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Investigation of the J-TEXT plasma events by k-means clustering algorithm

Plasma Science and Technology 2023年第8期25卷 38-43页

作者：李建超张晓卿张昱 Abba Alhaji BALA 柳惠平周帼红王能超李达陈忠勇杨州军陈志鹏董蛟龙丁永华 the J-TEXT Team Hubei Key Laboratory of Optical Information and Pattern Recognition Wuhan Institute of TechnologyWuhan 430205People's Republic of China International Joint Research Laboratory of Magnetic Confinement Fusion and Plasma Physics State Key Laboratory of Advanced Electromagnetic Engineering and TechnologySchool of Electrical and Electronic EngineeringHuazhong University of Science and TechnologyWuhan 430074People's Republic of China Department of Physics Federal University DutseJigawa 720101Nigeria 不详

Various types of plasma events emerge in specific parameter ranges and exhibit similar characteristics in diagnostic signals,which can be applied to identify these events.A semisupervised machine learning algorithm,the k-means clustering algorithm,is utilized to investigate and identify plasma events in the J-TEXT *** method can cluster diverse plasma events with homogeneous features,and then these events can be identified if given few manually labeled examples based on physical understanding.A survey of clustered events reveals that the k-means algorithm can make plasma events(rotating tearing mode,sawtooth oscillations,and locked mode)gathering in Euclidean space composed of multi-dimensional diagnostic data,like soft x-ray emission intensity,edge toroidal rotation velocity,the Mirnov signal amplitude and so *** on the cluster analysis results,an approximate analytical model is proposed to rapidly identify plasma events in the J-TEXT *** cluster analysis method is conducive to data markers of massive diagnostic data.

关键词： k-means cluster analysis plasma event machine learning

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Modulation of the refractive index in chiral molecules via Laguerre-Gaussian beams

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Physical Review A 2024年第5期110卷 053508-053508页

作者： Kang Zheng Yunran Ge Wei Li Xiangying Hao Chunling Ding Hubei Key Laboratory of Optical Information and Pattern Recognition Wuhan Institute of Technology Wuhan 430205 People's Republic of China

We investigate the coherent manipulation of the complex refractive index via the interaction of chiral molecules with Laguerre-Gaussian (LG) vortex beams and the microwave field. The results show that a zero index of refraction associated with zero absorption can be obtained at the vortex core. Moreover, chiral symmetry and symmetry breaking appear in the refractive index distributions, which depend not just on the topological charge lj (j=1,2) of LG beams but also on the phase of the microwave field. We find the following. (i) When the phase value of microwave field is an even multiple of π/2, if the value of |l1−l2| is an odd number, the spatial distributions of the complex refractive index for left-handed and right-handed molecules exhibit chiral symmetry; if |l1−l2| is an even number, the refractive index distributions for left-handed and right-handed molecules display chiral symmetry breaking. (ii) When the phase value of the microwave field is an odd multiple of π/2, the phenomena of chiral symmetry and symmetry breaking of the refractive index for the left-handed and right-handed molecules are just the opposite. These findings originate from the unique optical properties of vortex beams and the quantum interference between different transition pathways. This may provide new opportunities for next-generation chiroptical devices, chiral detection, and chiral molecular switches.

关键词： Light-matter interaction optical coherence optical vortices Refraction Spatial profiles of optical beams Structured light Molecules Chiral symmetry

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Ultrafast Picometer-Resolved Molecular Structure Imaging by Laser-Induced High-Order Harmonics

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Physical Review Letters 2024年第2期133卷 023201-023201页

作者： Lixin He C. H. Yuen Yanqing He Siqi Sun E. Goetz Anh-Thu Le Yu Deng Chengqing Xu Pengfei Lan Peixiang Lu C. D. Lin Wuhan National Laboratory for Optoelectronics and School of Physics Hubei Optical Fundamental Research Center Wuhan 430074 China Department of Physics Hubei Key Laboratory of Optical Information and Pattern Recognition

Real-time visualization of molecular transformations is a captivating yet challenging frontier of ultrafast optical science and physical chemistry. While ultrafast x-ray and electron diffraction methods can achieve the needed subangstrom spatial resolution, their temporal resolution is still limited to hundreds of femtoseconds, much longer than the few femtoseconds required to probe real-time molecular dynamics. Here, we show that high-order harmonics generated by intense femtosecond lasers can be used to image molecules with few-ten-attosecond temporal resolution and few-picometer spatial resolution. This is achieved by exploiting the sensitive dependence of molecular recombination dipole moment to the geometry of the molecule at the time of harmonic emission. In a proof-of-principle experiment, we have applied this high-harmonic structure imaging (HHSI) method to monitor the structural rearrangement in NH3, ND3, and N2 from one to a few femtoseconds after the molecule is ionized by an intense laser. Our findings establish HHSI as an effective approach to resolve molecular dynamics with unprecedented spatiotemporal resolution, which can be extended to trace photochemical reactions in the future.

关键词： Atomic & molecular processes in external fields High-harmonic generation

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A Robust Algorithm for Reading recognition of Pointer Instrument with Local Matching 12

A Robust Algorithm for Reading Recognition of Pointer Instru...

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SPIE 12th International Symposium on Multispectral Image Processing and pattern recognition, MIPPR 2023

作者： Niu, Tun Ye, Liang Hubei Key Laboratory of Optical Information and Pattern Recognition Wuhan430205 China Hubei Engineering Research Center of Video Image and HD Projection Wuhan430205 China School of Electrical and Information Engineering Wuhan Institute of Technology Wuhan430205 China

ISBN: (数字)9781510675001

ISBN: (纸本)9781510674998

The inspection and recognition of readings on pointer instruments are important tasks in power inspection. Due to the diversity and the complex dial information of pointer instruments, the adaptability and low accuracy of existing methods are not enough. In this paper, we proposed a pointer instrument reading recognition algorithm based on local fast matching. Firstly, YOLOv8 is used to locate and segment the instrument in the inspection image. The positions and values of key scale are marked in the template image. Based on the key local information, a mapping relationship is established between the instrument location region in the inspection image and the template image. Then, the Hough transform is used to detect the position of the pointer, map it to the template image, and finally calculate the instrument reading based on the relative positions of the key graduations on the template image and the mapped pointer position. Experimental results demonstrate that the proposed method achieves a relative error within 5% for pointer instrument reading recognition in indoor substations. © 2024 SPIE.

关键词： Inspection

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Semi-supervised polarimetric SAR images classification based on FixMatch 12

Semi-supervised polarimetric SAR images classification based...

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SPIE 12th International Symposium on Multispectral Image Processing and pattern recognition, MIPPR 2023

作者： Lv, Qiwen Wang, Lei Hong, Hanyu Zhao, Shuwei Peng, Lingmu Hubei Key Laboratory of Optical Information and Pattern Recognition Wuhan Institute of Technology 206 Guanggu 1st Road East Lake New Technology Development ZoneHubei Province Wuhan City430000 China

ISBN: (数字)9781510674929

ISBN: (纸本)9781510674912

Polarimetric synthetic aperture radar (PolSAR) images are widely used in the fields of disaster detection and military reconnaissance. PolSAR image classification is one of the most important applications in PolSAR image interpretation. Existing image classification methods based on deep learning usually rely on a large number of labeled training data. Labeling large-scale data sets is expensive and time-consuming Therefore, semi-supervised learning is an important research direction in the field of image classification. Fixmath has achieved excellent semi-supervised classification performance for nature image, so it is introduced into the field of PolSAR image interpretation, and to improve the performance of semi-supervised PolSAR image classification. Fixmatch has the following advantages: (1) It extends the training data, using generated, labeled and unlabeled data to train the network. (2) By utilizing the information of unlabeled data, FixMatch can improve the generalization ability of the classification model, thus allowing the model to better predict on unseen data. Because of these two advantages, FixMatch has shown excellent results in semi-supervised PolSAR image classification. Experiments on two real PolSAR datasets show that the overall accuracy reaches 89.9 % when the number of labeled samples is set to 110, and reaches 98.6 % when the number of labeled samples is set to 1000. © COPYRIGHT SPIE. Downloading of the abstract is permitted for personal use only.

关键词： Image classification

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Accurate Laser Line Extraction Algorithm Based on Morphological Features under Strong Interference 12

Accurate Laser Line Extraction Algorithm Based on Morphologi...

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SPIE 12th International Symposium on Multispectral Image Processing and pattern recognition, MIPPR 2023

作者： Wu, Yuanzhe Ye, Liang Hubei Key Laboratory of Optical Information and Pattern Recognition Wuhan430205 China Hubei Engineering Research Center of Video Image and HD Projection Wuhan430205 China School of Electrical and Information Engineering Wuhan Institute of Technology Wuhan430205 China

ISBN: (数字)9781510675001

ISBN: (纸本)9781510674998

In outdoor complex lighting environments, laser stripe extraction becomes challenging due to the possibility of strong exposures in the external environment as well as reflective interference on the road surface. In order to overcome these problems, this paper proposes a multi-feature structured light extraction algorithm based on seed neighborhoods, which utilizes multiple seed points and comprehensively considers the laser stripe features, especially the morphological features of the optical stripes in their surrounding neighborhoods, so as to obtain the approximate distribution location of the real laser stripe. Finally, the laser streak extraction is performed by the gradient difference of the optical streak boundary as well as its own brightness. The experimental results show that the method is still effective in extracting laser lines even in high exposure environments where there are interferences such as reflections on the road surface. © 2024 SPIE.

关键词： Luminance

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Toroidal dipole-modulated dipole-dipole double-resonance in colloidal gold rod-cup nanocrystals for improved SERS and secondharmonic generation

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Nano Research 2022年第10期15卷 9461-9469页

作者： Hao-Sen Kang Wen-Qin Zhao Tao Zhou Liang Ma Da-Jie Yang Xiang-Bai Chen Si-Jing Ding Qu-Quan Wang Hubei Key Laboratory of Optical Information and Pattern Recognition Wuhan Institute of TechnologyWuhan 430205China School of Mathematics and Physics China University of Geosciences(Wuhan)Wuhan 430074China Mathematics and Physics Department North China Electric Power UniversityBeijing 102206China School of Science Department of PhysicsSouthern University of Science and TechnologyShenzhen 518055China

Colloidal metal nanocrystals(NCs)show great potential in plasmon-enhanced spectroscopy owing to their attractive and structure-depended plasmonic ***,unique Au rod-cup NCs,where Au nanocups are embedded on the one or two ends of Au nanorods(NRs),are successfully prepared for the first time via a controllable wet-chemistry *** Au rod-cup NCs possess multiple plasmon modes including transverse and longitudinal electric dipole(TED and LED),magnetic dipole(MD),and toroidal dipole(TD)modulated LED resonances,producing large extinction cross-section and huge near-field enhancements for plasmon-enhanced ***,Au rod-cup NCs with two embedded cups show excellent surface-enhanced Raman spectroscopy(SERS)performance than Au NRs(75.6-fold enhancement excited at 633 nm)on detecting crystal violet owing to the strong electromagnetic hotspots synergistically induced by MD,LED,and TED-based plasmon coupling between Au cup and ***,the strong TD-modulated dipole-dipole double-resonance and MD modes in Au rod-cup NCs bring a 37.3-fold enhancement of second-harmonic generation intensity compared with bare Au NRs,because they can efficiently harvest photoenergy at fundamental frequency and generate large near-field enhancements at second-harmonic *** findings provide a strategy for designing optical nanoantennas for plasmon-enhanced applications based on multiple plasmon modes.

关键词： plasmon toroidal dipole near-field enhancement surface-enhanced Raman spectroscopy(SERS) second-harmonic generation

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An Improved Watershed Foreign Object Detection of Road Surface Based on Adaptive Gaussian Threshold 12

An Improved Watershed Foreign Object Detection of Road Surfa...

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SPIE 12th International Symposium on Multispectral Image Processing and pattern recognition, MIPPR 2023

作者： Liang, Yongjie Tian, keyun Hubei Key Laboratory of Optical Information and Pattern Recognition Wuhan430205 China Hubei Engineering Research Center of Video Image and HD Projection Wuhan430205 China School of Electrical and Information Engineering Wuhan Institute of Technology Wuhan430205 China

ISBN: (数字)9781510675001

ISBN: (纸本)9781510674998

To a certain extent, foreign objects on road surfaces can cause damage to vehicles and increase the risk of accidents, which is even more immeasurably harmful in such special scenarios as airports. Effective detection of foreign objects on road surfaces is of great significance to airport flight safety and road safety maintenance. Due to the traditional watershed segmentation method in the recognition of foreign objects, there are obvious over-segmentation, noise complexity and so on. Therefore, this paper proposes an improved watershed segmentation method based on Lab-color space using image filtering techniques and morphological operations to initially separate the image foreground and background, combined with Adaptive Gaussian thresholding, labeling method for detection. This effectively solves the problem of over-segmentation, can better suppress image noise, and accurately detects foreign objects on road surfaces. © 2024 SPIE.

关键词： Object detection

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An Improved Bilateral Filtering Based on Curvature Feature for Point Cloud Denoising in Road Surface Detection 12

An Improved Bilateral Filtering Based on Curvature Feature f...

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SPIE 12th International Symposium on Multispectral Image Processing and pattern recognition, MIPPR 2023

作者： Chen, Si Hubei Key Laboratory of Optical Information and Pattern Recognition Wuhan430205 China Hubei Engineering Research Center of Video Image and HD Projection Wuhan430205 China School of Electrical and Information Technology Wuhan Institute of Technology Wuhan430205 China

ISBN: (数字)9781510675001

ISBN: (纸本)9781510674998

To effectively remove noise from the point clouds obtained for road surface defect detection while preserving the feature information, a bilateral filtering algorithm based on curvature features is proposed for denoising road surface defect point clouds. First, divide the noise points in the point cloud into several regions based on their distribution characteristics and curvature features. Then use statistical filtering to remove noise points in the obvious noise area and the flat area. Finally, an improved bilateral filtering algorithm is applied to smooth the noise points in the complex detail area. © 2024 SPIE.

关键词： Surface defects

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Single-photon 3D Reconstruction Based on Compressive Sampling Matching Pursuit

Single-photon 3D Reconstruction Based on Compressive Samplin...

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Optoelectronics Global Conference (OGC)

作者： Jinglei Li Qing Liao Xuhui Wei Jialian Zhang Minghui Zheng Hubei Key Laboratory of Optical Information and Pattern Recognition Wuhan Institute of Technology Wuhan Hubei

ISBN: (数字)9798350391466

ISBN: (纸本)9798350391473

Traditional single-photon 3D reconstruction is often hindered by low-light conditions and backgroundnoise, making it difficult to accurately reconstruct the target object. To address these challenges, we propose a novel single-photon imaging algorithm that leverages the Compressive Sensing Reconstruction Algorithm, specifically the Compressive Sampling Matching Pursuit (CoSaMP) algorithm. Building upon existing imaging methods, our approach exploits the sparsity of the imaging scene to calculat e object depth information and filter out noise photons, thereby enhancing reconstruction accuracy. This method overcomes the li mitations of traditional algorithms regarding noise and temporal resolution. We innovatively apply CoSaMP to single-photon 3D reconstruction algorithms, achieving high-precision 3D scene reconstruction under low-light conditions. MATLAB simulation results demonstrate that, in human and sunflower data models, the me an absolute error (MAE) obtained by traditional single-photon 3 D reconstruction methods is approximately 35 cm, whereas our proposed method achieves an MAE of around 1.34 cm. These results indicate the feasibility of our approach in the realm of single-p hoton 3D reconstruction, offering new possibilities for application s in biomedical imaging and remote sensing.

关键词： Three-dimensional displays Accuracy Simulation Noise Imaging Matching pursuit algorithms Reconstruction algorithms Approximation algorithms Image reconstruction Photonics

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