Sample records for magnetic hysteresis loss

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

    Microsoft Academic Search

    E. Cardeffi; Romano Giannetti; Bernardo Tellini

    2005-01-01

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

  2. Perpendicular magnetic anisotropy and rotational hysteresis loss in Co-Cr films

    NASA Astrophysics Data System (ADS)

    Song, I. M.; Ishio, S.; Ishizuka, M.; Tsunoda, T.; Takahashi, M.

    1993-02-01

    Magnetic properties (Curie temperature, magnetization, magnetic anisotropy and rotational hysteresis loss) of Co 100- xCr x films (18 ? x ? 22) and bulk alloys (0 ? × ? 24) were measured to make clear the origin of the perpendicular magnetic anisotropy in Co-Cr films. The magnetization, magnetic anisotropy and rotational hysteresis loss in films are discussed by taking account of the dispersion of the magnetic anisotropy due to a microscopic compositional inhomogeneity. The rotational hysteresis loss of bubble materials such as YFeO 3 and Sm 0.4Y 2.6Fe 3.8Ga 1.2O 12 are also investigated and compared with that of the Co-Cr film.

  3. Hysteresis loss analysis of soft magnetic materials under direct current bias conditions

    NASA Astrophysics Data System (ADS)

    Turgut, Zafer; Kosai, Hiroyuki; Bixel, Tyler; Scofield, James; Semiatin, S. Lee; Horwath, John

    2015-05-01

    Direct current bias related hysteresis loss characteristics of three commercially available magnetic materials: (1) an iron based Metglas tape core, (2) a Sendust powder core, and (3) a Mn-Zn based ferrite in both un-gapped and gapped configurations were studied. The measurements are conducted for a fixed external field Hext, a fixed flux swing (?B), and a fixed maximum forward magnetization (Bmax) as a function of the external bias field. In all the measurements, a direct correlation is found between permeability and measured loss values as a function of dc bias field. Increased hysteresis losses are measured in the magnetization rotation region in which classical domain theory predicts minimal losses. The observed trends are discussed within the frame work of classical domain theory.

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

    NASA Astrophysics Data System (ADS)

    Hergt, Rudolf; Dutz, Silvio; Röder, Michael

    2008-09-01

    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.

  5. The magnetization process: Hysteresis

    NASA Technical Reports Server (NTRS)

    Balsamel, Richard

    1990-01-01

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

  6. Hysteresis loss in vector Preisach models

    Microsoft Academic Search

    E. Della Torre; E. Cardelli; L. H. Bennett

    2010-01-01

    Purpose – The magnetic modeling of materials has been focused on computing magnetization and forces in devices. With increasing efforts to make energy efficient devices, attention must now be paid to hysteresis losses in magnetizing processes. The purpose of this paper is to discuss the pertinent parameters that determine these losses and a method of identifying them. Design\\/methodology\\/approach – A

  7. Hysteresis losses and magnetic phenomena in ribbons of type II superconductors in the noncollinear regime

    NASA Astrophysics Data System (ADS)

    LeBlanc, M. A. R.; Lorrain, J. P.

    1984-06-01

    We have measured hysteresis losses, W(h0, hb, Hb0), in ribbons of VTi and Nb subjected to oscillating magnetic fields of various amplitudes h0 directed transverse to a static bias magnetic field Hb0, hence the name, noncollinear regime. A second bias field hb along h0 may also be introduced. Hb0 and h0 are directed along the length and width of the ribbon respectively or vice versa (90° rotation). The families of data curves are compared with the predictions of double critical state models where (i) dB/dx=±FP(B)/B governs the critical gradients of the magnetic induction and (ii) d?/dx=±FP(B)F(?)/B2, the spatial variation of the orientation of the sheets of flux lines, with ?=0 along Hb0. The effect on W(h0,hb,Hb0) of choosing F(?)=1/tan ?, k and k/(1+???)2 is illustrated and the latter is seen to yield the best agreement. The locus of the magnetization along the length and width of the samples, and , have been monitored separately and simultaneously during the cycles of h0(t) for various h0 and Hb0 with hb=0 or h0. These observations, in particular the curves of the magnetization along Hb0, constitute severe tests of any model. The corresponding curves generated by the model using F(?)=k/(1+???)2 are presented. The physical origin of F(?) is explored.

  8. Synthesis and magnetic properties of platelet ?-Fe 2O 3 particles for medical applications using hysteresis-loss heating

    NASA Astrophysics Data System (ADS)

    Kishimoto, Mikio; Minagawa, Makoto; Yanagihara, Hideto; Oda, Tatsuya; Ohkochi, Nobuhiro; Kita, Eiji

    2012-04-01

    Platelet ?-Fe2O3 particles of particle size less than 100 nm were prepared for medical applications that use the hysteresis-loss heating of ferromagnetic particles. The ?-Fe2O3 particles were obtained through the dehydration, reduction, and oxidation of platelet ?-FeOOH particles, which were synthesized by the precipitation of ferric ions in an alkaline solution containing ethanolamine, and the crystals grown using a hydrothermal treatment. The ?-Fe2O3 particles contained dimples formed by the dehydration of ?-FeOOH particles. The coercive force and the saturation magnetization of the ?-Fe2O3 particles were in the ranges 11.9 to 12.7 kA/m (150 to 160 Oe), and 70 to 72 Am2/kg (70 to 72 emu/g), respectively. The specific loss power of the ?-Fe2O3 particles, estimated from their temperature-raising property measured under a peak magnetic field of 50.9 kA/m (640 Oe) and at a frequency of 117 kHz, was 590 W/g. This value is higher than that of spherical cobalt-containing iron oxide particles having equivalent coercive force and saturation magnetization, reflecting the larger area of the minor hysteresis loop measured under a peak magnetic field of 50.9 kA/m (640 Oe).

  9. Magnetic hysteresis properties and rotational hysteresis losses of synthetic stress-controlled titanomagnetite (Fe_2.4Ti_0.6O_4) particles-II. Rotational hysteresis losses

    NASA Astrophysics Data System (ADS)

    Keller, R.; Schmidbauer, E.

    1999-08-01

    Rotational hysteresis losses W_RH of a ferro- or ferrimagnet (determined by torque measurements) give information on anisotropies related to irreversible magnetization processes. We measured W_RH as a function of magnetic field H for milled and etched synthetic titanomagnetite Fe_2.4Ti_0.6O_4 particles of 2.4, 12.5 and 165 ?m grain size, which are assumed to show stress-controlled magnetic properties, between room temperature and the Curie point. For uniaxial single-domain (SD) particles, typical parameters that can be determined are in the low-field range a critical field for the onset of W_RH, a peak W_RH and a further typical field in the high-field region where W_RH tends to zero; all these parameters are associated with the anisotropy constant. For 2.4 ?m particles, assumed to be SD, the large experimental W_RH at all fields in the whole temperature range is ascribed predominantly to the action of high internal microstresses arising from a large density of dislocations and other lattice defects introduced by the milling process. The reduced magnitude of W_RH for pseudo-single-domain 12.5 ?m particles and the still smaller W_RH for multidomain (MD) 165 ?m particles is thought to be in the first place the result of much lower defect densities in conjunction with irreversible domain rotations. For each particle size, a rise of some W_RH parameters is observed for temperatures >120 degC, which coincides for MD 165 ?m particles with an increase of magnetic hysteresis parameters. The non-zero W_RH at the maximum applied field of H=1200 kA m^-1~15 kOe for all particles in the whole temperature region analysed is attributed to some kind of exchange anisotropy, caused by centres or areas in a particle related to a very high anisotropy, due probably to Fe^2+ in the neighbourhood of lattice defects.

  10. Hysteresis in soft magnetic materials

    Microsoft Academic Search

    Vittorio Basso; Giorgio Bertotti

    2000-01-01

    The physical origin of hysteresis in soft magnetic materials is discussed and the various theoretical approaches proposed for its interpretation are reviewed. Particular attention is paid to the study of fundamental aspects of hysteresis through Barkhausen effect and thermal relaxation experiments, to the connection between hysteresis, macroscopic magnetic properties and microstructural features and finally to the development of mathematical formulations

  11. Hysteresis Losses in Rolling and Sliding Friction

    Microsoft Academic Search

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

    1961-01-01

    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

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

    NASA Astrophysics Data System (ADS)

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

    2013-03-01

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

  13. A constitutive model for the frequency dependence of magnetic hysteresis

    NASA Astrophysics Data System (ADS)

    Ho, Kwangsoo

    2014-10-01

    The magnetic properties of materials are characterized by the variation of flux density with magnetic field. The hysteresis loop is generally dependent on the frequency of excitation. It is well known that the dependence is attributed to the effects of eddy current loss and anomalous (excess) loss. The present work deals with a new approaching method to model the frequency dependence of magnetic hysteresis within the framework of internal state variable theory, the fundamental structure of which is originally based on viscoplasticity theory in continuum mechanics. The hysteresis equations are formulated to be consistent with the general principles of irreversible thermodynamics with internal variables.

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

    NASA Technical Reports Server (NTRS)

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

    1990-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1990-01-01

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

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

    SciTech Connect

    Wieserman, W.R. [Univ. of Pittsburgh, Johnstown, PA (United States); Schwarze, G.E. [National Aeronautics and Space Administration, Cleveland, OH (United States). Lewis Research Center; Niedra, J.M. [Sverdrup Technology, Inc., Brook Park, OH (United States). Lewis Research Center Group

    1994-09-01

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

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

    NASA Astrophysics Data System (ADS)

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

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

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

    Microsoft Academic Search

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

    1990-01-01

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

  19. High frequency, high temperature specific core loss and dynamic BH hysteresis loop characteristics of soft magnetic alloys

    Microsoft Academic Search

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

    1994-01-01

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

  20. High frequency, high temperature specific core loss and dynamic BH hysteresis loop characteristics of soft magnetic alloys

    Microsoft Academic Search

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

    1990-01-01

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

  1. Magnetic Hysteresis Loop Tracer Using Operational Amplifiers

    Microsoft Academic Search

    Homer Fay

    1972-01-01

    A magnetic hysteresis loop tracer has been built to measure the magnetic properties of small cylindrical samples of nonconductive ferromagnets. Applied fields of 10 000 Oe peak amplitude are obtained from a water cooled solenoid driven at 60 Hz, and the change in flux is detected with a coil on the sample. Two operational amplifiers convert the input variables to

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

    Microsoft Academic Search

    N. Schmidt; H. Guldner

    1996-01-01

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

  3. Hysteresis prediction inside magnetic shields and application

    NASA Astrophysics Data System (ADS)

    Mori?, Igor; De Graeve, Charles-Marie; Grosjean, Olivier; Laurent, Philippe

    2014-07-01

    We have developed a simple model that is able to describe and predict hysteresis behavior inside Mumetal magnetic shields, when the shields are submitted to ultra-low frequency (<0.01 Hz) magnetic perturbations with amplitudes lower than 60 ?T. This predictive model has been implemented in a software to perform an active compensation system. With this compensation the attenuation of longitudinal magnetic fields is increased by two orders of magnitude. The system is now integrated in the cold atom space clock called PHARAO. The clock will fly onboard the International Space Station in the frame of the ACES space mission.

  4. Hysteresis prediction inside magnetic shields and application.

    PubMed

    Mori?, Igor; De Graeve, Charles-Marie; Grosjean, Olivier; Laurent, Philippe

    2014-07-01

    We have developed a simple model that is able to describe and predict hysteresis behavior inside Mumetal magnetic shields, when the shields are submitted to ultra-low frequency (<0.01 Hz) magnetic perturbations with amplitudes lower than 60??T. This predictive model has been implemented in a software to perform an active compensation system. With this compensation the attenuation of longitudinal magnetic fields is increased by two orders of magnitude. The system is now integrated in the cold atom space clock called PHARAO. The clock will fly onboard the International Space Station in the frame of the ACES space mission. PMID:25085183

  5. Predictability of magnetic hysteresis and thermoremanent magnetization using Preisach theory

    NASA Astrophysics Data System (ADS)

    Newell, A. J.; Niemerg, M.; Bates, D.

    2014-12-01

    Preisach theory is a phenomenological model of hysteresis that is the basis for FORC analysis in rock magnetism. In FORC analysis, a system is characterized using first-order reversal curves (FORCs), each of which is a magnetization curve after a reversal in the direction of change of the magnetic field. Preisach theory uses the same curves to predict the magnetic response to changes in the magnetic field. In rock magnetism, the Preisach model has been adapted to predict general properties of thermoremanent magnetization (TRM), and even to inferpaleointensity from room-temperature FORCs. Preisach theory represents hysteresis by a collection of hysteresis units called hysterons; the distribution of hysterons is inferred from FORC measurements. Each hysteron represents a two-state system. This is similar to a single-domain (SD) magnet, but the first-order theory cannot represent the magnetism of a simple system of randomly oriented SD magnets. Such a system can be represented by a second-order Preisach theory, which requires the measurement of magnetization curves after two reversals of the direction of change. One can generalize this process to higher order reversal curves, although each increase in the number of reversals greatly increases the number of measurements that are needed. The magnetic hysteresis of systems of interacting SD magnets is calculated using numerical homotopy, a method that can find all the solutions of the equilibrium equations for such a system. The hysteresis frequently has features that cannot be represented by any order of Preisach theory. Furthermore, there are stable magnetic states that are not reachable during isothermal hysteresis unless thermal fluctuations are large enough. Such states would not be visible at room temperature but would contribute to TRM.

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

    SciTech Connect

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

    1999-05-01

    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.

  7. Coupled magnetoelastic theory of magnetic and magnetostrictive hysteresis

    Microsoft Academic Search

    Martin J. Sablik; David C. Jiles

    1993-01-01

    It is demonstrated that hysteresis in the magnetostriction k is coupled to hysteresis in the magnetization M because of the dependence of the magnetostriction on the magnetization. At the same time, when stress is present, the magnetization is in turn coupled to the behavior of the part of the magnetostriction associated with domain moment rotation. An expression for the magnetostriction

  8. Potbellies, wasp-waists, and superparamagnetism in magnetic hysteresis

    Microsoft Academic Search

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

    1996-01-01

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

  9. Ferrite core loss for power magnetic components design

    Microsoft Academic Search

    Waseem Roshen

    1991-01-01

    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

  10. Voltage control of magnetic hysteresis in a nickel nanoparticle

    NASA Astrophysics Data System (ADS)

    Gartland, P.; Jiang, W.; Davidovi?, D.

    2015-06-01

    The effects of voltage bias on magnetic hysteresis in single Ni particles 2 to 3 nm in diameter are measured between temperatures of 60 mK and 4.2 K by using sequential electron tunneling through the particle. While some Ni particles do not display magnetic hysteresis in tunneling current versus magnetic field, in the Ni particles that display hysteresis, the effect of bias voltage on magnetic switching field is nonlinear. The magnetic switching field changes weakly in the voltage interval ˜1 mV above the tunneling onset voltage, and rapidly decreases versus voltage above that interval. A voltage-driven mechanism explaining this nonlinear suppression of magnetic hysteresis is presented, where the key effect is a magnetization blockade due to the addition of spin-orbit anisotropy ?so to the particle by a single electron. A necessary condition for the particle to exhibit magnetization blockade is that ?so increases when the magnetization is slightly displaced from the easy axis. In that case, an electron will be energetically unable to access the particle if the magnetization is sufficiently displaced from the easy axis, which leads to a voltage interval where magnetic hysteresis is possible that is comparable to ?so/e , where e is the electronic charge. If ?so decreases vs magnetization displacement from the easy axis, there is no magnetization blockade and no hysteresis.

  11. Effect of Tension Upon Magnetization and Magnetic Hysteresis in Permalloy

    Microsoft Academic Search

    O. E. Buckley; L. W. McKeehan

    1925-01-01

    Magnetic properties of permalloy.-Effect of tension on magnetization and hysteresis. Wires of 5 nickel-iron alloys containing 45, 65, 78.5, 81 and 84 percent Ni, 60 cm long and 0.1 cm in diameter, were studied by a ballistic method, for tensions up to 10,000 lb per in.2 and fields up to saturation (10 to 20 gauss). Permalloy with 81 percent Ni

  12. Modelling hysteresis in magnetically ordered materials

    NASA Astrophysics Data System (ADS)

    Song, Tiancheng

    2003-06-01

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

  13. Hysteresis Modeling in An ElectroMagnetic Transients Program

    Microsoft Academic Search

    James Frame; Narendra Mohan; Tsu-huei Liu

    1982-01-01

    This paper describes an algorithm for representing the transformer hysteresis. This algorithm is useful under transient conditions and has the capability of representing minor loops. It allows the multi-valued hysteresis behavior to be represented as a linear element at each instant of time. This algorithm has been implemented into the BPA Electro-Magnetic Transients Program (EMTP), which is widely used on

  14. Characterization of power losses in soft magnetic materials

    Microsoft Academic Search

    Aleta T. Wilder

    2005-01-01

    The power density of electric machines may be increased by designing for operation at higher rotation speeds and temperatures. Such operation increases the mechanical stresses, frequency, and temperature attained in the soft magnetic materials. Increased power losses in the magnetic material can be quantified empirically by controlled hysteresis experiments allowing improved simulation of machine operation. Standard hysteresis experiments operate at

  15. Magnetic structure and hysteresis in hard magnetic nanocrystalline film: Computer simulation

    E-print Network

    Laughlin, David E.

    Magnetic structure and hysteresis in hard magnetic nanocrystalline film: Computer simulation simulations are used to study the effect of crystallographic textures on the magnetic properties of uniaxial nanocrystalline films of hard magnetic materials with arbitrary grain shapes and size distributions

  16. The significance of observed rotational magnetic hysteresis in lunar samples

    NASA Technical Reports Server (NTRS)

    Wasilewski, P.

    1974-01-01

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

  17. Optimizing hysteretic power loss of magnetic ferrite nanoparticles

    E-print Network

    Chen, Ritchie

    2013-01-01

    This thesis seeks to correlate hysteretic power loss of tertiary ferrite nanoparticles in alternating magnetic fields to trends predicted by physical models. By employing integration of hysteresis loops simulated from ...

  18. Numerical determination of hysteresis parameters for the modeling of magnetic properties using the theory of ferromagnetic hysteresis

    Microsoft Academic Search

    D. C. Jiles; J. B. Thoelke; M. K. Devine

    1992-01-01

    The authors describe how the various model parameters needed to describe hysteresis on the basis of the Jiles-Atherton theory can be calculated from experimental measurements of the coercivity, remanence, saturation magnetization, initial anhysteretic susceptibility, initial normal susceptibility, and maximum differential susceptibility. The determination of hysteresis parameters based on this limited set of magnetic properties is of the most practical use

  19. A new ferromagnetic hysteresis model for soft magnetic composite materials

    NASA Astrophysics Data System (ADS)

    Zidari?, Bogomir; Miljavec, Damijan

    2011-01-01

    A new ferromagnetic hysteresis model for soft magnetic composite materials based on their specific properties is presented. The model relies on definition of new anhysteretic magnetization based on the Cauchy-Lorentz distribution describing the maximum energy state of magnetic moments in material. Specific properties of soft magnetic composite materials (SMC) such as the presence of the bonding material, different sizes and shapes of the Fe particles, level of homogeneity of the Fe particles at the end of the SMC product treatment, and achieved overall material density during compression, are incorporated in both the anhysteretic differential magnetization susceptibility and the irreversible differential magnetization susceptibility. Together they form the total differential magnetization susceptibility that defines the new ferromagnetic hysteresis model. Genetic algorithms are used to determine the optimal values of the proposed model parameters. The simulated results show good agreement with the measured results.

  20. Element specific separation of bulk and interfacial magnetic hysteresis loops

    Microsoft Academic Search

    A. K. Suszka; C. J. Kinane; C. H. Marrows; B. J. Hickey; D. A. Arena; J. Dvorak; A. Lamperti; B. K. Tanner; S. Langridge

    2007-01-01

    We have studied the reversal of the bulk and interfacial magnetizations of the free layer of a spin valve using soft x-ray resonant magnetic scattering. By dusting the interface of the NiFe free layer with a few angströms of Co, we were able to distinguish between the interfacial and bulk magnetisms by tuning the x-ray photon energy. We measured hysteresis

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

    NASA Astrophysics Data System (ADS)

    Schmidbauer, E.

    1988-05-01

    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.

  2. Influence of eddy currents on magnetic hysteresis loops in soft magnetic materials

    Microsoft Academic Search

    Jan Szczyg?owski

    2001-01-01

    In this paper an attempt has been made to extend the Jiles and Atherton (J–A) quasi-static hysteresis model to describe magnetisation of a material with an alternating magnetic field. In low – industrial – and medium frequency of magnetic field it is possible to ignore the magnetic relaxation and resonance. The field penetration is assumed to be uniform through the

  3. Magnetostrictive hysteresis of TbCo\\/CoFe multilayers and magnetic domains

    Microsoft Academic Search

    J.-Ph. Jay; F. Petit; J. Ben Youssef; M. V. Indenbom; A. Thiaville; J. Miltat

    2006-01-01

    Magnetic and magnetostrictive hysteresis loops of TbCo\\/CoFe multilayers under field applied along the hard magnetization axis are studied using vectorial magnetization measurements, optical deflectometry, and magneto-optical Kerr microscopy. Even a very small angle misalignment between hard axis and magnetic field direction is shown to drastically change the shape of magnetization and magnetostrictive torsion hysteresis loops. Two kinds of magnetic domains

  4. Magnetostrictive hysteresis of TbCo\\/CoFe multilayers and magnetic domains

    Microsoft Academic Search

    F. Petit; J. Ben Youssef; M. V. Indenbom; A. Thiaville; J. Miltat

    2005-01-01

    Magnetic and magnetostrictive hysteresis loops of TbCo\\/CoFe multilayers under\\u000afield applied along the hard magnetization axis are studied using vectorial\\u000amagnetization measurements, optical deflectometry and magneto optical Kerr\\u000amicroscopy. Even a very small angle misalignment between hard axis and magnetic\\u000afield direction is shown to drastically change the shape of magnetization and\\u000amagnetostrictive torsion hysteresis loops. Two kinds of magnetic

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

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

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

  6. Specification of distribution functions for magnetic hysteresis modeling

    Microsoft Academic Search

    A. Pruksanubal

    2009-01-01

    This paper describes the combination of different statistical distributions to apply in the Preisach hysteresis model. The model is able to represent the hysteresis property of the ferromagnetic material if its distribution function is well determined. Various distributions, such as Gaussian, Weibull, Cauchy, Laplace, Rayleigh, etc., are combined to produce different distribution functions and to simulate the hysteresis loops. Finally,

  7. Eddy-current losses in magnetic conductors with abrupt magnetic transitions

    Microsoft Academic Search

    I. D. Mayergoyz; C. Serpico

    2000-01-01

    This paper presents an analysis of eddy-current losses in magnetic conductors with abrupt magnetic transitions. The study of the linear polarization of the magnetic flux is based on the Preisach model representation of eddy-current hysteresis. By using this representation, analytical formulas for the calculation of eddy-current losses in terms of simple experimental data are derived. The analysis of the circular

  8. Modeling of quasistatic magnetic hysteresis with feed-forward neural networks

    SciTech Connect

    Makaveev, Dimitre; Dupre, Luc; De Wulf, Marc; Melkebeek, Jan

    2001-06-01

    A modeling technique for rate-independent (quasistatic) scalar magnetic hysteresis is presented, using neural networks. Based on the theory of dynamic systems and the wiping-out and congruency properties of the classical scalar Preisach hysteresis model, the choice of a feed-forward neural network model is motivated. The neural network input parameters at each time step are the corresponding magnetic field strength and memory state, thereby assuring accurate prediction of the change of magnetic induction. For rate-independent hysteresis, the current memory state can be determined by the last extreme magnetic field strength and induction values, kept in memory. The choice of a network training set is motivated and the performance of the network is illustrated for a test set not used during training. Very accurate prediction of both major and minor hysteresis loops is observed, proving that the neural network technique is suitable for hysteresis modeling. {copyright} 2001 American Institute of Physics.

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

    Microsoft Academic Search

    Y. Zhai; L. Vu-Quoc

    2005-01-01

    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

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

    Microsoft Academic Search

    Y. Zhai; L. Vu-Quoc

    2007-01-01

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

  11. Two simplified methods for the iron losses prediction in soft magnetic materials supplied by PWM inverter

    Microsoft Academic Search

    A. Boglietti; A. Cavagnino; M. Lazzari; M. Pastorelli

    2001-01-01

    The aim of this work is to propose a mathematical model for the iron losses prediction in soft magnetic materials with any supply voltage. The starting point for the analysis is the knowledge of the iron losses with sinusoidal supply. The model is based on the separation of the losses contributions due to hysteresis, eddy current and excess losses with

  12. A simplified method for the iron losses prediction in soft magnetic materials with arbitrary voltage supply

    Microsoft Academic Search

    A. Boglietti; M. Lazzari; M. Pastorelli

    2000-01-01

    The aim of this work is to propose a new approach for the iron losses prediction, in soft magnetic materials with any voltage supply, starting from the knowledge of the iron losses with sinusoidal supply. The model is based on the separation of the loss contributions due to hysteresis, eddy currents and excess losses with sinusoidal supply. Since any contribution

  13. Predicting iron losses in soft magnetic materials with arbitrary voltage supply: an engineering approach

    Microsoft Academic Search

    Aldo Boglietti; Andrea Cavagnino; Mario Lazzari; Michele Pastorelli

    2003-01-01

    We propose a new approach for predicting iron losses in soft magnetic materials with any voltage supply, starting from the knowledge of the iron losses with a sinusoidal or pulsewidth modulation supply. The model is based on the separation of the loss contributions due to hysteresis, eddy currents, and excess losses with the two supplies. Since any contribution depends on

  14. High-frequency rotational losses in different soft magnetic composites

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

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

  15. Surface Aligned Magnetic Moments and Hysteresis of an Endohedral Single-Molecule Magnet on a Metal

    NASA Astrophysics Data System (ADS)

    Westerström, Rasmus; Uldry, Anne-Christine; Stania, Roland; Dreiser, Jan; Piamonteze, Cinthia; Muntwiler, Matthias; Matsui, Fumihiko; Rusponi, Stefano; Brune, Harald; Yang, Shangfeng; Popov, Alexey; Büchner, Bernd; Delley, Bernard; Greber, Thomas

    2015-02-01

    The interaction between the endohedral unit in the single-molecule magnet Dy2ScN @C80 and a rhodium (111) substrate leads to alignment of the Dy 4 f orbitals. The resulting orientation of the Dy2ScN plane parallel to the surface is inferred from comparison of the angular anisotropy of x-ray absorption spectra and multiplet calculations in the corresponding ligand field. The x-ray magnetic circular dichroism is also angle dependent and signals strong magnetocrystalline anisotropy. This directly relates geometric and magnetic structure. Element specific magnetization curves from different coverages exhibit hysteresis at a sample temperature of ˜4 K . From the measured hysteresis curves, we estimate the zero field remanence lifetime during x-ray exposure of a submonolayer to be about 30 seconds.

  16. Surface aligned magnetic moments and hysteresis of an endohedral single-molecule magnet on a metal.

    PubMed

    Westerström, Rasmus; Uldry, Anne-Christine; Stania, Roland; Dreiser, Jan; Piamonteze, Cinthia; Muntwiler, Matthias; Matsui, Fumihiko; Rusponi, Stefano; Brune, Harald; Yang, Shangfeng; Popov, Alexey; Büchner, Bernd; Delley, Bernard; Greber, Thomas

    2015-02-27

    The interaction between the endohedral unit in the single-molecule magnet Dy_{2}ScN@C_{80} and a rhodium (111) substrate leads to alignment of the Dy 4f orbitals. The resulting orientation of the Dy_{2}ScN plane parallel to the surface is inferred from comparison of the angular anisotropy of x-ray absorption spectra and multiplet calculations in the corresponding ligand field. The x-ray magnetic circular dichroism is also angle dependent and signals strong magnetocrystalline anisotropy. This directly relates geometric and magnetic structure. Element specific magnetization curves from different coverages exhibit hysteresis at a sample temperature of ?4??K. From the measured hysteresis curves, we estimate the zero field remanence lifetime during x-ray exposure of a submonolayer to be about 30 seconds. PMID:25768775

  17. Magnetoabsorption and magnetic hysteresis in Ni ferrite nanoparticles

    NASA Astrophysics Data System (ADS)

    Hernández-Gómez, P.; Muñoz, J. M.; Valente, M. A.; Torres, C.; de Francisco, C.

    2013-01-01

    Nickel ferrite nanoparticles were prepared by a modified sol-gel technique employing coconut oil, and then annealed at different temperatures in 400-1200 °C range. This route of preparation has revealed to be one efficient and cheap technique to obtain high quality nickel ferrite nanosized powder. Sample particles sizes obtained with XRD data and Scherrer's formula lie in 13 nm to 138 nm, with increased size with annealing temperature. Hysteresis loops have been obtained at room temperature with an inductive method. Magnetic field induced microwave absorption in nanoscale ferrites is a recent an active area of research, in order to characterize and explore potential novel applications. In the present work microwave magnetoabsorption data of the annealed nickel ferrite nanoparticles are presented. These data have been obtained with a system based on a network analyzer that operates in the frequency range 0 - 8.5 GHz. At fields up to 400 mT we can observe a peak according to ferromagnetic resonance theory. Sample annealed at higher temperature exhibits different absorption, coercivity and saturation magnetization figures, revealing its multidomain character.

  18. Magnetic hysteresis behavior and magnetic pinning in a d0 ferromagnet/superconductor nanostructure

    NASA Astrophysics Data System (ADS)

    Uchino, Takashi; Uenaka, Yuki; Soma, Haruka; Sakurai, Takahiro; Ohta, Hitoshi

    2014-02-01

    We investigate the interaction between superconductivity and defect-induced d0 ferromagnetism using a composite consisting of MgB2 and MgO nanocrystals. The composite exhibits a ferromagnetic hysteresis behavior in the temperature region from 40 to 300 K. Defective MgO nanocrystals (˜20 nm) embedded in the composite are considered to be responsible for the observed ferromagnetism. The zero field cool and field cool magnetization curves show that the superconducting transition occurs at Tc = 38.6 K, in agreement with Tc of pure MgB2. In the temperature region from Tc to 0.9Tc (˜35 K), the magnetization hysteresis curves show a superposition of ferromagnetic (F) and superconducting (S) signals. When the temperature of the system is decreased below 0.65Tc (˜25 K), the S signals dominate over the F signals. The resulting magnetic hysteresis loops are highly asymmetric and the descending filed branch is nearly flat, as predicted in the case of surface pinning. At temperatures below 0.5Tc (˜20 K), a sharp peak is developed near zero field in the magnetization hysteresis curves, implying an enhancement of superconducting vortex pinning. The observed pinning enhancement most likely results from magnetic pinning due to randomly distributed magnetic MgO grains, which yield the magnetic inhomogeneity and the related pinning potential in a length scale of ˜100 nm. Thus, the present ferromagnetic/superconducting composite provides an ideal model system that demonstrates the availability of d0 ferromagnetism as a source of magnetic potential for effective vortex pinning.

  19. A robust hysteresis current-controlled PWM inverter for linear PMSM driven magnetic suspended positioning system

    Microsoft Academic Search

    Bor-Jehng Kang; Chang-Ming Liaw

    2001-01-01

    Hysteresis current-controlled pulsewidth modulation (PWM) is very robust but it possesses nonconstant switching frequency, and it is difficult to use for high-performance position servo applications. This paper presents a robust hysteresis current-controlled PWM scheme for a magnetic suspended positioning system driven by an inverter-fed linear permanent-magnet synchronous motor having improved performance in these two areas. In the proposed control scheme,

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

    NASA Technical Reports Server (NTRS)

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

    1977-01-01

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

  1. High Gain Observer for Induction Motor in Presence of Magnetic Hysteresis , L. Dugard3

    E-print Network

    Paris-Sud XI, Université de

    High Gain Observer for Induction Motor in Presence of Magnetic Hysteresis H. Ouadi1 , F. Giri2 , L in induction motors is considered in this paper. In most previous works, motor observers have been designed using standard models, neglecting the saturation and hysteretic effects in the machine magnetic circuit

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

    SciTech Connect

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

    1988-11-15

    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.

  3. Pressure effect on magnetic hysteresis parameters of single-domain magnetite contained in natural plagioclase crystal

    NASA Astrophysics Data System (ADS)

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

    2015-07-01

    This study investigates pressure effects on the magnetic properties of non-interacting single-domain (SD) magnetite. Using a high-pressure cell specially designed for a Magnetic Property Measurement System, magnetic hysteresis measurements were conducted under high pressures of up to 1 GPa on natural plagioclase crystals containing much acicular SD magnetite. Coercivity and saturation magnetization were nearly constant with pressure, while saturation remanent magnetization and coercivity of remanence decreased with pressure at moderate rates of -8 per cent GPa-1 and -18 per cent GPa-1, respectively. These results suggest that temperature effects govern the magnetic behaviour of acicular SD magnetite grains in the middle and lower crusts.

  4. Quantum step heights in hysteresis loops of molecular magnets Roberto B. Diener,1

    E-print Network

    Niu, Qian

    Quantum step heights in hysteresis loops of molecular magnets Jie Liu,1 Biao Wu,1 Libin Fu,2 February 2002; published 16 May 2002 We present an analytical theory on the heights of the quantum steps molecular spins, our theory successfully yields the step heights measured in experiments, and reveals

  5. Anomalous eddy current loss and amorphous magnetic materials with low core loss (invited)

    NASA Astrophysics Data System (ADS)

    Fujimori, H.; Yoshimoto, H.; Masumoto, T.; Mitera, T.

    1981-03-01

    Heat-treatment methods for obtaining low core loss in Fe rich amorphous alloys with high magnetic induction and the physical mechanism concerned will be discussed. Field annealing is necessary to avoid inducing local magnetic anisotropies or magnetic domain wall fixing, and then to make stress relieving effective. Consequently, field annealing can reduce hysteresis energy loss. However, core loss at high frequencies involves a fairly large anomalous eddy current loss. This is due to a large size of 180° magnetic domains resulting from field annealing. Oblique field annealing is, on the other hand, effective to reduce anomalous eddy current loss, because of increase in the number of 180° domain walls. The experimental relation between core loss and domain structure obtained on Fe(72)Co(8)Si(5)B(15) has satisfactorily been explained by the simple model on the basis of bar-like 180° wall motion. Magnetic properties of Fe(81)-(B, C, Si) (19) amorphous alloys suitable for transformer materials will also be reported. In Fe(81)B(13)C(2)Si(4), for example, core loss at 50 Hz is 1.3 mw?sec/kg at 15 KG and 25°C (2.2 mw?sec/kg at 15 KG and 80°C).

  6. Design for Fermilab main injector magnet ramps which account for hysteresis

    SciTech Connect

    Brown, B.C.; Bhat, C.M.; Harding, D.J.; Martin, P.S.; Wu, G.

    1997-05-01

    Although the dominant fields in accelerator electromagnets are proportional to the excitation current, precise control of accelerator parameters requires a detailed understanding of the fields in Main Injector magnets including contribution from eddy currents, magnet saturation, and hysteresis. Operation for decelerating beam makes such considerations particularly significant. Analysis of magnet measurements and design of control system software is presented. Field saturation and its effects on low field hysteresis are accounted for in specifying the field ramps for dipole, quadrupole and sextupole magnets. Some simplifying assumptions are made which are accepted as limitations on the required ramp sequences. Specifications are provided for relating desired field ramps to required current ramps for the momentum, tune, and chromaticity control.

  7. Generalized formulation for the description of hysteresis in soft magnetic materials

    Microsoft Academic Search

    Paiboon Nakmahachalasint; Khai D. T. Ngo

    2002-01-01

    Presents a phenomenological formulation that broadens the range of applicability of the Basso-Bertotti hysteresis model to include soft magnetic materials with very gradual saturation, such as commercial manganese-zinc (MnZn) power ferrites. The formulation also enables the Basso-Bertotti model to better characterize both the major loop and the minor loops of these soft magnetic materials. The formulation introduces a model parameter

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

    NASA Technical Reports Server (NTRS)

    Wasilewski, P. J.

    1973-01-01

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

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

    SciTech Connect

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

    2008-10-14

    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.

  10. A mechanism of magnetic hysteresis in heterogeneous alloys

    Microsoft Academic Search

    E. C. Stoner; E. P. Wohlfarth

    1991-01-01

    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

  11. Magnetic properties and loss separation in iron powder soft magnetic composite materials

    NASA Astrophysics Data System (ADS)

    De Wulf, Marc; Anestiev, Ljubomir; Dupré, Luc; Froyen, Ludo; Melkebeek, Jan

    2002-05-01

    New developments in powder metallurgical composites make soft magnetic composite (SMC) material interesting for application in electrical machines, when combined with new machine design rules and new production techniques. In order to establish these design rules, one must pay attention to electromagnetic loss characteristics of SMC material. In this work, five different series of iron based SMCs are produced and studied: (1) Pure iron powder with resin; (2) sintered iron based powders; (3) pure iron powder with additions of Zn-st and carbon; (4) iron based powder alloys (Fe,Nb,Si); (5) commercially available iron powder "Somaloy." The specimens were shaped as rectangular rods and characterized on a miniature single sheet tester which was calibrated to Epstein. The measured energy losses are analyzed following the loss separation theory of Bertotti, in which the total energy loss is decomposed into hysteresis loss, classical Foucault loss, and an excess loss component.

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

    NASA Astrophysics Data System (ADS)

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

    2014-04-01

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

  13. MAGNETIC HYSTERESIS AND DOMAIN STRUCTURE By R. S. TEBBLE,

    E-print Network

    Boyer, Edmond

    'examen des processus d'aimantation mis en jeu dans les champs faibles sur des substances polycrystallines of polycrystalline materials. LE JOURNAL DE PHYSIQUE ET LE RADIUM TOME 20, FÉVRIER 1959, This paper represents of the elementary processes involved in low field magnetic hyste- resis in polycrystalline materials such as iron

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

    DOEpatents

    Humphrey, Floyd B. (Bradfordwoods, PA)

    1987-01-01

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

  15. Simulations of magnetic hysteresis loops at high temperatures

    NASA Astrophysics Data System (ADS)

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

    2014-09-01

    The kinetic Monte-Carlo algorithm as well as standard micromagnetics are used to simulate MH loops of high anisotropy magnetic recording media at both short and long time scales over a wide range of temperatures relevant to heat-assisted magnetic recording. Microscopic parameters, common to both methods, were determined by fitting to experimental data on single-layer FePt-based media that uses the Magneto-Optic Kerr effect with a slow sweep rate of 700 Oe/s. Saturation moment, uniaxial anisotropy, and exchange constants are given an intrinsic temperature dependence based on published atomistic simulations of FePt grains with an effective Curie temperature of 680 K. Our results show good agreement between micromagnetics and kinetic Monte Carlo results over a wide range of sweep rates. Loops at the slow experimental sweep rates are found to become more square-shaped, with an increasing slope, as temperature increases from 300 K. These effects also occur at higher sweep rates, typical of recording speeds, but are much less pronounced. These results demonstrate the need for accurate determination of intrinsic thermal properties of future recording media as input to micromagnetic models as well as the sensitivity of the switching behavior of thin magnetic films to applied field sweep rates at higher temperatures.

  16. Simulations of magnetic hysteresis loops at high temperatures

    SciTech Connect

    Plumer, M. L.; Whitehead, J. P.; Fal, T. J. [Department of Physics and Physical Oceanography, Memorial University of Newfoundland, St. John's, Newfoundland and Labrador A1B 3X7 (Canada); Ek, J. van [Western Digital Corporation, San Jose, California 94588 (United States); Mercer, J. I. [Department of Computer Science, Memorial University of Newfoundland, St. John's, Newfoundland and Labrador A1B 3X7 (Canada)

    2014-09-28

    The kinetic Monte-Carlo algorithm as well as standard micromagnetics are used to simulate MH loops of high anisotropy magnetic recording media at both short and long time scales over a wide range of temperatures relevant to heat-assisted magnetic recording. Microscopic parameters, common to both methods, were determined by fitting to experimental data on single-layer FePt-based media that uses the Magneto-Optic Kerr effect with a slow sweep rate of 700 Oe/s. Saturation moment, uniaxial anisotropy, and exchange constants are given an intrinsic temperature dependence based on published atomistic simulations of FePt grains with an effective Curie temperature of 680 K. Our results show good agreement between micromagnetics and kinetic Monte Carlo results over a wide range of sweep rates. Loops at the slow experimental sweep rates are found to become more square-shaped, with an increasing slope, as temperature increases from 300 K. These effects also occur at higher sweep rates, typical of recording speeds, but are much less pronounced. These results demonstrate the need for accurate determination of intrinsic thermal properties of future recording media as input to micromagnetic models as well as the sensitivity of the switching behavior of thin magnetic films to applied field sweep rates at higher temperatures.

  17. Experimental measurement and calculation of losses in planar radial magnetic bearings

    NASA Technical Reports Server (NTRS)

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

    1994-01-01

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

  18. Experimental measurement and calculation of losses in planar radial magnetic bearings

    NASA Astrophysics Data System (ADS)

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

    1994-05-01

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

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

    SciTech Connect

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

    1992-01-01

    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.

  20. The consequences of similarity of hysteresis loops for interpreting magnetic particle systems

    NASA Astrophysics Data System (ADS)

    Ruta, Sergiu; Hovorka, Ondrej; Booth, Ryan; Majetich, Sara; Chantrell, Roy

    2014-03-01

    One of the challenges in understanding interacting magnetic particle (MP) assemblies is the interpretation of their physical parameters from magnetization measurements. A common framework has been based on the Langevin function approach, applicable in the super-paramagnetic limit of weakly interacting MPs . If interactions are significant or in case of thermally blocked MPs the issue becomes complicated by the presence of memory effects and hysteresis, and the question of uniqueness of parameter identification arises. To study this question, we consider a kinetic Monte-Carlo model of dipolar interacting Stoner-Wohlfarth MP, including volume and anisotropy distributions. By applying the grid search methods combined with the least squares fitting approach we map the parameter regions of hysteresis loops indistinguishable within a statistical confidence. This allows to show that a unique extraction of model parameters is indeed possible only in a certain range of MP concentrations and temperatures. Thus the hysteresis loop similarity prohibits a reliable parameter identification - being a fundamental issue that may potentially be resolved only by devising different measurements protocols.

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

    NASA Astrophysics Data System (ADS)

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

    2013-07-01

    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.

  2. Step-induced magnetic-hysteresis anisotropy in ferromagnetic thin films D. Zhao, Feng Liu,a)

    E-print Network

    Liu, Feng

    of Physics. DOI: 10.1063/1.1433179 The magnetic properties of ferromagnetic thin films and multilayers haveStep-induced magnetic-hysteresis anisotropy in ferromagnetic thin films D. Zhao, Feng Liu,a) D. L dependence on film thickness. The simulations also suggest that the mechanism for the magnetization reversal

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

    Microsoft Academic Search

    F. Fiorillo; A. M. Rietto

    1990-01-01

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

  4. Effect of Magnetic Hysteresis of the Solid Phase on the Rheological Properties of Mr Fluids

    NASA Astrophysics Data System (ADS)

    de Vicente, J.; Durán, J. D. G.; Delgado, A. V.; González-Caballero, F.; Bossis, G.

    An experimental investigation is described concerning the effect of the existence of a remanent magnetization of the dispersed particles on the rheological properties of magnetorheological fluids (MRF). Two MRF's were used: (1) solid phase: cobalt ferrite particles + silica gel (1.5% w/w) liquid phase: silicone oil (viscosity 20 mPa.s) and (2) solid phase: carbonyl iron + silica gel; liquid phase; silicone oil. The cobalt ferrite particles were synthetized as monodisperse colloidal spheres with an average diameter of 850 nm. The dependence of the dimensionless shear stress (?*/?) vs. Mason number (Mn) fails to scale when a ``magnetorheological hysteresis procedure'' is followed, specially for the higher volume fractions used (~ 7.5%). The yield stress (?y) is first estimated from successive rheograms obtained decreasing the external field (H0) values for different ?. A more precise determination can be done by applying a stress ramp in the oscillatory regime. The critical stress amplitude (?c) needed to exceed the viscoelastic linear region (VLR) is obtained. It is found that both ?y and ?c strongly depend on the magnetic history of the sample. As expected, the previous results were not obtained in a classical MRF of carbonyl iron particles since they do not present magnetic hysteresis. We conclude that cobalt ferrite suspensions are an other kind of MRF which works at low fields (0 - 17.8 kA/m) with the opposite effect: decrease of the yield stress with the field. This property can be improved using particles with stronger remanent magnetization.

  5. Hysteresis Simulation

    NSDL National Science Digital Library

    Paul Houle

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

  6. Hysteresis Analysis and Positioning Control for a Magnetic Shape Memory Actuator

    PubMed Central

    Lin, Jhih-Hong; Chiang, Mao-Hsiung

    2015-01-01

    Magnetic shape memory alloys (MSM alloys), a new kind of smart materials, have become a potential candidate in many engineering fields. MSMs have the advantage of bearing a huge strain, much larger than other materials. In addition, they also have fast response. These characteristics make MSM a good choice in micro engineering. However, MSMs display the obvious hysteresis phenomenon of nonlinear behavior. Thus the difficulty in using the MSM element as a positioning actuator is increased due to the hysteresis. In this paper, the hysteresis phenomenon of the MSM actuator is analyzed, and the closed-loop positioning control is also implemented experimentally. For that, a modified fuzzy sliding mode control (MFSMC) is proposed. The MFSMC and the PID control are used to design the controllers for realizing the positioning control. The experimental results are compared under different experimental conditions, such as different frequency, amplitude, and loading. The experimental results show that the precise positioning control of MFSMC can be achieved satisfactorily. PMID:25853405

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

    NASA Technical Reports Server (NTRS)

    Wasilewski, P.

    1972-01-01

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

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

    SciTech Connect

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

    1983-01-01

    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.

  9. The effect of surface grain reversal on the AC losses of sintered Nd-Fe-B permanent magnets

    NASA Astrophysics Data System (ADS)

    Moore, Martina; Roth, Stefan; Gebert, Annett; Schultz, Ludwig; Gutfleisch, Oliver

    2015-02-01

    Sintered Nd-Fe-B magnets are exposed to AC magnetic fields in many applications, e.g. in permanent magnet electric motors. We have measured the AC losses of sintered Nd-Fe-B magnets in a closed circuit arrangement using AC fields with root mean square-values up to 80 mT (peak amplitude 113 mT) over the frequency range 50 to 1000 Hz. Two magnet grades with different dysprosium content were investigated. Around the remanence point the low grade material (1.7 wt% Dy) showed significant hysteresis losses; whereas the losses in the high grade material (8.9 wt% Dy) were dominated by classical eddy currents. Kerr microscopy images revealed that the hysteresis losses measured for the low grade magnet can be mainly ascribed to grains at the sample surface with multiple domains. This was further confirmed when the high grade material was subsequently exposed to DC and AC magnetic fields. Here a larger number of surface grains with multiple domains are also present once the step in the demagnetization curve attributed to the surface grain reversal is reached and a rise in the measured hysteresis losses is evident. If in the low grade material the operating point is slightly offset from the remanence point, such that zero field is not bypassed, its AC losses can also be fairly well described with classical eddy current theory.

  10. Modeling the effects of nanosized precipitates on magnetic hysteresis and Barkhausen effect signal

    NASA Astrophysics Data System (ADS)

    Lo, C. C. H.

    2012-04-01

    A model has been developed for describing the effects of randomly distributed precipitates on magnetic hysteresis and Barkhausen emissions based on a hysteretic-stochastic process model of domain wall dynamics. The pinning of magnetic domain walls by spherical precipitates is described in terms of the pinning strength, which is proportional to the number density and cross-sectional area of the precipitates, and of the interaction range, which depends on the particle spacing and grain size. The model was used to simulate hysteresis loops and Barkhausen effect signals of a series of thermally aged FeCu samples with different number densities and sizes of Cu-rich precipitates. The linear dependence of the coercivity on the sample hardness was reproduced in the simulations. The rms values and pulse height distributions of the measured and modeled Barkhausen signals show similar dependence on the aging time, which can be interpreted by considering the effects of varying the precipitate size and spacing on the strength and interaction range of domain wall pinning.

  11. Magnetic Biasing of a Ferroelectric Hysteresis Loop in a Multiferroic Orthoferrite

    NASA Astrophysics Data System (ADS)

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

    2014-01-01

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

  12. Magnetic biasing of a ferroelectric hysteresis loop in a multiferroic orthoferrite.

    PubMed

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

    2014-01-24

    In a multiferroic orthoferrite Dy0.7Tb0.3FeO3, which shows electric-field-(E-)driven magnetization (M) reversal due to a tight clamping between polarization (P) and M, a gigantic effect of magnetic-field (H) biasing on P-E hysteresis loops is observed in the case of rapid E sweeping. The magnitude of the bias E field can be controlled by varying the magnitude of H, and its sign can be reversed by changing the sign of H or the relative clamping direction between P and M. The origin of this unconventional biasing effect is ascribed to the difference in the Zeeman energy between the +P and -P states coupled with the M states with opposite sign. PMID:24484164

  13. Force of Adhesion Upon Loss of Contact Angle Hysteresis: When a Liquid Behaves Like a Solid

    NASA Astrophysics Data System (ADS)

    Escobar, Juan V.; Castillo, Rolando

    2013-11-01

    The theoretically predicted vanishment of the macroscopic contact angle hysteresis is found experimentally along with a small but finite force of adhesion (FAd?-0.5?N) that, unexpectedly, is independent of the history of the preload. Our results agree with the prediction of a model in which the surface tension of the liquid provides the counterpart of the restoring force of an elastic solid, evidencing that the dewetting of a liquid in the absence of strong pinning points is equivalent to the detachment of an elastic solid.

  14. Magnetic properties and loss separation in iron-silicone-MnZn ferrite soft magnetic composites

    SciTech Connect

    Wu, Shen; Sun, Aizhi; Xu, Wenhuan; Zou, Chao; Yang, Jun; Dong, Juan [School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing (China)

    2013-12-16

    This paper investigates the magnetic and structural properties of iron-based soft magnetic composites coated with silicone-MnZn ferrite hybrid. The organic silicone resin was added to improve the flexibility of the insulated iron powder and causes better adhesion between particles to increase the mechanical properties. Scanning electron microscopy and distribution maps show that the iron particle surface is covered with a thin layer of silicone-MnZn ferrite. Silicone-MnZn ferrite coated samples have higher permeability when compared with the non-magnetic silicone resin coated compacts. The real part of permeability increases by 34.18% when compared with the silicone resin coated samples at 20 kHz. In this work, a formula for calculating the total loss component by loss separation method is presented and finally the different parts of total losses are calculated. The results show that the eddy current loss coefficient is close to each other for the silicone-MnZn ferrite, silicone resin and MnZn ferrite coated samples (0.0078hysteresis loss coefficient is lower for the silicone-MnZn ferrite coated sample (k{sub 2} =1.4058) in comparison with other samples.

  15. Magnetic properties and loss separation in iron-silicone-MnZn ferrite soft magnetic composites

    NASA Astrophysics Data System (ADS)

    Wu, Shen; Sun, Aizhi; Xu, Wenhuan; Zou, Chao; Yang, Jun; Dong, Juan

    2013-12-01

    This paper investigates the magnetic and structural properties of iron-based soft magnetic composites coated with silicone-MnZn ferrite hybrid. The organic silicone resin was added to improve the flexibility of the insulated iron powder and causes better adhesion between particles to increase the mechanical properties. Scanning electron microscopy and distribution maps show that the iron particle surface is covered with a thin layer of silicone-MnZn ferrite. Silicone-MnZn ferrite coated samples have higher permeability when compared with the non-magnetic silicone resin coated compacts. The real part of permeability increases by 34.18% when compared with the silicone resin coated samples at 20 kHz. In this work, a formula for calculating the total loss component by loss separation method is presented and finally the different parts of total losses are calculated. The results show that the eddy current loss coefficient is close to each other for the silicone-MnZn ferrite, silicone resin and MnZn ferrite coated samples (0.0078hysteresis loss coefficient is lower for the silicone-MnZn ferrite coated sample (k2 =1.4058) in comparison with other samples.

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

    NASA Astrophysics Data System (ADS)

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

    2013-03-01

    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. 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. This work is supported by the Advanced Research Projects Agency - Energy (ARPA-E) program grant number DE-AR0000123.

  17. A New Magnetic-Field Electron-Irradiation Treatment for Producing Low-Coersive-Force Rectangular Hysteresis Loops in Supermalloy

    Microsoft Academic Search

    D. I. Gordon; R. S. Sery

    1964-01-01

    True magnetic-annealing effects, i. e., hysteresis loops with high remanence and rectangularity, with no increase in coercive force, can be induced in flat ring samples of bulk .015 cm thick polycrystalline Supermalloy at low temperatures by a new electron-radiomagnetic treatment. This treatment is possible because radiation produces vacancies in excess of the thermal equilibrium number, and this excess of vacancies

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

    NASA Technical Reports Server (NTRS)

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

    1992-01-01

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

  19. Ac loss measurement of SSC dipole magnets

    SciTech Connect

    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

    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.

  20. Core losses in permanent magnet motors

    Microsoft Academic Search

    G. R. Slemon; X. Liu

    1990-01-01

    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

  1. Ac loss measurement of SSC dipole magnets

    Microsoft Academic Search

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

    1992-01-01

    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

  2. HYSTERESIS LOSSES ALONG OPEN TRANSFORMATIONS By G. BIORCI and A. FERRO (*),

    E-print Network

    Boyer, Edmond

    . The theoretical data have been computed for a soft iron specimen and for an Alnico type material. The latter have on the macroscopic magnetic state of the specimen, but should be an intrisic property of the material. All the hyste of an arbitrary path of H if the magnetization curve and the saturation loop are known, can be extended to compute

  3. Study of thermal ageing behaviour of Fe-Cr model alloys by magnetic hysteresis loop technique

    NASA Astrophysics Data System (ADS)

    Mohapatra, J. N.; Kamada, Y.; Kikuchi, H.; Kobayashi, S.; Echigoya, J.; Park, D. G.; Cheong, Y. M.

    2011-01-01

    Fe-Cr alloys with different Cr content (5-20 wt. %) were prepared by arc melting technique. The alloys were solution annealed at 1050 oC/ 2h and air quenched and then tempered at 750 oC/ 1h followed by air cooling. Thermal ageing was carried at 475 oC for various lengths of time up to 1000 hours (hrs) to produce thermal embrittlement. The hardness and coercivity of Fe-20% Cr alloys were increased and the remanence was decreased, being due to the precipitation of Cr-rich a' phase and their subsequent growth. In Fe-15% Cr and Fe-10% Cr alloys, it was found that the coercivity decreased at the initial ageing period and then increased subsequently due to the competing effect of recovery of dislocations and precipitation of Cr rich phase. The change in magnetic properties in Fe-5% Cr alloy was different than other alloys since it was within the solubility limit of Cr in Fe. A linear relationship was found between the coercivity and hardness in Fe-20% Cr alloy, indicating that Magnetic Hysteresis Loop (MHL) technique would be a good tool for the Non-Destructive Evaluatiion (NDE) of embrittlement in Fe-Cr alloys.

  4. Experimental study of magnetization AC loss in MgB2 wires and cables with non-magnetic sheath

    NASA Astrophysics Data System (ADS)

    Ková?, Ján; Šouc, Ján; Ková?, Pavol; Hušek, Imrich; Gömöry, Fedor

    2013-12-01

    The influence of MgB2 wires design on the magnetization AC loss was studied. AC loss in external AC magnetic field perpendicular to the wire axis was measured in the temperature range from 18 K up to 40 K and at the frequencies of 72 Hz and 144 Hz, respectively. For this purpose the experimental apparatus combining magnetization measurement system and non-magnetic vacuum vessel with two-stage crycooler for sample cooling has been used. To clarify the influence of wire architecture on the AC loss in non-magnetic GlidCop sheathed MgB2 composites experiments on a single-core, 30-filament un-twisted and also twisted samples were performed. MgB2 cables containing 7 mono-core strands and 30 filament strands were also measured. While in the cable containing single core strands the hysteresis loss was dominant, in the un-twisted wire and the cable with un-twisted filaments the coupling loss prevailed. The effect of decoupling was observed in all twisted filamentary wires. The obtained results show that in 7 strands cable the AC loss of strands is crucial to the overall AC loss of a cable.

  5. Modelling of hysteresis in thin superconducting screens for mixed-mu suspension systems

    SciTech Connect

    Asher, G.M.; Williams, J.T.; Walters, C.R.; Joyce, H.; Paul, R.J.A.

    1982-03-01

    Mixed-mu levitation is the principle whereby iron is levitated in a magnetic field and stabilized by the proximity of diamagnetic superconducting screens. In a dynamic environment, the screens are subject to changing magnetic fields thus causing hysteresis losses in the superconducting material. This paper is concerned with the modeling of such hysteresis. A finite difference approximation to the current and field distributions is employed, the current distribution being made consistent with critical current values by iteration. Square and disc shaped screen samples are studied and hysteresis curves computed. It is shown that the method represents a fair approximation to the hysteresis behavior of thin superconducting screens. 8 refs.

  6. Mass loss from warm giants: Magnetic effects

    NASA Technical Reports Server (NTRS)

    Mullan, D. J.

    1980-01-01

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

  7. Sensorineural Hearing Loss after Magnetic Resonance Imaging

    PubMed Central

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

    2013-01-01

    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. PMID:23844303

  8. Kinetic effects on double hysteresis in spin crossover molecular magnets analyzed with first order reversal curve diagram technique

    NASA Astrophysics Data System (ADS)

    Stan, Raluca-Maria; Gaina, Roxana; Enachescu, Cristian; Tanasa, Radu; Stancu, Alexandru; Bronisz, Robert

    2015-05-01

    In this paper, we analyze two types of hysteresis in spin crossover molecular magnets compounds in the framework of the First Order Reversal Curve (FORC) method. The switching between the two stable states in these compounds is accompanied by hysteresis phenomena if the intermolecular interactions are higher than a threshold. We have measured the static thermal hysteresis (TH) and the kinetic light induced thermal hysteresis (LITH) major loops and FORCs for the polycrystalline Fe(II) spin crossover compound [Fe1-xZnx(bbtr)3](ClO4)2 (bbtr = 1,4-di(1,2,3-triazol-1-yl)butane), either in a pure state (x = 0) or doped with Zn ions (x = 0.33) considering different sweeping rates. Here, we use this method not only to infer the domains distribution but also to disentangle between kinetic and static components of the LITH and to estimate the changes in the intermolecular interactions introduced by dopants. We also determined the qualitative relationship between FORC distributions measured for TH and LITH.

  9. Core loss in buried magnet permanent magnet synchronous motors

    Microsoft Academic Search

    R. Schifer; T.A. Lipo

    1989-01-01

    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

  10. Ac loss measurement of SSC dipole magnets

    Microsoft Academic Search

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

    1992-01-01

    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

  11. Application of Barkhausen noise and ferromagnetic hysteresis for magnetic non-destructive evaluation of multiphase composites and structures

    NASA Astrophysics Data System (ADS)

    Prabhu Gaunkar, Neelam; Kypris, Orfeas; Nlebedim, Cajetan; Jiles, David

    2015-03-01

    Composite ferromagnetic materials with multiple magnetic phases are increasingly being used in applications such as magnetic data storage, magnetic sensors and actuators and exchange-spring magnets. These materials occur in single or multiphase conditions and can undergo phase changes over time or during processing. For these materials, we examine the interrelation between ferromagnetic hysteresis, Barkhausen noise and the material microstructure. We observe that the presence of a second phase in these materials can be detected with the help of Barkhausen noise signals due to the occurrence of additional peaks in the magnetization envelope. This behavior in the magnetic response can serve as a tool for non-destructive evaluation of ferromagnetic materials for which phase constitution and phase changes affect the structural performance.

  12. Experimental study and theoretical interpretation of hysteresis loops and Henkel plots in soft magnetic materials

    Microsoft Academic Search

    V. Basso; M. Lo Bue; A. Magni; G. Ummarino; G. Bertotti

    1994-01-01

    In this paper we discuss an application of the moving Preisach model (MPM) and the zero-temperature Sherrington-Kirkpatrick spin-glass model (SKM) to the interpretation of hysteresis phenomena in soft materials, with particular attention to the analogies and differences between the models. Both models are compared with hysteresis measurements performed on strips of amorphous Fe-B-Si alloy. We describe experimental data using the

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

    NASA Astrophysics Data System (ADS)

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

    2013-06-01

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

  14. Hysteresis in the Sky

    E-print Network

    Choudhury, Sayantan

    2015-01-01

    Hysteresis is a phenomenon occurring naturally in several magnetic and electric materials in condensed matter physics. When applied to cosmology, aka cosmological hysteresis, has interesting and vivid implications in the scenario of a cyclic bouncy universe. Most importantly, this physical prescription can be treated as an alternative proposal to inflationary paradigm. Cosmological hysteresis is caused by the asymmetry in the equation of state parameter during expansion and contraction phase of the universe, due to the presence of a single scalar field. This process is purely thermodynamical in nature, results in a non-vanishing hysteresis loop integral $(\\oint pdV)$ in cosmology. When applied to variants of modified gravity models -1) Dvali-Gabadadze-Porrati (DGP) brane world gravity, 2) Cosmological constant dominated Einstein gravity, 3) Loop Quantum Gravity (LQG), 4) Einstien-Gauss-Bonnet brane world gravity and 5) Randall Sundrum single brane world gravity (RSII), under certain circumstances, this phenom...

  15. Low-loss energy storage flywheel

    NASA Technical Reports Server (NTRS)

    Evans, H. E.; Studer, P. A.

    1977-01-01

    Magnetically-levitated, ironless-armature spokeless rotor is used. Ironless armature construction eliminates core losses due to hysteresis and eddy currents. Device combines features of homopolar salient poles and stationary ironless electronically commutated armature.

  16. Magnetic anisotropy, unusual hysteresis and putative “up-up-down” magnetic structure in EuTAl4Si2 (T = Rh and Ir)

    PubMed Central

    Maurya, Arvind; Thamizhavel, A.; Dhar, S. K.; Bonville, P.

    2015-01-01

    We present detailed investigations on single crystals of quaternary EuRhAl4Si2 and EuIrAl4Si2. The two compounds order antiferromagnetically at TN1?=?11.7 and 14.7?K, respectively, each undergoing two magnetic transitions. The magnetic properties in the ordered state present a large anisotropy despite Eu2+being an S-state ion for which the single-ion anisotropy is expected to be weak. Two features in the magnetization measured along the c-axis are prominent. At 1.8?K, a ferromagnetic-like jump occurs at very low field to a value one third of the saturation magnetization (1/3?M0) followed by a wide plateau up to 2 T for Rh and 4 T for Ir-compound. At this field value, a sharp hysteretic spin-flop transition occurs to a fully saturated state (M0). Surprisingly, the magnetization does not return to origin when the field is reduced to zero in the return cycle, as expected in an antiferromagnet. Instead, a remnant magnetization 1/3 M0 is observed and the magnetic loop around the origin shows hysteresis. This suggests that the zero field magnetic structure has a ferromagnetic component, and we present a model with up to third neighbor exchange and dipolar interaction which reproduces the magnetization curves and hints to an “up-up-down” magnetic structure in zero field. PMID:26156410

  17. Modeling of iron losses of permanent-magnet synchronous motors

    Microsoft Academic Search

    Chunting Mi; Gordon R. Slemon; Richard Bonert

    2003-01-01

    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

  18. Loss minimization control of permanent magnet synchronous motor drives

    Microsoft Academic Search

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

    1994-01-01

    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

  19. Numerical analysis of rotation loss of superconducting magnetic bearing

    Microsoft Academic Search

    K. Demachi; A. Miura; T. Uchimoto; K. Miya

    2001-01-01

    The degradation of levitation force and rotation speed is one of the most significant problems for the practical use of superconducting magnetic bearings (SMB) for flywheel energy storage systems. The rotation loss is caused by the AC magnetic field due to the inhomogeneous distribution of magnetic flux density of the permanent magnet (PM) rotor. A simulation method has been developed

  20. An H-formulation-based three-dimensional hysteresis loss modelling tool in a simulation including time varying applied field and transport current: the fundamental problem and its solution

    NASA Astrophysics Data System (ADS)

    Stenvall, A.; Lahtinen, V.; Lyly, M.

    2014-10-01

    When analytic solutions are not available, finite-element-based tools can be used to simulate hysteresis losses in superconductors with various shapes. A widely used tool for the corresponding magnetoquasistatic problem is based on the H-formulation, where H is the magnetic field intensity, eddy current model. In this paper, we study this type of tool in a three-dimensional simulation problem. We consider a case where we simultaneously apply both a time-varying external magnetic field and a transport current to a twisted wire. We show how the modelling decisions (air has high finite resistivity and applied field determines the boundary condition) affect the current density distribution along the wire. According to the results, the wire carries the imposed net current only on the boundary of the modelling domain, but not inside it. The current diffuses to the air and back to the boundary. To fix this problem, we present another formulation where air is treated as a region with 0 conductivity. Correspondingly, we express H in the air with a scalar potential and a cohomology basis function which considers the net current condition. As shown in this paper, this formulation does not fail in these so-called AC-AC (time varying transport current and applied magnetic field) simulations.

  1. Diagenetic alteration of natural Fe–Ti oxides identified by energy dispersive spectroscopy and low-temperature magnetic remanence and hysteresis measurements

    Microsoft Academic Search

    Melanie Dillon; Christine Franke

    2009-01-01

    Low-temperature (LT) magnetic remanence and hysteresis measurements, in the range 300–5K, were combined with energy dispersive spectroscopy (EDS) in order to characterize the magnetic inventory of strongly diagenetically altered sediments originating from the Niger deep-sea fan. We demonstrate the possibility of distinguishing between different compositions of members of the magnetite–ulvöspinel and ilmenite–hematite solid solution series on a set of five

  2. Evaluation of Ductile Cast Iron Microstructure by Magnetic Hysteresis and Barkhausen Noise Methods

    Microsoft Academic Search

    Oleksandr STUPAKOV; Tetsuya UCHIMOTO; Toshiyuki TAKAGI; Seyed Ali SANAEE; Ivan TOM

    The work investigates applicability of the magnetic hystere- sis and Barkhausen noise techniques for testing of ductile cast iron mi- crostructure. The measurements were performed on 4 series of difier- ent matrix structures with 5 samples in each series of difierent size of spheroidal graphite. The samples were magnetized by a single yoke at quasi-static regime; their magnetic fleld was

  3. Experimental observation of response to resonant magnetic perturbation and its hysteresis in LHD

    NASA Astrophysics Data System (ADS)

    Narushima, Y.; Sakakibara, S.; Ohdachi, S.; Suzuki, Y.; Watanabe, K. Y.; Nishimura, S.; Satake, S.; Huang, B.; Furukawa, M.; Takemura, Y.; Ida, K.; Yoshinuma, M.; Yamada, I.; The LHD Experiment Group

    2015-07-01

    The magnetic island in the large helical device (LHD) shows the dynamic behaviour of the healing/growth transition with the hysteretic behaviour. The thresholds of plasma beta and poloidal flow for island healing are larger than that for growth. The threshold of resonant magnetic perturbation (RMP) for healing is smaller than that for growth. Furthermore, thresholds of the amplitude of RMP depend on the magnetic axis position Rax in the LHD. The RMP threshold increases as the magnetic axis position Rax increases. The poloidal viscosity may be considered as a candidate to explain the experimental observation from the viewpoint of the relationship between the electromagnetic torque and the viscous torque.

  4. Eddy current losses in permanent magnets of the BLDC machine

    Microsoft Academic Search

    Damijan Miljavec; Bogomir Zidari?

    2007-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Garshelis, I. J.; Crevecoeur, G.

    2014-05-01

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

  6. Hysteresis nonlinearity identification by using RBF neural network approach

    Microsoft Academic Search

    Mohsen Firouzi; Saeed Bagheri Shouraki; Mohammad Reza Zakerzadeh

    2010-01-01

    In systems with hysteresis behavior like magnetic cores, Piezo actuators, Shape Memory Alloy(SMA), we essentially need an accurate modeling of hysteresis either for design or performance evaluation; also in some control applications accurate system identification is needed. One of the famous methods of Hysteresis modeling is Preisach model. In this numerical method hysteresis is modeled by linear combination of smaller

  7. Iron Loss and Magnet Eddy Current Loss Analysis of IPM Motors with Concentrated Windings

    NASA Astrophysics Data System (ADS)

    Yamazaki, Katsumi; Isoda, Yousuke

    In this paper, we investigate losses of interior permanent magnet motors with concentrated windings using the 3-D finite element method considering carrier harmonics of PWM inverters. The calculated results are compared with the measurement to verify the validity of the calculation. The motor with the distributed windings is also calculated to clarify the difference of the main loss factors. The measured and calculated results agree well. It is clarified that the losses generated at the rotor core and magnets especially increase, whereas the harmonic iron losses generated at the stator decrease, in the case of the motor with concentrated windings.

  8. Iron loss analysis of Mn-Zn ferrite cores

    Microsoft Academic Search

    H. Saotome; Y. Sakaki

    1997-01-01

    Iron loss measurements of Mn-Zn ferrite cores up to the megahertz range are reported. Taking the dc magnetic hysteresis, the eddy, and displacement currents into account, magnetic and electric field distributions in the cores are computed with the cylindrical coordinates and Bessel functions. The computed iron loss due to the magnetic and electric fields is compared with the experimental value

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

    Microsoft Academic Search

    Michel Lajoie-Mazenc; Carlos Villanueva; Jean Hector

    1985-01-01

    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

  10. Effect of applied tensile stress on the hysteresis curve and magnetic domain structure of grain-oriented transverse Fe-3%Si steel

    NASA Astrophysics Data System (ADS)

    Perevertov, O.; Thielsch, J.; Schäfer, R.

    2015-07-01

    The effect of an elastic applied tensile stress on the quasistatic hysteresis curve and domain structure in conventional (110) [001] Fe-3%Si steel, cut transversely to the rolling direction, is studied. The magnetic domains and magnetization processes were observed by longitudinal Kerr microscopy at different levels of stress. It is shown that above 8 MPa the bulk hysteresis loop can be described with a good accuracy by the action of an effective field, which is the product of the stress and a function of magnetization. Domain observation reveals that the reasons for the effective field are demagnetizing fields due to the disappearance of supplementary domains at low applied field and the formation of different domain systems in different grains at low and moderate fields. The latter are caused by differences in grain sensitivity to stress depending on the degree of misorientation and grain boundary orientation. A decrease of the effective field above 1 T is connected with a transformation of all grains into the same domain system - the column pattern. The hysteresis loop behavior is qualitatively the same as for strips cut in rolling direction and for non-oriented strips.

  11. Physical interpretation of induction and frequency dependence of power losses in soft magnetic materials

    Microsoft Academic Search

    Giorgio Bertotti; Massimo Pasquale

    1992-01-01

    A loss model based on a dynamic generalization of the Preisach hysteresis model, in which the standard Preisach algorithm is coupled to an equation for the rate of change of the flux associated with each elementary Preisach loop, is presented. The model is able to predict loss features not explained by previous treatments and provides a general interpretative frame for

  12. On the frequency dependence of power losses in soft magnetic materials

    Microsoft Academic Search

    G. Dietzmann; M. Schaefer

    1992-01-01

    It is shown that a model of hysteresis relaxation is well suited to describe the frequency dependence of power losses in a Mn-Zn ferrite. In a nanocrystalline ribbon the power loss is determined, even at higher induction amplitudes, by the frequency dependence of the complex reversible permeability.

  13. A general model of losses in soft magnetic materials

    Microsoft Academic Search

    G. Bertotti; P. Mazzetti; G. P. Soardo

    1982-01-01

    A general magnetic loss model is presented which takes account with proper approximations of the spatial and temporal non-homogeneities and stochastic character of the elementary dissipative mechanisms. An expression is obtained in which dynamic losses in a lamination of thickness d are linked to the energy spectrum of the emf measured between two points on the sample surface at a

  14. Design of experiment for hysteresis loops measurement

    NASA Astrophysics Data System (ADS)

    Tu?ková, Michaela; Harman, Radoslav; Tu?ek, Pavel; Tu?ek, Ji?í

    2014-11-01

    Hysteresis loop measurements are frequently used to assess the magnetic quality of a nanomaterial under an external magnetic field. Based on the values of the hysteresis parameters, it is possible to decide whether the nanomaterial meets requirements of a given application. In this work, we present a new approach to the measurement of the hysteresis loop based on the theory of optimal experimental design. We show that the maximin efficient design leads to a reduction in the measurements costs when compared to the standard equispaced measurement design. Moreover, a significantly higher accuracy in the estimation of hysteresis parameters is reached within a broad range of plausible values. The functionality of the proposed approach is successfully tested considering real experimental data obtained from the hysteresis loop measurements of the ?-Fe2O3 phase. The measurement procedure can be easily adapted to any magnetic nanomaterial for which the values of its hysteresis parameters are to be determined.

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

    SciTech Connect

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

    1992-01-01

    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.

  16. Passive magnetic bearing element with minimal power losses

    DOEpatents

    Post, Richard F. (Walnut Creek, CA)

    1998-01-01

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

  17. Passive magnetic bearing element with minimal power losses

    DOEpatents

    Post, R.F.

    1998-12-08

    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.

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

    SciTech Connect

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

    1992-05-01

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

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

    SciTech Connect

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

    1992-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2010-12-01

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

  1. Domain structure and magnetic losses in laminated magnetic circuits upon laser treatment

    NASA Astrophysics Data System (ADS)

    Pudov, V. I.; Dragoshanskii, Yu. N.

    2015-06-01

    Methods of optimizing the magnetic domain structure and functional characteristics of electrical-sheet anisotropic steel based on the Fe-Si alloy and the laminated magnetic circuits of transformers have been developed. The use of an efficient complex based on the local laser treatment and application of magnetically active electrically insulating coatings provided a significant reduction in the magnetic losses in the sheets of the steel (by 18-22%) and in the magnetic circuits of transformers (by 9-14%).

  2. Advances in core loss calculations for magnetic materials

    NASA Technical Reports Server (NTRS)

    Triner, J. E.

    1982-01-01

    A new analytical technique which predicts the basic magnetic properties under various operating conditions encountered in state-of-the-art dc-ac/dc converters is discussed. Using a new flux-controlled core excitation circuit, magnetic core characteristics were developed for constant values of ramp flux (square wave voltage excitation) and frequency. From this empirical data, a mathematical loss characteristics equation is developed to analytically predict the specific core loss of several magnetic materials under various waveform excitation conditions. In addition, these characteristics show the circuit designer for the first time the direct functional relatonships between induction level and specific core loss as a function of the two key dc-dc converter operating parameters of input voltage and duty cycle.

  3. Magnetic circular dichroism in reflection electron energy loss spectroscopy?

    SciTech Connect

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

    1996-07-01

    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}

  4. Connection between microstructure and magnetic properties of soft magnetic materials

    Microsoft Academic Search

    G. Bertotti

    2008-01-01

    The magnetic behavior of soft magnetic materials is discussed with some emphasis on the connection between macroscopic properties and underlying micromagnetic energy aspects. It is shown that important conceptual gaps still exist in the interpretation of macroscopic magnetic properties in terms of the micromagnetic formulation. Different aspects of hysteresis modeling, power loss prediction and magnetic non-destructive evaluation are discussed in

  5. Triimidosulfonates as Acute Bite-Angle Chelates: Slow Relaxation of the Magnetization in Zero Field and Hysteresis Loop of a Co(II) Complex.

    PubMed

    Carl, Elena; Demeshko, Serhiy; Meyer, Franc; Stalke, Dietmar

    2015-07-01

    Starting from a polyimido sulfonate the four-coordinate, N,N'-chelated Co(II) complex [Co{(NtBu)3 SMe}2 ] (1) was synthesized, and its molecular structure was elucidated by single-crystal X-ray structural analysis. The acute N-Co-N bite angle imposed by the N,N'-chelating ligand (NtBu)3 SMe(-) leads to pronounced C2v distortion of the tetrahedral coordination environment and thus to high anisotropy of the Co(II) ion (D?-58?cm(-1) ), favorable for single-molecule-magnet (SMM) properties. Magnetic measurements revealed a high barrier to spin reversal (Ueff =75?cm(-1) ) that gives rise to the observation of slow relaxation of the magnetization in zero field and a hysteresis loop at 2?K for this unique complex. PMID:26043416

  6. AC magnetic field losses in BSCCO-2223 superconducting tapes

    SciTech Connect

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

    1997-09-01

    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.

  7. An accurate experimental apparatus for measuring losses in magnetic components

    Microsoft Academic Search

    Shri Sridhar; R. M. Wolf; W. G. Odendaal

    1999-01-01

    An experimental apparatus has been designed and built to accurately measure losses in magnetic components. The apparatus consists of a highly conductive pedestal on which the device under test (DUT) is mounted. A heat flux sensor placed under the pedestal is used to measure the total heat generated in the DUT. The pedestal along with the heat-flux sensor is placed

  8. Magnetically controlled mass loss from extrasolar planets in close orbits

    E-print Network

    Owen, James E

    2014-01-01

    We consider the role magnetic fields play in guiding and controlling mass-loss via evaporative outflows from exoplanets that experience UV irradiation. First we present analytic results that account for planetary and stellar magnetic fields, along with mass-loss from both the star and planet. We then conduct series of numerical simulations for gas giant planets, and vary the planetary field strength, background stellar field strength, UV heating flux, and planet mass. These simulations show that the flow is magnetically controlled for moderate field strengths and even the highest UV fluxes, i.e., planetary surface fields $B_P\\gtrsim 0.3$ gauss and fluxes $F_{UV}\\sim10^{6}$ erg s$^{-1}$. We thus conclude that outflows from all hot Jupiters with moderate surface fields are magnetically controlled. The inclusion of magnetic fields highly suppresses outflow from the night-side of the planet. Only the magnetic field lines near the pole are open and allow outflow to occur. The fraction of open field lines depends s...

  9. Extended frequency analysis of the loss under rotating induction excitation in Soft Magnetic Composites (SMC)

    E-print Network

    Paris-Sud XI, Université de

    in such machines, an isotropic soft magnetic material is15 needed. Contrary to laminated materials, Soft Magnetic1 Extended frequency analysis of the loss under rotating induction excitation in Soft Magnetic.1063/1.3675177 #12;2 Abstract1 This article reports new results about the magnetic loss in Soft Magnetic Composites

  10. Spin flip loss in magnetic storage of ultracold neutrons

    E-print Network

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

    2013-07-19

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

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

    NASA Astrophysics Data System (ADS)

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

    2012-08-01

    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.

  12. Magnetic-field dependent trap loss of ultracold metastable helium

    E-print Network

    Borbely, J S; Knoop, S; Vassen, W

    2011-01-01

    We have experimentally studied the magnetic-field dependence of the decay of a Bose-Einstein condensate of metastable 4He atoms confined in an optical dipole trap, for atoms in the m=+1 and m=-1 magnetic substates, and up to 450 G. Our measurements confirm long-standing calculations of the two-body loss rate coefficient that show an increase above 50 G. We demonstrate that for m=-1 atoms, decay is due to three-body recombination only, with a three-body loss rate coefficient of 6.5(0.4)(0.6)10^(-27)cm^6s^(-1), which is interesting in the context of universal few-body theory. We have also searched for a recently-predicted d-wave Feshbach resonance, but did not observe it.

  13. Magnetic-field dependent trap loss of ultracold metastable helium

    E-print Network

    J. S. Borbely; R. van Rooij; S. Knoop; W. Vassen

    2011-11-24

    We have experimentally studied the magnetic-field dependence of the decay of a Bose-Einstein condensate of metastable 4He atoms confined in an optical dipole trap, for atoms in the m=+1 and m=-1 magnetic substates, and up to 450 G. Our measurements confirm long-standing calculations of the two-body loss rate coefficient that show an increase above 50 G. We demonstrate that for m=-1 atoms, decay is due to three-body recombination only, with a three-body loss rate coefficient of 6.5(0.4)(0.6)10^(-27)cm^6s^(-1), which is interesting in the context of universal few-body theory. We have also searched for a recently-predicted d-wave Feshbach resonance, but did not observe it.

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

    PubMed

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

    2013-10-22

    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

  15. Investigation of the Impact of Magnetic Permeability and Loss of Magnetic Composite Materials on RFID and RF Passives

    E-print Network

    Tentzeris, Manos

    Investigation of the Impact of Magnetic Permeability and Loss of Magnetic Composite Materials statistical tools, and it is found that the permeability of a practical magnetic composite can enable, statistical tools, hybrid optimization, fabrication tolerances, microstrip patch antenna I. INTRODUCTION

  16. Early pregnancy loss and exposure to 50-Hz magnetic fields

    SciTech Connect

    Juutilainen, J.; Matilainen, P.; Saarikoski, S.; Laeaerae Esuo; Suonio, S. (Univ. of Kuopio (Finland))

    1993-01-01

    The possibility of an association of early pregnancy loss (EPL) with residential exposure to ELF magnetic fields was investigated in a case-control study. Eighty-nine cases and 102 controls were obtained from the data of an earlier study aimed at investigating the occurrence of EPL in a group of women attempting to get pregnant. Magnetic-field exposure was characterized by measurements in residences. Strong magnetic fields were measured more often in case than in control residences. In an analysis based on fields measured at the front door, a cutoff score of 0.5 A/m (0.63 microT) resulted in an odds ratio of 5.1 (95% confidence interval 1.0-25). The results should be interpreted cautiously due to the small number of highly exposed subjects and other limitations of the data.

  17. Collisional trap losses of cold magnetically trapped Br atoms

    NASA Astrophysics Data System (ADS)

    Lam, J.; Rennick, C. J.; Softley, T. P.

    2014-12-01

    Near-threshold photodissociation of Br2 from a supersonic beam produces slow bromine atoms that are trapped in the magnetic-field minimum formed between two opposing permanent magnets. Here we quantify the dominant trap-loss rate due to collisions with two sources of residual gas: the background limited by the vacuum chamber base pressure and the carrier gas during the supersonic gas pulse. The loss rate due to collisions with residual Ar in the background follows pseudo-first-order kinetics and the bimolecular rate coefficient for collisional loss from the trap is determined by measurement of this rate as a function of the background Ar pressure. This rate coefficient is smaller than the total elastic collision rate coefficient, as it only samples those collisions that lead to trap loss, and is determined to be =(1.12 ±0.09 ) ×10-9cm3s-1 . The calculated differential cross section can be used with this value to estimate a trap depth of 293 ±24 mK . Carrier-gas collisions occur only during the tail of the supersonic beam pulse. Using the differential cross section verified by the background-gas collision measurements provides an estimate of the peak molecular-beam density of (3.0 ±0.3 ) ×1013cm-3 , in good agreement with the prediction of a simple supersonic expansion model. Finally, we estimate the trap-loss rate due to Majorana transitions to be negligible, owing to the relatively large trapped-atom phase-space volume.

  18. Simultaneous effects of surface spins: rarely large coercivity, high remanence magnetization and jumps in the hysteresis loops observed in CoFe2O4 nanoparticles

    NASA Astrophysics Data System (ADS)

    Xu, S. T.; Ma, Y. Q.; Zheng, G. H.; Dai, Z. X.

    2015-04-01

    Well-dispersed uniform cobalt ferrite nanoparticles were synthesized by thermal decomposition of a metal-organic salt in organic solvent with a high boiling point. Some of the nanoparticles were diluted in a SiO2 matrix and then the undiluted and diluted samples were characterized and their magnetic behavior explored. The undiluted and diluted samples exhibited maximum coercivity Hc of 23 817 and 15 056 Oe at 10 K, respectively, which are the highest values reported to date, and the corresponding ratios of remanence (Mr) to saturation (Ms) magnetization (Mr/Ms) were as high as 0.85 and 0.76, respectively. Interestingly, the magnetic properties of the samples changed at 200 K, which was observed in magnetic hysteresis M(H) loops and zero-field cooling curves as well as the temperature dependence of Hc, Mr/Ms, anisotropy, dipolar field, and the magnetic grain size. Below 200 K, both samples have large effective anisotropy, which arises from the surface spins, resulting in large Hc and Mr/Ms. Above 200 K, the effective anisotropy decreases because there is no contribution from surface spins, while the dipolar interaction increases, resulting in small Hc and Mr/Ms. Our results indicate that strong anisotropy and weak dipolar interaction tend to increase Hc and Mr/Ms, and also clarify that the jumps around H = 0 in M(H) loops can be attributed to the reorientation of surface spins. This work exposes the underlying mechanism in nanoscale magnetic systems, which should lead to improved magnetic performance.

  19. Simultaneous effects of surface spins: rarely large coercivity, high remanence magnetization and jumps in the hysteresis loops observed in CoFe2O4 nanoparticles.

    PubMed

    Xu, S T; Ma, Y Q; Zheng, G H; Dai, Z X

    2015-04-21

    Well-dispersed uniform cobalt ferrite nanoparticles were synthesized by thermal decomposition of a metal-organic salt in organic solvent with a high boiling point. Some of the nanoparticles were diluted in a SiO2 matrix and then the undiluted and diluted samples were characterized and their magnetic behavior explored. The undiluted and diluted samples exhibited maximum coercivity Hc of 23,817 and 15,056 Oe at 10 K, respectively, which are the highest values reported to date, and the corresponding ratios of remanence (Mr) to saturation (Ms) magnetization (Mr/Ms) were as high as 0.85 and 0.76, respectively. Interestingly, the magnetic properties of the samples changed at 200 K, which was observed in magnetic hysteresis M(H) loops and zero-field cooling curves as well as the temperature dependence of Hc, Mr/Ms, anisotropy, dipolar field, and the magnetic grain size. Below 200 K, both samples have large effective anisotropy, which arises from the surface spins, resulting in large Hc and Mr/Ms. Above 200 K, the effective anisotropy decreases because there is no contribution from surface spins, while the dipolar interaction increases, resulting in small Hc and Mr/Ms. Our results indicate that strong anisotropy and weak dipolar interaction tend to increase Hc and Mr/Ms, and also clarify that the jumps around H = 0 in M(H) loops can be attributed to the reorientation of surface spins. This work exposes the underlying mechanism in nanoscale magnetic systems, which should lead to improved magnetic performance. PMID:25787852

  20. Magnetic losses, critical currents and pinning in coated conductors

    NASA Astrophysics Data System (ADS)

    Ijaduola, Anota; Thompson, James; Christen, David; Feenstra, R.; Goyal, A.; Thieme, C. L. H.; Marken, K. R.

    2009-11-01

    The discovery of high temperature superconductors (HTS) in particular YBa2Cu3O7-? (YBCO) (Tc 92 K), sparked great interest in the use of HTS materials in practical applications such as transmission lines, motors and generators. Different techniques are used to fabricate these `coated conductors' from YBCO and other HTS. Ferromagnetic losses arise from the substrates that are used in the fabrication processes. I will talk about the studies we have done on these losses and also discuss the critical current (Jc) that flow in these coated conductors. On the other hand, exposing a type II superconductor to magnetic field generates vortices which are detrimental to the current carrying capabilities. These vortices have to be pinned (made immobile) in order to have significant and useful Jc flow in these conductors. I will discuss the different pining mechanisms used in these coated conductors and particularly focus on the pinning features we studied on some set of YBCO thin films.

  1. Magnetic circular dichroism in electron energy loss spectrometry.

    PubMed

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

    2008-02-01

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

  2. Effective Magnetic Parameters in the Presence of Hysteresis-based effective parameters (leHys and AeHys)

    E-print Network

    Vu-Quoc, Loc

    of a toroid with any practical kr [3]. For component-level design, lumped parameters, such as magnetic flux. INTRODUCTION Fundamental modeling of magnetic components usually starts at the field level between B and H. Magnetic designers often deal with the nonuniformity issue by assuming that B and H take

  3. A high-performance hysteresis loop tracer

    Microsoft Academic Search

    Tadeusz Kulik; Howard T. Savage; Antonio Hernando

    1993-01-01

    A high-performance and inexpensive hysteresis loop tracer has been developed to measure quasistatic (0.02 Hz or less) hysteresis loops of soft ferromagnetic materials. It was applied very successfully to measure straight pieces of amorphous and nanocrystalline ribbons and amorphous wires. Especially high-magnetic-field resolution is required when nanocrystalline ferromagnets and amorphous wires are measured. Nanocrystalline materials exhibit very low coercivity (Hc=0.1–0.5

  4. Mathematical modelling of transformer sheet steel magnetization

    NASA Astrophysics Data System (ADS)

    Jagie??o, A. St.

    1996-07-01

    A mathematical model for magnetizing ferromagnetic materials in sheet form is presented. The equations presented constitute a mathematical description of the processes occurring during magnetization by an external, uniform, planar magnetic field parallel to the sheet surface. With regard to the energy balance, the eddy current losses permit us to analyse the dynamic features of the hysteresis loop.

  5. An automated measurement system for core loss characterization in high frequency magnetic components

    Microsoft Academic Search

    Adalberto J. Batista; J. C. S. Fagundes; Philippe Viarouge

    1998-01-01

    This paper describes an automated measurement system for core loss characterization in high-frequency magnetic components. This system can accomplish these aims, within specified magnetic induction and frequency ranges, and at different temperatures, with high accuracy, due to the techniques used in the acquisition and computation of the waveforms involved in loss calculation. The core loss characterization, obtained by fitting the

  6. The extrinsic hysteresis behavior of dilute binary ferrofluids.

    PubMed

    Lin, Lihua; Li, Jian; Lin, Yueqiang; Liu, Xiaodong; Chen, Longlong; Li, Junming; Li, Decai

    2014-10-01

    We report on the magnetization behavior of dilute binary ferrofluids based on ?-Fe(2)O(3)/Ni(2)O(3) composite nanoparticles (A particles), with diameter about 11 nm, and ferrihydrite (Fe(5)O(7)(OH) ?4H2O) nanoparticles (B particles), with diameter about 6 nm. The results show that for the binary ferrofluids with A-particle volume fraction ?(A) = 0.2% and B-particle volume fractions ?(B) = 0.1% and ?(B) = 0.6%, the magnetization curves exhibit quasi-magnetic hysteresis behavior. The demagnetizing curves coincide with the magnetizing curves at high fields. However, for single ?-Fe(2)O(3)/Ni(2)O(3) ferrofluids with ?(A) = 0.2% and binary ferrofluids with ?(A) = 0.2% and ?(B) = 1.0%, the magnetization curves do not behave in this way. Additionally, at high field (750 kA/m), the binary ferrofluid with ?(B) = 1.0% has the smallest magnetization. From the model-of-chain theory, the extrinsic hysteresis behavior of these samples is attributed to the field-induced effects of pre-existing A particle chains, which involve both Brownian rotation of the chains'moments and a Néel rotation of the particles' moments in the chains. The loss of magnetization for the ferrofluids with ?(B) = 1.0% is attributed to pre-existing ring-like A-particle aggregates. These magnetization behaviors of the dilute binary ferrofluids not only depend on features of the strongly magnetic A-particle system, but also modifications of the weaker magnetic B-particle system. PMID:25365919

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

    Microsoft Academic Search

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

    1973-01-01

    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 .

  8. Experimentally determined rotor power losses in homopolar and heteropolar magnetic bearings

    Microsoft Academic Search

    M. E. F. Kasarda; P. E. Allaire; P. M. Norris; C. Mastrangelo; E. H. Maslen

    1999-01-01

    The identification of parameters that dictate the magnitude of rotor power losses in radial magnetic bearings is very important for many applications. Low loss performance of magnetic bearings in aerospace equipment such as jet engines and flywheel energy storage systems is especially critical. Two basic magnetic bearing designs are employed in industrial practice today: the homopolar design, where the flux

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

    Microsoft Academic Search

    Katsumi Yamazaki; Yoshiaki Seto

    2006-01-01

    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,

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

    NASA Technical Reports Server (NTRS)

    Niedra, Janis M.; Schwarze, Gene E.

    1999-01-01

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

  11. Applications of amorphous soft magnetic materials

    Microsoft Academic Search

    H. Warlimont; R. Boll

    1982-01-01

    An introduction is given to melt-quenched amorphous alloys suitable as soft magnetic materials based on their saturation magnetization, hysteresis loop, core loss, elasto-magnetic and technological properties. After a survey of potential applications, the following examples are treated in particular: power distribution transformers, 400 Hz transformers, components for switched-mode power supplies, flexible magnetic shielding, elasto-magnetic transducers, variable delay lines, and magnetic

  12. Unusual magnetic hysteresis and the weakened transition behavior induced by Sn substitution in Mn{sub 3}SbN

    SciTech Connect

    Sun, Ying, E-mail: sunying@buaa.edu.cn [Center for Condensed Matter and Materials Physics, Department of Physics, Beihang University, Beijing 100191 (China); International Center for Materials Nanoarchitectonics (WPI-MANA), National Institute for Materials Science, Tsukuba, Ibaraki 305-0044 (Japan); Guo, Yanfeng; Li, Jun; Wang, Xia [Superconducting Properties Unit, National Institute for Materials Science, Tsukuba, Ibaraki 305-0044 (Japan); Tsujimoto, Yoshihiro [Materials Processing Unit, National Institute for Materials Science, Tsukuba, Ibaraki 305-0047 (Japan); Wang, Cong [Center for Condensed Matter and Materials Physics, Department of Physics, Beihang University, Beijing 100191 (China); Feng, Hai L.; Sathish, Clastin I.; Yamaura, Kazunari, E-mail: yamaura.kazunari@nims.go.jp [Superconducting Properties Unit, National Institute for Materials Science, Tsukuba, Ibaraki 305-0044 (Japan); Graduate School of Chemical Sciences and Engineering, Hokkaido University, Sapporo, Hokkaido 060-0810 (Japan); Matsushita, Yoshitaka [Analysis Station, National Institute for Materials Science, Tsukuba, Ibaraki 305-0047 (Japan)

    2014-01-28

    Substitution of Sb with Sn was achieved in ferrimagnetic antiperovskite Mn{sub 3}SbN. The experimental results indicate that with an increase in Sn concentration, the magnetization continuously decreases and the crystal structure of Mn{sub 3}Sb{sub 1-x}Sn{sub x}N changes from tetragonal to cubic phase at around x of 0.8. In the doping series, step-like anomaly in the isothermal magnetization was found and this behavior was highlighted at x?=?0.4. The anomaly could be attributed to the magnetic frustration, resulting from competition between the multiple spin configurations in the antiperovskite lattice. Meantime, H{sub c} of 18 kOe was observed at x?=?0.3, which is probably the highest among those of manganese antiperovskite materials reported so far. With increasing Sn content, the abrupt change of resistivity and the sharp peak of heat capacity in Mn{sub 3}SbN were gradually weakened. The crystal structure refinements indicate the weakened change at the magnetic transition is close related to the change of c/a ratio variation from tetragonal to cubic with Sn content. The results derived from this study indicate that the behavior of Mn{sub 3}Sb{sub 1-x}Sn{sub x}N could potentially enhance its scientific and technical applications, such as spin torque transfer and hard magnets.

  13. Development of superconducting magnet with low electric power loss for SMES

    Microsoft Academic Search

    K. Hayakawa; T. Nakano; M. Minami; M. Fujiwara; T. Kanzawa; S. Terai; E. Haraguchi; A. Ryouman; Y. Murakami

    1993-01-01

    A superconducting magnet with a 0.01% electric power loss was developed. This magnet is used to store electric power as magnetic energy and to stabilize an electric power system. This magnet of 78-cm outer diameter and 27-cm width consists of 18 double-pancake-type coils and was designed with a 10-T\\/s pulse-discharge speed and 350-A transportation current. To reduce energy loss caused

  14. Hysteresis in Metal Hydrides.

    ERIC Educational Resources Information Center

    Flanagan, Ted B., And Others

    1987-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    2004-01-01

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

  16. Performance Calculation of High Temperature Superconducting Hysteresis Motor Using Finite Element Method

    NASA Astrophysics Data System (ADS)

    Konar, G.; Chakraborty, N.; Das, J.

    Hysteresis motors being capable of producing a steady torque at low speeds and providing good starting properties at loaded condition became popular among different fractional horse power electrical motors. High temperature superconducting materials being intrinsically hysteretic are suitable for this type of motor. In the present work, performance study of a 2-pole, 50 Hz HTS hysteresis motor with conventional stator and HTS rotor has been carried out numerically using finite element method. The simulation results confirm the ability of the segmented HTS rotor with glued circular sectors to trap the magnetic field as high as possible compared to the ferromagnetic rotor. Also the magnetization loops in the HTS hysteresis motor are obtained and the corresponding torque and AC losses are calculated. The motor torque thus obtained is linearly proportional to the current which is the common feature of any hysteresis motor. Calculations of torques, current densities etc are done using MATLAB program developed in-house and validated using COMSOL Multiphysics software. The simulation result shows reasonable agreement with the published results.

  17. Microwave losses of interferometers with many Josephson junctions versus DC magnetic field

    Microsoft Academic Search

    R. Lochschmied; W. Benzing; W. Jutzi

    1995-01-01

    The average microwave losses of interferometers with two and four strongly damped Josephson junctions biased by a microwave current source at 10 GHz much below the plasma frequency have been simulated as a function of an external magnetic field. Microwave losses appear periodically within distinct ranges of the magnetic field, with microwave amplitudes below and above threshold currents. The main

  18. Spring Model of Hysteresis Applied to Tape-Wound Cores

    Microsoft Academic Search

    John A. Baldwin; Jay S. Bayne; Thomas R. Calkins

    1971-01-01

    The theory of the spring model of hysteresis is compared with experiment for a number of magnetic materials. The properties of the spring model as they relate to minor hysteresis loops are summarized. Loops from tape-wound cores of various materials are compared with these predictions to see if the cores obey the model. It is found that some cores, square

  19. Simple approximations of the DC flux influence on the core loss power electronic ferrites and their use in design of magnetic components

    Microsoft Academic Search

    Wai Keung Mo; David K. W. Cheng; Y. S. Lee

    1997-01-01

    The effect of DC flux on the core loss is examined for the practical range of power and frequency. Relevant core loss equations are derived and applied to an optimization algorithm to determine the minimum core loss at a given ratio of s (DC flux density to AC peak flux density). It has been found that the curves of hysteresis

  20. Deep spin-glass hysteresis-area collapse and scaling in the three-dimensional ±J Ising model.

    PubMed

    Sar?yer, Ozan S; Kabakç?o?lu, Alkan; Berker, A Nihat

    2012-10-01

    We investigate the dissipative loss in the ±J Ising spin glass in three dimensions through the scaling of the hysteresis area, for a maximum magnetic field that is equal to the saturation field. We perform a systematic analysis for the whole range of the bond randomness as a function of the sweep rate by means of frustration-preserving hard-spin mean-field theory. Data collapse within the entirety of the spin-glass phase driven adiabatically (i.e., infinitely slow field variation) is found, revealing a power-law scaling of the hysteresis area as a function of the antiferromagnetic bond fraction and the temperature. Two dynamic regimes separated by a threshold frequency ?(c) characterize the dependence on the sweep rate of the oscillating field. For ?hysteresis area is equal to its value in the adiabatic limit ?=0, while for ?>?(c) it increases with the frequency through another randomness-dependent power law. PMID:23214529

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

    Microsoft Academic Search

    Schlueter

    1991-01-01

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

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

    Microsoft Academic Search

    Hani Vahedi; Abdolreza Sheikholeslami; Mohammad Tavakoli Bina

    2011-01-01

    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

  3. Plant thermal hysteresis proteins.

    PubMed

    Urrutia, M E; Duman, J G; Knight, C A

    1992-05-22

    Proteins which produce a thermal hysteresis (i.e. lower the freezing point of water below the melting point) are common antifreezes in cold adapted poikilothermic animals, especially fishes from ice-laden seas and terrestrial arthropods. However, these proteins have not been previously identified in plants. 16 species of plants collected from northern Indiana in autumn and winter had low levels of thermal hysteresis activity, but activity was absent in summer. This suggests that thermal hysteresis proteins may be a fairly common winter adaptation in angiosperms. Winter stem fluid from the bittersweet nightshade, Solanum dulcamara L., also showed the recrystallization inhibition activity characteristic of the animal thermal hysteresis proteins (THPs), suggesting a possible function for the THPs in this freeze tolerant species. Other potential functions are discussed. Antibodies to an insect THP cross reacted on immunoelectroblots with proteins in S. dulcamara stem fluid, indicating common epitopes in the insect and plant THPs. PMID:1599942

  4. Improvement of the magnetic core for eddy current losses decreasing in cylindrical linear actuators.

    E-print Network

    Boyer, Edmond

    . An other solution is the use of soft magnetic composite material. But the industrializationImprovement of the magnetic core for eddy current losses decreasing in cylindrical linear actuators in the magnetic circuit. This method has been applied in a multi-rod actuator. The comparison between several slot

  5. AC losses in type-II superconductors induced by nonuniform fluctuations of external magnetic field

    E-print Network

    amplitude. The results can be used to estimate the AC losses in flywheels, electric motors, magnetic shields in flywheel systems and magnetic bearings is promising because of no friction between the moving parts and, for example, in the case of a flywheel system, are induced by rotation of permanent magnets and may

  6. A study of the effect of iron island morphology and interface oxidation on the magnetic hysteresis of Fe-MgO (001) thin film composites

    NASA Astrophysics Data System (ADS)

    Spurgeon, Steven R.; Sloppy, Jennifer D.; Tao, Runzhe; Klie, Robert F.; Lofland, Samuel E.; Baldwin, Jon K.; Misra, Amit; Taheri, Mitra L.

    2012-07-01

    Fe-MgO tunnel junctions have received much attention for their use in hard drive read heads and other spintronic applications. The system is particularly interesting because of its magnetoresistive behavior and the abundance and low cost of its constituent elements. However, many questions remain about how the structure and chemistry of the Fe-MgO interface mediates magnetic behavior. In this study, we report on transmission electron microscopy, electron energy loss spectroscopy, and magnetic characterization of Fe-MgO composite films with various morphologies. We explore relationships between film morphology, intermixing, and the resulting effects on magnetic structure. We find the presence of oxidation at the Fe-MgO interface, with a detrimental impact on the saturation magnetization of the composite. We also observe changes in coercivity and magnetocrystalline anisotropy with film morphology and thickness. These results will inform the design of MgO-based tunnel junctions and improve our understanding of how processing conditions, resulting in morphological and chemical changes such as oxidation, affect magnetization.

  7. Hysteresis during Cycling of Nickel Hydroxide Active Material Venkat Srinivasan,a,

    E-print Network

    Weidner, John W.

    is changed. A common electro- chemical example of such a time-dependent hysteresis is cyclic vol- tammetry are stable, reproducible, and rate- independent. Such loops are termed permanent hysteresis,1-independent phenomenon. Hysteresis is well-studied in adsorption1 and magnetism,2 but there are only a few documented

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

    Microsoft Academic Search

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

    2002-01-01

    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

  9. Analysis of a hysteresis motor with overexcitation

    SciTech Connect

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

    1982-11-01

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

  10. Effect of capacitance on eddy-current loss in multi-layer magnetic films for MHz magnetic components

    Microsoft Academic Search

    Di Yao; Charles R. Sullivan

    2009-01-01

    High-frequency magnetic component designs using multilayer thin films require accurate estimation of eddy-current loss, because at high frequency, eddy-current loss can be much worse than would be predicted without considering displacement current in the dielectric layers of the thin films. A closed-form expression for predicting the loss is introduced and shown to be more accurate over a wider range of

  11. Mathematical models of hysteresis

    SciTech Connect

    NONE

    1998-08-01

    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.

  12. Problems of loss separation for crystalline and consolidated amorphous soft magnetic materials

    Microsoft Academic Search

    H. Pfutzner; P. Schonhuber; B. Erbil; G. Harasko; T. Klinger

    1991-01-01

    Losses were measured as a function of magnetization frequency fd for two advanced soft magnetic alloys: laser-scribed 0.23-mm HI-B steel ZDKH (designated HB) and consolidated amorphous Powercore (designated PC). Although domain observations on HB yielded distinct domain refinements due to the laser treatment, anomalous losses Wa still proved to be higher than the classical ones. A further refinement resulted from

  13. Calculation of eddy-current loss in multilayer magnetic films considering displacement current

    Microsoft Academic Search

    Di Yao; Charles R. Sullivan

    2009-01-01

    At high frequency, displacement current in dielectric layers of multilayer magnetic thin films becomes significant, and eddy-current loss can be much worse than would be predicted without considering displacement current. Two-dimensional finite-element method simulations were used to study the behavior of eddy-current loss in multilayer thin films from 1 kHz to 1 GHz. A closed-form expression for accurate loss prediction

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

    SciTech Connect

    Schlueter, R.D.

    1991-08-16

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

  15. Radiative parton energy loss in expanding quark-gluon plasma with magnetic monopoles

    E-print Network

    B. G. Zakharov

    2014-12-19

    We study radiative parton energy loss in an expanding quark-gluon plasma with magnetic monopoles. We find that for realistic number density of thermal monopoles obtained in lattice simulations parton rescatterings on monopoles can considerably enhance energy loss for plasma produced in $AA$ collisions at RHIC and LHC energies. However, contrary to previous expectations, monopoles do not lead to the surface dominance of energy loss.

  16. Dynamic Preisach model and energy dissipation in soft magnetic materials

    Microsoft Academic Search

    L. R. Dupre; Giorgio Bertotti; J. A. A. Melkebeek

    1998-01-01

    In this paper, the energy dissipation in soft magnetic materials using the dynamic Preisach model is discussed. The main goal is the establishment of the f1.5 law for the excess losses from this hysteresis model. By building up the energy balance of a lamination model combined with the dynamic Preisach theory, the connection with the statistical loss theory is identified

  17. AC current distribution and losses in multifilamentary superconductors exposed to longitudinal magnetic field

    SciTech Connect

    Le Naour, S. [CREEBEL, Belfort (France)] [CREEBEL, Belfort (France); Lacaze, A.; Laumond, Y. [GEC Alsthom-DEA, Belfort (France)] [GEC Alsthom-DEA, Belfort (France); Estop, P.; Verhaege, T. [Alcatel Alsthom Recherche, Marcoussis (France)] [Alcatel Alsthom Recherche, Marcoussis (France)

    1996-07-01

    The current distribution and also AC losses, in a multifilamentary superconductor carrying a transport current, are influenced by the self and the external magnetic field. By using the Maxwell equations, a model has been developed in order to calculate the temporal evolution of current distribution in a single wire exposed or not to external magnetic field. This model is based on the actual relationship of electrical field E with current density J and takes into account the twist pitch of the wire. AC losses are calculated by adding all local losses through the cross section. This paper presents calculations of the influence of the cable twist coupled with the longitudinal magnetic field, and also gives some ideas how to decrease losses.

  18. Magnetic Flux Loss and Flux Transport in a Decaying Active Region

    NASA Astrophysics Data System (ADS)

    Kubo, M.; Lites, B. W.; Shimizu, T.; Ichimoto, K.

    2008-10-01

    We estimate the temporal change of magnetic flux normal to the solar surface in a decaying active region by using a time series of the spatial distribution of vector magnetic fields in the photosphere. The vector magnetic fields are derived from full spectropolarimetric measurements with the Solar Optical Telescope aboard Hinode. We compare a magnetic flux loss rate to a flux transport rate in a decaying sunspot and its surrounding moat region. The amount of magnetic flux that decreases in the sunspot and moat region is very similar to magnetic flux transported to the outer boundary of the moat region. The flux loss rates [(dF/dt)loss] of magnetic elements with positive and negative polarities balance each other around the outer boundary of the moat region. These results suggest that most of the magnetic flux in the sunspot is transported to the outer boundary of the moat region as moving magnetic features, and then removed from the photosphere by flux cancellation around the outer boundary of the moat region.

  19. Magnetic Flux Loss and Flux Transport in a Decaying Active Region

    E-print Network

    M. Kubo; B. W. Lites; T. Shimizu; K. Ichimoto

    2008-07-28

    We estimate the temporal change of magnetic flux perpendicular to the solar surface in a decaying active region by using a time series of the spatial distribution of vector magnetic fields in the photosphere. The vector magnetic fields are derived from full spectropolarimetric measurements with the Solar Optical Telescope aboard Hinode. We compare a magnetic flux loss rate to a flux transport rate in a decaying sunspot and its surrounding moat region. The amount of magnetic flux that decreases in the sunspot and moat region is very similar to magnetic flux transported to the outer boundary of the moat region. The flux loss rates [$(dF/dt)_{loss}$] of magnetic elements with positive and negative polarities are balanced each other around the outer boundary of the moat region. These results suggest that most of the magnetic flux in the sunspot is transported to the outer boundary of the moat region as moving magnetic features, and then removed from the photosphere by flux cancellation around the outer boundary of the moat region.

  20. MODELING OF EDDY CURRENT LOSS AND TEMPERATURE OF THE MAGNETS

    E-print Network

    Mi, Chunting "Chris"

    (PM) motors in a hybrid electric vehicle (HEV) and plug-in HEV is usually not taken into consideration vehicles (EV), hybrid electric vehicles (HEV) and plug-in hybrid electric vehicles (PHEV) have attracted a lot attention lately. Per- manent magnet (PM) motors are popular choices for EV/HEV/PHEV traction

  1. Experimental evaluation of losses in magnetic components for power converters

    Microsoft Academic Search

    J. A. Ferreira; J. D. van Wyk

    1988-01-01

    Optimization of copper and core losses is an important aspect of converter technology in the trend towards high frequency and high power density, ranging from high-frequency high-Q inductors in resonant converters, to high-power thyristor converters that impress complex current waveforms with significant harmonic content on line frequency transformers and electric machines. Core materials are obtained from manufacturers, so that a

  2. An automated system for core loss measurement and characterization: a useful tool for high frequency magnetic components design

    Microsoft Academic Search

    Adalberto J. Batista; J. C. S. Fagundes; Philippe Viarouge

    1998-01-01

    This paper describes an automated measurement system for core loss characterization in high frequency magnetic components. This system can accomplish these aims, within specified magnetic induction and frequency ranges, and at different temperatures, with high accuracy, due to the techniques used in the acquisition and computation of the waveforms involved in loss calculation. The core loss characterization, obtained by fitting

  3. Three-dimensional multifluid simulations of ionospheric loss at Mars from nominal solar wind conditions to magnetic cloud events

    Microsoft Academic Search

    E. M. Harnett; R. M. Winglee

    2006-01-01

    Three-dimensional multifluid simulations of the solar wind interaction with a magnetized Mars are used to determine both the effect of the crustal magnetic field on ionospheric loss rate and the ionospheric loss rate as a function of solar wind conditions. Ionospheric losses on the order of 1025 O2+ ions per second are found for quiet solar wind conditions. This is

  4. Calorimetric method of ac loss measurement in a rotating magnetic field.

    PubMed

    Ghoshal, P K; Coombs, T A; Campbell, A M

    2010-07-01

    A method is described for calorimetric ac-loss measurements of high-T(c) superconductors (HTS) at 80 K. It is based on a technique used at 4.2 K for conventional superconducting wires that allows an easy loss measurement in parallel or perpendicular external field orientation. This paper focuses on ac loss measurement setup and calibration in a rotating magnetic field. This experimental setup is to demonstrate measuring loss using a temperature rise method under the influence of a rotating magnetic field. The slight temperature increase of the sample in an ac-field is used as a measure of losses. The aim is to simulate the loss in rotating machines using HTS. This is a unique technique to measure total ac loss in HTS at power frequencies. The sample is mounted on to a cold finger extended from a liquid nitrogen heat exchanger (HEX). The thermal insulation between the HEX and sample is provided by a material of low thermal conductivity, and low eddy current heating sample holder in vacuum vessel. A temperature sensor and noninductive heater have been incorporated in the sample holder allowing a rapid sample change. The main part of the data is obtained in the calorimetric measurement is used for calibration. The focus is on the accuracy and calibrations required to predict the actual ac losses in HTS. This setup has the advantage of being able to measure the total ac loss under the influence of a continuous moving field as experienced by any rotating machines. PMID:20687748

  5. Effect of Axial Segmentation of Permanent Magnets on Rotor Loss in Modular Permanent-Magnet Brushless Machines

    Microsoft Academic Search

    Jason D. Ede; Kais Atallah; Geraint W. Jewell; Jiabin B. Wang; David Howe

    2007-01-01

    This paper presents a computationally efficient technique in determining the influence of the finite axial length of the permanent magnets on the rotor eddy-current loss in modular brushless ac machines. The technique is employed to quantify the effectiveness of axially segmenting the permanent magnets of four-phase, eight-slot, ten-pole and five-phase, ten-slot, 12-pole brushless machines, which have been designed to meet

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

    NASA Astrophysics Data System (ADS)

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

    2013-03-01

    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.

  7. Computation of eddy current losses induced by magnetic domain walls motion with Ck-spline functions

    NASA Astrophysics Data System (ADS)

    Lakhdari, Zakaria; Adélaïde, Luca; Makany, Philippe

    2008-04-01

    This article presents a computation of the nonlinear dynamics of magnetic domain wall motion in ferromagnetic material such as crystalline, like Fe-Si, in formulation H, with interactions between walls, and bulk magnetic induction. These terms have important contributions to ferromagnetic losses in high exciting magnetic fields and are usually neglected. The dynamic trajectories of magnetic domain walls are given as nonlinear coupled ordinary differential time equations. Our simulations use the Ck-spline approach, which allows many algebraic facilities in algorithms and in boundary conditions.

  8. Inkjet printing of magnetic materials with aligned anisotropy

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

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

  9. Magnetic Resonance Studies of Proton Loss from Carotenoid Radical Cations

    SciTech Connect

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

    2007-06-11

    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.

  10. Hysteresis of ionization waves

    NASA Astrophysics Data System (ADS)

    Dinklage, A.; Bruhn, B.; Testrich, H.; Wilke, C.

    2008-06-01

    A quasi-logistic, nonlinear model for ionization wave modes is introduced. Modes are due to finite size of the discharge and current feedback. The model consists of competing coupled modes and it incorporates spatial wave amplitude saturation. The hysteresis of wave mode transitions under current variation is reproduced. Sidebands are predicted by the model and found in experimental data. The ad hoc model is equivalent to a general—so-called universal—approach from bifurcation theory.

  11. Elastic hysteresis in human eyes is age dependent value.

    PubMed

    Ishii, Kotaro; Saito, Kei; Kameda, Toshihiro; Oshika, Tetsuro

    2012-06-19

    Background:? The elastic hysteresis phenomenon is observed when cyclic loading is applied to a viscoelastic system. The purpose of this study was to quantitatively evaluate elastic hysteresis in living human eyes against an external force. Design:? Prospective case series. Participants:? Twenty-four eyes of 24 normal human subjects (mean age: 41.5 ± 10.6 years) were recruited. Methods:? A non-contact tonometry process was recorded with a high-speed camera. Central corneal thickness (CCT), corneal thickness at 4 mm from the center, corneal curvature, and anterior chamber depth (ACD) were measured. Intraocular pressure (IOP) was also measured using Goldmann applanation tonometry (GAT) and dynamic contour tonometer (DCT). Main Outcome Measures:? Energy loss due to elastic hysteresis was calculated and graphed. Results:? The mean CCT was 552.5 ± 36.1 µm, corneal curvature was 7.84 ± 0.26 mm, and ACD was 2.83 ± 0.29 mm. The mean GAT-IOP was 14.2 ± 2.7 mmHg and DCT-IOP was 16.3 ± 3.5 mmHg. The mean energy loss due to elastic hysteresis was 3.90 × 10(-6) ± 2.49 × 10(-6) Nm. Energy loss due to elastic hysteresis correlated significantly with age (Pearson correlation coefficient = 0.596, p = 0.0016). There were no significant correlations between energy loss due to elastic hysteresis and other measurements. Conclusion:? Energy loss due to elastic hysteresis in the eyes of subjects was found to positively correlate with age, independent of anterior eye structure or IOP. Therefore, it is believed that the viscosity of the eye increases with age. © 2010 The Authors. Clinical and Experimental Ophthalmology © 2010 Royal Australian and New Zealand College of Ophthalmologists. PMID:22713246

  12. High-Frequency Copper Losses in Magnetic Components With Layered Windings

    Microsoft Academic Search

    Georgios S. Dimitrakakis; Emmanuel C. Tatakis

    2009-01-01

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

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

    Microsoft Academic Search

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

    1992-01-01

    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

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

    PubMed

    Nersisyan, Hrachya B; Deutsch, Claude

    2011-06-01

    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

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

    SciTech Connect

    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

    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.

  16. Estimation of the iron loss in deep-sea permanent magnet motors considering seawater compressive stress.

    PubMed

    Xu, Yongxiang; Wei, Yanyu; Zou, Jibin; Li, Jianjun; Qi, Wenjuan; Li, Yong

    2014-01-01

    Deep-sea permanent magnet motor equipped with fluid compensated pressure-tolerant system is compressed by the high pressure fluid both outside and inside. The induced stress distribution in stator core is significantly different from that in land type motor. Its effect on the magnetic properties of stator core is important for deep-sea motor designers but seldom reported. In this paper, the stress distribution in stator core, regarding the seawater compressive stress, is calculated by 2D finite element method (FEM). The effect of compressive stress on magnetic properties of electrical steel sheet, that is, permeability, BH curves, and BW curves, is also measured. Then, based on the measured magnetic properties and calculated stress distribution, the stator iron loss is estimated by stress-electromagnetics-coupling FEM. At last the estimation is verified by experiment. Both the calculated and measured results show that stator iron loss increases obviously with the seawater compressive stress. PMID:25177717

  17. Hybrid superconducting magnetic bearing for kinetic energy storage applications and its frictional energy loss

    SciTech Connect

    Xia, Zule; Ma, Ki; Chen, Quark [Univ. of Houston, TX (United States)] [and others

    1996-12-31

    A hybrid superconducting magnetic bearing (HSMB) has been designed, constructed and implemented in a flywheel energy storage (FES) prototype. The HSMB design uses magnetic forces from permanent magnets for levitation and high temperature superconductor YBCO in between the magnets for stabilization. A 19 kg (42 lb.) flywheel currently can rotate up to 6,000 RPM with kinetic energy of 8 Wh stored. To identify the factors of frictional energy loss in the bearings, the authors have conducted a series of spin-down experiments in different operational conditions. The result from the recent test under the air pressure of 10{sup {minus}5} torr indicates an average frictional energy loss <2% per hour, with the imperfect system alignment and an unbalanced rotor.

  18. Estimation of the Iron Loss in Deep-Sea Permanent Magnet Motors considering Seawater Compressive Stress

    PubMed Central

    Wei, Yanyu; Zou, Jibin; Li, Jianjun; Qi, Wenjuan; Li, Yong

    2014-01-01

    Deep-sea permanent magnet motor equipped with fluid compensated pressure-tolerant system is compressed by the high pressure fluid both outside and inside. The induced stress distribution in stator core is significantly different from that in land type motor. Its effect on the magnetic properties of stator core is important for deep-sea motor designers but seldom reported. In this paper, the stress distribution in stator core, regarding the seawater compressive stress, is calculated by 2D finite element method (FEM). The effect of compressive stress on magnetic properties of electrical steel sheet, that is, permeability, BH curves, and BW curves, is also measured. Then, based on the measured magnetic properties and calculated stress distribution, the stator iron loss is estimated by stress-electromagnetics-coupling FEM. At last the estimation is verified by experiment. Both the calculated and measured results show that stator iron loss increases obviously with the seawater compressive stress. PMID:25177717

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

    SciTech Connect

    Dankongkakul, Ben; Araki, Samuel J.; Wirz, Richard E. [University of California, Los Angeles, California 90024 (United States)] [University of California, Los Angeles, California 90024 (United States)

    2014-04-15

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

  20. Theory of the hysteresis loop in ferromagnets 

    E-print Network

    Lyuksyutov, Igor F.; Nattermann, T.; Pokrovsky, Valery L.

    1999-01-01

    for the inter- face profile Z(x,t)5 ^ Z(x,t) & jv ,tv on large scales is given by 1 geff ]Z ]t 5G? 2Z1h2hp1heff~x,vt !. ~9! Here ^& jv ,tv denotes the spatial and time average over scales jv and tv , respectively, and heff is the renormalized... a brief review of HLA scaling results, see Ref. 9!. The scaling behavior of the HLA was first reported in the pioneer work1 for three-dimensional ~3D! magnets. While there exists an extended literature on the hysteresis of 3D magnets...

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

    SciTech Connect

    Candiani, A. [Foundation for Research and Technology-Hellas (FORTH), Institute of Electronic Structure and Laser (IESL), Heraklion 70013 Greece (Greece); Department of Information Engineering (DII), University of Parma, Parma 43124 (Italy); Argyros, A.; Leon-Saval, S. G.; Lwin, R. [Institute of Photonics and Optical Science (IPOS), School of Physics, The University of Sydney, Sydney (Australia); Selleri, S. [Department of Information Engineering (DII), University of Parma, Parma 43124 (Italy); Pissadakis, S., E-mail: pissas@iesl.forth.gr [Foundation for Research and Technology-Hellas (FORTH), Institute of Electronic Structure and Laser (IESL), Heraklion 70013 Greece (Greece)

    2014-03-17

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

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

  3. Two-dimensional calculation of winding losses in planar magnetic components

    Microsoft Academic Search

    Bernd Ackermann; Astrid Lewalter

    2001-01-01

    Calculating the winding losses is of major importance for the design of magnetic components for power electronics. Two-dimensional finite element programs provide sufficiently accurate results. However, using them is cumbersome. Therefore there is a considerable need for efficient analytical models suitable to assess a large number of design alternatives. State of the art one-dimensional models fail in many situations. A

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

    NASA Astrophysics Data System (ADS)

    Nándori, I.; Rácz, J.

    2012-12-01

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

  5. Angular Momentum Loss and Stellar spin-down in Magnetic Massive Stars

    E-print Network

    Asif ud-Doula; Stanley P. Owocki; Richard H. D. Townsend

    2008-12-15

    We examine the angular momentum loss and associated rotational spin-down for magnetic hot stars with a line-driven stellar wind and a rotation-aligned dipole magnetic field. Our analysis here is based on our previous 2-D numerical MHD simulation study that examines the interplay among wind, field, and rotation as a function of two dimensionless parameters, W(=Vrot/Vorb) and 'wind magnetic confinement', $\\eta_\\ast$ defined below. We compare and contrast the 2-D, time variable angular momentum loss of this dipole model of a hot-star wind with the classical 1-D steady-state analysis by Weber and Davis (WD), who used an idealized monopole field to model the angular momentum loss in the solar wind. Despite the differences, we find that the total angular momentum loss averaged over both solid angle and time follows closely the general WD scaling $\\dot {J} \\sim \\dot {M} \\Omega R_A^2$. The key distinction is that for a dipole field Alfv\\`en radius $R_A$ is significantly smaller than for the monopole field WD used in their analyses. This leads to a slower stellar spin-down for the dipole field with typical spin-down times of order 1 Myr for several known magnetic massive stars.

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

    Microsoft Academic Search

    Christos Mademlis; Nikos Margaris

    2002-01-01

    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.

  7. Correlation of magnetostriction variation on magnetic loss and noise for power transformer

    NASA Astrophysics Data System (ADS)

    Cheng, Shan-Jen; Liu, Jui-Jung; Chang, Yeong-Hwa; Fu, Chao-Ming; Hsu, Chang-Hung; Lee, Chun-Yao; Chang, Chia-Wen

    2015-05-01

    Magnetostriction (MS)-caused strain in single-phase three-legged cores with different core cutting forms, which suffer from induced magnetic loss and noise, was studied. It is found that adopting each different core form types induces magnetostriction ? variation in a transformer core operating with a high-frequency AC signal. The results are compared with finite element analysis simulations. It is also indicated that magnetostriction ? variations are significant in the rolling direction and along limbs and yokes. In this paper, it is proposed that core corner sides and T-joint parts without cutting structure, the core exhibits lower core loss and lower heat dissipation due to the fact that the magnetic flux that passes through corner sides shows lower magnetostriction variation. The magnetic properties resulting from magnetostriction variation in core loss and heat dissipation phenomena are significantly different from other core forms because of stronger contributions from magnetostatic forces. The main contribution for reducing core loss and noise, making them much less in corner numbers and cutting-fabricated forms, can be expected to come from lower magnetic flux and magnetostriction variation.

  8. Experimental Validation of Control Designs for Low-Loss Active Magnetic Bearings

    Microsoft Academic Search

    Brian C. Wilson; Bonnie Heck-Ferri

    This paper ofiers experimental validation of several recently developed nonlinear con- trol laws, derived from the theory of integrator backstepping, control Lyapunov functions (CLF), and dissipativity, by implementing them on a spacecraft reaction wheel that is sus- pended by a low-loss active magnetic bearing (AMB). The electromagnets of the AMB are constrained by a generalized complementary ?ux constraint (GCFC). This

  9. Angular Momentum Loss by Magnetic Braking and Gravitational Radiation in Relativistic Binary Stars

    E-print Network

    K. Yakut; B. Kalomeni; C. A. Tout

    2008-11-04

    Angular momentum loss (AML) mechanisms and dynamical evolution owing to magnetic braking and gravitational radiation in relativistic binary stars (RBS) are studied with use of physical parameters collected from the literature. We have calculated and compared AML time scales for the RBS with non-degenerate components and double degenerate (DD) systems.

  10. Mechanisms of AC losses in magnetic fluids based on substituted manganites.

    PubMed

    Kalita, V M; Tovstolytkin, A I; Ryabchenko, S M; Yelenich, O V; Solopan, S O; Belous, A G

    2015-07-01

    The ability to controllably tune the heating efficiency of magnetic nanoparticles in an AC magnetic field is highly desirable for their application as mediators of magnetic hyperthermia. Traditional approaches to understand and govern the behavior of hyperthermia mediators include a combination of quasistatic and high-frequency (?100 kHz) magnetic measurements with subsequent simulation of underlying processes. In this paper, we draw attention to the frequently overlooked fact that for an ensemble of magnetic nanoparticles, there is no straightforward complementarity between the dynamic characteristics obtained under different experimental conditions, as well as between corresponding underlying processes. This paper analyzes mechanisms of AC losses in a fluid based on magnetic nanoparticles, with special emphasis on the domains of their validity, and shows that the mechanisms may become qualitatively different as experimental conditions change from magnetostatic to high-frequency ones. Further, the work highlights new important features which can result from the employment of the refined approaches to interpret experimental results obtained on magnetic fluids based on La1-xSrxMnO3 (x = 0.22) nanoparticles. The gained knowledge provides necessary guidelines for tailoring the properties of magnetic nanoparticles to the needs of self-controlled magnetic hyperthermia. PMID:26100102

  11. A high-performance hysteresis loop tracer

    NASA Astrophysics Data System (ADS)

    Kulik, Tadeusz; Savage, Howard T.; Hernando, Antonio

    1993-05-01

    A high-performance and inexpensive hysteresis loop tracer has been developed to measure quasistatic (0.02 Hz or less) hysteresis loops of soft ferromagnetic materials. It was applied very successfully to measure straight pieces of amorphous and nanocrystalline ribbons and amorphous wires. Especially high-magnetic-field resolution is required when nanocrystalline ferromagnets and amorphous wires are measured. Nanocrystalline materials exhibit very low coercivity (Hc=0.1-0.5 A/m). The error of Hc measurement using this tracer does not exceed 0.05 A/m even though the amorphous wires have very small cross section (0.008 mm2). The examples of hysteresis loops measured at low (50 A/m) and high magnetic field (14 kA/m) are presented. The apparatus consists of an IBM-compatible computer equipped with 12 bit analog-to-digital and digital-to-analog converters, bipolar power supply, fluxmeter, solenoid and a pickup coil connected to a compensation coil. This equipment is free of 50 Hz noise, a significant problem in the performance of low-frequency loop tracers. The software was developed to enable measurement and immediate display of the M-H hysteresis loop. Previous loops also can be displayed and printed. Calibration of the setup is also possible. In the case of straight samples the measurements are followed by calculation of demagnetization factor Nd(calc.) using the ellipsoidal approximation of the sample shape. It was found that the experimental value of Nd is 30%-40% of the calculated value Nd(calc.) for the ribbons studied. Higher values of Nd correspond to the thicker ribbons where better agreement was obtained.

  12. Magnetization AC losses in MgB2 wires made by IMD process

    NASA Astrophysics Data System (ADS)

    Ková?, J.; Šouc, J.; Ková?, P.; Hušek, I.

    2015-01-01

    Magnetization AC losses of MgB2 superconductors with one and four filaments made by an internal magnesium diffusion (IMD) into boron process were measured and analyzed. For AC loss measurement a system based on a calibration-free method was used. Short samples of MgB2 wires were exposed to an external magnetic field with amplitudes up to 0.07 T, frequencies up to 1200 Hz, and a temperature range between 15 K and 40 K. A strong effect of eddy current losses was found in single-core wire containing pure copper sheath, which was proved by the same wire measurement after Cu etching. The impact of coupling current losses in non-twisted four-filament wire and the decoupling effect after twisting were observed. Coupling current losses in a low-frequency region were effectively reduced in agreement with theoretical assumption. The degradation of transport currents due to torsion stress by twisting was taken into account and the normalized AC losses of MgB2 wires made by IMD and powder-in-tube processes were compared. It appears that the IMD process is more perspective for AC applications due to much higher current densities and smaller degradation of current-carrying capability by twisting.

  13. Effects of different modulation index on the iron losses in soft magnetic materials supplied by PWM inverter

    Microsoft Academic Search

    A. Boglietti; P. Ferraris; M. Lazzari; F. Profumo

    1993-01-01

    The increase in iron-loss in soft magnetic materials due to the modulation depth in pulse width modulation (PWM) inverters is analyzed. In particular, the specific loss variations with different modulation indexes are measured, both in wound cores realized with high quality grain oriented magnetic material, and in induction motors

  14. Anomalous non-magnetic high field loss peak for a high Q copper TE011 microwave cavity

    Microsoft Academic Search

    Liam Kilcommons; Falko Kuester; Carl Patton

    2009-01-01

    Recent off resonance magnetic loss measurements with high quality factor (Q) TE011 cavities have revealed the presence of a small anomalous loss peak at high field overlying the usual magnetic response. Precision measurements of the cavity Q vs. field by the ABA metrological substitution method for a special 99.99% pure OFHC (oxygen free high conductivity) copper cavity have now confirmed

  15. Origin of recoil hysteresis loops in SmCo/Fe exchange-spring magnets J. S. Jiang, J. E. Pearson, and S. D. Bader

    E-print Network

    Liu, J. Ping

    ­Co/Fe exchange spring magnets, the authors found that the open recoil loops were present not only in the soft Fe anisotropy of a mag- netically hard phase and the high saturation moment of a magnetically soft phase field to a magnetic material, as the demagnetizing field is increased successively. Open recoil loops

  16. Cryogenic Beam Loss Monitors for the Superconducting Magnets of the LHC

    E-print Network

    Bartosik, MR; Sapinski, M; Kurfuerst, C; Griesmayer, E; Eremin, V; Verbitskaya, E

    2014-01-01

    The Beam Loss Monitor detectors close to the interaction points of the Large Hadron Collider are currently located outside the cryostat, far from the superconducting coils of the magnets. In addition to their sensitivity to lost beam particles, they also detect particles coming from the experimental collisions, which do not contribute significantly to the heat deposition in the superconducting coils. In the future, with beams of higher energy and brightness resulting in higher luminosity, distinguishing between these interaction products and dangerous quench-provoking beam losses from the primary proton beams will be challenging. The system can be optimised by locating beam loss monitors as close as possible to the superconducting coils, inside the cold mass in a superfluid helium environment, at 1.9 K. The dose then measured by such Cryogenic Beam Loss Monitors would more precisely correspond to the real dose deposited in the coil. The candidates under investigation for such detectors are based on p+-n-n+ si...

  17. LHC magnet quench test with beam loss generated by wire scan

    E-print Network

    Sapinski, M; Dahlerup-Petersen, K; Dehning, B; Emery, j; Ferrari, A; Guerrero, A; Holzer, E B; Koujili, M; Lechner, A; Nebot, E; Scheubel, M; Steckert, J; Verweij, A; Wenninger, J

    2011-01-01

    Beam losses with millisecond duration have been observed in the LHC in 2010 and 2011. They are thought to be provoked by dust particles falling into the beam. These losses could compromise the LHC availability if they provoke quenches of superconducting magnets. In order to investigate the quench limits for this loss mechanism, a quench test using a wire scanner has been performed, with the wire movement through the beam mimicking a loss with similar spatial and temporal distribution as in the case of dust particles. This paper will show the conclusions reached for millisecond-duration dust-provoked quench limits. It will include details on the maximum energy deposited in the coil as estimated using FLUKA code, showing a reasonable agreement with quench limit estimated from the heat transfer code QP3. In addition, information on the damage limit for carbon wires in proton beamswill be presented, following electronmicroscope analysis which revealed strong wire sublimation.

  18. Low hysteresis FeMn-based top spin valve.

    PubMed

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

    2012-09-01

    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

  19. Onset of rapid mass loss in cool giant stars - Magnetic field effects

    NASA Technical Reports Server (NTRS)

    Mullan, D. J.

    1982-01-01

    The possibility that closed magnetic field loops exist in steady state in stellar atmospheres in the HR diagram is examined. A model derived by Pneuman (1968) for helmet streamers in the solar corona is applied using a semi-empirical technique, to find that long-lived closed loops exist only below a certain boundary in the HR diagram. The region below this boundary is occupied by stars which are known to have hot coronae and slow mass loss. It is suggested that rapid mass loss sets in when closed field loops can no longer exist in steady state in the atmosphere.

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

    NASA Technical Reports Server (NTRS)

    Beggs, John H.

    2000-01-01

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

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

    E-print Network

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

    2012-01-01

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

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

    SciTech Connect

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

    2009-07-10

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

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

    SciTech Connect

    Sasada, Ichiro, E-mail: sasada@ence.kyushu-u.ac.jp [Applied Science for Electronics and Materials, Kyushu University, Kasuga (Japan)

    2014-05-07

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

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

    NASA Astrophysics Data System (ADS)

    Sasada, Ichiro

    2014-05-01

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

  5. Influence of irreversible losses on the performance of a two-stage magnetic Brayton refrigeration cycle

    NASA Astrophysics Data System (ADS)

    Zhang, X.; Chen, J.; Lin, G.; Brück, E.

    2010-03-01

    The general performance characteristics of a two-stage magnetic Brayton refrigeration cycle consisting of three constant magnetic fields and three irreversible adiabatic processes are investigated. Based on the thermodynamic properties of a magnetic material and the irreversible cycle model of a two-stage Brayton refrigerator, expressions for the cooling load and coefficient of performance of the refrigeration system are derived. The influence of the finite-rate heat transfer in the heat exchange processes, irreversibilities in the three adiabatic processes, ratios of two magnetic fields in the three constant magnetic field processes, and heat leak losses between two heat reservoirs on the performance of the two-stage magnetic Brayton refrigeration cycle are analyzed in detail. Some important performance curves, which can reveal the general characteristics of the refrigeration system, are presented and the maximum values of cooling load and coefficient of performance are numerically calculated. The optimal choices and matches of other parameters at the maximum cooling load or the maximum coefficient of performance are discussed and the optimally operating regions of some important parameters in the refrigeration system are determined. The results obtained here are compared with those derived from other models of the magnetic Brayton refrigeration cycles, and consequently, the advantage of an inter-cooled process is expounded.

  6. Hysteresis, Avalanches, and Noise Matthew C. Kuntz, Olga Perkovi'c, Karin A. Dahmen,

    E-print Network

    Sethna, James P.

    Hysteresis, Avalanches, and Noise Matthew C. Kuntz, Olga Perkovi'c, Karin A. Dahmen, Bruce W simulations. In our studies of hysteresis and avalanches in a sim­ ple model of magnetism (the random be triggered when one of its neighbors flips (by participating in an avalanche), or a spin can be triggered

  7. Frequency behaviour of SPD treated soft magnetic materials

    NASA Astrophysics Data System (ADS)

    Grössinger, R.; Mehboob, N.; Zehetbauer, M.

    2014-06-01

    The effect of SPD treatment on the hysteresis properties of selected soft magnetic materials such as Fe3%Si and Fe17%Co steel is presented. The enhancement of the coercivity due to the mechanical deformation can be explained by the magnetoelastic energy Ehe frequency dependence of the coercivity and of the losses can be described using an eddy current based model.

  8. Efficient calculation of winding-loss resistance matrices for magnetic components

    Microsoft Academic Search

    Donald R. Zimmanck; Charles R. Sullivan

    2010-01-01

    There are a number of different analytical and numerical methods for calculating the winding loss of magnetic components. Analytical methods such as Dowell's method and Bessel-function methods require assumptions which severely reduce their accuracy for designs with 2-D field geometries such as those present in gapped transformers and inductors. While numerical methods such as finite-element-analysis (FEA) are capable of calculating

  9. A method of local magnetic loss determination in punched ferromagnetic strips

    NASA Astrophysics Data System (ADS)

    Gmyrek, Z.; Str?kowska, M.; Wi?cek, B.

    2014-04-01

    The paper deals with results of measurement and numerical modelling of temperature increases at ferromagnetic strip heated by induced currents. The temperature rises are analysed both for transient and steady state. The ferromagnetic material used was subjected to mechanical punching. In the paper it is shown that magnetic losses at ferromagnetic material along the punched edge are several times larger than those in "green" material.

  10. Magnetic viscosity in strontium ferrite fine particles

    Microsoft Academic Search

    Hiroaki Nishio; Hitoshi Taguchi; Fumihiko Hirata; Taku Takeishi

    1993-01-01

    The magnetic viscosity coefficient (Sv) and the rotational hysteresis loss (Wr) are measured for M-type hexagonal strontium ferrite (SrM) fine particles whose average diameter (D) and coercive force (HcJ) differ. The relationship between Sv, HcJ, the activation volume (v) and Wr is studied, together with milling effects. This experiment shows that Sv is constant and independent of the magnetic field.

  11. Experimental Testing Of An Anisotropic Vector Hysteresis Model

    Microsoft Academic Search

    A. Bergqvist; A. Lundgren; G. Engdahl

    1997-01-01

    rolling direction (RD) and kTD in the transversal direction (TD) respectively. This leaves a total of four parameters related to hysteresis which were determined as follows: c was estimated from a small minor loop; then ~RD and U were adjusted to fit the measured alternating loss as a function of flux density amplitude in RD. Finally ~TD was adjusted to

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

    SciTech Connect

    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

    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.

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

    NASA Astrophysics Data System (ADS)

    Calmels, L.; Rusz, J.

    2011-04-01

    The quantitative analysis of magnetic oxide core level spectra can become complicated when the magnetic atoms are located at several nonequivalent atomic sites in the crystal. This is, for instance, the case for Fe atoms in magnetite, which are located in tetrahedral and octahedral atomic sites; in this case, the x-ray magnetic circular dichroic (XMCD) spectra recorded at the L2,3 edge of Fe contain contributions from the different nonequivalent atomic sites, which unfortunately cannot be separated. Energy loss magnetic chiral dichroic (EMCD) spectra are the transmission electron microscope analogies of the XMCD spectra. One of the important differences between these two techniques of magnetic analysis is that EMCD uses a fast electron beam instead of polarized light. The fast electrons behave like Bloch states in the sample, and the fine structure of the EMCD spectra is strongly influenced by channeling and dynamical diffraction effects. These effects can be adjusted by changing the experimental configuration. We use theoretical calculations, which include dynamical diffraction effects and in which electronic transitions are treated in the atomic multiplet formalism, to show that the relative weight of the Fe atoms in different nonequivalent atomic sites can be changed by a proper choice of the position of the detector and of the magnetite sample orientation and thickness. We conclude that EMCD spectra could be used to isolate the magnetic contribution of atoms in each of the nonequivalent atomic sites, which would not be possible with XMCD techniques.

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

    SciTech Connect

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

    1999-11-29

    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.

  15. Magnetism variations and susceptibility hysteresis at the metal-insulator phase transition temperature of VO2 in a composite film containing vanadium and tungsten oxides

    NASA Astrophysics Data System (ADS)

    Akande, Amos A.; Rammutla, Koena E.; Moyo, Thomas; Osman, Nadir S. E.; Nkosi, Steven S.; Jafta, Charl J.; Mwakikunga, Bonex W.

    2015-02-01

    We report on the magnetic property of 0.67-WO3+0.33-VOx mixture film deposit on the corning glass substrate using the chemical sol-gel and atmospheric pressure chemical vapor deposition (APCVD) methods. The XRD and Raman spectroscopy confirm species of both materials, and the morphological studies with FIB-SEM and TEM reveal segregation of W and V atoms. XPS reveals that V4+ from VO2 forms only 11% of the film; V3+ in the form of V2O3 form 1% of the film, 21% is V5+ from V2O5 and 67% is given to W6+ from WO3. The analysis of the ESR data shows some sharp changes in the magnetism near the metal-to-insulator (MIT), which could be theoretically interpreted as the ordering or alignment of electron spins from net moment nature to parallel alignment of magnetic moment. The derivatives of magnetic susceptibility established the thermally induced magnetic property: two distinct transitions of 339 K for heating data and 338 K for cooling data for 151.2 mT field were obtained. Similar results were also obtained for 308.7 mT field, 336 K for heating data and 335 K for cooling data. VSM results confirm a paramagnetic phase with a small amount of magnetically ordered phase.

  16. Local distribution on magnetic properties in grain-oriented silicon steel sheet

    NASA Astrophysics Data System (ADS)

    Enokizono, Masato; Tanabe, Ikuo; Kubota, Takeshi

    1998-06-01

    Grain-oriented silicon steel is the most important soft magnetic material used as core material of large transformers, large rotating machines, and pole transformers. Total loss of grain-oriented silicon steel tends to become lower with an increasing degree of texture. However, the material which has a higher degree of texture ordinarily contains larger grains, and the materials which have larger grains show higher total loss due to increased eddy current loss. As the gauge is reduced, the rate of decrease in total loss becomes lower for the thinner gauge due to increased hysteresis loss. However, the investigation of local magnetic properties due to grain situation in this sheet was not discussed from the viewpoint of the distribution of localized magnetic properties, for example, iron loss, hysteresis loop, behavior H vector (magnetic field strength) and B vector (Magnetic flux density). This paper describes the distribution of magnetic properties in high oriented silicon steel sheet, which are loss, hysteresis loop, and locus of field strength.

  17. Iterative compensation for hysteresis effects in positioning and tracking problems

    NASA Astrophysics Data System (ADS)

    Tseng, C.; Mayergoyz, I.; McAvoy, P.; Krafft, C.

    2008-04-01

    An iterative algorithm for hysteresis compensation in micropositioning applications is presented. It is demonstrated that this algorithm has a geometric rate of convergence. The results of the testing of this iterative algorithm in tracking problems related to magnetic recording are reported.

  18. 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

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

    1995-11-01

    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.

  19. Advanced theory of driven birdcage resonator with losses for biomedical magnetic resonance imaging and spectroscopy.

    PubMed

    Novikov, Alexander

    2011-02-01

    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 radiofrequency (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 B(1) 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 current loss is the major effect of coil shielding. PMID:20869184

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

    NASA Astrophysics Data System (ADS)

    Ma, Guang-Tong

    2014-06-01

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

  1. Abstract --For high-speed machines applications, eddy-current losses in the interior permanent magnet of synchronous

    E-print Network

    Paris-Sud XI, Université de

    -current losses in magnets of PMSM, due to time harmonics of stator currents, has been developed [4] to consider of PMSM, due to space harmonics of magnetomotive force (MMF), have been presented in order t

  2. Low loss pole configuration for multi-pole homopolar magnetic bearings

    NASA Technical Reports Server (NTRS)

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

    2001-01-01

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

  3. On the loss of relativistic electrons at geosynchronous altitude: Its dependence on magnetic configurations and external conditions

    Microsoft Academic Search

    S. Ohtani; Y. Miyoshi; H. J. Singer; J. M. Weygand

    2009-01-01

    The present study statistically examines geosynchronous magnetic configurations and external conditions that characterize the loss of geosynchronous MeV electrons. The loss of MeV electrons often takes place during magnetospheric storms, but it also takes place without any clear storm activity. It is found that irrespective of storm activity, the day-night asymmetry of the geosynchronous H (north-south) magnetic component is pronounced

  4. Vector hysteresis measurements of not oriented grain SiFe steels by a biaxial hall sensors array

    NASA Astrophysics Data System (ADS)

    Cardelli, E.; Faba, A.

    2014-02-01

    This work discusses the vector measurement of the effective magnetic field inside a not oriented grain SiFe steel sample, taking into account the effect of the demagnetizing field. We propose an array of biaxial Hall sensors, placed up to the sample surface. The calibration of the system and a suitable extrapolation data strongly reduce the uncertainties of the direct measurement and provide an accurate evaluation of the magnetic field inside the material sample. Although the approach proposed can be also used for industrial frequencies, 50-60 Hz or more, the analysis is limited here to the static case, because we are mainly interested in static magnetic measurements. These measurements are especially useful for the vector characterization of soft magnetic materials and, in particular, for the identification and the experimental validation of vector hysteresis models. The experimental analysis presented in the paper deals with commercial not oriented grain SiFe steels. Experimental data about hysteresis loops and static power losses are given.

  5. About the possibility of defining a standard method for iron loss measurement in soft magnetic materials with inverter supply

    Microsoft Academic Search

    Aldo Boglietti; Paolo Ferraris; Mario Lazzari; Michele Pastorelli

    1997-01-01

    Due to the increase of electromagnetic and electromechanical devices supplied by static converters, the classification and evaluation of the energetic behavior of soft magnetic materials, with nonsinusoidal supply, is becoming mandatory. In this paper, the possibility of defining a standard methodology for the specific iron loss measurement (iron losses per mass unity), with static supply, is analyzed. In particular, the

  6. Change of the iron losses with the switching supply frequency in soft magnetic materials supplied by PWM inverter

    Microsoft Academic Search

    A. Boglietti; P. Ferraris; M. Lazzari; M. Pastorelli

    1995-01-01

    In the paper change in iron losses due to the switching frequency in soft magnetic materials supplied by PWM inverter, is analyzed. Experimental tests with several samples of material and switching frequency from 1 kHz up to about 20 kHz, are reported. Values of iron losses vs switching frequency, for different values of the fundamental flux density and assigned modulation

  7. About the possibility of defining a standard method for iron loss measurement in soft magnetic materials with inverter supply

    Microsoft Academic Search

    A. Boglietti; P. Ferraris; M. Lazzari; M. Pastorelli

    1996-01-01

    Due to the increase of electromagnetic and electromechanical devices supplied by static converters, the classification and evaluation of energetic behaviour of soft magnetic materials, with nonsinusoidal supply, is becoming mandatory. In this paper the possibility of defining a standard methodology for the specific iron loss measurement (iron losses per mass unity), with static supply, is analyzed. In particular the paper

  8. Three-dimensional multifluid simulations of ionospheric loss at Mars from nominal solar wind conditions to magnetic cloud events

    Microsoft Academic Search

    E. M. Harnett; R. M. Winglee

    2006-01-01

    conditions. Ionospheric losses on the order of 1025 O2 + ions per second are found for quiet solar wind conditions. This is of the same order as that estimated from Phobos 2 measurements. Varying the orientation of Mars' magnetic anomalies relative to the incident solar wind direction leads to only minor variation in the ionospheric loss rates of O2 +

  9. Barkhausen discontinuities and hysteresis of ferromagnetics: New stochastic approach

    SciTech Connect

    Vengrinovich, Valeriy, E-mail: veng@iaph.bas-net.by [Institute of Applied Physics of the Belarus Academy of Sciences 220072, Akademicheskaya street 16, Minsk (Belarus)

    2014-02-18

    The magnetization of ferromagnetic material is considered as periodically inhomogeneous Markov process. The theory assumes both statistically independent and correlated Barkhausen discontinuities. The model, based on the chain evolution-type process theory, assumes that the domain structure of a ferromagnet passes successively the steps of: linear growing, exponential acceleration and domains annihilation to zero density at magnetic saturation. The solution of stochastic differential Kolmogorov equation enables the hysteresis loop calculus.

  10. Analysis of capacitive coupling and associated loss for a solenoidal magnetic resonance imaging radio-frequency coil.

    PubMed

    Harpen, M D

    1989-01-01

    Presented is an analysis of the capacitive coupling between a magnetic resonance imaging radio-frequency (rf) coil and a dielectric sample. Calculated is the coil self-capacitance and power loss in the medium. The capacitively coupled power loss is compared with the more familiar inductively coupled eddy current loss and the predicted dependence of self-capacitance on coil and sample size is studied experimentally in a series of single-turn slotted solenoids of various sizes. PMID:2716704

  11. An Energy-Based Hysteresis Model for Magnetostrictive Transducers

    NASA Technical Reports Server (NTRS)

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

    1997-01-01

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

  12. Eddy current disruption: effect on nuclear magnetic resonance coil impedance and power loss.

    PubMed

    Harpen, M D

    1989-01-01

    We present a theoretical development and experimental verification of a description of power loss and sample resistance for a lossy sample in a nuclear magnetic resonance radio frequency coil for a sample geometry where the eddy current streamlines are disrupted from their usually assumed circular paths. Specifically treated is the case of a lossy hemisphere. The problem is solved for two orientations; with the induction parallel and perpendicular to the flat surface of the hemisphere. Results of this analysis as well as those for the full sphere as presented by Hoult and Lauterbur are compared with observation for a variety of sample conductivities and orientation. PMID:2811760

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

    SciTech Connect

    Heidrich, J. E.

    1981-01-01

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

  14. Low core loss rotating flux transformer

    NASA Astrophysics Data System (ADS)

    Krause, R. F.; Del Vecchio, R. M.

    1988-11-01

    A rotating magnetic induction at saturation generates no hysteresis losses. In addition, because domain walls are absent, there are no anomalous eddy current losses. Thus, only classical eddy current losses are present. In materials with high resistivity such as ferrites or materials fabricated into thin sheets such as amorphous metals, these classical losses are small. A transformer has been designed which utilizes this principle. It consists of a hollow toroidal core with toroidal windings wrapped outside the core and poloidal windings wrapped through the interior channel. When these windings are energized by currents 90 electrical degrees apart or, with suitable winding schemes, by three-phase currents, rotating flux is generated throughout the core volume.

  15. Transient Thermal Analysis of Intense Proton Beam Loss on a Kicker Magnet Conductor Plate

    E-print Network

    Knaus, P

    2000-01-01

    The Super Proton Synchrotron SPS will be used as injector for the Large Hadron Collider LHC and needs adaptation to meet LHC requirements. The SPS injection kicker magnets MKP will undergo important modifications to comply with the requirements on magnetic field rise-time and ripple. The injection kicker presently installed has a return conductor of beryllium to minimise the risk of metal evaporation from its surface due to heating caused by beam impact. In the context of refurbishing the MKP to satisfy LHC requirements these conductors need replacement, preferably with a less delicate material. This article presents the transient thermal analysis of energy deposition caused by beam loss on the conductor plate. The expected time structure of the beam is taken into account. Simulations comparing different conductor materials have been performed, leading to the result that a significantly cheaper and fully inoffensive titanium alloy can satisfy the needs.

  16. Anomalous Beam-Ion Loss in TFTR Reversed Magnetic Shear Plasmas

    SciTech Connect

    Ruskov, E.; Bell, M.; Budny, R.V.; McCune, D.C.; Medley, S.S.; Redi, M.H.; Scott, S.; Synakowski, E.J.; von Goeler, S.; White, R.B.; Zweben, S.J. [Princeton Plasma Physics Laboratory, Princeton University, Princeton, New Jersey 08543 (United States)] [Princeton Plasma Physics Laboratory, Princeton University, Princeton, New Jersey 08543 (United States)

    1999-02-01

    Anomalous beam-ion loss has been observed in an experiment with short tritium beam pulses injected into deuterium-beam-heated Tokamak Fusion Test Reactor plasmas (P{sub NBI}=15 thinspthinspMW) with reversed magnetic shear (RS). Comparisons of the measured total 14thinspthinspMeV neutron emission, the neutron flux along eight radial locations, and the perpendicular plasma stored energy with predictions from an extensive set of TRANSP simulations suggest that about 40{percent} beam power is lost on a time scale much shorter than the tritium beam pulse length {Delta}t=70 thinspthinspms. In contrast with recent results [K. Tobita {ital et al.,} Nucl.thinspthinspFusion {bold 37}, 1583 (1997)] from RS experiments at JT-60U, we were not able to show conclusively that magnetic field ripple is responsible for this anomaly. {copyright} {ital 1999} {ital The American Physical Society}

  17. Anomalous Beam-Ion Loss in TFTR Reversed Magnetic Shear Plasmas

    NASA Astrophysics Data System (ADS)

    Ruskov, E.; Bell, M.; Budny, R. V.; McCune, D. C.; Medley, S. S.; Redi, M. H.; Scott, S.; Synakowski, E. J.; von Goeler, S.; White, R. B.; Zweben, S. J.

    1999-02-01

    Anomalous beam-ion loss has been observed in an experiment with short tritium beam pulses injected into deuterium-beam-heated Tokamak Fusion Test Reactor plasmas ( PNBI = 15 MW) with reversed magnetic shear (RS). Comparisons of the measured total 14 MeV neutron emission, the neutron flux along eight radial locations, and the perpendicular plasma stored energy with predictions from an extensive set of TRANSP simulations suggest that about 40% beam power is lost on a time scale much shorter than the tritium beam pulse length ?t = 70 ms. In contrast with recent results [K. Tobita et al., Nucl. Fusion 37, 1583 (1997)] from RS experiments at JT-60U, we were not able to show conclusively that magnetic field ripple is responsible for this anomaly.

  18. 3452 IEEE TRANSACTIONS ON MAGNETICS, VOL. 47, NO. 10, OCTOBER 2011 High Induction, Low Loss FeCo-Based Nanocomposite

    E-print Network

    McHenry, Michael E.

    3452 IEEE TRANSACTIONS ON MAGNETICS, VOL. 47, NO. 10, OCTOBER 2011 High Induction, Low Loss FeCo aimed at increasing inductions in FeCo- based nanocomposite alloys. Metalloid B and early transition, FeCo alloys, high magnetic flux density, nanocrystalline alloy. I. INTRODUCTION THERE is increasing

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

    NASA Technical Reports Server (NTRS)

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

    2002-01-01

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

  20. Minor hysteresis loops measurements for characterization of cast iron

    NASA Astrophysics Data System (ADS)

    Vértesy, G.; Uchimoto, T.; Takagi, T.; Tomáš, I.; Stupakov, O.; Mészáros, I.; Pávó, J.

    2006-02-01

    Structural variation in a series of cast iron samples was non-destructively characterized by means of sets of magnetic minor hysteresis loops. The flat samples were magnetized by an attached yoke, and reliable parameters were obtained from the series of minor loops, without magnetic saturation of the samples. It was found, that some magnetic quantities, well known to be closely connected to the samples’ structure variation, especially relative coercivity and remanent induction, could be distinguished more sensitively from minor loops, than from the major one.

  1. Process yield Co-Fe alloys with superior high temperature magnetic properties

    NASA Technical Reports Server (NTRS)

    Barranger, J. P.

    1966-01-01

    Cobalt-iron alloys containing from 7.0 to 9.3 percent iron prepared from ultrapure cobalt and iron have the highest Curie point of all known magnetically soft materials. Their high permeability, low hysteresis loss, good saturation induction, and square loop characteristics recommend them for use in power transformers and rotating machinery.

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

    PubMed Central

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

    2013-01-01

    OBJECTIVES The authors sought to measure the turbulent kinetic energy (TKE) in the ascending aorta of patients with aortic stenosis and to assess its relationship to irreversible pressure loss. BACKGROUND Irreversible pressure loss caused by energy dissipation in post-stenotic flow is an important determinant of the hemodynamic significance of aortic stenosis. The simplified Bernoulli equation used to estimate pressure gradients often misclassifies the ventricular overload caused by aortic stenosis. The current gold standard for estimation of irreversible pressure loss is catheterization, but this method is rarely used due to its invasiveness. Post-stenotic pressure loss is largely caused by dissipation of turbulent kinetic energy into heat. Recent developments in magnetic resonance flow imaging permit noninvasive estimation of TKE. METHODS The study was approved by the local ethics review board and all subjects gave written informed consent. Three-dimensional cine magnetic resonance flow imaging was used to measure TKE in 18 subjects (4 normal volunteers, 14 patients with aortic stenosis with and without dilation). For each subject, the peak total TKE in the ascending aorta was compared with a pressure loss index. The pressure loss index was based on a previously validated theory relating pressure loss to measures obtainable by echocardiography. RESULTS The total TKE did not appear to be related to global flow patterns visualized based on magnetic resonance–measured velocity fields. The TKE was significantly higher in patients with aortic stenosis than in normal volunteers (p < 0.001). The peak total TKE in the ascending aorta was strongly correlated to index pressure loss (R2 = 0.91). CONCLUSIONS Peak total TKE in the ascending aorta correlated strongly with irreversible pressure loss estimated by a well-established method. Direct measurement of TKE by magnetic resonance flow imaging may, with further validation, be used to estimate irreversible pressure loss in aortic stenosis. PMID:23328563

  3. Hysteresis errors of commonly used sensor materials

    Microsoft Academic Search

    Bulent Aydemir; Levent Yagmur; Sinan Fank

    2010-01-01

    In this study, the hysteresis errors of 17-4 PH precipitation hardened stainless steel, aged Cu–Be (copper beryllium) alloy and AISI 4340 steel, which are commonly used as spring materials for sensors, were determined. Various heat treatment processes were applied to the samples of sensor materials in order to decrease the hysteresis error. The effect of the microstructure on the hysteresis

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

    NASA Astrophysics Data System (ADS)

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

    2012-11-01

    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.

  5. Magnetic properties and magnetocaloric effects in HoPd intermetallic

    NASA Astrophysics Data System (ADS)

    Zhao-Jun, Mo; Jun, Shen; Xin-Qiang, Gao; Yao, Liu; Jian-Feng, Wu; Bao-Gen, Shen; Ji-Rong, Sun

    2015-03-01

    A large reversible magnetocaloric effect accompanied by a second order magnetic phase transition from PM to FM is observed in the HoPd compound. Under the magnetic field change of and the refrigerant capacity RC for the compound are evaluated to be 20 J/(kg · K) and 342 J/kg, respectively. In particular, large (11.3 J/(kg · K)) and RC (142 J/kg) are achieved under a low magnetic field change of 0–2 T with no thermal hysteresis and magnetic hysteresis loss. The large reversible magnetocaloric effect (both the large -?SM and the high RC) indicates that HoPd is a promising material for magnetic refrigeration at low temperature. Project supported by the National Natural Science Foundation of China (Grant Nos. 51322605, 11104337, 51271192, and 11274357) and the Knowledge Innovation Project of the Chinese Academy of Sciences.

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

    Microsoft Academic Search

    B. K. Bose

    1990-01-01

    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

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

    SciTech Connect

    Ghasemi, Ali, E-mail: ali13912001@yahoo.com [Materials Engineering Department, Malek Ashtar University of Technology, Shahin Shahr (Iran, Islamic Republic of); Paesano, Andrea; Cerqueira Machado, Carla Fabiana [Departamento de Física, Centro de Ciências Exatas, Universidade Estadual de Maringá, Maringá (Brazil); Shirsath, Sagar E. [Department of Physics, Dr. Babasaheb Ambedkar Marathwada University, Aurangabad (India); Spin Device Technology Center, Faculty of Engineering, Shinshu University, Nagano (Japan); Liu, Xiaoxi; Morisako, Akimitsu [Spin Device Technology Center, Faculty of Engineering, Shinshu University, Nagano (Japan)

    2014-05-07

    In current research work, Co{sub 1-x}Ni{sub x/2}Sr{sub x/2}Fe{sub 2}O{sub 4} (x?=?0–1 in a step of 0.2) ferrite nanoparticles were synthesized by a sol-gel method. According to the evolution in the subspectral areas obtained from Mössbauer spectroscopy, it was found that the relaxing iron belongs mostly to the site B, since the Mössbauer fraction of site A does not vary appreciably. With an increase in Ni-Sr substitution contents in cobalt ferrite, the coercivity and saturation of magnetization decrease. Variation of reflection loss versus frequency in microwave X-band demonstrates that the reflection peak shifts to lower frequency by adding substituted cations and the synthesized nanoparticles can be considered for application in electromagnetic wave absorber technology.

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

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

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

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

    PubMed Central

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

    2013-01-01

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

  10. A New Magnetic Material of High Permeability

    Microsoft Academic Search

    O. L. Boothby; R. M. Bozorth

    1947-01-01

    This paper describes the preparation, heat treatment, and properties of supermalloy, a magnetic alloy of iron, nickel, and molybdenum. In the form of 0.014 in. sheet it has an initial permeability of 50,000 to 150,000, a maximum permeability of 600,000 to 1,200,000, coercive force of 0.002 to 0.005 oersted, and a hysteresis loss of less than 5 ergs?cm3?cycle at B=5000.

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

    PubMed Central

    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

    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

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

    SciTech Connect

    GHOSH,A.

    2004-03-22

    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.

  13. Magnetic flux and heat losses by diffusive, advective, and Nernst effects in MagLIF-like plasma

    NASA Astrophysics Data System (ADS)

    Velikovich, A. L.; Giuliani, J. L.; Zalesak, S. T.

    2014-12-01

    The MagLIF approach to inertial confinement fusion involves subsonic/isobaric compression and heating of a DT plasma with frozen-in magnetic flux by a heavy cylindrical liner. The losses of heat and magnetic flux from the plasma to the liner are thereby determined by plasma advection and gradient-driven transport processes, such as thermal conductivity, magnetic field diffusion and thermomagnetic effects. Theoretical analysis based on obtaining exact self-similar solutions of the classical collisional Braginskii's plasma transport equations in one dimension demonstrates that the heat loss from the hot plasma to the cold liner is dominated by the transverse heat conduction and advection, and the corresponding loss of magnetic flux is dominated by advection and the Nernst effect. For a large electron Hall parameter ?e?e effective diffusion coefficients determining the losses of heat and magnetic flux are both shown to decrease with ?e?e as does the Bohm diffusion coefficient, which is commonly associated with low collisionality and two-dimensional transport. This family of exact solutions can be used for verification of codes that model the MagLIF plasma dynamics.

  14. Perovskite-fullerene hybrid materials suppress hysteresis in planar diodes.

    PubMed

    Xu, Jixian; Buin, Andrei; Ip, Alexander H; Li, Wei; Voznyy, Oleksandr; Comin, Riccardo; Yuan, Mingjian; Jeon, Seokmin; Ning, Zhijun; McDowell, Jeffrey J; Kanjanaboos, Pongsakorn; Sun, Jon-Paul; Lan, Xinzheng; Quan, Li Na; Kim, Dong Ha; Hill, Ian G; Maksymovych, Peter; Sargent, Edward H

    2015-01-01

    Solution-processed planar perovskite devices are highly desirable in a wide variety of optoelectronic applications; however, they are prone to hysteresis and current instabilities. Here we report the first perovskite-PCBM hybrid solid with significantly reduced hysteresis and recombination loss achieved in a single step. This new material displays an efficient electrically coupled microstructure: PCBM is homogeneously distributed throughout the film at perovskite grain boundaries. The PCBM passivates the key PbI3(-) antisite defects during the perovskite self-assembly, as revealed by theory and experiment. Photoluminescence transient spectroscopy proves that the PCBM phase promotes electron extraction. We showcase this mixed material in planar solar cells that feature low hysteresis and enhanced photovoltage. Using conductive AFM studies, we reveal the memristive properties of perovskite films. We close by positing that PCBM, by tying up both halide-rich antisites and unincorporated halides, reduces electric field-induced anion migration that may give rise to hysteresis and unstable diode behaviour. PMID:25953105

  15. Perovskite–fullerene hybrid materials suppress hysteresis in planar diodes

    PubMed Central

    Xu, Jixian; Buin, Andrei; Ip, Alexander H.; Li, Wei; Voznyy, Oleksandr; Comin, Riccardo; Yuan, Mingjian; Jeon, Seokmin; Ning, Zhijun; McDowell, Jeffrey J.; Kanjanaboos, Pongsakorn; Sun, Jon-Paul; Lan, Xinzheng; Quan, Li Na; Kim, Dong Ha; Hill, Ian G.; Maksymovych, Peter; Sargent, Edward H.

    2015-01-01

    Solution-processed planar perovskite devices are highly desirable in a wide variety of optoelectronic applications; however, they are prone to hysteresis and current instabilities. Here we report the first perovskite–PCBM hybrid solid with significantly reduced hysteresis and recombination loss achieved in a single step. This new material displays an efficient electrically coupled microstructure: PCBM is homogeneously distributed throughout the film at perovskite grain boundaries. The PCBM passivates the key PbI3? antisite defects during the perovskite self-assembly, as revealed by theory and experiment. Photoluminescence transient spectroscopy proves that the PCBM phase promotes electron extraction. We showcase this mixed material in planar solar cells that feature low hysteresis and enhanced photovoltage. Using conductive AFM studies, we reveal the memristive properties of perovskite films. We close by positing that PCBM, by tying up both halide-rich antisites and unincorporated halides, reduces electric field-induced anion migration that may give rise to hysteresis and unstable diode behaviour. PMID:25953105

  16. Iron loss in permanent-magnet brushless AC machines under maximum torque per ampere and flux weakening control

    Microsoft Academic Search

    Z. Q. Zhu; Y. S. Chen; D. Howe

    2002-01-01

    The airgap flux density distribution, flux density loci in the stator core, and the associated iron loss in two topologies of brushless AC motor, having a surface-mounted magnet rotor and an interior-mounted magnet rotor, respectively, are investigated when operated under maximum torque per ampere control in the constant torque mode and maximum power control in the flux-weakening mode. It is

  17. Asymmetrically shaped hysteresis loop in exchange-biased FeNi\\/FeMn film

    Microsoft Academic Search

    S. L. Gnatchenko; D. N. Merenkov; A. N. Bludov; V. V. Pishko; Yu. A. Shakhayeva; M. Baran; R. Szymczak; V. A. Novosad

    2006-01-01

    The magnetization reversal of the bilayer polycrystalline FeNi(50Å)\\/FeMn(50Å) film sputtered in a magnetic field has been studied by magnetic and magneto-optical techniques. The external magnetic fields were applied along the easy or hard magnetization axis of the ferromagnetic permalloy layer. The asymmetry of hysteresis loop has been found. Appreciable asymmetry and the exchange bias were observed only in the field

  18. Hysteresis, microstructure, and magneto-optical recording in Co\\/Pt and Co\\/Pd multilayers

    Microsoft Academic Search

    W. B. Zeper; H. W. van Kesteren; B. A. J. Jacobs; J. H. M. Spruit; P. F. Carcia

    1991-01-01

    The factors that influence the coercive field Hc and the shape of the magnetic hysteresis loop for Co\\/Pt multilayers (MLs), applied as a magneto-optical (MO) recording medium, have been investigated. The hysteresis loop of MLs, made by evaporation of Kr sputtering, became more rectangular when the total film thickness was reduced, i.e., the saturation field Hs decreased and the nucleation

  19. Efficient Computational Model of Hysteresis

    NASA Technical Reports Server (NTRS)

    Shields, Joel

    2005-01-01

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

  20. The effect of thermal resistances and regenerative losses on the performance characteristics of a magnetic Ericsson refrigeration cycle

    Microsoft Academic Search

    Jincan Chen; Zijun Yan

    1998-01-01

    The effect of the irreversibilities due to thermal resistances and regenerative losses on the performance of a magnetic Ericsson refrigeration cycle is investigated, based on the Curie law and Newtonian heat-transfer law. Some fundamental optimum relations and general performance characteristics of the cycle are obtained. The maximum cooling rate and some important performance parameters are calculated. The optimal operating regions

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

    SciTech Connect

    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

    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.

  2. Magnetic resonance temperature imaging-based quantification of blood flow-related energy losses.

    PubMed

    Dillon, Christopher; Roemer, Robert; Payne, Allison

    2015-07-01

    This study presents a new approach for evaluating bioheat transfer equation (BHTE) models used in treatment planning, control and evaluation of all thermal therapies. First, 3D magnetic resonance temperature imaging (MRTI) data are used to quantify blood flow-related energy losses, including the effects of perfusion and convection. Second, this information is used to calculate parameters of a BHTE model: in this paper the widely used Pennes BHTE. As a self-consistency check, the BHTE parameters are utilized to predict the temperatures from which they were initially derived. The approach is evaluated with finite-difference simulations and implemented experimentally with focused ultrasound heating of an ex vivo porcine kidney perfused at 0, 20 and 40 ml/min (n = 4 each). The simulation results demonstrate accurate quantification of blood flow-related energy losses, except in regions of sharp blood flow discontinuities, where the transitions are spatially smoothed. The smoothed transitions propagate into estimates of the Pennes perfusion parameter but have limited effect on the accuracy of temperature predictions using these estimates. Longer acquisition time periods mitigate the effects of MRTI noise, but worsen the effect of flow discontinuities. For the no-flow kidney experiments the estimates of a uniform, constant Pennes perfusion parameter are approximately zero, and at 20 and 40 ml/min the average estimates increase with flow rate to 3.0 and 4.2 kg/m(3) /s, respectively. When Pennes perfusion parameter values are allowed to vary spatially, but remain temporally constant, BHTE temperature predictions are more accurate than when using spatially uniform, constant Pennes perfusion values, with reductions in RMSE values of up to 79%. Locations with large estimated perfusion values correspond to high flow regions of the kidney observed in T1 -weighted MR images. This novel, MRTI-based technique holds promise for improving understanding of thermal therapy biophysics and for evaluating biothermal models. Copyright © 2015 John Wiley & Sons, Ltd. PMID:25973583

  3. Characterization of soft magnetic material Metglas 2605S-3A for power applications and transformers

    Microsoft Academic Search

    W. R. Wieserman; G. L. Kusic

    1995-01-01

    This experimental study separates the hysteresis, eddy current, and electromechanical motion losses of a soft magnetic material for electric power energy conversion applications. Mechanical responses of the magnetic material to sine and square wave voltage excitation are compared. Commercially available, Metglas 2605S3-A tape cores were evaluated up to 300 C for sine wave and square wave voltage excitation frequencies 1--100

  4. Study of the influence of structural hysteresis on polaron interactions of lightly doped poly(3-dodecylthiophene) with FeCl 3

    Microsoft Academic Search

    G. ?ík; L. Dlhá?; F. Šerše?; P. Rapta

    2007-01-01

    EPR, dc and ac magnetic measurements on lightly doped poly(3-dodecylthiophene) with FeCl3 are reported. The zero-field-cooled and field-cooled curves obtained by a SQUID magnetometer confirmed magnetic hysteresis, beginning close to the room temperature. Magnetic hysteresis is close-knit with structural irreversibility of polymeric chains. Structural irreversibility induces changes in proportions of diamagnetic, Pauli, Currie, and polaron magnetic contributions of the polymeric

  5. Electric and magnetic losses modeled by a stable hybrid with explicit-implicit time-stepping for Maxwell's equations

    SciTech Connect

    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

    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.

  6. Measurement of dynamic magnetization induced by a pulsed field: Proposal for a new rock magnetism method

    NASA Astrophysics Data System (ADS)

    Kodama, Kazuto

    2015-02-01

    This study proposes a new method for measuring transient magnetization of natural samples induced by a pulsed field with duration of 11 ms using a pulse magnetizer. An experimental system was constructed, consisting of a pair of differential sensing coils connected with a high-speed digital oscilloscope for data acquisition. The data were transferred to a computer to obtain an initial magnetization curve and a descending branch of a hysteresis loop in a rapidly changing positive field. This system was tested with synthetic samples (permalloy ribbon, aluminum plate, and nickel powder) as well as two volcanic rock samples. Results from the synthetic samples showed considerable differences from those measured by a quasi-static method using a vibrating sample magnetometer (VSM). These differences were principally due to the time-dependent magnetic properties or to electromagnetic effects, such as magnetic viscosity, eddy current loss, or magnetic relaxation. Results from the natural samples showed that the transient magnetization–field curves were largely comparable to the corresponding portions of the hysteresis loops. However, the relative magnetization (scaled to the saturation magnetization) at the end of a pulse was greater than that measured by a VSM. This discrepancy, together with the occurrence of rapid exponential decay after a pulse, indicates magnetic relaxations that could be interpreted in terms of domain wall displacement. These results suggest that with further developments, the proposed technique can become a useful tool for characterizing magnetic particles contained in a variety of natural materials.

  7. Asymmetrically shaped hysteresis loop in exchange-biased FeNi/FeMn film

    NASA Astrophysics Data System (ADS)

    Gnatchenko, S. L.; Merenkov, D. N.; Bludov, A. N.; Pishko, V. V.; Shakhayeva, Yu. A.; Baran, M.; Szymczak, R.; Novosad, V. A.

    2006-12-01

    The magnetization reversal of the bilayer polycrystalline FeNi(50 Å)/FeMn(50 Å) film sputtered in a magnetic field has been studied by magnetic and magneto-optical techniques. The external magnetic fields were applied along the easy or hard magnetization axis of the ferromagnetic permalloy layer. The asymmetry of hysteresis loop has been found. Appreciable asymmetry and the exchange bias were observed only in the field applied along the easy axis. The specific features of magnetization reversal were explained within the phenomenological model that involves high-order exchange anisotropy and misalignment of the easy axes of the antiferromagnetic and ferromagnetic layers. It has been shown that the film can exist in one of three equilibrium magnetic states in the field applied along the easy axis. The transitions between these states occur as first-order phase transitions. The observed hysteresis loop asymmetry is related to the existence of the metastable state.

  8. The effect of thermal resistances and regenerative losses on the performance characteristics of a magnetic Ericsson refrigeration cycle

    NASA Astrophysics Data System (ADS)

    Chen, Jincan; Yan, Zijun

    1998-08-01

    The effect of the irreversibilities due to thermal resistances and regenerative losses on the performance of a magnetic Ericsson refrigeration cycle is investigated, based on the Curie law and Newtonian heat-transfer law. Some fundamental optimum relations and general performance characteristics of the cycle are obtained. The maximum cooling rate and some important performance parameters are calculated. The optimal operating regions of the cycle are determined. The results obtained will be helpful for the optimal design and operation of real magnetic Ericsson refrigerators.

  9. NONLINEAR SEMIGROUP METHODS IN PROBLEMS WITH HYSTERESIS

    Microsoft Academic Search

    Jana Kopfov

    Results from a nonlinear semigroup theory are applied to get ex- istence and uniqueness for PDEs with hysteresis. The hysteresis nonlinearity considered is of the generalized play operator type, but can be easily extended to a generalized Prandtl-Ishlinskii operator of play type, both possibly discon- tinuous. 1. Introduction. We show in this paper how nonlinear semigroup theory can be used

  10. Wavelet implementation of Preisach model of hysteresis

    Microsoft Academic Search

    Yunhe Yu; Zhengchu Xiao; En-Bing Lin; Nagi G. Naganathan

    1999-01-01

    Preisach model has enjoyed extensive applications in describing the hysteresis phenomena. However an important open question in the analysis of hysteresis using Preisach models is the determination of the model parameters. This is to determine the parameter of Preisach function and is referred as the identification problem. However, no general mathematical methods appear to be available for the identification of

  11. A Test of HTS Power Cable in a Sweeping Magnetic Field

    SciTech Connect

    Piekarz, H.; Hays, S.; Blowers, J.; Shiltsev, V.; /Fermilab

    2011-11-29

    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.

  12. Magnetic properties and magnetocaloric effect in the RCu{sub 2}Si{sub 2} and RCu{sub 2}Ge{sub 2} (R?=?Ho, Er) compounds

    SciTech Connect

    Mo, Zhao-Jun [School of Material Science and Engineering, Hebei University of Technology, Tianjin (China); Key laboratory of cryogenics, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing (China); Shen, Jun, E-mail: jshen@mail.ipc.ac.cn, E-mail: tangcc@hebut.edu.cn; Wu, Jian-Feng [Key laboratory of cryogenics, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing (China); Yan, Li-Qin; Wang, Li-Chen; Sun, Ji-rong; Shen, Bao-Gen [State Key Laboratory of Magnetism, Beijing National Laboratory for Condensed Matter, Physics and Institute of Physics, Chinese Academy of Sciences, Beijing (China); Gao, Xin-Qiang; Tang, Cheng-Chun, E-mail: jshen@mail.ipc.ac.cn, E-mail: tangcc@hebut.edu.cn [School of Material Science and Engineering, Hebei University of Technology, Tianjin (China)

    2014-02-21

    The magnetic properties and magnetocaloric effect (MCE) in RCu{sub 2}Si{sub 2} and RCu{sub 2}Ge{sub 2} (R?=?Ho, Er) compounds have been investigated. All these compounds possess an antiferromagnetic (AFM)-paramagnetic (PM) transition around their respective Neel temperatures. The RCu{sub 2}Si{sub 2} compounds undergo spin-glassy behavior above Neel temperature. Furthermore, a field-induced metamagnetic transition from AFM to ferromagnetic (FM) states is observed in these compounds. The calculated magnetic entropy changes show that all RCu{sub 2}Si{sub 2} and RCu{sub 2}Ge{sub 2} (R?=?Ho, Er) compounds, especially, ErCu{sub 2}Si{sub 2} exhibits large MCEs with no thermal hysteresis and magnetic hysteresis loss. The value of ??S{sub M}{sup max} reaches 22.8?J/Kg K for magnetic field changes from 0 to 5?T. In particular, for field changes of 1 and 2?T, the giant reversible magnetic entropy changes ??S{sub M}{sup max} are 8.3 and 15.8?J/kg K at 2.5?K, which is lower than the boiling point of helium. The low-field giant magnetic entropy change, together with ignorable thermal hysteresis and field hysteresis loss of ErCu{sub 2}Si{sub 2} compound is expected to have effective applications in low temperature magnetic refrigeration.

  13. Influences of Magnetization Characteristics of the Materials on the Iron Loss of the Wound-Core Type Three-Phase Transformer

    NASA Astrophysics Data System (ADS)

    Shinya, Kunihiro; Saito, Koichi

    This paper describes the influences of magnetization characteristics of the materials on the iron loss of wound-core type three-phase transformer. In the analysis, magnetization characteristics are approximated by a Fourier-series, and it is assumed that the eddy current factor is proportional to the time-varying magnetic flux. Moreover harmonic balance method where the zero-phase-sequence and third harmonic components of flux density are taken into consider is used. From the results of numerical analysis, it is shown that iron loss decreases as the ratio of eddy currents loss to iron loss of the material becomes minor. The importance of non-linearity of magnetization characteristics of the materials to reduce iron loss of wound-core type three-phase transformer is also shown. The analytical results agree roughly with the experimental result.

  14. Estimation of iron losses of M3 and M5 magnetic core material with three phase PWM inverter supply

    Microsoft Academic Search

    S. Tadsuan

    2007-01-01

    This paper presents a comparision of iron losses of grain oriented magnetic steel with three 3 -phase PWM inverter supply. In this experiment, using 0.23 mm(M3)- thickness, 0.30 mm.(M5)- thick and by setting equal peak fundamental flux density for each test procedure, with 0.3, 0.6, 0.9 -modulation index and 1, 2, 3, 4, 5 kHz.-inverter switching frequencies. The results show

  15. High-performance Fe/SiO2 soft magnetic composites for low-loss and high-power applications

    NASA Astrophysics Data System (ADS)

    Yang, Bai; Wu, Zhangben; Zou, Zhiyu; Yu, Ronghai

    2010-09-01

    High-performance Fe/SiO2 soft magnetic composites (SMCs) by coating pure iron particles with amorphous SiO2 layers have been fabricated by controlled hydrolysation of tetraethyl orthosilicate (TEOS). Microstructural studies show that the pure iron particles are uniformly and entirely coated with the SiO2 insulating layers to form Fe/SiO2 core-shell structure. The dielectric SiO2 layers lead to the electrical insulation behaviour of the SiO2-coated iron particles, which results in low core loss of the compacted Fe/SiO2 SMCs in application of alternating current. The core loss measured at a frequency of 50 Hz and an induction level of 1 T is 3.5 W kg-1, which is much lower than that of the commercial SMCs prepared by coating iron particles with phosphate layers. The Fe/SiO2 SMCs exhibit nearly the same coercivity as that of pure iron, and saturation magnetization of 18.2 kG, a little lower than that of pure iron due to the nonmagnetic SiO2 layers. The low core loss and high saturation magnetization promise the great potential of Fe/SiO2 SMCs in high-power applications. High-frequency measurements reveal that the working frequency of the Fe/SiO2 SMCs can reach up to 20 MHz.

  16. Influence of irreversible losses on the performance of a two-stage magnetic Brayton refrigeration cycle

    Microsoft Academic Search

    X. Zhang; J. Chen; G. Lin; E. Brück

    2010-01-01

    The general performance characteristics of a two-stage magnetic Brayton refrigeration cycle consisting of three constant magnetic fields and three irreversible adiabatic processes are investigated. Based on the thermodynamic properties of a magnetic material and the irreversible cycle model of a two-stage Brayton refrigerator, expressions for the cooling load and coefficient of performance of the refrigeration system are derived. The influence

  17. Computational analysis of current-loss mechanisms in a post-hole convolute driven by magnetically insulated transmission lines

    NASA Astrophysics Data System (ADS)

    Rose, D. V.; Madrid, E. A.; Welch, D. R.; Clark, R. E.; Mostrom, C. B.; Stygar, W. A.; Cuneo, M. E.

    2015-03-01

    Numerical simulations of a vacuum post-hole convolute driven by magnetically insulated vacuum transmission lines (MITLs) are used to study current losses due to charged particle emission from the MITL-convolute-system electrodes. This work builds on the results of a previous study [E. A. Madrid et al. Phys. Rev. ST Accel. Beams 16, 120401 (2013), 10.1103/PhysRevSTAB.16.120401] and adds realistic power pulses, Ohmic heating of anode surfaces, and a model for the formation and evolution of cathode plasmas. The simulations suggest that modestly larger anode-cathode gaps in the MITLs upstream of the convolute result in significantly less current loss. In addition, longer pulse durations lead to somewhat greater current loss due to cathode-plasma expansion. These results can be applied to the design of future MITL-convolute systems for high-current pulsed-power systems.

  18. Thickness dependence of ac losses in circular disks of YBa2Cu3O7 films in perpendicular magnetic fields

    NASA Astrophysics Data System (ADS)

    Suenaga, M.; Li, Q.; Ye, Z.; Iwakuma, M.; Toyota, K.; Funaki, F.; Foltyn, S. R.; Wang, H.; Clem, John R.

    2004-01-01

    The ac losses in three disk-shaped YBa2Cu3O7 (YBCO) films, which were deposited on SrTiO3 by the pulsed-laser-deposition technique and had thicknesses, d, of 0.2, 1.0, and 3.0 ?m, were measured in perpendicular applied ac magnetic fields to ˜0.14 T at 10 Hz in liquid nitrogen. The losses at low fields were found to be a strong function of the film thickness. The measured losses were compared with the theoretically calculated losses. The ac losses calculated using a field-independent critical-current density, the Bean model [J. R. Clem and A. Sanchez, Phys. Rev. B 50, 9355 (1994)], agreed very well with the 0.2-?m-thick film, while the calculated losses agreed well with the measured ones when a field-dependent critical-current density, the Kim model [D. V. Shantsev, Y. M. Galperin, and T. H. Johansen, Phys. Rev. B 61, 9699 (2000)], was used for the films of thickness 1.0 and 3.0 ?m. However, a surprising discrepancy was found in the values of Bc and B0 for thinner YBCO films depending on whether they were determined by ac or dc measurements. Bc is defined as Bc=?0Jc(0)d/2, B0 is the characteristic field in the Kim-model critical-current density JcK(Ba)=Jc(0)/(1+Ba/B0), and Jc(0) is the critical-current density at applied magnetic field Ba=0.

  19. Magnetically-induced circular-polarization-dependent loss of magneto-optic fiber Bragg gratings with linear birefringence

    NASA Astrophysics Data System (ADS)

    Wu, Baojian; Wen, Feng; Qiu, Kun; Han, Rui; Lu, Xin

    2013-06-01

    The concept of magnetically-induced circular-polarization-dependent loss (MCDL) for magneto-optic fiber Bragg gratings (MFBGs) is introduced. The magnetic field dependency of MCDL for linearly birefringent MFBGs is simulated by use of the equivalent theoretical model given in the paper. This model is mainly composed of an elliptical polarization extractor and a couple of isotropic fiber Bragg gratings (FBGs) with different effective refractive indices. It is shown by simulation that, (1) when the magnetooptic-to-grating coupling coefficient ratio is less than 0.1, the peak MCDL is proportional to applied magnetic induction; (2) the MCDL method is more suitable for the magnetic field measurement than the conventional polarization dependent loss (PDL) for the linearly birefringent MFBGs. As an example, the MCDL of an erbium-doped MFBG (Er-MFBG) is measured and the experimental data are in agreement with the theoretical results. The effective Verdet constant for the Er-MFBG is about -11 rad/(T·m) and the peak MCDL is up to 1 dB at 1.15 T.

  20. Core losses in nanocrystalline soft magnetic materials under square voltage waveforms

    Microsoft Academic Search

    Vencislav Valchev; Alex Van den Bossche; Peter Sergeant

    2008-01-01

    The study of losses in nanocrystalline alloys under square voltage waveforms—often used in power electronics—is the aim of the presented numerical model and experiments. The model predicts the losses based on the theory of one-dimensional homogeneous transmission lines. The experiments are carried out by a specially designed high-current high-frequency platform in a full bridge configuration with phase shift. The losses

  1. A combined experimental and finite element analysis method for the estimation of eddy-current loss in NdFeB magnets.

    PubMed

    Fratila, Radu; Benabou, Abdelkader; Tounzi, Abdelmounaïm; Mipo, Jean-Claude

    2014-01-01

    NdFeB permanent magnets (PMs) are widely used in high performance electrical machines, but their relatively high conductivity subjects them to eddy current losses that can lead to magnetization loss. The Finite Element (FE) method is generally used to quantify the eddy current loss of PMs, but it remains quite difficult to validate the accuracy of the results with complex devices. In this paper, an experimental test device is used in order to extract the eddy current losses that are then compared with those of a 3D FE model. PMID:24831111

  2. Method for the measurement of anisotropy and rotational hysteresis using linear dichroism

    SciTech Connect

    Antel, W. J.; Coulthard, I.; Freeland, J. W.; Stampfl, A. P. J.; Schwickert, M. M.

    2001-08-13

    A technique combining x-ray magnetic linear dichroism absorption spectroscopy and rotational hysteresis loops is demonstrated. This technique, x-ray magnetic linear loops (XMLL), is used to extract magnetocrystalline anisotropy information. Results from two systems, a polycrystalline Fe film, and an epitaxial Fe film which exhibit different magnetic anisotropies, are shown. The measured XMLL is described using a simple single-domain anisotropy model. {copyright} 2001 American Institute of Physics.

  3. Core losses and efficiency of electrical motors using new magnetic materials

    Microsoft Academic Search

    D. Binesti; J. P. Ducreux

    1996-01-01

    Core losses of an 18.5 kW asynchronous motor were measured and computed, by means of a suitable electromagnetic fields package, improved for core loss calculation. The results show that a 1 to 3% improvement in efficiency is possible by replacing the conventional soft laminations by new materials. The differences between measurement and computation are mainly attributed to rotating fields inside

  4. Fatigue Hysteresis of Carbon Fiber-Reinforced Ceramic-Matrix Composites at Room and Elevated Temperatures

    NASA Astrophysics Data System (ADS)

    Li, Longbiao

    2015-05-01

    When the fiber-reinforced ceramic-matrix composites (CMCs) are first loading to fatigue peak stress, matrix multicracking and fiber/matrix interface debonding occur. Under fatigue loading, the stress-strain hysteresis loops appear as fiber slipping relative to matrix in the interface debonded region upon unloading/reloading. Due to interface wear at room temperature or interface oxidation at elevated temperature, the interface shear stress degredes with increase of the number of applied cycles, leading to the evolution of the shape, location and area of stress-strain hysteresis loops. The evolution characteristics of fatigue hysteresis loss energy in different types of fiber-reinforced CMCs, i.e., unidirectional, cross-ply, 2D and 2.5D woven, have been investigated. The relationships between the fatigue hysteresis loss energy, stress-strain hysteresis loops, interface frictional slip, interface shear stress and interface radial thermal residual stress, matrix stochastic cracking and fatigue peak stress of fiber-reinforced CMCs have been established.

  5. Effects of flux and torque hysteresis band amplitude in direct torque control of induction machines

    Microsoft Academic Search

    D. Casadei; G. Grandi; G. Serra; A. Tani

    1994-01-01

    Direct torque control of induction machines allows high dynamic performance to be obtained utilising a simple signal processing method. Furthermore, this control technique does not require current regulators so reducing the hardware requirements. In this paper, the influence of the amplitude of flux and torque hysteresis bands on switching frequency, torque and flux ripple, current distortion and drive losses is

  6. Transport, hysteresis and avalanches in artificial spin ice systems

    SciTech Connect

    Reichhardt, Charles [Los Alamos National Laboratory; Reichhardt, Cynthia J [Los Alamos National Laboratory; Libal, A [BABES-BOLYAI UNIV.

    2010-01-01

    We examine the hopping dynamics of an artificial spin ice system constructed from colloids on a kagome optical trap array where each trap has two possible states. By applying an external drive from an electric field which is analogous to a biasing applied magnetic field for real spin systems, we can create polarized states that obey the spin-ice rules of two spins in and one spin out at each vertex. We demonstrate that when we sweep the external drive and measure the fraction of the system that has been polarized, we can generate a hysteresis loop analogous to the hysteretic magnetization versus external magnetic field curves for real spin systems. The disorder in our system can be readily controlled by changing the barrier that must be overcome before a colloid can hop from one side of a trap to the other. For systems with no disorder, the effective spins all flip simultaneously as the biasing field is changed, while for strong disorder the hysteresis curves show a series of discontinuous jumps or avalanches similar to Barkhausen noise.

  7. Magnetic ordering of nuclear spins in an interacting two-dimensional electron gas Pascal Simon,1,2 Bernd Braunecker,1 and Daniel Loss1

    E-print Network

    Braunecker, Bernd

    Magnetic ordering of nuclear spins in an interacting two-dimensional electron gas Pascal Simon,1,2 Bernd Braunecker,1 and Daniel Loss1 1Department of Physics, University of Basel, Klingelbergstrasse 82

  8. Fast-ion losses induced by ELMs and externally applied magnetic perturbations in the ASDEX Upgrade tokamak

    NASA Astrophysics Data System (ADS)

    Garcia-Munoz, M.; Äkäslompolo, S.; de Marne, P.; Dunne, M. G.; Dux, R.; Evans, T. E.; Ferraro, N. M.; Fietz, S.; Fuchs, C.; Geiger, B.; Herrmann, A.; Hoelzl, M.; Kurzan, B.; Lazanyi, N.; McDermott, R. M.; Nocente, M.; Pace, D. C.; Rodriguez-Ramos, M.; Shinohara, K.; Strumberger, E.; Suttrop, W.; Van Zeeland, M. A.; Viezzer, E.; Willensdorfer, M.; Wolfrum, E.

    2013-12-01

    Phase-space time-resolved measurements of fast-ion losses induced by edge localized modes (ELMs) and ELM mitigation coils have been obtained in the ASDEX Upgrade tokamak by means of multiple fast-ion loss detectors (FILDs). Filament-like bursts of fast-ion losses are measured during ELMs by several FILDs at different toroidal and poloidal positions. Externally applied magnetic perturbations (MPs) have little effect on plasma profiles, including fast-ions, in high collisionality plasmas with mitigated ELMs. A strong impact on plasma density, rotation and fast-ions is observed, however, in low density/collisionality and q95 plasmas with externally applied MPs. During the mitigation/suppression of type-I ELMs by externally applied MPs, the large fast-ion bursts observed during ELMs are replaced by a steady loss of fast-ions with a broad-band frequency and an amplitude of up to an order of magnitude higher than the neutral beam injection (NBI) prompt loss signal without MPs. Multiple FILD measurements at different positions, indicate that the fast-ion losses due to static 3D fields are localized on certain parts of the first wall rather than being toroidally/poloidally homogeneously distributed. Measured fast-ion losses show a broad energy and pitch-angle range and are typically on banana orbits that explore the entire pedestal/scrape-off-layer (SOL). Infra-red measurements are used to estimate the heat load associated with the MP-induced fast-ion losses. The heat load on the FILD detector head and surrounding wall can be up to six times higher with MPs than without 3D fields. When 3D fields are applied and density pump-out is observed, an enhancement of the fast-ion content in the plasma is typically measured by fast-ion D-alpha (FIDA) spectroscopy. The lower density during the MP phase also leads to a deeper beam deposition with an inward radial displacement of ?2 cm in the maximum of the beam emission. Orbit simulations are used to test different models for 3D field equilibrium reconstruction including vacuum representation, the free boundary NEMEC code and the two-fluid M3D-C1 code which account for the plasma response. Guiding center simulations predict the maximum level of losses, ?2.6%, with NEMEC 3D equilibrium. Full orbit simulations overestimate the level of losses in 3D vacuum fields with ?15% of lost NBI ions.

  9. Cumulative growth of minor hysteresis loops in the Kolmogorov model

    SciTech Connect

    Meilikhov, E. Z., E-mail: meilikhov@imp.kiae.ru; Farzetdinova, R. M. [National Research Centre Kurchatov Institute (Russian Federation)] [National Research Centre Kurchatov Institute (Russian Federation)

    2013-01-15

    The phenomenon of nonrepeatability of successive remagnetization cycles in Co/M (M = Pt, Pd, Au) multilayer film structures is explained in the framework of the Kolmogorov crystallization model. It is shown that this model of phase transitions can be adapted so as to adequately describe the process of magnetic relaxation in the indicated systems with 'memory.' For this purpose, it is necessary to introduce some additional elements into the model, in particular, (i) to take into account the fact that every cycle starts from a state 'inherited' from the preceding cycle and (ii) to assume that the rate of growth of a new magnetic phase depends on the cycle number. This modified model provides a quite satisfactory qualitative and quantitative description of all features of successive magnetic relaxation cycles in the system under consideration, including the surprising phenomenon of cumulative growth of minor hysteresis loops.

  10. AC losses in HTS tapes in applied longitudinal magnetic fields at variable temperatures

    Microsoft Academic Search

    Torbjörn Wass; Sven P. Hörnfeldt

    2004-01-01

    In most power devices, the conductor is carrying an ac transport current while it is exposed to an ac magnetic field transverse to the current path. In certain applications, such as power cables or a control winding in a controllable reactor, the conductors are exposed to a magnetic field component longitudinal to the tape axis that is parallel to the

  11. Adhesion hysteresis of silane coated microcantilevers

    SciTech Connect

    DE BOER,MAARTEN P.; KNAPP,JAMES A.; MICHALSKE,TERRY A.; SRINIVASAN,U.; MABOUDIAN,R.

    2000-04-17

    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.

  12. Power losses of Finemet using nonsinusoidal waveforms

    NASA Astrophysics Data System (ADS)

    Ramin, D.; Riehemann, W.

    1999-08-01

    Though many practical applications preferably take advantage of nonsinusoidal induction waveforms the characterisation of soft magnetic materials is performed under sinusoidal induction waveforms. Therefore, it would be useful if results from magnetic measurements could be transformed to be valid for applications using different waveforms. This also enables to compare results obtained from measurements where sinusoidal waveforms could not be realised and thus makes them independent of the measuring device used. The dynamic hysteresis loops of differently prepared Finemet ribbons were measured with a computer controlled device at different frequencies and polarisations using sinusoidal and triangular waveforms of the magnetic field which leads to induction waveforms varying with frequency, amplitude of polarisation, waveform of the magnetising field and preparation of specimen material. The samples measured were strips of Fe 73.5Si 13.5Cu 1Nb 3B 9 nanocrystallised at 580°C for 1 h. Different types of samples were used which includes specimens surface treated prior to heat treatment in order to achieve domain refinement. A one to one functional dependency between power loss, frequency, and k-factor was found that enables the comparison of power losses for different induction signals characterised by their form factor as it is already known for grain oriented silicon steel sheets. This dependency is valid for all types of specimen investigated regardless of their different magnetic properties.

  13. Spatial versus time hysteresis in damping mechanisms

    NASA Technical Reports Server (NTRS)

    Banks, H. T.; Fabiano, R. H.; Wang, Y.; Inman, D. J.; Cudney, H., Jr.

    1988-01-01

    A description is given of continuing investigations on the task of estimating internal damping mechanisms in flexible structures. Specifically, two models for internal damping in Euler-Bernoulli beams are considered: spatial hysteresis and time hysteresis. A theoretically sound computational algorithm for estimation is described, and experimental results are discussed. It is concluded that both models perform well in the sense that they accurately predict response for the experiments conducted.

  14. Equivalent Circuit Modeling of Hysteresis Motors

    SciTech Connect

    Nitao, J J; Scharlemann, E T; Kirkendall, B A

    2009-08-31

    We performed a literature review and found that many equivalent circuit models of hysteresis motors in use today are incorrect. The model by Miyairi and Kataoka (1965) is the correct one. We extended the model by transforming it to quadrature coordinates, amenable to circuit or digital simulation. 'Hunting' is an oscillatory phenomenon often observed in hysteresis motors. While several works have attempted to model the phenomenon with some partial success, we present a new complete model that predicts hunting from first principles.

  15. Hysteresis in neural-type circuits

    Microsoft Academic Search

    N. El-Leithy; R. W. Newcomb

    1988-01-01

    The mechanism of generation of hysteresis in a neural-type cell is presented. To make the theory tractable, it is assumed that the hysteresis determining MOS transistors operate in their square-law region when turned on. A set of equations is obtained that can be used for the design of MOS transistor neural-type cells which give pulse code modulation for the coding

  16. Hysteresis effects in Bose-Einstein condensates

    NASA Astrophysics Data System (ADS)

    Sacchetti, Andrea

    2010-07-01

    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.

  17. Hysteresis during contact angles measurement.

    PubMed

    Diaz, M Elena; Fuentes, Javier; Cerro, Ramon L; Savage, Michael D

    2010-03-15

    A theory, based on the presence of an adsorbed film in the vicinity of the triple contact line, provides a molecular interpretation of intrinsic hysteresis during the measurement of static contact angles. Static contact angles are measured by placing a sessile drop on top of a flat solid surface. If the solid surface has not been previously in contact with a vapor phase saturated with the molecules of the liquid phase, the solid surface is free of adsorbed liquid molecules. In the absence of an adsorbed film, molecular forces configure an advancing contact angle larger than the static contact angle. After some time, due to an evaporation/adsorption process, the interface of the drop coexists with an adsorbed film of liquid molecules as part of the equilibrium configuration, denoted as the static contact angle. This equilibrium configuration is metastable because the droplet has a larger vapor pressure than the surrounding flat film. As the drop evaporates, the vapor/liquid interface contracts and the apparent contact line moves towards the center of the drop. During this process, the film left behind is thicker than the adsorbed film and molecular attraction results in a receding contact angle, smaller than the equilibrium contact angle. PMID:20060981

  18. Set-up for calorimetric measurements of the AC losses in HTS tapes due to longitudinal magnetic fields and transport currents

    Microsoft Academic Search

    N. Magnusson; S. Borsos; S. Hörnfeldt

    2002-01-01

    For the design of power applications based on high-temperature superconducting (HTS) tapes, knowledge of the AC losses is needed. In most such applications the HTS tape is exposed to a magnetic field oriented perpendicular to the current path. However, in certain applications, the HTS tape is exposed to a field oriented in parallel with the current path; a longitudinal magnetic

  19. Susceptibility and Inverted Hysteresis Loop of Prussian Blue Analogs with Orthorhombic Structure

    NASA Astrophysics Data System (ADS)

    Guo, An-Bang; Jiang, Wei

    2012-11-01

    The magnetic susceptibility of ternary metal Prussian blue analogues with orthorhombic structure is studied using Ising model. Within the frame work of effective-field theory with correlations, the roles of the mole fraction y, uniaxial magnetic anisotropy, transverse and longitudinal magnetic field are discussed in details. The temperature dependence of the magnetic susceptibility is also investigated. The interesting phenomenon of the inverted magnetic hysteresis loop has been found. The results can help to understand the experimental work of the molecule-based ferri-ferrimagnet.

  20. Analytical core loss calculations for magnetic materials used in high frequency high power converter applications. Ph.D. Thesis - Toledo Univ.

    NASA Technical Reports Server (NTRS)

    Triner, J. E.

    1979-01-01

    The basic magnetic properties under various operating conditions encountered in the state-of-the-art DC-AC/DC converters are examined. Using a novel core excitation circuit, the basic B-H and loss characteristics of various core materials may be observed as a function of circuit configuration, frequency of operation, input voltage, and pulse-width modulation conditions. From this empirical data, a mathematical loss characteristics equation is developed to analytically predict the specific core loss of several magnetic materials under various waveform excitation conditions.

  1. Connecting Flares and Transient Mass Loss Events in Magnetically Active Stars

    E-print Network

    Osten, Rachel A

    2015-01-01

    We explore the ramification of associating the energetics of extreme mag- netic reconnection events with transient mass loss in a stellar analogy with solar eruptive events. We establish energy partitions relative to the total bolometric radiated flare energy for different observed components of stellar flares, and show that there is rough agreement for these values with solar flares. We apply an equipartition between the bolometric radiated flare energy and kinetic energy in an accompanying mass ejection, seen in solar eruptive events and expected from reconnection. This allows an integrated flare rate in a particular waveband to be used to estimate the amount of associated transient mass loss. This approach is supported by a good correspondence between observational flare signatures on high flaring rate stars and the Sun, which suggests a common physical origin. If the frequent and extreme flares that young solar-like stars and low-mass stars experience are accompanied by transient mass loss in the form of ...

  2. SPECIAL FEATURE Social hysteresis and ecological hysteresis Maja Schlu ter Heather Leslie Simon Levin

    E-print Network

    Leslie, Heather

    complex and often conflicting demands for water among different uses and users in a river basinSPECIAL FEATURE Social hysteresis and ecological hysteresis Maja Schlu¨ ter Æ Heather Leslie Æ Simon Levin Managing water-use trade-offs in a semi-arid river delta to sustain multiple ecosystem

  3. Transport ac loss studies of YBCO coated conductors with nickel alloy substrates

    NASA Astrophysics Data System (ADS)

    Duckworth, R. C.; Thompson, J. R.; Gouge, M. J.; Lue, J. W.; Ijaduola, A. O.; Yu, D.; Verebelyi, D. T.

    2003-11-01

    Transport alternating current (ac) loss measurements were performed on a series of rolling-assisted biaxially textured substrate (RABiTS) processed YBa2Cu3Ox (YBCO) coated conductors at 77 K. While each sample possessed a 1 µm layer of YBCO and a 3 µm silver cap layer, two different nickel alloy substrates were used and their impact on the ac loss was examined. Both substrates possessed a 75 µm Ni-5 at%W base, but one substrate also had a 2 µm nickel overlayer as part of the buffer layer architecture. The ac losses, which were determined by thermal and electrical measurements, contained two dominant contributions: superconductive hysteresis in the YBCO and ferromagnetic hysteresis in the substrates. The superconductive component followed the Norris elliptic model for the substrate with the nickel overlayer and the Norris thin strip model for the substrate without the nickel overlayer. The substrates' ferromagnetic loss was determined separately through magnetization measurements, which showed that this loss contribution was independent of the presence of the nickel overlayer for effective ac currents less than 50 A. While the overall loss was lower for the thin-strip-like conductor with no nickel overlayer, further research is necessary to strengthen this connection.

  4. Magnetocaloric effect in the low hysteresis Ni-Mn-In metamagnetic shape-memory Heusler alloy

    NASA Astrophysics Data System (ADS)

    Stern-Taulats, Enric; Castillo-Villa, Pedro O.; Mañosa, Lluís; Frontera, Carlos; Pramanick, Sabyasachi; Majumdar, Subham; Planes, Antoni

    2014-05-01

    We have studied magnetocaloric properties of a Ni-Mn-In metamagnetic shape-memory alloy especially designed in order to display low thermal hysteresis. Magnetization and calorimetric measurements under a magnetic field have been used in order to determine isothermal magnetic field-induced entropy changes. Results obtained indirectly from magnetization data, quasi-directly from isofield calorimetric measurements, and directly from isothermal calorimetric runs are systematic and agree well with each other. We have analyzed the reproducibility of magnetocaloric properties with cycling from direct isothermal calorimetric measurements. Due to low thermal hysteresis, we have found that about 80% of the transition entropy change, ?St ? 25 J/kg K, can be reversibly induced under successive application and removal of a field of 6 T.

  5. Disorder-driven first-order phase transformations: A model for hysteresis

    SciTech Connect

    Dahmen, K.; Kartha, S.; Krumhansl, J.A.; Roberts, B.W.; Sethna, J.P.; Shore, J.D. (Laboratory of Atomic and Solid State Physics, Cornell University, Ithaca, New York 14853-2501 (United States))

    1994-05-15

    Hysteresis loops in some magnetic systems are composed of small avalanches (manifesting themselves as Barkhausen pulses). Hysteresis loops in other first-order phase transitions (including some magnetic systems) often occur via one large avalanche. The transition between these two limiting cases is studied, by varying the disorder in the zero-temperature random-field Ising model. Sweeping the external field through zero at weak disorder, we get one large avalanche with small precursors and aftershocks. At strong disorder, we get a distribution of small avalanches (small Barkhausen effect). At the critical value of disorder where a macroscopic jump in the magnetization first occurs, universal power-law behavior of the magnetization and of the distribution of (Barkhausen) avalanches is found. This transition is studied by mean-field theory, perturbative expansions, and numerical simulation in three dimensions.

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

    E-print Network

    Bornemann, Jens

    of vortex electron beam electron energy loss spectroscopy (EELS), or vortex-EELS for short, is presented, to calculate spatially resolved vortex-EELS maps of a metal split ring resonator (SRR). The vortex-EELS scattering cross section for the SRR structure is within an order of magnitude of conventional EELS typically

  7. 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)

    Su, Xing-liang; Xiong, Li-ting; Gao, Yuan-wen; Zhou, You-he

    2013-07-01

    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.

  8. Combinatorial search of thermoelastic shape-memory alloys with extremely small hysteresis width.

    PubMed

    Cui, Jun; Chu, Yong S; Famodu, Olugbenga O; Furuya, Yasubumi; Hattrick-Simpers, Jae; James, Richard D; Ludwig, Alfred; Thienhaus, Sigurd; Wuttig, Manfred; Zhang, Zhiyong; Takeuchi, Ichiro

    2006-04-01

    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

  9. A Semiempirical Model to Determine HF Copper Losses in Magnetic Components With Nonlayered Coils

    Microsoft Academic Search

    Georgios S. Dimitrakakis; Emmanuel C. Tatakis; Evangelos J. Rikos

    2008-01-01

    While in numerous power electronics applications, transformers and inductors with nonlayered windings are used, the absence up until now of any theoretical or even empirical model for their HF effective resistance calculation leads magnetic component designers to make high-error approximations. The typical approach until now has been to consider them as layered and apply some of the existent relevant models.

  10. Implementation of the Generalized Complementary Flux Constraint for Low-Loss Active Magnetic

    E-print Network

    Tsiotras, Panagiotis

    magnetic bearing FWB flywheel battery CMG control moment gyroscope ESCMG energy storage control moment) and advanced control moment gyroscopes (CMGs).6 In a FWB, kinetic energy is stored in the rotating flywheel outperform chemical batteries in terms of specific power. Advanced energy storage control moment gyroscopes

  11. Experimental Validation of Control Designs for Low-Loss Active Magnetic Bearings

    E-print Network

    Tsiotras, Panagiotis

    magnetic bearing FWB flywheel battery CMG control moment gyroscope ESCMG energy storage control moment in flywheel batteries (FWBs) and advanced control moment gyroscopes (CMGs).6 In a FWB, kinetic energy is stored in the rotating flywheel and converted back and forth to electrical energy using a motor

  12. Loss of bone calcium in exposure to 50 Hz magnetic fields.

    PubMed

    Hanafy, Enas; Elhafez, Salam; Aly, Fadel; Elazhary, Mohamed

    2008-01-01

    This study investigates the effect of whole body exposure to magnetic fields on the calcium level of blood and bone in a trial to avoid the liability of osteoporosis, fractures, and delayed union of fractures after exposure to magnetic fields present everywhere in the environment. The procedures of the study included analysis for calcium level in both bone and blood. The procedures were performed on 50 Guinea pigs equally divided into 5 groups. Groups A, B, C, and D were exposed to 50 Hz, 0.2 mT magnetic field for 30 d. Group E animals were the control. Group A was sacrificed immediately after exposure; Group B was left away from the field for 15 d for spontaneous repair; Group C received the drug Centrum dissolved in drinking water for 15 d after exposure to the magnetic field; and Group D received centrum in drinking water during the period of exposure (30 d). After sacrificing all animals, the calcium level in both bone and blood was evaluated. Values of blood analysis revealed significant increase in the blood calcium level in exposed animals compared with the control group (P < 0.002) with excess in Group A. This indicated that the calcium left the bone to the blood. Values of the bone analysis revealed significant decrease in bone calcium concentration level in Group A compared with the control group and improvement in the bone condition in Groups C and D, indicating the role of trace element after the exposure period as a compensatory agent of magnetic field damage and its role during the exposure period as a radio-protecting agent. PMID:19037789

  13. Steinmetz law in iron-phenolformaldehyde resin soft magnetic composites

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

    The validity of Steinmetz law describing the dc energy losses as a function of maximum induction has been investigated for iron based soft magnetic composites (SMCs) up to 1.4 T with the effort to find a physical meaning of the coefficients in Steinmetz law. In the Rayleigh region the coefficients were expressed mathematically using the Rayleigh law. Further the "range of validity of Steinmetz law" was found to be from 0.3 T to 1.2 T. The typical "straight" shape of hysteresis loops of SMCs at lower maximum induction was approximated by linear functions in order to express the dc losses in form of Steinmetz law.

  14. Low-loss ultracompact transverse-magnetic-pass polarizer with a silicon subwavelength grating waveguide.

    PubMed

    Guan, Xiaowei; Chen, Pengxin; Chen, Sitao; Xu, Peipeng; Shi, Yaocheng; Dai, Daoxin

    2014-08-01

    An ultracompact and low-loss TM-pass polarizer on silicon is proposed and demonstrated experimentally with a subwavelength-grating (SWG) waveguide. The SWG waveguide is designed to support Bloch mode for TM polarization so that the incident TM-polarized light goes through the SWG waveguide with very low excess loss. On the other hand, for TE polarization, the SWG waveguide works as a Bragg reflector, and consequently the incident TE-polarized light is reflected. For a fabricated ?9???m long polarizer (with the period number N=20), the measured extinction ratio is ?27??dB and the excess loss is ?0.5??dB at the central wavelength 1550 nm. The bandwidth to achieve an extinction ratio of 20 dB is about 60 nm (from 1520 to 1580 nm). When increasing the period number to N=40, the measured extinction ratio is up to 40 dB (which is not as high as the expected theoretical value 65 dB due to the limit of the measurement system). PMID:25078216

  15. Synthesis of Bio-Compatible SPION-based Aqueous Ferrofluids and Evaluation of RadioFrequency Power Loss for Magnetic Hyperthermia.

    PubMed

    Reena Mary, A P; Narayanan, T N; Sunny, Vijutha; Sakthikumar, D; Yoshida, Yasuhiko; Joy, P A; Anantharaman, M R

    2010-01-01

    Bio-compatible magnetic fluids having high saturation magnetization find immense applications in various biomedical fields. Aqueous ferrofluids of superparamagnetic iron oxide nanoparticles with narrow size distribution, high shelf life and good stability is realized by controlled chemical co-precipitation process. The crystal structure is verified by X-ray diffraction technique. Particle sizes are evaluated by employing Transmission electron microscopy. Room temperature and low-temperature magnetic measurements were carried out with Superconducting Quantum Interference Device. The fluid exhibits good magnetic response even at very high dilution (6.28 mg/cc). This is an advantage for biomedical applications, since only a small amount of iron is to be metabolised by body organs. Magnetic field induced transmission measurements carried out at photon energy of diode laser (670 nm) exhibited excellent linear dichroism. Based on the structural and magnetic measurements, the power loss for the magnetic nanoparticles under study is evaluated over a range of radiofrequencies. PMID:21076702

  16. Synthesis of Bio-Compatible SPION–based Aqueous Ferrofluids and Evaluation of RadioFrequency Power Loss for Magnetic Hyperthermia

    PubMed Central

    2010-01-01

    Bio-compatible magnetic fluids having high saturation magnetization find immense applications in various biomedical fields. Aqueous ferrofluids of superparamagnetic iron oxide nanoparticles with narrow size distribution, high shelf life and good stability is realized by controlled chemical co-precipitation process. The crystal structure is verified by X-ray diffraction technique. Particle sizes are evaluated by employing Transmission electron microscopy. Room temperature and low-temperature magnetic measurements were carried out with Superconducting Quantum Interference Device. The fluid exhibits good magnetic response even at very high dilution (6.28 mg/cc). This is an advantage for biomedical applications, since only a small amount of iron is to be metabolised by body organs. Magnetic field induced transmission measurements carried out at photon energy of diode laser (670 nm) exhibited excellent linear dichroism. Based on the structural and magnetic measurements, the power loss for the magnetic nanoparticles under study is evaluated over a range of radiofrequencies. PMID:21076702

  17. > FOR CONFERENCE-RELATED PAPERS, REPLACE THIS LINE WITH YOUR SESSION NUMBER, E.G., AB-02 (DOUBLE-CLICK HERE) Computation of eddy current losses in Soft Magnetic Composites1

    E-print Network

    Paris-Sud XI, Université de

    , Italy6 7 We compute the classical eddy current losses in Soft Magnetic Composite (SMC) materials, taking-CLICK HERE) Soft Magnetic Composites1 2 C. Appino1 , O. Bottauscio1 material, where the magnetic losses are measured in ring samples with a range of cross-sectional areas.15

  18. Iron loss of grain size controlled very thin grain-oriented silicon steels

    SciTech Connect

    Kim, Y.H.; Ohkawa, M.; Ishiyama, K.; Arai, K.I. (Tohoku Univ., Sendai (Japan). Research Institute of Electrical Communication)

    1993-11-01

    Very thin (less than 100 [mu]m) grain-oriented silicon steels are known to have lower iron loss than iron-based amorphous materials. It is possible to reduce the iron loss of very thin grain-oriented silicon steels further by applying new magnetic domain refining techniques. One method for magnetic domain refining is to control the grain size. The authors observed the magnetic domains and measured the iron loss of very thin grain-oriented silicon steels that had various grain sizes. They controlled grain size in samples to be from 0.25 mm to 2.3 mm without changing B[sub 8]. This experiment shows that the magnetic domain width can be made narrower by decreasing the grain size, which reduces the eddy current losses. On the other hand, samples with larger grain size have lower Hc and lower hysteresis losses. Therefore there is an optimum grain size for the lowest iron loss of very thin grain-oriented silicon steels.

  19. Spin-memory loss in magnetic multilayers with perpendicular current (CPP)

    E-print Network

    Fominov, Yakov

    1.2 mm2 #12;Spin-memory loss in F-metals and -alloys "Py" = Permalloy = Ni84Fe16 Py Py Cu Nb Nb FeMn valve "Py" = Ni84Fe16 Spin polarization detector nm5.5t Py sfPy =>> l Py Py Cu Nb Nb FeMn CPP Current X-layers )/texp(RA X sfX l- 1 3 Cu(6% Pt) nm111)Pt(Cu sf ±=l Spin-orbit scattering AR(fm2) FeMn nm1FeMn sf

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

    SciTech Connect

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

    1998-09-01

    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.

  1. Hysteresis properties of ordinary chondrites and implications for their thermal history

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

    We present a large dataset of magnetic hysteresis properties of ordinary chondrite falls. We show that hysteresis properties are distinctive of individual meteorites while homogeneous among meteorite subsamples. Except for the most primitive chondrites, these properties can be explained by a mixture of multidomain kamacite and tetrataenite (both in the cloudy zone and as larger grains in plessite and in the rim of zoned taenite). Kamacite dominates the induced magnetism whereas tetrataenite dominates the remanent magnetism, in agreement with previous microscopic magnetic observations. Type 5 and 6 chondrites have higher tetrataenite content than type 4 chondrites, suggesting they have lower cooling rates at least in the 650-450 °C interval, consistent with an onion-shell model. In equilibrated chondrites, shock-related transient heating events above ~500 °C result in the disordering of tetrataenite and associated drastic change in magnetic properties. As a good indicator of the amount of tetrataenite, hysteresis properties are a very sensitive proxy of the thermal history of ordinary chondrites, revealing low cooling rates during thermal metamorphism, and high cooling rates following shock reheating or excavation after thermal metamorphism.

  2. Effect of the phosphate component of electrical insulating coating on the magnetic losses in grain-oriented electrical steel

    NASA Astrophysics Data System (ADS)

    Karenina, L. S.; Korzunin, G. S.; Puzhevich, R. B.

    2011-01-01

    It is shown that one of the main methods improving quality of a grain-oriented electrical sheet steel (GOES) is the deposition of an electrical insulating coating (EIC) on its surface, which produces elastic tensile stresses in the metal. The EIC represents a composite consisting of a glass film and a phosphate coating deposited on it. Investigations performed in this direction are reviewed. A complex of the industrial experiments has been carried out, which were directed to studying the effect of both the insulating coating as a whole and, separately, its phosphate component (PC) on the level of magnetic losses. The values of elastic tensile stresses produced in the metal by the EIC and PC are presented. This work has been performed under the conditions of the OOO VIZ-stal' (Verkneisetsk Factory).

  3. Flexible pivot mount eliminates friction and hysteresis

    NASA Technical Reports Server (NTRS)

    Highman, C. O.

    1970-01-01

    Flexible steel pivot mount, suspended by flat vertical beryllium copper springs, is capable of rotation, free of hysteresis and starting friction. Mount requires no lubrication, is made in varying sizes, and is driven with either dc torque motor or mechanical linkage.

  4. Design of hysteresis circuits using differential amplifiers

    NASA Technical Reports Server (NTRS)

    Cooke, W. A.

    1971-01-01

    Design equations for hysteresis circuit are based on the following assumptions: amplifier input impedance is larger than source impedance; amplifier output impedance is less than load impedance; and amplifier switches state when differential input voltage is approximately zero. Circuits are designed to any given specifications.

  5. Circuit increases capability of hysteresis synchronous motor

    NASA Technical Reports Server (NTRS)

    Markowitz, I. N.

    1967-01-01

    Frequency and phase detector circuit enables a hysteresis synchronous motor to drive a load of given torque value at a precise speed determined by a stable reference. This technique permits driving larger torque loads with smaller motors and lower power drain.

  6. Hysteresis regimes in fuel burning processes

    Microsoft Academic Search

    S. P. Bardakhanov; A. V. Potapkin

    1999-01-01

    The results of experimental studies of thennoacoustic processes in tubes with local heat release are presented. The heat supply was ensured either by heated grids in the tube or by burning of gasoline vapors or hydrogen in the singing flame regime. The boundaries of acoustic regimes and hysteresis regions are determined. An increase in power of thermal energy facilities and

  7. Hysteresis and transition in swirling nonpremixed flames

    Microsoft Academic Search

    M. J. Tummers; A. W. Huebner; E. H. van Veen; K. Hanjalic; T. H. van der Meer

    2009-01-01

    Strongly swirling nonpremixed flames are known to exhibit a hysteresis when transiting from an attached long, sooty, yellow flame to a short lifted blue flame, and vice versa. The upward transition (by increasing the air and fuel flow rates) corresponds to a vortex breakdown, i.e. an abrupt change from an attached swirling flame (unidirectional or with a weak bluff-body recirculation),

  8. Role of hysteresis in stomatal aperture dynamics

    NASA Astrophysics Data System (ADS)

    Ramos, Antônio M. T.; Prado, Carmen P. C.

    2013-01-01

    Stomata are pores responsible for gas exchange in leaves. Several experiments indicate that stomata synchronize into clusters or patches. The patches’ coordination may produce oscillations in stomatal conductance. Previous studies claim to reproduce some experimental results. However, none was able to explain the variety of behavior observed in the stomatal dynamics. Recently, Ferraz and Prado suggested a realistic geometry of vein distribution. Although it reproduces the patches, no oscillation was observed and the patches remain static. Without exploring significant details, the authors stated that hysteresis in stomatal aperture could explain several experimental features. In this paper, the hysteresis hypothesis is further explored through the concept of hysteretic operators. We have shown that the hysteresis assumption is sufficient to obtain dynamical patches and oscillations in stomatal conductance. The robustness of this hypothesis is tested by using different hysteresis operators. The model analysis reveals a dependence between the period of oscillation in stomatal conductance and the water deficit between the leaf and the environment. This underlying feature of the model might inspire further experiments to test this hypothesis.

  9. Determination of energy release zones arising due to current losses in the convolution region of the magnetically insulated transmission lines of the ANGARA-5-1 facility

    NASA Astrophysics Data System (ADS)

    Grabovski, E. V.; Gribov, A. N.; Laukhin, Ya. N.; Shishlov, A. O.

    2015-05-01

    Among the factors limiting electromagnetic pulse transmission to the load in high-power electro-physical facilities, current losses in magnetically insulated transmission lines (MITLs) are of significant importance. One of such facilities is ANGARA-5-1—a multimodule facility with an output electric power of up to 6 TW. A fairly complicated configuration of the magnetic field in the convolution region of several MITLs makes it difficult to fix the places of current losses there. In this work, these places were determined by detecting the positions of IR sources in the convolution region of the MITLs of the ANGARA-5-1 facility.

  10. Torque meter aids study of hysteresis motor rings

    NASA Technical Reports Server (NTRS)

    Cole, M.

    1967-01-01

    Torque meter, simulating hysteresis motor operation, allows rotor ring performance characteristics to be analyzed. The meter determines hysteresis motor torque and actual stresses of the ring due to its mechanical situation and rotation, aids in the study of asymmetries or defects in motor rings, and measures rotational hysteresis.

  11. Quantum Hydrodynamic Simulation of Hysteresis in the Resonant Tunneling Diode

    E-print Network

    Jerome, Joseph W.

    Quantum Hydrodynamic Simulation of Hysteresis in the Resonant Tunneling Diode Zhangxin Chen \\Lambda Hysteresis in the current­voltage curve of a resonant tunneling diode is simulated and analyzed is an intrinsic property of the resonant tunneling diode. Hysteresis appears in many settings in fluid dynamics

  12. A physical model for hysteresis curves of ferroelectric ceramics

    Microsoft Academic Search

    G. Arlt

    1996-01-01

    A general model for the simulation and for the interpretation of hysteresis curves is presented. The model opens the possibility to calculate hysteresis curves if the electrostatic interaction of grains in a critical volume can be treated quantitatively. The hysteresis curve is described by a progress parameter ?. The effective polarization Peff(?) in the process of inversion is approximated by

  13. Quantum Hydrodynamic Simulation of Hysteresis in the Resonant Tunneling Diode

    Microsoft Academic Search

    Zhangxin Chen; Bernardo Cockburn; Carl L. Gardner; Joseph W. Jerome

    1995-01-01

    Hysteresis in the current-voltage curve of a resonant tunneling diode is simulated and analyzed in the quantum hydrodynamic (QHD) model for semiconductor devices. The simulations are the first to show hysteresis in the QHD equations and to confirm that bistability is an intrinsic property of the resonant tunneling diode. Hysteresis appears in many settings in fluid dynamics. The simulations presented

  14. A Domain Wall Model for Hysteresis in Ferroelastic Materials

    E-print Network

    and hysteresis inherent to ferro- elastic compounds, with emphasis placed on shape memory alloys. We formulate with experimental stress-strain data. Keywords: Ferroelastic hysteresis; shape memory alloy; domain wall theory. In shape memory alloys (SMAs), elastic hysteresis enables the materials to achieve very high work densities

  15. A Domain Wall Model for Hysteresis in Ferroelastic Materials

    E-print Network

    and hysteresis inherent to ferro­ elastic compounds, with emphasis placed on shape memory alloys. We formulate with experimental stress­strain data. Keywords: Ferroelastic hysteresis; shape memory alloy; domain wall theory. In shape memory alloys (SMAs), elastic hysteresis enables the materials to achieve very high work densities

  16. A high resolution magnetization sensor for AC loss measurement on cable-in-conduit conductors

    NASA Astrophysics Data System (ADS)

    Zhelamskij, Michail W.; Bruzzone, Pierluigi

    1998-12-01

    A special sensor is proposed for magnetization measurement of superconductors with round cross section under pulsed transversal field. The sensor consists of a saddle shaped pick-up coil attached to the cylindrical superconducting sample, with a controlled geometrical distribution of the turns. The pick up coil carries out a two-dimensional flux integration and the software calculates the loop area in Joules. The sensor has been used during a campaign of ITER subsize conductor tests, showing an excellent agreement (better than 1%) with the results of boil-off calorimetric measurements. The detailed design, the algorithm and the test results are discussed in the paper. Other applications of this test method are proposed.

  17. Application of the drag force method to evaluate magnetic property degradation near the cut edges of electrical steels

    NASA Astrophysics Data System (ADS)

    Garshelis, Ivan J.; Crevecoeur, Guillaume; Tollens, Stijn P. L.; Dupre, Luc

    2011-04-01

    The increase in hysteresis loss associated with the altered microstructure and residual stress fields in regions near the cut edges of electrical steels is investigated by means of drag force measurements. Measurements are made using relatively narrow magnets on samples of two grades of nonoriented steels cut by laser or mechanical processes. Largest drag forces, hence losses, are consistently found in slow laser cut samples, smallest drag forces with fast laser cut samples, and moderately higher losses in mechanically cut samples. These results are consistent with other measurement methods.

  18. Structural, Magnetic, and Reflection Loss Characteristics of Ni/Co/Sn-Substituted Strontium Ferrite/Functionalized MWCNT Nanocomposites

    NASA Astrophysics Data System (ADS)

    Mousavinia, Mohammad; Ghasemi, Ali; Paimozd, Ebrahim

    2014-07-01

    Ni/Co/Sn-substituted strontium ferrite [SrFe12- x (Ni0.5Co0.5Sn) x/2O19]/multiwalled carbon nanotube (MWCNT) nanocomposites were produced by assembling ferrite particles on the external surfaces of MWCNTs. Various techniques including x-ray diffraction (XRD) analysis, transmission electron microscopy, field-emission scanning electron microscopy (FE-SEM), and Fourier-transform infrared (FTIR) spectroscopy were used to demonstrate the successful attachment of ferrite particles onto the external surfaces of the MWCNTs. XRD analysis and FTIR spectroscopy confirmed the presence of strontium ferrite and carbon nanotube phases in ferrite and nanocomposite samples, respectively. FE-SEM micrographs indicated the formation of ferrite particles on the outer surfaces of MWCNTs in nanocomposite samples. Furthermore, vibrating-sample magnetometer (VSM) and reflection loss (RL) measurements were performed to assess the magnetic and microwave characteristics of the synthesized samples. VSM loops confirmed a relatively strong dependence of the saturation magnetization and coercivity on the volume percentage of MWCNTs. With the introduction of MWCNTs or an increase in the substitution, the saturation magnetization and coercivity were decreased. The RL properties of the nanocomposites were investigated in the 8 GHz to 12 GHz frequency range. The sample with 80 wt.% nanocomposite content showed a maximum RL of -35 dB at 8.3 GHz with a 4 GHz absorption bandwidth over the extended frequency range of 8 GHz to 12 GHz for absorber thickness of 1.8 mm. The RL evaluations indicated that these nanocomposites have high potential for application as wide-band electromagnetic wave absorbers at GHz frequencies.

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

    SciTech Connect

    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

    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.

  20. Application of linear magnetic loss model of ferrite to induction cavity simulation

    SciTech Connect

    DeFord, J.F.; Kamin, G.

    1990-09-05

    A linear, frequency independent model of the rf properties of unbiased, soft ferrite has been implemented in finite-difference, time-domain, electromagnetic simulation code AMOS for the purposes of studying linac induction cavities. The simple model consists of adding a magnetic conductivity term ({sigma}{sub m}H) to Faraday's Law. The value of {sigma}{sub m} that is appropriate for a given ferrite at a particular frequency is obtained via an rf reflection experiment on a very thin ferrite toroid in a shorted coaxial line. It was found that in the frequency range 100 to 1000 MHz, the required value of {sigma}{sub m} varies only slightly (<10%), and so we approximated it as a frequency independent parameter in AMOS. A description of the experimental setup and the technique used to extract the complex {mu} from the measurements is described. The model has been used to study the impedances of the DARHT induction cavity, and comparisons between these experimental measurements and AMOS calculations is presented. Implementation of a frequency dependent version of this model in AMOS is being pursued, and a discussion of this effort is given.

  1. 2432 IEEE TRANSACTIONS ON MAGNETICS, VOL. 41, NO. 9, SEPTEMBER 2005 Effective Parameters for Toroidal Cores Based on

    E-print Network

    Vu-Quoc, Loc

    , soft magnetic materials. I. INTRODUCTION TO facilitate its design and application, a magnetic core to approximate the initial magnetization curve. Material-independent, geometry-dependent expressions by core producers. Index Terms--Ferrites, ferrimagnetic materials, magnetic cores, magnetic hysteresis

  2. Magnetic properties and large magnetocaloric effect in Laves phase metallic compound

    NASA Astrophysics Data System (ADS)

    Gao, Tian; Qi, Ningning; Zhang, Yufeng; Zhou, Tao

    2014-12-01

    We investigated the magnetic properties and magnetocaloric effect of C15 Laves phase TbMn1.6Fe0.4 by magnetization and heat capacity measurements. A sharp second-order magnetic Tb-Tb ordering transition at Curie temperature TC ~ 120 K and a short-range Fe-Fe ordering transition at ~230 K are observed. Around TC, the compound shows a large magnetocaloric effect with no obvious thermal and magnetic hysteresis loss. The maximum value of magnetic entropy change reaches 8.72 J kg?1 K?1 for a magnetic field change ?H = 7 T over a wide temperature range. The obtained relative cooling power reaches 184, 560, and 803 J kg?1 for ?H = 2, 5 and 7 T, respectively. Large reversible magnetocaloric effect and the wide operating temperature range indicate that TbMn1.6Fe0.4 could be a promising candidate for magnetic refrigeration.

  3. A stability-based mechanism for hysteresis in the walk–trot transition in quadruped locomotion

    PubMed Central

    Aoi, Shinya; Katayama, Daiki; Fujiki, Soichiro; Tomita, Nozomi; Funato, Tetsuro; Yamashita, Tsuyoshi; Senda, Kei; Tsuchiya, Kazuo

    2013-01-01

    Quadrupeds vary their gaits in accordance with their locomotion speed. Such gait transitions exhibit hysteresis. However, the underlying mechanism for this hysteresis remains largely unclear. It has been suggested that gaits correspond to attractors in their dynamics and that gait transitions are non-equilibrium phase transitions that are accompanied by a loss in stability. In the present study, we used a robotic platform to investigate the dynamic stability of gaits and to clarify the hysteresis mechanism in the walk–trot transition of quadrupeds. Specifically, we used a quadruped robot as the body mechanical model and an oscillator network for the nervous system model to emulate dynamic locomotion of a quadruped. Experiments using this robot revealed that dynamic interactions among the robot mechanical system, the oscillator network, and the environment generate walk and trot gaits depending on the locomotion speed. In addition, a walk–trot transition that exhibited hysteresis was observed when the locomotion speed was changed. We evaluated the gait changes of the robot by measuring the locomotion of dogs. Furthermore, we investigated the stability structure during the gait transition of the robot by constructing a potential function from the return map of the relative phase of the legs and clarified the physical characteristics inherent to the gait transition in terms of the dynamics. PMID:23389894

  4. Large magnetic entropy changes in Gd-Co amorphous ribbons

    NASA Astrophysics Data System (ADS)

    Zhang, C. L.; Wang, D. H.; Han, Z. D.; Xuan, H. C.; Gu, B. X.; Du, Y. W.

    2009-01-01

    A series of magnetic amorphous ribbons with different Gd/Co ratios was prepared by melt-spun method. With the decrease in Gd/Co ratio, Curie temperatures increase gradually from 166 to 193 K. The maximum values of magnetic entropy changes under a magnetic field of 10 kOe are -3.1, -3.0, -2.9, and -2.8 J/kg K for Gd71Co29, Gd68Co32, Gd65Co35, and Gd62Co38 samples, respectively. The approximately constant peak values of ?SM at different working temperatures indicate that they are advantageous for an Ericsson refrigeration cycle. In addition, these samples have large resistivity and greatly reduced magnetic hysteresis losses, which could increase the refrigeration efficiency. These advantages make the Gd-Co amorphous ribbons good candidates for the practical magnetic refrigeration.

  5. 78 FR 73589 - Energy Conservation Program: Energy Conservation Standards for Commercial and Industrial Electric...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-12-06

    ...significant and are classified as either hysteresis or eddy current losses. Hysteresis losses are caused by magnetic domains...electrical steel of induction motors--hysteresis losses and losses due to eddy current. Electric motors can use thinner...

  6. Wetting Hysteresis at the Molecular Scale

    NASA Technical Reports Server (NTRS)

    Jin, Wei; Koplik, Joel; Banavar, Jayanth R.

    1996-01-01

    The motion of a fluid-fluid-solid contact line on a rough surface is well known to display hysteresis in the contact angle vs. velocity relationship. In order to understand the phenomenon at a fundamental microscopic level, we have conducted molecular dynamics computer simulations of a Wilhelmy plate experiment in which a solid surface is dipped into a liquid bath, and the force-velocity characteristics are measured. We directly observe a systematic variation of force and contact angle with velocity, which is single-valued for the case of an atomically smooth solid surface. In the microscopically rough case, however, we find (as intuitively expected) an open hysteresis loop. Further characterization of the interface dynamics is in progress.

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

    NASA Astrophysics Data System (ADS)

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

    2007-03-01

    Periodic magnetic fields with frequencies in the 5-100Hz range and peak strengths as low as 0.5nT have been detected at 300K by modulating at kHz rates the magneto-optical response of epitaxial (Tm,Bi)3(Ga,Fe)5O12 rare earth-iron garnet films at ? =532nm. By exploiting the ˜1°/?T slope of the magneto-optical transition region between the two magnetization states of these low coercivity (<0.5mT) films, sub3-30m/s for modulation frequencies in the 0.3-10kHz interval, and the noise generated by wall motion appears to be the primary barrier to further reductions in the detection sensitivity floor. Films with thicknesses of 2-4?m and mean domain widths of 3-6mm exhibit figures of merit (?/?) of ˜3°-8.5° at 532nm. Imaging of mesoscopic magnetic particles is demonstrated with a spatial resolution of <300?m.

  8. Hysteresis, avalanches, and disorder-induced critical scaling: A renormalization-group approach Karin Dahmen* and James P. Sethna

    E-print Network

    Sethna, James P.

    Hysteresis, avalanches, and disorder-induced critical scaling: A renormalization-group approach is added, one finds a transition where the jump in the magnetization corresponding to an infinite avalanche avalanches , and universal behavior. We expand the critical exponents about mean-field theory in 6 dimensions

  9. The degradation of polymer-bonded Nd-Fe-B magnets (abstract)

    SciTech Connect

    Mazany, A.M.; Dickens, E.D. Jr. (BFGoodrich Research and Development Center, Brecksville, Ohio 44141-3289 (USA))

    1991-04-15

    The susceptibility of Nd-Fe-B magnet powders to oxygen and chloride ions is well known, however, the interactions between magnet alloy powders and polymeric binders in bonded magnets can also lead to severe irreversible losses. The losses observed for polymer-bonded Nd-Fe-B magnets in some cases can be more substantial than the losses due to oxidation or corrosion alone. The aging characteristics of polymer-bonded magnets have been examined with respect to time, temperature, alloy treatment, particle size, molding method, and polymer composition. Each sample was evaluated for magnetic properties after thermal aging. The chemical effects of oxygen, chloride ions, and various polymers on Nd-Fe-B alloys and the resulting changes in magnetic properties can be very different, but all can lead to significant losses and each degradation process (oxidation, corrosion, or polymer-alloy interactions) exhibits a different magnetic hysteresis signature.'' The irreversible losses stemming from these processes can be alleviated through the use of passivating coatings.

  10. The effect of resistive filament interconnections on coupling losses in filamentary YBa2Cu3O7 coated conductors

    NASA Astrophysics Data System (ADS)

    Polak, M.; Takacs, S.; Barnes, P. N.; Levin, G. A.

    2009-02-01

    The effect of normal metal interfilamentary connections on AC losses was investigated for multifilamentary YBCO (YBa2Cu3O7) coated conductors. This effect was studied for resistive interconnections (thin copper strips) on samples of multifilament YBa2Cu3O7 coated conductor of two types in an applied harmonic external magnetic field with frequencies between 10 mHz and 0.9 Hz, and amplitudes up to ~0.1 T. For samples with well insulated filaments, the losses were of a purely hysteretic nature. The loss greatly increases when filaments are electrically connected at both ends of the sample due to the coupling losses. Additional normal metal bridges in the center of the sample only minimally increase the coupling losses. We also investigated the losses in samples with an artificially low resistance between the filaments, where the coupling loss is comparable to the hysteresis loss even at low frequencies. The effect of the bridge placement on coupling loss is the same as that for samples with well insulated filaments. For our samples we did not observe a reduction of coupling losses due to the normal metal bridges. However, they can be used to enable current sharing between the superconducting filaments without raising the overall level of losses if appropriately placed.

  11. Modeling of magnetic properties of heat treated Dy-doped NdFeB particles bonded in isotropic and anisotropic arrangements

    SciTech Connect

    Fang, X.; Shi, Y.; Jiles, D.C. [Ames Lab., IA (United States)] [Ames Lab., IA (United States)

    1998-07-01

    The effects of compacting methods, heat treatment and chemical additives on the magnetic properties of NdFeB articles have been studied. Five sets of NdFeB powder articles, doped with different amounts of Dy from 0.1--2.9 wt%, are prepared in powder form by gas atomization and annealed at 650--750 C for 600 seconds under an inert argon atmosphere. These were then bonded in epoxy, either in isotropic form, or aligned during fabrication under the action an applied magnetic field. The results showed that the combined effects of the addition of Dy and heat treatment could dramatically improve the coercive force, remanent magnetization and maximum energy product. The results have been interpreted using a model of hysteresis which takes into account energy losses, anisotropy and texture of a material. The modeling showed that these effects alter the magnetic properties by increasing the hysteresis loss via the loss coefficient and by reducing the reversible component of magnetization through the reversibility coefficient. The compacting process influences the density of the particles in the bonded magnet which alters the magnetic properties through the coupling coefficient. The major influence of particle alignment can be interpreted as a change in the texture which can be described by a texture parameter.

  12. Reduced losses in rolled Fe73.5Si15.5Nb3B7Cu1 nanocrystalline ribbon

    NASA Astrophysics Data System (ADS)

    Kernion, S. J.; Lucas, M. S.; Horwath, J.; Turgut, Z.; Michel, E.; Keylin, V.; Huth, J. F.; Leary, A. M.; Shen, S.; McHenry, M. E.

    2013-05-01

    Eddy currents in magnetic components undergoing high frequency switching can be mitigated by reducing the thickness of the component. Planar flow cast Fe73.5Si15.5Nb3B7Cu1 ribbon was plastically deformed by cold rolling, resulting in a thickness reduction of 38%. Shear band formation was seen and the coercivity was dramatically higher in the rolled ribbon. After crystallization, the hysteresis loop of the rolled ribbon was nearly identical to a non-rolled ribbon and losses were lower in the rolled ribbon above 25 kHz. Reductions in thickness by this method can lead to increases in operating frequency for power conversion applications.

  13. Rotational hysteresis of torque curves in polycrystalline ferro/antiferromagnetic systems

    SciTech Connect

    Zhang, K.; Kai, T.; Zhao, T.; Fujiwara, H.; Hou, C.; Kief, M. T.

    2001-06-01

    Rotational hysteresis of ferromagnetic (F)/antiferromagnetic (AF) exchange coupled systems was studied by using NiFe/IrMn, NiFe/FeMn, and NiFe/NiMn samples sputter deposited under almost the same conditions, although the sample of NiFe/NiMn was annealed later to obtain the antiferromagnetic phase for the NiMn layer. The rotational hysteresis of each sample exhibited quite a different feature from each other, especially in the rotational hysteresis{endash}magnetization angle curves. The NiFe/IrMn bilayer showed a dip at around the antiparallel direction to the applied field direction during sample preparation (pinning direction), while the NiFe/NiMn bilayer exhibited a large peak in that direction. The NiFe/FeMn bilayer did not show any noticeable structure in the rotational hysteresis{endash}magnetization curve. Based on the analysis of those data done by using the model recently proposed by the authors, the following was inferred: (1) The distribution of the anisotropy easy axes of IrMn of the NiFe/IrMn bilayer grains is limited in some range of angles around the pinning direction. Some direct exchange coupling exists between the IrMn grains. (2) The distribution of the anisotropy easy axes of FeMn grains of the NiFe/FeMn bilayer is almost random and the direct exchange coupling between the FeMn grains is negligible. (3) In the NiFe/NiMn bilayer, substantial strength of direct exchange coupling exists between some of the grains which switch and the ones which do not switch with the rotation of the magnetization of the NiFe layer, although the volume fraction of the former is much smaller than the latter. {copyright} 2001 American Institute of Physics.

  14. Rotational hysteresis of torque curves in polycrystalline ferro/antiferromagnetic systems

    NASA Astrophysics Data System (ADS)

    Zhang, K.; Kai, T.; Zhao, T.; Fujiwara, H.; Hou, C.; Kief, M. T.

    2001-06-01

    Rotational hysteresis of ferromagnetic (F)/antiferromagnetic (AF) exchange coupled systems was studied by using NiFe/IrMn, NiFe/FeMn, and NiFe/NiMn samples sputter deposited under almost the same conditions, although the sample of NiFe/NiMn was annealed later to obtain the antiferromagnetic phase for the NiMn layer. The rotational hysteresis of each sample exhibited quite a different feature from each other, especially in the rotational hysteresis-magnetization angle curves. The NiFe/IrMn bilayer showed a dip at around the antiparallel direction to the applied field direction during sample preparation (pinning direction), while the NiFe/NiMn bilayer exhibited a large peak in that direction. The NiFe/FeMn bilayer did not show any noticeable structure in the rotational hysteresis-magnetization curve. Based on the analysis of those data done by using the model recently proposed by the authors, the following was inferred: (1) The distribution of the anisotropy easy axes of IrMn of the NiFe/IrMn bilayer grains is limited in some range of angles around the pinning direction. Some direct exchange coupling exists between the IrMn grains. (2) The distribution of the anisotropy easy axes of FeMn grains of the NiFe/FeMn bilayer is almost random and the direct exchange coupling between the FeMn grains is negligible. (3) In the NiFe/NiMn bilayer, substantial strength of direct exchange coupling exists between some of the grains which switch and the ones which do not switch with the rotation of the magnetization of the NiFe layer, although the volume fraction of the former is much smaller than the latter.

  15. Scalar and vector hysteresis simulations using HysterSoft

    NASA Astrophysics Data System (ADS)

    Dimian, M.; Andrei, P.

    2015-02-01

    Hysteresis modeling has become an important research area with many applications in science and engineering. In this article we present a unified and robust simulation framework designed to perform scalar and vector hysteresis modeling. The framework is based on HysterSoft© which is a simulation platform that can be interfaced with other libraries and simulation programs to model various aspects of hysteresis. We describe the main features of our simulation framework by focusing on scalar and vector hysteresis modeling, direct and inverse modeling, dynamic hysteresis modeling, first-order reversal-curves analysis, identification of the scalar and vector Preisach distribution function using an experimental first- order reversal-curves, noise passage analysis through hysteretic systems, and thermal relaxation in scalar and vector hysteresis. The simulation modules, the user-defined features, and various parameter identification techniques are also presented.

  16. The Effect of Tensile Hysteresis and Contact Resistance on the Performance of Strain-Resistant Elastic-Conductive Webbing

    PubMed Central

    Shyr, Tien-Wei; Shie, Jing-Wen; Jhuang, Yan-Er

    2011-01-01

    To use e-textiles as a strain-resistance sensor they need to be both elastic and conductive. Three kinds of elastic-conductive webbings, including flat, tubular, and belt webbings, made of Lycra fiber and carbon coated polyamide fiber, were used in this study. The strain-resistance properties of the webbings were evaluated in stretch-recovery tests and measured within 30% strain. It was found that tensile hysteresis and contact resistance significantly influence the tensile elasticity and the resistance sensitivity of the webbings. The results showed that the webbing structure definitely contributes to the tensile hysteresis and contact resistance. The smaller the friction is among the yarns in the belt webbing, the smaller the tensile hysteresis loss. However the close proximity of the conductive yarns in flat and tubular webbings results in a lower contact resistance. PMID:22319376

  17. Thermal hysteresis of permeability and transport properties of Mn substituted Mg Cu Zn ferrites

    NASA Astrophysics Data System (ADS)

    Manjurul Haque, M.; Huq, M.; Hakim, M. A.

    2008-03-01

    Mn substituted Mg-Cu-Zn ferrites of composition Mg0.35Cu0.20Zn0.45O(Fe2-xMnx O3)0.97 have been prepared by the standard double sintering ceramic technique. X-ray diffraction patterns of the samples showed single phase cubic spinel structure without any detectable impurity phases. The lattice constant is found to increase linearly with increase in Mn3+ ion concentration obeying Vegard's law. The initial permeability (?i) of the Mg-Cu-Zn ferrites exhibits thermal hysteresis when the temperature is cycled from above the Curie temperature TC to below. The sharp decrease of ?i at T = TC indicates that the samples have high homogeneity according to Globus et al. The Curie temperature TC of the studied ferrite system was determined from the ?i-T curves where the Hopkinson type of effect at the TC has been observed with the manifestation of a sharp fall in permeability. The Curie temperature TC is found to increase with increasing Mn content. Dc electrical resistivity increases significantly with the increase in Mn content. The ac resistivity (?ac) and dielectric constant (?') of the samples are found to decrease with increase in frequency, exhibiting normal ferrimagnetic behaviour. Dielectric relaxation peaks were observed for the frequency dependence of dielectric loss tangent curves. ?' increases as the temperature increases, which is the normal dielectric behaviour of the magnetic semiconductor ferrite. The observed variation of electrical and dielectric properties are explained on the basis of Fe2+/Fe3+ ionic concentration as well as the electronic hopping frequency between Fe2+ and Fe3+ ions in the present samples.

  18. Crystal Orientation and Temperature Effects on the Double Hysteresis Loop Behavior of a PVDF- g-PS Graft Copolymer

    NASA Astrophysics Data System (ADS)

    Zhu, Lei; Yang, Lianyun; Guan, Fangxiao

    2013-03-01

    In a recent report, double hysteresis loop behavior is observed in a nanoconfined poly(vinylidene fluoride-co-trifluoroethylene-co-chlorotrifluoroethylene)-graft-polystyrene [P(VDF-TrFE-CTFE)- g-PS] copolymer. It is considered that the PS grafts are capable of reducing the compensation polarization and thus the polarization electric field during the reverse poling process, resulting in the double hysteresis loop behavior. In this study, we further investigated crystal orientation and temperature effects on this novel ferroelectric behavior. It is observed that with increasing the orientation factor, the electric displacement-electric field (D-E) loop changes from linear for non-oriented film to double loop for the well-oriented film. With increasing the temperature, the double hysteresis loop is gradually replaced by the single and open loop, which is attributed to the impurity ion migrational loss in the sample. In a recent report, double hysteresis loop behavior is observed in a nanoconfined poly(vinylidene fluoride-co-trifluoroethylene-co-chlorotrifluoroethylene)-graft-polystyrene [P(VDF-TrFE-CTFE)- g-PS] copolymer. It is considered that the PS grafts are capable of reducing the compensation polarization and thus the polarization electric field during the reverse poling process, resulting in the double hysteresis loop behavior. In this study, we further investigated crystal orientation and temperature effects on this novel ferroelectric behavior. It is observed that with increasing the orientation factor, the electric displacement-electric field (D-E) loop changes from linear for non-oriented film to double loop for the well-oriented film. With increasing the temperature, the double hysteresis loop is gradually replaced by the single and open loop, which is attributed to the impurity ion migrational loss in the sample. This work is supported by NSF (DMR-0907580).

  19. Proximity effect induced magnetoresistance hysteresis loops in a topological insulator/YIG heterostructure

    NASA Astrophysics Data System (ADS)

    Montazeri, Mohammad; Lang, Murong; Onbasli, Mehmet C.; Kou, Xufeng; He, Liang; Ross, Caroline A.; Wang, Kang L.

    2014-03-01

    We experimentally demonstrate the proximity effect induced hysteretic magnetoresistance in an 8 quintuple layers of Bi2Se3 films grown on Gallium Gadolinium Garnet (GGG) (111) substrates with a 50 nm Yttrium Iron Garnet (YIG) buffer layer by molecular beam epitaxy. With in-plane and out-of-plane magnetic field, square wave shaped and butterfly shaped resistance hysteresis loops can be observed up to 25 K, respectively. The relationship between the hysteretic MR curves and the magnetic switching of the YIG will be discussed in the context of a proximity effect between the YIG and the TI.

  20. Mechano-electric optoisolator transducer with hysteresis

    NASA Astrophysics Data System (ADS)

    Ciuru?, I. M.; Dimian, M.; Graur, A.

    2011-01-01

    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.

  1. Cold test facility for 1.8 m superconducting model magnets at the SSCL

    SciTech Connect

    LaBarge, A.; Althaus, R.; Bird, R.; Baron, J.; Chagnon, J.; Deak, M.; Scott, M.; Vasilyev, V.; Williamson, G.

    1993-05-01

    A new facility has been constructed to measure the characteristic features of superconducting model magnets and cable at cryogenic temperatures--a function which supports the design and development process for building full-scale accelerator magnets. There are multiple systems operating in concert to test the model magnets, namely, cryogenic, magnet power, data acquisition and system control. A typical model magnet test includes the following items: warm measurements of magnet coils, strain gauges and voltage taps; hipot testing of insulation integrity; cooling with liquid nitrogen and then liquid helium; measuring quench current and magnetic field; (5) magnet warm-up. While the magnet is being cooled to 4.22 K, the mechanical stress is monitored through strain gauges. Current is then ramped into the magnet until it reaches some maximum value and the magnet transitions from the superconducting state to the normal state. Normal-zone propagation is monitored using voltage taps on the magnet coils during this process, thus indicating where the transition began. The current ramp is usually repeated until a plateau current is reached, where the magnet has mechanically settled. Many variations on the current ramping sequence are used to study different phenomena associated with magnet performance, e.g. magnetization hysteresis, eddy current losses, cryogenic stability, etc. A warm bore cryostat with a rotating coil is inserted in the magnet to measure field strength and homogeneity. These types of measurements yield multipole and current versus field data.

  2. Experimental investigation of AC loss in a conduction-cooled layer-wound (RE)BCO magnet for continuous Adiabatic Demagnetization Refrigerator (ADR)

    NASA Astrophysics Data System (ADS)

    Park, Jiho; Kim, Seokho; Park, Inmyong; Jeong, Sangkwon

    2014-09-01

    This paper discusses the fabrication of a (RE)BCO solenoid magnet and its experimental results from the aspect of AC loss and thermal characteristics. A (RE)BCO coated conductor with polyimide tape insulation was utilized for a coil and wound by a standard layer-wound method. The (RE)BCO solenoid magnet consists of a stainless steel bore and a pair of OFHC copper supporting plates assembled at both ends. The coil winding has a novel thermal drain structure that can withstand high AC thermal loads generated externally and internally. The OFHC copper strips were installed between the interlayers in the perpendicular direction to the (RE)BCO conductor winding to mitigate both thermal resistance in the axial direction of the (RE)BCO coil and eddy current loss by an external magnetic field. Apiezon® N grease with hexane solution was applied on the entire (RE)BCO coil winding to minimize thermal contact resistance between the conductor and the OFHC copper strips. The (RE)BCO coil carried 150 A at 14.7 K and generated 3.5 T at the center of the coil. A sinusoidal current waveform (operating frequency from 0.1 Hz to 1.0 Hz) was applied with peaks of 25 A, 50 A, and 70 A (the corresponding magnetic field of 0.54 T, 1.08 T, and 1.54 T) and the corresponding AC losses were measured by both calorimetric and electrical methods. The AC losses measured by both methods were in good agreement. The experimental results were compared with theoretical and numerical solutions.

  3. Exchange anisotropy in polycrystalline FeNi/FeMn films with hysteresis loop assymmetry.

    SciTech Connect

    Merenkov, D. N.; Bludov, A. N.; Gnatchenko, S. L.; Baran, M.; Szymczak, R.; Novosad, V. A.; Materials Science Division; National Academy of Sciences of Ukraine; Polish Academy of Sciences

    2007-11-01

    The process of magnetization reversal of a FeNi(50 {angstrom})/FeMn(50 {angstrom}) polycrystalline film prepared in a magnetic field has been investigated at temperatures ranging from 25 to 300 K. The external field was oriented in the film plane along the easy or difficult axis of the ferromagnetic layer. In the process of magnetization reversal of the film along the easy axis, strong asymmetry of the hysteresis loop is observed together with an exchange shift. As temperature decreases, the asymmetry becomes more pronounced and the shift increases. The field dependences of the magnetization of the film are symmetric and are not shifted when the external field is applied along the difficult axis. The magnetization reversal process is examined on the basis of a model that takes account of the appearance of high-order exchange anisotropy in polycrystalline films. It is shown that the observed strong asymmetry of the hysteresis loop is associated with the formation of a canted phase and the existence of a metastable state. As the film temperature decreases, the interval of fields where the canted phase can exist becomes wider as a result of an increase of the exchange anisotropy constants.

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

    NASA Astrophysics Data System (ADS)

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

    2010-12-01

    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.

  5. Applications of a theory of ferromagnetic hysteresis

    SciTech Connect

    Hodgdon, M.L.

    1987-01-01

    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.

  6. A statistical mechanical description of metastable states and hysteresis in the 3D soft-spin random-field model at T = 0

    NASA Astrophysics Data System (ADS)

    Rosinberg, M. L.; Tarjus, G.

    2010-12-01

    We present a formalism for computing the complexity of metastable states and the zero-temperature magnetic hysteresis loop in the soft-spin random-field model in finite dimensions. The complexity is obtained as the Legendre transform of the free energy associated with a certain action in replica space and the hysteresis loop above the critical disorder is defined as the curve in the field-magnetization plane where the complexity vanishes; the nonequilibrium magnetization is therefore obtained without having to follow the dynamical evolution. We use approximations borrowed from condensed-matter theory and based on assumptions on the structure of the direct correlation functions (or proper vertices), such as a local approximation for the self-energies, to calculate the hysteresis loop in three dimensions, the correlation functions along the loop, and the second moment of the avalanche-size distribution.

  7. On the origin of giant magnetocaloric effect and thermal hysteresis in multifunctional ?-FeRh thin films

    NASA Astrophysics Data System (ADS)

    Zhou, Tiejun; Cher, M. K.; Shen, L.; Hu, J. F.; Yuan, Z. M.

    2013-12-01

    We report temperature and field dependent lattice structure, magnetic properties and magnetocaloric effect in epitaxial Fe50Rh50 thin films with (001) texture. Temperature-dependent XRD measurements reveal an irreversible first-order phase transition with 0.66% lattice change upon heating/cooling. First-principle calculation shows a state change of Rh from non-magnetic (0 ?B) for antiferromagnetic phase to magnetic (0.93 ?B) state for ferromagnetic phase. A jump of magnetization at temperature of 305 K and field more than 5 T indicates a field-assisted magnetic state change of Ru that contributes to the jump. Giant positive magnetic entropy change was confirmed by isothermal magnetization measurements and an in-situ temperature rise of 15 K. The magnetic state change of Rh between antiferromagnetic and ferromagnetic states is the main origin of giant magnetic entropy change and large thermal hysteresis observed.

  8. Laboratory Evidence That Line-Tied Toroidal Magnetic Fields Can Suppress Loss-of-Equilibrium Flux Rope Eruptions in the Solar Corona

    NASA Astrophysics Data System (ADS)

    Myers, C. E.; Yamada, M.; Belova, E.; Ji, H.; Yoo, J.; Fox, W. R., II; Jara-Almonte, J.

    2014-12-01

    Loss-of-equilibrium mechanisms such as the ideal torus instability [Kliem & Török, Phys. Rev. Lett. 96, 255002 (2006)] are predicted to drive arched flux ropes in the solar corona to erupt. In recent line-tied flux rope experiments conducted in the Magnetic Reconnection Experiment (MRX), however, we find that quasi-statically driven flux ropes remain confined well beyond the predicted torus instability threshold. In order to understand this behavior, in situ measurements from a 300 channel 2D magnetic probe array are used to comprehensively analyze the force balance between the external (potential) and internal (plasma-generated) magnetic fields. We find that forces due to the line-tied toroidal magnetic field, which are not included in the basic torus instability theory, can play a major role in preventing eruptions. The dependence of these toroidal magnetic forces on various potential field and flux rope parameters will be discussed. This research is supported by DoE Contract Number DE-AC02-09CH11466 and by the NSF/DoE Center for Magnetic Self-Organization (CMSO).

  9. Circuit measures hysteresis loop areas at 30 Hz

    NASA Technical Reports Server (NTRS)

    Hoffman, C.; Spilo, D.

    1967-01-01

    Analog circuit measures hysteresis loop areas as a function of time during fatigue testing of specimens subjected to sinusoidal tension-compression stresses at a frequency of Hz. When the sinusoidal stress signal is multiplied by the strain signal, the dc signal is proportional to hysteresis loop area.

  10. Preisach modeling of piezoceramic and shape memory alloy hysteresis

    Microsoft Academic Search

    Declan Hughes; John T. Wen

    1995-01-01

    Smart materials such as piezoceramics and shape memory alloys (SMAs) exhibit significant hysteresis and in order to estimate the effect on open and closed loop control a suitable model is needed. One promising candidate is the Preisach independent domain hysteresis model that is characterized by the congruent minor loop and wiping out properties. Comparable minor loop and decaying oscillation test

  11. A Free Energy Model for Hysteresis in Ferroelectric Materials

    E-print Network

    A Free Energy Model for Hysteresis in Ferroelectric Materials Ralph C. Smith Stefan Seelecke.ncsu.edu Abstract This paper provides a theory for quantifying the hysteresis and constitutive nonlinearities in homogenization techniques. In the first step of the model development, Helmholtz and Gibbs free energy relations

  12. Impact of relative permeability hysteresis on geological CO2 storage

    Microsoft Academic Search

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

    2006-01-01

    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

  13. Parameter Estimation Techniques for a Class of Nonlinear Hysteresis Models

    E-print Network

    frequency, temperature, and stress dependencies which makes it applicable for a wide range of transducer through comparison with experimental data. i #12;1 Introduction Hysteresis and constitutive nonlinearities and biomedical applications. In some regimes, hysteresis can be mitigated through restricted input levels

  14. PREFACE: International Workshop on Multi-Rate Processes and Hysteresis

    Microsoft Academic Search

    Michael P. Mortell; Robert E. O'Malley; Alexei Pokrovskii; Dmitrii Rachinskii; Vladimir A. Sobolev

    2008-01-01

    We are interested in singular perturbation problems and hysteresis as common strongly nonlinear phenomena that occur in many industrial, physical and economic systems. The wording `strongly nonlinear' means that linearization will not encapsulate the observed phenomena. Often these two types of phenomena are manifested for different stages of the same or similar processes. A number of fundamental hysteresis models can

  15. International Workshop on Multi-Rate Processes and Hysteresis

    Microsoft Academic Search

    Michael P Mortell; Robert E OMalley; Alexei Pokrovskii; Dmitrii Rachinskii; Vladimir A Sobolev

    2008-01-01

    We are interested in singular perturbation problems and hysteresis as common strongly nonlinear phenomena that occur in many industrial, physical and economic systems. The wording `strongly nonlinear' means that linearization will not encapsulate the observed phenomena. Often these two types of phenomena are manifested for different stages of the same or similar processes. A number of fundamental hysteresis models can

  16. Dynamic hysteresis control of lift on a pitching wing

    NASA Astrophysics Data System (ADS)

    Williams, David R.; An, Xuanhong; Iliev, Simeon; King, Rudibert; Reißner, Florian

    2015-05-01

    Dynamic hysteresis appearing in the lift force during pitching maneuvers is distinctly different from conventional static hysteresis. The size and shape of dynamic hysteresis loops are dependent on the degree of flow attachment, the dimensionless pitching frequency, and two time delays associated with the flow separation process. A linearized version of the Goman-Khrabrov model is derived and shown to capture the dynamic hysteresis characteristics when the pitching amplitude is small. Closed-loop control using a linearized version of the Goman-Khrabrov model is demonstrated, which incorporates a disturbance model into the feed-forward controller. The controller is shown to reduce the dynamic hysteresis during periodic pitching, step-up and step-down maneuvers, and quasi-random pitching maneuvers.

  17. Modelling of rotational magnetization in anisotropic sheets

    Microsoft Academic Search

    Witold Mazgaj

    2011-01-01

    Purpose – The aim of this paper is to present a new relatively simple model of the rotational magnetization process in anisotropic sheets. Design\\/methodology\\/approach – The surface of a sample of an anisotropic sheet is divided into an assumed number of specified directions. To each direction a certain hysteresis loop, the so-called direction hysteresis, is assigned. The parameters of the

  18. Hysteresis Affects Approximate Number Discrimination in Young Children

    PubMed Central

    Odic, Darko; Hock, Howard; Halberda, Justin

    2015-01-01

    Perceptual decisions are often affected not only by the evidence gathered during a trial but also by the history of preceding trials. This effect—termed perceptual hysteresis—provides evidence for how perceptual information is represented and how it is used. The present research focuses on how the difficulty of preceding trials affects subsequent ones—we find that how well 5-year-old children perform in a 2-alternative forced-choice numerical discrimination task depends on whether they have had a prior history of easier discriminations or a prior history of harder discriminations. Furthermore, this effect is modulated by the feedback children receive. In 3 experiments, we demonstrate that these effects are not related to practice or loss of interest due to negative feedback, or simply to trial difficulty or discriminability. Instead, children appear to have state-dependent confidence states such that prolonged experience making low-confidence decisions degrades performance, whereas prolonged experience making high-confidence decisions improves it. These results are discussed in the context of dynamical psychophysics, representations of confidence, and work on children’s and adults’ number perception abilities. PMID:23163765

  19. Structural phase transformation and hysteresis behavior of Cu-Zn ferrites

    NASA Astrophysics Data System (ADS)

    Maria, Kazi Hanium; Choudhury, Shamima; Hakim, Mohammad Abdul

    2013-06-01

    A series of Cu1- x Zn x Fe2O4 ferrite (with x = 0.0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6) compositions were synthesized using the standard solid-state reaction technique. X-ray diffraction was used to study the structure of the above investigated samples. The theoretical and experimental lattice parameters ( a th and a exp) were calculated for each composition. A significant decrease in density and subsequent increase in porosity were observed with increasing Zn content. Curie temperature, T C, has been determined from the temperature dependence of permeability and found to decrease with increasing Zn content. The anomaly observed in the temperature dependence of permeability was attributed to the existence of two structural phases: cubic phase and tetragonal phase. Low-field hysteresis measurements have been performed using a B- H loop trace from which hysteresis parameters have been determined. Coercivity and hysteresis loss were estimated with different Zn contents.

  20. Ripple field losses in direct current biased superconductors: Simulations and comparison with measurements

    NASA Astrophysics Data System (ADS)

    Lahtinen, Valtteri; Pardo, Enric; Šouc, Ján; Solovyov, Mykola; Stenvall, Antti

    2014-03-01

    In several superconducting applications, as, for example, in some supercondcuting generators, motors, and power transmission cables, the superconductor experiences a changing magnetic field in a DC background. Simulating the losses caused by this AC ripple field is an important task from the application design point of view. In this work, we compare two formulations, the H-formulation and the minimum magnetic energy variation-formulation, based on the eddy current model (ECM) and the critical state model (CSM), respectively, for simulating ripple field losses in a DC biased coated conductor tape. Furthermore, we compare our simulation results with measurements. We investigate the frequency-dependence of the hysteresis loss predictions of the power law based ECM and verify by measurements, that in DC use, ECM clearly over-estimates the homogenization of the current density profile in the coated conductor tape: the relaxation of the local current density is not nearly as prominent in the measurement as it is in the simulation. Hence, we suggest that the power law resistivity, used as the local relation between the electric field intensity E and current density J in ECM, is not an intrinsic property of high-temperature superconductors. The difference between the models manifests itself as discrepancies in ripple field loss simulations in very low AC fields with significant DC fields or currents involved. The results also show, however, that for many practical situations, CSM and ECM are both eligible models for ripple field loss simulations.

  1. Hysteresis in Pressure-Driven DNA Denaturation

    PubMed Central

    Hernández-Lemus, Enrique; Nicasio-Collazo, Luz Adriana; Castañeda-Priego, Ramón

    2012-01-01

    In the past, a great deal of attention has been drawn to thermal driven denaturation processes. In recent years, however, the discovery of stress-induced denaturation, observed at the one-molecule level, has revealed new insights into the complex phenomena involved in the thermo-mechanics of DNA function. Understanding the effect of local pressure variations in DNA stability is thus an appealing topic. Such processes as cellular stress, dehydration, and changes in the ionic strength of the medium could explain local pressure changes that will affect the molecular mechanics of DNA and hence its stability. In this work, a theory that accounts for hysteresis in pressure-driven DNA denaturation is proposed. We here combine an irreversible thermodynamic approach with an equation of state based on the Poisson-Boltzmann cell model. The latter one provides a good description of the osmotic pressure over a wide range of DNA concentrations. The resulting theoretical framework predicts, in general, the process of denaturation and, in particular, hysteresis curves for a DNA sequence in terms of system parameters such as salt concentration, density of DNA molecules and temperature in addition to structural and configurational states of DNA. Furthermore, this formalism can be naturally extended to more complex situations, for example, in cases where the host medium is made up of asymmetric salts or in the description of the (helical-like) charge distribution along the DNA molecule. Moreover, since this study incorporates the effect of pressure through a thermodynamic analysis, much of what is known from temperature-driven experiments will shed light on the pressure-induced melting issue. PMID:22496765

  2. Magnetic characterization of soft magnetic materials—experiments and analysis

    Microsoft Academic Search

    R. Grössinger; H. Sassik; D. Holzer; N. Pillmayr

    2003-01-01

    Various kinds of magnetic measurement methods suited for soft magnetic materials are critically surveyed. Emphasis was laid on AC-susceptibility methods, the hysteresis loop and the magnetostriction. The analysis of the temperature dependence of the magnetization and the magnetostriction is demonstrated on the amorphous system Fe–Co–B.

  3. Three dimensional magnetic field mathematical model and its applications to calculation of fields and losses in turbogenerator end

    E-print Network

    Boyer, Edmond

    (Appendix 1) where 03BCr, 03BC~ and M z are the components of stator core magnetic permeability tensor ; 03C661 Three dimensional magnetic field mathematical model and its applications to calculation of the generator design instead of creating a physical model much less correct and much more costly. Revue Phys

  4. Measurement and Modeling of Rotational Core Losses of Soft Magnetic Materials Used in Electrical Machines: A Review

    Microsoft Academic Search

    Youguang Guo; Jian Guo Zhu; Jinjiang Zhong; Haiyan Lu; Jian Xun Jin

    2008-01-01

    In many situations, for example, in the cores of a rotating electrical machine and the T-joints of multiphase transformers, the magnetic flux varies with time in terms of both magnitude and direction, i.e., the local flux density vector rotates with varying magnitude and varying speed. Therefore, it is important that the magnetic properties of the core materials under various rotational

  5. The heating effect of iron-cobalt magnetic nanofluids in an alternating magnetic field: application in magnetic hyperthermia treatment.

    PubMed

    Shokuhfar, Ali; Seyyed Afghahi, Seyyed Salman

    2013-01-01

    In this research, FeCo alloy magnetic nanofluids were prepared by reducing iron(III) chloride hexahydrate and cobalt(II) sulfate heptahydrate with sodium borohydride in a water/CTAB/hexanol reverse micelle system for application in magnetic hyperthermia treatment. X-ray diffraction, electron microscopy, selected area electron diffraction, and energy-dispersive analysis indicate the formation of bcc-structured iron-cobalt alloy. Magnetic property assessment of nanoparticles reveals that some samples are single-domain superparamagnetic, while others are single- or multi-domain ferromagnetic. The stability of the magnetic fluids was achieved by using a CTAB/1-butanol surfactant bilayer. Results of Gouy magnetic susceptibility balance experiments indicate good stability of FeCo nanoparticles even after dilution. The inductive properties of corresponding magnetic fluids including temperature rise and specific absorption rate were determined. Results show that with increasing of the nanoparticle size in the single-domain size regime, the generated heat increases, indicating the significant effect of the hysteresis loss. Finally, the central parameter controlling the specific absorption rate of nanoparticles was introduced, the experimental results were compared with those of the Stoner-Wohlfarth model and linear response theory, and the best sample for magnetic hyperthermia treatment was specified. PMID:24359163

  6. Hysteresis, feed-back mechanisms, and time-delays in the solar wind -magnetosphere energy circulation.

    NASA Astrophysics Data System (ADS)

    Koskinen, Hannu; Palmroth, Minna; Pulkkinen, Tuija

    We discuss various explanations for the asymmetric behaviour of the solar wind energy input to the magnetosphere when the IMF is rotated through due southward orientation, which has been revealed by global solar wind -magnetosphere -ionosphere simulations. When the V Bz electric field first increases and then starts to decrease, the energy input remains higher than it was for the corresponding IMF clock angle before the southward orientation. It appears that to reduce the energy input rate requires reaching smaller V Bz than is the case when increasing the input. Phenomenologically this is analogous to the hysteresis cycle in ferromagnetic media. As the magnetosphere is a complicated non-linear feedback system with several sources of inertia and time delays, the hysteresis itself may not be a big surprise, but we do not yet understand what it is telling us of the magnetospheric dynamics. While the proximate explanation may be possible to find in the local plasma and magnetic field properties at the magnetopause, the ultimate reason for the hysteresis and its quantitative aspects may well lie in the inertia and feed-back mechanisms in the coupling of the outer magnetospheric boundaries to the inner parts of the system, e.g., in the coupling of the Region 1 currents through the polar ionosphere, in the Region 1 -Region 2 -partial ring current system, in the connection of the polar cusp to the noon sector auroral zone, in the changing properties of plasma sheet due to the changing solar wind driver, or in any combination of two or more of these. Experimental confirmation, direct or indirect, of the hysteresis should be considered as one of the great challenges in magnetospheric plasma physics.

  7. Preisach model study of the connection between magnetic and microstructural properties of soft magnetic materials

    Microsoft Academic Search

    V. Basso; G. Berlotti; A. Infortuna; M. Pasquale

    1995-01-01

    The application of Preisach modelling to the study of the microstructure-hysteresis interplay in soft magnetic materials is reviewed. It is shown that mean-field effects are mainly due to the change of the total domain wall surface energy along the hysteresis loop. The reconstruction of the Preisach distribution from a proper set of experimental data is discussed and the microstructural evolution

  8. Static measurements of slender delta wing rolling moment hysteresis

    NASA Technical Reports Server (NTRS)

    Katz, Joseph; Levin, Daniel

    1991-01-01

    Slender delta wing planforms are susceptible to self-induced roll oscillations due to aerodynamic hysteresis during the limit cycle roll oscillation. Test results are presented which clearly establish that the static rolling moment hysteresis has a damping character; hysteresis tends to be greater when, due to either wing roll or side slip, the vortex burst moves back and forth over the wing trailing edge. These data are an indirect indication of the damping role of the vortex burst during limit cycle roll oscillations.

  9. Magnetic nanoparticles for applications in oscillating magnetic field

    SciTech Connect

    Peeraphatdit, Chorthip

    2010-12-15

    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.

  10. Suppression of the thermal hysteresis in magnetocaloric MnAs thin film by highly charged ion bombardment

    E-print Network

    Trassinelli, Martino; Eddrief, M; Etgens, V H; Gafton, V; Hidki, S; Lacaze, Emmanuelle; Lamour, Emily; Prigent, Christophe; Rozet, Jean-Pierre; Steydli, S; Zheng, Y; Vernhet, Dominique

    2014-01-01

    We present the investigation on the modifications of structural and magnetic properties of MnAs thin film epitaxially grown on GaAs induced by slow highly charged ions bombardment under well-controlled conditions. The ion-induced defects facilitate the nucleation of one phase with respect to the other in the first-order magneto-structural MnAs transition with a consequent suppression of thermal hysteresis without any significant perturbation on the other structural and magnetic properties. In particular, the irradiated film keeps the giant magnetocaloric effect at room temperature opening new perspective on magnetic refrigeration technology for everyday use.

  11. Efficiency of O-C diagrams as diagnostic tools for long-term period variations. I. Wind-driven mass loss and magnetic braking

    NASA Astrophysics Data System (ADS)

    Nanouris, N.; Kalimeris, A.; Antonopoulou, E.; Rovithis-Livaniou, H.

    2011-11-01

    Context. The credibility of an O-C diagram analysis is investigated when long-term processes are examined in binary systems. The morphology of period and O-C diagrams is thoroughly explored when mass loss and magnetic braking, induced by stellar winds, drive the orbital evolution of late-type detached binaries. Conditions are specified that determine which process dominates. Aims: Our objective is to determine the minimum time intervals that observations are expected to span for a physical mechanism to be detectable by means of an O-C diagram analysis. Computations for various values that account for the noise level and the orbital period are performed to find out to which degree these affect the inferred intervals. Methods: Generalized dot{J-dot{P}} relations that govern the orbital evolution of a binary system are set and solved analytically to determine in a closed form the period and the function expected to represent the respective O-C variations. Semi-empirical relations adapting mass loss and magnetic braking processes for single cool stars are adopted and properly modified to be consistent with the latest observational constraints. A standard Newton-Raphson numerical procedure is then employed to estimate the minimum temporal range over which a specific mechanism is rendered measurable. Results: Mass loss rates comparable to or greater than -10-9 M? yr-1 are measurable for typical noise levels of the O-C diagrams when the data span more than a century. Magnetic braking was proved to be very sensitive on the orbital period and on the braking law adopted for inference. It is expected to be detectable in current O-C diagrams of very short-period binaries only, for others it needs at least two centuries of observations to confirm its effects safely. Conclusions: Both wind driven mass loss and magnetic braking processes are able to drive the orbital evolution of short-period detached binaries (Porb1d) in amounts traced on human timescales. There are also special conditions under which their strength is equalized, locking the orbital period invariable in time. Several short-period RS CVn-type binaries are fine candidates where this regime is expected to prevail.

  12. The Radial Loss of Ions Trapped in the Thermal Barrier Potential and the Design of Divertor Magnetic Field in GAMMA10

    SciTech Connect

    Katanuma, I. [Plasma Research Center, University of Tsukuba (Japan); Ito, T. [Plasma Research Center, University of Tsukuba (Japan); Saimaru, H. [Plasma Research Center, University of Tsukuba (Japan); Sasagawa, Y. [Plasma Research Center, University of Tsukuba (Japan); Pastukhov, V.P. [I.V.Kuruchatov Atomic Energy Institute (Russian Federation); Ishii, K. [Plasma Research Center, University of Tsukuba (Japan); Tatematsu, Y. [Plasma Research Center, University of Tsukuba (Japan); Saito, T. [Plasma Research Center, University of Tsukuba (Japan); Islam, Md.K. [Plasma Research Center, University of Tsukuba (Japan); Nakashima, Y. [Plasma Research Center, University of Tsukuba (Japan); Cho, T. [Plasma Research Center, University of Tsukuba (Japan)

    2005-01-15

    The ion radial loss exists in the presence of a non-axisymmetric electrostatic potential in the end-mirror cells of GAMMA10, which leads to a formation of the thermal barrier potential. The non-axisymmetric electrostatic potential can also exist in the central cell. A design for divertor magnetic field of GAMMA10 is performed, the purpose of which is first to reduce an ion radial transport in the central cell by making electrostatic potential circular and second to assure the macroscopic plasma stability of GAMMA10 without help of non-axisymmetric anchor cells which enhances a neoclassical radial transport.

  13. Adaptive control with hysteresis estimation and compensation using RFNN for piezo-actuator

    Microsoft Academic Search

    Faa-Jeng Lin; Hsin-Jang Shieh; Po-Kai Huang; Li-Tao Teng

    2006-01-01

    Because the control performance of a piezoactuator is always severely deteriorated due to hysteresis effect, an adaptive control with hysteresis estimation and compensation using recurrent fuzzy neural network (RFNN) is proposed in this study to improve the control performance of the piezo-actuator. A new hysteresis model by modifying and parameterizing the hysteresis friction model is proposed. Then, the overall dynamics

  14. 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

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

    2007-01-01

    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. PMID:17672891

  15. Lodestone: Nature's own permanent magnet

    NASA Technical Reports Server (NTRS)

    Wasilewski, P.

    1976-01-01

    Magnetic hysteresis and microstructural details are presented which explain why the class of magnetic iron ores defined as proto-lodestones, can behave as permanent magnets, i.e. lodestones. Certain of these proto-lodestones which are not permanent magnets can be made into permanent magnets by charging in a field greater than 1000 oersted. This fact, other experimental observations, and field evidence from antiquity and the middle ages, which seems to indicate that lodestones are found as localized patches within massive ore bodies, suggests that lightning might be responsible for the charging of lodestones. The large remanent magnetization, high values of coercive force, and good time stability for the remanent magnetization are all characteristics of proto-lodestone iron ores which behave magnetically as fine scale ( 10 micrometer) intergrowths when subjected to magnetic hysteresis analysis. The magnetic results are easily understood by analysis of the complex proto lodestone microstructural patterns observable at the micrometer scale and less.

  16. Effects of sulfur content and slab reheating temperature on the magnetic properties of fully processed nonoriented electrical steels

    NASA Astrophysics Data System (ADS)

    Hou, Chun-Kan

    The effects of sulfur content and slab reheating temperature on the magnetic properties of four fully processed nonoriented electrical steels have been investigated. Four slabs of nonoriented electrical steels with sulfur content in the range of 0.0006-0.0126 wt% were reheated to 1100, 1200, and 1300 °C, respectively. Then, they were hot rolled and annealed at 700 °C, cold rolled at the same condition and annealed at 820 °C in the salt bath furnace for 1 min to simulate continuous annealing. The ac core loss, dc hysteresis loss, and ac and dc permeability were measured at 15 kG inductions. It was found that the amount of inclusions in the hot-rolled bands increased with increasing slab reheating temperature and increasing sulfur content in steels. After final annealing, grain sizes of cold-rolled steel sheets decreased with increasing sulfur content and increasing slab reheating temperature. The main preferred orientations in the final annealed steel sheets were (0 1 1) <1 0 0> and (1 1 1) < u v w> ? fiber texture. Steel sheets containing 0.0032 and 0.0060 wt% sulfur developed a more stronger (0 1 1)<1 0 0> texture than other steel sheets. However, steel sheets containing 0.0126 wt% sulfur had the weakest (1 1 1)< u v w> texture during slab reheating at temperatures higher than 1200 °C. Both ac core loss and dc hysteresis loss increased with increasing slab reheating temperature and increasing sulfur content in steel sheets. Both ac and dc permeability decreased with increasing slab reheating temperature and increasing sulfur content in steel sheets. If sulfur content decreased from 0.0060 to 0.0032 wt%, there were great improvements in ac core loss, dc hysteresis loss, and ac and dc permeability. However, eddy current loss was almost independent of the sulfur content and slab reheating temperature.

  17. Fine particle magnetic mineralogy of archaeological ceramics

    Microsoft Academic Search

    D. Atkinson; J. A. King

    2005-01-01

    This study investigated the magnetic mineralogy of a worldwide collection of archaeological pottery. The mineral types, the mass fractions and the domain states of the constituent magnetic fine particles were elucidated from a range of measurements including magnetic hysteresis behaviour, the acquisition of isothermal remanence, low field susceptibility and thermomagnetic curves. The magnetic mineralogy of most samples was dominated by

  18. Dynamic wetting on superhydrophobic surfaces: Droplet impact and wetting hysteresis

    E-print Network

    Smyth, Katherine M.

    We study the wetting energetics and wetting hysteresis of sessile and impacting water droplets on superhydrophobic surfaces as a function of surface texture and surface energy. For sessile drops, we find three wetting ...

  19. Low-Hysteresis Flow-Through Wind-Tunnel Balance

    NASA Technical Reports Server (NTRS)

    Kunz, N.; Luna, P. M.; Roberts, A. C.; Smith, R. C.; Horne, W. L.; Smith, K. M.

    1992-01-01

    Improved flow-through wind-tunnel balance includes features minimizing both spurious force readings caused by internal pressurized flow and mechanical hysteresis. Symmetrical forces caused by internal flow cancelled.

  20. Modeling and analysis of multiclass thresholdbased queues with hysteresis using

    E-print Network

    Tuffin, Bruno

    behaviour. Hysteresis is also inserted, so that the control mechanism will not switch too much. One motiva terms of throughput, delay or jitter for instance) are required for different applications such as video

  1. Essays on crime, hysteresis, poverty and conditional cash transfers 

    E-print Network

    Loureiro, Andre Oliveira Ferreira

    2013-07-03

    This thesis encompasses three essays around criminal behaviour with the first one analysing the impact of programmes aimed at poverty reduction, the second one developing a theoretical model of hysteresis in crime, and ...

  2. On the question of hysteresis in Hall magnetohydrodynamic reconnection

    SciTech Connect

    Sullivan, Brian P.; Bhattacharjee, A.; Huang Yimin [Center for Integrated Computation and Analysis of Reconnection and Turbulence, University of New Hampshire, Space Science Center, Durham, New Hampshire 03824 (United States)

    2010-11-15

    Controversy has been raised regarding the cause of hysteresis, or bistability, of solutions to the equations that govern the geometry of the reconnection region in Hall magnetohydrodynamic (MHD) systems. This brief communication presents a comparison of the frameworks within which this controversy has arisen and illustrates that the Hall MHD hysteresis originally discovered numerically by Cassak et al. [Phys. Rev. Lett. 95, 235002 (2005)] is a different phenomenon from that recently reported by Zocco et al. [Phys. Plasmas 16, 110703 (2009)] on the basis of analysis and simulations in electron MHD with finite electron inertia. We demonstrate that the analytic prediction of hysteresis in EMHD does not describe or explain the hysteresis originally reported in Hall MHD, which is shown to persist even in the absence of electron inertia.

  3. Theory of quantum tunneling of the magnetization in magnetic particles

    Microsoft Academic Search

    H. de Raedt; S. Miyashita; K. Saito; D. García-Pablos; N. García

    1997-01-01

    We study the response of the magnetization to a time-dependent applied magnetic field H(t) in a model for a uniaxial magnet. It is shown that a staircase structure in the magnetization curve results from Landau-Zener tunneling between different pairs of nearly-degenerate energy levels. This mechanism might be relevant to the analysis of the hysteresis of nanoscale magnets at low temperatures,

  4. Aileron roll hysteresis effects on entry of space shuttle orbiter

    NASA Technical Reports Server (NTRS)

    Powell, R. W.

    1977-01-01

    Six-degree-of-freedom simulations of the space shuttle orbiter entry with control hysteresis were conducted on the NASA Langley Research Center interactive simulator known as the automatic reentry flight dynamics simulator. These simulations revealed that the vehicle can tolerate control hysteresis producing a + or - 50 percent change in the nominal aileron roll characteristics and an offset in the nominal characteristics equivalent to a + or - 5 deg aileron deflection with little increase in the reaction control system's fuel consumption.

  5. Controlling hysteresis in superconducting constrictions with a resistive shunt

    NASA Astrophysics Data System (ADS)

    Kumar, Nikhil; Winkelmann, C. B.; Biswas, Sourav; Courtois, H.; Gupta, Anjan K.

    2015-07-01

    We demonstrate control of the thermal hysteresis in superconducting constrictions by adding a resistive shunt. In order to prevent thermal relaxation oscillations, the shunt resistor is placed in close proximity to the constriction, making the inductive current-switching time smaller than the thermal equilibration time. We investigate the current–voltage characteristics of the same constriction with and without the shunt-resistor. The widening of the hysteresis-free temperature range is explained on the basis of a simple model.

  6. Hysteresis and interfacial energies in smooth-walled microfluidic channels

    Microsoft Academic Search

    Yihong Liu; D. D. Nolte; L. J. Pyrak-Nolte

    2011-01-01

    Hysteresis in the capillary pressure-saturation relationship (Pc–Sw) for a porous medium has contributions from the complex geometry of the pore network as well as the physical chemistry of the grain surfaces. To isolate the role of wettability on hysteresis, we fabricated microfluidic cells that contain a single wedge-shaped channel that simulates a single pore throat. Using confocal microscopy of the

  7. Hysteresis in the Central African Rainforest

    NASA Astrophysics Data System (ADS)

    Pietsch, Stephan Alexander; Elias Bednar, Johannes; Gautam, Sishir; Petritsch, Richard; Schier, Franziska; Stanzl, Patrick

    2014-05-01

    Past climate change caused severe disturbances of the Central African rainforest belt, with forest fragmentation and re-expansion due to drier and wetter climate conditions. Besides climate, human induced forest degradation affected biodiversity, structure and carbon storage of Congo basin rainforests. Information on climatically stable, mature rainforest, unaffected by human induced disturbances, provides means of assessing the impact of forest degradation and may serve as benchmarks of carbon carrying capacity over regions with similar site and climate conditions. BioGeoChemical (BGC) ecosystem models explicitly consider the impacts of site and climate conditions and may assess benchmark levels over regions devoid of undisturbed conditions. We will present a BGC-model validation for the Western Congolian Lowland Rainforest (WCLRF) using field data from a recently confirmed forest refuge, show model - data comparisons for disturbed und undisturbed forests under different site and climate conditions as well as for sites with repeated assessment of biodiversity and standing biomass during recovery from intensive exploitation. We will present climatic thresholds for WCLRF stability, analyse the relationship between resilience, standing C-stocks and change in climate and finally provide evidence of hysteresis.

  8. HYSTERESIS OF BACKFLOW IMPRINTED IN COLLIMATED JETS

    SciTech Connect

    Mizuta, Akira [Center for Frontier Science, Chiba University Yayoi-cho 1-33, Inage-ku, Chiba 263-8522 (Japan); Kino, Motoki [National Astronomical Observatory of Japan, Mitaka 181-8588 (Japan); Nagakura, Hiroki [Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku, Tokyo 169-8555 (Japan)

    2010-01-20

    We report two different types of backflow from jets by performing two-dimensional special relativistic hydrodynamical simulations. One is anti-parallel and quasi-straight to the main jet (quasi-straight backflow), and the other is a bent path of the backflow (bent backflow). We find that the former appears when the head advance speed is comparable to or higher than the local sound speed at the hotspot, while the latter appears when the head advance speed is slower than the sound speed at the hotspot. Bent backflow collides with the unshocked jet and laterally squeezes the jet. At the same time, a pair of new oblique shocks is formed at the tip of the jet and new bent fast backflows are generated via these oblique shocks. The hysteresis of backflow collisions is thus imprinted in the jet as a node and anti-node structure. This process also promotes broadening of the jet cross-sectional area and also causes a decrease in the head advance velocity. This hydrodynamic process may be tested by observations of compact young jets.

  9. Hysteresis of Backflow Imprinted in Collimated Jets

    E-print Network

    Mizuta, Akira; Nagakura, Hiroki

    2009-01-01

    We report two different types of backflow from jets by performing 2D special relativistic hydrodynamical simulations. One is anti-parallel and quasi-straight to the main jet (quasi-straight backflow), and the other is bent path of the backflow (bent backflow). We find that the former appears when the head advance speed is comparable to or higher than the local sound speed at the hotspot while the latter appears when the head advance speed is slower than the sound speed bat the hotspot. Bent backflow collides with the unshocked jet and laterally squeezes the jet. At the same time, a pair of new oblique shocks are formed at the tip of the jet and new bent fast backflows are generated via these oblique shocks. The hysteresis of backflow collisions is thus imprinted in the jet as a node and anti-node structure. This process also promotes broadening of the jet cross sectional area and it also causes a decrease in the head advance velocity. This hydrodynamic process may be tested by observations of compact young je...

  10. Evidence of magnetic anisotropy and spin-reorientation in the textured MnBi crystal

    NASA Astrophysics Data System (ADS)

    Liu, Yongsheng; Peng, Lin; Zhang, Jincang; Ren, Zhongming; Yang, Jingjing; Yang, Zhenglong; Cao, Shixun; Fang, Wenjian

    2011-10-01

    Magnetic anisotropy is investigated systematically for the textured MnBi crystal. The magnetic anisotropy exists in magnetization behaviors, hysteresis loops, and remnant magnetization. An abnormal coercivity field Hc is found in the textured MnBi: Hc perpendicular to the c-axis is larger than that parallel to the c-axis. The mechanism of anisotropy is discussed based on magnetocrystalline anisotropy in MnBi. The behavior of a.c. susceptibility has similar trends with frequency variation, not displaying a spin-disorder characteristic. The MnBi with ferromagnetic order has a higher loss under high frequencies than under low frequencies. Some spin-reorientation evidence in the MnBi is also obtained.

  11. Adhesion hysteresis and friction at nanometer and micrometer lengths

    SciTech Connect

    Szoszkiewicz, Robert; Bhushan, Bharat; Huey, Bryan D.; Kulik, Andrzej J.; Gremaud, Gerard [Georgia Institute of Technology, School of Physics, 837 State Street, Atlanta, Georgia 30332 (United States); Nanotribology Laboratory for Information Storage and MEMS/NEMS (NLIM), Ohio State University, Columbus, Ohio 43210 (United States); Institute of Material Science, University of Connecticut, Storrs, Connecticut 06269 (United States); Institute of Physics of Complex Matter, EPFL, CH-1015 Lausanne (Switzerland)

    2006-01-01

    Comparisons between adhesion hysteresis and friction at nanometer and micrometer length scales were investigated experimentally and theoretically. Nanoscale adhesion hysteresis was measured using the ultrasonic force microscopy (UFM) on mica, calcite, and a few metallic samples (Pt, Au, Cu, Zn, Ti, and Fe). Obtained adhesion hysteresis ranged between 4x10{sup -19} and 4x10{sup -18} J. At the microscale a similar setup with a nanoindenter was used and the same samples were investigated. Adhesion hysteresis measured at the microscale ranged between 8x10{sup -17} and 14x10{sup -17} J. Friction was investigated via lateral force microscopy, as well as by scratch tests done with the nanoindenter. Numerical simulations based on the UFM model as well as established theories of contact mechanics studied qualitative dependencies of adhesion hysteresis on experimental parameters. Quantitative relations between adhesion hysteresis and friction were obtained through an analytic model relying on elastic and adhesive properties of the contact. The model agreed with measurements and simulations.

  12. Hysteresis of Magnetite, Hematite and Pyrrhotite Crystals at High and Low Temperatures

    NASA Astrophysics Data System (ADS)

    Dunlop, D. J.

    2008-12-01

    Alternating gradient force magnetometers and sensitive vibrating-sample magnetometers operating above, at, and below room temperature have enabled rapid reliable measurements of hysteresis and remanence curves. The hysteresis parameters Ms, Mrs, Hc, plus the remanence coercivity Hcr, are routinely determined, at room temperature at least, and reported in the form of a Day plot as an indication of domain state and inferred grain size. Yet our knowledge of the hysteresis and remanence properties of individual crystals or sized crystal aggregates of magnetite, titanomagnetite, hematite, pyrrhotite and other important magnetic minerals has scarcely advanced beyond what was known at the end of the 1980's. Applications have indeed outstripped fundamental studies. This presentation will focus on new hysteresis measurements for well-sized magnetites of a variety of origins; magnetite inclusions in plagioclase, pyroxene, amphiboles and biotite; hematite; and pyrrhotite. Measurements were made at 20oC intervals from 25oC to the Curie point for all magnetites and hematites and at 10oC intervals for pyrrhotite. For one set of sized magnetites (0.6, 3, 6, 9, 14 and 110 micrometers), hysteresis and back-field remanence curves were also measured below room temperature (every 10 K from 10 K to 70 K, every 5 K from 80 K to 140 K, and every 10 K from 150 K to 300 K). These data give a wealth of information about the individual mineral crystals and trends linking crystals of common origin but different sizes. From Ms(T) we obtain precise Curie points and transition temperatures. Mrs(T)/Ms(T) tracks sometimes subtle changes in domain structure with changing temperature. Hc(T) gives an indication of the mechanism(s) of anisotropy, important for understanding TRM acquisition in crystals above single-domain size. Mrs(T) and Hc(T) often show substantial irreversible changes in the first heating- cooling cycle, particularly but not exclusively for synthetic crystals, stabilizing in subsequent cycles. Finally, Mrs(T)/Ms(T) vs. Hcr(T)/Hc(T) data trace curves on a Day plot showing unmistakable differences in domain structure between monoclinic and cubic magnetite, as well as more subtle changes away from the Verwey transition.

  13. PREFACE: International Workshop on Multi-Rate Processes and Hysteresis

    NASA Astrophysics Data System (ADS)

    Mortell, Michael P.; O'Malley, Robert E.; Pokrovskii, Alexei; Rachinskii, Dmitrii; Sobolev, Vladimir A.

    2008-07-01

    We are interested in singular perturbation problems and hysteresis as common strongly nonlinear phenomena that occur in many industrial, physical and economic systems. The wording `strongly nonlinear' means that linearization will not encapsulate the observed phenomena. Often these two types of phenomena are manifested for different stages of the same or similar processes. A number of fundamental hysteresis models can be considered as limit cases of time relaxation processes, or admit an approximation by a differential equation which is singular with respect to a particular parameter. However, the amount of interaction between practitioners of theories of systems with time relaxation and systems with hysteresis (and between the `relaxation' and `hysteresis' research communities) is still low, and cross-fertilization is small. In recent years Ireland has become a home for a series of prestigious International Workshops in Singular Perturbations and Hysteresis: International Workshop on Multi-rate Processes and Hysteresis (University College Cork, Ireland, 3-8 April 2006). Proceedings are published in Journal of Physics: Conference Series, volume 55. See further information at http://euclid.ucc.ie/murphys2008.htm International Workshop on Hysteresis and Multi-scale Asymptotics (University College Cork, Ireland, 17-21 March 2004). Proceedings are published in Journal of Physics: Conference Series, volume 22. See further information at http://euclid.ucc.ie/murphys2006.htm International Workshop on Relaxation Oscillations and Hysteresis (University College Cork, Ireland, 1-6 April 2002). The related collection of invited lectures, was published as a volume Singular Perturbations and Hysteresis, SIAM, Philadelphia, 2005. See further information at http://euclid.ucc.ie/hamsa2004.htm International Workshop on Geometrical Methods of Nonlinear Analysis and Semiconductor Laser Dynamics (University College Cork, Ireland, 5-5 April 2001). A collection of invited papers has been published as a special issue of Proceedings of the Russian Academy of Natural Sciences: Nonlinear dynamics of laser and reacting systems, and is available online at http://www.ins.ucc.ie/roh2002.htm. See further information at http://www.ins.ucc.ie/roh2002.htm Among the aims of these workshops were to bring together leading experts in singular perturbations and hysteresis phenomena in applied problems; to discuss important problems in areas such as reacting systems, semiconductor lasers, shock phenomena in economic modelling, fluid mechanics, etc with an emphasis on hysteresis and singular perturbations; to learn and to share modern techniques in areas of common interest. The `International Workshop on Multi-Rate Processes and Hysteresis' (University College Cork, Ireland, April 3-8, 2006) brought together more than 70 scientists (including more than 10 students), actively researching in the areas of dynamical systems with hysteresis and singular perturbations, to analyze those phenomena that occur in many industrial, physical and economic systems. The countries represented at the Workshop included Czech Republic, England, France, Germany, Hungary, Ireland, Israel, Italy, Poland, Romania, Russia, Scotland, South Africa, Switzerland and USA. All papers published in this volume of Journal of Physics: Conference Series have been peer reviewed through processes administered by the Editors. Reviews were conducted by expert referees to the professional and scientific standards expected of a proceedings journal published by IOP Publishing. The Workshop has been sponsored by Science Foundation Ireland (SFI), KE Consulting group, Drexel University, Philadelphia, USA, University College Cork (UCC), Boole Centre for Research in Informatics, UCC, Cork, School of Mathematical Sciences, UCC, Cork, Irish Mathematical Society, Tyndall National Institute, Cork, University of Limerick, Cork Institute of Technology, and Heineken. The supportive affiliation of the European Geophysics Society, International Association of Hydrological Sciences, and Laboratoire Poncelet is grateful

  14. Numerical simulations of electromagnetic behavior and AC loss in rectangular bulk superconductor with an elliptical flaw under AC magnetic fields

    NASA Astrophysics Data System (ADS)

    Xia, Jing; Zhou, Youhe

    2015-07-01

    This paper presents a finite element model based on the H-formulation to solve the electromagnetic behavior and AC loss in rectangular bulk superconductor with an elliptical flaw in AC external field condition. Both the interior flaw and the edge flaw are considered. A modified E-J power law which is valid for an arbitrary current density range is adopted in order to predict the strong local enhancement of the current density in the vicinity of the flaw tip. The results for the usual E-J power law are calculated for comparison as well. The simulation results show that the existence of the flaw significantly blocks the flow of the induced current and forces the current to redistribute around it. Meanwhile, the strong local enhancement of the current density is observed in the vicinity of the flaw tip. Furthermore, the influences of the size and position of the flaw on the local enhancement of the current density in the vicinity of the flaw tip are investigated. In addition, it is found that the influence of the flaw on the AC loss of the sample is slight for both cases of the interior flaw and the edge flaw.

  15. Stress-induced variation in magnetization and the dynamic magnetostrictive characteristic of soft magnetic materials

    Microsoft Academic Search

    P. Gonda

    1980-01-01

    The low-field magnetostrictive properties of amorphous ribbons are examined. From the measured hysteresis loops of as-prepared samples of Fe35Co32B20Si10Al3, (FeNi)80B17.5Al2Si0.5 the stress-induced variation of the magnetization is used for the calculation of the dynamic magnetostrictive characteristic Deltalambda(H) and lambda(H). The resulting hysteresis loops may be attributed to the curling magnetization mode.

  16. Influence of Biquadratic Interaction in the Nano-Scaled Fibonacci Magnetic Multilayers

    NASA Astrophysics Data System (ADS)

    Cai, H. L.; Jiang, S. S.; Sheng, W. T.; Yang, L.; Du, J.

    The magnetization of the magnetic multilayers with Fibonacci sequence was studied theoretically. By considering the Zeeman, magnetic anisotropy, bilinear and biquadratic exchange energies in the multiplayer system, the angles of the magnetization between all magnetic layers were calculated numerically by minimizing the magnetic energy. The magnetization curves and hysteresis loops were obtained. By considering the different strengths of biquadratic interaction between the magnetic layers some novel phenomena appears. The magnetization in magnetic sub-layers may rotates reversibly or irreversibly by magnetic field.

  17. Magnetism

    NSDL National Science Digital Library

    University Corporation for Atmospheric Research Windows to the Universe team

    2007-12-12

    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.

  18. Persistent hysteresis in graphene-mica van der Waals heterostructures

    NASA Astrophysics Data System (ADS)

    Mohrmann, Jens; Watanabe, Kenji; Taniguchi, Takashi; Danneau, Romain

    2015-01-01

    We report the study of electronic transport in graphene-mica van der Waals heterostructures. We have designed various graphene field-effect devices in which mica is utilized as a substrate and/or gate dielectric. When mica is used as a gate dielectric we observe a very strong positive gate voltage hysteresis of the resistance, which persists in samples that were prepared in a controlled atmosphere down to even millikelvin temperatures. In a double-gated mica-graphene-hBN van der Waals heterostructure, we found that while a strong hysteresis occurred when mica was used as a substrate/gate dielectric, the same graphene sheet on mica substrate no longer showed hysteresis when the charge carrier density was tuned through a second gate with the hBN dielectric. While this hysteretic behavior could be useful for memory devices, our findings confirm that the environment during sample preparation has to be controlled strictly.

  19. Sinusoidal input describing function for hysteresis followed by elementary backlash

    NASA Technical Reports Server (NTRS)

    Ringland, R. F.

    1976-01-01

    The author proposes a new sinusoidal input describing function which accounts for the serial combination of hysteresis followed by elementary backlash in a single nonlinear element. The output of the hysteresis element drives the elementary backlash element. Various analytical forms of the describing function are given, depending on the a/A ratio, where a is the half width of the hysteresis band or backlash gap, and A is the amplitude of the assumed input sinusoid, and on the value of the parameter representing the fraction of a attributed to the backlash characteristic. The negative inverse describing function is plotted on a gain-phase plot, and it is seen that a relatively small amount of backlash leads to domination of the backlash character in the describing function. The extent of the region of the gain-phase plane covered by the describing function is such as to guarantee some form of limit cycle behavior in most closed-loop systems.

  20. Persistent hysteresis in graphene-mica van der Waals heterostructures.

    PubMed

    Mohrmann, Jens; Watanabe, Kenji; Taniguchi, Takashi; Danneau, Romain

    2015-01-01

    We report the study of electronic transport in graphene-mica van der Waals heterostructures. We have designed various graphene field-effect devices in which mica is utilized as a substrate and/or gate dielectric. When mica is used as a gate dielectric we observe a very strong positive gate voltage hysteresis of the resistance, which persists in samples that were prepared in a controlled atmosphere down to even millikelvin temperatures. In a double-gated mica-graphene-hBN van der Waals heterostructure, we found that while a strong hysteresis occurred when mica was used as a substrate/gate dielectric, the same graphene sheet on mica substrate no longer showed hysteresis when the charge carrier density was tuned through a second gate with the hBN dielectric. While this hysteretic behavior could be useful for memory devices, our findings confirm that the environment during sample preparation has to be controlled strictly. PMID:25483818

  1. Observations of Hysteresis Among Indicators of Solar Activity

    NASA Astrophysics Data System (ADS)

    Bachmann, K. T.; Ranganath, A.

    1999-05-01

    We show that filtered time series of five indicators of solar activity exhibit significant solar-cycle-dependent differences in their relative variations. This study expands upon previous work by including data from recent NASA missions, indicating that the detected hysteresis patterns continue through the decline of solar cycle 22. Among the indicators that we study, we find that the hysteresis effects are approximately simple phase shifts that we present qualitatively via plots similar to Lissajous figures. These phase shifts correspond to time delays of less than three months behind the leading indicator, the International Sunspot Number, and are small compared to the typical eleven-year solar cycle. We believe that hysteresis represents a real delay in the onset and decline for changing solar emission at various wavelengths. Our research is funded by the Research Corporation and by the NASA Joint Venture (JOVE) program.

  2. Dynamic hysteresis in cyclic deformation of crystalline solids.

    PubMed

    Laurson, Lasse; Alava, Mikko J

    2012-10-12

    The hysteresis or internal friction in the deformation of crystalline solids stressed cyclically is studied from the viewpoint of collective dislocation dynamics. Stress-controlled simulations of a dislocation dynamics model at various loading frequencies and amplitudes are performed to study the stress-strain rate hysteresis. The hysteresis loop areas exhibit a maximum at a characteristic frequency and a power law frequency dependence in the low frequency limit, with the power law exponent exhibiting two regimes, corresponding to the jammed and the yielding or moving phases of the system, respectively. The first of these phases of the system exhibits nontrivial critical-like viscoelastic dynamics, crossing over to intermittent viscoplastic deformation for higher stress amplitudes. PMID:23102332

  3. Susceptibility losses in heating of magnetic core/shell nanoparticles for hyperthermia: a Monte Carlo study of shape and size effects.

    PubMed

    Vasilakaki, M; Binns, C; Trohidou, K N

    2015-04-24

    Optimizing the heating properties of magnetic nanoparticles is of great importance for hyperthermia applications. Recent experimental results show that core/shell nanoparticles could give an increased specific absorption rate (SAR) compared to the magnetic oxide nanoparticles currently used. We have developed a modified phenomenological model based on the linear Néel-Brown relaxation model to calculate the SAR due to susceptibility losses in complex nanoparticles with ferromagnetic (FM) core/ferrimagnetic (FiM) shell morphology. We use the Monte Carlo (MC) simulation technique with the implementation of the Metropolis algorithm to investigate the effect of size and shape on the magnetisation behaviour of complex ferromagnetic/ferrimagnetic nanoparticles covered by a surfactant layer. The findings of our simulations are used as an input in our modified model for the calculation of the SAR. Our calculations show that for all the sizes and shapes the complex FM/FiM nanoparticles give higher SAR values than the pure ferrimagnetic ones due to their higher core saturation magnetisation. For all sizes the nanoparticles with the truncated cuboctahedral shape give the highest SAR values and the cubic ones the lowest ones. The decrease in the surfactant thickness results in an increase of the SAR values. Our results have the same characteristics as the available experimental data from Fe/Fe3O4 nanoparticles, confirming that the complex nanoparticles with core/shell morphology can optimise the heating properties for hyperthermia. PMID:25836990

  4. Magnetic properties of submicron circular permalloy dots

    Microsoft Academic Search

    Gianluca Gubbiotti; Giovanni Carlotti; Fabrizio Nizzoli; Roberto Zivieri; Takuya Okuno; Teruya Shinjo

    2002-01-01

    Both the static and the dynamical magnetic properties of a square array of circular permalloy dots, characterized by a magnetic vortex configuration of the magnetization, have been investigated by means of magneto-optical Kerr effect and Brillouin light scattering (BLS) from thermally excited spin waves. The measured hysteresis loop can be satisfactorily reproduced by micromagnetic simulations, showing that the vortex configuration

  5. Iron Loss of Supermalloy Film Core

    Microsoft Academic Search

    Y. Sakaki; H. Okuno; M. Ishikawa; M. Naito

    1987-01-01

    The suitability of a supermalloy thin film about 1 ¿m thick for use in 1 MHz power equipment was studied. The relationship between the hysteresis loss Wh and the maximum flux density Bm for the approximately 1 ¿m thick films deposited on SiO2 substrate is approximately Wh ¿ Bm1.75. This shows the same tendency as that for the rolled plate,

  6. A survey on hysteresis modeling, identification and control

    NASA Astrophysics Data System (ADS)

    Hassani, Vahid; Tjahjowidodo, Tegoeh; Do, Thanh Nho

    2014-12-01

    The various mathematical models for hysteresis such as Preisach, Krasnosel'skii-Pokrovskii (KP), Prandtl-Ishlinskii (PI), Maxwell-Slip, Bouc-Wen and Duhem are surveyed in terms of their applications in modeling, control and identification of dynamical systems. In the first step, the classical formalisms of the models are presented to the reader, and more broadly, the utilization of the classical models is considered for development of more comprehensive models and appropriate controllers for corresponding systems. In addition, the authors attempt to encourage the reader to follow the existing mathematical models of hysteresis to resolve the open problems.

  7. Large-scale separation and hysteresis in cascades

    NASA Technical Reports Server (NTRS)

    Rothmayer, A. P.; Smith, F. T.

    1985-01-01

    An approach using a two-dimensional thin aerofoil, allied with the theory of viscous bluff-body separation, is used to study the initial cross-over from massive separation to an attached flow in a single-row unstaggered cascade. Analytic solutions are developed for the limit of small cascade-spacing. From the analytic solutions several interesting features of the cascade are examined, including multiple-solution branches and multiple regions of hysteresis. In addition, numerical results are presented for several selected aerofoils. Some of the aerofoils are found to contain markedly enlarged regions of hysteresis for certain critical cascade spacings.

  8. Domain Nucleation and Hysteresis Loop Shape in Piezoresponse Force Spectroscopy

    SciTech Connect

    Morozovska, A. N. [National Academy of Science of Ukraine, Kiev, Ukraine; Eliseev, E. A. [National Academy of Science of Ukraine, Kiev, Ukraine; Kalinin, Sergei V [ORNL

    2006-01-01

    Electromechanical hysteresis loop measurements in piezoresponse force microscopy (PFM) [piezoresponse force spectroscopy (PFS)] have emerged as a powerful technique for probing ferroelectric switching behavior on the nanoscale. Interpretation of PFS data requires the relationship between the domain parameters and PFM signal to be established. Here, the authors analyze the switching process using modified point charge model. The charge parameters are selected to reproduce tip-induced surface potential and tip radius of curvature. The relationship between geometric parameters of semiellipsoidal domain and PFM signal is derived using linear Green's function theory. The role of domain nucleation on hysteresis loop is established.

  9. Hysteresis of boiling for different tunnel-pore surfaces

    NASA Astrophysics Data System (ADS)

    Pastuszko, Robert; Piasecka, Magdalena

    2015-05-01

    Analysis of boiling hysteresis on structured surfaces covered with perforated foil is proposed. Hysteresis is an adverse phenomenon, preventing high heat flux systems from thermal stabilization, characterized by a boiling curve variation at an increase and decrease of heat flux density. Experimental data were discussed for three kinds of enhanced surfaces: tunnel structures (TS), narrow tunnel structures (NTS) and mini-fins covered with the copper wire net (NTS-L). The experiments were carried out with water, R-123 and FC-72 at atmospheric pressure. A detailed analysis of the measurement results identified several cases of type I, II and III for TS, NTS and NTS-L surfaces.

  10. Estimation of Low-Concentration Magnetic Fluid Density with Gmr Sensor

    NASA Astrophysics Data System (ADS)

    Yamada, S.; Gooneratne, C.; Chomsuwan, K.; Iwahara, M.; Kakikawa, M.

    2008-02-01

    This paper describes a new application of a spin-valve type giant magnetoresistance sensor in the biomedical field. The hyperthermia treatment, based on the hysteresis loss of magnetite under external ac fields, requires determination of the content density of magnetite injected inside the body to control the heat capacity. We propose a low-invasive methodology to estimate the density of magnetite by measuring magnetic fields inside the cavity. For this purpose, we investigated the relationship between the density of magnetite and the magnetic fields, and developed a needle-type magnetic probe with a giant magnetoresistance sensor for low-invasive measurement. The experimental results demonstrate the possibility of estimating the low-concentration density of magnetite injected into the body.

  11. Wetting hysteresis and droplet roll off behavior on superhydrophobic surfaces by Katherine Marie Smyth.

    E-print Network

    Smyth, Katherine Marie

    2010-01-01

    Various states of hydrophobic wetting and hysteresis are observed when water droplets are deposited on micro-post surfaces of different post densities. Hysteresis is commonly defined as the difference between the advancing ...

  12. A Preisach Model for Quantifying Hysteresis in an Atomic Force Microscope

    E-print Network

    A Preisach Model for Quantifying Hysteresis in an Atomic Force Microscope Ralph C. Smith # , Murti Atomic force microscopes employ stacked or cylindrical piezoceramic actuators to achieve sub. Keywords: Atomic force microscope, hysteresis, constitutive nonlinearities, Preisach model 1. Introduction

  13. A Preisach Model for Quantifying Hysteresis in an Atomic Force Microscope

    E-print Network

    A Preisach Model for Quantifying Hysteresis in an Atomic Force Microscope Ralph C. Smith , Murti Atomic force microscopes employ stacked or cylindrical piezoceramic actuators to achieve sub in various control designs. Keywords: Atomic force microscope, hysteresis, constitutive nonlinearities

  14. Background Simulation Experiment Conclusion Hysteresis in the Nonlinear Tunnelling of Light

    E-print Network

    Petta, Jason

    Background Simulation Experiment Conclusion Hysteresis in the Nonlinear Tunnelling of Light Through of Light Through a Barrier #12;Background Simulation Experiment Conclusion Outline 1 Background Nonlinear Optics Hysteresis 2 Simulation Method Results 3 Experiment Images Analysis 4 Conclusion Stefan M

  15. A compensation method for the hysteresis error of DVD VCM

    Microsoft Academic Search

    Chih-Liang Chu; Kuang-Chao Fan; Ye-Jing Chen

    2004-01-01

    The present study considers an autofocusing laser probe system used for the measurement of the surface profile and roughness of an object. The system is based upon a modified pickup head of a commercially available DVD player which uses a voice coil motor (VCM) to drive an objective lens during the autofocusing process. It is known that hysteresis of the

  16. Elastic guides reduce hysteresis effect in Belleville spring package

    NASA Technical Reports Server (NTRS)

    Mc Glashan, W. F., Jr.; Toth, L. R.

    1967-01-01

    Peripheral support guides that elastically flex with the slight breathing on radial displacement during actuation can greatly reduce the hysteresis present in a Belleville spring package. This technique provides a control device that enhances the precision of pressure regulating valves, pressure switches, and vacuum actuators.

  17. Periodic solutions of a forced system with hysteresis.

    NASA Technical Reports Server (NTRS)

    Drew, J. H.

    1972-01-01

    Hysteresis damping arising in an oscillatory system due to the phenomenon of slip damping analyzed by Goodman and Klumpp (1956) is considered. An idealized physical model is proposed, and the existence of certain periodic motions is investigated in a system with small forcing which are near the largest periodic motion in a corresponding unforced system. Periodic solutions of the forced system are obtained.-

  18. Cavitation level-acoustic intensity hysteresis: experimental and numerical characterization

    E-print Network

    Boyer, Edmond

    Cavitation level-acoustic intensity hysteresis: experimental and numerical characterization P such as sonoporation, inertial cavitation is commonly considered as the main candidate inducing membrane poration. Thus, characterizing inertial cavitation, as related to bubble size distribution and medium history, is of great

  19. Combining Pattern Instability and Shape-Memory Hysteresis for Phononic

    E-print Network

    Combining Pattern Instability and Shape-Memory Hysteresis for Phononic Switching Ji-Hyun Jang Received April 10, 2009 ABSTRACT We report a fully reversible and robust shape-memory effect in a two simulations correctly capture the three steps of the shape-memory cycle observed experimentally. Structures

  20. Causes and implications of colloid and microorganism retention hysteresis

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Experiments were designed to better understand the causes and implications of colloid and microorganism retention hysteresis with transients in solution ionic strength (IS). Saturated packed column experiments were conducted using two sizes of carboxyl modified latex (CML) microspheres (0.1 and 1.1...

  1. A Micromechanics-Based Hysteresis Model for Ferroelectric Ceramics

    Microsoft Academic Search

    J. Li; G. J. Weng

    2001-01-01

    Based on the mechanics of domain switch and irreversible thermodynamics, a micromechanics-based model that incorporates the effect of polarization strain and electric polarization in the switched domain is developed to predict the evolution of new domain and the associated hysteresis loops of a ferroelectric ceramic. The new domain concentration cr associated with the remanent polarization Pr, and the new domain

  2. The mechanism by which fish antifreeze proteins cause thermal hysteresis

    Microsoft Academic Search

    Erlend Kristiansen; Karl Erik Zachariassen

    2005-01-01

    Antifreeze proteins are characterised by their ability to prevent ice from growing upon cooling below the bulk melting point. This displacement of the freezing temperature of ice is limited and at a sufficiently low temperature a rapid ice growth takes place. The separation of the melting and freezing temperature is usually referred to as thermal hysteresis, and the temperature of

  3. Hysteresis and energy demand: the Announcement Effects and

    E-print Network

    Watson, Andrew

    -series regressions on quarterly and annual data 1973-2003 for UK energy demand by using sectors. The demands expect a price effect when the tax was actually imposed, reducing energy consumption, due to the negativeHysteresis and energy demand: the Announcement Effects and the effects of the UK Climate Change

  4. Instantaneous Feedback Controlled PWM Inverter with Adaptive Hysteresis

    Microsoft Academic Search

    Atsuo Kawamura; Richard Hoft

    1984-01-01

    A new control strategy for a PWM inverter controlled through adaptive hysteresis in an instantaneous feedback loop is theoretically analyzed and verified through simulations and a low-power experimental circuit. This control gives excellent performance under various load conditions, and it is especially effective in reducing load injected harmonics.

  5. Clockwise Hysteresis Loops in the Macroscopic Fundamental Diagram

    E-print Network

    California at Berkeley, University of

    Clockwise Hysteresis Loops in the Macroscopic Fundamental Diagram Vikash V. Gayah and Carlos F in the Macroscopic Fundamental Diagram WORKING PAPER Vikash V. Gayah and Carlos F. Daganzo UC Berkeley Center A recent study reported that the Macroscopic Fundamental Diagram of a medium size city exhibited

  6. Hysteresis, Import Penetration, and Exchange Rate Pass-Through

    Microsoft Academic Search

    Avinash K Dixit

    1989-01-01

    A competitive industry has established home firms and foreign firms with entry and exit costs. The real exchange rate follows a Brownian motion. Industry equilibrium is determined using methods of option pricing. Entry requires the operating profit to exceed the interest on the entry cost, and similarly for exit. The middle band of rates without entry or exit yields hysteresis;

  7. Relative Permeability Hysteresis: Laboratory Measurements and a Conceptual Model

    Microsoft Academic Search

    E. M. Braun; R. F. Holland

    1995-01-01

    Relative permeability hysteresis has been measured for a water-wet outcrop rock sample and a mixed-wet reservoir core. For the oil phase, imbibition and drainage relative permeability curves differed significantly. The difference was much less pronounced for the water phase. Scanning curves, which characterize transitions between imbibition and drainage curves, were also measured. A notable characteristic of the oil relative permeability

  8. Hysteresis Can Grant Fitness in Stochastically Varying Environment

    PubMed Central

    Friedman, Gary; McCarthy, Stephen; Rachinskii, Dmitrii

    2014-01-01

    Although the existence of multiple stable phenotypes of living organisms enables random switching between phenotypes as well as non-random history dependent switching called hysteresis, only random switching has been considered in prior experimental and theoretical models of adaptation to variable environments. This work considers the possibility that hysteresis may also evolve together with random phenotype switching to maximize population growth. In addition to allowing the possibility that switching rates between different phenotypes may depend not only on a continuous environmental input variable, but also on the phenotype itself, the present work considers an opportunity cost of the switching events. This opportunity cost arises as a result of a lag phase experimentally observed after phenotype switching and stochastic behavior of the environmental input. It is shown that stochastic environmental variation results in maximal asymptotic growth rate when organisms display hysteresis for sufficiently slowly varying environmental input. At the same time, sinusoidal input does not cause evolution of memory suggesting that the connection between the lag phase, stochastic environmental variation and evolution of hysteresis is a result of a stochastic resonance type phenomenon. PMID:25068284

  9. Tracking control of a piezoceramic actuator with hysteresis compensation using inverse Preisach model

    Microsoft Academic Search

    G. Song; Jinqiang Zhao; Xiaoqin Zhou; J. Alexis De Abreu-García

    2005-01-01

    This paper presents the classical Preisach hysteresis modeling and tracking control of a curved pre-stressed piezoceramic patch actuator system with severe hysteresis. The actuator is also flexible with very small inherent damping. It has potential applications in active antennas. A series of tests are conducted to study the hysteresis properties of the piezoceramic actuator system. The numerical expressions of the

  10. Continuum damage mechanics for hysteresis and fatigue of quasi-brittle materials and structures

    Microsoft Academic Search

    R. Desmorat; F. Ragueneau; H. Pham

    2007-01-01

    For a material exhibiting hysteresis such as quasi-brittle materials, it is natural to consider that hysteresis and fatigue are related to each other. One shows in the present work that damage, from the continuum damage mechanics point of view, may be seen as the link between both phenomena. One attempts, hence, to set up a unified modelling of hysteresis and

  11. In-plane Anisotropy Anomalies in Magnetic Films

    Microsoft Academic Search

    Elizabeth Smith; Roy Clarke; R. A. Lukaszew; Ratna Naik

    1997-01-01

    We present a new approach for modeling magnetic hysteresis curves of ultrathin magnetic films and multilayers. The model is based on a free -energy minimization approach in which spin reorientation kinetics are treated via coherent rotation with the additional provision that the magnetization can jump between local minima. This introduces the possibility of a novel latched state when the magnetization

  12. Dynamic Modeling of Soft Magnetic Film Actuated Scanners

    Microsoft Academic Search

    Serhan O. Isikman; Hakan Urey

    2009-01-01

    Dynamic behavior of magnetic thin film actuators is investigated in detail and applied to various laser scanning applications. Magnetic hysteresis effects are incorporated into the model developed in the prior work, which assumes linear magnetization as a function of magnetic field and is based on the distributed point-by-point calculation of the magnetostatic moments and forces across the film surface. A

  13. Hysteresis assisted narrowband resonances in a chain of nonlinear plasmonic arrays

    NASA Astrophysics Data System (ADS)

    Fedorov, Sergey V.; Rosanov, Nikolay N.; Chipouline, Arkadi V.; Pertsch, Thomas

    2015-05-01

    The plasmonic structures exhibiting narrowband resonances (NBR) are of a great interest for various applications. We propose to use hysteresis behavior in a 1D system of nonlinear nanoresonators in order to achieve the NRB; the nonlinearity is provided by saturation of a two-level quantum system coupled with the nanoresonators (nanolaser/spaser con?guration). Quantum Dots (QD) were assumed as quantum systems; their numerical parameters have been adopted for estimations. Role of the loss compensation on the quality of the NBR is shown for below (under compensation) and above threshold (generating spasers) operation modes. Amplitude and phase detection schemes of the prospective experimental realization are compared using the developed model. Possible sensor oriented applications of the proposed system are discussed.

  14. Dynamics of magnetic field penetration into soft ferromagnets

    NASA Astrophysics Data System (ADS)

    Ducharne, B.; Sebald, G.; Guyomar, D.; Litak, G.

    2015-06-01

    We propose an approach to solve the coupled problem of the magnetic field penetration into soft ferromagnets and a frequency dependent magnetic hysteresis. The magnetic field diffusion is related to the macroscopic eddy currents. The hysteresis model is related to the microscopic eddy currents derived from the magnetic domain wall movements, and is responsible for the frequency dependence of hysteresis loops. In this paper, based on a lumped model and fractional derivative operators, we demonstrate that it is possible to replace the coupled diffusion/dynamic hysteresis in a simplest formulation using fractional operators. Such a formulation can be solved easily. Instead of solving a 1D problem of diffusion, we show here that a lumped model with appropriate fractional time derivative operator can be an exact formulation of the problem. In addition, we confirm that the model is using experimental available information, obtained by standard single sheet tester measuring bench (the tangential surface excitation field, and the cross section average induction).

  15. Liver steatosis (LS) evaluated through chemical-shift magnetic resonance imaging liver enzymes in morbid obesity; effect of weight loss obtained with intragastric balloon gastric banding.

    PubMed

    Folini, Laura; Veronelli, Annamaria; Benetti, Alberto; Pozzato, Carlo; Cappelletti, Marco; Masci, Enzo; Micheletto, Giancarlo; Pontiroli, Antonio E

    2014-01-01

    The aim of this study was to evaluate in morbid obesity clinical and metabolic effects related to weight loss on liver steatosis (LS), measured through chemical-shift magnetic resonance imaging (MRI) and liver enzymes. Forty obese subjects (8 M/32 W; BMI 42.8 ± 7.12 kg/m(2), mean ± SD) were evaluated for LS through ultrasound (US-LS), chemical-shift MRI (MRI-LS), liver enzymes [aspartate aminotransferase (AST), alanine aminotransferase (ALT), ?-glutamyltransferase (GGT), alkaline phosphatase (ALP)], anthropometric parameters [weight, BMI, waist circumference (WC)], lipids, insulin, insulin resistance (HOMA-IR), glycated hemoglobin (HbA1c), oral glucose tolerance test, and body composition [fat mass (FM) and fat-free mass (FFM) at bio-impedance analysis (BIA)]. Anthropometric measures, MRI-LS, BIA, and biochemical parameters were reevaluated 6 months later in 18 subjects undergoing restrictive bariatric approach, i.e., intragastric balloon (BIB, n = 13) or gastric banding (LAGB, n = 5), and in 13 subjects receiving hypocaloric diet. At baseline, US-LS correlates only with MRI-LS, and the latter correlates with ALT, AST, and GGT. After 6 months, subjects undergoing BIB or LAGB had significant changes of BMI, weight, WC, ALT, AST, GGT, ALP, HbA1c, insulin, HOMA-IR, FM, FFM, and MRI-LS. Diet-treated obese subjects had no significant change of any parameter under study; change of BMI, fat mass, and fat-free mass was significantly greater in LAGB/BIB subjects than in diet-treated subjects. Change of MRI-LS showed a significant correlation with changes in weight, BMI, WC, GGT, ALP, and basal MRI-LS. Significant weight loss after BIB or LAGB is associated with decrease in chemical-shift MRI-LS and with reduction in liver enzymes; chemical-shift MRI and liver enzymes allow monitoring of LS in follow-up studies. PMID:24085682

  16. UK-4 flight spacecraft magnetic tests

    NASA Technical Reports Server (NTRS)

    Pruett, W. E.

    1972-01-01

    Magnetic tests conducted on the UK-4 spacecraft are discussed. The objectives of the test are: (1) to determine the permanent, induced, and stray magnetic moments of the spacecraft, (2) to assess its magnetic stability, (3) to determine the dipole moment produced by energizing the magnetorquer coil, (4) to measure the despin torque due to eddy current and magnetic hysteresis, and (5) to deperm, compensate, and make other adjustments necessary to achieve satisfactory magnetic characteristics for the spacecraft.

  17. Susceptibility losses in heating of magnetic core/shell nanoparticles for hyperthermia: a Monte Carlo study of shape and size effects

    NASA Astrophysics Data System (ADS)

    Vasilakaki, M.; Binns, C.; Trohidou, K. N.

    2015-04-01

    Optimizing the heating properties of magnetic nanoparticles is of great importance for hyperthermia applications. Recent experimental results show that core/shell nanoparticles could give an increased specific absorption rate (SAR) compared to the magnetic oxide nanoparticles currently used. We have developed a modified phenomenological model based on the linear Néel-Brown relaxation model to calculate the SAR due to susceptibility losses in complex nanoparticles with ferromagnetic (FM) core/ferrimagnetic (FiM) shell morphology. We use the Monte Carlo (MC) simulation technique with the implementation of the Metropolis algorithm to investigate the effect of size and shape on the magnetisation behaviour of complex ferromagnetic/ferrimagnetic nanoparticles covered by a surfactant layer. The findings of our simulations are used as an input in our modified model for the calculation of the SAR. Our calculations show that for all the sizes and shapes the complex FM/FiM nanoparticles give higher SAR values than the pure ferrimagnetic ones due to their higher core saturation magnetisation. For all sizes the nanoparticles with the truncated cuboctahedral shape give the highest SAR values and the cubic ones the lowest ones. The decrease in the surfactant thickness results in an increase of the SAR values. Our results have the same characteristics as the available experimental data from Fe/Fe3O4 nanoparticles, confirming that the complex nanoparticles with core/shell morphology can optimise the heating properties for hyperthermia.Optimizing the heating properties of magnetic nanoparticles is of great importance for hyperthermia applications. Recent experimental results show that core/shell nanoparticles could give an increased specific absorption rate (SAR) compared to the magnetic oxide nanoparticles currently used. We have developed a modified phenomenological model based on the linear Néel-Brown relaxation model to calculate the SAR due to susceptibility losses in complex nanoparticles with ferromagnetic (FM) core/ferrimagnetic (FiM) shell morphology. We use the Monte Carlo (MC) simulation technique with the implementation of the Metropolis algorithm to investigate the effect of size and shape on the magnetisation behaviour of complex ferromagnetic/ferrimagnetic nanoparticles covered by a surfactant layer. The findings of our simulations are used as an input in our modified model for the calculation of the SAR. Our calculations show that for all the sizes and shapes the complex FM/FiM nanoparticles give higher SAR values than the pure ferrimagnetic ones due to their higher core saturation magnetisation. For all sizes the nanoparticles with the truncated cuboctahedral shape give the highest SAR values and the cubic ones the lowest ones. The decrease in the surfactant thickness results in an increase of the SAR values. Our results have the same characteristics as the available experimental data from Fe/Fe3O4 nanoparticles, confirming that the complex nanoparticles with core/shell morphology can optimise the heating properties for hyperthermia. Electronic supplementary information (ESI) available: Calculations of the total volume and the volume of the core, interface, shell of FM/FiM and FiM nanoparticles as a function of the nanoparticle size, for the four shapes. Monte Carlo simulations of the magnetisation for FM/FiM and FiM nanoparticles of different sizes and shapes. Calculation of the effective volume anisotropy KV and volume magnetisation MV for FM/FiM and FiM nanoparticles. Calculations of the SAR for FM/FiM and FiM nanoparticles in the frequency range of 0-50 kHz. Calculations of the SAR dependence on surfactant thickness for FiM nanoparticles. See DOI: 10.1039/c4nr07576e

  18. Reflected Light Microscopy, SEM and Rock Magnetic Characterization of Magnetic Minerals Through an Intact Sequence of Oceanic Crust, IODP Hole 1256D

    Microsoft Academic Search

    S. Rodriguez Durand; E. Herrero-Bervera; D. Krasa; S. Haggerty; G. Acton

    2007-01-01

    The identification of magnetic minerals throughout a complete oceanic crustal section yields important information about the carriers of the marine magnetic anomalies, one of the longest continuous archives of the behavior of the geomagnetic field. A study involving the determination of the magnetic hysteresis parameters, Curie temperatures, IRM acquisition curves, magnetic susceptibility, and the microscopic identification of magnetic minerals of

  19. Hydrogenation effect on the hysteresis properties of rapidly quenched Nd–Ho–Fe–Co–B alloys

    Microsoft Academic Search

    I. Tereshina; N. Kudrevatykh; E. Tereshina; G. Burkhanov; O. Chistyakov; R. Grechishkin; A. Salamova; V. Verbetsky

    2011-01-01

    The hydrogenation effect on the hysteresis properties of rapidly quenched (RQ) (Nd0.55Ho0.45)2.7(Fe0.8Co0.2)14B1.2 compound obtained by melt-spinning is studied. A comparative study of RQ alloy and its hydride (Nd0.55Ho0.45)2.7(Fe0.8Co0.2)14B1.2H2.5 has shown that hydrogenation resulted in the increase of magnetization without significant effect on the Curie temperature. In contrast to hydrogen-free alloy having a maximum on the Hc(T) curve, the Hc of

  20. Enhanced magnetic refrigeration properties in Mn-rich Ni-Mn-Sn ribbons by optimal annealing

    PubMed Central

    Zhang, Yu; Zhang, Linlin; Zheng, Qiang; Zheng, Xinqi; Li, Ming; Du, Juan; Yan, Aru

    2015-01-01

    The influence of annealing time on temperature range of martensitic phase transition (?TA-M), thermal hysteresis (?Thys), magnetic hysteresis loss (?Mhys), magnetic entropy change (?SM) and relative refrigeration capacity (RC) of the Mn-rich Ni43Mn46Sn11 melt spun ribbons have been systematically studied. By optimal annealing, an extremely large ?SM of 43.2?J.kg?1K?1 and a maximum RC of 221.0?J.kg?1 could be obtained respectively in a field change of 5?T. Both ?TA-M and ?Thys decreases after annealing, while ?Mhys and ?SM first dramatically increase to a maximum then degenerates as increase of annealing time. A large effective cooling capacity (RCeff) of 115.4?J.kg?1 was achieved in 60?min annealed ribbons, which increased 75% compared with that unannealed ribbons. The evolution of magnetic properties and magnetocaloric effect has been discussed and proved by atomic ordering degree, microstructure and composition analysis. PMID:26055884