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Impact of laser time structure on the evolution behavior of laser induced plasma and stress waves in the target

Optics Express 2025年第9期33卷 18659-18675页

作者： Yuan, Hang Kang, Shenghao Mei, Xiaochen Niu, Jincheng Miao, Jiajie Zhu, Chengyu National Key Laboratory of Laser Spatial Information Harbin Institute of Technology Harbin150080 China

This study investigates the impact of laser time structure on laser-induced plasma plume evolution and shock wave propagation within target. The theoretical analysis of plasma plume dynamics under various pulse rise times were carried by HELIOS code. An experimental setup incorporating spontaneous emission fast photography and time-resolved interferometry was developed to observe plasma dynamics and monitor the distribution of shock stresses at different stages. The results indicate that, under energy-limited conditions, short-rise-time pulses yield higher peak shock pressures, whereas long-rise-time pulses lead to elevated electron temperatures. By adjusting the laser time structure, effective control over both shock pressure and electron temperature can be achieved. This research provides valuable insights for optimizing laser parameters in applications such as laser shock peening and laser-induced breakdown spectroscopy. © 2025 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement.

关键词： Laser produced plasmas

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A Low-Cost Full-Range Hydrogen Sensor Based on Quartz Tuning Fork

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IEEE Sensors Journal 2025年第10期25卷 16943-16949页

作者： Li, Chuanning He, Ying Qiao, Shunda Ma, Yufei Harbin Institute of Technology National Key Laboratory of Laser Spatial Information Harbin150001 China Harbin Institute of Technology Zhengzhou Research Institute Zhengzhou450008 China

Hydrogen (H2) sensors have a wide range of applications in green energy, including fuel cell monitoring, hydrogen storage safety, and leak detection in renewable energy systems. This paper reports a quartz tuning fork (QTF) based low-cost full-range H2 sensor with a detection range of 0% to 100%. The system features a simple structure and easy fabrication. Firstly, the relationship between H2 concentration and the characteristics of QTF was theoretically analyzed. The influence of hydrogen viscosity on QTFs was utilized as sensing mechanism. Three QTFs with different resonant frequencies of 8 kHz, 32 kHz, and 100 kHz were experimentally compared, and the results indicated that the 100 kHz QTF exhibits the best performance, achieving a frequency sensitivity of 200 mHz/% and the fastest response. The findings revealed that higher-frequency QTFs exhibit superior sensitivity to H2 detection. The designed sensor platform enables H2 sensing at a low manufacturing cost and the sensors are easily replaceable, which opens up great potential for mass production and use in industry. The experiments also revealed that the quality factor (Q-factor) significantly increases when the QTF is immersed in a H2 environment, attributed to low density and low viscosity of H2 © 2001-2012 IEEE.

关键词： Hydrogen storage

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GPS flex power detection leveraging XGBoost machine learning based on LEO satellites

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GPS Solutions 2025年第3期29卷 1-15页

作者： Du, Yanjun Yang, Yuanxi Jia, Xiaolin Yao, Wanqiang Li, Qin College of Geomatics Xi’an University of Science and Technology Xi’an710054 China State Key Laboratory of Spatial Datum Xi’an710054 China Xi’an Research Institute of Surveying and Mapping Xi’an710054 China National Key Laboratory of Intelligent Geospatial Information Beijing100094 China

In recent years, the flex power of the global positioning system (GPS) Block IIR-M and Block IIF satellites has frequently been activated and deactivated. Ground-based GPS flex power monitoring faces several challenges, including uneven receiver distribution, multipath error arising from complex environments, and significant fluctuations in low-elevation carrier-to-noise ratio data. To overcome these challenges, we propose a novel GPS flex power detection method by introducing a detection metric, CN0el. Spaceborne receiver data from 15 low earth orbit (LEO) satellites and historical data from February 2022 to December 2023 are utilized to train an extreme gradient boosting (XGBoost) machine learning model. The detection model achieves an accuracy exceeding 99%, as validated by the measured data from January and February 2024. These findings demonstrate that integrating XGBoost machine learning with LEO satellite data offers a highly effective solution for GPS flex power detection. © The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature 2025.

关键词： Global positioning system

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212-km ultra-long-distance hybrid Φ-OTDR/BOTDR based on remotely pumped optical amplification

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Optics Express 2025年第7期33卷 15827-15837页

作者： Lei, Yanyang Tang, Xiaohui Xia, Meng Jiang, Taofei Liu, Shuaiqi Li, Tianfu Ba, Dexin Dong, Yongkang National Key Laboratory of Laser Spatial Information Harbin Institute of Technology Harbin150001 China Harbin Institute of Technology Zhengzhou Research Institute Zhengzhou450007 China Zhejiang Key Laboratory of 3d Micro/Nano Fabrication and Characterization Westlake Institute for Optoelectronics Fuyang Zhejiang Hangzhou311421 China

In this paper, we propose and demonstrate a 212 km ultra-long-distance hybrid distributed optical fiber sensing (DOFS) system capable of simultaneously measuring vibration and strain/temperature along the sensing fiber. This is achieved by integrating phase-sensitive optical time-domain reflectometry (Φ-OTDR) and Brillouin optical time-domain reflectometry (BOTDR) into a single interrogator. The extended sensing range is realized through the use of wavelength division multiplexing, time division multiplexing, co-pumped distributed Raman amplification, and remotely pumped optical amplification technologies. The system achieves a 20 m spatial resolution for vibration sensing and a 50 m resolution for strain/temperature sensing, with strain/temperature measurement accuracy reaching 4.3 MHz. Notably, the single-end operation and simplified system architecture make this solution highly suited for industrial on-site applications. To our knowledge, this is the longest measurement range reported for hybrid DOFS systems without the aid of active repeaters or bi-directional distributed amplification techniques. © 2025 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement.

关键词： Optical fibers

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DSMF-Net: A One-Stage SAR Ship Detection Network Based on Deformable Strip Convolution and Multiscale Feature Refinement and Fusion

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IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing 2025年 18卷 10694-10710页

作者： Liu, Xingyu Pan, Jun Hu, Rong Huang, Wenli Lin, Jiawei Hu, Jiarui Wuhan University School of Resources and Environmental Sciences Hubei 430079 China Wuhan University State Key Laboratory of Information Engineering in Surveying Mapping and Remote Sensing Hubei 430079 China Jilin University College of Geo-Exploration Science and Technology Key Laboratory of Geophysical Exploration Equipment Ministry of Education Changchun130021 China

Synthetic aperture radar (SAR), an all-weather and day-and-night remote sensing imaging technology, is crucial for ship detection. However, SAR images are hampered by speckle noise and coastal clutter, and ship targets exhibit multiscale and small-scale characteristics. To tackle these challenges, we introduce the DSMF-Net, a SAR ship detection network leveraging deformable strip convolution and multiscale feature refinement and fusion. First, to counter interference from complex backgrounds, such as nearshore ports and speckle noise, the deformable strip convolution (DSConv) is introduced and incorporated into the backbone network for SAR ship feature extraction, named SSFEBackbone. DSConv adaptively adjusts convolution sampling positions based on ship target characteristics, precisely extracting features with directional and strip structures. Second, the dual-stream self-attention feature refinement module is utilized to refine high-level semantic features. Through the mixing spatial and channel attention (MSCA) mechanism, differences and correlations between complex backgrounds and ship entities are further captured, enhancing feature expression. Finally, the adaptive selective feature pyramid network is proposed. By leveraging MSCA attention, high-level semantic and low-level spatial features are flexibly matched, enabling better key information retention during fusion and background clutter suppression, thus improving detection performance for complex backgrounds and multiscale ship targets. Experimental results demonstrate that DSMF-Net performs significantly better in ship detection in SAR images. It outperforms existing state-of-the-art methods on the SAR-Ship-Dataset, high-resolution SAR images dataset, and SAR ship detection dataset, achieving an AP50 of 96.8%, 93.1%, and 97.4%, respectively. © 2008-2012 IEEE.

关键词： Radar clutter

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Detection and interpretation of the time-varying seasonal signals in China with multi-geodetic measurements

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geodesy and geodynamics 2025年第1期16卷 42-54页

作者： Liansheng Deng Yugang Xiao Qusen Chen Wei Peng Zhao Li Hua Chen Zhiwen Wu School of Electrical and Electronic Information Engineering Hubei Polytechnic UniversityHuangshi 435003China Hubei Luojia Laboratory GNSS Research CenterWuhan UniversityWuhan 430079China Changjiang Spatial Information Technology Engineering Co. Ltd.Wuhan 430010China Key Laboratory of Spatial Data Mining&Information Sharing of the Ministry of Education Fuzhou UniversityFuzhou 350108China School of Geodesy and Geomatics Wuhan UniversityWuhan 430079China The First Surveying and Mapping Institute of Hunan Province Changsha 410114China

The time-varying periodic variations in Global Navigation Satellite System(GNSS)stations affect the reliable time series analysis and appropriate geophysical *** this study,we apply the singular spectrum analysis(SSA)method to characterize and interpret the periodic patterns of GNSS deformations in China using multiple geodetic *** include 23-year observations from the Crustal Movement Observation Network of China(CMONOC),displacements inferred from the Gravity Recovery and Climate Experiment(GRACE),and loadings derived from geophysical models(GM).The results reveal that all CMONOC time series exhibit seasonal signals characterized by amplitude and phase modulations,and the SSA method outperforms the traditional least squares fitting(LSF)method in extracting and interpreting the time-varying seasonal signals from the original time *** decrease in the root mean square(RMS)correlates well with the annual cycle variance estimated by the SSA method,and the average reduction in noise amplitudes is nearly twice as much for SSA filtered results compared with those from the LSF *** SSA analysis,the time-varying seasonal signals for all the selected stations can be identified in the reconstructed components corresponding to the first ten ***,both RMS reduction and correlation analysis imply the advantages of GRACE solutions in explaining the GNSS periodic variations,and the geophysical effects can account for 71%of the GNSS annual amplitudes,and the average RMS reduction is 15%.The SSA method has proved to be useful for investigating the GNSS timevarying seasonal *** could be applicable as an auxiliary tool in the improvement of nonlinear variations investigations.

关键词： GNSS coordinate time series Singularspectrumanalysis Time-varying seasonal signals Loading effects GRACE

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Improving atmospheric pressure vertical correction model using Gaussian function

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geodesy and geodynamics 2025年第1期16卷 67-74页

作者： Baoshuang Zhang Junyu Li Lilong Liu Yibin Yao Liangke Huang Chao Ren Hongchang He Tengxu Zhang Yuxin Wang College of Geomatics and Geoinformation Guilin University of TechnologyGuilin 541004China Guangxi Key Laboratory of Spatial Information and Geomatics Guilin 541004China School of Geodesy and Geomatics Wuhan UniversityWuhan 430079China Schoolof Resources and Environmental Science and Engineering Hubei University of Science and TechnologyXianning 437100China

The Zenith Hydrostatic Delay(ZHD)is essential for high-precision Global Navigation Satellite System(GNSS)and Very Long Baseline Interferometry(VLBI)data *** estimation of ZHD relies on in situ atmospheric pressure,which is primarily variable in the vertical *** atmospheric pressure is either site-specific or has limited spatial coverage,necessitating vertical corrections for broader *** study introduces a model that uses a Gaussian function for the vertical correction of atmospheric pressure when in situ meteorological observations are *** with the fifth-generation European Centre for Medium-Range Weather Forecasts reanalysis(ERA5)reveals an average Bias and RMS for the new model of 0.31 h Pa and 2.96 h Pa,*** corresponds to improvements of 37.5%and 80.3%in terms of RMS compared to two commonly used models(T0and Tvmodels)that require in situ meteorological observations,*** validation with radiosonde data shows an average Bias and RMS of 1.85 h Pa and 4.87 h Pa,corresponding to the improvement of 42.8%and 71.1%in RMS compared with T0and Tv models,*** accuracies are sufficient for calculating ZHD to an accuracy of 1 mm by performing atmospheric pressure vertical *** new model can correct atmospheric pressure from meteorological stations or numerical weather forecasts to different heights of the troposphere.

关键词： Atmospheric pressure Vertical correction Zenith hydrostatic delay(ZHD) Gauss function ERA5

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Hydrogen-enhanced light-induced thermoelastic spectroscopy sensing

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Photonics Research 2025年第1期13卷 194-200页

作者： YING HE YUANZHI WANG SHUNDA QIAO XIAOMING DUAN HONG QI YUFEI MA National Key Laboratory of Laser Spatial Information Harbin Institute of TechnologyHarbin 150000China School of Energy Science and Engineering Harbin Institute of TechnologyHarbin 150001China

A hydrogen(H_(2))-enhanced light-induced thermoelastic spectroscopy(LITES)sensor is proposed for the first time,to our knowledge,in this *** enhancement with H_(2)significantly reduces the resonance damping of a quartz tuning fork(QTF),leading to a 2.5-fold improvement in the quality factor(Q-factor)to 30,000 without introducing additional noise into the LITES sensor *** on the H_(2)-enhancement effect,a self-designed round-head QTF with a low resonance frequency(f_(0))of 9527 Hz and a fiber coupled multipass cell(MPC)with an optical length of 40 m were utilized to increase the energy accumulation time of QTF and the optical absorption of the target gas,respectively,to demonstrate an ultra-highly sensitive C2H_(2)-LITES *** longterm stability of the H_(2)-enhanced C2H_(2)-LITES sensor was investigated based on Allan deviation *** an optimal integration time of 140 s,the minimum detection limit(MDL)was improved to 290 parts per trillion(ppt).Compared to other reported state-of-the-art C2H_(2)-LITES techniques with similar parameters,this sensor shows a 241-fold improvement in the *** H_(2)-enhancement technique proves to be a highly effective method for achieving a high Q-factor QTF,characterized by its simplicity and *** offers substantial potential for applications in QTF-based gas sensing.

关键词： spectroscopy simplicity light

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250 km ultra-long distance single-end Φ-OTDR assisted by DRA and RPOA technology 4

250 km ultra-long distance single-end Φ-OTDR assisted by DR...

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4th International Computational Imaging Conference, CITA 2024

作者： Lei, Yanyang Zhang, Yutong Li, Tianfu Sui, Jinglin Ding, Jian Xiong, Zhang Dong, Yongkang National Key Laboratory of Laser Spatial Information Harbin Institute of Technology Harbin150001 China Harbin Institute of Technology Zhengzhou Research Institute Zhengzhou450007 China Heilongjiang Provincial Key Laboratory of Quantum Control Harbin University of Science and Technology Harbin150080 China

ISBN: (纸本)9781510688834

Phase-sensitive optical time-domain reflectometry (Φ-OTDR) can quickly characterize the weak vibration signals along the sensing fiber by demodulating the Rayleigh backscattering (RBS) light. It features a millisecond or sub-millisecond fast response and nanostrain detection sensitivity, and has broad application fields. However, the maximum measurement distance of Φ-OTDR system is limited by the nonlinear threshold and transmission loss of sensing fiber and the ultralow power of RBS light. In this paper, a 250 km ultra-long sensing distance single-end Φ-OTDR system with 20m spatial resolution (SR) is proposed and experimentally demonstrated, assisted by using a semiconductor optical amplifier (SOA) and an acoustic-optic modulator (AOM) cascade to obtain a high extinction ratio (ER) probe pulse, and combining co-pumping distributed Raman amplification (DRA) technology and remotely pumped optical amplification (RPOA) technology. With the elaborate design, the 250 km sensing fiber is divided into three segments, the first 25 km segment sensing fiber is used to delay the injection of the Raman pump, to further achieve the maximum sensing distance without triggering the nonlinear effects;then the co-pumping DRA based on 1480 nm pump laser diode provides gain mainly in the next 100 km segment, then the residual 1480nm pump source provides energy to the erbium-doped fiber to realize the inversion of the particle number, and finally amplifies the RBS light by the process of stimulated radiation in the last 125 km segment. According to our research, this is the maximum sensing distance of Φ-OTDR system achieved without assisted by active repeaters and counter-pumping distributed amplification. © 2025 SPIE.

关键词： Semiconductor optical amplifiers

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Research on the Evaluation and Optimization Strategy of Children's School Commuting Path in Cold Climate Cities from the Perspective of Child-Friendliness: Taking Harbin as an Example

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China City Planning Review 2025年第1期34卷 41-49页

作者： Liu Yibo Sun Cheng Qian Fang(Translated) School of Architecture and Design Harbin Institute of Technology Key Laboratory of National Territory Spatial Planning and Ecological Restoration in Cold Regions Ministry of Natural Resources Key Laboratory of Cold Region Urban and Rural Human Settlement Environment Science and Technology Ministry of Industry and Information Technology 不详

The school commuting path is an important space for elementary school students to engage with society and *** design of these paths reflects concerns for children's rights and healthy development and has crucial impacts on creating supportive environments for *** scientific evaluation of the child-friendly level of school commuting paths forms a significant basis for shaping child-friendly environments and promoting the comprehensive development of ***,due to the unique climatic conditions,cold climate cities excert a distinct impact on children's behavior,activities,and physical and mental health compared to cities in other climate *** study,from the perspective of child-friendliness,constructs an evaluation system for school commuting paths in cold climate cities,based on children's behavioral characteristics and environmental *** system includes dimensions such as safety,diversity,and *** children and their caregivers as the evaluators,the study applies structural equation modeling to assign weights to the various dimension indicators in the evaluation *** research focuses on five elementary schools in the Nangang District of Harbin City,using methods such as machine learning,space syntax,and field surveys to assess the school commuting *** upon these findings,the study constructs the characteristic profile of the commuting paths and proposes evidence-based control and optimization strategies for different types of school commuting paths in cold climate cities from a child-friendly perspective.

关键词： child-friendly cold climate cities children's school commuting path evaluation optimization strategy

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