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Electromagnetohydrodynamic (EMHD) flow of fractional viscoelastic fluids in a microchannel

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Applied Mathematics and Mechanics(English Edition) 2022年第6期43卷 917-930页

作者： Shujuan AN Kai TIAN zhaodong ding Yongjun JIAN School of Mathematical Science Inner Mongolia UniversityHohhot 010021China

This study investigates the electromagnetohydrodynamic(EMHD)flow of fractional viscoelastic fluids through a microchannel under the Navier slip boundary *** flow is driven by the pressure gradient and electromagnetic force where the electric field is applied horizontally,and the magnetic field is vertically(upward or downward).When the electric field direction is consistent with the pressure gradient direction,the changes of the steady flow rate and velocity with the Hartmann number Ha are irrelevant to the direction of the magnetic field(upward or downward).The steady flow rate decreases monotonically to zero with the increase in *** contrast,when the direction of the electric field differs from the pressure gradient direction,the flow behavior depends on the direction of the magnetic field,i.e.,symmetry breaking ***,when the magnetic field is vertically upward,the steady flow rate increases first and then decreases with *** the magnetic field is reversed,the steady flow rate first reduces to zero as Ha increases from *** Ha continues to increase,the steady flow rate(velocity)increases in the opposite direction and then decreases,and finally drops to zero for larger *** increase in the fractional calculus parameterαor Deborah number De makes it take longer for the flow rate(velocity)to reach the steady *** addition,the increase in the strength of the magnetic field or electric field,or in the pressure gradient tends to accelerate the slip velocity at the *** the other hand,the increase in the thickness of the electric double-layer tends to reduce it.

关键词： electromagnetohydrodynamic(EMHD)flow fractional viscoelastic fluid symmetry breaking

On the energy conversion in electrokinetic transports

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Applied Mathematics and Mechanics(English Edition) 2022年第2期43卷 263-274页

作者： zhaodong ding Long CHANG Kai TIAN Yongjun JIAN School of Mathematical Science Inner Mongolia UniversityHohhotInner Mongolia010021China School of Statistics and Mathematics Inner Mongolia University of Finance and EconomicsHohhotInner Mongolia010021China

Energy conversion in micro/nano-systems is a subject of current research,among which the electrokinetic energy conversion has attracted extensive ***,there exist two different definitions on the electrokinetic energy conversion efficiency in literature.A few researchers defined the efficiency using the pure pressure-driven flow rate,while other groups defined the efficiency based on the flow rate with the inclusion of the effect of the streaming potential *** this work,both definitions are investigated for different fluid types under the periodic electrokinetic flow *** Newtonian fluids,the two definitions give similar ***,for viscoelastic fluids,these two definitions lead to significant *** efficiency defined by the pure pressure-driven flow rate even exceeds 100%in a certain range of the *** result shows that in the case of viscoelastic flow,it is incorrect to define the energy conversion efficiency by pure pressure-driven flow *** the same time,the reason for this problem is clarified through comprehensive analysis.

关键词： electrokinetic transport energy conversion efficiency Newtonian fluid viscoelastic fluid streaming potential field

Allen-Cahn型表面活性剂浓度的两相流格子Boltzmann模型

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内蒙古工业大学学报（自然科学版） 2024年第3期43卷 206-212页

作者：刘紫寒岳利清丁兆东武汉轻工大学经济学院武汉430048 内蒙古大学数学科学学院呼和浩特010021

基于相场理论,提出了含表面活性剂两相流介观格子Boltzmann(LB)模型,与经典Cahn-Hillaird型方程用于描述流体界面以及表面活性剂浓度不同,推导了Allen-Cahn(AC)型的表面活性剂浓度方程,并设计了相应的LB数值格式。该模型除了保留算法的... 详细信息

基于相场理论,提出了含表面活性剂两相流介观格子Boltzmann(LB)模型,与经典Cahn-Hillaird型方程用于描述流体界面以及表面活性剂浓度不同,推导了Allen-Cahn(AC)型的表面活性剂浓度方程,并设计了相应的LB数值格式。该模型除了保留算法的简单性、并行性以及刻画流体组分与活性剂组分的微观相互作用外,还能准确收敛AC型宏观方程。最后利用两个算例,含表面活性剂的平板问题以及液滴问题,验证该模型准确性与稳定性。

关键词：表面活性剂格子Boltzmann模型 Allen-Cahn型方程

Numerical invariant tori of symplectic integrators for integrable Hamiltonian systems

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Science China Mathematics 2018年第9期61卷 1567-1588页

作者： zhaodong ding Zaijiu Shang School of Mathematical Sciences Inner Mongolia University Hohhot 010021 China HUA Loo-Keng Key Laboratory of Mathematics Academy of Mathematics and Systems Science Chinese Academy of Sciences Beijing 100190 China School of Mathematical Sciences University of Chinese Academy of Sciences Beijing 100190 China

In this paper, we study the persistence of invariant tori of integrable Hamiltonian systems satisfying Rssmann's non-degeneracy condition when symplectic integrators are applied to them. Meanwhile, we give an estimate of the measure of the set occupied by the invariant tori in the phase space. On an invariant torus,numerical solutions are quasi-periodic with a diophantine frequency vector of time step size dependence. These results generalize Shang's previous ones(1999, 2000), where the non-degeneracy condition is assumed in the sense of Kolmogorov.

关键词： Hamiltonian 系统 Kolmogorov 非退化条件估计集合时间周期

Time periodic electroosmotic flow of micropolar fluids through microparallel channel

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Applied Mathematics and Mechanics(English Edition) 2016年第6期37卷 769-786页

作者： zhaodong ding Yongjun JIAN Liangui YANG School of Mathematical Sciences Inner Mongolia University

The time periodic electroosmotic between two infinitely extended microparallel flow of an incompressible micropolar fluid plates is studied. The analytical solutions of the velocity and microrotation are derived under the Debye-Hiickel approximation. The effects of the related dimensionless parameters, e.g., the micropolar parameter, the frequency, the electrokinetic width, and the wall zeta potential ratio of the upper plate to the lower plate, on the electroosmotic velocity and rnicrorotation are investigated. The results show that the amplitudes of the velocity and the volume flow rate will drop to zero when the micropolar parameter increases from 0 to 1. The effects of the electrokinetic width and the frequency on the velocity of the micropolar fluid are similar to those of the Newtonian fluid. However, the dependence of the microrotation on the related parameters mentioned above is complex. In order to describe these effects clearly, the dimensionless microrotation strength and the penetration depth of the microrotation are defined, which are used to explain the variation of the microrotation. In addition, the effects of various parameters on the dimensionless stress tensor at the walls are studied.

关键词： micropolar fluid electroosmotic flow microrotation strength penetration depth

基于疲劳损伤模型的钢筋混凝土梁疲劳可靠度分析

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合肥工业大学学报（自然科学版） 2022年第7期45卷 931-938,966页

作者：丁兆东刘剑锋合肥工业大学土木与水利工程学院安徽合肥230009 土木工程结构与材料安徽省重点实验室安徽合肥230009

文章基于具有物理机制的混凝土疲劳损伤演化模型,根据物理随机系统的基本观点,确立混凝土随机疲劳损伤本构模型的基本随机参数;通过统计识别1批混凝土单轴受拉和受压疲劳试验数据,给出基本随机参数的概率分布,从而建立完整的混凝土疲劳... 详细信息

文章基于具有物理机制的混凝土疲劳损伤演化模型,根据物理随机系统的基本观点,确立混凝土随机疲劳损伤本构模型的基本随机参数;通过统计识别1批混凝土单轴受拉和受压疲劳试验数据,给出基本随机参数的概率分布,从而建立完整的混凝土疲劳损伤本构关系;将混凝土疲劳损伤本构关系与钢筋疲劳损伤本构关系相结合,通过设定受压区混凝土损伤破坏阈值,引入吸收边界条件与概率密度演化理论,评估预应力混凝土梁的疲劳可靠度,从而初步建立混凝土疲劳问题的精细化可靠度分析框架。

关键词：混凝土结构疲劳损伤模型概率密度演化

Large-scale self-normalizing neural networks

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Journal of Automation and Intelligence 2024年第2期3卷 101-110页

作者： zhaodong Chen Weiqin Zhao Lei Deng Yufei ding Qinghao Wen Guoqi Li Yuan Xie University of California Santa BarbaraSanta Barbara93106CAUnited States University of Hong Kong Hong Kong999077China Tsinghua University Beijing100084China University of California San DiegoSan Diego92093CAUnited States University of Sydney Sydney2006Australia Institute of Automation Chinese Academy of ScienceBeijing100190China University of Chinese Academy of Science Beijing100190China The Hong Kong University of Science and Technology Hong Kong999077China

Self-normalizing neural networks(SNN)regulate the activation and gradient flows through activation functions with the self-normalization *** SNNs do not rely on norms computed from minibatches,they are more friendly to data parallelism,kernel fusion,and emerging architectures such as ReRAM-based ***,existing SNNs have mainly demonstrated their effectiveness on toy datasets and fall short in accuracy when dealing with large-scale tasks like *** lack the strong normalization,regularization,and expression power required for wider,deeper models and larger-scale *** enhance the normalization strength,this paper introduces a comprehensive and practical definition of the self-normalization property in terms of the stability and attractiveness of the statistical fixed *** is comprehensive as it jointly considers all the fixed points used by existing studies:the first and second moment of forward activation and the expected Frobenius norm of backward *** practicality comes from the analytical equations provided by our paper to assess the stability and attractiveness of each fixed point,which are derived from theoretical analysis of the forward and backward *** proposed definition is applied to a meta activation function inspired by prior research,leading to a stronger self-normalizing activation function named‘‘bi-scaled exponential linear unit with backward standardized’’(bSELU-BSTD).We provide both theoretical and empirical evidence to show that it is superior to existing *** enhance the regularization and expression power,we further propose scaled-Mixup and channel-wise scale&*** these three techniques,our approach achieves 75.23%top-1 accuracy on the ImageNet with Conv MobileNet V1,surpassing the performance of existing self-normalizing activation *** the best of our knowledge,this is the first SNN that achieves comparable accuracy to batch normalization on ImageNet.

关键词： Self-normalizing neural network Mean-field theory Block dynamical isometry Activation function

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基于微-细观机理的混凝土疲劳损伤本构模型

力学学报 2014年第6期46卷 911-919页

作者：丁兆东李杰同济大学土木工程学院上海200092

该文致力于混凝土疲劳损伤发展机理的微细观解释.以速率过程理论为基础,通过考虑裂纹断裂过程区中的水分子动力作用,在细观尺度上建立了具有物理机理的疲劳损伤能量耗散表达式.结合细观随机断裂模型,以宏观损伤力学为框架,建立了疲劳损... 详细信息

该文致力于混凝土疲劳损伤发展机理的微细观解释.以速率过程理论为基础,通过考虑裂纹断裂过程区中的水分子动力作用,在细观尺度上建立了具有物理机理的疲劳损伤能量耗散表达式.结合细观随机断裂模型,以宏观损伤力学为框架,建立了疲劳损伤演化方程.通过数值模拟,计算了单轴受拉时的疲劳损伤演化以及不同加载幅度下的疲劳寿命.与相关试验结果的对比显示出该文模型能够很好地表现混凝土材料的疲劳损伤演化过程.

关键词：混凝土疲劳损伤演化本构关系速率过程理论

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混凝土结构疲劳全过程分析方法研究

建筑结构学报 2017年第5期38卷 149-157页

作者：梁俊松丁兆东李杰同济大学土木工程学院上海200092 合肥工业大学土木与水利工程学院安徽合肥230009

为研究混凝土结构疲劳破坏的全过程,提出一种基于损伤力学的疲劳分析方法。该方法通过引入疲劳损伤本构模型以描述混凝土材料在疲劳荷载作用下的劣化过程。为提高计算效率,将本构模型与非线性有限元方法相结合,发展了一种循环跳跃式疲... 详细信息

为研究混凝土结构疲劳破坏的全过程,提出一种基于损伤力学的疲劳分析方法。该方法通过引入疲劳损伤本构模型以描述混凝土材料在疲劳荷载作用下的劣化过程。为提高计算效率,将本构模型与非线性有限元方法相结合,发展了一种循环跳跃式疲劳加速算法。基于该算法,结构的疲劳破坏过程可仅通过少量疲劳加载循环的计算加以推测。为保证算法精度,进一步提出基于损伤演化速率的自适应精度控制策略,使分析可根据疲劳损伤演化速率的变化自动调整加速算法的时间跳跃步长。采用该分析方法对混凝土材料与钢筋混凝土梁的疲劳破坏过程进行模拟,并与相关疲劳试验数据进行对比。结果表明:该分析方法可准确预测混凝土结构在疲劳荷载作用下的非线性行为,特别是疲劳加载过程中裂缝的产生和扩展过程;结合疲劳损伤本构模型和疲劳加速算法能够高效及准确地模拟混凝土结构的疲劳破坏全过程。

关键词：混凝土结构疲劳全过程损伤本构模型加速算法精度控制非线性有限元分析