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Acta Mechanica Solida Sinica 2024年第2期37卷 271-284页

作者： Hanxing Zhao Pengyu Cao Fengfeng Li Xin Lan Liwu Liu Yanju Liu Jinsong Leng Centre of Composite Materials and Structures Harbin Institute of Technology(HIT)Harbin150080China department of Astronautical Science and mechanics Harbin Institute of Technology(HIT)Harbin150001China

The mismatch in thermal expansion coefficients between the fiber-rich and resin-rich regions of a shape memory polymer composite(SMPC)laminate,along with the residual strain during SMPC fabrication,results in buckling deformation of the inhomogeneous *** paper presents a macroscopic model for buckling of an inhomogeneous SMPC laminate under initial biaxial *** linear and nonlinear buckling analyses are carried out using the energy *** influences of prestrain biaxiality,temperature,and ply angle on the buckling wavelength,critical buckling prestrain,and buckling amplitude are *** results demonstrate that the critical buckling wavelength of the SMPC laminate is independent of the prestrain,while the amplitude is almost independent of *** addition,the optimal fiber stacking configuration with the maximum critical buckling prestrains of inhomogeneous SMPC laminates is determined by a genetic algorithm.

关键词： Shape memory polymer composite Buckling behavior Inhomogeneous laminate Biaxial prestrains

Induced magneto-conductivity in a two-nodeWeyl semimetal under Gaussian random disorder

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Chinese Physics B 2024年第9期33卷 566-574页

作者： Chuanxiong Xu Haoping Yu Mei Zhou Xuanting Ji department of Applied Physics China Agricultural UniversityBeijing 100083China department of Applied mechanics China Agricultural UniversityBeijing 100083China School of Physical Sciences University of Chinese Academy of SciencesBeijing 100049China

Measuring the magneto-conductivity induced from impurities may help determine the impurity distribution and reveal the structure of a Weyl semimetal *** verify this,we utilize the Gaussian random disorder to simulate charged impurities in a two-node Weyl semimetal model and investigate the impact of charged impurities on magneto-conductivity in Weyl *** first compute the longitudinal magnetic conductivity and find that it is positive and increases proportionally with the parameter governing the Gaussian distribution of charged impurities,suggesting the presence of negative longitudinal *** we consider both the intra-valley and inter-valley scattering processes to calculate the induced transverse magneto-conductivity in the *** findings indicate that both inter-valley and intravalley scattering processes play important roles in the transverse *** locations of Weyl nodes can also be determined by magneto-conductivity *** is possible if the magnetic field strength and the density of charged impurities are ***,the measurement of magnetic conductivity may reveal the distribution of charged impurities in a given sample once the locations of the Weyl nodes have been *** findings can aid in detecting the structure of a Weyl semimetal sample,enhancing comprehension of magnetotransport in Weyl semimetals and promoting the development of valley electronics.

关键词： Weyl semimetal inter-valley scattering magneto-conductivity

Performance of evolutionary optimized machine learning for modeling total organic carbon in core samples of shale gas fields

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Petroleum 2024年第1期10卷 150-164页

作者： Leonardo Goliatt C.M.Saporetti L.C.Oliveira E.Pereira department of Computational and Applied mechanics Federal University of Juiz de Fora department of Computational Modeling Polytechnic Institute Rio de Janeiro State University Petrobras department of Stratigraphy and Paleontology Rio de Janeiro State University

Rock samples' TOC content is the best indicator of the organic matter in source rocks. The origin rock samples' analysis is used to calculate it manually by specialists. This method requires time and resources because it relies on samples from many well intervals in source rocks. Therefore, research has been done to aid this effort. Machine learning algorithms can estimate total organic carbon instead of well logs and stratigraphic studies. In light of these efforts, the current work present a study on automating the total organic carbon estimation using machine learning approaches improved by an evolutionary methodology to give the model flexibility and precision. Genetic algorithms, differential evolution, particle swarm optimization, grey wolf optimization, artificial bee colony, and evolution strategies were used to improve machine learning models to predict TOC. The six metaheuristics were integrated into four machine learning methods: extreme learning machine, elastic net linear model, linear support vector regression, and multivariate adaptive regression splines. Core samples from the YuDong-Nan shale gas field, located in the Sichuan basin, were used to evaluate the hybrid strategy. The findings show that combining machine learning models with an evolutionary algorithms in a hybrid fashion produce flexible models that accurately predict TOC. The results show that, independent of the metaheuristic used to guide the model selection, optimized extreme learning machines attained the best performance scores according to six metrics. Such hybrid models can be used in exploratory geological research,particularly for unconventional oil and gas resources.

关键词： Total organic carbon Hybrid models Automated machine learning Evolutionary algorithms Geology

Topology Optimization of Two Fluid Heat Transfer Problems for Heat Exchanger Design

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Computer Modeling in Engineering & Sciences 2024年第8期140卷 1949-1974页

作者： Kun Yan Yunyu Wang Jun Yan School of Chemical Engineering Dalian University of TechnologyDalian116024China Jianghuai Advanced Technology Center Hefei230000China State Key Laboratory of Structural Analysis for Industrial Equipment Department of Engineering MechanicsInternational Research Center for Computational MechanicsDalian University of TechnologyDalian116024China

Topology optimization of thermal-fluid coupling problems has received widespread *** article proposes a novel topology optimization method for laminar two-fluid heat exchanger *** proposed method utilizes an artificial density field to create two permeability interpolation functions that exhibit opposing trends,ensuring separation between the two fluid ***,a Gaussian function is employed to construct an interpolation function for the thermal conductivity ***,a computational program has been developed on the OpenFOAM platform for the topology optimization of two-fluid heat *** program leverages parallel computing,significantly reducing the time required for the topology optimization *** enhance computational speed and reduce the number of constraint conditions,we replaced the conventional pressure drop constraint condition in the optimization problem with a pressure inlet/outlet boundary *** 3D optimization results demonstrate the characteristic features of a surface structure,providing valuable guidance for designing heat exchangers that achieve high heat exchange efficiency while minimizing excessive pressure *** the same time,a new structure appears in large-scale topology optimization,which proves the effectiveness and stability of the topology optimization program written in this paper in large-scale calculation.

关键词： Topology optimization two fluid heat exchanger OpenFOAM large scale

Updated Lagrangian Particle Hydrodynamics (ULPH)Modeling of Natural Convection Problems

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Computer Modeling in Engineering & Sciences 2024年第10期141卷 151-169页

作者： Junsong Xiong Zhen Wang Shaofan Li Xin Lai Lisheng Liu Xiang Liu Hubei Key Laboratory of Theory and Application of Advanced Materials mechanics Wuhan University of TechnologyWuhan430070China department of Engineering Structure and mechanics Wuhan University of TechnologyWuhan430070China department of Civil and Environmental Engineering The University of CaliforniaBerkeleyCA 94720USA

Natural convection is a heat transfer mechanism driven by temperature or density differences,leading to fluid motion without external *** occurs in various natural and engineering phenomena,influencing heat transfer,climate,and fluid mixing in industrial *** work aims to use the Updated Lagrangian Particle Hydrodynamics(ULPH)theory to address natural convection *** Navier-Stokes equation is discretized using second-order nonlocal differential operators,allowing a direct solution of the Laplace operator for temperature in the energy *** numerical simulations,including cases such as natural convection in square cavities and two concentric cylinders,were conducted to validate the reliability of the *** results demonstrate that the proposed model exhibits excellent accuracy and performance,providing a promising and effective numerical approach for natural convection problems.

关键词： Updated Lagrangian particle hydrodynamics(ULPH) natural convection meshless methods higher order Laplacian model

A Detailed Thermal Resistance Network Analysis of FCBGA Package

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Journal of Thermal Science 2024年第1期33卷 18-28页

作者： DANG Hao LU Yang DU Yanzheng ZHANG Xiu ZHANG Qian MA Weigang ZHANG Xing Key Laboratory for Thermal Science and Power Engineering of Ministry of Education Department of Engineering MechanicsTsinghua UniversityBeijing 100084China Zhongxing Telecom Equipment Corporation Shanghai 201203China

Using thermal models to describe the heat dissipation process of FCBGA is a significant topic in the field of ***,the thermal resistance model considering the structure of each part of the chip is still ambiguous and rare,but it is quite desirable in *** this work,we propose a detailed thermal resistance network model,and describe it by using thermal conduction resistance and thermal spreading *** a striking FCBGA case,we calculated the thermal resistance of each part of the structure according to the temperature field simulated by *** thermal resistance network can be used to predict the temperatures in the chip under different *** example,when the power changes by 40%,the relative error of junction temperature prediction is only 0.24%.The function of the detailed thermal resistance network in evaluating the optimization space and determining the optimization direction is *** work illustrates a potential thermal resistance analysis method for electronic devices such as FCBGA.

关键词： FCBGA package thermal resistance network thermal spreading resistance junction temperature

A Novel On-Site-Real-Time Method for Identifying Characteristic Parameters Using Ultrasonic Echo Groups and Neural Network

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Chinese Journal of Mechanical Engineering 2024年第1期37卷 215-228页

作者： Shuyong Duan Jialin Zhang Heng Ouyang Xu Han Guirong Liu State Key Laboratory of Reliability and Intelligence of Electrical Equipment Hebei University of TechnologyTianjin 300401China department of Aerospace Engineering and Engineering mechanics University of CincinnatiCincinnati 45221USA

On-site and real-time non-destructive measurement of elastic constants for materials of a component in a in-service structure is a challenge due to structural complexities,such as ambiguous boundary,variable thickness,nonuniform material *** work develops for the first time a method that uses ultrasound echo groups and artificial neural network(ANN)for reliable on-site real-time identification of material *** use of echo groups allows the use of lower frequencies,and hence more accommodative to structural *** train the ANNs,a numerical model is established that is capable of computing the waveform of ultrasonic echo groups for any given set of material properties of a given *** waveform of an ultrasonic echo groups at an interest location on the surface the structure with material parameters varying in a predefined range are then computed using the numerical *** results in a set of dataset for training the ANN *** the ANN is trained,the material parameters can be identified simultaneously using the actual measured echo waveform as input to the *** tests have been conducted both numerically and experimentally to evaluate the effectiveness and accuracy of the currently proposed *** results show that the maximum identification error of numerical example is less than 2%,and the maximum identification error of experimental test is less than 7%.Compared with currently prevailing methods and equipment,the proposefy the density and thickness,in addition to the elastic ***,the reliability and accuracy of inverse prediction is significantly ***,it has broad applications and enables real-time field measurements,which has not been fulfilled by any other available methods or equipment.

关键词： Parameter identification Ultrasonic echo group High-precision modeling Artificial neural network NDT

Quantitative Identification of Delamination Damage in Composite Structure Based on Distributed Optical Fiber Sensors and Model Updating

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Structural Durability & Health Monitoring 2024年第6期18卷 785-803页

作者： Hao Xu Jing Wang Rubin Zhu Alfred Strauss Maosen Cao Zhanjun Wu School of Materials Science and Engineering Dalian University of TechnologyDalian116000China School of mechanics and Aerospace Engineering Dalian University of TechnologyDalian116000China department of Civil Engineering and Natural Hazards University of Natural Resources and Life SciencesVienna1180Austria department of Engineering mechanics Hohai UniversityNanjingChina

Delamination is a prevalent type of damage in composite laminate *** accumulation degrades structural performance and threatens the safety and integrity of *** study presents a method for the quantitative identification of delamination identification in composite materials,leveraging distributed optical fiber sensors and a model updating ***,a numerical analysis is performed to establish a parameterized finite element model of the composite ***,this model subsequently generates a database of strain responses corresponding to damage of varying sizes and *** radial basis function neural network surrogate model is then constructed based on the numerical simulation results and strain responses captured from the distributed fiber optic ***,a multi-island genetic algorithm is employed for global optimization to identify the size and location of the *** efficacy of the proposed method is validated through numerical examples and experiment studies,examining the correlations between damage location,damage size,and strain *** findings confirm that the model updating technique,in conjunction with distributed fiber optic sensors,can precisely identify delamination in composite structures.

关键词： Composite structures fiber optic sensor damage identification model updating surrogate model

A Note on P m-Factorizable Topological Groups

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Journal of Mathematical Research with Applications 2024年第2期44卷 209-212页

作者： Chunjie MA Liangxue PENG Beijing University of Technology School of Mathematics department of Mathematics Statistics and mechanics

In this paper, we define a new class of P m-factorizable topological groups. A topological group G is called P m-factorizable if, for every continuous function f : G → M to a metrizable space M, one can find a perfect homomorphism π : G → K onto a second-countable topological group K and a continuous function g : K → M such that f = g■π. We show that a topological group G is P m-factorizable if and only if it is P R-factorizable. And we get that if G is a P m-factorizable topological group and K is any compact topological group, then the group G × K is P m-factorizable.

关键词： R-factorizable PR-factorizable m-factorizable Pm-factorizable M-factorizable

平板湍流边界层湍动能时空多尺度分布特征与典型结构

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Acta Mechanica Sinica 2024年第3期40卷 61-71页

作者：王芊翔范子椰岳巾会白建侠程肖岐田海平姜楠 department of mechanics School of Mechanical EngineeringTianjin UniversityTianjin300354China department of Mathematics Tianjin Renai CollegeTianjin301636China department of mechanics Taiyuan University of TechnologyTaiyuan030024China

应用四相机阵列高时间分辨粒子图像测速系统,测量平板湍流边界层7.26δ_(0.99)×1.18δ_(0.99)大视场瞬态速度场的大样本时间序列,实验雷诺数Re_(τ)=1046.在所有法向层沿流向方向进行空间多尺度连续小波变换,根据分尺度小波系数得到湍... 详细信息

应用四相机阵列高时间分辨粒子图像测速系统,测量平板湍流边界层7.26δ_(0.99)×1.18δ_(0.99)大视场瞬态速度场的大样本时间序列,实验雷诺数Re_(τ)=1046.在所有法向层沿流向方向进行空间多尺度连续小波变换,根据分尺度小波系数得到湍动能随脉动空间尺度和法向位置的分布;同时对每个空间点脉动速度时间序列在时间上进行多尺度连续小波变换,根据分尺度小波系数得到湍动能随脉动时间尺度和法向位置的分布;计算出去除多尺度相干结构前后的平坦因子随脉动空间尺度和法向位置的分布.使用空间小波系数过零点法对流场的湍流结构进行检测,用条件采样和空间相位平均的方法获得各尺度不同法向位置湍流结构的空间典型拓扑,发现湍流小尺度结构涡量的空间拓扑呈现沿流向和法向正负交替的四极子结构,流线表现为鞍点和焦点组成的动力系统,肯定了湍流小尺度结构的普适性;计算去除相干结构前后的标度指数ζ(p),发现多尺度相干结构是引起奇异标度律的原因.

关键词： Arrayed TRPIV Turbulent boundary layer Coherent structure Wavelet transform Scaling law