The intrinsic physical relationship of vorticity between modes A and B in the three-dimensional wake transition is investigated.Direct numerical simulations for the flow past a square-section cylinder are carried out ...The intrinsic physical relationship of vorticity between modes A and B in the three-dimensional wake transition is investigated.Direct numerical simulations for the flow past a square-section cylinder are carried out at Reynolds numbers of 180 and 250,associated with modes A and B,respectively.Based on the analysis of spacial distributions of vorticity in the near wake,characteristics of the vertical vorticity in modes A and B are identified.Moreover,the relationship of three vorticity components with specific signs is summarized into two sign laws,as intrinsic physical relationships between two instability modes.By the theory of vortex-induced vortex,such two sign laws confirm that there are two and only two kinds of vortex-shedding patterns in the near wake,just corresponding to modes A and B.In brief,along the free stream direction,mode A can be described by the parallel shedding vertical vortices with the same sign,while mode B is described by the parallel shedding streamwise vortices with the same sign.Finally,it is found out that the|-type vortex is a basic kind of vortex structure in both modes A and B.展开更多
This paper deals with the temperature correlation of gray scale of B-mode ultrasound image from heated tissue. In this study, many in-vitro fresh pig livers are heated in a temperature range from 28 ℃ to 45℃, from w...This paper deals with the temperature correlation of gray scale of B-mode ultrasound image from heated tissue. In this study, many in-vitro fresh pig livers are heated in a temperature range from 28 ℃ to 45℃, from which a series of B-mode ultrasonic images of livers were obtained. The gray-value is evaluated from the ultrasound images respectively. A correlation of the mean gray value of the selected regions (12×12 pixels) in B-mode ultrasonic images of liver and its temperature was pointed out. And the experiment results agreed the evaluation well. And it is possible to monitor the tissue temperature changing in hyperthermia using this correlation.展开更多
A B-spline active contour model based on finite element method is presented, into which the advantages of a B-spline active contour attributing to its fewer parameters and its smoothness is built accompanied with redu...A B-spline active contour model based on finite element method is presented, into which the advantages of a B-spline active contour attributing to its fewer parameters and its smoothness is built accompanied with reduced computational complexity and better numerical stability resulted from the finite element method. In this model, a cubic B-spline segment is taken as an element, and the finite element method is adopted to solve the energy minimization problem of the B-spline active contour, thus to implement image segmentation. Experiment results verify that this method is efficient for B-spline active contour, which attains stable, accurate and faster convergence.展开更多
To decrease the computational complexity of adaptive inter-layer prediction and improve the encoding efficiency in scalable video coding,a mode decision algorithm is proposed by exploiting the part of used candidate m...To decrease the computational complexity of adaptive inter-layer prediction and improve the encoding efficiency in scalable video coding,a mode decision algorithm is proposed by exploiting the part of used candidate modes of the co-located reference macroblocks for Hierarchical-B pictures.This scheme reduces the amount of the candidate modes to generate a dynamic list for the current encoding macroblock according to the statistical information derived from the co-located reference macroblocks in different temporal levels.The experimental results show that this fast algorithm reduces approximately 31% encoding time on average with the negligible loss of encoding performance.展开更多
The effect of heat treatment mode on the microstructure of Fe-Cr-B cast iron alloys was investigated inthis paper by comparing the difference of precipitation patterns of secondary particles after thermal cycling trea...The effect of heat treatment mode on the microstructure of Fe-Cr-B cast iron alloys was investigated inthis paper by comparing the difference of precipitation patterns of secondary particles after thermal cycling treatment(TCT) with those after normal heat treatment (NHT). No obvious differences were found in precipitation patterns ofsecondary particles between TCT and NHT when experimental temperature was below Ar1. However, whentemperature was over Ar1, there were significant differences, with secondary particles prominently segregated at thegrain boundaries under TCT, while the particles evenly distributed in the matrix under NHT. The reason for themicrostructure differences could be associated with the development of non-equilibrium segregation of boron duringTCT.展开更多
基金financially supported by the Strategic Priority Research Program of the Chinese Academy of Science (Grant XDB22030101)
文摘The intrinsic physical relationship of vorticity between modes A and B in the three-dimensional wake transition is investigated.Direct numerical simulations for the flow past a square-section cylinder are carried out at Reynolds numbers of 180 and 250,associated with modes A and B,respectively.Based on the analysis of spacial distributions of vorticity in the near wake,characteristics of the vertical vorticity in modes A and B are identified.Moreover,the relationship of three vorticity components with specific signs is summarized into two sign laws,as intrinsic physical relationships between two instability modes.By the theory of vortex-induced vortex,such two sign laws confirm that there are two and only two kinds of vortex-shedding patterns in the near wake,just corresponding to modes A and B.In brief,along the free stream direction,mode A can be described by the parallel shedding vertical vortices with the same sign,while mode B is described by the parallel shedding streamwise vortices with the same sign.Finally,it is found out that the|-type vortex is a basic kind of vortex structure in both modes A and B.
基金The research was supported by National Nature Science Foundation (30470450) Education Committee Foundation( KP0608200201 ) Elitist Foundation( KW5800200351 ) from Beijing City,China.
文摘This paper deals with the temperature correlation of gray scale of B-mode ultrasound image from heated tissue. In this study, many in-vitro fresh pig livers are heated in a temperature range from 28 ℃ to 45℃, from which a series of B-mode ultrasonic images of livers were obtained. The gray-value is evaluated from the ultrasound images respectively. A correlation of the mean gray value of the selected regions (12×12 pixels) in B-mode ultrasonic images of liver and its temperature was pointed out. And the experiment results agreed the evaluation well. And it is possible to monitor the tissue temperature changing in hyperthermia using this correlation.
基金the National Natural Science Foundation of China (No.59975057).
文摘A B-spline active contour model based on finite element method is presented, into which the advantages of a B-spline active contour attributing to its fewer parameters and its smoothness is built accompanied with reduced computational complexity and better numerical stability resulted from the finite element method. In this model, a cubic B-spline segment is taken as an element, and the finite element method is adopted to solve the energy minimization problem of the B-spline active contour, thus to implement image segmentation. Experiment results verify that this method is efficient for B-spline active contour, which attains stable, accurate and faster convergence.
基金Sponsored by the Fundamental Research Funds for the Central Universities(Grant No. HEUCF11805)
文摘To decrease the computational complexity of adaptive inter-layer prediction and improve the encoding efficiency in scalable video coding,a mode decision algorithm is proposed by exploiting the part of used candidate modes of the co-located reference macroblocks for Hierarchical-B pictures.This scheme reduces the amount of the candidate modes to generate a dynamic list for the current encoding macroblock according to the statistical information derived from the co-located reference macroblocks in different temporal levels.The experimental results show that this fast algorithm reduces approximately 31% encoding time on average with the negligible loss of encoding performance.
文摘The effect of heat treatment mode on the microstructure of Fe-Cr-B cast iron alloys was investigated inthis paper by comparing the difference of precipitation patterns of secondary particles after thermal cycling treatment(TCT) with those after normal heat treatment (NHT). No obvious differences were found in precipitation patterns ofsecondary particles between TCT and NHT when experimental temperature was below Ar1. However, whentemperature was over Ar1, there were significant differences, with secondary particles prominently segregated at thegrain boundaries under TCT, while the particles evenly distributed in the matrix under NHT. The reason for themicrostructure differences could be associated with the development of non-equilibrium segregation of boron duringTCT.
