A 3D ultrasound thermal model with a 3D finite element representation for modeling the thermal diffusion effects for hepatic ablation induced by spherical-section ultrasound phased array was developed. The model was f...A 3D ultrasound thermal model with a 3D finite element representation for modeling the thermal diffusion effects for hepatic ablation induced by spherical-section ultrasound phased array was developed. The model was first validated against available published measured data in rat liver. Using the validated model,effects of blood perfusion and heating schemes on lesion formation were studied for both single focus and split-focus intensity patterns. It was shown that for single focus sonication pattern the short-duration(～2 s) and high-intensity(～1250 W/cm2) heating scheme can completely reduce the cooling effect of the blood perfusion. The lesion shape and size were significantly altered by perfusion for split-focus pattern even with a rapid heating scheme when the focus spacing was larger than 2.4 mm. Underdosed areas might be present between two foci. Prolonging ex-posure time or shortening focus spacing can reduce the cool region between two foci. In addition,the influences of thermal and acoustic parameters were also studied. When the therapy depth is short(<5 cm) ,the lesion size monotonically increases with increasing attenuation coefficient that ranges from 5.4 to 11 Np/(m?MHz) .展开更多
The Phenomena of the interaction between a supersonic jet and an obstacle is a very interesting and important problem relating to the industrial engineering. This paper aims to investigate the characteristics of the t...The Phenomena of the interaction between a supersonic jet and an obstacle is a very interesting and important problem relating to the industrial engineering. This paper aims to investigate the characteristics of the two-dimensional temperature distribution on an inclined plate surface and the relation between the temperature distribution and some shock waves formed in the flow field. In this study, the measurement of temperature distribution on an inclined plate surface and the now visualization has carried out for various conditions using the thermo-sensitive liquid crystal sheet and the schlieren method. The two dimensional temperature distribution on the plate surface is clearly obtained by the thermo-sensitive liquid crystal sheet. The relation between the temperature distribution on an inclined plate surface and some shock waves reached at a plate surface is discussed. In this paper, the characteristics of the temperature distribution and the maximum temperature, and some other experimental evidences are presented.展开更多
The one-dimensional calculation of the gas/particle flows of a supersonic two-stage high-velocity oxy-fuel(HVOF) thermal spray process was performed. The internal gas flow was solved by numerically integrating theequa...The one-dimensional calculation of the gas/particle flows of a supersonic two-stage high-velocity oxy-fuel(HVOF) thermal spray process was performed. The internal gas flow was solved by numerically integrating theequations of the quasi-one-dimensional flow including the effects of pipe friction and heat transfer. As for the supersonicjet flow, semi-empirical equations were used to obtain the gas velocity and temperature along the centerline. The velocity and temperature of the particle were obtained by an one-way coupling method. The material ofthe spray particle selected in this study is ultra high molecular weight polyethylene (UHMWPE). The temperaturedistributions in the spherical UHMWPE particles of 50 and 150 m accelerated and heated by the supersonic gasflow was clarified.展开更多
基金Project (No. 2003CB716103) supported by the National Basic Research Program (973) of China
文摘A 3D ultrasound thermal model with a 3D finite element representation for modeling the thermal diffusion effects for hepatic ablation induced by spherical-section ultrasound phased array was developed. The model was first validated against available published measured data in rat liver. Using the validated model,effects of blood perfusion and heating schemes on lesion formation were studied for both single focus and split-focus intensity patterns. It was shown that for single focus sonication pattern the short-duration(～2 s) and high-intensity(～1250 W/cm2) heating scheme can completely reduce the cooling effect of the blood perfusion. The lesion shape and size were significantly altered by perfusion for split-focus pattern even with a rapid heating scheme when the focus spacing was larger than 2.4 mm. Underdosed areas might be present between two foci. Prolonging ex-posure time or shortening focus spacing can reduce the cool region between two foci. In addition,the influences of thermal and acoustic parameters were also studied. When the therapy depth is short(<5 cm) ,the lesion size monotonically increases with increasing attenuation coefficient that ranges from 5.4 to 11 Np/(m?MHz) .
文摘The Phenomena of the interaction between a supersonic jet and an obstacle is a very interesting and important problem relating to the industrial engineering. This paper aims to investigate the characteristics of the two-dimensional temperature distribution on an inclined plate surface and the relation between the temperature distribution and some shock waves formed in the flow field. In this study, the measurement of temperature distribution on an inclined plate surface and the now visualization has carried out for various conditions using the thermo-sensitive liquid crystal sheet and the schlieren method. The two dimensional temperature distribution on the plate surface is clearly obtained by the thermo-sensitive liquid crystal sheet. The relation between the temperature distribution on an inclined plate surface and some shock waves reached at a plate surface is discussed. In this paper, the characteristics of the temperature distribution and the maximum temperature, and some other experimental evidences are presented.
文摘The one-dimensional calculation of the gas/particle flows of a supersonic two-stage high-velocity oxy-fuel(HVOF) thermal spray process was performed. The internal gas flow was solved by numerically integrating theequations of the quasi-one-dimensional flow including the effects of pipe friction and heat transfer. As for the supersonicjet flow, semi-empirical equations were used to obtain the gas velocity and temperature along the centerline. The velocity and temperature of the particle were obtained by an one-way coupling method. The material ofthe spray particle selected in this study is ultra high molecular weight polyethylene (UHMWPE). The temperaturedistributions in the spherical UHMWPE particles of 50 and 150 m accelerated and heated by the supersonic gasflow was clarified.
