• Analytical Science and Technology
• /
• v.5 no.1
• /
• pp.91-96
• /
• 1992

A simple and cheap AC voltammeter was manufactured in our lab. This instrument consists of a DC function generator and a lock-in amplifier. We tested this instrument in some chemical systems. Our data, CV voltammogram and AC voltammogram, obtained form using a Pt working electrode in 1M $H_2SO_4$ and a reversible system of $1{\times}10^{-3}M$ ${Fe(CN)_6}^{3-}$ proved our system works well. The quantitative result of iodine is also obtained.

• Journal of IKEEE
• /
• v.23 no.1
• /
• pp.164-172
• /
• 2019

Current clinical methods for diagnosing urination disorder are invasive, expensive, and very inconvenient to perform continuous monitoring. EIT is a non-invasive technique that injects electrical current through an external electrodes and measures the induced voltage to visualize the internal electrical (impedance) characteristics, which makes it possible to monitor bladder conditions with low cost. The signal characteristics of the measured voltage data changes according to the current pattern injected through the electrode and affects reconstruction performance. In this paper, image reconstruction performance is compared and analyzed according to the injected current patterns to maximize the sensitivity to the variation of bladder size.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.27 no.1
• /
• pp.127-134
• /
• 2021

In this study, an anomaly detection (AD) algorithm was implemented to detect the failure of a marine air compressor. A lab-scale experiment was designed to produce fault datasets (time-series electric current measurements) for 10 failure modes of the air compressor. The results demonstrated that the temporal pattern of the datasets showed periodicity with a different period, depending on the failure mode. An AD model with a convolutional autoencoder was developed and trained based on a normal operation dataset. The reconstruction error was used as the threshold for AD. The reconstruction error was noted to be dependent on the AD model and hyperparameter tuning. The AD model was applied to the synthetic dataset, which comprised both normal and abnormal conditions of the air compressor for validation. The AD model exhibited good detection performance on anomalies showing periodicity but poor performance on anomalies resulting from subtle load changes in the motor.

• Electric Engineers Magazine
• /
• v.184 no.12
• /
• pp.41-46
• /
• 1997

본 시스템은 전기사용상태에서 컴퓨터를 통하여 변압기를 상시 감시할 수 있는 진단방법으로 절연유열화센서를 이용한 열화측정용 진단시스템으로서 절연유속에 절연유열화센서를 설치하고 DC2kV 전압을 센서 양단에 인가한 후 누설전류를 nA단위로 측정하고 현재온도 상태를 측정하여 이 신호를 진단장치에서 A/D변환, 증폭, 제어하여 컴퓨터로 전송함으로써 파형감시, 데이터저장, 분석, 진단결과 분석기록표 출력 등이 가능하며 이 데이터를 이용하여 절연유의 열화정도를 예측하거나 판정할 수 있다.

• Proceedings of the KIEE Conference
• /
• 2011.07a
• /
• pp.1197-1198
• /
• 2011

발전기 여자시스템(Excitation System)은 동기발전기의 계자권선에 직류전류를 공급하고 계자전압을 조정하여 발전기의 전압 및 계통의 무효전력을 제어하는 기능을 수행한다. 본 논문에서는 발전기 여자시스템의 모델링 기법과 현장 운전데이터를 이용한 여자시스템의 모델링 결과들을 기술하였다.

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.15 no.4
• /
• pp.205-209
• /
• 2015

The economic losses resulted from the accident in the power cables at the power station is not only huge but also requires a great amount of time and expenses to restore to the former condition. In order to prevent these, it is necessary to invent and apply a technique to expect and prevent the accidents. In order to measure insulation resistances of power cables in operation, we derived the relations between load current and temperature. By analyzing data obtained from our measuring equipments, we showed the expected time to change deteriorated cables before accident occurs. We present a result of our study on the effects of the load current on lifetime of 6.6 kV cable systems in operation. With the current flowing through the load of the cable a heat is generated reducing the lifetime of the cable. In order to find out the effect of load current on the lifetime of cable systems, we applied the lifetime theory to the development of two equipments to measure insulation resistance and current of cable systems in operation.

• Journal of the Korean Magnetics Society
• /
• v.14 no.3
• /
• pp.109-113
• /
• 2004

GMR isolator was modeled using a Wheatstone bridge which is profitable for transmitting rectangular wave digital data, and the output voltage characteristics in relation to the input current were investigated in time domain. GMR isolator modeling was divided into two parts, namely magnetic and electric parts. The flow chart of the modeling was drawn in which measured MR curve of the spin valves were incorporated to obtain the electrical voltage output. For magnetic modeling, 3-dimensional model of planar coil was analyzed by FEM method to obtain the magnetic field strength corresponding to the input current. For electric modeling, resistance, inductance and capacitance of the planar coil were calculated and magnetic field waveform was obtained corresponding to the coil current waveform in time domain. Finally, MR-H curves of spin valves and the magnetic field waveform at the spin valves were composited to obtain the output voltage waveform of the isolator. Even though the amplitude of the coil current waveform was increased by 100％, decreased by 90％, or delayed by 10％ of the period compared with the input current, similar transmitted output voltage waveform to the input current waveform was obtained due to hysteretic characteristics of the spin valves at the transmission speed of over 400 Mbit/s.

• Proceedings of the KIEE Conference
• /
• 2015.07a
• /
• pp.876-877
• /
• 2015

전동기의 고장 진단을 함에 있어 데이터의 수집은 필수적으로 이루어 져야 하며 데이터를 수집하는 과정에서 데이터의 손상이나 손실을 없애기 위해 어플리케이션을 만들었다. 제작한 어플리케이션은 모터의 전압과 전류, 소음과 진동을 실시간으로 측정 할 수 있으며, 고장 여부를 판단 할 수 있도록 파일로 저장 가능하게 만들었고, 저장하는 과정에서 데이터가 손실 되지 않도록 버퍼를 사용하였다. 더 효율적으로 측정이 가능하도록 하여 전동기의 고장 진단에 있어 확실한 데이터를 얻을 수 있도록 연구하였다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2016.10a
• /
• pp.674-675
• /
• 2016

원자번호 22번에 해당하는 티타늄(titanium)은 매우 단단하며 가볍고, 부식에도 강한 금속이다. 티타늄은 비슷한 강도의 강철에 비해서 가볍고 알루미늄 합금에 비해 2배나 강력하다. 뿐만 아니라 티타늄은 바닷물에도 부식되지 않아 선박이다 해양플랜트 산업에서 많이 쓰이는 금속이기도 하다. 본 연구는 해양플랜트 건설 사업에 쓰이는 티타늄 용접에 대한 모니터링 시스템을 연구하는데 있다. 티타늄 용접공정에 사용되는 용접 파라메타는 용접 전압, 전류, 용접 토치의 위빙속도 및 와이어 공급 속도로 선정하였으며, 이러한 용접 파라메타를 계측할 수 있는 MCU 기반의 계측 보드를 설계하여 TCP/IP 통신을 기반으로 원격지로 용접 데이터를 전송하도록 하였으며, 이러한 데이터를 실시간으로 데이터를 그래프로 표현하도록 개발하였다. 이러한 용접 데이터에 대한 모니터링을 통하여 용접 시 발생하는 다양한 현상을 파악할 수 있도록 하였다. 본 연구를 통해서 티타늄 용접 시 발생하는 각종 데이터를 실시간으로 모니터링 할 수 있도록 개발하였으며, 데이터베이스에 저장된 기록을 통해서 용접 시 발생한 전체적인 용접 과정을 날짜와 시간별로 저장하여 용접과정에서 발생하는 전 과정을 관리할 수 있도록 하여 어떤 부분에서 잘못된 용접이 발생했는지 파악할 수 있음을 확인하였다.

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.44 no.1
• /
• pp.45-50
• /
• 2007

This paper proposes a low power selective data write (SDW) scheme for a phase-change random access memory (PRAM). The PRAM consumes large write power because large write currents are required during long time. At first, the SDW scheme reads a stored data during write operation. And then, it writes an input data only when the input and stored data are different. Therefore, it can reduce the write power consumption to a half. The 1K-bit PRAM test chip with $128{\times}8bits$ is implemented with a $0.8{\mu}m$ CMOS technology with a $0.8{\mu}m$ GST cell.