• 한국신재생에너지학회:학술대회논문집
• /
• 한국신재생에너지학회 2006년도 추계학술대회
• /
• pp.325-328
• /
• 2006

고분자 전해질 연료전지의 전극을 gradient catalyst coating 방법을 이용하여 제조하였다. 촉매 잉크제조 시 나피온 이오노머의 함침 구성비를 다르게 하여 조성 비율이 다른 gradient 구조를 갖도록 하여 전극을 제조하였다. Anode Cathode의 두 전극을 각각 나피온 함량비가 다른 두 개의 gradient 층구조의 촉매층으로 9:1, 8:2, 7:3, 6:4 비율의 조성비로 성능을 측정하였으며, 전극의 전기화학적 반응 면적을 알아보기 위해 순위전위법을 그리고 분극 저항(Polarization resistance) 변화를 알아보기 위해서는 0.7V에서 임피던스 측정법의 전기화학분석법으로 전극 제조법에 따른 성능변화를 확인하였다. 특히 Gradient catalyst coating 방법을 이용하여 제조한 MEA는 종래 방식의 MEA보다 high current $density(1000mA/cm^2)$이상에서 향상된 성능을 보였다.

• 한국식품영양학회지
• /
• 제8권4호
• /
• pp.307-317
• /
• 1995

The purity of mtDNAs isolated from Archicitrus and Metacitrus leaves was higher in percoll density gradient centrifugation than differential and sucrose density gradient centrifugation. The most clear mtDNAs were obtained from mitochondria included in the Interface band of between 21% and 45% under isomotic, low viscosity conditions in the three step discontinuous percoll density gradient centrifugation. DNase treatment to the crude mitochondrlal suspension still more increased purity of mtDNA by the effective removal of the nuclear and chloroplast DNA and mtDNAs were appeared as a single band at middle position of tube by EtBr /cscl density gradient centrifugation. Agarose gel electrophoresis of mtDNAs resolved a single, broad band containing high molecular weight DNAs In all preparation. Yield of mtDNAs was about 110 and 2 ug Per 2009 in mature and immature leaves respectively. The mtDNA fragment patterns showed by EcoR I treatment were indistinguishable with respect to nom bet and position of bands in Archicitrus and Metacitrus. In the pattern of Hind E restriction, the Metacitrus displayed the unique band between 5.0 and 4.0kb, in addition to four fragments about 5.0, 2.4, 2.15, and 2.0kb, respectively, different from Archicitrus. Also the pattern of total mtDNAs fragment by the treatment of Pst I showed that the distinguishable fragment pat tern was not appeared in Archicitrus(C. iyo Tanaka), but about 6.0, 5.5, 5.0 and 2.Bkb fragments were appeared only in Metacitrus(C. junos Sieb). Therefore it was indicated that two species in intra-subgenus were identical each other, whereas considerable difference was revealed for inter-subgenus.

• 한국동물위생학회지
• /
• 제31권4호
• /
• pp.547-554
• /
• 2008

Bacteriospermia is a frequent finding in fresh boar semen and can result in detrimental effects on semen quality and longevity. The objectives of this study was to evaluate types of bacterial contaminants in porcine fresh semen and the reducing effect of antibiotic and density gradient with percoll on the bacterial contaminants. Fresh semen was collected by gloved-hand method into a pre-warmed($37^{\circ}C$) thermostable bottle, and was inoculated onto blood agar and MacConkey agar, respectively. After incubated for 48 hour, 7.5% $CO_2$ at $37^{\circ}C$, bacterial colonies were selected and identified by Gram staining, oxidase test, catalase test and finally identified using API kits and Vitek system. Aerobic culture yielded a variety of bacteria from different genera. The most prevalent contaminant of fresh semen were Leclecia adecarboxylata, Acineobacter banmanni, Staphylococcus epidermidis, Staphylococcus cohni spp urealyticus, Proteus mirabilis. Most of identified bacteria were Gram(-) and non-pathogenic bacteria. It seems that bacterial contaminants in fresh semen were seem originated from multiple sources at the stud/farm, and were from animal and non-animal origins. Gentamicin treatment did not eliminate the bacterial contaminants completely but 3 step-density gradient with percoll completely removed the bacterial contaminants in fresh semen. Therefore, future study is necessary to prove that density gradient method with percoll can eliminate bacteria in fresh semen without significantly affecting sperm viability or function.

• 한국환경과학회지
• /
• 제20권9호
• /
• pp.1141-1149
• /
• 2011

The three-dimensional hydrodynamic model was simulated to understand coastal sea front of formation and seasonal variation in the Southern Sea of Korea. In this study, we used to concept of stratification factor, to realize seasonal distribution of stratification coefficient which of seasonal residual flow, considered with, tide, wind and density effect. Tidal current tends to flow westward during the flood and eastward during ebb. The current by the wind stress showed to be much stronger the coastal than the offshore area in the surface layer. And the current by the horizontal gradient of water density showed to be relatively weak in the coastal area, with little seasonal differences. On the other hand, the flow in the offshore area showed results similar to that of the Tsushima Warm Current. The stratification factor (SHv) was calculated by taking into account the total flow of tide, wind and density effect. In summer, the calculated SHv distribution ranged from 2.0 to 2.5, similar to that of the coastal sea front. The horizontal temperature gradient showed to be strong during the winter, when the vertical stratification is weak. On the other hand, the horizontal gradient became weak in summer, during which vertical stratification is strong. Therefore, it is presume that the strength of vertical stratification and the horizontal temperature gradient affect the position of the coastal sea front.

• Journal of the Korean Wood Science and Technology
• /
• 제41권1호
• /
• pp.42-50
• /
• 2013

1980년대 중반 이후 국내 생산이 시작된 온돌마루(이하 합판마루)는 종전의 주택용 바닥재(PVC 바닥재)의 대체재로서 일반 소비자들의 폭발적인 수요를 얻어왔다. 그러나 최근 마루판 산업은 건축경기 악화 및 산업 환경의 변화로 인한 수요의 감소와 그에 따른 생산율의 저하 등의 근본적인 문제점이 있다. 최근 마루판용 합판의 원재료로 주로 사용된 동남아산 수종의 고갈 및 변화로 인한 양질의 합판원재료 확보가 어려워졌다. 이에 대한 대응책으로 중국산 유칼립투스를 원재료로 부분적으로 이용한 마루판용 합판의 대체이용이 시도되고 있다. 본 연구에서는 유칼립투스 단판을 부심판으로 제조한 복합합판의 마루판용 합판의 원재료로서의 사용 가능성을 실험을 통해 비교분석하였으며, 모든 단판이 동남아산 Meranti로 구성된 합판을 대조군으로 설정했다. 변형에 영향을 미치는 인자로 단판 간 밀도차이와 합판의 밀도경사를 이용하였다. 본 연구의 실험결과는 다음과 같다. 1) 남양재 시험편은 병판의 밀도가 다른 단판의 밀도보다 큰 M자형의 밀도경사, 유칼립투스 시험편은 반대성향의 W자형의 밀도경사를 나타내었다. 2) 종류에 따른 마루판의 변형은 마루 가공 시험편이 합판상태로 가공을 한 경우보다 최소 0.1~최대 6.25 mm 적게 나타났으며, Density Profile 측정 결과 단판 간의 밀도차가 클수록 변형이 많이 발생하였다.

• 한국지구물리탐사학회:학술대회논문집
• /
• 한국지구물리탐사학회 2006년도 공동학술대회 논문집
• /
• pp.161-166
• /
• 2006

수직 중력 변화율 탐사는 중력 탐사에 비하여 분해능과 탐지능이 높고 광역 효과를 억제하는 이점이 있다. 수직 변화율의 실제 측정은 어려움이 많아 정확성과 실용성에서 의문이 제기되기도 하였으나, 현대적인 중력계로는 요구되는 정확도를 유지하는 것이 크게 어려운 일이 아니다. 특히, 얕은 깊이의 소규모 구조를 대상으로 하는 토목, 환경 문제에는 효과적으로 적용될 수 있다. 이 논문은 수직 중력 변화율 탐사를 천부 고분해 밀도 구조 해석에 적용하기 위하여 수직 중력 변화율에 관한 전반적 고찰과 수치 역산 모델링을 통하여 중력 탐사와 비교, 분석하였으며, 전남 무안의 석회암 공동 지역에서 수행한 수직 중력 변화율 탐사를 수행하고 역산, 해석하였다.

• 대한의용생체공학회:학술대회논문집
• /
• 대한의용생체공학회 1996년도 추계학술대회
• /
• pp.165-168
• /
• 1996

Though the planar gradient coils, designed by the magnetic energy minimization procedure, have smaller inductance than conventional gradient coils, the planar gradient oils often suffer from their poor magnetic field linearity. Scaling the spatial frequencies of the current density function designed by the magnetic energy minimization procedure, magnetic field linearity of the planar gradient coils can be featly improved with small sacrifice of gradient coil inductance.

• KSBB Journal
• /
• 제14권1호
• /
• pp.109-113
• /
• 1999

이산화탄소를 용매로하는 초임계유체 크로마토그래퍼(SFC)방법을 이용하여 어유로부터 EPA및 DHA를 고순도로 분리정제하는 연구를 하였다. 질산은 칼럼을 이용하는 초임계 이산화탄소의 초기 압력조건 변화가 저 지방산의 용해도 및 분리도에 미치는 영향을 조사하였는데 압력이 증가될수록 저지방산의 용해도는 증가되었고, 반면에 EPA와의 분리도는 감소하는 경향을 나타내었다. EPA의 분리정제 효율을 높이기 위해 초임계 이산화탄소에 대한 단계별 밀도구매 방법을 적용하였다. 적용 결과 초기에 저지방산이 먼저 분리되었고, 계속해서 92.1%~97.8%EPA 순도를 갖는 분획들을 얻을 수 있었다. 순도가 높은 3개의 분획의 평균 순도는 95.6%이었고 회수율은 30%에 달하였다.

• 한국군사과학기술학회지
• /
• 제14권2호
• /
• pp.205-212
• /
• 2011

In this paper, we have proposed a method for quantization of the stratification strength in the sea water and analysing the distributions of the maximum stratification depths calculated by the method at the seas near the Korean peninsular. For calculating the stratification strength, modified and applied the potential energy anomaly formular which was suggested by Simpson in 1977. The data had been collected by NFRDI from 1971 to 2008 were used to determine the maximum vertical density gradient depth and the relative potential energy anomaly at that depth. In the East Sea, the stratification depth has become deepened about 20m in February and April since 1971. In Yellow-South Sea, the maximum density gradient depth has been deepened about 10m only in December during the same period and the difference of the stratification depth between summer and winter has been enlarged. These trends of variation of stratification strength and depth near the Korean peninsular should be investigated more carefully and continuously. And the results of these studies could be adopted for the more efficient operation of underwater weapon and detection systems.

• Archives of Pharmacal Research
• /
• 제13권4호
• /
• pp.325-329
• /
• 1990

Synaptosomal plasma membrane vesicles (SPMV) were isolated from fresh bovine cerebral cortex by several well-known procedures, and the best procedures was selected by enzymatic and morphological standards. The SPMV isolated by the modified procedure of Smith and Loh showed the highest purity. The specific activities of Na, K-ATPase, acetylcholinesterase and 5'-nucleotidase were about 5, 6-fold, 2, 5-fold and 3, 3-fold, respectively, enriched in the plasma membrane fraction as compared to those of the crude homogenate. Electron microscpic examination also showed that the membranes were in vesicular form.