Modelling strain localization in granular materials using micropolar theory: numerical implementation and verification

Implementation and applications for a constitutive numerical model on F‐75 silica sand, course silica sand and two sizes of glass beads compressed under plane strain conditions are presented in this work. The numerical model is used to predict the stress versus axial strain and volumetric strain versus axial strain relationships of those materials; moreover, comparisons between measured and predicted shear band thickness and inclination angles are discussed and the numerical results compare well with the experimental measurements. The numerical model is found to respond to the changes in confining pressure and the initial relative density of a given granular material. The mean particle size is used as an internal length scale. Increasing the confining pressure and the initial density is found to decrease the shear band thickness and increase the inclination angle. The micropolar or Cosserat theory is found to be effective in capturing strain localization in granular materials. The finite element formulations and the solution method for the boundary value problem in the updated Lagrangian frame (UP) are discussed in the companion paper. Copyright © 2006 John Wiley & Sons, Ltd.     

INTRASPECIFIC CROSSINGS OF UNDARIA PINNATIFIDA (HARV.) SUR.-A POSSIBLE TIME-SAVING WAY OF STRAIN SELECTION

ImODUcrONUndariaPinnatofdapearv.)Sur.inJapanisdividedintoanorthemtypewithdeeplydividedpinnatebladesandasoutherntypewithlighhydividedpinnateblades(Saito,l972,0hno,l994).Butinrmtyears,themutualtIansplantationsbeweensouthandnorthtendedtornakethecIJltivatalsporophpebeudrirminrnorphology.InChina,UndariaisaIsodhadedintoanortherntypeandasoutherntypemeng,l936).Theques-tionofWhetherthemorphologicalcharaedthaofdtaphentypesaredetenninedbygeneticfactorsoraresbolyinflUenaxlbyenvbonmentalfactorsdrewt…     

天文选址定点观测中大气透明度的测量方法

本文叙述了在天文选址定点观测中使用ＵＢＶ三色光电测光系统测量大气透明度的最佳方法和所用到的各个计算公式，也包括了某些经验。     

云南天文台DIMM的视宁度测量和评估

为对三孔ＤＩＭＭ数据的可靠性有进一步认识，作者对所用ＣＣＤ的曝光时间、不同大小的子瞳以及风向对观测结果的影响等方面做了试验，还进行了ＤＩＭＭ结果与一米望远镜的星像轮廓结果的比对。     

Evaluation of numerical earthquake forecasting models

Evaluation of numerical earthquake forecasting models needs to consider two issues of equal importance: the application scenario of the simulation, and the complexity of the model. Criterion of the evaluation-based model selection faces some interesting problems in need of discussion.     

湖南首个固体矿产勘查3000m科学深钻选址研究北大核心CSCD

湘南地区地处钦杭成矿带和南岭成矿带的结合部位,成矿条件优越。湘南深地资源勘查开采项目实施的单孔3000 m科学深钻主要目标是验证和完善Cu-Sn复合成矿理论的研究成果,探索华南复杂地层的深部钻探工艺及方法,推动深部探测技术示范与找矿突破。因此,科学深钻的孔位优选是实现科学目标的关键。本文通过对坪宝地区成矿地质条件、典型矿床特征、控矿因素、地球物理探测信息等的综合分析认为:湘南坪宝地区发育多处与花岗岩成因关系密切的Cu-Sn多金属矿床,是开展深部探测的有利部位。根据坪宝地区物性特征、广域电磁测量和坑道重力测量解译结果,认为区域控岩控矿构造在深部至少有3~5 km的延伸,且广域电磁法异常对浅部矿化蚀变构造带具有良好的反映,矿化蚀变构造带向深部具有较好延深趋势。综合见矿可能性、矿床垂向分带规律、矿种组合及前期深部物探成果,结合浅部地质背景、已知矿化延伸及野外施工条件等因素,选择在宝山铜多金属矿区北西部的165剖面线上开展3000 m钻探验证。     

一种改进的组合定权的指纹定位算法

室内场景复杂、WiFi信号不稳定等因素,造成基于信号空间K最近邻法的WiFi指纹定位算法匹配的邻近点会出现偏差,使用偏差较大的点计算待定点位置会直接影响定位结果。本文提出了一种改进的组合定权的指纹定位算法,对K个邻近点的几何结构进行分析,剔除其中偏离邻近点几何中心较远的点后,同时分析匹配邻近点中心同待定点几何位置存在理论上的关联,利用选择后的邻近点与其中心点的几何距离、待定点与指纹点欧氏距离组合定权,加权求取坐标。与KNN、WKNN算法定位结果分别进行比较,表明该方法提高了定位准确性和精度。