Towards realistic simulations of lava dome growth using the level set method

The level set method has been implemented in a computational volcanology context. New techniques are presented to solve the advection equation and the reinitialisation equation. These techniques are based upon an algorithm developed in the finite difference context, but are modified to take advantage of the robustness of the finite element method. The resulting algorithm is tested on a well documented Rayleigh–Taylor instability benchmark [19], and on an axisymmetric problem where the analytical solution is known. Finally, the algorithm is applied to a basic study of lava dome growth.     

公路路基支挡结构物加固技术研究

近年来,国内各地相继出现了公路路基支挡结构物失稳事件,对相关路桥的运营安全造成了严重威胁。由于条件特殊及环境制约,此类工程加固难度很大。结合山东省G104界河立交桥加筋土挡土墙和G205高峪铺公铁立交桥坡间挡土墙的加固,对此类工程失稳的特征、原因及相应的工程对策从理论到实践展开了深入研究,并得到了具有一定推广价值的结论。     

knowledge base model for evaluation of bio-physical tendency of dryland

The present study aims the evaluation of bio-physical characteristics towards soil-water-vegetation stress and a rule is envisaged to assess the degree of temporal changes. The digital rule for assessment is initialized through the index of land Instability (ILI) where the variance indicates the temporal instability of the pixel i.e., smallest land unit. It is assumed that the biophysical characteristic of land is in command of land-dynamics where there is no change in Land Use/Land Cover (LU&;LC). The intensity map on tendency of albedo (IALB) assesses the intensity of soil erosion and water stress whereas intensity map on tendency of NDVI (INDVI) appraises the stress on vegetation. The carry-out study covers a part of semiarid Western India. Primarily remote sensing technique, which carries the digital information of land temporally and spatially, is adopted in this paper. A part of the study area is represented using two sets of IRS 1A/1B LISS-I data of March with a decadal time domain (1989–1998) as a test area. It is assumed that the soil-water-vegetation stress is maximum during summer (March–April–May) in any tropical belt and decadal data will stretch the possibility of climate as well as man-made activity over the land.     

海底土体失稳过程分类及其声学特征

海底斜坡土体失稳是海底比较常见的重力侵蚀过程。由于人们无法直接接触海底，对其研究绝大多数是事后借助于声学和地质学调查手段进行。文章根据一般饱水土体运动机理及变形程度和运动状态对海底斜坡土体不稳定性进行分类：蠕动、滑动和流动，并探讨它们形成过程的力学基础以及声学识别特征。蠕动是指海底土颗粒之间发生相对位移，但整体上未发生明显的位移。其相应的声学识别特征是：连续不规则波状反射结构。滑动是指失稳土体在海底斜坡上做块体运动。其声学探测记录表现为：张性裂隙、内部结构完整的滑体以及伴有负载形成的地形等。流动是指失稳土体完全崩解形成流体在海底斜坡上运动。沉积物流在流动中出现线形纹理和平行层理非常清楚的中断为标志，而且被没有内部结构或层理的声学透明物质充填等声学识别特征。     

河南地热(中深)井金属井管腐蚀与结垢试验研究

地热(中深)井金属井管普遍存在着腐蚀与结垢现象。就河南地热(中深)井金属井管腐蚀与结垢问题进行了初步研究，进行了不同材质、不同水温的室内试验和井下彩色电视检测与分析，并提出了减少腐蚀与结垢的建议。     

Slope Instability in Static and Dynamic Conditions for Urban Planning: the ‘Oltre Po Pavese’ Case History (Regione Lombardia – Italy)

The paper describes a method for the evaluation of slope instability for urban planning purposes, applied in the test area Oltre Po Pavese (Regione Lombardia, Italy). A statistic and a probabilistic approach have been applied for the estimation of landslide activations and for the definition of potentially unstable areas. The displacement has been obtained through a simplified dynamic analysis, using deterministic methods: first the critical horizontal acceleration coefficient (K_c) has been evaluated, second the displacement has been calculated using the K_c values and the seismic input values, such as peak ground acceleration (PGA) and Arias intensity (Ia), through empirical relationships between displacement and Ia values for different K_c values. The results can be used by the regional government to give to the municipalities of the area a guide for the selection of the zones to be studied with future and more detailed analyses.     

双层套管井中单极子声波测井的响应特征

目前,在深井中采用多层套管实现层间封隔的方法已非常普遍,对多层套管井固井质量评价的需求越来越迫切,目前还未有针对外层套管与地层之间水泥胶结评价的有效手段.本文利用三维有限差分仿真了单极声波测井在双层套管井中的响应特征,探讨了利用套管波幅度和斯通利波频散特征识别外层套管与地层之间环空是否胶结水泥的可行性.数值计算结果显示在两层套管之间胶结水泥时,套管波的幅度或衰减对外层套管和地层之间是否胶结水泥非常敏感,外层环空若充填水泥则全波中的套管波幅度降低明显;在两层套管之间充填泥浆时,全波波形中首先到达的套管波幅度较大,其对外层套管的胶结状况不再敏感,通过对接收的阵列波形做频率-慢度相关分析发现,在外层套管和地层之间胶结水泥后,井孔内接收到的低于10 kHz的外斯通利波慢度明显增大,仿真波形的处理结果与解析计算的斯通利波的频散曲线吻合较好,进一步验证了可尝试利用内层环空激发的外斯通利波判断外层套管与地层之间是否胶结水泥.     

等离子体片边界层电磁不稳定性引起的波－粒输运

采用二级理论研究了在等离子体片边界层电磁不稳定性引起的波—粒输运．结果表明，束流离子被热化和各向同性化，离子最大加热率峰值与电磁不稳定性最大增长率峰值出现在大致相同的方向上．被热化和各向同性化的束流离子可能是等离子体片中心区热离子的来源．这些结果对于理解等离子体片边界层的输运过程具有重要的意义．     

中纬电离层的低频等离子体不稳定性

本文研究了中纬电离层Rayleigh-Taylor不稳定性和漂移不稳定性的基本性质.如果不存在中性风和背景电场,中纬Rayleigh-Taylor不稳定性的增长率比赤道相应条件下的小.中性风和电场对中纬Rayleigh-Taylor不稳定性有重要影响.当中性风速度达到10m/s时,其作用就超过了重力.漂移不稳定性也受到重力、中性风和电场的影响,离子-中性粒子碰撞能降低漂移不稳定性的增长率.本文的分析表明,在赤道电离层容易产生大尺度的Rayleigh-Taylor不稳定性,在中纬电离层易产生小尺度的漂移不稳定性.