• Economic and Environmental Geology
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• v.33 no.4
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• pp.309-320
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• 2000

Aperture is an important parameter for determining the hydraulic characteristics of fractured media. In this study the topography of artificial rock joint surface was measured using 3D laser profilometer to analyze the aperture distribution. The initial aperture distribution was determined when the contact area became one percent of total joint surface. The initial aperture distribution of granite joint, with the mean value of 0.78 mm and the standard deviation of 0.34 mm was much different from that of the marble joint, with the mean value of 0.57 mm and the standard deviation of 0.26 mm. Apertures of both granite and marble showed normal distributions. Aperture distribution with the contact area of 25% was also analyzed. Mean value was decreased to one third compared to the initial aperture, but the standard deviation was decreased slightly. To determine the spatial correlation of the aperture distribution variogram analysis was carried out on the initial aperture data. Most experimental variograms were fitted well with exponential model. It is expected that the measured aperture characteristics can be used for stochastic analysis of fluid flow through rock joints.

• Journal of the Optical Society of Korea
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• v.10 no.1
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• pp.23-27
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• 2006

We are studying the application of an adaptive optics system to upgrade the beam quality of a laser. The adaptive optics (AO) system consists of a bimorph deformable mirror, a Shack-Hartmann sensor and a control system. In most AO applications, the beam aperture is considered to be circular. However, in some cases such as laser beams from unstable resonators, the beam apertures are annulus or a holed-rectangle. In this paper, we investigate how well a bimorph deformable mirror of ${\Phi}120\;mm$ clear aperture can compensate phase distortions for three different beam configurations; 1) ${\Phi}120\;mm$ circular aperture, 2) ${\Phi}100\;mm$ annulus aperture with a ${\Phi}20\;mm$ hole and 3) $70\;mm{\times}70\;mm$ square aperture with a hole of $30\;mm{\times}30\;mm$. This study concludes that the bimorph mirror, which might be considered as a modal controller, can compensate tilt, defocus, coma and astigmatism, and spherical aberration for all three beams.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2001.10a
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• pp.214-217
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• 2001

Microwave continuous drier system mostly uses the ISM frequency band(915MHz or 2450MHz). It dry the material off from it's inside by the electromagnetic wave. The structure whose openings is needed for dry system to continuously feeds a materials into the system. So it is too difficult to shield the leakage of electromagnetic energy through the apertures. In this paper, we designed microwave continuous drier structure which operates at 2450MHz and analyzed the field distributions at the internal and external region of the structure.

• ETRI Journal
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• v.33 no.2
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• pp.291-294
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• 2011

This letter proposes an open-ended waveguide antenna with a single split-ring resonator. In contrast to the waveguide antennas incorporating multiple rings reported in a previous study, which exhibited narrow bandwidth, the proposed antenna uses only one ring to achieve broader bandwidth while keeping the aperture small. A single ring has a relatively low quality factor compared to multiple rings. The simulated and measured fractional bandwidth was 4.13% and 4.03%, respectively, which is much broader than the fractional bandwidth of about 1% demonstrated in a previous study. This simple technique can be used in many applications that require small apertures including near-field probes and array elements.

• Journal of Species Research
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• v.6 no.3
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• pp.232-236
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• 2017

The first occurrence of the genus Hornera (Bryozoa, Cyclostomata) is reported from waters around Jeju Island, Korean Peninsula. Hornera jeongsangi n. sp. differs from all known species of the genus Hornera in having very prominent spiny protrusions around the autozooidal apertures, which are not arranged in fascicles, the gonozooidal ooeciopore facing frontally and nonporous zooidal walls around the ooeciopore.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.28 no.11
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• pp.916-919
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• 2017

This paper examines electromagnetic leakage path of small shield cans employed in mobile devices such as smart-phones by using numerical simulation and analyzes near-field coupling due to each of the leakage electric and magnetic fields by using IC-stripline method. From the results, it is confirmed that the leakage from the apertures or slots on the top of shield can is dominated by magnetic field, whereas the leakage from the seam on the side of shield can is mostly caused by electric field.

• Journal of information and communication convergence engineering
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• v.11 no.2
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• pp.139-146
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• 2013

This paper proposes a new spatial filtering approach for increasing the depth-of-field (DOF) of imaging systems, which is very useful for obtaining sharp images for a wide range of axial positions of the object. Many different techniques have been reported to increase the depth of field. However the main advantage in our method is its simplicity, since we propose the use of purely absorbing beam-shaping elements, which allows a high focal depth with a minimum modification of the optical architecture. In the filter design, we have used the analogy between the axial behavior of a system with spherical aberration and the transverse impulse response of a 1D defocused system. This allowed us the design of a ring-shaded filter. Finally, experimental verification of the theoretical statements is also provided.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.422-423
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• 2005

RF Micro switches is a miniature device or an array of integration devices and mechanical components and fabricated with Ie batch-processing techniques. RF Micro switches application area are in phased arrays and reconfigurable apertures for defence and telecommunication systems, switching network for satellite communication, and single-pole double throw switches for wireless application. Recently, RF Micro switches have been developed for the application to the milimeter wave system. RF Micro switches offer a substantilly higher performance than PIN diode or FET switches. In this paper, SPDT(single-pole-double-throw) switch are designed to use 10 GHz. Actuation voltage and displacement are simulated by tool.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.318-321
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• 2005

FIB (Focused ion Beam) milling on a 500-nm-thick silicon nitride membrane was studied in order to fabricate a high-resolution shadow mask, or called a nanostencil. The silicon nitride membrane was fabricated by MEMS processes of LPCVD, photolithography, ICP etching and bulk silicon etching. The apertures made by FIB milling and normal photolithography were compared. The square metal pattern deposited through FIB milled shadow mask showed 6 times smaller comer radius than the case of photolithography. The results show high resolution patterning could be achieved by local deposition through FIB milled shadow-mask.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07b
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• pp.652-655
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• 2004

RF MEMS is a miniature device or an array of integration devices and mechanical components and fabricated with If batch-processing techniques. RF MEMS application area are in phased arrays and reconfigurable apertures for defence and telecommunication systems, switching network for satellite communication, and single-pole double throw switches for wireless application. Recently, RF MEMS switches have been developed for the application to the milimeter wave system. RF MEMS switches offer a substantilly higher performance than PM diode or FET switches. In this paper, SPDT(single-pole-double-throw) switch are designed to use 10 GHz. Actuation voltage and displacement are simulated by tool. And stress and distribution are simulated.