• Journal of the Korean Ceramic Society
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• v.44 no.4 s.299
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• pp.219-223
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• 2007

The ionic conductivity of $Li_2O-ZrO_2-SiO_2$ glasses has been designed and analyzed on the basis of a mixture design experiment with constraints. Fitted models for the activation energy and the ionic conductivity are as follows: $Q(kJ/moi)=54.8565x_1+144.825x_2+133.846x_3-170.908x_1x_3-334.338x_2x_3$ $log{\sigma}(300K)=-5.00245x_1-1.17876x_2-15.5173x_3+17.4522x_1x_3$. The electrical properties are very sensitive to the ratio of $Li_2O/SiO_2$. The effect of $ZrO_2$ is less than that of this ratio but $ZrO_2$ component attributes to the reduction of the activation energy. The optimal composition for best ionic conduction based on these fitted models is $55Li_2O{\cdot}10ZrO_2{\cdot}35SiO_2$. Its activation energy and ionic conductivity at 300 K are 46.98 kJ/mol and $1.08{\times}10^{-5}{\Omega}^{-1}{\cdot}cm^{-1}$, respectively.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.63 no.12
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• pp.1671-1674
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• 2014

This paper presents a frequency-dependent cell impedance analysis chip for use in cancer and normal cell discrimination. The previous cell impedance analysis chips for flowing cells cannot allow enough time for cell-to-electrode contact to monitor frequency-dependent impedance response. Another type of the previous cell impedance analysis chips for the cells clamped by membranes need complex sample control for making stable cell-to-electrode contact. We present a new impedance analysis chip using the microchamber array, on which a PDMS cover is placed to make stable cell-to-electrode contact for the individual cell trapped in each microchamber; thus achieving frequency-dependent single-cell impedance analysis without complex sample control. Compared to the normal cells, the magnitude of NHBE cells is $60.07{\sim}97.41k{\Omega}$ higher than A549 cells in the frequency range of 95.6 kHz~2MHz and the phase of NHBE is $3.96^{\circ}{\sim}20.8^{\circ}$ higher than A549 cells in the frequency range of 4.37 kHz~2MHz, respectively. It is demonstrated experimentally that the impedance analysis chip performs frequency-dependent cell impedance analysis by making stable cell-to-electrode contact with simple sample control; thereby applicable to the normal cell and cancer cell discrimination.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.193.1-193.1
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• 2014

This study was to investigate the electronic structure and optical properties of Na doped into NiO thin film using XPS and REELS. The films were grown by electron beam evaporation with varying the annealing temperature. The relationship between the electrical characteristics with the local structure of NiO thin films was also discussed. The x-ray photoelectron results showed that the Ni 2p spectra for all films consist of Ni 2p3/2 which indicate the presence of Ni-O bond from NiO phase and for the annealed film at temperature above $200^{\circ}C$ shows the coexist Ni oxide and Ni metal phase. The reflection electron energy loss spectroscopy spectra showed that the band gaps of the NiO thin films were slightly decreased with Na-doped into films. The Na-doped NiO showed relatively low resistivity compared to the undoped NiO thin films. In addition, the Na-doped NiO thin films deposited at room temperature showed the best properties, such as a p-type semiconducting with low electrical resistivity of $11.57{\Omega}.cm$ and high optical transmittance of ~80% in the visible light region. These results indicate that the Na doping followed by annealing process plays a crucial in enhancing the electrical and optical properties of NiO thin films. We believe that our results can be a good guide for those growing NiO thin films with the purpose of device applications, which require deposited at room temperature.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.241.2-241.2
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• 2014

We present highly transparent liquid crystal displays (LCDs) using hybrid films based on carbon nanomaterials, metal grid, and indium-tin-oxide (ITO) grid. Carbon based nanomaterials are used as transparent electrodes because of high transmittance. Despite of their high transmittance they have relatively high sheet resistance. To solve this problem, we applied grid and made hybrid conductive films based on carbon nanomaterials. Conventional photolithography processes were used to make a grid pattern of metal and ITO. To fabricate transparent conductive films, carbon nanotube (CNT) ink was spin coated on the grid pattern. The transparency of the conductive film was controlled by shape and size of the grid pattern and the thickness of CNT films. The optical transmittance of CNT-based hybrid films is 92.2% and sheet resistance is also reduced to $168{\Omega}/square$. These substrates were used for the fabrication of typical twisted nematic (TN) LCD cells. From the characteristics of LCD devices such as transmittance, operating voltage, voltage holding ratio our devices were comparable to those of pristine ITO substrates. The result shows that the hybrid conductive films based on carbon nanomaterials could be alternative of ITO for the highly transparent LCDs.

• Journal of Surface Science and Engineering
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• v.38 no.5
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• pp.193-197
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• 2005

Highly c-axis oriented Zinc oxide (ZnO) films were successfully deposited at room temperature by oxygen ion-assisted pulsed filtered vacuum arc. The effect of oxygen gas ratio ($O_{2}/O_{2}+Ar$ on the preferred orientation, surface morphology and resistivity of the ZnO films were investigated. Highly crystalline ZnO films with (002) orientation were obtained at over $13\%$ of oxygen gas ratio. Increasing oxygen gas ratio up to $80\%$ was found to improve crystallinity of the films. From hall measurements, it was found that the film has n-type characteristic and carrier concentration and its mobility were closely related with oxygen gas ratio. Minimal resistivity of $3.6{\times}10^{-3}{\Omega}{\cdot}cm$ was obtained in the range of $20\%$ to $40\%$ of oxygen gas ratio.

• Journal of Biomedical Engineering Research
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• v.31 no.4
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• pp.292-301
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• 2010

To restore visual sensation of blind patients, we have proposed a fully implantable retinal prosthesis comprising an three dimensionally (3D) stacked retinal chip for transforming optical signal to electrical signal, a flexible cable with stimulus electrode array for stimulating retina cells, and coupling coils for power transmission. The 3D stacked retinal chip is consisted of several LSI chips such as photodetector, signal processing circuit, and stimulus current generator. They are vertically stacked and electrically connected using 3D integration technology. Our retinal prosthesis has a small size and lightweight with high resolution, therefore it could increase the patients` quality of life (QOL). For realizing the fully implantable retinal prosthesis, we developed a retinal prosthesis module comprising a retinal prosthesis chip and a flexible cable with stimulus electrode array for generating optimal stimulus current. In this study, we used a 2D retinal chip as a prototype retinal prosthesis chip. We fabricated the polymide-based flexible cable of $20{\mu}m$ thickness where 16 channels Pt stimulus electrode array was formed in the cable. Pt electrode has an impedance of $9.9k{\Omega}$ at 400Hz frequency. The retinal prosthesis chip was mounted on the flexible cable by an epoxy and electrically connected by Au wire. The retinal prosthesis chip was cappted by a silicone to pretect from corrosive environments in an eyeball. Then, the fabricated retinal prosthesis module was implanted into an eyeball of a rabbit. We successfully recorded electrically evoked potential (EEP) elicited from the rabbit brain by the current stimulation supplied from the implanted retinal prosthesis module. EEP amplitude was increased linearly with illumination intensity and irradiation time of incident light. The retinal prosthesis chip was well functioned after implanting into the eyeball of the rabbit.

• Reproductive and Developmental Biology
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• v.33 no.4
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• pp.237-242
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• 2009

Pregnancy is a unique event in which a fetus develops in the uterus despite being genetically and immunologically different from the mother, and the underlying mechanisms remain poorly understood. To analyze the differential gene expression profiles in nonpregnant and 7 days post coitus (dpc) pregnant uterus of mice, we performed a global proteomic study by 2-D gel electrophoresis (2-DE) and MALDI-TOF-MS. The uterine proteins were separated using 2-DE, Approximately 1,000 spots were detected on staining with Coomassie brilliant blue. An image analysis using Melanie III (Swiss Institute for Bioinformatics) was performed to detect variations in protein spots between pregnant and nonpregnant uterus. Twenty-one spots were identified as differentially expressed proteins, of which 10 were up-regulated proteins such as alpha-fetoprotein, chloride intracellular channel 1, transgelin, heat-shock protein beta-1, and carbonic anhydrase II, while 11 were down-regulated proteins such as X-box binding protein, glutathione S-transferase omega 1, olfactory receptor Olfr204, and metalloproteinase-disintegrin domain containing protein TECADAM. Most of the identified proteins appeared to be related with catabolism, cell growth, metabolism, regulation, cell protection, protein repair, or protection. Our results uncovered key proteins of mouse uterus involved in pregnancy.

• The Korean Journal of Ceramics
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• v.6 no.3
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• pp.258-261
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• 2000

Highly (h00)-oriented (Ba, Sr)TiO$_3$(BST) thin films were grown by pulsed laser deposition on the perovskite LaNiO$_3$(LNO) metallic oxide layer as a bottom electrode. The LNO films were deposited on SiO$_2$/Si substrates by rf-magnetron sputtering method. The crystalline phases of the BST film were characterized by x-ray $\theta$-2$\theta$, $\omega$-rocking curve and $\psi$-scan diffraction measurements. The surface microsturcture observed by scanning electron microscopy was very dense and smooth. The low-frequency dielectric responses of the BST films grown at various substrate temperatures were measured as a function of frequency in the frequency range from 0.1 Hz to 10 MHz. The BST films have the dielectric constant of 265 at 1 kHz and showed multiple dielectric relaxation at the low frequency region. The origin of these low-frequency dielectric relaxation are attributed to the ionized space charge carriers such as the oxygen vacancies and defects in BST film, the interfacial polarization in the grain boundary region and the electrode polarization. We studied also on the capacitance-voltage characteristics of BST films.

• Proceedings of the KIEE Conference
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• 2000.11c
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• pp.479-481
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• 2000

The effect of $Al_{2}O_{3}+Y_{2}O_{3}$ additives on fracture toughness of $\beta-SiC-TiB_2$ composites by hot-pressed sintering were investigated. The f$\beta-SiC-TiB_2$ ceramic composites were hot-presse sintered and annealed by adding 16, 20, 24wt% $Al_{2}O_{3}+Y_{2}O_{3}$(6 : 4wt%) powder as a liquid forming additives at low temperature($1800^{\circ}C$) for 4h. In this microstructures, the relative density is over 95.88% of the theoretical density and the porosity increased with increasing $Al_{2}O_{3}+Y_{2}O_{3}$ contents because of the increasing tendency of pore formation. The fracture toughness showed the highest of $5.88MPa{\cdot}m^{1/2}$ for composites added with 20wt% $Al_{2}O_{3}+Y_{2}O_{3}$ additives at room temperature. The electrical resistivity showed the lowest of $5.22{\times}10^{-4}\Omega{\cdot}cm$ for composite added with 20wt% $Al_{2}O_{3}+Y_{2}O_{3}$ additives at room temperature and is all positive temperature coefficient resistance (PTCR) against temperature up to $700^{\circ}C$.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.29 no.8
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• pp.470-475
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• 2016

In this study, $Zn_xMn_{3-x}O_4$ (x=0.95~1.20) specimens were prepared by using a conventional mixed oxide method. All specimens were sintered in air at $1,200^{\circ}C$ for 12 h and cooled at a rate of $2^{\circ}C/min$ to $800^{\circ}C$, subsequently quenching to room temperature. We investigated the structural and electrical properties of $Zn_xMn_{3-x}O_4$ specimens with variation of ZnO amount for the application of NTC thermistors. As results of X-ray diffraction patterns, all specimens showed the formation of a complete solid solution with tetragonal spinel phase. And, the second phase was observed by the solubility limit of Zn ions in $x{\geq}1.10$ composition. The average grain size was increased from $2.72{\mu}m$ to $4.18{\mu}m$ with increasing the compositional ratio of Zn ion from x=0.95 to 1.20, respectively. $Zn_{1.10}Mn_{1.90}O_4$ specimen showed the minimum electrical resistance of $57.5k{\Omega}$ at room temperature and activation energy of 0.392 eV.