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ENSEMBLE DOMAIN DECOMPOSITION ALGORITHM FOR THE FULLY-MIXED RANDOM STOKES-DARCY MODEL WITH THE BEAVERS-JOSEPH INTERFACE CONDITIONS

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arXiv 2022年

作者： Shi, Feng Sun, Yizhong Zheng, Haibiao College of Science Harbin Institute of Technology Shenzhen China School of Mathematical Sciences East China Normal University Shanghai China School of Mathematical Sciences East China Normal University Shanghai Key Laboratory of Pure Mathematics and Mathematical Practice Key Laboratory of Advanced Theory and Application in Statistics and Data Science East China Normal University Shanghai China

In this paper, an efficient ensemble domain decomposition algorithm is proposed for fast solving the fully-mixed random Stokes-Darcy model with the physically realistic Beavers-Joseph (BJ) interface conditions. We utilize the Monte Carlo method for the coupled model with random inputs to derive some deterministic Stokes-Darcy numerical models and use the idea of the ensemble to realize the fast computation of multiple problems. One remarkable feature of the algorithm is that multiple linear systems share a common coefficient matrix in each deterministic numerical model, which significantly reduces the computational cost and achieves comparable accuracy with the traditional methods. Moreover, by domain decomposition, we can decouple the Stokes-Darcy system into two smaller sub-physics problems naturally. Both mesh-dependent and mesh-independent convergence rates of the algorithm are rigorously derived by choosing suitable Robin parameters. Optimized Robin parameters are derived and analyzed to accelerate the convergence of the proposed algorithm. Especially, for small hydraulic conductivity in practice, the almost optimal geometric convergence can be obtained by finite element discretization. Finally, two groups of numerical experiments are conducted to validate the exclusive features of the proposed algorithm. © 2022, CC BY-NC-ND.

关键词： Numerical models

HYPOTHESIS TEST ON A MIXTURE FORWARD-INCUBATION-TIME EPIDEMIC MODEL WITH application TO COVID-19 OUTBREAK

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arXiv 2022年

作者： Wang, Chunlin Li, Pengfei Liu, Yukun Zhou, Xiao-Hua Qin, Jing Department of Statistics and Data Science School of Economics Wang Yanan Institute for Studies in Economics MOE Key Lab of Econometrics Fujian Key Lab of Statistics Xiamen University Xiamen China Department of Statistics and Actuarial Sciences University of Waterloo Canada Key Laboratory of Advanced Theory and Application in Statistics and Data Science - MOE School of Statistics East China Normal University Shanghai China Department of Biostatistics School of Public Health Peking University Beijing China National Institute of Allergy and Infectious Diseases National Institutes of Health United States

The distribution of the incubation period of the novel coronavirus disease that emerged in 2019 (COVID-19) has crucial clinical implications for understanding this disease and devising effective disease-control measures. Qin et al. (2020) designed a cross-sectional and forward follow-up study to collect the duration times between a specific observation time and the onset of COVID-19 symptoms for a number of individuals. They further proposed a mixture forward-incubation-time epidemic model, which is a mixture of an incubation-period distribution and a forward time distribution, to model the collected duration times and to estimate the incubation-period distribution of COVID-19. In this paper, we provide sufficient conditions for the identifiability of the unknown parameters in the mixture forward-incubation-time epidemic model when the incubation period follows a two-parameter distribution. Under the same setup, we propose a likelihood ratio test (LRT) for testing the null hypothesis that the mixture forward-incubation-time epidemic model is a homogeneous exponential distribution. The testing problem is non-regular because a nuisance parameter is present only under the alternative. We establish the limiting distribution of the LRT and identify an explicit representation for it. The limiting distribution of the LRT under a sequence of local alternatives is also obtained. Our simulation results indicate that the LRT has desirable type I errors and powers, and we analyze a COVID-19 outbreak dataset from China to illustrate the usefulness of the LRT. Copyright © 2022, The Authors. All rights reserved.

关键词： COVID-19

The Coupled Effffects of Grain Boundary Strengthening and Orowan Strengthening Examined by Dislocation Dynamics Simulations

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SSRN

SSRN 2022年

作者： Jiang, Maoyuan Zhang, Xuzhi Mei, Hai Xu, Shuang Liu, Lisheng Hubei Key Laboratory of Theory and Application of Advanced Materials Mechanics Wuhan University of Technology Wuhan430070 China Department of Engineering Structure and Mechanics School of Science Wuhan University of Technology Wuhan430070 China

DD simulations are performed to unravel the coupled effects between grain boundary strengthening and Orowan strengthening. With the simulations of a plastically-deformed grain embedded in elastic matrix, the internal stresses associated with inter- and intragranular obstacles are quantified. First, plastic yielding is controlled by the length of dislocation sources. Then, in plastic deformation, the stress contribution of bypassing mechanism increases significantly with the size and number of precipitates, while the stress contribution of geometrically necessary dislocations at grain boundaries slightly decreases. Compared with regular spatial distribution of precipitates, random distribution induces a higher strengthening effect by reducing the dislocation mobility. Simulations of four-grain aggregates involving grain refinement and precipitation are systematically investigated. The volume fraction of precipitates is the key factor controlling the Orowan strengthening in addition to the grain size effect. A generalized Hall-Petch equation based on the mean free path of dislocations is proposed. At low strain, a relatively uniform internal stress field is found inside the aggregates with weak stress concentrations around grain boundaries and precipitates. The underlying mechanisms identified in this work are essential for understanding the plastic behavior of precipitate-strengthened polycrystals. © 2022, The Authors. All rights reserved.

关键词： Grain boundaries

Mechanical Behavior of Al-Si10-Mg Schwarz P Structure Fabricated by Selective Laser Melting and a Unified Mathematical Model with Geometrical Parameter

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SSRN

SSRN 2022年

作者： Zhang, Xiaonan Yan, Shilin Xie, Xiangyu Li, Yongjing Li, Bin Wen, Pin Hubei Key Laboratory of Theory and Application of Advanced Materials Mechanics School of Science Wuhan University of Technology Wuhan430070 China School of Mechanical Engineering Wuhan Polytechnic University Hubei Wuhan430023 China

Compared with the traditional lattice structure, the triply periodic minimal surface structure can avoid stress concentration effectively. Here, it is promising in the fields of lightweight and energy absorption. However, the number of structural parameters and mechanical properties of the triply periodic minimal surface structure is plentiful, and the relationship between them is unclassified. In this paper, it is firstly proposed a unified mathematical model of the relationship between TPMS structural design parameters and mechanical properties. Fifteen Primitive models were designed by changing the structural parameters (level-set value C and thickness T ) and manufacturing by selective laser melting. The geometric defects and surface quality of the structures were explored by optical microscope and SEM. The mechanical properties were investigated by quasi-static compression test and finite element (FE) simulation. The influence of building direction on structural mechanical behavior (failure mode, stress-strain curve) was studied. The real mechanical properties (Young's modulus and plateau stress) of the structure could be predicted according to different C and T combinations. Finally, the energy absorption characteristics were explored. The results showed that there is an optimal C value to maximize the energy absorption performance of the structure. © 2022, The Authors. All rights reserved.

关键词： Energy absorption

Peridynamic stress is the static first Piola-Kirchhoff Virial stress

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arXiv 2022年

作者： Li, Jun Li, Shaofan Lai, Xin Liu, Lisheng State Key Laboratory of Advanced Technology for Materials Synthesis and Processing Wuhan University of Technology Wuhan430070 China Department of Civil and Environmental Engineering University of California BerkeleyCA94720 United States Hubei Key Laboratory of Theory and Application of Advanced Materials Mechanics Wuhan University of Technology Wuhan430070 China

The peridynamic stress formula proposed by Lehoucq and Silling [1, 2] is cumbersome to be implemented in numerical computations. Here, we show that the peridynamic stress tensor has the exact mathematical expression as that of the first Piola-Kirchhoff static Virial stress originated from Irving-Kirkwood-Noll formalism [3, 4] through the Hardy-Murdoch procedure [5, 6], which offers a simple and clear expression for numerical calculations of peridynamic stress. Several numerical verifications have been carried out to validate the accuracy of proposed peridynamic stress formula in predicting the stress states in the vicinity of the crack tip and other sources of stress concentration. The peridynamic stress is evaluated within the bond-based peridynamics with prototype microelastic brittle (PMB) material model. It is found that the PMB material model may exhibit nonlinear constitutive behaviors at large deformations. The stress fields calculated through the proposed peridynamic stress formula show good agreements with finite element analysis results, analytical solutions, and experimental data, demonstrating the promising potential of derived peridynamic stress formula in simulating the stress states of problems with discontinuities, especially in the bond-based peridynamics. Copyright © 2022, The Authors. All rights reserved.

关键词： Continuum mechanics

Design of a Capsule Robot System for Gastric Hemorrhage Detection using Luminol 20

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Design of a Capsule Robot System for Gastric Hemorrhage Dete...

20th IEEE International Conference on Mechatronics and Automation, ICMA 2023

作者： Mao, Yuchen Guo, Jian Guo, Shuxiang Fu, Qiang Tianjin University of Technology Tianjin Key Laboratory for Control Theory & Application Complicated Systems Intelligent Robot Laboratory School of Electrical Engineering and Automation Binshui Xidao Extension 391 Tianjin300384 China Shenzhen Institute of Advanced Biomedical Robot Co. Ltd No.12 Ganli Sixth Road Jihua Street Longgang District Shenzhen518100 China Key Laboratory of Convergence Medical Engineering System and Healthcare Technology The Ministry of Industry and Information Technology School of Life Science Beijing Institute of Technology No.5 Zhongguancun South Street Beijing100081 China

ISBN: (纸本)9798350320831

Gastric hemorrhage in upper gastrointestinal bleeding is an obvious indicator of deteriorating gastric disease. This paper proposes a capsule robot system for detecting bleeding in the stomach. The patient ingests a capsule robot containing luminol reagent, which detects bleeding in the stomach via chemiluminescence. The MCU receives the optical sensor signal, and the data is transmitted via radio frequency. The external lower computer receives and forwards the data to the upper computer for processing and display. The data is used to determine the presence and amount of stomach bleeding. Chemiluminescence is an excellent sensor, requiring no external energy supply, and demonstrating excellent sensitivity and selectivity. Combining chemical and electronic sensors presents opportunities for further development. Capsule robot detection reduces the discomfort and risk of secondary injury associated with traditional endoscopy. This paper establishes an experimental platform using porcine blood to simulate human blood, demonstrating the feasibility of the system. © 2023 IEEE.

关键词： Chemiluminescence

Tailoring mechanical properties of PμSL 3D-printed structures via size effect

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International Journal of Extreme Manufacturing 2022年第4期4卷 261-268页

作者： Wenqiang Zhang Haitao Ye Xiaobin Feng Wenzhao Zhou Ke Cao Maoyuan Li Sufeng Fan Yang Lu Department of Mechanical Engineering City University of Hong KongKowloonHong Kong SAR 999077People's Republic of China Nano-Manufacturing Laboratory(NML) City University of Hong Kong Shenzhen Research InstituteShenzhen 518057People's Republic of China Department of Mechanical and Energy Engineering Southern University of Science and TechnologyShenzhen 518055People's Republic of China Hubei Key Laboratory of Theory and Application of Advanced Materials Mechanics Wuhan University of TechnologyWuhan 430070People's Republic of China School of Mechano-Electronic Engineering Xidian UniversityXi'an 710071People's Republic of China State Key Laboratory of Materials Processing and Die&Mould Technology School of Materials Science and EngineeringHuazhong University of Science and TechnologyWuhan 430074People's Republic of China School of Mechanics and Safety Engineering Zhengzhou UniversityZhengzhou 450001People's Republic of China

Projection micro stereolithography(PμSL)has emerged as a powerful three-dimensional(3D)printing technique for manufacturing polymer structures with micron-scale high resolution at high printing speed,which enables the production of customized 3D microlattices with feature sizes down to several ***,the mechanical properties of as-printed polymers were not systemically studied at the relevant length scales,especially when the feature sizes step into micron/sub-micron level,limiting its reliable performance prediction in micro/nanolattice and other metamaterial *** this work,we demonstrate that PμSL-printed microfibers could become stronger and significantly more ductile with reduced size ranging from 20μm to 60μm,showing an obvious size-dependent mechanical behavior,in which the size decreases to 20μm with a fracture strain up to~100%and fracture strength up to~100 *** size effect enables the tailoring of the material strength and stiffness of PμSL-printed microlattices over a broad range,allowing to fabricate the microlattice metamaterials with desired/tunable mechanical properties for various structural and functional applications.

关键词： 3D printing projection micro-stereolithography(PμSL) size effect microfiber mechanical properties microlattice metamaterial

Fractional stochastic wave equation driven by a Gaussian noise rough in space

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arXiv 2019年

作者： Song, Jian Song, Xiaoming Xu, Fangjun School of Mathematics Shandong University Jinan Shandong250100 China Department of Mathematics Drexel University PhiladelphiaPA19104 United States Key Laboratory of Advanced Theory and Application in Statistics and Data Science - MOE School of Statistics East China Normal University Shanghai200062 China NYU-ECNU Institute of Mathematical Sciences NYU Shanghai Shanghai200062 China

In this article, we consider fractional stochastic wave equations on R driven by a multiplicative Gaussian noise which is white/colored in time and has the covariance of a fractional Brownian motion with Hurst parameter H ∈ (1/4, 1/2) in space. We prove the existence and uniqueness of the mild Skorohod solution, establish lower and upper bounds for the p-th moment of the solution for all p ≥ 2, and obtain the Hölder continuity in time and space variables for the *** Codes 60H07, 60H15, 60G15 Copyright © 2019, The Authors. All rights reserved.

关键词： Gaussian noise (electronic)

A Review on Bio-inspired Fluid Mechanics via Deep Reinforcement Learning 1

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

作者： Wang, Jianxiong Jiang, Zhangze Yang, Yi Hu, Wulong Naval Research Institute Beijing100094 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 School of Naval Architecture Ocean and Energy Power Engineering Wuhan University of Technology Wuhan430063 China

ISBN: (数字)9789819915491

ISBN: (纸本)9789819915484

As a result of advancements in artificial intelligence and big data technology, the field of study on bio-inspired fluid mechanics is shifting toward data-driven methodologies. Deep reinforcement learning (DRL) has recently been adopted across a wide range of bio-inspired fluid mechanics domains due to its potential to solve problem-solving issues that were previously unsolvable due to a combination of non-linearity and high dimensionality. This study discusses the most recent advances in bio-inspired fluid mechanics using deep reinforcement learning. First, a timeline of bio-inspired fluid mechanics evolution is provided. Several popular deep reinforcement learning techniques are introduced in bio-inspired fluid mechanics, along with a detailed discussion of the benefits and drawbacks of each technique. Furthermore, data-driven bio-inspired fluid mechanical advancements are presented. Finally, several new challenges are proposed based on recent progress. The goal of this publication is to give researchers interested in tackling new problems with data-driven fluid mechanics a better understanding of DRL capabilities as well as cutting-edge applications in data-driven fluid mechanics. © 2023, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.

关键词： Reinforcement learning