• 한국전기전자재료학회논문지
• /
• 제29권10호
• /
• pp.625-629
• /
• 2016

Electrical and optical properties of the AC voltage driven organic light-emitting diodes were investigated by measuring the electroluminescence of the device. Device structure of ITO(170 nm)/TPD(40 nm)/Alq3(60 nm)/LiF(0.5 nm)/Al(100 nm) was manufactured using a thermal evaporation. Sinusoidal and square-type AC voltage was applied to the device using a function generator. Amplitude of the applied voltage was 9.0 V, and a frequency was varied from 50 Hz to 50 kHz. Electroluminescence out of the device was measured in a Si photodetector simultaneously with the applied voltage together. An intensity and a delayed residual luminescence from the device were depended on the frequency of the sinusoidal voltage. It is thought to be due to a contribution of the capacitive nature in the equivalent circuit of the device. An electron mobility was estimated using a time constant obtained from the luminescence of the device driven by the square-type AC voltage.

• 한국식품과학회지
• /
• 제39권5호
• /
• pp.506-514
• /
• 2007

비열 살균 기술인 high voltage PEF를 이용하여 당근 주스를 처리하였을 때 당근주스의 살균력과 저장 중 품질 변화를 관찰하였다. 전기장의 세기를 50, 60, 70kV/cm에서 처리 시간을 달리하여 당근주스를 처리한 결과 전기장의 세기가 증가함에 따라 일반 세균과 효모 및 곰팡이 모두 감소하였다. 효모 및 곰팡이는 65 kV/cm, $200{\mu}s$ 처리시 모든 균이 사멸되었고 일반세균은 멸균에까지 이르지는 못하였으나 70 kV/cm $200{\mu}s$ 처리 후 4 log cycle 정도 감소되었다. 고전압 펄스 전기장 처리에 사용되는 펄스 파형인 square wave pulse와 exponential decay pulse가 살균효과에 미치는 차이를 비교하기 위하여 각각 4.25와 6.25의 pH에서 PEF 처리를 하여 실험하였다. 그 결과 square wave pulse를 이용한 PEF의 살균효과가 exponential decay pulse를 이용하였을 때보다 우수하였으며 처리 시간이 길어질수록, 당근주스의 pH가 낮을수록 두 파형 사이의 살균효과는 더 큰 차이를 나타내었다. 온도 및 pH의 병합처리가 PEF의 살균효과에 미치는 영향을 알아보기 위하여 온도 및 pH를 달리하여 55kV/cm, $132{\mu}s$의 조건에서 PEF 처리한 결과 병합 처리시 살균효과가 눈에 띄게 증가하는 것을 관찰할 수 있었다. PEF 처리한 당근주스의 저장 시 품질변화를 관찰한 결과 pH 와 열처리를 PEF와 병합하여 처리한 후 $4^{\circ}C$ 저장한 당근 주스에서만 pH, $^{\circ}Brix$, 산도, 색도 그리고 ${\alpha}-,\;{\beta}-carotenes$함량에 눈에 띄는 차이를 나타나지 않았으며, 28일 동안 균의 생육을 관찰할 수 없었다.

• 한국전기전자재료학회논문지
• /
• 제33권5호
• /
• pp.386-392
• /
• 2020

In this study, the drift current characteristics of charged particles are analyzed for panels fabricated by varying the waveform biasing of the active particle loading method (APLM), which is a method driven by the electrophoretic principle of loading charged particles into a cell of a barrier rib-type electronic paper. We prepare 3 panels using APLM and 1 panel without APLM. The waveform of APLM uses square wave and ramp wave, and the step voltage wave is applied to the driving voltage. The drift currents measured from the square wave and ramp wave with the same period applied by APLM are 4.872 µC and 5.464 µC, respectively, and the ramp wave is shown to be relatively advantageous for loading charged particles that have a large q/m. The time-current curve results confirm that the abrupt movement of charged particles is occurring. When the step form wave signal with a short time of 1s is first applied, initial large movement of the charged particles is confirmed to occur in all samples, which is understood as the effect of applying the voltage necessary to remove the imaging force. The results of this study are expected to improve the loading of charged particles into the electronic paper cell, driven by the electrophoretic principle and optimization of the driving conditions.

• 대한전기학회논문지:전기물성ㆍ응용부문C
• /
• 제52권10호
• /
• pp.487-491
• /
• 2003

The low-cost, simple structured micropump which is actuated by piezoelectric-discs, is fabricated with polydimethylsiloxane (PDMS) and the performances of the micropump, such as pump rate and backpressure, are characterized. The PDMS micropump with diffusers instead of passive check valves as a flow-rectifying element was fabricated. The deflection of glass diaphragm measured by atomic force microscope (AFM) is about 0.4$\mu\textrm{m}$ when applying a 150V square wave voltage at 300Hz across a 300${\mu}\ell$ thick piezoelectric disc. While the square wave driving voltage is applied to the piezoelectric disc of the actuator, the flow rate is measured by fluid displacement variation of the outlet tube. The flow rate of micropump increases with enhancing the applied voltage due to the increase of diaphragm deflection. The flow rate and the backpressure of the micropump with diffusers are about 32.9${\mu}\ell$/min and 173Pa respectively for the above mentioned deflection conditions.

• 한국군사과학기술학회지
• /
• 제23권5호
• /
• pp.516-522
• /
• 2020

In this paper, the frequency detector which detects the clock frequency of the embedded system is proposed and analyzed. The proposed frequency detector is consisted of filter and peak voltage detector. The clock signal is converted from square wave to triangular wave by the filter. The peak voltage of the triangular wave is determined according to the frequency response of filter. The peak voltage detector detects and holds the peak voltage of the signal. Moreover, the proposed clock frequency detector can detect the frequency within 1ms and it gives guarantee of real-time operation.

• Journal of Power Electronics
• /
• 제11권4호
• /
• pp.449-455
• /
• 2011

Electric drive vehicles (EDV) have received much attention recently because of their environmental and energy benefits. In an EDV, the motor drive system directly influences the performance of the propulsion system. However, the available DC voltage is limited, which limits the maximum speed of the motors. At high speeds, the inverter voltage increases if the square wave (SW) voltage (six-step operation) is used. Although conventional direct torque control (DTC) has several advantages, it cannot work in the six-step mode required in high-speed applications. In this paper, a single-mode seamless DTC for AC motors is proposed. In this scheme, the trajectory of the reference flux changes continuously between circular and hexagonal paths. Therefore, the armature voltage changes smoothly from a high-frequency switching pattern to a square wave pattern without torque discontinuity. In addition, because multi-mode controllers are not used, implementation is more straightforward. Simulation results show the voltage pattern changes smoothly when the motor speed changes, and consequently, torque control without torque discontinuity is possible in the field weakening area even with a six-step voltage pattern.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2009년도 추계학술대회 논문집
• /
• pp.109-109
• /
• 2009

This paper represented driving characteristic of a thin-type ultrasonic motor by fabricating and utilizing two kinds of drivers which could generate sinusoidal wave, square wave, respectively. A thin brass plate was used as a cross shaped vibrator and sixteen ceramic plates were attached on upper and bottom side of the brass plate. From the thin stator, elliptical displacements of the four contact tips were obtained. Speed, torque, and current were measured by applying sinusoidal waves through driving equipment such as function generator, power amplifier: to measure characteristic of the motor. As a result, the speed and the torque changed linearly at either driving frequency of 88.6 ~ 87.6[kHz] or voltage of 24~36[V]. Two-drivers which generate sinusoidal waves and square waves were designed respectively, and then were compared through some experiments in order to be put to practical use. In conclusion, the drivers had similar characteristic of speed-torque at similar frequency and voltage. It was able to control the motor linearly by using the driver generating square wave among two-drivers. Besides, it also was possible to make the drivers smaller.

• 전력전자학회:학술대회논문집
• /
• 전력전자학회 2000년도 전력전자학술대회 논문집
• /
• pp.355-359
• /
• 2000

This paper deal with the harmonic reduction technique in three-phase square-wave inverter system formed by single-phase inverter. To reduce the harmonics six single-phase inverters are used for forming multi-phase inverter and zig-zag connected output transformer for eliminating the harmonic 6(2k-1)$\pm$1 orders. And an ac filter is furnished at output side. Computer simulations show that the THD of the output voltage can be reduced immensely.

• 전기전자학회논문지
• /
• 제12권3호
• /
• pp.172-175
• /
• 2008

An improved triangular/square-wave VCO using OTAs is presented. It consists of two OTAs, a timing capacitor, and a resistor. A prototype circuit built with commercially available components exhibits less than 0.01% nonlinearity in its current-to-frequency transfer characteristic from 0.2 to 14 kHz and 450 ppm/$^{\circ}C$ temperature coefficient of frequency over $-20^{\circ}C$ to $40^{\circ}$.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2001년도 하계학술대회 논문집 B
• /
• pp.1058-1060
• /
• 2001

The purpose of this paper is to analyze the harmonics of power electronics equipment, especially 3 phase square-wave inverter. In this paper, we simulated 3 phase square-wave inverter by using the matlab and analyzed the simulated output waveforms to analyze the harmonics included in the inverter. In the matlab we expressed to amplitude and phase of harmonics current, and calculated to total harmonics distortion of out voltage.