A dynamic space coupling model is developed for simulating the vibrations of wheel/rail systems as well as the torsion and bending vibrations of wheelsets. It is found that the slip stick vibrations of wheelsets are ...A dynamic space coupling model is developed for simulating the vibrations of wheel/rail systems as well as the torsion and bending vibrations of wheelsets. It is found that the slip stick vibrations of wheelsets are mainly caused and controlled by the crossing excitation or self excitation of the vertical vibrations of the whole system and by the bending vibrations and torsion vibrations of the wheelsets. It is found for the first time that the slip stick vibrations may occur in more than one forms, and one or another of the three kinds of vibrations is excited more strongly. Four typical kinds of slip stick vibrations are enumerated and described. The field investigation on rail corrugations shows that the four kinds of slip stick vibrations are most likely to exist and related with different corrugated features.展开更多
We carried out experimental investigations of the geometric effect on the electronic behavior in Pb_(1-x)Bi_(x) thin films by scanning tunneling microscopy and spectroscopy.Single crystal monolayer Pb_(0.74)Bi_(0.26) ...We carried out experimental investigations of the geometric effect on the electronic behavior in Pb_(1-x)Bi_(x) thin films by scanning tunneling microscopy and spectroscopy.Single crystal monolayer Pb_(0.74)Bi_(0.26) and two-monolayer Pb_(0.75)Bi_(0.25)Pb_(1-x)Bi_(x) thin films were fabricated by molecular beam epitaxy,where large surface corrugations were observed.Combined with tunneling spectroscopic measurements,it is found that atomic corrugations can widely change the electronic behaviors.These findings show that the Pb_(1-x)Bi_(x) system can be a promising platform to further explore geometry-decorated electronic behavior in two-dimensional metallic thin films.展开更多
This study experimentally investigates the influence of surfacewettability on the frosting characteristics of three types of corrugated structures(Types A,B,and C)under controlled low-temperature conditions.The experi...This study experimentally investigates the influence of surfacewettability on the frosting characteristics of three types of corrugated structures(Types A,B,and C)under controlled low-temperature conditions.The experiments were conducted in a constant-temperature bath at a cold surface temperature of–5℃,relative humidity of 90%,and ambient air temperature of 10℃.The results reveal that the variation trends of frost morphology,frost mass,and frost layer thickness are generally consistent across surfaces with different wettability.Among the tested surfaces,frost crystal formation and complete surface coverage occurred latest on the superhydrophobic surface(CA=153.9–165.8℃),next on the bare aluminumsurface(75.3–83.2℃),and earliest on the hydrophilic surface(5.3–7.5℃).At the same frosting duration,the superhydrophobic surface exhibited a sparse and fluffy frost layer,the bare aluminum surface formed a rough and dense frost,while the hydrophilic surface developed a fine and compact frost layer.The amount of frost formation decreased in the order of hydrophilic>bare aluminum>superhydrophobic,indicating that the superhydrophobic surface provides the most significant anti-frosting effect during the initial stages of frost formation.For instance,on the Type A corrugated structure,after 15 min of frosting,the frost mass on the superhydrophobic surface was 38.78%and 68.45%lower than those on the bare aluminum and hydrophilic surfaces,respectively.After 30 min,these differences were 4.99%and 25.26%,respectively.Overall,the superhydrophobic surface exhibited the smallest frost mass and frost layer thickness,demonstrating superior anti-frosting performance compared with the other surface types.展开更多
The effect of high-frequency curved track vibrations in the vertical direction on the formation and development of rail corrugation was analyzed. Kalker抯 non-Hertzian rolling contact theory was modified and used to c...The effect of high-frequency curved track vibrations in the vertical direction on the formation and development of rail corrugation was analyzed. Kalker抯 non-Hertzian rolling contact theory was modified and used to calculate the frictional work density on the contact area of the wheel and rail in rolling when a wheelset is steadily curving. The material loss unit area was assumed to be proportional to the frictional work density to determine the wear depth of the contact surface of the rail. The combined influences of the corrugation and the coupled dynamics of the railway vehicle and track were taken into consideration in the numerical simulation. For simplicity, the model considered one fourth of freight car without lateral motion, namely, a wheelset and the equivalent one fourth freight car body above it. The Euler beam was used to model the rails with the track structure under the rails replaced with equivalent springs, dumpers, and mass bodies. The numerical results show that the high-frequency track vibration causes formation of the initial corrugation on the smooth contact surface of the rail when a wheelset is steadily curving. The corrugation wave length depends on the frequencies and the rolling speed of the wheelset. The vibration frequencies also affect the depth and increase the corrugation.展开更多
Plate heat exchangers suffer from significant energy losses,which adversely affect the overall efficiency of thermal systems.To address this challenge,various heat transfer enhancement techniques have been investigate...Plate heat exchangers suffer from significant energy losses,which adversely affect the overall efficiency of thermal systems.To address this challenge,various heat transfer enhancement techniques have been investigated.Notably,the incorporation of surface corrugations is widely recognized as both effective and practical.Chevron corrugation is the most employed design.However,there remains a need to investigate alternative geometries that may offer superior performance.This study aims to find a novel corrugation design by conducting a comparative CFD analysis of flat,square,chevron,and cylindrical corrugated surfaces,assessing their impact on heat transfer enhancement within a plate heat exchanger.ANSYS Fluent software was used for simulation at four distinct Reynolds numbers(10,000,18,000,26,000,and 28,000),with a heat flux of 12,000 W/m^(2).A structured mesh was generated using Pointwise software.The material of the solid plates was modelled as aluminum,the fluid was modelled as water,and the flow was turbulent.To obtain a fully developed turbulent flow,a separate inlet duct was modelled,and the output velocity profile of the inlet duct was input into the plate heat exchanger.The Nusselt number(Nu)and heattransfer coefficient(h)were calculated to evaluate the performance of all surfaces.The results indicate that cylindrical corrugated surfaces exhibit higher Nusselt numbers than chevron,square,and flat plates.This higher performance is because of the generation of vortices in the middle of the cylindrical texture.Consequently,flow recirculation occurs,leading to reattachment to the mainstreamflow.This phenomenon induces increased turbulence,thereby enhancing the heat transfer efficiency.To validate the results,a grid-convergence independence test was performed for three different mesh sizes.In addition,empirical calculations were performed using the Dittus-Boelter and the Genilaski equations to validate the results of the flat-plate heat exchanger.It was concluded that the cylinder was the best corrugated surface and had a maximum heat transfer 35%higher than that of a flat plate.展开更多
Investigations into rail corrugation within metro systems have traditionally focused on specific mechanisms,thereby limiting the generalizability of proposed theories.Understanding the commonalities in rail corrugatio...Investigations into rail corrugation within metro systems have traditionally focused on specific mechanisms,thereby limiting the generalizability of proposed theories.Understanding the commonalities in rail corrugation across diverse metro lines remains pivotal for elucidating its underlying mechanisms.The present study conducted extensive field surveys and tracking tests across 14 Chinese metro lines.By employing t-distributed stochastic neighbor embedding(t-SNE)for dimensional reduction and employing the unsupervised clustering algorithm DBSCAN,the research redefines the classification of metro rail corrugation based on characteristic information.The analysis encompassed spatial distribution and temporal evolution of this phenomenon.Findings revealed that floating slab tracks exhibited the highest proportion of rail corrugation at 47%.Notably,ordinary monolithic bed tracks employing damping fasteners were more prone to inducing rail corrugation.Corrugation primarily manifested in curve sections with radii between 300 and 500 m,featuring ordinary monolithic bed track and steel-spring floating slab track structures,with wavelengths typically between 30 and 120 mm.Stick–slip vibrations of the wheel–rail system maybe led to short-wavelength corrugations(40–60 mm),while longer wavelengths(200–300 mm)exhibited distinct fatigue damage characteristics,mainly observed in steel-spring floating slab tracks and small-radius curve sections of ordinary monolithic bed tracks and ladder sleeper tracks.A classification system comprising 57 correlated features categorized metro rail corrugation into four distinct types.These research outcomes serve as critical benchmarks for validating various theories pertaining to rail corrugation formation.展开更多
Multi-cell structures and corrugated tubes illustrate excellent energy absorption capacities.Besides,bamboo with continuously changing contours demonstrates superior impact-resisting capacities.As a result,a bionic mu...Multi-cell structures and corrugated tubes illustrate excellent energy absorption capacities.Besides,bamboo with continuously changing contours demonstrates superior impact-resisting capacities.As a result,a bionic multi-cell double corrugated(BMDC)tube,inspired by Buddha bamboo,is investigated to assess whether it is an ideal energy absorber candidate.Compared to a corrugated tube,a BMDC contains an outer structure,an inner structure,and diaphragms,which are like webs bridging the inner and outer structures.A basic numerical model is correlated using a physical experiment,followed by an investigation of BMDC tubes’energy absorption performance under axial loading,considering thickness and mass effects.Results indicate that the EA,MCF,and SEA of a BMDC containing 5 diaphragms(BMDC-5)with a 1.5 mm thickness can improve their respective responses by 112.89,112.89,and 83.32%higher compared to a BMDC with no diaphragm(BMDC-0).In addition,the BMDC-5 with 0.156 kg mass generates the highest EA,MCF,and SEA,which is 79.78%higher than a BMDC-0 with the same mass.The parametric analysis illustrates that diaphragms’amplitude and diameter have a decisive influence on energy absorption characteristics.This study emphasizes that BMDC tubes are innovative and practical,possessing excellent energy absorption performance.展开更多
Rail corrugation, as a prevalent type of rail damage in heavy railways, induces diseases in the track structure. In order to ensure the safe operation of trains, an improved whale optimization algorithm is proposed to...Rail corrugation, as a prevalent type of rail damage in heavy railways, induces diseases in the track structure. In order to ensure the safe operation of trains, an improved whale optimization algorithm is proposed to optimize the rail corrugation evolution trend prediction model of the least squares support vector machine (IPCA-ELWOA-LSSVM). The elite reverse learning combined with the Lévy flight strategy is introduced to improve the whale optimization algorithm. The improved WOA (ELWOA) algorithm is used to continuously optimize the kernel parameter σ and the normalization parameter γ in the LSSVM model. Finally, the improved prediction model is validated using data from a domestic heavy-duty railway experimental line database and compared with the prediction model before optimization and the other commonly used models. The experimental results show that the ELWOA-LSSVM prediction model has the highest accuracy, which proves that the proposed method has high accuracy in predicting the rail corrugation evolution trend.展开更多
Purpose-Rail corrugation is still one of the unsolved challenges in the railway industry,and the abnormal vibration and high-frequency noise caused by it constitute serious adverse effects on the operating environment...Purpose-Rail corrugation is still one of the unsolved challenges in the railway industry,and the abnormal vibration and high-frequency noise caused by it constitute serious adverse effects on the operating environment.How to control corrugation has been an important research theme,and understanding corrugation evolution features is the necessary prerequisite.This study aims to investigate the specific evolution characteristics of corrugation from the contact stick-slip perspective.Design/methodology/approach-The formation and development processes of corrugation are analyzed by using a self-designed scale-down test device.Specifically,the contact stick-slip characteristics under different creepage conditions are analyzed and the formation mechanism of corrugation is summarized.On the basis of corrugation formation,the trend of corrugation development is further emphasized to completely describe the whole process of corrugation evolution.Findings-The results show that,under the determined vertical load condition,the contact interface appears the creep force-creepage negative slope phenomenon in the transverse direction.The cause of short-pitch corrugation on the rail wheel surface under the smaller angles of attack may be related to the inherent vibration frequency of the test device,and the cause of corrugation on the rail wheel surface under the larger angles of attack is mainly related to the stick-slip vibration induced by contact creep saturation.Originality/value-This research explores the evolution characteristics of corrugation by adopting a selfdesigned scale-down test device,and elucidates the mechanism of corrugation in detail.展开更多
This study examines the temperature field distribution characteristics and temperature effects during the prefabrication of composite box girders with corrugated steel webs(CBGCSWs),aiming to provide practical recomme...This study examines the temperature field distribution characteristics and temperature effects during the prefabrication of composite box girders with corrugated steel webs(CBGCSWs),aiming to provide practical recommendations for controlling temperature-induced cracking and technical guidance for concrete mix proportions and placement processes.Based on field measurement data,a three-dimensional finite element model was developed to simulate the temperature effects at critical locations during the prefabrication phase.By varying the concrete mix proportions,initial casting temperature,and ambient temperature,the study elucidates the variation patterns of the temperature field during precast placement.The results show that the temperature rise caused by hydration heat increases with higher cement and fly ash content,whereas reducing cement and using minimal fly ash effectively lower the hydration temperature.However,the influence of fly ash on prestress losses should be carefully evaluated during the design phase.Higher initial casting temperatures accelerate hydration rates,leading to a rapid temperature rise.Significant differences between the initial casting and ambient temperatures result in larger residual temperature stresses.Based on concrete mix proportions,curing conditions,and ambient temperatures,three recommended casting temperature ranges were identified:5℃–10℃,10℃–25℃,and 25℃–30℃.Variations in the average ambient temperature affect the peak temperature of the hydration reaction and indirectly influence the final temperature distribution of the concrete structure.Optimizing the demolding time and applying geotextiles and water curing effectively reduces the peak temperature,maximum internal-to-surface temperature gradients,and surface tensile stresses,thereby mitigating the risk of temperature-induced cracking.展开更多
The modification design of airfoil is a crucial aspect of aircraft design.Implementing corrugated structures on the lower wing surface can significantly affect the aerodynamic performance of the airfoil under specific...The modification design of airfoil is a crucial aspect of aircraft design.Implementing corrugated structures on the lower wing surface can significantly affect the aerodynamic performance of the airfoil under specific conditions.This study focuses on macroscale corrugated structures based on the Clark YM15 airfoil.A series of concave triangular corrugations were arranged on its lower surface,and various corrugated airfoil types were derived.Computational Fluid Dynamics(CFD)simulations were used to analyze the performance and flow characteristics of these corrugated airfoils,and to investigate the impact of structural parameters,quantity,and layout of the corrugations on the lift-to-drag performance of the airfoil.The results demonstrate that judiciously configured corrugated structures can enhance the lift-to-drag performance at a small angle of attack,with the double-corrugation structure showing the most significant improvement.Wind tunnel experiments were respectively conducted on the double-corrugation airfoil and the original airfoil,which validate the accuracy of the CFD simulations and confirm the lift and drag performance advantages of the corrugated airfoil over the original design.展开更多
As-rolled titanium/steel composite plate has poor plastic deformation ability,and it is difficult to achieve synergistic deformation,especially for dissimilar metals with very different plastic deformation abilities.T...As-rolled titanium/steel composite plate has poor plastic deformation ability,and it is difficult to achieve synergistic deformation,especially for dissimilar metals with very different plastic deformation abilities.The 304/TC4 composite plate with corrugated interface was manufactured using the asymmetric rolling with local strong stress method.The changing rules of bonding strength and synergistic deformation ability of corrugated interface under different annealing process parameters were studied.The results show that in the range of 550–850℃,especially after the temperature exceeds 650℃,with increasing the annealing temperature and time,the difference of microstructure between peak and trough positions increases,and the bonding strength of the composite plate decreases gradually.Especially,the interfacial bonding strength of the plate sharply decreases at 750℃ due to the rapid growth of intermetallic compounds at the interface and the diffusion holes caused by the difference of element diffusion.The 304/TC4 composite plate has the best synergistic deformation ability when annealing at 650℃/2 h,with the elongation reaching 35%and the tensile strength decreasing to 852 MPa.High interfacial bonding strength and moderate matrix recovery are important prerequisites for synergistic deformation of composite plates.展开更多
The effects of the reduction rate of the corrugated rolling on the microstructure and mechanical properties of TA1/TC4 composite plate that was prepared via corrugated rolling+flat rolling process were investigated.Th...The effects of the reduction rate of the corrugated rolling on the microstructure and mechanical properties of TA1/TC4 composite plate that was prepared via corrugated rolling+flat rolling process were investigated.The finite element model was developed and validated for the corrugated rolling process of the composite plate.Experimental findings reveal the absence of significant defects and intermetallic compounds at the bonding interface.When the rolling temperature is 700℃with the reduction rate of 44%in the first pass of corrugated rolling,the tensile and interfacial shear strengths of the composite plate reach 749 and 403.97 MPa,respectively.The simulation results demonstrate that the plastic strain in the TC4 substrate is enhanced by corrugated rolling and the compressive stress at the trough is high.These results confirm that interfacial bonding is promoted by corrugated rolling,and the mechanical properties of the composite plate are improved significantly with the increase of reduction rate.展开更多
Presetting tensile twins(TTs)can enhance the mechanical properties of magnesium(Mg)alloys.Two as-received(AR)sheets,as-received state-A(AR-A)with fiber texture and nonuniform grains and as-received state-B with basal ...Presetting tensile twins(TTs)can enhance the mechanical properties of magnesium(Mg)alloys.Two as-received(AR)sheets,as-received state-A(AR-A)with fiber texture and nonuniform grains and as-received state-B with basal texture and uniform equiaxial grains are selected to induce TTs via a novel method called corrugated wide limit alignment(CWLA),and the corresponding CWLA-processed sheets are denoted as CWLA-processed state-A(C-A)and CWLA-processed state-B(C-B).The results demonstrate that a larger initial average grain size correlates with a higher fraction of TTs induced in Mg sheets,thereby refining the grains and forming a new rolling direction(RD)tilted texture during CWLA.The ultimate tensile strength increases by 32%from AR-A to C-A,primarily due to refinement strengthening and twinning-induced strain hardening.The recrystallization mechanism of C-A is dominated by twinning-induced dynamic recrystallization(DRX),where DRX grains prefer to inherit the orientation of TTs,resulting in an enhanced RD-tilted texture and the formation of multi-modal texture.The recrystallization mechanism of C-B is mainly discontinuous DRX and continuous DRX,and the DRX grains prefer to inherit the orientation of matrix grains,ultimately forming a basal texture.In summary,the tensile mechanical behavior of pre-twinned Mg sheets significantly depends on the grain size and texture of the AR sheets,so they present similar changing trends during tensile deformation.展开更多
The accuracy of center height detection for corrugated beam guardrails is significantly affected by robot posture in the mobile highway guardrail detection systems based on structured light vision.To address the probl...The accuracy of center height detection for corrugated beam guardrails is significantly affected by robot posture in the mobile highway guardrail detection systems based on structured light vision.To address the problem,this paper proposes an integrated calibration method for structured light vision sensors.In the proposed system,the sensor is mounted on a crawler-type mobile robot,which scans and measures the center height of guardrails while in motion.However,due to external disturbances such as uneven road surfaces and vehicle vibrations,the posture of the robot may deviate,causing displacement of the sensor platform and resulting in spatial 3D measurement errors.To overcome this issue,the system integrates inertial measurement unit(IMU)data into the sensor calibration process,enabling realtime correction of posture deviations through sensor fusion.This approach achieves a unified calibration of the structured light vision system,effectively compensates for posture-induced errors,and enhances detection accuracy.A prototype was developed and tested in both laboratory and real highway environments.Experimental results demonstrate that the proposed method enables accurate center height detection of guardrails under complex road conditions,significantly reduces posture-related measurement errors,and greatly improves the efficiency and reliability of traditional detection methods.展开更多
This paper proposes a stable gain and a compact Antipodal Vivaldi Antenna(AVA)for a 38GHz band of 5G communication.A novel compact AVA is designed to provide constant gain,high front to back ratio(FBR),and very high e...This paper proposes a stable gain and a compact Antipodal Vivaldi Antenna(AVA)for a 38GHz band of 5G communication.A novel compact AVA is designed to provide constant gain,high front to back ratio(FBR),and very high efficiency.The performance of the proposed AVA is enhanced with the help of a dielectric lens(DL)and corrugations.A rectangular-shaped DL is incorporated in conventional AVA(CAVA)to enhance its gain up to 1 dBi and the bandwidth by 1.8 GHz.Next,the rectangular corrugations are implemented in CAVA with lens(CAVA-L)to further improve the gain and bandwidth.The proposed AVA with lens and corrugations(AVA-LC)gives a constant and high gain of 8.2 to 9 dBi.The designed AVA-LC operates from 34 to 45GHz frequency which covers 38GHz(37.5 to 43.5 GHz)band of 5G applications.Further,the presented AVA-LC mitigates the back lobe and sidelobe levels,resulting in FBR and efficiency improvement.The FBR is in the range of 12.2 to 22 dB,and efficiency is 99%,almost constant.The AVA-LC is fabricated on Roger’s RT/duroid 5880 substrate,and it is tested to verify the simulated results.The proposed compact AVA-LC with high gain,an improved FBR,excellent efficiency,and stable radiation patterns is suitable for the 38GHz band of 5G devices.展开更多
Objective] Field and laboratory observation was conducted to investigate Clubiona corrugate. [Method] The trials investigated the bio-ecology and behavior of the spider C. corrugate. [Result] The spider overwintered w...Objective] Field and laboratory observation was conducted to investigate Clubiona corrugate. [Method] The trials investigated the bio-ecology and behavior of the spider C. corrugate. [Result] The spider overwintered with spiderlings, adults and instars turn into adults after 6-8 molts. It had 2-3 generations each year in Hunan, and it owned the character of overlapping of generation in paddies. The average duration of generations of C. corrugate was 158.2 days, and the survival days av-eraged 223.2 days. The female and male mated several times without cannibalistic behavior, average number of eggs female laid throughout its adult life was 371.5, and hatchability can get 85.4%. The sex ratio was 1∶1. Its capability of resistance to starvation and drought was strong. Through indoor observation, the spider can sur-vive 25-61 days under the condition of no water and food. [Conclusion] The behav-ior of C. corrugate was also recorded in detail, and female usual y has a strong a-bility to protect their egg-sacs and spiderlings. At present, the bio-ecology and be-havior of the spider C. corrugate had not been reported.展开更多
A mathematical model was established for condensation on surfaces of verticalcorrugated plates based on the mechanism of heat transfer enhancement to thin down the liquid filmdue to surface tension effect between corr...A mathematical model was established for condensation on surfaces of verticalcorrugated plates based on the mechanism of heat transfer enhancement to thin down the liquid filmdue to surface tension effect between corrugated plate surfaces and liquid films. The relative heattransfer coefficients of condensation on corrugation plates were calculated in contrast withequivalent vertical plane ones. The heat transfer enhancement effects for the main geometricparameters such as pitch, height, corrugation angle, tilt angle, and fillet radii of corrugationswere analyzed to guide the optimization of corrugation structure for application. A two-scalecorrugation is suggested, which can compromise both the enhanced heat transfer effect and adequatecross section area for flows, and it makes the heat transfer coefficient 1 to 2 times more than thatof an equivalent plane one.展开更多
The current research of rail corrugation mainly focuses on the mechanisms of its formation and development. Compared with the root causes and development mechanisms, the wheel-rail impacts, the fatigue failure of vehi...The current research of rail corrugation mainly focuses on the mechanisms of its formation and development. Compared with the root causes and development mechanisms, the wheel-rail impacts, the fatigue failure of vehicle-track parts, and the loss of ride comfort due to rail corrugation should also be taken into account. However, the influences of rail corrugation on vehicle and track vibration, and failure of vehicle and track structural parts are barely discussed in the literature. This paper presents an experimental and numerical investigation of the structural vibration of metro bogies caused by rail corrugation. Extensive experiments are conducted to investigate the effects of short-pitch rail corrugation on the vibration accelerations of metro bogies. A dynamic model of a metro vehicle coupled with a concrete track is established to study the influence of rail corrugation on the structural vibration of metro bogies. The field test results indicate that the short-pitch rail corrugation generates strong vibrations on the axle-boxes and the bogie frames, therefore, accelerates the fatigue failure of the bogie components. The numerical results show that short-pitch rail corrugation may largely reduce the fatigue life of the coil spring, and improving the damping value of the primary vertical dampers is likely to reduce the strong vibration induced by short-pitch rail corrugation. This research systematically studies the effect of rail corrugation on the vibration of metro bogies and proposes some remedies for mitigating strong vibrations of metro bogies and reducing the incidence of failure in primary coil springs, which would be helpful in developing new metro bogies and track maintenance procedures.展开更多
文摘A dynamic space coupling model is developed for simulating the vibrations of wheel/rail systems as well as the torsion and bending vibrations of wheelsets. It is found that the slip stick vibrations of wheelsets are mainly caused and controlled by the crossing excitation or self excitation of the vertical vibrations of the whole system and by the bending vibrations and torsion vibrations of the wheelsets. It is found for the first time that the slip stick vibrations may occur in more than one forms, and one or another of the three kinds of vibrations is excited more strongly. Four typical kinds of slip stick vibrations are enumerated and described. The field investigation on rail corrugations shows that the four kinds of slip stick vibrations are most likely to exist and related with different corrugated features.
基金Project supported by the National Key Basic Research Program of China(Grant No.2017YFA0205004)the National Natural Science Foundation of China(Grant Nos.92165201,11474261,and 11634011)+1 种基金the Fundamental Research Funds for the Central Universities(Grant No.WK3510000006)the Anhui Initiative Fund in Quantum Information Technologies(Grant No.AHY170000)。
文摘We carried out experimental investigations of the geometric effect on the electronic behavior in Pb_(1-x)Bi_(x) thin films by scanning tunneling microscopy and spectroscopy.Single crystal monolayer Pb_(0.74)Bi_(0.26) and two-monolayer Pb_(0.75)Bi_(0.25)Pb_(1-x)Bi_(x) thin films were fabricated by molecular beam epitaxy,where large surface corrugations were observed.Combined with tunneling spectroscopic measurements,it is found that atomic corrugations can widely change the electronic behaviors.These findings show that the Pb_(1-x)Bi_(x) system can be a promising platform to further explore geometry-decorated electronic behavior in two-dimensional metallic thin films.
基金supported by the Science and Technology Research Project of Henan Province(No.232102241014)the Key scientific research project of Henan Province Colleges and Universities(No.22A470002)Doctoral Fund Project of Henan Polytechnic University(No.B2021-37).
文摘This study experimentally investigates the influence of surfacewettability on the frosting characteristics of three types of corrugated structures(Types A,B,and C)under controlled low-temperature conditions.The experiments were conducted in a constant-temperature bath at a cold surface temperature of–5℃,relative humidity of 90%,and ambient air temperature of 10℃.The results reveal that the variation trends of frost morphology,frost mass,and frost layer thickness are generally consistent across surfaces with different wettability.Among the tested surfaces,frost crystal formation and complete surface coverage occurred latest on the superhydrophobic surface(CA=153.9–165.8℃),next on the bare aluminumsurface(75.3–83.2℃),and earliest on the hydrophilic surface(5.3–7.5℃).At the same frosting duration,the superhydrophobic surface exhibited a sparse and fluffy frost layer,the bare aluminum surface formed a rough and dense frost,while the hydrophilic surface developed a fine and compact frost layer.The amount of frost formation decreased in the order of hydrophilic>bare aluminum>superhydrophobic,indicating that the superhydrophobic surface provides the most significant anti-frosting effect during the initial stages of frost formation.For instance,on the Type A corrugated structure,after 15 min of frosting,the frost mass on the superhydrophobic surface was 38.78%and 68.45%lower than those on the bare aluminum and hydrophilic surfaces,respectively.After 30 min,these differences were 4.99%and 25.26%,respectively.Overall,the superhydrophobic surface exhibited the smallest frost mass and frost layer thickness,demonstrating superior anti-frosting performance compared with the other surface types.
基金Supported by the National Natural Science Foundation of China (No. 59935100) and the Foundation of the Ministry of Education China (No. 20020613001) and the Foundation for the Author for National Excellent Doctoral Dissertation China (Nos. 200048 a
文摘The effect of high-frequency curved track vibrations in the vertical direction on the formation and development of rail corrugation was analyzed. Kalker抯 non-Hertzian rolling contact theory was modified and used to calculate the frictional work density on the contact area of the wheel and rail in rolling when a wheelset is steadily curving. The material loss unit area was assumed to be proportional to the frictional work density to determine the wear depth of the contact surface of the rail. The combined influences of the corrugation and the coupled dynamics of the railway vehicle and track were taken into consideration in the numerical simulation. For simplicity, the model considered one fourth of freight car without lateral motion, namely, a wheelset and the equivalent one fourth freight car body above it. The Euler beam was used to model the rails with the track structure under the rails replaced with equivalent springs, dumpers, and mass bodies. The numerical results show that the high-frequency track vibration causes formation of the initial corrugation on the smooth contact surface of the rail when a wheelset is steadily curving. The corrugation wave length depends on the frequencies and the rolling speed of the wheelset. The vibration frequencies also affect the depth and increase the corrugation.
文摘Plate heat exchangers suffer from significant energy losses,which adversely affect the overall efficiency of thermal systems.To address this challenge,various heat transfer enhancement techniques have been investigated.Notably,the incorporation of surface corrugations is widely recognized as both effective and practical.Chevron corrugation is the most employed design.However,there remains a need to investigate alternative geometries that may offer superior performance.This study aims to find a novel corrugation design by conducting a comparative CFD analysis of flat,square,chevron,and cylindrical corrugated surfaces,assessing their impact on heat transfer enhancement within a plate heat exchanger.ANSYS Fluent software was used for simulation at four distinct Reynolds numbers(10,000,18,000,26,000,and 28,000),with a heat flux of 12,000 W/m^(2).A structured mesh was generated using Pointwise software.The material of the solid plates was modelled as aluminum,the fluid was modelled as water,and the flow was turbulent.To obtain a fully developed turbulent flow,a separate inlet duct was modelled,and the output velocity profile of the inlet duct was input into the plate heat exchanger.The Nusselt number(Nu)and heattransfer coefficient(h)were calculated to evaluate the performance of all surfaces.The results indicate that cylindrical corrugated surfaces exhibit higher Nusselt numbers than chevron,square,and flat plates.This higher performance is because of the generation of vortices in the middle of the cylindrical texture.Consequently,flow recirculation occurs,leading to reattachment to the mainstreamflow.This phenomenon induces increased turbulence,thereby enhancing the heat transfer efficiency.To validate the results,a grid-convergence independence test was performed for three different mesh sizes.In addition,empirical calculations were performed using the Dittus-Boelter and the Genilaski equations to validate the results of the flat-plate heat exchanger.It was concluded that the cylinder was the best corrugated surface and had a maximum heat transfer 35%higher than that of a flat plate.
基金support extended by the Joint Funds of Beijing Municipal Natural Science Foundation and Fengtai Rail Transit Frontier Research(Grant No.L211006)the Fundamental Research Funds for the Central Universities(Science and technology leading talent team project,Grant No.2022JBXT010)+1 种基金the Fundamental Research Funds for the Central Universities(Grant No.2023YJS052)the National Natural Science Foundation of China(Grant No.52308426)。
文摘Investigations into rail corrugation within metro systems have traditionally focused on specific mechanisms,thereby limiting the generalizability of proposed theories.Understanding the commonalities in rail corrugation across diverse metro lines remains pivotal for elucidating its underlying mechanisms.The present study conducted extensive field surveys and tracking tests across 14 Chinese metro lines.By employing t-distributed stochastic neighbor embedding(t-SNE)for dimensional reduction and employing the unsupervised clustering algorithm DBSCAN,the research redefines the classification of metro rail corrugation based on characteristic information.The analysis encompassed spatial distribution and temporal evolution of this phenomenon.Findings revealed that floating slab tracks exhibited the highest proportion of rail corrugation at 47%.Notably,ordinary monolithic bed tracks employing damping fasteners were more prone to inducing rail corrugation.Corrugation primarily manifested in curve sections with radii between 300 and 500 m,featuring ordinary monolithic bed track and steel-spring floating slab track structures,with wavelengths typically between 30 and 120 mm.Stick–slip vibrations of the wheel–rail system maybe led to short-wavelength corrugations(40–60 mm),while longer wavelengths(200–300 mm)exhibited distinct fatigue damage characteristics,mainly observed in steel-spring floating slab tracks and small-radius curve sections of ordinary monolithic bed tracks and ladder sleeper tracks.A classification system comprising 57 correlated features categorized metro rail corrugation into four distinct types.These research outcomes serve as critical benchmarks for validating various theories pertaining to rail corrugation formation.
基金2022 Guangxi University Young and Middle-aged Teachers’Basic Research Ability Improvement Project,2022KY0781,Rui Liang。
文摘Multi-cell structures and corrugated tubes illustrate excellent energy absorption capacities.Besides,bamboo with continuously changing contours demonstrates superior impact-resisting capacities.As a result,a bionic multi-cell double corrugated(BMDC)tube,inspired by Buddha bamboo,is investigated to assess whether it is an ideal energy absorber candidate.Compared to a corrugated tube,a BMDC contains an outer structure,an inner structure,and diaphragms,which are like webs bridging the inner and outer structures.A basic numerical model is correlated using a physical experiment,followed by an investigation of BMDC tubes’energy absorption performance under axial loading,considering thickness and mass effects.Results indicate that the EA,MCF,and SEA of a BMDC containing 5 diaphragms(BMDC-5)with a 1.5 mm thickness can improve their respective responses by 112.89,112.89,and 83.32%higher compared to a BMDC with no diaphragm(BMDC-0).In addition,the BMDC-5 with 0.156 kg mass generates the highest EA,MCF,and SEA,which is 79.78%higher than a BMDC-0 with the same mass.The parametric analysis illustrates that diaphragms’amplitude and diameter have a decisive influence on energy absorption characteristics.This study emphasizes that BMDC tubes are innovative and practical,possessing excellent energy absorption performance.
文摘Rail corrugation, as a prevalent type of rail damage in heavy railways, induces diseases in the track structure. In order to ensure the safe operation of trains, an improved whale optimization algorithm is proposed to optimize the rail corrugation evolution trend prediction model of the least squares support vector machine (IPCA-ELWOA-LSSVM). The elite reverse learning combined with the Lévy flight strategy is introduced to improve the whale optimization algorithm. The improved WOA (ELWOA) algorithm is used to continuously optimize the kernel parameter σ and the normalization parameter γ in the LSSVM model. Finally, the improved prediction model is validated using data from a domestic heavy-duty railway experimental line database and compared with the prediction model before optimization and the other commonly used models. The experimental results show that the ELWOA-LSSVM prediction model has the highest accuracy, which proves that the proposed method has high accuracy in predicting the rail corrugation evolution trend.
基金funded by the Science and Technology Research Project of Universities in Hebei Province(No.QN2025314)Youth Specialization Fund for State Key Laboratory(No.50110010766)Shanghai Key Laboratory of Rail Infrastructure Durability and System Safety(No.R202405).
文摘Purpose-Rail corrugation is still one of the unsolved challenges in the railway industry,and the abnormal vibration and high-frequency noise caused by it constitute serious adverse effects on the operating environment.How to control corrugation has been an important research theme,and understanding corrugation evolution features is the necessary prerequisite.This study aims to investigate the specific evolution characteristics of corrugation from the contact stick-slip perspective.Design/methodology/approach-The formation and development processes of corrugation are analyzed by using a self-designed scale-down test device.Specifically,the contact stick-slip characteristics under different creepage conditions are analyzed and the formation mechanism of corrugation is summarized.On the basis of corrugation formation,the trend of corrugation development is further emphasized to completely describe the whole process of corrugation evolution.Findings-The results show that,under the determined vertical load condition,the contact interface appears the creep force-creepage negative slope phenomenon in the transverse direction.The cause of short-pitch corrugation on the rail wheel surface under the smaller angles of attack may be related to the inherent vibration frequency of the test device,and the cause of corrugation on the rail wheel surface under the larger angles of attack is mainly related to the stick-slip vibration induced by contact creep saturation.Originality/value-This research explores the evolution characteristics of corrugation by adopting a selfdesigned scale-down test device,and elucidates the mechanism of corrugation in detail.
基金supported by the National Natural Science Foundation of China(U22A20598,52279113)Key Research and Development Special Program of Henan Province(241111322500)Support Plan for University Science and Technology Innovation Team of Henan Province(24IRTSTHN009).
文摘This study examines the temperature field distribution characteristics and temperature effects during the prefabrication of composite box girders with corrugated steel webs(CBGCSWs),aiming to provide practical recommendations for controlling temperature-induced cracking and technical guidance for concrete mix proportions and placement processes.Based on field measurement data,a three-dimensional finite element model was developed to simulate the temperature effects at critical locations during the prefabrication phase.By varying the concrete mix proportions,initial casting temperature,and ambient temperature,the study elucidates the variation patterns of the temperature field during precast placement.The results show that the temperature rise caused by hydration heat increases with higher cement and fly ash content,whereas reducing cement and using minimal fly ash effectively lower the hydration temperature.However,the influence of fly ash on prestress losses should be carefully evaluated during the design phase.Higher initial casting temperatures accelerate hydration rates,leading to a rapid temperature rise.Significant differences between the initial casting and ambient temperatures result in larger residual temperature stresses.Based on concrete mix proportions,curing conditions,and ambient temperatures,three recommended casting temperature ranges were identified:5℃–10℃,10℃–25℃,and 25℃–30℃.Variations in the average ambient temperature affect the peak temperature of the hydration reaction and indirectly influence the final temperature distribution of the concrete structure.Optimizing the demolding time and applying geotextiles and water curing effectively reduces the peak temperature,maximum internal-to-surface temperature gradients,and surface tensile stresses,thereby mitigating the risk of temperature-induced cracking.
基金supported by the 2023 Shanghai Industrial Collaborative Innovation Project,China(No.CXXT-2023-05).
文摘The modification design of airfoil is a crucial aspect of aircraft design.Implementing corrugated structures on the lower wing surface can significantly affect the aerodynamic performance of the airfoil under specific conditions.This study focuses on macroscale corrugated structures based on the Clark YM15 airfoil.A series of concave triangular corrugations were arranged on its lower surface,and various corrugated airfoil types were derived.Computational Fluid Dynamics(CFD)simulations were used to analyze the performance and flow characteristics of these corrugated airfoils,and to investigate the impact of structural parameters,quantity,and layout of the corrugations on the lift-to-drag performance of the airfoil.The results demonstrate that judiciously configured corrugated structures can enhance the lift-to-drag performance at a small angle of attack,with the double-corrugation structure showing the most significant improvement.Wind tunnel experiments were respectively conducted on the double-corrugation airfoil and the original airfoil,which validate the accuracy of the CFD simulations and confirm the lift and drag performance advantages of the corrugated airfoil over the original design.
基金supported by the Major Program of National Natural Science Foundation of China(U22A20188)the Natural Science Foundation of Shanxi Province(202303021224002)+1 种基金the special fund for Science and Technology Innovation Teams of Shanxi Province(202304051001025)the Open Research Fund from the Hai’an and Taiyuan University of Technology Advanced Manufacturing and Intelligent Equipment Industrial Research Institute(2023HA-TYUTKFYF036).
文摘As-rolled titanium/steel composite plate has poor plastic deformation ability,and it is difficult to achieve synergistic deformation,especially for dissimilar metals with very different plastic deformation abilities.The 304/TC4 composite plate with corrugated interface was manufactured using the asymmetric rolling with local strong stress method.The changing rules of bonding strength and synergistic deformation ability of corrugated interface under different annealing process parameters were studied.The results show that in the range of 550–850℃,especially after the temperature exceeds 650℃,with increasing the annealing temperature and time,the difference of microstructure between peak and trough positions increases,and the bonding strength of the composite plate decreases gradually.Especially,the interfacial bonding strength of the plate sharply decreases at 750℃ due to the rapid growth of intermetallic compounds at the interface and the diffusion holes caused by the difference of element diffusion.The 304/TC4 composite plate has the best synergistic deformation ability when annealing at 650℃/2 h,with the elongation reaching 35%and the tensile strength decreasing to 852 MPa.High interfacial bonding strength and moderate matrix recovery are important prerequisites for synergistic deformation of composite plates.
基金supported by the National Natural Science Foundation of China(No.52275362)Natural Science Foundation of Shanxi Province,China(No.202303021224002)the Central Government Guides the Special Fund Projects of Local Scientific and Technological Development(Nos.YDZJSX2021A020,YDZJSX2022A023).
文摘The effects of the reduction rate of the corrugated rolling on the microstructure and mechanical properties of TA1/TC4 composite plate that was prepared via corrugated rolling+flat rolling process were investigated.The finite element model was developed and validated for the corrugated rolling process of the composite plate.Experimental findings reveal the absence of significant defects and intermetallic compounds at the bonding interface.When the rolling temperature is 700℃with the reduction rate of 44%in the first pass of corrugated rolling,the tensile and interfacial shear strengths of the composite plate reach 749 and 403.97 MPa,respectively.The simulation results demonstrate that the plastic strain in the TC4 substrate is enhanced by corrugated rolling and the compressive stress at the trough is high.These results confirm that interfacial bonding is promoted by corrugated rolling,and the mechanical properties of the composite plate are improved significantly with the increase of reduction rate.
基金supported by the National Natural Science Foundation of China(No.52005362)the Fundamental Research Program of Shanxi Province(Nos.202303021221005 and 202303021211045)+1 种基金the Patent Commercialization Program of Shanxi Province(No.202402003)the Key Research and Development Plan of Xinzhou City.
文摘Presetting tensile twins(TTs)can enhance the mechanical properties of magnesium(Mg)alloys.Two as-received(AR)sheets,as-received state-A(AR-A)with fiber texture and nonuniform grains and as-received state-B with basal texture and uniform equiaxial grains are selected to induce TTs via a novel method called corrugated wide limit alignment(CWLA),and the corresponding CWLA-processed sheets are denoted as CWLA-processed state-A(C-A)and CWLA-processed state-B(C-B).The results demonstrate that a larger initial average grain size correlates with a higher fraction of TTs induced in Mg sheets,thereby refining the grains and forming a new rolling direction(RD)tilted texture during CWLA.The ultimate tensile strength increases by 32%from AR-A to C-A,primarily due to refinement strengthening and twinning-induced strain hardening.The recrystallization mechanism of C-A is dominated by twinning-induced dynamic recrystallization(DRX),where DRX grains prefer to inherit the orientation of TTs,resulting in an enhanced RD-tilted texture and the formation of multi-modal texture.The recrystallization mechanism of C-B is mainly discontinuous DRX and continuous DRX,and the DRX grains prefer to inherit the orientation of matrix grains,ultimately forming a basal texture.In summary,the tensile mechanical behavior of pre-twinned Mg sheets significantly depends on the grain size and texture of the AR sheets,so they present similar changing trends during tensile deformation.
基金Supported by the Special Fund for Basic Scientific Research of Central-Level Public Welfare Scientific Research Institutes(2024-9007)。
文摘The accuracy of center height detection for corrugated beam guardrails is significantly affected by robot posture in the mobile highway guardrail detection systems based on structured light vision.To address the problem,this paper proposes an integrated calibration method for structured light vision sensors.In the proposed system,the sensor is mounted on a crawler-type mobile robot,which scans and measures the center height of guardrails while in motion.However,due to external disturbances such as uneven road surfaces and vehicle vibrations,the posture of the robot may deviate,causing displacement of the sensor platform and resulting in spatial 3D measurement errors.To overcome this issue,the system integrates inertial measurement unit(IMU)data into the sensor calibration process,enabling realtime correction of posture deviations through sensor fusion.This approach achieves a unified calibration of the structured light vision system,effectively compensates for posture-induced errors,and enhances detection accuracy.A prototype was developed and tested in both laboratory and real highway environments.Experimental results demonstrate that the proposed method enables accurate center height detection of guardrails under complex road conditions,significantly reduces posture-related measurement errors,and greatly improves the efficiency and reliability of traditional detection methods.
基金This research was funded by Princess Nourah bint Abdulrahman University Researchers Supporting Project number(PNURSP2022R79)Princess Nourah bint Abdulrahman University,Riyadh,Saudi Arabia,S.Urooj,www.pnu.edu.sa.
文摘This paper proposes a stable gain and a compact Antipodal Vivaldi Antenna(AVA)for a 38GHz band of 5G communication.A novel compact AVA is designed to provide constant gain,high front to back ratio(FBR),and very high efficiency.The performance of the proposed AVA is enhanced with the help of a dielectric lens(DL)and corrugations.A rectangular-shaped DL is incorporated in conventional AVA(CAVA)to enhance its gain up to 1 dBi and the bandwidth by 1.8 GHz.Next,the rectangular corrugations are implemented in CAVA with lens(CAVA-L)to further improve the gain and bandwidth.The proposed AVA with lens and corrugations(AVA-LC)gives a constant and high gain of 8.2 to 9 dBi.The designed AVA-LC operates from 34 to 45GHz frequency which covers 38GHz(37.5 to 43.5 GHz)band of 5G applications.Further,the presented AVA-LC mitigates the back lobe and sidelobe levels,resulting in FBR and efficiency improvement.The FBR is in the range of 12.2 to 22 dB,and efficiency is 99%,almost constant.The AVA-LC is fabricated on Roger’s RT/duroid 5880 substrate,and it is tested to verify the simulated results.The proposed compact AVA-LC with high gain,an improved FBR,excellent efficiency,and stable radiation patterns is suitable for the 38GHz band of 5G devices.
基金Supported by National Natural Science Foundation of China[31472017]National Natural Science Foundation of China[31272339]+1 种基金National Natural Science Foundation of China[31071943]Major Program of Department of Science and Technology of Hunan Province[2014FJ2003]~~
文摘Objective] Field and laboratory observation was conducted to investigate Clubiona corrugate. [Method] The trials investigated the bio-ecology and behavior of the spider C. corrugate. [Result] The spider overwintered with spiderlings, adults and instars turn into adults after 6-8 molts. It had 2-3 generations each year in Hunan, and it owned the character of overlapping of generation in paddies. The average duration of generations of C. corrugate was 158.2 days, and the survival days av-eraged 223.2 days. The female and male mated several times without cannibalistic behavior, average number of eggs female laid throughout its adult life was 371.5, and hatchability can get 85.4%. The sex ratio was 1∶1. Its capability of resistance to starvation and drought was strong. Through indoor observation, the spider can sur-vive 25-61 days under the condition of no water and food. [Conclusion] The behav-ior of C. corrugate was also recorded in detail, and female usual y has a strong a-bility to protect their egg-sacs and spiderlings. At present, the bio-ecology and be-havior of the spider C. corrugate had not been reported.
文摘A mathematical model was established for condensation on surfaces of verticalcorrugated plates based on the mechanism of heat transfer enhancement to thin down the liquid filmdue to surface tension effect between corrugated plate surfaces and liquid films. The relative heattransfer coefficients of condensation on corrugation plates were calculated in contrast withequivalent vertical plane ones. The heat transfer enhancement effects for the main geometricparameters such as pitch, height, corrugation angle, tilt angle, and fillet radii of corrugationswere analyzed to guide the optimization of corrugation structure for application. A two-scalecorrugation is suggested, which can compromise both the enhanced heat transfer effect and adequatecross section area for flows, and it makes the heat transfer coefficient 1 to 2 times more than thatof an equivalent plane one.
基金Supported by National Natural Science Foundation of China(Grant Nos.U1361117,51305360)PhD Programs Foundation of Ministry of Education of China(Grant No.20130184110005)+1 种基金Cultivation Program for the Excellent Doctoral Dissertation of Southwest Jiaotong UniversityGuangzhou Metro Corporation Program of China
文摘The current research of rail corrugation mainly focuses on the mechanisms of its formation and development. Compared with the root causes and development mechanisms, the wheel-rail impacts, the fatigue failure of vehicle-track parts, and the loss of ride comfort due to rail corrugation should also be taken into account. However, the influences of rail corrugation on vehicle and track vibration, and failure of vehicle and track structural parts are barely discussed in the literature. This paper presents an experimental and numerical investigation of the structural vibration of metro bogies caused by rail corrugation. Extensive experiments are conducted to investigate the effects of short-pitch rail corrugation on the vibration accelerations of metro bogies. A dynamic model of a metro vehicle coupled with a concrete track is established to study the influence of rail corrugation on the structural vibration of metro bogies. The field test results indicate that the short-pitch rail corrugation generates strong vibrations on the axle-boxes and the bogie frames, therefore, accelerates the fatigue failure of the bogie components. The numerical results show that short-pitch rail corrugation may largely reduce the fatigue life of the coil spring, and improving the damping value of the primary vertical dampers is likely to reduce the strong vibration induced by short-pitch rail corrugation. This research systematically studies the effect of rail corrugation on the vibration of metro bogies and proposes some remedies for mitigating strong vibrations of metro bogies and reducing the incidence of failure in primary coil springs, which would be helpful in developing new metro bogies and track maintenance procedures.
