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Increased Microalgae Growth and Nutrient Removal Using Balanced N:P Ratio in Wastewater
( Seung Hoon Lee ),( Chi Yong Ahn ),( Beom Ho Jo ),( Sang Ah Lee ),( Ji Yeon Park ),( Kwang Guk An ),( Hee Mock Oh ) 한국미생물 · 생명공학회 2013 Journal of microbiology and biotechnology Vol.23 No.1
Microalgal cultivation using wastewater is now regarded as essential for biodiesel production, as two goals can be achieved simultaneously; that is, nutrient removal efficiency and biomass production. Therefore, this study examined the effects of carbon sources, the N:P ratio, and the hydraulic retention time (HRT) to identify the optimal conditions for nutrient removal efficiency and biomass production. The effluent from a 2nd lagoon was used to cultivate microalgae. Whereas the algal species diversity and lipid content increased with a longer HRT, the algal biomass productivity decreased. Different carbon sources also affected the algal species composition. Diatoms were dominant with an increased pH when bicarbonate was supplied. However, 2% CO2 gas led to a lower pH and the dominance of filamentous green algae with a much lower biomass productivity. Among the experiments, the highest chlorophyll-a concentration and lipid productivity were obtained with the addition of phosphate up to 0.5 mg/l P, since phosphorus was in short supply compared with nitrogen. The N and P removal efficiencies were also higher with a balanced N:P ratio, based on the addition of phosphate. Thus, optimizing the N:P ratio for the dominant algae could be critical in attaining higher algal growth, lipid productivity, and nutrient removal efficiency.
Higher Biomass Productivity of Microalgae in an Attached Growth System, Using Wastewater
( Seung Hoon Lee ),( Hee Mock Oh ),( Beom Ho Jo ),( Sang A Lee ),( Sang Yoon Shin ),( Hee Sik Kim ),( Sang Hyup Lee ),( Chi Yong Ahn ) 한국미생물 · 생명공학회 2014 Journal of microbiology and biotechnology Vol.24 No.11
Although most algae cultivation systems are operated in suspended culture, an attached growth system can offer several advantages over suspended systems. Algal cultivation becomes light-limited as the microalgal concentration increases in the suspended system; on the other hand, sunlight penetrates deeper and stronger in attached systems owing to the more transparent water. Such higher availability of sunlight makes it possible to operate a raceway pond deeper than usual, resulting in a higher areal productivity. The attached system achieved 2.8-times higher biomass productivity and total lipid productivity of 9.1 g m-2 day-1 and 1.9 g m-2 day-1, respectively, than the suspended system. Biomass productivity can be further increased by optimization of the culture conditions. Moreover, algal biomass harvesting and dewatering were made simpler and cheaper in attached systems, because mesh-type substrates with attached microalgae were easily removed from the culture and the remaining treated wastewater could be discharged directly. When the algal biomass was dewatered using natural sunlight, the palmitic acid (C16:0) content increased by 16% compared with the freeze-drying method. There was no great difference in other fatty acid composition. Therefore, the attached system for algal cultivation is a promising cultivation system for mass biodiesel production.
한국산 Botryococcus braunii (Trebouxiophyceae)의 분리 및 계통분류학적 분석
이승훈 ( Seung Hoon Lee ),이찬희 ( Chan Hee Lee ),조범호 ( Beom Ho Jo ),안치용 ( Chi Yong Ahn ),김한순 ( Han Soon Kim ),오희목 ( Hee Mock Oh ) 한국환경생물학회 2012 환경생물 : 환경생물학회지 Vol.30 No.1
Abstract - Recently, energy security is one of the most important world-wide issues. Biodiesel derived from microalgae has received much attention as a renewable bioenergy. The green colonial alga, Botryococcous braunii, is characterized by the ability to produce and accumulate large amounts of hydrocarbons and fatty acids. In this study, we have isolated 5 strains of B. braunii from Korean surface waters using a microcapillary-pipetting method and identified them by morphological features and phylogenetic analysis of the 18S rRNA gene. Phylogenetic analysis indicates that 5 strains of B. braunii are placed in the class of Trebouxiophyceae, and strains belong to race A type producing hydrocarbons which are alkadienes and alkatrienes. In addition, we need further studies to find out optimal growth conditions for producing biodiesel.
소아 만성 두통 환자에서의 Magnetic Resonance Angiography 결과 분석
김승(Seung Kim),이재랑(Jae Rang Lee),윤춘식(Choon Sik Yoon),이영목(Young-Mock Lee),이준수(Young-Mock Lee),김흥동(Heung Dong Kim) 대한소아신경학회 2008 대한소아신경학회지 Vol.16 No.2
목 적 : 두통은 소아 인구에서 매우 흔하고 환자들의 삶의 질에 큰 영향을 끼칠 수 있는 질환으로, 이의 발생 기전에 대하여 많은 가능성이 제시되고 있다. 저자들은 뇌 MRA를 통해 만성 두통 소아 환아에서 뇌혈관 이상과의 연관성을 알아보고자 하였다. 방 법 : 2006년 1월부터 2008년 4월까지 만성 두통을 주소로 내원한 320명의 소아 환자 중 1달에 15일 이상, 3개월 이상 증상이 지속되어 만성 매일 두통의 진단에 부합되는 환아 중에서 1년 이상 증상이 지속되는 경우에 뇌 MRI 및 MRA를 시행하였으며, 정상뇌 MRI 소견을 보였던 44명 환자의 뇌 MRA 결과 및 의무기록을 후향적으로 분석하였다. 결 과: 뇌 MRA를 시행한 총 환자수는 44명이었으며. 그 중 8명(18.2%)에서 뇌혈관의 이상 소견이 발견되었다. 이상 뇌혈관 소견에는 편측 A1 형성저하 5례(11.4%), 편측 A1과 P1 형성저하 1례(2.3%), 편측 척추동맥 형성저하 1례(2.3%), 모야모야병 1례(2.3%)가 있었다. 44명의 환자 중 21명은 두통만을 호소한 환아였고, 나머지 23명은 두통과 함께 다른 신경학적 증상을 호소하는 환아였는데, 이 두 군 사이에 뇌 MRA 이상 빈도는 통계학적으로 유의한 차이를 보이지는 않았다. 결 론 : 소아 만성 두통 환아에서의 뇌혈관 이상 소견이 병인 가능성과 위험 요소로 제시될 수 있으며, 성인으로 성장하는 장기적인 과정에서 뇌혈관 변이와 신경학적 증상 사이의 연관성에 대한 전향적인 연구가 필요할 것으로 사료된다. Purpose : Headaches occur frequently in the pediatric population and have a significant impact on their quality of life. Several mechanisms are currently thought to contribute to headache pathogenesis. Our aim was to investigate the association of chronic headache in children and cerebral vascular anomaly by performing brain magnetic resonance angiography(MRA). Methods : We retrospectively reviewed medical records and MRA of 44 patients with chronic headache who visited the pediatric clinic of Young Dong Severance hospital from January 2006 to April 2008. Results : The number of enrolled patients was 44. Eight(18.2%) of them showed abnormal brain MRA findings. Abnormal findings included 5 cases of unilateral A1 hypoplasia, 1 case of unilateral vertebral artery hypoplasia, 1 case of unilateral A1 and P1 hypoplasia, 1 case of Moyamoya disease. Among the 44 patients, 21 had complained only headache and 23 had complained other neurological symptoms with headache. The ratio of abnormal MRA between the two groups showed no statistical difference. Conclusion : Vascular anomaly could be a possible pathogenesis and risk factor in chronic headache in children. Further investigation and long term follow up is needed.
폐수를 이용한 겨울철 경제적 미세조류 배양 시스템의 개발
이상아 ( Sang Ah Lee ),이창수 ( Chang Soo Lee ),이승훈 ( Seung Hoon Lee ),안광국 ( Kwang Guk An ),오희목 ( Hee Mock Oh ),김희식 ( Hee Sik Kim ),안치용 ( Chi Yong Ahn ) 한국환경생물학회 2014 환경생물 : 환경생물학회지 Vol.32 No.1
우리나라는 겨울철에 미세조류가 성장하기에 적합하지 않은 기후조건을 가진다. 따라서, 차세대 바이오매스의 공급원료로서의 미세조류 배양을 겨울철에 이룩하기는 쉽지 않다. 본 연구에서는 적은 에너지를 이용하여 미세조류가 성장이 불가한 영외환경에서 미세조류를 성장시키기 위해서, 삼중막의 비닐하우스를 설치하였다. 또한 투명한 아크릴 재질로 수조를 제작하여 빛을 수조의 모든 면에서 받을 수 있게 함으로써, 빛의 이용성을 최대화하였다. 6가지의 다양한 실험조건을 설정하여 겨울철 영하의 기후조건에서 최소한의 비용으로 하수종말처리장 폐수를 사용하여 미세조류를 배양하였다. 또한 미세조류 바이오매스를 증가시킴과 동시에 환경오염의 원인이 될 수 있는 영양염류 성분 중 질소를 최대 92%, 인을 최대 99%까지 제거시켰다. 본 연구에서 바이오디젤의 원료가 될 수 있는 가장 주된 지방산은 리놀렌산(C18: 3n3)으로 총 지질량의 최대 61%까지 차지했다. 지방산의 생산성은 2.4 g m-2 day-1이었다. 결론적으로, 본 연구를 통하여 차세대 바이오매스 생산을 위한 미세조류 배양을 저온 시기에서도 이룩하였으며, 그에 따른 폐수처리에서도 좋은 성과를 이루었다. The outdoor mass cultivation is not possible for microalgae in Korea all year round, due to cold winter season. It is not easy to maintain proper level of productivity of microalgae even in winter. To prevent a drastic decrease of temperature in a greenhouse, two layers were covered additionally, inside the original plastic layer of the greenhouse. The middle layer was made up of plastic and the inner layer, of non-woven fabric. Acrylic transparent bioreactors were constructed to get more sunlight, not only from the upper side but also from the lateral and bottom directions. In winter at freezing temperatures, six different culture conditions were compared in the triply covered, insulated greenhouse. Wastewater after anaerobic digestion was used for the cultivation of microalgae to minimize the production cost. Water temperature in the bioreactors remained above 10℃ on average, even without any external heating system, proving that the triple-layered greenhouse is effective in keeping heat. Algal biomass reached to 0.37g L--1 with the highest temperature, in the experimental group of light-reflection board at the bottom, with nitrogen and phosphorus removal rate of 92% and 99%, respectively. When fatty acid composition was analyzed using gas-chromatography, linoleate (C18 : 3n3) occupied the highest proportion up to 61%, in the all experiment groups. Chemical oxygen demand (COD), however, did not decrease during the cultivation, but rather increased. Although the algal biomass productivity was not comparable to warm seasons, it was possible to maintain water temperature for algae cultivation even in the coldest season, at the minimum cost.
Control Strategy of Single-Phase Active Front-End Cascaded H-Bridge Under Cell Fault Condition
Lee, Yoon-Ro,Yoo, Jeong-Mock,Jung, Hyun-Sam,Sul, Seung-Ki Institute of Electrical and Electronics Engineers 2019 IEEE transactions on power electronics Vol.34 No.5
<P>Cascaded H-bridge (CHB) inverter is the most widely used topology for a medium-voltage drive system due to the high degree of modularity, easier implementation of medium output voltage, and the ability to continuous operation under the cell fault condition. Because each power cell of CHB should have isolated dc source, multiwinding input transformer and three-phase active front end (AFE) are generally used for regenerative applications. The whole system can be simplified by replacing the three-phase AFE with single-phase AFE. However, if the control strategy of normal operation is adopted under the cell fault condition, input power imbalance among three phases inevitably occurs. In that situation, not only faulty cells, but also some unscathed cells should be excluded with giving up the maximum capability of the system, not to deteriorate grid current. This paper proposes a control scheme against the cell fault condition of the single-phase AFE CHB. By applying the proposed control scheme to the system, dc-link voltage of each cell and grid current are well regulated without imbalance even under the cell fault conditions. Finally, it can minimize the number of undamaged cells which should be turned <SMALL>off</SMALL> and maximize the capability of the system under the cell fault condition. Simulation and experimental results are provided to verify the effectiveness of the proposed scheme.</P>