• The Bulletin of The Korean Astronomical Society
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• v.39 no.2
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• pp.60.2-60.2
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• 2014

Hierarchical structure of star-forming regions is widespread and may be characteristic of all star formation. We studied the hierarchical structure of star-forming regions in the Local Group galaxies (M31, M33, Phoenix, Pegasus, Sextans A, Sextans B, WLM). The star-forming regions were selected from Galaxy Evolution Explorer (GALEX) far-UV imaging in various detection thresholds for investigating hierarchical structure. We examined the spatial distribution of the hot massive stars within star-forming regions from Hubble Space Telescope (HST) multi-band photometry. Small compact groups arranged within large complexes. The cumulative mass distribution follows a power law. The results allow us to understand the hierarchical structure of star formation and recent evolution of the Local Group galaxies.

• Journal of information and communication convergence engineering
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• v.15 no.2
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• pp.117-122
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• 2017

Three-dimensional integrated circuits (3D ICs), starting with memory cubes, have entered the mainstream recently. The benefits many predicted in the past are indeed delivered, including higher memory bandwidth, smaller form factor, and lower energy. However, 3D ICs have yet to find their deployment in aerospace applications. In this paper we first present key design tools and methodologies for high performance, low power, and reliable 3D ICs that mainly target terrestrial applications. Next, we discuss research needs to extend their capabilities to ensure reliable operations under the harsh space environments. We first present a design methodology that performs fine-grained partitioning of functional modules in 3D ICs for power reduction. Next, we discuss our multi-physics reliability analysis tool that identifies thermal and mechanical reliability trouble spots in the given 3D IC layouts. Our tools will help aerospace electronics designers to improve the reliability of these 3D IC components while not degrading their energy benefits.

• 한국전산유체공학회:학술대회논문집
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• 1995.10a
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• pp.182-187
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• 1995

The present paper explains some advancement made by the authors for the compressible flow computation of the Euler equations based on the unstructured grid and vertex- centered finite volume method. Accurate solutions to the unsteady axisymmetric shock wave propagation problems and three-dimensional airplane flows have been obtained by a high-order upwind TVD and FCT schemes. Unstructured grid adaption is made for the unsteady shock wave problems by the dynamic h-refinement/unrefinement procedure and for the three-dimensional steady flows by the Delaunay point-insertion method to generate three-dimensional tetrahedral mesh enrichment. Some physics of the shock wave diffraction phenomena and three-dimensional airplane flow are discussed.

• Interaction and multiscale mechanics
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• v.3 no.3
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• pp.257-266
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• 2010

A novel resonance based proximity DC current sensor is proposed. The sensor consists of a piezo sensed and actuated cantilever beam with a permanent magnet mounted at its free end. When the sensor is placed in proximity to a wire carrying DC current, resonant frequency of the beam changes with change in current. This change in resonant frequency is used to determine the current through the wire. The structure is simulated in micro and meso scale using COMSOL Multi physics software and the sensor is found to be linear with good sensitivity.

• Journal of IKEEE
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• v.24 no.2
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• pp.669-672
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• 2020

In this paper, we analyzed the characteristics of cyber attacks and major threat scenarios that could occur around intelligent building management Systems(IBS) by cyber attack security threats against cyber physics systems. Generally determined that lowering the likelihood of aggression against predictable threats would be a more realistic approach to attack response. The countermeasures against this need to be applied to multi-layered defense systems, and three alternatives were proposed: preliminary cyber safety diagnosis for protection targets and the establishment of mobile security control systems.

• Journal of the Optical Society of Korea
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• v.13 no.2
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• pp.261-266
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• 2009

The angular dispersion-type non-scanning Fabry-Perot was applied to an ethanol-water mixture in order to investigate its acoustic properties such as the sound velocity and the absorption coefficient. The scattered light from the mixture was analyzed by using the charge-coupled-device area detector, which made the measurement time much shorter than that obtained by using the conventional scanning tandem multi-pass Fabry-Perot interferometer. The sound velocity showed a deviation from ultrasonic sound velocities at low temperatures accompanied by the increase in the absorption coefficient, indicating acoustic dispersion due to the coupling between the acoustic waves and some relaxation process. Based on a simplified viscoelastic theory, the temperature dependence of the relaxation time was obtained. The addition of water molecules to ethanol reduced the relaxation time, consistent with dielectric measurements. The present study showed that the angular dispersion-type Fabry-Perot interferometer combined with an area detector could be a very powerful tool in the real-time monitoring of the acoustic properties of condensed matter.

• The Bulletin of The Korean Astronomical Society
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• v.42 no.1
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• pp.35.3-35.3
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• 2017

Neutrinos play an important role in astronomy and therefore they need to be observed as well as other astronomical messengers. The first observation of astronomical neutrinos is from the SN1987a by the Kamiokande neutrino telescope in Japan. Unlike other astronomical messengers neutrinos can cover all energy range of astronomical phenomena due to their weak interactions and neutrality. Multi messenger astronomy including optical, neutrino, and cosmic ray observations, provides more information on astronomical phenomena and thus such collaborational works are ongoing worldwide. A future Korean neutrino telescope consisting of huge (260 kiloton) water Cherenkov detector under a mountain was proposed in 2016 and the sensitivity studies on various topics are in progress with international collaborators. In this talk I will introduce the future Korean neutrino telescope and its science as well as the potential candidate sites in Korea. We invite all of you to work together for the future Korean neutrino telescope that will operate more than 30 years.

• Proceedings of the Acoustical Society of Korea Conference
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• autumn
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• pp.33-36
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• 2001

본 논문에서는 기존의 음성인식에서 사용하는 특징벡터인 MFCC(Mel-Frequency Cepstral Cefficients)를 대신하여 웨이블렛 변환을 이용한 새로운 특징벡터를 추출하는 방법을 제안한다. 새 특징벡터로는 MRA(Multi-Resolution Analysis)를 이용하여 구성하였다. 웨이블렛 변환을 이용한 새로운 특징벡터의 추출 목적은 시간축과 주파수축에서의 더 좋은 해상도를 가지는 성질을 이용하는 것이다. 실험결과에서 웨이블렛 변환을 이용한 새로운 특징벡터를 이용한 인식이 기존의 방식보다 더 좋은 인식률을 보이고 있음을 확인하였다.

• Journal of Powder Materials
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• v.22 no.4
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• pp.247-253
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• 2015

The sintering mechanisms of nanoscale copper powders have been investigated. A molecular dynamics (MD) simulation with the embedded-atom method (EAM) was employed for these simulations. The dimensional changes for initial-stage sintering such as characteristic lengths, neck growth, and neck angle were calculated to understand the densification behavior of copper nano-powders. Factors affecting sintering such as the temperature, powder size, and crystalline misalignment between adjacent powders have also been studied. These results could provide information of setting the processing cycles and material designs applicable to nano-powders. In addition, it is expected that MD simulation will be a foundation for the multi-scale modeling in sintering process.

• Journal of the Korean Society for Nondestructive Testing
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• v.21 no.4
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• pp.371-382
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• 2001

The recognition of such natural wave guides as plates, rods, hollow cylinders, multi-layer structures or simply an interface between two materials combined with an increased understanding of the physics and wave mechanics of guided wave propagation has led to a significant increase in the number of guided wave inspection applications being developed each year. Of primary attention Is the ability to inspect partially hidden structures, hard to access areas, and teated or insulated structures. An introduction to some physical consideration of guided waves followed by some sample problem descriptions in pipe, ice detection, fouling detection in the foods industry, aircraft, tar coated structures and acoustic microscopy is presented in this paper. A sample problem in Boundary Element Modeling is also presented to illustrate the move in guided wave analysis beyond detection and location analysis to quantification.