This paper studies the computation method of two step inversion of interface and velocity in a region. The 3 D interface is described by a segmented incomplete polynomial; while the reconstruction of 3 D velocity i...This paper studies the computation method of two step inversion of interface and velocity in a region. The 3 D interface is described by a segmented incomplete polynomial; while the reconstruction of 3 D velocity is accomplished by the principle of least squares in functional space. The computation is carried out in two steps. The first step is to inverse the shape of 3 D interface; while the second step is to do 3 D velocity inversion by distributing the remaining residual errors of travel time in accordance with their weights. The data of seismic sounding in the Tangshan Luanxian seismic region are processed, from which the 3 D structural form in depth of the Tangshan seismic region and the 3 D velocity distribution in the crust below the Tangshan Luanxian seismic region are obtained. The result shows that the deep 3 D structure in the Tangshan seismic region trends NE on the whole and the structure sandwiched between the NE trending Fengtai Yejituo fault and the NE trending Tangshan fault is an uplifted zone of the Moho. In the 3 D velocity structure of middle lower crust below that region, there is an obvious belt of low velocity anomaly to exist along the NE trending Tangshan fault, the position of which tallies with that of the Tangshan seismicity belt. The larger block of low velocity anomaly near Shaheyi corresponds to a denser earthquake distribution. In that region, there is an NW trending belt of high velocity anomaly, probably a buried fault zone. The lower crust below the epicentral region of the Tangshan M S=7.8 earthquake is a place where the NE trending belt of low velocity anomaly meets the NW trending belt of high velocity anomaly. The two sets of structures had played an important role in controlling the preparation and occurrence of the M S=7.8 Tangshan earthquake.展开更多
A continuum damage mechanics (CDM) meso-model was derived for both intraply and interply progressive failure behaviors of a 2D woven-fabric composite laminate under a transversely low velocity impact.An in-plane aniso...A continuum damage mechanics (CDM) meso-model was derived for both intraply and interply progressive failure behaviors of a 2D woven-fabric composite laminate under a transversely low velocity impact.An in-plane anisotropic damage constitutive model of a 2D woven composite ply was derived based on CDM within a thermodynamic framework,an elastic constitutive model with damage for the fibre directions and an elastic-plastic constitutive model with damage for the shear direction.The progressive failure behavior of a 2D woven composite ply is determined by the damage internal variables in different directions with appropriate damage evolution equations.The interface between two adjacent 2D woven composite plies with different ply orientations was modeled by a traction-separation law based interface element.An isotropic damage constitutive law with CDM properties was used for the interface element,and a damage surface which combines stress and fracture mechanics failure criteria was employed to derive the damage initiation and evolution for the mixed-mode delamination of the interface elements.Numerical analysis and experiments were both carried out on a 2D woven glass fibre/epoxy laminate.The simulation results are in agreement with the experimental counterparts,verifying the progressive failure model of a woven composite laminate.The proposed model will enhance the understanding of dynamic deformation and progressive failure behavior of composite laminate structures in the low velocity impact process.展开更多
Interfacial thermal resistance plays a crucial role in efficient heat dissipation in modern electronic devices.It is critical to understand the interfacial thermal transport from both experiments and underlying physic...Interfacial thermal resistance plays a crucial role in efficient heat dissipation in modern electronic devices.It is critical to understand the interfacial thermal transport from both experiments and underlying physics.This review is focused on the transient opto-thermal Raman-based techniques for measuring the interfacial thermal resistance between 2D materials and substrate.This transient idea eliminates the use of laser absorption and absolute temperature rise data,therefore provides some of the highest level measurement accuracy and physics understanding.Physical concepts and perspectives are given for the time-domain differential Raman(TD-Raman),frequency-resolved Raman(FRRaman),energy transport state-resolved Raman(ET-Raman),frequency domain ET-Raman(FET-Raman),as well as laser flash Raman and dual-wavelength laser flash Raman techniques.The thermal nonequilibrium between optical and acoustic phonons,as well as hot carrier diffusion must be considered for extremely small domain characterization of interfacial thermal resistance.To have a better understanding of phonon transport across material interfaces,we introduce a new concept termed effective interface energy transmission velocity.It is very striking that many reported interfaces have an almost constant energy transmission velocity over a wide temperature range.This physics consideration is inspired by the thermal reffusivity theory,which is effective for analyzing structure-phonon scattering.We expect the effective interface energy transmission velocity to give an intrinsic picture of the transmission of energy carriers,unaltered by the influence of their capacity to carry heat.展开更多
文摘This paper studies the computation method of two step inversion of interface and velocity in a region. The 3 D interface is described by a segmented incomplete polynomial; while the reconstruction of 3 D velocity is accomplished by the principle of least squares in functional space. The computation is carried out in two steps. The first step is to inverse the shape of 3 D interface; while the second step is to do 3 D velocity inversion by distributing the remaining residual errors of travel time in accordance with their weights. The data of seismic sounding in the Tangshan Luanxian seismic region are processed, from which the 3 D structural form in depth of the Tangshan seismic region and the 3 D velocity distribution in the crust below the Tangshan Luanxian seismic region are obtained. The result shows that the deep 3 D structure in the Tangshan seismic region trends NE on the whole and the structure sandwiched between the NE trending Fengtai Yejituo fault and the NE trending Tangshan fault is an uplifted zone of the Moho. In the 3 D velocity structure of middle lower crust below that region, there is an obvious belt of low velocity anomaly to exist along the NE trending Tangshan fault, the position of which tallies with that of the Tangshan seismicity belt. The larger block of low velocity anomaly near Shaheyi corresponds to a denser earthquake distribution. In that region, there is an NW trending belt of high velocity anomaly, probably a buried fault zone. The lower crust below the epicentral region of the Tangshan M S=7.8 earthquake is a place where the NE trending belt of low velocity anomaly meets the NW trending belt of high velocity anomaly. The two sets of structures had played an important role in controlling the preparation and occurrence of the M S=7.8 Tangshan earthquake.
文摘A continuum damage mechanics (CDM) meso-model was derived for both intraply and interply progressive failure behaviors of a 2D woven-fabric composite laminate under a transversely low velocity impact.An in-plane anisotropic damage constitutive model of a 2D woven composite ply was derived based on CDM within a thermodynamic framework,an elastic constitutive model with damage for the fibre directions and an elastic-plastic constitutive model with damage for the shear direction.The progressive failure behavior of a 2D woven composite ply is determined by the damage internal variables in different directions with appropriate damage evolution equations.The interface between two adjacent 2D woven composite plies with different ply orientations was modeled by a traction-separation law based interface element.An isotropic damage constitutive law with CDM properties was used for the interface element,and a damage surface which combines stress and fracture mechanics failure criteria was employed to derive the damage initiation and evolution for the mixed-mode delamination of the interface elements.Numerical analysis and experiments were both carried out on a 2D woven glass fibre/epoxy laminate.The simulation results are in agreement with the experimental counterparts,verifying the progressive failure model of a woven composite laminate.The proposed model will enhance the understanding of dynamic deformation and progressive failure behavior of composite laminate structures in the low velocity impact process.
基金supported by the National Natural Science Foundation of China(No.12204320 for J.L.and 52276080 for Y.X.)US National Science Foundation(CBET1930866 and CMMI2032464 for X.W)J.L.is grateful for the support from Shenzhen Science and Technology Program(JCYJ20220530153401003).
文摘Interfacial thermal resistance plays a crucial role in efficient heat dissipation in modern electronic devices.It is critical to understand the interfacial thermal transport from both experiments and underlying physics.This review is focused on the transient opto-thermal Raman-based techniques for measuring the interfacial thermal resistance between 2D materials and substrate.This transient idea eliminates the use of laser absorption and absolute temperature rise data,therefore provides some of the highest level measurement accuracy and physics understanding.Physical concepts and perspectives are given for the time-domain differential Raman(TD-Raman),frequency-resolved Raman(FRRaman),energy transport state-resolved Raman(ET-Raman),frequency domain ET-Raman(FET-Raman),as well as laser flash Raman and dual-wavelength laser flash Raman techniques.The thermal nonequilibrium between optical and acoustic phonons,as well as hot carrier diffusion must be considered for extremely small domain characterization of interfacial thermal resistance.To have a better understanding of phonon transport across material interfaces,we introduce a new concept termed effective interface energy transmission velocity.It is very striking that many reported interfaces have an almost constant energy transmission velocity over a wide temperature range.This physics consideration is inspired by the thermal reffusivity theory,which is effective for analyzing structure-phonon scattering.We expect the effective interface energy transmission velocity to give an intrinsic picture of the transmission of energy carriers,unaltered by the influence of their capacity to carry heat.
