• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.591-591
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• 2012

본 연구는 Transparent conducting oxide (TCO, 산화물투명전극)를 이용한 박막태양전지 효율향상에 관한 것으로, 이중의 TCO층(Double-stacked TCO layer)의 효과적인 광학 및 전기적 설계에 관한 것이다. 기존 박막 태양전지에서는 투명전극 TCO layer로서, ITO (Indium-Tin-Oxide), FTO (Fluorine- Tin-Oxide), 및 AZO(Aluminum-doped Zinc Oxide) 등을 사용해 왔다. 각 TCO layer마다 장점이 있지만 단점 또한 존재한다. ITO의 경우 높은 전기적 특성을 가지는 반면 수소 플라즈마에 취약하고 기계적 강도에 취약해 ITO 단일층만으로 박막 태양전지에 적용하는 것에 제한을 받는다. 한편, AZO의 경우 전기적 특성도 우수할 뿐만 아니라 수소 플라즈마에도 내구성이 강한 장점이 있지만, 일함수가 p형 반도체보다 낮아 Schottky junction이 되어, 높은 전위장벽이 형성된다. 이는 정공의 이동을 방해하고, 정공의 축적이 일어나서 순방향 전압을 인가할 때 많은 전류의 감소를 가져온다. 또한, AZO와 p형 반도체 사이의 높은 직렬저항으로 인해 광전압(Voc, Open circuit voltage)와 충실률 (FF, Fill factor)가 떨어진다는 단점이 있다. 본 실험에서는 ITO/AZO 2중구조의 TCO층을 적용하여 상기의 문제점을 해결하고자 한다. 이중 구조 TCO층은 Magnetron sputter system을 이용하여, 단계적으로 증착되었다. 빛이 입사하는 유리에 ITO를 제1전도층으로 증착하였는데, ITO는 입사광의 투과도와 전기전도성이 우수하다. 제2전도층으로는 AZO층을 이용하였으며, 실리콘 반도체층과 접하게 된다. AZO는 실리콘 증착시 발생하는 수소 플라즈마에 안정적이고, 물리적 강도 또한 우수한 장점이 있다. 이중 구조층위에 실리콘 광흡수층(Si absorber)을 증착하였으며, pin 구조를 가진다. 기존, 단일막 TCO층과 2중구조 TCO층을 이용하여, 실리콘 박막 태양전지를 구성하였다. 이때, ITO/AZO의 2중구조를 적용하였을 때 태양 전지 특성이 크게 향상된 결과를 얻을 수가 있었다. 특히, 전류밀도의 경우 ITO, FTO, AZO 각각 14.5 mA/cm2, 11.2 mA/cm2, 8.18 mA/cm2를 나타낸 반면 ITO/AZO 2중구조의 경우 약 17mA/cm2 로 크게 향상 되었고, 태양전지 변환 효율도 각각 7.5%, 6.9%, 4%에서 ITO/AZO 2중 구조의 경우 8.05%로 크게 향상되었다. 본 발표에서는 2중구조 TCO를 이용한 현공정에 적용 가능한 박막태양전지 효율향상 기법에 대해 논의하고자 한다.

• Membrane Journal
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• v.25 no.3
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• pp.231-238
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• 2015

Co-polyimide membranes were prepared by two-step polymerization using semi-alicyclic 5-(2,5-dioxotetrahydrofuryl)-3-methyl-cyclohexene-1,2-dicarboxylic anhydride (DOCDA) with five diamines such as 2,5-dimethyl-1,4-phenylene diamine (2M), 2,4,6-trimethyl-1,3-phenylene diamine (3M), 1,5-naphthalene diamine (NDA), 4,4-diaminodiphenyl methane (MDA), 4,4'-diaminodiphenyl ether (ODA). Synthesized co-polyimides were characterized by FT-IR, viscosity, solubility, DSC, TGA and gas permeation properties, compared with 6FDA-based co-polyimides. All co-polyimides had the intrinsic viscosity of 0.32~0.58 and excellent solubility in various solvents. DOCDA-based co-polyimides had thermal stability over $400^{\circ}C$ although those were lower than 6FDA-based co-polyimides. Gas permeabilities of the copolyimide membranes were measured for $CO_2$ and $CH_4$ at room temperature and presented the trade-off relationship.

• Membrane Journal
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• v.27 no.2
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• pp.154-166
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• 2017

Polymeric films for gas barrier applications such as food packaging and electronic devices have attracted great interest due to their cheap, light and easy processability among gas barrier materials. Especially in electronic devices, extremely low gas permeance is necessary for maintaining the device performance. However, current polymeric barrier films still suffer from relatively high gas permeance than other materials. Therefore, there have been strong needs to enhance the gas barrier performance of polymeric barrier films while keep their own advantages. Recently, graphene is highlighted as a 2D-layered material for gas barrier applications. However, owing to the poor workability and difficulty to produce in engineering scale, graphene oxide (GO) is on the rise. GO consists of oxygen-containing functional groups on surface with intrinsic 2D-layered structure and high aspect ratio, and it can be well-dispersed in aqueous polar solvents like water, resulting in scalable mass production. Here, we prepared GO incorporated polyimide (PI) nanocomposites. PI is widely used barrier polymer with high mechanical strength and thermal and chemical stability. We demonstrated that PI/GO nanocomposites could perform as a gas barrier. Furthermore, surfactants (Triton X-100 (TX) and Sodium deoxycholate (SDC)) are introduced to enhance the gas barrier performance by improving the degree of dispersion of GO in PI matrix. As a result, TX enhanced the gas barrier performance of PI/GO nanocomposites which is similar to predicted value. This finding will provide new insight to polymer nanocomposites for gas barrier applications.

• Applied Microscopy
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• v.29 no.3
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• pp.331-341
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• 1999

Examination of the morphology of red blood cells in the urine has been shown to be a promising adjunct in determining whether hematuria represents glomerular or nonglomerular bleeding. This is due to distortion of RBCs as they Pass across the basement membrane of the glomerular capillaries. It is concluded that is method can greatly help the clinician in distinguishing between glomerular and nonglomerular bleeding in patients with hematuria and channeling such patients toward the most appropriate investigations. We have experimented dysmorphic red blood cells that 5 patients of the hematuria are distorted with irregular outlines and often have small blobs extruding from the red cell membrane. Tried urinary sediments were seen with phase contrast microscope and confirmed scanning electron microscope. There are seen acanthocytes, anulocytes, ghost cells and sphero-echinocytes in dysmorphic erythrocytes. Clinical diagnosis was referred from the result of the biopsy-proven. Scanning electron microscopic findings of the hematuria are good diagnostic tool that disclose in distorted red blood cells from patients with glomerular disorders.

• Journal of the Korean Geotechnical Society
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• v.20 no.3
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• pp.23-31
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• 2004

Normally, coating is used for protecting reinforced concrete. For this purpose, both organic and inorganic coatings are used. The advantages of inorganic coatings are lower absorption of UV, non-burning etc. On the other hand, organic coatings have the advantage of low permeability of $CO_2, SO_2$ and water. Organic coatings provide better protection for reinforced concrete. However, organic coatings such as epoxy, urethane and acryl reduce long-term adhesive strength by the difference of their thermal expansion coefficients and elastic modules from those of concrete, and the formed coating cover of these is blistered by poor breathing. Also, when organic coatings are applied to the wet surface of concrete, they have a problem with adhesion. In this study, a new coating material for protecting concrete was hybridized with polymer and ceramics. And tests were carried out on its physical and durable characteristics, and safety characteristic on elution. All results were compared with organic coating materials and epoxies and showed that the performance of the developed coating material was not inferior to that of other organic coatings in protecting concrete. On the other hand, safety characteristic on elution was superior to epoxies which were used in this study. So, the developed coating material was considered as a suitable protecting coating material which have advantages of inorganic and organic coatings for protecting underground concrete structures, especially in contact with water.

• The Journal of Dong Guk Oriental Medicine
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• v.8 no.2
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• pp.83-96
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• 2000

Objective This experimental study was designed to investigate effects of Sam-chool-gun-bi-tang administration during carbohydrate loading diet to long distance runners on changes of the urine metabolic responses. Materials and Methods All subjects were divided randomly with two groups, Sam-chool-gun- bi-tang administration Group (N=5) and control group (N=5) and attended on domestic marathon race. The urine samples were collected by 15ml conical tube at rest, a day before race, immediately after race, a day after race. These samples were used to analyze for the factors of the change on metabolic responses. At First, the factors of the routine urine test were checked; RBC, WBC, glucose, protein, ketone, bilirubin, urobilirubin. Next, the factors on the changes of the electrolyte metabolism and creatinine were checked; $Na^+ $, $Cl^-$, $K^+$, $Ca^{+ +}$, Creatinine. Results 1. Urine RBC, WBC, glucose, protein, ketone, bilirubin, urobilirubin were all denoted negatively (-). 2. Urine pH response in Sam-chool-gun-bi-tang administration group was shown significant difference between two groups at immediately after race. 3. Urine $Na^+$ response in Sam-chool-gun- bi-tang administration group was shown significant difference between two groups at immediately after race. 4. Urine $K^+$ response in Sam-chool-gun-bi-tang administration group was shown significant difference between two groups at immediately after race and a day after race. 5. Urine $Cl^-$ response in Sam-chool-gun- bi-tang administration group was increased at immediately after race, but was not shown significant difference between two groups. 6. Urine $Ca^{+ +}$ response in Sam-chool-gun-bi-tang administration group was decreased gradually, but was not shown significant difference between two groups. 7. Urine Creatinine response in Control group was decreased significantly at immediately after race, but was not shown significant difference between two groups. Conclusion According to the above results, it was shown that Sam-chool-gun- bi-tang administration had the positive effects on changes of the urine matabolic responses during carbohydrate loading diet to the long distance runners.

• Journal of Korean Medicine for Obesity Research
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• v.12 no.1
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• pp.33-47
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• 2012

Objectives This study was designed to investigate the effects of fermented soybean upon anti-inflammation, cytotoxicity, antioxidant and intestinal mucous membrane permeability by measuring the cell viability, NO (nitric oxide) production, DPPH, Polyphenol, HRP and TEER in cells like Raw 264.7 and HCT 116 using fermented soybean. Methods Raw 264.7 cell and HCT 166 cell were used in this study. And fermented soybean powders were used for the experimental group and soybean powders for the control group. There was inflammation response upon using lipopolysaccharide(LPS). Fermented soybean powders and soybean powders were in a respectively different dose added to the cells with LPS. MTT assay, NO, DPPH and Polyphenol measurement, TEER, HRP were conducted for each cell. The results of this study were presented in mean and standard deviation. Results 1. In Raw 254.7 cells added with $100{\mu}l/ml$ unfermented soybean powders, 104.95% higher than 62.59% was measured. In Raw 254.7 cells added with $100{\mu}l/ml$ fermented soybean powders, there was 74.90% measured higher than 62.59%, which was a significant result. 2. By a gradual increase of unfermented soybean powders like $0.1{\mu}l/ml$, $1.0{\mu}l/ml$, $10{\mu}l/ml$, $100{\mu}l/ml$, the measured NO were also gradually decreased $53.12{\mu}M$, $47.57{\mu}M$, $37.02{\mu}M$, $28.16{\mu}M$. In case of cells added with fermented soybean powders, $43.95{\mu}M$ NO was measured in $0.1{\mu}l/ml$ which is significant, and in other cases, mostly measured over$ 56.72{\mu}M$. 3. It was inferred that fermented soybean powders have anti-inflammatory effects of maintaining intestinal mucous membrane permeability because the measured values of cells in both groups were all higher than $133.62{\Omega}$ measured of cells added with only LPS. And measured values of cells in both groups were all lower than 2.26 measured of cells added with only LPS. 4. In case of experiment DPPH and polyphenol measurement, fermented group was all higher than unfermented group. Conclusion From the results of conducting MTT assay, NO measurement, and TEER, HRP by using cells Raw 264.7 and HCT-116, even though there was no significance in the correlation between cytotoxicity, anti-inflammatory effects, both unfermented soybean powders and fermented soybean powders were shown to have intestinal mucous membrane permeability improvement effects. This effects could be applicable for autoimmune diseases, chronic inflammatory diseases and so additional studies are expected in the future. From the results of conducting DPPH, Polyphenol measurement, Fermented soybean may be useful as potential antioxidant.

• Solar Energy
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• v.17 no.4
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• pp.3-11
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• 1997

Because grain boundaries in polycrystalline silicon act as potential barriers and recombination centers for the photo-generated charge carriers, these defects degrade conversion effiency of solar cell. To reduce these effects of grain boundaries, we investigated various influencing factors such as thermal treatment, various grid pattern, selective wet etching for grain boundaries, buried contact metallization along grain boundaries, grid on metallic thin film. Pretreatment above $900^{\circ}C$ in $N_2$ atmosphere, gettering by $POCl_3$ and Al treatment for back surface field contributed to obtain a high quality poly-Si. To prevent carrier losses at the grain boundaries, we carried out surface treatment using Schimmel etchant. This etchant delineated grain boundaries of $10{\mu}m$ depth as well as surface texturing effect. A metal AI diffusion into grain boundaries on rear side reduced back surface recombination effects at grain boundaries. A combination of fine grid with finger spacing of 0.4mm and buried electrode along grain boundaries improved short circuit current density of solar cell. A ultra-thin Chromium layer of 20nm with transmittance of 80% reduced series resistance. This paper focused on the grain boundary effect for terrestrial applications of solar cells with low cost, large area, and high efficiency.

• Journal of the Korean Society of Food Science and Nutrition
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• v.31 no.3
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• pp.534-538
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• 2002

To investigate the antimicrobial effects of Scutellariae Radix extract against Vibrio parahaemolyticus from food samples, Vibrio parahaemolyticus strains isolated from Tapes philippinarum were examined for their sensitivity to Scutellariae Radix extract. Total 66 Vibrio parahaemolyticus strains were isolated from Tapes philippinarm 72 samples (91.7%). The serotypes of isolated Vibrio parahemolytics were K-I group 7 strains (10.6%), K-IV group 5 strains (7.6%), K-II group 2 strains (3.0%), K-V group 2 strains (3.0%), K-VII group 2 strains (3.0%), K-VI group 1 strains (1.5%), K-VIII group 1 strains (1.5%) and antisera UT K-group 46 strains (69.7%) on antisera agglutination test, but K-III group and K-IX group strains were not found. The growth curves of isolates showed lag phase, logarithmic phase, stationary phase and death phase as typical sigmoid curve on the shellfish samples. After 6 hours, the group containing Scutellariae Radix extract differs from the control on shellfish samples in the growth inhibition curves, and Vibrio parahaemolyticus were inhibited in more than 1000 ppm Scutellariae Radix extract. The morphological changes were observed by transmission electron microscope and the microbial cells membrane was destroyed by Scutellariae Radix extract.

• Applied Microscopy
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• v.29 no.2
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• pp.149-162
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• 1999

For investigation of the activated carbon on the mouse kidney treated with Pb, the activated carbon (40 mg/kg) and Pb (30 mg/kg) were treated orally for three and six weeks, respectivelly, and observed by the electron microscope. On the glomerulus of the group with only Pb, the basal membrane thicked, projected, and the foot processes fused. On the proximal convoluted tubules, the number of microvilli were decreased and the number of vacuoles and lysosome increased on the cytoplasm. The mitochondria and endoplasmic reticulum were extended and ribosomes dropped from the ER. On the giomerulus of the group with Pb-activated carbon, the basal membrane and the foot processes were merely changed. On the proximal convoluted tubules, the shapes and number of microvilli were not changed and the number of vacuoles, microbodies, and lysosomes decreased. The shapes of mitochondria and endoplasmic reticulum observed almost similar with control group. Th at is, elongated mitochondria and attached ribosomes to endoplasmic reticulum. As result, the activated carbon has positive effect on reducing toxicity of lead in the mouse kidney in the view of electron microscope.