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An adaptive phase-field method for structural topology optimization

JOURNAL OF COMPUTATIONAL PHYSICS 2024年 506卷

作者： Jin, Bangti Li, Jing Xu, Yifeng Zhu, Shengfeng Chinese Univ Hong Kong Dept Math Shatin Hong Kong Peoples R China East China Normal Univ Sch Math Sci Shanghai 200241 Peoples R China Shanghai Normal Univ Dept Math & Sci Comp Key Lab Shanghai Univ Shanghai 200234 Peoples R China East China Normal Univ Key Lab MEA Minist Educ Shanghai 200241 Peoples R China East China Normal Univ Shanghai Key Lab PMMP Shanghai 200241 Peoples R China

In this work, we develop an adaptive algorithm for the efficient numerical solution of the minimum compliance problem in topology optimization. The algorithm employs the phase field approximation and continuous density field. The adaptive procedure is driven by two residual type a posteriori error estimators, one for the state variable and the other for the first -order optimality condition of the objective functional. The adaptive algorithm is provably convergent in the sense that the sequence of numerical approximations generated by the adaptive algorithm contains a subsequence convergent to a solution of the continuous first -order optimality system. We provide several numerical simulations to show the distinct features of the algorithm.

关键词： Minimum compliance adaptive algorithm Topology optimization Convergence A posteriori error estimator

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Fault Diagnosis of Rolling Bearings Based on Acoustics and Vibration Engineering

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IEEE ACCESS 2024年 12卷 139632-139648页

作者： Guo, Xinwen Shenzhen Inst Technol Coll Continuing Educ Shenzhen 518116 Peoples R China

Currently, the fault diagnosis and maintenance of rolling bearings have become an urgent problem to be solved. A fault diagnosis method based on feature extraction and word bag model was designed based on the theories of acoustics and vibration engineering science. At the same time, the traditional word bag model was optimized, and a rolling bearing fault diagnosis method based on the adaptive extended word bag model was designed. This method mainly expands the word bag model into a 3-layer structure and constructs codebooks for the feature vectors of each layer. The results indicate that the fault diagnosis method for rolling bearings designed in the study has high diagnostic accuracy and stability, providing reliable technical support for the normal operation and safe maintenance of mechanical equipment.

关键词： Accuracy adaptive algorithm classification algorithms digital signal processing electromechanical devices fault detection feature detection image processing mechanical bearings rolling bearings adaptive algorithm classification algorithms digital signal processing electromechanical devices fault detection feature detection image processing mechanical bearings rolling bearings

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Spatiotemporal heterogeneous information fusion model for loitering anomaly detection

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SIGNAL IMAGE AND VIDEO PROCESSING 2024年第8-9期18卷 5733-5742页

作者： Li, Hongjun Huang, Xiezhou Nantong Univ Sch Informat Sci & Technol Nantong 226019 Peoples R China Nantong Res Inst Adv Commun Technol Nantong 226019 Jiangsu Peoples R China

In the field of video surveillance security in public places, loitering anomaly detection plays a crucial role. Currently, the complexity of public scenes and the difficulty in extracting apparent features due to limitations in the resolution of surveillance videos make tracking, which serves as the foundation for loitering anomaly detection, challenging. In order to solve the problem of low robustness of the tracker in low-resolution complex scenes, a reassessment module based on gait features and a matching algorithm based on spatial information are proposed. To locate loitering abnormal frames more sensitively and accurately, and to better distinguish normal and abnormal samples, an adaptive loitering detection algorithm based on motion states is proposed. The spatiotemporal heterogeneous information fusion model for loitering anomaly detection is tested on the IITB-Corridor dataset and compared with the most effective deep learning method, Semi-supervised Video Anomaly Detection and Anticipation, showing an increase in accuracy by 1.2% and recall by 1.8%.

关键词： Loitering anomaly detection Gait feature Angle shift adaptive algorithm

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Rate-optimal higher-order adaptive conforming FEM for biharmonic eigenvalue problems on polygonal domains

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COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING 2024年 425卷

作者： Carstensen, Carsten Graessle, Benedikt Humboldt Univ Dept Math D-10117 Berlin Germany

The a posteriori error analysis of the classical Argyris finite element methods dates back to 1996, while the optimal convergence rates of associated adaptive finite element schemes are established only very recently in 2021. It took a long time to realize the necessity of an extension of the classical finite element spaces to make them hierarchical. This paper establishes the novel adaptive schemes for the biharmonic eigenvalue problems and provides a mathematical proof of optimal convergence rates towards a simple eigenvalue and numerical evidence thereof. This makes the suggested algorithm highly competitive and clearly justifies the higher computational and implementational costs compared to low -order nonconforming schemes. The numerical experiments provide overwhelming evidence that higher polynomial degrees pay off with higher convergence rates and underline that adaptive mesh -refining is mandatory. Five computational benchmarks display accurate reference eigenvalues.

关键词： A posteriori adaptive algorithm Argyris element Optimal convergence Eigenvalue problem Reference values

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adaptive Shape Parameter RPIM for SP Log Analysis: Methods and Benchmarks

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IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING 2024年 62卷 1-1页

作者： Li, Yang Liu, Dejun Zhou, Hao Chen, Yun Yu, Xiaoyang China Univ Petr Coll Informat Sci & Engn Beijing 102249 Peoples R China Nanyang Technol Univ Sch Elect & Elect Engn Singapore 639798 Singapore

The attempt of a new general adaptive meshless method in simulating singular spontaneous potential (SP) logging problems is discussed in this article. This method was first proposed and designed by our team, and it is named adaptive overall shape parameter " c " radial base point interpolation method (OC-RPIM). A new model error evaluation method using twin matrices is proposed and used in the OC-RPIM local matrix construction. Based on this error evaluation index, the architecture of the adaptive ${c}$ algorithm is implemented. This method has excellent stability and accuracy without modifying the discrete point configuration and polynomial order. Furthermore, it is easier to deal with problems that have singularities. This study discusses the versatility and superiority of the architecture when the OC-RPIM algorithm is applied to SP simulation problems. The characteristic rules of c of the SP simulation curve under different formation conditions are analyzed. This method provides a new perspective on adaptive solving algorithms in computational geodetic electromagnetics (Geo-EM). The OC-RPIM code used for this study is already open source.

关键词： adaptive algorithm computational geoelectromagnetics electromagnetic modeling meshless method radial basis function (RBF) shape parameter spontaneous potential (SP) logging

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A posteriori error estimate and adaptivity for QM/MM models of defects

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COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING 2024年 428卷

作者： Wang, Yangshuai Kermode, James R. Ortner, Christoph Zhang, Lei Univ British Columbia 1984 Math Rd Vancouver BC Canada Univ Warwick Warwick Ctr Predict Modelling Sch Engn Coventry CV4 7AL England Shanghai Jiao Tong Univ Inst Nat Sci Sch Math Sci Shanghai 200240 Peoples R China Shanghai Jiao Tong Univ MOE LSC Shanghai 200240 Peoples R China

Hybrid quantum mechanics/molecular mechanics (QM/MM) models play a pivotal role in molecular simulations. These models provide a balance between accuracy, surpassing pure MM models, and computational efficiency, offering advantages over pure QM models. adaptive approaches have been developed to further improve this balance by allowing on -the -fly selection of the QM and MM subsystems as necessary. We propose a novel and robust adaptive QM/MM method for practical material defect simulations. To ensure mathematical consistency with the QM reference model, we employ machine -learning interatomic potentials (MLIPs) as the MM models (Chen et al., 2022 and Grigorev et al., 2023). Our adaptive QM/MM method utilizes a residual -based error estimator that provides both upper and lower bounds for the approximation error, thus indicating its reliability and efficiency. Furthermore, we introduce a novel adaptive algorithm capable of anisotropically updating the QM/MM partitions. This update is based on the proposed residual -based error estimator and involves solving a free interface motion problem, which is efficiently achieved using the fast marching method. We demonstrate the robustness of our approach via numerical tests on a range of crystalline defects comprising edge dislocations, cracks and di-interstitials.

关键词： QM/MM coupling Machine-learned interatomic potentials A posteriori error estimate adaptive algorithm Crystal defects

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adaptive mixed virtual element method for the fourth-order singularly perturbed problem

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JOURNAL OF COMPUTATIONAL PHYSICS 2025年 524卷

作者： Meng, Jian Qian, Xu Qiu, Jiali Xia, Jingmin Natl Univ Def Technol Coll Sci Dept Math Changsha 410073 Hunan Peoples R China Xi An Jiao Tong Univ Sch Math & Stat Xian 710049 Shaanxi Peoples R China Natl Univ Def Technol Coll Meteorol & Oceanog Changsha 410073 Hunan Peoples R China

The singularly perturbed theory mainly arises in the system of differential equations with the small enough perturbed parameters acting on the highest-order derivatives. In this paper, we introduce the adaptive mixed virtual element method for the fourth-order singularly perturbed problem and the associated eigenvalue problem. It allows to apply the H1-conforming virtual elements to discrete the continuous spaces and reduces the total number of required degrees of freedom of the H2-conforming virtual element method. Basically, the great flexibility of virtual element method becomes appealing in mesh refinement because the locally mesh post-processing to remove hanging nodes is never needed. This naturally motivates us to develop an a posteriori error estimate for the model problem. Based on the numerical solutions, the interior and edge residual terms, and the error terms related to the inconsistency of the virtual element scheme, the error estimators applied to adaptively refine meshes are constructed and then proved to be equivalent to numerical errors under the balanced energy norms. Moreover, we also consider the approximation method for the fourth-order singularly perturbed eigenvalue problem in twodimensional space. Analogous with the source problem, we not only discuss the boundedness of the eigenfunctions, but also present the upper bound for the error of the approximated eigenvalues by these error estimators. Necessitated by supporting the theoretical analysis, representative numerical examples are reported. We show that the current numerical method converges at the optimal rate uniformly with respect to the singularly perturbed parameters when using the adaptive polygonal meshes.

关键词： Mixed virtual element method adaptive algorithm Fourth-order singularly perturbed (eigenvalue) problems Boundary layers A posteriori error estimates

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Frequency-Domain IPNLMS-Based Sparse Direct adaptive Equalization for Underwater Acoustic Communications

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IEEE COMMUNICATIONS LETTERS 2025年第2期29卷 289-293页

作者： Hu, Changyue Liu, Zhiyong Ke, Miao Zhang, Qinyu Harbin Inst Technol Weihai Sch Informat Sci & Engn Weihai 264209 Shandong Peoples R China Minist Ind & Informat Technol Shandong Prov Key Lab Marine Elect Informat & Inte Weihai 264209 Shandong Peoples R China Minist Ind & Informat Technol Key Lab Cross Domain Synergy & Comprehens Support Weihai 264209 Shandong Peoples R China Harbin Inst Technol Shenzhen Commun Engn Res Ctr Shenzhen 518055 Guangdong Peoples R China Peng Cheng Lab Shenzhen 518055 Peoples R China

In this letter, we propose a frequency-domain improved proportionate normalized least mean square based sparse direct adaptive equalization (FD-IPNLMS-SDAE) algorithm for underwater acoustic communication. Compared with the existing methods, the proposed algorithm is implemented in the frequency domain, which not only significantly reduces the complexity, but also has the convergence performance advantage of the sparse algorithm. Simulation results verify the advantages of the proposed algorithm over the existing approaches.

关键词： Vectors Frequency-domain analysis Convergence Underwater acoustics Training Time-domain analysis Symbols adaptive equalizers Correlation Computational complexity adaptive algorithm underwater acoustic communications frequency-domain equalization sparse channel

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Optimal Low-Thrust Earth Orbit Transfers with Eclipses Using Indirect Heuristic Approaches

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JOURNAL OF GUIDANCE CONTROL AND DYNAMICS 2024年第5期47卷 857-873页

作者： Pontani, Mauro Corallo, Francesco Univ Roma La Sapienza Dept Astronaut Elect & Energy Engn I-00138 Rome Italy Thales Alenia Space Italy Mission & Operat Unit I-00131 Rome Italy

Low-thrust propulsion allows substantial propellant saving if compared to high-thrust systems. However, multirevolution orbit transfers are affected by the unavailability of electrical power along eclipse arcs. This research addresses the identification of minimum-time low-thrust Earth orbit transfers with spacecraft eclipsing. Two different indirect heuristic approaches, based on the use of the analytical conditions for optimality, in conjunction with stochastic fractal search, are applied: 1) regularization through the hyperbolic tangent function and 2) multi-arc formulation of the problem. Both of them require no averaging, and the respective advantages and shortcomings are identified. Approach 2 leads to an extended set of multipoint conditions for optimality, which are shown to be solvable sequentially in the numerical solution process. Implicit costate transformation is proven to be a key ingredient for the purpose of obtaining closed-form solutions of the jump relations that hold for the adjoint variables at light/eclipse transitions. Some illustrative examples prove effectiveness of the two indirect heuristic approaches 1 and 2 in finding minimum-time low-thrust orbit transfers between either two coplanar or two noncoplanar Earth orbits. Approach 2 proves to be superior in terms of both computational efficiency and accuracy of the numerical results.

关键词： adaptive algorithm Astronomical Events Aerodynamics Planets Solar Electric Propulsion Propellant Pontryagin's Minimum Principle Earth Centered Inertial Numerical Integration Equatorial Orbit

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A fast and accurate method for transport and dispersion of phosphogypsum in coastal zones: Application to Jorf Lasfar

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INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS 2024年第3期96卷 336-363页

作者： Ouardghi, Abdelouahed Seaid, Mohammed El-Amrani, Mofdi El Mocayd, Nabil Univ Mohammed VI Polytech Int Water Res Inst Sale Morocco Univ Durham Dept Engn Durham England Abdelmalek Essaadi Univ FSTT Lab Math & Applicat Tangier Morocco Univ Mohammed VI Polytech Inst Appl Phys Sale Morocco

We present a numerical method for modelling and simulation of transport and dispersion of phosphogypsum in the Jorf Lasfar coastal zone located on the Atlantic Ocean at Morocco. The governing equations consist of the well-established barotropic ocean model including the barometric pressure, friction terms, Coriolis and wind stresses. To model transport and dispersion of phosphogypsum we consider an advection-diffusion equation with an anisotropic dispersion tensor and source terms. As a numerical solver, we propose a novel multilevel adaptive semi-Lagrangian finite element method. The proposed method combines the modified method of characteristics to deal with convection terms, the finite element discretization to handle complex geometries, a projection-based algorithm to solve the Stokes problem, and an adaptive L-2-projection using quadrature rules to improve the efficiency and accuracy of the method. Numerical results are presented to demonstrate the high resolution of the proposed method and to confirm its capability to provide accurate and efficient simulations for transport and dispersion of phosphogypsum in the Jorf Lasfar coastal zone.

关键词： adaptive algorithm enriched finite elements incompressible Navier-Stokes equations Jorf Lasfar coastal zone L-2 projection semi-Lagrangian method

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