• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.112-112
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• 2016

열전 발전은 버려지는 폐열을 재사용 가능한 에너지로 전환할 수 있다는 점에서 차세대 청정 에너지원으로 분류되며, 19세기 초 발견된 이래 꾸준히 연구되어온 연구 분야이다. 특히 1990년대 열전소재로의 나노 기술의 접목에 따라 열전성능(figure of merit, ZT)이 2 배 이상 증가 되면서, 고성능의 열전 소재 개발을 위해 나노구조화 연구가 활발히 진행되고 있다. 하지만, 기존의 열전 특성 측정용 상용 장비의 경우, 벌크형 소재를 대상으로 설계되어 연구실 수준에서 개발되고 있는 마이크로미터 스케일의 두께를 가지는 박막형 열전 소재의 두께 방향 (cross-plane)의 열전 특성을 평가하는데 정밀성이 떨어져서 적합하지 않다. 이러한 표준화된 측정 기술의 부재로 인하여 최근 연구되고 있는 나노소재들의 열전 특성 측정 결과를 정확하게 측정하지 못하고 있다 [1] 본 연구에서는 박막형 열전 소재의 열전성능을 평가하는데 가장 중요한 요소인 열전도도를 측정하기 위해 장비를 설계하고, 장비의 측정 능력에 대해 평가하였다. 특히, 측정 포인트 간 큰 온도 차가 발생하여 비교적 쉽게 측정이 가능한 너비 방향 (in-plane) 이 아닌, 온도 차가 작은 박막의 두께 방향의 열전도도를 측정하였다. 그리고 센서의 측정 능력을 평가하기 위해, 폴리이미드를 대상으로 $-10-70^{\circ}C$ 온도 범위에서 측정한 결과와 벌크형 소재 대상으로 신뢰성이 확보된 보호열판법을 이용해 측정한 결과를 비교하였다.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2002.10a
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• pp.421-424
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• 2002

Deterministic and probabilistic approaches to the design of ultraviolet (UV) disinfection system for water reclamation are reviewed and discussed. The high inactivation of TC, FC and E. coli by UV disinfection was demonstrated and the inactivations of TC, FC and E. coli were 97%, 98% and 99%, respectively. Within the range of 0.3-4.5mWs/cm, the effect of UV does on the inactivation ratio was not observed. However, in the highest wattage of UV lamp, 39W, the inactivation ratio of TC, FC and E. coli was 100%, regardless of the UV does so the UV density was more effective on inactivation ratio of TC, FC and E. coli rather than UV does. Under the 0.4 mWs/cm and 16W of UV lamp, the effect of dissolved organic matter and turbidity on the inactivations of TC, FC and E. coli could not be observed in this study within the range of 0-60mg/L and 0-40 NTU respectively.

• Journal of Environmental Science International
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• v.20 no.6
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• pp.767-773
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• 2011

The objectives of this research are to investigate the proper coagulation conditions which are a type and doses of coagulants, mixing conditions (velocity gradients and mixing times), pH and so on through Jar-test, to evaluate the flux variations, permeate, backwashing according to characteristics of pretreatment of the wastewater by means of MF membranes for river maintenance water reuse. The effluent water from B-city K-sewage treatment plant are used for this research. Turbidity and suspended solids(SS) are 14.2 NTU and 10.4 mg/L respectively. This condition causes fouling for membrane process. The flux decline could be reduced when coagulation pretreatment was carried out. Optimal coagulations PAC which are commonly used in the sewage treatment plant was observed in this research. The results indicate that an optimal coagulation dose and pH are 80 ppm and pH of 7 respectively, but coagulation efficiency was lower at strong acid or strong base. Results showed that continuous and steady operations in membrane separation process by means of the effective removal of organic matter and turbidity with coagulation pretreatment of sewage secondary effluent were achieved.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.1503-1506
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• 2009

Bubble jet loop heat pipe is a newly devised variation of heat pipe in which heat is effectively transported by the latent heat of evaporation and condensation as well as the heat capacity of circulating working fluid. The circulatory and oscillating motion of the working fluid becomes possible by the motion of bubble jet which is generated at a narrow circular gap. These bubbles are condensed at the condensing section. Bubble jet loop heat pipe makes it possible to carry heat long distances upward and horizontal directions. Because Its structure is a very simple and a low cost, it is available for the floor heating, vinyl house heating, the defrosting of heat pump system and home refrigerator.

• Magazine of the Korean Society of Agricultural Engineers
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• v.45 no.3
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• pp.84-93
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• 2003

Photoreactivation of microorganism following UV-disinfection is one of the research topics of interest in assessing the UV-disinfection performance. Apparent photoreactivation was examined under fluorescent lamp and solar radiation as well as in darkness. Total coliform, fecal coliform, and Escherichia coli were used as indicator microorganisms, and their concentration was monitored with time after UV-disinfection. Under the darkness, their initial concentration of 10∼30 MPN/100 mL increased to the level of 100 MPN/100 mL after 24 hours, which implied that part of damaged microorganisms by UV-disinfection might be repairable with time. Under the fluorescent lamp, photoreactivation was more apparent that their concentration increased up to 1,000 MPN/100 mL which might significantly impair the water uses specially in reuse of reclaimed wastewater. However, their concentration further decreased down to below 2 MPN/100 mL under the solar radiation primarily due to additional disinfection by solar radiation rather than photoreactivation. Samples not disinfected by UV-disinfection also demonstrated substantial decrease of their concentration under solar radiation from about 5,000 MPN/100 mL to less than 30 MPN/100 mL in 24 hours. But direct reuse of effluent without disinfection is not recommended because natural decay by solar radiation may take time and be affected by climatic conditions. The result suggests that photoreactivation of pathogenic microorganisms may not be concerned in agricultural reuse of reclaimed wastewater because solar radiation may provide further disinfection after UV-disinfection.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2005.10a
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• pp.661-666
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• 2005

Wastewater reuse are exposed public health risk by pathogens. Therefore, this study was examined for microbial risk assessment after irrigation as treated wastewater in paddy rice plots. Five treatments were used: biofilter effluent, UV disinfected water, pond treatment, wetland treatment and conventional irrigation water. Risk assessment was calculated based on the beta-Poisson model by concentration of E. coli from 2003 to 2005. Monte-Carlo simulation (n=10,000) was used to estimate the risk characterization of uncertainty. The risk range was from $10^{-5}$ to $10^{-8}$ except biofilter effluent was $10^{-4}$ in June. The USEPA(1992) has recommended that risk of < $10^{-4}$ is acceptable level of safety for potable waters. In 2005, risk value was lower than 2003, 2004 because of the first irrigation for plowing water is lower E. coli concentration used tap water. It is shown that the first irrigation water quality was important for wastewater irrigation in paddy. UV disinfection and natural treatment used pond and wetland were thought to be an effective for wastewater reuse.

• Magazine of the Korean Society of Agricultural Engineers
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• v.45 no.2
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• pp.126-137
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• 2003

The feasibility study of UV-disinfection system was performed for disinfection of effluent from wastewater treatment plant. Three low-pressure UV lamps of 17, 25, and 41 W were examined with various flow rates. Low-pressure UV lamps of 17W were examined with various turbidity, DOM (dissolved organic matter), and SS (suspended solid). The pilot plant was a flow-through type UV-disinfection system, and the range of exposure time varied from 5 to 40 seconds, turbidity from 0 to 40 NTU, DOM from 0 to 30 mg/L, and SS from 10 to 40 mg/L. The 41W lamp demonstrated complete disinfection showing no survival ratio in all the experimental conditions, and generally 17W and 25W lamps also showed high removal ratio over 97%. For the same UV dose (UV intensity times exposure time), high intensity-short exposure conditions showed better disinfection efficiency than low intensity-long exposure conditions. While the effects of turbidity and DOM were not apparent, the effects of SS was significant on the disinfection efficiency which indicates that SS control before UV-disinfection appears to be necessary to increase removal efficiency. Considering characteristics of effluent from existing wastewater treatment plants, cost-effectiveness, stable performance, and minimum maintenance, the flow-through type UV-disinfection system with high intensity and low-pressure lamps was thought to be a competitive disinfection system for wastewater reclamation.

• Journal of Korean Society of Water and Wastewater
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• v.30 no.5
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• pp.545-551
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• 2016

This study compares characteristic of membrane fouling in MBR-RO systems. In lab. scale MBRs test, MBRs were operated at different Flux(10, 20, 30 & 40 LMH) and temperature(10, 15, 20, 25 & $30^{\circ}C$). The results show that MBR permeate was measured lower amounts of organic substances in Higher flux and lower temperature and led to lower RO fouling rates. The main cause was that due to cake fouling formed on membrane surfaces in MBRs. Under both cases, Cake layer of membrane surfaces formed in MBRs removed RO fouling factors, polysaccharide and protein, because of cake layer attached on membrane surfaces greater amounts of organic substances. This study implies that optimization of MBR with operating conditions is a crucial strategy to RO membrane fouling control.

• Journal of The Korean Society of Agricultural Engineers
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• v.46 no.1
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• pp.75-86
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• 2004

The objective of the research is to develop agricultural resue technologies of reclaiming the effluents from a municipal wastewater treatment plant and reusing for irrigated rice paddies. The Suwon wastewater treatment plant was selected for wastewater reuse tests. The control was the plots with groundwater irrigation (TR＃1), the treatment (TR＃2) using polluted stream water as it was, and three others using wastewater after treatment. Three levels of wastewater treatments were employed： the effluent from the wastewater treatment plant (TR＃3), sand filtering after treatment plant(TR＃4), and ultra-violet treatment after sand filtering (TR＃5). The randomized block method was applied to wastewater application to paddy rice with five treatments and six replica. The effects of various wastewater treatment levels on water quality, paddy soil, crop growth, yields, and the health hazards were investigated. The primary results indicate that cultivating rice with reclaimed wastewater irrigation did not cause a problem to adverse effects on crop growth and yields. Overall, wastewater could be used as a practical alternative measure for reclaimed wastewater irrigation. However, long-term monitoring is recommended on the effects on soil chemical characteristics and its related health concerns.

• Proceedings of the Korea Water Resources Association Conference
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• 2012.05a
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• pp.249-249
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• 2012

기후변화의 영향으로 폭우발생 빈도 및 강도는 최근 들어 급증하고 있다. 빈번히 발생하는 대형 폭우에 의해 도시는 홍수와 산사태 등 많은 자연재해가 발생하고 있다. 최근 도시에서 발생한 대형 폭우재해의 1차적인 원인은 도시방재시설물 설계빈도를 상회하는 집중호우이지만, 방재를 고려하지 않은 도시계획 및 설계가 피해를 가중시킨 것으로 판단되고 있다. 대형화 및 일상화되어가는 폭우재해에 적응하기 위해서는 하수관거, 제방 등 전통적인 방재시설물 설계기준을 상향조정하는 구조물적 대책뿐만 아니라, 도시의 토지이용, 공원, 녹지, 광장, 도로 등의 구성요소를 활용하여 우수유출 저감 및 지연시켜 최대홍수량을 낮추는 비구조물적 적응방안도 필요하다. 기후변화에 따른 폭우재해에 도시차원에서 효과적으로 적응하기 위해서는, 다양한 폭우재해 적응 도시계획 및 설계기법을 개발하고, 그 효과를 시뮬레이션 할 수 있는 시스템 개발이 필요하다. 본 연구에서는 기존에 개발된 홍수 및 산사태 관련 시스템들과 연계하고 정부의 다양한 부처에서 구축된 DB를 최대한 활용하여 폭우에 의해 발생하는 도시 홍수와 산사태 피해지점과 피해 영향권을 분석뿐만 아니라 폭우재해 적응 도시계획 및 설계기법을 효율적으로 적용할 수 있는 관리지역을 도출하고, 관리지역에 폭우재해 적응 도시계획 및 설계기법 적용시 효과를 분석할 수 있는 기후변화 폭우재해 적응 도시조성 시뮬레이션 시스템 개발방향을 제시한다.