• Journal of Broadcast Engineering
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• v.27 no.6
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• pp.936-939
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• 2022

As air combat system technologies developed in recent years, the development of air defense systems is required. In the operating concept of the anti-aircraft defense system, selecting an appropriate armament for the target is one of the system's capabilities in efficiently responding to threats using limited anti-aircraft power. Much of the flying threat identification relies on the operator's visual identification. However, there are many limitations in visually discriminating a flying object maneuvering high speed from a distance. In addition, as the demand for unmanned and intelligent weapon systems on the modern battlefield increases, it is essential to develop a technology that automatically identifies and classifies the aircraft instead of the operator's visual identification. Although some examples of weapon system identification with deep learning-based models by collecting video data for tanks and warships have been presented, aerial vehicle identification is still lacking. Therefore, in this paper, we present a model for classifying fighters, helicopters, and drones using a convolutional neural network model and analyze the performance of the presented model.

• Journal of Korea Water Resources Association
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• v.55 no.12
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• pp.1031-1039
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• 2022

As one of the hydrological factors closely related to landslides, precipitation indirectly affects slope stability by generating external forces. Groundwater level fluctuations have attracted more attention lately as factors that directly affect slope stability have become more prominent. Therefore, this study attempted to analyze the relationship between variables through changes in precipitation, groundwater levels, and land displacement. A time series-based analysis was conducted using satellite-based precipitation and point-based groundwater levels in conjunction with the PSInSAR technique to simulate land displacement in urban and mountainous areas. There was a sharp rise in groundwater levels in both urban and mountain areas during heavy rainfall, and a continuous decrease in urban areas when rainfall was low. 6 mm of displacements was observed in the mountainous area as a results of soil outflow from the topsoil layer, which was accompanied by an increased groundwater level. Meanwhile, different results were found in urban area. In response to the rise in groundwater level, the land displacement increases due to the expansion of soil skeletons, while the decrease seems to be attributed to anthropogenic influences. Overall, there was no consistent relationship between groundwater levels and land displacement, which appears to be caused by factors other than hydrological factors. Additional consideration of environmental factors could contribute to a deeper understanding of the relationship between the two factors.

• Journal of Space Technology and Applications
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• v.1 no.1
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• pp.33-40
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• 2021

Based on the requirements of a total weight of 42 kg or less, the NEXTSat-2 SAR (synthetic aperture radar) system was developed. As the NEXTSat-2 is a small-sized satellite, the SAR system was designed to account for about 40% of the dry mass of the payload relative to the total mass. Among the major components of the SAR system - which are an antenna, an RF transceiver, a baseband signal processor, and a power unit - a part with a particularly large dry mass is the antenna, the core of the SAR system. Whereas various selections are possible in consideration of gain and efficiency when designing the antenna, the micro-strip patch array antenna was adopted by reflecting the dry mass, power, and resolution required by the NEXTSat-2 project. In order to meet the mission requirement of the NEXTSat-2, the antenna was developed with a frequency of 9.65 GHz, a gain of 42.7 dBi, and a return loss of -15 dB. The performance of the antenna was verified by conducting a field test onboard the vehicle.

• Journal of Aerospace System Engineering
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• v.17 no.1
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• pp.42-50
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• 2023

In this study, hexagonal ferrite powder with chemical formula SrZn_2-xCo_xFe₁₆O₂₇ was synthesized by a solid-state reaction method and its electromagnetic (EM) wave absorption characteristics were evaluated in the frequency range of 0.1-18 GHz with absorber thickness range of 0 - 10 mm. Reflection loss (RL) affecting electromagnetic wave absorption performance was calculated based on the transmission line theory using measured complex permeabilities and permittivities. RL spectra were also directly measured for some samples. They were well matched with calculated results. High-frequency complex permeability characteristics were changed gradually according to the amount of Co substitution (x). The EM wave absorption frequency band could be tuned accordingly. Hexaferrite samples with x = 1.0, 1.25, and 1.5 exhibited remarkable maximum electromagnetic wave absorption performances with minimum RL (RL_min) lowered than -50 dB. They also showed a very broad frequency band (Δf > 10 GHz) in which more than 90% of the EM wave energy absorption occurred (RL ≤ -10 dB).

• Smart Media Journal
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• v.12 no.2
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• pp.27-35
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• 2023

Currently, online user authentication is perform using joint certificates issued by accredited certification authorities and simple certificates issued by private agency. In such a PKI(Public Key Infrastructure) system, various cryptographic technologies are used, and in particular, digital signatures are used as a core technology. The digital signature scheme is equally used in DID(Decentralized Identity), which is attracting attention to replace the existing centralized system. As such, the digital signature-based user authentication used in current online services is also applied in the metaverse, which is attracting attention as the next-generation online world. Metaverse, a compound word of "meta," which means virtual and transcendent, and "universe," means a virtual world that includes the existing online world. Due to various developments of the metaverse, it is expted that new authentication technologies including biometric authentication will be used, but existing authentication technologies are still being used. Therefore, in this study, we study digital signature scheme that can be efficiently used for user authentication in the developing metaverse. In particular, we experimentally analyze the effectiveness of ECDSA, which is currently used as a standard for digital signatures, and Schnorr signatures, which can quickly verify a large amount of signatures.

• Journal of Advanced Navigation Technology
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• v.27 no.2
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• pp.190-196
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• 2023

Recently, following the development of LIDAR technology which can detect distance from the object, the interest for LIDAR based 3D object detection network is getting higher. Previous networks generate inaccurate localization results due to spatial information loss during voxelization and downsampling. In this study, we propose an attention-based convergence method and a camera-LIDAR convergence system to acquire high-level features and high positional accuracy. First, by introducing the attention method into the Voxel-RCNN structure, which is a grid-based 3D object detection network, the multi-scale sparse 3D convolution feature is effectively fused to improve the performance of 3D object detection. Additionally, we propose the late-fusion mechanism for fusing outcomes in 3D object detection network and 2D object detection network to delete false positive. Comparative experiments with existing algorithms are performed using the KITTI data set, which is widely used in the field of autonomous driving. The proposed method showed performance improvement in both 2D object detection on BEV and 3D object detection. In particular, the precision was improved by about 0.54% for the car moderate class compared to Voxel-RCNN.

• Journal of Life Science
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• v.34 no.4
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• pp.215-226
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• 2024

Aralia continentalis is widely distributed in Far East Asian countries such as Korea, China, and Japan. A. continentalis has traditionally been used as an herbal remedy for various conditions, including analgesia, headache, inflammation, lameness, lumbago, rheumatism, and dental diseases in Korea. Previously, epi-continentalic acid, continentalic acid, and kaurenoic acid as major active biological compounds belonging to the diterpenoid class were identified. To synthesize diterpenoid derivatives with enhanced bioavailability, Fusarium fujikuroi was employed to biotransform diterpenoids due to its known antibacterial activity. This yielded two derivatives of kaurenoic acid, namely 16α-hydroxyent-kauran-2-on-19-oic acid and 2β, 16α-dihydroxy-ent-kauran-19-oic acid, with their chemical structures elucidated via NMR analysis. These derivatives exhibited increased polarity compared to kaur- enoic acid, as evidenced by their retention time on preparative HPLC using the ODS-A column and structural modifications. Evaluation of their antidiabetic activity targeting PTP1B, a negative regulator of the insulin signaling pathway, revealed inhibitory activities of 30.8% and 27.6%, respectively, at a concentration of 4 ㎍/ml. Additionally, both derivatives demonstrated low cytotoxicity, with an IC50 value 18 times higher than kaurenoic acid. Therefore, the augmented water solubility and reduced toxicity of 16α-hydroxy-ent-kauran-2-on-19-oic acid and 2β, 16α-dihydroxy-ent-kauran-19-oic acid, resulting from biotransformation by F. fujikuroi, render them promising candidates for industrial applications.

• Journal of the Korea Computer Graphics Society
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• v.30 no.3
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• pp.149-158
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• 2024

Photo booths have traditionally provided a fun and easy way to capture and print photos to cherish memories. These booths allow individuals to capture their desired poses and props, sharing memories with friends and family. To enable diverse expressions, generative AI-powered photo booths have emerged. However, existing AI photo booths face challenges such as difficulty in taking group photos, inability to accurately reflect user's poses, and the challenge of applying different concepts to individual subjects. To tackle these issues, we present CINEMAPIC, a photo booth system that allows users to freely choose poses, positions, and concepts for their photos. The system workflow includes three main steps: pre-processing, generation, and post-processing to apply individualized concepts. To produce high-quality group photos, the system generates a transparent image for each character and enhances the backdrop-composited image through a small number of denoising steps. The workflow is accelerated by applying an optimized diffusion model and GPU parallelization. The system was implemented as a prototype, and its effectiveness was validated through a user study and a large-scale pilot operation involving approximately 400 users. The results showed a significant preference for the proposed system over existing methods, confirming its potential for real-world photo booth applications. The proposed CINEMAPIC photo booth is expected to lead the way in a more creative and differentiated market, with potential for widespread application in various fields.

• Journal of Life Science
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• v.26 no.6
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• pp.633-639
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• 2016

Biomaterials including polymer, metal, ceramic, and composite have been widely applied for medical uses as medical fibers, artificial blood vessels, artificial joints, implants, soft tissue, and plastic surgery materials owing to their physicochemical properties. However, the biocompatibility and toxicity for film- and plate-form biomaterials is difficult to measure in mammalian cells because there is no appropriate incubation system. To solve these problems, we developed a novel mammalian cell culture system consisting of a silicone ring, top panel, and bottom panel and we applied two polymer films (PF) and one metal plate (MP). This system was based on the principal of sandwiching a test sample between the top panel and the bottom panel. Following the assembly of the culture system, SK-MEL-2 cells were seeded onto Styela Clava Tunic (SCT)-PF, NaHCO₃-added SCT (SCTN)-PF, and magnesium MP (MMP) and incubated at 37℃ for 24 hr and 48 hr. An MTT assay revealed that cell viability was maintained at a normal level in the SCT-PF culture group at 24 or 48 hr, although it rapidly decreased in the SCTN-PF culture group at 48 hr. Furthermore, the cell viability in the MMP culture group was very similar to that of the control group after incubation for 24 hr and 48 hr. Together, these results suggest the sandwich-type mammalian culture system developed here has the potential for the evaluation of the biocompatibility and toxicity of cells against PF- and MP-form biomaterials.

• Journal of the Mineralogical Society of Korea
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• v.25 no.4
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• pp.271-282
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• 2012

We explore the effect of removal of organic ligand on the atomic configurations around oxygen in hydroxyl groups in amorphous silica gel (synthesized through hydrolysis of $SiCl_4$ in diethyl-ether) using high resolution $^{17}O$ solid state NMR spectroscopy. $^1H$ and $^{29}Si$ MAS NMR spectra for amorphous silica gel showed diverse hydrogen environments including water, hydroxyl groups (e.g., hydrogen bonded silanol, isolated silanol), and organic ligands (e.g., alkyl chain) that may interact with surface hydroxyls in the amorphous silica gel, for instance, forming silica-organic ligand complex (e.g., Si-$O{\cdots}R$). These physically and chemically adsorbed organic ligands were partly removed by ultrasonic cleaning under ethanol and distilled water for 1 hour. Whereas $^{17}O$ MAS NMR spectra with short pulse length ($0.175{\mu}s$) at 9.4 T and 14.1 T for as-synthesized amorphous silica gel showed the unresolved peak for Si-O-Si and Si-OH structures, the $^{17}O$ MAS NMR spectra with long pulse length ($2{\mu}s$) showed the additional peak at ~0 ppm. The peak at ~0 ppm may be due to Si-OH structure with very fast relaxation rate as coupled to liquid water molecules or organic ligands on the surface of amorphous silica gel. The observation of the peak at ~0 ppm in $^{17}O$ MAS NMR spectra for amorphous silica gel became more significant as the organic ligands were removed. These results indicate that the organic ligands on the surface of amorphous silica gel interact with oxygen atoms in Si-OH and provide the information about atomic structure of silanol and siloxane in amorphous silica gel. The current results could enhance the understanding of dehydration mechanism of diverse silicates, which is known as atomic scale origins of intermediate depth (approximately, 70~300 km) earthquakes in subduction zone.