• 한국안전학회지
• /
• 제13권4호
• /
• pp.162-171
• /
• 1998

This paper presents the harmonics obstacle analysis and countermeasure of electrical consumption a place. Harmonics that can be cosidered as a environmental pollution of the power systems become the cause of the accidents and damages. The responsibility of eliminating the harmonics firstly lies on the generating side. But the original characteristics of the system sush as the harmonic transfer characteristics and the impedance of the system affect each other in the process of the generation and transmission of the harmonic. Therefore it is very difficult to specify clearly the harmonic controlling responsibility, because electric machinery generating harmonics are various in the industrial fields. The output of a inverter has a high harmonic content. There are several ways of minimizing the output harmonic content. One way is to use pulse width modulation techniques within inverter. An alternative method is to combine a number of square-wave inverters. In this research, we measure the harmonic of the countermeasure of electrical consumption a place. The paper present the problem of new harmonic elimination method of PWM inverter fed induction motor system using W-FT series. In the future, the proposed PWM pattern by W-FT series is effective not only to the induction motor but also to the electromagnetic machine such as voltage reglator, UPS.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1988년도 추계학술대회 논문집 학회본부
• /
• pp.252-257
• /
• 1988

This paper discribes an improved technique for locating partial discharge sites within operating transformers by ultrasonic method which utilizes the different travel times of the electrical and ultrasonic signals produced by partial discharges to determine the location of the sources. The technique was to develope the measurement system based on the enhancement of the acoustic emission signals using signal square, circuit to improve the detectable sensitivity and reliability. Also an ultrasonic pulse generator was designed and made to transmit periodically pulses equivalent to pratial discharges and to check the good performance of the system, echo effects and self-diagnosis. Through the laboratory work, it was confirmed that the system and the generator can be used satisfactorily for diagnosing power transformers and for studying echo effects and self-diagnosis of the system.

• E2M - 전기 전자와 첨단 소재
• /
• 제11권10호
• /
• pp.46-52
• /
• 1998

In this study, polarization switching characteristics of Pb(ZrxTil-x)O3 (PZT) thin films were investigated. Switching times(ts) were found to be decreased as the Zr mol% was increased. But, the switching peak currents(Imax) showed the largest value at 50 mol% Zr. As a result of this experiment, ts was found to be depended on the remanent polarization and coercive field and also Imax strongly depended on the dielectric constant of PZT thin films. In order to investigate the partial switching kinetics of PZT thin films, short and relatively small voltage pulses were applied to the MFM(metalferroelectric metal) PZT capacitors and polarization switching curves were measured with a variation of the total width of the applied pulses. Also, the switching curves were measured at different applied voltages(4, 8, 10, 12 and 14 volts). As the applied voltages increased, ts and Imax were found to be decreased and increased, respectively. In case of fatigued specimen which we applied $\pm$10 volts square pulse for 1010 cycles, ts and Imax were found to be shorter and smaller than those of virgin specimens. This is due to the decrease of the remanent polarization and the increase of the coercive field.

• 한국전자파학회논문지
• /
• 제7권3호
• /
• pp.201-210
• /
• 1996

본 논문에서는 페이딩환경에서 16QAM Radio 시스템의 심볼 타이밍 복원에 대한 성능을 분석하였다. 심볼 타이밍 복원 방식으로서 파형 성형 필터 즉 raised cosine filter(RCF)와 비선형 필터를 사용하여 비영점교차방식인 MAM(Maximum Amplitude Method)과 WDM (Wave Difference Method)을 비교 분석하였다. 시뮬레이션에 의한 결과로부터 비선형 필터를 사용한 심볼 동기 방식(MAM and WDM)이 RCF를 사용한 것보다 지터 성능이 더 우수함을 알 수 있었다. 또한 레일리 페이딩채널을 추정하고 보상하기 위해 PSAM(Pilot Symbol Assisted Modulation)방식과 공간 다이버시티방석을 적용하였으며, $E_b/N_o$가 20dB일 때 $10^{-4}$의 BER(Bit Error Rate)성능을 얻을 수 있었다.

• 전력전자학회논문지
• /
• 제20권3호
• /
• pp.239-246
• /
• 2015

A novel control method of a three-phase PWM inverter with LC filter is proposed. The transfer function of LC filter is the same as that of second-order low pass filter(LPF), which has a zero damping ratio. A simple method of implementing second-order LPF with damping ratio is to add a resistor in an LC circuit. However, in a real power system, adopting damping resistors is impractical because it results in losses proportional to the square of the current flowing through the resistors. Instead of inserting resistors, the proposed control strategy utilizes the measured capacitor voltages to control the oscillation of LC circuit. The overall transfer function of the proposed method is the same as a second-order LPF, and its damping ratio is controllable via control variables. The current controller can have overshoots caused by LC filter. Improved current controller is implemented by an equivalent second-order of LC filter. A 7.5 kVA PWM converter and a PWM inverter with a 5.5 kW induction motor are set up to verify the proposed control algorithm. Test waveforms are also presented to verify the proposed LC filter control algorithm.

• 전자공학회논문지
• /
• 제51권3호
• /
• pp.34-41
• /
• 2014

스태거 펄스 반복 주기 (pulse repetition interval, PRI)로 구성된 위협 레이더 신호에 대하여 실시간으로 PRI transform을 적용하여 스태거 PRI를 분석하고 측정 TOA와 추정된 PRI를 이용하여 능동 상쇄에 필요한 미래의 TOA (time of arrival)를 계산한다. 또한, 추정된 PRI와 TOA에 포함되어 있는 오차의 영향을 살펴보고 추정 PRI의 정확도를 향상시키는 기법과 TOA 오차의 영향을 감소시키기 위하여 TOA 평균화 기법을 제안한다. 마지막으로 TDOA와 최근 TOA를 이용하여 단순하게 예측된 미래 TOA와 제안된 방법을 통해 예측된 미래 TOA 간의 RMSE (root mean square error)를 비교하여 제안된 기법의 예측 정확도가 높음을 보인다.

• 제어로봇시스템학회:학술대회논문집
• /
• 제어로봇시스템학회 1992년도 한국자동제어학술회의논문집(국제학술편); KOEX, Seoul; 19-21 Oct. 1992
• /
• pp.388-393
• /
• 1992

An infrared range finder using a self-mixing laser diode (SM-LD), which has been proposed and developed by the Authors, can measure not only a range of a moving target but its velocity simultaneously. In this paper, described is that the precise mode-hop pulse train can be obtained by employing a new signal processing circuit even when the backscattered light returning into the SM-LD is much more weaker. As a result, the distance to a tilted square sheet made from aluminium or white paper, which is placed 10 cm through 60 cm from the SM-LD, is measured with accuracy of a few percent even when the tilting angle is less than 75 degrees or 85 degrees, respectively. And in this paper, described is the range-image recognition of a plane object under the condition of standstill. The output laser beam is scanned by scanning two plane mirrors-equipped with each stepping motor. And we succeeded in the acquisition of the range-image of a plane object in a few tens of seconds. Furthermore, described is a feasibility study about the range-image recognition of a slowly moving plane object.

• Applied Microscopy
• /
• 제25권3호
• /
• pp.1-19
• /
• 1995

The present study was performed to clarify the effect of vagus nerve stimulation on the enterochromaffin(EC) cells in the body of the stomach, the first part of the duodenum and the ceceum of rats by using routine electron microscopy and immunogold labelling. The changes in the ultrastructure and in the labelling density of the gold particles of the EC cells were investigated after vagus nerve stimulation. The vagus nerve was electrically stimulated with a square wave pulse generator for a duration of 5 minutes each, a total of 8 times at 2 minute intervals. Immunogold labelling demonstrated that the epithelial serotonin immunoreactive cells of the gastrointestinal tract are EC cells containing characteristic pleomorphic granules. Immunocytochemically labelled gold particles were largely concentrated in the dense matrix of the granules of the EC cell, and the labelling density of the gold particles considerably increased after the vagus nerve stimulation. Except for a slight activation of Golgi complexes, no remarkable changes in the ultrastructures of the EC cells were noted after the vagus nerve stimulation. The above results suggest that vagus nerve stimulation may activate serotonin biosynthesis in EC cells.

• 전기학회논문지
• /
• 제56권12호
• /
• pp.2265-2267
• /
• 2007

The purpose of this work is to compare the local fitting and global fitting approaches while applying regression model to the PTT-BP data for the prediction of exercise blood pressures. We used linear and nonlinear regression models to represent the PTT-BP relationship during exercise. PTT-BP data were acquired both under resting state and also after cycling exercise with several load conditions. PTT was calculated as the time between R-peak of ECG and the peak of differential photo-plethysmogram. For the identification of the regression models, we used local fitting which used only the resting state data and global fitting which used the whole region of data including exercise BP. The results showed that the global fitting was superior to the local fitting in terms of the coefficient of determination and the RMS (root mean square) error between the experimental and estimated BP. The nonlinear regression model which used global fitting showed slightly better performance than the linear one (no significant difference). We confirmed that the wide-range of data is required for the regression model to appropriately predict the exercise BP.

• 전력전자학회논문지
• /
• 제3권4호
• /
• pp.323-329
• /
• 1998

계통연계형 태양광발전시스템을 PWM 쵸퍼와 전류형 인버터로 구성하였다. 전류형 인버터의 직류리액터를 경감하는 방법으로, 직류측에 병렬공진회로를 삽입함에 따라 맥동전력의 일부를 교류 전해콘덴서에 축적하여 직류전류의 맥동을 억제하는 방법과, 쵸퍼의 변조파를 전원주파수의 2배로 제어하여 직류전류의 맥동을 억제하는 것을 비교 검토하였다. 그리고 태양전지전류와 쵸퍼의 변조율만을 이용하여 태양전지가 항상 최대출력점에서 동작하도록 하였다. 계통과 연계함으로서 출력전력이 부하전력보다 큰 경우에는 잉영전력을 계통전원에 공급하고, 발전전력 부하전력에 대해 부족한 경우에는 계통전원이 부족분을 공급하는 것을 확인하였다.