地幔氧逸度的研究进展

通过对目前国际上诸多有关地幔氧逸度的研究结果的系统分析和总结 ,提出了地幔中自由氧对地幔物质的性质、状态及运动过程产生影响的基本作用方式 ;介绍了目前地幔氧逸度研究的主要研究手段 ,包括本征氧逸度的实验室测量、模拟氧逸度的实验室测量、地幔氧逸度计及理论计算等及其优缺点 ;定性探讨了地幔氧逸度的时空分布规律 ,获得了地幔随时间的推移变得愈来愈氧化 ,随深度的增加变得愈来愈还原 ,以及在横向上不同大地构造部位的地幔区域具有不同的氧逸度等诸多结论。结合目前人们对地幔物质组成、性质、状态、运动过程及地球的起源与演化历史等的认识 ,初步提出了地幔不同圈层氧逸度的约束机制。最后 ,针对目前地幔氧逸度的研究现状 ,为今后提出了一些参考性的研究方向。     

Pastoralists’ perceptions and realities of vegetation change and browse consumption in the northern Kalahari, Namibia

Pastoral production around artificial watering points in semi-arid environments affects the density and composition of plant communities. In the Kalahari desert of southwestern Africa, bush encroachment is often regarded as the major form of land degradation resulting from pastoral production around watering points. We investigated the OvaHerero pastoralists’ perceptions of the extent of vegetation change since the establishment of artificial watering points in the northern Kalahari desert of Namibia, and related this to ecological data on vegetation change. We determined the utility of woody vegetation to pastoralists’ livelihoods in terms of provision of construction material, fuel wood and browse. We quantified local knowledge of cattle browse consumption and correlated this with field data. We also assessed the purposes for which major livestock types were used. Our results showed that: (1) pastoral knowledge of bush encroachment and browse consumption was consistent with concurrently collected field data, (2) the current level of bush encroachment was perceived to be beneficial for pastoral production, and (3) cattle played an important role in the production of milk and milk by-products for domestic use, and served as a source of cash income, while sheep and goats were primarily kept for meat consumption. This result contrasts with historical studies that mainly portray cattle as a symbol of social status among OvaHerero pastoralists.     

带权约束参数平差在工程控制网优化中的应用

介绍用带权约束平差原理编制的工程控制网试验修正法设计和平差程序,并用于设计工程导线和平差变形观测控制网等实际工程的例子,据此提供一些结论和建议.     

基于等高线数据的地性线追踪技术研究

通过研究特征点的提取技术和建立系统的特征点匹配的数学模型，研究了基于矢量等高线数据的地性线的自动追踪技术，利用所述方法，提取的特征点完整，准确；理论和实验表明，所建立的数学模型简捷，实用，有可靠的数学理论基础，且地性线追踪效果良好。     

用剩余信息量最小准则实现直流电测深数据的二维自动反演

自Pelton等发表第一篇直接电测深数据的二维反演文章以来，电测深数据的二维反演解释已广泛应用于资源勘探和环境监测，并取得一定效果。然而，由于该方法中加入了人为确定的平滑约束，其反演解释结果具有很大不确定性，使其在实际生产中普及应用受到限制。因此，如何在现有方法的基础上进一步改进完善成为该方法普及应用的关键。为了使反演解释结果既忠于实测数据，又合理地反映地下介质的变化，作者在本文中讨论了基于最大熵谱原理的剩余信息量最小准则实现电测深数据的二维自动反演。作者在文中还介绍了正演计算和偏导数求取中，提高精度和计算效率的技巧。用三个数值模式算例对本文的自动反演方法进行了验证。数值模拟结果表明，基于剩余信息量电小准则的二维自动反演给出的解释结果基本不受人为因素影响，能反映地下介质电阻率的详细变化。     

Smooth constraint inversion technique in genetic algorithms and its application to surface wave study in the Tibetan Plateau

IntroductionThe dispersion phenomena, which can be observed when surface wave travels through the Earth interior, has been extensively applied in investigating the velocity structure of the Earth interior. Usually, the dispersion curve is a nonlinear function of the thickness, S and P wave velocities and density of each layer. Because surface wave inversion is a multiple-minima problem, the result strongly depends on the initial model in traditional linear inversion. Genetic algorithm (GA) …     

Geodynamic settings of Mesozoic large-scale mineralization in North China and adjacent areas

Based on the summary of the highly precise datings of the metal deposits and related granitic rocks in North China craton and adjacent areas, such as the molybdenite Re-Os datings,⁴⁰Ar-³⁹Ar datings of mica, K-feldspar and quartz, some Rb-Sr isochrons, and the SHRIMP zircon U-Pb dating and single grain zircon U-Pb dating, we suggest that the large-scale mineralization in North China craton and adjacent areas take place in three periods of 200-160Ma, 140Ma±, and 130-110Ma. Their corresponding geodynamic settings are proposed to be the collision orogenic process, transformation of the tectonic regime, and delamination of the lithosphere, respectively, in light of analyzing the Mesozoic geodynamic evolution in the North China craton.     

视觉测量中相机外参数近似值的快速求解

提出了利用3个不共线的控制点对相机外参数近似值进行快速求解的一种方法.利用3个控制点与其像坐标间的几何关系求得3个控制点在摄站坐标系下的坐标;由控制点的已知控制坐标与求得的摄站坐标系下的坐标,进一步求得两坐标系的转换参数的初值;通过解析法或光束法对相机外参数用初值进行精确标定.并通过一组模拟数据验证了该方法的正确性.     

基于图模犁和拓扑约束的管网数据一致性检测

正确可靠的数据是GIS系统的核心。针对管网数据的复杂性，提出利用圈数据模型描述管网拓扑关系．并使用拓扑约束方法对管网数据一致性进行检测，以确保数据的正确性。该方法吸收了基于连接规则以及基于拓扑关系约束的方法的优点，能够更好的描述管网系统的整体结构并对其进行拓扑约束，使得一致性检测更加全面。