On the basis of summarizing the research on disaster risk at home and abroad, Shenyang, one of the cities with the most frequent meteorological disasters, was taken as an example. Cold chilling injury is one of the ma...On the basis of summarizing the research on disaster risk at home and abroad, Shenyang, one of the cities with the most frequent meteorological disasters, was taken as an example. Cold chilling injury is one of the major agricultural meteorological disasters, which poses a serious threat to the sustainable development of agriculture and food security in Jilin and Shenyang. Based on meteorological observation data of recent 65 years in Shenyang and microclimate monitoring data of agricultural facilities in two years, this paper makes statistical analysis by mathematical statistics and calculates the highest outdoor temperature, the lowest indoor air temperature and the highest ceiling temperature according to the meteorological grade index of agricultural facilities’ low temperature chilling damage, low temperature and other meteorological elements of grade indicators, analysis of greenhouse production trend of greenhouse climate change, and to discuss the relationship between temperature inside and outside the greenhouse and the facility microclimate conditions in agricultural cold weather disastrous and early warning services. The results showed that in the 21st century, the number of days with low temperature of ≤-20°C increased significantly compared with those in the 1970s, 1980s and 1990s. The risk of low temperature chilling injury in facility agriculture in Shenyang was dominated by mild and moderate low temperature risk. Shenyang low temperature cold damage warning services standards to reduce the impact of chilling injury on agricultural facilities and development.展开更多
To study the relationship between material composition, curing conditions and strength development, the study simulated high-strength precast concrete pile production, and a high-strength mortar up to 90 MPa was desig...To study the relationship between material composition, curing conditions and strength development, the study simulated high-strength precast concrete pile production, and a high-strength mortar up to 90 MPa was designed and a hot-water pool was built for concrete curing. The major point of the study was to achieve a high early strength by using cement/metakaolin systems without autoclave curing with high-pressure steam. By means of XRD and thermal analysis, the progress of the hydration of the cement pastes blended with metakaolin was characterized. The main results indicate that high strength can be obtained at early age by the use of metakaolin and thermal treatment （hot-water curing）. The improvement in strength of mortars with metakaolin can be explained by an increase in the amount of C-S-H and C-S-A-H hydrated phases and a decrease in the amount of calcium hydration（CH）. Further more, a decrease in Ca/Si ratio of the matrix was observed from the results of EDX analysis, which also leaded to an improvement of the compressive strength. These results are of great importance for the high-strength precast concrete manufacturing industry.展开更多
文摘On the basis of summarizing the research on disaster risk at home and abroad, Shenyang, one of the cities with the most frequent meteorological disasters, was taken as an example. Cold chilling injury is one of the major agricultural meteorological disasters, which poses a serious threat to the sustainable development of agriculture and food security in Jilin and Shenyang. Based on meteorological observation data of recent 65 years in Shenyang and microclimate monitoring data of agricultural facilities in two years, this paper makes statistical analysis by mathematical statistics and calculates the highest outdoor temperature, the lowest indoor air temperature and the highest ceiling temperature according to the meteorological grade index of agricultural facilities’ low temperature chilling damage, low temperature and other meteorological elements of grade indicators, analysis of greenhouse production trend of greenhouse climate change, and to discuss the relationship between temperature inside and outside the greenhouse and the facility microclimate conditions in agricultural cold weather disastrous and early warning services. The results showed that in the 21st century, the number of days with low temperature of ≤-20°C increased significantly compared with those in the 1970s, 1980s and 1990s. The risk of low temperature chilling injury in facility agriculture in Shenyang was dominated by mild and moderate low temperature risk. Shenyang low temperature cold damage warning services standards to reduce the impact of chilling injury on agricultural facilities and development.
基金Funded by the National Fundamental Scientific Research Project of China(2009CB623201)
文摘To study the relationship between material composition, curing conditions and strength development, the study simulated high-strength precast concrete pile production, and a high-strength mortar up to 90 MPa was designed and a hot-water pool was built for concrete curing. The major point of the study was to achieve a high early strength by using cement/metakaolin systems without autoclave curing with high-pressure steam. By means of XRD and thermal analysis, the progress of the hydration of the cement pastes blended with metakaolin was characterized. The main results indicate that high strength can be obtained at early age by the use of metakaolin and thermal treatment （hot-water curing）. The improvement in strength of mortars with metakaolin can be explained by an increase in the amount of C-S-H and C-S-A-H hydrated phases and a decrease in the amount of calcium hydration（CH）. Further more, a decrease in Ca/Si ratio of the matrix was observed from the results of EDX analysis, which also leaded to an improvement of the compressive strength. These results are of great importance for the high-strength precast concrete manufacturing industry.
