供、回水压差对于空调一次泵变流量冷冻水系统(Primary Pump Variable Flow System of Air-Conditioning Chilled Water,ACCW-PPVFS)的水力平衡和适应空调用户侧冷负荷的动态变化是至关重要的。目前,其较多采用整数阶PID调节方式,这会...供、回水压差对于空调一次泵变流量冷冻水系统(Primary Pump Variable Flow System of Air-Conditioning Chilled Water,ACCW-PPVFS)的水力平衡和适应空调用户侧冷负荷的动态变化是至关重要的。目前,其较多采用整数阶PID调节方式,这会导致出现供、回水压差的稳态误差、超调量较大和振荡过度等问题。鉴于此,本文提出了ACCW-PPVFS供、回水压差的分数阶PID(PI^(λ)D^(μ))分级调节方式和改进的生物地理学优化算法(Modified Biogeography-Based Optimization Algorithm,MBBOA)进行相应PIλDμ控制器参数整定的设计理念。首先,综合空调工艺要求和自动控制理论,对该ACCW-PPVFS供、回水压差控制系统中的各个环节,如供、回水压差被控对象、供、回水压差PI^(λ)D^(μ)控制器(Fractional Order PID Controller for Pressure Difference between Supply and Return Water,PDSRW-FOPIDC)、变频水泵和旁通水流量执行器等建立传递函数。其次,通过对生物地理学优化算法中的迁移因子(Migration Factor)φ进行线性递减改变,构建出MBBOA,且对该PDSRW-FOPIDC参数进行整定,获取5个参数最优值。同时,采取分级控制策略,分别对一次泵和分、集水器之间的旁通执行器进行变频和旁通流量qbypass的调节,以适应空调用户侧负荷的大、小需求和保证供、回水压差ΔP等于其设定值ΔPset。最后,借助MATLAB中的Simulink工具,对该供、回水压差PI^(λ)D^(μ)控制系统进行组态和数值仿真。结果表明:基于MBBOA的供、回水压差PI^(λ)D^(μ)控制器参数整定和该供、回水压差PI^(λ)D^(μ)控制系统在理论上是可行的,可适应空调用户侧冷负荷的动态变化,且满足ΔP=ΔPset空调工艺的相关要求和维持水力平衡。展开更多
Stomatal conductance was found to change from steady-state to a slate of oscillations during daytime when vapour pressure deficit (VPD) increased to a value of 1 kPa in Glycyrrhiza inflata Batalin grown under the cond...Stomatal conductance was found to change from steady-state to a slate of oscillations during daytime when vapour pressure deficit (VPD) increased to a value of 1 kPa in Glycyrrhiza inflata Batalin grown under the conditions of arid desert in north-west China. The injected metabolic inhibitors (NaN3 or carbonyl cyanide-m-chlorophenyl-hydrazone (CCCP)) slightly reduced the stomatal conductance but did not significantly decrease the intensity of stomatal oscillations (amplitude/average). The oscillation intensity was found to he significantly correlated with VPD and root resistance, but not with the respiration rate. There might exist a minimum threshold of VPD (0.8 kPa) and root resistance (1/4 relative value) that induced stomatal oscillations. These results suggested that stomatal oscillations induced by atmospheric drought stress and root resistance were mainly a type of hydropassive movement.展开更多
Under natural conditions, the use of vapor pressure deficit between mesophyll cell surface and ambient air ( VPD s ) instead of atmospheric humidity factors in some stomatal models may markedly promote the applicabil...Under natural conditions, the use of vapor pressure deficit between mesophyll cell surface and ambient air ( VPD s ) instead of atmospheric humidity factors in some stomatal models may markedly promote the applicability of stomatal models. It has been pointed out from theoretical analysis that the expression of the responses of stomatal conductance to VPD s is equivalent to the expression of responses of stomatal conductance to water loss of transpiration in stomatal models.展开更多
文摘供、回水压差对于空调一次泵变流量冷冻水系统(Primary Pump Variable Flow System of Air-Conditioning Chilled Water,ACCW-PPVFS)的水力平衡和适应空调用户侧冷负荷的动态变化是至关重要的。目前,其较多采用整数阶PID调节方式,这会导致出现供、回水压差的稳态误差、超调量较大和振荡过度等问题。鉴于此,本文提出了ACCW-PPVFS供、回水压差的分数阶PID(PI^(λ)D^(μ))分级调节方式和改进的生物地理学优化算法(Modified Biogeography-Based Optimization Algorithm,MBBOA)进行相应PIλDμ控制器参数整定的设计理念。首先,综合空调工艺要求和自动控制理论,对该ACCW-PPVFS供、回水压差控制系统中的各个环节,如供、回水压差被控对象、供、回水压差PI^(λ)D^(μ)控制器(Fractional Order PID Controller for Pressure Difference between Supply and Return Water,PDSRW-FOPIDC)、变频水泵和旁通水流量执行器等建立传递函数。其次,通过对生物地理学优化算法中的迁移因子(Migration Factor)φ进行线性递减改变,构建出MBBOA,且对该PDSRW-FOPIDC参数进行整定,获取5个参数最优值。同时,采取分级控制策略,分别对一次泵和分、集水器之间的旁通执行器进行变频和旁通流量qbypass的调节,以适应空调用户侧负荷的大、小需求和保证供、回水压差ΔP等于其设定值ΔPset。最后,借助MATLAB中的Simulink工具,对该供、回水压差PI^(λ)D^(μ)控制系统进行组态和数值仿真。结果表明:基于MBBOA的供、回水压差PI^(λ)D^(μ)控制器参数整定和该供、回水压差PI^(λ)D^(μ)控制系统在理论上是可行的,可适应空调用户侧冷负荷的动态变化,且满足ΔP=ΔPset空调工艺的相关要求和维持水力平衡。
文摘Stomatal conductance was found to change from steady-state to a slate of oscillations during daytime when vapour pressure deficit (VPD) increased to a value of 1 kPa in Glycyrrhiza inflata Batalin grown under the conditions of arid desert in north-west China. The injected metabolic inhibitors (NaN3 or carbonyl cyanide-m-chlorophenyl-hydrazone (CCCP)) slightly reduced the stomatal conductance but did not significantly decrease the intensity of stomatal oscillations (amplitude/average). The oscillation intensity was found to he significantly correlated with VPD and root resistance, but not with the respiration rate. There might exist a minimum threshold of VPD (0.8 kPa) and root resistance (1/4 relative value) that induced stomatal oscillations. These results suggested that stomatal oscillations induced by atmospheric drought stress and root resistance were mainly a type of hydropassive movement.
文摘Under natural conditions, the use of vapor pressure deficit between mesophyll cell surface and ambient air ( VPD s ) instead of atmospheric humidity factors in some stomatal models may markedly promote the applicability of stomatal models. It has been pointed out from theoretical analysis that the expression of the responses of stomatal conductance to VPD s is equivalent to the expression of responses of stomatal conductance to water loss of transpiration in stomatal models.
