Low thermal conductivity of binary fatty acid mixture of palmitic and lauric acids(PA-LA)within the value range of 0.15-0.17 W/(m·K)restricts its wide utilization as thermal energy storage material in the active ...Low thermal conductivity of binary fatty acid mixture of palmitic and lauric acids(PA-LA)within the value range of 0.15-0.17 W/(m·K)restricts its wide utilization as thermal energy storage material in the active regime of solar heating applications at low operating temperatures.Nevertheless,this mixture as phase change material(PCM)has a suitable phase-change temperature and heat of 36℃and 176.3 J/g,respectively.Hence,the objective of this study is to formulate a novel form-stable composite PCM with the PA-LA mixture and expanded graphite(EG)as a thermal enhancer.PA-LA eutectic mixture with varied concentrations of EG was prepared and characterized.The thermal conductivity of PA-LA/EG increased gradually with the mass of EG.Optimum thermal properties were observed in PA-LA/(5%EG)composite,where its melting(T_(m)),freezing temperature(T_(t)),latent melting heat and thermal conductivity was 35.53℃,34.84℃,174 J/g,and 1.19 W/(m·K),respectively.Also,the composite PCM is characterized by good chemical-thermal stability and thermal reliability for long-term usage.In conclusion,it can be utilized as a prospective form-stable PCM for thermal energy storage in solar heating systems,overheat treatment systems,and other thermal storage applications at low operating temperatures.展开更多
To evaluate the reliability of a landslide in a reservoir, the universal transfer coefficient method, which is popularized by the Chinese standard, is adopted as performance function in this study for： （1） common d...To evaluate the reliability of a landslide in a reservoir, the universal transfer coefficient method, which is popularized by the Chinese standard, is adopted as performance function in this study for： （1） common deterministic method stability evaluation; （2） reliability evaluation based on a Monte Carlo method; （3） comparison of landslide reliability under different water levels and under different correlation coefficients between soil shear strength parameters （c, Φ）, respectively with mean, standard deviation, reliability coefficient and failure probability. This article uses the Bazimen （八字门） landslide, which is located at the outlet of Xiangxi （香溪） River in the Three Gorges Reservoir, as an example to evaluate its stability and reliability under different water levels with two-dimensional deterministic and probabilistic methods. With the assumption that constant mean and normal distributed shear strength parameters （c, Φ）, correlation coefficient c, Φ=-1 based reliability analysis, compared with c, Φ=0 and 1, indicates obviously more increase of reliability index and lower standard deviation as water levels rise. To the case of a certain water level, c, Φ=-1 does not have constantly positive or negative effects on landslide reliability compared with c, Φ=0 or 1, but is associated with water level. Whereas the safety factor Fs by deterministic method, which is almost the same value as corresponding mean of safety factor from probabilistic analysis, will increase slightly as water level increases.展开更多
文摘Low thermal conductivity of binary fatty acid mixture of palmitic and lauric acids(PA-LA)within the value range of 0.15-0.17 W/(m·K)restricts its wide utilization as thermal energy storage material in the active regime of solar heating applications at low operating temperatures.Nevertheless,this mixture as phase change material(PCM)has a suitable phase-change temperature and heat of 36℃and 176.3 J/g,respectively.Hence,the objective of this study is to formulate a novel form-stable composite PCM with the PA-LA mixture and expanded graphite(EG)as a thermal enhancer.PA-LA eutectic mixture with varied concentrations of EG was prepared and characterized.The thermal conductivity of PA-LA/EG increased gradually with the mass of EG.Optimum thermal properties were observed in PA-LA/(5%EG)composite,where its melting(T_(m)),freezing temperature(T_(t)),latent melting heat and thermal conductivity was 35.53℃,34.84℃,174 J/g,and 1.19 W/(m·K),respectively.Also,the composite PCM is characterized by good chemical-thermal stability and thermal reliability for long-term usage.In conclusion,it can be utilized as a prospective form-stable PCM for thermal energy storage in solar heating systems,overheat treatment systems,and other thermal storage applications at low operating temperatures.
基金supported by the German Federal Ministry of Education and Research (BMBF)
文摘To evaluate the reliability of a landslide in a reservoir, the universal transfer coefficient method, which is popularized by the Chinese standard, is adopted as performance function in this study for： （1） common deterministic method stability evaluation; （2） reliability evaluation based on a Monte Carlo method; （3） comparison of landslide reliability under different water levels and under different correlation coefficients between soil shear strength parameters （c, Φ）, respectively with mean, standard deviation, reliability coefficient and failure probability. This article uses the Bazimen （八字门） landslide, which is located at the outlet of Xiangxi （香溪） River in the Three Gorges Reservoir, as an example to evaluate its stability and reliability under different water levels with two-dimensional deterministic and probabilistic methods. With the assumption that constant mean and normal distributed shear strength parameters （c, Φ）, correlation coefficient c, Φ=-1 based reliability analysis, compared with c, Φ=0 and 1, indicates obviously more increase of reliability index and lower standard deviation as water levels rise. To the case of a certain water level, c, Φ=-1 does not have constantly positive or negative effects on landslide reliability compared with c, Φ=0 or 1, but is associated with water level. Whereas the safety factor Fs by deterministic method, which is almost the same value as corresponding mean of safety factor from probabilistic analysis, will increase slightly as water level increases.
