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Fluid Dynamics & Materials Processing 2024年第1期20卷 127-145页

作者： Shiyang Song Tongxin Han Postgraduate Department China Academy of Railway SciencesBeijing100081China Loco.otive&Car Research Institute China Academy of Railway Sciences Corporation LimitedBeijing100081China

Aiming to mitigate the aerodynamic lift force imbalance between pantograph strips,which exacerbates wear and affects the current co.lection performance of the pantograph-catenary system,a study has been co.ducted to support the beam deflector optimization using a co.bination of experimental measurements and co.putational fluid dynamics(CFD)simulations.The results demonstrate that the size,position,and installation orientation of the wind deflectors significantly influence the amount of force co.pensation.They also indicate that the front strip deflectors should be installed downwards and the rear strip deflectors upwards,thereby forming a“π”shape.Moreover,the lift force co.pensation provided by the wind deflectors increases with the size of the deflector.Alternative wind co.pensation strategies,such as co.trol circuits,are also discussed,putting emphasis on the pros and co.s of various pantograph types and wind co.pensation approaches.

关键词： High-speed pantograph aerodynamic lift force supporting beam wind deflectors co.putational fluid dynamics(CFD)

Machine learning-based predictions of current and future susceptibility to retrogressive thaw slumps across the Northern Hemisphere

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Advances in Climate Change Research 2024年第2期15卷 253-264页

作者： Jing LUO Guo-An YIN Fu-Jun NIU Tian-Chun DONG Ze-Yong GAO Ming-Hao LIU Fan YU State Key Laboratory of Frozen Soil Engineering Northwest Institute of Eco-Environment and ResourcesChinese Academy of SciencesLanzhou 730000China china railway Qinghai-Tibet Group co. LtdXining 810000China University of Chinese academy of sciences Beijing 100049China

Retrogressive thaw slumps(RTSs)caused by the thawing of ground ice on permafrost slopes have dramatically increased and beco.e a co.mon permafrost hazard across the Northern Hemisphere during previous decades.However,a gap remains in our co.prehensive understanding of the spatial co.trolling factors,including the climate and terrain,that are co.ducive to these RTSs at a global scale.Using machine learning methodologies,we mapped the current and future RTSs susceptibility distributions by inco.porating a range of environmental factors and RTSs inventories.We identified freezing-degree days and maximum summer rainfall as the primary environmental factors affecting RTSs susceptibility.The final ensemble susceptibility map suggests that regions with high to very high susceptibility co.ld co.stitute(11.6±0.78)%of the Northern Hemisphere's permafrost region.When juxtaposed with the current(2000-2020)RTSs susceptibility map,the total area with high to very high susceptibility co.ld witness an increase ranging from(31.7±0.65)%(SSP585)to(51.9±0.73)%(SSP126)by the 2041-2060.The insights gleaned from this study not only offer valuable implications for engineering applications across the Northern Hemisphere,but also provide a long-term insight into the potential change of RTSs in permafrost regions in response to climate change.

关键词： Retrogressive thaw slump Machine learning Susceptibility map Permafrost Northern Hemisphere

Environmental factors co.trolling soil warming and wetting during 2000-2020 in permafrost and non-permafrost regions across the Qinghai-Tibet Plateau

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Advances in Climate Change Research 2024年第2期15卷 285-296页

作者： Guo-An YIN Jing LUO Fu-Jun NIU Ming-Hao LIU Ze-Yong GAO Tian-Chun DONG Wei-Heng NI State Key Laboratory of Frozen Soil Engineering Northwest Institute of Eco-Environment and ResourcesChinese Academy of SciencesLanzhou 730000China china railway Qinghai-Tibet Group co. Ltd.Xining 810000China University of Chinese academy of sciences Beijing 100049China

The Qinghai-Tibet Plateau(QTP)has experienced rapid environmental changes,including climate warming and wetting,since the 1980s.These environmental changes significantly impact the shallow soil hydrothermal co.ditions,which have key roles in land-atmosphere feedback and eco.ystem functions.However,the spatial variations and responses of soil hydrothermal co.ditions to environmental changes over the QTP with permafrost(PF)and seasonal frost(SF)remain unclear.In this study,we investigated the spatial variations in soil temperature(ST)and soil moisture(SM)changes over the QTP from 2000 to 2020 using 99 in-situ sites with observations at 4 depths(i.e.10,40,100 and 200 cm).The main environmental co.trolling factors were further identified using a calibrated statistical model.Results showed that significant(pco.tributed most to soil warming in the PF region,whereas changes in rainfall,Srad and evaporation(EVA)have been identified as the key factors in the SF region.As for soil wetting,changes in snowfall,freezing degree days and vegetation have noticeable nonlinear effects over the PF region,whereas changes in EVA,Srad and rainfall highlighted distinct linear and nonlinear effects in the SF region.These findings enhance our understanding of the hydrothermal impacts of future environmental changes over the QTP.

关键词： Warming amd wetting Soil hydrothermal change Factor Permafrost Seasonal frost

Efficient and fair PPO-based integrated scheduling method for multiple tasks of SATech-01 satellite

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Chinese Journal of Aeronautics 2024年第2期37卷 417-430页

作者： Qi SHI Lu LI Ziruo FANG Xingzi BI Huaqiu LIU Xiaofeng ZHANG Wen CHEN Jinpei YU Shanghai Satellite Network Research Institute co. LTDShanghai 201210China Innovation academy for Microsatellites of Chinese academy of sciences Shanghai 201306China University of Chinese academy of sciences Beijing 100039China

SATech-01 is an experimental satellite for space science exploration and on-orbit demonstration of advanced technologies.The satellite is equipped with 16 experimental payloads and supports multiple working modes to meet the observation requirements of various payloads.Due to the limitation of platform power supply and data storage systems,proposing reasonable mission planning schemes to improve scientific revenue of the payloads beco.es a critical issue.In this article,we formulate the integrated task scheduling of SATech-01 as a multi-objective optimization problem and propose a novel Fair Integrated Scheduling with Proximal Policy Optimization(FIS-PPO)algorithm to solve it.We use multiple decision heads to generate decisions for each task and design the action mask to ensure the schedule meeting the platform co.straints.Experimental results show that FIS-PPO co.ld push the capability of the platform to the limit and improve the overall observation efficiency by 31.5%co.pared to rule-based plans currently used.Moreover,fairness is co.sidered in the reward design and our method achieves much better performance in terms of equal task opportunities.Because of its low co.putational co.plexity,our task scheduling algorithm has the potential to be directly deployed on board for real-time task scheduling in future space projects.

关键词： Satellite observatories SATech-01 Multi-modes platform Scheduling algorithms Reinforcement learning Proximal Policy Optimization(PPO)

Mechanical behaviors of warm and ice-rich frozen soil stabilized with sulphoaluminate cement

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Journal of Mountain Science 2024年第1期21卷 335-345页

作者： WANG Honglei ZHANG Hu ZHANG Jianming ZHANG Qi YIN Zhenhua State Key Laboratory of Frozen Soil Engineering Northwest Institute of Eco-Environment and ResourcesChinese Academy of SciencesLanzhou 730000China University of Chinese academy of sciences Beijing 100049China School of Civil Engineering and Transportation Northeast Forestry UniversityHarbin 150040China National Key Laboratory of Green and Long-Life Road Engineering in Extreme Environment CCCC First Highway Consultants Co.LtdXi'an 710065China railway Engineering Research Institute China Academy of Railway Sciences Corporation LimitedBeijing 100081China

The warm and ice-rich frozen soil is characterized by high unfrozen water co.tent, low shear strength and large co.pressibility, which is unreliable to meet the stability requirements of engineering infrastructures and foundations in permafrost regions. In this study, a novel approach for stabilizing the warm and ice-rich frozen soil with sulphoaluminate cement was proposed based on chemical stabilization. The mechanical behaviors of the stabilized soil, such as strength and stress-strain relationship, were investigated through a series of triaxial co.pression tests co.ducted at -1.0℃, and the mechanism of strength variations of the stabilized soil was also explained based on scanning electron microsco.e test. The investigations indicated that the strength of stabilized soil to resist failure has been improved, and the linear Mohr-co.lomb criteria can accurately reflect the shear strength of stabilized soil under various applied co.fining pressure. The increase in both curing age and cement mixing ratio were favorable to the growth of co.esion and internal friction angle. More importantly, the strength improvement mechanism of the stabilized soil is attributed to the formation of structural skeleton and the generation of cementitious hydration products within itself. Therefore, the investigations co.ducted in this study provide valuable references for chemical stabilization of warm and ice-rich frozen ground, thereby providing a basis for in-situ ground improvement for reinforcing warm and ice-rich permafrost foundations by soil-cement co.umn installation.

关键词： Permafrost regions Frozen soil Mechanical behavior Chemical stabilization Ground improvement Ground modification

STGNN-LMR:A Spatial–Temporal Graph Neural Network Approach Based on sEMG Lower Limb Motion Reco.nition

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Journal of Bionic Engineering 2024年第1期21卷 256-269页

作者： Weifan Mao Bin Ma Zhao Li Jianxing Zhang Yizhou Lu Zhuting Yu Feng Zhang Shanghai Advanced Research Institute Chinese Academy of SciencesShanghai 201210China University of Chinese academy of sciences Beijing 101408China University of Science and Technology of china Hefei 230026China Shanghai Zhongyan Jiuyi Technology co. Ltd.Shanghai 201821China academy of Military Science Bejing 100091China

Lower limb motion reco.nition techniques co.monly employ Surface Electromyographic Signal(sEMG)as input and apply a machine learning classifier or Back Propagation Neural Network(BPNN)for classification.However,this artificial feature engineering technique is not generalizable to similar tasks and is heavily reliant on the researcher’s subject expertise.In co.trast,neural networks such as co.volutional Neural Network(CNN)and Long Short-term Memory Neural Network(LSTM)can automatically extract features,providing a more generalized and adaptable approach to lower limb motion reco.nition.Although this approach overco.es the limitations of human feature engineering,it may ignore the potential co.relation among the sEMG channels.This paper proposes a spatial–temporal graph neural network model,STGNN-LMR,designed to address the problem of reco.nizing lower limb motion from multi-channel sEMG.STGNN-LMR transforms multi-channel sEMG into a graph structure and uses graph learning to model spatial–temporal features.An 8-channel sEMG dataset is co.structed for the experimental stage,and the results show that the STGNN-LMR model achieves a reco.nition accuracy of 99.71%.Moreover,this paper simulates two unexpected scenarios,including sEMG sensors affected by sweat noise and sudden failure,and evaluates the testing results using hypothesis testing.Acco.ding to the experimental results,the STGNN-LMR model exhibits a significant advantage over the co.trol models in noise scenarios and failure scenarios.These experimental results co.firm the effectiveness of the STGNN-LMR model for addressing the challenges associated with sEMG-based lower limb motion reco.nition in practical scenarios.

关键词： Lower limb motion reco.nition Exoskeleton sEMG.Graph neural network Noise Sensor failure

FPGA and co.puter-vision-based atom tracking technology for scanning probe microsco.y

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Chinese Physics B 2024年第5期33卷 76-85页

作者：俞风度刘利王肃珂张新彪雷乐黄远志马瑞松郇庆 Beijing National Laboratory for co.densed Matter Physics Institute of PhysicsChinese Academy of SciencesBeijing 100190China University of Chinese academy of sciences Beijing 100049China ACME (Beijing) Technology co. Ltd.Beijing 101407China Key Laboratory for Vacuum Physics University of Chinese Academy of SciencesBeijing 100190China

Atom tracking technology enhanced with innovative algorithms has been implemented in this study,utilizing a co.prehensive suite of co.trollers and software independently developed domestically.Leveraging an on-board field-programmable gate array(FPGA)with a co.e frequency of 100 MHz,our system facilitates reading and writing operations across 16 channels,performing discrete incremental proportional-integral-derivative(PID)calculations within 3.4 microseco.ds.Building upon this foundation,gradient and extremum algorithms are further integrated,inco.porating circular and spiral scanning modes with a horizontal movement accuracy of 0.38 pm.This integration enhances the real-time performance and significantly increases the accuracy of atom tracking.Atom tracking achieves an equivalent precision of at least 142 pm on a highly oriented pyrolytic graphite(HOPG)surface under room temperature atmospheric co.ditions.Through applying co.puter vision and image processing algorithms,atom tracking can be used when scanning a large area.The techniques primarily co.sist of two algorithms:the region of interest(ROI)-based feature matching algorithm,which achieves 97.92%accuracy,and the feature description-based matching algorithm,with an impressive 99.99%accuracy.Both implementation approaches have been tested for scanner drift measurements,and these technologies are scalable and applicable in various domains of scanning probe microsco.y with broad application prospects in the field of nanoengineering.

关键词： atom tracking FPGA co.puter vision drift measurement

Application of Gaussian Beam Summation Migration in Reflected In-seam Wave Imaging

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Acta Geologica Sinica(English Edition) 2024年第1期98卷 276-284页

作者： HAN Jianguang LÜQingtian ZHANG Zhiheng YANG Shun WANG Shuo Chinese academy of Geological sciences Beijing 100037China Shandong Taishan Resources Exploration co. Ltd.Jinan 250104China

The geological co.ditions for co.l mining in china are co.plex,with various structural issues such as faults and co.lapsed co.umns seriously co.promising the safety of co.l mine production.In-seam wave exploration is an effective technique for acquiring detailed information on geological structures in co.l seam working faces.However,the existing reflected in-seam wave imaging technique can no longer meet the exploration precision requirements,making it imperative to develop a new reflected in-seam wave imaging technique.This study applies the Gaussian beam summation(GBS)migration method to imaging co.l seams'reflected in-seam wave data.Firstly,with regard to the characteristics of the reflected in-seam wave data,methods such as wavefield removal and enveloped superposition are employed for the co.responding wavefield separation,wave train co.pression and other processing of reflected in-seam waves.Thereafter,imaging is performed using the GBS migration technique.The feasibility and effectiveness of the proposed method for reflected in-seam wave imaging are validated by co.ducting GBS migration tests on 3D co.l-seam fault models with different dip angles and throws.By applying the method to reflected in-seam wave data for an actual co.l seam working face,accurate imaging of a fault structure is obtained,thereby validating its practicality.

关键词： reflected in-seam wave Gaussian beam summation migration numerical tests fault

An efficient CuZr-based metallic glasses electrode material for electrocatalytic degradation of azo dyes

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Journal of Environmental sciences 2024年第2期136卷 537-546页

作者： Zhiwang Deng Bowen Zhao Songtao Li Zhengkun Li Shiming Zhang Kewei Zhang Zhengwang Zhu Taiyuan University of Science and Technology School of materials science and engineeringTaiyuan 030024China Shi-changxu Innovation Center for Advanced Materials Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China Chinese academy of sciences Key Laboratory of Nuclear Materials and Safety Assessment Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China Qingdao Yunlu Advanced Materials Technology co. Ltd.Qingdao 266232China

Metallic glasses have received a lot of attention on wastewater treatment due to their unique atomic structure,and the use of metallic glasses as electrodes has produced unexpected electrocatalytic degradation effects for many pollutants through co.bining with electrochemical technology.However,it still is a formidable challenge to find a metallic glass electrode material with both efficient and clean for the catalytic degradation of pollutants.In this work,the Cu_(55)Zr_(45)metallic glassy ribbons are used as an electrode to degrade azo dyes and show the excellent degradation effect,which can reach 95.6%within 40 min.In the degradation process,almost no additives are produced and Cu_(55)Zr_(45)metallic glassy ribbons have excellent effects under different pH co.ditions.Meanwhile,it exhibits good stability for degradation efficiency during the 8 cycle degradation tests of the amorphous alloy electrode.When the co.per nanoparticles are exposed on the surface of the ribbons,the oxidized co.per obtained synergistically produce activated radicals is the primary degradation mechanism,where the auxiliary degradation mechanisms include electron transfer and the promotion of active chlorine.This research develops a new type of electrode material for wastewater treatment,and the eco.omy and high efficiency of Cu55Zr45metallic glass endow it the expandable functional applications.

关键词： Metallic glasses Azo dyes Electrocatalytic Degradation Oxidized co.per

Dynamic Scene Graph Generation of Point Clouds with Structural Representation Learning

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Tsinghua Science and Technology 2024年第1期29卷 232-243页

作者： Chao Qi Jianqin Yin Zhicheng Zhang Jin Tang School of Artificial Intelligence Beijing University of Posts and TelecommunicationsBeijing 100876China Standard and Metrology Research Institute China Academy of Railway Sciences Corporation LimitedBeijing 100081China

Scene graphs of point clouds help to understand object-level relationships in the 3D space.Most graph generation methods work on 2D structured data,which cannot be used for the 3D unstructured point cloud data.Existing point-cloud-based methods generate the scene graph with an additional graph structure that needs labor-intensive manual annotation.To address these problems,we explore a method to co.vert the point clouds into structured data and generate graphs without given structures.Specifically,we cluster points with similar augmented features into groups and establish their relationships,resulting in an initial structural representation of the point cloud.Besides,we propose a Dynamic Graph Generation Network(DGGN)to judge the semantic labels of targets of different granularity.It dynamically splits and merges point groups,resulting in a scene graph with high precision.Experiments show that our methods outperform other baseline methods.They output reliable graphs describing the object-level relationships without additional manual labeled data.

关键词： scene graph generation structural representation point cloud