混合整体最小二乘曲面拟合在点云滤波中的应用

针对传统点云滤波过程中拟合曲面不连续,参数求解不合理及高差阈值不明确的问题,本文提出一种基于混合整体最小二乘的曲面拟合约束法。利用中心网格加权坡度值构建了多尺度格网,探讨了依据网格邻域选取地面种子点的标准,分析了混合整体最小二乘曲面方程求解和根据滤波结果逐级调整高差阈值的方法和步骤。试验结果表明,该方法提高了复杂区域的点云滤波精度,为构建数字高程模型提供了精确数据。     

南方典型植被遥感丰度信息提取

针对遥感影像在南方丘陵地区典型植被丰度信息提取中存在的大量混合像元问题,为进一步提高线性解混精度,通过计算像元EVI值,构建了Landsat 8时间序列影像南方典型植被（端元）和混合像元的EVI时间序列曲线,分析了不同生育期内各种地物类型的植被指数变化曲线,发现不同地物在植被指数时间序列中具有各自独立的波动规律。选取多个端元及其EVI时间序列曲线,利用光谱匹配方法对匹配EVI时间序列曲线和多个端元进行了匹配,达到利用不同端元组合进行光谱解混的目的。试验结果表明,与传统方法相比,阔叶林解混精度有明显提高,针叶林解混精度也有所提高。该研究成果可以为南方丘陵地区植被环境的研究提供有力支撑。     

Mixed Primal–Dual Method for Nuclear Waste Disposal Far Field Simulation

A mixed finite volume method is applied in order to simulate a simplified Far Field model. We show how this method can be adapted to both the elliptic and the convection–diffusion equations describing the water flow and the variations of the concentration of the radioactive element respectively. For the water flow problem, we justify an a posteriori error estimator. Finally, we present some numerical results.     

A stability criterion for elasto‐viscoplastic constitutive relationships

In this paper, the onset of mechanical instability in time‐sensitive elasto‐viscoplastic solids is theoretically analyzed at the constitutive level and associated with the occurrence of ‘spontaneous accelerations’ under stationary external perturbations. For this purpose, a second‐order form of Perzyna's constitutive equations is first derived by time differentiation, and a sufficient stability condition is identified for general mixed loading programs. These loading conditions are in fact the most general in both laboratory tests and real boundary value problems, where a combination of certain stress and strain components is known/prescribed. The theoretical analysis leads to find precise stability limits in terms of material hardening modulus. In the case of constitutive relationships with isotropic strain‐hardening, no instabilities are possible while the hardening modulus is larger than the so‐called ‘controllability modulus’ defined for (inviscid) elasto‐plastic materials. It is also shown that the current stress/strain rate may also directly influence the occurrence of elasto‐viscoplastic instability, which is at variance with elasto‐plastic inviscid media. Copyright © 2015 John Wiley & Sons, Ltd.     

甘肃省龙首山牛角沟铀矿点钾钠混合交代作用研究

牛角沟铀矿点是甘肃省龙首山铀成矿带中段东部重要的钠交代型铀矿点,该矿点外围新发现的钾钠混合交代花岗岩在该区难得一见。为更细致的解析钾钠混合交代作用,本文从岩石学、矿物学、地球化学、同位素年代学等方面开展研究,认为牛角沟中粗粒花岗岩是早古生代（445.2±7.8Ma）祁连山—龙首山造山作用晚期,后碰撞伸展环境中产出的中硅、富碱弱过铝、低铁和钙而贫钛、镁、磷的高钾钙碱性花岗岩。钾钠混合交代作用形成蚀变岩从中心向外依次为孔洞状钾钠混合交代花岗岩→雪花状方解石化钾钠混合交代花岗岩→少石英无暗色矿物紫红色钾钠混合交代花岗岩→假象绿泥石化花岗岩逐渐过渡为正常花岗岩。钾钠混合交代作用的热液溶蚀萃取了流经花岗岩中的SiO2、TiO2、FeO、Fe2O3、MnO、MgO、CaO和P2O5,以及REE、Ba、Sr、Zr、Sc、Cr、Sr、Co、Mo、Hf、Bi、Sb、Pb等化学组分,迁入孔洞状钾钠混合交代花岗岩中的组分有Na2O、K2O、MnO、Th、U、Rb、Nb、Ta、W、Sr等。CaO、MnO、Na2O、Th、U、Nb、Ta、Rb、HREE等组分与方解石一起迁入雪花状方解石化钾钠混合交代蚀变带中,而TiO2、FeO、Fe2O3、MgO、CaO、P2O5、V、U、Se、Zr等化学组分在紫红色钾钠混合交代花岗岩中析出富集。钾钠混合交代花岗岩性脆、易碎、多孔、“疏松”,为之后钠交代铀成矿作用提供了良好的围岩基础。其侵位时代进一步印证了龙首山钠交代型铀矿成矿作用起始于444~442Ma前后的可靠性。     

西藏申扎地区德日昂玛-下拉剖面：冈瓦纳和特提斯晚石炭世-早二叠世地层和古生物对比的桥梁

西藏北部申扎县永珠地区德日昂玛-下拉剖面中石炭系和二叠系地层发育完整,出露良好,化石丰富。该剖面中查果罗玛组碳酸盐岩地层(泥盆纪—早石炭世)和下拉组(中二叠世)碳酸盐岩地层之间的碎屑岩夹灰岩地层,在沉积上表现为冰海相杂砾岩,在古生物化石面貌上表现为特提斯-冈瓦纳古生物群混生。古生物群混生的现象为石炭纪—二叠纪的特提斯生物区与冈瓦纳生物区之间的地层和古生物对比建立了一座桥梁。永珠组中上部地层中同时产有牙形石和腕足类,牙形石的研究表明其时代为晚石炭世莫斯科期,而腕足类的研究则表明其为早二叠世萨克马尔期。这一矛盾预示着在(亲)冈瓦纳相地区晚石炭世晚期地层缺失的意见需要重新审视。     

端元可变非线性混合像元分解模型

遥感影像中混合像元普遍存在。端元固定的情况下对混合像元进行分解,很难高精度地识别影像地物。本文基于支持向量机,提出了端元可变的非线性混合像元分解模型。首先,通过构建多个支持向量机获取每个像元的优化端元集,在优化端元集的基础上运用支持向量机与两两配对方法相结合的算法获取像元组分。试验结果表明,本文提出的方法效果优于传统的多端元光谱分解法。     

基于虚幻引擎的智能矿山数字孪生系统云渲染技术

HTML5、WebGL、云渲染等技术为浏览器、移动端、XR等多种终端的可视化渲染提供了重要技术支撑。本文分析比较了其优缺点,并采用虚幻引擎4的云渲染技术,采用某煤矿的倾斜摄影、BIM、巷道、设备、三维地质模型开展了系统设计与测试,分析了云渲染的效率和效果,实现了数字孪生云渲染技术在智能矿山的应用。     

Numerical Simulation of the Response of the Ocean Surface Layer to Precipitation

Numerical experiments were conducted to investigate the ocean's response to the precipitation. A squall line observed in TOGA COARE was simulated. The simulation reproduced some of the observed ocean responses to the precipitation, such as the formation of a fresh water layer, surface cooling and the variation of upper layer turbulent mixing. The precipitation-induced fresh layer can cause the vertical turbulent diffusivities to decrease from the surface to a depth of about 11–13 meters within a few hours. After the rainfall, the turbulence increases near the surface of the ocean due to the combined effect of increased shear and wind forcing, but decreases with depth due to the development of a stable layer. The main reason for the turbulence variation is the decrease in the vertical turbulence flux below the surface fresh layer because of increased static stability. Sensitivity experiments reveal that the sea-surface temperature increases faster after rainfall due to the formation of a shallow fresh water layer near the surface.     

山东金伯利岩的壳幔混染、部分熔融、Re-Os 同位素年龄及冰盖冰川搬运、人造金刚石干扰等领域研究最新进展

根据山东蒙阴各类金伯利岩及其相关幔源捕掳体的化学成分,研究了金伯利岩壳源混染程度与岩石类型之间的关系。发现橄榄岩—碎裂状橄榄岩—粗斑金伯利岩—细粒金伯利岩之间,其壳源混染程度逐渐增高。粗斑金伯利岩的壳源混染程度接近碎裂状橄榄岩,表明粗斑金伯利岩是碎裂状橄榄岩的进一步碎裂的产物;金伯利岩经历了地幔橄榄岩的部分熔融形成碎裂状橄榄岩、斑状金伯利岩。根据金伯利岩中大理岩包体、黄铁矿的Re-Os同位素研究,获得了蒙阴金伯利岩的侵位时间分别为227.97Ma和245.80Ma,属于三叠纪,与苏鲁-大别造山带的形成时间一致,由此分析蒙阴金伯利岩的侵位与扬子板块和华北板块的碰撞有关,也似乎暗示了华北克拉通破坏的初始阶段。华北冰盖冰川对于金刚石的搬运方式、搬运路径与流水搬运之间存在巨大差异,需要对金刚石的供源与分散进行重新认识。地表大量分布的人造金刚石对金刚石的找矿工作已经造成干扰与误导,需要引起重视。