Amyloid beta(Aβ)monomers aggregate to form fibrils and amyloid plaques,which are critical mechanisms in the pathogenesis of Alzheimer’s disease(AD).Given the important role of Aβ1-42 aggregation in plaque formation...Amyloid beta(Aβ)monomers aggregate to form fibrils and amyloid plaques,which are critical mechanisms in the pathogenesis of Alzheimer’s disease(AD).Given the important role of Aβ1-42 aggregation in plaque formation,leading to brain lesions and cognitive impairment,numerous studies have aimed to reduce Aβaggregation and slow AD progression.The diphenylalanine(FF)sequence is critical for amyloid aggregation,and magnetic fields can affect peptide alignment due to the diamagnetic anisotropy of aromatic rings.In this study,we examined the effects of a moderate-intensity rotating magnetic field(RMF)on Aβaggregation and AD pathogenesis.Results indicated that the RMF directly inhibited Aβamyloid fibril formation and reduced Aβ-induced cytotoxicity in neural cells in vitro.Using the AD mouse model APP/PS1,RMF restored motor abilities to healthy control levels and significantly alleviated cognitive impairments,including exploration and spatial and non-spatial memory abilities.Tissue examinations demonstrated that RMF reduced amyloid plaque accumulation,attenuated microglial activation,and reduced oxidative stress in the APP/PS1 mouse brain.These findings suggest that RMF holds considerable potential as a non-invasive,high-penetration physical approach for AD treatment.展开更多
The Al-5Cu alloys were prepared by different treatment methods,including adding a refiner Al-5Ti-1B,exerting a rotating magnetic field(RMF),and compound treatment of both refiner and RMF.The effects of treatment metho...The Al-5Cu alloys were prepared by different treatment methods,including adding a refiner Al-5Ti-1B,exerting a rotating magnetic field(RMF),and compound treatment of both refiner and RMF.The effects of treatment methods on the microstructure,properties,and solid solubility of the Al-5Cu alloy were investigated.The optimal magnetic field parameters and addition amount of refiner were confirmed by experiment.Results show that either RMF or adding refiner Al-5Ti-1B alone can refine the grain size,and the refining effect can be further improved by a compound refining treatment with optimized magnetic field parameters(120 A current and 8 Hz frequency) and 1.0wt.% Al-5Ti-1B refiner(RMF*+Al-5Ti-1B*).The average grain size is decreased to 68.1 μm,which is 60.8%,21.1%,and 83.5% lower than that of the alloy treated by the optimized rotating magnetic field,the Al-5Ti-1B refiner,and the alloy without any treatment,respectively.The tensile strength and elongation of the alloy reach 232.5 MPa and 18.6%,respectively,which are obviously higher than those of the alloys treated by rotating magnetic field,Al-5Ti-1B refiner,and the alloy without any treatment,respectively.Additionally,the solid solubility of the alloy is also obviously improved compared to the alloys treated by other methods.展开更多
We study the Hcisenberg moder under the influence of a rotating magnetic field. By using a time- dependent unitary transformation, the time evolution operator for the Schrodinger equation is obtained, which involves n...We study the Hcisenberg moder under the influence of a rotating magnetic field. By using a time- dependent unitary transformation, the time evolution operator for the Schrodinger equation is obtained, which involves no chronological product. The spin vectors (mean values of the spin operators) are obtained as explicit functions of time in the most general case. A series of cyclic solutions are presented. The nonadiabatic geometric phases of these cyclic solutions are caleulated, and are expressed in terms of the solid angle subtended by the closed trace of thc total spin vector, as well as in terms of those of the individual spins.展开更多
Rotating electromagnetic field is applied to the centrifugal casting, the macrostructure of centrifugal casting Al-1%Cu alloy stirred with driving or backing magnetic field are both examined. It is shown that both kin...Rotating electromagnetic field is applied to the centrifugal casting, the macrostructure of centrifugal casting Al-1%Cu alloy stirred with driving or backing magnetic field are both examined. It is shown that both kinds of electromagnetic filed can enforce the columnar-equiaxed transition, the driving one decrease the tendency of porosity occurring due to the increase in the bulk liquid pressure. Stirring with braking electromagnetic field produces the mixture of outer fine grains and inner coarse grains in the casting, this is analyzed to be contributed to the differences both in electric conductivity and density between the crystal and the melt, as well as skin effects.展开更多
The present paper describes an investigation conducted on metal detectors installed with a scanning probe.The authors applied a rotating magnetic field probe to metal detection.The rotating magnetic field probe is com...The present paper describes an investigation conducted on metal detectors installed with a scanning probe.The authors applied a rotating magnetic field probe to metal detection.The rotating magnetic field probe is comprised of two vertically placed rectangular exciting coils and a circular detecting coil.The experimental results confirmed that the probe can detect metal objects and provide more information about their shape,direction,and electromagnetic characteristics than conventional metal detector probes.A two-dimensional signal display shows a low-resolution image of the metal object and the signal phase indicates the object’s direction and electromagnetic characteristics.The experimental results show that excellent reconstruction of the surface shapes of metal objects can be obtained for both magnetic and nonmagnetic metals under present conditions.There is also the potential for the approximate shape of a metal object to be estimated from the reconstructed image.展开更多
AC loss presents a significant challenge for high-temperature superconducting (HTS) rotating machines. To date, the behaviour of total AC loss (Qtol) (with current) and magnetization loss (Qm) (without current) in a s...AC loss presents a significant challenge for high-temperature superconducting (HTS) rotating machines. To date, the behaviour of total AC loss (Qtol) (with current) and magnetization loss (Qm) (without current) in a single HTS tape under rotating magnetic fields (RF) have been explored. However, a research gap remains in understanding how these findings translate to the more complex HTS windings of rotating machines. Further exploration is needed to understand the loss behaviour of more complex HTS structures, such as HTS stacks. In this work, Qtol and Qm, in the HTS stacks under RF and a perpendicular AC standing wave magnetic field are numerically investigated. Two different RF models are considered: one is the Uni-RF model, characterized by a uniform field with equal field amplitudes and phases at each position, and the other is a non-uniform field created by a rotating Halbach array, referred to as the Hal-RF model. The dependence of AC loss on parameters such as the number of tapes in the stacks, tape width (2a), and the inclination angle (α) of tapes, which refers to the angle between the normal direction of the stack and the vertical direction, have been explored. The number of tapes in the stacks ranges from 1 to 16, α ranges from 0° to 90°, and the tape width includes 4 mm and 40 mm. Additionally, different rotating field directions are also considered. Interestingly, the analytical values from Brandt and Indenbom equation for Q_(m) of a superconducting strip (BI-strip) are close to Q_(m) results of the stacks under the standing wave at high fields, while they are over twice as high as those in the Hal-RF model at 1 T. This suggests the BI-strip equation is not reliable for predicting Q_(m) under RF at high fields. We also show in the Hal-RF model that different rotation directions of the field lead to varying Q_(m) and Qtol when asymmetric Jc (B, θ) data are applied. Moreover, it has been observed that the inclination angle has no impact on Q_(m) under uniform RF while significantly impacts both Q_(m) and Qtol in the Hal-RF model.展开更多
Composite biomaterials with controllable mi- crostructures play an increasingly important role in tissue engineering and regenerative medicine. Here, we report a magnetic hydrogel composite with disk-like microstructu...Composite biomaterials with controllable mi- crostructures play an increasingly important role in tissue engineering and regenerative medicine. Here, we report a magnetic hydrogel composite with disk-like microstructure fabricated by assembly of iron oxide nanopartides during the gelation process in the presence of rotating magnetic field. It should be mentioned that the iron oxide nanoparticles here were synthesized identically following techniques of Fer- umoxytol that is the only inorganic nanodrug approved by FDA for clinical applications. The microstructure of nano- particles inside the hydrogel was ordered three-dimensionally due to the twist of the aligned chains of magnetic nano- particles which leads to the lowest state of systematic energy. The size of microstructure can be tuned from several micro- meters to tens of micrometers by changing the assembly parameters. With the increase of microstructure size, the magnetothermal anisotropy was also augmented. This result confirmed that the assembly-induced anisotropy can occur even for the several micron aggregates of nanopartides. The rotating magnetic field-assisted technique is cost-effective, simple and flexible for the fabrication of composite hydrogel with ordered microstructure. We believe it will be favorable for the quick, green and intelligent fabrication of some com- posite materials.展开更多
According to the anti-phase sine current superposition theorem, the orientation, the magnetic flux density, the angular speed and the rotational direction of the spatial universal rotating magnetic field (SURMF) can...According to the anti-phase sine current superposition theorem, the orientation, the magnetic flux density, the angular speed and the rotational direction of the spatial universal rotating magnetic field (SURMF) can be controlled within the tri-axial orthogonal square Helmholtz coils (TOSHC). Nevertheless, three coupling direction angles of the normal vector of the SURMF in the Descartes coordinate system cannot be separately controlled, thus the adjustment of the orientation of the SURMF is difficult and the flexibility of the robotic posture control is restricted. For the dimension reduction and the decoupling of control variables, the orthogonal transformation operation theorem of the SURMF is proposed based on two independent rotation angular variables, which employs azimuth and altitude angles as two variables of the three-phase sine current superposition formula derived by the orthogonal rotation inverse transformation. Then the unique control rules of the orientation and the rotational direction of the SURMF are generalized in each spatial quadrant, thus the scanning of the normal vector of the SURMF along the horizontal or vertical direction can be achieved through changing only one variable, which simplifies the control process of the orientation of the SURMF greatly. To validate its feasibility and maneuverability, experiments were conducted in the animal intestine utilizing the innovative dual hemisphere capsule robot (DHCR) with active and passive modes. It was demonstrated that the posture adjustment and the steering rolling locomotion of the DHCR can be realized through single variable control, thus the orthogonal transformation operation theorem makes the control of the orientation of the SURMF convenient and flexible significantly. This breakthrough will lay a foundation for the human-machine interaction control of the SURMF.展开更多
In this study we investigate the flow structure in a liquid metal cylinder while a bubble-driven flow is superposed with a rotating magnetic field(RMF).Argon gas is injected through a nozzle into a column of the eutec...In this study we investigate the flow structure in a liquid metal cylinder while a bubble-driven flow is superposed with a rotating magnetic field(RMF).Argon gas is injected through a nozzle into a column of the eutectic alloy GalnSn. Without electromagnetic stirring the bubble plume in the centre region of the cylindrical vessel produces a recirculation with high velocities near the free surface while the fluid velocities in the bottom region remain rather low.The measurements revealed the potential of the RMF to control both the amplitude of the meridional flow and the bubble distribution and to provide an effective mixing in the whole fluid volume.Various periodic flow patterns were observed in a certain parameter range with respect to variations of the magnetic field strength and the gas flow rate.展开更多
This paper considers the situation where the liquid metal flow with a free surface covered by an oxide layer is driven by a rotating magnetic field.The cylindrical configuration was investigated in an experiment accom...This paper considers the situation where the liquid metal flow with a free surface covered by an oxide layer is driven by a rotating magnetic field.The cylindrical configuration was investigated in an experiment accompanied by numerical simulations.The oxide layer feels the effect of the viscous force arising from the moving liquid beneath and the friction force from the side walls.A complex interaction occurs if both forces are in the same order of magnitude.Our measurements demonstrate that the occurrence of the oxide layer may lead to an unexpected oscillating behaviour of the bulk flow.Our numerical model was shown to be able to reproduce essential features of the phenomenon in a qualitative way.展开更多
We present an experimental study concerning the flow inside a liquid metal column exposed to a pulsed rotating magnetic field.This paper is aimed at highly resolved,quantitative velocity measurements in the eutectic G...We present an experimental study concerning the flow inside a liquid metal column exposed to a pulsed rotating magnetic field.This paper is aimed at highly resolved,quantitative velocity measurements in the eutectic GalnSn alloy.A novel ultrasound Doppler system was used two measure two-dimensional velocity fields of the secondary flow in the radial-meridional plane.It employs an array of 25 transducer elements allowing a fast electronic traversing with concurrently high spatial and temporal resolution.The measurements revealed transient flow regimes showing distinct inertial oscillations and coherent vortex structures.The results demonstrate that the arising flow structure depends sensitively on the frequency of the RMF pulses.A maximum intensity of a periodic meridional flow can be observed,if the corresponding pulse frequency fp relates to the eigenperiod of the respective inertial mode in a developed regime.The electromagnetic stirring method that uses a modulated RMF offers considerable potential to enhance the stirring efficiency and to optimize the properties of castings by a well-aimed flow control during solidification.展开更多
A rotamak is one kind of compact spherically shaped magnetic-confinement device. In a rotamak the plasma current is driven by means of rotating magnetic field （RMF）. The driven current can reverse the original equil...A rotamak is one kind of compact spherically shaped magnetic-confinement device. In a rotamak the plasma current is driven by means of rotating magnetic field （RMF）. The driven current can reverse the original equilibrium field and generate a field-reversed-configuration. In a conventional rotamak, a toroidal field （TF） is not necessary for the RMF to drive plasma current, but it was found that the present of an additional TF can influence the RMF current drive. In this paper the effect of TF on the RMF current drive in a rotamak are investigated in some detail. The experimental results show that addition of TF increases the RMF driven current greatly and enhances the RMF penetration dramatically. Without TF, the RMF can only penetrate into plasma in the edge region. When a TF is added, the RMF can reach almost the whole plasma region. This is an optimal strength of toroidal magnetic field for getting maximum plasma current when Bv and radio frequency generator power are fixed. Besides driving current, the RMF generates high harmonic fields in rotamak plasma. The effect of TF on the harmonic field spectra are also reported.展开更多
Time-resolved Kerr rotation spectroscopy is used to determine the sign of the g factor of carriers in a semiconductor material, with the help of a rotatable magnetic field in the plane of the sample. The spin precessi...Time-resolved Kerr rotation spectroscopy is used to determine the sign of the g factor of carriers in a semiconductor material, with the help of a rotatable magnetic field in the plane of the sample. The spin precession signal of carriers at a fixed time delay is measured as a function of the orientation of the magnetic field with a fixed strength B. The signal has a sine-like form and its phase determines the sign of the g factor of carriers. As a natural extension of previous methods to measure the （time-resolved） photoluminescence or time-resolved Kerr rotation signal as a function of the magnetic field strength with a fixed orientation, such a method gives the correct sign of the g factor of electrons in GaAs. Furthermore, the sign of carriers in a （Ga, Mn）As magnetic semiconductor is also found to be negative.展开更多
In the present paper, we introduce the coupled theory （CD）, Lord-Schulman （LS） theory, and Green-Lindsay （GL） theory to study the influences of a magnetic field and rotation on a two-dimensional problem of fibre...In the present paper, we introduce the coupled theory （CD）, Lord-Schulman （LS） theory, and Green-Lindsay （GL） theory to study the influences of a magnetic field and rotation on a two-dimensional problem of fibre-reinforced thermoelasticity. The material is a homogeneous isotropic elastic half-space. The method applied here is to use normal mode analysis to solve a thermal shock problem. Some particular cases are also discussed in the context of the problem. Deformation of a body depends on the nature of the force applied as well as the type of boundary conditions. Numerical results for the temperature, displacement, and thermal stress components are given and illustrated graphically in the absence and the presence of the magnetic field and rotation.展开更多
In this paper, a spiral magnetic field electromagnetic stirrer, which can separately induce two different magnetic fields ,is introduced. The corresponding central magnetic flux curves of the stirrer were measured by ...In this paper, a spiral magnetic field electromagnetic stirrer, which can separately induce two different magnetic fields ,is introduced. The corresponding central magnetic flux curves of the stirrer were measured by two different probes of the Tesla meter. Meanwhile, the mentioned spiral magnetic field electromagnetic stirrer was used, the effect of the two different magnetic fields on solidification of Sn-I 1% Sb binary alloy was studied,and the segregations and metallographic structures of the ingot samples were analyzed. The research results show that, with the same electromagnetic stirring parameters,the spiral magnetic field electromagnetic stirring is more effective in reducing the composition difference between the upper and lower parts of the ingot. The microstructure photos show that the grain size was more refined.展开更多
We analyzed the data on co-rotating interaction regions （CIRs） measured by the Advanced Composition Explorer （ACE） and Solar TErrestrial RElations Observatory （STEREO） from 2007 to 2010. The CIRs were observed b...We analyzed the data on co-rotating interaction regions （CIRs） measured by the Advanced Composition Explorer （ACE） and Solar TErrestrial RElations Observatory （STEREO） from 2007 to 2010. The CIRs were observed by STEREO B （STB）, ACE and STEREOA （STA） one after another, and a total of 28 CIRs were identified in this work. Since the same characteristics of CIRs were detected by these three spacecraft at three different locations and times, these data can help us to study the evolutions of CIRs. For a single event, the properties of CIRs observed by the three spacecraft were quite different and could be explained by spatial or temporal variations. For all these 28 CIRs, STA and STB observed similar mean parameters, such as peak magnetic field strength （offset 11%）, peak and change in solar wind speed （offset 3% and 10% respectively）, peak proton temperature （offset 14%） and peak perpendicular pressure （offset 15%）. Surprisingly, STA detected much higher （41%） peak density of protons than STB.展开更多
In this work binary alloy of Pb-Sn is directionally solidified under transverse,slowly rotating magnetic field.For some alloys during directional solidification in the transverse magnetic field significant macrosegreg...In this work binary alloy of Pb-Sn is directionally solidified under transverse,slowly rotating magnetic field.For some alloys during directional solidification in the transverse magnetic field significant macrosegregation along the diameter of the ingot may appear if the growth velocity and magnetic field strength are chosen appropriately.This occurs as a result of thermoelectric current,driven by the applied temperature gradient at the solidification interface,and magnetic field interaction caused liquid phase forced convection(thermoelectrornagnetic convection). Magnetic field rotation velocity in chosen to be slow enough that induced electric current can be neglected but still fast enough not letting thermoelectromagnetic convection fully develop in the scale of crucible.In this case the effect caused by thermoelectromagnetic convection on the structure is expected to be different from the case with static magnetic field,which is already studied in many works.Newest experimental results as well as theoretical description and interpretation of the obtained results of direction solidification experiments under rotating magnetic field will be presented in this paper.Magnetic field of 0.5 T is created by rotating permanent magnet system driven by electric step motor.展开更多
Soft magnetic composites(SMCs)play a pivotal role in the development of high-frequency,miniaturization and complex forming of modern electronics.However,they usually suffer from a trade-off between high magnetization ...Soft magnetic composites(SMCs)play a pivotal role in the development of high-frequency,miniaturization and complex forming of modern electronics.However,they usually suffer from a trade-off between high magnetization and good magnetic softness(high permeability and low core loss).In this work,utilizing the order modulation strategy,a critical state in a FeSiBCCr amorphous soft magnetic composite(ASMC),consisting of massive crystal-like orders(CLOs,∼1 nm in size)with the feature ofα-Fe,is designed.This critical-state structure endows the amorphous powder with the enhanced ferromagnetic exchange interactions and the optimized magnetic domains with uniform orientation and fewer micro-vortex dots.Superior comprehensive soft magnetic properties at high frequency emerge in the ASMC,such as a high saturation magnetization(Ms)of 170 emu g^(-1)and effective permeability(µ_(e))of 65 combined with a core loss(Pcv)as low as 70 mW cm^(-3)(0.01 T,1 MHz).This study provides a new strategy for the development of high-frequency ASMCs,possessing suitable comprehensive soft magnetic performance to match the requirements of the modern magnetic devices used in the third-generation semiconductors and new energy fields.展开更多
The effect of RCMF-magnetic therapy apparatus on signal substances was studied. The radioimmunoassay (RIA) suggested that the magnetic field increased p-endorphin markedly in plasma. ELISA indicated that the magnetic ...The effect of RCMF-magnetic therapy apparatus on signal substances was studied. The radioimmunoassay (RIA) suggested that the magnetic field increased p-endorphin markedly in plasma. ELISA indicated that the magnetic field inhibited vomiting reaction induced by chemotherapy drug, with reversible decrease of serotonin (5-HT) level in brains, small intestine tissue and serum. Furthermore, the bioeffect of magnetic fields on 5-HT level presented a typical window effect and post-effect, and the inhibitory effect of magnetic field on the emesis was parallel to the decrease level of 5-HT. This result implied that the decrease of 5-HT might be the basis of rotating constant magnetic field (RCMF) inhibiting drug-induced emesis. The nitric acid reductase-spec-trophotometry and nicotinamide adenine dinucleotide-diaphorase/arginine-vasopressin (AVP) cytochemistry technique showed that the magnetic field induced nitric oxide (NO) increase in hypo-thalamus and the high NO(A) level lasted for 3 hours. The results suggested that NO(A) increases after the treatment of the magnetic field in hypothalamus, which may result from strong expression of NO-ergic neuron in paraventricular hypothalamic nucleus (PVN), periventricular hypothalamic nucleus (PEN) and supraoptic nucleus (SON). The coexistence of NO and AVP may play an important role in the regulation of endocrine and neuroendocrine by the magnetic field. And our data also confirmed that the magnetic field increased the content of NO so strongly that high NO level lasted for 3 hours, also made neuropeptide Y (NPY) cell in medulla stained heavily.展开更多
This paper presents an experimental study which in a first stage is focused on obtaining quantitative information about the isothermal flow field exposed to various magnetic field configurations.Melt stirring has been...This paper presents an experimental study which in a first stage is focused on obtaining quantitative information about the isothermal flow field exposed to various magnetic field configurations.Melt stirring has been realized by utilizing time-modulated AC magnetic fields in different variants.We consider time-modulated fields or combinations of traveling magnetic fields(TMF)and rotating magnetic fields(RMF).In a second step solidification experiments are carried out to verify the effect of a certain flow field on the solidification process.Our results demonstrate that the melt agitation using modulated magnetic fields offers a considerable potential for a well-aimed modification of casting properties by an effective control of the flow field.展开更多
基金National Key R&D Program of China(2023YFB3507004)National Natural Science Foundation of China(U21A20148)+2 种基金International Partnership Program of Chinese Academy of Sciences(116134KYSB20210052)Heye Health Technology Chong Ming Project(HYCMP2021010)CASHIPS Director’s Fund(BJPY2021A06)。
文摘Amyloid beta(Aβ)monomers aggregate to form fibrils and amyloid plaques,which are critical mechanisms in the pathogenesis of Alzheimer’s disease(AD).Given the important role of Aβ1-42 aggregation in plaque formation,leading to brain lesions and cognitive impairment,numerous studies have aimed to reduce Aβaggregation and slow AD progression.The diphenylalanine(FF)sequence is critical for amyloid aggregation,and magnetic fields can affect peptide alignment due to the diamagnetic anisotropy of aromatic rings.In this study,we examined the effects of a moderate-intensity rotating magnetic field(RMF)on Aβaggregation and AD pathogenesis.Results indicated that the RMF directly inhibited Aβamyloid fibril formation and reduced Aβ-induced cytotoxicity in neural cells in vitro.Using the AD mouse model APP/PS1,RMF restored motor abilities to healthy control levels and significantly alleviated cognitive impairments,including exploration and spatial and non-spatial memory abilities.Tissue examinations demonstrated that RMF reduced amyloid plaque accumulation,attenuated microglial activation,and reduced oxidative stress in the APP/PS1 mouse brain.These findings suggest that RMF holds considerable potential as a non-invasive,high-penetration physical approach for AD treatment.
文摘The Al-5Cu alloys were prepared by different treatment methods,including adding a refiner Al-5Ti-1B,exerting a rotating magnetic field(RMF),and compound treatment of both refiner and RMF.The effects of treatment methods on the microstructure,properties,and solid solubility of the Al-5Cu alloy were investigated.The optimal magnetic field parameters and addition amount of refiner were confirmed by experiment.Results show that either RMF or adding refiner Al-5Ti-1B alone can refine the grain size,and the refining effect can be further improved by a compound refining treatment with optimized magnetic field parameters(120 A current and 8 Hz frequency) and 1.0wt.% Al-5Ti-1B refiner(RMF*+Al-5Ti-1B*).The average grain size is decreased to 68.1 μm,which is 60.8%,21.1%,and 83.5% lower than that of the alloy treated by the optimized rotating magnetic field,the Al-5Ti-1B refiner,and the alloy without any treatment,respectively.The tensile strength and elongation of the alloy reach 232.5 MPa and 18.6%,respectively,which are obviously higher than those of the alloys treated by rotating magnetic field,Al-5Ti-1B refiner,and the alloy without any treatment,respectively.Additionally,the solid solubility of the alloy is also obviously improved compared to the alloys treated by other methods.
文摘We study the Hcisenberg moder under the influence of a rotating magnetic field. By using a time- dependent unitary transformation, the time evolution operator for the Schrodinger equation is obtained, which involves no chronological product. The spin vectors (mean values of the spin operators) are obtained as explicit functions of time in the most general case. A series of cyclic solutions are presented. The nonadiabatic geometric phases of these cyclic solutions are caleulated, and are expressed in terms of the solid angle subtended by the closed trace of thc total spin vector, as well as in terms of those of the individual spins.
文摘Rotating electromagnetic field is applied to the centrifugal casting, the macrostructure of centrifugal casting Al-1%Cu alloy stirred with driving or backing magnetic field are both examined. It is shown that both kinds of electromagnetic filed can enforce the columnar-equiaxed transition, the driving one decrease the tendency of porosity occurring due to the increase in the bulk liquid pressure. Stirring with braking electromagnetic field produces the mixture of outer fine grains and inner coarse grains in the casting, this is analyzed to be contributed to the differences both in electric conductivity and density between the crystal and the melt, as well as skin effects.
文摘The present paper describes an investigation conducted on metal detectors installed with a scanning probe.The authors applied a rotating magnetic field probe to metal detection.The rotating magnetic field probe is comprised of two vertically placed rectangular exciting coils and a circular detecting coil.The experimental results confirmed that the probe can detect metal objects and provide more information about their shape,direction,and electromagnetic characteristics than conventional metal detector probes.A two-dimensional signal display shows a low-resolution image of the metal object and the signal phase indicates the object’s direction and electromagnetic characteristics.The experimental results show that excellent reconstruction of the surface shapes of metal objects can be obtained for both magnetic and nonmagnetic metals under present conditions.There is also the potential for the approximate shape of a metal object to be estimated from the reconstructed image.
基金New Zealand Ministry of Business,Innovation and Employment under the Advanced Energy Technology Platform program“High power electric motors for large scale transport”contract number RTVU2004in part supported by the Air Force Office of Scientific Research under award number FA2386-22-1-4054Yuan Wang acknowledges financial supports from the Chinese Scholarship Council(CSC)and the CSC/Victoria University of Wellington Scholarship.
文摘AC loss presents a significant challenge for high-temperature superconducting (HTS) rotating machines. To date, the behaviour of total AC loss (Qtol) (with current) and magnetization loss (Qm) (without current) in a single HTS tape under rotating magnetic fields (RF) have been explored. However, a research gap remains in understanding how these findings translate to the more complex HTS windings of rotating machines. Further exploration is needed to understand the loss behaviour of more complex HTS structures, such as HTS stacks. In this work, Qtol and Qm, in the HTS stacks under RF and a perpendicular AC standing wave magnetic field are numerically investigated. Two different RF models are considered: one is the Uni-RF model, characterized by a uniform field with equal field amplitudes and phases at each position, and the other is a non-uniform field created by a rotating Halbach array, referred to as the Hal-RF model. The dependence of AC loss on parameters such as the number of tapes in the stacks, tape width (2a), and the inclination angle (α) of tapes, which refers to the angle between the normal direction of the stack and the vertical direction, have been explored. The number of tapes in the stacks ranges from 1 to 16, α ranges from 0° to 90°, and the tape width includes 4 mm and 40 mm. Additionally, different rotating field directions are also considered. Interestingly, the analytical values from Brandt and Indenbom equation for Q_(m) of a superconducting strip (BI-strip) are close to Q_(m) results of the stacks under the standing wave at high fields, while they are over twice as high as those in the Hal-RF model at 1 T. This suggests the BI-strip equation is not reliable for predicting Q_(m) under RF at high fields. We also show in the Hal-RF model that different rotation directions of the field lead to varying Q_(m) and Qtol when asymmetric Jc (B, θ) data are applied. Moreover, it has been observed that the inclination angle has no impact on Q_(m) under uniform RF while significantly impacts both Q_(m) and Qtol in the Hal-RF model.
基金supported by the National Key Research and Development Program of China(2017YFA0104301)the Fundamental Research Funds for the Central Universitiesthe supports from Collaborative Innovation Center of Suzhou Nano Science and Technology
文摘Composite biomaterials with controllable mi- crostructures play an increasingly important role in tissue engineering and regenerative medicine. Here, we report a magnetic hydrogel composite with disk-like microstructure fabricated by assembly of iron oxide nanopartides during the gelation process in the presence of rotating magnetic field. It should be mentioned that the iron oxide nanoparticles here were synthesized identically following techniques of Fer- umoxytol that is the only inorganic nanodrug approved by FDA for clinical applications. The microstructure of nano- particles inside the hydrogel was ordered three-dimensionally due to the twist of the aligned chains of magnetic nano- particles which leads to the lowest state of systematic energy. The size of microstructure can be tuned from several micro- meters to tens of micrometers by changing the assembly parameters. With the increase of microstructure size, the magnetothermal anisotropy was also augmented. This result confirmed that the assembly-induced anisotropy can occur even for the several micron aggregates of nanopartides. The rotating magnetic field-assisted technique is cost-effective, simple and flexible for the fabrication of composite hydrogel with ordered microstructure. We believe it will be favorable for the quick, green and intelligent fabrication of some com- posite materials.
基金supported by the National Natural Science Foundation of China (Grant Nos. 51277018, 61175102, & 51475115)the Open Fund of the State Key Laboratory of Mechanical Transmissions (Grant No.SKLMT-KFKT-201509)
文摘According to the anti-phase sine current superposition theorem, the orientation, the magnetic flux density, the angular speed and the rotational direction of the spatial universal rotating magnetic field (SURMF) can be controlled within the tri-axial orthogonal square Helmholtz coils (TOSHC). Nevertheless, three coupling direction angles of the normal vector of the SURMF in the Descartes coordinate system cannot be separately controlled, thus the adjustment of the orientation of the SURMF is difficult and the flexibility of the robotic posture control is restricted. For the dimension reduction and the decoupling of control variables, the orthogonal transformation operation theorem of the SURMF is proposed based on two independent rotation angular variables, which employs azimuth and altitude angles as two variables of the three-phase sine current superposition formula derived by the orthogonal rotation inverse transformation. Then the unique control rules of the orientation and the rotational direction of the SURMF are generalized in each spatial quadrant, thus the scanning of the normal vector of the SURMF along the horizontal or vertical direction can be achieved through changing only one variable, which simplifies the control process of the orientation of the SURMF greatly. To validate its feasibility and maneuverability, experiments were conducted in the animal intestine utilizing the innovative dual hemisphere capsule robot (DHCR) with active and passive modes. It was demonstrated that the posture adjustment and the steering rolling locomotion of the DHCR can be realized through single variable control, thus the orthogonal transformation operation theorem makes the control of the orientation of the SURMF convenient and flexible significantly. This breakthrough will lay a foundation for the human-machine interaction control of the SURMF.
基金Item Sponsored by the Deutsche Forschungsgemeinschaft (DFG) in Frame of the SFB 609"Electromagnetic Flow Control in MetallurgyCrystal Growth and Electrochemistry."
文摘In this study we investigate the flow structure in a liquid metal cylinder while a bubble-driven flow is superposed with a rotating magnetic field(RMF).Argon gas is injected through a nozzle into a column of the eutectic alloy GalnSn. Without electromagnetic stirring the bubble plume in the centre region of the cylindrical vessel produces a recirculation with high velocities near the free surface while the fluid velocities in the bottom region remain rather low.The measurements revealed the potential of the RMF to control both the amplitude of the meridional flow and the bubble distribution and to provide an effective mixing in the whole fluid volume.Various periodic flow patterns were observed in a certain parameter range with respect to variations of the magnetic field strength and the gas flow rate.
基金Item Sponsored by the Deutsche Forschungsgemeinschaft (DFG) in Frame of the SFB 609"Electromagnetic Flow Control in MetallurgyCrystal Growth and Electrochemistry"
文摘This paper considers the situation where the liquid metal flow with a free surface covered by an oxide layer is driven by a rotating magnetic field.The cylindrical configuration was investigated in an experiment accompanied by numerical simulations.The oxide layer feels the effect of the viscous force arising from the moving liquid beneath and the friction force from the side walls.A complex interaction occurs if both forces are in the same order of magnitude.Our measurements demonstrate that the occurrence of the oxide layer may lead to an unexpected oscillating behaviour of the bulk flow.Our numerical model was shown to be able to reproduce essential features of the phenomenon in a qualitative way.
基金Item Sponsored by Deutsche Forschungsgemeinschaft (DFG) in Form of the Collaborative Research Centre SFB 609"Electromagnetic Flow Control in MetallurgyCrystal Growth and Electrochemistry"
文摘We present an experimental study concerning the flow inside a liquid metal column exposed to a pulsed rotating magnetic field.This paper is aimed at highly resolved,quantitative velocity measurements in the eutectic GalnSn alloy.A novel ultrasound Doppler system was used two measure two-dimensional velocity fields of the secondary flow in the radial-meridional plane.It employs an array of 25 transducer elements allowing a fast electronic traversing with concurrently high spatial and temporal resolution.The measurements revealed transient flow regimes showing distinct inertial oscillations and coherent vortex structures.The results demonstrate that the arising flow structure depends sensitively on the frequency of the RMF pulses.A maximum intensity of a periodic meridional flow can be observed,if the corresponding pulse frequency fp relates to the eigenperiod of the respective inertial mode in a developed regime.The electromagnetic stirring method that uses a modulated RMF offers considerable potential to enhance the stirring efficiency and to optimize the properties of castings by a well-aimed flow control during solidification.
基金Project supported by the National Natural Science Foundation of China （Grant No 105750215） and by US D0E （Grant No DE-FG03-97ER54416）.
文摘A rotamak is one kind of compact spherically shaped magnetic-confinement device. In a rotamak the plasma current is driven by means of rotating magnetic field （RMF）. The driven current can reverse the original equilibrium field and generate a field-reversed-configuration. In a conventional rotamak, a toroidal field （TF） is not necessary for the RMF to drive plasma current, but it was found that the present of an additional TF can influence the RMF current drive. In this paper the effect of TF on the RMF current drive in a rotamak are investigated in some detail. The experimental results show that addition of TF increases the RMF driven current greatly and enhances the RMF penetration dramatically. Without TF, the RMF can only penetrate into plasma in the edge region. When a TF is added, the RMF can reach almost the whole plasma region. This is an optimal strength of toroidal magnetic field for getting maximum plasma current when Bv and radio frequency generator power are fixed. Besides driving current, the RMF generates high harmonic fields in rotamak plasma. The effect of TF on the harmonic field spectra are also reported.
基金Project supported by the National Basic Research Program of China (Grant No. 2009CB929301)the National Natural Science Foundation of China (Grant No. 10911130232)
文摘Time-resolved Kerr rotation spectroscopy is used to determine the sign of the g factor of carriers in a semiconductor material, with the help of a rotatable magnetic field in the plane of the sample. The spin precession signal of carriers at a fixed time delay is measured as a function of the orientation of the magnetic field with a fixed strength B. The signal has a sine-like form and its phase determines the sign of the g factor of carriers. As a natural extension of previous methods to measure the （time-resolved） photoluminescence or time-resolved Kerr rotation signal as a function of the magnetic field strength with a fixed orientation, such a method gives the correct sign of the g factor of electrons in GaAs. Furthermore, the sign of carriers in a （Ga, Mn）As magnetic semiconductor is also found to be negative.
文摘In the present paper, we introduce the coupled theory （CD）, Lord-Schulman （LS） theory, and Green-Lindsay （GL） theory to study the influences of a magnetic field and rotation on a two-dimensional problem of fibre-reinforced thermoelasticity. The material is a homogeneous isotropic elastic half-space. The method applied here is to use normal mode analysis to solve a thermal shock problem. Some particular cases are also discussed in the context of the problem. Deformation of a body depends on the nature of the force applied as well as the type of boundary conditions. Numerical results for the temperature, displacement, and thermal stress components are given and illustrated graphically in the absence and the presence of the magnetic field and rotation.
文摘In this paper, a spiral magnetic field electromagnetic stirrer, which can separately induce two different magnetic fields ,is introduced. The corresponding central magnetic flux curves of the stirrer were measured by two different probes of the Tesla meter. Meanwhile, the mentioned spiral magnetic field electromagnetic stirrer was used, the effect of the two different magnetic fields on solidification of Sn-I 1% Sb binary alloy was studied,and the segregations and metallographic structures of the ingot samples were analyzed. The research results show that, with the same electromagnetic stirring parameters,the spiral magnetic field electromagnetic stirring is more effective in reducing the composition difference between the upper and lower parts of the ingot. The microstructure photos show that the grain size was more refined.
基金supported by a National Natural Science Foundation of China (No. 11203083)
文摘We analyzed the data on co-rotating interaction regions （CIRs） measured by the Advanced Composition Explorer （ACE） and Solar TErrestrial RElations Observatory （STEREO） from 2007 to 2010. The CIRs were observed by STEREO B （STB）, ACE and STEREOA （STA） one after another, and a total of 28 CIRs were identified in this work. Since the same characteristics of CIRs were detected by these three spacecraft at three different locations and times, these data can help us to study the evolutions of CIRs. For a single event, the properties of CIRs observed by the three spacecraft were quite different and could be explained by spatial or temporal variations. For all these 28 CIRs, STA and STB observed similar mean parameters, such as peak magnetic field strength （offset 11%）, peak and change in solar wind speed （offset 3% and 10% respectively）, peak proton temperature （offset 14%） and peak perpendicular pressure （offset 15%）. Surprisingly, STA detected much higher （41%） peak density of protons than STB.
基金Item Sponsored by ESF project"Support for Doctoral studies at University of Latvia"and French ministry of education
文摘In this work binary alloy of Pb-Sn is directionally solidified under transverse,slowly rotating magnetic field.For some alloys during directional solidification in the transverse magnetic field significant macrosegregation along the diameter of the ingot may appear if the growth velocity and magnetic field strength are chosen appropriately.This occurs as a result of thermoelectric current,driven by the applied temperature gradient at the solidification interface,and magnetic field interaction caused liquid phase forced convection(thermoelectrornagnetic convection). Magnetic field rotation velocity in chosen to be slow enough that induced electric current can be neglected but still fast enough not letting thermoelectromagnetic convection fully develop in the scale of crucible.In this case the effect caused by thermoelectromagnetic convection on the structure is expected to be different from the case with static magnetic field,which is already studied in many works.Newest experimental results as well as theoretical description and interpretation of the obtained results of direction solidification experiments under rotating magnetic field will be presented in this paper.Magnetic field of 0.5 T is created by rotating permanent magnet system driven by electric step motor.
基金Guangdong Major Project of Basic and Applied Basic Research,China(Grant No.2019B030302010)the National Natural Science Foundation of China(Grant Nos.52301212,52071222,52101191,52001219)+1 种基金the National Key Research and Development Program of China(Grant No.2021YFA0716302)Guangdong Basic and Applied Basic Research,China(Grant Nos.2022A1515010347,2020B1515130007).
文摘Soft magnetic composites(SMCs)play a pivotal role in the development of high-frequency,miniaturization and complex forming of modern electronics.However,they usually suffer from a trade-off between high magnetization and good magnetic softness(high permeability and low core loss).In this work,utilizing the order modulation strategy,a critical state in a FeSiBCCr amorphous soft magnetic composite(ASMC),consisting of massive crystal-like orders(CLOs,∼1 nm in size)with the feature ofα-Fe,is designed.This critical-state structure endows the amorphous powder with the enhanced ferromagnetic exchange interactions and the optimized magnetic domains with uniform orientation and fewer micro-vortex dots.Superior comprehensive soft magnetic properties at high frequency emerge in the ASMC,such as a high saturation magnetization(Ms)of 170 emu g^(-1)and effective permeability(µ_(e))of 65 combined with a core loss(Pcv)as low as 70 mW cm^(-3)(0.01 T,1 MHz).This study provides a new strategy for the development of high-frequency ASMCs,possessing suitable comprehensive soft magnetic performance to match the requirements of the modern magnetic devices used in the third-generation semiconductors and new energy fields.
文摘The effect of RCMF-magnetic therapy apparatus on signal substances was studied. The radioimmunoassay (RIA) suggested that the magnetic field increased p-endorphin markedly in plasma. ELISA indicated that the magnetic field inhibited vomiting reaction induced by chemotherapy drug, with reversible decrease of serotonin (5-HT) level in brains, small intestine tissue and serum. Furthermore, the bioeffect of magnetic fields on 5-HT level presented a typical window effect and post-effect, and the inhibitory effect of magnetic field on the emesis was parallel to the decrease level of 5-HT. This result implied that the decrease of 5-HT might be the basis of rotating constant magnetic field (RCMF) inhibiting drug-induced emesis. The nitric acid reductase-spec-trophotometry and nicotinamide adenine dinucleotide-diaphorase/arginine-vasopressin (AVP) cytochemistry technique showed that the magnetic field induced nitric oxide (NO) increase in hypo-thalamus and the high NO(A) level lasted for 3 hours. The results suggested that NO(A) increases after the treatment of the magnetic field in hypothalamus, which may result from strong expression of NO-ergic neuron in paraventricular hypothalamic nucleus (PVN), periventricular hypothalamic nucleus (PEN) and supraoptic nucleus (SON). The coexistence of NO and AVP may play an important role in the regulation of endocrine and neuroendocrine by the magnetic field. And our data also confirmed that the magnetic field increased the content of NO so strongly that high NO level lasted for 3 hours, also made neuropeptide Y (NPY) cell in medulla stained heavily.
基金Item Sponsored by Deutsche Forschungsgemeinschaft (DFG) in Form of the Collaborative Research Centre SFB 609"Electromagnetic Flow Control in MetallurgyCrystal Growth and Electrochemistry"
文摘This paper presents an experimental study which in a first stage is focused on obtaining quantitative information about the isothermal flow field exposed to various magnetic field configurations.Melt stirring has been realized by utilizing time-modulated AC magnetic fields in different variants.We consider time-modulated fields or combinations of traveling magnetic fields(TMF)and rotating magnetic fields(RMF).In a second step solidification experiments are carried out to verify the effect of a certain flow field on the solidification process.Our results demonstrate that the melt agitation using modulated magnetic fields offers a considerable potential for a well-aimed modification of casting properties by an effective control of the flow field.
