• Journal of Korean Society of Steel Construction
• /
• v.18 no.3
• /
• pp.289-299
• /
• 2006

Orthotropic steel decks are manufactured by welding thin plates therefore it is inevitable that there are abundant works of welding process. On connection of transverse rib web, crossing point of longitudinal rib, transverse rib and deck plate and cut-out parts of transverse rib are the significant position of stress concentration phenomenon because of out of plane and oil-caning deformation caused by longitudinal rib distortion with shear force and distortion. In order to reduce the stress concentration phenomenon and improving fatigue performance at the crosing point and cut-out, structural analysis was performed considering the existence of scalop at conection and diaphragm which have same plane with transverse rib placed inside of longitudinal rib. Result o f the analysis show that there are the largest efect of stres concentration reduction when diaphragms are installed without scallop at connection, therefore these detail can improve the fatigue performance of orthotropic steel decks.

• Journal of KIISE:Computing Practices and Letters
• /
• v.16 no.3
• /
• pp.341-345
• /
• 2010

WMN is one of efficient solutions to provide Internet services for users by forming wireless backbone networks with wireless links. The dominant technology for WMNs is the IEEE 802.11, which provides multi-channel and multi-rate capabilities. One of important issues in WMNs is the network capacity and it is essential to design a multi-channel protocol that leverages the network capacity. However, when wireless links that use different data rates operate on the common channel, the performance of high-rate links is severely degraded by the presence of the low-rate links, which is often referred as performance anomaly. In this paper, we propose a Tree-based Channel Assignment (TreeCA) protocol to mitigate the performance anomaly problem by distributing data rates over multiple channels. TreeCA performs channel assignments based on the tree WMN architecture to accommodate the Internet traffics efficiently. Parent nodes on the tree distribute their child nodes over multiple channels so that the performance anomaly is reduced. Through simulations, we observed that the proposed TreeCA outperforms the existing multi-channel protocols for WMNs.

• The Journal of The Korea Institute of Intelligent Transport Systems
• /
• v.20 no.1
• /
• pp.70-85
• /
• 2021

Deep learning methodology, which has been actively studied in recent years, has improved the performance of artificial intelligence. Accordingly, systems utilizing deep learning have been proposed in various industries. In traffic systems, spatio-temporal graph modeling using GNN was found to be effective in predicting traffic speed. Still, it has a disadvantage that the model is trained inefficiently due to the memory bottleneck. Therefore, in this study, the road network is clustered through the graph clustering algorithm to reduce memory bottlenecks and simultaneously achieve superior performance. In order to verify the proposed method, the similarity of road speed distribution was measured using Jensen-Shannon divergence based on the analysis result of Incheon UTIC data. Then, the road network was clustered by spectrum clustering based on the measured similarity. As a result of the experiments, it was found that when the road network was divided into seven networks, the memory bottleneck was alleviated while recording the best performance compared to the baselines with MAE of 5.52km/h.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2022.05a
• /
• pp.320-320
• /
• 2022

기후변화와 도시화로 인한 영향으로 도시의 폭우, 폭염을 비롯한 현상이 빈번하게 발생하고 있다. 특히 시가화 지역의 높은 불투수율은 도시홍수를 야기한다. 이러한 현상을 완화하기 위해 도시지역에서는 그린인프라와 저영향개발이 도입되고 있다. 그 중 지속가능한 발전을 위한 필수요소로 자리매김한 옥상녹화는 도시에 위치한 건물의 상층부와 내부의 온도를 낮춤으로써 에너지절감효과와 강우 시 빗물을 저류함으로써 우수유출 저감효과, 그리고 도시 공간 내 녹지도입으로 인한 이산화탄소 배출 저감 효과 등을 기대할 수 있다. 본 연구에서는 열섬현상완화와 유출 저감의 방안 중 하나인 옥상녹화(Green roof)의 효과를 정량적으로 평가하기 위해 콘크리트로 이루어진 동일한 제원의 실험동을 구축하고, 실험동 내외부의 온도, 습도, 강우, 풍속, 일사량 등의 기상자료를 측정할 수 있는 센서를 설치하였다. 각 실험동에서 측정된 기상요소를 Flux Profile Method를 적용하여 공간 내에 있는 열에너지의 총량인 순복사열을 구성하는 현열속, 잠열속, 토양열속(H, LE, G)을 산정하였다. 또한 에너지 평형에 따라 산정된 각 실험동의 열속과 지표면 복사량 관측자료을 정량적으로 비교하여 옥상녹화의 적용성을 평가하였다. 2021년 7월 21일부터 2021년 7월 28일 까지 모니터링한 결과 옥상녹화의 열 효율은 일반 콘크리트 지붕에 비해 실내온도가 최대 6.83℃ 낮게 나타나며 이는 여름철 건물 내부의 온도조절에 필요한 에너지 저감효과를 볼 수 있다. Flux Profile Method를 적용한 결과 옥상녹화의 전체 열속 중 현열속 28.5% 잠열속 70.7%, 토양열속 0.5% 의 복사량 분포를 보였고, 일반 콘크리트 지붕은 현열속 45.3%, 잠열속 38.6%, 토양열속 16.2% 으로 나타났다. 이와 같은 방법은 옥상녹화의 정량적 평가를 가능하게 함으로서 향후 기후변화 대응방안 및 전략 수립 시 옥상녹화의 온도저감효과 분석에 적극 활용할 수 있을 것으로 판단된다.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.27 no.10
• /
• pp.1738-1747
• /
• 2003

Smoothed Particle Hydrodynamics (SPH), a pure Lagrangian numerical method, is applied to analysis of penetration phenomenon of bumper plate which is installed outside of spacecraft hull to protect the spacecraft against hypervelocity meteorite impact. Effects of SPH parameters, such as artificial viscosities, smoothing lengths, numbers of particles and time increments, are analysed by comparing the SPH simulation results with experimental ones with regard to subsequent formation of debris cloud. An optimum range of parameter values is determined by error analysis and various SPH numerical results are compared with experiments.

• Korean Journal of Crystallography
• /
• v.12 no.3
• /
• pp.157-161
• /
• 2001

The observe relaxation phenomena and freezing behavior in Pb(Mg/sub ⅓/Nb/sub ⅔/O₃, relaxor ferroelectrics, weak electric-field properties as well as strong electric-field properties were investigated. The temperature dependence of the dielectric properties obtained using the low electric-field of 1 V/w was investigated. The dielectric properties obtained from the slope of the dielectric hysteresis loop and the temperature dependence of the pyroelectric properties were also investigated. When fitting all the experimental data with the Vogel-Filcher relation, a close agreement between the experimental data and equation was observed. The freezing temperature could be consistently calculated by the various methods.

• Journal of the Korean Chemical Society
• /
• v.36 no.2
• /
• pp.329-334
• /
• 1992

Ultrasonic absorption was measured in bovine serum albumin (BSA) aqueous solution (50 g/l) in the frequency range from 100 kHz to 1600 MHz at neutral pH. Three experimental techniques were used to cover the wide frequency range : plano-concave resonator, conventional Bragg reflection, and high-resolution Bragg reflection methods. The absorption spectrum at neutral pH fitted the relaxation curve well using the distribution function of a mirror image of Davidson-Cole function. The relaxaition behavior was interpreted in terms of various degree of hydration of BSA molecules.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.18 no.7
• /
• pp.603-611
• /
• 2006

A variety of schemes were sought for a mitigation of thermal stratification phenomenon in the branch piping of domestic nuclear power plant. Several mechanisms of thermal stratification occurrence were introduced in this paper. A number of factors were selected to find out the schemes for thermal stratification mitigation and the computational analysis were performed. The length of vertical branch piping, the diameter, the radius of curvature of the elbow, the direction of connection between main piping and branch piping, the slope of branch piping, the leakage flow rate, the installation of additional valve, the change of the 1st valve position and another branch piping connected with branch piping were mentioned as factors in this paper.

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
• /
• v.28 no.4
• /
• pp.300-314
• /
• 1999

가스구동 흡수식 시스템은 인류와 환경에 여러 가지 유익을 가져다준다. 첫째, 시스템의 고효율에 따른 매력적인 경제성을 제공하고, 둘째 천연가스의 사용으로 인하여 여름철 피크 전력소요(peak electric demand)를 완화하고, 셋째 이산화탄소 ($CO_2$)의 발생을 감소시킴으로써 지구 온난화 현상을 완화한다 실제로 가스구동 흡수식 시스템으로부터의 $CO_2$발생량은 증기보일러를 사용하는 전기구동 냉동기에 비하여 85% 수준인 것으로 보고되었다(Suzuki 등). 넷째로 암모니아 및 물과 같은 환경 친화적인 냉매들을 사용함으로서 오존층을 파괴하는 Chlorofluorocarbon(CFC) 및 Hydrochlorofluorocarbon(FCFC)계 냉매들을 대체할 수 있는 이점이 있다.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2022.05a
• /
• pp.468-468
• /
• 2022

기후변화 및 도시열섬화 등의 영향으로 여름철 폭염 및 봄·겨울철 미세먼지 영향은 증가하고 있다. 최근 40년(1980년~2019년) 동안 서울의 최고기온은 2.2℃ 증가하였으며, 이는 전국에서 두 번째로 높은 증가추세이다. 서울시는 도시열섬과 미세먼지 저감을 일환으로 '스마트 물순환도시 조성사업'을 추진하고 있다. 본 연구에서는 서울형 물순환도시 소개와 더불어 쿨링포그, 쿨루프, 클린로드시스템, 투수블록, 식생수로 빗물정원 등 수자원을 활용한 기술을 조사하고 문헌조사를 통해 저감효과를 비교분석하였다. 이는 수자원을 활용한 도시 형태 개선으로 쾌적한 도시환경 조성 뿐만 아니라 시민의 행복과 만족감 증대에 기여할 것으로 판단되며, 향후 서울형 스마트 물순환도시 보다 많은 지역에 확대운영 할 수 되도록 기여하고자 한다.