• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.04a
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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.

• Journal of Mechanical Science and Technology
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• v.14 no.3
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• pp.314-319
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• 2000

Back-face strain compliance (BFS compliance) for the four-point bend specimen has been calibrated for various crack length ratios. Finite element technique was employed to simulate four-point loading and calculate back-face strain of the bend specimen. The numerically determined strain variation along the back face indicates that the sensitivity to gage placement increases with crack length and back-face strain at the gage length less than O.2W, where W is the width of the bend specimen, can be measured within 5% deviation of the maximum BFS. Non-dimensional back-face strain compliance, -E'BCW, was calibrated with FE analysis and experiment. The experimentally determined compliance indicates good agreement with the numerical compliance and can be expressed as a function of crack length ratio.

• 한국정보디스플레이학회:학술대회논문집
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• 2003.07a
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• pp.551-554
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• 2003

A novel geometric solution for uniform bend transition in a pi cell has proposed. In order to obtain the uniform bend transition, we applied hybrid domain structure to the edge of a LC cell by using ion-beam alignment method. As a result, we confirmed that the uniform bend transition has arisen from the edge to the center. From the proposed structure, we expect that the reliable and uniform bend transition can be achieved in the pi cell.

• Proceedings of the KSME Conference
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• 2000.11b
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• pp.627-632
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• 2000

Developing turbulent flows in a rotating 90 degree bend with square cross-section were measured by a hot-wire anemometer. The six orientation hot-wire technique was applied to measured the distributions of 3 mean velocities and 6 Reynolds stress components. Effects of Coriolis and centrifugal forces caused by the curvature and rotation of bend on the mean motion and turbulence structures were experimentally investigated Productive addition of Coriolis and centrifugal forces to the outward radial direction in the entrance region of bend increases the secondary flow intensity according to the rotational speeds. However, after 45 degree of bend, centrifugal force due to the rotation of bend may promote the break down of counter rotating vortex pair into multi-cellular pattern, thereby decreasing the production rate of turbulence energy and Reynolds stresses.

• Proceedings of the KSME Conference
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• 2001.11b
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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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• v.8 no.4
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• pp.5-9
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• 2007

We demonstrate an optically compensated bend (OCB) cell with pixel-isolating polymer wall. The polymer wall is formed by anisotropic phase separation of LCs and UV-curable polymer. The fabricated cell is initially in ${\pi}-twisted$ state so that it shows uniform and fast bend transition without any transition nucleus. The proposed cell has lower driving voltage than conventional OCB cell. Also, the polymer wall provides mechanical stability, hence preventing distortion of display image from external pressure.

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.3
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• pp.734-746
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• 1990

Velocities and Reynolds stresses in 3-dimensional turbulent flow in rectangular ducts with a 180.deg. bend were measured by hot wire anemometer. Slant wire was rotated to 4 directions and I type wire was rotated to 2 directions and the voltage outputs of them were combined to obtain the mean velocities and Reynolds stresses. Flow characteristics in the 1.5:1 and 2:1 cross secioned 180.deg. bend were measured and the results were compared with the data from Moon for the square sectioned 180.deg. bend flow. Flows in rectangular sectioned 180.deg. bend show the reduction in secondary flow and therefore the reduction of double maximum in local mean velocities.

• 한국연소학회:학술대회논문집
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• 1998.10a
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• pp.91-101
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• 1998

The effect of secondary flow on both methane/air and propane/air premixed flame was investigated experimentally. By changing the radius of curvature, various flame behavior was observed. In the V-bend nozzles, flame surface is deformed from axisymmetry. As the exit velocity increased, flame lifted off partially. When the radius of curvature of the V-bend increased, the region where premixed flame is entirely on the rim increased. Since the axial velocity field is changed due to the secondary flow effect, comparison of V-bend and straight tube with the same diameter shows larger V-bend nozzle exit velocity for both flash back and flame blowout. The flame characteristics are mapped with a equivalence ratio, a velocity, and a nozzle radius of curvature. To identify physical reasoning on the flame surface deformation, numerical calculations are conducted. OH radical distributions in flames are visualized by PLIF technique.

• Proceedings of the SAREK Conference
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• 2007.11a
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• pp.558-563
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• 2007

Detached Eddy Simulation(DES) is performed for turbulent flow of the $270^{\circ}$ bend at a Reynolds number of 56,690. A Fine grid generation is used near a wall in order to satisfy the wall boundary condition of y+<1. Turbulence models adopted for DES and Reynolds Average Navier Stokes(RANS) simulation are SST(Shear Stress Transfort) model. Solutions for both streamwise and circumferential velocity components are compared with the experimental data by Lee for $270^{\circ}$ bend and by Chang for $180^{\circ}$ bend.

• Journal of Information Display
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• v.5 no.2
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• pp.39-42
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• 2004

A novel fast-switching LCD with dual-domain bend (DDB) mode is described. DDB alignment is achieved using antiparallel-rubbed cell filled with chiral-doped LC. Initial alignment is mono-domain 180-degree twist. Tilt direction is controlled by oblique electric field to be counter direction in each domain. Twist-to-DDB deformation occurs continuously so that DDB mode does not require high-voltage initialization which is inevitable in Optically Compen sated Bend (OCB) mode. DDB gives wide and symmetric viewing angle in contrast to mono-domain bend formed from 180-degree twist showing strong asymmetry.