• The Korean Journal of Nuclear Medicine
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• v.38 no.1
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• pp.99-108
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• 2004

Purpose: The ability to noninvasively track the migration of neural progenitor cells would have significant clinical and research implications. We generated stably transfected F3 human neural progenitor cells with human sodium/iodide symporter (hNIS) for noninvasively tracking F3. In this study, the expression patterns of hNIS gene in F3-NIS were examined according to the cultured time and the epigenetic modulation. Materials and Methods: F3 human neural stem cells had been obtained from Dr. Seung U. Kim (Ajou University, Suwon, Korea). hNIS and hygromycin resistance gene were linked with IRES (Internal Ribosome Entry Site) under control of CMV promoter. This construct was transfected to F3 with Liposome. To investigate the restoration of hNIS gene expression in F3-NIS, cells were treated with demethylating agent (5-Azacytidine) and Histone deacetylase inhibitor (Trichostatin A: TSA). The expression of hNIS was measured by I-125 uptake assay and RT-PCR analysis. Results: The iodide uptake of the F3-NIS was higher 12.86 times than F3 cell line. According to the cell passage number, hNIS expression in F3-NIS gradually diminished. After treatment of 5-Azacytidine and TSA with serial doses (up to $20{\mu}M$, up to 62.5nM, respectively) for 24 hours, I-125 uptake and mRNA of hNIS in F3-NIS were increased. Conclusion: These results suggest that hNIS transfected F3 might undergo a change in its biological characters by cell passage. Therefore, the gene ex[ressopm of exogenous gene transferred human stem cell might be affected to the epigenetic modulation such as promoter methylation and Histone deacetylation and to the cell culture conditions.

• Journal of the Korean Solar Energy Society
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• v.32 no.4
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• pp.43-50
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• 2012

Metal-metal oxide (M-M oxide) cermet solar selective coatings with a double cermet layer film structure were deposited on the Al-deposited glass substrate by using a directed current (DC) magnetron sputtering technology. M oxide (CrO and ZrO) was used as the ceramic component in the cermets, and Cr and Zr used as the metallic components. In addition, black Cr (Cr-$Cr_2O_3$ cermet) solar selective coatings were deposited on the Ni-plated Cu substrate by using a electroplating method for comparison. The thermal stability tests were carried out for performance evaluation of solar coatings. Reflectance measurements were used to evaluate both solar absorptance(${\alpha}$) and thermal emittance (${\epsilon}$) of the solar coatings before and after thermal testing by using a spectrometer. Optical properties of optimized cermet solar coatings were ${\alpha}{\simeq}0.94-0.96$ and ${\epsilon}{\simeq}0.1$ ($100^{\circ}C$). The results of thermal stability test of M-M oxide solar coatings showed that the Cr-CrO cermet solar selective coatings were more stable than the Zr-ZrO cermet selective coatings at temperature of both $400^{\circ}C$ in air and $450^{\circ}C$ in vacuum. The black Cr solar selective coatings were degraded in air at temperature of $400^{\circ}C$. The main optical degradation modes of these coatings were diffusion of metal atoms, and oxidation.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.10
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• pp.1069-1074
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• 2014

In this study, the piezoelectric characteristics of a piezoelectric paint sensor were investigated in relation to the poling time. This piezoelectric paint sensor was composed of PNN-PZT powder and epoxy resin with a 1:1 weight ratio. The dimensions of the paint specimen were $40{\times}10{\times}1mm^3$, and the top and bottom sides were both coated with a silver paste to create electrodes. During the poling treatment, the poling time was controlled to examine the effect of the piezoelectric properties, while the poling temperature was fixed at room temperature and the electric field was set to 4 kV/mm. The piezoelectric properties were measured by comparing the output voltage from the paint sensor to the force signal from an impact hammer when the impact hammer hit the specimen. In conclusion, the optimal poling conditions were found to be an electric field of 4 kV/mm and a poling time of around 30 min at room temperature.

• Journal of Hydrogen and New Energy
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• v.3 no.2
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• pp.55-62
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• 1992

To improve the MCFC performance it is important to distingush between polarization losses occuring in the individual electrodes and other components. In this study a current interruption technique has been applied to a MCFC unit cell having a reference electrode to separately study the contributions of IR loss and other polarization losses. At a current density of $150mA/cm^2$ the IR-free polarization of a Ni anode was about 60mV while that of a NiO cathode was 130mV and the Ohmic loss of the cell was as large as 170mV suggesting that both the cathode and the cell structure need further improvement. The thin-film electrode model was used to simulate the performance of the electrodes. Both andoe data and cathode data were successfully fitted.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.11a
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• pp.201-201
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• 2006

영구자석은 크게 Hard ferrite와 희토류계 자석, 그리고 Alnico 주조자석으로 구별되어진다. 그동안 Hard ferrite는 산업적으로 전자기 응용제품 또는 각종 구동 모터에 응용되어 왔지만, 최근 Nd계 희토류 자것이 고성능 모터의 소재로 급격히 대체되고 있다. 하지만, 희토류계 원료에 비해 동일 중량 대비 40~60배 가량 저렴한 Hard ferrite의 사용은 현재까지도 꾸준히 유지되고 있으며, 최근 자동차 고성능 모터용 Sr ferrite의 개발이 연구 중이다.[2] 본 연구에서는 제일원리 전산모사를 통하여 HCP 구조의 기본 Unit Cell 64개 원자를 가진 Sr-ferrite의 격자상수를 계산하여 기존 연구결과와 비교하였으며, 자화에너지와 자기모멘트를 계산하였다. 또한 향후 각종 첨가물의 영향에 대한 연구를 위해 기본 구조 및 치환 구조에 대해 고찰하였다. 그 결과 가장 안정한 에너지를 갖는 격자상수는 a=5.88, b=23.03으로 계산되어 Kimura et al의 측정 결과와 유사한 결과를 얻을 수 있었으며, $E_F$가 3.9171, $M_B$는 46.6481로 계산되었다. 항후 Sr-ferrite의 구조에서 Fe atom의 일부를 동일주기 원소인 Cr, Mn, Co, Ni, Cu로 치환하여 자기적 특성을 계산하여 본 연구결과와 비교하고자 한다.

• Proceedings of the Korean Magnestics Society Conference
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• 1991.05a
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• pp.73-74
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• 1991

The films with ferromagnetic fine particles dispersed in nonmagnetic matrix, such as $Fe-Al_2O_3$ and Fe-Cu have been studied for use of magnetic recording medium, optically device and sensor. Their magnetic properties depend strongly on structural parameter such as size and volume fraction of ferromagnetic particles. Fe-Cr-Ni alloy sputtered films also have microstructure with ferromagnetic -- b.c.c phase and nonmagnetic f.c.c phase grains. Magnetic properties of these films depend strongly on such a unique structure. These are depend on the ratio in volume of ferromagnetic particles to nonmagnetic ones $V_F/V_N$, the saturation magnetization Ms increased with increase of $V_F/V_N$. The coercivity Hc of the as-deposited films took maximum value of about 200 Oe at adequate $V_F/V_N$ and then Ms and Squareness S were 500 emu/cc and 0.5, respectively.(omitted)

• Journal of Ocean Engineering and Technology
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• v.12 no.1
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• pp.32-38
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• 1998

This paper is to investigate of microhardness, adhesive strength, tensile strength, and fatigue strength of ceramic sprayed steel. Rotary bending fatigue tests have been conducted at room temperature in air and 3% NaCl solution using specimens of carbon steel(S45C) with sprayed coating layers of Ni-4.5% Al(under coating) and $TiO_2$ (top coating). The microhardness has been improved at $800^{\circ}C$ heat treatment and 150mm spraying distance. Tensile strength of the sprayed steel is dependent on the substrate strength. The fatigue strength of the sprayed steel is larger than that of substrate due to blasting and constraint surface of plastic deformation effect. In low stress level, the corrosion fatigue strength of the sprayed steel were lower than that of fatigue strength in air by corrosion.

• Journal of Ocean Engineering and Technology
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• v.15 no.4
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• pp.60-65
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• 2001

Thermal spray coating is formed by a process in which melted particles flying with high speed towards substrate, then crash and spread on the substrate surface cooled and solidified in a very short time, Stacking of the particles makes coating. In this study, the exfoliation of $Al_2$O$_3$ and Ni-4.5wt.%Al thermally sprayed coating which were deposited by an atmospheric plasma spray apparatus are investigated using an AE method. A tensile test is conducted on notch specimens in a stress range below the elastic limit of substrate. The wave forms of AE generated from the three coating specimens can be classified by FFT analysis into two types which low frequency(type I waveform is considered to corresponds exfoliation of coating layers and type II waveform corresponds the plastic deformation of notch tip or the resultant fracture of coating. The fracture of the coating layers can estimate by AE event and amplitude, because AE features increase when the deformation generates.

• 한국신재생에너지학회:학술대회논문집
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• 2007.06a
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• pp.129-132
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• 2007

Advanced structure of metal-supported solid oxide fuel cells was devised to overcome sealing problem and mechanical instability in ceramic-supported solid oxide fuel cells. STS430 whose dimensions were 26mm diameter, 1mm thickness and 0.4mm channel width was used as metal support. Thin ceramic layer composed of anode(Ni/YSZ) and electrolyte(YSZ) was joined with STS430 metal support by using a cermet adhesive. $La_{0.8}Sr_{0.2}Co_{0.4}Mn_{0.6}O_{3}$ perovskite oxide was used as cathode material. It was noted that oxygen reduction reaction of cathode governed the overall cell performance from oxygen partial pressure dependance.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.28A no.11
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• pp.874-879
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• 1991

The effect of air gap between specimen and jig on the material constant (permittivity, permeability) and attenuation characteristics of electromagnetic wave absorbers in the coaxial line method was investigated. The presence of a air gap made both permittivity and permeability measured lower than true value, and the tendency was greater in the case of permittivity. An inner gap compared to an outer gop was found to yield a larger difference between measured and true values. The effect of air gap was measured for a Ni0.3Zn0.7Fe2O4, with the gap eliminated by metallizing with Ag-paste. The measured characteristics were in good agreement with corrected values by calculation.