• Current Optics and Photonics
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• v.4 no.2
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• pp.115-120
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• 2020

A novel method is proposed for controlling the distance of an image plane in Fourier holograms using varifocal electric-field-driven liquid-crystal (ELC) lenses. Phase Fresnel lenses are employed to reduce the thickness and response time of the ELC lenses. The voltages applied to the electrodes of the ELC Fresnel lens are adjusted so that the lens has the same retardation distribution as an ideal lens. The focal length can be controlled by changing the retardation distribution with the applied voltages. Simulations were conducted for the image reconstruction of Fourier holograms with various focal lengths of the ELC Fresnel lenses. The simulation results indicate that the distance of the image plane can be properly controlled with the varifocal ELC Fresnel lens.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.11a
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• pp.514-517
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• 2004

We have studied motion of micro-particle immersed in liquid crystal (LC) controlled by in-plane field, which is an important technology in the electro-phoretic display (EPD). In the EPD on and off states are decided by movement of these charged particles and response time is influenced by moving velocity of charged particles. In addition, the velocity can be controlled by intensity of applied voltage such that the higher the applied voltage, the faster velocity of particles become. In this study, we investigated particles's motion as functions of applied voltage, temperature of LC, rubbing direction,

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.170-170
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• 2010

In this paper, we observed stretching of single-wall carbon nanotubes (SWCNTs) aggregates driven by the in-plane field in a homogeneously aligned nematic liquid crystal (LC) medium. Aggregates of SWCNTs started to stretch above the 0.5 V/${\mu}m$ and stretched up to $1.83\;{\mu}m$ from original size with $0.74\;{\mu}m$ at 3.5 V/${\mu}m$.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.239-242
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• 2001

Electronic Speckle Pattern Interferometry(ESPI) was proposed in the 1970's as a method of producing the interferogram without using traditional holographic technique. ESPI is more faster than Holography method, because the interferometric image is recorded and updated by the video camera every 1/30 second and whold-field inspection possibly. In this study using a non-contact optical technique that is suited for in-plane and out-of-plane deformation measurement. Thin plate with crack was analyzed by ESPI to determine the characteristics of vibration mode shape and natural frequency. Also, results of the experiment were compared with Finite Element Method(FEM).

• The Journal of the Acoustical Society of Korea
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• v.19 no.1E
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• pp.13-21
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• 2000

In this paper, we present the description and results of experimental study of the sound power measurements based on International Standards ISO 3741 and 3745. The sound power emitted by a calibrated reference sound source was measured in a reverberation room and a free field over a reflecting plane, using the precision methods of International Standards ISO 3741 direct method and ISO 3745, respectively. The sound power measurements carried out in this study give accurate estimation and also show that both methods for determining the sound power levels of a sound source in a reverberation room and a free field over a reflecting plane, according to the ISO 3741 and 3745, respectively, have proved equally good.

• 한국전산유체공학회:학술대회논문집
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• 2008.03b
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• pp.159-162
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• 2008

In this paper, a numerical simulation of three-dimensional flow field and heat transfer coefficient distribution are conducted for two types of gas turbine blade with plane and squealer tips. The numerical results show that gas turbine blade with squealer tip considerably changes the flow structures near the tip regions of pressure and suction sides, so the overall heat transfer coefficients on the tip and shroud with squealer tip are lower than those with the plane tip blade. Finally, the effect of tip gap clearance on the flow field and heat transfer characteristics are investigated.

• Proceedings of the KSME Conference
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• 2001.06a
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• pp.144-150
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• 2001

Considered is non-symmetric contact traction induced by the tilting of a contact body and/or by a far field bulk tensile load to the other body. The problem is under the regime of plane strain. General profile of the contact end is incorporated and partial slip condition is supposed. As an example contact configuration, an indentation of a punch with rounded corners onto a half plane is studied. The variation of the internal stress field due to the tilting and the bulk tension is investigated. An edge crack problem is analyzed to examine the influence of the non-symmetric traction. It is shown that the tilting of a punch does not influence the behaviour of the crack. Rather, the effect of the bulk tension on the cracking behaviour is found considerable.

• Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
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• 2003.04a
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• pp.321-326
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• 2003

The subjects of this study are to examine and to apply the methods of making 1:5,000 scale maps using 1m resolution stereo images of IKONOS for the Munsan area of Paju-city where aerial photo surveying cannot possible because of security conditions. GCP(Ground Control Point) were acquired from GPS surveying and were to perform geometric corrections on images. Digital Map used IKONOS stereo images and it worked from the digital analytical stereoplotter. From field investigation, RMSE errors of the plane and vertical positions are estimated to 1.706m and 1.231m, respectively. The plane accuracy is better than an accuracy required by NGIS (national GIS) programs. Local information from field investigation was added and the resulting maps should be good as digital map under the scale of 1/5,000.

• Proceedings of the KIEE Conference
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• 1988.07a
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• pp.756-760
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• 1988

The paper presents the measurement results on the parameters affecting the breakdown mechanism of a large air spacing under switching impulse voltages. Measured parameters are the velocities of leader channels, predischarge currents, electric charges injected into the rod-plane air gap and electric field intensities on the plane. For the 3m air gap under switching impulse voltages, the velocities of leader channel have been measured to be of 1cm/${\mu}s$ - 5cm/${\mu}s$, electric field intensity of 2kv/cm, predischarge current of 1.2A - 1.6A, the charges injected into the air gap of 11 - 40 ${\mu}$C for 400-887kV impulse voltages.

• Proceedings of the KIEE Conference
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• 1999.07e
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• pp.2120-2122
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• 1999

$SF_6$ gas has been widely used the gas insulated transmission line, gas insulated transformer and gas insulated substation and Polyester film used as the turn insulation with other material. $SF_6$ gas has been actively studied in domestic and foreign countries. In general, when dielectric surface electric field exceed any electric field strength on air, corona discharge is occurred from the dielectric surface. This paper presents the insulation strength of turn insulation of $SF_6$-PET film studied under application of AC voltage, constitute of the plane to plane with PET Film. The results obtained in experimental are summarized that Partial Discharge Initial Voltage(PDIV) of turn insulation depend on gas pressure, but Breakdown Voltage(BDV) did not depend on gas pressure.