• 한국철도학회:학술대회논문집
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• 한국철도학회 2005년도 추계학술대회 논문집
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• pp.783-788
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• 2005

Detection of small leakage current is the most important technique in arrester diagnosis. Various types of leakage current detector have been commercialized, but they are not available for the railway arresters including voltage harmonics, and do not furnish enough information needed for arrester diagnosis. This paper describes the development of a leakage current detector which is suitable for the railway arresters. The detector is consisted of a sensor unit with amplifier, an optical linker and main analyzer. Frequency bandwidth and measuring range of the detector is 9[Hz]$\~$850[Hz] and 50[uA]$\~$5[mA], respectively.

• 대한전자공학회논문지
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• 제15권5호
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• pp.13-18
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• 1978

본 논문에서는 PLL의 pull-in 특성을 개선하기 위하여 delay switching PL난을 제시하였다. phase detector와 low grass filter사이에 간단한 RC delay회로를 삽입하고, 90° shift 시킨 Phase detector출력에 의하여 delay time을 switching하였다. 그 결과 pull-in range는 lock range의 1/2이상으로 넓힐 수 있었으며 pull-in time도 개선되었다. 이 개선된 Pull-in특성은 근사적으로 해석되었으며 실험으로 확인되었다.

• Journal of electromagnetic engineering and science
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• 제15권1호
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• pp.59-61
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• 2015

A wideband H-band detector operating near 300 GHz has been developed based on SiGe HBT technology. The detector consists of an on-chip antenna and a HBT differential pair for square-law detection. It showed responsivity of more than 1,700 V/W and noise equivalent power (NEP) smaller than $180pW/Hz^{0.5}$ for the measured frequency range of 250-350 GHz. The maximum responsivity and the minimum NEP were 5,155 V/W and $57pW/Hz^{0.5}$, respectively; both were obtained at 330 GHz with DC power dissipation at 9.1 W.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2004년도 SMICS 2004 International Symposium on Maritime and Communication Sciences
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• pp.28-31
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• 2004

A Quadrature phase detector for high-speed delay-locked loop is introduced. The proposed Quadrature phase detector is composed of two nor gates and it determines if the phase difference of two input clocks is 90 degrees or not. The delay locked loop circuit including the Quadrature phase detector is fabricated in a 0.18 urn standard CMOS process and it operates at 5 ㎓ frequency. The phase error of the delay-locked loop is maximum 2 degrees and the circuits are robust with voltage, temperature variations.

• 전력전자학회논문지
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• 제26권1호
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• pp.32-37
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• 2021

This study proposes a DC series arc fault detector using a frequency analysis method called the discrete wavelet transform (DWT), in which the processing speed of the DWT algorithm is improved effectively. The processing time can be shortened because of the time characteristic of the DWT result. The performance of the developed DC series arc fault detector for a large photovoltaic system is verified with various DC series arc generation conditions. Successful DC series arc detection and improved calculation time were both demonstrated through the measured actual arc experimental result.

• Nuclear Engineering and Technology
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• 제55권5호
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• pp.1533-1540
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• 2023

Self-Powered Neutron Detectors(SPNDs) are used to calculate core power distributions, an essential factor in the safe operation of nuclear power plants. Some detectors may fail during normal operation, and signals from failed detectors are isolated from intact signals. The calculated detailed power distribution accuracy depends on the number of available detector signals. Failed detectors decrease the operating margin by enlarging the power distribution measurement error. Therefore, a thorough reconstruction of the failed detector signals is critical. This note suggests a compressive sensing based methodology that rationally reconstructs the readings of failed detectors. The methodology significantly improves reconstruction accuracy by sorting signals and removing high-frequency components from conventional compressive sensing methodology.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 하계학술대회 논문집 E
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• pp.1824-1827
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• 1998

A Laser Doppler Vibrometer(LDV) was developed using He-Ne laser as a light source. The heterodyne method was employed and its output signal was digitally processed with a $\mu$-processor and the result was displayed with LCD. The frequency shifted object beam(40 MHz) by a Bragg cell was focused on the surface of the moving target and the Doppler shifted reflected beam was recombined with reference beam at the fast photodetector to produce frequency modulated signal centered at 40 MHz. The signal from the detector was amplified and downconverted to intermediate frequency centered at 1 MHz after mixing process. The voltage output that was proportional to the velocity of the moving surface was obtained using PLL. With the same method, the fringe pattern signal of the moving surface is obtained. This fringe pattern signal is converted to TTL signal with ZCD(zero-crossing detector) and then counted to calculate the displacement due to the vibration, which is displayed with LCD. This LDV can be used to measure the resonant frequency of the electric equipments such as circuit breakers and transformers, of which resonant frequencies are changed when they are damaged.

• 한국음향학회지
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• 제30권2호
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• pp.73-79
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• 2011

본 논문에서는 음성 신호를 녹음하는 과정에서 발생하는 충격 잡음의 위치를 검출하는 새로운 알고리즘을 제안하였다. 제안한 방법은 충격 잡음의 주파수 축 특성을 반영하여 기존의 방법에 비해 높은 검출 정확도를 가지면서 음성의 피치를 충격 잡음과 구분하지 못하는 문제를 해결하였다. 또한, 시간 축, 주파수 축 파라미터의 단점을 상호 보완하여 false-alarm 문제를 최소화하는 시간-주파수 축 충격 잡음 검출 시스템을 제안하였다. 실제 녹음된 충격 잡음을 이용한 실험 결과, 제안한 시간-주파수 축 충격 잡음 검출기는 99.33 %의 가장 높은 검출 정확도와 1.49 %의 가장 낮은 false-alarm 비율을 나타내었다.

• 대한교통학회:학술대회논문집
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• 대한교통학회 1999년도 제36회 학술발표회논문집
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• pp.405-410
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• 1999

• 대한의용생체공학회:의공학회지
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• 제28권2호
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• pp.300-305
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• 2007

In this study, we have studied the fabrication and the performance evaluation of digital radiation detector of the based on selenium (a-Se) prototype which is widely researched about recently. The detector was fabricated using amorphous selenium in the specification of active area size $7{\times}8.5"$, pixel pitch $139{\mu}m$, and 12 bit ADC. In order for the performance evaluation of the fabricated detector, we used radiation quality RQA 5 that is suggested by the International Electrotechnical Commission (IEC), and evaluated modulation transfer function (MTF), noise power spectrum (NPS), and detective quantum efficiency (DQE). Concerning MTF measurement, we used slit camera (Nuclear Associates, Model : 07-624-2222), and evaluated in the slit method. Also so as to compare the performance evaluation on the detector fabricated in this study, we used Hologic Direct-Ray (DR-1000) and GE Revolution XQ/I system, and evaluated and compared in the same method MTF, NPS, and DQE which are image quality factors. And as a result, the MTF of each detector In Nyquist frequency were evaluated to be 58% (at 3.5 lp/mm) in the case of DR-1000 and 65% (at 2.5 lp/mm) in the case of XQ/I, and that for the detector fabricated in this study was evaluated to be 36% (at 3.51 lp/mm). Also in the case of DQE(0), the detector fabricated in this study, DR-1000 of Hologic company, and XQ/I system of GE company respectively were evaluated as 36%, 32%, and 50%.