排序方式: 共有43条查询结果,搜索用时 31 毫秒
41.
L. Sihver M. Lantz M. Takechi A. Kohama A. Ferrari F. Cerutti T. Sato 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2012
Understanding the interactions and propagations of high energy protons and heavy ions are essential when trying to estimate the biological effects of Galactic Cosmic Rays (GCR) and Solar Particle Events (SPE) on personnel in space. To be able to calculate the shielding properties of different materials and radiation risks, particle and heavy ion transport codes are needed. In all particle and heavy ion transport codes, the probability function that a projectile particle will collide within a certain distance x in the matter depends on the total reaction cross sections, and the calculated partial fragmentation cross sections scale with the total reaction cross sections. It is therefore crucial that accurate total reaction cross section models are used in the transport calculations. In this paper, different models for calculating nucleon–nucleus and nucleus–nucleus total reaction cross sections are compared with each other and with measurements. The uncertainties in the calculations with the different models are discussed, as well as their overall performances with respect to the available experimental data. Finally, a new compilation of experimental data is briefly presented. 相似文献
42.
K. Haze K. Enya L. Abe S. Tanaka T. Nakagawa T. Sato T. Wakayama T. Yamamuro 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2009
We present our first results from laboratory experiments on a binary-shaped checkerboard mask coronagraph that was fitted inside a vacuum chamber for the development of skills to the direct observation of extra-solar planets. The aim of this work was to utilize a vacuum chamber for our coronagraph experiments in order to achieve an environment with higher thermal stability and which is free from air turbulence. We also aimed to evaluate and improve the performance of such a system consisting of a vacuum chamber with a coronagraph set inside the chamber. Both the raw contrast and the contrast after point spread function (PSF) subtraction are evaluated. We sited the vacuum chamber in a clean room, and we installed an optical fiber coupled to a visible He–Ne laser, appropriate coronagraph optics, a temperature sensor and heaters in the chamber. This provided a vacuum environment and a temperature-controlled environment with a visible light source, and was shown to improve the stability of the coronagraph. A contrast of 1.7×10-7 was achieved for the raw coronagraphic images by analyzing the areal mean of all of the observed dark regions. A contrast of 7.3×10-9 was achieved for the PSF subtraction by areal variance (1σ) of all of the observed dark regions. Speckles were a major limiting factor throughout the dark regions of both the raw images and the PSF subtracted images. The application of PSF subtraction for the Space Infrared telescope for Cosmology and Astrophysics (SPICA) and for other platforms is discussed. 相似文献
43.
午后极光强度与太阳风-磁层耦合函数的相关 总被引:1,自引:0,他引:1
利用1997年和1998年南极中山站多通道扫描光度计的地面观测数据和Wind卫星在弓激波上游对行星际磁场和太阳风参数的观测数据,对午后高纬极光强度与太阳风-磁层耦合函数之间的相关性进行定量研究.研究表明,午后630.0nm极光强度与太阳风-磁层耦合函数间有很好的相关,而557.7nm的相关性差一些;在考察的所有耦合函数中,午后极光受太阳风电场和能量的影响更直接;同时,行星际磁场的时钟角对午后极光也有很强的控制作用. 相似文献