岩石块体理论中三维随机块体几何搜索

运用地质统计学与计算机技术随机模拟生成三维结构面网络,并在对前人关于结构面地质统计分析、结构面网络模拟、砍树、寻找封闭回路、搜索随机块体可能出现的最大区域等研究的基础上,运用交点组合法,通过交点旋转方向及空间位置的判断等过程,形成搜索三维随机块体的方法。运用该方法对边坡交棱处、洞室顶拱进行随机块体的搜索,并对块体的形态、大小及空间分布特征进行统计分析,从而实现了边坡和洞室工程的随机块体分析。算例表明,该方法可以在工程分析中得到较好的应用。     

Homogeneities in in vitro starch digestion of compositionally heterogenous white wheat breads

In vitro starch digestion of five fresh and shelved white wheat breads, compositionally heterogeneous, was investigated for heterogeneities or homogeneities in digestion patterns. The breads were significantly different (P ≤ 0.05) in some chemical and functional properties. The Rapid Visco-Analyser (RVA) revealed different pasting properties in the breads, but the breads showed monophasic starch digestograms, as there were no practical slope changes or discontinuities in the digestograms. The monophasic starch digestograms were suitably described (r² > 0.90; P ≤ 0.05) by five starch digestion kinetic models (the modified first-order kinetic, Peleg, Paolucci-Jeanjean, Logistic, and Weibull), and their parameters were mainly non-significant (P > 0.05) between the breads. The heterogeneous breads were, therefore, homogeneous in their in vitro starch digestion patterns. The study also strengthens a novel modelling approach for starch digestograms to be widely used in starch digestion research, easing inter-laboratory comparisons.     

岩体强度各向异性及其转化的应力条件

不连续面的存在导致岩体强度具有强烈的各向异性,然而随着围压的增大,岩体不连续性逐渐弱化,岩体强度的各向异性特征逐渐转化为各向同性特征。基于岩体硬性结构面的摩擦准则及岩体的Hoek-Brown强度准则,推导含坚硬结构面岩体强度各向异性转化为各向同性的临界围压23 c (54)/27m mσσ++≥,其中,σc为岩块单轴抗压强度,m为Hoek-Brown准则参数。利用前人开展的含结构面岩体试样的三轴试验,建立FLAC3D数值模型,对文中所采用的准则及所求得的临界围压进行验证。结果发现：数值模拟所得岩体强度与试验资料吻合较好;含单组硬性结构面岩体强度在围压低于临界围压时呈现各向异性,高于临界围压则呈现各向同性;含2组结构面(其中一组为贯通型结构面)的岩体,强度由各向异性转化为各向同性的临界围压符合所求得的临界围压;含3组非贯通型结构面岩体试样,因为锁固原因,试验所得的临界围压稍小于理论求得的转化围压。     

From continuum mechanics to fracture mechanics: the strong discontinuity approach

The paper deals with the strong discontinuity approach and shows the links with the decohesive fracture mechanics provided by that approach. On the basis of 1D continuum damage models it is shown that, by introducing some few ingredients like the strong discontinuity kinematics, discrete constitutive models (traction vs. displacement jumps) are automatically induced. For the general 2D-3D cases it is shown that the weak discontinuity concept is an additional ingredient, necessary in order to fulfill the strong discontinuity conditions, which allows to establish additional links with the fracture process zone concept. Also classical fracture mechanics properties as the fracture energy are related to the continuum model properties in a straightforward manner.     

A GSM analysis of E‐plane waveguide junctions filled with piecewise homogeneous dielectric

A specific generalized scattering matrix (GSM) approach to the analysis of a piecewise homogeneous E‐plane waveguide junction with plane interfaces is presented. The object is cascaded into homogeneously filled regions, whose GSMs are found in solving two uncoupled scalar problems related to longitudinal section electric and magnetic modes, and interfaces responsible for interaction of the said modes. The GSMs of irregular constituents are determined with the help of triangular blocks. Scattering parameters of the last ones are obtained by means of the domain‐product technique. The approach was successfully verified via test problems and was applied to the analysis of scattering of the TE₁₀ mode by an E‐plane slant interface between two dielectric media. Copyright © 2011 John Wiley & Sons, Ltd.     

电磁缺陷修复材料研究进展

研究了电磁缺陷修复材料在飞行器边缘、缝隙等表面电磁缺陷散射控制中的应用,阐述了其原理和发展状况。给出了表面电磁缺陷的基本定义,分析了其散射特点,并提出电磁缺陷修复原理及基本方法。电磁缺陷修复材料主要包括用于表面波抑制的磁性材料、用于窄缝隙保证电连续的导电材料和用于边缘散射控制的渐变阻抗材料等三类,重点介绍了用于边缘散射控制的渐变阻抗材料。该渐变阻抗材料基于图形渐变频率选择表面的概念,加载于边缘考虑平行极化和垂直极化两种情况,并与边缘锯齿化和未加载情况进行比较。从研究情况来看,经过恰当的材料选取和合理的阻抗梯度设计,渐变阻抗材料可以有效控制边缘散射,并能取得宽带效果。最后展望了渐变阻抗材料在电磁散射及电磁辐射领域的应用前景。     

岩体结构面对边坡爆破的影响及改进措施

分析了结构面垂直水平面的边坡、顺层边坡和反倾斜边坡的光面爆破效果。结构面垂直水平面边坡爆破后,容易形成锯齿形坡面,可以通过多打孔、少装药等措施改善爆破效果。顺层边坡爆破后,容易发生滑坡,可通过爆破前边坡加固、间隔装药爆破降低爆破对边坡保留岩体的破坏作用。反倾斜边坡爆破后容易形成局部超挖,可通过减小边坡坡面角和分段装药爆破的方法改进爆破效果。本研究对改善类似边坡爆破效果有一定的参考价值。     

Solution of plane elasticity problems for orthotropic bodies with cracks by the displacement discontinuity method

 The force problem of fracture mechanics for orthotropic body is solved by boundary element method. The equations of plane strain state are used. The key point of this paper is obtaining the influence functions for finite segment with constant displacement discontinuities in the main axes of orthotropy. They have been deduced by means of two-dimensional Fourier transform and theory of generalized functions. The straight crack under the action of uniform tension in the infinity is considered by using obtained influence functions. The calculations were carried out for isotropic and two orthotropic materials. Received 6 November 2000     

Probabilistic Detection and Tracking of Motion Boundaries

We propose a Bayesian framework for representing and recognizing local image motion in terms of two basic models: translational motion and motion boundaries. Motion boundaries are represented using a non-linear generative model that explicitly encodes the orientation of the boundary, the velocities on either side, the motion of the occluding edge over time, and the appearance/disappearance of pixels at the boundary. We represent the posterior probability distribution over the model parameters given the image data using discrete samples. This distribution is propagated over time using a particle filtering algorithm. To efficiently represent such a high-dimensional space we initialize samples using the responses of a low-level motion discontinuity detector. The formulation and computational model provide a general probabilistic framework for motion estimation with multiple, non-linear, models.     

图像引导的二阶总广义变分稀疏深度图的稠密重构

利用图像颜色信息进行深度图重构,可以恢复对象边界处的深度不连续性,但无法保证对象内部的深度均匀性。为解决该问题,提出图像引导下总广义变分正则化的深度图重构模型。该模型利用扩散张量将图像提供的边缘信息引入二阶总广义变分正则项,使得重构深度在保持对象边缘的同时逼近分段仿射平面,从而保证恢复深度既保持对象边界处的不连续性,又具有对象内部的均匀性。通过Legendre-Fenchel变换将模型转换成等效的凸凹鞍点问题,从而得到高效的一阶原始对偶求解算法。实验结果表明,该方法能够恢复尖锐的对象边缘,同时保持对象内部的深度均匀性。与现有算法相比,所提方法具有更高的峰值信噪比、归一化互协方差和更低的平均绝对误差。