• Proceedings of the KSME Conference
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• 2000.04b
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• pp.465-471
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• 2000

The flow characteristics around an elliptic cylinder with axis ratio of AR=2 located near a flat plate were investigated experimentally to study the interaction between the cylinder wake and the turbulent boundary layer. The pressure distributions on the cylinder surface and on the flat plate were measured with varying the angle of attack of the cylinder. In addition, the velocity profiles of wake behind the cylinder were measured using a hot-wire anemometry As the angle of attack increases, the location of peak pressure on the windward and leeward surfaces of the cylinder moves toward the rear and front of the cylinder, respectively. At positive angles of attack, the position of the minimum pressure on the flat plate surface is moved downstream, but it is moved upstream at negative angles of attack. With increasing the angle of attack, the vortex shedding frequency is gradually decreased and the critical angel of attack exists in terms of the gap ratio. By installing the elliptic cylinder at negative angle of attack, the turbulent boundary layer over the flat plate is disturbed more than that at positive incidence. This may be attributed to the shift of separation point on the lower surface of the cylinder according to the direction of the angle of attack.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.7
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• pp.976-983
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• 2000

The flow characteristics around an elliptic cylinder with axis ratio of AR=2 located near a flat plate were investigated experimentally to study the interaction between the cylinder wake and the turbulent boundary layer. The pressure distributions on the cylinder surface and on the flat plate were measured with varying the angle of attack of the cylinder. In addition, the velocity profiles of wake behind the cylinder were measured using a hot-wire anemometry As the angle of attack increases, the location of peak pressure on the windward and leeward surfaces of the cylinder moves toward the rear and front of the cylinder, respectively. At positive angles of attack, the position of the minimum pressure on the flat plate surface is moved downstream, but it is moved upstream at negative angles of attack. With increasing the angle of attack, the vortex shedding frequency is gradually decreased and the critical angle of attack exists in terms of the gap ratio. By installing the elliptic cylinder at negative angle of attack, the turbulent boundary layer over the flat plate is disturbed more than that at positive incidence. This may be attributed to the shift of separation point on the lower surface of the cylinder due to the presence of a ground plate nearby.

• Korean Journal of Optics and Photonics
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• v.24 no.5
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• pp.271-278
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• 2013

The effective reflection coefficients of an obliquely incident wave on a multi-layered substrate coated with a uniaxially anisotropic alignment layer are derived. The effective reflection coefficients as well as explicit ellipsometric expressions are provided as a function of film constants of multiple layers together with magnitude of anisotropy, direction of optic axis, and thickness of the alignment layer. It is expected that by adapting these expressions to the conventional modelling technique, the ordinary refractive index, the extra-ordinary refractive index, the azimuth angle and the tilt angle of the optic axis, and the thickness of the aligned surface can be determined simultaneously together with the thickness and volume fraction of each layer beneath the alignment layer.

• International Journal of Precision Engineering and Manufacturing
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• v.7 no.3
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• pp.35-38
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• 2006

A study of electrowetting using an Octadecyltrichlorosilane (OTS) self-assembled monolayer (SAM) and Z- Tetraol 2000 perfluoropolyether lubricant as hydrophobic layers on Si and $SiO_2$ wafer was performed. The $SiO_2$ layer used as insulating layer was thermally grown on the silicon wafer to a thickness of 220-230 nm. The results demonstrated that the contact angle decreased from $100^{\circ}$ to $80^{\circ}$ at 28 V applied potential on $SiO_2$ wafer coated with OTS and the contact angle appeared to be reversible. However, the contact angle on the $SiO_2$ wafer coated with Z- Tetraol 2000 was not observable at 28 V applied potential. Furthermore, the contact angle on the Si wafer coated with OTS or Z- Tetraol 2000 appeared to be irreversible due to the generation of electrolysis in the droplet. It is concluded that it is feasible to use SAM as a hydrophobic layer in electrowetting applications.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2001.04a
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• pp.108-119
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• 2001

The Spectral Analysis of surface Waves(SASW) Method has a great has a great potential for rapid determination of shear wave velocity profile of ground. However, it has an inherent limitation in the interpretation of test results due to the assumption that the ground is layered horizontally. The reason of the assumption is that difficulties exist in obtaining analytical solutions of wave equation when a soil system is composed of inclined soil layer. In this study, a finite-element method has been employed to assess the effects of dip angle and stiffness contrast of inclined soil layers and the testing direction on the dispersion curve. The propagation of wave front in the inclined soil layer was also investigated. The results indicated that the influence of dip angle on the dispersion curve is getting obvious as the dip angle increases and the propagation of wave front in the inclined layer also entirely different compared with the case of the horizontal layer.

• Journal of the Korean Institute of Telematics and Electronics
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• v.22 no.4
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• pp.84-91
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• 1985

Acute angle etching Process of thermally grown silicon dioxide layer has been Proposed by depositing a thin layer of silicafilm on the thermal oxide layer. As densification temper-ature of silicafilm is varied from 175$^{\circ}C$ to 1,15$0^{\circ}C$, taper angles from 3$^{\circ}$ to 40$^{\circ}$ are ob-tained. Analytical model of the acute angle etching process has also been presented and etched profile equations of the silicon dioxide layer have been derived using format's principle of lease time. Etched profiles obtained from scanning electron microscope analysis show good agreement with the theoretically calculated profiles.

• 한국정보디스플레이학회:학술대회논문집
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• 2003.07a
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• pp.311-314
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• 2003

Holographic diffuser(HD) layer was demonstrated to be located inside LC cell for a transmissive LCD of TFT-array on Color Filter structure. Master pattern of this layer was generated by holographic method and this pattern was replicated by the stamping of the master pattern on UV resin. Combined with a compensation film, TN-mode LCD with this layer showed improved viewing angle characteristics, especially along the up-down direction.

• Journal of Information Display
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• v.10 no.1
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• pp.19-23
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• 2009

In this paper, we review the proposed liquid crystal display (LCD) with a tunable viewing angle consisting of a conventional liquid crystal display (LCD) panel and a thermally variable retardation layer (TVRL) characterized by uniformly aligned LC film with transparent indium-tin-oxide electrodes for Joule heating. In the TVRL, nematic phase is transitioned into isotropic by Joule heating. The numerical calculation showed that the intrinsic wide viewing angle was achieved at the isotropic phase of the TVRL by Joule heating, whereas the narrow viewing angle was obtained at the nematic phase of the TVRL. The simulated and experimental results of the proposed LCD show continuous and symmetrical viewing angle characteristics by tuning the retardation of TVRL using Joule heating. The structure of the viewing angle control proposed here is adoptable to all LCD modes with wide viewing angle characteristics.

• 유체기계공업학회:학술대회논문집
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• 2001.11a
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• pp.30-34
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• 2001

In the present study, we studied the method of predicting the on-design and on-design point performance of axial flow fan with adjustable pitch blades. With the change of stagger angle of axial flow fan with adjustable pitch blade, flow rate and pressure can be changed. Because of this merit adjustable pitch fans are used in many industrial facility. When changing stagger angle or estimating the performance at a wide range of off-design condition, incidence angle changes greatly as the flow rate changes. Therefore, the deviation angle at the blade exit is estimated by the correlation considering the effects of blade design, incidence angle variation. In the loss model, we used known pressure loss model for blade boundary layer and wake, secondary flow, endwall boundary layer and tip leakage flow. The results of modified deviation angle model and experiment were compared for the usefulness of the modified model.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.11a
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• pp.49-50
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• 2006

We have developed vertical alignment liquid crystal display (VA-LCD), of which the viewing angle can be controlled. The VA-LCD has the function of switching between the wide viewing mode and narrow viewing angle mode using one homogeneous aligned (HA) LC layer and one compensation film with a negative C-plate. The retardation of the HA layer at off axis can be controlled by applying an electric field while keeping the retardation value to be zero at normal direction. Consequently, the device exhibits a viewing mode over $170^{\circ}$ in terms of CR = 10 in wide viewing mode and about $60^{\circ}$ in terms of CR = 2 in narrow viewing angle mode m horizontal direction.