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
This paper presents a high-fidelity lumpedparameter(LP)thermal model(HF-LPTM)for permanent magnet synchronous machines(PMSMs)in electric vehicle(EV)applications,where various cooling techniques are considered,includin...This paper presents a high-fidelity lumpedparameter(LP)thermal model(HF-LPTM)for permanent magnet synchronous machines(PMSMs)in electric vehicle(EV)applications,where various cooling techniques are considered,including frame forced air/liquid cooling,oil jet cooling for endwinding,and rotor shaft cooling.To address the temperature misestimation in the LP thermal modelling due to assumptions of concentrated loss input and uniform heat flows,the developed HF-LPTM introduces two compensation thermal resistances for the winding and PM components,which are analytically derived from the multi-dimensional heat transfer equations and are robust against different load/thermal conditions.As validated by the finite element analysis method and experiments,the conventional LPTMs exhibit significant winding temperature deviations,while the proposed HF-LPTM can accurately predict both the midpoint and average temperatures.The developed HFLPTM is further used to assess the effectiveness of various cooling techniques under different scenarios,i.e.,steady-state thermal states under the rated load condition,and transient temperature profiles under city,freeway,and hybrid(city+freeway)driving cycles.Results indicate that no single cooling technique can maintain both winding and PM temperatures within safety limits.The combination of frame liquid cooling and oil jet cooling for end winding can sufficiently mitigate PMSM thermal stress in EV applications.展开更多
Permanent magnet synchronous motor based electro-mechanical actuation servo drives have widespread applications in the aviation field,such as unmanned aerial vehicle electric servos,electric cabin doors,and mechanical...Permanent magnet synchronous motor based electro-mechanical actuation servo drives have widespread applications in the aviation field,such as unmanned aerial vehicle electric servos,electric cabin doors,and mechanical arms.The performance of the servo drive,which encompasses the response to the torque,efficiency,control bandwidth and the steady-state positioning accuracy,significantly influences the performance of the aviation actuation.Consequently,enhancing the control bandwidth and refining the positioning accuracy of aviation electro-mechanical actuation servo drives have emerged as a focal point of research.This paper investigates the multi-source disturbances present in aviation electro-mechanical actuation servo systems and summarizes recent research on high-performance servo control methods based on active disturbance rejection control(ADRC).We present a comprehensive overview of the research status pertaining to servo control architecture,strategies for suppressing disturbances in the current loop,and ADRC-based strategies for the position loop.We delineate the research challenges and difficulties encountered by aviation electro-mechanical actuation servo drive control technology.展开更多
The combination of dual-main-phase(DMP)(Nd,Ce)-Fe-B magnets and grain boundary diffusion process(GBDP)is currently a research topic for obtaining high-cost performance materials in rare earth permanent magnet fields.T...The combination of dual-main-phase(DMP)(Nd,Ce)-Fe-B magnets and grain boundary diffusion process(GBDP)is currently a research topic for obtaining high-cost performance materials in rare earth permanent magnet fields.The novel structural features of GBDP(Nd,Ce)-Fe-B magnets give a version of different domain reversal processes from those of non-diffused magnets.In this work,the in-situ magnetic domain evolution of the DMP magnets was observed at elevated temperatures,and the temperature demagnetization and coercivity mechanism of the GBDP dual-main-phase(Nd,Ce)-Fe-B magnets are discussed.The results show that the shell composition of different types of grains in DMP magnets is similar,while the magnetic microstructure results indicate the Ce-rich grains tend to demagnetize first.Dy-rich shell with a high anisotropic field caused by GBDP leads to an increase in the nucleation field,which enhances the coercivity.It is found that much more grains exhibit single domain characteristics in the remanent state for GBDP dual-main-phase(Nd,Ce)-Fe-B magnets.In addition,the grains that undergo demagnetization first are Ce-rich or Nd-rich grains,which is different from that of non-diffused magnets.These results were not found in previous studies but can be intuitively characterized from the perspective of magnetic domains in this work,providing a new perspective and understanding of the performance improvement of magnetic materials.展开更多
The property IR was introduced by Friis and Rordam in 1996.They proved that any pair of almost commuting self-adjoint elements is norm close to a pair of exactly commuting self-adjoint elements in any C^(*)-algebras w...The property IR was introduced by Friis and Rordam in 1996.They proved that any pair of almost commuting self-adjoint elements is norm close to a pair of exactly commuting self-adjoint elements in any C^(*)-algebras with the property IR.In this paper,we will prove some permanence results for IR-algebras,approximate IR-algebras and local IR-algebras.Finally,we will also show that any pair of almost commuting self-adjoint elements is norm close to a pair of exactly commuting self-adjoint elements in any local IR-algebra.展开更多
The aim of this study is to address the issues associated with traditional magnetorheological fluid(MRF)dampers,such as insufficient damping force after power failure and susceptibility to settlement.In order to achie...The aim of this study is to address the issues associated with traditional magnetorheological fluid(MRF)dampers,such as insufficient damping force after power failure and susceptibility to settlement.In order to achieve this,a bidirectional adjustable MRF damper was designed and developed.Magnetic field simulation analysis was conducted on the damper,along with simulation analysis on its dynamic characteristics.The dynamic characteristics were ultimately validated through experimental testing on the material testing machine,thereby corroborating the theoretical simulation results.Concurrently,this process generated valuable test data for subsequent implementation of the semi-active vibration control system.The simulation and test results demonstrate that the integrated permanent magnet effectively accomplishes bidirectional regulation.The magnetic induction intensity of the damping channel is 0.2 T in the absence of current,increases to 0.5 T when a maximum forward current of 4 A is applied,and becomes 0 T when a maximum reverse current of 3.8 A is applied.When the excitation amplitude is 8 mm and the frequency is 2 Hz,with the applied currents varying,the maximum damping force reaches 8 kN,while the minimum damping force measures at 511 N.Additionally,at zero current,the damping force stands at 2 kN,which aligns closely with simulation results.The present paper can serve as a valuable reference for the design and research of semi-active MRF dampers.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
We proposed a new measure to optimize the comprehensive magnetic properties of SmCo_(5)alloy.By compounding Fe-15Ni-3Al-1Ti(FNAT)alloy with high saturation magnetization and Sm(Co,Cu)_(5) matrix alloy in the liquid st...We proposed a new measure to optimize the comprehensive magnetic properties of SmCo_(5)alloy.By compounding Fe-15Ni-3Al-1Ti(FNAT)alloy with high saturation magnetization and Sm(Co,Cu)_(5) matrix alloy in the liquid state,an innovative two-phase separation microstructure or cellular microstructure is formed after melt-spinning using the phase separation effect of the two alloys.At the same time,the element concentration,relative phase content,and microstructure are adjusted by adding different contents of FNAT alloy.The results show that FNAT addition promotes the as-spun ribbons phase separation(or spinodal decomposition)into Co-rich SmCo_(5)-and Sm-Ni-rich CeCo_(5)-or Sm_(2)Co_(7)-type phases.Adding 3 wt.%FNAT increases the coercivity,saturation magnetization,and remanence of the ribbons by 320.6%,39.8%,and 82.8%,respectively.Adding 5 wt.%FNAT promotes forming the Sm_(2)(Co,M)_(7) cell-wall phase and increases the coercivity and remanence by 272.7%and 48.1%,respectively.Finally,the corresponding microstructure evolution models,magnetization,and demagnetization mechanisms are proposed.展开更多
ThMn_(12)-type iron-rich rare-earth permanent magnetic materials have garnered significant attention due to their exceptional intrinsic magnetic properties.However,challenges such as the metastable nature of the ThMn1...ThMn_(12)-type iron-rich rare-earth permanent magnetic materials have garnered significant attention due to their exceptional intrinsic magnetic properties.However,challenges such as the metastable nature of the ThMn12-type phase,excessively small single-domain grain size,and complex fabrication processes have hindered the achievement of high phase purity,uniform microstructure,and desirable extrinsic performance.In this study,we directly synthesized ThMn_(12)-type Sm_(0.8)Zr_(0.2)Fe_(11)SiB_(x)(x=0-0.2)ribbon magnets via boron doping combined with a one-step rapid solidification method.This approach not only simplifies the fabrication process but also enhances phase stability and achieves a uniform microstructure with high ThMn12-type phase purity.By optimizing the boron content and cooling rate,the resulting magnets exhibit a coercivity(H_(c))of 6222 Oe,a remanence(M_(r))of 80 emu/g,and a remanence ratio(M_(r)/M_(s))of 0.71.This work demonstrates a streamlined approach to producing high-performance ThMn12-type magnets and provides insights into their practical application potential.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
In this work, nanocrystalline SmCo_(5)-Cu nanocomposite powders were fabricated from the ball-milled amorphous matrix by crystallization annealing which is lower than the traditional sintering temperature ~ 1000℃ for...In this work, nanocrystalline SmCo_(5)-Cu nanocomposite powders were fabricated from the ball-milled amorphous matrix by crystallization annealing which is lower than the traditional sintering temperature ~ 1000℃ for bulk SmCo_(5) bulk magnets. Annealed Cu-doped SmCo_(5) powders have a higher coercivity compared to that of Cu-free SmCo_(5) one due to the combined effects of refinement effect of grain size and the pinning effect induced by Cu doping. The peak of coercivity (Hc) is located at 600℃ for annealed Cu-doped SmCo_(5), which is ascribed to the improved pinning field. The pinning effect became reduced when the annealing was done at even higher temperatures. More importantly, the best comprehensive magnetic properties, including a maximum magnetic energy product (BH)max of 12.2 MGOe together with a coercivity of 31.8 kOe and a remanence of 64.3 emu/g, could be achieved for SmCo_(5)-3 wt% Cu by low temperature annealing. These results demonstrate that isotropic Cu-doped SmCo_(5) nanocrystalline powders are promising precursors for the fabrication of high-performance bulk magnets.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
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
The arc-linear motor(ALM) is a new type of special motor derived from the linear motor, which has the merits of high torque, compact structure and fast dynamic response. This kind of motor does not need a complex inte...The arc-linear motor(ALM) is a new type of special motor derived from the linear motor, which has the merits of high torque, compact structure and fast dynamic response. This kind of motor does not need a complex intermediate transmission device, it is used in some direct-drive applications for continuous rotation or limited angle motion. However, there is no systematic summary and generalization of the ALMs so far.Therefore, this paper systematically overviews the recent advances in ALMs for direct-drive systems. First, the evolution process and basic structure of the ALM are introduced. And then, various ALMs are reviewed with particular reference to motor topologies, working principle, motor performance,optimization design and control techniques. To heel, a comprehensive comparison of several typical ALMs is carried out. Finally, the application areas, main challenges and development trends of the ALMs are highlighted.展开更多
In recent years,high coercivity nanocrystalline magnets based on the critical single domain size theory have received increasing attention.However,nanocrystalline magnets are difficult to enhance the remanent magnetiz...In recent years,high coercivity nanocrystalline magnets based on the critical single domain size theory have received increasing attention.However,nanocrystalline magnets are difficult to enhance the remanent magnetization by forming textures with conventional magnetic field orientation.Texturing of nanocrystalline magnets is usually done using the hot pressing and hot deformation technique,but there are some difficulties in applying this technique to form texture in SmCo systems.To discover and solve the difficulties of obtaining texturized nanocrystalline magnets during the deformation process,samarium cobalt magnets with different degrees of deformation were first experimentally prepared by low strain rate hot deformation method.Then,molecular dynamics simulations were utilized to study the micro structural changes and the multi-phase formation process during hot deformation.The process of deformation together with the reason why it is difficult to form textures in SmCo systems by lowtemperature hot deformation is discussed,and the strain energy densities of SmCo multiphase in multiple directions were calculated,which gives a feasible method to form low-temperature hot deformation textures in SmCo systems experimentally.展开更多
Numerous uncertainties in practical production and operation can seriously affect the drive performance of permanent magnet synchronous machines(PMSMs).Various robust control methods have been developed to mitigate or...Numerous uncertainties in practical production and operation can seriously affect the drive performance of permanent magnet synchronous machines(PMSMs).Various robust control methods have been developed to mitigate or eliminate the effects of these uncertainties.However,the robustness to uncertainties of electrical drive systems has not been clearly defined.No systemic procedures have been proposed to evaluate a control system's robustness(how robust it is).This paper proposes a systemic method for evaluating control systems'robustness to uncertainties.The concept and fundamental theory of robust control are illustrated by considering a simple uncertain feedback control system.The effects of uncertainties on the control performance and stability are analyzed and discussed.The concept of design for six-sigma(a robust design method)is employed to numerically evaluate the robustness levels of control systems.To show the effectiveness of the proposed robustness evaluation method,case studies are conducted for second-order systems,DC motor drive systems,and PMSM drive systems.Besides the conventional predictive control of PMSM drive,three different robust predictive control methods are evaluated in terms of two different parametric uncertainty ranges and three application requirements against parametric uncertainties.展开更多
Chuan Qin,MD,PhD,is the President of the Chinese Association for Laboratory Animal Sciences(CALAS),and the permanent professor of Chinese Academy of Medical Sciences(CAMS)&Peking Union Medical College(PUMC).Moreov...Chuan Qin,MD,PhD,is the President of the Chinese Association for Laboratory Animal Sciences(CALAS),and the permanent professor of Chinese Academy of Medical Sciences(CAMS)&Peking Union Medical College(PUMC).Moreover,she is the senior scientist of Institute of Laboratory Animal Sciences(ILAS),CAMS&PUMC.She is also the Vice-President of the Asian Federation of Laboratory Animal Science Associations(AFLAS),a board member of the International Council for Laboratory Animal Science(ICLAS),and Chairman of the National Standardization Technical Committee of Laboratory Animals.In addition to Animal Models and Experimental Medicine,Prof.Qin is also the Editor-in-Chief of Acta Laboratorium Animalis Scientia Sinica and Chinese Journal of Comparative Medicine.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
Bedding parallel stepped rock slopes exist widely in nature and are used in slope engineering.They are characterized by complex topography and geological structure and are vulnerable to shattering under strong earthqu...Bedding parallel stepped rock slopes exist widely in nature and are used in slope engineering.They are characterized by complex topography and geological structure and are vulnerable to shattering under strong earthquakes.However,no previous studies have assessed the mechanisms underlying seismic failure in rock slopes.In this study,large-scale shaking table tests and numerical simulations were conducted to delineate the seismic failure mechanism in terms of acceleration,displacement,and earth pressure responses combined with shattering failure phenomena.The results reveal that acceleration response mutations usually occur within weak interlayers owing to their inferior performance,and these mutations may transform into potential sliding surfaces,thereby intensifying the nonlinear seismic response characteristics.Cumulative permanent displacements at the internal corners of the berms can induce quasi-rigid displacements at the external corners,leading to greater permanent displacements at the internal corners.Therefore,the internal corners are identified as the most susceptible parts of the slope.In addition,the concept of baseline offset was utilized to explain the mechanism of earth pressure responses,and the result indicates that residual earth pressures at the internal corners play a dominant role in causing deformation or shattering damage.Four evolutionary deformation phases characterize the processes of seismic responses and shattering failure of the bedding parallel stepped rock slope,i.e.the formation of tensile cracks at the internal corners of the berm,expansion of tensile cracks and bedding surface dislocation,development of vertical tensile cracks at the rear edge,and rock mass slipping leading to slope instability.Overall,this study provides a scientific basis for the seismic design of engineering slopes and offers valuable insights for further studies on preventing seismic disasters in bedding parallel stepped rock slopes.展开更多
In this article, an inter-turn short-circuit(ITSC) fault diagnosis and severity estimation method based on extended state observer(ESO) and convolutional neural network(CNN) is proposed for five-phase permanent magnet...In this article, an inter-turn short-circuit(ITSC) fault diagnosis and severity estimation method based on extended state observer(ESO) and convolutional neural network(CNN) is proposed for five-phase permanent magnet synchronous motor(PMSM) drives. The relationship between fault parameters and motor parameters is analyzed and the equivalent model of ITSC faults in the natural reference frame is accordingly derived. To achieve fault detection and location, the short-circuit turn ratio and short-circuit current are integrated as the fault diagnosis index. According to the model of the shortcircuit current, an ESO is designed for the estimation of the fault diagnosis index. Further, the sensitivity analysis among fault parameters is conducted to evaluate the short-circuit turn ratio and the short-circuit resistance. Subsequently, the postfault current, back electromotive force, electrical angular velocity, q1-axis current reference and the fault diagnosis index are selected as the input signals of CNN to estimate the short-circuit turn ratio. This approach not only resolves parameter coupling challenges but also provides a quantitative assessment of fault severity. Finally, simulations and experiments under different operating points validate the effectiveness of the proposed method.展开更多
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This paper presents a high-fidelity lumpedparameter(LP)thermal model(HF-LPTM)for permanent magnet synchronous machines(PMSMs)in electric vehicle(EV)applications,where various cooling techniques are considered,including frame forced air/liquid cooling,oil jet cooling for endwinding,and rotor shaft cooling.To address the temperature misestimation in the LP thermal modelling due to assumptions of concentrated loss input and uniform heat flows,the developed HF-LPTM introduces two compensation thermal resistances for the winding and PM components,which are analytically derived from the multi-dimensional heat transfer equations and are robust against different load/thermal conditions.As validated by the finite element analysis method and experiments,the conventional LPTMs exhibit significant winding temperature deviations,while the proposed HF-LPTM can accurately predict both the midpoint and average temperatures.The developed HFLPTM is further used to assess the effectiveness of various cooling techniques under different scenarios,i.e.,steady-state thermal states under the rated load condition,and transient temperature profiles under city,freeway,and hybrid(city+freeway)driving cycles.Results indicate that no single cooling technique can maintain both winding and PM temperatures within safety limits.The combination of frame liquid cooling and oil jet cooling for end winding can sufficiently mitigate PMSM thermal stress in EV applications.
基金supported by the National Natural Science Foundation of China(Nos.52177059 and 52407064).
文摘Permanent magnet synchronous motor based electro-mechanical actuation servo drives have widespread applications in the aviation field,such as unmanned aerial vehicle electric servos,electric cabin doors,and mechanical arms.The performance of the servo drive,which encompasses the response to the torque,efficiency,control bandwidth and the steady-state positioning accuracy,significantly influences the performance of the aviation actuation.Consequently,enhancing the control bandwidth and refining the positioning accuracy of aviation electro-mechanical actuation servo drives have emerged as a focal point of research.This paper investigates the multi-source disturbances present in aviation electro-mechanical actuation servo systems and summarizes recent research on high-performance servo control methods based on active disturbance rejection control(ADRC).We present a comprehensive overview of the research status pertaining to servo control architecture,strategies for suppressing disturbances in the current loop,and ADRC-based strategies for the position loop.We delineate the research challenges and difficulties encountered by aviation electro-mechanical actuation servo drive control technology.
基金supported by the National Key Research and Development Program of China(Nos.2021YFB3503003,2021YFB3503100,and 2022YFB3505401).
文摘The combination of dual-main-phase(DMP)(Nd,Ce)-Fe-B magnets and grain boundary diffusion process(GBDP)is currently a research topic for obtaining high-cost performance materials in rare earth permanent magnet fields.The novel structural features of GBDP(Nd,Ce)-Fe-B magnets give a version of different domain reversal processes from those of non-diffused magnets.In this work,the in-situ magnetic domain evolution of the DMP magnets was observed at elevated temperatures,and the temperature demagnetization and coercivity mechanism of the GBDP dual-main-phase(Nd,Ce)-Fe-B magnets are discussed.The results show that the shell composition of different types of grains in DMP magnets is similar,while the magnetic microstructure results indicate the Ce-rich grains tend to demagnetize first.Dy-rich shell with a high anisotropic field caused by GBDP leads to an increase in the nucleation field,which enhances the coercivity.It is found that much more grains exhibit single domain characteristics in the remanent state for GBDP dual-main-phase(Nd,Ce)-Fe-B magnets.In addition,the grains that undergo demagnetization first are Ce-rich or Nd-rich grains,which is different from that of non-diffused magnets.These results were not found in previous studies but can be intuitively characterized from the perspective of magnetic domains in this work,providing a new perspective and understanding of the performance improvement of magnetic materials.
基金Supported by NSFC(No.11401256)Scientific Research Fund of Zhejiang Provincial Education Department(No.Y202249575)Zhejiang Provincial NSF(No.LQ13A010016).
文摘The property IR was introduced by Friis and Rordam in 1996.They proved that any pair of almost commuting self-adjoint elements is norm close to a pair of exactly commuting self-adjoint elements in any C^(*)-algebras with the property IR.In this paper,we will prove some permanence results for IR-algebras,approximate IR-algebras and local IR-algebras.Finally,we will also show that any pair of almost commuting self-adjoint elements is norm close to a pair of exactly commuting self-adjoint elements in any local IR-algebra.
文摘The aim of this study is to address the issues associated with traditional magnetorheological fluid(MRF)dampers,such as insufficient damping force after power failure and susceptibility to settlement.In order to achieve this,a bidirectional adjustable MRF damper was designed and developed.Magnetic field simulation analysis was conducted on the damper,along with simulation analysis on its dynamic characteristics.The dynamic characteristics were ultimately validated through experimental testing on the material testing machine,thereby corroborating the theoretical simulation results.Concurrently,this process generated valuable test data for subsequent implementation of the semi-active vibration control system.The simulation and test results demonstrate that the integrated permanent magnet effectively accomplishes bidirectional regulation.The magnetic induction intensity of the damping channel is 0.2 T in the absence of current,increases to 0.5 T when a maximum forward current of 4 A is applied,and becomes 0 T when a maximum reverse current of 3.8 A is applied.When the excitation amplitude is 8 mm and the frequency is 2 Hz,with the applied currents varying,the maximum damping force reaches 8 kN,while the minimum damping force measures at 511 N.Additionally,at zero current,the damping force stands at 2 kN,which aligns closely with simulation results.The present paper can serve as a valuable reference for the design and research of semi-active MRF dampers.
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.
基金supported by the General Program from the National Natural Science Foundation of China(NNSFC)(No.52371185)Central Government Guides Local Funds for Science and Technology Development(No.216Z1008G)the Natural Science Foundation of Hebei province,China(No.E2022202017).
文摘We proposed a new measure to optimize the comprehensive magnetic properties of SmCo_(5)alloy.By compounding Fe-15Ni-3Al-1Ti(FNAT)alloy with high saturation magnetization and Sm(Co,Cu)_(5) matrix alloy in the liquid state,an innovative two-phase separation microstructure or cellular microstructure is formed after melt-spinning using the phase separation effect of the two alloys.At the same time,the element concentration,relative phase content,and microstructure are adjusted by adding different contents of FNAT alloy.The results show that FNAT addition promotes the as-spun ribbons phase separation(or spinodal decomposition)into Co-rich SmCo_(5)-and Sm-Ni-rich CeCo_(5)-or Sm_(2)Co_(7)-type phases.Adding 3 wt.%FNAT increases the coercivity,saturation magnetization,and remanence of the ribbons by 320.6%,39.8%,and 82.8%,respectively.Adding 5 wt.%FNAT promotes forming the Sm_(2)(Co,M)_(7) cell-wall phase and increases the coercivity and remanence by 272.7%and 48.1%,respectively.Finally,the corresponding microstructure evolution models,magnetization,and demagnetization mechanisms are proposed.
基金Project supported by the National Key R&D Program of China(Grant Nos.2021YFB3500300 and 2023YFB3507000)the Scientific Research Foundation of the High Education Institutions for Distinguished Young Scholars in Anhui Province(Grant No.2022AH020012)+1 种基金partially supported by the Innovation Project for Overseas Researcher in Anhui Province(Grant No.2022LCX004)the facilities at the Center of Free Electron Laser&High Magnetic Field(FEL&HMF)in Anhui University。
文摘ThMn_(12)-type iron-rich rare-earth permanent magnetic materials have garnered significant attention due to their exceptional intrinsic magnetic properties.However,challenges such as the metastable nature of the ThMn12-type phase,excessively small single-domain grain size,and complex fabrication processes have hindered the achievement of high phase purity,uniform microstructure,and desirable extrinsic performance.In this study,we directly synthesized ThMn_(12)-type Sm_(0.8)Zr_(0.2)Fe_(11)SiB_(x)(x=0-0.2)ribbon magnets via boron doping combined with a one-step rapid solidification method.This approach not only simplifies the fabrication process but also enhances phase stability and achieves a uniform microstructure with high ThMn12-type phase purity.By optimizing the boron content and cooling rate,the resulting magnets exhibit a coercivity(H_(c))of 6222 Oe,a remanence(M_(r))of 80 emu/g,and a remanence ratio(M_(r)/M_(s))of 0.71.This work demonstrates a streamlined approach to producing high-performance ThMn12-type magnets and provides insights into their practical application potential.
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 Key Research and Development Program of China(Grant No.2023YFB3507600)the National Natural Science Foundation of China(Nos.U23A20549 and 52171184).
文摘In this work, nanocrystalline SmCo_(5)-Cu nanocomposite powders were fabricated from the ball-milled amorphous matrix by crystallization annealing which is lower than the traditional sintering temperature ~ 1000℃ for bulk SmCo_(5) bulk magnets. Annealed Cu-doped SmCo_(5) powders have a higher coercivity compared to that of Cu-free SmCo_(5) one due to the combined effects of refinement effect of grain size and the pinning effect induced by Cu doping. The peak of coercivity (Hc) is located at 600℃ for annealed Cu-doped SmCo_(5), which is ascribed to the improved pinning field. The pinning effect became reduced when the annealing was done at even higher temperatures. More importantly, the best comprehensive magnetic properties, including a maximum magnetic energy product (BH)max of 12.2 MGOe together with a coercivity of 31.8 kOe and a remanence of 64.3 emu/g, could be achieved for SmCo_(5)-3 wt% Cu by low temperature annealing. These results demonstrate that isotropic Cu-doped SmCo_(5) nanocrystalline powders are promising precursors for the fabrication of high-performance bulk magnets.
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.
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supported in part by the National Natural Science Foundation of China under Grants 52307049 and U23A20644in part by the Fundamental Research Funds for the Central Universities under Grant JZ2023HGTB0243+1 种基金in part by the Key Laboratory of Electric Drive and Control of Anhui Province under Grant DQKJ202403in part by the China Postdoctoral Science Foundation under Grant 2024M751073。
文摘The arc-linear motor(ALM) is a new type of special motor derived from the linear motor, which has the merits of high torque, compact structure and fast dynamic response. This kind of motor does not need a complex intermediate transmission device, it is used in some direct-drive applications for continuous rotation or limited angle motion. However, there is no systematic summary and generalization of the ALMs so far.Therefore, this paper systematically overviews the recent advances in ALMs for direct-drive systems. First, the evolution process and basic structure of the ALM are introduced. And then, various ALMs are reviewed with particular reference to motor topologies, working principle, motor performance,optimization design and control techniques. To heel, a comprehensive comparison of several typical ALMs is carried out. Finally, the application areas, main challenges and development trends of the ALMs are highlighted.
基金supported by the National Key R&D Program of China (2023YFB3507601)the National Natural Science Foundation of China(52171184,U23A20549)。
文摘In recent years,high coercivity nanocrystalline magnets based on the critical single domain size theory have received increasing attention.However,nanocrystalline magnets are difficult to enhance the remanent magnetization by forming textures with conventional magnetic field orientation.Texturing of nanocrystalline magnets is usually done using the hot pressing and hot deformation technique,but there are some difficulties in applying this technique to form texture in SmCo systems.To discover and solve the difficulties of obtaining texturized nanocrystalline magnets during the deformation process,samarium cobalt magnets with different degrees of deformation were first experimentally prepared by low strain rate hot deformation method.Then,molecular dynamics simulations were utilized to study the micro structural changes and the multi-phase formation process during hot deformation.The process of deformation together with the reason why it is difficult to form textures in SmCo systems by lowtemperature hot deformation is discussed,and the strain energy densities of SmCo multiphase in multiple directions were calculated,which gives a feasible method to form low-temperature hot deformation textures in SmCo systems experimentally.
文摘Numerous uncertainties in practical production and operation can seriously affect the drive performance of permanent magnet synchronous machines(PMSMs).Various robust control methods have been developed to mitigate or eliminate the effects of these uncertainties.However,the robustness to uncertainties of electrical drive systems has not been clearly defined.No systemic procedures have been proposed to evaluate a control system's robustness(how robust it is).This paper proposes a systemic method for evaluating control systems'robustness to uncertainties.The concept and fundamental theory of robust control are illustrated by considering a simple uncertain feedback control system.The effects of uncertainties on the control performance and stability are analyzed and discussed.The concept of design for six-sigma(a robust design method)is employed to numerically evaluate the robustness levels of control systems.To show the effectiveness of the proposed robustness evaluation method,case studies are conducted for second-order systems,DC motor drive systems,and PMSM drive systems.Besides the conventional predictive control of PMSM drive,three different robust predictive control methods are evaluated in terms of two different parametric uncertainty ranges and three application requirements against parametric uncertainties.
文摘Chuan Qin,MD,PhD,is the President of the Chinese Association for Laboratory Animal Sciences(CALAS),and the permanent professor of Chinese Academy of Medical Sciences(CAMS)&Peking Union Medical College(PUMC).Moreover,she is the senior scientist of Institute of Laboratory Animal Sciences(ILAS),CAMS&PUMC.She is also the Vice-President of the Asian Federation of Laboratory Animal Science Associations(AFLAS),a board member of the International Council for Laboratory Animal Science(ICLAS),and Chairman of the National Standardization Technical Committee of Laboratory Animals.In addition to Animal Models and Experimental Medicine,Prof.Qin is also the Editor-in-Chief of Acta Laboratorium Animalis Scientia Sinica and Chinese Journal of Comparative Medicine.
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supported by the National Natural Science Foundation of China (Grant No.52108361)the Sichuan Science and Technology Program of China (Grant No.2023YFS0436)the State Key Laboratory of Geohazard Prevention and Geoenvironment Protection Independent Research Project (Grant No.SKLGP2022Z015).
文摘Bedding parallel stepped rock slopes exist widely in nature and are used in slope engineering.They are characterized by complex topography and geological structure and are vulnerable to shattering under strong earthquakes.However,no previous studies have assessed the mechanisms underlying seismic failure in rock slopes.In this study,large-scale shaking table tests and numerical simulations were conducted to delineate the seismic failure mechanism in terms of acceleration,displacement,and earth pressure responses combined with shattering failure phenomena.The results reveal that acceleration response mutations usually occur within weak interlayers owing to their inferior performance,and these mutations may transform into potential sliding surfaces,thereby intensifying the nonlinear seismic response characteristics.Cumulative permanent displacements at the internal corners of the berms can induce quasi-rigid displacements at the external corners,leading to greater permanent displacements at the internal corners.Therefore,the internal corners are identified as the most susceptible parts of the slope.In addition,the concept of baseline offset was utilized to explain the mechanism of earth pressure responses,and the result indicates that residual earth pressures at the internal corners play a dominant role in causing deformation or shattering damage.Four evolutionary deformation phases characterize the processes of seismic responses and shattering failure of the bedding parallel stepped rock slope,i.e.the formation of tensile cracks at the internal corners of the berm,expansion of tensile cracks and bedding surface dislocation,development of vertical tensile cracks at the rear edge,and rock mass slipping leading to slope instability.Overall,this study provides a scientific basis for the seismic design of engineering slopes and offers valuable insights for further studies on preventing seismic disasters in bedding parallel stepped rock slopes.
基金supported in part by the National Natural Science Foundation of China under Grant 52307056in part by the Natural Science Foundation of Jiangsu Province under Grant BK20210475。
文摘In this article, an inter-turn short-circuit(ITSC) fault diagnosis and severity estimation method based on extended state observer(ESO) and convolutional neural network(CNN) is proposed for five-phase permanent magnet synchronous motor(PMSM) drives. The relationship between fault parameters and motor parameters is analyzed and the equivalent model of ITSC faults in the natural reference frame is accordingly derived. To achieve fault detection and location, the short-circuit turn ratio and short-circuit current are integrated as the fault diagnosis index. According to the model of the shortcircuit current, an ESO is designed for the estimation of the fault diagnosis index. Further, the sensitivity analysis among fault parameters is conducted to evaluate the short-circuit turn ratio and the short-circuit resistance. Subsequently, the postfault current, back electromotive force, electrical angular velocity, q1-axis current reference and the fault diagnosis index are selected as the input signals of CNN to estimate the short-circuit turn ratio. This approach not only resolves parameter coupling challenges but also provides a quantitative assessment of fault severity. Finally, simulations and experiments under different operating points validate the effectiveness of the proposed method.
