活性粉末混凝土(Reactive Power Concrete,RPC)具有较好的韧性和强度,将其应用于开孔梁是提高开孔梁受剪性能的有效方法。基于RPC梁的抗剪试验模型,利用有限元方法分析了10根开孔梁的抗剪性能,分别考虑混凝土类型、孔高、孔长以及孔洞...活性粉末混凝土(Reactive Power Concrete,RPC)具有较好的韧性和强度,将其应用于开孔梁是提高开孔梁受剪性能的有效方法。基于RPC梁的抗剪试验模型,利用有限元方法分析了10根开孔梁的抗剪性能,分别考虑混凝土类型、孔高、孔长以及孔洞偏心对梁的受剪性能的影响,在试验验证的基础上,对比分析了所得承载力、变形曲线、破坏形态和剪切延性。结果表明:开孔对RPC梁抗剪承载力影响较大,随着孔高、孔长的增加,梁的抗剪承载力降低;孔洞偏心条件下,偏向于受拉区开孔的梁具有更高的抗剪承载力;与普通混凝土开孔梁相比,RPC开孔梁具有更高的抗剪承载力,两者破坏形态基本相似;对于孔洞较小的普通混凝土梁,其剪切延性明显优于RPC梁,但随着孔洞尺寸的增加,两者的剪切延性逐渐接近,其可为实际结构中类似建筑构件设计提供参考依据。展开更多
The addition of silicon(Si)and organic fertilizers to soil conditioners can inhibit the transfer of heavy metal ions from soil to crops.However,it is not clear how Si and organic fertilizers affect soil properties and...The addition of silicon(Si)and organic fertilizers to soil conditioners can inhibit the transfer of heavy metal ions from soil to crops.However,it is not clear how Si and organic fertilizers affect soil properties and the micro-ecological environment and thereby reduce cadmium(Cd)accumulation in rice.In this study,the effects of L-type soil conditioners containing Si and organic fertilizers on bacterial and fungal community diversity,soil pH,organic matter,and available Si were analyzed with field experiments at two sites in Liuzhou City and Hezhou City,respectively,in Guangxi,China.With the increase of Si and organic fertilizer content in soil conditioner,rice yield respectively increased by 16.8–25.8 and 6.8–13.1%,and rice Cd content decreased significantly by 8.2–21.1 and 10.8–40.6%,respectively,at the two experimental sites.Soil microbiome analysis showed that the increase in abundance of Firmicutes and Actinobacteriota bacteria associated with Cd adsorption and sequestration,and Basidiomycota fungal populations associated with degradation of macromolecules favored the inhibition of soil Cd activity(soil exchangeable Cd decreased by 14.4–14.8 and 18.1–20.6%).This was associated with an increase in organic matter and Si content caused by applying soil conditioners.In conclusion,L-type soil conditioners,rich in Si and organic fertilizer,can reduce soil Cd bioavailability by regulating the dominant Cd passivating flora in the soil and ultimately reduce Cd accumulation in rice.展开更多
This paper presents a comprehensive study that includes the sizing and power flow by series and parallel inverters in a distributed generation system(DGs)that integrates the system of hybrid wind photovoltaic with a u...This paper presents a comprehensive study that includes the sizing and power flow by series and parallel inverters in a distributed generation system(DGs)that integrates the system of hybrid wind photovoltaic with a unified power quality conditioner(UPQC).In addition to supplying active power to the utility grid,the system of hybrid wind photovoltaic functions as a UPQC,compensating reactive power and suppressing the harmonic load currents.Additionally,the load is supplied with harmonic-free,balanced and regulated output voltages.Since PVWind-UPQC is established on a dual compensation scheme,the series inverter works like a sinusoidal current source,while the parallel inverter works like a sinusoidal voltage source.Consequently,a smooth alteration from interconnected operating modes to island operating modes and vice versa can be achieved without load voltage transients.Since PV-Wind-UPQC inverters handle the energy generated through the hybrid wind photovoltaic system and the energy demanded through the load,the converters should be sized cautiously.A detailed study of the flow of power via the PV-Wind-UPQC is imperative to gain a complete understanding of the system operation and the proper design of the converters.Thus,curves that allow the sizing of the power converters according to the power flow via the converters are presented and discussed.Simulation results are presented to assess both steady state and dynamic performances of the grid connected hybrid system of PV-Wind-UPQC.This investigation is verified by simulating and analyzing the results with Matlab/Simulink.展开更多
文摘活性粉末混凝土(Reactive Power Concrete,RPC)具有较好的韧性和强度,将其应用于开孔梁是提高开孔梁受剪性能的有效方法。基于RPC梁的抗剪试验模型,利用有限元方法分析了10根开孔梁的抗剪性能,分别考虑混凝土类型、孔高、孔长以及孔洞偏心对梁的受剪性能的影响,在试验验证的基础上,对比分析了所得承载力、变形曲线、破坏形态和剪切延性。结果表明:开孔对RPC梁抗剪承载力影响较大,随着孔高、孔长的增加,梁的抗剪承载力降低;孔洞偏心条件下,偏向于受拉区开孔的梁具有更高的抗剪承载力;与普通混凝土开孔梁相比,RPC开孔梁具有更高的抗剪承载力,两者破坏形态基本相似;对于孔洞较小的普通混凝土梁,其剪切延性明显优于RPC梁,但随着孔洞尺寸的增加,两者的剪切延性逐渐接近,其可为实际结构中类似建筑构件设计提供参考依据。
基金supported by the National Natural Science Foundation of China(31560122)the Guangxi Key Laboratory of Agro-Environment and Agric-Products Safety,China。
文摘The addition of silicon(Si)and organic fertilizers to soil conditioners can inhibit the transfer of heavy metal ions from soil to crops.However,it is not clear how Si and organic fertilizers affect soil properties and the micro-ecological environment and thereby reduce cadmium(Cd)accumulation in rice.In this study,the effects of L-type soil conditioners containing Si and organic fertilizers on bacterial and fungal community diversity,soil pH,organic matter,and available Si were analyzed with field experiments at two sites in Liuzhou City and Hezhou City,respectively,in Guangxi,China.With the increase of Si and organic fertilizer content in soil conditioner,rice yield respectively increased by 16.8–25.8 and 6.8–13.1%,and rice Cd content decreased significantly by 8.2–21.1 and 10.8–40.6%,respectively,at the two experimental sites.Soil microbiome analysis showed that the increase in abundance of Firmicutes and Actinobacteriota bacteria associated with Cd adsorption and sequestration,and Basidiomycota fungal populations associated with degradation of macromolecules favored the inhibition of soil Cd activity(soil exchangeable Cd decreased by 14.4–14.8 and 18.1–20.6%).This was associated with an increase in organic matter and Si content caused by applying soil conditioners.In conclusion,L-type soil conditioners,rich in Si and organic fertilizer,can reduce soil Cd bioavailability by regulating the dominant Cd passivating flora in the soil and ultimately reduce Cd accumulation in rice.
文摘双流制线路实现了25 kV交流供电制式市域(郊)铁路与1500 V直流供电制式城市地铁的跨线运行和互联互通,成为助力轨道交通高效节能运行的重要手段。然而,双流制牵引供电系统间存在的制式壁垒制约着系统能流高效利用,造成大量列车再生能量难以完全利用,电费成本不断增加。本文提出一种集成混合储能的铁路功率调节器(railway power conditioner,RPC)拓扑及其优化运行模型,以双流制牵引供电系统电费成本最低为优化目标,以功率平衡、变流器容量、储能装置容量与荷电状态为约束条件,以混合储能装置充放电策略、RPC端口潮流调控方法为决策变量,实现交流制市域(郊)铁路与直流制地铁之间的能量高效调控。优化结果表明:相较于既有双流制牵引供电系统,本文所提出方案可以降低牵引变电所的用电量和需量功率,总电费的节费率为22.64%,验证了所提出协调运行方法的有效性。
文摘This paper presents a comprehensive study that includes the sizing and power flow by series and parallel inverters in a distributed generation system(DGs)that integrates the system of hybrid wind photovoltaic with a unified power quality conditioner(UPQC).In addition to supplying active power to the utility grid,the system of hybrid wind photovoltaic functions as a UPQC,compensating reactive power and suppressing the harmonic load currents.Additionally,the load is supplied with harmonic-free,balanced and regulated output voltages.Since PVWind-UPQC is established on a dual compensation scheme,the series inverter works like a sinusoidal current source,while the parallel inverter works like a sinusoidal voltage source.Consequently,a smooth alteration from interconnected operating modes to island operating modes and vice versa can be achieved without load voltage transients.Since PV-Wind-UPQC inverters handle the energy generated through the hybrid wind photovoltaic system and the energy demanded through the load,the converters should be sized cautiously.A detailed study of the flow of power via the PV-Wind-UPQC is imperative to gain a complete understanding of the system operation and the proper design of the converters.Thus,curves that allow the sizing of the power converters according to the power flow via the converters are presented and discussed.Simulation results are presented to assess both steady state and dynamic performances of the grid connected hybrid system of PV-Wind-UPQC.This investigation is verified by simulating and analyzing the results with Matlab/Simulink.
