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Aero-optic imaging deviation prediction based on ISSA-ELM

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光电子快报:英文版 2023年第7期19卷 425-431页

作者： XU Liang ZHAO Shiwei WANG Tao Tianjin Key Laboratory for Control Theory&Applications in Complicated Systems School of Electrical Engineering and AutomationTianjin University of TechnologyTianjin 300384China School of Intelligent Engineering Sun Yat-sen UniversityGuangzhou 510275China

When the aircraft is moving at high speed in the atmosphere,aero-optical imaging deviation will appear due to the influence of aero-optical effect.In order to achieve real-time compensation during the flight of the aircraft,it is necessary to analyze and predict the obtained imaging deviation data.In order to improve the search speed and accuracy of the prediction algorithm and the ability to jump out of local optimum,in this paper,an improved sparrow search algorithm optimized extreme learning machine(ISSA-ELM) neural network model is proposed to predict the aero-optical imagine deviation.Finally,the performance of ISSA-ELM,ELM neural network and SSA-ELM neural network was tested.The results showed that compared with ELM and SSA-ELM algorithms,the convergence speed of ISSA-ELM was significantly enhanced,and the accuracy of data prediction was also significantly improved.

关键词： effect. deviation extreme

Elman neural network for predicting aero optical imaging deviation based on improved slime mould algorithm

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Optoelectronics Letters 2023年第5期19卷 290-295页

作者： XU Liang WANG Luyang XUE Wei ZHAO Shiwei ZHOU Liye Tianjin Key Laboratory of Complex Control Theory and Application School of Electronic Engineering and AutomationTianjin University of TechnologyTianjin 300384China China Academy of Aerospace Science and Innovation Beijing 100048China

This research suggests a methodology to optimize Elman neural network based on improved slime mould algorithm(ISMA) to anticipate the aero optical imaging deviation.The improved Tent chaotic sequence is added to the SMA to initialize the population to accelerate the algorithm’s speed of convergence.Additionally,an improved random opposition-based learning was added to further enhance the algorithm’s performance in addressing problems that the SMA has such as weak convergence ability in the late iteration and an easy tendency to fall into local optimization in the optimization process when solving the optimization problem.Finally,the algorithm model is compared to the Elman neural network and the SMA optimization Elman neural network model.The three models are assessed using four evaluation indicators,and the findings demonstrate that the ISMA optimization model can anticipate the aero optical imaging deviation in an accurate way.

关键词： neural Elman network

Adaptive navigation assistance based on eye movement features in virtual reality

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Virtual Reality & Intelligent Hardware 2023年第3期5卷 232-248页

作者： Song zhao shiwei CHENG School of Computer Science and Technology Zhejiang University of TechnologyHangzhou 310023China

Background Navigation assistance is essential for users when roaming virtual reality scenes;however,the traditional navigation method requires users to manually request a map for viewing,which leads to low immersion and poor user experience.Methods To address this issue,we first collected data on who required navigation assistance in a virtual reality environment,including various eye movement features,such as gaze fixation,pupil size,and gaze angle.Subsequently,we used the boosting-based XGBoost algorithm to train a prediction model and finally used it to predict whether users require navigation assistance in a roaming task.Results After evaluating the performance of the model,the accuracy,precision,recall,and F1-score of our model reached approximately 95%.In addition,by applying the model to a virtual reality scene,an adaptive navigation assistance system based on the real-time eye movement data of the user was implemented.Conclusions Compared with traditional navigation assistance methods,our new adaptive navigation assistance method could enable the user to be more immersive and effective while roaming in a virtual reality(VR)environment.

关键词： Eye movement Navigation Human-computer interaction Virtual reality Eye tracking

Analysis of light propagation characteristic in the aero-optic flow field of cone-headed vehicle with side window

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Optoelectronics Letters 2024年第1期20卷 58-64页

作者： XU Liang ZHOU Liye WANG Luyang ZHAO Shiwei WANG Tao Tianjin Key Laboratory of Complex Control Theory and Application School of Electrical Engineering and AutomationTianjin University of TechnologyTianjin 300384China School of Intelligent Engineering Sun Yat-sen UniversityGuangzhou 510275China Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai) Zhuhai 519000China

Aero-optic imaging deviation research is carried out for infrared-guided vehicle with cone-head side window,with a focus on the propagation characteristics of light in an aero-optic flow field.When the light entering the aero-optic flow field from the free-stream should be close to the normal,numerous data indicate that the light is refracted away from the normal.This paper divides the aero-optic flow field into two parts and uses the gas density distribution in the aero-optic flow field to propose the hypothesis that there are two modes of refraction when light propagates through the flow field.The results show that light propagates from the optically denser medium to the optically thinner medium after passing through the shock wave and eventually leads to refraction away from the normal when the light enters the aero-optic flow field.

关键词： flow propagation light

Coupled effects of particle overall regularity and sliding friction on the shear behavior of uniformly graded dense sands

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Journal of Rock Mechanics and Geotechnical Engineering 2022年第3期14卷 873-885页

作者： Jiayan Nie shiwei zhao Yifei Cui Yu Wang State Key Laboratory of Hydroscience and Engineering Tsinghua UniversityBeijing100084China South China Institute of Geotechnical Engineering South China University of TechnologyGuangzhou510640China Key Laboratory of Mountain Hazards and Surface Process Institute of Mountain Hazards and EnvironmentChinese Academy of SciencesChengdu610041China University of Chinese Academy of Sciences Beijing100049China

Particle morphology has been regarded as an important factor affecting shear behaviors of sands,and covers three important aspects,i.***.global form(overall shape),local roundness(large-scale smoothness),and surface texture(roughness)in terms of different observation scales.Shape features of different aspects can be independent of each other but might have coupled effects on the bulk behavior of sands,which has been not explored thoroughly yet.This paper presents a systematic investigation of the coupled effects of the particle overall regularity(OR)and sliding friction on the shear behavior of dense sands using three-dimensional(3D)discrete element method(DEM).The representative volume elements consisting of ideal spheres and irregular clumps of different mass proportions are prepared to conduct drained triaxial compression simulations.A well-defined shape descriptor named OR is adopted to quantify particle shape differences of numerical samples at both form and roundness aspects,and the particle sliding friction coefficient varies from 0.001 to 1 to consider the surface roughness effect equivalently in DEM.The stress-strain relationships as well as peak and critical friction angles of these assemblies are examined systematically.Moreover,contact network and anisotropic fabric characteristics within different granular assemblies are analyzed to explore the microscopic origins of the multi-scale shape-dependent shear strength.This study helps to improve the current understanding with respect to the influence of the particle shape on the shear behavior of sands from different shape aspects.

关键词： Discrete element method(DEM) Overall regularity(OR) Particle sliding friction Peak and critical friction angles Fabric anisotropy Dense sands

DEM investigation of angle of repose for super-ellipsoidal particles

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Particuology 2020年第3期18卷 53-66页

作者： Hao Chen shiwei zhao Xiaowen Zhou State Key Laboratory of Subtropical Building Science South China University of TechnologyGuangzhou 510641China

We explore the effect of particle shape on the angle of repose (AoR) in granular packing using a three-dimensional discrete element method.Non-spherical particles were modeled using super-ellipsoids characterized by aspect ratio and blockiness.The relationship between AoR and particle shape was examined,followed by a series of analyses on the origin of AoR from a microscopic perspective.Results show that,with blockiness deviating from unity,AoR has an approximate "M" shape that exhibits a strong to weak trend with aspect ratio,matching results of previous reports.Another finding suggests a parabolic relationship between normalized AoR and normalized coordination number,AoR increases with anisotropy related more with the anisotropy of particle orientation than with the anisotropy of contact normal.Particle shape is more likely to affect AoR by affecting the tangential force than the normal contact force.An analysis based on traction indicates that dips in stress associated with the tangential force (compared with the normal force) and non-spherical particles (compared with spheres) are more significant.For various particle shapes,AoR is positively correlated with friction mobilization but is negatively correlated with friction mobilization for various coefficient of friction.

关键词： Discrete element Angle of repose Non-spherical particles Granular fabric Packing

Computation and analysis of aero-optic imaging deviation of a blunt nosed aircraft with Mach number 0.5—3

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Optoelectronics Letters 2023年第1期19卷 55-59页

作者： XU Liang ZHAO Shiwei XUE Wei WANG Tao Tianjin Key Laboratory for Control Theory&Applications in Complicated Systems School of Electrical Engineering and AutomationTianjin University of TechnologyTianjin300384China China Academy of Aerospace Science and Innovation Beijing100083China School of Intelligent Engineering Sun Yat-sen UniversityGuangzhou510275China

Aero-optic imaging is a kind of optical effect,which describes the imaging deviation on the imaging plane.In this paper,the effect of the change of Mach number of blunt aircraft on the aero-optic imaging deviation is studied.The imaging deviations of Mach number 0.5—3 are analyzed systematically.The results show that with the increase of Mach number,imaging deviation increases gradually,and the increase rate is gradually slow.Imaging deviation slope decreases gradually with the increase of Mach number,and gradually tends to be zero,suggesting that imaging deviation is not sensitive to the change of the larger Mach number.In other words,the Mach number of smaller changes can lead to larger imaging deviation.As the Mach number of the aircraft increases,the slope of the imaging offset tends to be closer and closer to 0.When the Mach number of the aircraft increases to a certain extent,the change of the imaging offset will not have much influence.Therefore,in order to reduce the impact of flight speed on imaging migration,the aircraft should fly at a higher Mach number.

关键词： deviation closer number

Re-fluidising the aged gel for high-density alumina green body

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Journal of Advanced Ceramics 2022年第9期11卷 1375-1382页

作者： Xiaolang WU Jin zhao Shunzo SHIMAI Xiaojian MAO Jian ZHANG shiwei WANG State Key Laboratory of High Performance Ceramics and Superfine Microstructure Shanghai Institute of CeramicsChinese Academy of SciencesShanghai 200050China Center of Materials Science and Optoelectronics Engineering University of Chinese Academy of SciencesBeijing 100049China

A green body with a density as high as possible is critical to diminish the crisis of deformation or cracking when large-size parts are sintered.Here,a new method,i.e.,re-fluidising the aged ceramic gel is developed to prepare the high-density green body.Alumina slurry with 56 vol%solid loading and copolymers of isobutylene and maleic anhydride were aged without vaporisation and re-fluidised by non-intrusive shearing after removing the exuded water.The re-fluidised slurry was re-casted.The resultant wet gel was dried and deboned at a low temperature.The relative density of the obtained green body was 64.6%,1.5%higher than that without aging and re-fluidising.The linear sintering shrinkage of the body decreased by 0.7%.The enhanced green density is explained from the viewpoint of the solid loading and the structure of the slurry.

关键词： high density green body re-fluidising alumina colloid formation

Availability evaluation model for space-based optical aerial target detection system

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Optoelectronics Letters 2023年第10期19卷 599-604页

作者： zhao Jiaqing ZHANG Lei DING Xiang XU Zhongchao FAN shiwei LIU Rongke Beijing Institute of Tracking and Telecommunication Technology Beijing100094China Shanghai Aerospace Electronic Technology Research Institute Shanghai201109China Beihang University Beijing100191China

For space-based optical detection systems,there is usually a difference between actual on-orbit operational performance and designed requirements based on fixed scenarios.To assess the availability of space-based optical detection systems in different backgrounds,the radiation characteristics of aerial targets have been simulated using body radiation and atmospheric transmission models.The background radiation characteristics were also statistically analyzed.Then,for the parameters of the fixed space-based optical detection system,the signal-to-clutter and availability were evaluated under different conditions.A linear relationship between the radiation intensity and the flight height of the target was obtained.For a space-based optical detection system,the analytical availability model was constructed.Finally,multiple groups of data under different simulation conditions were used to validate the universality and reliability of the model.This availability model could significantly reduce the time required to predict the availability of the space-based optical detection system.The model was also adopted to analyze the influence of flight height,mean and variance,and background clutter on the space-based optical detection availability.

关键词： optical system space