• Journal of Power Electronics
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• 제9권2호
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• pp.198-206
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• 2009

An algorithm is developed that enables a single-phase matrix converter (SPMC) to perform functions of a generalized single phase power electronics converter such as acting as a frequency changer, rectifier, inverter, and chopper. This reduces the need for new converter hardware. The algorithm is implemented first on computer simulation software Orcad Capture CIS version 9.1. Simulation results are presented for five types of converters with a control input variable that decides the 1) type of converter and 2) type of output waveform. The simulated results verify the working and operation of a generalized converter based on SPMC. Simulated results are verified with experimental results. Hardware design is obtained using readily available ICs and other components. The trigger circuit has been tested qualitatively by observing waveforms on CRO. The operation of the proposed system has been found to be satisfactory.

• 소음진동
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• 제9권6호
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• pp.1157-1165
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• 1999

Dynamic stability of a flying structure undertaking constnat and pulsating thrust force is investigated in this paper. The equations of motion of the structure, which is idealized as a free-free beam, are derived by using the hybrid variable method and the assumed mode method. The structural system includes a directional control unit to obtain the directional stability. Unstable regions due to periodically pulsating thrust forces are obtained by using the Floquet's theory. Stability diagrams are presented to illustrate the influence of the constant force, the location of gimbal, and the frequency of pulsating force. The validity of the diagrams are confirmed by direct numerical simulations of the dynamic system.

• 대한기계학회논문집A
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• 제29권10호
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• pp.1430-1437
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• 2005

It is very important to achieve a high reproducibility in the ultrasonic measurement of bone mineral density. In this study, we examined number of sampling waveform, control of temperature, diameter of region of interest as factors to improve reproducibility. We decided the optimal number of waveforms to be converted to frequency domain as period of 1. We have minimized the effects of variable temperature and constrained generation of micro bubble by keeping temperature within a range of $32\pm0.5^{\circ}C$ with a precise temperature controlling algorithm. We also found the optimal diameter of region of interest to be 13mm. In this paper, we demonstrated the improved reproducibility by controlling various factors affecting the ultrasonic measurement of bone mineral density.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2018년도 전력전자학술대회
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• pp.422-423
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• 2018

쇄교자속 기반 센서리스 제어는 저속에서 위치 추정 특성이 우수해 낮은 속도의 운전 영역을 가지는 애플리케이션에 많이 쓰인다. 그러나 계측 정보 오차와 모터 파라미터 변동으로 DC-offset이 발생하는 문제가 있다. 이러한 현상을 방지하기 위해 운전 주파수를 고려한 낮은 차단주파수를 갖는 HPF를 사용했으나, 낮은 DC 저감률로 인해 추정 자속에 DC 성분이 남는 문제점이 있다. 따라서 본 논문에서는 HPF의 차단주파수를 모터 운전주파수에 동기화하여 DC-offset 저감률을 높이고 DC-offset이 시스템에 미치는 정도에 따라 선택적으로 차단주파수를 가변함으로써 위상 앞섬도 감소시키는 방법을 제안한다. 제안된 방법은 Matlab/Simulink에 의해 검증된다.

• Journal of Electrical Engineering and Technology
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• 제9권5호
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• pp.1632-1642
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• 2014

This paper presents an interleaved resonant converter to reduce the voltage stress of power MOSFETs and achieve high circuit efficiency. Two half-bridge converters are connected in series at high voltage side to limit MOSFETs at $V_{in}/2$ voltage stress. Flying capacitor is used between two series half-bridge converters to balance two input capacitor voltages in each switching cycle. Variable switching frequency scheme is used to control the output voltage. The resonant circuit is operated at the inductive load. Thus, the input current of the resonant circuit is lagging to the fundamental input voltage. Power MOSFETs can be turn on under zero voltage switching. Two resonant circuits are connected in parallel to reduce the current stress of transformer windings and rectifier diodes at low voltage side. Interleaved pulse-width modulation is adopted to decrease the output ripple current. Finally, experiments are presented to demonstrate the performance of the proposed converter.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2010년도 추계학술대회
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• pp.337-338
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• 2010

다이어프램은 고정된 주파수의 전압을 이용하여 저전력으로 고압력의 공기를 공급하는 장치로 연료전지 및 산업용 공기 공급장치로 사용되고 있다. 본 논문에서는 다이어프램의 공기유량 및 유압을 저소음 및 저진동으로 제어하기 위해서 인버터를 이용한 가변주파수의 전류제어를 수행하였다. 제안된 다이어프램의 공기압 제어 방식은 지령 압력을 추종하기 위한 최대주파수 운전 방식으로, 토출압력이 만족하는 최대 주파수의 전류제어를 수행한다. 제안된 방식을 실험을 통하여 검증하였다.

• 대한간호학회지
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• 제27권4호
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• pp.912-922
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• 1997

The purpose of this study was to examine the effect of supportive nursing on stress reaction of breast cancer patients undergoing chemotherapy. The nonequivalent control group pre-test/post-test design was used for this experimental study. The subjects were 32 patients who were receiving chemotherapy after mastectomies at K hospital in Taegu from June, 1994 to June 1995. Among 32 subjects, 16 were placed in the experimental group and 16 in the control group. The experimental and control groups were tested for general characteristics, trait anxiety, health locus of control, family support, state anxiety, hopelessness, physical stress, and anxiety behavior. Collected data was analized by means of a chisquare test and a t-test for the comparative analysis of the general characteristics and homogeneity of subjects. ANOVA, and MANOVA were used for testing the hypothesis. Reliability of the tools were analyzed using the Pearson Correlation coefficient. The results of this study were as follows : 1. The hypothesis : The stress reaction of the experimental group which took supportive nursing was lower than the stress reaction of the control group : this was supported statistically. The main variable influenced in stress reaction was hopelessness. Supportive nursing for breast cancer patients, who are receiving chemotherapy, was especially effective in the reduction of hopelessness compared to state anxiety, physical stress, and anxiety behavior. 2. An analysis of the difference on stress reaction, according to the frequency of supportive nursing between the control and experimental group, showed the level of hopelessness of the experimental group was lower than the control group after four supportive meeting sessions. But there was no statistical difference in state anxiety, physical stress, and anxiety behavior. In conclusion, this study supported utilization of supportive care as well as demonstrating the effectiveness of the System-Developmental Stress Model developed by Chrisman and Riehl-Sisca.

• 성인간호학회지
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• 제12권1호
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• pp.64-76
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• 2000

The purpose of this study was to identify the major factors affecting performance in health promoting lifestyle of the elderly. The subjects for this study were 244 elderly person over the age of 60, living in K country, Kyongnam. Data were collected from August 31 to September 30, 1998. The collected data were analyzed with an SPSS program using frequency, percent, mean, cronbach alpha, t-test, ANOVA, Pearson' coefficients of correlation, Duncan test, and stepwise multiple regression. The results are summarized as follows. 1) The average score of performance in the health promoting lifestyle was 2.73. The variable with the highest degree of performance was regular diet(3.29), whereas the one with the lowest degree was self-control(2.22). 2) Performance in the health promoting lifestyle was significantly correlated with self esteem(r=.28, p=0.00), internal health locus of control(r=.58, p=0.00), powerful others health locus of control(r=.48, p=0.00), chance health locus of control(r=.25, p=0.00), perceived health status(r=.53, p=0.00). 3) Performance in the health promoting lifestyle was significantly correlated with such demographic variables as education level (F=9.47, P=0.00), marital status(F=2.63, P=0.05) and previous occupation(F=3.85, P=0.00). 4) The combination of internal health locus of control, powerful others health locus of control and perceived health status explained 43.4percent of the variance of health promoting lifestyle On the basis of this study, other factors affecting others health promoting lifestyle should be identified.

• 한국정밀공학회지
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• 제26권2호
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• pp.54-62
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• 2009

The purpose of this study is to develop a piezo injector driver for common-rail direct injection diesel engines. In this research, we analyzed the electrical and mechanical characteristics of the piezo actuator through experiments. Current flow and charging voltage of the piezo injector are controlled by the PWM signal of variable duty ratio in order to realize both fast response and low peak current. The optimal switching duty ratio was designed by modeling and analyzing of the piezo driver circuit. In order to avoid resonance and unacceptably long settling time, appropriate frequency range of the PWM signal was derived based on the driver circuit model. The developed injector driver was validated by experiments under various fuel rail pressure, injection duration, and charging voltage.

• 한국정밀공학회지
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• 제14권12호
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• pp.114-120
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• 1997

For compensating the error motion of hydrostatic tables, we have introduced a way that the clearance of table is controlled corresponding to the amount of eror with the actively controlled variable capillary, named as ACC. In previous paper, through the basic test, it was confirmed that by the use of ACC, the error motion within 2.7$\mu$ m of a hydrostatic table could be compensated with the resolution of 27nm, 1/100 contollable range, and with the frequency bandwidth of 5.5Hz, structurally. In this paper, we performed practical compensation of the linear and angular motion error of hydrostatic table using ACC. For improving the compensated motion accuracy, iterative control method is put into the control system. The experimental results show that by the simultaneous compensation of error, the linear and angular motion error are improved upto 0.25$\mu$ m and 0.4arcsec, which are about 1/10 and 1/3 of the non-compensated motion errors respectively.