• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.28 no.11
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• pp.865-871
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• 2017

In this paper, a gelatin layer was formed on the surface of the twisted fiber-optic couplers fabricated by hydrofluoric acid, which can be used to measure relative humidity. The proposed method of sensors has advantage of low cost compared with the sensors based on the conventional electronic devices and takes beneficial characteristics of optical fibers and light. The fiber-optic sensors presented in this study show a measurement from about 40% to 85% relative humidity, and the experimental results agree well with the calculated results. Based on the design presented in this paper, the structure will enable promising applications in the detecting humidity and various hazardous gases.

• KEPCO Journal on Electric Power and Energy
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• v.1 no.1
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• pp.15-20
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• 2015

To examine the magnetic shielding effect for carbon-based materials at extremely low frequencies (60 Hz), two types of carbon black (Super-P and Denka Black) and a natural graphite (HC-198) were mixed into organic binder at 10 wt.% to produce a coating solution, and a powder coating with varying thickness was applied on an aluminum disk measuring 88 mm in radius. A device was developed to measure the sheielding effect at extremely low frequencies. A closed circuit was achieved by connecting a transformer and a resistor. The applied voltage was fixed at 65 V, and the magnetic field was measured to being the range of 4.95~5.10 mG. Depending on the thickness of the coating layer, the magnetic field showed a decreasing trend. The maximum decrease in the magnetic field of 38.3% was measured when natural graphite was coated with specimens averaging $455{\mu}m$. This study confirmed that carbon-based materials enable magnetic shielding at extremely low frequencies, and that the magnetic shielding effect can be enhanced by varying the coating thickness.

• Journal of the Microelectronics and Packaging Society
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• v.6 no.2
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• pp.63-68
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• 1999

We have fabricated $WO_3$ thick film gas sensor under various firing conditions in order to study gas sensing properties in terms of the variation of microstructure and non-stoichiometric structure of gas sensing layer. $WO_3$ paste mixed homogeneously with organic vehicle was coated by screen printing method on alumina substrate composed of Au electrode and $RuO_2$heater on each side. To change filing condition, sensing materials were fared at 600-$800^{\circ}C$ for 1 hour and refired at $700^{\circ}C$ for 1 hour in the mixtures of $_Ar/O2$gas. In the result of heat-treatment, $WO_3$ gas sensor fared at $700^{\circ}C$ showed best gas sensing properties of 210 gas sensitivity and 2 second response time and the best firing environment was 40-50% of $Ar/O_2$gas.

• Proceedings of the KIEE Conference
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• 2003.07c
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• pp.1574-1576
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• 2003

Carbon nanotubes (CNTs) were grown on the TiN-coated silicon substrate with different thickness of Ni and Co catalysts layer at $600^{\circ}C$ using inductively coupled plasma-chemical vapor deposition (ICP-CVD). The Ni and Co catalysts were formed using the RF magnetron sputtering system with various deposition times. It was found that the growth of CNTs was strongly influenced by the surface morphology of Ni and Co catalysts. With increasing deposition time, the thickness of catalysts increased and the grain boundary size of catalysts increased. The surface morphology of catalysts and CNTs were elucidated by SEM. The Raman spectrum further confirmed the graphitic structure of the CNTs. The turn-on field of CNTs grown on Ni and Co catalysts was about 2.7V/pm and 1.9V/pm respectively. Field emission current density of CNTs grown on Ni and Co catalysts was measured as $11.67mA/cm^2$ at $5.5V/{\mu}m$ and $1.5mA/cm^2$ at $5.5V/{\mu}m$ respectively.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.27 no.8
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• pp.516-521
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• 2014

An excellent hydrophobic surface has a high contact angle over 147 degree and the contact angle hysteresis below $5^0$ was produced by using roughness combined with hydrophobic PTFE coatings, which were also confirmed to exhibit an extreme adhesion to glass substrate. To form the rough surface, the glass was etched by Ar-plasma. A very thin PTFE film was coated on the plasma etched glass surface. Roughness factors before or after PTFE coating on the plasma etched glass surface, based on Wensel's model were calculated, which agrees well with the dependence of the contact angle on the roughness factor is predicted by Wensel's model. The PTFE films deposited on glass by using a conventional rf-magnetron sputtering. The glass substrates were etched Ar-plasma prior to the deposition of PTFE. Their hydrophobicities are investigated for application as a anti-fouling coating layer on the screen of displays. It is found that the hydrophobicity of PTFE films mainly depends on the sputtering conditions, such as rf-power, Ar gas content introduced during deposition. These conditions are closely related to the deposition rate or thickness of PTFE film. Thus, it is also found that the deposition rate or the film thickness affects sensitively the geometrical morphology formed on surface of the rf-sputtered PTFE films. In particular, 1,950-nm-thick PTFE films deposited for 30 minute by rf-power 50 watt under Ar gas content of 20 sccm shows a very excellent optical transmittance and a good anti-fouling property and a good durability.

• Applied Microscopy
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• v.15 no.2
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• pp.98-110
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• 1985

This study was performed to clarify the morphological structures of the epithelia of the renal papilla, renal pelvis and ureter of the sheep (Ovis aries L.) through the light and scanning electron microscopes, Tissue specimens were taken from the renal papilla (common renal papilla and peripelvic column) and the renal pelvis (pelvis proper and pelvic pouch) of the kidney and the ureter. For the light microscopy, tissue blocks were fixed in 10 % neutral buffered formalin and embedded in paraffin wax, serially sectioned at a thickness of $6{\mu}m$. These sections were stained with hematoxylin-eosin and periodic acid-Schiff reaction. For the scanning electron microscopy, tissue blocks were prefixed in 1% glutaral-dehyde-1.5% paraformaldehyde solution and postfixed in 1% osmium tetroxide solution, dehydrated in graded alcohol, transferred to isoamyl acetate, and then dried by the critical point dryer (Polaron E 3000). These dried tissues were coated with gold and observed with a scanning electron microscope (JSM-35C), The results were as follows: The apex of the common renal papilla was lined with simple columnar epithelium having many microvilli on its luminal surface. Lateral portion of the papilla was lined with stratified epithelium $2{\sim}3$ layers thick, and its superficial cells were microvillar cells having many microvilli. The epithelium lining the peripelvic column was $1{\sim}2$ layers thick. The superficial layer was made of the microvillar cells, but a few microplica cells were appeared in the region near the pelvic pouch. The epithelium of the pelvic pouch was $1{\sim}2$ layered transitional type, and its superficial cells were microplica cells. The epithelia of the pelvis proper and ureter were $4{\sim}6$ layered transitional type, and their superficial cells were typical facet cells existing many round depressions and ridges of cell membranes of the luminal side.

• Journal of Crop Science and Biotechnology
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• v.10 no.2
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• pp.92-97
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• 2007

Antibiotics used for suppressing Agrobacterium in plant transformation procedure might have negligible effects on plant tissues and regeneration. The effects of antibiotics on growth suppression of Agrobacterium and plant regeneration were investigated for enhancing Agrobacterium-mediated transformation using wheat mature embryos. Antibiotics tested, except carbenicillin, were able to suppress that embryos were coated with a layer of Agrobacterium cells in callus induction medium. Agrobacterium growth was suppressed minimally at 50 mg/l of timentin, while cefotaxime and clavamox were completely suppressed at relative high concentration of 250 mg/l. In the treatment of carbenicillin, initiation of growth suppression of Agrobacterium occurred at 750 mg/l of concentration because Agrobacterium KYRT1 contains the carbenicillin resistant gene. In Agrobacterium inoculation, effects of antibiotics were significantly different on the rate of callus induction and shoot formation. Almost embryos were induced calli at 50 mg/l of timentin whereas callus induction rate was achieved above 90% at 100 mg/l and 250 mg/l of cefotaxime and clavamox, respectively. Shoot formation rate was higher in the treatment of timentin than that of cefotaxime and clavamox at 500 mg/l of concentration, respectively. Timentin can be used as a good antibiotics in Agrobacterium-mediated wheat transformation.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.20-20
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• 2007

Nanowire-based field-effect transistors (FETs) decorated with nanoparticles have been greatly paid attention as nonvolatile memory devices of next generation due to their excellent transportation ability of charge carriers in the channel and outstanding capability of charge trapping in the floating gate. In this work, top-gate single ZnO nanowire-based FETs with and without Au nanoparticles were fabricated and their memory effects were characterized. Using thermal evaporation and rapid thermal annealing processes, Au nanoparticles were formed on an $Al_2O_3$ layer which was semi cylindrically coated on a single ZnO nanowire. The family of $I_{DS}-V_{GS}$ curves for the double sweep of the gate voltage at $V_{DS}$ = 1 V was obtained. The device decorated with nanoparticles shows giant hysterisis loops with ${\Delta}V_{th}$ = 2 V, indicating a significant charge storage effect. Note that the hysterisis loops are clockwise which result from the tunneling of the charge carriers from the nanowire into the nanoparticles. On the other hand, the device without nanoparticles shows a negligible countclockwise hysterisis loop which reveals that the influence of oxide trap charges or mobile ions is negligible. Therefore, the charge storage effect mainly comes from the nanoparticles decorated on the nanowire, which obviously demonstrates that the top-gate single ZnO nanowire-based FETs decorated with Au nanoparticles are the good candidate for the application in the nonvolatile memory devices of next generation.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.430-430
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• 2007

In this study, the nematic liquid crystal (NLC) alignment effects treated on the ZnO thin film layers using ion beam irradiation were successfully studied for the first time. The ZnO thin films were deposited on indium-tin-oxide (ITO) coated glass substrates by rf-sputter and The ZnO thin films were deposited at the three kinds of rf power. The used DuoPIGatron type ion beam system, which can be advantageous in a large area with high density plasma generation. The ion beam parameters were as follows: energy of 1800 eV, exposure time of 1 min and ion beam current of $4\;mA/cm^2$ at exposure angles of $15^{\circ}$, $30^{\circ}$, $45^{\circ}$, and $60^{\circ}$. The homogeneous and homeotropic LC aligning capabilities treated on the ZnO thin film surface with ion beam exposure of $45^{\circ}$ for 1 min can be achieved. The low pretilt angle for a NLC treated on the ZnO thin film surface with ion beam irradiation for all incident angles was measured. The good LC alignment treated on the ZnO thin film with ion beam exposure at rf power of 150 W can be measure. For identifying surfaces topography of the ZnO thin films, atomic force microscopy (AFM) was introduced. After ion beam irradiation, test samples were fabricated in an anti-parallel configuration with a cell gap of $60{\mu}m$.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.26 no.3
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• pp.232-239
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• 2013

Thin light-active layers of the $CuInSe_2$ solar cell were prepared on Mo-coated sodalime glass substrates by one-step electrodeposition and post-annealing. The structure, morphology, and composition of $CuInSe_2$ film could be controlled by deposition parameters, such as the composition of metallic precursors, the concentration of complexing agents, and the temperature of post-annealing with elemental selenium. A dense and uniform Cu-poor $CuInSe_2$ film was successfully obtained in a range of parametric variation of electrodeposition with a constant voltage of -0.5 V vs. a Ag/AgCl reference electrode. The post-annealing of the film at high temperature above $500^{\circ}C$ induced crystallization of $CuInSe_2$ with well-developed grains. The KCN-treatment of the annealed $CuInSe_2$ films further induced Cu-poor $CuInSe_2$ films without secondary phases, such as $Cu_2Se$. The structure, morphology, and composition of $CuInSe_2$ films were compared with respect to the conditions of electrodeposition and post-annealing using SEM, XRD, Raman, AES and EDS analysis. And the conditions for preparing device-quality $CuInSe_2$ films by electrodeposition were proposed.