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Greedy is Good:Constrained Non-submodular Function maximization via Weak Submodularity

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Journal of the Operations Research Society of China 2024年第3期12卷 627-648页

作者： ma-jun Shi Wei Wang School of Statistics Xi’an University of Finance and EconomicsXi’an710100ShaanxiChina School of mathematics and Statistics Xi’an Jiaotong UniversityXi’an710049ShaanxiChina

The widely used greedy algorithm has been recently shown to achieve near-optimal theoretical guarantees for the problems of constrained monotone non-submodular function maximization,with competitive performances in *** this paper,we investigate the problems of maximizing monotone non-submodular set functions under three classes of independent system constraints,including p-matroid intersection constraints,p-extendible system constraints and p-system *** prove that the greedy algorithm yields an approximation ratio ofγ/p+γfor the former two problems,andξγ/p+ξγfor the last problem,which further has been improved toγ/p+γ,whereγ,ξdenote the submodularity ratio and the diminishing returns ratio of set function *** addition,we also show that the greedy guarantees have a further refinement of for all the problems mentioned above,whereαis the generalized curvatureξ/p+αγof set ***,we show that our greedy algorithm does yield competitive practical performances using a variety of experiments on synthetic data.

关键词： Non-submodular function p-matroid intersection p-extendible system p-system Greedy algorithm

Switching fault-tolerant control for a class of nonlinear systems with actuator faults 25th

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Switching fault-tolerant control for a class of nonlinear sy...

An adaptive energy regulation in a memristive map linearized from a circuit with two memristive channels

第25届中国控制与决策会议

作者： hong-jun ma Guang-hong Yang Dan Ye School of Information Science and Engineering Northeastern University State Key Laboratory of Synthetical Automation for Process Industries Northeastern University

ISBN: (纸本)9781467355322

This paper presents a fault-tolerant control （FTC） strategy for a class of uncertain nonlinear systems with actuator faults. The faults acting on the actuator are described by a unified model of bias, loss-of-effectiveness, stuck and hard-over faults. By constructing a logic-based switching rule, the actuator faults can be automatically accommodated by switching from the stuck actuator to a healthy one （or even a partly-losing-effectiveness one with bias）, even in the presence of large parametric uncertainty. A simulation example of single-link flexible-joint robot is given to show the effectiveness of the proposed FTC controller.

关键词： Actuator faults Nonlinear systems Fault-tolerant control Uncertain systems switching control.

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Communications in Theoretical Physics 2024年第3期76卷 42-50页

作者： Feifei Yang Ping Zhou jun ma School of Science Chongqing University of Posts and TelecommunicationsChongqing 430065China College of Electrical and Information Engineering Lanzhou University of TechnologyLanzhou 730050China Department of Physics Lanzhou University of TechnologyLanzhou 730050China

Nonlinear circuits can show multistability when a magnetic flux-dependent memristor(MFDM) or a charge-sensitive memristor(CSM) is incorporated into a one branch circuit,which helps estimate magnetic or electric field *** this paper,two different kinds of memristors are incorporated into two branch circuits composed of a capacitor and a nonlinear resistor,thus a memristive circuit with double memristive channels is *** circuit equations are presented,and the dynamics in this oscillator with two memristive terms are ***,the memristive oscillator is converted into a memristive map by applying linear transformation on the sampled time series for the memristive *** Hamilton energy function for the memristive oscillator is obtained by using the Helmholtz theorem,and it can be mapped from the field energy of the memristive *** energy function for the dual memristive map is suggested by imposing suitable weights on the discrete energy *** dynamical behaviors of the new memristive map are investigated,and an adaptive law is proposed to regulate the firing mode in the memristive *** work will provide a theoretical basis and experimental guidance for oscillator-to-map transformation and discrete map energy calculation.

关键词： Hamilton energy dual memristive map adaptive energy regulation

Two simple memristive maps with adaptive energy regulation and digital signal process verification

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2024年第5期25卷 382-394页

作者： Feifei YANG Lujie REN jun ma Zhigang ZHU College of Electrical and Information Engineering Lanzhou University of TechnologyLanzhou 730050China Department of Physics Lanzhou University of TechnologyLanzhou 730050China School of Information Science and Engineering Dalian Polytechnic UniversityDalian 116034China

mathematical models can produce desired dynamics and statistical properties with the insertion of suitable nonlinear terms,while energy characteristics are crucial for practical application because any hardware realizations of nonlinear systems are relative to energy *** involvement of memristive terms relative to memristors enables multistability and initial-dependent property in memristive *** this study,two kinds of memristors are used to couple a capacitor or an inductor,along with a nonlinear resistor,to build different neural *** corresponding circuit equations are derived to develop two different types of memristive oscillators,which are further converted into two kinds of memristive maps after linear *** Hamilton energy function for memristive oscillators is obtained by applying the Helmholz theorem or by mapping from the field energy of the memristive *** Hamilton energy functions for both memristive maps are obtained by replacing the gains and discrete variables for the memristive oscillator with the corresponding parameters and *** two memristive maps have rich dynamic behaviors including coherence resonance under noisy excitation,and an adaptive growth law for parameters is presented to express the self-adaptive property of the memristive maps.A digital signal process(DSP)platform is used to verify these *** scheme will provide a theoretical basis and experimental guidance for oscillator-to-map transformation and discrete map-energy calculation.

关键词： Hamilton energy Discrete memristor Self-adaptive regulation Digital signal process(DSP)implementation

Memristive oscillator to memristive map,energy characteristic

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Science China(Technological Sciences) 2024年第5期67卷 1567-1578页

作者： GUO YiTong ma jun ZHANG XiaoFeng HU XiKui College of Electrical and Information Engineering Lanzhou University of TechnologyLanzhou730050China Department of Physics Lanzhou University of TechnologyLanzhou730050China School of Science Chongqing University of Posts and TelecommunicationsChongqing400065China

Most of nonlinear oscillators composed of capacitive and inductive variables can obtain the Hamilton energy by using the Helmholtz theorem when the models are rewritten in equivalent vector *** energy functions for biophysical neurons can be obtained by applying scale transformation on the physical field energy in their equivalent neural *** dynamical systems often have exact energy functions,while some mathematical models just suggest generic Lyapunov functions,and the energy function is effective to predict mode *** this paper,a memristive oscillator is approached by two kinds of memristor-based nonlinear circuits,and the energy functions are defined to predict the dependence of oscillatory modes on energy *** absence of capacitive variable for capacitor,the physical time t and charge q are converted into dimensionless variables by using combination of resistance and inductance(L,R),e.g.,τ=t×R/*** energy function for each memristive map is proposed by applying the similar weights as energy function for the memristive *** example,energy function for the map is obtained by replacing the variables and parameters of the memristive oscillator with corresponding variables and parameters for the memristive *** memristive map prefers to keep lower average energy than the memristive oscillator,and chaos is generated in a discrete system with two *** scheme is helpful for energy definition in maps,and it provides possible guidance for verifying the reliability of maps by considering the energy characteristic.

关键词： Hamilton energy memristor Helmholtz theorem scale transformation memristive circuit

Advances in the study of protein folding and endoplasmic reticulum-associated degradation in mammal cells

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Journal of Zhejiang University-Science B(Biomedicine & Biotechnology) 2024年第3期25卷 212-232页

作者： hong CAO Xuchang ZHOU Bowen XU Han HU Jianming GUO Yuwei ma Miao WANG Nan LI jun ZOU Department of Sport Rehabilitation Shanghai University of SportShanghai 200438China National Key Laboratory of Immunity and Inflammation Naval Medical UniversityShanghai 200433China

The endoplasmic reticulum is a key site for protein production and quality *** than one-third of proteins are synthesized and folded into the correct three-dimensional conformation in the endoplasmic ***,during protein folding,unfolded and/or misfolded proteins are prone to occur,which may lead to endoplasmic reticulum *** can monitor the quality of the proteins produced by endoplasmic reticulum quality control(ERQC)and endoplasmic reticulum-associated degradation(ERAD),which maintain endoplasmic reticulum protein homeostasis by degrading abnormally folded *** underlying mechanisms of protein folding and ERAD in mammals have not yet been fully ***,this paper reviews the process and function of protein folding and ERAD in mammalian cells,in order to help clinicians better understand the mechanism of ERAD and to provide a scientific reference for the treatment of diseases caused by abnormal ERAD.

关键词： Endoplasmic reticulum-associated degradation(ERAD) Protein folding Ubiquitination Retrotranslocation

Angiosperm-wide analysis of fruit and ovary evolution aided by a new nuclear phylogeny supports association of the same ovary type with both dry and fleshy fruits

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Journal of Integrative Plant Biology 2024年第2期66卷 228-251页

作者： Yezi Xiang Taikui Zhang Yiyong Zhao hongjin Dong hongyi Chen Yi Hu Chien-Hsun Huang jun Xiang hong ma State Key Laboratory of Genetic Engineering Ministry of Education Key Laboratory of Biodiversity and Ecological EngineeringInstitute of Plant BiologyCenter of Evolutionary BiologySchool of Life SciencesFudan UniversityShanghai 200438China Department of Biology Howard Hughes Medical InstituteDuke UniversityDurhamNC 27708USA Department of Biology the Eberly College of Scienceand the Huck Institutes of the Life Sciencesthe Pennsylvania State UniversityUniversity ParkPA 16802USA Hubei Key Laboratory of Economic Forest Germplasm Improvement and Resources Comprehensive Utilization College of Biology and Agricultural ResourcesHuanggang Normal UniversityHuanggang 438000China

Fruit functions in seed protection and dispersal and belongs to many dry and fleshy types,yet their evolutionary pattern remains unclear in part due to uncertainties in the phylogenetic relationships among several orders and *** we used nuclear genes of 502 angiosperm species representing 231 families to reconstruct a well supported phylogeny,with resolved relationships for orders and families with previously uncertain *** this phylogeny as a framework,molecular dating supports a Triassic origin of the crown angiosperms,followed by the emergence of most orders in the Jurassic and Cretaceous and their rise to ecological dominance during the Cretaceous Terrestrial *** robust phylogeny allowed an examination of the evolutionary pattern of fruit and ovary types,revealing a trend of parallel carpel fusions during early diversifications in eudicots,monocots,and ***,taxa in the same order or family with the same ovary type can develop either dry or fleshy fruits with strong correlations between specific types of dry and fleshy fruits;such associations of ovary,dry and fleshy fruits define several ovaryfruit"modules"each found in multiple *** of the frequent modules has an ovary containing multiple ovules,capsules and berries,and another with an ovary having one or two ovules,achenes(or other single-seeded dry fruits)and *** new perspective of relationships among fruit types highlights the closeness of specific dry and fleshy fruit types,such as capsule and berry,that develop from the same ovary type and belong to the same module relative to dry and fleshy fruits of other modules(such as achenes and drupes).Further analyses of gene families containing known genes for ovary and fruit development identified phylogenetic nodes with multiple gene duplications,supporting a possible role of whole-genome duplications,in combination with climate changes and animal behaviors,in angiosperm fruit and ovary diversificat

关键词： angiosperm fruit evolution maDS-box molecular clock nuclear phylogeny ovary and fruit developmental genes

Directly predicting N_(2) electroreduction reaction free energy using interpretable machine learning with non-DFT calculated features

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Journal of Energy Chemistry 2024年第10期97卷 139-148,I0004页

作者： Yaqin Zhang Yuhang Wang Ninggui ma jun Fan Department of materials Science and Engineering City University of Hong KongHong Kong 999077China Center for Advanced Nuclear Safety and Sustainable Development City University of Hong KongHong Kong 9077China Department of Mechanical Engineering City University of Hong KongHong Kong 999077China

Electrocatalytic nitrogen reduction to ammonia has garnered significant attention with the blooming of single-atom catalysts(SACs),showcasing their potential for sustainable and energy-efficient ammonia ***,cost-effectively designing and screening efficient electrocatalysts remains a *** this study,we have successfully established interpretable machine learning(ML)models to evaluate the catalytic activity of SACs by directly and accurately predicting reaction Gibbs free *** models were trained using non-density functional theory(DFT)calculated features from a dataset comprising 90 graphene-supported *** results underscore the superior prediction accuracy of the gradient boosting regression(GBR)model for bothΔg(N_(2)→NNH)andΔG(NH_(2)→NH_(3)),boasting coefficient of determination(R^(2))score of 0.972 and 0.984,along with root mean square error(RMSE)of 0.051 and 0.085 eV,***,feature importance analysis elucidates that the high accuracy of GBR model stems from its adept capture of characteristics pertinent to the active center and coordination environment,unveilling the significance of elementary descriptors,with the colvalent radius playing a dominant ***,Shapley additive explanations(SHAP)analysis provides global and local interpretation of the working mechanism of the GBR *** analysis identifies that a pyrrole-type coordination(flag=0),d-orbitals with a moderate occupation(N_(d)=5),and a moderate difference in covalent radius(r_(TM-ave)near 140 pm)are conducive to achieving high ***,we extend the prediction of activity to more catalysts without additional DFT calculations,validating the reliability of our feature engineering,model training,and design *** findings not only highlight new opportunity for accelerating catalyst design using non-DFT calculated features,but also shed light on the working mechanism of"black box"ML ***,the model provides valuable g

关键词： Nitrogen reduction Single-atom catalyst Interpretable machine learning Graphene Non-DFT features

Enhanced Flexoelectric Response from Functionally Gradient Electrets Undergoing Crumpling Deformation

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Acta Mechanica Solida Sinica 2024年第4期37卷 541-554页

作者： Jianhua ma Jinrui Xu jun Li Binglei Wang Department of Engineering Mechanics Shandong UniversityJinan250061China

Non-uniform deformation of the dielectric subjected to external forces can induce the flexoelectric effect, a phenomenon that couples electrical polarization to strain gradients. However, limited by the size effects, flexoelectricity is not significant at the macroscale and only becomes catchable at the microscale and nanoscale. In recent work, we obtained a considerable flexoelectric-like response by crumpling the dielectric embedded with charges, i.e., the electret, which significantly improved the flexoelectric effect at the macroscale. In this work, we further optimize the macroscopic performance of the flexoelectric response by applying gradient treatment to the electret films. Specifically, we analytically derive the electromechanical coupling of crumpled electret films with gradients of different thicknesses, charge densities, and Young’s moduli as key design variables. It is shown that the gradient-oriented electret film can be tuned to nearly five times that of a uniform electret film.

关键词： Functionally gradient electret Size effects Crumpling Flexoelectric-like response