• Journal of Astronomy and Space Sciences
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• v.39 no.3
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• pp.87-98
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• 2022

The Far-UltraViolet (FUV) imager onboard the Ionospheric Connection Explorer (ICON) spacecraft provides two-dimensional limb images of oxygen airglow in the nightside low-latitude ionosphere that are used to determine the oxygen ion density. As yet, no FUV limb imager has been used for climatological analyses of Equatorial Plasma Bubbles (EPBs). To examine the potential of ICON/FUV for this purpose, we statistically investigate small-scale (~180 km) fluctuations of oxygen ion density in its limb images. The seasonal-longitudinal variations of the fluctuation level reasonably conform to the EPB statistics in existing literature. To further validate the ICON/FUV data quality, we also inspect climatology of the ambient (unfiltered) nightside oxygen ion density. The ambient density exhibits (1) the well-known zonal wavenumber-4 signatures in the Equatorial Ionization Anomaly (EIA) and (2) off-equatorial enhancement above the Caribbean, both of which agree with previous studies. Merits of ICON/FUV observations over other conventional data sets are discussed in this paper. Furthermore, we suggest possible directions of future work, e.g., synergy between ICON/FUV and the Global-scale Observations of the Limb and Disk (GOLD) mission.

• The Bulletin of The Korean Astronomical Society
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• v.44 no.2
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• pp.43.1-43.1
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• 2019

In this study, we apply a deep learning model to denoising solar magnetograms. For this, we design a model based on conditional generative adversarial network, which is one of the deep learning algorithms, for the image-to-image translation from a single magnetogram to a denoised magnetogram. For the single magnetogram, we use SDO/HMI line-of-sight magnetograms at the center of solar disk. For the denoised magnetogram, we make 21-frame-stacked magnetograms at the center of solar disk considering solar rotation. We train a model using 7004 paris of the single and denoised magnetograms from 2013 January to 2013 October and test the model using 1432 pairs from 2013 November to 2013 December. Our results from this study are as follows. First, our model successfully denoise SDO/HMI magnetograms and the denoised magnetograms from our model are similar to the stacked magnetograms. Second, the average pixel-to-pixel correlation coefficient value between denoised magnetograms from our model and stacked magnetogrmas is larger than 0.93. Third, the average noise level of denoised magnetograms from our model is greatly reduced from 10.29 G to 3.89 G, and it is consistent with or smaller than that of stacked magnetograms 4.11 G. Our results can be applied to many scientific field in which the integration of many frames are used to improve the signal-to-noise ratio.

• Biomedical Science Letters
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• v.29 no.3
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• pp.130-136
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• 2023

In this study, the anti-bacterial activity of three medicinal herbs such as Dioscorea batatas, Morus alba, and Tagetes erecta, have been applied in oriental medicine against Escherichia coli and Staphylococcus aureus. The antibacterial activity of Dioscorea batatas ethanol extract (DBEE), Morus alba ethanol extract (MAEE), and Tagetes erecta ethanol extract (TEEE) was analyzed by disk diffusion, minimum inhibitory concentration (MIC), and minimum bactericidal concentration (MBC) assays. As a result, three medicinal herbs exhibited antibacterial activity in a dose-dependent manner as well as MAEE and TEEE showed the most potent antibacterial activity followed by disk diffusion assay against E. coli and S. aureus, respectively. MIC against E. coli and S. aureus was 1.6 mg/mL of MAEE and TEEE as well as 0.2 mg/mL of TEEE. MBC against both strains was 5 mg/mL of DBEE and 2.5 mg/mL of TEEE. Consequently, three medicinal herbs in this study showed potent antibacterial activity through the inhibited growth of E. coli and S. aureus, which is considered as a potential candidate for cosmeceutic agents to attenuate the pruritus. In addition, antibacterial and antihistamine effects followed by the extraction solvents should be analyzed in future studies.

• Tribology and Lubricants
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• v.40 no.2
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• pp.67-70
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• 2024

Chemical mechanical planarization (CMP) is an essential process for ensuring high integration when manufacturing semiconductor devices. CMP mainly requires the use of polyurethane-based polishing pads as an ultraprecise process to achieve mechanical material removal and the required chemical reactions. A diamond disk performs pad conditioning to remove processing residues on the pad surface and maintain sufficient surface roughness during CMP. However, the diamond grits attached to the disk cause uneven wear of the pad, leading to the poor uniformity of material removal during CMP. This study investigates the pad wear rate profile according to the swing motion of the conditioner during swing-arm-type CMP conditioning using deep learning. During conditioning, the motion of the swing arm is independently controlled in eight zones of the same pad radius. The experiment includes six swingmotion conditions to obtain actual data on the pad wear rate profile, and deep learning learns the pad wear rate profile obtained in the experiment. The absolute average error rate between the experimental values and learning results is 0.01%. This finding confirms that the experimental results can be well represented by learning. Pad wear rate profile prediction using the learning results reveals good agreement between the predicted and experimental values.

• Annual Conference of KIPS
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• 2006.05a
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• pp.1167-1170
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• 2006

웹 인프라와 P2P 기술 개념을 기반으로 연구되고 있는 데이터 그리드 컴퓨팅 환경에서 중요한 문제 중 하나는 거대한 데이터 자료 접근에 관한 이슈이다. 요청된 자원 공간을 확보하기위해 저장되어 있는 자원을 선택하는 '캐쉬 교체 정책' 연구는 많이 연구되어 왔으나, 상항을 미리 예측하거나 스택과 같은 추가적인 자원이 필요하다. 본 논문은 기존 연구의 문제점을 해결하고 요청된 파일에 대응되는 파일의 개수가 되도록 적게 하기위해 파일 크기를 고려한 캐쉬 교체 정책을 제안하고 있다.

• Review of KIISC
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• v.28 no.5
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• pp.5-8
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• 2018

현대인에게 필수적인 스마트폰에는 통화기록, 문자 메시지, 이메일과 같은 사용자 개인 정보뿐 아니라 사진, 동영상, 문서 등과 같은 미디어 파일이 저장된다. 이러한 스마트폰 데이터는 포렌식 수사 입장에서 중요한 증거로써 사용될 수 있기 때문에 필수적으로 획득해야 하는 데이터이다. 하지만, 스마트폰의 꾸준한 업데이트와 FDE (Full Disk Encryption), FBE(File Based Encryption)과 같은 암호 기능의 적용으로 인해 스마트폰에서 사용자 데이터를 추출하는데 어려움이 있다. 이에 따라 스마트폰에서 사용자 데이터를 추출하는 연구가 지속적으로 수행되고 있으며, 본 논문에서는 그 중 하나인 백업 데이터에서 스마트폰의 데이터를 획득하는 연구 동향에 대해 설명한다.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2010.05a
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• pp.521-522
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• 2010

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2010.05a
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• pp.181-182
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• 2010

• Proceedings of the KIEE Conference
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• 2006.10c
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• pp.263-265
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• 2006

The pure electric braking system need to be developed to stop the electric train to zero speed by electricity. This system has advantages like reduction of weight, maintenance cost, noise, and dust generated by disk friction. Therefore, we will study this system for Korean urban transit system.

• The Journal of the Acoustical Society of Korea
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• v.15 no.4E
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• pp.37-44
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• 1996

To get accurate vibration analysis of rotor-bearing systems, finite element models of high speed rotating shaft, unbalance disk, and fluid film journal bearing are developed. The study includes the effects of rotary inertia, gyroscopic moment, damping, shear deformation, and axial torque in the same model. It does not include the axial force effect, but the extension is straighforward. The finite elements developed can be used in the analysis design of any type of multiple rotor bearing system. To show the accuracy of the models, numerical examples are demonstrated.