Tunnelling through weak and fragile rocks of Himalayas

A considerable amount of tunnelling has been going on in India for various projects such as hydroelectric power, irrigation, roads and railways. Most of these projects are located in Himalayas, far awa...     

基于样条插值的爆破振动时域波形预测方法

针对现有的爆破振动预测方法存在工程现场适用性差,不易于应用,无法准确预测完整的爆破振动信号在爆破时间段内的振动历程等问题,提出了一种基于样条插值的爆破振动预测方法。通过爆破中质点峰值速度、炸药量与爆心距的关系式,建立监测波形与预测波形的关系,对实测数据波形时域部分进行三次样条插值得到插值函数和预测目标点波形。通过实验和工程实践对该方法进行验证,并与传统的爆破振动预测方法进行质点峰值速度比对,结果表明:该爆破振动预测方法能够完整且较好地预测振动信号在爆破时间段内的振动历程,预测效果优于传统的爆破振动预测方法。     

浸水与一般挡土墙特性探究

挡土墙是用来抵抗土体位移变形的支承构筑物。浸水挡土墙主要位于水域环境,其与一般挡土墙在环境条件、受力模式、计算方法、工程造价等几个方面存在较大差异。通过对比分析,探究了浸水挡土墙与一般挡土墙的特性,得出了具有实践意义的结论,可以指导挡土墙的设计。     

Ribbon-based transfinite surfaces

One major issue in CAGD is to model complex objects using free-form surfaces of general topology. A natural approach is curvenet-based design, where designers directly create and modify feature curves. These are interpolated by smoothly connected, multi-sided patches, which can be represented by transfinite surfaces, defined as a combination of side interpolants or ribbons. A ribbon embeds Hermite data, i.e., prescribed positional and cross-derivative functions along boundary curves.The paper focuses on two transfinite schemes: the first is an enhanced and extended variant of a multi-sided generalization of the classical Coons patch (Várady et al., 2011); the second one is based on a new concept of combining doubly curved composite ribbons, each one interpolating three adjacent sides. Main contributions include various ribbon parameterizations that surpass former methods in quality and computational efficiency. It is proven that these surfaces smoothly interpolate the prescribed ribbon data. Both formulations are based on non-regular convex polygonal domains and distance-based, rational blending functions. A few examples illustrate the results.     

多块变形网格在非定常计算中的应用

介绍了一种适用于包含运动边界非定常计算的高效多块贴体变形网格生成方法,在每块网格中变形网格生成采用基于弧长的超限插值生成方法,能够较好保持原始网格的正交性、光滑性和质量.在采用双时间步的非定常RANS解算器中发展了此网格变形方法.通过两段翼型襟翼俯仰振荡和导弹的纵向舵偏控制的非定常计算对此网格变形方法进行了验证.本方法生成的变形网格质量良好.     

复杂装备健康管理模式综述

在复杂装备的使用过程中,在不同的环境和人为因素的影响下,装备的健康状态会发生变化,性能会逐渐衰退。为了确保装备安全运行,装备的健康问题引起了人们的关注。装备健康管理是一种对装备及其部件健康状态的影响因素进行全面管理的过程。状态监测是复杂装备健康管理的重要组成部分,科学的装备健康管理是开展装备状态维修的支撑条件。为了实现装备健康管理模式确定的目标,提出了装备健康管理的核心思想,分析了装备健康管理的重点环节,阐述了装备健康管理应该采取的主要措施。     

吐哈盆地致密砂岩气成藏条件与有利勘探领域分析

结合致密砂岩气藏特征及成藏条件,认为哈密四道沟低产含气区为典型的致密砂岩气藏发育区,有望通过新型大型压裂试油采出工艺技术攻关,获得稳定的工业气流,盘活哈密四道沟大型致密砂岩气藏。根据致密砂岩气勘探理论,认为吐哈盆地具备发育大型致密砂岩气藏的基本地质条件。分析认为吐哈盆地发育胜北、丘东、小草湖、哈密、托克逊五大成煤领域,气源岩条件优越,源储一体,紧密接触,致密砂岩气藏成藏条件好;巴喀水西沟群气藏的发现及大面积活跃的油气显示展示了吐哈盆地巨大的致密砂岩气勘探潜力。     

A G space theory and a weakened weak (W2) form for a unified formulation of compatible and incompatible methods: Part II applications to solid mechanics problems

In part I of this paper, we have established the G space theory and fundamentals for W² formulation. Part II focuses on the applications of the G space theory to formulate W² models for solid mechanics problems. We first define a bilinear form, prove some of the important properties, and prove that the W² formulation will be spatially stable, and convergent to exact solutions. We then present examples of some of the possible W² models including the SFEM, NS‐FEM, ES‐FEM, NS‐PIM, ES‐PIM, and CS‐PIM. We show the major properties of these models: (1) they are variationally consistent in a conventional sense, if the solution is sought in a proper H space (compatible cases); (2) They pass the standard patch test when the solution is sought in a proper G space with discontinuous functions (incompatible cases); (3) the stiffness of the discretized model is reduced compared with the finite element method (FEM) model and possibly to the exact model, allowing us to obtain upper bound solutions with respect to both the FEM and the exact solutions and (4) the W² models are less sensitive to the quality of the mesh, and triangular meshes can be used without any accuracy problems. These properties and theories have been confirmed numerically via examples solved using a number of W² models including compatible and incompatible cases. We shall see that the G space theory and the W² forms can formulate a variety of stable and convergent numerical methods with the FEM as one special case. Copyright © 2009 John Wiley & Sons, Ltd.     

Progressive cutting tool wear detection from machined surface images using Voronoi tessellation method

Tool condition monitoring by machine vision approach has been gaining popularity day by day since it is a low cost and flexible method. In this paper, a tool condition monitoring technique by analysing turned surface images has been presented. The aim of this work is to apply an image texture analysis technique on turned surface images for quantitative assessment of cutting tool flank wear, progressively. A novel method by the concept of Voronoi tessellation has been applied in this study to analyse the surface texture of machined surface after the creation of Voronoi diagram. Two texture features, namely, number of polygons with zero cross moment and total void area of Voronoi diagram of machined surface images have been extracted. A correlation study between measured flank wear and extracted texture features has been done for depicting the tool flank wear. It has been found that number of polygons with zero cross moment has better linear relationship with tool flank wear than that of total void area.     

不同场地条件下钢筋混凝土框架结构的地震反应分析

从"5.12"汶川强震记录中挑选出四川省自贡地形台阵8个台站和宝兴县2个台站的加速度记录,进行了不同场地条件下的地震波频谱特性分析,比较了复杂场地地形条件下的地震动差异。以某钢筋混凝土框架结构教学楼为工程背景,利用ANSYS软件建立教学楼结构的有限元模型,进行了结构动力特性分析;在此基础上,以10条不同场地条件下的地震动时程按照规范调幅后作为输入,对这一钢筋混凝土框架结构进行了地震反应分析,探讨了不同场地条件下结构地震反应的差异。结果表明:自贡地形台阵随着测站高程的增加,地震动幅值递增明显;与基岩地震波的频带分布相比较,土层地震波的频带主要集中在较低频段,土层的高频滤波效应明显;场地条件对结构地震反应的影响较为明显,高程最大的地震波作用下结构的最大剪力响应增大明显。