Special cooling methods are needed for normal growth of crops in closed greenhouses which permit no ventilation, especially during warm seasons. Experi- ments were designed to evaluate two cooling methods （Watergy ch...Special cooling methods are needed for normal growth of crops in closed greenhouses which permit no ventilation, especially during warm seasons. Experi- ments were designed to evaluate two cooling methods （Watergy chimney method and pool method） in a closed greenhouse in Beijing during warm seasons. Prelimi- nary results showed that average temperature at daytime （from 8：00 to 18：00） at 100 cm above ground surface in the closed greenhouse could be reduced by 8 with the Watergy chimney method. Average relative humidity fluctuated between 45% and 75% during daytime at 100 cm above ground surface within the closed greenhouse. With the pool method, average temperature was about 10 ℃ lower than that of the control greenhouse without pool at 50 cm above the ground surface. The peak temperature at 50 cm height was about 32℃ between 11：30 and 15：00 and, close to outside temperature. Temperature in this system satisfied normal growth of most crops, but relative humidity at 50 cm height were above 90% at daytime.展开更多
High-temperature creep properties of sintered uranium dioxide pellets with two grain sizes （9.0 μm and 23.8μm） were studied. The results indicate that the creep rate becomes a little faster with the reduction of t...High-temperature creep properties of sintered uranium dioxide pellets with two grain sizes （9.0 μm and 23.8μm） were studied. The results indicate that the creep rate becomes a little faster with the reduction of the uranium dioxide grain size at the same temperature and the same load. At the same temperature, the logarithmic value of the steady creep rate vs stress has linear relation, and with increasing load, the steady creep rate of the sintered uranium dioxide pellet increases. Under the same load, the steady creep rate of the sintered uranium dioxide pellet increases with increasing temperature; and the creep rates of sintered uranium dioxide pellet with the grain size of 9.0 μm and 23.8 μm under 10 MPa are almost the same. The creep process is controlled both by Nabarro--Herring creep and Hamper-Dorn creep for uranium dioxide pellet with grain size of 9.0 μm, while Hamper---Dora creep is the dominantmechanism for uranium dioxide with grain size of 23.8 μm.展开更多
In this study the authors apply the chemistry version of the Weather Research and Forecasting model （WRF-Chem） to examine the impacts of black carbon （BC）-induced changes in snow albedo on simulated temperature an...In this study the authors apply the chemistry version of the Weather Research and Forecasting model （WRF-Chem） to examine the impacts of black carbon （BC）-induced changes in snow albedo on simulated temperature and precipitation during the severe snowstorm that occurred in southern China during 0800 26 January to 0800 29 January 2008 （Note that all times are local time except when otherwise stated）. Black carbon aerosol was simulated online within the WRF-Chem. The model resuits showed that surface-albedo, averaged over 27-28 January, can be reduced by up to 10% by the deposition of BC. As a result, relative to a simulation that does not consider deposition of BC on snow/ice, the authors predicted surface air temperatures during 27-28 January can differ by -1.95 to 2.70 K, and the authors predicted accumulated precipitation over 27-28 January can differ by -2.91 to 3.10 mm over Areas A and B with large BC deposition. Different signs of changes are determined by the feedback of clouds and by the availability of water vapor in the atmosphere.展开更多
In this study, the sensitivities of net primary production(NPP), soil carbon, and vegetation carbon to precipitation and temperature variability over China are discussed using the state-of-the-art Lund-Potsdam-Jena dy...In this study, the sensitivities of net primary production(NPP), soil carbon, and vegetation carbon to precipitation and temperature variability over China are discussed using the state-of-the-art Lund-Potsdam-Jena dynamic global vegetation model(LPJ DGVM). The impacts of the sensitivities to precipitation variability and temperature variability on NPP, soil carbon, and vegetation carbon are discussed. It is shown that increasing precipitation variability, representing the frequency of extreme precipitation events, leads to losses in NPP, soil carbon, and vegetation carbon over most of China, especially in North and Northeast China where the dominant plant functional types(i.e., those with the largest simulated areal cover) are grass and boreal needle-leaved forest. The responses of NPP, soil carbon, and vegetation carbon to decreasing precipitation variability are opposite to the responses to increasing precipitation variability. The variations in NPP, soil carbon, and vegetation carbon in response to increasing and decreasing precipitation variability show a nonlinear asymmetry. Increasing precipitation variability results in notable interannual variation of NPP. The sensitivities of NPP, soil carbon, and vegetation carbon to temperature variability, whether negative or positive, meaning frequent hot and cold days, are slight. The present study suggests, based on the LPJ model, that precipitation variability has a more severe impact than temperature variability on NPP, soil carbon, and vegetation carbon.展开更多
[Objective] The aim was to provide references for development of industries engaging in flowers and trees in Beipei area in Chongqing. [Method] The occurring trend, intensity trend of summer drought, relationship of i...[Objective] The aim was to provide references for development of industries engaging in flowers and trees in Beipei area in Chongqing. [Method] The occurring trend, intensity trend of summer drought, relationship of intensity with rainfall and extremely highest temperature, occurring trend during initial period of summer drought and the effects in mountain cities were analyzed, based on information on lasting period, rainfall, average temperature, extremely highest temperature of sum- mer drought in Beipei area in mountain cities during 1981-2010 and, growth condi- tion and phenological phenomena of Michelia champaca during 2005-2007. [Result] The occurring probability of summer drought in mountain cities was 57% and the probabilities of light, moderate, heavy and extreme drought were 30%, 10%, 7% and 10%; intensity of summer drought was none of linear relation with rainfall and ex- tremely highest temperature. In summer drought, daily average rainfall was less than 0.9 ram; extremely highest temperature was 35.0-45.0 ℃ with probability at 30%; initial period of summer drought was from later June to middle August and of extreme drought was later June-later July; the ending period was early September. During drought, when the extremely highest temperature （〉35.0 ℃） occurred in three days within a Hou, flowers and trees were affected by the hot drought and when the extreme temperature （〉40.0 ℃） occurred in three days within a Hou, the plants were seriously affected. [Conclusion] Based on characters of summer drought, pre- cautions can be taken to reduce effects of summer drought on flowers and trees with the help of weather forecast.展开更多
基金Supported by National High Technology Research and Development Program of China(2012AA101903,2011AA100504)Natural Science Foundation of Shaanxi Province(K3320215199)Research Fund for the Doctoral Program of Northwest A&F University(2452015291)~~
文摘Special cooling methods are needed for normal growth of crops in closed greenhouses which permit no ventilation, especially during warm seasons. Experi- ments were designed to evaluate two cooling methods （Watergy chimney method and pool method） in a closed greenhouse in Beijing during warm seasons. Prelimi- nary results showed that average temperature at daytime （from 8：00 to 18：00） at 100 cm above ground surface in the closed greenhouse could be reduced by 8 with the Watergy chimney method. Average relative humidity fluctuated between 45% and 75% during daytime at 100 cm above ground surface within the closed greenhouse. With the pool method, average temperature was about 10 ℃ lower than that of the control greenhouse without pool at 50 cm above the ground surface. The peak temperature at 50 cm height was about 32℃ between 11：30 and 15：00 and, close to outside temperature. Temperature in this system satisfied normal growth of most crops, but relative humidity at 50 cm height were above 90% at daytime.
基金Project(50874126)supported by the National Natural Science Foundation of China
文摘High-temperature creep properties of sintered uranium dioxide pellets with two grain sizes （9.0 μm and 23.8μm） were studied. The results indicate that the creep rate becomes a little faster with the reduction of the uranium dioxide grain size at the same temperature and the same load. At the same temperature, the logarithmic value of the steady creep rate vs stress has linear relation, and with increasing load, the steady creep rate of the sintered uranium dioxide pellet increases. Under the same load, the steady creep rate of the sintered uranium dioxide pellet increases with increasing temperature; and the creep rates of sintered uranium dioxide pellet with the grain size of 9.0 μm and 23.8 μm under 10 MPa are almost the same. The creep process is controlled both by Nabarro--Herring creep and Hamper-Dorn creep for uranium dioxide pellet with grain size of 9.0 μm, while Hamper---Dora creep is the dominantmechanism for uranium dioxide with grain size of 23.8 μm.
基金supported by the Knowledge Innovation Program of the Chinese Academy of Sciences (Grant KZCX2-YW-205)the National Natural Science Foundation of China (Grant Nos.40825016,90711004,and 40775083)
文摘In this study the authors apply the chemistry version of the Weather Research and Forecasting model （WRF-Chem） to examine the impacts of black carbon （BC）-induced changes in snow albedo on simulated temperature and precipitation during the severe snowstorm that occurred in southern China during 0800 26 January to 0800 29 January 2008 （Note that all times are local time except when otherwise stated）. Black carbon aerosol was simulated online within the WRF-Chem. The model resuits showed that surface-albedo, averaged over 27-28 January, can be reduced by up to 10% by the deposition of BC. As a result, relative to a simulation that does not consider deposition of BC on snow/ice, the authors predicted surface air temperatures during 27-28 January can differ by -1.95 to 2.70 K, and the authors predicted accumulated precipitation over 27-28 January can differ by -2.91 to 3.10 mm over Areas A and B with large BC deposition. Different signs of changes are determined by the feedback of clouds and by the availability of water vapor in the atmosphere.
基金Funding was provided by grants from the National Basic Research Program of China (Grant No. 2012CB955202)the National Natural Science Foundation of China (Grant No. 41375111)+1 种基金the LASG Free Exploration Fundthe LASG State Key Laboratory Special Fund
文摘In this study, the sensitivities of net primary production(NPP), soil carbon, and vegetation carbon to precipitation and temperature variability over China are discussed using the state-of-the-art Lund-Potsdam-Jena dynamic global vegetation model(LPJ DGVM). The impacts of the sensitivities to precipitation variability and temperature variability on NPP, soil carbon, and vegetation carbon are discussed. It is shown that increasing precipitation variability, representing the frequency of extreme precipitation events, leads to losses in NPP, soil carbon, and vegetation carbon over most of China, especially in North and Northeast China where the dominant plant functional types(i.e., those with the largest simulated areal cover) are grass and boreal needle-leaved forest. The responses of NPP, soil carbon, and vegetation carbon to decreasing precipitation variability are opposite to the responses to increasing precipitation variability. The variations in NPP, soil carbon, and vegetation carbon in response to increasing and decreasing precipitation variability show a nonlinear asymmetry. Increasing precipitation variability results in notable interannual variation of NPP. The sensitivities of NPP, soil carbon, and vegetation carbon to temperature variability, whether negative or positive, meaning frequent hot and cold days, are slight. The present study suggests, based on the LPJ model, that precipitation variability has a more severe impact than temperature variability on NPP, soil carbon, and vegetation carbon.
基金Supported by Key Program of Chongqing Meteorological Bureau(ywgg-201217)~~
文摘[Objective] The aim was to provide references for development of industries engaging in flowers and trees in Beipei area in Chongqing. [Method] The occurring trend, intensity trend of summer drought, relationship of intensity with rainfall and extremely highest temperature, occurring trend during initial period of summer drought and the effects in mountain cities were analyzed, based on information on lasting period, rainfall, average temperature, extremely highest temperature of sum- mer drought in Beipei area in mountain cities during 1981-2010 and, growth condi- tion and phenological phenomena of Michelia champaca during 2005-2007. [Result] The occurring probability of summer drought in mountain cities was 57% and the probabilities of light, moderate, heavy and extreme drought were 30%, 10%, 7% and 10%; intensity of summer drought was none of linear relation with rainfall and ex- tremely highest temperature. In summer drought, daily average rainfall was less than 0.9 ram; extremely highest temperature was 35.0-45.0 ℃ with probability at 30%; initial period of summer drought was from later June to middle August and of extreme drought was later June-later July; the ending period was early September. During drought, when the extremely highest temperature （〉35.0 ℃） occurred in three days within a Hou, flowers and trees were affected by the hot drought and when the extreme temperature （〉40.0 ℃） occurred in three days within a Hou, the plants were seriously affected. [Conclusion] Based on characters of summer drought, pre- cautions can be taken to reduce effects of summer drought on flowers and trees with the help of weather forecast.
