In this study,the permeabilities of Berea and Otway sandstones were measured under different confining pressures,and porosity was investigated through mercury intrusion porosimetry(MIP).The total porosities of the Ber...In this study,the permeabilities of Berea and Otway sandstones were measured under different confining pressures,and porosity was investigated through mercury intrusion porosimetry(MIP).The total porosities of the Berea and Otway sandstones were approximately 17.4%and 25%,respectively.Pore size distributions of each sandstone were almost the same,but the pores in the Otway sandstone were slightly narrower.However,the permeability of the Otway sandstone was smaller than that of the Berea sandstone by one order of magnitude.Three-dimensional(3D)void geometry and geometrical properties of the void spaces relevant to flow were compared to obtain the relation between the permeability differences and porosities of the two sandstones.The 3D geometrical analysis using microfocus X-ray computed tomography(CT)was performed,and the pore geometries of both sandstones were compared using the 3D medial axis(3DMA)method.Pore and throat radii,pore coordination number,tortuosity,number of connecting paths,connecting path volume,and other factors were determined using 3DMA.The Otway sandstone was characterized by a small effective throat/pore radius ratio.Based on the fluid flow mechanism,the lower effective throat/pore radius ratio results in a lower permeability induced by the fluid energy loss,which means that the 3D geometrical shape of void spaces affects the permeability value.展开更多
Instantaneous three-dimensional (3D) density distributions of a shock-cell structure of perfectly and imperfectly expanded supersonic microjets escaping into an ambient space are measured. For the 3D observation of su...Instantaneous three-dimensional (3D) density distributions of a shock-cell structure of perfectly and imperfectly expanded supersonic microjets escaping into an ambient space are measured. For the 3D observation of supersonic microjets, non-scanning 3D computerized tomography (CT) technique using a 20-directional quantitative schlieren optical system with flashlight source is employed for simultaneous schlieren photography. The 3D density distributions data of the microjets are obtained by 3D-CT reconstruction of the projection’s images using maximum likelihood-expectation maximization. Axisymmetric convergent-divergent (Laval) circular and square micro nozzles with operating nozzle pressure ratio 5.0, 4.5, 4.0, 3.67, and 3.5 have been studied. This study examines perfectly expanded, overexpanded, and underexpanded supersonic microjets issued from micro nozzles with fully expanded jet Mach numbers <em>M</em><em><sub>j</sub></em> ranging from 1.47 - 1.71, where the design Mach number is <em>M<sub>d</sub></em> = 1.5. A complex phenomenon for free square microjets called axis switching is clearly observed with two types “upright” and “diagonal” of “cross-shaped”. The initial axis-switching is 45<span style="white-space:nowrap;">°</span> within the first shock-cell range. In addition, from the symmetry and diagonal views of square microjets for the first shock-cells, two different patterns of shock waves are viewed. The shock-cell spacing and supersonic core length for all nozzle pressure ratios are investigated and reported.展开更多
Two novel ultrasound imaging techniques with imaging contrast mechanisms are in the works:X-ray-induced acoustic computed tomography(XACT),and nanoscale photoacoustic tomogra-phy(nPAT).XACT has incredible potential in...Two novel ultrasound imaging techniques with imaging contrast mechanisms are in the works:X-ray-induced acoustic computed tomography(XACT),and nanoscale photoacoustic tomogra-phy(nPAT).XACT has incredible potential in:(1)biomedical imaging,through which a 3D image can be generated using only a single X-ray projection,and(2)radiation dosimetry.nPATas a new alternative of super-resolution microscopy can break through the optical difraction limitand is capable of exploring sub-celular structures without reliance on fuorescence labeling.We expect these new imaging techniques to find widespread applications in both pre-clinical andclinical biomedical research.展开更多
To the Editor:Bronchial rupture due to blunt chest injury in children is very rare and can go undiagnosed for over 48 h.Despite surgical repair following definitive diagnosis by three-dimensional computed tomography(3...To the Editor:Bronchial rupture due to blunt chest injury in children is very rare and can go undiagnosed for over 48 h.Despite surgical repair following definitive diagnosis by three-dimensional computed tomography(3D-CT)and bronchoscopy,complications from anastomotic stricture can arise,particularly in very young patients.This study aimed to present an algorithm for improved early diagnosis and report learnings from treatment of bronchial rupture after blunt chest trauma in nine children.展开更多
基金This work was supported by the Basic Research and Development Project of the Korea Institute of Geoscience and Mineral Resources(Grant No.20-3115).
文摘In this study,the permeabilities of Berea and Otway sandstones were measured under different confining pressures,and porosity was investigated through mercury intrusion porosimetry(MIP).The total porosities of the Berea and Otway sandstones were approximately 17.4%and 25%,respectively.Pore size distributions of each sandstone were almost the same,but the pores in the Otway sandstone were slightly narrower.However,the permeability of the Otway sandstone was smaller than that of the Berea sandstone by one order of magnitude.Three-dimensional(3D)void geometry and geometrical properties of the void spaces relevant to flow were compared to obtain the relation between the permeability differences and porosities of the two sandstones.The 3D geometrical analysis using microfocus X-ray computed tomography(CT)was performed,and the pore geometries of both sandstones were compared using the 3D medial axis(3DMA)method.Pore and throat radii,pore coordination number,tortuosity,number of connecting paths,connecting path volume,and other factors were determined using 3DMA.The Otway sandstone was characterized by a small effective throat/pore radius ratio.Based on the fluid flow mechanism,the lower effective throat/pore radius ratio results in a lower permeability induced by the fluid energy loss,which means that the 3D geometrical shape of void spaces affects the permeability value.
文摘Instantaneous three-dimensional (3D) density distributions of a shock-cell structure of perfectly and imperfectly expanded supersonic microjets escaping into an ambient space are measured. For the 3D observation of supersonic microjets, non-scanning 3D computerized tomography (CT) technique using a 20-directional quantitative schlieren optical system with flashlight source is employed for simultaneous schlieren photography. The 3D density distributions data of the microjets are obtained by 3D-CT reconstruction of the projection’s images using maximum likelihood-expectation maximization. Axisymmetric convergent-divergent (Laval) circular and square micro nozzles with operating nozzle pressure ratio 5.0, 4.5, 4.0, 3.67, and 3.5 have been studied. This study examines perfectly expanded, overexpanded, and underexpanded supersonic microjets issued from micro nozzles with fully expanded jet Mach numbers <em>M</em><em><sub>j</sub></em> ranging from 1.47 - 1.71, where the design Mach number is <em>M<sub>d</sub></em> = 1.5. A complex phenomenon for free square microjets called axis switching is clearly observed with two types “upright” and “diagonal” of “cross-shaped”. The initial axis-switching is 45<span style="white-space:nowrap;">°</span> within the first shock-cell range. In addition, from the symmetry and diagonal views of square microjets for the first shock-cells, two different patterns of shock waves are viewed. The shock-cell spacing and supersonic core length for all nozzle pressure ratios are investigated and reported.
文摘Two novel ultrasound imaging techniques with imaging contrast mechanisms are in the works:X-ray-induced acoustic computed tomography(XACT),and nanoscale photoacoustic tomogra-phy(nPAT).XACT has incredible potential in:(1)biomedical imaging,through which a 3D image can be generated using only a single X-ray projection,and(2)radiation dosimetry.nPATas a new alternative of super-resolution microscopy can break through the optical difraction limitand is capable of exploring sub-celular structures without reliance on fuorescence labeling.We expect these new imaging techniques to find widespread applications in both pre-clinical andclinical biomedical research.
文摘To the Editor:Bronchial rupture due to blunt chest injury in children is very rare and can go undiagnosed for over 48 h.Despite surgical repair following definitive diagnosis by three-dimensional computed tomography(3D-CT)and bronchoscopy,complications from anastomotic stricture can arise,particularly in very young patients.This study aimed to present an algorithm for improved early diagnosis and report learnings from treatment of bronchial rupture after blunt chest trauma in nine children.
