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지오그리드의 크리프 거동 평가 및 크리프 감소계수 산정
차동환(Dong-Hwan Cha),윤광중(Kwang-Jung Yoon),구현진(Hyun-Jin Koo),전한용(Han-Yong Jeon) 한국토목섬유학회 2008 한국토목섬유학회 학술발표회 Vol.2008 No.4
There are some methods such as conventional creep test, TTS(Time-Temperature superposition), and SIM(Stepped Isothermal Method) for creep behavior evaluation of geogrid. The estimation of reduction factor from the creep behavior is based on creep rupture or limit creep strain. In this study, using conventional creep test and SIM we evaluated the creep behavior of the geogrid which was composed of high tenacity PET fibers and polyolefin polymer for low creep deformation and excellent resistance to installation damage. And then the creep reduction factor was estimated. The creep reduction factors on criteria evaluated from the results of the creep test methods and their combination are in the range of 1.571 ~ 1.615, which have no significant difference. Therefore it was concluded that all of creep test methods and the criteria for creep reduction factor used in this study are useful, and for creep reduction factor it is possible to use the criterion of creep rupture combination from conventional method and SIM method but not that of limit creep strain combination from them because their strain values with methods are different each other.
복사전달모의를 통한 중적외 파장역의 민감도 분석 및 지표면온도 산출 가능성 평가
최윤영,서명석,차동환,서두천,Choi, Youn-Young,Suh, Myoung-Seok,Cha, DongHwan,Seo, DooChun 대한원격탐사학회 2022 大韓遠隔探査學會誌 Vol.38 No.6
In this study, the sensitivity of the mid-infrared radiance to atmospheric and surface factors was analyzed using the radiative transfer model, MODerate resolution atmospheric TRANsmission (MODTRAN6)'s simulation data. The possibility of retrieving the land surface temperature (LST) using only the mid-infrared bands at night was evaluated. Based on the sensitivity results, the LST retrieval algorithm that reflects various factors for night was developed, and the level of the LST retrieval algorithm was evaluated using reference LST and observed LST. Sensitivity experiments were conducted on the atmospheric profiles, carbon dioxide, ozone, diurnal variation of LST, land surface emissivity (LSE), and satellite viewing zenith angle (VZA), which mainly affect satellite remote sensing. To evaluate the possibility of using split-window method, the mid-infrared wavelength was divided into two bands based on the transmissivity. Regardless of the band, the top of atmosphere (TOA) temperature is most affected by atmospheric profile, and is affected in order of LSE, diurnal variation of LST, and satellite VZA. In all experiments, band 1, which corresponds to the atmospheric window, has lower sensitivity, whereas band 2, which includes ozone and water vapor absorption, has higher sensitivity. The evaluation results for the LST retrieval algorithm using prescribed LST showed that the correlation coefficient (CC), the bias and the root mean squared error (RMSE) is 0.999, 0.023K and 0.437K, respectively. Also, the validation with 26 in-situ observation data in 2021 showed that the CC, bias and RMSE is 0.993, 1.875K and 2.079K, respectively. The results of this study suggest that the LST can be retrieved using different characteristics of the two bands of mid-infrared to the atmospheric and surface conditions at night. Therefore, it is necessary to retrieve the LST using satellite data equipped with sensors in the mid-infrared bands.