The transpiration experiment was done under greenhouse conditions with a C3 plant sweet pepper （Capsicum annuum Linn.） and two C4 plants, sorghum （Sorghum bicolor L.Moench） and maize （Zea mays Linn.）. Three spec...The transpiration experiment was done under greenhouse conditions with a C3 plant sweet pepper （Capsicum annuum Linn.） and two C4 plants, sorghum （Sorghum bicolor L.Moench） and maize （Zea mays Linn.）. Three species were irrigated with three different water treatment levels of 100%, 66% and 33% which gave a comparison of tolerance and adaptation to irrigation and two different levels of water stress. The measurements of transpiration rate and stomatal conductance were done between 8.00 a.m. and 16.00 p.m. with measurements about each 1.5 h with an infrared gas analyzer. The results showed that Z. mays probably due to a higher leaf area had very low values and was significantly different （LSD pairwise comparison） from C. annuum and S. bicolor. The hypotheses that C4 plants and C3 plants have different transpiration rates and stomatal conductance could not be shown with the results. However, the hypotheses that for the same species, the highest values in transpiration rate and stomatal conductance were with the 100% irrigation treatment and the lowest values were with the 33% irrigation treatment could be accepted due to the results of this trial.展开更多
This paper represents a physical model of two -dimensional transpiration cooling control system with surface heating and ablating. The governing equation is derived and the third boundary conditions are given. They co...This paper represents a physical model of two -dimensional transpiration cooling control system with surface heating and ablating. The governing equation is derived and the third boundary conditions are given. They constitute a two -dimensional variable -domain distributed parameter control system in which the control parameter appears in both the governing equation and the boundary conditions. Applying time semi-step alternating direction method to difference this mathematical model, the tridiagonal difference equations are obtained. For a flying shell of electromagnetic railgun, the mathematical simulation results agree with the realistic physical process, and the control parameter not only can control the temperature of heat shield, but also can control the boundary motion effectively.展开更多
This problem is a nonlinear control system with variable-domain distributed parameter. In this paper, the numerical simulation of the dynamic functions has been carried out by transforming this problem to a fixed-dom...This problem is a nonlinear control system with variable-domain distributed parameter. In this paper, the numerical simulation of the dynamic functions has been carried out by transforming this problem to a fixed-domain initial-boundary value problem, and the numerical results are obtained: (1) Thedistribution of temperature rises, the ablation amount and velocity of the thermal shield vary with the time; (2) The maximum ablating velocity, the time of the ablation beginning and ending related to thetranspiration quantity. This method succeeds in overcoming the difficulty brought up by variable domain.On the other hand, the critical transpiration quantity for the surface to start ablating, the maximum ablating velocity and time of the ablation ending are obtained theoretically.展开更多
[目的]叶面积指数(leaf area index, LAI)作为生态系统水循环过程模拟研究的关键参数,其快速动态模拟可解决土壤水-汽-热-气耦合模型STEMMUS(simultaneous transfer of energy, mass and momentum in unsaturated soil)只能使用固定或实...[目的]叶面积指数(leaf area index, LAI)作为生态系统水循环过程模拟研究的关键参数,其快速动态模拟可解决土壤水-汽-热-气耦合模型STEMMUS(simultaneous transfer of energy, mass and momentum in unsaturated soil)只能使用固定或实测LAI作为输入参数的局限性。[方法]将EPIC模型中的“植物叶面积发育子模块”与STEMMUS模型耦合,采用2019年和2020年子洲县山地苹果试验示范基地苹果生长条件下实测的果树蒸腾、土壤水分和土壤温度数据对模型进行率定与验证,以评估耦合模型在黄土高原的适用性。[结果]通过优化植物生长参数,耦合叶面积发育子模块后的STEMMUS模型对苹果树蒸腾耗水过程的模拟精度显著提高,率定年和验证年的归一化均方根误差(NRMSE)和平均绝对误差(MAE)分别从原模型的40.2%、61.9%和0.52、0.64 mm/d降低到耦合模型的30.0%、33.2%和0.42、0.38 mm/d。同时,耦合模型可较好地模拟苹果园的土壤水热动态过程,在率定期和验证期模拟土壤水分体积分数和土壤温度的NRMSE分别为1.4%~32.9%和2.9%~9.5%,MAE分别为0.13~4.26 cm^(3)/cm^(3)、0.34~1.49℃。[结论]模拟值与实测值吻合度较高,表明耦合模型可准确描述黄土高原苹果园果树叶面积动态生长和生态水文过程,研究结果可为黄土区果园生态水文过程的研究提供技术支撑。展开更多
基金Supported by the Major Program of the National Natural Science Foundation of China (30671679)National Key Technology R&D Program in the 11th Five Year Plan of China (2006BAD03A04-03)
文摘The transpiration experiment was done under greenhouse conditions with a C3 plant sweet pepper （Capsicum annuum Linn.） and two C4 plants, sorghum （Sorghum bicolor L.Moench） and maize （Zea mays Linn.）. Three species were irrigated with three different water treatment levels of 100%, 66% and 33% which gave a comparison of tolerance and adaptation to irrigation and two different levels of water stress. The measurements of transpiration rate and stomatal conductance were done between 8.00 a.m. and 16.00 p.m. with measurements about each 1.5 h with an infrared gas analyzer. The results showed that Z. mays probably due to a higher leaf area had very low values and was significantly different （LSD pairwise comparison） from C. annuum and S. bicolor. The hypotheses that C4 plants and C3 plants have different transpiration rates and stomatal conductance could not be shown with the results. However, the hypotheses that for the same species, the highest values in transpiration rate and stomatal conductance were with the 100% irrigation treatment and the lowest values were with the 33% irrigation treatment could be accepted due to the results of this trial.
基金The project is supported by Natural Science Foundation of China
文摘This paper represents a physical model of two -dimensional transpiration cooling control system with surface heating and ablating. The governing equation is derived and the third boundary conditions are given. They constitute a two -dimensional variable -domain distributed parameter control system in which the control parameter appears in both the governing equation and the boundary conditions. Applying time semi-step alternating direction method to difference this mathematical model, the tridiagonal difference equations are obtained. For a flying shell of electromagnetic railgun, the mathematical simulation results agree with the realistic physical process, and the control parameter not only can control the temperature of heat shield, but also can control the boundary motion effectively.
文摘This problem is a nonlinear control system with variable-domain distributed parameter. In this paper, the numerical simulation of the dynamic functions has been carried out by transforming this problem to a fixed-domain initial-boundary value problem, and the numerical results are obtained: (1) Thedistribution of temperature rises, the ablation amount and velocity of the thermal shield vary with the time; (2) The maximum ablating velocity, the time of the ablation beginning and ending related to thetranspiration quantity. This method succeeds in overcoming the difficulty brought up by variable domain.On the other hand, the critical transpiration quantity for the surface to start ablating, the maximum ablating velocity and time of the ablation ending are obtained theoretically.
文摘[目的]叶面积指数(leaf area index, LAI)作为生态系统水循环过程模拟研究的关键参数,其快速动态模拟可解决土壤水-汽-热-气耦合模型STEMMUS(simultaneous transfer of energy, mass and momentum in unsaturated soil)只能使用固定或实测LAI作为输入参数的局限性。[方法]将EPIC模型中的“植物叶面积发育子模块”与STEMMUS模型耦合,采用2019年和2020年子洲县山地苹果试验示范基地苹果生长条件下实测的果树蒸腾、土壤水分和土壤温度数据对模型进行率定与验证,以评估耦合模型在黄土高原的适用性。[结果]通过优化植物生长参数,耦合叶面积发育子模块后的STEMMUS模型对苹果树蒸腾耗水过程的模拟精度显著提高,率定年和验证年的归一化均方根误差(NRMSE)和平均绝对误差(MAE)分别从原模型的40.2%、61.9%和0.52、0.64 mm/d降低到耦合模型的30.0%、33.2%和0.42、0.38 mm/d。同时,耦合模型可较好地模拟苹果园的土壤水热动态过程,在率定期和验证期模拟土壤水分体积分数和土壤温度的NRMSE分别为1.4%~32.9%和2.9%~9.5%,MAE分别为0.13~4.26 cm^(3)/cm^(3)、0.34~1.49℃。[结论]模拟值与实测值吻合度较高,表明耦合模型可准确描述黄土高原苹果园果树叶面积动态生长和生态水文过程,研究结果可为黄土区果园生态水文过程的研究提供技术支撑。
