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

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

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

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

Recombinant Cyanide Hydratases에 의한 시안화물 분해

권성현(Kwon, Sung-Hyun),조대철(Cho, Dae-Chul) 한국산학기술학회 2009 한국산학기술학회논문지 Vol.10 No.6

시안화물을 포름아미드로 변환시키는 nitrilase의 일종인 시안 수화효소 (cyanide hydratase, CHT) 를 진균류인 Neurospora crassa 와 Aspergillus nidulans로부터 유전자 조작을 통하여 His에 태그 또는 언태그된 형태로 대장균에 형질변환시켜 발현하였다. 발현된 효소를 고정 metal affinity chromatography로 정제하였다. 정제된 효소들의 pH 안정성, 동력학적 매개변수의 값을 검토하였다. 실험 결과 N. crassa 의 CHT가 50% 정도 더 넓은 pH 안정 범위를 가졌고 3배 가량 turnover rate도 높았다. 반면 A. nidulans CHT의 Km 값 (효소포화 용량)이 N. crassa CHT보다 더 크게 나타났다. 두 진균류에서 CHT의 유도발현은 질소성분과 상관없이 KCN에 의해 가능하였으며, 생분해 실험결과 N. crassa CHT에 의해 최대 82%/h의 시안분해가 가능하였다. The genes of cyanide hydratase(CHT), a kind of nitrilases whichhydrolyze cyanide to formamide were extracted from N. crassa and A. nidulans, the two fungal strains. The recombinant forms of the CHT originated from N. crassa and A. nidulans were prepared with N-terminal hexahistidine purificationtags or no tags, and expressed in E. coli. The enzymes were purified using immobilized metal affinity chromatography. They were compared according to their pH activity profiles, and kinetic parameters. The N. crassa CHT has the wider pH range of activity above 50% and three-fold higher turnover rate (6.6 x 10⁸ min⁻¹) than the A. nidulans, meanwhile the CHT of A. nidulans has the higher K_m value. Expression of CHT in both N. crassa and A. nidulans were induced by the presence of KCN, regardless of any presence of nitrogen sources. Max. 82% of KCN was degraded in 60 min for biological degradation tests.

재활용 패각의 산-염기치환 반응을 통한 과산화칼슘의 제조와 산소발생 특성

권성현 ( Sung Hyun Kwon ),유길선 ( Gilsun Yoo ),조대철 ( Daechul Cho ) 한국폐기물자원순환학회 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.

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.

굴패각 배합 석고재료의 열전도 특성 연구

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

굴패각 모르타르에의 휘발성 유기화합물 흡착에 대한 연구

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

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.

목재재질의 담체를 혼합한 토양에서 Bacillus subtilis에 의한 PAH분해에 대한 연구

권성현(Kwon, Sung-Hyun),유승희(Yoo, Seung-Hye),조대철(Cho, Dae-Chul),허남수(Huh, Nam-Soo),김종향(Kim, Jong-Hyang) 한국산학기술학회 2005 한국산학기술학회논문지 Vol.6 No.3

PAHs는 2개 이상의 벤젠링을 가지는 방향족 탄회수소로, 특성과 분자량에 의해 크게 두 가지로 구분되며, 독성 유기물질들이 직·간접적으로 인간에게 피해를 준다. 이러한 PAHs에 오염된 토양을 복구하기 위해서 PAHs를 완전분해 또는 무독성 화합물로 전환시켜야 한다. 본 연구에서는 PAHs분해를 위해 Bacillus subtilis을 사용하였고, 담체로 코르크분말과 톱밥을 선정하였다. Phenanthrene을 분해한 경우 코르크분말 담체와 톱밥담체가 비슷한 분해양상을 보였으며, pyrene을 분해한 두 담체의 경우 톱밥 담체가 우수하다고 판명되었다. 또한 토양함수율은 분해제거효율의 주 영향요소로서 45~55%의 함수율 일 때 최적의 효율을 나타냈다. PAHs are aromatic hydrocarbon compunds with two or more benzene rings. Because they are mostly toxic to human life, they need to be converted to non-toxic compunds or to be degraded completely. This work aims to degrade PAHs (phenanthrene and pyrene) using Bacillus bacteria covered on cork or sawdust. The results show that media effect on phenanthrene was negligible whereas biodegradation ability of sawdust carrying the bacteria was better than that of biofilm-covered cork when pyrene was tested. PAH removal was also affected by soil moisture content with 45~55% of the optimal content.