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991.
Douglas O. ReVelle 《Earth, Moon, and Planets》2008,102(1-4):345-356
We have developed a new approach to modeling the acoustic-gravity wave (AGW) radiation from bolide sources. This first effort
involves entry modeling of bolide sources that have available satellite data through procedures developed in ReVelle (Earth
Moon Planets 95, 441–476, 2004a; in: A. Milani, G. Valsecchi, D. Vokrouhlicky (eds) NEO Fireball Diversity: Energetics-based Entry Modeling and Analysis Techniques, Near-earth Objects: Our Celestial Neighbors
(IAU S236), 2007b). Results from the entry modeling are directly coupled to AGW production through line source blast wave theory for the initial
wave amplitude and period at (at 10 blast wave radii and perpendicular to the trajectory). The second effort involves the prediction of the formation
and or dominance of the propagation of the atmospheric Lamb, edge-wave composite mode in a viscous fluid (Pierce, J. Acoust.
Soc. Amer. 35, 1798–1807, 1963) as a function of the source energy, horizontal range and source altitude using the Lamb wave frequency that was deduced
directly during the entry modeling and that is used as a surrogate for the source energy. We have also determined that Lamb
wave production by bolides at close range decreases dramatically as either the source energy decreases or the source altitude
increases. Finally using procedures in Gill (Atmospheric-Ocean Dynamics, 1982) and in Tolstoy (Wave Propagation, 1973), we have analyzed two simple dispersion relationships and have calculated the expected dispersion for the Lamb edge-wave
mode and for the excited, propagating internal acoustic waves. Finally, we have used the above formalism to fully evaluate
these techniques for four large bolides, namely: the Tunguska bolide of June 30, 1908; the Revelstoke bolide of March 31,
1965; the Crete bolide of June 6, 2002 and the Antarctic bolide of September 3, 2004. Due to page limitations, we will only
present results in detail for the Revelstoke bolide. 相似文献
992.
Using a 12th order expansion of the perturbative potential in powers of the eccentricities and the inclinations, we study
the secular effects of two non-coplanar planets which are not in mean–motion resonance. By means of Lie transformations (which
introduce an action–angle formulation of the Hamiltonian), we find the four fundamental frequencies of the 3-D secular three-body
problem and compute the long-term time evolutions of the Keplerian elements. To find the relations between these elements,
the main combinations of the fundamental frequencies common to these evolutions are identified by frequency analysis. This
study is performed for two different reference frames: a general one and the Laplace plane. We underline the known limitations
of the linear Laplace–Lagrange theory and point out the great sensitivity of the 3-D secular three-body problem to its initial
values. This analytical approach is applied to the exoplanetary system Andromedae in order to search whether the eccentricities evolutions and the apsidal configuration (libration of ) observed in the coplanar case are maintained for increasing initial values of the mutual inclination of the two orbital
planes.
Anne-Sophie Libert is FNRS Research Fellow. 相似文献
993.
Tadross A. L. 《中国天文和天体物理学报》2008,8(3):362-368
As a continuation of a series of work, we aim to refine and re-determine the physical parameters of previously rarely or un-studied open star clusters with good quality CMDs using Near-IR JHK photometry. Here we present a morphological analysis of the 2MASS database (the digital "Two Micron All Sky Survey") for the open cluster Pismis 3. Some of the physical parameters are estimated for the first time, and some others, re-determined. 相似文献
994.
GRB 060124 is the first event that both prompt and afterglow emission were observed simultaneously by the three Swift instruments. Its main peak also triggered Konus-Wind and HETE-II. Therefore, investigation on both the temporal and spectral properties of the prompt emission can be extended to X-ray bands. We perform a detailed analysis on the two well identified pulses of this burst, and find that the pulses are narrower at higher energies, and both X-rays and γ-rays follow the same w–E relation for an individual pulse. However, there is no a universal power-law index of the w–E relation among pulses. We find also that the rise-to-decay ratio r/d seems not to evolve with E and the r/d values are well consistent with that observed in typical GRBs. The broadband spectral energy distribution also suggests that the X-rays are consistent with the spectral behavior of the γ-rays. These results indicate that the X-ray emission tracks the γ-ray emission and the emissions in the two energy bands are likely to be originated from the same physical mechanism. 相似文献
995.
Comet 73P-B/Schwassmann-Wachmann 3 was observed with IRCS/Subaru at geocentric distance of 0.074 AU on UT 10 May 2006. Multiple H2O emission lines were detected in non-resonant fluorescence near 2.9 μm. No significant variation in total H2O production rate was found during the (3 h) duration of our observations. H2O rotational temperatures and ortho-to-para abundance ratios were measured for several positions in the coma. The temperatures extracted from two different time intervals show very similar spatial distributions. For both, the rotational temperature decreased from ∼110 to ∼90 K as the projected distance from the nucleus increased from ∼5 to ∼30 km. We see no evidence for OPR change in the coma. The H2O ortho-para ratio is consistent with the statistical equilibrium value (3.0) for all spatially resolved measurements. This implies a nuclear spin temperature higher than ∼45 K. 相似文献
996.
城市地下空间开发利用容量评估的基础研究 总被引:10,自引:1,他引:9
该文探讨了城市地下空间开发利用容量评估的必要性,容量评估研究的基本内容及其关键技术。指出当前城市地下空间容量评估基础研究包括指标体系、评估模型、评估平台与评估示范四方面。城市地下空间容量评估研究不仅有利于城市地下空间的合理利用和有序开发,也有利于引导城市地面设施的合理布局与科学规划,对保障现代城市的可持续发展具有重要意义。 相似文献
997.
基于计算机视觉的地形3D重建 总被引:1,自引:0,他引:1
构造3D地形模型有很多种方法.本文提出一种用数码相机获得的未标定照片获取三维地形模型的简单方法.这种方法仅需要从两幅或多幅照片中选取对应点,根据这些对应点,求出基本矩阵,摄像机矩阵,进而进行三维地形表面的估计,实验结果及算法分析表明,本文提出的特征匹配算法精确度较高,实现地形重建方法切实可行,生成的模型可视效果较好。 相似文献
998.
大尺度断层往往控制了沉积盆地的形成和油气成藏,而小尺度断层则影响着注水开发效果和剩余油分布.大尺度断层可以通过二维或三维地震资料识别,而小尺度断层的识别则特别困难.本文提出了一种基于断层分形生长模式和三维地质力学模拟相结合来确定小尺度断层的数量、发育位置和方位的方法,并根据油田开发动态资料来确定小尺度断层对注水开发和剩余油分布的影响.将地震上识别的大尺度断层引入到三维数值力学模型中,模拟大尺度断层形成时期断裂带附近的应力扰动作用,然后结合破裂准则来建立最易发生破裂的方位和最大库伦剪切应力网格,以这两套网格和断层尺度的幂律分布确定的小尺度断层数量为约束条件来确定随机模型,对小尺度断层的密度、产状和发育位置进行定量预测.研究表明:利用分形理论和三维地质力学模拟可以对大尺度断层伴生小尺度断层进行有效预测;小尺度断层对注水开发效果和剩余油分布的影响取决于小尺度断层的规模(断距)以及小尺度断层方位和注采方向的关系. 相似文献
999.
1000.
虚拟仿真技术是目前计算机科学研究热点,将虚拟仿真技术应用到非开挖领域是非开挖教学及研究的发展趋势。针对水平定向钻进(Horizontal Directional Drilling,HDD)这一非开挖的主要施工工法,采用SolidWorks、3ds MAX、Photoshop等软件对三维场景、钻机以及钻头等施工设备进行三维建模,通过研究场景漫游技术、多摄像机跟随技术、物理效应仿真技术和轨迹记录及跟随等技术在Unity3D平台上开发培训系统,并将系统发布至桌面系统。该系统具有场景漫游、多视角显示、控制钻进、显示参数功能。测试结果表明培训系统运行流畅,场景切换迅速,具有良好的三维展示和教学功能。 相似文献