Differential scanning calorimeter technique combined with the traditional fluxing treatment was used to investigate the specific heat and related thermodynamic properties of under-cooled pure silver melts. The specifi...Differential scanning calorimeter technique combined with the traditional fluxing treatment was used to investigate the specific heat and related thermodynamic properties of under-cooled pure silver melts. The specific heat of the under-cooled melt showed a linear dependence on the temperature in the range of the obtained under-cooling from 0 to 198 K. The related thermodynamic properties of silver, such as the entropy change, the enthalpy change and the Gibbs free energy difference between the under-cooled melt and the solid phase, were derived from the measured specific heat. The relations between the temperature and the thermal diffusion or the thermal conductivity of the under-cooled melt were analyzed respectively.展开更多
利用耦合了碘化银催化过程的WRF(Weather Research and Forecast)模式,对2014年8月16日南京青奥会开幕式当天实施的人工催化作业开展数值模拟,评估催化效果并通过敏感性数值试验调查低空环境干层对催化效果的影响。结果表明,催化作业产...利用耦合了碘化银催化过程的WRF(Weather Research and Forecast)模式,对2014年8月16日南京青奥会开幕式当天实施的人工催化作业开展数值模拟,评估催化效果并通过敏感性数值试验调查低空环境干层对催化效果的影响。结果表明,催化作业产生了减雨效果,低空干区的存在是影响催化效果的关键。当低空存在深厚的相对湿度很小的干层时,催化导致减雨效果;当增加低层的相对湿度即弱化低空干层,催化减雨效果减弱甚至出现增雨效果。催化增强了雪的形成过程但减弱了雪的增长过程尤其是凝华增长,导致雪粒子浓度增加但粒径减小,融化产生更多的小雨滴增强了蒸发过程,最终导致地面降水减少。展开更多
The purity of the brazing alloys applied is necessary to be improved with the increasing cleanness of steel. Calcium is easily brought into the widely ased brazing alloy, Ag-Cu-Zn, during the producing process. This p...The purity of the brazing alloys applied is necessary to be improved with the increasing cleanness of steel. Calcium is easily brought into the widely ased brazing alloy, Ag-Cu-Zn, during the producing process. This paper aims at revealing the effect of calcium on the melting behavior of the brazing alloy. The thermal analysis kinetics of silver alloy with trace calcium was studied by using differential scanning calorimetry （ DSC ） , and the enthalpy peaks were analyzed by differential methods. The rate constant of phase transformation in the probable brazing temperature range goes up with increasing calcium content, according to the values of the apparent activation energy, E, and the frequeney constant, A. It is concluded that the calcium addition could improve the melting performance of Ag-Cu-Zn brazing alloy.展开更多
基金Supported by the National Natural Science Foundation of China (Grant No.50731005/50821001)the National Basic Research Program of China (Grant Nos. 2009CB626603 and 2007CB616915)+1 种基金PCSIRT (Grant No. IRT0650)the Hebei Technology Department Foundation (Grant No. 08965109D)
文摘Differential scanning calorimeter technique combined with the traditional fluxing treatment was used to investigate the specific heat and related thermodynamic properties of under-cooled pure silver melts. The specific heat of the under-cooled melt showed a linear dependence on the temperature in the range of the obtained under-cooling from 0 to 198 K. The related thermodynamic properties of silver, such as the entropy change, the enthalpy change and the Gibbs free energy difference between the under-cooled melt and the solid phase, were derived from the measured specific heat. The relations between the temperature and the thermal diffusion or the thermal conductivity of the under-cooled melt were analyzed respectively.
文摘利用耦合了碘化银催化过程的WRF(Weather Research and Forecast)模式,对2014年8月16日南京青奥会开幕式当天实施的人工催化作业开展数值模拟,评估催化效果并通过敏感性数值试验调查低空环境干层对催化效果的影响。结果表明,催化作业产生了减雨效果,低空干区的存在是影响催化效果的关键。当低空存在深厚的相对湿度很小的干层时,催化导致减雨效果;当增加低层的相对湿度即弱化低空干层,催化减雨效果减弱甚至出现增雨效果。催化增强了雪的形成过程但减弱了雪的增长过程尤其是凝华增长,导致雪粒子浓度增加但粒径减小,融化产生更多的小雨滴增强了蒸发过程,最终导致地面降水减少。
文摘The purity of the brazing alloys applied is necessary to be improved with the increasing cleanness of steel. Calcium is easily brought into the widely ased brazing alloy, Ag-Cu-Zn, during the producing process. This paper aims at revealing the effect of calcium on the melting behavior of the brazing alloy. The thermal analysis kinetics of silver alloy with trace calcium was studied by using differential scanning calorimetry （ DSC ） , and the enthalpy peaks were analyzed by differential methods. The rate constant of phase transformation in the probable brazing temperature range goes up with increasing calcium content, according to the values of the apparent activation energy, E, and the frequeney constant, A. It is concluded that the calcium addition could improve the melting performance of Ag-Cu-Zn brazing alloy.
