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1

Modeling of Hysteresis Losses Applied to Slotless Permanent Magnet Motors  

Microsoft Academic Search

The paper presents a method to determine hysteresis losses in synchronous permanent magnet (PM) slotless motors. The method comprises four steps : (1) experimental determination of the B-H loop, (2) analytical modeling of the B-H loop by applying different models, (3) analytical modeling of the hysteresis losses, and (4) determination of the hysteresis losses in a synchronous PM motor, and

Pierre-Daniel Pfister; Christian Koechli; Miroslav Markovic; Y. Perriard

2007-01-01

2

Analysis of Hysteresis Losses in Synchronous Permanent Magnet Motors  

Microsoft Academic Search

The paper presents a method to determine hysteresis losses in synchronous permanent magnet (PM) motors. The method comprises four steps: (1) experimental determination of the B-H loop, (2) analytical modeling of the B-H loop by applying different models, (3) analytical modeling of the hysteresis losses, and (4) determination of the hysteresis losses in a synchronous PM motor, and results' verification

P.-D. Pfister; C. Koechli; M. Markovic; Y. Perriard

2006-01-01

3

Numerical characterization of dynamic hysteresis loops and losses in soft magnetic materials  

Microsoft Academic Search

This paper deals with the characterization of dynamic loops shapes and losses in soft magnetic materials. An experimental and theoretical analysis has been done in order to describe static and dynamic hysteresis on soft ferrite cores. A parallelogram-loop-based hysteresis modeling is described and discussed. The possibility of the model to include vector hysteresis and the related properties are then discussed,

E. Cardeffi; Romano Giannetti; Bernardo Tellini

2005-01-01

4

The magnetization process: Hysteresis  

NASA Technical Reports Server (NTRS)

The magnetization process, hysteresis (the difference in the path of magnetization for an increasing and decreasing magnetic field), hysteresis loops, and hard magnetic materials are discussed. The fabrication of classroom projects for demonstrating hysteresis and the hysteresis of common magnetic materials is described in detail.

Balsamel, Richard

1990-01-01

5

Magnetization Process: Hysteresis.  

National Technical Information Service (NTIS)

The magnetization process, hysteresis (the difference in the path of magnetization for an increasing and decreasing magnetic field), hysteresis loops, and hard magnetic materials are discussed. The fabrication of classroom projects for demonstrating hyste...

R. Balsamel

1990-01-01

6

Hysteresis force loss and damping properties in a practical magnet superconductor maglev test vehicle  

NASA Astrophysics Data System (ADS)

In order to investigate the feasible application of a permanent magnet-high-temperature superconductor (PM-HTS) interaction maglev system to a maglev train or a space vehicle launcher, we have constructed a demonstration maglev test vehicle. The force dissipation and damping of the maglev vehicle against external disturbances are studied in a wide range of amplitudes and frequencies by using a sine vibration testing set-up. The dynamic levitation force shows a typical hysteresis behavior, and the force loss is regarded as the hysteresis loss, which is believed to be due to flux motions in superconductors. In this study, we find that the hysteresis loss has weak frequency dependence at small amplitudes and that the dependence increases as the amplitude grows. To analyze the damping properties of the maglev vehicle at different field cooling (FC) conditions, we also employ a transient vibration testing technique. The maglev vehicle shows a very weak damping behavior, and the damping is almost unaffected by the trapped flux of the HTSs in different FC conditions, which is believed to be attributed to the strong pinning in melt-textured HTSs.

Yang, Wenjiang; Liu, Yu; Wen, Zheng; Chen, Xiaodong; Duan, Yi

2008-01-01

7

Effect of the distribution of anisotropy constants on hysteresis losses for magnetic hyperthermia applications  

NASA Astrophysics Data System (ADS)

Magnetic hyperthermia using magnetic nanoparticles is a potential remedial therapy for the reduction of cancer and other tumours. The dominant heating mechanism is hysteresis heating. This means that control of the particle size distribution is essential. However, control of the anisotropy dispersion is also required. We have calculated the effect of the anisotropy distribution on the hysteresis heating in magnetic nanoparticles for hyperthermia applications. Where there is a wide distribution of anisotropy constants the heat output is controlled by the distribution of anisotropy constants. This effect is significant in systems such as magnetite particles where shape anisotropy dominates.

Vallejo-Fernandez, G.; O'Grady, K.

2013-09-01

8

Predicting loss in magnetic steels under arbitrary induction waveform and with minor hysteresis loops  

Microsoft Academic Search

We have studied ways of predicting power losses in soft magnetic laminations for generic time dependence of the periodic magnetic polarization J(t). We found that, whatever the frequency and the induction waveform, the loss behavior can be quantitatively assessed within the theoretical framework of the statistical loss model. The prediction requires a limited set of preemptive experimental data, depending on

Edoardo Barbisio; Fausto Fiorillo; Carlo Ragusa

2004-01-01

9

A magnetic hysteresis model  

NASA Technical Reports Server (NTRS)

The Passive Aerodynamically Stabilized Magnetically Damped Satellite (PAMS) will be deployed from the Space Shuttle and used as a target for a Shuttle-mounted laser. It will be a cylindrical satellite with several corner cube reflectors on the ends. The center of mass of the cylinder will be near one end, and aerodynamic torques will tend to align the axis of the cylinder with the spacecraft velocity vector. Magnetic hysteresis rods will be used to provide passive despin and oscillation-damping torques on the cylinder. The behavior of the hysteresis rods depends critically on the 'B/H' curves for the combination of materials and rod length-to-diameter ratio ('l-over-d'). These curves are qualitatively described in most Physics textbooks in terms of major and minor 'hysteresis loops'. Mathematical modeling of the functional relationship between B and H is very difficult. In this paper, the physics involved is not addressed, but an algorithm is developed which provides a close approximation to empirically determined data with a few simple equations suitable for use in computer simulations.

Flatley, Thomas W.; Henretty, Debra A.

1995-01-01

10

Drag force measurement: A means for determining hysteresis loss  

SciTech Connect

A method for determining hysteresis losses in thin strips of soft magnetic materials is described. It is based on the measurement of a drag force which arises with the movement of the sample through the strong field existing in the space near a permanent magnet. Not associated with macro eddy currents, the force is shown to originate from the magnetic hysteresis of the material, having, in fact, an amplitude equal to the product of hysteresis loss and the area of the sample cross section. Correlation within 18% with the measurements made by conventional methods is shown for a wide range of experimental materials.

Garshelis, Ivan J.; Tollens, Stijn P. L.; Kari, Ryan J.; Vandenbossche, Lode P.; Dupre, Luc R. [Magnova, Inc., Pittsfield, Massachusetts 01201 and MagCanica, Inc., San Diego, California 92117 (United States); MagCanica, Inc., San Diego, California 92117 (United States); Department of Electrical Energy, Systems and Automation, Ghent University, Ghent B-9000 (Belgium)

2006-04-15

11

Magnetic hysteresis loss and corrosion behavior of LaFe11.5Si1.5 particles coated with Cu  

NASA Astrophysics Data System (ADS)

The existence of porosity is useful for releasing the strain during the magnetization and demagnetization processes of La(Fe, Si)13-based magnetocaloric materials, resulting in the decreases of magnetic hysteresis loss and the improvement of mechanical stability. But the porosity would affect the heat transfer and corrosion behavior. In this work, we studied the effect of highly plastic Cu coating on the magnetocaloric properties and corrosion resistance of LaFe11.5Si1.5 particles. It was found that Cu coating had less influence on the magnetic entropy changes, but presented a less magnetic hysteresis loss. Under a maximum field of 1.5 T, both particles with and without coating showed the similar magnetic entropy changes of 8 J/kg K. Magnetic hysteresis loss was decreased from 2.2 to 1.8 J/kg after Cu coating. The corrosion current density was decreased and the corrosion potential was increased, indicating an improvement of the corrosion resistance with Cu coating.

Tian, N.; Zhang, N. N.; You, C. Y.; Gao, B.; He, J.

2013-03-01

12

Influence of magnetostriction on hysteresis loss of electrical steel sheet  

NASA Astrophysics Data System (ADS)

To reveal influence of magnetostriction on hysteresis loss of electrical steel sheet, hysteresis loss and magnetostriction of non-oriented electrical steel sheets (NOs) with various Si and Al content and grain size and grain oriented electrical steel sheet (GO) were measured under compressive or tensile stress. Here, Si and Al content and stress were focused on as the way to change magnetostriction. Stress direction and magnetizing direction were parallel to the rolling direction. Following three main results were obtained. The first is hysteresis loss of NO with same grain size which increased with magnetostriction independently of Si and Al content and stress. The second is hysteresis loss of NO was larger than that of GO under same magnetostriction. The third is hysteresis loss of NO at magnetostriction of zero was inversely proportional to grain size. Even if the grain size of NO increased to be similar size of GO without changing texture, the hysteresis loss of NO at magnetostriction of zero would be larger than that of GO because of the difference in texture.

Tada, Hirotoshi; Fujimura, Hiroshi; Yashiki, Hiroyoshi

2013-01-01

13

Magnetic Hysteresis Model.  

National Technical Information Service (NTIS)

The Passive Aerodynamically Stabilized Magnetically Damped Satellite (PAMS) will be deployed from the Space Shuttle and used as a target for a Shuttle-mounted laser. It will be a cylindrical satellite with several corner cube reflectors on the ends. The c...

T. W. Flatley D. A. Henretty

1995-01-01

14

High frequency, high temperature specific core loss and dynamic B-H hysteresis loop characteristics of soft magnetic alloys  

NASA Technical Reports Server (NTRS)

Limited experimental data exists for the specific core loss and dynamic B-H loops for soft magnetic materials for the combined conditions of high frequency and high temperature. This experimental study investigates the specific core loss and dynamic B-H loop characteristics of Supermalloy and Metglas 2605SC over the frequency range of 1 to 50 kHz and temperature range of 23 to 300 C under sinusoidal voltage excitation. The experimental setup used to conduct the investigation is described. The effects of the maximum magnetic flux density, frequency, and temperature on the specific core loss and on the size and shape of the B-H loops are examined.

Wieserman, W. R.; Schwarze, G. E.; Niedra, J. M.

1990-01-01

15

High frequency, high temperature specific core loss and dynamic B-H hysteresis loop characteristics of soft magnetic alloys  

NASA Technical Reports Server (NTRS)

Limited experimental data exists for the specific core loss and dynamic B-H loop for soft magnetic materials for the combined conditions of high frequency and high temperature. This experimental study investigates the specific core loss and dynamic B-H loop characteristics of Supermalloy and Metglas 2605SC over the frequency range of 1 to 50 kHz and temperature range of 23 to 300 C under sinusoidal voltage excitation. The experimental setup used to conduct the investigation is described. The effects of the maximum magnetic flux density, frequency, and temperature on the specific core loss and on the size and shape of the B-H loops are examined.

Wieserman, W. R.; Schwarze, G. E.; Niedra, J. M.

1990-01-01

16

High Frequency, High Temperature Specific Core Loss and Dynamic BH Hysteresis Loop Characteristics of Soft Magnetic Alloys  

Microsoft Academic Search

Limited experimental data exists for the specific core loss and dynamic B-H loops for s oft magnetic materials for the combined conditions of high frequency and high temperature. This experimental study investigates the specific core loss and dynamic B-H loop characteristics of Supermalloy and Metglas 2605SC over the frequency range of 1-50 kHz and temperature range of 23-300 C under

W. R. Wieserman; G. E. Schwarze; J. M. Niedra

1990-01-01

17

PERFORMANCE OF HYSTERESIS PERMANENT MAGNET MOTORS  

Microsoft Academic Search

There is an increasing interest in using permanent magnet (PM) hysteresis motors because of their superior performances over the conventional hysteresis motors. Recent NdBFe magnets have the advantages of higher magnetic energy product and remanence. It can develop significant accelerating torque during run-up and synchronization with limited temperature tolerance. The application of the NdBFe magnets in electrical machines Is attracting

A. M. OSHEIBA; J. QIAN; M. A. RAHMAN

1989-01-01

18

A thermodynamically consistent model for magnetic hysteresis  

NASA Astrophysics Data System (ADS)

A phenomenological constitutive model is presented to describe the magnetization curve within the context of thermodynamics. Due to the phenomenological analogy between the magnetic hysteresis and the stress hysteresis, the basic structure of the proposed model comes from rate-dependent plasticity in continuum mechanics, namely viscoplasticity. The total magnetic flux density is assumed to be the sum of reversible and irreversible parts. The model introduces the evolution laws of two internal state variables to incorporate the effect of the ever-changing internal microstructure on the current state. The conception originated from viscoplasticity enables the frequency dependence of the hysteresis curve to be modeled.

Ho, Kwangsoo

2014-05-01

19

Hysteresis Loss as a Measure of Metal-Rubber Adhesion  

Microsoft Academic Search

As in the case of reinforcing-filler-induced increase in hysteresis in rubbers, attachment of aluminium (Al) foil onto the surface of a rubber blend (chlorobutyl rubber-carboxylated nitrile rubber) also causes an increase in hysteresis of the rubber. Changes in the hysteresis loss due to Al foil can be correlated with the Al\\/rubber adhesion.

Tinku Bhattacharya; S. K. De

1993-01-01

20

Rotational Hysteresis of Exchange-Spring Magnets.  

National Technical Information Service (NTIS)

We highlight our experimental studies and micromagnetic simulations of the rotational hysteresis in exchange-spring magnets. Magneto-optical imaging and torque magnetometry measurements for SmCo/Fe exchange-spring films with uniaxial in-plane anisotropy s...

J. S. Jiang R. D. Shull S. D. Bader H. Kaper A. J. Shapiro

2002-01-01

21

A simple method to determine dynamic hysteresis loops of soft magnetic materials  

Microsoft Academic Search

An approach to plotting hysteresis curves of soft magnetic materials using a personal computer assisted measuring system is presented. The resulting hysteresis curves provide enough detail to allow determination of the parameters required for a simulation with PSPICE (Jiles-Atherton model) or the Hodgdon\\/Carpenter model. The magnetic core loss for different materials and core shapes can be determined at frequencies up

N. Schmidt; H. Guldner

1996-01-01

22

Dynamic Hysteresis in Compacted Magnetic Nanoparticles  

NASA Astrophysics Data System (ADS)

The frequency and temperature dependent magnetic response of a bulk soft magnetic nanocomposite made by compacting Fe10Co 90 nanoparticles was measured and modeled. Electron microscopy and x-ray diffraction were used to characterize the size, composition, and structure of the nanoparticles and nanocomposite. Polyol synthesis was used to produce 200 nm particles with average grain size 20 nm and large superparamagnetic fraction. The nanoparticles were consolidated to 90% theoretical density by plasma pressure compaction. The compacted nanoparticles retained the 20 nm average grain size and large superparamagnetic fraction. The nanocomposite resistivity was more than three times that of the bulk alloy. Vibrating sample and SQUID-MPMS magnetometers were used for low frequency magnetic measurements of the nanoparticles and nanocomposite. Compaction reduced the coercivity from 175 Oe to 8 Oe and the effective anisotropy from 124 x 10 3 ergs/cc to 7.9 x 103 ergs/cc. These reductions were caused by increased exchange coupling between surface nanograins, consistent with predictions from the Random Anisotropy model. Varying degrees of exchange coupling existed within the nanocomposite, contributing to a distribution of energy barriers. A permeameter was used for frequency dependent magnetic measurements on a toroid cut from the nanocomposite. Complex permeability, coercivity, and power loss were extracted from dynamic minor hysteresis loops measured over a range of temperatures (77 K - 873 K) and frequencies (0.1 kHz - 100 kHz). The real and imaginary parts of the complex permeability spectrum showed asymmetries consistent with a distribution of energy barriers and high damping. When the complex permeability, power loss, and coercivity were scaled relative to the peak frequency of the imaginary permeability, all fell on universal curves. Various microscopic and macroscopic models for the complex permeability were investigated. The complex permeability was successfully fit by modifying the Cole-Davidson model with a scaling factor that extended the model to higher damping. The additional damping was consistent with the damping from eddy current modeling, showing that the nanocomposite's complex permeability could be explained by combining microscopic effects (the distribution of energy barriers represented by the Cole-Davidson model) with macroscopic effects (damping due to eddy currents).

Chowdary, Krishna M.

23

Magnetic hysteresis dynamics of thin Co films on Cu(001)  

NASA Astrophysics Data System (ADS)

Hysteresis properties of ultrathin (2-4 monolayers) epitaxial Co films grown on Cu(001) surfaces are studied as a function of film thickness, temperature and the strength (H0), in-plane direction, and frequency (?) of applied sinusoidal magnetic field. Scaling of the hysteresis loop area (power loss) of the form A=A0+H?0???(H,?) where ? is a scaling function is explored. All films exhibit a threshold field (Ht) where switching between equivalent magnetized states is initiated. Hysteresis loop areas measured over five decades in frequency exhibit very weak power-law dependence (?~0.02). No evidence of a dynamic phase transition is observed and no indication of a low-frequency (?0~102 Hz) characteristic resonance is apparent over the drive frequency range covered. The observed weak power-law scaling does not support results of prior experiments that have been interpreted as corroborating the mean-field Ising model (?=?=23) and continuum spin models of thin-film hysteresis energy-loss scaling. The measured frequency and applied field-dependent scaling of the dynamic coercive force (H*c) also appears to be inconsistent with recent phenomenological models of hysteresis behavior based on domain-wall motion that predict that H*c scales as ln H?. The results of this study of Co on Cu(001) and a corresponding study of Fe on W(110) suggest that the dynamics of magnetization reversal in real ultrathin film systems do not exhibit universal behavior in the low-field low-frequency limit. Recent theoretical results based on a more realistic model that accounts for thermal noise and spatial fluctuations in the dynamics yield logarithmic scaling at low ? and effective exponents ? that are compatible with the experiments. A simple physical picture of low drive-frequency energy-loss scaling is described that accounts for the experimental observations.

Suen, Jih-Shin; Lee, M. H.; Teeter, G.; Erskine, J. L.

1999-02-01

24

Analysis of wasp-waisted hysteresis loops in magnetic rocks.  

PubMed

The random-field Ising model of hysteresis is generalized to dilute magnets and is solved on a Bethe lattice. Exact expressions for the major and minor hysteresis loops are obtained. In the strongly dilute limit the model provides a simple and useful understanding of the shapes of hysteresis loops in magnetic rock samples. PMID:22400529

Kharwanlang, R S; Shukla, Prabodh

2012-01-01

25

Magnetic equivalent circuit of PM hysteresis synchronous motor  

Microsoft Academic Search

This paper presents the magnetic equivalent circuit of a permanent magnet hysteresis synchronous motor (PMHS). The hybrid synchronous motor consists of 36% cobalt steel hysteresis alloys with neodymium iron boron permanent magnets to improve the overall performances of such a motor. Based on the magnetic equivalent circuit, the control strategy of the PMHS motor is developed. Experimental results confirm the

R. Qin; M. A. Rahman

2003-01-01

26

Starting and synchronization of permanent magnet hysteresis motors  

Microsoft Academic Search

This paper presents the design and application of permanent magnets in hysteresis motors with a view to improve the overall performances of such motors. The novel rotor consists of 36% cobalt steel alloys with neodymium boron iron permanent magnets. This hybrid design combines advantageous performance features of both typical permanent magnet motors and conventional hysteresis motors. Machine models for steady

M. A. Rahman; Ruifeng Qin

1994-01-01

27

Starting and synchronization of permanent magnet hysteresis motors  

Microsoft Academic Search

This paper presents the design, analysis, and application of permanent magnets in a hysteresis motor with a view to improve the overall performance of such motors. The novel rotor consists of 36% cobalt steel alloys with neodymium boron iron permanent magnets. This hybrid design combines the advantageous performance features of both typical permanent magnet motors and conventional hysteresis motors. The

M. Azizur Rahman; Ruifeng Qin

1996-01-01

28

Magnetic equivalent circuit of PM hysteresis synchronous motor  

Microsoft Academic Search

This paper presents the magnetic equivalent circuit of a permanent magnet hysteresis synchronous (PMHS) motor. The hybrid synchronous motor consists of 30% Cobalt-steel hysteresis alloys Neodymium Iron Boron (NdFeB) permanent magnets to improve the overall performances of motors.

Ruifeng Qin; M. A. Rahman

2003-01-01

29

Hysteresis analysis for the permanent magnet assisted synchronous reluctance motor by coupled FEM and Preisach modelling  

SciTech Connect

In high speed applications of PMASynRM, hysteresis losses can become the major cause of power dissipation. Therefore, whereas in other kind of machines a rough estimation of hysteresis can be accepted, their importance in PMASynRM justifies a greater effort in calculating them more precisely. This study investigates the hysteresis phenomena of the Permanent Magnet Assisted Synchronous Reluctance Motor (PMASynRM) using coupled FEM and Preisach modelling. Preisach's model, which allows accurate prediction of hysteresis, is adopted in this procedure to provide a nonlinear solution. The computer simulation and experimental result for the i-[lambda] loci show the propriety of the proposed method.

Lee, J.H.; Hyun, D.S. (Hanyang Univ., Seoul (Korea, Republic of). Dept. of Electrical Engineering)

1999-05-01

30

Three-dimensional hysteresis of soft magnetic composite  

NASA Astrophysics Data System (ADS)

Hysteresis phenomenon is one of the important characteristics of soft magnetic materials. A three-dimensional (3D) magnetic property measurement system has been developed. This system can effectively control the locus of the time-varying magnetic flux density vector B and measure the corresponding magnetic field strength vector H in a cubic sample of soft magnetic material. The sample involved in this study is a soft magnetic composite sample made of highly pure iron powder. This paper investigates the B and H loci in 3D space and the power loss when the B loci are controlled to become circles and ellipses lying in three orthogonal planes. It is found that the B and H loci lie in the same magnetization plane, but the H loci and losses depend strongly on the orientation, position, and process of magnetization. On the other hand, the H vectors evolve into a unique locus pattern, and the power losses approach a unique value when the B vectors evolve into the same loci through either a series of small circles or ellipses.

Lin, Z. W.; Zhu, J. G.; Guo, Y. G.; Wang, X. L.; Ding, S. Y.

2006-04-01

31

Potbellies, wasp-waists, and superparamagnetism in magnetic hysteresis  

Microsoft Academic Search

Because the response of a magnetic substance to an applied field depends strongly on the physical properties of the material, much can be learned by monitoring that response through what is known as a ``magnetic hysteresis loop.'' The measurements are rapid and quickly becoming part of the standard set of tools supporting paleomagnetic research. Yet the interpretation of hysteresis loops

L. Tauxe; T. A. T. Mullender; T. Pick

1996-01-01

32

A permanent magnet hysteresis hybrid synchronous motor for electric vehicles  

Microsoft Academic Search

This paper presents the design, analysis and PWM vector control of a hybrid permanent magnet hysteresis synchronous (PMHS) motor with a view to improve the performances of motors for electric vehicle applications. This hybrid design combines the advantageous performance features of both conventional hysteresis motors and permanent magnet motors. Electrical equivalent circuits of the PMHS motor are developed for both

M. Azizur Rahman; Ruifeng Qin

1997-01-01

33

Transient performance analysis for permanent magnet hysteresis synchronous motor  

Microsoft Academic Search

The combination of hysteresis and permanent magnet materials in the rotor of a self-starting synchronous motor makes the motor analysis very difficult due to its inherent nonlinearity. This paper presents the simulation results of the transient performance of permanent magnet hysteresis synchronous (PMHS) motors. The major feature in this study is to combine the time-stepping finite element technique with the

Kazumi Kurihara; M. Azizur Rahman

2002-01-01

34

A permanent magnet hysteresis hybrid motor drive for electric vehicles  

Microsoft Academic Search

This paper presents the design, analysis and PWM vector control of a hybrid permanent magnet hysteresis synchronous motor with a view to improve the performances of the motors for electric vehicle application. This hybrid design combines the advantageous performance features of both the conventional hysteresis motors and the permanent magnet motors. A PWM vector control simulation and experimental results for

M. A. Rahman; Ruifeng Qin

1996-01-01

35

Modelling hysteresis in magnetically ordered materials  

NASA Astrophysics Data System (ADS)

This thesis presents a generalized version of the Preisach model of hysteresis which is designed to describe the temperature dependence and field dependence of the irreversible response of magnetically ordered materials everywhere below their critical temperature Tc. The model decomposes the magnetizing process into a sequence of Barkhausen events, each of which is represented by a double well potential with moment mu two states ? = +/-mu, a dissipation energy Wd = mu hc and a stored energy Ws = 2muhi. A given magnetic material is characterized by an ensemble of Barkhausen elements with a distribution of characteristic fields p(hc, hi). The distribution is allowed to vary with temperature in order to reflect intrinsic variations with temperature of the anisotropy and pinning mechanisms, in such a way that the coercive field distribution collapses into a delta-function delta( hc) as T approaches Tc from below. Thermal fluctuations are represented by a thermal viscosity field h*T = (kBT/mu)ln( texp/tau0). The model was used to simulate numerically various standard experimental response functions, including the temperature dependence of the zero field cooled moment in a fixed applied field ha, the temperature dependence of the field cooled moment in a fixed applied field, initial magnetizing and major hysteresis loop isotherms, and remanences, and the influence of each model parameter on the magnetic response functions was studied systematically. The model simulation sidentified the ratio eta of the mean zero temperature dissipation barrier W¯d(0) to the critical thermal fluctuation energy Wc = k BTcln(texp/tau 0) ass an important parameter which influences the principal structural characteristics of the response, and which can be used to classify materials as fluctuation-dominated or anisotropy-dominated. The model was applied to the analysis of the measured response functions five systems, two nanoparticulate systems, Fe/SiO 2 and NiFe2O 4, which were fluctuation-dominated, and three ferromagnetic perovskites SrRuO3, La0.5Sr 0.5-CoO3, and La0.7 Sr0.3MnO3, which were anisotropy-dominated. The analysis yielded the spectrum of Barkhausen characteristic fields p(hc, hi, T) and the Barkhausen moment mu(T), from which it is possible to reconstruct a physical picture of the evolution of the Barkhausen free energy barriers with temperature, as well as some description of the reversible component of the response.

Song, Tiancheng

2003-06-01

36

Calculation of hysteresis losses in hard super- conductors carrying ac: isolated conductors and edges of thin sheets  

Microsoft Academic Search

Two methods of calculating hysteresis losses in hard superconductors are described. The London model is assumed in which the critical current density is taken independent of magnetic field. Losses in isolated wires of different cross section are considered but it is found that losses for solid wires vary by at most a factor of 3 for different shaped wires of

W. T. NORRIS

37

Measurements and modeling of hysteresis in magnetic materials under the action of an orthogonal bias field  

SciTech Connect

The effect of an orthogonal dc bias field on hysteresis in isotropic magnetic materials under the action of an ac exciting field was investigated. The experimental results indicated that the orthogonal field rotated the hysteresis loops on the BH plane and reduced the enclosed area. As a result, the effective permeability, hysteresis loss, coercivity and remanence decreased with increasing orthogonal bias field. By including the orthogonal field in the anhysteretic model equation and incorporating a variable reversibility coefficient, the Jiles-Atherton hysteresis model was extended to describe the behavior of magnetic materials under the action of an orthogonal bias field. Using finite element modeling for evaluating the effective internal orthogonal field, the modeled hysteresis curve showed quantitative agreement with experimental results.

Bi, Y.; Jiles, D.C.

1999-09-01

38

Magnetic hysteresis curve influenced by power-semiconductor characteristics in pulse-width-modulation inverter  

NASA Astrophysics Data System (ADS)

The influence of power semiconductor characteristic in Pulse-width-modulation (PWM) inverter on the magnetic hysteresis curve in silicon steel is discussed through the measured magnetic hysteresis curves. The magnetic hysteresis curve of PWM inverter-fed silicon steel has a lot of minor loops as closed loops and open loops, which make an influence on the iron loss. Two shapes of minor loops are found to be caused by the voltage shifts and they are derived from the on-voltage of the semiconductors in PWM inverter circuit. Therefore, it is concluded that the power-semiconductor characteristic in PWM inverter makes an influence on the magnetic hysteresis curve in silicon steel.

Fujisaki, Keisuke; Liu, Sungju

2014-05-01

39

Transient performance analysis for permanent-magnet hysteresis synchronous motor  

Microsoft Academic Search

The combination of hysteresis and permanent-magnet materials in the rotor of a self-starting synchronous motor makes the motor analysis very difficult due to its inherent nonlinearity. This paper presents the simulation results of the transient performance of permanent magnet hysteresis synchronous (PMHS) motors. The major feature in this study is to combine the time-stepping finite-element technique with the model for

Kazumi Kurihara; M. Azizur Rahman

2004-01-01

40

The significance of observed rotational magnetic hysteresis in lunar samples  

NASA Technical Reports Server (NTRS)

Rotational magnetic hysteresis curves for lunar soils 10084, 12070, and 14259, and rock 14053 have been published. There is no adequate explanation to date for the observed large hysteresis at high fields. Lunar rock magnetism researchers consider fine particle iron to be the primary source of stable magnetic remanence in lunar samples. Iron has cubic anisotropy with added shape anisotropy for extreme particle shapes. The observed high-field hysteresis must have its source in uniaxial or unidirectional anisotropy. This implies the existence of minerals with uniaxial anisotropy or exchange-coupled spin states. Therefore, the source of this observed high-field hysteresis must be identified and understood before serious paleointensity studies are made. It is probable that the exchange-coupled spin states and/or the source of uniaxial anisotropy responsible for the high-field hysteresis might be influenced by the lunar surface diurnal temperature cycling. The possible sources of high-field hysteresis in lunar samples are presented and considered.

Wasilewski, P.

1974-01-01

41

Hysteresis of Two Inequivalent Planar Magnets with Anisotropy  

Microsoft Academic Search

We study the hysteresis loops for two inequivalent planar magnets with equal magnetic moments and perpendicular anisotropy, which interact via the dipole-dipole interaction. We emphasize locating distinct zero net-magnetization states in zero applied field. We consider a wide range of perpendicular anisotropy constants K1 and K_2and dipole interaction strength g. For a wide range of parameter space (K_2\\/K_1, g\\/K_1) and

Benjamin T. King; M. Amin Kayali; Wayne M. Saslow

2004-01-01

42

Magnetic Hysteresis Damping of Satellite Attitude Motion, Volume I.  

National Technical Information Service (NTIS)

The attitude dynamics of a gravity-gradient oriented satellite, which employs soft nickel-iron rods as magnetic hysteresis dampers, is simulated by a digital computer program. A subroutine was generated to compute the flux induced in the rods for an arbit...

1964-01-01

43

Hysteresis and relaxation in granular permanent magnets  

NASA Astrophysics Data System (ADS)

Some nontrivial aspects of the magnetic and structural characterization of hard-magnetic nanoparticles are investigated. Dilute ensembles are well-described by mean-field theory, although there is an asymmetry between exchange and magnetostatic interaction fields. Corrections to the mean-field approximation are caused by cooperative effects and have the character of Onsager reaction fields, which are much stronger in micromagnetism than in atomic-scale magnetism. The slow dynamics of zero-field-cooled (ZFC) magnetization curves is strongly affected by the particles' magnetic anisotropy, which reduces the corresponding energy-barrier height from 25 to 19.1 kBT.

Skomski, Ralph; Balamurugan, B.; George, Tom A.; Chipara, Mircea; Wei, Xiao-Hui; Shield, Jeff E.; Sellmyer, D. J.

2012-04-01

44

Hysteresis and saturation effects with the ALS lattice magnets  

SciTech Connect

The primary purpose of the magnetic measurements performed on the ALS storage ring lattice magnets was to ascertain their compliance with the strict tolerances established for this third-generation synchrotron light source. In the course of the data evaluation, an approximation method has been developed that leads to four-parameter representations of all magnet transfer functions. The expressions for the transfer functions were now used to change the standard working point of the ALS storage ring from the upper to the lower hysteresis branches of all lattice magnet families, and later to ramp the ring from the customary 1.5 GeV to the maximum design energy of 1.9 GeV in one uninterrupted process that did not require any intermediate tune correction. This achievement is all the more remarkable as no remnant fields had directly been measured with any of these magnets. A specific remnant field effect that led to anomalous machine behavior-when trying to recuperate the betatron tunes on the lower hysteresis branch at standard energy could be ascribed to the C-shape of the quadrupole yokes.

Keller, R.

1995-04-01

45

A method for the determination of the parameters of the hysteresis model of magnetic materials  

Microsoft Academic Search

Many methods have been proposed for the determination of the hysteresis loops of magnetic materials, and many mathematical approaches have been proposed to find a good model for the hysteresis phenomenon. However, very few attempts have been made to determine the parameters of the hysteresis model experimentally. This paper shows how, starting from a digital method for the experimental determination

L. D'Alessandro; A. Ferrero

1994-01-01

46

A new method of calculating magnetic hysteresis and thermal effects  

NASA Astrophysics Data System (ADS)

All the easy theoretical problems in rock magnetism have been solved. Further advances involve models of hysteresis and thermal fluctuations in increasingly complex systems. To model the physics of such systems accurately, rock magnetists will need to solve two seemingly unrelated technical challenges. First, for models of thermal relaxation (with applications to magnetic viscosity, thermoremanent magnetization and so on), they will need to locate energy barriers in multidimensional parameter spaces - a difficult and computationally expensive problem. Second, they will need to improve calculations of magnetization curves near jumps, where the slope of the curve almost always approaches infinity. Micromagnetic models have trouble locating jumps accurately. A new algorithm is presented that tackles both of these problems while greatly reducing the time needed to calculate magnetization curves. The most novel aspect of this algorithm is the way it treats the magnetic field. Other methods solve for the magnetization at a given magnetic field, change the field, and then solve for the magnetization again while the field is kept fixed at the new value. The result is an equilibrium curve in a space of magnetization and field components. The new algorithm treats the field the same way as it treats the magnetization. It uses a tangent to the magnetization curve to estimate the next point on the curve and a corrector algorithm that refines the estimate. There is also an adaptive algorithm to determine an appropriate distance to step along the curve. This algorithm is much more robust near jumps. It can also calculate energy barriers because the top of an energy barrier (a saddle point) is on the same solution curve as the stable magnetization states. Previous methods could not follow the solution curve past the point of instability, but this method can because of the way it handles the field. This makes it possible to calculate energy barriers much faster and more accurately than any previous method. Applications to interacting fine particles will be presented.

Newell, A.

2008-12-01

47

Magnetic hysteresis minor loops in Fe single crystal  

NASA Astrophysics Data System (ADS)

Magnetic hysteresis minor loops were measured with step by step increase of the magnetic field amplitude, Ha, in plastically deformed Fe single crystal. In order to analyse minor loops in connection with the lattice defects, we defined some magnetic parameters, such as the pseudo-coercive force, Hc*, and the differential susceptibility under the pseudo-coercive force khgrH*. Hc*, for instance, is the magnetic field where the magnetization becomes zero in minor loops. In this work, we found the relationship 2Hc* = Ha to hold over a fairly wide Ha range. These parameters are important for representing Bloch wall displacement and the potential energy. The parameters are remarkably sensitive to lattice defects in the field range below the coercive force Hc. The relation of 1/khgrH* and Hc* shows better sensitivity—90 times higher than that for Hc—for revealing information on dislocations. In the minor loop measurement, for getting full information on dislocations it is sufficient to have Ha = 400 A m-1.

Takahashi, S.; Zhang, L.; Ueda, T.

2003-11-01

48

Evaluation of Magnetic Field Hysteresis and Flux Creep of a QMG Coil Magnet  

Microsoft Academic Search

This paper presents an evaluation of the magnetic hysteresis of a coil type QMG magnet for a high field application of oxide bulk high Tc superconductors (HTS). The QMG is a high Jc bulk material, which consists of single crystalline 123 with finely dispersed 211. The bulk coil is made from a slice of Ag doped Gd based QMG by

Masanori Tsuchimoto; Shinichiro Osanai; Mitsuru Morita

2007-01-01

49

Magnetic properties modeling of soft magnetic composite materials using two-dimensional vector hybrid hysteresis model  

NASA Astrophysics Data System (ADS)

A 2-D vector hybrid hysteresis model for a soft magnetic composite (SMC) material is established, which is combined with classical Preisach model and Stoner-Wohlfarth (S-W) model. The rotational magnetic properties of SMC materials were studied using the vector model, and the computed results were compared with the experimental measurement. It is shown that the vector hybrid model can effectively simulate the rotational magnetic properties under low magnetization fields.

Li, Dandan; Liu, Fugui; Li, Yongjian; Zhao, Zhigang; Zhang, Changgeng; Yang, Qingxin

2014-05-01

50

Analysis and microprocessor implementation of field oriented control for permanent magnet hysteresis synchronous motor  

Microsoft Academic Search

An analytical motor for a permanent magnet hysteresis hybrid synchronous motor has been developed. A microprocessor-based field oriented control scheme has been successfully experimented for a laboratory magnet hysteresis motor. A scheme for measuring the torque angle is proposed. The test results confirm the improvement of the dynamic performances using a field-oriented control strategy

J. Qian; M. Azizur Rahman

1991-01-01

51

The Unsymmetrical Hysteresis Loop  

Microsoft Academic Search

The paper gives results and analyses of tests to determine losses in hysteresis loops wherein the magnetism is carried through cycles in which limiting values of flux are different in amount or the mean values of flux differ from zero. Such variations of magnetism occur in inductor generators, in teeth of induction machines and in materials magnetized from rectifier circuits,

John D. Ball

1915-01-01

52

Modeling of quasistatic magnetic hysteresis with feed-forward neural networks  

NASA Astrophysics Data System (ADS)

A modeling technique for rate-independent (quasistatic) scalar magnetic hysteresis is presented, using neural networks. Based on the theory of dynamic systems and the wiping-out and congruency properties of the classical scalar Preisach hysteresis model, the choice of a feed-forward neural network model is motivated. The neural network input parameters at each time step are the corresponding magnetic field strength and memory state, thereby assuring accurate prediction of the change of magnetic induction. For rate-independent hysteresis, the current memory state can be determined by the last extreme magnetic field strength and induction values, kept in memory. The choice of a network training set is motivated and the performance of the network is illustrated for a test set not used during training. Very accurate prediction of both major and minor hysteresis loops is observed, proving that the neural network technique is suitable for hysteresis modeling.

Makaveev, Dimitre; Dupré, Luc; de Wulf, Marc; Melkebeek, Jan

2001-06-01

53

Analysis of Power Magnetic Components With Nonlinear Static Hysteresis: Proper Orthogonal Decomposition and Model Reduction  

Microsoft Academic Search

We applied the proper orthogonal decomposition (POD) method to extract reduced-order models to efficiently solve nonlinear electromagnetic problems governed by Maxwell's equations with nonlinear hysteresis at low frequency (10 kHz), called static hysteresis, discretized by a finite-element method. We used a new domain-wall-motion hysteresis model for Power MAgnetic Components (POMACs) in the finite-element potential formulation via an efficient implicit-inverse model

Y. Zhai; L. Vu-Quoc

2007-01-01

54

Analysis of power magnetic components with nonlinear static hysteresis: finite-element formulation  

Microsoft Academic Search

We present a new systematic methodology to efficiently solve coupled electromagnetic problems with nonlinear hysteresis at low frequency (10 kHz), called static hysteresis, by the finite-element method. The methodology integrates a new domain-wall-motion hysteresis model for power magnetic components (POMACs) into a finite-element potential formulation via an implicit-inverse model calculation. It uses a novel two-level iterative algorithm incorporating the efficient

Y. Zhai; L. Vu-Quoc

2005-01-01

55

Nondestructive characterization of recovery and recrystallization in cold rolled low carbon steel by magnetic hysteresis loops  

Microsoft Academic Search

How structure sensitive parameters derived from hysteresis loops can provide nondestructive information about the evolution of the microstructure of cold rolled low carbon steel as a result of recovery and recrystallization processes during the annealing is shown. The coercive field, remanent induction and hysteresis losses can be used to monitor the decrease in the dislocation density during recovery. These parameters

A. Martínez-de-Guerenu; K. Gurruchaga; F. Arizti

2007-01-01

56

Hysteresis analysis for the permanent magnet assisted synchronous reluctance motor by coupled FEM and Preisach modelling  

Microsoft Academic Search

This study investigates the hysteresis phenomena of the permanent magnet assisted synchronous reluctance motor (PMASynRM) using coupled FEM and Preisach modelling. Preisach's model, which allows accurate prediction of hysteresis, is adopted in this procedure to provide a nonlinear solution. The computer simulation and experimental results for the i-? loci show the propriety of the proposed method

Jung Ho Lee; Dong Seek Hyun

1999-01-01

57

Simulation of magnetic hysteresis in pseudo-single-domain grains of magnetite  

Microsoft Academic Search

Magnetic hysteresis has been simulated in grains of magnetite for the size range 0.1-0.7 microns. This was achieved using an unconstrained three-dimensional micromagnetic model of single grains of magnetite with cubic magnetocrystalline anisotropy. Hysteresis loops were obtained for fields applied along both the easy and hard magnetocrystalline axes. Both discrete (Barkhausen) jumps and gradual changes in the magnetic structure are

W. Williams; David J. Dunlop

1995-01-01

58

Improved approach to power losses in magnetic laminations under non-sinusoidal induction wave form.  

National Technical Information Service (NTIS)

This paper shows how it is possible to accurately predict power losses in ferromagnetic laminations (in transformer and rotating machine cores) under non-sinusoidal magnetic flux by specifically considering the dependence of hysteresis, classical, and exc...

F. Fiorillo A. Novikov

1990-01-01

59

Isothermal magnetization of samples with stable Preisach function: A survey of hysteresis, remanence, and rock magnetic parameters  

Microsoft Academic Search

Isothermal magnetization curves, like hysteresis loops, initial curves, back field curves, acquisition curves and demagnetizing curves of isothermal remanent magnetization, are commonly used for rock magnetic purposes. In this study we investigate the relations among these curves and other useful magnetization curves (saturation initial curve and induced and remanent hysteretic magnetization curves) in order to compare coercivity and domain state

Karl Fabian; Tilo von Dobeneck

1997-01-01

60

Calculation of the magnetic field in the active zone of a hysteresis clutch  

NASA Technical Reports Server (NTRS)

The initial distribution of magnetic induction in the armature stationary was calculated relative to the polar system of a hysteresis clutch. Using several assumptions, the problem is reduced to calculating the static magnetic field in the ferromagnetic plate with finite and continuous magnetic permeability placed in the air gap between two identical, parallel semiconductors with rack fixed relative to the tooth or slot position.

Ermilov, M. A.; Glukhov, O. M.

1977-01-01

61

Nature of dislocation hysteresis losses and nonlinear effect in lead at high vibration amplitudes  

SciTech Connect

The nature of the dislocation hysteresis was established and changes in this hysteresis were determined by investigating the dependence of the dislocation-induced absorption of ultrasound (coefficient ..cap alpha..) on the amplitude of ultrasound epsilon-c/sub 0/ in single crystals of pure lead and of lead containing Tl and Sn impurities. The investigation was carried out in a wide range of epsilon-c/sub 0/ under superconducting transition conditions. In the superconducting (s) state both pure Pb and that doped with T1 exhibited a maximum in the dependence ..cap alpha..(epsilon-c/sub 0/) at high values of epsilon-c/sub 0/; on transition to the normal (n) state this maximum changed to a plateau. This provided a direct proof of a change in the static nature of the dislocation hysteresis to the dynamic process because of an increase in the coefficient of the electron drag of dislocations. Estimates were obtained of the range of lengths of dislocation loops: 2.4 x 10/sup -4/ cmhysteresis occurred both in the normal and superconducting states. In the range of amplitudes above that of the maximum and at the beginning of the plateau all single crystals exhibited a rise of ..cap alpha.. on increase of epsilon-c/sub 0/ in the superconducting and normal states; this rise was due to nonlinear effects observed in the case of strong bending of L/sub N/ loops. An analysis was made of the amplitude dependence of the losses associated with this effect. The results were in good agreement with the experimental data.

Lomakin, V.V.; Pal-Val, L.N.; Platkov, V.Y.; Roshchupkin, A.M.

1982-11-01

62

High-frequency rotational losses in different soft magnetic composites  

NASA Astrophysics Data System (ADS)

The isotropic properties of Soft Magnetic Composites (SMC) favor the design of new machine topologies and their granular structure can induce a potential decrease of the dynamic loss component. This paper is devoted to the characterization of the broadband magnetic losses of different SMC types under alternating and circular induction. The investigated materials differ by their grain size, heat treatment, compaction rate, and binder type. It is shown that, up to peak polarization Jp = 1.25 T, the ratios between the rotational and the alternating loss components (classical, hysteresis, and excess) are quite independent of the material structural details, quite analogous to the known behavior of nonoriented steel laminations. On the contrary, at higher inductions, it is observed that the Jp value at which the rotational hysteresis loss attains its maximum, related to the progressive disappearance of the domain walls under increasing rotational fields, decreases with the material susceptibility.

de la Barrière, O.; Appino, C.; Ragusa, C.; Fiorillo, F.; Mazaleyrat, F.; LoBue, M.

2014-05-01

63

Fourier analysis of digital hysteresis data: rock magnetic applications  

Microsoft Academic Search

The approach to saturation of a ferromagnetic material can be characterized in terms of the frequency content of its hysteresis loop. This is done by `unfolding' the loop into a pseudo-waveform, which is then analyzed using standard Fourier methods. In experiments on samples with discrete grain sizes of magnetite, the decay of Fourier component amplitude as a function of harmonic

Mike Jackson; Horst-Ulrich Worm; Subir K. Banerjee

1990-01-01

64

Compensation of hysteresis in magnetic field sensors employing Fiber Bragg Grating and magneto-elastic materials  

Microsoft Academic Search

The paper proposes a novel magnetic field sensor where a technique for hysteresis compensation is employed. The sensor integrates a magnetostrictive material with a Fiber Bragg Grating (FBG) strain sensor. Because of hysteresis and non-linear phenomena taking place in such materials, the sensor’s performances may be sensibly reduced. To this aim, magneto-elastic material is accurately modelled in order to compensate

D. Davino; C. Visone; C. Ambrosino; S. Campopiano; A. Cusano; A. Cutolo

2008-01-01

65

Magnetic resonance imaging (MRI) study of jet height hysteresis in packed beds  

NASA Astrophysics Data System (ADS)

The jet-spout transition in fluidized beds can show hysteretic behavior. In this study the jet-spout transition was studied as a function of orifice velocity for particles of different size and shape using Magnetic Resonance Imaging (MRI). The measurements showed that the particle shape primarily affect to the width of the hysteresis loop whereas particle size governs the position of the hysteresis loop with regards to the orifice velocity.

Köhl, Maximilian H.; Lu, Guang; Third, James R.; Prüssmann, Klaas P.; Müller, Christoph R.

2013-06-01

66

Analysis of field oriented control for permanent magnet hysteresis synchronous motors  

Microsoft Academic Search

A microprocessor implementation of the field-oriented control scheme for the permanent magnet (PM) hysteresis synchronous motor is reported. The basic principle is to decouple the torque-current component from the flux-current component so that these two components can be independently controlled. A d-q axis model of the PM hysteresis synchronous motor is presented, and the field-oriented control obtained from the basic

Jianhua Qian; M. Azizur Rahman

1993-01-01

67

Hydrostatic pressure effect on magnetic hysteresis parameters of multidomain magnetite: Implication for crustal magnetization  

NASA Astrophysics Data System (ADS)

Hydrostatic pressure effects on magnetic parameters for crustal rock have been poorly investigated yet, while it is important for an understanding of source of long-wavelength magnetic anomaly, which is considered to reside in deep crust. In this study we have conducted the in situ magnetic hysteresis measurements on multidomain (MD) magnetite under high pressure up to 1 GPa. With special attention to hydrostatic condition and sample preparation, pressure dependences of its magnetic hysteresis parameters (saturation magnetization, Ms; saturation remanence, Mrs; coercivity, Bc; coercivity of remanence, Bcr) are revealed as follows: (1) Bc monotonically increases with pressure at a rate of +91%/GPa; (2) Ms is constant under high pressure up to 1 GPa; (3) Mrs increases with pressure up to 0.5 GPa by ?30% and reaches to saturation above the pressure; (4) Bcr is nearly constant at low pressure, and it increases above ?0.6 GPa; and (5) the changes in ratios Mrs/Ms and Bcr/Bc correlate with each other, resulting in systematic movement on the Day plot. These findings allow us to estimate change in a relaxation time of magnetic remanence carried by MD magnetite as a function of depth in the continental crust. In the model calculation, we consider no effect of plastic deformation on magnetic properties of magnetite, and the relaxation time is calculated using the theoretical thermal gradient. In consequence, the relaxation time monotonously decreases with depth, and primary remanence is considered to be replaced by a viscous remanent magnetization (VRM) over the Brunhes chron. Therefore, it is suggested that MD magnetite in deep crustal rocks can contribute to the source of the anomaly over the continental crust by VRM and induced magnetization.

Sato, Masahiko; Yamamoto, Yuhji; Nishioka, Takashi; Kodama, Kazuto; Mochizuki, Nobutatsu; Tsunakawa, Hideo

2014-08-01

68

Hybrid models of hysteresis for mixed hysteretic loops in heterogeneous magnetic materials  

NASA Astrophysics Data System (ADS)

The mixed hysteresis behavior of counter-clockwise and clockwise loops has recently attracted the attention of the magnetics community, due to several experimental findings in inhomogeneous and hetero-structure magnetic systems. Various hybrid models are proposed here to address this behavior based on the superposition of standard hysteresis models and their newly developed clockwise variants. A special attention is also devoted to Bouc-Wen model, a typical clockwise often used by applied mechanics community, and to its relevance for mixed hysteresis. These clockwise and hybrid models have been implemented in an open-access academic software and their performance is illustrated by examples of hysteretic loops, first order reversal curves and diagrams simulated in this framework.

Dimian, M.; Andrei, P.; Grayson, M.

2014-05-01

69

Hysteresis of transport critical current of high Tc superconductors in strong magnetic fields. Theory  

Microsoft Academic Search

A new model is developed to describe the properties of a Josephson junction critical current in a strong magnetic field. A comparison with experiments shows the possibility of the existence of a surface barrier to the Abrikosov vortex motion in YBCO-124 metalceramics. Characteristic features of this barrier appear in the abnormal hysteresis loop of the transport critical current.

A. I. D'Yachenko

1993-01-01

70

Hysteresis of switching waves and dissipative solitons in nonlinear magnetic metamaterials  

NASA Astrophysics Data System (ADS)

Localized structures forming in the bistable regimes in a chain of weakly coupled split ring resonators, which are the building blocks of a nonlinear magnetic metamaterial, where electric current is generated by external electromagnetic radiation, have been studied analytically and numerically. The hysteresis of the velocity of switching waves (fronts) has been revealed and discrete dissipative solitons have been found.

Rosanov, N. N.; Vysotina, N. V.; Shatsev, A. N.; Shadrivov, I. V.; Kivshar, Yu. S.

2011-08-01

71

DSP based torque and speed controls of the permanent magnet hysteresis synchronous motor  

Microsoft Academic Search

This paper presents the detailed derivation of the permanent magnet hysteresis synchronous motor (PMHS) torque equation and the design of the digital speed controller for the DSP based PMHS motor vector control system. The torque control that regulates the speed of the PMHS motor, is provided by a quadrature axis current command developed by the speed controller. The digital speed

Ruifeng Qin; M. A. Rahman

1997-01-01

72

Analysis of field oriented control for permanent magnet hysteresis synchronous motors  

Microsoft Academic Search

Field oriented control schemes provide significant improvement to the dynamic performance of ac motors. A microprocessor implementation of the field oriented control scheme for the permanent magnet hysteresis synchronous motor has been reported for the first time. The basic principle is to decouple the torque-current component from the flux-current component so that these two components can be independently controlled. A

J. Qian; M. A. Rahman

2009-01-01

73

Minor Hysteresis Loop in Fe Metal and Alloys  

Microsoft Academic Search

The minor hysteresis loops were measured with increasing magnetic field amplitude Ha step by step and analyzed in Fe single crystal, polycrystalline metals and A533B steel. We have defined several new magnetic properties in the minor loops: they are pseudo magnetization {Ba}*, pseudo coercive force {Hc}*, pseudo remanence {BR}*, pseudo hysteresis loss {WF}*, pseudo remanence work {WR}*, and three pseudo

Seiki Takahashi; Lefu Zhang

2004-01-01

74

Hysteresis measurement of individual multilayered Fe-Ga/Cu nanowires using magnetic force microscopy  

NASA Astrophysics Data System (ADS)

We have investigated nano-scale magnetic structures to learn how magnetic behaviors differ from what is observed in bulk materials. In this study, we have measured the magnetic hysteresis of individual multilayered nanowire using a magnetic force microscopy (MFM). The nanowires were composed of low-aspect ratio segments of iron-gallium (Galfenol, Fe80Ga20) and copper layers. Individual wires were released from nano-porous anodized aluminum oxide (AAO) templates and separated from other nanowires to avoid significant interactions between nearby nanowires. In this experiment, structures with aspects ratios c/a of ~3 were studied. Different MFM phase magnitudes in response to the interaction of magnetic film coated MFM tips and Fe-Ga/Cu nanowire were observed as a function of applied external magnetic field (-850 Oe < H < 850 Oe). Amplitude differences between bright and dark responses in MFM images were used to demonstrate hysteresis. Coercivity measured was about 125 Oe, which is almost same as the coercivity value (~150 Oe) of a nanowire array measured with a vibrating sample magnetometer (VSM). When fields are applied perpendicular to the nanowires, the hysteresis loops sheared, indicating that the easy axis is along the nanowire axis. Remanence magnetizations of an individual nanowire and a nanowire array were compared to demonstrate inter-wire magnetostatic dipolar interaction.

Jin Park, Jung; Reddy, Madhukar; Stadler, Bethanie J. H.; Flatau, Alison B.

2013-05-01

75

Hysteresis-free switching between vortex and collinear magnetic states  

NASA Astrophysics Data System (ADS)

We demonstrate a lossless switching between vortex and collinear magnetic states in circular FePd disks arranged in a square lattice. Above a bifurcation temperature (Te) we show that thermal fluctuations are enough to facilitate flipping between the two distinctly different magnetic states. We find that the temperature dependence of the vortex annihilation and nucleation fields can be described by a simple power law relating them to the saturation magnetization.

Östman, Erik; Arnalds, Unnar B.; Melander, Emil; Kapaklis, Vassilios; Pálsson, Gunnar K.; Saw, Alexander Y.; Verschuuren, Marc A.; Kronast, Florian; Papaioannou, Evangelos Th; Fadley, Charles S.; Hjörvarsson, Björgvin

2014-05-01

76

Discontinuous Double Power Law Scaling of Magnetic Hysteresis  

NASA Astrophysics Data System (ADS)

Frequency(?), applied field(H), and temperature(T) -dependent hysteresis loops of ultrathin Fe films on flat and stepped W(001) surface are measured using the magneto-optic Kerr effect. Power law scaling of the loop area A ~ H^??^? is observed over five decades in ? with exponents similar to those observed for Fe on W(110)^1. In cases where the dynamic coercivity H_c(?) exceeds the applied field, an abrupt collapse of the loop occurs leading to a double-power-law scaling behavior similar to that reported by Luse and Zangwill^2 based on a periodically driven kinetic Ising model. The exponent ?' describing the abrupt loop collapse above the amplitude dependent critical frequency is very large compared to the low frequency range value ?, and ?' is much more sensitive to film thickness than the low frequency regime ?. Supported by DMR-9623494 ^1 Jih-Shin Suen and J. L. Erskine, Bull. Am. Phys. Soc. 41, B22 7 (1996) (and submitted to PRL) ^2 C. N. Luse and A. Zangwill, Phys. Rev. E50, 224 (1994)

Suen, Jih-Shin; Erskine, J. L.

1997-03-01

77

Hysteresis and baseline shift in permanent magnet stabilized MR\\/SAL heads  

Microsoft Academic Search

Hysteresis and baseline shift in shielded permanent magnet stabilized MR\\/SAL playback heads are studied via a 3D micromagnetic simulation. The hysteretic behavior is examined by calculation of playback voltages and uniform field transfer curves. The overlap region between the MR\\/SAL layers and the permanent magnet is seen to have a strong effect on the stability of the device. The amount

Eric Champion; H. Neal Bertram

1996-01-01

78

Magnetic hysteresis in natural materials. [chondrites, lunar samples and terrestrial rocks  

NASA Technical Reports Server (NTRS)

Magnetic hysteresis loops and the derived hysteresis ratios R sub H and R sub I are used to classify the various natural dilute magnetic materials. R sub I is the ratio of saturation isothermal remanence (I sub R) to saturation (I sub S) magnetization, and R sub H is the ratio of remanent coercive force (H sub R) to coercive force (H sub C). The R sub H and R sub I values depend on grain size, the characteristics of separate size modes in mixtures of grains of high and low coercivity, and the packing characteristics. Both R sub H and R sub I are affected by thermochemical alterations of the ferromagnetic fraction. Hysteresis loop constriction is observed in lunar samples, chondrite meteorites, and thermochemically altered basaltic rocks, and is due to mixtures of components of high and low coercivity. Discrete ranges of R sub H and R sub I for terrestrial and lunar samples and for chondrite meteorites provide for a classification of these natural materials based on their hysteresis properties.

Wasilewski, P. J.

1973-01-01

79

Influence of applied tensile stress on the hysteresis curve and magnetic domain structure of grain-oriented Fe–3%Si steel  

NASA Astrophysics Data System (ADS)

The influence of applied tensile stress on the hysteresis curve and domain structure in conventional (1?1?0)[0?0?1] Fe–3%Si steel, cut parallel to the rolling direction, is studied on samples with different grain sizes. Quasistatic hysteresis loops under tensile stresses up to 70 MPa were measured. The magnetic domains and magnetization processes were observed by longitudinal Kerr microscopy at different levels of stress. It is shown that for stresses exceeding 5–10 MPa the bulk hysteresis loop can be described with good accuracy by the action of an effective field, which is the product of a function of stress and a function of magnetization. The function of stress is approximately linear with a slope of one. Except for the sample with the smallest grains, the function of magnetization is linear in the magnetization range ±1.2–1.5 T, i.e. it has a typical demagnetizing field shape. Domain observation reveals that the effective field is caused by the demagnetizing fields occurring at grain boundaries and at the sheet surface due to the removal of closure domains transverse to the rolling direction by the tensile stress. The closure structure reappears at higher fields. Another indirect indication of demagnetizing fields is the fact that the hysteresis losses drop continuously with stress and changes in the coercive force are small. The effective field of the sample with the smallest grains increases most nonlinearly with stress similar to the behaviour obtained for non-oriented material.

Perevertov, O.; Schäfer, R.

2014-05-01

80

Asymmetric Magnetization Reversal in Exchange-Biased Hysteresis Loops  

Microsoft Academic Search

Polarized neutron reflectometry is used to probe the in-plane projection of the net-magnetization vector M--> of polycrystalline Fe films exchange coupled to twinned (110) MnF 2 or FeF 2 antiferromagnetic (AF) layers. The magnetization reversal mechanism depends upon the orientation of the cooling field with respect to the twinned microstructure of the AF, and whether the applied field is increased

M. R. Fitzsimmons; P. Yashar; C. Leighton; Ivan K. Schuller; J. Nogués; C. F. Majkrzak; J. A. Dura

2000-01-01

81

Mechanisms of magnetic and temperature hysteresis in ErFeO3 and TmFeO3 single crystals  

NASA Astrophysics Data System (ADS)

Magnetic hysteresis is studied in the orthoferrites ErFeO3 and TmFeO3 using the single crystal samples of millimeter dimensions. It is shown that in both materials one observes a temperature transition manifesting itself through the temperature hysteresis of the magnetic moment and a peculiar temperature evolution of the field hysteresis loop shapes near this transition. Experiments rule out the hypothesis that the ordering of the orthoferrite's rare-earth magnetic moments plays an important role in these phenomena. The hysteresis curves can be explained by a few-domain magnetic state of the samples that results from the weak ferromagnetism of the orthoferrites. The phenomenon is generic for weak ferromagnets with temperature dependent magnetization. A large characteristic magnetic length makes the behavior of the relatively big samples analogous to that observed in the nanosize samples of strong ferromagnets.

Tsymbal, L. T.; Bazaliy, Ya. B.; Kakazei, G. N.; Vasiliev, S. V.

2010-10-01

82

Appearance of magnetization jumps in magnetic hysteresis curves in spinel oxide FeV2O4  

NASA Astrophysics Data System (ADS)

We report the appearance of magnetization jumps in the magnetic hysteresis curves of the spinel oxide FeV2O4, in which two different magnetic transition ions appeared, both of them having orbital degrees of freedom. The spin-glass-like transition was observed from ac magnetic susceptibilities and the transition temperature was estimated to be Tg=85.5 K. The magnetization jumps appear below 90 K at B=0. In addition, jumps at B=+/-1.2 T appear below 4.6 K. The magnetization jumps at B=0 may be correlated with spin-glass-like behaviors.

Nishihara, Sadafumi; Doi, Wataru; Ishibashi, Hiroki; Hosokoshi, Yuko; Ren, Xiao-Ming; Mori, Shigeo

2010-05-01

83

Strong nonlinearity and hysteresis of Hall resistance versus magnetization in nickel thin films  

NASA Astrophysics Data System (ADS)

The anomalous Hall effect (AHE) in ferromagnetic materials is perhaps one of the oldest unresolved mysteries in physics. First observed in 1881, its mechanism is still a controversial topic today. The question remains whether AHE is caused by intrinsic (Berry phase and band structure) or extrinsic (defect scattering) effects or a combination of both. Here we present experimental observation in nickel thin films that seems to add to the mystery, but may in fact provide crucial clues for ultimately resolving the controversy. The key observation is that the Hall resistivity of nickel films is a strongly nonlinear function of the magnetization and displays clear hysteresis with respect to M. Specifically, at low temperatures, the anomalous Hall coefficient switches between two saturated values under the magnetic field with a narrow transition region, but with a strong hysteresis, in contrast to the slow saturation of the magnetization. The nonlinearity and the hysteresis become more apparent with decreasing temperature or film thickness. Despite the simplicity of the lattice and magnetic structure of nickel films, these results are outside our current understanding of AHE, whether using intrinsic or extrinsic mechanisms of AHE. It presents a challenge for these models, and may be used as a test of validity for both types of theories.

Song, Xiaohui; Fan, Jie; Zhang, X.-G.; Zhang, Dianlin

2010-08-01

84

Dynamic magnetic hysteresis behavior and dynamic phase transition in the spin-1 Blume-Capel model  

NASA Astrophysics Data System (ADS)

The nature (time variation) of response magnetization m( wt) of the spin-1 Blume-Capel model in the presence of a periodically varying external magnetic field h( wt) is studied by employing the effective-field theory (EFT) with correlations as well as the Glauber-type stochastic dynamics. We determine the time variations of m( wt) and h( wt) for various temperatures, and investigate the dynamic magnetic hysteresis behavior. We also investigate the temperature dependence of the dynamic magnetization, hysteresis loop area and correlation near the transition point in order to characterize the nature (first- or second-order) of the dynamic transitions as well as obtain the dynamic phase transition temperatures. The hysteresis loops are obtained for different reduced temperatures and we find that the areas of the loops are decreasing with the increasing of the reduced temperatures. We also present the dynamic phase diagrams and compare the results of the EFT with the results of the dynamic mean-field approximation. The phase diagrams exhibit many dynamic critical points, such as tricritical (•), zero-temperature critical (Z), triple (TP) and multicritical (A) points. According to values of Hamiltonian parameters, besides the paramagnetic (P), ferromagnetic (F) fundamental phases, one coexistence or mixed phase region, (F+P) and the reentrant behavior exist in the system. The results are in good agreement with some experimental and theoretical results.

Deviren, Bayram; Keskin, Mustafa

2012-03-01

85

Ginzburg-Landau Theory of Surface Superconductivity and Magnetic Hysteresis  

Microsoft Academic Search

The magnetization properties of a long superconducting cylinder with an ideal surface and a radius much larger than the low-field penetration depth are discussed on the basis of numerical solutions to the one-dimensional Ginzburg-Landau equations for a half-space. The current-carrying properties of the complete set of nodeless surface solutions and Meissner solutions are discussed in detail, and a separate numerical

P. Voetmann Christiansen; Henrik Smith

1968-01-01

86

Metal phases in ordinary chondrites: Magnetic hysteresis properties and implications for thermal history  

NASA Astrophysics Data System (ADS)

Magnetic properties are sensitive proxies to characterize FeNi metal phases in meteorites. We present a data set of magnetic hysteresis properties of 91 ordinary chondrite falls. We show that hysteresis properties are distinctive of individual meteorites while homogeneous among meteorite subsamples. Except for the most primitive chondrites, these properties can be explained by a mixture of multidomain kamacite that dominates the induced magnetism and tetrataenite (both in the cloudy zone as single-domain grains, and as larger multidomain grains in plessite and in the rim of zoned taenite) dominates the remanent magnetism, in agreement with previous microscopic magnetic observations. The bulk metal contents derived from magnetic measurements are in agreement with those estimated previously from chemical analyses. We evidence a decreasing metal content with increasing petrologic type in ordinary chondrites, compatible with oxidation of metal during thermal metamorphism. Types 5 and 6 ordinary chondrites have higher tetrataenite content than type 4 chondrites. This is compatible with lower cooling rates in the 650-450 °C interval for higher petrographic types (consistent with an onion-shell model), but is more likely the result of the oxidation of ordinary chondrites with increasing metamorphism. In equilibrated chondrites, shock-related transient heating events above approximately 500 °C result in the disordering of tetrataenite and associated drastic change in magnetic properties. As a good indicator of the amount of tetrataenite, hysteresis properties are a very sensitive proxy of the thermal history of ordinary chondrites, revealing low cooling rates during thermal metamorphism and high cooling rates (e.g., following shock reheating or excavation after thermal metamorphism). Our data strengthen the view that the poor magnetic recording properties of multidomain kamacite and the secondary origin of tetrataenite make equilibrated ordinary chondrites challenging targets for paleomagnetic study.

Gattacceca, J.; Suavet, C.; Rochette, P.; Weiss, B. P.; Winklhofer, M.; Uehara, M.; Friedrich, Jon M.

2014-04-01

87

A limitation of hysteresis in the correction of the sextupole field in a magnetic quadrupole lens  

NASA Astrophysics Data System (ADS)

Parasitic sextupole fields present in magnetic quadrupole lenses can be corrected by shunting the current flowing through one or two adjacent pole piece coils. It is shown here that this procedure can be limited by hysteresis in the quadrupole lens. This means that the sextupole field strength and also the size of the current shunts required to correct it depend on the direction of the current flow in the lens.

Breese, M. B. H.; Swietlicki, E.; Pallon, J.

1993-12-01

88

Losses in Magnetic Flux Compression Generators: Part 2, Radiation Losses.  

National Technical Information Service (NTIS)

This is the second monograph devoted to the analysis of flux losses in explosive driven magnetic flux compression generators. In the first monograph, flux losses from magnetic field penetration into conductor walls was studied by conventional diffusion th...

C. M. Fowler

1988-01-01

89

Nondestructive indication of plastic deformation of cold-rolled stainless steel by magnetic minor hysteresis loops measurement  

Microsoft Academic Search

Cold-rolled austenitics stainless steel samples were non-destructively characterized by means of sets of magnetic minor hysteresis loops. The flat samples were magnetized by an attached yoke, and reliable parameters were obtained from the series of minor loops, without magnetic saturation of the samples. It was found, that some magnetic quantities, well known to be closely connected to the samples’ structure

G. Vértesy; I. Mészáros; I. Tomáš

2005-01-01

90

Mechanical characterization of journal superconducting magnetic bearings: stiffness, hysteresis and force relaxation  

NASA Astrophysics Data System (ADS)

Superconducting magnetic bearings (SMBs) can provide stable levitation without direct contact between them and a magnetic source (typically a permanent magnet). In this context, superconducting magnetic levitation provides a new tool for mechanical engineers to design non-contact mechanisms solving the tribological problems associated with contact at very low temperatures. In the last years, different mechanisms have been proposed taking advantage of superconducting magnetic levitation. Flywheels, conveyors or mechanisms for high-precision positioning. In this work the mechanical stiffness of a journal SMBs have been experimentally studied. Both radial and axial stiffness have been considered. The influence of the size and shape of the permanent magnets (PM), the size and shape of the HTS, the polarization and poles configuration of PMs of the journal SMB have been studied experimentally. Additionally, in this work hysteresis behavior and force relaxation are considered because they are essential for mechanical engineer when designing bearings that hold levitating axles.

Cristache, Cristian; Valiente-Blanco, Ignacio; Diez-Jimenez, Efren; Alvarez-Valenzuela, Marco Antonio; Pato, Nelson; Perez-Diaz, Jose Luis

2014-05-01

91

Article surveillance magnetic marker having an hysteresis loop with large Barkhausen discontinuities  

DOEpatents

A marker for an electronic article surveillance system is disclosed comprising a body of magnetic material with retained stress and having a magnetic hysteresis loop with a large Barkhausen discontinuity such that, upon exposure of the marker to an external magnetic field whose field strength in the direction opposing the instantaneous magnetic polarization of the marker exceeds a predetermined threshold value, there results a regenerative reversal of the magnetic polarization of the marker. An electronic article surveillance system and a method utilizing the marker are also disclosed. Exciting the marker with a low frequency and low field strength, so long as the field strength exceeds the low threshold level for the marker, causes a regenerative reversal of magnetic polarity generating a harmonically rich pulse that is readily detected and easily distinguished.

Humphrey, Floyd B. (Bradfordwoods, PA) [Bradfordwoods, PA

1987-01-01

92

Magnetic hysteresis behavior and microstructure of severely cold-worked and aged Co-Fe-Nb alloy  

Microsoft Academic Search

The magnetic hysteresis behavior of severely cold-worked and aged 85Co-12Fe-3Nb alloy was studied in relation to the microstructure. Magnetic hardening of the alloy can be attributed to the pinning of the domain wall by quasispherical Co3Nb precipitates. Alloys cold worked to 97.8% reduction in area and aged at 700, 800, and 900 °C showed the hysteresis behavior characteristic of inhomogeneous

Yuichi Suzuki; Masato Sagawa; Masanori Okada; Zenzo Henmi

1979-01-01

93

Magnetization hysteresis studies in Sm1-xGdxAl2 alloys  

NASA Astrophysics Data System (ADS)

SmAl2 (Tc ˜ 125 K, ?sat= 0.23 ?B/f.u.) is known to exhibit magnetic compensation when doped with Gd (< 3 at.%). In such stoichiometries though the magnetization gets closer to zero, there exists a large spin polarization. This makes such materials attractive candidates for applications. We have performed detailed magnetization hysteresis and other studies in the series Sm1-xGdxAl2. In x=0.02 alloy, the loops are shifted (notion of exchange bias) along negative H-axis for temperatures just above Tcomp , and along positive H-axis for temperatures T < Tcomp. We argue that the change in the sign of exchange bias is due to the magnetic contribution of conduction electron polarization as well as that of local magnetic moments reversing the signs. At Tcomp the width of the hysteresis loop collapses. In the given series, one can set up the system in either spin-surplus or orbital-surplus state and control the exchange bias field. The compositions with 0.03 <= x < 0.06 do not exhibit zero cross over of magnetization and remain spin surplus. Our various studies and analysis shall be presented.

Vaidya, U. V.; Venkatesh, S.; Rakhecha, V. C.; Ramakrishnan, S.; Grover, A. K.

2009-03-01

94

Application of magnetomechanical hysteresis modeling to magnetic techniques for monitoring neutron embrittlement and biaxial stress  

SciTech Connect

The objective is to investigate experimentally and theoretically the effects of neutron embrittlement and biaxial stress on magnetic properties in steels, using various magnetic measurement techniques. Interaction between experiment and modeling should suggest efficient magnetic measurement procedures for determining neutron embrittlement biaxial stress. This should ultimately assist in safety monitoring of nuclear power plants and of gas and oil pipelines. In the first six months of this first year study, magnetic measurements were made on steel surveillance specimens from the Indian Point 2 and D.C. Cook 2 reactors. The specimens previously had been characterized by Charpy tests after specified neutron fluences. Measurements now included: (1) hysteresis loop measurement of coercive force, permeability and remanence, (2) Barkhausen noise amplitude; and (3) higher order nonlinear harmonic analysis of a 1 Hz magnetic excitation. Very good correlation of magnetic parameters with fluence and embrittlement was found for specimens from the Indian Point 2 reactor. The D.C. Cook 2 specimens, however showed poor correlation. Possible contributing factors to this are: (1) metallurgical differences between D.C. Cook 2 and Indian Point 2 specimens; (2) statistical variations in embrittlement parameters for individual samples away from the stated men values; and (3) conversion of the D.C. Cook 2 reactor to a low leakage core configuration in the middle of the period of surveillance. Modeling using a magnetomechanical hysteresis model has begun. The modeling will first focus on why Barkhausen noise and nonlinear harmonic amplitudes appear to be better indicators of embrittlement than the hysteresis loop parameters.

Sablik, M.J.; Kwun, H.; Rollwitz, W.L.; Cadena, D.

1992-01-01

95

Hysteresis Simulation  

NSDL National Science Digital Library

You can choose from three values for disorder of the system and select a goal for the external magnetic field by clicking in a "control bar" area. Output graphs show qualitative information, but no numbers. A brief explanation of the physics of hysteresis is provided and the java source code can be downloaded.

Houle, Paul

96

The YBa2Cu3O7- anomalous second peak and irreversible magnetic field in the magnetization hysteresis cycles  

NASA Astrophysics Data System (ADS)

The flux jumps, the second peak and the irreversible magnetic field in the magnetization hysteresis cycles have been investigated in the high temperature superconductor YBa2Cu3O7- single crystals. These cycles were obtained for different temperature values, the applied magnetic fields up to 6 T and the angle between the applied magnetic field and c-axis. The magnetization curves exhibit a remarkable second peak fishtail, this second peak was not observed for the low temperature, but we observed the flux jumps saw tooth. The temperature dependence of the irreversible magnetic field, Hirr, for the applied magnetic field perpendicular to the ab planes is given by an extended expression, Hirr ? (1-T/Tc )?, where ? is a constant, the Abrikosov flux dynamics can explain this behavior. The Hirr as a function of has been strongly influenced by the flux pinning and the thermally assisted flux motion.

Taoufik, A.; Ramzi, A.; Senoussi, S.; Labrag, A.

2004-05-01

97

Compositional, morphological, and hysteresis characterization of magnetic airborne particulate matter in Rome, Italy  

NASA Astrophysics Data System (ADS)

The magnetic properties of tree leaves may be used to delineate the abundance and dispersal of anthropogenic airborne particulate matter (PM) in urban environments. In the city of Rome, Italy, circulating vehicles are the main source of magnetic PM, already characterized as prevalently low-coercivity, magnetite-like particles. To further constrain the nature and origin of such magnetic particles, we carried out coupled field emission scanning electron microscopy and a variety of rock magnetic analyses on PM specimens from Quercus ilex leaves and from potential PM sources in circulating motor vehicles in Rome. Fe-rich particles are mostly 0.1-5 ?m in size, with irregular shapes and moss-like surface. Particles from disk brakes and diesel and gasoline exhaust pipes show distinct compositional and magnetic hysteresis signatures, suggesting that the magnetic PM collected on tree leaves consists of a mixture of particle populations deriving mostly from the abrasion of disk brakes and, to a lesser extent, from fuel combustion residuals emitted by diesel and gasoline exhausts. The contribution of fine superparamagnetic particles to the overall magnetic assemblage has been evaluated with specific rock magnetic analyses. The combined magnetic and microtextural-compositional analyses provide an effective and original tool to characterize urban PM air pollution.

Sagnotti, Leonardo; Taddeucci, Jacopo; Winkler, Aldo; Cavallo, Andrea

2009-08-01

98

Self-magnetic compensation and shifted hysteresis loops in ferromagnetic samarium systems  

NASA Astrophysics Data System (ADS)

For Sm3+ ions in a vast majority of metallic systems, the following interesting scenario has been conjured up for long, namely, a magnetic lattice of tiny self- (spin-orbital) compensated 4f -moments exchange coupled (and phase reversed) to the polarization in the conduction band. We report here the identification of a self-compensation behavior in a variety of ferromagnetic Sm intermetallics via the fingerprint of a shift in the magnetic hysteresis (M-H) loop from the origin. Such an attribute, designated as exchange bias in the context of ferromagnetic/antiferromagnetic multilayers, accords these compounds a potential for niche applications in spintronics. We also present results on magnetic compensation behavior on small Gd doping (2.5at.%) in one of the Sm ferromagnets (viz., SmCu4Pd ). The doped system responds like a pseudoferrimagnet and it displays a characteristic left-shifted linear M-H plot for an antiferromagnet.

Kulkarni, P. D.; Dhar, S. K.; Provino, A.; Manfrinetti, P.; Grover, A. K.

2010-10-01

99

Magnetic hysteresis classification of the lunar surface and the interpretation of permanent remanence in lunar surface samples  

NASA Technical Reports Server (NTRS)

A magnetic hysteresis classification of the lunar surface is presented. It was found that there is a distinct correlation between natural remanence (NRM), saturation magnetization, and the hysteresis ratios for the rock samples. The hysteresis classification is able to explain some aspects of time dependent magnetization in the lunar samples and relates the initial susceptibility to NRM, viscous remanence, and to other aspects of magnetization in lunar samples. It is also considered that since up to 60% of the iron in the lunar soil may be super paramagnetic at 400 K, and only 10% at 100 K, the 50% which becomes ferromagnetic over the cycle has the characteristics of thermoremanence and may provide for an enhancement in measurable field on the dark side during a subsatellite magnetometer circuit.

Wasilewski, P.

1972-01-01

100

Permanent magnet online magnetization performance analysis of a flux mnemonic double salient motor using an improved hysteresis model  

NASA Astrophysics Data System (ADS)

The concept of the memory motor is based on the fact that the magnetization level of the AlNiCo permanent magnet in the motor can be regulated by a temporary current pulse and memorized automatically. In this paper, a new type of memory motor is proposed, namely a flux mnemonic double salient motor drive, which is particularly attractive for electric vehicles. To accurately analyze the motor, an improved hysteresis model is employed in the time-stepping finite element method. Both simulation and experimental results are given to verify the validity of the new method.

Zhu, Xiaoyong; Quan, Li; Chen, Yunyun; Liu, Guohai; Shen, Yue; Liu, Hui

2012-04-01

101

Ba-ferrite particles for magnetic liquids with enhanced Neel relaxation time and loss investigations  

NASA Astrophysics Data System (ADS)

Nanometer-scale particles are interesting because of their unique magnetic properties. Barium ferrite with particle sizes ? 10 nm behave superparamagnetically and show at bigger sizes the transition to single domain behaviour. Beside the particle size, the anisotropy energy K_1\\cdot V, and thus the Neel relaxation time, depends also on the amount of doping. The glass crystallisation method was used for preparation of different Ba-ferrites. Ferrofluids have been prepared using Isopar^{circledR} M or dodecane as a carrier liquid. Magnetic parameters were obtained by VSM, hysteresis losses (specific loss power) of ferrite powders by a hysteresometer at 50 Hz. Magnetic core sizes were calculated from hysteresis loops. SANS curves of a ferrofluid reveal single magnetic particles and aggregated magnetic particles with an incomplete organic shell. Figs 3, Refs 9.

Muller, R.; Hiergeist, R.; Gawalek, W.; Hoell, A.

2003-03-01

102

Magnetic Biasing of a Ferroelectric Hysteresis Loop in a Multiferroic Orthoferrite  

NASA Astrophysics Data System (ADS)

In a multiferroic orthoferrite Dy0.7Tb0.3FeO3, which shows electric-field-(E-)driven magnetization (M) reversal due to a tight clamping between polarization (P) and M, a gigantic effect of magnetic-field (H) biasing on P-E hysteresis loops is observed in the case of rapid E sweeping. The magnitude of the bias E field can be controlled by varying the magnitude of H, and its sign can be reversed by changing the sign of H or the relative clamping direction between P and M. The origin of this unconventional biasing effect is ascribed to the difference in the Zeeman energy between the +P and -P states coupled with the M states with opposite sign.

Tokunaga, Y.; Taguchi, Y.; Arima, T.; Tokura, Y.

2014-01-01

103

Experimental measurement and calculation of losses in planar radial magnetic bearings  

NASA Technical Reports Server (NTRS)

The loss mechanisms associated with magnetic bearings have yet to be adequately characterized or modeled analytically and thus pose a problem for the designer of magnetic bearings. This problem is particularly important for aerospace applications where low power consumption of components is critical. Also, losses are expected to be large for high speed operation. The iron losses in magnetic bearings can be divided into eddy current losses and hysteresis losses. While theoretical models for these losses exist for transformer and electric motor applications, they have not been verified for magnetic bearings. This paper presents the results from a low speed experimental test rig and compares them to calculated values from existing theory. Experimental data was taken over a range of 90 to 2,800 rpm for several bias currents and two different pole configurations. With certain assumptions agreement between measured and calculated power losses was within 16 percent for a number of test configurations.

Kasarda, M. E. F.; Allaire, P. E.; Hope, R. W.; Humphris, R. R.

1994-01-01

104

3D MAGNETIC FIELD AND EDDY LOSS CALCULATIONS FOR IRON DOMINATED ACCELERATOR MAGNETS USING ANSYS COMPARED WITH RESULTS OF NONCOMMERCIAL CODES  

Microsoft Academic Search

The design of fast ramped superferric magnets with repetition rates in the order of 1Hz requires reliable software tools to calculate the complex 3D magnetic field quality as well as the impact of eddy currents and hysteresis losses. Various technological construction details should be taken into account to obtain a high field quality. We present a methodical study of these

P. Shcherbakov; E. Fischer; R. Kurnyshov

105

Rotational and alternating energy loss vs. magnetizing frequency in SiFe laminations  

Microsoft Academic Search

Rotational energy losses Wr have been measured as a function of magnetizing frequency fm and working induction Bm in non-oriented SiFe laminations and compared with losses in alternating fields Wa. Wr and Wa exhibit a same non-linear dependence on fm, while the ratio Wr\\/Wa is a monotonically decreasing function of Bm. A phenomenological approach to the behavior of hysteresis and

F. Fiorillo; A. M. Rietto

1990-01-01

106

AC loss in energy doubler magnets  

Microsoft Academic Search

A computerized ac loss measurement system was developed and more than 50 magnets were measured. The ac losses were very much dependent on various factors such as conductor surface and pressure applied to coil windings. Statistical correlation between quench current and ac loss will be shown. From the measurements of magnets made of different kinds of cables, most of the

M. Wake; D. Gross; R. Yamada; D. Blatchley

1979-01-01

107

A new stator-flux orientation strategy for flux-switching permanent magnet motor based on current-hysteresis control  

Microsoft Academic Search

A stator-flux orientation strategy based on current hysteresis for the flux-switching permanent magnet (FSPM) motor is proposed, in which the stator-PM FSPM motor is considered as a conventional rotor-PM surface-mounted motor and an equivalent rotor-orientated dq-axes synchronous reference frame is built although there are actually no rotary magnetic motive force produced by the stator magnets in the FSPM motor. Based

Wei Hua; Ming Cheng; Wei Lu; Hongyun Jia

2009-01-01

108

Identification and simulation of a circuit-based model of magnetic hysteresis  

Microsoft Academic Search

Purpose – The scope of the work is to provide an identification procedure for an hysteresis model based on nonlinear circuit cells. Design\\/methodology\\/approach – An identification procedure for an hysteresis model based on nonlinear circuit cells is presented. The response of elementary cell is equal to a generalized play operator. The procedure allows the identification of the limit symmetric hysteresis

G. Gruosso; M. Repetto

2005-01-01

109

Magnetic and eddy current effects in an open-loop pulsed hysteresis graph system for magnetization of rare-earth magnets  

Microsoft Academic Search

Describes an open-loop pulsed hysteresis graph system that is capable of magnetizing ceramic and rare-earth permanent magnets such as neodymium, samarium cobalt, and Alnico in cylindrical and rectangular shapes. The prototype system relies on an air-core excitation coil with an inner diameter of 3 cm and a length of 10 cm. A pulsed power supply provides a transient current pulse

R. Ludwig; P. Bretchko; S. Makarov

2002-01-01

110

Magnetic Barkhausen Noise and hysteresis loop in commercial carbon steel: influence of applied tensile stress and grain size  

Microsoft Academic Search

The influence of applied tensile stress and grain size on Magnetic Barkhausen Noise and hysteresis loops in 1005 commercial steel is studied in this work. The peak amplitude of the Barkhausen voltage increases with the applied stress, reaching a maximum value and then beginning to decrease at higher tensile stress. This behavior is explained regarding the domain wall dynamics by

J. Anglada-Rivera; L. R Padovese; J. Capo-Sanchez

2001-01-01

111

Surface magnetic anisotropy of CoFe2O4 nanoparticles with a giant low-temperature hysteresis  

NASA Astrophysics Data System (ADS)

Ferrimagnetic nanoparticles of CoFe2O4 about 4-16 nm in diameter were synthesized by pyrolysis of a mixture of Fe and Co acetylacetonates. The field dependences of magnetization and hysteresis loops were investigated in magnetic fields up to 4000 kA/m at various temperatures from 4.2 to 500 K. A considerable contribution, positive or negative depending on the temperature, of ``surface'' anisotropy to the effective magnetic anisotropy of the nanoparticles was observed. A correlation was found between the magnetic properties that represent the specificity of small particles, namely, between ``surface'' anisotropy, magnetization, and high-field susceptibility.

Mozul', K. A.; Ol'khovik, L. P.; Sizova, Z. I.; Bludov, A. N.; Pashchenko, V. A.; Baumer, V. N.; Vashchenko, V. V.; Kolosov, M. O.; Kryshtal', A. P.; Prodanov, M. F.

2013-04-01

112

Losses in magnetic flux compression generators. Part 2: Radiation losses  

Microsoft Academic Search

An analysis of flux losses in explosive driven magnetic flux compression generators is given. Flux loss by radiation from the outer conductor walls is treated. Flux leakage rates through walls of finite thickness are first obtained by diffusion theory. It is shown, for normal wall thicknesses, that flux leakage is determined essentially by the wall conductance, defined as the product

C. M. Fowler

1988-01-01

113

Magnetic hysteresis of p(+) and He-3(2+) irradiated melt-textured YBa2Cu3O(7-delta)  

NASA Technical Reports Server (NTRS)

We have measured the magnetic hysteresis loops and temperature dependent trapped fields in melt-textured YBa2Cu3O(7-delta) samples before and after p(+) and He-3(2+) irradiation using a Hall effect magnetometer (HEM) as well as a commercial vibrating sample magnetometer (VSM). For proper He-3(2+) fluence, the critical current density may be enhanced by a factor of 10. Calculations based on various critical state models show that before the irradiation, the hysteresis loops can be well accounted for by a critical current density of a modified power law field dependence. After the irradiation, the best fit has been achieved by using an exponential form. Jc and its field dependence deduced from HEM hysteresis loops are in good agreement with those deduced from the VSM loops, suggesting that the Hall effect magnetometer can be conveniently used to characterize bulk high Tc oxide superconductors.

Song, S. N.; Liu, J.; Chen, I. G.; Weinstein, Roy

1992-01-01

114

The origin of noise and magnetic hysteresis in crystalline permalloy ring-core fluxgate sensors  

NASA Astrophysics Data System (ADS)

6-81.3 Mo permalloy, developed in the 1960s for use in high performance ring-core fluxgate sensors, remains the state-of-the-art for permalloy-cored fluxgate magnetometers. The magnetic properties of 6-81.3, namely magnetocrystalline and magnetoelastic anisotropies and saturation induction are all optimum in the Fe-Ni-Mo system. In such polycrystalline permalloy fluxgate sensors a single phenomenon may cause both fluxgate noise and magnetic hysteresis, explain Barkhausen jumps, remanence and coercivity, and avoid domain denucleation. The phenomenon, domain wall reconnection, is presented as part of a theoretical model. In the unmagnetized state a coarse-grain high-quality permalloy foil ideally forms stripe domains, which present at the free surface as parallel, uniformly spaced domain walls that cross the entire thickness of the foil. Leakage flux "in" and "out" of alternating domains is a requirement of the random orientation, grain-by-grain, of magnetic easy axes' angles with respect to the foil free surface. Its magnetostatic energy together with domain wall energy determines an energy budget to be minimized. Throughout the magnetization cycle the free surface domain pattern remains essentially unchanged, due to the magnetostatic energy cost such a change would elicit. Thus domain walls are "pinned" to free surfaces. Driven to saturation, domain walls first bulge then reconnect via Barkhausen jumps to form a new domain configuration this author has called "channel domains", that are attached to free surfaces. The approach to saturation now continues as reversible channel domain compression. Driving the permalloy deeper into saturation compresses the channel domains to arbitrarily small thickness, but will not cause them to denucleate. Returning from saturation the channel domain structure will survive through zero H, thus explaining remanence. The Barkhausen jumps being irreversible exothermic events are sources of fluxgate noise, powered by the energy available from domain wall reconnection. A simplified domain energy model can then provide a predictive relation between ring core magnetic properties and fluxgate sensor noise power. Four properties are predicted to affect noise power, two of which, are well known: saturation total magnetic flux density and magnetic anisotropy. The two additional properties are easy axes alignment and foil thickness. Flux density and magnetic anisotropy are primary magnetic properties determined by an alloy's chemistry and crystalline lattice properties. Easy axes alignment and foil thickness are secondary, geometrical properties related to an alloy's polycrystalline fabric and manufacture. Improvements to fluxgate noise performance can in principle be achieved by optimizing any of these four properties in such a way as to minimize magnetostatic energy. Fluxgate signal power is proportional to B-H loop curvature (d2B/dH2). The degree to which Barkhausen jumps coincide with loop curvature is a measure of noise that accompanies fluxgate signal. B-H loops with significant curvature beyond the open hysteresis loop may be used to advantage to acquire fluxgate signal with reduced noise.

Narod, B. B.

2014-06-01

115

Optimum energy loss in electro magnetic bearing  

Microsoft Academic Search

This paper includes weight optimization method of rotor and analysis of total power loss in radial magnetic bearing consisting of four, eight and twelve poles. Weight optimization reduces copper loss in bearing since the electromagnetic force is reduced due to optimized rotor. Further numbers of poles in magnetic bearing are varied for same electromagnetic force 350 N and stator is

Santosh Shelke; R. V. Chalam

2011-01-01

116

Rotor power losses in planar radial magnetic bearings -- Effects of number of stator poles, air gas thickness, and magnetic flux density  

SciTech Connect

Rotor power losses in magnetic bearings cannot be accurately calculated at this time because of the complexity of the magnetic field distribution and several other effects. The losses are due to eddy currents, hysteresis, and windage. This paper presents measured results in radial magnetic bearing configurations with eight pole and 16 pole stators and two laminated rotors. Two different air gaps were tested. The rotor power losses were determined by measuring the rundown speed of the rotor after the rotor was spun up to speeds of approximately 30,000 rpm, DN + 2,670,000 mm-rpm, in atmospheric air. The kinetic energy of the rotor is converted to heat by magnetic and air drag power loss mechanisms during the run down. Given past publications and the opinions of researchers in the field, the results were quite unexpected. The measured power losses were found to be nearly independent of the number of poles in the bearing. Also, the overall measured rotor power loss increased significantly as the magnetic flux density increased and also increased significantly as the air gap thickness decreased. A method of separating the hysteresis, eddy current and windage losses is presented. Eddy current effect were found to be the most important loss mechanism in the data analysis, for large clearance bearings. Hysteresis and windage effects did not change much from one configuration to the other.

Allaire, P.E.; Kasarda, M.E.F.; Fujita, L.K.

1999-10-01

117

Characterization of monofilamentary and multifilamentary 2223-BSCCO tapes by magnetic loss measurements  

NASA Astrophysics Data System (ADS)

The results of measurements of hysteresis loops and related power losses in monofilamentary and multifilamentary 2223-BCCO tapes are presented and discussed in this paper. It is shown that magnetic properties considerably depend on technological processes and differ significantly between mono- and multifilamentary specimens. In particular, the variation of magnetic quantities, e.g. coercive field and residual magnetization, with applied outer magnetic field, as well as the comparison with critical current measurements, support the Bean model and, moreover, help to deduce the effective cross section of the superconductor.

Montanari, G. C.; Ghinello, I.; Gherardi, L.; Caracino, P.

1996-05-01

118

Magnetic field hysteresis under various sweeping rates for Ni-Co-Mn-In metamagnetic shape memory alloys  

NASA Astrophysics Data System (ADS)

Magnetic field-induced transition of Ni45Co5Mn36.7In13.3 was investigated under magnetic fields with different sweeping rates. A static magnetic field produced by a superconducting magnet, a semi-static magnetic field created by a flywheel DC generator-powered magnet, and a pulsed magnetic field resulting from a condenser bank-powered magnet were used in this study, which covers sweeping rates of more than 6 orders. The magnetic field hysteresis is enlarged with increasing sweeping rate. The experimental results were consistent with a phenomenological model, and the activation energy for the thermally activated process was determined to be 0.7 eV for this alloy.

Xu, Xiao; Kihara, Takumi; Tokunaga, Masashi; Matsuo, Akira; Ito, Wataru; Umetsu, Rie Y.; Kindo, Koichi; Kainuma, Ryosuke

2013-09-01

119

A new stator-flux orientation strategy for flux-switching permanent magnet motor based on current-hysteresis control  

NASA Astrophysics Data System (ADS)

A stator-flux orientation strategy based on current hysteresis for the flux-switching permanent magnet (FSPM) motor is proposed, in which the stator-PM FSPM motor is considered as a conventional rotor-PM surface-mounted motor and an equivalent rotor-orientated dq-axes synchronous reference frame is built although there are actually no rotary magnetic motive force produced by the stator magnets in the FSPM motor. Based on the proposed model, a vector-control strategy with current hysteresis for the FSPM motor drive is investigated and implemented on a dSPACE-based platform, and both the simulated and experimental results validate the effectiveness. It should be emphasized that the proposed stator-flux orientation strategy can be applied to other stator-PM machines (including doubly salient and flux-reversal PM machines) and other control methods (including space-vector pulsed-width-modification and direct torque control).

Hua, Wei; Cheng, Ming; Lu, Wei; Jia, Hongyun

2009-04-01

120

Hysteresis in weak ferromagnets  

NASA Astrophysics Data System (ADS)

Magnetic hysteresis is studied in the orthoferrites ErFeO3 and TmFeO3 using the single crystal samples of millimeter dimensions. It is shown that in both materials one observes a temperature transition manifesting itself through the temperature hysteresis of the magnetic moment and a peculiar temperature evolution of the field hysteresis loop shapes near this transition. Experiments rule out the hypothesis that the ordering of the orthoferrite's rare earth magnetic moments plays an important role in these phenomena. The hysteresis curves can be explained by a few-domain magnetic state of the samples that results from the weak ferromagnetism of the orthoferrites. The phenomenon is generic for weak ferromagnets with temperature dependent magnetization. A large characteristic magnetic length makes the behavior of the relatively big samples analogous to that observed in the nano-size samples of strong ferromagnets.

Bazaliy, Ya. B.; Tsymbal, L. T.; Kakazei, G. N.; Vasiliev, S. V.

2011-03-01

121

Ac hysteresis loop measurement of stator-tooth in induction motor  

SciTech Connect

The properties of ac hysteresis loop of a stator tooth in a 5 hp induction motor was measured and analyzed. The load increase on the motor decreased magnetic induction, however increase the minor hysteresis loops in the high induction region. This effect caused increase in the core loss. Depending on condition of the motor, the core loss of the stator tooth can be 50% greater than the core loss under sinusoidal magnetic induction waveform.

Son, D.

1999-09-01

122

Magnetic hysteresis and compensation behaviors in spin-1 bilayer Ising model  

NASA Astrophysics Data System (ADS)

The hysteresis and compensation behaviors of spin-1 bilayer Ising model on a square lattice is studied within the framework of the effective-field theory with correlation. The effects of Hamiltonian parameters on hysteresis behaviors are discussed in detail. We also obtained the Q-, R-, P-, S- and L-type compensation behaviors in the system. A number of interesting phenomena such as the shape of the hysteresis loops and compensation types have been found. The obtained results are compared with some experimental and theoretical results and found to be in a qualitatively good agreement.

Kantar, Ersin; Erta?, Mehmet

2014-06-01

123

Ac loss measurement of SSC dipole magnets  

SciTech Connect

AC losses in full length and 1.5 m model SSC collider dipoles were successfully measured by the direct observation of energy flow into and out of magnets during a ramp cycle. The measurement was performed by using two double-integrating type digital volt meters (DVM`s) for current and voltage measurement. Measurements were performed for six is m long ASST magnets and five 1.5 m long model magnets, inducting one 40 mm diameter magnet. There were large variations in the eddy current losses. Since these magnets use conductors with slight deviations in their internal structures and processing of the copper surface depending on the manufacturer, it is likely that there are differences in the contact resistance between strands. Correlation between the ramp rate dependence of the,quench current and the eddy current loss was evident.

Delchamps, S.; Hanft, R.; Jaffery, T.; Kinney, W.; Koska, W.; Lamm, M.J.; Mazur, P.O.; Orris, D.; Ozelis, J.P.; Strait, J.; Wake, M.

1992-09-01

124

Analytical formulation for magnetic shields taking into account hysteresis effects in the Rayleigh region  

Microsoft Academic Search

Purpose – To study the magnetic shielding and the losses of non-linear, hysteretic multilayered shields by using fast to evaluate analytical expressions. Design\\/methodology\\/approach – In order to evaluate the shield in the frequency domain, the non-linear shield is divided into a sufficient number of piecewise linear sublayers. Each sublayer has a permeability that is constant (space independent) and complex (to

Peter Sergeant; Luc Dupré; Lode Vandenbossche; Jan Melkebeek

2005-01-01

125

Calorimetric equipment for measuring magnetic losses  

Microsoft Academic Search

The above calorimetric equipment with an “adiabatic” sheathing eliminates almost completely the heat exchange between the calorimeter and the ambient medium. The equipment is suitable for measuring losses in toroidal magnetically soft samples (with an external diameter not exceeding 60 mm), when they are magnetized with alternating currents of several megahertz.

V. V. Kogen-Dalin; Khusein Nigm

1965-01-01

126

Analysis of iron loss in interior permanent magnet synchronous motor over a wide-speed range of constant output power operation  

Microsoft Academic Search

The paper presents the analysis of iron loss in interior permanent magnet synchronous motor over a wide-speed range of constant output power operation. The analysis is based on finite element method and uses the information on local flux density variation in the motor components. The total iron loss is calculated by summing up separately the hysteresis, classical eddy current and

B. Stumberger; A. Hamler; B. Hribernik

2000-01-01

127

Magnetic sensing for microstructural assessment of power station steels: Differential permeability and magnetic hysteresis  

NASA Astrophysics Data System (ADS)

Failure of power station steel components can have severe economic impacts and also present significant risks to life and the environment. Currently components are inspected during costly shut-downs as no in-situ technique exists to monitor changes in microstructure of in-service steel components. Electromagnetic inspection has the potential to provide information on microstructure changes in power station steels in-situ. In this paper, tests have been carried out on pipe and tube samples in different microstructural conditions, using a lab-based closed magnetic circuit and impedance measurement systems. EM properties have been identified with correlations to material properties, which can quantify degradation in-situ and at elevated temperatures.

Karimian, N.; Wilson, J. W.; Yin, W.; Liu, J.; Davis, C. L.; Peyton, A. J.

2013-06-01

128

Magnetic losses evolution of a semi-processed steel during forced aging treatments  

NASA Astrophysics Data System (ADS)

An ultra-low carbon steel (30 ppm after decarburization) containing Al and Si was aged for distinct soaking times at 210 °C. The core loss increased continuously until around 24 h. After that, only slight changes were verified. It was found that only the hysteresis loss component changed during the aging treatment. By internal friction test and transmission electron microscopy it was seen that carbon precipitation caused the magnetic aging. By scanning electron microscopy it could be concluded that the increase of aging index was attributed to the high number of carbides larger than 0.1 ?m.

Marra, K. M.; Landgraf, F. J. G.; Buono, V. T.

129

Mass loss from warm giants: Magnetic effects  

NASA Technical Reports Server (NTRS)

Among warm giant stars, rapid mass loss sets in along a well defined velocity dividing line (VDL). Hot corona also disappear close to the VDL and thermal pressure cannot drive the observed rapid mass loss in these stars. The VDL may be associated with magnetic fields changing from closed to open. Such a change is consistent with the lack of X-rays from late-type giants. A magnetic transition locus based on Pneuman's work on helmet streamer stability agrees well with the empirical VDL. The change from closed to open fields not only makes rapid mass loss possible, but also contributes to energizing the mass loss in the form of discrete bubbles.

Mullan, D. J.

1980-01-01

130

Tuning size and magnetic thermal hysteresis in a new near room temperature spin crossover compound.  

PubMed

A mononuclear spin crossover compound Fe(AP-Mesal)2, which exhibits spin transitions near room temperature and light induced excited spin state trapping (LIESST) effects at low temperature, was synthesized and substructured in the form of micro- and nanoscaled particles. A thermal hysteresis loop was detected with particle size reduction to microscale and nanoscale. PMID:23633082

Zhang, Li; Wang, Juan-Juan; Xu, Guan-Cheng; Li, Jing; Jia, Dian-Zeng; Gao, Song

2013-06-21

131

Computer simulation of magnetic switching circuits and magnetic energy losses  

Microsoft Academic Search

A computer simulation has been developed to model the actions of magnetic switching circuits. Simulations are compared to experimental data obtained from a one-stage magnetically switched circuit. Comparisons between experimental and computed switch voltage and current waveforms are made for various operating conditions, pre-saturation leakage currents, and for energy losses. The computer simulation models the actual core saturation process, including

Rhinehart; H. E. Jr

1989-01-01

132

Introduction of thermal activation in forward modeling of hysteresis loops for single-domain magnetic particles and implications for the interpretation of the Day diagram  

Microsoft Academic Search

Synthetic hysteresis loops were generated by numerically solving the classical Stoner-Wohlfarth model and a thermally activated Stoner-Wohlfarth model for a set of randomly oriented magnetic grains. Although computationally intensive this method allows forward modeling of hysteresis loops of single-domain (SD) and viscous grains. In the classic Stoner-Wohlfarth model the shape of the modeled loops can be modified by changing the

Luca Lanci; Dennis V. Kent

2003-01-01

133

AC loss measurement of SSC dipole magnets.  

National Technical Information Service (NTIS)

AC losses in full length and 1.5 m model SSC collider dipoles were successfully measured by the direct observation of energy flow into and out of magnets during a ramp cycle. The measurement was performed by using two double-integrating type digital volt ...

S. Delchamps R. Hanft T. Jaffery W. Kinney W. Koska

1992-01-01

134

Magnetization, anomalous Barkhausen effect, and core loss of Supermendur under high temperature cycling.  

NASA Technical Reports Server (NTRS)

The magnetization and core loss of Supermendur were measured up to 900 C under conditions of slow temperature cycling in vacuum. As a consequence of this heating, the coercivity at 25 C increased from 21 A/m to about 110 A/m. This increase is less than previously reported. A prominent anomalous Barkhausen effect, pinched-in hysteresis loops, and a magnetic viscosity field in excess of 20 A/m were observed in the range of 600 to 700 C. At 850 C, Supermendur had a coercivity of 23 A/m, a saturation induction exceeding 1.5 T, a core loss of 26 W/kg at 400 Hz, and a maximum induction of 1.5 T. Supermendur may be useful for high temperature soft magnetic material applications where some history dependence of properties and instability of minor loops at lower temperatures is acceptable.

Niedra, J. M.; Schwarze, G. E.

1971-01-01

135

Evaluation of Power Heat Losses in Multidomain Iron Particles Under the Influence of AC Magnetic Field in RF Range  

NASA Astrophysics Data System (ADS)

The magnetic properties and hyperthermia effect were studied in a magnetorheological fluid (MRF) containing iron particles of 1 \\upmu m to 5 \\upmu m in diameter. The measurements showed that the magnetization in the saturation state reaches a value of 171 A\\cdot m2\\cdot kg^{-1} with very small values of coercivity and remanence. They also showed the ferromagnetic behavior in the system together with a value of the magnetic susceptibility of 1.7. Theoretical and experimental results of the calorimetric effect investigation under a changeable magnetic field of high frequency (f = 504 kHz) in an MRF will be presented in the article. The sample was subjected to an alternating magnetic field of different strengths (H = 0 to 4 kA\\cdot m^{-1}). It results from a theoretical analysis that the heat power density (released in the MRF sample) referenced to the eddy current is proportional to the square of frequency, the magnetic field amplitude, and the iron grain diameter. Experimental results indicate that there are some reasons for the released heat energy such as: energy losses from magnetic hysteresis and eddy currents induced in the iron grains. If the magnetic field intensity amplitude grows, the participation of losses connected with magnetic hysteresis is increased. From the calorimetric measurements, the conclusion is as follows: for a magnetic field H<1946 text{ A}\\cdot m^{-1}, the eddy current processes dominate in the heat generation mechanism, whereas hysteresis processes for the total release of thermal energy dominate for higher magnetic fields. Both mechanisms take equal parts in heating the tested sample at a magnetic field intensity amplitude H= 1946 A\\cdot m^{-1}. The specific absorption rate referenced to the mass unit of the MRF sample at the amplitude of the magnetic field strength 4 kA\\cdot m^{-1} equals 24.94 W \\cdot kg^{-1} at a frequency f = 504 kHz.

Skumiel, Andrzej; Kaczmarek-Klinowska, Milena; Timko, Milan; Molcan, Matus; Rajnak, Micha?

2013-04-01

136

Cryogenic hysteretic loss analysis for (Fe,Co,Ni)-Zr-B-Cu nanocrystalline soft magnetic alloys  

NASA Astrophysics Data System (ADS)

The present study compares the hysteretic losses of a series of eight nanocrystalline soft magnetic alloys with compositions (Fe,Co,Ni)-Zr-B-Cu. The alloys were produced by a single wheel melt spinning technique followed by isothermal annealing to promote primary crystallization. As determined by x-ray diffraction experiments, these samples consist of fcc and/or bcc crystallites with average grain diameters of less than 15 nm. Vibrating sample magnetometry was employed to measure hysteresis loops at 110 and 300 K. The integrated hysteresis loops were larger for the (Fe0.22Ni0.78)89-xZr7B4Cux alloys and nearly unchanged for the other alloys with one exception [i.e., (Fe0.75Co0.125Ni0.125)85.5Zr8.5B5Cu1]. Additional hysteresis measurements with varying degrees of maximum flux density (between 0.03 and 1.1 T) were performed at 110 and 300 K for the alloy with composition (Fe0.75Co0.125Ni0.125)85.5Zr8.5B5Cu1, annealed at 823 K for 1 h. A 50% reduction in hysteretic losses was observed for this sample when measured at 110 K (compared to room temperature).

Willard, M. A.; Heil, T. M.

2007-05-01

137

PSPICE computer modeling of hysteresis effects  

Microsoft Academic Search

Recent versions of PSPICE, a personal computer implementation of the SPICE circuit simulation computer software program, have the capability of simulating the hysteresis loops of magnetic materials. In order to model the hysteresis loop of a particular manufacturer's magnetic core material, the values of five parameters that affect the shape of the hysteresis loop must be established. A method for

S. Prigozy

1993-01-01

138

Hysteresis loops of individual Co nanostripes measured by magnetic force microscopy  

PubMed Central

High-resolution magnetic imaging is of utmost importance to understand magnetism at the nanoscale. In the present work, we use a magnetic force microscope (MFM) operating under in-plane magnetic field in order to observe with high accuracy the domain configuration changes in Co nanowires as a function of the externally applied magnetic field. The main result is the quantitative evaluation of the coercive field of the individual nanostructures. Such characterization is performed by using an MFM-based technique in which a map of the magnetic signal is obtained as a function of both the lateral displacement and the magnetic field.

2011-01-01

139

STP Hysteresis Program  

NSDL National Science Digital Library

The STP Hysteresis program is a Monte Carlo simulation of a two-dimensional Ising model demonstrating that the magnetization does not immediately change when the external magnetic field is changed. The default is a lattice of linear dimension L=32 (for a total of N=L^2 spins), a temperature T=1.8 and an external field that changes from H=1 to H=-1 and then returns to its original value. STP Hysteresis is part of a suite of Open Source Physics programs that model aspects of Statistical and Thermal Physics (STP). The program is distributed as a ready-to-run (compiled) Java archive. Double clicking the stp_Hysteresis.jar file will run the program if Java is installed on your computer. Additional programs can be found by searching ComPADRE for Open Source Physics, STP, or Statistical and Thermal Physics.

Gould, Harvey; Tobochnik, Jan; Christian, Wolfgang; Cox, Anne

2009-03-13

140

Local Identification of Magnetic Hysteresis Properties Near Cutting Edges of Electrical Steel Sheets  

Microsoft Academic Search

Technological processes performed on electrical steel influence drastically their magnetic properties. The local mechanical state, changed by the introduction of cutting stresses and strains, degrades the local magnetic properties of the material. Therefore, the need exists to characterize accurately the change of the magnetic properties as a function of the distance from the cutting edge. We present a nondestructive experimental

Guillaume Crevecoeur; Luc Dupre; Lode Vandenbossche; Rik Van de Walle

2008-01-01

141

Compositional, morphological, and hysteresis characterization of magnetic airborne particulate matter in Rome, Italy  

Microsoft Academic Search

The magnetic properties of tree leaves may be used to delineate the abundance and dispersal of anthropogenic airborne particulate matter (PM) in urban environments. In the city of Rome, Italy, circulating vehicles are the main source of magnetic PM, already characterized as prevalently low-coercivity, magnetite-like particles. To further constrain the nature and origin of such magnetic particles, we carried out

Leonardo Sagnotti; Jacopo Taddeucci; Aldo Winkler; Andrea Cavallo

2009-01-01

142

Influence of experimental methods on crossing in magnetic force-gap hysteresis curve of HTS maglev system  

NASA Astrophysics Data System (ADS)

The crossing in magnetic levitation force-gap hysteresis curve of melt high-temperature superconductor (HTS) vs. NdFeB permanent magnet (PM) was experimentally studied. One HTS bulk and PM was used in the experiments. Four experimental methods were employed combining of high/low speed of movement of PM with/without heat insulation materials (HIM) enclosed respectively. Experimental results show that crossing of the levitation force-gap curve is related to experimental methods. A crossing occurs in the magnetic force-gap curve while the PM moves approaching to and departing from the sample with high or low speed of movement without HIM enclosed. When the PM is enclosed with HIM during the measurement procedures, there is no crossing in the force-gap curve no matter high speed or low speed of movement of the PM. It was found experimentally that, with the increase of the moving speed of the PM, the maximum magnitude of levitation force of the HTS increases also. The results are interpreted based on Maxwell theories and flux flow-creep models of HTS.

Lu, Yiyun; Qin, Yujie; Dang, Qiaohong; Wang, Jiasu

2010-12-01

143

Mathematical Models of Hysteresis (Dynamic Problems in Hysteresis).  

National Technical Information Service (NTIS)

This research has further advanced the current state of the art in the areas of dynamic aspects of hysteresis and nonlinear large scale magnetization dynamics. The results of this research will find important engineering applications in the areas of magne...

I. Mayergoyz

2006-01-01

144

Loss minimization in surface permanent-magnet synchronous motor drives  

Microsoft Academic Search

The loss minimization in surface permanent-magnet synchronous motor drives is investigated. Based on theoretical analysis, a loss model controller is introduced to specify the optimal air-gap flux that minimizes losses. Theoretical results are verified experimentally. The proposed loss model controller is simple and does not adversely affect the cost and complexity of the drive. Implementation of the loss model controller

Christos Mademlis; Jannis Xypteras; Nikos Margaris

2000-01-01

145

Spatially resolved magnetic hysteresis in a YBa2Cu3O7-y crystal measured by a Hall-probe array  

Microsoft Academic Search

We report local-magnetic-field measurements near a YBa2Cu3O7-y crystal by a linear array of Hall probes. Two distinct features are observed in the local-field hysteresis Hl vs H, which are not present in the integrated magnetization measured by a SQUID: (1) a peak in Hl right after the field reversal that we attribute to the field generated by the current flow

T. Tamegai; L. Krusin-Elbaum; P. Santhanam; M. J. Brady; W. T. Masselink; C. Feild; F. Holtzberg

1992-01-01

146

Application of magnetomechanical hysteresis modeling of magnetic techniques for monitoring neutron embrittlement and biaxial stress  

SciTech Connect

Objective of this project is to investigate experimentally and theoretically the effects of neutron embrittlement and biaxial stress on magnetic properties in steels, using various magnetic measurement techniques. If neutron embrittlement and biaxial stress can be measured via changes in magnetic properties, this should ultimately assist in safety monitoring of nuclear power plants and of gas and oil pipelines. This first-year report addresses the issue of using magnetic property changes to detect neutron embrittlement. The magnetic measurements were all done on irradiated specimens previously broken in two in a Charpy test to determine their embrittlement. The magnetic properties of the broken charpy specimens from D.C. Cook did not correlate well with fluence or embrittlement parameters, possible due to metallurgical reasons. correlation was better with Indian Point 2 specimens, with the nonlinear harmonic amplitudes showing the best correlation (R[sup 2][approximately]0.7). However, correlation was not good enough. It is recommended that tests be done on unbroken irradiated Charpy specimens, for which magnetic characterization data prior to irradiation is available, if possible.

Sablik, M.J.; Kwun, H.; Burkhardt, G.L.; Rollwitz, W.L.; Cadena, D.G.

1993-01-31

147

Application of magnetomechanical hysteresis modeling of magnetic techniques for monitoring neutron embrittlement and biaxial stress  

SciTech Connect

Research was done on the biaxial stress problem accomplished in the first half of the second year. All of the work done was preparatory to magnetic measurements. Issues addressed were: construction of a model for extracting changes in the magnetic properties of a specimen from the readings of an indirect sensor; initial development of a model for how biaxial stress alters the intrinsic magnetic properties of thespecimen; use of finite element stress analysis modeling to determine a detailed shape for the cruciform biaxial stress specimen; and construction of the biaxial stress loading apparatus.

Sablik, M.J.; Kwun, H.; Burkhardt, G.L.

1993-01-31

148

Characterizing local anisotropy of coercive force in motor laminations with the moving magnet hysteresis comparator  

NASA Astrophysics Data System (ADS)

Non oriented silicon steels are widely used within rotating electrical machines and are assumed to have no anisotropy. There exists a need to detect the anisotropic magnetic properties and to evaluate the local changes in magnetic material properties due to manufacturing cutting processes. In this paper, the so called moving magnet hyteresis comparator is applied to non destructively detect directional variations in coercive force in a variety of local regions of rotor and stator laminations of two materials commonly used to construct induction motors cores. Maximum to minimum coercive force ratios were assessed, varying from 1.4 to 1.7.

Garshelis, I. J.; Crevecoeur, G.

2014-05-01

149

Evaluation of Iron Loss in Interior Permanent Magnet Synchronous Motor with Consideration of Rotational Field  

NASA Astrophysics Data System (ADS)

Loss evaluation is an important issue in the design of electrical machines. Due to the complicate structure and flux distribution, it is difficult to predict the iron loss in the machines exactly. This paper studies the iron loss in interior permanent magnet synchronous motors based on the finite element method. The iron loss test data of core material are used in the fitting of the hysteresis and eddy current loss constants. For motors in practical operation, additional iron losses due to the appearance of rotation of flux density vector and harmonic flux density distribution makes the calculation data deviates from the measured ones. Revision is made to account for these excess iron losses which exist in the practical operating condition. Calculation results show good consistence with the experimental ones. The proposed method provides a possible way to predict the iron loss of the electrical machine with good precision, and may be helpful in the selection of the core material which is best suitable for a certain machine.

Ma, Lei; Sanada, Masayuki; Morimoto, Shigeo; Takeda, Yoji; Kaido, Chikara; Wakisaka, Takeaki

150

Study and Implementation of Hysteresis Controlled Inverter on a Permanent Magnet Synchronous Machine  

Microsoft Academic Search

In order to set up brushless dc servomotors, a specially designed permanent magnet machine has been associated with a transistorized inverter. First, the different parts of the machine\\/inverter\\/control assembly are described. Then a numerical simulation of this assembly is presented. This simulation has been used to study different control strategies that have been implemented on the experimental device: the results

Michel Lajoie-Mazenc; Carlos Villanueva; Jean Hector

1985-01-01

151

Modeling of iron losses of permanent-magnet synchronous motors  

Microsoft Academic Search

Permanent-magnet (PM) motors offer potential energy savings as compared with induction motors because of the virtual elimination of rotor loss and the reduction of stator loss from operation near unity power factor. In PM machines, iron losses form a significant fraction of the total loss partly due to the nonsinusoidal flux density distribution. Design optimization therefore requires good means of

Chunting Mi; Gordon R. Slemon; Richard Bonert

2003-01-01

152

Realization of small intrinsic hysteresis with large magnetic entropy change in La0.8Pr0.2(Fe0.88Si0.10Al0.02)13 by controlling itinerant-electron characteristics  

NASA Astrophysics Data System (ADS)

Tuning of phase-transition characteristics in La(FexSi1-x)13 was conducted in view of the correlation between microscopic itinerant electron natures and macroscopic thermodynamic (magnetocaloric) quantities. To realize a small hysteresis loss QH accompanied by a large magnetic entropy change ?SM in La(FexSi1-x)13, two types of modulation based on itinerant electron characteristics, namely, the Fermi-level shift and the magnetovolume effect were combined by complex partial substitution of Al and Pr. Ab-initio calculations predict the reduction of a transition hysteresis owing to the Fermi-level shift after partial substitution of Al. On the other hand, the chemical pressure arisen from partial substitution of Pr enhances ?SM through magnetovolume effect. The selective enhancement of ?SM apart from QH by the magnetovolume effect is well explained by the phenomenological Landau model. Consequently, ?SM of La0.8Pr0.2(Fe0.88Si0.10Al0.02)13 is -18 J/kg K under a magnetic field change of 0-1.2 T, while the maximum value of QH becomes 1/6 of that for La(Fe0.88Si0.12)13.

Fujita, A.; Matsunami, D.; Yako, H.

2014-03-01

153

Magnetoresistance hysteresis in granular HTSCs as a manifestation of the magnetic flux trapped by superconducting grains in YBCO + CuO composites  

SciTech Connect

Hysterestic behavior of the magnetoresistance of granular HTSCs and its interaction with the magnetic hysteresis are studied by measuring magnetoresistance R(H) and critical current I{sub c}(H) of composites formed by HTSC Y{sub 0.75}Lu{sub 0.25}Ba{sub 2}Cu{sub 3}O{sub 7} and CuO. A network of Josephson junctions is formed in such composites, in which the nonsuperconducting component plays the role of barriers between HTSC grains. Hysteretic dependences R(H) of magnetoresistance are studied in a wide range of transport current density j and are analyzed in the framework of the two-level model of a granular superconductor, in which dissipation takes place in the Josephson medium and the magnetic flux can be pinned both in grains and in the Josephson medium. The interrelation between the hysteresis of critical current I{sub c}(H) and the evolution of the hysterestic dependence R(H) of the magnetoresistance upon transport current variation is demonstrated experimentally. The effect of the magnetic past history on the hysteretic behavior of R(H) and the emergence of a segment with a negative magnetoresistance are analyzed. It is shown for the first time that the R(H) dependences are characterized by a parameter that is independent of the transport current, viz., the width of the R(H) hysteresis loop.

Balaev, D. A., E-mail: smp@iph.krasn.ru; Gokhfeld, D. M.; Dubrovskii, A. A.; Popkov, S. I.; Shaikhutdinov, K. A.; Petrov, M. I. [Russian Academy of Sciences, Kirenskii Institute of Physics, Siberian Branch (Russian Federation)

2007-12-15

154

Application of magnetomechanical hysteresis modeling to magnetic techniques for monitoring neutron embrittlement and biaxial stress. Progress report, June 1991--December 1991  

SciTech Connect

The objective is to investigate experimentally and theoretically the effects of neutron embrittlement and biaxial stress on magnetic properties in steels, using various magnetic measurement techniques. Interaction between experiment and modeling should suggest efficient magnetic measurement procedures for determining neutron embrittlement biaxial stress. This should ultimately assist in safety monitoring of nuclear power plants and of gas and oil pipelines. In the first six months of this first year study, magnetic measurements were made on steel surveillance specimens from the Indian Point 2 and D.C. Cook 2 reactors. The specimens previously had been characterized by Charpy tests after specified neutron fluences. Measurements now included: (1) hysteresis loop measurement of coercive force, permeability and remanence, (2) Barkhausen noise amplitude; and (3) higher order nonlinear harmonic analysis of a 1 Hz magnetic excitation. Very good correlation of magnetic parameters with fluence and embrittlement was found for specimens from the Indian Point 2 reactor. The D.C. Cook 2 specimens, however showed poor correlation. Possible contributing factors to this are: (1) metallurgical differences between D.C. Cook 2 and Indian Point 2 specimens; (2) statistical variations in embrittlement parameters for individual samples away from the stated men values; and (3) conversion of the D.C. Cook 2 reactor to a low leakage core configuration in the middle of the period of surveillance. Modeling using a magnetomechanical hysteresis model has begun. The modeling will first focus on why Barkhausen noise and nonlinear harmonic amplitudes appear to be better indicators of embrittlement than the hysteresis loop parameters.

Sablik, M.J.; Kwun, H.; Rollwitz, W.L.; Cadena, D.

1992-01-01

155

Magnetic field analysis of rotational loss tester with vertical yoke  

NASA Astrophysics Data System (ADS)

The measurement apparatus of magnetic loss in electrical steel under the condition of rotational flux has been developed. In order to improve the accuracy of this apparatus, it is necessary to clear its fundamental characteristic and construction. In this paper, the results of the finite element analysis for the influence of sample shape and of the air gap length between yoke and sample on the measurement accuracy of the magnetic field strength and of the magnetic loss are presented.

Enokizono, M.; Todaka, T.; Sashikata, T.; Sievert, J. D.; Ahlers, H.

1992-07-01

156

Eddy current losses in permanent magnets of the BLDC machine  

Microsoft Academic Search

Purpose – This study aims to calculate eddy current losses in permanent magnets of BLDC machine in the generator mode of operation with no-load. Design\\/methodology\\/approach – Stator slot openings and special design of the stator poles cause changes in the magnetic flux density changes in permanent magnets. The stator windings are not connected to an outer source and no currents

Damijan Miljavec; Bogomir Zidari?

2007-01-01

157

Components of the core losses under low frequency magnetic field of the bulk Ni-Fe compacted powder material  

NASA Astrophysics Data System (ADS)

Permalloy is the name of nickel-iron alloys, which after heat treatment have an initial permeability much larger than that one of pure iron and are produced usually in the form of thin sheet. Therefore it is logical to attempt to prepare such material in more "bulk" form, for example in the form of a cylinder or a ring, which would be more convenient for some industrial applications. The aim of this work was to investigate the influence of the powder size on ac and dc magnetic properties of the bulk samples prepared by a hot compaction of the powder. By analysis of the contributions of the hysteresis losses, the eddy current losses and the anomalous losses to the core losses we obtained that the fraction of all contributions strongly depends on the particle size of the powder used for preparation of the bulk material.

Olekšáková, Denisa; Füzer, Ján; Kollár, Peter; Roth, S.

2013-05-01

158

Magnetic hysteresis and relaxation in Ag-sheathed TlBaCaCuO (1223) and Bi(Pb)SrCaCuO (2223) superconducting tapes  

SciTech Connect

Magnetic hysteresis (7--75 K in magnetic fields up to 5 T) and relaxation characteristics (5--50 K in magnetic fields up to 2 T) have been measured with the field perpendicular to the surface of Ag-sheathed TlBaCaCuO (1223 phase) and Bi(Pb)SrCaCuO (2223 phase) superconducting tapes. A study of the difference in the magnetic hysteresis between precursor powders and as-processed tapes was also carried out. The relaxation data were curve-fit using a rate equation for thermally activated flux motion, U{sub eff}/[kG(T)] = {minus}T[ln(dM/dt) {minus} ln (H{omega}{sub o} a/2{pi}d)] with the temperature dependence of U{sub eff} scaled by the functional form G(T) = 1 {minus} (T/Tx){sup 2}. By comparing the results obtained from magnetic characterization with those from transport current measurement, these observations suggest that (1) Tl-1223 tapes have a weaker field dependence for J{sub c} at T > 35 K than Bi-2223 tapes due to the special crystal structure of the 1223 phase, and (2) weak links limit the transport critical current densities in Tl-1223 tapes to 10{sup 3} A/cm{sup 2} at 5 T and 35 K, for instance.

Kung, P.J.; Maley, M.P.; Coulter, J.Y.; Willis, J.O.; Peterson, D.E. [Los Alamos National Lab., NM (United States); McHenry, M.E. [Carnegie-Mellon Univ., Pittsburgh, PA (United States). Dept. of Metallurgical Engineering and Materials Science; Wahlbeck, P.G. [Wichita State Univ., KS (United States). Dept. of Chemistry

1992-05-01

159

Magnetic hysteresis and relaxation in Ag-sheathed TlBaCaCuO (1223) and Bi(Pb)SrCaCuO (2223) superconducting tapes  

SciTech Connect

Magnetic hysteresis (7--75 K in magnetic fields up to 5 T) and relaxation characteristics (5--50 K in magnetic fields up to 2 T) have been measured with the field perpendicular to the surface of Ag-sheathed TlBaCaCuO (1223 phase) and Bi(Pb)SrCaCuO (2223 phase) superconducting tapes. A study of the difference in the magnetic hysteresis between precursor powders and as-processed tapes was also carried out. The relaxation data were curve-fit using a rate equation for thermally activated flux motion, U{sub eff}/(kG(T)) = {minus}T(ln(dM/dt) {minus} ln (H{omega}{sub o} a/2{pi}d)) with the temperature dependence of U{sub eff} scaled by the functional form G(T) = 1 {minus} (T/Tx){sup 2}. By comparing the results obtained from magnetic characterization with those from transport current measurement, these observations suggest that (1) Tl-1223 tapes have a weaker field dependence for J{sub c} at T > 35 K than Bi-2223 tapes due to the special crystal structure of the 1223 phase, and (2) weak links limit the transport critical current densities in Tl-1223 tapes to 10{sup 3} A/cm{sup 2} at 5 T and 35 K, for instance.

Kung, P.J.; Maley, M.P.; Coulter, J.Y.; Willis, J.O.; Peterson, D.E. (Los Alamos National Lab., NM (United States)); McHenry, M.E. (Carnegie-Mellon Univ., Pittsburgh, PA (United States). Dept. of Metallurgical Engineering and Materials Science); Wahlbeck, P.G. (Wichita State Univ., KS (United States). Dept. of Chemistry)

1992-01-01

160

Transformations of magnetic mineralogy in rocks revealed by difference of hysteresis loops measured after stepwise heating: theory and case studies  

Microsoft Academic Search

A new approach for tracking mineralogical alterations during laboratory stepwise heating experiments is proposed. It uses the hysteresis loop obtained as a difference between the loops measured after thermal treatment at two different consecutive temperatures. Depending on the nature of the mineralogical alterations (the formation of a new ferrimagnetic phase from a paramagnetic one, the thermal transformation of the originally

Bernard Henry; Diana Jordanova; Neli Jordanova; Maxime Le Goff

2005-01-01

161

Investigation of the power losses in a laminated dipole magnet with superconducting coils  

Microsoft Academic Search

Dynamic processes in a window-frame dipole with superconducting windings and a cold, laminated iron yoke have been investigated experimentally at JINR (Dubna, Russia), and theoretically at GSI (Darmstadt, Germany). The main aim of these investigations was a reduction of energy losses in the yoke during ramping. These losses are produced mainly by energy dissipation due to eddy currents and hysteresis

Alexander Kalimov; Egbert Fischer; Guenter Hess; Gebhard Moritz; Carsten Mühle

2004-01-01

162

Passive magnetic bearing element with minimal power losses  

DOEpatents

Systems employing passive magnetic bearing elements having minimal power losses are provided. Improved stabilizing elements are shown, employing periodic magnet arrays and inductively loaded circuits, but with improved characteristics compared to the elements disclosed in US Patent No. 5,495,221 entitled ``Dynamically Stable Magnetic Suspension/Bearing System.`` The improvements relate to increasing the magnitude of the force derivative, while at the same time reducing the power dissipated during the normal operation of the bearing system, to provide a passive bearing system that has virtually no losses under equilibrium conditions, that is, when the supported system is not subject to any accelerations except those of gravity. 8 figs.

Post, R.F.

1998-12-08

163

Passive magnetic bearing element with minimal power losses  

DOEpatents

Systems employing passive magnetic bearing elements having minimal power losses are provided. Improved stabilizing elements are shown, employing periodic magnet arrays and inductively loaded circuits, but with improved characteristics compared to the elements disclosed in U.S. Patent No. 5,495,221 entitled "Dynamically Stable Magnetic Suspension/Bearing System." The improvements relate to increasing the magnitude of the force derivative, while at the same time reducing the power dissipated during the normal operation of the bearing system, to provide a passive bearing system that has virtually no losses under equilibrium conditions, that is, when the supported system is not subject to any accelerations except those of gravity.

Post, Richard F. (Walnut Creek, CA)

1998-01-01

164

Magnetic hysteresis of the zero-resistance critical temperature of high-T{sub c} granular superconductors  

SciTech Connect

The authors have found a notorious hysteretic behavior in the dependence of the zero-resistance critical temperature obtained through resistivity ({rho}) versus temperature (T) measurements with applied field (H{sub c}) in High-T{sub c} granular superconductors. This behavior is explained semi-quantitatively based on the analogy between the present observation and a similar hysteresis found in the field dependence of the transport critical current in these materials.

Flores, L.; Altshuler, E.; Garcia, S. [Univ. of Havana (Cuba)] [and others

1995-10-01

165

Hysteresis-Loop Overskewing  

NASA Astrophysics Data System (ADS)

The performance of permanent magnets is largely determined by the magnetostatic energy stored in free space (energy product), which depends on both materials properties and magnet geometry. The latter usually differs from laboratory shapes such as spherical samples, and demagnetizing-field corrections must be applied to compare different geometries. However, in nanostructures, especially in thin films, the macroscopic demagnetizing factors D predicted from Maxwell's equations [1] yield unphysical overskewed hysteresis loops [2]. The overskewing is probably a nanoscale effect, but its origin has remained controversial. Our explanation is that nanoscale magnetization processes violate a main condition for the applicability of macroscopy demagnetizing factors, namely the uniform character of the magnetization. In bulk magnets, the magnetization inhomogeneities effectively average to zero, but this is no longer the case if any of the dimension of the magnet becomes small. We explicitly consider granular thin films, where we find a real-structure dependent reduction D, as contrasted to the sometimes assumed infinite slope M(H) at coercivity. --- This research is supported by BREM (RS), ARPA-E, DOE (DJS), and NCMN. --- References: [1] J. A. Osborn, Phys. Rev. 67, 351 (1945); [2] R. Skomski, J.- P. Liu, and D. J. Sellmyer, Phys. Rev. B 60, 7359 (1999).

Skomski, Ralph; George, T. A.; Sellmyer, D. J.

2011-03-01

166

Analysis of the magnetic losses in iron-based soft magnetic composites with MgO insulation produced by sol-gel method  

NASA Astrophysics Data System (ADS)

This work investigated the magnetic losses of heat treated iron-based soft magnetic composites with a thin MgO insulating layer produced by sol-gel method. The samples were characterized by energy dispersive X-ray spectroscopy, X-ray analysis and Fourier transform infrared spectroscopy. The results show that the surface of the powders contains a thin layer of MgO insulation. The loss results indicate that the hysteresis part for both the core loss and total loss factor was approximately the same for the MgO-insulated compacts and conventional SOMALOY TM samples with phosphate insulation after annealing at 600 °C. But the MgO-insulated compacts exhibited significantly lower eddy current contribution of both core loss and total loss factor with respect to SOMALOY TM samples after annealing. Also the contribution of eddy current in the iron particles for MgO insulated compacts ( kp=0.91) was noticeably higher than this contribution for SOMALOY TM samples ( kp=0.18) after annealing due to the higher electrical resistivity of the MgO-insulated compacts.

Hossein Taghvaei, Amir; Ebrahimi, Azadeh; Gheisari, Khalil; Janghorban, Kamal

2010-12-01

167

Phonon bottleneck effect leads to observation of quantum tunneling of the magnetization and butterfly hysteresis loops in ( Et4 N)3 Fe2 F9  

NASA Astrophysics Data System (ADS)

A detailed investigation of the unusual dynamics of the magnetization of (Et4N)3Fe2F9 (Fe2) , containing isolated [Fe2F9]3- dimers, is presented and discussed. Fe2 possesses an S=5 ground state with an energy barrier of 2.40K due to an axial anisotropy. Poor thermal contact between sample and bath leads to a phonon bottleneck situation, giving rise to butterfly-shaped hysteresis loops below 5K concomitant with slow decay of the magnetization for magnetic fields Hz applied along the Fe?Fe axis. The butterfly curves are reproduced using a microscopic model based on the interaction of the spins with resonant phonons. The phonon bottleneck allows for the observation of resonant quantum tunneling of the magnetization at 1.8K , far above the blocking temperature for spin-phonon relaxation. The latter relaxation is probed by ac magnetic susceptibility experiments at various temperatures and bias fields HDC . At HDC=0 , no out-of-phase signal is detected, indicating that at T?1.8K Fe2 does not behave as a single-molecule magnet. At HDC=1kG , relaxation is observed, occurring over the barrier of the thermally accessible S=4 first excited state that forms a combined system with the S=5 state.

Schenker, Ralph; Leuenberger, Michael N.; Chaboussant, Grégory; Loss, Daniel; Güdel, Hans U.

2005-11-01

168

ENERGY LOSSES BY ANISOTROPIC VISCOUS DISSIPATION IN TRANSIENT MAGNETIC RECONNECTION  

SciTech Connect

Global energy losses associated with transient magnetic reconnection in a viscous resistive plasma are examined. The Braginskii stress tensor is used to model the plasma viscosity for conditions typical of the solar corona. Analytic arguments are used to show that the large-scale advective flows associated with magnetic merging are likely to generate significant viscous losses. It is pointed out that the development of a visco-resistive reconnection scale, predicted for the classical shear viscosity, is not expected in the more realistic case of the Braginskii viscosity. Numerical simulations of planar coalescence merging show that viscous losses should easily dominate resistive losses for physically plausible parameters in flaring regions. Our computations imply that flare-like rates exceeding 10{sup 29} erg s{sup -1} can be achieved under plausible coronal conditions.

Craig, I. J. D.; Litvinenko, Yuri E. [Department of Mathematics, University of Waikato, P.O. Box 3105, Hamilton (New Zealand)

2010-12-10

169

AC Loss Analysis on the Superconducting Coupling Magnet in MICE  

SciTech Connect

A pair of coupling solenoids is used in MICE experiment to generate magnetic field which keeps the muons within the iris of thin RF cavity windows. The coupling solenoids have a 1.5-meter inner diameter and will produce 7.4 T peak magnetic field. Three types of AC losses in coupling solenoid are discussed. The affect of AC losses on the temperature distribution within the cold mass during charging and rapid discharging process is analyzed also. The analysis result will be further confirmed by the experiment of the prototype solenoid for coupling solenoid, which will be designed, fabricated and tested at ICST.

Wu, Hong; Wang, Li; Green, Michael; Li, LanKai; Xu, FengYu; Liu, XiaoKun; Jia, LinXinag

2008-07-08

170

Anomalous Ferroelectric Hysteresis Loops.  

National Technical Information Service (NTIS)

Materials that exhibit anomalous ferroelectric hysteresis loops appear throughout the literature. These loops have irregular shapes that diverge from the normal hysteresis loop which is characteristic of most ferroelectrics. The observation of a unique hy...

F. J. Murdoch

1971-01-01

171

Measured losses in superconductor magnets for 60-Hertz ac operation.  

NASA Technical Reports Server (NTRS)

Results of an experimental study of electrical losses in superconductor magnets. Preliminary 60-Hz ac loss data are presented for coils constructed of Nb3Sn ribbon, Nb-Ti cable, and multifilament Nb-Ti. Losses have been measured for different size coils up to approximately 20 cm in diameter. Of the conductor types tested, Nb3Sn ribbon has the lowest losses for ac operation. In Nb3Sn-ribbon coils of different sizes, the loss per unit length of conductor is shown to decrease with a decrease in the rate of change of current and to increase, in general, with increase in coil size. An important aspect of the study is the high degree of repeatability of the data.

Hamlet, I. L.; Kilgore, R. A.

1971-01-01

172

Real and causal hysteresis elements.  

PubMed

Hysteresis is a phenomenon that has been observed across many different materials and situations. Under small-amplitude cyclical motion, classical hysteresis designates a constant loss per cycle over a wide range of frequencies. This is also consistent with an increase in losses or attenuation with frequency that is strictly proportional to the first power of frequency. Unfortunately, the classical (and simple) frequency domain description of hysteresis does not result in a real and causal impulse response, and therefore is not useful for predicting laboratory results. This problem has led to many errors as well as other more fruitful approaches over the years. The frequency domain requirements for hysteresis are re-examined and it is demonstrated that there is a family of solutions that provide real and causal impulse responses over some extended frequency range. The family is conveniently divided into highpass, lowpass, and bandpass causal systems. These are populated by closed form analytical solutions which can be applied to the prediction of motion and waves in hysteretic materials and systems. PMID:24907801

Parker, Kevin J

2014-06-01

173

Rotational magnetization and rotational losses of grain oriented silicon steel sheets-fundamental aspects and theory  

Microsoft Academic Search

Rotational magnetization of grain oriented SiFe sheets involves three mechanisms: anisotropy, hysteresis and eddy currents. Apart from describing the respective physical background, the paper is focused on a separation of mechanisms. It discusses dependencies between field quantities which in the dynamic case are complicated by the fact that a three-dimensional field problem arises here. It is demonstrated that within a

H. Pfiitzner

1994-01-01

174

Heat Transfer in Pulsed Superconducting Magnets.  

National Technical Information Service (NTIS)

The first section of the report summarizes design problems for the development of advanced superconducting pulse magnets, leading to recommendations for future work, primarily in (1) evaluation of eddy-current, hysteresis, and frictional losses, and (2) t...

V. Arp P. J. Giarratano R. C. Hess M. C. Jones

1974-01-01

175

Loss Analysis of Permanent-Magnet Motors With Concentrated Windings—Variation of Magnet Eddy-Current Loss Due to Stator and Rotor Shapes  

Microsoft Academic Search

In this paper, we investigate losses, including magnet eddy-current loss of permanent-magnet synchronous motors with concentrated windings. A 3-D finite-element method that considers carrier harmonics of pulsewidth modulation inverters is utilized to calculate the losses in each part of the motor separately. A simple linear magnetic circuit model is also introduced in order to understand the mechanism of eddy-current loss

Katsumi Yamazaki; Yu Fukushima; Makoto Sato

2009-01-01

176

Hysteresis regime in the operation of a dual-free-layer spin-torque nano-oscillator with out-of-plane counter-precessing magnetic moments  

NASA Astrophysics Data System (ADS)

We studied the operation of a dual-free-layer (DFL) spin-torque nano-oscillator (STNO) and demonstrated that in a practically interesting regime when the magnetizations of the two free layers (FLs) precess in opposite directions along large-angle out-of-plane trajectories, thus doubling the generation frequency, the operation of the DFL STNO is strongly hysteretic as a function of a bias dc current. The stable magnetization dynamics starts at a rather large magnitude of the bias dc current density J>Jthhigh when the bias current is increased, but the regime of stable counter-precession of the FLs persists till rather low magnitudes of the bias dc current density Jthlowhysteresis is caused by the dipolar coupling between the FLs, and is especially pronounced for small distances between the FLs and the small magnetic damping in them. The discovered hysteretic behavior of the DFL STNO implies the possibility of application of a strong initial pulse of the bias current (greater than the upper threshold Jthhigh of the stable dynamics) and subsequent reduction of the bias current to a working point (Jthlow

Prokopenko, O. V.; Krivorotov, I. N.; Bankowski, E. N.; Meitzler, T. J.; Tiberkevich, V. S.; Slavin, A. N.

2013-11-01

177

Magnetic hysteresis and flux creep of YBa sub 2 Cu sub 3 O sub x grown by the melt-powder-melt-growth (MPMG) process  

SciTech Connect

Magnetic hysteresis and flux creep of melt-powder-melt-growth (MPMG) YBa{sub 2}Cu{sub 3}O{sub x} containing nominal 0, 25 and 40 mole% Y{sub 2}BaCuO{sub 5} (21 1) were measured in the temperature range of 5 to 80 K and in magnetic fields up to 5 T. With the introduced fine dispersion of second phase 211 particles, the critical magnetization current density J{sub c} shows a weak field dependence over a wide range of temperature, and the effective pinning energy U{sub eff} is much enhanced. From these results, a functional expression U{sub eff}(J,T) = {minus} U{sub o} G(T) (J {vert bar}J{sub i}){sup n} is obtained, where G(T) = (1 {minus} (T{vert bar}T{sub x}){sup 2}){sup 2} with Tx = 82.5 K near the irreversibility temperature. The observed power-law relationship of U{sub eff}(J, T) clearly demonstrates two of three regimes as predicted by the theory of collective flux creep, namely n = 3/2 and 7/9 for J < J{sub c} and J {much lt} J{sub c}, respectively. In addition, the divergence of U{sub eff} at low current densities also suggests the existence of a vortex-glass state.

Kung, P.J.; McHenry, M.E. (Los Alamos National Lab., NM (United States) Carnegie-Mellon Univ., Pittsburgh, PA (United States). Dept. of Materials Science and Engineering); Maley, M.P.; Willis, J.O. (Los Alamos National Lab., NM (United States)); Murakami, M.; Tanaka, S. (International Superconductivity Technology Center, Tokyo (Japan). Superconductivity Research Lab.)

1992-08-24

178

Magnetic hysteresis and flux creep of YBa{sub 2}Cu{sub 3}O{sub x} grown by the melt-powder-melt-growth (MPMG) process  

SciTech Connect

Magnetic hysteresis and flux creep of melt-powder-melt-growth (MPMG) YBa{sub 2}Cu{sub 3}O{sub x} containing nominal 0, 25 and 40 mole% Y{sub 2}BaCuO{sub 5} (21 1) were measured in the temperature range of 5 to 80 K and in magnetic fields up to 5 T. With the introduced fine dispersion of second phase 211 particles, the critical magnetization current density J{sub c} shows a weak field dependence over a wide range of temperature, and the effective pinning energy U{sub eff} is much enhanced. From these results, a functional expression U{sub eff}(J,T) = {minus} U{sub o} G(T) (J {vert_bar}J{sub i}){sup n} is obtained, where G(T) = [1 {minus} (T{vert_bar}T{sub x}){sup 2}]{sup 2} with Tx = 82.5 K near the irreversibility temperature. The observed power-law relationship of U{sub eff}(J, T) clearly demonstrates two of three regimes as predicted by the theory of collective flux creep, namely n = 3/2 and 7/9 for J < J{sub c} and J {much_lt} J{sub c}, respectively. In addition, the divergence of U{sub eff} at low current densities also suggests the existence of a vortex-glass state.

Kung, P.J.; McHenry, M.E. [Los Alamos National Lab., NM (United States)]|[Carnegie-Mellon Univ., Pittsburgh, PA (United States). Dept. of Materials Science and Engineering; Maley, M.P.; Willis, J.O. [Los Alamos National Lab., NM (United States); Murakami, M.; Tanaka, S. [International Superconductivity Technology Center, Tokyo (Japan). Superconductivity Research Lab.

1992-08-24

179

Spin Flip Loss in Magnetic Storage of Ultracold Neutrons  

NASA Astrophysics Data System (ADS)

We analyze the depolarization of ultracold neutrons confined in a magnetic field configuration similar to those used in existing or proposed magneto-gravitational storage experiments aiming at a precise measurement of the neutron lifetime. We use an approximate quantum mechanical analysis such as pioneered by Walstrom et al. [Nucl. Instrum. Methods Phys. Res. A 599, 82 (2009)]. Our analysis is not restricted to purely vertical modes of neutron motion. The lateral motion is shown to cause the predominant depolarization loss in a magnetic storage trap.

Steyerl, A.; Kaufman, C.; Müller, G.; Malik, S. S.; Desai, A. M.

2014-03-01

180

Losses in Sensorless Controlled Permanent-Magnet Synchronous Machines  

Microsoft Academic Search

The aim of the research is to investigate how much the losses in a permanent-magnet synchronous machine (PMSM) increase by the test pulses that are injected for sensorless control, i.e., to obtain rotor position information without using a position sensor. The current responses to the voltage test pulses in the machine are used as input of a 2-D transient finite

Peter Sergeant; Frederik De Belie; Luc Dupre; Jan Melkebeek

2010-01-01

181

Maximizing hysteretic losses in magnetic ferrite nanoparticles via model-driven synthesis and materials optimization.  

PubMed

This article develops a set of design guidelines for maximizing heat dissipation characteristics of magnetic ferrite MFe2O4 (M = Mn, Fe, Co) nanoparticles in alternating magnetic fields. Using magnetic and structural nanoparticle characterization, we identify key synthetic parameters in the thermal decomposition of organometallic precursors that yield optimized magnetic nanoparticles over a wide range of sizes and compositions. The developed synthetic procedures allow for gram-scale production of magnetic nanoparticles stable in physiological buffer for several months. Our magnetic nanoparticles display some of the highest heat dissipation rates, which are in qualitative agreement with the trends predicted by a dynamic hysteresis model of coherent magnetization reversal in single domain magnetic particles. By combining physical simulations with robust scalable synthesis and materials characterization techniques, this work provides a pathway to a model-driven design of magnetic nanoparticles tailored to a variety of biomedical applications ranging from cancer hyperthermia to remote control of gene expression. PMID:24016039

Chen, Ritchie; Christiansen, Michael G; Anikeeva, Polina

2013-10-22

182

Thermo-magnetic history effects in the giant magnetostriction across the first-order transition and minor hysteresis loops modeling in Fe0.955Ni0.045Rh alloy  

NASA Astrophysics Data System (ADS)

Results of temperature- and magnetic field-dependent strain measurements across the first-order antiferromagnetic to ferromagnetic phase transition in Fe0.955Ni0.045Rh are presented. Distinct thermal and magnetic field hystereses are observed in the measured strain across the phase transition. The minor hysteresis loops inside the hysteretic regime across the temperature-driven transition are modeled using the Preisach model of hysteresis. The applicability of the Preisach model to explain the general features of minor hysteresis loops is discussed for a disorder influenced first-order transition. The minor hysteresis loops show the property of retaining the memory of the starting or end point of the temperature cycle followed within the hysteretic region. A larger temperature excursion within the hysteretic region wipes out the memory of a smaller temperature cycle which contains one of the extrema of the larger cycle. The end-point memory and the wiping-out property of the minor hysteresis loops can be described quite well within the Preisach model, irrespective of the temperature history followed to reach a particular starting point. Thermo-magnetic history effects across the magnetic field-induced transition are explained, which will enable the choice of the starting point of an experimental cycle in the field-temperature phase space so as to achieve the desired functionality. Our results highlight the necessity to understand the influence of disorder on a first-order phase transition so as to achieve a repeatable performance of materials whose functionalities are based on such a transition.

Manekar, Meghmalhar; Sharma, V. K.; Roy, S. B.

2012-05-01

183

Magnetostriction and effect of stress on hysteresis and anhysteretic magnetization of multilayered FeNi-Fe heterostructures  

Microsoft Academic Search

We report on the low-field magnetic properties of thin film FeNi-Fe multilayered samples under tensile stress. Anhysterretic magnetization as a function of stresses was measured using a conventional vibrating sample magnetometer combined with a specially designed loading fixture providing controlled uniaxial stresses. Stresses are deduced from the characteristic resonant frequency of the sample in the fixture. Anhysteretic permeability was extracted

Peter Finkel; Ed Garrity

2007-01-01

184

Sensorless evaluation of asymmetric hysteresis loops of ferromagnetic materials  

Microsoft Academic Search

The sensorless determination of the dynamic hysteresis loop of magnetic materials, and in particular those of magnetic plates, can be obtained under ac symmetric conditions in a relatively simple way. This paper proposes a new digital method and instrument for the sensorless evaluation of the dynamic hysteresis loop under ac asymmetric conditions, in the presence of a dc polarization of

Loredana Cristaldi; Alessandro Ferrero; Massimo Lazzaroni; Adriano P. Morando

2003-01-01

185

Rare-earth-gallium-iron glasses. I. Magnetic ordering and hysteresis in alloys based on Gd, Tb, and Er  

Microsoft Academic Search

Results of magnetic measurements are presented on the new metallic glass systems (R80Ga20)100-xFex and (R80Ga20)90B10, where R denotes the heavy rare earths Gd, Tb, and Er, for x=10, 20, and 30, respectively. High-field magnetization (to 80 kOe) and ac and dc susceptibility measurements were made from 1.4 to 300 K. The Gd-Fe glasses are simple ferrimagnets with opposing Gd and

S. G. Cornelison; D. J. Sellmyer

1984-01-01

186

Mathematical models of hysteresis  

Microsoft Academic Search

A new approach to Preisach's hysteresis model, which emphasizes its phenomenological nature and mathematical generality, is briefly described. Then the theorem which gives the necessary and sufficient conditions for the representation of actual hysteresis nonlinearities by Preisach's model is proven. The significance of this theorem is that it establishes the limits of applicability of this model.

I. Mayergoyz

1986-01-01

187

Hysteresis in Metal Hydrides.  

ERIC Educational Resources Information Center

This paper describes a reproducible process where the irreversibility can be readily evaluated and provides a thermodynamic description of the important phenomenon of hysteresis. A metal hydride is used because hysteresis is observed during the formation and decomposition of the hydride phase. (RH)

Flanagan, Ted B., And Others

1987-01-01

188

Dynamic hysteresis modelling  

Microsoft Academic Search

A viscous-type dynamic hysteresis model (DHM) is developed. The DHM is compatible with static underlying model of any type and nature (Preisach or non-Preisach). The distinguishing features of the DHM are its arbitrary frequency dependence and the ability to control the shape of the dynamic hysteresis loop. The numerical method for the incorporation of the DHM in magnetodynamic computations is

S. E. Zirka; Y. I. Moroz; P. Marketos; A. J. Moses

2004-01-01

189

Comparison of losses and efficiency in alternate flux-switching permanent magnet machines  

Microsoft Academic Search

The performance of the optimized conventional, novel E- and C-core flux-switching permanent magnet (FSPM) machines having different combination of stator and rotor pole numbers is compared by finite element analyses, with particular reference to the conductor and magnet eddy current loss and iron loss. Both iron loss and conductor eddy current loss increase with the rotor pole number, while the

J. T. Chen; Z. Q. Zhu; S. Iwasaki; R. Deodhar

2010-01-01

190

Energy loss of slowly moving magnetic monopoles in matter  

NASA Astrophysics Data System (ADS)

It is pointed out that a quantitative understanding of the mechanisms by which slowly moving monopoles lose energy when passing through matter is important both for a description of monopole interactions in the solar system and for the interpretation and design of noninduction experiments. The present investigation is concerned with a calculation of this energy loss for simple atoms. It is found that the calculated energy loss for atomic hydrogen and helium is larger by an order of magnitude or more than that found in previous studies for other materials. The study takes into account also Zeeman splittings, diamagnetic shifts, and crossings of the energy levels caused by the interaction of the atomic electrons with the monopole magnetic field. A slow monopole passing through a hydrogen atom is considered, taking into account the effects due to electron spin. Atomic helium is found to be of interest as a practical substance for a noninduction experiment.

Drell, S. D.; Mueller, M. T.; Parke, S. J.; Kroll, N. M.; Ruderman, M. A.

1983-02-01

191

Magnetic circular dichroism in electron energy loss spectrometry.  

PubMed

The measurement of circular dichroism in the electron microscope is a new, emerging method and, as such, it is subject to constant refinement and improvement. Different ways can be envisaged to record the signal. We present an overview of the key steps in the energy-loss magnetic chiral dichroism (EMCD) experiment as well as a detailed review of the methods used in the intrinsic way where the specimen is used as a beam splitter. Lateral resolution up to 20-30 nm can be achieved, and the use of convergent beam techniques leads to an improved S/N ratio. Dichroic effects are shown for Ni and Co single crystal; as a counterexample, measurements were carried also for a non-magnetic (Ti) sample, where no dichroic effect was found. PMID:18060698

Hébert, C; Schattschneider, P; Rubino, S; Novak, P; Rusz, J; Stöger-Pollach, M

2008-02-01

192

Low Thermal Loss Cryogenic Transfer Line with Magnetic Suspension  

NASA Astrophysics Data System (ADS)

An energy efficient, cost effective cryogenic distribution system (up to several miles) is crucial for spaceport and in-space cryogenic systems. The conduction heat loss from the supports that connect the cold inner lines to the warm support structure is ultimately the most serious heat leak after thermal radiation has been minimized. The use of magnetic levitation by permanent magnets and high temperature superconductors provides support without mechanical contact and thus, the conduction part of the heat leak can be reduced to zero. A stop structure is carefully designed to hold the center tube when the system is warm. The novel design will provide the potential of extending many missions by saving cryogens, or reducing the overall launch mass.

Shu, Quan-Sheng; Cheng, Guangfeng; Yu, Kun; Hull, John R.; Demko, Jonathan A.; Britcher, Colin P.; Fesmire, James E.; Augustynowicz, Stan D.

2004-06-01

193

Dynamic Modeling of Three-Phase Asymmetric Power Transformers With Magnetic Hysteresis: No-Load and Inrush Conditions  

Microsoft Academic Search

A new dynamic model of a three-phase three-leg transformer for steady-state and transient operating conditions is proposed in this paper. With very few exceptions, the existing models oversimplify the magnetic interactions in multileg core topologies and employ single-value nonlinear functions for modeling core nonlinearities. Unfortunately, this does not provide sufficient accuracy for a wide range of dynamic disturbances such as

Paul S. Moses; M. A. S. Masoum; Hamid A. Toliyat

2010-01-01

194

Fabrication of a high temperature superconductor micro-superconducting-quantum-interference-device magnetometer for magnetic hysteresis measurements  

Microsoft Academic Search

A high-temperature-superconductor-type micrometer-sized dc-SQUID (SQUID denotes superconducting quantum interference divice) magnetometer with much higher sensitivity than a commercial system has been developed. Several kinds of YBa2Cu3O7-delta micro-SQUIDs were fabricated with photolithography techniques to have a hole of 4×9 mum2 and 2-mum-wide grain boundary Josephson junctions. Combined with a three dimensional magnetic field coil system, the voltage modulation was observed for

Keiji Takeda; Hatsumi Mori; Akira Yamaguchi; Hidehiko Ishimoto; Takayoshi Nakamura; Shinya Kuriki; Toshiya Hozumi; Shin-Ichi Ohkoshi

2008-01-01

195

AC loss measurements of model and full size 50mm SSC collider dipole magnets at Fermilab  

SciTech Connect

Tests have recently been performed at Fermilab in order to measure the energy losses due to eddy currents and iron and superconductor magnetization. These measurements were performed on six 1.5m long model magnets and eight 15m long full scale collider dipole magnets. AC losses were measured as a function of ramp rate using sawtooth ramps from 500, to 5000 Amps for both types of magnets, while bipolar studies were additionally performed on some of the short magnets. The measured magnet voltage and current for a complete cycle are digitally integrated to yield the energy loss per cycle. Measurement reproducibility is typically 5%, with good agreement between long magnet measurements and extrapolations from short magnet measurement results. Magnetization loss measurements among similar magnet types agree to within experimental error, while eddy current losses correlate strongly with the observed dependence of quench current on ramp rate.

Ozelis, J.P.; Delchamps, S.W.; Gourlay, S.; Jaffery, T.; Kinney, W.; Koska, W.; Kuchnir, M.; Lamm, M.J.; Mazur, P.O.; Orris, D.; Strait, J.; Wake, M. (Fermi National Accelerator Lab., Batavia, IL (United States)); Dimarco, J.; Kuzminski, J.; Zheng, H. (Superconducting Super Collider Lab., Dallas, TX (United States))

1992-09-01

196

Dynamic modelling of magnetic materials for high frequency applications  

Microsoft Academic Search

Magnetic materials are very popular for high frequency power conversion and their operation frequencies are usually in the region of kHz. This paper examines the processing of the ferrites, and the modelling of the magnetic core loss for high frequency operation. The proposed method is a dynamic model which considers the eddy current, hysteresis and anomalous losses. The loss analysis

K. W. E. Cheng; W. S. Lee; C. Y. Tang; L. C. Chan

2003-01-01

197

Energy losses in magnetically insulated transmission lines due to microparticles  

SciTech Connect

We discuss the effects of high-velocity and hypervelocity microparticles in the magnetically insulated transmission lines of multiterawatt accelerators used for particle beam fusion and radiation effects simulation. These microparticles may be a possible source for plasma production near the anode and cathode in early stages of the voltage pulse, and current carriers during and after the power pulse, resulting in power flow losses. Losses in the current pulse, due to microparticles, are estimated to be approximately 12 mA/cm/sup 2/ (0.3 kA) as a lower limit, and --0.3 A/cm/sup 2/ (7.2 kA) for microparticle initiated, anode plasma positive ion transport. We have calculated the velocities reached by these microparticles and the effects on them of Van der Waals forces. Field emission from the particles and their effects on cathode and anode plasma formation have been examined. Particle collision with the electrodes is also examined in terms of plasma production, as in the electron deposition in the particles in transit across the anode-cathode gap. Blistering of the electrode surface, thought to be due to H/sup -/ bombardment was also observed and appears to be consistent with losses due to negative ions previously reported by J. P. VanDevender, R. W. Stinnett, and R. J. Anderson (App. Phys. Lett. 38, 229 (1981)).

Gray, E.W.; Stinnett, R.W.

1987-06-15

198

Circular magnetization and energy loss in Fe-based soft magnetic wires  

NASA Astrophysics Data System (ADS)

The circular permeability, ?=?'-j??, of two Fe-based soft magnetic wires with longitudinal (S1) and transverse (S2) domain structure, respectively, were determined from the measurements of impedance, Z=R+j?L, as functions of frequency (f=102-104 Hz), AC current amplitude (I=0.1-100 mA) and DC axially applied field (H=0-5.4 kA/m). So the influences of f and H upon the circular magnetization have been studied experimentally. Although the two samples exhibit similar changes of ?=?'-j?? with the circular-field, H?, different technique magnetization processes, referred to different domain structures of samples, has been discussed by analyzing the energy loss according to a current theoretical model. Consequently, we have concluded that the circular magnetization is dominated by domain magnetization rotations and domain wall displacements in samples S1 and S2, respectively.

Li, Y. F.; Liu, P.; Zhao, X. M.; Meng, Y.; Chen, P. Y.; Liu, Q. H.

2014-01-01

199

Magnetic Field Shielding by Vacuum Chambers of Magnetic Material for Beam Loss Reduction  

NASA Astrophysics Data System (ADS)

One of the reasons of a beam loss in a high power accelerator is leakage magnetic field from a magnet at a close beam line, which distorts the beam orbit and makes the beam hit the wall of the beam pipe. The most effective way to shield such leakage field is to cover the beam by the magnetic materials at the nearest space. This means that beam pipes and bellows be made of the magnetic materials. We plan to apply this method to the vacuum chambers of the beam extraction section of the J-PARC 3 GeV synchrotron, where the effect of the leakage magnetic field to the beam orbit is evident. However, there is few proven evidence of the vacuum chambers made of magnetic materials. Therefore we clarify the problems in producing beam pipes and bellows, which satisfy the magnetic and vacuum performance. In this article, we deliver the over view of the magnetic shielding project and our approaches to the problems in producing the vacuum chambers of magnetic materials.

Kamiya, Junichiro; Ogiwara, Norio; Hayashi, Naoki; Hotchi, Hideaki; Yoshimoto, Masahiro; Kinsho, Michikazu

200

AC Losses in the MICE Channel Magnets -- Is This a Curse or aBlessing?  

SciTech Connect

This report discusses the AC losses in the MICE channelmagnets during magnet charging and discharging. This report talks aboutthe three types of AC losses in the MICE magnets; the hysteretic AC lossin the superconductor, the coupling AC loss in the superconductor and theeddy current AC loss in the magnet mandrel and support structure. AClosses increase the heat load at 4 K. The added heat load increases thetemperature of the second stage of the cooler. In addition, AC losscontributes to the temperature rise between the second stage cold headand the high field point of the magnet, which is usually close to themagnet hot spot. These are the curses of AC loss in the MICE magnet thatcan limit the rate at which the magnet can be charge or discharged. Ifone is willing to allow some of the helium that is around the magnet toboil away during a magnet charge or discharge, AC losses can become ablessing. The boil off helium from the AC losses can be used to cool theupper end of the HTS leads and the surrounding shield. The AC losses arepresented for all three types of MICE magnets. The AC loss temperaturedrops within the coupling magnet are presented as an example of how boththe curse and blessing of the AC losses can be combined.

Green, M.A.; Wu, H.; Wang, L.; Kai, L.L.; Jia, L.X.; Yang, S.Q.

2008-01-31

201

Hysteresis loops of polarization and magnetization in (BiNd 0.05)(Fe 0.97Mn 0.03)O 3\\/Pt\\/CoFe 2O 4 layered epitaxial thin film grown by pulsed laser deposition  

Microsoft Academic Search

(BiNd0.05)(Fe0.97Mn0.03)O3 (BNFM)\\/Pt\\/CoFe2O4 (CFO) layered thin film was fabricated on (100) SrTiO3 substrate by pulsed laser deposition. BNFM, Pt, and CFO layers were epitaxially grown on the substrate. Almost no increase of leakage current due to the formation of heteroepitaxial structure was found, and well-saturated hysteresis loops in the polarization vs electric field and magnetization vs magnetic field curves coexist at

Takeshi Kawae; Jie Hu; Hiroshi Naganuma; Takeshi Nakajima; Yuki Terauchi; Soichiro Okamura; Akiharu Morimoto

2011-01-01

202

Wide Temperature Core Loss Characteristics of Transverse Magnetically Annealed Amorphous Tapes for High Frequency Aerospace Magnetics  

NASA Technical Reports Server (NTRS)

100 kHz core loss properties of sample transverse magnetically annealed, cobalt-based amorphous and iron-based nanocrystalline tape wound magnetic cores are presented over the temperature range of -150 C to 150 C, at selected values of B(sub peak). For B-fields not close to saturation, the core loss is not sensitive to temperature in this range and is as low as seen in the best MnZn power ferrites at their optimum temperatures. Frequency resolved characteristics are given over the range of 50 kHz to 1 MHz, but at B(sub peak) = 0.1 T and 50 C only. For example, the 100 kHz specific core loss ranged from 50 - 70 mW/cubic cm for the 3 materials, when measured at 0.1 T and 50 C. This very low high frequency core loss, together with near zero saturation magnetostriction and insensitivity to rough handling, makes these amorphous ribbons strong candidates for power magnetics applications in wide temperature aerospace environments.

Niedra, Janis M.; Schwarze, Gene E.

1999-01-01

203

Hysteresis behavior of the anisotropic quantum Heisenberg model  

NASA Astrophysics Data System (ADS)

The effect of the anisotropy in the exchange interaction on the hysteresis loops within the anisotropic quantum Heisenberg model has been investigated with the effective field theory for two spin cluster. Particular attention has been devoted on the behavior of the hysteresis loop area, coercive field and remanent magnetization with the anisotropy in the exchange interaction for both ferromagnetic and paramagnetic phases.

Ak?nc?, Ümit

2013-10-01

204

Analysis and experiment of eddy current loss in Homopolar magnetic bearings with laminated rotor cores  

NASA Astrophysics Data System (ADS)

This paper analyses the eddy current loss in Homopolar magnetic bearings with laminated rotor cores produced by the high speed rotation in order to reduce the power loss for the aerospace applications. The analytical model of rotational power loss is proposed in Homopolar magnetic bearings with laminated rotor cores considering the magnetic circuit difference between Homopolar and Heteropolar magnetic bearings. Therefore, the eddy current power loss can be calculated accurately using the analytical model by magnetic field solutions according to the distribution of magnetic fields around the pole surface and boundary conditions at the surface of the rotor cores. The measurement method of rotational power loss in Homopolar magnetic bearing is proposed, and the results of the theoretical analysis are verified by experiments in the prototype MSCMG. The experimental results show the correctness of calculation results.

Jinji, Sun; Dong, Chen

2013-08-01

205

Rotor Eddy-Current Loss in Permanent-Magnet Brushless AC Machines  

Microsoft Academic Search

This paper analyzes rotor eddy-current loss in permanent-magnet brushless ac machines. It is shown that analytical or finite-element techniques published in literature for predicting rotor eddy-current loss using space harmonic based approaches may not yield correct results in each magnet segment when one magnet-pole is circumferentially segmented into more than two pieces. It is also shown that the eddy-current loss

Jiabin Wang; K. Atallah; R. Chin; W. M. Arshad; H. Lendenmann

2010-01-01

206

Evaluation of Iron Loss in Interior Permanent Magnet Synchronous Motor with Consideration of Rotational Field  

Microsoft Academic Search

Loss evaluation is an important issue in the design of electrical machines. Due to the complicate structure and flux distribution, it is difficult to predict the iron loss in the machines exactly. This paper studies the iron loss in interior permanent magnet synchronous motors based on the finite element method. The iron loss test data of core material are used

Lei Ma; Masayuki Sanada; Shigeo Morimoto; Yoji Takeda; Chikara Kaido; Takeaki Wakisaka

2004-01-01

207

Topological hysteresis in stripe domain structures  

Microsoft Academic Search

Irreversible evolution in stripe domain structures in a bubble material was investigated. Equilibrium parallel stripe structure folds progressively up to the labyrinth one under normal magnetic field cycles. This topological hysteresis, not related to wall-pinning by defects but to nucleation and collapse field problems, shows memory effects of upper fields encountered.

P. Molho; J. Gouzerh; J. C. S. Levy; J. L. Porteseil

1986-01-01

208

Topological hysteresis in stripe domain structures  

NASA Astrophysics Data System (ADS)

Irreversible evolution in stripe domain structures in a bubble material was investigated. Equilibrium parallel stripe structure folds progressively up to the labyrinth one under normal magnetic field cycles. This topological hysteresis, not related to wall-pinning by defects but to nucleation and collapse field problems, shows memory effects of upper fields encountered.

Molho, P.; Gouzerh, J.; Levy, J. C. S.; Porteseil, J. L.

1986-02-01

209

Dynamical aspects of the adsorption hysteresis phenomenon  

Microsoft Academic Search

Equilibrium and nonequilibrium transport properties of adsorbates in mesoporous Vycor porous glass have been experimentally studied using nuclear magnetic resonance techniques. With the known geometrical characteristics of porous glass and with measured self- diffusivities, transient sorption curves have been quantitatively compared to those predicted within a Fick's law model. This model correctly describes data outside a hysteresis region. In contrast,

Rustem Valiullina; Sergej Naumov; Peter A. Monson

210

Role of reversible susceptibility in ferromagnetic hysteresis  

NASA Astrophysics Data System (ADS)

An equation of state based upon saturation magnetization, Ms, coercive field, Hc, and the reversible susceptibility function of magnetization is proposed for ferromagnetic hysteresis. Reversible susceptibility divided by the initial susceptibility is the anisotropy function of magnetization, ?r, ranging from one in the demagnetized state to zero at saturation, and varying with magnetic history. Its dependence on scaled magnetization, m=M/Ms on the interval (-1,1) varies with material, allowing characterization of anisotropy classes. Precise measurements have been made of reversible susceptibility, initial and saturate magnetization curves, and loops for Orthonol™, annealed 3% nickel steel and as-received 1018 steel, representing crystals, isotropic polycrystals and composite ferromagnets, respectively. Magnetization change is the product of the reversible susceptibility, change in the applied field and the cooperative function due to domain interactions. This function is 1+?m for the virgin curve with half this slope from any reversal, where ?=Ms/XiHc is the hysteresis coefficient. Variation of ? for 1018 steel is due to distributed coercivities, and causes sigmoid B(H) curves. In the scaled field representation, where h=H/Hc, the cooperative function is 1/(1-h?r), a hyperbolic field dependence smeared by the anisotropy function. Constant anisotropy causes closed hysteresis loops, while variable anisotropy causes creeping of cycled asymmetric loops. In ferromagnetism, 1/?=1/?r-h, normal scaled reluctivity is reduced from its reversible value by the scaled field.

Schneider, Carl S.

2002-05-01

211

Analysis of a hysteresis motor with overexcitation  

SciTech Connect

The performance of a hysteresis motor can be improved greatly if it is overexcited for a short period when running at synchronous speed. The change in the magnetic state of the rotor hysteresis material, when the stator voltage is raised and then reduced to the original value, is described in detail. Based on this, a method for the calculation of the motor performance after overexcitation is proposed, and the effect of overexcitation on the motor performance is clarified by using this method. Good agreement is found between the calculated and the measured results.

Kataoka, T.; Ishikawa, T.; Takahasi, T.

1982-11-01

212

Integrated on-line instrumentation for simultaneous automated measurement of magnetic field, induction, Barkhausen effect, magnetoacoustic emission, and magnetostriction  

SciTech Connect

A microcomputer-controlled instrument for simultaneous measurement of magnetic hysteresis, magnetostriction, Barkhausen effect, and magnetoacoustic emission is described. It incorporates custom designed software for control of the magnetic field during operations such as demagnetization, field sweeping, and anhysteretic magnetization, and for data logging and analysis. Results are recorded using a 12-bit analog to digital converter and are then stored on floppy disk. The magnetic hysteresis data are converted into six important magnetic parameters: coercivity, remanence, hysteresis loss, initial permeability, maximum differential permeability, and anhysteretic permeability. These, together with the magnetostriction, Barkhausen, and magnetoacoustic emission, are then related to the microstructure of the material.

Jiles, D.C.

1988-04-15

213

Insulator coated magnetic nanoparticulate composites with reduced core loss and method of manufacture thereof  

NASA Technical Reports Server (NTRS)

A series of bulk-size magnetic/insulating nanostructured composite soft magnetic materials with significantly reduced core loss and its manufacturing technology. This insulator coated magnetic nanostructured composite is comprises a magnetic constituent, which contains one or more magnetic components, and an insulating constituent. The magnetic constituent is nanometer scale particles (1-100 nm) coated by a thin-layered insulating phase (continuous phase). While the intergrain interaction between the immediate neighboring magnetic nanoparticles separated by the insulating phase (or coupled nanoparticles) provide the desired soft magnetic properties, the insulating material provides the much demanded high resistivity which significantly reduces the eddy current loss. The resulting material is a high performance magnetic nanostructured composite with reduced core loss.

Zhang, Yide (Inventor); Wang, Shihe (Inventor); Xiao, Danny (Inventor)

2004-01-01

214

Major hysteresis loop modeling of two-dimensional arrays of single domain particles  

Microsoft Academic Search

We have studied the effect of magnetostatic interactions on the overall shape of hysteresis loops for arrays of single domain particles. A computational model was used to calculate major hysteresis loops of arrays of particles with an easy axis along the applied field. The shear of the hysteresis loop, and consequent loss of squareness, is found to increase both with

M. Hwang; M. Farhoud; Y. Hao; M. Walsh; T. A. Savas; Henry I. Smith; C. A. Ross

2000-01-01

215

Determination of the Foucault Current Coefficients and Magnetic Hysteresis Energy Dissipation Onboard a Spinning Satellite Determination des Coefficients Lies aux Dissipations d'Energie Par Courants de Foucault et Hysteresis Magnetique a Bord d'UN Satellite Spinne.  

National Technical Information Service (NTIS)

A mathematical model for the prediction of the spin rate evolution of a satellite during its orbital life is proposed, based on SRET II satellite data. The spin rate decreases mainly results from electromagnetic interaction with the earth's magnetic field...

J. Runavot

1976-01-01

216

Inverse Compensation for Ferromagnetic Hysteresis.  

National Technical Information Service (NTIS)

This paper addresses the validation of an energy-based inverse compensator for hysteresis in ferromagnetic transducers. At moderate to high drive levels such transducers exhibit significant constitutive non-linearities and hysteresis due to domain mechani...

R. C. Smith R. Zrostlik

1999-01-01

217

The hysteresis behavior of an Ising nanowire with core/shell morphology: Monte Carlo treatment  

NASA Astrophysics Data System (ADS)

We have used Monte Carlo Simulations (MCS) to study the hysteresis behavior of the magnetic nanowire with core/shell morphology described by the spin {1}/{2} Ising particles in the core and the spin {3}/{2} Ising particles in the surface shell. The hysteresis curves are obtained for different temperatures. We find that the hysteresis loop areas decrease when the temperature increases and the hysteresis loops disappear at certain temperatures. Barkhausen jumps are observed for the ferromagnetic nanowire system. An unusual form of triple hysteresis behaviors is observed for the ferrimagnetic nanowire system. The thermal behaviors of the coercivity and the remanent magnetization are also investigated.

Boughazi, B.; Boughrara, M.; Kerouad, M.

2014-08-01

218

Numerical analysis of magnetization loss in finite-length multifilamentary YBCO coated conductors  

Microsoft Academic Search

In typical YBCO coated conductors with a width of 10 mm, a large AC loss is generated in a perpendicular transverse magnetic field. One of the means of reducing the AC loss is to divide the YBCO film into narrow filaments. The AC loss characteristics of multifilamentary YBCO coated conductors having a finite length were studied by numerical electromagnetic analysis

Satoshi Kasai; Naoyuki Amemiya

2005-01-01

219

Novel platform for minimizing cell loss on separation process: Droplet-based magnetically activated cell separator  

Microsoft Academic Search

To reduce the problem of cell loss due to adhesion, one of the basic phenomena in microchannel, we proposed the droplet-based magnetically activated cell separator (DMACS). Based on the platform of the DMACS-which consists of permanent magnets, a coverslip with a circle-shaped boundary, and an injection tube-we could collect magnetically (CD45)-labeled (positive) cells with high purity and minimize cell loss

Youngho Kim; Su Hong; Sang Ho Lee; Kangsun Lee; Seok Yun; Yuri Kang; Kyeong-Kap Paek; Byeong-Kwon Ju; Byungkyu Kim

2007-01-01

220

Study of eddy current power loss from outer-winding coils of a magnetic position sensor  

Microsoft Academic Search

The present analysis is concerned with eddy current power loss of a magnetic position sensor, which arises from a non-uniform flux linkage distribution between magnetic material and position sensor. In the paper, a magnetic position sensor system is simplified to be an outer-winding coil along the axial direction of a low carbon steel bar, and developed a numerical model to

Chung-Ping Liu; Tsung-Kun Lin; Yeong-Hwa Chang; Chang-Shen Yu; Kun-Ton Wu; Shyh-Jier Wang; Tai-Fa Ying; Der-Ray Huang

2000-01-01

221

Prediction of iron losses in doubly salient permanent magnet machine with rectangular current waveform  

NASA Astrophysics Data System (ADS)

Iron losses in doubly salient permanent magnet (DSPM) machine are difficult to predict, as the flux waveforms are complex and dc bias existed. This paper measures iron losses at no load for different rotor speeds and these measured loss data are used to calibrate the iron loss model of the DSPM machine. Then the iron losses at rated load are predicted under three phase rectangular currents exerting on the armature windings. The result shows that small increment of iron losses is in the rotor at rated load which do benefit to the rotor thermal dissipation design.

Zhang, Jianzhong; Wang, Minxi; Cheng, Ming

2012-04-01

222

Hysteresis and acoustic emission as non-destructive measures of the fatigue process in metals  

NASA Astrophysics Data System (ADS)

Metal fatigue is a result of a cumulative damage process due to repeated cyclic loading which causes premature and unpredictable failure. It is a complicated metallurgical process at the microscopic level which is difficult to accurately explain or model. Despite the complexities, fatigue analysis methods have been developed and are being developed to facilitate fatigue damage assessment and the prediction of fatigue life. This research project is concerned with the behavior of metals subjected to cyclic loading carried to failure. The purpose of this investigation is to develop a relationship between hysteresis loss, hysteresis loop drift, strain amplitudes, and the number of cycles to failure and to correlate this phenomenological description of the fatigue process with mesoscopic observables such as acoustic emission and stress-induced magnetization.

Guralnick, S. A.

1995-03-01

223

Appropriateness of magnetic resonance imaging in sudden sensorineural hearing loss  

Microsoft Academic Search

Idiopathic sudden sensorineural hearing loss is an enigmatic condition of unknown cause. Although the treatment for sudden sensorineural hearing loss is controversial, the evaluation for a cause should not be. All patients are evaluated with a complete history, physical examination, audiologic examination, and blood draw to evaluate complete blood count, general chemistry screen, thyroid function test results, erythrocyte sedimentation rate,

PETER C. WEBER; ROSS I. ZBAR; BRUCE J. GANTZ

1997-01-01

224

Power losses of soft magnetic composite materials under two-dimensional excitation  

NASA Astrophysics Data System (ADS)

Soft magnetic composite materials produced by powder metallurgy techniques can be very useful for construction of low cost small motors. However, the rotational core losses and the corresponding B-H relationships of soft magnetic composite materials with two-dimensional rotating fluxes have neither been supplied by the manufacturers nor reported in the literature. This article reports the core loss measurement of a soft magnetic composite material, SOMALOY™ 500, Höganäs AB, Sweden, under two-dimensional excitations. The principle of measurement, testing system, and power loss calculation are presented. The results are analyzed and discussed.

Zhu, J. G.; Zhong, J. J.; Ramsden, V. S.; Guo, Y. G.

1999-04-01

225

Investigation of magnetic fluids exhibiting field-induced increasing loss peaks  

NASA Astrophysics Data System (ADS)

A theoretical analysis to explain an increase of the Brownian loss peak with increasing polarizing field, H, in a magnetic fluid, is presented. The model is based on the competition between the Brownian and Néel relaxation processes. It is demonstrated that in magnetic fluids with particles having small anisotropy constant, small average magnetic diameter and narrow particle size distribution an increase of the Brownian loss peak with the polarizing field can be observed. The theoretical results are compared with the experimental results of an Isopar M-based magnetic fluid with magnetite particles stabilized with oleic acid and the model explains qualitatively the main characteristics of the experimental results.

Fannin, P. C.; Marin, C. N.; Couper, C.

2010-05-01

226

Analysis of power loss in Ni-Zn ferrites  

NASA Astrophysics Data System (ADS)

The power loss (Pcv) was analyzed by combining two methods. The first, Pcv, is divided into hysteresis loss (Ph) and residual loss (Pr) from the frequency dependence of the power loss according to the method of Otsuki et al., and, second, the loss factors are attributed to domain wall motion (Pw) and the rotation magnetization (Prot) by adapting the method proposed by Visser et al. It was found that Pw coincides with Ph in the lower frequency range, but the difference between them becomes significant as frequency goes up. The higher value of Pw, in comparison with Ph in the higher frequency range, can be attributed to the enhancement of loss due to the dynamic motion of the domain wall (Pwd) by raising the frequency. The hysteresis loss dominates Pcv in the frequency range below 500 kHz, while Pwd becomes predominant factor in the higher frequency range more than 500 kHz.

Kondo, K.; Chiba, T.; Yamada, S.; Otsuki, E.

2000-05-01

227

Simulation of magnetic component models in electric circuits including dynamic thermal effects  

Microsoft Academic Search

It is essential in the simulation of power electronics applications to model magnetic components accurately. In addition to modeling the nonlinear hysteresis behavior, eddy currents and winding losses must be included to provide a realistic model. In practice the losses in magnetic components give rise to significant temperature increases which can lead to major changes in the component behavior. In

Peter R. Wilson; J. Neil Ross; Andrew D. Brown

2002-01-01

228

On the ratio of magnetic losses in Fe-3% Si single crystals in rotating and linear-polarized magnetic fields  

NASA Astrophysics Data System (ADS)

The behavior of the magnetic losses in Fe-Si crystals in rotating and linear-polarized fields has been studied and particular features of the dependence of the ratio of these losses on the induction amplitude have been revealed. It has been demonstrated that abnormally high magnitudes of magnetic losses in rotating fields at low induction values ( B < 1.0 T) are caused by the nonuniformity of the displacement speeds of 180° walls of the stripe domain structure. At high induction values ( B > 1.0 T), the high magnitude of magnetic losses is caused by particular features of the motion of 90° and 180° walls of the closure domain structure of the tested samples.

Tiunov, V. F.

2012-12-01

229

Proximity Loss Study In High Speed Flux-Switching Permanent Magnet Machine  

Microsoft Academic Search

High speed flux-switching permanent magnet (FSPM) machines have been identified as key technologies for aerospace and hybrid electric vehicle applications. The open slot geometry, high stator flux densities and high operating frequencies result in high variable cross slot leakage and proximity losses within the armature windings. The aim of this study is to reduce AC losses in the armature of

A. S. Thomas; Z. Q. Zhu; G. W. Jewell

2009-01-01

230

Eddy Current Loss in the Frame of a Flux-Switching Permanent Magnet Machine  

Microsoft Academic Search

In flux-switching permanent magnet machines, a significant leakage flux exists at the outer surface of the stator core. Since the leakage flux varies as the rotor rotates, a significant eddy current loss may be induced in the nonmagnetic frame. The leakage flux and the associated eddy current loss in a representative flux-switching machine are investigated by finite element analysis, on

Y. Pang; Z. Q. Zhu; D. Howe; S. Iwasaki; R. Deodhar; A. Pride

2006-01-01

231

Iron yoke eddy current induced losses with application to the ALS septum magnets  

SciTech Connect

The theoretical development of relations governing the eddy current induced losses in iron electromagnet yokes is reviewed. A baseline laminated electromagnet design is analyzed and a parametric study illustrates the sensitivity of core losses to perturbations of various geometrical, material, and excitation parameters. Core losses and field gradients for the ALS septum magnets are calculated. Design modifications capable of eliminating transverse and longitudinal field gradients are discussed.

Schlueter, R.D.

1991-08-16

232

Analysis of Rotor Core Eddy-Current Losses in Interior Permanent-Magnet Synchronous Machines  

Microsoft Academic Search

This paper presents the results of an investigation focused on the rotor core eddy-current losses of interior permanent-magnet (IPM) synchronous machines. First, analytical insight into the rotor core eddy-current losses of IPM machines is developed. Next, major design parameters that have the most significant impact on the rotor core eddy-current losses of IPM machines are identified. Finite-element analysis results are

Seok-Hee Han; Thomas M. Jahns; Z. Q. Zhu

2010-01-01

233

Three-Dimensional Magnetic Resonance Imaging of the Inner Ear in Idiopathic Sudden Sensorineural Hearing Loss  

Microsoft Academic Search

Five patients with idiopathic sudden sensorineural hearing loss (ISSHL) were examined by a combination of high-resolution computed tomography and special magnetic resonance imaging techniques. By three-dimensional constructive interference in steady state magnetic resonance imaging excellent visualization of the membranous labyrinth was obtained. No fibrous or osseous obliteration of the intralabyrinthine fluid spaces was observed in all investigated temporal bones. The

F. W. J. Albers; K. M. N. P. Demuynck; J. W. Casselman

1994-01-01

234

Characterisation of metal loss defects from magnetic flux leakage signals with discrete wavelet transform  

Microsoft Academic Search

Metal loss defects in a buried pipeline are detected by magnetic flux leakage technique. Characterisation of the defects and sentencing according to the severity is extremely important for organised maintenance of pipelines. In this paper we identify the parameters that characterise a defect and the features of magnetic flux leakage signal (MFL) that are affected by those parameters. We show

S Mukhopadhyay; G. P Srivastava

2000-01-01

235

Enhancement of AC-losses of magnetic nanoparticles for heating applications  

Microsoft Academic Search

Aqueous ferrofluids of maghemite nanoparticles coated with carboxydextran were investigated with respect to their specific loss power (SLP) in dependence on frequency and field amplitude of magnetic AC-fields. In order to elucidate the effect of the size distribution on SLP fluid fractions with different mean particle core size were prepared by a magnetic separation procedure from the original ferrofluid. Structural

R. Hergt; R. Hiergeist; M. Zeisberger; G. Glöckl; W. Weitschies; L. P Ramirez; I. Hilger; W. A Kaiser

2004-01-01

236

Interpretation of hysteresis loops of cobalt-rare-earth single particles  

Microsoft Academic Search

The magnetic behavior of single particles of Co5Sm is being studied in an effort to understand the origin of the coercive force in cobalt rare earths. It has been found that the complex hysteresis loops often observed, containing several magnetization discontinuities, can be analyzed as the linear sum of single-discontinuity hysteresis loops, implying that regions of a particle can act

J. Becker

1971-01-01

237

Distribution of AC loss in a HTS magnet for SMES with different operating conditions  

NASA Astrophysics Data System (ADS)

The AC loss induced in superconducting tape may affect the performance of a superconducting device applied to power system, such as transformer, cable, motor and even Superconducting Magnetic Energy Storage (SMES). The operating condition of SMES is changeable due to the need of compensation to the active or reactive power according to the demand of a power grid. In this paper, it is investigated that the distribution of AC loss for a storage magnet on different operating conditions, which is based on finite element method (FEM) and measured properties of BSCCO/Ag tapes. This analytical method can be used to optimize the SMES magnet.

Xu, Y.; Tang, Y.; Ren, L.; Jiao, F.; Song, M.; Cao, K.; Wang, D.; Wang, L.; Dong, H.

2013-11-01

238

Scan rate dependence of magnetization hysteresis in weakly pinned crystals of 2 H-NbSe 2 and Ca 3Rh 4Sn 13: A vibrating sample magnetometer study  

NASA Astrophysics Data System (ADS)

We present experimental data relating to magnetic field ( H) scan rate (d H/d t) dependence in the magnetization ( M) hysteresis width across the field regions of the second magnetization peak (SMP) and the peak effect (PE) in weakly pinned crystals of 2 H-NbSe 2 and Ca 3Rh 4Sn 13. We note that the said dependence is small at the low field end, where individual/small bundle pinning dominates, as well as at the high field end (i.e., above the peak field of the PE), where disordered amorphous state is the stationary state. In between the onset field of the SMP anomaly and the peak field of PE, the scan rate dependence in magnetization data displays a non-monotonic variation. We conjecture that the healing of the transient disordered vortex states injected into a superconducting sample during field ramping process could be responsible for the observed behavior. We believe that the disordering commencing at the onset field of SMP has a window to heal between its peak field ( Hsmpp) and the onset field ( Hpon) of the PE. A comparison of the scan rate dependence in two different crystals of 2 H-NbSe 2, one of which displays only the PE phenomenon and the other one that displays both SMP and PE anomalies, show that while enhancement in quenched random pinning invokes the occurrence of SMP anomaly, it slows down the temporal decay of currents across the PE region.

Thakur, A. D.; Pal, D.; Higgins, M. J.; Ramakrishnan, S.; Grover, A. K.

2007-11-01

239

Anomalous position of the maximum in magnetic hysteresis loops measured on (Bi,Pb){sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub 10}/Ag tapes  

SciTech Connect

An anomalous position of the central peak of magnetic hysteresis loops is observed in (Bi,Pb)-2223/Ag tapes at positive external fields B{sub ext} for dB{sub ext}/dt{lt}0. We model the grain structure by a system of superconducting disk-shaped grains touching each other in small, but highly conducting contacts at the disk circumferences. The sign of the internal field B{sub i} at the circumference of large, thin well oriented grains in the tape plays an important role. While in great majority of the sample volume B{sub i} is delayed behind B{sub ext}, just at the grain circumferences B{sub i} might be considerably ahead of B{sub ext}. Based on these considerations, a model sample which should exhibit similar features of the central peak is proposed. {copyright} {ital 1997} {ital American Institute of Physics}

Koblischka, M.R.; Galkin, L.P.; Nalevka, P. [Institute of Physics, Academy of Sciences of the Czech Republic, Na Slovance 2, CZ-18040 Praha 8, (Czech Republic).] [Institute of Physics, Academy of Sciences of the Czech Republic, Na Slovance 2, CZ-18040 Praha 8, (Czech Republic).

1997-01-01

240

The hypergiant masers: episodic mass loss, convection and magnetic fields  

NASA Astrophysics Data System (ADS)

The cool hypergiants are the most luminous known stars in the upper HR Diagram in the apparent temperature range represented by spectral types A to M. Most of the stars in this regime are unstable as evidenced by their high mass loss rates, variability, and in some cases large IR excesses and circumstellar ejecta. We have obtained high resolution multi-wavelength images with HST/WFPC2 of several of the most known evolved cool stars including several well known stellar masers. VX Sgr and S Per were marginally resolved, while NML Cyg has a peculiar asymmetric envelope that has been shaped by its environment. The powerful maser sources IRC+10420 and VY CMa have extensive and complex circumstellar ejecta due to high mass loss episodes apparently driven by large-scale convective activity.

Humphreys, Roberta M.

2007-03-01

241

Local Hysteresis in Relaxation Oscillators.  

National Technical Information Service (NTIS)

Relaxation oscillations or 'integrate and fire' phenomena are very commonly found in nature. When modulated by an external force a global hysteresis connected with chaos is often encountered. Besides this kind of hysteresis a local form is found in some s...

P. Alstroem B. Christiansen M. T. Levinsen

1988-01-01

242

Moisture Sorption Hysteresis in Wood.  

National Technical Information Service (NTIS)

The occurrence of moisture sorption hysteresis in wood, and several proposed theories for explaining it, are discussed. Hysteresis is shown to be beneficial when wood is in use because it reduces changes in moisture content (lower effective slope of the s...

C. Skaar

1979-01-01

243

Finite element analysis of hysteresis effects in piezoelectric transducers  

NASA Astrophysics Data System (ADS)

The design of ultrasonic transducers for high power applications, e.g. in medical therapy or production engineering, asks for effective computer aided design tools to analyze the occurring nonlinear effects. In this paper the finite-element-boundary-element package CAPA is presented that allows to model different types of electromechanical sensors and actuators. These transducers are based on various physical coupling effects, such as piezoelectricity or magneto- mechanical interactions. Their computer modeling requires the numerical solution of a multifield problem, such as coupled electric-mechanical fields or magnetic-mechanical fields as well as coupled mechanical-acoustic fields. With the reported software environment we are able to compute the dynamic behavior of electromechanical sensors and actuators by taking into account geometric nonlinearities, nonlinear wave propagation and ferroelectric as well as magnetic material nonlinearities. After a short introduction to the basic theory of the numerical calculation schemes, two practical examples will demonstrate the applicability of the numerical simulation tool. As a first example an ultrasonic thickness mode transducer consisting of a piezoceramic material used for high power ultrasound production is examined. Due to ferroelectric hysteresis, higher order harmonics can be detected in the actuators input current. Also in case of electrical and mechanical prestressing a resonance frequency shift occurs, caused by ferroelectric hysteresis and nonlinear dependencies of the material coefficients on electric field and mechanical stresses. As a second example, a power ultrasound transducer used in HIFU-therapy (high intensity focused ultrasound) is presented. Due to the compressibility and losses in the propagating fluid a nonlinear shock wave generation can be observed. For both examples a good agreement between numerical simulation and experimental data has been achieved.

Simkovics, Reinhard; Landes, Hermann; Kaltenbacher, Manfred; Hoffelner, Johann; Lerch, Reinhard

2000-06-01

244

Hysteresis model for finite-element analysis of permanent-magnet demagnetization in a large synchronous motor under a fault condition  

Microsoft Academic Search

This paper describes a rare-earth-transition metal alloy permanent-magnet (Nd2Fe14B) hysteretic behavior model within finite-element analysis. The present work analyzes the demagnetization states of permanent magnets during fault conditions in a permanent-magnet synchronous motor and characterizes the ability of the motor to sustain the designed rated outputs after the fault conditions occur.

Marius Rosu; Július Saitz; Antero Arkkio

2005-01-01

245

Power loss separation in Fe-based composite materials  

NASA Astrophysics Data System (ADS)

The frequency dependence of total losses measured in the frequency range from dc to 1 kHz of two Fe-based soft magnetic composites (prepared by compaction of an ASC 100.29 iron powder mixture with 10 vol% of commercial thermoset resin and of a Somaloy® 700 powder) was analyzed. We found out that hysteresis losses (per volume unit) are higher for the composite with lower volume concentration of iron particles (i.e. mixture of iron with resin) and consequently weaker magnetic interaction between particles. On the other hand, higher specific resistivity of the sample with lower magnetic fraction causes lower contribution of eddy current losses to the total losses. A linear dependence of the total energy losses on frequency was observed and from them the contribution of excess losses was obtained. The detailed study of the excess losses resulted in an explanation of the frequency dependence of these losses in composite materials.

Kollár, Peter; Bir?áková, Zuzana; Füzer, Ján; Bureš, Radovan; Fáberová, Mária

2013-02-01

246

Magnetic Resonance Studies of Proton Loss from Carotenoid Radical Cations  

SciTech Connect

Carotenoids, intrinsic components of reaction centers and pigment-protein complexes in photosynthetic membranes, play a photoprotective role and serve as a secondary electron donor. Before optimum use of carotenoids can be made in artificial photosynthetic systems, their robust nature in living materials requires extensive characterization of their electron transfer, radical trapping ability, stability, structure in and on various hosts, and photochemical behavior. Pulsed ENDOR and 2D-HYSCORE studies combined with DFT calculations reveal that photo-oxidation of natural zeaxanthin (I) and violaxanthin (II) on silica-alumina produces not only the carotenoid radical cations (Car•+) but also neutral radicals (#Car•) by proton loss from the methyl groups at positions 5 or 5', and possibly 9 or 9' and 13 or 13'. Notably, the proton loss favored in I at the 5 position by DFT calculations, is unfavorable in II due to the epoxide at the 5, 6 position. DFT calculations predict the isotropic methyl proton couplings of 8-10 MHz for Car•+ which agree with the ENDOR for carotenoid ?-conjugated radical cations. Large ?-proton hyperfine coupling constants (>10 MHz) determined from HYSCORE are assigned from the DFT calculations to neutral carotenoid radicals. Proton loss upon photolysis was also examined as a function of carotenoid polarity [Lycopene (III) versus 8'-apo-?-caroten-8'-al (IV)]; hydrogen bonding [Lutein (V) versus III]; host [silica-alumina versus MCM-41 molecular sieve]; and substituted metal in MCM-41. Loss of H+ from the 5(5'), 9(9') or 13(13') methyl positions has importance in photoprotection. Photoprotection involves nonphotochemical quenching (NPQ) in which 1Ch1* decays via energy transfer to the carotenoid which returns to the ground state by thermal dissipation; or via electron transfer to form a charge transfer state (I •+…Chl•-), lower in energy than 1Chl*. Formation of I •+ results in bond lengthening, a mechanism for nonradiative energy dissipation. Quenching requires zeaxanthin, a pigment-binding protein PsbS, and low pH in the thylalkoid lumen. Low pH in excess light activates the xanthophyll cycle through the enzyme violaxanthin deepoxidase (VDE) which drives deepoxidation of violaxanthin to zeaxanthin. Also a low thylakoid lumen pH activates binding of zeaxanthin to PsbS by protonating carboxylate chains of VDE and PsbS, facilitating attachment to the membrane and the conversion of violaxanthin to zeaxanthin. The low pH also drives ATP synthesis.

Kispert, Lowell D.; Focsan, A. Ligia; Konovalova, Tatyana A.; Lawrence, Jesse; Bowman, Michael K.; Dixon, David A.; Molnar, Peter; Deli, Jozsef

2007-06-11

247

Selective loss of progenitor subsets following clinical CD34+ cell enrichment by magnetic field, magnetic beads or chromatography separation  

Microsoft Academic Search

In this preclinical evaluation we have compared the efficacy of three clinical CD34+enrichment procedures with respect to purity, yield and recovery, as well as risk of selective loss of CD34+ lineage-specific subsets. The three devices work by different principles and have several different manipulation steps: The magnetic field separator uses paramagnetic iron-dextran particles; the magnetic microbead selection is based on

HE Johnsen; M Hutchings; E Taaning; T Rasmussen; LM Knudsen; SW Hansen; H Andersen; E Gaarsdal; L Jensen; K Nikolajsen; E Kjæsgård; NE Hansen

1999-01-01

248

Improved calculation of core loss with nonsinusoidal waveforms  

Microsoft Academic Search

An extension to the Steinmetz equation is proposed, to enable estimation of hysteresis losses in magnetic core materials with nonsinusoidal flux waveforms. The new formulation is shown to avoid anomalies present in previous modified-Steinmetz-equation calculations of loss with nonsinusoidal waveforms. Comparison with experimental measurements in MnZn ferrite shows improved accuracy. The result may be optionally formulated in terms of an

Jieli Li; Tarek Abdallah; Charles R. Sullivan

2001-01-01

249

Low eddy loss axial hybrid magnetic bearing with gimballing control ability for momentum flywheel  

NASA Astrophysics Data System (ADS)

For a magnetically suspended momentum flywheel (MSMF), the spinning rotor can be tilted by a pair of the presented axial hybrid magnetic bearing (AHMB) with eight poles and rotates around the radial axes to generate a large torque to maneuver the spacecraft. To improve the control performance and gimballing control ability of the AHMB, characteristics such as magnetic suspension force, angular stiffness and tilting momentum are researched. These segmented stator poles cause the magnetic density in the thrust rotor plate to be uneven unavoidably and the rotational loss is large at high speed, but we optimized the stator poles configuration and caused the thrust rotor plate formed by bulk DT4C and laminated material to make the magnetic density in the thrust rotor plate change less and be smoother. Laminated material such as 1J50 film with a thickness of 0.1 mm can make the variation of the magnetic density in DT4C become very small and the eddy loss of it be negligible, but the stress produced in the "O" shape stacks by reeling has a bad effect on its power loss. Nanocrystalline can reduce eddy losses and is not affected by the reeling process. Based on the AHBM consisting of the stator with eight improved poles and the presented thrust rotor plate with DT4 and nanocrystalline, the rotational loss of 5-DOF magnetically suspended momentum flywheel with angular momentum of 15 N m s at 5000 rpm has reduced from 23.4 W to 3.2 W, which proved that this AHMB has low eddy loss for the gimballing control ability.

Tang, Jiqiang; Sun, Jinji; Fang, Jiancheng; Shuzhi Sam, Ge

2013-03-01

250

Loss measurement and analysis for the prototype generator with HTS stator and permanent magnet rotor  

NASA Astrophysics Data System (ADS)

A prototype HTS synchronous generator with a permanent magnet rotor and HTS armature windings was developed. The rated armature frequency is 10 Hz. The cryogenic Dewar is tightly surrounded outside the iron core. Both HTS coils and the iron core were cooled by using conduction cooling method. During the process of no-load running, the no-load loss power data were obtained through the torque measurement. The temperature evolution characteristics of the stator was measured by PT-100 temperature sensors. These results show that the no-load loss power at around 77 K are much larger than that at room temperature. The possible reason for the no-load loss increment is discussed. The ac loss power of one individual HTS coil used in this generator was also tested. Compared with the iron loss power, the ac loss power is rather small and could be neglected.

Song, Peng; Qu, Timing; Yu, Xiaoyu; Li, Longnian; Gu, Chen; Li, Xiaohang; Wang, Dewen; Hu, Boping; Chen, Duxing; Han, Zhenghe

2013-11-01

251

A numerical method for analyzing a passive fault current limiter considering hysteresis  

Microsoft Academic Search

Fast transient analysis of a passive fault current limiter (FCL) using permanent magnets can be done by direct numerical solution of a single non-linear differential equation. The non-linear B-H excursion that is caused by hysteresis is incorporated in the computation using a transient hysteresis model. Rational fractions are used to represent the parent hysteresis loop curves. Since the method uses

A. Mukherjee; S. C. Mukhopadhyay; M. Iwahara; S. Yamada; F. P. Dawson

1998-01-01

252

Electrodynamic model for low loss microwave nanocomposite magnets using autonomous blocks with Floquet channels  

NASA Astrophysics Data System (ADS)

The diagonal and off-diagonal components of the effective permeability tensor and the effective permittivity of three-dimensional (3D) periodic magnetic nanosystems, depending on the size and separation of the magnetic nanoparticles, were calculated using the computed values of the propagation constants and the dispersion relations of clockwise and counterclockwise polarized electromagnetic waves (EMWs), as well as for the ordinary and extraordinary modes in the gyromagnetic medium. The propagation constants of EMWs in a 3D periodic array of 150 nm iron nanospheres in a dielectric matrix, depending on the ratio of the period of the array to the radius of the nanospheres, were obtained at a frequency f=30 GHz for longitudinal and transverse orientations of the bias magnetic field. It is shown that the magnetic and dielectric losses of weakly interacting systems are lower than that of yttrium iron garnet (YIG); however, losses increase due to spin wave (SW) excitations upon reduced separation.

Pardavi-Horvath, M.; Makeeva, G. S.; Golovanov, O. A.

2009-04-01

253

Magnetization hysteresis and time decay measurements in FeSe0.50Te0.50: Evidence for fluctuation in mean free path induced pinning  

NASA Astrophysics Data System (ADS)

We present results of magnetic measurements relating to vortex phase diagram in a single crystal of FeSe0.5Te0.5 which displays a second magnetization peak anomaly for H?c. The possible role of the crystalline anisotropy on vortex pinning is explored via magnetic torque magnetometry. We present evidence in favor of pinning related to spatial variations of the charge carrier mean free path leading to small bundle vortex pinning by randomly distributed (weak) pinning centers for both H?c and H?c. This is further corroborated using magnetization data for H?c in a single crystal of FeSe0.35Te0.65. Dynamical response across the second magnetization peak (SMP) anomaly in FeSe0.5Te0.5 has been compared with that across the well-researched phenomenon of peak effect (PE) in a single crystal of CeRu2.

Das, P.; Thakur, Ajay D.; Yadav, Anil K.; Tomy, C. V.; Lees, M. R.; Balakrishnan, G.; Ramakrishnan, S.; Grover, A. K.

2011-12-01

254

Calorimetry in superfluid He II to measure losses in superconducting magnets  

SciTech Connect

A method using calorimetry to measure magnet losses in pressurized Helium II is described. The isothermal nature of He II is used in measuring the overall heat capacity of the system and the net refrigeration power. During the measurements, the refrigeration power is held fixed, and the system (400 liters) temperature is near 1.92 K. The calorimetric measurement was calibrated against known power inputs between 1 and 20 W. This technique can even measure heat loads higher than the available refrigeration. Results of loss measurement on two dipole magnets are reported.

Caspi, S.

1982-04-01

255

High-Frequency Copper Losses in Magnetic Components With Layered Windings  

Microsoft Academic Search

Copper losses in magnetic coils depend on several geometrical parameters, as well as on frequency, in a way that makes their analytical modeling a quite difficult task. In this paper, we describe how we use a finite-element-analysis software to investigate a series of issues critical to the accurate determination of high-frequency copper losses in layered coils. Some of the issues

Georgios S. Dimitrakakis; Emmanuel C. Tatakis

2009-01-01

256

Evaluation of eddy current losses in axial flux permanent magnet (AFPM) machine with an ironless stator  

Microsoft Academic Search

This paper presents a hybrid method for the calculation of eddy current losses in axial flux permanent magnet (AFPM) machines with an ironless stator. The method combines two-dimensional (2-D) finite element (FE) field solutions with the closed-form formula for eddy current loss calculation. The computational limitations of using 2-D FE modeling are discussed and a multi-slice and multi-layer FE model

R. Wang; A. J. Kamper

2002-01-01

257

Energy loss of ions by electric-field fluctuations in a magnetized plasma  

NASA Astrophysics Data System (ADS)

The results of a theoretical investigation of the energy loss of charged particles in a magnetized classical plasma due to the electric-field fluctuations are reported. The energy loss for a test particle is calculated through the linear-response theory. At vanishing magnetic field, the electric-field fluctuations lead to an energy gain of the charged particle for all velocities. It has been shown that in the presence of strong magnetic field, this effect occurs only at low velocities. In the case of high velocities, the test particle systematically loses its energy due to the interaction with a stochastic electric field. The net effect of the fluctuations is the systematic reduction of the total energy loss (i.e., the sum of the polarization and stochastic energy losses) at vanishing magnetic field and reduction or enhancement at strong field, depending on the velocity of the particle. It is found that the energy loss of the slow heavy ion contains an anomalous term that depends logarithmically on the projectile mass. The physical origin of this anomalous term is the coupling between the cyclotron motion of the plasma electrons and the long-wavelength, low-frequency fluctuations produced by the projectile ion. This effect may strongly enhance the stochastic energy gain of the particle.

Nersisyan, Hrachya B.; Deutsch, Claude

2011-06-01

258

Application of magnetomechanical hysteresis modeling of magnetic techniques for monitoring neutron embrittlement and biaxial stress. First year report, June 1991--June 1992  

SciTech Connect

Objective of this project is to investigate experimentally and theoretically the effects of neutron embrittlement and biaxial stress on magnetic properties in steels, using various magnetic measurement techniques. If neutron embrittlement and biaxial stress can be measured via changes in magnetic properties, this should ultimately assist in safety monitoring of nuclear power plants and of gas and oil pipelines. This first-year report addresses the issue of using magnetic property changes to detect neutron embrittlement. The magnetic measurements were all done on irradiated specimens previously broken in two in a Charpy test to determine their embrittlement. The magnetic properties of the broken charpy specimens from D.C. Cook did not correlate well with fluence or embrittlement parameters, possible due to metallurgical reasons. correlation was better with Indian Point 2 specimens, with the nonlinear harmonic amplitudes showing the best correlation (R{sup 2}{approximately}0.7). However, correlation was not good enough. It is recommended that tests be done on unbroken irradiated Charpy specimens, for which magnetic characterization data prior to irradiation is available, if possible.

Sablik, M.J.; Kwun, H.; Burkhardt, G.L.; Rollwitz, W.L.; Cadena, D.G.

1993-01-31

259

Application of magnetomechanical hysteresis modeling of magnetic techniques for monitoring neutron embrittlement and biaxial stress. Second year interim report, June 1992--December 1992  

SciTech Connect

Research was done on the biaxial stress problem accomplished in the first half of the second year. All of the work done was preparatory to magnetic measurements. Issues addressed were: construction of a model for extracting changes in the magnetic properties of a specimen from the readings of an indirect sensor; initial development of a model for how biaxial stress alters the intrinsic magnetic properties of thespecimen; use of finite element stress analysis modeling to determine a detailed shape for the cruciform biaxial stress specimen; and construction of the biaxial stress loading apparatus.

Sablik, M.J.; Kwun, H.; Burkhardt, G.L.

1993-01-31

260

Inkjet printing of magnetic materials with aligned anisotropy  

NASA Astrophysics Data System (ADS)

3-D printing processes, which use drop-on-demand inkjet printheads, have great potential in designing and prototyping magnetic materials. Unlike conventional deposition and lithography, magnetic particles in the printing ink can be aligned by an external magnetic field to achieve both high permeability and low hysteresis losses, enabling prototyping and development of novel magnetic composite materials and components, e.g., for inductor and antennae applications. In this work, we report an inkjet printing technique with magnetic alignment capability. Magnetic films with and without particle alignment are printed, and their magnetic properties are compared. In the alignment-induced hard axis direction, an increase in high frequency permeability and a decrease in hysteresis losses are observed. Our results suggest that unique magnetic structures with arbitrary controllable anisotropy, not feasible otherwise, may be fabricated via inkjet printing.

Song, Han; Spencer, Jeremy; Jander, Albrecht; Nielsen, Jeffrey; Stasiak, James; Kasperchik, Vladek; Dhagat, Pallavi

2014-05-01

261

Vector hysteresis measurements via a single disk tester  

NASA Astrophysics Data System (ADS)

In this paper we present a single disk tester (SDT) developed for vector hysteresis measurements of magnetic steels. The measurement system deals with a stator of a 3-phase induction motor and some suitable magnetic field and magnetic induction probes. Numerical calculations based to a FEM approach in time domain and experimental tests are shown in order to describe both accuracy and efficiency of this measurement system.

Cardelli, E.; Faba, A.

2006-02-01

262

Magnetic field structure influence on primary electron cusp losses for micro-scale discharges  

NASA Astrophysics Data System (ADS)

An experimental effort was used to examine the primary electron loss behavior for micro-scale (?3 cm diameter) discharges. The experiment uses an electron flood gun source and an axially aligned arrangement of ring-cusps to guide the electrons to a downstream point cusp. Measurements of the electron current collected at the point cusp show an unexpectedly complex loss pattern with azimuthally periodic structures. Additionally, in contrast to conventional theory for cusp losses, the overall radii of the measured collection areas are over an order of magnitude larger than the electron gyroradius. Comparing these results to Monte Carlo particle tracking simulations and a simplified analytical analysis shows that azimuthal asymmetries of the magnetic field far upstream of the collection surface can substantially affect the electron loss structure and overall loss area.

Dankongkakul, Ben; Araki, Samuel J.; Wirz, Richard E.

2014-04-01

263

A loss-based, magnetic field sensor implemented in a ferrofluid infiltrated microstructured polymer optical fiber  

NASA Astrophysics Data System (ADS)

We report an in-fiber magnetic field sensor based on magneto-driven optical loss effects, while being implemented in a ferrofluid infiltrated microstructured polymer optical fiber. We demonstrate that magnetic field flux changes up to 2000 gauss can be detected when the magnetic field is applied perpendicular to the fiber axis. In addition, the sensor exhibits high polarization sensitivity for the interrogated wavelengths, providing the possibility of both field flux and direction measurements. The underlying physical and guidance mechanisms of this sensing transduction are further investigated using spectrophotometric, light scattering measurements, and numerical simulations, suggesting photonic Hall effect as the dominant physical, transducing mechanism.

Candiani, A.; Argyros, A.; Leon-Saval, S. G.; Lwin, R.; Selleri, S.; Pissadakis, S.

2014-03-01

264

Control of magnetic loss tangent of hexaferrite for advanced radio frequency antenna applications  

NASA Astrophysics Data System (ADS)

We demonstrate that magnetic loss tangent of M-type hexaferrite can be controlled by a small dc magnetic field, thereby improving radio frequency (RF) antenna radiation efficiency and realizing antenna miniaturization. Magnetic loss tangent (tan ??) of the M-type BaFe9.6Co1.2Ti1.2O19 hexaferrite at 200 MHz decreased significantly from 11.8% to less than 1% as the applied dc magnetic field increased from 0 to 400 Oe. This is because the contribution of domain wall motion to permeability dispersion is decreased, and the ferromagnetic resonance frequency increases with the magnetic field. Antenna simulation results showed that radiation efficiency of the designed ferrite helical antenna increased from -22.9 to -9.2 dB with dc magnetic field of 400 Oe. Therefore, the small dc magnetic field played a key role in reduction of tan ?? of hexaferrite and improvement of antenna performance in the RF range.

Lee, Jaejin; Hong, Yang-Ki; Lee, Woncheol; Abo, Gavin S.; Park, Jihoon; Seong, Won-Mo; Ahn, Won-Ki

2013-02-01

265

Enhanced loss of magnetic-mirror-trapped fast electrons by a shear Alfvén wavea)  

NASA Astrophysics Data System (ADS)

Laboratory observations of enhanced loss of magnetic mirror trapped fast electrons irradiated by a shear Alfvén Wave (SAW) are reported. The experiment is performed in the quiescent after-glow plasma in the Large Plasma Device [Gekelman et al., Rev. Sci. Instrum. 62(12), 2875-2883 (1991)]. A trapped energetic electron population (>100 keV) is generated in a magnetic mirror section (mirror ratio ? 2, length = 3.5 m) by an X-mode high power microwave pulse, and forms a hot electron ring due to the grad-B and curvature drift. SAWs of arbitrary polarization are launched externally by a Rotating Magnetic Field source (?B/B0 ? 0.1%, ?? ? 9 m). Irradiated by a right-handed circularly polarized SAW, the loss of electrons, in both the radial and the axial direction of the mirror field, is significantly enhanced and is modulated at fAlfvén. The periodical loss continues even after the termination of the SAW. Experimental observations suggest that a spatial distortion of the ring is formed in the SAW field and creates a collective mode of the hot electron population that degrades its confinement and leads to electron loss from the magnetic mirror. The results could have implications on techniques of radiation belt remediation.

Wang, Y.; Gekelman, W.; Pribyl, P.; Papadopoulos, K.

2014-05-01

266

Magnetic particle hyperthermia: Power losses under circularly polarized field in anisotropic nanoparticles  

NASA Astrophysics Data System (ADS)

The deterministic Landau-Lifshitz-Gilbert equation has been used to investigate the nonlinear dynamics of magnetization and the specific power loss in magnetic nanoparticles with uniaxial anisotropy driven by a rotating magnetic field, generalizing the results obtained for the isotropic case found by P. F. de Châtel, I. Nándori, J. Hakl, S. Mészáros, and K. Vad [J. Phys. Condens. Matter10.1088/0953-8984/21/12/124202 21, 124202 (2009)]. As opposed to many applications of magnetization reversal in single-domain ferromagnetic particles, where losses must be minimized, in this paper, we study the mechanisms of dissipation used in cancer therapy by hyperthermia, which requires the enhancement of energy losses. We show that for circularly polarized field, the energy loss per cycle is decreased by the anisotropy compared to the isotropic case when only dynamical effects are taken into account. Thus, in this case, in the low-frequency limit, a better heating efficiency can be achieved for isotropic nanoparticles. The possible role of thermal fluctuations is also discussed. Results obtained are compared to experimental data.

Nándori, I.; Rácz, J.

2012-12-01

267

Experimental study on magnetizing and loss characteristics of electrical strip for different frequencies  

Microsoft Academic Search

This paper mainly aims at studying on the magnetic measurements of electrical strip for different frequencies. The loss coefficient curve and BH curve for different high frequencies can be sketched through the measurement of the transformer using a digital memory oscilloscope. The power of transformer is supplied by an inverter through LC filter and voltage regulator. The cores of experimental

Yunlong Xu; Fengxiang Wang

2008-01-01

268

Analysis of the Magnetic Losses from the Induction Machines Supplied by Inverters  

Microsoft Academic Search

In the paper are being analyzed the magnetic losses that occur in the induction machines of low and medium power while being supplied by inverters realized with IGBT transistors. The analysis method is based on the over-position effect principle. As a working hypothesis is being neglected the saturation effect. During analyzes is being deduced the computing relations which allow the

Sorin Musuroi; Doru Vatau; Petru Andea; Flavius-Dan Surianu; Flaviu Frigura; Constantin Barbulescu

2007-01-01

269

Loss minimization in vector-controlled interior permanent-magnet synchronous motor drives  

Microsoft Academic Search

An efficiency optimization method for vector-controlled interior permanent-magnet synchronous motor drives is presented. Based on theoretical analysis, a loss minimization condition that determines the optimal d-axis component of the armature current is derived. Selected experimental results are presented to validate the effectiveness of the proposed control method.

Christos Mademlis; Nikos Margaris

2002-01-01

270

Transport and magnetization ac losses of ROEBEL assembled coated conductor cables: measurements and calculations  

NASA Astrophysics Data System (ADS)

Many superconductor applications require cables with a high current capacity. This is not feasible with single-piece coated conductors because their ac losses are too large. Therefore, it is necessary to develop superconducting cables with a high current capacity and low ac losses. One promising solution is given by ROEBEL cables. We assembled three ROEBEL cables from commercial YBCO coated conductors. The cables have the same width but a different number of strands, which results in different aspect ratios and current capacities. We experimentally studied their ac losses under a transport current or a perpendicular magnetic field. In addition, we performed numerical calculations, which agree with the experiments, especially for the transport case. We found that in the cables there is good current sharing between the strands. We also found that stacking the strands reduces the magnetization losses. For a given critical current, thicker cables have lower magnetization ac losses. In addition, a conducting matrix is not required for a good current sharing between strands.

Terzieva, Stanimira; Vojen?iak, Michail; Pardo, Enric; Grilli, Francesco; Drechsler, Antje; Kling, Andrea; Kudymow, Andrej; Gömöry, Fedor; Goldacker, Wilfried

2010-01-01

271

Modeling microstructural effects on hysteresis loops with the same maximum flux density  

Microsoft Academic Search

Microstructural attributes such as grain size d and dislocation density ?d affect the hysteretic magnetic properties of steels because they affect domain wall movement and pinning. In an earlier paper, a model was proposed for computing hysteresis loops based on the effect of grain size and dislocation density. In that paper, hysteresis loops were compared that all had the same

M. J. Sablik; F. J. G. Landgraf

2003-01-01

272

Modeling plastic deformation effects in steel on hysteresis loops with the same maximum flux density  

Microsoft Academic Search

Plastic deformation affects the hysteretic magnetic properties of steels because it changes the dislocation density, which affects domain-wall movement and pinning, and also because it places the specimen under residual strain. An earlier paper proposed a model for computing hysteresis loops on the basis of the effect of grain size d and dislocation density ?d. In that paper, hysteresis loops

Martin J. Sablik; Taeko Yonamine; Fernando J. G. Landgraf

2004-01-01

273

Novel Hysteresis Current Controller for Active Power Filter  

Microsoft Academic Search

The switching losses of Active Power Filter (APF) is one of the important factors that influence the performance-price ratio of APF. In this paper, a novel method is suggested. Under this new method, each phase output reference current of APF is compared to adjust hysteresis of each phase, so that the switching number of the phase that has greater switching

Zeng Jiang; Liu Yan; Ouyang Sen; Zhen Zaitian

2010-01-01

274

An Accurate Hysteresis Model for Ferroresonance Analysis of a Transformer  

Microsoft Academic Search

This paper introduces an accurate transformer core model, using the Preisach theory, to represent the core magnetization characteristic. This modeling approach provides the required precision to match major and minor hysteresis loops of the model with those of the actual transformer core material. Using the proposed model, the ferroresonance phenomenon of a voltage transformer (VT) is simulated and compared to

Afshin Rezaei-Zare; Reza Iravani; Majid Sanaye-Pasand; Hossein Mohseni; Shahrokh Farhangi

2008-01-01

275

Hysteresis heating based induction bonding of composite materials  

Microsoft Academic Search

The viability of using magnetic particulate susceptor materials for induction heating during bonding of polymer matrix composites is well established in this work. The unique ability to offer localized heating, geometric flexibility, and self-controlled temperature is the major advantage of this technique. Hysteresis heating is tailored through careful design of the microstructure of nickel particulate polymer films (Ni\\/PSU). An excellent

Witchuda Suwanwatana

2004-01-01

276

Magnetic testing  

NASA Technical Reports Server (NTRS)

Magnetic techniques are described for the nondestructive evaluation of defects in materials. The physical principles, and the magnetic-particle method are discussed along with magnetic-hysteresis measurements and electric current perturbations.

Pasley, R. L.; Barton, J. R.

1973-01-01

277

Energy loss in YBCO-123 coated conductor due to AC\\/DC transport current and AC external perpendicular magnetic field  

Microsoft Academic Search

In the paper we present experimental results of power losses measurements in a YBCO-123 coated conductor carrying a DC (or AC) transport current when subjected simultaneously to an external AC magnetic field. Two kinds of measurements were carried out; the first was AC transport current losses as a function of the current amplitude and the AC external magnetic field (“AC–AC”

M. Ciszek; O. Tsukamoto; J. Ogawa; M. Shiokawa

2003-01-01

278

Application of a Rare-Earth Cobalt Magnet to Synchronous Motors.  

National Technical Information Service (NTIS)

An experimental hysteresis rotor structure was produced in which a ring made of radially oriented anisotropic magnet material, Alnico 5 which has a large magnetic hysteresis loop, and a yoke made of inner steel are utilized. The prototype hysteresis motor...

H. Yamada

1981-01-01

279

A Permanent Magnet Synchronous Motor drive employing a three-level Very Spars Matrix Converter with soft switching and SVM hysteresis current control  

Microsoft Academic Search

Proposed in this paper is a three-phase three-level Very Sparse Matrix Converter (VSMC) fed Permanent Magnet Synchronous Motor (PMSM). Such a system may be designed to draw and sinusoidal input current, have high efficiency and is free of a DC-link energy storage element (inductor and\\/or capacitor). As discussed in this paper, the three-level inverter output stage produces reduced distortion waveforms

Mohamed Aner; N. Benaifa; E. Nowicki

2010-01-01

280

Theory of molecular hysteresis switch  

NASA Astrophysics Data System (ADS)

Molecular hysteresis switching has been recently observed in a series of experiments that measured the I-V spectrum of bipyridyl-dinitro oligophenylene-ethylene dithiol (BPDN) based molecular devices [1]. The experimental observations clearly show the presence of Coulomb blockade in single organic molecules that is responsible for the voltage-induced switching. We present the theory of the hysteresis switch which explains the non-linear hysteresis I-V characteristics based on the mechanisms of Coulomb blockade and the existence of two different molecular conformations of neutral and charged states of the molecule. [1] A.S. Blum, J.G. Kushmerick, D.P. Long, C.H. Patterson, J.C. Yang, J.C. Henderson, Y.X. Yao, J.M. Tour, R. Shashidhar, and B.R. Ratna, ``Molecularly inherent voltage-controlled conductance switching'' , Nature Materials 4, 167 (2005).

Kozhushner, Mortko; Oleynik, Ivan

2006-03-01

281

Magnetopause Losses of Radiation Belt Electrons During a Recent Magnetic Storm  

NASA Astrophysics Data System (ADS)

We present results from Van Allen Probes observations during the magnetic storm of June 1, 2013, and compare them with simulations of the same event using the RCM-E model. The RCM-E calculates ion and electron transport in self-consistently computed electric and magnetic fields. We examine the effect of the perturbed ring current magnetic field on the transport of energetic electrons, and the significance of this transport for explaining the observed evolution of radiation belt fluxes during this event. The event is notable because it is a relatively simple storm in which strong convection persists for approximately 7 hours, injecting a moderately strong ring current (minimum Dst of -120 nT); convection then quickly shuts off, leading to a long and smooth recovery phase. We use RCM-E simulations, constrained by Van Allen Probes data, to asses the rate of magnetopause losses of electrons (magnetopause shadowing), and to calculate electron drift times and the evolution of electron phase space densities during the storm event. We recently modified the RCM-E plasma drift calculations to include relativistic treatment of electrons and a more realistic electron loss model. The new electron loss model, although still somewhat simplistic, gives much more accurate loss rates in the inner magnetosphere (including the radiation belts), which significantly affects the resulting electron fluxes compared to previous simulations. This, in turn, modifies the transport of ions and electrons via feedback with both the electric and magnetic fields. Our results highlight the effect of the ring current on the evolution of the radiation belt electrons, with particular emphasis on the role that magnetopause losses play in the observed variation of radiation belt electron fluxes during the storm.

Lemon, C. L.; Chen, M.; Roeder, J. L.; Fennell, J. F.; Mulligan, T. L.; Claudepierre, S. G.

2013-12-01

282

Disc formation in turbulent cloud cores: is magnetic flux loss necessary to stop the magnetic braking catastrophe or not?  

NASA Astrophysics Data System (ADS)

Recent numerical analysis of Keplerian disc formation in turbulent, magnetized cloud cores by Santos-Lima et al. demonstrated that reconnection diffusion is an efficient process to remove the magnetic flux excess during the buildup of a rotationally supported disc. This process is induced by fast reconnection of the magnetic fields in a turbulent flow. In a similar numerical study, Seifried et al. concluded that reconnection diffusion or any other non-ideal magnetohydrodynamic effects would not be necessary and turbulence shear alone would provide a natural way to build up a rotating disc without requiring magnetic flux loss. Their conclusion was based on the fact that the mean mass-to-flux ratio (?) evaluated over a spherical region with a radius much larger than the disc is nearly constant in their models. In this paper, we compare the two sets of simulations and show that this averaging over large scales can mask significant real increases of ? in the inner regions where the disc is built up. We demonstrate that turbulence-induced reconnection diffusion of the magnetic field happens in the initial stages of the disc formation in the turbulent envelope material that is accreting. Our analysis is suggestive that reconnection diffusion is present in both sets of simulations and provides a simple solution for the `magnetic braking catastrophe' which is discussed in the literature in relation to the formation of protostellar accretion discs.

Santos-Lima, R.; de Gouveia Dal Pino, E. M.; Lazarian, A.

2013-03-01

283

On the Treatment of Electric and Magnetic Loss in the Linear Bicharacteristic Scheme for Electromagnetics  

NASA Technical Reports Server (NTRS)

The upwind leapfrog or Linear Bicharacteristic Scheme (LBS) has previously been extended to treat lossy dielectric and magnetic materials. This paper examines different methodologies for treatment of the electric loss term in the Linear Bicharacteristic Scheme for computational electromagnetics. Several different treatments of the electric loss term using the LBS are explored and compared on one-dimensional model problems involving reflection from lossy dielectric materials on both uniform and nonuniform grids. Results using these LBS implementations are also compared with the FDTD method for convenience.

Beggs, John H.

2000-01-01

284

AC Loss in the Superconducting Cables of the CERN Fast Cycled Magnet Prototype  

NASA Astrophysics Data System (ADS)

Fast Cycled Superconducting Magnets (FCM's) are an option of interest for the long-term consolidation and upgrade plan of the LHC accelerator complex. The economical advantage of FCM's in the range of 2 T bore field, continuously cycled at 0.5 Hz repetition rate, depends critically on the AC loss property of strand and cable. In this paper we report the results of the AC loss measurements that we have performed both on strands and cables manufactured for the CERN FCM prototype program.

Borgnolutti, F.; Bottura, L.; Nijhuis, A.; Zhou, C.; Liu, B.; Miyoshi, Y.; Krooshoop, H. J. G.; Richter, D.

285

THE EFFECT OF MAGNETIC SPOTS ON STELLAR WINDS AND ANGULAR MOMENTUM LOSS  

SciTech Connect

We simulate the effect of latitudinal variations in the location of star spots, as well as their magnetic field strength, on stellar angular momentum loss (AML) to the stellar wind. We use the Michigan solar corona global magnetohydrodynamic model, which incorporates realistic relation between the magnetic field topology and the wind distribution. We find that the spots' location significantly affects the stellar wind structure, and as a result, the total mass loss rate and AML rate. In particular, we find that the AML rate is controlled by the mass flux when spots are located at low latitudes but is controlled by an increased plasma density between the stellar surface and the Alfven surface when spots are located at high latitudes. Our results suggest that there might be a feedback mechanism between the magnetic field distribution, wind distribution, AML through the wind, and the motions at the convection zone that generate the magnetic field. This feedback might explain the role of coronal magnetic fields in stellar dynamos.

Cohen, O.; Drake, J. J.; Kashyap, V. L. [Harvard-Smithsonian Center for Astrophysics, 60 Garden St., Cambridge, MA 02138 (United States); Gombosi, T. I. [Center for Space Environment Modeling, University of Michigan, 2455 Hayward St., Ann Arbor, MI 48109 (United States)

2009-07-10

286

Alternating current loss reduction for rectangular busbars by covering their edges with low permeable magnetic caps  

NASA Astrophysics Data System (ADS)

A method to reduce ac conductive losses in a thin rectangular busbar made of copper is presented. The method is based on a technique, which makes the distribution of the ac current in the cross section of a busbar flatter. Edges of a thin busbar are covered with low permeability magnetic thin layers as caps. The magnetic cap makes the impedance experienced by the current flowing near the edge comparatively larger so that currents cannot get crowded near the edges of a busbar. This method is numerically verified.

Sasada, Ichiro

2014-05-01

287

Vortex electron energy loss spectroscopy for near-field mapping of magnetic plasmons.  

PubMed

The theory of vortex electron beam electron energy loss spectroscopy (EELS), or vortex-EELS for short, is presented. This theory is applied, using Green function calculations within the finite-difference time-domain method, to calculate spatially resolved vortex-EELS maps of a metal split ring resonator (SRR). The vortex-EELS scattering cross section for the SRR structure is within an order of magnitude of conventional EELS typically for metal nanoparticles. This is promising in terms of feasibility for future measurements to map out the local magnetic response of metal nanostructures and to characterize their magnetic plasmon response in applications, including metamaterials. PMID:22772198

Mohammadi, Zeinab; Van Vlack, Cole P; Hughes, Stephen; Bornemann, Jens; Gordon, Reuven

2012-07-01

288

AC loss and dynamic resistance of a high T(sub c) strand carrying a direct current in a transverse AC magnetic field  

NASA Astrophysics Data System (ADS)

A superconducting wire (diameter, d) exposed to an AC longitudinal or transverse magnetic field (amplitude, H(sub m)) experiences a hysteretic power loss, W(sub h). If a DC transport current (density, J) is next applied, extra dissipation is encountered as the current interacts with the moving mixed-state vortices. But if J and H(sub m) are sufficiently small, and J(sub c) and d sufficiently large it is possible for loss-free current to flow down the central core of the wire out of range of the oscillating field. In other words, H(sub m) should be less than some 'penetration value,' H*(J) = H*(1-j), where H* is the usual penetration field and j is equivalent to J/J(sub c). The current-related dissipation, W(sub dyn), can be interpreted as taking place within a dynamic resistivity, rho(sub dyn). Below H*(J) the only dissipation is W(sub h); above it the dissipation is W(sub t) = W(sub h) + W(sub dyn). In the latter regime, as J increases W(sub h) decreases and W(sub dyn), increases. The result is a net increase in W(sub t) during which, as J approaches J(sub c), W(sub h) tends to zero and W(sub dyn) undergoes a smooth transition to the flux-flow (and eventually, normal) state. Some of these predictions were confirmed in a series of studies of dynamic resistivity in two samples of high-(Tc) YBCO strand--a low-J(sub c) braid and a high-J(sub c) monofilament--passing DC transport currents in transverse AC fields with H(sub m)s of up to about 800 gauss. Also described are the results of hysteresis loss measurements, taken at J = 0 using vibrating-sample magnetometry.

Collings, E. W.; Marken, K. R.; Sumption, M. D.; Clem, J. R.; Boggs, S. A.; Parish, M. V.

289

Unconventional dynamic hysteresis in a periodic assembly of paramagnetic colloids.  

PubMed

Dynamic hysteresis phenomena are widespread in physical sciences and describe the complex behavior of systems driven out of equilibrium by a periodic forcing. We use here paramagnetic colloids above a stripe-patterned garnet film as the model system to study dynamic hysteresis, the latter induced when the particles are periodically translated by an oscillating magnetic field. In contrast to the expected behavior for a bistable system, we observe that the area of the hysteresis loop decreases by increasing the driving frequency and reduces to zero for frequencies higher than 5-7s(-1). To explain the experimental results, we develop a simple model based on an overdamped Brownian particle driven by a periodic potential with an oscillating amplitude. PMID:23848669

Tierno, Pietro; Johansen, Tom H; Sancho, J M

2013-06-01

290

Direct recursive identification of the Preisach hysteresis density function  

NASA Astrophysics Data System (ADS)

In this paper, a novel direct method of recursive identification of the Preisach hysteresis density function is proposed. Using the discrete dynamic Preisach model, which is a state-space realization of the classical scalar Preisach model, the method is designed based on the output increment error. After giving the general formulation, the identification scheme implemented for a discretized Preisach plane is introduced and evaluated through the use of numerical simulations. Two cases of Gaussian mixtures are considered for mapping the hysteresis system to be identified. The parameter convergence is shown for a low-pass filtered white-noise input. Further, the proposed identification method is applied to a magnetism-related application example, where the flux linkage hysteresis of a proportional solenoid is assumed from the measurements, and then the inverse of a standard demagnetization procedure is utilized as the identification sequence.

Ruderman, Michael

2013-12-01

291

An Energy-Based Hysteresis Model for Magnetostrictive Transducers  

NASA Technical Reports Server (NTRS)

This paper addresses the modeling of hysteresis in magnetostrictive transducers. This is considered in the context of control applications which require an accurate characterization of the relation between input currents and strains output by the transducer. This relation typically exhibits significant nonlinearities and hysteresis due to inherent properties of magnetostrictive materials. The characterization considered here is based upon the Jiles-Atherton mean field model for ferromagnetic hysteresis in combination with a quadratic moment rotation model for magnetostriction. As demonstrated through comparison with experimental data, the magnetization model very adequately quantifies both major and minor loops under various operating conditions. The combined model can then be used to accurately characterize output strains at moderate drive levels. The advantages to this model lie in the small number (six) of required parameters and the flexibility it exhibits in a variety of operating conditions.

Calkins, F. T.; Smith, R. C.; Flatau, A. B.

1997-01-01

292

Hysteresis Modeling in Magnetostrictive Materials Via Preisach Operators  

NASA Technical Reports Server (NTRS)

A phenomenological characterization of hysteresis in magnetostrictive materials is presented. Such hysteresis is due to both the driving magnetic fields and stress relations within the material and is significant throughout, most of the drive range of magnetostrictive transducers. An accurate characterization of the hysteresis and material nonlinearities is necessary, to fully utilize the actuator/sensor capabilities of the magnetostrictive materials. Such a characterization is made here in the context of generalized Preisach operators. This yields a framework amenable to proving the well-posedness of structural models that incorporate the magnetostrictive transducers. It also provides a natural setting in which to develop practical approximation techniques. An example illustrating this framework in the context of a Timoshenko beam model is presented.

Smith, R. C.

1997-01-01

293

Magnetic resonance imaging of the inner ear in patients with idiopathic sudden sensorineural hearing loss  

Microsoft Academic Search

Although gadolinium-enhanced magnetic resonance imaging (Gd-MRI) has been used to indicate the presence of a subclinical\\u000a labyrinthitis in patients with idiopathic sudden sensorineural hearing loss (ISSHL), its sensitivity in daily clinical practice\\u000a is unknown. We describe Gd-MRI findings in 27 ISSHL patients taking part in a prospective multicenter clinical trial. MRI\\u000a findings were related to the severity of the hearing

R. J. Stokroos; F. W. J. Albers; A. P. Krikke; J. W. Casselman

1998-01-01

294

Magnetic properties and AC-losses of superconductors with power law current-voltage characteristics  

Microsoft Academic Search

In many high-Tc superconductors the critical current density jc is an ill-defined quantity due to the smooth current-voltage characteristic. Since jc is the basic parameter entering the critical state model, its application to such materials becomes problematic. In this paper, a theory of magnetic properties and AC-losses in superconductors with smooth current-voltage characteristics is proposed. It is applied to superconductors

Jakob Rhyner

1993-01-01

295

Simulation of Eddy-Current Losses in a Fast Ramped Superconductive Dipole Magnet  

Microsoft Academic Search

The eddy-current losses in the yoke of a superconductive dipole magnet are simulated using a transient, magnetoquasistatic formulation discretized in 3D by the finite integration technique. The laminated yoke material is modeled by an anisotropic, nonlinear material characteristic. The system is linearized by the successive approximation technique with backtracking and solved by a curl-curl algebraic multigrid solver. The results show

S. Koch; H. De Gersem; E. Fischer; G. Moritz; T. Weiland

2006-01-01

296

Losses and forces due to eddy currents in a magnetically non-linear conductive half space  

Microsoft Academic Search

A simple soft magnetically non-linear moving conductor model (“iron”) as “half-space” is presented under the inducing effect\\u000a of a sinusoidal distributed current loading at different current amplitudes, covering the low to very high saturation level\\u000a of 1–4 T. Eddy current losses, penetration depth of field and tangential braking and normal attractive forces are compared\\u000a with the results for a linear conductor

Bogdan Funieru; Andreas Binder

2007-01-01

297

Use of magnetic iron oxide to determine soil losses in rainfed olive orchard plots  

NASA Astrophysics Data System (ADS)

Soil erosion is a major threat for sustainability of olive cropped areas in Mediterranean countries, like southern Spain where ~17% of its surface is covered by olive orchards (Gómez et al. 2005). Despite the large number of research dedicated to the study of soil erosion in olive orchards, a significant uncertainty persists in the estimation of actual erosion rates in these areas (Gómez et al. 2008; Fleskens and Stroosnijder, 2007). Due to the technical and economic limitations of traditional methods used in erosion measurement, there is a growing interest in the use of new methods including tracking of soil incorporating tracers in experiments performed at different scales and time periods. Magnetic iron oxide particles are good tracers to complement, or even replace traditional techniques of soil loss measurement after rainfall events under controlled rainfall conditions, especially at the small scale (Guzmán et al. 2010). From October 2008 to August 2010 soil losses were measured in two olive orchard runoff plots. During that period magnetic iron oxide concentration changes were also determined to estimate total soil losses and soil redistribution by water and tillage erosion in the plots, differentiating between the inter-tree rows, tree rows and rill areas influence. Average measured and estimated soil losses in the plots were 14.1 and 14.2 kg·m-2 respectively. Magnetic iron oxide as a sediment tracer allowed the estimation of soil losses with a RSME of 0.72 kg·m-2. Although soil erosion rates from tree rows were lower (0.6 kg·m-2·month-1) compared to inter-tree row rates (1.1 kg·m-2·month-1), the contribution of tree row areas to total soil losses was considerably high because of the great volume of the tree canopies in the plots and therefore, covered area (53.5 %). Magnetite content variations both overland and within the soil profile, selectivity of the tracer for finer soil particles, and soil bulk density changes, due to tillage-compaction and swelling-shrinking processes were the key factors for the precision of the estimation of soil losses. Detachment and erosion areas were identified in the plots through changes of iron oxide content in the soil. This study indicates that magnetic iron oxide can be a useful method to assess the suitability of different olive orchard management methods and to monitor sediment dynamics at a similar scale to that of the studied plots, albeit controlling with great care the factors identified in this study.

Guzmán, G.; Gómez, J. A.; Giráldez, J. V.

2012-04-01

298

Efficiency Wage, Commitment and Hysteresis  

Microsoft Academic Search

The efficiency wage model is usually thought of as a plausible model of the natural rate of unemployment which has little to say about its dynamics. This paper establishes that if firms pay efficiency wages and have some degree of commitment over their employment policy, then employment dynamics exhibit hysteresis. The implied behaviour of unemployment, however, is more similar to

Gilles SAINT-PAUL

1995-01-01

299

Role of Loss of Equilibrium and Magnetic Reconnection in Coronal Eruptions: Resistive and Hall MHD simulations  

NASA Astrophysics Data System (ADS)

It has long been suggested that eruptive phenomena such as coronal mass ejections, prominence eruptions, and large flares might be caused by a loss of equilibrium in a coronal flux rope (Van Tend and Kuperus, 1978). Forbes et al. (1994) developed an analytical two-dimensional model in which eruptions occur due to a catastrophic loss of equilibrium and relaxation to a lower-energy state containing a thin current sheet. Magnetic reconnection then intervenes dynamically, leading to the release of magnetic energy and expulsion of a plasmoid. We have carried out high-Lundquist-number simulations to test the loss-of equilibrium mechanism, and demonstrated that it does indeed occur in the quasi-ideal limit. We have studied the subsequent dynamical evolution of the system in resistive and Hall MHD models for single as well as multiple arcades. The typical parallel electric fields are super-Dreicer, which makes it necessary to include collisionless effects via a generalized Ohm's law. It is shown that the nature of the local dissipation mechanism has a significant effect on the global geometry and dynamics of the magnetic configuration. The presence of Hall currents is shown to alter the length of the current sheet and the jets emerging from the reconnection site, directed towards the chromosphere. Furthermore, Hall MHD effects break certain symmetries of resistive MHD dynamics, and we explore their observational consequences.

Yang, H.; Bhattacharjee, A.; Forbes, T. G.

2008-12-01

300

Impact of magnetic field inhomogeneity on electron cyclotron radiative loss in tokamak reactors  

NASA Astrophysics Data System (ADS)

The potential importance of electron cyclotron (EC) emission in the local electron power balance in the steady-state regimes of ITER operation with high temperatures, as well as in the DEMO reactor, requires accurate calculation of the one-dimensional (over magnetic surfaces) distribution of the net radiated power density, P EC(?). When the central electron temperature increases to ˜30 keV, the local EC radiative loss comprises a substantial fraction of the heating power from fusion alphas and is close to the total auxiliary NBI heating power, P EC(0) ? 0.3 P ?(0) ? P aux(0). In the present paper, the model of EC radiative transport in an axisymmetric toroidal plasma is extended to the case of an inhomogeneous magnetic field B( R, Z). The impact of such inhomogeneity on local and total power losses is analyzed in the framework of this model by using the CYNEQ code. It is shown that, for the magnetic field B, temperature T e , density n e , and wall reflection coefficient R w expected in ITER and DEMO, accurate simulations of the EC radiative loss require self-consistent 1.5D transport analysis (i.e., one-dimensional simulations of plasma transport and two-dimensional simulations of plasma equilibrium). It is shown that EC radiative transport can be described with good accuracy in the 1D approximation with the surface-averaged magnetic field, B(?) = < B( R, Z)> ms . This makes it possible to substantially reduce the computational time required for time-dependent self-consistent 1.5D transport analysis. Benchmarking of the CYNEQ results with available results of the RAYTEC, EXACTEC, and CYTRAN codes is performed for various approximations of the magnetic field.

Kukushkin, A. B.; Minashin, P. V.; Polevoi, A. R.

2012-03-01

301

Impact of magnetic field inhomogeneity on electron cyclotron radiative loss in tokamak reactors  

SciTech Connect

The potential importance of electron cyclotron (EC) emission in the local electron power balance in the steady-state regimes of ITER operation with high temperatures, as well as in the DEMO reactor, requires accurate calculation of the one-dimensional (over magnetic surfaces) distribution of the net radiated power density, P{sub EC}({rho}). When the central electron temperature increases to {approx}30 keV, the local EC radiative loss comprises a substantial fraction of the heating power from fusion alphas and is close to the total auxiliary NBI heating power, P{sub EC}(0) Asymptotically-Equal-To 0.3P{sub {alpha}}(0) Asymptotically-Equal-To P{sub aux}(0). In the present paper, the model of EC radiative transport in an axisymmetric toroidal plasma is extended to the case of an inhomogeneous magnetic field B(R, Z). The impact of such inhomogeneity on local and total power losses is analyzed in the framework of this model by using the CYNEQ code. It is shown that, for the magnetic field B, temperature T{sub e}, density n{sub e}, and wall reflection coefficient R{sub w} expected in ITER and DEMO, accurate simulations of the EC radiative loss require self-consistent 1.5D transport analysis (i.e., one-dimensional simulations of plasma transport and two-dimensional simulations of plasma equilibrium). It is shown that EC radiative transport can be described with good accuracy in the 1D approximation with the surface-averaged magnetic field, B({rho}) = Left-Pointing-Angle-Bracket B(R, Z) Right-Pointing-Angle-Bracket {sub ms}. This makes it possible to substantially reduce the computational time required for time-dependent self-consistent 1.5D transport analysis. Benchmarking of the CYNEQ results with available results of the RAYTEC, EXACTEC, and CYTRAN codes is performed for various approximations of the magnetic field.

Kukushkin, A. B.; Minashin, P. V. [National Research Centre Kurchatov Institute, Tokamak Physics Institute (Russian Federation); Polevoi, A. R. [Route de Vinon sur Verdon, ITER Organization (France)

2012-03-15

302

Loss of angular momentum of magnetic Ap stars in the pre-main sequence phase  

NASA Astrophysics Data System (ADS)

A model for rotation evolution of an intermediate mass star with the primordial magnetic field in the pre-main sequence (PMS) phase was developed. It takes into account the accretion of matter along the magnetic field lines, the stellar field-disk interaction and a magnetized wind. Variations of stellar moment of inertia were included based on evolutionary models of PMS evolution of such stars. Stellar mass and magnetic moment were assumed constant during the PMS evolution. Values of the parameters describing the strength of the magnetic field, accretion rate and mass loss rate were taken from observations. In addition, the life time of the disk was varied. An equation describing the evolution of the rotation rate of a magnetic PMS star was derived and solved for different stellar masses. The results indicate that the interaction of the stellar ymagnetic field with circumstellar environment wipes out quickly a memory of the initial rotation period. The ZAMS period depends solely on the details of this interaction. Accretion spins up a star early in its PMS life and if the disk disappears right after that the star may keep its faster rotation until ZAMS and appear there as a Be star. A wide variety of parameters describing the evolution of stellar AM results in typical ZAMS rotation periods of magnetic stars several times longer than of normal stars. This agrees well with the observations. Under special circumstances a star can reach an exceptionally long rotation period of several years (up to 100 years). This requires a long PMS life time, an existence of a disk for only a part of the PMS phase and the wind in the strong magnetic field existing for the rest of the PMS life. The observations confirm indeed that extremely slowly rotating Ap stars are lower mass stars with strong magnetic fields.

St?pie?, K.

2000-01-01

303

Control of Hysteresis: Theory and Experimental Results.  

National Technical Information Service (NTIS)

Hysteresis in smart materials hinders the wider applicability of such materials in actuators. In this paper, a systematic approach for coping with hysteresis is presented. The method is illustrated through the example of controlling a commercially availab...

X. Tan R. Venkataraman P. S. Krishnaprasad

2001-01-01

304

Temperature Dependent Hysteresis Study in Polyvinylidene Fluoride.  

National Technical Information Service (NTIS)

An experimental study of temperature dependent ferroelectric hysteresis phenomena of polyvinylidene fluoride is presented. The temperature dependence of the remanent polarization and coercive field was measured from saturated ferroelectric hysteresis curv...

R. B. Olsen J. C. Hicks M. G. Broadhurst G. T. Davis

1983-01-01

305

Hysteresis Development in Superconducting Josephson Junctions.  

National Technical Information Service (NTIS)

The resistively and capacitive shunted junction model is used to investigate hysteresis development in superconducting Josephson junctions. Two empirical formulas that relate the hysteresis width and the quasi-particle diffusion length in terms of the jun...

T. F. Refai L. N. Shehata

1988-01-01

306

Atomic site sensitivity of the energy loss magnetic chiral dichroic spectra of complex oxides  

SciTech Connect

The quantitative analysis of magnetic oxide core level spectra can become complicated when the magnetic atoms are located at several nonequivalent atomic sites in the crystal. This is, for instance, the case for Fe atoms in magnetite, which are located in tetrahedral and octahedral atomic sites; in this case, the x-ray magnetic circular dichroic (XMCD) spectra recorded at the L{sub 2,3} edge of Fe contain contributions from the different nonequivalent atomic sites, which unfortunately cannot be separated. Energy loss magnetic chiral dichroic (EMCD) spectra are the transmission electron microscope analogies of the XMCD spectra. One of the important differences between these two techniques of magnetic analysis is that EMCD uses a fast electron beam instead of polarized light. The fast electrons behave like Bloch states in the sample, and the fine structure of the EMCD spectra is strongly influenced by channeling and dynamical diffraction effects. These effects can be adjusted by changing the experimental configuration. We use theoretical calculations, which include dynamical diffraction effects and in which electronic transitions are treated in the atomic multiplet formalism, to show that the relative weight of the Fe atoms in different nonequivalent atomic sites can be changed by a proper choice of the position of the detector and of the magnetite sample orientation and thickness. We conclude that EMCD spectra could be used to isolate the magnetic contribution of atoms in each of the nonequivalent atomic sites, which would not be possible with XMCD techniques.

Calmels, L. [CEMES-CNRS, Universite de Toulouse, BP 94347, F-31055 Toulouse Cedex 4 (France); Rusz, J. [Department of Physics and Astronomy, Uppsala University, PO Box 516, SE-75120 (Sweden)

2011-04-01

307

Calculating transport AC losses in stacks of high temperature superconductor coated conductors with magnetic substrates using FEM  

NASA Astrophysics Data System (ADS)

In this paper, the authors investigate the electromagnetic properties of stacks of high temperature superconductor (HTS) coated conductors with a particular focus on calculating the total transport AC loss. The cross-section of superconducting cables and coils is often modeled as a two-dimensional stack of coated conductors, and these stacks can be used to estimate the AC loss of a practical device. This paper uses a symmetric two dimensional (2D) finite element model based on the H formulation, and a detailed investigation into the effects of a magnetic substrate on the transport AC loss of a stack is presented. The number of coated conductors in each stack is varied from 1 to 150, and three types of substrate are compared: non-magnetic weakly magnetic and strongly magnetic. The non-magnetic substrate model is comparable with results from existing models for the limiting cases of a single tape (Norris) and an infinite stack (Clem). The presence of a magnetic substrate increases the total AC loss of the stack, due to an increased localized magnetic flux density, and the stronger the magnetic material, the further the flux penetrates into the stack overall. The AC loss is calculated for certain tapes within the stack, and the differences and similarities between the losses throughout the stack are explained using the magnetic flux penetration and current density distributions in those tapes. The ferromagnetic loss of the substrate itself is found to be negligible in most cases, except for small magnitudes of current. Applying these findings to practical applications, where AC transport current is involved, superconducting coils should be wound where possible using coated conductors with a non-magnetic substrate to reduce the total AC loss in the coil.

Ainslie, Mark D.; Flack, Tim J.; Campbell, Archie M.

2012-01-01

308

Analysis of rotor eddy current loss in fractional slot permanent magnet machine with solid rotor back-iron  

Microsoft Academic Search

This paper analyses the eddy current losses induced in the permanent magnets and rotor back-iron which is made of a solid piece of mild steel. Time-stepping finite element method (FEM) is employed for simulation of fractional slot surface-mounted permanent magnet brushless machine having 12 slots\\/10 poles and concentrated windings when the magnets are isolated\\/non-isolated and magnetized\\/unmagnetized. For the prototype machine

G. Ugalde; Z. Q. Zhu; J. Poza; A. Gonzalez

2010-01-01

309

Simulation of a vector hysteresis measurement system taking hysteresis into account by the vector Preisach model  

NASA Astrophysics Data System (ADS)

The paper deals with the numerical analysis of a rotational single sheet tester with round-shaped specimen (RRSST) which is now under construction. The measurement setup consists of an induction motor the rotor of which has been removed, and its windings have been replaced to a special two phase one which can generate homogeneous magnetic field inside the motor. The two orthogonal components of the magnetic field intensity and of the magnetic flux density vectors can be measured by H-coils and B-coils, respectively. The Finite Element Method (FEM) with the T, ?-? potential formulation has been applied in the simulations. The vector hysteresis property of the specimen has been approximated by the vector Preisach model. Finally, the nonlinear problem has been solved by the fixed-point technique. The aim of the present work is to focus on the design aspects of this kind of measurement system.

Kuczmann, Miklós

2008-02-01

310

Control designs for low-loss active magnetic bearings: Theory and implementation  

NASA Astrophysics Data System (ADS)

Active Magnetic Bearings (AMB) have been proposed for use in Electromechanical Flywheel Batteries. In these devices, kinetic energy is stored in a magnetically levitated flywheel which spins in a vacuum. The AMB eliminates all mechanical losses, however, electrical loss, which is proportional to the square of the magnetic flux, is still significant. For efficient operation, the flux bias, which is typically introduced into the electromagnets to improve the AMB stiffness, must be reduced, preferably to zero. This zero-bias (ZB) mode of operation cripples the classical control techniques which are customarily used and nonlinear control is required. As a compromise between AMB stiffness and efficiency, a new flux bias scheme is proposed called the generalized complementary flux condition (gcfc). A flux-bias dependent trade-off exists between AMB stiffness, power consumption, and power loss. This work theoretically develops and experimentally verifies new low-loss AMB control designs which employ the gcfc condition. Particular attention is paid to the removal of the singularity present in the standard nonlinear control techniques when operating in ZB. Experimental verification is conduced on a 6-DOF AMB reaction wheel. Practical aspects of the gcfc implementation such as flux measurement and flux-bias implementation with voltage mode amplifiers using IR compensation are investigated. Comparisons are made between the gcfc bias technique and the standard constant-flux-sum (cfs) bias method. Under typical operating circumstances, theoretical analysis and experimental data show that the new gcfc bias scheme is more efficient in producing the control flux required for rotor stabilization than the ordinary cfs bias strategy.

Wilson, Brian Christopher David

311

Early Prediction of Postmeningitic Hearing Loss in Children Using Magnetic Resonance Imaging  

PubMed Central

Objective To determine whether early gadolinium-enhanced magnetic resonance imaging (GdMRI) can reliably detect meningitic labyrinthitis and thereby predict which children are at high risk for hearing loss. Permanent sensorineural hearing loss (SNHL) remains a common sequela of bacterial meningitis, and early diagnosis of the associated suppurative labyrinthitis can be difficult, especially in critically ill, sedated patients and young children. Design Retrospective cohort study. Setting Tertiary pediatric hospital. Participants Twenty-three survivors of bacterial meningitis (median age, 15 months [range, 3 months–14 years]) who had undergone brain GdMRI during the acute disease and had subsequent ear-specific audiometric data. Main Outcome Measure Blinded to disease and outcome, a neuroradiologist rated the relative enhancement of each cochlea on T1-weighted images using a 4-point scale. Scores were then correlated with the degree of hearing loss on subsequent testing. Results Sensorineural hearing loss occurred in 15 of 46 ears (8 of 23 patients). Enhancement on GdMRI was detected in 13 of the 15 ears that later developed SNHL but was absent in all 31 unaffected ears. Thus, GdMRI was 87% sensitive and 100% specific for predicting which ears would develop permanent SNHL. In the subgroup with pneumococcal meningitis (n=15), GdMRI was 100% sensitive and 100% specific. Labyrinthine enhancement was detectable as early as 1 day after diagnosis. Conclusion Gadolinium-enhanced MRI detected meningitic labyrinthitis at early stages and accurately predicted which patients would later develop hearing loss.

Kopelovich, Jonathan C.; Germiller, John A.; Laury, Adrienne M.; Shah, Samir S.; Pollock, Avrum N.

2013-01-01

312

Advanced Theory of Driven Birdcage Resonator with Losses for Biomedical Magnetic Resonance Imaging and Spectroscopy  

PubMed Central

A complete time-dependent physics theory of symmetric unperturbed driven Hybrid Birdcage resonator was developed for general application. In particular, the theory can be applied for RF coil engineering, computer simulations of coil-sample interaction, etc. Explicit time dependence is evaluated for different forms of driving voltage. The major steps of the solution development are shown and appropriate explanations are given. Green’s functions and spectral density formula were developed for any form of periodic driving voltage. The concept of distributed power losses based on transmission line theory is developed for evaluation of local losses of a coil. Three major types of power losses are estimated as equivalent series resistances in the circuit of the Birdcage resonator. Values of generated resistances in Legs and End-Rings are estimated. An application of the theory is shown for many practical cases. Experimental curve of B1 field polarization dependence is measured for eight-sections Birdcage coil. It was shown, that the steady-state driven resonance frequencies do not depend on damping factor unlike the free oscillation (transient) frequencies. An equivalent active resistance is generated due to interaction of RF electromagnetic field with a sample. Resistance of the conductor (enhanced by skin effect), Eddy currents and dielectric losses are the major types of losses which contribute to the values of generated resistances. A biomedical sample for magnetic resonance imaging and spectroscopy is the source of the both Eddy current and dielectric losses of a coil. As demonstrated by the theory, Eddy currents losses is the major effect of coil shielding.

Novikov, Alexander

2010-01-01

313

Loss of plasma scaling with magnetic field, pressure and discharge current in a CUSP confined plasma  

NASA Astrophysics Data System (ADS)

The confinement properties of a low beta argon discharge plasma in a spindle cusp magnetic field was investigated. Plasma was produced by ionisation collisions by the electrons which were produced by thermionic emission of electrons. The central problem involved with plasma confinement by a cusped magnetic field is the loss of particles along the flux lines. Electron and ion leak widths were studied in the ring and point cusps and measured over a range of magnetic field strengths (B), neutral pressures (P) and discharge currents (I_d). It was found that the leak width was reduced with increase in I_d and B. The ion leak widths were found to be larger than the electron leak widths. The normalised effect of magnetic field and pressure on ion and electron leak widths in cusps are reported, compared and discussed. The dependence of electron and ion leak widths on plasma densities were also studied. At very low pressures, high plasma densities and high magnetic field strengths, a quasineutrality condition was attained.

Anukaliani, A.; Selvarajan, V.

2001-09-01

314

Low loss pole configuration for multi-pole homopolar magnetic bearings  

NASA Technical Reports Server (NTRS)

A new pole configuration for multi-pole homopolar bearings proposed in this invention reduces rotational losses caused by eddy-currents generated when non-uniform flux distributions exist along the rotor surfaces. The new homopolar magnetic bearing includes a stator with reduced pole-to-pole and exhibits a much more uniform rotor flux than with large pole-to-pole gaps. A pole feature called a pole-link is incorporated into the low-loss poles to provide a uniform pole-to-pole gap and a controlled path for pole-to-pole flux. In order to implement the low-loss pole configuration of magnetic bearings with small pole-to-pole gaps, a new stator configuration was developed to facilitate installation of coil windings. The stator was divided into sector shaped pieces, as many pieces as there are poles. Each sector-shaped pole-piece can be wound on a standard coil winding machine, and it is practical to wind precision layer wound coils. To achieve maximum actuation efficiency, it is desirable to use all the available space for the coil formed by the natural geometric configuration. Then, the coils can be wound in a tapered shape. After winding, the sectored-pole-pieces are installed into and fastened by bonding or other means, to a ring of material which encloses the sectored-pole-pieces, forming a complete stator.

Blumenstock, Kenneth A. (Inventor); Hakun, Claef F. (Inventor)

2001-01-01

315

Modeling of stochastic magnetic flux loss from the edge of a poloidally diverted tokamak  

NASA Astrophysics Data System (ADS)

A field line integration code is used to study the loss of edge poloidal magnetic flux due to stochastic magnetic fields produced by an error field correction coil (C-coil) in DIII-D [J. L. Luxon, Nucl. Fusion 42, 614 (2002)] for various plasma shapes, coil currents and edge magnetic shear profiles. We find that the boundary of a diverted tokamak is more sensitive to stochastic flux loss than a nondiverted tokamak. The C-coil has been used to produce a stochastic layer in an ohmic diverted discharge with characteristics similar to those seen in stochastic boundary experiments in circular limiter ohmic plasmas, including (1) an overall increase in recycling, (2) a broadening of the recycling profile at the divertor, and (3) a flattening of the boundary profiles over the extent of the stochastic layer predicted by the field line integration code. Profile flattening consistent with field line integration results is also seen in some high performance discharges with edge transport barriers. The prediction of a significant edge stochastic layer even in discharges with high performance and edge radial transport barriers indicates that either the self-consistent plasma response heals the stochastic layer or that edge stochastic layers are compatible with edge radial transport barriers.

Evans, T. E.; Moyer, R. A.; Monat, P.

2002-12-01

316

Hysteretic ac loss in a coated superconductor subjected to oscillating magnetic fields: ferromagnetic effect and frequency dependence  

NASA Astrophysics Data System (ADS)

Numerical simulations of the hysteretic ac loss in a coated superconductor with a more realistic version of the architecture were performed via the finite-element technique in the presence of an oscillating magnetic field. The coated superconductor was electromagnetically modeled by resorting to the quasistatic approximation of a vector potential approach in conjunction with nonlinear descriptions of the superconducting layer and the ferromagnetic substrate therein by a power-law model and the Langevin equation, respectively. A diverse effect of the ferromagnetic substrate on the hysteretic ac loss, depending on the strength of the applied magnetic field, was displayed, and its underlying cause was identified. The dependence of the hysteretic ac loss on the applied frequency is found to be related to a critical amplitude of the applied magnetic field, and the eddy-current loss dissipated in the metal coatings becomes prominent as the frequency increases only at high applied magnetic fields.

Ma, Guang-Tong

2014-06-01

317

Efficient Computational Model of Hysteresis  

NASA Technical Reports Server (NTRS)

A recently developed mathematical model of the output (displacement) versus the input (applied voltage) of a piezoelectric transducer accounts for hysteresis. For the sake of computational speed, the model is kept simple by neglecting the dynamic behavior of the transducer. Hence, the model applies to static and quasistatic displacements only. A piezoelectric transducer of the type to which the model applies is used as an actuator in a computer-based control system to effect fine position adjustments. Because the response time of the rest of such a system is usually much greater than that of a piezoelectric transducer, the model remains an acceptably close approximation for the purpose of control computations, even though the dynamics are neglected. The model (see Figure 1) represents an electrically parallel, mechanically series combination of backlash elements, each having a unique deadband width and output gain. The zeroth element in the parallel combination has zero deadband width and, hence, represents a linear component of the input/output relationship. The other elements, which have nonzero deadband widths, are used to model the nonlinear components of the hysteresis loop. The deadband widths and output gains of the elements are computed from experimental displacement-versus-voltage data. The hysteresis curve calculated by use of this model is piecewise linear beyond deadband limits.

Shields, Joel

2005-01-01

318

Effect of toothless stator design and core and stator conductors eddy current losses in permanent magnet generators  

Microsoft Academic Search

Some advantages of toothless stator design in high-speed permanent magnet generators are presented. A computer-aided method was implemented to study the effect of stator teeth on the eddy current loss in the stator conductors as well as the core loss in the laminations of high-speed permanent magnet generators. The computer-aided method was applied to a 75 kVA, 208 V, 400

A. A. Arkadan; R. Vyas; J. G. Vaidya; M. J. Shah

1992-01-01

319

The effect of coolant loss on current leads for superconducting magnets  

NASA Astrophysics Data System (ADS)

In this paper, the recovery of current leads for superconducting magnets after loss of coolant is examined. It is found that if a lead is without cooling for longer than a time in which a lead can completely lose coolant and still recover, thermal runaway can be prevented by an increase in cooling or a decrease in current through the lead. It is evident that designing a lead away from its optimal values can make the lead significantly less susceptible to problems of thermal runaway.

Chyba, C.; Hyman, L. G.; Roberts, L.

1981-10-01

320

Transient loss of plasma from a theta pinch having an initially reversed magnetic field  

SciTech Connect

The results of an experimental study of the transient loss of plasma from a 25-cm-long theta pinch initially containing a reversed trapped magnetic field are presented. The plasma, amenable to MHD analyses, was a doubly ionized helium plasma characterized by an ion density N/sub i/ = 2 x 10/sup 16/ cm/sup -3/ and an ion temperature T/sub i/ = 15 eV at midcoil and by N/sub i/ = 0.5 x 10/sup 16/ cm/sup -3/ and T/sub i/ = 6 eV at a position 2.5 cm beyond the end of the theta coil.

Heidrich, J. E.

1981-01-01

321

Physical interpretation of hysteresis loops: Micromagnetic modeling of fine particle magnetite  

Microsoft Academic Search

Hysteresis measurements have become an important part of characterizing magnetic behavior of rocks in paleomagnetic studies. Theoretical interpretation is often difficult owing to the complexity of mineral magnetism and published data sets demonstrate remanence and coercivity behavior that is currently unexplained. In the last decade, numerical micromagnetic modeling has been used to simulate magnetic particles. Such simulations reveal the existence

Lisa Tauxe; H. Neal Bertram; Christian Seberino

2002-01-01

322

Triangular hysteresis loops in the spin-rotation region of orthoferrites  

NASA Astrophysics Data System (ADS)

A theory is proposed that qualitatively explains the shapes of the hysteresis loops in orthoferrites within the temperature interval of the magnetic reorientation transition. Triangular loops result from the strong temperature dependence of both the magnetic moment and the magnetic domain wall structure.

Bazaliy, Ya. B.; Tsymbal, L. T.

2010-08-01

323

Particle Events as a Possible Source of Large Ozone Loss during Magnetic Polarity Transitions  

NASA Technical Reports Server (NTRS)

The energy deposition in the mesosphere and stratosphere during large extraterrestrial charged particle precipitation events has been known for some time to contribute to ozone losses due to the formation of potential ozone destroying species like NO(sub x), and HO(sub x). These impacts have been measured and can be reproduced with chemistry models fairly well. In the recent past, however, even the impact of the largest solar proton events on the total amount of ozone has been small compared to the dynamical variability of ozone, and to the anthropogenic induced impacts like the Antarctic 'ozone hole'. This is due to the shielding effect of the magnetic field. However, there is evidence that the earth's magnetic field may approach a reversal. This could lead to a decrease of magnetic field strength to less than 25% of its usual value over a period of several centuries . We show that with realistic estimates of very large solar proton events, scenarios similar to the Antarctic ozone hole of the 1990s may occur during a magnetic polarity transition.

vonKoenig, M.; Burrows, J. P.; Chipperfield, M. P.; Jackman, C. H.; Kallenrode, M.-B.; Kuenzi, K. F.; Quack, M.

2002-01-01

324

Torque and efficiency calculation of an interior permanent magnet motor considering harmonic iron losses of both the stator and rotor  

Microsoft Academic Search

A method to estimate characteristics of interior permanent magnet motors considering effects of iron loss is introduced. The equivalent circuit parameters including the iron loss resistance are calculated as functions of d-q axis currents by the finite-element method with the consideration of movement of the rotor. The characteristics of the motor are calculated from the equivalent circuit. By using this

Katsumi Yamazaki

2003-01-01

325

Nonmonotonic behavior of magnetoresistance, R(H) hysteresis, and low-temperature heat capacity of the BaPb{sub 0.75}Bi{sub 0.25}O{sub 3} superconductor in a magnetic field: Possible manifestations of phase separation  

SciTech Connect

The transport properties (R(T) and R(H) dependences at various values of the transport current in magnetic fields up to 65 kOe) and low-temperature heat capacity in magnetic fields up to 90 kOe of the BaPb{sub 0.75}Bi{sub 0.25}O{sub 3} superconductor (T{sub C} {approx} 11.3 K) are investigated with the goal of clarifying the mechanisms determining the nonmonotonic behavior and hysteresis of its magnetoresistance R(H). The type of R(H) hysteretic dependences for BaPb{sub 0.75}Bi{sub 0.25}O{sub 3} is analogous to that observed in granular high-T{sub c} superconductors (HTSCs); however, unlike classical HTSC systems, the field width of the magnetoresistance hysteresis loop for polycrystalline BaPb{sub 0.75}Bi{sub 0.25}O{sub 3} depends on the transport current. This means that although the mechanisms responsible for the magnetoresistance hysteresis (the influence of the magnetic flux trapped in superconducting regions on the effective field in Josephson interlayers) are identical in these objects, the transport current in BaPb{sub 0.75}Bi{sub 0.25}O{sub 3} may considerably affect the diamagnetic response of the superconductor. A considerable effect of transport current on the field in which the R(H) dependences have a peak and exhibit hysterestic properties is observed. Such a behavior can be adequately interpreted using the model of the spatially inhomogeneous superconductor-insulator state proposed by Gorbatsevich et al. [JETP Lett. 52, 95 (1990)]. The nonmonotonic dependence of quantity C/T (C is the heat capacity) on the magnetic field discovered in the present study also agrees with the conclusions based on this model.

Balaev, D. A., E-mail: smp@iph.krasn.ru; Dubrovskiy, A. A.; Popkov, S. I.; Shaikhutdinov, K. A. [Russian Academy of Sciences, Kirenskii Institute of Physics, Siberian Branch (Russian Federation); Mart'yanov, O. N. [Russian Academy of Sciences, Boreskov Institute of Catalysis, Siberian Branch (Russian Federation); Petrov, M. I. [Russian Academy of Sciences, Kirenskii Institute of Physics, Siberian Branch (Russian Federation)

2010-04-15

326

Analysis of the AC loss measurements on the one-metre dipole model magnets for the CERN LHC  

Microsoft Academic Search

Superconducting single- and twin-aperture dipole model magnets for the future CERN Large Hadron Collider have been built in industry and tested at CERN. In this paper the results of AC loss measurements are presented that are performed on 6 magnets all having a bore of 50 mm diameter and coils wound of 17 mm wide superconducting cables. The cables that

A. P. Verweij; D. Leroy; L. Walckiers; R. Wolf; H. H. J. ten Kate

1994-01-01

327

Simulations of the Photospheric Magnetic Activity and Outer Atmospheric Radiative Losses of Cool Stars Based on Characteristics of the Solar Magnetic Field  

Microsoft Academic Search

The observed disk-integrated radiative losses from the outer atmospheres of stars with convective envelopes are determined by the distribution of magnetic field over their surfaces. Earlier modeling of the random walk transport of the solar photospheric magnetic field with the classical Leighton model has given us insight into how field patterns form and evolve on large scales. This paper presents

Carolus J. Schrijver

2001-01-01

328

Hysteresis heating based induction bonding of composite materials  

NASA Astrophysics Data System (ADS)

The viability of using magnetic particulate susceptor materials for induction heating during bonding of polymer matrix composites is well established in this work. The unique ability to offer localized heating, geometric flexibility, and self-controlled temperature is the major advantage of this technique. Hysteresis heating is tailored through careful design of the microstructure of nickel particulate polymer films (Ni/PSU). An excellent heating rate can be attained in the frequency range of 1 to 10 MHz for particle volume fraction below percolation of 0.26. The diameter of nickel particle should be kept between 65 nm to 10 mum to ensure multi-domain heating, Curie temperature control, negligible shielding effect, minimum eddy current, and slight particle oxidation. The hysteresis heating behavior of the Ni/PSU films is found to be volumetric in nature and proportional to the cube of applied magnetic field. On the other hand, heat generation is inversely proportional to the size of the multi-domain particles. The frequency effect; however, provide maximum heat generation at the domain wall resonance frequency. Curie temperature control is observed when sufficiently high magnetic fields (˜138 Oe) are applied. The master curves of AC heat generation in Ni/PSU films are established and show a strong particle size effect. Hysteresis fusion bonding of glass/polyphenylene sulfide thermoplastic composites using a magnetic film as the thermoplastic adhesive shows that the bond strength of hysteresis-welded materials is comparable to that of autoclave-welded materials while offering an order of magnitude reduction in cycle time. The relative contribution of the intimate contact and healing mechanisms to the fusion bonding process indicates that hysteresis bonding is controlled by intimate contact. The macroscopic failure modes vary from mostly adhesive composite/film (low bond strength) to a combination of adhesive composite/film, cohesive film, cohesive composite and mostly cohesive composite (high bond strength). Inspection of the microscopic failure at the nickel particle/polymer interface in the film indicates quasi-brittle failure mode. The amount of adhesive failure increases with decreasing particle size and increasing particle volume fraction. The XPS peaks confirm nickel oxide in the form of NiO on the failure surface of particle/polymer debonding of hysteresis susceptor film.

Suwanwatana, Witchuda

329

Resistive hysteresis in BiFeO 3 thin films  

Microsoft Academic Search

Capacitor-like Au\\/BiFeO3\\/SrRuO3 thin film with (111) orientation was grown on the SrTiO3 (111) substrate by radio frequency magnetic sputtering. It shows a resistive switching behavior, where a stable hysteresis in current–voltage curve was well developed by applying an optimum voltage at room temperature, and it reached the saturation at a bias voltage of 8V. The Child's law in Vmax?0 direction

Jiagang Wu; John Wang; Dingquan Xiao; Jianguo Zhu

2011-01-01

330

Research on the dynamic hysteresis loop model of the residence times difference (RTD)-fluxgate.  

PubMed

Based on the core hysteresis features, the RTD-fluxgate core, while working, is repeatedly saturated with excitation field. When the fluxgate simulates, the accurate characteristic model of the core may provide a precise simulation result. As the shape of the ideal hysteresis loop model is fixed, it cannot accurately reflect the actual dynamic changing rules of the hysteresis loop. In order to improve the fluxgate simulation accuracy, a dynamic hysteresis loop model containing the parameters which have actual physical meanings is proposed based on the changing rule of the permeability parameter when the fluxgate is working. Compared with the ideal hysteresis loop model, this model has considered the dynamic features of the hysteresis loop, which makes the simulation results closer to the actual output. In addition, other hysteresis loops of different magnetic materials can be explained utilizing the described model for an example of amorphous magnetic material in this manuscript. The model has been validated by the output response comparison between experiment results and fitting results using the model. PMID:24002230

Wang, Yanzhang; Wu, Shujun; Zhou, Zhijian; Cheng, Defu; Pang, Na; Wan, Yunxia

2013-01-01

331

Research on the Dynamic Hysteresis Loop Model of the Residence Times Difference (RTD)-Fluxgate  

PubMed Central

Based on the core hysteresis features, the RTD-fluxgate core, while working, is repeatedly saturated with excitation field. When the fluxgate simulates, the accurate characteristic model of the core may provide a precise simulation result. As the shape of the ideal hysteresis loop model is fixed, it cannot accurately reflect the actual dynamic changing rules of the hysteresis loop. In order to improve the fluxgate simulation accuracy, a dynamic hysteresis loop model containing the parameters which have actual physical meanings is proposed based on the changing rule of the permeability parameter when the fluxgate is working. Compared with the ideal hysteresis loop model, this model has considered the dynamic features of the hysteresis loop, which makes the simulation results closer to the actual output. In addition, other hysteresis loops of different magnetic materials can be explained utilizing the described model for an example of amorphous magnetic material in this manuscript. The model has been validated by the output response comparison between experiment results and fitting results using the model.

Wang, Yanzhang; Wu, Shujun; Zhou, Zhijian; Cheng, Defu; Pang, Na; Wan, Yunxia

2013-01-01

332

Mass-loss rates, ionization fractions, shock velocities, and magnetic fields of stellar jets  

NASA Technical Reports Server (NTRS)

In this paper we calculate emission-line ratios from a series of planar radiative shock models that cover a wide range of shock velocities, preshock densities, and magnetic fields. The models cover the initial conditions relevant to stellar jets, and we show how to estimate the ionization fractions and shock velocities in jets directly from observations of the strong emission lines in these flows. The ionization fractions in the HH 34, HH 47, and HH 111 jets are approximately 2%, considerably smaller than previous estimates, and the shock velocities are approximately 30 km/s. For each jet the ionization fractions were found from five different line ratios, and the estimates agree to within a factor of approximately 2. The scatter in the estimates of the shock velocities is also small (+/- 4 km/s). The low ionization fractions of stellar jets imply that the observed electron densities are much lower than the total densities, so the mass-loss rates in these flows are correspondingly higher (approximately greater than 2 x 10(exp -7) solar mass/yr). The mass-loss rates in jets are a significant fraction (1%-10%) of the disk accretion rates onto young stellar objects that drive the outflows. The momentum and energy supplied by the visible portion of a typical stellar jet are sufficient to drive a weak molecular outflow. Magnetic fields in stellar jets are difficult to measure because the line ratios from a radiative shock with a magnetic field resemble those of a lower velocity shock without a field. The observed line fluxes can in principle indicate the strength of the field if the geometry of the shocks in the jet is well known.

Hartigan, Patrick; Morse, Jon A.; Raymond, John

1994-01-01

333

Hysteresis modeling of sequential application of orthogonal fields  

NASA Astrophysics Data System (ADS)

In a cumulative effort to characterize the sizes, shapes, and distributions of the domains of the structurally superior high strength steels, a characteristic magnetization measurement and a Preisach model are presented to explain and model the distinctive trends observed in the data. The study investigates the effect of a constant transverse magnetic field and a cycling longitudinal magnetic field, applied sequentially, on the major hysteresis loop of solid cylinders of high strength steel. A coupled-hysteron vector Preisach model is extended to model the longitudinal magnetization of the samples under the effect of an applied transverse field. Insights about the microstructure of the rods and the contribution of different domains and magnetization mechanisms to the magnetic response are drawn.

ElBidweihy, H.; Della Torre, E.; Burgy, C. D.

2014-05-01

334

A hysteresis model for a vanadium dioxide transition-edge microbolometer  

Microsoft Academic Search

This paper presents the adaptation of the Preisach model, originally developed for magnetic hysteresis, to describe mathematically the hysteresis in the resistance-temperature characteristics of vanadium-dioxide (VO2) thin film radiation sensors. The necessary and sufficient conditions for the applicability of the Preisach model to a VO2 film sensor are experimentally verified. Experimentally measured characteristics are compared with those given by the

L. A. L. de Almeida; G. S. Deep; A. M. N. Lima; H. F. Neff; R. C. S. Freire

2001-01-01

335

A frequency-dependent hysteresis model for power ferrites up to curie temperatures  

Microsoft Academic Search

A methodology is presented for the modeling of hysteresis in bulk manganese-zinc (MnZn) power ferrites over the practical ranges of amplitude and frequency from room temperature up to their Curie temperatures. The model parameters of an existing frequency-dependent hysteresis model are related to the typical magnetic properties such as the saturation flux density, the coercive force, and initial permeability. Temperature

Paiboon Nakmahachalasint; Khai D. T. Ngo; Loc Vu-Quoc

2004-01-01

336

Magnetic Resonance Measurement of Turbulent Kinetic Energy for the Estimation of Irreversible Pressure Loss in Aortic Stenosis  

PubMed Central

OBJECTIVES The authors sought to measure the turbulent kinetic energy (TKE) in the ascending aorta of patients with aortic stenosis and to assess its relationship to irreversible pressure loss. BACKGROUND Irreversible pressure loss caused by energy dissipation in post-stenotic flow is an important determinant of the hemodynamic significance of aortic stenosis. The simplified Bernoulli equation used to estimate pressure gradients often misclassifies the ventricular overload caused by aortic stenosis. The current gold standard for estimation of irreversible pressure loss is catheterization, but this method is rarely used due to its invasiveness. Post-stenotic pressure loss is largely caused by dissipation of turbulent kinetic energy into heat. Recent developments in magnetic resonance flow imaging permit noninvasive estimation of TKE. METHODS The study was approved by the local ethics review board and all subjects gave written informed consent. Three-dimensional cine magnetic resonance flow imaging was used to measure TKE in 18 subjects (4 normal volunteers, 14 patients with aortic stenosis with and without dilation). For each subject, the peak total TKE in the ascending aorta was compared with a pressure loss index. The pressure loss index was based on a previously validated theory relating pressure loss to measures obtainable by echocardiography. RESULTS The total TKE did not appear to be related to global flow patterns visualized based on magnetic resonance–measured velocity fields. The TKE was significantly higher in patients with aortic stenosis than in normal volunteers (p < 0.001). The peak total TKE in the ascending aorta was strongly correlated to index pressure loss (R2 = 0.91). CONCLUSIONS Peak total TKE in the ascending aorta correlated strongly with irreversible pressure loss estimated by a well-established method. Direct measurement of TKE by magnetic resonance flow imaging may, with further validation, be used to estimate irreversible pressure loss in aortic stenosis.

Dyverfeldt, Petter; Hope, Michael D.; Tseng, Elaine E.; Saloner, David

2013-01-01

337

Magnetic core test stand for energy loss and permeability measurements at a high constant magnetization rate and test results for nanocrystalline and ferrite materials.  

PubMed

A test stand was developed to measure the energy losses and unsaturated permeability of toroidal magnetic cores, relevant to applications of magnetic switching requiring a constant magnetization rate of the order of 1-10 T/micros. These applications in pulsed power include linear induction accelerators, pulse transformers, and discharge switches. The test stand consists of a coaxial transmission line pulse charged up to 100 kV that is discharged into a magnetic core load. Suitable diagnostics measure the voltage across and the current through a winding on the magnetic core load, from which the energy losses and unsaturated permeability are calculated. The development of the test stand is discussed, and test results for ferrite CN20 and the nanocrystalline material Finemet FT-1HS are compared to demonstrate the unique properties of a nanocrystalline material. The experimental data are compared with published data in a similar parameter space to demonstrate the efficacy of the experimental methods. PMID:19044442

Burdt, Russell; Curry, Randy D

2008-09-01

338

Synthesis of bulk FeHfBO soft magnetic materials and its loss characterization at megahertz frequency  

NASA Astrophysics Data System (ADS)

Magnetic core materials with low loss, high saturation magnetization, large permeability, and operating frequency above 1 MHz are in high demands for the next generation of miniaturized power electronics. Amorphous FeHfB ribbons with thickness around 20 ?m have been fabricated through melt-spinning. Different heat treatments were performed on the FeHfB ribbons, and the relations among heat treatments, microstructure, and magnetic properties have been explored. Properties such as coercivity (Hc) of 2.0 Oe and saturation magnetic flux density (BS) of 1.2 T have been achieved in samples with exchange coupling. The losses can be minimized by balancing the hysteretic and eddy current losses and can be further reduced with additional magnetic field annealing. At 5 MHz with peak magnetic flux density of 20 mT, the materials show core losses comparable to the best ferrites, but with higher permeability value of about 200 and superior saturation induction of more than 1 T.

Zhou, Yang; Kou, Xiaoming; Mu, Mingkai; Warsi Muhammad, Asif; Lin, Shuo; Harris, Brendan S.; Parsons, Paul E.; Zhu, Hao; Lee, Fred C.; Xiao, John Q.

2013-05-01

339

New Tc-tuned magnetic nanoparticles for self-controlled hyperthermia  

NASA Astrophysics Data System (ADS)

Manganese perovskite nanoparticles of the XRD size in the range of 30-49 nm were synthesized via sol-gel technique employing citric acid and ethylene glycol. Their magnetic properties were investigated in the static and alternating magnetic fields. Particular attention was paid to the relation between the size of particles and resulting magnetic power losses, measured by the calorimetric heating experiments on the stable water suspensions and of the hysteresis loops in the alternating fields on powdered samples.

Pollert, E.; Knížek, K.; Maryško, M.; Kašpar, P.; Vasseur, S.; Duguet, E.

2007-09-01

340

Understanding the Link Between Nanoscale Microstructural Features and Dynamic Hysteresis Phenomena  

SciTech Connect

A Nd–Dy–Fe–B alloy was designed to exhibit high coercivity and optimum loop shapes utilizing a combination of intrinsic and extrinsic alloy design principles. After achieving these initial goals, conventional structural analysis using X-ray and TEM could explain the salient features of the observed hysteresis behavior. However, greater understanding could be gained on the complex dynamic behavior of hysteresis through the exploitation of a new recoil technique that was developed, which focuses on switching field distributions arising from irreversible magnetic behavior. Utilizing this approach, we have successfully linked specific magnetic reversal behavior with distinct magnetic phases that have characteristic microstructural length scales. This new approach may become a powerful tool for the study of the structure–property–hysteresis behavior of hard magnetic materials.

Meacham, Brian Eugene; Branagan, Daniel James; Shield, J. E.

2004-06-01

341

Mössbauer spectroscopy, magnetic characteristics, and reflection loss analysis of nickel-strontium substituted cobalt ferrite nanoparticles  

NASA Astrophysics Data System (ADS)

In current research work, Co1-xNix/2Srx/2Fe2O4 (x = 0-1 in a step of 0.2) ferrite nanoparticles were synthesized by a sol-gel method. According to the evolution in the subspectral areas obtained from Mössbauer spectroscopy, it was found that the relaxing iron belongs mostly to the site B, since the Mössbauer fraction of site A does not vary appreciably. With an increase in Ni-Sr substitution contents in cobalt ferrite, the coercivity and saturation of magnetization decrease. Variation of reflection loss versus frequency in microwave X-band demonstrates that the reflection peak shifts to lower frequency by adding substituted cations and the synthesized nanoparticles can be considered for application in electromagnetic wave absorber technology.

Ghasemi, Ali; Paesano, Andrea; Cerqueira Machado, Carla Fabiana; Shirsath, Sagar E.; Liu, Xiaoxi; Morisako, Akimitsu

2014-05-01

342

Low-loss directional cloaks without superluminal velocity or magnetic response.  

PubMed

The possibility of making an optically large (many wavelengths in diameter) object appear invisible has been a subject of many recent studies. Exact invisibility scenarios for large (relative to the wavelength) objects involve (meta)materials with superluminal phase velocity [refractive index (RI) less than unity] and/or magnetic response. We introduce a new approximation applicable to certain device geometries in the eikonal limit: piecewise-uniform scaling of the RI. This transformation preserves the ray trajectories but leads to a uniform phase delay. We show how to take advantage of phase delays to achieve a limited (directional and wavelength-dependent) form of invisibility that does not require loss-ridden (meta)materials with superluminal phase velocities. PMID:23114333

Urzhumov, Yaroslav; Smith, David R

2012-11-01

343

Simple Model Analysis of Hysteresis Phenomenon of Gas Discharge Plasma  

NASA Astrophysics Data System (ADS)

The hysteresis and multiple-steady states of gas discharge plasma are analyzed by a simple model of chemical-reaction system. In our analysis the emergence of multiple-steady states is explained by using a fact that a function describing the energy balance has three different real roots. The condition that the function has three roots depends on the ratio of the bulk energy increase to the surface energy loss of plasma. The criterion of taking place of the jump between two steady states is examined in a similar manner to order-disorder transition. The critical parameter contains the non-thermodynamic variables such as conductivity and surface quantities. Stabilities of three obtained solutions are discussed by using linear analysis of differential equations and we find that a root represents a saddle point and other two roots represent stable points. The first step to explain the hysteresis phenomenon in Ar gas discharge plasma is found.

Matsunaga, Yasushi; Kato, Tomokazu

1997-01-01

344

Hysteresis modeling of synchronous reluctance motor considering PWM input voltage  

NASA Astrophysics Data System (ADS)

This paper deals with the hysteresis characteristics analysis in PWM fed synchronous reluctance motor (SynRM) using a coupled finite element method (FEM) and Preisach's modeling, which is presented to analyze the characteristics under the effect of saturation and hysteresis loss. With regard to the PWM characteristics, a vector control inverter is combined with an analysis tool. Also, a moving mesh technique is used with regard to rotation due to velocity. The focus of this paper is the applied method of Preisach modeling for rotating machines and the characteristics analysis of a SynRM using the proposed method of analysis. For the propriety of proposed method of analysis, TMS320C31 DSP-installed experimental devices are used. And then, computer simulation and experimental result for the i- ? loci, speed, current response, show the propriety of the proposed method. The characteristic analysis is performed in relation to the maximum efficiency condition for a SynRM in simulation and experiment.

Lee, J. H.; Kim, J. C.; Hyun, D. S.

2000-01-01

345

Tunable negligible-loss energy transfer between dipolar-coupled magnetic disks by stimulated vortex gyration  

PubMed Central

A wide variety of coupled harmonic oscillators exist in nature. Coupling between different oscillators allows for the possibility of mutual energy transfer between them and the information-signal propagation. Low-energy input signals and their transport with negligible energy loss are the key technological factors in the design of information-signal processing devices. Here, utilizing the concept of coupled oscillators, we experimentally demonstrated a robust new mechanism for energy transfer between spatially separated dipolar-coupled magnetic disks - stimulated vortex gyration. Direct experimental evidence was obtained by a state-of-the-art experimental time-resolved soft X-ray microscopy probe. The rate of energy transfer from one disk to the other was deduced from the two normal modes' frequency splitting caused by dipolar interaction. This mechanism provides the advantages of tunable energy transfer rates, low-power input signals and negligible energy loss in the case of negligible intrinsic damping. Coupled vortex-state disks might be implemented in applications for information-signal processing.

Jung, Hyunsung; Lee, Ki-Suk; Jeong, Dae-Eun; Choi, Youn-Seok; Yu, Young-Sang; Han, Dong-Soo; Vogel, Andreas; Bocklage, Lars; Meier, Guido; Im, Mi-Young; Fischer, Peter; Kim, Sang-Koog

2011-01-01

346

Complex permeability and core loss of soft magnetic Fe-based nanocrystalline powder cores  

NASA Astrophysics Data System (ADS)

Rapidly quenched ribbons of Fe73Cu1Nb3Si16B7 were ball milled and cryomilled to get powder and warm consolidated to get bulk compacts. The data presented here are relative to different experimental procedures, one corresponding to milling at room temperature (sample R1) and the other corresponding to cryomilling at temperature of liquid nitrogen (sample L1). It was found that the properties of the initial powder influenced the density, the electrical resistivity and electromagnetic properties of the resulting bulk alloys. Permeability and core loss are structure sensitive and depend on factors such as powder size and shape, porosity, purity, and internal stress. Permeability spectra of sample R1 decreases with increasing the frequency and its values are larger than that for sample L1 at low frequencies. On the other hand the permeability of sample L1 remains steady up to 1 kHz and at certain frequency is larger than that for sample R1. Also there are different frequency dependences of the imaginary parts of permeability and loss factor, respectively. The cryomilling of the amorphous ribbon positively influences on the AC magnetic properties at higher frequencies (above 100 Hz) of resulting bulk sample.

Füzerová, Jana; Füzer, Ján; Kollár, Peter; Bureš, Radovan; Fáberová, Mária

2013-11-01

347

Thermal Hysteresis Analysis of MEMS Pressure Sensors  

Microsoft Academic Search

Thermal hysteresis reduction is usually a difficult task to tackle for micromachined pressure sensors especially when shrinking piezoresistive transducer (PRT) sensing elements. Since thermal hysteresis involves the entire thermal cycling history and complicated material properties that vary with temperatures, viscoplastic deformation makes the problem very complicated when dealing with high-precision sensor signals. The approach to simplify and quickly resolve the

J. Albert Chiou; Steven Chen

2005-01-01

348

Thermohaline circulation hysteresis: A model intercomparison  

Microsoft Academic Search

We present results from an intercomparison of 11 different climate models of intermediate complexity, in which the North Atlantic Ocean was subjected to slowly varying changes in freshwater input. All models show a characteristic hysteresis response of the thermohaline circulation to the freshwater forcing; which can be explained by Stommel's salt advection feedback. The width of the hysteresis curves varies

Stefan Rahmstorf; Michel Crucifix; Andrey Ganopolski; Hugues Goosse; Igor Kamenkovich; Reto Knutti; Gerrit Lohmann; Robert Marsh; Lawrence A. Mysak; Zhaomin Wang; Andrew J. Weaver

2005-01-01

349

A theory of DE hysteresis loop  

Microsoft Academic Search

The D-E hysteresis loop of ferroelectrics is theoretically studied on the basis of the Avrami model, extended for the case of applied field dependent sidewise velocity. The exponent for the frequency dependence of the extended volume is obtained. The exponent of the area of hysteresis loop, with respect to the frequncy, is also obtained.

Yoshihiro Ishibashi; Hiroshi Orihara

1995-01-01

350

Corneal hysteresis following descemetorhexis with endokeratoplasty  

Microsoft Academic Search

The corneal biomechanical properties following descemetorhexis with endokeratoplasty (DXEK) and in normal subjects were studied\\u000a in 100 eyes (12 DXEK and 88 age-matched normal subjects). Corneal hysteresis measurements were significantly lower in DXEK\\u000a vs normal subjects. DXEK has a direct effect on corneal hysteresis and corneal biomechanical properties of the human cornea.

Thomas John; David A. Taylor; Mitsugu Shimmyo; Bruce E. Siskowski

2007-01-01

351

Dependence of the relativistic electron energy spectra during the magnetic storm recovery phase on the acceleration and loss rates  

NASA Astrophysics Data System (ADS)

The dependence of the particle energy spectra on the acceleration and loss rates is studied based on the analytical solutions to the equation for the particle distribution function, taking into account diffusion in the momentum space (stochastic acceleration) and loss (due to particle escape from the acceleration region). The energy spectra and time dynamics of the MeV electron fluxes, observed based on the geostationary satellite data during the prolonged recovery phases of the known magnetic storms of June 11, 1980 and November 3-4, 1993, have been analytically described. The acceleration and loss rates have been estimated for these storms. A comparison is performed with the preciously studied energy spectra of MeV electrons and with the acceleration and loss rates during the recovery phases of the magnetic storms of January 10, 1997, and April 6, 2000.

Bakhareva, M. F.; Orlova, K. G.

2009-10-01

352

The effects of stress on a ferromagnet on a minor hysteresis loop  

Microsoft Academic Search

Reversible and irreversible changes in magnetization due to stress on a minor hysteresis loop were studied at various magnetic field strengths. It was found that the irreversible changes were not always directed toward the principal anhysteretic, contrary to Jiles and Atherton's hypothesis (1986). Also, two different demagnetization methods were used within the minor loop to test the existence of postulated

DAVID L. ATHERTON; V. Ton

1990-01-01

353

Critical state and magnetization loss in multifilamentary superconducting wire solved through the commercial finite element code ANSYS  

NASA Astrophysics Data System (ADS)

The commercially available finite element code ANSYS has been adapted to solve the critical state of single strips and multifilamentary tapes. We studied a special algorithm which approaches the critical state by an iterative adjustment of the material resistivity. Then, we proved its validity by comparing the results obtained for a thin strip to the Brand theory for the transport current and magnetization cases. Also, the challenging calculation of the magnetization loss of a real multifilamentary BSCCO tape showed the usefulness of our method. Finally, we developed several methods to enhance the speed of convergence, making the proposed process quite competitive in the existing survey of ac losses simulations.

Farinon, S.; Fabbricatore, P.; Gömöry, F.

2010-11-01

354

The magnetic field analysis and AC loss calculation for the cable-in-conduit super-conductor coil  

Microsoft Academic Search

The magnetic field distribution of Nb3Sn super-conducting coil is analyzed and obtained when the coil flows the maximum current, the field intensity values of some particular points are given. When the pulse current flows through the super-conducting coil, the large alternate current (AC) loss will appear. Therefore, based on the calculation of the coupling loss time constant for the super-conducting

Hongmei Li; Tian Tian; Jiangming Yang

2010-01-01

355

Study of a Radial-Exiting Hysteresis Gyro Motor.  

National Technical Information Service (NTIS)

Conventional hysteresis motors have small ratios of the output power to the motor volume as compared with conventional induction motors, because the hysteresis materials have small hysteresis loops. A new rotor structure is proposed in which anisotropic m...

H. Yamada

1973-01-01

356

Joining of parts via magnetic heating of metal aluminum powders  

DOEpatents

A method of joining at least two parts includes steps of dispersing a joining material comprising a multi-phase magnetic metal-aluminum powder at an interface between the at least two parts to be joined and applying an alternating magnetic field (AMF). The AMF has a magnetic field strength and frequency suitable for inducing magnetic hysteresis losses in the metal-aluminum powder and is applied for a period that raises temperature of the metal-aluminum powder to an exothermic transformation temperature. At the exothermic transformation temperature, the metal-aluminum powder melts and resolidifies as a metal aluminide solid having a non-magnetic configuration.

Baker, Ian

2013-05-21

357

The Near Elimination of Hysteresis in Pd/Cr2O3 Composites  

SciTech Connect

Although its value varies with the microstructure, hysteresis always accompanies hydride formation and decomposition in Pd(pure)-H, e.g., it is present even in nano-crystalline and thin films. Internal oxidation of Pd0.93Cr0.07 alloys leads to a pure Pd matrix containing nano-crystalline chromia precipitates. The characteristic hysteresis of Pd-H almost disappears in this form of Pd. The reasons for this are discussed. Hysteresis is an almost universal feature of first order solid state transitions. Its presence means that when such a transition is reversed, it follows a different path than that taken in the forward direction leading to a loss of useful work. Hysteresis is, of course, a reflection of the irreversibility of the transition.

SHANAHAN, KIRKL

2004-07-14

358

Amplitude-Dependent Internal Friction and Harmonic Generation in Media with Hysteresis Nonlinearity and Linear Dissipation  

NASA Astrophysics Data System (ADS)

Based on generalization and integration of models for dislocation mechanisms of the hysteresis nonlinearity, we propose a hysteresis equation of state of polycrystalline solids with saturated amplitude-dependent losses. Using the perturbation method, we study, both theoretically and numerically, the nonlinear effects during propagation of acoustic waves in the media with hysteresis nonlinearity and linear viscous dissipation. Nonlinear damping rate and propagation velocity of the wave at the fundamental frequency, as well as regularities for the amplitudes and phase velocities at its second and third harmonics, are determined. It is shown that the media described by such hysteresis equations of state have a nonlinear dispersion, which leads to a nonmonotonic rise and amplitude beats of the higher harmonics as the wave amplitude increases at the fundamental frequency.

Nazarov, V. E.; Kiyashko, S. B.

2014-03-01

359

Isotropic vector hysteresis modeling with feed-forward neural networks  

NASA Astrophysics Data System (ADS)

A new vector hysteresis model is presented, based on the function approximation capabilities of feed-forward neural networks. Two-dimensional circular and elliptical magnetization of laminated SiFe steel sheets can be successfully handled by the model. A feed-forward neural network with four inputs, derived at each time step from the time-dependent magnetic induction vector, yields an accurate prediction of the magnetic field strength vector. Measurement results for a steel sheet sample are used to train and test the neural network. The model accuracy is good and can be easily adapted to the requirements of the application by extending or reducing the network training set and thus the required amount of measurement data. Besides, the presented technique is fast, requires no large data set, and applies standard neural network algorithms. Future extension of the model to other magnetization patterns is possible.

Makaveev, Dimitre; Dupré, Luc; de Wulf, Marc; Melkebeek, Jan

2002-05-01

360

Relationship of parallel model and series model for permanent magnet synchronous motors taking iron loss into account  

Microsoft Academic Search

This paper investigates the relationship of parallel model and series model for permanent magnet synchronous motor taking iron loss into account. The expressions of flux linkage, terminal voltage, and electromagnetic torque are compared. It follows from the investigation that the parallel and series models are mathematically the same. In addition, the properties of the models are exhibited. The parallel model

Naomitsu Urasaki; Tomonobu Senjyu; Katsumi Uezato

2004-01-01

361

Magnetic Configuration Effects on Fast Ion Losses Induced by Fast Ion Driven Toroidal Alfven Eigenmodes in the Large Helical Device  

SciTech Connect

Beam-ion losses induced by fast-ion-driven toroidal Alfven eigenmodes (TAE) were measured with a scintillator-based lost fast-ion probe (SLIP) in the large helical device (LHD). The SLIP gave simultaneously the energy E and the pitch angle chi = arccos(v(parallel to)/v) distribution of the lost fast ions. The loss fluxes were investigated for three typical magnetic configurations of R{sub ax{_}vac} = 3.60 m, 3.75 m, and 3.90 m, where R{sub ax{_}vac} is the magnetic axis position of the vacuum field. Dominant losses induced by TAEs in these three configurations were observed in the E/chi regions of 50 similar to 190 keV/40 degrees, 40 similar to 170 keV/25 degrees, and 30 similar to 190 keV/30 degrees, respectively. Lost-ion fluxes induced by TAEs depend clearly on the amplitude of TAE magnetic fluctuations, R{sub ax{_}vac} and the toroidal field strength B{sub t}. The increment of the loss fluxes has the dependence of (b{sub TAE}/B{sub t}){sup s}. The power s increases from s = 1 to 3 with the increase of the magnetic axis position in finite beta plasmas.

Ogawa, K. [Nagoya University, Japan; Isobe, M. [National Institute for Fusion Science, Toki, Japan; Watanabe, F. [Kyoto University, Japan; Spong, Donald A [ORNL; Shimizu, A. [National Institute for Fusion Science, Toki, Japan; Osakabe, M. [National Institute for Fusion Science, Toki, Japan; Ohdachi, S. [National Institute for Fusion Science, Toki, Japan; Sakakibara, S. [National Institute for Fusion Science, Toki, Japan

2012-01-01

362

CABLE DESIGN FOR FAST RAMPED SUPERCONDUCTING MAGNETS (COS-0 DESIGN).  

SciTech Connect

The new heavy ion synchrotron facility proposed by GSI will have two superconducting magnet rings in the same tunnel, with rigidities of 300 T-m and 100 T-m. Fast ramp times are needed, which can cause significant problems for the magnets, particularly in the areas of ac loss and magnetic field distortion. The development of the low loss Rutherford cable that can be used is described, together with a novel insulation scheme designed to promote efficient cooling. Measurements of contact resistance in the cable are presented and the results of these measurements are used to predict the ac losses, in the magnets during fast ramp operation. For the high energy ring, a lm model dipole magnet was built, based on the RHIC dipole design. This magnet was tested under boiling liquid helium in a vertical cryostat. The quench current showed very little dependence on ramp rate. The ac losses, measured by an electrical method, were fitted to straight line plots of loss/cycle versus ramp rate, thereby separating the eddy current and hysteresis components. These results were compared with calculated values, using parameters which had previously been measured on short samples of cable. Reasonably good agreement between theory and experiment was found, although the measured hysteresis loss is higher than expected in ramps to the highest field levels.

GHOSH,A.

2004-03-22

363

Phase-Coexistence and Thermal Hysteresis in Samples Comprising Adventitiously Doped MnAs Nanocrystals: Programming of Aggregate Properties in Magnetostructural Nanomaterials.  

PubMed

Small changes in the synthesis of MnAs nanoparticles lead to materials with distinct behavior. Samples prepared by slow heating to 523 K (type-A) exhibit the characteristic magnetostructural transition from the ferromagnetic hexagonal (?) to the paramagnetic orthorhombic (?) phase of bulk MnAs at Tp = 312 K, whereas those prepared by rapid nucleation at 603 K (type-B) adopt the ? structure at room temperature and exhibit anomalous magnetic properties. The behavior of type-B nanoparticles is due to P-incorporation (up to 3%), attributed to reaction of the solvent (trioctylphosphine oxide). P-incorporation results in a decrease in the unit cell volume (?1%) and shifts Tp below room temperature. Temperature-dependent X-ray diffraction reveals a large region of phase-coexistence, up to 90 K, which may reflect small differences in Tp from particle-to-particle within the nearly monodisperse sample. The large coexistence range coupled to the thermal hysteresis results in process-dependent phase mixtures. As-prepared type-B samples exhibiting the ? structure at room temperature convert to a mixture of ? and ? after the sample has been cooled to 77 K and rewarmed to room temperature. This change is reflected in the magnetic response, which shows an increased moment and a shift in the temperature hysteresis loop after cooling. The proportion of ? present at room temperature can also be augmented by application of an external magnetic field. Both doped (type-B) and undoped (type-A) MnAs nanoparticles show significant thermal hysteresis narrowing relative to their bulk phases, suggesting that formation of nanoparticles may be an effective method to reduce thermal losses in magnetic refrigeration applications. PMID:24893115

Zhang, Yanhua; Regmi, Rajesh; Liu, Yi; Lawes, Gavin; Brock, Stephanie L

2014-07-22

364

Characterization of strain-induced martensite phase in austenitic stainless steel using a magnetic minor-loop scaling relation  

SciTech Connect

We propose a combined magnetic method using a scaling power-law rule and initial permeability in magnetic minor hysteresis loops for characterization of ferromagnetic {alpha}{sup '} martensites in austenitic stainless steel. The scaling power law between the hysteresis loss and remanence is universal, being independent of volume fraction of strain-induced {alpha}{sup '} martensites. A coefficient of the power law largely decreases with volume fraction, while the initial permeability linearly increases, reflecting a change in the morphology and quantity of martensites, respectively. The present method is highly effective for integrity assessment of austenitic stainless steels because of the sensitivity and extremely low measurement field.

Kobayashi, Satoru; Saito, Atsushi; Takahashi, Seiki; Kamada, Yasuhiro; Kikuchi, Hiroaki [NDE and Science Research Center, Faculty of Engineering, Iwate University, Ueda 4-3-5, Morioka 020-8551 (Japan)

2008-05-05

365

Ni3Zn ferrite octahedral nanoparticles with high microwave permeability and high magnetic loss tangent  

NASA Astrophysics Data System (ADS)

Ni3Zn ferrite octahedral nanoparticles with grain size of about 40 nm were synthesized via a low temperature hydrothermal route. The saturation magnetization (Ms) and coercive force (Hc) of the sample are 57.5 emu/g and 197 Oe, respectively. In 50 MHz-8 GHz frequency range, the complex permeability and complex permittivity for Ni3Zn ferrite/wax composites containing 60 wt% ferrite powders were measured by a vector network analyzer. The real part ?r' of the permeability exhibits high values between 4 and 1.65 in 50 MHz-2 GHz range, and the imaginary part ?r'' of the permeability presents a broad peak with a maximum value of 1.53 at 2.1 GHz, the calculated reflection loss of ferrite/wax coating with the thickness of 8 mm reaches -13 dB at 2.1 GHz. The results indicate the as-prepared Ni3Zn ferrite octahedral nanoparticles can have applications in biomedicine, and microwave absorption and electric devices.

Wang, Zhongzhu; Wu, Mingzai; Jin, Shaowei; Li, Guang; Ma, Yongqing; Wang, Peihong

2013-10-01

366

Free Energy Model for Hysteresis Ferroelectric Materials.  

National Technical Information Service (NTIS)

This paper provides a theory for quantifying the hysteresis and constitutive nonlinearities inherent to piezoceramic compounds through a combination of free energy analysis and stochastic homogenization techniques. In the first step of the model developme...

R. C. Smith Z. Ounaies S. Seelecke J. Smith

2003-01-01

367

Hydrodynamic Model of Dynamic Contact Angle Hysteresis.  

National Technical Information Service (NTIS)

A qualitative hydrodynamic description of dynamic contact angle hysteresis is developed in terms of the interaction of capillary, viscous, and disjoining forces by considerating the slow motion of a fluid-fluid interface being driven through a capillary t...

R. J. Prutow S. Ostrach

1971-01-01

368

Adhesion hysteresis of silane coated microcantilevers  

SciTech Connect

The authors have developed a new experimental approach for measuring hysteresis in the adhesion between micromachined surfaces. By accurately modeling the deformations in cantilever beams that are subject to combined interfacial adhesion and applied electrostatic forces, they determine adhesion energies for advancing and receding contacts. They draw on this new method to examine adhesion hysteresis for silane coated micromachined structures and found significant hysteresis for surfaces that were exposed to high relative humidity (RH) conditions. Atomic force microscopy studies of these surfaces showed spontaneous formation of agglomerates that they interpreted as silages that have irreversibly transformed from uniform surface layers at low RH to isolated vesicles at high RH. They used contact deformation models to show that the compliance of these vesicles could reasonably account for the adhesion hysteresis that develops at high RH as the surfaces are forced into contact by an externally applied load.

DE BOER,MAARTEN P.; KNAPP,JAMES A.; MICHALSKE,TERRY A.; SRINIVASAN,U.; MABOUDIAN,R.

2000-04-17

369

Thermal Hysteresis of Interface Biased Ferromagnetic Dots.  

National Technical Information Service (NTIS)

We present a theoretical investigation of the thermal hysteresis of iron dots exchange-coupled to an antiferromagnetic substrate. We consider a temperature interval bounded by the Neel temperature of the substrate, and we calculate the heating and cooling...

A. L. Dantas, A. S. Carrico, A. S. Silva, G. O. Reboucas, R. E. Camley

2007-01-01

370

Inversion of hysteresis and creep operators  

NASA Astrophysics Data System (ADS)

The explicit inversion formula for rate dependent Prandtl-Ishlinskii operators is extended to cases without the threshold dilation condition. This solves a problem in hysteresis and creep modeling of magnetostrictive behavior.

Krej?í, Pavel; Al Janaideh, Mohammad; Deasy, Fergal

2012-05-01

371

Homogenized Energy Framework for Ferromagnetic Hysteresis.  

National Technical Information Service (NTIS)

In this paper, we develop a macroscopic framework quantifying the hysteresis and constitutive nonlinearities inherent to ferromagnetic materials. In the first step of the development, we construct Helmholtz and Gibbs energy relations at the mesoscopic or ...

R. C. Smith M. J. Dapino T. R. Braun A. P. Mortensen

2005-01-01

372

Hyperthermic effects of dissipative structures of magnetic nanoparticles in large alternating magnetic fields  

PubMed Central

Targeted hyperthermia treatment using magnetic nanoparticles is a promising cancer therapy. However, the mechanisms of heat dissipation in the large alternating magnetic field used during such treatment have not been clarified. In this study, we numerically compared the magnetic loss in rotatable nanoparticles in aqueous media with that of non-rotatable nanoparticles anchored to localised structures. In the former, the relaxation loss in superparamagnetic nanoparticles has a secondary maximum because of slow rotation of the magnetic easy axis of each nanoparticle in the large field in addition to the known primary maximum caused by rapid Néel relaxation. Irradiation of rotatable ferromagnetic nanoparticles with a high-frequency axial field generates structures oriented in a longitudinal or planar direction irrespective of the free energy. Consequently, these dissipative structures significantly affect the conditions for maximum hysteresis loss. These findings shed new light on the design of targeted magnetic hyperthermia treatments.

Mamiya, Hiroaki; Jeyadevan, Balachandran

2011-01-01

373

Experimental comparison of some phenomenological hysteresis models in characterizing hysteresis behavior of shape memory alloy actuators  

Microsoft Academic Search

Among the phenomenological hysteresis models, the Preisach model, Krasnosel’skii–Pokrovskii model, and Prandtl–Ishlinskii model have found extensive applications for modeling hysteresis in shape memory alloys and other smart actuators. Since the mathematical complexity of the identification and inversion problem depends directly on the type of phenomenological hysteresis modeling method, choosing a proper phenomenological model among the mentioned models for modeling the

Mohammad R Zakerzadeh; Hassan Sayyaadi

2012-01-01

374

Hysteresis effects in Bose-Einstein condensates  

SciTech Connect

Here, we consider damped two-component Bose-Einstein condensates with many-body interactions. We show that, when the external trapping potential has a double-well shape and when the nonlinear coupling factors are modulated in time, hysteresis effects may appear under some circumstances. Such hysteresis phenomena are a result of the joint contribution of the appearance of saddle node bifurcations and the damping effect.

Sacchetti, Andrea [Faculty of Sciences, University of Modena e Reggio Emilia, Via Campi 213/B, I-41100 Modena (Italy)

2010-07-15

375

Equivalent Circuit Modeling of Hysteresis Motors  

SciTech Connect

We performed a literature review and found that many equivalent circuit models of hysteresis motors in use today are incorrect. The model by Miyairi and Kataoka (1965) is the correct one. We extended the model by transforming it to quadrature coordinates, amenable to circuit or digital simulation. 'Hunting' is an oscillatory phenomenon often observed in hysteresis motors. While several works have attempted to model the phenomenon with some partial success, we present a new complete model that predicts hunting from first principles.

Nitao, J J; Scharlemann, E T; Kirkendall, B A

2009-08-31

376

Spatial versus time hysteresis in damping mechanisms  

NASA Technical Reports Server (NTRS)

A description is given of continuing investigations on the task of estimating internal damping mechanisms in flexible structures. Specifically, two models for internal damping in Euler-Bernoulli beams are considered: spatial hysteresis and time hysteresis. A theoretically sound computational algorithm for estimation is described, and experimental results are discussed. It is concluded that both models perform well in the sense that they accurately predict response for the experiments conducted.

Banks, H. T.; Fabiano, R. H.; Wang, Y.; Inman, D. J.; Cudney, H., Jr.

1988-01-01

377

Anomalous hysteresis properties of iron films deposited on liquid surfaces  

SciTech Connect

A nearly free sustained iron film system, deposited on silicone oil surfaces by vapor-phase deposition method, has been fabricated and its crystal structure as well as magnetic properties has been studied. Both the temperature-dependent coercivity H{sub c}(T) and exchange anisotropy field H{sub E}(T) of the iron films possess a maximum peak around the critical temperature T{sub crit}=10-15 and 4 K, respectively. Our experimental results show that the anomalous hysteresis properties mainly result from the oxide surfaces of the films with spin-glass-like phase below freezing temperature T{sub f}=30-50 K.

Ye Quanlin; Feng Chunmu; Xu Xiaojun; Jin Jinsheng; Xia Agen; Ye Gaoxiang [Department of Physics, Zhejiang University, Hangzhou 310027 (China); Test and Analysis Center, Zhejiang University, Hangzhou 310028 (China); Department of Physics, Zhejiang University, Hangzhou 310027 (China)

2005-07-01

378

Anomalous hysteresis properties of iron films deposited on liquid surfaces  

NASA Astrophysics Data System (ADS)

A nearly free sustained iron film system, deposited on silicone oil surfaces by vapor-phase deposition method, has been fabricated and its crystal structure as well as magnetic properties has been studied. Both the temperature-dependent coercivity Hc(T) and exchange anisotropy field HE(T) of the iron films possess a maximum peak around the critical temperature Tcrit=10-15 and 4 K, respectively. Our experimental results show that the anomalous hysteresis properties mainly result from the oxide surfaces of the films with spin-glass-like phase below freezing temperature Tf=30-50 K.

Ye, Quan-Lin; Feng, Chun-Mu; Xu, Xiao-Jun; Jin, Jin-Sheng; Xia, A.-Gen; Ye, Gao-Xiang

2005-07-01

379

A dynamic model for hysteresis in magnetostrictive devices  

NASA Astrophysics Data System (ADS)

In this paper, a dynamic model for the description and design of hysteresis in magnetostrictive devices is presented. The model is based on Preisach theory and its dynamic extension. A procedure for determining the Preisach distribution function is given. This procedure is based on neural networks. The model is able to reconstruct both the magnetization relation and the field-strain relation. The model is validated through comparison and prediction of data collected from a typical Terfenol-D sample and a novel experimental technique dedicated to the validation of dynamic models is proposed.

Trapanese, M.; Franzitta, V.; Viola, A.

2014-05-01

380

Transport, hysteresis and avalanches in artificial spin ice systems  

SciTech Connect

We examine the hopping dynamics of an artificial spin ice system constructed from colloids on a kagome optical trap array where each trap has two possible states. By applying an external drive from an electric field which is analogous to a biasing applied magnetic field for real spin systems, we can create polarized states that obey the spin-ice rules of two spins in and one spin out at each vertex. We demonstrate that when we sweep the external drive and measure the fraction of the system that has been polarized, we can generate a hysteresis loop analogous to the hysteretic magnetization versus external magnetic field curves for real spin systems. The disorder in our system can be readily controlled by changing the barrier that must be overcome before a colloid can hop from one side of a trap to the other. For systems with no disorder, the effective spins all flip simultaneously as the biasing field is changed, while for strong disorder the hysteresis curves show a series of discontinuous jumps or avalanches similar to Barkhausen noise.

Reichhardt, Charles [Los Alamos National Laboratory; Reichhardt, Cynthia J [Los Alamos National Laboratory; Libal, A [BABES-BOLYAI UNIV.

2010-01-01

381

Negative remanent magnetization  

NASA Astrophysics Data System (ADS)

A new model to explore negative remanent magnetization is presented. Recently, a model for magnetic materials that have wasp-waist hysteresis loops was applied to a homogeneous thin film. This model postulated two interacting antiferromagnetically coupled media: one medium with low moment and relatively high coercivity, and one medium with a relatively high moment and low coercivity. This model is applicable to the situation where the "width" of the loop near zero is "negative." The major loop of such a material crosses itself, leading to negative remanent magnetization. The present paper introduces a new concept of a need for a third dimension to add to the usual magnetization versus applied field graph, demonstrates that there is no crossing, and discusses the nature of the losses in these materials.

Torre, Edward Della; Bennett, Lawrence H.

2014-05-01

382

Electric and magnetic losses modeled by a stable hybrid with explicit-implicit time-stepping for Maxwell's equations  

SciTech Connect

A stable hybridization of the finite-element method (FEM) and the finite-difference time-domain (FDTD) scheme for Maxwell's equations with electric and magnetic losses is presented for two-dimensional problems. The hybrid method combines the flexibility of the FEM with the efficiency of the FDTD scheme and it is based directly on Ampere's and Faraday's law. The electric and magnetic losses can be treated implicitly by the FEM on an unstructured mesh, which allows for local mesh refinement in order to resolve rapid variations in the material parameters and/or the electromagnetic field. It is also feasible to handle larger homogeneous regions with losses by the explicit FDTD scheme connected to an implicitly time-stepped and lossy FEM region. The hybrid method shows second-order convergence for smooth scatterers. The bistatic radar cross section (RCS) for a circular metal cylinder with a lossy coating converges to the analytical solution and an accuracy of 2% is achieved for about 20 points per wavelength. The monostatic RCS for an airfoil that features sharp corners yields a lower order of convergence and it is found to agree well with what can be expected for singular fields at the sharp corners. A careful convergence study with resolutions from 20 to 140 points per wavelength provides accurate extrapolated results for this non-trivial test case, which makes it possible to use as a reference problem for scattering codes that model both electric and magnetic losses.

Halleroed, Tomas [Department of Signals and Systems, Chalmers University of Technology, S-412 96 Goeteborg (Sweden)], E-mail: tomas.hallerod@chalmers.se; Rylander, Thomas [Department of Signals and Systems, Chalmers University of Technology, S-412 96 Goeteborg (Sweden)], E-mail: rylander@chalmers.se

2008-04-20

383

Preisach modeling of piezoceramic and shape memory alloy hysteresis  

Microsoft Academic Search

Smart materials such as piezoceramics, magnetostrictive materials, and shape memory alloys exhibit significant hysteresis, especially when driven with large input signals. Hysteresis can lead to unwanted harmonics, inaccuracy in open loop control, and instability in closed loop control. The Preisach independent domain hysteresis model has been shown to capture the major features of hysteresis arising in ferromagnetic materials. Noting the

Declan C. Hughes; John T. Wen

1996-01-01

384

Preisach modeling of piezoceramic and shape memory alloy hysteresis  

Microsoft Academic Search

Smart materials such as piezoceramics, magnetostrictive materials, and shape memory alloys exhibit hysteresis, and the larger the input signal the larger the effect. Hysteresis can lead to unwanted harmonics, inaccuracy in open loop control, and instability in closed loop control. The Preisach independent domain hysteresis model has been shown to capture the major features of hysteresis arising in ferromagnetic materials.

Declan Hughes; John T. Wen

1997-01-01

385

Cumulative growth of minor hysteresis loops in the Kolmogorov model  

SciTech Connect

The phenomenon of nonrepeatability of successive remagnetization cycles in Co/M (M = Pt, Pd, Au) multilayer film structures is explained in the framework of the Kolmogorov crystallization model. It is shown that this model of phase transitions can be adapted so as to adequately describe the process of magnetic relaxation in the indicated systems with 'memory.' For this purpose, it is necessary to introduce some additional elements into the model, in particular, (i) to take into account the fact that every cycle starts from a state 'inherited' from the preceding cycle and (ii) to assume that the rate of growth of a new magnetic phase depends on the cycle number. This modified model provides a quite satisfactory qualitative and quantitative description of all features of successive magnetic relaxation cycles in the system under consideration, including the surprising phenomenon of cumulative growth of minor hysteresis loops.

Meilikhov, E. Z., E-mail: meilikhov@imp.kiae.ru; Farzetdinova, R. M. [National Research Centre Kurchatov Institute (Russian Federation)] [National Research Centre Kurchatov Institute (Russian Federation)

2013-01-15

386

Influence of External Magnetic Field on AC Losses at EF Coil Joints of JT-60SA  

Microsoft Academic Search

We experimentally and numerically evaluated the AC loss occurred in joints of the EF coil in JT60-SA. There are two kinds of the joints (pancake joint and terminal joint) in the EF coil. Firstly, the AC losses of the joints were experimentally obtained. The experimental results showed that the AC losses in the pancake and the terminal joints were smaller

Tomoaki Takao; Kazuya Nakamura; Toshiyuki Takagi; Naoki Tanoue; Haruyuki Murakami; Kiyoshi Yoshida

2012-01-01

387

Analysis and comparison for rotor eddy current losses of permanent magnet synchronous generator according to dc and ac load conditions  

NASA Astrophysics Data System (ADS)

This paper presents an analytical procedure for the calculation of the eddy current losses of permanent magnet synchronous generator (PMSG). The dc and ac loading effects on the eddy current is examined through the suggested analytical procedure that considers the radial and tangential flux density waveform through a phase current harmonic analysis. The corresponding test results are also presented to quantify and compare those loading effects on the eddy current. The results verified the suggested analytical procedures and show that the rotor eddy current losses for PMSG with the dc loads turned out to be more significant than those with the ac loads.

Jang, Seok-Myeong; Kim, Hyun-Kyu; Choi, Jang-Young; Ko, Kyoung-Jin

2009-04-01

388

Finite element analysis of AC loss in non-twisted Bi2223 tape carrying AC transport current and\\/or exposed to DC or AC external magnetic field  

Microsoft Academic Search

AC losses in Bi-2223 superconducting tapes carrying AC transport current and\\/or exposed to DC or AC magnetic field are calculated with a numerical model based on the finite element method. Superconducting property is given by the E–J characteristic represented by a power law using equivalent conductivity. First, transport loss and magnetization loss are calculated numerically and compared with measured values.

Naoyuki Amemiya; Kengo Miyamoto; Shun-ichi Murasawa; Hideki Mukai; Kazuya Ohmatsu

1998-01-01

389

Superconducting-magnetic heterostructures: a method of decreasing AC losses and improving critical current density in multifilamentary conductors.  

PubMed

Magnetic materials can help to improve the performance of practical superconductors on the macroscale/microscale as magnetic diverters and also on the nanoscale as effective pinning centres. It has been established by numerical modelling that magnetic shielding of the filaments reduces AC losses in self-field conditions due to decoupling of the filaments and, at the same time, it increases the critical current of the composite. This effect is especially beneficial for coated conductors, in which the anisotropic properties of the superconductor are amplified by the conductor architecture. However, ferromagnetic coatings are often chemically incompatible with YBa(2)Cu(3)O(7) and (Pb,Bi)(2)Sr(2)Ca(2)Cu(3)O(9) conductors, and buffer layers have to be used. In contrast, in MgB(2) conductors an iron matrix may remain in direct contact with the superconducting core. The application of superconducting-magnetic heterostructures requires consideration of the thermal and electromagnetic stability of the superconducting materials used. On one hand, magnetic materials reduce the critical current gradient across the individual filaments but, on the other hand, they often reduce the thermal conductivity between the superconducting core and the cryogen, which may cause destruction of the conductor in the event of thermal instability. A possible nanoscale method of improving the critical current density of superconducting conductors is the introduction of sub-micron magnetic pinning centres. However, the volumetric density and chemical compatibility of magnetic inclusions has to be controlled to avoid suppression of the superconducting properties. PMID:21828430

Glowacki, B A; Majoros, M

2009-06-24

390

AC losses and heat removal in three-dimensional winding pack of Samsung superconducting test facility under pulsed magnetic field operation  

NASA Astrophysics Data System (ADS)

The Samsung superconducting test facility (SSTF) will be operated under the highly pulsed field to simulate the operating conditions of KSTAR. An analysis has been performed to study the transient heat removal characteristics and temperature margin for the main, blip and compensating coils in the SSTF. This method is based on a quasi-three-dimensional model, which the thermal coupling of turn-to-turn, pancake-to-pancake and channel-to-channel is taken into account, to simulate the conductor temperature rise and the thermal expansion of supercritical helium due to the high AC losses under the pulsed field. The local AC losses, which include coupling loss, eddy current loss and hysteresis loss in the cable-in-conduit conductor, are estimated. The temperature margin, mass flow rate, distribution of AC losses are studied under the given operating scenario. The mass flow reduction and peak temperature rise depending on the inlet pressure and inlet position of CICC are studied. It is shown that the initial mass flow rate remarkably influences on the peak temperature of superconducting strands. The large mass flow rate can reduce the temperature rise when the inlet of helium is located at the high field region. By contrast, because of heat induced flow to improve the cooling condition of the superconducting strands, the small initial mass flow rate results in the low peak temperature in strands when the inlet of helium is located at the low field region.

Wang, Qiuliang; Seong Yoon, Cheon; Baang, Sungkeun; Kim, Myungkyu; Park, Hyunki; Kim, Yongjin; Lee, Sangil; Kim, Keeman

2001-04-01

391

Heat dissipation and magnetic properties of surface-coated Fe3O4 nanoparticles for biomedical applications  

NASA Astrophysics Data System (ADS)

In this study, the influence of surface coating on the magnetic and heat dissipation properties of Fe3O4 nanoparticles was investigated. Fe3O4 nanoparticles that ranged in size between (particle sizes of 20 and 30 nm) were coated with polyethylenimine (PEI), oleic acid, and Pluronic F-127. Surface coatings that were composed of thick layers of oleic acid and Pluronic F-127 reduced dipole interactions between the particles, and resulted in reduced coercivity and decreased Néel relaxation times. The ac magnetization measurements revealed that the heat dissipation of the PEI-coated Fe3O4 nanoparticles was induced by hysteresis loss and Brownian relaxation loss and that of the oleic-acid-coated Fe3O4 nanoparticles was mainly induced by hysteresis loss and Néel relaxation loss.

Tomitaka, Asahi; Ueda, Koji; Yamada, Tsutomu; Takemura, Yasushi

2012-10-01

392

MEASURED AND CALCULATED LOSSES IN A MODEL DIPOLE FOR GSI'S HEAVY ION SYNCHROTRON.  

SciTech Connect

The new heavy ion synchrotron facility proposed by GSI will have two superconducting magnet rings in the same tunnel, with rigidities of 300T{center_dot}m and 10OT{center_dot}m. Fast ramp times are needed. These can cause problems of ac loss and field distortion in the magnets. For the high energy ring, a lm model dipole magnet has been built, based on the RHIC dipole design. This magnet was tested under boiling liquid helium in a vertical dewar. The quench current showed very little dependence on ramp rate. The ac losses, measured by an electrical method, were fitted to straight line plots of loss/cycle versus ramp rate, thereby separating the eddy current and hysteresis components. These results were compared with calculated values, using parameters which had previously been measured on short samples of cable. Reasonably good agreement between theory and experiment was found, although the measured hysteresis loss is higher than expected in ramps to the highest field levels.

WANDERER,P.; ANERELLA,M.; GANETIS,G.; GHOSH,A.K.; JOSHI,P.; MARONE,A.; MURATORE,J.; ET AL.

2003-06-15

393

Magnetically-induced circular-polarization-dependent loss of magneto-optic fiber Bragg gratings with linear birefringence  

NASA Astrophysics Data System (ADS)

The concept of magnetically-induced circular-polarization-dependent loss (MCDL) for magneto-optic fiber Bragg gratings (MFBGs) is introduced. The magnetic field dependency of MCDL for linearly birefringent MFBGs is simulated by use of the equivalent theoretical model given in the paper. This model is mainly composed of an elliptical polarization extractor and a couple of isotropic fiber Bragg gratings (FBGs) with different effective refractive indices. It is shown by simulation that, (1) when the magnetooptic-to-grating coupling coefficient ratio is less than 0.1, the peak MCDL is proportional to applied magnetic induction; (2) the MCDL method is more suitable for the magnetic field measurement than the conventional polarization dependent loss (PDL) for the linearly birefringent MFBGs. As an example, the MCDL of an erbium-doped MFBG (Er-MFBG) is measured and the experimental data are in agreement with the theoretical results. The effective Verdet constant for the Er-MFBG is about -11 rad/(T·m) and the peak MCDL is up to 1 dB at 1.15 T.

Wu, Baojian; Wen, Feng; Qiu, Kun; Han, Rui; Lu, Xin

2013-06-01

394

Susceptibility and Inverted Hysteresis Loop of Prussian Blue Analogs with Orthorhombic Structure  

NASA Astrophysics Data System (ADS)

The magnetic susceptibility of ternary metal Prussian blue analogues with orthorhombic structure is studied using Ising model. Within the frame work of effective-field theory with correlations, the roles of the mole fraction y, uniaxial magnetic anisotropy, transverse and longitudinal magnetic field are discussed in details. The temperature dependence of the magnetic susceptibility is also investigated. The interesting phenomenon of the inverted magnetic hysteresis loop has been found. The results can help to understand the experimental work of the molecule-based ferri-ferrimagnet.

Guo, An-Bang; Jiang, Wei

2012-11-01

395

Dynamics and hysteresis in square lattice artificial spin ice  

NASA Astrophysics Data System (ADS)

Dynamical effects under geometrical frustration are considered in a model for artificial spin ice on a square lattice in two dimensions. Each island of the spin ice has a three-component Heisenberg-like dipole moment subject to shape anisotropies that influence its direction. The model has real dynamics, including rotation of the magnetic degrees of freedom, going beyond the Ising-type models of spin ice. The dynamics is studied using a Langevin equation solved via a second-order Heun algorithm. Thermodynamic properties such as the specific heat are presented for different couplings. A peak in specific heat is related to a type of melting-like phase transition present in the model. Hysteresis in an applied magnetic field is calculated for model parameters where the system is able to reach thermodynamic equilibrium.

Wysin, G. M.; Moura-Melo, W. A.; Mól, L. A. S.; Pereira, A. R.

2013-04-01

396

A Test of HTS Power Cable in a Sweeping Magnetic Field  

SciTech Connect

Short sample HTS power cable composed of multiple 344C-2G strands and designed to energize a fast-cycling dipole magnet was exposed to a sweeping magnetic field in the (2-20) T/s ramping rate. The B-field orientation toward the HTS strands wide surface was varied from 0{sup 0} to 10{sup 0}, in steps of 1{sup 0}. The test arrangement allowed measurement of the combined hysteresis and eddy current power losses. For the validity of these measurements, the power losses of a short sample cable composed of multiple LTS wire strands were also performed to compare with the known data. The test arrangement of the power cable is described, and the test results are compared with the projections for the eddy and hysteresis power losses using the fine details of the test cable structures.

Piekarz, H.; Hays, S.; Blowers, J.; Shiltsev, V.; /Fermilab

2011-11-29

397

Disorder-driven first-order phase transformations: A model for hysteresis  

SciTech Connect

Hysteresis loops in some magnetic systems are composed of small avalanches (manifesting themselves as Barkhausen pulses). Hysteresis loops in other first-order phase transitions (including some magnetic systems) often occur via one large avalanche. The transition between these two limiting cases is studied, by varying the disorder in the zero-temperature random-field Ising model. Sweeping the external field through zero at weak disorder, we get one large avalanche with small precursors and aftershocks. At strong disorder, we get a distribution of small avalanches (small Barkhausen effect). At the critical value of disorder where a macroscopic jump in the magnetization first occurs, universal power-law behavior of the magnetization and of the distribution of (Barkhausen) avalanches is found. This transition is studied by mean-field theory, perturbative expansions, and numerical simulation in three dimensions.

Dahmen, K.; Kartha, S.; Krumhansl, J.A.; Roberts, B.W.; Sethna, J.P.; Shore, J.D. (Laboratory of Atomic and Solid State Physics, Cornell University, Ithaca, New York 14853-2501 (United States))

1994-05-15

398

Magnetocaloric effect in the low hysteresis Ni-Mn-In metamagnetic shape-memory Heusler alloy  

NASA Astrophysics Data System (ADS)

We have studied magnetocaloric properties of a Ni-Mn-In metamagnetic shape-memory alloy especially designed in order to display low thermal hysteresis. Magnetization and calorimetric measurements under a magnetic field have been used in order to determine isothermal magnetic field-induced entropy changes. Results obtained indirectly from magnetization data, quasi-directly from isofield calorimetric measurements, and directly from isothermal calorimetric runs are systematic and agree well with each other. We have analyzed the reproducibility of magnetocaloric properties with cycling from direct isothermal calorimetric measurements. Due to low thermal hysteresis, we have found that about 80% of the transition entropy change, ?St ? 25 J/kg K, can be reversibly induced under successive application and removal of a field of 6 T.

Stern-Taulats, Enric; Castillo-Villa, Pedro O.; Mañosa, Lluís; Frontera, Carlos; Pramanick, Sabyasachi; Majumdar, Subham; Planes, Antoni

2014-05-01

399

Influence of slitting on core losses and magnetization curve of grain-oriented electrical steels  

Microsoft Academic Search

An experimental investigation was carried out by means of a single sheet and strip tester for electrical steels to find the effect of slitting on the magnetic properties of electrical strips of various widths (from 40 to 660 mm). Individual effects have been analyzed separately (slitting only, tension, and bending) regarding their influence on the deterioration of the magnetic properties

ZDENKO GODEC

1977-01-01

400

A Combined Experimental and Finite Element Analysis Method for the Estimation of Eddy-Current Loss in NdFeB Magnets  

PubMed Central

NdFeB permanent magnets (PMs) are widely used in high performance electrical machines, but their relatively high conductivity subjects them to eddy current losses that can lead to magnetization loss. The Finite Element (FE) method is generally used to quantify the eddy current loss of PMs, but it remains quite difficult to validate the accuracy of the results with complex devices. In this paper, an experimental test device is used in order to extract the eddy current losses that are then compared with those of a 3D FE model.

Fratila, Radu; Benabou, Abdelkader; Tounzi, Abdelmounaim; Mipo, Jean-Claude

2014-01-01

401

A combined experimental and finite element analysis method for the estimation of eddy-current loss in NdFeB magnets.  

PubMed

NdFeB permanent magnets (PMs) are widely used in high performance electrical machines, but their relatively high conductivity subjects them to eddy current losses that can lead to magnetization loss. The Finite Element (FE) method is generally used to quantify the eddy current loss of PMs, but it remains quite difficult to validate the accuracy of the results with complex devices. In this paper, an experimental test device is used in order to extract the eddy current losses that are then compared with those of a 3D FE model. PMID:24831111

Fratila, Radu; Benabou, Abdelkader; Tounzi, Abdelmounaïm; Mipo, Jean-Claude

2014-01-01

402

Magnetic Force Microscopy and Energy Loss Imaging of Superparamagnetic Iron Oxide Nanoparticles”  

NASA Astrophysics Data System (ADS)

We present quantitative, high spatially resolved magnetic force microscopy imaging of samples based on 11 nm diameter superparamagnetic iron oxide nanoparticles in air at room temperature. By a proper combination of the cantilever resonance frequency shift, oscillation amplitude and phase lag we obtain the tip-sample interaction maps in terms of force gradient and energy dissipation. These physical quantities are evaluated in the frame of a tip-particle magnetic interaction model also including the tip oscillation amplitude. Magnetic nanoparticles are characterized both in bare form, after deposition on a flat substrate, and as magnetically assembled fillers in a polymer matrix, in the form of nanowires. The latter approach makes it possible to reveal the magnetic texture in a composite sample independently of the surface topography.

Torre, Bruno; Bertoni, Giovanni; Fragouli, Despina; Falqui, Andrea; Salerno, Marco; Diaspro, Alberto; Cingolani, Roberto; Athanassiou, Athanassia

2011-12-01

403

"Magnetic force microscopy and energy loss imaging of superparamagnetic iron oxide nanoparticles".  

PubMed

We present quantitative, high spatially resolved magnetic force microscopy imaging of samples based on 11 nm diameter superparamagnetic iron oxide nanoparticles in air at room temperature. By a proper combination of the cantilever resonance frequency shift, oscillation amplitude and phase lag we obtain the tip-sample interaction maps in terms of force gradient and energy dissipation. These physical quantities are evaluated in the frame of a tip-particle magnetic interaction model also including the tip oscillation amplitude. Magnetic nanoparticles are characterized both in bare form, after deposition on a flat substrate, and as magnetically assembled fillers in a polymer matrix, in the form of nanowires. The latter approach makes it possible to reveal the magnetic texture in a composite sample independently of the surface topography. PMID:22355717

Torre, Bruno; Bertoni, Giovanni; Fragouli, Despina; Falqui, Andrea; Salerno, Marco; Diaspro, Alberto; Cingolani, Roberto; Athanassiou, Athanassia

2011-01-01

404

"Magnetic Force Microscopy and Energy Loss Imaging of Superparamagnetic Iron Oxide Nanoparticles"  

PubMed Central

We present quantitative, high spatially resolved magnetic force microscopy imaging of samples based on 11?nm diameter superparamagnetic iron oxide nanoparticles in air at room temperature. By a proper combination of the cantilever resonance frequency shift, oscillation amplitude and phase lag we obtain the tip-sample interaction maps in terms of force gradient and energy dissipation. These physical quantities are evaluated in the frame of a tip-particle magnetic interaction model also including the tip oscillation amplitude. Magnetic nanoparticles are characterized both in bare form, after deposition on a flat substrate, and as magnetically assembled fillers in a polymer matrix, in the form of nanowires. The latter approach makes it possible to reveal the magnetic texture in a composite sample independently of the surface topography.

Torre, Bruno; Bertoni, Giovanni; Fragouli, Despina; Falqui, Andrea; Salerno, Marco; Diaspro, Alberto; Cingolani, Roberto; Athanassiou, Athanassia

2011-01-01

405

Magnetic features in REMeO3 perovskites and their solid solutions (RE=rare-earth, Me=Mn, Cr)  

NASA Astrophysics Data System (ADS)

Magnetic hysteresis displacement, thermal inversion of the magnetization, hysteresis loops jumps and crossing branches of hysteresis loops at low magnetic fields are reviewed. Most of these phenomena have been observed in magnetic oxide systems, particularly in perovskite-type manganites and chromites. The paper takes into account structural considerations and different geometrical parameters, such as volume or thin layers.

Moure, Carlos; Peña, Octavio

2013-07-01

406

The loss rates of O+ in the inner magnetosphere caused by both magnetic field line curvature scattering and charge exchange reactions  

NASA Astrophysics Data System (ADS)

With consideration of magnetic field line curvature (FLC) pitch angle scattering and charge exchange reactions, the O+ (>300 keV) in the inner magnetosphere loss rates are investigated by using an eigenfunction analysis. The FLC scattering provides a mechanism for the ring current O+ to enter the loss cone and influence the loss rates caused by charge exchange reactions. Assuming that the pitch angle change is small for each scattering event, the diffusion equation including a charge exchange term is constructed and solved; the eigenvalues of the equation are identified. The resultant loss rates of O+ are approximately equal to the linear superposition of the loss rate without considering the charge exchange reactions and the loss rate associated with charge exchange reactions alone. The loss time is consistent with the observations from the early recovery phases of magnetic storms.

Ji, Y.; Shen, C.

2014-03-01

407

On the mechanisms of transport losses in high-temperature superconductors  

SciTech Connect

Monte Carlo simulations of a high-temperature superconductor carrying an alternating transport current have been performed. The influence of defect concentration and external magnetic field on the transport energy losses is investigated. We show that there are two components of the losses in a superconductor carrying an alternating transport current: a hysteresis component related to the superconductor remagnetization by the self-current field and a dynamic component related to the steady flow of vortices-antivortices and their annihilation in the superconductor.

Odintsov, D. S., E-mail: dodintsov@mail.ru; Rudnev, I. A., E-mail: iarudnev@mephi.ru; Kashurnikov, V. A. [Moscow Engineering Physics Institute (State University) (Russian Federation)], E-mail: kashur@rol.ru

2007-07-15

408

Effect of Stabilization Heat Treatment on Time-Dependent Polarization Losses in Sintered Nd-Fe-B Permanent Magnets  

NASA Astrophysics Data System (ADS)

Some companies in the motor and generator industry utilizing sintered NdFeB magnets have adopted pre-ageing heat treatment in order to improve the stability of the magnets. The parameters of this stabilization heat treatment are based mainly on assumptions rather than on any published research results. In this work, the effects of pre-ageing treatment on the time-dependent polarization losses of two different types of commercial sintered NdFeB magnets were studied. The material showing the squarer J(H) curve did not benefit from the pre-ageing treatment, since it seems to be stable under a certain critical temperature. In contrast, a stabilizing effect was observed in the material showing rounder J(H) curve. After the stabilization heat treatment, the polarization of the magnets was found to be at lower level, but unchanged over a certain period of time. The length of this period depends on the temperature and the duration of the pre-ageing treatment. In addition, our analysis reveals that the stabilization heat treatment performed in an open circuit condition does not stabilize the magnet uniformly.

Haavisto, M.; Kankaanpää, H.; Santa-Nokki, T.; Tuominen, S.; Paju, M.

2013-01-01

409

Combinatorial search of thermoelastic shape-memory alloys with extremely small hysteresis width.  

PubMed

Reversibility of structural phase transformations has profound technological implications in a wide range of applications from fatigue life in shape-memory alloys (SMAs) to magnetism in multiferroic oxides. The geometric nonlinear theory of martensite universally applicable to all structural transitions has been developed. It predicts the reversibility of the transitions as manifested in the hysteresis behaviour based solely on crystal symmetry and geometric compatibilities between phases. In this article, we report on the verification of the theory using the high-throughput approach. The thin-film composition-spread technique was devised to rapidly map the lattice parameters and the thermal hysteresis of ternary alloy systems. A clear relationship between the hysteresis and the middle eigenvalue of the transformation stretch tensor as predicted by the theory was observed for the first time. We have also identified a new composition region of titanium-rich SMAs with potential for improved control of SMA properties. PMID:16518396

Cui, Jun; Chu, Yong S; Famodu, Olugbenga O; Furuya, Yasubumi; Hattrick-Simpers, Jae; James, Richard D; Ludwig, Alfred; Thienhaus, Sigurd; Wuttig, Manfred; Zhang, Zhiyong; Takeuchi, Ichiro

2006-04-01

410

Fast-ion losses induced by ELMs and externally applied magnetic perturbations in the ASDEX Upgrade tokamak  

NASA Astrophysics Data System (ADS)

Phase-space time-resolved measurements of fast-ion losses induced by edge localized modes (ELMs) and ELM mitigation coils have been obtained in the ASDEX Upgrade tokamak by means of multiple fast-ion loss detectors (FILDs). Filament-like bursts of fast-ion losses are measured during ELMs by several FILDs at different toroidal and poloidal positions. Externally applied magnetic perturbations (MPs) have little effect on plasma profiles, including fast-ions, in high collisionality plasmas with mitigated ELMs. A strong impact on plasma density, rotation and fast-ions is observed, however, in low density/collisionality and q95 plasmas with externally applied MPs. During the mitigation/suppression of type-I ELMs by externally applied MPs, the large fast-ion bursts observed during ELMs are replaced by a steady loss of fast-ions with a broad-band frequency and an amplitude of up to an order of magnitude higher than the neutral beam injection (NBI) prompt loss signal without MPs. Multiple FILD measurements at different positions, indicate that the fast-ion losses due to static 3D fields are localized on certain parts of the first wall rather than being toroidally/poloidally homogeneously distributed. Measured fast-ion losses show a broad energy and pitch-angle range and are typically on banana orbits that explore the entire pedestal/scrape-off-layer (SOL). Infra-red measurements are used to estimate the heat load associated with the MP-induced fast-ion losses. The heat load on the FILD detector head and surrounding wall can be up to six times higher with MPs than without 3D fields. When 3D fields are applied and density pump-out is observed, an enhancement of the fast-ion content in the plasma is typically measured by fast-ion D-alpha (FIDA) spectroscopy. The lower density during the MP phase also leads to a deeper beam deposition with an inward radial displacement of ?2 cm in the maximum of the beam emission. Orbit simulations are used to test different models for 3D field equilibrium reconstruction including vacuum representation, the free boundary NEMEC code and the two-fluid M3D-C1 code which account for the plasma response. Guiding center simulations predict the maximum level of losses, ?2.6%, with NEMEC 3D equilibrium. Full orbit simulations overestimate the level of losses in 3D vacuum fields with ?15% of lost NBI ions.

Garcia-Munoz, M.; Äkäslompolo, S.; de Marne, P.; Dunne, M. G.; Dux, R.; Evans, T. E.; Ferraro, N. M.; Fietz, S.; Fuchs, C.; Geiger, B.; Herrmann, A.; Hoelzl, M.; Kurzan, B.; Lazanyi, N.; McDermott, R. M.; Nocente, M.; Pace, D. C.; Rodriguez-Ramos, M.; Shinohara, K.; Strumberger, E.; Suttrop, W.; Van Zeeland, M. A.; Viezzer, E.; Willensdorfer, M.; Wolfrum, E.

2013-12-01

411

Sol-Gel Synthesis of Mn-Sn-Ti-Substituted Strontium Hexaferrite Nanoparticles: Structural, Magnetic, and Reflection-Loss Properties  

NASA Astrophysics Data System (ADS)

Substituted strontium hexaferrite nanoparticles with the chemical formula SrFe12- x (MnSn0.5Ti0.5) x/2O19( x = 0-2.5, in a step of 0.5) were prepared by a sol-gel method. Phase identities and crystal structure of the synthesized nanoparticles were investigated by x-ray diffraction. The morphology of the nanopowders was determined by field emission scanning electron microscopy. Results obtained from Fourier-transform infrared spectroscopy revealed the presence of stretching and bending modes in the citrate complex. Mössbauer spectroscopy ( M S) revealed occupancy of the hexagonal lattice structure by non-magnetic Mn2+ -Sn4+ -Ti4+ cations. Magnetic properties were measured by use of a vibrating sample magnetometer. The results showed that saturation magnetization and coercivity decreased with increasing x content. Microwave absorption properties were investigated by use of a vector network analyzer. It was found that the maximum reflection loss of substituted Sr-ferrite 1.6 mm thick reached -41.8 dB at a frequency of 4.3 GHz and a bandwidth of 7.5 GHz, with reflection loss being higher than -25 dB. These results imply that the prepared composites are good candidates for absorbers in the gigahertz frequency range.

Jamalian, Majid; Ghasemi, Ali; Paimozd, Ebrahim

2014-04-01

412

Re-Examination of Mechanical Hysteresis.  

National Technical Information Service (NTIS)

Mechanical-hysteresis loops have been obtained for cycles of torsion applied to copper, brass, low-carbon steel, titanium. It is shown that the slope of the unloading line is determined by a plastic recovery p together with elastic recovery e, that p/e is...

W. A. Wood

1967-01-01

413

Design of hysteresis circuits using differential amplifiers  

NASA Technical Reports Server (NTRS)

Design equations for hysteresis circuit are based on the following assumptions: amplifier input impedance is larger than source impedance; amplifier output impedance is less than load impedance; and amplifier switches state when differential input voltage is approximately zero. Circuits are designed to any given specifications.

Cooke, W. A.

1971-01-01

414

Circuit increases capability of hysteresis synchronous motor  

NASA Technical Reports Server (NTRS)

Frequency and phase detector circuit enables a hysteresis synchronous motor to drive a load of given torque value at a precise speed determined by a stable reference. This technique permits driving larger torque loads with smaller motors and lower power drain.

Markowitz, I. N.

1967-01-01

415

Flexible pivot mount eliminates friction and hysteresis  

NASA Technical Reports Server (NTRS)

Flexible steel pivot mount, suspended by flat vertical beryllium copper springs, is capable of rotation, free of hysteresis and starting friction. Mount requires no lubrication, is made in varying sizes, and is driven with either dc torque motor or mechanical linkage.

Highman, C. O.

1970-01-01

416

A phenomenological mathematical model of hysteresis  

Microsoft Academic Search

This paper starts with the description of a purely mathematical model of the saturation curve and the hysteresis loop based on the fundamental similarities between the Langevin function the specified T(x) function and the sigmoid shape. The T(x) function which is composed of tangent hyperbolic and linear functions with its free parameters can describe the regular anhysteretic magnetisation curve. Developed

J. Takács

2001-01-01

417

Equivalent Circuit Modeling of Hysteresis Motors.  

National Technical Information Service (NTIS)

We performed a literature review and found that many equivalent circuit models of hysteresis motors in use today are incorrect. The model by Miyairi and Kataoka (1965) is the correct one. We extended the model by transforming it to quadrature coordinates,...

B. A. Kirkendall E. T. Scharlemann J. J. Nitao

2009-01-01

418

Managing Hysteresis: Three Cornerstones to Fiscal Stability  

ERIC Educational Resources Information Center

The effects of the Great Recession of 2007-2009 continue to challenge school business officials (SBOs) and other education leaders as they strive to prepare students for the global workforce. Economists have borrowed a word from chemistry to describe this state of affairs: hysteresis--the lingering effects of the past on the present. Today's SBOs…

Weeks, Richard

2012-01-01

419

Role of hysteresis in stomatal aperture dynamics  

NASA Astrophysics Data System (ADS)

Stomata are pores responsible for gas exchange in leaves. Several experiments indicate that stomata synchronize into clusters or patches. The patches’ coordination may produce oscillations in stomatal conductance. Previous studies claim to reproduce some experimental results. However, none was able to explain the variety of behavior observed in the stomatal dynamics. Recently, Ferraz and Prado suggested a realistic geometry of vein distribution. Although it reproduces the patches, no oscillation was observed and the patches remain static. Without exploring significant details, the authors stated that hysteresis in stomatal aperture could explain several experimental features. In this paper, the hysteresis hypothesis is further explored through the concept of hysteretic operators. We have shown that the hysteresis assumption is sufficient to obtain dynamical patches and oscillations in stomatal conductance. The robustness of this hypothesis is tested by using different hysteresis operators. The model analysis reveals a dependence between the period of oscillation in stomatal conductance and the water deficit between the leaf and the environment. This underlying feature of the model might inspire further experiments to test this hypothesis.

Ramos, Antônio M. T.; Prado, Carmen P. C.

2013-01-01

420

Correlation of AC Loss Data from Magnetic Susceptibility Measurements with YBCO Film Quality (Postprint).  

National Technical Information Service (NTIS)

It has been previously suggested that with spreading of the temperature-dependent ac susceptibility curves with increasing applied magnetic field, the quality of the YBCO film generally decreases. However, a documented study of this correlation to current...

A. L. Westerfield L. B. Brunke P. N. Barnes S. Sathiraju T. J. Haugan

2012-01-01

421

Influence of Nanocrystalline Ferrite Particles on Properties of Magnetic Systems  

NASA Astrophysics Data System (ADS)

Nanocrystalline mainly superparamagnetic ferrite particles ? 10 nm are used for the preparation of magnetic fluids. Barium hexaferrite BaFe12-2xTixCoxO19 powders with mean particle sizes < 30 nm show the transition to single domain Stoner-Wohlfarth behaviour. Hysteresis parameters, losses and the initial susceptibility versus temperature were obtained by VSM. Ba-ferrite ferrofluids have been prepared using Isopar M or dodecane as carrier liquid. Small Angle Neutron Scattering curves lead to a bimodal size distribution consisting of single magnetic particles and aggregated magnetic particles. Particle size investigations were done by TEM.

Mueller, Robert; Habisreuther, Tobias; Hiergeist, Robert; Steinmetz, Hanna; Zeisberger, Matthias; Gawalek, Wolfgang

422

Loss of Magnetic Insulation in a Crossed-Field Diode: Ion and Collisional Effects  

Microsoft Academic Search

The effect of ion production through ionizing collisions in a magnetically insulated crossed-field gap is studied by using one-dimensional particle-in-cell software. These results are compared with the predictions from previous efforts that assumed immobile sheets of positive charge at different positions within the gap. Our results with mobile ions created via collisions indicate that the diode can lose magnetic insulation

Brooke S. Stutzman; John W. Luginsland

2010-01-01

423

Geometric Hysteresis of Alveolated Ductal Architecture  

PubMed Central

Low Reynolds number airflow in the pulmonary acinus and aerosol particle kinetics therein are significantly conditioned by the nature of the tidal motion of alveolar duct geometry. At least two components of the ductal structure are known to exhibit stress-strain hysteresis: smooth muscle within the alveolar entrance rings, and surfactant at the air-tissue interface. We hypothesize that the geometric hysteresis of alveolar duct is largely determined by the interaction of the amount of smooth muscle & connective tissue in ductal rings, septal tissue properties, and surface tension-surface area characteristics of surfactant. To test this hypothesis, we have extended the well-known structural model of the alveolar duct by Wilson and Bachofen (J. Appl. Physiol. 52(4): 1064–1070, 1982) by adding realistic elastic and hysteretic properties of 1) the alveolar entrance ring, 2) septal tissue, and 3) surfactant. With realistic values for tissue and surface properties, we conclude that: 1) there is a significant, and underappreciated, amount of geometric hysteresis in alveolar ductal architecture; and 2) the contribution of smooth muscle and surfactant to geometric hysteresis are of opposite senses, tending toward cancellation. Quantitatively, the geometric hysteresis found experimentally by Miki et al. (J. Appl. Physiol. 75(4): 1630–1636, 1993) is consistent with little or no smooth muscle tone in anesthetized rabbits in control conditions, and with substantial smooth muscle activation following methacholine challenge. The observed local hysteretic boundary motion of the acinar duct would result in irreversible acinar flow fields, which might be important mechanistic contributors to aerosol mixing and deposition deep in the lung.

Kojic, M.; Butler, J. P.; Vlastelica, I.; Stojanovic, B.; Rankovic, V.; Tsuda, A.

2013-01-01

424

Hybrid magnetic field formulation based on the losses separation method for modified dynamic inverse Jiles-Atherton model  

NASA Astrophysics Data System (ADS)

Dynamic formulation based on the losses separation method in conducting media for the inverse Jiles-Atherton model is proposed. This formulation is based on the concept of the Hybrid Magnetic Field model (HMF). The HMF consists of the modification of the effective field by introducing two counter-fields associated, respectively, with the eddy current and excess losses. Such a formulation is characterized by seven parameters with five parameters issued from the quasi-static Jiles-Atherton model. Thus, two new parameters related to these fields are added to that defined in the quasi-static model. The identification of these new parameters is based on the measurements of the volumetric energy density. To validate this formulation, measurements are carried out on grain non-oriented Fe-Si 3% electrical sheets.

Hamimid, M.; Mimoune, S. M.; Feliachi, M.

2011-07-01

425

Loss of confinement at the density limit due to the suppression of stabilizing zonal flows by magnetic turbulence  

SciTech Connect

The character of particle and energy transport in numerical simulations of drift-ballooning turbulence changes dramatically as the density exceeds a critical limit. When the density is not too large, then unstable drift-ballooning fluctuations grow and nonlinearly generate a sheared zonal (flux surface averaged) flow that saturates the turbulence. But when diamagnetic drift effects are small and the density increases beyond a critical limit, then the turbulent density flux increases monotonically in time to large values without saturation. This loss of confinement is caused by the suppression of the stabilizing zonal flow by the magnetic component of the turbulence. A Kelvin-Helmholtz-like shear-flow instability does not play any role in reducing the magnitude of the zonal flow. The magnetic turbulence prevents the zonal flow from growing large enough to become shear-flow unstable.

Kleva, Robert G.; Guzdar, Parvez N. [Institute for Research in Electronics and Applied Physics, University of Maryland, College Park, Maryland 20742 (United States)

2008-08-15

426

Power losses of Finemet using nonsinusoidal waveforms  

NASA Astrophysics Data System (ADS)

Though many practical applications preferably take advantage of nonsinusoidal induction waveforms the characterisation of soft magnetic materials is performed under sinusoidal induction waveforms. Therefore, it would be useful if results from magnetic measurements could be transformed to be valid for applications using different waveforms. This also enables to compare results obtained from measurements where sinusoidal waveforms could not be realised and thus makes them independent of the measuring device used. The dynamic hysteresis loops of differently prepared Finemet ribbons were measured with a computer controlled device at different frequencies and polarisations using sinusoidal and triangular waveforms of the magnetic field which leads to induction waveforms varying with frequency, amplitude of polarisation, waveform of the magnetising field and preparation of specimen material. The samples measured were strips of Fe 73.5Si 13.5Cu 1Nb 3B 9 nanocrystallised at 580°C for 1 h. Different types of samples were used which includes specimens surface treated prior to heat treatment in order to achieve domain refinement. A one to one functional dependency between power loss, frequency, and k-factor was found that enables the comparison of power losses for different induction signals characterised by their form factor as it is already known for grain oriented silicon steel sheets. This dependency is valid for all types of specimen investigated regardless of their different magnetic properties.

Ramin, D.; Riehemann, W.

1999-08-01

427

Torque meter aids study of hysteresis motor rings  

NASA Technical Reports Server (NTRS)

Torque meter, simulating hysteresis motor operation, allows rotor ring performance characteristics to be analyzed. The meter determines hysteresis motor torque and actual stresses of the ring due to its mechanical situation and rotation, aids in the study of asymmetries or defects in motor rings, and measures rotational hysteresis.

Cole, M.

1967-01-01

428

Hysteresis and gold in metal-insulator-semiconductor (MIS) capacitors  

Microsoft Academic Search

Measurements on gold diffused MIS capacitors, using different dielectric materials, have shown that in addition to changing the surface charge densities present at the silicon-dielectric interface, the gold also reduces the voltage hysteresis commonly observed in the capacitor C-V curves. Some orientation dependent hysteresis results, taken with these gold results, would indicate that the centres responsible for the hysteresis are

S. D. BROTHERTON

1968-01-01

429

Quantum Hydrodynamic Simulation of Hysteresis in the Resonant Tunneling Diode  

Microsoft Academic Search

Hysteresis in the current-voltage curve of a resonant tunneling diode is simulated and analyzed in the quantum hydrodynamic (QHD) model for semiconductor devices. The simulations are the first to show hysteresis in the QHD equations and to confirm that bistability is an intrinsic property of the resonant tunneling diode. Hysteresis appears in many settings in fluid dynamics. The simulations presented

Zhangxin Chen; Bernardo Cockburn; Carl L. Gardner; Joseph W. Jerome

1995-01-01

430

Empirical structure for characterizing metal loss defects from radial magnetic flux leakage signal  

Microsoft Academic Search

Magnetic flux leakage (MFL) technique is one of the oldest and most commonly used technique for detecting corrosion in the pipe wall as well as pipeline features like welds, valves, supports, attachments, etc. The MFL data obtained is processed for detecting (isolating) defect or feature signal and characterizing it for the purpose of sizing or assigning a template. This paper

S. Saha; S. Mukhopadhyay; U. Mahapatra; S. Bhattacharya; G. P. Srivastava

2010-01-01

431

Analytical core loss calculations for magnetic materials used in high frequency high power converter applications. Ph.D. Thesis - Toledo Univ.  

NASA Technical Reports Server (NTRS)

The basic magnetic properties under various operating conditions encountered in the state-of-the-art DC-AC/DC converters are examined. Using a novel core excitation circuit, the basic B-H and loss characteristics of various core materials may be observed as a function of circuit configuration, frequency of operation, input voltage, and pulse-width modulation conditions. From this empirical data, a mathematical loss characteristics equation is developed to analytically predict the specific core loss of several magnetic materials under various waveform excitation conditions.

Triner, J. E.

1979-01-01

432

Loss of bone calcium in exposure to 50 Hz magnetic fields.  

PubMed

This study investigates the effect of whole body exposure to magnetic fields on the calcium level of blood and bone in a trial to avoid the liability of osteoporosis, fractures, and delayed union of fractures after exposure to magnetic fields present everywhere in the environment. The procedures of the study included analysis for calcium level in both bone and blood. The procedures were performed on 50 Guinea pigs equally divided into 5 groups. Groups A, B, C, and D were exposed to 50 Hz, 0.2 mT magnetic field for 30 d. Group E animals were the control. Group A was sacrificed immediately after exposure; Group B was left away from the field for 15 d for spontaneous repair; Group C received the drug Centrum dissolved in drinking water for 15 d after exposure to the magnetic field; and Group D received centrum in drinking water during the period of exposure (30 d). After sacrificing all animals, the calcium level in both bone and blood was evaluated. Values of blood analysis revealed significant increase in the blood calcium level in exposed animals compared with the control group (P < 0.002) with excess in Group A. This indicated that the calcium left the bone to the blood. Values of the bone analysis revealed significant decrease in bone calcium concentration level in Group A compared with the control group and improvement in the bone condition in Groups C and D, indicating the role of trace element after the exposure period as a compensatory agent of magnetic field damage and its role during the exposure period as a radio-protecting agent. PMID:19037789

Hanafy, Enas; Elhafez, Salam; Aly, Fadel; Elazhary, Mohamed

2008-01-01

433

Measurement of magnetic losses by thermal method applied to power ferrites at high level of induction and frequency.  

PubMed

Classically, low frequency losses in soft magnetic materials and ferrites in particular are measured by flux metric method under sinusoidal waveform excitation voltage. However, in typical application of modern power electronics, the frequency currently exceeds 100 kHz. This feature is at the origin of a difficulty: the phase shift between current and voltage can be disturbed by current probe delay. Thus, the results can be affected by large errors. As a consequence, it becomes more and more important to develop alternative methods to measure losses in magnetic materials. It is proposed to use calorimetric method which is by principle free of the above mentioned problems. The experimental device is described in details and the results are reported for experiments conducted on a commercial Mn-Zn ferrite under sinusoidal waveform regime for frequencies varying from 10 to 200 kHz. Comparisons with flux metric measurement show that significant differences appear typically for Bf products above 5000 V/m(2) (50 kHzx100 mT). PMID:19256669

Loyau, V; Lo Bue, M; Mazaleyrat, F

2009-02-01

434

Origin of the constricted hysteresis loop in cobalt ferrites revisited  

NASA Astrophysics Data System (ADS)

A series of Co ferrites (Co xFe 3- xO 4 ( x=0-1)) were prepared using solid-state method in this work. The aging effect of their structures and constrictions of hysteresis loops under low magnetic field were investigated. It was found that during the aging process, the migration of trivalent (bivalent) ions between tetrahedral (A-site) and octahedral (B-site) coordination induced a shrinking of the lattice, which would expand again due to the precipitation of Fe 3+ after a much longer aging time. The first process caused a pronounced constriction of the loops, due to the uniaxial anisotropy led by this migration. The depression of constriction could attribute to both the expansion of lattice and the change of ionic ratios as a result of the second-phase-precipitation. The impacts of Co content, aging time and temperature upon the constriction were also discussed.

Zhang, Hong-guo; Zhang, Yu-Jie; Wang, Weng-Hong; Wu, Guang-Heng

2011-08-01

435

Wetting Hysteresis at the Molecular Scale  

NASA Technical Reports Server (NTRS)

The motion of a fluid-fluid-solid contact line on a rough surface is well known to display hysteresis in the contact angle vs. velocity relationship. In order to understand the phenomenon at a fundamental microscopic level, we have conducted molecular dynamics computer simulations of a Wilhelmy plate experiment in which a solid surface is dipped into a liquid bath, and the force-velocity characteristics are measured. We directly observe a systematic variation of force and contact angle with velocity, which is single-valued for the case of an atomically smooth solid surface. In the microscopically rough case, however, we find (as intuitively expected) an open hysteresis loop. Further characterization of the interface dynamics is in progress.

Jin, Wei; Koplik, Joel; Banavar, Jayanth R.

1996-01-01

436

Element-specific hysteresis loop measurements on Individual 35 nm islands with scanning transmission X-ray microscopy.  

PubMed

Using scanning transmission X-ray microscopy combined with X-ray magnetic circular dichroism, element-specific hysteresis loops with a 25 nm X-ray probe are obtained on 35 nm Fe/Gd multilayer nanoislands fabricated by extreme ultra-violet interference lithography. Local hysteresis loops measured for the individual islands and the antidot film between the islands display similar behavior resulting from the lateral confinement. Line scan measurements confirm ferrimagnetic coupling between Fe and Gd in the patterned region. The ability to measure magnetization reversal with X-rays at high spatial resolution will provide an important tool for future characterization of sub-50 nm nanostructures. PMID:22755078

Luo, Feng; Eimüller, Thomas; Amaladass, Edward; Lee, Ming Sang; Heyderman, Laura J; Solak, Harun H; Tyliszczak, Tolek

2012-03-01

437

Sorption hysteresis of benzene in charcoal particles.  

PubMed

Charcoal is found in water, soil, and sediment where it may act as a sorbent of organic pollutants. The sorption of organic compounds to natural solids often shows hysteresis. The purpose of this study was to determine the source of pronounced hysteresis that we found in the sorption of a hydrophobic compound (benzene) in water to a maple-wood charcoal prepared by oxygen-limited pyrolysis at 673 K. Gas adsorption (N2, Ar, CO2), 13C NMR, and FTIR show the charcoal to be a microporous solid composed primarily of elemental (aromatic) C and secondarily of carboxyl and phenolic C. Nonlocal density functional theory (N2, Ar) and Monte Carlo (CO2) calculations reveal a porosity of 0.15 cm3/g, specific surface area of 400 m2/g, and appreciable porosity in ultramicropores < 10 A. Benzene sorption-desorption conditions were chosen to eliminate artificial causes of hysteresis (rate-limiting diffusion, degradation, colloids effect). Charcoal sorbed up to its own weight of benzene at approximately 69% of benzene water solubility. Sorption was highly irreversible over most of the range tested (10(-4)-10(3) microg/mL). A dimensionless irreversibility index (/i) (0 < or = /i < or = 1) based on local slopes of adsorption and desorption branches was evaluated at numerous places along the isotherm. /i decreases as C increases, from 0.9-1 at low concentration to approximately 0 (approximately fully reversible) at the highest concentrations. Using sedimentation and volumetric displacement measurements, benzene is observed to cause pronounced swelling (up to > 2-fold) of the charcoal particles. It is proposed that hysteresis is due to pore deformation by the solute, which results in the pathway of sorption being different than the pathway of desorption and which leads to entrapment of some adsorbate as the polyaromatic scaffold collapses during desorption. It is suggested that intra-charcoal mass transport may be influenced by structural rearrangement of the solid, in addition to molecular diffusion. PMID:12564916

Braida, Washington J; Pignatello, Joseph J; Lu, Yuefeng; Ravikovitch, Peter I; Neimark, Alexander V; Xing, Baoshan

2003-01-15

438

The role of multi-walled carbon nanotubes on the magnetic and reflection loss characteristics of substituted strontium ferrite nanoparticles  

NASA Astrophysics Data System (ADS)

Substituted strontium ferrite SrFe12-x(Ni0.5Mn0.5Zr)x/2O19/multi-walled carbon nanotubes (MWCNTs) composites were prepared by a sol-gel method. X-ray diffraction patterns confirm the formation of single phase ferrite nanoparticle and nanocomposites of ferrite/carbon nanotubes. Fourier transform infrared spectroscopy demonstrates the existence of functional groups on the surface of carbon nanotubes. Superconducting quantum interference device measurements showed that the values of specific saturation magnetization increases, while coercivity decreases with an increase in substitution content. Zero field cooled magnetization and field cooled magnetization curves display that with an increase in substitution content, the blocking temperature increases. Field emission scanning electron microscopy micrographs demonstrate that ferrite nanoparticles were attached on external surfaces of the carbon nanotubes. The investigation of the microwave absorption indicates that with an addition of carbon nanotubes, the real and imaginary parts of permittivity and reflection loss enhanced. It is found that with increasing the thickness of absorbers, the resonance frequencies shift to lower regime.

Ghasemi, Ali

2013-03-01

439

Angular Dependence of Transport AC Losses in Superconducting Wire with Position-Dependent Critical Current Density in a DC Magnetic Field  

NASA Astrophysics Data System (ADS)

Transport AC losses play a very important role in high temperature superconductors (HTSs), which usually carry AC transport current under applied magnetic field in typical application-like conditions. In this paper, we propose the analytical formula for transport AC losses in HTS wire by considering critical current density of both inhomogeneous and anisotropic field dependent. The angular dependence of critical current density is described by effective mass theory, and the HTS wire has inhomogeneous distribution cross-section of critical current density. We calculate the angular dependence of normalized AC losses under different DC applied magnetic fields. The numerical results of this formula agree well with the experiment data and are better than the results of Norris formula. This analytical formula can explain the deviation of experimental transport current losses from the Norris formula and apply to calculate transport AC losses in realistic practical condition.

Su, Xing-liang; Xiong, Li-ting; Gao, Yuan-wen; Zhou, You-he

2013-07-01

440

Enhanced Magnetic and Ferroelectric Properties and Current-Voltage Hysteresis by Addition of La and Ti to BiFeO3 on 0.7%Nb-SrTiO3  

Microsoft Academic Search

By adding La and Ti, we improve the magnetic and ferroelectric properties of Bi0.8La0.2Fe0.92Ti0.08O3 and Bi0.8La0.2FeO3 films on 0.7% Nb-SrTiO3. In Bi0.8La0.2Fe0.92Ti0.08O3 and Bi0.8La0.2FeO3, the saturation magnetization and the coercivity are several times higher than those in BiFeO3. The La and Ti additions reduce the leakage current, and increase the remnant electric polarization. A resistance switching is observed in Bi0.8La0.2Fe0.92Ti0.08O3\\/0.7%Nb-SrTiO3

Hong Chang; Yong-Gang Zhao

2011-01-01

441

Synthesis of Bio-Compatible SPION-based Aqueous Ferrofluids and Evaluation of RadioFrequency Power Loss for Magnetic Hyperthermia  

PubMed Central

Bio-compatible magnetic fluids having high saturation magnetization find immense applications in various biomedical fields. Aqueous ferrofluids of superparamagnetic iron oxide nanoparticles with narrow size distribution, high shelf life and good stability is realized by controlled chemical co-precipitation process. The crystal structure is verified by X-ray diffraction technique. Particle sizes are evaluated by employing Transmission electron microscopy. Room temperature and low-temperature magnetic measurements were carried out with Superconducting Quantum Interference Device. The fluid exhibits good magnetic response even at very high dilution (6.28 mg/cc). This is an advantage for biomedical applications, since only a small amount of iron is to be metabolised by body organs. Magnetic field induced transmission measurements carried out at photon energy of diode laser (670 nm) exhibited excellent linear dichroism. Based on the structural and magnetic measurements, the power loss for the magnetic nanoparticles under study is evaluated over a range of radiofrequencies.

2010-01-01

442

Influence of cooling rate on iron loss behavior in 6.5 wt% grain-oriented silicon steel  

NASA Astrophysics Data System (ADS)

The influence of cooling rate on iron loss behaviors has been investigated in 6.5 wt% grain-oriented silicon steels. To fabricate 6.5 wt% grain-oriented silicon steels and control the microstructure, 3.0 wt% grain-oriented silicon steels covered with SiO2 materials were annealed at 1200 °C and then cooled to room temperature using oil quenching, air cooling, or furnace cooling. The magnetic loss of furnace-cooled samples was reduced by 25% compared with oil-quenched samples due to lower anomalous and hysteresis losses. Microstructural analysis showed that these loss behaviors were strongly related to the formation and growth of ordered phases, i.e., B2 and D03. These correlations could be ascribed to the formation of antiphase boundaries, which acted as pinning sites of the magnetic domain walls.

Jung, Heejong; Kim, Jongryoul

2014-03-01

443

Soft Magnetic Properties of Obliquely Deposited Co-Zr-O Granular Films  

Microsoft Academic Search

This work first studied the magnetic properties of obliquely deposited granular Co-Zr-O films. It was found that the oblique deposition induces increased hysteresis and decreased permeability in the films, which leads to larger loss and less inductance in the micro-inductor applications. Applying substrate bias during film deposition is an effective method to eliminate the influence of oblique deposition in Permalloy

Y. Sun; W. Li; D. Kopp; F. Johnson; S. T. Taylor; C. R. Sullivan

2006-01-01

444

A stability-based mechanism for hysteresis in the walk-trot transition in quadruped locomotion.  

PubMed

Quadrupeds vary their gaits in accordance with their locomotion speed. Such gait transitions exhibit hysteresis. However, the underlying mechanism for this hysteresis remains largely unclear. It has been suggested that gaits correspond to attractors in their dynamics and that gait transitions are non-equilibrium phase transitions that are accompanied by a loss in stability. In the present study, we used a robotic platform to investigate the dynamic stability of gaits and to clarify the hysteresis mechanism in the walk-trot transition of quadrupeds. Specifically, we used a quadruped robot as the body mechanical model and an oscillator network for the nervous system model to emulate dynamic locomotion of a quadruped. Experiments using this robot revealed that dynamic interactions among the robot mechanical system, the oscillator network, and the environment generate walk and trot gaits depending on the locomotion speed. In addition, a walk-trot transition that exhibited hysteresis was observed when the locomotion speed was changed. We evaluated the gait changes of the robot by measuring the locomotion of dogs. Furthermore, we investigated the stability structure during the gait transition of the robot by constructing a potential function from the return map of the relative phase of the legs and clarified the physical characteristics inherent to the gait transition in terms of the dynamics. PMID:23389894

Aoi, Shinya; Katayama, Daiki; Fujiki, Soichiro; Tomita, Nozomi; Funato, Tetsuro; Yamashita, Tsuyoshi; Senda, Kei; Tsuchiya, Kazuo

2013-04-01

445

A stability-based mechanism for hysteresis in the walk-trot transition in quadruped locomotion  

PubMed Central

Quadrupeds vary their gaits in accordance with their locomotion speed. Such gait transitions exhibit hysteresis. However, the underlying mechanism for this hysteresis remains largely unclear. It has been suggested that gaits correspond to attractors in their dynamics and that gait transitions are non-equilibrium phase transitions that are accompanied by a loss in stability. In the present study, we used a robotic platform to investigate the dynamic stability of gaits and to clarify the hysteresis mechanism in the walk–trot transition of quadrupeds. Specifically, we used a quadruped robot as the body mechanical model and an oscillator network for the nervous system model to emulate dynamic locomotion of a quadruped. Experiments using this robot revealed that dynamic interactions among the robot mechanical system, the oscillator network, and the environment generate walk and trot gaits depending on the locomotion speed. In addition, a walk–trot transition that exhibited hysteresis was observed when the locomotion speed was changed. We evaluated the gait changes of the robot by measuring the locomotion of dogs. Furthermore, we investigated the stability structure during the gait transition of the robot by constructing a potential function from the return map of the relative phase of the legs and clarified the physical characteristics inherent to the gait transition in terms of the dynamics.

Aoi, Shinya; Katayama, Daiki; Fujiki, Soichiro; Tomita, Nozomi; Funato, Tetsuro; Yamashita, Tsuyoshi; Senda, Kei; Tsuchiya, Kazuo

2013-01-01

446

Rotational hysteresis and training effect of ferro\\/antiferromagnetic exchange-coupled systems  

Microsoft Academic Search

This dissertation presents experimental results and explanations about two fundamental phenomena of ferromagnetic (F)\\/antiferromagnetic (AF) exchange coupled polycrystalline layer systems, i.e., the 360°-symmetry rotational hysteresis and the magnetic training effect. Various F\\/AF exchange coupled systems were prepared, studied and compared. The results imply that the direct exchange coupling between the AF grains is playing a decisive role in governing the

Kunliang Zhang

2002-01-01

447

Modeling of micromagnetic Barkhausen activity using a stochastic process extension to the theory of hysteresis  

SciTech Connect

Recent work by Bertotti [IEEE Trans. Magn. [bold MAG]-[bold 24], 621 (1988)] and others has shown that it is possible to model the micromagnetic Barkhausen discontinuities at the coercive point using a two-parameter stochastic model. However, the present formulation of the model is restricted to limited regions of the hysteresis curve over which [ital dM]/[ital dH] is approximately constant and when [ital dH]/[ital dt] is held at a constant rate. A natural extension of this model is to take the basic result, in which the level of Barkhausen activity in one time period is related to the activity in the previous time period, and increment it by a small amount which is dependent on the differential permeability. The extension of the model proposed here uses the theory of ferromagnetic hysteresis to determine the differential permeability at any point of the hysteresis loop. The Barkhausen activity is then assumed to vary in proportion to the differential permeability. The resulting model allows the Barkhausen sum of discontinuous changes in magnetization to be modelled around the entire hysteresis loop, leading to an important generalization of the basic model.

Jiles, D.C. (Ames Laboratory, Center for Nondestructive Evaluation, Department of Materials Science and Engineering and Department of Electrical Engineering, Iowa State University, Ames, Iowa 50011 (United States)); Sipahi, L.B. (Ames Laboratory, Center for Nondestructive Evaluation, and Department of Physics, Iowa State University, Ames, Iowa 50011 (United States)); Williams, G. (Ames Laboratory, Iowa State University, Ames, Iowa 50011 (United States))

1993-05-15

448

Hysteresis Loop for a No-loaded, Delta-connected Transformer Model Deduced from Measurements  

NASA Astrophysics Data System (ADS)

At a transformer's steady-state condition, whereby a transformer and its load are constantly supplied by a sinusoidal source, the current-flux pair within the transformer core and its windings will cycle along a hysteresis loop. This nonlinear current-flux characteristic becomes important while at transformer gets reenergized. A remaining residual flux and the fact that a transformer is typically used up to its saturation level can lead to high-amplitude magnetizing inrush currents and associated voltage disturbances. These disturbances can be reduced by controlled transformer switching. In order to pre-evaluate the effect of a specific controlled transformer energization, pre-simulations can be applied. In that case the hysteresis loop and its saturation characteristic will become the most important model parameter. If the corresponding manufacturer specifications are not available a standard hysteresis loops can be used, but might come up with an inaccurate simulation result. Therefore, this paper analyses the measured 3-phase currents from two delta-connected power transformers by “Fourier Series” in order to deduce a single-phase hysteresis loop, which can be implemented into a typical 3-phase transformer model. Additionally, the saturation behavior of a power-transformer will be estimated and a comparison of ATP/EMTP simulations will conclude this paper.

Corrodi, Yves; Kamei, Kenji; Kohyama, Haruhiko; Ito, Hiroki

449

Untangling perceptual memory: hysteresis and adaptation map into separate cortical networks.  

PubMed

Perception is an active inferential process in which prior knowledge is combined with sensory input, the result of which determines the contents of awareness. Accordingly, previous experience is known to help the brain "decide" what to perceive. However, a critical aspect that has not been addressed is that previous experience can exert 2 opposing effects on perception: An attractive effect, sensitizing the brain to perceive the same again (hysteresis), or a repulsive effect, making it more likely to perceive something else (adaptation). We used functional magnetic resonance imaging and modeling to elucidate how the brain entertains these 2 opposing processes, and what determines the direction of such experience-dependent perceptual effects. We found that although affecting our perception concurrently, hysteresis and adaptation map into distinct cortical networks: a widespread network of higher-order visual and fronto-parietal areas was involved in perceptual stabilization, while adaptation was confined to early visual areas. This areal and hierarchical segregation may explain how the brain maintains the balance between exploiting redundancies and staying sensitive to new information. We provide a Bayesian model that accounts for the coexistence of hysteresis and adaptation by separating their causes into 2 distinct terms: Hysteresis alters the prior, whereas adaptation changes the sensory evidence (the likelihood function). PMID:23236204

Schwiedrzik, Caspar M; Ruff, Christian C; Lazar, Andreea; Leitner, Frauke C; Singer, Wolf; Melloni, Lucia

2014-05-01

450

Hysteresis in stress cycling of amorphous ribbons  

NASA Astrophysics Data System (ADS)

The permeability of soft amorphous ribbons shows significant hysteresis through stress cycling. The response of a circuit incorporating an amorphous CoFeNiSiB based ribbon, as a function of longitudinal stress, with a longitudinal excitation field, is measured. The behaviour of the stress impedance is related to domain wall behaviour, at a range of different frequencies, through a simple model of eddy currents in sheets. It is suggested that changes in the pinning mechanism have a profound effect on the measured impedance.

Tomka, G. J.; Milne, J.; Tweed, S.; Thomas, O.

2004-05-01

451

Mechano-electric optoisolator transducer with hysteresis  

NASA Astrophysics Data System (ADS)

This article presents a theoretical and experimental study of designing a mechano-electric optoisolator transducer with hysteresis. Our research is centred upon designing transducers on the basis of optical sensors, as photoelectric conversions eliminate the influence of electromagnetic disturbances. Conversion of the rotation/translation motions into electric signals is performed with the help of a LED-photoresistor Polaroid optocoupler. The driver of the optocoupler's transmitter module is an independent current source. The signal conditioning circuit is a Schmitt trigger circuit. The device is designed to be applied in the field of automation and mechatronics.

Ciuru?, I. M.; Dimian, M.; Graur, A.

2011-01-01

452

Numerical and theoretical evaluations of AC losses for single and infinite numbers of superconductor strips with direct and alternating transport currents in external AC magnetic field  

NASA Astrophysics Data System (ADS)

AC losses in a superconductor strip are numerically evaluated by means of a finite element method formulated with a current vector potential. The expressions of AC losses in an infinite slab that corresponds to a simple model of infinitely stacked strips are also derived theoretically. It is assumed that the voltage-current characteristics of the superconductors are represented by Bean’s critical state model. The typical operation pattern of a Superconducting Magnetic Energy Storage (SMES) coil with direct and alternating transport currents in an external AC magnetic field is taken into account as the electromagnetic environment for both the single strip and the infinite slab. By using the obtained results of AC losses, the influences of the transport currents on the total losses are discussed quantitatively.

Kajikawa, K.; Funaki, K.; Shikimachi, K.; Hirano, N.; Nagaya, S.

2010-11-01

453

Structural, Magnetic, and Reflection Loss Characteristics of Ni/Co/Sn-Substituted Strontium Ferrite/Functionalized MWCNT Nanocomposites  

NASA Astrophysics Data System (ADS)

Ni/Co/Sn-substituted strontium ferrite [SrFe12- x (Ni0.5Co0.5Sn) x/2O19]/multiwalled carbon nanotube (MWCNT) nanocomposites were produced by assembling ferrite particles on the external surfaces of MWCNTs. Various techniques including x-ray diffraction (XRD) analysis, transmission electron microscopy, field-emission scanning electron microscopy (FE-SEM), and Fourier-transform infrared (FTIR) spectroscopy were used to demonstrate the successful attachment of ferrite particles onto the external surfaces of the MWCNTs. XRD analysis and FTIR spectroscopy confirmed the presence of strontium ferrite and carbon nanotube phases in ferrite and nanocomposite samples, respectively. FE-SEM micrographs indicated the formation of ferrite particles on the outer surfaces of MWCNTs in nanocomposite samples. Furthermore, vibrating-sample magnetometer (VSM) and reflection loss (RL) measurements were performed to assess the magnetic and microwave characteristics of the synthesized samples. VSM loops confirmed a relatively strong dependence of the saturation magnetization and coercivity on the volume percentage of MWCNTs. With the introduction of MWCNTs or an increase in the substitution, the saturation magnetization and coercivity were decreased. The RL properties of the nanocomposites were investigated in the 8 GHz to 12 GHz frequency range. The sample with 80 wt.% nanocomposite content showed a maximum RL of -35 dB at 8.3 GHz with a 4 GHz absorption bandwidth over the extended frequency range of 8 GHz to 12 GHz for absorber thickness of 1.8 mm. The RL evaluations indicated that these nanocomposites have high potential for application as wide-band electromagnetic wave absorbers at GHz frequencies.

Mousavinia, Mohammad; Ghasemi, Ali; Paimozd, Ebrahim

2014-07-01

454

Structural, Magnetic, and Reflection Loss Characteristics of Ni/Co/Sn-Substituted Strontium Ferrite/Functionalized MWCNT Nanocomposites  

NASA Astrophysics Data System (ADS)

Ni/Co/Sn-substituted strontium ferrite [SrFe12-x (Ni0.5Co0.5Sn) x/2O19]/multiwalled carbon nanotube (MWCNT) nanocomposites were produced by assembling ferrite particles on the external surfaces of MWCNTs. Various techniques including x-ray diffraction (XRD) analysis, transmission electron microscopy, field-emission scanning electron microscopy (FE-SEM), and Fourier-transform infrared (FTIR) spectroscopy were used to demonstrate the successful attachment of ferrite particles onto the external surfaces of the MWCNTs. XRD analysis and FTIR spectroscopy confirmed the presence of strontium ferrite and carbon nanotube phases in ferrite and nanocomposite samples, respectively. FE-SEM micrographs indicated the formation of ferrite particles on the outer surfaces of MWCNTs in nanocomposite samples. Furthermore, vibrating-sample magnetometer (VSM) and reflection loss (RL) measurements were performed to assess the magnetic and microwave characteristics of the synthesized samples. VSM loops confirmed a relatively strong dependence of the saturation magnetization and coercivity on the volume percentage of MWCNTs. With the introduction of MWCNTs or an increase in the substitution, the saturation magnetization and coercivity were decreased. The RL properties of the nanocomposites were investigated in the 8 GHz to 12 GHz frequency range. The sample with 80 wt.% nanocomposite content showed a maximum RL of -35 dB at 8.3 GHz with a 4 GHz absorption bandwidth over the extended frequency range of 8 GHz to 12 GHz for absorber thickness of 1.8 mm. The RL evaluations indicated that these nanocomposites have high potential for application as wide-band electromagnetic wave absorbers at GHz frequencies.

Mousavinia, Mohammad; Ghasemi, Ali; Paimozd, Ebrahim

2014-04-01

455

Application of linear magnetic loss model of ferrite to induction cavity simulation  

SciTech Connect

A linear, frequency independent model of the rf properties of unbiased, soft ferrite has been implemented in finite-difference, time-domain, electromagnetic simulation code AMOS for the purposes of studying linac induction cavities. The simple model consists of adding a magnetic conductivity term ({sigma}{sub m}H) to Faraday's Law. The value of {sigma}{sub m} that is appropriate for a given ferrite at a particular frequency is obtained via an rf reflection experiment on a very thin ferrite toroid in a shorted coaxial line. It was found that in the frequency range 100 to 1000 MHz, the required value of {sigma}{sub m} varies only slightly (<10%), and so we approximated it as a frequency independent parameter in AMOS. A description of the experimental setup and the technique used to extract the complex {mu} from the measurements is described. The model has been used to study the impedances of the DARHT induction cavity, and comparisons between these experimental measurements and AMOS calculations is presented. Implementation of a frequency dependent version of this model in AMOS is being pursued, and a discussion of this effort is given.

DeFord, J.F.; Kamin, G.

1990-09-05

456

Critical state and AC losses in multifilamentary BiSrCaCuO-2223/Ag tapes studied by transport and magnetic measurements  

NASA Astrophysics Data System (ADS)

AC losses in two multifilamentary BiSrCaCuO-2223/Ag tapes differing in number of filaments were determined by transport and magnetic measurements. In the latter, the AC field was directed perpendicularly to the wide side of the tape and the model of a superconducting strip was used in the calculations. Comparison of the experimental data with theoretical models confirmed that when the tape carries a transport AC current, strong electromagnetic coupling between filaments leads to non-uniform distribution of curre