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1

Effects of size distribution on hysteresis losses of magnetic nanoparticles for hyperthermia  

Microsoft Academic Search

For understanding hysteresis losses of magnetic nanoparticles to be used for magnetic particle hyperthermia the effect of size distribution on the dependence of hysteresis losses on magnetic field amplitude is studied on the basis of a phenomenological model in the size range from superparamagnetism to magnetic multi-domains---roughly 10 up to 100 nm. Relying on experimental data for the size dependence

Rudolf Hergt; Silvio Dutz; Michael Röder

2008-01-01

2

Rate-dependent hysteresis losses in ensembles of magnetic nanoparticle clusters  

NASA Astrophysics Data System (ADS)

Hysteresis is ubiquitous in magnetic nanoparticle systems and understanding how it emerges from complex interactions and for different time scales is a long-standing issue in magnetism research. Understanding the phenomenon is most important for engineering magnetic nanoparticle structures of well-controlled properties in magnetic recording, hysteresis loss optimization in hyperthermia cancer treatment in biomedicine, or biological and chemical sensing, to name a few examples. In this work we address one of the general questions related to the influence of thermal activation processes on hysteresis loss. Employing large-scale computational modeling based on the master-equation framework we investigate the influence of dipolar interactions on thermal hysteresis loops in ensembles of magnetic nanoparticle chains and clusters. We show that the directional dependence of dipolar interactions results in enhanced or reduced hysteresis loss, depending on the distribution of particles' anisotropy axes and particle chain orientations with respect to the external field. Additional hysteresis loss reduction occurs in case of particle clusters due to possibility of the frustration phenomenon not present for topologically simpler chains.

Hovorka, Ondrej; Evans, Richard; Friedman, Gary; Chantrell, Roy

2012-02-01

3

Effects of size distribution on hysteresis losses of magnetic nanoparticles for hyperthermia  

NASA Astrophysics Data System (ADS)

For understanding hysteresis losses of magnetic nanoparticles to be used for magnetic particle hyperthermia the effect of size distribution on the dependence of hysteresis losses on magnetic field amplitude is studied on the basis of a phenomenological model in the size range from superparamagnetism to magnetic multi-domains—roughly 10 up to 100 nm. Relying on experimental data for the size dependence of coercivity, an empirical expression for the dependence of hysteresis loss on field amplitude and particle size is derived for hypothetical monodisperse particle ensembles. Considering experimentally observable size distributions, the dependence of loss on distribution parameters—mean particle size and variance—is studied. There, field amplitude is taken into account as an important parameter, which for technical and biomedical reasons in hyperthermia equipment is restricted. Experimental results for different particle types with mean diameter of 30 nm may be well reproduced theoretically if a small loss contribution of Rayleigh type is taken into account. Results show that the Stoner-Wohlfarth model for single domain magnetization reversal via homogeneous rotation cannot explain experimental observations. In particular, in magnetosomes which are distinguished by nearly ideal crystallographic shapes and narrow size distribution large friction-like losses occur even for small field amplitude. Parameters of the high frequency field for hyperthermia (amplitude and frequency) as well as of the size distribution of applied particles are discussed with respect to attaining maximum specific heating power.

Hergt, Rudolf; Dutz, Silvio; Röder, Michael

2008-09-01

4

Hysteresis losses of magnetic nanoparticle powders in the single domain size range  

NASA Astrophysics Data System (ADS)

Magnetic iron oxide nanoparticle powders were investigated in order to optimise the specific hysteresis losses for biomedical heating applications. Different samples with a mean particle size in the transition range from superparamagnetic to ferromagnetic behaviour (i.e. 10 100 nm) were prepared by two different chemical precipitation routes. Additionally, the influence of milling and annealing on hysteresis losses of the nanoparticles was investigated. Structural investigations of the samples were carried out by X-ray diffraction, measurement of specific surface area, and scanning and transmission electron microscopy. The dependence of hysteresis losses of minor loops on the field amplitude was determined using vibrating sample magnetometry and caloric measurements. For small field amplitudes, a power law was found which changes into saturation at amplitudes well above the coercive field. Maximum hysteresis losses of 6.6 J/kg per cycle were observed for milled powder. For field amplitudes below about 10 kA/m, which are especially interesting for medical and technical applications, hysteresis losses of all investigated powders were at least by one order of magnitude lower than reported for magnetosomes of comparable size.

Dutz, S.; Hergt, R.; Mürbe, J.; Müller, R.; Zeisberger, M.; Andrä, W.; Töpfer, J.; Bellemann, M. E.

2007-01-01

5

Amplitude and frequency dependence of hysteresis loss in a magnet-superconductor levitation system  

SciTech Connect

Using an electromagnetically controlled mechanical pendulum, we measured the energy loss for different amplitudes in a magnetic levitation system that contained high temperature superconductors (HTSs). Two procedures were followed to measure losses at 77 K for frequencies of 93.8 mHz to 80 Hz. In the first procedure, the distance between the permanent magnet and the HTS levitator was the same as that during (field) cooling. In the second procedure, the magnet was lowered (after cooling) closer to the HTS levitator before the measurements were performed. The experimental data show that these two procedures give essentially the same results at the same distance despite different cooling (and magnetization) histories for melt-textured YBaCuO levitators, and the frequency-independent energy loss is a power-law function of amplitude. We attribute the energy loss to magnetic hysteresis in the superconductor. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.

Yang, Z.J.; Hull, J.R.; Mulcahy, T.M. [Argonne National Laboratory, Argonne, Illinois 60439 (United States); Rossing, T.D. [Department of Physics, Northern Illinois University, DeKalb, Illinois 60115 (United States)

1995-08-01

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

On Hysteresis Loss as affected by Previous Magnetic History at Liquid Air Temperature  

Microsoft Academic Search

This Paper is concerned with hysteresis loss in iron at atmospheric and liquid air temperatures under three different conditions: (1) after the iron has been carefully demagnetised, (2) after it has been subjected to a large force (previous history) of about 26 C.G.S. units, and (3) whilst it is under the influence of an external constant magnetising force after demagnetisation.

Ernest Wilson; B C Clayton; A E Power

1911-01-01

9

Reduction of hysteresis losses in the magnetic refrigerant Gd5Ge2Si2 by the addition of iron.  

PubMed

The magnetocaloric effect is the change in temperature of a material as a result of the alignment of its magnetic spins that occurs on exposure to an external magnetic field. The phenomenon forms the basis for magnetic refrigeration, a concept purported to be more efficient and environmentally friendly than conventional refrigeration systems. In 1997, a 'giant' magnetocaloric effect, between 270 K and 300 K, was reported in Gd5Ge2Si2, demonstrating its potential as a near-room-temperature magnetic refrigerant. However, large hysteretic losses (which make magnetic refrigeration less efficient) occur in the same temperature range. Here we report the reduction (by more than 90 per cent) of these hysteretic losses by alloying the compound with a small amount of iron. This has the additional benefit of shifting the magnetic entropy change peak (a measure of the refrigerator's optimal operating temperature) from 275 K to 305 K, and broadening its width. Although the addition of iron does not significantly affect the refrigerant capacity of the material, a greater net capacity is obtained for the iron-containing alloy when the hysteresis losses are accounted for. The iron-containing alloy is thus a much-improved magnetic refrigerant for near-room-temperature applications. PMID:15215859

Provenzano, Virgil; Shapiro, Alexander J; Shull, Robert D

2004-06-24

10

Hysteresis Losses in Rolling and Sliding Friction  

Microsoft Academic Search

Previous work on the mechanism of rolling friction has shown that it is mainly due to elastic hysteresis losses in the rolling elements. Under conditions of uniform tension or torsion it is generally assumed that the energy dissipated by hysteresis is a constant fraction (the hysteresis loss factor) of the elastic energy introduced during the cycle. This elastic input energy

J. A. Greenwood; H. Minshall; D. Tabor

1961-01-01

11

Effects of a ferromagnetic substrate on hysteresis losses of a YBa2Cu3O7 coated conductor in perpendicular ac applied magnetic fields  

NASA Astrophysics Data System (ADS)

The effects of a ferromagnetic substrate on ac losses of a YBa2Cu3O7, YBCO, coated conductor in perpendicular ac magnetic fields were investigated by measuring the losses of a set of the specimens which were made by placing one Ni-5 at. % W tape on one or both sides of a YBCO layer on a Hastelloy tape. For applied field amplitude, ?0H0, < ~ 5 mT, the losses with the Ni-W tape(s) were higher than those of the YBCO tape, but for ~ 5 mT < ?0H0 < ~ 0.1 T, the losses were reduced by putting the Ni-W tape(s) on the YBCO tape. For ?0H0 > ~ 0.1 T, the losses became the same for all of the specimens. Also, the geometric actor ?0 of the susceptibility ? was determined from the hysteresis loops for these specimens, and was found to decease with the addition of the magnetic substrate. These observations agreed very well with the theoretical calculations for the losses and ?0 for a YBCO layer on a ferromagnetic substrate by Y Mawatari (unpublished).

Suenaga, M.; Iwakuma, M.; Sueyoshi, T.; Izumi, T.; Mimura, M.; Takahashi, Y.; Aoki, Y.

2008-02-01

12

Effects of a ferromagnetic substrate on hysteresis losses of a YBa2Cu3O7 coated conductor in perpendicular ac applied magnetic fields  

NASA Astrophysics Data System (ADS)

The effects of a ferromagnetic substrate on ac losses of a YBa2Cu3O7, YBCO, coated conductor in perpendicular ac magnetic fields were investigated by measuring the losses of a set of the specimens which were made by placing one Ni-5 at.% W tape on one or both sides of a YBCO layer on a Hastelloy tape. For applied field amplitude, ?0H0, <˜5 mT, the losses with the Ni-W tape(s) were higher than those of the YBCO tape, but for ˜5 mT < ?0H0 < ˜0.1 T, the losses were reduced by putting the Ni-W tape(s) on the YBCO tape. For ?0H0 > ˜0.1 T, the losses became the same for all of the specimens. Also, the geometric portion ?0 of the susceptibility ? was determined from the hysteresis loops for these specimens, and was found to decease with the addition of the magnetic substrate. These observations agreed very well with the theoretical calculations for the losses and ?0 for a YBCO layer on a ferromagnetic substrate, by [Mawatari, arVir:0710:2151v1, (cond-mat.supr-con)].

Suenaga, M.; Iwakuma, M.; Sueyoshi, T.; Izumi, T.; Mimura, M.; Takahashi, Y.; Aoki, Y.

2008-09-01

13

MITIGATION OF MAGNET HYSTERESIS EFFECTS AT LANSCE  

Microsoft Academic Search

We have developed a scheme to mitigate the effects of magnet hysteresis in a beamline with a complex arrangement of magnets. The complexity is due to the fact that two power supplies power eight magnets. While some of the magnets are powered by just one of the two supplies, others are excited with the currents from both supplies, with the

R. McCrady; R. Keller

2006-01-01

14

Energetic model of ferromagnetic hysteresis: Isotropic magnetization  

NASA Astrophysics Data System (ADS)

The model is based on considerations of energy balance and statistical domain behavior. The parameters are related to macroscopic hysteresis features such as coercivity, initial susceptibility, saturation, and remanence and identification strategies are presented for static and dynamic magnetization processes. Furthermore, the model parameters are related to spontaneous magnetization, magnetocrystalline anisotropy, magnetostriction, and microstructure geometry which assist in the interpretation of the hysteresis dependence on stress, temperature, and direction of magnetization. Examples and predictions are the magnetization reversal in low dimensional structures, stress demagnetization, temporary decay of magnetization, Barkhausen noise, and the behavior of materials with multiple phases. Finally, the fictitious statistical domains (or unit magnetization reversals) are related to the magnetic spin moments, which enables a quantum-mechanical interpretation of the model.

Hauser, Hans

2004-09-01

15

Calculation of hysteresis losses in hard superconductors 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

1970-01-01

16

Rotational hysteresis of exchange-spring magnets.  

SciTech Connect

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 show that the magnetization rotation created in the magnetically soft Fe layer by a rotating magnetic field is hysteretic. The rotational hysteresis is due to the reversal of the chirality of the spin spiral structure. Micromagnetic simulations reveal two reversal modes of the chirality, one at low fields due to an in-plane untwisting of the spiral, and the other, at high fields, due to an out-of-plane fanning of the spiral.

Jiang, J.S.; Bader, S.D.; Kaper, H.; Leaf, G.K.; Shull, R.D.; Shapiro, A.J.; Gornakov, V.S.; Nikitenko, V.I.; Platt, C.L.; Berkowitz, A.E.; David, S.; Fullerton, E.E.

2002-03-27

17

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

2012-01-17

18

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

19

Calculation of the Eddy Current and Hysteresis Losses in Sheathed Cables Inside a Steel Pipe  

Microsoft Academic Search

This paper presents an analytical method for approximating the eddy current and hysteresis losses in a system of multiple sheathed cables placed in any configuration inside a steel pipe. The method is based on the theory of images, which this paper expands to apply to pipes having high magnetic permeability and high electric conductivity at the same time. The method

Wael Moutassem; George J. Anders

2010-01-01

20

AC losses in the SSC high energy booster dipole magnets  

Microsoft Academic Search

The baseline design for the SSC (Superconducting Super Collider) high energy booster (HEB) has dipole bending magnets with a 50-mm aperture. An analysis of the cryogenic heat load due to AC losses generated in the HEB ramp cycle is reported for this magnet. Included in this analysis are losses from superconductor hysteresis, yoke hysteresis, strand eddy currents, and cable eddy

R. Jayakumar; V. Kovachev; D. Orrell; G. Snitchler

1992-01-01

21

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

22

Ferrite core loss for power magnetic components design  

Microsoft Academic Search

A practical method is presented for computing high-frequency ferrite core losses in the magnetic component for arbitrary voltage waveforms. The model presented requires only a few material parameters as input. To calculate ferrite hysteresis losses, a model based on empirical rules is employed. For high-frequency eddy current losses, a built phenomenon is assumed. It is demonstrated that the hysteresis model

Waseem Roshen

1991-01-01

23

Thermal output of a current-carrying ferromagnetic wire: hysteresis loss versus Joule heat  

NASA Astrophysics Data System (ADS)

When an alternating current flows through a ferromagnetic wire, its thermal output is higher than predicted by the familiar Joule law. An additional contribution arises from the heat liberated due to the hysteresis loss in the self-induced magnetic field inside the wire. Simple calculations, based on the formulae derived here, show that in some cases this contribution may be comparable to, or even larger than, the Joule heat.

Ogorelec, Z.

1999-05-01

24

Quantitative evaluation of magnet hysteresis effects at LANSCE with respect to magnet power supply specifications  

Microsoft Academic Search

The proton beam in the LANSCE accelerator is guided and focused almost exclusively by electromagnets. Magnet hysteresis has had significant impacts on the tuning of the LANSCE accelerator. Magnet hysteresis can also have an impact on magnet power supply (MPS) control, regulation and repeatability requirements. To date, MPS performance requirements have been driven by the requirements on the magnetic fields

J. Bradley; W. Roybal; W. Reass; J. Sandoval; M. Fresquez; L. Fernandez; C. Andrews

2007-01-01

25

Loss separation and parameters for hysteresis modelling under compressive and tensile stresses  

NASA Astrophysics Data System (ADS)

The study of the energy loss in electrical steels is based on the separation of total losses into hysteresis, classical and excess losses according to the statistical theory. In this article, the stress dependence of the hysteresis loss Wh and of the excess loss parameter V0, both related to the microstructure, is investigated for a nonoriented 3% Si-Fe grade under compressive and tensile stress and at plastic deformation. Parameters Wh and V0 for hysteresis and excess losses modeling increase under compression and high plastic tension and decrease under small elastic tension.

Permiakov, Viatcheslav; Dupré, Luc; Pulnikov, Alexandre; Melkebeek, Jan

2004-05-01

26

Influence of a transverse static magnetic field on the magnetic hyperthermia properties and high-frequency hysteresis loops of ferromagnetic FeCo nanoparticles  

NASA Astrophysics Data System (ADS)

The influence of a transverse static magnetic field on the magnetic hyperthermia properties is studied on a system of large-losses ferromagnetic FeCo nanoparticles. The simultaneous measurement of the high-frequency hysteresis loops and of the temperature rise provides an interesting insight into the losses and heating mechanisms. A static magnetic field of only 40 mT is enough to cancel the heating properties of the nanoparticles, a result reproduced using numerical simulations of hysteresis loops. These results cast doubt on the possibility to perform someday magnetic hyperthermia inside a magnetic resonance imaging setup.

Mehdaoui, B.; Carrey, J.; Stadler, M.; Cornejo, A.; Nayral, C.; Delpech, F.; Chaudret, B.; Respaud, M.

2012-01-01

27

Medium strain hysteresis loss of natural rubber and styrene-butadiene rubber vulcanizates: a predictive model  

Microsoft Academic Search

A model for hysteresis loss of rubber vulcanizates at medium strain (less than 100%) under dynamic condition has been proposed by using Boltzmann superposition principle, statistical theory of rubber elasticity and phenomenological theory. The theory incorporates both experimental and analytical parameters to quantify hysteresis loss. The model with no adjustment parameter has been successfully tested using the experimental results for

Kamal K. Kar; Anil K. Bhowmick

1999-01-01

28

Re-examination of the Steinmetz law for unsymmetrical magnetic hysteresis loops  

NASA Astrophysics Data System (ADS)

We have re-examined the Steinmetz law for unsymmetrical flux-density(B)-field(H) loops in an arbitrary magnetized state for cold rolled steels from the viewpoint of magnetization mechanism. Under the criterion of B-H loops with |B|<˜ 1.1 T, a relation between the hysteresis loss and flux density change was found to fall almost the same curve as that for symmetrical loops obtained conventionally. In the intermediate B regime, the relation follows the usual Steinmetz law with a power-law exponent of 1.6, whose coefficient increases with defect density. These observations demonstrate that the hysteresis loss is only the function of the flux density change and the Steinmetz law always holds true in an arbitrary magnetized state if the pinning mechanism of irreversible Bloch wall motion prevails.

Kobayashi, Satoru; Ishibashi, Yusuke; Baba, Ryo

2013-03-01

29

Simple models for dynamic hysteresis loop calculations of magnetic single-domain nanoparticles: Application to magnetic hyperthermia optimization  

NASA Astrophysics Data System (ADS)

To optimize the heating properties of magnetic nanoparticles (MNPs) in magnetic hyperthermia applications, it is necessary to calculate the area of their hysteresis loops in an alternating magnetic field. The separation between ``relaxation losses'' and ``hysteresis losses'' presented in several articles is artificial and criticized here. The three types of theories suitable for describing hysteresis loops of MNPs are presented and compared to numerical simulations: equilibrium functions, Stoner-Wohlfarth model based theories (SWMBTs), and a linear response theory (LRT) using the Néel-Brown relaxation time. The configuration where the easy axis of the MNPs is aligned with respect to the magnetic field and the configuration of a random orientation of the easy axis are both studied. Suitable formulas to calculate the hysteresis areas of major cycles are deduced from SWMBTs and from numerical simulations; the domain of validity of the analytical formula is explicitly studied. In the case of minor cycles, the hysteresis area calculations are based on the LRT. A perfect agreement between the LRT and numerical simulations of hysteresis loops is obtained. The domain of validity of the LRT is explicitly studied. Formulas are proposed to calculate the hysteresis area at low field that are valid for any anisotropy of the MNP. The magnetic field dependence of the area is studied using numerical simulations: it follows power laws with a large range of exponents. Then analytical expressions derived from the LRT and SWMBTs are used in their domains of validity for a theoretical study of magnetic hyperthermia. It is shown that LRT is only pertinent for MNPs with strong anisotropy and that SWMBTs should be used for weakly anisotropic MNPs. The optimum volume of MNPs for magnetic hyperthermia is derived as a function of material and experimental parameters. Formulas are proposed to allow to the calculation of the optimum volume for any anisotropy. The maximum achievable specific absorption rate (SAR) is calculated as a function of the MNP anisotropy. It is shown that an optimum anisotropy increases the SAR and reduces the detrimental effects of the size distribution of the MNPs. The optimum anisotropy is simple to calculate; it depends only on the magnetic field used in the hyperthermia experiments and the MNP magnetization. The theoretical optimum parameters are compared to those of several magnetic materials. A brief review of experimental results as well as a method to analyze them is proposed. This study helps in the determination of suitable and unsuitable materials for magnetic hyperthermia and provides accurate formulas to analyze experimental data. It is also aimed at providing a better understanding of magnetic hyperthermia to researchers working on this subject.

Carrey, J.; Mehdaoui, B.; Respaud, M.

2011-04-01

30

Magnetic rotational hysteresis study on spherical 85-160 nm Fe3O4 particles  

NASA Astrophysics Data System (ADS)

Rotational hysteresis losses Wr were determined as a function of magnetic field H for dispensed spherical Fe3O4 particles of mean grain sizes 85 nm, 127 nm and 162 nm between 78 K and 294 K. The observed Wr-H curves are compared with theoretical curves for single domain particles. The analysed particles reveal centers of high magnetic anisotropy. Such centers can be of importance during the generation of a thermoremanent magnetization, as they may be the origin of enhanced magnetic stability.

Schmidbauer, E.

1988-05-01

31

Magnetic Nonuniformity and Thermal Hysteresis of Magnetism in a Manganite Thin Film  

NASA Astrophysics Data System (ADS)

We measured the chemical and magnetic depth profiles of a single crystalline (La1-xPr?x)1-yCayMnO3-? (x=0.52ą0.05, y=0.23ą0.04, ?=0.14ą0.10) film grown on a NdGaO3 substrate using x-ray reflectometry, electron microscopy, electron energy-loss spectroscopy, and polarized neutron reflectometry. Our data indicate that the film exhibits coexistence of different magnetic phases as a function of depth. The magnetic depth profile is correlated with a variation of chemical composition with depth. The thermal hysteresis of ferromagnetic order in the film suggests a first-order ferromagnetic transition at low temperatures.

Singh, Surendra; Fitzsimmons, M. R.; Lookman, T.; Thompson, J. D.; Jeen, H.; Biswas, A.; Roldan, M. A.; Varela, M.

2012-02-01

32

Three-Phase Transformer Modeling Using a Vector Hysteresis Model and Including the Eddy Current and the Anomalous Losses  

Microsoft Academic Search

This paper presents a 2-D finite-element model to analyze the iron losses in a three-phase transformer. In this model, the effects of nonlinear core behavior are taken into account by means of a vector hysteresis model incorporated in the finite-element formulation by using a magnetic differential reluctivity tensor. The reluctivity tensor emerges naturally from the vectorized Jiles-Atherton model. The complete

Mauricio Valencia Ferreira da Luz; Jean Vianei Leite; Abdelkader Benabou; Nelson Sadowski

2010-01-01

33

Element-specific magnetic hysteresis measurements, a new application of circularly polarized soft x-rays  

SciTech Connect

Element-specific magnetic hysteresis measurements on heteromagnetic materials have been achieved by using circularly polarized soft-x- rays. Dramatically different Fe and Co hysteresis curves of Fe/Cu/Co trilayers were obtained by recording the magnetic circular dichroism (MCD) at their respective L{sub 3} white lines as a function of applied magnetic field. The data resolve the complicated hysteresis curves, observed by conventional magnetometry, and determine the individual magnetic moments for the Fe and Co layers. Fine hysteresis features, imperceptible in the conventional curves, were also observed, demonstrating a new application of circularly polarized soft-x-rays in the investigation of magnetic systems.

Lin, H.J.; Chen, C.T.; Meigs, G. [AT and T Bell Labs., Murray Hill, NJ (United States); Idzerda, Y.U.; Chaiken, A.; Prinz, G.A. [Naval Research Lab., Washington, DC (United States); Ho, G.H. [Pennsylvania Univ., Philadelphia, PA (United States). Dept. of Physics

1993-09-07

34

Monitoring Recovery and Recrystallization in Interstitial Free (IF) Steel by Magnetic Hysteresis Loop Measurements  

Microsoft Academic Search

In this paper, how structure-sensitive parameters derived from the hysteresis loop, like coercive field, remanent induction, and hysteresis losses, can be used to characterise recovery and recrystallization in cold rolled Ti-Nb stabilised interstitial free ultra low carbon steel is shown. The effect on hysteresis measurements of isothermal annealing treatments applied to industrially cold rolled samples at different temperatures is related

Ane MARTÍNEZ-DE-GUERENU; Fernando ARIZTI; San Sebastián; Kizkitza GURRUCHAGA

2006-01-01

35

Magnetic hysteresis and refrigeration capacity of Ni-Mn-Ga alloys near Martensitic transformation  

Microsoft Academic Search

This paper studies the magnetic hysteresis and refrigeration capacity of Ni-Mn-Ga alloys in detail during heating and cooling isothermal magnetisation processes. The Ni-Mn-Ga alloys show larger magnetic hysteresis when they transform from austenite to martensite, but smaller magnetic hysteresis when they transform from martensite to austenite. This behaviour is independent of either the pure Ni-Mn-Ga alloys or the alloys doped

Bin Fu; Yi Long; Jing-Fang Duan; Chao-Lun Wang; Yong-Qin Chang; Rong-Chang Ye; Guang-Heng Wu

2010-01-01

36

Differences of the magnetic hysteresis behaviors in the magnetostructural transformation Mn1-xVxCoGe alloys  

NASA Astrophysics Data System (ADS)

The magnetic hysteresis behaviors and the magnetocaloric properties of the Mn1-xVxCoGe (x=0.01 and 0.02) alloys in the heating and cooling runs have been investigated comparatively in the vicinity of the first-order magnetostructural phase transition. The magnetic hysteresis behaviors reveal an evident discrepancy between the heating and cooling processes. The average hysteresis losses estimated from the initial magnetization isotherms M(H) measured upon cooling are much larger than that upon heating. Considering the thermodynamics conditions and the potential barrier of phase transition, we analyzed the possible origin for this discrepancy and discussed the effects on the magnetocaloric properties for these two alloys.

Ma, S. C.; Zhong, Z. C.; Wang, D. H.; Ke, H.; Cao, Q. Q.; Huang, Y. L.; Luo, J. M.; Xu, J. L.; Hou, Y. H.; Du, Y. W.

2013-12-01

37

Angle-resolved analysis of magnetic hysteresis for micro-magnetic clusters with local deformations  

NASA Astrophysics Data System (ADS)

Magnetic dynamic process for an octagonal micro-magnetic cluster with one dislocation loop was simulated by pseudo-nonequilibrial Monte Carlo method including pseudo-dipole interaction. The results showed that the magnetic hysteresis curves of micro-magnetic clusters with one dislocation loop and of those without any deformation differ. The difference is more clearly shown for noise pattern of magnetization process, which depends on dynamic behavior of spin ensemble. A series of snapshots for spin ensemble displays that the magnetization process depends on the direction of the applied magnetic field. We propose usefulness of angle-resolved analysis of magnetic dynamic process to evaluate magnetic clusters.

Yamaguchi, Katsuhiko; Suzuki, Kenji; Nittono, Osamu; Takagi, Toshiyuki; Yamada, Koji

2008-02-01

38

Comparison of calculated and measured hysteresis loss in multifilamentary superconducting wire  

Microsoft Academic Search

A previously developed theory for a single round filament of type II superconductor is applied to hysteresis losses in multifilamentary composite conductors. The single filament theory was extended for a wider range of time varying field amplitudes. Two contrasting wires were used to test the theory which predicts a universal curve for the loss in all conductors. A very close

M. Ashkin; G. R. Wagner

1986-01-01

39

Programming finite element method based hysteresis loss computation software using non-linear superconductor resistivity and T - phiv formulation  

NASA Astrophysics Data System (ADS)

Due to the rapid development of personal computers from the beginning of the 1990s, it has become a reality to simulate current penetration, and thus hysteresis losses, in superconductors with other than very simple one-dimensional (1D) Bean model computations or Norris formulae. Even though these older approaches are still usable, they do not consider, for example, multifilamentary conductors, local critical current dependency on magnetic field or varying n-values. Currently, many numerical methods employing different formulations are available. The problem of hysteresis losses can be scrutinized via an eddy current formulation of the classical theory of electromagnetism. The difficulty of the problem lies in the non-linear resistivity of the superconducting region. The steep transition between the superconducting and the normal states often causes convergence problems for the most common finite element method based programs. The integration methods suffer from full system matrices and, thus, restrict the number of elements to a few thousands at most. The so-called T - phiv formulation and the use of edge elements, or more precisely Whitney 1-forms, within the finite element method have proved to be a very suitable method for hysteresis loss simulations of different geometries. In this paper we consider making such finite element method software from first steps, employing differential geometry and forms.

Stenvall, A.; Tarhasaari, T.

2010-07-01

40

Effect of compressive stress on hysteresis loss and magnetostriction of grain oriented Si-Fe sheets  

NASA Astrophysics Data System (ADS)

Changes in hysteresis loss and magnetostriction ? due to compressive stress ? are discussed for grain oriented Si-Fe sheets. L and T samples are prepared for each kind of sheets, where the longitudinal direction of the L/T sample is parallel/transverse to the rolling direction of the sheets. Hysteresis loss of all samples increases owing to compressive stress ?, and the increased value is in proportion to ??. The proportional ratio between them varies depending on the conditions of the sample and measuring maximum flux density.

Yamamoto, Ken-Ichi; Yamashiro, Yasumasa

2003-05-01

41

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

42

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

43

Mathematical models of hysteresis  

NASA Astrophysics Data System (ADS)

Progress is reported in 7 areas: development of vector Preisach-type models of hysteresis; modeling of rotational hysteretic losses; experimental testing of generalized vector Preisach models of hysteresis; development of Preisach-type models for after-effect; analytical investigation of penetration of electromagnetic fields into superconductors with gradual resistive transitions; computation of magnetic fields in hysteretic media; and development of new techniques for calculating 3-D eddy current problems.

Mayergoyz, I. D.

1993-09-01

44

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

45

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

Microsoft Academic Search

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

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

1999-01-01

46

Hysteresis properties of magnetic spherules and whole rock specimens from some Paleozoic platform carbonate rocks  

Microsoft Academic Search

It is widely established that many Paleozoic carbonate rocks were remagnetized during the late Paleozoic Kiaman reversed superchron. Yet the paleomagnetic recorders of this event have remained elusive. Magnetic spherules have been candidates for this role, because they are probably authigenic. Therefore we have studied the hysteresis properties of individual magnetic spherules from two formations, the remagnetized Onondaga (Devonian, New

Dongwoo Sukand; Susan L. Halgedahl

1996-01-01

47

The Principle Mechanical and Electrical Features of a Hysteresis Clutch  

Microsoft Academic Search

The hysteresis loss that occurs in magnetic devices subjected to changing magnetic fields usually represents a detrimental condition. One exception, however, is the hysteresis clutch where this loss is utilized to perform a useful function. One particular type1 clutch is described and its chief mechanical and electrical features are summarized. Its utility as a variable speed drive is also illustrated.

Lowell B. Brown

1956-01-01

48

Magnetic Study of Martensitic Transformation in Austenitic Stainless Steel by Low Field Hysteresis Loops Analysis  

SciTech Connect

Magnetic method has been used to evaluate the volume percentage of {alpha}' martensitic phase in austenitic stainless steels by measuring saturation magnetization, and it is said to be a candidate NDE method. However, nondestructive detection of saturation magnetization without high magnetic field is difficult. In the current work, we present a NDE method for evaluating the magnetic properties of strain induced {alpha}' martensitic phase. Low field hysteresis loops of an austenitic stainless steels type SUS 304 after cold rolling were measured by using a yoke sensor. The results show that the initial permeability {mu}i and the relative coercive field Hcl calculated by low field hysteresis loop analysis keep monotonic relation with saturation magnetization and coercive force measured by VSM, respectively. By this method, it is possible to characterize the volume content and particle properties of {alpha}' martensitic phase in stainless steels.

Zhang Lefu; Takahashi, Seiki; Kamada, Yasuhiro; Kikuchi, Hiroaki; Mumtaz, Khalid; Ara, Katsuyuki; Sato, Masaya [NDE Center, Faculty of Engineering, Iwate University, Morioka, 020-8551 (Japan)

2005-04-09

49

Investigations of magnetic hysteresis of barium ferrite using the torsion pendulum method  

SciTech Connect

The magnetic stiffness is measured by the torsion pendulum method as a function of the applied field. Measurements are performed on random assemblies of chemically coprecipitated barium ferrite powders. The magnetic stiffness for both minor and major loops of the hysteresis cycle is measured and compared with calculated curves based on the model of coherent rotation. The discrepancies between theory and experiment are partly due to the effect of magnetic interaction.

Richter, H.J.; Hempel, K.A.

1988-11-15

50

Extracting the hysteresis loops of magnetic interfaces from optical second-harmonic intensity measurements  

NASA Astrophysics Data System (ADS)

Surface- and interface-sensitive optical techniques, such as optical second-harmonic generation (SHG), allow the buried interfacial structure of centrosymmetric materials to be explored through thin capping layers, and magnetic SHG (MSHG) extends this to magnetic interfaces. However, the variation of the MSHG intensity with magnetic field does not measure hysteresis loops directly, because the loops are displaced by an amount dependent on the crystallographic response and its phase difference with respect to the magnetic response, and also because there is a quadratic magnetization contribution to the SH intensity that may be significant. Two new procedures are reported for extracting hysteresis loops directly from the MSHG intensity. The first is applicable to all magnetic interfaces, including exchange-biased structures, where the saturation magnetization for positive and negative magnetic fields is equal and opposite. The second applies to all centrosymmetric hysteresis loops. These procedures correct for the quadratic response, allowing experimental geometries to be chosen that maximize the magnetic contribution, thus improving the signal-to-noise ratio and the sensitivity of the technique.

McGilp, J. F.; Carroll, L.; Fleischer, K.

2007-10-01

51

Magnetic hysteresis studies of Tl-2223 substituted by Fe and Zn  

NASA Astrophysics Data System (ADS)

Effect of Fe and Zn substitutions on the magnetic hysteresis of Tl-2223 are investigated in high magnetic fields up to 9 Tesla and at different temperatures (T= 6, 20, 40 and 80 K). The results of magnetic hysteresis loops show that the area of these loops decreases as Fe-content increases, whereas it increases for Zn-substitutions till x = 0.2 and then decreases for x > 0.2. The magnetization difference ?M is found to decay exponentially with temperature at low magnetic fields, according to ?M ? exp (-T/T0). The characteristic temperature T0 is found to be varied from 6 K to 40 K and it is related to the applied magnetic field B according to T0? B-1/n. The critical current density is calculated for the prepared samples from magnetic hysteresis measurements and compared with that determined from ac magnetic susceptibility. The results are discussed according to the flux motion and flux pinning.

Abou-Aly, Aly; Awad, Ramadan; Ibrahim, Ibrahim; Faraj, Ahmed

2009-03-01

52

Hysteresis of the shape of a magnetic fluid volume near a line conductor  

NASA Astrophysics Data System (ADS)

Hysteresis behaviour and break-up of a magnetic fluid volume situated between two concentric cylinders in the presence of magnetic field are considered analytically. The situation investigated is the break-up and the formation of the magnetic fluid volume between the cylinders and the change of the thickness of drops on the inner and outer cylinders as the line current in the inner cylinder is increased or decreased. It is shown that an adequate qualitative and numerical description of such phenomena must take into account the dependence of the fluid magnetization on the magnetic field. Tables 1, Figs 7, Refs 4.

Naletova, V. A.; Kiryushin, V. V.; Reks, A. G.; Suvchuk, E.

2008-06-01

53

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

54

Scaling Behavior of Barkhausen Avalanches along the Hysteresis loop in Nucleation-Mediated Magnetization Reversal Process  

SciTech Connect

We report the scaling behavior of Barkhausen avalanches for every small field step along the hysteresis loop in CoCrPt alloy film having perpendicular magnetic anisotropy. Individual Barkhausen avalanche is directly observed utilizing a high-resolution soft X-ray microscopy that provides real space images with a spatial resolution of 15 nm. Barkhausen avalanches are found to exhibit power-law scaling behavior at all field steps along the hysteresis loop, despite their different patterns for each field step. Surprisingly, the scaling exponent of the power-law distribution of Barkhausen avalanches is abruptly altered from 1 {+-} 0.04 to 1.47 {+-} 0.03 as the field step is close to the coercive field. The contribution of coupling among adjacent domains to Barkhausen avalanche process affects the sudden change of the scaling behavior observed at the coercivity-field region on the hysteresis loop of CoCrPt alloy film.

Im, Mi-Young; Fischer, Peter; Kim, D.-H.; Shin, S.-C.

2008-10-14

55

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

56

A mechanism of magnetic hysteresis in heterogeneous alloys  

Microsoft Academic Search

It is suggested that in many ferromagnetic materials there may occur particles distinct in magnetic character from the general matrix, and below the critical size, depending on shape, for which domain boundary formation is energetically possible. For such single-domain particles, change of magnetization can take place only by rotation of the magnetization vector. As the field changes continuously, the resolved

E. C. Stoner; E. P. Wohlfarth

1991-01-01

57

Magnetization process as a combined function of field and temperature in the product model of hysteresis  

NASA Astrophysics Data System (ADS)

In the product model of hysteresis the magnetization was proposed to be an indirect function of the magnetic field. The reversible paramagnetic and the irreversible hysteretic contributions to the magnetization appeared together as additional terms in the argument of a sigmoid type envelope function. Recent experimental data suggest that this enveloping sigmoid should be the Brillouin function. Therefore it is proposed that the mean-field theory for the temperature dependence can be generalized for the description of the combined field and temperature dependence of magnetization processes.

Kádár, György; Szabó, Zsolt

2004-05-01

58

Sweep rate dependence of magnetic hysteresis loops and peak effect in high-? superconductors  

NASA Astrophysics Data System (ADS)

The origin of the peak effect in QMG-processed YBCO was investigated using the sweep rate dependence of magnetic hysteresis loops. A numerical analysis of magnetic hysteresis loops demonstrated that electric field E versus current density J characteristics can be accurately derived from the sweep rate dependence using the Mawatari method rather than the conventional Bean one. The pinning potential energy can be obtained from the slope of the log E versus log J plot accurately. By analysing the experimental data with the peak effect using the Mawatari method, it was found that the pinning potential energy and the critical current density have the peak values at different magnetic fields. This anomalous phenomenon incidental to the peak effect can be explained by the Klein model which is based on the concept of the field-induced flux pinning.

Sueyoshi, T.; Fujiyoshi, T.; Miyahara, K.; Awaji, S.

1999-02-01

59

Enhancement of the magnetic hysteresis in ultrathin PdNi films by hydrogen absorption-desorption cycling  

NASA Astrophysics Data System (ADS)

Measurements of the magnetic hysteresis in ultrathin PdNi films (d <~ 100 Ĺ) show a marked increase of the perpendicular coercitive field after hydrogen absorption-desorption cycling; a squaring up of the magnetic hysteresis is observed at the same time. We attribute temtatively this effect to an irreversible change of the stress state of the film in relation with the film-substrate interaction.

Raffy, H.; Dumoulin, L.; Burger, J. B.

1987-11-01

60

Simulations of magnetic hysteresis loops for dual layer recording media  

NASA Astrophysics Data System (ADS)

A Kinetic Monte-Carlo algorithm is applied to examine MH loops of dual-layer magnetic recording media at finite temperature and long time scales associated with typical experimental measurements. In contrast with standard micromagnetic simulations, which are limited to the ns-?s time regime, our approach allows for the direct calculation of magnetic configurations over periods from minutes to years. The model is used to fit anisotropy and coupling parameters to experimental data on exchange-coupled composite media which are shown to deviate significantly from standard micromagnetic results. Sensitivities of the loops to anisotropy, inter-layer exchange coupling, temperature, and sweep rate are examined.

Fal, T. J.; Plumer, M. L.; Whitehead, J. P.; Mercer, J. I.; van Ek, J.; Srinivasan, K.

2013-05-01

61

Magnetic hysteresis of interface-biased flat iron dots  

NASA Astrophysics Data System (ADS)

We report a theoretical study of the coercivity and bias of iron dots exchange coupled with an antiferromagnetic substrate. We show that flat dots, with height close to the iron exchange length, and lateral dimensions of a few exchange lengths, exhibit large enhancement of coercivity and exchange bias. For small interface field strength the magnetization reversal is nearly a coherent rotation with symmetrical loops. Interface pinning leads to large reduction in coercivity and asymmetrical loops, if the interface field strength is comparable to the value of the iron exchange field. We discuss the impact of geometrical confinement and interface pinning on the magnetization reversal mechanisms. We show that small area dots with height larger than the exchange length display stronger interface effects.

Rebouças, G. O. G.; Silva, A. S. W. T.; Dantas, Ana L.; Camley, R. E.; Carriço, A. S.

2009-03-01

62

Hysteresis and switching dynamics of patterned magnetic elements  

Microsoft Academic Search

The hystersis properties and the switching time of Co nano-elements were calculated using finite element micromagnetics. The calculated coercive field of 200×40×25nm Co nano-elements strongly depends on the model of the polycrystalline microstructure assumed in the simulations. For small, randomly oriented grains the magnetocrystalline anisotropy may be neglected, since the effective anisotropy vanishes due to averaging. Quasistatic simulations of magnetization

T. Schrefl; J. Fidler; D. Süss; W. Scholz

2000-01-01

63

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

64

Nonlinear susceptibility and dynamic hysteresis loops of magnetic nanoparticles with biaxial anisotropy  

NASA Astrophysics Data System (ADS)

The nonlinear ac susceptibility and dynamic magnetic hysteresis (DMH) of a single domain ferromagnetic particle with biaxial anisotropy subjected to both external ac and dc fields of arbitrary strength and orientation are treated via Brown's continuous diffusions model [W. F. Brown, Jr., Phys. Rev. 130, 1677 (1963)] of magnetization orientations. The DMH loops and nonlinear ac susceptibility strongly depend on the dc and ac field strengths, the polar angle between the easy axis of the particle, the external field vectors, temperature, and damping. In contrast to uniaxial particles, the nonlinear ac stationary response and DMH strongly depend on the azimuthal direction of the ac field and the biaxiality parameter ?.

Ouari, Bachir; Titov, Serguey V.; El Mrabti, Halim; Kalmykov, Yuri P.

2013-02-01

65

Measurement method for determining the magnetic hysteresis effects of reluctance actuators by evaluation of the force and flux variation  

NASA Astrophysics Data System (ADS)

A measurement method is presented which identifies the magnetic hysteresis effects present in the force of linear reluctance actuators. The measurement method is applied to determine the magnetic hysteresis in the force of an E-core reluctance actuator, with and without pre-biasing permanent magnet. The force measurements are conducted with a piezoelectric load cell (Kistler type 9272). This high-bandwidth force measurement instrument is identified in the frequency domain using a voice-coil actuator that has negligible magnetic hysteresis and eddy currents. Specifically, the phase delay between the current and force of the voice-coil actuator is used for the calibration of the measurement instrument. This phase delay is also obtained by evaluation of the measured force and flux variation in the E-core actuator, both with and without permanent magnet on the middle tooth. The measured magnetic flux variation is used to distinguish the phase delay due to magnetic hysteresis from the measured phase delay between the current and the force of the E-core actuator. Finally, an open loop steady-state ac model is presented that predicts the magnetic hysteresis effects in the force of the E-core actuator.

Vrijsen, N. H.; Jansen, J. W.; Compter, J. C.; Lomonova, E. A.

2013-07-01

66

Stress-induced magnetic hysteresis in amorphous microwires probed by microwave giant magnetoimpedance measurements  

NASA Astrophysics Data System (ADS)

We report the results of a detailed study of the effects of tensile and torsional stresses on the giant magnetoimpedance (GMI) characteristics of vanishing-magnetostrictive Co-rich microwires at microwave frequency. A complex stress-induced hysteresis behaviour is identified in the GMI response in the presence of tensile and torsional stresses. It is also revealed that there exists a competition between these two kinds of stresses on the critical field via the interactions with the intrinsic anisotropy. An ``enhanced core-shell'' model is proposed here to resolve the physical origin of the low-field hysteresis and the dependence of induced anisotropy field on the applied tensile and/or torsional stress. Our results are of both technical importance to the design of non-contact stress sensors exploiting the GMI of microwires and fundamental significance to the understanding of the microwave GMI characteristics of soft magnetic microwires in the presence of external stresses.

Popov, V. V.; Berzhansky, V. N.; Gomonay, H. V.; Qin, F. X.

2013-05-01

67

Hysteresis properties of magnetic spherules and whole rock specimens from some Paleozoic platform carbonate rocks  

NASA Astrophysics Data System (ADS)

It is widely established that many Paleozoic carbonate rocks were remagnetized during the late Paleozoic Kiaman reversed superchron. Yet the paleomagnetic recorders of this event have remained elusive. Magnetic spherules have been candidates for this role, because they are probably authigenic. Therefore we have studied the hysteresis properties of individual magnetic spherules from two formations, the remagnetized Onondaga (Devonian, New York) and the effectively unremagnetized Wabash (Silurian, Indiana). Also, we have compared the hysteresis properties of spherules to those of remagnetized limestones from the Onondaga, Trenton (Ordovician, New York), and Helderberg (Devonian, New York) formations and from the unremagnetized Wabash formation. The spherules studied here vary from about 20 ľm to over 100 ľm in diameter. Nevertheless, on the basis of hysteresis behavior this spherule population spans the full range of domain states, from truly multidomain (MD) to pseudo-single-domain (PSD) to single domain (SD). Because these spherules are so large, it is remarkable that more than half display the highly PSD-like behavior typical of many remagnetized carbonate rocks. Equally as remarkable is the lack of dependence on spherule size of various hysteresis properties such as coercive force (Hc), remanent coercive force (Hcr), the ratio of saturation remanence to saturation moment (Mrs/Ms), and the ratio of remanent coercive force to coercive force (Hcr/Hc). These findings dispel the preconception that large spherules are too magnetically soft to be stable carriers of ancient magnetization. Surprisingly, Onondaga and Wabash spherules yield virtually identical suites of hysteresis properties. On the one hand, this high degree of similarity could indicate that spherules are irrelevant to remagnetization. More intriguing, however, is that this similarity could mean that the Wabash formation, although effectively unremagnetized, nevertheless contains magnetic mineralogical traces of a regional remagnetization event. It is significant that for these spherules a bilogarithmic plot of Mrs/Ms versus Hcr/Hc does not define a simple linear trend. Instead, Mrs/Ms increases more rapidly with decreasing Hcr/Hc for spherules in the PSD range than in the MD range. When a power law is fit solely to the hysteresis ratios of PSD-like to SD-like spherules, extrapolation to the SD limit gives Mrs/Ms = 0.75. Similarly, a power law fit to the hysteresis ratios obtained here from remagnetized carbonate rocks yields Mrs/Ms = 0.72 at the SD boundary. These results could indicate that a large percentage of SD-like spherules, like the SD carriers in remagnetized carbonate rocks, are governed by magnetocrystalline anisotropy. Finally, the present data point to values of Hc near 350 Oe both for SD-like spherules and for the SD grains thought to carry remanence in remagnetized carbonates. Clearly, PSD- and SD-like spherules share several key rock magnetic properties with remagnetized carbonate rocks. Thus spherules still are likely candidates for carrying the remagnetization signal.

Suk, Dongwoo; Halgedahl, Susan L.

1996-11-01

68

Hysteresis, thermomagnetic, and low-temperature magnetic properties of Southwestern U.S. obsidians  

NASA Astrophysics Data System (ADS)

Geochemical signatures of Southwestern U.S. obsidians have been intensively studied, in part to use as a provenance method for archaeological obsidians (Shackley, 2005). We reported (Sternberg et al. 2010) examined magnetic properties of 50 unoriented samples from 10 geologic obsidian sources in Arizona, Nevada, and New Mexico; here we provide additional results measured at the Institute for Rock magnetism. Room-temperature hysteresis curves were measured using a vibrating sample magnetometer on 58 specimens from all 50 samples. The Quantum Designs Magnetic Properties Measurement System was used to measure low temperature cycling of the natural remanence and/or of a room-temperature saturation isothermal remanence for 10 specimens, and frequency dependence of susceptibility for 7 specimens. A Princeton VSM was used to measure hysteresis curves and thermomagnetic curves for 19 specimens from 17 samples. Eleven of the thermomagnetic curves show Curie temperatures close to that for magnetite, and most of them are almost perfectly reversible. Many of the specimens also show a less well-defined Curie point around 150-200°C; for a few specimens the thermomagnetic behavior is dominated by paramagnetic iron and no ferromagnetic phases can be identified. The low-temperature remanence and susceptibility measurements show the magnetite Verwey transition in almost all specimens, and a significant superparamagnetic presence in only a few cases. Hysteresis parameters plot mainly in the lower half of the PSD domain on a Day plot, and saturation magnetization values indicate magnetite concentrations of about 0.2% to 0.5% for most specimens. The coercivity of remanence decreased considerably for one specimen after surface cleaning, although for 5 other comparisons there was no change.

Sternberg, R. S.; Jackson, M. J.; Shackley, M. S.

2011-12-01

69

Hysteresis Modeling of Magnetic Shape Memory Alloy Actuator Based on Krasnosel'skii-Pokrovskii Model  

PubMed Central

As a new type of intelligent material, magnetically shape memory alloy (MSMA) has a good performance in its applications in the actuator manufacturing. Compared with traditional actuators, MSMA actuator has the advantages as fast response and large deformation; however, the hysteresis nonlinearity of the MSMA actuator restricts its further improving of control precision. In this paper, an improved Krasnosel'skii-Pokrovskii (KP) model is used to establish the hysteresis model of MSMA actuator. To identify the weighting parameters of the KP operators, an improved gradient correction algorithm and a variable step-size recursive least square estimation algorithm are proposed in this paper. In order to demonstrate the validity of the proposed modeling approach, simulation experiments are performed, simulations with improved gradient correction algorithm and variable step-size recursive least square estimation algorithm are studied, respectively. Simulation results of both identification algorithms demonstrate that the proposed modeling approach in this paper can establish an effective and accurate hysteresis model for MSMA actuator, and it provides a foundation for improving the control precision of MSMA actuator.

Wang, Shoubin; Gao, Wei

2013-01-01

70

Hysteresis modeling of magnetic shape memory alloy actuator based on Krasnosel'skii-Pokrovskii model.  

PubMed

As a new type of intelligent material, magnetically shape memory alloy (MSMA) has a good performance in its applications in the actuator manufacturing. Compared with traditional actuators, MSMA actuator has the advantages as fast response and large deformation; however, the hysteresis nonlinearity of the MSMA actuator restricts its further improving of control precision. In this paper, an improved Krasnosel'skii-Pokrovskii (KP) model is used to establish the hysteresis model of MSMA actuator. To identify the weighting parameters of the KP operators, an improved gradient correction algorithm and a variable step-size recursive least square estimation algorithm are proposed in this paper. In order to demonstrate the validity of the proposed modeling approach, simulation experiments are performed, simulations with improved gradient correction algorithm and variable step-size recursive least square estimation algorithm are studied, respectively. Simulation results of both identification algorithms demonstrate that the proposed modeling approach in this paper can establish an effective and accurate hysteresis model for MSMA actuator, and it provides a foundation for improving the control precision of MSMA actuator. PMID:23737730

Zhou, Miaolei; Wang, Shoubin; Gao, Wei

2013-04-28

71

Nanomechanical Detection of Magnetic Hysteresis of a Single-crystal Yttrium Iron Garnet Micromagnetic Disk  

NASA Astrophysics Data System (ADS)

A micromagnetic disk was milled from a monocrystalline yttrium iron garnet film using a focused ion beam and micromanipulated onto a nanoscale torsional resonator. Nanomechanical torque magnetometry results show a unipolar magnetic hysteresis characteristic of a magnetic vortex state. Landau-Lifshitz-Gilbert-based micromagnetic simulations of the disk show a rich, flux-enclosed, three-dimensional domain structure. On the top and bottom faces of the disk, a skewed vortex state exists with a very small core. The core region extends through the thickness of the disk with a smooth variation in core diameter reaching a maximum along the midplane of the disk. The single crystalline nature of the disk lends to an observed absence of Barkhausen-like steps in the magnetization-versus-field curves, qualitatively different in comparison to the magnetometry results of an individual polycrystalline permalloy microdisk. Prospects for the mechanical detection of spin dynamical modes in these structures will also be discussed.

Losby, Joseph; Diao, Zhu; Burgess, Jacob; Compton, Shawn; Fani Sani, Fatemeh; Firdous, Tayyaba; Vick, Douglas; Belov, Miro; Hiebert, Wayne; Freeman, Mark

2013-03-01

72

Low-hysteresis materials for magnetic refrigeration: Gd/sub 1-x/Er/sub x/Al/sub 2/  

SciTech Connect

The series of ferromagnetic intermetallics Gd/sub 1-x/Er/sub x/Al/sub 2/ are candidate working materials for magnetic refrigeration because of their large moment, small anisotropy, and the fact that their Curie temperatures span the range 14 K to 164 K. We have measured the magnitude of the magnetic hysteresis as a function of temperature from 4 K to T/sub c/ for polycrystalline samples of these materials via ac magnetic susceptibility and magnetization hysteresis loops. We found, as expected, virtually no hysteresis in GdAl/sub 2/, and more surprisingly, less than 3000 A/m hysteresis in ErAl/sub 2/, and 2 x 10/sup 4/ A/m in Gd/sub 0/ /sub 5/Er/sub 0/ /sub 5/Al/sub 2/. Moreover, the hysteresis in Gd/sub 0/ /sub 5/Er/sub 0/ /sub 5/Al/sub 2/ was less than or equal to 100 A/m for T - T/sub c/ < 20 K.

Zimm, C.B.; Barclay, J.A.; Johanson, W.R.

1983-01-01

73

Use of magnetic hysteresis properties and electron spin resonance spectroscopy for the identification of volcanic ash: a preliminary study  

NASA Astrophysics Data System (ADS)

This initial study investigates the possible use of hysteresis parameters and electron spin resonance (ESR) spectroscopy to identify and correlate volcanic ash. ESR and hysteresis properties are sensitive to characteristics such as the chemical composition, mineralogy, and grain size and shape. These characteristics are determined by the tectonic setting of the volcano and by the magmatic and eruptive history of the volcanic ash. Hysteresis properties and ESR spectra, therefore, should be distinct for each ash eruption and may help to identify the eruptive source of the ash and to correlate ash from unknown sources. We conducted ESR spectroscopy at room temperature and magnetic hysteresis measurements on 19 samples of a single ash, the 1974 October 14 eruption of the Fuego volcano, Guatemala, and on single samples of ash obtained from eight different volcanoes. The Fuego ash samples were obtained at increasing distances from the volcano. For the single Fuego ash, ESR spectra and hysteresis parameters become increasingly similar as the distance from the volcano increases. At distances greater than 30km, ESR spectra and hysteresis properties are uniform. The variability of magnetic and ESR properties with distance from Fuego is due to the preferential fall-out of phenocrysts closer to the volcano. At large distances, the ash is more uniform, containing more glass and microcrystals. All eight ash samples from the different volcanoes can be distinguished from the distal Fuego 1974 October 14 ash using ESR spectra and hysteresis parameters. These results suggest that ESR and hysteresis measurements have a potential to be used as tools to identify distal ash when used in conjunction with geochemical, mineralogical and/or other types of data.

Pawse, Archana; Beske-Diehl, Suzanne; Marshall, S. A.

1998-03-01

74

Effect of the magnetic field applied during cooling on magnetic hysteresis in the low-temperature phase of magnetite: First-order reversal curve (FORC) analysis  

Microsoft Academic Search

The strength of a magnetic field applied during cooling through the Verwey transition can control the low-temperature (LT) magnetic hysteresis properties of magnetite. This effect is investigated using the first-order reversal curve (FORC) technique. LT FORC distributions were measured at 20 K from four polycrystalline samples after cooling from 300 K in zero magnetic field or in the presence of

A. V. Smirnov

2007-01-01

75

Initial observation of magnetization hysteresis and quantum tunneling in mixed manganese-lanthanide single-molecule magnets.  

PubMed

The preparation of a new family of mixed transition metal/lanthanide clusters is reported. The reaction of [Mn3O(O2CPh)6(py)2(H2O)] with Ln(NO3)3 (Ln = Nd, Gd, Dy, Ho, and Eu) in a 1:2 molar ratio in MeOH/MeCN (1:20 v/v) leads to dark crystals in 55-60% isolated yield of complexes all containing the [Mn11Ln4]45+ core. The Dy compound has been found to give out-of-phase AC susceptibility signals, suggesting it might be a single-molecule magnet (SMM). This was confirmed by the observation of magnetization hysteresis loops. An Arrhenius plot constructed from magnetization decay data gave a barrier to relaxation of 9.3 K and showed the temperature-independent relaxation at very low temperatures indicative of quantum tunneling of magnetization. This is the initial demonstration of hysteresis and quantum behavior in a mixed 3d/4f SMM. PMID:15571379

Mishra, Abhudaya; Wernsdorfer, Wolfgang; Abboud, Khalil A; Christou, George

2004-12-01

76

Magnetic Losses of Iron in High Frequency Alternating Current Fields  

Microsoft Academic Search

A number of investigators have studied the power loss due to eddy currents and hysteresis in iron when placed in high frequency alternating current fields, but the results obtained are in wide disagreement. Using a new method, the author has investigated the variation of this loss with the frequency for several areas of cross section. The total loss is considered

John R. Martin

1929-01-01

77

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

78

Calculation of the even harmonics of emf in the winding of a ring core magnetized by an external constant field, with magnetic hysteresis taken into account  

SciTech Connect

The calculation of the even harmonics of electromotive force in the secondary winding of a ferromagnetic ring core or a core extended in one direction, having a closed magnetic circuit in relation to the magnetic excitation flux and being magnetized in the plane of the core (ring) by a weak magnetic field, is carried out taking into account magnetic hysteresis and using the criterion of physical similarity.

Ponomarev, Yu.V.

1988-09-01

79

Theoretical investigation on the magnetocaloric effect in MnAs using a microscopic model to describe the magnetic and thermal hysteresis  

NASA Astrophysics Data System (ADS)

We report the thermal and magnetic hysteresis diagram for MnAs that comes from a microscopic description of a magnetic system through a model Hamiltonian that takes into account the magnetoelastic interaction. The temperature and magnetic hysteresis intervals are governed by the magnetoelastic interaction parameter, which leads to the energy barrier between stable and metastable minima in the exact free energy, obtained from our microscopic model. Application of the model to the MnAs first-order magnetic material, which presents high hysteresis effect, leads to a good agreement with the experimental magnetic and magnetocaloric data.

Alho, B. P.; de Oliveira, N. A.; de Sousa, V. S. R.; Gama, Sergio; Coelho, A. A.; Carvalho, A. Magnus G.; von Ranke, P. J.

2012-06-01

80

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

81

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

82

Magnetic viscosity, hysteresis reptation, and their relationship with adjacent track interference in advanced perpendicular recording media  

NASA Astrophysics Data System (ADS)

The role of exchange interactions and thermal relaxation in advanced three-layer exchange-coupled composite perpendicular recording media with graded anisotropy was investigated through studies on magnetic viscosity, magnetic hysteresis reptation, and spin-stand adjacent track interference. For this purpose, thickness series in the NiW seed and the three magnetic layers were made and studied. For each sample, both magnetic viscosity and reptation were evaluated using a magnetometer over a series of initial magnetic states. Magnetic viscosity, which is the change in the magnetization of the sample with time, showed a distinct second-order dependence on a logarithmic time-scale. In general, viscosity appeared to be more strongly influenced by exchange-coupling interactions in the media than the thermal stability. Magnetic reptation, which is the change in the magnetization when the external field was repeatedly cycled between a nonzero field and zero field, i.e., remanence, showed two types of distinct reptation phenomena--field reptation and remanence reptation--depending on whether the magnetic state was evaluated with the external field present or removed, respectively. Both field and remanence reptation showed a second-order logarithmic dependence on the number of cycles. A comparison of viscosity and field reptation revealed a correlation, indicating that the origin of field reptation in perpendicular recording media can be associated with viscosity. Such a correlation could not be established between viscosity and remanence reptation. Spin-stand signal amplitude change of written tracks, due to adjacent track interference, also followed a second-order logarithmic dependence on the number of adjacent writes. When compared appropriately, the signal amplitude change showed an excellent correlation with remanence reptation across all media samples. This suggests that adjacent track interference in magnetic recording can be associated with remanence reptation evaluated using a magnetometer, despite their vast difference in time-scales. Moreover, this correlation was observed irrespective of the thermal stability of the media, which corroborates the hypothesis that in composite media, exchange interaction effects have a more dominant role than thermal relaxation effects in influencing switchability vis-ŕ-vis adjacent track interference. In consequence, remanence reptation can be a useful technique to study the interplay of exchange and thermal effects in magnetic media.

Srinivasan, Kumar; Roddick, Eric

2012-08-01

83

Core losses in permanent magnet motors  

Microsoft Academic Search

It is pointed out that the conventional approach to core loss prediction using the Fourier series of the space wave of air gap flux density is not applicable to surface mounted permanent magnet (PM) motors. An alternative approach based on the concept that eddy current losses are proportional to the square of the time rate of change of the flux

G. R. Slemon; X. Liu

1990-01-01

84

Magnetic and Dielectric Loss in Magnetic Insulators.  

National Technical Information Service (NTIS)

Domain-wall motion in single crystals of silicon doped YIG has been studied over the temperature range 4.2-300 K. Samples were cut in the form of picture frames to obtain a simple domain configuration having magnetic properties essentially determined by a...

D. J. Epstein M. H. Wanas

1967-01-01

85

Application of hysteresis modeling to magnetic techniques for monitoring biaxial stress  

SciTech Connect

A probe, consisting of two excitation coils and a detection coil wrapped around a core with a Hall probe between the pole pieces, has been used to measure indirectly the influence of biaxial stress on the magnetic properties of a ferromagnetic specimen, in this case annealed SAE-4130 steel. Properties measured indirectly included remanence, coercivity, and first, third and fifth harmonic amplitudes. The properties were extracted from the voltage measured across the detection coil and incorporate the magnetic influence of the soft iron core, but with the effect of air gap variation between pole piece and sample kept to a controlled range. Results were compared to a micromagnetic model for the effect of biaxial stress on hysteresis and on magnetic properties. The micromagnetic model is a modified version of a model previously employed by Schneider et al. The experimental remanence variation due to biaxial stress compared very well to the predictions of the model. Furthermore, the model predict,s and experiment bears out, that the remanence with the field along one stress axis minus the remanence with the field along the other stress axis falls in a straight-line band of values when plotted against the difference of the two stresses. This suggests a possible NDE technique for detecting differences in biaxial stresses at a given location in a steel specimen.

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

1993-12-31

86

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

87

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

88

Synthesis, characterization, and fabrication of magnetic nanoparticles for low energy loss applications  

NASA Astrophysics Data System (ADS)

It is important to increase operating frequency of power electronics for miniaturization of components. Magnetic materials are used as inductor cores to increase inductance proportional to their magnetic permeability. However, traditional magnetic materials are not used at high frequency (100MHz) because of large hysteresis and eddy current loss. Superparamagnetic nanoparticles are good candidates to resolve these problems because they have zero hysteresis loss. In addition, eddy currents can be reduced due to their high electric resistivity originating from the organic ligands on the surface. Magnetic nanoparticles such as NiFe2O4, Ni1-xZnxFe2O4, MnFe3O4 and ZnFe2O4 have been synthesized via high temperature thermal decomposition method and can be tuned to desired size, shape and chemical composition. To understand structural and magnetic properties of nanoparticles, the nanoparticles have been characterized by TEM, SQUID, PPMS, and Network Analyzer. UV-induced polymerization and pressing method have been implemented for film deposition. Finally, AC susceptibility of the nanoparticle film have been measured and discussed for low energy-loss applications.

Yun, Hongseok; Chen, Jun; Doan-Nguyen, Vicky; Kikkawa, James; Murray, Christopher

2013-03-01

89

Magnetic hysteresis parameters for two Antarctic (Yamato-82050, Yamato-791717) and two African (Acfer-059, Acfer-202) carbonaceous chondrites  

NASA Astrophysics Data System (ADS)

We have selected four carbonaceous chondrites of CO3 type for the study of meteoritic magnetism. We apply the approach regarding carbonaceous chondrites in terms of a magnetic binary system. This model explains meteoritic magnetism as the mixture of two magnetic components: a high coercivity magnetic mineral including SD particles and a low coercivity carrier including MD particles. The construction of the model is based on parameters of magnetic hysteresis loop. We have measured the average magnetic susceptibility per unit mass and made AF demagnetization of NRM (measured using the SQUID magnetometer) to determine the size of the medium destructive field. The thermal experiments to find the Curie unblocking temperatures of magnetic carriers has been also performed. Data indicate differentiations among studied chondrites of type CO3.

Krol, Elizabeth A.; Lang, Bruno

1997-03-01

90

Theoretical calculations of magnetic hysteresis and critical sizes for transitions between single-domain and multi-domain properties in titanomagnetites  

NASA Astrophysics Data System (ADS)

In this dissertation, I develop some theoretical tools to interpret measurements of magnetization in rocks, sediments and soils. I show that the magnetization curve for an ensemble of superparamagnetic particles depends only on odd moments of the volume distribution (< V>,< Vsp3>,\\...). As long as the ensemble is isotropic, the magnetic anisotropies of individual particles do not affect the curve. I derive analytical expressions for acquisition and loss of isothermal remanent magnetization in single-domain (SD) particles with uniaxial anisotropy. These curves depend only on the volume-average anisotropy. Plots of acquisition against loss of remanence can be used to distinguish uniaxial anisotropy from cubic anisotropy. I show that existing multi-domain (MD) hysteresis models, including the theory of Neel (1955) for thermoremanent magnetization, are internally inconsistent. I develop a simple self-consistent two-domain model and show that the slope of the hysteresis curve is always 1/N, where N is the demagnetizing factor for a two-domain particle. Using micromagnetic theory, I derive analytical expressions for the critical sizes Lsb{sw}, the upper limit for SD hysteresis, and Lsb{n}, the upper limit for stability of the SD remanent state. Lsb{sw} depends weakly on elongation and not at all on magnetocrystalline anisotropy, but$Lsbn = Lsbsw\\ ?ft({Nsbb/ Nsba}right)sp{sp{1/2}}?ft(1-{2kappa/musb0M{sbsps{2}}Nsba}right)sp{sp{-1/2}}where Nsba > Nsbb are demagnetizing factors and kappa depends on the combined magnetocrystalline and magnetoelastic anisotropy. Mainly because of the the difference in Ms,\\ Lsb{n} is orders of magnitude larger for a particle of Fesb{2.4}Tisb{0.6}Osb4 than for a particle of magnetite with the same aspect ratio. I develop a technique for eliminating unstable solutions of three-dimensional numerical micromagnetic models. I show that nucleation theory can be extended to non-ellipsoidal particles. The nucleation field Hsbn for a cuboid can be precisely located by a change in slope dM/dH and the appearance of curl in the magnetization. For a cube with Ksb1 = 0, the plot of Hsbn against 1/Lsp2 has the same slope as for a sphere, but the intercept is lower, reflecting a smaller average demagnetizing field. Hsbn$ is not affected by the demagnetizing field in the corners of the particle.

Newell, Andrew James

91

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

92

Core loss in buried magnet permanent magnet synchronous motors  

Microsoft Academic Search

The steady-state core-loss characteristics of buried-magnet synchronous motors operating from a sinusoidal constant frequency voltage supply are investigated. Measured and calculated core loss, with constant shaft load, is shown to increase with decreasing terminal voltage due to an increase in armature reaction-induced stator flux-density time harmonics. Finite-element modeling is used to show that the additional loss due to the time-harmonic

R. Schifer; T.A. Lipo

1989-01-01

93

Sensorineural Hearing Loss after Magnetic Resonance Imaging  

PubMed Central

Magnetic resonance imaging (MRI) devices produce noise, which may affect patient's or operators' hearing. Some cases of hearing impairment after MRI procedure have been reported with different patterns (temporary or permanent, unilateral or bilateral, with or without other symptoms like tinnitus). In this report, a case of bilateral sensorineural hearing loss in an otherwise healthy patient underwent brain MRI was described. The patient's hearing loss was accompanied with tinnitus and was not improved after 3 months of followup.

Mollasadeghi, Abolfazl; Mehrparvar, Amir Houshang; Atighechi, Saeid; Mostaghaci, Mehrdad

2013-01-01

94

Magnetic Hysteresis Parameters and Day-Plot Analysis to Delineate Diagenetic Alteration in Gas Hydrate-Bearing Sediments  

NASA Astrophysics Data System (ADS)

Gas hydrates are naturally occurring cage structures of ice found in continental slope and permafrost sediments. They contain vast quantities of methane which is important both as a climate driver and an energy resource. Hydrate formation alters the redox potential of interstitial fluids which can in turn alter magnetic minerals. Thus magnetic methods can help delineate diagenetic pathways, provide a proxy method to map out past hydrate occurrences, and eventually lead to new remote sensing methods in prospecting for gas hydrates. We present data acquired using a J-Meter Coercivity Spectrometer. Induced and remanent magnetism are simultaneously measured on 1.5 cc samples as they spin on a 50 cm diameter disk, 20 times per second. The applied field ramps between ą 500 mT to produce a hysteresis loop in 7 minutes. Sub-second viscous decay is measured to provide a proxy for the amount of superparamagnetism present. The rapid and simple measurements made possible by this robust machine are ideal for core logging. Measurements made on frozen core from the Mallik permafrost gas hydrate field in Canada's Northwest Territories demonstrates that the magnetic properties are dependent on the concentration of gas hydrate present. Day-plots of magnetic hysteresis parameter ratios distinguish the magnetic carriers in gas hydrate rich sediments. The original magnetite is often reduced to sulphide when gas hydrate concentration exceeds 40%. In other high-concentration gas hydrate horizons, fine single-domain (SD) grains of magnetite apparently dissolve leaving nothing but large multi-domain (MD) magnetite grains. Independently measured superparamagnetism is shown to push hysteresis ratios off the hyperbola expected for SD-MD mixtures, as predicted by Dunlop [JGR, 10.10291/2001JB000486, 2002]. Magnetic study of host sediments in gas hydrate systems provides a powerful core-logging tool, offers a window into the processes of gas hydrate formation, and forms the basis for quantitative analysis of magnetic surveys over gas hydrate fields.

Enkin, R. J.; Baker, J.; Nourgaliev, D.; Iassonov, P.

2005-12-01

95

Three-Phase Asymmetric Transformer Aging Considering Voltage-Current Harmonic Interactions, Unbalanced Nonlinear Loading, Magnetic Couplings, and Hysteresis  

Microsoft Academic Search

A new aging calculation method for three-phase three-leg power transformers under (un)balanced and (non)sinusoidal operating conditions is proposed where the impacts of magnetic saturation, couplings, and hysteresis are accurately included. The aging estimation is carried out through a recently developed and validated time-domain model of a nonlinear three-phase three-leg transformer. The model outputs are used to compute aging based on

Paul S. Moses; Mohammad A. S. Masoum

2012-01-01

96

Drag loss in retaining rings of permanent magnet motors  

Microsoft Academic Search

Slot openings modulate the magnetic field present in the air-gap of permanent magnet motors. If the magnets are conductive or if there is present a conductive magnet retention cylinder, losses will be present. This is no-load loss which appears as a drag on the rotor. It is difficult to distinguish from core loss, at least from terminal measurements, but in

E. C. Lovelace

2003-01-01

97

Asymmetric hysteresis loops and its dependence on magnetic anisotropy in exchange biased Co/CoO core-shell nanoparticles  

NASA Astrophysics Data System (ADS)

The origin of asymmetry in field cooled (FC) hysteresis loops exhibiting exchange bias (EB) is investigated by studying the static and dynamic magnetic properties of core-shell Co/CoO nanoparticles. Two distinct freezing temperatures coresponding to the core (Tf-cr ~ 190 K) and the shell moments (Tf-sh ~ 95 K) are obtained from the energy barrier distribution. The FC loops are symmetric in the temperature range Tf-sh <= T <= Tf-cr, however, asymmetry in hysteresis is observed immediately below Tf-sh. These intriguing features are also probed by radio frequency transverse susceptibility (TS) experiments. We show that the first anisotropy fields obtained from the demagnetization and return curves of field cooled TS measurement, shift along the negative field axis and strikingly resemble the temperature dependence of EB. Field cooled TS measurements reveal the effect of competing Zeeman and anisotropy energy above and below Tf-sh to account for the development of asymmetry. Our study indicates that asymmetry in FC hysteresis loops is intrinsic to core-shell nanoparticles and develops only below the freezing temperature of the shell due to enhanced magnetic anisotropy.

Chandra, Sayan; Khurshid, Hafsa; Phan, Manh-Huong; Srikanth, Hariharan

2012-12-01

98

Alternating current losses in stacked Bi2Sr2Ca2Cu3O10\\/Ag tapes in perpendicular magnetic fields  

Microsoft Academic Search

Alternating current losses in stacks of powder-in-tube-processed Bi2Sr2Ca2Cu3O10\\/Ag tapes were measured in perpendicular magnetic fields and compared with calculated hysteresis losses based on the critical-state model. Four main factors had to be taken into account for the calculations of the losses: (1) the inclusion of the area of the Ag sheath in determining the critical-current densities of the stacks, (2)

M. Suenaga; T. Chiba; S. P. Ashworth; D. O. Welch; T. G. Holesinger

2000-01-01

99

Impacts of Hysteresis and Magnetic Couplings on the Stability Domain of Ferroresonance in Asymmetric Three-Phase Three-Leg Transformers  

Microsoft Academic Search

This paper investigates the stability domain of fer- roresonance in asymmetric three-phase three-leg transformers considering magnetic couplings and hysteresis effects of the core. A newly developed and accurate time-domain transformer model capable of simulating dynamic and transient operating conditions is implemented in this study. The model is based on electromag- netic circuit theory and considers dynamic hysteresis effects (major and

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

2011-01-01

100

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

NASA Astrophysics Data System (ADS)

Superconducting single- and twin-aperture dipole model magnets for the future CERN Large Hadron Collider have been built in industry and tested at CERN (1). 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 are used in these models differ with respect to the filament diameter, the strand coating and the fact whether the cable is (partially) soldered or not. The energy loss, determined electrically as the difference between the stored energy and the extracted energy during a current cycle, consists mainly of filament hysteresis and inter-strand coupling loss. The hysteresis component is in fair agreement with calculations. The inter-strand coupling loss varies with about a factor 5 between the models due to a different contact resistance between crossing strands in the cable (varying in the range from 1 to 10 mu Omega). Even for model magnets which are made with the same cable the inter-strand coupling loss can differ significantly.

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

1994-07-01

101

Magnetic hyperthermia investigation of cobalt ferrite nanoparticles: Comparison between experiment, linear response theory, and dynamic hysteresis simulations  

NASA Astrophysics Data System (ADS)

Considerable effort has been made in recent years to optimize materials properties for magnetic hyperthermia applications. However, due to the complexity of the problem, several aspects pertaining to the combined influence of the different parameters involved still remain unclear. In this paper, we discuss in detail the role of the magnetic anisotropy on the specific absorption rate of cobalt-ferrite nanoparticles with diameters ranging from 3 to 14 nm. The structural characterization was carried out using x-ray diffraction and Rietveld analysis and all relevant magnetic parameters were extracted from vibrating sample magnetometry. Hyperthermia investigations were performed at 500 kHz with a sinusoidal magnetic field amplitude of up to 68 Oe. The specific absorption rate was investigated as a function of the coercive field, saturation magnetization, particle size, and magnetic anisotropy. The experimental results were also compared with theoretical predictions from the linear response theory and dynamic hysteresis simulations, where exceptional agreement was found in both cases. Our results show that the specific absorption rate has a narrow and pronounced maxima for intermediate anisotropy values. This not only highlights the importance of this parameter but also shows that in order to obtain optimum efficiency in hyperthermia applications, it is necessary to carefully tailor the materials properties during the synthesis process.

Verde, E. L.; Landi, G. T.; Gomes, J. A.; Sousa, M. H.; Bakuzis, A. F.

2012-06-01

102

Evolution of Recrystallization by Changes in Magnetic Hysteresis Loop in a Non-Oriented Electric Steel Cold Rolled  

NASA Astrophysics Data System (ADS)

Non-oriented steels, with low carbon, are widely used in the fabrication of electrical motor nucleus. The performance of these motors is affected by the level of recrystallization. These steels can come from the steel plant in two different conditions: totally processed or semi-processed. The semi-processed steels have a partially deformed structure and are submitted to the final annealing process after reaching the end shape. An adequate annealing heat treatment is important to get an appropriate magnetic property. In the present study, samples of an electric steel, with the composition (0.05 wt% C, 1.28wt% Si, 0.29wt% Mn), cold rolled 50% in thickness, were withdrawn during the industrial heat treatment at temperatures of 575, 580, 600, 620 and 730 °C with the objective of evaluating the evolution of recrystalization with temperature. Magnetic properties were measured at room temperature in a vibrating sample magnetometer. Although the changes in magnetic hysteresis loop with temperature are difficult to observe, they have been identified by using pattern classification techniques, such as principal-component analysis and Karhunen-Ločve expansion. These tools have been applied to vectors which are built from each hysteresis loop, properly renormalized, whose components correspond to amplitude of the loop at given equally spaced values of the renormalized field. The samples have been classified in four sets, namely, set A corresponding to temperatures 575/580, set B corresponding to temperatures 600/620, set C corresponding to the samples without annealing heat treatment, and set D corresponding to recrystallized samples. The results for the classification of the different microstructures have been obtained by using both techniques, and in particular a 100% success rate has been reached by using Karhunen-Ločve expansion.

da Silva, F. E.; Freitas, F. N. C.; Abreu, H. F. G.; Gonçalves, L. L.; Moura, E. P.; Silva, M. R.

2011-06-01

103

Iron Loss Reduction Method for Permanent Magnet Machine with Beveling Magnet  

Microsoft Academic Search

Permanent magnet (PM) machines can save energy compared with induction motors, because of the elimination of rotor copper loss and the reduction of stator iron losses. In PM machines, iron losses form a most portion of the total losses. In order to further reduce the iron losses, the method of beveling magnet edges is proposed. The expressions of the peak

Haitian Wang; Ge Li; Liang Cao; Xuan Hong; Ruyi Wan

2010-01-01

104

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

105

Loss minimization control of permanent magnet synchronous motor drives  

Microsoft Academic Search

This paper aims to improve efficiency in permanent magnet synchronous (PM) motor drives. The controllable electrical loss which consists of the copper loss and the iron loss can be minimized by the optimal control of the armature current vector. The control algorithm of the current vector minimizing the electrical loss is proposed and the optimal current vector can be decided

Shigeo Morimoto; Yi Tong; Yoji Takeda; T. Hirasa

1994-01-01

106

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

107

Magnetic hysteresis loop technique as a tool for the evaluation of ? phase embrittlement in Fe–Cr alloys  

NASA Astrophysics Data System (ADS)

Fe-48 wt% Cr alloy was isothermally aged at 700 °C up to 250 h for the formation and growth of ? phase. Micro Vicker's hardness and magnetic hysteresis loop (MHL) measurements were carried out at various lengths of time by interrupting the test to observe the change in mechanical and magnetic properties respectively. A small volume fraction of ? phase did not produce any change in the hardness whereas a drastic decrease in remanence was found for its demagnetizing effect. The existence of ? phase was confirmed by transmission electron microscopy. The maximum induction of the alloy decreased with thermal ageing as the volume of ferrites decreased for the formation of non-magnetic ? phase. The volume fraction of ? phase was estimated from the maximum induction. The results showed that MHL technique can even detect 1% of ? phase in the alloy considering remanence as a measuring parameter. Hence MHL would be a powerful non-destructive evaluation technique for the evaluation of ? phase embrittlement in Fe–Cr alloys.

Mohapatra, J. N.; Kamada, Y.; Murakami, T.; Echigoya, J.; Kikuchi, H.; Kobayashi, S.

2013-02-01

108

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

109

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

Microsoft Academic Search

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.

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

1992-01-01

110

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

111

Magnetocrystalline anisotropy constants, rotational hysteresis energy and magnetic domain structure in UFe 6Al 6, UFe 9AlSi 2 and ScFe 10Si 2 intermetallic compounds  

Microsoft Academic Search

The magnetic torque, T, was applied to determine the anisotropy constants K1 and K2 of the UFe6Al6, UFe9AlSi2 and ScFe10Si2 compounds. The mechanism of magnetization reversal processes in these compounds was investigated on the basis of the analysis of the rotational hysteresis energy, Wr and rotational hysteresis integral, R, calculated from the magnetic torque curves. Applying the powder pattern method,

J. J. Wyslocki; W. Suski; P. Pawlik; K. Wochowski; B. Kotur; O. I. Bodak

1996-01-01

112

Beam based measurements of hysteresis effects in Fermilab main injector magnets  

SciTech Connect

Operation of the Fermilab Main Injector is sensitive to magnetic field differences due to hysteretic effects. Measurements using the beam are reported with various current ramps. This will provide magnetic field information for accelerator operations with better ramp control than is available from magnet test facility data. This makes possible improved low field reproducibility with mixed 120 GeV and 150 GeV operation of the Main Injector.

Bruce C. Brown and David P Capista

2003-05-27

113

Application of the Preisach and Jiles{endash}Atherton models to the simulation of hysteresis in soft magnetic alloys  

SciTech Connect

This article describes the advances in unification of model descriptions of hysteresis in magnetic materials and demonstrates the equivalence of two widely accepted models, the Preisach (PM) and Jiles{endash}Atherton (JA) models. Recently it was shown that starting from general energy relations, the JA equation for a loop branch can be derived from PM. The unified approach is here applied to the interpretation of magnetization measured in nonoriented Si{endash}Fe steels with variable grain size {l_angle}s{r_angle}, and also in as-cast and annealed Fe amorphous alloys. In the case of NO Fe{endash}Si, the modeling parameter {ital k} defined by the volume density of pinning centers is such that k{approx}A+B/{l_angle}s{r_angle}, where the parameters {ital A} and {ital B} are related to magnetocrystalline anisotropy and grain texture. The value of {ital k} in the amorphous alloys can be used to estimate the microstructural correlation length playing the role of effective grain size in these materials. {copyright} {ital 1999 American Institute of Physics.}

Pasquale, M.; Bertotti, G. [IEN Galileo Ferraris and INFM, Corso Massimo DAzeglio 42, 10125 Torino (Italy); Jiles, D.C.; Bi, Y. [Ames Laboratory, Iowa State University, Ames, Iowa 50011 (United States)

1999-04-01

114

Three-Phase Transformer Model Including Magnetic Hysteresis and Eddy Currents Effects  

Microsoft Academic Search

In this paper, a three-phase transformer model is developed to be suitable for slow transient and power-quality studies. The proposed model takes into account the eddy currents, the magnetic core topology, and the nonlinear characteristics of the core material. In order to model the eddy currents effects in the magnetic core, Bertotti's work for the eddy currents is used and

Andreas D. Theocharis; John Milias-Argitis; Thomas Zacharias

2009-01-01

115

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

116

Effect of Air gap variation on characteristics of an Axial flux hysteresis motor  

Microsoft Academic Search

Axial flux hysteresis motor (AFHM) such as other types of hysteresis motor is self-starting synchronous motor that use the hysteresis characteristics of magnetic materials. It is known that the magnetic characteristics of hysteresis motor could be easily affected by air gap and structure dimensions variation. Air gap length plays an important role in flux distribution in hysteresis ring that can

Mohammad Modarres; Abolfazl Vahedi; Mohammadreza Ghazanchaei

2010-01-01

117

Use of magnetic hysteresis properties and electron spin resonance spectroscopy for the identification of volcanic ash: a preliminary study  

Microsoft Academic Search

This initial study investigates the possible use of hysteresis parameters and electron spin resonance (ESR) spectroscopy to identify and correlate volcanic ash. ESR and hysteresis properties are sensitive to characteristics such as the chemical composition, mineralogy, and grain size and shape. These characteristics are determined by the tectonic setting of the volcano and by the magmatic and eruptive history of

Archana Pawse; Suzanne Beske-Diehl; S. A. Marshall

1998-01-01

118

Magnetic network model including loss separation and Preisach principles for the evaluation of core losses in devices  

NASA Astrophysics Data System (ADS)

In this paper, a method is developed to calculate the core loss in a switched reluctance machine. The magnetic circuit of the motor is described as a magnetic network. The electromagnetic behavior of each magnetic network element takes into account the iron loss using the Preisach model and the principle of loss separation. Using the numerical routines, the local core loss in the different motor sections is calculated. The global core loss is compared with the experimentally determined core loss.

Dupré, Luc; Sergeant, Peter; Vandenbossche, Lode

2005-05-01

119

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

120

Rotor Losses Measurements in an Axial Flux Permanent Magnet Machine  

Microsoft Academic Search

MMF space harmonics and slot openings produce considerable rotor losses in permanent magnet (PM) machines, especially if fractional-slot windings are adopted. This paper aims to measure the rotor losses of a 12-slot 10-pole axial flux phase modulation machine. Both MMF space harmonics and slot open- ings are considered. The prototype is an axial flux machine with open slots, equipped with

Luigi Alberti; Emanuele Fornasiero; Nicola Bianchi; Silverio Bolognani

2011-01-01

121

AC Losses in Multifilamentary Strands With Magnetic and Non-Magnetic Sheath Materials  

Microsoft Academic Search

AC applied magnetic field loss measurements have been performed on MgB2 superconducting strands. We measured strands with six untwisted filaments made via an in-situ route with Nb chemical barriers, a Cu-inter-filamentary matrix, and with either non-magnetic (glidcop) or magnetic (monel) outer sheaths. AC losses in magnetic fields applied perpendicular to the wire axis have been measured in fields up to

M. Majoros; Mike D. Sumption; M. A. Susner; M. Tomsic; M. Rindfleisch; E. W. Collings

2009-01-01

122

Butterfly Hysteresis Loop at Nonzero Bias Field in Antiferromagnetic Molecular Rings: Cooling by Adiabatic Magnetization  

Microsoft Academic Search

At low temperatures, the magnetization of the molecular ferric wheel NaFe6 exhibits a step at a critical field Bc due to a field-induced level crossing. By means of high-field torque magnetometry we observed a hysteretic behavior at the level crossing with a characteristic butterfly shape which is analyzed in terms of a dissipative two-level model. Several unusual features were found.

O. Waldmann; R. Koch; S. Schromm; P. Müller; I. Bernt; R. W. Saalfrank

2002-01-01

123

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

124

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

125

Magnetic domain structure and rotational hysteresis energy in Alnico magnets with different crystallographic orientation of the sample surface  

NASA Astrophysics Data System (ADS)

It was found that changes in the magnetization of the Alnico magnet occur by the curling mechanism for the samples with easy axis direction parallel to the surface sample, while for the samples with easy axis direction perpendicular to the sample surface coherent rotations take place.

Wysllocki, J. J.; Wysllocki, B.

1990-01-01

126

A Best-Fit Model of Power Losses in Cold Rolled-Motor Lamination Steel Operating in a Wide Range of Frequency and Magnetization  

Microsoft Academic Search

A procedure is described for identifying a mathematical model of core losses in ferromagnetic steel based on a minimal amount of experimental data. The new model has a hysteresis loss multiplicative coefficient variable only with frequency, a hysteresis loss power coefficient variable both with frequency and induction and a combined coefficient for eddy-current and excess losses that is, within a

Mircea Popescu; Dan M. Ionel

2007-01-01

127

Effect of tensile and compressive stress on dynamic loop shapes and power losses of Fe-Si electrical steels  

NASA Astrophysics Data System (ADS)

Magnetic energy losses and hysteresis loops have been determined in Fe-Si non-oriented laminations as a function of the applied compressive and tensile stress, made to range between -50 and +50 MPa. The loss separation analysis has been carried out in association with hysteresis loop calculation by means of the Dynamic Preisach Model. The strong modifications to the hysteresis loop and area introduced in a specific way by compressive stresses can be correctly accounted for by modelling.

Lobue, M.; Basso, V.; Fiorillo, F.; Bertotti, G.

1999-05-01

128

Magnetic circular dichroism in reflection electron energy loss spectroscopy?  

SciTech Connect

We evaluate the possibility of using dichroic electron energy loss spectroscopy (DEELS) as an alternative to x-ray magnetic circular dichroism (XMCD). It is well known that electron energy loss spectroscopy and x-ray absorption spectroscopy provide similar information. A simple semiclassical model suggests that reflection DEELS might have a magnetic sensitivity similar to that of XMCD. This sensitivity will be reduced, however, by multiple scattering of the probe electron before and after the energy loss event. Thus, it is difficult to predict the magnitude of the DEELS effect. Experiments were performed at the {ital L} edges of polycrystalline Fe, Co, and Ni thin-film samples prepared {ital in} {ital situ} with a uniaxial magnetic bias. Even in these most favorable cases, the DEELS effect is limited to less than one-tenth of related effects in XMCD. {copyright} {ital 1996 American Vacuum Society}

Harp, G.R. [Department of Physics and Astronomy, Ohio University, Athens, Ohio 45701 (United States); Farrow, R.F.; Marks, R.F. [IBM Research Division, Almaden Research Center, San Jose, California 95120-6099 (United States)

1996-07-01

129

Evaluation of case depth in induction-hardened steels: Magnetic hysteresis measurements and hardness-depth profiling by differential permeability analysis  

NASA Astrophysics Data System (ADS)

We have studied case depth of induction-hardened steel rods using magnetic hysteresis technique. A step-like behavior of magnetization curve, a decrease of maximum flux density, and an increase of coercivity with case depth, typical for surface-hardened steels, were observed, reflecting a mixture of magnetically hard hardened layer and soft core. Differential permeability exhibited a double peak structure with high- and low-field peaks due to hardened layer and core, respectively. Analysis for the area and position of the permeability peaks, based on a simple model, demonstrated that the volume fraction of hardened layer can be quantitatively and directly inferred from the permeability data alone. Although this method is generally restricted to the case in which a double peak structure in differential permeability is observed, this analysis method can be a possible technique to non-destructively construct depth profile of Vickers hardness from magnetic measurements.

Kobayashi, Satoru; Takahashi, Hiroko; Kamada, Yasuhiro

2013-10-01

130

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

131

[Mathematical models of hysteresis  

SciTech Connect

The research described in this proposal is currently being supported by the US Department of Energy under the contract Mathematical Models of Hysteresis''. Thus, before discussing the proposed research in detail, it is worthwhile to describe and summarize the main results achieved in the course of our work under the above contract. Our ongoing research has largely been focused on the development of mathematical models of hysteretic nonlinearities with nonlocal memories''. The distinct feature of these nonlinearities is that their current states depend on past histories of input variations. It turns out that memories of hysteretic nonlinearities are quite selective. Indeed, experiments show that only some past input extrema leave their marks upon future states of hysteretic nonlinearities. Thus special mathematical tools are needed in order to describe nonlocal selective memories of hysteretic nonlinearities. Our research has been primarily concerned with Preisach-type models of hysteresis. All these models have a common generic feature; they are constructed as superpositions of simplest hysteretic nonlinearities-rectangular loops. Our study has by and large been centered around the following topics: various generalizations and extensions of the classical Preisach model, finding of necessary and sufficient conditions for the representation of actual hysteretic nonlinearities by various Preisach type models, solution of identification problems for these models, numerical implementation and experimental testing of Preisach type models. Although the study of Preisach type models has constituted the main direction of the research, some effort has also been made to establish some interesting connections between these models and such topics as: the critical state model for superconducting hysteresis, the classical Stoner-Wohlfarth model of vector magnetic hysteresis, thermal activation type models for viscosity, magnetostrictive hysteresis and neural networks.

Mayergoyz, I.D.

1991-01-01

132

Frequency dependence of magnetic ac loss in a Roebel cable made of YBCO on a Ni-W substrate  

NASA Astrophysics Data System (ADS)

We have investigated the frequency dependent contributions to the magnetic ac loss in a 10 strand Roebel cable with 2 mm wide non-insulated strands and a transposition length of 90 mm. This cable is made from 40 mm wide YBCO coated conductor tape manufactured by AMSC and stabilized by electroplating 25 ľm thick copper on either side prior to the mechanical punching of the cable strands. The measurements were carried out in both perpendicular and parallel field orientation, at frequencies in the range of 30-200 Hz. While the loss in the perpendicular orientation is predominantly hysteretic in nature, we observe some frequency dependence of the loss when the cable approaches full flux penetration at high field amplitudes. The magnitude is consistent with eddy current losses in the copper stabilization layer. This supports the fact that the inter-strand coupling loss is not significant in this frequency range. In the parallel field orientation, the hysteresis loss in the Ni-W alloy substrate dominates, but we see an unusually strong frequency dependent contribution to the loss which we attribute to intra-strand current loops.

Lakshmi, L. S.; Staines, M. P.; Badcock, R. A.; Long, N. J.; Majoros, M.; Collings, E. W.; Sumption, M. D.

2010-08-01

133

AC magnetic field losses in BSCCO-2223 superconducting tapes  

SciTech Connect

The AC magnetic losses at power frequencies (60 Hz) were investigated for mono- and multifilament Ag-sheathed (Bi, Pb){sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub y} (BSCCO-2223) tapes with similar transport critical current (I{sub c}) values at 77 K. The multifilament sample exhibited higher losses than the monofilament under the same conditions. Loss peaks are discussed in terms of intergranular, intragranular and eddy current losses. Because of BSCCO`s anisotropy, field orientation has a large effect on the magnitude of these peaks, even at relatively small angles. Losses for fields applied parallel to the c-axis of the textured BSCCO grains are larger by more than one order of magnitude than those applied perpendicular.

Lelovic, M.; Mench, S.; Deis, T. [Univ. of Pittsburgh, PA (United States). Dept. of Materials Science] [and others

1997-09-01

134

Hysteresis loss and critical current density of multifilamentary (NbW)3Sn composite conductor for AC use  

NASA Astrophysics Data System (ADS)

A multifilamentary Nb3Sn composite conductor for AC use was fabricated by the internal tin-core method. In this conductor, Nb-1at.%W is used for filaments and Cu-1at.%Ni for matrix. The conductor has 33,252 filaments of a diameter of 0.36 ?m. Samples of conductor were heat treated at 450-700°C for 24-740 h and the critical current and magnetization were measured at 4.2 K in transverse fields up to 5 T. Overall critical current density of 4.9 GA/m2 at 1.5 T is obtained with a heat treated at 600°C for 200 h. The effective filament diameter was estimated to be 3-5 ?m at 1.5 T.

Yasohama, K.; Kubota, Y.; Kobayashi, H.; Ogasawara, T.; Kasahara, H.; Torii, S.; Akita, S.

2001-05-01

135

Low frequency hysteresis loops of superparamagnetic nanoparticles with uniaxial anisotropy  

NASA Astrophysics Data System (ADS)

The low frequency hysteresis loops of superparamagnetic nanoparticles with uniaxial anisotropy are calculated as a function of the particle diameter, alternating magnetic field amplitude H0, frequency, and particle magnetic parameters both for oriented and nonoriented assemblies. The magnetic field frequency is assumed so high, f>50-100 kHz, that the mechanical rotation of a particle in surrounding medium is restricted. Thus, only the Neel-Brown magnetization relaxation process is taken into account. Pronounced dependence of the specific loss power on the particle diameter is found in the linear regime pertaining to small magnetic field amplitudes. For an oriented assembly of Co nanoparticles with optimal diameter D~6 nm the specific power loss can be as high as 1600 W/g for typical values H0=200 Oe and f=500 kHz. It is three times less for the corresponding nonoriented assembly. Nevertheless, using of particles with low anisotropy field, i.e., particles of soft magnetic type, seems to be preferable for the purpose of magnetic nanoparticle hyperthermia. For such an assembly the nonlinear regime can be easily accessed. Hence the hysteresis loop area increases and is comparable with its maximum possible value.

Usov, N. A.

2010-06-01

136

Hysteresis measurement in LabView  

Microsoft Academic Search

This paper deals with the computer-aided automated magnetic scalar hysteresis measurement on ferromagnetic toroidal-shape material. The measurement has been developed in LabView environment using National Instrument Data Acquisition Cards. The measurement technique of symmetric minor loops and first-order reversal curves are presented. It is necessary to measure the magnetic hysteresis curves of ferromagnetic material to describe the material from magnetic

Péter Kis; Miklós Kuczmann; János Füzi; Amália Iványi

2004-01-01

137

Analysis of a hysteresis motor with overexcitation  

Microsoft Academic Search

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

T. Kataoka; T. Ishikawa; T. Takahashi

1982-01-01

138

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

2013-09-12

139

Dielectric loss, conductivity relaxation process and magnetic properties of Mg substituted Ni-Cu ferrites  

NASA Astrophysics Data System (ADS)

The dielectric properties, dc and ac electrical resistivities of Mg substituted Ni-Cu ferrites with general formula Ni0.5Cu0.5-xMgxFe2O4 (0.0?x?0.5) have been investigated as a function of frequency, temperature and composition. ac resistivity of all the samples decreases with increase in the frequency exhibiting normal ferrimagnetic behavior. The frequency dependence of dielectric loss tangent showed a maximum in between 10 Hz and 1 kHz in all the ferrites. The conductivity relaxation of the charge carriers was examined using the electrical modulus formulism, and the results indicate the presence of the non-Debye type of relaxation in the prepared ferrites. Similar values of activation energies for dc conduction and for conductivity relaxation reveal that the mechanism of electrical conduction and dielectric polarization is the same in these ferrites. A single ‘master curve’ for normalized plots of all the modulus isotherms observed for a given composition indicates that the distribution of relaxation time is temperature independent. The saturation magnetization and coercivity as calculated from the hysteresis loop measurement show striking dependence on composition.

Singh, Navneet; Agarwal, Ashish; Sanghi, Sujata; Khasa, Satish

2012-08-01

140

A digital hysteresis loop experiment  

NASA Astrophysics Data System (ADS)

A toroid with primary and secondary windings is used as a transformer to generate magnetic hysteresis curves. The primary winding is driven by a signal generator, which induces an alternating voltage in the secondary winding. Both input and output voltages are captured using a digital storage oscilloscope and processed to generate and display a hysteresis curve. We show such curves are representative of the material used as the transformer core. Data acquisition and processing steps are presented in a manner suitable for use in an undergraduate laboratory or lecture demonstration.

Francavilla, T. L.; Claassen, J. H.; Willard, M. A.

2013-10-01

141

Monitoring the fatigue state of steel by evaluating the quasistatic and dynamic magnetic behavior  

SciTech Connect

For the evaluation of fatigue damage progression the application of quasistatic and dynamic magnetic measurements combined with the Preisach hysteresis model and the statistical loss theory is investigated. Throughout the fatigue lifetime hysteresis and excess magnetic behavior, both known to be sensitive to microstructural variations, are monitored. The magnetic evaluation results for fatigue tests executed on two steels depend on their initial microstructure and chemical composition. In addition the effect of low stress amplitude cyclic loading on the magnetic properties of electrical steel is investigated: after 1000 cycles the excess losses are slightly decreased, while hysteresis properties stay invariant.

Vandenbossche, Lode; Dupre, Luc; Melkebeek, Jan [Department of Electrical Energy, Systems and Automation, Ghent University, Sint-Pietersnieuwstraat 41, B-9000 Gent (Belgium)

2005-05-15

142

Commutation-caused eddy-current losses in permanent-magnet brushless DC motors  

Microsoft Academic Search

An analytical approach based on a two-dimensional electromagnetic field analysis in polar coordinates is developed to predict the commutation losses in a permanent magnet brushless dc (PMBD) motor. These losses are essentially the eddy-current losses induced in the PMBD motor's rotor magnets and core and are caused by the rotor sweeping of the stationary stator magnetic field before each current

Fang Deng

1997-01-01

143

Analytical calculation of rotor magnet eddy-current losses for high speed IPMSM  

Microsoft Academic Search

For high-speed machines applications, eddy-current losses in the interior permanent magnet of synchronous machine (IPMSM) form a portion of the total losses which can be significant. Indeed, the magnets are exposed to the harmonic fields which rotate with respect to the rotor. The induced losses in the magnets provoke temperature arising that must be limited to avoid the risk of

Adel Bettayeb; Xavier Jannot; Jean-Claude Vannier

2010-01-01

144

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

145

The power losses in magnetic laminations—the influence of the frequency and DC-bias magnetisation  

Microsoft Academic Search

The usual separation of the loss components is based upon the assumption that the hysteresis losses persist as a constant contribution multiplied by the frequency value. The question arises if this assumption is correct. The author of this paper presents the cases in which this way of treating the problem proves to be wrong. Another area of investigations concerns the

Zbigniew Gmyrek

2006-01-01

146

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

147

Generalization of radiative jet energy loss to non-zero magnetic mass  

NASA Astrophysics Data System (ADS)

Reliable predictions for jet quenching in ultra-relativistic heavy ion collisions require accurate computation of radiative energy loss. While all available energy loss formalisms assume zero magnetic mass - in accordance with the one-loop perturbative calculations - different non-perturbative approaches report a non-zero magnetic mass at RHIC and LHC. We here generalize a recently developed energy loss formalism in a realistic finite size QCD medium, to consistently include a possibility for existence of non-zero magnetic screening. We also present how the inclusion of finite magnetic mass changes the energy loss results. Our analysis suggests a fundamental constraint on magnetic to electric mass ratio.

Djordjevic, Magdalena; Djordjevic, Marko

2012-03-01

148

Thermal hysteresis in low-frequency noise of La0.7Sr0.3Mn0.92Fe0.08O3 thin films at low magnetic field  

NASA Astrophysics Data System (ADS)

The low-frequency 1/f voltage noise of epitaxial La0.7Sr0.3Mn0.92Fe0.08O3 thin films has been studied as a function of temperature (80-300 K) and magnetic field (up to 1500 G). It is found that the noise power spectral density (PSD) shows a peak at T?238 K which coincides with the peak temperature of the resistivity, and is below the Curie temperature. When a small magnetic field of 1500 G is applied, the noise PSD shows a large thermal hysteresis and changes with the magnetic history. This thermal hysteresis, lacking at B = 0, is distinctively different from other reported results on manganites without Mn-site doping. The origin of the noise peak at B = 0 is analysed on the basis of the magnetic fluctuation, and the scaling analysis of the normalized noise PSD is consistent with a three-dimensional random-void percolation model. The thermal hysteresis of the noise PSD further supports the assertions of a contribution from magnetic fluctuations and of a spin-dependent conduction process in Fe-doped colossal-magnetoresistance materials.

Han, K.-H.; Huang, Q.; Ong, P. C.; Ong, C. K.

2001-10-01

149

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

150

Indices of Multidomain Magnetic Behavior in Basic Igneous Rocks: Alternating-Field Demagnetization, Hysteresis, and Oxide Petrology  

Microsoft Academic Search

Lowtie and Fuller [1971] have recently proposed a simple test of the domain state of grains carrying natural remanent magnetization (NRM) in igneous rocks. The test is based on their observation that the 'hardness,' or resistance to alternating-field (AF) demagnetization, of weak-field thermoremanent magnetization .

D. J. Dunlop; J. A. Hanes; K. L. Buchan

1973-01-01

151

Magnetic properties of bacterial magnetosomes as potential diagnostic and therapeutic tools  

Microsoft Academic Search

Suspensions of bacterial magnetosomes are investigated with respect to magnetic losses. Mean core diameter of about 30nm results from TEM, XRD and magnetic analysis. Specific loss power is determined from hysteresis loops, susceptibility spectra and calorimetry with a maximum value of 960W\\/g at 410kHz and field amplitude 10kA\\/m. Results may be understood by relaxation effects on hysteresis.

Rudolf Hergt; Robert Hiergeist; Matthias Zeisberger; Dirk Schüler; Udo Heyen; Ingrid Hilger; Werner A. Kaiser

2005-01-01

152

Magnetic properties of bacterial magnetosomes as potential diagnostic and therapeutic tools  

NASA Astrophysics Data System (ADS)

Suspensions of bacterial magnetosomes are investigated with respect to magnetic losses. Mean core diameter of about 30 nm results from TEM, XRD and magnetic analysis. Specific loss power is determined from hysteresis loops, susceptibility spectra and calorimetry with a maximum value of 960 W/g at 410 kHz and field amplitude 10 kA/m. Results may be understood by relaxation effects on hysteresis.

Hergt, Rudolf; Hiergeist, Robert; Zeisberger, Matthias; Schüler, Dirk; Heyen, Udo; Hilger, Ingrid; Kaiser, Werner A.

2005-05-01

153

Iron loss analysis of interior permanent-magnet synchronous motors-variation of main loss factors due to driving condition  

Microsoft Academic Search

In this paper, the authors investigate the iron loss of interior permanent magnet motors driven by pulsewidth modulation (PWM) inverters from both results of the experiments and the finite-element analysis. In the analysis, the iron loss of the motor is decomposed into several components due to their origins, for instance, the fundamental field, carrier of the PWM inverter, slot ripples,

Katsumi Yamazaki; Yoshiaki Seto

2006-01-01

154

Correlation of frictional losses of spinning levitated magnets with ac susceptibility in high-temperature superconductors  

SciTech Connect

Measurements of both the ac magnetic susceptibility in melt processed and film Y{endash}Ba{endash}Cu{endash}O and frictional losses of spinning permanent magnets levitated above Y{endash}Ba{endash}Cu{endash}O are presented. A direct correlation is observed only when large susceptibility samples are studied indicative of the importance of grain boundary loss mechanisms. The increasing loss per revolution with increasing frequency for a spinning permanent magnet is explored. {copyright} {ital 1997 American Institute of Physics.}

Rossman, C.E.; Budnick, J.I.; Weinberger, B.R. [Department of Physics, University of Connecticut, Storrs, Connecticut 06269 (United States)

1997-01-01

155

Space-time correlation properties of the magnetization process and eddy current losses: Theory  

Microsoft Academic Search

The relationship between eddy current losses and magnetization dynamics is investigated on general bases, starting directly from Maxwell equations. The intrinsically stochastic character of the magnetization process is conveniently dealt with by describing the magnetization rate I˙(r,t) as a random sequence of elementary magnetization jumps, each corresponding to a sudden and localized displacement of a domain wall segment in the

G. Bertotti

1983-01-01

156

Low-Hysteresis Materials for Magnetic Refrigeration: Gd/sub 1-X/Er/sub X/Al sub 2.  

National Technical Information Service (NTIS)

The series of ferromagnetic intermetallics Gd/sub 1-x/Er/sub x/Al sub 2 are candidate working materials for magnetic refrigeration because of their large moment, small anisotropy, and the fact that their Curie temperatures span the range 14 K to 164 K. We...

C. B. Zimm J. A. Barclay W. R. Johanson

1983-01-01

157

The a.c. losses in (Bi,Pb) 2Sr 2Ca 2Cu 3O x silver-sheathed superconducting wires  

Microsoft Academic Search

In this study, a.c. losses in BSCCO silver-sheathed wires, both single- and multi-filamentary, were investigated by means of a.c.-magnetization and a.c.-transport techniques. It was shown that the longitudinal magnetization a.c. loss in a single-filamentary wire could be quantitatively explained by the simple sum of the magnetic hysteresis loss of the superconducting core and the eddy current loss in the silver

H. Ishii; S. Hirano; T. Hara; J. Fujikami; K. Sato

1996-01-01

158

Modeling of Iron Losses in Permanent Magnet Motors with Field-Weakening Capability  

Microsoft Academic Search

Finite element analysis is usually used to calculate iron losses in permanent magnet motors under field-weakening operation. Analytical models for the iron losses taking into account the rate of change of the flux densities and stator leakages are presented and compared to FEM results for surface- mounted permanent magnet motors.

Juliette Soulard; Stephan Meier; Yung-kang Chin

159

Measurement of AC loss and magnetic field during ramps in the LHC model dipoles  

Microsoft Academic Search

We describe the systems for AC loss and magnetic field measurements developed for the LHC superconducting magnets. AC loss measurements are performed using an electric method, while field measurements are performed using either fixed pick-ups or rotating coils. We present results obtained on 1-m long model dipoles, and compare the results of the different methods in terms of average interstrand

Z. Ang; I. Bejar; L. Bottura; D. Richter; M. Sheahan; L. Walckiers; R. Wolf

1999-01-01

160

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

161

Digital Hysteresis Circuit.  

National Technical Information Service (NTIS)

Noise induced hunting is eliminated in successive ranged digital/analog converter bias correction circuits by means of a digital hysteresis circuit. The digital hysteresis circuit comprehends a first up/down counter that counts to its extremums from a pre...

S. Morrison

1978-01-01

162

New magnetic material impact in electric machine design: high speed operation and reduction of losses  

Microsoft Academic Search

The paper presents electrical actuator design considerations introduced by exploiting new magnetic material characteristics. The materials considered are amorphous alloy ribbons as well as neodymium alloy permanent magnets involving very low eddy current losses. Such materials enable electric machine operation at higher frequencies compared with the standard iron laminations used in the traditional magnetic circuit construction and provide better efficiency.

G. Kalokiris; A. Kladas

2003-01-01

163

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

164

Analysis of Noise Spectral Density for Phenomenological Models of Hysteresis  

Microsoft Academic Search

A statistical technique based on Monte Carlo simulations is developed to compute the spectral densities of the output variable in phenomenological models of hysteresis. The input signal is described by an Ornstein-Uhlenbeck process and the magnetization is computed by using various hysteresis models: the Energetic, Jiles-Atherton, and Preisach models. General qualitative features of these spectral densities are examined and their

Ayodeji Adedoyin; Mihai Dimian; Petru Andrei

2009-01-01

165

Hysteresis modeling of synchronous reluctance motor considering PWM input voltage  

Microsoft Academic Search

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

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

2000-01-01

166

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

167

A novel hysteresis bandwidth (NHB) calculation to fix the switching frequency employed in active power filter  

Microsoft Academic Search

Variable switching process is the main issue in practical implementation of fixed band hysteresis current controller in active power filters (APF) that increases the switching frequency and switching losses in power systems. Preventing this case, the Adaptive Hysteresis Current Control (AHCC) has been introduced and developed by many researchers. By this way, The Hysteresis Band (HB) will change adaptively by

Hani Vahedi; Abdolreza Sheikholeslami; Mohammad Tavakoli Bina

2011-01-01

168

Analytical Modeling and Analysis of Open-Circuit Magnet Loss in Surface-Mounted Permanent-Magnet Machines  

Microsoft Academic Search

The paper presents an analytical model for predicting the open-circuit magnet eddy-current loss due to slotting in surface-mounted permanent-magnet machines based on the exact subdomain field model. The spatial and temporal characteristics of field harmonics due to slotting and corresponding eddy-current harmonics in the magnet are analyzed in both stator and rotor reference frames. The contribution of interaction between eddy-current

L. J. Wu; Z. Q. Zhu; D. Staton; M. Popescu; D. Hawkins

2012-01-01

169

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

170

Hysteresis and fatigue  

SciTech Connect

Energy dissipation associated with damage of materials is irreversible and loading cycles are accompanied by the evolution of heat. The relation between energy dissipation and loading therefore exhibits a memory dependence or hysteresis. Conversely, sustained hysteresis is a necessary condition for fatigue and is related to the rate of damage accumulation. Standards for estimating fatigue life are partially based on the Manson-Coffin relations between the width of stress strain hysteresis loops and the number of loading cycles required to produce failure in test pieces. In the present study, experimental and theoretical results demonstrate that this relation can be extended into a simple phenomenological description of fatigue that directly links total hysteresis energy dissipation, the cumulation of material damage, and the average number of loading cycles leading to failure. Analogies between the incremental collapse of structures and the inception and organization of damage in materials are used to aid understanding of the detailed features of hysteresis. Scanning tunneling microscope measurements of the threshold of mechanical irreversibility and acoustic emission patterns are used to detect the evolution of hysteresis at the microscopic level. 61 refs., 14 figs., 1 tab.

Erber, T. (Univ. of California, Los Angeles (United States)); Guralnick, S.A.; Michels, S.C. (Illinois Institute of Technology, Chicago (United States))

1993-06-01

171

On-Line System to Measure Magnetic Characteristics of Steel Samples.  

National Technical Information Service (NTIS)

Using an on-line system, one investigates the effects of low-temperature (up to 4.2 K) cooling on magnetic properties of electrotechnical steel samples. Dependence of hysteresis losses in proper cycles of reverse magnetization with values of magnetic indu...

G. M. Antonichev O. V. Afanas'ev Y. B. Dubasov

1988-01-01

172

Hysteresis and magnetostriction of TbxDyyHo1-x-yFe1.95 [112] dendritic rods  

NASA Astrophysics Data System (ADS)

The magnetization and magnetostriction of a variety of 3/16-in.-diam Laves phase rods of TbxDyyHo1-x-yFe1.95 grown in the form of [112] oriented dendritic compounds were measured as a function of applied magnetic field -3000hysteresis with only slightly lower magnetostriction. The Ho concentration was kept relatively small (<=0.3) to avoid a substantial decrease in the magnetostriction, while the ratio of x and y was chosen to examine alloys spanning the line of minimum magnetic anisotropy. Most of the compositions have twice the Ho content of the previous study. As expected, alloys with higher Ho concentrations showed narrower hysteresis curves. The data shows that at 22 MPa, the Tb0.28Dy0.57Ho0.15Fe1.95 composition has a minimal (3%) loss of magnetostriction, while the hysteresis width decreased by 15%. Between 15% and 20% Ho content, the magnetostriction drops abruptly. For alloys with a fixed Ho concentration, the strain showed a peak near the expected anisotropy minimum, but the hysteresis width always increased with increasing Tb content.

Wun-Fogle, M.; Restorff, J. B.; Clark, A. E.

1999-04-01

173

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

174

Effect of electrical resistivity on core losses in soft magnetic iron powder materials  

Microsoft Academic Search

Iron powder should be electrically insulated with a dielectric to reduce eddy current losses in components fabricated by powder metallurgy intended for AC soft magnetic applications. However, most of the dielectrics act as distributed air gaps and reduce the apparent permeability of the material. To obtain materials with good magnetic properties, the dielectric amount should then be kept as low

L. P. Lefebvre; S. Pelletier; C. Gélinas

1997-01-01

175

Part i: Energy Loss of Magnetic Monopoles. Part II: the Functional Integral Measure in Quantum Gravity  

Microsoft Academic Search

Part I. The energy loss of slowly moving magnetic monopoles in atomic Hydrogen and Helium is investigated. It is found that magnetic monopoles can cause large shifts in the energy levels of atoms, thus providing a mechanism for excitation of the atoms. Probabilities for such excitation processes in atomic Hydrogen and Helium are computed. It is suggested that the Helium

Mark Theodore Mueller

1984-01-01

176

The calculation of iron losses in brushless permanent magnet dc motors  

NASA Astrophysics Data System (ADS)

The paper describes a procedure developed for the prediction of the flux density waveforms and iron losses in the stator core of a brushless permanent magnet dc motor. The procedure is applied to a low-cost drive system, and it is shown that the operating condition can have a marked effect on both the magnitude and distribution of the iron loss.

Atallah, K.; Howe, D.

1994-05-01

177

Core loss measurements including higher harmonics of magnetic induction in electrical steel  

Microsoft Academic Search

In this work, we have constructed a single sheet tester to measure the core loss of non-oriented electrical steel under arbitrary waveform of magnetic induction. The core loss was measured using this system under high harmonic frequencies from 3 to 39f0 (f0 = 60 Hz), amplitudes from 1 to 10% of the maximum induction Bmax, with phase angle 0°. When

D. Son; J. D. Sievert; Y. Cho

1996-01-01

178

Semi-empirical modeling of hysteresis compensation in magnetostrictive actuator  

NASA Astrophysics Data System (ADS)

Hysteresis causes a delayed response to a given input in a magnetostrictive actuator (MA). It becomes critical when the MA has to be controlled in precise and real-time mode. An efficient way to compensate hysteresis must be considered. The Jiles-Atherton and Preisach models have been applied mostly in the literature, but these models need complex mathematics that makes them difficult to be applied in precise and real-time mode. Thus, this paper presents a semi-empirical model to compensate hysteresis in the MA. The idea comes from the similarity of the shapes between the hysteresis-compensated input voltage to the MA, and the output voltage of R-C circuit. The respective hysteresis-compensated input voltage and R-C circuit are expressed as polynomial and exponential equations, resulting in two closed-form equations about capacitance. One set of capacitance values for each frequency is selected by simulating the derived equations. Experiments are performed to choose one capacitance value among a set of capacitance values from simulation, based on trial-and-error. The concept of the hysteresis loss is introduced and defined as the ratio of areas between the hysteretic and reference curves. It is observed that the percent change of hysteresis loss increases as the frequency increases up to 400 Hz, but decreases with further increase of the frequency up to 800 Hz. It can be concluded that the proposed approach is effective to compensate hysteresis in the MA, and that hysteresis loss definition introduced by us can be used as a helpful measure of hysteresis compensation.

Ji, Ki-Hyun; Park, Hae-Jung; Park, Young-Woo; Wereley, Norman M.

2013-04-01

179

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

180

Mathematical models of hysteresis  

SciTech Connect

The ongoing research has largely been focused on the development of mathematical models of hysteretic nonlinearities with nonlocal memories. The distinct feature of these nonlinearities is that their current states depend on past histories of input variations. It turns out that memories of hysteretic nonlinearities are quite selective. Indeed, experiments show that only some past input extrema (not the entire input variations) leave their marks upon future states of hysteretic nonlinearities. Thus special mathematical tools are needed in order to describe nonlocal selective memories of hysteretic nonlinearities. The origin of such tools can be traced back to the landmark paper of Preisach. Their research has been primarily concerned with Preisach-type models of hysteresis. All these models have a common generic feature; they are constructed as superpositions of simplest hysteretic nonlinearities-rectangular loops. During the past four years, the study has been by and large centered around the following topics: (1) further development of Scalar and vector Preisach-type models of hysteresis; (2) experimental testing of Preisach-type models of hysteresis; (3) development of new models for viscosity (aftereffect) in hysteretic systems; (4) development of mathematical models for superconducting hysteresis in the case of gradual resistive transitions; (5) software implementation of Preisach-type models of hysteresis; and (6) development of new ideas which have emerged in the course of the research work. The author briefly describes the main scientific results obtained in the areas outlined above.

NONE

1998-08-01

181

Factors affecting eddy current losses of segmented Nd-Fe-B sintered magnets without insulation in large PM motors  

Microsoft Academic Search

In large permanent magnet motors, the permanent magnet in the motor is segmented into parts in order to reduce the eddy current loss in permanent magnet. It is reported that the insulation between sintered Nd-Fe-B magnets is possible only by contacting the segmented permanent magnets without insulation. But the mechanism for such a phenomenon has not been clear. We have

Norio Takahashi; Hirofumi Shinagawa; Daisuke Miyagi; Yuhito Doi; Koji Miyata

2009-01-01

182

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

183

Magnetism and ferromagnetic loss in Ni-W textured substrates for coated conductors  

NASA Astrophysics Data System (ADS)

A study has been conducted on the magnetic properties of a series of biaxially textured Ni1-xWx materials with compositions x=0,3,5,6, and 9 at.% W. These materials are important as substrates for ``RABiTS''-type coated conductors that incorporate high temperature superconductors for current transport. The quasi-static dc and ac hysteretic loss W was determined to support estimates of the ferromagnetic contribution to the overall ac loss in potential ac applications. The alloys were prepared by either vacuum casting or powder metallurgy methods, and the hysteretic loss tended to be lower in materials that were recrystallized at higher temperatures. Some samples were progressively deformed (0.4% bending strain) to simulate winding operations; this increased the hysteretic loss, as did sample cutting operations that create localized damage. In ac magnetization measurements, the effects of ac frequency and dc bias field on the ferromagnetic loss were determined.

Ijaduola, A. O.; Thompson, J. R.; Goyal, A.; Thieme, C. L. H.; Marken, K.

2004-04-01

184

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 SomaloyŽ 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

185

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

186

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

187

Equivalent Circuit Parameter Calculation of Interior Permanent Magnet Motor Involving Iron Loss Resistance Using Finite Element Method  

Microsoft Academic Search

In this paper, we propose a method to calculate the equivalent circuit parameters of interior permanent magnet motors including iron loss resistance using the finite element method. First, the finite element analysis considering harmonics and magnetic saturation is carried out to obtain time variations of magnetic fields in the stator and the rotor core. Second, the iron losses of the

Katsumi Yamazaki

2004-01-01

188

Investigation of the effect of magnet thickness on motor losses of PM BLDC machines using parametric approach method  

Microsoft Academic Search

In this study, 500 Watts PM BLDC has been investigated using parametric approach method for determining the effect of magnet thickness on motor losses. Copper, iron losses and efficiency variation with magnet thickness calculated and represented graphically. The best performance\\/efficiency ratio determined versus magnet thickness. 24 slot, 4 pole and inner rotor configuration PM BLDC motor investigated. I. INTRODUCTION Nowadays,

Ramazan Bayindir; Ismail Topaloglu; Cemil Ocak

2011-01-01

189

Coupling loss time constants in full-size NbâSn CIC model conductors for fusion magnets  

Microsoft Academic Search

The cable-in-conduit conductor for the ITER coils have to perform at magnetic fields up to 13 T under the conditions of normal high ramp rates as well as extreme magnetic pulses during a plasma disruption. Modelling, ac loss computations and design optimisations require to understand and identify the coupling loss time constants in multistage cables. For this AC loss measurements

A. Nijhuis; H. H. J. ten Kate; J. L. Duchateau

1997-01-01

190

Magnetic Properties of Magnetic Fluids near Melting Point  

Microsoft Academic Search

The magnetization (M), field-induced magnetic anisotropy (Ku), rotational hysteresis loss (Erot) and melting point (Tm) of water-and paraffin-base ferrofluids were investigated in the temperature range from 77 K~300°K, as functions of the density of the colloidal particles. Both paraffin and paraffin-base fluids were melted down at temperatures between 180 and 210°K. In this range, the values of M and Erot

N. Inaba; H. Miyajima; S. Taketomi; S. Chikazumi

1990-01-01

191

Low losses left-handed materials with optimized electric and magnetic resonance  

NASA Astrophysics Data System (ADS)

We propose that the losses in left-handed materials (LHMs) can be significantly affected by changing the coupling relationship between electric and magnetic resonance. A double bowknot shaped structure (DBS) is used to construct the LHMs. And the magnetic resonance of the DBS, which resonated in the case of lower and higher frequencies than the electric resonant dip, is studied in simulation and experiment by tailoring the structural parameters. The case of magnetic resonance located at low electric resonance frequencies band is confirmed to have relatively low losses. Using full wave simulation of prism shaped structure composed of DBS unit cells, we prove the negative refraction behavior in such a frame. This study can serve as a guide for designing other similar metal-dielectric-metal (MDM) in low losses at terahertz or higher frequencies.

Zhou, Xin; Liu, Yahong; Zhao, Xiaopeng

2010-03-01

192

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

193

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

SciTech Connect

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. [Institute of Radiophysics and Electronics, 0203 Ashtarak (Armenia); Centre of Strong Fields Physics, Yerevan State University, Alex Manoogian str. 1, 0025 Yerevan (Armenia); Deutsch, Claude [LPGP - UMR-CNRS 8578, Universite Paris XI, F-91405 Orsay (France)

2011-06-15

194

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

PubMed

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. PMID:21797500

Nersisyan, Hrachya B; Deutsch, Claude

2011-06-23

195

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

196

Low losses left-handed materials with optimized electric and magnetic resonance  

Microsoft Academic Search

We propose that the losses in left-handed materials (LHMs) can be significantly affected by changing the coupling relationship\\u000a between electric and magnetic resonance. A double bowknot shaped structure (DBS) is used to construct the LHMs. And the magnetic\\u000a resonance of the DBS, which resonated in the case of lower and higher frequencies than the electric resonant dip, is studied\\u000a in

Xin Zhou; Yahong Liu; Xiaopeng Zhao

2010-01-01

197

A low loss permanent magnet brushless DC motor utilizing tape wound amorphous iron  

Microsoft Academic Search

An axial-field permanent magnet brushless DC motor which utilizes tape-wound amorphous iron is proposed. Simplified waveforms and performance equations for this type of machine are presented. The machine equations and waveforms are verified with a proof-of-concept machine. No-load iron losses are compared with manufacturers' data, and full-load iron losses are also presented. Output torques for rectangular and trapezoidal current waveforms

CHRIS C. JENSEN; FRANCO PROFUMO; T.A. Lipo

1990-01-01

198

A low-loss permanent-magnet brushless DC motor utilizing tape wound amorphous iron  

Microsoft Academic Search

An axial field permanent-magnet brushless DC motor that utilizes tape wound amorphous iron and an air gap winding is proposed. Simplified waveforms and performance equations for this type of machine are presented. The machine equations and waveforms are verified with a proof-of-concept machine. No-load iron losses are compared with manufacturer's data, and full-load iron losses are also presented. Output torque

Chris C. Jensen; Francesco Profumo; Thomas A. Lipo

1992-01-01

199

Low-Loss Magnetic Metamaterial Based on Analog of Electromagnetically Induced Transparency  

Microsoft Academic Search

In this paper, a low-loss magnetic metamaterial configuration consisting of coupled radiative and dark resonators is proposed based on analog of electromagnetically induced transparency. Full-wave numerical simulations are carried out to validate the metamaterial. Absorptions curves, transmission spectrums, surface current distributions, and effective constitutive parameters for the metamaterial are presented. These results, showing a low-loss transparency window and strong dispersion

F.-Y. Meng; F. Zhang; K. Zhang; Q. Wu; J.-Y. Kim; J.-J. Choi; B. Lee; J.-C. Lee

2011-01-01

200

Ultra low loss soft magnetic nanoparticles for applications up to S-band  

NASA Astrophysics Data System (ADS)

Magnetic and dielectric properties of sol-gel auto combustion processed soft spinel nanoferrite (NZFO) and hexa nanoferrite (Co2Z) were investigated for microwave antenna applications in the frequency range from 1.5 GHz to 3.5 GHz. Selection of dopants and optimized physical conditions have been used to control the high frequency electromagnetic properties of soft NZFO and Co2Z nanoparticles. At frequency 3.5 GHz the magnetic and electric losses of single phased Co2Z are 0.006, 0.002 and for NZFO are 0.004, 0.0018, respectively. The microwave measurements are supported by magnetization data and Mössbauer analysis.

Sharma, Sucheta; Daya, K. S.; Sharma, S.; Singh, M.

2013-09-01

201

Inverted hysteresis loops in CoO-based multilayers  

NASA Astrophysics Data System (ADS)

We have observed inverted hysteresis loops in a number of multilayer [Co-O]/Cu and [Co-O]/Al multilayers. In this phenomenon, the forward and reverse branches of a hysteresis loop are shifted along the magnetic field axis in such a way that they cross each other and we report the dependence of this phenomenon on magnetic layer thickness. In many cases the Cu or Al layer is thick enough that interlayer interactions between magnetic layers are not possible. It is suggested that interface exchange between Co and Co-O phases within the magnetic layer is important in these multilayers and that this phenomenon is closely related to shifted hysteresis loops which are also produced by interface exchange. We do not find this behavior in nominally homogeneous Co-O films indicating that the multilayer nature of the material is important. A two-phase model is presented which is able to qualitatively explain some of the observed results.

Gao, C.; O'Shea, M. J.

1993-10-01

202

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

203

Blood loss during radical retropubic prostatectomy: relationship to morphologic features on preoperative endorectal magnetic resonance imaging  

Microsoft Academic Search

Objectives. To determine whether morphologic features at preoperative magnetic resonance imaging (MRI) are related to intraoperative blood loss during radical retropubic prostatectomy.Methods. Endorectal MRI was performed in 143 patients with newly diagnosed prostate cancer before radical retropubic prostatectomy. Two independent readers rated the prominence of the periprostatic veins (on the basis of number and size) at four anatomic sites on

Fergus V Coakley; Steven Eberhardt; David C Wei; Evan S Wasserman; Stefan B. J Heinze; Peter T Scardino; Hedvig Hricak

2002-01-01

204

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

PubMed

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. Matter 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. PMID:23367947

Nándori, I; Rácz, J

2012-12-11

205

Collisionless fast electron losses in magnetic toroidal ripples during lower hybrid current drive in Tore Supra  

NASA Astrophysics Data System (ADS)

A consistent estimation of the losses of collisionless fast electrons driven by the lower hybrid wave and trapped in magnetic ripples in the Tokamak Tore Supra [Equipe TORE SUPRA, in Proceedings of the 15th Conference on Plasma Physics and Controlled Nuclear Fusion Research, Seville (International Atomic Energy Agency, Vienna, 1995), Vol. 1, IAEA-CN-60/A1-5, p. 105], is carried out using a two-dimensional relativistic bounce-averaged Fokker-Planck solver. A reasonable agreement is found between the simulations and the experimentally observed results obtained by the diagnostic named DRIPPLE (Diagnostic-Ripple) dedicated to magnetic ripple loss measurements. The analysis shows that the radial profile of the ripple loss current is dominated by the shape of the supertrapped domain in momentum space, and is therefore weakly dependent on the lower hybrid wave power absorption.

Ju, M.; Peysson, Y.; Basiuk, V.

2002-11-01

206

Magnetic field tuning of polaron losses in Fe doped BaTiO3 single crystals.  

PubMed

Artificial tuning of dielectric parameters can result from interface conductivity in polycrystalline materials. In ferroelectric single crystals, it has already been shown that ferroelectric domain walls can be the source of such artificial coupling. We show here that low-temperature dielectric losses can be tuned by a dc magnetic field. Since such losses were previously ascribed to polaron relaxation we suggest this results from the interaction of hopping polarons with the magnetic field. The fact that this loss alteration has no counterpart in the real part of the dielectric permittivity confirms that no interface is involved in this purely dynamical effect. The contribution of mobile charges hopping among Fe-related centers was confirmed by ESR spectroscopy, showing a maximum intensity at ca T ~ 40 K. PMID:22951582

Theerthan, R Anand; Artemenko, Alla; Maglione, Mario

2012-09-06

207

Magnetic field tuning of polaron losses in Fe doped BaTiO3 single crystals  

NASA Astrophysics Data System (ADS)

Artificial tuning of dielectric parameters can result from interface conductivity in polycrystalline materials. In ferroelectric single crystals, it has already been shown that ferroelectric domain walls can be the source of such artificial coupling. We show here that low-temperature dielectric losses can be tuned by a dc magnetic field. Since such losses were previously ascribed to polaron relaxation we suggest this results from the interaction of hopping polarons with the magnetic field. The fact that this loss alteration has no counterpart in the real part of the dielectric permittivity confirms that no interface is involved in this purely dynamical effect. The contribution of mobile charges hopping among Fe-related centers was confirmed by ESR spectroscopy, showing a maximum intensity at ca T ˜ 40 K.

Anand Theerthan, R.; Artemenko, Alla; Maglione, Mario

2012-10-01

208

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

209

The Evolution of Magnetic Binaries with Mass Loss. I. Calculations with Magnetic Field  

Microsoft Academic Search

The tensions of magnetic field in the stream which connects the primary component with the gas disc rotating around the secondary produces a force moment decelerating the disc. Two situations are considered: (1) the limiting case of a \\

E. M. Drobyshevskii; B. I. Reznikov

1974-01-01

210

Alpha particle loss in TFTR deuterium-tritium plasmas with reversed magnetic shear  

SciTech Connect

The confinement and loss of fusion alpha particles are examined for reversed magnetic shear plasmas in TFTR. Such plasmas, with high central q and non-monotonic q profiles can exhibit remarkably reduced energy and particle transport of the thermal ions. However, these same conditions are theoretically predicted to produce high levels of stochastic ripple loss of suprathermal particles, which may reduce the efficiency of plasma heating by the alpha particles and other heating schemes involving fast ions. This paper presents calculations of guiding-center code alpha particle orbit loss from deuterium-tritium (DT) simulations of TFTR deuterium-only experiments. They are compared to results of measurements made in DT reversed shear plasmas of both the confined alpha particle distribution and the alpha particles lost from the plasma. Large fast particle losses have also been found in reversed shear ITER simulations (up to 20%) and from measurements of triton burnup in reversed shear experiments on JT-60U (12%).

Redi, M.H.; Batha, S.H.; Budny, R.V. [and others

1997-06-01

211

Stiffness and hysteresis properties of some prosthetic feet.  

PubMed

A prosthetic foot is an important element of a prosthesis, although it is not always fully recognized that the properties of the foot, along with the prosthetic knee joint and the socket, are in part responsible for the stability and metabolic energy cost during walking. The stiffness and the hysteresis, which are the topics of this paper, are not properly prescribed, but could be adapted to improve the prosthetic walking performance. The shape is strongly related to the cosmetic appearance and so can not be altered to effect these improvements. Because detailed comparable data on foot stiffness and hysteresis, which are necessary to quantify the differences between different types of feet, are absent in literature, these properties were measured by the authors in a laboratory setup for nine different prosthetic feet, bare and with two different shoes. One test cycle consisted of measurements of load deformation curves in 66 positions, representing the range from heel strike to toe-off. The hysteresis is defined by the energy loss as a part of the total deformation energy. Without shoes significant differences in hysteresis between the feet exist, while with sport shoes the differences in hysteresis between the feet vanish for the most part. Applying a leather shoe leads to an increase of hysteresis loss for all tested feet. The stiffness turned out to be non-constant, so mean stiffness is used.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:2095529

van Jaarsveld, H W; Grootenboer, H J; de Vries, J; Koopman, H F

1990-12-01

212

A Best-Fit Model of Power Losses in Cold Rolled Motor Lamination Steel Operating in a Wide Range of Frequency and Magnetization  

Microsoft Academic Search

The new model has hysteresis loss coefficients variable with frequency and a combined coefficient for eddy-current and excess losses that is variable with induction. The described mathematical algorithm employed for identifying the coefficients is based on a minimum of 15 measured curves, covering frequencies between 20 Hz and 2 kHz and inductions from 0.05T up to 2T. Over the entire

Mircea Popescu; Dan M. Ionel

2006-01-01

213

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

Microsoft Academic Search

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.

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

1992-01-01

214

The Effect of Magnetic Spots on Stellar Winds and Angular Momentum Loss  

NASA Astrophysics Data System (ADS)

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 Alfvén 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.; Gombosi, T. I.

2009-07-01

215

Magnetism and ferromagnetic loss in Ni-W textured substrates for coated conductors  

NASA Astrophysics Data System (ADS)

We studied magnetic properties of biaxially textured Ni_1-xWx materials with x = 0, 3, 5, 6, and 9 at% W. They are important as substrates for ``RABiTS'' coated conductors containing high temperature superconductors. The quasi-static dc and ac hysteretic loss W was determined to estimate the ferromagnetic (FM) contribution to the overall ac loss in applications. Alloys were prepared by vacuum casting or powder metallurgy, and the hysteretic loss tended to be lower in materials that were recrystallized at higher temperatures. Progressive deformation (0.4 % bending strain) to simulate winding operations increased the FM loss, as did sample cutting operations making localized damage. In ac studies, the effects of ac frequency and DC bias field on the FM loss were determined. For fully coated tapes (with no effective ``grooving''), estimates of ac loss show that the FM part can be modest compared with the superconductive loss, for peak ac currents I0 ˜(0.6-0.8)I_c, where Ic = critical current. Work at UTK was supported by AFOSR Grant F49620-02-1-0182. ORNL is managed by UT-Battelle, LLC for the USDOE.

Ijaduola+, A. O.; Thompson; Goyal, A.; Thieme, C. L. H.; Marken, K.

2004-03-01

216

Hysteresis and terrestrial hydrology  

NASA Astrophysics Data System (ADS)

An examination of the physics of the land phase of the hydrological cycle shows that the most important non-linearities occur in the unsaturated zone of the soil. These have been studied by Dooge, his co-workers, and others, using switched boundary conditions applied to the one-dimensional form of Richards equation, modelling a one-square meter column of bare soil. Soil water responds to alternating wet and dry periods. Each period starts with a surface flux in or out of the soil that is set by atmospheric conditions. The moisture profile at the end of one period provides the initial condition for the next period. Within each period, a switch from atmosphere control to soil control may occur if the atmospheric conditions are strong enough and if they last for sufficient time. We refer to these times as the "time to ponding" in the case of infiltration of rain, and the "time to stage-two drying" in the case of evaporation. Consequently, there are two sets of switches in the computational clock: an outer pair always switching between wet and dry periods, and an inner pair switching intermittently from atmosphere control to soil control. Their effect has been studied on simplified forms of Richards equation. However the strongly non-linear, hysteretic property of the soil moisture characteristic is always ignored. It is more pronounced for sands than for clays. The presence of macropores changes, but does not eliminate, the hysteresis. The GRIZZLY database brings together a wide range of data sets on soil hysteresis. For many years the description of hysteresis in soils was largely based on Poulovassilis' application of the independent domain theory. Significant progress has since been made on the mathematical properties of hysteresis and its incorporation into models of unsaturated flow in porous media. The purpose of this presentation is to summarise these advances and to examine their implications for hydrology from the pedon (1 meter) scale to the catchment scale starting with the simplest models.

O Kane, J. P.; Pokrovski, A.; Kreichi, P.; Haverkamp, R.

2003-04-01

217

Studies of suprathermal electron loss in the magnetic ripple of Tore Supra  

NASA Astrophysics Data System (ADS)

A new prototype for protection of the vertical port against fast electrons escaping from the plasma due to trapping in magnetic field ripple was installed on Tore Supra in 1998. It is actively cooled and designed to withstand a steady state high heat flux, up to 20 MW/m2, due to fast electrons accelerated by the LH wave and lost in the magnetic field ripple. Results demonstrating the effectiveness of this prototype protection are presented. Important information concerning modelling of fast electron losses, which will play a crucial role in the final design, are also discussed.

Basiuk, V.; Peysson, Y.; Lipa, M.; Martin, G.; Chantant, M.; Guilhem, D.; Imbeaux, F.; Mitteau, R.; Surle, F.

2001-05-01

218

On-line system to measure magnetic characteristics of steel samples  

Microsoft Academic Search

Using on-line system, one investigates the effect of low-temperaturre (up to 4.2 K) cooling on magnetic properties of electrotechnical steel samples. Dependence of hysteresis losses in proper cycles of reverse magnetization with values of magnetic induction in a sample, which reach saturation induction, is studied. Application of the system allows one to carry out routine monitoring of magnetic characteristics of

G. M. Antonichev; O. V. Afanasev; Yu. B. Dubasov

1988-01-01

219

Low hysteresis FeMn-based top spin valve.  

PubMed

FeMn-based top spin valves Ta/[FeNi/CoFe]/Cu/CoFe/FeMn/Ta with different Cu and FeMn layers thicknesses were prepared by DC magnetron sputtering at room temperature. It was shown that low field hysteresis due to free layer magnetization reversal can be reduced down to (0.1 divided by 0.2) Oe keeping the GMR ratio higher 8% by using both layers thicknesses optimization and non-collinear geometry of magnetoresistance measurements. Dependence of low field hysteresis and GMR ratio on the angle between applied magnetic field and pinning direction are presented. PMID:23035516

Ustinov, V V; Krinitsina, T P; Milyaev, M A; Naumova, L I; Proglyado, V V

2012-09-01

220

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

221

AC Loss Characteristics of Stacked Conductors Composed of HTS Coated Conductors With Magnetic Substrates  

Microsoft Academic Search

HTS coated conductors (CC's) with substrates of magnetic materials such as Ni-alloys are expected to be promising for practical applications because Ni-alloys are well-texturized by simple processes and production costs of the conductors are significantly reduced. In the former works, it was shown by experiments that HoBaCuO-123 CC's with Ni-alloy substrates exhibit higher AC transport current losses than CC's with

O. Tsukamoto; A. K. M. Alamgir; M. Liu; D. Miyagi; K. Ohmatsu

2007-01-01

222

APPARATUS FOR MINIMIZING ENERGY LOSSES FROM MAGNETICALLY CONFINED VOLUMES OF HOT PLASMA  

DOEpatents

An apparatus is described for controlling electron temperature in plasma confined in a Pyrotron magnetic containment field. Basically the device comprises means for directing low temperature electrons to the plasma in controlled quantities to maintain a predetermined optimum equilibrium electron temperature whereat minimum losses of plasma ions due to ambipolar effects and energy damping of the ions due to dynamical friction with the electrons occur. (AEC)

Post, R.F.

1961-10-01

223

Spin wave spectroscopy and microwave losses in granular two-phase magnetic nanocomposites  

Microsoft Academic Search

We investigate the composition dependence of microwave properties of a series of cold-pressed powder compacts prepared from nanoparticles of ZnO, Ni, Co, and gamma-Fe2O3 using the microstrip line method and spin wave spectroscopy (SWS). The microwave spectra of these magnetic nanocomposites (NCs) are found to possess a double-peak behavior in the losses over the 2-16 GHz frequency range. The observed

Leonid Lutsev; Sergey Yakovlev; Christian Brosseau

2007-01-01

224

Magnetism and ferromagnetic loss in Ni–W textured substrates for coated conductors  

Microsoft Academic Search

A study has been conducted on the magnetic properties of a series of biaxially textured Ni1?xWx materials with compositions x=0,3,5,6, and 9 at.% W. These materials are important as substrates for “RABiTS”-type coated conductors that incorporate high temperature superconductors for current transport. The quasi-static dc and ac hysteretic loss W was determined to support estimates of the ferromagnetic contribution to

A. O. Ijaduola; J. R. Thompson; A. Goyal; C. L. H. Thieme; K. Marken

2004-01-01

225

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 kgˇm-2 respectively. Magnetic iron oxide as a sediment tracer allowed the estimation of soil losses with a RSME of 0.72 kgˇm-2. Although soil erosion rates from tree rows were lower (0.6 kgˇm-2ˇmonth-1) compared to inter-tree row rates (1.1 kgˇm-2ˇmonth-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

226

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

227

Kinematic theory of piezoelectric hysteresis  

Microsoft Academic Search

A biasing voltage applied across a bonded piezoelectric plate causes a transverse deflection. For slowly varying voltages, the displacement shows a characteristic hysteresis. A kinematic model is proposed which relates nonlinearly the displacement and its rate to the applied voltage. The analysis is developed to account quantitatively for the measured quasistatic hysteresis and decay, and to predict resonant dynamical effects.

P. G. Harper

1981-01-01

228

Depinning of flux lines and AC losses in magnet-superconductor levitation system  

SciTech Connect

The AC loss characteristics of a magnet-superconductor system were studied with the magnet fixed to the free end of an oscillating cantilever located near a stationary melt-textured YBCO pellet. Below a threshold AC field amplitude {approx}2Oe, the dissipation of the oscillator is amplitude-independent, characteristic of a linear, non-hysteretic regime. Above threshold,dissipation increases with amplitude, reflecting the depinning and hysteretic motion of flux lines. The threshold AC field is an order of magnitude higher than that measured for the same YBCO material via AC susceptometry in a uniform DC magnetic field, A partial lock-in of flux lines between YBCO ab planes is proposed as the mechanism for the substantial increase of the depinning threshold.

Terentiev, A. N.; Hull, J. R.; De Long, L. E.

1999-11-29

229

On the energy losses of hot worked Nd-Fe-B magnets and ferrites in a small alternating magnetic field perpendicular to a bias field  

SciTech Connect

Torsion pendulum magnetometer measurements on ferrites and on neodymium-iron-boron permanent magnets are presented. The damping of the oscillation of the pendulum leads to information on the magnetic energy losses of the magnets in a small alternating magnetic field applied perpendicular to a bias field. The origin of the energy absorption is explained by the magnetization reversal of single-domain particles. It is shown experimentally that the energy absorption mechanism requires the ferromagnetic order of the sample, and that the magnetic field strength of maximal energy absorption coincides with the effective anisotropy field strength.

Staa, F. von; Hempel, K.A.; Artz, H. [Aachen Univ. of Technology (Germany). Institut fuer Werkstoffe der Elektrotechnik

1995-11-01

230

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

231

Enhancement of AC-losses of magnetic nanoparticles for heating applications  

NASA Astrophysics Data System (ADS)

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 characterisation by means of TEM and XRD as well as reconstruction of core size distributions from magnetisation curves reveals that the narrow size distributions of the fractions cover a range of mean core sizes from about 8 up to 20nm. Spectra of the complex susceptibility were measured for a frequency range of 20Hz to 1 MHz. From the imaginary part of the susceptibility the specific loss power is calculated in dependence on frequency. The results are compared with calorimetrical measurements performed in dependence on field amplitude up to 11kA/m at 410kHz. A very high specific loss power in the order of 400W per gram maghemite was found at 410kHz and 11kA/m for the fluid fraction having the largest mean core diameter. A deviation from linear response behaviour is found for this sample showing a power law field dependence of the specific loss power SLP~H2.5. In addition to liquid suspensions measurements were performed with particles immobilised in mannitol or gel in order to elucidate the role of Brownian relaxation. The experimentally found dependence of SLP on the mean particle core diameter may be understood in the frame of the Debye dispersion model. Results are discussed with respect to applications of ferrofluids in RF-magnetic hyperthermia.

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

2004-09-01

232

Enhanced Magnetic and Ferroelectric Properties and Current-Voltage Hysteresis by Addition of La and Ti to BiFeO3 on 0.7%Nb-SrTiO3  

NASA Astrophysics Data System (ADS)

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 and Bi0.8La0.2FeO3/0.7%Nb-SrTiO3 interfaces. Also, it is observed that Bi0.8La0.2Fe0.92Ti0.08O3/0.7%Nb-SrTiO3 has a wider current-voltage hysteresis and a larger resistance difference than Bi0.8La0.2FeO3/0.7%Nb-SrTiO3. In the interface of Bi0.8La0.2Fe0.92Ti0.08O3/0.7%Nb-SrTiO3, the ratio of high to low resistance is 103 and 105 times, at 300 K and 10 K, respectively. The voltage pulses can switch the resistance to vary in the 2 states. The transport mechanisms show that a trap-controlled space-charge-limited current induces current-voltage hysteresis and resistance switching. The current of Bi0.8La0.2Fe0.92Ti0.08O3/0.7%Nb-SrTiO3 decays with the Curie—Von Schweidler law.

Chang, Hong; Zhao, Yong-Gang

2011-06-01

233

Analysis of magnetic field distribution and AC losses of a 600 kJ SMES  

NASA Astrophysics Data System (ADS)

Development of a 600 kJ superconducting magnetic energy storage (SMES) system is being in progress by Korea Electrotechnology Research Institute (KERI). 3-ply BSCCO-2223 wire was considered as a conductor for the winding of the SMES system and auto-tuning niching genetic algorithm was adopted for an optimization method of the HTS magnets in the 600 kJ SMES system. Several constraint conditions were considered for optimal design of HTS magnet of SMES system such as operating current, length of HTS wire in piece, gap between double pancake coils, stored magnetic energy, etc. As a result, output parameters for 6 case designs of 600 kJ SEMS were obtained as optimal design results according to the operating currents. In this research, one of the 6 cases was chosen to analyze magnetic field distribution of the 600 kJ SMES system. AC loss for each double pancake module of SMES during discharge period was also calculated. These HTS windings will be applied to the SMES system whose purpose is stabilization of the power grid.

Park, Myung-Jin; Kwak, Sang-Yeop; Kim, Woo-Seok; Lee, Seung-Wook; Lee, Ji-Kwang; Choi, Kyeong-Dal; Jung, Hyun-Kyo; Seong, Ki-Chul; Hahn, Song-Yop

2007-07-01

234

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

235

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

236

Loss of counterstreaming suprathermal electrons on closed heliospheric magnetic flux by pitch-angle scattering  

NASA Astrophysics Data System (ADS)

Suprathermal electrons can be used as tracers of magnetic field topology in the heliosphere, with counterstreaming electrons (CSEs) interpreted as a signature of closed magnetic loops (i.e., heliospheric magnetic field lines with both ends rooted at the photosphere). As the apex of a closed loop moves anti-sunward, however, pitch-angle scattering of suprathermal electrons on the increasing field-line length most likely results in eventual loss of the sunward beam and, hence, loss of the CSE signature. To test for the feasibility of this proposed phenomenon, we use a simple numerical model of electron evolution in which electrons undergo adiabatic focusing and pitch-angle scattering. The degree of scattering is a free parameter which is fixed by matching observed properties of suprathermal electron evolution in fast wind associated with open field from coronal holes. We then apply this model to closed loops to determine the how far out into the heliosphere a loop can travel before the CSE signature is lost and discuss the implications for coronal mass ejections.

Owens, M. J.; Crooker, N. U.

2008-05-01

237

Stability and Rate of Superconducting Magnet Winding Transition into Normal State as a Result of Energy Losses During Energy Removal.  

National Technical Information Service (NTIS)

Calculations of the effect of energy losses on stability and rate of superconducting magnet winding transition into normal state under adiabatic conditions during energy removal are conducted. The effects of properties and parameters of conductors on stab...

D. Kabat V. G. Luppov

1982-01-01

238

Hysteresis in dielectric electroactive polymers  

NASA Astrophysics Data System (ADS)

In this paper experimental results indicating the presents of hysteresis in the acrylic tape VHB 4910 produced by 3M are presented. It is shown that there are large stress relaxation times associated with this material making it difficult to separate viscoelastic effects and hysteresis. Additionally, a set of Preisach hysteresis models is presented and it is shown that these models fit the experimental results well. The simplest model having only 5 fitting parameters is suggested as the best model as the parameters can be uniquely determined, this not being the case for the other models.

Lassen, B.; Jaffari, M.; Melvad, C.; Kristjánsdóttir, G. R.; Jones, R.

2009-07-01

239

Low rare-earth Nd{endash}Fe{endash}B bonded magnets with improved irreversible flux loss  

SciTech Connect

The effects of Nb addition on magnetic properties and irreversible flux loss were studied on bonded magnets with compositions of Nd{sub 8}Fe{sub 86{minus}x}B{sub 6}Nb{sub x}, where x=0{endash}3. An irreversible flux loss was measured at P{sub c}=2 after exposure at 393 K for 3.6 ks in air. It was found that the Nb addition of 2 at.{percent} or more decreased the irreversible flux loss. The value was less than 5{percent}, similar to that obtained with MQP-B magnets. B{sub r} decreased with the increase in Nb content. The effect of Nd content on the magnetic properties and irreversible flux loss was also studied on the bonded magnets with compositions of Nd{sub x}Fe{sub 92{minus}x}B{sub 6}Nb{sub 2}, where x=6{endash}8. The bonded magnet with the optimum composition of Nd{sub 6.5}Fe{sub 85.5}B{sub 6}Nb{sub 2} had B{sub r} similar to that of MQP-Q magnets that did not contain Nb, and the value of irreversible flux loss was comparable to that of MQP-B magnets. A multipole magnetizability test on the bonded magnets with the above optimum composition was carried out, and the total flux of the bonded magnets was about 10{percent} higher than that of MQP-B magnets for the 23 mm outside diameter magnet with 48 poles. {copyright} {ital 1997 American Institute of Physics.}

Nishio, T.; Koyama, S.; Kasai, Y. [R D Laboratory, Daido Steel Co., Ltd., Nagoya 457 (Japan); Panchanathan, V. [Magnequench International Inc., Anderson, Indiana 46013 (United States)

1997-04-01

240

Magnetic hysteresis of dynamic response of one-dimensional magnonic crystals consisting of homogenous and alternating width nanowires observed with broadband ferromagnetic resonance  

NASA Astrophysics Data System (ADS)

We systematically probed the dynamic behavior of homogenous and alternating width (AW) Ni80Fe20 nanowire (NW) arrays using broadband ferromagnetic resonance (FMR) spectroscopy as a function of geometrical parameters such as wire width and interwire spacing. For homogenous width NWs, the FMR responses are markedly sensitive to wire widths and interwire spacing due to spatially varying demagnetizing field. The collective spin-wave mode profile for ferromagneticly and antiferromagneticly ordered ground state has been investigated by controlling the relative alignment of magnetization of neighboring NWs. We show that magnetic ground states of coupled AW NW arrays can be controlled by applying different magnetic field histories, and the collective spin-wave mode is very sensitive to the difference in the widths of wires constituting AW wire arrays. We have also mapped the ferromagnetic and antiferromagnetic ground states magnetic configurations using magnetic force microscopy. Our experimental results are in good agreements with a simple analytical theory we suggest for phenomenological description of the collective oscillations.

Ding, J.; Kostylev, M.; Adeyeye, A. O.

2011-08-01

241

Efficiency Optimization of a 100-W 500 000-r\\/min Permanent-Magnet Machine Including Air-Friction Losses  

Microsoft Academic Search

This paper proposes a method for the efficiency optimization of ultrahigh-speed permanent-magnet machines. Analytical methods are applied for the modeling of the machine that is equipped with a diametrically magnetized rotor and a slotless stator. The outer dimensions of the machine are design constraints, and the internal dimensioning is optimized for minimum losses. The air-friction losses are taken into account

Jorma Luomi; Christof Zwyssig; Andreas Looser; Johann W. Kolar

2009-01-01

242

Efficiency Optimization of a 100-W, 500 000-rpm Permanent-Magnet Machine Including Air Friction Losses  

Microsoft Academic Search

This paper proposes a method for the efficiency optimization of ultra-high-speed permanent-magnet machines. Analytical methods are applied for the modeling of the machine that is equipped with a diametrically magnetized rotor and a slotless stator. The outer dimensions of the machine are design constraints, and the internal dimensioning is optimized for minimum losses. The air friction losses are taken into

J. Luomi; C. Zwyssig; A. Looser; J. W. Kolar

2007-01-01

243

Prediction and Measurement of Iron Loss in a Short-Stroke, Single-Phase, Tubular Permanent Magnet Machine  

Microsoft Academic Search

This paper describes analytical prediction and measurement techniques for quantifying iron loss in a short-stroke, single-phase, tubular permanent-magnet machine which is developed for direct-drive linear compressors in domestic refrigeration applications. The technique is based on the analytically derived magnetic field distributions in three discrete regions of the stator core and a well established iron loss model, and is validated by

Jiabin Wang; Taib Ibrahim; David Howe

2010-01-01

244

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

245

A Design Approach to Reduce Rotor Losses in High-Speed Permanent Magnet Machine for Turbo-Compressor  

Microsoft Academic Search

In this paper, a design approach to reduce rotor losses in high-speed permanent magnet machines for turbo-compressor is discussed. In particular, the influence of materials chosen for the retaining sleeve is highlighted. The two topologies of high-speed permanent magnet machines with Inconel718 and Carbon-Fiber\\/Epoxy sleeves are employed for comparison of computed rotor losses by two-dimensional finite-element method and analytical field

Han-Wook Cho; Seok-Myeong Jang; Sang-Kyu Choi

2006-01-01

246

A neural networks model for hysteresis nonlinearity  

Microsoft Academic Search

This paper presents a new approach for modeling hysteresis nonlinearity in piezo-actuators. Under a mild assumption, a mapping, which can be approximated by multi-layer neural networks (MNN), is defined to describe Preisach model. Then, the neural networks (NN) hysteresis model is extended to describe hysteresis function, which relaxes the requirements on hysteresis to be described by Preisach model. An advantage

Li Chuntao; Tan Yonghong

2004-01-01

247

A polycrystal hysteresis model for ferroelectric ceramics  

Microsoft Academic Search

Most key elements of ferroelectric properties are defined through the hysteresis loops. For a ferroelectric ceramic, its loop is contributed collectively by its constituent grains, each having its own hysteresis loop when the ceramic polycrystal is under a cyclic electric field. In this paper, we propose a polycrystal hysteresis model so that the hysteresis loop of a ceramic can be

Y. Su; G. J. Weng

2006-01-01

248

Static and Dynamic Hysteresis Models for Studying Transformer Transients  

Microsoft Academic Search

Shortcomings of the classical approach in describing magnetization processes in grain-oriented transformer steel is analyzed. A noniterative method of accounting for hysteresis and dynamic properties of transformer core is proposed. Fitting the model to catalog data is described. The method is illustrated by calculating inrush current produced by subsequent transformer energizations.

Sergey E. Zirka; Yuriy I. Moroz; Anthony J. Moses; Cesare Mario Arturi

2011-01-01

249

Why do hysteresis loops stabilise in a few runs?  

NASA Astrophysics Data System (ADS)

Hysteresis loops of ferromagnets are usually stabilised after four or five field cycles. A tentative explanation is given in the spirit of learning models of spin glasses. It is suggested that loops approach their limit like 2-n, due to the binary nature of magnetic elements (Preisach grains).

Porteseil, J. L.

1987-04-01

250

Hysteresis effect in reactive sputtering: a problem of system stability  

Microsoft Academic Search

The hysteresis effect occurring in reactive sputtering is shown by pumping speed analysis to arise from loss in gettering throughput, consequent on reduction in target yield, without consequent rise in pumping throughput. Change in this balance due to higher pumping speed can result in stable conditions.

S. Kadlec; J. Musil; H. Vyskocil

1986-01-01

251

Low-loss optical magnetic metamaterials on Ag-Au bimetallic fishnets  

NASA Astrophysics Data System (ADS)

We have designed a low-loss magnetic metamaterial with double-fishnet structures of silver and gold operating at near-infrared wavelength. A Particle swarm optimization algorithm was employed to optimize the geometry dimensions of Ag-dielectric-Au unit cell. The Ag-Au bimetallic fishnet produces a maximum figure of merit value of 21, transmission as high as 62%, moderate negative permeability Re(?) of -0.5, and Re(n) of -1 at 1463 nm. The negative permeability Re(?) reaches minimum value of -5 at 1573 nm, where the antisymmetric charge distribution in fishnet metamaterials was observed. The antisymmetric plasmonic resonance at 1573 nm is a mixed mode of asymmetric magnetic dipole and symmetric electrical quadrupole in Ag-MgF2-Au fishnet structures.

Chen, Fuyi; Yuan, Li; Johnston, Roy L.

2012-08-01

252

Energy deposition in TEVATRON magnets from beam losses in interaction regions  

SciTech Connect

In addition to interacting in the detector, particles produced at an interaction region also deposit energy, with less desirable consequences, in magnets and other components of the accelerator. This note briefly assesses the damage potential of these (essentially unavoidable) beam losses from the viewpoint of quenching of superconducting magnets in an upgraded Tevatron, specifically for the 1 TeV p-/ovr string/p option with a luminosity of 10/sup 31/ cm/sup - 2/ sec/sup -1/, through the results carry more generality. Related issues such as radiation damage to detector electronics or other components are not addressed here. These are thought to be less problematic at the Tevatron, as in thus far supported by operational experience. 8 refs., 10 figs.

Ginneken, A.V.

1988-10-01

253

Mach, methodology, hysteresis and economics  

NASA Astrophysics Data System (ADS)

This methodological note examines the epistemological foundations of hysteresis with particular reference to applications to economic systems. The economy principles of Ernst Mach are advocated and used in this assessment.

Cross, R.

2008-11-01

254

Brain pathology in first-episode psychosis: Magnetization transfer imaging provides additional information to MRI measurements of volume loss  

Microsoft Academic Search

BackgroundLoss of brain volume in first-episode psychosis can be detected using conventional magnetic resonance imaging (MRI), but subtle changes – not leading to reduction in volume – that may contribute to clinical and cognitive abnormalities, may go undetected. Magnetization transfer imaging (MTI), a technique more sensitive to subtle neuropathological changes than conventional MRI, could yield important information on the extent

Gary Price; Mara Cercignani; Elvina M. Chu; Thomas R. E. Barnes; Gareth J. Barker; Eileen M. Joyce; Maria A. Ron

2010-01-01

255

Age-related metabolite changes and volume loss in the hippocampus by magnetic resonance spectroscopy and imaging  

Microsoft Academic Search

Magnetic resonance imaging (MRI) studies have produced controversial results concerning the correlation of hippocampal volume loss with increasing age. The goals in this study were: 1) to test whether levels of N-acetyl aspartate (NAA, a neuron marker) change in the hippocampus during normal aging and 2) to determine the relationship between hippocampal NAA and volume changes. Proton magnetic resonance spectroscopic

Norbert Schuff; Diane L. Amenda; Robert Knowltonf; David Norman; George FeinbPcye; Michael W Weiner

1999-01-01

256

The corrosion and oxidation of Nd-Fe-B magnets  

SciTech Connect

The susceptibility of Nd-Fe-B magnet powders to oxidation and corrosion is well known and presents problems in processing and in service. Although the oxidation of Nd-Fe-B magnet powders can lead to severe irreversible losses, such losses can be stemmed by the application of antidegradation coatings. The effects of oxidation on Nd-Fe-B magnet powders and magnets at elevated temperatures have been examined with respect to time, particle size, and treatment, using isothermal thermogravimetric analysis and long-term oven aging. The magnetic properties of each sample were then evaluated by hysteresis testing. The effects of corrosive agents were also examined, and although the oxidation and corrosion of Nd-Fe-B magnet powders may yield similar weight gains and losses in magnetic properties, each process exhibits a different magnetic hysteresis signature.'' The correlations between the weight gain and magnetic measurements have proven quite reliable. The application of coatings to magnet powders can reduce the weight gain due to degradation by more than 98%, while the losses in magnetic properties are reduced from over 75% (for uncoated powders) to less than 10% (for coated powders).

Dickens, E.D. Jr.; Mazany, A.M. (B. F. Goodrich Research and Development Center, 9921 Brecksville Road, Brecksville, Ohio 44141 (USA))

1990-05-01

257

Hysteresis phenomena in hydraulic measurement  

NASA Astrophysics Data System (ADS)

Hysteresis phenomena demonstrate the lag between the generation and the removal of some physical phenomena. This paper studies the hysteresis phenomena of the head-drop in a scaled model pump turbine using experiment test and CFD methods. These lag is induced by complicated flow patterns, which influenced the reliability of rotating machine. Keeping the same measurement procedure is concluded for the hydraulic machine measurement.

Ran, H. J.; Luo, X. W.; Chen, Y. L.; Xu, H. Y.; Farhat, M.

2012-11-01

258

Aligned Crystallite Powder of NdFeAsO0.86F0.14: Magnetic Hysteresis and Penetration Depth  

SciTech Connect

We report the basal-plane superfluid density and critical current of magnetically aligned NdFeAsO0.86F0.14 powder. This sample has individual crystallite grains permanently oriented with their c axis along the external field. The small particles provide a sensitive indicator of dc flux penetration, and allow analysis of the temperature dependence that suggests two-gap characteristics. A quantitative determination of the absolute magnitude is hindered by the need for accurate knowledge of the particle size distribution. Magnetic irreversibilities at high field suggest strong flux pinning of basal-plane critical currents, with monotonic field dependence and no evidence of the fishtail effect.

Zuev, Yuri L [ORNL; Specht, Eliot D [ORNL; Cantoni, Claudia [ORNL; Christen, David K [ORNL; Thompson, J. R. [University of Tennessee, Knoxville (UTK); Jin, Rongying [ORNL; Sefat, A. S. [Oak Ridge National Laboratory (ORNL); Mandrus, David [ORNL; McGuire, Michael A [ORNL; Sales, Brian C [ORNL

2009-01-01

259

Newton-Raphson method and fixed-point technique in finite element computation of magnetic field problems in media with hysteresis  

Microsoft Academic Search

A comparison between the Newton-Raphson method and the fixed-point technique in hysteretic magnetic field problems is presented. Four different approaches are studied and contrast between them in terms of the convergence rate and computation time consumption is highlighted. The Newton-Raphson-based approaches are found better than the iteration schemes associated with the fixed-point technique for a model problem

Jlilius Saitz

1999-01-01

260

An inclusive model of ferromagnetic hysteresis  

NASA Astrophysics Data System (ADS)

A new inclusive macroscopic model of ferromagnetic hysteresis is proposed. The model is developed from a Stoner-Wohlfarth approach by adding mean field or nearest neighbour dipole-dipole interactions. Pinning of domain rotation is also postulated, and a rotational pinning extension included. The model includes the principal features of the Jiles-Atherton model in the previous Atherton-Beattie extension of the Stoner-Wohlfarth model, but still omits the domain wall energy effects included in the Globus model. The new model describes both reversible and irreversible processes, and hysteresis caused by combinations of interaction, anisotropy, and pinning. Computational approaches to both two and three dimensional calculations are detailed, and examples given. Simulations of hard magnetic materials are done, including major loops to near saturation, minor loops, and demagnetizations. The complete 2 x 2 magnetization tensor response is shown, including fan diagram representations. The minor loop simulations involve complicated sets of field turning points typical of the Preisach model, and the minor loops are seen to exhibit incongruence and eventual closure. The demagnetization simulations are done for both rotating and oscillating applied field cycles. Both isotropic and anisotropic polycrystalline easy axis distributions are treated.

Phelps, Brian Fletcher

261

Finite Element Three-Phase Transformer Modeling Taking Into Account a Vector Hysteresis Model  

Microsoft Academic Search

In this work an approach for modeling a transformer core taking into account magnetic hysteresis is presented. For this purpose, the inverse vector Jiles-Atherton hysteresis model is incorporated in a 2D finite element code. This model allows writing naturally the differential reluctivity tensor which can be directly used in the magnetic field equations. A three-phase transformer is modeled. The excitation

Jean V. Leite; Abdelkader Benabou; Nelson Sadowski; Mauricio V. Ferreira da Luz

2009-01-01

262

Investigation of magnetic properties of 2223-BSCCO steel-reinforced tapes  

Microsoft Academic Search

Reinforcing multifilamentary Bi2Sr2Ca2Cu3Oy (2223-BSCCO) requires careful evaluation of magnetic losses and, in general, of the quantities related to the hysteresis loop (e.g., coercive field and residual magnetization). In this paper, the results of magnetic quantity measurements performed on superconductive tapes reinforced by both AISI 304 and AISI 316 stainless steel layers are discussed. It is shown that the former kind

D. Fabiani; G. C. Montanari

2004-01-01

263

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

264

Effect of Cobalt Substitution on the Magnetic Properties of Ni-Cu Ferrite  

NASA Astrophysics Data System (ADS)

Single-phase polycrystalline Ni0.85-xCu0.15CoxFe2O4 (x = 0, 0.02, 0.04 and 0.06) were synthesized by a standard ceramic technology. The mean particle sizes, obtained by SEM, vary between 2 and 8 ?m. The main magnetic parameters such as saturation magnetization, remanence and coercivity were obtained from the entire hysteresis loops plotted in AC (2 kHz) magnetic field at room temperature. Hysteresis losses were evaluated from the same curves by using the Fourier decomposition. The initial permeabilities were obtained from the minor hysteresis loops, plotted in low enough magnetic fields. The remanence decreases almost linear with increasing Co-concentration. Both saturation magnetization and initial permeability have maxima at x = 0.02, but the coercivity and hysteresis losses have minima at the same Co-concentration. All the magnetic parameters, obtained at x = 0.02 are better than those of the starting composition with x = 0. The influence of the Co-substitution on the magnetic parameters is discussed.

Goev, G.; Masheva, V.; Ilkov, L.; Nihtianova, D.; Katerska, B.

2010-01-01

265

Domain-wall motion in random potential and hysteresis modeling  

SciTech Connect

Two different approaches to hysteresis modeling are compared using a common ground based on energy relations, defined in terms of dissipated and stored energy. Using the Preisach model and assuming that magnetization is mainly due to domain-wall motion, one can derive the expression of magnetization along a major loop typical of the Jiles{endash}Atherton model and then extend its validity to cases where mean-field effects and reversible contributions are present. {copyright} {ital 1998 American Institute of Physics.}

Pasquale, M.; Basso, V.; Bertotti, G. [IEN Galileo Ferraris and INFM C. so M. DAzeglio42, 10125Torino (Italy); Jiles, D.C.; Bi, Y. [Ames Laboratory, Iowa State University, 50011Ames, Iowa (United States)

1998-06-01

266

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

2013-06-03

267

Unconventional dynamic hysteresis in a periodic assembly of paramagnetic colloids  

NASA Astrophysics Data System (ADS)

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.

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

2013-06-01

268

Modeling of magnetic properties of polymer bonded Nd-Fe-B magnets with surface modifications  

NASA Astrophysics Data System (ADS)

The effects of surface modification on the magnetic properties of polymer-bonded Nd-Fe-B magnets have been studied. Two sets of Nd-Fe-B powders, coated and uncoated, were blended and compression molded with polyphenylene sulfide in isotropic form. Their magnetic properties were measured using a Helmholtz coil and a SQUID. The results showed that the effect of the coating significantly improved the irreversible loss in flux and energy product of the polymer-bonded magnets. The results have been interpreted using an isotropic model of hysteresis that takes into account energy losses. The modeling showed that the presence of soft magnetic materials in the Nd-Fe-B powders caused by oxidation reduces the interaction among magnetic particles, however, the coating treatment alters the magnetic properties by increasing the remanence of polymer-bonded magnets via increasing the interparticle coupling coefficient.

Xiao, J.; Otaigbe, J. U.; Jiles, D. C.

2000-07-01

269

Maghemite nanoparticles with very high AC-losses for application in RF-magnetic hyperthermia  

NASA Astrophysics Data System (ADS)

Maghemite nanoparticles covalently coated with polyethylene glycol are investigated with respect to different loss processes in magnetic AC-fields. Transmission electron microscopy reveals a narrow size distribution which may be well approximated by a normal distribution (mean diameter 15.3nm and distribution width 4.9nm). Aqueous ferrofluids were characterised by DC-magnetometry, by measuring susceptibility spectra for a frequency range 20Hz to 1MHz and by calorimetric measurements of specific loss power (SLP) at 330 and 410kHz for field amplitudes up to 11.7kA/m. Extremely high values of SLP in the order of 600W/g result for 400kHz and 11kA/m. In addition to liquid ferrofluids measurements were performed with suspensions in gel in order to elucidate the role of Brownian relaxation. The measured susceptibility spectra may be well reproduced by a model using a superposition of Néel and Brown loss processes under consideration of the observed narrow normal size distribution. In this way the observed very high specific heating power may be well understood. Results are discussed with respect to further optimisation of SLP for medical as well as technical RF-heating applications.

Hergt, R.; Hiergeist, R.; Hilger, I.; Kaiser, W. A.; Lapatnikov, Y.; Margel, S.; Richter, U.

2004-04-01

270

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

271

Calorimetric AC loss measurement of MgB2 superconducting tape in an alternating transport current and direct magnetic field  

NASA Astrophysics Data System (ADS)

Applications of MgB2 superconductors in electrical engineering have been widely reported, and various studies have been made to define their alternating current (AC) losses. However, studies on the transport losses with an applied transverse DC magnetic field have not been conducted, even though this is one of the favored conditions in applications of practical MgB2 tapes. Methods and techniques used to characterize and measure these losses have so far been grouped into ‘electrical’ and ‘calorimetric’ approaches with external conditions set to resemble the application conditions. In this paper, we present a new approach to mounting the sample and employ the calorimetric method to accurately determine the losses in the concurrent application of AC transport current and DC magnetic fields that are likely to be experienced in practical devices such as generators and motors. This technique provides great simplification compared to the pickup coil and lock-in amplifier methods and is applied to a long length (˜10 cm) superconducting tape. The AC loss data at 20 and 30 K will be presented in an applied transport current of 50 Hz under external DC magnetic fields. The results are found to be higher than the theoretical predictions because of the metallic fraction of the tape that contributes quite significantly to the total losses. The data, however, will allow minimization of losses in practical MgB2 coils and will be used in the verification of numerical coil models.

See, K. W.; Xu, X.; Horvat, J.; Cook, C. D.; Dou, S. X.

2012-11-01

272

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

273

The magnetic anisotropy and its distribution in CoCrPtTa\\/CrV thin film recording media  

Microsoft Academic Search

CoCrPtTa\\/CrV thin films for longitudinal media, with high coercivity and small thickness, are studied. Particularly, the magnetic anisotropy is analyzed with determination of the distribution of anisotropy fields and measurement of rotational hysteresis energy losses. The results are correlated to the basic processes of magnetization and to the thermal stability of the magnetization. The role of the grain segregation state

G. Bottoni; D. Candolfo; A. Cecchetti

2002-01-01

274

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

275

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

PubMed

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. PMID:22355578

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

2011-08-10

276

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

277

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

278

Maximum efficiency drives of synchronous reluctance motors by a novel loss minimization controller considering cross-magnetic saturation  

Microsoft Academic Search

This paper presents a method to maximize the driving efficiency of synchronous reluctance motors having cross-magnetic saturation effect. A novel method to calculate the optimum d- and q-axis currents that minimize the loss is proposed. In this method, an approximation equation for expressing inductance variation and a simple repetition method are employed to consider the cross-magnetic saturation. This method can

Shu Yamamoto; John B. Adawey; Takahiro Ara

2009-01-01

279

Monte Carlo simulation study of exchange biased hysteresis loops in nanoparticles  

NASA Astrophysics Data System (ADS)

We present the results of Monte Carlo simulations of the magnetic properties of a model for a single nanoparticle consisting in a ferromagnetic core surrounded by an antiferromagnetic shell. The simulations of hysteresis loops after cooling in a magnetic field display exchange bias effects. In order to understand the origin of the loop shifts, we have studied the thermal dependence of the shell and interface magnetizations under field cooling. These results, together with inspection of the snapshots of the configurations attained at low temperature, show the existence of a net magnetization at the interface which is responsible for the bias of the hysteresis loops.

Iglesias, Ňscar; Labarta, Amílcar

2006-02-01

280

An adaptive hysteresis-band current control technique of a voltage-fed PWM inverter for machine drive system  

Microsoft Academic Search

An adaptive hysteresis-band control method where the band is modulated with the system parameters to maintain the modulation frequency to be nearly constant is described. Although the technique is applicable to general AC motor drives and other types of load, an interior permanent magnet (IPM) synchronous machine load is considered. Systematic analytical expressions of the hysteresis band are derived as

B. K. Bose

1990-01-01

281

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

282

Recursive identification of hysteresis in smart materials  

Microsoft Academic Search

This paper studies recursive identification of hysteresis in smart materials. A Preisach operator with a piece-wise uniform density function is used to model the hysteresis. Persistent excitation conditions for parameter convergence are discussed in terms of the input to the Preisach operator. Two classes of recursive identification schemes are explored, one based on the hysteresis output, the other based on

Xiaobo Tan; John S. Baras

2004-01-01

283

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

284

Hysteresis in East Asian unemployment  

Microsoft Academic Search

High-performing Asian economies are quite distinctive with efficient, flexible and responsive labour markets. Comparing the persistence of unemployment in East Asian economies to that in Western countries is difficult due to the data's short time spans and possible structural breaks. This article employs advanced unit root tests to deal with these problems and fails to reject ‘hysteresis’ in the unemployment

Hsiu-Yun Lee; Jyh-Lin Wu; Chiung-Hsiang Lin

2010-01-01

285

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

286

Hyperthermic effects of dissipative structures of magnetic nanoparticles in large alternating magnetic fields  

NASA Astrophysics Data System (ADS)

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

2011-11-01

287

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

NASA Astrophysics Data System (ADS)

Beam-ion losses induced by fast-ion-driven toroidal Alfvén 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 ? = arccos(?///?) distribution of the lost fast ions. The loss fluxes were investigated for three typical magnetic configurations of Rax_vac = 3.60 m, 3.75 m, and 3.90 m, where Rax_vac is the magnetic axis position of the vacuum field. Dominant losses induced by TAEs in these three configurations were observed in the E/? regions of 50~190 keV/40°, 40~170 keV/25°, and 30~190 keV/30°, respectively. Lost-ion fluxes induced by TAEs depend clearly on the amplitude of TAE magnetic fluctuations, Rax_vac and the toroidal field strength Bt. The increment of the loss fluxes has the dependence of (bTAE/Bt)s. The power s increases from s = 1 to 3 with the increase of the magnetic axis position in finite beta plasmas.

Ogawa, K.; Isobe, M.; Toi, K.; Watanabe, F.; A. Spong, D.; Shimizu, A.; Osakabe, M.; S. Darrow, D.; Ohdachi, S.; Sakakibara, S.; LHD Experiment Group

2012-04-01

288

Computer Calculations of Eddy-Current Power Loss in Rotating Titanium Wheels and Rims in Localized Axial Magnetic Fields.  

National Technical Information Service (NTIS)

We have performed preliminary computer-based, transient, magnetostatic calculations of the eddy-current power loss in rotating titanium-alloy and aluminum wheels and wheel rims in the predominantly axially-directed, steady magnetic fields of two small, so...

D. J. Mayhall J. B. Gronberg W. Stein

2006-01-01

289

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

290

AC losses in Bi-2223 tapes and in the 1-kA transmission line model.  

SciTech Connect

We present here results of our study of the 5-m-long AC transmission tine model with 1 kA current capability at 77 K. Primary attention was paid to the current characteristics and AC losses in individual tapes and in the core of the cable. The losses were measured as a function of AC magnetic field amplitude in various orientations of magnetic field with respect to the plane of the tape and filaments. Hysteresis losses were. close to the losses in the AC regime, meaning that eddy current losses in tapes may be neglected when compared with hysteresis losses. We designed and constructed a 5-m-long model of the AC transmission line using multi filamentary Bi-2223 tapes. The current core of the model contains 120 tapes for the forward line and 120 tapes for the backward line. The AC losses in the current core were substantially greater than those seen in the individual tapes. The reason for this is related to a complex magnetic field distribution inside the current core.

Fisher, L. M.

1998-09-04

291

Hysteresis characteristics computation on PWM fed synchronous reluctance motor using coupled FEM and Preisach modeling  

Microsoft Academic Search

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. TMS320C31 DSP installed experimental devices are equipped for the propriety of the proposed method of analysis, and then, both computer

Jung Ho Lee; Dong Seok Hyun

2000-01-01

292

Magnetic losses and mechanical properties of Fe-4 to 7.8 wt% Si rapidly quenched alloys  

SciTech Connect

Magnetic and mechanical properties have been investigated in Fe-4 to 7.8 wt% Si rapidly quenched and annealed ribbons. The roles played by composition and microstructure on the magnetic energy losses and the tensile stress-strain behavior have been put in evidence, by carrying out the related experiments as a function of grain size. The energy losses attain a minimum value at the 6.7% Si composition at all frequencies in the investigated range d.c.-10 kHz. The vanishing of a demonstrably important magnetostriction-related coercivity contribution, which can be singled out in these stress-free samples, is recognized as the leading cause of loss minimization. The composition and grain size dependent stress-strain curves are found to obey a Hall-Petch law for the yield stress. While the elastic limit increases with the Si content, a decrease of the strain at fracture is correspondingly observed.

Fiorillo, F.; Ferrara, E.; Ferrando, L.; Appino, C. [Ist. Elettrotecnico Nazionale Galileo Ferraris, Torino (Italy); Lebourg, C.; Degauque, J. [CNRS INSA, Toulouse (France). Lab. de Physique des Solides; Baricco, M. [IFM dell`Univ., Torino (Italy). Dipt. di Chimica

1997-09-01

293

Vortex system dynamics and energy losses in a current-carrying 2D superconducting wafer  

SciTech Connect

The dynamic processes occurring in the vortex system of a 2D superconducting wafer carrying transport current are investigated using the model of the vortex system of high-temperature superconductors. Calculations are performed by the Monte Carlo method. For the first time, the dynamics of magnetic field penetration in a current-carrying HTSC wafer is demonstrated and the energy losses associated with a change in transport current are calculated. It is shown that changes in the transport current amplitude and in the number of defects lead to a change in the energy liberation mechanism: hysteresis energy losses are replaced by the losses in the saturated layer.

Odintsov, D. S., E-mail: dodintsov@hotmail.com; Rudnev, I. A.; Kashurnikov, V. A. [Moscow Institute of Engineering Physics (Russian Federation)

2006-07-15

294

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

295

Radiation effects in rare-earth permanent magnets. [Nd-Fe-B; Sm-Co  

Microsoft Academic Search

Nd-Fe-B and Sm-Co permanent magnets have been irradiated with fission neutrons and gamma rays. Irradiated samples were periodically removed for room temperature measurements of the open-circuit remanence. Hysteresis loops were measured before and after irradiation. For neutron irradiation, two magnets showed a rapid loss of remanence, while a third decayed more slowly. Irradiation in the Omega West Reactor at Los

R. D. Brown; A. L. Giorgi; J. T. Stanley

1987-01-01

296

Hysteresis in vibrated granular media  

NASA Astrophysics Data System (ADS)

Some general dynamical properties of models for compaction of granular media based on master equations are analyzed. In particular, a one-dimensional lattice model with short-ranged dynamical constraints is considered. The stationary state is consistent with Edward's theory of powders. The system is submitted to processes in which the tapping strength is monotonically increased and decreased. In such processes the behavior of the model resembles the reversible-irreversible branches which have been recently obaserved in experiments. This behavior is understood in terms of the general dynamical properties of the model, and related to the hysteresis cycles exhibited by structural glasses in thermal cycles. The existence of a "normal" solution, i.e., a solution of the master equation which is monotonically approached by all the other solutions, plays a fundamental role in the understanding of the hysteresis effects.

Prados, A.; Brey, J. J.; Sanchez-Rey, B.

2000-09-01

297

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

298

Monte Carlo simulation study of exchange biased hysteresis loops in nanoparticles  

Microsoft Academic Search

We present the results of Monte Carlo simulations of the magnetic properties of a model for a single nanoparticle consisting in a ferromagnetic core surrounded by an antiferromagnetic shell. The simulations of hysteresis loops after cooling in a magnetic field display exchange bias effects. In order to understand the origin of the loop shifts, we have studied the thermal dependence

Ňscar Iglesias; Amílcar Labarta

2006-01-01

299

Tailoring anisotropic magnetoresistance and giant magnetoresistance hysteresis loops with spin-polarized current injection  

NASA Astrophysics Data System (ADS)

Current pulses were injected into magnetic nanowires. Their effect on the magnetoresistance hysteresis loops was studied for three morphologies: homogeneous Ni wires, copper wires containing five cobalt/copper bilayers, and hybrid structures composed of a homogeneous Ni half wire and a multilayered Co/Cu half wire. The characteristic features of the action of the current on the magnetization are shown and discussed.

Wegrowe, J.-E.; Kelly, D.; Hoffer, X.; Guittienne, Ph.; Ansermet, J.-Ph.

2001-06-01

300

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

2009-05-29

301

Superconducting-magnetic heterostructures: a method of decreasing AC losses and improving critical current density in multifilamentary conductors  

NASA Astrophysics Data System (ADS)

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 YBa2Cu3O7 and (Pb,Bi)2Sr2Ca2Cu3O9 conductors, and buffer layers have to be used. In contrast, in MgB2 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.

Glowacki, B. A.; Majoros, M.

2009-06-01

302

Objective perimetry using functional magnetic resonance imaging in patients with visual field loss.  

PubMed

In ophthalmic clinics, subjective perimetry is a standard examination method. However, for certain patients, objective perimetry is useful since it avoids the need for subjective judgments. The purpose of the present study is to demonstrate the feasibility of objective perimetry using functional magnetic resonance imaging (fMRI). fMRI was performed in 8 patients with visual field defects caused by cerebral lesions. The composite stimulus was either the combination of an expanding ring and a clockwise rotating wedge, or a contracting ring and a counter-clockwise rotating wedge. The largest radius was a 10 degrees visual angle with magnifying glasses. The cycle period for the ring and wedge components differed, enabling us to distinguish the two targets within a single time series. Data were analyzed using custom software that interprets the two stimuli and estimates visual field maps. Regions of interest (ROIs) were set covering the entirety of the occipital lobes, and the most effective visual field location for each voxel was calculated from these two response components. The visual field maps obtained with fMRI were compared with the 10-2 Humphrey visual field (HVF) program. While some divergences were observed, in most subjects the visual field defects on fMRI agreed with those on HVF. Cross-correlation coefficients between grayscale values of visual field maps obtained with fMRI and decibel values obtained with HVF were significant (P<0.05) in all subjects. fMRI in conjunction with our method is feasible for objectively and efficiently measuring the visual field of patients with visual field loss. PMID:19348794

Furuta, Ayumu; Nakadomari, Satoshi; Misaki, Masaya; Miyauchi, Satoru; Iida, Tomohiro

2009-04-05

303

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; Peńa, Octavio

2013-07-01

304

Loss analysis of permanent-magnet synchronous motor using three-dimensional finite-element method with homogenization method  

Microsoft Academic Search

This paper describes an iron-loss analysis of permanent-magnet synchronous motor (PMSM) taking into account lamination of iron core by a finite-element method (FEM) with a homogenization method. The detailed modeling of the laminated structure by the FEM with gap elements and double nodes requires a huge number of elements, which results in the limitation of the problem size. In order

Y. Takahashi; S. Wakao; M. Kondo; N. Terauchi

2008-01-01

305

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

306

Semi-analytical study of AC losses in an infinitely long superconducting cylinder surrounded by a metallic sheath: magnetic field dependent critical current density and generation of harmonics  

NASA Astrophysics Data System (ADS)

We study the AC losses in an infinitely long cylinder made of a superconducting core surrounded by a non-magnetic metallic sheath and subjected to an axial magnetic field. The losses are computed by assuming the Bean-Kim model for the superconductor and Ohmic dissipation for the metal. The time varying magnetic flux crossing the superconductor induces eddy currents in the metal sheath and, due to the nonlinear response of the superconducting material, generates harmonics in the metal current density. In turn, these currents generate distorted magnetic fields acting back on the superconductor. This coupling mechanism is sensitive to the magnetic constitutive law of the superconductor and affects both the waveform of the fields and the total losses. In this paper, we study the importance of the harmonics in the metal on the total losses, as well as their sensitivity to a field dependent critical current density following Kim’s law.

Kirsch, S.; Fagnard, J.-F.; Vanderbemden, P.; Vanderheyden, B.

2013-11-01

307

Energy-loss magnetic circular dichroism measurements of ferromagnetic ordering in LaSrCoO3  

NASA Astrophysics Data System (ADS)

Experimental results show that tuning the ferromagnetism of LaSrCoO3 can be achieved at various temperatures by doping bulk sample with smaller atoms or straining thin film sample. In this work, we will use atomic-resolution Z-contrast imaging, annular bright field (ABF) imaging and electron energy-loss spectroscopy in the aberration-corrected JEOL JEM-ARM200CF in combination with in-situ heating and cooling experiments to examine the magnetic and spin-state transitions in La1-xSrxCoO3 (x=0-0.3) between 80 K and 600 K. Using energy-loss magnetic circular dichroism method, we confirm the magnetic ordering transition at room temperature with increasing doping concentrations. Differences in the O K- and Co-L-edges will be utilized to determine the Co valence of the samples. A magnetic transition is observed in 5% doped sample during in-situ cooling experiment to 95 K. Additionally, with increasing the doping concentration, a change in crystal structure is measured using ABF imaging, more specifically a distortion of the CoO6 octahedra.

Gulec, Ahmet; Klie, Robert F.; Mitchell, John F.

2013-03-01

308

Influence of geometry and wave shape on magnetic amorphous material  

NASA Astrophysics Data System (ADS)

The magnetic performance of 0.03 mm thick Co-based and 0.026 mm thick Fe-based amorphous ribbon in toroidal and strip form was measured under sine and pulse width modulation (PWM) waveform conditions. The measured loss, at 100 Hz fundamental frequency and a peak flux density of 91% of the saturation of each material, was separated into classical eddy current, hysteresis and anomalous loss components and the effect of geometry and waveform on these loss components was analysed. The results in general show a dimensional and waveform dependence which is not so great as in electrical steels.

Moses, A. J.; Leicht, J.; Fox, D.

2005-04-01

309

Hysteresis of thin film IPRTs in the range 100 °C to 600 °C  

NASA Astrophysics Data System (ADS)

As opposed to SPRTs, the IPRTs succumb to hysteresis when submitted to change of temperature. This uncertainty component, although acknowledged as omnipresent at many other types of sensors (pressure, electrical, magnetic, humidity, etc.) has often been disregarded in their calibration certificates' uncertainty budgets in the past, its determination being costly, time-consuming and not appreciated by customers and manufacturers. In general, hysteresis is a phenomenon that results in a difference in an item's behavior when approached from a different path. Thermal hysteresis results in a difference in resistance at a given temperature based on the thermal history to which the PRTs were exposed. The most prominent factor that contributes to the hysteresis error in an IPRT is a strain within the sensing element caused by the thermal expansion and contraction. The strains that cause hysteresis error are closely related to the strains that cause repeatability error. Therefore, it is typical that PRTs that exhibit small hysteresis also exhibit small repeatability error, and PRTs that exhibit large hysteresis have poor repeatability. Aim of this paper is to provide hysteresis characterization of a batch of IPRTs using the same type of thin-film sensor, encapsulated by same procedure and same company and to estimate to what extent the thermal hysteresis obtained by testing one single thermometer (or few thermometers) can serve as representative of other thermometers of the same type and manufacturer. This investigation should also indicate the range of hysteresis departure between IPRTs of the same type. Hysteresis was determined by cycling IPRTs temperature from 100 °C through intermediate points up to 600 °C and subsequently back to 100 °C. Within that range several typical sub-ranges are investigated: 100 °C to 400 °C, 100 °C to 500 °C, 100 °C to 600 °C, 300 °C to 500 °C and 300 °C to 600 °C . The hysteresis was determined at various temperatures by comparison calibration with SPRT. The results of investigation are presented in a graphical form for all IPRTs, ranges and calibration points.

Zvizdi?, D.; Šestan, D.

2013-09-01

310

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

311

Nonlinearity and hysteresis of resonant strain gauges  

Microsoft Academic Search

The nonlinearity and hysteresis effects of the electrostatically activated voltage-driven resonant microbridges have been studied theoretically and experimentally. It is shown that in order to avoid vibration instability and hysteresis to occur, the choices of the ac and dc driving voltages and of the quality factor of a resonator, with a given geometry and choice of materials, are limited by

Chengqun Gui; Rob Legtenberg; Harrie A. C. Tilmans; Jan H. J. Fluitman; Miko Elwenspoek

1998-01-01

312

Low-loss left-handed materials using metallic magnetic cylinders  

Microsoft Academic Search

We discuss materials based on arrays of metallic magnetic cylindrical structures near ferromagnetic resonance with applied magnetic fields at microwave frequencies. We have found that the materials have a negative refraction index by combining the effective negative permittivity and permeability. Numerical finite-difference time-domain simulations were performed, after a very large number of geometries were swept. The simulations reveal that ferromagnetic

N. García; E. V. Ponizovskaia

2005-01-01

313

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

314

Magnetic properties and magnetocaloric effect of the HoAgGa compound  

NASA Astrophysics Data System (ADS)

Magnetic properties and magnetocaloric effect (MCE) of the HoAgGa compound are investigated by magnetization and heat capacity measurements. A giant reversible MCE was observed around TC = 7.2 K. The maximum values of magnetic entropy change and adiabatic temperature are found to be 16 J kg-1 K-1 and 6 K, respectively, with a refrigerant capacity value of 262 J kg-1 for field change of 5 T. These magnetocaloric parameters also remain large for a wide range of temperature above TC. The large MCE as well as no hysteresis loss make HoAgGa an attractive candidate for low temperature magnetic refrigerant.

da Silva, L. M.; dos Santos, A. O.; Coelho, A. A.; Cardoso, L. P.

2013-10-01

315

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

316

Influence of plasma loss area on transport of charged particles through a transverse magnetic field  

SciTech Connect

Plasma transport in a double plasma device from the source region to the target region through a physical window comprising of electrically grounded magnet channels (filled with permanent magnet bars) for transverse magnetic field (TMF) and a pair of stainless steel (SS) plates is studied and presented in this manuscript. The study has relevance in negative ion source research and development where both TMF created by magnet channels and bias plate are used. The experiment is performed in two stages. In the first stage, a TMF is introduced between the two regions along with the SS plates, and corresponding plasma parameter data in the two regions are recorded by changing the distance between the TMF channels. In the second stage, the TMF is withdrawn from the system, and corresponding data are taken by changing the separation between the SS plates. The experimental results are then compared with a theoretical model. In the presence of TMF, where electrons are magnetized and ions are un-magnetized, it is observed that plasma transport perpendicular to the TMF is dominated by the ambipolar diffusion of ions. In the absence of TMF, plasma is un-magnetized, and plasma transport through the SS window aperture is almost independent of open area of the SS window.

Das, B. K.; Chakraborty, M. [Centre of Plasma Physics-Institute for Plasma Research, Tepesia, Kamrup, Assam (India); Bandyopadhyay, M. [ITER-India, Institute for Plasma Research, Gandhinagar, Gujarat (India)

2012-01-15

317

Loss rates of energetic particles in the inner magnetosphere in a realistic magnetic field using a new chorus wave model  

NASA Astrophysics Data System (ADS)

Energetic electrons in the inner magnetosphere show high variability during the geomagnetically disturbed conditions. Quasi-linear diffusion theory provides a framework for global prediction of the loss of particles at different energies and understanding of dynamics of particle populations. It was recently shown that the pitch angle scattering of electrons due to wave-particle interaction with chorus waves modeled in a realistic magnetic field may be significantly different from those estimated in a dipole model. In this work we present the loss rates of 1 keV - 2 MeV electrons in a realistic and a dipole field models and give a physical explanation of the differences between them. In this study we use Tsyganenko 89 magnetic field model and estimate scattering rates for different levels of geomagnetic activity. Electrons are assumed to be scattered by oblique lower band and upper band chorus waves. We develop a realistic chorus wave model in three MLT sectors (night, dawn, and day) using the recent results of wave amplitude, wave normal angle, and wave spectral density distributions as functions of magnetic latitude, distance, and geomagnetic activity. The obtained electron lifetimes are parameterized and can be used in 2D-3D-4D diffusion codes.

Orlova, Ksenia; Shprits, Yuri; Spasojevic, Maria

2013-04-01

318

Spin-down measurements and loss calculation of multi-layer, multi-pole HTS magnetic bearings  

NASA Astrophysics Data System (ADS)

Superconducting (SC) bearings are one of the most promising applications of superconductors, which could contribute significantly to a relevant progress to kinetic energy storage. A key feature of these bearings with a special view on their industrial applications is the coefficient of friction. Losses of different configurations are intensively investigated worldwide. Numerous structures and geometric arrangements have been developed in order to decrease the coefficient of friction and to increase the utilization of the superconductors (SCs) and permanent magnets (PMs) (Mulcahy et al 2001 IEEE Trans. Appl. Supercond. 1 1729-32 Sung et al 2002 Cryogenics 42 357-62 Filatov and Maslen 2001 IEEE Trans. Magn. 37 3913-23) In this paper we present mostly experimental analysis of multi-layer, multi-pole magnetic configurations. On the basis of the results of these measurements we tried to determine the best configuration regarding the losses, stability and load capability of the bearings. Spin-down measurements were performed in a vacuum chamber (10-4 mbar), in order to measure the coefficient of friction, and to verify the stability of the superconducting bearings over a high speed range. For the measurements a special small brushless permanent magnet DC motor with an ironless stator was developed and used. A maximum speed of 11 000 rpm was successfully reached.

Kohari, Z.; Vajda, I.

2005-02-01

319

Coercivity dynamics and origin of time-delayed magneto-optical hysteresis loops in pump-probe Kerr spectroscopy  

NASA Astrophysics Data System (ADS)

Time-resolved magneto-optical Kerr effect (TR-MOKE) is used to measure hysteresis loops of a magnetic film at a different delayed time after femtosecond laser excitations. Coercivity dynamics of the magnetic film is obtained from TR-MOKE loops as usual. However, we point out that the dynamics of coercivity does not reflect the evolution of initial coercivity shown by the initial hysteresis loop with no laser excitation, but that of the final coercivity under laser excitation, where the final coercivity means one given by the hysteresis loop measured at a negative pump-probe delay time under pump excitation. TR-MOKE loops usually cannot track the evolution of coercivity of a magnetic system upon strong laser shot, and can do that only when the magnetic system is reversible under a low excitation. The oscillatory recovery behavior of the final coercivity is observed, and is ascribed to metastability of zero magnetization state.

Li, Shufa; Chen, Zhifeng; Cheng, Chuyuan; Li, Jiaming; Zhou, Shiming; Lai, Tianshu

2013-02-01

320

Efficient hysteresis loop simulations of nanoparticle assemblies beyond the uniaxial anisotropy  

NASA Astrophysics Data System (ADS)

We propose a modified Stoner-Wohlfarth model combined with the geometrical approach of the coherent rotation of magnetization for simulating the hysteresis loops of an assembly of magnetic nanoparticles. The temperature and the size distribution are taken into account. This combined model enables the computation of hysteresis loops at low temperatures for assemblies of particles having an arbitrary type of anisotropy. The applicability of this model for fitting experimental data is discussed and results are compared to the zero-field-cooled and field-cooled fits. As an application, the hysteresis loops measured on Co clusters embedded in carbon and germanium matrices are fitted revealing unambiguously the presence of a biaxial anisotropy.

Tamion, Alexandre; Bonet, Edgar; Tournus, Florent; Raufast, Cécile; Hillion, Arnaud; Gaier, Oksana; Dupuis, Véronique

2012-04-01

321

FEM Computation of Magnetic Field and Iron Loss in Laminated Iron Core Using Homogenization Method  

Microsoft Academic Search

This paper presents a novel method for analyzing transient magnetic fields in laminated iron cores. It is based on the finite-element method and a newly developed homogenization method is applied to model the lamination effectively. The homogenized constitutive relations, of which the approximation is only applicable to low-frequency problems, are derived analytically, neglecting eddy currents induced by time-varying magnetic fluxes

Hiroyuki Kaimori; Akihisa Kameari; Koji Fujiwara

2007-01-01

322

Pressure vessel steel embrittlement monitoring by magnetic properties measurements  

SciTech Connect

The magnetic properties of specimens of one heat of A533B nuclear pressure vessel grade steel have been examined in the as-received condition and after neutron irradiation to various fluence levels up to 4 [times] 10[sup 18] cm[sup [minus]2] (E > 0.1 MeV) in the University of Illinois Advanced TRIGA reactor core at two temperatures, approximately 120 and 260[degrees]C. The effect of some heat treatments was also investigated. The magnetic properties were measured by an automated hysteresis curve tracing method using a miniature transformer which incorporated the specimens in its core. Changes in magnetic hysteresis energy loss were correlated with neutron fluence in the case of certain irradiated specimens, and with microhardness measurements in the case of heat treated specimens. At the higher irradiation temperatures, no significant changes in either the magnetic hysteresis properties or the microhardness were noted for the present fluences. The relationship between the observed magnetic properties response and irradiation-induced embrittlement is discussed.

Stubbins, J.F.; Shong, W-J.; Giacobbe, M.; Ougouag, A.M. (Illinois Univ., Urbana, IL (United States). Dept. of Nuclear Engineering); Williams, J.G. (Arizona Univ., Tucson, AZ (United States). Dept. of Nuclear Engineering)

1992-01-01

323

Pressure vessel steel embrittlement monitoring by magnetic properties measurements  

SciTech Connect

The magnetic properties of specimens of one heat of A533B nuclear pressure vessel grade steel have been examined in the as-received condition and after neutron irradiation to various fluence levels up to 4 {times} 10{sup 18} cm{sup {minus}2} (E > 0.1 MeV) in the University of Illinois Advanced TRIGA reactor core at two temperatures, approximately 120 and 260{degrees}C. The effect of some heat treatments was also investigated. The magnetic properties were measured by an automated hysteresis curve tracing method using a miniature transformer which incorporated the specimens in its core. Changes in magnetic hysteresis energy loss were correlated with neutron fluence in the case of certain irradiated specimens, and with microhardness measurements in the case of heat treated specimens. At the higher irradiation temperatures, no significant changes in either the magnetic hysteresis properties or the microhardness were noted for the present fluences. The relationship between the observed magnetic properties response and irradiation-induced embrittlement is discussed.

Stubbins, J.F.; Shong, W-J.; Giacobbe, M.; Ougouag, A.M. [Illinois Univ., Urbana, IL (United States). Dept. of Nuclear Engineering; Williams, J.G. [Arizona Univ., Tucson, AZ (United States). Dept. of Nuclear Engineering

1992-12-01

324

Hysteresis variations of (Pb, La)(Zr, Ti)O3 capacitors baked in a hydrogen atmosphere  

NASA Astrophysics Data System (ADS)

Baking (Pb, La)(Zr, Ti)O3 capacitors in a hydrogen atmosphere causes a significant loss of remanent polarization even at 150 °C. The hysteresis variations depend on the polarization states during baking. The hysteresis loop showed voltage shifts when the capacitor was polarized before baking, whereas it became a cramped shape when the baking was carried out on a virgin capacitor. Although remanent polarization diminished in all cases, saturation polarization was not suppressed. The clamped hysteresis loop can be described as an average of two loops shifted to positive and negative voltages. The results indicate that the loss of remanent polarization is not due to the suppression of switching, but due to the shift of the hysteresis of each domain larger than the coercive voltage.

Tamura, T.; Matsuura, K.; Ashida, H.; Kondo, K.; Otani, S.

1999-05-01

325

Coronary artery stent mimicking intracardiac thrombus on cardiac magnetic resonance imaging due to signal loss: case report.  

PubMed

Since the introduction of percutaneous coronary intervention for coronary artery disease, thousands of patients have been treated with the implantation of coronary stents. Moreover, several of the patients with coronary stent undergo cardiac magnetic resonance (CMR) imaging every year. This case report is of a 77-year-old man who was previously treated with the implantation of a coronary stent in the left circumflex artery. He underwent CMR imaging, which revealed a process 14×21 mm in the left atrium. Cardiac contrast computed tomography did not demonstrate any cardiac pathology. While the signal loss on MRI associated with implanted metallic devices is known, we report a case where an implanted coronary stent in the left circumflex artery led to an intracardiac signal loss mimicking intracardiac thrombus/tumor. PMID:22495236

Qayyum, Abbas Ali; Vejlstrup, Niels Grove; Ahtarovski, Kiril Aleksov; Kofoed, Klaus Fuglsang; Kastrup, Jens

2012-04-09

326

Magnon supersolid and anomalous hysteresis in spin dimers on a triangular lattice  

NASA Astrophysics Data System (ADS)

We study the magnetic phase diagram and hysteresis behavior of weakly coupled spin dimers on a triangular lattice using the cluster mean-field method with cluster-size scaling. We find that the magnetization curve has plateaus at 1/3 and 2/3 of the total magnetization, in which local singlet and triplet states form a superlattice pattern. Moreover, if increasing (decreasing) the magnetic field from the 1/3 (2/3) plateau, the Bose-Einstein condensation (BEC) of triplons occurs on the superlattice background, leading to the transition into “magnon supersolid” phase. We also find that the first-order transition between these solid states and the standard magnon BEC state exhibits an anomalous hysteresis upon cycling the magnetic field; the transition can occur only from solid to BEC, and the system cannot return to the initial solid state in the reverse process.

Yamamoto, Daisuke; Danshita, Ippei

2013-07-01

327

Ac losses for the self field of an ac transport current with a dc transport current offset in high {Tc} superconducting magnet coils for MagLev application  

SciTech Connect

Although much research has been conducted concerning the losses of high-{Tc} superconductors, very little has concentrated on the self-field losses in an actual magnet arrangement. The coils studied in this work were designed for use as actual magnets in an industrial application. Self field loss measurements were made upon tape-wound 2223 superconducting helix coils. The self-field losses were produced by an AC transport current with a DC transport current offset. Losses were taken for single, double and triple tape windings, giving essentially monofilament, dual, and three filament cases. The losses measured here were varied over a range of AC current values for several different DC values, and over a range of frequencies. The currents were all AC sinusoids with a DC offset. All measurements were made at T = 77K.

Koosh, V.F.

1993-10-01

328

FePBNbCr soft-magnetic glassy alloys with low loss characteristics for inductor cores  

Microsoft Academic Search

Fe-based glassy alloys with both high saturation magnetization and low magnetic anisotropy have attracted interest in recent study on Mr. Inoue, 2004, and we have succeeded in developing novel glassy Fe97?x?yPxByNb2Cr1 (x=5–13, y=7–15) alloys for an inductor material. The glassy alloy series of Fe97?x?yPxByNb2Cr1 (x=5–13, y=7–15) have high glass-forming ability with the large critical thickness of 110–150?m and low coercivity

Hiroyuki Matsumoto; Akiri Urata; Yasunobu Yamada; Akihisa Inoue

2010-01-01

329

Novel Glassy Alloys With High Magnetization and Low Loss Characteristics for Inductor Core Materials  

Microsoft Academic Search

Fe-based glassy alloys with both high saturation magnetization and low magnetic anisotropy have attracted interest recently , and we have succeeded in developing novel glassy Fe(97-x-y)PxByNb2Cr1 (x=5 -13, y=7-15) alloys for an inductor material with high corrosion resistance by added Cr is 1 at%. The glassy alloy series of Fe(97-x-y)PxByNb2Cr (x=5-13, y=7-15) have high glass-forming ability with wide range super-cooled

H. Matsumoto; A. Urata; Y. Yamada; A. Inoue

2010-01-01

330

Adaptive identification and control of hysteresis in smart materials  

Microsoft Academic Search

Hysteresis hinders the effective use of smart materials in sensors and actuators. This paper addresses recursive identification and adaptive inverse control of hysteresis in smart material actuators, where hysteresis is modeled by a Preisach operator with a piecewise uniform density function. Two classes of identification schemes are proposed and compared, one based on the hysteresis output, the other based on

Xiaobo Tan; John S. Baras

2005-01-01

331

Cost-effective evaluation of asymmetric sensorineural hearing loss with focused magnetic resonance imaging  

Microsoft Academic Search

The poor sensitivity of audiometric brain stem response for small vestibular schwannomas (acoustic neuromas) creates a dilemma for the physician evaluating a patient with signs and symptoms of retrocochlear disease. Magnetic resonance imaging is recognized as the gold standard for the evaluation of these problems, but if a complete examination of the internal auditory canals and head is done on

DAVID A. CARRIER; MOISES A. ARRIAGA

1997-01-01

332

Winding factors and Joule losses of permanent magnet machines with concentrated windings  

Microsoft Academic Search

The torque to MMF ratio of a permanent magnet machine with concentrated windings is normally much lower than for the more traditionally used distributed windings. BLDC and AC machines with concentrated windings usually have a slot pitch of only 2\\/3 the length of the pole pitch, which results in a poor fundamental winding factor of 0,866. This can be compared

Freddy Magnussen; Chandur Sadarangani

2003-01-01

333

Development of a Low-Loss Magnetic Composite Utilizing Amorphous Metal Flake.  

National Technical Information Service (NTIS)

It is estimated that more than 35 x 10 exp 9 kWhrs of electrical energy are lost annually in the USA in the core laminations of motors. Analysis and experimental measurements indicate that if amorphous metals were used in motors, these motor iron losses c...

L. Johnson

1981-01-01

334

Constricted Hysteresis Loops of Barium Titanate.  

National Technical Information Service (NTIS)

An empirical analysis was made of the change in polarization with time for a constricted hysteresis loop at fixed field strengths. Synthetic constricted loops were obtained by placing two polarized disks in antiparallel and applying a high alternating pot...

G. W. Marks R. D. Redin

1967-01-01

335

Percolation model of relative permeability hysteresis  

NASA Astrophysics Data System (ADS)

A mathematical model of relative permeability hysteresis in drainage and imbibition is constructed on the basis of percolation theory. It is shown that the results are in qualitatively agreement with experimental data.

Kadet, V. V.; Galechyan, A. M.

2013-05-01

336

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

337

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

338

Computer Program to Calculate Composite Conductor Losses in Pulsed Poloidal Coil Systems.  

National Technical Information Service (NTIS)

The code was used to analyze the present design for the poloidal coil system of the ORNL Experimental Power Reactor (EPR). This design requires that superconductor hysteresis losses, superconductor coupling losses, stabilizing material eddy current losses...

W. H. Gray J. K. Ballou

1976-01-01

339

Hysteresis of Electronic Transport in Graphene Transistors  

Microsoft Academic Search

Graphene field effect transistors commonly comprise graphene flakes lying on SiO2 surfaces. The gate-voltage dependent conductance shows hysteresis depending on the gate sweeping rate\\/range. It is shown here that the transistors exhibit two different kinds of hysteresis in their electrical characteristics. Charge transfer causes a positive shift in the gate voltage of the minimum conductance, while capacitive gating can cause

Haomin Wang; Yihong Wu; Chunxiao Cong; Jingzhi Shang; Ting Yu

2010-01-01

340

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

341

Dependence of pitch-angle scattering rates and loss timescales on the magnetic field model  

NASA Astrophysics Data System (ADS)

Radiation belt diffusion codes require, as inputs, precomputed scattering rates, which are currently bounce-averaged in the dipole magnetic field. We present the results of computations of the bounce-averaged quasi-linear pitch-angle diffusion coefficients of relativistic electrons for various distances and two MLT in the Tsyganenko 89c magnetic field model. The coefficients were computed for quiet and storm-time conditions. We compare scattering rates bounce-averaged in a non-dipole field model with those in the dipole field. We demonstrate that on the day side the effects of taking into account a realistic magnetic field are negligible at distances less than six Earth radii. On the night side diffusion coefficients may significantly depend on the assumed field model. Pitch-angle scattering rates calculated in the non-dipole field can explain the often observed night-side chorus induced precipitation. The physical explanation for the changes of pitch-angle scattering rates with the field model is presented and discussed.

Orlova, Ksenia G.; Shprits, Yuri Y.

2010-03-01

342

Plasmaspheric mass loss and refilling as a result of a magnetic storm  

NASA Astrophysics Data System (ADS)

Using the sounding measurements from the radio plasma imager on IMAGE and a plasma density inversion algorithm, we derive the plasma density profiles along the magnetic field in a few L shells every 14 hours at magnetic local noon before, during, and after the 31 March 2001 magnetic storm. An empirical model of the plasmaspheric plasma density distribution is derived as a reference using the measurements before the storm. During the storm the equatorial plasma was substantially depleted in a range of L shells. The flux tubes were refilled after the storm. The filling ratio, the equatorial plasma density normalized by its quiet time value before the storm, is introduced to assess the time evolution of the depletion and refilling processes. The depletion, more than two thirds of the quiet time content, appeared to occur rather quickly after the storm onset, as determined by the limited temporal resolution of the measurements. The refilling proceeded, although more slowly than the depletion process, significantly faster than the theoretical prediction of a 3-day timescale. Dynamic structures are observed in situ and confirmed by the extreme ultraviolet imager (EUV) measurements.

Reinisch, B. W.; Huang, X.; Song, P.; Green, J. L.; Fung, S. F.; Vasyliunas, V. M.; Gallagher, D. L.; Sandel, B. R.

2004-01-01

343

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

344

Radiative power losses from impurities in high-density plasmas confined by high magnetic fields  

NASA Astrophysics Data System (ADS)

Quantifying and controlling the radiative power losses from impurities in the tokamak fusion plasma is crucial for obtaining ignition conditions. In the present work, therefore, losses from impurities have been measured in different operating regimes of the Alcator C-Mod Tokamak and the Frascati Tokamak Upgrade (FTU) plasmas. The major radiating intrinsic impurity in both tokamaks was molybdenum sputtered from the armor tiles covering all the plasma facing surfaces. The radiative power losses from the molybdenum ions accounted for [>]80/% of the total radiative power losses in ICRF heated plasmas and ~60/% in ohmically heated plasmas. Molybdenum could radiate as much as several thousand kW with concentrations as high as ~1× 1011/ particles/cm3 or ~0.001 of the plasma (electron) density. The radiative losses were found to increase linearly with increasing ICRF power and to vary weakly with the central electron density of the plasma. The other major intrinsic impurities in Alcator C-Mod Tokamak, carbon and boron, radiated at most ~100 kW from the plasma and had concentrations in ohmically heated plasmas of ~1.7× 10/ particles/cm3 and ~6.3× 1011/ particles/cm3, respectively. At Alcator C-Mod Tokamak, the total radiative power losses were measured with bolometric systems. The contribution to the total radiative losses from each major impurity and the impurity concentrations were determined spectroscopically from the line brightnesses of XUV (soft X-ray and extreme ultraviolet) transitions. The line brightnesses were interpreted via a detailed atomic physics model which included the Multiple Ionization State Transport (MIST) code, the ab initio atomic rates from the Hebrew University-Jerusalem Lawrence Livermore Atomic Code (HULLAC) and a collisional radiative model. At the FTU Tokamak, brightnesses from impurity emission measured with an X-ray crystal spectrometer were interpreted with a similar atomic physics model which included the molybdenum rates from HULLAC. The prototype XUV Polychromator which used low resolution MLMs as dispersive elements was designed, constructed and photometrically calibrated at The Johns Hopkins University and was extensively used for the work presented here. The resolution of the MLM varied from /Delta/lambda~ 0.5/A at /lambda = 30/A to /Delta/lambda~ 7/A at /lambda = 120/A . The XUV Polychromator had each of its three channels configured for a different region of the XUV spectral range. The molybdenum spectral lines of interest were the resonant 3s-3p transition of Mo31+ at 127.9 A, the 3s2-3s3p transition of Mo30+ at 116.0 A, and the 3p-3d transitions of Mo23+ to Mo25+ between 65 and 85 A. The resonant transitions of C4+ at 40 A, C5+ at 33.4 A and B4+ at 48.6 A were also monitored as well as the low charge states of Mo14+ and Mo15+ between 45 to 55 A. The XUV Polychromator measured both the spectra and the time histories of the emission lines. The temporal response of the instrument was ~1 ms. The photometric and wavelength calibrations of the XUV Polychromator are presented. (Abstract shortened by UMI.)

May, Mark Joseph

1998-07-01

345

Tailoring anisotropic magnetoresistance and giant magnetoresistance hysteresis loops with spin-polarized current injection  

SciTech Connect

Current pulses were injected into magnetic nanowires. Their effect on the magnetoresistance hysteresis loops was studied for three morphologies: homogeneous Ni wires, copper wires containing five cobalt/copper bilayers, and hybrid structures composed of a homogeneous Ni half wire and a multilayered Co/Cu half wire. The characteristic features of the action of the current on the magnetization are shown and discussed. {copyright} 2001 American Institute of Physics.

Wegrowe, J.-E.; Kelly, D.; Hoffer, X.; Guittienne, Ph.; Ansermet, J.-Ph.

2001-06-01

346

Loss Cone Evolution and Particle Escape In Collapsing Magnetic Trap Models  

NASA Astrophysics Data System (ADS)

Collapsing Magnetic Traps (CMTs) have been suggested as one possible mechanism responsible for the acceleration of high-energy particles during solar flares. It has been predicted on the basis of simple CMT models that the majority of the particles should escape towards the end of the trap collapse. This, however, is not seen in the study of particle orbits in more sophisticated trap models, which show that in particular the highest-energy particles remain trapped at all times. It is shown that this apparent contradiction can be resolved by a comparison of the assumptions made in the different CMT models.

Eradat Oskoui, Solmaz; Neukirch, Thomas

2013-04-01

347

Application of a rare-earth cobalt magnet to synchronous motors  

NASA Astrophysics Data System (ADS)

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 has a large ratio of output power to magnet volume and a large starting torque as compared with conventional hysteresis motors. The structure, torque analysis, torque characteristics and equivalent circuit of the synchronous condition of the prototype synchronous motors are discussed. A comparison of the hysteresis and the permanent-magnet-type synchronous motor is also given.

Yamada, H.

1981-10-01

348

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

2006-03-05

349

Fetal loss in mice exposed to magnetic fields during early pregnancy  

SciTech Connect

The effects of low-frequency magnetic fields (MFs) on early pregnancy were studied in CBA/S mice. The magnetic field was a 20 kHz, 15 {micro}T sawtooth. Pregnant females were divided into four groups, two control groups and two exposed groups. One group was exposed to MFs continuously from day 1 postconception (pc) until day 5.5 pc, and the other group was exposed continuously until day 7 pc. All animals were sacrificed on day 19 pc, the day before partus, and their uterine contents were analyzed. No significant increase in the resorption (early fetal death) rate was found in the exposed animals compared to the sham controls. In the group exposed during days 1.0--5.5 pc, the body weight and length of the living fetuses were significantly decreased. Except on day 3 pc (progesterone) and day 13 pc (calcium) in the treated groups, there were no significant differences in progesterone and calcium levels in peripheral blood. Implantation occurred on the same day in MF-treated and control animals.

Svedenstaal, B.M.; Johanson, K.J. [Swedish Univ. of Agricultural Sciences, Uppsala (Sweden). Dept. of Radioecology

1995-12-01

350

Monte Carlo simulation of the hysteresis phenomena on ferromagnetic nanotubes.  

PubMed

In this work the hysteretic properties of single wall ferromagnetic nanotubes were studied. Hysteresis loops were computed on the basis of a classical Heisenberg model involving nearest neighbor interactions and using a Monte Carlo method implemented with a single spin movement Metropolis dynamics. Nanotubes with square and hexagonal unit cells were studied varying their diameter, temperature and magneto-crystalline anisotropy. Effects of the diameter were found stronger in the square unit cell magnetic nanotubes (SMNTs) than in the hexagonal unit cell magnetic nanotubes (HMNTs). The ferromagnetic behavior was observed in SMNTs at higher temperature than in HMNTs. Moreover in both cases, SMNTs and HMNTs, the magneto-crystalline anisotropy in the longitudinal direction showed a linear correspondence with the coercive field. PMID:22905518

Salazar-Enríquez, C D; Restrepo, J; Restrepo-Parra, E

2012-06-01

351

Computation of hysteresis and closure domains in micromagnetism  

NASA Astrophysics Data System (ADS)

In this paper, we report some results obtained in computational micromagnetism, particularly the numerical approximation of hysteresis phenomenon and the numerical approximation of closure domains. We successively consider a brief recall about micromagnetism, a mathematical modelization of a ferromagnetic material by using the total energy functional of the system, a choice of an appropriate functional space and an associated existence theorem, a convenient minimization algorithm based on an augmented Lagrangian method used in combination with an appropriated finite element method. These developments are illustrated upon the study of a piece of a very thin rectangular plate of a ferromagnetic material located in a coplanar unidirectional exterior magnetic field Hest. Under the action of Hest, we compute the internal magnetization of the plate and then, by decreasing step by step the external field from Hmaxex to -Hmaxex, we find back numerically two physical phenomena, the hysterisis and the motion of walls of the closure domains.

Bernadou, Michel J.; He, Song

1998-07-01

352

Analytical modeling of eddy-current losses caused by pulse-width-modulation switching in permanent-magnet brushless direct-current motors  

SciTech Connect

Because of their high efficiency and power density the PM brushless dc motor is a strong candidate for electric and hybrid vehicle propulsion systems. An analytical approach is developed to predict the inverter high frequency pulse width modulation (PWM) switching caused eddy-current losses in a permanent magnet brushless dc motor. The model uses polar coordinates to take curvature effects into account, and is also capable of including the space harmonic effect of the stator magnetic field and the stator lamination effect on the losses. The model was applied to an existing motor design and was verified with the finite element method. Good agreement was achieved between the two approaches. Hence, the model is expected to be very helpful in predicting PWM switching losses in permanent magnet machine design.

Deng, F. [General Motors Corp., Flint, MI (United States). Delphi-Energy and Engine Management Systems; Nehl, T.W. [General Motors Corp., Warren, MI (United States). Research and Development Center

1998-09-01

353

Statistical mechanical origin of hysteresis in ferroelectrics  

NASA Astrophysics Data System (ADS)

Hysteresis in ferroelectric materials is a strong non-linear phenomenon, the origin of which has drawn considerable attention. Based on the hopping probability function of the lattice-center ion crossing the ferroelectric double-well potential, a statistical mechanical theory is proposed to model ferroelectric hysteresis behavior. The hopping probability function is obtained from the statistical distribution function of ions in energy space, which is derived from the mathematical permutation and combination of the occupy-states of lattice-center ion. The calculated hysteresis agrees well with experimental measurements. In particular, the model provides interesting explanations to the polarization current and the coercive field, which differ from traditional microscopic models and thermodynamic theories.

Yang, Feng; Hu, Guangda; Xu, Baixiang; Wu, Weibing; Yang, Changhong; Wu, Haitao

2012-08-01

354

Synthesis and characterization of polymer nanocomposites containing magnetic nanoparticles  

Microsoft Academic Search

Magnetic poly(methyl methacrylate) nanocomposites were prepared using oleic acid coated cobalt ferrite and magnetite nanoparticles. Both nanofillers had a similar effect in shifting the glass transition temperature from that of the neat polymer. The cobalt ferrite nanocomposite had magnetic hysteresis at 2 and 300 K and the magnetite nanocomposite had magnetic hysteresis at 2 K and superparamagnetic behavior at 300

Edwin de La Cruz-Montoya; Carlos Rinaldi

2010-01-01

355

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

356

Conditioning laboratory columns for hysteresis studies  

NASA Astrophysics Data System (ADS)

Evaluating surface area effects on chemical transport properties required estimating the role of hysteresis in the chemical transport processes. To evaluate hysteresis effect unsaturated soil columns at comparable water contents and flow rates were needed. But one column needed to be wetting and a comparable column needed to undergoing drying. Taking advantage of the nearly non-hysteretic behavior in the hydraulic conductivity-water content function, the wetting column was brought to a constant flux rate from a dry condition. The second column was brought to the same flow rate but was started from a wet condition. The apparatus and equilibration times are presented.

Sisson, J. B.; Schaffer, A.

2002-12-01

357

Estimate Interface Shear Stress of Woven Ceramic Matrix Composites from Hysteresis Loops  

NASA Astrophysics Data System (ADS)

An approach to estimate the fiber/matrix interface shear stress of woven ceramic matrix composites during fatigue loading has been developed in this paper. Based on the analysis of the microstructure, the woven ceramic matrix composites were divided into four elements of 0o warp yarns, 90o weft yarns, matrix outside of the yarns and the open porosity. When matrix cracking and fiber/matrix interface debonding occur upon first loading to the peak stress, it is assumed that fiber slipping relative to matrix in the interface debonded region of the 0o warp yarns is the mainly reason for the occurrence of the hysteresis loops of woven ceramic matrix composiets during unloading and subsequent reloading. The unloading interface reverse slip length and reloading interface new slip length are determined by the interface slip mechanisms. The hysteresis loops of three different cases have been derived. The hysteresis loss energy for the strain energy lost per volume during corresponding cycle is formulated in terms of the fiber/matrix interface shear stress. By comparing the experimental hysteresis loss energy with the computational values, the fiber/matrix interface shear stress of woven ceramic matrix composites corresponding to different cycles can then be derived. The theoretical results have been compared with experimental data of two different woven ceramic composites.

Li, Longbiao; Song, Yingdong

2013-03-01

358

Microstructural Characterization of Ferromagnetic Materials Using Magnetic NDE Techniques.  

National Technical Information Service (NTIS)

Magnetic NDE techniques, namely, the acoustic Barkhausen noise, the magnetic Barkhausen noise and the magnetic hysteresis curves, were simultaneously used for microstructural characterization of nickel and steels. Results showed that, in nickel, the non-1...

R. Ranjan

1987-01-01

359

A new magnetic anisotropy  

Microsoft Academic Search

A new discovery has been made in the field of magnetic materials that manifests itself in the form of a displaced hysteresis loop. In addition, although from the same basic phenomena, the magnetic material has only one stable orientation in a magnetic field. In particular, it can be turned through 180° and it will still return to its original orientation.

William H. Meiklejohn; Charles P. Bean

2001-01-01

360

Computational micromagnetic study of particulate media hysteresis and recording  

NASA Astrophysics Data System (ADS)

A description of the micromagnetic theory, algorithms, computer software and computer hardware built and used to study particulate media particles, hysteresis and recording is first provided. This includes a derivation and analysis of the modified version of the Fast Multipole Method used in this dissertation. Results will then be presented on particulate media particle nucleation field dependence on particle shape, particle aspect ratio, ferromagnetic exchange energy and external magnetic field angle. Results on the discretization necessary to accurately model a particle will also be provided. The reversal mode of a particle will be simulated and analyzed. Simulated longitudinal and transverse hysteresis loops will be presented. Results will also be presented on particulate media coercivity and squareness dependence on volumetric packing fraction. Simulated recorded transition results will be given as well as total power spectra results for AC and DC erased particulate media. Numerical results will be compared to experimental data and analytical theories. Advice is provided on how to build a personal supercomputer like the one used in the numerical experiments of this dissertation.

Seberino, Christian

2000-11-01

361

Magnetic configuration effects on TAE-induced losses and a comparison with the orbit-following model in the Large Helical Device  

SciTech Connect

Fast-ion losses from Large Helical Device (LHD) plasmas due to toroidal Alfven eigenmodes (TAEs) were measured by a scintillator-based lost fast-ion probe (SLIP) to understand the loss processes. TAE-induced losses measured by the SLIP appeared in energy E ranges of around 50-180 keV with pitch angles. between 35 degrees-45 degrees, and increased with the increase in TAE amplitudes. Position shifts of the magnetic axis due to a finite plasma pressure led not only to an increase in TAE-induced losses but also to a stronger scaling of fast-ion losses on TAE amplitudes. Characteristics of the observed fast-ion losses were compared with a numerical simulation based on orbit-following models in which the TAE fluctuations are taken into account. The calculation indicated that the number of lost fast ions reaching the SLIP increased with the increase in the TAE amplitude at the TAE gap. Moreover, the calculated dependence of fast-ion loss fluxes on the fluctuation amplitude became stronger in the case of large magnetic axis shifts, compared with the case of smaller shifts, as was observed in the experiments. The simulation results agreed qualitatively with the experimental observations in the LHD.

Ogawa, K. [Nagoya University, Japan; Isobe, M. [National Institute for Fusion Science, Toki, Japan; Toi, K. [National Institute for Fusion Science, Toki, Japan; Spong, Donald A [ORNL; Osakabe, M. [National Institute for Fusion Science, Toki, Japan

2012-01-01

362

Magnetic configuration effects on TAE-induced losses and a comparison with the orbit-following model in the Large Helical Device  

NASA Astrophysics Data System (ADS)

Fast-ion losses from Large Helical Device (LHD) plasmas due to toroidal Alfvén eigenmodes (TAEs) were measured by a scintillator-based lost fast-ion probe (SLIP) to understand the loss processes. TAE-induced losses measured by the SLIP appeared in energy E ranges of around 50-180 keV with pitch angles ? between 35°-45°, and increased with the increase in TAE amplitudes. Position shifts of the magnetic axis due to a finite plasma pressure led not only to an increase in TAE-induced losses but also to a stronger scaling of fast-ion losses on TAE amplitudes. Characteristics of the observed fast-ion losses were compared with a numerical simulation based on orbit-following models in which the TAE fluctuations are taken into account. The calculation indicated that the number of lost fast ions reaching the SLIP increased with the increase in the TAE amplitude at the TAE gap. Moreover, the calculated dependence of fast-ion loss fluxes on the fluctuation amplitude became stronger in the case of large magnetic axis shifts, compared with the case of smaller shifts, as was observed in the experiments. The simulation results agreed qualitatively with the experimental observations in the LHD.

Ogawa, Kunihiro; Isobe, Mitsutaka; Toi, Kazuo; Spong, Donald A.; Osakabe, Masaki; LHD Experiment Group

2012-09-01

363

Improvement of azimuthal homogeneity in permanent-magnet bearing rotors  

SciTech Connect

Permanent magnets that are levitated and rotating over a bulk high-temperature superconductor (HTS) form the basis of many superconducting bearing designs. Experiments have shown that the rotational-loss coefficient of friction'' for thrust bearings of this type can be as low as 8 [times] 10[sup [minus]6]. While the loss mechanisms of such bearings are not well understood, the azimuthal homogeneity of the rotating permanent magnet is believed to play an important role in determining the loss. One possible loss mechanism is magnetic hysteresis in the HTS, where the energy loss E per cycle is derived from the critical state model and given by E = K ([Delta]B[sup 3]/J[sub c]) where K is a geometric coefficient, [Delta]B is the variation in magnetic field at the surface of the HTS experienced during a rotation of the levitated magnet, and J[sub c] is the critical current density of the HTS. It is clear that a small decrease in [Delta]B (i.e., decreasing the azimuthal inhomogeneity of the rotating magnetic field) could have profound effects on decreasing E and the rotational coefficient of friction. The role of [Delta]B is also expected to be significant in reducing losses from eddy currents and other mechanisms. Low rotational losses in HTS bearings have been demonstrated only for levitated masses of several grams. For practical bearings, it is important to obtain these low losses with larger levitated masses. There are two main routes toward decreasing [Delta]B. The first is to improve the alignment of the magnetic particles during fabrication and to maintain close tolerances on grinding angles during manufacture of the permanent magnet. The second, the subject of this paper, is to provide correctional procedures after the magnet is fabricated.

Hull, J.R.; Rossing, T.D.; Mulcahy, T.M.; Uherka, K.L.

1992-10-23

364

Improvement of azimuthal homogeneity in permanent-magnet bearing rotors  

SciTech Connect

Permanent magnets that are levitated and rotating over a bulk high-temperature superconductor (HTS) form the basis of many superconducting bearing designs. Experiments have shown that the rotational-loss``coefficient of friction`` for thrust bearings of this type can be as low as 8 {times} 10{sup {minus}6}. While the loss mechanisms of such bearings are not well understood, the azimuthal homogeneity of the rotating permanent magnet is believed to play an important role in determining the loss. One possible loss mechanism is magnetic hysteresis in the HTS, where the energy loss E per cycle is derived from the critical state model and given by E = K ({Delta}B{sup 3}/J{sub c}) where K is a geometric coefficient, {Delta}B is the variation in magnetic field at the surface of the HTS experienced during a rotation of the levitated magnet, and J{sub c} is the critical current density of the HTS. It is clear that a small decrease in {Delta}B (i.e., decreasing the azimuthal inhomogeneity of the rotating magnetic field) could have profound effects on decreasing E and the rotational coefficient of friction. The role of {Delta}B is also expected to be significant in reducing losses from eddy currents and other mechanisms. Low rotational losses in HTS bearings have been demonstrated only for levitated masses of several grams. For practical bearings, it is important to obtain these low losses with larger levitated masses. There are two main routes toward decreasing {Delta}B. The first is to improve the alignment of the magnetic particles during fabrication and to maintain close tolerances on grinding angles during manufacture of the permanent magnet. The second, the subject of this paper, is to provide correctional procedures after the magnet is fabricated.

Hull, J.R.; Rossing, T.D.; Mulcahy, T.M.; Uherka, K.L.

1992-10-23

365

Improvement of azimuthal homogeneity in permanent-magnet bearing rotors  

NASA Astrophysics Data System (ADS)

Permanent magnets that are levitated and rotating over a bulk high-temperature superconductor (HTS) form the basis of many superconducting bearing designs. Experiments have shown that the rotational-loss 'coefficient of friction' for thrust bearings of this type can be as low as 8 x 10(exp -6). While the loss mechanisms of such bearings are not well understood, the azimuthal homogeneity of the rotating permanent magnet is believed to play an important role in determining the loss. One possible loss mechanism is magnetic hysteresis in the HTS, where the energy loss E per cycle is derived from the critical state model and given by E = K (Delta B)(sup 3)/J(sub c) where K is a geometric coefficient, Delta B is the variation in magnetic field at the surface of the HTS experienced during a rotation of the levitated magnet, and J(sub c) is the critical current density of the HTS. It is clear that a small decrease in Delta B (i.e., decreasing the azimuthal inhomogeneity of the rotating magnetic field) could have profound effects on decreasing E and the rotational coefficient of friction. The role of Delta B is also expected to be significant in reducing losses from eddy currents and other mechanisms. Low rotational losses in HTS bearings have been demonstrated only for levitated masses of several grams. For practical bearings, it is important to obtain these low losses with larger levitated masses. There are two main routes toward decreasing Delta B. The first is to improve the alignment of the magnetic particles during fabrication and to maintain close tolerances on grinding angles during manufacture of the permanent magnet. The second, the subject of this paper, is to provide correctional procedures after the magnet is fabricated.

Hull, J. R.; Rossing, T. D.; Mulcahy, T. M.; Uherka, K. L.

1992-10-01

366

A note on the macroeconomic modelling of unemployment hysteresis  

Microsoft Academic Search

In macroeconomics, unemployment hysteresis typically arises as a special case of an otherwise stationary model. Imposing hysteresis is often equivalent to imposing a random walk, i.e. a situation in which the permanent fraction of a shock is equal to unity. This paper develops a more general linear model of unemployment hysteresis in which permanency is viewed as a continuous, rather

Knut Roed

1999-01-01

367

Robust control for uncertain systems preceded by hysteresis and disturbances  

Microsoft Academic Search

This paper discusses the robust control for the uncertain discrete time linear systems preceded with hysteresis and disturbances. The contribution of the paper is the fusion of the hysteresis model with the adaptive sliding mode control techniques without constructing the inverse hysteresis nonlinearity. The proposed scheme eliminates the traditional over-parameterization by only adapting the parameters (which are generated from the

Xinkai Chen; Takeshi Hisayama

2007-01-01

368

Eliminating the hysteresis effect for reactive sputtering processes  

Microsoft Academic Search

Reactive sputter processes frequently exhibit stability problems. The cause of this is that these processes normally exhibit hysteresis effects in the processing curves. Eliminating the hysteresis would significantly simplify the use of reactive sputtering processes. So far the only known way of eliminating the hysteresis is to increase the pumping speed to unrealistically high values. By an increased understanding of

T. Nyberg; S. Berg; U. Helmersson; K. Hartig

2005-01-01

369

Preisach modeling and compensation for smart material hysteresis  

Microsoft Academic Search

Many of the Smart materials being investigated (e.g., Shape Memory Alloys (SMAs), piezoceramics, and magnetostrictives) exhibit significant hysteresis effects, especially when driven with large control signals. In this paper the similarity between the microscopic domain kinematics that generate static hysteresis effects, or ferromagnetics, piezoceramics and SMAs is noted. The Preisach independent domain hysteresis model, and its derivatives, have been shown

Declan C. Hughes; John T. Wen

1995-01-01

370

EMTP simulation of a STATCOM using hysteresis current control  

Microsoft Academic Search

An alternative control strategy of a STATCOM, based on hysteresis current control of the switches is presented. It is shown that a STATCOM under hysteresis current control will have nearly sinusoidal output current for reactive power compensation while keeping the STATCOM in its simplest configuration. The proposed device was simulated using ATP-EMTP, and the results demonstrate the advantages of hysteresis

D. Sutanto; L. A. Snider; K. L. Mok

1999-01-01

371

Ultra high resolution nonenhanced fast spin echo magnetic resonance imaging: Cost-effective screening for acoustic neuroma in patients with sudden sensorineural hearing loss  

Microsoft Academic Search

The financial burden for the evaluation of patients for acoustic neuroma in an otolaryngology practice is substantial. Patients with sudden sensorineural hearing loss represent a portion of that population seen with unilateral, asymmetric auditory symptoms who require investigation for acoustic neuroma. For these patients, gadolinium-enhanced magnetic resonance imaging is the diagnostic gold standard. Auditory brain stem response testing has been

ROBERT L. DANIELS; CLOUGH SHELTON; H. RIC HARNSBERGER

1998-01-01

372

Effect of magnetic fields on the dose estimates due to beam halo loss in the ring collimation straight of the SNS  

Microsoft Academic Search

The collimation straight section of the SNS ring consists of three collimators with magnets (doublets and correctors) between them. It has been determined that a large fraction of the particle halo loss occurs at the primary and secondary collimators. The dose to ring components in this location has been studied in the past. In this revised dose estimate the effect

H. Ludewig; A. Mallen; N. Catalan-Lasheras; N. Simos; J. Wei; M. Todosow

2001-01-01

373

The Energy-loss Rate of Neutrinos in the Urca Process of Strange Quark Matter in Weak and Ultra-strong Magnetic Fields  

Microsoft Academic Search

The influence of magnetic field on the energy-loss rate of neutrinos in the direct Urca process of quarks in the model of strange stars is investigated in this article. First, an improvement is made on the method of approximate calculation in the case of weak field, which can be extended to other processes of weak interactions. Then, a rigorous calculation

Xue-Wen Liu; Miao Kang; Yun-Wei Yu; Xia Zhou; Xiao-Ping Zheng

2007-01-01

374

Loss of the muscle silent period evoked by transcranial magnetic stimulation of the motor cortex in patients with cervical cord lesions  

Microsoft Academic Search

The silent period following motor evoked potentials in small hand muscles after transcranial magnetic stimulation (TMS) of the human motor cortex is considered to be cortical origin. The authors report three patients with cervical spinal cord lesions who showed loss of the cortical silent period (CSP) after TMS. One patient had traumatic cervical cord injury, and the other two patients

Toshio Shimizu; Taro Hino; Tetsuo Komori; Shunsaku Hirai

2000-01-01

375

Perceptual Hysteresis Thresholding: Towards Driver Visibility Descriptors  

Microsoft Academic Search

To develop driving assistance systems which alert the driver in case of inadequate speed according to the visibility conditions, it is necessary to have descriptors of the driver visibility and in particular to detect the visible features in the image grabbed by the camera. In this aim, a hysteresis filter is proposed, which is based on the visibility level (VL)

Nicolas Hautičre; Jean-Philippe Tarel; Roland Brémond

2007-01-01

376

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

377

Shear hysteresis of rock at intermediate strains  

Microsoft Academic Search

Rocks with appropriate microsctructure are nonlinear with hysteresis in the strain range 10-6 to 10-3 while showing little permanent damage during deformation. Nonlinear effects alter strong motions produced by earthquakes and explosions and may lead to new methods for relating the mechanical properties of rock to microstructure and transport properties. Results of laboratory torsion experiments will be presented to demonstrate

Brian P. Bonner; C. Aracne-Ruddle; C. Shew

1995-01-01

378

Detection of weak (?0.5–300 nT), low frequency (5–100 Hz) magnetic fields at room temperature by kilohertz modulation of the magneto-optical hysteresis in rare earth–iron garnet films  

Microsoft Academic Search

Periodic magnetic fields with frequencies in the 5–100 Hz range and peak strengths as low as 0.5 nT have been detected at 300 K by modulating at kHz rates the magneto-optical response of epitaxial (Tm,Bi)3(Ga,Fe)5O12 rare earth–iron garnet films at ?=532 nm. By exploiting the ?1°??T slope of the magneto-optical transition region between the two magnetization states of these low

J. M. Hafez; J. Gao; J. G. Eden

2007-01-01

379

Detection of weak (~0.5-300 nT), low frequency (5-100 Hz) magnetic fields at room temperature by kilohertz modulation of the magneto-optical hysteresis in rare earth-iron garnet films  

Microsoft Academic Search

Periodic magnetic fields with frequencies in the 5-100 Hz range and peak strengths as low as 0.5 nT have been detected at 300 K by modulating at kHz rates the magneto-optical response of epitaxial (Tm,Bi)3(Ga,Fe)5O12 rare earth-iron garnet films at lambda=532 nm. By exploiting the ~1°\\/muT slope of the magneto-optical transition region between the two magnetization states of these low

J. M. Hafez; J. Gao; J. G. Eden

2007-01-01

380

Investigation of Magnetic Drag Torque in Permanent Magnet Brushless Motors  

Microsoft Academic Search

In permanent magnet (PM) brushless motors, a magnetic drag torque, which results from the effect of magnetic hysteresis, exists at low speeds but is often neglected. However, in some applications it can have potentially serious consequences. In this paper, a practical method for predicting the magnetic drag torque in a PM brushless motor is presented. It is based on the

Y. S. Chen; Z. Q. Zhu

2007-01-01

381

Magnetism and compressive modulus of magnetic fluid containing gels  

Microsoft Academic Search

We have investigated the magnetism and have measured the compressive modulus of magnetic fluid containing gels, called ferrogels, in the presence of magnetic field. No hysteresis was shown in the magnetization curve of the ferrogel suggesting a super paramagnetic response. The equilibrium compressive modulus of the ferrogel was measured up to 4 kOe and the modulus with field was much

Tetsu Mitsumata; Kazuo Ikeda; Jian Ping Gong; Yoshihito Osada; Dénes Szabó; Miklós Zrínyi

1999-01-01

382

Magnetism and compressive modulus of magnetic fluid containing gels  

Microsoft Academic Search

We have investigated the magnetism and have measured the compressive modulus of magnetic fluid containing gels, called ferrogels, in the presence of magnetic field. No hysteresis was shown in the magnetization curve of the ferrogel suggesting a super paramagnetic response. The equilibrium compressive modulus of the ferrogel was measured up to 4 kOe and the modulus with field was much

Tetsu Mitsumata; Kazuo Ikeda; Jian Ping Gong; Yoshihito Osada

2005-01-01

383

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

384

Basic AC loss properties of IBAD/CVD-YBCO tapes for pancake-type coils  

NASA Astrophysics Data System (ADS)

We are experimentally studying basic AC loss properties of IBAD/CVD-YBCO coated conductors with a copper layer for stabilizing, especially the temperature dependence of perpendicular field loss in alternating electromagnetic environments. We prepared two types of short specimens with and without a copper layer and measured AC losses by a saddle-shaped pickup coil in an alternating magnetic field perpendicular to the wide surfaces at liquid helium temperature. In the ranges of the amplitude up to 4 T and the frequency up to 0.2 Hz, the AC losses both of the two specimens are hardly dependent upon the frequency. The results show that hysteresis loss is a major component of the AC loss in the specimens and the effects of the copper layer can be negligible. We also measured AC losses for the specimens with the copper layer at liquid nitrogen temperature to estimate the dependence on measurement temperature. The results suggested that the AC loss vs. the amplitude of applied field can be scaled by a critical current at a zero magnetic field.

Funaki, K.; Sueyoshi, T.; Iwakuma, M.; Shikimachi, K.; Hirano, N.; Nagaya, S.

2008-09-01

385

Continuous Depinning Transition with an Unusual Hysteresis Effect  

NASA Astrophysics Data System (ADS)

We identify a strange hysteresis which occurs in models of the depinning transition with both elastic and transient overshoot stresses. This hysteresis occurs generically despite the fact that the phase transition is still second order. We calculate the size of the hysteresis gap exactly in a large class of models. Because it is caused by irrelevant perturbations, the hysteresis does not show up in the field theory of the continuum limit. But since it is a real phenomenon it may be a cause for the hysteresis observed in natural depinning. We therefore discuss its experimental and numerical signatures which include microscopic nucleation.

Maimon, Ron; Schwarz, J. M.

2004-06-01

386

Initial magnetization curve and weak-link properties in Ag2O-doped LaBa2Cu3O7-y  

NASA Astrophysics Data System (ADS)

Low-field (0-10 mT) magnetization hysteresis curves which are related to the weak-link properties have been investigated in the Ag2O-doped LaBa2Cu3O7-y system. A kink anomaly is observed in the initial magnetization curve at a certain field H* less than 1 mT. It is neither a lower critical field of the weak-link region Hc1j nor a critical field for flux entry at sample surface Hen. Sample thickness dependence of the irreversible magnetization width ?M and field sweep width dependence of the hysteresis loss Q suggest a relationship between the kink anomaly and the maximum applied field He which can be screened at the midplane of the thin plate samples in the framework of the Bean's critical-state model.

Mizuno, F.; Masuda, H.; Hirabayashi, I.; Tanaka, S.

1990-04-01

387

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

388

NC-(CF2)4-CNSSN radical containing 1,2,3,5-dithiadiazolyl radical dimer exhibiting triplet excited states at low temperature and thermal hysteresis on melting-solidification: structural, spectroscopic, and magnetic characterization.  

PubMed

A high yield, one-pot synthesis of the 1,2,3,5-dithiadiazolyl radical NC-(CF2)4-CNSSN radical by reduction of the corresponding 1,3,2,4-dithiadiazolium salt is reported. In the solid state, the title compound is dimerized in trans-cofacial fashion with intra-dimeric Sdelta+...N(delta-) interactions of ca. 3.2 angstroms, and the dimeric units are linked by electrostatic -C triple bond N(delta-)...Sdelta+ interactions forming an infinite chain. Magnetic susceptibility measurements performed on the solid state sample indicate a magnetic moment of 1.8 microB per dimer (1.3 microB per monomer) at 300 K and a good fit to the Bleaney-Bowers model in the temperature range 2-300 K with 2J = -1500 +/- 50 cm(-1), g = 2.02(5), rho = 0.90(3)%, and TIP = 1.25(4) x 10(-3) emu mol(-1). The [NC-(CF2)4-CNSSN radical]2 dimer is the second example of a 1,2,3,5-dithiadiazolyl radical dimer with an experimentally detected triplet excited state as probed by solid-state EPR [2J = -1730 +/- 100 cm(-1), |D| = 0.0278(5) cm(-1), |E| = 0.0047(5) cm(-1)]. The value of the singlet-triplet gap has enabled us to estimate the "in situ" dimerization energy of the radical dimer as ca. -10 kJ mol(-1). The diradical character of the dimer was calculated [CASSCF(6,6)/6-31G*] as 35%. The title radical shows magnetic bistability in the temperature range of 305-335 K as probed by the solid-state EPR presumably arising from the presence of a metastable paramagnetic supercooled phase. Bistability is accompanied by thermochromic behavior with a color change from dark green (dimeric solid) to dark brown (paramagnetic liquid). PMID:18648707

Shuvaev, Konstantin V; Decken, Andreas; Grein, Friedrich; Abedin, Tareque S M; Thompson, Laurence K; Passmore, Jack

2008-06-26

389

Magnetic and hydrogel composite materials for hyperthermia applications.  

PubMed

Micron-sized magnetic particles (Fe3O4) were dispersed in a polyvinyl alcohol hydrogel to study their potential for hyperthermia applications. Heating characteristics of this ferrogel in an alternating magnetic field (375 kHz) were investigated. The results indicate that the amount of heat generated depends on the Fe3O4 content and magnetic field amplitude. A stable maximum temperature ranging from 43 to 47 degrees C was successfully achieved within 5-6 min. The maximum temperature was a function of Fe3O4 concentration. A specific absorption rate of up to 8.7 W/g Fe3O4 was achieved; this value was found to depend on the magnetic field strength. Hysteresis loss is the main contribution to the heating effect experienced by the sample. PMID:15516865

Lao, L L; Ramanujan, R V

2004-10-01

390

Domain theory for capillary condensation hysteresis  

NASA Astrophysics Data System (ADS)

We discuss how the original domain theory for capillary condensation hysteresis [D. H. Everett, The Solid-Gas Interface, Vol. 2 (Marcel Dekker, New York, 1967), pp. 1055-1113] must be modified to account for the presence of the film adsorbed at the pore surface. We show that the original predictions (scanning behavior, congruence) are not valid unless the existence of the adsorbed film is neglected or the dependence of its thickness on the pressure is neglected. We also calculate the scanning curves and subloops that are expected for an assembly of pores having either a regular or irregular (nonconstant) section. These predictions over the scanning behavior within capillary condensation hysteresis can be used to check whether real materials are made up of independent pores or not. Our results are discussed in the light of experiments and density functional theory calculations for adsorption in porous media.

Coasne, Benoit; Gubbins, Keith E.; Pellenq, Roland J.-M.

2005-07-01

391

Contact angle hysteresis due to surface roughness  

Microsoft Academic Search

By means of the calculus of variations it is shown that even on rough surfaces the Young equation applies and that the Wenzel\\u000a equation relies on a false assumption. Contact angle hysteresis, i .e. the difference in the apparent advancing and receding\\u000a angles, for homogeneous rough solid substrates is due to the local slope of the solid surface at the

M. Brackel; F. De Bisschop; P. Joos

392

A novel hysteresis model in unsaturated soil  

Microsoft Academic Search

This study presents a novel hysteresis model based on van Genuchten's soil-moisture relationships. The proposed model yields a series of closed-form relationships in which two shape factors and are determined from the main drying and wetting curves. Experimental and literature-cited data were used to assess model accuracy. The proposed model was also compared with the Scott and KP models. Analytical

Han-Chen Huang; Yih-Chi Tan; Chen-Wuing Liu; Chu-Hui Chen

2005-01-01

393

The hysteresis limit in relaxation oscillation problems  

NASA Astrophysics Data System (ADS)

A singularly perturbed differential equation with a small coefficient multiplying the derivative is shown to exhibit a limiting hysteresis behavior as the singular parameter tends to zero. The convergence takes place in the space of left-continuous regulated functions and is related to the generalized Helly selection principle for regulated functions established by Franková. Examples show that convergence cannot be expected in general if no regularity is assumed either for the forcing term or for the equilibrium set.

Krejcí, P.

2005-01-01

394

Hysteresis-Induced Long-Time Tails  

NASA Astrophysics Data System (ADS)

It is shown analytically that the output of the standard model for complex, nonlocal hysteresis, the Preisach model, exhibits long-time tails under quite general conditions. For uncorrelated input signals the exponent of the algebraic output correlation decay is determined solely by the tails of the input and the Preisach density. Correspondingly we identify universality classes leading to identical algebraic tails. These results predict the occurrence of 1/f noise for a large class of hysteretic systems.

Radons, Günter

2008-06-01

395

Dielectric hysteresis measurement in lossy ferroelectrics  

Microsoft Academic Search

The conventional Sawyer-Tower circuit is modified so as to employ a quasi-DC electric-field rather than the 60Hz AC electric-field. By using this modified Sawyer-Tower method, the P-E hysteresis loop can be determined using 1 cycle of electric field. This technique enables the samples to avoid the joule heating induced breakdown, which often occurred under the cyclic load of the 60

Jae-Hwan Park; Byung-Kook Kim; Jae-Gwan Park; In-Tae Kim; Hae-June Je; Yoonho Klm; Soon Ja Park

1999-01-01

396

Hysteresis effects in stereopsis and binocular rivalry.  

PubMed

Neural hysteresis plays a fundamental role in stereopsis and reveals the existence of positive feedback at the cortical level [Wilson, H. R., & Cowan, J. D. (1973). A mathematical theory of the functional dynamics of cortical and thalamic nervous tissue. Kybernetik 13(2), 55-80]. We measured hysteresis as a function of orientation disparity in tilted gratings in which a transition is perceived between stereopsis and binocular rivalry. The patterns consisted of sinusoidal gratings with orientation disparities (0 degrees, 1 degrees, 2 degrees,..., 40 degrees) resulting in various degrees of tilt. A movie of these 41 pattern pairs was shown at a rate of 0.5, 1 or 2 pattern pairs per second, in forward or reverse order. Two transition points were measured: the point at which the single tilted grating appeared to split into two rivalrous gratings (T1), and the point at which two rivalrous gratings appeared to merge into a single tilted grating (T2). The transitions occurred at different orientation disparities (T1=25.4 degrees, T2=17.0 degrees) which was consistent with hysteresis and far exceeded the difference which could be attributed to reaction time. The results are consistent with a cortical model which includes positive feedback and recurrent inhibition between neural units representing different eyes and orientations. PMID:18234273

Buckthought, Athena; Kim, Jeounghoon; Wilson, Hugh R

2008-01-29

397

Magnetism.  

National Technical Information Service (NTIS)

This program describes magnets and magnetic materials by pointing out the characteristics of the magnetic field, the molecular arrangement of magnetized and unmagnetized metals, the laws of attraction and repulsion, and the factors that affect the amount ...

1972-01-01

398

The effect of TiO2 on the magnetic power losses and electrical resistivity of polycrystalline MnZn-ferrites  

Microsoft Academic Search

In this paper the mechanism through which TiO2 affects the magnetic power losses of iron excess polycrystalline MnZn-ferrites is investigated. It has been found that TiO2, on being diluted in the bulk of the grains, promotes the homogeneous accumulation of calcium and silicon along the grain boundaries, by providing high specific resistivity properties to the resulting microstructure. This calcium and

V. T. Zaspalis; E. Eleftheriou

2005-01-01

399

Amplitude loss of electrically and magnetically evoked sympathetic skin responses in early stages of type 1 (insulin-dependent) diabetes mellitus without signs of dysautonomia  

Microsoft Academic Search

The sympathetic skin responses following both electrical nerve (eSSRs) and magnetic (mSSRs) brain stimulations have been investigated in 19 insulin-dependent diabetic patients with no evidence of a peripheral neuropathy or dysautonomia and compared to those obtained in 10 age-matched healthy subjects. SSR was recorded from the right hand and foot, controlateral to the stimulated side.The main findings were amplitude loss

Laura Sagliocco; Ferdinando Sartucci; Ottavio Giampietro; Luigi Murri

1999-01-01

400

[Mathematical models of hysteresis]. Progress report No. 4, [January 1, 1991--December 31, 1991  

SciTech Connect

The research described in this proposal is currently being supported by the US Department of Energy under the contract ``Mathematical Models of Hysteresis``. Thus, before discussing the proposed research in detail, it is worthwhile to describe and summarize the main results achieved in the course of our work under the above contract. Our ongoing research has largely been focused on the development of mathematical models of hysteretic nonlinearities with ``nonlocal memories``. The distinct feature of these nonlinearities is that their current states depend on past histories of input variations. It turns out that memories of hysteretic nonlinearities are quite selective. Indeed, experiments show that only some past input extrema leave their marks upon future states of hysteretic nonlinearities. Thus special mathematical tools are needed in order to describe nonlocal selective memories of hysteretic nonlinearities. Our research has been primarily concerned with Preisach-type models of hysteresis. All these models have a common generic feature; they are constructed as superpositions of simplest hysteretic nonlinearities-rectangular loops. Our study has by and large been centered around the following topics: various generalizations and extensions of the classical Preisach model, finding of necessary and sufficient conditions for the representation of actual hysteretic nonlinearities by various Preisach type models, solution of identification problems for these models, numerical implementation and experimental testing of Preisach type models. Although the study of Preisach type models has constituted the main direction of the research, some effort has also been made to establish some interesting connections between these models and such topics as: the critical state model for superconducting hysteresis, the classical Stoner-Wohlfarth model of vector magnetic hysteresis, thermal activation type models for viscosity, magnetostrictive hysteresis and neural networks.

Mayergoyz, I.D.

1991-12-31

401

Improved formulations for rotational core losses in rotating electrical machines  

Microsoft Academic Search

This paper presents the measurement and modeling of rotational core losses in electrical steel sheets and rotating electrical machines. Novel formulations of rotational hysteresis, eddy current, and excess losses in electrical sheet steels with circular and elliptical rotating flux density vectors are reported. These formulations are used together with the finite element method to calculate the core losses in rotating

Jian Guo Zhu; Victor Stuart Ramsden

1998-01-01

402

Quantum oscillations and ferromagnetic hysteresis observed in iron filled multiwall carbon nanotubes.  

PubMed

We report on the electrical transport properties of single multiwall carbon nanotubes with and without an iron filling as a function of temperature and magnetic field. For the iron filled nanotubes the magnetoresistance shows a magnetic behavior induced by iron, which can be explained by taking into account a contribution of s-d hybridization. In particular, ferromagnetic-like hysteresis loops were observed up to 50 K for the iron filled multiwall carbon nanotubes. The magnetoresistance shows quantum interference phenomena such as universal conductance fluctuations and weak localization effects. PMID:22155967

Barzola-Quiquia, J; Klingner, N; Krüger, J; Molle, A; Esquinazi, P; Leonhardt, A; Martínez, M T

2011-12-08

403

Alternating current losses in mono- and multicored silver sheathed (Bi,Pb)2Sr2Ca2Cu3O10 tapes at T=27 K in direct current magnetic fields  

Microsoft Academic Search

Alternating current (ac) losses in silver sheathed mono- and multicored (Bi,Pb)2Sr2Ca2Cu3O10 superconducting tapes were investigated at liquid neon temperature (27 K) under various direct current (dc) background magnetic fields. The loss behavior was well accounted for by the Bean critical state model with the inclusion of eddy current loss in the silver sheath. The interfilamentary coupling loss was found to

Y. Fukumoto; H. J. Wiesmann; M. Garber; M. Suenaga; P. Haldar

1995-01-01

404

Alternating current losses in mono- and multicored silver sheathed (Bi,Pb)âSrâCaâCuâOââ tapes at {ital T}=27 K in direct current magnetic fields  

Microsoft Academic Search

Alternating current (ac) losses in silver sheathed mono- and multicored (Bi,Pb)âSrâCaâCuâOââ superconducting tapes were investigated at liquid neon temperature (27 K) under various direct current (dc) background magnetic fields. The loss behavior was well accounted for by the Bean critical state model with the inclusion of eddy current loss in the silver sheath. The interfilamentary coupling loss was found to

Y. Fukumoto; H. J. Wiesmann; M. Garber; M. Suenaga; P. Haldar

1995-01-01

405

Thermal hysteresis of interface biased dipolar coupled nanoelements  

NASA Astrophysics Data System (ADS)

We report a theoretical investigation of thermal hysteresis of a pair of interface biased elliptical iron nanoelements, separated by an ultrathin layer of nonmagnetic material. The thermal hysteresis originates in the strong dipolar interaction, and is tunable by the nature of the low temperature state and the eccentricity of the nanoelements. The width of the thermal hysteresis varies from 500 K to 100 K for lateral dimensions of 125 nm × 65 nm and 145 nm × 65 nm.

Dantas, Ana L.; Queiroz, Idalmir; Reboucas, Gustavo; Dias, Maria G.; Carriço, A. S.

2013-05-01

406

Analysis of Time-Delay Magnetic Damping of Spacecraft Librations in Near-Synchronous Equatorial Orbits.  

National Technical Information Service (NTIS)

Time-lag magnetic damping provides a method of using the earth's magnetic field for rapid libration damping of satellites when the field strength is insufficient to dissipate energy with magnetic hysteresis material. This consists of generating a spacecra...

D. L. Mackison

1967-01-01

407

Optical hysteresis in liquid crystals with helicoidal distributed feedback  

SciTech Connect

A new method is reported whereby optical hysteresis and optical bistability are achieved through resonant absorption of light by an impurity in a cholesteric liquid crystal with a natural helicoidal distributed feedback. The resonant absorption in this system leads to an optical hysteresis at comparatively low light intensities, with a short response time and a simultaneous polarization of light. An implementation of the method is described in which cavity-free optical hysteresis has been achieved with a threshold energy of 10 to the -5th J or less and a response time of 10 to the -8th s. Such a hysteresis may find applications in optical information processing. 7 references.

Zagainova, L.I.; Klimusheva, G.V.; Kryzhanovskii, I.P.; Kukhtarev, N.V.

1985-11-01

408

Optical hysteresis in liquid crystals with helicoidal distributed feedback  

NASA Astrophysics Data System (ADS)

A new method is reported whereby optical hysteresis and optical bistability are achieved through resonant absorption of light by an impurity in a cholesteric liquid crystal with a natural helicoidal distributed feedback. The resonant absorption in this system leads to an optical hysteresis at comparatively low light intensities, with a short response time and a simultaneous polarization of light. An implementation of the method is described in which cavity-free optical hysteresis has been achieved with a threshold energy of 10 to the -5th J or less and a response time of 10 to the -8th s. Such a hysteresis may find applications in optical information processing.

Zagainova, L. I.; Klimusheva, G. V.; Kryzhanovskii, I. P.; Kukhtarev, N. V.

1985-11-01

409

Hysteresis phenomena of the intelligent driver model for traffic flow.  

PubMed

We present hysteresis phenomena of the intelligent driver model for traffic flow in a circular one-lane roadway. We show that the microscopic structure of traffic flow is dependent on its initial state by plotting the fraction of congested vehicles over the density, which shows a typical hysteresis loop, and by investigating the trajectories of vehicles on the velocity-over-headway plane. We find that the trajectories of vehicles on the velocity-over-headway plane, which usually show a hysteresis loop, include multiple loops. We also point out the relations between these hysteresis loops and the congested jams or high-density clusters in traffic flow. PMID:17677531

Dahui, Wang; Ziqiang, Wei; Ying, Fan

2007-07-12

410

Electrical and magnetic properties of multilayer polymer structures with nano inclusions as prepared by selective laser sintering.  

PubMed

Selective laser sintering (SLS) was used to prepare porous polymer nanocomposites comprising of a polycarbonate (PC) matrix doped with 30-50 wt% nano Ni or/and 10-30 wt% nano Cu. The electrical conductivity was measured at f = 1 MHz, bias dc voltage 40 V, and 300-400 K. Magnetic measurements were carried out at r.t. in magnetic fields of up to 10 kOe. Temperature dependence of electrophysical properties was studied for 3D samples derived from PC-Cu powders. Magnetic properties were measured for alternating ferromagnetic/non-magnetic layers with Ni and/or Cu core/polymer shell structures. Temperature dependencies for a real part of a dielectric permeability, loss tangent, and magnetization were found to have a hysteresis character. The structure of sintered items was found to depend of external dc magnetic field. PMID:23646656

Shishkovsky, Igor; Morozov, Yury

2013-02-01

411

Irreversible Disability and Tissue Loss in Multiple Sclerosis: A Conventional and Magnetization Transfer Magnetic Resonance Imaging Study of the Optic Nerves  

Microsoft Academic Search

Objectives: To assess, by magnetic resonance imag- ing, the volumes and magnetization transfer ratio (MTR) values of optic nerves (ONs) from patients with mul- tiple sclerosis (MS) who had incomplete or no visual re- covery after optic neuritis; and to compare these quan- tities with those derived from ONs from patients with MS who showed a marked clinical recovery after

Matilde Inglese; Angelo Ghezzi; Stefania Bianchi; Simonetta Gerevini; Maria Pia Sormani; Vittorio Martinelli; Giancarlo Comi; Massimo Filippi

2002-01-01

412

Data-driven techniques to estimate parameters in a rate-dependent ferromagnetic hysteresis model  

NASA Astrophysics Data System (ADS)

The quantification of rate-dependent ferromagnetic hysteresis is important in a range of applications including high speed milling using Terfenol-D actuators. There exist a variety of frameworks for characterizing rate-dependent hysteresis including the magnetic model in Ref. [2], the homogenized energy framework, Preisach formulations that accommodate after-effects, and Prandtl-Ishlinskii models. A critical issue when using any of these models to characterize physical devices concerns the efficient estimation of model parameters through least squares data fits. A crux of this issue is the determination of initial parameter estimates based on easily measured attributes of the data. In this paper, we present data-driven techniques to efficiently and robustly estimate parameters in the homogenized energy model. This framework was chosen due to its physical basis and its applicability to ferroelectric, ferromagnetic and ferroelastic materials.

Hu, Zhengzheng; Smith, Ralph C.; Ernstberger, Jon M.

2012-05-01

413

What we can learn from the hysteresis properties of metal-bearing meteorites  

NASA Astrophysics Data System (ADS)

Metallic iron-nickel alloys are the main magnetic minerals in many meteorite groups, mostly in the form of kamacite, taenite and tetrataenite. We present here new room temperature hysteresis measurements on more than a hundred FeNi-bearing meteorite falls, mostly ordinary chondrites, as well as a synthesis of pre-existing data. Low temperature hysteresis measurements (down to 10 K) are also presented. These data are compared to other magnetic (magnetic susceptibility in particular) and petrographic parameters (intensity of thermal metamorphism, shock stage...). The bulk magnetic properties of these meteorites are primarily controlled by the relative proportion of the three above-mentioned minerals, and in particular the presence of tetrataenite. Discussion will focus on, but not be limited to: 1) The the elongated shape of metallic grains that is is revealed by the discrepancy between ferromagnetic susceptibility and saturation magnetization, whose ratio is too high for FeNi alloys; 2) The existence of a low temperature transition around 60 K; 3) The comparison between ordinary chondrites, carbonaceous chondrites, HED achondrites and lunar samples.

Gattacceca, J.; Rochette, P.; Suavet, C.; Uehara, M.

2010-12-01

414

Nanoscale Magnetic Domains in Mesoscopic Magnets  

PubMed

The basic magnetic properties of three-dimensional nanostructured materials can be drastically different from those of a continuous film. High-resolution magnetic force microscopy studies of magnetic submicrometer-sized cobalt dots with geometrical dimensions comparable to the width of magnetic domains reveal a variety of intricate domain patterns controlled by the details of the dot geometry. By changing the thickness of the dots, the width of the geometrically constrained magnetic domains can be tuned. Concentric rings and spirals with vortex configurations have been stabilized, with particular incidence in the magnetization reversal process as observed in the ensemble-averaged hysteresis loops. PMID:8662483

Hehn; Ounadjela; Bucher; Rousseaux; Decanini; Bartenlian; Chappert

1996-06-21

415

Loss and Rating Considerations of a Wind Energy Conversion System with Reactive Compensation by Magnetic Energy Recovery Switch (MERS)  

Microsoft Academic Search

Electrical conversion system for permanent magnet wind generators is challenging due to the large rating of power electronics devices needed and the associated costs. Additionally, due to the large inductance present in the generator (synchronous reactance), voltage drops results with resistive load and the generator output power is limited. A solution utilizing an active series compensation device called magnetic energy

JanArild Wiik; Arkadiusz Kulka; Takanori Isobe; Kazuhiro Usuki; M. Molinas; T. Takaku; T. Undeland; R. Shimada

2008-01-01

416

Feedback compensation of shape memory alloy hysteresis  

NASA Astrophysics Data System (ADS)

Traditionally, actuators have been large and heavy (eg., motors). Because of their physical size and structure, they increase the size and weight of the entire system. In many applications, it is desirable to find an alternative to these conventional type of actuators. Shape memory alloy (SMA) has been considered as an actuator for applications that require large force and displacement. SMA are small and light weight which greatly reduces the overall size of a system. However, two factors have hampered the usefulness of such actuators, hysteresis and bandwidth limitation. This thesis examines the hysteresis phenomenon from a control point of view. Particular focus is placed on SMA wires attached to a flexible structure. Generally speaking, there are two ways to compensate for hysteresis, open loop compensation and closed loop feedback compensation. The open loop compensation requires an accurate model; this thesis uses a closed loop approach which considers the feedback of the SMA wire force or length. Very little previous work exists in the literature in this area since most researchers consider SMA to be essentially a static device. However even at low bandwidths, SMA cannot be considered a static device due in part to its intrinsic hysteretic properties. By using a simple lumped temperature model, it is shown that proportional feedback with a suitable range of gains would render the closed loop system stable. This is verified experimentally in a simple experimental setup consisting of a flexible aluminum beam and to a Nitinol shape memory alloy wire that applies it bending force to the end of the beam.

Dickinson, Carrie A.

417

Alternating Current Losses and Magnetic Field Aberrations Associated with Use of High Field Superconducting Wire in Adiabatic Demagnetization Apparatus  

Microsoft Academic Search

Experiments were conducted to determine ac losses, principally near 105 cps, in coils and leads fabricated from high field superconducting wires. The samples were placed in an environment similar to what might be experienced in actual use in a low temperature experiment utilizing adiabatic demagnetization. The measurements showed that losses associated with the use of high field superconducting wire could

A. C. Anderson; W. R. Roach; R. E. Sarwinski

1966-01-01

418

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

419

On the origin of contact angle hysteresis  

NASA Astrophysics Data System (ADS)

In this study, we consider a simple distribution of defects on a substrate, or a sinusoidal surface, and show explicitly how the pinning and depinning occur for a two dimensional liquid drop on such non-ideal surfaces as the volume of the drop is increased or decreased. We show that the contact angle hysteresis (CAH) emerges from this simple model even though we do not take any effect of viscous dissipation into account, which is in contrast with the conventional theory where the CAH originates from the viscous dissipation inside the liquid around the contact line just after depinning.

Yoshitaki, Yumiko; Okumura, Ko

2009-11-01

420

Single molecule magnets from magnetic building blocks  

NASA Astrophysics Data System (ADS)

We provide a basic set of magnetic building blocks that can be rationally assembled, similar to magnetic LEGO bricks, in order to create a huge variety of magnetic behavior. Using rare-earth centers and multipyridine ligands, fine-tuning of intra and intermolecular exchange interaction is demonstrated. We have investigated a series of molecules with monomeric, dimeric and trimeric lanthanide centers using SQUID susceptometry and Hall bar magnetometry. A home-made micro-Hall-probe magnetometer was used to measure magnetic hysteresis loops at mK temperatures and fields up to 17 T. All compounds show hysteresis below blocking temperatures of 3 to 4 K. The correlation of the assembly of the building blocks with the magnetic properties will be discussed.

Kroener, W.; Paretzki, A.; Cervetti, C.; Hohloch, S.; Rauschenbach, S.; Kern, K.; Dressel, M.; Bogani, L.; M&üLler, P.

2013-03-01

421

Magnetic hardening in iron-neodymium-boron permanent magnets  

Microsoft Academic Search

The origin of magnetic hardening has been examined in Fe-Nd-B magnets by correlating the magnetic properties with the microstructure and magnetic domain structure observed with electron microscopy. Hysteresis loops and susceptibility studies show a magnetic anomaly at around 140 K. Microstructure studies reveal the presence of at least four phases with compositions Fe14R2B, Fe4NdB4, a high-Nd-content phase, and ?-Fe. Initial

G. C. Hadjipanayis; K. R. Lawless; R. C. Dickerson

1985-01-01

422

Magnetic hardening in iron-neodymium-boron permanent magnets  

Microsoft Academic Search

The origin of magnetic hardening has been examined in Fe-Nd-B magnets by correlating the magnetic properties with the microstructure and magnetic domain structure observed with electron microscopy. Hysteresis loops and susceptibility studies show a magnetic anomaly at around 140 K. Microstructure studies reveal the presence of at least four phases with compositions Fe14R2B, Fe4NdB4, a high-Nd-content phase, and alpha-Fe. Initial

G. C. Hadjipanayis; K. R. Lawless; R. C. Dickerson

1985-01-01

423

Magnetic nanoparticles for applications in oscillating magnetic field  

SciTech Connect

Enzymatic and thermochemical catalysis are both important industrial processes. However, the thermal requirements for each process often render them mutually exclusive: thermochemical catalysis requires high temperature that denatures enzymes. One of the long-term goals of this project is to design a thermocatalytic system that could be used with enzymatic systems in situ to catalyze reaction sequences in one pot; this system would be useful for numerous applications e.g. conversion of biomass to biofuel and other commodity products. The desired thermocatalytic system would need to supply enough thermal energy to catalyze thermochemical reactions, while keeping the enzymes from high temperature denaturation. Magnetic nanoparticles are known to generate heat in an oscillating magnetic field through mechanisms including hysteresis and relaxational losses. We envisioned using these magnetic nanoparticles as the local heat source embedded in sub-micron size mesoporous support to spatially separate the particles from the enzymes. In this study, we set out to find the magnetic materials and instrumental conditions that are sufficient for this purpose. Magnetite was chosen as the first model magnetic material in this study because of its high magnetization values, synthetic control over particle size, shape, functionalization and proven biocompatibility. Our experimental designs were guided by a series of theoretical calculations, which provided clues to the effects of particle size, size distribution, magnetic field, frequency and reaction medium. Materials of theoretically optimal size were synthesized, functionalized, and their effects in the oscillating magnetic field were subsequently investigated. Under our conditions, the materials that clustered e.g. silica-coated and PNIPAM-coated iron oxides exhibited the highest heat generation, while iron oxides embedded in MSNs and mesoporous iron oxides exhibited the least bulk heating. It is worth noting that the specific loss power of PNIPAM-coated Fe{sub 3}O{sub 4} was peculiarly high, and the heat loss mechanism of this material remains to be elucidated. Since thermocatalysis is a long-term goal of this project, we also investigated the effects of the oscillating magnetic field system for the synthesis of 7-hydroxycoumarin-3-carboxylic acid. Application of an oscillating magnetic field in the presence of magnetic particles with high thermal response was found to effectively increase the reaction rate of the uncatalyzed synthesis of the coumarin derivative compared to the room temperature control.

Peeraphatdit, Chorthip

2010-12-15

424

Applications of a theory of ferromagnetic hysteresis  

SciTech Connect

The differential equation dB/dt = ..cap alpha.. absolute value of dH/dt (f(H) - B) + dH/dt g(H) and a set of restrictions on the material functions f and g yield a theory of rate independent hysteresis for isoperm ferromagnetic materials. A modification based on exchanging the positions of B and H in the differential equation and on allowing for the dependence of the material functions on dH/dt extends the theory to rate dependent, nonisoperm materials. The theory and its extension exhibit all of the important features of ferromagnetic hysteresis, including the existence and stability of minor loops. Both are well suited for use in numerical field solving codes. Examples in which the material functions are simple combinations of analytic functions are presented here for Mn-Zn ferrite, Permalloy, CMD5005, and CoCr thin film. Also presented is a procedure for constructing a two dimensional vector model that yields bell-shaped and M-shaped curves for graphs of the angular variation of the coercive field.

Hodgdon, M.L.

1987-01-01

425

Percolation and hysteresis in macroscopic capillarity  

NASA Astrophysics Data System (ADS)

The concepts of relative permeability and capillary pressure are crucial for the accepted traditional theory of two phase flow in porous media. Recently a theoretical approach was introduced that does not require these concepts as input [1][2][3]. Instead it was based on the concept of hydraulic percolation of fluid phases. The presentation will describe this novel approach. It allows to simulate processes with simultaneous occurence of drainage and imbibition. Furthermore, it predicts residual saturations and their spatiotemporal changes during two phase immiscible displacement [1][2][3][4][5]. [1] R. Hilfer. Capillary Pressure, Hysteresis and Residual Saturation in Porous Media, Physica A, vol. 359, pp. 119, 2006. [2] R. Hilfer. Macroscopic Capillarity and Hysteresis for Flow in Porous Media, Physical Review E, vol. 73, pp. 016307, 2006. [3] R. Hilfer. Macroscopic capillarity without a constitutive capillary pressure function, Physica A, vol. 371, pp. 209, 2006. [4] R. Hilfer. Modeling and Simulation of Macrocapillarity, in: P. Garrido et al. (eds.) Modeling and Simulation of Materials vol. CP1091, pp. 141, American Institute of Physcis, New York, 2009. [5] R. Hilfer and F. Doster. Percolation as a basic concept for macroscopic capillarity, Transport in Porous Media, DOI 10.1007/s11242-009-9395-0, in print, 2009.

Hilfer, Rudolf

2010-05-01

426

Hysteresis and the Dynamic Elasticity of Consolidated Granular Materials  

Microsoft Academic Search

Quasistatic elasticity measurements on rocks show them to be strikingly nonlinear and to have elastic hysteresis with end point memory. When the model for this quasistatic elasticity is extended to the description of nonlinear dynamic elasticity the elastic elements responsible for the hysteresis dominate the behavior. Consequently, in a resonant bar, driven to nonlinearity, the frequency shift and the attenuation

R. A. Guyer; James Tencate; Paul Johnson

1999-01-01

427

Impact of relative permeability hysteresis on geological CO2 storage  

Microsoft Academic Search

Relative permeabilities are the key descriptors in classical formulations of multiphase flow in porous media. Experimental evidence and an analysis of pore-scale physics demonstrate conclusively that relative permeabilities are not single functions of fluid saturations and that they display strong hysteresis effects. In this paper, we evaluate the relevance of relative permeability hysteresis when modeling geological CO2 sequestration processes. Here

R. Juanes; E. J. Spiteri; F. M. Orr Jr; M. J. Blunt

2006-01-01

428

Hysteresis effects in the two-mode dye ring laser  

Microsoft Academic Search

By inserting an optical diode consisting of Faraday and quartz rotators into the cavity of a dye ring laser and by applying a sinusoidal current at 10 Hz to the Faraday rotator, we have been able to observe hysteresis in the intensity of each counterpropagating laser mode. The hysteresis results from the laser's attempts to switch among metastable states in

Edward C. Gage; Leonard Mandel

1989-01-01

429

Formulation of capillary hysteresis with internal state variables  

Microsoft Academic Search

A thermodynamically consistent framework is proposed for modeling the hysteresis of capillarity in partially saturated porous media. Capillary hysteresis is viewed as an intrinsic dissipation mechanism, which can be characterized by a set of internal state variables. The volume fractions of pore fluids are assumed to be additively decomposed into a reversible part and an irreversible part. The irreversible part

Changfu Wei; Mandar M. Dewoolkar

2006-01-01

430

Influence of frequency noise on nascent hysteresis in optical bistability  

SciTech Connect

The authors study the influence of frequency noise on optical bistability in the neighborhood of the critical point where the hysteresis loop appears. They show that when the transmitted field evolves on a faster time scale than that of the noise, the hysteresis loop shifts toward lower values of the incident pumping field.

Lefever, R.; Turner, J.W.; Lugiato, L.A.

1987-09-01

431

Abrupt transitions and hysteresis in thermohaline laboratory models  

Microsoft Academic Search

Steady ocean circulation models can change in three different ways as the forcing parameters are slowly altered: smooth evolution, abrupt transition without hysteresis, and abrupt transition with hysteresis. In the second, the transition point is independent upon whether the driving parameter is increased or decreased. In the third, the transition points differ depending upon whether the driving parameter approachs from

Jack Whitehead

2008-01-01

432

Influence of frequency noise on nascent hysteresis in optical bistability  

Microsoft Academic Search

We study the influence of frequency noise on optical bistability in the neighborhood of the critical point where the hysteresis loop appears. We show that when the transmitted field evolves on a faster time scale than that of the noise, the hysteresis loop shifts toward lower values of the incident pumping field.

R. Lefever; J. Wm. Turner; L. A. Lugiato

1987-01-01

433

Interpreting diel hysteresis between soil respiration and temperature  

Microsoft Academic Search

Increasing use of high-frequency automated soil respiration measurement techniques has revealed complex diel relationships between soil respiration and temperature. Soil surface flux is often lagged from soil temperature by several hours, which results in semi-elliptical hysteresis loops when surface flux is plotted as a function of soil temperature. Both biological and physical explanations have been suggested for hysteresis patterns, and

N. R. Nickerson; C. L. Phillips; D. A. Risk; B. J. Bond

2009-01-01

434

Hysteresis in Thin-Film Rechargeable Lithium Batteries.  

National Technical Information Service (NTIS)

Discharge - charge cycling of thin-film rechargeable lithium batteries with an amorphous or nanocrystalline LiXMn2.Y04 cathode reveals evidence for a true hysteresis in the lithium insertion reaction. This is compared with an apparent hysteresis attribute...

J. B. Bates N. J. Dudney C. D. Evans F. X. Hart

1999-01-01

435

Compensation of Scanner Creep and Hysteresis for AFM Nanomanipulation  

Microsoft Academic Search

Nanomanipulation with atomic force microscopes (AFMs) for nanoparticles with overall sizes on the order of 10 nm has been hampered in the past by the large spatial uncertainties encountered in tip positioning. This paper addresses the compensation of nonlinear effects of creep and hysteresis on the piezo scanners which drive most AFMs. Creep and hysteresis are modeled as the superposition

Babak Mokaberi; Aristides A. G. Requicha

2008-01-01

436

BNL alternating gradient synchrotron with four helical magnets to minimize the losses of the polarized proton beam  

NASA Astrophysics Data System (ADS)

The principle of using multiple partial helical magnets to preserve the polarization of the proton beam during its acceleration was applied successfully to the alternating gradient synchrotron (AGS) which currently operates with two partial helical magnets. In this paper we further explore this idea by using four partial helical magnets placed symmetrically in the AGS ring. This provides many advantages over the present setup of the AGS, which uses two partial helical magnets. First, the symmetric placement of the four helical magnets and their relatively lower field of operation allows for better control of the AGS optics with reduced values of the beta functions especially near beam injection and allows both the vertical and horizontal tunes to be placed within the “spin tune gap,” therefore eliminating the horizontal and vertical intrinsic spin resonances of the AGS during the acceleration cycle. Second, it provides a wider spin tune gap. Third, the vertical spin direction during beam injection and extraction is closer to vertical. Although the spin tune gap, which is created with four partial helices, can also be created with a single or two partial helices, the high field strength of a single helical magnet which is required to generate such a spin tune gap makes the use of the single helical magnet impractical, and that of the two helical magnets rather difficult. In this paper we will provide results on the spin tune and on the optics of the AGS with four partial helical magnets, and compare them with those from the present setup of the AGS that uses two partial helical magnets. Although in this paper we specifically discuss the effect of the four partial helices on the AGS, this method which can eliminate simultaneously the vertical and horizontal intrinsic spin resonances is a general method and can be applied to any medium energy synchrotron which operates in similar energy range like the AGS and provides the required space to accommodate the four helices. In addition, the four partial helix solution is an optimum solution because it eliminates all the spin resonances for any synchrotron which operates in the same energy range as the AGS.

Tsoupas, N.; Huang, H.; MacKay, W. W.; Meot, F.; Roser, T.; Trbojevic, D.

2013-04-01

437

Fe-based nanoparticles as tunable magnetic particle hyperthermia agents  

NASA Astrophysics Data System (ADS)

Magnetic hyperthermia, an alternative anticancer modality, is influenced by the composition, size, magnetic properties, and degree of aggregation of the corresponding nanoparticle heating agents. Here, we attempt to evaluate the AC magnetic field heating response of Fe-based nanoparticles prepared by solar physical vapor deposition, a facile, high-yield methodology. Nanoparticle systems were grown by evaporating targets of Fe and Fe3O4 with different stoichiometry. It is observed that Fe3O4 nanoparticles residing in the magnetic monodomain region exhibit increased heating efficiency together with high specific loss power values above 0.9 kW/g at 765 kHz and 24 kA/m, compared with that of 0.1 kW/g for zero-valent Fe nanoparticles under the same conditions. The enhanced performance of Fe3O4 nanoparticles under the range of field explored (12-24 kA/m) may be attributed to the activation of a magnetic hysteresis loss mechanism when the applied AC field surpasses the particle anisotropy field at H >= 0.5HA. This is also illustrated by the smaller coercivity of Fe3O4 nanoparticles compared with that of their Fe counterparts. Therefore, understanding the interconnection between intrinsic parameters (composition, size and magnetic properties), the dosage (concentration, volume) and the intensity and frequency of the AC field can lead to essential design guidelines for in vitro, in vivo, and clinical applications of magnetic nanoparticles for hyperthermia.

Simeonidis, K.; Martinez-Boubeta, C.; Balcells, Ll.; Monty, C.; Stavropoulos, G.; Mitrakas, M.; Matsakidou, A.; Vourlias, G.; Angelakeris, M.

2013-09-01

438

The effects of partial insulation winding on the charge-discharge rate and magnetic field loss phenomena of GdBCO coated conductor coils  

NASA Astrophysics Data System (ADS)

GdBCO single-pancake coils wound with Kapton insulation every 3, 6, 9 turns, and without insulation, were characterized by charge-discharge and over-current tests. The magnetic field saturation at higher currents than the critical current was affected by the portion of the insulated turns that restricted the surplus current flow away from the azimuthal current path. The charge-discharge delay decreased with the increase of the portion of the insulated turns, which suggested that partial insulation winding may be effective for use in HTS power applications. Magnetic field loss of the coils with reduced insulation at excessive high currents was mainly affected by the decrease in ampere-turns due to the electrically shorted-circuits between the non-insulated turns, which resulted in the over-current flow bypass through the turn-to-turn contacts.

Choi, Y. H.; Kim, K. L.; Kwon, O. J.; Kang, D. H.; Kang, J. S.; Ko, T. K.; Lee, H. G.

2012-10-01

439

Macroscopic quantum tunneling of magnetization explored by quantum-first-order reversal curves  

NASA Astrophysics Data System (ADS)

A method to study the fundamental problem of quantum double well potential systems that display magnetic hysteresis is proposed. The method, coined quantum-first-order reversal curve (QFORC), is inspired by the first-order reversal curve, based on the Preisach model for hysteresis. We successfully tested the QFORC method in the hysteresis of the Mn12Ac molecular magnet, which is governed by macroscopic quantum tunneling of magnetization. The QFORC reproduces well the experimental magnetization behavior. It is possible to separate the thermal activation and tunneling contributions from the magnetization variation, as well as associate the magnetization jumps with specific quantum transitions.

Béron, Fanny; Novak, Miguel A.; Vaz, Maria G. F.; Guedes, Guilherme P.; Knobel, Marcelo; Caldeira, Amir; Pirota, Kleber R.

2013-07-01

440

The influence of interfacial roughness on the coherence of structure and magnetic coupling across barriers in Fe/MgO multilayers  

NASA Astrophysics Data System (ADS)

Single-crystal Fe/MgO multilayers are model systems in which to study magnetic tunnel junctions. We find that the interfacial roughness leads to the loss of coherence of the crystal structure. For thick MgO layers ferromagnetic (FM) ordering is found using polarized neutron reflectivity (PNR). For thin MgO layers magnetization measurements reveal the presence of antiferromagnetic (AF) interactions, but no long-range AF order is found using PNR. After cycling in a hysteresis loop, FM correlations are found at the coercive point, and this will limit the maximum tunnelling magnetoresistance.

Fan, R.; Lee, S. J.; Goff, J. P.; Ward, R. C. C.; Wang, S. G.; Kohn, A.; Wang, C.; Wildes, A. R.; Collins, S. P.

2010-06-01

441

Magnetic properties of as-cast and nanocrystallized Fe73,5Cu1Nb3Si13,5B9 ribbons  

NASA Astrophysics Data System (ADS)

This work concerns the study of soft iron-based magnetic materials. More specifically, concerning based iron amorphous materials, it will be done by combining structure and magnetic properties while acting on various parameters, by annealing to characterize the nanocrytallization. An experimental approach of magnetic properties is applied to the amorphous or nanocrystalline ultra soft materials evaluation of power losses, permeability as properties of the cycle of hysteresis. According to the scale of constraints and the nature of heat treatment (without magnetic field or magnetic field), it is induced an anisotropy which changes the magnetization properties. Thus, for ferromagnetic amorphous alloys, the anisotropy induced constraints is eliminated giving rise to a uniaxial anisotropy. FeBSi amorphous type materials can therefore, after introduction of copper (multiplication of germs) and niobium (growth inhibition), get nanocrystallized compositions of Fe73,5Cu1Nb3Si13,5B9 after annealing around of 500 - 600 °C.

Soltani, M.-L.; Mansri, A.; Lahoubi, M.

2011-05-01

442

Giant reversible magnetocaloric effect in ErMn2Si2 compound with a second order magnetic phase transition  

NASA Astrophysics Data System (ADS)

The magnetic properties and magnetocaloric effect (MCE) in the ternary intermetallic compound ErMn2Si2 have been studied by magnetization and heat capacity measurements. A giant reversible MCE has been observed, accompanied by a second order magnetic phase transition from paramagnetic to ferromagnetic at ~4.5 K. Under a field change of 5 T, the maximum value of magnetic entropy change (-?SMmax) is 25.2 J kg-1 K-1 with no thermal and field hysteresis loss, and the corresponding maximum value of adiabatic temperature change (?Tadmax) is 12.9 K. Particularly, the values of -?SMmax and ?Tadmax reached 20.0 J kg-1 K-1 and 5.4 K for a low field change of 2 T, respectively. The present results indicate that the ErMn2Si2 compound is an attractive candidate for low temperature magnetic refrigeration.

Li, Lingwei; Nishimura, Katsuhiko; Hutchison, Wayne D.; Qian, Zhenghong; Huo, Dexuan; NamiKi, Takahiro

2012-04-01

443

Magnetism  

NSDL National Science Digital Library

This webpage is part of the University Corporation for Atmospheric Research (UCAR) Windows to the Universe program. It describes the nature and configuration of magnetic fields, which are the result of moving electric charges, including how they cause magnetic objects to orient themselves along the direction of the magnetic force points, which are illustrated as lines. Magnetic field lines by convention point outwards at the north magnetic pole and inward at the south magnetic pole. The site features text, scientific illustrations and an animation. Text and vocabulary are selectable for the beginning, intermediate, or advanced reader.

Team, University C.

2007-12-12

444

Wave Tunneling and Hysteresis in Nonlinear Junctions  

SciTech Connect

We consider the nonlinear tunneling of a plane wave through a small barrier potential in a medium with self-defocusing, or repulsive, interactions. We show that nonlinearity can either suppress or enhance transmission rates, determined by whether the initial kinetic energy is above or below the barrier height. Associated with this threshold is the appearance of two distinct hysteresis loops, going clockwise or counterclockwise, respectively. Spatial dynamics upon reflection and transmission reveals the formation of dispersive shock waves (dark soliton trains) due to phase jumps at the interfaces and wave steepening during propagation. The results are demonstrated experimentally for optical wave tunneling through a refractive index defect but will hold for any Schroedinger system that contains a nonlinear junction.

Wan Wenjie; Muenzel, Stefan; Fleischer, Jason W. [Department of Electrical Engineering, Princeton University, Princeton, New Jersey 08544 (United States); Princeton Institute for the Science and Technology of Materials, Princeton University, Princeton, New Jersey 08544 (United States)

2010-02-19

445

Wave Tunneling and Hysteresis in Nonlinear Junctions  

NASA Astrophysics Data System (ADS)

We consider the nonlinear tunneling of a plane wave through a small barrier potential in a medium with self-defocusing, or repulsive, interactions. We show that nonlinearity can either suppress or enhance transmission rates, determined by whether the initial kinetic energy is above or below the barrier height. Associated with this threshold is the appearance of two distinct hysteresis loops, going clockwise or counterclockwise, respectively. Spatial dynamics upon reflection and transmission reveals the formation of dispersive shock waves (dark soliton trains) due to phase jumps at the interfaces and wave steepening during propagation. The results are demonstrated experimentally for optical wave tunneling through a refractive index defect but will hold for any Schrödinger system that contains a nonlinear junction.

Wan, Wenjie; Muenzel, Stefan; Fleischer, Jason W.

2010-02-01

446

Wave tunneling and hysteresis in nonlinear junctions.  

PubMed

We consider the nonlinear tunneling of a plane wave through a small barrier potential in a medium with self-defocusing, or repulsive, interactions. We show that nonlinearity can either suppress or enhance transmission rates, determined by whether the initial kinetic energy is above or below the barrier height. Associated with this threshold is the appearance of two distinct hysteresis loops, going clockwise or counterclockwise, respectively. Spatial dynamics upon reflection and transmission reveals the formation of dispersive shock waves (dark soliton trains) due to phase jumps at the interfaces and wave steepening during propagation. The results are demonstrated experimentally for optical wave tunneling through a refractive index defect but will hold for any Schrödinger system that contains a nonlinear junction. PMID:20366886

Wan, Wenjie; Muenzel, Stefan; Fleischer, Jason W

2010-02-18

447

Risk factors associated with the loss of cartilage volume on weight-bearing areas in knee osteoarthritis patients assessed by quantitative magnetic resonance imaging: a longitudinal study  

PubMed Central

The objective of this study was to identify, on a symptomatic knee osteoarthritis (OA) cohort, the risk factors associated with the progression of the disease. More specifically, we investigated the correlation between knee cartilage volume loss from subregions over the span of 24 months by means of quantitative magnetic resonance imaging (qMRI) with demographic, clinical, radiological, and MRI structural changes. A cohort of 107 patients with knee OA selected from a large trial evaluating the effect of a bisphosphonate underwent x-rays and MRI of the knee at baseline and 24 months. Joint space width (JSW) and joint space narrowing (JSN) and cartilage volume loss over time in subregions of the tibial plateaus and femoral condyles were quantitated. Structural changes in the subchondral bone (hypersignal) and in the menisci (tear and extrusion) were also evaluated. The greatest cartilage volume loss was found in the medial compartment, and risk factors included female gender, JSW, meniscal lesions, and bone changes at baseline. Subregion analysis revealed that the greatest cartilage volume loss at 24 months was found in the central area of the medial tibial plateau (15%; p < 0.0001) and of the medial femoral condyle (12%; p < 0.0001). These findings were associated with the presence at baseline of meniscal extrusion, particularly severe meniscal extrusion, medial and severe meniscal tear, bone hypersignal, high body mass index (BMI), smaller JSW, increases in Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) pain and patient global scores over time, and greater JSN. Parameters predicting medial central femoral condyle cartilage volume loss at 24 months were lateral meniscal tear, SF-36 and BMI at baseline, and JSN. At the medial central tibial plateau, the parameters were severe meniscal extrusion, severe lateral meniscal tear, and bone hypersignal in the lateral compartment at baseline, and WOMAC pain change. Meniscal damage and bone changes are the features most closely associated with the greatest subregional cartilage volume loss. Interestingly, for the first time, JSN was strongly associated with cartilage loss in the central areas of plateaus and condyles. This study also further confirms the correlation between cartilage volume loss and JSN and symptomatic changes at 24 months.

Pelletier, Jean-Pierre; Raynauld, Jean-Pierre; Berthiaume, Marie-Josee; Abram, Francois; Choquette, Denis; Haraoui, Boulos; Beary, John F; Cline, Gary A; Meyer, Joan M; Martel-Pelletier, Johanne

2007-01-01

448

Losses in a high-temperature superconductor exposed to AC and DC transport currents and magnetic fields  

Microsoft Academic Search

Summary form only given, as follows. The development of high-temperature superconductors (HTSs) is for the moment intensive and it is likely that HTSs will be used in different electric devices in a few years. In some of these devices that conductor will be exposed to both AC and DC transport currents and magnetic fields. In the design of electric devices,

Niclas Schönborg; Sven P. Hörnfeldt

2001-01-01

449

Alternating current loss calculation in a high-TC superconducting transmission cable considering the magnetic field distribution  

Microsoft Academic Search

We have calculated the alternating current (ac) losses of a 114 MVA high-TC superconducting (HTS) transmission cable using an electric-circuit (EC) model. The HTS cable is fabricated by Tokyo Electric Power Company and Sumitomo Electric Industries, Ltd. The EC model is comprised of a resistive part and an inductive part. The resistive part is obtained by the approximated Norris equation

H. Noji; K. Haji; T. Hamada

2003-01-01

450

Hysteretic and AC losses of high T(sub c) superconductors by numerical solution of the nonlinear magnetic diffusion equation.  

National Technical Information Service (NTIS)

The complex AC susceptibility ((chi)) of high T(sub c) superconducting materials has been described in terms of hysteretic and AC losses. By including both flux creep and flux flow resistivities in the expression of the flux diffusivity, induction profile...

D. Di Gioacchino P. Tripodi F. Celani A. M. Testa S. Pace

1996-01-01

451

Sediment Hysteresis Patterns In Singapore Urban Residential Lined Channels  

NASA Astrophysics Data System (ADS)

A study involving Jurong West (JW)(68.7 ha) and Ang Mo Kio (AMK)(34.9 ha) residential catchments in Singapore was conducted to analyse temporal total suspended sediment concentrations (TSS) in lined drainage channels during rain events. 53 and 25 storm events were sampled respectively for JW and AMK. 3 types of hysteresis patterns namely, clockwise, eight shaped and random shaped were identified. Data suggested that different impervious cover configurations in both catchments has accounted for different types of hysteresis patterns. Higher impervious cover (84%) in JW produced mainly clockwise, followed by eight shaped and random hysteresis patterns. Lower impervious cover (60%) in AMK produced mainly clockwise hysteresis. Eight shaped and random hysteresis only appeared in AMK when sediment sources like construction activities emerged. Data also showed eight shaped and random hysteresis appeared during higher magnitude of rain events in JW catchment. Different configurations of impervious cover in both catchments also resulted in variations of TSS during rain events. This led to different tightness of hysteresis patterns loops in both catchments. Conclusively, this study has shown that degree of impervious cover, rain magnitude and emergence of new sediment sources in small urban residential has effects on temporal loadings and variations of sediment in small urban residential catchments.

Lee, W.

2006-12-01

452

Second harmonic generation in magnetic nanoparticles with vortex magnetic state  

NASA Astrophysics Data System (ADS)

Nonlinear optical properties of a regular array of triangular-shaped vortex magnetic nanoparticles is studied using the optical second harmonic generation (SHG) technique. We demonstrate that the SHG azimuthal anisotropy is consistent with the 3m symmetry of individual Co nanodots placed in a square surface lattice. Qualitatively different SHG magnetic hysteresis loops are obtained for circular and linear polarizations of the fundamental radiation. In the first case, a wide SHG hysteresis at zero DC magnetic field H is observed, which is attributed to a macroscopic magnetic toroid moment in Co nanodots induced by a noncentrosymmetric distribution of the magnetization. On the contrary, for the linear pump polarization the SHG loop is similar to observed commonly in linear magnetooptics for vortex magnetic structures and reveals a rather narrow width at H=0. A phenomenological SHG description based on the introduction of the SHG polarization induced by a magnetic toroid moment in vortex magnetic nanostructures is presented.

Krutyanskiy, V. L.; Kolmychek, I. A.; Gribkov, B. A.; Karashtin, E. A.; Skorohodov, E. V.; Murzina, T. V.

2013-09-01

453

Diffraction hysteresis loop modelisation in transverse magneto-optical Kerr effect  

NASA Astrophysics Data System (ADS)

We theoretically study the diffraction of light by a magneto-optical grating for the transverse magneto-optical Kerr effect (TMOKE) case when the magnetization runs from saturation in one direction to saturation in the opposite direction. We use a vectorial theory of diffraction based on a perturbative approximation to the Rayleigh-Fano method, which leads to analytical formulae. We plot diffraction hysteresis loops (DHL) for several diffracted harmonics. We show that for a particular angle of incidence, the loop corresponding to one diffracted harmonic is flat.

Vial, Alexandre; van Labeke, Daniel

1998-07-01

454

Magnetic properties and magnetocaloric effect of NdMn2?xTixSi2 compounds  

NASA Astrophysics Data System (ADS)

The structural and magnetic properties of the intermetallic compounds NdMn2?xTixSi2(x = 0, 0.1, 0.2, and 0.3) have been studied by x-ray and high resolution neutron powder diffraction, specific heat, dc magnetization, and differential scanning calorimetry measurements over the temperature range 3–450 K. The Curie temperature and Néel temperature of NdMn2Si2 decrease from TC = 36 K and TN = 380 K to TC = 14 K and TN = 360 K, respectively, on substitution of Ti (x = 0.3) for Mn. The magnetocaloric effect at the first order ferromagnetic phase transition at TC, has been investigated in detail. Under a change of magnetic field of 0–5 T, the maximum value of the magnetic entropy change is 27 J kg?1 K?1 at x = 0, reducing to 15.3 J kg?1 K?1 at x = 0.1 and 10 J kg?1 K?1 at x = 0.3 importantly, no thermal or field hysteresis losses occur (eliminated from 0.3 K and 28.5 J kg?1 at x = 0 around TC) with increase in Ti concentration. Combined with the lack of any hysteresis effects, these findings indicate that NdMn1.9Ti0.1Si2 compound offers potential as a candidate for magnetic refrigerator applications in the temperature region below 35 K.

Din, M. F. Md; Wang, J. L.; Campbell, S. J.; Zeng, R.; Hutchison, W. D.; Avdeev, M.; Kennedy, S. J.; Dou, S. X.