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Steady State Behavior of the Free Recall Dynamics of Working Memory

Journal of systems Science & Complexity 2024年第6期37卷 2424-2450页

作者： LI Tianhao LIU Zhixin LIU Lizheng HU Xiaoming Key Laboratory of Systems and Control Academy of Mathematics and Systems ScienceChinese Academy of SciencesSchool of Mathematical SciencesUniversity of Chinese Academy of SciencesBeijing 100190China Academy for Engineering and Technology Fudan UniversityShanghai 200433China Optimization and Systems Theory KTH Royal Institute of TechnologyStockholm 10044Sweden

This paper studies a dynamical system that models the free recall dynamics of working *** model is an attractor neural network with n modules,named hypercolumns,and each module consists of m *** mild conditions on the connection weights between minicolumns,the authors investigate the long-term evolution behavior of the model,namely the existence and stability of equilibria and limit *** authors also give a critical value in which Hopf bifurcation ***,the authors give a sufficient condition under which this model has a globally asymptotically stable equilibrium consisting of synchronized minicolumn states in each hypercolumn,which implies that in this case recalling is *** simulations are provided to illustrate the proposed theoretical ***,a numerical example the authors give suggests that patterns can be stored in not only equilibria and limit cycles,but also strange attractors(or chaos).

关键词： Asymptotic stability bifurcation free recall strange attractor working memory

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Model-Based Feature Selection for Neural Networks: A Mixed-Integer Programming Approach 1

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17th International Conference on Learning and Intelligent optimization, LION-17 2023

作者： Zhao, Shudian Tsay, Calvin Kronqvist, Jan Optimization and Systems Theory Department of Mathematics KTH Royal Institute of Technology Stockholm Sweden Department of Computing Imperial College London London United Kingdom

ISBN: (数字)9783031445057

ISBN: (纸本)9783031445040

In this work, we develop a novel input feature selection framework for ReLU-based deep neural networks (DNNs), which builds upon a mixed-integer optimization approach. While the method is generally applicable to various classification tasks, we focus on finding input features for image classification for clarity of presentation. The idea is to use a trained DNN, or an ensemble of trained DNNs, to identify the salient input features. The input feature selection is formulated as a sequence of mixed-integer linear programming (MILP) problems that find sets of sparse inputs that maximize the classification confidence of each category. These "inverse" problems are regularized by the number of inputs selected for each category and by distribution constraints. Numerical results on the well-known MNIST and FashionMNIST datasets show that the proposed input feature selection allows us to drastically reduce the size of the input to ∼ 15% while maintaining a good classification accuracy. This allows us to design DNNs with significantly fewer connections, reducing computational effort and producing DNNs that are more robust towards adversarial attacks. © 2023, The Author(s), under exclusive license to Springer Nature Switzerland AG.

关键词： Deep neural networks

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Robust formation control for unicycle robots with directional sensor information

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Autonomous Intelligent systems 2023年第1期3卷 66-74页

作者： Yibei Li Lizheng Liu Zhongxue Gan Xiaoming Hu Optimization and Systems Theory KTH Royal Institute of TechnologySE 10044 StockholmSweden. School of Electrical and Electronic Engineering Nanyang Technological UniversitySingaporeSingapore. Academy for Engineering and Technology Fudan UniversityShanghaiChina.

In this paper,the formation control problem for a multi-agent system is *** new robust control algorithms for serial and parallel formations respectively are proposed,which take the constraints of limited field of view into *** the need for any global information,the only relative information required is distance and bearing angle,thus is easy to implement with onboard directional *** is then demonstrated how complex formations can be realized by combining the proposed basic ***,effectiveness of the proposed algorithms is illustrated by numerical examples.

关键词： Formation control Serial and parallel formation Leader-follower control Multi-agent systems

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Infinite-dimensional port-Hamiltonian systems: a system node approach

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Mathematics of Control, Signals, and systems 2025年 1-48页

作者： Philipp, Friedrich M. Reis, Timo Schaller, Manuel Optimization-Based Control Group Technische Universität Ilmenau Weimarer Straße Ilmenau98696 Germany Systems Theory and Partial Differential Equations Group Technische Universität Ilmenau Weimarer Straße Ilmenau98696 Germany Faculty of Mathematics Chemnitz University of Technology Reichenhainer Straße Chemnitz09126 Germany

We consider an operator-theoretic approach to linear infinite-dimensional port-Hamiltonian systems. In particular, we use the theory of system nodes as reported by Staffans (Well-posed linear systems. Encyclopedia of mathematics and its applications, Cambridge University Press, Cambridge, UK, 2005) to formulate a suitable concept for port-Hamiltonian systems, which allows a unifying approach to systems with boundary as well as distributed control and observation. The concept presented in this article is further neither limited to parabolic nor hyperbolic systems, and it also covers partial differential equations on multi-dimensional spatial domains. Our presented theory is substantiated by means of several physical examples. © The Author(s) 2025.

关键词： Hamiltonians

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Considering solid shear stress in MP-PIC simulation of a CFB riser

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Particuology 2024年第6期89卷 79-87页

作者： Tagir Kadyrov Fei Li Atta Ullah Nature-inspired Engineering Center University of TyumenTyumen 625003Russia Laboratory of Theory and Optimization of Chemical and Technological Processes University of TyumenTyumen625003Russia State Key Laboratory of Multi-phase Complex Systems Institute of Process EngineeringChinese Academy of SciencesBeijing 100190China Department of Chemical Engineering Pakistan Institute of Engineering&Applied SciencesIslamabad 45650Pakistan

To enable successful multi-phase particle-in-cell(MP-PIC)simulations of circulating fluidized beds(CFBs),both the interphase drag force and interparticle collisions need to be carefully *** collisions are usually represented by the solid stress consisting of the normal and shear components,in which the normal stress was found to have a leading role in the numerical stability of MP-PIC simulations,whereas the impact of the shear stress has seldom been *** this work,the effects of the solid shear stress are investigated by using two-dimensional simulations of the moderately dense laboratory-scale CFB riser with in-house MP-PIC code implemented on MFIX open-source *** including only normal solid stress and those considering both normal and shear solid stresses are *** results of solids flux,axial and radial solids profiles are compared with available experimental *** results show that the solid shear stress plays a minor role on the accuracy of simulation,and the increase of PPP(number particles per parcel)leads to a lower accuracy of simulation.

关键词： Simulation Fluidization Multiphase particle-in-cell(MP-PIC) Solid shear stress

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Cosmological perturbations in the energy-momentum squared gravity theory:constraints from gravitational wave standard sirens and redshift space distortions

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Chinese Physics C 2025年第4期49卷 199-208页

作者： Qi-Ming Fu Xin Zhang Institute of Physics Shaanxi University of TechnologyHanzhong 723000China Lanzhou Center for Theoretical Physics Key Laboratory of Theoretical Physics of Gansu Provinceand Key Laboratory of Quantum Theory and Applications of MoELanzhou UniversityLanzhou 730000China Key Laboratory of Cosmology and Astrophysics(Liaoning)&College of Sciences Northeastern UniversityShenyang 110819China Key Laboratory of Data Analytics and Optimization for Smart Industry(Ministry of Education) Northeastern UniversityShenyang 110819China National Frontiers Science Center for Industrial Intelligence and Systems Optimization Northeastern UniversityShenyang 110819China

We investigate the linear cosmological perturbations in the context of the so-called energy-momentum squared gravity(EMSG)*** research shows that the EMSG theory can reproduce a viable background cosmological evolution comparable toΛCDM,whereas the matter-dominated era exhibits slight *** this paper,we focus on power-law EMSG models and derive the equations for the linear cosmological *** explore the propagation of the gravitational wave(GW)and the growth of matter density perturbation at the first order,and we estimate the model parameters from the simulated GW and observed redshift space distortion *** analysis reveals that the model parameters should be small and positive in the confidence interval,which indicates that the theory agrees closely with the observational data and can be considered an alternative to the standard cosmological model.

关键词： energy-momentum squared gravity cosmological perturbations gravitational wave cosmological parameters

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A CUTTING PLANE ALGORITHM FOR GLOBALLY SOLVING LOW DIMENSIONAL K-MEANS CLUSTERING PROBLEMS

arXiv

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arXiv 2024年

作者： Ryner, Martin Kronqvist, Jan Karlsson, Johan Division of Numerical Analysis Optimization and Systems Theory Department of Mathematics KTH Royal Institute of Technology Stockholm Sweden

Clustering is one of the most fundamental tools in data science and machine learning, and k-means clustering is one of the most common such methods. There is a variety of approximate algorithms for the k-means problem, but computing the globally optimal solution is in general NP-hard. In this paper we consider the k-means problem for instances with low dimensional data and formulate it as a structured concave assignment problem. This allows us to exploit the low dimensional structure and solve the problem to global optimality within reasonable time for large data sets with several clusters. The method builds on iteratively solving a small concave problem and a large linear programming problem. This gives a sequence of feasible solutions along with bounds which we show converges to zero optimality gap. The paper combines methods from global optimization theory to accelerate the procedure, and we provide numerical results on their *** Codes 90C26 (Primary) 90C27 (Secondary) © 2024, CC BY.

关键词： Global optimization

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Two-Stage Transpotation Problem with Unknown Consumer Demands: Consistency Aspects 3

Two-Stage Transpotation Problem with Unknown Consumer Demand...

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3rd International Conference on Problems of Logistics, Management and Operation in the East-West Transport Corridor, PLMO 2024

作者： Stovba, Viktor Khomiak, Olha V.M. Glushkov Institute of Cybernetics of the Nas of Ukraine Department of Nonsmooth Optimization Methods Kyiv Ukraine V.M. Glushkov Institute of Cybernetics of the Nas of Ukraine Department of Mathematical Methods of Reliability Theory of Complex Systems Kyiv Ukraine

ISBN: (纸本)9798350353099

A mathematical model of a two-stage transportation problem with unknown consumer demands and their lower and upper bounds is studied. The necessary and sufficient conditions for consistency of the constraints system of the linear programming problem, which corresponds to this model, are formulated, and justified. The classical two-stage transportation problem is given, to which the above problem is transformed if consumer demands are known, as well as the consistency conditions for constraints system of the problem. Modification of the initial model that permits product transportation only to the fixed number of consumers, which is less than their total number, is given. © 2024 IEEE.

关键词： constraints system consistency linear programming problem two-stage transportation problem

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Stabilization of nonlinear safety-critical systems by relaxed converse Lyapunov-barrier approach and its applications in robotic systems

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Autonomous Intelligent systems 2024年第1期4卷 73-80页

作者： Haoqi Li Jiangping Hu Xiaoming Hu Bijoy K.Ghosh School of Automation Engineering University of Electronic Science and Technology of ChinaChengdu611731China Yangtze Delta Region Institute(Huzhou) University of Electronic Science and Technology of ChinaHuzhou313000China Optimization and Systems Theory Royal Institute of TechnologyStockholmSE-10044Sweden Department of Mathematics and Statistics Texas Tech UniversityLubbock79409-1042TXUSA

Combining safety objectives with stability objectives is crucial for safety-critical *** studies generally unified these two objectives by constructing Lyapunov-type barrier ***,insufficient analysis of key set relationships within the system may render the proposed safety and stability conditions conservative,and these studies also did not provide how to use such conditions to design safety-stability control *** paper proposed a feasible and constructive design to achieve stabilization of safety-critical systems by a relaxed converse Lyapunov-barrier *** analyzing the relationships between a series of sets associated with the safety-critical system,the stability and safety conditions can be appropriately ***,with the help of relaxed converse control Lyapunov-barrier functions(RCCLBFs),a theoretical result was obtained for the stability of affine nonlinear systems with safety ***,a constructive method was developed for a second-order strict-feedback system to transform the process of solving RCCLBFs into a Lyapunov-like stabilization ***,the proposed safety-stability control method is exerted on a robotic system and demonstrated by simulations.

关键词： Lyapunov functions Barrier functions Safety Stability

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Globally solving the Gromov-Wasserstein problem for point clouds in low dimensional Euclidean spaces 23

Globally solving the Gromov-Wasserstein problem for point cl...

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Proceedings of the 37th International Conference on Neural Information Processing systems

作者： Martin Ryner Jan Kronqvist Johan Karlsson Vironova AB Stockholm Sweden and Division of Numerical Analysis Optimization and Systems Theory Department of Mathematics KTH Royal Institute of Technology Stockholm Sweden Division of Numerical Analysis Optimization and Systems Theory Department of Mathematics KTH Royal Institute of Technology Stockholm Sweden

This paper presents a framework for computing the Gromov-Wasserstein problem between two sets of points in low dimensional spaces, where the discrepancy is the squared Euclidean norm. The Gromov-Wasserstein problem is a generalization of the optimal transport problem that finds the assignment between two sets preserving pairwise distances as much as possible. This can be used to quantify the similarity between two formations or shapes, a common problem in AI and machine learning. The problem can be formulated as a Quadratic Assignment Problem (QAP), which is in general computationally intractable even for small problems. Our framework addresses this challenge by reformulating the QAP as an optimization problem with a low-dimensional domain, leveraging the fact that the problem can be expressed as a concave quadratic optimization problem with low rank. The method scales well with the number of points, and it can be used to find the global solution for large-scale problems with thousands of points. We compare the computational complexity of our approach with state-of-the-art methods on synthetic problems and apply it to a near-symmetrical problem which is of particular interest in computational biology.

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