가정용 가습기의 사용자 습관에 따른 실내공기 중 바이오에어로졸의 발생특성

김익현,김기연,김대근,Kim, Ik-Hyeon,Kim, Ki Youn,Kim, Daekeun 한국환경보건학회 2012 한국환경보건학회지 Vol.38 No.6

Objectives: This study was performed in order to evaluate the generation characteristics of airborne bacteria and fungi while operating a household humidifier, in consideration of user habits. Methods: Microbial samples were collected in a closed chamber with a total volume of 2.76 $m^3$, in which a humidifier was operated according to experimental strategies. A cultivation method based on the viable counts of mesophilic heterotrophic bacteria and fungi was performed. Experimental strategies were divided into three classes: the type of water in the water reservoir (tap water, cooled boiled water); the frequency of filling the reservoir (refill every day, no refill); and the sterilization method (sterilization function mode, humidifier disinfectants). Results: Significant increases in the concentration of airborne bacteria were observed while the humidifier was in operation. The concentration had increased to 2,407 $CFU/m^3$ by 120 hours when tap water filled the reservoir without any application of sterilization, while for cooled boiled water, it was merely 393 $CFU/m^3$ at a similar time point. Usages of disinfectant in the water tank were more effective in decreasing bioaerosol generation compared to sterilization function mode operation. Generation characteristics of airborne fungi were similar to those of bacteria, but the levels were not significant in all experiments. Calculated exposure factor can be used as an indicator to compare biorisk exposure. Conclusion: This study identified the potential for bioaerosol generation in indoor environments while operating a household humidifier. User practices were critical in the generation of bioaerosol, or more specifically, airborne bacteria. Proper usage of a humidifier ensures that any biorisks resulting from generated bioaerosol can be prevented.

Effect of Different Sol Concentrations on the Properties of Nanocrystalline ZnO Thin Films Grown on FTO Substrates by Sol-gel Spin-coating

김익현,김영규,남기웅,김동완,Minju Park,Haeun Kim,Wookbin Lee,임재영,김종수,김진수 한국물리학회 2014 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.65 No.4

Nanocrystalline ZnO thin films grown on fluorine-doped tinoxide (FTO) substrates were fabricatedusing the spin-coating method. The structural and the optical properties of the ZnO thin filmsprepared using different sol concentrations were investigated by using field-emission scanning electronmicroscopy (FE-SEM), X-ray diffractometry (XRD), photoluminescence (PL) measurements,and ultraviolet-visible (UV-vis) spectrometry. The surface morphology of the ZnO thin films, asobserved in the SEM images, exhibited a mountain-chain structure. XRD results indicated thatthe thin films were preferentially orientated along the direction of the c-axis and that the grain sizeof the ZnO thin films increased with increasing sol concentration. The PL spectra showed a strongultraviolet emission peak at 3.22 eV and a broad orange emission peak at 2.0 eV. The intensities ofdeep-level emission (DLE) gradually increased with increasing sol concentration from 0.4 to 1.0 M. The transmittance spectra of the ZnO thin films showed that the ZnO thin films were transparent(85%) in the visible region and exhibited sharp absorption edges at 375 nm. Thus, The Urbachenergy of ZnO thin films decreased with increasing sol concentration.

아연을 코팅한 테프론 기판 위에 성장된 산화아연 박막의 후열처리 효과

김익현 ( Ik Hyun Kim ),남기웅 ( Gi Woong Nam ),이철언 ( Cheol Eon Lee ),김동완 ( Dong Whan Kim ),최현광 ( Hyon Kwang Choi ),김양수 ( Yang Soo Kim ),김진수 ( Jin Soo Kim ),김종수 ( Jong Su Kim ),손정식 ( Jeong-sik Son ),임재영 ( Ja 대한금속재료학회(구 대한금속학회) 2015 대한금속·재료학회지 Vol.53 No.6

ZnO thin films were first grown on Zn-coated Teflon substrates using a spin-coating method, with various post-heating temperatures. The structural and optical properties of the ZnO thin films were then investigated using field-effect scanning-electron microscopy, X-ray diffractometry, and photoluminescence (PL) spectroscopy. The surface morphology of these ZnO thin films exhibited dendritic structures. With increasing post-heating temperature, all samples preferentially exhibited preferential c-axis orientation and increased residual tensile stress. All of the films exhibited preferential c-axis orientation, and the residual tensile stress of those increased with increasing post-heating temperature. The near-band-edge emission (NBE) peaks were red-shifted after post-heating treatment at 400 ℃. The intensity of the deep-level emission (DLE) peaks gradually decreased with increasing post- heating temperature. Moreover, the narrowest ‘full width at half maximum’ (FWHM) and the highest intensity ratio of the NBE to the DLE for thin films, were observed after post-heating at 400 ℃. The ZnO thin films fabricated with the 400 ℃ post-heating process provided the highest crystallinity and optical properties.(Received March 04, 2014)

실험실 규모 하수슬러지 퇴비화공정에서 기계적 교반이 배출가스 내 부유세균과 내독소의 발생특성에 미치는 영향

김익현(Ik Hyeon Kim),김기연(Ki Youn Kim),배재근(Chae Gun Phae),김대균(Dae Kyun Kim) 大韓環境工學會 2012 대한환경공학회지 Vol.34 No.3

본 연구는 퇴비화 공정에서 발생되는 배출가스 내 생물학적 인자의 발생 특성을 파악하기 위하여 퇴비단 온도변화에 따른 부유세균과 내독소의 발생농도를 관찰하였다. 실험은 도시하수슬러지를 대상으로 실험실 규모의 기계적 교반이 가능한 퇴비화 장치(반응기 부피 0.06 m3)에서 실시되었다. 부유세균은 미교반 퇴비화 공정에서 퇴비단 온도변화와 유사한 발생경향을 보였지만 통계적 유의성이 다소 낮았고(p > 0.05), 최고 발생농도는 1.03 × 105 CFU/m3이었다. 내독소는 기계교반 퇴비화 공정에서 퇴비단의 온도변화와 유사한 발생경향을 보였으며(통계적 유의성: p < 0.05), 최고 발생농도는 1,415 EU/m3이었다. 퇴비화 공정의 기계적 교반이 퇴비단 미생물의 활성과 이에 따른 배출가스 중 내독소 발생 증가에 영향을 미친 것으로 보인다. 내독소의 발생농도와 부유세균의 발생농도는 유사한 발생 경향을 보였으며, 특히 미교반 퇴비화공정에서 높은 통계적 상관성이 나타났다(통계적 유의성: p < 0.01). This study was performed to investigate the concentration variation of airborne bacteria and endotoxin by the temperature in the compost pile in order to identify the generation characteristics of biological factors in the exhaust gases generated from labscale sludge compositing reactors (0.06 m3 of total reactor volume). Airborne bacteria showed the highest concentration of generation (1.03 × 105 CFU/m3) in the composting reactor without mechanical agitation, and similar change tendency to temperature variation of composting, but somewhat lower statistical significance (p > 0.05). In the compost reactor with mechanical agitation, endotoxin showed similar generation characteristic to temperature variation of composting (statistical significance; p < 0.05) and the highest generation concentration to 1,415 EU/m3. Mechanical agitation of the composting process affected activity of microorganism and positive generation of endotoxin in exhaust gases. Endotoxin and airborne bacteria showed similar tendency of generation, especially the highest statistical correlation was observed in the compost reactor without mechanical agitation (statistical significance; p < 0.01).

강화도의 지질별 지하수 중 자연방사성 물질의 특성

김익현(Ikhyun Kim),김문수(MoonSu Kim),함세영(Se-Yeong Hamm),김현구(Hyunkoo Kim),김동수(Dongsoo Kim),조성진(Seongjin Jo),이헌민(Heonmin Lee),황종연(Jongyeon Hwang),조훈제(Hunje Jo),박선화(Sunhwa Park),정현미(Hyenmi Chung) 대한자원환경지질학회 2018 자원환경지질 Vol.51 No.1

인천시 강화도의 지질별(중생대 화강암, 선캠브리아 편마암, 편암) 지하수의 자연방사성 물질과 수리지화학 성분의 특성을 연구하였다. 이 연구를 위하여, 8년 동안 69개 관정에서 지하수 시료를 채수하였다. 통계 분석을 이용하여 지하수의 수리지화학 성분과 자연방사성 물질의 관계를 분석하였다. 연구 지역 지하수의 수질유형은 Ca(Na)-HCO 3 형으로 나타났다. 우라늄은 3 개 지하수 시료에서 US EPA의 MCL(최대 오염 물질 수준)인 30 ug/L을 초과하였다. 라돈은 28개 지하수 시료에서 US EPA의 제안치인 AMCL(대체 최대 오염 물질 수준)인 4,000 pCi/L을 초과하였다. 모든 지하수 시료의 전알파(Gross-alpha)는 US EPA MCL인 15 pCi/L를 초과하지 않았다. 지하수에서의 우라늄과 라돈의 평균농도는 화강암에서 가장 높고, 그 다음으로 편마암, 편암의 순이다. 편암 지역의 라돈은 HCO 3 와 –0.40, 우라늄은 SO 4 과 0.54의 상관계수를 보였고, 편마암 지역의 경우 라돈은 우라늄과 0.55, 우라늄은 SO 4 과 0.41의 상관계수를 보였다. 요인분석에 의하면, 지질별로 각각 다른 거동특성을 가진다. 전체 지하수의 통계 분석 결과, 우라늄과 라돈 그리고 지화학 성분들 간에는 대체로 특이한 상관성을 나타내지 않았다. 자연방사성 물질의 거동과 운명을 보다 명확하게 이해하기 위해서는 자연방사성 물질의 수리지질학적, 지구화학적, 지질학적 특성에 대한 보다 상세한 연구가 요구된다. Groundwaters in different rock types (Mesozoic granite, Precambrian gneiss, and schist) of Ganghwa island, Incheon City were characterized by using naturally occurring radioactive materials (NORM) and hydrogeochemical constituents. For the study, groundwater samples from 69 wells had been collected over eight years. Statistical methods were applied to relate hydrogeochemical components and NORM in the groundwater samples. The groundwater samples belonged to Ca(Na)-HCO 3 types. The uranium concentrations in three groundwater samples exceeded 30 ug/L of United States Environmental Protection Agency (US EPA) maximum contaminant level (MCL). The radon concentrations in 28 groundwater samples exceeded 4,000 pCi/L (picocuries per Liter) of US EPA alternative maximum contaminant level (AMCL). Gross-alpha in all the groundwater samples did not exceed 15 pCi/L of US EPA MCL. The average concentrations of uranium and radon in groundwater were the highest in granite area, and then gneiss, schist areas in order. In schist area, the correlation coefficient (R) between radon and HCO 3 is –0.40 and R between uranium and SO 4 is 0.54. In gneiss area, the R between radon and uranium is 0.55 and the R between uranium and SO 4 is 0.41. According to factor analysis, each geological area shows different chemical characteristics. The statistical analysis of whole groundwater resulted in nearly no significant relationship among uranium, radon and chemical constituents. Subsequently, more detailed studies on hydrogeological, geochemical, and geological characteristics related to NORM are required to better understand the behavior and fate of NORM.

동하중을 받는 전장 브라켓에 대한 진동 내구 해석에 관한 연구

김익현(Ikhyun Kim),김성현(Sunghyun Kim),박상근(Sangkeun Park),김용석(Yongsuk Kim) 한국자동차공학회 2017 한국자동차공학회 부문종합 학술대회 Vol.2017 No.5

논문 : 재일 조선인 지식인의 민족관 -서경식을 중심으로-

김익현 ( Ik Hyun Kim ) 한국철학사상연구회 2012 시대와 철학 Vol.23 No.2

이 글의 목표는 코리언 디아스포라의 디아스포라성과 제국주의가 한민 족에게 남긴 상처를 통합적으로 사유하고 있는 서경식의 민족관의 특징을 살펴보려는 데 있다. 재일 조선인 지식인 김태영은 민족 정체성을 긍정적으로 사유하기는 하 지만, 그것을 개인을 억압하는 집단 정체성으로 간주하는 한계 때문에, 민족 에 대한 이론적 사유는 더 이상 전개시키지 않고, 실천적 차원에서 민족과 개인을 오가는 개인의 상황 대응적 선택을 중시하는 데 비해, 또 다른 재일 조선인 지식인 윤건차는 민족을 일본의 식민지배에서 유래하는 출신과 내력 에 대한 자각으로 그리고 그러한 자각을 통해서 머저리티와의 투쟁 속에서 표출되고 재구성되는 것으로 간주하면서, 이러한 민족이라는 회로를 거쳐야 비로소 세계시민으로서 거듭날 수 있음을 강조한다. 서경식이 이들과 다른 점은 본질주의적 민족론을 해체시키는 민족관을 제시하고 있다는 것과 그러한 민족관을 기초로 미래의 공동체를 구상하고 있다는 것이다. 서경식의 민족관에 따르면, 민족은 한 민족으로서의 본질적 요소들을 공유하고 있는 종족적 공동체가 아니라 제국주의의 폭력에 의해 국적도 다르고 언어도 다르고 문화도 상당히 변용되어 공통의 요소를 찾기 힘들지만, 그럼에도 역사적이고 현실적인 상처와 고통을 공유하고 그것에 저항하면서 서로 연대하는 집단이다. 그리고 그러한 민족이 구성하는 미래의 공동체는 더 이상 국가 폭력에 의한 차별과 억압이 존재하지 않는 곳이다. The purpose of this paper is to reflect together with cultural hybridity, multi-identities of Korean diaspora and hurt of the Korean people under Japanese imperialism. This reflection is best expressed through Jainichi Korean intellectuals as Kim Tae Young, Yoon Kun Cha and Seo Kyung Sik. The common point of them is that they have thought together with the positive function of multi-identities of Korean diaspora and pains of the Korean people in 20th century. Kim Tae Young takes the national identity as collective identity oppressing the individual. He does not develop the theoretical thinking of Nation and practically puts emphasis on situational choice between nation and individual. On the other hand, Yoon Kun Cha takes the Nation as the self-consciousness about history of Japan`s colonial rule and being reconstructed in struggle with the majority. He emphasizes that Jainichi Korean need to go through the nation to reform as cosmopolitan. Seo Kyung Sik suggests the new and original view of the nation and designs the nation from the point of view of Jainichi Korean. According to the creative view of nation that Seo Kyung Sik suggests, the nation is community to be formed in sharing the historical and realistic hurts and pains and standing up against them. And such community is the place that hurts, pains and discrimination are no longer in existence.

울산 울주지역 소규모 수도시설 지하수의 수리지화학적 특성 연구

김동수,김문수,조성진,김익현,이헌민,황종연,박선화,조훈제,김태승,김현구,Kim, Dongsoo,Kim, MoonSu,Jo, Sungjin,Kim, Ikhyun,Lee, Heonmin,Hwang, Jongyoen,Park, Sunhwa,Jo, Hunje,Kim, Taeseung,Kim, Hyunkoo 한국지하수토양환경학회 2017 지하수토양환경 Vol.22 No.5

The hydrogeochemical characteristics of groundwater in the small waterworks are examined with 81 groundwater samples in Ulju region, Ulsan. The pH ranged in 6.3-8.2 and did not exceed the drinking water standards. Electrical conductivity ranged from $50{\mu}S/cm$ to $1,719{\mu}S/cm$. It indicated that the electrical conductivities in groundwaters at the study area are relatively low, compared with other groundwaters in Ulsan area. The calcium concentrations in groundwaters ranged from 3.55 to 113.01 mg/L, and sodium concentrations ranged from 2.02 to 65.50 mg/L. Nitrate concentrations ranged from 0 to 100.56 mg/L and potassium concentrations ranged from N.D (not detected) to 2.50 mg/L. Major cations and anions were mainly derived from the water-rock interaction involving feldspar, gypsum and calcite. The groundwaters were mainly the $Ca-(Na)-HCO_3$ type, classified as the early stage of groundwater evolutions. The correlation between electrical conductivities and Ca concentrations in groundwaters was relatively high ($R^2=0.74$). In the correlations between ions, the correlation coefficient between $SO_4$ and Ca was 0.65 and between Mg and $HCO_3$ was 0.65.

면외 변형률 분포의 비선형성을 고려한 RC 기둥의 2차원 해석에 관한 연구

김익현(Kim, Ick Hyun),이종석(Lee, Jong Seok),정혁창(Jeong, Hyeok Chang) 한국콘크리트학회 2003 한국콘크리트학회 학술대회 논문집 Vol.2003 No.11

우리나라 社會保障制度의 問題点과 그 改善方案

金益鉉(Kim Ihkhyun) 조선대학교 지식경영연구원 1978 기업과 혁신연구 Vol.1 No.-