Coupled HM analysis using zero‐thickness interface elements with double nodes. Part I: Theoretical model

In recent years, the authors have proposed a new double‐node zero‐thickness interface element for diffusion analysis via the finite element method (FEM) (Int. J. Numer. Anal. Meth. Geomech. 2004; 28 (9): 947–962). In the present paper, that formulation is combined with an existing mechanical formulation in order to obtain a fully coupled hydro‐mechanical (or HM) model applicable to fractured/fracturing geomaterials. Each element (continuum or interface) is formulated in terms of the displacements (u) and the fluid pressure (p) at the nodes. After assembly, a particular expression of the traditional ‘u–p’ system of coupled equations is obtained, which is highly non‐linear due to the strong dependence between the permeability and the aperture of discontinuities. The formulation is valid for both pre‐existing and developing discontinuities by using the appropriate constitutive model that relates effective stresses to relative displacements in the interface. The system of coupled equations is solved following two different numerical approaches: staggered and fully coupled. In the latter, the Newton–Raphson method is used, and it is shown that the Jacobian matrix becomes non‐symmetric due to the dependence of the discontinuity permeability on the aperture. In the part II companion paper (Int. J. Numer. Anal. Meth. Geomech. 2008; DOI: 10.1002/nag.730 ), the formulation proposed is verified and illustrated with some application examples. Copyright © 2008 John Wiley & Sons, Ltd.     

基于DEVS形式理论和面向对象方法学的DEVS系统建模仿真框架

描述了一个基于离散事件系统（ＤＥＶＳ）形式理论和面向对象方法学的 ＤＥＶＳ系统建模仿真框架ＳｉｍｕＣｌａｓｓ,它不但在 ＶｉｓｕａｌＣ＋＋环境下实现了 ＤＥＶＳ形式理论及其相关的层次仿真算法,而且结合了两种强大的系统开发框架：ＤＥＶＳ形式理论和面向对象范形,ＳｉｍｕＣｌａｓｓ支持在Ｃ＋＋面向对象环境中运用层次模块化方法进行离散事件模型的开发。     

九江市城市垃圾卫生填埋场场址适宜性评价优选

利用层次分析法对九江市5个候选垃圾场地进行了适宜性评价优选,通过场地评价影响因子定权重和采用多目标线性加权函数数学模型计算各候选场址的综合评价得分,结果依次为场地5>场地1>场地2>场地3>场地4。可见场地5为5个候选场地中最佳适宜性垃圾填埋场场址,在很大程度上减少了选址过程中人为主观因素影响和定性分析过多的缺点,为九江市重建垃圾填埋场地选址提供了客观依据。     

J2 Invariant Relative Orbits for Spacecraft Formations

An analytic method is presented to establish J ₂ invariant relative orbits. Working with mean orbit elements, the secular drift of the longitude of the ascending node and the sum of the argument of perigee and mean anomaly are set equal between two neighboring orbits. By having both orbits drift at equal angular rates on the average, they will not separate over time due to the J₂ influence. Two first order conditions are established between the differences in momenta elements (semi-major axis, eccentricity and inclination angle) that guarantee that the drift rates of two neighboring orbits are equal on the average. Differences in the longitude of the ascending node, argument of perigee and initial mean anomaly can be set at will, as long as they are setup in mean element space. For near polar orbits, enforcing both momenta element constraints may result in impractically large relative orbits. It this case it is shown that dropping the equal ascending node rate requirement still avoids considerable relative orbit drift and provides substantial fuel savings.This revised version was published online in October 2005 with corrections to the Cover Date.     

A fuzzy set based approach for integration of thematic maps for landslide susceptibility zonation

Spatial prediction of landslides is termed landslide susceptibility zonation (LSZ). In this study, an objective weighting approach based on fuzzy concepts is used for LSZ in a part of the Darjeeling Himalayas. Relevant thematic layers pertaining to landslide causative factors have been generated using remote sensing and geographic information system (GIS) techniques. The membership values for each category of thematic layers have been determined using the cosine amplitude fuzzy similarity method and are used as ratings. The integration of these ratings led to the generation of LSZ map. The integration of different ratings to generate an LSZ map has been performed using a fuzzy gamma operator apart from the arithmetic overlay approach. The process is based on determination of combined rating known as the landslide susceptibility index (LSI) for all the pixels using the fuzzy gamma operator and classification using the success rate curve method to prepare the LSZ map. The results indicate that as the gamma value increases, the accuracy of the LSZ map also increases. It is observed that the LSZ map produced by the fuzzy algebraic sum has reflected a more real situation in terms of landslides in the study area.     

解析信号和水平导数法超贫铁矿磁探测 ——-以内蒙古凉城铁矿为例

高分辨率高精度磁法勘探可以准确定位围岩与磁铁矿的边界。本文以内蒙古凉城铁矿高精度磁法勘探为例,利用解析信号和水平导数法处理了磁异常数据,在工作区发现一宽度 60 ～ 100 m、埋深为 30 ～60 m、品位为 12% ～19% ( TFe) 的超贫铁矿。在平面等值线图中任取一条剖面用上述两种方法计算计算的水平宽度分别为81 m 和83 m,与正演宽度86 m、反演宽度75 m 相吻合。此方法大幅度提高了其水平分辨率,准确定位了超贫磁铁矿与围岩的边界,取得了较好的找矿效果,为用于同类型贫铁矿探测提供了基础。     

基于单应矩阵约束的黑白棋盘格角点提取

针对Harris算子提取棋盘格角点存在的问题,提出基于单应矩阵的黑白棋盘格角点提取方法.方法首先通过人机交互确定角点提取范围以及计算单应矩阵;然后根据单应矩阵将物方平面上其他点映射到影像上以确定初始的角点位置;最后以初始点位为基准,根据最小距离法确定最终Harris算子角点提取结果.实验结果表明,文中提出算法能有效提取黑白棋盘格角点.     

Discrete element modeling of tool‐rock interaction II: rock indentation

The failure mechanisms induced by a wedge‐shaped tool indenting normally against a rock surface are investigated using the discrete element method (DEM). The main focus of this study is to explore the conditions controlling the transition from a ductile to a brittle mode of failure. The development of a damage zone and the initiation and propagation of a brittle fracture is well captured by the DEM simulations. The numerical results support the conjecture that initiation of brittle fractures is governed by a scaled flaw length Λ, a ratio between the flaw size λ and the characteristic length (where K_Ic is the toughness and σ_c the uniaxial compressive strength). The size of the damage zone agrees well with analytical predictions based on the cavity expansion model. The effects of a far‐field confining stress and the existence of a relief surface near the indenter are also examined.Copyright © 2012 John Wiley & Sons, Ltd.     

一类与算子有关的级数转化公式

利用算子之间的相互关系将算子g(xΔ)展成3种不同的形式,构造一些级数转化公式,并结合Eulerian多项式简化这些级数转化公式、最后讨论这些级数转化公式在寻找求和公式及组合恒等式证明中的一些应用。