排序方式: 共有54条查询结果,搜索用时 18 毫秒
1.
Euler方程无网格算法及布点技术 总被引:4,自引:0,他引:4
研究了Bitina的显式无网格算法。在该算法的基础上,给出了Euler方程无网格离散形式,运用RungeKutta显式时间推进格式推进求解。文中的耗散项采用了与非结构网格上类似的守恒型耗散算子,边界条件的处理借鉴了结构化网格处理技术。此外,本文还描述了一种区域离散布点方法,研究了点云生成的选点准则,并成功地数值模拟了二维翼型的典型绕流。 相似文献
2.
V. Yurchyshyn Q. Hu R.P. Lepping B.J. Lynch J. Krall 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2007,40(12):1821-1826
Coronal mass ejections (CMEs) observed near the Sun via LASCO coronographic imaging are the most important solar drivers of geomagnetic storms. ICMEs, their interplanetary, near-Earth counterparts, can be detected in situ, for example, by the Wind and ACE spacecraft. An ICME usually exhibits a complex structure that very often includes a magnetic cloud (MC). They can be commonly modelled as magnetic flux ropes and there is observational evidence to expect that the orientation of a halo CME elongation corresponds to the orientation of the flux rope. In this study, we compare orientations of elongated CME halos and the corresponding MCs, measured by Wind and ACE spacecraft. We characterize the MC structures by using the Grad–Shafranov reconstruction technique and three MC fitting methods to obtain their axis directions. The CME tilt angles and MC fitted axis angles were compared without taking into account handedness of the underlying flux rope field and the polarity of its axial field. We report that for about 64% of CME–MC events, we found a good correspondence between the orientation angles implying that for the majority of interplanetary ejecta their orientations do not change significantly (less than 45 deg rotation) while travelling from the Sun to the near-Earth environment. 相似文献
3.
A. Antoniou E. Danezis E. Lyratzi L.Č. Popović D. Stathopoulos M.S. Dimitrijević 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2014
In this paper, using the Gauss-Rotation model (GR model), we analyse the UV C IV resonance lines in the spectra of 20 Oe-stars of different spectral subtypes, in order to detect the structure of C IV region. We study the presence and behavior of absorption clouds and analyse their characteristics. From this analysis we can calculate the values of a group of physical parameters, such as the apparent rotational and radial velocities, the random velocities of the thermal motions of the ions, the Full Width at Half Maximum (FWHM), the optical depth, as well as the absorbed energy and the column density of the independent regions of matter, which produce the main and the satellite clouds of the studied spectral lines. Finally, we present the relations between these physical parameters and the spectral subtypes of the studied stars and we give our results about the structure of the C IV region in their atmosphere. 相似文献
4.
在中国空气动力研究与发展中心(CARDC)超高速碰撞中心(HIRC)7.6 mm超高速碰撞设备的基础上,搭建纳秒级脉冲激光数字全息系统。提出滤波片和衰减片组合布置,减弱超高速碰撞等离子体自发光、提高信噪比的方法。实验获得了2.25 mm铝球弹丸以4.0 km/s的速度撞击0.5 mm厚铝板形成碎片云的全息图。采用小波变换算法对碎片云全息图进行重建,得到超高速撞击碎片云的三维结构和碎片大小。碎片云的轮廓呈椭球型,分为碎片云的前端、核心和外壳,碎片主要分布在弹丸破碎形成的碎片云核心,存在大碎片,且分布较集中,对后板的损伤也严重 相似文献
5.
Coronal mass ejections and post-shock streams driven by them are the most efficient drivers of strong magnetospheric activity,
magnetic storms. For this reason there is considerable interest in trying to make reliable forecasts for the effects of CMEs
as much in advance as possible. To succeed this requires understanding of all aspects related to CMEs, starting from their
emergence on the Sun to their propagation to the vicinity of the Earth and to effects within the magnetosphere. In this article
we discuss some recent results on the geoeffectivity of different types of CME/shock structures. A particularly intriguing
observation is that smoothly rotating magnetic fields within CMEs are most efficient in driving storm activity seen in the
inner magnetosphere due to enhanced ring current, whereas the sheath regions between the shock and the ejecta tend to favour
high-latitude activity. 相似文献
6.
In seeking to understand the formation of the giant planets and the origin of their atmospheres, the heavy element abundance
in well-mixed atmosphere is key. However, clouds come in the way. Thus, composition and condensation are intimately intertwined
with the mystery of planetary formation and atmospheric origin. Clouds also provide important clues to dynamical processes
in the atmosphere. In this chapter we discuss the thermochemical processes that determine the composition, structure, and
characteristics of the Jovian clouds. We also discuss the significance of clouds in the big picture of the formation of giant
planets and their atmospheres. We recommend multiprobes at all four giant planets in order to break new ground. 相似文献
7.
Nat Gopalswamy 《Space Science Reviews》2006,124(1-4):145-168
Interplanetary coronal mass ejections (ICMEs) originating from closed field regions on the Sun are the most energetic phenomenon
in the heliosphere. They cause intense geomagnetic storms and drive fast mode shocks that accelerate charged particles. ICMEs
are the interplanetary manifestations of CMEs typically remote-sensed by coronagraphs. This paper summarizes the observational
properties of ICMEs with reference to the ordinary solar wind and the progenitor CMEs. 相似文献
8.
9.
Merlin C. Köhnke Christian von Savigny Charles E. Robert 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2018,61(10):2531-2539
Previous studies have identified solar 27-day signatures in several parameters in the Mesosphere/Lower thermosphere region, including temperature and Noctilucent cloud (NLC) occurrence frequency. In this study we report on a solar 27-day signature in NLC altitude with peak-to-peak variations of about 400?m. We use SCIAMACHY limb-scatter observations from 2002 to 2012 to detect NLCs. The superposed epoch analysis method is applied to extract solar 27-day signatures. A 27-day signature in NLC altitude can be identified in both hemispheres in the SCIAMACHY dataset, but the signature is more pronounced in the northern hemisphere. The solar signature in NLC altitude is found to be in phase with solar activity and temperature for latitudes N. We provide a qualitative explanation for the positive correlation between solar activity and NLC altitude based on published model simulations. 相似文献
10.
叶片气膜孔的几何参数对其冷却效率具有十分重要的影响,需采取有效手段对加工的气膜孔几何参数进行检测。基于光场成像原理,初步探索了单光场相机快照式三维测量技术在气膜孔检测上的应用。与其他光学测量技术相比,该技术仅通过一次拍摄,即可快速从捕获的单张原始光场图像中计算得到气膜孔的三维点云数据,其数据采集效率很高。实验中对一组标准量块进行了测量,展示了单光场相机应用于工业级精密测量的潜力。对实际叶片上气膜孔几何参数的检测结果初步表明了该技术应用于气膜孔三维测量的可能性。由于单光场相机成像系统的结构简单,易于操作且便于与其他传感器设备集成,可为气膜孔三维测量问题提供一种新的解决方案。 相似文献