• Journal of the Korean institute of surface engineering
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• v.36 no.1
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• pp.14-21
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• 2003

Thin films of ZrO$_2$ and TiO$_2$ were deposited on Si(100) substrates using RF magnetron sputtering technique. To study an influence of the sputtering parameters, systematic experiments were carried out in this work. XRD data show that the $ZrO_2$ films were mainly grown in the [111] orientation at the annealing temperature between 800 and $1000^{\circ}C$ while the crystal growth direction was changed to be [012] at above $1000^{\circ}C$. FT-IR spectra show that the oxygen stretching peaks become strong due to $SiO_2$ layer formation between film layers and silicon surface after annealing, and proved that a diffusion caused by either oxygen atoms of $ZrO_2$ layers or air into the interface during annealing. Different crystal growth directions were observed with the various deposition parameters such as annealing temperature, RF power magnitude, and added $O_2$ amounts. The growth rate of $TiO_2$ thin films was increased with RF power magnitude up to 150 watt, and was then decreased due to a sputtering effect. The maximum growth rate observed at 150 watt was 1500 nm/hr. Highly oriented, crack-free, stoichiometric polycrystalline $TiO_2$<110> thin film with Rutile phase was obtained after annealing at $1000^{\circ}C$ for 1 hour.

• Korean Journal of Materials Research
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• v.3 no.3
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• pp.207-214
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• 1993

Glass-ceramic monoliths with an ultra-low thermal expansion coefficient have been synthesized by the sol-gel technique using metal alkoxides as starting materials and dimethyl formamide as a drying control chemical additive. The ternary gels: $Li_2O\cdot Al_2O_3\cdot 2, 4 or $6SiO_2$ were obtained by hydrolysis and polycondensation reactions of metal alkoxides of silicon, aluminum and lithium. To produce cylindrical crack-free gel monoliths, excess water was used to the starting solutions and drying rates were controlled precisely to prevent cracking. In conversion process ,${\beta}$-eucryptite, $Li_2O\cdot Al_2O_3\cdot 3SiO_2$ and P-spodumene with ,${\beta}$-quartz solid solution phase were obtained by heating at the range of 750 ~$1000^{\circ}C$. Above $800^{\circ}C$, the ,${\beta}$-spodumene phase increased while ,${\beta}$-eucryptite phase decreased. The thermal expansion coefficient of the crystallized specimens were -15~ $+5{\times}{10^{-7}}/{\circ}C$ over the temperature range from room temperature to $600^{\circ}C$.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.3
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• pp.988-1004
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• 1996

The characteristics of flow and oxygen concentration are numerically studied in Czochralski 8" silicon crystal growing process considering radiative heat transfer. The analysis of net radiative heat flux on all relevant surfaces shows growing crystal affects the heater power. Furthermore, the variation of the radiative heat flux along the crystal surface in the growing direction is confirmed and should be a cause of thermal stress and defect of the crystal. The calculated distributions of temperature and, heat flux along the wall boundaries including melt/crystal interface, free surface and crucible wall indicate that the frequently used assumption of the thermal boundary conditions of insulated crucible bottom and constant temperature at crucible side wall is not suitable to meet the real physical boundary conditions. It is necessary, therefore, to calculate radiative heat transfer simultaneously with the melt flow in order to simulate the real CZ crystal growth. If only natural convection is considered, the oxygen concentration on the melt/crystal interface decreases and becomes uniform by the application of a cusp magnetic filed. The heater power needed also increases with increasing the magnetic field. For the case of counter rotation of the crystal and crucible, the magnetic field suppresses azimutal flow produced by the crucible rotation, which results in the higher oxygen concentration near the interface.

• Journal of Convergence for Information Technology
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• v.11 no.10
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• pp.270-276
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• 2021

The purpose of this study was to investigate the effects of home care hair treatment characteristics and frequency on hair during permanent wave treatment. The hair treatments distributed on the market were classified into cationic surfactants and silicone oil. Hair treatment was performed 5 times, 10 times, 20 times differently according to the frequency of use, and hair permanent wave was performed. The hair thickness, tensile strength, epidermal observation using SEM, and hair component analysis using EDS were performed as experimental methods. The results of the experiment showed that the natural-derived ingredient was the main ingredient, and the cationic surface activity and silicon oil-free product group had high hair protection effect. Therefore, the product group using natural ingredients should be further researched and developed, and the study on the method and frequency of use of products with irritant chemical ingredients should be conducted.

• Journal of the Economic Geographical Society of Korea
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• v.25 no.3
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• pp.420-450
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• 2022

Texas has recently emerged as a phenomenal industrial destination, which attracts headquarters, production facilities, and/or regional centers of global corporations including Tesla and Samsung. Known as "Texit", this trend of corporate investment to Texas has concentrated in highly developed industrial clusters (such as Dallas-Fort Worth, Houston, Austin, and San Antonio) since the early 2000s. Against this background, this paper examines sectoral and geographical characteristics of those clusters, and investigates associated state initiatives that have been introduced and implemented. As a result, key policy measures in the state are found to be aligned to free-market liberalism, diversified incentives, and regional specialization. Unlike Silicon Valley where Bohemian liberalism engendered vibrant entrepreneurship and innovative start-up formation, it is the strong state government that leads industrial cluster upgrading in Texas, while successfully harnessing lower income taxes and deregulation, affordable land and infrastructure, and quality higher education and human capital as regional assets for attracting inward investment.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2001.06a
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• pp.72-72
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• 2001

Plasma polymerized thin films have been deposited on Si(lOO) substrates at $25-400^{\circ}C$ using thiophene ($C_4H_4S$) precursor by plasma assisted chemical vapor deposition (PACVD) method for low-dielectric device application. In order to compare physical properties of the as-grown thin films, the effects of the plasma power, gas flow ratio and deposition temperature on the dielectric constant and thermal stability were mainly studied. XRD and TED studies revealed that the as-grown thin films have highly oriented amorphous polymer structure. XPS data showed that the polymerized thin films that grown under different RF power and deposition temperature as well as different gas ratio of $Ar:H_2$ have different stoichiometric ratio of C and S compared with that of monomer, indicating a formation of mixture polymers. Moreover, we also realized that oxygen free and thermally stable polymer thin films could be grown at even $400^{\circ}C$. The results of SEM, AFM and TEM showed that the polymer films with smooth surface and sharp interface could be grown under various deposition conditions. From the electrical property measurements such as I-V and C-V characteristics, the minimum dielectric constant and the best leakage current were obtained to be about 3.22 and $10-11{\;}A/\textrm{cm}^2$, respectively.

• Steel and Composite Structures
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• v.49 no.3
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• pp.307-323
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• 2023

In this research, the study of the thermoelastic flexural analysis of silicon carbide/Aluminum graded (FG) sandwich 2D uniform structure (plate) under harmonic sinusoidal temperature load over time is presented. The plate is modeled using a simple two dimensional integral shear deformation plate theory. The current formulation contains an integral terms whose aim is to reduce a number of variables compared to others similar solutions and therefore minimize the computation time. The transverse shear stresses vary according to parabolic distribution and vanish at the free surfaces of the structure without any use of correction factors. The external load is applied on the upper face and varying in the thickness of the plates. The structure is supposed to be composed of "three layers" and resting on nonlinear visco-Pasternak's-foundations. The governing equations of the system are deduced and solved via Hamilton's principle and general solution. The computed results are compared with those existing in the literature to validate the current formulation. The impacts of the parameters (material index, temperature exponent, geometry ratio, time, top/bottom temperature ratio, elastic foundation type, and damping coefficient) on the dynamic flexural response are studied.

• Korean Journal of Optics and Photonics
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• v.35 no.4
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• pp.170-174
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• 2024

A laser beam propagating in free space can be negatively affected by atmospheric turbulence. To overcome this and correct the wavefront error of the laser beam itself, a deformable mirror (DM), which is a key component of adaptive optics, is widely used. In this paper, a novel precision assembling method is suggested for a multi-channel high-density DM. The material of the mirror sheet of the DM is silicon carbide (SiC), and the actuator is a stacked-type lead-magnesium-niobate (Pb(Mg_1/3Nb_2/3)O₃; PMN). To connect the mirror sheet and each actuator, a flexure is inserted. The flexure can make the DM operate with full strokes without the failure of adhesive. A series of jigs were designed and applied in order to assemble these three parts (the mirror sheet, actuators, and flexures) precisely. After assembly, the performance of the DM was also checked.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.39 no.4
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• pp.16-24
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• 2002

This work describes a 10b 120 MSample/s CMOS pipelined A/D converter(ADC) based on a merged-capacitor switching(MCS) technique for high signal processing speed and high resolution. The proposed ADC adopts a typical multi-step pipelined architecture to optimize sampling rate, resolution, and chip area, and employs a MCS technique which improves sampling rate and resolution reducing the number of unit capacitor used in the multiplying digital-to-analog converter (MDAC). The proposed ADC is designed and implemented in a 0.25 um double-poly five-metal n-well CMOS technology. The measured differential and integral nonlinearities are within ${\pm}$0.40 LSB and ${\pm}$0.48 LSB, respectively. The prototype silicon exhibits the signal-to-noise-and-distortion ratio(SNDR) of 58 dB and 53 dB at 100 MSample/s and 120 MSample/s, respectively. The ADC maintains SNDR over 54 dB and the spurious-free dynamic range(SFDR) over 68 dB for input frequencies up to the Nyquist frequency at 100 MSample/s. The active chip area is 3.6 $mm^2$(＝ 1.8 mm ${\times}$ 2.0 mm) and the chip consumes 208 mW at 120 MSample/s.

• Korean Journal of Optics and Photonics
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• v.16 no.4
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• pp.384-391
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• 2005

A polymer optical microring resonator, which is laterally coupled to a straight bus waveguide, has been proposed and demonstrated using a nanoimprint technique. The propagation loss of the ring waveguide and the optical power coupling between the ring and bus waveguides was calculated by using a beam propagation method, then the dependence of the device performance on them was investigated using a transfer matrix method. We have especially introduced an imprint stamp incorporating a smoothing buffer layer made of a silicon nitride thin film. This layer played an efficient role in improving the sidewall roughness of the waveguide pattern engraved on the stamp and thus reducing the scattering loss. As a result the overall Q factor of the resonator was greatly increased. Also it reduced the gap between the ring and bus waveguides effectively to enhance the coupling between them, without relying on the direct writing method based on an e-beam writer. As for the achieved device performance at the wavelength of 1550 nm, the quality factor, the extinction ratio, and the free spectral range were ~103800, ~11 dB, and 1.16 m, respectively.