INTRODUCTION.Crustal velocity model is crucial for describing the subsurface composition and structure,and has significant implications in offshore oil and gas exploration and marine geophysical engineering(Xie et al....INTRODUCTION.Crustal velocity model is crucial for describing the subsurface composition and structure,and has significant implications in offshore oil and gas exploration and marine geophysical engineering(Xie et al.,2024).Currently,travel time tomography is the most commonly used method for velocity modeling based on ocean bottom seismometer(OBS)data(Zhang et al.,2023;Sambolian et al.,2021).This method usually assumes that the sub-seafloor structure is layered,and therefore faces challenges in high-precision modeling with strong lateral discontinuities.展开更多
This study explores the combination of ultrasound technology with a detection algorithm to categorize flow regimes in bubble columns used for aeration in aquaculture.An ultrasonic velocity profiler is used to obtain t...This study explores the combination of ultrasound technology with a detection algorithm to categorize flow regimes in bubble columns used for aeration in aquaculture.An ultrasonic velocity profiler is used to obtain the standard deviation of the bubble velocity distributed throughout the column.The bubble velocity data for three known flow regimes were used to develop a probability density function(PDF)classification model.The experimental apparatus consisted of a circular tank equipped with a bubble generator and gas hold-up monitoring systems.The flow regimes of the experimental fluid were determined,and the classification was conducted via the PDF method.The results demonstrate that the classification accuracy is not lower than that of traditional machine learning methods.展开更多
The Sichuan-Yunnan Block is located on the southeastern margin of the Qinghai-Xizang Plateau and has frequent seismic activity on the western border,posing a potential threat to human society and economic development....The Sichuan-Yunnan Block is located on the southeastern margin of the Qinghai-Xizang Plateau and has frequent seismic activity on the western border,posing a potential threat to human society and economic development.Therefore,it is important to understand its geological evolution,assess earthquake risks,and formulate scientific and reasonable disaster prevention and mitigation strategies.Using 23 months of continuous ambient noise records from 81 seismic stations,we obtained 1248 phasevelocity dispersion curves of the fundamental Rayleigh wave at 5–50 s.The three-dimensional(3D)S-wave velocity structure in the northwestern Sichuan-Yunnan Block was obtained by pure-path and depth inversion.The results show that three lowvelocity anomalous bands were distributed nearly north-to-south(N-S)at depths of 10–35 km.The overall shape of the lowvelocity channel gradually shifted from southeast to southwest because of the influence of the Panzhihua high-velocity blocks.The low-velocity strip consists of three branches,with the first branch extending southwest from the northern part of the Lancangjiang Fault.The second branch is distributed in the N-S direction and is blocked by two high-velocity bodies near the Longpan-Qiaohou and Honghe faults.The third branch crosses the research area from N-S and gradually extends from southeast to southwest and from shallow to deep.The three low-velocity anomaly distribution areas are likely the most severely deformed areas of the collision between the Qinghai-Xizang Plateau and Yangtze Block.The results provide a more detailed understanding of the deep structure of the western boundary of the Sichuan-Yunnan Block crustal low-velocity anomalies and reliable geophysical evidence for the morphology and continuity of crustal flows.展开更多
Structure and composition of Earth are fundamental importance in exploring the dynamic evolution of the crust and mantle.The Qinling Orogenic Belt(QOB)is located between the North China plate and the South China Plate...Structure and composition of Earth are fundamental importance in exploring the dynamic evolution of the crust and mantle.The Qinling Orogenic Belt(QOB)is located between the North China plate and the South China Plate,and is one of the main orogenic belts in China.To explore the composition and origin of anisotropy and the low wave velocity zone of the QOB,ten rock samples(gneiss and schist)were collected from the five sites of the QOB and the P-and S-wave velocities of these samples were measured under 0.6 to 2.0 GPa and 100 to 550℃.The wave velocities increase with increasing pressure and decreasing temperature.The V_(P)and V_(S)of the schist and gneiss match the velocity of the middle and lower crust of the QOB,indicating that schist and gneiss are important component of the QOB.All the schist and gneiss samples exhibit obvious seismic anisotropy with 1.64%-17.42%for V_(S)and 2.93%-14.78%for V_(P)under conditions of crust and upper mantle.The CPO/LPO and layering distribution of mica in rock samples are the main reasons for this anisotropy.The V_(S)structures below the five sampled sites from seismic ambient noise tomography were built to explore the effect of schist and gneiss on the composition and structure of the QOB.The results indicate that orientation-arranged gneiss and schist driven by the tectonic stresses might be a new origin of the character of V_(P)/V_(S),seismic anisotropy,and the low velocity zone in the QOB.展开更多
This study presents a machine learning-based method for predicting fragment velocity distribution in warhead fragmentation under explosive loading condition.The fragment resultant velocities are correlated with key de...This study presents a machine learning-based method for predicting fragment velocity distribution in warhead fragmentation under explosive loading condition.The fragment resultant velocities are correlated with key design parameters including casing dimensions and detonation positions.The paper details the finite element analysis for fragmentation,the characterizations of the dynamic hardening and fracture models,the generation of comprehensive datasets,and the training of the ANN model.The results show the influence of casing dimensions on fragment velocity distributions,with the tendencies indicating increased resultant velocity with reduced thickness,increased length and diameter.The model's predictive capability is demonstrated through the accurate predictions for both training and testing datasets,showing its potential for the real-time prediction of fragmentation performance.展开更多
The transformation from multibody models to lumped-parameter models is a crucial aspect of vehicle dynamics research.The velocity transformation method is adopted in this research,and the suspension multibody model is...The transformation from multibody models to lumped-parameter models is a crucial aspect of vehicle dynamics research.The velocity transformation method is adopted in this research,and the suspension multibody model is described using only one degree of freedom.It is found that the equivalent mass of the system is time-dependent during the simulation process,as observed in numerical simulations.Further symbolic calculations are conducted to derive the analytical form of the equivalent mass,and the results show that once the static parameters are determined,the equivalent mass of the suspension system is determined solely by the vertical position of the suspension upright,which reveals the kinematics characteristic of the equivalent mass of the suspension system.It is found that the equivalent mass experiences smaller changes when the suspension is compressed from the middle position,but larger changes when the suspension is extended.Furthermore,by comparing the multibody model,the lumped-parameter model with static mass,and the proposed lumped-parameter model considering the kinematics characteristic of the equivalent unsprung mass,the proposed model produces simulation results that more closely match the original multibody model than the model with static mass.The improvements in accuracy can be up to 20%under certain evaluation metrics.展开更多
The Longmenshan(LMS)fault zone is located at the junction of the eastern Tibetan Plateau and the Sichuan Basin and is of great significance for studying regional tectonics and earthquake hazards.Although regional velo...The Longmenshan(LMS)fault zone is located at the junction of the eastern Tibetan Plateau and the Sichuan Basin and is of great significance for studying regional tectonics and earthquake hazards.Although regional velocity models are available for the LMS fault zone,high-resolution velocity models are lacking.Therefore,a dense array of 240 short-period seismometers was deployed around the central segment of the LMS fault zone for approximately 30 days to monitor earthquakes and characterize fine structures of the fault zone.Considering the large quantity of observed seismic data,the data processing workflow consisted of deep learning-based automatic earthquake detection,phase arrival picking,and association.Compared with the earthquake catalog released by the China Earthquake Administration,many more earthquakes were detected by the dense array.Double-difference seismic tomography was adopted to determine V_(p),V_(s),and V_(p)/V_(s)models as well as earthquake locations.The checkerboard test showed that the velocity models have spatial resolutions of approximately 5 km in the horizontal directions and 2 km at depth.To the west of the Yingxiu–Beichuan Fault(YBF),the Precambrian Pengguan complex,where most of earthquakes occurred,is characterized by high velocity and low V_(p)/V_(s)values.In comparison,to the east of the YBF,the Upper Paleozoic to Jurassic sediments,where few earthquakes occurred,show low velocity and high V_(p)/V_(s)values.Our results suggest that the earthquake activity in the LMS fault zone is controlled by the strength of the rock compositions.When the high-resolution velocity models were combined with the relocated earthquakes,we were also able to delineate the fault geometry for different faults in the LMS fault zone.展开更多
This study presents an inversion method to recover the tidal flow velocity using tidal signals extracted from geomagnetic satellite dataset.By integrating the latest Earth conductivity profile and the Earth's magn...This study presents an inversion method to recover the tidal flow velocity using tidal signals extracted from geomagnetic satellite dataset.By integrating the latest Earth conductivity profile and the Earth's magnetic field model,the limited memory quasi-Newton method(L-BFGS)is used to directly invert seawater flow velocities.We used the radial component of the induced magnetic field as the observed data,constructed an L_(2)-norm-based data misfit term using theoretical response and observed data,and applied smoothness constraints to the ocean flow velocity.The results agree well with the widely used HAMTIDE model in low-and mid-latitude regions,which is attributed to Macao Science Satellite-1's(MSS-1)unique low-inclination orbit of full coverage in these areas.These findings underscore MSS-1's potential to advance research on tidal-induced magnetic fields and their applications in ocean dynamics studies.展开更多
Pre-stack depth migration velocity analysis is one of the keys to influencing the imaging quality of pre-stack migration.In this paper we cover a residual curvature velocity analysis method on angle-domain common imag...Pre-stack depth migration velocity analysis is one of the keys to influencing the imaging quality of pre-stack migration.In this paper we cover a residual curvature velocity analysis method on angle-domain common image gathers（ADCIGs） which can depict the relationship between incident angle and migration depth at imaging points and update the migration velocity.Differing from offset-domain common image gathers（ODCIGs）,ADCIGs are not disturbed by the multi-path problem which contributes to imaging artifacts,thus influencing the velocity analysis.On the basis of horizontal layers,we derive the residual depth equation and also propose a velocity analysis workflow for velocity scanning.The tests to synthetic and field data prove the velocity analysis methods adopted in this paper are robust and valid.展开更多
Purpose:This study aimed to examine the reliability and validity of load-velocity(L-V)relationship variables obtained through the 2-point method using different load combinations and velocity variables.Methods:Twenty ...Purpose:This study aimed to examine the reliability and validity of load-velocity(L-V)relationship variables obtained through the 2-point method using different load combinations and velocity variables.Methods:Twenty men performed 2 identical sessions consisting of 2 countermovement jumps against 4 external loads(20 kg,40 kg,60 kg,and80 kg)and a heavy squat against a load linked to a mean velocity(MV)of 0.55 m/s(load_(0.55)).The L-V relationship variables(load-axis intercept(L_(0)),velocity-axis intercept(v_(0)),and area under the L-V relationship line(A_(line)))were obtained using 3 velocity variables(MV,mean propulsive velocity(MPV),and peak velocity)by the multiple-point method including(20-40-60-80-load_(0.55))and excluding(20-40-60-80)the heavy squat,as well as from their respective 2-point methods(20-load_(0.55)and 20-80).Results:The L-V relationship variables were obtained with an acceptable reliability(coefncient of variation(CV)≤7.30%;intra-class correlation coefficient>0.63).The reliability of L_(0)and v_(0)was comparable for both methods(CV_(ratio)(calculated as higher value/lower value):1.11-1.12),but the multiple-point method provided Al_(ine)with a greater reliability(CV_(ratio)=1.26).The use of a heavy squat provided the L-V relationship variables with a comparable or higher reliability than the use of a heavy countermovement jump load(CV_(ratio):1.06-1.19).The peak velocity provided the load-velocity relationship variables with the greatest reliability(CV_(ratio):1.15-1.86)followed by the MV(CV_(ratio):1.07-1.18),and finally the MPV.The 2-point methods only revealed an acceptable validity for the MV and MPV(effect size≤0.19;Pearson s product-moment correlation coefficient≥0.96;Lin's concordance correlation coefficient≥0.94).Conclusion:The 2-point method obtained from a heavy squat load and MV or MPV is a quick,safe,and reliable procedure to evaluate the lower-body maximal neuromuscular capacities through the L-V relationship.展开更多
The distinctive characteristics exhibited by the aftershocks of Ms6.0 induced earthquakes in Changning,Sichuan,China,have attracted significant attention.The prevalence of salt rock(halite)in this area is closely asso...The distinctive characteristics exhibited by the aftershocks of Ms6.0 induced earthquakes in Changning,Sichuan,China,have attracted significant attention.The prevalence of salt rock(halite)in this area is closely associated with induced seismic events.The present study was conducted to examine the role of halite in frictional properties.To this end,laboratory measurements were taken for simulated fault gouge composed of halite.Slide-hold-slide(SHS)shear experiments were performed on gouges with grain size<106 mm at constant normal stress from 5 MPa to 30 MPa and constant shear velocity in the range of 1-10 mm/s.Halite gouge shows higher frictional strength and frictional healing rate than most minerals.The results reveal that the fault within halite can potentially generate intense seismic events and more significant aftershocks.An increase in normal stress leads to a reduction in frictional healing,with frictional strength initially increasing and then decreasing.The elevated shear velocity following fault activation facilitates fault dilation,diminishes the frictional strength of the fault,and contributes to fault healing during the inter-seismic period.The aforementioned findings will contribute to a comprehensive understanding of the potential for the healing property of induced seismicity on faults containing halite,particularly in the Changning region of China.展开更多
This study investigates the paradoxical detonation behavior of TKX-50,a nitrogen-rich energetic material,exhibiting higher detonation velocities but lower metal acceleration ability compared to HMX.Through experimenta...This study investigates the paradoxical detonation behavior of TKX-50,a nitrogen-rich energetic material,exhibiting higher detonation velocities but lower metal acceleration ability compared to HMX.Through experimental measurements and theoretical calculations,we propose a novel three-factor competition mechanism to explain this phenomenon.TKX-50-based PBX formulations achieved detonation velocities up to 9100 m/s,surpassing HMX-based counterparts.However,cylinder expansion tests revealed a 15%reduction in metal acceleration ability.Thermochemical measurements showed lower detonation heat for TKX-50(4900 J/g)versus HMX(5645 J/g).Our mechanism involves:(1)compositional effects prevailing at high pressures;(2)Energy release becoming essential as pressure drops;(3)Pressure-dependent product composition evolution functioning at low pressure.VLW code calculations unveiled a"crossover"in Hugoniot curves,lending support to this mechanism.This study furnishes a new framework for comprehending the performance of nitrogen-rich energetic materials,with significant implications for the design and optimization of future high-energy density materials.展开更多
Whipple shields as sacrificial bumpers,safeguard the satellites against extremely fast,different-sized projectiles traveling through space in the low earth orbit.Typical Whipple shields comprise a front and rear plate...Whipple shields as sacrificial bumpers,safeguard the satellites against extremely fast,different-sized projectiles traveling through space in the low earth orbit.Typical Whipple shields comprise a front and rear plate,separated by a gap or space.Recent advancements have explored the use of foam,cellular cores,and alternative materials such as ceramics instead of aluminium for the plates.In the current work,the effect of including fluid cores(air/water)sandwiched between the front and rear plates,on the response to hypervelocity impact was explored through a numerical approach.The numerical simulation consisted of hypervelocity impact by a 2 mm diameter,stainless steel projectile,launched at speeds of 3 e9 km/s with a normal impact trajectory towards the Whipple shield.The front and rear bumpers,made of AA6061-T6,were each 1 mm thick.A space of 10 mm was taken between the plates(occupied by fluid).The key metrics analyzed were the perforation characteristics,stages of the debris cloud generation and propagation,energy variations(internal,kinetic and plastic work),temperature variations,and the fragmentation summary.From the computational analysis,employing water-core in Whipple shields could prevent the rear bumper perforation till 6 km/s,lower the peak temperatures at the front bumper perforation zones and debris tip,and generate fewer,larger fragments.展开更多
In this study,the flow characteristics around a group of three piers arranged in tandem were investigated both numerically and experimentally.The simulation utilised the volume of fluid(VOF)model in conjunction with t...In this study,the flow characteristics around a group of three piers arranged in tandem were investigated both numerically and experimentally.The simulation utilised the volume of fluid(VOF)model in conjunction with the k–ɛmethod(i.e.,for flow turbulence representations),implemented through the ANSYS FLUENT software,to model the free-surface flow.The simulation results were validated against laboratory measurements obtained using an acoustic Doppler velocimeter.The comparative analysis revealed discrepancies between the simulated and measured maximum velocities within the investigated flow field.However,the numerical results demonstrated a distinct vortex-induced flow pattern following the first pier and throughout the vicinity of the entire pier group,which aligned reasonably well with experimental data.In the heavily narrowed spaces between the piers,simulated velocity profiles were overestimated in the free-surface region and underestimated in the areas near the bed to the mid-stream when compared to measurements.These discrepancies diminished away from the regions with intense vortices,indicating that the employed model was capable of simulating relatively less disturbed flow turbulence.Furthermore,velocity results from both simulations and measurements were compared based on velocity distributions at three different depth ratios(0.15,0.40,and 0.62)to assess vortex characteristic around the piers.This comparison revealed consistent results between experimental and simulated data.This research contributes to a deeper understanding of flow dynamics around complex interactive pier systems,which is critical for designing stable and sustainable hydraulic structures.Furthermore,the insights gained from this study provide valuable information for engineers aiming to develop effective strategies for controlling scour and minimizing destructive vortex effects,thereby guiding the design and maintenance of sustainable infrastructure.展开更多
Flow velocity uniformity of the microchannel plate is a major factor affecting the performance of microchannel devices.In order to improve the velocity distribution uniformity of the microchannel plate,we designed two...Flow velocity uniformity of the microchannel plate is a major factor affecting the performance of microchannel devices.In order to improve the velocity distribution uniformity of the microchannel plate,we designed two new microchannel structures:V-type and A-type.The effects of various structural parameters of the manifolds on the velocity distribution are reported.The V-type and A-type microchannel plates had a more uniform velocity distribution compared to the Z-type microchannel plate.The final result showed that it is beneficial for the V-type microchannel plate to obtain a more uniform velocity distribution when the manifold structure parameters are X_(in)=-1,X_(out)=0,Y_(in)=10,Y_(out)=6,Hin=4,H_(out)=1,and R=0.5.展开更多
In the present study,three layers of aluminum(Al)and a single layer of copper(Cu)were joined by resistance rolling welding(RRW)and the impact of welding velocity on microstructure,mechanical property and electrical pr...In the present study,three layers of aluminum(Al)and a single layer of copper(Cu)were joined by resistance rolling welding(RRW)and the impact of welding velocity on microstructure,mechanical property and electrical property was investigated.The results showed that the welding velocity was identified as the most significant parameter.With decreasing the welding velocity from 11 mm/s to 1 mm/s,the mechanical property of the joints initially showed an increase,reaching a maximum coach-peel peak load of 185.25 N,due to the larger well bonded region,then decreased owing to the high-temperature softening of the base metal.The elec-trical resistance of the joint demonstrated a consistent varying,characterized by an initial decrease owing to the larger completely bonded region and then increased with the decreasing welding velocity due to the excessive generation of Al2Cu with high electrical resistance.A cooling system was thus utilized to reduce the welding temperature to relieve the high-temperature softening,that suc-cessfully improved the welding quality of the joint by an 11.5%increase in the coach-peel peak load.展开更多
To ensure the safety of power energy transmission channel and mitigate the harm caused by galloping of iced transmission lines,the axial time-delay velocity feedback strategy is adopted to suppress the galloping.The p...To ensure the safety of power energy transmission channel and mitigate the harm caused by galloping of iced transmission lines,the axial time-delay velocity feedback strategy is adopted to suppress the galloping.The par-tial differential equation of galloping with axial time-delay velocity feedback strategy is established based on the variational principle for Hamiltonian.Then,the partial differential equation of galloping is transformed into or-dinary differential equation based on normalization and the Galerkin method.The primary amplitude-frequency response equation,the first-order steady-state approximate solution,and the harmonic amplitude-frequency re-sponse equation are derived by the multiscale method.The impact of different parameters such as time-delay value,control coefficient,and amplitude of external excitation on the galloping response are analyzed.The am-plitude under the primary resonance exhibits periodicity as time-delay value varies.The amplitude diminishes with increased control coefficient and increases with external excitation.Comprehensive consideration of vari-ous influences of parameters on vibration characteristics is crucial when employing the axial time-delay velocity feedback strategy to suppress galloping.Therefore,to achieve the best vibration suppression effect,it is crucial to adjust the time-delay parameter for modifying the range and amplitude of the resonance zone.The conclusions obtained by this study are expected to advance the refinement of active control techniques for iced transmission lines,and may provide valuable insights for practical engineering applications.展开更多
Ischemic stroke is the leading cause of death in the Chinese population.The incidence of cerebral infarction is higher in high-altitude regions,particularly those above 3,500 m,than in populations residing at lower al...Ischemic stroke is the leading cause of death in the Chinese population.The incidence of cerebral infarction is higher in high-altitude regions,particularly those above 3,500 m,than in populations residing at lower altitudes[1].There are various speculations regarding the mechanisms behind this phenomenon,one of which is that the low oxygen content and cold climate at high altitudes may increase the occurrence of vascular diseases[2].The multifactorial effect of high-altitude environments on residential populations makes it challenging for researchers to determine the specific pathways through which these diseases occur.展开更多
Graphene platelets(GPLs)-reinforced metal foam structures enhance the mechanical properties while maintaining the lightweight characteristics of metal foams.Further bonding piezoelectric actuator and sensor layers on ...Graphene platelets(GPLs)-reinforced metal foam structures enhance the mechanical properties while maintaining the lightweight characteristics of metal foams.Further bonding piezoelectric actuator and sensor layers on the surfaces of GPLs-reinforced metal foam beams enables active vibration control,greatly expanding their applications in the aerospace industry.For the first time,this paper investigates the vibration characteristics and active vibration control of GPLs-reinforced metal foam beams with surfacebonded piezoelectric layers.The constant velocity feedback scheme is used to design the closed-loop controller including piezoelectric actuators and sensors.The effects of the GPLs on the linear and nonlinear free vibrations of the beams are numerically studied.The Newmark-βmethod combined with Newton's iteration technique is used to calculate the nonlinear responses of the beams under different load forms including harmonic loads,impact loads,and moving loads.Additionally,special attention is given to the vibration reduction performance of the velocity feedback control on the responses of the beam.展开更多
Hydraulic sandblasting perforation plays a crucial role in the fracturing and reconstruction of unconventional oil and gas reservoirs.The jet nozzle is an essential part of the hydraulic perforation tool.Insufficient ...Hydraulic sandblasting perforation plays a crucial role in the fracturing and reconstruction of unconventional oil and gas reservoirs.The jet nozzle is an essential part of the hydraulic perforation tool.Insufficient penetration depth,caused by excessive jet distances,presents challenges during the perforation process.To overcome this,an optimization design of the nozzle structure is required to enhance the perforation efficiency.In this paper,a computational fluid-dynamic model for conical-cylindrical nozzles has been elaborated.To further improve the rock-breaking efficiency of the jet nozzle,a fillet design is introduced at the nozzle inlet section.The SST k-ωmodel is employed to account for turbulent flow effects in submerged conditions.The results indicate that the nozzle’s geometric parameters greatly influence the flow characteristics.The orthogonal experimental method is employed to optimize the flow channel structure of the nozzle,taking the length of constant velocity core as the evaluation index.The following optimized geometric parameters for the conical-cylindrical nozzle have been determined accordingly:a cylindrical segment diameter of 3.2 mm,a contraction angle of 12°,a contraction segment length of 8 mm,a cylindrical segment length of 6.4 mm,and a fillet radius of 2 mm.展开更多
基金financially supported by the National Key R&D Program of China(No.2023YFF0803404)the Zhejiang Provincial Natural Science Foundation(No.LY23D040001)+4 种基金the Open Research Fund of Key Laboratory of Engineering Geophysical Prospecting and Detection of Chinese Geophysical Society(No.CJ2021GB01)the Open Re-search Fund of Changjiang River Scientific Research Institute(No.CKWV20221011/KY)the ZhouShan Science and Technology Project(No.2023C81010)the National Natural Science Foundation of China(No.41904100)supported by Chinese Natural Science Foundation Open Research Cruise(Cruise No.NORC2019–08)。
文摘INTRODUCTION.Crustal velocity model is crucial for describing the subsurface composition and structure,and has significant implications in offshore oil and gas exploration and marine geophysical engineering(Xie et al.,2024).Currently,travel time tomography is the most commonly used method for velocity modeling based on ocean bottom seismometer(OBS)data(Zhang et al.,2023;Sambolian et al.,2021).This method usually assumes that the sub-seafloor structure is layered,and therefore faces challenges in high-precision modeling with strong lateral discontinuities.
基金supported by the Center of Excellence on Instru-mentation Technology and Automation(CEITA),Department of Instru-mentation and Electronics Engineering,Faculty of Engineering,King Mongkut’s University of Technology North Bangkok,Thailand。
文摘This study explores the combination of ultrasound technology with a detection algorithm to categorize flow regimes in bubble columns used for aeration in aquaculture.An ultrasonic velocity profiler is used to obtain the standard deviation of the bubble velocity distributed throughout the column.The bubble velocity data for three known flow regimes were used to develop a probability density function(PDF)classification model.The experimental apparatus consisted of a circular tank equipped with a bubble generator and gas hold-up monitoring systems.The flow regimes of the experimental fluid were determined,and the classification was conducted via the PDF method.The results demonstrate that the classification accuracy is not lower than that of traditional machine learning methods.
基金support from the National Natural Science Foundation of China(No.42474081)Basic Research Business of the Institute of Geophysics,China Earthquake Administration(Nos.DQJB 22R29 and DQJB19B30)Basic Research Business Special Project of the Earthquake Prediction Institute of the China Earthquake Administration(No.CEAIEF20220204).
文摘The Sichuan-Yunnan Block is located on the southeastern margin of the Qinghai-Xizang Plateau and has frequent seismic activity on the western border,posing a potential threat to human society and economic development.Therefore,it is important to understand its geological evolution,assess earthquake risks,and formulate scientific and reasonable disaster prevention and mitigation strategies.Using 23 months of continuous ambient noise records from 81 seismic stations,we obtained 1248 phasevelocity dispersion curves of the fundamental Rayleigh wave at 5–50 s.The three-dimensional(3D)S-wave velocity structure in the northwestern Sichuan-Yunnan Block was obtained by pure-path and depth inversion.The results show that three lowvelocity anomalous bands were distributed nearly north-to-south(N-S)at depths of 10–35 km.The overall shape of the lowvelocity channel gradually shifted from southeast to southwest because of the influence of the Panzhihua high-velocity blocks.The low-velocity strip consists of three branches,with the first branch extending southwest from the northern part of the Lancangjiang Fault.The second branch is distributed in the N-S direction and is blocked by two high-velocity bodies near the Longpan-Qiaohou and Honghe faults.The third branch crosses the research area from N-S and gradually extends from southeast to southwest and from shallow to deep.The three low-velocity anomaly distribution areas are likely the most severely deformed areas of the collision between the Qinghai-Xizang Plateau and Yangtze Block.The results provide a more detailed understanding of the deep structure of the western boundary of the Sichuan-Yunnan Block crustal low-velocity anomalies and reliable geophysical evidence for the morphology and continuity of crustal flows.
基金supported by the National Natural Science Foundation of China(42174115 and 42330311)the Special Fund of the Institute of Earthquake Forecasting,China Earthquake Administration(CEAIEF20230301)the State key laboratory of earthquake dynamics(LED2021B02).
文摘Structure and composition of Earth are fundamental importance in exploring the dynamic evolution of the crust and mantle.The Qinling Orogenic Belt(QOB)is located between the North China plate and the South China Plate,and is one of the main orogenic belts in China.To explore the composition and origin of anisotropy and the low wave velocity zone of the QOB,ten rock samples(gneiss and schist)were collected from the five sites of the QOB and the P-and S-wave velocities of these samples were measured under 0.6 to 2.0 GPa and 100 to 550℃.The wave velocities increase with increasing pressure and decreasing temperature.The V_(P)and V_(S)of the schist and gneiss match the velocity of the middle and lower crust of the QOB,indicating that schist and gneiss are important component of the QOB.All the schist and gneiss samples exhibit obvious seismic anisotropy with 1.64%-17.42%for V_(S)and 2.93%-14.78%for V_(P)under conditions of crust and upper mantle.The CPO/LPO and layering distribution of mica in rock samples are the main reasons for this anisotropy.The V_(S)structures below the five sampled sites from seismic ambient noise tomography were built to explore the effect of schist and gneiss on the composition and structure of the QOB.The results indicate that orientation-arranged gneiss and schist driven by the tectonic stresses might be a new origin of the character of V_(P)/V_(S),seismic anisotropy,and the low velocity zone in the QOB.
基金supported by Poongsan-KAIST Future Research Center Projectthe fund support provided by the National Research Foundation of Korea(NRF)grant funded by the Korea government(MSIT)(Grant No.2023R1A2C2005661)。
文摘This study presents a machine learning-based method for predicting fragment velocity distribution in warhead fragmentation under explosive loading condition.The fragment resultant velocities are correlated with key design parameters including casing dimensions and detonation positions.The paper details the finite element analysis for fragmentation,the characterizations of the dynamic hardening and fracture models,the generation of comprehensive datasets,and the training of the ANN model.The results show the influence of casing dimensions on fragment velocity distributions,with the tendencies indicating increased resultant velocity with reduced thickness,increased length and diameter.The model's predictive capability is demonstrated through the accurate predictions for both training and testing datasets,showing its potential for the real-time prediction of fragmentation performance.
基金This work was supported by the National Natural Science Foundation of China(Grant No.12272141)The financial support is gratefully acknowledged.
文摘The transformation from multibody models to lumped-parameter models is a crucial aspect of vehicle dynamics research.The velocity transformation method is adopted in this research,and the suspension multibody model is described using only one degree of freedom.It is found that the equivalent mass of the system is time-dependent during the simulation process,as observed in numerical simulations.Further symbolic calculations are conducted to derive the analytical form of the equivalent mass,and the results show that once the static parameters are determined,the equivalent mass of the suspension system is determined solely by the vertical position of the suspension upright,which reveals the kinematics characteristic of the equivalent mass of the suspension system.It is found that the equivalent mass experiences smaller changes when the suspension is compressed from the middle position,but larger changes when the suspension is extended.Furthermore,by comparing the multibody model,the lumped-parameter model with static mass,and the proposed lumped-parameter model considering the kinematics characteristic of the equivalent unsprung mass,the proposed model produces simulation results that more closely match the original multibody model than the model with static mass.The improvements in accuracy can be up to 20%under certain evaluation metrics.
基金supported by the Scientific Research Foundation for High-level Talents of Anhui University of Science and Technology under Grant 2024yjrc64the National Key R&D Program of China under Grant 2018YFC1504102。
文摘The Longmenshan(LMS)fault zone is located at the junction of the eastern Tibetan Plateau and the Sichuan Basin and is of great significance for studying regional tectonics and earthquake hazards.Although regional velocity models are available for the LMS fault zone,high-resolution velocity models are lacking.Therefore,a dense array of 240 short-period seismometers was deployed around the central segment of the LMS fault zone for approximately 30 days to monitor earthquakes and characterize fine structures of the fault zone.Considering the large quantity of observed seismic data,the data processing workflow consisted of deep learning-based automatic earthquake detection,phase arrival picking,and association.Compared with the earthquake catalog released by the China Earthquake Administration,many more earthquakes were detected by the dense array.Double-difference seismic tomography was adopted to determine V_(p),V_(s),and V_(p)/V_(s)models as well as earthquake locations.The checkerboard test showed that the velocity models have spatial resolutions of approximately 5 km in the horizontal directions and 2 km at depth.To the west of the Yingxiu–Beichuan Fault(YBF),the Precambrian Pengguan complex,where most of earthquakes occurred,is characterized by high velocity and low V_(p)/V_(s)values.In comparison,to the east of the YBF,the Upper Paleozoic to Jurassic sediments,where few earthquakes occurred,show low velocity and high V_(p)/V_(s)values.Our results suggest that the earthquake activity in the LMS fault zone is controlled by the strength of the rock compositions.When the high-resolution velocity models were combined with the relocated earthquakes,we were also able to delineate the fault geometry for different faults in the LMS fault zone.
基金financially supported by the National Natural Science Foundation of China(42250102,42250101)the Macao Foundation。
文摘This study presents an inversion method to recover the tidal flow velocity using tidal signals extracted from geomagnetic satellite dataset.By integrating the latest Earth conductivity profile and the Earth's magnetic field model,the limited memory quasi-Newton method(L-BFGS)is used to directly invert seawater flow velocities.We used the radial component of the induced magnetic field as the observed data,constructed an L_(2)-norm-based data misfit term using theoretical response and observed data,and applied smoothness constraints to the ocean flow velocity.The results agree well with the widely used HAMTIDE model in low-and mid-latitude regions,which is attributed to Macao Science Satellite-1's(MSS-1)unique low-inclination orbit of full coverage in these areas.These findings underscore MSS-1's potential to advance research on tidal-induced magnetic fields and their applications in ocean dynamics studies.
基金supported by the National 863 Program (Grant No.2006AA06Z206,Sustained supported)the National Science and Technology Major Project (Grant No.2008ZX05006-004)SinoPec Group Marine Facies Research (Grant No.08370502000410)
文摘Pre-stack depth migration velocity analysis is one of the keys to influencing the imaging quality of pre-stack migration.In this paper we cover a residual curvature velocity analysis method on angle-domain common image gathers（ADCIGs） which can depict the relationship between incident angle and migration depth at imaging points and update the migration velocity.Differing from offset-domain common image gathers（ODCIGs）,ADCIGs are not disturbed by the multi-path problem which contributes to imaging artifacts,thus influencing the velocity analysis.On the basis of horizontal layers,we derive the residual depth equation and also propose a velocity analysis workflow for velocity scanning.The tests to synthetic and field data prove the velocity analysis methods adopted in this paper are robust and valid.
文摘Purpose:This study aimed to examine the reliability and validity of load-velocity(L-V)relationship variables obtained through the 2-point method using different load combinations and velocity variables.Methods:Twenty men performed 2 identical sessions consisting of 2 countermovement jumps against 4 external loads(20 kg,40 kg,60 kg,and80 kg)and a heavy squat against a load linked to a mean velocity(MV)of 0.55 m/s(load_(0.55)).The L-V relationship variables(load-axis intercept(L_(0)),velocity-axis intercept(v_(0)),and area under the L-V relationship line(A_(line)))were obtained using 3 velocity variables(MV,mean propulsive velocity(MPV),and peak velocity)by the multiple-point method including(20-40-60-80-load_(0.55))and excluding(20-40-60-80)the heavy squat,as well as from their respective 2-point methods(20-load_(0.55)and 20-80).Results:The L-V relationship variables were obtained with an acceptable reliability(coefncient of variation(CV)≤7.30%;intra-class correlation coefficient>0.63).The reliability of L_(0)and v_(0)was comparable for both methods(CV_(ratio)(calculated as higher value/lower value):1.11-1.12),but the multiple-point method provided Al_(ine)with a greater reliability(CV_(ratio)=1.26).The use of a heavy squat provided the L-V relationship variables with a comparable or higher reliability than the use of a heavy countermovement jump load(CV_(ratio):1.06-1.19).The peak velocity provided the load-velocity relationship variables with the greatest reliability(CV_(ratio):1.15-1.86)followed by the MV(CV_(ratio):1.07-1.18),and finally the MPV.The 2-point methods only revealed an acceptable validity for the MV and MPV(effect size≤0.19;Pearson s product-moment correlation coefficient≥0.96;Lin's concordance correlation coefficient≥0.94).Conclusion:The 2-point method obtained from a heavy squat load and MV or MPV is a quick,safe,and reliable procedure to evaluate the lower-body maximal neuromuscular capacities through the L-V relationship.
基金supported by the National Key Research and Development Project(Grant No.2023YFE0110900)the National Natural Science Foundation of China(Grant Nos.42320104003 and 42077247).
文摘The distinctive characteristics exhibited by the aftershocks of Ms6.0 induced earthquakes in Changning,Sichuan,China,have attracted significant attention.The prevalence of salt rock(halite)in this area is closely associated with induced seismic events.The present study was conducted to examine the role of halite in frictional properties.To this end,laboratory measurements were taken for simulated fault gouge composed of halite.Slide-hold-slide(SHS)shear experiments were performed on gouges with grain size<106 mm at constant normal stress from 5 MPa to 30 MPa and constant shear velocity in the range of 1-10 mm/s.Halite gouge shows higher frictional strength and frictional healing rate than most minerals.The results reveal that the fault within halite can potentially generate intense seismic events and more significant aftershocks.An increase in normal stress leads to a reduction in frictional healing,with frictional strength initially increasing and then decreasing.The elevated shear velocity following fault activation facilitates fault dilation,diminishes the frictional strength of the fault,and contributes to fault healing during the inter-seismic period.The aforementioned findings will contribute to a comprehensive understanding of the potential for the healing property of induced seismicity on faults containing halite,particularly in the Changning region of China.
基金support provided by the National Natural Science Foundation of China(Grant No.12102405)the Presidential Foundation of CAEP(Grant No.YZJJZQ2023008).
文摘This study investigates the paradoxical detonation behavior of TKX-50,a nitrogen-rich energetic material,exhibiting higher detonation velocities but lower metal acceleration ability compared to HMX.Through experimental measurements and theoretical calculations,we propose a novel three-factor competition mechanism to explain this phenomenon.TKX-50-based PBX formulations achieved detonation velocities up to 9100 m/s,surpassing HMX-based counterparts.However,cylinder expansion tests revealed a 15%reduction in metal acceleration ability.Thermochemical measurements showed lower detonation heat for TKX-50(4900 J/g)versus HMX(5645 J/g).Our mechanism involves:(1)compositional effects prevailing at high pressures;(2)Energy release becoming essential as pressure drops;(3)Pressure-dependent product composition evolution functioning at low pressure.VLW code calculations unveiled a"crossover"in Hugoniot curves,lending support to this mechanism.This study furnishes a new framework for comprehending the performance of nitrogen-rich energetic materials,with significant implications for the design and optimization of future high-energy density materials.
文摘Whipple shields as sacrificial bumpers,safeguard the satellites against extremely fast,different-sized projectiles traveling through space in the low earth orbit.Typical Whipple shields comprise a front and rear plate,separated by a gap or space.Recent advancements have explored the use of foam,cellular cores,and alternative materials such as ceramics instead of aluminium for the plates.In the current work,the effect of including fluid cores(air/water)sandwiched between the front and rear plates,on the response to hypervelocity impact was explored through a numerical approach.The numerical simulation consisted of hypervelocity impact by a 2 mm diameter,stainless steel projectile,launched at speeds of 3 e9 km/s with a normal impact trajectory towards the Whipple shield.The front and rear bumpers,made of AA6061-T6,were each 1 mm thick.A space of 10 mm was taken between the plates(occupied by fluid).The key metrics analyzed were the perforation characteristics,stages of the debris cloud generation and propagation,energy variations(internal,kinetic and plastic work),temperature variations,and the fragmentation summary.From the computational analysis,employing water-core in Whipple shields could prevent the rear bumper perforation till 6 km/s,lower the peak temperatures at the front bumper perforation zones and debris tip,and generate fewer,larger fragments.
文摘In this study,the flow characteristics around a group of three piers arranged in tandem were investigated both numerically and experimentally.The simulation utilised the volume of fluid(VOF)model in conjunction with the k–ɛmethod(i.e.,for flow turbulence representations),implemented through the ANSYS FLUENT software,to model the free-surface flow.The simulation results were validated against laboratory measurements obtained using an acoustic Doppler velocimeter.The comparative analysis revealed discrepancies between the simulated and measured maximum velocities within the investigated flow field.However,the numerical results demonstrated a distinct vortex-induced flow pattern following the first pier and throughout the vicinity of the entire pier group,which aligned reasonably well with experimental data.In the heavily narrowed spaces between the piers,simulated velocity profiles were overestimated in the free-surface region and underestimated in the areas near the bed to the mid-stream when compared to measurements.These discrepancies diminished away from the regions with intense vortices,indicating that the employed model was capable of simulating relatively less disturbed flow turbulence.Furthermore,velocity results from both simulations and measurements were compared based on velocity distributions at three different depth ratios(0.15,0.40,and 0.62)to assess vortex characteristic around the piers.This comparison revealed consistent results between experimental and simulated data.This research contributes to a deeper understanding of flow dynamics around complex interactive pier systems,which is critical for designing stable and sustainable hydraulic structures.Furthermore,the insights gained from this study provide valuable information for engineers aiming to develop effective strategies for controlling scour and minimizing destructive vortex effects,thereby guiding the design and maintenance of sustainable infrastructure.
基金supported by Scientific Research Project of Guangdong Provincial Department of Education(2024KQNCX152).
文摘Flow velocity uniformity of the microchannel plate is a major factor affecting the performance of microchannel devices.In order to improve the velocity distribution uniformity of the microchannel plate,we designed two new microchannel structures:V-type and A-type.The effects of various structural parameters of the manifolds on the velocity distribution are reported.The V-type and A-type microchannel plates had a more uniform velocity distribution compared to the Z-type microchannel plate.The final result showed that it is beneficial for the V-type microchannel plate to obtain a more uniform velocity distribution when the manifold structure parameters are X_(in)=-1,X_(out)=0,Y_(in)=10,Y_(out)=6,Hin=4,H_(out)=1,and R=0.5.
基金supported by the National Key Research and Development Program of China(Grant No.2023YFB3407400)the National Natural Science Foundation of China(Grant No.52475386,Grant No.52025058).
文摘In the present study,three layers of aluminum(Al)and a single layer of copper(Cu)were joined by resistance rolling welding(RRW)and the impact of welding velocity on microstructure,mechanical property and electrical property was investigated.The results showed that the welding velocity was identified as the most significant parameter.With decreasing the welding velocity from 11 mm/s to 1 mm/s,the mechanical property of the joints initially showed an increase,reaching a maximum coach-peel peak load of 185.25 N,due to the larger well bonded region,then decreased owing to the high-temperature softening of the base metal.The elec-trical resistance of the joint demonstrated a consistent varying,characterized by an initial decrease owing to the larger completely bonded region and then increased with the decreasing welding velocity due to the excessive generation of Al2Cu with high electrical resistance.A cooling system was thus utilized to reduce the welding temperature to relieve the high-temperature softening,that suc-cessfully improved the welding quality of the joint by an 11.5%increase in the coach-peel peak load.
基金supported by the National Natural Science Foundation of China(Grant No.51507106)China Postdoctoral Science Foundation(Grant No.2021M702371)。
文摘To ensure the safety of power energy transmission channel and mitigate the harm caused by galloping of iced transmission lines,the axial time-delay velocity feedback strategy is adopted to suppress the galloping.The par-tial differential equation of galloping with axial time-delay velocity feedback strategy is established based on the variational principle for Hamiltonian.Then,the partial differential equation of galloping is transformed into or-dinary differential equation based on normalization and the Galerkin method.The primary amplitude-frequency response equation,the first-order steady-state approximate solution,and the harmonic amplitude-frequency re-sponse equation are derived by the multiscale method.The impact of different parameters such as time-delay value,control coefficient,and amplitude of external excitation on the galloping response are analyzed.The am-plitude under the primary resonance exhibits periodicity as time-delay value varies.The amplitude diminishes with increased control coefficient and increases with external excitation.Comprehensive consideration of vari-ous influences of parameters on vibration characteristics is crucial when employing the axial time-delay velocity feedback strategy to suppress galloping.Therefore,to achieve the best vibration suppression effect,it is crucial to adjust the time-delay parameter for modifying the range and amplitude of the resonance zone.The conclusions obtained by this study are expected to advance the refinement of active control techniques for iced transmission lines,and may provide valuable insights for practical engineering applications.
基金supported by the National Natural Science Foundation of Chongqing,China(CSTB2022NSCQ-MSX1100)National Natural Science Foundation of China(grant no.82101499).
文摘Ischemic stroke is the leading cause of death in the Chinese population.The incidence of cerebral infarction is higher in high-altitude regions,particularly those above 3,500 m,than in populations residing at lower altitudes[1].There are various speculations regarding the mechanisms behind this phenomenon,one of which is that the low oxygen content and cold climate at high altitudes may increase the occurrence of vascular diseases[2].The multifactorial effect of high-altitude environments on residential populations makes it challenging for researchers to determine the specific pathways through which these diseases occur.
基金Project supported by the National Natural Science Foundation of China(Nos.12102015 and 12472003)the R&D Program of Beijing Municipal Education Commission of China(No.KM202110005030)。
文摘Graphene platelets(GPLs)-reinforced metal foam structures enhance the mechanical properties while maintaining the lightweight characteristics of metal foams.Further bonding piezoelectric actuator and sensor layers on the surfaces of GPLs-reinforced metal foam beams enables active vibration control,greatly expanding their applications in the aerospace industry.For the first time,this paper investigates the vibration characteristics and active vibration control of GPLs-reinforced metal foam beams with surfacebonded piezoelectric layers.The constant velocity feedback scheme is used to design the closed-loop controller including piezoelectric actuators and sensors.The effects of the GPLs on the linear and nonlinear free vibrations of the beams are numerically studied.The Newmark-βmethod combined with Newton's iteration technique is used to calculate the nonlinear responses of the beams under different load forms including harmonic loads,impact loads,and moving loads.Additionally,special attention is given to the vibration reduction performance of the velocity feedback control on the responses of the beam.
基金The authors gratefully acknowledge the financial support by the National Natural Science Foundation of China(No.52405272)the CNOOC’s major project during the 14th Five-Year Plan period“Key Technologies and Equipment for Measurement,Recording,and Testing-Development and Engineering of Integrated Perforation Technology Equipment Based on Reservoir Geology”and the National Science Foundation of Jiangsu Province(No.BK20220533).
文摘Hydraulic sandblasting perforation plays a crucial role in the fracturing and reconstruction of unconventional oil and gas reservoirs.The jet nozzle is an essential part of the hydraulic perforation tool.Insufficient penetration depth,caused by excessive jet distances,presents challenges during the perforation process.To overcome this,an optimization design of the nozzle structure is required to enhance the perforation efficiency.In this paper,a computational fluid-dynamic model for conical-cylindrical nozzles has been elaborated.To further improve the rock-breaking efficiency of the jet nozzle,a fillet design is introduced at the nozzle inlet section.The SST k-ωmodel is employed to account for turbulent flow effects in submerged conditions.The results indicate that the nozzle’s geometric parameters greatly influence the flow characteristics.The orthogonal experimental method is employed to optimize the flow channel structure of the nozzle,taking the length of constant velocity core as the evaluation index.The following optimized geometric parameters for the conical-cylindrical nozzle have been determined accordingly:a cylindrical segment diameter of 3.2 mm,a contraction angle of 12°,a contraction segment length of 8 mm,a cylindrical segment length of 6.4 mm,and a fillet radius of 2 mm.
