First-principles Study on Equilibrium Sn Isotope Fractionations in Hydrothermal Fluids

Tin (Sn) isotope geochemistry has great potential in tracing geological processes. However, lack of equilibrium Sn isotope fractionation factors of various Sn species limits the development of Sn isotope geochemistry. Equilibrium Sn isotope fractionation factors (124Sn/116Sn and 122Sn/116Sn) among various Sn(II, IV) complexes in aqueous solution were calculated using first-principles calculations. The results show that the oxidation states and the change of Sn(II, IV) species in hydrothermal fluids are the main factors leading to tin isotope fractionation in hydrothermal systems. For the Sn(IV) complexes, Sn isotope fractionation factors depend on the number of H2O molecules. For the Sn(II) complexes, the Sn isotope fractionation between Sn(II)?F, Sn(II)?Cl and Sn(II)?OH complexes is mainly affected by the bond length and the coordination number of anion, whereas the difference in 1000lnβ values of Sn(II)?SO4 and Sn(II)?CO3 complexes is insignificant with the change of anion coordination number. By comparing the 1000lnβ values of all Sn(II, IV) complexes, the enrichment trend in heavy Sn isotopes is Sn(IV) complexes > Sn(II) complexes. The equilibrium Sn isotopic fractionation factors enhance our understanding of the tin transportation and enrichment processes in hydrothermal systems.     

基于第一性原理的Si掺杂磁铁矿稳定性研究

磁铁矿中出现的杂质元素及其赋存形式具有很好的环境指示意义。Si是磁铁矿中常见的杂质之一,尽管Si与Fe在离子半径、化合价、置换能量效应等方面均存在较大差别,但无论磁铁矿的原位成分数据还是湿法化学分析数据均表明,磁铁矿中含有一定数量(热液环境中生成的磁铁矿晶体的SiO₂的质量分数可达6.19%)的Si。为探究Si在磁铁矿中是否能稳定存在及其具体存在位置,在VASP中建立Si在磁铁矿中不同位置的模型,然后利用密度泛函理论第一性原理计算Si在磁铁矿晶体中不同位置的形成能,以此判断Si在磁铁矿晶体中的稳定性。结果表明,Si替代磁铁矿八面体中心的Fe的掺杂形成能为-4.13 eV,替代四面体中心的Fe的掺杂形成能为-3.85 eV。值得注意的是,1个磁铁矿原胞内2个Fe³⁺(四面体中心)全部被Si替代的形成能为-8.87 eV。从掺杂形成能的角度来看,Si在磁铁矿四面体及八面体的中心位置均可存在,但Si代替四面体中心位置的全部Fe³⁺得到的结构最稳定。     

A Gestalt rules and graph-cut-based simplification framework for urban building models

To visualize large urban models efficiently, this paper presents a framework for generalizing urban building footprints and facade textures by using multiple Gestalt rules and a graph-cut-based energy function. First, an urban scene is divided into different blocks by main road networks. In each block, the building footprints are partitioned into potential Gestalt groups. A footprint may satisfy several Gestalt principles. We employ the graph-cut-based optimization function to obtain a consistent segmentation of the buildings into optimal Gestalt groups with minimal energy. The building footprints in each Gestalt group are aggregated into different levels of detail (LODs). Building facade textures are also abstracted and simplified into multiple LODs using the same approach as the building footprint simplification. An effective data structure termed SceneTree is introduced to manage these aggregated building footprints and facade textures. Combined with the parallelization scheme, the rendering efficiency of large-scale urban buildings is improved. Compared with other methods, our presented method can efficiently visualize large urban models and maintain the city's image.     

地图注记自动配置规则及其实现策略

在分析自动注记与手工注记差异的基础上,探讨了确定自动注记原则要考虑的因素,提出了一种适合小比例尺地图注记自动配置的方案,介绍了此方案的实现策略。     

Least action principle,equilibrium states,iterative adjustment and the stability of alluvial channels

The energy based least action principle (LAP) has proven to be very successful for explaining natural phenomena in both classical and modern physics. This paper briefly reviews its historical development and details how, in three ways, it governs the behaviour and stability of alluvial rivers. First, the LAP embodies the special stationary equilibrium state of motion and so its incorporation with the principle of energy conservation explains why so many optimizing hypotheses have been proposed in fluvial geomorphology. Second, the variational approach underlying the LAP provides a more straightforward and simpler fuzzy‐object orientated method for solving river regime problems than do the various complex Newtonian formulations. Third, it is shown that in fluvial systems with surplus energy the surplus can be expended with slope and/or channel geometry adjustments, with the degree of channel geometry adjustment quantified by the dimensionless numbers F for depth dominated adjustment and H for width/depth dominated adjustment. Different planforms are preferred at different energy levels, with H providing a quantitative measure of the flow's efficiency for moving sediment. In rivers with insufficient energy, the interactions of endogenous and exogenous factors are shown to be capable, in certain circumstances, of achieving a stationary equilibrium condition which acts as the attractor state. Importantly, this study describes how iterative changes enable systems to achieve such a stable equilibrium. Copyright © 2007 John Wiley & Sons, Ltd.     

A NEW MODEL FOR THE ANALYSIS OF SETTLEMENT OF DRILLED PIERS

A variational model for the analysis of axially loaded piers is presented. A closed-form solution technique employing an iterative procedure, is developed to obtain the displacement and forces in the pier along its axial direction. The method is suitable for similar analyses of pile foundations. It is shown that displacements and the load distribution along the axis of the pier compare well with a more sophisticated finite element solution. Furthermore, the new model complements the well-known Reese model employing t–z curves for the analysis of settlement of axially loaded piers. This new formulation using continuum mechanics principles, distributes the work done by the applied load as compressive strain energy in the pier, and as shear strain energy in the soil, as well as, the compressive strain energy in the soil surrounding the pier and at the bottom of the pier.     

网络地图的设计原则

本文从网络地图的特点与功能入手,分析国内外主要地图学网站上的网络地图,结合笔者所进行过的纸质地图与电子地图设计研究及网络地图的设计,总结网络地图的设计特点,提出网络地图的设计原则。认为网络地图不同于一般的电子地图,网络地图的设计应有自己的特点。目前国内外主要地图学网站上的网络地图在地图设计上存在着这样或那样的问题,因此影响了网络地图的信息传输效果,不能发挥其应有的作用。笔者对此进行了分析,结合分析结果,提出了网络地图在界面设计、色彩设计、符号设计、分层设计等方面的设计原则。     

王鹏飞教授气象学分科理论的学术研究——纪念校庆60周年暨纪念王鹏飞先生诞辰100周年

重点介绍王鹏飞先生在气象学分科之一的中国气象史志研究方面的卓越贡献,尤其是在理论研究的深化和专业研究的推进两个方面的重要建树。王鹏飞先生是中国气象史志研究的主要开拓者和领导者之一,他的辛勤努力将中国气象史志研究推向了新高度。尽管所回顾的是王鹏飞先生多年前的工作,但对今天日益繁荣的气象史志研究仍然有具体指导作用。2020年是南京信息工程大学60周年校庆,王鹏飞先生作为学校早期主要建校骨干之一,为学校今日的双一流学科做出了显著贡献。今年也是王鹏飞先生诞辰100周年,此文也表达了对王鹏飞先生的诚挚纪念。     

矿井全方位钻孔测斜技术的研究

论述了全方位钻孔测斜的方法原理、数学模型、误差分析与校正。形成了一套完整的全方位钻孔测斜技术。      

试井多解性问题研究

试井成果是油气田制定开发方案、措施选井及评估的重要依据,但资料的多解性严重制约着试井成果的准确性和可靠性,降低了使用价值。从产生试井资料多解性的来源入手,通过实例分析试井设计、资料录取、模型选择（重点分析井筒、近井筒效应,油气藏类型,外边界）等因素对试井解释结果的影响,确定有效排除试井成果多解性的原则和途径。