A simple two-dimensional phononic crystal hosting topologically protected edge states is proposed to emulate the quantum spin Hall effect in electronic systems, whose phononic topological phase can be reconfigured thr...A simple two-dimensional phononic crystal hosting topologically protected edge states is proposed to emulate the quantum spin Hall effect in electronic systems, whose phononic topological phase can be reconfigured through the rotation of scatters. In particular, the band inversion occurs between two pairs of high-order compound states, resulting in topological phase transition from trivial to nontrivial over a relatively broad high-frequency range. This is further evidenced by an effective Hamiltonian derived by the k·p perturbation theory. The phononic topology is related to a pseudo-timereversal symmetry constructed by the point group symmetry of two doubly degenerate eigenstates. Numerical simulations unambiguously demonstrate robust helical edge states whose pseudospin indices are locked to the propagation direction along the interface between topologically trivial and nontrivial phononic crystals. Our designed phononic systems provide potential applications in robust acoustic signal transport along any desired path over a high-frequency range.展开更多
This article compiles the actual knowledge of the biogenic volatile organic compound（BVOC） emissions estimated using model methods in the Pearl River Delta（PRD） region, one of the most developed regions in China. ...This article compiles the actual knowledge of the biogenic volatile organic compound（BVOC） emissions estimated using model methods in the Pearl River Delta（PRD） region, one of the most developed regions in China. The developed history of BVOC emission models is presented briefly and three typical emission models are introduced and compared. The results from local studies related to BVOC emissions have been summarized. Based on this analysis, it is recommended that local researchers conduct BVOC emission studies systematically, from the assessment of model inputs, to compiling regional emission inventories to quantifying the uncertainties and evaluating the model results. Beyond that,more basic researches should be conducted in the future to close the gaps in knowledge on BVOC emission mechanisms, to develop the emission models and to refine the inventory results. This paper can provide a perspective on these aspects in the broad field of research associated with BVOC emissions in the PRD region.展开更多
分析了一种复合式高速直升机的飞行原理,设计了不同飞行模式下的操纵策略,并建立了飞行动力学模型。考虑传感器噪声和复杂飞行环境导致的系统状态难以准确测量的问题,提出了一种基于高阶滑模微分器的姿态自抗扰控制算法。在MATLAB/Simul...分析了一种复合式高速直升机的飞行原理,设计了不同飞行模式下的操纵策略,并建立了飞行动力学模型。考虑传感器噪声和复杂飞行环境导致的系统状态难以准确测量的问题,提出了一种基于高阶滑模微分器的姿态自抗扰控制算法。在MATLAB/Simulink环境下构建了复合式高速直升机姿态控制系统,并与PID(proportion integral differential)控制器和LQG(linear quadratic Gaussian)控制器进行了仿真对比。研究结果表明:所提出的基于高阶滑模微分器的姿态自抗扰控制器能够实现对姿态角的无超调跟踪,相较于PID控制器和LQG控制器,误差收敛速度分别提升31.5%和64.2%,且在噪声干扰下,最大跟踪误差比LQG控制器小34.2%,比PID控制器小39.5%。展开更多
基金Project supported by the Young Scientists Fund of the Natural Science Foundation of Shandong Province,China(Grant No.ZR2016AQ09)Young Scientists Fund of the National Natural Science Foundation of China(Grant No.11704219).
文摘A simple two-dimensional phononic crystal hosting topologically protected edge states is proposed to emulate the quantum spin Hall effect in electronic systems, whose phononic topological phase can be reconfigured through the rotation of scatters. In particular, the band inversion occurs between two pairs of high-order compound states, resulting in topological phase transition from trivial to nontrivial over a relatively broad high-frequency range. This is further evidenced by an effective Hamiltonian derived by the k·p perturbation theory. The phononic topology is related to a pseudo-timereversal symmetry constructed by the point group symmetry of two doubly degenerate eigenstates. Numerical simulations unambiguously demonstrate robust helical edge states whose pseudospin indices are locked to the propagation direction along the interface between topologically trivial and nontrivial phononic crystals. Our designed phononic systems provide potential applications in robust acoustic signal transport along any desired path over a high-frequency range.
基金supported by the National Science Fund for Outstanding Young Scholars(No.41425020)the China Special Fund for Meteorological Research in the Public Interest(No.GYHY201406031)and the Key Projects in the National Science&Technology Pillar Program(No.2014BAC21B02)
文摘This article compiles the actual knowledge of the biogenic volatile organic compound（BVOC） emissions estimated using model methods in the Pearl River Delta（PRD） region, one of the most developed regions in China. The developed history of BVOC emission models is presented briefly and three typical emission models are introduced and compared. The results from local studies related to BVOC emissions have been summarized. Based on this analysis, it is recommended that local researchers conduct BVOC emission studies systematically, from the assessment of model inputs, to compiling regional emission inventories to quantifying the uncertainties and evaluating the model results. Beyond that,more basic researches should be conducted in the future to close the gaps in knowledge on BVOC emission mechanisms, to develop the emission models and to refine the inventory results. This paper can provide a perspective on these aspects in the broad field of research associated with BVOC emissions in the PRD region.
文摘分析了一种复合式高速直升机的飞行原理,设计了不同飞行模式下的操纵策略,并建立了飞行动力学模型。考虑传感器噪声和复杂飞行环境导致的系统状态难以准确测量的问题,提出了一种基于高阶滑模微分器的姿态自抗扰控制算法。在MATLAB/Simulink环境下构建了复合式高速直升机姿态控制系统,并与PID(proportion integral differential)控制器和LQG(linear quadratic Gaussian)控制器进行了仿真对比。研究结果表明:所提出的基于高阶滑模微分器的姿态自抗扰控制器能够实现对姿态角的无超调跟踪,相较于PID控制器和LQG控制器,误差收敛速度分别提升31.5%和64.2%,且在噪声干扰下,最大跟踪误差比LQG控制器小34.2%,比PID控制器小39.5%。
