• The KSFM Journal of Fluid Machinery
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• v.17 no.6
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• pp.44-51
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• 2014

The disinfection method using UV has emerged as photodissociation in water disinfection. In order to predict performance for UV disinfection, CFD analysis was performed due to saving cost. Most CFD studies of UV reactor have used particle tracking method. However it demands additional analysis time, computing resource and phase besides working fluid. In this paper, pathogenic microorganisms' route is assumed to streamline of fluid to save computing time. the computational results are in good agreement with experimental results. The results of streamline method are compared with the particle tracking method. In conclusion, the effectiveness of streamline method for UV disinfection are confirmed.

• Journal of Korean Society of Water and Wastewater
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• v.22 no.4
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• pp.421-427
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• 2008

UV disinfection is widely used in water treatment facilities and wastewater treatment plant because of its effectiveness to removal of pathogen and Giardia which is resistant to traditional chemical disinfection. As a design and performance tool of UV disinfection system, 3 dimensional UV intensity models were composed and simulated to compare each other and to find affecting factors in this study. Reflection, refraction and absorption are important parameters in UV intensity model and MPSS and MSSS model can reflect these parameters while LSI model can not. Absorption is the most important parameters among the reflection, refraction, absorption and shadowing so, this should not be neglect. Based on this simulation, shadowing effect is negligible when the number of installed lamp is a few but, this effect can not be neglectable when the number of installed lamp is quite a few. The errors according to shadowing effect is increased as the number of lamp installed increased.

• The KSFM Journal of Fluid Machinery
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• v.18 no.2
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• pp.54-59
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• 2015

The performance of UV reactor which is used in water treatment is strongly affected by UV fluence rate and water flow in the UV reactor. Therefore, CFD tools are widely used in designing process of UV reactors. This paper describes the development of a computational fluid dynamics (CFD) methodology that can be used to calculate the performance of open channel type UV reactor used in wastewater treatment plant. All computations were performed using commercial CFD code, CFX, by considering three dimensional, steady, incompressible flow. The Eulerian-Eulerian multi-phase method were used to capture the water-air interface. The MSSS model, provided by UVCalc3D, was used to calculate the UV intensity field. The numerical predictions and calculated UV Dose were compared with experimental dataset to validate the CFD methodology. The reactor performance based on MS2 log reduction was well matched with measurements within 6%.

• Proceedings of the KIEE Conference
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• 2005.10a
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• pp.169-172
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• 2005

The simulation of Hydraulic pressure distribution of discharge tube with globular beads and the removal characteristic of Escherichia coli by the discharge tube with globular beads were estimated. The removal characteristic of Escherichia coli was related to the input voltage because the electric field is increased according to input voltage. As the passing amount of test water in discharge tube is increased, the removal ratio of Escherichia coli was increased because passing numbers of electric field section is increased.

• Journal of the Korean Society of Food Science and Nutrition
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• v.40 no.1
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• pp.116-122
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• 2011

This study was conducted to investigate the microbiological hazard of spoons and their cases carried by nursery school children and to evaluate the reduction effects of washing methods and ultraviolet (UV) treatments against Escherichia coli on the spoon and spoon case. A total of 78 spoons and their cases were sampled to test about total aerobic bacteria, coliform bacteria, Staphylococcus aureus, Bacillus cereus and Salmonella spp. Total aerobic bacteria were detected over 2.7 log CFU/100 $cm^2$ in 20 out of 36 spoons (55.6%), 9 out of 20 zipper-type spoon cases (45.0%) and 13 out of 22 plastic-type spoon cases (59.1%). Coliform bacteria were also detected in 19 out of 36 spoons (52.8%), 14 out of 20 zipper-type spoon cases (70.0%) and 14 out of 22 plastic-type spoon cases (63.6%). The pathogens tested in this study were not found in all samples except for the zipper-type spoon cases which were contaminated with Staph. aureus (2 samples) and B. cereus (3 samples). The results indicated that the sanitary conditions of spoons and their cases should be improved promptly. To evaluate the reduction effects of washing methods and UV treatments against E. coli, the spoons and their cases were treated at different cleaning times with and without soap, and different UV exposure times, respectively. E. coli with initial cell number of 4 log CFU on the spoons and their cases was not detected when they were cleaned at running water for 30 sec after dish sponging with soap for 30 sec. In UV treatments, E. coli with the same level of washing method was not detected after UV exposure for 15 minute in the spoons and their cases. From the results, the washing and UV treatment should be used to control the microbial contamination of spoons and their cases for more than 1 and 15 minutes, respectively.

• Journal of Korean Society of Water and Wastewater
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• v.35 no.6
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• pp.489-496
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• 2021

Water disinfection using UV-LED(Light emitting diode) has many advantages, such as smaller footprint and power consumption as well as relatively longer lifespan than those of conventional mercury-UV lamps. Moreover, UV-LED disinfection is considered an environmentally benign process due to its mercury-free nature. In this study, disinfection using an LED module emitting 275nm UV was carried out. 384 UV-LEDs were put into a cylinder tube with a capacity of 1.7 liters. The UV intensity of the UV-LED module was controlled from 1.7 to 8.4 mW/cm². The disinfection efficiency for the model microorganism solutions(E. coli ) was monitored. As the UV intensity(I) and contact time(t) varied, inactivation of the microorganisms from 2 to 4-log-removals(i.e., 99 to 99.99% of disinfection efficiency) was achieved. Disinfection using UV-LED was followed to 1^st order reaction and the reaction rate constant, k was determined. In addition, the relationship between UV intensity(I) and contact time(t) in order to obtain 99.99% of disinfection efficiency was modeled: I^1.2·t= 460, which indicates that the product of UV intensity and contact time requiring 4-log-removals is always constant.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.331-331
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• 2014

3족 질화물에 기반한 발광다이오드는 비소화물이나 인화물에 비해 여러 가지 장점을 가져 각광받아왔다. 특히, (Al)GaN 에 기반한 자외선 영역 발광 다이오드는 자외선 경화, 소독 등의 여러 가지 응용 가능성을 가진다 [1]. 하지만, 심자외선 영역으로 갈수록 높은 접촉 저항과 투명전극에서의 광흡수에 의해 전류주입 효율과 광추출 효율이 감소하여 결국 외부양자 효율이 더욱 열화되는 특성을 보인다. 이는 넓은 밴드갭을 가지는 물질을 이용하여 p-(Al)GaN 층에서 오믹접촉을 이루어야만 해결이 가능하지만 아직까지 이러한 결과가 보고된 바 없다. 본 연구에서는, 우리는 넓은 밴드갭을 가지는 silicon dioxide (SiO2) 에 전기장을 인가하여 p-GaN, and p-AlGaN 층에 전도성 필라멘트를 형성하여 전기전도도를 부여하는 연구를 진행하였다. p-GaN 과 p-AlGaN 위에서 5 nm 두께의 SiO2는 schottky 한 특성과 280 nm의 파장대역에서 약 97%의 투과율을 보였다. 비록 schottky 장벽이 형성되었지만, 전기전도도가 크게 향상되었으며 심자외선 영역에서 매우 낮은 흡수율을 보였다. 이는 기존의 증착후 열처리를 거쳐 제조된 전극에 비하여 우수한 특성을 지니며 향후 심자외선 영역 발광다이오드의 p-(Al)GaN 층 위에 오믹접촉을 이룰수 있는 가능성을 제시한다.

• Journal of Korean Society of Water and Wastewater
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• v.30 no.2
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• pp.139-145
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• 2016

Disinfection of microorganisms using UV light is widely used in the field of water supply and wastewater treatment plant, In spite of high germicidal effect and relatively clean by-product, UV disinfection has fundamental defeat that is accumulation of fouling materials at the interface of water and lamp sleeve. Non-contact type of UV photoreactor which can avoid this fouling generation was developed and the experimental performance evaluation of the system was carried out in this study. Log inactivation rate of E. coli was selected as a disinfection index. The concentration of E. coli of second clarifier effluent was $8.2{\times}10^1-8.2{\times}10^3$ colony per mL and was well inactivated by the non-contact type of UV photoreactor. Under the UV intensity condition of $2.1-2.5mW/cm^2$, E. coli removal rate was observed in the range of 54 - 95% when the HRT was increased from 10 to 52 seconds. Experimental results showed that log inactivation of E. coli was proportional to UV dosage and $200mJ/cm^2$ of UV dose is expected for the 2.0 log inactivation of E. coli from the second clarifier effluent. Between the two parameters of UV intensity and contact time which are consist of UV dose, UV intensity was 4 times more effective than contact time.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.4
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• pp.2602-2608
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• 2015

The aim of this research was microbiological hazard analysis which is required to application of HACCP(Hazard Analysis Critical Control Point) system to chili powder. A processing had been conducted in Yong-Geum Agricultural Production located in Dongnyang-myeon, Chungju-si between January 10, 2014 to June 13, 2014. A manufacturing process chart was prepared by entire level of processing. A changes of microorganism was tested by changing sterilization time in ultraviolet ray sterilization processing which can control microbiological Hazard. As a result, critical Limits is decided as ultraviolet rays lamp $20W{\times}12EA$, sterilization $63{\pm}3$ min of each. The result of the microorganism test after ultraviolet ray sterilization was safe. On the other hand, a microorganism test of manufacturing environment and workers suggested that the microbiological hazard should be reduced through systematic cleaning and disinfection accompanied by personal hygiene based on hygiene education on workers.

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2003.05b
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• pp.383-384
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• 2003

오존은 산업적으로 널리 활용되고 있으며 특히, 매우 넓은 환경공학적 응용분야를 가지고 있다. 오존의 산업적 적용은 1900년대 초부터 음용수 처리를 위해 시작되었으며 현재까지 폐수처리, 화학물질 합성, 재료의 부식 정도 측정, 수영장 소독, 치료용 목적, 냉각수 살균, pulp bleaching, 악취 및 대기 오염물질 처리 등의 광범위한 산업적 응용분야를 가지고 있다. 오존을 생성시키기 위한 대표적인 공정으로는 무성방전(dielectric barrier discharge, DBD) 공정, 전기 분해법(electrolysis), 자외선 조사법(UV irradiation)을 들 수 있으며 가장 널리 활용되고 있는 공정은 1857년 Simens에 의해 개발된 DBD 공정이다. (중략)