Ditroid is a directed version of matroid. In this paper we investigate transversal theory of ditroids. Directed versions of Rado-Hall and Edmonds-Fulkerson theorems are obtained. Our results provide partial answers to...Ditroid is a directed version of matroid. In this paper we investigate transversal theory of ditroids. Directed versions of Rado-Hall and Edmonds-Fulkerson theorems are obtained. Our results provide partial answers to two questions raised by L. Qi.展开更多
AIM:To compare and evaluate the phacoemulsification parameters and postoperative endothelial cell changes of two different phacoemulsification machines, each with different modes, but also to assess the relationship b...AIM:To compare and evaluate the phacoemulsification parameters and postoperative endothelial cell changes of two different phacoemulsification machines, each with different modes, but also to assess the relationship between postoperative endothelial cell loss and the phacoemulsification parameters, as well as the other factors in both groups.METHODS:This prospective observational study was comprised of consecutive eligible cataract patients operated with phacoemulsification technique performed by the same surgeon using either a WHITESTAR Signature Ellips FX(transversal, group 1) or Infiniti OZil IP(torsional, group 2) machine.RESULTS:The study included 86 patients. Baseline characteristics in the groups were similar. The median nuclear sclerosis grade was 3(2-4) in the first group and2(2-4) in the second group(P =0.265). Both groups had similar phacoemulsification needle times(group 1: 60.63±36 s; group 2: 55.98±30 s; P =0.789). The percentage of endothelial cell loss 30 d after surgery ranged from 3% to15% with a median of 7% in group 1, and from 2% to13% with a median of 6% in group 2; however, there was no statistically significant difference between the groups(P =0.407). Hexagonality(P =0.794) and the coefficient of variation(CV; P =0.142) did not differ significantly between the groups before and 30 d after surgery. Asignificant positive correlation was found between the endothelial cell loss and nuclear sclerosis grade(group1: P 【0.001; group 2: P 【0.001) and between the endothelial cell loss and average phacoemulsification power(group 1: P =0.007; group 2: P =0.008).CONCLUSION:Both of these machines were efficient,with similar endothelial cell loss. This endothelial cell loss was related to the increased nuclear sclerosis grade and increased phacoemulsification power.展开更多
Behavior of transversal crack notched on slab corner during vertical-horizontal rolling process was simulated by FEM. The crack tip stress in the whole rolling process was obtained. Influences of the friction coeffici...Behavior of transversal crack notched on slab corner during vertical-horizontal rolling process was simulated by FEM. The crack tip stress in the whole rolling process was obtained. Influences of the friction coefficient, the initial crack size, the edger roll profile, and the groove fillet radii of grooved edger roll on crack tip stress were analyzed. For vertical rolling, the tension stress appears at crack tip near the slab top surface and the compression stress appears at crack tip near the slab side surface for the flat edger roll; however, the compression stress appears at crack tip near the slab top surface and the tension stress appears at crack tip near the slab side surface in the exit stage for the grooved edger roll. For horizontal rolling, the tension stress appears at crack tip just at the exit stage for the flat edger roll, and the tension stress appears in whole rolling stage; the tension stress value near the slab side surface is much larger than that near the slab top surface for the grooved edger roll.展开更多
In the continuous casting of steels, surface transversal cracks are often found. These defects may severely influence the final quality of the products. The evolution of transversal V-shaped cracks with different dept...In the continuous casting of steels, surface transversal cracks are often found. These defects may severely influence the final quality of the products. The evolution of transversal V-shaped cracks with different depth on the surface of a continuously cast steel slab during hot rolling was studied. The artificial V-shaped cracks were made on the surface. The rolling process parameters from an industrial rolling mill have been used as a reference. The speci- mens of rolled workpiece in intermediate slabs were obtained after different rolling passes. The morphology of sur- face crack and microstructure evolution in the rolling process were investigated by optical microscopy. The results show that the depth of surface transversal crack gradually decreased with the increase of rolling passes. The grain size of ferrite and pearlite on the sample surface also gradually reduced. The microstructures around cracks with the dif ferent depth are almost identical, without direct correlation with the initial crack depth.展开更多
Finite volume schemes for the two-dimensional(2D) wave system are taken to demonstrate the role of the genuine dimensionality of Lax-Wendroff flow solvers for compressible fluid flows. When the finite volume schemes a...Finite volume schemes for the two-dimensional(2D) wave system are taken to demonstrate the role of the genuine dimensionality of Lax-Wendroff flow solvers for compressible fluid flows. When the finite volume schemes are applied, the transversal variation relative to the computational cell interfaces is neglected, and only the normal numerical flux is used, thanks to the Gauss-Green formula. In order to offset such defects, the Lax-Wendroff flow solvers or the generalized Riemann problem(GRP) solvers are adopted by substituting the time evolution of flows into the spatial variation. The numerical results show that even with the same convergence rate, the error by the GRP2D solver is almost one ninth of that by the multistage Runge-Kutta(RK) method.展开更多
文摘Ditroid is a directed version of matroid. In this paper we investigate transversal theory of ditroids. Directed versions of Rado-Hall and Edmonds-Fulkerson theorems are obtained. Our results provide partial answers to two questions raised by L. Qi.
文摘AIM:To compare and evaluate the phacoemulsification parameters and postoperative endothelial cell changes of two different phacoemulsification machines, each with different modes, but also to assess the relationship between postoperative endothelial cell loss and the phacoemulsification parameters, as well as the other factors in both groups.METHODS:This prospective observational study was comprised of consecutive eligible cataract patients operated with phacoemulsification technique performed by the same surgeon using either a WHITESTAR Signature Ellips FX(transversal, group 1) or Infiniti OZil IP(torsional, group 2) machine.RESULTS:The study included 86 patients. Baseline characteristics in the groups were similar. The median nuclear sclerosis grade was 3(2-4) in the first group and2(2-4) in the second group(P =0.265). Both groups had similar phacoemulsification needle times(group 1: 60.63±36 s; group 2: 55.98±30 s; P =0.789). The percentage of endothelial cell loss 30 d after surgery ranged from 3% to15% with a median of 7% in group 1, and from 2% to13% with a median of 6% in group 2; however, there was no statistically significant difference between the groups(P =0.407). Hexagonality(P =0.794) and the coefficient of variation(CV; P =0.142) did not differ significantly between the groups before and 30 d after surgery. Asignificant positive correlation was found between the endothelial cell loss and nuclear sclerosis grade(group1: P 【0.001; group 2: P 【0.001) and between the endothelial cell loss and average phacoemulsification power(group 1: P =0.007; group 2: P =0.008).CONCLUSION:Both of these machines were efficient,with similar endothelial cell loss. This endothelial cell loss was related to the increased nuclear sclerosis grade and increased phacoemulsification power.
基金State Basic Research Key Projects (973) of China (2006CB605208-1)National Natural Science Foundation of China (50534020)
文摘Behavior of transversal crack notched on slab corner during vertical-horizontal rolling process was simulated by FEM. The crack tip stress in the whole rolling process was obtained. Influences of the friction coefficient, the initial crack size, the edger roll profile, and the groove fillet radii of grooved edger roll on crack tip stress were analyzed. For vertical rolling, the tension stress appears at crack tip near the slab top surface and the compression stress appears at crack tip near the slab side surface for the flat edger roll; however, the compression stress appears at crack tip near the slab top surface and the tension stress appears at crack tip near the slab side surface in the exit stage for the grooved edger roll. For horizontal rolling, the tension stress appears at crack tip just at the exit stage for the flat edger roll, and the tension stress appears in whole rolling stage; the tension stress value near the slab side surface is much larger than that near the slab top surface for the grooved edger roll.
基金Item Sponsored by National Natural Science Foundation of China(50271060)
文摘In the continuous casting of steels, surface transversal cracks are often found. These defects may severely influence the final quality of the products. The evolution of transversal V-shaped cracks with different depth on the surface of a continuously cast steel slab during hot rolling was studied. The artificial V-shaped cracks were made on the surface. The rolling process parameters from an industrial rolling mill have been used as a reference. The speci- mens of rolled workpiece in intermediate slabs were obtained after different rolling passes. The morphology of sur- face crack and microstructure evolution in the rolling process were investigated by optical microscopy. The results show that the depth of surface transversal crack gradually decreased with the increase of rolling passes. The grain size of ferrite and pearlite on the sample surface also gradually reduced. The microstructures around cracks with the dif ferent depth are almost identical, without direct correlation with the initial crack depth.
基金Project supported by the National Natural Science Foundation of China(Nos.11771054 and 91852207)
文摘Finite volume schemes for the two-dimensional(2D) wave system are taken to demonstrate the role of the genuine dimensionality of Lax-Wendroff flow solvers for compressible fluid flows. When the finite volume schemes are applied, the transversal variation relative to the computational cell interfaces is neglected, and only the normal numerical flux is used, thanks to the Gauss-Green formula. In order to offset such defects, the Lax-Wendroff flow solvers or the generalized Riemann problem(GRP) solvers are adopted by substituting the time evolution of flows into the spatial variation. The numerical results show that even with the same convergence rate, the error by the GRP2D solver is almost one ninth of that by the multistage Runge-Kutta(RK) method.
