• Journal of Korean Society of Environmental Engineers
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• v.28 no.3
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• pp.276-285
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• 2006

When polluted stream water was treated with biological aerated filter(BAF) in pilot plant, all operation with 90, 60, 45 and 30 min of EBCT at fixed $0.1m^3air/m^2min$ of aeration showed 80% or higher treatment efficiency of particle materials(SS, turbidity and Chl.-a) and 85% or higher efficiency of ammonia nitrogen removal. It was thought that, in case of BOD, biological stability may sufficiently be assured with BAF because grade III or IV inflow water was changed to grade I for outflow water. In case of $COD_{Mn}$, about 60% of removal efficiency was found. When the mechanism of the result was investigated, about 30% of COD materials was produced by algae clogged in the reactor. There was almost no biological decomposition because specific substrate utilization rate of algogenic organic materials were $0.0245mg{\cdot}COD_{Mn}/mg{\cdot}VSS{\cdot}day$, thus partial backwashing(washing the media in 1 m upper of the reactor once a day) was required. It is thought that elevation of removal rate about 10% of $COD_{Mn}$ and 5.5% of $BOD_5$ could be obtained with partial backwashing resulting in assurance of biologically more stable raw water and that saving backwashing water may be significant.

• Journal of Conservation Science
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• v.25 no.1
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• pp.25-38
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• 2009

The Gyeongju Seokbinggo (Treasure No. 66) is an ice-storing stone warehouse, consisting mainly of alkaligranite which shows milky white color and medium-grained textures with drusy cavities. As results of deterioration assessment, the deterioration rates were determined as crack (12.5%), disjoining (6.7%), breaking-out (25.1%), exfoliation (20.9%), efflorescence (6.5%), brown discoloration (9.8%), darkgray discoloration (2.0%) and biological discoloration (36.5%). Comprehensive physical deterioration rate and discoloration rate were calculated as 43.7% and 68.7%, respectively, that indicates the Seokbinggo has been severely weathered. Indoor relative humidity was above 90% except in winter season. Indoor microclimate was hardly fluctuating although indoor microclimate was dependent on the outdoor climate. The main cause of deterioration was high relative humidity and a long time of wetness due to penetration of rain, underground water and condensation. It was identified that the water brought out biological discoloration, dissolution of minerals, structural movement and efflorescence, and the dust from the ground soil in front of the entrance accelerated brown and dark gray discoloration on the stone surface.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2005.11a
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• pp.57-60
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• 2005

자연채광은 실내공간의 쾌적성을 향상시키며, 재실자의 건강을 증진시킬 뿐만 아니라 에너지 절약적인 측면에서 시너지 효과를 발휘하고 있다. 이에 반사거울형 태양광채광시스템은 도시가 과밀하고 고층화됨에 따라 자연채광의 도입이 어려운 실내공간에 태양광을 도입할 수 있는 자연에너지 활용장치라 할 수 있다. 본 연구는 태양광채광시스템을 이용하여 주거건물 옥상에 1차반사거울을 설치하고, 반지하의 상부에 2차반사거울을 설치하여 거실공간에 태양광을 유입하였다. 시스템 미설치시와 설치시에 대한 거실의 바닥면조도와 외부조도를 동시에 측정하여 외부조도에 대한 내부조도의 비율인 주광조도비를 분석하고, 증감율을 구하여 반사거울형 태양광채광시스템의 성능을 평가하였다. 채광성능평가 결과 채광시스템의 설치로 인한 실내 주광조도비는 평균 $80{\sim}1,400%$정도 증가하는 것으로 나타났으며, 또한 창면부에 비해 실의 후면부가 2배 이상 증가한 것으로 나타나 채광성능이 매우 큰 것으로 나타났다. 따라서 본 연구에서 실험한 반사거울형 태양광 채광시스템은 주거건물에서의 적용이 용이하고 높은 채광성능을 제공할 수 있어 실내 빛환경 향상에 크게 기여할 수 있을 것으로 기대된다.

• Journal of the Korean Society of Marine Environment & Safety
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• v.17 no.4
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• pp.419-427
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• 2011

The characteristics for hydrogen production and the thermochemical properties of high temperature steam electrolysis(HTSE) device have been numerically analyzed in a two-dimension, steady-state with using the COMSOL $Multiphysics^{(R)}$. The main parameters for the calculation are applied voltage, ASR(Area-specific Resistance), temperature and pressure of the inlet gas flow. The results showed that thermal-neutral voltage was 1.2454 V and rather than the cell temperature increases or decreases with increasing applied voltage by thermal-neutral voltage starting this voltage the temperature in high voltage tended to rise and temperature in the low voltage tended to fall. And with, increasing the values of ASR, temperature inside the cell and the hydrogen production rate were decreased.

• Polymer(Korea)
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• v.33 no.5
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• pp.477-484
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• 2009

Suspension polymerization with hydrophobic silica as a stabilizer and AIBN as an initiator was conducted to synthesize PBMA particles and PBMA composite particles containing carbon black. Surface modification of silica particles by controlling pH revealed that 90% of them functioned as stabilizer and 10% were incorporated into PBMA particles. While stabilizer concentration had no impact on reaction kinetics and particle diameter, an increase in stabilizer concentration displayed an increase in molecular weights when it exceeded 1.67 wt%. An increase in initiator concentration and reaction temperature decreased molecular weights in close agreement with the theoretical equation. An increase in carbon black concentration from 1 to 7 wt%, relative to the monomer, showed a progressive decrease in reaction conversion. As carbon black was increased from 3 to 5 wt%, glass transition showed a $4^{\circ}C$ increase. The presence of carbon black was confirmed by TEM while its concentration was measured by TGA.

• Journal of the Korean Society for Library and Information Science
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• v.52 no.2
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• pp.125-142
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• 2018

Local innovation cities that have recently been being constructed have a large share of the population with highly educated young family with children. There are high demand for children's libraries because of this high percentage of children in the population. In this regard, this study analyzed the economic feasibility of establishing a new children's library in an innovation city as viewed through the case of the C innovation city, where population inflows are increasing recently. In this study, based on a survey, we conducted a cost benefit analysis, as estimating the cost of constructing the library and calculating the benefits from the construction. The economic feasibility was analyzed by calculating the benefit cost ratio, net present value, and internal rate of return.

• Clean Technology
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• v.25 no.3
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• pp.231-237
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• 2019

The BOD removal efficiency according to HRT of the continuous inflow SBR process was decreased from 92.1 ~ 96.0% at HRT 9 ~ 15 h to 86.9 ~ 90.7% at HRT 6 h, but a stable removal efficiency was shown up to HRT 6 h. The T-N removal rate was decreased to 80.1 ~ 87.9% at HRT 12 ~ 15 h, to 71.9 ~ 87.0% at HRT 9 h, and to 60.1 ~ 65.7% at HRT 6 h. As a result of the test of removing organic matter and nitrogen, the optimum HRT of the continuous inflow SBR reactor is determined as 9 h. The TCODcr removal efficiency was 88.4 ~ 96.0% and the TBOD removal efficiency was 92.1 ~ 98.1% as a result of examination of organic matter removal efficiency according to a change in the recycling rate (1 ~ 5Q) at HRT 9 h, suggesting that the a change in the recycling rate has a minimal effect on the removal of organic matter. The T-N removal efficiency was 70.3 ~ 80.4% at 1 ~ 2Q, 77.2 ~ 85.6% at 3Q and 61.5 ~ 80.8% at 4 ~ 5Q according to a change in the recycling rate. The TP removal efficiency was reduced to 75.0 ~ 84.6% at 1 ~ 4Q and to 63.3 ~ 72.4% at 5Q. This is presumably because the release and ingestion of phosphorus (P) by microorganisms is not performed smoothly at 5Q or more. Therefore, the optimum recycling rate for removing organic matter and nutrients was found to be 3Q.

• Journal of Korean Society of Environmental Engineers
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• v.36 no.3
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• pp.172-177
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• 2014

Low pressure air flotation (LAF) pilot plant for sludge thickening was installed in Chung Nam N.S. municipal waste water treatment plant to verify its application possibility. Effects of operating conditions such as coagulant dosages and microbubble water ratio on thickening of the mixed sludge were examined. Microbubbles which were generated in the chamber of $1.5kgf/cm^2$ by high speed collision method with foaming agent were used to float sludge. Solid loading of $30kg/m^2/hr$, solid contents in thickened sludge of 60,300 mg/L and SS removal efficiency of 99% were obtained through long period operating LAF in conditions of mixed sludge concentration of 14,400 mg/L, coagulant dosage of 27.6 mg/L, foaming agent addition of 4.0 mg/L and microbubble water injection ratio of 9.7%.

• Proceedings of the Korea Water Resources Association Conference
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• 2006.05a
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• pp.588-593
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• 2006

자연하천은 일반적으로 만곡수로나 사행수로 형태를 보이고 있으며, 직선수로에서와 달리 원심력에 기인한 이차류 영향을 받게 된다. 이차류에 의해서 수면에서는 만곡부 바깥쪽으로, 하상에서는 만곡부 안쪽으로의 흐름특성을 보이게 된다. 만곡부 안쪽으로 가해지는 하상 전단응력에 기인하여 하상에서의 입자가 만곡부 안쪽으로 이송되며, 결과적으로 만곡부 안쪽에는 점사주가, 바깥쪽에는 소(pool)가 생성된다. 또한 지형경사의 생성으로 입자에 가해지는 중력효과도 변화된다. 따라서 이와 같은 자연하천의 흐름과 하상변동을 수치모의 하기 위해서는 만곡부 이차류 특성을 고려한 모형이 필요하다. 본 연구에서는 수심 적분된 흐름방정식과 하상토 보존방정식 (Exner equation)을 이용한 하상변동을 위한 비연계 수치모형을 위해서 하상토 보존방정식의 유한요소 알고리즘을 개발하였다. 하상토 보존방정식은 흐름 특성에 따른 평형 유사량의 공간변화율을 이용하여 일정 기간 동안의 하상 변화량을 계산한다. 이 때 이차류에 의한 하상 전단응력의 편각 및 지형경사 변화에 따른 실제 입자의 이송방향을 보정하여 평형 유사량이 계산된다. 이러한 보정식을 적용시키기 위해서는 유속성분의 공간변화량 및 지형경사의 공간성분이 필요하다. 유한요소법은 연속성 변수를 이산화시켜 근사해를 구하는 수치기법의 일종이기 때문에, 요소망이 불규칙적으로 구성되었을 경우 임의의 절점에서 연속성을 지닌 변수의 공간변화율을 계산하는데 어려움이 있다. 따라서 본 연구에서는 평형 유사량 계산 시에 절점이 아닌 요소 내부에서 평형 유사량을 계산하는, 하상토 보존방정식의 새로운 유한요소 알고리즘을 개발하고, 새로운 알고리즘을 적용시킨 수치모형의 검증을 행하였다. 경계조건 알고리즘의 검증으로 위해서 Soni 등 (1980)이 행한 상류 유입 유사량에 따른 하상변동을 수치 모의하고 실험치와 비교하였으며, Sutmuller와 Glerum (1980)이 수행한 만곡수로에서의 하상변동을 모의하고 실험과 비교하였다. 새로운 알고리즘을 적용시킨 하상토 보존방정식의 유한요소 수치모형의 결과는 매우 안정적이며, 실험과 매우 유사한 결과를 얻을 수 있었다. 본 수치모델은 현재 균일한 입자의 하상토만을 고려하므로, 입자분급이나 하상 장갑화 현상 등은 무시한다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.8
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• pp.4763-4768
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• 2014

Recently, aluminum pipes have been used instead of steel pipes for open and shut machines in vinyl housing because of its corrosion-resistance and light weight. In particular, the light weight is very useful for fitting and removal by human resources. On the other hand, an aluminum pipe is weak in winter because aluminum has a larger thermal expansion coefficient than steel. This study examined the freezing and bursting of aluminum pipes by numerical analysis. The mechanical-thermal deformation characteristics were analyzed under the condition of ice volumetric expansion in aluminum pipes reaching 50%. From numerical analysis, large stresses above the yield stress occurred in aluminum pipe after ice expanded in the net diameter immediately. In addition, the freezing and bursting of aluminum pipes was predicted around an ice volumetric expansion of 6 - 7% because the thickness of the aluminum pipe reached an aluminum elongation ratio of 17%. Therefore, it is recommended that aluminum pipes be sealed perfectly to prevent water flow in the pipe. These results suggest that it is very difficult to prevent freezing and bursting of aluminum pipes by water freezing in the pipe.