• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.6
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• pp.545-550
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• 2013

We present a tactile information transceiver using a friction-tunable slider-pad. While previous tactile information devices were focused on either input or output functions, the present device offers lateral position/vertical direction detection and texture expression. In characterizing the tactile input performance, we measured the capacitance change due to the displacement of the slider-pad. The measured difference for a z-axis click was 0.146 nF/$40{\mu}m$ when the x-y axis navigation showed 0.09 nF/$750{\mu}m$ difference. In characterizing the texture expression, we measured the lateral force due to a normal load. We applied a voltage between parallel electrodes to induce electrostatic attraction in DC and AC voltages. We measured the friction under identical fingertip action conditions, and obtained friction in the range of 32-152 mN and lateral vibration in the force range of 128.1 mN at 60 V, 2 Hz. The proposed device can be applied to integrated tactile interface devices for mobile appliances.

• Progress in Superconductivity
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• v.7 no.2
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• pp.140-144
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• 2006

We fabricated the YBCO films on single crystal $LaAlO_3$ substrates via a metal organic deposition (MOD) process. In the process, $Y_2Ba_1Cu_1O_x$ and $Ba_3Cu_5O_8$ powders were dissolved in trifluoroacetic acid (TFA) followed by calcining and firing heat treatments. To evaluate the effects of the firing temperature on YBCO phase formation and critical properties, the films were fired at $750^{\circ}C,\;775^{\circ}C\;and\;800^{\circ}C$ after calcining at $430^{\cric}C$. Microstructure observation indicated that a crack-free surface formed and a strong biaxial texture was developed. The FWHM of out-of-plane texture was measured to be in the range of $4.3^{\cric}-7.0^{\circ}$ for all the films. When the YBCO film was fired at $775^{\cric}C$, it had the highest critical properties: 88.5 K of critical temperature and 16 A/cm-width of critical current ($1MA/cm^2$ as critical current density). On the other hand, those properties were degraded as firing at $750^{\circ}C\;and\;800^{\circ}C$. It is considered that the improved critical values are partly owing to dense and homogeneous microstructure, strong texture, and high oxygen content.

• Proceedings of the Materials Research Society of Korea Conference
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• 2009.05a
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• pp.24.1-24.1
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• 2009

The zinc oxide (ZnO) material as the II-VI compound semiconductor is useful in various fields of device applications such as light-emitting diodes (LEDs), solar cells and gas sensors due to its wide direct band gap of 3.37eV and high exciton binding energy of 60meV at room temperature. In this study, the ZnO nanorods were deposited onto homogenous buffer layer/Si(100) substrates by a hydrothermal synthesis. The Effects of the buffer layer annealing and post annealing temperature on the structural and optical properties of ZnO nanorods grown by a hydrothermal synthesis were investigated. For the buffer layer annealing case, the annealed buffer layer surface became rougher with increasing of annealing temperature up to $750^{\circ}C$, while it was smoothed with more increasing of annealing temperature due to the evaporation of buffer layer. It was found that the roughest surface of buffer layer improved the structural and optical properties of ZnO nanorods. For the post annealing case, the hydrothermally grown ZnO nanorods were annealed with various temperatures ranging from 450 to $900^{\circ}C$. Similarly in the buffer layer annealing case, the post annealing enhanced the properties of ZnO nanorods with increasing of annealing temperature up to $750^{\circ}C$. However, it was degraded with further increasing of annealing temperature due to the violent movement of atoms and evaporation. Finally, the buffer layer annealing and post annealing treatment could efficiently improve the properties of hydrothermally grown ZnO nanorods. The morphology and structural properties of ZnO nanorods grown by the hydrothermal synthesis were measured by atomic force microscopy (AFM), field emission scanning electron microscopy (SEM), and x-ray diffraction (XRD). The optical properties were also analyzed by photoluminescence (PL) measurement.

• Polymer(Korea)
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• v.28 no.4
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• pp.344-351
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• 2004

Poly(ethylene glycol)-based diblock and triblock polyester copolymers stimulating to temperature were studied as injectable biomaterials in drug delivery system because of their nontoxicity, biocompatibility and biodegradability. We synthesized the diblock copolymers consisting of methoxy poly(ethylene glycol) (MPEG) (M$_{n}$=750 g/mole) and poly($\varepsilon$-caprolactone) (PCL) by ring opening polymerization of $\varepsilon$-CL with MPEG as an initiator in the presence of HCl . Et$_2$O. The aqueous solution of synthesized diblock copolymers represented sol phase at room temperature and a sol to gel phase transition as the temperature increased from room temperature to body temperature. To confirm the in vivo gel formation, we observed the formation of gel in the mice body after injection of 20 wt% aqueous solution of each block copolymer. After 2 months, we observed the maintenance of gel without dispersion in mice. In this study, we synthesized diblock copolymers exhibiting sol-gel phase transition and confirmed the feasibility as biomaterials of injectable implantation.n.

• Journal of Korea Foundry Society
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• v.22 no.5
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• pp.238-244
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• 2002

Water and oil were completely synthesised with ultrasonic vibration energy irradiation. Pure Pb were added into Al melt during irradiated the ultrasonic vibration energy in 750. And the ultrasonic vibration energy was applied to Al-Pb melt to enhance the miscibility. Microstructural analysis, thermal analysis and X-ray diffraction analysis were carried out to evaluate the effect of the ultrasonic vibration energy on the castability and microstructural reliability. (1) Using the ultrasonic vibration energy irradiation, the complete mixing of water and oil was obtained. (2) The microstructure was refined by the application of ultrasonic vibration energy in Al-Pb alloys. (3) Relatively large Pb particles, $5{\mu}m$ were most distributed alone the grain boundaries with fine Pb particles evenly distributed in the matrix. (4) The solubility of Ph in Al-Pb alloys was increases up to 5% with the application of ultrasonic vibration energy.

• Korean Journal of Crystallography
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• v.3 no.2
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• pp.67-71
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• 1992

The crystal structure of the title compound was determined from single crystal X-ray dirt fraction study : C16H16NO3, Mr=271.316, orthorh ombic, Aba2, a=15.750(3), b=13.470(2), c=13.356 (2) A, V=2833A, Z=8, Dx=1.26 Mgm-3, λ(MoK a) =0.71069A, r=0.51mm-2, F(000)=1136, T=291 K, R=0.0414 for 728 unique observed [F≥3e(F)] reflections and 240 parameters. The molecule is nearly planar within 0.2 A with the torsion angle -179(2)°for C(4)-C(7)-C(8)-C(9).The into rmolecular interactions are mainly by van der Waals force with the nearest intermolecular distance 3.647A between O(3) and C(4) translated by half unit along band c-axes.

• Journal of IKEEE
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• v.16 no.3
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• pp.159-166
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• 2012

In this paper, we designed and implemented the MIMO (Multiple-Input Multiple-Output) antenna for the mobile handset that could be used for multiple services. Simulation results were obtained using SEMCAD X by SPEAG based on the FDTD (Finite Difference Time Domain) Method which showed that S11 values were less than -6 dB (VSWR < 3) for LTE (Long Term Evolution) 700/2300/2500, K-PCS (Korea-Personal Communication Service : 1,750 ~ 1,870 MHz), US-PCS (US-Personal Communication Service : 1,850 ~ 1,990 MHz), Wibro (2,300 ~ 2,390 MHz), Bluetooth (2,400 ~ 2,483 MHz), and US-WiMAX (US-World interoperability for Microwave Access: 2,400 ~ 2,590 MHz) frequency bands. Measured results of the fabricated antenna also showed that it could be used for LTE 700/2300/2500, K-PCS, US-PCS, Wibro, Bluetooth, and US-WiMAX. services.

• Electrical & Electronic Materials
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• v.9 no.3
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• pp.298-303
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• 1996

A double diffusion technique is developed to enhance the effective mode index of optical waveguides in $LiTaO_3$. It consists of Zn diffusion from the vapor phase at relatively low temperatures (750->$800^{\circ}C$), into waveguides initially produced by Ti indiffusion at higher temperature (1150->$1200^{\circ}C$). Both X- and Z-cut substrates are investigated. A model that combines profiles of both diffusion is formulated to calculate the expected effective index values for planar waveguides. Good agreement is found between experimental results and model predictions which assume that the initial Ti profile is not affected by the lower temperature Zn diffusion. Effective index enhancements as high as 0.005 and 0.003 are obtained by this method for the fundamental extraordinary and ordinary modes, respectively.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1995.10a
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• pp.167-171
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• 1995

The formation of preferred orientations in cold rolled and recrystallized Inconel 690 sheets was studied by the x-ray texture measurements and TEM observations. The increasing{220} pole intensity in the plane normal at the higher reductions was related to the{110}<112> texture component. The rolling texture of the Inconel 690 was the pure metal type. THe dislocation cells were found in the near{110}<112> oriented grains. The onset of deformation twins in the {112}<111>oriented grains. The onset of deformation twins in the {112}<111> oriented grains. The onset of deformation twins in the {112}<111> oriented grains caused the weakening of {112}<111> and the development of {552}<115> in the rolling texture. The annealing texture of the Inconel 690 sheets was dependent on the annealing temperature. The annealing texture of 750$^{\circ}C$ annealed sheets was similar to the cold rolling texture. The major preferred orientations of the 950$^{\circ}C$ annealed specimens were {112}<110> and {001}<110>. The formation of fine and closely spaced annealing twins in the specimen annealed at 1150$^{\circ}C$ led to the randomization of the annealing texture.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1996.05a
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• pp.193-197
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• 1996

BaTiO$_3$films in pure Ar atmosphere were prepared by RF sputtering method at low substrate temperature(100$^{\circ}C$). The structural and crystallographic properties were studied with deposition conditions and annealing methodes. Deposition rates and structural properties of BaTiO$_3$ thin filles were investigated by the SEM and X-ray diffraction. The chemical composition of BaTiO$_3$ thin films grown on Si(100) wafer was studied by tole EDS and EPHA. The optimised Ar pressure and RF power were 8[mtorr] and 180[W], respectively. The thickness of BaTiO$_3$ thin films deposited at optimised conditions was ∼3400[${\AA}$], and the dielectric constant of the thin films heat-treated at 750[$^{\circ}C$] for 1[hr] was 259.