• Proceedings of the KSME Conference
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• 2004.04a
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• pp.204-209
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• 2004

SiC materials have been extensively studied for high temperature components in advanced energy system and advanced gas turbine. However, the brittle characteristics of SiC such as low fracture toughness and low strain-to fracture still impose a severe limitation on practical applications of SiC materials. For these reasons, $SiC_f/SiC$ composites can be considered as a promising for various structural materials, because of their good fracture toughness compared with monolithic SiC ceramics. But, high temperature and pressure lead to the degradation of the reinforcing fiber during the hot pressing. Therefore, reduction of sintering temperature and pressure is key requirements for the fabrication of $SiC_f/SiC$ composites by hot pressing method. In the present work, Monolithic LPS-SiC was fabricated by hot pressing method in Ar atmosphere at 1760 $^{\circ}C$, 1780 $^{\circ}C$, 1800 $^{\circ}C$ and 1820 $^{\circ}C$ under 20 MPa using $Al_2O_3-Y_2O_3$ system as sintering additives in order to low sintering temperature. The starting powder was high purity ${\beta}-SiC$ nano-powder with an average particle size of 30 nm. Monolithic LPS-SiC was evaluated in terms of sintering density, micro-structure, flexural strength, elastic modulus and so on. Sintered density, flexural strength and elastic modulus of fabricated LPS-SiC increased with increasing the sintering temperature. In the micro-structure of this specimen, it was found that grain of sintered body was grown from 30 nm to 200 nm.

• The Journal of Advanced Prosthodontics
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• v.8 no.1
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• pp.37-42
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• 2016

PURPOSE. This study investigated the effect of amount of thickness reduction on color and translucency of dental monolithic zirconia ceramics. MATERIALS AND METHODS. One-hundred sixty-five monolithic zirconia specimens ($16.3mm{\times}16.3mm{\times}2.0mm$) were divided into 5 groups (Group I to V) according to the number of A2-coloring liquid applications. Each group was then divided into 11 subgroups by reducing the thickness up to 1.0 mm in 0.1-mm increments (Subgroup 0 to 10, n=3). Colors and spectral distributions were measured according to CIELAB on a reflection spectrophotometer. All measurements were performed on five different areas of each specimen. Color difference (${\Delta}E^*{^_{ab}}$) and translucency parameter (TP) were calculated. Data were analyzed using one-way ANOVA and multiple comparison $Scheff{\acute{e}}$ test (${\alpha}=.05$). RESULTS. There were significant differences in CIE $L^*$ between Subgroup 0 and other subgroups in all groups. CIE $a^*$ increased (0.52<$R^2$<0.73), while CIE $b^*$ decreased (0.00<$R^2$<0.74) in all groups with increasing thickness reduction. Perceptible color differences (${\Delta}E^*{^_{ab}}$>3.7) were obtained between Subgroup 0 and other subgroups. TP values generally increased as the thickness reduction increased in all groups ($R^2$>0.89, P<.001). CONCLUSION. Increasing thickness reduction reduces lightness and increases a reddish, bluish appearance, and translucency of monolithic zirconia ceramics.

• Advances in materials Research
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• v.1 no.1
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• pp.37-49
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• 2012

In this paper, we present modeling and characterization of CNT-based TSVs to be used in high-frequency RF applications. We have developed an integrated model of CNT-based TSVs by incorporating the quantum confinement effects of CNTs with the kinetic inductance phenomenon at high frequencies. Substrate parasitics have been appropriately modeled as a monolithic microwave capacitor with the resonant line technique using a two-polynomial equation. Different parametric variations in the model have been outlined as case studies. Furthermore, electrical performance and signal integrity analysis on different cases have been used to determine the optimized configuration for CNT-based TSVs for high frequency RF applications.

• Proceedings of the IEEK Conference
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• 1999.11a
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• pp.177-180
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• 1999

A two-stage monolithic microwave integrated circuits (MMIC) broad-band power amplifier with AlGaAs/InGaAs/GaAs pseudomorphic high electron mobility transistor (PHEMT) has been developed for the up-link and down-link applications for local multipoint distribution systems (LMDS) in the frequency range of 24~28㎓. The amplifier has a small signal gain of 18.6㏈ at 24.5㎓ and 16.7㏈ at 27.1㎓. It achieved output powers of 19.8㏈m with PAE of 19.8% at 24.5㎓ and 18.8㏈m at 27.1㎓.

• Proceedings of the IEEK Conference
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• 2003.07a
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• pp.617-620
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• 2003

In this paper, a monolithic VCO has been designed for Wireless Local Area Network(WLAN) applications. The differential form VCO is constructed using positive feedback with capacitor and phase shift for low phase noise performance. The VCO shows the phase noise of -92.725 dBc/Hz at an offset frequency of 10KHz and the tunning range of 5.822~6.154GHz.

• The KIPS Transactions:PartA
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• v.11A no.3
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• pp.139-148
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• 2004

The number of applications of small embedded systems such as PDAs, electronic note books, etc. based on Kinux, have increased. Due to the monolithic characteristic of Linux kernel, it is not suitable to satisfy the various kinds of embedded application requirement. To assist the shortcoming of monolithic kernel, we implement uJFFS 113th file system as an application program process which runs in user space. This solution consists of a file system and a flash device driver, and makes Linux kernel smaller by separating the file system from the kernel. uJFFS consists of ujffs_fs that plays a part of file system and ujffs_drv that controls a flash device. Which provides the same user interface as Linux does. A Device driver for the physical device is implemented in user pace, which prevents kernel failures from file system errors. So uJFFS can increase stability of the system.

• Journal of IKEEE
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• v.1 no.1 s.1
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• pp.1-10
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• 1997

It is well-known that rectangular bulk-Si sensors prepared by etch or epi etch-stop micromachining technology are already in practical use today, but the conventional bulk-Si sensor shows some drawbacks such as large chip size and limited applications as silicon sensor device is to be miniaturized. We consider a circular-shape SOI(Silicon-On-Insulator) micro-cavity technology to facilitate multiple sensors on very small chip, to make device easier to package than conventional sensor like pressure sensor and to provide very high over-pressure capability. This paper demonstrates the cross-functional results for stress analyses(targeting $5{\mu}m$ deflection and 100MPa stress as maximum at various applicable pressure ranges), for finding permissible diaphragm dimension by output sensitivity, and piezoresistive sensor theory from two-type SOI structures where the double SOI structure shows the most feasible deflection and small stress at various ambient pressures. Those results can be compared with the ones of circular-shape bulk-Si based sensor$^{[17]}. The SOI micro-cavity formed the sensors is promising to integrate with calibration, gain stage and controller unit plus high current/high voltage CMOS drivers onto monolithic chip.

• ETRI Journal
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• v.38 no.5
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• pp.972-980
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• 2016

An ultra-wideband microwave monolithic integrated circuit high-power amplifier with excellent input and output return losses for phased array jammer applications was designed and fabricated using commercial $0.25-{\mu}m$ AlGaN/GaN technology. To improve the wideband performance, resistive matching and a shunt feedback circuit are employed. The input and output return losses were improved through a balanced design using Lange-couplers. This three-stage amplifier can achieve an average saturated output power of 15 W, and power added efficiency of 10% to 28%, in a continuous wave operation over a frequency range of 6 GHz to 18 GHz. The input and output return losses were demonstrated to be lower than -15 dB over a wide frequency range.

• JSTS:Journal of Semiconductor Technology and Science
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• v.15 no.4
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• pp.501-505
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• 2015

In this paper, we demonstrated a 4W power amplifier monolithic microwave integrated circuit (MMIC) for Ku-band satellite communication applications. The used device technology relies on $0.25{\mu}m$ GaAs pseudomorphic high electron mobility transistor (PHEMT) process. The 4W power amplifier MMIC has linear gain of over 30 dB and saturated output power of over 36.1 dBm in the frequency range of 13.75 GHz ~ 14.5 GHz. Power added efficiency (PAE) is over 30 %.

• Proceedings of the IEEK Conference
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• 1999.11a
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• pp.187-190
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• 1999

We have developed fabrication processes that form a wide-head T-gate with a 0.2 ${\mu}{\textrm}{m}$ gate length using the combination of thickness of each PMMA layer, line doses and development times for applications in millimeter- and micro-waves monolithic integrated circuits. The three-layer resist structure (PMMA/P(MMA-MAA)/PMMA = 1800 $\AA$/5800 A/1900$\AA$), 4nC/cm and over development were used for fabrication of a wide-head T-gate by the conventional double E-beam exposure technology. The experimented results show that the cross sectional area of T-gate fabricated by the proposed method is easily enlarged without additional processes.