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정태훈(Tae-hoon Chung),김한종(Han-Jong Kim) 한국생산제조학회 2005 한국생산제조시스템학회 학술발표대회 논문집 Vol.2005 No.5
The head penetrations for control rod drive mechanism and instrumentation systems are installed at the reactor pressure vessel head of PWRs. Primary coolant water and the operating conditions of PWR plants can cause cracking of these nickel-based alloy through a process called primary water stress corrosion cracking (PWSee). Inspection of the head penetrations to ensure the integrity of the head penetrations has been interested since reactor coolant leakages were found at U. S. reactors in 2000 and 2001. The complex geometry of the head penetrations and the very low echo amplitude from the fine, multiple flaws due to the nature of the SCC made it difficult to detect and size the flaws using conventional pulse-echo UT methods. Time-of-flight-diffraction technique, which utilizes the time difference between the flaw tips while pulse-echo does the flaw response amplitude from the flaw, has been selected for this inspection for it's best performance of the detection and sizing of the head penetration see flaws. This study defines the limits of the detectable and accurately sizable minimum flaw size which can be detected by the General TOFD and the Delta TOFD techniques for circumferentially and axially oriented flaws respectively. These results assures the reliability of the inspection techniques to detect and accurately size for various kind of flaws, and will also be utilized for the future development and qualifications of the TOFD techniques to enhance the detecting sensitivity and sizing accuracy of the flaws of the reactor head penetrations in nuclear power plants.
고각 환형 암시야 주사투과전자현미경기법과 투과전자현미경기법을 이용한 상용 청색 발광다이오드의 종합적인 구조분석
김동엽,홍순구,정태훈,이상헌,백종협,Kim, Dong-Yeob,Hong, Soon-Ku,Chung, Tae-Hoon,Lee, Sang Hern,Baek, Jong Hyeob 한국재료학회 2015 한국재료학회지 Vol.25 No.1
This study suggested comprehensive structural characterization methods for the commercial blue light emitting diodes(LEDs). By using the Z-contrast intensity profile of Cs-corrected high-angle annular dark field scanning transmission electron microscope(HAADF-STEM) images from a commercial lateral GaN-based blue light emitting diode, we obtained important structural information on the epilayer structure of the LED, which would have been difficult to obtain by conventional analysis. This method was simple but very powerful to obtain structural and chemical information on epi-structures in a nanometer-scale resolution. One of the examples was that we could determine whether the barrier in the multi-quantum well(MQW) was GaN or InGaN. Plan-view TEM observations were performed from the commercial blue LED to characterize the threading dislocations(TDs) and the related V-pit defects. Each TD observed in the region with the total LED epilayer structure including the MQW showed V-pit defects for almost of TDs independent of the TD types: edge-, screw-, mixed TDs. The total TD density from the region with the total LED epilayer structure including the MQW was about $3.6{\times}10^8cm^{-2}$ with a relative ratio of Edge- : Screw- :Mixed-TD portion as 80%: 7%: 13%. However, in the mesa-etched region without the MQW total TD density was about $2.5{\times}10^8cm^{-2}$ with a relative ratio of Edge- : Screw- :Mixed-TD portion of 86%: 5%: 9 %. The higher TD density in the total LED epilayer structure implied new generation of TDs mostly from the MQW region.
김현철(Hyun Chul Kim),최찬오(Chan Oh Choi),정태훈(Tae Hoon Chung),서영숙(Young Suk Seo),박성배(Sung Bae Park),박관규(Kwan Kyu Park),이상숙(Sang Sook Lee) 대한내과학회 1991 대한내과학회지 Vol.40 No.4
A clinical observation was made on 150 adult patients with idiopathic nephrotic syndrome according to their histological types classified by light microscopic findings at Keimyung University Hospital for the past 6 years. The majority of patients with nephrotic syndrome were young (mean age, 29.6), and the 80% of patients were less then 40 years old. The male-to-female ratio was 2.2:1 with male predominence. Histopathologic findings of 150 renal biopsy tissues were classified into minimal change nephrotic syndrome (MCNS) 58%, focal glomerulosclerosis (16. 7%), membranoproliferative glomerulonephritis (10. 0%), membranous nephropathy (9.3%), mesangial proliferative glomerulonephritis (3.3%), and chronic glomerulonephritis (2.7%). The incidence of hypoalbuminemia and hypercholesterolemia was more frequent in MCNS than in other histological types. Microscopic hematuria (RBC≥3 in HPF) was seen in 45% of MCNS and in 66% of other histological types. The time interval between the onset of symptoms and diagnosis was shorter in MCNS than in other histological types. The average age at onset was youngest in MCNS (mean age, 25) and oldest in membranous nephropathy Microscopic hematuria, renal insufficiency, and hypocomplementemia was most frequently seen in membranoproliferative glomerulonephritis than in other histological types, and hypertension was most frequent in membranous nephropathy. In reaction to steroid therapy, the highest response rate was seen in MCNS, which showed complete remission in 54%, partial remission in 21%, and no response in 24%. Meanwhile, those with other histological types showed only partial remission or no response at all. Sixty-six percent of patients with with MCNS experienced remission in 4 weeks, and 93% of patients with MCNS went into remission within 8 weeks of steroid therapy. Major side effects of steroid therapy were Cushingoid appearance (27.1%, facial ance (10. 2%, diabetes mellitus (8.5%), and peptic ulcer (3.4%), in decreasing order of frequency. With cyclophosphamide therapy, complete remission was obtainded in 60% of patients with MCNS, while 20% of patients with MCNS had partial remission. In contrast, none of the patients with other histological types except mesangial proliferative glomerulonephritis showed complete remission During the follow-up period, the majority of patients with MCNS were in complete or partial remission, wherease patients with other histological types showed persistent nephrotic syndrome. Five patients died within 2 years after diagnosis, 2 from miliary tuberculosis and the other 3 from uremia, diabetic ketoacidosis, and suicide.