• Proceedings of the Korean Society of Dyers and Finishers Conference
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• 2012.03a
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• pp.106-106
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• 2012

막구조(Membrane structure)란 건축분야에서 "fabric structure" 또는 tension structure"와 같이 사용되는 용어로 코팅된 직물(coated fabrics)을 주재료로 사용하는 구조를 말한다. 특히 구조체로서 연성의 막을 이용 이것에 초기 장력을 주어 강성을 늘림으로서 외부하중에 대하여 안정된 형태를 유지하는 장점을 갖고 있다. 초기 창안된 독일의 온화한 기후에 적용되는 반면 한국이나 일본에는 60m/sec를 넘나드는 태풍의 피해와 많은 적설량을 보이는 기후적 제약으로 발달되지 못하였다. 그러나 최근 새로운 소재의 막구조 제품 개발과 구조해석 방법 및 시공기술 등이 개발되어 보편화되어지고 있는 실정이다. 막구조용 재료로 사용되는 섬유소재는 주로 Polyester직물을 기재로 한 PVC 코팅 제품으로 일반 PVC 막재는 장력이 약하고, 광선에 의한 물성이 쉽게 변화되어 내구연한이 5~15년에 불과하다. 유리섬유나 아라미드섬유 등으로 제직한 기재에 고내열 실리콘이나 PTFE 수지를 코팅한 제품은 약품에 대한 내구성이 높고 자외선에 대해서는 매우 큰 저항성을 가지기 때문에 내구연한이 10년에서 30년 까지도 향상된다. 그러나 실리콘 코팅막은 세계적으로 가장 좋은 막재로 알려졌으나 자정능력(Self Cleaning)에 문제가 발생되어 사용량이 감소 추세라고 할 수 있다. 일반적인 코팅 가공의 경우 MEK, Toluene, DMF 등과 같은 유기용제를 다량 사용함에 따라 작업환경 및 대기오염, 화재 위험 등의 문제점이 있으며 특히 가공시 잔류되는 유기용제의 심각성이 대두되고 있는 상황이다. 이와 같이 코팅 가공제 자체를 친환경적인 물질로 대체하여 각종 환경규제에 대응하고 유해 폐기물의 발생을 줄일 수 있는 코팅 가공제 및 가공기술 개발이 절실하다. 이에 본 연구에서는 Glass-Fiber, Aramid 등의 슈퍼 섬유와 고 강력 섬유 등을 이용하여 PTFE 코팅제품과 비슷한 수준의 성능을 부여하는 무용제형 실리콘 코팅 수지를 개발하고 내구성능 향상, Self Cleaning성, 난연성, 자외선 차단, 인장강도 및 인열 강도의 향상 등 다양한 기능성을 부여하는 최적의 환경 친화적 코팅 공정 기술을 개발하여 차세대 건축용 막구조 제품을 개발하고자 한다.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.45 no.12
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• pp.74-82
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• 2008

In this paper, we propose a P2P based IPTV system using a multiple chain architecture. Proposed system is robust to the peer churn. As opposed to the internet the IPTV network managed by a single ISP has fewer bandwidth constraints and end-to-end connectivity. So, we emphasize preferentially robustness of a P2P network in IPTV environment. A single chain structure which was proposed previously emphasizes simplicity, however there exists considerable delay time at the end part of peers as the number of peers increasing. As a solution to the problem, we propose the scheme which seperates the chain into several levels and again divides each level into spans to diminish a delay time. Though the chain is separated into level and span, basic structure of proposed scheme is still a chain structure. So the scheme simplifies the recovery procedure caused by join or departure of peers. We will show the improved performance of proposed scheme rather than single chain structure with respect to the delay time and reliability.

• Journal of Aerospace System Engineering
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• v.18 no.4
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• pp.96-101
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• 2024

The Synthetic Aperture Radar (SAR) is equipped with a Transmitter/Receiver (TR) module, which serves as the signal transmission and reception unit for acquiring image data. The TR module generates significant heat during signal generation and amplification, potentially degrading performance or causing mission failure. Furthermore, launch and operational environments may result in structural damage to the components. Thus, assessing the thermal and structural safety of the TR module through thermal and vibration tests is essential to guarantee its safety. Safety assessments can be verified through environmental tests prescribed in MIL-STD-883. This paper explores the thermal and structural safety characteristics of the TR module by simulating test environments using finite element analysis prior to conducting environmental tests.

• Journal of Aerospace System Engineering
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• v.18 no.4
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• pp.34-42
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• 2024

This study developed a morphing technology applicable to unmanned aerial vehicles (UAVs) with diverse flight characteristics. Existing morphing technologies require additional mechanisms and driving devices, posing challenges in constructing features such as ribs and spars within the wing structure, leading to structural instability. To address this, we developed a Variable-Camber and Variable-Chord (VCC) morphing flap that could maintains a continuously transforming surface during deformation, altering both camber shape and chord length simultaneously. Furthermore, we conducted design and fabrication of UAV wings incorporating these morphing flaps, ensuring structural stability by developing specialized shapes. Furthermore, structural experiments were conducted to simulate flight loads, followed by actual flight tests to validate performances of both morphing mechanism and wings. Finally, wind tunnel tests were conducted to compare results with aerodynamic analysis, confirming the effective applicability of this morphing technology.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2006.11a
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• pp.34-40
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• 2006

For a cooling performance research of the combustor operated in a extreme environment of a high temperature and high pressure, we accomplished a cooling performance analysis. Generally a heat transfer characteristic in cooling passage is known well experimentally and theoretically, however heat flux in the combustion chamber isn't. In this study, fluid flow combined with heat transfer and thermal structural analysis is accomplished about a combustor nozzle. We tried to analyze the cooling performance with a heat transfer characteristic of a gas and coolant side in the view point of quantity on the mass flow rate to be supplied to the cooling channel. And finally, evaluation on the thermal and structural safety of nozzle wall material was accomplished.

• Journal of the Korea Concrete Institute
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• v.23 no.6
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• pp.817-826
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• 2011

Concrete using eco-cement has a problem with long-term strength development. However, currently, a long-term strength development mechanism is not confirmed, resulting in a lack of application of eco-cement in construction fields. In this study, the curing humidity influence on development in long-term strength of concrete using eco-cement and the relationship between strength and pore structure were examined. The results showed that wet cured eco-cement with a high water/cement ratio showed serious long-term strength reduction due to non-reduction of pore volume (pore size over 10 nm) in mortar caste with eco-cement. Also, the study results on improvement of long-term strength of eco-cement by partial replacement with ordinary portland cement and finely-ground fly ash showed that both of these alternatives improved long-term strength of concrete caste with eco-cement due to gradual refinement of their micro-structure.

• The Journal of Engineering Geology
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• v.18 no.4
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• pp.433-437
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• 2008

It's essential to build an earth retaining structure at the beginning and end point of a tunnel constructed in a colluvium area. A large scale of colluvial soil may cause a problem to the stability of the excavation ground. An excavation in colluvium has different behavior characteristics from those in a sandy soil due to unstable elements and needs counter measures for it. There are few systematic research efforts on the behavior characteristics of an earth retaining structure installed in colluvial soil. Thus this study set out to collect measuring data from an excavation site at the tunnel pit mouth in colluvium and set quantitative criteria for the safety of an earth retaining structure. After comparing and analyzing the theoretical and empirical earth pressure from the measuring data, the lateral earth pressure distribution acted on the earth retaining wall was suggested.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.32 no.1
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• pp.45-54
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• 2019

The damage detection method using the extended Kalman filter(EKF) technique has been continuously used since EKF can estimation the responses of the damaged building structure and the stiffness of the structure. However, in the use of EKF, the requirement of setting the initial paramters P, Q, and R has caused the divergence and instability of the state vector, and various researches have been conducted to determine theses parameters. In this paper, adaptive extended Kalman filter(AEKF) method is proposed to solve the problem of setting the values of P, Q, and R, which are important parameters determining the convergence performance of the EKF state vector. By using the AEKF method proposed in this study, the P, Q, and R parameters are updated every k steps. The proposed algorithm is applied for the estimation of stiffness and the damage detection of 3-DOF problem. Based of the verification, it can be found that the selection process for the values of P, Q, and R can improve the convergence performance of EKF.

• Journal of the Microelectronics and Packaging Society
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• v.29 no.1
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• pp.43-47
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• 2022

In this study, we demonstrated an eco-friendly thin-metallic-film-based heater which can be operated in water. Based on the materials stability, Mo was selected as the heating element to secure long-term stability. Using a magnetron sputtering, 40 nm-thick Mo layers were deposited onto a glass substrate, followed by the deposition of 60-nm-thick ZnO layer to prevent oxidation during the heater fabrication process. Then, PVB (Polyvinyl Butyral) was applied on top of ZnO layer and an additional glass substrate was placed, which were heated at 150℃ for 2 hr. The PVB was cured with strong adhesion by the processing condition. We operated the Glass/Mo/ZnO/Glass heater in water, and it was shown that the water temperature reached 50℃ within 2 minutes, with a minimal resistance change of the heater. Finally, the heaters exhibit a semi-transparency, and this aesthetic advantage is expected to contribute to the added value of the heater.

• Tunnel and Underground Space
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• v.33 no.4
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• pp.265-280
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• 2023

Water leakage in tunnels is a defect that can affect tunnel stability and the ground movement by changing the stress and pore water pressure of the surrounding ground. Long-term or large-scale water leaks may lead to damage of tunnel structure and the surrounding environment, such as tunnel lining instability and ground surface settlement. The present study numerically investigated the effects of water leakage on the structural stability of a tunnel and the ground behavior. The tunnel was assumed to be under undrained conditions for preventing the inflow of the surrounding water and leaks occurred in the concrete lining after completion of the tunnel construction. A coupled hydro-mechanical analysis using a TOUGH-FLAC simulator developed in Python was conducted for assessing the leakage induced-behavior of the tunnel structure and ground under different conditions of the amount and location of water leak. Additionally, the effect of hydro-mechanical coupling terms on the results of coupled response was investigated and discussed.