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생애주기비용 분석을 통한 저소음포장 및 방음둑 설치방안 연구
조형환 ( Cho Hyung-hwan ),김가선 ( Kim Ga-sun ),조항신 ( Cho Hang-shin ) 한국구조물진단유지관리공학회 2022 한국구조물진단유지관리공학회 학술발표대회 논문집 Vol.26 No.1
도로에서 발생하는 교통소음 저감을 위한 대책으로 과거에는 주로 방음벽을 설치하였으나 과도한 높이로 인한 도시미관의 저해 및 통풍, 일조 차단으로 민원이 빈발하고 있으며 방음벽의 유지ㆍ관리에 소요되는 비용과 시간, 인력이 급격히 증가하고 있는 추세이다. 이에 최근에는 방음벽을 대체하기 위한 저소음포장, 방음둑, ANC 등과 같은 대안들이 연구되고 있으나 실제 도입을 위한 객관적 근거, 예컨대 대안별 소음저감성능 및 경제성 분석결과 등의 미비로 도입이 지연되는 문제를 해결하고자 본 연구에서는 다양한 도로상황을 가정한 시나리오별로 시뮬레이션을 실시하여 방음시설 규모를 예측하고 생애주기 비용(LCC) 분석을 통하여 최적대안 도입기준을 작성하고 더 나아가 설계 도입절차와 설계기준까지 제안함.
마찰접합 된 A6063 합금의 미세조직과 기계적 특성 평가
김은혜,조형환,송국현,Kim, Eun-Hye,Cho, Hyung-Hwan,Song, Kuk-Hyun 한국재료학회 2017 한국재료학회지 Vol.27 No.5
This study was carried out to evaluate the developed microstructures and mechanical properties of friction welded A6063 alloy. For this work, specimens were prepared at a size of 12 mm ${\O}{\times}80mm$, and friction welding was carried out at a rotation speed of 2,000 RPM, friction pressure of $12kgf/cm^2$ and upset pressure of $25kgf/cm^2$. To perform an analysis of the grain boundary characteristic distributions, such as the grain size, orientation and misorientation angle distributions, the electron back-scattering diffraction method was used. In addition, in order to identify the dispersed intermetallic compounds of the base and welded materials, transmission electron microscopy was used. The experimental results found that the application of friction welding on A6063 led to significant grain refinement of the welded zone relative to that of the base material. Besides this, intermetallic compounds such as AlMnSi and $Al_2Cu$ were found to be dispersed with more refined size relative to that of the base material. This formation retains the mechanical properties of the welds, which results in the fracture aspect at the base material zone. Therefore, based on the developed microstructures and mechanical properties, the application of friction welding on A6063 could be used to obtain a sound weld zone.
Ba3V4O13-BaV2O6계 초저온 동시소성 세라믹스의 마이크로파 유전 특성
윤상옥,홍서영,조형환,김신 한국전기전자재료학회 2021 전기전자재료학회논문지 Vol.34 No.5
Phase evolution, sintering behavior, microstructure, and microwave dielectric properties of (1-x) mol Ba3V4O13 - (x) mol BaV2O6 system were investigated. The sintered specimens of all compositions consisted of Ba3V4O13 and BaV2O6, and no secondary phase was observed. As x increased, the linear shrinkage decreased to the composition of x=0.5, and then increased again, implying that Ba3V4O13 and BaV2O6 phases interfered mutually with each other during sintering. All compositions showed a dense microstructure with a large grain growth. Cracks were observed in some compositions because of the relatively high sintering temperature of 620~640℃. As x increased, the dielectric constant increased, while the quality factor was maintained from about 50,000 GHz to about 70,000 GHz up to the composition of x=0.9, and then decreased to 20,987~27,180 GHz at the composition of x=1.0. As x increased, the temperature coefficient of the resonance frequency showed a (+) value from a (-) value. The dielectric constant, the quality factor, and the temperature coefficient of resonant frequency of x=0.7 composition sintered at 640℃ for 4 hours were 10.61, 71,126 GHz, and -4.9 ppm/℃, respectively. This composition showed a good chemical compatibility with Al powder, indicating that the Ba3V4O13-BaV2O6 ceramics are a candidate material for ULTCC (Ultra-Low Temperature Co-fired Ceramics) applications.
Phase Evolution, Microstructure, and Electrical Resistivity of CaMnO3-CaZrO3 Composites
윤상옥,김신,이주식,조형환,박훈 한국전기전자재료학회 2022 Transactions on Electrical and Electronic Material Vol.23 No.4
The phase evolution, microstructure, and electrical resistivity of (1-x) CaMnO 3 -(x) CaZrO 3 composites were investigated. A mixture of the CaMnO 3 -type and CaZrO 3 -type phases with an orthorhombic structure was formed with the compositions of x = 0.25, 0.5, and 0.75. The diff raction peaks of the CaZrO 3 -type phase and those of the CaMnO 3 -type one were shifted toward the higher angle and the lower one, respectively, indicating that the substitutional solid solution occurred mutually. All the specimens exhibited dense microstructures except the composition of x = 1.0. The value of the linear shrinkage for the compositions of x = 0.25, 0.50, and 0.75, i.e., the mixture of the CaMnO 3 -type and CaZrO 3 -type phases, is higher than that for the single phases, i.e., CaMnO 3 and CaZrO 3 . The composition of x = 0.0, i.e., CaMnO 3 , showed an electrical resistivity of about 1 Ω·cm. Since CaZrO 3 is an insulator, the electrical resistivity of (1-x) CaMnO 3 -(x) CaZrO 3 composites can be controlled from about 1 Ω·cm to infi nity by changing the x value.