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이순기 대한영상의학회 1983 대한영상의학회지 Vol.19 No.2
Total 3347 liver scintigrams which had been performed for 2 year, Apr. 1979 to Apr. 1981 were reviewed retrospectively and 293 of them revealed "tree-like" defects extending from porta hepatis to the periphery. Forobtaining correlation of such defects with hepatobiliary disorders and the clinical significance of them, we studied 61 cases which were confirmed by PTC, ERCP and/or surgery, and we established 3 subjective grades accoridng to size of the defects seen on the ant. scintiscan. After analysis of these scintigraphic findings and the relation to the clinical findings, the results obtained were as follows : 1. The apperance of "tree-like" defects on the liver scan is suggested characterstic of obstructive lesion in biliary system. 2. The hepatobiliary disorders with more severe biliary obstruction showed more distinct defects on the liver scan. 3. "Tree-like" defects could be seen in the patient with cholecysitis or clonorchiasis. 4. The longer duration of jaundice and higher level of serum bilirubin and alkaline phosphatase are, the large and more distinct defects could be seen on the liver scan. Based on the results of this study, it is concluded that tree-like defects of porta hepatis on the liver scan might be an important finding strongly suggesting obstutive hepatobiliary disorders even though scintigram using 99mTc sulfur-colloid has been considered as a diagnostic method for hepatic parenchymal disorders such as liver cirrhosis and space-occupying lesion. Colloid scintigram is also thought as a noninvasive useful diagnostic method in differential diagnosis, of icteric patients. Futhermore, when "tree-like defect" on the liver scan is shown, invasive procedures such as PTC, PTCD, ERCP and ERCD should be done on these patients to determine the nature of the lesion and to give adequate treatment.esion and to give adequate treatment.
이순기 대한금속·재료학회 2009 METALS AND MATERIALS International Vol.15 No.4
The spatial arrangement and heterogeneity of microstructural features, in particular, porosity in the cast microstructures, adversely affect the mechanical properties, and consequently lead to significant variability in the properties. Clearly, successful applications of cast alloys require production of castings that exhibit reproducible mechanical responses and low variability in the properties. Therefore, it is essential to thoroughly understand how the spatial arrangement and heterogeneity of porosity govern the mechanical properties. In this respect, new techniques that can simulate the microstructures with different degrees of spatial clustering and arrangement of porosity are presented. New parameters to describe different degrees of microstructural simulations were developed and corresponding virtual 2D microstructures were created. The simulated microstructures were implemented in a Finite Elements (FE) framework in order to study and predict the mechanical properties, which show a good agreement with the experiments. The spatial arrangement and heterogeneity of microstructural features, in particular, porosity in the cast microstructures, adversely affect the mechanical properties, and consequently lead to significant variability in the properties. Clearly, successful applications of cast alloys require production of castings that exhibit reproducible mechanical responses and low variability in the properties. Therefore, it is essential to thoroughly understand how the spatial arrangement and heterogeneity of porosity govern the mechanical properties. In this respect, new techniques that can simulate the microstructures with different degrees of spatial clustering and arrangement of porosity are presented. New parameters to describe different degrees of microstructural simulations were developed and corresponding virtual 2D microstructures were created. The simulated microstructures were implemented in a Finite Elements (FE) framework in order to study and predict the mechanical properties, which show a good agreement with the experiments.
Particle Cracking and Rotation during Plastic Deformation of 7075 Aluminum Alloy
이순기 대한금속·재료학회 2009 METALS AND MATERIALS International Vol.15 No.4
The utility of a novel digital image processing technique for automatic detection and separation of cracked constituent particles was applied to quantitatively characterize the microstructural damage on Fe-rich intermetallic particles that were cracked in a 7075 Al-alloy. This cracking of the Fe-rich intermetallic particles was due to a function of strain under uniaxial tension, compression, and torsion. The comparison of the data on the strained samples revealed that at tensile strain, the number fraction of the cracked Fe-rich particles was significantly higher than those at torsion while the compression strains and the average volume of the cracked Fe-rich particles increased when the strain increased. The percentage-cracked particles had a linear relationship with all of the strains for all of the loading conditions. Significant rotations of Fe-rich intermetallic particles occurred during the deformation of this alloy under torsion. These rotations tended to align themselves along the direction of applied/induced tensile stretch, which in turn affected the progression of damage due to particle cracking. The utility of a novel digital image processing technique for automatic detection and separation of cracked constituent particles was applied to quantitatively characterize the microstructural damage on Fe-rich intermetallic particles that were cracked in a 7075 Al-alloy. This cracking of the Fe-rich intermetallic particles was due to a function of strain under uniaxial tension, compression, and torsion. The comparison of the data on the strained samples revealed that at tensile strain, the number fraction of the cracked Fe-rich particles was significantly higher than those at torsion while the compression strains and the average volume of the cracked Fe-rich particles increased when the strain increased. The percentage-cracked particles had a linear relationship with all of the strains for all of the loading conditions. Significant rotations of Fe-rich intermetallic particles occurred during the deformation of this alloy under torsion. These rotations tended to align themselves along the direction of applied/induced tensile stretch, which in turn affected the progression of damage due to particle cracking.
이순기,윤군진 국제구조공학회 2013 Smart Structures and Systems, An International Jou Vol.12 No.2
In this paper, a statistical reference-free real-time damage detection methodology is proposed for detecting joint and member damage of truss bridge structures. For the statistical damage sensitive index (DSI), wavelet packet decomposition (WPD) in conjunction with the log likelihood ratio was suggested. A sensitivity test for selecting a wavelet packet that is most sensitive to damage level was conducted and determination of the level of decomposition was also described. Advantages of the proposed method for applications to real-time health monitoring systems were demonstrated by using the log likelihood ratios instead of likelihood ratios. A laboratory truss bridge structure instrumented with accelerometers and a shaker was used for experimental verification tests of the proposed methodology. The statistical reference-free real-time damage detection algorithm was successfully implemented and verified by detecting three damage types frequently observed in truss bridge structures – such as loss of bolts, loosening of bolts at multiple locations, sectional loss of members – without reference signals from pristine structure. The DSI based on WPD and the log likelihood ratio showed consistent and reliable results under different damage scenarios.