This study focuses on permanent surface dislocations caused by a strike-slip fault in an alluvial valley.A twodimensional mathematical model is utilized,considering the valley to have a half-cylindrical shape.The vall...This study focuses on permanent surface dislocations caused by a strike-slip fault in an alluvial valley.A twodimensional mathematical model is utilized,considering the valley to have a half-cylindrical shape.The valley medium is assumed to be isotropic,linear elastic and nonhomogeneous,such that the shear modulus of the valley has spatial dependency.The valley is surrounded by an isotropic,linear elastic and homogeneous half-space.A strike-slip fault is located at the intersection between the valley and the half-space.The problem is solved analytically by using finite Fourier transform.Displacement functions are obtained in closed-form,in terms of power series and hypergeometric function series.Unknown coefficients of these series are determined from the boundary conditions,leading to an analytical exact solution.Numerical results indicate that the nonhomogeneity of the alluvial valley material has a limited impact on permanent surface dislocations unless there is a significant variation in the material properties within the functionally graded zone.In many cases,approximating the nonhomogeneous alluvial valley as a homogeneous medium is suitable.展开更多
Alloying with transition metal elements akin to Sm(CoFeCuZr)z can effectively enhance the magnetic properties of SmCo-based permanent magnets.However,the effects of transition metals doping on its magnetic properties,...Alloying with transition metal elements akin to Sm(CoFeCuZr)z can effectively enhance the magnetic properties of SmCo-based permanent magnets.However,the effects of transition metals doping on its magnetic properties,detailed atomic occupancy and the mechanism for structural stability remain unclear.Specifically,for SmCo3 magnets,there is minimal theoretical study available.Herein,based on first-principles calculations,we systematically investigated the influence of 3d transition metals(TMs)doping on the structural stability,magnetic properties and electronic characteristics of SmCo3 magnets.Our results show that Sc,Ti,V,Fe,Ni,Cu and Zn preferentially occupy the 18h lattice site,while Cr and Mn occupy the 3b and 6c lattice sites,respectively.Doping with Ti,Cr,Mn,Fe,Ni,Cu and Zn contributes to enhancing the stability of SmCo3,whereas the doping of Sc and V adversely affects structural stability.The magnetic calculations reveal that Cr,Mn and Fe doping significantly enhances the total magnetic moment.It is also found that lower concentrations of Cr doping can significantly enhance the magnetocrystalline anisotropy energy(MAE).More intriguingly,when the doping concentrations of Sc,Ni and Cu reach 14.81 at%,22.22 at%and 22.22 at%,respectively,the magnetic easy axis of the system shifts from out-of-plane to in-plane.The optimal doping concentration of Fe in the SmCo_(3) system is determined to be 37.04 at%.The Curie temperature of pure SmCo_(3) is 483.9 K.Our theoretical study offers valuable theoretical guidance for experimental exploration toward SmCo-based permanent magnets with higher performance.展开更多
Permanent magnet synchronous motor(PMSM),known for their compact size and high-power density,is widely used in fields such as electric vehicles and servo drives.However,traditional PID control methods for PMSM cannot ...Permanent magnet synchronous motor(PMSM),known for their compact size and high-power density,is widely used in fields such as electric vehicles and servo drives.However,traditional PID control methods for PMSM cannot dynamically adjust parameters according to varying operating conditions.To address this issue,this paper proposes a PID control method based on a radial basis function(RBF)neural network,which adaptively tunes the PID controller parameters.First,an offline RBF neural network with optimal structural parameters is trained using the current and speed data of the PMSM,and then employed to construct the RBF-PID controller.During online training,the Jacobian information calculated via the RBF neural network is used to adaptively adjust the PID parameters.Simultaneously,the structural parameters of the RBF network are updated in reverse based on the error between the predicted and reference speed values.Finally,numerical simulations and experiments in the context of electric vehicle drive control show that the maximum speed errors of the SMC controller and the RBF-PID controller are 1.97 km/h and 0.17 km/h,respectively.Moreover,the RBF-PID controller outperforms both the SMC and traditional PID controllers in handling sudden speed changes.展开更多
This paper introduces a novel chattering-free terminal sliding mode control(SMC)strategy to address chaotic behavior in permanent magnet synchronous generators(PMSG)for offshore wind turbine systems.By integrating an ...This paper introduces a novel chattering-free terminal sliding mode control(SMC)strategy to address chaotic behavior in permanent magnet synchronous generators(PMSG)for offshore wind turbine systems.By integrating an adaptive exponential reaching law with a continuous barrier function,the proposed approach eliminates chattering and ensures robust performance under model uncertainties.The methodology combines adaptive SMC with dynamic switching to estimate and compensates for unknown uncertainties,providing smooth and stable control.Finally,the performance and effectiveness of the proposed approach are compared with those of a previous study.展开更多
BACKGROUND Autoimmune myocarditis(AM)associated with autoimmune diseases can cause complete atrioventricular block(CAVB),but the related autoantigens and the underlying mechanisms are unclear.Anti-SSA/Ro antibodies ma...BACKGROUND Autoimmune myocarditis(AM)associated with autoimmune diseases can cause complete atrioventricular block(CAVB),but the related autoantigens and the underlying mechanisms are unclear.Anti-SSA/Ro antibodies may play an important role in this process,but cases of AM with positive anti-SSA/Ro antibodies are rare.In addition,arrhythmias,such as atrioventricular block,are very common in patients with autoimmune diseases,but severe atrioventricular block requiring permanent pacemaker implantation is extremely rare.CASE SUMMARY The patient in this case had AM with anti-SSA/Ro antibody positivity,which was associated with connective tissue disease,and the patient subsequently developed CAVB.After intensive immunosuppressive therapy,the antibody test results became negative,and pulmonary hypertension significantly improved.However,the outcome of permanent pacemaker implantation did not change.CONCLUSION In clinical practice,the awareness of adult AM associated with autoimmune diseases combined with CAVB should be strengthened in clinicians,and anti-SSA/Ro antibodies may play a role in this process.Therefore,improving the detection of antibodies and early intervention,such as active immunosuppression therapy,may be very important for improving disease prognosis.For patients who do not respond to immunosuppressive therapy,implantation of a permanent pacemaker may become an essential treatment option.展开更多
Objective:To investigate the distribution of health literacy(HL)levels and the association of HL with proactive personality in patients with permanent colostomy.Methods:A cross-sectional study was conducted to measure...Objective:To investigate the distribution of health literacy(HL)levels and the association of HL with proactive personality in patients with permanent colostomy.Methods:A cross-sectional study was conducted to measure proactive personality and HL using validated scales.A total of 172 patients with permanent colostomy were selected from January 2021 to May 2022 in Yantai City,China.Descriptive statistics,t-test,ANOVA,Pearson correlation analysis,and multiple linear regression analysis techniques were used.Results:The results obtained from the study showed that the HL status of the participants was moderate.The correlation between participants’total HL scores and proactive personality scores was 0.417(P-value<0.001).In addition,HL showed statistically significant differences according to education level,place of residence,profession,and average monthly household income.Conclusions:This study showed that patients with higher proactive personality scores had higher HL.The key stakeholders require several positive strategies to improve the HL of patients with permanent colostomy by cultivating their proactive personalities,and these important policies will help to improve patient health and quality of life.展开更多
Micro/nanorobots have significant potential applications in biomedicine.However,their small size and the need for intricate control make long-distance navigation of microswarms composed of such robots challenging in c...Micro/nanorobots have significant potential applications in biomedicine.However,their small size and the need for intricate control make long-distance navigation of microswarms composed of such robots challenging in complex environments.To address this problem,we have developed a permanent-magnet-actuated microswarm navigation system to achieve precise control of micro/nanorobots in complex fluid environments.The controlled microswarm is composed of monodisperse Fe_(3)O_(4)@PVP nanoclusters synthesized using the polyol method.These nanoclusters can self-assemble into highly controllable microswarm structures under a rotating magnetic field and are then guided by the robotic system for precise navigation.The system uses visual positioning and motion control to enable real-time dynamic navigation.In experiments,it successfully performed autonomous navigation over a 55 mm distance in a transparent channel,with flow rates ranging from 0 to 10 mm/s.It completed the task in 132 s at an average speed of over 0.45 mm/s,with an average trajectory tracking error of only 0.28 mm.These results demonstrate excellent path accuracy and stability under various flow rate conditions,validating the system’s adaptability and efficiency in fluid environments and highlighting its potential for biomedical applications.This study offers a robust and versatile platform for expanding micro/nanorobot applications in biomedicine.展开更多
Collapses of seismic slopes demonstrate the characteristics of three-dimensional(3D)shapes.Conducting a 3D analysis of seismic slope stability is more complicated than doing a simplified two-dimensional(2D)analysis.Th...Collapses of seismic slopes demonstrate the characteristics of three-dimensional(3D)shapes.Conducting a 3D analysis of seismic slope stability is more complicated than doing a simplified two-dimensional(2D)analysis.The upper-bound solutions derived from limit analysis of seismic slopes using the pseudo-static method are used to generate an approximate solution for the factor of 3D safety through regression analysis.Such a solution can degenerate to a 2D result when the slope width tends to infinity.The approximation method also can be extended for determining the permanent displacements of 3D slopes under seismic loading.The method is non-iterative and relatively accurate through comparisons with analytical results.Involving stochastic ground motions could easily be used to assess the distribution of permanent displacement that is induced in 3D slopes.展开更多
A new flow control technology in continuous casting process named permanent magnet flow control-mold(PMFC-Mold)was proposed,in which the permanent magnets are arranged in Halbach array near the narrow region of the mo...A new flow control technology in continuous casting process named permanent magnet flow control-mold(PMFC-Mold)was proposed,in which the permanent magnets are arranged in Halbach array near the narrow region of the mold.The behavior of molten steel flow and the fluctuation of molten steel/slag interface in the PMFC-Mold under different continuous casting speeds were investigated.Firstly,a physical experiment of liquid Ga-In-Sn alloy circulating flow was carried out in Perspex mold with Halbach’s permanent magnets(HPMs)to investigate the magnetic field distribution of HPMs and its impactful electromagnetic braking effect.The numerical simulation of 1450 mm×230 mm slab shows that a stronger magnetic field over 0.3-0.625 T is formed at the wide surface and the narrow surface of the mold,which provides an effective electromagnetic braking for controlling the impingement of molten steel jet and suppressing the fluctuation of molten steel/slag interface.The numerical simulation results show that in the PMFC-Mold,the region with the turbulent kinetic energy greater than 0.01 and 0.04 m^(2)s^(-2)on the upper backflow zone and near the narrow surface of the mold are significantly reduced.The maximum turbulent kinetic energy of the submerged entry nozzle(SEN)jet in front of the narrow surface is significantly reduced,and the SEN jet moves downward before impacting the narrow surface of the mold.In the PMFC-Mold,the region with the surface velocity greater than 0.2 m s^(-1)on the steel/slag interface is eliminated,the flow pattern and fluctuation profiles on the molten steel/slag interface become regular on both sides of SEN,and the vortex near SEN disappears.The maximum fluctuation height of molten steel/slag interface is controlled below 2.59 and 5.40 mm corresponding to the casting speed of 1.6 and 2.0 m min-1,respectively.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
Linear flux-switching permanent magnet motors(LFSPMs) have been proposed for long stator applications such as rail transit. However, the conventional linear permanent magnet synchronous motor(LPMSM) suffers from thrus...Linear flux-switching permanent magnet motors(LFSPMs) have been proposed for long stator applications such as rail transit. However, the conventional linear permanent magnet synchronous motor(LPMSM) suffers from thrust ripple, which degrades the motor performance. The thrust ripple in LFSPMs is mainly caused by detent force and asymmetric electromagnetic parameters, excluding external disturbances. Moreover, the 12/13 slot-pole LFSPM exhibits unique inductance characteristics, which lead to different effects on thrust ripple. First, the detent force in the LFSPM is analyzed through finite element method(FEM). In addition, new finite element(FE) models are proposed for further analysis of the cogging force in LFSPMs. Second, the unique inductance characteristics of the 12/13 slot-pole LFSPM are investigated, and then the thrust ripple caused by asymmetric electromagnetic parameters is calculated by the virtual displacement method. Third, the mathematical model considering the thrust ripple is established for the LFSPM, which provides a foundation for subsequent research on thrust ripple suppression control strategies. Finally, the thrust ripple analysis is validated by comparing FEM results, modeling simulations, and experimental data.展开更多
The rapid development of magnetic materials provides the possibility for the application of permanent magnet stirring(PMS).Numerical and experimental investigations were employed with respect to the solidification pro...The rapid development of magnetic materials provides the possibility for the application of permanent magnet stirring(PMS).Numerical and experimental investigations were employed with respect to the solidification process of the Al—2Sc alloy controlled by a novel PMS using NdFeB permanent magnets under various rotation speeds(0,50,100 and 150 r/min).The simulated results reveal that the maximum electromagnetic force increases proportionally from 4.14 to 12.39 kN/m^(3)and the maximum tangential velocity increases from 0.13 to 0.36 m/s when the rotation speed of PMS enhances from 50 to 150 r/min in the ingot melt.Besides,the experimental results demonstrate that PMS can achieve a uniform distribution of blocky Al_(3)Sc precipitated phase in the longitudinal direction under the impact of a forced fluid flow.Moreover,increasing rotation speed of PMS is beneficial to refining aluminum grain size significantly and decreasing the texture intensity in the alloy.In addition,the Brinell hardness of Al-2Sc alloy is increased by 33%to 27.8 HB and the tensile strength is enhanced by 34%-128.2 MPa,due to the improved distribution of the strengthening Al_(3)SC phase and the grain refinement of Al matrix under the impact of PMS.This work provides an effective application of NdFeB permanent magnets in the metal cast field.展开更多
The axial field hybrid permanent magnet memory machine(AFHPM-MM)employs a hybrid permanent magnet excitation combining NdFeB and AlNiCo,achieving high torque density and a wide flux adjustment range.A separated stator...The axial field hybrid permanent magnet memory machine(AFHPM-MM)employs a hybrid permanent magnet excitation combining NdFeB and AlNiCo,achieving high torque density and a wide flux adjustment range.A separated stator structure is adopted to enhance its antidemagnetization capability.To analyze the contributions of AlNiCo and NdFeB to the induced electromotive force(EMF)in the AFHPM-MM,a frozen permeability-based induced EMF calculation method is proposed.Theoretical analysis reveals that the conventional method exhibits substantial errors in calculating the AlNiCo-induced EMF,primarily attributed to its failure to adequately account for the dynamic magnetization characteristic discrepancies of AlNiCo under varying magnetization states.Through the analysis of magnetization variations in AlNiCo during the flux adjustment process under different magnetization states,an improved induced EMF calculation method is proposed.Comparative results indicate that,during the flux enhancement process,the average calculation error of the AlNiCo-induced EMF is reduced from 19.84%to 2.09%,whereas during the flux weakening process,the error is reduced from 3.87%to 1.67%.The proposed method achieves accurate induced EMF calculation for the AFHPM-MM.展开更多
The coupling effect of dual-parallel rotor connected stator permanent magnet synchronous motor not only affects the magnetic field in the coupling area, but also generates an additional magnetic field in the uncoupled...The coupling effect of dual-parallel rotor connected stator permanent magnet synchronous motor not only affects the magnetic field in the coupling area, but also generates an additional magnetic field in the uncoupled area.The characteristics of the additional magnetic field and its influence on electromagnetic torque are studied in this paper.The topology and parameters of motor are described briefly.The existence of additional magnetic field is proved by the simulation models under two boundary conditions, and its characteristics and source are analyzed. The analytical model is established, and the influence of key parameters on the additional magnetic field is discussed. On this basis, the influence of the additional magnetic field on the electromagnetic torque of the motor is studied, and the analytical expression of the additional torque is constructed.The fluctuation rule is analyzed, and the additional magnetic field separation model is proposed. The theoretical analysis and simulation results reveal and improve the internal mechanism of reducing motor torque ripple by optimizing the duty angle and coupling distance. Finally, a prototype test platform is built to verify the correctness of the proposed theory and the accuracy of the simulation model.展开更多
Previous studies have demonstrated that increasing Fe doping content can enhance the saturation magnetization and maximum energy product of 2:17-type Sm-Co rare-earth permanent magnets.Howeve r,syste matic theo retica...Previous studies have demonstrated that increasing Fe doping content can enhance the saturation magnetization and maximum energy product of 2:17-type Sm-Co rare-earth permanent magnets.Howeve r,syste matic theo retical calculations and the effects of other transition metal dopants have yet to be explored.This study employed first-principles computational methods to investigate the effects of doping with 3d and Zr transition metal elements on the structural stability,magnetic properties,and electronic structure of Sm_(2)Co_(17)permanent magnets.The results indicate that Sc and Zr tend to occupy the Sm-6c site,while Ni,Cu and Zn preferentially occupy the 18h site,and Ti,V,Cr,Mn and Fe primarily occupy the Co-6c site.Except for V and Cu,all other elements effectively improve the structural stability of the doped systems.Additionally,Mn and Fe doping can significantly enhance the total magnetic moment and magnetocrystalline anisotropy energies of the Sm_(2)Co_(17)system,while Cr only increases the total magnetic moment.More importantly,doping with Cr,Mn and Fe within the doping co ntent range of9.8 at%<x<35.29 at% can simultaneously improve the structural stability,total magnetic moment and magnetocrystalline anisotropy energy of the Sm_(2)Co_(17) system.Our study provides valuable theoretical guidance for experimental exploration and is expected to promote the development and application of novel rare-earth permanent magnetic materials.展开更多
To address the issue of increased electromagnetic vibration in permanent magnet(PM) motors for electric vehicles under flux-weakening speed extension operation, this paper proposes a low-vibration design method for PM...To address the issue of increased electromagnetic vibration in permanent magnet(PM) motors for electric vehicles under flux-weakening speed extension operation, this paper proposes a low-vibration design method for PM motors from the perspective of saliency ratio. First, by establishing a theoretical model for vibration analysis under flux-weakening operation, it reveals the vibration mechanism whereby high-order armature magnetomotive force(ARM-MMF) harmonics under fluxweakening operation leads to enhanced radial electromagnetic force(REF). Second, an in-depth investigation into the intrinsic relationship between saliency ratio and ARM-MMF is conducted. This study proposes a novel methodology to design key ARM-MMF harmonics that induce significant electromagnetic vibration from the perspective of the saliency ratio. An innovative rotor topology featuring elliptical-arc composite flux barriers is developed to implement this approach. Furthermore, and synergistic optimization is performed with the saliency ratio and torque as optimization objectives to balance vibration suppression and torque output performance. Finally, a prototype is manufactured and tested. Both theoretical and experimental analyses validated the effectiveness of the motor and the proposed design method.展开更多
Permanently shadowed regions(PSRs)on the Moon are potential reservoirs for water ice,making them hot spots for future lunar exploration.The water ice in PSRs would cause distinctive changes in space weathering there,i...Permanently shadowed regions(PSRs)on the Moon are potential reservoirs for water ice,making them hot spots for future lunar exploration.The water ice in PSRs would cause distinctive changes in space weathering there,in particular reduction-oxidation processes that diff er from those in illuminated regions.To determine the characteristics of products formed during space weathering in PSRs,the lunar meteorite NWA 10203 with artifi cially added water was irradiated with a nanosecond laser to simulate a micro-meteorite bombardment of lunar soil containing water ice.The TEM results of the water-incorporated sample showed distinct amorphous rims that exhibited irregular thickness,poor stratifi cation,the appearance of bubbles,and a reduced number of npFe^(0).Additionally,EELS analysis showed the presence of ferric iron at the rim of the nanophase metallic iron particles(npFe^(0))in the amorphous rim with the involvement of water.The results suggest that water ice is another possible factor contributing to oxidation during micrometeorite bombardment on the lunar surface.In addition,it off ers a reference for a new space weathering model that incorporates water in PSRs,which could be widespread on asteroids with volatiles.展开更多
Permanent magnet synchronous motor(PMSM)is widely used in alternating current servo systems as it provides high eficiency,high power density,and a wide speed regulation range.The servo system is placing higher demands...Permanent magnet synchronous motor(PMSM)is widely used in alternating current servo systems as it provides high eficiency,high power density,and a wide speed regulation range.The servo system is placing higher demands on its control performance.The model predictive control(MPC)algorithm is emerging as a potential high-performance motor control algorithm due to its capability of handling multiple-input and multipleoutput variables and imposed constraints.For the MPC used in the PMSM control process,there is a nonlinear disturbance caused by the change of electromagnetic parameters or load disturbance that may lead to a mismatch between the nominal model and the controlled object,which causes the prediction error and thus affects the dynamic stability of the control system.This paper proposes a data-driven MPC strategy in which the historical data in an appropriate range are utilized to eliminate the impact of parameter mismatch and further improve the control performance.The stability of the proposed algorithm is proved as the simulation demonstrates the feasibility.Compared with the classical MPC strategy,the superiority of the algorithm has also been verified.展开更多
文摘This study focuses on permanent surface dislocations caused by a strike-slip fault in an alluvial valley.A twodimensional mathematical model is utilized,considering the valley to have a half-cylindrical shape.The valley medium is assumed to be isotropic,linear elastic and nonhomogeneous,such that the shear modulus of the valley has spatial dependency.The valley is surrounded by an isotropic,linear elastic and homogeneous half-space.A strike-slip fault is located at the intersection between the valley and the half-space.The problem is solved analytically by using finite Fourier transform.Displacement functions are obtained in closed-form,in terms of power series and hypergeometric function series.Unknown coefficients of these series are determined from the boundary conditions,leading to an analytical exact solution.Numerical results indicate that the nonhomogeneity of the alluvial valley material has a limited impact on permanent surface dislocations unless there is a significant variation in the material properties within the functionally graded zone.In many cases,approximating the nonhomogeneous alluvial valley as a homogeneous medium is suitable.
基金supported by the National Key Research and Development Program of China(No.2022YFB3505301)the National Key Research and Development Program of Shanxi Province(No.202302050201014)+2 种基金the National Natural Science Foundation of China(No.12304148)the Natural Science Basic Research Program of Shanxi Province(No.202203021222219)the China Postdoctoral Science Foundation(No.2023M731452).
文摘Alloying with transition metal elements akin to Sm(CoFeCuZr)z can effectively enhance the magnetic properties of SmCo-based permanent magnets.However,the effects of transition metals doping on its magnetic properties,detailed atomic occupancy and the mechanism for structural stability remain unclear.Specifically,for SmCo3 magnets,there is minimal theoretical study available.Herein,based on first-principles calculations,we systematically investigated the influence of 3d transition metals(TMs)doping on the structural stability,magnetic properties and electronic characteristics of SmCo3 magnets.Our results show that Sc,Ti,V,Fe,Ni,Cu and Zn preferentially occupy the 18h lattice site,while Cr and Mn occupy the 3b and 6c lattice sites,respectively.Doping with Ti,Cr,Mn,Fe,Ni,Cu and Zn contributes to enhancing the stability of SmCo3,whereas the doping of Sc and V adversely affects structural stability.The magnetic calculations reveal that Cr,Mn and Fe doping significantly enhances the total magnetic moment.It is also found that lower concentrations of Cr doping can significantly enhance the magnetocrystalline anisotropy energy(MAE).More intriguingly,when the doping concentrations of Sc,Ni and Cu reach 14.81 at%,22.22 at%and 22.22 at%,respectively,the magnetic easy axis of the system shifts from out-of-plane to in-plane.The optimal doping concentration of Fe in the SmCo_(3) system is determined to be 37.04 at%.The Curie temperature of pure SmCo_(3) is 483.9 K.Our theoretical study offers valuable theoretical guidance for experimental exploration toward SmCo-based permanent magnets with higher performance.
文摘Permanent magnet synchronous motor(PMSM),known for their compact size and high-power density,is widely used in fields such as electric vehicles and servo drives.However,traditional PID control methods for PMSM cannot dynamically adjust parameters according to varying operating conditions.To address this issue,this paper proposes a PID control method based on a radial basis function(RBF)neural network,which adaptively tunes the PID controller parameters.First,an offline RBF neural network with optimal structural parameters is trained using the current and speed data of the PMSM,and then employed to construct the RBF-PID controller.During online training,the Jacobian information calculated via the RBF neural network is used to adaptively adjust the PID parameters.Simultaneously,the structural parameters of the RBF network are updated in reverse based on the error between the predicted and reference speed values.Finally,numerical simulations and experiments in the context of electric vehicle drive control show that the maximum speed errors of the SMC controller and the RBF-PID controller are 1.97 km/h and 0.17 km/h,respectively.Moreover,the RBF-PID controller outperforms both the SMC and traditional PID controllers in handling sudden speed changes.
文摘This paper introduces a novel chattering-free terminal sliding mode control(SMC)strategy to address chaotic behavior in permanent magnet synchronous generators(PMSG)for offshore wind turbine systems.By integrating an adaptive exponential reaching law with a continuous barrier function,the proposed approach eliminates chattering and ensures robust performance under model uncertainties.The methodology combines adaptive SMC with dynamic switching to estimate and compensates for unknown uncertainties,providing smooth and stable control.Finally,the performance and effectiveness of the proposed approach are compared with those of a previous study.
文摘BACKGROUND Autoimmune myocarditis(AM)associated with autoimmune diseases can cause complete atrioventricular block(CAVB),but the related autoantigens and the underlying mechanisms are unclear.Anti-SSA/Ro antibodies may play an important role in this process,but cases of AM with positive anti-SSA/Ro antibodies are rare.In addition,arrhythmias,such as atrioventricular block,are very common in patients with autoimmune diseases,but severe atrioventricular block requiring permanent pacemaker implantation is extremely rare.CASE SUMMARY The patient in this case had AM with anti-SSA/Ro antibody positivity,which was associated with connective tissue disease,and the patient subsequently developed CAVB.After intensive immunosuppressive therapy,the antibody test results became negative,and pulmonary hypertension significantly improved.However,the outcome of permanent pacemaker implantation did not change.CONCLUSION In clinical practice,the awareness of adult AM associated with autoimmune diseases combined with CAVB should be strengthened in clinicians,and anti-SSA/Ro antibodies may play a role in this process.Therefore,improving the detection of antibodies and early intervention,such as active immunosuppression therapy,may be very important for improving disease prognosis.For patients who do not respond to immunosuppressive therapy,implantation of a permanent pacemaker may become an essential treatment option.
文摘Objective:To investigate the distribution of health literacy(HL)levels and the association of HL with proactive personality in patients with permanent colostomy.Methods:A cross-sectional study was conducted to measure proactive personality and HL using validated scales.A total of 172 patients with permanent colostomy were selected from January 2021 to May 2022 in Yantai City,China.Descriptive statistics,t-test,ANOVA,Pearson correlation analysis,and multiple linear regression analysis techniques were used.Results:The results obtained from the study showed that the HL status of the participants was moderate.The correlation between participants’total HL scores and proactive personality scores was 0.417(P-value<0.001).In addition,HL showed statistically significant differences according to education level,place of residence,profession,and average monthly household income.Conclusions:This study showed that patients with higher proactive personality scores had higher HL.The key stakeholders require several positive strategies to improve the HL of patients with permanent colostomy by cultivating their proactive personalities,and these important policies will help to improve patient health and quality of life.
基金supported by the National Natural Science Foundation of China(Grant No.52073222)the Fundamental Research Funds for the Central Universities(Grant No.WUT:104972024JYS0027).
文摘Micro/nanorobots have significant potential applications in biomedicine.However,their small size and the need for intricate control make long-distance navigation of microswarms composed of such robots challenging in complex environments.To address this problem,we have developed a permanent-magnet-actuated microswarm navigation system to achieve precise control of micro/nanorobots in complex fluid environments.The controlled microswarm is composed of monodisperse Fe_(3)O_(4)@PVP nanoclusters synthesized using the polyol method.These nanoclusters can self-assemble into highly controllable microswarm structures under a rotating magnetic field and are then guided by the robotic system for precise navigation.The system uses visual positioning and motion control to enable real-time dynamic navigation.In experiments,it successfully performed autonomous navigation over a 55 mm distance in a transparent channel,with flow rates ranging from 0 to 10 mm/s.It completed the task in 132 s at an average speed of over 0.45 mm/s,with an average trajectory tracking error of only 0.28 mm.These results demonstrate excellent path accuracy and stability under various flow rate conditions,validating the system’s adaptability and efficiency in fluid environments and highlighting its potential for biomedical applications.This study offers a robust and versatile platform for expanding micro/nanorobot applications in biomedicine.
基金National Natural Science Foundation of China under Grant No.52322808the Fundamental Research Funds for the Central Universities under Grant No.B220202013。
文摘Collapses of seismic slopes demonstrate the characteristics of three-dimensional(3D)shapes.Conducting a 3D analysis of seismic slope stability is more complicated than doing a simplified two-dimensional(2D)analysis.The upper-bound solutions derived from limit analysis of seismic slopes using the pseudo-static method are used to generate an approximate solution for the factor of 3D safety through regression analysis.Such a solution can degenerate to a 2D result when the slope width tends to infinity.The approximation method also can be extended for determining the permanent displacements of 3D slopes under seismic loading.The method is non-iterative and relatively accurate through comparisons with analytical results.Involving stochastic ground motions could easily be used to assess the distribution of permanent displacement that is induced in 3D slopes.
基金the National Natural Science Foundation of China(Grant No.U1760206 and Grant No.51574083)the 111 Project(2.0)of China(No.BP0719037)for the financial support.
文摘A new flow control technology in continuous casting process named permanent magnet flow control-mold(PMFC-Mold)was proposed,in which the permanent magnets are arranged in Halbach array near the narrow region of the mold.The behavior of molten steel flow and the fluctuation of molten steel/slag interface in the PMFC-Mold under different continuous casting speeds were investigated.Firstly,a physical experiment of liquid Ga-In-Sn alloy circulating flow was carried out in Perspex mold with Halbach’s permanent magnets(HPMs)to investigate the magnetic field distribution of HPMs and its impactful electromagnetic braking effect.The numerical simulation of 1450 mm×230 mm slab shows that a stronger magnetic field over 0.3-0.625 T is formed at the wide surface and the narrow surface of the mold,which provides an effective electromagnetic braking for controlling the impingement of molten steel jet and suppressing the fluctuation of molten steel/slag interface.The numerical simulation results show that in the PMFC-Mold,the region with the turbulent kinetic energy greater than 0.01 and 0.04 m^(2)s^(-2)on the upper backflow zone and near the narrow surface of the mold are significantly reduced.The maximum turbulent kinetic energy of the submerged entry nozzle(SEN)jet in front of the narrow surface is significantly reduced,and the SEN jet moves downward before impacting the narrow surface of the mold.In the PMFC-Mold,the region with the surface velocity greater than 0.2 m s^(-1)on the steel/slag interface is eliminated,the flow pattern and fluctuation profiles on the molten steel/slag interface become regular on both sides of SEN,and the vortex near SEN disappears.The maximum fluctuation height of molten steel/slag interface is controlled below 2.59 and 5.40 mm corresponding to the casting speed of 1.6 and 2.0 m min-1,respectively.
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partly supported by the CAS Project for Young Scientists in Basic Research under Grant YSBR-045the National Natural Science Foundation of China under Grant 52307071。
文摘Linear flux-switching permanent magnet motors(LFSPMs) have been proposed for long stator applications such as rail transit. However, the conventional linear permanent magnet synchronous motor(LPMSM) suffers from thrust ripple, which degrades the motor performance. The thrust ripple in LFSPMs is mainly caused by detent force and asymmetric electromagnetic parameters, excluding external disturbances. Moreover, the 12/13 slot-pole LFSPM exhibits unique inductance characteristics, which lead to different effects on thrust ripple. First, the detent force in the LFSPM is analyzed through finite element method(FEM). In addition, new finite element(FE) models are proposed for further analysis of the cogging force in LFSPMs. Second, the unique inductance characteristics of the 12/13 slot-pole LFSPM are investigated, and then the thrust ripple caused by asymmetric electromagnetic parameters is calculated by the virtual displacement method. Third, the mathematical model considering the thrust ripple is established for the LFSPM, which provides a foundation for subsequent research on thrust ripple suppression control strategies. Finally, the thrust ripple analysis is validated by comparing FEM results, modeling simulations, and experimental data.
基金Project supported by the Natural Science Foundation of Hunan Province(2024JJ4056)the Key Project of Guangxi Zhuang Autonomous Region(AB22080089)the Government of Chongzuo,Guangxi Zhuang Autonomous Region(FA20210716)。
文摘The rapid development of magnetic materials provides the possibility for the application of permanent magnet stirring(PMS).Numerical and experimental investigations were employed with respect to the solidification process of the Al—2Sc alloy controlled by a novel PMS using NdFeB permanent magnets under various rotation speeds(0,50,100 and 150 r/min).The simulated results reveal that the maximum electromagnetic force increases proportionally from 4.14 to 12.39 kN/m^(3)and the maximum tangential velocity increases from 0.13 to 0.36 m/s when the rotation speed of PMS enhances from 50 to 150 r/min in the ingot melt.Besides,the experimental results demonstrate that PMS can achieve a uniform distribution of blocky Al_(3)Sc precipitated phase in the longitudinal direction under the impact of a forced fluid flow.Moreover,increasing rotation speed of PMS is beneficial to refining aluminum grain size significantly and decreasing the texture intensity in the alloy.In addition,the Brinell hardness of Al-2Sc alloy is increased by 33%to 27.8 HB and the tensile strength is enhanced by 34%-128.2 MPa,due to the improved distribution of the strengthening Al_(3)SC phase and the grain refinement of Al matrix under the impact of PMS.This work provides an effective application of NdFeB permanent magnets in the metal cast field.
基金The National Natural Science Foundation of China(No.52107039)the Fujian Provincial Natural Science Foundation for Youth(No.2021J05133)the Key Project of the National Natural Science Foundation of China(No.51937002)。
文摘The axial field hybrid permanent magnet memory machine(AFHPM-MM)employs a hybrid permanent magnet excitation combining NdFeB and AlNiCo,achieving high torque density and a wide flux adjustment range.A separated stator structure is adopted to enhance its antidemagnetization capability.To analyze the contributions of AlNiCo and NdFeB to the induced electromotive force(EMF)in the AFHPM-MM,a frozen permeability-based induced EMF calculation method is proposed.Theoretical analysis reveals that the conventional method exhibits substantial errors in calculating the AlNiCo-induced EMF,primarily attributed to its failure to adequately account for the dynamic magnetization characteristic discrepancies of AlNiCo under varying magnetization states.Through the analysis of magnetization variations in AlNiCo during the flux adjustment process under different magnetization states,an improved induced EMF calculation method is proposed.Comparative results indicate that,during the flux enhancement process,the average calculation error of the AlNiCo-induced EMF is reduced from 19.84%to 2.09%,whereas during the flux weakening process,the error is reduced from 3.87%to 1.67%.The proposed method achieves accurate induced EMF calculation for the AFHPM-MM.
基金supported in part by the Natural Science Foundation of Heilongjiang Province under Grant LH2023E084by the National Natural Science Foundation of China under Grant 51777048。
文摘The coupling effect of dual-parallel rotor connected stator permanent magnet synchronous motor not only affects the magnetic field in the coupling area, but also generates an additional magnetic field in the uncoupled area.The characteristics of the additional magnetic field and its influence on electromagnetic torque are studied in this paper.The topology and parameters of motor are described briefly.The existence of additional magnetic field is proved by the simulation models under two boundary conditions, and its characteristics and source are analyzed. The analytical model is established, and the influence of key parameters on the additional magnetic field is discussed. On this basis, the influence of the additional magnetic field on the electromagnetic torque of the motor is studied, and the analytical expression of the additional torque is constructed.The fluctuation rule is analyzed, and the additional magnetic field separation model is proposed. The theoretical analysis and simulation results reveal and improve the internal mechanism of reducing motor torque ripple by optimizing the duty angle and coupling distance. Finally, a prototype test platform is built to verify the correctness of the proposed theory and the accuracy of the simulation model.
基金Project supported by the National Key R&D Program of China(2022YFB3505301)the National Key R&D Program of Shanxi Province(202302050201014)+2 种基金the National Natural Science Foundation of China(12304148)the Natural Science Basic Research Program of Shanxi Province(202203021222219)the China Postdoctoral Science Foundation(2023M731452)。
文摘Previous studies have demonstrated that increasing Fe doping content can enhance the saturation magnetization and maximum energy product of 2:17-type Sm-Co rare-earth permanent magnets.Howeve r,syste matic theo retical calculations and the effects of other transition metal dopants have yet to be explored.This study employed first-principles computational methods to investigate the effects of doping with 3d and Zr transition metal elements on the structural stability,magnetic properties,and electronic structure of Sm_(2)Co_(17)permanent magnets.The results indicate that Sc and Zr tend to occupy the Sm-6c site,while Ni,Cu and Zn preferentially occupy the 18h site,and Ti,V,Cr,Mn and Fe primarily occupy the Co-6c site.Except for V and Cu,all other elements effectively improve the structural stability of the doped systems.Additionally,Mn and Fe doping can significantly enhance the total magnetic moment and magnetocrystalline anisotropy energies of the Sm_(2)Co_(17)system,while Cr only increases the total magnetic moment.More importantly,doping with Cr,Mn and Fe within the doping co ntent range of9.8 at%<x<35.29 at% can simultaneously improve the structural stability,total magnetic moment and magnetocrystalline anisotropy energy of the Sm_(2)Co_(17) system.Our study provides valuable theoretical guidance for experimental exploration and is expected to promote the development and application of novel rare-earth permanent magnetic materials.
基金supported in part by the Modern Agriculture Major Core Technology Innovation Project of Jiangsu Province under Grant CX(22)1005in part by the National Natural Science Foundation of China under Grant 52177046in part by the Project of Innovation of Postgraduate of Jiangsu Province under Grant KYCX25_4228。
文摘To address the issue of increased electromagnetic vibration in permanent magnet(PM) motors for electric vehicles under flux-weakening speed extension operation, this paper proposes a low-vibration design method for PM motors from the perspective of saliency ratio. First, by establishing a theoretical model for vibration analysis under flux-weakening operation, it reveals the vibration mechanism whereby high-order armature magnetomotive force(ARM-MMF) harmonics under fluxweakening operation leads to enhanced radial electromagnetic force(REF). Second, an in-depth investigation into the intrinsic relationship between saliency ratio and ARM-MMF is conducted. This study proposes a novel methodology to design key ARM-MMF harmonics that induce significant electromagnetic vibration from the perspective of the saliency ratio. An innovative rotor topology featuring elliptical-arc composite flux barriers is developed to implement this approach. Furthermore, and synergistic optimization is performed with the saliency ratio and torque as optimization objectives to balance vibration suppression and torque output performance. Finally, a prototype is manufactured and tested. Both theoretical and experimental analyses validated the effectiveness of the motor and the proposed design method.
基金support from the Youth Innovation Promotion Association,Chinese Academy of Sciences(2020395)Strategic Priority Research Program of the Chinese Academy of Sciences grant XDB 41000000(Y.L.)+4 种基金National Natural Science Foundation of China(Nos.42273042 and 41931077)"From 0 to 1"Original Exploration Cultivation Project,Institute of Geochemistry,Chinese Academy of Sciences(DHSZZ2023-3)Guizhou Provincial Foundation for Excellent Scholars Program(No.GCC[2023]088)Guizhou Provincial Science and Technology Projects:QKHJCZK[2023]-General 473NSFC Young Scientist Fund(Nos.42303041 and 42403043)。
文摘Permanently shadowed regions(PSRs)on the Moon are potential reservoirs for water ice,making them hot spots for future lunar exploration.The water ice in PSRs would cause distinctive changes in space weathering there,in particular reduction-oxidation processes that diff er from those in illuminated regions.To determine the characteristics of products formed during space weathering in PSRs,the lunar meteorite NWA 10203 with artifi cially added water was irradiated with a nanosecond laser to simulate a micro-meteorite bombardment of lunar soil containing water ice.The TEM results of the water-incorporated sample showed distinct amorphous rims that exhibited irregular thickness,poor stratifi cation,the appearance of bubbles,and a reduced number of npFe^(0).Additionally,EELS analysis showed the presence of ferric iron at the rim of the nanophase metallic iron particles(npFe^(0))in the amorphous rim with the involvement of water.The results suggest that water ice is another possible factor contributing to oxidation during micrometeorite bombardment on the lunar surface.In addition,it off ers a reference for a new space weathering model that incorporates water in PSRs,which could be widespread on asteroids with volatiles.
文摘Permanent magnet synchronous motor(PMSM)is widely used in alternating current servo systems as it provides high eficiency,high power density,and a wide speed regulation range.The servo system is placing higher demands on its control performance.The model predictive control(MPC)algorithm is emerging as a potential high-performance motor control algorithm due to its capability of handling multiple-input and multipleoutput variables and imposed constraints.For the MPC used in the PMSM control process,there is a nonlinear disturbance caused by the change of electromagnetic parameters or load disturbance that may lead to a mismatch between the nominal model and the controlled object,which causes the prediction error and thus affects the dynamic stability of the control system.This paper proposes a data-driven MPC strategy in which the historical data in an appropriate range are utilized to eliminate the impact of parameter mismatch and further improve the control performance.The stability of the proposed algorithm is proved as the simulation demonstrates the feasibility.Compared with the classical MPC strategy,the superiority of the algorithm has also been verified.
