The effect of vegetation on the water-heat exchange in the freezing-thawing processes of active layer is one of the key issues in the study of land surface processes and in predicting the response of alpine ecosystems...The effect of vegetation on the water-heat exchange in the freezing-thawing processes of active layer is one of the key issues in the study of land surface processes and in predicting the response of alpine ecosystems to climate change in permafrost regions. In this study, we used the simultaneous heat and water model to investigate the effects of plant canopy on surface and subsurface hydrothermal dynamics in the Fenghuoshan area of the QinghaiTibet Plateau by changing the leaf area index(LAI) and keeping other variables constant. Results showed that the sensible heat, latent heat and net radiation are increased with an increase in the LAI. However, the ground heat flux decreased with an increasing LAI. The annual total evapotranspiration and vegetation transpiration ranged from-16% to 9% and-100% to 15%, respectively, in response to extremes of doubled and zero LAI, respectively. There was a negative feedback between vegetation and the volumetric unfrozen water content at 0.2 m through changing evapotranspiration. The simulation results of soil temperature and moisture suggest that better vegetation conditions are conducive to maintaining the thermal stability of the underlying permafrost, and the advanced initial thawing time and increasing thawing rate of soil ice with the increase in the LAI may have a great influence on the timing and magnitude of supra-permafrost groundwater. This study quantifies the impact of vegetation change on surface and subsurface hydrothermal processes and provides a basic understanding for evaluating the impact of vegetation degradation on the water-heat exchange in permafrost regions under climate change.展开更多
With an aim of rationing use of energy, energy safety, and to reduce carbon emission, our interest was geared towards the refrigerators and all the refrigerating machines. Indeed the heat yielded by the exchanger cond...With an aim of rationing use of energy, energy safety, and to reduce carbon emission, our interest was geared towards the refrigerators and all the refrigerating machines. Indeed the heat yielded by the exchanger condenser can be developed for the water heating, floors heating etc. After an encouraging theoretical study, two prototypes were produced in order to validate the theoretical results. A first refrigerator was coupled with a water-heater and another with a heating floor. The water temperature reached, in one day, is of 60℃;which makes it possible to predict better results with a continuously used refrigerator. In the same way for the heating floor coupled with the second refrigerator, the temperature reached high values because the surface is reduced;however for the heating floors the standard fixes the temperature between 28℃ and 30℃.展开更多
温度控制在生产生活中发挥着举足轻重的作用。位式控制算法在调节具有滞后性的水暖床垫温度控制系统时容易导致温度在目标值上下波动,控制效果不理想。为了解决此问题,设计了一种基于位置式PID的水暖床垫温度控制系统,系统以51内核的微...温度控制在生产生活中发挥着举足轻重的作用。位式控制算法在调节具有滞后性的水暖床垫温度控制系统时容易导致温度在目标值上下波动,控制效果不理想。为了解决此问题,设计了一种基于位置式PID的水暖床垫温度控制系统,系统以51内核的微处理器为核心控制器、以负温度系数热敏电阻(Negative Temperature Coefficient,NTC)为温度传感器、以PTC为加热器、以直流电机作为循环水泵。经实际测试结果表明,该系统运行稳定,控温精度在±0.5℃以内,达到了理想的温度控制效果。展开更多
基金This study was supported by the National Nature Science Foundation of China(No.41671015,No.42071027,No.41890821)。
文摘The effect of vegetation on the water-heat exchange in the freezing-thawing processes of active layer is one of the key issues in the study of land surface processes and in predicting the response of alpine ecosystems to climate change in permafrost regions. In this study, we used the simultaneous heat and water model to investigate the effects of plant canopy on surface and subsurface hydrothermal dynamics in the Fenghuoshan area of the QinghaiTibet Plateau by changing the leaf area index(LAI) and keeping other variables constant. Results showed that the sensible heat, latent heat and net radiation are increased with an increase in the LAI. However, the ground heat flux decreased with an increasing LAI. The annual total evapotranspiration and vegetation transpiration ranged from-16% to 9% and-100% to 15%, respectively, in response to extremes of doubled and zero LAI, respectively. There was a negative feedback between vegetation and the volumetric unfrozen water content at 0.2 m through changing evapotranspiration. The simulation results of soil temperature and moisture suggest that better vegetation conditions are conducive to maintaining the thermal stability of the underlying permafrost, and the advanced initial thawing time and increasing thawing rate of soil ice with the increase in the LAI may have a great influence on the timing and magnitude of supra-permafrost groundwater. This study quantifies the impact of vegetation change on surface and subsurface hydrothermal processes and provides a basic understanding for evaluating the impact of vegetation degradation on the water-heat exchange in permafrost regions under climate change.
文摘With an aim of rationing use of energy, energy safety, and to reduce carbon emission, our interest was geared towards the refrigerators and all the refrigerating machines. Indeed the heat yielded by the exchanger condenser can be developed for the water heating, floors heating etc. After an encouraging theoretical study, two prototypes were produced in order to validate the theoretical results. A first refrigerator was coupled with a water-heater and another with a heating floor. The water temperature reached, in one day, is of 60℃;which makes it possible to predict better results with a continuously used refrigerator. In the same way for the heating floor coupled with the second refrigerator, the temperature reached high values because the surface is reduced;however for the heating floors the standard fixes the temperature between 28℃ and 30℃.
文摘温度控制在生产生活中发挥着举足轻重的作用。位式控制算法在调节具有滞后性的水暖床垫温度控制系统时容易导致温度在目标值上下波动,控制效果不理想。为了解决此问题,设计了一种基于位置式PID的水暖床垫温度控制系统,系统以51内核的微处理器为核心控制器、以负温度系数热敏电阻(Negative Temperature Coefficient,NTC)为温度传感器、以PTC为加热器、以直流电机作为循环水泵。经实际测试结果表明,该系统运行稳定,控温精度在±0.5℃以内,达到了理想的温度控制效果。
