The energy-intensive Haber-Bosch process currently dominants the production of ammonia (NH3), an indispensable chemical forhumans. For the sustainable development of society, highly efficient and green strategies to c...The energy-intensive Haber-Bosch process currently dominants the production of ammonia (NH3), an indispensable chemical forhumans. For the sustainable development of society, highly efficient and green strategies to convert nitrogen (N2) to NH3 are urgentlyrequired. Electrocatalytic N2 reduction reaction (eNRR) is universally regarded as a promising strategy owing to the mild operatingconditions and renewable energy supply. The key for eNRR is the high-performance catalysts, which activate the inert N-N triple bondand thus decrease the energy barrier. Herein, the recent theoretical and experimental progress on eNRR catalysts at room temperatureand ambient pressure is summarized, aiming to provide a reference for future design of high-performance eNRR catalysts.展开更多
Vario ELⅢ元素分析仪在分析有机化合物中的C、H、O、N、S元素含量时能够达到相当高的精度。但对元素有机化合物的测量范围有限(由于其含有特殊的杂原子),为了解决其在测量有机元素化合物中氧元素方面的局限性,扩大仪器的使用范围,本研...Vario ELⅢ元素分析仪在分析有机化合物中的C、H、O、N、S元素含量时能够达到相当高的精度。但对元素有机化合物的测量范围有限(由于其含有特殊的杂原子),为了解决其在测量有机元素化合物中氧元素方面的局限性,扩大仪器的使用范围,本研究以测定简单氧化物中的氧含量代替元素有机化合物,结果表明Vario ELⅢ元素分析仪也可以用来测定部分氧化物和元素有机化合物中的氧含量。并通过测定大量氧化物,结合元素周期表找出了可测元素的分布规律,对以后使用Vario ELⅢ元素分析仪测定样品的分析工作具有指导意义。展开更多
The Differential Longitudinal Cyclic Pitch(DLCP)in coaxial compound helicopter is found to be useful in mitigating low-speed rotor interactions and improving flight performance.The complex mutual interaction is simula...The Differential Longitudinal Cyclic Pitch(DLCP)in coaxial compound helicopter is found to be useful in mitigating low-speed rotor interactions and improving flight performance.The complex mutual interaction is simulated by a revised rotor aerodynamics model,where an improved Blade Element Momentum Theory(BEMT)is proposed.Comparisons with the rotor inflow distributions and aircraft trim results from literature validate the accuracy of the model.Then,the influence of the DLCP on the flight dynamics of the aircraft is analysed.The trim characteristics indicate that a negative DLCP can reduce collective and differential collective inputs in low speed forward flight,and the negative longitudinal gradient is alleviated.Moreover,a moderate DLCP can reduce the rotor and total power consumption by 4.68%and 2.9%,respectively.As DLCP further increases,the increased propeller power and unbalanced thrust allocation offset the improvement.In high-speed flight,DLCP does not improve the performance except for extra lateral and heading stick displacements.In addition,the tip clearance is degraded throughout the speed envelope due to the differential pitching moment and the higher thrust from the lower rotor.Meanwhile,the changed rotor efficiency and induced velocity alter low-speed dynamic stability and controllability.The pitch and roll subsidences are slightly degraded with the DLCP,while the heave subsidence,dutch roll and phugoid modes are improved.Lastly,the on-axis controllability,including collective,differential collective pitch,longitudinal and lateral cyclic pitches,varies with DLCP due to its effect on rotor efficiency and inflow distribution.In conclusion,a reasonable DLCP is recommended to adjust the rotor interaction and improve aircraft performance,and further to alter the flight dynamics and aerodynamics of aircraft.展开更多
基金This project is financially supported by the National Natural Science Foundation of China(Nos.61674069 and 51631004)the Key Scientific and Technological Research and Development Project of Jilin Province(20180201080GX)the Fundamental Research Funds for the Central Universities,and the Program for JLU Science and Technology Innovative Research Team(No.2017TD-09).
文摘The energy-intensive Haber-Bosch process currently dominants the production of ammonia (NH3), an indispensable chemical forhumans. For the sustainable development of society, highly efficient and green strategies to convert nitrogen (N2) to NH3 are urgentlyrequired. Electrocatalytic N2 reduction reaction (eNRR) is universally regarded as a promising strategy owing to the mild operatingconditions and renewable energy supply. The key for eNRR is the high-performance catalysts, which activate the inert N-N triple bondand thus decrease the energy barrier. Herein, the recent theoretical and experimental progress on eNRR catalysts at room temperatureand ambient pressure is summarized, aiming to provide a reference for future design of high-performance eNRR catalysts.
基金supported by A Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions,China。
文摘The Differential Longitudinal Cyclic Pitch(DLCP)in coaxial compound helicopter is found to be useful in mitigating low-speed rotor interactions and improving flight performance.The complex mutual interaction is simulated by a revised rotor aerodynamics model,where an improved Blade Element Momentum Theory(BEMT)is proposed.Comparisons with the rotor inflow distributions and aircraft trim results from literature validate the accuracy of the model.Then,the influence of the DLCP on the flight dynamics of the aircraft is analysed.The trim characteristics indicate that a negative DLCP can reduce collective and differential collective inputs in low speed forward flight,and the negative longitudinal gradient is alleviated.Moreover,a moderate DLCP can reduce the rotor and total power consumption by 4.68%and 2.9%,respectively.As DLCP further increases,the increased propeller power and unbalanced thrust allocation offset the improvement.In high-speed flight,DLCP does not improve the performance except for extra lateral and heading stick displacements.In addition,the tip clearance is degraded throughout the speed envelope due to the differential pitching moment and the higher thrust from the lower rotor.Meanwhile,the changed rotor efficiency and induced velocity alter low-speed dynamic stability and controllability.The pitch and roll subsidences are slightly degraded with the DLCP,while the heave subsidence,dutch roll and phugoid modes are improved.Lastly,the on-axis controllability,including collective,differential collective pitch,longitudinal and lateral cyclic pitches,varies with DLCP due to its effect on rotor efficiency and inflow distribution.In conclusion,a reasonable DLCP is recommended to adjust the rotor interaction and improve aircraft performance,and further to alter the flight dynamics and aerodynamics of aircraft.
