为了得出溴化锂吸收式制冷系统的制冷系数(coefficient of performance,COP)随热源温度变化的曲线,本文基于单效溴化锂吸收式制冷系统的工作原理,采用集中参数法,建立了单效溴化锂吸收式太阳能制冷系统数学模型,并以Matlab/Simulink为...为了得出溴化锂吸收式制冷系统的制冷系数(coefficient of performance,COP)随热源温度变化的曲线,本文基于单效溴化锂吸收式制冷系统的工作原理,采用集中参数法,建立了单效溴化锂吸收式太阳能制冷系统数学模型,并以Matlab/Simulink为仿真平台进行了数值仿真。仿真结果表明,在溶液循环量不变的情况下,随着热源水进口温度的升高,发生器的换热量增加,该研究表明出口的溴化锂浓溶液的质量分数增加,放气范围变大,产生的制冷量增多,循环倍率减小,COP上升;当热源温度减小时,浓溶液的质量分数降低,放气范围减小,机组制冷量也减小,COP减小。该研究表明制冷系统COP与热源温度的变化趋势一致。该研究具有较大的应用前景。展开更多
In this work, the difference in number of dominant species in a community on global scale and successional trajectories was analyzed based on the published data. We explained the reasons of these differ-ences using a ...In this work, the difference in number of dominant species in a community on global scale and successional trajectories was analyzed based on the published data. We explained the reasons of these differ-ences using a resource availability hypothesis, proposed in this work, that the distribution of available resource determined the pattern of commu-nity dominance. The results showed that on global scale the number of dominant species of community varied across latitudinal forest zone, namely from single-species dominance in boreal and temperate forest to multi-species codominance, even no dominant species in tropical forest. This was consistent with the pattern of resource distribution on global scale. Similarly, in successional trajectories, the number of dominant species gradually radiated from single-species dominance to multi-species codominance, even no dominant species in tropical forest. The changing available resources in trajectories were responsible for this difference. By contrary, a community was often dominated by single species in temperate or boreal forest. This was determined by the low available resource, especially low available water and temperature. In boreal forest, low temperature greatly reduced availability of water and nutrient, which were responsible for the single-species dominance. In addition, the conclusion that high available resources sustained low dominance of community might be deduced, based on the fact that the dominance of community declined with the increasing of species diversity. To sum up, the richer the available resources were, the lower the dominance of community was, and vice versa. The hypothesis that the resource availability controlled the dominance of community could well elucidate the difference of community dominance on global and community scale.展开更多
文摘为了得出溴化锂吸收式制冷系统的制冷系数(coefficient of performance,COP)随热源温度变化的曲线,本文基于单效溴化锂吸收式制冷系统的工作原理,采用集中参数法,建立了单效溴化锂吸收式太阳能制冷系统数学模型,并以Matlab/Simulink为仿真平台进行了数值仿真。仿真结果表明,在溶液循环量不变的情况下,随着热源水进口温度的升高,发生器的换热量增加,该研究表明出口的溴化锂浓溶液的质量分数增加,放气范围变大,产生的制冷量增多,循环倍率减小,COP上升;当热源温度减小时,浓溶液的质量分数降低,放气范围减小,机组制冷量也减小,COP减小。该研究表明制冷系统COP与热源温度的变化趋势一致。该研究具有较大的应用前景。
基金This paper was supported by Normal Projects of National Natural Science Foundation of China (30870419, 40971151)Project "948" of State Forestry Administration (2006-4-13)Scientific Research Fund of Hunan Provincial Education Department (08C674)
文摘In this work, the difference in number of dominant species in a community on global scale and successional trajectories was analyzed based on the published data. We explained the reasons of these differ-ences using a resource availability hypothesis, proposed in this work, that the distribution of available resource determined the pattern of commu-nity dominance. The results showed that on global scale the number of dominant species of community varied across latitudinal forest zone, namely from single-species dominance in boreal and temperate forest to multi-species codominance, even no dominant species in tropical forest. This was consistent with the pattern of resource distribution on global scale. Similarly, in successional trajectories, the number of dominant species gradually radiated from single-species dominance to multi-species codominance, even no dominant species in tropical forest. The changing available resources in trajectories were responsible for this difference. By contrary, a community was often dominated by single species in temperate or boreal forest. This was determined by the low available resource, especially low available water and temperature. In boreal forest, low temperature greatly reduced availability of water and nutrient, which were responsible for the single-species dominance. In addition, the conclusion that high available resources sustained low dominance of community might be deduced, based on the fact that the dominance of community declined with the increasing of species diversity. To sum up, the richer the available resources were, the lower the dominance of community was, and vice versa. The hypothesis that the resource availability controlled the dominance of community could well elucidate the difference of community dominance on global and community scale.
