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A machine learning based solver for pressure Poisson equations

Theoretical & Applied Mechanics Letters 2022年第5期12卷 315-321页

作者： Ruilin Chen Xiaowei Jin Hui Li Key Lab of Smart Prevention and Mitigation of Civil Engineering Disasters of the Ministry of Industry and Information Technology Harbin Institute of TechnologyHarbin 150090China Key Lab of Structures Dynamic Behavior and Control of the Ministry of Education Harbin Institute of TechnologyHarbin 150090China Guangdong-Hong Kong-Macao Joint Laboratory for Data-Driven Fluid Mechanics and Engineering Applications Harbin Institute of Technology(Shenzhen)Shenzhen 518055China

When using the projection method(or fractional step method)to solve the incompressible Navier-Stokes equations,the projection step involves solving a large-scale pressure Poisson equation(PPE),which is computationally expensive and *** this study,a machine learning based method is proposed to solve the large-scale *** machine learning(ML)-block is used to completely or partially(if not sufficiently accurate)replace the traditional PPE iterative solver thus accelerating the solution of the incompressible Navier-Stokes *** ML-block is designed as a multi-scale graph neural network(GNN)framework,in which the original high-resolution graph corresponds to the discrete grids of the solution domain,graphs with the same resolution are connected by graph convolution operation,and graphs with different resolutions are connected by down/up prolongation *** well trained MLblock will act as a general-purpose PPE solver for a certain kind of flow *** proposed method is verified via solving two-dimensional Kolmogorov flows(Re=1000 and Re=5000)with different source *** the premise of achieving a specified high precision(ML-block partially replaces the traditional iterative solver),the ML-block provides a better initial iteration value for the traditional iterative solver,which greatly reduces the number of iterations of the traditional iterative solver and speeds up the solution of the *** experiments show that the ML-block has great advantages in accelerating the solving of the Navier-Stokes equations while ensuring high accuracy.

关键词： Pressure Poisson equation Machine learning Projection method Multi-scale GNN

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Effect of trigger system on experimental dispersion characteristics of active surface wave testing

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Earthquake Engineering and Engineering Vibration 2024年第2期23卷 311-318页

作者： Lin Shibin Jeramy C.Ashlock Zhu Liming Qin Zexiang Li Bo Zhu Xingji Zhai Changhai State Key Laboratory of Precision Blasting Jianghan UniversityWuhan 430056China Hubei Key Laboratory of Blasting Engineering Jianghan UniversityWuhan 430056China Department of Civil Construction&Environmental EngineeringIowa State UniversityAmesIA 50010USA Wuhan Airport Road Development Co. Ltd.Wuhan 430065China School of Civil and Environmental Engineering Harbin Institute of TechnologyShenzhen 518055China Key Lab of Structures Dynamic Behavior and Control of the Ministry of Education Harbin Institute of TechnologyHarbin 150090China Key Lab of Smart Prevention and Mitigation of Civil Engineering Disaster of the Ministry of Industry and Information Technology Harbin Institute of TechnologyHarbin 150090China

A trigger system is typically employed in active seismic testing to trigger and synchronize multichannel surface wave data *** effect of the trigger system on the dispersion image of surface waves is empirically known to be negligible,however,theoretical explanation regarding the effect of the trigger system is *** study systematically examines the theory for surface wave dispersion analysis and proves that the effect of the trigger system on a dispersion image is negligible via a solid theoretical ***,based on the new theoretical explanation,an alternative method that uses only the relative phase difference between sensors to extract dispersion characteristics with better conceptual clarity is *** active surface wave testing cases are considered to validate the theory and *** results indicate that(1)an accurate trigger system is not necessary for surface wave data acquisition,and(2)it is unnecessary to assume that the impact point is the generation point of the surface waves for the experimental dispersion analysis.

关键词： site investigation surface waves data acquisition dispersion

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Ultrasonic guided waves sensing using optical fiber sensor 7

Ultrasonic guided waves sensing using optical fiber sensor

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7th International Conference on Structural Health Monitoring of Intelligent Infrastructure, SHMII 2015

作者： Zhou, W. Li, H. Dong, Y. Wang, A. Key Lab. of Structures Dynamic Behavior and Control of the Ministry of Education Harbin Institute of Technology Harbin150090 China School of Civil Engineering Harbin Institute of Technology Harbin150090 China National Key Laboratory of Science and Technology on Tunable Laser Harbin Institute of Technology Harbin150001 China

Optical fiber sensors have been proven that they have potential as ultrasonic guided waves sensor for structural health monitoring and damage detection. They can be used to receive acoustic emission signals from dynamic structural damages or guided waves propagating in waveguide and excited by ultrasonic actuators. Optical fiber sensors based on Mach-Zehnder interferometer were investigated in this work. Their sensing properties were explored experimentally using Lamb waves excited by a piezoelectric wafer in an aluminum plate. Spiral shape with different size was selected to increase their sensitivity. Experiments were also conducted to examine the voltage responses received by this type of sensor, and investigate results of tuning frequency. © 2015, International Society for Structural Health Monitoring of Intelligent Infrastructure, ISHMII. All rights reserved.

关键词： Structural health monitoring

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Review and analysis on spalling critical temperature of concrete and fibers dosage to prevent spalling at elevated temperatures

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Jianzhu Jiegou Xuebao/Journal of Building structures 2017年第1期38卷 161-170页

作者： Chen, Mingyang Hou, Xiaomeng Zheng, Wenzhong Wu, Bo Key Lab of Structures Dynamic Behavior and Control of China Ministry of Education Harbin Institute of Technology Harbin150090 China State Key Laboratory of Subtropical Building Science South China University of Technology Guangzhou510640 China

The principle of fire safety design is to ensure that concrete structures will not collapse or spall during fire and can be repaired after fire. There is important significance to research the spalling critical temperature of concrete without fibers or with lower fibers and rational fibers dosage to prevent spalling at elevated temperatures. The test results on fire-induced concrete spalling were analyzed. The relationship of spalling critical temperature and concrete cube compressive strength was obtained. Results show that the spalling critical temperature decreases with the increase of concrete compressive *** relationship of volume dosage of polypropylene (PP) fibers and steel fibers to prevent spalling and concrete compressive strength was obtained. The dosage of PP fibers increases linearly with the increase of concrete compressive strength, while the dosage of steel fibers increases with the increase of concrete compressive strength and the relationship can be expressed as an exponent *** is not safe to apply the recommendation in EN 1992-1-2: 2004 'Design of concrete structures: part 1-2: general rules: structural fire design' that the volume dosage 0.22% of PP fibers in concrete to prevent spalling. The proposed formula for fibers dosage will reduce the fire-induced spalling of concrete effectively. © 2017, Editorial Office of Journal of Building structures. All right reserved.

关键词： Steel fibers

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Experimental investigation on the impingement of synthetic jet vortex rings on a spherical wall

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Physical Review Fluids 2022年第4期7卷 044703-044703页

作者： Changlong Chen Donglai Gao Wen-Li Chen Key Laboratory of Smart Prevention and Mitigation of Civil Engineering Disasters The Ministry of Industry and Information Technology Harbin Institute of Technology Harbin 150090 China Key Laboratory of Structures Dynamic Behavior and Control The Ministry of Education Harbin Institute of Technology Harbin 150090 China

An experimental study was conducted to investigate the influence of sphere diameter and Reynolds number on synthetic jet vortex rings impinging on a spherical wall. Laser-induced fluorescence and two-dimensional particle image velocimetry techniques were applied to visualize flow and measure flow velocity, respectively. In this experiment, the stroke length was kept constant (L=3.6), and different diameters (d/D=1, 6, and 16) and Reynolds numbers (Resj=227 and 682) were analyzed. In addition to flow visualization images and phase-averaged λci fields, the vortex ring trajectories and circulation are presented to reveal the evolution features of the vortex rings. The results demonstrated that the Reynolds number mainly determined the strength and induced ability of the primary vortex ring (PVR) and the sphere-diameter effect was reflected by the expansion distance of the PVR and its separation from the wall boundary layer. It was found that only a secondary vortex ring (SVR) was induced in the case of a small diameter or a low Reynolds number. As the diameter and Reynolds number increased, the PVR expanded continuously along the wall and induced a SVR and tertiary vortex ring. In particular, driven by the curve, the strength of the induced vortex ring decreased with the increase in the sphere diameter.

关键词： Vortex flows Wakes & jets

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Analysis of measured data of snow loads on roof with parapets based on comparison of foreign codes

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Jianzhu Jiegou Xuebao/Journal of Building structures 2019年第6期40卷 32-39页

作者： Zhang, Guolong Zhang, Qingwen Mo, Huamei Fan, Feng Key Lab of Structures Dynamic Behavior and Control of the Ministry of Education Harbin Institute of Technology Harbin150090 China Key Laboratory of Smart Prevention and Mitigation of Civil Engineering Disasters of the Ministry of Industry and Information Technology Harbin Institute of Technology Harbin150090 China

In the calculation of the snow load on the roof with parapets, standards of Japan, America, and Europe have given full consideration to the erosion effect on the snow load of the fully exposed roof caused by wind field, the movement of snow induced by wind, the supplementation of upstream snow to snow heaped up around downstream obstruction. In addition, factors such as the indoor heating and the combined effect of rain and snow are introduced to realize an accurate estimation of snow load on building roofs. By contrast, the Chinese code only considers the influence of the parapet height. Therefore, based on the measured snow distribution on an actual parapet roof on ages and the influencing factors in foreign codes introduced above, the snow distribution characteristics on the parapet roof were analyzed. The results show that: more snow is blown downstream towards the parapet;the peak snow depth close to the downstream parapet is proportional to the upstream roof width, and with an increasing wind velocity, the drifting effect is enhanced;the upstream roof width and the ground snow load have a great influence on the peak snow depth at the parapet, and the influence of wind velocity depends on the ground snow load;the larger the ground snow load is, the greater influence the wind velocity has;the ratio of the snowdrift length to the parapet height is around 3.75, and it is suggested to adopt a value of 4.0 in Chinese code. © 2019, Editorial Office of Journal of Building structures. All right reserved.

关键词： Roofs

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Water absorptivity and frost resistance performance of self-ignition coal gangue autoclaved aerated concrete

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Journal of Infrastructure Preservation and Resilience 2021年第1期2卷 1-10页

作者： Cong, Xinyu Tan, Yiqiu Lu, Shuang Wang, Zhaojia Huang, Tianyong School of Transportation Science and Engineering Harbin Institute of Technology Huanghe Road 73 Harbin150090 China School of Civil Engineering Harbin Institute of technology Harbin150090 China Key Lab of Structures Dynamic Behavior and Control of the Ministry of Education 9 Harbin Institute of Technology Harbin150090 China State Key Laboratory of Solid Waste Reuse for Building Materials Beijing Building 11 Materials Academy of Science Research Beijing100041 China

Self-ignition coal gangue (SCG) used as one of precursors to fabricate autoclaved aerated concrete (AAC). Aiming at studying water absorptivity and frost resistance performance of SCG-based AAC (SCGAAC), three-period water absorption tests and freeze-thaw tests were carried out and the corresponding results were recorded and analyzed. In order to modify the water absorptivity of SCGAAC, foam stabilizer was applied to adjust pore structure while calcium stearate was expected to change hydrophilic feature of SCG. It was demonstrated that the compressive strength of SCGAAC containing foam stabilizer or calcium stearate declined at different levels. For water absorption, foam stabilizer failed to decrease the water content and even increased water absorption rates. Calcium stearate controlled water absorption rate successfully although the ultimate water content hardly reduced. All of the SCGAAC samples exhibited intact appearance after 50 freeze-thaw cycles and showed excellent frost resistance performance. Three models were proposed to predict water absorptivity and frost resistance performance of SCGAAC and the corresponding prediction results matched test resulted well. © The Author(s) 2021.

关键词： Coal

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Comparative study and optimal selection for different cable-stiffened latticed shells

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Thin-Walled structures 2022年 181卷

作者： Zhao, Lin Cao, Zhenggang Wang, Zhicheng Fan, Feng Key Lab of Structures Dynamic Behaviour and Control of the Ministry of Education Harbin Institute of Technology Harbin150090 China Key Lab of Smart Prevention and Mitigation of Civil Engineering Disasters of the Ministry of Industry and Information Technology Harbin Institute of Technology Harbin150090 China

The cable-stiffened latticed shell can be constructed in varied structural forms by diverse types of single-layer latticed shells and cable-strut systems. So, to provide references for model selection, this paper studied the efficient combination of latticed shells and cable-strut systems in different boundary conditions and proposed a performance evaluation method. The general modeling process was illustrated firstly, and several new structural forms with folded curved surfaces were proposed. Then, based on the improved equilibrium matrix theory, the force-finding analysis was carried out for the initial state, which can guarantee actual mechanical properties in the numerical model. Thus, the overall stiffness, the bearing capacity, and the cable reinforcement effect were obtained through the nonlinear stability analysis. And for the optimal selection from multiple structural forms, AHP-TOPSIS was used to judge the latticed shell system for the first time. The comprehensive structural performances were evaluated and ranked by this multi-attribute decision-making method. Finally, the results showed that the complicated cable-strut system could not necessarily lead to higher structural efficiency. Regardless of the cable-strut layouts, the spherical cable-stiffened latticed shell had a high bearing capacity when the ribbed grid was adopted. For the cylindrical structure, the folded latticed shell divided by orthogonal grids maximized the role of in-plane cables and was considered the best choice. © 2022 Elsevier Ltd

关键词： Cables

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Seismic Behavior of Steel Plate Shear Walls-Steel Frame

Seismic Behavior of Steel Plate Shear Walls-Steel Frame

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The 2nd International Conference on Materials Science and Engineering Technology (MSET 2015)

作者： SHAO Fengru SHAO Yongsong Transportation Dept China Academy of Civil Aviation Science and Technology Key Lab of Structures Dynamic Behaviour and Control (Harbin Institute of Technology) Ministry of Education School of Civil Engineering Harbin Institute of Technology

A model with the ratio of 1:4 of a six layers' semi-rigid steel frame-steel plate shear wallssystem has been tested on the shaking *** strain variation of the steel plate shear wallsand the system's seismic behaviors to different kinds of seismic waves from four different siteclassification and with different peakaccelerationwere analyzed to provide theoretical and experimental evidence to the real projects.

关键词： semi-rigidjoints frame-shearwalls shaking table testing seismic behavior

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Topological Defects Induced HighSpin Quartet State in Truxene-Based Molecular Graphenoids

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CCS Chemistry 2023年第3期5卷 695-703页

作者： Can Li Yu Liu Yufeng Liu Fu-Hua Xue Dandan Guan Yaoyi Li Hao Zheng Canhua Liu Jinfeng Jia Pei-Nian Liu Deng-Yuan Li Shiyong Wang Key Laboratory of Artificial Structures and Quantum Control Ministry of EducationShenyang National Laboratory for Materials ScienceSchool of Physics and AstronomyShanghai Jiao Tong UniversityShanghai 200240 Key Laboratory for Advanced Materials and Feringa Nobel Prize Scientist Joint Research Center Frontiers Science Center for Materiobiology and Dynamic ChemistrySchool of Chemistry and Molecular EngineeringEast China University of Science and TechnologyShanghai 200237 Tsung-Dao Lee Institute Shanghai Jiao Tong UniversityShanghai 200240 Shanghai Research Center for Quantum Sciences Shanghai 201315

Topological defects in graphene materials introduce exotic properties with both fundamental importance and technological implications,absent in their defect-free *** individual topological defects have been widely studied,collective magnetic behaviors originating from well-organized multiple topological defects remain a great ***,we examined the collective magnetic properties originating from three pentagon topological defects in truxene-based molecular graphenoids using scanning tunneling microscopy(STM)and non-contact atomic force ***πelectrons were introduced into the aromatic topology of truxene molecular graphenoids one by one by dissociating hydrogen atoms at the pentagon defects via atom *** measurements,together with density functional theory calculations,suggested that the unpaired electrons were ferromagnetically coupled,forming a collective highspin quartet state of S=3/*** work demonstrates that collective spin ordering could be realized through engineering regular patterned topological defects in molecular graphenoids,providing a new platform for designing one-dimensional ferromagnetic spin chains and two-dimensional ferromagnetic networks.

关键词： πelectron magnetism STM/nc-AFM highspin molecules atom manipulation surface chemistry

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