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Local-contrastive-learning machine with both generalization and adversarial robustness: A statistical physics analysis

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Science China(Physics,Mechanics & Astronomy) 2025年第1期Mechanics & Astronomy) .卷 109-123页

作者： Mingshan Xie yuchen wang Haiping Huang PMI Lab School of Physics Sun Yat-sen University Guangdong Provincial Key Laboratory of Magnetoelectric Physics and Devices Sun Yat-sen University

Distinct from human cognitive processing, deep neural networks trained by backpropagation can be easily fooled by adversarial examples. To design a semantically meaningful representation learning, we discard backpropagation, and instead, propose a local contrastive learning, where the representations for the inputs bearing the same label shrink(akin to boson) in hidden layers,while those of different labels repel(akin to fermion). This layer-wise learning is local in nature, being biologically plausible.A statistical mechanics analysis shows that the target fermion-pair-distance is a key parameter. Moreover, the application of this local contrastive learning to MNIST benchmark dataset demonstrates that the adversarial vulnerability of standard perceptron can be greatly mitigated by tuning the target distance, i.e., controlling the geometric separation of prototype manifolds.

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Quaternion-Based Adaptive Trajectory Tracking Control of a Rotor-Missile with Unknown Parameters Identification

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Defence Technology（防务技术） 2024年第1期31卷 375-386页

作者： Jie Zhao Zhongjiao Shi yuchen wang Wei wang Beijing Institute of Technology Beijing 100081China

This paper investigates the adaptive trajectory tracking control problem and the unknown parameter identification problem of a class of rotor-missiles with parametric system ***,considering the uncertainty of structural and aerodynamic parameters,the six-degree-of-freedom(6Do F) nonlinear equations describing the position and attitude dynamics of the rotor-missile are established,respectively,in the inertial and body-fixed reference ***,a hierarchical adaptive trajectory tracking controller that can guarantee closed-loop stability is proposed according to the cascade characteristics of the 6Do F ***,a memory-augmented update rule of unknown parameters is proposed by integrating all historical data of the regression *** long as the finitely excited condition is satisfied,the precise identification of unknown parameters can be ***,the validity of the proposed trajectory tracking controller and the parameter identification method is proved through Lyapunov stability theory and numerical simulations.

关键词： Rotor-missile Adaptive control Parameter identification Quaternion control

Observer-based robust high-order fully actuated attitude autopilot design for spinning glide-guided projectiles

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Defence Technology（防务技术） 2024年第4期34卷 282-294页

作者： Wei wang yuchen wang Shiwei Chen Yongcang Guo Zhongjiao Shi School of Aerospace Engineering Beijing Institute of TechnologyBeijing 10081China Northwest Industries Group CO. Ltd.Xi'an 710043China

This paper investigates the design of an attitude autopilot for a dual-channel controlled spinning glideguided projectile(SGGP),addressing model uncertainties and external *** on fixed-time stable theory,a disturbance observer with integral sliding mode and adaptive techniques is proposed to mitigate total disturbance effects,irrespective of initial *** introducing an error integral signal,the dynamics of the SGGP are transformed into two separate second-order fully actuated ***,employing the high-order fully actuated approach and a parametric approach,the nonlinear dynamics of the SGGP are recast into a constant linear closed-loop system,ensuring that the projectile's attitude asymptotically tracks the given goal with the desired *** the proposed composite control framework,the ultimately uniformly bounded stability of the closed-loop system is rigorously demonstrated via the Lyapunov *** of the effectiveness of the proposed attitude autopilot design is provided through extensive numerical simulations.

关键词： Spinning glide-guided projectile Attitude control Sliding mode disturbance observer Fixed-time stable theory High-order fully actuated approach

Intrinsic Strengthening of Coherent Twin Boundaries in Copper

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Journal of Materials Science & Technology 2009年第2期25卷 211-214页

作者： Yanfen Luo yuchen wang Yanbo wang Yuanming wang Manling Sui Shenyang National Laboratory for Materials Science （SYNL） Institute of Metal Research Chinese Academy of Sciences Shenyang 110016 China

Molecular dynamics （MD） simulations were applied to simulate the deformation process of copper with different density of parallel coherent twin boundaries （TBs）. It is shown that the strength of perfect copper crystal enhances with increasing coherent TB density. Based on the local hydrostatic pressure analysis, we found that stress concentrations are more likely to form in the interior of the crystal rather than around the TBs. Since the dislocation nucleation is suppressed in the vicinity of the coherent TBs and each TB plane hinders dislocations from propagating, the coherent TBs can be regarded as an intrinsic strengthening phase relative to perfect crystal.

关键词： Twin boundary Dislocation Molecular dynamic simulation

Electrical switching of spin-polarized current in multiferroic tunneling junctions

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npj Computational Materials 2022年第1期8卷 1877-1885页

作者： Ligong Zhang yuchen wang Xiaoyan Liu Fei Liu School of Integrated Circuits Peking University100871BeijingChina Beijing Advanced Innovation Center for Integrated Circuits 100871BeijingChina

The generation and manipulation of spin-polarized current are critical for spintronic *** this work,we propose a mechanism to generate and switch spin-polarized current by an electric field in multiferroic tunnel junctions(MFTJs),with symmetric interface terminations in an antiparallel magnetic *** such devices,different spin tunneling barriers are realized by the magnetoelectric coupling effect,resulting in a spin-polarized *** reversing the electric polarization of the ferroelectric layer,the spin polarization of current is efficiently switched for the exchange of spin tunneling *** first-principles quantum transport calculations,we show that a highly spin-polarized current is obtained and manipulated by the electric field in hafnia-based MFTJs based on the proposed *** also demonstrate that four resistance states are realized in Co/HfO_(2)/Co junctions with asymmetric interface *** work provides a promising approach for realizing the electrical control of spin current for spintronic applications.

关键词： mechanism. polarized tunneling

Electrodeposited 3D hierarchical NiFe microflowers assembled from nanosheets robust for the selective electrooxidation of furfuryl alcohol

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Green Energy & Environment 2023年第3期8卷 874-882页

作者： Biying Liu Man Zhang Yaoyu Liu yuchen wang Kai Yan Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology School of Environmental Science and EngineeringSun Yat-sen University135 Xingang Xi RoadGuangzhou510275China

A robust and green strategy for the selective upgrading of biomass-derived platform chemicals towards highly valuable products is important for the sustainable ***,the efficient electrocatalytic oxidation of biomass-derived furfuryl alcohol(FFA)into furoic acid(FurAc)catalyzed by the electrodeposited non-precious NiFe microflowers was successfully reached under the low temperature and ambient *** 3D hierarchical NiFe microflowers assembled from ultrathin nanosheets were controllably synthesized by the electrodeposition method and uniformly grown on carbon fiber paper(CFP).Electrochemical analysis confirmed that NiFe nanosheets more preferred in the selective oxidation of FFA(FFAOR)than oxygen evolution reaction(OER).The linear sweep voltammetry(LSV)in FFAOR displayed a clear decrease towards lower potential,resulting in 30 mV reduction of overpotential at 20 mA cm^(-2) compared with that of *** optimal catalyst Ni_(1)Fe_(2) nanosheets exhibited the highest selectivity of FurAc(94.0%)and 81.4%conversion of FFA within 3 ***,the influence of various reaction parameters on FFAOR was then explored in *** that,the reaction pathway was investigated and rationally *** outstanding performance for FFAOR can be ascribed to the unique structure of 3D flower-like NiFe nanosheets and oxygen vacancies,resulting in large exposure of active sites,faster electron transfer and enhanced adsorption of *** findings highlight a facile and convenient mean with a promising green future,which is promising for processing of various biomass-derived platform chemicals into value-added products.

关键词： Electrodeposition Microflowers assembled by nanosheets NiOOH Oxygen vacancies Electrochemical oxidation Furfuryl alcohol Furoic acid

Corrosion and aging of organic aviation coatings:A review

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Chinese Journal of Aeronautics 2023年第4期36卷 1-35页

作者： Tianyu ZHANG Teng ZHANG Yuting HE yuchen wang Yaping BI Air Force Engineering University Xi’an 710038China

Organic anticorrosive aviation coatings are an effective guarantee for aviation structure,since aircraft corrosion can lead to great economic *** it is during ground parking or air cruises,organic aviation coatings are important barriers to the corrosion of aviation *** the vigorous development of the aviation industry,organic aviation coatings continue to meet the challenges of diverse,complex,and harsh service *** review analyzes and summarizes the research status of the types and development of organic aviation coatings,influencing factors and mechanisms,experimental methods,calendar life research methods,and modification *** also summarizes the research results that have been achieved to *** current research deficiencies in the equivalence relationship between atmospheric exposure and artificial acceleration,failure criteria and life prediction were pointed out,and nano-modification technology,and future research strategies and directions that need breakthroughs are discussed.

关键词： Aging Calendar life Classification Corrosion Experimental methods Modification Organic aviation coatings

Enhancing photocatalytic performance of metal-organic frameworks for CO_(2) reduction by a bimetallic strategy

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Chinese Chemical Letters 2022年第4期33卷 2065-2068页

作者： Jihong Zhang yuchen wang Hongjuan wang Dichang Zhong Tongbu Lu MOE International Joint Laboratory of Materials Microstructure Institute for New Energy Materials and Low Carbon TechnologiesSchool of Materials Science and EngineeringTianjin University of TechnologyTianjin 300384China

Metal-organic frameworks(MOFs) as a type of crystalline heterogeneous catalysts have shown potential application in photocatalytic CO_(2)***,MOF catalysts with high efficiency and selectivity are still in ***,by a bimetallic strategy,the catalytic performance of a Co-MOF for photocatalytic CO_(2)reduction was ***,the Co-MOF based on 4,5-dicarboxylic acid(H;IDC) and4,4’-bipydine(4,4’-bpy) can catalyze CO;reduction to CO,with high efficiency but relatively low *** replacement of 2/3 Co(Ⅱ) with Ni(Ⅱ) within Co-MOF,the resulted isostructural Co_(1)Ni_(2)-MOF not only retains high efficiency for photocatalytic CO_(2)reduction,but also shows enhanced CO *** CO evolution rate reaches 1160 μmol g^(-1)h^(-1)and the CO selectivity reaches as high as 94.6%.The enhanced photocatalytic CO_(2)reduction performance is supported by theoretical calculation *** case demonstrates that bimetallic strategy is an effective mean to optimize the catalytic performance of MOF catalysts for photochemical CO_(2)reduction.

关键词： Metal-organic framework Photocatalytic CO_(2)reduction Bimetallic strategy CO_(2)–to–CO conversion Photocatalysis Dinuclear metal synergistic catalysis

Gas permeability and emission in unsaturated vegetated landfill cover with biochar addition

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Biochar 2023年第1期5卷 815-829页

作者： Junjun Ni Jingsong Zhou yuchen wang Haowen Guo School of Transportation Southeast UniversityNanjingChina Department of Civil and Environmental Engineering The Hong Kong University of Science and TechnologyHong Kong SARChina

Plant-biochar interaction has been recognized to affect the hydraulic properties of landfill cover soils,while its influence on landfill gas emission is rarely *** study investigated the coupled effects of biochar and vegetation on gas permeability and emission in unsaturated landfill cover through an integrated theoretical modelling and laboratory ***,a gas permeability model was developed for vegetated coarse-grained soils with biochar ***,a well-instrumented laboratory column test and two tests from the literature,considering bare,grass,biochar and grass+biochar conditions,were used for model ***,a numerical parametric study was conducted to investigate the influence of root growth and drought conditions on the gas emission *** showed that the developed model can satisfactorily capture the gas permeability of unsaturated soils at various degrees of *** lowest water retention capacity,the highest gas permeability and gas emission rate after 24 months of growth were observed in the grassed ***,adding biochar in vegetated soils can maximize the water retention capacity and decrease the gas permeability,resulting in the lowest gas emission *** measured gas emission rates for the four cases meet the recommended value by the design *** parametric study showed that the increased root depth from 0.2 m to 0.4 m improved the gas emission rate by 170%in the grass case but decreased by 97%in the grass+biochar *** the severe drought condition with soil suction around 500 kPa,the gas emission rate in the grassed case exceeded the design value by 18%,while those in the biochar cases were far below the allowable ***,peanut shell biochar should be considered to amend the grassed landfill cover using coarse-grained soils as it can significantly improve engineering performance in reducing gas emissions under extreme drought conditions.

关键词： Plant-biochar interaction Gas permeability model Gas emission Numerical simulation