• 한국조명전기설비학회지:조명전기설비
• /
• 제11권2호
• /
• pp.110-118
• /
• 1997

본 논문은 DSP를 이용한 주상변압기 유전정접($tan\;delta$) 활선 측정기법을 제안하였다. 변압기 내부에 콘덴서를 삽입한 후 센서에 전압을 인가하고, 인가된 전압과 콘덴서에 흐르는 전류를 측정하여 본 논문에서 제안한 상호 상관 함수 기법을 이용하여 유전정접을 구하였다. 측정의 성능 향상을 위해 TMS320C31 DSP 보드를 사용하였으며 상호 상관 함수 기법을 사용하였다. 또한 노이즈 영향을 검토하기 위해 컴퓨터 시뮬레이션을 수행하였다. 본 연구의 검증을 위해 본 논문에서 구현한 측정장치와 Schering bridge을 사용하여 비고 실험을 하였다. 실험 결과 주상 변압기 절연진단에 충분히 활용할 수 있음을 알 수 있었다.

• 한국해양공학회지
• /
• 제33권4호
• /
• pp.358-363
• /
• 2019

The acoustic power is used as a primary index characterizing underwater sound sources and could be defined by its source level. The source level has been assessed using various experimental techniques such as the reverberation time method and reverberant tank plot method. While the reverberation time method requires reverberation time data extracted in a preliminary experiment in a reverberant water tank, the reverberant tank plot method only needs acoustic pressure data directly obtained at the reverberation water tank. In this research, these experimental techniques were studied in comparative experiments to estimate the source levels of underwater sources in a reverberant water tank. This paper summarizes the basic theories and procedures of these experimental techniques and presents the experimental results for an underwater source in a long cuboid water tank using each technique, along with a discussion.

• 지능정보연구
• /
• 제15권4호
• /
• pp.99-121
• /
• 2009

최근 데이터마이닝 기법을 이용하여 기업의 부실을 예측하고자 하는 연구가 많이 이루어져 왔다. 여러 연구자들에 의해 다양한 데이터마이닝 기법이 연구되었으나 각 방법론이 장단점을 가지고 있기에 이를 보완적으로 사용하고자하는 결합기법에 대한 연구도 꾸준하게 발표되고 있다. 본 연구에서는 데이터마이닝 기법을 각 기법의 특성을 바탕으로 4가지 형태로 구분하고 각 형태의 대표적인 기법을 선택하여 이를 유전자알고리즘을 통하여 통합하는 기법을 제안한다. 유전자알고리즘은 전역최적화기법으로 다양한 기법의 결과를 유기적으로 통합하여 최적해 또는 유사최적해를 찾게 해 줄 것이다. 본 연구에서는 기업부실예측에서 유용한 모형을 찾기 위하여 단일모형, 기존의 통합모형과 본 연구에서 제안하는 유전자알고리즘 통합기법의 결과를 비교한다.

• International Journal of Advanced Culture Technology
• /
• 제5권3호
• /
• pp.40-45
• /
• 2017

This data mining technique was used to extract useful information from percutaneous coronary intervention data obtained from the US public data homepage. The experiment was performed by extracting data on the area, frequency of operation, and the number of deaths. It led us to finding of meaningful correlations, patterns, and trends using various algorithms, pattern techniques, and statistical techniques. In this paper, information is obtained through efficient decision tree and cluster analysis in predicting the incidence of percutaneous coronary intervention and mortality. In the cluster analysis, EM algorithm was used to evaluate the suitability of the algorithm for each situation based on performance tests and verification of results. In the cluster analysis, the experimental data were classified using the EM algorithm, and we evaluated which models are more effective in comparing functions. Using data mining technique, it was identified which areas had effective treatment techniques and which areas were vulnerable, and we can predict the frequency and mortality of percutaneous coronary intervention for heart disease.

• Journal of Hydrospace Technology
• /
• 제2권2호
• /
• pp.24-35
• /
• 1996

This paper describes parameter identification techniques formulated for the estimation of maneuvering coefficients of a submerged body. The first part of this paper is concerned with the identifiability of the system parameters. The relationship between a stochastic linear time-invariant system and the equivalent dynamic system is investigated. The second is concerned with the development of the numerically stable identification technique. Two identification techniques are tested; one is the ma7mum likelihood (ML) methods using the Holder & Mead simplex search method and using the modified Newton-Raphson method, and the other is the modified extended Kalman filter (MEKF) method with a square-root algorithm, which can improve the numerical accuracy of the extended Kalman filter. As a results, it is said that the equations of motion for a submerged body have higher probability to generate simultaneous drift phenomenon compared to general state equations and only the ML method using the Holder & Mead simplex search method and the MEKF method with a square-root algorithm gives acceptable results.

• 설비공학논문집
• /
• 제16권4호
• /
• pp.349-354
• /
• 2004

Scale is formed when hard water is heated or cooled in heat transfer equipments such as heat exchangers, condensers, evaporators, cooling towers, boilers, and pipe walls. When the scale deposits in a heat exchanger surface, it is conventionally called fouling. The objective of the present study is to analyze the process of the fouling formation in a heat exchanger according to different types of water using visualization techniques. In order to experimentally investigate the formation of the fouling, this study built a lab-scaled heat exchanging system. Using the visualization techniques of Scanning Electron Microscopy (SEM) and X-Ray diffraction method, the three dimensional configurations of the fouling formation could be successfully obtained. Based on the experimental results, it was found that the configurations of the fouling formation were different when using tap water compared to river water.

• 해양환경안전학회지
• /
• 제26권3호
• /
• pp.254-261
• /
• 2020

Welding is the most convenient method for fabricating steel materials to build ships and of shore structures. However, welding using high heat processes inevitably produces welding displacements on welded structures. To mitigate these, heavy industries introduce various welding techniques such as back-step welding and skip-step welding. These techniques effect on the change of the distribution of high heat on welded structures, leading to a reduction of welding displacements. In the present study, various cases using different and newly introduced welding techniques are numerically simulated to ascertain the most efficient technique to minimize welding displacements. A numerical simulation using a finite element method based on the inherent strain, interface element and multi-point constraint function is introduced herein. Based on several simulation results, the optimal welding technique for minimizing welding displacements to build a general ship grillage structure is finally proposed.

• 전자통신동향분석
• /
• 제34권3호
• /
• pp.34-42
• /
• 2019

This study introduces artificial intelligence (AI) techniques for video generation. For an effective illustration, techniques for video generation are classified as either semi-automatic or automatic. First, we discuss some recent achievements in semi-automatic video generation, and explain which types of AI techniques can be applied to produce films and improve film quality. Additionally, we provide an example of video content that has been generated by using AI techniques. Then, two automatic video-generation techniques are introduced with technical details. As there is currently no feasible automatic video-generation technique that can generate commercial videos, in this study, we explain their technical details, and suggest the future direction for researchers. Finally, we discuss several considerations for more practical automatic video-generation techniques.

• 대한전자공학회논문지
• /
• 제27권12호
• /
• pp.1916-1924
• /
• 1990

In this paper attenuation effect on the measurement and the tomography of nonlinear parameter is discussed. We perform computer simulation with the method using harmonic components and the method using secondary wave components, and then estimate attenuation effect through the results and compare two measurement techniques. According to simulation result the attenuation effect is more intensive as large n and \ulcorner, and the degree of the attenuation effect is represented as error functions. In the aspect of measuremnet techniques, the method using secondary wave components is more insensitive to attenuation effect than the method using harmonic compnents. We obtain the same result in the nonlinear tomography, and show that the attenuation compensive filter is required because the whole tomogram is affected by frequency dependent attenuation(or nonlinear attenuation)

• Journal of Mechanical Science and Technology
• /
• 제15권9호
• /
• pp.1240-1247
• /
• 2001

A robust control design scheme using well-developed SISO techniques is proposed for maglev vehicles that are inherently unstable MIMO systems. The proposed separate control method has basically two control loops: a stabilizing loop by a pole-placement technique, and a performance loop using a novel optimal LQ loop-shaping technique. This paper shows that the coupling terms involved in maglev vehicles with multimagnets should not be neglected but compensated for their stability and performance robustness. The robustness properties of the proposed control system are then evaluated under variations of vehicle masses and air gaps through a computer simulation. This paper also describes the reason why the proposed control technique can be suggested as a tool using only SISO techniques in controlling unstable MIMO systems such as maglev vehicles.