A digital modeling system method is put forward for modeling constitutive relation of geomaterial including digital image subsystem for deformation measurement, numerical modeling subsystem and numerical simulation su...A digital modeling system method is put forward for modeling constitutive relation of geomaterial including digital image subsystem for deformation measurement, numerical modeling subsystem and numerical simulation subsystem. A non-contact measurement method based on digital image processing is introduced to improve measurement of specimen deformation. Based on the method, a series of conventional tri-axial compression tests under diverse stress paths are done. Then an elasto-plastic constitutive model of soil is acquired through the numerical method of modeling constitutive law for geomaterial. Two examples of specimen deformation and ground subsidence are presented and discussed. It indicated that this method can rationally simulate the stress-strain relationship of soil, which reflects the effect of stress path on soil stress-strain relationship.展开更多
A new coarse-to-fine strategy was proposed for nonrigid registration of computed tomography(CT) and magnetic resonance(MR) images of a liver.This hierarchical framework consisted of an affine transformation and a B-sp...A new coarse-to-fine strategy was proposed for nonrigid registration of computed tomography(CT) and magnetic resonance(MR) images of a liver.This hierarchical framework consisted of an affine transformation and a B-splines free-form deformation(FFD).The affine transformation performed a rough registration targeting the mismatch between the CT and MR images.The B-splines FFD transformation performed a finer registration by correcting local motion deformation.In the registration algorithm,the normalized mutual information(NMI) was used as similarity measure,and the limited memory Broyden-Fletcher- Goldfarb-Shannon(L-BFGS) optimization method was applied for optimization process.The algorithm was applied to the fully automated registration of liver CT and MR images in three subjects.The results demonstrate that the proposed method not only significantly improves the registration accuracy but also reduces the running time,which is effective and efficient for nonrigid registration.展开更多
The mechanical size effect of nanostructured,dual-phase CrCoNi medium-entropy alloy(MEA)was investigated by combining in-situ micro-compression testing with post-mortem electron microscopy analysis.The alloy possesses...The mechanical size effect of nanostructured,dual-phase CrCoNi medium-entropy alloy(MEA)was investigated by combining in-situ micro-compression testing with post-mortem electron microscopy analysis.The alloy possesses a superior yield strength up to~4 GPa,primarily due to its hierarchical microstructure including column nanograins,preferred orientation,a high density of planar defects and the presence of the hexagonal close packed(HCP)phase.While the yield strength of the alloy has shown sizeindependency,the deformation behaviour was strongly dependent on the sample size.Specifically,with decreasing the pillar diameters,the dominant deformation mode changed from highly localized and catastrophic shear banding to apparently homogeneous deformation with appreciable plasticity.This transition is believed to be governed by the sizedependent critical stress required for a shear band traversing the pillar and mediated by the competition between shearinduced softening and subsequent hardening mechanisms.In addition,an unexpected phase transformation from HCP to face-centered cubic(FCC)was observed in the highly localized deformation zones,leading to strain softening that contributed to accommodating plasticity.These findings provide insights into the criticality of sample dimensions in influencing mechanical behaviors of nanostructured metallic materials used for nanoelectromechanical systems.展开更多
文摘A digital modeling system method is put forward for modeling constitutive relation of geomaterial including digital image subsystem for deformation measurement, numerical modeling subsystem and numerical simulation subsystem. A non-contact measurement method based on digital image processing is introduced to improve measurement of specimen deformation. Based on the method, a series of conventional tri-axial compression tests under diverse stress paths are done. Then an elasto-plastic constitutive model of soil is acquired through the numerical method of modeling constitutive law for geomaterial. Two examples of specimen deformation and ground subsidence are presented and discussed. It indicated that this method can rationally simulate the stress-strain relationship of soil, which reflects the effect of stress path on soil stress-strain relationship.
基金Project(61240010)supported by the National Natural Science Foundation of ChinaProject(20070007070)supported by Specialized Research Fund for the Doctoral Program of Higher Education of China
文摘A new coarse-to-fine strategy was proposed for nonrigid registration of computed tomography(CT) and magnetic resonance(MR) images of a liver.This hierarchical framework consisted of an affine transformation and a B-splines free-form deformation(FFD).The affine transformation performed a rough registration targeting the mismatch between the CT and MR images.The B-splines FFD transformation performed a finer registration by correcting local motion deformation.In the registration algorithm,the normalized mutual information(NMI) was used as similarity measure,and the limited memory Broyden-Fletcher- Goldfarb-Shannon(L-BFGS) optimization method was applied for optimization process.The algorithm was applied to the fully automated registration of liver CT and MR images in three subjects.The results demonstrate that the proposed method not only significantly improves the registration accuracy but also reduces the running time,which is effective and efficient for nonrigid registration.
基金supported by the Australian Research Council Discovery Projects Grantpartly supported by the Fundamental Research Funds for the Central Universities(SWU118105)+1 种基金the financial support from Australia Research Council(DE170100053)the Robinson Fellowship Scheme of the University of Sydney(G200726)。
文摘The mechanical size effect of nanostructured,dual-phase CrCoNi medium-entropy alloy(MEA)was investigated by combining in-situ micro-compression testing with post-mortem electron microscopy analysis.The alloy possesses a superior yield strength up to~4 GPa,primarily due to its hierarchical microstructure including column nanograins,preferred orientation,a high density of planar defects and the presence of the hexagonal close packed(HCP)phase.While the yield strength of the alloy has shown sizeindependency,the deformation behaviour was strongly dependent on the sample size.Specifically,with decreasing the pillar diameters,the dominant deformation mode changed from highly localized and catastrophic shear banding to apparently homogeneous deformation with appreciable plasticity.This transition is believed to be governed by the sizedependent critical stress required for a shear band traversing the pillar and mediated by the competition between shearinduced softening and subsequent hardening mechanisms.In addition,an unexpected phase transformation from HCP to face-centered cubic(FCC)was observed in the highly localized deformation zones,leading to strain softening that contributed to accommodating plasticity.These findings provide insights into the criticality of sample dimensions in influencing mechanical behaviors of nanostructured metallic materials used for nanoelectromechanical systems.
