• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.2
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• pp.260-266
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• 2002

DLC films were deposited on Si wafer by RF plasma assisted CVD using CH4 gas. Tribological tests were conducted using rotating type ball on disk friction tester in dry air. Four kinds of mating balls were used. The mating balls were made with stainless steel but apply different annealing conditions to achieve different hardness conditions. Testing results in all load conditions showed that the harder the mating materials, the lower the friction coefficient among the three kind of martensite mating balls. In case of austenite balls, the friction coefficients were lower than fully annealed martensite ball. The high friction coefficient in soft martensite balls seems to be caused by the larger contact area between DLC film and ball. The wear tracks of DLC films and mating balls could have proven that effect. Measuring the wear track of both DLC films and mating balls have similar tendency comparing to the results of friction coefficients. Wear rate of austenite balls were also smaller than that of fully annealed martensite ball. The results of effect of applying load showed, the friction coefficients were become decrease when the applying loads exceed critical load conditions. The wear track of mating balls showed that some material transfer occurs from DLC film to mating ball during the high friction process. Raman spectra analysis showed that transferred material was a kind of graphite and contact surface of DLC film seems to undergo phase transition from carbon to graphite during the high friction process.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.11a
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• pp.280-284
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• 2004

Multicrystalline silicon wafers were textured in an alkaline bath, basically using sodium hydroxide and in acidic bath, using mainly hydrofluoric acid (HF), nitric acid $(HNO_3)$ and de-ionized water (DIW). Some wafers were also acid polished for the comparative study. Comparison of average reflectance of the samples treated with the new recipe of acidic solution showed average diffuse reflectance less than even 5 percent in the optimized condition. Solar cells were thus fabricated with the samples following the main steps such as phosphorus doping for emitter layer formation, silicon nitride deposition for anti-reflection coating by plasma enhanced chemical vapor deposition (PECVD) and front surface passivation, screen printing metallization, co-firing in rapid thermal processing (RTP) Furnace and laser edge isolation and confirmed >14 % conversion efficiency from the best textured samples. This isotropic texturing approach can be instrumental to achieve high efficiency in mass production using relatively low cost silicon wafers as starting material.

• Proceedings of the Korean Society of Applied Pharmacology
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• 1998.11a
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• pp.154-155
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• 1998

Taurine, 2-aminoethanesulfonic acid is widely distributed in animal tissues and has a variety of biological activities. A recent worldwide study demonstrated beneficial effects of taurine on aging and age-associated disorders. In general, taurine levels in the brain decrease when an animal is subjected to pathologic conditions such as ischemia-anoxia and seizure. But taurine levels tend to increase in the brain in hypertention. In the present study, the blood-brain barrier BBB) transport of [$^3$H]taurine was compared between spontaneously hypertensive rats (SHR) and normotensive Sprague-Dawley rats (SD) using Internal artery carotid perfusion (ICAP) at a rate of 4$m\ell$/min for 10, 15 and 30 second. Calculated V$\_$D/, volume of distribution in brain, and PS, the permeability surface area product of [$^3$H]taurine through the BBB in SHR was a little lower than that in SD. PS for 15s is more higher than that of other seconds in both of them. It could be followed by taurine efflux back into blood after 15s. We also obtained pharmacokinetic parameters using intravenous injection of plasma volume marker, [$\^$14/C]sucrose and [$^3$H] taurine. PS value of [$^3$H]taurine in SHR (16.1 ${\pm}$ 2.9 ${\times}$ 10$\^$-3/ $m\ell$/min/g) was significantly higher than that in SD (7.4 ${\pm}$ 0.8 ${\times}$ 10$\^$-3/ $m\ell$/min/g). There is also significant difference for %ID/g in brain between SHR (0.195 ${\pm}$ 0.031) and SD (0.058 ${\pm}$ 0.003).

• Proceedings of the Materials Research Society of Korea Conference
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• 2012.05a
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• pp.88.1-88.1
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• 2012

Silicon nanowires (SiNWs), due to their unusual quantum-confinement effects that lead to superior electrical and optical properties compared to those of the bulk silicon, have been widely researched as a potential building block in a variety of novel electronic devices. The conventional means for the synthesis of SiNWs has been the vapor-liquid-solid method using chemical vapor deposition; however, this method is time consuming, environmentally unfriendly, and do not support vertical growth. As an alternate, the electroless etching method has been proposed, which uses metal catalysts contained in aqueous hydrofluoric acids (HF) for vertically etching the bulk silicon substrate. This new method can support large-area growth in a short time, and vertically aligned SiNWs with high aspect ratio can be readily synthesized with excellent reproducibility. Nonetheless, there still are rooms for improvement such as the poor surface characteristics that lead to degradation in electrical performance, and non-uniformity of the diameter and shapes of the synthesized SiNWs. Here, we report a facile method of SiNWs synthesis having uniform sizes, diameters, and shapes, which may be other than just cylindrical shapes using a modified nanosphere lithography technique. The diameters of the polystyrene nanospheres can be adjustable through varying the time of O2 plasma treatment, which serve as a mask template for metal deposition on a silicon substrate. After the removal of the nanospheres, SiNWs having the exact same shape as the mask are synthesized using wet etching technique in a solution of HF, hydrogen peroxide, and deionized water. Different electrical and optical characteristics were obtained according to the shapes and sizes of the SiNWs, which implies that they can serve specific purposes according to their types.

• Journal of Chest Surgery
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• v.10 no.2
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• pp.299-314
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• 1977

Clinical experience on 16 cases of open heart surgery under the extracorporeal circulation with mild or moderate hypothermia and partial hemodilution technique at the National Medical Center during the period from June 1976 to October 1977. Nine of sixteen were congenital heart disease and seven were acquired heart disease. The age of the patient ranged between 6 and 48 years. The body weight varied from 18.5kg to 60kg and body surface area 0. 79-1.70m2. The average priming volume of pump oxygenator was 2080 ml, which was consisted fresh ACD blood, buffered Hartmann`s solution, Mannitol, 50% dextrose in water and Vit. C. The average hemodilution rate was 27%. The average flow 2.3 L/min/m2 or 80 ml/min and the duration of perfusion varied from 31 min to 270 min with average of 107 min. The perfusion was carried out under the mild or moderate hypothermia using core cooling alone in 10 cases, core cooling and local myocardial cooling with $0-4^{\circ}C$ physiologic saline in 2 cases. From a hemodynamic point of view, the blood pressure dropped down around 80 mmHg after the initiation of perfusion follwed by increase to safety level and stable during the perfusion. The central venous pressure remained within normal limits. In most cases, hemoglobin and hematocrit decreased during and after the perfusion. Hemogiobin level was decreased, average of 20.6 %, hematocrit 18.6%, pletelets 55% postoperatively. Plasma hemoglobin increased moderately, from preperfusion average valve of 7.79 mg % to post-perfusion value of 54.7 mg %. Electrolytes changes during cardiopulmonary bypass showed definite hypokalemia but changes of Na, Ca were not definite. Arterial blood gas analysis during cardiopulmonary bypass suggested that the metabolic acidosis which was accompanied by respiratory alkalosis which was corrected postoperatively. As the opera tive complication, transient hemoglobinuria in 4 cases and neurological signs in 2 cases were all cured. There were 2 death cases and operative mortality rate was 12.5%.

• Biotechnology and Bioprocess Engineering:BBE
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• v.6 no.6
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• pp.402-409
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• 2001

Different bioligands carrying synthetic adsorbents have been reported in the literature for protein separation, We have developed a novel and new approach to obtain high protein ad-sorption capacity utilizing 2-methacrylamidohistidine(MAH) as a bioligand. MAH was synthe-sized by reacting methacrylocholride and histidine, Spherical beads with an average size of 150-200㎛ were obtained by the radical suspension polymerization of MAH and 2-hydrosyethyl-methacrylate(HEMA) conducted in an aqueous dispersion medium. p(HEMA-co-MAH) beads had a specific surface area of 17.6㎡/g . Synthesized MAH monomer was characterized by NMR. p(HEMA-co-MAH) beads were characterized by swelling test, FTIR and elemental analysis. Then Cu(II) ions were incorporated onto the beads and Cu(II) loading was found to be 0.96 mmol/g.These affinity beads with a swelling ration of 65% and containing, 1.6 mmol MAH/g were used in the adsorption/desorption of human serum albumin(HSA) from both aqueous solutions and hu-man serum. The adsorption of HSA onto p(HEM-co-MAH) was low(8.8 mg/g). Cu(II) chelation onto the beads significantly increased the HSA adsorption (56.3 mg/g). The maximum HSA ad-sorption ws observed at pH 8.0 Higher HSA adsorption was observed from human plasma(94.6 mgHSA/g) Adsorption of other serum proteins were obtained as 3.7 mg/g for fibrinogen and 8.5mg/g for γ-globulin. The total protein adsorption was determined as 107.1mg/g. Desorption of HSA was obtained using 0.1 M Tris/HCl buffer containing 0.5 M NaSCN, High desorption rations(up to 98% of the adsorbed HSA) were observed. It was possible to reuse Cu(II) chelated-p(HEMA-co-MAH) beads without significant decreases in the adsorption capacities.

• 한국태양에너지학회:학술대회논문집
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• 2012.03a
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• pp.243-247
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• 2012

The paper focuses on an anti-reflection (AR) coating deposited by PECVD in silicon solar cell fabrication. AR coating is effective to reduce the reflection of the light on the silicon wafer surface and then increase substantially the solar cell conversion efficiency. In this work, we carried out experiments to optimize double AR coating layer with silicon nitride and silicon oxide for the silicon solar cells. The p-type mono crystalline silicon wafers with $156{\times}156mm^2$ area, 0.5-3 ${\Omega}{\cdot}cm$ resistivity, and $200{\mu}m$ thickness were used. All wafers were textured in KOH solution, doped with $POCl_3$ and removed PSG before ARC process. The optimized thickness of each ARC layer was calculated by theoretical equation. For the double layer of AR coating, silicon nitride layer was deposited first using $SiH_4$ and $NH_3$, and then silicon oxide using $SiH_4$ and $N_2O$. As a result, reflectance of $SiO_2/SiN_x$ layer was lower than single $SiN_x$ and then it resulted in increase of short-circuit current and conversion efficiency. It indicates that the double AR coating layer is necessary to obtain the high efficiency solar cell with PECVD already used in commercial line.

• Korean Journal of Organic Agriculture
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• v.21 no.2
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• pp.265-270
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• 2013

Cooking oil and yolk mixture (COY) was applied to control the powdery mildew of sweet persimmon at the research field of Gyeongsangnam-do Agricultural Research and Extension Services from 2010 to 2011. COY was sprayed three times with 10 days interval on foliar parts of sweet persimmon and the disease development was monitored after 5 days of final spray. Diseased leaf area rate was 13.4% and the control efficacy of COY against powdery mildew was 80.5%. Disease rate was 68.6% on negative control. Using scanning electron microscope (SEM), the morphological changes of the powdery mildew fungus on the leaf surface were observed. On COY-treated leaves, fungal mycellia were morphologically characterized by a loss in cell volume, shriveling, plasma membrane rupture, and subsequent loss of intracellular contents. It may due to the destruction of fungal cell wall or membrane structure.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.80-80
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• 2010

Graphene has attracted tremendous attention for the last a few years due to it fascinating electrical, mechanical, and chemical properties. Up to now, several methods have been developed exclusively to prepare graphene, which include micromechanical cleavage, polycrystalline Ni employing chemical vapor deposition technique, solvent thermal reaction, thermal desorption of Si from SiC substrates, chemical routes via graphite intercalation compounds or graphite oxide. In particular, polycrystalline Ni foil and conventional chemical vapor deposition system have been widely used for synthesis of large-area graphene. [1-3] In this study, synthesis of mono-layer graphene on a Ni foil, the mixing ratio of hydrocarbon ($CH_4$) gas to hydrogen gas, microwave power, and growth time were systemically optimized. It is possible to synthesize a graphene at relatively lower temperature ($500^{\circ}C$) than those (${\sim}1000^{\circ}C$) of previous results. Also, we could control the number of graphene according to the growth conditions. The structural features such as surface morphology, crystallinity and number of layer were investigated by scanning electron microscopy (SEM) and atomic force microscopy (AFM), transmission electron microscopy (TEM) and resonant Raman spectroscopy with 514 nm excitation wavelength. We believe that our approach for the synthesis of mono-layer graphene may be potentially useful for the development of many electronic devices.

• KSBB Journal
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• v.13 no.5
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• pp.577-584
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• 1998

A sensitive membrane strip assay for plasma lipoprotein cholesterol that can be performed without handling reagents has been investigated. We previously developed an assay system with immobilized enzymes (cholesterol esterase and cholesterol oxidase) on the surfaces of nitrocellulose membrane(1). In such a case, the amount of enzymes present on the membrane was limited by its surface area and, thus, the detection capability was relatively poor (> 50 mg/dL cholesterol). To overcome this problem, we devised a new system with non-immobilized enzymes by placing them within interstitial spaces of a celullose membrane pad in a dry state. Upon contact with sample medium, the enzymes were immediately dissolved and participated in the reactions with cholesterol in a liquid phase. We constructed a user-friendly system consisting of four membrane pads fro sample application, cholesterol decomposition, color development as signal, and medium absorption to invoke a continuous flow (sequential location from the bottom). A sample containing lipoproteins was added into the application pad by capillary action and transferred to the next pad for decomposition. The decomposition pad (namely, enzyme pad) contained a detergent (sodium cholate) for the destruction of lipoprotein particles, the two enzymes for cholesterol decomposition, and a chromogen (3,3'-diaminobenzidine). As a consequence of the enzyme reactions, hydrogen peroxide was produced, and then reacted in the presence of the chromogen with horseradish peroxidase immobilized on the signal generation pad. Finally, a colorimetric signal directly proportional to the cholesterol concentration was produced. The detection limit determined from this system under optimal conditions was at least 2 times lower than of the enzyme-immobilized system.