• Journal of the Korean Society of Marine Environment & Safety
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• v.24 no.5
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• pp.553-568
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• 2018

Chromophoric Dissolved Organic Matter (CDOM) plays a dominant role in absorbing UV-VIS light and is also important in the biogeochemical carbon cycle due to the production of carbon dioxide from photo-oxidation at the sea surface in marine environments. Since absorption by CDOM was recently found to be responsible for increasing the energy absorbed in the mixed layer by 40 % over pure seawater, the importance of CDOM absorption in seawater for increasing sea surface temperature has come to be well recognized. We measured aCDOM and the absorption characteristics of CDOM during spring 2012 and 2014 in the southwestern East Sea. Distribution of CDOM in spring 2012 and 2014 was compared and S value was used to find the source of CDOM in the study area. As a result, the average $a_{CDOM}$ was $0.237m^{-1}$ ($0.009{\sim}0.988m^{-1}$) and the average S value was $16{\mu}m^{-1}$,which shows coastal properties. Also a positive correlation between Chl a and CDOM was observed ($r^2=0.34$), with an especially strong correlation near coastal stations. aCDOM in 2014 was about 40 % higher than aCDOM in 2012 during spring in the study area. This difference in aCDOM concentration resulted not only from annual variation but also from stratification and photobleaching in late spring 2012. This observation implies the possibility of flux of carbon dioxide into the atmosphere as a result of photo-oxidation in the East Sea.

• Journal of the Mineralogical Society of Korea
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• v.30 no.4
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• pp.205-217
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• 2017

Mineral carbonation by indirect method has been studied by serpentinite as cation source. Through the carbonation of $CO_2$ and alkaline earth ions (calcium and magnesium) from serpentinite, the pure carbonates including $MgCO_3$ and $CaCO_3$ were synthesized. The extraction solvent used to extract magnesium (Mg) was ammonium sulfate ($(NH_4)_2SO_4$), and the investigated experimental factors were the concentration of $(NH_4)_2SO_4$, reaction temperature, and ratio of serpentinite to the extraction solvent. From this study, the Mg extraction efficiency of approximately 80 wt% was obtained under the conditions of 2 M $(NH_4)_2SO_4$, $300^{\circ}C$, and a ratio of 5 g of serpentinite/75 mL of extraction solvent. The Mg extraction efficiency was proportional to the concentration and reaction temperature. $NH_3$ produced from the Mg extraction of serpentinite was used as a pH swing agent for carbonation to increase the pH value. About 1.78 M of $NH_3$ as the form of $NH_4{^+}$ was recovered after Mg extraction from serpentinite. And, the main step in Mg extraction process of serpentinite was estimated by geochemical modeling.

• Membrane Journal
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• v.24 no.3
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• pp.213-222
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• 2014

In this study, 2-stage recirculation membrane process was developed for purification of high purity bio-methane for the vehicle fuel application. Pure gas permeation and mixture gas permeation test were done as a function of methane content and pressure in the feed using polysulfone membrane modules. 2-stage membrane plant was designed, constructed in a food waste treatment cite. Dehumidification, dry desulfurization, and desiloxane plants are installed for the removal of $H_2O$, $H_2S$ and siloxane in the biogas. Permeation test were done with the pre-treated methane mixture in terms of methane purity and recovery by adjusting the ratio of membrane area (1:1, 1:3, 2:2) in the first and second membrane modules in the plant. When membrane area of 2 stage increased to $3m^2$ from $1m^2$ at 1-stage membrane area of $1m^2$, the feed rate and $CH_4$ recovery at 95% methane purity were increased from 47.1% to 92.5% respectively. When the membrane area increased two-fold (1:1 to 2:2), $CH_4$ recovery increased from 47.1% to 88.3%. When the feed flow rate was increased, in 1:3 ratio, final purity of the methane is reduced, the methane recovery is increased. When operating pressure was increased, the feed rate was increased and recovery was slightly decreased. From this result, membrane area, feed pressure and feed rate could be the important factor to the performance of the membrane process.

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.152.2-152.2
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• 2010

LFG는 매립된 폐기물 중 유기성분이 혐기성조건에서 미생물에 의해 분해가 되면서 발생하며, 이러한 매립지가스는 주변 지역의 자연 및 생활환경에 악영향을 미치기 때문에 소각 등의 방법으로 LFG를 처리하고 있다. 일반적으로 매립지로부터 발생하는 가스의 량은 폐기물 1톤 당 $150{\sim}250m^3$로서 매립 후 2~3년 후에 최대량이 발생하며 매립 후 20~30년 후까지 지속적으로 발생함으로 안정적인 LFG의 공급이 가능하며, 메탄함량이 50%인 경우 약 $5,000kcal/m^3$의 높은 발열량을 가지므로 대체에너지원으로 이용할 경우 환경적인 문제 해결 및 신재생에너지원으로 활용할 수 있다. LFG 자원화 할 경우 가장 안정적인 방안으로 발전 및 중질가스로 활용하는 것이나, 발전의 경우 최소 200만톤 이상의 매립용량을 갖추어야 경제적인 사업성을 확보할 수 있으며, 중질가스로 활용하는 경우 인근에 가스 수요처를 확보해야 하는 어려움이 있다. 만약 중 소규모의 매립장에서 발생하는 LFG를 안전하고 경제적인 조건으로 저장 및 수송할 수 있다면 중 소규모의 매립지에서 발생하는 LFG도 활용할 수 있을 것으로 기대되며, 안전하고 경제적인 저장과 수송기술을 통하여 발전이 아닌 중질가스로의 활용도 가능하게 될 것이다. 또한 여러 곳의 매립장에서 발생한 LFG를 한 곳으로 집중시켜 고질가스로 전환하는 설비비용을 절감할 수 있으며, 정제된 고질가스를 이용하여 발전보다 경제적인 자동차 연료나 도시가스로 활용할 수 있을 것이다. 본 연구에서는 LFG의 저장과 수송기술 중 GTS 기술을 통하여 저장과 수송에 제약이 크고 많은 비용이 소비되는 기체 상태의 에너지원을 하이드레이트화 시킴으로서 중 소규모 매립지에서 상대적으로 적은 비용으로 가스저장과 지상수송이 가능하게 할 수 있다. 본 연구의 결과로 LFG 에너지화 실증화 플랜트를 설계/제작 하였으며, 메탄+이산화탄소+물 하이드레이트 형성 실험 결과 4.56 Mpa, 277.2 K 조건에서 3시간을 한 사이클로 하는 공정운전을 가지는 것을 확인하였다. 이때 생성된 슬러리상의 하이드레이트를 고압으로 배출하여 펠릿으로 형성시켰으며, 형성된 하이드레이트 펠릿의 경우 92.27%의 메탄을 포함하는 것을 확인하였다.

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.112.2-112.2
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• 2010

지구의 온난화로 인한 기상변화 등이 계속적으로 발생하는 가운데 전 세계는 지구 온난화의 가장 근본적인 원인인 이산화탄소의 방출을 줄이기 위한 방안을 찾기 위해 많은 노력을 하고 있다. 이에 대해 전 세계적으로 각종의 기후협약 체결, 리우선언, 도쿄의정서 등을 통해 온실가스 배출원인인 석유 등 화석에너지 배출을 억제하기 위한 활동이 행해지고 있으며, 기존의 화석연료를 대체할 수 있는 새로운 에너지를 발견하기 위한 연구개발에도 박차를 가하고 있다. 이러한 계속적인 연구개발에서, 세계의 국가들은 친환경 에너지인 태양열, 풍력, 지열 및 수소에너지와 같이 화석연료를 대체할 수 있는 다양한 에너지를 조사하고 개발해왔고 현재도 가장 적합한 에너지 자원을 찾기 위하여 노력 중에 있다. 최근에, 수많은 대체에너지 중 수소 에너지는 유해배출가스가 없기 때문에 가장 유망한 대안이라고 판단되어 전 세계가 수소에너지 연구개발에 주목하고 있다. 이러한 수소에너지를 교통수단에 적용하기 위하여 전 세계적으로 안전성 및 기술 확보를 위한 기술개발과 안전기준의 확립하기 위해 노력하고 있다. 현재 기술적으로 수소를 자동차용 연료로 사용하기 위해서는 수소를 액체 상태 및 압축 상태로 저장하는 것이다. 두 가지 저장방법 중 세계 대부분의 자동차 메이커들은 수소를 압축하는 방식을 채택하고 있으며, 자동차의 주행거리를 최대한 확보하기 위하여 수소가스를 고압으로 압축한 상태로 저장하는 방식을 사용하고 있다. 이에 따라 고압의 수소를 안전하게 저장할 수 있는 고압수소용기의 개발이 필요하다. 수소연료전지 자동차에 장착이 가능한 고압으로 압축된 수소를 저장할 수 있고, 자동차에 탑재할 수 있도록 적합한 크기의 가벼운 용기의 개발이 진행되어지고 있다. 자동차용 용기는 크게 4가지 타입으로 구분지어 진다. 현재는 4가지 타입의 압축용기 중 안전성과 중량을 만족시키기 위해 Type3와 Type4 형태의 용기가 수소자동차에 시범적으로 적용되어 운용되고 있다. 또한 고압수소용기의 신뢰성과 안전성을 확보하기 위한 기준 및 코드가 국 내외에서 연구 개발되고 있다. 본 연구에서는 수소연료전지자동차에 장착되는 고압수소용기의 국제기준 동향에 따른 국내의 차량용 고압수소용기를 위한 KGS 안전기준의 개발현황과 개발방향을 제시하고자 한다.

• Journal of the Korean Institute of Gas
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• v.21 no.4
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• pp.76-83
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• 2017

Biogas, combine with ever-increasing natural gas demand, has been on the center stage in South Korea for the early part of twenty first century in an effort to reduce the emission of global warming gases. With the passage of legal system of City Gas Business Law in 2014, the biogas has its place of production and distribution to consumers. However, it has a room for its technological improvements in terms of enrichment, by separating carbon dioxide and removing impurities efficiently. For these improvements, four different methane enrichment processes were tested in this study; membrane separation, water absorption, Chemical Absorption and Adsorption. A variety of operation scenarios were applied to the processes and the best practices were drawn out. The optimum process was selected based on case study results. Methane produced in this study showed 97% purity and 98% recovery rate, which meets the requirements of the City Gas quality standards.

• KSBB Journal
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• v.16 no.1
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• pp.66-70
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• 2001

Factors affecting the supercritical carbon dioxide extraction of camptothecin(CPT) and 10-hydroxycamptothecin(HCPT) from the dried powder of Cmptotheca acuminata were studied. Only a few amount of CPT and HCPT was extracted with pure supercritical carbon dioxide. Methanol and ethanol were efficient modifiers to extract CPT and HCPT. At $40^{\circ}C$, 250 bar, 1 mL/min flow rate, 41% of CPT and 35% of HCPT were extracted with supercritical carbon dioxide modified with 16% of methanol. The diffusion effect of HCPT on extraction efficiency was studied in this solid-fluid system. Round matrix hot-ball model assumption revealed that the value of D/$r^2$ was 0.0072 $min^{-1}$ which was higher than that of solvent extraction with methanol.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.3
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• pp.335-342
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• 2012

Nowadays, automobile manufacturers are focusing on the reduction of exhaust-gas emissions because of the harmful effects on humans and the environment, such as global warming by greenhouse gases. Gasoline direct injection (GDI) combustion is a promising technology that can improve fuel economy significantly compared to conventional port fuel injection (PFI) gasoline engines. In the present study, ultra-lean combustion with an excess air ratio of over 2.0 is realized with a spray-guided-type GDI combustion system, so that the fuel consumption is improved by about 13%. The level of exhaust-gas emissions and the operation performance with the multiple injection strategy and exhaust-gas recirculation (EGR) are examined in comparison with the emission regulations and from the point of view of commercialization.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.11
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• pp.999-1004
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• 2010

Recently, many technologies have been developed in order to satisfy stringent emission regulations. However, in the case of diesel engines, the stringent emission regulations with respect to NOx and PM have not yet been satisfied. A dramatic reduction in the NOx and PM emissions could be achieved by using after-treatment systems such as lean NOx trap (LNT) and urea-SCR systems. However, the high temperature in the exhaust pipe affects the spray behavior of the secondary injector, which is used for supplying the Urea-SCR. Because of this high temperature, it is difficult to achieve uniform distribution of the reducing agent in the manifold. In this paper, the characteristics of a urea-SCR injector used for injecting in the exhaust pipe are presented. The purpose of this study was to investigate the spray characteristics of the injector, such as the spray angle, injection quantity, and SMD. In addition, laser diagnostics and high-speed-camera images were used to analyze the injector spray characteristics and to present a distribution of reduction in the transparent manifold.

• Journal of Korean Society of Environmental Engineers
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• v.33 no.8
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• pp.591-597
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• 2011

The purpose of this study was to determine optimum conditions for the cultivation of Chlorella sp. FC-21 using light emitting diodes (LEDs). Specific growth rate and cell concentration were measured for the reactors at the illuminations of different wavelengths of LEDs. Among various types of LEDs, red LEDs were the most effective light source, and also greatest increases of specific growth rate and cell concentrations were obtained when light intensity of red LEDs increased. The specific growth rate decreased when initial cell concentration increased due to the shading effect of each cell in the reactor. To determine beneficial effect of aeration to cell cultivation, micro-air bubbles were aerated at 0.35 vvm in the reactor at the illumination of red LEDs. Two and ten times greater specific growth rate and cell concentration were obtained when aeration was applied. From this study, we found that red LEDs with aeration were the most appropriate light source for the cultivation of Chlorella sp. FC-21.