• Korean Journal of Materials Research
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• v.30 no.11
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• pp.573-580
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• 2020

YAG (Yttrium Aluminum Garnet, Y₃Al₅O₁₂) has excellent plasma resistance and recently has been used as an alternative to Y₂O₃ as a chamber coating material in the semiconductor process. However, due to the presence of an impurity phase and difficulties in synthesis and densification, many studies on YAG are being conducted. In this study, YAG powder is synthesized by an organic-inorganic complex solution synthesis method using PVA polymer. The PVA solution is added to the sol in which the metal nitrate salts are dissolved, and the precursor is calcined into a porous and soft YAG powder. By controlling the molecular weight and the amount of PVA polymer, the effect on the particle size and particle shape of the synthesized YAG powder is evaluated. The sintering behavior of the YAG powder compact according to PVA type and grinding time is studied through an examination of its microstructure. Single phase YAG is synthesized at relatively low temperature of 1,000 ℃ and can be pulverized to sub-micron size by ball milling. In addition, sintered YAG with a relative density of about 98 % is obtained by sintering at 1,650 ℃.

• Journal of Powder Materials
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• v.13 no.3 s.56
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• pp.205-210
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• 2006

The effect of Cu content on hydrogen reduction behavior of ball-milled $WO_3$-CuO nanocomposite powders was investigated. Hydrogen reduction behavior and reduction percent(${\alpha}$) of nanopowders were characterized by thermogravimetry (TG) and hygrometry measurements. Activation energy for hydrogen reduction of $WO_3$ nanopowders with different Cu content was calculated at each heating rate and reduction percent(${\alpha}$). The activation energy for reduction of $WO_3$ obtained in this study existed in the ranging from 129 to 139 kJ/mol, which was in accordance with the activation energy for $WO_3$ powder reduction of conventional micron-sized.

• JSTS:Journal of Semiconductor Technology and Science
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• v.9 no.3
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• pp.148-152
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• 2009

Recent CMOS technology scaling has seriously eroded the bit-line noise immunity of register files due to the consequent increase in active bit-line leakage currents. To restore its noise immunity while maintaining performance, we propose and evaluate a $256{\times}40$-bit register file incorporating dual-$V_t$ bit-lines with a boosted gate overdrive voltage in 65 nm bulk CMOS technology. Simulation results show that the proposed bootsrapping scheme lowers leakage current by a factor of 450 without its performance penalty.

• Journal of the Korean Ceramic Society
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• v.41 no.5
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• pp.370-374
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• 2004

Sr$_{l-x}$Ba$_{x}$Al$_2$O$_4$:Eu (x = 0, 0.1, 0.2, and 0.3 mol) phosphor was synthesized by the hydrothermal method and its properties of photoluminescence and long-afterglow were investigated. The mixtures of Sr(NO$_3$)$_2$, Al(NO$_3$)$_3$9$H_2O$, and Eu(NO$_3$)$_3$$.$6$H_2O$ salts dissolved in distilled water, after controlling their pH by NH$_4$OH solution, put into an Autoclave reactor with high temperature and pressure to react. Such synthesized SrAl$_2$O$_4$:Eu powders showed homogeneous and ultra-fine particles of sub-micron size. In order to have the photoluminescence characteristic, powders were heat treated at 1100 -140$0^{\circ}C$ for 2 h in Ar/H$_2$ reduction atmosphere. Photoluminescence spectra showed a excitation along the wide wavelength of 250 ∼ 450 nm, and broaden emission with maxima peak at 520 nm. Also, it showed a good long afterglow with decaying over 1000 sec after excitation illumination for 10 min. In addition, the microstructure and crystal structure of SrAl$_2$O$_4$:Eu powders were investigated by an SEM and XRD, respectively.

• Journal of the Korean Society of Industry Convergence
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• v.23 no.4_2
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• pp.669-674
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• 2020

Liquid-phase-sintered (LPS) SiC materials were briefly examined with their microstructure and mechanical property. Especially, effect of high-temperature exposure on the tendency of fracture toughness of LPS-SiC were introduced. The LPS-SiC was fabricated in hot-press by sintering powder mixture of sub-micron SiC and sintering additives of Al₂O₃-Y₂O₃. LPS-SiC represented dense morphology and SiC grain-growth with some amount of micro-pores and clustered additives as pore-filling. The strength of LPS-SiC might affected by distribution of micro-pores. LPS-SiC tended to decrease fracture toughness depending on increasing exposure temperature and time.

• Journal of Electrochemical Science and Technology
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• v.12 no.2
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• pp.217-224
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• 2021

In this study, Monte Carlo (MC) simulation is conducted with recurrence relation to study the effect of SiO₂ with different particle size and their roles in enhancing the ionic conductivity and lithium transference number of PMMA composite polymer electrolytes (CPEs). The MC simulated ionic conductivity is verified with the measurements from Electrochemical Impedance Spectroscopy (EIS). Then, the lithium transference number of CPEs is calculated using recurrence relation with the MC simulated current density and the reference transference number obtained. Incorporation of micron-size SiO₂ (≤10 ㎛) fillers into the mixture improves the ionic conductivity from 8.60×10^-5 S/cm to 2.35×10^-4 S/cm. The improvement is also observed on the lithium transference number, where it increases from 0.088 to 0.3757. Furthermore, the addition of nano-sized SiO₂ (≤12 nm) fillers further increases the ionic conductivity up towards 3.79×10^-4 S/cm and lithium transference number of 0.4105. The large effective surface area of SiO₂ fillers is responsible for the improvement in ionic conductivity and the transference number in PMMA composite polymer electrolytes.

• Korean Chemical Engineering Research
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• v.47 no.1
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• pp.84-88
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• 2009

Al doped $LiMn_2O_4$ cathode powders with fine size were synthesized by an ultrasonic spray pyrolysis method from the spray solution with citric acid and ethylene glycol. The as-prepared powders with spherical shape, porous structure and micron size turned into $LiMn_{11/6}Al_{1/6}O_4$ powders with micron size and regular morphology after post-treatment above $800^{\circ}C$. The $LiMn_{11/6}Al_{1/6}O_4$ powders had low initial discharge capacity of 94 mAh/g at a post-treatment temperature of $700^{\circ}C$. As the post-temperature increased from $750^{\circ}C$ to $1,000^{\circ}C$, the initial discharge capacities of the $LiMn_{11/6}Al_{1/6}O_4$ powders changed from 103 to 117 mAh/g. The $LiMn_{11/6}Al_{1/6}O_4$ powders had the maximum discharge capacity at a post-treatment temperature of $750^{\circ}C$. However, the $LiMn_{11/6}Al_{1/6}O_4$ powders post-treated at a temperature of $900^{\circ}C$ had the good cycle properties. The discharge capacities of the $LiMn_{11/6}Al_{1/6}O_4$ powders dropped from 107 to 100 mAh/g (93% capacity retention) by the 70th cycle at a current density of 0.1 C.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.41 no.10
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• pp.95-104
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• 2004

This paper propose a motion estimator architecture to reduce the power consumption of the most-power-consuming motion estimation method when designing multimedia SoC with deep submicron technologies below 0.13${\mu}{\textrm}{m}$. The proposed architecture considers both dynamic and static power consumption so that it is suitable for large leakage process technologies, while conventional architectures consider only dynamic power consumption. Consequently, it is suitable for mobile information terminals such as mobile videophone where efficient power management is essential. It exploits full search method for simple hardware implementation. It also exploits early break-off method to reduce dynamic power consumption. To reduce static power consumption, megablock shutdown method considering power line noise is also employed. To evaluate the proposed architecture when applied multimedia SoC, system-level control flow and low-power control algorithm are developed and the power consumption was calculated based on thor From the simulation results, power consumption was reduced to about 60%. Considering the line width reduction and increased leakage current due to heat dissipation in chip core, the proposed architecture shows steady power reduction while it goes worse in conventional architectures.

• Food Engineering Progress
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• v.21 no.3
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• pp.273-279
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• 2017

Curcumin have various health-beneficial properties in numerous studies. However, its bioavailability is low due to its limited intestinal uptake and rapid metabolism. This study aimed to evaluate the pharmacokinetics of newly developed sub-micron particle curcumin with increased water dispersibility (Theracurmin(R) CR-033P). Plasma curcumin levels were measured at 0, 1, 2, 4, 8 h after Theracurmin(R) CR-033P intake using high-performance liquid chromatography. For analyzing pharmacokinetics of Theracurmin(R) CR-033P, eighteen healthy subjects were recruited and received Theracurmin(R) CR-033P at a single oral dose containing curcumin 30 mg. $C_{max}$ was 28.14 ng/ml, and the area under the curve for 8 h was estimated to be 104.36 ng/ml. Based on the area under the plasma concentration (AUC), the bioavailability of sub-micron particle curcumin was higher 22-, 35-, 28-fold than native curcumin in men, women, and all subjects, respectively. For comparing by formulation, seven healthy subjects were recruited and received two type of treatment: (1) existing dosage form 300 mg (contained curcumin 30 mg) ${\times}$ 3 capsule, (2) high dosage form 300 mg (contained curcumin 90 mg) ${\times}$ 1 capsule + placebo 300 mg ${\times}$ 2 capsule. In the cross-over study, there was no significant differences in $C_{max}$ and AUC of plasma curcumin. In conclusion, submicron particle curcumin with increased water dispersibility significantly improved its oral bioavailability and women absorbed curcumin more effectively than men. Different formulation of Theracurmin(R) CR-033P has shown equivalent to the reference in terms of pharmacokinetics.

• Journal of the Korean institute of surface engineering
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• v.51 no.1
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• pp.79-85
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• 2018

We systematically investigated the optical properties of sub-micron sized methylammonium lead tribromide ($CH_3NH_3PbBr_3$) cubes in the range of 100 to 700 nm, which were prepared by a surfactant-free precipitation method. We found that despite the strong absorbance, their photoluminescence quantum yield (PLQY) is very low as 0.009~0.011 % for whole range of sizes. Surfactant-free synthesis approach results in nanocubes that has no surface passivating reagents (e.g. surfactants) on their surface. As-prepared particles contain a large number of surface defects that may cause the low PLQY. The role of the surface defects were investigated in their photoluminescence decay process, which can be correlated with the particle size. Larger particles are characterized by a slower decay rate compared to smaller particles due to a large number of surface defects in the smaller particles that trap more excitons in the fluorescence decay process. These experimental results provide new insights into the fundamental relationship between surface state and optical properties.