• Proceedings of the KIPE Conference
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• 1998.10a
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• pp.998-1002
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• 1998

The electronic fluorescent lamp ballast can promote the lighting efficiency up to 10-20% by driving high frequency with frequency transformation technique, and can completely eliminate the flickering phenomenon occurring from 60Hz frequency. The electronic ballast provides very high energy saving effects for it has high power factor than traditional ballast, and it is convenient to use, can extend the life cycle of fluorescent lamp for it starts at once by driving with high frequency. However electronic ballast needs high price, and it has the bad stability and reliability. This paper provides illumination systems, which drive dozens of fluorescent lamps at the same time, to overcome these shortcomings of electronic ballast and utilize the advantage of electronic ballast.

• Proceedings of the KIPE Conference
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• 2002.07a
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• pp.763-768
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• 2002

In this paper digitally based excitation systems for the synchronous brushless generators are presented. System configuration, control functions with their structure functions are also shown. The control system has two feedback loops: main one based on a generator's voltage with digital controller and inner one based on excitation voltage of the exciter with analog controller. Usually the generator regulation of voltage Is made with transducers for the voltage measurement. This paper shows technique of measuring the voltage without harmonics affect, using Park's equation transformation.

• Proceedings of the KIPE Conference
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• 2010.07a
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• pp.174-175
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• 2010

본 논문에서는 wavelet 변환을 이용하여 태양광 발전 시스템의 외란을 측정하는 방법을 연구하였다. MLD(Multi-Level Decomposition) 기법을 이용하여, 계산량이 적으면서도 빠른 시간내에 외란의 종류와 크기를 알아낼 수 있다. Wavelet 이론 소개와 컴퓨터 모의실험, DSP 제어기를 이용한 실험 결과로서 본 연구의 타당성을 입증하였다.

• Journal of Power System Engineering
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• v.9 no.4
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• pp.90-95
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• 2005

The wire-arc process is a low-cost thermal spray method simply utilizes electrical energy to melt the feedstock wire. It is more userful for field applications, especially to coat large surface area. In this paper, a special Fe-based alloy coatings by using the wire-arc process were developed. Nanoscale composite coatings were achieved either during spraying or through a post heat treatment. As-sprayed Fe-based alloy coatings had been an amorphous matrix structure, after heating to $700^{\circ}C$ for 10 minutes a solid state transformation occurred in the some fraction of amorphous matrix which resulted in the formation of nanostructured recrystallized phase. Scanning electron microscopy (SEM) and field emotional scanning electron microscope(FE-SEM) were applied to analyze the microstructure of the coatings. Additionally hardness and bend resistance of the Fe-based alloy coatings were examined, and these results were compared with those of partially stabilized zirconia(PSZ) coatings by using the plasma spray process.

• Journal of Power System Engineering
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• v.3 no.3
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• pp.14-21
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• 1999

The wave nature of heat conduction has been developed in situations involving extreme thermal gradients, very short times, or temperatures near absolute zero. Under the excitation of a periodic surface heating in a finite medium, the hyperbolic and parabolic heat conduction equations and the damped wave equations in heat flux are presented for comparative analysis by using the Green's function with the integral transform technique. The Kummer transformation is also utilized to accelerate the rate of convergence of these solutions. On the other hand, the temperature distributions are obtained through integration of the energy conservation law with respect to time. For hyperbolic heat conduction, the heat flux distribution does not exist throughout all the region in a finite medium within the range of very short times(${\xi}<{\eta}_l$). It is shown that due to the thermal relaxation time, the hyperbolic heat conduction equation has thermal wave characteristics as the damped wave equation has wave nature.

• Journal of Electrical Engineering and information Science
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• v.2 no.4
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• pp.59-65
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• 1997

In this paper, a general fuzzy syntactic method for recognition of flaw patterns and for the measurement of flaw characteristic parameters for a non-destructive inspections signal, called eddy-current, is presented. Solutions are given to the subtasks of primitive pattern selection, signal to symbol transformation, pattern grammar formulation, and event-synchronous flaw pattern extraction based on the grammars. Fuzzy attribute grammars are used as the model for the pattern grammar because of their descriptive power in the face of uncertain constraints caused by nose or distortion in the signal waveform, due to their ability to handle syntactic as well as semantic information. This approach has been implemented and the performance of eh resultant system has been evaluated using a library of law patterns obtained from steam generator tubes in nuclear power plants by an eddy current-based non-destructive inspection method.

• Laser Solutions
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• v.3 no.3
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• pp.39-45
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• 2000

The volume and depth of the craters produced on silicon samples during high power laser ablation show a strong nonlinear change as the laser irradiance increases across a threshold value, approximately 2.2$\times$10$\^$10/ W/㎠. Time-resolved shadowgraph images of the ablation plume reveal the ejection of large particulates from the sample for laser irradiance above the threshold, with a time delay of about 300-400 ㎱. The numerically estimated thickness of the superheated liquid layer, considering the transformation of liquid metal into liquid dielectric near the critical state, agrees with the measured agrees with crater depths. It is suggested that a phase explosion of the deep superheated liquid layer near the critical state is responsible for the measured sudden increase of crater volume and the ejection of large particulates.

• Nuclear Engineering and Technology
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• v.29 no.6
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• pp.433-443
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• 1997

In this work, an analytic approach to the dependability of software in the operational phase is suggested with special attention to the hardware fault effects on the software behavior : The hardware faults considered are memory faults and the dependability measure in question is the reliability. The model is based on the simple reliability theory and the graph theory which represents the software with graph composed of nodes and arcs. Through proper transformation, the graph can be reduced to a simple two-node graph and the software reliability is derived from this graph. Using this model, we predict the reliability of an application software in the digital system (ILS) in the nuclear power plant and show the sensitivity of the software reliability to the major physical parameters which affect the software failure in the normal operation phase. We also found that the effects of the hardware faults on the software failure should be considered for predicting the software dependability accurately in operation phase, especially for the software which is executed frequently. This modeling method is particularly attractive for the medium size programs such as the microprocessor-based nuclear safety logic program.

• KEPCO Journal on Electric Power and Energy
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• v.6 no.1
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• pp.1-5
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• 2020

사물인터넷, 인공지능, 로봇공학, 증강현실, 가상현실과 같은 고급 기술의 융합과 사용자 행동의 변화가 미래 사업의 모습을 다시 만들고 있다. 기업이 어떻게 잠재적 변화, 작업 공간의 설계, 업무의 정의, 업무 절차를 인식하느냐가 기업이 경쟁 우위를 갖게 하는 데 도움이 되는 중요한 요인이다. Frost & Sullivan은 사회적 진화, 미래에도 견고한 사업 모델, 기술 혁신 등 미래 사업의 모습을 만들어갈 3개의 중요한 동인을 찾아냈다. 실제 작업 공간에서 작업자와 기계의 융합, 사람과 공간의 융합과 같은 트랜드가 사이버 작업 공간에 일어날 것으로, 이를 통해 점진적으로 사업과 업무의 미래 모습을 만들 것이다. 하지만 디지털 전환을 받아들이는 와중에 기업은 숙련된 인력의 부족, 기술의 정렬, 직원 반발, 사이버 보안, 조직 구조와 사고 방식 등과 같은 문제를 해결해야만 한다. 이런 문제들을 해결하기 위해 SHARED 방법론이 기술 수용과 업무 절차 개선에 관심이 있는 기업을 위한 가이드라인 역할을 할 수 있다. 시장에서 성공하기 위해 기술 솔루션 제공자(Technology Solution Provider)는 서비스 제공자로서 역할을 계속하는 동시에, 고객에게 인력 관리 솔루션의 필요성을 교육해야 한다. 기술 솔루션 제공자는 디지털 전환 과정에서 기업과 동반할 믿음직한 조언자이자 장기적 파트너에 기초한 사업 관계를 구축해야만 한다.

• Proceedings of the KIEE Conference
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• 1998.07a
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• pp.79-81
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• 1998

STATCOM can compensate industrial load's reactive power and filter the harmonic of nonlinear load's with the rapid dynamic response. In this paper, STATCOM is modelled to synchronous rotating coordinate by circuit dq transformation, and space vector PWM method is applied for broad voltage modulation. Also predict current controller is used for harmonic current filtering.