• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.11a
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• pp.334-337
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• 2002

In this study, the microstructure, dielectric and piezoelectric properties of $0.15Pb(Ni_{1/3}Nb_{2/3})O_3-0.85(PbZr_{0.5}Ti_{0.5})O_3$(0.15PNN-0.85PZT) ceramics having compositions near the morphotropic phase boundary(MPB) was investigated with respect to the variation of $Y_2O_3$ and $Ga_2O_3$ addition amount. The dielectric properties increased and piezoelectric properties decreased with increasing the amount of $Ga_2O_3$. The solubility limit of $Y_2O_3$ is 0.5mol% in this system. The electro-mechanical coupling factor$(K_p)$ and dielectric constant(${\varepsilon}_r$) were 58.6% and 1755 when the amount of $Y_2O_3$ are 0.5mol%.

• Journal of electromagnetic engineering and science
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• v.17 no.2
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• pp.105-107
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• 2017

The self-biasing circuit through a feedback resistor is applied to a gallium nitride (GaN) distributed power amplifier (PA) monolithic microwave circuit (MMIC). The self-biasing circuit is a useful scheme for biasing depletion-mode compound semiconductor devices with a negative gate bias voltage, and is widely used for common source amplifiers. However, the self-biasing circuit is rarely used for PAs, because the large DC power dissipation of the feedback resistor results in the degradation of output power and power efficiency. In this study, the feasibility of applying a self-biasing circuit through a feedback resistor to a GaN PA MMIC is examined by using the high operation voltage of GaN high-electron mobility transistors. The measured results of the proposed GaN PA are the average output power of 41.1 dBm and the average power added efficiency of 12.2% over the 6-16 GHz band.

• Korean Journal of Dental Materials
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• v.44 no.3
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• pp.207-216
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• 2017

The effect of cooling rate on precipitation hardening of a Pd-Cu-Ga-Zn metal-ceramic alloy during porcelain firing simulation was investigated and the following results were obtained. When the cooling rate was fast (Stage 0), the hardness of the alloy increased at each firing step and the high hardness value was maintained. When the cooling rate was slow (Stage 3), the hardness was the highest at the first stage of the firing, but the final hardness of the alloy after complete firing was lower. The increase in hardness of the specimens cooled at the cooling rate of Stage 0 after each firing step was caused by precipitation hardening. The decrease in hardness of the specimens cooled at the cooling rate of Stage 3 after each firing step was attributed to the coarsening of the spot-like precipitates formed in the matrix and plate-like precipitates. The matrix and the plate-like precipitates were composed of the $Pd_2(Cu,Ga,Zn)$ phase of CsCl-type, and the particle-like structure was composed of the Pd-rich ${\alpha}$-phase of face-centered cubic structure. Through the porcelain firing process, Cu, Ga, and Zn, which were dissolved in Pd-rich ${\alpha}$ particles, precipitated with Pd, resulting in the phase separation of the Pd-rich ${\alpha}$ particles into the Pd-rich ${\alpha}^{\prime}$ particles and ${\beta}^{\prime}$ precipitates composed of $Pd_2(Cu,Ga,Zn)$. These results suggested that the durability of the final prosthesis made of the Pd-Cu-Ga-Zn alloy can be improved when the cooling rate is fast during porcelain firing simulation.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.20 no.1
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• pp.8-13
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• 2007

In MIS capacitor structure, we have studied the electrical properties in Ammonium Sulfide solution treatment while AIN thin film as a insulator is being formed by reactive sputtering method. The deposition process conditions of AIN thin film we temperature $250^{\circ}C$, DC Power 150 W, pressure 5 mTorr and 8 sccm(Ar : 4 sccm, $N_{2}$ : 4 sccm). The surface of GaAs was treated with Ammonium Sulfide solution, it was shown the leakage current was less than $10^{-8}\;A/cm^{2}$. The deep depletion phenomena of inverse area with treating Ammonium Sulfide solution in C-V analysis was improved as compared the condition of without Ammonium Sulfide solution and hysteresis property as well.

• Proceedings of the KIPE Conference
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• 2002.07a
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• pp.447-450
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• 2002

A study on control of BLDC Is studying In progress, because of radical increase of survo motor at industrial machine and home machine. Nowaday, we study on control of BLDC, because of radical increase of survo motor at Industry and home. Although control ratio and output of the unit volume are good than the others , BLDC motor demands high cost. Therefor, the study on low cost BLDC have square wave back-emf is studing in progress. Therefor, BLDC Motor was studied to reduce high cost that have square wave back-emf at recently. This paper shows that BLDC Motor, developed highly responsility by using Genetic Algorithm(GA) that the advantages of learning ability, Also, this paper shows experiment and simulation at 200W BLDC that have squarewave back-emf by using Genetic Algorithm. At the result of this methods, the study prove experiment's right.

• Korean Journal of Veterinary Research
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• v.44 no.2
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• pp.201-206
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• 2004

Norfloxacin (NFX) is a fluorquinolone antibacterial agent with a high antimicrobial activity and might have great potential for treating common infections in poultry. The objective of this study was to obtain comparative pharmacokinetic data after a single oral administration and medication with drinking water of norfloxacin-glycine acetate (NFX-GA) at the dose rate of 10 mg/kg bw in broilers. Fifty minutes following oral administration of NFX-GA, serum concentrations peaked at $1.32{\mu}g/mL$ (range $1.03-1.45{\mu}g/mL$). Serum concentration of NFX declined with a half-life of $7.21{\pm}1.81$ h. On the third day after administration of medicated drinking water, steady-state was reached, with mean concentrations of NFX of $0.70{\pm}0.35{\mu}g/mL$. The concentration of NFX after medication of NFX-GA with drinking for 3 days provides sufficient levels to obtain maximum therapeutic effects and maintains the serum persistence of concentration exceeding MIC.

• Journal of the Korean Society of Food Culture
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• v.29 no.1
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• pp.61-83
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• 2014

The aim of this study was to review Byung-Kwa-Ryu recipes in old cookbooks of the head & noble family (Jong-Ga). As for details and classification, we examined the materials and recipes of Byung-Kwa-Ryu. To accomplish this, old cookbooks of the head & noble family ("Soowoonjabbang", "Eumsikdimibang", "Onjubub", and "Jusiksiui") were reviewed. The introduced Byung-Kwa-Ryu recipes numbered 47 total; four from "Soowoonjabbang", 18 from "Eumsikdimibang", nine from "Onjubub", and 16 from "Jusiksiui". We classified the foods (Byung-Kwa_Ryu) into two categories, Tteok-Ryu (Korean rice cake) and Kwa-Jung-Ryu (Korean traditional cookie), on the basis of previous studies. These were further classified into 11 categories: Tteok-Ryu (Jjin-tteok, Salmeun-tteok, Chin-tteok, Jijin-tteok), Kwa-Jung-Ryu (Yumilkwa, Yukwa, Jeongkwa, Dasik, Kwapyun, Dang (Yeot), and others. The most common Byung-Kwa-Ryu type was Jjin-tteok in Tteok-Ryu (14). The next most common Byung-Kwa-Ryu types were Yukwa in Kwa-Jung-Ryu (6) and Yumilkwa in Kwa-Jung-Ryu (5).

• Proceedings of the IEEK Conference
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• 2006.06a
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• pp.553-554
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• 2006

In this paper, 77 GHz CPW power amplifier MMIC, which are consisted of a 2 stage driver stage and a power stage employing $8{\times}50um$ gate width, have been successfully developed by using 120nm $In_{0.4}AlAs/In_{0.35}GaAs$ Metamorphic high electron mobility transistors (MHEMTs). The devices show an extrinsic transconductance $g_m$ of 660 mS/mm, a maximum drain current of 700 mA/mm, and a gate drain breakdown voltage of -8.5 V. A cut-off frequency ($f_T$) of 172 GHz and a maximum oscillation frequency ($f_{max}$) of over 300 GHz are achieved. The fabricated PA exhibited high power gain of 20dB only with 3 stages. The output power is measured to be 12.5 dBm.

• Journal of Magnetics
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• v.15 no.4
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• pp.155-158
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• 2010

The HDDR (hydrogenation, disproportionation, desorption, and recombination) process can be used as an effective way of converting a no coercivity Nd-Fe-B ingot material, with a coarse $Nd_2Fe_{14}B$ grain structure, to a highly coercive one with a fine grain structure. Careful control of the HDDR process can lead to an anisotropic powder with good $Nd_2Fe_{14}B$ grain texture; the most critical step for inducing texture is disproportionation. The critical conditions (hydrogen pressure and temperature) for the disproportionation reaction of fully hydrogenated $Nd_{12.5}Fe_{81.1-(x+y)}B_{6.4}Ga_xNb_y$ (x = 0 or 0.3, y = 0 or 0.2) alloys, in different atmospheres of pure hydrogen and a mixed gas of hydrogen and argon, was investigated with TPA (thermopiezic analyser). From this, the hydrogen pressure-temperature diagram showing the critical conditions was established. The critical disproportionation temperature of the fully hydrogenated $Nd_{12.5}Fe_{81.1-(x+y)}B_{6.4}Ga_xNb_y$ alloys was slightly increased as the hydrogen pressure decreased in both pure hydrogen and mixed gas. The critical disproportionation temperature of the hydrogenated alloys was higher in the mixed gas than in pure hydrogen. Addition of Ga and Nb increased the critical disproportionation temperature of the fully hydrogenated Nd-Fe-B alloys.

• Journal of the Microelectronics and Packaging Society
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• v.16 no.4
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• pp.29-32
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• 2009

Dense and periodic arrays of nano-sized holes were patterned in oxide thin film on GaAs substrate. To obtain the nano-size patterns, self-assembling diblock copolymer was used to produce thin film of uniformly distributed parallel cylinders of polymethylmethacrylate (PMMA) in polystyrene (PS) matrix. The PMMA cylinders were removed with UV expose and acetic acid rinse to produce PS nanotemplate. By reactive ion etching, pattern of the PS template was transferred to under laid silicon oxide layer. Transferred patterns were reached to the GaAs substrate by controlling the dry etching time. We confirmed the achievement of etching through the removing oxide layer and observation of GaAs substrate surface. Optimized etching time was 90 to 100 sec. Pore sizes of the nanopattern in the silicon oxide layer were 20~22 nm.