A new technology for fabrication of silica on silicon arrayed waveguide grating (AWG) based on deep etching and thermal oxidation is presented.Using this method,a silicon layer is remained at the side of waveguide.The...A new technology for fabrication of silica on silicon arrayed waveguide grating (AWG) based on deep etching and thermal oxidation is presented.Using this method,a silicon layer is remained at the side of waveguide.The stress distribution and effective refractive index of waveguide fabricated by this approach are calculated using finite element and finite difference beam propagation method,respectively.The results of these studies indicate that the stress of silica on silicon optical waveguide can be matched in parallel and vertical direction and AWG polarization dependent wavelength (PDλ) can be reduced effectively due to side-silicon layer.展开更多
To study the grouting reinforcement mechanism in jointed rock slope, first, the theoretical deduction was done to calculate the critical length of slipping if the slope angle is larger than that of joint inclination; ...To study the grouting reinforcement mechanism in jointed rock slope, first, the theoretical deduction was done to calculate the critical length of slipping if the slope angle is larger than that of joint inclination; Second, the numerical calculation model was founded by FLAG^3D, so as to find the stress and deformation responses of rock mass in the state before and after grouting, the analysis results show that the range between the boundary of critical slipping block and the joint plane that passes the slope toe is the effective grouting area （EGA）. After excavation, large deformation occurs along the joint plane. After grouting, the displacements of rock particles become uniform and continuous, and large deformations along the joint plane are controlled; the dynamic displacement can re- flect the deformation response of slope during excavation in the state before and after grouting, as well as the shear location of potential slip plane. After grouting, the dynamic displacement of each monitoring point reaches the peak value with very few time steps, which indicate that the parameters of the joint plane, such as strength and stiffness, are improved; the stress field becomes uniform. Tensile area reduces gradually; whole stability of the slope and its ability to resist tensile and shear stress are improved greatly.展开更多
A hybrid method is established by combining photoelastic experiment and finite element analysis.The method is used to evaluate contact stress distribution on dry friction interfaces,such as the contact interfaces betw...A hybrid method is established by combining photoelastic experiment and finite element analysis.The method is used to evaluate contact stress distribution on dry friction interfaces,such as the contact interfaces between shrouds of fan blades and turbine blades.The photoelastic stress frozen experiment method is used to decide the displacement boundary conditions of numerical calculation.Higher accuracy and efficiency of solving problems are improved by the method.Technical difficulty and high cost of experiment are also avoided by the method.Good agreement of the stress distribution by using the hybrid method and experiment is obtained.展开更多
Besides opening geometry, in situ stress and material properties, opening support also has significant effects on stress redistribution around a roadway. To investigate these effects of rock bolts on the stress redist...Besides opening geometry, in situ stress and material properties, opening support also has significant effects on stress redistribution around a roadway. To investigate these effects of rock bolts on the stress redistribution around a roadway, a series of numerical studies were carried out using the finite difference method. Since the stress changes around a roadway caused by rock bolting is small relative to the in situ stress, they cannot obviously be observed in stress contour plots. To overcome this difficulty, a new result processing methodology was developed using the contouring program Surfer. With this methodology, the effects of rock bolts on stress redistribution can obviously be analyzed. Numerical results show that in the three patterns of rock bolts installed in the roof, in the roof and the two lateral sides, and in all the four sides of the rectangular roadway, the maximum stress magnitude of the increase is 0.931 MPa, 2.46 MPa,and 6.5 MPa, respectively; the bolt number of 5 can form an integrated ground arch; the appropriate length and pre-tensioned force of the rock bolt is 2.0 m and 60 k N, respectively. What is more, the ground arch action under the function of rock bolting is able to be effectively examined. The rock bolts dramatically increase the minor principal stress around a roadway which results in significant increase in material strength. Consequently, the major principal stress that the material can carry will greatly increase.With adequate supports, an integrated ground arch which is critical for the stability of roadway will be formed around the roadway.展开更多
We adopt the concept of generalized plane strain to model a roadway in a stress field.This can avoid limitations caused by simplifying the stress analysis as plane strain.FLAC3D was used to investigate the maximum ten...We adopt the concept of generalized plane strain to model a roadway in a stress field.This can avoid limitations caused by simplifying the stress analysis as plane strain.FLAC3D was used to investigate the maximum tensile stress and displacement of a roadway in a known stress field for angles,α,between the roadway axial direction and the maximum principal stress of 0°,30°,45°,60° and 90°.This theory was applied to the analysis of an engineering case.The results indicate that stress and displacement of the surrounding rock increase as the angle,α,increases.This provides some significant guidance for a reasonable layout of roadways in a known stress field.展开更多
By using numerical analysis methods to simulate the deep excavation,a lot of analyses are established on the basis of two-dimensional plane strain,ignoring the fact that foundation pit possesses three dimensions. For ...By using numerical analysis methods to simulate the deep excavation,a lot of analyses are established on the basis of two-dimensional plane strain,ignoring the fact that foundation pit possesses three dimensions. For soil constitutive relation,people always take linear and nonlinear model,without considering the plastic behavior of soil. Using plastic-elastic hardening model to simulate constitutive relation of soil characteristics,the authors carried out mechanical analysis for pit excavation and support. The results show that the analysis for the stress state of pile anchor system is an effective way which provides theoretical basis for calculation of soil displacement.展开更多
In order to compensate for limitations of microscopic study on loess triaxial tests, taking the loess in Longxi area as an example, the authors established the loess triaxial test model by using PFC3D software and sim...In order to compensate for limitations of microscopic study on loess triaxial tests, taking the loess in Longxi area as an example, the authors established the loess triaxial test model by using PFC3D software and simulating tfiaxial shear test under the different confining pressures in 0 kPa, 50 kPa and 300 kPa. Compared with laboratory triaxial shear test, the numerical simulation test has a guiding role in loess mechanical strength analysis.展开更多
Arthritis, most notably rheumatoid arthritis, can destroy the surfaces of the bones; the ideal solution for this is T JR （total joint replacement）, which would restore joint functionality, maintain correct aesthetic...Arthritis, most notably rheumatoid arthritis, can destroy the surfaces of the bones; the ideal solution for this is T JR （total joint replacement）, which would restore joint functionality, maintain correct aesthetics and eradicate pain for the patient. Current metacarpophalangeal TJR do not provide the normal biomechanical range of motion and functionality. The proposed design attempts to correct this through the use of design geometry and functional anatomy. Numerical analysis is used in conjunction with computational solid modeling to compare a one-piece silicone implant with the proposed T JR. Peak stresses during flexion for the proposed design did not exceed 1.2 MPa, where as soft implants approach 100 MPa to 1,000 MPa for peak stress values. The proposed design, due to high stress tolerances with low deformation, along with functionality and biomechanics, seems to be an appropriate replacement for one-piece silicone implant.展开更多
In order to determine how a roadway withstands a momentum wave and determinethe extent of damage to rock surrounding the roadway under different force wavepeak impacts,the roadway dynamic response state was analysed u...In order to determine how a roadway withstands a momentum wave and determinethe extent of damage to rock surrounding the roadway under different force wavepeak impacts,the roadway dynamic response state was analysed using numerical simulationmethod.The roadway's critical peak force wave and fracture region under dynamicwave action were put forward.It is concluded that the method has practical value to roadwaysupport and rockburst prevention.展开更多
文摘A new technology for fabrication of silica on silicon arrayed waveguide grating (AWG) based on deep etching and thermal oxidation is presented.Using this method,a silicon layer is remained at the side of waveguide.The stress distribution and effective refractive index of waveguide fabricated by this approach are calculated using finite element and finite difference beam propagation method,respectively.The results of these studies indicate that the stress of silica on silicon optical waveguide can be matched in parallel and vertical direction and AWG polarization dependent wavelength (PDλ) can be reduced effectively due to side-silicon layer.
基金Supported by the National Natural Science Foundation of China (50099620, 40804027)
文摘To study the grouting reinforcement mechanism in jointed rock slope, first, the theoretical deduction was done to calculate the critical length of slipping if the slope angle is larger than that of joint inclination; Second, the numerical calculation model was founded by FLAG^3D, so as to find the stress and deformation responses of rock mass in the state before and after grouting, the analysis results show that the range between the boundary of critical slipping block and the joint plane that passes the slope toe is the effective grouting area （EGA）. After excavation, large deformation occurs along the joint plane. After grouting, the displacements of rock particles become uniform and continuous, and large deformations along the joint plane are controlled; the dynamic displacement can re- flect the deformation response of slope during excavation in the state before and after grouting, as well as the shear location of potential slip plane. After grouting, the dynamic displacement of each monitoring point reaches the peak value with very few time steps, which indicate that the parameters of the joint plane, such as strength and stiffness, are improved; the stress field becomes uniform. Tensile area reduces gradually; whole stability of the slope and its ability to resist tensile and shear stress are improved greatly.
基金Youth Foundation of Beijing Polytechnic University
文摘A hybrid method is established by combining photoelastic experiment and finite element analysis.The method is used to evaluate contact stress distribution on dry friction interfaces,such as the contact interfaces between shrouds of fan blades and turbine blades.The photoelastic stress frozen experiment method is used to decide the displacement boundary conditions of numerical calculation.Higher accuracy and efficiency of solving problems are improved by the method.Technical difficulty and high cost of experiment are also avoided by the method.Good agreement of the stress distribution by using the hybrid method and experiment is obtained.
基金Financial support for this work provided by the National Key Scientific Apparatus Development of Special Item (No.2012YQ24012705)is deeply appreciated
文摘Besides opening geometry, in situ stress and material properties, opening support also has significant effects on stress redistribution around a roadway. To investigate these effects of rock bolts on the stress redistribution around a roadway, a series of numerical studies were carried out using the finite difference method. Since the stress changes around a roadway caused by rock bolting is small relative to the in situ stress, they cannot obviously be observed in stress contour plots. To overcome this difficulty, a new result processing methodology was developed using the contouring program Surfer. With this methodology, the effects of rock bolts on stress redistribution can obviously be analyzed. Numerical results show that in the three patterns of rock bolts installed in the roof, in the roof and the two lateral sides, and in all the four sides of the rectangular roadway, the maximum stress magnitude of the increase is 0.931 MPa, 2.46 MPa,and 6.5 MPa, respectively; the bolt number of 5 can form an integrated ground arch; the appropriate length and pre-tensioned force of the rock bolt is 2.0 m and 60 k N, respectively. What is more, the ground arch action under the function of rock bolting is able to be effectively examined. The rock bolts dramatically increase the minor principal stress around a roadway which results in significant increase in material strength. Consequently, the major principal stress that the material can carry will greatly increase.With adequate supports, an integrated ground arch which is critical for the stability of roadway will be formed around the roadway.
基金supported by the National Basic Research Program of China (No.2010CB226805)the National Natural Science Foundation of China (Nos.50874103 and 50974115)+1 种基金the Natural Science Foundation of Jiangsu Province (No.KB2008135)the State Key Laboratory Fund (No.SKLGDUEK 0905)
文摘We adopt the concept of generalized plane strain to model a roadway in a stress field.This can avoid limitations caused by simplifying the stress analysis as plane strain.FLAC3D was used to investigate the maximum tensile stress and displacement of a roadway in a known stress field for angles,α,between the roadway axial direction and the maximum principal stress of 0°,30°,45°,60° and 90°.This theory was applied to the analysis of an engineering case.The results indicate that stress and displacement of the surrounding rock increase as the angle,α,increases.This provides some significant guidance for a reasonable layout of roadways in a known stress field.
文摘By using numerical analysis methods to simulate the deep excavation,a lot of analyses are established on the basis of two-dimensional plane strain,ignoring the fact that foundation pit possesses three dimensions. For soil constitutive relation,people always take linear and nonlinear model,without considering the plastic behavior of soil. Using plastic-elastic hardening model to simulate constitutive relation of soil characteristics,the authors carried out mechanical analysis for pit excavation and support. The results show that the analysis for the stress state of pile anchor system is an effective way which provides theoretical basis for calculation of soil displacement.
文摘In order to compensate for limitations of microscopic study on loess triaxial tests, taking the loess in Longxi area as an example, the authors established the loess triaxial test model by using PFC3D software and simulating tfiaxial shear test under the different confining pressures in 0 kPa, 50 kPa and 300 kPa. Compared with laboratory triaxial shear test, the numerical simulation test has a guiding role in loess mechanical strength analysis.
文摘Arthritis, most notably rheumatoid arthritis, can destroy the surfaces of the bones; the ideal solution for this is T JR （total joint replacement）, which would restore joint functionality, maintain correct aesthetics and eradicate pain for the patient. Current metacarpophalangeal TJR do not provide the normal biomechanical range of motion and functionality. The proposed design attempts to correct this through the use of design geometry and functional anatomy. Numerical analysis is used in conjunction with computational solid modeling to compare a one-piece silicone implant with the proposed T JR. Peak stresses during flexion for the proposed design did not exceed 1.2 MPa, where as soft implants approach 100 MPa to 1,000 MPa for peak stress values. The proposed design, due to high stress tolerances with low deformation, along with functionality and biomechanics, seems to be an appropriate replacement for one-piece silicone implant.
基金Supported by the National Key Technology R&D Program in 11 th Five Years Plan of China(2006BAK03B06)
文摘In order to determine how a roadway withstands a momentum wave and determinethe extent of damage to rock surrounding the roadway under different force wavepeak impacts,the roadway dynamic response state was analysed using numerical simulationmethod.The roadway's critical peak force wave and fracture region under dynamicwave action were put forward.It is concluded that the method has practical value to roadwaysupport and rockburst prevention.
