• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2022년도 봄 학술논문 발표대회
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• pp.247-248
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• 2022

3D printer-based self-healing capsules have been proposed to heal cracks by enabling various structural designs, repeatable fabrication, and strength analysis of the capsules. The Fusion Deposition Modeling (FDM) method was used to design, analyze, and produce new self-healing capsules that are widely used at low cost. However, PLA extruded from FDM has low interlayer adhesion energy, and thus strength varies depending on the angle of load applied to the laminated layer and the concrete structure, thereby degrading the performance of the self-healing capsule. Therefore, in this paper, the structure of the capsule manufactured by the FDM PLA method has isotropic strength was designed. In addition, the fracture strength in the x, y, and z directions of the load applied through the compression test was analyzed. As a result, it was confirmed that the newly proposed capsule design has an isotropic fracture strength of 1400% in all directions compared to the existing spherical thin-film capsule.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제17권6호
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• pp.1516-1529
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• 2023

In this paper, a motor gearbox fault-detection system based on a hierarchical flow-based model is proposed. The proposed system is used for the anomaly detection of a motion sound-based actuator module. The proposed flow-based model, which is a generative model, learns by directly modeling a data distribution function. As the objective function is the maximum likelihood value of the input data, the training is stable and simple to use for anomaly detection. The operation sound of a car's side-view mirror motor is converted into a Mel-spectrogram image, consisting of a folding signal and an unfolding signal, and used as training data in this experiment. The proposed system is composed of an encoder and a decoder. The data extracted from the layer of the pretrained feature extractor are used as the decoder input data in the encoder. This information is used in the decoder by performing an interlayer cross-scale convolution operation. The experimental results indicate that the context information of various dimensions extracted from the interlayer hierarchical data improves the defect detection accuracy. This paper is notable because it uses acoustic data and a normalizing flow model to detect outliers based on the features of experimental data.

• Structural Engineering and Mechanics
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• 제67권2호
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• pp.175-183
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• 2018

This research deals with the wave dispersion analysis of functionally graded double-layered nanobeam systems (FG-DNBSs) considering the piezoelectric effect based on nonlocal strain gradient theory. The nanobeam is modeled via Euler-Bernoulli beam theory. Material properties are considered to change gradually along the nanobeams' thickness on the basis of the rule of mixture. By implementing a Hamiltonian approach, the Euler-Lagrange equations of piezoelectric FG-DNBSs are obtained. Furthermore, applying an analytical solution, the dispersion relations of smart FG-DNBSs are derived by solving an eigenvalue problem. The effects of various parameters such as nonlocality, length scale parameter, interlayer stiffness, applied electric voltage, relative motions and gradient index on the wave dispersion characteristics of nanoscale beam have been investigated. Also, validity of reported results is proven in the framework of a diagram showing the convergence of this model's curve with that of a previous published attempt.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.357.1-357.1
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• 2014

Superhydrophobic WOx nanowire (NW) arrays were fabricated using a thermal evaporation and surface chemistry modification methods by self-assembled monolayer (SAM). As-prepared non-wetting WOx NWs surface shows water contact angle of $163.2^{\circ}$ and has reliable stability in underwater conditions. Hence the superhydrophobic WOx NWs surface exhibits silvery surface by total reflection of water layer and air interlayer. The stability analysus of underwater superhydrophobicity of WOx NWs arrays was conducted by changing hydrostatic pressure and surface energy of WOx NWs arrays. The stability of superhydrophobicity in underwater conditions decreased exponentially as hydrostatic pressure applied to the substrates increased3. In addition, as surface energy decreased, the underwater stability of superhydrophobic surface increased sharply. Specifically, sueprhydrophobic stability increased exponentially as surface energy of WOx NWs arrays was decreased. Based on these results, the models for explaining tendencies of superhydrophobic stability underwater resulting from hydrostatic pressure and surface energy were designed. The combination of fugacity and Laplace pressure explained this exponential decay of stability according to hydrostatic pressure and surface energy. This study on fabrication and modeling of underwater stability of superhydrophobic W18O49 NW arrays will help in designing highly stable superhydrophobic surfaces and broadening fields of superhydrophobic applications even submerged underwater.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제44회 동계 정기학술대회 초록집
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• pp.601-601
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• 2013

Superhydrophobic W18O49 nanowire (NW) arrays were synthesizedusing a thermal evaporation and surface chemistry modification methods by self-assembled monolayer (SAM). As-prepared non-wetting W18O49 NWs surface shows water contact angle of $163.2^{\circ}$ and has reliable stability in underwater conditions. Hence the superhydrophobic W18O49 NWs surface exhibits silvery surface by total reflection of water layer and air interlayer. The stability analysus of underwater superhydrophobicity of W18O49 NWs arrays was conducted by changing hydrostatic pressure and surface energy of W18O49 NWs arrays. The stability of superhydrophobicity in underwater conditions decreased exponentially as hydrostatic pressure applied to the substrates increased3. In addition, as surface energy decreased, the underwater stability of superhydrophobic surface increased sharply. Specifically, sueprhydrophobic stability increased exponentially as surface energy of W18O49 NWs arrays was decreased. Based on these results, the models for explaining tendencies of superhydrophobic stability underwater resulting from hydrostatic pressure and surface energy were designed. The combination of fugacity and Laplace pressure explained this exponential decay of stability according to hydrostatic pressure and surface energy. This study on fabrication and modeling of underwater stability of superhydrophobic W18O49 NW arrays will help in designing highly stable superhydrophobic surfaces and broadening fields of superhydrophobic applications even submerged underwater.

• 한국광물학회지
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• 제25권4호
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• pp.211-220
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• 2012

최근 물질의 특성과 구조를 해석하기 위해서 수치해석학적 모델과 컴퓨터 시뮬레이션이 많이 사용된다. 이러한 관점에서 물질의 미세구조를 해석하는 데 있어 분자동역학 해석법은 매우 유용한 방법이다. 이번 연구에서는 점토광물에 대한 확산계수 및 점착력과 같은 물리화학적 특성을 계산하기 위한 수치해석학적 방법을 소개한다. 이번연구에서 지질학적으로 심부에 위치하는 포화된 점토광물과 물을 포함한 점토광물에 대한 특성을 분자동역학을 이용해서 계산하고 균질화해석법을 활용하여 점착력과 같은 외부조건에 따라 결정되는 점토광물의 확산거동을 해석하였다. 그 결과 수치해석에 의한 해석결과 값과 기존의 실내 투수실험에 의한 결과 값이 매우 흡사한 결과를 보인다는 것을 알 수 있다. 이는 여러 가지 복합적인 조건하에서의 점토광물의 물리화학적 거동을 해석하는 데 수치해석학적 방법이 매우 유용하게 사용될 수 있다는 것을 의미한다.

• Journal of the Korean Wood Science and Technology
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• 제45권3호
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• pp.343-359
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• 2017

건축물에서 사용되는 에너지를 줄이기 위하여 다양한 연구 및 정책이 진행되고 있으나 건축물에서 구조재 및 실내 외 마감재로 폭넓게 사용되는 목재의 열적 특성에 관한 연구는 미미한 실정이다. 이에 따라, 본 연구는 목질재료와 비 목질재료의 전열성능을 분석하기 위하여 목질재료가 주로 이용되는 주거용 건축물을 대상으로 열성능이 취약한(열교 발생) 부위를 선정하고, 각 부위별로 구조재와 마감재의 구성에 따라 총 16 Case에 대해 전열성능 분석을 실시하였다. 전열 해석 시뮬레이션 도구는 ISO 10211의 계산 방법을 따르는 Physibel Trisco를 이용하였다. 해석 부위의 모델링 역시 ISO 10211에서 제시된 기준에 의해 실시하였으며, 경계 온도 조건은 에너지절약설계기준에 따라 실내온도 $20^{\circ}C$, 실외온도 $-11.3^{\circ}C$(서울 기준)로 설정하였다. 구조는 콘크리트구조와 비 목질재료마감, 콘크리트구조와 목질재료마감 그리고 목구조에 목질재료마감의 경우에 따라 구분하였다. 부위는 벽체, 지붕, 층간바닥 및 최하층 바닥 등으로 구분하여 시뮬레이션을 진행하였다. 결과로서, 콘크리트구조의 경우 형상적 원인에 의해, 목구조의 경우 형상적인 원인에 재료적 원인이 더해져 다발적으로 열교가 발생함을 확인할 수 있었다. 추가적으로 콘크리트구조에서는 단열재의 불연속 부위에서 구조적인 열교가 발생하고 목구조에서는 구조적인 열교와 이질재료의 적용 부위에서 재료적 원인에 의한 열교가 발생하는 것을 확인할 수 있었다. 또한 콘크리트 구조에 목질 실내마감재를 적용하였을 경우에는 벽체의 선형 열관류율 값이 감소하는 것을 확인할 수 있었다.