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排序方式: 共有318条查询结果,搜索用时 15 毫秒
181.
Grenfell JL Griessmeier JM Patzer B Rauer H Segura A Stadelmann A Stracke B Titz R Von Paris P 《Astrobiology》2007,7(1):208-221
Planets orbiting in the habitable zone of M dwarf stars are subject to high levels of galactic cosmic rays (GCRs), which produce nitrogen oxides (NOx) in Earth-like atmospheres. We investigate to what extent these NO(Mx) species may modify biomarker compounds such as ozone (O3) and nitrous oxide (N2O), as well as related compounds such as water (H2O) (essential for life) and methane (CH4) (which has both abiotic and biotic sources). Our model results suggest that such signals are robust, changing in the M star world atmospheric column due to GCR NOx effects by up to 20% compared to an M star run without GCR effects, and can therefore survive at least the effects of GCRs. We have not, however, investigated stellar cosmic rays here. CH4 levels are about 10 times higher on M star worlds than on Earth because of a lowering in hydroxyl (OH) in response to changes in the ultraviolet. The higher levels of CH4 are less than reported in previous studies. This difference arose partly because we used different biogenic input. For example, we employed 23% lower CH4 fluxes compared to those studies. Unlike on Earth, relatively modest changes in these fluxes can lead to larger changes in the concentrations of biomarker and related species on the M star world. We calculate a CH4 greenhouse heating effect of up to 4K. O3 photochemistry in terms of the smog mechanism and the catalytic loss cycles on the M star world differs considerably compared with that of Earth. 相似文献
182.
乘波构型飞行器磁流体进气道一体化概念设计 总被引:1,自引:1,他引:1
采用准一维的磁流体方程组对设计状态下内磁流体发生器进行参数设计,利用斜激波理论设计磁流体进气道一体化的外形.以该外形为基点,对安装五对电极的内磁流体发生器采用五方程模型进行三维数值模拟,并通过调节其磁作用数以满足准一维假设下设计的进气道外形.研究表明,磁流体进气道最小出口流动均匀参数可以作为判别内发生器最优磁作用数的准则,在该磁作用数下内磁流体发生器可以有效地提高进气道的性能. 相似文献
183.
高超声速二方程湍流模型的数值模拟对比 总被引:1,自引:0,他引:1
对基于Reynolds和Favré(密度加权)混合平均的二方程湍流模型进行了修正,同时根据数值模拟高超声速流动时必须具有高分辨率捕捉间断面与在边界层内抑制数值粘性的能力的要求,提出了新的总变差减小(TVD)格式熵修正函数.在此基础上,通过对压缩拐角的高超声速湍流的数值模拟,对基于Reynolds和Favré混合平均的二方程湍流模型,以及其它不可压缩模型及可压缩性修正模型进行了对比,显示了不同湍流模型及可压缩性修正在计算壁面压力分布和热流分布上的特点,说明了对高超声速压缩拐角型流动,湍流模型可压缩修正的必要性,得到了基于Reynolds和Favré混合平均的二方程湍流模型的计算结果最接近实验结果. 相似文献
184.
M. I. Panasyuk S. I. Svertilov V. V. Bogomolov G. K. Garipov V. O. Barinova A. V. Bogomolov N. N. Veden’kin I. A. Golovanov A. F. Iyudin V. V. Kalegaev P. A. Klimov A. S. Kovtyukh E. A. Kuznetsova V. S. Morozenko O. V. Morozov I. N. Myagkova V. L. Petrov A. V. Prokhorov G. V. Rozhkov E. A. Sigaeva B. A. Khrenov I. V. Yashin S. I. Klimov D. I. Vavilov V. A. Grushin T. V. Grechko V. V. Khartov V. A. Kudryashov S. V. Bortnikov P. V. Mzhel’skiy A. P. Papkov S. V. Krasnopeev V. V. Krug V. E. Korepanov S. Belyaev A. Demidov Ch. Ferenz L. Bodnar P. Szegedi H. Rotkel M. Moravskiy Il Park Jin-A Jeon Ji-In Kim Jik Lee 《Cosmic Research》2016,54(5):343-350
We present the first experimental results on the observation of optical transients, gamma-ray bursts, relativistic electrons, and electromagnetic waves obtained during the experiment with the RELEC complex of scientific equipment on the Vernov satellite. 相似文献
185.
本文为对当量比乙炔氧气混合气体中爆轰波与激波正面对撞产生稳定波系的实验和理论研究.实验主要以高速扫描摄影获取两波对撞的x-t纹影图,一维理论分析则基于三种热完全的组分求解两波对撞的稳定解并探寻它们的规律.实验发现透射波系包括一道激波和爆轰波,以及紧随爆轰波后的稀疏波区,这种波系情况与一维理论分析中CJ解一致.透射CJ爆轰与人射爆轰相比马赫数降低,而相对波前来流的传播速度有轻微提高,但在实验室坐标下其速度显著降低.透射波系受初始压强影响不大;初始温度提高使得爆轰波速度降低,而透射激波速度增加;对波系起实质影响作用的是入射激波强度,激波越强,则整个透射流场呈现偏向激波的趋势;理论分析还指出,稀疏波区的出现不可避免,当激波强度趋于声波时稀疏波区趋于消失,激波越强则疏波区趋于扩大. 相似文献
186.
D. J. McComas F. Allegrini P. Bochsler M. Bzowski M. Collier H. Fahr H. Fichtner P. Frisch H. O. Funsten S. A. Fuselier G. Gloeckler M. Gruntman V. Izmodenov P. Knappenberger M. Lee S. Livi D. Mitchell E. Möbius T. Moore S. Pope D. Reisenfeld E. Roelof J. Scherrer N. Schwadron R. Tyler M. Wieser M. Witte P. Wurz G. Zank 《Space Science Reviews》2009,146(1-4):11-33
The Interstellar Boundary Explorer (IBEX) is a small explorer mission that launched on 19 October 2008 with the sole, focused science objective to discover the global interaction between the solar wind and the interstellar medium. IBEX is designed to achieve this objective by answering four fundamental science questions: (1) What is the global strength and structure of the termination shock, (2) How are energetic protons accelerated at the termination shock, (3) What are the global properties of the solar wind flow beyond the termination shock and in the heliotail, and (4) How does the interstellar flow interact with the heliosphere beyond the heliopause? The answers to these questions rely on energy-resolved images of energetic neutral atoms (ENAs), which originate beyond the termination shock, in the inner heliosheath. To make these exploratory ENA observations IBEX carries two ultra-high sensitivity ENA cameras on a simple spinning spacecraft. IBEX’s very high apogee Earth orbit was achieved using a new and significantly enhanced method for launching small satellites; this orbit allows viewing of the outer heliosphere from beyond the Earth’s relatively bright magnetospheric ENA emissions. The combination of full-sky imaging and energy spectral measurements of ENAs over the range from ~10 eV to 6 keV provides the critical information to allow us to achieve our science objective and understand this global interaction for the first time. The IBEX mission was developed to provide the first global views of the Sun’s interstellar boundaries, unveiling the physics of the heliosphere’s interstellar interaction, providing a deeper understanding of the heliosphere and thereby astrospheres throughout the galaxy, and creating the opportunity to make even greater unanticipated discoveries. 相似文献
187.
Markus J. Aschwanden L. F. Burlaga M. L. Kaiser C. K. Ng D. V. Reames M. J. Reiner T. I. Gombosi N. Lugaz W. Manchester IV I. I. Roussev T. H. Zurbuchen C. J. Farrugia A. B. Galvin M. A. Lee J. A. Linker Z. Mikić P. Riley D. Alexander A. W. Sandman J. W. Cook R. A. Howard D. Odstrčil V. J. Pizzo J. Kóta P. C. Liewer J. G. Luhmann B. Inhester R. W. Schwenn S. K. Solanki V. M. Vasyliunas T. Wiegelmann L. Blush P. Bochsler I. H. Cairns P. A. Robinson V. Bothmer K. Kecskemety A. Llebaria M. Maksimovic M. Scholer R. F. Wimmer-Schweingruber 《Space Science Reviews》2008,136(1-4):565-604
We summarize the theory and modeling efforts for the STEREO mission, which will be used to interpret the data of both the remote-sensing (SECCHI, SWAVES) and in-situ instruments (IMPACT, PLASTIC). The modeling includes the coronal plasma, in both open and closed magnetic structures, and the solar wind and its expansion outwards from the Sun, which defines the heliosphere. Particular emphasis is given to modeling of dynamic phenomena associated with the initiation and propagation of coronal mass ejections (CMEs). The modeling of the CME initiation includes magnetic shearing, kink instability, filament eruption, and magnetic reconnection in the flaring lower corona. The modeling of CME propagation entails interplanetary shocks, interplanetary particle beams, solar energetic particles (SEPs), geoeffective connections, and space weather. This review describes mostly existing models of groups that have committed their work to the STEREO mission, but is by no means exhaustive or comprehensive regarding alternative theoretical approaches. 相似文献
188.
Klecker B. Mewaldt R.A. Bieber J.W. Cummings A.C. Drury L. Giacalone J. Jokipii J.R. Jones F.C. Krainev M.B. Lee M.A. Le Roux J.A. Marsden R.G. Mcdonald F.B. McKibben R.B. Steenberg C.D. Baring M.G. Ellison D.C. Lanzerotti L.J. Leske R.A. Mazur J.E. Moraal H. Oetliker M. Ptuskin V.S. Selesnick R.S. Trattner K.J. 《Space Science Reviews》1998,83(1-2):259-308
We review the observed properties of anomalous cosmic rays and the present status of our knowledge of the processes by which they originate. We compiled a comprehensive set of ACR energy spectral data from various spacecraft throughout the heliosphere during the passes of Ulysses over the poles of the Sun and present first results of a detailed modeling effort. In several contributions, we discuss the questions of injection and possible pre-acceleration of pickup ions, summarize new observations on the ionic charge composition, and present new results on the composition of minor ions in ACRs. 相似文献
189.
在Reynolds平均的框架下推导了可压缩湍流Reynolds应力方程和湍动能方程。根据一定的假设和尺度分析简化并封闭了所推导的湍动能方程。在均匀湍流假设下,湍动能耗散率可分解成可压缩性耗散和旋度耗散,并对其中的可压缩性耗散进行了封闭;同时认为旋度耗散不受可压缩性影响,直接引用传统的Reynolds平均不可压缩湍动能耗散率模型方程。由此构造了适用于高马赫数的二方程可压缩湍流模型。应用所发展的模型计算了高超声速平板绕流,并与若干现有模型的计算、实验与半经验公式的计算结果进行了对比,验证了所发展的模型。在此基础上,通过对压缩拐角的高超声速湍流的数值模拟,对所发展的湍流模型,以及若干现有模型进行了对比,显示了不同湍流模型及可压缩性修正在计算壁面压力分布和热流分布上的特点,说明了湍流模型可压缩修正的必要性,得到了所发展模型的计算结果最接近实验结果的结论。 相似文献
190.
Modeling quaternion errors in SDINS: computer frame approach 总被引:2,自引:0,他引:2
Hyung Keun Lee Jang Gyu Lee Yong Kyu Roh Chan Gook Park 《IEEE transactions on aerospace and electronic systems》1998,34(1):289-300
We propose new equivalent tilt error models which are applicable to the analysis of the terrestrial strapdown inertial navigation systems (SDINS), based on the quaternions. The currently available equivalent tilt error models, like the conventional Φ model of the gimbaled inertial navigation systems (GINS), are derived only by the true frame approach. The true frame approach has a computational disadvantage that it produces an error model where the attitude error equation is coupled with its position and velocity error equations. The motivation of this work is to solve this problem. As a result, two kinds of error models are derived. Among them, one is derived by the computer frame approach for practical onboard implementations. Thus, like the conventional GINS Ψ model, its attitude error equation is decoupled from the position and velocity error equations. The other is derived in order to show the relationship between the true frame approach and the computer frame approach which are applied to the quaternion-based SDINS. Thus, like the GINS δΘ model, it can be used to transform the error variables into each other which are calculated by the two different approaches 相似文献