A high-speed single-mode vertical-cavity surface-emitting laser(VCSEL)is one of the most important light sources for optical interconnects in data centers.Single-mode VCSEL can improve the transmission distance.In thi...A high-speed single-mode vertical-cavity surface-emitting laser(VCSEL)is one of the most important light sources for optical interconnects in data centers.Single-mode VCSEL can improve the transmission distance.In this letter,we demonstrate a single-mode 850 nm VCSEL with a bit rate of 60 Gb/s under NRZ modulation and 104 Gb/s under PAM4 modulation across a 100 m length of OM5 fiber,without the need for equalization or a filter.In addition,by using optical injection locking,the 3 dB bandwidth is enhanced to 68.5 GHz.展开更多
High Speed on/off Valve(HSV)is an essential component in Aerospace Digital Hydraulic Systems(ADHS),which impose stringent requirements on the dynamic performance and reliability of HSV due to the extreme application e...High Speed on/off Valve(HSV)is an essential component in Aerospace Digital Hydraulic Systems(ADHS),which impose stringent requirements on the dynamic performance and reliability of HSV due to the extreme application environments.However,the faster dynamic leads to increased impact between the spool and valve body,causing severe vibration and wear,which creates a conflict between rapid dynamic and high reliability.To address this problem,a Pre-Excitation Soft Switching Control(PESSC)with both pre-excitation and reverse deceleration functionalities is proposed.The initial current is optimized through pre-excitation to accelerate the opening time,while the application of reverse voltage hastens the decline of electromagnetic force,thereby reducing the spool velocity.The PESSC simultaneously achieves both faster dynamic performance and smaller impact velocity.Moreover,the optimal deceleration voltage parameters are obtained through multi-objective optimization.Experimental results demonstrate that the optimized PESSC shortens the opening time from 2.22 ms to 1.65 ms,reduces the impact velocity by 58.3%,and lowers wear by 55.4%.These findings underline the huge potential of PESSC in enhancing the dynamic performance and reliability of HSVs,offering promising applications in aerospace.展开更多
The z-axis-inclined 3D printing process using short carbon fiber-reinforced thermoplastic composites offers the potential for the support-free fabrication of complex structures and theoretically unlimited extension of...The z-axis-inclined 3D printing process using short carbon fiber-reinforced thermoplastic composites offers the potential for the support-free fabrication of complex structures and theoretically unlimited extension of printed components.It has emerged as a promising approach for in-orbit manufacturing of high-performance thermoplastic composite truss structures.However,extreme conditions of the space environment,such as high vacuum and fluctuating high-low temperatures,significantly alter the heat-transfer behavior during the printing process,often resulting in dimensional inaccuracies and degraded mechanical performance.Existing process optimization strategies fail to account for the coupled effects of vacuum and thermal extremes,limiting their applicability in guiding process design under varying vacuum temperature conditions.To address this gap,this study establishes a truss3D printing experimental platform with in situ temperature-monitoring capability under ground-simulated space conditions.It systematically investigates the effects of printing speed and structural geometry on the pre-bonding surface temperature and forming quality of truss structures in high-low temperature vacuum environments.This study reveals the mechanism by which processing and structural parameters affect the component performance through their influence on the pre-bonding surface temperature and dimensional accuracy.The experimental results show that under high-temperature vacuum conditions,the pre-bonding surface temperature is relatively high,resulting in good interfacial bonding.However,increasing the printing speed reduces the forming accuracy and leads to a decline in mechanical performance.In contrast,under low-temperature vacuum conditions,where the pre-bonding surface temperatures are lower,increasing the printing speed within a specific range effectively increases the surface temperature and bonding quality,thereby improving mechanical properties.Additionally,owing to frequent path transitions,the diagonal-strut truss exhibits a lower forming accuracy and pre-bonding surface temperature than the infilling truss,resulting in inferior mechanical performance in high-low temperature vacuum environments.展开更多
Due to the coexistence of compressibility,viscosity,and threedimensional effects,laminar flow is difficult to maintain for high-speed boundary layer on complex geometries.The unstable disturbance waves in the boundary...Due to the coexistence of compressibility,viscosity,and threedimensional effects,laminar flow is difficult to maintain for high-speed boundary layer on complex geometries.The unstable disturbance waves in the boundary layer are excited and rapidly increase during the receptivity process,so sufficiently large Reynolds stress causes the basic flow velocity profile to change,and the formation of turbulence is inevitable.展开更多
Fe-based metallic glass(MG)coatings draw great attentions due to their excellent mechanical properties.The recently developed extreme high-speed laser cladding(EHLC)provides a promising method for their fabrication bu...Fe-based metallic glass(MG)coatings draw great attentions due to their excellent mechanical properties.The recently developed extreme high-speed laser cladding(EHLC)provides a promising method for their fabrication but its application is challenged by pronounced cracking behavior.In this study,crack-free Fe-based MG coatings were prepared for the first time via EHLC.The effects of precipitated phases(i.e.,(Fe,Ni),(Fe,Ni)_(3)P and Fe_(7)C_(3))on cracking in the Fe-Ni-P-C MG coatings were investigated.展开更多
High-speed railway holds a pivotal position in China's transportation system,closely intertwined with the production and daily lives of people.It serves as a critical carrier for fostering a new development paradi...High-speed railway holds a pivotal position in China's transportation system,closely intertwined with the production and daily lives of people.It serves as a critical carrier for fostering a new development paradigm,supporting high-quality growth,and building a modernized strong nation.Up to 2025,the high-speed railway operating mileage in China has exceeded 50000 km,ranking the first in the world and surpassing the combined total of high-speed railway operating mileage in all other countries.展开更多
The finite element software was used to simulate the hot rolling finishing process,and the distribution of force,heat and velocity in the deformation zone was analyzed.Based on the high temperature friction and wear t...The finite element software was used to simulate the hot rolling finishing process,and the distribution of force,heat and velocity in the deformation zone was analyzed.Based on the high temperature friction and wear tester,the friction process of high speed steel(HSS)roll and strip during hot rolling was simulated.The results show that the process can be divided into three stages based on the observed changes in the friction coefficient throughout the rolling process.In the initial state,owing to the instability of the rolling process,the friction coefficient rapidly attains its maximum value within a brief interval and subsequently declines rapidly.Subsequently,the friction coefficient undergoes a gradual increase due to the formation of finer oxide layer particles during the growth period.Ultimately,the friction coefficient will be maintained at a stable value between 0.34 and 0.37.At this time,the HSS roll matrix mainly contains MC,M_(2)C and M_(6)C carbides.Additionally,the surface oxide layer particles become larger and more densely distributed,which can inhibit the wear of HSS rolls to a certain extent.展开更多
Axially-swept light-sheet microscopy(ASLM)has emerged as a distinguished tool for 3D imaging owing to its excellent spatial resolution.However,the acquisition time is significantly elongated due to the extra time cons...Axially-swept light-sheet microscopy(ASLM)has emerged as a distinguished tool for 3D imaging owing to its excellent spatial resolution.However,the acquisition time is significantly elongated due to the extra time consumed in axial scanning.Meanwhile,the spatial information provided in a single scan is fundamentally limited by the compromise between field-of-view and resolution.The overall inadequate optical throughput of current ASLM techniques impedes their widespread application in acquiring large samples.Here we demonstrate a spinning-disk-based ASLM(SDLM)approach that enables wide field-of-view(15×confocal range of the gaussian beam),isotropic 3D imaging of large organisms at 100 Hz full camera frame rate.In addition to the new optical design,we combine a recurrent neural network image restoration model to further improve the resolution of raw images.We demonstrate seconds scale stitching-free 3D imaging of the entire mouse brain(~9*8*5 mm size)at isotropic single-cell resolution(1.5μm voxel).With the high-quality data readily obtained by our approach,we also demonstrate the visualization of long projecting neurons and two genotypes of whole mouse brain cell profiling across the 3D space.Further transformation into in vivo research would broaden the application of SDLM.展开更多
The pantograph area is a critical source of aerodynamic noise in high-speed trains,generating noise both directly and through its cavity,a factor that warrants considerable attention.One effective method for reducing ...The pantograph area is a critical source of aerodynamic noise in high-speed trains,generating noise both directly and through its cavity,a factor that warrants considerable attention.One effective method for reducing aerodynamic noise within the pantograph cavity involves the introduction of a jet at the leading edge of the cavity.This study investigates the mechanisms driving cavity aerodynamic noise under varying jet velocities,using Improved Delayed Detached Eddy Simulation(IDDES)and Ffowcs Williams-Hawkings(FW-H)equations.The numerical simulations reveal that an increase in jet velocity results in a higher elevation of the shear layer above the cavity.This elevation,in turn,diminishes the interaction area between the vortices produced by jet shedding and the trailing edge of the cavity wall.Consequently,the amplitude of pressure pulsations on the cavity surface is reduced,leading to a decrease in radiated far-field noise.Specifically,simulations conducted with a jet velocity of 111.11 m/s indicate a remarkable noise reduction of approximately 4 dB attributable to this mechanism.To further enhance noise mitigation,alterations to the inclination angles of the cavity’s front and rear walls are also explored.The findings demonstrate that,at a constant jet velocity,such modifications significantly diminish pressure pulsations at the intersection of the rear wall and cavity floor,optimizing overall noise reduction and achieving a maximum reduction of approximately 6 dB.展开更多
The centralized traffic control(CTC)system is the command center for high-speed railway transport,and its failure will have severe impact on the higheffective train operation.The existing operation and maintenance(O&a...The centralized traffic control(CTC)system is the command center for high-speed railway transport,and its failure will have severe impact on the higheffective train operation.The existing operation and maintenance(O&M)mode relies on manual inspections and on-site experience,which are inadequate for the current needs of intelligent CTC construction in HSRs.There is an urgent need to establish an intelligent O&M system for the CTC that incorporates information fusion,real-time monitoring,and aided decision-making.By collecting and integrating multi-source heterogeneous data from the CTC system,key features and implicit information therein that indicate the system faults are extracted.Control chart algorithms and hidden Markov models are utilized for real-time monitoring and evaluation of system status,enabling the detection of subtle anomalies and early warning of potential faults.On this basis,a maintenance strategy library is generated by integrating expert experiences,operational guidelines,and historical fault maintenance records,allowing for the automatic matching of solutions.The application of the intelligent O&M system for the CTC allows for a shift from“fault maintenance”to“preventive maintenance”,effectively enhancing O&M efficiency of the system,and thus providing a strong guarantee for the safe and high-effective operation of HSRs.展开更多
The noise generated by high-speed hair dryers significantly affects user experience,with aerodynamic design playing a crucial role in controlling sound emissions.This study investigates the aerodynamic noise character...The noise generated by high-speed hair dryers significantly affects user experience,with aerodynamic design playing a crucial role in controlling sound emissions.This study investigates the aerodynamic noise characteristics of a commercial high-speed hair dryer through Computational Fluid Dynamics(CFD)analysis.The velocity field,streamline patterns,and vector distribution within the primary flow path and internal cavity were systematically examined.Results indicate that strong interactions between the wake flow generated by the guide vanes and the straight baffle in the rear flow path induce vortex structures near the outlet,which are primarily responsible for highfrequency noise.To address this,the guide vanes and rear flow path geometry were redesigned and optimized for improved acoustic and aerodynamic performance.Underrated operating conditions(28 V,20,000 rpm),the optimized configuration achieves a noise reduction of more than 2.2 dB while increasing outlet wind speed by over 9%.Moreover,the noise suppression effect becomes more pronounced at lower rotational speeds.展开更多
1. Introduction High-speed gas-particle flows are crucial in engineering applications and natural phenomena, such as volcanic eruptions,combustion, and hypersonic flight. These flows involve complex gas-particle inter...1. Introduction High-speed gas-particle flows are crucial in engineering applications and natural phenomena, such as volcanic eruptions,combustion, and hypersonic flight. These flows involve complex gas-particle interactions, posing significant challenges for simulations and experiments. This research highlight summarizes recent advancements in gas-particle dynamics under compressible conditions, covering key findings, numerical and experimental progress, and future directions. Details can be found in the work of Capecelatro and Wagner (Gas-particle dynamics in high-speed flows. Annual Review of Fluid Mechanics 2024;56:379–403).展开更多
For the purpose to improve a design quality of high-speed spindle units, we have developed mathematical models and software to simulate a rotation accuracy of spindles running on ball bearings. In order to better unde...For the purpose to improve a design quality of high-speed spindle units, we have developed mathematical models and software to simulate a rotation accuracy of spindles running on ball bearings. In order to better understand the mechanics of ball bearings, the dynamic interaction of ball bearings and spindle unit, and the influence of the bearing imperfections on the spindle rotation accuracy, we have carried out computer aided analysis and experimental studies. When doing this, we have found that the spindle rotation accuracy can vary drastically with rotational speed. The influence of bearing preload has a secondary importance. Comparison of the results of these studies has demonstrated adequacy of the models developed to the real spindle units.展开更多
LEADSFON(XIAMEN)TEXTILE TECH CO.,LTD.is a manufacturer of knitting circular machines.Since 2002,the company has served as an ODM and supporting partner for the Italian brand"PILOTELLI".In 2014,LEADSFON offic...LEADSFON(XIAMEN)TEXTILE TECH CO.,LTD.is a manufacturer of knitting circular machines.Since 2002,the company has served as an ODM and supporting partner for the Italian brand"PILOTELLI".In 2014,LEADSFON officially acquired PILOTELLI,integrating advanced Italian technology into its core operations.展开更多
Safer,smarter,faster...In China,people prefer high-speed trains to flights if the journey time is under five hours.High-speed train travel is set to become even more attractive with the addition of a new member to the...Safer,smarter,faster...In China,people prefer high-speed trains to flights if the journey time is under five hours.High-speed train travel is set to become even more attractive with the addition of a new member to the high-speed train family:the CR450,the world’s fastest electric multiple unit(EMU).展开更多
The efficient manufacture technique involves a high-speed control of platform mobile system. A linear acutor is presented in this paper. The linear acutor is constructed as a linear stepper motor. However, to sustain ...The efficient manufacture technique involves a high-speed control of platform mobile system. A linear acutor is presented in this paper. The linear acutor is constructed as a linear stepper motor. However, to sustain both high accuracy and high speed for the position and speed control, A single-stack computer system is constructed and a special control algorithm is prescribed to controled the linear actuator continuously. In this paper, the nonlinear errors resulted from the magnetic saturation and the hysteresis is anaysis and discussed. In the view of electromagnetic propotional control, the actuator is a stage proportional magnet, because the driving current to the linear acuator changes for a number of cycles and a series of reset points will occur as the current undergoes cyclic changes. At each reset point the original starting characteristics of the system are re-established. A large number of reset points across the full stroke of the platform results in a significant reduction in the nonlinear behavior. The stage control is first discussed. Experiments carried out to obtain the characteristics of the mobile platform control system. It is demonstrated that with the introduction of stage control, nonlinearities, such as saturation and hysteresis, are greatly reduced, system stiffness is increased, and the positioning accuracy and resolution are improved. The effect of dither due to a "digital fragment" signal is also examined and found to be crucial in reducing the hysteresis and in improving the resolution accuracy.展开更多
Surface integrity of a new damage-tolerant titanium alloy （TC21）, including surface roughness, microhardness and metallurgical structure is investigated when normal and high speed milling are used at different tool ...Surface integrity of a new damage-tolerant titanium alloy （TC21）, including surface roughness, microhardness and metallurgical structure is investigated when normal and high speed milling are used at different tool wear status. Results show that good surface integrity of TC21 can be obtained in high speed milling. In addition, even in acutely worn stages, there is no so-called serious hardening layer （or white layer） according to the studies on microhardness and metallurgical structure.展开更多
The engineblock production lines need high speed tapping with tungsten carbide taps. In the tapping process, the machining precision and the tool life of taps are directly influenced by tapping forces. And the paramet...The engineblock production lines need high speed tapping with tungsten carbide taps. In the tapping process, the machining precision and the tool life of taps are directly influenced by tapping forces. And the parameter optimization of tap structures is also correlated with the variation of tapping forces. Therefore, the study of tapping forces is necessary in developing new style taps. Several experiments about some novel carbide taps are performed on a vertical machining center by a Kistler dynamometer system in blind tapping both gray cast iron and ductile cast iron. And the variations of tapping forces are analyzed in tapping-in and tapping-out periods. It indicates that cutting forces hardly vary with the tap wear in tapping cast iron. Contrarily, tapping forces are closely correlated with the holding method. Besides, it also depends on the helix angle, the flute numbers and the plasticity of the work material to some extent.展开更多
The influence of rare earth metals and heat treatment on the microstructure and performance of M42 steel has been investigated by means of an optical microscope OM scanning electron microscope SEM energy dispersive sp...The influence of rare earth metals and heat treatment on the microstructure and performance of M42 steel has been investigated by means of an optical microscope OM scanning electron microscope SEM energy dispersive spectroscopy EDS transmission electron microscope TEM electron back-scatter diffraction EBSD and X-ray diffraction XRD . The results show that M2 C is the prevailing type of eutectic carbides in M42 steel. After modification with rare earth metals M2 C eutectic carbides change from the ordered lamellar structure into a circular structure.Despite different morphologies the two carbides present the same characteristics of microstructure and growth orientation.Compared with lamellar carbides M2 C carbides with the circular structure are much easier to decompose and spheroidize after heating which remarkably refines the carbide dimensions.The refined carbides improve the supersaturation of alloying elements in martensite and increase the hardness of M42 steel by 1.5 HRC.展开更多
Shaped charge jet formation process is studied under the conditions of different background lights by means of high speed frame photography. In order to shoot true jet appearance, the glass tube in which jet moves is...Shaped charge jet formation process is studied under the conditions of different background lights by means of high speed frame photography. In order to shoot true jet appearance, the glass tube in which jet moves is vacuumized. The experiment results show that observing jet appearance with the double reflecting mirrors system is feasible as long as the vacuum of the glass tube can meet the requirement of experiment.展开更多
基金supported by the National Key R&D Program of China(2021YFB2801000).
文摘A high-speed single-mode vertical-cavity surface-emitting laser(VCSEL)is one of the most important light sources for optical interconnects in data centers.Single-mode VCSEL can improve the transmission distance.In this letter,we demonstrate a single-mode 850 nm VCSEL with a bit rate of 60 Gb/s under NRZ modulation and 104 Gb/s under PAM4 modulation across a 100 m length of OM5 fiber,without the need for equalization or a filter.In addition,by using optical injection locking,the 3 dB bandwidth is enhanced to 68.5 GHz.
基金supported in part by the “Pioneer”and “Leading Goose”R&D Program of Zhejiang Province(Nos.2022C01132 and 2022C01122)the National Natural Science Foundation of China(No.52005441)+3 种基金the Young Elite Scientist Sponsorship Program by CAST(No.20222024QNRC001)the State Key Laboratory of Mechanical System and Vibration,China(No.MSV202316)the Fundamental Research Funds for the Provincial Universities of Zhejiang,China(RF-A2023007)the Research Project of ZJUT,China(No.GYY-ZH-2023075)。
文摘High Speed on/off Valve(HSV)is an essential component in Aerospace Digital Hydraulic Systems(ADHS),which impose stringent requirements on the dynamic performance and reliability of HSV due to the extreme application environments.However,the faster dynamic leads to increased impact between the spool and valve body,causing severe vibration and wear,which creates a conflict between rapid dynamic and high reliability.To address this problem,a Pre-Excitation Soft Switching Control(PESSC)with both pre-excitation and reverse deceleration functionalities is proposed.The initial current is optimized through pre-excitation to accelerate the opening time,while the application of reverse voltage hastens the decline of electromagnetic force,thereby reducing the spool velocity.The PESSC simultaneously achieves both faster dynamic performance and smaller impact velocity.Moreover,the optimal deceleration voltage parameters are obtained through multi-objective optimization.Experimental results demonstrate that the optimized PESSC shortens the opening time from 2.22 ms to 1.65 ms,reduces the impact velocity by 58.3%,and lowers wear by 55.4%.These findings underline the huge potential of PESSC in enhancing the dynamic performance and reliability of HSVs,offering promising applications in aerospace.
基金supported by National Key Research and Development Program of China(Grant No.2023YFB4605301)the National Natural Science Foundation of China(Grant No.52130506)。
文摘The z-axis-inclined 3D printing process using short carbon fiber-reinforced thermoplastic composites offers the potential for the support-free fabrication of complex structures and theoretically unlimited extension of printed components.It has emerged as a promising approach for in-orbit manufacturing of high-performance thermoplastic composite truss structures.However,extreme conditions of the space environment,such as high vacuum and fluctuating high-low temperatures,significantly alter the heat-transfer behavior during the printing process,often resulting in dimensional inaccuracies and degraded mechanical performance.Existing process optimization strategies fail to account for the coupled effects of vacuum and thermal extremes,limiting their applicability in guiding process design under varying vacuum temperature conditions.To address this gap,this study establishes a truss3D printing experimental platform with in situ temperature-monitoring capability under ground-simulated space conditions.It systematically investigates the effects of printing speed and structural geometry on the pre-bonding surface temperature and forming quality of truss structures in high-low temperature vacuum environments.This study reveals the mechanism by which processing and structural parameters affect the component performance through their influence on the pre-bonding surface temperature and dimensional accuracy.The experimental results show that under high-temperature vacuum conditions,the pre-bonding surface temperature is relatively high,resulting in good interfacial bonding.However,increasing the printing speed reduces the forming accuracy and leads to a decline in mechanical performance.In contrast,under low-temperature vacuum conditions,where the pre-bonding surface temperatures are lower,increasing the printing speed within a specific range effectively increases the surface temperature and bonding quality,thereby improving mechanical properties.Additionally,owing to frequent path transitions,the diagonal-strut truss exhibits a lower forming accuracy and pre-bonding surface temperature than the infilling truss,resulting in inferior mechanical performance in high-low temperature vacuum environments.
文摘Due to the coexistence of compressibility,viscosity,and threedimensional effects,laminar flow is difficult to maintain for high-speed boundary layer on complex geometries.The unstable disturbance waves in the boundary layer are excited and rapidly increase during the receptivity process,so sufficiently large Reynolds stress causes the basic flow velocity profile to change,and the formation of turbulence is inevitable.
基金financially supported by the National Natural Science Foundation of China(No.U23A20621)
文摘Fe-based metallic glass(MG)coatings draw great attentions due to their excellent mechanical properties.The recently developed extreme high-speed laser cladding(EHLC)provides a promising method for their fabrication but its application is challenged by pronounced cracking behavior.In this study,crack-free Fe-based MG coatings were prepared for the first time via EHLC.The effects of precipitated phases(i.e.,(Fe,Ni),(Fe,Ni)_(3)P and Fe_(7)C_(3))on cracking in the Fe-Ni-P-C MG coatings were investigated.
文摘High-speed railway holds a pivotal position in China's transportation system,closely intertwined with the production and daily lives of people.It serves as a critical carrier for fostering a new development paradigm,supporting high-quality growth,and building a modernized strong nation.Up to 2025,the high-speed railway operating mileage in China has exceeded 50000 km,ranking the first in the world and surpassing the combined total of high-speed railway operating mileage in all other countries.
基金funded by Central Government Guide Local Science and Technology Development Fund Project(No.216Z1602G).
文摘The finite element software was used to simulate the hot rolling finishing process,and the distribution of force,heat and velocity in the deformation zone was analyzed.Based on the high temperature friction and wear tester,the friction process of high speed steel(HSS)roll and strip during hot rolling was simulated.The results show that the process can be divided into three stages based on the observed changes in the friction coefficient throughout the rolling process.In the initial state,owing to the instability of the rolling process,the friction coefficient rapidly attains its maximum value within a brief interval and subsequently declines rapidly.Subsequently,the friction coefficient undergoes a gradual increase due to the formation of finer oxide layer particles during the growth period.Ultimately,the friction coefficient will be maintained at a stable value between 0.34 and 0.37.At this time,the HSS roll matrix mainly contains MC,M_(2)C and M_(6)C carbides.Additionally,the surface oxide layer particles become larger and more densely distributed,which can inhibit the wear of HSS rolls to a certain extent.
基金supported by the funding from National Natural Science Foundation of China(T2225014,82270238,21927802,22404065,62405099)National Key Research and Development Program of China(2022YFC3401102,2023ZD0519900)+1 种基金China Postdoctoral Science Foundation(2024T170296,2023M741258,2024M750994)Postdoctor Project of Hubei Province under Grant Number(2024HBBHCXA015).
文摘Axially-swept light-sheet microscopy(ASLM)has emerged as a distinguished tool for 3D imaging owing to its excellent spatial resolution.However,the acquisition time is significantly elongated due to the extra time consumed in axial scanning.Meanwhile,the spatial information provided in a single scan is fundamentally limited by the compromise between field-of-view and resolution.The overall inadequate optical throughput of current ASLM techniques impedes their widespread application in acquiring large samples.Here we demonstrate a spinning-disk-based ASLM(SDLM)approach that enables wide field-of-view(15×confocal range of the gaussian beam),isotropic 3D imaging of large organisms at 100 Hz full camera frame rate.In addition to the new optical design,we combine a recurrent neural network image restoration model to further improve the resolution of raw images.We demonstrate seconds scale stitching-free 3D imaging of the entire mouse brain(~9*8*5 mm size)at isotropic single-cell resolution(1.5μm voxel).With the high-quality data readily obtained by our approach,we also demonstrate the visualization of long projecting neurons and two genotypes of whole mouse brain cell profiling across the 3D space.Further transformation into in vivo research would broaden the application of SDLM.
基金supported by National Natural Science Foundation of China(12172308).
文摘The pantograph area is a critical source of aerodynamic noise in high-speed trains,generating noise both directly and through its cavity,a factor that warrants considerable attention.One effective method for reducing aerodynamic noise within the pantograph cavity involves the introduction of a jet at the leading edge of the cavity.This study investigates the mechanisms driving cavity aerodynamic noise under varying jet velocities,using Improved Delayed Detached Eddy Simulation(IDDES)and Ffowcs Williams-Hawkings(FW-H)equations.The numerical simulations reveal that an increase in jet velocity results in a higher elevation of the shear layer above the cavity.This elevation,in turn,diminishes the interaction area between the vortices produced by jet shedding and the trailing edge of the cavity wall.Consequently,the amplitude of pressure pulsations on the cavity surface is reduced,leading to a decrease in radiated far-field noise.Specifically,simulations conducted with a jet velocity of 111.11 m/s indicate a remarkable noise reduction of approximately 4 dB attributable to this mechanism.To further enhance noise mitigation,alterations to the inclination angles of the cavity’s front and rear walls are also explored.The findings demonstrate that,at a constant jet velocity,such modifications significantly diminish pressure pulsations at the intersection of the rear wall and cavity floor,optimizing overall noise reduction and achieving a maximum reduction of approximately 6 dB.
文摘The centralized traffic control(CTC)system is the command center for high-speed railway transport,and its failure will have severe impact on the higheffective train operation.The existing operation and maintenance(O&M)mode relies on manual inspections and on-site experience,which are inadequate for the current needs of intelligent CTC construction in HSRs.There is an urgent need to establish an intelligent O&M system for the CTC that incorporates information fusion,real-time monitoring,and aided decision-making.By collecting and integrating multi-source heterogeneous data from the CTC system,key features and implicit information therein that indicate the system faults are extracted.Control chart algorithms and hidden Markov models are utilized for real-time monitoring and evaluation of system status,enabling the detection of subtle anomalies and early warning of potential faults.On this basis,a maintenance strategy library is generated by integrating expert experiences,operational guidelines,and historical fault maintenance records,allowing for the automatic matching of solutions.The application of the intelligent O&M system for the CTC allows for a shift from“fault maintenance”to“preventive maintenance”,effectively enhancing O&M efficiency of the system,and thus providing a strong guarantee for the safe and high-effective operation of HSRs.
基金supported by Research Project of Zhuhai City Polytechnic(Grant No.2024KYBS06)Education Research Project of Zhuhai City Polytechnic(Grant No.JY20250404).
文摘The noise generated by high-speed hair dryers significantly affects user experience,with aerodynamic design playing a crucial role in controlling sound emissions.This study investigates the aerodynamic noise characteristics of a commercial high-speed hair dryer through Computational Fluid Dynamics(CFD)analysis.The velocity field,streamline patterns,and vector distribution within the primary flow path and internal cavity were systematically examined.Results indicate that strong interactions between the wake flow generated by the guide vanes and the straight baffle in the rear flow path induce vortex structures near the outlet,which are primarily responsible for highfrequency noise.To address this,the guide vanes and rear flow path geometry were redesigned and optimized for improved acoustic and aerodynamic performance.Underrated operating conditions(28 V,20,000 rpm),the optimized configuration achieves a noise reduction of more than 2.2 dB while increasing outlet wind speed by over 9%.Moreover,the noise suppression effect becomes more pronounced at lower rotational speeds.
文摘1. Introduction High-speed gas-particle flows are crucial in engineering applications and natural phenomena, such as volcanic eruptions,combustion, and hypersonic flight. These flows involve complex gas-particle interactions, posing significant challenges for simulations and experiments. This research highlight summarizes recent advancements in gas-particle dynamics under compressible conditions, covering key findings, numerical and experimental progress, and future directions. Details can be found in the work of Capecelatro and Wagner (Gas-particle dynamics in high-speed flows. Annual Review of Fluid Mechanics 2024;56:379–403).
文摘For the purpose to improve a design quality of high-speed spindle units, we have developed mathematical models and software to simulate a rotation accuracy of spindles running on ball bearings. In order to better understand the mechanics of ball bearings, the dynamic interaction of ball bearings and spindle unit, and the influence of the bearing imperfections on the spindle rotation accuracy, we have carried out computer aided analysis and experimental studies. When doing this, we have found that the spindle rotation accuracy can vary drastically with rotational speed. The influence of bearing preload has a secondary importance. Comparison of the results of these studies has demonstrated adequacy of the models developed to the real spindle units.
文摘LEADSFON(XIAMEN)TEXTILE TECH CO.,LTD.is a manufacturer of knitting circular machines.Since 2002,the company has served as an ODM and supporting partner for the Italian brand"PILOTELLI".In 2014,LEADSFON officially acquired PILOTELLI,integrating advanced Italian technology into its core operations.
文摘Safer,smarter,faster...In China,people prefer high-speed trains to flights if the journey time is under five hours.High-speed train travel is set to become even more attractive with the addition of a new member to the high-speed train family:the CR450,the world’s fastest electric multiple unit(EMU).
文摘The efficient manufacture technique involves a high-speed control of platform mobile system. A linear acutor is presented in this paper. The linear acutor is constructed as a linear stepper motor. However, to sustain both high accuracy and high speed for the position and speed control, A single-stack computer system is constructed and a special control algorithm is prescribed to controled the linear actuator continuously. In this paper, the nonlinear errors resulted from the magnetic saturation and the hysteresis is anaysis and discussed. In the view of electromagnetic propotional control, the actuator is a stage proportional magnet, because the driving current to the linear acuator changes for a number of cycles and a series of reset points will occur as the current undergoes cyclic changes. At each reset point the original starting characteristics of the system are re-established. A large number of reset points across the full stroke of the platform results in a significant reduction in the nonlinear behavior. The stage control is first discussed. Experiments carried out to obtain the characteristics of the mobile platform control system. It is demonstrated that with the introduction of stage control, nonlinearities, such as saturation and hysteresis, are greatly reduced, system stiffness is increased, and the positioning accuracy and resolution are improved. The effect of dither due to a "digital fragment" signal is also examined and found to be crucial in reducing the hysteresis and in improving the resolution accuracy.
基金Supported by the National Natural Science Foundation of China(50975141)the National Scienceand Technology Major Project(2010ZX04012-042)the Aeronautical Science Foundation(2010352005)~~
文摘Surface integrity of a new damage-tolerant titanium alloy （TC21）, including surface roughness, microhardness and metallurgical structure is investigated when normal and high speed milling are used at different tool wear status. Results show that good surface integrity of TC21 can be obtained in high speed milling. In addition, even in acutely worn stages, there is no so-called serious hardening layer （or white layer） according to the studies on microhardness and metallurgical structure.
文摘The engineblock production lines need high speed tapping with tungsten carbide taps. In the tapping process, the machining precision and the tool life of taps are directly influenced by tapping forces. And the parameter optimization of tap structures is also correlated with the variation of tapping forces. Therefore, the study of tapping forces is necessary in developing new style taps. Several experiments about some novel carbide taps are performed on a vertical machining center by a Kistler dynamometer system in blind tapping both gray cast iron and ductile cast iron. And the variations of tapping forces are analyzed in tapping-in and tapping-out periods. It indicates that cutting forces hardly vary with the tap wear in tapping cast iron. Contrarily, tapping forces are closely correlated with the holding method. Besides, it also depends on the helix angle, the flute numbers and the plasticity of the work material to some extent.
基金The National Natural Science Foundation of China(No.51301038,51201031,51371050)the Industry-AcademiaResearch Cooperative Innovation Fund of Jiangsu Province(No.BY2014127-03)+1 种基金the Natural Science Foundation of Jiangsu Province(No.BK20141306)the Scientific and Technological Innovation Fund of Danyang(No.SY201305)
文摘The influence of rare earth metals and heat treatment on the microstructure and performance of M42 steel has been investigated by means of an optical microscope OM scanning electron microscope SEM energy dispersive spectroscopy EDS transmission electron microscope TEM electron back-scatter diffraction EBSD and X-ray diffraction XRD . The results show that M2 C is the prevailing type of eutectic carbides in M42 steel. After modification with rare earth metals M2 C eutectic carbides change from the ordered lamellar structure into a circular structure.Despite different morphologies the two carbides present the same characteristics of microstructure and growth orientation.Compared with lamellar carbides M2 C carbides with the circular structure are much easier to decompose and spheroidize after heating which remarkably refines the carbide dimensions.The refined carbides improve the supersaturation of alloying elements in martensite and increase the hardness of M42 steel by 1.5 HRC.
文摘Shaped charge jet formation process is studied under the conditions of different background lights by means of high speed frame photography. In order to shoot true jet appearance, the glass tube in which jet moves is vacuumized. The experiment results show that observing jet appearance with the double reflecting mirrors system is feasible as long as the vacuum of the glass tube can meet the requirement of experiment.
