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Staring-imaging satellite pointing estimation based on sequential ISAR images

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Chinese Journal of Aeronautics 2024年第8期37卷 261-276页

作者： Canyu WAnG Libing JIAnG Weijun ZHOnG Xiaoyuan ren Zhuang WAnG national Key Laboratory of Automatic Target Recognition National University of Defense TechnologyChangsha 410073China Xi’an Satellite Control Center Xi’an 710600China

Pointing estimation for spacecraft using Inverse Synthetic Aperture Radar(ISAR)images plays a significant role in space situational awareness and ***,feature extraction and cross-range scaling of ISAR images create bottlenecks that limit performances of current estimation ***,the emergence of staring imaging satellites,characterized by complex kinematic behaviors,presents a novel challenge to this *** address these issues,this article proposes a pointing estimation method based on Convolutional neural networks(Cnns)and a numerical optimization algorithm.A satellite’s main axis,which is extracted from ISAR images by a proposed Semantic Axis Region Regression net(SARRn),is chosen for investigation in this article due to its unique ***,considering the kinematic characteristic of the staring satellite,an ISAR imaging model is established to bridge the target pointing and the extracted *** on the imaging model,pointing estimation and cross-range scaling can be described as a maximum likelihood estimation problem,and an iterative optimization algorithm modified by using the strategy of random sampling-consistency check and weighted least squares is proposed to solve this ***,the pointing of targets and the cross-range scaling factors of ISAR images are *** experiments based on actual satellite orbital parameters verify the effectiveness of the proposed *** work can improve the performance of satellite reconnaissance warning,while accurate cross-range scaling can provide a basis for subsequent data processes such as 3D reconstruction and attitude estimation.

关键词： Staring-imaging Agile satellite Inverse Synthetic Aperture Radar(ISAR) Pointing estimation Cross-range scaling

Integral precession calibration method of PIGA on linear vibration table

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Chinese Journal of Aeronautics 2024年第3期37卷 219-236页

作者： Chuang SUn Shun-qing ren Jun-wei CAO Ru HUO Department of Automation Tsinghua UniversityBeijing 100084China School of Astronautics Harbin Institute of TechnologyHarbin 150001China Beijing national Research Center for Information Science and Technology Tsinghua UniversityBeijing 100084China Faculty of Information technology Beijing University of TechnologyBeijing 100124China

Linear vibration table can provide harmonic accelerations to excite the nonlinear error terms of Pendulous Integrating Gyro Accelerometer(PIGA).Integral precession calibration method is proposed to calibrate PIGA on a linear vibration table in this *** on the precise expressions of PIGA’s inputs,the error calibration model of PIGA is *** angular velocity errors of PIGA are suppressed by integer periodic precession and the errors caused by non-integer periods vibrating are *** complete calibration process,including planning,preparation,PIGA testing,and coefficient identification,is designed to optimize the test operations and evaluate the calibration *** effect of the main errors on calibration uncertainty is analyzed and the relative sensitivity function is proposed to further optimize the test *** and simulation results verify that the proposed 10-position calibration method can improve calibration uncertainties after compensating for the related *** order of calibration uncertainties of the second-and third-order coefficients are decreased to 10^(-8)(rad.s^(-1))/g^(2)and 10^(-8)(rad.s^(-1))/g3,*** with the other two classical calibration methods,the calibration uncertainties of PIGA’s nonlinear error coefficients can be effectively reduced and the proportional residual errors are decreased less than 3×10-6(rad.s^(-1))/g by using the proposed calibration method.

关键词： PIGA Linear vibration table Vibration measurement Calibration Error analysis Uncertainty analysis

Graphene enables equiatomic FeniCrCoCu high-entropy alloy with improved TWIP and TRIP effects under shock compression

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Journal of Materials Science & Technology 2024年第3期170卷 186-199页

作者： Hongcai Xie Zhichao Ma Wei Zhang Hongwei Zhao Luquan ren School of Mechanical and Aerospace Engineering Jilin UniversityChangchun 130025China Key Laboratory of CnC Equipment Reliability Ministry of Education Jilin UniversityChangchun 130025China Key Laboratory of Bionic Engineering Ministry of Education Jilin UniversityChangchun 130025China Weihai Institute for Bionics-Jilin University Weihai 264400China Institute of Structured and Architected Materials Liaoning Academy of MaterialsShenyang 110167China

Graphene(Gr)reinforced high-entropy alloy(HEA)matrix composites are expected as potential candidates for next-generation structural applications in light of outstanding mechanical properties.A deep comprehension of the underlying deformation mechanisms under extreme shock loading is of paramount importance,however,remains lacking due to experimentally technical limitations in *** the present study,by means of nonequilibrium molecular dynamics simulations,dynamic deformation behaviors and corresponding mechanisms in equiatomic FeniCrCoCu HEA/Gr composite systems were investigated in terms of various shock *** resistance to dislocation propagation imparted by Gr was corroborated to encourage the elevated local stress level by increasing the likelihood of dislocation interplays,which facilitated the onset of twins and hexagonal close-packed(HCP)martensite ***,the advent of Gr was demonstrated to endow the HEA with an additional twinning pathway that induced a structural conversion from HCP to parent face-centered cubic(FCC)inside HCP martensite laths,different from the classical one that necessitated undergoing the intermediate procedure of extrinsic stacking fault(ESF)*** than that,by virtue of an increase in flow stress,the transformation-induced plasticity(TRIP)effect was validated to be additionally evoked as the predominant strain accommodation mechanism at higher strains on the one hand,but which only assisted plasticity in pure systems,and on the other hand,can also act as an auxiliary regulation mode together with the twinning-induced plasticity(TWIP)effect under intermediate strains,but with enhanced contributions relative to pure *** may expect that TRIP and TWIP effects promoted by introducing Gr would considerably inspire a synergistic effect between strength and ductility,contributing to the exceptional shock-resistant performance of FeniCrCoCu HEAs under extreme regimes.

关键词： Molecular dynamics High-entropy alloy Graphene TRIP TWIP Shock

Rapid Energy Exchange between In Situ Formed Bromine Vacancies and CO_(2)Molecules Enhances CO_(2)Photoreduction

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Research 2024年第2期2023卷 763-771页

作者： Qin ren Ye He Hong Wang Yanjuan Sun Fan Dong Research Center for Environmental and Energy Catalysis Institute of Fundamental and Frontier SciencesUniversity of Electronic Science and Technology of ChinaChengdu 611731China School of Resources and Environment University of Electronic Science and Technology of ChinaChengdu 611731China

Photocatalytic reduction of CO_(2)into fuels provides a prospective tactic for regulating the global carbon balance utilizing renewable solar ***,CO_(2)molecules are difficult to activate and reduce due to the thermodynamic stability and chemical *** this work,we develop a novel strategy to promote the adsorption and activation of CO_(2)molecules via the rapid energy exchange between the photoinduced Br vacancies and CO_(2)*** in situ continuous wave-electron paramagnetic resonance(cw-EPR)and pulsed EPR technologies,we observe that the spin-spin relaxation time(T_(2))of BiOBr is decreased by 198 ns during the CO_(2)photoreduction reaction,which is further confirmed by the broadened EPR *** result reveals that there is an energy exchange interaction between in situ formed Br vacancies and CO_(2)molecules,which promotes the formation of high-energy CO_(2)molecules to facilitate the subsequent reduction *** addition,theoretical calculations indicate that the bended CO_(2)adsorption configuration on the surface of BiOBr with Br vacancies caused the decrease of the lowest unoccupied molecular orbital of the CO_(2)molecule,which makes it easier for CO_(2)molecules to acquire electrons and get *** situ diffuse reflectance infrared Fourier transform spectroscopy further shows that the activated CO_(2)molecules are favorably converted to key intermediates of COOH*,resulting in a CO generation rate of 9.1μmol g^(-1)h^(-1)and a selectivity of 100%.This study elucidates the underlying mechanism of CO_(2)activation at active sites and deepens the understanding of CO_(2)photoreduction reaction.

关键词： reaction. adsorption activation

Resource utilization of drinking water treatment aluminum sludge in green cementing materials: Hydration characteristics and hydration kinetics

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Journal of Environmental Sciences 2024年第10期144卷 236-248页

作者： Jing Yang Cheng Chen Shuoyu Chen Yujie ren Jinsuo Lu School of Environmental and Municipal Engineering Xi’an University of Architecture and TechnologyXi’an 710055China

As a byproduct of water treatment,drinking water treatment aluminum sludge(DWTAS)has challenges related to imperfect treatment and disposal,which has caused potential harm to human health and the *** this paper,heat treatment DWTAS as a supplement cementitious material was used to prepare a green cementing *** results show that the 800℃ is considered as the optimum heat treatment temperature for ***-800℃ is fully activated after thermal decomposition to form incompletely crystallized highly activeγ-Al2O3 and active SiO_(2).The addition of DWTAS promoted the formation of ettringite and C-(A)-S-H gel,which could make up for the low early compressive strength of cementing materials to a certain *** cured for 90 days,the compressive strength of the mortar with 30% DWTAS-800℃ reached 44.86 *** dynamic process was well simulated by Krstulovi′c-Dabi′c hydration kinetics *** study provided a methodology for the fabrication of environmentally friendly and cost-effective compound cementitiousmaterials and proposed a“waste-to-resource”strategy for the sustainable management of typical solid wastes.

关键词： Drinking water treatment aluminum sludge Green cementing material Hydration characteristics Hydration kinetics

Visible Light Indoor Positioning System Based on Pisarenko Harmonic Decomposition and neural network

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Chinese Journal of Electronics 2024年第1期33卷 195-203页

作者： Li ZHAO Yi ren Qi WAnG Lange DEnG Feng ZHAnG School of Electronic Information Engineering Xi’an Technological University

Visible-light indoor positioning is a new generation of positioning technology that can be integrated into smart lighting and optical communications. The current received signal strength(RSS)-based visible-light positioning systems struggle to overcome the interferences of background and indoor-reflected noise. Meanwhile, when ensuring the lighting, it is impossible to use the superposition of each light source to accurately distinguish light source information; furthermore, it is difficult to achieve accurate positioning in complex indoor environments. This study proposes an indoor positioning method based on a combination of power spectral density detection and a neural network. The system integrates the mechanism for visible-light radiation detection with RSS theory, to build a back propagation neural network model fitting for multiple reflection channels. Different frequency signals are loaded to different light sources at the beacon end, and the characteristic frequency and power vectors are obtained at the location end using the Pisarenko harmonic decomposition method. Then, a complete fingerprint database is established to train the neural network model and conduct location tests. Finally, the location effectiveness of the proposed algorithm is verified via actual positioning experiments. The simulation results show that, when four groups of sinusoidal waves with different frequencies are superimposed with white noise, the maximum frequency error is 0.104 Hz and the maximum power error is 0.0362 W. For the measured positioning stage, a 0.8 m × 0.8 m × 0.8 m solid wood stereoscopic positioning model is constructed, and the average error is 4.28 cm. This study provides an effective method for separating multi-source signal energies, overcoming background noise, and improving indoor visible-light positioning accuracies.

关键词： neural networks Measurement uncertainty Position measurement Harmonic analysis Light emitting diodes Frequency estimation Indoor positioning systems

Can soil organic carbon sequestration and the carbon management index be improved by changing the film mulching methods in the semiarid region?

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Journal of Integrative Agriculture 2024年第5期23卷 1541-1556页

作者： Jialin Yang Liangqi ren nanhai Zhang Enke Liu Shikun Sun Xiaolong ren Zhikuan Jia Ting Wei Peng Zhang College of Agronomy Northwest A&F UniversityYangling 712100China Key Laboratory of Crop Physi-Ecology and Tillage Science in northwestern Loess Plateau Ministry of Agriculture and Rural AfairsNorthwest A&FUniversityYangling 712100China Institute of Environment and Sustainable Development in Agriculture Chinese Academy of Agricultural SciencesBeijing 100081China College of Water Resources and Architectural Engineering Northwest A&F UniversityYangling 712100China

Plastic film mulching has been widely used to increase maize yield in the semiarid area of ***, whether long-term plastic film mulching is conducive to agricultural sustainability in this region remains controversial.A field experiment was initiated in 2013 with five different film mulching methods:(i) control method, flat planting without mulching (CK),(ii) flat planting with half film mulching (P),(iii) film mulching on ridges and planting in narrow furrows(S),(iv) full film mulching on double ridges (D), and (v) film mulching on ridges and planting in wide furrows (R).The effects on soil organic carbon (SOC) content, storage, and fractions, and on the carbon management index (CMI)were evaluated after nine consecutive years of plastic film *** results showed that long-term plastic film mulching generally maintained the initial SOC *** with no mulching, plastic film mulching increased the average crop yield, biomass yield, and root biomass by 48.38, 35.06, and 37.32%, respectively, which led to the improvement of SOC ***, plastic film mulching significantly improved CMI, and increased the SOC content by 13.59%, SOC storage by 7.47%and easily oxidizable organic carbon (EOC) by 13.78%on average,but it reduced the other labile *** sequestration and CMI were improved by refining the plastic film mulching *** S treatment had the best effect among the four mulching methods, so it can be used as a reasonable film mulching method for sustainable agricultural development in the semiarid area.

关键词： plastic film mulching soil organic carbon labile organic carbon fractions semiarid area

A blockchain-empowered authentication scheme for worm detection in wireless sensor network

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Digital Communications and networks 2024年第2期10卷 265-272页

作者： Yuling Chen Xiong Yang Tao Li Yi ren Yangyang Long State Key Laboratory of Public Big Data College of Computer Science and TechnologyGuizhou UniversityGuiyang550025China School of Computing Science University of East AngliaNorwichNR57TJUK

Wireless Sensor network(WSn)is a distributed sensor network composed a large number of nodes with low cost,low performance and *** special structure of WSn brings both convenience and *** example,a malicious participant can launch attacks by capturing a physical ***,node authentication that can resist malicious attacks is very important to network ***,blockchain technology has shown the potential to enhance the security of the Internet of Things(IoT).In this paper,we propose a Blockchain-empowered Authentication Scheme(BAS)for *** our scheme,all nodes are managed by utilizing the identity information stored on the ***,the simulation experiment about worm detection is executed on BAS,and the security is evaluated from detection and infection *** experiment results indicate that the proposed scheme can effectively inhibit the spread and infection of worms in the network.

关键词： Wireless Sensor network(WSn) node authentication Blockchain Tangle Worm detection

Effects of the nozzle structure and fluidized gas composition on the gas-particle two-phase jet characteristic in a powder fuel scramjet

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Particuology 2024年第9期92卷 166-179页

作者： Changfei Zhuo Hongming Ding Xiaobin ren Hanyu Deng Xiong Chen School of Mechanical and Engineering Key Laboratory of Special Engine TechnologyMinistry of EducationNanjing University of Science and TechnologyNanjing210094China Department of Mechanical Engineering National University of Singapore9 Engineering Drive 1Singapore117576 Shanxi north Xing'an Chemical Industry Co. Ltd.Taiyuan030008China

The interaction between nozzle design and fluidization gas composition significantly influences the dynamics within a powder fuel scramjet's combustion *** investigate this relationship,an experimental study utilized high-speed shadow imaging technology to explore the macroscopic aspects of powder fuel *** investigation examined various convergence angles,nozzle throat lengths,and fluidized gas *** findings include:During jet development,powder fuel initially concentrates near the axis,with non-convergence angle nozzles exhibiting longer concentrated distribution periods than convergence angle *** nozzle convergence angles lead to increased penetration distance,frontal velocity,and radial diffusion distance during the initial stages of jet ***,stable jet shapes show larger divergence angles as nozzle convergence angle decreases,with the largest divergence angle observed atα=60°.In the initial 0-7 ms of jet development,the powder fuel jet demonstrates greater penetration distance and frontal velocity under certain ***,penetration distance and frontal velocity increase with throat length from 7 to 20 ms,accompanied by changes in divergence ***,at a throat length(l)of 2 mm,the near-field divergence angle measures 46.50°,and the far-field divergence angle is 22.25°.Conversely,at l=8mm,the near-field divergence angle is 33.49°,and the far-field divergence angle is 23.21°.The fluidization gas composition minimally affects jet penetration distance and frontal velocity during the initial 0-3 ***,due to hydrogen's low density,hydrogen/powder fuel jets exhibit shorter distances and velocities compared to nitrogen/powder fuel *** fluidization also results in larger divergence angles,particularly in the near *** findings underscore the importance of nozzle design and fluidization gas composition in optimizing scramjet performance and efficiency.

关键词： Multiphase flows Gas-particle two-phase jet nozzle contraction angle Powder fuel scramjet