• 한국입자에어로졸학회지
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• 제15권4호
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• pp.149-157
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• 2019

Infiltration characteristics of airborne particulate matter had been investigated in real-life for about 90 days over 2 years in a Korean apartment building where a 3-person household had lived and the exclusive private area was 84.9 ㎡. Airtightness was measured by fan depressurization, and the ACH₅₀ was 2.41 times per hour. In and outdoor particle concentrations were measured by optical particle counters. Infiltration factors and filtration efficiencies of the house, which reflect the removal of outdoor particles penetrating building envelope and the deposition inside a building, were obtained from data screened based on an empirical evaluation process. Infiltration factor of fine particles showed a range from about 42% at 0.4 m/s of wind speed to 72% at 4.2 m/s of wind speed with closed windows and doors. Filtration efficiency was like a MERV 13 grade filter with an open window outside at a balcony at low outdoor wind speed under 1 m/s. The grade decreased to MERV 11 by opening another outside window at the other balcony. Filtration efficiencies decreased as much as 29% in average at a range of 0.3~2.5 ㎛.

• 상하수도학회지
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• 제25권4호
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• pp.597-604
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• 2011

This study was performed to compare finished water quality among three different processes. A detailed assessment of performance was carried out during the five months of operation. Finished water quality was evaluated on the basis of parameters such as Dissolved organic carbon (DOC), $UV_{254}$ absorbance, haloacetic acid formation potential (HAAFP), geosmin, 2-methylisoborneol (2-MIB), heterotrophic bacteria and total coliform bacteria. The treatment processes were Process 1 (coagulation-flocculation-sedimentation-sand filtration-ozone-GAC), Process 2 (coagulation-flocculation-sedimentation -microfiltration-ozone-GAC), and Process 3 (coagulation-flocculation-sedimentation- sand filtration-GAC), compared side by side in the pilot testing. Process 2 was found to have better removal efficiency of DOC, $UV_{254}$ absorbance, HAAFP and heterotrophic bacteria in comparison with process 1 and process 3 under identical conditions. Geosmin, 2-MIB and total coliform bacteria were not detected in finished water from each process.

• 한국정밀공학회지
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• 제18권10호
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• pp.208-213
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• 2001

High speed milling(HSM) is one of the emerging cutting process having tremendous potential not only in increased metal removal rates but also in improved surface finish, burr free edge, dimensional accuracy and a virtually stress free component after machining. The High efficiency and accuracy in machining of die/mold materials can be obtained in high speed machining, so it is necessary to analytic the mechanism of high speed cutting process : cutting force, acoustic emission signal.

• 해양환경안전학회:학술대회논문집
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• 해양환경안전학회 2017년도 공동학술발표회
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• pp.168-168
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• 2017

• 항공우주시스템공학회지
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• 제14권4호
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• pp.40-46
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• 2020

Recently, the aviation industry has sought to reduce its carbon usage in aircraft operations. Specifically, the industry is proceeding with the development of ultra-large turbofan engines and the development of hybrid electric engines to reduce the fuel consumption of aircraft. In one case, Airbus is developing as its future goal an aircraft with a short take-off distance that uses a catapult. In this study, when a b747-400 aircraft with two of the four engines removed was tested using a catapult, its fuel consumption was compared with that of the original aircraft. Fuel consumption was calculated using the mass flow consumption formula. Further, the aircraft L/D ratio caused by engine removal was interpreted using the CFD Tool, Ansys Fluent. The results showed that the lift ratio was improved by about 7% and that the fuel efficiency was improved by about 14%.

• Environmental Engineering Research
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• 제10권1호
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• pp.15-21
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• 2005

A computer program is developed for the prediction of the flow pattern and the removal efficiency of suspended solid (SS) in a circular secondary clarifier. In this study the increased density effect by SS on hydrodynamics has been systematically investigated in terms of Froude Number (Fr), baffle existence, and a couple of important empirical models associated with the particle settling and Reynolds stresses. A control-volume based-finite difference method by Patankar is employed together with the SIMPLEC algorithm for the resolution of pressure-velocity coupling. The k-ε turbulence and its modified version are incorporated for the evaluation of Reynolds stresses. The calculation results predicts well the overall flow pattern such as the waterfall phenomenon at the front end of the clarifier and the bottom density current with the formation of strong recirculation especially for the case of decrease of Fr. Even if there are some noticeable differences in the prediction of two turbulence models, the calculated results of the radial velocity profiles are generally in good agreement against experimental data appeared in open literature. Parametric investigation has been systematically made with the Fr and baffle condition with detailed analysis.

• 한국포장학회지
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• 제26권1호
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• pp.1-9
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• 2020

We evaluated the applicability of baking soda, charco'al, coffee, and green tea as a natural deodorant in Kimchi packaging. Moreover, to evaluate the potential usage of these deodorants in packaging materials and confirm their applicability in high-temperature melt-extrusion processing, the thermal stabilities of the deodorants were investigated, and heat-treated deodorants were evaluated in terms of the deodorizing function compared with non-treated deodorants. Aroma patterns were decreased after deodorizing treatment with all-natural deodorants. Dimethyl disulfide, methyl trisulfide, and diallyl disulfide, the most significant odorous Volatile organic compounds (VOCs) of Kimchi, decreased after treatment with the deodorants. In particular, baking soda and charcoal showed the highest efficiency in removing odorous compounds and VOCs from Kimchi, even after high-temperature processing. The acetic acid removal rates for both baking soda and charcoal were 99.9±0.0%. The heating process increases the deodorizing effects of baking soda. Sensory evaluation results showed that there is a significant increase (p < 0.05) in the overall preference for Kimchi samples packaged with charcoal and baking soda. This study provides useful information for the deodorization effects of natural deodorants for Kimchi smell and their applicability for packaging materials.

• 환경위생공학
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• 제17권3호
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• pp.115-120
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• 2002

This study was performed on a questionnaire survey of 500 people about their awareness for indoor air pollution, and measured efficiency of air cleaner which can remove the CO and air-borne particulate of ETS(Environmental Tobacco Smoke) in air clean chamber. The room-size cleaner for measuring indoor air contaminants has been applied to evaluation of two different air cleaner such as the mechanic air cleaner with hepafilter(HPA) and the electrostatic air cleaner with metal plate. The measuring experiment was carried out in a chamber by sampling the air. The results obtained were as follows; As respondents are having their 90% of daytime indoors a day, and 38% of them can feel indoor air pollutions degrees directly by their sense of smell, For the installation of indoor pollution control equipment, 34% of all respondents installed air cleaner because of the problem of economical charge and almost respondents was not satisfied the trust of ability purified indoor air pollutants. In the experimental results, it was found that more than 95% of CD and air-borne particulate of ETS were removed within 20 minutes. The reaction kinetics of removal pollutants was verified as the pseudo-first order, Finally, it appeared that the room-sire air cleaner can be applied to new technology for removing indoor air contaminants.

• 한국환경과학회지
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• 제24권9호
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• pp.1163-1170
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• 2015

This study carried out continuous column test for estimating the regeneration efficiency with regeneration times and temperatures. More times regenerated granular activated carbon (GAC) has more ash in the GAC and has less apparent density. Two times regenerated GAC ($2^{nd}$ re-GAC) could removed the Trihalomethanes (THMs) in the water for the first two week after starting continuous column test, on the other hand five times regenerated GAC ($5^{th}$ re-GAC) did not have adsorption capacity. The THMs concentration in the effluent was almost equal or higher than that of influent at the first time of continuous column test. $2^{nd}$ re-GAC showed much more DOC adsorption capacity than $5^{th}$ re-GAC and the GAC which was regenerated with $700^{\circ}C$ had highest DOC removal efficiency among the GACs with 600, 700, 800, $900^{\circ}C$ regeneration temperatures. It is anticipated the cost of GAC regeneration could be saved more 100 million won by reducing the furnace temperature of 3rd~4th and 5th~6th about $150^{\circ}C$ compared to the current regeneration condition.

• 유기물자원화
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• 제24권2호
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• pp.51-58
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• 2016

일체형 2상 혐기성소화 방식은 기존 분리형 2상 혐기성소화의 단점을 보완할 수 있는 기술로 산발효조와 메탄발효조가 병합된 형태의 일체형으로 구성되어 유기물 부하변동 대처 용이, 설치부지면적 감소 등의 이점이 있다. 본 연구는 음폐수를 기질로 일체형 2상 혐기성소화의 유기물 분해효율 및 바이오가스 생산량 등에 대한 실험을 실시하여 기존 분리형 2상 혐기성소화와의 효율 비교를 통해 대규모 플랜트 설치의 타당성 여부를 검토하였다. 5ton/일 규모의 Pilot Plant를 구성하여 약 130일 간 소화조 내 유기물 변화, 바이오가스 생산량 및 메탄함량 등의 실험을 실시하였다. 실험 결과, 평균 음폐수 투입량은 $4.1m^3$/일이었으며, 이때 VS 제거효율은 약 77%로 나타났다. 바이오가스는 평균적으로 투입 음폐수 ton당 약 $63.0m^3$($0.724m^3/kg-VS_{added}$)가 발생되었으며, 메탄함량은 약 61.3%로 분석되었다. 일체형 2상 혐기성소화는 기존 산발효조와 메탄발효조가 분리된 소화방식과 유기물 제거 측면에서 다소 높게 나타났다. 결과적으로 일체형 2상 혐기성소화 방식은 충분히 고농도 유기성 폐수인 음폐수 처리에 있어서 상용화가 가능하다는 결론을 내릴 수 있었다.