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조익현(Ig-hyun Cho),이충호(Choong-ho Lee),권창영(Chang-young Kwon),김준대(Jun-dea Kim),윤동한(Dong-han Yoon) 한국정보기술학회 2007 Proceedings of KIIT Conference Vol.2007 No.-
이 논문은 신호 f(t)의 실제적인 스케일 정보를 나타내는 웨이브렛 플랜을 중심으로 연속 웨이브렛 역변환의 특성에 대하여 논하였다. 웨이브렛 변환에 비해 역변환의 적용이 상대적으로 미비한 이유는 수치적인 연산의 복잡성에 기인한 것이며, 이 논문은 웨이브렛 역변환의 안정된 복원을 위한 방법에 대하여 연구하였다. 웨이브렛 역변환이 안정적으로 실현될 경우 신호 f(t)에 대한 실제적인 스케일 정보를 지니고있는 웨이브렛 플랜 이라는 새로운 “시간-스케일” 공간을 구할 수 있으며, 이는 완전한 멀티 필터 뱅크 시스템과 동일한 특성을 나타낸다. 즉 연속 웨이브렛 변환을 통해 신호 f(t)의 모든 스케일 성분을 독립적으로 주파수 전체 대역에 걸쳐 분산하고 다시 역변환을 통해 원래의 신호를 복원하는 과정은 필터뱅크이론의 분석(analysis)과 합성(synthesis) 과정과 일치한다. 이 논문에서는 연속 웨이브렛 역변환을 이용하여 “시간-스케일” 필터를 통한 신호 f(t)의 스케일 분해와 웨이브렛 멀티 필터 뱅크이론에 대하여 논하였다. This paper is contribute to Inverse continuous wavelets transform which permits to determine real “time-scale” plan. The application of Inverse wavelets transform is not yet represented because of the numerical difficulty. If the signal can be reconstructed stably by Inverse Continuous Wavelets Transform, the multi scale filter bank system which composed by analysis and synthesis process can be designed. In this work, we represent the Inverse Continuous Wavelets Transform which leads to nearly perfect reconstruction of signal and the multi-scale filter bank system.
조익현(Ig-hyun Cho),전후동(Hoo-dong Jeon),김준대(Jun-dea Kim),백청택(Chung-taek Baik),박상우(Sang-woo Park),윤동한(Dong-han Yoon) 한국정보기술학회 2007 Proceedings of KIIT Conference Vol.2007 No.-
본 연구는 외부전극 형광램프를 구동하기 위한 인버터를 제작하였다. 인버터의 구동방식은 Half- Bridge 방식과 Full-Bridge 방식을 사용하여 단일램프 특성과 멀티램프 특성을 비교하였다. EEFL의 전기적 특성을, 전압, 선류, 주파수, 효율에 따라 분석하였고 전기적 실험 조건을 제시하였다. This research manufactured inverter to run external electrode fluorescent lamp. Drive method of inverter compared single lamp characteristic and multi lamp characteristic using Half-Bridge method and Full-Bridge method. Analyzed electrical special quality of EEFL by voltage, current, frequency, efficiency and presented electrical experiment condition.
마이크로프로세서를 이용한 디지탈 제어방식의EEFL Inverter 연구
김준대(Kim jun-dea),조익현(Ig-hyun Cho),이충호(Choong-ho Lee),권창영(Chang-young Kwon),윤동한(Yoon dong-han) 한국정보기술학회 2007 Proceedings of KIIT Conference Vol.2007 No.-
본 논문에서는 마이크로프로세서를 이용하여 Dimming control이 있는 EEFL inverter 설계방법을 제안하였다. EEFL Inverter는 half-bridge 방식을 이용하였으며 마이크로 프로세서로는 Megal28을 사용하였고 프로그램은 C언어를 이용하였으며 제작한 Invertor를 이용하여 효율 실험 및 부하실험을 수행하였다. Design and implementation method of Dimming mode EEFL Inverter using micro-processor is described in this paper. The EEFL Invertor use a half-bridge topology. micro-processor use MEGAl28 and program language use C language. Achieved an efficient experiment and a load experiment using EEFL Inverter that design.
4대강 유역 및 공단지역 환경 중 PFOS 및 PFOA의 잔류수준 비교평가
조천래 ( Chon Rae Cho ),엄익춘 ( Ig Chun Eom ),김은주 ( Eun Ju Kim ),김수진 ( Sue Jin Kim ),최경희 ( Kyung Hee Choi ),조현서 ( Hyeon Seo Cho ),윤준헌 ( Jun Heon Yoon ) 한국환경분석학회 2009 환경분석과 독성보건 Vol.12 No.4
PFCs are group of fluorochemicals that have been produced and used for over 50 years for various purpose including soil/stain resistance and surfactant applications. These chemicals were degraded to Perfluorooctane sulfonate (PFOS) and Perfluorooctanoic acid (PFOA) that were kinds of persistence metabolites. Previous studies showed that these chemicals can be accumulated in various environmental media. In this study, the concentration level of PFOS and PFOA were measured in 59 samples collected from 4 major river watersheds and 6 industrial complex areas in 2006 and 2007. Mean concentration of PFOS in water, sediment and soil were N.D.-1180.0 ng/L, N.D.-9.17 ng/g dry-wt. and N.D.-10.97 ng/g dry-wt. respectively. Mean concentrations of PFOA in water, sediment and soil were N.D.-13850.0 ng/L, N.D.-2.07 ng/g dry-wt. and N.D.-1.04 ng/g drywt., respectively. The concentration of PFOS in water samples were significant difference among river, industrial complex stream and waste water treatment effluent (p<0.05). But PFOA were no significant difference among those samples. These results suggested that concentration of PFOS in water was direct effected by industrial complex activities.
Oxidative stress in juvenile common carp (Cyprinus carpio) exposed to $TiO_2$ nanoparticles
Lee, Byoung Cheun,Kim, Kyung Tae,Cho, Jae Gu,Lee, Jae Woo,Ryu, Tae Kwon,Yoon, Jun Heon,Lee, Sang Hee,Duong, Cuong N.,Eom, Ig Chun,Kim, Pil Je,Choi, Kyung Hee 대한독성유전단백체학회 2012 Molecular & cellular toxicology Vol.8 No.4
Acute toxicity and oxidative stress caused by exposure of titanium dioxide nanoparticles ($TiO_2$-NPs) in juvenile common carp (Cyprinus carpio) were investigated. $TiO_2$-NPs solution was prepared using deionized water and dispersed by sonication. Juvenile carp were exposed to different concentrations (5, 10, 20, 40, and 80 mg/L) of $TiO_2$-NPs. $TiO_2$-NP characteristics (particle morphology, size distribution, and zeta-potential) were analyzed using transmission electron microscopy (TEM) and dynamic light scattering (DLS). Different tissue samples (skin, liver, brain, and gill) of fish were dissected, and the biochemical responses (catalase [CAT] and glutathione S-transferase [GST] activities) were measured. The results showed that acute exposure to $TiO_2$-NPs induced GST and CAT levels to vary in all observed organs. The effective concentration of $TiO_2$-NPs was 20 mg/L in the liver and brain and 40 mg/L in the gill. Histopathological changes were as follows: (1) skin: hypertrophy and increased number of mucous cells and thickening of the epidermal layer; (2) gill: hypertrophy of chloride cells, degeneration of mucous cells, and increased acidification of mucous cells; and (3) liver: hyperplasia and cytoplasm vacuolation of hepatic cells. No lethal effects were observed during the acute test. Our results show that there is a potential risk of $TiO_2$-NP exposure to aquatic organisms in the environment.