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        검색결과 983

        724.
        2013.03 KCI 등재 서비스 종료(열람 제한)
        The amount of municipal solid waste (MSW) is steadily increasing leading to an urgent need for the effective treatment of these wastes. Incineration is one of the methods for the treatment of these solid wastes. The bottom ashes produced from the incineration process are very unstable at standard atmospheric conditions, so there is need for process to alleviate the ash problems. In this study, the bottom ashes were first converted into the slurry form and then the slurry was made to react with CO2 to produce the carbonates. This carbonate process by using bottom ashes and carbon dioxide will be source recovery technology from waste material and, moreover, will also help to reduce the amount of CO2 emissions. The aim of this study was to determine the optimum conditions for the precipitation of CaCO3 using Aspen plus modeling program. The temperature and pressure for the precipitation of CaCO3 process were varied 25 to 500oC and 1.05 bar to 90bar, respectively. For producing the slurry, the optimum ratio of H2O to calcium oxide was determined to be 10 : 1. And the optimum precipitating conditions for calcium carbonate process system were found to be at 35 bar - 210oC.
        725.
        2013.03 KCI 등재 서비스 종료(열람 제한)
        충남 부여군 홍산면 일대의 백운사층 셰일에서 산출되는 운모류 광물(혼합상 백운모)과 십자석에 대한 EPMA 연구를 수행하여, 혼합상 백운모와 십자석 생성 과정과의 관계 및 백운사층 셰일의 변성환경을 규명하고자 하였다. 암석에서 산출되는 운모류 광물의 평균 화학조성은 (K1.11Na0.26Ca0.04)(Al3.93Fe0.21Mg0.07)(Si6.08Al1.92)O20(OH)4로 층간 양이온 함량이 낮으며(1.41) 팔면체 자리에 Fe, Mg를 함유한 일라이트, 즉 백운모/파이로필라이트/녹니석 혼합상(Mu70.5Py23.5Ch6.0)의 화학조성을 보인다. 한편 십자석은 암석 내에서 혼합상 백운모, 단일 결정의 파이로필라이트 및 알루미늄 규산염 광물과 함께 산출되는데, 이들 중 파이로필라이트가 십자석 생성에 참여한 것으로 판단된다. 혼합상 백운모에서 분리된 파이로필라이트와 녹니석이 반응하여 클로리토이드를 형성한 이후, 변성도가 증가하면서 파이로필라이트와 클로리토이드가 반응하여 십자석이 생성된 것으로 보이며, 이때 클로리토이드는 모두 소모되어 암석 내에서 관찰되지 않는 것으로 판단된다. 결국 일라이트가 백운모로 전이되는 과정에서 형성되는 혼합상 백운모는 십자석 생성에 필요한 광물을 공급하는 중요한 역할을 하는 것으로 보인다. 이 반응이 300℃ 이상에서 일어나는 점과 혼합상 백운모에서 분리된 파이로필라이트가 약 350℃에서 알루미늄 규산염 광물로 전이되는 점을 감안할 때, 백운사층 셰일은 300~350℃의 변성환경을 경험한 것으로 판단된다.
        726.
        2013.02 KCI 등재 서비스 종료(열람 제한)
        A* algorithm is a global path generation algorithm, and typically create a path using only the distance information. Therefore along the path, a moving vehicle is usually not be considered by driving characteristics. Deceleration at the corner is one of the driving characteristics of the vehicle. In this paper, considering this characteristic, a new evaluation function based path algorithm is proposed to decrease the number of driving path corner, in order to reduce the driving cost, such as driving time, fuel consumption and so on. Also the potential field method is applied for driving of UGV, which is robust against static and dynamic obstacle environment during following the generated path of the mobile robot under. The driving time and path following test was occurred by experiments based on a pseudo UGV, mobile robot in downscaled UGV’s maximum and driving speed in corner. The experiment results were confirmed that the driving time by the proposed algorithm was decreased comparing with the results from A* algorithm.
        727.
        2013.01 KCI 등재 서비스 종료(열람 제한)
        The effects of NaCl concentration on bio-hydrogen production and microbial community by dark-fermentation were evaluated. The examined NaCl concentration was varied from 0 to 5%. When NaCl concentration ranged from 0 to 3%, the hydrogen production was insignificantly affected. 4% or more NaCl concentration decreased accumulated hydrogen production and the lag time was longer. In addition, the metabolite pathway of the bacteria were shifted from butyrate to acetate by microbial community changes with high concentration of NaCl. FISH analysis was achieved to analyze the microbial community after the dark-fermentation performance. Hydrogen producing bacteria, Clostridium sp. Cluster I and Cluster XI, was dominated with 0 ~ 3% of NaCl, while Eubacteria, general bacteria, was dominated with 4 ~ 5% of NaCl. Therefore, the growth and hydrogen production of the hydrogen producing bacteria were inhibited with over 4% of NaCl.
        728.
        2013.01 KCI 등재 서비스 종료(열람 제한)
        The most effective chemical pretreatment method for Scenedesmus dimorphus was evaluated based on solubilization rate and saccharification yield. When 1% of S. dimorphus with 0.5 N of chemicals such as HCl, H2SO4, HNO3, NaOH and KOH was autoclaved at 120oC and 1.1 atm for 60 min, the solubilization rate was high with alkali chemicals while the saccharification yield was low compared to that with acid chemicals. The pretreatment efficiency was significant in order in HNO3, HCl and H2SO4, however, HCl would be effective for field application considering the cost. The proper concentration and time to treat with HCl were concluded in 1 N and 10 min. In the conditions with 1 : 1 mixed acid chemicals such as H2SO4+ HNO3, HCl + HNO3 and HCl + H2SO4, the solubilization rate was similar to that with single acid treatment, while the saccharification yield was enhanced about 34% in the mixed condition with H2SO4 and HNO3 compared to that treated with H2SO4.
        729.
        2012.12 KCI 등재 서비스 종료(열람 제한)
        대류권의 건조가스 및 수증기에 의한 GPS 신호의 지연은 GPS 측위 정확도를 저하시키는 주요 원인으로 정밀 측위를 위해서 반드시 소거해야할 대상이다. 이 논문에서는 실시간으로 대류권 지연정보를 생성하여 GPS 측위에 적용하기 앞서, 대류권 지연정보 생성 알고리즘의 가용성을 파악하기 위해 후처리 기반으로 전국의 GPS 상시관측망을 이용하여 한반도 상공의 대류권 지연량 격자 지도를 생성하는 과정을 구현하였다. GPS 자료처리 소프트웨어는 GIPSY 5.0을 사용하였고, 건조지연량과 습윤지연량을 구분하여 산출하기 위해 전국의 AWS 관측망의 관측자료를 이용하였다. 대류권 지연정보에 대한 격자 지도를 생성한 후 격자 지도의 정확도를 검증한 결과, 격자 지도와 GPS 관측소 위치에서 산출된 대류권 지연량의 RMSE는 ZHD 0.7mm, ZWD 7.5mm, ZTD 8.7mm로 나타났다. 산출된 대류권 지연정보를 단일주파수 기반 상대 측위 알고리즘에 적용하여 대류권 지연정보 보정시 측위정확도 향상 정도를 분석하였다. 결과로 측위정확도는 기선거리가 약 297km인 수원(SUWN)과 목포(MKPO)의 상대처리 결과에서 최대 36%가 향상됨을 확인할 수 있었다.
        730.
        2012.12 KCI 등재 서비스 종료(열람 제한)
        Korea has adopted a federal renewable electricity standard that begins at 2% in 2012 and requires companies to source 10% of their electricity from renewables by 2022. Therefore the interest in the use of biomass as a renewable energy resource is growing. By importing biomass, the Korea, which produces too little biomass of its own, can meet the needs of the renewable energy sectors. In the case of import biomass, it will cost a great deal on the transportation and logistics of biomass materials. Therefore new research and development on the biomass fuel with high energy density is needed to reduce logistics cost on transportation of the biomass fuel. Torrefaction is a thermochemical treatment process of biomass at temperatures ranging between 200 and 300oC. Typically, 70% of the mass is retained as a char product, containing 90% of the initial energy content. Torrefaction experiments on samples of EFB were performed in a fixed bed reactor to determine the effect of operation variables such as reaction temperature (205-310oC), reaction time (20-40 min) and air ratio (0-0.18) on char yield and characteristics. Increase of the torrefaction temperature led to a decrease of the yield of the char. The heating value of char increased with the increase of the reaction temperature, because the carbon content increased and hydrogen and oxygen content decreased. The yield of char decreased with increasing air ratio. This suggested that oxidation of EFB occurred during torrefaction in the presence of oxygen.
        731.
        2012.12 KCI 등재 서비스 종료(열람 제한)
        리퀴리티게닌과 이소리퀴리티게닌은 감초의 주요 플라보노이드 성분이다. 이들 플라보노이드는 수용성 감초추출물과 β-glucosidase를 생성하는 잎새버섯 HB0071 균사체 발효배양을 통하여 생산하였다. 감초추출물 내 리퀴리티게닌과 이소리퀴리티게닌은 잎새버섯 발효배양 동안 현저히 증가하였다. 이 균주의 β-glucosidase의 활성은 배양 96시간을 기준으로 최고 91.5 mU/mL로 확인되었으며, 감초추출발효물로부터 생성된 리퀴리티게닌과 이소리퀴리티게닌의 함량은 HPLC 분석을 통하여 최대 568.5 μg/mL과 89.6 μg/mL로 확인되었다. 본 연구에서는 감초추출물의 잎새버섯 발효 전․후의 시료가 처리된 각질형성세포를 이용하여 자외선 UVB에 조사로 발현된 염증유발인자(COX-2)와 사이토카인(IL-1β, IL-6) 모두 감초추출발효물(FLEx)에서 농도의존적으로 발현이 억제되는 것을 확인하였다. 결론적으로 리퀴리티게닌과 이소리퀴리티게닌의 함량이 증가된 감초추출발효물은 자외선으로부터 손상된 피부 염증반응을 완화시켜줄 것으로 사료된다.
        732.
        2012.10 KCI 등재 서비스 종료(열람 제한)
        Batch cultivations were performed to evaluate the influences of the initial pH condition on mesophilic and thermophilic acidogenic fermentation with food waste recycling wastewater. In both conditions of mesophilic and thermophilic fermentation, TVFAs production rates were maximized at the initial pH 7 condition as 0.15 and 0.23 g TVFAs/L·hr, respectively. And pH was also maintained stably between 6 and 7 during 72hr acidogenic cultivation at both conditions. However, predominant VFA components were different according to reaction temperature conditions. In mesophilic condition, propionic acid which has low conversion efficiency to methane was accumulated up to 1,348 mg/L while acetic and butyric acid were predominant in thermophilic condition. Therefore, thermophilic acidogenic fermentation was superior for the effective VFAs production than mesophilic condition. From the DGGE analysis, the band patterns were different according to the initial pH conditions but the correlations of the each band were increased in similar pH conditions. These results mean that microbial communities were certainly affected by the initial pH condition. Consequently, the adjustment of the initial pH to neutral region and thermophilic operation are needed to enhance acidogenic fermentation of food waste recycling wastewater.
        733.
        2012.10 KCI 등재 서비스 종료(열람 제한)
        We studied the ozone concentrations generated by low-temperature dielectric barrier discharge plasma reactor after adding air and phytoplankton to control the ozone concentrations in seawater. We also examined the numbers of bacteria and Vibrio spp. after treatment using the plasma reactor. As the airflow rate was increased, more ozone was removed. Although marked variation in the ozone decrease was observed with and without airflow, the rate of ozone removal did not increase proportionately with the airflow rates. The ozone concentration decreased with increasing organic matter and time. The amount of organic matter seems to be an important factor decreasing the dissolved ozone concentration in liquid. The ozone concentration was 0.07, 0.32, 1.28, and 2.3 mg/L when operating the plasma reactor for 30, 60, 180, and 300 s, respectively; i.e., the ozone concentration increased with the reactor operating time. The initial numbers of bacteria and Vibrio spp. were 800 and 480 CFU/mL, respectively. After operating the plasma reactor at a flow rate of 6 L/min for 30 s, no bacteria or Vibrio spp. were detected. The disinfection effect of this plasma reactor seems to be superior to that of a conventional ozone generator.
        734.
        2012.10 KCI 등재 서비스 종료(열람 제한)
        This study was carried out to investigate the antibacterial activity against pathogens of acne and the anti-inflammatory effect of 75% ethanol extract and its fractions from the leaves of Prunus sargentii. In the antibacterial activity by the disc diffusion assay, the extract showed the highest effect against Propionibacterium acnes, Staphylococcus aureus and Staphylococcus epidermidis in 5 mg/disc. However, the ethyl acetate fraction showed the highest antibacterial activity in 1 mg/disc. On the other hand, the hexane and chloroform fraction showed strong nitric oxide (NO) production inhibitory effect in lipopolysaccharide (LPS)-stimulated Raw 264.7 cell. In the cell viability of Raw 264.7 by MTT assay, the extract and all fractions were exhibited normal viabilities as nontoxic result. Consequently, the extract from the leaves of P. sargentii and its ethyl acetate fraction could be applicable to functional materials for antibacterial activity related fields. Moreover, the hexane and chloroform fraction could be applicable to candidate materials as anti-inflammatory agent.
        735.
        2012.10 KCI 등재 서비스 종료(열람 제한)
        합산 영역 테이블은 모든 픽셀에 대해 임의의 크기 사각영역의 이미지 필터링 처리를 일정시간 안에 가능케 한다. 이러한 특성은 각각의 픽셀에 대해서 주변 픽셀의 밝기의 합 혹은 평균을 필요로 하는 이미지 처리 적용 분야에 유용하게 쓰일 수 있다. 합산 영역 테이블의 생성은 단지 행 혹은 열 단위의 합만을 구하는 메모리 바운드 작업임에도 불구하고 기존 연구들은 이미 존재하는 데이터 병렬성만을 활용하기 위하여 대기 시간이 긴 전역 메모리에 과도한 접근을 하여야만 했다. 본 논문에서는 입력 데이터를 정방의 서브 이미지로 분할하고 매개 데이터를 이들 간에 파급시킴으로써 GPGPU 환경 적합한 알고리즘을 제안하고자 한다. 이를 통하여 기존 방법 대비 전역 메모리 접근 량을 거의 반으로 줄임으로써 주어진 메모리 대역폭을 효율적으로 사용한다. 결과에서도 성능이 대폭 향상되었다.
        736.
        2012.09 KCI 등재 서비스 종료(열람 제한)
        본 연구에서는 미계측 강수자료를 생성하여 공간 해석함으로써 제주도의 정확한 수문총량을 산정하였다. 미계측 강수자료는 본 연구에서 제시된 수정된 다중회귀선형 모형으로 생성하였으며 공간강수량은 PRISM을 적용하여 구하였다. 수정된 다중선형회귀 모형에 의한 미계측 강수자료의 추정 값들은 기존의 강수 패턴과 유사한 양상을 나타내어 모형의 정확도가 우수한 것으로 나타났으며, 공간강수량의 해석 결과는 Case 1(원자료)과 Case 2(미계측 강수자료를 보완한 자료)의 연평균 강수량이 약 1.5%의 미미한 차이를 나타내었으나 고도별 연평균 강수량 차이는 최대 37.4%가 증가하는 것으로 산정되었다. 따라서 본 연구에서 제안한 미계측 관측 자료 생성방법은 현재 관측소의 밀도가 낮은 곳과 국지적으로 강수량의 변화가 큰 곳에서의 수문총량의 산정시 유용할 것으로 판단된다.
        737.
        2012.08 KCI 등재 서비스 종료(열람 제한)
        Formation of disinfection by-products (DBPs) including trihalomethans (THMs), haloacetic acid (HAAs), haloacetonitriles (HANs) and others from chlorination of algogenic organic matter (AOM) of Microcystis sp., a blue-green algae. AOM of Microcystis sp. exhibited a high potential for DBPs formation. HAAs formation potential was higher than THMs and HANs formation potential. The percentages of dichloroacetic acid (DCAA) and trichloroacetic acid (TCAA) formation potential were 43.4% and 51.4% in the total HAAs formation potential. In the case of HANs formation potential, percentage of dichloroacetonitrile (DCAN) formation potential was 97.7%. Other DBPs were aldehydes and nitriles such as acetaldehyde, methylene chloride, isobutyronitrile, cyclobutanecarbonitrile, pentanenitrile, benzaldehyde, propanal, 2-methyl, benzyl chloride, (2-chloroethyl)-benzene, benzyl nitrile, 2-probenenitrile and hexanal.
        738.
        2012.08 KCI 등재 서비스 종료(열람 제한)
        We evaluated the inhibitory effects of extracts and components of Geranium thunbergii on aldose reductase (AR) and galactitol formation in rat lenses with high levels of galactose as a part of our ongoing search of natural sources for therapeutic and preventive agents for diabetic complications. The inhibitory effects of water, methanol and ethanol extracts of G. thunbergii on rat lens AR (RLAR) were determined. Comparing inhibitory effects of various solvent extracts, ethanol extract showed RLAR inhibitory activity (IC50 values, 5.24 and 6.39μg/ml, respectively). The ethanol extract was fractionated to chloroform, ethyl acetate and water. Of these, the ethyl acetate fraction from ethanol extract of G. thunbergii exhibited RLAR inhibitory activity (IC50 value, 2.64μg/ml). In order to identify the bioactive components of ethyl acetate soluble fraction of ethanol extract from G. thunbergii, eight compounds, namely gallic acid (1), protocatechuic acid (2), p-hydroxybenzoic acid (3), brevifolin carboxylic acid (4), geraniin (5), ellagic acid (6), kaempferol-3-O-arabinofuranosyl-7-O-rhamnopyranoside (7), kaempferitrin (8) were isolated. The isolates were subjected to in vitro bioassays to evaluate their inhibitory activity on RLAR and galactitol formation in rat lenses. The ellagic tannins (5, 6) and flavonoid (7) exhibited strong inhibitory effects on RLAR. Also, these three compounds (5, 6 and 7) suppressed galactitol accumulation in rat lens under high galactose conditions, demonstrating the potential to prevent galactitol accumulation exo vivo. These results suggest that the extracts and components of G. thunbergii are a promising agent in the prevention or treatment of diabetic complications.
        739.
        2012.06 KCI 등재 SCOPUS 서비스 종료(열람 제한)
        Obesity, a strong risk factor for the development of chronic diseases, is characterized by an increase in the number and size of adipocytes differentiated from precursor cells, preadipocytes. Recent research suggests that increased reactive oxygen species (ROS) production in 3T3-L1 adipocyte facilitates adipocyte differentiation and fat accumulation. This study was to investigate whether reduced ROS production by Sargassum micracanthum extract (SME) could protect the development of obesity through inhibition of adipogenesis. 3T3-L1 preadipocytes were treated SME for up to 8 days following standard induction of differentiation. The extent of differentiation reflected by amount of lipid accumulation and ROS production was determined by Oil red O staining and nitroblue tetrazolium (NBT) assay. Treatment of SME significantly inhibited ROS production and adipocyte differentiation that is depend on down regulation of NADPH oxidase 4 (NOX4), a major ROS generator, and peroxisome proliferator-activated receptor gamma (PPARγ) and CCAAT/enhancer-binding protein alpha (C/EBPα), a key adipogenic transcription factor. These results indicate that SME can inhibit adipogenesis through a reduced ROS level that involves down-regulation of NOX4 expression or via modulation of adipogenic transcription factor.
        740.
        2012.06 KCI 등재 SCOPUS 서비스 종료(열람 제한)
        Recently, NADPH oxidase 4 (NOX4)-mediated generation of intracellular reactive oxygen species (ROS) was proposed to accelerate adipogenesis of 3T3-L1 cell. We have previously shown that Cheonnyuncho (Opuntia humifusa) extract significantly inhibited adipocyte differentiation via downregulation of PPARγ (peroxisome proliferator-activated receptor gamma) gene expression. In this study, we focused on the molecular mechanism(s) of NOX4, G6PDH (glucose-6-phosphate dehydrogenase) and antioxidant enzymes in anti-oxidative activities of 3T3-L1 adipocytes. Our results indicate that Cheonnyuncho extracts markedly inhibits ROS production during adipogenesis in 3T3-L1 cells. Cheonnyuncho extracts suppressed the mRNA expression of the pro-oxidant enzyme such as NOX4 and theNADPH-producing G6PDH enzyme. In addition, treatment with Cheonnyuncho extract was found to upregulate mRNA levels of antioxidant enzymes such as Mn-SOD (manganese-superoxide dismutase), Cu/Zn-SOD (copper/zinc-SOD), glutathione peroxidase (GPx), glutathion reductase (GR), and catalase, all of which are important for endogenous antioxidant responses. These data suggest that Cheonnyuncho extract may be effective in preventing the rise of oxidative stress during adipocyte differentiation through mechanism(s) that involves direct down regulation of NOX4 and G6PDH gene expression or via upregulation of endogenous antioxidant responses.