The development of fracture around pre-existing cylindrical cavities in brittle rocks was examined using physical models and acoustic emission technique. The experimental results indicate that when granite blocks cont...The development of fracture around pre-existing cylindrical cavities in brittle rocks was examined using physical models and acoustic emission technique. The experimental results indicate that when granite blocks containing one pre-existing cylindrical cavity are loaded in uniaxial compression condition, the profiles of cracks around the cavity can be characterized by tensile cracking （splitting parallel to the axial compression direction） at the roof-floor, compressive crack at two side walls, and remote or secondary cracks at the perimeter of the cavity. Moreover, fracture around cavity is size-dependent. In granite blocks containing pre-existing half-length cylindrical cavities, compressive stress concentration is found to initiate at the two sidewalls and induce shear crack propagation and coalescence. In granite blocks containing multiple parallel cylindrical cavities, the adjacent cylindrical cavities can influence each other and the eventual failure mode is determined by the interaction of tensile, compressive and shear stresses. Experimental results show that both tensile and compressive stresses play an important role in fracture evolution process around cavities in brittle rocks.展开更多
针对传统数据流频繁项集挖掘算法在挖掘频繁k-项集时会有候选项集产生,在有新的数据流到来时的数据更新以及频繁项集支持度更新的效率不高,造成挖掘的时间和空间效率不高等一系列问题,提出一种高效的数据流频繁项集挖掘算法BTA(bit tabl...针对传统数据流频繁项集挖掘算法在挖掘频繁k-项集时会有候选项集产生,在有新的数据流到来时的数据更新以及频繁项集支持度更新的效率不高,造成挖掘的时间和空间效率不高等一系列问题,提出一种高效的数据流频繁项集挖掘算法BTA(bit table with and algorithm)算法。将数据高效压缩进位表中,对窗口更新采用取余覆盖;在频繁k-项集的挖掘采用与操作避免候选项集产生;在支持度更新采用加减运算得到数据更新后的支持度。实验结果表明,该算法在时间和空间效率上均有良好效果。展开更多
基金Projects(51004025,51174044)supported by the National Natural Science Foundation of ChinaProject(2011AA060400)supported by the National High-tech Research and Development Program of China+1 种基金Project(N120501003)supported by Ministry of Education of the People’s Republic of ChinaProject(LJQ2012024)supported by Department of Education of Liaoning Province,China
文摘The development of fracture around pre-existing cylindrical cavities in brittle rocks was examined using physical models and acoustic emission technique. The experimental results indicate that when granite blocks containing one pre-existing cylindrical cavity are loaded in uniaxial compression condition, the profiles of cracks around the cavity can be characterized by tensile cracking （splitting parallel to the axial compression direction） at the roof-floor, compressive crack at two side walls, and remote or secondary cracks at the perimeter of the cavity. Moreover, fracture around cavity is size-dependent. In granite blocks containing pre-existing half-length cylindrical cavities, compressive stress concentration is found to initiate at the two sidewalls and induce shear crack propagation and coalescence. In granite blocks containing multiple parallel cylindrical cavities, the adjacent cylindrical cavities can influence each other and the eventual failure mode is determined by the interaction of tensile, compressive and shear stresses. Experimental results show that both tensile and compressive stresses play an important role in fracture evolution process around cavities in brittle rocks.
文摘针对传统数据流频繁项集挖掘算法在挖掘频繁k-项集时会有候选项集产生,在有新的数据流到来时的数据更新以及频繁项集支持度更新的效率不高,造成挖掘的时间和空间效率不高等一系列问题,提出一种高效的数据流频繁项集挖掘算法BTA(bit table with and algorithm)算法。将数据高效压缩进位表中,对窗口更新采用取余覆盖;在频繁k-项集的挖掘采用与操作避免候选项集产生;在支持度更新采用加减运算得到数据更新后的支持度。实验结果表明,该算法在时间和空间效率上均有良好效果。
