• Transactions on Electrical and Electronic Materials
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• v.18 no.6
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• pp.334-337
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• 2017

In this paper, to develop the ceramics with high $d_{33}$ and high $Q_m$ for ultrasonic transducer applications, $0.10Pb(Ni_{1/3}Nb_{2/3})O_3-0.07Pb(Mn_{1/3}Nb_{2/3})O_3-0.83Pb(Zr_{0.5}Ti_{0.5})_{0.83}O_3$ (PNN-PMN-PZT) ceramics were sintered at $940^{\circ}C$ using $CuO-Li_2CO_3-Bi_2O_3$ (CLBO) as a sintering aid by a traditional solid-state technique. The influence of zinc oxide additive on the physical properties of the prepared ceramics were systematically investigated. The R-T (rhombohedral-tetragonal) phase coexistence was found in the ceramics without zinc oxide additive and with increasing amounts of ZnO additive, the specimens showed a tetragonal phase. The formation of a liquid phase between ZnO and $Bi_2O_3$ contributed significantly to the grain growth of specimens. For the 0.1 wt% ZnO ceramics, the optimal physical properties of $d_{33}=370pC/N$, ${\varepsilon}_r=1,344$, $k_p=0.621$, and $Q_m=1,523$ were obtained.

• Journal of Power Electronics
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• v.11 no.3
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• pp.294-303
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• 2011

In this paper an effective five-phase induction motor (IM) and its drive methods are proposed. Due to the additional degrees of freedom, the five-phase IM drive presents unique characteristics for enhancing the torque producing capability of the motor. Also the five-phase motor drives possess many other advantages when compared to traditional three-phase motor drives. Some of these advantages include, reducing the amplitude and increasing the frequency of the torque pulsation, reducing the amplitude of the current without increasing the voltage per phase and increasing the reliability. In order to maximize the torque per ampere, the proposed motor has concentrated winding, the produced back electromotive force (EMF) is almost trapezoidal, and the motor is supplied with the combined sinusoidal plus the third harmonic of the currents. For demonstrating the superior performance of the proposed five-phase IM, the motors are also analyzed on the synchronously rotating reference frame. To supply trapezoidal current waveform and to exclude the effect of the $3^{rd}$ harmonic current, a new control stratagem is proposed. The proposed control method is based on direct torque control (DTC) and rotor flux oriented control (RFOC) of the five-phase IM drives. It is able to reduce the acoustical noise, the torque, the flux, the current, and the speed pulsations during the steady state. The DTC transient merits are preserved, while a better quality steady-state performance is produced in the five phase motor drive for a wide speed range. Experimental results clearly demonstrated a more dynamic steady state performance with the proposed control system.

• Bulletin of the Korean Chemical Society
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• v.34 no.1
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• pp.139-142
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• 2013

A study was carried out to evaluate the solid phase micro-extraction (SPME) for formaldehyde emission analysis of uncoated plywood. In SPME, formaldehyde was on-fiber derivatized through headspace extraction and analyzed by gas chromatography coupled with mass spectrometry (GC/MS). The SPME was compared with desiccators (DC-JAS 233), small-scale chamber (SSC-ASTM D6007) and liquid-liquid extraction (LLE-EPA 556) methods which were performed in accordance with their respective standards. Compared to SSC (RSD 4.3%) and LLE (RSD 5.0%), the SPME method showed better repeatability (RSD 1.8%) and not much difference from DC (RSD 1.4%). The SPME has proven to be highly precise (at 95% confidence level) with better recovery (REC 102%). Validation of the SPME method for formaldehyde quantitative analysis was evidenced. In addition, the SPME by air sampling directly from plywood specimens (SPME-W) correlated best with DC ($r^2$ = 0.983), followed by LLE ($r^2$ = 0.950) and SSC ($r^2$ = 0.935).

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.13 no.9
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• pp.907-915
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• 2002

In this paper, a compact digital phase shifter to be used an active phased array antenna system for satellite communications was proposed. The even and odd mode analysis for a given reflection-type phase shifter, which uses a folded hybrid coupler as a base element, was performed and the design parameters were derived. Also, to verify experimentally the electrical performances of the proposed structure, X-band 4-bit digital phase shifter was designed and fabricated using Teflon soft substrate $({\varepsilon}_r; =\;2.17)$. Its circuit size was less than 3.5 cm $\times$ 3.0 cm, and it exhibited at least 50 % size reduction as compared with the conventional unfolded configuration. The experimental results of the fabricated phase shifter showed that the average insertion loss and insertion loss variation were less than 3.5 dB, $\pm$ 0.6 dB within the operating band, 7.9 ~ 8.4 GHz, respectively. And, input and output return loss were more than 10 dB, respectively. Also, the phase response of the phase shifter showed 4-bit operation with $\pm$3$^{\circ}$ rms phase error.

• Journal of the Optical Society of Korea
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• v.1 no.1
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• pp.41-43
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• 1997

We report the operation of a self-adaptive vector phase conjugate laser (VPCL) oscillator which compensates intracavity polarization distortion and wavefront aberration simultaneously. The VPCL in Nd:YAG gain media produce an output with energy of 125mJ in a 20ns single-longitudinal-mode pulse at 10Hz, which is unaffected by intracavity polarization distortion.

• The Journal of the Korea Contents Association
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• v.13 no.2
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• pp.512-521
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• 2013

This paper presents the user needs analysis and information visualization for the development of a semantic-based national R&D information navigation service in information service planning phase, which converges and fuses NDSL databases and NTIS databases. To investigate and analyze the user needs for improving usability, we make an improvement plan for R&D information services via a survey targeted at 30 persons, and on-site interviews targeted at 12 persons, almost of who are researchers in industries, universities and government-funded institutes. To design new information visualization service, we propose an interactive national R&D information visualization service, which is provided in navigation type, and prescribe persona and screen prototyping according to the user needs analysis. We design the national R&D information convergence/fusion architecture based on the NDSL databases, including 345,411 academic articles, 620,555 co-authors and 49,958 reports and NTIS databases including 187,466 national R&D projects. We expect that the national R&D information convergence/fusion architecture contributes to R&D information convergence/fusion as a leading model/standard and the interactive navigation-typed information visualization service strengthens usability continuously.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.36D no.1
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• pp.8-14
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• 1999

The active devices used at microwave frequency have the different phase shift according to input power. Especially, The difference of the phase shift is large in the saturation region of the amplifier. In this paper, we disigned the phase control system for fixing the different phase shift at device. With the high frequency nonlinear amplifier, we fabricated such system that the phase shift to be fixed automatically using the varible phase shifter. The variable phase shifter fixed total phase variation of the circuit using the information that was obtained from the comparison of imputsignal phase with output signal phase. Even though the input signal is 2-tone or FM type, we could estimate and also fix the phase variation on DUT Dynamic range is about 10dB. It has been experimented at 1960MHz using Teflon (H=31mil, ${\varepsilon}r$=3.2)

• Asian-Australasian Journal of Animal Sciences
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• v.19 no.12
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• pp.1784-1789
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• 2006

Two experiments were conducted to determine the effect of phytobiotics and organic acids on growth performance of nursery pigs as an alternative to antibiotics. Phytobiotics refer bioactive compounds from plant materials including essential oils and herbal extracts. In Exp. 1,144 pigs, weaned at 23.4${\pm}$0.3 d age, were allotted to three dietary treatments. Treatment diets were: 1) NC (no antibiotics and no phytobiotics); 2) PC (NC+carbadox, 50 mg/kg); and 3) PB (NC+phytobiotics; 0.1% PEP1000-$1^{(R)}$. Each treatment had six replicates with eight pigs per pen. Pigs were fed the experimental diets for 5 wks in 3 phases (phase 1 for 2 wk; phase 2 for 2 wk; phase 3 for 1 wk). In Exp. 2, 192 pigs, weaned at 19.2${\pm}$0.3 d age, were allotted to three dietary treatments: 1) NC; 2) PC; and 3) PBO (NC+phytobiotics; 0.2% or 0.1% PEP1000-$1^{(R)}$ and organic acids; 0.4% or 0.2% $Biotronic^{(R)}$for the phase 1 and 2, respectively) with eight replicates per treatment and eight pigs per pen. Pigs were fed the assigned diets for 5 wks in 2 phases (phase 1 for 2 wk; phase 2 for 3 wk). Body weights were measured at the beginning of the experiment and at the end of each week in both Exp. 1 and 2. Feed intake was measured at the end of each week in both Exp. 1 and 2. Diarrhea score was measured daily during the entire period for Exp. 1 and during the phase 1 for Exp. 2. In Exp. 1, the PC had a higher (p<0.05) overall ADG than the NC, but the overall ADG of the PB did not differ (p>0.05) from the NC or the PC. In Exp. 2, the overall ADG did not differ (p>0.05) among all the treatments during the entire experimental period. The overall ADFI and the overall gain:feed ratio did not differ (p>0.05) among all the treatments during the entire experimental period in both Exp. 1 and 2. The PC had a higher (p<0.05) overall diarrhea score (harder stools) than the NC and the PB in Exp. 1, and a higher (p<0.05) overall diarrhea score than the NC in Exp. 2. The overall diarrhea score of the PB and the PBO did not differ (p>0.05) from the NC or the PC in Exp. 1 and 2. Results from this study show that the growth of pigs fed the diets with phytobiotics or the combination of phytobiotics and organic acids did not differ from those both with antibiotics and without antibiotics when tested in an environmentally controlled research facility. Further experiments are required to study the growth performance in disease challenged conditions.

• Transactions of the Korean hydrogen and new energy society
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• v.7 no.2
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• pp.173-180
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• 1996

4-probe resistivity measurement technique was used to study kinetics of hydrogen absorption-desorption on Pd film($520{\AA}$ thick) at room temperature upto 1 bar. Kinetics data are fitted well to 1st order kinetics equation in ${\alpha}$ and ${\alpha}^{\prime}$ phases. In ${\alpha}+{\alpha}^{\prime}$ phase, absorption kinetics was very complicated, but it could be explained partially with nucleation and growth process. Ln(dR/dt) vs. time plot gives rate constant k value(R is resistance of sample, t is time). k value for absorption is $4^{-6}{\times}10^{-4}/sec$ in ${\alpha}$ phase. k is increasing upto $4^{\times}10^{-2}/sec$ as hydrogen pressure increasing in ${\alpha}^{\prime}$ phase. k is proportional to ln(Pop/Peq), where Peq is equilibrium plateau pressure and Pop is the opposing pressure. In contrast to bulk sample k value was decreasing with increasing number of A-D cycling in ${\alpha}^{\prime}$ phase absorption.

• Journal of Korea Foundry Society
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• v.36 no.4
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• pp.117-125
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• 2016

The effects of the Zn content on the microstructure and corrosion behavior in 1M NaCl solution were investigated in Mg-(0~6)%Zn casting alloys. The MgZn phase was scarcely observed in the Mg-1%Zn alloy, while the Mg-(2~6)%Zn alloy consisted of ${\alpha}$-(Mg) and MgZn phases. With an increase in the Zn content, the amount of the MgZn phase was gradually increased. Immersion and electrochemical corrosion tests indicated that the Mg-1%Zn alloy had the lowest corrosion rate among the alloys, and a further increase in the Zn content resulted in the deterioration of the corrosion resistance. Microstructural examinations of the corroded surfaces and EIS analyses of surface corrosion films revealed that the best corrosion resistance at 1%Zn was associated with the absence of MgZn phase particles in the microstructure and the contribution of Zn element to the formation of a protective film on the surface. A micro-galvanic effect by the MgZn particles led to the increased rate of corrosion at a higher Zn content.