Granular materials are ubiquitous in nature and important in various applications such as road and railway engineering. Granular materials exhibit complicated mechanical behaviors, which are affected significantly by ...Granular materials are ubiquitous in nature and important in various applications such as road and railway engineering. Granular materials exhibit complicated mechanical behaviors, which are affected significantly by the irregular shape of particles. Currently, the discrete element method (DEM) has been accepted as an effective approach to investigate the mechanical behaviors of granular materials. However, there are scarce simulations based on DEM in literatures considering the irregularity of particle shape. A new method is proposed to simulate individual real particle with irregular shape using clump constituted by overlapping spheres. First, the geometric model of real particle with surface nodes and inner nodes is established through digitally processing the computerized tomography (CT) scanning data. Second, a clump consisting of spheres is generated to simulate the real particle using a minimum distance criterion. The criterion is implemented by tree optimization algorithm. Influential factors are also introduced to balance the model accuracy and computing cost. Effects of the influential factors, including the density of geometric grid and the minimum distance, on simulations are discussed. Results show that this new method is simpler and more efficient than the previous methods in terms of the model accuracy and computing cost.展开更多
A method for packing irregular particles with a prescribed volume fraction is proposed.Furthermore,the generated granular material adheres to the prescribed statistical distribution and satisfies the desired complex s...A method for packing irregular particles with a prescribed volume fraction is proposed.Furthermore,the generated granular material adheres to the prescribed statistical distribution and satisfies the desired complex spatial arrangement.First,the irregular geometries of the realistic particles were obtained from the original particle images.Second,the Minkowski sum was used to check the overlap between irregular particles and place an irregular particle in contact with other particles.Third,the optimised advance front method(OAFM)generated irregular particle packing with the prescribed statistical dis-tribution and volume fraction based on the Minkowski sum.Moreover,the signed distance function was introduced to pack the particles in accordance with the desired spatial arrangement.Finally,seven biaxial tests were performed using the UDEC software,which demonstrated the accuracy and potential usefulness of the proposed method.It can model granular material efficiently and reflect the meso-structural characteristics of complex granular materials.This method has a wide range of applications where discrete modelling of granular media is necessary.展开更多
Non-spherical particles are widely present in industrial production,and significantly affect the macro and micro characteristics of granular materials.Although the superquadric equation can be used to construct non-sp...Non-spherical particles are widely present in industrial production,and significantly affect the macro and micro characteristics of granular materials.Although the superquadric equation can be used to construct non-spherical particles,its disadvantage is that the particle shape is geometrically symmetric and strictly convex.In this study,two composed approaches are used to describe geometrically asymmetric and concave particle shapes,including a multi-superquadric model and a poly-superquadric model.The multi-superquadric model is a combination of several superquadric elements,and can construct concave and geometrically asymmetric particle shapes.The poly-superquadric model is a combination of eight one-eighth superquadric elements,and can construct convex and geometrically asymmetric particle shapes.Both composed models are based on superquadric equations,and Newton’s iterative method is used to calculate the contact force between the elements.Furthermore,superquadric elements,multi-superquadric elements,and poly-superquadric elements are applied for the formation of complex granular beds,and the influences of particle shape on the packing fraction can be successfully captured by the proposed models.展开更多
The characterization of track irregularities is crucial in railway dynamics,as track irregularities are the primary source of internal excitation in railway systems.In this paper,three mathematical models are proposed...The characterization of track irregularities is crucial in railway dynamics,as track irregularities are the primary source of internal excitation in railway systems.In this paper,three mathematical models are proposed to characterize the track irregularities under different circumstances.The first model is a novel explicit track spectrum function,which performs better in reflecting the inherent periodic components of track irregularities than the existing track spectra.On this foundation,the second model,a parameterized track spectrum random model,is proposed to represent the vast measured track irregularities from the probabilistic perspective.Finally,the third model,an imprecise track spectrum interval model based on a neighborhood uniform sampling Bootstrap method,is presented to identify the confidential interval of the track spectra when the track irregularity data are limited.Three examples are illustrated to demonstrate the feasibility of the three track irregularity models in characterizing the track irregularities in different conditions.This research can help capture the railway deformation status and optimize track maintenance strategies.展开更多
Inner wrinkling phenomenon is more likely to develop during hydrodynamic deep drawing （HDD） of complicated component-forms due to the higher demand for controlling deformation sequences. Aiming at the problems in co...Inner wrinkling phenomenon is more likely to develop during hydrodynamic deep drawing （HDD） of complicated component-forms due to the higher demand for controlling deformation sequences. Aiming at the problems in control of inner wrinkling for an irregular surface part featured with both concavity and convex, this research proposes an optimal design method of drawbead parameters to change the material flow. According to theoretical analysis of the mechanism of inner wrinkling, optimizing cavity pressure only is unreasonable to form a wrinkle-free deep-drawn part, so semi-circular drawbeads are employed. The effects of layout and height of drawbeads on forming results are discussed, and a process window is established based on evaluation indicators including the anti-wrinkle coefficient and the minimum wall thickness. Experiments are carried out to validate the process window, and the wall thickness and the wrinkle height are measured and compared with numerical findings. The results show that the anti-wrinkle ability of drawbeads weakens with increasing oblique angle and distance from the die center, while the wall thickness increases with increasing oblique angle and distance, and the inner wrinkling can be completely suppressed by drawbeads arranged in zones I and II with optimum penetration.展开更多
Accurately acquiring catalyst size and morphology is essential for supporting catalytic reaction process design and optimal control. We report an intelligent catalyst sizing and morphological classification method bas...Accurately acquiring catalyst size and morphology is essential for supporting catalytic reaction process design and optimal control. We report an intelligent catalyst sizing and morphological classification method based on the Mask-RCNN framework. A dataset of 9880 high-resolution images was captured by using a self-made fiber-optic endoscopic system for 13 kinds of silicoaluminophosphate-34 (SAPO-34) catalyst samples with different coke. Then there were approximately 877881 individual particles extracted from this dataset by our AI-based particle recognition algorithm. To clearly describe the morphology of irregular particles, we proposed a hybrid classification criterion that combines five different parameters, which are deformity, circularity, roundness, aspect ratio, and compactness. Therefore, catalyst morphology can be classified into two categories with four types. The first category includes regular types, such as the spherical, ellipsoidal, and rod-shaped types. And all the irregular types fall into the second category. The experimental results showed that a catalyst particle tends to be larger when its coke deposition increased. Whereas particle morphology remained primarily spherical and ellipsoidal, the ratio of each type varied slightly according to its coke. Our findings illustrate that this is a promising approach to be developing intelligent instruments for catalyst particle sizing and classification.展开更多
As an attractive collector medium for hypervelocity particles,combined with outstanding physical properties and suitable compositional characteristics,SiO2 aerogel has been deployed on outer space missions and laser s...As an attractive collector medium for hypervelocity particles,combined with outstanding physical properties and suitable compositional characteristics,SiO2 aerogel has been deployed on outer space missions and laser shock-loaded collection experiments.In this paper,impact experiments were conducted to understand the penetration process of irregular grains,irregular Al_(2)O_(3) grains with two different sizes and speeds(~110μm@7 km/s,~251μm@2.3 km/s)at various density silica aerogels.By classifying the shapes of projectile residues and tracks,the morphology of tracks was analyzed.It was observed that there were several kinds of typical tracks in the penetration of irregular grains,accompanied by residues with the shapes of near-sphere,polyhedron,streamlined body wedge,and rotator.The rotational behavior was demonstrated by the final status of one flake projectile as direct evidence.In addition,there was no obvious relationship between the track length and experimental parameters,which may be caused by the uncertain interaction between aerogels and irregular particles.In addition,it confirmed the existence of fragmentation,melting situation by observing the shape of the impact entrance hole.At the same time,optical coherence tomography was used to observe the detail of tracks clearly,which provided a method to characterize the tracks nondestructively.展开更多
This study examines the reflection of regular and irregular waves from a partially perforated caisson breakwater located on a step bed. The step bed is treated as an idealized rubble mound foundation. Based on the lin...This study examines the reflection of regular and irregular waves from a partially perforated caisson breakwater located on a step bed. The step bed is treated as an idealized rubble mound foundation. Based on the linear potential theory, an analytical solution is developed to calculate the reflection coefficient of the structure subjected to regular waves. The matched eigenfunction expansion method is used for the solution. The regular wave method is also extended to irregular waves using a linear transfer function. The calculated results obtained for limiting cases are exactly the same as corresponding results given by the previous researchers. The present predictions also agree well with experimental data in the published literatures. Numerical experiments are conducted to examine the variations of the reflection coefficient versus its main effect factors, and some interesting results are presented.展开更多
We investigate the flow patterns of irregular sand particles under avalanching mode in a rotating drum by using the spatial filtering velocimetry technique.By exploring the variations of velocity distribution of granu...We investigate the flow patterns of irregular sand particles under avalanching mode in a rotating drum by using the spatial filtering velocimetry technique.By exploring the variations of velocity distribution of granular flow,we find a type of avalanching pattern of irregular sand particles which is similar to that of spherical particles flow.Due to the fact that the initial position of avalanche in this pattern locates at the middle of the drum and the avalanche propagates toward the edge area gradually,we named it as mid-to-edge avalanching pattern.Furthermore,we find another avalanching pattern which slumps from the edge and propagates toward the opposite edge of the flow surface,named as edge-to-edge pattern.By analyzing the temporal and spatial characteristics of these two types of avalanching patterns,we discover that these two types of avalanche patterns are caused by that the avalanching particles constantly perturb the axial adjacent particles.Thus,the particles on the flow surface are involved in avalanching sequentially in order of the axial distance from the initial position.展开更多
Two-Dimensional Irregular Strip Packing Problem is a classical cutting/packing problem. The problem is to assign, a set of 2-D irregular-shaped items to a rectangular sheet. The width of the sheet is fixed, while its ...Two-Dimensional Irregular Strip Packing Problem is a classical cutting/packing problem. The problem is to assign, a set of 2-D irregular-shaped items to a rectangular sheet. The width of the sheet is fixed, while its length is extendable and has to be minimized. A sequence-based approach is developed and tested. The approach involves two phases;optimization phase and placement phase. The optimization phase searches for the packing sequence that would lead to an optimal (or best) solution when translated to an actual pattern through the placement phase. A Particle Swarm Optimization algorithm is applied in this optimization phase. Regarding the placement phase, a combined algorithm based on traditional placement methods is developed. Competitive results are obtained, where the best solutions are found to be better than, or at least equal to, the best known solutions for 10 out of 31 benchmark data sets. A Statistical Design of Experiments and a random generator of test problems are also used to characterize the performance of the entire algorithm.展开更多
The reflection of regular and irregular waves from a partially perforated caisson breakwater with a rock-filled core is examined. The present mathematical model is developed by means of the matched eigenfunction metho...The reflection of regular and irregular waves from a partially perforated caisson breakwater with a rock-filled core is examined. The present mathematical model is developed by means of the matched eigenfunction method. Numerical results of the present model are compared with the experimental data of different researchers. Numerical examples are given to examine the effect of rock fill on the reflection coefficient. The differences between regular and irregular waves are also investigated by means of theoretical and experimental results. It is found that the minimum reflection coefficient of irregular waves is larger than that of corresponding regular waves, but the contrary is the case for the maximum reflection coefficient.展开更多
Radiative heat flux at wall boundaries is important for its thermal design.Numerical methods based on structured grids are becoming trendy due to their simplicity and efficiency.Existing radiative transfer equation so...Radiative heat flux at wall boundaries is important for its thermal design.Numerical methods based on structured grids are becoming trendy due to their simplicity and efficiency.Existing radiative transfer equation solvers produce oscillating radiative heat flux at the irregular boundary if they are based on structured grids.Reverse Monte Carlo method and analytical discrete ordinates method are adopted to calculate the radiative heat flux at complex boundaries.The results show that the reverse Monte Carlo method can generate a smooth radiative heat flux profile and it is smoother with larger energy bundles.The results from the analytical discrete ordinates method show that the fluctuations are due to the ray effect.For the total or the mean radiative heat flux,the results from the analytical discrete ordinates method are very close to those from the reverse Monte Carlo method.展开更多
In the conventional differential quadrature （DQ） method the functional values along a mesh line are used to approximate derivatives and its application is limited to regular regions. In this paper, a local different...In the conventional differential quadrature （DQ） method the functional values along a mesh line are used to approximate derivatives and its application is limited to regular regions. In this paper, a local differential quadrature （LDQ） method was developed by using irregular distributed nodes, where any spatial derivative at a nodal point is approximated by a linear weighted sum of the functional values of nodes in the local physical domain. The weighting coefficients in the new approach are determined by the quadrature rule with the aid of nodal interpolation. Since the proposed method directly approximates the derivative, it can be consistently well applied to linear and nonlinear problems and the mesh-free feature is still kept. Numerical examples are provided to validate the LDQ method.展开更多
With the continued expansion of oil and gas exploration,both in the eastern and western regions,the quality of seismic acquisition has become a key factor in oil and gas exploration in complex areas.However,convention...With the continued expansion of oil and gas exploration,both in the eastern and western regions,the quality of seismic acquisition has become a key factor in oil and gas exploration in complex areas.However,conventional seismic acquisition methods cannot efficiently avoid challenging acquisition locations and produce high-quality seismic data.In this regard,based on the curvelet transform,this paper proposes an irregular seismic acquisition method,which utilizes the high-precision characteristics of the curvelet transform and simulated annealing algorithm to establish a method for the evaluation of the coherence of irregular sampling matrices and design of observation systems.The method was verified using forward simulation and actual acquisition data.The results suggest the superior quality of seismic data gathered in complicated areas through this method over those acquired using traditional methods,which can provide technical guidance for the design of observation systems in complex areas.展开更多
Objective:To explore the clinical correlation between the detection of irregular antibodies in red blood cell blood groups and hemolytic disease of the newborn.Methods:This study selected newborns who underwent examin...Objective:To explore the clinical correlation between the detection of irregular antibodies in red blood cell blood groups and hemolytic disease of the newborn.Methods:This study selected newborns who underwent examinations and were diagnosed with hemolytic disease at our hospital from October 2024 to October 2025 as the research subjects.Based on the severity of their hemolytic disease,the infants were divided into a severe group and a mild group.All the infants underwent detection for irregular antibodies in their red blood cell blood groups.General information,blood types,and irregular antibody test results of the two groups were recorded.Univariate analysis was conducted,and variables with statistical significance from the univariate analysis were included in a multivariate logistic regression analysis to explore the clinical correlation between the detection of irregular antibodies in red blood cell blood groups and hemolytic disease of the newborn.Results:Through univariate analysis,it was found that IgG1 and IgG3 subclass antibodies,as well as ABO blood group incompatibility,were statistically significant(p<0.05).When these factors were included in a multivariate logistic regression analysis,it was discovered that IgG1(OR=2.461,95%CI:1.859-2.709),IgG3(OR=2.509,95%CI:1.918-2.893),and ABO blood group incompatibility(OR=2.998,95%CI:2.149-3.493)all exhibited a positive correlation with hemolytic disease of the newborn.Conclusion:As levels of IgG1,IgG3,and ABO blood group incompatibility increase,the incidence of hemolytic disease of the newborn also rises,warranting clinical attention.展开更多
Rail weld irregularities are one of the primary excitation sources for vehicle-track interaction dynamics in modern high-speed railways.They can cause significant wheel-rail dynamic interactions,leading to wheel-rail ...Rail weld irregularities are one of the primary excitation sources for vehicle-track interaction dynamics in modern high-speed railways.They can cause significant wheel-rail dynamic interactions,leading to wheel-rail noise,component damage,and deterioration.Few researchers have employed the vehicle-track interaction dynamic model to study the dynamic interactions between wheel and rail induced by rail weld geometry irregularities.However,the cosine wave model used to simulate rail weld irregularities mainly focuses on the maximum value and neglects the geometric shape.In this study,novel theoretical models were developed for three categories of rail weld irregularities,based on measurements of the high-speed railway from Beijing to Shanghai.The vertical dynamic forces in the time and frequency domains were compared under different running speeds.These forces generated by the rail weld irregularities that were measured and modeled,respectively,were compared to validate the accuracy of the proposed model.Finally,based on the numerical study,the impact force due to rail weld irrregularity is modeled using an Artificial Neural Network(ANN),and the optimum combination of parameters for this model is found.The results showed that the proposed model provided a more accurate wheel/rail dynamic evaluation caused by rail weld irregularities than that established in the literature.The ANN model used in this paper can effectively predict the impact force due to rail weld irrregularity while reducing the computation time.展开更多
Axle box bearings are critical components of high-speed trains.Localized defects,such as pitting and spalling,on raceways or rollers pose significant threats to the operational safety of railway vehicles.In this work,...Axle box bearings are critical components of high-speed trains.Localized defects,such as pitting and spalling,on raceways or rollers pose significant threats to the operational safety of railway vehicles.In this work,a novel bearing-flexible axle boxvehicle coupling model is established to explore the vibration characteristics of axle box bearings with irregular localized defects.First,based on the contact and kinematic relationship between rollers and raceways,the three-dimensional(3D)bearing force elements are analyzed and formulated.Second,the established model and a flexible axle box are integrated into the vehicle,and the responses of the normal and faulty bearings under the combined excitations of wheel roughness and track irregularities are simulated.Third,the simulation results are verified through a rolling-vibrating test bench for full-scale wheelsets of high-speed trains.The comparisons of the fault-induced repetitive transients in the time-domain and the fault characteristic frequencies in the envelope spectra demonstrate the efficiency of the proposed model.Finally,based on the flexible axle box model,a sensitivity analysis of the accelerometer placements to the bearing faults is carried out,and the optimal one is identified based on both the time-domain and frequency-domain signal-to-noise ratios(SNRs)for engineering applications.展开更多
As one of the major high-speed railway ballastless track structures in China,CRTSIII slab ballastless track has been laid for more than 6500 km.However,there are no detailed studies on its track irregularity deteriora...As one of the major high-speed railway ballastless track structures in China,CRTSIII slab ballastless track has been laid for more than 6500 km.However,there are no detailed studies on its track irregularity deterioration throughout extended service periods,which may threaten the safety and stability of high-speed vehicles(HSV).In this study,a long-term tracking detection of CRTSIII slab ballastless track irregularities has been conducted,revealing its annual evolution law.An HSV-track coupled dynamics model was established to investigate the HSV dynamic responses under annual evolution of track irregularities.Considering the potential deterioration of track irregularities to extremely bad condition,the recommended classified limits for irregularity are proposed by analyzing the limit-exceeding probability of the safety and stability indexes of HSV.The results show that:taking 10 m wavelength as a demarcation,longer-wavelength irregularities exhibit larger amplitudes,faster evolution rates and a linear increasing trend,primarily affecting the stability of HSV.Conversely,shorter-wavelength irregularities exhibit smaller amplitudes and an insignificant evolution trend,predominantly affecting the safety of HSV.Furthermore,the periodic irregularity induced by the arching of 32 m simply-supported beam bridge should be paid closer attention to,as their evolution rate significantly surpasses that of irregularities at other wavelengths.展开更多
Offshore wind power plays a crucial role in energy strategies.The results of traditional small-scale physical models may be unreliable when extrapolated to large field scales.This study addressed this limitation by co...Offshore wind power plays a crucial role in energy strategies.The results of traditional small-scale physical models may be unreliable when extrapolated to large field scales.This study addressed this limitation by conducting large-scale(1:13)experiments to investigate the scour hole pattern and equilibrium scour depth around both slender and large monopiles under irregular waves.The experiments adopted KeuleganeCarpenter number(NKC)values from 1.01 to 8.89 and diffraction parameter(D/L,where D is the diameter of the monopile,and L is the wave length)values from 0.016 to 0.056.The results showed that changes in the maximum scour location and scour hole shape around a slender monopile were associated with NKC,with differences observed between irregular and regular waves.Improving the calculation of NKC enhanced the accuracy of existing scour formulae under irregular waves.The maximum scour locations around a large monopile were consistently found on both sides,regardless of NKC and D/L,but the scour hole topography was influenced by both parameters.Notably,the scour range around a large monopile was at least as large as the monopile diameter.展开更多
Track irregularity from rail alternate side wear is manifested as uneven rail wear waveforms alternating in the left and right rails with equal intervals,which will cause carbody sway behaviour of railway vehicles and...Track irregularity from rail alternate side wear is manifested as uneven rail wear waveforms alternating in the left and right rails with equal intervals,which will cause carbody sway behaviour of railway vehicles and greatly influences the passenger comfort.In this work,the carbody sway behaviour and mechanism due to track irregularity from rail alternate side wear and possible solutions to this issue were studied by the field testing and numerical calculation approaches.First,the carbody sway of an urban rail transit train is introduced with full-scale field tests,through which the rail alternate side wear is characterized and the formatted track irregularity are presented.Then,multibody vehicle dynamic models are developed to reproduce the carbody sway behaviour induced by the track irregularity from the rail alternate side wear.The creep forces acting on the wheel and rail are preliminarily discussed to study the influence of the carbody sway on the wear of the wheel flange and the rail corner.Finally,some potential solutions,e.g.improving the damping ratio of carbody rigid mode and rail grinding,are proposed to relieve this issue.It is concluded that an increased damping ratio of the carbody mode can alleviate the carbody sway and wheel–rail interactions,while properly maintaining track conditions can improve the vehicle performance.展开更多
基金Supported by the National Natural Science Foundation of China (51178358)the Key Project of Hubei Provincial Natural Science Foundation(2010CDA057)
文摘Granular materials are ubiquitous in nature and important in various applications such as road and railway engineering. Granular materials exhibit complicated mechanical behaviors, which are affected significantly by the irregular shape of particles. Currently, the discrete element method (DEM) has been accepted as an effective approach to investigate the mechanical behaviors of granular materials. However, there are scarce simulations based on DEM in literatures considering the irregularity of particle shape. A new method is proposed to simulate individual real particle with irregular shape using clump constituted by overlapping spheres. First, the geometric model of real particle with surface nodes and inner nodes is established through digitally processing the computerized tomography (CT) scanning data. Second, a clump consisting of spheres is generated to simulate the real particle using a minimum distance criterion. The criterion is implemented by tree optimization algorithm. Influential factors are also introduced to balance the model accuracy and computing cost. Effects of the influential factors, including the density of geometric grid and the minimum distance, on simulations are discussed. Results show that this new method is simpler and more efficient than the previous methods in terms of the model accuracy and computing cost.
基金The authors would like to acknowledge the financial support provided by the National Key R&D Program of China(Grant No.2018YFC1504802)the National Natural Science Foundation of China(Grant Nos.41972266,12102230).
文摘A method for packing irregular particles with a prescribed volume fraction is proposed.Furthermore,the generated granular material adheres to the prescribed statistical distribution and satisfies the desired complex spatial arrangement.First,the irregular geometries of the realistic particles were obtained from the original particle images.Second,the Minkowski sum was used to check the overlap between irregular particles and place an irregular particle in contact with other particles.Third,the optimised advance front method(OAFM)generated irregular particle packing with the prescribed statistical dis-tribution and volume fraction based on the Minkowski sum.Moreover,the signed distance function was introduced to pack the particles in accordance with the desired spatial arrangement.Finally,seven biaxial tests were performed using the UDEC software,which demonstrated the accuracy and potential usefulness of the proposed method.It can model granular material efficiently and reflect the meso-structural characteristics of complex granular materials.This method has a wide range of applications where discrete modelling of granular media is necessary.
基金financially supported by the National Key Research and Development Program of China(Grants2018YFA0605902,2016YFC1401505,and 2016YFC1402706)the National Natural Science Foundation of China(Grants 11872136and 11772085)the Fundamental Research Funds for the Central Universities(Grants DUT19GJ206 and DUT19ZD207)。
文摘Non-spherical particles are widely present in industrial production,and significantly affect the macro and micro characteristics of granular materials.Although the superquadric equation can be used to construct non-spherical particles,its disadvantage is that the particle shape is geometrically symmetric and strictly convex.In this study,two composed approaches are used to describe geometrically asymmetric and concave particle shapes,including a multi-superquadric model and a poly-superquadric model.The multi-superquadric model is a combination of several superquadric elements,and can construct concave and geometrically asymmetric particle shapes.The poly-superquadric model is a combination of eight one-eighth superquadric elements,and can construct convex and geometrically asymmetric particle shapes.Both composed models are based on superquadric equations,and Newton’s iterative method is used to calculate the contact force between the elements.Furthermore,superquadric elements,multi-superquadric elements,and poly-superquadric elements are applied for the formation of complex granular beds,and the influences of particle shape on the packing fraction can be successfully captured by the proposed models.
基金supported by the National Natural Science Foundation of China(Grant No.52208445,52478321,52378468)the Fundamental Research Funds for the Central Universities(Grant No.G2021KY05105)+7 种基金the Basic Research Program of Natural Science in Shaanxi Province(Grant No.2022JQ-369)the Open Foundation of National Engineering Laboratory for High Speed Railway Construction(No.HSR202001)the Youth Talent Support Program Project of Xi’an Association for Science and Technology(Grant No.959202413090)Science and Technology Research and Development Program Project of China railway group limited(Major Special Project,No.:2020-Special-022021-Special-082023-Special-07)Innovation-driven project of Central South University(2023CXQD072)the National Natural Science Foundation of Hunan Province(Grant No.:2022-JJ-20071).
文摘The characterization of track irregularities is crucial in railway dynamics,as track irregularities are the primary source of internal excitation in railway systems.In this paper,three mathematical models are proposed to characterize the track irregularities under different circumstances.The first model is a novel explicit track spectrum function,which performs better in reflecting the inherent periodic components of track irregularities than the existing track spectra.On this foundation,the second model,a parameterized track spectrum random model,is proposed to represent the vast measured track irregularities from the probabilistic perspective.Finally,the third model,an imprecise track spectrum interval model based on a neighborhood uniform sampling Bootstrap method,is presented to identify the confidential interval of the track spectra when the track irregularity data are limited.Three examples are illustrated to demonstrate the feasibility of the three track irregularity models in characterizing the track irregularities in different conditions.This research can help capture the railway deformation status and optimize track maintenance strategies.
基金supported by Chengdu Aircraft Industrial Corporation
文摘Inner wrinkling phenomenon is more likely to develop during hydrodynamic deep drawing （HDD） of complicated component-forms due to the higher demand for controlling deformation sequences. Aiming at the problems in control of inner wrinkling for an irregular surface part featured with both concavity and convex, this research proposes an optimal design method of drawbead parameters to change the material flow. According to theoretical analysis of the mechanism of inner wrinkling, optimizing cavity pressure only is unreasonable to form a wrinkle-free deep-drawn part, so semi-circular drawbeads are employed. The effects of layout and height of drawbeads on forming results are discussed, and a process window is established based on evaluation indicators including the anti-wrinkle coefficient and the minimum wall thickness. Experiments are carried out to validate the process window, and the wall thickness and the wrinkle height are measured and compared with numerical findings. The results show that the anti-wrinkle ability of drawbeads weakens with increasing oblique angle and distance from the die center, while the wall thickness increases with increasing oblique angle and distance, and the inner wrinkling can be completely suppressed by drawbeads arranged in zones I and II with optimum penetration.
基金supported by the National Natural Science Foundation of China(22308348)the Natural Science Foundation of Liaoning Province of China(2024-MSBA-65)+1 种基金the Qin Chuangyuan Project for Introducing High-Level Innovative and Entrepreneurial Talents(QCYRCXM-2023-024)the Energy Revolution S&T Program of Yulin Innovation Institute of Clean Energy(E201041206).
文摘Accurately acquiring catalyst size and morphology is essential for supporting catalytic reaction process design and optimal control. We report an intelligent catalyst sizing and morphological classification method based on the Mask-RCNN framework. A dataset of 9880 high-resolution images was captured by using a self-made fiber-optic endoscopic system for 13 kinds of silicoaluminophosphate-34 (SAPO-34) catalyst samples with different coke. Then there were approximately 877881 individual particles extracted from this dataset by our AI-based particle recognition algorithm. To clearly describe the morphology of irregular particles, we proposed a hybrid classification criterion that combines five different parameters, which are deformity, circularity, roundness, aspect ratio, and compactness. Therefore, catalyst morphology can be classified into two categories with four types. The first category includes regular types, such as the spherical, ellipsoidal, and rod-shaped types. And all the irregular types fall into the second category. The experimental results showed that a catalyst particle tends to be larger when its coke deposition increased. Whereas particle morphology remained primarily spherical and ellipsoidal, the ratio of each type varied slightly according to its coke. Our findings illustrate that this is a promising approach to be developing intelligent instruments for catalyst particle sizing and classification.
基金the National Key Research and Development Program of China(No.2017YFA0204600)the National Natural Science Foundation of China(No.11874284).
文摘As an attractive collector medium for hypervelocity particles,combined with outstanding physical properties and suitable compositional characteristics,SiO2 aerogel has been deployed on outer space missions and laser shock-loaded collection experiments.In this paper,impact experiments were conducted to understand the penetration process of irregular grains,irregular Al_(2)O_(3) grains with two different sizes and speeds(~110μm@7 km/s,~251μm@2.3 km/s)at various density silica aerogels.By classifying the shapes of projectile residues and tracks,the morphology of tracks was analyzed.It was observed that there were several kinds of typical tracks in the penetration of irregular grains,accompanied by residues with the shapes of near-sphere,polyhedron,streamlined body wedge,and rotator.The rotational behavior was demonstrated by the final status of one flake projectile as direct evidence.In addition,there was no obvious relationship between the track length and experimental parameters,which may be caused by the uncertain interaction between aerogels and irregular particles.In addition,it confirmed the existence of fragmentation,melting situation by observing the shape of the impact entrance hole.At the same time,optical coherence tomography was used to observe the detail of tracks clearly,which provided a method to characterize the tracks nondestructively.
基金The Natural Science Foundation of Shandong Province under contract No Q2008F01the Specialized Research Fund for the Doctoral Program of Higher Education under contract No 200804231006the National Natural Science Foundation of China under contract Nos 40876047 and 50609001
文摘This study examines the reflection of regular and irregular waves from a partially perforated caisson breakwater located on a step bed. The step bed is treated as an idealized rubble mound foundation. Based on the linear potential theory, an analytical solution is developed to calculate the reflection coefficient of the structure subjected to regular waves. The matched eigenfunction expansion method is used for the solution. The regular wave method is also extended to irregular waves using a linear transfer function. The calculated results obtained for limiting cases are exactly the same as corresponding results given by the previous researchers. The present predictions also agree well with experimental data in the published literatures. Numerical experiments are conducted to examine the variations of the reflection coefficient versus its main effect factors, and some interesting results are presented.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11572201,91634202,and 11902190).
文摘We investigate the flow patterns of irregular sand particles under avalanching mode in a rotating drum by using the spatial filtering velocimetry technique.By exploring the variations of velocity distribution of granular flow,we find a type of avalanching pattern of irregular sand particles which is similar to that of spherical particles flow.Due to the fact that the initial position of avalanche in this pattern locates at the middle of the drum and the avalanche propagates toward the edge area gradually,we named it as mid-to-edge avalanching pattern.Furthermore,we find another avalanching pattern which slumps from the edge and propagates toward the opposite edge of the flow surface,named as edge-to-edge pattern.By analyzing the temporal and spatial characteristics of these two types of avalanching patterns,we discover that these two types of avalanche patterns are caused by that the avalanching particles constantly perturb the axial adjacent particles.Thus,the particles on the flow surface are involved in avalanching sequentially in order of the axial distance from the initial position.
文摘Two-Dimensional Irregular Strip Packing Problem is a classical cutting/packing problem. The problem is to assign, a set of 2-D irregular-shaped items to a rectangular sheet. The width of the sheet is fixed, while its length is extendable and has to be minimized. A sequence-based approach is developed and tested. The approach involves two phases;optimization phase and placement phase. The optimization phase searches for the packing sequence that would lead to an optimal (or best) solution when translated to an actual pattern through the placement phase. A Particle Swarm Optimization algorithm is applied in this optimization phase. Regarding the placement phase, a combined algorithm based on traditional placement methods is developed. Competitive results are obtained, where the best solutions are found to be better than, or at least equal to, the best known solutions for 10 out of 31 benchmark data sets. A Statistical Design of Experiments and a random generator of test problems are also used to characterize the performance of the entire algorithm.
文摘The reflection of regular and irregular waves from a partially perforated caisson breakwater with a rock-filled core is examined. The present mathematical model is developed by means of the matched eigenfunction method. Numerical results of the present model are compared with the experimental data of different researchers. Numerical examples are given to examine the effect of rock fill on the reflection coefficient. The differences between regular and irregular waves are also investigated by means of theoretical and experimental results. It is found that the minimum reflection coefficient of irregular waves is larger than that of corresponding regular waves, but the contrary is the case for the maximum reflection coefficient.
基金Project supported by the Startup Foundation for Introducing Talent of Nanjing University of Information Science and Technology,the Anhui Provincial Natural Science Foundation,China(Grant No.2008085ME151)the National Natural Science Foundation of China(Grant Nos.51976057 and 51827808).
文摘Radiative heat flux at wall boundaries is important for its thermal design.Numerical methods based on structured grids are becoming trendy due to their simplicity and efficiency.Existing radiative transfer equation solvers produce oscillating radiative heat flux at the irregular boundary if they are based on structured grids.Reverse Monte Carlo method and analytical discrete ordinates method are adopted to calculate the radiative heat flux at complex boundaries.The results show that the reverse Monte Carlo method can generate a smooth radiative heat flux profile and it is smoother with larger energy bundles.The results from the analytical discrete ordinates method show that the fluctuations are due to the ray effect.For the total or the mean radiative heat flux,the results from the analytical discrete ordinates method are very close to those from the reverse Monte Carlo method.
文摘In the conventional differential quadrature （DQ） method the functional values along a mesh line are used to approximate derivatives and its application is limited to regular regions. In this paper, a local differential quadrature （LDQ） method was developed by using irregular distributed nodes, where any spatial derivative at a nodal point is approximated by a linear weighted sum of the functional values of nodes in the local physical domain. The weighting coefficients in the new approach are determined by the quadrature rule with the aid of nodal interpolation. Since the proposed method directly approximates the derivative, it can be consistently well applied to linear and nonlinear problems and the mesh-free feature is still kept. Numerical examples are provided to validate the LDQ method.
基金innovation consortium project of China Petroleum and Southwest Petroleum University(No.2020CX010201)Sichuan Science and Technology Program(No.2024NSFSC0081)。
文摘With the continued expansion of oil and gas exploration,both in the eastern and western regions,the quality of seismic acquisition has become a key factor in oil and gas exploration in complex areas.However,conventional seismic acquisition methods cannot efficiently avoid challenging acquisition locations and produce high-quality seismic data.In this regard,based on the curvelet transform,this paper proposes an irregular seismic acquisition method,which utilizes the high-precision characteristics of the curvelet transform and simulated annealing algorithm to establish a method for the evaluation of the coherence of irregular sampling matrices and design of observation systems.The method was verified using forward simulation and actual acquisition data.The results suggest the superior quality of seismic data gathered in complicated areas through this method over those acquired using traditional methods,which can provide technical guidance for the design of observation systems in complex areas.
文摘Objective:To explore the clinical correlation between the detection of irregular antibodies in red blood cell blood groups and hemolytic disease of the newborn.Methods:This study selected newborns who underwent examinations and were diagnosed with hemolytic disease at our hospital from October 2024 to October 2025 as the research subjects.Based on the severity of their hemolytic disease,the infants were divided into a severe group and a mild group.All the infants underwent detection for irregular antibodies in their red blood cell blood groups.General information,blood types,and irregular antibody test results of the two groups were recorded.Univariate analysis was conducted,and variables with statistical significance from the univariate analysis were included in a multivariate logistic regression analysis to explore the clinical correlation between the detection of irregular antibodies in red blood cell blood groups and hemolytic disease of the newborn.Results:Through univariate analysis,it was found that IgG1 and IgG3 subclass antibodies,as well as ABO blood group incompatibility,were statistically significant(p<0.05).When these factors were included in a multivariate logistic regression analysis,it was discovered that IgG1(OR=2.461,95%CI:1.859-2.709),IgG3(OR=2.509,95%CI:1.918-2.893),and ABO blood group incompatibility(OR=2.998,95%CI:2.149-3.493)all exhibited a positive correlation with hemolytic disease of the newborn.Conclusion:As levels of IgG1,IgG3,and ABO blood group incompatibility increase,the incidence of hemolytic disease of the newborn also rises,warranting clinical attention.
基金supported by Natural Science Foundation of China(52178441)the Scientific Research Projects of the China Academy of Railway Sciences Co.,Ltd.(Grant No.2022YJ043).
文摘Rail weld irregularities are one of the primary excitation sources for vehicle-track interaction dynamics in modern high-speed railways.They can cause significant wheel-rail dynamic interactions,leading to wheel-rail noise,component damage,and deterioration.Few researchers have employed the vehicle-track interaction dynamic model to study the dynamic interactions between wheel and rail induced by rail weld geometry irregularities.However,the cosine wave model used to simulate rail weld irregularities mainly focuses on the maximum value and neglects the geometric shape.In this study,novel theoretical models were developed for three categories of rail weld irregularities,based on measurements of the high-speed railway from Beijing to Shanghai.The vertical dynamic forces in the time and frequency domains were compared under different running speeds.These forces generated by the rail weld irregularities that were measured and modeled,respectively,were compared to validate the accuracy of the proposed model.Finally,based on the numerical study,the impact force due to rail weld irrregularity is modeled using an Artificial Neural Network(ANN),and the optimum combination of parameters for this model is found.The results showed that the proposed model provided a more accurate wheel/rail dynamic evaluation caused by rail weld irregularities than that established in the literature.The ANN model used in this paper can effectively predict the impact force due to rail weld irrregularity while reducing the computation time.
基金supported by the National Natural Science Foundation of China(Nos.12372056,12032017,12393783)the S&T Program of Hebei of China(No.24465001D)。
文摘Axle box bearings are critical components of high-speed trains.Localized defects,such as pitting and spalling,on raceways or rollers pose significant threats to the operational safety of railway vehicles.In this work,a novel bearing-flexible axle boxvehicle coupling model is established to explore the vibration characteristics of axle box bearings with irregular localized defects.First,based on the contact and kinematic relationship between rollers and raceways,the three-dimensional(3D)bearing force elements are analyzed and formulated.Second,the established model and a flexible axle box are integrated into the vehicle,and the responses of the normal and faulty bearings under the combined excitations of wheel roughness and track irregularities are simulated.Third,the simulation results are verified through a rolling-vibrating test bench for full-scale wheelsets of high-speed trains.The comparisons of the fault-induced repetitive transients in the time-domain and the fault characteristic frequencies in the envelope spectra demonstrate the efficiency of the proposed model.Finally,based on the flexible axle box model,a sensitivity analysis of the accelerometer placements to the bearing faults is carried out,and the optimal one is identified based on both the time-domain and frequency-domain signal-to-noise ratios(SNRs)for engineering applications.
基金Project(2022YFB2602900)supported by the National Key Research and Development Program of ChinaProject(K2022T002)supported by the Scientific Research Plan of China Railway。
文摘As one of the major high-speed railway ballastless track structures in China,CRTSIII slab ballastless track has been laid for more than 6500 km.However,there are no detailed studies on its track irregularity deterioration throughout extended service periods,which may threaten the safety and stability of high-speed vehicles(HSV).In this study,a long-term tracking detection of CRTSIII slab ballastless track irregularities has been conducted,revealing its annual evolution law.An HSV-track coupled dynamics model was established to investigate the HSV dynamic responses under annual evolution of track irregularities.Considering the potential deterioration of track irregularities to extremely bad condition,the recommended classified limits for irregularity are proposed by analyzing the limit-exceeding probability of the safety and stability indexes of HSV.The results show that:taking 10 m wavelength as a demarcation,longer-wavelength irregularities exhibit larger amplitudes,faster evolution rates and a linear increasing trend,primarily affecting the stability of HSV.Conversely,shorter-wavelength irregularities exhibit smaller amplitudes and an insignificant evolution trend,predominantly affecting the safety of HSV.Furthermore,the periodic irregularity induced by the arching of 32 m simply-supported beam bridge should be paid closer attention to,as their evolution rate significantly surpasses that of irregularities at other wavelengths.
基金supported by the National Nature Science Foundation of China National Outstanding Youth Science Fund Project(Grant No.52122109)the National Natural Science Foundation of China(Grants No.51861165102 and 52039005).
文摘Offshore wind power plays a crucial role in energy strategies.The results of traditional small-scale physical models may be unreliable when extrapolated to large field scales.This study addressed this limitation by conducting large-scale(1:13)experiments to investigate the scour hole pattern and equilibrium scour depth around both slender and large monopiles under irregular waves.The experiments adopted KeuleganeCarpenter number(NKC)values from 1.01 to 8.89 and diffraction parameter(D/L,where D is the diameter of the monopile,and L is the wave length)values from 0.016 to 0.056.The results showed that changes in the maximum scour location and scour hole shape around a slender monopile were associated with NKC,with differences observed between irregular and regular waves.Improving the calculation of NKC enhanced the accuracy of existing scour formulae under irregular waves.The maximum scour locations around a large monopile were consistently found on both sides,regardless of NKC and D/L,but the scour hole topography was influenced by both parameters.Notably,the scour range around a large monopile was at least as large as the monopile diameter.
基金supported by the National Natural Science Foundation of China(Grant Nos.52002344,U2034210,and 61960206010)the Development Project of State Key Laboratory of Rail Transit Vehicle System(Grant No.2022TPL_T09)。
文摘Track irregularity from rail alternate side wear is manifested as uneven rail wear waveforms alternating in the left and right rails with equal intervals,which will cause carbody sway behaviour of railway vehicles and greatly influences the passenger comfort.In this work,the carbody sway behaviour and mechanism due to track irregularity from rail alternate side wear and possible solutions to this issue were studied by the field testing and numerical calculation approaches.First,the carbody sway of an urban rail transit train is introduced with full-scale field tests,through which the rail alternate side wear is characterized and the formatted track irregularity are presented.Then,multibody vehicle dynamic models are developed to reproduce the carbody sway behaviour induced by the track irregularity from the rail alternate side wear.The creep forces acting on the wheel and rail are preliminarily discussed to study the influence of the carbody sway on the wear of the wheel flange and the rail corner.Finally,some potential solutions,e.g.improving the damping ratio of carbody rigid mode and rail grinding,are proposed to relieve this issue.It is concluded that an increased damping ratio of the carbody mode can alleviate the carbody sway and wheel–rail interactions,while properly maintaining track conditions can improve the vehicle performance.
