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- 저자 : 이현동(Lee Hyun Dong) (검색결과 253 건)
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이현동,김충년,박광서,이광식,이동인,Lee, Hyun-Dong,Kim, Chung-Nyun,Park, Kwang-Seo,Lee, Kwang-Sik,Lee, Dong-In 대한전기학회 2000 전기학회논문지C Vol.55 No.12
This paper deals with the multiresolution analysis of wavelet transform for partial discharge(PD). Test arrangement is based on the needle-plane electrode system and applied AC high voltage. The measured PD signal was decomposed into "approximations" and "details". The approximation are the high scale, low-frequency components of the PD signal. The details are the low-scale, high frequency components. The decomposition process are iterated to 3 level, with successive approximation being decomposed in turn, so that PD signal is broken down into many lower-resolution components. Through the procedure of signal wavelet transform, signal noise extraction and signal reconstruction, the signal is analyzed to determine the magnitude of PD.
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브롬이온 존재하에서 오존에 의한 암모니아성 질소의 산화에 관한 연구
이현동,종궁공 (宗宮功),이의신 ( Hyun Dong Lee,Isao Somia,Eui Sin Lee ) 한국물환경학회 1995 한국물환경학회지 Vol.11 No.3
This study was conducted in order to elucidate basic conditions for the oxidation of ammonia-nitrogen with ozone in bromide containing water. The denitrification rates were observed under the batch and the continuous types at various concentrations of Br, initial pH and ozone dosages. The result showed that the oxidation reaction of ammonia-nitrogen with ozone was not occurred in the presence of BrO₃, but denitrification and nitrification took place in the presence of Br. This implies that OBr functioned as the oxidant for the oxidation of ammonia-nitrogen. The reaction rate of denitrification was quasi Zero-order with respect to dissolved nitrogen compound concentration and the reaction rate constant, K can be expressed in terms of [Br] and [O₃]: K=0.023 [O₃]·[1-10 ^(m [Br])] The initial pH effect on denitrification rate was not significant in the range of pH 5.6∼10 but the removal rate was low at pH 3 presumably due to the retardation of OBr production under the low pH condition. Also with raising Br concentration, nitrification rate decreased but with raising initial pH, denitrification rate increased because ozone can react with NH₄ at fast rate. The denitrification kinetics obtained from batch experiment was used and applied to the continuous type process.
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공기 살균 장치 적용 팽이버섯 재배사의 Listeria Innocua 저감 효과
이현동,유병기,서다솜,김세리,이찬중,곽강수,Lee, Hyun-Dong,Yu, Byeong-Kee,Seo, Da-Som,Kim, Se-Ri,Lee, Chan-Jung,Kwak, Kang-Su 한국버섯학회 2021 한국버섯학회지 Vol.19 No.3
팽이버섯 재배사의 Listera속 미생물 살균을 위하여 공기 살균 장치가 부착된 파일럿 버섯 재배사를 개발하여 물리적, 화학적 살균처리에 대한 살균 효과 검증실험을 수행하였다. 파일럿 버섯 재배사의 내부 온도는 상부 6.62℃±0.30, 중간 6.46℃±0.24, 하부 6.48℃±0.25, 습도는 79.97%±4.42, 79.43%±4.06, 79.94±4.30%로 설정 온도 6.5℃, 상대습도 75%에 근사하게 제어되었다. 공기 살균 장치 적용에 적합한 팽이버섯 재배단계는 생육단계 조건인 온도 6.5~8.5℃, 습도 70~80% 범위였고 유사 조건에서 이온 클러스터 발생기의 오존 발생농도는 160 ppb 수준으로 나타났다. 물리적 살균처리 후 Listeria innocua의 생존율은 이온클러스터 살균의 경우 0.1~0.9%, UV공기 살균은 9.3~10.6%로 나타났고, 화학적 살균처리인 75% 에탄올과 3% 유기산 수용액 처리구에서는 모두 사멸하는 것으로 나타났다. 소재에 대한 Listeria innocua 생존율은 금속시편의 경우 9.3~10.6%, 플라스틱 권지 9.9~16.2%로 나타났는데, 특히 권지의 거친면에서 생존율이 높게 나타났다. 본 연구 결과에 따르면 버섯 재배사의 Listeria균 발생을 억제하기 위해서 금속 소재로 구성된 재배사 벽면과 재배 선반에 대해서는 이온클러스터 공기 살균처리가 노동력을 절감하면서 살균 가능한 방법이며, 플라스틱 재질의 권지의 경우 화학적 살균처리가 효과적인 것으로 나타났다. For sterilization of microorganisms of the Listeria genus contaminating enoki mushroom, pilot mushroom grower equipped with air sterilization devices were developed. Sterilization experiments were performed using physical and chemical treatments. Internal temperature and humidity were controlled, maintaining 6.62℃±0.30 in the upper shelves, 6.46℃±0.24 in the middle shelves, and 6.48℃±0.25 in the lower shelves. Humidities were 79.97%±4.42, 79.43%±4.06, and 79.94±4.30%, respectively, with a temperature setting of 6.5℃, and a relative humidity of 75%. A suitable enoki mushroom cultivation stage for air sterilizer application was during the growth stage, with temperature in the 6.5~8.5℃ range, and humidity of 70~80%. At these same internal conditions, the ozone concentration in the mushroom cultivator was found to be 160 ppb during ion-cluster generator operation. After physical sterilization, the Listeria innocua survival rate was 0.1 to 0.9% using ion cluster sterilization, and 9.3 to 10.6% using UV air sterilization. The Listeria innocua survival rates on different materials were 9.3~10.6% on the metal specimen, and 9.9~16.2% on the plastic wrapper. The survival rate was particularly high on the rough side of the plastic wrapper. Ion cluster air sterilization is a labor-saving and effective method for suppressing the occurrence of Listeria bacteria on mushroom growers walls and shelves. For the plastic wrapper, chemical sterilization is more effective than physical sterilization.
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이현동,정원식,지재성 ( Hyun Dong Lee,Won Sik Chung,Chai Sung Gee ) 한국물환경학회 1998 한국물환경학회지 Vol.14 No.1
Water quality in water distribution system is changed biological, physicochemical and organoleptic qualities, and then it has been more worse. Chlorine residual was used to as indicator for prediction of water quality behavior, characteristics and ensurement of regulatory requirment. Therefore, M&O of chlorine residual is to be important for water quality management in water distribution system. This study was performed to study the relationship for water quality changes and characteristic of chlorine residual decay according to pipe type and diameter, hydraulic effect, and water quality parameter. Results of this study indicated decay coefficient of chlorine residual was to characterized with pipe type and diameter. Also it was to different hydraulic effect and initial chlorine residual concentration and water quality parameter as temperature, TOC, etc.
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이현동(Hyun Dong Lee),이지은(Ji Eun Lee),곽필재(Phill Jae Kwak) 大韓環境工學會 2008 대한환경공학회지 Vol.30 No.3
본 연구에서는 국내에서의 생산되는 강관의 도복장 재료 및 방법별로 관체 시편을 이용하여 도복장강관의 성능을 시험하였다. 도복장강관의 원관의 물성 및 화학조성의 분석결과 모두 기준에 적합하였다. 강관의 도복장 재료의 물성시험 결과, 블론아스팔트와 콜타르에나멜은 비용이 저렴하고 기계적 성질은 매우 우수하나, 유기용매에 녹는 단점을 지니고 있고, 도복장강관이 도복장 재료로서 성능이 떨어지는 것으로 나타났다. 또한 두껍게 도복할 경우, 강관 자체의 하중이 필요 이상으로 높아지는 문제가 발생할 수 있다. 당김강도 시험과 음극박리 시험결과, PE-3층 도복장방식이 우수하였으며, PE의 도복장방법에 따라서는 압출식(T-Die) 3층 폴리에틸렌(PE 3-Layer)이 분말용착식 폴리에틸렌(PE Fluidized)보다 당김강도가 강하며 음극박리 면적도 작았다. 압출식(T-Die) 3층 폴리에틸렌(PE 3-Layer)은 기계적 특성, 열적 특성 모두 우수하였고, 내화학성도 뛰어났다. 액상에폭시는 수지 선정과 경화 조건에 따라서 도장재의 특성을 변화시킬 수 있다. 본 시험에서 사용된 폴리우레탄은 강관과의 접착력도 에폭시에 비하여 낮았으며, 수분 흡수율은 에폭시 보다 높은 결과를 나타내었다. 폴리우레탄을 도복장재료로 사용하기 위해서는 우레탄의 기본물성과 최적의 도장조건을 도출하는 연구가 진행되어야 할 것으로 판단된다. 본 연구에서 실험한 시편 중에서는 현재 압출식으로 제조한 PE-3층 도복장방법이 가장 우수한 것으로 평가되었지만, 앞으로 기타 다른 도복장재료와의 추가 검증시험이 필요할 것으로 판단된다. Coal-tar enamel, blown asphalt and polyethylene have been used as wrapping materials of steel pipe in Korea. Currently, every manufacturer produces wrapped steel pipes with different materials and methods, and little research has been performed to get on wrapping methods and materials. In this research, properties of wrapping material of steel pipe used for water supply have been evaluated. All of the materials tested in this work were found to meet the standard. Among the wrapping materials of steel pipe tested, blown asphalt and coal-tar enamel were reasonable in price, and their mechanical properties were excellent. The quality of the wrapped steel pipes was being melted easily in organic solvent. When coated thick, the load of the steel pipes was higher than necessary. Tensile strength of cathode exfoliation and PE 3-layer wrapping method was excellent. The pulling intensity of T-Die PE 3-layer was stronger than PE fluidized in PE wrapping method. Cathode exfoliation area was smaller than PE fluidized. Mechanical property and thermo-property of T-Die PE 3-layer were excellent and its anti-chemical property was great. Liquid epoxy can change the property of coating materials depending on the hardening condition and resin selection. Polyurethane used in this test showed a less adhesive strength with steel pipes than epoxy. Moisture absorbance rate was higher than Epoxy`s, however. To utilize polyurethane as wrapping materials, basic property of the matter should be improved followed by finding the best suited coating condition. The method of PE 3-layer by extrude method appeared to be the best in this study. However, identification of other wrapping materials requires further additional tests.
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2008년 상주시 일개 고등학교에서 발생한 바실루스 세레우스 식중독 유행에 관한 역학조사
이현동(Hyun-Dong Lee),이순옥(Sun-Ok Lee),임현술(Hyun-Sul Lim),이경찬(Kyoung-Chan Lee),장규진(Kyu-Jin Chang),강영아(Young-A Kang) 한국역학회 2008 Epidemiology and Health Vol.30 No.2
Purpose: In May 2008, a diarrhea outbreak occurred among students of in a girls’ high school (S school) in Sangju-si, Korea. An epidemiological investigation was carried out to clarify the cause and transmission route of the outbreak. Methods: S school has been providing meals directly since July 2007. We conducted a questionnaire survey among 591 persons, and examined 283 rectal swabs and 98 environmental specimens. The patient case was defined as a member of S school who had diarrhea more than one time in a day, accompanied with one or more symptoms among abdominal pain or tenesmus from May 19th to May 26th 2008. Results: The attack rate was 24.0%. Bacillus cereus were cultured from three of the rectal swabs and five of the preserved foods. It was suspicious that contamination was possible in seasoning vegetables, and we found some foods were seasoned with spices after being cooled by moving cooler for about 20 minutes. Enterotoxin positive B. cereus were cultured from two foods cooled by moving cooler. Enterotoxin negative B. cereus were cultured from two environmental specimens of the moving cooler. Conclusions: We presumed the cause of the diarrhea outbreak in S school was food poisoning by B. cereus. Because enterotoxin positive B. cereus were cultured from rectal swabs and foods, and the symptoms were corresponded. We estimated the outbreak was occurred by this process that B. cereus in the moving cooler contaminated foods during cooling and then rapidly proliferated.
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