The effect of La addition(0-0.30 wt%)on the microstructure and hardness of rheological squeeze casting brass alloys was experimentally investigated.The rheological squeeze casting process is improved by controlling th...The effect of La addition(0-0.30 wt%)on the microstructure and hardness of rheological squeeze casting brass alloys was experimentally investigated.The rheological squeeze casting process is improved by controlling the wall surface crystals and melt flow rate to realise the preparation of semi-solid melt with flow,and a brass alloy workpiece with La is produced.The microstructure and properties of the brass alloy samples were investigated using metallography,scanning electron microscopy,energy-dispersive X-ray spectroscopy,X-ray diffraction and hardness testing.The results indicate that the hardness of the rheological squeeze casting brass alloy is increased by 20.4%from 108 to 130 HBW with an increase in the La content from 0 to 0.30 wt%.The micro structural analysis results show that La significantly refines the primary a-phase grains,and the main mechanism is the constitutional undercooling and heterogeneous nucleation caused by the La enrichment in the front of the solid-liquid interface.The squeeze pressure promotes undercooling,which improves the nucleation rate and affects the solute diffusion and nucleus growth.The dual effects of these two aspects aggravate the grain refinement process,consequently increasing the number of grain boundaries and improving the hardness of the brass alloy.展开更多
A method for gearbox fault diagnosis consists of feature extraction andfault identification. Many methods for feature extraction have beendevised for exposing nature of vibration data of a defective gearbox. Inadditio...A method for gearbox fault diagnosis consists of feature extraction andfault identification. Many methods for feature extraction have beendevised for exposing nature of vibration data of a defective gearbox. Inaddition, features extracted from gearbox vibration data are identifiedby various classifiers. However, existing literatures leave much to bedesired in assessing performance of different combinatorial methods forgearbox fault diagnosis. To this end, this paper evaluated performance ofseveral typical combinatorial methods for gearbox fault diagnosis byassociating each of multifractal detrended fluctuation analysis (MFDFA),empirical mode decomposition (EMD) and wavelet transform (WT) witheach of neural network (NN), Mahalanobis distance decision rules(MDDR) and support vector machine (SVM). Following this,performance of different combinatorial methods was compared using agroup of gearbox vibration data containing slightly different faultpatterns. The results indicate that MFDFA performs better in featureextraction of gearbox vibration data and SVM does the same in faultidentification. Naturally, the method associating MFDFA with SVMshows huge potential for fault diagnosis of gearboxes. As a result, thispaper can provide some useful information on construction of a methodfor gearbox fault diagnosis.展开更多
In order to study the influence of thermal deformation of long-span cable- stayed bridge (LSCSB) on the dynamic characteristics of metro vehicle on the bridge, based on the theory of vehicle-track coupled dynamic...In order to study the influence of thermal deformation of long-span cable- stayed bridge (LSCSB) on the dynamic characteristics of metro vehicle on the bridge, based on the theory of vehicle-track coupled dynamics, the rigid-flexible coupled dynamic model of metro vehicle-track-LSCSB system is established by using finite element method and multi-rigid-body dynamics. Adopting this model, the deformation of LSCSB subject to temperature is analyzed, then the comprehensive effect of track random irregularity and rail deformation caused by temperature load is considered to study the dynamic characteristics of metro vehicle running through the bridge, and finally the influences of temperature increment and running speed on concerned dynamic indices of vehicle are studied. The results show that the LSCSB deforms obviously subject to temperature load, and the overall performance is that the cooling is arched, and the heating is bent, and the shape variable changes almost linearly with the temperature load. According to the parameters studied in this paper, the rail deformation caused by temperature load increases the wheel-rail vertical force, derailment coefficient and wheel load reduction rate by 1.5%, 3.1% and 5% respectively. The vertical acceleration of the vehicle body decreases by 2.4% under the cooling condition, while increases by 3.7% under the heating condition. The dynamic response of the bridge changes under temperature load. The maximum vertical and horizontal displacement in the middle of the main beam span are 6.24 mm and 2.19 mm respectively, and the maximum vertical and horizontal acceleration are 1.29 cm/s<sup>2</sup> and 2.54cm/s<sup>2</sup> respectively. The derailment coefficient and vertical acceleration of vehicle body are more affected by temperature load, and the wheel load reduction rate and wheel-rail vertical force are more affected by speed. The conclusion of this paper provides a reference for subsequent scholars to study the influence of thermal deformation on the dynamic response of vehicles on LSCSB.展开更多
Autonomous driving technology is constantly developing to a higher level of complex scenes,and there is a growing demand for the utilization of end-to-end data-driven control.However,the end-to-end path tracking proce...Autonomous driving technology is constantly developing to a higher level of complex scenes,and there is a growing demand for the utilization of end-to-end data-driven control.However,the end-to-end path tracking process often encounters challenges in learning efficiency and generalization.To address this issue,this paper designs a deep deterministic policy gradient(DDPG)-based reinforcement learning strategy that integrates imitation learning and feedforward exploration in the path following process.In imitation learning,the path tracking control data generated by the model predictive control(MPC)method is used to train an end-to-end steering control model of a deep neural network.Another feedforward exploration behavior is predicted by road curvature and vehicle speed,and adds it and imitation learning to the DDPG reinforcement learning to obtain decision-making experience and action prediction behavior of the path tracking process.In the reinforcement learning process,imitation learning is used to update the pre-training parameters of the actor network,and a feedforward steering technique with random noise is adopted for strategy exploration.In the reward function,a hierarchical progressive reward form and a constrained objective reward function referring to MPC are designed,and the actor-critic network architecture is determined.Finally,the path tracking performance of the designed method is verified by comparing various training results,simulations,and HIL tests.The results show that the designed method can effectively utilize pre-training and feedforward prior experience to obtain optimal path tracking performance of an autonomous vehicle,and has better generalization ability than other methods.This study provides an efficient control scheme for improving the end-to-end control performance of autonomous vehicles.展开更多
Ceramics are extensively used in protective structures which are often subjected to projectile impacts.During an impact process of a ceramic target by a projectile,fragmentation occurs in both the target and the proje...Ceramics are extensively used in protective structures which are often subjected to projectile impacts.During an impact process of a ceramic target by a projectile,fragmentation occurs in both the target and the projectile.It is challenging to simulate such events and predict residual mass and velocity of the projectile.In this work,we attempt to use smoothed particle hydrodynamics(SPH)in LS-DYNA to reproduce fragmentation of the target and the projectile and predict residual mass and velocity of the projectile during a projectile impact of a ceramic target.SPH models for an alumina ceramic tile impacted by a blunt tungsten heavy alloy projectile are established.SPH simulation results of residual mass and velocity of the projectile as well as ejecta and bulge movements of the ceramic tile are obtained and compared with experimental data and simulation results of other numerical approaches.It is found that SPH simulation can properly reproduce the impact fragmentation of the target and the projectile,and shows advantages over existing numerical approaches in the prediction accuracy of residual mass and velocity.Moreover,effects of some numerical aspects of SPH,including particle spacing,contact treatment and parameters in artificial viscosity and smoothing length,on simulation results are identified.A simple approach using identical smoothing length and balanced artificial viscosity is proposed to reduce particle spacing sensitivity.The observed parametric effects and the proposed approach will provide guidance to set appropriate parameters values for SPH simulation of impact fragmentation.展开更多
Prosthesis implantation and fat transplantation are common breast reconstructionmethods.In general,prosthesis implantation alone does not achieve a realistic enough appearance,and fat transplantation alone is difficul...Prosthesis implantation and fat transplantation are common breast reconstructionmethods.In general,prosthesis implantation alone does not achieve a realistic enough appearance,and fat transplantation alone is difficult to achieve in the correct capacity.To date,no reports have focused on methods of combining fat with implanted prostheses for breast reconstruction.Using a newly designed bionic ink(i.e.,polyether F127 diacrylate(F127DA)&poly(ethylene glycol)diacrylate(PEGDA))and projection-based three-dimensional bioprinting(PBP),we report the development of a new method for printing porous prostheses.PEGDA was used to improve the printing precision of the prosthesis by increasing the gel point of F127DA and reducing the impact of external temperature.The compression modulus of the printed prosthesis was very close to that of prostheses currently used in clinical practice and to that of natural breasts.Finally,stromal vascular fraction gel(SVF-gel),a human fat extract,was injected into the pores of the synthesized prostheses to prepare a prosthesis mixed with adipose tissue.These were implanted subcutaneously in nude mice to observe their biological performance.After 14 and 28 days of observation,the prosthesis showed good biocompatibility,and adipose tissues grew well in and around the prosthesis.This result shows that a porous prosthesis containing pre-placed adipose tissues is a promising breast reconstruction material.展开更多
Wind turbine is a key device to realize the utilization of wind energy,and it has been highly valued by all countries.But the mechanical gear transmission of the existing wind power device has the disadvantages of hig...Wind turbine is a key device to realize the utilization of wind energy,and it has been highly valued by all countries.But the mechanical gear transmission of the existing wind power device has the disadvantages of high vibration and noise,high failure rate,and short service time.Magneticfield modulation electromagnetic gear transmission is a new non-contact transmission method.However,the conventional modulation magnetic gear has low torque density and torque defects with largefluctuations.In order to overcome the gear transmis-sion problems of the existing semi-direct drive wind power generation machinery and improve the electromag-netic performance of the traditional magnetic gear transmission,this paper proposes a new transmission scheme of a non-contact semi-direct drive wind generator with a surface mount Halbach array modulated mag-netic gear method,and considers the electromagnetic properties of the semi-direct drive modulation magnetic gear of the wind turbine.Thefinite element software is used to construct the model of the surface-mounted Halbach array magnetic gear and the conventional gear,analyzed the distribution of magneticfield lines of the two magnetic gears,calculated the air gap magneticflux density of the inner and outer air gap,and obtained the main harmonics of the inner and outer air gap magnetic density;calculated the static torque and steady-state operating torque of the inner and outer rotors in the model,compared the air gapflux density,harmonics and torque of the magnetic gears.The simulation results show that the magneticfield modulation type mag-netic gear of the surface mount Halbach array magnetic gear method improves the magnetic induction wave-form of the inner and outer air gap,reduces the pulse torquefluctuation,and has a 60%higher static torque.Applying it to semi-direct drive wind power generation equipment not only overcomes the shortcomings of mechanical gears,but also has higher electromagnetic performance.Therefore,the surface-mounted Halbach array modulated magnetic gear can be used to replace the mechanical gearbox in the semi-direct drive wind power generation equipment.展开更多
This study employs friction stir welding(FSW)technology to achieve the butt welding of 2mm thick 1060 aluminum and T2 copper.The research investigates the macroscopic formation,tensile properties,microhardness,and ele...This study employs friction stir welding(FSW)technology to achieve the butt welding of 2mm thick 1060 aluminum and T2 copper.The research investigates the macroscopic formation,tensile properties,microhardness,and electrochemical corrosion behavior of the welded joints.The results indicate that the welded joints exhibit excellent formation,with a tensile strength reaching 84.76%of that of the 1060 aluminum material.Well-formed welded joints can be obtained by controlling the rotation speed and welding speed within a certain range.However,the rotation speed has a more significant impact on the microhardness in the weld zone.The corrosion potential of T2 copper is higher than that of 1060 aluminum,forming a macroscopic galvanic couple between the two materials.The corrosion potential of the welded joint falls between that of T2 copper and 1060 aluminum.展开更多
Aiming at the problems of traditional centralized cloud computing which occupies large computing resources and creates high latency,this paper proposes a fault detection scheme for insulator self-explosion based on ed...Aiming at the problems of traditional centralized cloud computing which occupies large computing resources and creates high latency,this paper proposes a fault detection scheme for insulator self-explosion based on edge computing and DL(deep learning).In order to solve the high amount of computation brought by the deep neural network and meet the limited computing resources at the edge,a lightweight SSD(Single Shot MultiBox Detector)target recognition network is designed at the edge,which adopts the MobileNets network to replace VGG16 network in the original model to reduce redundant computing.In the cloud,three detection algorithms(Faster-RCNN,Retinanet,YOLOv3)with obvious differences in detection performance are selected to obtain the coordinates and confidence of the insulator self-explosion area,and then the self-explosion fault detection of the overhead transmission line is realized by a novel multimodel fusion algorithm.The experimental results show that the proposed scheme can effectively reduce the amount of uploaded data,and the average recognition accuracy of the cloud is 95.75%.In addition,it only increases the power consumption of edge devices by about 25.6W/h in their working state.Compared with the existing online monitoring technology of insulator selfexplosion at home and abroad,the proposed scheme has the advantages of low transmission delay,low communication cost and high diagnostic accuracy,which provides a new idea for online monitoring research of power internet of things equipment.展开更多
Copper sulfide(Cu_(x)S)as a plasmonic solar photothermal semiconductor material that expands the light collection range by altering localized surface plasmon resonance(LSPR)to the near-to mid-infrared(IR)spectral regi...Copper sulfide(Cu_(x)S)as a plasmonic solar photothermal semiconductor material that expands the light collection range by altering localized surface plasmon resonance(LSPR)to the near-to mid-infrared(IR)spectral region.The versatile synthesis strategies of Cu_(x)S nanostructure offer its variability of morphology and provide additional freedom in tuning the optical property.Particularly,nanocage(or nanoshell)has hybridized plasmon resonances as a result of super-positioned nanosphere and nanocavity,which extends its receiving range of solar spectrum and increases light-to-heat conversion rate.Here,we offer novel“nanoink”and“nanofilm”developed from colloidal Cu_(27)S_(24)nanocages with excellent solar photothermal response.Via combining experimental measurement and theoretical calculation,we estimated the optical properties of covellite Cu_(27)S_(24).And based on obtained dielectric functions,we then calculated its solar photothermal performance,which was further validated by our experimental measurement.The simulation results showed that hollow Cu_(27)S_(24)nanocages have excellent solar photothermal performance,and exhibit much higher solar photothermal conversion efficiency than solid Cu_(27)S_(24)nanospheres.展开更多
The research on rolling bearing early fault detection is mainly focused on degradation index extraction and adaptive setting of alarm threshold.The mainstream methods are to extract degradation indicators based on ada...The research on rolling bearing early fault detection is mainly focused on degradation index extraction and adaptive setting of alarm threshold.The mainstream methods are to extract degradation indicators based on adaptive features and set adaptive alarm thresholds based on the Shewhart control chart.However,the adaptive feature extraction method does not consider the correlation between features,and the Shewhart control chart is not sensitive to small fluctuations caused by early faults.In this study,a rolling bearing early fault detection method based on a feature clustering fusion degradation index is proposed.The multidomain statistical features are extracted to form the initial feature set,and the improved hierarchical clustering algorithm is combined with the feature evaluation index to select features to form a preferred feature subset,to ensure the richness of index information and reduce redundancy.After the construction of the degradation index,to suppress the interference caused by nonstationary and abnormal shocks in early fault detection,the accurate evaluation method and anomaly determination strategy of control chart parameters are studied,and an improved exponential weighted move average control chart is designed to monitor the degradation index.The effectiveness and superiority of the proposed method are verified by public data sets.This research provides a rolling bearing early fault detection method,which can provide comprehensive degradation indicators,eliminate interference caused by random anomalies and running in periods,and achieve an accurate detection of early bearing failures.展开更多
The transient heat transfer behaviours in a packed bed have been studied using coupled computational fluid dynamics(CFD)and discrete element method(DEM).Intra-particle thermal diffusion,which is a crucial but rarely e...The transient heat transfer behaviours in a packed bed have been studied using coupled computational fluid dynamics(CFD)and discrete element method(DEM).Intra-particle thermal diffusion,which is a crucial but rarely explored issue,is considered by introducing a one-dimensional diffusion equation in the DEM solver.To achieve a sufficiently long physical time of simulations,we further reduce the computational cost by applying periodic boundary condition to a small segment of the packed bed.Our study demonstrates a shifting peak heat flow rate from the bottom to the top of the packed bed during the initial warming phase.We affirm that the influence of thermal diffusion within a particle is noteworthy only for particles exhibiting a high Biot number(e.g.,Bi=1.2).This insight enriches our understanding of heat transfer mechanisms in packed beds and their practical engineering applications.展开更多
Background and objectives:Current technology of X-ray imaging can recognize hard foreign materials(FMs)such as metal and high-density plastic.However,low-density foreign bodies are still a challenge for food quality a...Background and objectives:Current technology of X-ray imaging can recognize hard foreign materials(FMs)such as metal and high-density plastic.However,low-density foreign bodies are still a challenge for food quality and safety assessment.Materials and methods:An electromagnetic vibration feeder aided by terahertz time-domain spectroscopy(THz-TDS)and imaging was inves-tigated for non-destructively detecting tea stalk and insect FMs mixed with tea leaves.Results:THz time-domain signals were employed directly to develop the K-nearest neighbor model with a precision of 100%,accuracy of 95.6%and recall of 98.7%in predicting the unknown samples.High contrast THz-TDS images were obtained by the separation method for the samples using electromagnetic vibration feeder.The characteristic parameters of the ratio of maximum length(L)to maximum width(W)and hue extracted from THz-TDS images indicated significant difference between tea leaves and FMs.Conclusions:The results suggested that electromagnetic vibration feeder combination with THz-TDS was feasible for detecting FMs in fin-ishingteaproducts.展开更多
To investigate the dynamical load sharing behaviors of multi-floating components in the heavy load planetary gear system,a multi-floating planetary gear system that includes a floating central component and a quasi-fl...To investigate the dynamical load sharing behaviors of multi-floating components in the heavy load planetary gear system,a multi-floating planetary gear system that includes a floating central component and a quasi-floating planet flexible supporting pin is employed.Then a 21 degree of freedom lumped parameters dynamical model of this system is presented to study the dynamical load sharing behaviors.Some influencing factors,such as supporting stiffness,positions error of sun or carrier,and external input load are analyzed on the dynamical load sharing of the planetary gear system with multi-floating components.The results demonstrate that the load sharing condition of the system is best when both the sun gear and planet gears are multi-floating at the same time.When the planet gear position errors remain constant,reducing the flexible pin stiffness of planet gear or increasing external input load can effectively improve the load sharing.These conclusions are verified by the relevant experiments.展开更多
基金Project supported by the financial support of the Fundamental Research Funds for the Central Universities(2020YJS146)。
文摘The effect of La addition(0-0.30 wt%)on the microstructure and hardness of rheological squeeze casting brass alloys was experimentally investigated.The rheological squeeze casting process is improved by controlling the wall surface crystals and melt flow rate to realise the preparation of semi-solid melt with flow,and a brass alloy workpiece with La is produced.The microstructure and properties of the brass alloy samples were investigated using metallography,scanning electron microscopy,energy-dispersive X-ray spectroscopy,X-ray diffraction and hardness testing.The results indicate that the hardness of the rheological squeeze casting brass alloy is increased by 20.4%from 108 to 130 HBW with an increase in the La content from 0 to 0.30 wt%.The micro structural analysis results show that La significantly refines the primary a-phase grains,and the main mechanism is the constitutional undercooling and heterogeneous nucleation caused by the La enrichment in the front of the solid-liquid interface.The squeeze pressure promotes undercooling,which improves the nucleation rate and affects the solute diffusion and nucleus growth.The dual effects of these two aspects aggravate the grain refinement process,consequently increasing the number of grain boundaries and improving the hardness of the brass alloy.
基金supported by Shandong ProvincialNatural Science Foundation China (ZR2012EEL07).
文摘A method for gearbox fault diagnosis consists of feature extraction andfault identification. Many methods for feature extraction have beendevised for exposing nature of vibration data of a defective gearbox. Inaddition, features extracted from gearbox vibration data are identifiedby various classifiers. However, existing literatures leave much to bedesired in assessing performance of different combinatorial methods forgearbox fault diagnosis. To this end, this paper evaluated performance ofseveral typical combinatorial methods for gearbox fault diagnosis byassociating each of multifractal detrended fluctuation analysis (MFDFA),empirical mode decomposition (EMD) and wavelet transform (WT) witheach of neural network (NN), Mahalanobis distance decision rules(MDDR) and support vector machine (SVM). Following this,performance of different combinatorial methods was compared using agroup of gearbox vibration data containing slightly different faultpatterns. The results indicate that MFDFA performs better in featureextraction of gearbox vibration data and SVM does the same in faultidentification. Naturally, the method associating MFDFA with SVMshows huge potential for fault diagnosis of gearboxes. As a result, thispaper can provide some useful information on construction of a methodfor gearbox fault diagnosis.
文摘In order to study the influence of thermal deformation of long-span cable- stayed bridge (LSCSB) on the dynamic characteristics of metro vehicle on the bridge, based on the theory of vehicle-track coupled dynamics, the rigid-flexible coupled dynamic model of metro vehicle-track-LSCSB system is established by using finite element method and multi-rigid-body dynamics. Adopting this model, the deformation of LSCSB subject to temperature is analyzed, then the comprehensive effect of track random irregularity and rail deformation caused by temperature load is considered to study the dynamic characteristics of metro vehicle running through the bridge, and finally the influences of temperature increment and running speed on concerned dynamic indices of vehicle are studied. The results show that the LSCSB deforms obviously subject to temperature load, and the overall performance is that the cooling is arched, and the heating is bent, and the shape variable changes almost linearly with the temperature load. According to the parameters studied in this paper, the rail deformation caused by temperature load increases the wheel-rail vertical force, derailment coefficient and wheel load reduction rate by 1.5%, 3.1% and 5% respectively. The vertical acceleration of the vehicle body decreases by 2.4% under the cooling condition, while increases by 3.7% under the heating condition. The dynamic response of the bridge changes under temperature load. The maximum vertical and horizontal displacement in the middle of the main beam span are 6.24 mm and 2.19 mm respectively, and the maximum vertical and horizontal acceleration are 1.29 cm/s<sup>2</sup> and 2.54cm/s<sup>2</sup> respectively. The derailment coefficient and vertical acceleration of vehicle body are more affected by temperature load, and the wheel load reduction rate and wheel-rail vertical force are more affected by speed. The conclusion of this paper provides a reference for subsequent scholars to study the influence of thermal deformation on the dynamic response of vehicles on LSCSB.
基金Supported by National Natural Science Foundation of China(Grant No.52405104)Jiangxi Provincial Natural Science Foundation(Grant Nos.20242BAB20249 and 20232BAB204041)Science and Technology Project of Department of Transportation of Jiangxi Province(Grant No.2025QN003).
文摘Autonomous driving technology is constantly developing to a higher level of complex scenes,and there is a growing demand for the utilization of end-to-end data-driven control.However,the end-to-end path tracking process often encounters challenges in learning efficiency and generalization.To address this issue,this paper designs a deep deterministic policy gradient(DDPG)-based reinforcement learning strategy that integrates imitation learning and feedforward exploration in the path following process.In imitation learning,the path tracking control data generated by the model predictive control(MPC)method is used to train an end-to-end steering control model of a deep neural network.Another feedforward exploration behavior is predicted by road curvature and vehicle speed,and adds it and imitation learning to the DDPG reinforcement learning to obtain decision-making experience and action prediction behavior of the path tracking process.In the reinforcement learning process,imitation learning is used to update the pre-training parameters of the actor network,and a feedforward steering technique with random noise is adopted for strategy exploration.In the reward function,a hierarchical progressive reward form and a constrained objective reward function referring to MPC are designed,and the actor-critic network architecture is determined.Finally,the path tracking performance of the designed method is verified by comparing various training results,simulations,and HIL tests.The results show that the designed method can effectively utilize pre-training and feedforward prior experience to obtain optimal path tracking performance of an autonomous vehicle,and has better generalization ability than other methods.This study provides an efficient control scheme for improving the end-to-end control performance of autonomous vehicles.
基金National Natural Science Foundation of China(Grant No.11862005)Natural Science Foundation of Jiangxi Province of China(Grant No.20181BAB211012)Tianjin Natural Science Foundation of China(Grant No.18JCYBJC88500)is gratefully acknowledged.
文摘Ceramics are extensively used in protective structures which are often subjected to projectile impacts.During an impact process of a ceramic target by a projectile,fragmentation occurs in both the target and the projectile.It is challenging to simulate such events and predict residual mass and velocity of the projectile.In this work,we attempt to use smoothed particle hydrodynamics(SPH)in LS-DYNA to reproduce fragmentation of the target and the projectile and predict residual mass and velocity of the projectile during a projectile impact of a ceramic target.SPH models for an alumina ceramic tile impacted by a blunt tungsten heavy alloy projectile are established.SPH simulation results of residual mass and velocity of the projectile as well as ejecta and bulge movements of the ceramic tile are obtained and compared with experimental data and simulation results of other numerical approaches.It is found that SPH simulation can properly reproduce the impact fragmentation of the target and the projectile,and shows advantages over existing numerical approaches in the prediction accuracy of residual mass and velocity.Moreover,effects of some numerical aspects of SPH,including particle spacing,contact treatment and parameters in artificial viscosity and smoothing length,on simulation results are identified.A simple approach using identical smoothing length and balanced artificial viscosity is proposed to reduce particle spacing sensitivity.The observed parametric effects and the proposed approach will provide guidance to set appropriate parameters values for SPH simulation of impact fragmentation.
基金This work was supported by the National Key Research andDevelopment Program of China(No.2018YFA0703000)the National Natural Science Foundation of China(Nos.T2121004,52235007,and 82203602)+2 种基金Zhejiang Provincial Natural Science Foundation of China under Grant No.LQ22H160020 to JWThis work was also supported by Start-up Funding of Zhejiang Provincial People’s Hospital(No.ZRY2021A001 to JW)Basic Scientific Research Funds of Department of Education of Zhejiang Province(No.KYQN202109 to JW).
文摘Prosthesis implantation and fat transplantation are common breast reconstructionmethods.In general,prosthesis implantation alone does not achieve a realistic enough appearance,and fat transplantation alone is difficult to achieve in the correct capacity.To date,no reports have focused on methods of combining fat with implanted prostheses for breast reconstruction.Using a newly designed bionic ink(i.e.,polyether F127 diacrylate(F127DA)&poly(ethylene glycol)diacrylate(PEGDA))and projection-based three-dimensional bioprinting(PBP),we report the development of a new method for printing porous prostheses.PEGDA was used to improve the printing precision of the prosthesis by increasing the gel point of F127DA and reducing the impact of external temperature.The compression modulus of the printed prosthesis was very close to that of prostheses currently used in clinical practice and to that of natural breasts.Finally,stromal vascular fraction gel(SVF-gel),a human fat extract,was injected into the pores of the synthesized prostheses to prepare a prosthesis mixed with adipose tissue.These were implanted subcutaneously in nude mice to observe their biological performance.After 14 and 28 days of observation,the prosthesis showed good biocompatibility,and adipose tissues grew well in and around the prosthesis.This result shows that a porous prosthesis containing pre-placed adipose tissues is a promising breast reconstruction material.
基金supported by the National Natural Science Foundation of China(Grant No.51765020)the Natural Science Foundation of Jiangxi Province(Grant No.20161BAB206153).
文摘Wind turbine is a key device to realize the utilization of wind energy,and it has been highly valued by all countries.But the mechanical gear transmission of the existing wind power device has the disadvantages of high vibration and noise,high failure rate,and short service time.Magneticfield modulation electromagnetic gear transmission is a new non-contact transmission method.However,the conventional modulation magnetic gear has low torque density and torque defects with largefluctuations.In order to overcome the gear transmis-sion problems of the existing semi-direct drive wind power generation machinery and improve the electromag-netic performance of the traditional magnetic gear transmission,this paper proposes a new transmission scheme of a non-contact semi-direct drive wind generator with a surface mount Halbach array modulated mag-netic gear method,and considers the electromagnetic properties of the semi-direct drive modulation magnetic gear of the wind turbine.Thefinite element software is used to construct the model of the surface-mounted Halbach array magnetic gear and the conventional gear,analyzed the distribution of magneticfield lines of the two magnetic gears,calculated the air gap magneticflux density of the inner and outer air gap,and obtained the main harmonics of the inner and outer air gap magnetic density;calculated the static torque and steady-state operating torque of the inner and outer rotors in the model,compared the air gapflux density,harmonics and torque of the magnetic gears.The simulation results show that the magneticfield modulation type mag-netic gear of the surface mount Halbach array magnetic gear method improves the magnetic induction wave-form of the inner and outer air gap,reduces the pulse torquefluctuation,and has a 60%higher static torque.Applying it to semi-direct drive wind power generation equipment not only overcomes the shortcomings of mechanical gears,but also has higher electromagnetic performance.Therefore,the surface-mounted Halbach array modulated magnetic gear can be used to replace the mechanical gearbox in the semi-direct drive wind power generation equipment.
文摘This study employs friction stir welding(FSW)technology to achieve the butt welding of 2mm thick 1060 aluminum and T2 copper.The research investigates the macroscopic formation,tensile properties,microhardness,and electrochemical corrosion behavior of the welded joints.The results indicate that the welded joints exhibit excellent formation,with a tensile strength reaching 84.76%of that of the 1060 aluminum material.Well-formed welded joints can be obtained by controlling the rotation speed and welding speed within a certain range.However,the rotation speed has a more significant impact on the microhardness in the weld zone.The corrosion potential of T2 copper is higher than that of 1060 aluminum,forming a macroscopic galvanic couple between the two materials.The corrosion potential of the welded joint falls between that of T2 copper and 1060 aluminum.
基金supported by the Natural Science Foundation of China(52167008)Outstanding Youth Fund Project of Jiangxi Natural Science Foundation(20202ACBL214021)+1 种基金Key Research and Development Plan of Jiangxi Province(20202BBGL73098)Science and Technology Project of Education Department of Jiangxi Province(GJJ210650)。
文摘Aiming at the problems of traditional centralized cloud computing which occupies large computing resources and creates high latency,this paper proposes a fault detection scheme for insulator self-explosion based on edge computing and DL(deep learning).In order to solve the high amount of computation brought by the deep neural network and meet the limited computing resources at the edge,a lightweight SSD(Single Shot MultiBox Detector)target recognition network is designed at the edge,which adopts the MobileNets network to replace VGG16 network in the original model to reduce redundant computing.In the cloud,three detection algorithms(Faster-RCNN,Retinanet,YOLOv3)with obvious differences in detection performance are selected to obtain the coordinates and confidence of the insulator self-explosion area,and then the self-explosion fault detection of the overhead transmission line is realized by a novel multimodel fusion algorithm.The experimental results show that the proposed scheme can effectively reduce the amount of uploaded data,and the average recognition accuracy of the cloud is 95.75%.In addition,it only increases the power consumption of edge devices by about 25.6W/h in their working state.Compared with the existing online monitoring technology of insulator selfexplosion at home and abroad,the proposed scheme has the advantages of low transmission delay,low communication cost and high diagnostic accuracy,which provides a new idea for online monitoring research of power internet of things equipment.
基金The authors acknowledge the finical support from the Key Laboratory Functional Molecular Solids,Ministry of Education(No.FMS202002)the National Key Research and Development Project(No.2020YFA0210703)+5 种基金the National Natural Science Foundation of China(Nos.U2032158,U2032159,and 62005292)the Key Research and Development Program of Anhui Province(Nos.S202104a05020085 and 201904a05020009)the Science and Technology Service Network Initiative of Chinese Academy of China(grant No.KFJ-STS-ZDTP-080)the Collaborative Innovation Program of Hefei Science Center,CAS(No.2020HSCCIP003)the Major Scientific and the CASHIPS Director’s Fund(No.YZJJZX202015)the Technological Innovation Projects of Shandong Province(No.2019JZZY020243).
文摘Copper sulfide(Cu_(x)S)as a plasmonic solar photothermal semiconductor material that expands the light collection range by altering localized surface plasmon resonance(LSPR)to the near-to mid-infrared(IR)spectral region.The versatile synthesis strategies of Cu_(x)S nanostructure offer its variability of morphology and provide additional freedom in tuning the optical property.Particularly,nanocage(or nanoshell)has hybridized plasmon resonances as a result of super-positioned nanosphere and nanocavity,which extends its receiving range of solar spectrum and increases light-to-heat conversion rate.Here,we offer novel“nanoink”and“nanofilm”developed from colloidal Cu_(27)S_(24)nanocages with excellent solar photothermal response.Via combining experimental measurement and theoretical calculation,we estimated the optical properties of covellite Cu_(27)S_(24).And based on obtained dielectric functions,we then calculated its solar photothermal performance,which was further validated by our experimental measurement.The simulation results showed that hollow Cu_(27)S_(24)nanocages have excellent solar photothermal performance,and exhibit much higher solar photothermal conversion efficiency than solid Cu_(27)S_(24)nanospheres.
基金Supported by National Key Research and Development Program(Grant No.2023YFB4203402)National Natural Science Foundation of China(Grant No.52375042)+1 种基金Chongqing Technology Innovation and Application Development Project(Grant No.CSTB2022TIAD-KPX0078)Chongqing Transportation Technology Project(Grant No.CQJT-CZKJ2024-10).
文摘The research on rolling bearing early fault detection is mainly focused on degradation index extraction and adaptive setting of alarm threshold.The mainstream methods are to extract degradation indicators based on adaptive features and set adaptive alarm thresholds based on the Shewhart control chart.However,the adaptive feature extraction method does not consider the correlation between features,and the Shewhart control chart is not sensitive to small fluctuations caused by early faults.In this study,a rolling bearing early fault detection method based on a feature clustering fusion degradation index is proposed.The multidomain statistical features are extracted to form the initial feature set,and the improved hierarchical clustering algorithm is combined with the feature evaluation index to select features to form a preferred feature subset,to ensure the richness of index information and reduce redundancy.After the construction of the degradation index,to suppress the interference caused by nonstationary and abnormal shocks in early fault detection,the accurate evaluation method and anomaly determination strategy of control chart parameters are studied,and an improved exponential weighted move average control chart is designed to monitor the degradation index.The effectiveness and superiority of the proposed method are verified by public data sets.This research provides a rolling bearing early fault detection method,which can provide comprehensive degradation indicators,eliminate interference caused by random anomalies and running in periods,and achieve an accurate detection of early bearing failures.
基金National Natural Science Foundation of China(grant No.51906011)Fundamental Research Funds for the Central Universities(grant No.YWF-23-L-1151).
文摘The transient heat transfer behaviours in a packed bed have been studied using coupled computational fluid dynamics(CFD)and discrete element method(DEM).Intra-particle thermal diffusion,which is a crucial but rarely explored issue,is considered by introducing a one-dimensional diffusion equation in the DEM solver.To achieve a sufficiently long physical time of simulations,we further reduce the computational cost by applying periodic boundary condition to a small segment of the packed bed.Our study demonstrates a shifting peak heat flow rate from the bottom to the top of the packed bed during the initial warming phase.We affirm that the influence of thermal diffusion within a particle is noteworthy only for particles exhibiting a high Biot number(e.g.,Bi=1.2).This insight enriches our understanding of heat transfer mechanisms in packed beds and their practical engineering applications.
基金supported by the National Natural Science Foundation of China(No.31960497)the Natural Science Foundation of Jiangxi Province(No.20202BAB205009),China.
文摘Background and objectives:Current technology of X-ray imaging can recognize hard foreign materials(FMs)such as metal and high-density plastic.However,low-density foreign bodies are still a challenge for food quality and safety assessment.Materials and methods:An electromagnetic vibration feeder aided by terahertz time-domain spectroscopy(THz-TDS)and imaging was inves-tigated for non-destructively detecting tea stalk and insect FMs mixed with tea leaves.Results:THz time-domain signals were employed directly to develop the K-nearest neighbor model with a precision of 100%,accuracy of 95.6%and recall of 98.7%in predicting the unknown samples.High contrast THz-TDS images were obtained by the separation method for the samples using electromagnetic vibration feeder.The characteristic parameters of the ratio of maximum length(L)to maximum width(W)and hue extracted from THz-TDS images indicated significant difference between tea leaves and FMs.Conclusions:The results suggested that electromagnetic vibration feeder combination with THz-TDS was feasible for detecting FMs in fin-ishingteaproducts.
基金support provided by the National Natural Science Foundation of China Nos.51405048 and 51375519the China Postdoctoral Science Foundation No.2016M590861+2 种基金the Chongqing Research Program of Frontier and Application Foundation No.cstc2014jcyjA70010the Foundation of Municipal Education Committee of Chongqing No.KJ1705129the CQJTU Program of Study Abroad for Young Scholar for their support of this research.
文摘To investigate the dynamical load sharing behaviors of multi-floating components in the heavy load planetary gear system,a multi-floating planetary gear system that includes a floating central component and a quasi-floating planet flexible supporting pin is employed.Then a 21 degree of freedom lumped parameters dynamical model of this system is presented to study the dynamical load sharing behaviors.Some influencing factors,such as supporting stiffness,positions error of sun or carrier,and external input load are analyzed on the dynamical load sharing of the planetary gear system with multi-floating components.The results demonstrate that the load sharing condition of the system is best when both the sun gear and planet gears are multi-floating at the same time.When the planet gear position errors remain constant,reducing the flexible pin stiffness of planet gear or increasing external input load can effectively improve the load sharing.These conclusions are verified by the relevant experiments.
