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11.
J.J. Podesta 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2008,41(1):148-152
Solar wind data is used to estimate the autocorrelation function for the stochastic process x(τ) = y(t + τ) − y(t), considered as a function of τ, where y(t) is any one of the quantities B2(t), np(t)V2(t), or np(t). This process has stationary increments and a variance that increases like a power law τ2γ where γ is the scaling exponent. For the kinetic energy density and the proton density the scaling exponent is close to the Kolmogorov value γ = 1/3, for the magnetic energy density it is slightly larger. In all three cases, it is shown that the autocorrelation function estimated from the data agrees with the theoretical autocorrelation function for a self-similar stochastic process with stationary increments and finite variance. This is far from proof, but it suggests that these stochastic processes may be self-similar for time scales in the small scale inertial range of the turbulence, that is, from approximately 10 to 103 s. 相似文献
12.
U.W. Langner M.S. Potgieter 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2008,41(2):368-372
A numerical model, based on Parker’s transport equation, describing the modulation of anomalous cosmic rays and containing diffusive shock acceleration is applied. The role of radial perpendicular diffusion at the solar wind termination shock, and as the dominant diffusion coefficient in the outer heliosphere, is studied, in particular the role it plays in the effectiveness of the acceleration of anomalous protons and helium when its latitude dependence is changed. It is found that the latitudinal enhancement of radial perpendicular diffusion towards the heliospheric poles and along the termination shock has a prominent effect on the acceleration of these particles. It results in a ‘break’ in the energy spectrum for anomalous protons at ∼6.0 MeV, causing the spectral index to change from E−1.38 to E−2.23, but for anomalous helium at ∼3.0 MeV, changing the spectral index from E−1.38 to E−2.30. When approaching the simulated TS, the changes in the modulated spectra as they unfold to a ‘steady’ power law shape at energies below 50 MeV are much less prominent as a function of radial distances when radial perpendicular diffusion is increased with heliolatitude. 相似文献
13.
网格计算是一种新兴的解决大规模复杂问题的应用技术,充分利用现有资源提供高性能的计算能力。现在的生产过程越来越向大规模复杂化方向发展,过程控制需要新的控制模型和控制方法来解决这些问题。但现有的计算能力无疑又限制了控制技术的应用,将高性能的网格计算运用到过程控制当中可以提高控制模型和控制算法的计算速度,也将大大提高其控制品质和应用范围。 相似文献
14.
基于结构随机跳变系统的反干扰信息处理方法 总被引:4,自引:2,他引:2
为了解决在复杂的干扰对抗环境中提高信息处理的准确性问题(例如,对具有多种干扰对抗手段的机动目标的跟踪问题),基于结构随机跳变系统理论提出了一种反干扰信息处理的新方法,该方法针对干扰环境的随机剧烈变化,适时地辨识干扰环境的当前状态,并作出相应的决策来优化和利用系统的资源(例如传感器的优化重组、信息融合算法的转换等),最大限度地降低干扰对信息处理精度的影响.以有效地提高信息优化处理的精确度.在本文中就该方法的性能与其它算法做了仿真比较,其仿真结果证实了该方法的有效性. 相似文献
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16.
S.V. Veretenenko V.A. DergachevP.B. Dmitriyev 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2010
Long-term changes of the Arctic frontal zone characteristics near the south-eastern coasts of Greenland were considered, the NCEP/NCAR reanalysis data being used. It was found that in the cold half of the year the temperature gradients in the layer 1000–500 hPa in the region under study reveal strong ∼10-yr and ∼22-yr periodicities that seem to be related to solar activity cycles. The results obtained suggest the influence of solar activity and cosmic ray variations on the structure of the temperature field of the troposphere resulting in the changes of the temperature contrasts in the Arctic frontal zone that, in turn, may affect the intensity of cyclogenesis at middle latitudes. The detected effects seem to indicate an important part of frontal zones in the mechanism of solar activity and cosmic ray variation influence on the development of extratropical baric systems. It is suggested that the variations of the temperature gradients revealed in the Arctic frontal zone are due to the radiative forcing of cloudiness changes which may be associated with geomagnetic activity and cosmic ray variations. 相似文献
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18.
Ballistic Missile Trajectory Prediction(BMTP) is critical to air defense systems. Most Trajectory Prediction(TP) methods focus on the coast and reentry phases, in which the Ballistic Missile(BM) trajectories are modeled as ellipses or the state components are propagated by the dynamic integral equations on time scales. In contrast, the boost-phase TP is more challenging because there are many unknown forces acting on the BM in this phase. To tackle this difficult problem, a novel BMTP method by ... 相似文献
19.
箔条云团的布朗运动扩散模型 总被引:9,自引:0,他引:9
假定箔条所在位置处大气运动速度是一个维纳随机过程,同时在忽略箔条的质量时箔条的运动完全反应当地大气的运动,在此基础上建立箔条云团的扩散模型及数值仿真模型. 对扩散模型进行分析得到了箔条云团扩散过程中的数字特征.对数值仿真模型的分析表明必须对大气的运动方差进行时间离散化补偿,进行离散化补偿后箔条云团的数字特征不受模拟时时间步长的影响.模拟结果证明了分析的正确性. 相似文献
20.
纺织复合材料的细观力学分析通常以胞元模型为基础,胞元边界条件的合理施加是获得精确分析结果的关键之一。本文以平面机织复合材料为例,讨论了细观胞元的选取和周期边界条件的施加方法,在此基础上建立了二维细观有限元模型,通过与全厚度模型分析结果的比较,研究了周期胞元模型的合理性,特别是边界效应和局部损伤等非周期因素对分析结果的影响,给出了这些因素下胞元边界条件的处理方法。 相似文献