• 대한한방내과학회지
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• 제33권3호
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• pp.257-271
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• 2012

Objectives : The purpose of this study was to confirm that the pulse analyzer is useful for analyzing characteristics of variables of pulse waves in age categories, evaluating pulse waves of the metabolic syndrome group, compared with those of the non-metabolic syndrome group in Korean adults. Methods : The pulse wave variables were measured in Guan of all 1,056 subjects by the pulse analyzer, using a pen-type piezoresistive sensor. The physical measurement, blood test and survey were also performed by each subject. Results : In the age categories, height of pre-incisura (h2), height of tidal wave (h3), area of percussion wave (Aw), and width of percussion wave (w) increased in accordance with increase in age. While ratio of systolic period area (As) went up according to the increase of age, ratio of diastolic period area (Ad) went down. Radial augmentation index (R-AI), h2/h1, h3/h1, w/t and angle of percussion wave went up by aging, generally. Aw rate (Aw/At) also increased. Among the metabolic syndrome group, in the ages of 19 and 44, ratio of systolic period area (As) was higher and ratio of diastolic period area (Ad) was lower than in the non-metabolic group. w/t, Aw/At, and angle of percussion wave were higher than in the non-metabolic syndrome group. Among the metabolic syndrome group over the age of 60, height of pre-incisura (h2), height of tidal wave (h3), total area (At), area of percussion wave (Aw), radial augmentation index (R-AI), h2/h1 and h3/h1 were higher than in the non-metabolic syndrome group. Conclusions : The pulse analyzer is useful to analyze arterial stiffness in the age categories and in the metabolic syndrome group by some measures.

• 전자공학회논문지
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• 제52권2호
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• pp.89-96
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• 2015

본 논문에서는 휴대용 기기를 위한 고효율 삼중 모드 부스트 변환기를 나타낸다. 제안하는 부스트 변환기는 펄스폭변조 방식를 사용하며 부하 전류에 따라 펄스 스키핑 모드 (Pulse Skipping Mode, PSM), 불연속 전류 모드(Discontinuous Conduction Mode, DCM) 및 연속 전류 모드 (Continuous Conduction Mode, CCM)의 세 가지 동작 모드를 갖는 것을 특징으로 한다. 또한, 전류 불연속 모드에서 역 전류 흐름 및 인덕터의 공진에 의한 발진 현상을 효과적으로 방지하기 위해 발진 억제기 (Ringing suppressor)를 적용하여 효율을 극대화 시켰다. 제안하는 부스트 변환기는 동부 $0.18{\mu}m$ BCD 공정을 사용하여 구현되었다. 단일 셀 리튬-이온 배터리로부터 2.5V-4.2V의 가변 입력전압을 받아서 4.8V의 고정 전압을 출력하며 최대 300mA의 부하전류를 공급할 수 있다. 이 때 최대 리플 전압은 3.1mV이며, 연속 전류 모드에서 92%, 불연속 전류 모드에서 87% 이상의 높은 효율을 나타낸다. 또한, 펄스 스키핑 모드를 통해 적은 부하전류 조건하에서도 60% 이상의 효율을 가지며 모드 변경 구간에서의 효율 감소가 최소화되는 것을 특징으로 한다.

• 대한전자공학회논문지SD
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• 제43권11호
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• pp.14-18
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• 2006

광간섭계는 물체의 기하학적 구조 및 의료 계측등 다양한 분야의 광계측에서 매우 일반적으로 사용된다. 이러한 광간섭계에서 광지연단은 측정대상의 기준을 위해 사용되고. 광간섭계의 계측속도는 광지연단에 의해 제한된다. 본 논문에서는 고속 광지연단을 위해 기존의 기계적 방식을 배제하고, 광학적 방식의 광 간섭계를 구성하였다. 고속 광간섭계의 구성은 1304nm의 10GHz광원을 이용하였으며, 광지연단으로 광위상변조기와 광섬유를 이용하여 안정적이고 고속의 광 간섭계를 구성하였다. 구성된 광간섭계는 광위상변조기의 변조전압, 변조주파수에 의해 광지연시간을 가변할 수 있으며, 10MHz 반복율에 대해 11ps의 광지연시간을 얻을 수 있었다.

• Journal of Power Electronics
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• 제15권5호
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• pp.1235-1243
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• 2015

This paper presents a modified Space Vector Pulse Width Modulation Technique (SVPWM), which solves the well-known problem of voltage imbalance in the capacitors of a single-phase multilevel inverter. The proposed solution is based on the measurement of DC voltage levels at each capacitor of the inverter DC bus. The measurements are then used to adjust the size of the active vectors within the SVPWM algorithm to keep the voltage waveform sinusoidal regardless of any voltage imbalance on the DC link capacitors. When a voltage deviation exceeds a predetermined hysteresis band, the correspondent voltage vector is restricted to restore the voltage level to an acceptable threshold. Hence, the need for external voltage regulators for the voltage capacitors is eliminated. The functionality of the proposed algorithm is successfully demonstrated through simulations and experiments on a grid tied application.

• Journal of Power Electronics
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• 제18권4호
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• pp.1140-1153
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• 2018

The harmonic impedance characteristic of a traction power supply system (TPSS) is necessary for taking actions to suppress the high-order harmonic resonances caused by AC electric locomotives. This paper proposes a controllable harmonic generating method (CHGM) for measuring the TPSS harmonic impedance by injecting harmonic disturbances of different frequencies and amplitudes into the TPSS. This method applies phase shifted pulse-width modulation (PSPWM) and ensures that the undesired sideband harmonics can be negligible while the desired harmonic is both controllable and adjustable. Multiple harmonics can be emitted at the same time. The implementation of the method is also presented. Simulations are carried out to validate the performance of the proposed method. Finally, experimental results on a 5 H-bridge converters platform verified the effectiveness and feasibility of the proposed method.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2012년도 추계학술대회 논문집
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• pp.211-212
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• 2012

This paper proposes a single current sensor control technique for controlling motors that use only a single DC-Link current sensing resistor to obtain the information of three line currents. However, the measurement is distorted due to the too narrow current pulse width in the shunt resistor. To solve this problem, the existing phase current reconstruction methods are voltage split methods. They have a disadvantage which makes noise. A new dedicated observer is applied to decrease noise problem. Experimental results showed the effectiveness of the proposed method.

• 대한인간공학회지
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• 제18권3호
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• pp.1-12
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• 1999

This study investigated human operator's perceptual and psychophysical responses to vibrotactile stimulation on various parts of the hand. Using a small vibrotactile display, the effects of three mechanical parameters consisting vibrotactile stimulations, i.e., vibration frequency, pulse-width modulation duty cycle, and number of contactors, on differential thresholds were examined at five different loci of the hand. It was observed that differential threshold varies with vibration frequency and number of active contactors. Differential sensitivity was the greatest at the vibration frequency of 120 Hz. The differential sensitivity was not found to be affected by loci on the hand. The area of stimulation on the hand was also found to be significant in that the sensitivity increased with the number of active contactors. It should be noted that the conclusions from this study generally correspond to those from the previous study on the absolute sensitivity. which means that tactile sensitivity to vibrotactile stimulations can be controlled with a systematic and consistent passion for emulating normal everyday contact on human hands in teleoperation and virtual reality applications.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2007년도 추계학술대회 논문집
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• pp.1445-1450
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• 2007

Induction motors are the main driving force of electric vehicles and operated by pulse width modulation (PWM) inverters in speed control. Contrary to full-voltage operation of induction motors, inverter-fed induction motors (IFM) generates transient overvoltages up to 10 kV/us and transient overvoltages accelerate the deterioration of winding insulation. We investigated transient overvoltages produced by the operation of IFM and analyzed its peak value and dv/dt depending on power cable length and operation frequency. The experimental results showed that transient overvoltages measured at the motor terminal increased with the cable length between inverter and motor.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1990년도 하계학술대회 논문집
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• pp.430-432
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• 1990

This paper concerns a method for high precision torque control of induction motor supplied with power via a Transister inverter. The control system is totaly digitized using DSP - TMS32010.Since operation time leads to control delay in such a system, torque ripples are more significient than relieved considerably by using current preview control and vector pulse width control. The usefulness of these techniques will be demonstrated by showing the results of a simulation,and results of measurement on a 2.2Kw induction motor.

• Journal of Photoscience
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• 제5권1호
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• pp.33-37
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• 1998

One macroscopic effect in the free-running Er:YAG laser is an accumulation of microscopic effects. Understanding of the exogenous water induced mechanical effect on the dental hard tissue by the Qswitched Er:YAG laser has an important impact on the further understanding of the free-running Er:YAG laser ablation on the dental hard tissue. The Q-switched Er:YAG laser (1-$\mu$s-long pulse width) was used in the recoil pressure measurement with an aid of water-jet system and a pressure transducer. The amplitude of the recoil pressure depends on the tooth surface conditions (dry and wet) and the volume of the water upon it. Wet surfaces yielded higher recoil pressure than that of dry, surface, and as the volume of the exogenous water drop increased, the amplitude of the recoil pressure increased also.