Multiscale Modeling of Magnetic Distribution of Ribbon Magnetic Cores

The multiscale finite element method(MsFEM)combined with conventional finite element method(CFEM)is proposed to solve static magnetic field in the ribbon magnetic core with non-periodical corners considered.Firstly,a simple 2-dimensional electrostatic problem is used to introduce the MsFEM implementation process.The results are compared to analytical method,as well as conventional FEM.Then,an exam-ple of magneto-static problem is considered for a ribbon magnetic core built sheet by sheet as well as corners taken into considera-tion.Conventional FEM and MsFEM are used to compute the magneto-static field by adopting scalar magnetic potential.Both magnetic potential and magnetic flux density on a certain path are compared.It is shown that the results obtained by MsFEM agree well with the one from conventional FEM.Moreover,MsFEM combined with FEM is potentially a general strategy for mul-tiscale modeling of ribbon magnetic cores with complex and non-periodical structures considered,like corners and T-joints,which can effectively reduce the computational cost.

Facile in situ synthesis and characterization of Fe@Si/zeolite Na composites with magnetic core–shell structures from natural materials for enhanced curcumin loading capacity

Curcumin is a natural polyphenol that is used in various traditional medicines.However,its inherent properties,such as its rapid degradation and metabolism,low bioavailability,and short half-life,are serious problems that must be resolved.To this end,a drug carrier incorporating natural magnetic cores in a zeolite framework was developed and applied to the loading of curcumin in ethanol solutions.In this system,curcumin is encapsulated in a zeolite Na(ZNA)magnetic core–shell structure(Fe@Si/ZNA),which can be easily synthesized using an in situ method.Synthesis of Fe_(3)O_(4) nanoparticles was carried out from natural materials using a co-precipitation method.Analysis of the prepared magnetic core–shell structures and composites was carried out using vibrating-sample magnetometery,Fourier transform infrared spectroscopy,transmission electron microscopy,and x-ray diffraction.The cumulative loading of curcumin in the ZNA composite with 9%nanoparticles was found to reach 90.70%with a relatively long half-life of 32.49 min.Stability tests of curcumin loading in the composite showed that adding magnetic particles to the zeolite framework also increased the stability of the composite structure.Adsorption kinetics and isotherm studies also found that the system follows the pseudo-second-order and Langmuir isotherm models.

Effects of two silicone resin coatings on performance of FeSiAl magnetic powder cores

Two silicon resins with excellent thermal stability,JH1123 and JH7102,are used as the insulated agents and binders for the gas-atomized FeSiAl powder,and corresponding magnetic powder cores(MPCs)are fabricated.The insulation capability and application prospects of the two silicon resins are evaluated by comparing the magnetic properties of the coated powder and MPCs.The scanning electron microscopy,energy dispersive X-ray spectroscopy and Fourier transform infrared spectroscopy results show that uniform insulation layers are both formed on the powder surfaces.JH1123 has stronger binding ability,and the JH1123-coated powder exhibits severe agglomeration,with d50(average particle size)approximately twice that of the JH7102-coated powder.Both as-prepared MPCs exhibit outstanding soft magnetic properties.Wherein,the permeability of FeSiAl@JH1123 is up to 74.0,which is 35.5%higher than that of FeSiAl@JH7102 because JH1123 can further improve the density of the MPCs.As for FeSiAl@JH7102,it has better direct current bias and lower core loss of 716.9 mW cm^(−3) at 20 mT and 1000 kHz due to its lower coercivity and greater anti-magnetic saturation ability.A comprehensive comparison shows that FeSiAl@JH1123 is suitable for medium and high frequency applications,while FeSiAl@JH7102 is more suitable for high frequency applications.This indicates that the use of JH1123 and JH7102 silicon resins for binding and insulated coating not only simplifies the preparation process of MPCs,but also enables the controlled production of MPCs for different applications.

Energy Harvesting Based on Magnetic Dispersion for Three-Phase Power System

This paper presents a comparative study on Magnetic-Dispersion based Energy Harvesting Systems (MD-EHS) on electrical conductors that supply power for a three-phase AC motor. It introduces two MD-EHS which are based on magnetic cores of different material, named, nanocrystalline, ferrite and iron powder. The first one consists of harvesting energy from magnetic flux through three symmetrical magnetic cores installed on each power conductors of a three-phase AC motor. The second one consists of a single magnetic core for harvesting energy from magnetic flux of only one of these conductors. Both ones have an AC/DC converter and a variable resistor based load. Experimental results have agreed with the theoretical analysis and show that the first proposed MD-EHS is capable of supplying 14 times more energy than the second MD-EHS, considering nanocrystalline cores and phase current of 3 A, and 7.5 times more energy, considering ferrite cores and phase current of 9 A. Such energy can be applied to various low-power devices, especially in wireless sensor network.

Development of a large nanocrystalline soft magnetic alloy core with highμ'_(p)Qf products for CSNS-Ⅱ

A waterproof nanocrystalline soft magnetic alloy core with a size of O.D.850 mm×I.D.316 mm×H.25 mm for radio frequency acceleration was successfully developed by winding 18μm 1k107b MA ribbons.Theμ'_(p)Qf products reached 7.5,10,and 12 GHz at 1,3,and 5 MHz,respectively.Theμ'_(p)Qf products of the MA core(O.D.250 mm×I.D.100 mm×H.25 mm)manufactured using a 13μm MA ribbon further increased by 30%.Detailed improvements on the MA core manufacture process are discussed herein.Continuous high-power tests on the new MA cores demonstrated its good performance of waterproofness,particularly its stability of highμ'_(p)Qf products.The MA core with highμ'pQf product and large size can operate under a high average RF power,high electric field,and in deionized water,which will be used in the China Spallation Neutron Source PhaseⅡ(CSNS-Ⅱ).

Torque Ripple Reduction of Synchronous Reluctance Machine by Using Asymmetrical Barriers and Hybrid Magnetic Core

As there is no need of permanent magnet(PM)material and only silicon steel sheet required on the rotor,synchronous reluctance machine(SynRM)can be used for many applications and draws a great research interest.For the SynRM,the torque ripple is a big issue and a great of work could been done on reducing it.In this paper,asymmetrical magnetic flux barriers in the SynRM rotor were studied comprehensively,including angle and width of each layer and each side of the magnetic barrier.The SynRMb with asymmetrical and parallel magnetic flux barrier was found as the best way to design SynRM based on the multi-objective design optimization method.Moreover,each parameter was studied to show the design rule of the asymmetrical magnetic flux barrier.As the average torque will be reduced with the asymmetrical barrier is used,the grain-oriented silicon steel is used on stator teeth of the SynRMb(SynRMbG)was proposed and studied.The analysis results show that the proposed new method can make the SynRM have better performance.

Behavior of Medium-frequency Core Loss in Fe-based Nanocrystalline Soft Magnetic Alloys

The dependences of the power loss per cycle on frequency have been investigated in the ranges of 100 Hz<= f<=25000 Hz and 0.1 T< =Bm <=1.0 T for three main original magnetic states in five sorts of Fe-based nanocrystalline soft magnetic alloys. The measured and calculated results showed that the total power loss per cycle clearly exhibited a nonlinear behavior in the range below 3 kHz～5 kHz depending on both the magnetic state and the value of Dm, whereas it showed a quasi-linear behavior above this range. The total loss was decomposed into hysteresis loss, classical eddy current loss and excess loss, the obvious nonlinear behavior has been confirmed to be completely determined by the dependence of the excess loss on frequency. It has been indicated that the change rate of the excess loss per cycle with respect to frequency sharp decreases with increasing frequency in the range below about 3 kHz～5 kHz, wherease the rate of change slowly varies above this range, thus leading to the quasilinear behavior of the total loss per cycle. In this paper, some linear expressions of the total loss per cycle has been given in a wider medium-frequency segment, which can be used for roughly estimating the total loss.

Design of a Rogowski Coil with a Magnetic Core Used for Measurements of Nanosecond Current Pulses

A Rogowski coil is developed to detect the nanosecond pulse signals of the discharge current with a wide bandwidth of 800 kHz to 106 MHz and high sensitivity of 2.22 V/A. Performance tests show that the Rogowski coil has both excellent dynamic and static characteristics. Calibrating results and the comparison between the standard current shunt and the developed Rogowski coil for the measurement of nanosecond discharge pulses demonstrate that the developed Rogowski coil can reproduce the actual waveform of the discharge current accurately.

Fabrication of solenoid-type microinductor with different magnetic core schemes by MEMS technique

Two micromachined solenoid-type inductors with different electroplated core structures, ellipse and rectangle, were fabricated, tested and compared in order to reach optimum designs for integrated induetoes and transformers. In the process of fabrication, UV-LIGA, dry. etching technique, fine polishing and eleetroplating techniques have been adopted to achieve high performance mieminduetor. Experimental results show that both types of the induetors are characterized by high inductance, Q-factor and low electrical resistance. While the inductance of the inductor with rectangular magnetic core is slightly higher than that with elliptical magnetic core, the quality factor of the latter is larger than that of the former.

A 400 MHz Low Noise Amplifier at Cryogenic Temperature for Superconductor Filter System

A cryogenic low noise amplifier （LNA） using Agilent high electron mobility transistor （HEMT） for 380 MHzto 480 MHz is designed and fabricated, and the excellent cryogenic performance in superconducting receiver front-end for communication system is achieved. A special input impedance matching topology is implemented to provide low noise figure （NF） and good input matching in this cryogenic LNA design. The measurement results show that the NF is within 0.25 dB from the minimum NF of a single transistor, the power gain is above 20 dB, the flatness is within 1 dB, and the maximum input return loss is lower than -20 dB in bandwidth.

Novel CoFeAlMn high-entropy alloys with excellentsoft magnetic properties and high thermal stability

High-entropy alloys(HEAs),which are composed of 3d transition metals such as Fe,Co,and Ni,exhibit an exceptional combination of magnetic and other properties;however,the addition of non-ferromagnetic elements always negatively affects the saturation magnetization strength(M s).Co_(4)Fe_(2)Al_(x)Mn_(y) alloys were designed and investigated in this study to develop a novel HEA with excellent soft magnetic properties.The Co_(4)Fe_(2)Al_(1.5)Mn_(1.5) HEA possesses the highest M s of 161.3 emu g^(-1) thus far reported for magnetic HEAs,a low coercivity of 1.9 Oe,a high electrical resistivity of 173μΩ cm,a superior thermal stability up to 600℃,which originates from the novel microstructure of B2 nanoparticles distributed in a DO_(3) matrix phase,and the crucial transition of Mn from antiferromagnetism to ferromagnetism with the assistance of Al.The Co_(4)Fe_(2_)Al_(1.5)Mn_(1.5) HEA was selected to produce micron-sized powder and soft magnetic powder cores(SMPCs)for application in the exploration field.The SMPCs exhibit a high stable effective perme-ability of 35.9 up to 1 MHz,low core loss of 38.1 mW cm^(-3)(@100 kHz,20 mT),and an excellent direct current(DC)bias performance of 87.7%at 100 Oe.This study paves the way for the development of soft magnetic HEAs with promising applications as magnetic functional materials.

Faster vortex core switching with lower current density using three-nanocontact spin-polarized currents in a confined structure

We perform micromagnetic simulations on the switching of magnetic vortex core by using spin-polarized currents through a three-nanocontact geometry. Our simulation results show that the current combination with an appropriate current flow direction destroys the symmetry of the total effective energy of the system so that the vortex core can be easier to excite,resulting in less critical current density and a faster switching process. Besides its fundamental significance, our findings provide an additional route to incorporating magnetic vortex phenomena into data storage devices.

Paleozoic Multi-Stage Magmatic Events Related to Proto-Tethys and Paleo-Tethys Evolution:Insights from Intrusive Rocks in the Eastern Altyn Orogen,NW China

Abundant mafic-felsic intrusions distributed in the Altyn Orogen record orogenic histories related to Proto-Tethys and Paleo-Tethys evolution.Zircon U-Pb dating of the intrusive rocks in the eastern Altyn Orogen identifies at least three major tectono-magmatic episodes,yielding ages of∼426,∼376–373 and∼269–254 Ma.The first two emplacement episodes correspond to the post-collisional magmatism in the Altyn Orogen.The∼426 Ma granitoids possess adakitic characteristics coupled with enriched isotopes,suggesting that they originated from partial melting of thickened lower continental crust induced by upwelling asthenospheric mantle after slab break-off of the South Altyn Ocean Plate.Next,the∼376–373 Ma mafic-intermediate rocks and coeval granitoids represent a large thermal event that involved mantle melting with induced new juvenile lower continental crust melting in a post-collisional extensional setting.Finally,the∼254 Ma diabase dykes intruded into the∼269 Ma granitoids,which were related to the widespread Late Paleozoic magmatism resulting from Paleo-Tethys Ocean subduction.Post-collisional magmatism in the Altyn Orogen significantly enhances understanding of the tectono-magmatic evolution in the northern Tibetan Plateau.The penetrative influence of Paleo-Tethys Ocean subduction was more extensive than previously thought.

变形和能量注入协同作用制备可控非晶纳米晶结构超高饱和磁化强度FeCoB粉末

非晶纳米晶磁粉芯(ANMPCs)是电子元器件在高频应用的关键软磁材料.但其相对较低的饱和磁化强度无法满足器件的小型化要求.强Fe-Co交换耦合非晶纳米晶粉是制备高磁化强度ANMPCs的潜在材料.本文采用机械球磨法制备了一系列(Fe_(0.8)Co_(0.2))_(87)B_(13)软磁粉末,这些粉末的非晶相、纳米晶相含量和粒径可调.在球磨过程中,出现了合金化、玻璃化和纳米化三个阶段以及粉末形貌和尺寸的非线性变化,进而导致ANMPCs软磁性能的非单调变化.磁粉具有超高饱和磁化强度达239 emu g^(-1),有效磁导率为33.球磨150 h后,FeCoB粉末非晶-纳米晶双相结构达到动态平衡,同时粒径达亚微米尺度,从而提高了粉末高频稳定性且降低了磁芯损耗.在变形和能量注入的协同作用下,机械球磨实现了含极高铁磁元素的非晶-纳米晶双相粉末可控制备、提高了高磁化强度ANMPCs综合软磁性能.

Determination of Hydrocortisone in Cosmetics by CdSe/CdS Quantum Dots-Based Fluoroimmunoassay Using Magnetic Fe304/Au Nanoparticles as Solid Carriers

This work demonstrated the feasibility of detecting hydrocortisone in cosmetics using a novel CdSe/CdS quan- tum dots-based competitive fluoroimmunoassay with magnetic core/shell Fe3Oa/Au nanoparticles （MCFN） as solid carriers. Hydrocortisone antigen was labeled with the synthesized core/shell CdSe/CdS quantum dots （QDs） to form the antigen-QDs conjugate. Meanwhile, hydrocortisone antibody was incubated with MCFN and the immobilized antibody was obtained. The immobilized antibody was then mixed sequentially with hydrocortisone and a slightly excess amount of the QDs-labeled hydrocortisone antigen, allowing their competition for binding with the antibody immobilized on MCFN. The bound hydrocortisone and the antigen-QDs conjugates on MCFN were removed subsequently after the mixture was applied to a magnetic force. The analyte concentration was obtained by measuring the fluorescence intensity of the unbound hydrocortisone antigen-QDs conjugates. The proposed method was characterized by simplicity, rapidity, and high sensitivity with a wide linear working range of 0.5 to 15000 pg·mL^-1 and a low detection limit of 0.5 pg.mL^- 1. The proposed method was successfully applied to the determination of hydrocortisone in cosmetics with satisfactory results.

Study of a magnetic alloy-loaded cavity for compact synchrotrons

Magnetic alloy（MA）-loaded cavities have been widely used in compact proton and heavy-ion synchrotrons,and the MA core is the key issue in their development.Chinese-produced MA has never yet been adopted as core material for an MA-loaded cavity.To use Chinese-produced MA as the core material,it is necessary to study its properties,and compare with MA material produced elsewhere.In this paper,the properties of several MA cores made of Chinese-produced material are measured.Based on the measured results,a schematic design is produced for a cavity which could obtain 1 kV gap voltage with less than 1.5 kW power dissipation in the frequency range of0.5-7 MHz.The difference between resonant frequencies obtained from simulation and analytical results is less than10%.

Feasibility of Applying Home-Made Amorphous Core to Induction Module

The application of the homemade 1K101 amorphous core in induction module is reported in this paper.The properties of magnetic,insulation and stability are studied with the cores.A pulse with pulse width of 120ns(FWFM), flattop of 72ns(±1%)and rise time of 17ns can be obtained with single-pulse induction module.Triple-pulse with the rise time of 35us,flat-top of 60ns(±1%)and pulse width of 120us(FWFM)was obtained when tested with a formal linear induction module at MHz repetition burst mode.The effective average flux swing of the amorphous core is about 1.41T.The cores work well with triple-pulse of 282kV.The properties of the cores are stable and suitable for induction module.

Design, optimization, and measurement of closed-loop Hall effect current sensor

A kind of closed-loop Hall effect sensor is designed and fabricated by considering several factors such as iron core material, Hall device, as well as selected integrated circuit. Through studying the effect of the iron material and structures of current sensor, a kind of optimal Hall effect current sensor is found. The experimental results show that the presented closed-loop Hall effect current sensor achieves 1 mA/A sensitivity. And its lineafity and accuracy are 0.1% and 0.35% FS, respectively, at cur- rents ranging from 0 to 50 A.

Newly-modeled graphene-based ternary nanocomposite for the magnetophotocatalytic reduction of CO_(2) with electrochemical performance

The development of CO_(2)into hydrocarbon fuels has emerged as a green method that could help mitigate global warning.The novel structured photocatalyst is a promising material for use in a photocatalytic and magneto-electrochemical method that fosters the reduction of CO_(2)by suppressing the recombination of electron−hole pairs and effectively transferring the electrons to the surface for the chemical reaction of CO_(2)reduction.In our study,we have developed a novel-structured AgCuZnS_(2)–graphene–TiO_(2)to analyze its catalytic activity toward the selective evolution of CO_(2).The selectivity of each nanocomposite substantially enhanced the activity of the AgCuZnS_(2)–graphene–TiO_(2)ternary nanocomposite due to the successful interaction,and the selectivity of the final product was improved to a value 3 times higher than that of the pure AgCuZnS_(2)and 2 times higher than those of AgCuZnS_(2)–graphene and AgCuZnS_(2)–TiO_(2)under ultraviolet(UV)-light(λ=254 nm)irradiation in the photocatalytic process.The electrochemical CO_(2)reduction test was also conducted to analyze the efficacy of the AgCuZnS_(2)–graphene–TiO_(2)when used as a working electrode in laboratory electrochemical cells.The electrochemical process was conducted under different experimental conditions,such as various scan rates(mV·s^(–1)),under UV-light and with a 0.07 T magneticcore.The evolution of CO_(2)substantially improved under UV-light(λ=254 nm)and with 0.07 T magnetic-core treatment;these improvements were attributed to the facts that the UV-light activated the electron-transfer pathway and the magnetic core controlled the pathway of electrontransmission/prevention to protect it from chaotic electron movement.Among all tested nanocomposites,AgCuZnS_(2)–graphene–TiO_(2)absorbed the CO_(2)most strongly and showed the best ability to transfer the electron to reduce the CO_(2)to methanol.We believe that our newly-modeled ternary nanocomposite opens up new opportunities for the evolution of CO_(2)to methanol through an electrochemical and photocatalytic process.

Transverse Flux Induction Coil for Uniform Bar Heating Excluding Edge

This work particularly focuses on compensating Joule heat in under-heated areas occurred when thin steel bar is(<20 mm)heated by transverse flux induction heater(TFIH).The under-heated areas take place in range of 50~150 mm from the both edges,so Transverse Flux Induction Coil(TFIC)including a magnetic core is proposed and optimized to supplement this fault.The solutions on the electromagnetic field are obtained numerically by commercial code MAXWELL 3D software from ANSYS Corp.and then,verified experimentally by pilot-scale tests,in which the TFIH was manufactured with a nominal power of 100 kW at a fundamental frequency of 1 kHz.Ultimately,TFIC having geometrically the optimized magnetic core made the heating pattern U-shaped,so could supply a desirable temperature profile for the rolling process.