The MohroCoulomb criterion has been widely used to explain formation of fractures. However, it fails to explain large strain deformation that widely occurs in nature. There is presently a new theory, the MEMC, which i...The MohroCoulomb criterion has been widely used to explain formation of fractures. However, it fails to explain large strain deformation that widely occurs in nature. There is presently a new theory, the MEMC, which is mathematically expressed as Meff = （（σ1-σ3） L.sin 2α sin α）/2, where σ1-σ3 represents the yield strength of the related rock, L is a unit length and a is the angle between σ1 and deformation bands. This criterion demonstrates that the maximum value appears at angles of ±54.7° to σ1 and there is a slight difference in the moment in the range of 55°±10°. The range covers the whole observations available from nature and experiments. Its major implications include： （1） it can be used to determine the stress state when the related deformation features formed; （2） it provides a new approach to determine the Wk of the related ductile shear zone if only the ratio of the vorticity and strain rate remains fixed; （3） It can be used to explain （a） the obtuse angle in the contraction direction of conjugate kink-bands and extensional crenulation cleavages, （b） formation of low-angle normal faults and high-angle reverse faults, （c） lozenge ductile shear zones in basement terranes, （d） some crocodile structures in seismic profiles and （e） detachment folds in foreland basins.展开更多
In order to discover characteristics of various kinds of weld pool image and identify a single image, seven image features are extracted to describe the corresponding surface formation quality by the moment iavariants...In order to discover characteristics of various kinds of weld pool image and identify a single image, seven image features are extracted to describe the corresponding surface formation quality by the moment iavariants method. An image feature matrix is composed by the seven characteristics. Then the matrix is projected on a line through the Fisher criterion in order to entirely distinguish various kinds of image features. And finally, transforming a seven-dimensional problem into a one-dimensional problem has been done. Compared with the three kinds of samples included in the arc welding process and quality weld pool visual image database, the images are classified into the three kinds such as superior weld formation in the condition of optimal gas flow, poor weld formation image in the condition of insuffwient gas flow, inferior weld formation in the condition of too low gas flow. Experiments show that the Fisher classification method based on moment invariants can recognize various weld pool images effectively, and it achieves a correct recognizable rate of 100%.展开更多
为得出腿式着陆器着陆稳定性判据及提高其着陆稳定性的方法,给出腿式着陆器的结构原理,结合腿式着陆器的结构特点,基于零力矩点(Zero moment point,ZMP)理论研究腿式着陆器着陆过程的稳定性及其相关理论,给出基于ZMP的腿式着陆器着陆稳...为得出腿式着陆器着陆稳定性判据及提高其着陆稳定性的方法,给出腿式着陆器的结构原理,结合腿式着陆器的结构特点,基于零力矩点(Zero moment point,ZMP)理论研究腿式着陆器着陆过程的稳定性及其相关理论,给出基于ZMP的腿式着陆器着陆稳定性分析流程,为腿式着陆器着陆稳定性研究提供参考。为验证所提出基于零力矩点理论的腿式着陆器着陆稳定性研究方法的正确性,以哈尔滨工业大学研制的四腿桁架式月球着陆器样机为例,结合所提出的腿式着陆器着陆稳定性研究方法,给出四腿桁架式月球着陆器样机的支撑多边形与ZMP的关系图,并得到了该样机在着陆过程中的ZMP及支撑多边形的计算公式,最后给出通过判断着陆器的ZMP是否位于其支撑多边形内部来判断腿式着陆器是否稳定的方法。展开更多
基金This work is financed by the grants of the National Natural Science Foundation of China （Grant No 40272084, 40472101 and 40572123）.
文摘The MohroCoulomb criterion has been widely used to explain formation of fractures. However, it fails to explain large strain deformation that widely occurs in nature. There is presently a new theory, the MEMC, which is mathematically expressed as Meff = （（σ1-σ3） L.sin 2α sin α）/2, where σ1-σ3 represents the yield strength of the related rock, L is a unit length and a is the angle between σ1 and deformation bands. This criterion demonstrates that the maximum value appears at angles of ±54.7° to σ1 and there is a slight difference in the moment in the range of 55°±10°. The range covers the whole observations available from nature and experiments. Its major implications include： （1） it can be used to determine the stress state when the related deformation features formed; （2） it provides a new approach to determine the Wk of the related ductile shear zone if only the ratio of the vorticity and strain rate remains fixed; （3） It can be used to explain （a） the obtuse angle in the contraction direction of conjugate kink-bands and extensional crenulation cleavages, （b） formation of low-angle normal faults and high-angle reverse faults, （c） lozenge ductile shear zones in basement terranes, （d） some crocodile structures in seismic profiles and （e） detachment folds in foreland basins.
基金Fund projects： National Natural Science Foundation of China（ No 51075214）funding.
文摘In order to discover characteristics of various kinds of weld pool image and identify a single image, seven image features are extracted to describe the corresponding surface formation quality by the moment iavariants method. An image feature matrix is composed by the seven characteristics. Then the matrix is projected on a line through the Fisher criterion in order to entirely distinguish various kinds of image features. And finally, transforming a seven-dimensional problem into a one-dimensional problem has been done. Compared with the three kinds of samples included in the arc welding process and quality weld pool visual image database, the images are classified into the three kinds such as superior weld formation in the condition of optimal gas flow, poor weld formation image in the condition of insuffwient gas flow, inferior weld formation in the condition of too low gas flow. Experiments show that the Fisher classification method based on moment invariants can recognize various weld pool images effectively, and it achieves a correct recognizable rate of 100%.
文摘为得出腿式着陆器着陆稳定性判据及提高其着陆稳定性的方法,给出腿式着陆器的结构原理,结合腿式着陆器的结构特点,基于零力矩点(Zero moment point,ZMP)理论研究腿式着陆器着陆过程的稳定性及其相关理论,给出基于ZMP的腿式着陆器着陆稳定性分析流程,为腿式着陆器着陆稳定性研究提供参考。为验证所提出基于零力矩点理论的腿式着陆器着陆稳定性研究方法的正确性,以哈尔滨工业大学研制的四腿桁架式月球着陆器样机为例,结合所提出的腿式着陆器着陆稳定性研究方法,给出四腿桁架式月球着陆器样机的支撑多边形与ZMP的关系图,并得到了该样机在着陆过程中的ZMP及支撑多边形的计算公式,最后给出通过判断着陆器的ZMP是否位于其支撑多边形内部来判断腿式着陆器是否稳定的方法。
