Tooth cracks may occur in spiral bevel gear transmission system of the aerospace equipment.In this study,an accurate and efficient loaded tooth contact analysis(LTCA)model is developed to predict the contact behavior ...Tooth cracks may occur in spiral bevel gear transmission system of the aerospace equipment.In this study,an accurate and efficient loaded tooth contact analysis(LTCA)model is developed to predict the contact behavior and time-varying meshing stiffness(TVMS)of spiral bevel gear pair with cracked tooth.The tooth is sliced,and the contact points on slices are computed using roll angle surfaces.Considering the geometric complexity of crack surface,a set of procedures is formulated to generate spatial crack and determine crack parameters for contact points.According to the positional relationship between contact point and crack path,each sliced tooth is modeled as a non-uniform cantilever beam with varying reduced effective load-bearing tooth thickness.Then the compliance model of the cracked tooth is established to perform contact analysis,along with TVMS calculations utilizing three different models.By employing spiral bevel gear pairs with distinct types of cracks as examples,the accuracy and efficiency of the developed approach are validated via comparative analyses with finite element analysis(FEA)outcomes.Furthermore,the investigation on effects of cracks shows that tooth cracks can induce alterations in meshing performance of both entire gear pair and individual tooth pairs,including not only cracked tooth pair but also adjacent non-cracked tooth pairs.Hence,the proposed model can serve as a useful tool for analyzing the variations in contact behavior and meshing stiffness of spiral bevel gears due to different cracks.展开更多
During the propagation of high-power lasers within internal channels,the laser beam heats the propagation medium,causing the thermal blooming effect that degrades the beam quality at the output.The intricate configura...During the propagation of high-power lasers within internal channels,the laser beam heats the propagation medium,causing the thermal blooming effect that degrades the beam quality at the output.The intricate configuration of the optical path within the internal channel necessitates complex and time-consuming efforts to assess the impact of thermal blooming effect on the optical path.To meet the engineering need for rapid evaluation of thermal blooming effect in optical paths,this study proposed a rapid simulation method for the thermal blooming effect in internal optical paths based on the finite element method.This method discretized the fluid region into infinitesimal elements and employed finite element method for flow field analysis.A simplified analytical model of the flow field region in complex internal channels was established,and regions with similar thermal blooming effect were divided within this model.Based on the calculated optical path differences within these regions,numerical simulations of phase distortion caused by thermal blooming were conducted.The calculated result were compared with those obtained using the existing methods.The findings reveal that for complex optical paths,the discrepancy between the two approaches is less than 3.6%,with similar phase distortion patterns observed.For L-type units,this method and the existing methods identify the same primary factors influencing aberrations and exhibit consistent trends in their variation.This method was used to analyze the impact of thermal blooming effect in a straight channel under different gravity directions.The results show that phase distortion varies with changes in the direction of gravity,and the magnitude of the phase difference is strongly correlated with the component of gravity perpendicular to the optical axis.Compared to the existing methods,this approach offers greater flexibility,obviates the need for complex custom analysis programming.The analytical results of this method enable a rapid assessment of the thermal blooming effect in optical paths within the internal channel.This is especially useful during the engineering design.These results also provide crucial references for developing strategies to suppress thermal blooming effect.展开更多
1故障一故障现象:治疗过程中报错“PCP communication error”,重启后停留在初始化状态。故障分析:PCP为机器外壳前部上方左右2个12寸显示屏,该报错一般为通信故障。单个PCP故障时,首先检查输入电源,确认电源线接触是否良好,输入电压是...1故障一故障现象:治疗过程中报错“PCP communication error”,重启后停留在初始化状态。故障分析:PCP为机器外壳前部上方左右2个12寸显示屏,该报错一般为通信故障。单个PCP故障时,首先检查输入电源,确认电源线接触是否良好,输入电压是否正常,并进行针对性处理。其次检查网络通信,确认IP地址和TOMO内部电脑主机在同一网段,利用service PC通过ping指令确认通信是否正常。显示屏本身故障以及PCP软件丢失均是产生故障的因素,通过维修显示屏或重刷软件可解决该故障。两个PCP同时故障时,除了上述单个故障排除的方法以外,需要检查机器前外壳和显示屏之间的72芯排线各个针脚有无折损、氧化,并用万用表检测两侧针脚通信是否良好。该排线由于长期暴露在空气中,受机房环境影响较大,容易氧化导致接触不良,引起故障,排查故障时需重点关注。展开更多
Current research on wind energy piezoelectric energy harvesters(PEHs)mainly focuses on tandem smooth cylinder energy harvesters;however,the traditional tandem smooth cylinder energy harvester has low voltage output an...Current research on wind energy piezoelectric energy harvesters(PEHs)mainly focuses on tandem smooth cylinder energy harvesters;however,the traditional tandem smooth cylinder energy harvester has low voltage output and narrow energy harvest bandwidth.In this study,a D-type bionic fin is designed and installed on a smooth cylindrical surface to improve its performance.The influence of the spacing ratio on the amplitude and voltage of PEHs with D-type bionic fins added under elastic interference was investigated through wind tunnel tests.Three installation positions were designed:only installed upstream,only installed downstream,and not installed upstream and downstream(BARE).It was found that the maximum displacement of the upstream PEH(UPEH)was not apparently affected by the D-type bionic fin.Contrastingly,the fin changed the maximum amplitude from a small to a large spacing ratio for the downstream PEH(DPEH).D-type bionic fin can enhance energy harvest performance by coupling“coupled vortex-induced vibration”and wake induced galloping,increasing the surface velocity of PEHs and expanding the bandwidth of the voltage harvested by the PEHs.Analysis of the power under the experimental wind speed showed that installing D-type fins in the PEHs can increase the output power of the upstream and downstream PEHs by 392.28%and 13%,respectively,compared with that of the BARE-PEH.Additionally,computational fluid dynamics was used to analyze the flow pattern,wake structure,and lift coefficient of the PEHs,and to explain why the upstream D-type bionic fin installation has an impact on the harvest performance of the upstream and downstream PEHs at a spacing ratio of 1.5.This study provides an efficient and simple scheme for designing wind PEHs.展开更多
Accurate water level measurement in nuclear reactors,particularly in PWRs(pressurized water reactors)and BWRs(boiling water reactors),is essential for ensuring the safety and efficiency of reactor operations.K-type HJ...Accurate water level measurement in nuclear reactors,particularly in PWRs(pressurized water reactors)and BWRs(boiling water reactors),is essential for ensuring the safety and efficiency of reactor operations.K-type HJTCs(heated junction thermocouples)are widely used for this purpose due to their ability to withstand extreme temperatures and radiation conditions.This article explores the role of HJTCs in reactor water level measurement and compares the performance of 2-wire and 3-wire connections.While the 2-wire connection is simple and cost-effective,it can introduce measurement inaccuracies due to wire resistance.In contrast,the 3-wire connection compensates for lead resistance,offering more precise and reliable measurements,particularly in long-distance applications.This paper discusses the operational considerations of these wiring configurations in the context of nuclear reactors and highlights the importance of choosing the appropriate connection type to optimize safety and measurement accuracy in PWR and BWR reactors.展开更多
In a series of three papers published in 2024[1-3],physicists in Austria,Germany,and the United States reported the first direct observations with table-top lasers of a new nuclear process,in which the nucleus of a th...In a series of three papers published in 2024[1-3],physicists in Austria,Germany,and the United States reported the first direct observations with table-top lasers of a new nuclear process,in which the nucleus of a thorium atom absorbs a photon and goes into an excited state,then re-emits the photon and returns to its ground state.This“thorescence”phenomenon“is exactly the same process as fluorescence,but it takes place inside the nucleus,”said Ekkehard Peik,professor and head of the department of time and frequency at the Physikalisch-Technische Bundesanstalt(the German national metrology institute)in Braunschweig,Germany.展开更多
The contact characteristics of the rough tooth surface during the meshing process are significantly affected by the lubrication state.The coupling effect of tooth surface roughness and lubrication on meshing character...The contact characteristics of the rough tooth surface during the meshing process are significantly affected by the lubrication state.The coupling effect of tooth surface roughness and lubrication on meshing characteristics of planetary gear is studied.An improved three-dimensional(3 D)anisotropic tooth surface roughness fractal model is proposed based on the experimental parameters.Considering asperity contact and elastohydrodynamic lubrication(EHL),the contact load and flexibility deformation of the tooth surface are derived,and the deformation compatibility equation of the 3 D loaded tooth contact analysis(3 D-LTCA)method is improved.The asperity of the tooth surface changes the system from EHL to mixed lubrication and reduces the stiffness of the oil film.Compared with the sun planet gear,the asperity has a greater effect on the meshing characteristics of the ring-planet gear.Compared with the proposed method,the comprehensive stiffness obtained by the traditional calculation method considering the lubrication effect is smaller,especially for the ring-planet gear.Compared with roughness,speed and viscosity,the meshing characteristics of planetary gears are most sensitive to torque.展开更多
Meshing temperature analyses of polymer gears reported in the literature mainly concern the effects of various material combinations and loading conditions,as their impacts could be seen in the first few meshing cycle...Meshing temperature analyses of polymer gears reported in the literature mainly concern the effects of various material combinations and loading conditions,as their impacts could be seen in the first few meshing cycles.However,the effects of tooth geometry parameters could manifest as the meshing cycles increase.This study investigated the effects of tooth geometry parameters on the multi-cycle meshing temperature of polyoxymethylene(POM)worm gears,aiming to control the meshing temperature elevation by tuning the tooth geometry.Firstly,a finite element(FE)model capable of separately calculating the heat generation and simulating the heat propagation was established.Moreover,an adaptive iteration algorithm was proposed within the FE framework to capture the influence of the heat generation variation from cycle to cycle.This algorithm proved to be feasible and highly efficient compared with experimental results from the literature and simulated results via the full-iteration algorithm.Multi-cycle meshing temperature analyses were conducted on a series of POM worm gears with different tooth geometry parameters.The results reveal that,within the range of 14.5°to 25°,a pressure angle of 25°is favorable for reducing the peak surface temperature and overall body temperature of POM worm gears,which influence flank wear and load-carrying capability,respectively.However,addendum modification should be weighed because it helps with load bearing but increases the risk of severe flank wear.This paper proposes an efficient iteration algorithm for multi-cycle meshing temperature analysis of polymer gears and proves the feasibility of controlling the meshing temperature elevation during multiple cycles by tuning tooth geometry.展开更多
Spiral bevel gears are critical transmission components,and are widely used in the aerospace field.This paper proposes a new multi-DOF envelope forming process for fabricating spiral bevel gears.Firstly,the multi-DOF ...Spiral bevel gears are critical transmission components,and are widely used in the aerospace field.This paper proposes a new multi-DOF envelope forming process for fabricating spiral bevel gears.Firstly,the multi-DOF envelope forming principle of spiral bevel gears is proposed.Secondly,the design methods for the envelope tool geometry and movement are proposed based on the envelope geometry and movement relationships.Thirdly,the metal flow and tooth filling laws are revealed through 3D FE simulation of the multi-DOF envelope forming process of a typical spiral bevel gear.Fourthly,a new method for separating the envelope tool and the formed spiral bevel gear with back taper tooth is proposed to avoid their interference.Finally,experiments on multi-DOF envelope forming of this typical spiral bevel gear are conducted using new heavy load multi-DOF envelope forming equipment.The simulation and experimental results show the feasibility of the proposed multi-DOF envelope forming process for fabricating spiral bevel gears with back taper tooth and the corresponding process design methods.展开更多
The rising flexible and intelligent electronics greatly facilitate the noninvasive and timely tracking of physiological information in telemedicine healthcare.Meticulously building bionic-sensitive moieties is vital f...The rising flexible and intelligent electronics greatly facilitate the noninvasive and timely tracking of physiological information in telemedicine healthcare.Meticulously building bionic-sensitive moieties is vital for designing efficient electronic skin with advanced cognitive functionalities to pluralistically capture external stimuli.However,realistic mimesis,both in the skin’s three-dimensional interlocked hierarchical structures and synchronous encoding multistimuli information capacities,remains a challenging yet vital need for simplifying the design of flexible logic circuits.Herein,we construct an artificial epidermal device by in situ growing Cu_(3)(HHTP)_(2) particles onto the hollow spherical Ti_(3)C_(2)T_(x) surface,aiming to concurrently emulate the spinous and granular layers of the skin’s epidermis.The bionic Ti_(3)C_(2)T_(x)@Cu_(3)(HHTP)_(2) exhibits independent NO_(2) and pressure response,as well as novel functionalities such as acoustic signature perception and Morse code-encrypted message communication.Ultimately,a wearable alarming system with a mobile application terminal is self-developed by integrating the bimodular senor into flexible printed circuits.This system can assess risk factors related with asthmatic,such as stimulation of external NO_(2) gas,abnormal expiratory behavior and exertion degrees of fingers,achieving a recognition accuracy of 97.6%as assisted by a machine learning algorithm.Our work provides a feasible routine to develop intelligent multifunctional healthcare equipment for burgeoning transformative telemedicine diagnosis.展开更多
For space-borne gravitational wave detection missions based on the heterodyne interferometry principle,tilt-to-length(TTL)coupling noise is an important optical noise source,significantly influencing the accuracy of t...For space-borne gravitational wave detection missions based on the heterodyne interferometry principle,tilt-to-length(TTL)coupling noise is an important optical noise source,significantly influencing the accuracy of the measurement system.We present a method for analyzing TTL coupling noise under the joint influence of multiple factors.An equivalent simulated optical bench for the test mass interferometer was designed,and Gaussian beam tracing was adopted to simulate beam propagation.By simulating the interference signal,it can analyze the impact of various factors on the TTL coupling noise,including positional,beam parameters,detector parameters,and signal definition factors.On this basis,a random parameter space composed of multiple influential factors was constructed within a range satisfying the analysis requirement,and the corresponding simulation results from random sampling were evaluated via variance-based global sensitivity analysis.The calculated results of the main and total effect indexes show that the test mass rotation angle and the piston effect(lateral)significantly influence the TTL coupling noise in the test mass interferometer.The analysis provides a qualitative reference for designing and optimizing space-borne laser interferometry systems.展开更多
Background:The risk of internal fixation failure remains relatively high in stable femoral neck fracture(FNF)(Garden I or II).Preoperative sagittal displacement of the femoral head has been proposed as a potential inf...Background:The risk of internal fixation failure remains relatively high in stable femoral neck fracture(FNF)(Garden I or II).Preoperative sagittal displacement of the femoral head has been proposed as a potential influencing factor.This study aimed to evaluate the impact of sagittal displacement on the outcomes of cannulated screw internal fixation(CSIF)in patients with stable FNF(Garden I or II)by reconstructing the axial sagittal oblique plane of the fracture using preoperative computed tomography(CT)imaging.Methods:This study included 167 patients with FNF who underwent CSIF.The sagittal tilt angle of the femoral head(STAFH)was evaluated using three-dimensional CT(3D-CT).The distribution of preoperative STAFH was analyzed,and its independent association with treatment failure was assessed.Treatment failure was defined as the need for revision surgery within 2 years postoperatively due to avascular necrosis,nonunion,or internal fixation failure.Results:Among the 167 patients,9(5.4%)exhibited anterior tilt(AT)of the femoral head,158(94.60%)presented with posterior tilt(PT).A total of 50 patients(29.9%)demonstrated excessive sagittal displacement(AT≥10°or PT≥20°).In the failure group,80.0%of patients had excessive sagittal displacement compared to 28.1%in the healed group.Excessive sagittal displacement was significantly associated with an increased risk of surgical failure(odds ratio:11.953,95%CI:3.656-39.083,p<0.05).Conclusions:In patients with Garden I or II FNF,greater preoperative sagittal displacement of the femoral head was correlated with a higher likelihood of CSIF failure.AT≥10°or PT≥20°were identified as independent predictors of CSIF failure in FNF patients.Nevertheless,these findings still require confirmation through prospective,multi-center clinical trials with large sample sizes.展开更多
Researching the dispersion as well as the stability of metals on the oxide surfaces is essentially important for understanding the interaction mecha-nisms at the metal/oxide interfaces and thus optimizing the activiti...Researching the dispersion as well as the stability of metals on the oxide surfaces is essentially important for understanding the interaction mecha-nisms at the metal/oxide interfaces and thus optimizing the activities of the heterogeneous catalysts.Here in this work,we have investigated the growth behavior of Pd particles on the polar surfaces of ZnO with scanning tunneling microscopy(STM).By systematically varying the coverages as well as the annealing temperatures,we found that at room temperature Pd tends to form three-dimensional(3D)round particles on the ZnO(000)surface but grow into monolayer two-dimensional(2D)hexagonal islands on the ZnO(0001)surface.During annealing processes,the Pd particles on ZnO(000)aggregate gently while maintaining the 3D morphology in the mild temperature range but then quickly transform in-to tall hexagonal islands at elevated temperatures.In contrast,the segregation of Pd islands on ZnO(0001)occurs gradually along with the temperature rising without changing the 2D morphology.These results directly reflect the different interaction strengths of Pd on the dis-tinct ZnO polar surfaces.They also provide important input for understanding the facet-de-pendent catalytic mechanisms of the Pd/ZnO catalytic systems.展开更多
基金co-supported by the National Natural Science Foundation of China (No. 52175104)the Postdoctoral Fellowship Program of CPSF (No. GZC20233008)
文摘Tooth cracks may occur in spiral bevel gear transmission system of the aerospace equipment.In this study,an accurate and efficient loaded tooth contact analysis(LTCA)model is developed to predict the contact behavior and time-varying meshing stiffness(TVMS)of spiral bevel gear pair with cracked tooth.The tooth is sliced,and the contact points on slices are computed using roll angle surfaces.Considering the geometric complexity of crack surface,a set of procedures is formulated to generate spatial crack and determine crack parameters for contact points.According to the positional relationship between contact point and crack path,each sliced tooth is modeled as a non-uniform cantilever beam with varying reduced effective load-bearing tooth thickness.Then the compliance model of the cracked tooth is established to perform contact analysis,along with TVMS calculations utilizing three different models.By employing spiral bevel gear pairs with distinct types of cracks as examples,the accuracy and efficiency of the developed approach are validated via comparative analyses with finite element analysis(FEA)outcomes.Furthermore,the investigation on effects of cracks shows that tooth cracks can induce alterations in meshing performance of both entire gear pair and individual tooth pairs,including not only cracked tooth pair but also adjacent non-cracked tooth pairs.Hence,the proposed model can serve as a useful tool for analyzing the variations in contact behavior and meshing stiffness of spiral bevel gears due to different cracks.
文摘During the propagation of high-power lasers within internal channels,the laser beam heats the propagation medium,causing the thermal blooming effect that degrades the beam quality at the output.The intricate configuration of the optical path within the internal channel necessitates complex and time-consuming efforts to assess the impact of thermal blooming effect on the optical path.To meet the engineering need for rapid evaluation of thermal blooming effect in optical paths,this study proposed a rapid simulation method for the thermal blooming effect in internal optical paths based on the finite element method.This method discretized the fluid region into infinitesimal elements and employed finite element method for flow field analysis.A simplified analytical model of the flow field region in complex internal channels was established,and regions with similar thermal blooming effect were divided within this model.Based on the calculated optical path differences within these regions,numerical simulations of phase distortion caused by thermal blooming were conducted.The calculated result were compared with those obtained using the existing methods.The findings reveal that for complex optical paths,the discrepancy between the two approaches is less than 3.6%,with similar phase distortion patterns observed.For L-type units,this method and the existing methods identify the same primary factors influencing aberrations and exhibit consistent trends in their variation.This method was used to analyze the impact of thermal blooming effect in a straight channel under different gravity directions.The results show that phase distortion varies with changes in the direction of gravity,and the magnitude of the phase difference is strongly correlated with the component of gravity perpendicular to the optical axis.Compared to the existing methods,this approach offers greater flexibility,obviates the need for complex custom analysis programming.The analytical results of this method enable a rapid assessment of the thermal blooming effect in optical paths within the internal channel.This is especially useful during the engineering design.These results also provide crucial references for developing strategies to suppress thermal blooming effect.
文摘1故障一故障现象:治疗过程中报错“PCP communication error”,重启后停留在初始化状态。故障分析:PCP为机器外壳前部上方左右2个12寸显示屏,该报错一般为通信故障。单个PCP故障时,首先检查输入电源,确认电源线接触是否良好,输入电压是否正常,并进行针对性处理。其次检查网络通信,确认IP地址和TOMO内部电脑主机在同一网段,利用service PC通过ping指令确认通信是否正常。显示屏本身故障以及PCP软件丢失均是产生故障的因素,通过维修显示屏或重刷软件可解决该故障。两个PCP同时故障时,除了上述单个故障排除的方法以外,需要检查机器前外壳和显示屏之间的72芯排线各个针脚有无折损、氧化,并用万用表检测两侧针脚通信是否良好。该排线由于长期暴露在空气中,受机房环境影响较大,容易氧化导致接触不良,引起故障,排查故障时需重点关注。
基金Supported by National Natural Science Foundation of China(Grant No.21978202).
文摘Current research on wind energy piezoelectric energy harvesters(PEHs)mainly focuses on tandem smooth cylinder energy harvesters;however,the traditional tandem smooth cylinder energy harvester has low voltage output and narrow energy harvest bandwidth.In this study,a D-type bionic fin is designed and installed on a smooth cylindrical surface to improve its performance.The influence of the spacing ratio on the amplitude and voltage of PEHs with D-type bionic fins added under elastic interference was investigated through wind tunnel tests.Three installation positions were designed:only installed upstream,only installed downstream,and not installed upstream and downstream(BARE).It was found that the maximum displacement of the upstream PEH(UPEH)was not apparently affected by the D-type bionic fin.Contrastingly,the fin changed the maximum amplitude from a small to a large spacing ratio for the downstream PEH(DPEH).D-type bionic fin can enhance energy harvest performance by coupling“coupled vortex-induced vibration”and wake induced galloping,increasing the surface velocity of PEHs and expanding the bandwidth of the voltage harvested by the PEHs.Analysis of the power under the experimental wind speed showed that installing D-type fins in the PEHs can increase the output power of the upstream and downstream PEHs by 392.28%and 13%,respectively,compared with that of the BARE-PEH.Additionally,computational fluid dynamics was used to analyze the flow pattern,wake structure,and lift coefficient of the PEHs,and to explain why the upstream D-type bionic fin installation has an impact on the harvest performance of the upstream and downstream PEHs at a spacing ratio of 1.5.This study provides an efficient and simple scheme for designing wind PEHs.
文摘Accurate water level measurement in nuclear reactors,particularly in PWRs(pressurized water reactors)and BWRs(boiling water reactors),is essential for ensuring the safety and efficiency of reactor operations.K-type HJTCs(heated junction thermocouples)are widely used for this purpose due to their ability to withstand extreme temperatures and radiation conditions.This article explores the role of HJTCs in reactor water level measurement and compares the performance of 2-wire and 3-wire connections.While the 2-wire connection is simple and cost-effective,it can introduce measurement inaccuracies due to wire resistance.In contrast,the 3-wire connection compensates for lead resistance,offering more precise and reliable measurements,particularly in long-distance applications.This paper discusses the operational considerations of these wiring configurations in the context of nuclear reactors and highlights the importance of choosing the appropriate connection type to optimize safety and measurement accuracy in PWR and BWR reactors.
文摘In a series of three papers published in 2024[1-3],physicists in Austria,Germany,and the United States reported the first direct observations with table-top lasers of a new nuclear process,in which the nucleus of a thorium atom absorbs a photon and goes into an excited state,then re-emits the photon and returns to its ground state.This“thorescence”phenomenon“is exactly the same process as fluorescence,but it takes place inside the nucleus,”said Ekkehard Peik,professor and head of the department of time and frequency at the Physikalisch-Technische Bundesanstalt(the German national metrology institute)in Braunschweig,Germany.
基金Project(2024A1515240020)supported by the Guangdong Basic and Applied Basic Research Foundation,China。
文摘The contact characteristics of the rough tooth surface during the meshing process are significantly affected by the lubrication state.The coupling effect of tooth surface roughness and lubrication on meshing characteristics of planetary gear is studied.An improved three-dimensional(3 D)anisotropic tooth surface roughness fractal model is proposed based on the experimental parameters.Considering asperity contact and elastohydrodynamic lubrication(EHL),the contact load and flexibility deformation of the tooth surface are derived,and the deformation compatibility equation of the 3 D loaded tooth contact analysis(3 D-LTCA)method is improved.The asperity of the tooth surface changes the system from EHL to mixed lubrication and reduces the stiffness of the oil film.Compared with the sun planet gear,the asperity has a greater effect on the meshing characteristics of the ring-planet gear.Compared with the proposed method,the comprehensive stiffness obtained by the traditional calculation method considering the lubrication effect is smaller,especially for the ring-planet gear.Compared with roughness,speed and viscosity,the meshing characteristics of planetary gears are most sensitive to torque.
基金Supported by National Key R&D Program of China(Grant No.2019YFE0121300)。
文摘Meshing temperature analyses of polymer gears reported in the literature mainly concern the effects of various material combinations and loading conditions,as their impacts could be seen in the first few meshing cycles.However,the effects of tooth geometry parameters could manifest as the meshing cycles increase.This study investigated the effects of tooth geometry parameters on the multi-cycle meshing temperature of polyoxymethylene(POM)worm gears,aiming to control the meshing temperature elevation by tuning the tooth geometry.Firstly,a finite element(FE)model capable of separately calculating the heat generation and simulating the heat propagation was established.Moreover,an adaptive iteration algorithm was proposed within the FE framework to capture the influence of the heat generation variation from cycle to cycle.This algorithm proved to be feasible and highly efficient compared with experimental results from the literature and simulated results via the full-iteration algorithm.Multi-cycle meshing temperature analyses were conducted on a series of POM worm gears with different tooth geometry parameters.The results reveal that,within the range of 14.5°to 25°,a pressure angle of 25°is favorable for reducing the peak surface temperature and overall body temperature of POM worm gears,which influence flank wear and load-carrying capability,respectively.However,addendum modification should be weighed because it helps with load bearing but increases the risk of severe flank wear.This paper proposes an efficient iteration algorithm for multi-cycle meshing temperature analysis of polymer gears and proves the feasibility of controlling the meshing temperature elevation during multiple cycles by tuning tooth geometry.
基金the National Science and Technology Major Project of China(No.2019-VII0017e0158)the National Natural Science Foundation of China(No.U21A20131)+1 种基金the Industry-University Research Cooperation Project,China(No.HFZL2020CXY025)the National Key Laboratory of Science and Technology on Helicopter Transmission,China(No.HTL-O-21G05).
文摘Spiral bevel gears are critical transmission components,and are widely used in the aerospace field.This paper proposes a new multi-DOF envelope forming process for fabricating spiral bevel gears.Firstly,the multi-DOF envelope forming principle of spiral bevel gears is proposed.Secondly,the design methods for the envelope tool geometry and movement are proposed based on the envelope geometry and movement relationships.Thirdly,the metal flow and tooth filling laws are revealed through 3D FE simulation of the multi-DOF envelope forming process of a typical spiral bevel gear.Fourthly,a new method for separating the envelope tool and the formed spiral bevel gear with back taper tooth is proposed to avoid their interference.Finally,experiments on multi-DOF envelope forming of this typical spiral bevel gear are conducted using new heavy load multi-DOF envelope forming equipment.The simulation and experimental results show the feasibility of the proposed multi-DOF envelope forming process for fabricating spiral bevel gears with back taper tooth and the corresponding process design methods.
基金supported by the National Natural Science Foundation of China(Grant Nos.U22A20184,52250077,and 52272080)the Jilin Province Natural Science Foundation of China(No.20220201093GX)+2 种基金the Fundamental Research Funds for the Central Universitiessupported by the National Research Foundation of Korea(2018R1A3B1052702 to JSK)the Starting growth Technological R&D Program(TIPS Program,No.S3201803,2021,MW)funded by the Ministry of SMEs and Startups(MSS,Korea).
文摘The rising flexible and intelligent electronics greatly facilitate the noninvasive and timely tracking of physiological information in telemedicine healthcare.Meticulously building bionic-sensitive moieties is vital for designing efficient electronic skin with advanced cognitive functionalities to pluralistically capture external stimuli.However,realistic mimesis,both in the skin’s three-dimensional interlocked hierarchical structures and synchronous encoding multistimuli information capacities,remains a challenging yet vital need for simplifying the design of flexible logic circuits.Herein,we construct an artificial epidermal device by in situ growing Cu_(3)(HHTP)_(2) particles onto the hollow spherical Ti_(3)C_(2)T_(x) surface,aiming to concurrently emulate the spinous and granular layers of the skin’s epidermis.The bionic Ti_(3)C_(2)T_(x)@Cu_(3)(HHTP)_(2) exhibits independent NO_(2) and pressure response,as well as novel functionalities such as acoustic signature perception and Morse code-encrypted message communication.Ultimately,a wearable alarming system with a mobile application terminal is self-developed by integrating the bimodular senor into flexible printed circuits.This system can assess risk factors related with asthmatic,such as stimulation of external NO_(2) gas,abnormal expiratory behavior and exertion degrees of fingers,achieving a recognition accuracy of 97.6%as assisted by a machine learning algorithm.Our work provides a feasible routine to develop intelligent multifunctional healthcare equipment for burgeoning transformative telemedicine diagnosis.
文摘For space-borne gravitational wave detection missions based on the heterodyne interferometry principle,tilt-to-length(TTL)coupling noise is an important optical noise source,significantly influencing the accuracy of the measurement system.We present a method for analyzing TTL coupling noise under the joint influence of multiple factors.An equivalent simulated optical bench for the test mass interferometer was designed,and Gaussian beam tracing was adopted to simulate beam propagation.By simulating the interference signal,it can analyze the impact of various factors on the TTL coupling noise,including positional,beam parameters,detector parameters,and signal definition factors.On this basis,a random parameter space composed of multiple influential factors was constructed within a range satisfying the analysis requirement,and the corresponding simulation results from random sampling were evaluated via variance-based global sensitivity analysis.The calculated results of the main and total effect indexes show that the test mass rotation angle and the piston effect(lateral)significantly influence the TTL coupling noise in the test mass interferometer.The analysis provides a qualitative reference for designing and optimizing space-borne laser interferometry systems.
基金supported by the National Natural Science Foundation of China(82422045).
文摘Background:The risk of internal fixation failure remains relatively high in stable femoral neck fracture(FNF)(Garden I or II).Preoperative sagittal displacement of the femoral head has been proposed as a potential influencing factor.This study aimed to evaluate the impact of sagittal displacement on the outcomes of cannulated screw internal fixation(CSIF)in patients with stable FNF(Garden I or II)by reconstructing the axial sagittal oblique plane of the fracture using preoperative computed tomography(CT)imaging.Methods:This study included 167 patients with FNF who underwent CSIF.The sagittal tilt angle of the femoral head(STAFH)was evaluated using three-dimensional CT(3D-CT).The distribution of preoperative STAFH was analyzed,and its independent association with treatment failure was assessed.Treatment failure was defined as the need for revision surgery within 2 years postoperatively due to avascular necrosis,nonunion,or internal fixation failure.Results:Among the 167 patients,9(5.4%)exhibited anterior tilt(AT)of the femoral head,158(94.60%)presented with posterior tilt(PT).A total of 50 patients(29.9%)demonstrated excessive sagittal displacement(AT≥10°or PT≥20°).In the failure group,80.0%of patients had excessive sagittal displacement compared to 28.1%in the healed group.Excessive sagittal displacement was significantly associated with an increased risk of surgical failure(odds ratio:11.953,95%CI:3.656-39.083,p<0.05).Conclusions:In patients with Garden I or II FNF,greater preoperative sagittal displacement of the femoral head was correlated with a higher likelihood of CSIF failure.AT≥10°or PT≥20°were identified as independent predictors of CSIF failure in FNF patients.Nevertheless,these findings still require confirmation through prospective,multi-center clinical trials with large sample sizes.
基金supported by the National Natural Science Foundation of China(No.22172152,No.21872130)the National Key R&D Program of China(No.2021YFA1502801).
文摘Researching the dispersion as well as the stability of metals on the oxide surfaces is essentially important for understanding the interaction mecha-nisms at the metal/oxide interfaces and thus optimizing the activities of the heterogeneous catalysts.Here in this work,we have investigated the growth behavior of Pd particles on the polar surfaces of ZnO with scanning tunneling microscopy(STM).By systematically varying the coverages as well as the annealing temperatures,we found that at room temperature Pd tends to form three-dimensional(3D)round particles on the ZnO(000)surface but grow into monolayer two-dimensional(2D)hexagonal islands on the ZnO(0001)surface.During annealing processes,the Pd particles on ZnO(000)aggregate gently while maintaining the 3D morphology in the mild temperature range but then quickly transform in-to tall hexagonal islands at elevated temperatures.In contrast,the segregation of Pd islands on ZnO(0001)occurs gradually along with the temperature rising without changing the 2D morphology.These results directly reflect the different interaction strengths of Pd on the dis-tinct ZnO polar surfaces.They also provide important input for understanding the facet-de-pendent catalytic mechanisms of the Pd/ZnO catalytic systems.
