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A star identification algorithm for rolling shutter exposure based on Hough transform

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Chinese Journal of Aeronautics 2024年第6期37卷 319-330页

作者： tao wang Gangyi wang Xinguo WEI Yongyong LI School of Instrumentation and Optoelectronic Engineering Beihang UniversityBeijing 100191China

The star identification algorithm usually identifies stars by angular distance ***,under high dynamic conditions,the rolling shutter effect distorts the angular distances between the measured and true star positions,leading to plethoric false matches and requiring complex and time-consuming verification for star *** identification rate hinders the application of low-noise and cost-effective rolling shutter image *** this work,we first study a rolling shutter distortion model of angular distances between stars,and then propose a novel three-stage star identification algorithm to identify distorted star images captured by the rolling shutter star *** first stage uses a modified grid algorithm with adaptive error tolerance and an expanded pattern database to efficiently eliminate spurious *** second stage performs angular velocity estimation based on Hough transform to verify the matches that follow the same distortion *** third stage applies a rolling shutter error correction method for further *** the simulation and night sky image test demonstrate the effectiveness and efficiency of our algorithm under high dynamic *** accuracy of angular velocity estimation method by Hough transform is evaluated and the root mean square error is below 0.5(°)/*** algorithm achieves a 95.7% identification rate at an angular velocity of 10(°)/s,which is much higher than traditional algorithms.

关键词： Star trackers Star identification Rolling shutter Angular velocity estimation Hough transform

Nitsche-XFEM for a time fractional diffusion interface problem

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Science China Mathematics 2024年第3期67卷 665-682页

作者： tao wang Yanping Chen China Nuclear Power Technology Research Institute Co.Ltd. Shenzhen 518028China School of Mathematical Sciences South China Normal UniversityGuangzhou 510631China

In this paper, we propose a space-time finite element method for a time fractional diffusion interface problem. This method uses the low-order discontinuous Galerkin(DG) method and the Nitsche extended finite element method(Nitsche-XFEM) for temporal and spatial discretization, respectively. Sharp pointwise-in-time error estimates in graded temporal grids are derived, without any smoothness assumptions on the ***, three numerical examples are provided to verify the theoretical results.

关键词： fractional diffusion interface discontinuous Galerkin Nitsche-XFEM error estimates

A tendon system to re-center steel moment frames with weak stories

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Earthquake Engineering and Engineering Vibration 2024年第4期23卷 1057-1072页

作者： wang, tao wang, Fei Nakashima, Masayoshi Institute of Engineering Mechanics China Earthquake Administration Beijing China Key Laboratory of Earthquake Engineering and Engineering Vibration Institute of Engineering Mechanics China Earthquake Administration Harbin China Disaster Prevention Research Institute Kyoto University Uji Kyoto Japan

A wide open bottom story of a frame building is often expected by owners for use as a garage or shops. However, this leads to weak stories due to abrupt changes in lateral stiffness and often results in unexpected story collapse as observed in many previous earthquakes. To retrofit frame buildings that have experienced weak story damage, a tendon system is proposed in this study, which consists of a set of swaying columns and tendons. The swaying columns are used to uniformly redistribute the lateral deformation along the height, while the tendons provide extra lateral stiffness and renders the entire structural system a re-centering capability. To avoid unnecessary forces to swaying columns, pin-connections are used at the bottom. Tendons are placed over the entire story to gain large elastic displacements. Parametric analysis reveals that the swaying column, with a stiffness of about 0.9 times that of the weak story, and the tendons attached at the roof, with a stiffness of 0.04 times that of the weak story, can provide the optimal performance with a maximum residual story drift angle of less than 0.5%. Online hybrid tests were carried out, which demonstrated that uniformly distributed story drifts and acceptable residual deformation could be achieved by the proposed tendon system.

关键词： tendon system re-centering capability residual deformation rehabilitation collapse prevention

Study on theoretical model for electrical explosion resistivity of Al/Ni reactive multilayer foil

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Defence Technology（防务技术） 2024年第2期32卷 348-356页

作者： Zehao wang tao wang Pengfei Xue Mingyu Li Qingxuan Zeng State Key Laboratory of Explosion Science and Technology Beijing Institute of TechnologyBeijing 100081China China Ship Development and Design Center Wuhan 430064China

Al/Ni reactive multilayer foil(RMF)possesses excellent comprehensive properties as a promising substitute for traditional Cu bridge.A theoretical resistivity model of Al/Ni RMF was developed to guide the optimization of ***/Ni RMF with different bilayer thicknesses and bridge dimensions were prepared by MEMS technology and electrical explosion tests were carried *** to physical and chemical reactions in bridge,the electrical explosion process was divided into 5 stages:heating of condensed bridge,vaporization and diffusion of Al layers,intermetallic combination reaction,intrinsic explosion,ionization of metal gases,which are obviously shown in measured voltage *** of interface and grain boundary scattering on the resistivity of film metal were *** on variations of substance and state,the resistivity was developed as a function of temperature at each *** explosion curves were calculated by this model at different bilayer thicknesses,bridge dimensions and capacitor voltages,which showed an excellent agreement with experimental ones.

关键词： Al/Ni reactive multilayer foil Electrical explosion Resistivity model Phase transition Calculation

Control of fine particulate nitrate during severe winter haze in“2+26”cities

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Journal of Environmental Sciences 2024年第2期136卷 261-269页

作者： Chuang Qin Xiao Fu tao wang Jian Gao Jiaqi wang Institute of Environment and Ecology Tsinghua Shenzhen International Graduate SchoolTsinghua UniversityShenzhen 518055China Department of Civil and Environmental Engineering Hong Kong Polytechnic UniversityHong Kong 99907China State Key Laboratory of Environmental Criteria and Risk Assessment Chinese Research Academy of Environmental SciencesBeijing 10084China

The“2+26”cities,suffering the most severe winter haze pollution,have been the key region for air quality improvement in *** prominent nitrate pollution is one of the most challenging environmental issues in this region,necessitating development of an effective control ***,we use observations,and state-of-the-art model simulations with scenario analysis and process analysis to quantify the effectiveness of the future SO_(2)-NO_(X)-VOC-NH_(3) emission control on nitrate pollution mitigation in“2+26”*** on a serious winter haze episode,we find that limited NO_(X)emission reduction alone in the short-term period is a less effective choice than VOC or NH_3emission reduction alone to decrease nitrate concentrations,due to the accelerated NO_(X)-HNO_(3)conversion by atmospheric oxidants and the enhanced HNO_(3)to NO_(3)^(-)partition by ammonia,although deep NO_(X)emission reduction is essential in the long-term *** synergistic NH_(3) and VOC emission control is strongly recommended,which can counteract the adverse effects of nonlinear photochemistry and aerosol chemical feedback to decrease nitrate *** extra benefits will be reduced if the synergistic NH_(3) and VOC reduction is delayed,and thus reducing emission of multiple precursors is urgently required for the effective control of increasingly severe winter nitrate pollution in“2+26”cities.

关键词： Nitrate Winter haze pollution Emission reduction “2+26”cities

Combustion and Self-Desulfurization Characterization of Blended Low-Rank Coals for Improved Resource Utilization in Fluidized Bed Boilers

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Journal of Thermal Science 2024年第3期33卷 1242-1256页

作者： SU Lipeng ZHANG Cong ZHANG Yongsheng wang tao wang Jiawei Key Laboratory of Power Station Energy Transfer Conversion and System Ministry of EducationNorth China Electric Power UniversityBeijing102206China

The co-combustion of low-rank coals through fluidized bed boiler(CFB)is an effective approach to enhance the level of resource *** date,there has been a lack of investigation concerning the co-combustion kinetics and self-desulfurization characteristics of coal slime,coal gangue,and raw *** this study,we adopted multiple model-free and model-fitting methods to comparatively analyze co-combustion kinetics of blended coals on the basis of thermogravimetric ***,the sulfur balance and self-desulfurization of blended coals in the co-combustion were intensively investigated using a tube furnace *** results reveal that in the presence of coal gangue in blended coals,the average activation energy(E_(a))falls within the range of 65.7 kJ/mol to 100.4 kJ/mol,as determined by four model-free ***,in the absence of coal gangue,only the Flynn-Wall-Ozawa(FWO)and Friedman(FM)methods are deemed appropriate for calculating the average E_(a),yielding a value of 77.3 kJ/*** first order reaction model is confirmed to be reliable for analyzing the co-combustion kinetics of low-rank blended *** of the specific composition of the blended coal,a significant linear correlation exists between the Ea and the natural logarithm of the pre-exponential factor(lnA)within an extensive range of ***,the addition of coal gangue to the blended coal substantially enhances the self-desulfurization level,resulting in an increase from 25.7%to60.7%at 1073 *** self-desulfurization efficiency exhibits a good linear relationship with both the mass ratio of coal gangue to coal slime and the molar ratio of calcium to *** a practical implementation,the optimal addition ratio of coal gangue is a trade-off between the self-desulfurization efficiency and the ignition capacity.

关键词： coal slime coal gangue fluidized bed boilers self-desulfurization resource utilization

Spatio-temporal variability of surface chlorophyll a in the Yellow Sea and the East China Sea based on reconstructions of satellite data of 2001-2020

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Journal of Oceanology and Limnology 2024年第2期42卷 390-407页

作者： Weichen XIE tao wang Wensheng JIANG Key Laboratory of Marine Environment and Ecology Ocean University of ChinaQingdao 266100China College of Oceanic and Atmospheric Sciences Ocean University of ChinaQingdao 266100China

Chlorophyll-a(Chl-a)concentration is a primary indicator for marine environmental *** spatio-temporal variations of sea surface Chl-a concentration in the Yellow Sea(YS)and the East China Sea(ECS)in 2001-2020 were investigated by reconstructing the MODIS Level 3 products with the data interpolation empirical orthogonal function(DINEOF)*** reconstructed results by interpolating the combined MODIS daily+8-day datasets were found better than those merely by interpolating daily or 8-day ***-a concentration in the YS and the ECS reached its maximum in spring,with blooms occurring,decreased in summer and autumn,and increased in late autumn and early *** performing empirical orthogonal function(EOF)decomposition of the reconstructed data fields and correlation analysis with several potential environmental factors,we found that the sea surface temperature(SST)plays a significant role in the seasonal variation of Chl a,especially during spring and *** increase of SST in spring and the upper-layer nutrients mixed up during the last winter might favor the occurrence of spring *** high sea surface temperature(SST)throughout the summer would strengthen the vertical stratification and prevent nutrients supply from deep water,resulting in low surface Chl-a *** sea surface Chl-a concentration in the YS was found decreased significantly from 2012 to 2020,which was possibly related to the Pacific Decadal Oscillation(PDO).

关键词： chlorophyll a(Chl a) data interpolation empirical orthogonal function(DINEOF) empirical orthogonal function(EOF)analysis Yellow Sea East China Sea

Securing multi-chain consensus against diverse miner behavior attacks in blockchain networks

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Frontiers of Information Technology & Electronic Engineering 2024年第4期25卷 540-554页

作者： Wenbo ZHANG tao wang Chaoyang ZHANG Jingyu FENG School of Cyberspace Security Xi’an University of Posts and TelecommunicationsXi’an 710121China Postal Savings Bank of China Xi’an 710000China

As cross-chain technologies enable interactions among different blockchains(hereinafter“chains”),multi-chain consensus is becoming increasingly important in blockchain ***,more attention has been paid to single-chain consensus ***-chain consensus schemes with trusted miner participation have not been considered,thus offering opportunities for malicious users to launch diverse miner behavior(DMB)attacks on different *** attackers can be friendly in the consensus process on some chains,called mask chains,to enhance their trust value,while on others,called kill chains,they engage in destructive behaviors on the *** this paper,we propose a multi-chain consensus scheme named Proof-of-DiscTrust(PoDT)to defend against DMB *** idea of distinctive trust(DiscTrust)is introduced to evaluate the trust value of each user across different *** trustworthiness of a user is split into local and global trust values.A dynamic behavior prediction scheme is designed to enforce DiscTrust to prevent an intensive DMB attacker from maintaining strong trust by alternately creating true or false blocks on the kill *** trusted miner selection algorithms for multi-chain environments can be implemented to select network miners,chain miners,and chain miner leaders,*** results show that PoDT is secure against DMB attacks and more effective than traditional consensus schemes in multi-chain environments.

关键词： Blockchain Cross-chain Trust mechanism Multi-chain consensus

Ballistic performance of additive manufacturing 316l stainless steel projectiles based on topology optimization method

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Defence Technology（防务技术） 2024年第5期35卷 1-17页

作者： Hao Xue tao wang Xinyu Cui Yifan wang Guangyan Huang State Key Laboratory of Explosion Science and Technology Beijing Institute of TechnologyBeijing 100081China

Material and structure made by additive manufacturing(AM)have received much attention lately due to their flexibility and ability to customize complex *** study first implements multiple objective topology optimization simulations based on a projectile perforation model,and a new topologic projectile is *** two types of 316L stainless steel projectiles(the solid and the topology)are printed in a selective laser melt(SLM)machine to evaluate the penetration performance of the projectiles by the ballistic *** experiment results show that the dimensionless specific kinetic energy value of topologic projectiles is higher than that of solid projectiles,indicating the better penetration ability of the topologic ***,microscopic studies(scanning electron microscope and X-ray micro-CT)are performed on the remaining projectiles to investigate the failure mechanism of the internal structure of the topologic *** explicit dynamics simulation was also performed,and the failure locations of the residual topologic projectiles were in good agreement with the experimental results,which can better guide the design of new projectiles combining AM and topology optimization in the future.

关键词： Additive manufacturing Topology optimization Ballistic performance Projectile design