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Paths towards enhanced electrochemical CO2 reduction

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National Science Review 2020年第1期7卷 7-9页

作者： Wenhao Ren Chuan zhao School of Chemistry University of New South Wales

Anthropogenic CO2emissions engender a severe threat to the global ecosystem and consequently are a growing concern associated with traditional means of energy production. Direct electrocatalytic reduction of CO2into energyrich fuels and value-added chemical feedstocks provides a promising route to realize a carbon-neutral energy cycle, and at the same time, store the electricity generated from intermittent renewable-energy

关键词： Cu Paths towards enhanced electrochemical CO2 reduction

Approximate Nonlinear Modeling of Aircraft Engine Surge Margin Based on Equilibrium Manifold Expansion

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Chinese Journal of Aeronautics 2012年第5期25卷 663-674页

作者： LIU Xiaofeng zhao Lei School of Transportation Science and Engineering Beihang UniversityBeijing 100191China

Stable operation of aircraft engine compressions is constrained by rotating surge. In this paper, an approximate nonlinear surge margin model of aircraft engine compression system by using equilibrium manifold is presented. Firstly, this paper gives an overview of the current state of modeling aerodynamic flow instabilities in engine compressors. Secondly, the expansion form of equilibrium manifold is introduced, and the choosing scheduling variable method is discussed. Then, this paper also gives the identification procedure of modeling the approximate nonlinear model. Finally, the modeling and simulations with high pressure （liP） compressor surge margin of the aircraft engine show that this real-time model has the same accuracy with the thermody- namic model, but has simpler structure and shorter computation time.

关键词： aircraft engine surge margin system identification equilibrium manifold scheduling variable perpendicular expan-sion

Methane dehydro-aromatization over Mo/HZSM-5 catalysts in the absence of oxygen:Effect of steam-treatment on catalyst stability

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Journal of Natural Gas Chemistry 2011年第5期20卷 547-552页

作者： Tingting zhao Hongxia Wang Key Laboratory of design and Synthesis of Functional Materials and Green Catalysis Colleges of Heilongjiang Province Harbin Normal University Harbin 150025 Heilongjiang China

The effect of steam-treatment to HZSM-5 zeolite and Mo/HZSM-5 with a steaming time range of 0.5-1 h on the catalytic performance of methane dehydro-aromatization （MDA） over Mo/HZSM-5 catalyst prepared with impregnation has been studied in detail in combination with the characterization of 1H MAS NMR technique. Both the deactivation rate constant （kd） and the Brtnsted acid sites per unit cell were calculated to quantitatively evaluate the stability of Mo/HZSM-5 catalysts treated with steam at 813 K before and after impregnation of molybdenum species, and the corresponding variation of their Brtnsted acid sites. The results reveal that a V-shape relationship between kd and the number of B 1 acid sites per unit cell is presented on Mo/HZSM-5 catalyst under the tested steam-treatment and reaction conditions.

关键词： steam-treatment HZSM-5 zeolite Mo/HZSM-5 methane dehydro-aromatization in the absence of oxygen

Adaptive sliding mode control of the A-axis used for blisk manufacturing

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Chinese Journal of Aeronautics 2014年第3期27卷 708-715页

作者： zhao Pengbing Shi Yaoyao The Key Laboratory of Contemporary design and Integrated Manufacturing Technology Ministry of EducationNorthwestern Polytechnical University

As a key assembly in the 5-axis CNC machine tools, positioning precision of the A-axis directly affects the machining accuracy and surface quality of the parts. First of all, mechanical structure and control system of the A-axis are designed. Then, considering the influence of nonlin- ear friction, backlash, unmodeled dynamics, uncertain cutting force and other external disturbance on the control precision of the A-axis, an adaptive sliding mode control （ASMC） based on extended state observer （ESO） is proposed. ESO is employed to estimate the state variables of the unknown system and an adaptive law is adopted to compensate for the input dead-zone caused by friction, backlash and other nonlinear characteristics. Finally, stability of the closed-loop system is guaran- teed by the Lyapunov theory. Positioning experiments illustrate the perfect estimation of ESO and the stronger anti-interference and robustness of ASMC, which can improve the control precision of the A-axis by about 40 times. Processing experiments show that the ASMC can reduce the waviness, averaKe error and roughness of the nrocessed surface by 35.63%, 31.31% and 30.35%, respectively.

关键词： A-axis Blisk processing Nonlinear compensation Positioning control Sliding mode control

A ESTIMATE OF THE RATE OF ENTROPY DISSIPATION OF HIGH RESOLUTION MUSCL TYPE GODUNOV SCHEMES

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Journal of Computational Mathematics 1999年第4期17卷 369-378页

作者： Tang, HZ zhao, N Chinese Acad Sci ICMSEC State Key Lab Sci & Engn Comp Beijing 100080 Peoples R China Nanjing Univ Aeronaut & Astronaut Dept Aerodynam Nanjing 210016 Peoples R China

In this paper, following the paper [7], we analysis the 'sharp' estimate of the rate of entropy dissipation of the fully discrete MUSCL type Godunov schemes by the general compact theory introduced by Coquel-LeFloch [1, 2], and find: because of small viscosity of the above schemes, in the vincity of shock wave, the estimate of the above schemes is more easily obtained, but for rarefaction wave, we must impose a 'sharp' condition on limiter function in order to keep its entropy dissipation and its convergence.

关键词： hyperbolic conservation laws MUSCL type Godunov schemes entropy dissipation shock wave rarefaction wave

Effective local dynamic routing strategy for air route networks

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Chinese Journal of Aeronautics 2015年第6期28卷 1709-1717页

作者： Wu Wenjun zhao Lingxi School of Electronic and Information Engineering Beihang University

With the rapid development of air transportation, network service ability has attracted a lot of attention in academe. Aiming to improve the throughput of the air route network （ARN）, we propose an effective local dynamic routing strategy in this paper. Several factors, such as the rout- ing distance, the geographical distance and the real-time local traffic, are taken into consideration. When the ARN is in the normal free-flow state, the proposed strategy can recover the shortest path routing （SPR） strategy. When the ARN undergoes congestion, the proposed strategy changes the paths of flights based on the real-time local traffic information. The throughput of the Chinese air route network （CARN） is evaluated. Results confirm that the proposed strategy can significantly improve the throughput of CARN. Meanwhile, the increase in the average flying distance and time is tiny. Results also indicate the importance of the distance related factors in a routing strategy designed for the ARN.

关键词： Air route network Air transportation Dynamic routing Network throughput Routing strategies

Parity–time symmetric photonics

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National Science Review 2018年第2期5卷 183-199页

作者： Han zhao Liang Feng department of Electrical and Systems Engineering University of Pennsylvania department of Materials Science and Engineering University of Pennsylvania

The establishment of non-Hermitian quantum mechanics(such as parity–time(PT) symmetry) stimulates a paradigmatic shift for studying symmetries of complex potentials. Owing to the convenient manipulation of optical gain and loss in analogy to complex quantum potentials, photonics provides an ideal platform for the visualization of many conceptually striking predictions from non-Hermitian quantum theory. A rapidly developing field has emerged, namely, PT-symmetric photonics, demonstrating intriguing optical phenomena including eigenstate coalescence and spontaneous PT-symmetry breaking. The advance of quantum physics, as the feedback, provides photonics with brand-new paradigms to explore the entire complex permittivity plane for novel optical functionalities. Here, we review recent exciting breakthroughs in PT-symmetric photonics while systematically presenting their underlying principles guided by non-Hermitian symmetries. The potential device applications for optical communication and computing,biochemical sensing and healthcare are also discussed.

关键词： photonics parity–time symmetry non-Hermitian phase transition exceptional point

A dimensional analysis on asphalt binder fracture and fatigue cracking

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Frontiers of Structural and Civil Engineering 2018年第2期12卷 201-206页

作者： Qian zhao Zhoujing YE National Center for Materials Service Safety University of Science and Technology Beijing Beijing 100083 China

Fracture and fatigue cracking in asphalt binder are two of most serious problems for pavement engineers. In this paper, we present a new comprehensive approach, which consists both of dimensional analysis using Buckingham H Theorem and J-integral analysis based on classic fracture mechanics, to evaluate the fracture and fatigue on asphalt binder. It is discovered that the dimensional analysis could provide a new perspective to analyze the asphalt fracture and fatigue cracking mechanism.

关键词： Dimensional analysis asphalt fracture fatigue cracking

Particle swarm optimization applied to hypersonic reentry trajectories

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Chinese Journal of Aeronautics 2015年第3期28卷 822-831页

作者： zhao Jiang Zhou Rui School of Automation Science and Electrical Engineering Beihang University

Abstract This paper presents the novel use of the particle swarm optimization （PSO） to generate the end-to-end trajectory for hypersonic reentry vehicles in a quite simple formulation. The velocity- dependent bank angle profile is developed to reduce the search space of unknown parameters based on the constrained PSO algorithm. The path constraints are enforced by setting the fitness function to be infinite on condition that the particles violate the maximum allowable values. The PSO algo- rithm also provides a much easier means to satisfy the terminal conditions by adding penalty terms to the fitness function. Furthermore, the approximate reentry landing footprint is fast constructed by incorporating an interpolation model into the standardized bank angle profiles. Numerical sim ulations demonstrate that the PSO method is a feasible and flexible tool to generate the end-to-end trajectory and landing footprint for hypersonic reentry vehicles.

关键词： Footprint Hypersonic vehicles Particle swarm optimization(PSO) Reentry Trajectories