A novel speed sensor-less direct torque control induction motor drive system for the mining locomotive haulage is presented in the paper. Rotor speed identification is based on the model reference adaptive control the...A novel speed sensor-less direct torque control induction motor drive system for the mining locomotive haulage is presented in the paper. Rotor speed identification is based on the model reference adaptive control theory with neural network using back propagation algorithm. The system is implemented using a real-time TMS320F240 digital signal processor. The simulation study and experiment results indicate that the suggested system has good performance.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
Recent advancements in power electronics technology evolves inverter fed electric motors.Speed signals and rotor position are essential for controlling an electric motor accurately.In this paper,the sensorless speed c...Recent advancements in power electronics technology evolves inverter fed electric motors.Speed signals and rotor position are essential for controlling an electric motor accurately.In this paper,the sensorless speed control of surface-mounted permanent magnet synchronous motor(SPMSM)has been attempted.SPMSM wants a digital inverter for its precise working.Hence,this study incor-poratesfifteen level inverter to the SPMSM.A sliding mode observer(SMO)based sensorless speed control scheme is projected to determine rotor spot and speed of the multilevel inverter(MLI)fed SPMSM.MLI has been operated using a multi carrier pulse width modulation(MCPWM)strategy for generation offif-teen level voltages.The simulation works are executed with MATLAB/SIMU-LINK software.The steadiness and the heftiness of the projected model have been investigated under no loaded and loaded situations of SPMSM.Furthermore,the projected method can be adapted for electric vehicles.展开更多
In this paper,a novel guidance law is proposed which can achieve the desired impact speed and angle simultaneously for unpowered gliding vehicles.A guidance law with only impact angle constraint is used to produce the...In this paper,a novel guidance law is proposed which can achieve the desired impact speed and angle simultaneously for unpowered gliding vehicles.A guidance law with only impact angle constraint is used to produce the guidance profile,and its convergence in the varying speed scenario is proved.A relationship between flight states,guidance input and impact speed is established.By applying the fixed-time convergence control theory of error dynamics,an impact speed corrector is built with the above guidance profile,which can implement impact speed correction without affecting the impact angle constraint.Numerical simulations with various impact speed and angle constraints are conducted to demonstrate the performance of the proposed guidance law,and the robustness is also verified by Monte Carlo tests.展开更多
To reveal the rock burst mechanism,the stress and failure characteristics of coal-rock strata under different advancing speeds of mining working face were explored by theoretical analysis,simulation,and engineering mo...To reveal the rock burst mechanism,the stress and failure characteristics of coal-rock strata under different advancing speeds of mining working face were explored by theoretical analysis,simulation,and engineering monitoring.The relationship between energy accumulation and release was analyzed,and a reasonable mining speed according to specific projects was recommended.The theoretical analysis shows that as the mining speed increases from 4 to 15 m/d,the rheological coefficient of coal mass ranges from 0.9 to 0.4,and the elastic energy of coal mass accumulation varies from 100 to 900 kJ.Based on the simulation,there is a critical advancing speed,the iteration numbers of simulation are less than 15,000 per mining 10 m coal seam,the overburden structure is obvious,the abutment pressure in coal mass is large,and the accumulated energy is large,which is easy to cause strong rock burst.When the iteration number is greater than 15,000,the static force of coal mass increases slightly,but there is no obvious rock burst.Based on engineering monitoring,the mining speed of a mine is less than 8 m/d,and the periodic weighting distance is about 17 m;as the mining speed is greater than 10 m/d,and the periodic weighting distance is greater than 20 m;as the mining speed is 3-8 m/d,and the range of high stress in surrounding rock is 48 m;as the advancing speed is 8-12 m/d,and the high-stress range in surrounding rock is 80 m.Moreover,as the mining speed is less than 8 cut cycles,the micro seismic energy is less than 10,000 J;as the mining speed is 12 cut cycles,the microseismic energy is about 20,000 J.In summary,the advancing speed is positively correlated with the micro seismic event;as the mining speed increases,the accumulated elastic energy of surrounding rock is greater,which is easy to cause rock burst.The comprehensive analysis indicates the daily advance speed of the mine is not more than 12 cut cycles.展开更多
Switched Reluctance Motors(SRMs),outfitted with rugged construction,good speed range,high torque density,and rare earth-free nature that outweigh induction motors(IM)and permanent magnet synchronous motor(PMSM),afford...Switched Reluctance Motors(SRMs),outfitted with rugged construction,good speed range,high torque density,and rare earth-free nature that outweigh induction motors(IM)and permanent magnet synchronous motor(PMSM),afford a broad range of applications in the domain of electric vehicles(EVs).Standard copper magnetic wire and low-carbon steel laminations are used to construct SRMs,which give them high efficiency in the range of 85-95%.Despite SRM's desirable features over traditional motor-speed drives,high torque ripples and radial distortions constrain their deployment in EVs.Precise rotor position is imperative for effective management of the speed and torque of SRMs.This paper provides an illustrative compendium on review of the torque-speed control and ripple mitigation techniques using design enhancements and control methods for SRM drives for EV applications.The various schemes were evaluated on their performance metricsoperational speed range,control complexity,practical realization,need for pre-stored parameters(look-up tables of current,inductance and torque profiles)and motor controller memory requirements.The findings provide valuable insights into balancing the gains and trade-offs associated with EV applications.Furthermore,they pinpoint opportunities for enhancement by analyzing the cost and technical aspects of different SRM controllers.展开更多
This paper deals with the monotonicity of limit wave speed c0(h)to a perturbed g KdV equation.We show the decrease of c0(h)by combining the analytic method and the numerical technique.Our results solve a special case ...This paper deals with the monotonicity of limit wave speed c0(h)to a perturbed g KdV equation.We show the decrease of c0(h)by combining the analytic method and the numerical technique.Our results solve a special case of the open question presented by Yan et al.,and the method potentially provides a way to study the monotonicity of c0(h)for general m∈N^(+).展开更多
Ultrasound computed tomography(USCT)is a noninvasive biomedical imaging modality that offers insights into acoustic properties such as the sound speed(SS)and acoustic attenuation(AA)of the human body,enhancing diagnos...Ultrasound computed tomography(USCT)is a noninvasive biomedical imaging modality that offers insights into acoustic properties such as the sound speed(SS)and acoustic attenuation(AA)of the human body,enhancing diagnostic accuracy and therapy planning.Full waveform inversion(FWI)is a promising USCT image reconstruction method that optimizes the parameter fields of a wave propagation model via gradient-based optimization.However,twodimensional FWI methods are limited by their inability to account for three-dimensional wave propagation in the elevation direction,resulting in image artifacts.To address this problem,we propose a three-dimensional time-domain full waveform inversion algorithm to reconstruct the SS and AA distributions on the basis of a fractional Laplacian wave equation,adjoint field formulation,and gradient descent optimization.Validated by two sets of simulations,the proposed algorithm has potential for generating high-resolution and quantitative SS and AA distributions.This approach holds promise for clinical USCT applications,assisting early disease detection,precise abnormality localization,and optimized treatment planning,thus contributing to better healthcare outcomes.展开更多
Application of variable speed limits(VSL)is gradually increasingly implemented especially on highways.As a result of conducted studies and implementations,it is observed that the variable speed limits have reduced the...Application of variable speed limits(VSL)is gradually increasingly implemented especially on highways.As a result of conducted studies and implementations,it is observed that the variable speed limits have reduced the number of car accidents as well as proved positive results in terms of delays and environmental factors.Purpose of this study is to develop an algorithm for VSL application that is considered to be applied on Istanbul D100 highway and to assess the effects of application.Algorithm that is developed for VSL is a different VSL algorithm and compared with the constant speed system.According to obtained results,when the proposed system is compared to current system,it is observed that the number of delays and average stops are reduced%30 and%40 respectively and also emissions reduced at the rate of%12.展开更多
When the proton exchange membrane fuel cell(PEMFC)system is running,there will be a condition that does not require power output for a short time.In order to achieve zero power output under low power consumption,it is...When the proton exchange membrane fuel cell(PEMFC)system is running,there will be a condition that does not require power output for a short time.In order to achieve zero power output under low power consumption,it is necessary to consider the diversity of control targets and the complexity of dynamic models,which brings the challenge of high-precision tracking control of the stack output power and cathode intake flow.For system idle speed control,a modelbased nonlinear control framework is constructed in this paper.Firstly,the nonlinear dynamic model of output power and cathode intake flow is derived.Secondly,a control scheme combining nonlinear extended Kalman filter observer and state feedback controller is designed.Finally,the control scheme is verified on the PEMFC experimental platform and compared with the proportion-integration-differentiation(PID)controller.The experimental results show that the control strategy proposed in this paper can realize the idle speed control of the fuel cell system and achieve the purpose of zero power output.Compared with PID controller,it has faster response speed and better system dynamics.展开更多
This paper explores the development of interpretable data elements from raw data using Kolmogorov-Arnold Networks(KAN).With the exponential growth of data in contemporary society,there is an urgent need for effective ...This paper explores the development of interpretable data elements from raw data using Kolmogorov-Arnold Networks(KAN).With the exponential growth of data in contemporary society,there is an urgent need for effective data processing methods to unlock the full potential of this resource.The study focuses on the application of KAN in the transportation sector to transform raw traffic data into meaningful data elements.The core of the research is the KANT-GCN model,which synergizes Kolmogorov-Arnold Networks with Temporal Graph Convolutional Networks(T-GCN).This innovative model demonstrates superior performance in predicting traffic speeds,outperforming existing methods in terms of accuracy,reliability,and interpretability.The model was evaluated using real-world datasets from Shenzhen,Los Angeles,and the San Francisco Bay Area,showing significant improvements in different metrics.The paper highlights the potential of KAN-T-GCN to revolutionize data-driven decision-making in traffic management and other sectors,underscoring its ability to handle dynamic updates and maintain data integrity.展开更多
Enhancing the mining speed of a working face has become the primary approach to achieve high production and efficiency in coal mines,thereby further improving the production capacity.However,the problem of rock bursts...Enhancing the mining speed of a working face has become the primary approach to achieve high production and efficiency in coal mines,thereby further improving the production capacity.However,the problem of rock bursts resulting from this approach has become increasingly serious.Therefore,to implement coal mine safety and efficient extraction,the impact of deformation pressure caused by different mining speeds should be considered,and a reasonable mining speed of the working face should be determined.The influence of mining speed on overlying rock breaking in the stope is analyzed by establishing a key layer block rotation and subsidence model.Results show that with the increasing mining speed,the compression amount of gangue in the goaf decreases,and the rotation and subsidence amount of rock block B above goaf decreases,forcing the rotation and subsidence amount of rock block A above roadway to increase.Consequently,the contact mode between rock block A and rock block B changes from line contact to point contact,and the horizontal thrust and shear force between blocks increase.The increase in rotation and subsidence of rock block A intensifies the compression degree of coal and rock mass below the key layer,thereby increasing the stress concentration degree of coal and rock mass as well as the total energy accumulation.In addition,due to the insufficient compression of gangue in the goaf,the bending and subsidence space of the far-field key layer are limited,the length of the suspended roof increases,and the influence range of mining stress and the energy accumulation range expand.Numerical test results and underground microseismic monitoring results verify the correlation between mining speed and stope energy,and high-energy events generally appear 1-2 d after the change in mining speed.On this basis,the statistical principle confirms that the maximum mining speed of the working face at 6 m/d is reasonable.展开更多
Sea-surface wind is a vital meteorological element in marine activities and climate research.This study proposed the spectral attention enhanced multidimensional feature fusion convolutional long short-term memory(LST...Sea-surface wind is a vital meteorological element in marine activities and climate research.This study proposed the spectral attention enhanced multidimensional feature fusion convolutional long short-term memory(LSTM)network(SAMFF-Conv-LSTM),a novel approach for sea-surface wind-speed prediction that emphasizes the temporal characteristics of data samples.The model incorporates the Fourier transform to extract time-and frequency-domain features from wave and wind variables.For the 12 h prediction,the SAMFF-ConvLSTM achieved a correlation coefficient of 0.960 and a root mean square error(RMSE)of 1.350 m/s,implying a high prediction accuracy.For the 24 h prediction,the RMSE of the SAMFF-ConvLSTM was reduced by 38.11%,14.26%,and 13.36%compared with those of the convolutional neural network,gated recurrent units,and convolutional LSTM(ConvLSTM),respectively.These results confirm the superior reliability and accuracy of the SAMFF-ConvLSTM over traditional models in theoretical and practical applications.展开更多
This paper is devoted to investigating the spreading speed of a time-space periodic epidemic model with vital dynamics and standard incidence in discrete media. We establish the existence of the leftward and rightward...This paper is devoted to investigating the spreading speed of a time-space periodic epidemic model with vital dynamics and standard incidence in discrete media. We establish the existence of the leftward and rightward spreading speeds for the infective individuals, which can be used to estimate how fast the disease spreads. To overcome the difficulty arising from the lack of comparison principle for such time-space periodic nonmonotone systems, our proof is mainly based on constructing a series of scalar time-space periodic equations, establishing the spreading speeds for such auxiliary equations and using comparison methods. It may be the first work to study the spreading speed for time-space periodic non-monotone systems.展开更多
By applying the convolution-based Hilbert transform in the zonal direction on six-hourly streamfunction fields at200 h Pa, we present the climatology and trends of the local wave period, and zonal and meridional phase...By applying the convolution-based Hilbert transform in the zonal direction on six-hourly streamfunction fields at200 h Pa, we present the climatology and trends of the local wave period, and zonal and meridional phase speeds, of Rossby waves over the globe during the solstice seasons of 1979–2023. While partly similar to and inspired by Fragkoulidis and Wirth(2020), our method differs in its ability to cover both planetary-scale and synoptic-scale waves over not only the extratropics, but also the tropics and subtropics. Based on a physically reasonable global distribution of wave periods, our key new finding is a robust prolonging of wave periods over most regions of the tropics and subtropics during both solstice seasons of 1979–2023, except for the tropical Atlantic, which experiences a shortened wave period during June–July–August of 1979–2022. Both the prolonging and shortening of wave periods are mainly associated with the changes in planetary-scale waves. Regionally varying trends of the zonal phase speed(Cpx) of synoptic waves are consistent in sign with, but smaller in magnitude than, the trends of local zonal wind, confirming the conclusion of Wu and Lu(2023)on the opposite effects of zonal wind and the meridional gradient of potential vorticity on Cpx. Meanwhile, the Cpx trends of planetary-scale waves are relatively weak, and do not exhibit a robust relation with the trend of zonal wind. These new results are helpful toward better understanding the changes in atmospheric waves and extreme events under global warming.展开更多
The spatiotemporal variations of sound speed, particularly the drastic variation in depth, significantly affect seafloor geodetic positioning precision. For this reason, the global navigation satellite system-acoustic...The spatiotemporal variations of sound speed, particularly the drastic variation in depth, significantly affect seafloor geodetic positioning precision. For this reason, the global navigation satellite system-acoustic(GNSS-A) positioning technology typically uses in-situ sound speed profiles(SSPs) and considers the impact of these variations at the data post-processing stage. However, in-situ SSP measurement is costly and somewhat hinders the timeliness of seafloor geodetic monitoring. We generalize the bilinear SSP(BL-SSP) to be a piecewise-linear SSP, whose model parameters are estimated from GNSS-A observations. In addition, we construct a set of constraints based on a priori marine environment observation to stabilize SSP inversion and propose an algorithm to recursively conduct the inversion, e.g.,the trilinear SSP(TL-SSP) inversion is initialized using the BL-SSP inversion result. The proposed model is verified by long-term GNSS-A seafloor geodetic observations. It shows that the root mean square error(RMSE) of the TL-SSP inversion result is 10.87 m/s, compared to 11.08 m/s for the traditional BL-SSP, with significant improvements observed in shallow and middle water layers. Furthermore, when replacing the in-situ SSP with the inverted SSP for precise seafloor geodetic positioning and incorporating the acoustic delay parameters, the TL-SSP-based positioning demonstrates higher accuracy than the BL-SSP-based approach. Relative to the positioning result based on the in-situ SSP, the mean bias, standard deviation and RMSE of the horizontal positioning error are better than 0.003 m, 0.005 m,and 0.006 m, respectively, while those of the vertical positioning error are better than 0.03 m, 0.04 m, and 0.04 m,respectively. Compared with BL-SSP, TL-SSP can achieve a positioning error reduction along the E-direction, Ndirection, and U-direction by 16.7%, 15.0%, and 5.5%, respectively.展开更多
The challenge of aerodynamic noise is a key obstacle in the advancement of low-pressure tube ultra-high-speed maglev transportation,demanding urgent resolution.This study utilizes a broadband noise source model to per...The challenge of aerodynamic noise is a key obstacle in the advancement of low-pressure tube ultra-high-speed maglev transportation,demanding urgent resolution.This study utilizes a broadband noise source model to perform a quantitative analysis of the aerodynamic noise produced by ultra-high-speed maglev trains operating in low-pressure environments.Initially,an external flow field calculation model for the ultra-high-speed maglev train is presented.Subsequently,numerical simulations based on the broadband noise source model are used to examine the noise characteristics.The impact of the train speed and pressure level on noise generation is investigated accordingly.Subsequently,a correlation formula is derived.The results reveal that the amplitude of sound source changes in the streamlined region of the head and tail cars of the train is large,and the amplitude of changes for the middle car is smaller.The noise source strength increases with speed,with a quadrupole noise source becoming dominant when the train speed exceeds 600 km/h.At a speed of 1000 km/h,the noise source intensity from the streamlined area at the rear of the train overcomes that at the front.Furthermore,the noise source decreases as the pressure level in the tube decreases.When the pressure level drops to 0.01 atm,the quadrupole noise source intensity of a train running at 600 km/h significantly weakens and falls below that of the dipole noise source.展开更多
Commonly,the standards for the geometric design of roads refer to a given set of values for the friction coefficient(longitudinal and transverse friction).These"reference"values imply corresponding visibilit...Commonly,the standards for the geometric design of roads refer to a given set of values for the friction coefficient(longitudinal and transverse friction).These"reference"values imply corresponding visibility sights,curvature radii,and speed limits.Unfortunately,not only do these reference values not correspond to a given standard to measure them,but nothing is said about the decrease of the posted speed limit(variable speed limits)when roads become slippery and lanes for autonomous vehicle(AV)are concerned.Furthermore,the same assessment of the friction coefficient has plenty of uncertainties due to measurement device,temperature,location,time passed from the construction,alignment-related variables(e.g.,curve,tangent,transition curve,convexity/crests or concavity/sags,longitudinal slope,superelevation,and ruling gradient),and supplementary singularities such as joints and bridge approaches.All the issues above may harm road safety and the complexity of forensic investigations of pavements.Consequently,this study's objectives were confined to(1)carrying out friction measurements and analyzing the problem of friction decay over time;(2)setting up a method to lower the speed limits where friction decays are detected;(3)setting up a method to handle friction decays for autonomous vehicles.Results demonstrate that:(1)a power law describes how the speed limits are affected by friction;(2)for speeds up to 170 km/h,due to the lower reaction time,AV reaction distance is lower,which benefits AV traffic(lower stopping distance);(3)on the contrary,for higher values of friction and higher speeds,under the hypothesis of having the same reaction time law for non-AV(NAV)(i.e.,decreasing with the initial speed),AV speed limits become lower than NAV speed limits;(4)not only do comfort-based speed profiles for AVs bring higher braking distances,but also,in the median part(of the deceleration process),this could pose safety issues and reduce the distance between the available and the needed friction.展开更多
The output regulation approach has effectively addressed the speed tracking and disturbance rejection problem of permanent magnet synchronous motor(PMSM).Although accurate speed tracking under time-varying load torque...The output regulation approach has effectively addressed the speed tracking and disturbance rejection problem of permanent magnet synchronous motor(PMSM).Although accurate speed tracking under time-varying load torque disturbance has been achieved,the number of disturbance frequencies should be known.In this paper,an adaptive observer-based error feedback control method is proposed,which can solve the speed tracking control problem of PMSM subject to completely unknown multi-frequency sinusoidal load torque disturbance,requiring only the upper bound of the number of disturbance frequencies.The design steps of this method can be divided into the following three steps.In step one,a filtered transformation is applied to convert the observer canonical form of the error system and the transformed exosystem into an adaptive observer form.In step two,an adaptive observer is designed to estimate the unknown parameters of the exosystem and states of the adaptive observer form.In step three,an adaptive observer-based error feedback controller is designed to solve this control problem.The effectiveness of the proposed method is demonstrated by experimental results.展开更多
Surface wind speed(SWS)not only plays a crucial role in regulating the Earth's energy and hydrological cycle,but also is an important source of sustainable renewable energy.This study assesses the credibility of s...Surface wind speed(SWS)not only plays a crucial role in regulating the Earth's energy and hydrological cycle,but also is an important source of sustainable renewable energy.This study assesses the credibility of sws in three reanalyses(ERA5,MERRA2,and JRA-55)in East Asia using both satellite and in-situ observations.Results show all three reanalyses can capture the spatial pattern of swS as in observations,yet there are notable differences in magnitude.On land,ERA5 and MERRA2 overestimate the SWS by about 0.6 and 1.5 m s^(-1),respectively,whereas JRA-55 underestimates it.The biases over the oceans are opposite to those on land and are relatively small due to the assimilation of observations of oceanic surface winds.Overall,JRA-55 and ERA5 offer better estimates of seasonal means and variances of SWS than MERRA2.The observed SWS shows a negative trend of-0.08 m s^(-1)/10 yr on land and a positive trend of 0.09 m s^(-1)/10 yr in the western North Pacific.Only JRA-55 shows similar trends to observations over both land and ocean,while ERA5 and MERRA2 show varying degrees of deviation from the observations.Further investigation shows that there is a strong link between the trend of SWS and that of the large-scale circulation,and that a large part of the SwS trend can be attributed to changes in large-scale circulations.展开更多
文摘A novel speed sensor-less direct torque control induction motor drive system for the mining locomotive haulage is presented in the paper. Rotor speed identification is based on the model reference adaptive control theory with neural network using back propagation algorithm. The system is implemented using a real-time TMS320F240 digital signal processor. The simulation study and experiment results indicate that the suggested system has good performance.
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Recent advancements in power electronics technology evolves inverter fed electric motors.Speed signals and rotor position are essential for controlling an electric motor accurately.In this paper,the sensorless speed control of surface-mounted permanent magnet synchronous motor(SPMSM)has been attempted.SPMSM wants a digital inverter for its precise working.Hence,this study incor-poratesfifteen level inverter to the SPMSM.A sliding mode observer(SMO)based sensorless speed control scheme is projected to determine rotor spot and speed of the multilevel inverter(MLI)fed SPMSM.MLI has been operated using a multi carrier pulse width modulation(MCPWM)strategy for generation offif-teen level voltages.The simulation works are executed with MATLAB/SIMU-LINK software.The steadiness and the heftiness of the projected model have been investigated under no loaded and loaded situations of SPMSM.Furthermore,the projected method can be adapted for electric vehicles.
基金supported by the National Natural Science Foundation of China(No.52175214)。
文摘In this paper,a novel guidance law is proposed which can achieve the desired impact speed and angle simultaneously for unpowered gliding vehicles.A guidance law with only impact angle constraint is used to produce the guidance profile,and its convergence in the varying speed scenario is proved.A relationship between flight states,guidance input and impact speed is established.By applying the fixed-time convergence control theory of error dynamics,an impact speed corrector is built with the above guidance profile,which can implement impact speed correction without affecting the impact angle constraint.Numerical simulations with various impact speed and angle constraints are conducted to demonstrate the performance of the proposed guidance law,and the robustness is also verified by Monte Carlo tests.
基金supported by the National Natural Science Foundation of China(52174109)Program for Innovative Research Team(in Science and Technology)in University of Henan Province(22IRTSTHN005)+1 种基金Key Research and Development Project of Henan Province(242102240029)Key Research Project of Institutions of Higher Education in Henan Province(24A580001).
文摘To reveal the rock burst mechanism,the stress and failure characteristics of coal-rock strata under different advancing speeds of mining working face were explored by theoretical analysis,simulation,and engineering monitoring.The relationship between energy accumulation and release was analyzed,and a reasonable mining speed according to specific projects was recommended.The theoretical analysis shows that as the mining speed increases from 4 to 15 m/d,the rheological coefficient of coal mass ranges from 0.9 to 0.4,and the elastic energy of coal mass accumulation varies from 100 to 900 kJ.Based on the simulation,there is a critical advancing speed,the iteration numbers of simulation are less than 15,000 per mining 10 m coal seam,the overburden structure is obvious,the abutment pressure in coal mass is large,and the accumulated energy is large,which is easy to cause strong rock burst.When the iteration number is greater than 15,000,the static force of coal mass increases slightly,but there is no obvious rock burst.Based on engineering monitoring,the mining speed of a mine is less than 8 m/d,and the periodic weighting distance is about 17 m;as the mining speed is greater than 10 m/d,and the periodic weighting distance is greater than 20 m;as the mining speed is 3-8 m/d,and the range of high stress in surrounding rock is 48 m;as the advancing speed is 8-12 m/d,and the high-stress range in surrounding rock is 80 m.Moreover,as the mining speed is less than 8 cut cycles,the micro seismic energy is less than 10,000 J;as the mining speed is 12 cut cycles,the microseismic energy is about 20,000 J.In summary,the advancing speed is positively correlated with the micro seismic event;as the mining speed increases,the accumulated elastic energy of surrounding rock is greater,which is easy to cause rock burst.The comprehensive analysis indicates the daily advance speed of the mine is not more than 12 cut cycles.
基金supported in part by the Universitat Politècnica de València under grant PAID-10-21supported through AMRITA Seed Grant(Proposal ID:ASG2022188)。
文摘Switched Reluctance Motors(SRMs),outfitted with rugged construction,good speed range,high torque density,and rare earth-free nature that outweigh induction motors(IM)and permanent magnet synchronous motor(PMSM),afford a broad range of applications in the domain of electric vehicles(EVs).Standard copper magnetic wire and low-carbon steel laminations are used to construct SRMs,which give them high efficiency in the range of 85-95%.Despite SRM's desirable features over traditional motor-speed drives,high torque ripples and radial distortions constrain their deployment in EVs.Precise rotor position is imperative for effective management of the speed and torque of SRMs.This paper provides an illustrative compendium on review of the torque-speed control and ripple mitigation techniques using design enhancements and control methods for SRM drives for EV applications.The various schemes were evaluated on their performance metricsoperational speed range,control complexity,practical realization,need for pre-stored parameters(look-up tables of current,inductance and torque profiles)and motor controller memory requirements.The findings provide valuable insights into balancing the gains and trade-offs associated with EV applications.Furthermore,they pinpoint opportunities for enhancement by analyzing the cost and technical aspects of different SRM controllers.
基金Supported by the National Natural Science Foundation of China(12071162)the Natural Science Foundation of Fujian Province(2021J01302)the Fundamental Research Funds for the Central Universities(ZQN-802)。
文摘This paper deals with the monotonicity of limit wave speed c0(h)to a perturbed g KdV equation.We show the decrease of c0(h)by combining the analytic method and the numerical technique.Our results solve a special case of the open question presented by Yan et al.,and the method potentially provides a way to study the monotonicity of c0(h)for general m∈N^(+).
基金supported by the National Key Research and Development Program of China(2022YFA1404400)the National Natural Science Foundation of China(62122072,12174368,61705216,62405306)+4 种基金Anhui Provincial Department of Science and Technology(202203a07020020,18030801138)Anhui Provincial Natural Science Foundation(2308085QA21,2408085QF187)the USTC Research Funds of the Double First-Class Initiative(YD2090002015)the Institute of Artificial Intelligence at Hefei Comprehensive National Science Center(23YGXT005)the Fundamental Research Funds for the Central Universities(WK2090000083).
文摘Ultrasound computed tomography(USCT)is a noninvasive biomedical imaging modality that offers insights into acoustic properties such as the sound speed(SS)and acoustic attenuation(AA)of the human body,enhancing diagnostic accuracy and therapy planning.Full waveform inversion(FWI)is a promising USCT image reconstruction method that optimizes the parameter fields of a wave propagation model via gradient-based optimization.However,twodimensional FWI methods are limited by their inability to account for three-dimensional wave propagation in the elevation direction,resulting in image artifacts.To address this problem,we propose a three-dimensional time-domain full waveform inversion algorithm to reconstruct the SS and AA distributions on the basis of a fractional Laplacian wave equation,adjoint field formulation,and gradient descent optimization.Validated by two sets of simulations,the proposed algorithm has potential for generating high-resolution and quantitative SS and AA distributions.This approach holds promise for clinical USCT applications,assisting early disease detection,precise abnormality localization,and optimized treatment planning,thus contributing to better healthcare outcomes.
文摘Application of variable speed limits(VSL)is gradually increasingly implemented especially on highways.As a result of conducted studies and implementations,it is observed that the variable speed limits have reduced the number of car accidents as well as proved positive results in terms of delays and environmental factors.Purpose of this study is to develop an algorithm for VSL application that is considered to be applied on Istanbul D100 highway and to assess the effects of application.Algorithm that is developed for VSL is a different VSL algorithm and compared with the constant speed system.According to obtained results,when the proposed system is compared to current system,it is observed that the number of delays and average stops are reduced%30 and%40 respectively and also emissions reduced at the rate of%12.
基金Supported by the Major Science and Technology Projects in Jilin Province and Changchun City(20220301010GX).
文摘When the proton exchange membrane fuel cell(PEMFC)system is running,there will be a condition that does not require power output for a short time.In order to achieve zero power output under low power consumption,it is necessary to consider the diversity of control targets and the complexity of dynamic models,which brings the challenge of high-precision tracking control of the stack output power and cathode intake flow.For system idle speed control,a modelbased nonlinear control framework is constructed in this paper.Firstly,the nonlinear dynamic model of output power and cathode intake flow is derived.Secondly,a control scheme combining nonlinear extended Kalman filter observer and state feedback controller is designed.Finally,the control scheme is verified on the PEMFC experimental platform and compared with the proportion-integration-differentiation(PID)controller.The experimental results show that the control strategy proposed in this paper can realize the idle speed control of the fuel cell system and achieve the purpose of zero power output.Compared with PID controller,it has faster response speed and better system dynamics.
基金supported by the EU H2020 Research and Innovation Program under the Marie Sklodowska-Curie Grant Agreement(Project-DEEP,Grant No.101109045)the National Natural Science Foundation of China(No.NSFC 61925105 and 62171257)the Tsinghua University-China Mobile Communications Group Co.,Ltd.Joint Institute,and the Fundamental Research Funds for the Central Universities,China(No.FRF-NP-20-03).
文摘This paper explores the development of interpretable data elements from raw data using Kolmogorov-Arnold Networks(KAN).With the exponential growth of data in contemporary society,there is an urgent need for effective data processing methods to unlock the full potential of this resource.The study focuses on the application of KAN in the transportation sector to transform raw traffic data into meaningful data elements.The core of the research is the KANT-GCN model,which synergizes Kolmogorov-Arnold Networks with Temporal Graph Convolutional Networks(T-GCN).This innovative model demonstrates superior performance in predicting traffic speeds,outperforming existing methods in terms of accuracy,reliability,and interpretability.The model was evaluated using real-world datasets from Shenzhen,Los Angeles,and the San Francisco Bay Area,showing significant improvements in different metrics.The paper highlights the potential of KAN-T-GCN to revolutionize data-driven decision-making in traffic management and other sectors,underscoring its ability to handle dynamic updates and maintain data integrity.
基金supported by Technology Innovation Fund of China Coal Research Institute(2022CX-I-04)Science and Technology Innovation Venture Capital Project of China Coal Technology Engineering Group(2020-2-TD-CXY005)。
文摘Enhancing the mining speed of a working face has become the primary approach to achieve high production and efficiency in coal mines,thereby further improving the production capacity.However,the problem of rock bursts resulting from this approach has become increasingly serious.Therefore,to implement coal mine safety and efficient extraction,the impact of deformation pressure caused by different mining speeds should be considered,and a reasonable mining speed of the working face should be determined.The influence of mining speed on overlying rock breaking in the stope is analyzed by establishing a key layer block rotation and subsidence model.Results show that with the increasing mining speed,the compression amount of gangue in the goaf decreases,and the rotation and subsidence amount of rock block B above goaf decreases,forcing the rotation and subsidence amount of rock block A above roadway to increase.Consequently,the contact mode between rock block A and rock block B changes from line contact to point contact,and the horizontal thrust and shear force between blocks increase.The increase in rotation and subsidence of rock block A intensifies the compression degree of coal and rock mass below the key layer,thereby increasing the stress concentration degree of coal and rock mass as well as the total energy accumulation.In addition,due to the insufficient compression of gangue in the goaf,the bending and subsidence space of the far-field key layer are limited,the length of the suspended roof increases,and the influence range of mining stress and the energy accumulation range expand.Numerical test results and underground microseismic monitoring results verify the correlation between mining speed and stope energy,and high-energy events generally appear 1-2 d after the change in mining speed.On this basis,the statistical principle confirms that the maximum mining speed of the working face at 6 m/d is reasonable.
基金supported by the National Natural Science Foundation(No.42176020)the Open Research Fund of State Key Laboratory of Target Vulnerability Assessment(No.YSX2024KFYS001)+1 种基金the National Key Research and Development Program(No.2022YFC3105002)the Project from Key Laboratory of Marine Environmental Information Technology(No.2023GFW-1047).
文摘Sea-surface wind is a vital meteorological element in marine activities and climate research.This study proposed the spectral attention enhanced multidimensional feature fusion convolutional long short-term memory(LSTM)network(SAMFF-Conv-LSTM),a novel approach for sea-surface wind-speed prediction that emphasizes the temporal characteristics of data samples.The model incorporates the Fourier transform to extract time-and frequency-domain features from wave and wind variables.For the 12 h prediction,the SAMFF-ConvLSTM achieved a correlation coefficient of 0.960 and a root mean square error(RMSE)of 1.350 m/s,implying a high prediction accuracy.For the 24 h prediction,the RMSE of the SAMFF-ConvLSTM was reduced by 38.11%,14.26%,and 13.36%compared with those of the convolutional neural network,gated recurrent units,and convolutional LSTM(ConvLSTM),respectively.These results confirm the superior reliability and accuracy of the SAMFF-ConvLSTM over traditional models in theoretical and practical applications.
基金supported by the Natural Science Basic Research Program of Shanxi(Grant No.2024JC-YBMS-025)the Innovation Capability Support Program of Shanxi(Grant No.2024RS-CXTD-88)。
文摘This paper is devoted to investigating the spreading speed of a time-space periodic epidemic model with vital dynamics and standard incidence in discrete media. We establish the existence of the leftward and rightward spreading speeds for the infective individuals, which can be used to estimate how fast the disease spreads. To overcome the difficulty arising from the lack of comparison principle for such time-space periodic nonmonotone systems, our proof is mainly based on constructing a series of scalar time-space periodic equations, establishing the spreading speeds for such auxiliary equations and using comparison methods. It may be the first work to study the spreading speed for time-space periodic non-monotone systems.
基金the support from the National Natural Science Foundation of China (Grant No. 42175070)supported by the National Natural Science Foundation of China (Grant No. 42288101)supported by the National Key Scientific and Technological Infrastructure project “Earth System Numerical Simulation Facility” (Earth Lab)。
文摘By applying the convolution-based Hilbert transform in the zonal direction on six-hourly streamfunction fields at200 h Pa, we present the climatology and trends of the local wave period, and zonal and meridional phase speeds, of Rossby waves over the globe during the solstice seasons of 1979–2023. While partly similar to and inspired by Fragkoulidis and Wirth(2020), our method differs in its ability to cover both planetary-scale and synoptic-scale waves over not only the extratropics, but also the tropics and subtropics. Based on a physically reasonable global distribution of wave periods, our key new finding is a robust prolonging of wave periods over most regions of the tropics and subtropics during both solstice seasons of 1979–2023, except for the tropical Atlantic, which experiences a shortened wave period during June–July–August of 1979–2022. Both the prolonging and shortening of wave periods are mainly associated with the changes in planetary-scale waves. Regionally varying trends of the zonal phase speed(Cpx) of synoptic waves are consistent in sign with, but smaller in magnitude than, the trends of local zonal wind, confirming the conclusion of Wu and Lu(2023)on the opposite effects of zonal wind and the meridional gradient of potential vorticity on Cpx. Meanwhile, the Cpx trends of planetary-scale waves are relatively weak, and do not exhibit a robust relation with the trend of zonal wind. These new results are helpful toward better understanding the changes in atmospheric waves and extreme events under global warming.
基金The National Key Research and Development Program under contract No. 2024YFB3909702the National Natural Science Foundation of China under contract Nos 42474014, 41931076, and 42388102+2 种基金the Scientific and Technology Inmo-vation Program of Laoshan Laboratory under contract Nos LSKJ202205100 and LSKJ202205105the Independent Research Project of State Key Laboratory of Geo-information Engineering under contract SKLGIE2023-ZZ-8the Scientific Research Project of Chinese Academy of Surveying and Mapping under contract No. AR2501。
文摘The spatiotemporal variations of sound speed, particularly the drastic variation in depth, significantly affect seafloor geodetic positioning precision. For this reason, the global navigation satellite system-acoustic(GNSS-A) positioning technology typically uses in-situ sound speed profiles(SSPs) and considers the impact of these variations at the data post-processing stage. However, in-situ SSP measurement is costly and somewhat hinders the timeliness of seafloor geodetic monitoring. We generalize the bilinear SSP(BL-SSP) to be a piecewise-linear SSP, whose model parameters are estimated from GNSS-A observations. In addition, we construct a set of constraints based on a priori marine environment observation to stabilize SSP inversion and propose an algorithm to recursively conduct the inversion, e.g.,the trilinear SSP(TL-SSP) inversion is initialized using the BL-SSP inversion result. The proposed model is verified by long-term GNSS-A seafloor geodetic observations. It shows that the root mean square error(RMSE) of the TL-SSP inversion result is 10.87 m/s, compared to 11.08 m/s for the traditional BL-SSP, with significant improvements observed in shallow and middle water layers. Furthermore, when replacing the in-situ SSP with the inverted SSP for precise seafloor geodetic positioning and incorporating the acoustic delay parameters, the TL-SSP-based positioning demonstrates higher accuracy than the BL-SSP-based approach. Relative to the positioning result based on the in-situ SSP, the mean bias, standard deviation and RMSE of the horizontal positioning error are better than 0.003 m, 0.005 m,and 0.006 m, respectively, while those of the vertical positioning error are better than 0.03 m, 0.04 m, and 0.04 m,respectively. Compared with BL-SSP, TL-SSP can achieve a positioning error reduction along the E-direction, Ndirection, and U-direction by 16.7%, 15.0%, and 5.5%, respectively.
基金funded by the Talent Program(Ph.D.Fund)of Chengdu Technological University(grant number 2024RC025)the Natural Science Foundation of Sichuan Province(grant number 2022NSFSC1892)Fundamental Research Funds for the Central Universities(grant number XJ2021KJZK054).
文摘The challenge of aerodynamic noise is a key obstacle in the advancement of low-pressure tube ultra-high-speed maglev transportation,demanding urgent resolution.This study utilizes a broadband noise source model to perform a quantitative analysis of the aerodynamic noise produced by ultra-high-speed maglev trains operating in low-pressure environments.Initially,an external flow field calculation model for the ultra-high-speed maglev train is presented.Subsequently,numerical simulations based on the broadband noise source model are used to examine the noise characteristics.The impact of the train speed and pressure level on noise generation is investigated accordingly.Subsequently,a correlation formula is derived.The results reveal that the amplitude of sound source changes in the streamlined region of the head and tail cars of the train is large,and the amplitude of changes for the middle car is smaller.The noise source strength increases with speed,with a quadrupole noise source becoming dominant when the train speed exceeds 600 km/h.At a speed of 1000 km/h,the noise source intensity from the streamlined area at the rear of the train overcomes that at the front.Furthermore,the noise source decreases as the pressure level in the tube decreases.When the pressure level drops to 0.01 atm,the quadrupole noise source intensity of a train running at 600 km/h significantly weakens and falls below that of the dipole noise source.
文摘Commonly,the standards for the geometric design of roads refer to a given set of values for the friction coefficient(longitudinal and transverse friction).These"reference"values imply corresponding visibility sights,curvature radii,and speed limits.Unfortunately,not only do these reference values not correspond to a given standard to measure them,but nothing is said about the decrease of the posted speed limit(variable speed limits)when roads become slippery and lanes for autonomous vehicle(AV)are concerned.Furthermore,the same assessment of the friction coefficient has plenty of uncertainties due to measurement device,temperature,location,time passed from the construction,alignment-related variables(e.g.,curve,tangent,transition curve,convexity/crests or concavity/sags,longitudinal slope,superelevation,and ruling gradient),and supplementary singularities such as joints and bridge approaches.All the issues above may harm road safety and the complexity of forensic investigations of pavements.Consequently,this study's objectives were confined to(1)carrying out friction measurements and analyzing the problem of friction decay over time;(2)setting up a method to lower the speed limits where friction decays are detected;(3)setting up a method to handle friction decays for autonomous vehicles.Results demonstrate that:(1)a power law describes how the speed limits are affected by friction;(2)for speeds up to 170 km/h,due to the lower reaction time,AV reaction distance is lower,which benefits AV traffic(lower stopping distance);(3)on the contrary,for higher values of friction and higher speeds,under the hypothesis of having the same reaction time law for non-AV(NAV)(i.e.,decreasing with the initial speed),AV speed limits become lower than NAV speed limits;(4)not only do comfort-based speed profiles for AVs bring higher braking distances,but also,in the median part(of the deceleration process),this could pose safety issues and reduce the distance between the available and the needed friction.
基金supported by the National Natural Science Foundation of China(Nos.62273127 and 62073217)the Dreams Foundation of Jianghuai Advance Technology Center(No.2023-ZM01J006)the Anhui Provincial Key Research and Development Project(No.2022a05020025).
文摘The output regulation approach has effectively addressed the speed tracking and disturbance rejection problem of permanent magnet synchronous motor(PMSM).Although accurate speed tracking under time-varying load torque disturbance has been achieved,the number of disturbance frequencies should be known.In this paper,an adaptive observer-based error feedback control method is proposed,which can solve the speed tracking control problem of PMSM subject to completely unknown multi-frequency sinusoidal load torque disturbance,requiring only the upper bound of the number of disturbance frequencies.The design steps of this method can be divided into the following three steps.In step one,a filtered transformation is applied to convert the observer canonical form of the error system and the transformed exosystem into an adaptive observer form.In step two,an adaptive observer is designed to estimate the unknown parameters of the exosystem and states of the adaptive observer form.In step three,an adaptive observer-based error feedback controller is designed to solve this control problem.The effectiveness of the proposed method is demonstrated by experimental results.
基金supported by the National Natural Science Foundation of China[grant numbers 42361144708,42205041,and 42175165]a scientific research project of the Shanghai Investigation,Design and Research Institute Co.,Ltd.[grant number 2023CN(83)-001]the National Key Scientific and Technological Infrastructure project“Earth System Science Numerical Simulator Facility”(EarthLab).
文摘Surface wind speed(SWS)not only plays a crucial role in regulating the Earth's energy and hydrological cycle,but also is an important source of sustainable renewable energy.This study assesses the credibility of sws in three reanalyses(ERA5,MERRA2,and JRA-55)in East Asia using both satellite and in-situ observations.Results show all three reanalyses can capture the spatial pattern of swS as in observations,yet there are notable differences in magnitude.On land,ERA5 and MERRA2 overestimate the SWS by about 0.6 and 1.5 m s^(-1),respectively,whereas JRA-55 underestimates it.The biases over the oceans are opposite to those on land and are relatively small due to the assimilation of observations of oceanic surface winds.Overall,JRA-55 and ERA5 offer better estimates of seasonal means and variances of SWS than MERRA2.The observed SWS shows a negative trend of-0.08 m s^(-1)/10 yr on land and a positive trend of 0.09 m s^(-1)/10 yr in the western North Pacific.Only JRA-55 shows similar trends to observations over both land and ocean,while ERA5 and MERRA2 show varying degrees of deviation from the observations.Further investigation shows that there is a strong link between the trend of SWS and that of the large-scale circulation,and that a large part of the SwS trend can be attributed to changes in large-scale circulations.
