By combining the classic dislocation theory with the principle of dissipative structure and synergetics, an evolution model of dislocation patterns has been developed. Using this model, the evolution of dislocation pa...By combining the classic dislocation theory with the principle of dissipative structure and synergetics, an evolution model of dislocation patterns has been developed. Using this model, the evolution of dislocation patterns and the corresponding mechanical behavior have been analyzed, discussed and simulated under different deformation conditions of constant strain rate, creep and static recovery. As one of the most essential problems in the plastic deformation, the evolution of dislocation patterns has been dealt with by using non-linear methods. Results show that various problems in plastic deformation may be solved in a unified theoretical framework.展开更多
Relocation result shows that the aftershocks of the Lushan MS7.0 earthquake spatially distribute in a shape like"half bowl",indicating that the rupture structure of the mainshock is a highly curved surface.K...Relocation result shows that the aftershocks of the Lushan MS7.0 earthquake spatially distribute in a shape like"half bowl",indicating that the rupture structure of the mainshock is a highly curved surface.Kinematic analysis reveals that a laterally varied dislocation pattern occurs on this curved fault even though a single relative horizontal movement controls slip on this fault.Reverse slip prevails on curved fault.However,significant normal slip is predicted near the edge of north flank.Moreover,the north flank features left-lateral slip while the south flank contrarily features right-lateral slip.The relative scope of aftershock distribution implies inadequate breaking of the curved fault during the mainshock,calling for the attention to potential earthquake risk on the neighboring portions of the coseismic rupture due to significant increase of the coseismic Coulomb stress.Coseismic stress modeling also reveals that it is unnecessary for the stress on ruptured part to be unloaded following the earthquakes on the curved fault.The coseismic stress loading on ruptured elements unveils the specialty of faulting for the Lushan earthquake and we conclude that this specialty is due to the highly curved fault geometry.展开更多
Aim:?To elucidate the pattern of presentation and management of traumatic major joint dislocations as seen in Irrua Specialist Teaching Hospital. Method: A five-year retrospective review of 44 cases in 43 patients. Da...Aim:?To elucidate the pattern of presentation and management of traumatic major joint dislocations as seen in Irrua Specialist Teaching Hospital. Method: A five-year retrospective review of 44 cases in 43 patients. Data were retrieved from the Medical Records Department of the hospital. Results:?Forty-four cases of traumatic dislocations were reviewed in 43 patients. Male to female ratio was 7.6:1. Median age was 33 years. The majority of patients were in the 3rd?decade of life. Patients below 40 years accounted for 62.79% of cases. Twenty-four (55.81%) patients had hip dislocation. Knee dislocations were the least, accounting for 2.32% of cases. All cases except three resulted from road traffic accidents (RTAs). None had neurologic deficits. Nineteen (44.23%) patients had isolated injuries. 76.7% cases presented in less than 6 hours. All shoulder dislocations were anterior while all elbow dislocations were posterior. All except 3 cases were managed by closed manipulation under general anaesthesia. Two patients died from associated head injury. Fourteen patients discharged against medical advice while recuperating in the ward. Follow-up was however difficult as a significant number did not turn up. Conclusion: Hip dislocation is the commonest variety of traumatic dislocation in our setting. A majority of cases were amenable to closed manipulation and immobilization. Road traffic accidents accounted for the majority.展开更多
The microstructure of crystal defects,e.g.,dislocation patterns,are not arbitrary,and it is possible that some of them may be related to the microstructure of crystals itself,i.e.,the lattice structure.We call those d...The microstructure of crystal defects,e.g.,dislocation patterns,are not arbitrary,and it is possible that some of them may be related to the microstructure of crystals itself,i.e.,the lattice structure.We call those dislocation patterns or substructures that are related to the corresponding crystal microstructure as the Geometrically Compatible Dislocation Patterns(GCDP).Based on this notion,we have developed a Multiscale Crystal Defect Dynamics(MCDD)to model crystal plasticity without or with minimum empiricism.In this work,we employ the multiscale dislocation pattern dynamics,i.e.,MCDD,to simulate crystal plasticity in body-centered cubic(BCC)single crystals,mainlyα-phase Tantalum(α-Ta)single crystals.The main novelties of the work are:(1)We have successfully simulated crystal plasticity at micron scale without any empirical parameter inputs;(2)We have successfully employed MCDD to perform direct numerical simulation of inelastic hysteresis of the BCC crystal;(3)We have used MCDD crystal plasticity model to demonstrate the size-effect of crystal plasticity and(4)We have captured cross-slip which may lead to size-effect.展开更多
The paper deals with different plastic deformation behavior of electroformed copper liner of shaped charge, deformed at high strain rate (about 1×107s-1) and normal strain rate (4×10-4s-1). The crystallograp...The paper deals with different plastic deformation behavior of electroformed copper liner of shaped charge, deformed at high strain rate (about 1×107s-1) and normal strain rate (4×10-4s-1). The crystallographic orientation distribution of grains in recovered slugs which had undergone high-strain-rate plastic deformation during explosive detonation was investigated by electron backscattering Kikuchi pattern technique. Cellular structures formed by tangled dislocations and sub-grain boundaries consisting of dislocation arrays were detected in the recovered slugs. Some twins and slip dislocations were observed in specimen deformed at normal strain rate. It was found that dynamic recovery and recrystallization take place during high-strain-rate deformation due to the temperature rising, whereas the conventional slip mechanism operates during deformation at normal strain rate.展开更多
The growth process of three-dimensional growth mode（3D） switching to two-dimensional growth mode （2D） is investigated when GaN films are grown on cone-shaped patterned sapphire substrates by metal-organic chemical...The growth process of three-dimensional growth mode（3D） switching to two-dimensional growth mode （2D） is investigated when GaN films are grown on cone-shaped patterned sapphire substrates by metal-organic chemical vapor deposition.The growth condition of the 3D-2D growth process is optimized to reduce the threading dislocation density（TDD）.It is found that the condition of the 3D layer is critical.The 3D layer keeps growing under the conditions of lowⅤ/Ⅲratio,low temperature,and high pressure until its thickness is comparable to the height of the cone-shaped patterns.Then the 3D layer surrounds the cone-shaped patterns and has inclined side facets and a top（0001） plane.In the following 2D-growth process,inclined side facets coalesce quickly and the interaction of TDs with the side facets causes the TDs to bend over.As a result,the TDD of GaN films can decrease to 1×10~8 cm^（-2）,giving full-width at half maximum values of 211 and 219 arcsec for（002） and（102） omega scans, respectively.展开更多
文摘By combining the classic dislocation theory with the principle of dissipative structure and synergetics, an evolution model of dislocation patterns has been developed. Using this model, the evolution of dislocation patterns and the corresponding mechanical behavior have been analyzed, discussed and simulated under different deformation conditions of constant strain rate, creep and static recovery. As one of the most essential problems in the plastic deformation, the evolution of dislocation patterns has been dealt with by using non-linear methods. Results show that various problems in plastic deformation may be solved in a unified theoretical framework.
基金supported by the Fundamental Research Funds for Central Public Welfare Research Institutes(DF-IGCEA-0608-2-18)the Special Fund for China Earthquake Research Project(201008003)
文摘Relocation result shows that the aftershocks of the Lushan MS7.0 earthquake spatially distribute in a shape like"half bowl",indicating that the rupture structure of the mainshock is a highly curved surface.Kinematic analysis reveals that a laterally varied dislocation pattern occurs on this curved fault even though a single relative horizontal movement controls slip on this fault.Reverse slip prevails on curved fault.However,significant normal slip is predicted near the edge of north flank.Moreover,the north flank features left-lateral slip while the south flank contrarily features right-lateral slip.The relative scope of aftershock distribution implies inadequate breaking of the curved fault during the mainshock,calling for the attention to potential earthquake risk on the neighboring portions of the coseismic rupture due to significant increase of the coseismic Coulomb stress.Coseismic stress modeling also reveals that it is unnecessary for the stress on ruptured part to be unloaded following the earthquakes on the curved fault.The coseismic stress loading on ruptured elements unveils the specialty of faulting for the Lushan earthquake and we conclude that this specialty is due to the highly curved fault geometry.
文摘Aim:?To elucidate the pattern of presentation and management of traumatic major joint dislocations as seen in Irrua Specialist Teaching Hospital. Method: A five-year retrospective review of 44 cases in 43 patients. Data were retrieved from the Medical Records Department of the hospital. Results:?Forty-four cases of traumatic dislocations were reviewed in 43 patients. Male to female ratio was 7.6:1. Median age was 33 years. The majority of patients were in the 3rd?decade of life. Patients below 40 years accounted for 62.79% of cases. Twenty-four (55.81%) patients had hip dislocation. Knee dislocations were the least, accounting for 2.32% of cases. All cases except three resulted from road traffic accidents (RTAs). None had neurologic deficits. Nineteen (44.23%) patients had isolated injuries. 76.7% cases presented in less than 6 hours. All shoulder dislocations were anterior while all elbow dislocations were posterior. All except 3 cases were managed by closed manipulation under general anaesthesia. Two patients died from associated head injury. Fourteen patients discharged against medical advice while recuperating in the ward. Follow-up was however difficult as a significant number did not turn up. Conclusion: Hip dislocation is the commonest variety of traumatic dislocation in our setting. A majority of cases were amenable to closed manipulation and immobilization. Road traffic accidents accounted for the majority.
文摘The microstructure of crystal defects,e.g.,dislocation patterns,are not arbitrary,and it is possible that some of them may be related to the microstructure of crystals itself,i.e.,the lattice structure.We call those dislocation patterns or substructures that are related to the corresponding crystal microstructure as the Geometrically Compatible Dislocation Patterns(GCDP).Based on this notion,we have developed a Multiscale Crystal Defect Dynamics(MCDD)to model crystal plasticity without or with minimum empiricism.In this work,we employ the multiscale dislocation pattern dynamics,i.e.,MCDD,to simulate crystal plasticity in body-centered cubic(BCC)single crystals,mainlyα-phase Tantalum(α-Ta)single crystals.The main novelties of the work are:(1)We have successfully simulated crystal plasticity at micron scale without any empirical parameter inputs;(2)We have successfully employed MCDD to perform direct numerical simulation of inelastic hysteresis of the BCC crystal;(3)We have used MCDD crystal plasticity model to demonstrate the size-effect of crystal plasticity and(4)We have captured cross-slip which may lead to size-effect.
文摘The paper deals with different plastic deformation behavior of electroformed copper liner of shaped charge, deformed at high strain rate (about 1×107s-1) and normal strain rate (4×10-4s-1). The crystallographic orientation distribution of grains in recovered slugs which had undergone high-strain-rate plastic deformation during explosive detonation was investigated by electron backscattering Kikuchi pattern technique. Cellular structures formed by tangled dislocations and sub-grain boundaries consisting of dislocation arrays were detected in the recovered slugs. Some twins and slip dislocations were observed in specimen deformed at normal strain rate. It was found that dynamic recovery and recrystallization take place during high-strain-rate deformation due to the temperature rising, whereas the conventional slip mechanism operates during deformation at normal strain rate.
文摘The growth process of three-dimensional growth mode（3D） switching to two-dimensional growth mode （2D） is investigated when GaN films are grown on cone-shaped patterned sapphire substrates by metal-organic chemical vapor deposition.The growth condition of the 3D-2D growth process is optimized to reduce the threading dislocation density（TDD）.It is found that the condition of the 3D layer is critical.The 3D layer keeps growing under the conditions of lowⅤ/Ⅲratio,low temperature,and high pressure until its thickness is comparable to the height of the cone-shaped patterns.Then the 3D layer surrounds the cone-shaped patterns and has inclined side facets and a top（0001） plane.In the following 2D-growth process,inclined side facets coalesce quickly and the interaction of TDs with the side facets causes the TDs to bend over.As a result,the TDD of GaN films can decrease to 1×10~8 cm^（-2）,giving full-width at half maximum values of 211 and 219 arcsec for（002） and（102） omega scans, respectively.
