• Elastomers and Composites
• /
• 제46권1호
• /
• pp.54-59
• /
• 2011

점탄성 흐름의 특성은 압출시 다이 스웰 현상에서 확인 할 수 있다. 본 연구는 이러한 점탄성 특성을 갖는 고무 컴파운드를 모세관 다이에서 비선형 점탄성 모델인 PTT 모델과 간략화된 점탄성 모델을 이용하여 압출현상을 모사하고 다이 스웰을 실험과 비교 하였다. 실험은 Fluidity Tester를 이용하였고 해석은 상용화된 CFD Code인 Polyflow를 이용하였다. 두 모델에 의해 예측된 다이 스웰은 실험과 유사한 결과를 보였다. 그러나 PTT 모델에서는 압력과 속도분포, 레저버의 모서리에서의 와류현상을 예측할 수 있었지만 간략화된 점탄성 모델에서는 예측할 수 없었다. 간략화된 점탄성 모델은 다이 내부의 세밀한 흐름현상을 예측하지는 못하지만 다이 스웰은 잘 예측할 수 있으며 PTT모델보다 해석시간이 매우 짧아서 이의 응용에 큰 장점을 갖고 있다고 판단된다.

• 한국해양공학회지
• /
• 제18권6호
• /
• pp.8-15
• /
• 2004

Wave power distribution is investigated to determine the optimal sites for wave power generation at Jeju sea which has the highest wave energy density in the Korean coastal waters. The spatial and seasonal variation of wave power per unit length is calculated in the Jeju sea area based on the monthly mean wave data from 1979 to 2002 which is produced by the SWAN wave model simulation in prior research. The selected favorable locations for wave power generation are compared in terms of magnitude of wave energy density and distribution characteristics of wave parameters. The results suggest that Chagui-Do is the most optimal site for wave power generation in the Jeju sea. The seasonal distribution of wave energy density reveals that the highest wave energy density occurs in the northwest sea in the winter and it is dominated by wind waves, while the second highest one happens at south sea in the summer and it is dominated by a swell sea. The annual average of wave energy density shows that it gradually increases from east to west of the Jeju sea. At Chagui-Do, the energy density of the sea swell sea is relatively uniform while the energy density of the wind waves is variable and strong in the winter.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2002년도 하계학술대회 논문집 B
• /
• pp.657-659
• /
• 2002

Power quality refers to voltage quality and current quality. Voltage quality means supply reliance such as voltage sag, voltage swell. and short-time interruption. Current quality is related to power factor, harmonic distortion, negative-sequence and zero-sequence current. We fabricated Customer STATCOM to improve current quality such as reactive power, harmonic distortion, and load imbalance. In this paper. We summarize the spec, of STATCOM. its hardware configuration, and control system.

• 한국지반공학회지:지반
• /
• 제6권1호
• /
• pp.15-24
• /
• 1990

This paper describes the results of study on major factors influencing time-dependent deformation behaviour of swelling shales. The study was carried out by analyzing all the swell test results available for shales from southern Ontario. Major factors studied are (1) the presence of ambient water, (2) calcite content and (3) the applied stress. The results of the study on seven shales show that the swelling of shale is associated with the formation of cracks and the absorption of water in these cracks. The magnitude of swelling potential is related linearly to the amount of absorbed water. The presence of calcite inhibits the swelling of shales studied, reducing the swelling to zero at about 30% of calcite content. All the shales studied exhibit the stress-dependent swelling behaviour, though there Is a difference in the degree of dependency.

• 유변학
• /
• 제2권2호
• /
• pp.35-44
• /
• 1990

자유표면 유동을 수반하여 복잡한 구조를 지나는 유동문제를 수치모사할 수 있는 삼차원 유한요소법코드를 개발하였다. 정사각관을 대상으로 하는 삼차원 압출팽창 문제를 등온 뉴톤 유동뿐만아니라 비뉴톤유동 및 비등온 유동문제의 경우까지 다룰수 있도록 확장 하여 수치모사하였다. 삼차원 유한요소법 알고리듬에 pathline approach 방법과 사상방법을 적용시켜 등온 뉴톤 유체의 미동흐름에 대하여 압출 팽창문제를 푼 결과 팽창비가 대칭면에 서 최대 21.0%관의 모서리 부분에서 최소 4.1%로 나타났다 전단박화현상이 있는 비뉴톤 유 동의 경우 뉴톤유동에 비해 팽창이 작게 일어났고 비등온 유동의 경우 관벽온도가 낮은 쪽 이 높은 쪽에 비해 팽창이 크게 일어남을 알수 있었다.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2001년도 추계학술대회 논문집 전기물성,응용부문
• /
• pp.84-86
• /
• 2001

Acrylonitrile Butadiene Rubber (NBR) has been used as a transformer gasket material because the transformer gaskets should have high resistivity to oil and should not swell and deform when it contact to insulating oils. Serious cracks were observed in the gaskets being used and ozone test was performed on new, specimens. Cracks were also observed on specimens. So we have performed the following tests on the anti-oxidants containing new gaskets according in accordance with KEPCO purchase specifications; ozone resistance, oil resistance, mechanical properties before and after aging.

• Geomechanics and Engineering
• /
• 제6권5호
• /
• pp.437-453
• /
• 2014

This paper studies the swelling and strength characteristics of unimproved and improved expansive soils in terms of the swell potential, swelling pressure, rate of secondary swelling, unconfined compressive strength and California bearing ratio (CBR). The admixtures used in this study are locally available cement and fly ash. The soils used in this study were taken from the Mae Moh power plant, Lampang Province, in northern Thailand. A conventional consolidation test apparatus was used to determine the swelling of the soil specimen. The optimum admixture contents are determined to efficiently reduce the swelling of unimproved soil. The rate of secondary swelling for unimproved soil is within the range of highly plastic montmorillonite clay, whereas the specimens improved with optimum admixture contents can be classified as non-swelling kaolinite. A soil type affects the swelling pressure. Expansive soil improvement with fly ash alone can reduce swelling percentage but cannot enhance the unconfined compressive strength and CBR. The strength and swelling characteristics can be predicted well by the swelling percentage in this study.

• 제어로봇시스템학회:학술대회논문집
• /
• 제어로봇시스템학회 1997년도 한국자동제어학술회의논문집; 한국전력공사 서울연수원; 17-18 Oct. 1997
• /
• pp.1348-1351
• /
• 1997

The federated Kaman filter(FKF) is being widely used in many multisensor navigatiion systems. It is know that the FKF has advantages of simplicity and fault-tolerance over other decentralized filter techniques. In this paper, optimal and suboptimal FKF configuratiions are mentioned and a covariance analysis technique for the suboptimal FKF is newly presented. The suboptimal FKF configuration, known as No-reset(NR) mode, has better fault tolerance capability than the optimal FKF coniguratioin. In the suggested technique, a suboptimal fusion process of FKF is considered a swell as suboptimal gains of local filters. An upper boun of error covariance for suboptimal FKF is derived. Also, it is mathematically shown that this bound is smaller thanexisting bound in the literatrue. A vehicle-navigaion system is designed using the FKF. In thissystem, a map constraing equation is introduced and used as a measurement equatioin of Kalman filter. Performance analysis is done by the suggested covariance analysis techniques.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2006년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
• /
• pp.244-246
• /
• 2006

This paper deals with an analysis of SCR thyristor switching pattern for a power quality disturbance generator with phase jump function. The proposed generator can be applied to the performance test of custom power devices. Voltage sag, swell, outage, unbalance and phase jump after outage are provided by the generator. The phase jump operating principle of the generator is described and analysed. Especially, a proper switching of the SCR thyristors for the proposed generator is important to guarantee the system reliability. Therefore the switching patterns for the thyristors in each made were analysed.

• 대한전기학회논문지:전력기술부문A
• /
• 제52권5호
• /
• pp.279-286
• /
• 2003

A new UPQC(unified power quality conditioner), which consists of series inverter, shunt inverter, dc/dc converter, and energy storage, is proposed. The proposing UPQC can compensate reactive power, harmonics, voltage sag and swell, voltage unbalance, and voltage interruption. The control strategy for the proposing UPWQC was derived using the instantaneous power method. The performance of proposing system was analyzed by means of the EMTDC/PSCAD simulation and the experimental work with the hardware prototype. The proposing UPQC has the ultimate capability of improving power quality at the point of installation on power distribution systems or industrial power systems and can be utilized for the custom power device in the future distribution system.