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이찬용,김철환,최경민,박종열 경상대학교 농업생명과학연구원 2001 농업생명과학연구 Vol.35 No.-
접촉각(Contact Angle)이란 액체가 고체표면 위에서 열역학적으로 평형을 이룰 때 형성하는 각을 의미하며, 고체와 액체 사이에서 이루는 접촉각의 측정은 접착, 표면처리, 폴리머 표면 분석과 같은 많은 분야에서 잘 알려진 기술이다. 이러한 접촉각은 종이의 내수성에 대한 정밀한 예측을 가능하게 하는데 본 연구를 통하여 개발된 접촉각 자동 측정 시스템(AMS-2001)은 종이에 부여된 내수성을 종이 시료 상에 형성된 접촉각 측정을 통하여 정량화 할 수 있었다. 본 연구에서 개발한 AMS-2001을 이용하면 사이징 처리된 종이의 접촉각, 발수각, 액적의 폭, 지름, 표면장력 등을 측정할 수 있었고, 액적이 변화되는 모양을 디지털 화상을 통하여 추적할 수 있었으며 또한 기존의 Stockigt 실험 방법과 거의 유사한 재현성 및 신뢰성을 나타낼 수 있었다. The contact angle formed by a droplet of water used to estimate a repellency property of paper. The conventional systems measuring a contact angle are based on a manual measurement of the angle by a 3-point determination such as a far-left or far-right point, and a top point of a water droplet on a sample sheet. Thus the manual method to analyze a water repellency property can be greatly affected by an operator's bias. The new method to measure a sizing degree by a contact angle was developed using an automatic determination of 3-end point coordinates of the water droplet, which could diminish the operator's bias during measurement. The system could also quantify width and height of a water droplet, a surface tension of a solid specimen, and a time elapsed during complete absorption of water into a sheet. Finally, the values measured by the system were quite reproducible and reliable.
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Power Quality 向上을 위한 Wavelet Transform을 利用한 高調波 除去 技法에 관한 硏究
박성원,백진욱,강승호,김철환 成均館大學校 科學技術硏究所 1998 論文集 Vol.49 No.1
In recent years, electric power quality(PQ) has become an important issue in power systems. This is due to the fact that the usage of power electronics equipments and electronic-based loads which are sensitive to power quality disturbances has been increased. and thus normal operations in industrial and commercial facilities are becoming more vulnerable to the electric power quality disturbances. For improvement of power quality, this thesis presents a new approach to cancel the harmonic of canons types of lest is power quality disturbances using discrete wavelet transforms. This method is io decompose a given disturbance signal into other signals which represent a smoothed version and a detailed version of the original signal. The decomposition is performed using multiesolution signal decomposition techniques. The result shows that the discrete wavelet transform was able to detedct the electric power quality disturbances and to remove the harmonic of electric power quality disturbances.
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EMTP MODELS를 이용한 2차 아크 모델링 기법에 관한 연구
안상필,김병천,김철환 成均館大學校 科學技術硏究所 1998 論文集 Vol.49 No.2
The most frequent faults on overhead transmission lines are single-phase to ground arc faults in air. On HV/EHV lines, the single-phase autoreclosure is an effective means to clear the fault while retaining the system stability. For the improvement of an adaptive SPAR(Single-Phase Auto-Reclosure) and novel protection schemes, it is important to simulate arc faults. But, it is difficult to reproduce the real arc behaviour, i.e. the extinction phenomenon exactly by computer simulations due to extremely random behavior of secondary arc. For simplicity of simulation processing, a simulation language, called MODELS, is used. It has been added to the EMTP, which permits to interface control system with power system. This paper proposes a new computer modeling techniques for the primary and the secondary arc separately, which can be implemented with EMTP MODELS routine, and the the performance of the proposed model is simulated on a typical 154 [kV] korean transmission line system.
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