• Journal of the Korean Ceramic Society
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• v.26 no.4
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• pp.479-486
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• 1989

According to the phase diagram, 6Bi2O3.GeO2 composition melts congruently at 93$0^{\circ}C$ and forms a stable ${\gamma}$-6Bi2O3.GeO2 crystal phase below the melting point. But when the melt of this composition was cooled at a rate 1-15$0^{\circ}C$/min without tapping by a glass rod or impurity addition, a metastable $\delta$-6Bi2O3.GeO2 crystal phase was formed. It is due to that as the nucleation energy barrier of $\delta$-6Bi2O3.GeO2 crystals, which have more open and defective structure, is lower than that of ${\gamma}$-6Bi2O3.GeO2 crystals. When impurities or ${\gamma}$-6Bi2O3.GeO2 crystals existed in the melt, stable ${\gamma}$-6Bi2O3.GeO2 crystal phase was formed at various cooling rate. It is because of that the impurities or the ${\gamma}$-6Bi2O3.GeO2 crystals role as a seed crystal and as a result the nucleation energy barrier of ${\gamma}$-6Bi2O3.GeO2 crystals is lowered.

• Polymer(Korea)
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• v.30 no.2
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• pp.108-111
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• 2006

In this work, the effect of the hydrophobicity of acrylic polymers on the membrane morphology was investigated. The membranes were prepared with poly(methyl methacrylate) (PMMA), poly(ethyl methacrylate) (PEMA), poly (butyl methacrylate) (PBMA), poly(isobutyl methacrylate), and their blends using the wet phase inversion method. PMMA and PEMA having a relatively less hydrophobicity formed the channel-like structure, whereas PBMA and PIBMA having more hydrophobic units formed the finger-like structure. These morphological changes were attributed to differences in the solidification process of the polymer-rich phase determine d by the polymer/solvent/nonsolvent ternary phase diagram. The membrane structures of the blends were controlled by the main component of their blends.

• Korean Journal of Crystallography
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• v.13 no.3_4
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• pp.172-176
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• 2002

Pyroelectric properties and relaxation phenomena in Pb(Mg /sub 1/3/Nb/sub 2/3/)O₃-PbTiO₃ solid solution system were studied to establish the phase relation of the solid solution system. The dielectric constants and the pyroelectric coefficients of (1-x)PMN-xPT (x = 0.1∼0.4) system were investigated in the phase transition temperature range of -40°C∼200°C. The freezing temperature was calculated by fitting the experimental data with the Vogel-Fulcher relation. With all the experimental data, a modified phase diagram of the (1-x)PMN-xPT system was suggested.

• Proceedings of the KIPE Conference
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• 2008.10a
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• pp.124-126
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• 2008

Grid Connected inverter is produced current to deliver power to grid. To provide low THD current, LCL filters is effective to filter high frequency component of current output from inverter. To provide sinusoidal waveform, there are many researchers have been proposed several controllers for grid-connected inverter controllers. Synchronous Reference Frame (SRF)-based controller is the most popular methods. SRF-based controller is capable for reducing both of zero-steady state error and phase delay. But SRF based controller is contained cross-coupling components, which generate some difficulties to analyze. In this paper, SRF based controller is analyzed. By applying decoupling control, cross-coupling component is eliminated and single phase model of the system is obtained. Through this single phase model, gain controller is designed. To reduce steady state error, proportional gain is set as high as possible, but it may produce instability. To compromise between a minimum steady state error and stability, the single phase model is evaluate through Root Locus and Bode diagram. PSIM simulation is used to verify the analysis.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.11a
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• pp.69-72
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• 1999

A Well oriented Bi$_2$re$_2$CaCu$_2$O$\sub$8/(Bi2212) superconductor thick films were formed successfully on a copper substrate by liquid reaction between a Cu-free precursor and Cu tape using method in which Cu-free BSCO powder mixture was printed on copper plate and heat-treated. And we examined the mechanism for the rapid formation of Bi2212 superconducting films from observing the surface microstructure with heat-treatment time. At heat-treatment temperature, the printing layer partially melt by reacting with CuO of the oxidizing copper plate, and the nonsuperconducting phases present in the melt are typically Bi-free phases and Cu-free phases. Following the partial melting, the Bi$_2$Sr$_2$CaCu$_2$O$\sub$8/ superconducting phase is formed at Bi-free phase/liquid interface by nucleation and grows. It was confirmed that the phase colony from the phase diagram of Bi$_2$O$_3$-(SrO+CaO)/2-CuO system is similar to the observed result.

• Archives of Metallurgy and Materials
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• v.66 no.4
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• pp.1001-1005
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• 2021

Liquid Metal Extraction process using molten Mg was carried out to obtain Nd-Mg alloys from Nd based permanent magnets at 900℃ for 24 h. with a magnet to magnesium mass ratio of 1:10. Nd was successfully extracted from magnet into Mg resulting in ~4 wt.% Nd-Mg alloy. Nd was recovered from the obtained Nd-Mg alloys based on the difference in their vapor pressures using vacuum distillation. Vacuum distillation experiments were carried out at 800℃ under vacuum of 2.67 Pa at various times for the recovery of high purity Nd. Nd having a purity of more than 99% was recovered at distillation time of 120 min and above. The phase transformations of the Nd-Mg alloy during the process, from Mg₁₂Nd to α-Nd, were confirmed as per the phase diagram at different distillation times. Pure Nd was recovered as a result of two step recycling process; Liquid Metal Extraction followed by Vacuum Distillation.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.1862-1866
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• 2003

A control system design with Coefficient Diagram Method (CDM) is proven that effective for SISO control design. But the control system design for MIMO via CDM is not concrete procedure. In this paper presents the control system design method for quadruple-tank process via CDM. By using the decentralized method for both non-minimum phase and minimum phase are made. The results from Integral-Proportional (I-P) controller’s design via CDM and standard Proportional-Integral (PI) controls are also shown to compare the merits of the proposed controllers.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.22 no.5
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• pp.573-583
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• 1998

Effects of the oscillating incoming flow on vortex shedding and lock-on behind a square cylinder are investigated using numerical simulations at a Reynolds number of 100. Vortex shedding occurred at low forcing frequencies of the incoming flow similar to the natural vortex shedding. As the forcing frequency further increases, the shedding frequency decreases to the half of the forcing freqnency. For a sufficiently large frequency, vortex shedding returns to the natural vortex shedding irrespective of the forcing amplitude. Also, the lock-on region becomes wider with higher forcing amplitudes. The phase diagram between the drag and lift shows a simple periodic behavior in the lock-on region, while a complicated periodic phase relation is observed when there is no lock-on.

• Journal of the korean Society of Automotive Engineers
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• v.7 no.4
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• pp.49-56
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• 1985

This study consists of instrumenting and running tests on variable compression engines and measuring the following combustion characterics: (a)flame speed, (b) emission and (c)performance parameter such as power and economy. The results were as follows: 1) The phase separation diagram of substitute fuels were obtained from phase separation experiment. 2) The flame propagation speed of substitute fuels were higher than gasoline and increased with increasing methanol weight percent of substitute fuels. 3) BEMP of substitute fuels was slightly less than that of gasoline but in the range of small weight percent, BEMP was compatible to gasoline. 4) Concentration of NOx decreased significantly with delaying spark advancing time. Also, it decreased for rich equivalence ratio but increased with high compression ratio. In general, NOx concentration was much lower than that of gasoline. 5) Concentration of HC and CO increased for rich equivalence ratio. Also it was lower than that of gasoline.

• 한국초전도학회:학술대회논문집
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• v.16
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• pp.32-32
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• 2006