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Coherent terahertz wave emission from laser-induced plasma in isotropic transparent solid dielectrics

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Chinese Optics Letters 2024年第7期22卷 121-125页

作者： Yuxuan Chen Yuhang He Chenyin Dai Xiangyu La Zhen Tian Jianming Dai Center for Terahertz Waves and School of Precision instrument and Opto-electronics engineering Tianjin UniversityTianjin 300072China

In this Letter,we employ fused silica and two types of optical glass as examples to investigate the coherent terahertz(THz)wave emission from laser-ionized isotropic transparent *** on the laser energy and incident angle dependences,we ascribe the THz emission to the ponderomotive force-induced dipole ***,our investigation on the dependence of THz amplitude on the laser pulse duration confirms the dominant role of avalanche ionization in solid *** THz emission can be utilized to indirectly monitor the ultrafast dynamics of carrier generation and motion during the laser ionization process of solid dielectrics.

关键词： terahertz wave emission laser-induced plasma laser-solid interaction ponderomotive force fused silica.

Improving autoencoder-based unsupervised damage detection in uncontrolled structural health monitoring under noisy conditions

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仪器仪表学报 2024年第6期45卷 91-100页

作者： Yang Kang Wang Linyuan Gao Chao Chen Mozhi Tian Zhihui Zhou Dunzhi Liu Yang department of Electrical and Computer engineering University of FloridaGainesville 32611USA department of Electrical and Computer engineering Temple UniversityPhiladelphia 19122USA School of Precision instrument and Opto-electronics engineering Tianjin UniversityTianjin 300072China

Structural health monitoring is widely utilized in outdoor environments,especially under harsh conditions,which can introduce noise into the monitoring ***,designing an effective denoising strategy to enhance the performance of guided wave damage detection in noisy environments is *** paper introduces a local temporal principal component analysis(PCA)reconstruction approach for denoising guided waves prior to implementing unsupervised damage detection,achieved through novel autoencoder-based *** results demonstrate that the proposed denoising method significantly enhances damage detection performance when guided waves are contaminated by noise,with SNR values ranging from 10 to-5 *** the implementation of the proposed denoising approach,the AUC score can elevate from 0.65 to 0.96 when dealing with guided waves corrputed by noise at a level of-5 ***,the paper provides guidance on selecting the appropriate number of components used in the denoising PCA reconstruction,aiding in the optimization of the damage detection in noisy conditions.

关键词： structural health monitoring guided waves principal component analysis deep learning denoising dynamic environmental condition

Multi-path navigation method using solar panel-reflected solar oscillations for Earth satellites

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Science China(Information Sciences) 2024年第7期67卷 327-328页

作者： Yuqing YANG Haonan YANG Xiaolin NING Weiren WU Jiancheng FANG School of instrument Science & Opto-electronics engineering Beihang University Lunar Exploration and Space Program Center China National Space Administration

Several autonomous navigation methods have been studied to reduce reliance on the ground stations. Geomagnetic navigation, gravity gradient navigation, and celestial navigation using optical sensors are typical autonomous navigation methods. Geomagnetic and gravity gradient navigation have low navigation accuracy (1301 m [1] and 235 m [2], respectively) due to the poor accuracy of the geomagnetic and gravity gradient maps.

关键词： Solar panels

Grating-free autofocus for single-pixel microscopic imaging

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Photonics Research 2024年第6期12卷 1313-1321页

作者： GUAN WANG HUAXIA DENG YU CAI MENGCHAO MA XIANG ZHONG XINGLONG GONG CAS Key Laboratory of Mechanical Behavior and Design of Materials Department of Modern MechanicsUniversity of Science and Technology of ChinaHefei 230027China School of instrument Science and Opto-electronics engineering Hefei University of TechnologyHefei 230009China

As a computational technology,single-pixel microscopic imaging(SPMI)transfers the target’s spatial information into a temporal *** traditional focusing method of imaging before evaluation is not applicable to the SPMI *** propose a grating-free autofocus strategy derived from the physical mechanism of optical *** the amplitude information of just one high-frequency point in the spectrum is all that is needed to achieve fast autofocus with the SPMI ***,only four patterns need to be cyclically projected,enabling efficient localization of the focal plane based on the measurement *** demonstrate SPMI autofocus experiments at micrometer and even nanometer depths of *** proposed method can be extended to achieve SMPI autofocus with invisible optical pattern illumination.

关键词： optical system illumination

Distributed Multicircular Circumnavigation Control for UAVs with Desired Angular Spacing

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Defence Technology（防务技术） 2024年第1期31卷 429-446页

作者： Shixiong Li Xingling Shao Wendong Zhang Qingzhen Zhang National Key Laboratory for Electronic Measurement Technology School of Instrument and ElectronicsNorth University of ChinaTaiyuan 030051China School of Automation Science and Electrical engineering Beihang UniversityBeijing 100086China

This paper addresses a multicircular circumnavigation control for UAVs with desired angular spacing around a nonstationary *** defining a coordinated error relative to neighboring angular spacing,under the premise that target information is perfectly accessible by all nodes,a centralized circular enclosing control strategy is derived for multiple UAVs connected by an undirected graph to allow for formation behaviors concerning the moving ***,to avoid the requirement of target’s states being accessible for each UAV,fixed-time distributed observers are introduced to acquire the state estimates in a fixed-time sense,and the upper boundary of settling time can be determined offline irrespective of initial properties,greatly releasing the burdensome communication ***,with the aid of fixed-time distributed observers,a distributed circular circumnavigation controller is derived to force all UAVs to collaboratively evolve along the preset circles while keeping a desired angular *** is inferred from Lyapunov stability that all errors are demonstrated to be *** are offered to verify the utility of proposed protocol.

关键词： Angular spacing Distributed observer Multicircular circumnavigation Moving target UAVs

Polarization-entangled photon pairs with factorable spectra engineered by using an uneven four-stage nonlinear interferometer

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Chinese Optics Letters 2024年第5期22卷 106-110页

作者：崔亮陈浩然李嘉敏李小英 College of Precision instrument and Opto-electronics engineering Key Laboratory of Opto-Electronics Information TechnologyMinistry of EducationTianjin UniversityTianjin 300072China School of Physics Taiyuan University of TechnologyTaiyuan 030000China

We report the generation of polarization-entangled photon pairs in the 1550 nm band by pumping an uneven nonlinear interferometer loop with two orthogonally polarized counterpropagating pump *** uneven nonlinear interferometer,providing a more ideal interference pattern due to the elimination of secondary maxima,consists of four pieces of dispersion-shifted fibers sandwiched with three pieces of standard single-mode fibers,and the lengths of the nonlinear fibers follow the binomial *** mode number of the photon pairs deduced from the measured joint spectrum is∼*** collection efficiency of the photon pairs is found to be∼94%(after background noise correction).The directly measured visibility of two-photon interference of the polarization-entangled photon pairs is∼92%,while no interference is observed in the direct detection of either the signal or idler photons.

关键词： polarization-entangled photon pairs nonlinear interferometer quantum state engineering optical fiber

Research on Driver’s Fatigue Detection Based on Information Fusion

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Computers, Materials & Continua 2024年第4期79卷 1039-1061页

作者： Meiyan Zhang Boqi Zhao Jipu Li Qisong Wang Dan Liu Jinwei Sun Jingxiao Liao Harbin Institute of Technology School of Instrument Science and EngineeringHarbin150036China department of Industrial and Systems engineering The Hong Kong Polytechnic UniversityHong Kong100872China

Driving fatigue is a physiological phenomenon that often occurs during *** the driver enters a fatigued state,the attentionis lax,the response is slow,and the ability todeal with emergencies is significantly reduced,which can easily cause traffic ***,studying driver fatigue detectionmethods is significant in ensuring safe ***,the fatigue state of actual drivers is easily interfered with by the external environment(glasses and light),which leads to many problems,such as weak reliability of fatigue driving ***,fatigue is a slow process,first manifested in physiological signals and then reflected in human face *** improve the accuracy and stability of fatigue detection,this paper proposed a driver fatigue detection method based on image information and physiological information,designed a fatigue driving detection device,built a simulation driving experiment platform,and collected facial as well as physiological information of drivers during ***,the effectiveness of the fatigue detection method was *** movement feature parameters and physiological signal features of drivers’fatigue levels were *** driver fatigue detection model was trained to classify fatigue and non-fatigue states based on the extracted *** rates of the image,electroencephalogram(EEG),and blood oxygen signals were 86%,82%,and 71%,*** fusion theory was presented to facilitate the fatigue detection effect;the fatigue features were fused using multiple kernel learning and typical correlation analysis methods to increase the detection accuracy to 94%.It can be seen that the fatigue driving detectionmethod based onmulti-source feature fusion effectively detected driver fatigue state,and the accuracy rate was higher than that of a single information *** summary,fatigue drivingmonitoring has broad development prospects and can be used in traffic accident prevention and wearable dr

关键词： Driving fatigue information fusion EEG blood oxygen

Sawtooth-enhanced bend sensor for gesture recognition

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Science China(Technological Sciences) 2024年第6期67卷 1727-1736页

作者： BAI YanRu ZHANG ZiHang WANG HaoYu GUO Rui LI XiSheng School of Automation and Electrical engineering University of Science and Technology BeijingBeijing100083China School of Advanced engineering University of Science and Technology BeijingBeijing100083China School of Precision instrument and Opto-electronics engineering Tianjin UniversityTianjin300072China School of Computer and Communication engineering University of Science and Technology BeijingBeijing100083China

Gesture recognition has diverse application prospects in the field of human-computer ***,gesture recognition devices based on strain sensors have achieved remarkable results,among which liquid metal materials have considerable advantages due to their high tensile strength and *** improve the detection sensitivity of liquid metal strain sensors,a sawtooth-enhanced bending sensor is proposed in this *** with the results from previous studies,the bending sensor shows enhanced resistance *** addition,combined with machine learning algorithms,a gesture recognition glove based on the sawtooth-enhanced bending sensor is also fabricated in this study,and various gestures are accurately *** the fields of human-computer interaction,wearable sensing,and medical health,the sawtooth-enhanced bending sensor shows great potential and can have wide application prospects.

关键词： liquid metal bending sensor gesture recognition machine learning

Dielectric size optimization for high power density in large-scale triboelectric nanogenerators

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Nano Research 2024年第9期17卷 8455-8464页

作者： Abdulkerim Karabiber Ömer Dirik Feyyaz Koc Faruk Ozel department of Electrical and electronics engineering Bingol UniversityBingol 12000Turkey department of Metallurgical and Materials engineering Karamanoglu Mehmetbey UniversityKaraman 70200Turkey

Triboelectric nanogenerators(TENGs)have emerged as a promising technology to harvest electrical energy from natural motions such as human movement,wind,and water *** TENGs show significant potential in small-scale applications,developing large-scale TENGs capable of generating high power remains a significant *** factors that can affect the performance of large-scale TENGs are being investigated to overcome this challenge,including the size and configuration of dielectric *** study optimizes dielectrics regarding surface area,thickness,and multicell configuration to improve harvested electrical power density in large-scale *** the studies,glass fiber was used as the positive dielectric,and multipurpose white silicone was used as the negative dielectric because of their high tribo-potential,durability,and easy *** the size optimization phase,dielectric thicknesses and surface areas that provide the maximum power density were ***,horizontal and vertical multicell configurations were examined to efficiently integrate size-optimized *** results reveal that large-scale TENGs with vertical multicell configurations can achieve high and usable energy density for *** findings provide valuable insight into the development of large-scale TENGs with advanced power generation capabilities.

关键词： triboelectric nanogenerator dielectric layer size optimization multi-cell structure high power density