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AstroPose: Astronaut pose estimation using a monocular camera during extravehicular activities

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Science China Technological Sciences 2024年第6期67卷 1933-1945页

作者： LIU ZiBin LI You WANG ChunHui LIU Liang GUAN BangLei SHANG Yang YU QiFeng college of aerospace Science and engineering National University of Defense Technology Key Laboratory of Human Factors engineering China Astronaut Research and Training Center

With the completion of the Chinese space station, an increasing number of extravehicular activities will be executed by astronauts,which is regarded as one of the most dangerous activities in human space exploration. To guarantee the safety of astronauts and the successful accomplishment of missions, it is vital to determine the pose of astronauts during extravehicular activities. This article presents a monocular vision-based pose estimation method of astronauts during extravehicular activities, making full use of the available observation resources. First, the camera is calibrated using objects of known structures, such as the spacesuit backpack or the circular handrail outside the space station. Subsequently, the pose estimation is performed utilizing the feature points on the spacesuit. The proposed methods are validated both on synthetic and semi-physical simulation experiments, demonstrating the high precision of the camera calibration and pose estimation. To further evaluate the performance of the methods in real-world scenarios, we utilize image sequences of Shenzhou-13 astronauts during extravehicular activities. The experiments validate that camera calibration and pose estimation can be accomplished solely with the existing observation resources, without requiring additional complicated equipment. The motion parameters of astronauts lay the technological foundation for subsequent applications such as mechanical analysis, task planning, and ground training of astronauts.

关键词： monocular camera astronaut pose estimation camera calibration

Bimagnetic metal constructed core-shell structure of Fe@Co nanowires for multi-band microwave absorption

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Progress in Natural Science:materials International 2024年第2期34卷 354-361页

作者： Ping-an Yang Rui Cai Haibo Ruan Nanqing Zhang Xin Huang Rui Li Yuxin Zhang Yi Lu Zhihao Zhou School of Automation Chongqing University of Posts and Telecommunications Chongqing Key Laboratory of materials Surface & Interface Science Chongqing University of Arts and Sciences college of engineering and Technology Zunyi Normal College college of material Science and engineering Chongqing University

Controlled fabrication of materials by surface modification techniques has been a hot research topic. In this paper,one-dimensional(1D) core-shell structure Fe@Co nanowires(NWs) were successfully prepared by anchoring 0-dimensional(0D) Co nanoparticles on 1D Fe NWs based on the in situ reduction method. The electromagnetic parameters of the specimens at a filler mass fraction of 25 wt% were tested and the microwave loss mechanism was deeply analyzed. Binary magnetic metals in a core-shell structure have excellent multi-band microwave absorption capability(S-band, X-band and Ku-band). This is due to the heterogeneous interface and magnetic coupling effects tuning the dielectric and magnetic loss. This study offers a workable plan for creating effective multi-band magnetic metal-based microwave absorbers.

关键词： Core-shell structure Interface Magnetic coupling Microwave absorption One-dimensional nanowires

A unified intelligent control strategy synthesizing multi-constrained guidance and avoidance penetration

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Science China(Information Sciences) 2024年第7期67卷 329-330页

作者： Sibo ZHAO Jianwen ZHU Weimin BAO Xiaoping LI School of aerospace Science and Technology Xidian University college of Missile engineering Rocket Force University of Engineering China aerospace Science and Technology Corporation

Satisfying various terminal constraints and achieving evasive flight in no-flying-zones (NFZs) are two important flight missions undertaken by high velocity vehicles. We studied an intelligent maneuvering guidance strategy using deep reinforcement learning (DRL) methods to achieve the coordination and unification of evasive flight and multi-constrained guidance with minimal energy loss.

关键词： Energy dissipation

Effect of kerosene injection states on mixing and combustion characteristics in a cavity-based supersonic combustor

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Chinese Journal of Aeronautics 2024年第4期37卷 308-320页

作者： Xu LIU Peibo LI Fei LI Hongbo WANG Mingbo SUN Chao WANG Yixin YANG Dapeng XIONG Yanan WANG Science and Technology on Scramjet Laboratory College of Aerospace Science and EngineeringNational University of Defense TechnologyChangsha 410073China

It has been found that the static pressure distribution along the axial direction of liquid kerosene is lower than that of the gaseous kerosene under the same flow condition and overall equivalent ratio from previous studies.To further investigate this phenomenon,a compressible two-phase parallel simulation method is utilized to analyze the mixing and combustion characteristics of gaseous and liquid kerosene jets in a cavity-based supersonic combustor.The numerical results are consistent with the experiments and demonstrate that gaseous injection leads to a cavity shear layer that dives deeper into the cavity,forming two recirculation zones in the front and rear of the cavity.In contrast,the cavity shear layer is closer to the mainstream during liquid injection,and only a large recirculation zone is formed in the rear of the cavity.As a result of the cavity shear layer and the recirculating flow,the fuel vapor of gaseous injection accumulates in the front of the cavity,while for the liquid injection,the fuel vapor disperses in the cavity,cavity shear layer,and the region above,and the rear of the cavity has a higher fuel vapor concentration than the front.This unique fuel distribution causes the combustion area to be concentrated in the cavity during the gaseous injection but dispersed inside and downstream of the cavity during the liquid injection.As a result,forming a thermal throat under the same conditions is more challenging during liquid injection,and the generated static pressure distribution is lower than that during the gaseous injection.

关键词： Gaseous injection Liquid injection Mixing process Combustion Supersonic flow

Improvement of the conversion efficiency of Mg_(3)Sb_(2)thermoelectric devices through optimizing the resistivity of the MgSbNi barrier layer

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Journal of materials Science & Technology 2024年第1期168卷 208-214页

作者： Huimin Zhang Yachao Wang Zuhair A.Munir Yongzhong Zhang Wenhao Fan Shaoping Chen college of materials Science and engineering Taiyuan University of TechnologyTaiyuan030024China Capital aerospace Machinery Company Beijing100076China Department of material Science and engineering University of CaliforniaDavisCalifornia95616United States of America college of Physics and Optoelectronics Taiyuan University of TechnologyTaiyuan030024China Instrumental Analysis Center of Taiyuan University of Technology Taiyuan030024China

Mg_(3)Sb_(2)-based thermoelectric materials have been the focus of widespread investigations as promising candidates for the harvesting of waste heat.Interface stability and service performance are key points for the commercial applications of these materials.We utilized Mg_(4.3)Sb_(3)Ni as a barrier layer to improve the thermal stability of Mg 3 Sb 2-based devices.However,its intrinsic high resistivity contributed nega-tively to the desired performance of the device.In this work,we investigated two other Mg-Sb-Ni ternary phases,MgSbNi and MgSbNi_(2),as new barrier layer materials to connect with Mg_(3.2)Sb_(2)Y_(0.05).The results show that the efficiency of the Mg_(1.2)SbNi/Mg_(3.2)Sb_(2)Y_(0.05)/Mg_(1.2)SbNi joint is increased by 33%relative to the higher Mg-content barriers due to lower resistivity.The system exhibited good interfacial compatibility and showed little change with aging at 673 K for 20 days.

关键词： Mg_(3)Sb_(2) Mg_(1.2)SbNi Barrier layer Conversion efficiency

Transient flameout process of boron-magnesium agglomerates during combustion in oxygen-rich atmospheres

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Particuology 2024年第5期88卷 290-301页

作者： Lian Duan Zhixun Xia Yunchao Feng Binbin Chen Likun Ma Jianxin Hu college of aerospace Science and engineering National University of Defense TechnologyChangsha 410073China School of Mechanical engineering and Mechanics Xiangtan UniversityXiangtan 411105China

In this study,boron–magnesium agglomerates with varying mass ratios were prepared by drying a micron-sized boron–magnesium mixed suspension,and the combustion process of these agglomerates under different oxygen-rich concentrations were investigated using a laser ignition system.The test results showed that when the mass fraction of magnesium powder in boron-magnesium agglomerates exceeded a certain threshold(between 2%and 5%),flame extinction and reignition occurred after a significant reduction in the agglomerate volume during combustion.This process is referred to as the transient flameout process,which is affected by the magnesium content of the agglomerate and the oxygen concentration in the ambient atmosphere.An increase in the magnesium content or oxygen concentration makes this phenomenon more pronounced.During weakening of the flame intensity,a dark film gradually covered the particle surfaces.X-ray diffraction and elemental analyses of the cross-section and outer surface of the condensed combustion product suggested that the dark film is primarily composed of Mg-B-O ternary oxides.This film prevents direct contact between boron and oxygen,thereby inhibiting surface and gas-phase reactions and leading to the occurrence of the transient flameout phenomenon.

关键词： Agglomerated particle Boron–magnesium fuel Boron combustion Transient flameout process Solid fuel ramjet

Critical layer in liquid-solid system influencing the remediation of chromium using zeolite-supported sulfide nano zero-valent iron

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Journal of Environmental Sciences 2024年第1期135卷 232-241页

作者： Chundi Zhou Caiyun Han Nengsheng Liu Faculty of material and Environment Guangxi University for NationalitiesNanning 530008China college of Environmental Science and engineering Tongji UniversityShanghai 200092China Faculty of Metallurgical and Energy engineering Kunming University of Science and TechnologyKunming 650093China

Sulfidated nano zero-valent iron particles were immobilized on ZSM-5 zeolite(Z/S-nZⅥ)and used for hexavalent chromium(Cr(Ⅵ))remediation.The performance of Z/S-nZⅥimproved with the increase in Cr(Ⅵ)concentration(0.6).Moreover,the removal mechanisms of Cr(Ⅵ)were elucidated through XRD,transmission electron microscopy(TEM)and XPS techniques.This results demonstrate that the species of chromium in the critical layer changed from Cr(Ⅲ)to Cr(Ⅵ)as the concentration of chromium increased from low to high.Furthermore,the critical layer was composed of Cr(Ⅵ),Fe(Ⅱ),O and H elements.Additionally,the experiments of coexisting ions and aging time confirmed that Z/S-nZⅥpossessed high selectivity and stability to ensure efficiency and cost-effectiveness in practical applications.

关键词： Cr(VI) Corrosion Critical layer Selectivity Stability

Kinetic-boosted CO_(2) electroreduction to formate via synergistic electric-thermal field on hierarchical bismuth with amorphous layer

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Journal of Energy Chemistry 2024年第3期90卷 233-243,I0007页

作者： Bing Yang Junyi Zeng Zhenlin Zhang Lin Meng Donglin Shi Liang Chen Youju Huang college of material Chemistry and Chemical EngineeringKey Laboratory of Organosilicon Chemistry and Material TechnologyMinistry of EducationHangzhou Normal UniversityHangzhou 311121ZhejiangChina State Key Laboratory of Metastable materials Science and Technology College of Materials Science and EngineeringYanshan UniversityQinhuangdao 066004HebeiChina

Electrocatalytic converting CO_(2) into chemical products has emerged as a promising approach to achieving carbon neutrality.Herein,we report a bismuth-based catalyst with high curvature terminal and amorphous layer which fabricated via two-step electrodeposition achieves stable formate output in a wide voltage window of 600 mV.The Faraday efficiency(FE) of formate reached up to 99.4% at-0.8 V vs.RHE and it remained constant for more than 92 h at-15 mA cm^(-2).More intriguingly,FE formate of95.4% can be realized at a current density of industrial grade(-667.7 mA cm^(-2)) in flow cell.The special structure promoted CO_(2) adsorption and reduced its activation energy and enhanced the electric-thermal field and K^(+) enrichment which accelerated the reaction kinetics.In situ spectroscopy and theoretical calculation further confirmed that the introduction of amorphous structure is beneficial to adsorpting CO_(2)and stabling*OCHO intermediate.This work provides special insights to fabricate efficient electrocatalysts by means of structural and crystal engineering and makes efforts to realize the industrialization of bismuth-based catalysts.

关键词： CO_(2) electroreduction Hierarchical bismuth Amorphous layer Electric-thermal field Kinetic-boosting

Robust multi-sensor image matching based on normalized self-similarity region descriptor

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Chinese Journal of Aeronautics 2024年第1期37卷 271-286页

作者： Xuecong LIU Xichao TENG Jing LUO Zhang LI Qifeng YU Yijie BIAN college of aerospace Science and engineering National University of Defense TechnologyChangsha 410073China High-Tech Institute Qingzhou 262500China

Multi-modal image matching is crucial in aerospace applications because it can fully exploit the complementary and valuable information contained in the amount and diversity of remote sensing images.However,it remains a challenging task due to significant non-linear radiometric,geometric differences,and noise across different sensors.To improve the performance of heterologous image matching,this paper proposes a normalized self-similarity region descriptor to extract consistent structural information.We first construct the pointwise self-similarity region descriptor based on the Euclidean distance between adjacent image blocks to reflect the structural properties of multi-modal images.Then,a linear normalization approach is used to form Modality Independent Region Descriptor(MIRD),which can effectively distinguish structural features such as points,lines,corners,and flat between multi-modal images.To further improve the matching accuracy,the included angle cosine similarity metric is adopted to exploit the directional vector information of multi-dimensional feature descriptors.The experimental results show that the proposed MIRD has better matching accuracy and robustness for various multi-modal image matching than the state-of-the-art methods.MIRD can effectively extract consistent geometric structure features and suppress the influence of SAR speckle noise using non-local neighboring image blocks operation,effectively applied to various multi-modal image matching.

关键词： Remote sensing Multi-modal image matching Template matching Feature descriptor Similarity metric Synthetic Aperture Radar(SAR)