• 한국응용과학기술학회지
• /
• 제30권1호
• /
• pp.49-56
• /
• 2013

Excellent electron transport properties with enhanced light scattering ability for light harvesting have made well-ordered one dimensional $TiO_2$ nanotube(TNT) arrays an alternative candidate over $TiO_2$ nanoparticles in the area of solar energy conversion applications. The principal drawback of TNT arrays being activated only by UV light has been addressed by coupling the TNT with secondary materials which are visible light-triggered. As well as extending the absorption region of sunlight, the introduction of these foreign components is also found to influence the charge separation and electron lifetime of TNT. In this study, a novel method to fabricate the TNT-based composite photoelectrodes employing visible responsive $CuInS_2$ (CIS) nanoparticles is presented. The developed method is a square wave pulse-assisted electrochemical deposition approach to wrap the inner and outer walls of a TNT array with CIS nanoparticles. Instead of coating as a dense compact layer of CIS by a conventional non-pulsed-electrochemical deposition method, the nanoparticles pack relatively loosely to form a rough surface which increases the surface area of the composite and results in a higher degree of light scattering within the tubular channels and hence a greater chance of absorption. The excellence coverage of CIS on the tubular $TiO_2$ allows the construction of an effective heterojunction that exhibits enhanced photoelectrochemical performance.

• 터널과지하공간
• /
• 제23권1호
• /
• pp.78-85
• /
• 2013

열에너지를 성층화하여 저장하는 주된 목적은 에너지의 열역학적 질을 유지하기 위한 것으로서 열에너지의 성층화를 통해 필요시 원하는 온도에서 열에너지 활용이 가능하다. 저장소 내 열에너지의 온도에 따른 분리, 즉 열성층화는 이와 같은 열에너지의 활용에 영향을 미치는 핵심 인자이다. 본 논문에서는 열성층화의 정도를 평가할 수 있는 기존에 제안된 기법들을 소개하였으며, 특히 열에너지의 주입, 저장, 배출 과정 동안 열저장소의 성층화와 관련된 성능을 결정하는 데 사용될 수 있는 기법들을 중심으로 개념 및 특징을 살펴보았다. 또한 열성층화 지수를 이용하는 방법을 토대로 스웨덴 Lyckebo 암반공동 내 열에너지의 성층도를 비교 분석하여 기법의 적용성을 조사하였다.

• 생명과학회지
• /
• 제14권2호
• /
• pp.345-350
• /
• 2004

한국내 물오리나무(Ainus hirsuta) 집단의 미소지리적 변이를 공간적 상관관계에 적용하였다. 분리된 등급간 대립유전자의 각 형태의 산출을 정규분포 편차 통계에서 임의분포를 하고 있는지를 검정하였다. 모든 경우에서 예상 값이 유의성을 가지는지 Moran의 I값으로 추정한 결과 120 경우 준 24 경우(20.0%)에서 유의성을 나타내었다. 이들 값 중에서 17 경우는 음의 값을 나타내었는데 이는 한국의 물오리집단이 10등급 간격에서 유사하지 않다는 점을 시사하였다. 그 한 원인으로는 화목(火木)을 위한 인간의 간섭을 추정할 수 있다. 열매를 맺는 가지나 줄기의 간헐적인 벌목에 의해 유전자 유동이 조장되었기 때문일 것이다. 한편, 그루터기나 밑둥으로부터 영양번식을 할 수 있는 능력 또한 유전적 구조를 어지럽히는 한 요인으로 작용한 것으로 사료된다.

• 한국수소및신에너지학회논문집
• /
• 제18권2호
• /
• pp.109-115
• /
• 2007

Solar energy conversion to hydrogen was carried out via a two-step thermochemical water splitting using metal oxide redox pair. To simulate the solar radiation, a 7 kW short arc Xe-lamp was used. Partially reduced iron oxide and cerium oxide have the water splitting ability, respectively. So, $Fe_3O_4$ supported on $CeO_2$ was selected as the active material. $Fe_3O_4/CeO_2$(20 wt/80 wt%) was prepared by impregnation method, then the active material was washcoated on the ceramic honeycomb monolith made of mullite and cordierite. Oxygen was released at the reduction step($1673{\sim}1823\;K$) and hydrogen was produced from water at lower temperature($873{\sim}1273\;K$). The result demonstrate the possibility of the 2-step thermochemical water splitting hydrogen production by the active material washcoated monolith. And hydrogen and oxygen was produced separately without any separation process in a monolith installed reactor. But the SEM and EDX analysis results revealed that the support used in this experiment is not suitable due to the thermal instability and coating material migration.

• 대한화학회지
• /
• 제38권2호
• /
• pp.122-128
• /
• 1994

거대고리 리간드는 금속이온과 선택적으로 결합하는데, 이를 이용하여 에멀젼 액체막을 통한 금속이온의 이동에 관하여 연구를 수행하였다. 금속이온은 유기층에 있는 운반체에 의하여 source phase에서 recevinng phase으로 이동한다. 운반체로는 거대고리 리간드인 $DBN_3O_3$를 사용하였다. 여기에서 에멀젼 액체막을 통한 금속이온의 이동에 관한 요인과 어떤 금속이온의 선택적 분리에 관하여 검토하였다. 금속이온과 거대고리 리간드 그리고 금속이온과 recevinng phase내에 있는 음이온에 대한 안정도 상수를 금속이온의 선택적 이동에 대한 척도로 조사하였다. 납이온이 혼합 용액에서 다른 금속이온보다 높은 이동속도를 나타내었다. Recevinng phases내의 음이온이 금속이온의 이동에 중요한 역할을 한다.Recevinng phases내에 있는 $NO_3^-$을 $S_2O_3^{2-}$대치하면 이동량이 증가함을 보였는데 이는 $Pb^{2-}-S_2O_3^{2-}$상호작용이 $Pb^{2+}-NO_3^-$상호작용보다 크기 때문이다.

• 한국축산식품학회지
• /
• 제36권6호
• /
• pp.791-798
• /
• 2016

Free radicals may attack cells or tissue, leading to chronic diseases, and antioxidant consumption is potentially useful for removing free radicals. Egg proteins may be used as potential sources of antioxidant considering their ability of scavenging free radicals to apply for food or cosmetics industry. In this study, we obtained a natural antioxidant protein from fertilized eggs, which was a dietary supplement in some Asian countries. Meanwhile, antioxidant activities of these proteins were evaluated using different oxidation systems. With increasing incubation time, the antioxidant activity of these proteins increased during 15 d of incubation. The samples on day 15 were performed for isolation of antioxidant protein. The protein, named P4-1 (MW, 45 kDa), was isolated and purified by consecutive chromatographic methods. P4-1 contained 17 amino acids, which was determined by liquid chromatography-mass spectrometry and Amino Acid Analyzer. Moreover, the amino acid sequence was highly similar to that of ovalbumin. Differential scanning calorimetry showed that the denaturation temperature of P4-1 was $57.16^{\circ}C$. Furthermore, P4-1 suggested high oxygen radical-absorbance activity in ${\cdot}OH$ assays, and its antioxidant activity was stable at $30-50^{\circ}C$ in acidic and neutral pH. Thus, these results revealed that P4-1 may be a potential resource as a natural antioxidant.

• 한국수소및신에너지학회논문집
• /
• 제24권1호
• /
• pp.29-35
• /
• 2013

A dense mixed ionic and electronic conducting ceramic membrane is one of the most promising materials because it can be used for separation of oxygen from the mixture gas. The $ABO_3$ perovskite structure shows high chemical stability at high temperatures under reduction and oxidation atmospheres. $BaCo_{1-x-y}Fe_xZr_yO_{3-{\delta}}$ (BCFZ) was well-known material as high mechanical strength, low thermal conductivity and stability in the high valence state. Glycine Nitrate Process (GNP) is rapid and effective method for powder synthesis using glycine as a fuel and show higher product crystallinity compared to solid state reaction and citrate-EDTA method. BCFZ was fabricated by modified glycine nitrate process. In order to control the burn-up reaction, $NH_4NO_3$ was used as extra nitrate. According to X-Ray Diffraction (XRD) results, BCFZ was single phase regardless of Zr dopants from y=0.1 to 0.3 on B sites. The green compacts were sintered at $1200^{\circ}C$ for 2 hours. Oxygen permeability, methane partial oxidation rate and hydrogen production ability of the membranes were characterized by using Micro Gas Chromatography (Micro GC) under various condition. The high oxygen permeation flux of BCFZ 1-451 was about $1ml{\cdot}cm^{-2}s^{-1}$. Using the humidified Argon gas, BCFZ 1-433 produced hydrogen about $1ml{\cdot}cm^{-2}s^{-1}$.

• Macromolecular Research
• /
• 제16권2호
• /
• pp.139-148
• /
• 2008

Biodegradable and elastic poly(L-lactide-co-$\varepsilon$-caprolactone) (PLCL) was electrospun to prepare nanofibers, and N-isopropylacrylamide (NIPAAm) was then grafted onto their surfaces under aqueous conditions using $^{60}Co-{\gamma}$ irradiation. The graft yield increased with increasing irradiation dose from 5 to 10 kGy and the nanofibers showed a greater graft yield compared with the firms. SEM confirmed that the PLCL nanofibers maintained an interconnected pore structure after grafting with NIPAAm. However, overdoses of irradiation led to the excessive formation of homopolymer gels on the surface of thc PLCL nanofibers. The equilibrium swelling and deswelling ratio of the PNIPAAm-g-PLCL nanofibers (prepared with 10 kGy) was the highest among the samples, which was consistent with the graft yield results. The phase-separation characteristics of PNIPAAm in aqueous conditions conferred a unique temperature-responsive swelling behavior of PNIPAAm-g-PLCL nanofibers, showing the ability to absorb a large amount of water at < $32^{\circ}C$, and abrupt collapse when the temperature was increased to $40^{\circ}C$. In accordance with the temperature-dependent changes in swelling behavior, the release rate of indomethacin and FITC-BSA loaded in PNIPAAm-g-PLCL nanofibers by a diffusion-mediated process was regulated by the change in temperature. Both model drugs demonstrated greater release rate at $40^{\circ}C$ relative to that at $25^{\circ}C$. This approach of the temperature-controlled release of drugs from PNIPAAm-g-PLCL nanofibers using gamma-ray irradiation may be used to design drugs and protein delivery carriers in various biomedical applications.

• 한국식품영양과학회지
• /
• 제29권5호
• /
• pp.814-821
• /
• 2000

나박김치의 저장성 향상을 위한 천연보존제로서 이용 가능성을 검토하기 위해 오미자 물추출물을 제조하여 이들 시료의 농도를 0.5, 1.0, 1.5, 2.0%로 사용하여 항산화력 및 전자공여능을 측정하고 나박김치 발효에 관여하는 젖산균에 대해 항균활성을 조사하였다. 항산호력은 TBA값을 측정하였는데, 오미자 물추출물의 농도가 높을수록 항산화 효과가 뚜렷이 나타났고, 시간이 경과할수록 그 효과는 현저하였다. 전자공여능 또한 오미자 물추출물의 농도가 높을수록 높은 전자공여능을 나타냈고, 1.0% 이상이 높은 전자공여능을 보였다. 나박김치에서 잦산균을 분리한 결과 117균주를 1차 분리하였고, 이 가운데 성장이 우수하고 산 생성력이 강한 4균주를 2차 선별하여 Lactobacillus brevis, Lactococcus faecalis, Leuconostoc mesenteroides, Lactobacillus plantarum을 확인하였다. 이들의 항균활성을 측정한 결과 Lactobacillus brevis를 제외한 세 균주 모두 오미자 물추출물 첨가에 의한 뚜렷한 성장 억제현상을 나타내었다. 따라서 나막김치 담금시에 항산화성과 항균활성이 있는 오미자 물추출물을 이용할 수 있는 가능성이 높을 것으로 생각되었다.

• 대한원격탐사학회지
• /
• 제22권1호
• /
• pp.25-40
• /
• 2006

Synthetic aperture radar (SAR) from satellites provides the opportunity to regularly incorporate microwave information into forest classification. Radar backscatter can improve classification accuracy, and SAR interferometry could provide improved thematic information through the use of coherence. This research examined the potential of using multi-temporal JERS-l SAR (L band) backscatter information and interferometry in distinguishing forest classes of mountainous areas in the Northeastern U.S. for future forest mapping and monitoring. Raw image data from a pair of images were processed to produce coherence and backscatter data. To improve the geometric characteristics of both the coherence and the backscatter images, this study used the interferometric techniques. It was necessary to radiometrically correct radar backscatter to account for the effect of topography. This study developed a simplified method of radiometric correction for SAR imagery over the hilly terrain, and compared the forest-type discriminatory powers of the radar backscatter, the multi-temporal backscatter, the coherence, and the backscatter combined with the coherence. Statistical analysis showed that the method of radiometric correction has a substantial potential in separating forest types, and the coherence produced from an interferometric pair of images also showed a potential for distinguishing forest classes even though heavily forested conditions and long time separation of the images had limitations in the ability to get a high quality coherence. The method of combining the backscatter images from two different dates and the coherence in a multivariate approach in identifying forest types showed some potential. However, multi-temporal analysis of the backscatter was inconclusive because leaves were not the primary scatterers of a forest canopy at the L-band wavelengths. Further research in forest classification is suggested using diverse band width SAR imagery and fusing with other imagery source.