Objective To explore three-dimensional relations of pedicle screw channel (PSC) ,screw entry point and lateral surface of cervical vertebral body by digital techniques. Methods CT scan images of cervical
In alloy bar rolling process, the component of alloyed steel influenced the spread coefficient greatly, therefore, the component influence coefficient m of different alloyed steel has been determined firstly to calcul...In alloy bar rolling process, the component of alloyed steel influenced the spread coefficient greatly, therefore, the component influence coefficient m of different alloyed steel has been determined firstly to calculate the maximum spread. Then the curvature radius of stress free surface and the ＂critical point on the contact boundary＂ have been solved, the surface profile of outgoing workpiece has been obtained. Furthermore, the formula of the equivalent contact section area has been proposed and the mean roll radius has been calculated. The bar rolling experiment and the rigid-plastic FEM （finite element method） simulation have been carried out to verify the novel approach. Compared with experimental data and simulation results, the novel approach can be used in setting processing parameter and design of finishing groove.展开更多
The authors have developed a new line-spring boundary element method in the present paper, which combines the advantage of the line-spring model with that of the boundary element method. This method reduces the three-...The authors have developed a new line-spring boundary element method in the present paper, which combines the advantage of the line-spring model with that of the boundary element method. This method reduces the three-dimension problem of the surface cracks into a quasi-one-dimension problem and can be used to analyze the surface cracked plate under various loading conditions. In this paper theoretical analyses and numerical verifications are carried out. The calculated results are reported, which indicate that the present method is efficient and can be used to analyze the surface crack problem on a personal computer.展开更多
Drumheadlike surface states are typical characteristics in nodal line semimetals and bring varieties of unusual attractive properties.Here we demonstrate the double drumheadlike surface states in group V elemental sem...Drumheadlike surface states are typical characteristics in nodal line semimetals and bring varieties of unusual attractive properties.Here we demonstrate the double drumheadlike surface states in group V elemental semimetals As,Sb,Bi,which family materials behave a nodal line topology with a 3D flowerlike nodal line,using first-principles calculations.On(001)surface of group V elemental semimetals,the projection pattern of the nodal line overlaps and a complicated double drumheadlike surface state appears inside the overlapped region.This double surface state is widely distributed on the surface region up to a penetration depth of 3.5 nm,which is much deeper than the depth of single surface state on(111)surface.Given that the simplicity of the elemental structure and the small gap induced by the spin orbit coupling,this family materials are promising candidates for the experimental observation of the novel double drumheadlike surface state.展开更多
In this paper,we present a novel surface mesh generation approach that splits B-rep geometry models into isotropic triangular meshes based on neural networks and splitting lines.In the first stage,a recursive method i...In this paper,we present a novel surface mesh generation approach that splits B-rep geometry models into isotropic triangular meshes based on neural networks and splitting lines.In the first stage,a recursive method is designed to generate plentiful data to train the neural network model offline.In the second stage,the implemented mesh generator,ISpliter,maps each surface patch into the parameter plane,and then the trained neural network model is applied to select the optimal splitting line to divide the patch into subdomains continuously until they are all triangles.In the third stage,ISpliter remaps the 2D mesh back to the physical space and further optimizes it.Several typical cases are evaluated to compare the mesh quality generated by ISpliter and two baselines,Gmsh and NNW-GridStar.The results show that ISpliter can generate isotropic triangular meshes with high average quality,and the generated meshes are comparable to those generated by the other two software under the same configuration.展开更多
文摘Objective To explore three-dimensional relations of pedicle screw channel (PSC) ,screw entry point and lateral surface of cervical vertebral body by digital techniques. Methods CT scan images of cervical
文摘In alloy bar rolling process, the component of alloyed steel influenced the spread coefficient greatly, therefore, the component influence coefficient m of different alloyed steel has been determined firstly to calculate the maximum spread. Then the curvature radius of stress free surface and the ＂critical point on the contact boundary＂ have been solved, the surface profile of outgoing workpiece has been obtained. Furthermore, the formula of the equivalent contact section area has been proposed and the mean roll radius has been calculated. The bar rolling experiment and the rigid-plastic FEM （finite element method） simulation have been carried out to verify the novel approach. Compared with experimental data and simulation results, the novel approach can be used in setting processing parameter and design of finishing groove.
文摘The authors have developed a new line-spring boundary element method in the present paper, which combines the advantage of the line-spring model with that of the boundary element method. This method reduces the three-dimension problem of the surface cracks into a quasi-one-dimension problem and can be used to analyze the surface cracked plate under various loading conditions. In this paper theoretical analyses and numerical verifications are carried out. The calculated results are reported, which indicate that the present method is efficient and can be used to analyze the surface crack problem on a personal computer.
文摘Drumheadlike surface states are typical characteristics in nodal line semimetals and bring varieties of unusual attractive properties.Here we demonstrate the double drumheadlike surface states in group V elemental semimetals As,Sb,Bi,which family materials behave a nodal line topology with a 3D flowerlike nodal line,using first-principles calculations.On(001)surface of group V elemental semimetals,the projection pattern of the nodal line overlaps and a complicated double drumheadlike surface state appears inside the overlapped region.This double surface state is widely distributed on the surface region up to a penetration depth of 3.5 nm,which is much deeper than the depth of single surface state on(111)surface.Given that the simplicity of the elemental structure and the small gap induced by the spin orbit coupling,this family materials are promising candidates for the experimental observation of the novel double drumheadlike surface state.
基金the National Key Research and Development Program of China(No.2021YFB0300101)the National Natural Science Foundation of China(Nos.12102467 and 12102468)+1 种基金the Foundation of National University of Defense Technology(No.ZK21-02)the Foundation of State Key Laboratory of High Performance Computing of China(Nos.202101-01 and 202101-19).
文摘In this paper,we present a novel surface mesh generation approach that splits B-rep geometry models into isotropic triangular meshes based on neural networks and splitting lines.In the first stage,a recursive method is designed to generate plentiful data to train the neural network model offline.In the second stage,the implemented mesh generator,ISpliter,maps each surface patch into the parameter plane,and then the trained neural network model is applied to select the optimal splitting line to divide the patch into subdomains continuously until they are all triangles.In the third stage,ISpliter remaps the 2D mesh back to the physical space and further optimizes it.Several typical cases are evaluated to compare the mesh quality generated by ISpliter and two baselines,Gmsh and NNW-GridStar.The results show that ISpliter can generate isotropic triangular meshes with high average quality,and the generated meshes are comparable to those generated by the other two software under the same configuration.
