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오늘 본 자료
정윤성,신정환,장철훈,손한철,정석훈,이용성,김병국,이채훈,김성률 대한화학요법학회 1999 대한화학요법학회지 Vol.17 No.2
배경 : Penicillin 내성 폐렴구균의 분리율이 증가하고 있으며 내성균에 의한 중증 감염은 치료에 대한 반응이 나쁘다. 이에 본 연구에서는 영남지역에 있는 병원들의 임상 검체에서 분리된 폐렴구균들 대상으로 항균제 감수성 검사를 실시하여 폐렴구균에 의한 감염증의 적절한 치료에 도움을 주고자 하였다. 방법 : 영남지역의 5개 병원에서 분리된 폐렴구균 61균주를 대상으로 디스크 확산법 또는 한천희석법으로 감수성 검사를 실시하였다. 결과 : Oxacillin 디스크를 이용한 penicillin 감수성 검사에서는 내성율이 91.2%였고 한천희석법에서는 감수성 9.8%, 중등도 및 고도 내성 각각 37.7%, 52.5%였다. 디스크 확산법에서 6개의 감수성 균주 중 한 개를 찾아내는데 실패하여 16.7%의 major error를 나타내었다. Ceftriaxone은 감수성 45.9%, 중등도 및 고도 내성 각각 42.6%, 11.5%였다. Penicillin과 ceftriaxone에 모두 내성인 경우는 전체의 54.1%, penicillin 내성 균주의 60.0%였다. 디스크 확산법에 의한 감수성 검사에서 vancomycin은 모두 감수성이었고, chloramphenicol 21%, erythromycin 82%, trimethoprim/sulfamethoxazole 79%, tetracycline 84%의 내성을 보였고 다약제 내성율은 59%였다. 결론 : 영남 지역 임상 검체에서 분리된 폐렴구균의 항균제 내성 비율이 매우 높아서 폐렴구균에 의한 중증 감염증의 적절한 치료를 위해서는 penicillin 이외의 여러 항균제에 대한 감수성 검사가 반드시 필요하다고 생각한다. Background : The resistance rate of Streptococcus pneumoniae to penicillin has been rapidly increasing worldwide, and treatment failures coupled with severe infections due to penicillin-resistant S. pnemoniae have been reported. In this study, we evaluated antimicrobial susceptibilities of S. pnemoniae isolated from clinical specimens in the Southeastern area of Korea. Methods: A total of 61 pneumococcal isolates obtained from patients who visited or were admitted to 5 hospitals in the Southeastern area of Korea during the period 1997 to 1998. Antimicrobial susceptibility tests for 61 isolates were performed using disk diffusion or agar dilution methods. Results : Penicillin susceptibility tests showed that 91.8% and 90.2% of isolates were not susceptible to penicillin by oxacillin disk diffusion and dilution methods, respectively. Moderate and high level resistance rate to penicillin were 37.7% and 52.5%, respectively. Using the oxacillin disk diffusion method, we failed to find one among 6 penicillin-susceptible isolates, with 16.7% major error. Moderate and high level resistance rate to ceftriaxone were 42.6% and 11.5%, respectively. The concomitant resistance rate to penicillin and ceftriaxone was 54.1% of the total and 60.0% of penicillm-resislant isolates. Resistance rates of the isolates to vancomycin, chloramphenicol, erythromycin, trimethoprim/sulfamethoxazole, and tetracycline were 0%, 21%,82%, 79%, and 84%, respectively. Multidrug-resistance to three or more classes of antimicrobials was 59.0%. Conclusion: In this study, we revealed that extremely high resistance rate of 5. pneumoniae to many antimicrobial agents in Southeastern area of Korea. Therefore, accurate susceptibility tests to penicillin, 3rd generation cephalosporin and other antimicrobial agents are highly recommended for adequate treatment of severe pneumococcal infections.
진동의 주파수분석을 통한 결함 식별 - 회전기계를 중심으로-
정윤성,왕지남,김광섭,Jeong, Yoon-Seong,Wang, Gi-Nam,Kim, Gwang-Sub 한국정밀공학회 1995 한국정밀공학회지 Vol.12 No.11
This paper pressents a condition-based maintenance (CBM) method through bibration analysis. The well known frequency analysis is employed for performing machine fault diagnosis. The statistical control chart is also applied for analyzing the trend of the bearing wear. Vibration sensors are attached to prototype machine and signals are continuously monitored. The sampled data are utilized to evaluate how well the fast fourier transform(FFT) and the statistical control chart techniques could be used to identify defects of machine and to analyze the machine degradation. Experimental results show that the propowed approach could classify every mal-function and could be utilized for real machine diagnosis system.
직응집성형법을 이용한 질화규소의 실형상 성형공정 및 성형특성
정윤성,정연길,백운규,Jung, Yun-Sung,Pagnoux, Cecile,Jung, Yeon-Gil,Paik, Un-Gyu 한국세라믹학회 2002 한국세라믹학회지 Vol.39 No.3
본 연구에서는 복잡 형상의 세라믹체를 효율적으로 성형할 수 있어 새로운 성형기법으로 부각되고 있는 직응집성형(Direct Coagulation Casing, DCC)공정기술에 관하여 콜로이드 계면화학을 이용하여 연구하였다. 높은 고형분량을 가지는 안정된 질화규소 슬립을 제조하기 위하여 분산제, 소결조제 그리고 응집제 각각이 다양한 공정변수에 미치는 영향에 대하여 평가하였다. 1.0 wt% Tetraethylammonium Hydroxide(TEAH)를 첨가하여 염기영역에서 소결조제를 포함한 안정된 51vol%의 질화규소 슬립을 제조할 수 있었다. 질화규소 슬립은 첨가된 $Al(CH_3COO)_2OH$의 온도증가에 따른 열분해를 이용하여 직응집성 유도하였다. 염기영역에서 $Al^{3+}$ 이온들이 aluminum hydroxide$(Al(OH)_3)$ 석출되면서 슬립내 $OH^-$ 농도를 감소시켜 질화규소 슬립을 직응집시켰다. In this proposed study, a new emerging shape forming technique Direct Coagulation Casting(DCC) which enables to fabricate complex-shaped ceramic parts has been investigated using colloid surface chemistry. Various process variables affected by dispersant, coagulation agent and sintering additives, have been evaluated in order to achieve highly concentrated stabilized silicon nitride suspensions. A high solid loading of 51 vol% in the dispersed silicon nitride suspension was prepared with 1.0wt% Tetraethylammonium Hydroxide (TEAH), which obtained a stable silicon nitride suspension with sintering additives $(Al_2O_3\;and\;Y_2O_3)$ in alkaline regions. The addition of hydroxyaluminium diacetate into the suspension, which decomposed at elevated temperatures, led to coagulate of a silicon nitride suspension. In a basic medium, aluminum ions precipitated to aluminum hydroxide $(Al(OH)_3)$, leading to decreased $OH^-$ concentration and, thus, coagulated suspension.
실리콘 단결정 잉곳용 석영유리 도가니의 brownish ring에 대한 연구
정윤성,최재호,민경원,변영민,임원빈,노성훈,강남훈,김형준,Jung, YoonSung,Choi, Jae Ho,Min, Kyung Won,Byun, Young Min,Im, Won Bin,Noh, Sung-Hun,Kang, Nam-Hun,Kim, Hyeong-Jun 한국결정성장학회 2022 한국결정성장학회지 Vol.32 No.3
A brown ring (hereinafter referred to as BR) on the inner surface of a quartz glass crucible used in the manufacturing process of a silicon ingot for semiconductor wafers was studied. BR is 20~30 ㎛ in size and has an asymmetric brown ring shape. The size and distribution of BR were different depending on the crucible location, and the size and distribution of BR were the largest and most abundant in the round part with the highest crucible temperature during Si ingot growth. BR contains cristobalite, which has a higher coefficient of thermal expansion than quartz glass, so it is considered that surface cracks appear. The color development of BR and pin holes are presumed to be due to oxygen vacancies.
GLOBAL EXISTENCE OF WEAK SOLUTIONS FOR A KELLER-SEGEL-FLUID MODEL WITH NONLINEAR DIFFUSION
정윤성,강경근,김재우 대한수학회 2014 대한수학회지 Vol.51 No.3
We consider the Cauchy problem for a Keller-Segel-fluid mo- del with degenerate diffusion for cell density, which is mathematically formulated as a porus medium type of Keller-Segel equations coupled to viscous incompressible fluid equations. We establish the global-in- time existence of weak solutions and bounded weak solutions depending on some conditions of parameters such as chemotactic sensitivity and consumption rate of oxygen for certain range of diffusive exponents of cell density in two and three dimensions.