• Geomechanics and Engineering
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• v.32 no.6
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• pp.653-671
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• 2023

In practice, the interference influence caused by adjacent footings of structures on geo-reinforced loose soil has a considerable impact on their behavior. Thus, the goal of this study is to evaluate the behavior of two strip footings in close proximity on both geocell and geogrid reinforced soil with different reinforcement layers. Geocell was made from geogrid material used to compare the performance of cellular and planar reinforcement on the bearing pressure of twin footings. Extensive experimental tests have been performed to attain the optimum embedment depth and vertical distance between reinforcement layers. Particle image velocimetry (PIV) analysis has been conducted to monitor the deformation, tilting and movement of soil particles beneath and between twin footings. Results of tests and PIV technique were verified using finite element modeling (FEM) and the results of both PIV and FEM were used to utilize failure mechanisms and influenced shear strain around the loading region. The results show that the performance of twin footings on geocell-reinforced sand at allowable and ultimate settlement ranges are almost 4% and 25% greater than the same twin footings on the same geogrid-reinforced sand, respectively. By increasing the distance between twin footings, soil particle displacements become smaller than the settlement of the foundations.

• Journal of Advanced Navigation Technology
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• v.22 no.4
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• pp.295-301
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• 2018

Recently, GPS(Global Positioning System) array antenna technology is generally used and widely adopted as a national infrastructure structure and aero-vehicles for protection the GPS signal reception. Until now, the 2-dimensional planar array is universally used for its applications in the array antenna signal processing, however relatively higher altitude air vehicles such as UAV experiences additional null zones induced by low altitude GPS interferences which is located in a symmetry zone of antenna horizontal plane and this could make the receiving antenna pattern coverage reduction. In this paper, we improved 20% of the beam pattern receiving performance and 13 dB correlation value improvement by eliminating the interference mirror images.

• The Journal of the Convergence on Culture Technology
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• v.9 no.6
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• pp.113-122
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• 2023

This study was conducted on the premise of the development of cultural products using relic assets of traditional culture in a knowledge and information society led by culture and soft power. It was conducted in the context of exploring the possibility of cultural content products of Wa-Dang relics excavated from traditional architecture in the Unified Silla Period and expanding the scalability of commercialization motifs that are highly useful in jewelry design. First, the original form, material, use, size, meaning, and formative aesthetics of Wa-Dang were identified through literature and media research. Among the considered Wa-Dang, 10 types of Wa-Dang which represent the category and have values in modules and patterns were selected, and, then, circular images were extracted and modularized with a "formal simplification technique." Based on the "mathematical symmetry analysis technique," which is a method of systematizing pattern composition arrangement format. we derived a planar formative element that can be used in the development of the cultural content industry and jewelry design. In order to expand its usability in the jewelry industry in the future, it was presented as a 2D digital image. In the future, we hope more studies on the various cultural content industry utilizing the traditional culture will be carried out.

• The Journal of the Petrological Society of Korea
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• v.23 no.2
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• pp.139-144
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• 2014

A series of the planar cathodoluminescence (CL) and backscattered-electron (BSE) images of magmatic zircon from the Paleozoic Yeongdeok pluton in the southeastern Korean Peninsula were taken using a scanning electron microscope for a 3D reconstruction of internal zonation of zircon. Seven zircon crystals mounted in epoxy were serially polished with average $3{\mu}m$ thickness to their disappearance. Their 3D reconstruction of zonation was performed using the Volume Viewer function in the ImageJ software. The 3D oscillatory zoning pattern of zircon was apparently shown in all the analyzed crystals. This method can further be applied to zircon crystals of multiple growth histories as well as other geological materials.

• Proceedings of the KSRS Conference
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• 2008.10a
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• pp.441-444
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• 2008

This paper describes the development of a circularly polarized microstrip antenna, as a part of the Circularly Polarized Synthetic Aperture Radar (CP-SAR) sensor which is currently under developed at the Microwave Remote Sensing Laboratory (MRSL) in Chiba University. CP-SAR is a new type of sensor developed for the purpose of remote sensing. With this sensor, lower-noise data/image will be obtained due to the absence of depolarization problems from propagation encounter in linearly polarized synthetic aperture radar. As well the data/images obtained will be investigated as the Axial Ratio Image (ARI), which is a new data that hopefully will reveal unique various backscattering characteristics. The sensor will be mounted on an Unmanned Aerial Vehicle (UAV) which will be aimed for fundamental research and applications. The microstrip antenna works in the frequency of 1.27 GHz (L-Band). The microstrip antenna utilized the proximity-coupled method of feeding. Initially, the optimization process of the single patch antenna design involving modifying the microstrip line feed to yield a high gain (above 5 dBi) and low return loss (below -10 dB). A minimum of 10 MHz bandwidth is targeted at below 3 dB of Axial Ratio for the circularly polarized antenna. A planar array from the single patch is formed next. Consideration for the array design is the beam radiation pattern in the azimuth and elevation plane which is specified based on the electrical and mechanical constraints of the UAV CP-SAR system. This research will contribute in the field of radar for remote sensing technology. The potential application is for landcover, disaster monitoring, snow cover, and oceanography mapping.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.174-175
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• 2012

(In, Ga) N-based III-nitride semiconductor materials have been viewed as the most promising materials for the applications of blue and green light emitting devices such as light-emitting diodes (LEDs) and laser diodes. Although the InGaN alloy can have wide range of visible wavelength by changing the In composition, it is very hard to grow high quality epilayers of In-rich InGaN because of the thermal instability as well as the large lattice and thermal mismatches. In order to avoid phase separation of InGaN, various kinds of structures of InGaN have been studied. If high-quality In-rich InGaN/GaN multiple quantum well (MQW) structures are available, it is expected to achieve highly efficient phosphor-free white LEDs. In this study, we proposed a novel InGaN double hetero-structure grown on GaN nano-pyramids to generate broad-band red-color emission with high quantum efficiency. In this work, we systematically studied the optical properties of the InGaN pyramid structures. The nano-sized hexagonal pyramid structures were grown on the n-type GaN template by metalorganic chemical vapor deposition. SiNx mask was formed on the n-type GaN template with uniformly patterned circle pattern by laser holography. GaN pyramid structures were selectively grown on the opening area of mask by lateral over-growth followed by growth of InGaN/GaN double hetero-structure. The bird's eye-view scanning electron microscope (SEM) image shows that uniform hexagonal pyramid structures are well arranged. We showed that the pyramid structures have high crystal quality and the thickness of InGaN is varied along the height of pyramids via transmission electron microscope. Because the InGaN/GaN double hetero-structure was grown on the nano-pyramid GaN and on the planar GaN, simultaneously, we investigated the comparative study of the optical properties. Photoluminescence (PL) spectra of nano-pyramid sample and planar sample measured at 10 K. Although the growth condition were exactly the same for two samples, the nano-pyramid sample have much lower energy emission centered at 615 nm, compared to 438 nm for planar sample. Moreover, nano-pyramid sample shows broad-band spectrum, which is originate from structural properties of nano-pyramid structure. To study thermal activation energy and potential fluctuation, we measured PL with changing temperature from 10 K to 300 K. We also measured PL with changing the excitation power from 48 ${\mu}W$ to 48 mW. We can discriminate the origin of the broad-band spectra from the defect-related yellow luminescence of GaN by carrying out PL excitation experiments. The nano-pyramid structure provided highly efficient broad-band red-color emission for the future applications of phosphor-free white LEDs.