• Transactions on Electrical and Electronic Materials
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• v.2 no.3
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• pp.18-23
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• 2001

For the piezoelectric transformer application, Pb(Sb$\_$1/2/ Nb$\_$1/2/)O$_3$-Pb(Zr,Ti)O$_3$ ceramics were produced by attrition milling. Microstructural, dielectric and piezoelectric characteristics of the ceramics were investigated as a function of milling time. The particle size and grain size decreased while dielectric constant, density and mechanical quality factor (Q$\_$m/) increased with milling time. Temperature coefficient of resonant frequency (TCf$\_$r/) was shifted to positive side with increasing milling time. The attrition milling process proved to be one of the effective routes to produce transformers for high power application.

• The Korean Journal of Food And Nutrition
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• v.32 no.2
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• pp.79-88
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• 2019

This study was conducted to evaluate the characteristics of bread and the rheology of flour dough containing jochung. In the farinogram test, the addition of jochung changed water absorption, development time and mixing tolerance index for making bread As the amount of jochung increased, the water absorption, mixing tolerance index decreased and the development time increased. In the extensograph test, the degree of extension decreased with increasing of jochung content whereas degree of resistance was enhanced with addition of jochung. After fermentation treatment, the volume of the dough with 20% sucrose were less than that of the dough containing 20% of jochung. The dough with 5% jochung showed the lowest dough raising power compared to the other doughs. The bread consisting of 15% jochung showed the highest volume of loaf and specific volume. Therefore, high quality of bread can be achieved by adding jochung instead of sucrose for making bread.

• Journal of the Korean Wood Science and Technology
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• v.50 no.2
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• pp.104-112
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• 2022

Indoor air quality is a very important environmental factor in modern society. However, air pollutants generated from various interior construction materials significantly affect the human body, including formaldehyde (HCHO) and volatile organic compounds that threaten public health by deteriorating indoor air quality. Effective in removing these harmful substances are porous materials, such as woodceramics. In this study, charcoal, a porous material, was added to rice husk, an agricultural by-product, and sawdust generated during the sawing process to prepare boards and ceramics at different mixing ratios, and the HCHO deodorization performance and far-infrared emission characteristics were measured. As the mixing ratio of charcoal increased, the deodorization rate of the boards and ceramics tended to increase. Overall, the deodorization rate was measured to be 80% to 90%, indicating that the boards and ceramics prepared with charcoal are suitable to be used for the purpose of deodorization. The effect of the material mixing ratio on far-infrared emissivity and emission power was insignificant.

• Proceedings of the KSR Conference
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• 2011.05a
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• pp.634-643
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• 2011

The neutral section was installed in order to prevent conflict with different phase angle source in electric railway catenary system. The speed of electric train reduced due to coasting operation by notch off when it passed the neutral section. And, the catenary wire was damaged and the accident might be happened because of the arc generation when the electric train passed the neutral section with notch off condition. The inrush current of main transformer installed tiling train is analyzed during the operation of MCB(main circuit break) passing through the neutral section. The instantaneous waveform of load current were analyzed in case of powering and regenerative braking. Inrush current waveform with run of AC railway train showed that inrush current waveform and harmonics, the inrush current generated from main transformer in train has bad effects on power quality problem. In order to reduce these inrush currents, the MCB is connected when the phase angle of voltage is 90 degree. This paper is to measure inrush current and harmonics in main transformer of high speed train in neutral section of electric railway. This measurement report is used to control minimum inrush current in algorithm and power phase angle.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.53 no.11
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• pp.610-618
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• 2004

With the development of industry and the improvement of living standards, better quality in power electric service is required more than ever before. Under these circumstances, to deliver reasonable voltage regulation methods in distribution systems need to be developed. So, This paper deals with optimal introduction of the line voltage regulator (SVR : Step Voltage Regulator) in power distribution systems. First, This paper investigates characteristics of SVR and performs economic evaluation of SVR's introduction by using Present Worth Method. This paper, also suggests proper location and optimal voltage regulation algorithm. In order to deliver suitable voltages to as many customers as possible, the optimal sending voltage of SVR should be decided by the effective operation of voltage regulators at the distribution feeders. The simulation results using a model distribution system and real distribution systems show that the proposed methods can be a practical tool for the voltage regulation in distribution systems.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.20 no.3
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• pp.6-11
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• 2006

This paper describes the novel control techniques design of VSC(Voltage Sag Corrector) for the purpose of power line quality enhancement. A fast detecting technique of voltage sag is implemented through the detection of instantaneous value on synchronous rotating dq-reference frame. The first order digital filter is added in the detection algorithm to protect the insensitive characteristics against the noise. The relationship between the total detection time and cut-off frequency of the filter is described. The size of the capacitor bank used as the energy storage element is designed from the point of view of input/output energy with circuit analysis. Finally, the validity of the proposed scheme is proven through the simulated results.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.16 no.1
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• pp.76-84
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• 2002

Voltage sags caused by line faults in transmission and distribution lines have become one of the most important power quality problems facing industrial customers and utilities. Voltage sags are normally described by characteristics of both magnitude and duration, but phase angle shifts should be taken account in identifying sag phenomena and finding their solutions. In this paper, voltage sags due to line faults such as three phase-to-ground, single line-to-ground, and line-to-line faults are characterized by using symmetrical component analysis, for fault impedance variations. Voltage sags and their effect on the magnitude and phase angle are examined. Balanced sags of three phase-to-ground faults show that voltages and currents are changed with equivalent levels to all phases and the zero sequence components become zero. However, for unbalanced faults such as single line-to-ground and line-to-line faults, voltage sags give different magnitude variations and phase angle shifts for each phase. In order to verify the analyzed results, some simulations based on power circuit models are also discussed.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.13 no.1
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• pp.74-79
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• 2002

The EM(Engineering Model) VCO(Voltage Controlled Oscillator) is nonlinear designed for LO(Local Oscillator) of Ka-band satellite transponder. The microstripline coupled with dielectric resonator is implemented as a high impedance inverter to improve the phase noise, and the quality factor of resonant circuit can be transferred to active device with the enhanced loaded quality factor. The developed VCO has the oscillating tuning range of 9.7965~9.8032 GHz for the control voltage range of 0~12 V. This VCO requires the DC power of 8 V and 17 mA. The phase noise characteristics are -96.51 dBc/Hz @10 KHz and -116.5 dBc/Hz @100 KHz, respectively. And, the output power of 7.33 dBm is measured.

• Korean journal of food and cookery science
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• v.22 no.5 s.95
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• pp.583-590
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• 2006

This study was carried out to investigate the acceptable ratio of Sulgidduk with added soybean curd residue powder. The moisture content of Sulgidduk with added soybean curd residue powder (0${\sim}$ 10%) ranged from 40.54 ${\sim}$41.38%, and there were no significant differences between the addition of soybean curd residue powder and control. There were also no significant differences in swelling power and pore ratio from control to the addition of 4% soybean curd residue powder. However, these decreased with increasing addition of soybean curd residue powder of more than 6%. The L (lightness) value decreased with increasing addition of soybean curd residue powder, but the a (redness) and b (yellowness) values increased significantly. As the amount of soybean curd residue powder increased, the hardness, cohesiveness, springiness and gumminess decreased, and, the decrease was especially significant with addition of more than 6%. With increases in the storage period, the hardness, springiness and gumminess increased, while cohesiveness decreased for all additions of soybean curd residue powder. In sensory evaluations, Sulgidduk with the addition of 4% soybean curd residue powder was the most preferred with regard to overall quality. These results indicated that the Sulgidduk with 2% and 4% added soybean curd residue powder exhibited the best quality.

• The Korean Journal of Food And Nutrition
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• v.21 no.4
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• pp.448-456
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• 2008

In this study, domestic wheat white breads were prepared with the substitution of 1.5, 3.0, 4.5, and 6.0% Nelumbo nucifera G. tea powder(NNTP). The samples and a control were then compared with regard to quality characteristics, including pH, total titratable acidity, fermentation power of dough expansion, specific volume, baking loss, moisture content, color, textural characteristics, external and internal surface appearances, and sensory qualities in order to determine the optimal ratio of NNTP in the formulation. As the NNTP contents increased, the pH of dough and bread, baking loss, and lightness decreased, whereas the total titratable acidity of dough and bread increased. The fermentation power of dough expansion increased with increasing incubation time. The NNTP samples evidenced significantly higher specific volume, greenness, yellowness, resilience, and crumb consistency than were observed in the control group. However, hardness and fracturability evidenced the opposite effect. The water content and uniformity of the crumb pores were highest at a substitution level of 1.5%, and were lowest at a level of 4.5%. Crumb color, flavor, and delicious taste decreased with increasing NNTP contents, whereas lotus leaf flavor, astringency, bitterness, and off-flavor increased. Density of the crumb pore and crumb springiness were not significantly different among the samples. Softness, chewiness, and overall acceptability were maximal with the 1.5% substitution, and were minimal in the 6.0% group. In conclusion, our results demonstrate that $1.5{\sim}3.0%$ NNTP may prove quite useful as a substitute for domestic wheat flour in the production of white bread, and may evidence favorable nutritional and functional properties.