• Journal of the Korean Magnetics Society
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• v.10 no.4
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• pp.159-163
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• 2000

MR characteristics in magnetic tunnel junction using CoO as the oxide barrier were investigated. Spin-dependent tunnel junctions were fabricated on 4$\^$o/ tilt-cut (111)Si substrates in 3-gun magnetron sputtering system. The top and bottom ferromagnetic electrodes were Ni$\_$80/Fe$\_$20/(300 $\AA$) and Co(300 $\AA$), respectively. The oxide barriers (CoO) were formed by the thermal oxidation at room temperature in an O$_2$ atmosphere and the plasma oxidation. The increase of coercive field due to antiferromagnetic-ferromagnetic coupling has been observed in O$_2$plasma-oxidized CoO based junctions at room temperature. At a sensing current of 1 mA, MR ratios of O$_2$plasma-oxidized CoO based junction and thermal-oxidized CoO based junction at room temperature were 1% and 5%, respectively. Larger MR ratios are observed in magnetic tunnel juctions with thermal oxidized CoO when sensing current more than applied 1.5 mA. At a sensing current of 1.5 mA, we have observed MR value of 28 % and specific resistance (RA=R$\times$A) value of 10.9 ㏀$\times$㎛$^2$. When specific resistance values reached 2.28 ㏀$\times$㎛$^2$, we have observed that MR ratios become as high as 120%.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.4
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• pp.373-379
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• 2002

We investigated the evolution of magnetoresistance and magnetic property of tunneling magnetoresistive(TMR) device with microstructure and plasma oxidation time. TMR devices have potential applications for non volatile MRAM and high density HDD reading head. We prepared the tunnel magnetoresistance(TMR) devices of Ta($50{\AA}$)/NiFe($50{\AA}$)/IrMn($150{\AA}$)/CoFe($50{\AA}$)/Al($13{\AA}$)-O/CoFe($40{\AA}$)/FiFe($400{\AA}$)/Ta(($50{\AA}$) structure which have $100{\times}100\mu\textrm{m}^2$ junction area on $2.5{\times}2.5\textrm{cm}^2$ Si/$SiO_2$(($1000{\AA}$) substrates by an inductively coupled plasma(ICP) magnetron sputter. We fabricated the insulating layer using an ICP plasma oxidation method by with various oxidation time from 30 sec to 360 sec, and measured resistances and magnetoresistance(MR) ratios of TMR devices. We found that the oxidized sample for oxidation time of 80 sec showed the highest MR radio of 30.31 %, while the calculated value regarding inhomogeneous current effect indicated 25.18 %. We used transmission electron microscope(TEM) to investigate microstructural evolution of insulating layer. Comparing the cross-sectional TEM images at oxidation time of 150 sec and 360 sec, we found that the thickness and thickness variation of 360 sec-oxidized insulating layer became 30% and 40% larger than those of 150 sec-oxidized layer, repectively. Therefore, our results imply that increase of thickness variation with oxidation time may be one of the major treasons of the MR decrease.

• Proceedings of the Korean Society of Applied Pharmacology
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• 1996.04a
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• pp.232-232
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• 1996

DA-1131은 gram positive bacteria와 Pseudomonas aeruginosa를 포함한 gram negative bacteria에 대하여 광범위한 항균 spectrum과 우수한 항균력을 나타내었다. 각종 임상분리균주에 대한 항균력 시험 결과, gram positive bacteria 중 methicillin-resistant Staphylococcus aureus(MRSA)에 대하여는 DA-1131이 가장 우수한 항균력을 나타내었으며, methicillin-susceptible S. aureus(MSSA)에 대하여는 MEPM, CPR 및 CAZ보다 약 2-50배의 우수한 항균력을 나타내었으나 IPM/CS보다는 동등이하의 항균력을 나타내었다. Gram negative bacteria에 대하여는 IPM/CS, CAZ 및 CPR보다 우수한 항균력을 나타내어 0.2 $\mu\textrm{g}$/$m\ell$ 이하의 농도에서 91%의 Serratia marcescens, 89%의 Proteus mirabilis, 76%의 Morganella morganii 및 시험에 사용된 Enterobacteriaceae에 속하는 전균주의 생육이 억제되었다. P. aeruginosa 에 대하여 DA-1131은 1.56 $\mu\textrm{g}$/$m\ell$ 이하의 농도로 시험균주 전체의 생육을 저해하였으며, MEPM의 약 2배, IPM/CS의 약 4배의 강한 항균력을 나타내었다. CAZ에 내성인 Enterobacteriaceae 임상분리균주에 대한 DA-1131의 항균력은 CAZ 감수성균주에 대한 항균력과 동일한 것으로 나타났다.

• Journal of Bio-Environment Control
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• v.8 no.3
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• pp.192-201
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• 1999

This study was aimed to introduce the measurement of $CO_2$ concentration and leaf area index in the phytotron for predicting the effect of CO.E, light and leaf area index on the instantaneous photosynthetic rate of sweet pepper with the existing ASKAM model. Measurements were made in 2 semi-closed phytotron compartments in which three different $CO_2$ concentrations were applied at random. Plants were grown on containers with circulating nutrient solution at 21$^{\circ}C$ and 80-95% relative humidity. The model estimates crop net $CO_2$ uptake for short time intervals during the day based on short-term data of daily radiation, temperature and $CO_2$ concentration. During the photosynthesis measurements, $CO_2$ concentrations in both compartments and in the basement were measured every minute. This was also done for the flow of pure $CO_2$ into the compartment, global radiation, photosynthetic active radiation inside the compartment, temperature and relative humidity. Crop growth models summarize our knowledge on crop behavior and have as such a wide range of applications in analysis, crop management and thus as a farm management tool.

• Journal of the Korean Vacuum Society
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• v.4 no.1
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• pp.26-31
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• 1995

본 연구에서는 Co/Si 계에 대한 이온선 혼합실험을 온도와 이온선량을 변수로 하여 실시하였고, Co/Si 계에 대한 상형성 과정을 금속/Si 계에 대한 이온선 혼합시의 비정질상 및 결정상 형성예측 모델(ADF Model)과 초기 결정상 예측 모델(PDF Model)을 이용하여 해석하였다. 이온선 혼합은 80KeV 가속기를 이용하여 상온$-400^{\circ}C$의 온도 범위에서 1.0X1015Ar+/$\extrm{cm}^2$-2.0X1016Ar+/$\textrm{cm}^2$의 이온선량을 변화시키면서 실험하였으며 상분석은 투과전자현미경(TEM)과 X선 회절 분석을 이용하였다. Co/Si 계에서 이온선 혼합시 형성되는 초기 결정상은 Co2Si이며 이온선량의 증가에 따라 CoSi로 상전이하였다. 이러한 실험 결과는 비정질상 및 결정상 형성 예측 모델(ADF model)과 초기 결정상 예측모델(PDF model)의 예측결과와 매우 잘 일치하고 있다. 이상의 연구 결과로부터 ADF 모델과 PDF모델을 이용하여 박막에서 형성되는 상을 보다 정확히 예측할 수 있음을 알 수 있었다.

• Korean Journal of Materials Research
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• v.10 no.1
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• pp.55-61
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• 2000

The sintering characteristics of PVA-Al(III) complex added $UO_2$ pellet and AlOOH added $UO_2$pellet were compared. The major phase of PVA-Al(III) complex and AlOOH decomposed at $1000^{\circ}C$ in $H_2$atmosphere was $\theta-Al_2O_3$. Compared with the apparent density of pure $UO_2$, that of AlOOH added $UO_2$ powder was higher but that of PVA-Al(III) complex was lower. the densification of AlOOH added $UO_2$ pellet was initiated at about $800^{\circ}C$, the densification of PVA-Al(III) complex added $UO_2$ pellet was initiated at about $900^{\circ}C$ respectively. In a view of pore size distribution, the PVA-Al(III) complex added $UO_2$ pellet appeared as monomodal type, whereas the AlOOH added $UO_2$ pellet appeared as bimodal type. The grain size of AlOOH added $UO_2$ pellet was about $13\mu\textrm{m}$ but the grain size of PVA-Al(III) complex added $UO_2$ pellet was increased up to about $36\mu\textrm{m}$.

• Korean Journal of Materials Research
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• v.12 no.10
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• pp.803-808
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• 2002

Nickel powders were prepared from nickel chloride solution by wet reduction process, and the size control of the particles was investigated with reactant concentration, dispersant agent, and the addition of ethanol as an organic solvent in NiCl$_2$ aqueous solution. The size of the particle decreased with the increase of nickel chloride concentration. Their average particle size were 1.9$\mu\textrm{m}$, 1.6$\mu\textrm{m}$ and $1.5\mu\textrm{m}$ with 0.5M, 0.8M and 1.0M of nickel chloride concentration respectively. The spherical particle was easily controlled by the addition of ethanol as an organic solvent. Especially, in 30 vol% of ethanol, the average particle size and specific surface area were about 0.2$\mu\textrm{m}$ and 8.98m$^2$/g, respectively.

• Food Science and Preservation
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• v.5 no.3
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• pp.207-210
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• 1998

To prolong the shelf life of green chili pepper, packaging films such as 30 $\mu\textrm{m}$ low density polyethylene(LDPE), 20 $\mu\textrm{m}$ perforated polyolefin (SM250), 30 $\mu\textrm{m}$ cast polypropylene (CPP) and 15 $\mu\textrm{m}$ polyolefin (MPD) were used. LDPE showed a suitable gas concentration which consisted of 3-5% O$_2$ and below 5% CO$_2$for keeping quality of green chili peppers after 10 days. Though weight loss was 9.3% for SM250 after 5 days, others showed below 2.0% weight loss after 40 days. Green chili peppers inside CPP package revealed a great decrease in ascorbic acid content after 30 days. SM250 showed a less total microbial count among packages, but there was no great differences among packages.

• Journal of Oral Medicine and Pain
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• v.20 no.2
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• pp.429-447
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• 1995

This study was designed to determine the most effective concentration of fluoride and levels of laser irradiation for the remineralization of decayed teeth. After irradiation with a pulsed Nd:YAG laser and the topical application of fluoride, phosphate and fluoride concentration in enamel were measured. And then the changes on surface enamel using an scanning electron microscope were observed. Samples by extraction healthy, permanent, mandibular bovine teeth with no caries were obtained. Among them 371 healthy samples were selected and artificial carious lesions were made. 20 samples were assigned to each experimental group. After irradiation with a pulsed Nd:YAG laser with total energy densities of 10J/$\textrm{cm}^2$, 20J/$\textrm{cm}^2$ for each group. On the teeth, 2% NaF, 1.9% NH4F, 1.6% TiF4 Elmex gel(amine fluoride) and 1.23% APF gel were applied. After pH circulatory procedures, concentrations of fluoride with and Ionalyzer (Orion Research, Model 901, USA) and phosphates with an Uv/V is spectrophotometer (Uvikon 860, Kontrom Co, Switzerland) were measured. By etching the teeth in layers and measuring fluoride concentrations, a profile of fluoride penetration according to depth could be developed. And also the changes on the surface of the enamel using an electron scanning microscope were observed. The comparative analysis yielded the following results : 1. Phosphate concentration was low in all groups compared with the control group except for teeth treated Elmex gel, irradiated with 10J/$\textrm{cm}^2$ and 30J/$\textrm{cm}^2$ energy densities. Teeth treated with APF gel and 30J/$\textrm{cm}^2$ irradiation gad the lowest phosphate concentration. 2. Among all groups, fluoride concentrations in tooth enamel were highest in APF gel and NaF groups irradiated at 30J/$\textrm{cm}^2$. The APF gel group had the highest fluoride concentrations across all energy densities. 3. In the APF gel group, and the NaF group, the greater the energy density of the laser, the higher the fluoride concentrations in the enamel. 4. In all groups, the concentration of fluoride in the enamel by depth tended to decrease with depth. 5. Under the scanning electron microscope, under the condition of irradiation with 20J/$\textrm{cm}^2$, enamel crack was detected for the first time. In the NH4F group, spherical deposits were found on the surface of the enamel, and in the TiF4 group the surface of enamel was covered with an irregular, thin membranous mass in places. In the APF gel and NaF groups irradiated with 10J/$\textrm{cm}^2$, spherical and irregular particles covered the teeth. When these groups were irradiated at 20J/cm2, they were covered with amorphous crystals. These results suggest that one could obtain more effective anticariogenic effects without damage to teeth when less than 20J/$\textrm{cm}^2$ energy densities and APF gel are used.

• Korean Journal of Animal Reproduction
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• v.14 no.4
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• pp.253-261
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• 1990

This study was carried out to investigate the factors affecting development in vitro of follicular oocytes fertilized in vitro in Korean Native Cattle. The bovine ovaries were obtained at a slaughter house and the follicular oocytes were recovered by aspirating the follicular fluid from the visible follciles of 3~6mm. The bovine oocytes were matured in vitro for 20~24 hours in TCM0-199 containing 10% FCS and hormones (0.02AU/ml FSH, 10$\mu\textrm{g}$/ml LH, 1$\mu\textrm{g}$/ml estradiol-17$\beta$). The matured oocytes were fertilized in vitro using Percoll-separated frozen-thawed spermatozoa in BO solution containing caffeine(5mM) and heparin(10$\mu\textrm{g}$/ml). Twenty-four hours after insemination, the oocytes were cultured in vitro and then the effects of cumulus cell layer, co-culture with cumulus cells, bovine oviduct epithelial cells from ampulla or isthmus on development of ova, were studied. The results obtained are summarized as follows : 1. The in vitro development degree of oocytes attached with compact and dense layered cumulus cells was higher than that with 3~4 layered cumulus cells to be 9~16cells(P<0.01). 2. When the in vitro fertilized oocytes were co-cultured with bovine oviduct epithelial cells or cumulus cells, the development rate to be morula was 20.2% and 12.7%, respectively and the rates were higher than that of control, 2.1%(P<0.05). 3. The development rate to be morula was 15.8% and 23.8%, respectively when the in vitro fertilized oocytes were co-cultured with bovine oviduct epithelial cells from ampulla or isthmus, and the rates were higher than that of control, 0%(P<0.05%).