• KSBB Journal
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• 제18권6호
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• pp.448-454
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• 2003

세 가지 다른 공극률을 가진 담체를 충전한 바이오필터에서 기상의 톨루엔 제거실험을 수행하였다. 유입 유량과 유입 농도의 변화에 따른 바이오필터의 제거성능을 조사하고 공극률에 따른 영향을 알아보았다. 15일 동안 수행된 실험을 통해 빠른 환경변화에 대한 각 바이오필터의 동특성을 파악할 수 있었다. 바이오필터 설계에 중요한 변수인 제거량은 BF2 (25 PPI)가 115g/㎥h로 가장 큰 값은 나타내었다. 이는 제거량과 밀접한 관련이 있는 미생물 균체량이 초기 고정화 단계에서 각 바이오필터가 공극의 크기별로 각각 다른 부착 특성을 가져서 그 양과 수분 함량에 영향을 주었기 때문이다. 과도한 바이오매스의 축적은 바이오필터 성능을 저하시키는 요인임을 확인할 수 있었고 초기에 담체의 공극률이 장기적인 바이오필터 운전에 있어서 일정한 공기 흐름을 주기 위해서 매우 중요한 변수로 작용함을 알 수 있었다. 마지막으로 폴리우레탄 폼 담체는 균일하고 충분한 공극을 제공하므로 미생물의 흡탈착이 유리하고 충분한 미생물 서식공간을 제공함으로써 많은 미생물을 담지할 수 있어 단일 담체로 상업적 적용 가능성을 가지고 있다고 사료된다.

• 한국환경과학회지
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• 제15권10호
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• pp.945-949
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• 2006

For a membrane bio-reactor, it is possible to fillet and separate activated sludge and effluent by head loss of centimeters, if non-woven fabric material is used as titration media. However, if non-woven fabric material is used to thicken high-concentration sludge, excessive sludge attachment causes the rapid decrease of flux. Mesh with fore sizes of $100{\mu}m,\;150{\mu}m,\;and\;200{\mu}m$ allows for easy separation of attached sludge. This study examined the possibility of mesh as filtration media. Existing close-flow filtration process, which requires maintaining sludge movement, makes It difficult to obtain high thickening rate. With a view of complementing this weakness, this study has made an experimental examination on how high-concentration sludge (about 3,000mg/L to 10,000mg/L) will be filtered and thickened when mesh module is submersed in the bio-reactor. Effluent flowed from the bottom of the bio-reactor by head loss of 65cm. In case of pore size of $100{\mu}m$, SS showed high recovery of 80% to 96%; therefore, it has been decided that mesh can be used as filtration media. Filtration lasted for more than 9 hours, until sludge with 9,000mg/L in MLSS concentration was thickened 9 times as dense. In the range from 3,610mg/L to 9,060mg/L in MLSS concentration, it was possible to obtain effluent with less than 2mg/L in MLSS concentration within 10 minutes.

• 한국수자원학회논문집
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• 제54권11호
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• pp.863-873
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• 2021

다공성 매질에서 오염물 이동에 지배적인 기작인 역학적 분산은 공극 내 유속 차이에 의해서 발생한다. 종분산계수와 종분산지수는 이송확산 모형의 수리분산 매개변수이며, 실험을 통하여 얻어야만 한다. 수리평균반경은 공극 내 물의 흐름 양의 크기와 강도를 표현할 수 있으며, 매질의 물리적 특성인자를 이용하여 계산할 수 있다. 본 연구는 순간주입 추적자실험을 통하여 자갈 다공성매질에서 수리평균반경을 이용하여 종분산지수를 구할 수 있는 거듭제곱형의 경험식을 도출하였다. 경험식은 스케일상수 계산식이 포함되어 있어 이동거리에 따른 종분산지수의 산정이 가능하며, 소규모 유량의 균질한 자갈로 구성된 수로에 적용이 가능할 것으로 기대된다.

• 대한환경공학회지
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• 제27권6호
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• pp.573-580
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• 2005

본 연구에서는 제올라이트/폴리에틸렌 복합 담체를 충진한 biotrickling filter에서 톨루엔 제거특성을 살펴보았다. 본 연구에 사용된 메디아의 물리적 특성을 살펴본 결과 비표면적과 공극율이 각각 $500\;m^2/m^3$, 82%로 나타났으며, 특히 미생물 부착과 생물막 형성에 영향을 주는 표면거칠기는 첨가된 제올라이트에 의해 담체표면이 상당히 거칠어짐을 확인할 수 있었다. 본 담체를 충진한 biotrickling filter 장치에서 톨루엔의 제거효율은 유입농도와 처리유량이 증가할수록 감소하였으며, 톨루엔의 최대 제거용량은 $64\;g/m^3{\cdot}hr$를 보였다. 또한 200일 동안의 연속실험결과, 미생물 순응이 완료된 뒤부터 167일까지 $90{\sim}98%$의 제거효율을 보였으며, 이후 과잉 미생물의 중식으로 인한 압력손실의 증가로 시간에 따라 제거효율은 감소하는 경향을 보였다. 역세척 후 압력강하와 톨루엔 제거능은 신속히 회복되어 정상상태를 유지하였다.

• 한국의상디자인학회지
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• 제16권3호
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• pp.33-48
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• 2014

Based on the advent and dissemination of new developments concerning information & telecommunications technology, web services have brought new paradigms into society, thus facilitating the birth and evolution of various service industries to society as a whole. This study is aimed at investigating the expansion of the first Birthday party culture and design examples of the first Birthday partywear appearing in social media, through an inquiry into the communication functions inherent in social media. Also, the development of the first Birthday partywear designs for women aged 20 to 30 years was accomplished by categorically analyzing design characteristics in preferred fashion styles uploaded and shared within online childcare communities. First, it can be concluded that due to the bidirectional flow of information between corporations and consumers occurring from the expansion of social media, the entire structure of the market is undergoing great changes. Next, the need for the supply of professionalized the first Birthday partywear can be proved by the influx of party planners and caterers into this new industry. Third, Through a categorical analysis of these 523 photos, elegance style was the most preferred while classic and romantic styles followed. Last of all, 5 pieces of partywear reflecting contemporary consumer lifestyles which focus on 'enjoying one's own life' were created under the concept of 'Romantic chic'. The created designs aim to present a style which follows the predominant trend of elegance, classic and romantic, whilst keeping sensitivity in moderation. In this context, this study has aimed to present fundamental research data in the field of online the first Birthday partywear, through the development of the first Birthday partywear design based on the first Birthday party consumer characteristics gleaned from various forms of social media.

• 한국콘텐츠학회논문지
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• 제15권5호
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• pp.179-190
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• 2015

본 연구는 우리 사회에서 나타나는 정치적 소통 현상에 주목하여 소통 만족에 영향을 미치는 요인을 논의하였다. 정치적 소통의 주요 영향요인으로 개인의 정치적 성향과 미디어 이용을 살펴봄으로써 정치 커뮤니케이션 행위와 정치적 소통 만족도를 평가했다. 전국 16개 시도에 거주하는 만19세 이상 성인 1000명을 대상으로 면접원 설문조사를 실시한 결과, 진보적 정치성향은 온라인 미디어 이용이 많았으며, 개인의 의견을 적극 게재하는 '쓰기/대화'의 정치 커뮤니케이션 행위가 소통 만족에 긍정적인 영향을 미치는 것으로 나타났다. 반면 보수, 중도적 정치성향은 오프라인 미디어를 주로 이용하였고, 타인의 의견을 살피는 '읽기/시청'의 소극적 정치 커뮤니케이션 행위가 중점적으로 나타났다. 따라서 우리 사회에서 정치적 소통을 원활히 하기 위해서는 시민의 정치적 특성에 대한 이해가 선행되어야 하며, 이에 따른 차별화된 미디어 활용 정치커뮤니케이션이 제고되어야 함을 논의할 수 있었다.

• Geomechanics and Engineering
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• 제17권4호
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• pp.367-374
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• 2019

This study concluded the results of a research on the features of cement based permeation grout, based on some important grout parameters, such as the rheological properties (yield stress and viscosity), coefficient of permeability to grout ($k_G$) and the inject ability of cement grout (N and $N_c$ assessment), which govern the performance of cement based permeation grouting in porous media. Due to the limited knowledge of these important grout parameters and other influencing factors (filtration pressure, rate and time of injection and the grout volume) used in the field work, the application of cement based permeation grouting is still largely a trial and error process in the current practice, especially in the local construction industry. It is seen possible to use simple formulas in order to select the injection parameters and to evaluate their inter-relationship, as well as to optimize injection spacing and times with respect to injection source dimensions and in-situ permeability. The validity of spherical and cylindrical flow model was not verified by any past research works covered in the literature review. Therefore, a theoretical investigation including grout flow models and significant grout parameters for the design of permeation grouting was conducted in this study. This two grout flow models were applied for three grout mixes prepared for w/c=0.75, w/c=1.00 and w/c=1.25 in this study. The relations between injection times, radius, pump pressure and flow rate for both flow models were investigated and the results were presented. Furthermore, in order to investigate these two flow model, some rheological properties of the grout mixes, particle size distribution of the cement used in this study and some geotechnical properties of the sand used in this work were defined and presented.

• Biotechnology and Bioprocess Engineering:BBE
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• 제4권1호
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• pp.51-58
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• 1999

A mathematical model for a three phase fluidized bed bioreactor (TFBBR) was proposed to describe oxygen utilization rate, biomass concentration and the removal efficiency of Chemical Oxygen Demand (COD) in wastewater treatment. The model consisted of the biofilm model to describe the oxygen uptake rate and the hydraulic model to describe flow characteristics to cause the oxygen distribution in the reactor. The biofilm model represented the oxygen uptake rate by individual bioparticle and the hydrodynamics of fluids presented an axial dispersion flow with back mixing in the liquid phase and a plug flow in the gas phase. The difference of setting velocity along the column height due to the distributions of size and number of bioparticle was considered. The proposed model was able to predict the biomass concentration and the dissolved oxygen concentration along the column height. The removal efficiency of COD was calculated based on the oxygen consumption amounts that were obtained from the dissolved oxygen concentration. The predicted oxygen concentration by the proposed model agreed reasonably well with experimental measurement in a TFBBR. The effects of various operating parameters on the oxygen concentration were simulated based on the proposed model. The media size and media density affected the performance of a TFBBR. The dissolved oxygen concentration was significantly affected by the superficial liquid velocity but the removal efficiency of COD was significantly affected by the superficial gas velocity.

• 대한기계학회논문집B
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• 제33권9호
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• pp.688-698
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• 2009

Using the multi-dimensional, multi-phase, nonisothermal Polymer Electrolyte Fuel Cell (PEFC) model presented in Part I, the effects of land/channel flow-field on temperature and liquid saturation distributions inside PEFCs are investigated in Part II. The focus is placed on exploring the coupled water transport and heat transfer phenomena within the nonisothermal and two-phase zone existing in the diffusion media (DM) of PEFCs. Numerical simulations are performed varying the land and channel widths and simulation results reveal that the water profile and temperature rise inside PEFCs are considerably altered by changing the land and channel widths, which indicates that oxygen supply and heat removal from the channel to the land regions and liquid water removal from the land toward the gas channels are key factors in determining the water and temperature distributions inside PEFCs. In addition, the adverse liquid saturation gradient along the thru-plane direction is predicted near the land regions by the numerical model, which is due to the vapor-phase diffusion driven by the temperature gradient in the nonisothermal two-phase DM where water evaporates at the hotter catalyst layer, diffuses as a vapor form and then condenses on the cooler land region. Therefore, the vapor phase diffusion exacerbates DM flooding near the land region, while it alleviates DM flooding near the gas channel.

• 한국해양공학회지
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• 제28권6호
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• pp.517-526
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• 2014

The leakage of cryogenic LNG through cracks in the insulation membrane of an LNG carrier causes the hull structure to experience a cold spot as a result of the heat transfer from the LNG. The hull structure will become brittle at this cold spot and the evaporated natural gas may potentially lead to a hazard because of its flammability. This paper presents a computational model for the LNG flow and heat diffusion in an LNG insulation panel subject to leakage. The temperature distribution in the insulation panel and the speed of gas diffusion through it are simulated to assess the safety level of an LNG carrier subject that experiences a leak. The behavior of the leaked LNG is modeled using a multiphase flow that considers the mixture of liquid and gas. The simulation model considers the phase change of the LNG, gas-liquid multiphase interactions in the porous media, and accompanying rates of heat transfer. It is assumed that the NO96-GW membrane storage is composed of glass wool and plywood for the numerical simulation. In the numerical simulation, the seepage, heat diffusion, and evaporation of the LNG are investigated. It is found that the diffusion speed of the leakage is very high to accelerate the evaporation of the LNG.