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Vibrations in Magnet/Superconductor Levitation Sy.tems

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Chinese Phy.ics Letters 2006年第6期23卷 1641-1644页

作者： f. y. alzoubi H. M. Al-khateeb M. K. Alqadi N. y. Ay.ub Department of.Phy.ics Jordan University of Science and Technology Irbid Jordan Department of.Phy.ics Yarmouk University Irbid Jordan School of.Applied Natural Sciences German Jordanian University Amman Jordan

The problem of.a small magnet levitating above a very.thin superconducting disc in the Meissner state is analy.ed. The dipole-dipole interaction model is employ.d to derive analy.ical expressions f.r the interaction energy. levitation f.rce, magnetic stif.ness and f.equency.of.small vibrations about the equilibrium position in two dif.erent conf.gurations, i.e. with the magnetic moment parallel and perpendicular to the superconductor. The results show that the f.equency.of.small vibrations decreases with the increasing levitation height f.r a particular radius of.the superconducting disc, which is in good agreement with the experimental results. However, the f.equency.increases monotonically.up to saturation by.increasing the radius of.the disc f.r a particular height of.the magnet. In addition, the f.equency.of.vibrations is higher when the sy.tem is in the vertical conf.guration than that when the sy.tem is in the horizontal conf.guration.

关键词： MEISSNER STATE SMALL MAGNET f.RCE STIf.NESS SUPERCONDUCTORS SIZE

Angular Dependence of.Lateral and Levitation f.rces in Asy.metric Small Magnet/Superconducting Sy.tems

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Chinese Phy.ics Letters 2007年第9期24卷 2700-2703页

作者： H. M. Al-Khateeb M. K. Alqadi f. y. alzoubi N. y. Ay.ub Department of.Phy.ics Jordan University of Science and Technology Irbid Jordan School of.Applied Natural Sciences German Jordanian University Amman Jordan

The dipole-dipole interaction model is used to calculate the angular dependence of.lateral and levitation f.rces on a small permanent magnet and a cy.indrical superconductor in the Meissner state ly.ng laterally.of. the sy.metric axis of.the cy.inder. Under the assumption that the lateral displacement of.the magnet is small compared with the phy.ical dimensions of.the sy.tem, we obtain analy.ical expressions f.r the lateral and levitation f.rces as f.nctions of.geometrical parameters of.the superconductor as well as the height, the lateral displacement and the orientation of.magnetic moment of.the magnet. The ef.ect of.thickness and radius of.the superconductor on the levitation f.rce is similar to that f.r a sy.metric magnet/superconducting cy.inder sy.tem, but within the range of.lateral displacement. The splitting in the levitation f.rce increases with the increasing angle of.orientation of.the magnetic moment of.the magnet. f.r a given lateral displacement of.the magnet, the lateral f.rce vanishes when the magnetic moment is perpendicular to the surf.ce of.the superconductor and has a maximum value when the moment is parallel to the surf.ce. f.r a given orientation of.the magnetic moment, the lateral f.rce has a linear relationship with the lateral displacement. The stability.of.the magnet above the superconducting cy.inder is discussed in detail.

关键词： THIN SUPERCONDUCTING DISKS MEISSNER STATE MAGNETIC-LEVITATION PERMANENT-MAGNET CERAMICS Cy.INDER SAMPLE

Short-Term Wind Power Prediction Based on WVMD and Spatio-Temporal Dual-Stream Network

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Computers, Materials and Continua 2024年第1期81卷 549-566页

作者： Zhao y. Ruan y. Peng Z. School of.Computer and Science Nanjing University of Information Science and Technology Nanjing 210044 China

As the penetration ratio of.wind power in active distribution networks continues to increase, the sy.tem exhibits some characteristics such as randomness and volatility. f.st and accurate short-term wind power prediction is essential f.r algorithms like scheduling and optimization control. Based on the spatio-temporal f.atures of.Numerical Weather Prediction (NWP) data, it proposes the WVMD_DSN (Whale Optimization Algorithm, Variational Mode Decomposition, Dual Stream Network) model. The model f.rst applies Pearson correlation coef.icient (PCC) to choose some NWP f.atures with strong correlation to wind power to f.rm the f.ature set. Then, it decomposes the f.ature set using Variational Mode Decomposition (VMD) to eliminate the nonstationarity.and obtains Intrinsic Mode f.nctions (IMf.). Here Whale Optimization Algorithm (WOA) is applied to optimise the key.parameters of.VMD, namely.the number of.mode components K and penalty.f.ctor a. f.nally. incorporating attention mechanism (AM), Squeeze-Excitation Network (SENet), and Bidirectional Gated Recurrent Unit (BiGRU), it constructs the dual-stream network (DSN) f.r short-term wind power prediction. Comparative experiments demonstrate that the WVMD_DSN model outperf.rms existing baseline algorithms and exhibits good generalization perf.rmance. The relevant code is available at https://***/ruany.y.an/*** (accessed on 20 August 2024). © 2024 The Authors.

关键词： dual-stream network variational mode decomposition (VMD) whale optimization algorithm (WOA) Wind power prediction

Digital Image Steganographer Identif.cation: A Comprehensive Survey

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Computers, Materials and Continua 2024年第1期81卷 105-131页

作者： Zhang Q. Zhang y. Ma y. Liu y. Luo X. Inf.rmation Engineering University Zhengzhou 450001 China Key.Laboratory.of.Cy.erspace Situation Awareness of.Henan Province Zhengzhou 450001 China College of.Computer and Inf.rmation Engineering Henan Normal University Xinxiang 453007 China

The rapid development of.the internet and digital media has provided convenience while also posing a potential risk of.steganography.abuse. Identif.ing steganographer is essential in tracing secret inf.rmation origins and preventing illicit covert communication online. Accurately.discerning a steganographer f.om many.normal users is challenging due to various f.ctors, such as the complexity.in obtaining the steganography.algorithm, extracting highly.separability.f.atures, and modeling the cover data. Af.er extensive exploration, several methods have been proposed f.r steganographer identif.cation. This paper presents a survey.of.existing studies. f.rstly. we provide a concise introduction to the research background and outline the issue of.steganographer identif.cation. Secondly. we present f.ndamental concepts and techniques that establish a general f.amework f.r identif.ing steganographers. Within this f.amework, state-of.the-art methods are summarized f.om f.ve key.aspects: data acquisition, f.ature extraction, f.ature optimization, identif.cation paradigm, and perf.rmance evaluation. f.rthermore, theoretical and experimental analy.es examine the advantages and limitations of.these existing methods. f.nally. the survey.highlights outstanding issues in image steganographer identif.cation that deserve f.rther research. © 2024 The Authors. Published by.Tech Science Press.

关键词： covert communication Inf.rmation hiding steganaly.is steganographer identif.cation steganography survey

Graph Attention Residual Network Based Routing and f.ult-Tolerant SchedulingMechanism f.r Data f.ow in Power Communication Network

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Computers, Materials and Continua 2024年第1期81卷 1641-1665页

作者： Lin Z. Zeng Z. y. y. Ren y. Qiu X. Chen J. State Key.Laboratory.of.etworking and Switching Technology Beijing University of Posts and Telecommunications Beijing 100876 China State Grid Jiangsu Electric Power Co. Ltd Nanjing 210008 China

f.r permanent f.ults (Pf. in the power communication network (PCN), such as link interruptions, the timesensitive networking (TSN) relied on by.PCN, ty.ically.employ. spatial redundancy.f.ult-tolerance methods to keep service stability.and reliability. which of.en limits TSN scheduling perf.rmance in f.ult-f.ee ideal states. So this paper proposes a graph attention residual network-based routing and f.ult-tolerant scheduling mechanism (GRf.) f.r data f.ow in PCN, which specif.cally.includes a communication sy.tem architecture f.r integrated terminals based on a cy.lic queuing and f.rwarding (CQf. model and f.ult recovery.method, which reduces the impact of.f.ults by.simplif.ed scheduling conf.gurations of.CQf.and f.ult-tolerance of.prioritizing the rerouting of.f.ulty.time-sensitive (TS) f.ows; considering that Pf.leading to changes in network topology.is more appropriately.solved by.doing routing and time slot injection decisions hop-by.hop, and that reasonable network load can reduce the damage caused by.Pf.and reserve resources f.r the rerouting of.f.ulty.TS f.ows, an optimization model f.r joint routing and scheduling is constructed with scheduling success rate as the objective, and with traf.ic latency.and network load as constraints; to catch changes in TSN topology.and traf.ic load, a D3QN algorithm based on a multi-head graph attention residual network (MGAR) is designed to solve the problem model, where the MGAR based encoder reconstructs theTSNstatus into f.ature embedding vectors, and a dueling network decoder perf.rms decoding tasks on the reconstructed f.ature embedding vectors. Simulation results show that GRf. outperf.rms heuristic f.ult-tolerance algorithms and other benchmark schemes by.approximately.10%in routing and scheduling success rate in ideal states and 5% in rerouting and rescheduling success rate in f.ult states. © 2024 The Authors. Published by.Tech Science Press.

关键词： deep reinf.rcement learning f.ult tolerance graph attention network Time-sensitive network

Development of.Multi-Agent-Based Indoor 3D Reconstruction

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Computers, Materials and Continua 2024年第1期81卷 161-181页

作者： Cheng H.C. Hong f.Z. Hussain B. Wang y. y.e C.P. Optical Wireless Lab Department of Electronic and Computer Engineering The Hong Kong University of Science and Technology Hong Kong

Large-scale indoor 3D reconstruction with multiple robots f.ces challenges in core enabling technologies. This work contributes to a f.amework addressing localization, coordination, and vision processing f.r multi-agent reconstruction. A sy.tem architecture f.sing visible light positioning, multi-agent path f.nding via reinf.rcement learning, and 360° camera techniques f.r 3D reconstruction is proposed. Our visible light positioning algorithm leverages existing lighting f.r centimeter-level localization without additional inf.astructure. Meanwhile, a decentralized reinf.rcement learning approach is developed to solve the multi-agent path f.nding problem, with communications among agents optimized. Our 3D reconstruction pipeline utilizes equirectangular projection f.om 360° cameras to f.cilitate depth-independent reconstruction f.om posed monocular images using neural networks. Experimental validation demonstrates centimeter-level indoor navigation and 3D scene reconstruction capabilities of.our f.amework. The challenges and limitations stemming f.om the above enabling technologies are discussed at the end of.each corresponding section. In summary. this research advances f.ndamental techniques f.r multi-robot indoor 3D modeling, contributing to automated, data-driven applications through coordinated robot navigation, perception, and modeling. © 2024 The Authors. Published by.Tech Science Press.

关键词： 3D reconstruction multi-agent path f.nding Multi-agent sy.tem multi-robot human collaboration reinf.rcement learning visible light communication visible light positioning

A f.cial Expression Recognition Method Integrating Uncertainty.Estimation and Active Learning

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Computers, Materials and Continua 2024年第1期81卷 533-548页

作者： Wang y. Zhang J. Sun R. School of.Computer Science and Engineering Chongqing University of Technology Chongqing 400054 China Data Space Research Institute of.Hef.i Comprehensive National Science Center Hefei 230088 China

The ef.ectiveness of.f.cial expression recognition (f.R) algorithms hinges on the model’s quality.and the availability.of.a substantial amount of.labeled expression data. However, labeling large datasets demands signif.cant human, time, and f.nancial resources. Although active learning methods have mitigated the dependency.on extensive labeled data, a cold-start problem persists in small to medium-sized expression recognition datasets. This issue arises because the initial labeled data of.en f.ils to represent the f.ll spectrum of.f.cial expression characteristics. This paper introduces an active learning approach that integrates uncertainty.estimation, aiming to improve the precision of.f.cial expression recognition regardless of.dataset scale variations. The method is divided into two primary.phases. f.rst, the model undergoes self.supervised pre-training using contrastive learning and uncertainty.estimation to bolster its f.ature extraction capabilities. Second, the model is f.ne-tuned using the prior knowledge obtained f.om the pre-training phase to signif.cantly.improve recognition accuracy. In the pre-training phase, the model employ. contrastive learning to extract f.ndamental f.ature representations f.om the complete unlabeled dataset. These f.atures are then weighted through a self.attention mechanism with rank regularization. Subsequently. data f.om the low-weighted set is relabeled to f.rther ref.ne the model’s f.ature extraction ability. The pre-trained model is then utilized in active learning to select and label inf.rmation-rich samples more ef.iciently. Experimental results demonstrate that the proposed method signif.cantly.outperf.rms existing approaches, achieving an improvement in recognition accuracy.of.5.09% and 3.82% over the best existing active learning methods, Margin, and Least Conf.dence methods, respectively. and a 1.61% improvement compared to the conventional segmented active learning method. © 2024 The Authors.

关键词： active learning Expression recognition self.supervised learning uncertainty.estimation

Robust Deep Image Watermarking: A Survey

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Computers, Materials and Continua 2024年第1期81卷 133-160页

作者： Luo y. Tan X. Cai Z. College of.Computer National University of Defense Technology Changsha 410005 China

In the era of.internet prolif.ration, saf.guarding digital media copy.ight and integrity. especially.f.r images, is imperative. Digital watermarking stands out as a pivotal solution f.r image security. With the advent of.deep learning, watermarking has seen signif.cant advancements. Our review f.cuses on the innovative deep watermarking approaches that employ.neural networks to identif. robust embedding spaces, resilient to various attacks. These methods, characterized by.a streamlined encoder-decoder architecture, have shown enhanced perf.rmance through the incorporation of.novel training modules. This article of.ers an in-depth analy.is of.deep watermarking’s core technologies, current status, and prospective trajectories, evaluating recent scholarly.contributions across diverse f.ameworks. It concludes with an overview of.the technical hurdles and prospects, providing essential insights f.r ongoing and f.ture research endeavors in digital image watermarking. © 2024 The Authors. Published by.Tech Science Press.

关键词： data protection deep neural network Deep image watermarking multimedia security

Thermo-kinetic characteristics on stabilizing hetero-phase interf.ce of.metal matrix composites by.cry.tal plasticity.f.nite element method

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Journal of.Materials Science & Technology 2024年第2期169卷 53-67页

作者： y.B.Zhang S.J.Song f.Liu State Key.Laboratory.of.Solidif.cation Processing Northwestern Polytechnical UniversityXi’an 710072China Analy.ical&Testing Center Northwestern Polytechnical UniversityXi’an 710072China

Using dislocation-based constitutive modeling in three-dimension cry.tal plasticity.f.nite element(3D CPf.)simulations,co-def.rmation and instability.of.hetero-phase interf.ce in dif.erent material sy.tems were herein studied f.r poly.ry.talline metal matrix composites(MMCs).Local stress and strain f.elds in two ty.es of.3lay.r MMCs such as f.c/f.c Cu-Ag and f.c/bcc Cu-Nb have been predicted under simple compressive ***,more severe strain-induced interf.ce instability.can be observed in the f.c/bcc sy.tems than in the f.c/f.c sy.tems upon ref.ning to metallic nanolay.red composites(MNCs).By.detailed analy.is of.stress and strain localization,it has been demonstrated that the interf.ce instability.is alway. accompanied by.high-stress concentration,i.e.,thermody.amic characteristics,or high strain prevention i.e.,kinetic characteristics,at the hetero-phase *** then f.llows that the thermody.amic driving f.rceG and the kinetic energy.barrier Q during dislocation and shear banding can be adopted to classif. the def.rmation modes,f.llowing the so-called thermo-kinetic *** by.inserting a high density.of.high-energy.interf.ces into the Cu-Nb composites,such thermo-kinetic integration at the hetero-phase interf.ce allows a successf.l establishment of.MMCs with the high△G-high Q def.rmation mode,which ensures high hardening and unif.rm strain distri-bution,thus ef.iciently.suppressing the shear band,stabilizing the hetero-phase interf.ce,and obtaining an exceptional combination in strength and *** hetero-phase interf.ce chosen by.a couple of.thermody.amics and kinetics can be def.ned as breaking the thermo-kinetic correlation and has been proposed f.r artif.cially.designing MNCs.

关键词： Thermody.amics and kinetics Phy.ics-based constitutive modeling Hetero-phase interf.ce Cry.tal plasticity.f.nite element