Tests were carried out to study the strength deterioration of concrete cooled in air or by water after sub-high temperature at different level and varying with cycles. It is proved that the cross-shaped cracks turned ...Tests were carried out to study the strength deterioration of concrete cooled in air or by water after sub-high temperature at different level and varying with cycles. It is proved that the cross-shaped cracks turned up and extended little by little on the surface of specimen subjected to repeat sub-high temperature, the splitting failure is characterized by cross-shaped cracks after 30 cycles, the concrete strengths decrease rapidly at early stage and to be steady subsequently with the increase of the temperature cycles, the splitting-tensile strength is more sensitive to temperature cycles than the compressive strength, the decline of concrete strength is mainly controlled by the maximum temperature having reached, the ultrasonic velocity in concrete is also declined. On the basis of test results, the mechanisms of sub-high temperature to the strength deterioration of concrete are analyzed.The formulas for calculating the compressive and splitting-tensile strength of concrete relating to the variation of temperature are proposed.展开更多
National Meteorological Information Center （NMIC） rainfall data and NCEP/NCAR daily circulation reanalysis data are employed to establish the onset-pentad time index of the spring persistent rains （SPR） and the de...National Meteorological Information Center （NMIC） rainfall data and NCEP/NCAR daily circulation reanalysis data are employed to establish the onset-pentad time index of the spring persistent rains （SPR） and the decay-pentad time index of the South China Sea （SCS） sub-high. These indexes are used to study the relationship between the factors in SPR period and their relations to the circulation and precipitation of the East Asian summer monsoon （EASM）. Results show that, the summer rainfall over southeastern China decreases when SPR onset is late. For then EASM strengthens and the cyclonic circulation around the Tibetan Plateau （TP） strengthens, which makes abnormal anti-cyclonic circulation （cyclonic convergent circulation weakens） appear over southeastern China. When the decay of SCS sub-high delays, abnormal flood prevails over the middle and lower reaches of the Yangtze River （MLYR） and to the south. That is mainly caused by EASM weakening while SCS sub-high strengthening, then the abnormal southwesterly over South China and the abnormal northerlies of anti-cyclonic circulation around the TP converge over the Yangtze Valley. The two indexes have high correlations with multivariate ENSO index （MEI） in March, indicating that the climate abnormity in East Asia is related to global climate abnormity tightly. The two time indexes are independent of each other, which is favorable for the prediction of the anomalies of the circulation and precipitation of EASM. From this point of view, we must take the global climate background into account when we analyze and predict the East Asian summer circulation and precipitation.展开更多
WASP(Wallops Arc Second Pointer)是由美国国家航空航天局(NASA)开发的一种临近空间天文台亚角秒级指向系统,旨在构建可适配多类科学载荷的临近空间天文观测平台.WASP系统由指向控制系统(PCS)和星跟踪器子系统(CARDS)组成,该系统结合...WASP(Wallops Arc Second Pointer)是由美国国家航空航天局(NASA)开发的一种临近空间天文台亚角秒级指向系统,旨在构建可适配多类科学载荷的临近空间天文观测平台.WASP系统由指向控制系统(PCS)和星跟踪器子系统(CARDS)组成,该系统结合精密机械和电子组件,辅以超压气球技术,能在临近空间执行长时飞行任务,同时保持亚角秒级的指向精度.WASP系统的灵活性和标准化设计使其能够适配多种科学载荷,满足不同的任务需求.在空间科学领域,WASP系统的应用不仅拓宽了高空科学气球的研究范围,也为临近空间天文台的建设提供了创新方案,推动了对临近空间的探索.WASP系统的成功试飞和应用,为其在行星科学、天体物理学和地球观测等领域的应用奠定了基础,也为中国临近空间科学的发展提供了可靠的参考.展开更多
基金Funded by Outstanding Youth Science Foundation of Henan Province of China (No. 04120002300)
文摘Tests were carried out to study the strength deterioration of concrete cooled in air or by water after sub-high temperature at different level and varying with cycles. It is proved that the cross-shaped cracks turned up and extended little by little on the surface of specimen subjected to repeat sub-high temperature, the splitting failure is characterized by cross-shaped cracks after 30 cycles, the concrete strengths decrease rapidly at early stage and to be steady subsequently with the increase of the temperature cycles, the splitting-tensile strength is more sensitive to temperature cycles than the compressive strength, the decline of concrete strength is mainly controlled by the maximum temperature having reached, the ultrasonic velocity in concrete is also declined. On the basis of test results, the mechanisms of sub-high temperature to the strength deterioration of concrete are analyzed.The formulas for calculating the compressive and splitting-tensile strength of concrete relating to the variation of temperature are proposed.
基金Supported by the National"973"Program under No.2006CB403600the National Natural Science Foundation of China Project under Nos.40475027,40220503,and 40523001.
文摘National Meteorological Information Center （NMIC） rainfall data and NCEP/NCAR daily circulation reanalysis data are employed to establish the onset-pentad time index of the spring persistent rains （SPR） and the decay-pentad time index of the South China Sea （SCS） sub-high. These indexes are used to study the relationship between the factors in SPR period and their relations to the circulation and precipitation of the East Asian summer monsoon （EASM）. Results show that, the summer rainfall over southeastern China decreases when SPR onset is late. For then EASM strengthens and the cyclonic circulation around the Tibetan Plateau （TP） strengthens, which makes abnormal anti-cyclonic circulation （cyclonic convergent circulation weakens） appear over southeastern China. When the decay of SCS sub-high delays, abnormal flood prevails over the middle and lower reaches of the Yangtze River （MLYR） and to the south. That is mainly caused by EASM weakening while SCS sub-high strengthening, then the abnormal southwesterly over South China and the abnormal northerlies of anti-cyclonic circulation around the TP converge over the Yangtze Valley. The two indexes have high correlations with multivariate ENSO index （MEI） in March, indicating that the climate abnormity in East Asia is related to global climate abnormity tightly. The two time indexes are independent of each other, which is favorable for the prediction of the anomalies of the circulation and precipitation of EASM. From this point of view, we must take the global climate background into account when we analyze and predict the East Asian summer circulation and precipitation.
文摘WASP(Wallops Arc Second Pointer)是由美国国家航空航天局(NASA)开发的一种临近空间天文台亚角秒级指向系统,旨在构建可适配多类科学载荷的临近空间天文观测平台.WASP系统由指向控制系统(PCS)和星跟踪器子系统(CARDS)组成,该系统结合精密机械和电子组件,辅以超压气球技术,能在临近空间执行长时飞行任务,同时保持亚角秒级的指向精度.WASP系统的灵活性和标准化设计使其能够适配多种科学载荷,满足不同的任务需求.在空间科学领域,WASP系统的应用不仅拓宽了高空科学气球的研究范围,也为临近空间天文台的建设提供了创新方案,推动了对临近空间的探索.WASP系统的成功试飞和应用,为其在行星科学、天体物理学和地球观测等领域的应用奠定了基础,也为中国临近空间科学的发展提供了可靠的参考.
