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Highly ductile hypereutectic Al-Si alloys fabricated by selective laser melting

Journal of Materials Science & Technology 2022年第15期110卷 84-95页

作者： Yafeng Yang Kang Geng Shaofu Li Michael Bermingham R.D.K.Misra State Key Laboratory of Multiphase Complex Systems Institute of Process EngineeringChinese Academy of SciencesBeijing 100190China University of Chinese Academy of Sciences Beijing 100049China School of Mechanical and Mining Engineering University of QueenslandSaint LuciaQueensland 4072Australia Department of Metallurgical Materials and Biomedical EngineeringUniversity of Texas at El Paso500 W University AvenueEl PasoTX 79968USA

In the endeavor to maximize the refinement effect of primary Si and alleviate the inherent brittleness of hypereutectic Al-Si alloy,the approach of coating P as a modifier on powder was *** ultimate aim was to create more heterogeneous fine Al P nucleus and enhance the nucleation efficiency of primary Si on Al P to refine the coarse primary Si to nano-scale during 3D *** the combination of large undercooling and high density of nucleation sites,the size of primary Si was successfully refined to 200–300 nm and the divorced eutectic was also induced to modify the microstructure of *** the presence of nano-scale primary Si,the melting pool boundary(MPB)feature disappeared and the fracture mechanism also changed from load transfer to interfacial *** with the pristine alloy,the ductility was increased four times without significantly changing the ultimate tensile strength(UTS)and wear *** improvement of ductility is attributed to the refinement of primary Si,the disappearance of MPB features and the formation of divorced *** optimal tensile properties were:UTS-482 MPa,yield strength-320 MPa and ductility of 8.1%at 0.05 wt.%*** are comparable to those for high-strength Al alloys.

关键词： Al-Si alloys Heterogeneous nucleation Ductility Powder processing Selective laser melting

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Self-powered tactile sensor for real-time recognition of Morse code based on machine learning

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Nano Research 2025年第2期18卷 760-768页

作者： Shenxing Tan Yang Jiang Xujiang Chao Fei Liang Ripeng Li Tao Jiang Hai-Dong Yu Zhong Lin Wang Guangzhou Institute of Blue Energy Guangzhou 510555China Frontiers Science Center for Flexible Electronics Xi'an Institute of Flexible Electronics(IFE)and Xi'an Institute of Biomedical Materials&EngineeringNorthwestern Polytechnical UniversityXi'an 710072China Beijing Key Laboratory of Micro-Nano Energy and Sensor Center for High-Entropy Energy and SystemsBeijing Institute of Nanoenergy and NanosystemsChinese Academy of SciencesBeijing 101400China School of Nanoscience and Engineering University of Chinese Academy of SciencesBeijing 100049China School of Mechanical Engineering Northwestern Polytechnical UniversityXi’an 710072China School of Computer Science(National Pilot Software Engineering School) Beijing University of Posts and TelecommunicationsBeijing 100876China

Developing lightweight,green,and flexible wearable electronics with high sensitivity and multifunctional sensing capabilities is of important significance in the field of outdoor sports,such as mountaineering,animal tracking and *** work proposes a silk fibroin fibers-based triboelectric nanogenerator(SF TENG)to harvest tiny energy from human fingertip tapping and act as a self-powered tactile *** SF-TENG adopts a green,efficient,and low-cost fabrication strategy,in which a breathable and electropositive silk fibroin fiber membrane and a silver conductive layer are prepared by electrostatic spinning and magnetron sputtering,and combined with a conductive cloth and a breathable tape to form a flexible sensor that can be attached to a human *** thin and soft portable TENG device,having a thickness of only 0.3 mm and a mass of 354 mg at the dimension of 4.5 cm×4.5 cm,can generate a maximum power density of 1.0 mW·m^(–2).Furthermore,the SF-TENG has excellent sensitivity of 1.767 mV·Pa^(–1) with good cyclic *** superior sensing characteristics provide new avenues for Morse code applications toward outdoor wearable autonomous *** proposed SF-TENG offers promising solutions in multi-scenario outdoor sport,human-machine interface interaction,and security systems.

关键词： flexible electronics triboelectric nanogenerator silk fibroin Morse code translation

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Incentivizing Fresh Information Acquisition via Age-Based Reward

IEEE Transactions on Networking

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IEEE Transactions on Networking 2025年第3期33卷 1174-1188页

作者： Zhiyuan Wang Qingkai Meng Shan Zhang Hongbin Luo School of Computer Science and Engineering Beihang University Beijing China Zhongguancun Laboratory Beijing China State Key Laboratory of Virtual Reality Technology and Systems Beijing China Institute of Artificial Intelligence Beihang University Beijing China State Key Laboratory of Software Development Environment Beijing China

Many Internet platforms are information-oriented and crowd-based. They collect fresh information of various points of interest (PoIs) relying on users who happen to be nearby the PoIs. The platform will offer rewards to incentivize users and compensate their costs incurred from information acquisition. In practice, a user’s cost is his/her private information, thus both the user cost and its distribution are hidden to the platform, making it challenging to determine the optimal rewarding decision. In this paper, we investigate how the platform dynamically rewards the users, aiming to jointly reduce the age of information (AoI) and the operational expenditure (OpEx). Due to the hidden cost distribution, this is an online non-convex learning problem with bandit feedback. To overcome the challenge, we first design an age-based reward scheme, which decouples the OpEx from the unknown cost distribution and enables the platform to accurately control its OpEx. We then take advantage of the age-based reward scheme and propose an exponentially discretizing and learning (EDAL) policy for platform operation. We prove that the EDAL policy performs asymptotically as well as the optimal decision (derived from the cost distribution). Simulation results show that the age-based reward scheme protects the platform’s OpEx from the influence of the user crowd characteristics, and also verify the asymptotic optimality of the EDAL policy.

关键词： Costs Reviews Soft sensors Pricing Optimization Electronic mail Stochastic processes Simulation Laboratories Internet

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Nonrigid Object Contact Estimation With Regional Unwrapping Transformer

arXiv

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arXiv 2023年

作者： Xie, Wei Zhao, Zimeng Li, Shiying Zuo, Binghui Wang, Yangang Southeast University China The Key Laboratory of Measurement and Control of Complex Systems of Engineering Ministry of Education Nanjing China

Acquiring contact patterns between hands and nonrigid objects is a common concern in the vision and robotics community. However, existing learning-based methods focus more on contact with rigid ones from monocular images. When adopting them for nonrigid contact, a major problem is that the existing contact representation is restricted by the geometry of the object. Consequently, contact neighborhoods are stored in an unordered manner and contact features are difficult to align with image cues. At the core of our approach lies a novel hand-object contact representation called RUPs (Region Unwrapping Profiles), which unwrap the roughly estimated hand-object surfaces as multiple high-resolution 2D regional profiles. The region grouping strategy is consistent with the hand kinematic bone division because they are the primitive initiators for a composite contact pattern. Based on this representation, our Regional Unwrapping Transformer (RUFormer) learns the correlation priors across regions from monocular inputs and predicts corresponding contact and deformed transformations. Our experiments demonstrate that the proposed framework can robustly estimate the deformed degrees and deformed transformations, which makes it suitable for both nonrigid and rigid contact. © 2023, CC BY-NC-SA.

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Full-State Planning of Nonholonomic Mobile Robots via Dynamic Velocity Vector Fields

Full-State Planning of Nonholonomic Mobile Robots via Dynami...

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Chinese Control and Decision Conference, CCDC

作者： Xiaodong He Zhongkui Li Department of Mechanics and Engineering Science State Key Laboratory for Turbulence and Complex Systems College of Engineering Peking University Beijing China

As a rigid body, the nonholonomic mobile robot contains both states of position and orientation. In order to plan these states simultaneously, this paper investigates the full-state planning problem of nonholonomic mobile robots, in the sense that the robots should reach the specified positions and meanwhile point to the desired orientations at the terminal time. To this end, we propose a velocity vector field which guides the mobile robots to the goal points. Particularly, the dynamics of the robot orientation is brought into the vector field, so that the attitude angle of the robot can converge to the specified value following the orientation dynamics. Furthermore, we study the obstacle avoidance and mutual-robot-collision avoidance by proposing another velocity vector field, which guides the robots moving along the tangential direction of the dangerous areas. Finally, several numerical simulation examples are provided to support the theoretical results.

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Multi-agent Coordination Under Temporal Logic Tasks and Team-Wise Intermittent Communication

Multi-agent Coordination Under Temporal Logic Tasks and Team...

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IEEE Conference on Decision and Control

作者： Junjie Wang Meng Guo Zhongkui Li Department of Mechanics and Engineering Science State Key Laboratory for Turbulence and Complex Systems College of Engineering Peking University Beijing China

Multi-agent systems outperform single agent in complex collaborative tasks. However, in large-scale scenarios, ensuring timely information exchange during decentralized task execution remains a challenge. This work presents an online decentralized coordination scheme for multi-agent systems under complex local tasks and intermittent communication constraints. Unlike existing strategies that enforce all-time or intermittent connectivity, our approach allows agents to join or leave communication networks at aperiodic intervals, as deemed optimal by their online task execution. This scheme concurrently determines local plans and refines the communication strategy, i.e., where and when to communicate as a team. A decentralized potential game is modeled among agents, for which a Nash equilibrium is generated iteratively through online local search. It guarantees local task completion and intermittent communication constraints. Extensive numerical simulations are conducted against several strong baselines.

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Multi-agent Coordination Under Temporal Logic Tasks and Team-Wise Intermittent Communication

arXiv

引用

arXiv 2023年

作者： Wang, Junjie Guo, Meng Li, Zhongkui State Key Laboratory for Turbulence and Complex Systems Department of Mechanics and Engineering Science College of Engineering Peking University Beijing China

关键词： Multi agent systems

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Effectiveness of Koopman Autoencoder Predicting Nonlinear System States: Effect of Latent Layer Neuron Number

Effectiveness of Koopman Autoencoder Predicting Nonlinear Sy...

引用

2022 Chinese Automation Congress, CAC 2022

作者： Zhou, Jun Jia, Yubin Liu, Zhimin Yong, Panxiao Guo, Jun The School of Automation Southeast University Jiangsu Nanjing210096 China The Key Laboratory of Measurement and Control of Complex Systems of Engineering Ministry of Education Southeast University Nanjing210096 China

ISBN: (纸本)9781665465335

Researchers have always been popular with analyzing and controlling nonlinear systems, yet most methods are based on local linearized models. As an alternative, Koopman theory was introduced to solve global linearization problems. Koopman operator is infinite-dimensional and has the ability to globally linearize nonlinear systems without information loss. In this work, a Koopman autoencoder, which combines the Koopman operator and autoencoder network, is used for predicting nonlinear systems. The autoencoder network is designed to find an approximate finite-dimensional Koopman operator. An inverted pendulum dynamic system is used to evaluate the effectiveness of the Koopman autoencoder, and accurate prediction results have been achieved. Furthermore, we discussed the effect of latent layer neuron number in the Koopman autoencoder, prediction results are given, and the best number of latent layer neurons for this system is found. © 2022 IEEE.

关键词： Nonlinear systems

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4D Myocardium Reconstruction with Decoupled Motion and Shape Model

arXiv

引用

arXiv 2023年

作者： Yuan, Xiaohan Liu, Cong Wang, Yangang Southeast University China The Key Laboratory of Measurement Control of Complex Systems of Engineering Ministry of Education Nanjing China

Estimating the shape and motion state of the myocardium is essential in diagnosing cardiovascular diseases. However, cine magnetic resonance (CMR) imaging is dominated by 2D slices, whose large slice spacing challenges inter-slice shape reconstruction and motion acquisition. To address this problem, we propose a 4D reconstruction method that decouples motion and shape, which can predict the inter-/intra- shape and motion estimation from a given sparse point cloud sequence obtained from limited slices. Our framework comprises a neural motion model and an end-diastolic (ED) shape model. The implicit ED shape model can learn a continuous boundary and encourage the motion model to predict without the supervision of ground truth deformation, and the motion model enables canonical input of the shape model by deforming any point from any phase to the ED phase. Additionally, the constructed ED-space enables pre-training of the shape model, thereby guiding the motion model and addressing the issue of data scarcity. We propose the first 4D myocardial dataset as we know and verify our method on the proposed, public, and cross-modal datasets, showing superior reconstruction performance and enabling various clinical applications. Copyright © 2023, The Authors. All rights reserved.

关键词： Motion estimation

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A Secure Clock Synchronization Scheme for Wireless Sensor Networks Against Malicious Attacks

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Journal of systems Science & complexity 2021年第6期34卷 2125-2138页

作者： ZHANG Xuxin LIU Yanzhang ZHANG Ya School of Automation Southeast UniversityNanjing 210096China Key Laboratory of Measurement and Control of Complex Systems of Engineering Ministry of EducationNanjing 210096China China Electric Power Research Institute Nanjing 210003China

This paper studies the secure and accurate clock synchronization problem for sensor networks with time-varying delays and malicious attacks.A novel clock synchronization scheme based on the attack detection mechanism,attack compensation,and maximum consensus protocol is *** proposed scheme starts with the detection of the malicious attacks and the clock data under attacks is *** the basis,software clock parameters are updated so that all the nodes in the network can have the same software skew and offset,so the clock synchronization can be ***,it is theoretically proved that the proposed scheme can achieve the attack detection correctly,and further can guarantee a secure and accurate clock *** addition,extensive simulations are also conducted to validate the effectiveness of the proposed scheme.

关键词： Clock synchronization communication delays consensus malicious attacks wireless sensor networks

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