Al7075-Cu composite joints were prepared by the squeeze overcast process.The effects of melt temperature,die temperature,and squeeze pressure on hardness and ultimate tensile strength(UTS)of squeeze overcast Al7075-Cu...Al7075-Cu composite joints were prepared by the squeeze overcast process.The effects of melt temperature,die temperature,and squeeze pressure on hardness and ultimate tensile strength(UTS)of squeeze overcast Al7075-Cu composite joints were studied.The experimental results depict that squeeze pressure is the most significant process parameter affecting the hardness and UTS.The optimal values of UTS(48 MPa)and hardness(76 HRB)are achieved at a melt temperature of 800℃,a die temperature of 250℃,and a squeeze pressure of 90 MPa.Scanning electron microscopy(SEM)shows that fractured surfaces show flatfaced morphology at the optimal experimental condition.Energy-dispersive spectroscopy(EDS)analysis depicts that the atomic weight percentage of Zn decreases with an increase in melt temperature and squeeze pressure.The optimal mechanical properties of the Al7075-Cu overcast joint were achieved at the Al2Cu eutectic phase due to the large number of copper atoms that dispersed into the aluminum melt during the solidification process and the formation of strong intermetallic bonds.Gray relational analysis integrated with the Taguchi method was used to develop an optimal set of control variables for multi-response parametric optimization.Confirmatory tests were performed to validate the effectiveness of the employed technique.The manufacturing of squeeze overcast Al7075-Cu composite joints at optimal process parameters delivers a great indication to acknowledge a new method for foundry practitioners to manufacture materials with superior mechanical properties.展开更多
Based on the analysis of one year of observation data of solar radiation at the ground in Beijing in 1990, a simple empirical formula for calculating UV radiation in overcast sky is established. The formula is Quv/Quv...Based on the analysis of one year of observation data of solar radiation at the ground in Beijing in 1990, a simple empirical formula for calculating UV radiation in overcast sky is established. The formula is Quv/Quv0 = A1S + A0, where Quv and Quvo are monthly mean daily sums of UV exposure in overcast sky and clear sky, respectively. 5 is the daily sunshine hours. The calculated results agree well with the observed. The maximum and minimum relative biases are 9.9% and 0.1%, respectively, and the yearly relative bias is 2.9%. The ratio of ultraviolet radiation of overcast sky to clear sky in 1990 is between 44.6% and 61.8%, and the yearly average is 53.9%. Thus, almost half of the UV energy is lost in the atmosphere in overcast sky in 1990.展开更多
Autumn continuous overcast and rainfall weather affects normal rice harvest and often causes higher rice output which is not accompanied by a higher income,and it is one of main agrometeorological disasters in harvest...Autumn continuous overcast and rainfall weather affects normal rice harvest and often causes higher rice output which is not accompanied by a higher income,and it is one of main agrometeorological disasters in harvesting period of middle and late rice in Hubei Province. Especially in recent years,plantation area of single-season rice in Hubei Province is larger,and it is mostly harvested from last dekad of September to middle dekad of October,and the opportunity of encountering autumn continuous overcast and rainfall in harvesting period is larger. From later period of last dekad of September to first and middle dekads of October,2017,continuous overcast and rainfall weather occurred in most areas of east Hubei Province,which caused serious influence on the harvesting of semilate rice. In this paper,adverse influence on semilate rice harvest by the autumn continuous overcast and rainfall was investigated and analyzed,and the suggestions on defending and reducing the harm of continuous overcast and rainfall in the harvesting period of semilate rice were proposed.展开更多
Continuous overcast and hazy days are common for the winter in Hebei Province,these disastrous weathers have tremendous negative effect on the production of protected strawberry cultivation,for leading to the problems...Continuous overcast and hazy days are common for the winter in Hebei Province,these disastrous weathers have tremendous negative effect on the production of protected strawberry cultivation,for leading to the problems such as degrading photosynthesis of leaves,poor pollination and fertilization,more malformed fruits,low percentage of fertile fruits,delayed maturation of fruits,degraded quality and yield,and aggravated diseases.In view of the disastrous weathers and problems,the authors put forward the measures for the management of protected strawberry cultivation in continuous overcast and hazy days,to provide technical support for strawberry farmers.展开更多
A continuous overcast-rainy weather(CORW) process occurred over the mid-lower reaches of the Yangtze River(MLRYR) in China from February 14 to March 9 in 2009,with a large stretch and long duration that was rarely see...A continuous overcast-rainy weather(CORW) process occurred over the mid-lower reaches of the Yangtze River(MLRYR) in China from February 14 to March 9 in 2009,with a large stretch and long duration that was rarely seen in historical records.Using the empirical orthogonal function(EOF),we analyzed the geopotential height anomaly field of the NCEP-DOE Reanalysis II in the same period,and defined the stable components of extended-range(10-30 days) weather forecast(ERWF).Furthermore,we defined anomalous and climatic stable components based on the variation characteristics of the variance contribution ratio of EOF components.The climatic stable components were able to explain the impact of climatically averaged information on the ERWF,and the anomalous stable components revealed the abnormal characteristics of the continuous overcast-rainy days.Our results show that the stable components,especially the anomalous stable components,can maintain the stability for a longer time(more than 10 days) and manifest as monthly scale low-frequency variation and ultra-long-wave activities.They also behave as ultra-long waves of planetary scale with a stable and vertically coherent structure,reflect the variation of general circulation in mid-high latitudes,display the cycle of the zonal circulation and the movement and adjustment of the ultra-long waves,and are closely linked to the surface CORW process.展开更多
文摘Al7075-Cu composite joints were prepared by the squeeze overcast process.The effects of melt temperature,die temperature,and squeeze pressure on hardness and ultimate tensile strength(UTS)of squeeze overcast Al7075-Cu composite joints were studied.The experimental results depict that squeeze pressure is the most significant process parameter affecting the hardness and UTS.The optimal values of UTS(48 MPa)and hardness(76 HRB)are achieved at a melt temperature of 800℃,a die temperature of 250℃,and a squeeze pressure of 90 MPa.Scanning electron microscopy(SEM)shows that fractured surfaces show flatfaced morphology at the optimal experimental condition.Energy-dispersive spectroscopy(EDS)analysis depicts that the atomic weight percentage of Zn decreases with an increase in melt temperature and squeeze pressure.The optimal mechanical properties of the Al7075-Cu overcast joint were achieved at the Al2Cu eutectic phase due to the large number of copper atoms that dispersed into the aluminum melt during the solidification process and the formation of strong intermetallic bonds.Gray relational analysis integrated with the Taguchi method was used to develop an optimal set of control variables for multi-response parametric optimization.Confirmatory tests were performed to validate the effectiveness of the employed technique.The manufacturing of squeeze overcast Al7075-Cu composite joints at optimal process parameters delivers a great indication to acknowledge a new method for foundry practitioners to manufacture materials with superior mechanical properties.
基金supported by the National Natural Science Foundation of China(No.40175031)the Knowledge Creative Project(KZCX2-204)of the Chinese Academy of Sciencesthe LAPC-KF-2002-02 program.
文摘Based on the analysis of one year of observation data of solar radiation at the ground in Beijing in 1990, a simple empirical formula for calculating UV radiation in overcast sky is established. The formula is Quv/Quv0 = A1S + A0, where Quv and Quvo are monthly mean daily sums of UV exposure in overcast sky and clear sky, respectively. 5 is the daily sunshine hours. The calculated results agree well with the observed. The maximum and minimum relative biases are 9.9% and 0.1%, respectively, and the yearly relative bias is 2.9%. The ratio of ultraviolet radiation of overcast sky to clear sky in 1990 is between 44.6% and 61.8%, and the yearly average is 53.9%. Thus, almost half of the UV energy is lost in the atmosphere in overcast sky in 1990.
文摘Autumn continuous overcast and rainfall weather affects normal rice harvest and often causes higher rice output which is not accompanied by a higher income,and it is one of main agrometeorological disasters in harvesting period of middle and late rice in Hubei Province. Especially in recent years,plantation area of single-season rice in Hubei Province is larger,and it is mostly harvested from last dekad of September to middle dekad of October,and the opportunity of encountering autumn continuous overcast and rainfall in harvesting period is larger. From later period of last dekad of September to first and middle dekads of October,2017,continuous overcast and rainfall weather occurred in most areas of east Hubei Province,which caused serious influence on the harvesting of semilate rice. In this paper,adverse influence on semilate rice harvest by the autumn continuous overcast and rainfall was investigated and analyzed,and the suggestions on defending and reducing the harm of continuous overcast and rainfall in the harvesting period of semilate rice were proposed.
文摘Continuous overcast and hazy days are common for the winter in Hebei Province,these disastrous weathers have tremendous negative effect on the production of protected strawberry cultivation,for leading to the problems such as degrading photosynthesis of leaves,poor pollination and fertilization,more malformed fruits,low percentage of fertile fruits,delayed maturation of fruits,degraded quality and yield,and aggravated diseases.In view of the disastrous weathers and problems,the authors put forward the measures for the management of protected strawberry cultivation in continuous overcast and hazy days,to provide technical support for strawberry farmers.
基金supported by National Natural Science Foundation of China (Grant No.40930952)Science and Technology Supporting Project (Grant No.2009BAC51B04)
文摘A continuous overcast-rainy weather(CORW) process occurred over the mid-lower reaches of the Yangtze River(MLRYR) in China from February 14 to March 9 in 2009,with a large stretch and long duration that was rarely seen in historical records.Using the empirical orthogonal function(EOF),we analyzed the geopotential height anomaly field of the NCEP-DOE Reanalysis II in the same period,and defined the stable components of extended-range(10-30 days) weather forecast(ERWF).Furthermore,we defined anomalous and climatic stable components based on the variation characteristics of the variance contribution ratio of EOF components.The climatic stable components were able to explain the impact of climatically averaged information on the ERWF,and the anomalous stable components revealed the abnormal characteristics of the continuous overcast-rainy days.Our results show that the stable components,especially the anomalous stable components,can maintain the stability for a longer time(more than 10 days) and manifest as monthly scale low-frequency variation and ultra-long-wave activities.They also behave as ultra-long waves of planetary scale with a stable and vertically coherent structure,reflect the variation of general circulation in mid-high latitudes,display the cycle of the zonal circulation and the movement and adjustment of the ultra-long waves,and are closely linked to the surface CORW process.
