• Journal of Power Electronics
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• v.15 no.3
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• pp.741-752
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• 2015

This study proposes a new solution for the parallel operation of microgrid inverters in terms of circuit topology and control structure. A combined three-phase four-wire inverter composed of three single-phase full-bridge circuits is adopted. Moreover, the control structure is based on adaptive three-order sliding-mode control and wireless load-sharing control. The significant contributions are as follows. 1) Adaptive sliding-mode control performance in inner voltage loop can effectively reject both voltage and load disturbances. 2) Virtual resistive-output-impedance loop is applied in intermediate loop to achieve excellent power-sharing accuracy, and load power can be shared proportionally to the power rating of the inverter when loads are unbalanced or nonlinear. 3) Transient droop terms are added to the conventional power outer loop to improve dynamic response and disturbance rejection performance. Finally, theoretical analysis and test results are presented to validate the effectiveness of the proposed control scheme.

• Journal of the Korean Society for Precision Engineering
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• v.24 no.12
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• pp.95-103
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• 2007

This paper presents a liquid cooling concept for heat rejection of high power electronic devices existing in notebook computers etc. The design, fabrication, and performance of the planar ECF pump and farced-liquid cooling system are summarized. The electro-conjugate fluid (ECF) is a kind of dielectric and functional fluids, which generates jet flows (ECF-jets) by applying static electric field through a pair of rod-like electrodes. The ECF-jet directly acts on the working fluid, so the proposed planar ECF pump needs no moving part, produces no vibration and noise. The planar ECF pump, consists of a pump housing and electrode substrate, achieves maximum flow rate and output pressure of $5.5\;cm^3/s$ and 7.2 kPa, respectively, at an applied voltage of 2.0 kV. The farced-liquid cooling system, constructed with the planar ECF pump, liquid-cooled heat sink and thermal test chip, removes input power up to 80 W keeping the chip surface temperature below $70\;^{\circ}C$. The experimental results demonstrate that the feasibility of forced-liquid cooling system using ECF is confirmed as an advanced cooling solution on the next-generation high power electronic devices.

• The Journal of the Acoustical Society of Korea
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• v.18 no.1
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• pp.86-91
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• 1999

This paper presents the text-prompt method to overcome the weakness of text-dependent and text-independent speaker recognition. Enhanced dynamic time warping for speaker recognition algorithm is applied. For the real-time processing, we use a simple algorithm for end-point detection without increasing computational complexity. The test shows that the weighted-cepstrum is most proper for speaker recognition among various speech parameters. As the experimental results of the proposed algorithm for three prompt words, the speaker identification error rate is 0.02%, and when the threshold is set properly, false rejection rate is 1.89%, false acceptance rate is 0.77% and verification total error rate is 0.97% for speaker verification.

• Korean Journal of Human Ecology
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• v.7 no.3
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• pp.73-82
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• 2004

The purpose of this study was to investigate the relationship of spouse character perceived by mother's child - rearing behavior and child rearing behavior - children's social competence. The subjects of this study were 115 children's mothers in Jeon-ju city. The data were collected using questionaries and analyzed by the statistical methods of frequencies, percentages, t-test, ANOVA, pearson's correlation with SPSS pc program: The results of this study were summarized as follows: 1. There were significant differences according to economics status in spouse character Perceived by mother's. In other words. got higher income to authoritarian character and also there were significant differences according to economic status in child - rearing behavior. In other words. got higher income mother's child - rearing behavior such as rejection - blame and sensitivity. 2. There were significant differences according to economic status in children's social competence. In particular. got higher income to children's social competence such as ability and leadership. 3. There were significant differences according to economic status in relation of spouse character perceived by mother's. child - rearing behavior and children's social competence.

• Journal of the Korean Society for Precision Engineering
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• v.27 no.3
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• pp.41-49
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• 2010

Two promising control candidates have been selected to test the sinusoidal reference tracking performance for a brush-type polishing machine having strong nonlinearities and disturbances. The controlled target system is an oscillating mechanism consisting of a common positioning stage of one degree-of-freedom with a screw and a ball nut driven by a servo motor those can be obtained commercially. Beside the strong nonlinearity such as stick-slip friction, the periodic contact of the polishing brush and the work piece adds an external disturbance. Selected control candidates are a Sliding Mode Control (SMC) and a variant of a feedback linearization control called Smooth Robust Nonlinear Control (SRNC). A SMC and SRNC are selected since they have good theoretical backgrounds, are suitable to be implemented in a digital environment and show good disturbance and modeling uncertainty rejection performance. It should be also noted that SRNC has a nobel approach in that it uses the position information to compensate the stickslip friction. For both controllers analytical and experimental studies have been conducted to show control design approaches and to compare the performance against the strong nonlinearity and the disturbances.

• Journal of Families and Better Life
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• v.30 no.3
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• pp.13-27
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• 2012

This study explored the parental belief types of mothers who had defected from North Korea and found out its relationship to the mother's child-rearing behaviors and socio-demographical variables and the child's age. 89 mothers who had defected from North Korea with the youngest child being under 20 years old, responded to the questionnaire. The data were statistically analyzed by cluster analysis, MANOVA, and $X^2$-test. The results showed that the parental beliefs were clustered into 3 types: 'high child- and parent-centered & low cultural transformation'(cluster 1)(37.08%), 'low child- and parent-centered & middle cultural transformation'(cluster 2)(46.03%), and 'high child- and parent-centered & high cultural transformation'(cluster 3)(16.85%). The differences among the clusters were found in the warmth-acceptance and rejection-restriction dimensions of the mother's child-rearing behaviors. The frequencies of each cluster were meaningfully different depending on the mother's age, educational level, length of residence in South Korea, and their child's age. Based on these findings, the implications and suggestions were discussed.

• Membrane and Water Treatment
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• v.7 no.6
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• pp.495-505
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• 2016

Mesoporous MCM-41 was deposited on an inexpensive disk shaped ceramic support through hydrothermal technique for ultrafiltration of $Fe^{3+}$ from aqueous solution. The ceramic support was fabricated using uni-axial compaction technique followed by sintering at $950^{\circ}C$. The characteristics of MCM-41 powder as well as the composite membrane were examined by X-ray diffraction (XRD), thermogravimetric analysis (TGA), field emission scanning electron microscope (FESEM), porosity and pure water permeation test. The XRD result revealed the good crystallinity and well-resolved hexagonally arranged pore geometry of MCM-41. TGA profile of synthesized MCM-41 zeolite displayed the three different stepwise mechanisms for the removal of organic template. The formation of MCM-41 on the porous support was verified by FESEM analysis. The characterization results clearly indicated that the accumulation of MCM-41 by repeated coating on the ceramic disk directs to reduce the porosity and pore size from 47% to 23% and 1.0 to $0.173{\mu}m$, respectively. Moreover, the potential of the fabricated MCM-41 membrane was investigated by ultrafiltration of $Fe^{3+}$ from aqueous stream at various influencing parameters such as applied pressure, initial feed concentration and pH of solution. The maximum rejection 85% was obtained at applied pressure of 276 kPa and the initial feed concentration of 250 ppm at pH 2.

• Journal of Advanced Navigation Technology
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• v.21 no.3
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• pp.243-250
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• 2017

GPS(Global Positioning System) signal structure uses spread spectrum and the received power is relatively lower than the receiver noise figure. Therefore, it is vulnerable to the RF interferences and it could restrict on the safety navigation. The objective of this paper is to research on the spectral domain GPS interference rejection algorithm using proposed K-median filtering threshold setting method. In the performance test, the proposed algorithm has a relatively higher ISR(interference to signal ratio) compared with the conventional temporal domain technique in case of time variant interference signals.

• Journal of the korean Society of Automotive Engineers
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• v.2 no.1
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• pp.39-50
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• 1980

This paper presents the variations obtained in heat flow rate and engine performance of a four-stroke cycle Diesel engine when there were changes in the temperature of cooling water, compression ratio, injection timing of fuel, and other factors. Heat dissipation of engine cylinder was calculated by the heat transfer coefficient of Nusselt's empirical equation and the analysis of distribution of temperature in cylinder barrel was obtained by the finite element method of two-dimensional steady state heat conduction. In this experiment, the out side temperature of cylinder liner was measured by the data logger, and the temperature distribution of liner was computed by the analysis of triangular finite element model under the assumption due to surface heat flux of cylinder inner surface. The results obtained by this study are as follows. Under the given operating condition, the temperature distribution of cylinder liner by using finite element method shows that the mean temperature of barrel is in accordance with the experimental results of Eichelberg and temperature difference is lower than 4.23.deg. C. The heat dissipation of engine decrease in accordance with the decrease of piston mean velocity, compression ratio, and the increase of coolant temperature. Influence on the delay of injection timing of fuel brings about the decrease of heat rejection over the cylinder at constant test conditions.

• Journal of the Korean Society of Food Culture
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• v.26 no.3
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• pp.261-270
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• 2011

The purpose of this study was to investigate the relationship between 'family-work conflict/work-family conflict', job burnout, job satisfaction, and individual job performance in the employees at the restaurants in Daegu City. The sample of this study consisted of employees at the restaurants in Daegu City who visited the 2010 Daegu Food Tour Expo between October 7 and October 10. A total of 302 questionnaires were analyzed using statistical methods of factor analysis, reliability test, and covariance structural analysis. The research findings were as follows; firstly, work-family conflict was positively related to job burnout, secondly, job burnout was negatively related to job satisfaction and individual job performance and thirdly, job satisfaction was positively related to individual job performance. However, there was no relationship between family-work conflict and job burnout. The reason for rejection of the relationship between family-work conflict and job burnout was that family-related affairs were not important enough to affect job burnout among restaurant employees in Korea. This phenomenon happened differently in the US. Therefore, currently, restaurant managers in Daegu City should pay much attention to work-related affairs so as to mitigate job burnout as much as possible among their employees.