여과담체에 대한 BTX ( Benzene , Toluene , Xylene ) 의 제거

권성현(Sung Hyun Kwon) 경상대학교 해양산업연구소 2001 해양산업연구소보 Vol.14 No.-

공정시스템,이동현상,화학공정안전 : 엔도설판류의 광 및 초음파분해

권성현 ( Sung Hyun Kwon ),김종향 ( Jong Hyang Kim ),조대철 ( Dae Chul Cho ) 한국화학공학회 2007 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.45 No.5

해양 퇴적물의 혐기적 용출특성과 이에 미치는 산소발생제 CaO<SUB>2</SUB>의 영향에 대한 연구

권성현(Kwon, Sung-Hyun),조대철(Cho, Dae-Chul) 한국산학기술학회 2010 한국산학기술학회논문지 Vol.11 No.10

실험실 규모의 모사 실험을 통하여 해양 부영양화를 촉진하는 퇴적물의 용출 특성을 연구하였다. 즉 pH, ORP, 질소성분, 인성분 등 주요 환경인자를 분석하고 그에 따른 용출율을 계산하였다. 또한 산소발생제인 과산화칼 슘을 이용하여 자연적 용출의 제어효과를 분석하였다. 산소발생제 처리에 따라 호기적 조건으로의 퇴적토 환경변화 가 일어났으며 COD, NH3-N의 용출율이 감소하고 질산화 촉진으로 NOx 성분은 증가하였다. 총인과 인산염인도 Ca 이온의 불용화 기작에 의거 감소하였다. 이에 따라 퇴적토의 용출로 인한 해양 부영양화 억제 방법론을 정립하고자 한다. We studied the release characteristics of the marine sediment which could facilitate sea eutrophication through some lab-scale simulation experiments. Environmental indicators such as pH, ORP(oxidation reduction potential), nitrogens, and phosphates were measured in order to calculate the corresponding release rates. CaO2, an oxygen releasing compound was used to determine how it would effect on the natural process of sedimental release. COD, ammonia nitrogen, phosphorous compounds were less released under the oxic environment caused by CaO2. This basic data will help developing methodology for reducing marine eutrophication which may be initiated by the sedimental release.

재활용 패각의 산-염기치환 반응을 통한 과산화칼슘의 제조와 산소발생 특성

권성현 ( Sung Hyun Kwon ),유길선 ( Gilsun Yoo ),조대철 ( Daechul Cho ) 한국폐기물자원순환학회(구 한국폐기물학회) 2019 한국폐기물자원순환학회지 Vol.36 No.2

The Korean coastal sediment area is apt to be contaminated by prevailing aquafarming and inland eutrophic sources. Furthermore, oyster shells are being overproduced every year with little recycling. Oxygen-releasing compounds (ORCs) are paramount in bioremediation or bioaugmentation. Calcium peroxide, one of the primary ORCs, was prepared using recyclable oyster shells via acid?base reactions based on double replacement, and this was followed by oxidation with hydrogen peroxide. Hydrogen peroxide, which is known to be effective as oxidizing agent, required an optimum dose for higher content of oxygen in the final product, because the literature shows that the oxidative reaction is reversible. A variety of concentrations of HCl and NaOH were examined in stoichiometry for the breakdown of calcium carbonates (or CO₂ production) and formation of calcium hydroxide in the initiation reaction. Acid and base overdoses helped the oxygenation reaction to be extended further, thus leading to calcium peroxide with the highest content of oxygen at a combination of 6 N-12 N acid-base treatment. With an elevated temperature, more oxygenated calcium peroxide was likely to be formed. Carbon dioxide and free oxygen during the experiments were determined with DO probing and gas capture in a water bath.

굴패각 모르타르에의 휘발성 유기화합물 흡착에 대한 연구

권성현(Sung-Hyun Kwon),조대철(Daechul Cho) 한국청정기술학회 2013 청정기술 Vol.19 No.2

굴패각과 석고를 대상으로 고형화시킨 후 포름알데히드 및 벤젠으로 대표되는 휘발성 유기화합물(volatile organic compounds, VOCs)를 흡착챔버 내에서 노출시켜 흡착특성을 관찰하였다. VOC를 챔버에 노출 후 굴패각과 같은 친환경재료를 혼입한 모르타르를 각각 개별적으로 주입한 후 180분간 흡착특성을 고찰하였다. 굴 패각분말을 0, 10, 30, 50%로 혼입한 시험체를 대상으로 포름알데히드와 VOC(벤젠, 톨루엔, 자일렌)를 27.7~28.5 mg/㎥의 고농도 조건과 175~150 μg/㎥의 저농도 조건에서 각각 노출시켜 흡착성 실험을 수행한 결과, 전반적으로 노출된 조건과 무관하게 굴패각의 혼입 함량이 많을수록 흡착성이 증가함을 관찰할 수 있었다. 또한 대류-확산-흡착이 고려된 모델을 사용하여 실험과 비교하였다. 확산계수 및 확산 길이(diffusion length)로 대변되는 흡착재의 친화력(affinity)을 고려한 모델을 시험한 결과, 피흡착제의 종류와 흡착재의 친화성에 따른 차이를 잘 표현하였으며 전반적으로 실험데이터와 일치하는 경향을 보였다. VOCs such as formaldehyde and benzene in a control chamber were adsorbed onto gypsum incorporating oyster shell powder, which was solidified and dried. VOC was first exposed in air and then gypsum mortar was placed in the chamber for 180 min for adsorption. The mortar was prepared with 0, 10, 30, and 50% of oyster shell powder. Two initial concentrations of VOCs including formaldehyde were 27.7~28.5 mg/㎥ or 175~150 μg/㎥. We found out that the initial concentrations did not seem to make any difference in adsorption performance but higher oyster content strongly led to higher adsorption. We used a convectiondiffusion-adsorption model to compare the experiment. The model which considers diffusion coefficients of adsorbates and affinity of the adsorbents well represented the experimental data with a fair agreement.

재무제표를 활용한 사이클 타임 측정방안에 관한 연구

권성현(Sung Hyun Kwon),황국재(Kook Jae Hwang),김길선(Kil Sun Kim) 한국경영학회 2004 經營學硏究 Vol.33 No.6

As manufacturing firms in today’s environment have involved more and more in time- based competition, an ability to manage and allocate cycle time efficiently becomes one of core competencies for the firms. However the absence of appropriate measurement and evaluation tools for cycle time prevents firms from actively utilizing the notion of cycle time as a performance measure. Furthermore, since no extant research provides sound explanation of factors that systematically influence the measured cycle time, it is important to identify and understand the factors to make sound managerial judgments on inter- and intra-firm comparisons and consequent improvement of cycle time.The purposes of present study are to develop a model of cycle time measurement using publicly available financial data and to identify non-operational factors that systematically influence the measure cycle time, which enables managers performance evaluation, competitive benchmarking, and effective managerial decision making processes with respect to cycle time performance. In the current study, we have utilized a panel of financial data for domestic manufacturing firms through the periods of 1981-2002, and generated the following results. First, a model of cycle time measurement using financial data is proposed. Second, we identify non-operational factors such as gross margin ratio, capital intensity, and input-output ratio that systematically influence the measured cycle time, and show that the proposed model per se has some inherent limits to be used as a sound operational measure of cycle time. Third, we also propose an adjusted measure of cycle time which takes into account of the effect of the factors on cycle time measurement, and show through case analyses how the adjusted measure can be used to make within-firm analyses and between-firms comparisons of cycle time. Our results show that the overall cycle time performance is deteriorating over the past 20 years, which is consistent with the results from other researches: Kekre and Srinivasan (199), Rajagopalan and Malhotra (2001), Gaur et al. (2004), and Ginter and La Londe (2004). Reasons include increased product variety, shorter product life cycle, increasing degree of global outsourcing that leads to longer manufacturing cycle time, and the increased degree of complexity in supply chain network.Some of the limits encountered during the course of the current study include the methodological limits that are known to exist in panel data analyses, reliability and consistency of accounting policies across firms, the use of fixed effect model that prevents us from understanding variance that could possibly be explained by the time and firm specific variables, and lack of more detail analyses to understand the differences across industry sectors.Based the limits addressed, the current study shed some lights on the directions for the future research. First, to make our model more useful in practice, it is necessary to verify the directional consistency between the results from the model and the observations from the industry in terms of actual cycle time. The theoretically verified consistency will provide more concrete support for the use of the model. Second, using the model, one can study how the operational improvements and changes initiated by managers can be linked to actual improvement of cycle time. Thus, one can systematically track the effectiveness of cycle time improvement programs using financial data. Third, while the current study employed time and firm specific effects as fixed effects in the model, one can study the factors that influence the changes in firm and time specific effects. Furthermore, one can identify other significant non-operational factors to be included in the model that influence the cycle time performance. Last, similar studies can be done to understand the differences among industry sectors, and can also be extended to non-manufacturing sectors such as distribution and re

연구논문 : 액상 PAHs의 자외선에너지와 초음파를 이용한 분해

권성현 ( Sung Hyun Kwon ),김종향 ( Jong Hyang Kim ),조대철 ( Dae Chul Cho ) 한국환경과학회 2006 한국환경과학회지 Vol.15 No.7

연구논문 : MFC의 금속 및 탄소전극에 의한 전기생산 특성과 오염저감 효과

권성현 ( Sung Hyun Kwon ),송형진 ( Hyung Jin Song ),이은미 ( Eun Mi Lee ),조대철 ( Dae Chul Cho ),이인형 ( In Hyoung Rhee ) 한국환경과학회 2010 한국환경과학회지 Vol.19 No.8

미세조류 Botryococcus braunii의 배양조건 최적화 및 지질축적 향상

권성현 ( Sung Hyun Kwon ),이은미 ( Eun Mi Lee ),조대철 ( Dae Chul Cho ) 한국환경과학회 2012 한국환경과학회지 Vol.21 No.7

Several tests and experimental work have been done for identifying the best growth conditions and accumulated amount of lipid moiety in B. braunii, a microalga(UTEX 572) in terms of media composition. The specific growth rate was found to be the highest at 0.15 g/L-day when the phosphorus concentration was doubled with the other ingredients at the normal level. Experiments for varied media compositions revealed that the accumulation of lipid was the highest at 48% (dry cell weight based) in the nitrogen deficient medium and its corresponding specific growth rate was comparative to that in the normal BG 11 medium. In the bubble column experiments, carbon dioxide containing air produced four times more cell mass than air only. Light and glucose addition also enhanced cell mass with maximum, 1.8 g/L and accordingly 42% of lipid composition, which turned out to be a better strategy for higher lipid-producing microalgal culture.

해양생물 Botryococcus braunii에서 유래한 바이오연료의 고급생산기술: 전처리 용매추출법

권성현 ( Sung-hyun Kwon ),조대철 ( Daechul Cho ) 한국환경과학회 2019 한국환경과학회지 Vol.28 No.11

A lipid-enriched strain of Botryococcus braunii (UTEX 572) was cultivated in a semi-batch aeration tank to enhance biomass as well as to develop intracellular lipids and fatty acids. A 30 day period of incubation produced 1.39 g/L of biomass and 0.31 g/L of total lipids in the biomass. The grown biomass was pre-treated using several methods to extract the total lipid content efficiently: ultrasonication was found to yield the highest percentage of lipids-namely 19.8% per biomass. Direct heating of biomass in an autoclave also showed better performance than when using only conventional solvent extraction. To enhance the biomass harvest and lipid extraction efficiency, coagulation and flocculation steps were added to the extraction process. It is noteworthy that not only the solvent type but also the solvent/biomass ratio greatly affected efficiency. In addition, the moisture content of the harvested(wet) biomass affected the efficiency significantly. This study elucidated the need for future research on optimizing this extraction process.