An auto-B?cklund transformation for the quad equation Q1_(1) is considered as a discrete equation,called H2^(a),which is a so called torqued version of H2.The equations H2^(a) and Q1_(1) compose a consistent cube,from...An auto-B?cklund transformation for the quad equation Q1_(1) is considered as a discrete equation,called H2^(a),which is a so called torqued version of H2.The equations H2^(a) and Q1_(1) compose a consistent cube,from which an auto-B?cklund transformation and a Lax pair for H2^(a) are obtained.More generally it is shown that auto-B?cklund transformations admit auto-Backlund transformations.Using the auto-Backlund transformation for H2^(a)we derive a seed solution and a one-soliton solution.From this solution it is seen that H2^(a) is a semi-autonomous lattice equation,as the spacing parameter q depends on m but it disappears from the plane wave factor.展开更多
As a torqued version of the lattice potential Korteweg–de Vries equation, the H1^(a) is an integrable nonsymmetric lattice equation with only one spacing parameter. In this paper, we present the Cauchy matrix scheme ...As a torqued version of the lattice potential Korteweg–de Vries equation, the H1^(a) is an integrable nonsymmetric lattice equation with only one spacing parameter. In this paper, we present the Cauchy matrix scheme for this equation. Soliton solutions, Jordan-block solutions and soliton-Jordan-block mixed solutions are constructed by solving the determining equation set. All the obtained solutions have jumping property between constant values for fixed n and demonstrate periodic structure.展开更多
A full-face rock tunnel boring machine(TBM)has two main parameters:cutterhead thrust and cutterhead torque.Cutterhead thrust can be predicted numerically using different methods,such as the rated thrust of the disc cu...A full-face rock tunnel boring machine(TBM)has two main parameters:cutterhead thrust and cutterhead torque.Cutterhead thrust can be predicted numerically using different methods,such as the rated thrust of the disc cutter,the indentation test of the disc cutter,a linear breaking experiment,or applying statistical models based on field data.However,cutterhead torque prediction still lacks the necessary and sufficient theoretical analysis and corresponding research.Consequently,we studied the rock-breaking characteristics of the disc cutter on the cutterhead and found a difference between the lateral friction resistance and the inner and outer rock breaking.We then proposed the cutterhead torque composition of the full-face rock tunnel boring machine,shoveling and transporting ballast torque,rolling resistance torque,lateral friction resistance torque,and disc cutter lateral imbalance torque,and established the corresponding theory.Through practical engineering ver-ification,we found that the relative error between the cutterhead torque value calculated by the theory and the actual value was only 0.51%.If the lateral friction resistance moment of the disc cutter rock breaking and the lateral imbalance moment of the disc cutter are not considered,the relative error between the calculated value of cutterhead torque and the actual value is 7.48%.Therefore,the accuracy of the established cutterhead torque theory is 6.97%higher than that of the disc cutter linear rolling crushing rock test theory.The research results provide an important reference for determining the cutterhead torque of a full-face rock tunnel boring machine.展开更多
We report the development of the[Pt_(0.75)Ti_(0.25)/Co-Ni multilayer/Ta]_n superlattice with strong spin-orbit torque,large perpendicular magnetic anisotropy,and remarkably low switching current density.We demonstrate...We report the development of the[Pt_(0.75)Ti_(0.25)/Co-Ni multilayer/Ta]_n superlattice with strong spin-orbit torque,large perpendicular magnetic anisotropy,and remarkably low switching current density.We demonstrate that the efficiency of the spin-orbit torque increases nearly linearly with the repetition number n,which is in excellent agreement with the spin Hall effect of the Pt_(0.75)Ti_(0.25)being essentially the only source of the observed spin-orbit torque.The perpendicular magnetic anisotropy field is also substantially enhanced by more than a factor of 2 as n increases from 1 to6.The[Pt_(0.75)Ti_(0.25)/Co-Ni multilayers/Ta]_n superlattice additionally exhibits deterministic,low-current-density magnetization switching despite the very large total layer thicknesses.The unique combination of strong spin-orbit torque,robust perpendicular magnetic anisotropy,low-current-density switching,and excellent high thermal stability makes the[Pt_(0.75)Ti_(0.25)/Co-Ni multilayer/Ta]_n superlattice a highly compelling material candidate for ultrafast,energy-efficient,and long-data-retention spintronic technologies.展开更多
Permanent-magnet(PM)machines are the important driving components of various mechanical equipment and industrial applications,such as robot joints,aerospace equipment,electric vehicles,actuators,wind generators and el...Permanent-magnet(PM)machines are the important driving components of various mechanical equipment and industrial applications,such as robot joints,aerospace equipment,electric vehicles,actuators,wind generators and electric traction systems.The PM machines are usually expected to have high torque/power density,low torque ripple,reduced rotor mass,a large constant power speed range or strong anti-magnetization capability to match different requirements of industrial applications.The structural topology of the electric machines,including stator/rotor arrangements and magnet patterns of rotor,is one major concern to improve their electromagnetic performance.However,systematic reviews of structural topology are seldom found in literature.Therefore,the objective of this paper is to summarize the stator/rotor arrangements and magnet patterns of the permanent-magnet brushless machines,in depth.Specifically,the stator/rotor arrangements of the PM machines including radial-flux,axialflux and emerging hybrid axial-radial flux configurations are presented,and pros and cons of these topologies are discussed regarding their electromagnetic performance.The magnet patterns including various surface-mounted and interior magnet patterns,such as parallel magnetization pole pattern,Halbach arrays,spoke-type designs and their variants are summarized,and the characteristics of those magnet patterns in terms of flux-focusing effect,magnetic self-shielding effect,torque ripple,reluctance torque,magnet utilization ratio,and anti-demagnetization capability are compared.This paper can provide guidance and suggestion for the structure selection and design of PM brushless machines for high-performance industrial applications.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
In recent decades,optical micro/nano manipulation has made remarkable strides in the fields of biology and the physical sciences,benefiting from both theoretical and experimental advances in optical forces.The emergen...In recent decades,optical micro/nano manipulation has made remarkable strides in the fields of biology and the physical sciences,benefiting from both theoretical and experimental advances in optical forces.The emergence of optical torques has further enhanced the capabilities and possibilities of optical micro/nano manipulation,opening the door to exciting new applications.In this review,we delve into the fundamentals and recent breakthroughs in the realm of optical micro/nano manipulation using optical torques.We introduce the advancements in optical manipulation based on optical torques from engineered light fields and objects,and highlight the latest developments in applying optical torques to cutting-edge physical and biological scenarios,with a special emphasis on the detection and manipulation of biological structures.Finally,we conclude by outlining our vision for the current and future directions of this field,including the integration of optical torque and micro/nano technologies,the utilization of special light fields,and the development of deeplearning-assisted optical torque design.展开更多
The growing demand for artificial intelligence and complex computing has underscored the urgent need for advanced data storage technologies.Spin-orbit torque(SOT)has emerged as a leading candidate for high-speed,high-...The growing demand for artificial intelligence and complex computing has underscored the urgent need for advanced data storage technologies.Spin-orbit torque(SOT)has emerged as a leading candidate for high-speed,high-density magnetic random-access memory due to its ultrafast switching speed and low power consumption.This review systematically explores the generation and switching mechanisms of electron-mediated torques(including both conventional SOTs and orbital torques)and magnon-mediated torques.We discuss key materials that enable these effects:heavy metals,topological insulators,low-crystal-symmetry materials,non-collinear antiferromagnets,and altermagnets for conventional SOTs;3d,4d,and 5d transition metals for orbital torques;and antiferromagnetic insulator Ni O-and multiferroic Bi Fe O_(3)-based sandwich structures for magnon torques.We emphasize that although key components of SOT devices have been demonstrated,numerous promising materials and critical questions regarding their underlying mechanisms remain to be explored.Therefore,this field represents a dynamic and rapidly evolving frontier in spintronics,offering significant potential for advancing next-generation information storage and computational technologies.展开更多
Compared to the conventional permanent magnet synchronous machine(PMSM),the main characteristic of permanent magnet torque machine(PMTM)with high torque is that armature current is high,which has a great influence on ...Compared to the conventional permanent magnet synchronous machine(PMSM),the main characteristic of permanent magnet torque machine(PMTM)with high torque is that armature current is high,which has a great influence on magnetic circuit saturation,so this paper proposes a novel analytical method(AM)considering this problem.The key of this new AM is to consider armature reaction flux and armature leakage flux,which are closely related to output torque.Firstly,the expressions,including magnetomotive force(MMF)generated by permanent magnets(PMs)and armature windings are derived,and meanwhile slotting effect is considered by planning flux path.In addition,the expression of leakage flux density generated by armature windings are calculated,and flux density equivalence coefficient of tooth is calculated to be 2/3,which is used to solve the problem of uneven saturation of each tooth.Then,based on main flux factor and leakage flux factor proposed,an improved iteration process is proposed,and by this new process,the flux density of each yoke and tooth can be obtained,which is beneficial to obtain more accurate air-gap flux density and flux linkage.Finally,a prototype of 60-pole 54-slot is fabricated,and the performances of the electric machine,such as back electromotive force(EMF)and output torque,are calculated by this new AM and finite element method(FEM).The results of FEM and experimental test show that this new AM is good enough to calculate the performance of PMTM.展开更多
Accurate quantification of the spin–orbit torques(SOTs) is critical for the identification and applications of new spin-orbitronic effects. One of the most popular techniques to quantify the SOTs is the “switching a...Accurate quantification of the spin–orbit torques(SOTs) is critical for the identification and applications of new spin-orbitronic effects. One of the most popular techniques to quantify the SOTs is the “switching angle shift”, where the applied direct current is assumed to shift, via domain wall depinning during anti-domain expansion, the switching angle of a perpendicular magnetization in a linear proportional manner under a large rotating magnetic field. Here, we report that, for the most commonly employed perpendicular magnetization heterostructures in spintronics(e.g., those based on FeCoB, Co, and Co/Ni multilayers), the switching angle shift considerably misestimates the SOT within the domain wall depinning analysis of the slope of linear-in-current scaling and may also have a non-zero residual value at zero direct current. Our experiments and simulations unveil that the switching angle shift is most likely dominated by chiral asymmetric nucleation rather than expansion of anti-domains. The in-plane field from external magnets and current-induced SOTs lowers the perpendicular nucleation field and thus reduces the required switching angle, ultimately leading to an underestimation of SOTs by domain wall depinning analysis. These results have advanced our understanding of magnetization switching in spintronic devices.展开更多
Armored vehicles,to accomplish missions in complex harsh conditions with high mobility,require the transmission system to achieve high energy density and high reliability.The wet multi-disc clutch becomes the perishab...Armored vehicles,to accomplish missions in complex harsh conditions with high mobility,require the transmission system to achieve high energy density and high reliability.The wet multi-disc clutch becomes the perishable component under heavy load,large speed difference,and frequent engagement.Due to the difficulty of maintenance in battlefield,clutch carrying post-buckling separate plate is common,and the clutch working process is obstructed.Therefore,considering the post-buckling plate,the multi-physics thermodynamic model of a wet multi-disc clutch is established to describe the entire engagement and separation process.The influence of the buckling degree on the stress-strain,uniformity of gaps,torque,and temperature characteristics is investigated by the numerical method and testified by bench tests.The results show that with the increasing buckling degree,the clutch engagement and separation times decrease gradually.For the separation process,the non-uniformity of gaps is increased,and gaps are eventually occupied,leading to the continuous rough contact among friction pairs.Therefore,the drag torque is increased.Squeezed by the post-buckling plate,the cooling rates of separate plates are decreased.During repeated engagement-separation,temperatures of plates may reach balance points.Since continuous sliding and temperature concentration,the wear form and degree changes,especially at outer radius.Extra drag torque,heat,and wear threats the friction components which increases the risk of failures of the transmission system and affects the mobility of armored vehicles.展开更多
Background:Residual force enhancement(rFE),defined as increased isometric force following active lengthening compared to a fixed-end isometric contraction at the same muscle length and level of activation,is present a...Background:Residual force enhancement(rFE),defined as increased isometric force following active lengthening compared to a fixed-end isometric contraction at the same muscle length and level of activation,is present across all scales of muscle.While rFE is always present at the cellular level,often rFE"non-re sponders"are observed during joint-level voluntary contractions.Methods:We compared rFE between the joint level and single fiber level(vastus lateralis biopsies)in 16 young males.In vivo voluntary kneeextensor rFE was measured by comparing steady-state isometric torque between a stretch-hold(maximal activation at 150°,stretch to 70°,hold)and a fixed-end isometric contraction,with ultrasonographic recording of vastus lateralis fascicle length(FL).Fixed-end contractions were performed at 67.5°,70.0°,72.5°,and 75.0°;the joint angle that most closely matched FL of the stretch-hold contraction's isometric steady-state was used to calculate rFE.The starting and ending FLs of the stretch-hold contraction were expressed as%optimal FL,determined via torqueangle relationship.Resu lts:In single fiber experiments,the starting and ending fiber lengths were matched relative to optimal length determined from in vivo testing,yielding an average sarcomere excursion of~2.2-3.4μm.There was a greater magnitude of rFE at the single fiber(~20%)than joint level(~5%)(p=0.004),with"non-re sponders"only observed at the joint level.Conclusion:By comparing rFE across scales within the same participants,we show the development of the rFE non-responder phenomenon is upstream of rFE's cellular mechanisms,with rFE only lost rather than gained when scaling from single fibers to the joint level.展开更多
Geological deformations are generally attributed to compressional, extensional and strike-slip processes. Since the breakup of Gondwana, torque deformation has been responsible for the current configuration of the wes...Geological deformations are generally attributed to compressional, extensional and strike-slip processes. Since the breakup of Gondwana, torque deformation has been responsible for the current configuration of the western coasts of Africa and the eastern shore of South America and the morphotectonic geometry of the rift basins of South America, conditioning the morphostructure of the Andean chain and the current geoforms of the foreland.展开更多
In this paper,a 12/14-pole permanent magnet in-wheel motor is studied for potential in-wheel application,and the torque and loss are improved simultaneously based on designing and optimizing the corresponding dominant...In this paper,a 12/14-pole permanent magnet in-wheel motor is studied for potential in-wheel application,and the torque and loss are improved simultaneously based on designing and optimizing the corresponding dominant harmonics.The key of this study is to evaluate the contributions of harmonics on torque and loss,and further determines the harmonics related to them.Based on this,the torque enhancement factor and loss suppression factor are defined based on the selected dominant harmonics.And,the two factors are set as the optimization objectives,aiming at improving the characteristics of torque and loss.At the same time,to achieve an efficient optimization,a layered optimization method is presented,which includes magnet source layer and permeance layer.Based on the optimization,the motor torque is improved effectively,while the rotor iron loss is also reduced significantly.Then,a prototype motor is manufactured for experimental test.Finally,the simulation analysis and test results verify the validation of the studied motor and the proposed optimization method based on dominant harmonics.展开更多
Ferrimagnets are important for next-generation high-density ultrafast spintronic device applications.Magnetization compensation temperature(TM)is a fundamentally critical magnetic parameter for ferrimagnets besides th...Ferrimagnets are important for next-generation high-density ultrafast spintronic device applications.Magnetization compensation temperature(TM)is a fundamentally critical magnetic parameter for ferrimagnets besides their Curie temperature.Around TM,the spin-orbit switching efficiencies are extraordinarily high.Therefore,the accurate manipulation of TM from the material fabrication process is essential for the electrical steering of ferrimagnetic spins.In this work,CoTb thin films,with the 3 d and 4 f magnetic sublattices antiferromagnetically coupled to each other,are deposited at different temperatures.The magnetotransport and magnetic properties of these films are systematically investigated.It was found that the TM of this rare-earth ferrimagnet largely depends on the growth temperature and it can be tuned by over 100 K.Accordingly,the spins of an optimized ferrimagnetic CoTb thin film with its TM close to room temperature can be efficiently switched by the current-pulse-induced spin-orbit torque.Moreover,an artificial neural network utilizing the spin-orbit torque device was constructed,demonstrating an image recognition accuracy of approximately 92.5%,which is comparable to that of conventional software solutions.Thus,this work demonstrates the large tunability of TM of a rare earth ferrimagnet by chemical ordering and the great potential of such a ferrimagnet for electrically operated spintronic devices.展开更多
The dynamic model of the ball screw mechanism(BSM)in spatial motion,developed in Part I of the study titled‘research and experimental analysis on precision degradation of BSM at low speed’,has been validated through...The dynamic model of the ball screw mechanism(BSM)in spatial motion,developed in Part I of the study titled‘research and experimental analysis on precision degradation of BSM at low speed’,has been validated through a comparison between calculated values and experimentally measured data obtained from a comprehensive ball-screw test bench.In order to study the perform-ance parameters related to the precision degradation characteristics of ball screw under different pre-loads and speeds,the precision degradation test bench for ball screw is set up.Through the experi-ment on the ball-screw comprehensive test bench,the drag torque,stroke deviation,acceleration peak value,axial contact stiffness and other parameters of the BSM under different speeds are ob-tained,and the different preloads are obtained by the drag torque,the changing regularity of which is consistent with the simulation results.A comprehensive analysis of the experimental data reveals that the dynamic characteristics of the ball screw’s spatial motion are significantly influenced by gy-roscopic torque effects.By incorporating these parametric effects,the accuracy degradation charac-teristics of ball screw under different preloads and speeds can be well analyzed.This methodology establishes a technical foundation for investigating ball screw accuracy retention characteristics.展开更多
Accurate landing detection is crucial for humanoid robots performing high dynamic motions.Unlike common methods that rely on redundant force-torque sensors and low-precision observers to estimate landing states,this p...Accurate landing detection is crucial for humanoid robots performing high dynamic motions.Unlike common methods that rely on redundant force-torque sensors and low-precision observers to estimate landing states,this paper proposes a novel landing detection method characterized by high precision and low noise,synthesizing a learning-based Improved Momentum Observer(IMO-Net)for the ankles’external torque estimation with a Gated Recurrent Unit(GRU)-based network for state judgment.Since the movement and external torque of the ankle undergo drastic changes during high dynamic motions,achieving accurate and real-time estimation presents a challenge.To address this problem,IMO-Net employs a new Improved Momentum Observer(IMO),which does not depend on acceleration data derived from second-order differentials or friction model,and significantly reduces noise effects from sensors data and robot foot wobble.Furthermore,an Elman network is utilized to accurately calculate the ankle output torque(IMO input),significantly reducing the estimation error.Finally,leveraging IMO-Net and extensive experimental data,we developed and optimized a GRU-based landing detection network through comprehensive ablation experiments.This refined network reliably determines the robot’s landing states in real-time.The effectiveness of our methods has been validated through experiments.展开更多
The digital twin,as the decision center of the automated drilling system,incorporates physical or data-driven models to predict the system response(rate of penetration,down-hole circulating pressure,drilling torques,e...The digital twin,as the decision center of the automated drilling system,incorporates physical or data-driven models to predict the system response(rate of penetration,down-hole circulating pressure,drilling torques,etc.).Real-time drilling torque prediction aids in drilling parameter optimization,drill string stabilization,and comparing the discrepancy between observed signal and theoretical trend to detect down-hole anomalies.Due to their inability to handle huge amounts of time series data,current machine learning techniques are unsuitable for the online prediction of drilling torque.Therefore,a new way,the just-in-time learning(JITL)framework and local machine learning model,are proposed to solve the problem.The steps in this method are:(1)a specific metric is designed to measure the similarity between time series drilling data and scenarios to be predicted ahead of bit;(2)parts of drilling data are selected to train a local model for a specific prediction scenario separately;(3)the local machine learning model is used to predict drilling torque ahead of bit.Both the model data test results and the field data application results certify the advantages of the method over the traditional sliding window methods.Moreover,the proposed method has been proven to be effective in drilling parameter optimization and pipe sticking trend detection.Finally,we offer suggestions for the selection of local machine learning algorithms and real-time prediction with this approach based on the test results.展开更多
A new electrical toothed band brake is proposed based on the planetary gear shifting transmission.The corresponding mathematical model and the finite element model are established to investigate the braking dynamic ch...A new electrical toothed band brake is proposed based on the planetary gear shifting transmission.The corresponding mathematical model and the finite element model are established to investigate the braking dynamic characteristics and the stress distribution of brake components.According to the structural features and working principle of the brake,the braking process can be divided into a gap elimination stage,a sliding stage,a meshing stage,and a collision stage.The greater the initial speed of brake drum,the higher the impact torque in the collision stage,and the larger the stress of brake components.The ideal range of initial speed is 50-100 r/min,and the ultimate stress is 514 MPa appeared in the right brake band.This study present a wide range of possibilities for further investigation and application of the electrical toothed band brake.展开更多
Toroidal torques,generated by the resonant magnetic perturbation(RMP)and acting on the plasma column,are numerically systematically investigated for an ITER baseline scenario.The neoclassical toroidal viscosity(NTV),i...Toroidal torques,generated by the resonant magnetic perturbation(RMP)and acting on the plasma column,are numerically systematically investigated for an ITER baseline scenario.The neoclassical toroidal viscosity(NTV),in particular the resonant portion,is found to provide the dominant contribution to the total toroidal torque under the slow plasma flow regime in ITER.While the electromagnetic torque always opposes the plasma flow,the toroidal torque associated with the Reynolds stress enhances the plasma flow independent of the flow direction.A peculiar double-peak structure for the net NTV torque is robustly computed for ITER,as the toroidal rotation frequency is scanned near the zero value.This structure is found to be ultimately due to a non-monotonic behavior of the wave-particle resonance integral(over the particle pitch angle)in the superbanana plateau NTV regime in ITER.These findings are qualitatively insensitive to variations of a range of factors including the wall resistivity,the plasma pedestal flow and the assumed frequency of the rotating RMP field.展开更多
基金supported by a La Trobe University China studies seed-funding research grantthe NSF of China[Grant Numbers 11875040 and 11631007]。
文摘An auto-B?cklund transformation for the quad equation Q1_(1) is considered as a discrete equation,called H2^(a),which is a so called torqued version of H2.The equations H2^(a) and Q1_(1) compose a consistent cube,from which an auto-B?cklund transformation and a Lax pair for H2^(a) are obtained.More generally it is shown that auto-B?cklund transformations admit auto-Backlund transformations.Using the auto-Backlund transformation for H2^(a)we derive a seed solution and a one-soliton solution.From this solution it is seen that H2^(a) is a semi-autonomous lattice equation,as the spacing parameter q depends on m but it disappears from the plane wave factor.
基金supported by the National Natural Science Foundation of China (No. 12071432)Zhejiang Provincial Natural Science Foundation (No. LZ24A010007)。
文摘As a torqued version of the lattice potential Korteweg–de Vries equation, the H1^(a) is an integrable nonsymmetric lattice equation with only one spacing parameter. In this paper, we present the Cauchy matrix scheme for this equation. Soliton solutions, Jordan-block solutions and soliton-Jordan-block mixed solutions are constructed by solving the determining equation set. All the obtained solutions have jumping property between constant values for fixed n and demonstrate periodic structure.
基金Supported by National Natural Science Foundation of China(Grant No.51475163)National Hi-tech Research and Development Program of China(Grant No.2012AA041803).
文摘A full-face rock tunnel boring machine(TBM)has two main parameters:cutterhead thrust and cutterhead torque.Cutterhead thrust can be predicted numerically using different methods,such as the rated thrust of the disc cutter,the indentation test of the disc cutter,a linear breaking experiment,or applying statistical models based on field data.However,cutterhead torque prediction still lacks the necessary and sufficient theoretical analysis and corresponding research.Consequently,we studied the rock-breaking characteristics of the disc cutter on the cutterhead and found a difference between the lateral friction resistance and the inner and outer rock breaking.We then proposed the cutterhead torque composition of the full-face rock tunnel boring machine,shoveling and transporting ballast torque,rolling resistance torque,lateral friction resistance torque,and disc cutter lateral imbalance torque,and established the corresponding theory.Through practical engineering ver-ification,we found that the relative error between the cutterhead torque value calculated by the theory and the actual value was only 0.51%.If the lateral friction resistance moment of the disc cutter rock breaking and the lateral imbalance moment of the disc cutter are not considered,the relative error between the calculated value of cutterhead torque and the actual value is 7.48%.Therefore,the accuracy of the established cutterhead torque theory is 6.97%higher than that of the disc cutter linear rolling crushing rock test theory.The research results provide an important reference for determining the cutterhead torque of a full-face rock tunnel boring machine.
基金supported by the Beijing Natural Science Foundation(Grant No.Z230006)the National Key Research and Development Program of China(Grant No.2022YFA1204000)the National Natural Science Foundation of China(Grant Nos.12274405 and 12393831)。
文摘We report the development of the[Pt_(0.75)Ti_(0.25)/Co-Ni multilayer/Ta]_n superlattice with strong spin-orbit torque,large perpendicular magnetic anisotropy,and remarkably low switching current density.We demonstrate that the efficiency of the spin-orbit torque increases nearly linearly with the repetition number n,which is in excellent agreement with the spin Hall effect of the Pt_(0.75)Ti_(0.25)being essentially the only source of the observed spin-orbit torque.The perpendicular magnetic anisotropy field is also substantially enhanced by more than a factor of 2 as n increases from 1 to6.The[Pt_(0.75)Ti_(0.25)/Co-Ni multilayers/Ta]_n superlattice additionally exhibits deterministic,low-current-density magnetization switching despite the very large total layer thicknesses.The unique combination of strong spin-orbit torque,robust perpendicular magnetic anisotropy,low-current-density switching,and excellent high thermal stability makes the[Pt_(0.75)Ti_(0.25)/Co-Ni multilayer/Ta]_n superlattice a highly compelling material candidate for ultrafast,energy-efficient,and long-data-retention spintronic technologies.
基金Supported by National Natural Science Foundation of China(NSFC)(Grant No.52130505)Zhejiang Provincial Natural Science Foundation of China(Grant No.LD24E050005)+1 种基金Ningbo Key Scientific and Technological Project of China(Grant No.2022Z040)Academic Excellence Foundation of BUAA for PhD Students.
文摘Permanent-magnet(PM)machines are the important driving components of various mechanical equipment and industrial applications,such as robot joints,aerospace equipment,electric vehicles,actuators,wind generators and electric traction systems.The PM machines are usually expected to have high torque/power density,low torque ripple,reduced rotor mass,a large constant power speed range or strong anti-magnetization capability to match different requirements of industrial applications.The structural topology of the electric machines,including stator/rotor arrangements and magnet patterns of rotor,is one major concern to improve their electromagnetic performance.However,systematic reviews of structural topology are seldom found in literature.Therefore,the objective of this paper is to summarize the stator/rotor arrangements and magnet patterns of the permanent-magnet brushless machines,in depth.Specifically,the stator/rotor arrangements of the PM machines including radial-flux,axialflux and emerging hybrid axial-radial flux configurations are presented,and pros and cons of these topologies are discussed regarding their electromagnetic performance.The magnet patterns including various surface-mounted and interior magnet patterns,such as parallel magnetization pole pattern,Halbach arrays,spoke-type designs and their variants are summarized,and the characteristics of those magnet patterns in terms of flux-focusing effect,magnetic self-shielding effect,torque ripple,reluctance torque,magnet utilization ratio,and anti-demagnetization capability are compared.This paper can provide guidance and suggestion for the structure selection and design of PM brushless machines for high-performance industrial applications.
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(62192770,62305252,62205246,62020106009,62192771,61925504)National Key Research and Development Program of China(2023YFF0615604 and 2023YFF0613600)+6 种基金Science and Technology Commission of Shanghai Municipality(21JC1406100)Shanghai Municipal Science and Technology Major Project(2021SHZDZX0100)Science and Technology Commission of Shanghai Municipality(No.22ZR1432400)Shanghai Pilot Program for Basic Research,and Fundamental Research Funds for the Central Universities.D.P.T.acknowledges National Natural Science Foundation of China(No.62375232)University Grants Committee/Research Grants Council of the Hong Kong Special Administrative Region,China[Project No.AoE/P-502/20,CRF Project:C5031-22G and C1015-21E,GRF Project:CityU15303521CityU11305223,and Germany/Hong Kong Joint Research Scheme:GCityU101/22]City University of Hong Kong[Project No.9380131,9610628,and 7005867].
文摘In recent decades,optical micro/nano manipulation has made remarkable strides in the fields of biology and the physical sciences,benefiting from both theoretical and experimental advances in optical forces.The emergence of optical torques has further enhanced the capabilities and possibilities of optical micro/nano manipulation,opening the door to exciting new applications.In this review,we delve into the fundamentals and recent breakthroughs in the realm of optical micro/nano manipulation using optical torques.We introduce the advancements in optical manipulation based on optical torques from engineered light fields and objects,and highlight the latest developments in applying optical torques to cutting-edge physical and biological scenarios,with a special emphasis on the detection and manipulation of biological structures.Finally,we conclude by outlining our vision for the current and future directions of this field,including the integration of optical torque and micro/nano technologies,the utilization of special light fields,and the development of deeplearning-assisted optical torque design.
基金supported by the National Natural Science Foundation of China(Grant Nos.U24A6002,12174237(X.X.),52471253(F.W.),12404091(J.L.),52171183(Z.Q.))the support from the National Key Research and Development Program of China(Grant No.2022YFB3505301)+4 种基金the support from the Fund Program for the Scientific Activities of Selected Returned Overseas Professionals in Shanxi Province(Grant No.20240019)Central Government’s Special Fund for Local Science and Technology Development(Grant No.YDZJSX2024D058)the support from the Basic Research Plan of Shanxi Province(Grant No.202403021212016)the support from the Fundamental Research Program of Shanxi Province(Grant No.202403021222252)the Higher Education Science and Technology Innovation Plan Project of Shanxi(Grant No.2024L146)。
文摘The growing demand for artificial intelligence and complex computing has underscored the urgent need for advanced data storage technologies.Spin-orbit torque(SOT)has emerged as a leading candidate for high-speed,high-density magnetic random-access memory due to its ultrafast switching speed and low power consumption.This review systematically explores the generation and switching mechanisms of electron-mediated torques(including both conventional SOTs and orbital torques)and magnon-mediated torques.We discuss key materials that enable these effects:heavy metals,topological insulators,low-crystal-symmetry materials,non-collinear antiferromagnets,and altermagnets for conventional SOTs;3d,4d,and 5d transition metals for orbital torques;and antiferromagnetic insulator Ni O-and multiferroic Bi Fe O_(3)-based sandwich structures for magnon torques.We emphasize that although key components of SOT devices have been demonstrated,numerous promising materials and critical questions regarding their underlying mechanisms remain to be explored.Therefore,this field represents a dynamic and rapidly evolving frontier in spintronics,offering significant potential for advancing next-generation information storage and computational technologies.
基金supported in part by the National Natural Science Foundation of China under Grant 52125701.
文摘Compared to the conventional permanent magnet synchronous machine(PMSM),the main characteristic of permanent magnet torque machine(PMTM)with high torque is that armature current is high,which has a great influence on magnetic circuit saturation,so this paper proposes a novel analytical method(AM)considering this problem.The key of this new AM is to consider armature reaction flux and armature leakage flux,which are closely related to output torque.Firstly,the expressions,including magnetomotive force(MMF)generated by permanent magnets(PMs)and armature windings are derived,and meanwhile slotting effect is considered by planning flux path.In addition,the expression of leakage flux density generated by armature windings are calculated,and flux density equivalence coefficient of tooth is calculated to be 2/3,which is used to solve the problem of uneven saturation of each tooth.Then,based on main flux factor and leakage flux factor proposed,an improved iteration process is proposed,and by this new process,the flux density of each yoke and tooth can be obtained,which is beneficial to obtain more accurate air-gap flux density and flux linkage.Finally,a prototype of 60-pole 54-slot is fabricated,and the performances of the electric machine,such as back electromotive force(EMF)and output torque,are calculated by this new AM and finite element method(FEM).The results of FEM and experimental test show that this new AM is good enough to calculate the performance of PMTM.
基金supported by the National Key Research and Development Program of China (Grant No.2022YFA1204000)partly by the National Natural Science Foundation of China (Grant Nos.12274405,12304155,and 12393831)the Beijing Natural Science Foundation (Grant No.Z230006)。
文摘Accurate quantification of the spin–orbit torques(SOTs) is critical for the identification and applications of new spin-orbitronic effects. One of the most popular techniques to quantify the SOTs is the “switching angle shift”, where the applied direct current is assumed to shift, via domain wall depinning during anti-domain expansion, the switching angle of a perpendicular magnetization in a linear proportional manner under a large rotating magnetic field. Here, we report that, for the most commonly employed perpendicular magnetization heterostructures in spintronics(e.g., those based on FeCoB, Co, and Co/Ni multilayers), the switching angle shift considerably misestimates the SOT within the domain wall depinning analysis of the slope of linear-in-current scaling and may also have a non-zero residual value at zero direct current. Our experiments and simulations unveil that the switching angle shift is most likely dominated by chiral asymmetric nucleation rather than expansion of anti-domains. The in-plane field from external magnets and current-induced SOTs lowers the perpendicular nucleation field and thus reduces the required switching angle, ultimately leading to an underestimation of SOTs by domain wall depinning analysis. These results have advanced our understanding of magnetization switching in spintronic devices.
基金supported by the National Natural Science Foundations of China(Grant Nos.52205047,52175037)Frontier Cross Project of Beijing Institute of Technology(Grant No.2024CX11006)。
文摘Armored vehicles,to accomplish missions in complex harsh conditions with high mobility,require the transmission system to achieve high energy density and high reliability.The wet multi-disc clutch becomes the perishable component under heavy load,large speed difference,and frequent engagement.Due to the difficulty of maintenance in battlefield,clutch carrying post-buckling separate plate is common,and the clutch working process is obstructed.Therefore,considering the post-buckling plate,the multi-physics thermodynamic model of a wet multi-disc clutch is established to describe the entire engagement and separation process.The influence of the buckling degree on the stress-strain,uniformity of gaps,torque,and temperature characteristics is investigated by the numerical method and testified by bench tests.The results show that with the increasing buckling degree,the clutch engagement and separation times decrease gradually.For the separation process,the non-uniformity of gaps is increased,and gaps are eventually occupied,leading to the continuous rough contact among friction pairs.Therefore,the drag torque is increased.Squeezed by the post-buckling plate,the cooling rates of separate plates are decreased.During repeated engagement-separation,temperatures of plates may reach balance points.Since continuous sliding and temperature concentration,the wear form and degree changes,especially at outer radius.Extra drag torque,heat,and wear threats the friction components which increases the risk of failures of the transmission system and affects the mobility of armored vehicles.
基金supported by the Natural Sciences and Engineering Research Council of Canada(NSERC,Grant No.RGPIN-2024-03782).
文摘Background:Residual force enhancement(rFE),defined as increased isometric force following active lengthening compared to a fixed-end isometric contraction at the same muscle length and level of activation,is present across all scales of muscle.While rFE is always present at the cellular level,often rFE"non-re sponders"are observed during joint-level voluntary contractions.Methods:We compared rFE between the joint level and single fiber level(vastus lateralis biopsies)in 16 young males.In vivo voluntary kneeextensor rFE was measured by comparing steady-state isometric torque between a stretch-hold(maximal activation at 150°,stretch to 70°,hold)and a fixed-end isometric contraction,with ultrasonographic recording of vastus lateralis fascicle length(FL).Fixed-end contractions were performed at 67.5°,70.0°,72.5°,and 75.0°;the joint angle that most closely matched FL of the stretch-hold contraction's isometric steady-state was used to calculate rFE.The starting and ending FLs of the stretch-hold contraction were expressed as%optimal FL,determined via torqueangle relationship.Resu lts:In single fiber experiments,the starting and ending fiber lengths were matched relative to optimal length determined from in vivo testing,yielding an average sarcomere excursion of~2.2-3.4μm.There was a greater magnitude of rFE at the single fiber(~20%)than joint level(~5%)(p=0.004),with"non-re sponders"only observed at the joint level.Conclusion:By comparing rFE across scales within the same participants,we show the development of the rFE non-responder phenomenon is upstream of rFE's cellular mechanisms,with rFE only lost rather than gained when scaling from single fibers to the joint level.
文摘Geological deformations are generally attributed to compressional, extensional and strike-slip processes. Since the breakup of Gondwana, torque deformation has been responsible for the current configuration of the western coasts of Africa and the eastern shore of South America and the morphotectonic geometry of the rift basins of South America, conditioning the morphostructure of the Andean chain and the current geoforms of the foreland.
文摘In this paper,a 12/14-pole permanent magnet in-wheel motor is studied for potential in-wheel application,and the torque and loss are improved simultaneously based on designing and optimizing the corresponding dominant harmonics.The key of this study is to evaluate the contributions of harmonics on torque and loss,and further determines the harmonics related to them.Based on this,the torque enhancement factor and loss suppression factor are defined based on the selected dominant harmonics.And,the two factors are set as the optimization objectives,aiming at improving the characteristics of torque and loss.At the same time,to achieve an efficient optimization,a layered optimization method is presented,which includes magnet source layer and permeance layer.Based on the optimization,the motor torque is improved effectively,while the rotor iron loss is also reduced significantly.Then,a prototype motor is manufactured for experimental test.Finally,the simulation analysis and test results verify the validation of the studied motor and the proposed optimization method based on dominant harmonics.
基金financial support from the National Key R&D Program of China(Nos.2022YFB3506000 and 2022YFA1602700)financial support from Fundamental Research Funds for the Central Universities+6 种基金financial support from the National Natural Science Foundation of China(Nos.52425106,52121001,and 52271235)financial support from the Beijing Natural Science Foundation(No.JQ23005)financial support from the National Natural Science Foundation of China(No.52401300)funding from the China National Postdoctoral Program for Innovative Talents(No.BX20230451)from the China Postdoctoral Science Foundation(No.2024M754058)financial support from the National Natural Science Foundation of China(No.62401276)financial support from the National Natural Science Foundation of China(No.524B2003).
文摘Ferrimagnets are important for next-generation high-density ultrafast spintronic device applications.Magnetization compensation temperature(TM)is a fundamentally critical magnetic parameter for ferrimagnets besides their Curie temperature.Around TM,the spin-orbit switching efficiencies are extraordinarily high.Therefore,the accurate manipulation of TM from the material fabrication process is essential for the electrical steering of ferrimagnetic spins.In this work,CoTb thin films,with the 3 d and 4 f magnetic sublattices antiferromagnetically coupled to each other,are deposited at different temperatures.The magnetotransport and magnetic properties of these films are systematically investigated.It was found that the TM of this rare-earth ferrimagnet largely depends on the growth temperature and it can be tuned by over 100 K.Accordingly,the spins of an optimized ferrimagnetic CoTb thin film with its TM close to room temperature can be efficiently switched by the current-pulse-induced spin-orbit torque.Moreover,an artificial neural network utilizing the spin-orbit torque device was constructed,demonstrating an image recognition accuracy of approximately 92.5%,which is comparable to that of conventional software solutions.Thus,this work demonstrates the large tunability of TM of a rare earth ferrimagnet by chemical ordering and the great potential of such a ferrimagnet for electrically operated spintronic devices.
基金Supported by the National Natural Science Foundation of China(No.51575014,51505020)the Key Foundation Project of China Academy of Railway Sciences(No.2021YJ200).
文摘The dynamic model of the ball screw mechanism(BSM)in spatial motion,developed in Part I of the study titled‘research and experimental analysis on precision degradation of BSM at low speed’,has been validated through a comparison between calculated values and experimentally measured data obtained from a comprehensive ball-screw test bench.In order to study the perform-ance parameters related to the precision degradation characteristics of ball screw under different pre-loads and speeds,the precision degradation test bench for ball screw is set up.Through the experi-ment on the ball-screw comprehensive test bench,the drag torque,stroke deviation,acceleration peak value,axial contact stiffness and other parameters of the BSM under different speeds are ob-tained,and the different preloads are obtained by the drag torque,the changing regularity of which is consistent with the simulation results.A comprehensive analysis of the experimental data reveals that the dynamic characteristics of the ball screw’s spatial motion are significantly influenced by gy-roscopic torque effects.By incorporating these parametric effects,the accuracy degradation charac-teristics of ball screw under different preloads and speeds can be well analyzed.This methodology establishes a technical foundation for investigating ball screw accuracy retention characteristics.
基金supported in part by the Beijing Natural Science Foundation under Grant L243004in part by the National Natural Science Foundation of China under Grant 62073041in part by the“111”Project under Grant B08043.
文摘Accurate landing detection is crucial for humanoid robots performing high dynamic motions.Unlike common methods that rely on redundant force-torque sensors and low-precision observers to estimate landing states,this paper proposes a novel landing detection method characterized by high precision and low noise,synthesizing a learning-based Improved Momentum Observer(IMO-Net)for the ankles’external torque estimation with a Gated Recurrent Unit(GRU)-based network for state judgment.Since the movement and external torque of the ankle undergo drastic changes during high dynamic motions,achieving accurate and real-time estimation presents a challenge.To address this problem,IMO-Net employs a new Improved Momentum Observer(IMO),which does not depend on acceleration data derived from second-order differentials or friction model,and significantly reduces noise effects from sensors data and robot foot wobble.Furthermore,an Elman network is utilized to accurately calculate the ankle output torque(IMO input),significantly reducing the estimation error.Finally,leveraging IMO-Net and extensive experimental data,we developed and optimized a GRU-based landing detection network through comprehensive ablation experiments.This refined network reliably determines the robot’s landing states in real-time.The effectiveness of our methods has been validated through experiments.
基金support from the Natural Science Foundation of China(Grant numbers:U23B6010 and 52122401).
文摘The digital twin,as the decision center of the automated drilling system,incorporates physical or data-driven models to predict the system response(rate of penetration,down-hole circulating pressure,drilling torques,etc.).Real-time drilling torque prediction aids in drilling parameter optimization,drill string stabilization,and comparing the discrepancy between observed signal and theoretical trend to detect down-hole anomalies.Due to their inability to handle huge amounts of time series data,current machine learning techniques are unsuitable for the online prediction of drilling torque.Therefore,a new way,the just-in-time learning(JITL)framework and local machine learning model,are proposed to solve the problem.The steps in this method are:(1)a specific metric is designed to measure the similarity between time series drilling data and scenarios to be predicted ahead of bit;(2)parts of drilling data are selected to train a local model for a specific prediction scenario separately;(3)the local machine learning model is used to predict drilling torque ahead of bit.Both the model data test results and the field data application results certify the advantages of the method over the traditional sliding window methods.Moreover,the proposed method has been proven to be effective in drilling parameter optimization and pipe sticking trend detection.Finally,we offer suggestions for the selection of local machine learning algorithms and real-time prediction with this approach based on the test results.
基金funded by the National Natural Science Foundation of China(Nos.52205047,52175037)China Postdoctoral Science Foundation(No.2021M700422)Beijing Key Laboratory Foundation(No.KF20212223201).
文摘A new electrical toothed band brake is proposed based on the planetary gear shifting transmission.The corresponding mathematical model and the finite element model are established to investigate the braking dynamic characteristics and the stress distribution of brake components.According to the structural features and working principle of the brake,the braking process can be divided into a gap elimination stage,a sliding stage,a meshing stage,and a collision stage.The greater the initial speed of brake drum,the higher the impact torque in the collision stage,and the larger the stress of brake components.The ideal range of initial speed is 50-100 r/min,and the ultimate stress is 514 MPa appeared in the right brake band.This study present a wide range of possibilities for further investigation and application of the electrical toothed band brake.
基金funded by National Natural Science Foundation of China(NSFC)(Nos.12075053,11505021 and 11975068)by National Key R&D Program of China(No.2022YFE 03060002)+1 种基金by Fundamental Research Funds for the Central Universities(No.2232024G-10)supported by the U.S.DoE Office of Science(No.DE-FG02–95ER54309)。
文摘Toroidal torques,generated by the resonant magnetic perturbation(RMP)and acting on the plasma column,are numerically systematically investigated for an ITER baseline scenario.The neoclassical toroidal viscosity(NTV),in particular the resonant portion,is found to provide the dominant contribution to the total toroidal torque under the slow plasma flow regime in ITER.While the electromagnetic torque always opposes the plasma flow,the toroidal torque associated with the Reynolds stress enhances the plasma flow independent of the flow direction.A peculiar double-peak structure for the net NTV torque is robustly computed for ITER,as the toroidal rotation frequency is scanned near the zero value.This structure is found to be ultimately due to a non-monotonic behavior of the wave-particle resonance integral(over the particle pitch angle)in the superbanana plateau NTV regime in ITER.These findings are qualitatively insensitive to variations of a range of factors including the wall resistivity,the plasma pedestal flow and the assumed frequency of the rotating RMP field.
