A new hypersonic inlet named three-dimensional section controllable internal waverider inlet is presented in this paper to achieve the goal of section shape geometric transition and complete capture of the upstream ma...A new hypersonic inlet named three-dimensional section controllable internal waverider inlet is presented in this paper to achieve the goal of section shape geometric transition and complete capture of the upstream mass. On the basis of the association between hypersonic waverider airframe and streamtraced hypersonic inlet, the waverider concept is extended to yield results for the internal flows, namely internal waverider concept. It is proven theoretically that not osculating cones but osculating axisymmetric theory is appropriate for the design of section controllable internal waverider inlet. And two design methods out of the internal waverider concept are proposed subsequently to construct two inlets with specific section shape request, triangle to ellipse and rectangle to ellipse ones. The calculation results show that the inlets are capable of keeping their shock structures and the main flow characteristics exactly as their derived flowfield. Further, the inlets successfully capture all the upstream mass despite their complicated cross-section transitions. It is believed that the concept proposed ex- plores a new way of designing three-dimensional hypersonic inlets with special demand of section shape transition. However, the detailed flow characteristic and the performance of the internal waverider inlets are still under investigation.展开更多
With high penetration of distributed energy resources(DERs)into power systems,microgrid has showed great advantages of enabling efficient and reliable operation of distribution grids with high flexibilities and robust...With high penetration of distributed energy resources(DERs)into power systems,microgrid has showed great advantages of enabling efficient and reliable operation of distribution grids with high flexibilities and robustness.This paper discusses the recent advancements of microgrid development with particular focus on different dispatch,and control schemes using distributed communication technologies,load management technology,and protection strategies applied in a microgrid environment.It also describes typical R&D activities and projects worldwide in e.g.European Union(EU),Japan and the United States(US).Based on comprehensive review,it is convinced to conclude that microgrids could provide electricity supply with higher efficiency,reliability and quality to regional customers and will make contributions to smart grids development at large.展开更多
Synthesizing a stable and efficient photocatalyst has been the most important research goal up to now. Owing to the dominant performance of g-C3N4 (graphitized carbonitride), an ordered assemble of a composite photoca...Synthesizing a stable and efficient photocatalyst has been the most important research goal up to now. Owing to the dominant performance of g-C3N4 (graphitized carbonitride), an ordered assemble of a composite photocatalyst, Zn-Ni-P@g-C3N4, was successfully designed and controllably prepared for highly efficient photocatalytic H2 evolution. The electron transport routes were successfully adjusted and the H2 evolution was greatly improved. The maximum amount of H2 evolved reached about 531.2 μmol for 5 h over Zn-Ni-P@g-C3N4 photocatalyst with a molar ratio of Zn to Ni of 1:3 under illumination of 5 W LED white light (wavelength 420 nm). The H2 evolution rate was 54.7 times higher than that over pure g-C3N4. Moreover, no obvious reduction in the photocatalytic activity was observed even after 4 cycles of H2 production for 5 h. This synergistically increased effect was confirmed through the results of characterizations such as XRD, TEM, SEM, XPS, N2 adsorption, UV-vis DRS, transient photocurrent, FT-IR, transient fluorescence, and Mott-Schottky studies. These studies showed that the Zn-Ni-P nanoparticles modified on g-C3N4 provide more active sites and improve the efficiency of photogenerated charge separation. In addition, the possible mechanism of photocatalytic H2 production is proposed.展开更多
Nanocrystalline intermetallics and alloys are novel materials with high surface areas which are potential low-cost and high-performance catalysts.Here,we report a general approach to the synthesis of a large variety o...Nanocrystalline intermetallics and alloys are novel materials with high surface areas which are potential low-cost and high-performance catalysts.Here,we report a general approach to the synthesis of a large variety of nanocrystalline intermetallics and alloys with controllable composition,size,and morphology:these include Au-,Pd-,Pt-,Ir-,Ru-,and Rh-based bi-or tri-metallic nanocrystals.We find that only those intermetallics and alloys whose effective electronegativity is larger than a critical value(1.93)can be prepared by co-reduction in our synthetic system.Our methodology provides a simple and convenient route to a variety of intermetallic and alloyed nanomaterials which are promising candidates for catalysts for reactions such as methanol oxidation,hydroformylation,the Suzuki reaction,cyclohexene hydroconversion,and the selective hydrogenation of acetylene.展开更多
Halide perovskite （CsPbX3, X = C1, Br, or I） quantum dots have received increasing attention as novel colloidal nanocrystals （NCs）. Accurate control of emission bands and NC morphologies are vital prerequisites fo...Halide perovskite （CsPbX3, X = C1, Br, or I） quantum dots have received increasing attention as novel colloidal nanocrystals （NCs）. Accurate control of emission bands and NC morphologies are vital prerequisites for most CsPbX3 NC practical applications. Therefore, a facile method of synthesizing CsPbX3 （X = C1, Br, or I） NCs in the nonpolar solvent octane was developed. The process was conducted in air at - 90℃ to synthesize high-quality CsPbX3 NCs showing 12-44 nm wide emission and high photoluminescence quantum yield, exceeding 90%. An in situ anion-exchange method was developed to tune CsPbX3 NC photoluminescence emission, using PbX2 dissolved in octane as the halide source. NC morphology was controlled by dissolving specific metal-organic salts in the precursor solution prior to nucleation, and nanocubes, nanodots, nanosheets, nanoplatelets, nanorods, and nanowires were obtained following the same general method providing a facile, versatile route to controlling CsPbX3 NC emission bands and morphologies, which will broaden the range of CsPbX3 NC practical applications.展开更多
Electric trains typically travel across the railway networks in an inter-provincial,inter-city and intra-city manner.The electric train generally serves as a load/source in tractive/brake mode,through which power netw...Electric trains typically travel across the railway networks in an inter-provincial,inter-city and intra-city manner.The electric train generally serves as a load/source in tractive/brake mode,through which power networks and railway networks are closely coupled and mutually influenced.Based on the operational mode of rail trains and the characteristics of their load power,this paper proposes a coordinated optimal decisionmaking method of demand response for controllable load of rail trains and energy storage systems.First,a coordinated approach of dynamically adjusting the load of the controllable rail train in considering the driving comfort and energy storage battery is designed.Secondly,under the time conditions that satisfy the train’s operational diagram,the functional relationship between the train speed and the load power is presented.Based on this,in considering the constraints of the train’s arrival time,driving speed,motor power,and driving comfort,the capacity of energy storage batteries and other constraints,an optimization model for demand response in managing the traction power supply system under a two-part price and time-of-use(TOU)price is proposed.The objective is to minimize the energy consumption costs of rail transit trains,and optimize the speed trajectory of rail trains,the load power of traction system,and the output of energy storage batteries.展开更多
基金Supported by the National Natural Science Foundation of China(Grant No.90405009)
文摘A new hypersonic inlet named three-dimensional section controllable internal waverider inlet is presented in this paper to achieve the goal of section shape geometric transition and complete capture of the upstream mass. On the basis of the association between hypersonic waverider airframe and streamtraced hypersonic inlet, the waverider concept is extended to yield results for the internal flows, namely internal waverider concept. It is proven theoretically that not osculating cones but osculating axisymmetric theory is appropriate for the design of section controllable internal waverider inlet. And two design methods out of the internal waverider concept are proposed subsequently to construct two inlets with specific section shape request, triangle to ellipse and rectangle to ellipse ones. The calculation results show that the inlets are capable of keeping their shock structures and the main flow characteristics exactly as their derived flowfield. Further, the inlets successfully capture all the upstream mass despite their complicated cross-section transitions. It is believed that the concept proposed ex- plores a new way of designing three-dimensional hypersonic inlets with special demand of section shape transition. However, the detailed flow characteristic and the performance of the internal waverider inlets are still under investigation.
基金This work was partially supported by Hong Kong RGC Theme Based Research Scheme Grants No.T23-407/13N and T23-701/14NNational High Technology Research and Development Program 863 of China,Grant No.2012AA050204.
文摘With high penetration of distributed energy resources(DERs)into power systems,microgrid has showed great advantages of enabling efficient and reliable operation of distribution grids with high flexibilities and robustness.This paper discusses the recent advancements of microgrid development with particular focus on different dispatch,and control schemes using distributed communication technologies,load management technology,and protection strategies applied in a microgrid environment.It also describes typical R&D activities and projects worldwide in e.g.European Union(EU),Japan and the United States(US).Based on comprehensive review,it is convinced to conclude that microgrids could provide electricity supply with higher efficiency,reliability and quality to regional customers and will make contributions to smart grids development at large.
基金supported by the National Natural Science Foundation of China(21862002,41663012)the Innovation Team Project of North Minzu University(YCX18082)the Scientific Research Project of North Minzu University(2016 HG-KY 06)~~
文摘Synthesizing a stable and efficient photocatalyst has been the most important research goal up to now. Owing to the dominant performance of g-C3N4 (graphitized carbonitride), an ordered assemble of a composite photocatalyst, Zn-Ni-P@g-C3N4, was successfully designed and controllably prepared for highly efficient photocatalytic H2 evolution. The electron transport routes were successfully adjusted and the H2 evolution was greatly improved. The maximum amount of H2 evolved reached about 531.2 μmol for 5 h over Zn-Ni-P@g-C3N4 photocatalyst with a molar ratio of Zn to Ni of 1:3 under illumination of 5 W LED white light (wavelength 420 nm). The H2 evolution rate was 54.7 times higher than that over pure g-C3N4. Moreover, no obvious reduction in the photocatalytic activity was observed even after 4 cycles of H2 production for 5 h. This synergistically increased effect was confirmed through the results of characterizations such as XRD, TEM, SEM, XPS, N2 adsorption, UV-vis DRS, transient photocurrent, FT-IR, transient fluorescence, and Mott-Schottky studies. These studies showed that the Zn-Ni-P nanoparticles modified on g-C3N4 provide more active sites and improve the efficiency of photogenerated charge separation. In addition, the possible mechanism of photocatalytic H2 production is proposed.
基金This work was supported by the National Natural Science Foundation of China(NSFC)(No.90606006)the State Key Project of Fundamental Research for Nanoscience and Nanotechnology(No.2006CB932300).
文摘Nanocrystalline intermetallics and alloys are novel materials with high surface areas which are potential low-cost and high-performance catalysts.Here,we report a general approach to the synthesis of a large variety of nanocrystalline intermetallics and alloys with controllable composition,size,and morphology:these include Au-,Pd-,Pt-,Ir-,Ru-,and Rh-based bi-or tri-metallic nanocrystals.We find that only those intermetallics and alloys whose effective electronegativity is larger than a critical value(1.93)can be prepared by co-reduction in our synthetic system.Our methodology provides a simple and convenient route to a variety of intermetallic and alloyed nanomaterials which are promising candidates for catalysts for reactions such as methanol oxidation,hydroformylation,the Suzuki reaction,cyclohexene hydroconversion,and the selective hydrogenation of acetylene.
基金Supported by the National Natural Science Foundation of China under Grant No.90412012 (国家自然科学基金)the China Postdoctoral Science Foundation under Grant No.20060400063 (中国博士后科学基金)the Orange France Telecom R&D Lab. (Beijing) (北京法国电信研发中心有限公司资助项目)
文摘Halide perovskite （CsPbX3, X = C1, Br, or I） quantum dots have received increasing attention as novel colloidal nanocrystals （NCs）. Accurate control of emission bands and NC morphologies are vital prerequisites for most CsPbX3 NC practical applications. Therefore, a facile method of synthesizing CsPbX3 （X = C1, Br, or I） NCs in the nonpolar solvent octane was developed. The process was conducted in air at - 90℃ to synthesize high-quality CsPbX3 NCs showing 12-44 nm wide emission and high photoluminescence quantum yield, exceeding 90%. An in situ anion-exchange method was developed to tune CsPbX3 NC photoluminescence emission, using PbX2 dissolved in octane as the halide source. NC morphology was controlled by dissolving specific metal-organic salts in the precursor solution prior to nucleation, and nanocubes, nanodots, nanosheets, nanoplatelets, nanorods, and nanowires were obtained following the same general method providing a facile, versatile route to controlling CsPbX3 NC emission bands and morphologies, which will broaden the range of CsPbX3 NC practical applications.
基金This work was supported in part by the National Natural Science Foundation of China(71931003)the Science and Technology Projects of Hunan Province and Changsha City(2018GK4002,2019CT5001,2019WK2011,2019GK5015 and kq1907086).
文摘Electric trains typically travel across the railway networks in an inter-provincial,inter-city and intra-city manner.The electric train generally serves as a load/source in tractive/brake mode,through which power networks and railway networks are closely coupled and mutually influenced.Based on the operational mode of rail trains and the characteristics of their load power,this paper proposes a coordinated optimal decisionmaking method of demand response for controllable load of rail trains and energy storage systems.First,a coordinated approach of dynamically adjusting the load of the controllable rail train in considering the driving comfort and energy storage battery is designed.Secondly,under the time conditions that satisfy the train’s operational diagram,the functional relationship between the train speed and the load power is presented.Based on this,in considering the constraints of the train’s arrival time,driving speed,motor power,and driving comfort,the capacity of energy storage batteries and other constraints,an optimization model for demand response in managing the traction power supply system under a two-part price and time-of-use(TOU)price is proposed.The objective is to minimize the energy consumption costs of rail transit trains,and optimize the speed trajectory of rail trains,the load power of traction system,and the output of energy storage batteries.
