The main mean motion commensurabilities in the planar circular and elliptic problem     

Michèle Moons  Alessandro Morbidelli 《Celestial Mechanics and Dynamical Astronomy》1993,57(1-2):99-108

We study the motion of asteroids in the main mean motion commensurabilities in the frame of the planar restricted three-body problem. No assumption is made about the size of the eccentricity of the asteroid. At small to moderate eccentricity, we recover existing results (shape of the phase space and location of secondary resonances). We also provide global pictures of the dynamics in the region of secondary resonances. At high eccentricity, the phase space portraits of the integrable part of the Hamiltonian show new families of stable orbits for the 3:2 and 2:1 cases and the secular resonances ₅ and ₆ are located.  相似文献   

Reflection of wide-angle acoustic waves from a high velocity interface     

Ian Lerche 《Pure and Applied Geophysics》1990,134(1):109-115

At angles other than normal incidence a pencil of plane acoustic waves, incident on a planar interface separating a low velocity medium from a high velocity medium, gives rise to a reflected pencil of waves which is laterally displaced from the illumination point of the incident pencil. The importance of this planar shift for understanding and interpreting wide-angle acoustic reflections is discussed, as is the variation of the equivalent depth below the interface at which a point-like reflection would be considered as an equivalent reflecting horizon.  相似文献   

鄂东南区域化探异常特征及评序   总被引：1，自引：0，他引：1  

况蜀鄂  曾春明 《物探与化探》2000,24(5):373-376

以异常规格化面金属量对鄂东南区域化探异常进行评序,对其构成特点及分布规律进行分析,指出用该方法评序可以提高区化异常的检查效果及发现新的找矿线索。  相似文献   

黄土高原复杂地形上高质量湍流通量数据获取方法          下载免费PDF全文

苑广辉  张镭  李遥  梁捷宁 《地球物理学报》2016,59(6):1971-1982

利用兰州大学半干旱气候与环境观测站(Semi-Arid Climate and Environment Observatory of Lanzhou University,SACOL)湍流观测资料,分析了二次坐标旋转(double rotation,DR)、平面拟合(planar fit,PF)和分风区平面拟合(fetch planar fit,FPF)在复杂地形上的适用性,总结出一套适用于SACOL的总体湍流特征参数化方案.经过超声虚温订正、坐标旋转、空气密度脉动订正以及平稳性检验、总体湍流特征检验、总体质量分级处理,摩擦速度(u*)、感热通量、潜热通量、CO_2通量高质量数据所占比例分别为45%~62%、66%~68%、62%~65%、52%~54%.采用DR得到的高质量数据比例与采用PF相比,u*提高了17%,后三种通量略降低2%~3%.PF和FPF两种结果的差别主要体现在u*上,只考虑主导风向数据DR得到的u*质量仍最好.综合兼顾数据质量和计算工作量,在复杂地形上处理湍流观测资料的最优坐标旋转方法是DR.  相似文献   

霍甫水丝蚓(Limnodrilus hoffmeisteri)扰动下沉积物-水界面pH值的二维、高分辨分布特征          下载免费PDF全文

姚磊  韩超  丁士明 《湖泊科学》2016,28(1):156-162

采用平面光电极技术研究了霍甫水丝蚓(Limnodrilus hoffmeisteri)扰动对湖泊沉积物-水界面二维pH值分布特征的影响.结果表明水丝蚓扰动能将沉积物-水界面处pH值的变化梯度由2.5 mm内降低1.6个pH值单位减缓至约1 cm内降低0.6个pH值单位,并在界面处形成约1 cm深的pH值缓冲区域.水丝蚓的造穴活动也会对沉积物的二维pH值分布产生影响,洞穴内的pH值高于洞穴周边沉积物约0.6个pH值单位.  相似文献   

Shock metamorphism in plagioclase and selective amorphization     

Lidia Pittarello  Luke Daly  Annemarie E. PickersgilL  Ludovic Ferrire  Martin R. Lee 《Meteoritics & planetary science》2020,55(5):1103-1115

Plagioclase feldspar is one of the most common rock‐forming minerals on the surfaces of the Earth and other terrestrial planetary bodies, where it has been exposed to the ubiquitous process of hypervelocity impact. However, the response of plagioclase to shock metamorphism remains poorly understood. In particular, constraining the initiation and progression of shock‐induced amorphization in plagioclase (i.e., conversion to diaplectic glass) would improve our knowledge of how shock progressively deforms plagioclase. In turn, this information would enable plagioclase to be used to evaluate the shock stage of meteorites and terrestrial impactites, whenever they lack traditionally used shock indicator minerals, such as olivine and quartz. Here, we report on an electron backscatter diffraction (EBSD) study of shocked plagioclase grains in a metagranite shatter cone from the central uplift of the Manicouagan impact structure, Canada. Our study suggests that, in plagioclase, shock amorphization is initially localized either within pre‐existing twins or along lamellae, with similar characteristics to planar deformation features (PDFs) but that resemble twins in their periodicity. These lamellae likely represent specific crystallographic planes that undergo preferential structural failure under shock conditions. The orientation of preexisting twin sets that are preferentially amorphized and that of amorphous lamellae is likely favorable with respect to scattering of the local shock wave and corresponds to the “weakest” orientation for a specific shock pressure value. This observation supports a universal formation mechanism for PDFs in silicate minerals.  相似文献   

基于平面地质图的地质体三维建模          下载免费PDF全文

高士娟  毛先成  张宝一  任佳  李勇 《地质找矿论丛》2015,30(4):594-601

文章针对大尺度研究区域勘探范围有限、不能直接基于勘探数据构建区域地质体三维结构模型的问题,提出了一种以平面地质图为研究对象的地质体三维建模方法。此方法以平面地质图为基础,利用Section软件在DEM模型(数字高程模型)约束下半自动绘制一系列图切剖面图,将二维剖面映射到三维空间,利用三维剖面上轮廓线的对应性和连续性构建地质体三维模型。通过广西东平地区地质体三维模型构建实例,验证了该方法的可行性。  相似文献   

3维城市景观阴影绘制算法的研究与实现     

肖永辉  徐青  周杨 《测绘科学技术学报》2006,23(4):307-309

真实感3维可视化技术是数字城市的关键技术之一,随着CPU和GPU能力的不断增强,使得实时的真实感阴影得到广泛的应用.在3维城市景观中,通过多边形模拟建筑物,利用阴影数学的原理,在建筑物渲染过程中利用变换矩阵来生成阴影,并通过多边形偏移和模板测试来改善阴影效果;通过BillBoard技术构建树木,采用光影贴图的方法来生成阴影.实验证明该算法计算简单、速度快,能够满足3维场景真实性与实时性的要求.  相似文献   

岫岩陨石坑石英的冲击变质特征   总被引：3，自引：0，他引：3  

陈鸣 《矿物学报》2011,31(2):161-165

直径1.8 km的岫岩陨石坑位于辽宁省岫岩县苏子沟镇。坑区基岩为下元古界变质岩,由变粒岩、片麻岩、角闪岩、透闪岩和大理岩等岩石组成。坑内充填的撞击角砾岩石英颗粒呈现典型的冲击变质特征,其中包括沿着石英(0001)、{10 11}、{10 12}和{10 13}等方向发育的多组面状变形页理,以及石英发生相转变形成二氧化硅玻璃和柯石英。产出在二氧化硅玻璃中的针状和粒状柯石英表明从二氧化硅熔体中结晶形成。石英面状变形页理的发育特点限定冲击压力高达35 GPa,而二氧化硅熔体玻璃的存在表明冲击压力高达50 GPa。当压力释放和温度升高,二氧化硅熔体首先被形成。随着压力进一步释放到2.5～13 GPa,柯石英从二氧化硅熔体中结晶析出。岫岩陨石坑中石英面状变形页理和柯石英的存在提供了矿物冲击变质的诊断性证据。  相似文献   

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荣敏  周巍 《大地测量与地球动力学》2015,35(1):58-61

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