This work attempts to extend the fundamental theory for classic gas dynamics to viscous compressible flow,of which aeroacoustics will naturally be a special branch.As a continuation of Part I.Unbounded fluid(Mao et al...This work attempts to extend the fundamental theory for classic gas dynamics to viscous compressible flow,of which aeroacoustics will naturally be a special branch.As a continuation of Part I.Unbounded fluid(Mao et al.,2022),this paper studies the source of longitudinal field at solid boundary,caused by the on-wall kinematic and viscous dynamic coupling of longitudinal and transverse processes.We find that at this situation the easiest choice for the two independent thermodynamic variables is the dimensionless pressure P and temperature T.The two-level structure of boundary dynamics of longitudinal field is obtained by applying the continuity equation and its normal derivative to the surface.We show that the boundary dilatation flux represents faithfully the boundary production of vortex sound and entropy sound,and the mutual generation mechanism of the longitudinal and transverse fields on the boundary does not occur symmetrically"at the samc level,but appears along a zigzag route.At the first level,it is the pressure gradient that generates vorticity unidirectionally;while at the second level,it is the vorticity that generates dilatation unidirectionally.展开更多
The development of bifunctional catalysts with excellent catalytic properties is an important focus in alkaline electrolytic water splitting,and accordingly,the construction of novel crystalline/amorphous heterojuncti...The development of bifunctional catalysts with excellent catalytic properties is an important focus in alkaline electrolytic water splitting,and accordingly,the construction of novel crystalline/amorphous heterojunction catalysts has been proven to be an effective strategy to realize bifunctional electrocatalytic hydrogen evolution reaction(HER)and oxygen evolution reaction(OER).In this study,uniformly dispersed and highly active Ru/NiO_(x) heterojunctions anchored onto GA composites(Ru/NiO_(x)@GA)were successfully synthesized by freeze-drying and calcination processes.The results of XRD,TEM,and XPS analyses indicated strong interactions in the Ru/NiO_(x) heterojunction,where the NiO_(x) in the outer layer exerted a squeezing effect on the Ru in the inner layer,generating charge transfer from Ni to Ru.As an excellent bifunctional electrocatalyst,Ru/NiO_(x)@GA required overpotentials of only 32 mV(HER)and 237 mV(OER)to achieve a current density of 10 mA cm^(-2) in a 1 M KOH electrolyte while exhibiting robust cycling stability for over 200 h.A low decomposition voltage of 1.53 V and high faradaic efficiency of 100%were obtained for the assembled overall water splitting(OWS)device.All these properties were attributed to the Ru/NiO_(x) interaction,resulting in charge-enriched Ru sites and oxidation state-corrected Ni sites.This study highlights the unique advantages of the synergistic effect of both crystalline/amorphous heterojunctions and GA,which provides a new approach to prepare GA-based materials for advanced multifunctional electrocatalytic applications.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.12102365,91752202,11472016,11621202,and 12272371).
文摘This work attempts to extend the fundamental theory for classic gas dynamics to viscous compressible flow,of which aeroacoustics will naturally be a special branch.As a continuation of Part I.Unbounded fluid(Mao et al.,2022),this paper studies the source of longitudinal field at solid boundary,caused by the on-wall kinematic and viscous dynamic coupling of longitudinal and transverse processes.We find that at this situation the easiest choice for the two independent thermodynamic variables is the dimensionless pressure P and temperature T.The two-level structure of boundary dynamics of longitudinal field is obtained by applying the continuity equation and its normal derivative to the surface.We show that the boundary dilatation flux represents faithfully the boundary production of vortex sound and entropy sound,and the mutual generation mechanism of the longitudinal and transverse fields on the boundary does not occur symmetrically"at the samc level,but appears along a zigzag route.At the first level,it is the pressure gradient that generates vorticity unidirectionally;while at the second level,it is the vorticity that generates dilatation unidirectionally.
基金supported by the Key projects of Intergovernmental International Cooperation in Key R&D Programs of the Ministry of Science and Technology of China(No.2021YFE0115800)the National Science Funding Committee of China(No.U20A20250)the Programs of the Science and Technology of Yulin City(No.CXY-2023-ZX04).
文摘The development of bifunctional catalysts with excellent catalytic properties is an important focus in alkaline electrolytic water splitting,and accordingly,the construction of novel crystalline/amorphous heterojunction catalysts has been proven to be an effective strategy to realize bifunctional electrocatalytic hydrogen evolution reaction(HER)and oxygen evolution reaction(OER).In this study,uniformly dispersed and highly active Ru/NiO_(x) heterojunctions anchored onto GA composites(Ru/NiO_(x)@GA)were successfully synthesized by freeze-drying and calcination processes.The results of XRD,TEM,and XPS analyses indicated strong interactions in the Ru/NiO_(x) heterojunction,where the NiO_(x) in the outer layer exerted a squeezing effect on the Ru in the inner layer,generating charge transfer from Ni to Ru.As an excellent bifunctional electrocatalyst,Ru/NiO_(x)@GA required overpotentials of only 32 mV(HER)and 237 mV(OER)to achieve a current density of 10 mA cm^(-2) in a 1 M KOH electrolyte while exhibiting robust cycling stability for over 200 h.A low decomposition voltage of 1.53 V and high faradaic efficiency of 100%were obtained for the assembled overall water splitting(OWS)device.All these properties were attributed to the Ru/NiO_(x) interaction,resulting in charge-enriched Ru sites and oxidation state-corrected Ni sites.This study highlights the unique advantages of the synergistic effect of both crystalline/amorphous heterojunctions and GA,which provides a new approach to prepare GA-based materials for advanced multifunctional electrocatalytic applications.
