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An Updated Lagrangian Particle Hydrodynamics (ULPH)-NOSBPD Coupling Approach for Modeling Fluid-Structure Interaction Problems

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arXiv 2023年

作者： Wang, Zhen Xiong, Junsong Liu, Xiang Liu, Lisheng Lai, Xin Hubei Key Laboratory of Theory and Application of Advanced Materials Mechanics Wuhan University of Technology Wuhan430070 China Department of Engineering Structure and Mechanics Wuhan University of Technology Wuhan430070 China

In order to solve the fluid-structure interaction problem of Newtonian fluid, a fluid-structure interaction approach is proposed based on Non-ordinary State-based Peridynamics (NOSB-PD) and Updated Lagrangian particle Hydrodynamics (ULPH), to simulate the fluid-structure interaction problem in which large geometric deformation and material failure are considered. In the coupled framework, the NOSB-PD theory is used to describe the deformation and fracture of the solid material structure. ULPH is applied to describe the flow of Newtonian fluids due to its advantages in computational accuracy. The framework effectively utilizes the advantages of NOSB-PD theory for solving discontinuous problems and ULPH theory for solving fluid problems and has good computational stability and robustness. To deal with the interface of fluid structure, a fluid-structure coupling algorithm using pressure as the transmission medium is established. The dynamic model of solid structure and the PD-ULPH fluid-structure interaction model involving large deformation are verified by several numerical validations, which are in good agreement with the analytical solution, the available experimental data and other numerical results, that demonstrates the accuracy and effectiveness of the proposed method in solving the fluid-structure interaction problem. Overall, the fluid-structure interaction model based on ULPH and NOSB-PD established in this paper provides a new idea for the numerical solution of fluid-structure interaction and a promising approach for engineering design and experimental prediction. Copyright © 2023, The Authors. All rights reserved.

关键词： Fluid structure interaction

An Updated Lagrangian Particle Hydrodynamics (ULPH) Implementation of Heat Conduction Model for Weakly-Compressive Fluid

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arXiv 2023年

作者： Xiong, Junsong Wang, Zhen Lai, Xin Liu, Lisheng Liu, Xiang Hubei Key Laboratory of Theory and Application of Advanced Materials Mechanics Wuhan University of Technology Wuhan430070 China Department of Engineering Structure and Mechanics Wuhan University of Technology Wuhan430070 China

Heat conduction is quite common in natural, industrial, and military applications. In this work, the updated Lagrangian particle hydrodynamics (ULPH) theory, is utilized and applied to solve heat conduction problems. Since heat conduction is a second-order problem, the high-order ULPH theory is employed to establish the governing equations of heat conduction in ULPH, which is then validated using various numerical simulations. In this work, numerical simulations have been carried out to solve both static heat conduction problems and dynamic heat convection problems. The results show good accuracy and capability of the ULPH heat conduction model, suggesting promising prospects of the ULPH theory in multiphysics problems. The findings of this paper suggest that ULPH is effective in addressing convective heat transfer problems. Copyright © 2023, The Authors. All rights reserved.

关键词： Heat conduction

Multi-scale Simulations of Flow in the Upper Open Area of a Luxury Cruise Ship 1

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17th International Conference on Bio-Inspired Computing: Theories and applications, BIC-TA 2022

作者： Yan, Zhongqiu Zhang, Liujun Wu, Weiguo Song, Zhenguo Luo, Heng Yang, Yi Hu, Wulong Jiangsu Institute of Automation Lianyungang222061 China Green & Smart River-Sea-Going Ship Cruise and Yacht Research Center Wuhan University of Technology Wuhan430070 China Hubei Key Laboratory of Theory and Application of Advanced Materials Mechanics School of Science Wuhan University of Technology Wuhan430070 China China Ship Development and Design Center Wuhan430000 China

ISBN: (数字)9789819915491

ISBN: (纸本)9789819915484

Luxury cruise ships have complicated superstructures, which are greatly affected by wind loads. At present, the research on the external flow field of luxury cruise ships mainly adopts the method of directly calculating the whole ship model. Due to the limited computing resources, this method is difficult to accurately describe the local complex flow field structure. This paper proposes a multi-scale simulation method based on the entire ship model of the luxury cruise ship and the refined model of the superstructure. Firstly, the flow field around the cruise ship is obtained through the whole ship simulation, and the local flow field data is extracted;then the local flow field data is imported into the local refined model of the cruise ship as the speed entrance boundary condition;finally, the refined simulation analysis of the cruise ship is carried out. In this paper, a multi-scale simulation method is used to analyze the characteristics of the flow field around the superstructure of the cruise ship by combining pressure, flow velocity and vorticity. The results show that the local simulation can obtain a finer flow field structure than the whole ship simulation, and the result obtained by using multi-scale simulation is more accurate than the result obtained by directly using the natural wind speed profile velocity entrance. This article provides a new idea for wind field simulation of luxury cruise ships and other ship types with complex superstructures. © 2023, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.

关键词： Flow velocity

Speculations on the W-mass measurement at CDF

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Chinese Physics C 2022年第12期46卷 145-161页

作者： Jiayin Gu Zhen Liu Teng Ma Jing Shu Department of Physics and Center for Field Theory and Particle Physics Fudan UniversityShanghai 200438China Key Laboratory of Nuclear Physics and Ion-beam Application(MOE) Fudan UniversityShanghai 200433China School of Physics and Astronomy University of MinnesotaMinneapolisMN 55455USA Physics Department Technion Israel Institute of TechnologyHaifa 3200003Israel CAS Key Laboratory of Theoretical Physics Institute of Theoretical PhysicsChinese Academy of SciencesBeijing 100190China School of Physical Sciences University of Chinese Academy of SciencesBeijing 100049China School of Fundamental Physics and Mathematical Sciences Hangzhou Institute for Advanced StudyUniversity of Chinese Academy of SciencesHangzhou 310024China International Center for Theoretical Physics Asia-Pacific Beijing/HangzhouChina

The W mass determination at the Tevatron CDF experiment reported a deviation from the SM expectation at the 7σ*** discuss a few possible interpretations and their collider *** perform electroweak global fits under various frameworks and *** consider three types of electroweak global fits in the effective-field-theory framework:the S-T,S-T-δG_(F),and eight-parameter flavor-universal *** discuss the amounts of tensions between different m_(W)measurements reflected in these fits and the corresponding shifts in central values of these *** these electroweak fit pictures in hand,we present a few different classes of models and discuss their compatibility with these *** find that while explaining the m_(W)discrepancy,the single gauge boson extensions face strong LHC direct search constraints unless the Z′is fermiophobic(leptophobic),which can be realized if extra vector fermions(leptons)mix with the SM fermions(leptons).Vector-like top partners can partially generate the needed shift to the electroweak *** compatibility with the top squark is also studied in *** find that the non-degenerate top squark soft masses enhance the needed operator coefficients,enabling an allowed explanation compatible with current LHC ***,more theoretical and experimental developments are highly in demand to reveal the physics behind this discrepancy.

关键词： W mass EWPT Z-prime vector-like quark SUSY squark

Class-Imbalanced Semi-Supervised Learning for Large-Scale Point Cloud Semantic Segmentation via Decoupling Optimization

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arXiv 2024年

作者： Li, Mengtian Lin, Shaohui Wang, Zihan Shen, Yunhang Zhang, Baochang Ma, Lizhuang Shanghai University China Shanghai Engineering Research Center of Motion Picture Special Effects China East China Normal University China Key Laboratory of Advanced Theory and Application in Statistics and Data Science Ministry of Education China Beihang University China Tencent Youtu Lab China

Semi-supervised learning (SSL), thanks to the significant reduction of data annotation costs, has been an active research topic for large-scale 3D scene understanding. However, the existing SSL-based methods suffer from severe training bias, mainly due to class imbalance and long-tail distributions of the point cloud data. As a result, they lead to a biased prediction for the tail class segmentation. In this paper, we introduce a new decoupling optimization framework, which disentangles feature representation learning and classifier in an alternative optimization manner to shift the bias decision boundary effectively. In particular, we first employ two-round pseudo-label generation to select unlabeled points across head-to-tail classes. We further introduce multi-class imbalanced focus loss to adaptively pay more attention to feature learning across head-to-tail classes. We fix the backbone parameters after feature learning and retrain the classifier using ground-truth points to update its parameters. Extensive experiments demonstrate the effectiveness of our method outperforming previous state-of-the-art methods on both indoor and outdoor 3D point cloud datasets (i.e., S3DIS, ScanNet-V2, Semantic3D, and SemanticKITTI) using 1% and 1pt evaluation. Copyright © 2024, The Authors. All rights reserved.

关键词： Semantic Segmentation

An asymptotic analysis of minibatch-based momentum methods for linear regression models

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arXiv 2021年

作者： Gao, Yuan Zhu, Xuening Qi, Haobo Li, Guodong Zhang, Riquan Wang, Hansheng School of Statistics East China Normal University Shanghai China Key Laboratory of Advanced Theory and Application in Statistics and Data Science - MOE East China Normal University Shanghai China School of Data Science Fudan University Shanghai China Guanghua School of Management Peking University Beijing China Department of Statistics and Actuarial Science University of Hong Kong Hong Kong

Momentum methods have been shown to accelerate the convergence of the standard gradient descent algorithm in practice and theory. In particular, the minibatch-based gradient descent methods with momentum (MGDM) are widely used to solve large-scale optimization problems with massive datasets. Despite the success of the MGDM methods in practice, their theoretical properties are still underexplored. To this end, we investigate the theoretical properties of MGDM methods based on the linear regression models. We first study the numerical convergence properties of the MGDM algorithm and further provide the theoretically optimal tuning parameters specification to achieve faster convergence rate. In addition, we explore the relationship between the statistical properties of the resulting MGDM estimator and the tuning parameters. Based on these theoretical findings, we give the conditions for the resulting estimator to achieve the optimal statistical efficiency. Finally, extensive numerical experiments are conducted to verify our theoretical results. © 2021, CC BY.

关键词： Gradient methods

Robust Online Detection in Serially Correlated Directed Network

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arXiv 2021年

作者： Yu, Miaomiao Zhou, Yuhao Tsung, Fugee Key Laboratory of Advanced Theory and Application in Statistics and Data Science MOE Academy of Statistics and Interdisciplinary Sciences East China Normal University Shanghai China Department of Statistics and Operations Research University of North Carolina at Chapel Hill Chapel HillNC27599 United States Department of Industrial Engineering and Decision Analytics Hong Kong University of Science and Technology Kowloon Hong Kong

As the complexity of production processes increases, the diversity of data types drives the development of network monitoring technology. This paper mainly focuses on an online algorithm to detect serially correlated directed networks robustly and sensitively. First, we consider a transition probability matrix to resolve the double correlation of primary data. Further, since the sum of each row of the transition probability matrix is one, it standardizes the data, facilitating subsequent modeling. Then we extend the spring length based method to the multivariate case and propose an adaptive cumulative sum (CUSUM) control chart on the strength of a weighted statistic to monitor directed networks. This novel approach assumes only that the process observation is associated with nearby points without any parametric time series model, which is in line with reality. Simulation results and a real example from metro transportation demonstrate the superiority of our design. Copyright © 2021, The Authors. All rights reserved.

关键词： Digital storage

Preparation of a Bigel System Based on K-Carrageenan Hydrogel and Beeswax Oleogel and the Effect of Starch on the Bigel Properties

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SSRN

SSRN 2023年

作者： Zhou, Mengjing Li, Bin Wu, Aolin Hu, Zhigang Liu, Jizhen Wang, Ying Liu, Haiying School of Mechanical Engineering Wuhan Polytechnic University Hubei Wuhan430023 China Hubei Key Laboratory of Theory and Application of Advanced Materials Mechanics Wuhan University of Technology Hubei Wuhan430070 China

Oleogel and hydrogel were prepared by using beeswax and carrageenan as gelling agents, respectively, and bigel was prepared by mixing the oleogel and hydrogel thoroughly in ice *** structure of bigel was observed by metallurgical microscope, which proved that there existed water-in-oil, water-in-oil and mixed structure of the bigel as the ratio of hydrogel and oleogel changed. The mechanical properties, rheological properties and freeze-thaw stability of the bigel were investigated. The results showed that the addition of starch enhanced the mechanical properties of bigel, and the hardness of bigel increased by an average of 32.3% and the modulus of elasticity by 54.2% after the addition of starch. At the same time, Bigel had excellent freeze-thaw stability, which was increased by about 5% on average compared with that of Bigel without starch. This study provides a method for preparing bigel with excellent freeze-thaw stability and rheological properties. © 2023, The Authors. All rights reserved.

关键词： Hydrogels

Influence of Lattice Strain on the Mechanical Properties of Cosb3 Skutterudites

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SSRN

SSRN 2023年

作者： Duan, Bo Li, Jialiang Zhang, Xiaolian Li, Guodong Ma, Yuxi Xu, Hao School of Civil Engineering & Architecture Wuhan Polytechnic University Wuhan430023 China Hubei Key Laboratory of Theory and Application of Advanced Materials Mechanics Wuhan University of Technology Wuhan430070 China State Key Laboratory of Advanced Technology for Materials Synthesis and Processing Wuhan University of Technology Wuhan430070 China

Elemental doping has been widely employed to manipulate the electrical and thermal transport properties of thermoelectric materials, without considering the influence to mechanical properties. In skutterudites, electronegative S-dopants have been found to reduce the lattice thermal conductivity. However, the effect of the covalent S-Sb bond on the mechanical properties of CoSb3 skutterudites remains unexplored. Compressive strength, in particular, exhibits a significant reduction in S-doped skutterudites, measuring only 249 MPa, representing a nearly 50% decrease compared to binary skutterudites. Additionally, there is a noticeable drop in the elastic, bulk and shear modulus. With molecular dynamics calculations, the shear strength of S-doped skutterudites also follows a sharp drop at a small ultimate strain. The evolutions of atomic configurations reveal that the lattice strain induced by S-dopants softens the Sb-Sb bond, ultimately leading to structure collapse under low shear stress conditions. These findings underscore the necessity for a comprehensive approach to elemental doping in thermoelectric community. © 2023, The Authors. All rights reserved.

关键词： Strain