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제주도 지하수 질산염 농도의 시·공간적 변화 특성: 장기(1993-2015) 모니터링 자료의 평가
김호림(Ho-Rim Kim),오준섭(Junseop Oh),도현권(Hyun-Kwon Do),이경진(Kyung-Jin Lee),현익현(Ik-Hyun Hyun),오상실(Sang-Sil Oh),감상규(Sang-Kyu Kam),윤성택(Seong-Taek Yun) 대한자원환경지질학회 2018 자원환경지질 Vol.51 No.1
1993년부터 2015년까지 관측된 제주도 지하수 장기모니터링 관측정(N = 4,835)에서 수집된 지하수 수질자료(N = 21,568)를 기반으로 질산성질소의 시공간적 변동 특성을 평가하였다. 제주도 지하수의 질산성질소 농도의 중앙값은 2.5 mg/L로서 다른 국가나 대륙의 조사 결과에 비해 다소 높거나 유사한 것으로 나타났다. 또한 지하수 용도, 행정구역 및 고도 별로 유의한 차이를 보였다. 특히, 산간 지역에 비해 저지대 해안가에 위치한 농업 및 주거지역에서 농도가 높음을 확인하였다. Mann-Kendall 및 Sen’s slope 분석을 활용한 질산성질소 농도의 추세 분석 결과, 하류 저지 대에 비해 중산간지역에서의 질산성질소 농도 증가 경향이 뚜렷하였다. 제주도 내 토지 피복의 시계열 변화 특성과 결부 지어 보면, 중산간지역의 오염 증가 추세는 농업지역의 확장 등 인위적 활동 증가에 기인한 결과로 판단된다. 반면,기지정된 지하수자원특별관리구역에서는 전반적으로 질산성질소 농도의 감소 경향이 나타났는데, 이는 지하수 관리 측면에서 수질관리를 위한 적극적인 정책이 유효함을 시사한다. 본 연구에서는 제주도 지하수의 질산성질소 오염관리를 위한 적정 방안을 제안한다. The spatio-temporal variations of nitrate concentrations in groundwater of Jeju Island were evaluated by an analysis of time series groundwater quality data (N = 21,568) that were collected from regional groundwater monitoring (number of wells = 4,835) for up to 20 years between 1993 and 2015. The median concentration of NO 3 -N is 2.5 mg/L, which is slightly higher than those reported from regional surveys in other countries. Nitrate concentrations of groundwater in wells tend to significantly vary according to different water usage (of the well), administrative districts, and topographic elevations: nitrate level is higher in low-lying agricultural and residential areas than those in high mountainous areas. The Mann-Kendall trend test and Sen’s slope analysis show that nitrate concentration in mid-mountainous areas tends to increase, possibly due to the expansion of agricultural areas toward highland. On the other hand, nitrate concentrations in the Specially Designated Groundwater Quality Protection Zones show the temporally decreasing trend, which implies the efficiency of groundwater management actions in Jeju. Proper measures for sustainable groundwater quality management are suggested in this study.
Sang-Pil Mun,Chil-Ryong Kim,Jong-Kurl Lee,Man-Kyu Park,Soon-Kurl Kwon 한국조명·전기설비학회 2008 조명·전기설비학회논문지 Vol.22 No.3
This paper presents a simple circuit topology of the auxiliary active quasi-resonant DC link snubber-assisted three phase voltage source soft-switching inverter for small scale PM motor drive applications. The pulse processing drive circuit interface and its soft-switching operation are discussed from an experimental point of view. Moreover, its conductive noise is measured and evaluated for electrical AC servo motor drive as compared with that of the conventional hard switching inverter.
Sung Ku Kwon,김병환,박종문,김보우,Seong Wook Yoo,Kun Sik Park,Yoon Kyu Bae,Kwang Ho Kwon 한국전자통신연구원 2002 ETRI Journal Vol.24 No.3
This study characterizes an oxide etching process in a magnetically enhanced reactive ion etching (MERIE) reactor with a CHF3/CF4 gas chemistry. We use a statistical 24-1 experimental design plus one center point to characterize the relationships between the process factors and etch responses. The factors that we varied in the design include RF power, pressure, and gas composition, and the modeled etch responses were the etch rate, etch selectivity to TiN, and uniformity. The developed models produced 3D response plots. Etching of SiO2 mainly depends on F density and ion bombardment. SiO2 etch selectivity to TiN sensitively depends on the F density in the plasma and the effects of ion bombardment. The process conditions for a high etch selectivity are a 0.3 to 0.5 CF4 flow ratio and a –600 V to –650 V DC bias voltage according to the process pressure in our experiment. Etching uniformity was improved with an increas e in the CF4 flow ratio in the gas mixture, an increase in the source power, and a higher pressure. Our characterization of via etching in a CHF3/CF4 MERIE using neural networks was successful, economical, and effective. The results provide highly valuable information about etching mechanisms and optimum etching conditions.
Kwon, Sang-Jik,Jang, Chan-Kyu The Korean Infomation Display Society 2004 Journal of information display Vol.5 No.4
Effects of base vacuum level on the electrical and optical characteristics of the plasma display panel (PDP) were investigated. The relationship between efficiency and base vacuum level before filling discharge gas was analyzed. For the base vacuum level of $1{\times}10^{-4}$ torr, firing voltage of a 2-inch diagonal PDP panel was 232 V at the discharge gas pressure of 400 torr and luminous efficiency was 1.5 lm/W at 180V sustaining pulse. On the other hand for $1{\times}10^{-6}$torr, the firing voltage was reduced to 215 V and luminous efficiency was improved considerably to 2.5 lm/W. We successfully demonstrated the smooth operation of tip-less PDP fabricated using vacuum in-line sealing method.
Removal Efficiency of Arsenic by Adsorbents having Different Type of Metal Oxides
Sang Yoon Min,Byeong Kwon Kim,Sun Ju Park,Yoon Young Chang,Jae Kyu Yang 대한환경공학회 2009 Environmental Engineering Research Vol.14 No.2
In this study, oxidation of As (Ⅲ) as well as removal of total arsenic by adsorbents coated with single oxides or multi-oxides (Fe (Ⅲ), Mn (Ⅳ), Al (Ⅲ)) was investigated. In addition, multi-functional properties of adsorbents coated with multi-oxides were evaluated. Finally, application of activated carbon impregnated with Fe or Mn-oxides on the treatment of As (Ⅲ) or As (Ⅴ) was studied. As (Ⅴ) adsorption results with adsorbents containing Fe and Al shows that adsorbents containing Fe show a greater removal of As (Ⅴ) at pH 4 than at pH 7. In contrast adsorbents containing Al shows a favorable removal of As (Ⅴ) at pH 7 than at pH 4. In case of iron sand, it has a negligible adsorption capacity for As (Ⅴ) although it contains 217.9 g-Fe/kg-adsorbent. Oxidation result shows that manganese coated sand (MCS) has the greatest As (Ⅲ) oxidation capacity among all metal oxides at pH 4. Oxidation efficiency of As (Ⅲ) by IMCS (iron and manganese coated sand) was less than that by MCS. However the total removed amount of arsenic by IMCS was greater than that by MCS.