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Broadband Terahertz Transmission Modulation Based on Hybrid Graphene-Metal Metamaterial

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Journal of Electronic Science and Technology 2018年第2期16卷 98-104页

作者： Lan-Ju Liang Zhang Zhang Xin Yan Xin Ding De-quan Wei Qi-Li Yang Zhen-Hua Li jian-quan yao College of Precision Instrument and Opto-Electronics Engineering Tianjin UniversityTianjin 300072 School of Opto-Electronic Engineering Zaozhuang UniversityZaozhuang 277160

A novel patterned metamaterial,composed of graphene layer and metal periodic array of split ring resonators （SRRs） and cross-shapedresonators （CSRs）, with broadband terahertz （THz） wave modulation was proposed and theoretically studied. It demonstrated that a broad passband high transmission of over 96.1% in the frequency range from 1.02 THz to 1.66 THz and two narrow band resonance frequencies f1 and f2 could be generated. The modulation depth of transmission was 29.2% when the graphene layer was covered on the metal metamaterial surface, and the modulation depth could be further increased by increasing the Fermi energy of graphene layer and reached approximately 79.5% at 1.0 eV in a broadband THz frequency range. The resonance frequencies of f1 and f2 were blue-shifted, and their modulation depths reached about 63.2% and 18%, respectively. These results show that the ultrathin graphene-metal metamaterial exhibits potential to achieve highperformance active THz devices and may offer widespread applications.

关键词： Graphene metamaterial modulator terahertz

Review of a New IR Nonlinear Optical BaGa_4Se_7 Crystal

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Journal of Electronic Science and Technology 2016年第1期14卷 6-11页

作者： Wen-Tao Xu De-Gang Xu Yu-Ye Wang Peng-Xiang Liu Wei Shi jian-quan yao the Institute of Laser & Opto-Electronic College of Precision Instruments and Opto-Electronic EngineeringTianjin University

A newly grown Ba Ga4Se7 crystal has been synthesized via the Bridgman-Stockbarger *** new crystal has advantages of high nonlinear optics（NLO） coefficients,high laser damage thresholds,and wide transparent *** Ba Ga4Se7 crystal has bright application prospects as a nonlinear gain medium in mid-infrared and terahertz *** this paper,the crystalline structure and synthetic method of the Ba Ga4Se7 crystal are *** refractive indices and absorption coefficients along three dielectric axes between 0.1 THz and 1.0 THz are also *** terahertz difference frequency generation（THz-DFG） characteristics based on the BaG a4Se7 crystal in the frequency range of 0.1 THz to 1.0 THz are analyzed theoretically and the phase-matching conditions are *** application of Ba Ga4Se7 crystals in terahertz wave generation is also discussed.

关键词： BaGa4Se7 Bridgman-Stockbarger mid-infrared nonlinear gain medium THz-DFG

Photoexcited Blueshift and Redshift Switchable Metamaterial Absorber at Terahertz Frequencies

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Chinese Physics Letters 2019年第12期36卷 28-31页

作者： Zong-Cheng Xu Liang Wu Ya-Ting Zhang De-Gang Xu jian-quan yao Department of Physics Tianjin University Renai CollegeTianjin 301636 Institute of Laser and Opto-electronics and Key Laboratory of Opto-electronies Information Science and Technology(Ministry of Education) Tianjin UniversityTianjin 300072

We propose a design and numerical study of an optically blueshift and redshift switchable metamaterial(MM)absorber in the terahertz *** MM absorber comprises a periodic array of metallic split-ring resonators(SRRs)with semiconductor silicon embedded in the gaps of MM *** absorptive frequencies of the MM can be shifted by applying an external pump *** simulation results show that,for photoconductivity of silicon ranging between 1 S/m and 4000 S/m,the resonance peak of the absorption spectra shifts to higher frequencies,from 0.67 THz to 1.63 THz,with a resonance tuning range of 59%.As the conductivity of silicon increases,the resonance frequencies of the MM absorber are continuously tuned from 1.60 THz to 1.16 THz,a redshift tuning range of 28%.As the conductivity increases above 30000 S/m,the resonance frequencies tend to be stable while the absorption peak has a merely tiny *** optical-tuned absorber has potential applications as a terahertz modulator or switch.

关键词： tuning modulator pump

Initial costates derived by near-optimal reference sequence and least-squares method

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Chinese Journal of Aeronautics 2024年第5期37卷 377-391页

作者： Shaozhao LU yao ZHANG quan HU School of Aerospace Engineering Beijing Institute of TechnologyBeijing 100081China

In this paper,we present a novel initial costates solver for initializing time-optimal trajectory problems in relative motion with continuous low *** proposed solver consists of two primary components:training a Multilayer Perceptron(MLP)for generating reference sequence and Time of Flight(TOF)to the target,and deriving a system of linear algebraic equations for obtaining the initial *** overcome the challenge of generating training samples for the MLP,the backward generation method is proposed to obtain five different training *** training database and sample form are determined by analyzing the input and output correlation using the Pearson correlation *** best-performing MLP is obtained by analyzing the training results with various hyper-parameter combinations.A reference sequence starting from the initial states is obtained by integrating forward with the near-optimal control vector from the output of ***,a system of linear algebraic equations for estimating the initial costates is derived using the reference sequence and the necessary conditions for *** results demonstrate that the proposed initial costates solver improves the convergence ratio and reduce the function calls of the shooting ***,Monte-Carlo simulation illustrates that the initial costates solver is applicable to different initial velocities,demonstrating excellent generalization ability.

关键词： Relative motion Expanding training database Multilayer perceptron Initial costates Least-squares method

Characterizing the oil and water distribution in low permeability core by reconstruction of terahertz images

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Science China(Physics,Mechanics & Astronomy) 2016年第6期59卷 89-90页

作者： Ri Ma Bao Xin Yang Miao Cheng Jing Feng Ying Zhi Zhang Hong Lei Zhan Kun Zhao Mao Rong Wang jian quan yao Beijing Key Laboratory of Optical Detection Technology for Oil and Gas China University of Petroleum Beijing 102249 China Qingxin Oil Field Development Company Limited Anda 151400 China College of Precision Instrument and Opto-electronics Engineering Tianjin University Tianjin 300072 China

Dear Editors,Exploitation of low permeability oilfield has become an interest of the world due to the decline of conventional oil *** has been observed to be able to enhance oil recovery in tight sandstone reservoir.

关键词：成像特征低渗透太赫兹岩心表征水

Active Fault Tolerant Nonsingular Terminal Sliding Mode Control for Electromechanical System Based on Support Vector Machine

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Chinese Journal of Mechanical Engineering 2024年第3期37卷 189-203页

作者： jian Hu Zhengyin Yang jianyong yao School of Mechanical Engineering Nanjing University of Science and TechnologyNanjing 210094China

Effective fault diagnosis and fault-tolerant control method for aeronautics electromechanical actuator is concerned in this *** borrowing the advantages of model-driven and data-driven methods,a fault tolerant nonsingular terminal sliding mode control method based on support vector machine(SVM)is proposed.A SVM is designed to estimate the fault by off-line learning from small sample data with solving convex quadratic programming method and is introduced into a high-gain observer,so as to improve the state estimation and fault detection accuracy when the fault *** state estimation value of the observer is used for state reconfiguration.A novel nonsingular terminal sliding mode surface is designed,and Lyapunov theorem is used to derive a parameter adaptation law and a control *** is guaranteed that the proposed controller can achieve asymptotical stability which is superior to many advanced fault-tolerant *** addition,the parameter estimation also can help to diagnose the system faults because the faults can be reflected by the parameters *** comparative simulation and experimental results illustrate the effectiveness and advancement of the proposed controller compared with several other main-stream controllers.

关键词： Aeronautics electromechanical actuator Fault tolerant control Support vector machine State observer Parametric uncertainty

Theoretical and experimental study on broadband terahertz atmospheric transmission characteristics

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Chinese Physics B 2017年第1期26卷 597-602页

作者： Shi-Bei Guo Kai Zhong Mao-Rong Wang Chu Liu Yong Xiao Wen-Peng Wang De-Gang Xu jian-quan yao Institute of Laser and Opto-electronics College of Precision Instrument and Opto-electronics Engineering Tianjin University Tianjin 300072 China Key Laboratory of Opto-electronics Information Technology (Ministry of Education) Tianjin University Tianjin 300072 China National Key Laboratory of Science and Technology on Millimeter-wave Remote Sensing Beijing 100039 China

Broadband terahertz（THz） atmospheric transmission characteristics from 0 to 8 THz are theoretically simulated based on a standard Van Vleck–Weisskopf line shape, considering 1696 water absorption lines and 298 oxygen absorption *** influences of humidity, temperature, and pressure on the THz atmospheric absorption are analyzed and experimentally verified with a Fourier transform infrared spectrometer（FTIR） system, showing good consistency. The investigation and evaluation on high-frequency atmospheric windows are good supplements to existing data in the low-frequency range and lay the foundation for aircraft-based high-altitude applications of THz communication and radar.

关键词： terahertz atmospheric propagation line absorption continuum absorption

Ultrafast Carrier Dynamics and Terahertz Photoconductivity of Mixed-Cation and Lead Mixed-Halide Hybrid Perovskites

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Chinese Physics Letters 2019年第2期36卷 83-91页

作者： Wan-Ying Zhao Zhi-Liang Ku Li-Ping Lv Xian Lin Yong Peng Zuan-Ming Jin Guo-Hong Ma jian-quan yao Department of Physics Shanghai University State Key Laboratory of Advanced Technology for Materials Synthesis and Processing Wuhan University of Technology Department of Chemical Engineering School of Environmental and Chemical EngineeringShanghai University STU & SIOM Joint Laboratory for Superintense Lasers and Applications College of Precision Instrument and Opto-electronics Engineering Institute of Laser and Opto-electronicsTianjin University

Using time-dependent terahertz spectroscopy, we investigate the role of mixed-cation and mixed-halide on the ultrafast photoconductivity dynamics of two different methylammonium(MA) lead-iodide perovskite thin films. It is found that the dynamics of conductivity after photoexcitation reveals significant correlation on the microscopy crystalline features of the samples. Our results show that mixed-cation and lead mixed-halide affect the charge carrier dynamics of the lead-iodide perovskites. In the(5-AVA)_(0.05)(MA)_(0.95) PbI_(2.95) Cl_(0.05)/spiro thin film, we observe a much weaker saturation trend of the initial photoconductivity with high excitation fluence, which is attributed to the combined effect of sequential charge carrier generation, transfer, cooling and polaron formation.

关键词： Ultrafast Carrier Dynamics Terahertz Photoconductivity Mixed-Cation Lead Mixed-Halide Hybrid Perovskites

Reinforcement learning based adaptive control for uncertain mechanical systems with asymptotic tracking

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Defence Technology（防务技术） 2024年第4期34卷 19-28页

作者： Xiang-long Liang Zhi-kai yao yao-wen Ge jian-yong yao School of Mechanical Engineering Nanjing University of Science and TechnologyNanjing210094China College of Automation&College of Artificial Intelligence Nanjing University of Post and TelecommunicationNanjing210023China

This paper mainly focuses on the development of a learning-based controller for a class of uncertain mechanical systems modeled by the Euler-Lagrange *** considered system can depict the behavior of a large class of engineering systems,such as vehicular systems,robot manipulators and *** these systems are often characterized by highly nonlinear characteristics,heavy modeling uncertainties and unknown perturbations,therefore,accurate-model-based nonlinear control approaches become *** by the challenge,a reinforcement learning(RL)adaptive control methodology based on the actor-critic framework is investigated to compensate the uncertain mechanical *** approximation inaccuracies caused by RL and the exogenous unknown disturbances are circumvented via a continuous robust integral of the sign of the error(RISE)control *** from a classical RISE control law,a tanh(·)function is utilized instead of a sign(·)function to acquire a more smooth control *** developed controller requires very little prior knowledge of the dynamic model,is robust to unknown dynamics and exogenous disturbances,and can achieve asymptotic output ***,co-simulations through ADAMS and MATLAB/Simulink on a three degrees-of-freedom(3-DOF)manipulator and experiments on a real-time electromechanical servo system are performed to verify the performance of the proposed approach.

关键词： Adaptive control Reinforcement learning Uncertain mechanical systems Asymptotic tracking