites is controlled by matrix lattice diffusion. It is found that the creep-strengthening effect of high volume fraction of silicon carbide particles is significant, although the particles do not form effective obstacles to dislocation motion. 相似文献
73.
WANG Shu-juan GAO Hong-liang ZHAI Guo-fu 《中国航空学报》2007,20(3):253-259
The existence of remnant particles, which significantly reduce the reliability of relays, is a serious problem for aerospace relays. The traditional method for detecting remnant particles—particle impact noise detection (PIND)—can be used merely to detect the existence of the particle; it is not able to provide any information about the particles’ material. However, information on the material of the particles is very helpful for analyzing the causes of remnants. By analyzing the output acoustic signals from a PIND tester, this paper proposes three feature extraction methods: unit energy average pulse durative time, shape parameter of signal power spectral density (PSD), and pulse linear predictive coding coefficient sequence. These methods allow identified remnants to be classified into four categories based on their material. Furthermore, we prove the validity of this new method by processing PIND signals from actual tests. 相似文献
74.
This brief report summarized the latest advances of the interplanetary physics research in China during the period of 2006-2007,made independently by Chinese space physicists and through international collaboration.The report covers all aspects of the interplanetary physics,including theoretical studies,numerical simulation and data analysis. 相似文献
75.
Angela Gardini Monica Laurenza Marisa Storini 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2011
Fifteen solar energetic particle (SEP) events have been analyzed using proton flux data recorded by the Helios 1, Helios 2, and IMP 8 spacecraft in the energy range ∼4–40 MeV during 1974–1982. For each of the events at least two of the spacecraft have their nominal magnetic footpoint within 20° in heliocentric longitude from each other. The SEP events are sub-grouped as a function of their heliocentric longitudinal separation and heliocentric radial distance from the SEP associated solar flare and several case studies are presented in this paper. Main results concerning their usage in estimating the SEP radial dependence are given. Moreover, we investigate the behavior of the third not connected spacecraft in order to study the dependence of the proton flux as a function of flare location. It is found that the contribution of the longitudinal gradient in determining variations in the SEP proton flux is particularly relevant for spacecraft having their magnetic connection footpoint separated from the flare between 30° and 50°. 相似文献
76.
Renaud Allioux Philippe Louarn Nicolas André 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2013
A model is developed to study the energetic particle populations in Ganymede’s magnetosphere. The main objective is to estimate to what extent the moon could protect an orbiter from radiations. Using Liouville’s theorem, the phase space density of particles coming from Jupiter’s magnetosphere is calculated at any point of Ganymede’s environment. Up to energies of ∼50–100 keV for ions and ∼10–20 MeV for electrons, Ganymede’s magnetic field appears to be able to form distinctive populations as loss-cones over the polar caps and radiation belts. At larger energies, these features are blurred by Larmor radius effects; the moon absorption simply creates a quasi-isotropic layer of ∼500 km thickness where the flux is reduced by ∼40–50%. The predictions are compared to Galileo measurements. In particular, we demonstrate the importance of the moon sweeping in reducing the flux over the polar caps. Interestingly, this can be accounted for by assuming that the particles bouncing between Jupiter and Ganymede are ideally scattered in pitch angle and permanently re-fill the loss-cone, which increases the precipitation on Ganymede’s polar cap. In overall, it is estimated that the radiation dose received by an orbiter of Ganymede will be reduced by more than 50–60% compared to the expected dose at Jupiter/Ganymede distance. This should have a positive impact on the design of a future orbiter of Ganymede. 相似文献
77.
78.
James F. Carbary Stamatios M. KrimigisDonald G. Mitchell C. ParanicasP. Brandt 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2009
The Magnetospheric Imaging Instrument (MIMI) on the Cassini spacecraft has observed energetic neutral atoms (ENA) and charged particles at Saturn from mid-2004 to the present. The particles often but not always reveal striking periodic behavior that seems to depend on the type of particle and spacecraft location. When subjected to a Lomb periodogram analysis, energetic electrons (>150 keV) exhibited strong frequency peaks near 10.80 h (the nominal or “base” period of Saturn kilometric radiation) during 2006–2008, but essentially no periodicity during 2005. The electron periodograms also show pronounced “double” frequency peaks in 2007 and 2008. Energetic protons (3–26 keV) show strong peaks near the same period for 2005–2007, but none for 2008. Oxygen ions at the same energies display strong peaks for 2005 and 2006, but not for 2007 and 2008. By projecting the ENA images onto Saturn’s equatorial plane or onto a plane perpendicular to the equatorial plane and then summing the data in the appropriate dimension, “strip” images can be constructed from which a time history can be derived. These time histories of ENA emissions are also subjected to a Lomb periodogram analyses. The energetic hydrogen neutrals (20–50 keV) exhibited periodic behavior only during 2007, while energetic oxygen neutrals (64–144 keV) displayed a strong SKR-like period in 2005 and 2006 but not for 2007 or 2008. Some of this behavior may be due to changing spacecraft aspect relative to the ENA emissions, and some of it may be real. This periodic behavior may be consistent with a rotating anomaly that “flashes” brightly in the midnight-to-dawn sector once per 10.8 h, with the flash parameters depending on particle species and energy. 相似文献
79.
80.
Solar transients and their related interplanetary counterparts have severe effects on the space environments of the Earth. Therefore, the research of solar corona and interplanetary physics has become the focus of study for both solar and space scientists. Considerable progress has been achieved in these aspects by the solar and space physics community of China during 2012–2014, which will be given in this report. The brief report summarizes the research advances of solar corona and interplanetary physics into the following parts: solar wind origin and turbulence, coronal waves and seismology, solar eruptions, solar energetic particle and galactic cosmic ray, magnetic reconnection,Magnetohydrodynamic(MHD) models and their applications, waves and structures in solar wind,propagation of ICMEs/shocks and their arrival time predictions. These research achievements have been achieved by Chinese solar and space scientists independently or via international collaborations. 相似文献