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Predict the evolution of mechanical property of Al-Li alloys in a marine environment

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Defence Technology（防务技术） 2024年第1期31卷 557-566页

作者： Wei Li Lin Xiang Guang Wu Hongli Si Jinyan Chen Yiming Jin Yan Su Jianquan Tao Chunyang Huang State Key Laboratory of Explosion Science and Technology Beijing Institute of TechnologyBeijing100036China Chongqing Innovation Center Beijing Institute of TechnologyChongqing400044China First Research institute of the Ministry of Public Security for PR China Beijing100036China Southwest Technology and Engineering Research institute Chongqing400039China

The ocean is one of the essential fields of national defense in the future,and more and more attention is paid to the lightweight research of Marine equipment and *** study it is to develop a Machine learning(ML)-based prediction method to study the evolution of the mechanical properties of Al-Li alloys in the marine *** obtained the mechanical properties of Al-Li alloy samples under uniaxial tensile deformation at different exposure times through Marine exposure *** obtained the strain evolution by digital image correlation(DIC).The strain field images are voxelized using 2D-Convolutional Neural Networks(CNN)autoencoders as input data for Long Short-Term Memory(LSTM)neural ***,the output data of LSTM neural networks combined with corrosion features were input into the Back Propagation(BP)neural network to predict the mechanical properties of Al-Li *** main conclusions are as follows:*** variation law of mechanical properties of2297-T8 in the Marine atmosphere is *** the increase in outdoor exposure test time,the tensile elastic model of 2297-T8 changes slowly,within 10%,and the tensile yield stress changes significantly,with a maximum attenuation of 23.6%.*** prediction model can predict the strain evolution and mechanical response simultaneously with an error of less than 5%.*** study shows that a CNN/LSTM system based on machine learning can be built to capture the corrosion characteristics of Marine exposure *** results show that the relationship between corrosion characteristics and mechanical response can be predicted without considering the microstructure evolution of metal materials.

关键词： Marine environment Al-Li alloy Machine learning Corrosion

Absolute pose estimation of UAV based on large-scale satellite image

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Chinese Journal of Aeronautics 2024年第6期37卷 219-231页

作者： Hanyu WANG Qiang SHEN Zilong DENG Xinyi CAO Xiaokang Wang School of Mechatronical Engineering Beijing Institute of TechnologyBeijing 100081China Beijing institute of Technology Chongqing Innovation Center Chongqing 401120China

Obtaining absolute pose based on pre-loaded satellite images is one of the important means of autonomous navigation for small Unmanned Aerial Vehicles(UAVs)in Global Navigation Satellite System(GNSS)denied *** of the previous works have tended to build Convolutional Neural Networks(CNNs)to extract features and then directly regress the pose,which will fail when solving the challenges caused by the huge viewpoint and size differences between“UAV-satellite”image pairs in real-world ***,this paper proposes a probability distribution/regression integrated deep model with the attention-guided triple fusion mechanism,which estimates discrete distributions in pose space and three-dimensional vectors in translation *** order to overcome the shortage of the relevant dataset,this paper simulates image datasets captured by UAVs with forward-facing cameras during target searching and autonomous *** effectiveness,superiority,and robustness of the proposed method are verified by simulated datasets and flight tests.

关键词： Satellite imagery Unmanned Aerial Vehicle(UAV) Deep neural networks Vision navigation von Mises-Fisher distribution

Early chatter identification based on optimized VMD with multi-band information fusion and compression method in robotic milling process

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Chinese Journal of Aeronautics 2024年第6期37卷 464-484页

作者： Sichen CHEN Zhiqiang LIANG Yuchao DU Zirui GAO Haoran ZHENG Zhibing LIU Tianyang QIU Xibin WANG School of Mechanical Engineering Beijing Institute of TechnologyBeijing 100081China Beijing institute of Technology Chongqing Innovation Center Chongqing 401120China

Undesirable self-excited chatter has always been a typical issue restricting the improvement of robotic milling quality and *** chatter identification based on processing signals can prompt operators to adjust the machining process and prevent chatter *** with the traditional machine tool,the uncertain multiple chatter frequency bands and the band-moving of the chatter frequency in robotic milling process make it more challenging to extract chatter *** paper proposes a novel method of chatter identification using optimized variational mode decomposition(OVMD)with multi-band information fusion and compression technology(MT).During the robotic milling process,the number of decomposed modes k and the penalty coefficient a are optimized based on the dominant component of frequency scope partition and fitness of the mode center ***,the mayfly optimization algorithm(MA)is employed to obtain the global optimal parameter *** order to conquer information collection about the uncertain multiple chatter frequency bands and the band-moving of the chatter frequency in robotic milling process,MT is presented to reduce computation and extract signal ***,the cross entropy of the image(CEI)is proposed as the final chatter indicator to identify the chatter *** robotic milling experiments are carried out to verify the proposed method,and the results show that it can distinguish the robotic milling condition by extracting the uncertain multiple chatter frequency bands and overcome the band-moving of the chatter frequency in robotic milling process.

关键词： Robotic milling Chatter detection Variational mode decomposition Information fusion and compression Chatter featur

Swarm intention identification via dynamic distribution probability image

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Chinese Journal of Aeronautics 2024年第10期37卷 380-392页

作者： Yinhan WANG Jiang WANG Shaoming HE Fei WANG Qi WANG School of Aerospace Engineering Beijing Institute of TechnologyBeijing 100081China institute of Computing Technology Chinese Academy of SciencesBeijing 100190China

In the realm of decision-making for defense and security applications,it is paramount to swiftly and accurately identify the intentions of incoming *** identification methods predominantly focus on single-target applications and overlook the perturbations introduced by measurement *** this study,we propose a novel concept:the Dynamic Distribution Probability(DDP)image,which is constructed using the estimated state and its covariance *** grayscale pixel value within the image signifies the probability of the presence of the agent within the *** proposed identification scheme integrates the use of Extended Kalman Filter(EKF),Convolutional Neural Network(CNN),Back Propagation(BP)network,and Gated Recurrent Unit(GRU)***,the DDP image is processed through a CNN to distill the formation characteristics,and the estimated swarm state from EKF is inputted into a BP network to deduce the kinematic *** outputs from both networks are summed and subsequently channeled into a GRU network to capture temporal *** numerical simulations and flight experiments are presented to demonstrate the robust anti-noise capability of the proposed scheme compared with conventional methods,as well as its superior training efficiency.

关键词： Intention Identification Kalman filters Convolutional neural networks Swarm intelligence

Free-Form Deformation with Rational DMS-Spline Volumes

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Journal of Computer Science & Technology 2008年第5期23卷 862-873页

作者：徐岗汪国昭陈小雕 institute of Computer graphics and image Processing Zhejiang University Department of Mathematics Zhejiang University College of Computer Science Hangzhou Dianzi University INRIA Nancy France

In this paper, we propose a novel free-form deformation （FFD） technique, RDMS-FFD （Rational DMS-FFD）, based on rational DMS-spline volumes. RDMS-FFD inherits some good properties of rational DMS-spline volumes and combines more deformation techniques than previous FFD methods in a consistent framework, such as local deformation, control lattice of arbitrary topology, smooth deformation, multiresolution deformation and direct manipulation of deformation. We first introduce the rational DMS-spline volume by directly generalizing the previous results related to DMS-splines. How to generate a tetrahedral domain that approximates the shape of the object to be deformed is also introduced in this paper. Unlike the traditional FFD techniques, we manipulate the vertices of the tetrahedral domain to achieve deformation results. Our system demonstrates that RDMS-FFD is powerful and intuitive in geometric modeling.

关键词： free-form deformation rational DMS-spline volume control lattice of arbitrary topology multiresolution deformation direct manipulation

Approximate merging of multiple Bézier segments

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Progress in Natural Science:Materials International 2008年第6期18卷 757-762页

作者： Min Chenga,b,Guojin Wanga,* ainstitute of Computer graphics and image Processing,Zhejiang University,Hangzhou 310027,China bCollege of Science,Zhejiang University of Technology,Hangzhou 310032,China institute of Computer graphics and image Processing Zhejiang University Hangzhou 310027 China College of Science Zhejiang University of Technology Hangzhou 310032 China

This paper deals with the approximate merging problem of multiple adjacent Bézier curves with dierent degrees by a single Bézier curve,which is a frequently seen problem in *** unified matrix representation for precise merging is presented and the approx-imate merging curve is further derived based on matrix *** at the endpoints of curves is also discussed in the merging *** show that the method in this paper achieves satisfying merging results.

关键词： Computer-aided geometric design Bézier curve Approximate merging Matrix representation

Application of dynamic image analysis to the optical characterisation of fibrous bulk material

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Particuology 2024年第7期90卷 51-60页

作者： Johannes Lunewski Eberhard Schmidt institute of Particle Technology University of WuppertalGermany

Dynamic image analysis provides an automated evaluation method to determine the size and shape of multiple particles. This method represents a common application for ordinary bulk material. The latest draft of ISO 13322–2:2021 describes the state of the art, but lacks instructions for handling fibrous bulk material. Interlocking fibres complicate the measurement conditions and require a disentanglement of fibrous samples during a pre-dispersion step. A further error source includes the fibre orientation inside the measurement zone of the device. If the thresholding algorithm fails to differentiate between the fibre projection area and the background, a subsequent image optimisation solves the problem. This article addresses the mentioned problems by analysing cotton cellulose and polyacrylonitrile fibres. Besides the execution of a pre-dispersion step, the experiments compare the discrepancies between dry and wet dispersion. Here, the software packages PAQXOS and imageJ perform the image evaluation. In this case, the wet dispersion setup with a subsequent image evaluation by imageJ provides comprehensible results.

关键词： Bootstrap method Dynamic image analysis Fibre diameter Fibre length distribution Natural fibres Synthetic fibres

Artificial hawk-eye camera for foveated, tetrachromatic, and dynamic vision

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Journal of Semiconductors 2024年第9期45卷 1-3页

作者： Wenhao Ran Zhuoran Wang Guozhen Shen School of Integrated Circuits and Electronics Beijing Institute of TechnologyBeijing 100081China institute of Flexible Electronics Beijing Institute of TechnologyBeijing 102488China

With the rapid development of drones and autonomous vehicles, miniaturized and lightweight vision sensors that can track targets are of great interests. Limited by the flat structure, conventional image sensors apply a large number of lenses to achieve corresponding functions, increasing the overall volume and weight of the system.

关键词： awk vision system.

Degree elevation operator and geometric construction of C-B-spline curves

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Science China(Information Sciences) 2010年第9期53卷 1753-1764页

作者： ZHU Ping1,2*,WANG GuoZhao1 & YU JingJing1 1institute of Computer graphics and image Processing,Zhejiang University,Hangzhou 310027,China 2Laboratory of Scientific Computing,Southeast University,Nanjing 211189,China institute of Computer graphics and image Processing Zhejiang University Hangzhou China Laboratory of Scientific Computing Southeast University Nanjing China

Unlike a B'ezier curve,a spline curve is hard to be obtained through geometric corner cutting on control polygons because the degree elevation operator is difficult to be obtained and geometric convergence is hard to be *** order to obtain geometric construction algorithm on C-B-splines,firstly we construct the degree elevation operator by using bi-order splines in this *** we can obtain a control polygon sequence by degree elevation based on the degree elevation operator derived from a C-B-spline ***,we prove that this polygon sequence will converge to initial C-B-spline *** geometric construction algorithm possesses strong geometric *** is also simple,stable and suitable for hardware to *** algorithm is important for CAD modeling systems,since many common engineering curves such as ellipse,helix,*** be represented explicitly by C-B-splines.

关键词： C-B-spline degree elevation operator bi-order C-B-spline geometric convergence geometric construction