• Proceedings of the KIEE Conference
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• 2009.04b
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• pp.3-5
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• 2009

교류 자기장의 정밀측정, 자기장 측정기의교정 및 관련 시험 등 을 지원하기 위해 교류자기장 표준장치를 개발하였다. 주파수에 따른 확장분확도(expanded uncertainty, 2 $\sigma$)는 1 MBz 이하에서 0.16 %, 1 kHz $\sim$ 5 kHz 에서 0.26 %, 5 kHz $\sim$ 20 kHz에서 0.44 % 이었다. 측정결과에 대한 국제적 신뢰성 및 상호인증을 확보하기 위하여 핵심측정표준 국제비교(international key comparison)에 참여하였으며, 또한 측정능력, 교정 및 시험방법 등에 대한 국제적 전문가로부터 평가(peer review)를 수감하였다. 따라서 한국표준과학연구원 (KRISS)에서 교정 및 측정한 결과에 대해서는 국제적 상호인증을 받을 수 있다.

• The Korean Journal of Physiology and Pharmacology
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• v.2 no.3
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• pp.385-393
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• 1998

Human neutrophil elastase (HNElastase, EC 3.4.21.37), a causative factor of inflammatory diseases, was purified by Ultrogel AcA54 gel filtration and CM-Sephadex ion exchange chromatography. HNElastase was inhibited by phenylbutazone in a concentration dependent manner up to 0.4 mM, but as the concentration increased, the inhibitory effect gradually diminished. Binding of phenylbutazone to the human neutrophil elastase caused strong Raman shifts at 200, 440, and 1194 $cm^{-1}$. The peak at 1194 $cm^{-1}$ might be evidence of the presence $of\;-N=N-{\Phi}$ radical. The core area of the elastase, according to the visual molecular model of human neutrophil elastase, was structurally stable. A deeply situated active center was at the core area surrounded by hydrophobic amino acids. Directly neighboring the active site was one positively charged atom and two atoms carrying a negative charge, which enabled the enzyme and the drug to form a strong interaction. Phenylbutazone may form a binding, similar to a key & lock system to the atoms carrying opposite charges near the active site of the enzyme molecule. Furthermore, the hydrophobicity of the surrounding amino acid near the active site seemed to enhance the binding strength of phenylbutazone. Binding of phenylbutazone near the active site may cause masking of the active site, preventing the substrate from approaching the active site and inhibiting elastase activity.

• The Transactions of the Korean Institute of Power Electronics
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• v.2 no.4
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• pp.36-44
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• 1997

For high performance ac drives, the speed sensorless vector control and the stator flux orientation concept have received increasing attention. This paper describes a speed and flux sensorless vector-controlled induction machine(IM) drive based on the stator flux-oriented control. To improve the accuracy and operating range, the control system employs the previously presented speed and flux estimation methods, and then we present a developed method of estimating the speed of IM. In the proposed method all differential and integral terms have been eliminated by giving a very fast, low-cost, effective and practical alternative to the methods currently available. The effectiveness of the proposed method is verified by simulations and experimental results.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.614-615
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• 2007

There are roughly a hundred types of cables in power plants. The distribution of circuits in a nuclear plant is comprised of 20% instrument cables, 61% control cables, 13% AC power cables, 1% DC power cables, and 5% communication lines. In the nuclear power plant, medium voltage cables are generally included in the scope of systems reviewed for safety and are included in a plant's maintenance program. Medium voltage cables provide power to many critical components in plants, including feed water pumps, circulating water pumps, and condensate pumps. Among these cables, high temperature sections of cables feeding electrical power to the circulating water pump and the condenser extraction pump were found. The evaluation for these cables is performed to find the maximum allowable current and temperature. The result shows that the load current flowed about 85% of the allowable current ampacity, and the temperature of conductor at full load current did not exceed the limited temperature. Therefore, existing cables for circulating water pump and condenser extraction pump system are going to be used during design life.

• Journal of Electrical Engineering and Technology
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• v.8 no.4
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• pp.752-759
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• 2013

This paper proposes a method for fault diagnosis and fault-tolerant control of DC-link voltage sensor for two-stage three-phase grid-connected PV inverters. Generally, the front-end DC-DC boost converter tracks the maximum power point (MPP) of PV array and the rear-end DC-AC inverter is used to generate a sinusoidal output current and keep the DC-link voltage constant. In this system, a sensor is essential for power conversion. A sensor fault is detected when there is an error between the sensed and estimated values, which are obtained from a DC-link voltage sensorless algorithm. Fault-tolerant control is achieved by using the estimated values. A deadbeat current controller is used to meet the dynamic characteristic of the proposed algorithm. The proposed algorithm is validated by simulation and experiment results.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.12 no.4
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• pp.81-89
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• 1998

In the field of industrial drives, the vector control of the induction motor has been widely used to achieve the good control performance. In this paper, to require the information of rotor flux in direct vector control scheme, the flux observer by current model of rotor circuit is used. This flux observer is not only available at low-speed region bt good for the error reduction by feedback properties. Also, employing the flux observer on rotor reference frame, the robustness of decoupling control to the observation of rotor flux can be achieved. Through digital simulation and DSP-based IGBT inverter system, the validity for practical implementation is verified.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.17 no.4
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• pp.50-56
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• 2003

It is well known that a partial-discharge(PD) in insulation oil is the source of various physical and chemical phenomena, such as heat, light, gas, chemical transformation, electric current, electromagnetic radiation and ultrasonics. The PD can be detected by measuring one of these changes. Although some techniques are employed in this purpose, several obstacles interfere with an on-line measurement. Ultrasonic-wave detection is a useful method for the diagnosis of the transformer-insulation condition. Conventionally, ulyrasonic waves are detected by Piezo-electric transducer, but we use optical method that has many advantages. In this paper, we constructed a Mach-Zehnder interferometer with optical fiber and investigated the principle of operation. Test arrangement is based on the needle-plane electrode system in oil and applied AC high voltage. Ultrasonic waves were detected and analyzed with wavelet transform.

• Journal of the Korean Society of Safety
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• v.19 no.1
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• pp.56-59
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• 2004

In this paper, we investigated the influence of gap length and tip radius on breakdown of mineral based insulation oil. Applied voltages were DC and AC voltage. Electrode system was needle-plane structure. The tip radius of needle electrode was 5, 10, 20 and 25${\mu}m$, respectively. We measured breakdown voltage for each of tip radius with increasing electrode gap, 2mm to 12mm. Electric breakdown strength at tip was calculated using Mason's equation contained geometric figure. As gap length increased, breakdown strength increased linearly. But, as tip radius of needle increased, breakdown strength decreased exponentially. It can be explained by the phenomenon that electron is easily injected, as tip radius increases, and effective work function decreases. When appling DC voltage, breakdown strength was higher when polarity of needle was negative than positive. It is because of the space charge effect in accordance with the influence of liquid motion.

• Proceedings of the Korea Information Processing Society Conference
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• 2014.11a
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• pp.333-335
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• 2014

스마트폰의 보급에 따라 사용자간에 공유되는 정보가 점점 늘어나고 있다. 시간표 관리 시스템의 경우 과거에는 개별 사용자의 시간표를 관리하는 것이 주요 기능이었으나, 사용자간의 시간표를 비교함으로써 공통으로 가능한 비어있는 시간을 찾는 등 공유 기능에 대한 필요성이 증대되고 있다. 본 논문에서는 이화여대 학생들에게 특화된 편의성과 공유기능을 제공하는 시간표 관리 어플리케이션과 서버 프로그램을 설계하고 개발한다. 제공되는 편의성으로는 사용자가 자신의 시간표를 직접 입력하는 것이 아니라 이화 포탈(eportal.ewha.ac.kr)에서 내 시간표 정보를 자동으로 바로 받아 볼 수 있는 기능과 관련 교과목의 담당교수와 강의실 등의 추가적인 정보가 같이 저장되도록 하여 시간표 작성 시간이 획기적으로 줄일 수 있도록 한다. 또한 모든 사용자가 계정을 등록하여 타 사용자와 함께 듣는 수업과 공강 시간을 자동으로 계산해서 보여주는 공유 기능을 제공한다. 사용자 피드백을 통한 본 논문에서 개발된 시스템을 평가한 결과 편의성과 공유 기능에 만족함을 확인하였다.

• The Transactions of the Korean Institute of Power Electronics
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• v.12 no.2
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• pp.131-138
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• 2007

In this paper, a novel nonlinear control method of the CVCF(constant voltage and constant frequency) output voltage for the three-phase PWM inverter with LC output filters is proposed. A nonlinear modeling including the output LC filters is linearized by feedback linearization theory, the controllers of which can be designed based on a linear control theory. It is applied to the DC/AC power conversion of the PWM inverter for stand-alone wind power generation system. It has been verified by the experimental results that the proposed control scheme gives high dynamic responses at load variation as well as a zero steady-state error.