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A quantitative microplasticity-based approach to rationalize the poor strengthening response of polycrystalline Mg alloys

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Journal of Magnesium and Alloys 2023年第5期11卷 1656-1671页

作者： X.Z.Jin W.C.Xu D.B.Shan B.Guo B.Jin M.T.Pérez-Prado National Key Laboratory for Precision Hot Processing of Metals&School of Materials Science and Engineering Harbin Institute of TechnologyHarbin 150001PR China IMDEA Materials Institute C/Eric Kandel2GetafeMadrid 28906Spain Advanced Composites Simulation Lab University of Southern CaliforniaLos AngelesCA 90089U.S.A M.C.Gill Composites Center University of Southern CaliforniaLos AngelesCA 90089U.S.A

This work aims to understand the inefficiency of nanoprecipitates to strengthen a weakly textured,polycrystalline Mg-Gd-Y-Zr *** experimental micromechanical approach consisting on micropillar compression combined with analytical electron microscopy is put in place to analyze the effect of nanoprecipitation on soft and hard basal slip and twinning in individual grains with different *** study shows that,in grains that are favorably oriented for basal slip(“soft”basal slip),aging leads to extreme localization due to the ability of basal dislocations to shear the nanoparticles,resulting overall in the softening of basal ***,in grains in which the c-axis is almost perpendicular to the compression axis,prismatic slip dominates deformation in the solid solution state and nanoprecipitation favors twinning due to the concomitant lattice solute ***,in grains oriented with their c-axis making an angle of about 5-7°with respect to the compression axis,which deform mainly by“hard”basal slip,precipitation leads to the strengthening of basal systems in the absence of obvious *** work reveals that the poor hardening response of the polycrystalline alloy is related to the capability of basal dislocations to shear the nanoparticles,in the absence of Orowan looping events,and to the associated basal slip localization.

关键词： Magnesium Precipitation Basal slip Particle shearing Slip localization

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Semi-supervised Open-set Recognition of Radar Active Jamming

Semi-supervised Open-set Recognition of Radar Active Jamming

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2021 CIE International Conference on Radar, Radar 2021

作者： Li, Hao Fang, Xueli Zhang, Lei Kang, Hui Zhang, Wei School of Information and Communication Engineering University of Electronic Science and Technology of China Chengdu China Key Laboratory of Complex Aviation Simulation System Beijing China

ISBN: (纸本)9781665498142

With the emergence of various kinds of complex radar jamming, radar jamming intelligent recognition technology has increasingly become the key to electronic counter-counter measures. To achieve radar jamming open-set recognition with a small number of tagged samples, Generative adversarial network-based pseudolabeled convolutional neural network (GAN-PL-CNN) model is proposed in this paper. Firstly, radar jamming is modelled, and the radar jamming datasets with known and unknown types are established after time-frequency transformation and image processing. Then, the adaptive pseudolabeling method is used to achieve semi-supervised recognition of radar jamming by combining the learning capability of convolutional neural networks and the characteristics of pseudolabeling to increase labeled samples intelligently. Finally, generative adversarial networks are introduced to enhance the recognition ability of the model and the discrimination ability of the unknown type through the game between the generator and the discriminator in the iterative process. Experimental results show that the GAN-PL-CNN model achieves 89.7%-95.1% for known types and 30.7%-86.8% for unknown types at 3%-6% labeling rate. As the number of labeled samples increases, the recognition effect becomes better and has a greater ability to exclude unknown type. © 2021 IEEE.

关键词： convolutional neural network open-set recognition pseudo-label Radar active jamming

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Plating Al Coating on High-Strength Steel in Chloroaluminate Ionic Liquid Under Pulse Current Modes

SSRN

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SSRN 2024年

作者： Nan, Yang Li, Wen Li, Shaojie Wei, Qi Li, Weiping Aviation Key Laboratory of Science and Technology on Advanced Surface Engineering AVIC Manufacturing Technology Institute Beijing100024 China School of Materials Science and Engineering Beihang University Beijing100191 China

Aluminum coating is a potential candidate for cadmium coating replacement due to its excellent corrosion resistance and nontoxicity. Among the fabrication methods of Al coating, plating Al via ionic liquids has drawn major attention of researchers because of the superiority of controllability, stability and low energy consumption. However, the evolution rules of plating aluminum on high-strength steel via pulse current modes at room temperature requires deeper investigation. In this work, pulse current density and pulse duty factor are regulated to reveal the plating patterns of Al on 300M high-strength steel in AlCl3-EMIC (2:1 in mole) ionic liquid. It is found that higher current density can significantly facilitate the nucleation of Al grains and the compactness of morphology, while an enlarged pulse duty factor tends to result in more regular Al crystals. When the current density and the pulse duty factor are fixed at 20 mA cm−2 and 80%, the densest and most uniform aluminum coating is obtained. The component of Al coating is verified to be pure Al crystals with good adhesion and the plating process achieves a high current efficiency of 97.27%. Under the protection of Al coating, the impedance and galvanic corrosion current density of 300M steel substrate are optimized by two orders of magnitude, while the corrosion current density is markedly decreased from 5.58 μA cm−2 to 0.77 μA cm−2. © 2024, The Authors. All rights reserved.

关键词： Morphology

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Radar Signal Modulation Recognition Based on Bispectrum Features and Deep learning 2

Radar Signal Modulation Recognition Based on Bispectrum Feat...

引用

2nd International Conference on Computer Engineering and Application, ICCEA 2021

作者： Dong, Zeyu Lv, Fengrong Wan, Tao Jiang, Kaili Fang, Xueli Zhang, Lei University of Electronic Science and Technology of China School of Information and Communication Engineering Chengdu China Key Laboratory of Complex Aviation Simulation System Beijing China

ISBN: (纸本)9781665426169

Signal bispectral transformation can not only suppress the influence of Gaussian white noise on signal modulation recognition, but also retain the signal amplitude and phase information. It is also used to extract the non-linear characteristics. Compared with other high-order spectra, bispectrum has a simple processing flow. However, the direct use of all bispectrum as signal features will lead to two-dimensional template matching, causing lots of calculations. Converting two-dimensional bispectrum into one-dimensional sequence, for example, extracting slice information of bispectrum, or using integral bispectrum apparently reduce the amount of data to be processed while retaining part of the bispectrum information. We input the extracted bispectral transformation of radar signals into the neural network to realize modulation recognition. The simulations validate our conclusions that our proposed methods still have a high recognition probability while SNR is low. © 2021 IEEE.

关键词： Template matching

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Radar Signal Detection Based on Ambiguity Function and Deep Learning 2

Radar Signal Detection Based on Ambiguity Function and Deep ...

引用

2nd International Conference on Computer Engineering and Application, ICCEA 2021

作者： Lv, Fengrong Dong, Zeyu Wan, Tao Jiang, Kaili Fang, Xueli Zhang, Lei University of Electronic Science and Technology of China School of Information and Communication Engineering Chengdu China Key Laboratory of Complex Aviation Simulation System Beijing China

ISBN: (纸本)9781665426169

The ambiguity function describes the joint characteristics of the signal in the time domain and the frequency domain, and is usually used for signal recognition. The time domain and frequency domain distribution of noise is more spurious than the signal. Its ambiguity function can also reflect its characteristics. However, the direct use of the ambiguity function as the signal feature will increase the amount of calculation of the detection system, so slice it, which reduces the burden on the system for detecting signal information while preserving the information. At the same time, the radar signal detection based on neural network can avoid the influence of artificially setting the threshold on the detection performance of the system. So, we propose an algorithm for inputting the extracted fuzzy function slice sequence into a neural network to realize signal detection. simulation proves that when the signal-To-noise ratio of the received signal is very low, our proposed method still has a high detection probability. © 2021 IEEE.

关键词： Signal detection

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Study on Microstructure and Corrosion Behavior of Welded Joints of 2a12 and 2a97 Aluminum Alloys by Fsw

SSRN

引用

SSRN 2024年

作者： Li, Wen Li, Shaojie Nan, Yang Bai, Xuepiao Li, Weiping School of Materials Science and Engineering Beihang University Beijing100191 China Aviation Key Laboratory of Science and Technology on Advanced Surface Engineering AVIC Manufacturing Technology Institute Beijing100024 China

T-shaped joints of high-strength aluminum alloy welded by friction stir welding (FSW) are expected to replace the traditional riveting structures. However, the corrosion of T-joint still hinder the popularization of FSW in aerospace industry. Herein, T-joints of 2A12 and 2A97 aluminum alloys are prepared and studied via structural characterization and corrosion tests. The microstructures and constituents of different micro zones in T-joints before and after corrosion tests are characterized and analyzed particularly. The internal relationship between different micro zones in T-joints and their corrosion behaviors are clarified, which provides theoretical basis for improving welding process and surface protection after welding. © 2024, The Authors. All rights reserved.

关键词： Friction stir welding

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HMAFlow: Learning More Accurate Optical Flow via Hierarchical Motion Field Alignment

arXiv

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arXiv 2024年

作者： Ma, Dianbo Imamura, Kousuke Gao, Ziyan Wang, Xiangjie Yamane, Satoshi Graduate School of Natural Science & Technology Kanazawa University Japan Information Science Japan Advanced Institute of Science and Technology Japan State Key Laboratory of Automotive Simulation and Control Jilin University China

Optical flow estimation is a fundamental and longstanding visual task. In this work, we present a novel method, dubbed HMAFlow, to improve optical flow estimation in challenging scenes, particularly those involving small objects. The proposed model mainly consists of two core components: a Hierarchical Motion Field Alignment (HMA) module and a Correlation Self-Attention (CSA) module. In addition, we rebuild 4D cost volumes by employing a Multi-Scale Correlation Search (MCS) layer and replacing average pooling in common cost volumes with a search strategy utilizing multiple search ranges. Experimental results demonstrate that our model achieves the best generalization performance compared to other state-of-the-art methods. Specifically, compared with RAFT, our method achieves relative error reductions of 14.2% and 3.4% on the clean pass and final pass of the Sintel online benchmark, respectively. On the KITTI test benchmark, HMAFlow surpasses RAFT and GMA in the Fl-all metric by relative margins of 6.8% and 7.7%, respectively. To facilitate future research, our code will be made available at https://***/BooTurbo/HMAFlow. Copyright © 2024, The Authors. All rights reserved.

关键词： Motion estimation

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粉末床熔融的多材料铺粉过程中粉末扩散的数值研究

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Acta Mechanica Sinica 2023年第1期39卷 23-29页

作者：王林李二垒周宗彦张百成余艾冰 ARC Hub for Computational Particle Technology Department of Chemical & Biological Engineering Monash University Clayton VIC 3800 Australia Delft University of Technology Stevinweg 1 2628 CN Delft The Netherlands Jiangxi Provincial Key Laboratory for Simulation and Modelling of Particulate Systems Jiangxi University of Science and Technology Nanchang 330013 China Beijing Advanced Innovation Center Materials Genome Engineering Advanced Material & Technology Institute University of Science and Technology Beijing Beijing 100083 China

粉末床熔融增材制造技术已应用于功能梯度材料的制造.文献中报道了一种材料成分沿垂直于粉末铺粉方向变化的新设计.基于此设计,本工作采用离散单元数值模拟研究了两种密度差异较大的金属粉末在铺粉过程中颗粒的偏析情况.结果发现,在铺... 详细信息

粉末床熔融增材制造技术已应用于功能梯度材料的制造.文献中报道了一种材料成分沿垂直于粉末铺粉方向变化的新设计.基于此设计,本工作采用离散单元数值模拟研究了两种密度差异较大的金属粉末在铺粉过程中颗粒的偏析情况.结果发现,在铺粉过程中,较大密度粉末(重颗粒)一侧的铺粉量小于较小密度粉末(轻颗粒)的一侧的铺粉量.这种现象表明重颗粒从粉末密度大的一侧向粉末密度较小的一侧扩散.这种扩散受铺粉速度影响较大,铺粉速度越快,扩散越明显.但粉末层厚度对扩散影响不大.结果还表明,重颗粒与轻颗粒间的粒径差异影响扩散较大,减小重颗粒的粒径可能是控制颗粒偏析的一种方案.

关键词：材料成分颗粒偏析功能梯度材料离散单元金属粉末密度差异增材制造技术扩散影响

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Time-varying reliability analysis based on improved toughness exhaustion model and probability density evolution method to predict fatigue damage life

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Engineering Fracture Mechanics 2022年第PartB期276卷

作者： Xu, Huimin Liu, Yating Zhao, Gongwei Ye, Nanhai Key Laboratory of Advanced Design and Simulation Technology for Special Equipment Ministry of Education Hunan University Changsha410082 China

This paper proposed an improved toughness exhaustion model through introducing a stress ratio weighting factor k. Specifically, the k is adopted as a coefficient of the stress amplitude ratio into the damage equivalence equation, which can reflect the influences of loading sequence and interaction effect simultaneously. Then, the value range of k is determined from the theoretical derivation and experimental verification. The experimental results have shown that the improved model can predict the residual life more precisely. Moreover, to solve the problem of the stochastic uncertainty of the fatigue life, the damage state equation using the improved model is evaluated by the probability density evolution method (PDEM). Finally, two sets of experimental data under two-level were used for model validation. Results indicate that the accuracy of time-varying fatigue reliability can be improved with the proposed model. © 2022 Elsevier Ltd

关键词： Reliability analysis

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Symmetry-oriented enumeration method for molecular crystal structure prediction and its application

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Physical Review B 2025年第13期111卷 134112-134112页

作者： Yu Xin Zhuohang Xie Yongshuo Chen Pengyue Gao Hong Jian Zhao Jian Lv Yanchao Wang Yanming Ma Key Laboratory of Material Simulation Methods and Software of Ministry of Education College of Physics Jilin University Changchun 130012 China International Center of Future Science Jilin University Changchun 130012 China Key Laboratory of Physics and Technology for Advanced Batteries (Ministry of Education) College of Physics Jilin University Changchun 130012 China State Key Laboratory of High Pressure and Superhard Materials College of Physics Jilin University Changchun 130012 China

Predicting the thermodynamically stable arrangements of molecular building blocks is crucial for understanding the properties and behaviors of crystalline molecular compounds. Several molecular structure prediction methods have been proposed, leading to successful applications. However, some evolutionary approaches that involve direct sampling within the infinite atomic coordinate space, without symmetry-preserving constraints, tend to suffer from biased sampling, where structures with P1 symmetry become disproportionately dominant. To overcome this limitation, we propose a method that utilizes a finite set of symmetrically inequivalent Wyckoff encodes to sparsely represent the search space of crystalline molecular compounds, thereby improving the coverage of the search space. This method can be used to predict the molecular crystal structures with varying numbers of molecules in the asymmetric unit, from fractional to multiple integers. The applications of this method to three-dimensional molecular crystals of ammonia dihydrate, the NH3−H2O−CH4 mixture, and two-dimensional layered ices revealed a series of energetically quasidegenerate structures with diverse crystal packing motifs. This method expands the scope and utility of molecular building blocks for designing stable molecular crystals, providing a robust framework for achieving extensive tunability in molecular materials design.

关键词： Molecular crystals

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