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排序方式: 共有830条查询结果,搜索用时 31 毫秒
741.
Jarvis A. Caffrey D.M. Hamby 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2011
Instruments and methods recently used for space radiation dosimetry are reviewed for the purposes of comparison and reference. Passive detection methods mentioned include track-etch, luminescent, nuclear emulsion, and metal foil detectors. These can provide a reliable source of data for all types of radiation, but often require processing that cannot occur in space. Experimental methods of LET determination using TLDs, such as the high temperature peak ratio (HTR) method, are also discussed. Portable readout passive detectors including Pille, MOSFET, and bubble detector systems provide a novel alternative to traditional passive detectors, but research is more limited and their widespread use has yet to be established. Active detectors including DOSTEL, CPDS, RRMD-III, TEPC, R-16, BBND, and the Liulin series are examined for technical details. These instruments allow the determination of dose in real-time, and some can determine LET of incident particles by measuring energy deposition over a known path-length, but size and power consumption limit their practical use for dosimetry. Improved neutron dosimetry and development of a small active or portable readout personnel dosimeter capable of accurate LET determination are important steps for managing the effects of long-term exposure to the space radiation environment. 相似文献
742.
R. Manuel S.E.S. FerreiraM.S. Potgieter 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2011
Time dependent cosmic ray modulation in the outer heliosphere is calculated and results are compared to Voyager 1 and 2 observations using a two-dimensional time-dependent cosmic ray transport model. We predict possible future 133–242 MeV proton observations along the Voyager 1 and 2 spacecraft trajectories. Recent theoretical advances in cosmic ray transport parameters are introduced in order to provide a time-dependence for the assumed transport parameters used in the model. This leads to results that are in general compatible with the spacecraft observations in the inner and outer heliosphere over multiple solar cycles. However, for the outer heliosphere, we find that the Voyager 1 and 2 spacecraft observations cannot be fitted with an identical set of parameters along both trajectories. This indicates a possible asymmetric heliosphere or a symmetric heliosphere but with different diffusion parameters in the northern and southern hemispheres, respectively. Furthermore, results indicate that Voyager 2 observations are still under the influence of solar cycle related changes because of the large modulation volume between the heliopause and spacecraft location in contrast to Voyager 1 which shows a steady increase in cosmic ray intensities. 相似文献
743.
V. Florinski 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2011
This paper discusses the transport of energetic charged particles through a sectored magnetic field in distant regions of the inner heliosheath. As the plasma flow slows down on approach to the stagnation point on the heliopause, the distance between the folds of the current sheet decreases to the point where it becomes comparable to the cyclotron radius of a cosmic ray particle. Under these conditions a particle can effectively drift across the stack of magnetic sectors with a speed comparable with the particle’s velocity. For a random distribution of current sheet separation distances, a diffusive transport across the stack of sectors occurs instead. The proposed mechanism could have contributed to unusually high intensities of galactic cosmic rays measured by Voyager 1 in the heliosheath during 2009–2010. 相似文献
744.
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746.
光学头罩超声速绕流流场光学传输效应风洞试验研究 总被引:3,自引:0,他引:3
在Ma=3连续超声速风洞中,开展了光学头罩绕流流场光学传输效应的风洞模拟试验方法研究,进行了现场振动测量与隔离,研制了专用试验装置,采用哈特曼传感器和剪切干涉仪两种手段进行了光学传输效应的试验测量。试验中,针对试验装置各部分的不同组合状态,进行了大量的测试,研究了试验装置有效性以及试验数据重复性,着重分析了探测光束的PV值与RMS值。结果表明:导流板可明显抑制风洞洞壁边界层干扰,试验装置与方法可行,对于连续式风洞中模型绕流流场光学传输效应测试有一定参考价值。 相似文献
747.
在超燃冲压发动机扩张型燃烧室中,对凹腔内局部补氧的点火强化方法进行了试验研究。采用高速摄影手段研究了不同的补氧方式对凹腔内火焰分布特征和燃烧强度的影响,并针对并联双凹腔燃烧室构型,研究了在单侧凹腔补氧条件下向异侧凹腔的火焰传播过程。试验结果表明,采用凹腔内补氧的方式能调节凹腔内的燃料浓度分布、改善凹腔内的燃烧过程,控制燃烧放热强度;稳态燃烧情况下,观察到凹腔驻留火焰的两种存在特征,分别表现为:由回流区热量反馈机制作用下的凹腔局部驻留火焰和燃烧室全局压力反馈影响下的凹腔剪切层火焰。只有在单侧凹腔燃烧建立了全局压力反馈的条件下才能实现凹腔火焰的异侧传播。 相似文献
748.
S.E.S. Ferreira K. Scherer M.S. Potgieter 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2008,41(2):351-360
Cosmic ray modulation in the outer heliosphere is discussed from a modeling perspective. Emphasis is on the transport and acceleration of these particles at and beyond the solar wind termination shock in the inner heliosheath region and how this changes over a solar cycle. We will show that by using numerical models, and by comparing results to spacecraft observations, much can be learned about the dependence of cosmic ray modulation on solar cycle changes in the solar wind and heliospheric magnetic field. While the first determines the heliospheric geometry and shock structure, the latter results in a time-dependence of the transport coefficients. Depending on energy, both these effects contribute to cosmic ray intensities in the inner heliosheath changing over a solar cycle. 相似文献
749.
综合介绍了高能X射线测试系统在航空发动机试验中的作用和基本组成以及国内外高能X射线测试技术开发应用情况。 相似文献
750.
Observations in the solar wind have revealed important insights into how energetic particles are accelerated in astrophysical
plasmas. In circumstances where stochastic acceleration is expected, a suprathermal tail on the distribution function is formed
with a common spectral shape: the spectrum is a power law in particle speed with a spectral index of −5. Recent theories for
this phenomenon, in which thermodynamic constraints are applied to explain the common spectral shape, are reviewed. As an
example of potential extensions of this theoretical work, consideration is given to the acceleration of Anomalous Cosmic Rays
in the heliosheath. 相似文献