• 한국방재학회 논문집
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• 제7권2호통권25호
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• pp.65-71
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• 2007

본 연구는 만곡하천의 단면을 만곡률에 따라 1 2차원 수치해석을 실시하였다. 수치해석 결과 유 출입각에 따른 수위 편차가 발생하였으며, 홍수량 변동에 따른 편차가 증가하였다. 2차원 수치모형에 의한 수위편차를 보면 유 출입각 105도 일 때 홍수량 500CMS에서 최대경사가 6.67%가 나타났다. 우측은 90도를 초과하는 경우 1차원 수치모형과의 편차가 감소하였으며, 좌측의 수위는 105도를 초과하는 경우 1차원 수치모형과의 편차가 감소하는 것을 확인하였다. 이는 90도 이상의 만곡하천의 경우 수치해석보다는 수리모형실험을 통하여 검증하는 것이 바람직하겠다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 춘계학술대회 및 기술 세미나 논문집 디스플레이 광소자
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• pp.49-50
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• 2008

OCB mode has advantages such as fast response time and wide viewing angle. But it has inevitable shortcoming which initial splay state must be changed to bend state. To overcoming this problem, OCB cell filled LC with RM monomer was cured by UV when voltage applied. Through previously mentioned methods, even if electric field is none, bend state was made by stabilized LC director. In this paper, we investigated the electric characteristics of polymer stabilized OCB mode.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집B
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• pp.456-461
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• 2001

This paper depicts the weak shock wave propagating inside some kinds of pipe bends. Computational work is to solve the two-dimensional, compressible, unsteady Euler Equations. The second-order TVD scheme is employed to discretize the governing equations. For the computations, the incident normal shock wave is assumed at the entrance of the pipe bend, and its Mach number is changed between 1.1 and 1.7. The turning angle and radius of the curvature of the pipe bend are changed to investigate the effects on the shock wave structure. The present computational results clearly show the shock wave reflection and diffraction occurring in the pipe bend. In particular, the vortex generation, which occurs at the edge of the bend, and its shedding mechanism are discussed in details.

• Journal of Information Display
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• 제5권2호
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• pp.19-22
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• 2004

A ${\pi}$ cell is initially in splay state. Before driving a ${\pi}$ cell, transition from splay to bend state is always necessary which originates from nucleation. We propose a novel technique to make bend transition fast and effectively by forming transition cores around the pixels with the technique of multi-domain alignment, where domain boundaries play a crucial role in splay to bend transition. This noble technique enables the splay to bend transition to occur within less than 2 seconds with a low applied voltage.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2004년도 Asia Display / IMID 04
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• pp.1137-1141
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• 2004

In this paper, we have improved a novel ECB mode using bend structure with high tilt angle in the unique condition by Hot plate equipment. The new control of tilt angle for nematic liquid crystal (NLC) with negative and positive dielectric anisotropy on the rubbed homeotropic polyimide (PI) using baking method by Hot plate equipment was investigated. LC tilt angle decreased with increasing baking temperature and time. We suggest that the development of the novel ECB cell using control of tilt angle on the homeotropic surface is a promising technique for the achievement of fast response time and high contrast ratio.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2005년도 춘계학술대회 논문집
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• pp.237-243
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• 2005

항만의 계획 및 개발단계에서 중요한 요소 중 하나는 항로의 설계이다. 항로를 설계할 때 가능한 한 굴곡부를 피해야 하지만, 그렇지 못할 경우에는 변침과정에서 추가적으로 발생하는 항과면적의 증가를 고려하여 항로의 폭을 확장하고 항로를 배치하는 것이 선박의 안전한 통항에 필수적이다. 본 연구에서는 가변범퍼영역모델을 이용하여 굴곡부에서의 항로의 폭과 항로의 배치를 결정하는 기법을 다룬다. 모델실험결과 굴곡부 중심교각이 30도 미만인 경우 굴곡부 항로의 폭을 확장할 필요가 없는 것으로 분석되었으며, 굴곡부 중심교각이 60도 인 경우에는 대상선박이 길이와 굴곡부의 중심교각에 따라 항로의 폭을 확장해야 할 것으로 분석되었다.

• Wind and Structures
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• 제32권3호
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• pp.267-281
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• 2021

Bending-twisting coupling induced in big composite wind turbine blades is one of the passive control mechanisms which is exploited to mitigate loads incurred due to deformation of the blades. In the present study, flutter characteristics of bend-twist coupled blades, designed for load alleviation in wind turbine systems, are investigated by time-domain analysis. For this purpose, a baseline full GFRP blade, a bend-twist coupled full GFRP blade, and a hybrid GFRP and CFRP bend-twist coupled blade is designed for load reduction purpose for a 5 MW wind turbine model that is set up in the wind turbine multi-body dynamic code PHATAS. For the study of flutter characteristics of the blades, an over-speed analysis of the wind turbine system is performed without using any blade control and applying slowly increasing wind velocity. A detailed procedure of obtaining the flutter wind and rotational speeds from the time responses of the rotational speed of the rotor, flapwise and torsional deformation of the blade tip, and angle of attack and lift coefficient of the tip section of the blade is explained. Results show that flutter wind and rotational speeds of bend-twist coupled blades are lower than the flutter wind and rotational speeds of the baseline blade mainly due to the kinematic coupling between the bending and torsional deformation in bend-twist coupled blades.

• International Journal of Fluid Machinery and Systems
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• 제3권1호
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• pp.11-19
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• 2010

The performance of the crossover system of a centrifugal compressor stage consisting of static components of $180^{\circ}$ U-bend, return channel vanes and exit ducting with a $90^{\circ}$ bend is investigated. This study is confined to the assessment of performance of the crossover system by varying the shape of the return channel vanes. For this purpose two different types of Return Channel Vanes (RCV1 and RCV2) were experimentally investigated. The performance of the crossover system is discussed in terms of total pressure loss coefficient, static pressure recovery coefficient and vane surface pressure distribution. The experimentation was carried out on a test setup in which static swirl vanes were used to simulate the flow at the exit of an actual centrifugal compressor impeller with a design flow coefficient of 0.053. The swirl vanes are connected to a mechanism with which the flow angle at the inlet of U-bend could be altered. The measurements were taken at five different operating conditions varying from 70% to 120% of design flow rate. On an overall assessment RCV1 is found to give better performance in comparison to RCV2 for different U-bend inlet flow angles. The performance of RCV2 was verified using numerical studies with the help of a CFD Code. Three dimensional sector models were used for simulating the flow through the crossover system. The turbulence was predicted with standard k-$\varepsilon$, 2-equation model. The iso-Mach contour plots on different planes and development of secondary flows were visualized through this study.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2007년도 춘계학술대회 논문집
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• pp.302-305
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• 2007

The springback characteristics of AZ31B magnesium alloy sheet was investigated in OSU draw/bend test. Springback is the elastically-driven change of shape of a part after forming and it should be estimated and controlled to manufacture more precise products in sheet forming. The demands are increasing for magnesium alloy sheet press forming, but the study on its springback characteristics is insufficient. Strip draw/bend tests were conducted with various conditions - die radius, sheet thickness and controlled tensile force. The springback angles were measured from 'sidewall curl' of deformed shape. The tendency of springback angle was observed from the tests.

• 물과 미래
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• 제27권4호
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• pp.155-160
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• 1994

순간적인 밸브의 개폐 등에 의해 생성된 압력파가 관의 만곡부를 지날 때 만곡부에 미치는 힘은 변화한다. 본 연구에서는 이러한 힘의 변화량을 해석적으로 유도하였다. 본 해석에 의하면 힘의 변화량은 유체의 운동량 변화보다는 주로 정수압에 의해 결정되며, 압력파가 만곡각의 90$^{\circ}$ 이상인 만곡부를 지날 때에는 여기에 미치는 연직성분 힘의 방향이 바뀌는 것으로 나타났다.