• Journal of Astronomy and Space Sciences
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• 제16권2호
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• pp.131-138
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• 1999

We present the results of a model calculation of the stellar distribution in a UV and centered at 2175$\AA$ corresponding to the well-known bump in the interstellar extinction curve. The stellar distribution model used here is based on the Bahcall-Soneira galaxy model (1980). The source code for model calculation was designed by Brosch (1991) and modified to investigate various designing factors for UV satellite payload. The model predicts UV stellar densities in different sky directions, and its results are compared with the TD-1 star counts for a number of sky regions. From this study, we can determine the field of view, size of optics, angular resolution, and number of stars in one orbit. There will provide the basic constrains in designing a satellite payload for UV observations.

• 상하수도학회지
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• 제26권2호
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• pp.257-264
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• 2012

The concept of a non-contact type of UV disinfection system was introduced in this study. UV lamps and their quartz sleeves hang over the water surface and there is no interface between the sleeve and water. Obviously, there is no fouling. Based on optical laws and other UV distribution models, a detail mathematical model for a non-contact type UV disinfection system was developed in this study. Pathway length of UV light in a non-contact type photoreactor is longer than that in a submerged type photoreactor because the light is more refractive while passing through 3 interfaces of medium. But the pathway length passing through the water media is not significantly longer than that in a submerged type photoreactor so, the absorption of UV light by water is not significantly different from the other system. Due to the reflection effect, UV intensity is rapidly decreased as the horizontal distance from the light source is increased. The reflective attenuation in a non-contact type photoreactor is higher than that in a submerged type photoreactor. These mean that the short photoreactor is advantageous than the narrow-long photoreactor for the non-contact type photoreactor in an optical point of view.

• 한국표면공학회지
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• 제41권2호
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• pp.76-82
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• 2008

We investigated sterilization characteristics of UV lights by counting the number of bacteria units with varying sterilization time and distance from the light source. We focused on an idea that UV light of 184.9 nm could generate ozone and developed a new sterilizer. The UV-ozone duplex system sterilized bacteria faster than UV-only sterilizers. To reduce shadowing effects by target objects, we used UV transparent quartz plate as a support and put a reflecting plate. Distribution of UV irradiation intensity and ozone supply were analyzed by a 3D model and measured by a semiconductor UV sensor. But even with an Al reflector, multi-layered pens could not be treated properly from UV irradiation only. Ozone generating lamp could treat more uniformly multi-layered pens with a stirring fan by supplying ozone to shadowed surfaces.

• 대한토목학회논문집
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• 제41권5호
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• pp.505-512
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• 2021

침지형 자외선 살균조의 자외선 강도를 계산하기 위한 3차원 모델을 개발하였으며, 실제 하수처리장에 설치되어있는 개수로형 살균조와 관로형 살균조에 각각 적용하여 수치실험을 실시하였다. 모델링을 통해 계산한 살균조의 평균 자외선 강도는 각각 7.87 mW/cm²와 13.09 mW/cm²로 계산되었다. 자외선 조사 시간을 반영하고, 혼합 불균형, 램프 노화, 온도 및 파울링에 의한 감쇄효과를 고려한 자외선 조사량은 각각 21.1 mJ/cm², 24.8 mJ/cm²로 예측되었는데 이 값은 목표 자외선 조사량인 20 mJ/cm²보다 각각 5 %, 24 % 높은 것으로 예측되었다. 개발한 UV3D 모델을 사용하면 살균조의 조사 시간이나 램프의 출력을 높이지 않고도 수치실험을 통해 평균 자외선 강도가 가장 큰 최적의 램프 위치를 찾을 수 있다. 램프 위치 조정만으로 본 연구에서 적용한 개수로형 살균조와 관로형 살균조의 자외선 조사량은 각각 0.9 %, 0.5 % 향상시킬 수 있다. 개수로형 살균조의 경우 살균조의 체적은 그대로 유지하면서 가로와 세로의 비율을 조정하고, 램프의 위치를 바꾸면 평균 자외선 강도는 현재보다 7.4 % 더 증가한다.

• 한국우주과학회:학술대회논문집(한국우주과학회보)
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• 한국우주과학회 1998년도 한국우주과학회보 제7권1호
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• pp.26.2-26
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• 1998

No Abstract.See Full-text

• 천문학회보
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• 제46권1호
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• pp.53.2-53.2
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• 2021

Quasar luminosity function (QLF) shows the active galactic nucleus (AGN) demography as a result of the combination of the growth and the evolution of black holes, galaxies, and dark matter halos along the cosmic time. The recent wide and deep surveys have improved the census of high-redshift quasars, making it possible to construct reliable ultraviolet (UV) QLFs at 2 < z < 6 down to M1450 = -23 mag. By parameterizing these up-to-date observed UV QLFs that are the most extensive in both luminosity and survey area coverage at a given redshift, we show that the UV QLF has a universal shape, and their evolution can be approximated by a pure density evolution (PDE). In order to explain the observed QLF, we construct a model QLF employing the halo mass function, a number of empirical scaling relations, and the Eddington ratio distribution. We also include the outshining of AGN over its host galaxy, which made it possible to reproduce a moderately flat shape of the faint end of the observed QLF (slope of ~ -1.1). This model successfully explains the observed PDE behavior of UV QLF at z > 2, meaning that the QLF evolution at high redshift can be understood under the framework of halo mass function evolution. The importance of the outshining effect in our model also implies that there could be a hidden population of faint AGNs (M1450 > -24 mag), which are buried under their host galaxy light.

• 한국결정성장학회지
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• 제7권1호
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• pp.126-136
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• 1997

$p^+$/n/n 메사(mesa) 구조를 갖는 6H-SiC UV 광다이오드를 제작하여 입사 파장 200~600 nm의 영역에서 광전류(photocurrent)를 측정하였다. 광다이오드의 파장의 변화에 따라 측정된 광전류는 자외선 영역에서 민감하며 260 nm 근처에서 최대값을 나타내었다. 광다이오드의 광전류 분포를 해석하기 위하여 소수 운반자의 확산모델로 양자효율을 계산하였으며, 계산된 양자효율은 측정된 광전류 분포와 상대적으로 비교되었다. 6H-SiC UV 광다이오드의 광전류 분포는 공핍층에서 광흡수가 포함된 소수운반자의 확산모델에 의하여 해석되었다.

• International Journal of Safety
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• 제6권2호
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• pp.22-26
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• 2007

An episode of corona is a heterogeneity-caused electric discharge that occurs when electric fields are formed layer on layer and concentrated on an electrode. Electric wires built at the tip of 154kV private facilities use dead end clamp spawns corona from homogeneity caused by field concentration. Corona induces power loss, noise, insulator failure and more. In this research, we've studied the characteristics of coronas that take place in porcelain insulators and terminal electric wires of supporting hard wares (dead end clamp) that are set up as spares in the 154kV private facilities use hydroelectricity installations to support electric wires. Corona, which cannot be identified by regular methods, was measured utilizing UV image camera. As the result of measuring corona via UV image camera, we've confirmed that the depletion of insulators was accelerated following the wire end treatment method and validated the stress intensity of insulators at various lengths of bare wires caused by electric fields via FEMLAB. We have also proposed a new model for relieving homogeneity-caused field concentration, and after analyzing the proposed model via FEMLAB, we've confirmed that the concentration of field distribution was indeed reduced. Such results are exploited in installation of private facilities use equipments, maintenance of insulators and hard wares as well as safety enhancement, and are anticipated to be effectively utilized in corona prevention measures.

• 한국대기환경학회지
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• 제24권1호
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• pp.91-99
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• 2008

A multilayer tower-type photoreactor, in which $TiO_2$-coated glass-tubes were installed, was used to measure the vapor-phase BTEX removal efficiencies by ozone oxidation ($O_3$/UV), photocatalytic oxidation ($TiO_2$/UV) and the combination of ozone and photocatalytic oxidation ($O_3/TiO_2$/UV) process, respectively. The experiments were conducted under various relative humidities, temperatures, ozone concentrations, gas flow rates and BTEX concentrations. As a result, the BTEX removal efficiency and the oxidation rate by $O_3/TiO_2$/UV system were highest, compared to $O_3$/UV and $TiO_2$/UV system. The $O_3/TiO_2$/UV system accelerated the low oxidation rate of low-concentration organic compounds and removed organic compounds to a large extent in a fixed volume of reactor in a short time. Therefore, $O_3/TiO_2$/UV system as a superimposed oxidation technology was developed to efficiently and economically treat refractory VOCs. Also, this study demonstrated feasibility of a technology to scale up a photoreactor from lab-scale to pilot-scale, which uses (i) a separated light-source chamber and a light distribution system, (ii) catalyst fixing to glass-tube media, and (iii) unit connection in series and/or parallel. The experimental results from $O_3/TiO_2$/UV system showed that (i) the highest BTEX removal efficiencies were obtained under relative humidity ranging from 50 to 55% and temperature ranging from 40 to $50^{\circ}C$, and (ii) the removal efficiencies linearly increased with ozone dosage and decreased with gas flow rate. When applying Langmuir-Hinshelwood model to $TiO_2$/UV and $O_3/TiO_2$/UV system, reaction rate constant for $O_3/TiO_2$/UV system was larger than that for $TiO_2$/UV system, however, it was found that adsorption constant for $O_3/TiO_2$/UV system was smaller than that for $TiO_2$/UV system due to competitive adsorption between organics and ozone.

• 한국물환경학회지
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• 제26권3호
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• pp.460-467
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• 2010

For D-WTP's sedimentation basin and distribution reservoir, and water tap the predictive models proposed tentatively herein included the models for estimating TTHM concentration in precipitated water, for treated water and for tap water, and the estimated correlation formula between treated water's TTHM concentration and tap water. As for TTHM-concentration predictive model in sedimentation water, the coefficient of determination is 0.866 for best-fitted short-term $DOC{\times}UV_{254}$ based Model (TTHM). As for $HAA_5$-concentration predictive model in sedimentation water, the coefficient of determination is 0.947 for the suitable $UV_{254}$-based model ($HAA_5$). In case of the predictive model in treated water, the coefficient of determination is 0.980 for best-fitted $DOC{\times}UV_{254}$ based model (TTHM) using coagulated waters, while the coefficient of determination is 0.983 for best-fitted $DOC{\times}UV_{254}$ based model ($HAA_5$) using coagulated waters, which described the $HAA_5$ concentration well. However, the predictive model for tap water could not be compatible with the one for treated water, only except for possibility inducing correlation formula for prediction, [i.e., the correlation formula between TTHM concentration and tap water was verified as TTHM (tap water) = $1.162{\times}TTHM$ (treated water), while $HAA_5$ (tap water) = $0.965{\times}HAA_5$ (treated water).] The correlation analysis between DOC and $KMnO_4$ consumption by process resulted in higher relationship with filtrated water, showing that its regression is $DOC=0.669{\times}KMnO_4$ consumption - 0.166 with 0.689 of determination coefficient. By substituting it to the existing DOC-based model ($HAA_5$) for treated water, the consequential model formula was made as follows; $HAA_5=8.35(KMnO_4\;consumption{\times}0.669-0.166)^{0.701}(Cl_2)^{0.577}t^{0.150}0.9216^{(pH-7.5)}1.022^{(Temp-20^{\circ}C)}$