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Real-time adaptive particle image velocimetry for accurate unsteady flow field measurements

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Science China(Technological Sciences) 2022年第9期65卷 2143-2155页

作者： OUYANG ZhenXing YANG Hua Lu Jin HUANG YongAn YIN ZhouPing State Key Laboratory of Digital Manufacturing Equipment and Technology School of Mechanical Science and EngineeringHuazhong University of Science and TechnologyWuhan 430074China

Almost all conventional open-loop particle image velocimetry(PIV) methods employ fixed-interval-time optical imaging technology and the time-consuming cross-correlation-based PIV measurement algorithm to calculate the velocity field.In this study,a novel real-time adaptive particle image velocity(RTA-PIV) method is proposed to accurately measure the instantaneous velocity field of an unsteady flow field.In the proposed closed-loop RTA-PIV method,a new correlation-filter-based PIV measurement algorithm is introduced to calculate the velocity field in real time.Then,a Kalman predictor model is established to predict the velocity of the next time instant and a suitable interval time can be determined.To adaptively adjust the interval time for capturing two particle images,a new high-speed frame-straddling vision system is developed for the proposed RTA-PIV method.To fully analyze the performance of the RTA-PIV method,we conducted a series of numerical experiments on ground-truth image pairs and on real-world image sequences.

关键词： real-time adaptive particle image velocimetry flow field measurement high-speed vision correlation filter

A Molecular Analysis of Critical Factors for Interface and Size Effects on Heat Conduction in Nanoconfined Water Film

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Journal of Thermal Science 2022年第4期31卷 1155-1166页

作者： jin lu ZHOU Leping DU Xiaoze Key Laboratory of Power Station Energy Transfer Conversion and System Ministry of Education School of Energy Power and Mechanical EngineeringNorth China Electric Power UniversityBeijing 102206China

Heat conduction of nanoconfined liquid may differ from its bulk because of the effects of size,geometry,interface,temperature,etc.In this study,the roles of some critical factors for the heat conduction of nanoconfined water film are systematically analyzed by using the molecular dynamics method.With decreasing thickness,the normal thermal conductivity of nanoconfined water film between two copper plates decreases exponentially,while the thermal resistance,peak of the radial distribution function,and atomistic heat path increase exponentially.The average bond order,radial distribution function,mean squared displacement,and vibrational density of states are calculated to analyze the effects of structure,distribution,molecular diffusion,and vibration of water molecules on heat conduction especially in a region having no oxygen atoms(which is observed by the near-wall density profile).The results show that phonon scattering is dominant for determining the reduced thermal conductivity in this near-wall region.The thermal conductivity ratio of confined water film to bulk water has a roughly linear relationship with the logarithm of the proportion of the near-wall region.Moreover,the high interfacial thermal resistance is positively correlated to the film thickness,but it has a negligible impact on heat conduction.This work provides insights into the contribution of water molecules near the solid/liquid interface to the heat conduction of nanoconfined liquid for process intensification.

关键词： near-wall region molecular dynamics study thermal conductivity interfacial thermal resistance nanoconfined liquid

Numerical analysis of slope collapse using SPH and the SIMSAND critical state model

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Journal of Rock Mechanics and Geotechnical Engineering 2022年第1期14卷 169-179页

作者： Zhao lu Zhuang jin Panagiotis Kotronis Civil and Environmental Engineering University of MacaoMacaoChina Research and Development Center Shenzhen Foundation Engineering Co.Ltd.Shenzhen518000China Department of Civil and Environmental Engineering The Hong Kong Polytechnic UniversityHong KongChina Southern Marine Science and Engineering Guangdong Laboratory(Guangzhou) Guangzhou510000China Department of Ocean Science and Engineering Southern University of Science and TechnologyShenzhen518000China Institut de Recherche en Génie Civil et Mécanique(GeM) École Centrale de NantesUniversitéde NantesRue de la NoëNantes44321France

Geological disasters such as slope failure and landslides can cause loss of life and property.Therefore,reproducing their evolution process is of great importance for risk assessment and mitigation.The recently developed SIMSAND critical state sand model combined with the smoothed particle hydrodynamics(SPH)method is adopted in this work to study slope failure under large deformations.To illustrate the efficiency and accuracy of the SIMSAND-SPH approach,a series of slope collapse studies using the discrete element method(DEM)considering various particle shapes(i.***.spherical,tetrahedral and elongated)is adopted as benchmarks.The parameters of the SIMSAND model are calibrated using DEM triaxial tests.In comparison to the DEM simulations,the runout distance and final slope height are well characterized with the SIMSAND-SPH approach with less computational cost.All comparisons show that the SIMSAND-SPH approach is highly efficient and accurate,which can be an alternative numerical tool to simulate real scale granular flow.

关键词： Granular material Smoothed particle hydrodynamics(SPH) Large deformations Landslide Critical state Slope failure Sand

Crack Fault Diagnosis and Location Method for a Dual-Disk Hollow Shaft Rotor System Based on the Radial Basis Function Network and Pattern Recognition Neural Network

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Chinese Journal of Mechanical Engineering 2023年第2期36卷 180-197页

作者： Yuhong jin Lei Hou Zhenyong lu Yushu Chen School of Astronautics Harbin Institute of TechnologyHarbin 150001China Institute of Dynamics and Control Science Shandong Normal UniversityJi’nan 250014China

The crack fault is one of the most common faults in the rotor system,and researchers have paid close attention to its fault diagnosis.However,most studies focus on discussing the dynamic response characteristics caused by the crack rather than estimating the crack depth and position based on the obtained vibration signals.In this paper,a novel crack fault diagnosis and location method for a dual-disk hollow shaft rotor system based on the Radial basis function(RBF)network and Pattern recognition neural network(PRNN)is presented.Firstly,a rotor system model with a breathing crack suitable for a short-thick hollow shaft rotor is established based on the finite element method,where the crack's periodic opening and closing pattern and different degrees of crack depth are considered.Then,the dynamic response is obtained by the harmonic balance method.By adjusting the crack parameters,the dynamic characteristics related to the crack depth and position are analyzed through the amplitude-frequency responses and waterfall plots.The analysis results show that the first critical speed,first subcritical speed,first critical speed amplitude,and super-harmonic resonance peak at the first subcritical speed can be utilized for the crack fault diagnosis.Based on this,the RBF network and PRNN are adopted to determine the depth and approximate location of the crack respectively by taking the above dynamic characteristics as input.Test results show that the proposed method has high fault diagnosis accuracy.This research proposes a crack detection method adequate for the hollow shaft rotor system,where the crack depth and position are both unknown.

关键词： Hollow shaft rotor Breathing crack Radial basis function network Pattern recognition neural network Machine learning

Optimal synthesis of heat-integrated distillation configurations using the two-column superstructure

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Chinese Journal of Chemical Engineering 2024年第2期66卷 238-249页

作者： Xiaodong Zhang Lu Jin jinsheng Sun School of Chemical Engineering and Technology Tianjin UniversityTianjin 300072China

In the realm of the synthesis of heat-integrated distillation configurations,the conventional approach for exploring more heat integration possibilities typically entails the splitting of a single column into a twocolumn configuration.However,this approach frequently necessitates tedious enumeration procedures,resulting in a considerable computational burden.To surmount this formidable challenge,the present study introduces an innovative remedy:The proposition of a superstructure that encompasses both single-column and multiple two-column configurations.Additionally,a simultaneous optimization algorithm is applied to optimize both the process parameters and heat integration structures of the twocolumn configurations.The effectiveness of this approach is demonstrated through a case study focusing on industrial organosilicon separation.The results underscore that the superstructure methodology not only substantially mitigates computational time compared to exhaustive enumeration but also furnishes solutions that exhibit comparable performance.

关键词： Superstructure Process synthesis Heat integration Simulation-based optimization Industrial organosilicon separation

An effective crack position diagnosis method for the hollow shaft rotor system based on the convolutional neural network and deep metric learning

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Chinese Journal of Aeronautics 2022年第9期35卷 242-254页

作者： Yuhong jin Lei HOU Yushu CHEN Zhenyong lu School of Astronautics Harbin Institute of TechnologyHarbin 150001China Institute of Dynamics and Control Science Shandong Normal UniversityJi'nan 250014China

In recent years, the crack fault is one of the most common faults in the rotor system and it is still a challenge for crack position diagnosis in the hollow shaft rotor system. In this paper, a method based on the Convolutional Neural Network and deep metric learning(CNN-C) is proposed to effectively identify the crack position for a hollow shaft rotor system. Center-loss function is used to enhance the performance of neural network. Main contributions include: Firstly, the dynamic response of the dual-disks hollow shaft rotor system is obtained. The analysis results show that the crack will cause super-harmonic resonance, and the peak value of it is closely related to the position and depth of the crack. In addition, the amplitude near the non-resonant region also has relationship with the crack parameters. Secondly, we proposed an effective crack position diagnosis method which has the highest 99.04% recognition accuracy compared with other algorithms. Then,the influence of penalty factor on CNN-C performance is analyzed, which shows that too high penalty factor will lead to the decline of the neural network performance. Finally, the feature vectors are visualized via t-distributed Stochastic Neighbor Embedding(t-SNE). Naive Bayes classifier(NB) and K-Nearest Neighbor algorithm(KNN) are used to verify the validity of the feature vectors extracted by CNN-C. The results show that NB and KNN have more regular decision boundaries and higher recognition accuracy on the feature vectors data set extracted by CNN-C,indicating that the feature vectors extracted by CNN-C have great intra-class compactness and inter-class separability.

关键词： Convolutional neural networks Cracked rotor Deep metric learning Fault diagnosis Hollow shaft rotor

Harmonic Measures and Numerical Computation of Cauchy Problems for Laplace Equations

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Chinese Annals of Mathematics,Series B 2023年第6期44卷 913-928页

作者： Yu CHEN jin CHENG Shuai lu Masahiro YAMAMOTO School of Mathematics Shanghai University of Finance and EconomicsShanghai 200433China. School of Mathematical Sciences Fudan UniversityShanghai 200433China School of Mathematical Sciences the University of TokyoTokyo 153Japan

It is well known that the Cauchy problem for Laplace equations is an ill-posed problem in Hadamard’s sense.Small deviations in Cauchy data may lead to large errors in the solutions.It is observed that if a bound is imposed on the solution,there exists a conditional stability estimate.This gives a reasonable way to construct stable algorithms.However,it is impossible to have good results at all points in the domain.Although numerical methods for Cauchy problems for Laplace equations have been widely studied for quite a long time,there are still some unclear points,for example,how to evaluate the numerical solutions,which means whether they can approximate the Cauchy data well and keep the bound of the solution,and at which points the numerical results are reliable?In this paper,the authors will prove the conditional stability estimate which is quantitatively related to harmonic measures.The harmonic measure can be used as an indicate function to pointwisely evaluate the numerical result,which further enables us to find a reliable subdomain where the local convergence rate is higher than a certain order.

关键词： Conditional stability Cauchy problem Laplace equation Indicate function

Curing Process of Phenol Formaldehyde Resin for Plywood under Vacuum Conditions

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Journal of Renewable Materials 2023年第9期11卷 3447-3461页

作者： Guobing Xiong lu Hong Zehui Ju Xiaoning lu Juwan jin College of Furnishings and Industrial Design Nanjing Forestry UniversityNanjing210037China School of Forestry&Landscape Architecture Anhui Agricultural UniversityHefei230036China College of Materials Science and Engineering Nanjing Forestry UniversityNanjing210037China

The study characterized the curing behaviors of phenol formaldehyde(PF)resin under different vacuum degrees and explored the properties of 9-ply plywood panels hot-pressed under both vacuum and atmospheric conditions.The changes in core temperature and moisture content of the plywood mats during hot pressing were investigated as well.It was found that the gel times and gel temperatures of PF resin decreased with the increase of vacuum degree using a self-made device.FTIR spectra indicated the degree of polycondensation of hydroxymethyl gradu-ally increased with the increase in temperature.It was also observed that a higher degree of vacuum led to a slower polycondensation reaction rate of PF resin.During different hot-pressing processes,the bonding strengths in the innermost and uppermost gluelines of the vacuum hot-pressed plywood panels were up to 30%–50%higher than their counterparts of conventional hot-pressed products.A less difference in the bonding strengths between these two gluelines was also observed for vacuum hot-pressed products.In addition,the core of vacuum hot-pressed plywood was found to have a greater heating rate and higher temperature at thefinal stage of hot pressing,which was beneficial to cure the PF resin.The results from this study indicate a promising potential of introducing a vacuum during hot pressing to improve the quality and productivity of plywood products and provide a basis for adopting vacuum to hot press wood composites.

关键词： Phenol formaldehyde resin vacuum gel time FTIR plywood bonding strength

Anti-pseudo-allergic components in licorice extract inhibit mast cell degranulation and calcium influx

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Chinese Journal of Natural Medicines 2022年第6期20卷 421-431页

作者： WANG lu HU Gui-Zhou lu Yin JIANG Shu-Jun QI jin SU Hua National Center of Colorectal Disease Nanjing Hospital of Chinese Medicine Affiliated to Nanjing University of Chinese MedicineNanjing 210022China Department of Pharmacy Jinling HospitalNanjing 210002China Jiangsu Key Laboratory of TCM Evaluation and Translation Research School of Traditional Chinese PharmacyChina Pharmaceutical UniversityNanjing 211198China

Pseudo-allergic reactions(PARs)widely occur upon application of drugs or functional foods.Anti-pseudo-allergic ingredients from natural products have attracted much attention.This study aimed to investigate anti-pseudo-allergic compounds in licorice.The anti-pseudo-allergic effect of licorice extract was evaluated in rat basophilic leukemia 2H3(RBL-2H3)cells.Anti-pseudo-allergic compounds were screened by using RBL-2H3 cell extraction and the effects of target components were verified further in RBL-2H3 cells,mouse peritoneal mast cells(MPMCs)and mice.Molecular docking and human MRGPRX2-expressing HEK293T cells(MRGPRX2-HEK293T cells)extraction were performed to determine the potential ligands of MAS-related G protein-coupled receptor-X2(MRGPRX2),a pivotal target for PARs.Glycyrrhizic acid(GA)and licorice chalcone A(LA)were screened and shown to inhibit Compound48/80-induced degranulation and calcium influx in RBL-2H3 cells.GA and LA also inhibited degranulation in MPMCs and increase of histamine and TNF-a in mice.LA could bind to MRGPRX2,as determined by molecular docking and MRGPRX2-HEK293T cell extraction.Our study provides a strong rationale for using GA and LA as novel treatment options for PARs.LA is a potential ligand of MRGPRX2.

关键词： Glycyrrhiza uralensis Anti-pseudo-allergy Glycyrrhizic acid Licorice chalcone A MAS-related G protein-coupled receptor-X2