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1

Hysteresis losses in soft magnetic composite materials  

Microsoft Academic Search

Purpose – To analyze the Jiles and Atherton hysteresis model used for hysteresis losses estimation in soft magnetic composite (SMC) material. Design\\/methodology\\/approach – The Jiles and Atherton hysteresis model parameters are optimized with genetic algorithms (GAs) according to measured symmetric hysteresis loop of soft magnetic composite material. To overcome the uncertainty, finding the best-optimized parameters in a wide predefined searching

Bogomir Zidari?; Mykhaylo Zagirnyak; Konrad Lenasi; Damijan Miljavec

2006-01-01

2

The magnetization process: Hysteresis  

NASA Technical Reports Server (NTRS)

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

Balsamel, Richard

1990-01-01

3

A magnetic hysteresis model  

NASA Technical Reports Server (NTRS)

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

Flatley, Thomas W.; Henretty, Debra A.

1995-01-01

4

Hysteresis losses in MgB2 superconductors exposed to combinations of low AC and high DC magnetic fields and transport currents  

NASA Astrophysics Data System (ADS)

MgB2 superconductors are considered for generator field coils for direct drive wind turbine generators. In such coils, the losses generated by AC magnetic fields may generate excessive local heating and add to the thermal load, which must be removed by the cooling system. These losses must be evaluated in the design of the generator to ensure a sufficient overall efficiency. A major loss component is the hysteresis losses in the superconductor itself. In the high DC - low AC current and magnetic field region experimental results still lack for MgB2 conductors. In this article we reason towards a simplified theoretical treatment of the hysteresis losses based on available models in the literature with the aim of setting the basis for estimation of the allowable magnetic fields and current ripples in superconducting generator coils intended for large wind turbine direct drive generators. The resulting equations use the DC in-field critical current, the geometry of the superconductor and the magnitude of the AC magnetic field component as parameters. This simplified approach can be valuable in the design of MgB2 DC coils in the 1-4 T range with low AC magnetic field and current ripples.

Magnusson, N.; Abrahamsen, A. B.; Liu, D.; Runde, M.; Polinder, H.

2014-11-01

5

A constitutive model for the frequency dependence of magnetic hysteresis  

NASA Astrophysics Data System (ADS)

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.

Ho, Kwangsoo

2014-10-01

6

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

NASA Technical Reports Server (NTRS)

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

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

1990-01-01

7

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

NASA Technical Reports Server (NTRS)

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

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

1990-01-01

8

Numerical Analysis of Hysteresis and Eddy Current Losses in Solid Cylindrical Rods of No. 1010 Steel  

Microsoft Academic Search

A procedure is given which utilizes the digital computer to solve eddy current loss and hysteresis loss problems. The relationship between flux density and magnetic intensity is taken from the actual magnetization curve and major hysteresis loop, thus eliminating the approximations employed in most previous investigations. The nonlinear partial differential equations are replaced by finite difference equations and solved by

Marshall Abrams; Donald Gillott

1967-01-01

9

A thermodynamically consistent model for magnetic hysteresis  

NASA Astrophysics Data System (ADS)

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

Ho, Kwangsoo

2014-05-01

10

Power losses in thick steel laminations with hysteresis  

NASA Astrophysics Data System (ADS)

Magnetic power losses have been experimentally investigated and theoretically predicted over a range of frequencies (direct current—1.5 kHz) and peak inductions (0.5-1.5 T) in 1-mm-thick FeSi 2 wt. % laminations. The direct current hysteresis properties of the system are described by the Preisach model, with the Preisach distribution function reconstructed from the measurement of the recoil magnetization curve (Bp=1.7 T). On this basis, the time behavior of the magnetic induction vs frequency at different lamination depths is calculated by a finite element method numerical solution of Maxwell equations, which takes explicitly into account the Preisach model hysteretic B(H) relationship. The computed loop shapes are, in general, in good agreement with the measured ones. The power loss dependence on frequency is predicted and experimentally found to change from a ˜f3/2 to a ˜f2 law with increasing peak induction.

Appino, C.; Bertotti, G.; Bottauscio, O.; Fiorillo, F.; Tiberto, P.; Binesti, D.; Ducreux, J. P.; Chiampi, M.; Repetto, M.

1996-04-01

11

Specific absorption rate dependence on temperature in magnetic field hyperthermia measured by dynamic hysteresis losses (ac magnetometry)  

NASA Astrophysics Data System (ADS)

Magnetic nanoparticles (NPs) are intensively studied for their potential use for magnetic hyperthermia, a treatment that has passed a phase II clinical trial against severe brain cancer (glioblastoma) at the end of 2011. Their heating power, characterized by the ‘specific absorption rate (SAR)’, is often considered temperature independent in the literature, mainly because of the difficulties that arise from the measurement methodology. Using a dynamic magnetometer presented in a recent paper, we measure here the thermal dependence of SAR for superparamagnetic iron oxide (maghemite) NPs of four different size-ranges corresponding to mean diameters around 12 nm, 14 nm, 15 nm and 16 nm. The article reports a parametrical study extending from 10 to 60 {}^\\circ C in temperature, from 75 to 1031 kHz in frequency, and from 2 to 24 kA m?1 in magnetic field strength. It was observed that SAR values of smaller NPs decrease with temperature whereas for the larger sample (16 nm) SAR values increase with temperature. The measured variation of SAR with temperature is frequency dependent. This behaviour is fully explained within the scope of linear response theory based on Néel and Brown relaxation processes, using independent magnetic measurements of the specific magnetization and the magnetic anisotropy constant. A good quantitative agreement between experimental values and theoretical values is confirmed in a tri-dimensional space that uses as coordinates the field strength, the frequency and the temperature.

Garaio, Eneko; Sandre, Olivier; Collantes, Juan-Mari; Garcia, Jose Angel; Mornet, Stéphane; Plazaola, Fernando

2015-01-01

12

Dynamic Hysteresis in Compacted Magnetic Nanoparticles  

NASA Astrophysics Data System (ADS)

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

Chowdary, Krishna M.

13

Abstract --In electromagnetic applications, hysteresis phenomena in magnetic materials are responsible of  

E-print Network

13. M M Abstract -- In electromagnetic applications, hysteresis phenomena in magnetic materials, electrical engineering is concerned with energy efficiency. In addition, in the case of electromagnetic.. Following the predefined criteria such as induction response and losses computation, some compatible models

Boyer, Edmond

14

Hysteresis prediction inside magnetic shields and application  

NASA Astrophysics Data System (ADS)

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.

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

2014-07-01

15

Hysteresis prediction inside magnetic shields and application.  

PubMed

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

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

2014-07-01

16

Magnetic hysteresis in integrated low T sub c SQUID gradiometers  

SciTech Connect

We have measured the magnetic hysteresis of thin-film superconducting gradiometers. The fractional hysteresis error {ital h} was found to be about 10{sup {minus}9}--10{sup {minus}11} in several devices.

Koch, R.H.; Ketchen, M.B.; Gallagher, W.J.; Sandstrom, R.L.; Kleinsasser, A.W. (IBM Research Division, Yorktown Heights, New York 10598 (USA)); Gambrel, D.R.; Field, T.H. (IBM Federal Sector Division, Manassas, Virginia 22110 (USA)); Matz, H. (University Karlsruhe, D-7500 Karlsruhe 21, (Germany))

1991-04-22

17

Potbellies, wasp-waists, and superparamagnetism in magnetic hysteresis  

Microsoft Academic Search

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

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

1996-01-01

18

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

NASA Astrophysics Data System (ADS)

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

Fujisaki, Keisuke; Liu, Sungju

2014-05-01

19

A MHO-based magnetic hysteresis model for amorphous materials  

NASA Astrophysics Data System (ADS)

A magnetic hysteretic operator (MHO) is proposed in this paper. Based on the constructed MHO, the input space of neural networks is expanded from one-dimension to two-dimension using the expanded space method so that the one-to-multiple mapping of magnetic hysteresis is transformed into one-to-one mapping. Based on the expanded input space, a neural network is employed to identify magnetic hysteresis. The result of an experimental example suggests the proposed approach is effective.

Ma, Lianwei; Shen, Yu; Li, Jinrong; Zhao, Xinlong

2014-12-01

20

Magnetic hysteresis under compressive stress at high applied field  

Microsoft Academic Search

n Abstract-The magnetic properties of material are sensitive to applied stress. The aim of this paper is to designed and fabricated a hysteresis imaging apparatus for nondestructive evaluation of stress concentration in ferromagnetic material. It has been applied successfully to measure the hysteresis loops of Q235 steel under various fixed compressive stress. The remanence Br derived from the loops is

Dongyan Huang; Bing Han; Zonggang Wang; Tao Zhang

2011-01-01

21

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

E-print Network

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

Laughlin, David E.

22

Modeling biaxial stress effects on magnetic hysteresis in steel with the field and stress axes noncoaxial  

NASA Astrophysics Data System (ADS)

A model based on the domain wall pinning magnetomechanical hysteresis model of Sablik and Jiles [M. J. Sablik and D. C. Jiles, IEEE Trans. Magn. 29, 2113 (1993)] was formulated to compute changes in magnetic hysteresis under biaxial stress conditions with the magnetic field and stress axes noncoaxial. The model included the Villari effect and other asymmetric stress effects. The magnetic field was taken at various angles relative to the stress axis. The Barkhausen noise, hysteresis loss, and maximum flux density were computed for fields varying between ±1 kA/m. The results compared favorably to experimental data on several steels—Polish St3 steel, Polish St41 steel, and US commercial grade steel pipe.

Sablik, M. J.; Augustyniak, B.; Chmielewski, M.

1999-04-01

23

The significance of observed rotational magnetic hysteresis in lunar samples  

NASA Technical Reports Server (NTRS)

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

Wasilewski, P.

1974-01-01

24

The influence of magnetic hysteresis on magnetorheological fluid clutch operation  

Microsoft Academic Search

Purpose – The purpose of this paper is to elaborate upon the mathematical model of coupled electromagnetic, fluid dynamic and motion phenomena that will allow for investigation of the magnetic hysteresis influence on the axial symmetry magnetorheological fluid (MRF) clutch operation. Design\\/methodology\\/approach – To solve the partial differential equations describing magnetic vector and fluid velocity potential distributions in axial symmetry

Cezary J?dryczka; Piotr Sujka; Wojciech Szel?g

2009-01-01

25

Modeling of a Magnetorheological Actuator Including Magnetic Hysteresis  

Microsoft Academic Search

Magnetorheological (MR) actuators provide controlled torque through control of an applied magnetic field. Therefore knowledge of the relationship between the applied current and output torque is required. This paper presents a new nonlinear modeling of MR actuators considering magnetic hysteresis to determine the torque-current nonlinear relationship. Equations for transmitted torque are derived according to mechanical shear configurations of the MR

Jinung An; Dong-Soo Kwon

2003-01-01

26

Optimizing hysteretic power loss of magnetic ferrite nanoparticles  

E-print Network

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 ...

Chen, Ritchie

2013-01-01

27

Attachment/detachment hysteresis of fiber-based magnetic grabbers.  

PubMed

We developed an experimental protocol to analyze the behaviour of a model fiber-based magnetic grabber. A fiber is vertically suspended and fixed to the substrate by its upper end. A magnetic droplet is attached to the free end of the fiber and when a permanent magnet approaches the droplet, the fiber is forced to bow and finally jumps to the magnet. It appears that one can flex the micro-fibers by very small micro or even nano-Newton forces. Using this setup, we discovered a hysteresis of fiber attachment/detachment: the pathway of the fiber jumping to and off the magnet depends on the distance between the magnet and the clamped end. This phenomenon was successfully explained by the Euler-Benoulli model of an elastic beam. The observed hysteresis of fiber attachment/detachment was attributed to the multiple equilibrium configurations of the fiber tip placed in a dipole-type magnetic field. PMID:24668160

Gu, Yu; Kornev, Konstantin G

2014-04-28

28

A new ferromagnetic hysteresis model for soft magnetic composite materials  

NASA Astrophysics Data System (ADS)

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.

Zidari?, Bogomir; Miljavec, Damijan

2011-01-01

29

Core losses in claw pole permanent magnet machines with soft magnetic composite stators  

Microsoft Academic Search

This paper presents the core loss calculation in soft magnetic composite (SMC) samples and a claw pole permanent magnet machine with SMC stator. By using finite-element analysis of the magnetic field, the total core loss is computed by separating the hysteresis (alternating and rotational, both purely circular and elliptical), eddy current, and anomalous losses in each element when the rotor

Youguang Guo; Jian Guo Zhu; Jin Jiang Zhong; Wei Wu

2003-01-01

30

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

NASA Astrophysics Data System (ADS)

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

Kobayashi, Satoru; Ishibashi, Yusuke; Baba, Ryo

2013-03-01

31

An improved iron loss estimation for permanent magnet brushless machines  

Microsoft Academic Search

This paper presents an improved approach for predicting iron losses in permanent magnet brushless machines. The new approach is based on the fundamental concept that eddy current losses are proportional to the square of the time rate of change of flux density. Expressions are derived for predicting hysteresis and eddy current losses in the stator teeth and yoke. The so-called

Fang Deng

1999-01-01

32

Characterization of hysteresis in magnetic systems: A Preisach approach  

NASA Astrophysics Data System (ADS)

The phenomenon of hysteresis is perhaps the most widely recognized microscopic manifestation of magnetic ordering, and is the principal feature which is responsible for technologically-oriented applications of magnetic materials such as permanent magnets and recording media. Interest in a phenomenological model of hysteresis originally proposed by Preisach in 1935 has been renewed recently, particularly in engineering applications, such as the characterization of magnetic recording media and magnetostrictive materials. Thus, a rigorous assessment of the capabilities and limitations of the Preisach model for characterizing magnetic materials is of considerable importance from both fundamental and technological perspectives. The fundamental characteristics of hysteresis are discussed and a theoretical background for the processes involved in magnetic systems is established. A generalized version of the scalar Preisach model, which includes original contributions, is developed to extend the model's abilities to describe the effects of the structure of the initially demagnetized state, the presence and nature of interactions, the system's coercive field distribution, and especially, the effects of temperature and experimental wart time, on the observed hysteretic properties of a variety of magnetic systems including spin glasses, ferromagnets, ferrimagnets, and superparamagnets. The moment and remanence of magnetic systems are measured as a function of applied field and temperature, using both a vibrating sample magnetometer (VSM) and a SQUID-based magnetometer. A Preisach analysis of the data is used to characterize the irreversible response of six magnetic systems: CrO 2 audio tape; magnetoferritin; a Nd2Fe14B permanent magnet; a floppy disk medium; and longitudinal and perpendicular cobalt-chromium-based hard disk materials. The ambiguous nature of tools presently used to analyze the nature of magnetic systems, such as the application of Henkel plots to the analysis of interaction effects, is demonstrated and alternative Preisach-based analysis schemes are presented. The physical significance of parameters, which emerged from the Preisach calculations, is discussed in detail and modifications are proposed to model this array of real magnetic systems. These changes to the scalar Preisach model extend its capabilities, while maintaining the inherent simplicity of a scalar model. Limitations of the model are also discussed critically, and suggestions for future generalizations are made.

Mitchler, Patricia Darlene

33

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

SciTech Connect

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

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

1993-09-07

34

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

35

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

Microsoft Academic Search

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

Y. Zhai; L. Vu-Quoc

2007-01-01

36

Magnetic hysteresis of cerium doped bismuth ferrite thin films  

NASA Astrophysics Data System (ADS)

The influence of Cerium doping on the structural and magnetic properties of BiFeO3 thin films have been investigated. Rietveld refinement of X-ray diffraction data and successive de-convolution of Raman scattering spectra of Bi1-xCexFeO3 (BCFO) thin films with x=0-0.20 reflect the single phase rhombohedral (R3c) formation for x<0.08, whereas concentration-driven gradual structural phase transition from rhombohedral (R3c) to partial tetragonal (P4mm) phase follows for x?0.08. All low wavenumber Raman modes (<300 cm-1) showed a noticeable shift towards higher wavenumber with increase in doping concentration, except Raman E-1 mode (71 cm-1), shows a minor shift. Sudden evolution of Raman mode at 668 cm-1, manifested as A1-tetragonal mode, accompanied by the shift to higher wavenumber with increase in doping concentration (x) affirm partial structural phase transition. Anomalous wasp waist shaped (M-H) hysteresis curves with improved saturation magnetization (Ms) for BCFO thin films is attributed to antiferromagnetic interaction/hybridization between Ce 4f and Fe 3d electronic states. The contribution of both hard and soft phase to the total coercivity is calculated. Polycrystalline Bi0.88Ce0.12FeO3 thin film found to exhibit better magnetic properties with Ms=15.9 emu/g without any impure phase.

Gupta, Surbhi; Tomar, Monika; Gupta, Vinay

2015-03-01

37

High-frequency rotational losses in different soft magnetic composites  

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

38

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

NASA Technical Reports Server (NTRS)

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

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

1977-01-01

39

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

Microsoft Academic Search

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

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

2008-01-01

40

A. C. losses in the SSC high energy booster dipole magnets  

SciTech Connect

The baseline design for the SSC High Energy Booster (HEB) has dipole bending magnets with a 50 mm aperture. An analysis of the cryogenic heat load due to A.C. losses generated in the HEB ramp cycle are reported for this magnet. Included in this analysis are losses from superconductor hysteresis, yoke hysteresis, strand eddy currents, and cable eddy currents. The A.C. loss impact of 2.5 {mu}m vs. 6 {mu}m filament conductor is presented. A 60 mm aperture design is also investigated. 8 refs., 3 tabs.

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

1991-06-01

41

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

NASA Astrophysics Data System (ADS)

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

Zhang, Lefu; Takahashi, Seiki; Kamada, Yasuhiro; Kikuchi, Hiroaki; Mumtaz, Khalid; Ara, Katsuyuki; Sato, Masaya

2005-04-01

42

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

SciTech Connect

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

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

1988-11-15

43

Hysteresis loops and adiabatic Landau-Zener-Stückelberg transitions in the magnetic molecule {V6}.  

PubMed

We have observed hysteresis loops and abrupt magnetization steps in the magnetic molecule {V(6)}, where each molecule comprises a pair of identical spin triangles, in the temperature range 1-5 K for external magnetic fields B with sweep rates of several Tesla per millisecond executing a variety of closed cycles. The hysteresis loops are accurately reproduced using a generalization of the Bloch equation based on direct one-phonon transitions between the instantaneous Zeeman-split levels of the ground state (an S=1/2 doublet) of each spin triangle. The magnetization steps occur for B approximately 0, and they are explained in terms of adiabatic Landau-Zener-Stückelberg transitions between the lowest magnetic energy levels as modified by an intertriangle anisotropic exchange of order 0.4 K. PMID:15904102

Rousochatzakis, I; Ajiro, Y; Mitamura, H; Kögerler, P; Luban, M

2005-04-15

44

Hysteresis Loops and Adiabatic Landau-Zener-Stückelberg Transitions in the Magnetic Molecule {V6}  

NASA Astrophysics Data System (ADS)

We have observed hysteresis loops and abrupt magnetization steps in the magnetic molecule {V6}, where each molecule comprises a pair of identical spin triangles, in the temperature range 1 5 K for external magnetic fields B with sweep rates of several Tesla per millisecond executing a variety of closed cycles. The hysteresis loops are accurately reproduced using a generalization of the Bloch equation based on direct one-phonon transitions between the instantaneous Zeeman-split levels of the ground state (an S=1/2 doublet) of each spin triangle. The magnetization steps occur for B?0, and they are explained in terms of adiabatic Landau-Zener-Stückelberg transitions between the lowest magnetic energy levels as modified by an intertriangle anisotropic exchange of order 0.4 K.

Rousochatzakis, I.; Ajiro, Y.; Mitamura, H.; Kögerler, P.; Luban, M.

2005-04-01

45

Hysteresis of switching waves and dissipative solitons in nonlinear magnetic metamaterials  

NASA Astrophysics Data System (ADS)

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

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

2011-08-01

46

A Mechanism of Magnetic Hysteresis in Heterogeneous Alloys  

Microsoft Academic Search

The Becker-Kersten treatment of domain boundary movements is widely applicable in the interpretation of magnetization curves, but it does not account satisfactorily for the higher coercivities obtained, for example, in permanent magnet alloys. It is suggested that in many ferromagnetic materials there may occur 'particles' (this term including atomic segregates or 'islands' in alloys), distinct in magnetic character from the

E. C. Stoner; E. P. Wohlfarth

1948-01-01

47

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

NASA Technical Reports Server (NTRS)

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

Wasilewski, P. J.

1973-01-01

48

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

SciTech Connect

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

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

2008-10-14

49

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

NASA Astrophysics Data System (ADS)

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

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

2014-04-01

50

Magneto-optic waveguide hysteresis loops of ``planar'' magnetic garnet films  

NASA Astrophysics Data System (ADS)

Epitaxial films of modified yttrium iron garnet which are used as optical waveguides for magneto-optic devices have nominally planar anisotropy so that their magnetization can be aligned by small in-plane fields. Films grown on (111) substrates usually have some residual cubic anisotropy that is difficult to measure in the active layer of the double- or triple-layer films used in single-mode waveguides. A new method to determine the magnetic properties of the optically active layer itself has been developed. It is based on magneto-optical hysteresis loops in which the Faraday rotation of the waveguided light is plotted against one component of a rotating in-plane magnetic field. Steps in these hysteresis loops are directly related to the sixfold symmetry of the magnetocrystalline anisotropy of these films. The influence of linear birefringence on the measured Faraday rotation, the magnetostrictive effects associated with the pressure of the prism used for optical coupling into the waveguide, and the advantages of end-fire coupling are discussed. These hysteresis loops are being used in the design of materials for magneto-optic isolators and other waveguide devices.

McGlashan-Powell, M.; Wolfe, R.; Dillon, J. F., Jr.; Fratello, V. J.

1989-10-01

51

Evaluation of thermal ageing conditions in 17-4 PH stainless steel by Fourier descriptor analysis of magnetic hysteresis loops  

Microsoft Academic Search

Fourier descriptor analysis of magnetic hysteresis loops has been used to assess the conditions of isothermal and isochronal ageing in quench-aged precipitation hardening 17-4 PH stainless steel. The Fourier descriptors (i.e. sine harmonic coefficients in the Fourier series expansion of the magnetic flux density as a function of current arc length value of the ascending branch of hysteresis loop) have

N. I. Shakshin; G. I. Deordiev; V. E. Scherbinin; V. Moorthy; T. Jayakumar; D. K. Bhattacharya; P. Kalyanasundaram; Baldev Raj

1996-01-01

52

Simulations of magnetic hysteresis loops at high temperatures  

NASA Astrophysics Data System (ADS)

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.

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

2014-09-01

53

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

DOEpatents

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

Humphrey, Floyd B. (Bradfordwoods, PA)

1987-01-01

54

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

55

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

SciTech Connect

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

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

1992-01-01

56

Experimental measurement and calculation of losses in planar radial magnetic bearings  

NASA Technical Reports Server (NTRS)

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

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

1994-01-01

57

Influence of the magnetization damping on dynamic hysteresis loops in single domain particles  

NASA Astrophysics Data System (ADS)

This article reports on the influence of the magnetization damping on dynamic hysteresis loops in single-domain particles with uniaxial anisotropy. The approach is based on the Néel-Brown theory and the hierarchy of differential recurrence relations, which follow from averaging over the realizations of the stochastic Landau-Lifshitz equation. A new method of solution is proposed, where the resulting system of differential equations is solved directly using optimized algorithms to explore its sparsity. All parameters involved in uniaxial systems are treated in detail, with particular attention given to the frequency dependence. It is shown that in the ferromagnetic resonance region, novel phenomena are observed for even moderately low values of the damping. The hysteresis loops assume remarkably unusual shapes, which are also followed by a pronounced reduction of their heights. Also demonstrated is that these features remain for randomly oriented ensembles and, moreover, are approximately independent of temperature and particle size.

Landi, Gabriel T.

2012-02-01

58

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

NASA Astrophysics Data System (ADS)

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

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

2013-05-01

59

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

Microsoft Academic Search

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

F. Fiorillo; A. M. Rietto

1990-01-01

60

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

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

61

Hysteresis Simulation  

NSDL National Science Digital Library

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

Houle, Paul

62

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

PubMed Central

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

Wang, Shoubin; Gao, Wei

2013-01-01

63

Computation of self-field hysteresis losses in conductors with helicoidal structure using a 2D finite element method  

NASA Astrophysics Data System (ADS)

It is well known that twisting current-carrying conductors helps to reduce their coupling losses. However, the impact of twisting on self-field hysteresis losses has not been as extensively investigated as that on the reduction of coupling losses. This is mostly because the reduction of coupling losses has been an important issue to tackle in the past, and it is not possible to consider twisting within the classical two-dimensional (2D) approaches for the computation of self-field hysteresis losses. Recently, numerical codes considering the effect of twisting in continuous symmetries have appeared. For general three-dimensional (3D) simulations, one issue is that no robust, widely accepted and easy to obtain model for expressing the relationship between the current density and the electric field is available. On the other hand, we can consider that in these helicoidal structures currents flow only along the helicoidal trajectories. This approach allows one to use the scalar power-law for superconductor resistivity and makes the eddy current approach to a solution of a hysteresis loss problem feasible. In this paper we use the finite element method to solve the eddy current model in helicoidal structures in 2D domains utilizing the helicoidal symmetry. The developed tool uses the full 3D geometry but allows discretization which takes advantage of the helicoidal symmetry to reduce the computational domain to a 2D one. We utilize in this tool the non-linear power law for modelling the resistivity in the superconducting regions and study how the self-field losses are influenced by the twisting of a 10-filament wire. Additionally, in the case of high aspect ratio tapes, we compare the results computed with the new tool and a one-dimensional program based on the integral equation method and developed for simulating single layer power cables made of ReBCO coated conductors. Finally, we discuss modelling issues and present open questions related to helicoidal structures and AC-loss computations in three dimensions.

Stenvall, A.; Siahrang, M.; Grilli, F.; Sirois, F.

2013-04-01

64

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

NASA Technical Reports Server (NTRS)

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

Wasilewski, P.

1972-01-01

65

Electric field controlled magnetic hysteresis loops in a Metglas®/PMN-PT heterostructure  

NASA Astrophysics Data System (ADS)

An electric field tunable magnetic hysteresis loop was studied in a multiferroic heterostructure consisting of a 25 µm thick Metglas® ribbon affixed to a lead magnesium niobate-lead titanate (PMN-PT) crystal. This multiferroic heterostructure exhibits a considerably strong converse magnetoelectric effect, CME = -80%, where CME = [M(E) - M(0)]/M(0), and a converse magnetoelectric coupling constant, A = 23 Oe cm kV-1, in the vicinity of the saturation electric polarization. This work systematically demonstrates the tunability of magnetic parameters including magnetization, coercivity, remanence and squareness, under the application of an electric field of 0-8 kV cm-1. Additionally, the physical mechanism of the CME is discussed. These results provide useful resources for the design of a new generation of electrically controlled devices.

Chen, Yajie; Fitchorov, Trifon; Cai, Zhuhua; Ziemer, K. S.; Vittoria, Carmine; Harris, V. G.

2010-04-01

66

New soft magnetic amorphous cobalt based alloys with high hysteresis loop linearity  

NASA Astrophysics Data System (ADS)

The new amorphous Co56÷59(Fe,Ni,Mn)21÷24(Si0.2B0.8)20-based metal alloys (AMA) with high saturation induction (BS>=1T) were developed. Toroidal tape wound magnetic cores made from these AMA after heat-magnetic treatment (HMT) in a reversal field are characterized by high hysteresis loop linearity, minimum effective magnetic permeability and its high field stability in combination with low coercivity Hc (1-3 A/m, 1 kHz). For the most prospecting alloy compositions the value of effective magnetic permeability decreases compared to known alloys up to 550 - 670 units and remains constant in the wide magnetic field range 1100 - 1300 A/m. Maximum remagnetization loop linearity is achieved after optimum HMT in high Ni containing AMAs, which are characterized by the record low squareness ratio values Ks=0.002-0.02 and Hc=1.0 A/m. Magnetic cores made from the new amorphous alloys can be used both in filter chokes of switch-mode power supply units and in matching mini-transformers of telecommunication systems; at that, high efficiency and accuracy of signal transmission including high frequency pulses are ensured under conditions of long-term influence of dc magnetic bias.

Nosenko, V. K.; Maslov, V. V.; Kochkubey, A. P.; Kirilchuk, V. V.

2008-02-01

67

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

NASA Astrophysics Data System (ADS)

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.

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

2015-02-01

68

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

PubMed

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

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

2014-01-24

69

Local hysteresis loops measurements on irradiated FeSiB patterned dots by magnetic force microscopy  

NASA Astrophysics Data System (ADS)

Magnetic Force Microscopy (MFM) has been exploited to develop a technique capable of investigating the field-dependent magnetisation reversal processes in patterned systems, allowing the full reconstruction of a local hysteresis loop. Fe-Si-B dots with a lateral size of 6 ?m and a thickness of 250 nm have been prepared by sputtering and optical lithography. In the as-prepared state, the dots are characterised by a dense stripe domain configuration, clearly visible at the MFM. Subsequently, the dots have been thinned by means of exposition to a focussed ion beam, consisting of Ga+ ions having an energy of 30 keV. The local hysteresis loops have been measured by means of the MFM-derived technique. The progressive thinning of the dots results in the disappearance of the perpendicular anisotropy responsible for the dense stripe domain configuration, with the dominance of the shape anisotropy for thickness values below ?70 nm. The results are consistent with the spin reorientation transition effect studied on similar systems in the form of continuous thin films.

Coïsson, M.; Barrera, G.; Celegato, F.; Enrico, E.; Olivetti, E. S.; Tiberto, P.; Vinai, F.

2015-01-01

70

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

Microsoft Academic Search

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

R. Ludwig; P. Bretchko; S. Makarov

2002-01-01

71

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

NASA Astrophysics Data System (ADS)

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.

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

2013-12-01

72

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

SciTech Connect

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.

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

73

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

NASA Technical Reports Server (NTRS)

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

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

1992-01-01

74

Eddy current losses in passive magnetic bearings  

NASA Astrophysics Data System (ADS)

Passive magnetic bearings built with permanent magnets, such as NdFeB (neodynium-iron-boron) or SmCo (samarium-cobalt), are very reliable systems when used for industrial applications such as centrifuges or flywheels, as they do not require any electromagnetic coil supply. Nevertheless, during the rotational motion, gyroscopic effects (like precession) or inhomogeneous magnetization can lead to power losses created by eddy currents flowing over the magnetic materials. This article provides a theoretical description and quantification of these phenomena by means of Ampere's laws. For this purpose, the magnets are assumed to be ring-shaped and axially magnetized. Virtual surface and volume current densities are applied to the calculation of the time-dependent electric field, and consequently to the power loss. Numerical applications are presented for a typical bearing configuration.

Bouty, Olivier

2002-12-01

75

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

NASA Astrophysics Data System (ADS)

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

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

2009-04-01

76

An air-cooled Litz wire coil for measuring the high frequency hysteresis loops of magnetic samples--a useful setup for magnetic hyperthermia applications.  

PubMed

A setup for measuring the high-frequency hysteresis loops of magnetic samples is described. An alternating magnetic field in the range 6-100 kHz with amplitude up to 80 mT is produced by a Litz wire coil. The latter is air-cooled using a forced-air approach so no water flow is required to run the setup. High-frequency hysteresis loops are measured using a system of pick-up coils and numerical integration of signals. Reproducible measurements are obtained in the frequency range of 6-56 kHz. Measurement examples on ferrite cylinders and on iron oxide nanoparticle ferrofluids are shown. Comparison with other measurement methods of the hysteresis loop area (complex susceptibility, quasi-static hysteresis loops, and calorific measurements) is provided and shows the coherency of the results obtained with this setup. This setup is well adapted to the magnetic characterization of colloidal solutions of magnetic nanoparticles for magnetic hyperthermia applications. PMID:25273736

Connord, V; Mehdaoui, B; Tan, R P; Carrey, J; Respaud, M

2014-09-01

77

MODELING OF EDDY CURRENT LOSS AND TEMPERATURE OF THE MAGNETS  

E-print Network

MODELING OF EDDY CURRENT LOSS AND TEMPERATURE OF THE MAGNETS IN PERMANENT MAGNET MACHINES@umich.edu Received 24 November 2010 Accepted 16 June 2011 The eddy current loss in the magnets of permanent magnet- mium-iron-boron (NdFeB), and slot/tooth harmonics, there is eddy current loss generated inside

Mi, Chunting "Chris"

78

A neural network for incorporating the thermal effect on the magnetic hysteresis of the 3F3 material using the Jiles-Atherton model  

NASA Astrophysics Data System (ADS)

The present paper deals with the temperature dependent modeling approach for the generation of hysteresis loops of ferromagnetic materials. The physical model is developed to study the effect of temperature on the magnetic hysteresis loop using the Jiles-Atherton (J-A) model. The thermal effects were incorporated through temperature dependent hysteresis parameters of JA model. The temperature-dependent J-A model was validated by measurements made on the ferrite material. The results of proposed model were in good agreement with the measurements.

Nouicer, A.; Nouicer, E.; Feliachi, Mouloud

2015-01-01

79

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

NASA Astrophysics Data System (ADS)

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

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

2013-06-01

80

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

NASA Astrophysics Data System (ADS)

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

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

2011-06-01

81

Mass Losses of Magnetized Rheological Mediums Subjected to Magnetic Field  

NASA Astrophysics Data System (ADS)

Theoretical analysis and experimental research of the film flowing of magnetorheologic fluids when infinitive solid plate is retrieving from the former mediums were carried out. We have got dependencies of fluids mass losses m vs: velocity of moving plate V; magnitude of magnetic intensity, its gradient and angle ? between direction of intensity lines and normal vector to plane of plate. It is shown that theoretical and experimental m(?) is anisotropy one and may change its magnitude more than 10 times. Real behavior and extreme characteristics of m(?) depends on rhelogiacal parameters of MRS and its magnetization. Obtained experimental data of dependence m(V) are in qualitative and quantitative agreement with the modernized theory.

Baev, A. R.; Matoussevitch, N. P.

82

Assessment of Retained Austenite in AISI D2 Tool Steel Using Magnetic Hysteresis and Barkhausen Noise Parameters  

NASA Astrophysics Data System (ADS)

Inaccurate heat treatment process could result in excessive amount of retained austenite, which degrades the mechanical properties, like strength, wear resistance, and hardness of cold work tool steel parts. Thus, to control the mechanical properties, quantitative measurement of the retained austenite is a critical step in optimizing the heat-treating parameters. X-ray diffraction method is the most frequently used technique for this purpose. This technique is, however, destructive and time consuming. Furthermore, it is not applicable to 100% quality inspection of industrial parts. In the present paper, the influence of austenitizing temperature on the retained austenite content and hardness of AISI D2 tool steel has been studied. Additionally, nondestructive magnetic hysteresis parameters of the samples including coercivity, magnetic saturation, and maximum differential permeability as well as their magnetic Barkhausen noise features (RMS peak voltage and peak position) have been investigated. The results revealed direct relations between magnetic saturation, differential permeability, and MBN peak amplitude with increasing austenitizing temperature due to the retained austenite formation. Besides, both parameters of coercivity and peak position had an inverse correlation with the retained austenite fraction.

Kahrobaee, Saeed; Kashefi, Mehrdad

2015-01-01

83

STP Hysteresis Program  

NSDL National Science Digital Library

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

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

2009-03-13

84

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)

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.

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

2014-10-01

85

Rotor eddy-current loss in permanent magnet brushless machines  

Microsoft Academic Search

This paper presents an analysis of the rotor eddy-current loss in modular and conventional topologies of permanent magnet brushless machine. The loss is evaluated both analytically and by time-stepped finite-element analysis, and it is shown that it can be significant in both machine topologies. It is also shown that the loss can be reduced significantly by segmenting the magnets.

Hiroaki Toda; Zhenping Xia; Jiabin Wang; Kais Atallah; David Howe

2004-01-01

86

Effect of niobium addition on the martensitic transformation and magnetocaloric effect in low hysteresis NiCoMnSn magnetic shape memory alloys  

NASA Astrophysics Data System (ADS)

The effect of Nb substitution for Ni in Ni45Co5Mn40Sn10 magnetic shape memory alloys on their magnetic properties, martensitic transformation characteristics, transformation hysteresis, and magnetocaloric properties was studied using wavelength-dispersive X-ray spectroscopy, differential scanning calorimetry, and the temperature and field dependence of the magnetization. Ni45Co5Mn40Sn10 alloy has a very low transformation hysteresis; however, the martensitic transformation temperatures are notably above room temperature, which is not desirable for magnetic refrigeration applications. In this study, small quantities of Nb substitution were shown to drastically shift the transformation temperatures to lower temperatures, at a rate of 68 K/at. % Nb, which is needed for household refrigeration. The austenite Curie temperature also decreased with increasing Nb content. However, a decrease in the latent heat of the martensitic transition was observed, which negatively affects the magnetic field-induced adiabatic temperature change capability. Still, the relatively large transformation entropy and the low transformation hysteresis make the Nb-doped Ni45Co5Mn40Sn10 alloys potential candidates for solid state refrigeration near room temperature.

Emre, Baris; Bruno, Nickolaus M.; Yuce Emre, Suheyla; Karaman, Ibrahim

2014-12-01

87

Eddy current losses in permanent magnets of the BLDC machine  

Microsoft Academic Search

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

Damijan Miljavec; Bogomir Zidari?

2007-01-01

88

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

SciTech Connect

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

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

1993-01-31

89

Energy losses in a thin-wall tube multifilament composite superconductor carrying a transport current in a time-varying transverse magnetic field  

NASA Astrophysics Data System (ADS)

An approach and formulae are given to calculate the hysteresis, coupling, eddy-current and Ohmic losses in a thin-wall tube multifilament composite superconductor carrying a transport current under low excitation by a homogeneous transverse time-varying magnetic field, taking into account possible filament saturation and current sharing effects. The technique can be applied to a single layer superconducting cable twisted around a thin-wall normal conducting tube.

Egorov, S.; Astrov, M.; Fedotova, S.

1998-12-01

90

Energy losses in a thin-wall tube multifilament composite superconductor carrying a transport current in a time-varying transverse magnetic field  

Microsoft Academic Search

An approach and formulae are given to calculate the hysteresis, coupling, eddy-current and Ohmic losses in a thin-wall tube multifilament composite superconductor carrying a transport current under low excitation by a homogeneous transverse time-varying magnetic field, taking into account possible filament saturation and current sharing effects. The technique can be applied to a single layer superconducting cable twisted around a

S. Egorov; M. Astrov; S. Fedotova

1998-01-01

91

Superconducting pulsed magnets  

Microsoft Academic Search

Lecture 1. Introduction to Superconducting Materials Type 1,2 and high temperature superconductors; their critical temperature, field & current density. Persistent screening currents and the critical state model. Lecture 2. Magnetization and AC Loss How screening currents cause irreversible magnetization and hysteresis loops. Field errors caused by screening currents. Flux jumping. The general formulation of ac loss in terms of magnetization.

Martin N Wilson

2006-01-01

92

Magnetic losses of the soft magnetic composites consisting of iron and Ni–Zn ferrite  

Microsoft Academic Search

Ferromagnetic powders which are surrounded by an electrically insulating film (soft magnetic composites (SMCs)) exhibit unique magnetic properties, such as relatively low magnetic losses and 3D isotropic magnetic behavior. In some electromagnetic applications, including microwave frequency range applications, it is necessary to increase electrical resistivity without any noticeable reduction in magnetic properties. To achieve this purpose, electrically resistant materials, for

Kh. Gheisari; S. Javadpour; H. Shokrollahi; B. Hashemi

2008-01-01

93

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

SciTech Connect

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

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

2007-12-15

94

Cell-dynamical simulation of magnetic hysteresis in the two-dimensional Ising system  

NASA Astrophysics Data System (ADS)

We present results from numerical simulations using a ``cell-dynamical system'' to obtain solutions to the time-dependent Ginzburg-Landau equation for a scalar, two-dimensional (2D), (?2)2 model in the presence of a sinusoidal external magnetic field. Our results confirm a recent scaling law proposed by Rao, Krishnamurthy, and Pandit [Phys. Rev. B 42, 856 (1990)], and are also in excellent agreement with recent Monte Carlo simulations of hysteretic behavior of 2D Ising spins by Lo and Pelcovits [Phys. Rev. A 42, 7471 (1990)].

Sengupta, Surajit; Marathe, Yatin; Puri, S.

1992-04-01

95

Zero loss magnetic metamaterials using powered active unit cells  

E-print Network

Zero loss magnetic metamaterials using powered active unit cells Yu Yuan, Bogdan-Ioan Popa, Steven A. Cummer Center for Metamaterials and Integrated Plasmonics and Department of Electrical@ee.duke.edu Abstract: We report the design and experimental measurement of a powered active magnetic metamaterial

Cummer, Steven A.

96

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

SciTech Connect

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

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

1992-01-01

97

Passive magnetic bearing element with minimal power losses  

DOEpatents

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

Post, Richard F. (Walnut Creek, CA)

1998-01-01

98

Passive magnetic bearing element with minimal power losses  

DOEpatents

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

Post, R.F.

1998-12-08

99

Effects of striations on magnetization loss of transposed coated conductors  

NASA Astrophysics Data System (ADS)

Even though a coated conductor is more superior in some performances than a BSCCO PIT wire, its AC loss is still high. One of the solutions to decrease the AC loss of the coated conductor is to make striations on it and to twist it. But we cannot use the twisted single coated conductor for a winding of an AC machine. Instead of the twist, the transposed coated conductors which have striations on themselves can be used. To estimate the effect of magnetization loss reduction, several short samples having or not having striations and transposition are prepared. Each sample is tested in perpendicular external magnetic fields. Test results of several samples with a striation and transposition give the possibility on lower magnetization loss.

Lee, J. K.; Park, M. J.; Lee, S. W.; Kim, W. S.; Park, C.; Lee, H.; Park, S. H.; Hwang, Y. I.; Byun, S. B.; Choi, K.

2008-09-01

100

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

SciTech Connect

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

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

1992-05-01

101

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

SciTech Connect

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

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

1992-01-01

102

Collisional trap losses of cold, magnetically-trapped Br atoms  

E-print Network

Near-threshold photodissociation of Br$_2$ 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 $\\langle\

Lam, J; Softley, T P

2014-01-01

103

AC Loss Analysis on the Superconducting Coupling Magnet in MICE  

SciTech Connect

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

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

2008-07-08

104

Classical and hyperbolic approximation of hysteresis loops  

NASA Astrophysics Data System (ADS)

Analytical approximation of symmetrical and unsymmetrical hysteresis loops is based on the general description of magnetization consisting of the slow reversible process and more violent irreversible process. The coercivity term in the irreversible component generates symmetrical hysteresis loops, which are used for the approximation of first-order reversal curves and their distribution. Model has been applied to materials with typical S-shaped and rectangular hysteresis loops.

W?odarski, Zdzis?aw

2007-02-01

105

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

NASA Technical Reports Server (NTRS)

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

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

1971-01-01

106

Rotor loss in permanent magnet brushless AC machines  

Microsoft Academic Search

The eddy current loss in the permanent magnets of brushless AC machines is usually neglected, since the fundamental airgap field rotates in synchronism with the rotor and time harmonics in the current waveform and space harmonics in the winding distribution are generally small. However, machine designs are emerging for which the fundamental component of the stator MMF has fewer poles

K. Atallah; D. Howe; P. H. Mellor; D. A. Stone

1999-01-01

107

Rotor loss in permanent-magnet brushless AC machines  

Microsoft Academic Search

The eddy-current loss in the permanent magnets of brushless AC machines is usually neglected, since the fundamental air-gap field usually rotates in synchronism with the rotor, and time harmonics in the current waveform and space harmonics in the winding distribution are generally small. However, an important category of brushless AC machine design is emerging in which the fundamental component of

Kais Atallah; David Howe; Philip H. Mellor; David A. Stone

2000-01-01

108

Analytical Model of Magnet Eddy-Current Volume Losses in Multi-phase PM Machines  

E-print Network

Analytical Model of Magnet Eddy-Current Volume Losses in Multi-phase PM Machines with Concentrated, 94000 Créteil France Abstract--this paper studies magnet eddy-current losses in permanent magnet (PM calculations. Keywords--Traction, Concentrated Winding, Eddy- Current, Volume Magnet Losses, Multiphase Machine

Paris-Sud XI, Université de

109

Spin Flip Loss in Magnetic Storage of Ultracold Neutrons  

NASA Astrophysics Data System (ADS)

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

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

2014-03-01

110

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

E-print Network

.1063/1.3675177 #12;2 Abstract1 This article reports new results about the magnetic loss in Soft Magnetic Composites1 Extended frequency analysis of the loss under rotating induction excitation in Soft Magnetic in such machines, an isotropic soft magnetic material is15 needed. Contrary to laminated materials, Soft Magnetic

Paris-Sud XI, Université de

111

Classical eddy current losses in soft magnetic composites  

NASA Astrophysics Data System (ADS)

This paper deals with the problem of loss evaluation in Soft Magnetic Composites (SMCs), focusing on the classical loss component. It is known that eddy currents can flow in these granular materials at two different scales, that of the single particle (microscopic eddy currents) and that of the specimen cross-section (macroscopic eddy currents), the latter ensuing from imperfect insulation between particles. It is often argued that this macroscopic loss component can be calculated considering an equivalent homogeneous material of same bulk resistivity. This assumption has not found so far clear and general experimental validation. In this paper, we discuss energy loss experiments in two different SMC materials, obtained using different binder types, and we verify that a classical macroscopic loss component, the sole size-dependent term, can be separately identified. It is also put in evidence that, depending on the material, the measured sample resistivity and the equivalent resistivity entering the calculation of the macroscopic eddy currents may not be the same. A corrective coefficient is, therefore, introduced and experimentally identified. This coefficient appears to depend on the material type only. An efficient way to calculate the macroscopic classical loss in these materials is thus provided.

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

2013-05-01

112

Early pregnancy loss and exposure to 50-Hz magnetic fields  

SciTech Connect

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.

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

1993-01-01

113

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

Microsoft Academic Search

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

Fang Deng

1997-01-01

114

Collisional trap losses of cold magnetically trapped Br atoms  

NASA Astrophysics Data System (ADS)

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.

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

2014-12-01

115

Measurement of Microwave Magnetic Hysteresis of Thin Film HTSC and Comparison with a Modified Critical State Model  

NASA Astrophysics Data System (ADS)

The hysteretic flux density B(H) of thin film HTSC resonators is measured through measurements of microwave surface impedance Z_s(H,T). A modified critical state model is examined to explain the data. The model generalizes Bean's original proposition by (i)including the demagnetization effects of perpendicular geometry which is commonly employed in experiments, (ii) including more than one critical currents as would be expected to exist in thin films and polycrystals, and (iii) generalizing the hysteresis law that is generally ascribed to this case. All this is done while still retaining the fundamental notions of a critical state. Our model shows good agreement with characteristic features of the data. Experimentally observed novel effects when the microwave and the DC fields are of comparable magnitude are also described. Implications of our experiment towards harmonic generation and intermods will also be presented.

Choudhury, Durga P.; Willemsen, Balam A.; Derov, John S.; Sridhar, S.

1997-03-01

116

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

SciTech Connect

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

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

1992-09-01

117

Construction of hysteresis loops of single domain elements and coupled permalloy ring arrays by magnetic force microscopy  

E-print Network

by magnetic force microscopy Xiaobin Zhua) and P. Gru¨tter Department of Physics, Center for the Physics particle array were studied by magnetic force microscopy MFM . For single domain permalloy particles: 10.1063/1.1540129 I. INTRODUCTION Magnetic force microscopy MFM is a powerful tool for studying

Grütter, Peter

118

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

NASA Astrophysics Data System (ADS)

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

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

2013-11-01

119

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

Microsoft Academic Search

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

Marc de Wulf; Ljubomir Anestiev; Luc Dupré; Ludo Froyen; Jan Melkebeek

2002-01-01

120

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

NASA Astrophysics Data System (ADS)

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

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

121

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

Microsoft Academic Search

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

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

1973-01-01

122

Analytical Computation of the Full Load Magnetic Losses in the Soft Magnetic Composite Stator of High-Speed Slotless Permanent Magnet Machines  

Microsoft Academic Search

This paper presents an analytical model for predicting the stator full load magnetic losses in high-speed slotless permanent-magnet machines with surface-mounted magnets on the rotor and a stator core made of isotropic and conductive soft magnetic composite material (SMC). The losses are derived from the computation of the two-dimensional magnetic field distribution created by the rotor magnets, the currents in

Ahmed Chebak; Philippe Viarouge; Jérôme Cros

2009-01-01

123

The extrinsic hysteresis behavior of dilute binary ferrofluids.  

PubMed

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

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

2014-10-01

124

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

NASA Technical Reports Server (NTRS)

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

Niedra, Janis M.; Schwarze, Gene E.

1999-01-01

125

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

SciTech Connect

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.

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

126

Hysteresis in Metal Hydrides.  

ERIC Educational Resources Information Center

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

Flanagan, Ted B., And Others

1987-01-01

127

Mathematical models of hysteresis  

Microsoft Academic Search

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

I. Mayergoyz

1986-01-01

128

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

NASA Astrophysics Data System (ADS)

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

Jiles, D. C.

1988-04-01

129

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

NASA Technical Reports Server (NTRS)

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

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

2004-01-01

130

Rare-earth-gallium-iron glasses. II. Anomalous magnetic hysteresis in alloys based on Pr, Nd, and Sm  

NASA Astrophysics Data System (ADS)

Giant magnetic coercivity is reported in several metallic glasses of the form (R80G20)100-xFex where R represents Pr, Nd, or Sm, G represents Ga or Au, and 15<=x<=30. An unusual temperature variation of the coercive field is observed showing peaks at intermediate temperatures (~=90 K). In contrast to similar glasses based on heavy rare-earth metals, these glasses exhibit significant chemical short-range order and even phase separation as is shown by the Mössbauer effect and other measurements. The results are consistent with a recent theory which predicts that large coercivity can result from the presence of site-to-site variations in magnetic properties.

Cornelison, S. G.; Zhao, J. G.; Sellmyer, D. J.

1984-09-01

131

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

Microsoft Academic Search

Soft magnetic composite materials produced by powder metallurgy techniques can be very useful for construction of low cost small motors. However, the rotational core losses and the corresponding B-H relationships of soft magnetic composite materials with two-dimensional rotating fluxes have neither been supplied by the manufacturers nor reported in the literature. This article reports the core loss measurement of a

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

1999-01-01

132

Modelling of the outer electron belt flux dropout and losses during magnetic storm main phase  

Microsoft Academic Search

In this paper we analyze the flux dropout and loss of outer belt electrons during magnetic storms. Using observations of the outer belt variation during the 26 March 1995 magnetic storm by the REM detector onboard the STRV-1b satellite, we show that a real loss of electrons occurred during the storm main phase. In order to simulate the outer belt

L. Desorgher; E. Flückiger; P. Bühler; A. Zehnder

2000-01-01

133

Characterization of the evolution of recrystallization by fluctuation and fractal analyses of the magnetic hysteresis loop in a cold rolled non-oriented electric steel  

Microsoft Academic Search

Silicon steels with non-oriented grains are widely used in the fabrication of electrical motor nucleus where a low magnetic\\u000a loss is an important point. The performance of these motors is affected by the level of recrystallization of these steels\\u000a which can come from the steel plant in a semi-processed condition. In this condition, they have a partially deformed structure\\u000a and

Francisco E. da Silva; Francisco Nelio C. Freitas; Hamilton Ferreira G. Abreu; Lindberg L. Gonçalves; Elineudo P. de Moura; Manoel R. Silva

2011-01-01

134

Eddy current and total power loss separation in the iron–phosphate–polyepoxy soft magnetic composites  

Microsoft Academic Search

This work investigates the magnetic properties of iron–phosphate–polyepoxy soft magnetic composite materials. FTIR spectra, EDX analysis, distribution maps, X-ray diffraction pattern and density measurements show that the particles surface layer contains a thin layer of nanocrystalline\\/amorphous phosphate with high coverage of powders surface. In this paper, a formula for calculating the eddy current loss and total loss components by loss

A. H. Taghvaei; H. Shokrollahi; K. Janghorban; H. Abiri

2009-01-01

135

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

E-print Network

Improvement of the magnetic core for eddy current losses decreasing in cylindrical linear actuators the power) increases, the iron losses become high [1]. One classical method for reducing the eddy current the eddy current losses in a longitudinal flux multi-rod actuator and to compute improvement. 2 The linear

Boyer, Edmond

136

Plant thermal hysteresis proteins.  

PubMed

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

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

1992-05-22

137

Loss separation in soft magnetic composites5 O. de la Barrire1  

E-print Network

1 1 2 3 4 Loss separation in soft magnetic composites5 6 7 8 9 O. de la Barrière1 , C. Appino2 , F and their frequency dependence26 in soft magnetic composites. Two types of bonded Fe-based materials have been/or high working frequencies [3] [4]. Soft46 magnetic composites (SMCs) are therefore often proposed

Paris-Sud XI, Université de

138

The simulation of low core loss high speed permanent magnet motor based on soft-magnetic ferrite  

NASA Astrophysics Data System (ADS)

High core loss is the most outstanding problem in high speed permanent magnet motors. To solve this problem, water cooling or oil cooling is usually adopted, which increase the complexity and cost. Considering the characters of high permeability, high resistivity, low loss and low cost for soft magnetic ferrite, this paper proposes a novel high speed PM motor based on soft magnetic ferrite. Soft magnetic ferrite ring is used as stator core, rare earth PM ring serves as the rotor poles, and the slotless configuration with long effective air gap is adopted. The size matching design between the stator magnetic ring and the PM magnetic ring can make themselves work in their best operating points respectively, lower core loss and higher power density will be ensured in the motor. The results of magnetic field analysis, core loss analysis and the prototype test prove that the core loss can be greatly reduced, which verifies that the high speed PM BLDC motor based on soft magnetic ferrite is feasible.

Wang, Xinghua; Fang, Xue; Guo, Yingjie; Wang, Xiuhe

2006-11-01

139

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

NASA Astrophysics Data System (ADS)

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

Zhang, Jianzhong; Wang, Minxi; Cheng, Ming

2012-04-01

140

A high-speed hysteresis drive with pulsed overdrive  

NASA Astrophysics Data System (ADS)

The pulsed overdrive (Delektorskii and Tarasov, 1974) is a special magnetization mode of a hysteresis motor. Consideration is given here to a drive with pulsed overdrive in which field extinction is used to improve the energy characteristics of the motor.

Pozdnykhov, S. F.; Tarasov, V. N.

141

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

Microsoft Academic Search

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

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

2002-01-01

142

Constricted hysteresis loops in Fe and Ni single crystals  

NASA Astrophysics Data System (ADS)

Magnetic hysteresis loops reflect the variety of magnetic domain structures and have been considered to have normal rectangular or leaf-like shapes in standard ferromagnets such as Fe and Ni metals. We report on observations of constricted hysteresis loops in Fe and Ni single crystals with very low defect densities. The constricted loops were observed below T=150 K and in a medium temperature range from 150 to 430 K in Fe and Ni single crystals, respectively. These constricted loops disappear by weak plastic deformation for both single crystals. The origin of constricted hysteresis loops was explained by eddy current effects under less domain wall pinning due to dislocations.

Takahashi, Seiki; Kobayashi, Satoru; Shishido, Toetsu

2010-11-01

143

Magnetic and electric contributions to the energy loss in a dynamical QCD medium  

E-print Network

The computation of radiative energy loss in a finite size QCD medium with dynamical constituents is a key ingredient for obtaining reliable predictions for jet quenching in ultra-relativistic heavy ion collisions. It was previously shown that energy loss in dynamical QCD medium is significantly higher compared to static QCD medium. To understand this difference, we here analyze magnetic and electric contributions to energy loss in dynamical QCD medium. We find that the significantly higher energy loss in the dynamical case is entirely due to appearance of magnetic contribution in the dynamical medium. While for asymptotically high energies, the energy loss in static and dynamical medium approach the same value, we find that the physical origin of the energy loss in these two cases is different.

Magdalena Djordjevic

2011-05-21

144

Development of soft magnetic composites for low-loss applications  

Microsoft Academic Search

Soft magnetic composite materials have been pressed into cylinders using both monotonic and cyclic loading over the pressure range 200–800MPa. Some samples have subsequently been heat treated over the temperature range 200–600°C. Magnetic Barkhausen noise (MBN) analysis has been used to look at the effects of these various processing stages. Increasing pressing pressure shows an increase in the MBN peak

I. P. Gilbert; V. Moorthy; S. J. Bull; J. T. Evans; A. G. Jack

2002-01-01

145

Development of soft magnetic composites for low-loss applications  

Microsoft Academic Search

Soft magnetic composite materials have been pressed into cylinders using both monotonic and cyclic loading over the pressure range 200-800MPa. Some samples have subsequently been heat treated over the temperature range 200-600°C. Magnetic Barkhausen noise (MBN) analysis has been used to look at the effects of these various processing stages. Increasing pressing pressure shows an increase in the MBN peak

I. P. Gilbert; V. Moorthy; S. J. Bull; J. T. Evans; A. G. Jack

2002-01-01

146

Eddy current losses in magnetic sheet with simple bar-like 180° domain structures  

Microsoft Academic Search

The eddy current losses in thin magnetic sheets have finite width (W), thickness (d) and simple bar-like domain structures are calculated numerically assuming sinusoidal time variation of flux and uniform domain wall speeds. The Pry and Bean values for the ratio of calculated eddy current loss (Pe) to its classical value (Pc) are attained for fixed domain width (2L) in

S. H. Charap

1979-01-01

147

The inverter drive loss of induction motor made by soft magnetic composite  

Microsoft Academic Search

This paper presents the loss analysis of the induction motor made of soft magnetic composite which is driven by inverter. SMC is used for the stator core of the induction motor. The loss of SMC motor increased by the inverter harmonics is lower than that of conventional electromagnetic steel motor. SMC motor has advantage in the high frequency drive.

Yutaka Sasaki; Masayuki Morimoto

2009-01-01

148

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

E-print Network

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.

B. G. Zakharov

2014-12-19

149

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

E-print Network

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.

Zakharov, B G

2014-01-01

150

Calorimetric method of ac loss measurement in a rotating magnetic field  

Microsoft Academic Search

A method is described for calorimetric ac-loss measurements of high-Tc 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

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

2010-01-01

151

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

SciTech Connect

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

Schlueter, R.D.

1991-08-16

152

Dynamical Hysteresis without Static Hysteresis: Scaling Laws and Asymptotic Expansions  

Microsoft Academic Search

Abstract. We study dynamical,hysteresis in a simple class of nonlinear ordinary dierential equations, namely rst-order equations subject to sinusoidal forcing. The assumed nonlinearities are such that the area of the hysteresis loop vanishes as the forcing frequency tends to zero; in other words, there is no static hysteresis. Using regular and singular perturbation techniques, we derive the rst term in

Guillermo H. Goldsztein; Fernando Broner; Steven H. Strogatz

1997-01-01

153

AC losses in stacks and arrays of YBCO/hastelloy and monofilamentary Bi-2223/Ag tapes  

NASA Astrophysics Data System (ADS)

Formulae are presented for the eddy current AC power loss and the AC hysteresis loss of z-stacks and x-arrays made of metal-superconductor strips. The AC self-field case and the applied AC magnetic field case are examined for different stacking spacings of a z-stack and different lateral spacings of an x-array. The effect of different metal-to-superconductor width-ratios on the losses is investigated. Numerical values are given for the two losses in YBCO/hastelloy and in monofilamentary Bi-2223/Ag tapes. At 50 Hz, the eddy current loss in a z-stack or an x-array made of YBCO/hastelloy tapes is small compared to the hysteresis loss while in a z-stack or an x-array made of monofilamentary Bi-2223/Ag tapes, the eddy current loss contributes significantly at small current or small magnetic field amplitudes.

Müller, K.-H.

1999-01-01

154

Effects of processing upon the properties of soft magnetic composites for low loss applications  

Microsoft Academic Search

We have investigated the effects of processing variables and methods on the density, structure and magnetic properties of soft magnetic composite (SMC) materials primarily for use in low loss applications. Two commercially available SMC materials from Höganäs AB, Sweden were used throughout the study. The materials differed only in terms of the solid state lubricant incorporated in the powder. This

I. Gilbert; S. Bull; T. Evans; A. Jack; D. Stephenson; A. De Sa

2004-01-01

155

Analytical Prediction of Eddy-Current Loss in Armature Windings of Permanent Magnet Brushless AC Machines  

Microsoft Academic Search

This paper presents an analytical model for prediction of eddy current loss in armature windings of permanent magnet brushless AC machines. The developed model can either be used in the case of internal or external rotor radial-field machines topologies. First, a 2-D exact analytical solution of magnetic field distribution in an actual geometry of slotted surface mounted PM radial flux

Yacine Amara; Pascal Reghem; Georges Barakat

2010-01-01

156

Magnetically controlled mass-loss from extrasolar planets in close orbits  

NASA Astrophysics Data System (ADS)

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 BP ? 0.3 G and fluxes FUV ˜ 106 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 sensitively on the strength (and geometry) of the background magnetic field from the star, along with the UV heating rate. The net effect of the magnetic field is to suppress the mass-loss rate by (approximately) an order of magnitude. Finally, some open field lines do not allow the flow to pass smoothly through the sonic point; flow along these streamlines does not reach a steady state, resulting in time-variable mass-loss.

Owen, James E.; Adams, Fred C.

2014-11-01

157

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

Microsoft Academic Search

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

S. Le Naour; A. Lacaze; Y. Laumond; P. Estop; T. Verhaege

1996-01-01

158

Power loss separation in Fe-based composite materials  

NASA Astrophysics Data System (ADS)

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

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

2013-02-01

159

Magnetic Flux Loss and Flux Transport in a Decaying Active Region  

E-print Network

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.

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

2008-07-28

160

Simple models for dynamic hysteresis loops calculation: Application to hyperthermia optimization  

E-print Network

To optimize the heating properties of magnetic nanoparticles (MNPs) in magnetic hyperthermia applications, it is necessary to calculate the area of their hysteresis loops in an alternating magnetic field. The three types of theories suitable to describe the hysteresis loops of MNPs are presented and compared to numerical simulations: equilibrium functions, Stoner-Wohlfarth model based theories (SWMBTs) and linear response theory (LRT). Suitable formulas to calculate the hysteresis area of major cycles are deduced from SWMBTs and from numerical simulations; the domain of validity of the analytical formula is explicitly studied. In the case of minor cycles, the hysteresis area calculations are based on the LRT. A perfect agreement between LRT and numerical simulations of hysteresis loops is obtained. The domain of validity of the LRT is explicitly studied. Formulas to calculate the hysteresis area at low field valid for any anisotropy of the MNP are proposed. Numerical simulations of the magnetic field dependen...

Carrey, J; Respaud, M

2010-01-01

161

Calorimetric method of ac loss measurement in a rotating magnetic field  

NASA Astrophysics Data System (ADS)

A method is described for calorimetric ac-loss measurements of high-Tc 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.

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

2010-07-01

162

Calorimetric method of ac loss measurement in a rotating magnetic field  

SciTech Connect

A method is described for calorimetric ac-loss measurements of high-T{sub 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.

Ghoshal, P. K. [Oxford Instruments NanoScience, Abingdon, Oxfordshire OX13 5QX (United Kingdom); Coombs, T. A.; Campbell, A. M. [Department of Engineering, Electrical Engineering, University of Cambridge, Cambridge CB3 0FA (United Kingdom)

2010-07-15

163

Magnetic Resonance Studies of Proton Loss from Carotenoid Radical Cations  

SciTech Connect

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

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

2007-06-11

164

Characteristic energy losses of electrons in a two-dimensional electron gas in a magnetic field  

NASA Astrophysics Data System (ADS)

The electron energy loss function is calculated in the random phase approximation for a two-dimensional electron gas in a quantizing magnetic field. Local states of electrons at impurity atoms are taken into consideration. The energy losses due to one-particle and collective excitations of two-dimensional electrons are determined. The activation of electrons localized at impurities leads to the emergence of steps on the dependence of loss function on the energy of an incident electron. Cerenkov losses associated with emission of magnetoplasmons appear starting from a threshold velocity of the electron. When the velocity exceeds the threshold value significantly, the losses are due only to spontaneous emission of magnetoplasmons. The corresponding loss function decreases in inverse proportion to the electron velocity.

Ermolaev, A. M.; Haghighi, Babak

1999-12-01

165

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

Microsoft Academic Search

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

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

1990-01-01

166

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

Microsoft Academic Search

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

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

1992-01-01

167

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

SciTech Connect

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

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

2011-06-15

168

with very high saturation magnetization and negligible dielectric loss synthesized via a soft chemical route  

NASA Astrophysics Data System (ADS)

Materials with high saturation magnetization and low dielectric loss are in great demand due to the great boom in communication industry. In this paper, we report the synthesis of nanoferrites with the generic formula Zn x Ni(1- x)Fe2O4 ( x = 0.0, 0.1, 0.3 and 0.5) through chemical co-precipitation technique. The sample with x = 0.5 showed a saturation magnetization of 8.2 ? B which is the highest reported for any ferrite. Coupled to this excellent magnetic property, this ferrite has shown a negligible dielectric loss tangent over a large frequency window from 100 Hz to 1 MHz. The high values of saturation magnetization have been attributed to the composite effect of large-scale cationic migration and surface spin disorder.

Mukherjee, S.; Pradip, S.; Mishra, A. K.; Das, D.

2014-07-01

169

The electric properties of low-magnetic-loss magnetic composites containing Zn-Ni-Fe particles.  

PubMed

Recently, magnetic composites consisting of magnetic particles dispersed in a polymer matrix have been widely discussed for miniaturizing high-frequency electronic components such as antennae. Previously, we investigated the influence of the manufacturing process on the homogeneous dispersion of magnetic particles in the polymer and on the magnetic properties of the magnetic composites. In order to miniaturize electronic components, it is crucial to be able to independently control the permeability and permittivity in magnetic composites. This paper investigates the anisotropy and frequency dependence of the dielectric properties of magnetic composites fabricated from 20 vol% Zn(5)Ni(75)Fe(20) flaked particles. The permittivity of magnetic composites fabricated from Zn(5)Ni(75)Fe(20) flaked particles is anisotropic: at 1 GHz, the relative permittivities parallel and perpendicular to the plane of the specimens are 27.2 and 16.9, respectively. The permittivity varied little between frequencies of 50 MHz and 10 GHz. PMID:21832455

Hidaka, Nobuhiro; Ishitsuka, Masayuki; Shirakata, Yasushi; Teramoto, Akinobu; Ohmi, Tadahiro

2009-10-28

170

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

SciTech Connect

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

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

2014-04-15

171

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

SciTech Connect

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

Candiani, A. [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

172

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

SciTech Connect

Laboratory observations of enhanced loss of magnetic mirror trapped fast electrons irradiated by a shear Alfvén Wave (SAW) are reported. The experiment is performed in the quiescent after-glow plasma in the Large Plasma Device [Gekelman et al., Rev. Sci. Instrum. 62(12), 2875–2883 (1991)]. A trapped energetic electron population (>100?keV) is generated in a magnetic mirror section (mirror ratio???2, length?=?3.5?m) by an X-mode high power microwave pulse, and forms a hot electron ring due to the grad-B and curvature drift. SAWs of arbitrary polarization are launched externally by a Rotating Magnetic Field source (?B/B{sub 0}???0.1%, ?{sub ?}???9?m). Irradiated by a right-handed circularly polarized SAW, the loss of electrons, in both the radial and the axial direction of the mirror field, is significantly enhanced and is modulated at f{sub Alfvén}. The periodical loss continues even after the termination of the SAW. Experimental observations suggest that a spatial distortion of the ring is formed in the SAW field and creates a collective mode of the hot electron population that degrades its confinement and leads to electron loss from the magnetic mirror. The results could have implications on techniques of radiation belt remediation.

Wang, Y.; Gekelman, W.; Pribyl, P. [Department of Physics and Astronomy, University of California, Los Angeles, California 90095 (United States)] [Department of Physics and Astronomy, University of California, Los Angeles, California 90095 (United States); Papadopoulos, K. [Department of Physics and Astronomy, University of Maryland, College Park, Maryland 20742 (United States)] [Department of Physics and Astronomy, University of Maryland, College Park, Maryland 20742 (United States)

2014-05-15

173

A Multiscale Approach to Predict Classical Losses in Soft Magnetic Composites  

Microsoft Academic Search

This paper presents the application of a finite element multiscale method, based on the homogenization technique, to the prediction of classical losses in soft magnetic composite materials. The experimental results, obtained for a wide range of frequencies and for various toroidal samples with different cross sections, are explained by using the considered model. It has been found that the classical

Adelina Bordianu; Olivier de la Barriere; Oriano Bottauscio; Mario Chiampi; Alessandra Manzin

2012-01-01

174

Classical eddy current losses in Soft Magnetic Composites , O. de la Barrire2a  

E-print Network

1 Classical eddy current losses in Soft Magnetic Composites C. Appino1 , O. de la Barrière2a , F. It is known that eddy currents can flow in these granular materials at3 two different scales, that of the single particle (microscopic eddy currents) and that of the specimen4 cross-section (macroscopic eddy

Paris-Sud XI, Université de

175

Modelling of the Outer Electron Belt Flux Dropout and Losses During Magnetic Storm Main Phase  

NASA Astrophysics Data System (ADS)

In this paper we analyze the flux dropout and loss of outer belt electrons during magnetic storms. Using observations of the outer belt variation during the 26 March 1995 magnetic storm by the REM detector onboard the STRV-lb satellite, we show that a real loss of electrons occurred during the storm main phase. In order to simulate the outer belt variation during this storm, fully adiabatic motion of equatorial electrons was simulated with the non stationary Tsyganenko96 magnetic field model. We discuss the effect of adiabatic deceleration during the storm main phase and conclude that drift of particles into the magnetopause may be a possible mechanism. Simulations with different field configurations show that the result are sensitive to the various field components

Desorgher, L.; Flückiger, E.; Bühler, P.; Zehnder, A.

176

Magnetization AC losses in MgB2 wires made by IMD process  

NASA Astrophysics Data System (ADS)

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.

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

2015-01-01

177

Modeling hysteresis in piezoceramic actuators  

Microsoft Academic Search

A major deficiency of piezoceramic actuators is that their open-loop control accuracy is seriously limited by hysteresis. This paper discusses the adaptation of the Preisach model to describe the nonlinear hysteresis behavior of these actuators. The adapted model is used to predict the response of a piezoceramic actuator to a sinusoidal input and a triangular input. The predictions are compared

Ping Ge; Musa Jouaneh

1995-01-01

178

Magnetic testing  

NASA Technical Reports Server (NTRS)

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

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

1973-01-01

179

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

E-print Network

Abstract -- For high-speed machines applications, eddy- current losses in the interior permanent carries out a prediction of eddy current losses in PM where the skin effect is considered. A complete by analytical method. Index Terms-- High speed, Permanent magnet machines, Eddy-currents, power losses, skin

Paris-Sud XI, Université de

180

Thermal hysteresis proteins.  

PubMed

Extreme environments present a wealth of biochemical adaptations. Thermal hysteresis proteins (THPs) have been found in vertebrates, invertebrates, plants, bacteria and fungi and are able to depress the freezing point of water (in the presence of ice crystals) in a non-colligative manner by binding to the surface of nascent ice crystals. The THPs comprise a disparate group of proteins with a variety of tertiary structures and often no common sequence similarities or structural motifs. Different THPs bind to different faces of the ice crystal, and no single mechanism has been proposed to account for THP ice binding affinity and specificity. Experimentally THPs have been used in the cryopreservation of tissues and cells and to induce cold tolerance in freeze susceptible organisms. THPs represent a remarkable example of parallel and convergent evolution with different proteins being adapted for an anti-freeze role. PMID:11240367

Barrett, J

2001-02-01

181

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

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

182

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

NASA Technical Reports Server (NTRS)

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.

Mullan, D. J.

1982-01-01

183

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

NASA Technical Reports Server (NTRS)

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

Beggs, John H.

2000-01-01

184

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

NASA Astrophysics Data System (ADS)

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

Sasada, Ichiro

2014-05-01

185

Eddy-current loss in the rotor magnets of permanent-magnet brushless machines having a fractional number of slots per pole  

Microsoft Academic Search

We develop an analytical model for predicting the eddy-current loss in the rotor magnets of permanent-magnet brushless machines that have a fractional number of slots per pole, when either all the teeth or only alternate teeth are wound, and in which the unwound teeth may be narrower than the wound teeth. The model enables the magnetic field distribution in the

Dahaman Ishak; Z. Q. Zhu; David Howe

2005-01-01

186

The role of the Martian crustal magnetic fields in controlling ionospheric loss  

NASA Astrophysics Data System (ADS)

hybrid particle code has been used to examine the interaction of the solar wind with Mars. It is found that the presence of the crustal magnetic fields modifies the heavy ion (O+ and O2+) loss rates. In the case of the solar minimum situation the modification was found to be significant and reported in Brecht and Ledvina (2012). In this paper both solar minimum and solar maximum results are reported and compared with data. The crustal magnetic fields reduce the ionospheric loss rate; and when the energy limits imposed on the data fits are considered, the results of the simulations are in reasonable agreement with data. The agreement with the data provides a strong argument for the physical control demonstrated by the simulations being realistic.

Brecht, Stephen H.; Ledvina, Stephen A.

2014-08-01

187

Alternating current loss calculation in a high-TC superconducting transmission cable considering the magnetic field distribution  

NASA Astrophysics Data System (ADS)

We have calculated the alternating current (ac) losses of a 114 MVA high-TC superconducting (HTS) transmission cable using an electric-circuit (EC) model. The HTS cable is fabricated by Tokyo Electric Power Company and Sumitomo Electric Industries, Ltd. The EC model is comprised of a resistive part and an inductive part. The resistive part is obtained by the approximated Norris equation for a HTS tape. The Norris equation indicates hysteresis losses due to self-fields. The inductive part has two components, i.e. inductances related to axial fields and those related to circumferential fields. The layer currents and applied fields of each layer were calculated by the EC model. By using both values, the ac losses of the one-phase HTS cable were obtained by calculation considering the self-field, the axial field and the circumferential field of the HTS tape. The measured ac loss transporting 1 kArms is 0.7 W m-1 ph-1, which is equal to the calculation. The distribution of each layer loss resembles in shape the distribution of the circumferential field in each layer, which indicates that the circumferential fields strongly influence the ac losses of the HTS cable.

Noji, H.; Haji, K.; Hamada, T.

2003-01-01

188

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

NASA Astrophysics Data System (ADS)

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

St?pie?, K.

2000-01-01

189

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

SciTech Connect

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

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

1993-01-31

190

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

E-print Network

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

Sethna, James P.

191

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

SciTech Connect

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

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

1999-11-29

192

Ferroelectric non-hysteresis actuator for microwave tuneable devices  

Microsoft Academic Search

Low loss and highly tuneable microwave filters controlled by piezoelectric actuator are discussed. Dielectric or metallic parts of device should have the piezo-dirigible air gap between them. The most important for these devices is to use non-hysteresis relaxor ferroelectric ceramics with large electrostriction. Electromechanic way of control has restriction in the speed of operation, and this problem is estimated by

Y. M. Poplavko; S. A. Voronov

2010-01-01

193

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)

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.

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

2015-02-01

194

Heating efficiency in magnetic nanoparticle hyperthermia  

NASA Astrophysics Data System (ADS)

Magnetic nanoparticles for hyperthermic treatment of cancers have gained significant attention in recent years. In magnetic hyperthermia, three independent mechanisms result in thermal energy upon stimulation: Néel relaxation, Brownian relaxation, and hysteresis loss. The relative contribution of each is strongly dependent on size, shape, crystalline anisotropy, and degree of aggregation or agglomeration of the nanoparticles. We review the effects of each of these physical mechanisms in light of recent experimental studies and suggest routes for progress in the field.

Deatsch, Alison E.; Evans, Benjamin A.

2014-03-01

195

Structural studies, magnetic properties and loss separation in iron–phenolicsilane soft magnetic composites  

Microsoft Academic Search

In this work, six different series of iron based soft magnetic composites are produced and studied: (1) passive iron powder; (2) passive iron powder-0.7% resin with coupling agent; (3) passive iron powder-0.7% resin without coupling agent; (4) passive iron powder-1.5% resin with coupling agent; (5) passive iron powder-1.5% resin without coupling agent; (6) pure iron-1.5% resin. The specimens were shaped

A. H. Taghvaei; H. Shokrollahi; K. Janghorban

2010-01-01

196

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

PubMed Central

A complete time-dependent physics theory of symmetric unperturbed driven Hybrid Birdcage resonator was developed for general application. In particular, the theory can be applied for RF coil engineering, computer simulations of coil-sample interaction, etc. Explicit time dependence is evaluated for different forms of driving voltage. The major steps of the solution development are shown and appropriate explanations are given. Green’s functions and spectral density formula were developed for any form of periodic driving voltage. The concept of distributed power losses based on transmission line theory is developed for evaluation of local losses of a coil. Three major types of power losses are estimated as equivalent series resistances in the circuit of the Birdcage resonator. Values of generated resistances in Legs and End-Rings are estimated. An application of the theory is shown for many practical cases. Experimental curve of B1 field polarization dependence is measured for eight-sections Birdcage coil. It was shown, that the steady-state driven resonance frequencies do not depend on damping factor unlike the free oscillation (transient) frequencies. An equivalent active resistance is generated due to interaction of RF electromagnetic field with a sample. Resistance of the conductor (enhanced by skin effect), Eddy currents and dielectric losses are the major types of losses which contribute to the values of generated resistances. A biomedical sample for magnetic resonance imaging and spectroscopy is the source of the both Eddy current and dielectric losses of a coil. As demonstrated by the theory, Eddy currents losses is the major effect of coil shielding. PMID:20869184

Novikov, Alexander

2010-01-01

197

Numerical simulations of the angular dependence of magnetization AC losses: coated conductors, Roebel cables and double pancake coils  

NASA Astrophysics Data System (ADS)

The AC losses in ReBCO coated conductors are large in situations when the conductors are subjected to a considerable magnetic field, as in rotating machines, transformers and high-field magnets. Roebel cables can reduce the AC losses in these cases. However, computer simulations are needed to interpret the experiments, understand the loss mechanisms, reduce the AC losses by optimizing the Roebel cable and design the cryogenic system. In this paper, we simulate and discuss the AC losses due to an applied magnetic field with an arbitrary angle with respect to the cable and taking into account a realistic anisotropic field dependence of the critical current density. We study the AC losses in the superconductor parts for the limits of very high coupling currents and completely uncoupled strands. The simulations for the uncoupled case also describe a double pancake coil with no transport current. For the simulations, we use two different numerical methods with complementary strengths. This serves as a mutual check of the correctness of the simulation results, which agree with each other. As opposed to what was expected, we found that the AC losses do not only depend on the perpendicular component of the applied magnetic field. We also found that the AC losses for applied fields with an orientation below 7° with the strand surface are reduced by more than one order of magnitude as compared with an untransposed cable. Therefore, we recommend to use Roebel cables for windings with important parallel components, such as transformers and high-field magnets.

Pardo, Enric; Grilli, Francesco

2012-01-01

198

Influence of losses on the stability of a high current density superconducting magnet winding during the energy removal process  

NASA Astrophysics Data System (ADS)

The possibility of a high-current-density superconducting magnet winding quench due to losses generated during energy removal from the magnet is demonstrated using a computer program to calculate the specific losses and temperature rise of a composite superconductor. The experiments carried out on a laboratory solenoid with a nearly adiabatically insulated winding and a storage energy of 50 kJ at critical current are in good agreement with theory. It is shown that under certain conditions, the quench magnetic field level is independent of the magnetic field decay velocity.

Luppov, V. G.; Kabat, D.; Shishov, Y. A.; Datskov, V. I.

1980-10-01

199

Temperature effect on the magnetic properties of the coprecipitation derived ferrimagnetic glass-ceramics  

NASA Astrophysics Data System (ADS)

Ferrimagnetic glass-ceramic materials are promising candidates for destruction of cancerous cells by hysteresis loss, as a consequence of the increase of the local temperature when an alternating magnetic field is applied. The glass-ceramics prepared in this work contain magnetite and hematite crystals in a glassy matrix. They can be prepared by melting the coprecipitation-derived precursors at temperatures higher than 1400°C. The influence of the melting temperature on the magnetic properties of these glass-ceramics has been analysed. Room temperature hysteresis cycles in quasi-static conditions were performed using two different magnetic field, one of 12 kOe, and the other one of 500 Oe. The heat generation was estimated from calorimetric measurements, using a magnetic induction furnace. The magnetic hysteresis parameters are strongly affected by the glass-ceramics microstructure, which is influenced by the melting temperature.

Bretcanu, O.; Verné, E.; Cöisson, M.; Tiberto, P.; Allia, P.

2006-05-01

200

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

SciTech Connect

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

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

1995-11-01

201

Sensor Saturation for Hysteresis Reduction in GMR Magnetometers  

E-print Network

Sensor Saturation for Hysteresis Reduction in GMR Magnetometers Philip S. Mease and Robert R technologies for the development of general-purpose magnetometers. They are applicable for both AC and DC of a magnetic field and instruments that make this measurement are known as magnetometers. The most common

Krchnavek, Robert R.

202

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

PubMed

To reduce the problem of cell loss due to adhesion, one of the basic phenomena in microchannel, we proposed the droplet-based magnetically activated cell separator (DMACS). Based on the platform of the DMACS-which consists of permanent magnets, a coverslip with a circle-shaped boundary, and an injection tube-we could collect magnetically (CD45)-labeled (positive) cells with high purity and minimize cell loss due to adhesion. To compare separation efficiency between the MACS and the DMACS, the total number of cells before and after separation with both the separators was counted by flow cytometry. We could find that the number (3241/59 940) of cells lost in the DMACS is much less than that (22 360/59 940) in the MACS while the efficiency of cell separation in the DMACS (96.07%) is almost the same as that in the MACS (96.72%). Practically, with fluorescent images, it was visually confirmed that the statistical data are reliable. From the viability test by using Hoechst 33 342, it was also demonstrated that there was no cell damage on a gas-liquid interface. Conclusively, DMACS will be a powerful tool to separate rare cells and applicable as a separator, key component of lab-on-a-chip. PMID:17672779

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

2007-07-01

203

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

NASA Astrophysics Data System (ADS)

To reduce the problem of cell loss due to adhesion, one of the basic phenomena in microchannel, we proposed the droplet-based magnetically activated cell separator (DMACS). Based on the platform of the DMACS—which consists of permanent magnets, a coverslip with a circle-shaped boundary, and an injection tube—we could collect magnetically (CD45)-labeled (positive) cells with high purity and minimize cell loss due to adhesion. To compare separation efficiency between the MACS and the DMACS, the total number of cells before and after separation with both the separators was counted by flow cytometry. We could find that the number (3241/59940) of cells lost in the DMACS is much less than that (22360/59940) in the MACS while the efficiency of cell separation in the DMACS (96.07%) is almost the same as that in the MACS (96.72%). Practically, with fluorescent images, it was visually confirmed that the statistical data are reliable. From the viability test by using Hoechst 33 342, it was also demonstrated that there was no cell damage on a gas-liquid interface. Conclusively, DMACS will be a powerful tool to separate rare cells and applicable as a separator, key component of lab-on-a-chip.

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

2007-07-01

204

Mutual influence of electrical insulating coatings and structural barriers on the level of magnetic losses in anisotropic electrical sheet steel  

Microsoft Academic Search

Changes in the magnetic losses that occur in the electrical-sheet anisotropic steel under the joint influence of electrical\\u000a insulating coatings and structural barriers in the form of scratches have been investigated. It is shown that both the coatings\\u000a and scratches separately reduce the level of magnetic losses to a considerable extent, but their combined influence is not\\u000a additive. The work

R. V. Puzhevich; G. S. Korzunin; L. S. Karenina; M. B. Tsyrlin

2009-01-01

205

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

Microsoft Academic Search

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

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

2010-01-01

206

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

Microsoft Academic Search

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 +

E. M. Harnett; R. M. Winglee

2006-01-01

207

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

SciTech Connect

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

Heidrich, J. E.

1981-01-01

208

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

NASA Astrophysics Data System (ADS)

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

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

2012-08-01

209

Convective Power Loss Measurements in a Field Reversed Configuration with Rotating Magnetic Field Current Drive  

NASA Astrophysics Data System (ADS)

The Translation, Confinement, and Sustainment Upgrade (TCSU) experiment achieves direct formation and sustainment of a field reversed configuration (FRC) plasma through rotating magnetic fields (RMF). The pre-ionized gas necessary for FRC formation is supplied by a magnetized cascade arc source that has been developed for TCSU. To ensure ideal FRC performance, the condition of the vacuum chamber prior to RMF start-up has been characterized with the use of a fast response ion gauge. A circuit capable of gating the puff valves with initial high voltage for quick response and then indefinite operational voltage was also designed. A fully translatable combination Langmuir / Mach probe was also built to measure the electron temperature, electron density, and ion velocity of the FRC. These measurements were also successfully completed in the FRC exhaust jets allowing for an accurate analysis of the FRC power loss through convection.

Melnik, Paul

210

A.C. energy losses of Nb-Ti multifilamentary superconductors for the magnets of the nuclotron  

Microsoft Academic Search

The performances of the installation used to measure a.c. energy losses of short superconducting samples in an external pulsed magnetic field are given. The calorimetric method at 4.2 K is used. The measurable range of losses is from 10 up to 1000 mW. The results of loss measurements of superconducting wires and tubular cables with a various diameter of superconducting

N. N. Agapov; G. L. Dorofeev; V. M. Drobin; A. D. Kovalenko; H. G. Khodzhibagiyan; N. M. Vladimirova

2002-01-01

211

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

Microsoft Academic Search

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

Jlilius Saitz

1999-01-01

212

Magnetoimpedance hysteresis in amorphous microwires induced by core-shell interaction  

NASA Astrophysics Data System (ADS)

We report on magneto-impedance (MI) hysteresis at MHz and GHz frequencies in amorphous microwires subject to a sufficiently high applied axial magnetic field HE. We show that this hysteresis originates from the magnetic hysteresis of the inner core which biases the outer shell causing a shift of the MI curve along the HE axis. Combined experiments (longitudinal and off-diagonal MI Z(HE), hysteresis loops M(HE) by vibrating sample magnetometer, and induction method) reveal the details of the magnetization reversal process in these microwires: Partial field dependencies Z(HE) and M(HE) are shown to be practically anhysteretic but shifted to the left or to the right about the origin by a residual magnetic field of the inner core HC. This shift can vary in the range from -35 to +35 A/m, depending on the magnetic history of the sample. We demonstrate that the hysteresis can be suppressed by application of a high enough axial magnetic field that saturates the magnetization of the inner core. A potential application of this hysteresis for memory devices is also proposed.

Ipatov, M.; Zhukova, V.; Gonzalez, J.; Zhukov, A.

2014-09-01

213

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

NASA Technical Reports Server (NTRS)

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

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

2002-01-01

214

Barkhausen discontinuities and hysteresis of ferromagnetics: New stochastic approach  

SciTech Connect

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.

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

215

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

Microsoft Academic Search

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

Carolus J. Schrijver

2001-01-01

216

Hysteresis modeling in ballistic carbon nanotube field-effect transistors  

PubMed Central

Theoretical models are adapted to describe the hysteresis effects seen in the electrical characteristics of carbon nanotube field-effect transistors. The ballistic transport model describes the contributions of conduction energy sub-bands over carbon nanotube field-effect transistor drain current as a function of drain-source and gate-source voltages as well as other physical parameters of the device. The limiting-loop proximity model, originally developed to understand magnetic hysteresis, is also utilized in this work. The curves obtained from our developed model corroborate well with the experimentally derived hysteretic behavior of the transistors. Modeling the hysteresis behavior will enable designers to reliably use these effects in both analog and memory applications. PMID:25187698

Liu, Yian; Moura, Mateus S; Costa, Ademir J; de Almeida, Luiz Alberto L; Paranjape, Makarand; Fontana, Marcio

2014-01-01

217

Hysteresis Modeling in Magnetostrictive Materials Via Preisach Operators  

NASA Technical Reports Server (NTRS)

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

Smith, R. C.

1997-01-01

218

Unconventional dynamic hysteresis in a periodic assembly of paramagnetic colloids.  

PubMed

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

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

2013-06-01

219

Impact of RMP magnetic field simulation models on fast ion losses  

NASA Astrophysics Data System (ADS)

Two opposing approaches to include resonant magnetic perturbations (RMPs) in fast ion simulations are compared, one where the vacuum field caused by the RMP current coils is added to the axisymmetric MHD equilibrium, the other where the MHD equilibrium includes the plasma response within the 3D deformation of its flux-surfaces. The first model admits large regions of stochastic field-lines that penetrate the plasma without alteration. The second assumes nested flux-surfaces with a single magnetic axis, which excludes stochastic field-lines, and embeds the RMPs within a 3D saturated ideal MHD state. The two descriptions of RMPs have been implemented in the VENUS-LEVIS guiding-centre orbit code. Simulations of fast ion populations resulting from MAST neutral beam injection have been applied to MAST n = 3 RMP coil configuration. At low beam energies, particle losses are dominated by parallel transport due to the stochasticity of the field-lines (vacuum-RMP model), whereas at higher energies, losses are accredited to the 3D structure of the perturbed plasma and the resulting drifts (equilibrium-RMP model).

Pfefferlé, David; Misev, Cyril; Cooper, Wilfred A.; Graves, Jonathan P.

2015-01-01

220

Magnetic measurement of creep damage: modeling and measurement  

NASA Astrophysics Data System (ADS)

Results of inspection of creep damage by magnetic hysteresis measurements on Cr-Mo steel are presented. It is shown that structure-sensitive parameters such as coercivity, remanence and hysteresis loss are sensitive to creep damage. Previous metallurgical studies have shown that creep changes the microstructure of he material by introducing voids, dislocations, and grain boundary cavities. As cavities develop, dislocations and voids move out to grain boundaries; therefore, the total pinning sources for domain wall motion are reduced.This, together with the introduction of a demagnetizing field due to the cavities, results in the decrease of both coercivity, remanence and hence, concomitantly, hysteresis loss. Incorporating these structural effects into a magnetomechanical hysteresis model developed previously by us produces numerical variations of coercivity, remanence and hysteresis loss consistent with what is measured. The magnetic model has therefore been used to obtain appropriately modified magnetization curves for each element of creep-damaged material in a finite element (FE) calculation. The FE calculation has been used to simulate magnetic detection of non-uniform creep damage around a seam weld in a 2.25 Cr 1Mo steam pipe. In particular, in the simulation, a magnetic C-core with primary and secondary coils was placed with its pole pieces flush against the specimen in the vicinity of the weld. The secondary emf was shown to be reduced when creep damage was present inside the pipe wall at the cusp of the weld and in the vicinity of the cusp. The calculation showed that the C- core detected creep damage best if it spanned the weld seam width and if the current in the primary was such that the C- core was not magnetically saturated. Experimental measurements also exhibited the dip predicted in emf, but the measurements are not yet conclusive because the effects of magnetic property changes of weld materials, heat- affected material, and base material have not yet been sorted out experimentally form the effects of creep damage.

Sablik, Martin J.; Jiles, David C.

1996-11-01

221

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

NASA Technical Reports Server (NTRS)

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

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

1994-01-01

222

Development of a composite material with high magnetic permeability and low loss factor for high frequency application  

NASA Astrophysics Data System (ADS)

A flexible composite suitable for MHz frequency application has been developed by combining Fe3O4 and polyvinyl alcohol (PVA). The loss factor and the permeability have been evaluated. At an optimum weight percentage of Fe3O4 in the PVA matrix, the frequency at which the loss factor gives a minimum shifts to the MHz region. The loss factor has been found to be lower by one order of magnitude at 70 MHz compared to the presently used nickel zinc ferrite. The Henkel plot and the Cole-Cole plot have been obtained for the understanding of the high magnetic permeability and the low loss factor.

Roy, Debangsu; Anil Kumar, P. S.

2012-04-01

223

HYSTERESIS ANALYSIS BASED ON INTEGRAL QUADRATIC CONSTRAINTS  

Microsoft Academic Search

It is shown how the framework of Integral Quadratic Constraints can be applied to analyze systems with hysteresis, in spite of the fact that hysteresis operators are unbounded and that not all system variable can be expected to approach zero.

A. Rantzer; A. Megretski

224

A simple model of hysteresis behavior using spreadsheet analysis  

NASA Astrophysics Data System (ADS)

Hysteresis loops occur in many scientific and technical problems, especially as field dependent magnetization of ferromagnetic materials, but also as stress-strain-curves of materials measured by tensile tests including thermal effects, liquid-solid phase transitions, in cell biology or economics. While several mathematical models exist which aim to calculate hysteresis energies and other parameters, here we offer a simple model for a general hysteretic system, showing different hysteresis loops depending on the defined parameters. The calculation which is based on basic spreadsheet analysis plus an easy macro code can be used by students to understand how these systems work and how the parameters influence the reactions of the system on an external field. Importantly, in the step-by-step mode, each change of the system state, compared to the last step, becomes visible. The simple program can be developed further by several changes and additions, enabling the building of a tool which is capable of answering real physical questions in the broad field of magnetism as well as in other scientific areas, in which similar hysteresis loops occur.

Ehrmann, A.; Blachowicz, T.

2015-01-01

225

New Tc-tuned magnetic nanoparticles for self-controlled hyperthermia  

NASA Astrophysics Data System (ADS)

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

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

2007-09-01

226

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

SciTech Connect

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

Zhou Yang; Kou Xiaoming; Warsi Muhammad, Asif; Lin Shuo; Harris, Brendan S.; Parsons, Paul E.; Xiao, John Q. [Department of Physics and Astronomy, University of Delaware, Newark, Delaware 19716 (United States); Mu Mingkai; Lee, Fred C. [Center for Power Electronics System, Virginia Polytechnic and State University, Blacksburg, Virginia 24060 (United States); Zhu Hao [Spectrum Magnetics LLC, Wilmington, Delaware 19804 (United States)

2013-05-07

227

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

NASA Astrophysics Data System (ADS)

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

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

2012-11-01

228

Modeling of soft magnetic composite material using a non linear homogenization method  

Microsoft Academic Search

This paper presents the modeling of soft magnetic composite materials (SMC) using a non linear homogenization technique. This study provides useful information for the powder development and design. A new method to take into account the real geometry of the iron particles and the insulation layer is developed. This method permits to evaluate the equivalent permeability and the hysteresis losses

M. Belkadi; D. Trichet; B. Ramdane; J. Fouladgar

2010-01-01

229

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

SciTech Connect

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.

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

230

Experimentally determined transport and magnetization ac losses of small cable models constructed from YBCO coated conductors  

NASA Astrophysics Data System (ADS)

Several short cable models were constructed from YBCO coated conductor (YBCO CC) to study their basic dc and ac electrical properties. They were prepared using superconducting tapes helically wound on fiberglass former of different diameter (5, 8 and 10 mm) with different twist pitch (from 1.7 up to 2.4 cm). The number of parallel-connected tapes ranged from 1 up to 6. The standard length of the models was 11 cm. In one case a 35 cm long model has been manufactured in order to perform a bending test. We observed that the critical currents of the models were proportional to the number of tapes used for their construction. Transport and magnetization ac loss were measured at 36 and 72 Hz.

Šouc, J.; Vojen?iak, M.; Gömöry, F.

2010-04-01

231

Theoretical evaluation of longitudinal a.c. losses in large-capacity superconducting cables for 50/60 Hz use  

NASA Astrophysics Data System (ADS)

When an a.c. transport current and/or an a.c. magnetic field are applied to multiply twisted superconducting cables, a magnetic field along strands composed of homogeneous and spatially periodic components is induced in addition to the field perpendicular to the strands. The time variation of this longitudinal field along the strands also brings about hysteresis and coupling-current losses. Theoretical expressions for the additional losses are derived both in the self-field configuration of the cable and in the external transverse field configuration. In the self-field configuration, the hysteresis loss due to the homogeneous component is dominant, which can be sufficiently decreased by the cabling procedure and optimization of the twist pitch in the strand. In the external transverse field, on the other hand, the development of high current density superconductors may be necessary for decreasing the a.c. cables in addition to optimization of the cable structure.

Funaki, K.; Ueda, H.; Yoshlya, F.; Iwakuma, M.; Takeo, M.; Yamafuji, K.

232

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

PubMed Central

A wide variety of coupled harmonic oscillators exist in nature. Coupling between different oscillators allows for the possibility of mutual energy transfer between them and the information-signal propagation. Low-energy input signals and their transport with negligible energy loss are the key technological factors in the design of information-signal processing devices. Here, utilizing the concept of coupled oscillators, we experimentally demonstrated a robust new mechanism for energy transfer between spatially separated dipolar-coupled magnetic disks - stimulated vortex gyration. Direct experimental evidence was obtained by a state-of-the-art experimental time-resolved soft X-ray microscopy probe. The rate of energy transfer from one disk to the other was deduced from the two normal modes' frequency splitting caused by dipolar interaction. This mechanism provides the advantages of tunable energy transfer rates, low-power input signals and negligible energy loss in the case of negligible intrinsic damping. Coupled vortex-state disks might be implemented in applications for information-signal processing. PMID:22355578

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

2011-01-01

233

Impedance loss due to ion-ion collisions in a high power magnetically immersed electron diode  

NASA Astrophysics Data System (ADS)

In a magnetically immersed electron diode, [1] electrons are emitted from a needle cathode of 0.5--5 mm diameter and confined in a 10-50 Tesla solenoidal field. These electrons, striking a high Z anode converter, can potentially deliver a high brightness source of x-rays for flash radiography. In recent experiments on the 150 kA, 4-MV RITS-3 accelerator at Sandia National Laboratories, for < 4 mm radius needles, these diodes exhibit anomalously fast gap closure velocities that limit the x-ray pulse length. In typical pulse-power diodes, electrode plasma velocities are of order 1-3 cm/?s. For an immersed diode with a small cathode radius, the effective speed associated with the rate of impedance loss is roughly 600 cm/?s - consistent with that of 2-4 MeV, 10-20 amu ions. Here, we postulate a new mechanism for the impedance loss that is driven by the subsequent ionization of anode ions due to ion-ion collisions. Simulations with the Lsp [2] particle-in-cell code demonstrate that such a mechanism causes a steady increase of both ion and electron currents above that of bipolar Child-Langmuir flow. Assuming ion-ion cross sections of order 10-15 cm2, this situation leads to an impedance loss with characteristics similar to those observed in RITS-3 experiment. 1. M.G. Mazarakis et al Appl. Phys. Lett 70, 832 (1997) 2. Lsp is a software product of Mission Research Corporation, http://mrcabq.com

Welch, Dale; Oliver, Bryan; Rose, David; Rovang, Dean; Maenchen, John

2003-10-01

234

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

NASA Astrophysics Data System (ADS)

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.

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

2014-12-01

235

Modeling and analysis of proximity losses in high-speed surface permanent magnet machines with concentrated windings  

Microsoft Academic Search

Surface permanent magnet (SPM) machines can be designed with fractional slot-concentrated windings (FSCW) to achieve extended speed ranges. High-speed operation can lead to significant levels of proximity losses in the stator windings due to substantial spatial harmonic magnetic fields in the air-gap as well as the high-frequency currents themselves. An integrated analysis tool is presented in this paper to calculate

Patel B. Reddy; T. M. Jahns; T. P. Bohn

2010-01-01

236

Kinetic Hysteresis in Collagen Folding  

PubMed Central

Abstract The triple helix of collagen shows a steep unfolding transition upon heating, whereas less steep and more gradual refolding is observed upon cooling. The shape of the hysteresis loop depends on the rate of temperature change as well as the peptide concentration. Experimental heating and cooling rates are usually much faster than rates of unfolding and refolding. In this work, collagen model peptides were used to study hysteresis quantitatively. Their unfolding and refolding profiles were recorded at different heating and cooling rates, and at different peptide concentrations. Data were fitted assuming kinetic mechanisms in which three chains combine to a helix with or without an intermediate that acts as a nucleus. A quantitative fit was achieved with the same kinetic model for the forward and backward reactions. Transitions of exogenously trimerized collagen models were also analyzed with a simplified kinetic mechanism. It follows that true equilibrium transitions can only be measured at high concentrations of polypeptide chains with slow scanning rates, for example, 0.1°C/h at 0.25 mM peptide concentration of (Gly-Pro-Pro)10. (Gly-Pro-4(R)Hyp)10 folds ?2000 times faster than (Gly-Pro-Pro)10. This was explained by a more stable nucleus, whereas the rate of propagation was almost equal. The analysis presented here can be used to derive kinetic and thermodynamic data for collagenous and other systems with kinetically controlled hysteresis. PMID:20550913

Mizuno, Kazunori; Boudko, Sergei P.; Engel, Jürgen; Bächinger, Hans Peter

2010-01-01

237

Efficient Computational Model of Hysteresis  

NASA Technical Reports Server (NTRS)

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

Shields, Joel

2005-01-01

238

Magnetic properties and magnetocaloric effect in the RCu2Si2 and RCu2Ge2 (R = Ho, Er) compounds  

NASA Astrophysics Data System (ADS)

The magnetic properties and magnetocaloric effect (MCE) in RCu2Si2 and RCu2Ge2 (R = Ho, Er) compounds have been investigated. All these compounds possess an antiferromagnetic (AFM)-paramagnetic (PM) transition around their respective Neel temperatures. The RCu2Si2 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 RCu2Si2 and RCu2Ge2 (R = Ho, Er) compounds, especially, ErCu2Si2 exhibits large MCEs with no thermal hysteresis and magnetic hysteresis loss. The value of -?SMmax 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 -?SMmax 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 ErCu2Si2 compound is expected to have effective applications in low temperature magnetic refrigeration.

Mo, Zhao-Jun; Shen, Jun; Yan, Li-Qin; Gao, Xin-Qiang; Wang, Li-Chen; Tang, Cheng-Chun; Wu, Jian-Feng; Sun, Ji-rong; Shen, Bao-Gen

2014-02-01

239

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

SciTech Connect

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

GHOSH,A.

2004-03-22

240

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

NASA Astrophysics Data System (ADS)

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

Kobayashi, Satoru; Saito, Atsushi; Takahashi, Seiki; Kamada, Yasuhiro; Kikuchi, Hiroaki

2008-05-01

241

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

PubMed Central

Targeted hyperthermia treatment using magnetic nanoparticles is a promising cancer therapy. However, the mechanisms of heat dissipation in the large alternating magnetic field used during such treatment have not been clarified. In this study, we numerically compared the magnetic loss in rotatable nanoparticles in aqueous media with that of non-rotatable nanoparticles anchored to localised structures. In the former, the relaxation loss in superparamagnetic nanoparticles has a secondary maximum because of slow rotation of the magnetic easy axis of each nanoparticle in the large field in addition to the known primary maximum caused by rapid Néel relaxation. Irradiation of rotatable ferromagnetic nanoparticles with a high-frequency axial field generates structures oriented in a longitudinal or planar direction irrespective of the free energy. Consequently, these dissipative structures significantly affect the conditions for maximum hysteresis loss. These findings shed new light on the design of targeted magnetic hyperthermia treatments. PMID:22355672

Mamiya, Hiroaki; Jeyadevan, Balachandran

2011-01-01

242

Improved charge amplifier using hybrid hysteresis compensation  

NASA Astrophysics Data System (ADS)

We present a novel charge amplifier, with a robust feedback circuit and a method for compensating piezoelectric actuator's hysteresis at low frequencies. The amplifier uses a modified feedback circuit which improves robustness to the addition of series load impedance such as in cabling. We also describe a hybrid hysteresis compensation method for enabling the charge amplifier to reduce hysteresis at low frequencies. Experimental results demonstrate the utility of the new amplifier design.

Amin-Shahidi, Darya; Trumper, David L.

2013-08-01

243

Magnetic properties and magnetocaloric effect of the compound NdSi  

NASA Astrophysics Data System (ADS)

The magnetic properties and magnetocaloric effect (MCE) of the compound NdSi have been studied. The magnetic ground state of this compound is determined to be ferromagnetic and a second-order phase transition occurs at the Curie temperature TC=46 K. Large magnetic-entropy changes (?S) with no hysteresis loss are found with field variation. Maximum values of ?S -6.8 J/kg K and -12.4 J/kg K are found for field changes of 0-20 kOe and 0-50 kOe, respectively. With the merits of the large ?S and without hysteresis loss, NdSi can be considered as a competitive candidate magnetic refrigerant.

Zhang, Q. M.; Gao, R. L.; Cui, L.; Wang, L. C.; Fu, C. L.; Xu, Z. Y.; Mo, Z. J.; Cai, W.; Chen, G.; Deng, X. L.

2015-01-01

244

Large thermal hysteresis for iron(II) spin crossover complexes with N-(pyrid-4-yl)isonicotinamide.  

PubMed

A new series of iron(II) 1D coordination polymers with the general formula [FeL1(pina)]·xsolvent with L1 being a tetradentate N2O2(2-) coordinating Schiff-base-like ligand [([3,3']-[1,2-phenylenebis(iminomethylidyne)]bis(2,4-pentanedionato)(2-)-N,N',O(2),O(2)'], and pina being a bridging axial ligand N-(pyrid-4-yl)isonicotinamide, are discussed. The X-ray crystal structure of [FeL1(pina)]·2MeOH was solved for the low-spin state. The compound crystallizes in the monoclinic space group P21/c, and the analysis of the crystal packing reveals the formation of a hydrogen bond network where additional methanol molecules are included. Different magnetic properties are observed for the seven samples analyzed, depending on the nature of the included solvent molecules. The widest hysteresis loop is observed for a fine crystalline sample of composition [FeL1(pina)]·xH2O/MeOH. The 88 K wide thermal hysteresis loop (T1/2? = 328 K and T1/2? = 240 K) is centered around room temperature and can be repeated without of a loss of the spin transition properties. For the single crystals of [FeL1(pina)]·2MeOH, a 51 K wide hysteresis loop is observed (T1/2? = 296 K and T1/2? = 245 K) that is also stable for several cycles. For a powder sample of [FeL1(pina)]·0.5H2O·0.5MeOH a cooperative spin transition with a 46 K wide hysteresis loop around room temperature is observed (T1/2? = 321 K and T1/2? = 275 K). This compound was further investigated using Mössbauer spectroscopy and DSC. Both methods reveal that, in the cooling mode, the spin transition is accompanied by a phase transition while in the heating mode a loss of the included methanol is observed that leads to a loss of the spin transition properties. These results show that the pina ligand was used successfully in a crystal-engineering-like approach to generate 1D coordination polymers and improve their spin crossover properties. PMID:25314334

Lochenie, Charles; Bauer, Wolfgang; Railliet, Antoine P; Schlamp, Stephan; Garcia, Yann; Weber, Birgit

2014-11-01

245

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

SciTech Connect

A stable hybridization of the finite-element method (FEM) and the finite-difference time-domain (FDTD) scheme for Maxwell's equations with electric and magnetic losses is presented for two-dimensional problems. The hybrid method combines the flexibility of the FEM with the efficiency of the FDTD scheme and it is based directly on Ampere's and Faraday's law. The electric and magnetic losses can be treated implicitly by the FEM on an unstructured mesh, which allows for local mesh refinement in order to resolve rapid variations in the material parameters and/or the electromagnetic field. It is also feasible to handle larger homogeneous regions with losses by the explicit FDTD scheme connected to an implicitly time-stepped and lossy FEM region. The hybrid method shows second-order convergence for smooth scatterers. The bistatic radar cross section (RCS) for a circular metal cylinder with a lossy coating converges to the analytical solution and an accuracy of 2% is achieved for about 20 points per wavelength. The monostatic RCS for an airfoil that features sharp corners yields a lower order of convergence and it is found to agree well with what can be expected for singular fields at the sharp corners. A careful convergence study with resolutions from 20 to 140 points per wavelength provides accurate extrapolated results for this non-trivial test case, which makes it possible to use as a reference problem for scattering codes that model both electric and magnetic losses.

Halleroed, Tomas [Department of Signals and Systems, Chalmers University of Technology, S-412 96 Goeteborg (Sweden)], E-mail: tomas.hallerod@chalmers.se; Rylander, Thomas [Department of Signals and Systems, Chalmers University of Technology, S-412 96 Goeteborg (Sweden)], E-mail: rylander@chalmers.se

2008-04-20

246

Influence of PWM on the Proximity Loss in Permanent-Magnet Brushless AC Machines  

Microsoft Academic Search

A winding copper loss can be significantly increased due to skin and proximity eddy-current effects. The skin and proximity losses due to fundamental frequency current have been investigated in literature, but the influence of pulsewidth modulation (PWM) on the skin and proximity losses has not been reported. In this paper, a 2-D finite element method is employed to analyze the

S. Iwasaki; Rajesh P. Deodhar; Yong Liu; Adam Pride; Z. Q. Zhu; Jonathan James Bremner

2009-01-01

247

Experimental characterization and modeling of rate-dependent asymmetric hysteresis of magnetostrictive actuators  

NASA Astrophysics Data System (ADS)

The hysteresis nonlinearities of a magnetostrictive actuator were characterized under different amplitudes of simple and complex harmonic excitations over a wide range of frequencies (10-200 Hz) and magnetic bias levels (35-75 kA m-1). The measured data revealed asymmetric output-input characteristics and strong dependence on the magnetic bias, amplitude and frequency of the input. Output saturation was also observed under moderate to high amplitude excitations. A phenomenological hysteresis model is proposed in this study to model the hysteresis nonlinearities of a magnetostrictive actuator. A rate-dependent Prandtl-Ishlinskii model integrating a memoryless function of deadband operator was subsequently formulated to describe both the rate dependence and the asymmetric hysteresis loops of the magnetostrictive actuator in addition to the output saturation. Comparisons of the integrated Prandtl-Ishlinskii model responses with the measured data suggested that the model can effectively describe the nonlinear hysteresis properties of the magnetostrictive actuator over a broad range of excitation amplitudes and frequencies. The inverse of the proposed rate-dependent Prandtl-Ishlinskii model can be obtained analytically. Then, the inverse model can be applied as feedforward compensator for compensation of asymmetric rate-dependent hysteresis nonlinearities without using feedback control techniques.

Aljanaideh, Omar; Rakheja, Subhash; Su, Chun-Yi

2014-03-01

248

The influence of the magnetic field orientation on the angular momentum loss in the pre-main sequence phase: The case of very slowly rotating magnetic Ap stars  

NASA Astrophysics Data System (ADS)

Landstreet & Mathys (\\cite{lan00}) have discovered that almost all the magnetic Ap stars having rotation periods longer than about one month have their magnetic and rotation axes fairly closely aligned, in contrast to the more common magnetic Ap stars of shorter period, in which the two axes are usually inclined to one another at a large angle. Furthermore, as shown earlier by Mathys et al. (\\cite{mathys}) and by Hubrig et al. (\\cite{hnm00}), these most slowly rotating magnetic Ap stars have also magnetic fields several times larger than are typical for shorter period magnetic Ap stars, and generally have masses below 3 Msun. In this paper, we present calculations to show that the observed axial alignment in the slowest rotators may have arisen during the pre-main sequence (PMS) phase, when stars of a few solar masses are observed as Herbig Ae/Be stars. During the PMS phase, a star is expected to exchange angular momentum with a disk and with a stellar wind. As shown by St?pie? (\\cite{ste00}), a disk around a PMS magnetic Ap star tends to lock the rotation rate at a few days, while mass loss in the absence of a disk is able to slow the star to quite long periods. We argue that is it plausible to assume that the fraction of the PMS phase during which a disk persists depends on the orientation of the field axis to the plane of the disk, and that disk dissipation may have occurred more quickly in magnetic stars with aligned magnetic and rotation axes than in stars in which the angle between these axes is large. In this case, the magnetic Ap stars with aligned rotation and magnetic axes, especially those with large fields, could lose much more angular momentum than the stars of large obliquity. However, it is also shown that loss of nearly all the angular momentum is only possible for stars with masses below about 3 Msun (and with relatively large fields); for higher masses the available time is too short. Our model thus provides a reasonable explanation for all of the principle observational facts about the very slowly rotating magnetic Ap stars.

St?pie?, K.; Landstreet, J. D.

2002-03-01

249

Microstructure and hysteresis curves of the barium hexaferrite from co-precipitation by organic agent  

NASA Astrophysics Data System (ADS)

This work correlates the magnetic hysteresis curves to the microstructure of the sintered polycrystalline barium hexaferrite discs produced from co-precipitated barium and iron citrates. Citric acid was used as the organic precipitating agent. Thermogravimetric and differential thermal analyses were performed on the co-precipitated product in order to guide its calcination into barium hexaferrite crystals, which was confirmed by means of the X-ray fluorescence and X-ray diffraction. After that, the hexaferrite powder was pressed in a steel die and submitted to firing in air at various temperatures. The final ceramic pieces were characterized by means of scanning electron microscopy and magnetic hysteresis grapher. The obtained results indicate a strong effect of the firing temperature on the microstructure, which in turn affected the magnetic hysteresis curve.

Ogasawara, T.; Oliveira, M. A. S.

2000-07-01

250

Thermohaline circulation hysteresis: A model intercomparison  

Microsoft Academic Search

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

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

2005-01-01

251

Hysteresis and anisotropy in ultrathin Fe/Si(001) films  

NASA Astrophysics Data System (ADS)

It is challenging to investigate the magnetic anisotropy of Fe/Si(001) film in the case a limited magnetic field strength, when both coherent rotation and domain wall displacement coexist in the magnetization reversal process. Owing to the domain wall displacement, the magnetization reversal switching field is far lower than the magnetic anisotropy field, and, consequently, only the magnetization reversal process near easy axis can be treated as coherent rotation. Here, we record the slope of the magnetic torque curve of an iron film grown on a Si(001) substrate measured near the easy axis by anisotropic magnetoresistance (AMR) to separate the coherent rotation of magnetization reversal process from domain wall displacement. Furthermore, the magnitudes of various magnetic anisotropy constants were derived from the magnetic torque curves. Our work suggests that the AMR at low fields can clearly separate the detailed contributions of various magnetic anisotropies when domain wall displacement existed in Fe(001) ultrathin film. We also report on the hysteresis behavior of such films as measured by magneto-optic Kerr effect.

Ye, Jun; He, Wei; Wu, Qiong; Hu, Bo; Tang, Jin; Zhang, Xiang-Qun; Chen, Zi-Yu; Cheng, Zhao-Hua

2014-09-01

252

MEASURED AND CALCULATED LOSSES IN A MODEL DIPOLE FOR GSI'S HEAVY ION SYNCHROTRON.  

SciTech Connect

The new heavy ion synchrotron facility proposed by GSI will have two superconducting magnet rings in the same tunnel, with rigidities of 300T{center_dot}m and 10OT{center_dot}m. Fast ramp times are needed. These can cause problems of ac loss and field distortion in the magnets. For the high energy ring, a lm model dipole magnet has been built, based on the RHIC dipole design. This magnet was tested under boiling liquid helium in a vertical dewar. The quench current showed very little dependence on ramp rate. The ac losses, measured by an electrical method, were fitted to straight line plots of loss/cycle versus ramp rate, thereby separating the eddy current and hysteresis components. These results were compared with calculated values, using parameters which had previously been measured on short samples of cable. Reasonably good agreement between theory and experiment was found, although the measured hysteresis loss is higher than expected in ramps to the highest field levels.

WANDERER,P.; ANERELLA,M.; GANETIS,G.; GHOSH,A.K.; JOSHI,P.; MARONE,A.; MURATORE,J.; ET AL.

2003-06-15

253

A comparison between magnetic and reflection loss characteristics of substituted strontium ferrite and nanocomposites of ferrite/carbon nanotubes  

NASA Astrophysics Data System (ADS)

Large-scale carbon nanotubes (CNTs)/substituted strontium ferrite nanocomposites have been fabricated by hetero-coagulation. The structure and morphology of nanoparticles and nanocomposites were evaluated by high-resolution transmission electron microscopy (HRTEM). HRTEM confirmed that strontium ferrite was successfully attached to carbon nanotubes. The vibrating sample magnetometer (VSM) confirmed the relatively strong dependence of saturation magnetization with the volume percentage of multi-walled carbon nanotubes (MWCNTs). Reflection loss of nanocomposites at 12-18 GHz was evidently enhanced, as compared to that of strontium ferrite nanoparticles. The maximum reflection loss increased significantly with an increase in volume percentage of MWCNTs. It was proved that the microwave absorbing bandwidth was modulated simply by manipulating the thickness of nanocomposites. Reflection loss evaluations indicate that the nanocomposites display a great potential application as wide-band electromagnetic wave absorbers.

Ghasemi, Ali; Shirsath, Sagar E.; Liu, Xiaoxi; Morisako, Akimitsu

2012-04-01

254

Magnetic properties of ?' martensite in austenitic stainless steel studied by a minor-loop scaling law  

NASA Astrophysics Data System (ADS)

We study the scaling behavior of magnetic minor hysteresis loops in strain-induced ferromagnetic ?' martensites in an austenitic 316-type stainless steel. A scaling relationship between the hysteresis loss and the remanence, with a power law exponent of approximately 1.35, was found irrespective of the volume fraction of the ?' martensites as well as temperature. The coefficient of the power law largely decreases with volume fraction, whereas it increases with a decrease in temperature and exhibits a kink at around 40 K, close to the Néel temperature of an austenitic ?' phase. The behavior of the coefficient was interpreted from the viewpoint of the morphology and exchange interaction of ?' martensites.

Kobayashi, Satoru; Kikuchi, Nobuhiro; Takahashi, Seiki; Kamada, Yasuhiro; Kikuchi, Hiroaki

2010-08-01

255

X-ray absorption spectra and X-ray magnetic circular dichroism studies at Fe and Co L 2,3 edges of mixed cobalt–zinc ferrite nanoparticles: cationic repartition, magnetic structure and hysteresis cycles  

Microsoft Academic Search

X-ray absorption spectra (XAS) and X-ray magnetic circular dichroism (XMCD) spectra at Co and Fe L2,3 edges are performed on mixed cobalt–zinc ferrite nanoparticles Co0.73yZn0.73(1?y)Fe2.18?0.09 O4 (with y=0.4, 2.8 and 3.7nm average diameter; the symbol ? represents a vacancy). Simulation of the spectra thanks to ligand field multiplet theory allows an evaluation of the cationic repartition. Co2+ occupies preferentially octahedral

J. F Hochepied; Ph Sainctavit; M. P Pileni

2001-01-01

256

A Test of HTS Power Cable in a Sweeping Magnetic Field  

SciTech Connect

Short sample HTS power cable composed of multiple 344C-2G strands and designed to energize a fast-cycling dipole magnet was exposed to a sweeping magnetic field in the (2-20) T/s ramping rate. The B-field orientation toward the HTS strands wide surface was varied from 0{sup 0} to 10{sup 0}, in steps of 1{sup 0}. The test arrangement allowed measurement of the combined hysteresis and eddy current power losses. For the validity of these measurements, the power losses of a short sample cable composed of multiple LTS wire strands were also performed to compare with the known data. The test arrangement of the power cable is described, and the test results are compared with the projections for the eddy and hysteresis power losses using the fine details of the test cable structures.

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

2011-11-29

257

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

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.

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

258

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

PubMed

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

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

2014-01-01

259

Measurement and modeling of core losses of soft magnetic composites under 3-D magnetic excitations in rotating motors  

Microsoft Academic Search

Soft magnetic composite (SMC) materials are especially suitable for construction of low-cost high-performance motors with three-dimensional (3-D) magnetic fields. The 3-D finite-element analysis (FEA) conducted in the design of a claw pole transverse flux motor (CPTFM) with an SMC core reveals very complicated B (flux density) loci in the core when the motor rotates. In order to understand and account

YouGuang Guo; Jian Guo Zhu; Zhi Wei Lin; Jin Jiang Zhong

2005-01-01

260

Magnetic properties of iron-based soft magnetic composites with MgO coating obtained by sol–gel method  

Microsoft Academic Search

Soft magnetic composites with a thin MgO insulating layer were produced by a sol–gel method. Energy dispersive X-ray spectroscopy, X-ray analysis, Fourier transform infrared spectroscopy, density measurement and compositional maps confirmed that thin layers of MgO covered the iron powders. Coercivity measurement showed that the stress relaxation and reduction of hysteresis loss efficiently occurred at 600°C. At this temperature, the

A. H. Taghvaei; A. Ebrahimi; M. Ghaffari; K. Janghorban

2010-01-01

261

The loss rates of O{sup +} in the inner magnetosphere caused by both magnetic field line curvature scattering and charge exchange reactions  

SciTech Connect

With consideration of magnetic field line curvature (FLC) pitch angle scattering and charge exchange reactions, the O{sup +} (>300?keV) in the inner magnetosphere loss rates are investigated by using an eigenfunction analysis. The FLC scattering provides a mechanism for the ring current O{sup +} to enter the loss cone and influence the loss rates caused by charge exchange reactions. Assuming that the pitch angle change is small for each scattering event, the diffusion equation including a charge exchange term is constructed and solved; the eigenvalues of the equation are identified. The resultant loss rates of O{sup +} are approximately equal to the linear superposition of the loss rate without considering the charge exchange reactions and the loss rate associated with charge exchange reactions alone. The loss time is consistent with the observations from the early recovery phases of magnetic storms.

Ji, Y., E-mail: yji@spaceweather.ac.cn [State Key Laboratory of Space Weather, Center for Space Science and Applied Research, Chinese Academy of Sciences, Beijing 100190 (China); College of Earth Science, University of Chinese Academy of Sciences, Beijing 100049 (China); Shen, C. [State Key Laboratory of Space Weather, Center for Space Science and Applied Research, Chinese Academy of Sciences, Beijing 100190 (China)] [State Key Laboratory of Space Weather, Center for Space Science and Applied Research, Chinese Academy of Sciences, Beijing 100190 (China)

2014-03-15

262

Corneal hysteresis and its relevance to glaucoma  

PubMed Central

Purpose of review Glaucoma is a leading cause of irreversible blindness worldwide. It is estimated that roughly 60.5 million people had glaucoma in 2010 and that this number is increasing. Many patients continue to lose vision despite apparent disease control according to traditional risk factors. The purpose of this review is to discuss the recent findings with regard to corneal hysteresis, a variable that is thought to be associated with the risk and progression of glaucoma. Recent findings Low corneal hysteresis is associated with optic nerve and visual field damage in glaucoma and the risk of structural and functional glaucoma progression. In addition, hysteresis may enhance intraocular pressure (IOP) interpretation: low corneal hysteresis is associated with a larger magnitude of IOP reduction following various glaucoma therapies. Corneal hysteresis is dynamic and may increase in eyes after IOP-lowering interventions are implemented. Summary It is widely accepted that central corneal thickness is a predictive factor for the risk of glaucoma progression. Recent evidence shows that corneal hysteresis also provides valuable information for several aspects of glaucoma management. In fact, corneal hysteresis may be more strongly associated with glaucoma presence, risk of progression, and effectiveness of glaucoma treatments than central corneal thickness. PMID:25611166

Deol, Madhvi; Taylor, David A.; Radcliffe, Nathan M.

2015-01-01

263

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

264

Transport, hysteresis and avalanches in artificial spin ice systems  

SciTech Connect

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

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

2010-01-01

265

Analysis of hunting in Synchronous Hysteresis Motor  

E-print Network

The Synchronous Hysteresis Motor has an inherent instability when it is used to drive a gyroscope wheel. The motor ideally should spin at a constant angular velocity, but it instead sporadically oscillates about synchronous ...

Truong, Cang Kim, 1979-

2004-01-01

266

Cumulative growth of minor hysteresis loops in the Kolmogorov model  

SciTech Connect

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

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

2013-01-15

267

Equivalent Circuit Modeling of Hysteresis Motors  

SciTech Connect

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

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

2009-08-31

268

Spatial versus time hysteresis in damping mechanisms  

NASA Technical Reports Server (NTRS)

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

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

1988-01-01

269

Loss of Magnetic Insulation in a Crossed-Field Diode: Ion and Collisional Effects  

Microsoft Academic Search

The effect of ion production through ionizing collisions in a magnetically insulated crossed-field gap is studied by using one-dimensional particle-in-cell software. These results are compared with the predictions from previous efforts that assumed immobile sheets of positive charge at different positions within the gap. Our results with mobile ions created via collisions indicate that the diode can lose magnetic insulation

Brooke S. Stutzman; John W. Luginsland

2010-01-01

270

Polymethyl methacrylate (PMMA)-bismuth ferrite (BFO) nanocomposite: low loss and high dielectric constant materials with perceptible magnetic properties.  

PubMed

Herein, poly(methyl methacrylate)-bismuth ferrite (PMMA-BFO) nanocomposites were successfully prepared by an in situ polymerization method for the first time. Initially, the as prepared bismuth ferrite (BFO) nanoparticles were dispersed in the monomer, (methyl methacrylate) by sonication. Benzoyl peroxide was used to initiate the polymerization reaction in ethyl acetate medium. The nanocomposite films were subjected to X-ray diffraction analysis (XRD), (1)H NMR, field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), thermogravimetric analysis (TGA), infrared spectroscopy (IR), dielectric and magnetic characterizations. The dielectric measurement of the nanocomposites was investigated at a frequency range of 10 Hz to 1 MHz. It was found that the nanocomposites not only showed a significantly increased value of the dielectric constant with an increase in the loading percentage of BFO as compared to pure PMMA, but also exhibited low dielectric loss values over a wide range of frequencies. The values of the dielectric constant and dielectric loss of the PMMA-BFO5 (5% BFO loading) sample at 1 kHz frequency was found be ~14 and 0.037. The variation of the ferromagnetic response of the nanocomposite was consistent with the varying volume percentage of the nanoparticles. The remnant magnetization (Mr) and saturation magnetization (Ms) values of the composites were found to be enhanced by increasing the loading percentage of BFO. The value of Ms for PMMA-BFO5 was found to be ~6 emu g(-1). The prima facie observations suggest that the nanocomposite is a potential candidate for application in high dielectric constant capacitors. Significantly, based on its magnetic properties the composite will also be useful for use in hard disk components. PMID:25050918

Tamboli, Mohaseen S; Palei, Prakash K; Patil, Santosh S; Kulkarni, Milind V; Maldar, Noormahmad N; Kale, Bharat B

2014-09-21

271

HYSTERESIS MODELLING FOR A MR DAMPER Jorge de-J. Lozoya-Santos1  

E-print Network

of a commercial Magneto-Rheological (MR) damper is exploited for identification of a Hysteresis-based Control The Magneto-Rheological (MR) damper is a non-linear component with dissipative capability used in the con a certain magnetic field is applied to the MR fluids, the particles in the fluids are polarized

Boyer, Edmond

272

PM motor sensorless position detection based on iron BH local hysteresis  

Microsoft Academic Search

A sensorless position detection technique for a permanent magnet (PM) motor with non-salient rotor is presented. It is shown that the phase self inductances and resistances measured at higher frequencies vary slightly with the rotor position. The origin of the variations is found in the iron B-H hysteresis characteristics. In order to exploit these small variations for the rotor position

Omar Scaglione; Miroslav Markovic; Yves Perriard

2009-01-01

273

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

NASA Technical Reports Server (NTRS)

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

Triner, J. E.

1979-01-01

274

Charge Exchange Loss of High Temperature Plasma Confined by Mirror Magnetic Field  

Microsoft Academic Search

Relaxation of the distribution function of ions confined in a mirror field is in investigated theoretically taking both the charge exchange and scattering effects into account. The result is compared with experiment. If the particles are not thermalized sufficiently, the ion density decays exponentially due to the charge exchange, but only linearly due to the mirror loss. The life time,

Ichiro Mori; Tokuo Suita

1966-01-01

275

Possible loss of mechanical stability by degenerate charged Fermi gases in intense magnetic fields  

SciTech Connect

The exact equations of state of a nonrelativistic degnerate ideal electron gas in an intense magnetic field are considered, and it is shown that its adiabatic index Gamma oscillates between 0 and a value just over 5/3 as a function of a given variable. Gamma reaches the critical points 0 when the variable = integer, corresponding to the filling of a Landau level. It is thus analogous to the de Haas-van Alphen effect, the normal quantized Hall effect, and magnetic domain formation. Corrections for a real gas, which could lead to Gamma less than 0 and mechanical stability breakdown, are considered qualitatively. In particular, an average index, valid in stars due to nonnegligible Newtonian self-gravition, suggest the possibility of observing this effect in astrophysical objects dominated by degenerate electrons in intense enough magnetic fields. 16 references.

Ingraham, R.L.

1986-10-01

276

Influence of fourfold anisotropy form on hysteresis loop shape in ferromagnetic nanostructures  

SciTech Connect

The dependence of the form of different mathematical depictions of fourfold magnetic anisotropies has been examined, using a simple macro-spin model. Strong differences in longitudinal and transverse hysteresis loops occur due to deviations from the usual phenomenological model, such as using absolute value functions. The proposed possible models can help understanding measurements on sophisticated magnetic nanosystems, like exchange bias layered structures employed in magnetic hard disk heads or magnetic nano-particles, and support the development of solutions with specific magnetization reversal behavior needed in novel magneto-electronic devices.

Ehrmann, Andrea [Niederrhein University of Applied Sciences, Faculty of Textile and Clothing Technology, 41065 Mönchengladbach (Germany); Blachowicz, Tomasz [Silesian University of Technology, Institute of Physics, Center for Science and Education, 44-100 Gliwice (Poland)

2014-08-15

277

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

E-print Network

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 � Heather Leslie � Simon Levin Managing water-use trade-offs in a semi-arid river delta to sustain multiple ecosystem

Leslie, Heather

278

Analysis on operational power and eddy current losses for applying coreless double-sided permanent magnet synchronous motor/generator to high-power flywheel energy storage system  

NASA Astrophysics Data System (ADS)

This paper deals with analytical approach of operational power defined as load power and rotor loss represented as eddy current loss for applying a permanent magnet (PM) synchronous motor/generator to the high-power flywheel energy storage system. The used model is composed of a double-sided Halbach magnetized PM rotor and coreless three-phase winding stator. For one such motor/generator structure, we provide the magnetic field and eddy current with space and time harmonics via magnetic vector potential in two-dimensional (2D) polar coordinate system. From these, the operational power is estimated by backelectromotive force according to the PM rotor speed, and the rotor loss is also calculated from Poynting theorem.

Jang, Seok-Myeong; Park, Ji-Hoon; You, Dae-Joon; Choi, Sang-Ho

2009-04-01

279

Magnetic Fields, Eddy Currents, and Losses, Taking the Variable Permeability into Account  

Microsoft Academic Search

An analog method is described in which a network, consisting of semiconductor diodes, capacitors, and resistors, is used to solve the partial differential equations. The magnetization curves of electrical sheet steels and solid iron are simulated to a high degree of accuracy by specially selected silicon zener diodes. With constant permeability any two-dimensional region, consisting of solid or laminated iron,

K. Oberretl

1969-01-01

280

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

E-print Network

. Specifically, the tradeoff between bearing stiffness, power consumption, and power dissipation as a function magnetic bearing FWB flywheel battery CMG control moment gyroscope ESCMG energy storage control moment, hard disk drives, high-speed centrifuges Electrical Engineer, Space Vehicles Directorate, 3550 Aberdeen

Tsiotras, Panagiotis

281

Energy loss of a charged particle in a magnetized quantum plasma  

Microsoft Academic Search

This paper investigates the stopping power of a weakly coupled magnetized plasma. The effect of the Larmor rotation of the heavy charged test particle is carefully analyzed. The dielectric formalism is employed to obtain a general expression for the stopping power. A quantum mechanical form of the random-phase approximation dielectric function is used so that an abitrary cutoff procedure is

M. Steinberg; J. Ortner

2001-01-01

282

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

PubMed

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

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

2008-01-01

283

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

SciTech Connect

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

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

1994-05-15

284

The role of multi-walled carbon nanotubes on the magnetic and reflection loss characteristics of substituted strontium ferrite nanoparticles  

NASA Astrophysics Data System (ADS)

Substituted strontium ferrite SrFe12-x(Ni0.5Mn0.5Zr)x/2O19/multi-walled carbon nanotubes (MWCNTs) composites were prepared by a sol-gel method. X-ray diffraction patterns confirm the formation of single phase ferrite nanoparticle and nanocomposites of ferrite/carbon nanotubes. Fourier transform infrared spectroscopy demonstrates the existence of functional groups on the surface of carbon nanotubes. Superconducting quantum interference device measurements showed that the values of specific saturation magnetization increases, while coercivity decreases with an increase in substitution content. Zero field cooled magnetization and field cooled magnetization curves display that with an increase in substitution content, the blocking temperature increases. Field emission scanning electron microscopy micrographs demonstrate that ferrite nanoparticles were attached on external surfaces of the carbon nanotubes. The investigation of the microwave absorption indicates that with an addition of carbon nanotubes, the real and imaginary parts of permittivity and reflection loss enhanced. It is found that with increasing the thickness of absorbers, the resonance frequencies shift to lower regime.

Ghasemi, Ali

2013-03-01

285

Plasmaspheric Mass Loss and Refilling as a Result of a Magnetic Storm  

NASA Technical Reports Server (NTRS)

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

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

2003-01-01

286

Fetal loss in mice exposed to magnetic fields during early pregnancy  

SciTech Connect

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

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

1995-12-01

287

Steinmetz law in iron-phenolformaldehyde resin soft magnetic composites  

NASA Astrophysics Data System (ADS)

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.

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

2014-03-01

288

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

SciTech Connect

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

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

289

Application of superconducting coils to the NASA prototype magnetic balance  

NASA Technical Reports Server (NTRS)

Application of superconducting coils to a general purpose magnetic balance was studied. The most suitable currently available superconducting cable for coils appears to be a bundle of many fine wires which are transposed and are mechanically confined. Sample coils were tested at central fields up to .5 Tesla, slewing rates up to 53 Tesla/ sec and frequencies up to 30 Hz. The ac losses were measured from helium boil-off and were approximately 20% higher than those calculated. Losses were dominated by hysteresis and a model for loss calculation which appears suitable for design purposes is presented along with computer listings. Combinations of two coils were also tested and interaction losses are reported. Two feasible geometries are also presented for prototype magnetic balance using superconductors.

Haldeman, C. W.; Kraemer, R. A.; Phey, S. W.; Alishahi, M. M.; Covert, E. E.

1981-01-01

290

Computational micromagnetic study of particulate media hysteresis and recording  

NASA Astrophysics Data System (ADS)

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

Seberino, Christian

2000-11-01

291

Hysteresis properties of ordinary chondrites and implications for their thermal history  

NASA Astrophysics Data System (ADS)

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.

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

2013-12-01

292

Design of hysteresis circuits using differential amplifiers  

NASA Technical Reports Server (NTRS)

Design equations for hysteresis circuit are based on the following assumptions: amplifier input impedance is larger than source impedance; amplifier output impedance is less than load impedance; and amplifier switches state when differential input voltage is approximately zero. Circuits are designed to any given specifications.

Cooke, W. A.

1971-01-01

293

Circuit increases capability of hysteresis synchronous motor  

NASA Technical Reports Server (NTRS)

Frequency and phase detector circuit enables a hysteresis synchronous motor to drive a load of given torque value at a precise speed determined by a stable reference. This technique permits driving larger torque loads with smaller motors and lower power drain.

Markowitz, I. N.

1967-01-01

294

Flexible pivot mount eliminates friction and hysteresis  

NASA Technical Reports Server (NTRS)

Flexible steel pivot mount, suspended by flat vertical beryllium copper springs, is capable of rotation, free of hysteresis and starting friction. Mount requires no lubrication, is made in varying sizes, and is driven with either dc torque motor or mechanical linkage.

Highman, C. O.

1970-01-01

295

Managing Hysteresis: Three Cornerstones to Fiscal Stability  

ERIC Educational Resources Information Center

The effects of the Great Recession of 2007-2009 continue to challenge school business officials (SBOs) and other education leaders as they strive to prepare students for the global workforce. Economists have borrowed a word from chemistry to describe this state of affairs: hysteresis--the lingering effects of the past on the present. Today's SBOs…

Weeks, Richard

2012-01-01

296

Role of hysteresis in stomatal aperture dynamics  

NASA Astrophysics Data System (ADS)

Stomata are pores responsible for gas exchange in leaves. Several experiments indicate that stomata synchronize into clusters or patches. The patches’ coordination may produce oscillations in stomatal conductance. Previous studies claim to reproduce some experimental results. However, none was able to explain the variety of behavior observed in the stomatal dynamics. Recently, Ferraz and Prado suggested a realistic geometry of vein distribution. Although it reproduces the patches, no oscillation was observed and the patches remain static. Without exploring significant details, the authors stated that hysteresis in stomatal aperture could explain several experimental features. In this paper, the hysteresis hypothesis is further explored through the concept of hysteretic operators. We have shown that the hysteresis assumption is sufficient to obtain dynamical patches and oscillations in stomatal conductance. The robustness of this hypothesis is tested by using different hysteresis operators. The model analysis reveals a dependence between the period of oscillation in stomatal conductance and the water deficit between the leaf and the environment. This underlying feature of the model might inspire further experiments to test this hypothesis.

Ramos, Antônio M. T.; Prado, Carmen P. C.

2013-01-01

297

Bipolar and unipolar tests of 1. 5m model SSC collider dipole magnets at Fermilab  

SciTech Connect

Tests have been performed at Fermilab on 1.5 m magnetic length model SSC collider dipoles using both bipolar and unipolar ramp cycles. Hysteresis energy loss due to superconductor and iron magnetization and eddy currents is measured and compared as a function of various ramp parameters. Additionally, magnetic field measurements have been performed for both unipolar and bipolar ramp cycles. Measurements such as these will be used to estimate the heat load during collider injection for the SSC High Energy Booster dipoles. 9 refs., 4 figs.

Lamm, M.J.; Ozelis, J.P.; Coulter, K.J.; Delchamps, S.; Jaffery, T.S.; Kinney, W.; Koska, W.; Strait, J.; Wake, M. (Fermi National Accelerator Lab., Batavia, IL (USA)); Fortunato, D.; Johnson, D.E. (Superconducting Super Collider Lab., Dallas, TX (USA))

1991-05-01

298

Structural, Magnetic, and Reflection Loss Characteristics of Ni/Co/Sn-Substituted Strontium Ferrite/Functionalized MWCNT Nanocomposites  

NASA Astrophysics Data System (ADS)

Ni/Co/Sn-substituted strontium ferrite [SrFe12- x (Ni0.5Co0.5Sn) x/2O19]/multiwalled carbon nanotube (MWCNT) nanocomposites were produced by assembling ferrite particles on the external surfaces of MWCNTs. Various techniques including x-ray diffraction (XRD) analysis, transmission electron microscopy, field-emission scanning electron microscopy (FE-SEM), and Fourier-transform infrared (FTIR) spectroscopy were used to demonstrate the successful attachment of ferrite particles onto the external surfaces of the MWCNTs. XRD analysis and FTIR spectroscopy confirmed the presence of strontium ferrite and carbon nanotube phases in ferrite and nanocomposite samples, respectively. FE-SEM micrographs indicated the formation of ferrite particles on the outer surfaces of MWCNTs in nanocomposite samples. Furthermore, vibrating-sample magnetometer (VSM) and reflection loss (RL) measurements were performed to assess the magnetic and microwave characteristics of the synthesized samples. VSM loops confirmed a relatively strong dependence of the saturation magnetization and coercivity on the volume percentage of MWCNTs. With the introduction of MWCNTs or an increase in the substitution, the saturation magnetization and coercivity were decreased. The RL properties of the nanocomposites were investigated in the 8 GHz to 12 GHz frequency range. The sample with 80 wt.% nanocomposite content showed a maximum RL of -35 dB at 8.3 GHz with a 4 GHz absorption bandwidth over the extended frequency range of 8 GHz to 12 GHz for absorber thickness of 1.8 mm. The RL evaluations indicated that these nanocomposites have high potential for application as wide-band electromagnetic wave absorbers at GHz frequencies.

Mousavinia, Mohammad; Ghasemi, Ali; Paimozd, Ebrahim

2014-07-01

299

Experimental evaluation of longitudinal field loss in multiply-twisted superconducting cables for a.c. use  

NASA Astrophysics Data System (ADS)

In multiply-twisted superconducting cables exposed to an external a.c. transverse magnetic field, a component of the magnetic field parallel to the strand axis brings about an additional a.c. loss (longitudinal field loss) in the strands. We have experimentally evaluated the longitudinal field loss in two types of triply-twisted superconducting cables composed of insulated strands with different diameters, by eliminating the hysteresis loss and the transverse coupling-current loss from the total loss in the strands. The evaluated longitudinal field losses were quantitatively explained by a theoretical expression obtained, to date, from consideration of the effects of the longitudinal component of the applied field on the strand. The present results suggest that the longitudinal field loss can be dominant in an a.c. magnetic field with relatively large amplitude. To minimize the total loss of the strand in the multiply-twisted cables, an optimum condition for the twist pitch of the strand was discussed.

Kanetaka, H.; Ueda, H.; Eguchi, Y.; Iwakuma, M.; Funaki, K.; Takeo, M.; Yamafuji, K.; Miyake, S.; Kumano, T.; Ichihara, M.

300

Torque meter aids study of hysteresis motor rings  

NASA Technical Reports Server (NTRS)

Torque meter, simulating hysteresis motor operation, allows rotor ring performance characteristics to be analyzed. The meter determines hysteresis motor torque and actual stresses of the ring due to its mechanical situation and rotation, aids in the study of asymmetries or defects in motor rings, and measures rotational hysteresis.

Cole, M.

1967-01-01

301

Modeling rate-dependent hysteresis in piezoelectric actuators  

Microsoft Academic Search

Hysteresis of a piezoelectric actuator is rate dependent. Most hysteresis models are based on elementary rate independent operators and are not suitable for modeling actuator behavior across a wide frequency band. This work proposes a rate dependent modified Prandtl-Ishlinskii (PI) operator to account for the hysteresis of a piezoelectric actuator at varying frequency. We have shown experimentally that the relationship

Francisco Alija Garmón; Pradeep K. Khosla; Cameron N. Riviere

2003-01-01

302

Some Properties of Factors of Specific Total Loss Components in Electrical Steel  

Microsoft Academic Search

One of the most important parameters of electrical steel sheet is specific total loss. In order to analyze the specific total loss, seven electrical steel grades were separated into three components: the hysteresis loss component and both the classical and additional eddy current loss components. Parameters used for the description of loss components in statistical loss models were analyzed and

Wojciech A. Pluta

2010-01-01

303

Wetting Hysteresis at the Molecular Scale  

NASA Technical Reports Server (NTRS)

The motion of a fluid-fluid-solid contact line on a rough surface is well known to display hysteresis in the contact angle vs. velocity relationship. In order to understand the phenomenon at a fundamental microscopic level, we have conducted molecular dynamics computer simulations of a Wilhelmy plate experiment in which a solid surface is dipped into a liquid bath, and the force-velocity characteristics are measured. We directly observe a systematic variation of force and contact angle with velocity, which is single-valued for the case of an atomically smooth solid surface. In the microscopically rough case, however, we find (as intuitively expected) an open hysteresis loop. Further characterization of the interface dynamics is in progress.

Jin, Wei; Koplik, Joel; Banavar, Jayanth R.

1996-01-01

304

Soft x-ray magneto-optic Kerr rotation and element-specific hysteresis measurement  

SciTech Connect

Soft x-ray magneto-optic Kerr rotation has been measured using a continuously tunable multilayer linear polarizer in the beam reflected form samples in applied magnetic fields. Like magnetic circular dichroism, Kerr rotation in the soft x-ray can be element - specific and much larger than in the visible spectral range when the photon energy is tuned near atomic core resonances. Thus sensitive element-specific hysteresis measurements are possible with this technique. Examples showing large Kerr rotation from an Fe film and element-specific hysteresis loops of the Fe and Cr in an Fe/Cr multilayer demonstrate these new capabilities. Some consequences of the strong anomalous dispersion near the FeL{sub 2,3} edges to the Kerr rotation are discussed.

Kortright, J.B.; Rice, M.

1996-03-01

305

A stability-based mechanism for hysteresis in the walk–trot transition in quadruped locomotion  

PubMed Central

Quadrupeds vary their gaits in accordance with their locomotion speed. Such gait transitions exhibit hysteresis. However, the underlying mechanism for this hysteresis remains largely unclear. It has been suggested that gaits correspond to attractors in their dynamics and that gait transitions are non-equilibrium phase transitions that are accompanied by a loss in stability. In the present study, we used a robotic platform to investigate the dynamic stability of gaits and to clarify the hysteresis mechanism in the walk–trot transition of quadrupeds. Specifically, we used a quadruped robot as the body mechanical model and an oscillator network for the nervous system model to emulate dynamic locomotion of a quadruped. Experiments using this robot revealed that dynamic interactions among the robot mechanical system, the oscillator network, and the environment generate walk and trot gaits depending on the locomotion speed. In addition, a walk–trot transition that exhibited hysteresis was observed when the locomotion speed was changed. We evaluated the gait changes of the robot by measuring the locomotion of dogs. Furthermore, we investigated the stability structure during the gait transition of the robot by constructing a potential function from the return map of the relative phase of the legs and clarified the physical characteristics inherent to the gait transition in terms of the dynamics. PMID:23389894

Aoi, Shinya; Katayama, Daiki; Fujiki, Soichiro; Tomita, Nozomi; Funato, Tetsuro; Yamashita, Tsuyoshi; Senda, Kei; Tsuchiya, Kazuo

2013-01-01

306

Rheological Hysteresis in Soft Glassy Materials  

NASA Astrophysics Data System (ADS)

The nonlinear rheology of a soft glassy material is captured by its constitutive relation, shear stress versus shear rate, which is most generally obtained by sweeping up or down the shear rate over a finite temporal window. For a huge amount of complex fluids, the up and down sweeps do not superimpose and define a rheological hysteresis loop. By means of extensive rheometry coupled to time-resolved velocimetry, we unravel the local scenario involved in rheological hysteresis for various types of well-studied soft materials. We introduce two observables that quantify the hysteresis in macroscopic rheology and local velocimetry, respectively, as a function of the sweep rate ?t-1. Strikingly, both observables present a robust maximum with ?t, which defines a single material-dependent time scale that grows continuously from vanishingly small values in simple yield stress fluids to large values for strongly time-dependent materials. In line with recent theoretical arguments, these experimental results hint at a universal time scale-based framework for soft glassy materials, where inhomogeneous flows characterized by shear bands and/or pluglike flow play a central role.

Divoux, Thibaut; Grenard, Vincent; Manneville, Sébastien

2013-01-01

307

Untangling perceptual memory: hysteresis and adaptation map into separate cortical networks.  

PubMed

Perception is an active inferential process in which prior knowledge is combined with sensory input, the result of which determines the contents of awareness. Accordingly, previous experience is known to help the brain "decide" what to perceive. However, a critical aspect that has not been addressed is that previous experience can exert 2 opposing effects on perception: An attractive effect, sensitizing the brain to perceive the same again (hysteresis), or a repulsive effect, making it more likely to perceive something else (adaptation). We used functional magnetic resonance imaging and modeling to elucidate how the brain entertains these 2 opposing processes, and what determines the direction of such experience-dependent perceptual effects. We found that although affecting our perception concurrently, hysteresis and adaptation map into distinct cortical networks: a widespread network of higher-order visual and fronto-parietal areas was involved in perceptual stabilization, while adaptation was confined to early visual areas. This areal and hierarchical segregation may explain how the brain maintains the balance between exploiting redundancies and staying sensitive to new information. We provide a Bayesian model that accounts for the coexistence of hysteresis and adaptation by separating their causes into 2 distinct terms: Hysteresis alters the prior, whereas adaptation changes the sensory evidence (the likelihood function). PMID:23236204

Schwiedrzik, Caspar M; Ruff, Christian C; Lazar, Andreea; Leitner, Frauke C; Singer, Wolf; Melloni, Lucia

2014-05-01

308

Hysteresis Loop for a No-loaded, Delta-connected Transformer Model Deduced from Measurements  

NASA Astrophysics Data System (ADS)

At a transformer's steady-state condition, whereby a transformer and its load are constantly supplied by a sinusoidal source, the current-flux pair within the transformer core and its windings will cycle along a hysteresis loop. This nonlinear current-flux characteristic becomes important while at transformer gets reenergized. A remaining residual flux and the fact that a transformer is typically used up to its saturation level can lead to high-amplitude magnetizing inrush currents and associated voltage disturbances. These disturbances can be reduced by controlled transformer switching. In order to pre-evaluate the effect of a specific controlled transformer energization, pre-simulations can be applied. In that case the hysteresis loop and its saturation characteristic will become the most important model parameter. If the corresponding manufacturer specifications are not available a standard hysteresis loops can be used, but might come up with an inaccurate simulation result. Therefore, this paper analyses the measured 3-phase currents from two delta-connected power transformers by “Fourier Series” in order to deduce a single-phase hysteresis loop, which can be implemented into a typical 3-phase transformer model. Additionally, the saturation behavior of a power-transformer will be estimated and a comparison of ATP/EMTP simulations will conclude this paper.

Corrodi, Yves; Kamei, Kenji; Kohyama, Haruhiko; Ito, Hiroki

309

> 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

-CLICK HERE) eddy current losses in Soft Magnetic Composites1 2 C. Appino1 , O. Bottauscio1, Italy6 7 We compute the classical eddy current losses in Soft Magnetic Composite (SMC) materials, taking into account the eddy current8 paths appearing at the scale of the sample cross-section because of random

Paris-Sud XI, Université de

310

Hysteresis analysis of CoTi substituted M-type BaSr hexagonal ferrite Charanjeet Singh a,  

E-print Network

Hysteresis analysis of Co­Ti substituted M-type Ba­Sr hexagonal ferrite Charanjeet Singh a, , S.5Sr0.5CoxTixFe(12 - 2x)O19 ferrite have been investigated by XRD, SEM and VSM. XRD and SEM confirm M ferrites are known for their strong uniaxial magne- tocrystalline anisotropy with ease of magnetization

Koledintseva, Marina Y.

311

Hysteresis, avalanches, and disorder-induced critical scaling: A renormalization-group approach Karin Dahmen* and James P. Sethna  

E-print Network

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

Sethna, James P.

312

Investigation of scaling laws in frequency-dependent minor hysteresis loops for ferromagnetic steels  

NASA Astrophysics Data System (ADS)

Scaling laws in dynamical magnetic minor hysteresis loops have been investigated in the magnetizing frequency range of 0.05-300 Hz for various steels including Cr-Mo-V steel subjected to creep, cold rolled steels, and plastically deformed Ni. Although scaling laws in the medium magnetization range found previously fail in the high magnetization frequency regime owing to a significant contribution of eddy currents, a scaling power law of the relation between remanence and remanence work of minor loops, associated with a constant exponent of approximately 1.9, holds true in a very low magnetization regime, irrespective of magnetization frequency and investigated materials. The coefficient of the law is proportionally related to Vickers hardness over the wide frequency range. These observations demonstrate that the scaling analysis of dynamical minor loops enables us to evaluate materials degradation in a short measurement time with low measurement field and high sensitivity to defect density.

Kobayashi, S.; Tsukidate, S.; Kamada, Y.; Kikuchi, H.; Ohtani, T.

2012-01-01

313

Adsorption kinetics in the solution of a thermal hysteresis protein  

NASA Astrophysics Data System (ADS)

According to the properties of the interactions between the thermal hysteresis proteins (THPs) and an ice crystal surface in the THP solution, we present a kinetic theory of the adsorption of thermal hysteresis proteins on the ice crystal surface. The thermal hysteresis activities of the THP solutions are given. The cooperative properties in the adsorption process of the THPs on the ice crystal surface are discussed.

Li, Qianzhong; Luo, Liaofu

2000-04-01

314

The Effect of Tensile Hysteresis and Contact Resistance on the Performance of Strain-Resistant Elastic-Conductive Webbing  

PubMed Central

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

Shyr, Tien-Wei; Shie, Jing-Wen; Jhuang, Yan-Er

2011-01-01

315

Efficient modeling of vector hysteresis using a novel Hopfield neural network implementation of Stoner–Wohlfarth-like operators  

PubMed Central

Incorporation of hysteresis models in electromagnetic analysis approaches is indispensable to accurate field computation in complex magnetic media. Throughout those computations, vector nature and computational efficiency of such models become especially crucial when sophisticated geometries requiring massive sub-region discretization are involved. Recently, an efficient vector Preisach-type hysteresis model constructed from only two scalar models having orthogonally coupled elementary operators has been proposed. This paper presents a novel Hopfield neural network approach for the implementation of Stoner–Wohlfarth-like operators that could lead to a significant enhancement in the computational efficiency of the aforementioned model. Advantages of this approach stem from the non-rectangular nature of these operators that substantially minimizes the number of operators needed to achieve an accurate vector hysteresis model. Details of the proposed approach, its identification and experimental testing are presented in the paper.

Adly, Amr A.; Abd-El-Hafiz, Salwa K.

2012-01-01

316

Magnetic fluid control for viscous loss reduction of high-speed MRF brakes and clutches with well-defined fail-safe behavior  

NASA Astrophysics Data System (ADS)

No-load losses within brakes and clutches based on magnetorheological fluids are unavoidable and represent a major barrier towards their wide-spread commercial adoption. Completely torque free rotation is not yet possible due to persistent fluid contact within the shear gap. In this paper, a novel concept is presented that facilitates the controlled movement of the magnetorheological fluid from an active, torque-transmitting region into an inactive region of the shear gap. This concept enables complete decoupling of the fluid engaging surfaces such that viscous drag torque can be eliminated. In order to achieve the desired effect, motion in the magnetorheological fluid is induced by magnetic forces acting on the fluid, which requires an appropriate magnetic circuit design. In this investigation, we propose a methodology to determine suitable magnetic circuit designs with well-defined fail-safe behavior. The magnetically induced motion of magnetorheological fluids is modeled by the use of the Kelvin body force, and a multi-physics domain simulation is performed to elucidate various transitions between an engaged and disengaged operating mode. The modeling approach is validated by captured high-speed video frames which show the induced motion of the magnetorheological fluid due to the magnetic field. Finally, measurements performed with a prototype actuator prove that the induced viscous drag torque can be reduced significantly by the proposed magnetic fluid control methodology.

Güth, Dirk; Schamoni, Markus; Maas, Jürgen

2013-09-01

317

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

Microsoft Academic Search

In this paper, the authors investigate the electromagnetic properties of stacks of high temperature superconductor (HTS) coated conductors with a particular focus on calculating the total transport AC loss. The cross-section of superconducting cables and coils is often modeled as a two-dimensional stack of coated conductors, and these stacks can be used to estimate the AC loss of a practical

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

318

Friction and Adhesion Hysteresis between Surfactant Monolayers in Water  

E-print Network

Friction and Adhesion Hysteresis between Surfactant Monolayers in Water Wuge H. Briscoe Physical friction between two surfaces in adhesive contact with the loading­unloading adhesion hysteresis between them. We then examine in light of this model the observed low friction between two mica surfaces coated

Klein, Jacob

319

Circuit measures hysteresis loop areas at 30 Hz  

NASA Technical Reports Server (NTRS)

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.

Hoffman, C.; Spilo, D.

1967-01-01

320

Scaling Laws for Dynamical Hysteresis in a Multidimensional Laser System  

Microsoft Academic Search

We examine scaling laws for dynamical hysteresis in an optically bistable semiconductor laser. An analytic derivation of these laws from multidimensional laser equations is outlined and they are expected to be universal for systems that exhibit a cusp catastrophe. The scaling laws for the hysteresis loop area or width are numerically verified and experimentally measured for operation of the bistable

Angela Hohl; Rajarshi Roy; Guillermo Goldsztein; Fernando Broner; Steven H. Strogatz

1995-01-01

321

The origin of hysteresis in the flag instability  

Microsoft Academic Search

The flapping flag instability occurs when a flexible cantilevered plate is immersed in a uniform airflow. To this day, the nonlinear aspects of this aeroelastic instability are largely unknown. In particular, experiments in the literature all report a large hysteresis loop, while the bifurcation in numerical simulations is either supercritical or subcritical with a small hysteresis loop. In this paper,

Christophe Eloy; Nicolas Kofman; Lionel Schouveiler

2011-01-01

322

Generalized preisach model for hysteresis nonlinearity of piezoceramic actuators  

Microsoft Academic Search

This paper presents a new approach for modeling the hysteresis nonlinearity of a piezoceramic actuator using a modified generalized Preisach model, and the use of this model in a linearizing control scheme. The developed generalized Preisach model relaxes the congruency requirement on the hysteresis loops of a piezoceramic actuator, which must be satisfied when using the classical Preisach model. The

Ping Ge; Musa Jouaneh

1997-01-01

323

A Domain Wall Theory for Ferroelectric Hysteresis Ralph C. Smith  

E-print Network

A Domain Wall Theory for Ferroelectric Hysteresis Ralph C. Smith Center for Research in Scientific.hom@lmco.com Abstract This paper addresses the modeling of hysteresis in ferroelectric materials through consideration comparison with experimental data from a PMN­PT­BT actuator operating at a temperature within

324

A Domain Wall Theory for Ferroelectric Hysteresis Ralph C. Smith  

E-print Network

A Domain Wall Theory for Ferroelectric Hysteresis Ralph C. Smith Center for Research in Scienti c.hom@lmco.com Abstract This paper addresses the modeling of hysteresis in ferroelectric materials through consideration comparison with experimental data from a PMN-PT-BT actuator operating at a temperature within

325

Superconductor coil geometry and ac losses  

NASA Technical Reports Server (NTRS)

An empirical relation is presented which allows simple computation of volume-averaged winding fields from central fields for coils of small rectangular cross sections. This relation suggests that, in certain applications, ac-loss minimization can be accomplished by use of low winding densities, provided that hysteresis losses are independent of winding density. The ac-loss measurements on coils wound of twisted multifilamentary composite superconductors show no significant dependence on ac losses on winding density, thus permitting the use of winding density as an independent design parameter in loss minimization.

Pierce, T. V., Jr.; Zapata, R. N.

1976-01-01

326

Preisach Polarization-Electric Field Hysteresis Model with Iteration Method  

NASA Astrophysics Data System (ADS)

In this study, we introduce an iteration method for obtaining the distribution function of the Preisach polarization-electric field (P-E) hysteresis model for piezoelectric actuators. In a previously proposed method, numerous experimental hysteresis curves were indispensable for this function. On the other hand, by using the iteration method, only one major-loop experiment is sufficient. From this distribution function, any minor-loop hysteresis can be simulated by the Preisach distribution function F(i,j) with high resolution. First, we measured a hysteresis property of the polarization P versus input voltage V of the ferroelectric material. On the basis of this one hysteresis curve, the distribution function was obtained using the iteration method. Using this function, we could simulate the minor loops, and the simulation results showed good agreement with experimental data.

Ikeda, Hideyuki; Kadota, Yoichi; Morita, Takeshi

2012-09-01

327

The influence of hysteresis on the determination of the magnetocaloric effect in Gd5Si2Ge2  

NASA Astrophysics Data System (ADS)

We present a non-equilibrium Preisach-type hysteresis model based on the first order magnetocaloric material Gd5Si2Ge2. The model is developed from isofield magnetization measurements and first order reversal curves, both of which constitute a new and detailed approach to characterizing and modelling magnetocaloric materials. It is shown that the model reproduces the magnetization data, directly measured adiabatic temperature changes and provides a good description of the material behavior under application conditions. We find that the material settles in an area of metastability under continuous magnetization cycles, which effectively limits the adiabatic temperature change by the amount of thermal hysteresis present. We suggest a straightforward method for realistic estimation of the magnetocaloric effect from indirect measurements.

von Moos, L.; Bahl, C. R. H.; Nielsen, K. K.; Engelbrecht, K.

2015-01-01

328

Neural networks dynamic hysteresis model for piezoceramic actuator based on hysteresis operator of first-order differential equation  

Microsoft Academic Search

A new neural networks dynamic hysteresis model for piezoceramic actuator is proposed by combining the Preisach model with diagonal recurrent neural networks. The Preisach model is based on elementary rate-independent operators and is not suitable for modeling piezoceramic actuator across a wide frequency band because of the rate-dependent hysteresis characteristic of the piezoceramic actuator. The structure of the developed model

Xuanju Dang; Yonghong Tan

2005-01-01

329

Measurement and Modeling of Rotational Core Losses of Soft Magnetic Materials Used in Electrical Machines: A Review  

Microsoft Academic Search

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

Youguang Guo; Jian Guo Zhu; Jinjiang Zhong; Haiyan Lu; Jian Xun Jin

2008-01-01

330

A Hysteresis Model for Piezoceramic Materials  

NASA Technical Reports Server (NTRS)

This paper addresses the modeling of nonlinear constitutive relations and hysteresis inherent to piezoceramic materials at moderate to high drive levels. Such models are, necessary to realize the, full potential of the materials in high performance control applications, and a necessary prerequisite is the development of techniques which permit control implementation. The approach employed here is based on the qualification of reversible and irreversible domain wall motion in response to applied electric fields. A comparison with experimental data illustrates that because the resulting ODE model is physics-based, it can be employed for both characterization and prediction of polarization levels throughout the range of actuator operation. Finally, the ODE formulation is amenable to inversion which facilitates the development of an inverse compensator for linear control design.

Smith, Ralph C.; Ounaies, Zoubeida

1999-01-01

331

Hysteresis in forced oscillations of pendant drops  

SciTech Connect

A hysteresis phenomenon has been revealed through experiments conducted with large-amplitude forced oscillations of pendant drops in air. Under strong excitation, the frequency response of a drop forced at constant amplitude exhibits jump behavior; a larger peak response amplitude {epsilon}{sub {down_arrow}} appears at a lower frequency {omega}{sub {down_arrow}} during a downward ({down_arrow}) variation of forcing frequency than during an upward ({up_arrow}) variation, viz. {epsilon}{sub {down_arrow}}{gt}{epsilon}{sub {up_arrow}} and {omega}{sub {down_arrow}}{lt}{omega}{sub {up_arrow}}. Similar results are obtained when forcing amplitude is varied at constant frequency. This behavior is characteristic of a system with a soft nonlinearity. These findings indicate that oscillating pendant drops constitute a convenient system for studying nonlinear dynamics.

DePaoli, D.W.; Feng, J.Q.; Basaran, O.A.; Scott, T.C. [Chemical Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6224 (United States)] [Chemical Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6224 (United States)

1995-06-01

332

Contact angle hysteresis on superhydrophobic stripes  

NASA Astrophysics Data System (ADS)

We study experimentally and discuss quantitatively the contact angle hysteresis on striped superhydrophobic surfaces as a function of a solid fraction, ?S. It is shown that the receding regime is determined by a longitudinal sliding motion of the deformed contact line. Despite an anisotropy of the texture the receding contact angle remains isotropic, i.e., is practically the same in the longitudinal and transverse directions. The cosine of the receding angle grows nonlinearly with ?S. To interpret this we develop a theoretical model, which shows that the value of the receding angle depends both on weak defects at smooth solid areas and on the strong defects due to the elastic energy of the deformed contact line, which scales as ? _S^2 ln ? _S. The advancing contact angle was found to be anisotropic, except in a dilute regime, and its value is shown to be determined by the rolling motion of the drop. The cosine of the longitudinal advancing angle depends linearly on ?S, but a satisfactory fit to the data can only be provided if we generalize the Cassie equation to account for weak defects. The cosine of the transverse advancing angle is much smaller and is maximized at ?S ? 0.5. An explanation of its value can be obtained if we invoke an additional energy due to strong defects in this direction, which is shown to be caused by the adhesion of the drop on solid sectors and is proportional to ? _S^2. Finally, the contact angle hysteresis is found to be quite large and generally anisotropic, but it becomes isotropic when ?S ? 0.2.

Dubov, Alexander L.; Mourran, Ahmed; Möller, Martin; Vinogradova, Olga I.

2014-08-01

333

Contact angle hysteresis on superhydrophobic stripes.  

PubMed

We study experimentally and discuss quantitatively the contact angle hysteresis on striped superhydrophobic surfaces as a function of a solid fraction, ?S. It is shown that the receding regime is determined by a longitudinal sliding motion of the deformed contact line. Despite an anisotropy of the texture the receding contact angle remains isotropic, i.e., is practically the same in the longitudinal and transverse directions. The cosine of the receding angle grows nonlinearly with ?S. To interpret this we develop a theoretical model, which shows that the value of the receding angle depends both on weak defects at smooth solid areas and on the strong defects due to the elastic energy of the deformed contact line, which scales as ?S(2)ln?S. The advancing contact angle was found to be anisotropic, except in a dilute regime, and its value is shown to be determined by the rolling motion of the drop. The cosine of the longitudinal advancing angle depends linearly on ?S, but a satisfactory fit to the data can only be provided if we generalize the Cassie equation to account for weak defects. The cosine of the transverse advancing angle is much smaller and is maximized at ?S ? 0.5. An explanation of its value can be obtained if we invoke an additional energy due to strong defects in this direction, which is shown to be caused by the adhesion of the drop on solid sectors and is proportional to ?S(2). Finally, the contact angle hysteresis is found to be quite large and generally anisotropic, but it becomes isotropic when ?S ? 0.2. PMID:25149809

Dubov, Alexander L; Mourran, Ahmed; Möller, Martin; Vinogradova, Olga I

2014-08-21

334

Ripple field losses in direct current biased superconductors: Simulations and comparison with measurements  

NASA Astrophysics Data System (ADS)

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.

Lahtinen, Valtteri; Pardo, Enric; Šouc, Ján; Solovyov, Mykola; Stenvall, Antti

2014-03-01

335

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

PubMed

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

Shishkovsky, Igor; Morozov, Yury

2013-02-01

336

Understanding the Hysteresis Loop Conundrum in Pharmacokinetic / Pharmacodynamic Relationships  

PubMed Central

Hysteresis loops are phenomena that sometimes are encountered in the analysis of pharmacokinetic and pharmacodynamic relationships spanning from pre-clinical to clinical studies. When hysteresis occurs it provides insight into the complexity of drug action and disposition that can be encountered. Hysteresis loops suggest that the relationship between drug concentration and the effect being measured is not a simple direct relationship, but may have an inherent time delay and disequilibrium, which may be the result of metabolites, the consequence of changes in pharmacodynamics or the use of a non-specific assay or may involve an indirect relationship. Counter-clockwise hysteresis has been generally defined as the process in which effect can increase with time for a given drug concentration, while in the case of clockwise hysteresis the measured effect decreases with time for a given drug concentration. Hysteresis loops can occur as a consequence of a number of different pharmacokinetic and pharmacodynamic mechanisms including tolerance, distributional delay, feedback regulation, input and output rate changes, agonistic or antagonistic active metabolites, uptake into active site, slow receptor kinetics, delayed or modified activity, time-dependent protein binding and the use of racemic drugs among other factors. In this review, each of these various causes of hysteresis loops are discussed, with incorporation of relevant examples of drugs demonstrating these relationships for illustrative purposes. Furthermore, the effect that pharmaceutical formulation has on the occurrence and potential change in direction of the hysteresis loop, and the major pharmacokinetic / pharmacodynamic modeling approaches utilized to collapse and model hysteresis are detailed. PMID:24735761

Louizos, Christopher; Yáñez, Jaime A.; Forrest, Laird; Davies, Neal M.

2015-01-01

337

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)

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.

Nanouris, N.; Kalimeris, A.; Antonopoulou, E.; Rovithis-Livaniou, H.

2011-11-01

338

Static measurements of slender delta wing rolling moment hysteresis  

NASA Technical Reports Server (NTRS)

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.

Katz, Joseph; Levin, Daniel

1991-01-01

339

Adaptive feed-forward hysteresis compensation for piezoelectric actuators  

NASA Astrophysics Data System (ADS)

Piezoelectric actuators are often employed for high-resolution positioning tasks. Hysteresis and creep nonlinearities inherent in such actuators deteriorate positioning accuracy. An online adaptive nonlinear hysteresis compensation scheme for the case of symmetric hysteretic responses and certain periodic reference trajectories is presented. The method has low complexity and is well suited for real-time implementation. Experimental results are presented in order to verify the method, and it is seen that the error due to hysteresis is reduced by more than 90% compared to when assuming a linear response.

Eielsen, Arnfinn Aas; Gravdahl, Jan Tommy; Pettersen, Kristin Y.

2012-08-01

340

Electrical and Magnetic Study of Bulk Amorphous Alloys Fe-Al-Ga-P-B-Si  

NASA Astrophysics Data System (ADS)

Bulk amorphous alloys Fe-Al-Ga-P-B-Si were prepared by a single-roller melt spinning method. Electrical resistivity of alloys is of the order of 200 cm. The structural and magnetic components of resistivity are separated. The anomalous rise of resistivity during crystallization observed in Fe-Al-Ga-P-B-Si alloys with higher Si content is related to the precipitation of high resistivity crystalline phases. The strong exchange interaction is revealed by the Curie temperatures reaching 640 K. The room temperature values of the effective magnetic moment vary between 1.79 and 1.83 B depending weakly on alloy composition. The AC hysteresis loops were recorded in magnetic fields up to 50 A/cm and frequencies between 10 Hz to 400 kHz. The frequency variation of power losses shows that high resistivity reduces eddy current losses.

P?ka?a, K.; Ja?kiewicz, P.; Grabski, J.; Latuch, J.; P?ka?a, M.

2002-02-01

341

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

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

342

Energy Loss of Solar p Modes due to the Excitation of Magnetic Sausage Tube Waves: Importance of Coupling the Upper Atmosphere  

NASA Astrophysics Data System (ADS)

We consider damping and absorption of solar p modes due to their energy loss to magnetic tube waves that can freely carry energy out of the acoustic cavity. The coupling of p modes and sausage tube waves is studied in a model atmosphere composed of a polytropic interior above which lies an isothermal upper atmosphere. The sausage tube waves, excited by p modes, propagate along a magnetic fibril which is assumed to be a vertically aligned, stratified, thin magnetic flux tube. The deficit of p-mode energy is quantified through the damping rate, ?, and absorption coefficient, ?. The variation of ? and ? as a function of frequency and the tube's plasma properties is studied in detail. Previous similar studies have considered only a subphotospheric layer, modeled as a polytrope that has been truncated at the photosphere. Such studies have found that the resulting energy loss by the p modes is very sensitive to the upper boundary condition, which, due to the lack of an upper atmosphere, have been imposed in a somewhat ad hoc manner. The model presented here avoids such problems by using an isothermal layer to model the overlying atmosphere (chromosphere, and, consequently, allows us to analyze the propagation of p-mode-driven sausage waves above the photosphere. In this paper, we restrict our attention to frequencies below the acoustic cut off frequency. We demonstrate the importance of coupling all waves (acoustic, magnetic) in the subsurface solar atmosphere with the overlying atmosphere in order to accurately model the interaction of solar f and p modes with sausage tube waves. In calculating the absorption and damping of p modes, we find that for low frequencies, below ?3.5 mHz, the isothermal atmosphere, for the two-region model, behaves like a stress-free boundary condition applied at the interface (z = -z 0).

Gascoyne, A.; Jain, R.; Hindman, B. W.

2014-07-01

343

The heating effect of iron-cobalt magnetic nanofluids in an alternating magnetic field: application in magnetic hyperthermia treatment  

NASA Astrophysics Data System (ADS)

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.

Shokuhfar, Ali; Seyyed Afghahi, Seyyed Salman

2013-12-01

344

Engineering double-shifted hysteresis loops in Co/IrMn/Cu/Co films  

NASA Astrophysics Data System (ADS)

Co(3 nm)/IrMn(15 nm)/Cu(dCu)/Co(7 nm) films were subjected to magnetic annealing where its temperature and duration as well as the direction and amplitude of the applied field were varied. We demonstrate that the exchange-bias field magnitude and sign of the subloop of the bottom-pinned Co layer can be tailored in a controlled manner allowing the whole hysteresis loop to be tuned from a double negatively/negatively shifted to a double negatively/positively shifted with the shifts of the subloops in antiphase.

Cichelero, R.; Pereira, L. G.; Dias, T.; Schmidt, J. E.; Deranlot, C.; Petroff, F.; Geshev, J.

2009-09-01

345

A new approach to the characterization of reverse osmosis membrane by dynamic hysteresis  

Microsoft Academic Search

Physical aspects of dynamic hysteresis for characterizing reverse osmosis (RO) membranes have been investigated. Dynamic hysteresis was used as a parameter of showing physical surface characteristics of RO membranes. Automated microbalance was utilized to determine dynamic hysteresis based on the Wilhelmy plate method. Dynamic hysteresis determined with non-polar liquid was related to physical surface characteristics including surface roughness and heterogeneity

Eunsu Lee; Sangyoup Lee; Seungkwan Hong

2010-01-01

346

The hysteresis motor-advances whick permit economical fractional horsepower ratings  

Microsoft Academic Search

The theory of the development of torque in a hysteresis motor is analyzed from both the hysteresis lag angle and total loop energy points of view. A new development, comprising the use of a closed slot stator in co-operation with a hysteresis rotor, which permits building hysteresis motors of high power output at high efficiency is explained qualitatively and supplemented

Herbert C. Roters

1947-01-01

347

Low-Hysteresis Flow-Through Wind-Tunnel Balance  

NASA Technical Reports Server (NTRS)

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.

Kunz, N.; Luna, P. M.; Roberts, A. C.; Smith, R. C.; Horne, W. L.; Smith, K. M.

1992-01-01

348

On the question of hysteresis in Hall magnetohydrodynamic reconnection  

SciTech Connect

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.

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

349

Titration and hysteresis in epigenetic chromatin silencing  

NASA Astrophysics Data System (ADS)

Epigenetic mechanisms of silencing via heritable chromatin modifications play a major role in gene regulation and cell fate specification. We consider a model of epigenetic chromatin silencing in budding yeast and study the bifurcation diagram and characterize the bistable and the monostable regimes. The main focus of this paper is to examine how the perturbations altering the activity of histone modifying enzymes affect the epigenetic states. We analyze the implications of having the total number of silencing proteins, given by the sum of proteins bound to the nucleosomes and the ones available in the ambient, to be constant. This constraint couples different regions of chromatin through the shared reservoir of ambient silencing proteins. We show that the response of the system to perturbations depends dramatically on the titration effect caused by the above constraint. In particular, for a certain range of overall abundance of silencing proteins, the hysteresis loop changes qualitatively with certain jump replaced by continuous merger of different states. In addition, we find a nonmonotonic dependence of gene expression on the rate of histone deacetylation activity of Sir2. We discuss how these qualitative predictions of our model could be compared with experimental studies of the yeast system under anti-silencing drugs.

Dayarian, Adel; Sengupta, Anirvan M.

2013-06-01

350

Hysteresis in the Central African Rainforest  

NASA Astrophysics Data System (ADS)

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.

Pietsch, Stephan Alexander; Elias Bednar, Johannes; Gautam, Sishir; Petritsch, Richard; Schier, Franziska; Stanzl, Patrick

2014-05-01

351

Hysteresis as an implicit prior in tactile spatial decision making.  

PubMed

Perceptual decisions not only depend on the incoming information from sensory systems but constitute a combination of current sensory evidence and internally accumulated information from past encounters. Although recent evidence emphasizes the fundamental role of prior knowledge for perceptual decision making, only few studies have quantified the relevance of such priors on perceptual decisions and examined their interplay with other decision-relevant factors, such as the stimulus properties. In the present study we asked whether hysteresis, describing the stability of a percept despite a change in stimulus property and known to occur at perceptual thresholds, also acts as a form of an implicit prior in tactile spatial decision making, supporting the stability of a decision across successively presented random stimuli (i.e., decision hysteresis). We applied a variant of the classical 2-point discrimination task and found that hysteresis influenced perceptual decision making: Participants were more likely to decide 'same' rather than 'different' on successively presented pin distances. In a direct comparison between the influence of applied pin distances (explicit stimulus property) and hysteresis, we found that on average, stimulus property explained significantly more variance of participants' decisions than hysteresis. However, when focusing on pin distances at threshold, we found a trend for hysteresis to explain more variance. Furthermore, the less variance was explained by the pin distance on a given decision, the more variance was explained by hysteresis, and vice versa. Our findings suggest that hysteresis acts as an implicit prior in tactile spatial decision making that becomes increasingly important when explicit stimulus properties provide decreasing evidence. PMID:24587045

Thiel, Sabrina D; Bitzer, Sebastian; Nierhaus, Till; Kalberlah, Christian; Preusser, Sven; Neumann, Jane; Nikulin, Vadim V; van der Meer, Elke; Villringer, Arno; Pleger, Burkhard

2014-01-01

352

Stabilization of supercooled fluids by thermal hysteresis proteins.  

PubMed

It has been reported that thermal hysteresis proteins found in many cold-hardy, freeze-avoiding arthropods stabilize their supercooled body fluids. We give evidence that fish antifreeze proteins, which also produce thermal hysteresis, bind to and reduce the efficiency of heterogenous nucleation sites, rather than binding to embryonic ice nuclei. We discuss both possible mechanisms for stabilization of supercooled body fluids and also describe a new method for measuring and defining the supercooling point of small volumes of liquid. PMID:7612853

Wilson, P W; Leader, J P

1995-05-01

353

Asymmetric Hysteresis Loops and the Pyroelectric Effect in Triglycine Sulfate  

Microsoft Academic Search

Dynamic pyroelectric techniques have been used to study single crystal triglycine sulfate hysteresis loops at room temperature. An apparent polarization bias is observed and is similar to that reported earlier for BaTiO3. The apparent polarization bias can be shifted with the application of a dc electric field. When precautions are taken to eliminate electrode-edge effects, the pyroelectric hysteresis loops are

Albert Savage; Robert C. Miller

1959-01-01

354

Aileron roll hysteresis effects on entry of space shuttle orbiter  

NASA Technical Reports Server (NTRS)

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.

Powell, R. W.

1977-01-01

355

A new model of hysteresis in piezoelectric actuators  

Microsoft Academic Search

Piezoelectric actuators (PEAs) are widely used in micromanipulations for their high-accuracy positioning, fast response, and high mechanical stiffness. However, dynamic nonlinearity introduced by hysteresis phenomena causes system instability and positioning errors. In this paper, a new simple physical model is proposed to characterize the symmetric and asymmetric rate-dependent hysteresis. A nonlinear spring (or capacitor) element is incorporated into a second-order

Issam M. Bahadur; James K. Mills

2011-01-01

356

Modeling and control of hysteresis in magnetostrictive actuators  

Microsoft Academic Search

Abstract A novel dynamic model is proposed for the hysteresis in magnetostrictive actuators by coupling a Preisach operator to an ordinary di0erential equation, and a parameter identi2cation method is described. An e3cient inversion algorithm for a class of Preisach operators with piecewise uniform density functions is then introduced, based upon which an inverse control scheme for the dynamic hysteresis model

Xiaobo Tan; John S. Baras

2004-01-01

357

The shape, energy, eddy current loss, and relaxation damping of magnetic domain walls in glassy iron wire  

Microsoft Academic Search

A magnetostatic model is developed for extended domain boundaries of the type observed by O'Handley [1] separating opposed axially magnetized sections of glassy iron wire. The domains in any circular wire cross section are separated by a boundary that has the minimum length consistent with their areas, and the distribution of polarization over the wire length is such as to

JOHN E. L. BISHOP

1977-01-01

358

Lodestone: Nature's own permanent magnet  

NASA Technical Reports Server (NTRS)

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.

Wasilewski, P.

1976-01-01

359

Adhesion hysteresis and friction at nanometer and micrometer lengths  

SciTech Connect

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.

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

360

Perceptual hysteresis in the judgment of auditory pitch shift.  

PubMed

Perceptual hysteresis can be defined as the enduring influence of the recent past on current perception. Here, hysteresis was investigated in a basic auditory task: pitch comparisons between successive tones. On each trial, listeners were presented with pairs of tones and asked to report the direction of subjective pitch shift, as either "up" or "down." All tones were complexes known as Shepard tones (Shepard, 1964), which comprise several frequency components at octave multiples of a base frequency. The results showed that perceptual judgments were determined both by stimulus-related factors (the interval ratio between the base frequencies within a pair) and by recent context (the intervals in the two previous trials). When tones were presented in ordered sequences, for which the frequency interval between tones was varied in a progressive manner, strong hysteresis was found. In particular, ambiguous stimuli that led to equal probabilities of "up" and "down" responses within a randomized context were almost fully determined within an ordered context. Moreover, hysteresis did not act on the direction of the reported pitch shift, but rather on the perceptual representation of each tone. Thus, hysteresis could be observed within sequences in which listeners varied between "up" and "down" responses, enabling us to largely rule out confounds related to response bias. The strength of the perceptual hysteresis observed suggests that the ongoing context may have a substantial influence on fundamental aspects of auditory perception, such as how we perceive the changes in pitch between successive sounds. PMID:24874257

Chambers, Claire; Pressnitzer, Daniel

2014-07-01

361

Models of radio galaxies with tangled magnetic fields. I - Calculation of magnetic field transport, Stokes parameters and synchrotron losses. II - Numerical simulations and their interpretation  

Microsoft Academic Search

Consideration is given to numerical simulations of radio sources in which a randomly tangled magnetic field is introduced in the jet and is convected passively with the fluid flow. The intrinsic polarization distribution of the source model is determined by the distortion of the field by compression and shear in the flow. Results are presented from calculations of the distortion

A. P. Matthews; P. A. G. Scheuer

1990-01-01

362

On the Mechanism of Energetic Electron Losses from the Magnetic Mirror Trap at the ECR Discharge Startup  

NASA Astrophysics Data System (ADS)

In this work, we discuss experimental evidence for the existence of an effective mechanism of energetic-electron losses at the initial stage of the discharge during electron cyclotron resonance (of the ECR discharge) when the electron scattering to the loss cone is caused by the development of the electron cyclotron instabilities of a strongly nonequilibrium plasma. The spectral composition of the transient pulses of electromagnetic radiation is studied in a wide frequency range at the initial stage of the ECR discharge, when the hot-particle density exceeds that of cold particles. The observed electromagnetic-radiation bursts and synchronous energetic-electron precipitation from the trap can be related to the development of a cyclotron instability of the fast extraordinary wave in the rarefied plasma.

Viktorov, M. E.; Golubev, S. V.; Gospodchikov, E. D.; Izotov, I. V.; Mansfeld, D. A.; Shalashov, A. G.

2013-09-01

363

Analysis of effective resistance and eddy-current losses in multiturn winding of high-frequency magnetic components  

Microsoft Academic Search

This paper develops a numerical model for calculation of eddy-current losses in a multiturn winding of a high-frequency transformer. The model assumes periodic arrangement of conductors, and uses the repeat elementary cell concept. The paper proposes analytical expressions and graphic dependences to determine effective frequency-dependent resistance of the winding. It computes the leakage field in the transformer window, taking into

Alexander D. Podoltsev; Irina N. Kucheryavaya; Boris B. Lebedev

2003-01-01

364

Alternating current losses in superconducting coils  

NASA Technical Reports Server (NTRS)

Report examines relationship between coil loss and frequency and heat loss in coil as a function of the magnetic field H. Information is of value to manufacturers of superconducting magnets, motors and generators.

Wipf, S. L.; Guderjahn, C. A.

1972-01-01

365

Microstructure and magnetic properties of Sn-substituted MnZn ferrites  

NASA Astrophysics Data System (ADS)

Sn-substituted MnZn ferrites were prepared by conventional oxide ceramic process. The influences of Sn substitution on microstructure and magnetic properties of MnZn ferrites were investigated. The results indicated that with increase of Sn substitute concentration, the diffraction peaks shifted slightly towards the lower angles and the lattice parameter ( a) increased. And at room temperature, the bulk density ( dm), initial permeability ( ?i), saturation magnetic induction ( Bs) and electrical resistivity ( ?) of Sn-substituted MnZn ferrites all increased initially and then decreased with the further increase of Sn substitute concentration, while the power losses decreased first and then increased subsequently. Meanwhile, the temperature of secondary maximum peak of ?i- T curve and the minimum losses moved to lower temperature while the Sn substitute concentration increased. When the content of Sn substitution was 0.3 mol%, at room temperature, the initial permeability, saturation magnetic induction, density and electrical resistivity reached their maxima, while the hysteresis loss ( Ph), eddy current loss ( Pe) and total losses ( Pcv) achieved their minima. The Ph˜ T and ?i- T curves varied contrarily, and due to the contribution of extra eddy current loss ( Pe,exc) that was proportional to Ph, the Pe- T curve did not agree with its classical expression. Finally, MnZn ferrite substituted with 0.3 mol% SnO 2 shows the highest initial permeability (3894) and lowest losses (303 kW/m 3) at room temperature.

Xu, Zhiyong; Yu, Zhong; Sun, Ke; Li, Lezhong; Ji, Haining; Lan, Zhongwen

2009-09-01

366

Journal of Magnetism and Magnetic Materials 316 (2007) e31e34 Cross-over from coherent rotation to inhomogeneous reversal  

E-print Network

hysteresis loops (in-plane magnetization components parallel and perpendicular to the applied field) recorded-axis hysteresis loops as a function of wires thickness. In detail, the analysis of the saturation field vs. wires has become a crucial key as it can affect the magnetization reversal processes and the domain

Adeyeye, Adekunle

367

Alternating magnetic field energy absorption in the dispersion of iron oxide nanoparticles in a viscous medium  

NASA Astrophysics Data System (ADS)

Magnetic iron oxide nanoparticles were obtained by a coprecipitation method in a controlled growth process leading to the formation of uniform highly crystalline nanoparticles with average size of 13 nm, which corresponds to the superparamagnetic state. Nanoparticles obtained are a mixture of single-phase nanoparticles of magnetite and maghemite as well as nanoparticles of non-stoichiometric magnetite. The subsequent annealing of nanoparticles at 300 °C in air during 6 h leads to the full transformation to maghemite. It results in reduced value of the saturation magnetization (from 56 emu g-1 to 48 emu g-1) but does not affect the heating ability of nanoparticles. A 2-7 wt% dispersion of as-prepared and annealed nanoparticles in glycerol provides high heating rate in alternating magnetic fields allowed for application in magnetic hyperthermia; however the value of specific loss power does not exceed 30 W g-1. This feature of heat output is explained by the combined effect of magnetic interparticle interactions and the properties of the carrier medium. Nanoparticles coalesce during the synthesis and form aggregates showing ferromagnetic-like behavior with magnetization hysteresis, distinct sextets on Mössbauer spectrum, blocking temperature well about room temperature, which accounts for the higher energy barrier for magnetization reversal. At the same time, low specific heat capacity of glycerol intensifies heat transfer in the magnetic dispersion. However, high viscosity of glycerol limits the specific loss power value, since predominantly the Neel relaxation accounts for the absorption of AC magnetic field energy.

Smolkova, Ilona S.; Kazantseva, Natalia E.; Babayan, Vladimir; Smolka, Petr; Parmar, Harshida; Vilcakova, Jarmila; Schneeweiss, Oldrich; Pizurova, Nadezda

2015-01-01

368

Factors affecting core losses in oriented electrical steels at moderate inductions (invited)  

Microsoft Academic Search

The effects of sheet thickness, orientation, grain size, silicon content, stress, domain control, and surface condition on core losses of both regular grain oriented (RGO) and high permeability (HGO) silicon steels in the induction range of 1.0 to 1.5 T were reviewed. Where possible, the effects of these factors were discussed in terms of total loss PT hysteresis loss Ph

K. Foster; M. F. Littmann

1985-01-01

369

Free-piston Stirling engine experimental program: Part 2. An evaluation of loss mechanisms  

Microsoft Academic Search

A series of experiments is described in which measurements were taken on a free-piston Stirling engine to isolate effects believed to degrade engine performance. The effects examined were: compression-space hysteresis, regenerator losses, displacer seal clearance loss, and displacer appendix gap loss. The experimental data from these experiments are given and represent a valuable resource for validation of Stirling engine analysis

T. Moynihan; R. Berggren; G. Dochat

1983-01-01

370

PREFACE: International Workshop on Multi-Rate Processes and Hysteresis  

NASA Astrophysics Data System (ADS)

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

Mortell, Michael P.; O'Malley, Robert E.; Pokrovskii, Alexei; Rachinskii, Dmitrii; Sobolev, Vladimir A.

2008-07-01

371

Magnetic power losses in [(Fe1-xCox)75B20Si5]93Nb4Y3 (x = 0, 0.2, 0.4) bulk metallic glasses  

NASA Astrophysics Data System (ADS)

Magnetic power losses of [(Fe1-xCox)75B20Si5]93Nb4Y3 (x = 0, 0.2, 0.4) metallic glasses have been investigated. Bulk samples were prepared by water-cooled Cu-mold injection casting technique with shapes of cylinders (0.8 mm diameter and 30 mm length) and toroids (10 mm external diameter and 0.5 mm thickness). Ribbons prepared by the melt- spinning technique were also analyzed. Glassy structures were confirmed by the presence of a main halo in XRD and by crystallization signal in DSC. Power losses were studied with a digital wattmeter over a range of frequencies from 1 to 400 Hz at selected peak inductions. Ribbons show smaller losses than bulk samples, presenting 24.5 J/m3 at 50 Hz and 0.65 T peak induction. It was observed that the Co addition reduces significantly the power losses. A separation theory was applied in order to explain the square root behavior of the measured power losses as a function of frequency and the results are in good agreement with the experimental data. The magnetic data were used to identify the presence of crystalline inclusions in the magnetic bulk metallic glasses. The effect of sample shape and composition on magnetic properties will be discussed.

Piccin, R.; Tiberto, P.; Chiriac, H.; Baricco, M.

2009-01-01

372

Magnetism  

NSDL National Science Digital Library

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

Team, University C.

2007-12-12

373

Saturation overshoot and hysteresis for twophase flow in porous media  

NASA Astrophysics Data System (ADS)

Saturation overshoot and hysteresis for two phase flow in porous media are briefly reviewed. Old and new challenges are discussed. It is widely accepted that the traditional Richards model for twophase flow in porous media does not support non-monotone travelling wave solutions for the saturation profile. As a concequence various extensions and generalizations have been recently discussed. The review highlights different limits within the traditional theory. It emphasizes the relevance of hysteresis in the Buckley-Leverett limit with jump-type hysteresis in the relative permeabilities. Reviewing the situation it emerges that the traditional theory may have been abandoned prematurely because of its inability to predict saturation overshoot in the Richards limit.

Hilfer, R.; Steinle, R.

2014-10-01

374

Sinusoidal input describing function for hysteresis followed by elementary backlash  

NASA Technical Reports Server (NTRS)

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.

Ringland, R. F.

1976-01-01

375

Persistent hysteresis in graphene-mica van der Waals heterostructures  

NASA Astrophysics Data System (ADS)

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.

Mohrmann, Jens; Watanabe, Kenji; Taniguchi, Takashi; Danneau, Romain

2015-01-01

376

Hysteresis and interfacial energies in smooth-walled microfluidic channels  

NASA Astrophysics Data System (ADS)

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 three-dimensional interfaces under imbibition and drainage, we demonstrate an accurate balance between mechanical work and surface free energy that was evaluated using measured advancing and receding contact angles. The closed-loop mechanical work per surface water molecule is 95 kJ/mol, which is consistent with physisorption. Therefore, the hysteresis in the Pc-Sw relationship for a single pore throat is defined by advancing and receding contact angles that are controlled by dissipative surface adsorption chemistry.

Liu, Yihong; Nolte, D. D.; Pyrak-Nolte, L. J.

2011-01-01

377

Contact Hysteresis and Friction of Alkanethiol SAMs on Au  

SciTech Connect

Nanoindentation has been combhed with nanometer-scale friction measurements to identi~ dissipative mechanisms responsible for friction in hexadecanethiol self-assembled monolayer on Au. We have demonstrated that friction is primarily due to viscoelastic relaxations within the films, which give rise to contact hysteresis when deformation rates are within the ranges of 5 and 200 k. We observe that this contact hysteresis increases with exposure to air such that the friction coefficient increases from 0.004 to 0.075 when films are exposed to air for 40 days. Both hysteresis and friction increase with probe speed, and we present a model of friction that characterizes this speed dependence and which also predicts a linear dependence of friction on normal force in thin organic films. Finally, we identify several short-term wear regimes and identify that wear changes dramatically when fdms age.

Houston, J.E.; Kiely, J.D.

1998-10-14

378

Dynamic Hysteresis in Cyclic Deformation of Crystalline Solids  

NASA Astrophysics Data System (ADS)

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.

Laurson, Lasse; Alava, Mikko J.

2012-10-01

379

Dynamic hysteresis in cyclic deformation of crystalline solids.  

PubMed

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

Laurson, Lasse; Alava, Mikko J

2012-10-12

380

Modeling of Switching and Hysteresis in Molecular Transport  

NASA Technical Reports Server (NTRS)

The conventional way of modeling current transport in two and three terminal molecular devices could be inadequate for certain cases involving switching and hysteresis. Here we present an alternate approach. Contrary to the regular way where applied bias directly modulates the conducting energy levels of the molecule, our method introduces a nonlinear potential energy surface varying with the applied bias as a control parameter. A time-dynamics is also introduced properly accounting for switching and hysteresis behavior. Although the model is phenomenological at this stage, we believe any detailed model would contain similar descriptions at its core.

Samanta, Manoj P.; Partridge, Harry (Technical Monitor)

2002-01-01

381

Large-scale separation and hysteresis in cascades  

NASA Technical Reports Server (NTRS)

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.

Rothmayer, A. P.; Smith, F. T.

1985-01-01

382

Memory loss  

MedlinePLUS

Forgetfulness; Amnesia; Impaired memory; Loss of memory; Amnestic syndrome; Dementia - memory loss ... or severe illness, including brain surgery Transient global amnesia (sudden, temporary loss of memory) of unclear cause ...

383

Torque from hysteresis machines with type-II superconducting segmented rotors  

NASA Astrophysics Data System (ADS)

Electrical machines having rotors constructed from different numbers of type-II superconducting segments have been modelled numerically. The hollow cylindrical rotors are subjected to a rotating applied field that induces currents in the superconducting pieces and the resulting torque is evaluated. The mathematical technique used is based on the critical state model and solves for the current and field distributions within the superconducting pieces using the finite element method. In a two-pole rotating field, a rotor made from two half-ringed pieces is found to behave like a reluctance machine, having a larger peak torque than hysteresis type rotors constructed from other numbers of segments. In general, splitting the rotor up into more segments is advantageous when the flux penetration is small since this increases the hysteresis loss and equivalently, the torque. The modelling results indicate the number of segments which will result in the largest torque for a given rotor size, material critical current density and applied field amplitude. Such information is valuable when considering the performance optimisation of such machines.

Barnes, G. J.; McCulloch, M. D.; Dew-Hughes, D.

2000-04-01

384

Magnetization rotation in spin-valve multilayers  

Microsoft Academic Search

The magnetic hysteresis associated with the magnetization reversal of the free layer in a spin valve is analysed. A model is proposed which assumes a single-domain behavior of the free layer, and a fixed magnetization of the pinned layer. The model is then developed in the framework of the Stoner—Wohlfarth coherent rotation model, where geometrical solutions are obtained by the

M. Labrune; J. C. S. Kools; A. Thiaville

1997-01-01

385

Magnetism  

NSDL National Science Digital Library

This radio broadcast discusses the history of magnetism from the time of its discovery by an apocryphal Greek sheperd until the late 16th century and the work of William Gilbert. There is also discussion of who pioneered the study of magnetism, what theories they constructed from its curious abilities, and how the power of the magnet was brought out of the realm of magic and into the service of science. The broadcast concludes with a discussion of why magnetism is still mysterious and how the modern search for the single magnetic pole, or magnetic monopole, could provide a fundamental unit of magnetism, essential for ultimate explanation. The broadcast is 41 minutes and 45 seconds in length.

386

Quantification of Hysteresis and Nonlinear Effects on the Frequency Response of Ferroelectric and  

E-print Network

. Introduction Ferromagnetic and ferroelectric materials are increasingly considered for use as actuators, charge or current controlled amplifiers can minimize observed hysteresis in ferroelectric actuators [15Quantification of Hysteresis and Nonlinear Effects on the Frequency Response of Ferroelectric

387

A Homogenized Energy Model for Hysteresis in Ferroelectric Materials: General Density Formulation  

E-print Network

of ferroelectric compounds as actuators and sensors in high performance control applications has burgeonedA Homogenized Energy Model for Hysteresis in Ferroelectric Materials: General Density Formulation hysteresis and constitutive nonlinearities in ferroelectric compounds based on energy analysis at mesoscopic

388

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

389

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

390

Dislocation movement and hysteresis in Maraging blades  

NASA Astrophysics Data System (ADS)

All seismic isolation systems developed for gravitational-wave interferometric detectors, such as LIGO, Virgo and TAMA, make use of Maraging steel blades. The dissipation properties of these blades have been studied at low frequencies, by using a geometric anti-spring (GAS) filter, which allowed the exploration of resonant frequencies below 100 mHz. At this frequency an anomalous transfer function was observed in the GAS filter: this is one of several motivations for this work. The many unexpected effects observed and measured are explainable by the collective movement of dislocations inside the material described with the statistic of self-organised criticality. At low frequencies, below 200 mHz, the dissipation mechanism can subtract elasticity from the system even leading to sudden collapse. While Young's modulus is weaker, excess dissipation is observed. At higher frequencies the applied stress is probably too fast to allow the full growth of dislocation avalanches, and less losses are observed, thus explaining the higher Q-factor in this frequency range. The domino effect that leads to the release of entangled dislocations allows the understanding of the random walk of the Virgo and TAMA inverted pendula, the anomalous GAS filter transfer function as well as the loss of predictability of the ring-down decay in the LIGO seismic attenuation system inverted pendula.

Di Cintio, Arianna; Marchesoni, Fabio; Ascione, Maria; Bhawal, Abhik; De Salvo, Riccardo

2009-10-01

391

Magnetic behavior of nanocrystalline MnCo 2O 4 spinels  

NASA Astrophysics Data System (ADS)

A series of powders with different particle sizes of the spinel MnCo2O4 was synthesized by the Pechini method. The resulting precursor was calcined between 400 and 900C and characterized by thermogravimetric analyses (TGA), X-ray diffraction (XRD), scanning electron microscopy (SEM) and magnetization measurements. TGA analysis showed a loss of mass in the region from 200 to 650C and stability after this. XRD patterns showed an increase of the crystallite size with calcination temperature. Magnetization measurements on the sample calcined at 900C showed an unusual behavior of the hysteresis curve and irreversibility of the magnetization with field cooled (FC) and zero field cooled (ZFC) procedures. An evolution of this behavior was observed with increasing crystallite size.

Borges, F. M. M.; Melo, D. M. A.; Câmara, M. S. A.; Martinelli, A. E.; Soares, J. M.; de Araújo, J. H.; Cabral, F. A. O.

2006-07-01

392

Silica encapsulated manganese perovskite nanoparticles for magnetically induced hyperthermia without the risk of overheating.  

PubMed

Nanoparticles of manganese perovskite of the composition La(0.75)Sr(0.25)MnO(3) uniformly coated with silica were prepared by encapsulation of the magnetic cores (mean crystallite size 24 nm) using tetraethoxysilane followed by fractionation. The resulting hybrid particles form a stable suspension in an aqueous environment at physiological pH and possess a narrow hydrodynamic size distribution. Both calorimetric heating experiments and direct measurements of hysteresis loops in the alternating field revealed high specific power losses, further enhanced by the encapsulation procedure in the case of the coated particles. The corresponding results are discussed on the basis of complex characterization of the particles and especially detailed magnetic measurements. Moreover, the Curie temperature (335 K) of the selected magnetic cores resolves the risk of local overheating during hyperthermia treatment. PMID:19531865

Kaman, O; Pollert, E; Veverka, P; Veverka, M; Hadová, E; Knízek, K; Marysko, M; Kaspar, P; Klementová, M; Grünwaldová, V; Vasseur, S; Epherre, R; Mornet, S; Goglio, G; Duguet, E

2009-07-01

393

Influence of clamping plate permeability and metal screen structures on three-dimensional magnetic field and eddy current loss in end region of a turbo-generator by numerical analysis  

NASA Astrophysics Data System (ADS)

A significant problem of turbogenerators on complex end structures is overheating of local parts caused by end losses in the end region. Therefore, it is important to investigate the 3-D magnetic field and eddy current loss in the end. In end region of operating large turbogenerator at thermal power plants, magnetic leakage field distribution is complex. In this paper, a 3-D mathematical model used for the calculation of the electromagnetic field in the end region of large turbo-generators is given. The influence of spatial locations of end structures, the actual shape and material of end windings, clamping plate, and copper screen are considered. Adopting the time-step finite element (FE) method and taking the nonlinear characteristics of the core into consideration, a 3-D transient magnetic field is calculated. The objective of this paper is to investigate the influence of clamping plate permeability and metal screen structures on 3-D electromagnetic field distribution and eddy current loss in end region of a turbo-generator. To reduce the temperature of copper screen, a hollow metal screen is proposed. The eddy current loss, which is gained from the 3D transient magnetic field, is used as heat source for the thermal field of end region. The calculated temperatures are compared with test data.

Likun, Wang; Weili, Li; Yi, Xue; Chunwei, Guan

2013-11-01

394

Rainflow Counting and Energy Dissipation for Hysteresis Models in Elastoplasticity  

E-print Network

Republic Abstract The rainflow counting method is widely used in the context of fatigue analy- sis. The rainflow counting method due to Endo is widely used to decompose an arbitrary sequence of (scalar) loadsRainflow Counting and Energy Dissipation for Hysteresis Models in Elastoplasticity Martin Brokate

Krejcí, Pavel

395

Subharmonic ferroresonance in an LCR circuit with hysteresis  

E-print Network

, requires the use of nonlinear dynamics methods. A sinusoidally­driven series LCR circuit is one the Preisach model to simulate numerically a series LCR circuit (the same method can of course be appliedSubharmonic ferroresonance in an LCR circuit with hysteresis H. LAMBA # M.GRINFELD # S.McKEE # R

Lamba, Harbir

396

The back transition and hysteresis effects in DIII-D  

SciTech Connect

The back transition from H-mode to L-mode has been studied on DIII-D as a part of the investigation of the L-H transition power threshold scaling. Based on a density-dependent scaling for the H-mode power threshold, ITER will require substantial hysteresis in this parameter to remain in H-mode as n{sub e} rises. Defining the hysteresis in terms of the ratio of sustaining to threshold power, P{sub HL}/P{sub LH} may need to be as small as 50% for ITER. Operation of DIII-D at injection powers slightly above the H-mode threshold results in an oscillatory behavior with multiple forward-backward transitions in the course of a discharge. These discharges represent a unique system for studying various control parameters that may influence the H{leftrightarrow}L state transition. Careful analysis of the power flow through the edge gives values for the sustaining power which are well below the corresponding threshold powers (P{sub HL}/P{sub LH} = 35--70%), indicating substantial hysteresis can be achieved in this parameter. Studies of other control parameter candidates such as edge temperature during the back transitions are less clear: the amount of hysteresis seen in these parameters, if any, is primarily dependent on the nature (ELMing, ELM-free) of the parent H-state.

Thomas, D.M.; Groebner, R.J.; Burrell, K.H.; Osborne, T.H.; Carlstrom, T.N. [General Atomics, San Diego, CA (United States)

1997-09-01

397

The mechanism by which fish antifreeze proteins cause thermal hysteresis  

Microsoft Academic Search

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

Erlend Kristiansen; Karl Erik Zachariassen

2005-01-01

398

Idealized Hysteresis Modeling of Electrorheological and Magnetorheological Dampers  

Microsoft Academic Search

The hysteresis behavior of a linear stroke magnetorheological damper is characterized for sinusoidal displacement excitation at 2.0 Hz (nominal). Four different modeling perspectives are discussed for purposes of system identification procedures, including: (1) equivalent viscous damping, (2) nonlinear Bingham plastic model, (3) nonlinear biviscous model, and (4) nonlinear hysteretic biviscous model. By progressively adding model parameters with which to better

Norman M. Wereley; Li Pang; Gopalakrishna M. Kamath

1998-01-01

399

Elastic guides reduce hysteresis effect in Belleville spring package  

NASA Technical Reports Server (NTRS)

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.

Mc Glashan, W. F., Jr.; Toth, L. R.

1967-01-01

400

Periodic solutions of a forced system with hysteresis.  

NASA Technical Reports Server (NTRS)

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.-

Drew, J. H.

1972-01-01

401

A Domain Wall Model for Hysteresis in Piezoelectric Materials  

E-print Network

to attain the full potential of the materials as sensors and actuators in high performance applications. The model employed here is based on theory developed in [18, 19] for hysteresis in general ferroelectric design. i #12; 1 Introduction Piezoelectric materials provide the capability for designing actuators

402

Electroelastic equations describing slow hysteresis in polarized ferroelectric ceramic plates  

Microsoft Academic Search

Rotationally invariant electroelastic equations are extended to account for slow hysteretic effects in polarized ferroelectric ceramic plates by employing an internal variable in a thermodynamic state function. All material irreversibility is taken to be a consequence of the ferroelectric polarization-electric-field irreversibility. Since we are concerned with the slowest possible hysteresis, we ignore the evolution equation and take the known irreversible

L. Huang; H. F. Tiersten

1998-01-01

403

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 The capability of piezoelectric materials to both actuate and sense derives from the noncentrosym­ metric nature. This generates strains in the material and provides it with actuator capabilities. Alternatively, applied

404

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 The capability of piezoelectric materials to both actuate and sense derives from the noncentrosym- metric nature. This generates strains in the material and provides it with actuator capabilities. Alternatively, applied

405

A Stress-Dependent Hysteresis Model for Ferroelectric Materials  

E-print Network

exploiting ferroelectric compounds -- e.g., PZT, PLZT and PMN -- offer unique actuator and sensorA Stress-Dependent Hysteresis Model for Ferroelectric Materials Brian L. Ball 1 , Ralph C. Smith 2 models which characterize the fer- roelastic switching mechanisms inherent to ferroelectric materials

406

A TemperatureDependent Hysteresis Model for Relaxor Ferroelectrics  

E-print Network

. Introduction Actuators constructed from the relaxor ferroelectric material Pb(Mg 1=3 , Nb 2=3 )O 3 (PMNA Temperature­Dependent Hysteresis Model for Relaxor Ferroelectrics Ralph C. Smith 1 and Craig L addresses the development of a temperature­dependent constitutive model for relaxor ferroelectrics which

407

Parameter Estimation Techniques for a Class of Nonlinear Hysteresis Models  

E-print Network

materials employed in a wide range of actuators and sensors. These models are formulated as integral through comparison with experimental data. i #12;1 Introduction Hysteresis and constitutive nonlinearities frequency, temperature, and stress dependencies which makes it applicable for a wide range of transducer

408

PID Control of Second-Order Systems with Hysteresis  

E-print Network

PID Control of Second-Order Systems with Hysteresis Bayu Jayawardhana, Hartmut Logemann & Eugene P 2007 Abstract. The efficacy of proportional, integral and derivative (PID) control for set point on the PID gains, explicitly formulated in terms of the system data, are determined under which asymptotic

Ryan, E.P.

409

A Differential Model of Adsorption Hysteresis with Applications to Chromatography  

E-print Network

A Differential Model of Adsorption Hysteresis with Applications to Chromatography M. Peszy- ena occuring in chromatography or other related disciplines, see [21]. These models have the general rise in the beginning of 20th century, chromatography has become a wide industrial domain delivering

Peszynska, Malgorzata

410

Magnetic Properties of Pb-Doped Bi-Sr-Ca-Cu-O Superconductors  

Microsoft Academic Search

The D.C. magnetization of Bi-Sr-Ca-Cu-O compound was significantly increased by Pb-doping. However, the hysteresis \\\\varDelta M in magnetization curves rapidly decreased with increasing magnetic field, and became almost zero above 0.5 T. This small hysteresis may be related to the thin layers of superconducting phases. Low-temperature tails in superconducting resistive transition curves measured in magnetic fields were drastically decreased by

Hiroaki Kumakura; Kazumasa Togano; Mitsuru Uehara; Hiroshi Maeda; Kazuhiko Takahashi; Eiji Yanagisawa

1988-01-01

411

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

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

Folini, Laura; Veronelli, Annamaria; Benetti, Alberto; Pozzato, Carlo; Cappelletti, Marco; Masci, Enzo; Micheletto, Giancarlo; Pontiroli, Antonio E

2014-01-01

412

Open-loop position tracking control of a piezoceramic flexible beam using a dynamic hysteresis compensator  

NASA Astrophysics Data System (ADS)

This paper proposes a novel hysteresis compensator to enhance control accuracy in open-loop position tracking control of a piezoceramic flexible beam. The proposed hysteresis compensator consists of two components: a rate-independent hysteresis compensator and a nonlinear filter. The compensator is formulated based on the inverse Preisach model, while the weight coefficients of the filter are identified adaptively using a recursive least square (RLS) algorithm. In this work, two dynamic hysteresis compensators (or rate-independent hysteresis compensators) are developed by adopting two different nonlinear filters: Volterra and bilinear filters. In order to demonstrate the improved control accuracy of the proposed dynamic compensators, a flexible beam associated with the piezoceramic actuator is modeled using the finite element method (FEM) and Euler-Bernoulli beam theory. The beam model is then integrated with the proposed hysteresis model to achieve accurate position tracking control at the tip of the beam. An experimental investigation on the tip position tracking control is undertaken by realizing three different hysteresis compensators: a rate-independent hysteresis compensator, a rate-dependent hysteresis compensator with a Volterra nonlinear filter and a rate-independent hysteresis compensator with a bilinear nonlinear filter. It is shown that the proposed dynamic hysteresis compensators can provide much better tracking control accuracy than conventional rate-independent hysteresis compensators.

Nguyen, Phuong-Bac; Choi, Seung-Bok

2010-12-01

413

Modeling and control with hysteresis and creep of ionic polymer-metal composite (IPMC) actuators  

Microsoft Academic Search

Hysteresis and creep hinder the effective use of IPMC in sensors and actuators. This paper proposes a hybrid model that can precisely portray hysteresis and creep in piezoelectric actuators, which is constructed by a Preisach operator with a piecewise uniform density function and creep operator. Then, the corresponding inverse models for both hysteresis and creep are developed. It studies online

Zhen Chen; Lina Hao; Dingyu Xue; Xinhe Xu; Yanmei Liu

2008-01-01

414

Unit Root in the Wage-Price Spiral Is Not Hysteresis in Unemployment  

Microsoft Academic Search

Hysteresis is one of the main concepts used in Layard, Nickell and Jackman's book, Unemployment: Macroeconomic Performance and the Labour Market. Attempts to clarify the concept of hysteresis, from its formal representation to its empirical applications. Emphasizes the idea that hysteresis refers back to a given set of formal properties, independently of the phenomenologies within which it is liable to

Bruno Amable; Jérôme Henry; Frédéric Lordon; Richard Topol

1993-01-01

415

A.c. losses of a 10 kA NbTi cable-in-conduit superconductor for SMES applications  

NASA Astrophysics Data System (ADS)

In this paper we present a.c. loss investigations performed on a 10 kA prototype cable-in-conduit superconductor with a NbTi basis. The twisted and braided conductor was under development for a superconducting 180 MJ energy storage model coil with Bmax = 5.4 T at Imax = 10 kA. Special aspects of our measurements are the coupling loss dependence on the Cr coating and on the plastic deformation of the basic multifilament wires in the cable. Further, we separately determined the individual contributions from the different conductor components to the coupling losses. Also, the influence of the void fraction in the conductor on the coupling losses was investigated. In addition, d.c. transverse resistance measurements were performed on the cable. The measured hysteresis and coupling losses are small for such a large current conductor and were sufficiently low for our purposes. Further a.c. loss reduction could be achieved by a proper choice of the basic multifilament wire in the cable. Our a.c. loss results should also be useful for other pulsed magnetic field applications of this conductor type.

Kwasnitza, K.; Sultan, A.; Al-Wakeel, S.

416

On the Physical Basis of Power Losses in Laminated Steel and Minimum-Effort Modeling in an Industrial Design Environment  

Microsoft Academic Search

A procedure is described for identifying a general mathematical model of core losses in ferromagnetic steel based on a minimal amount of experimental data. This model has a hysteresis loss multiplicative coefficient variable with frequency and induction and a combined coefficient for eddy-current and excess losses that is also variable with frequency and induction. A physical interpretation and a test

Mircea Popescu; TJE Miller; D. M. Ionel; S. J. Dellinger; R. Heidemann

2007-01-01

417

Enhancing cancer therapeutics using size-optimized magnetic fluid hyperthermia  

E-print Network

Enhancing cancer therapeutics using size-optimized magnetic fluid hyperthermia Amit P. Khandhar, R. Appl. Phys. 111, 07B317 (2012) Analysis of heating effects (magnetic hyperthermia) in Fe magnetic field on the magnetic hyperthermia properties and high-frequency hysteresis loops of ferromagnetic

Krishnan, Kannan M.

418

Online Computation of Hysteresis Boundary for Constant Switching Frequency Current-Error Space-Vector-Based Hysteresis Controller for VSI-Fed IM Drives  

Microsoft Academic Search

This paper proposes a current-error space-vector-based hysteresis controller with online computation of boundary for two-level inverter-fed induction motor (IM) drives. The proposed hysteresis controller has got all advantages of conventional current-error space-vector-based hysteresis controllers like quick transient response, simplicity, adjacent voltage vector switching, etc. Major advantage of the proposed controller-based voltage-source-inverters-fed drive is that phase voltage frequency spectrum produced is

Rijil Ramchand; K. Gopakumar; Chintan Patel; K. Sivakumar; Anandarup Das; Haitham Abu-Rub

2012-01-01

419

Generalization of the Classical Method for Calculating Dynamic Hysteresis Loops in Grain-Oriented Electrical Steels  

Microsoft Academic Search

We have studied the ability of two one-dimensional (1-D) time-stepping models, both based on the concept of magnetic viscosity, to reproduce dynamic loops and losses in grain-oriented (GO) electrical steels under arbitrary magnetization regimes. We found that GO steels (0.3 mm thick) can be modeled quite accurately at magnetizing frequencies up to 200 Hz by a thin sheet representation, which

Sergey E. Zirka; Yuri I. Moroz; Philip Marketos; Anthony J. Moses; David C. Jiles; T. Matsuo

2008-01-01

420

Supplementary comparison COOMET.EM-S12: Measurements of magnetic loss power in electrical steel at frequencies of 50 Hz and 60 Hz  

NASA Astrophysics Data System (ADS)

The decision to carry out a COOMET supplementary comparison in the field of magnetic loss power measurements was taken in October 2010. It is registered in the BIPM key comparison database with the identifier COOMET.EM-S12. The comparison was piloted by UNIIM (Russia) and two other laboratories participated, namely PTB (Germany) and CMI (Czech Republic). The results of the comparison allow one to demonstrate the equivalence of the standards of the three National Metrology Institutes, and thus confirm the corresponding claimed Calibration and Measurement Capabilities (CMCs). It is noted that the deviation of the measurement results obtained with sheet samples exceeds that obtained with samples of toroidal form and of Epstein strips, a point that requires further investigation. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCEM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Didik, Yury I.; Malyagin, Mikhail A.

2014-01-01

421

PRINCIPAL FEATURES OF METAL MAGNETIC MEMORY METHOD AND INSPECTION TOOLS AS COMPARED TO KNOWN MAGNETIC NDT METHODS  

Microsoft Academic Search

Principal features of method of metal magnetic memory (MMM) as compared to known magnetic NDT methods are considered. Among the basic features of the MMM method, that it is based on use of the own magnetic leakage field (SMLF), arising in ferromagnetic and paramagnetic products on accumulations of high-density dislocations. Magnetodislocation hysteresis underlying effect of metal magnetic memory, takes place

A. Dubov

2004-01-01

422

Mass loss  

NASA Technical Reports Server (NTRS)

Observational evidence for mass loss from cool stars is reviewed. Spectra line profiles are used for the derivation of mass-loss rates with the aid of the equation of continuity. This equation implies steady mass loss with spherical symmetry. Data from binary stars, Mira variables, and red giants in globular clusters are examined. Silicate emission is discussed as a useful indicator of mass loss in the middle infrared spectra. The use of thermal millimeter-wave radiation, Very Large Array (VLA) measurement of radio emission, and OH/IR masers are discussed as a tool for mass loss measurement. Evidence for nonsteady mass loss is also reviewed.

Goldberg, Leo

1987-01-01

423

A modeling approach of a magnetic amplifier  

NASA Astrophysics Data System (ADS)

New soft magnetic materials made possible the use of the magnetic amplifier technology in designing competitive electric power supplies. This technology is used in the Swedish fighter aircraft Gripen, being also attractive for future more electrical aircraft systems due to the possibility to achieve a compact and robust design. A modeling approach of a magnetic amplifier based on the magnetic hysteresis of the core material is presented here for a common amorphous magnetic alloy. Also to be corresponded to.

Austrin, L.; Krah, J. H.; Engdahl, G.

2004-05-01

424

CMR of Co/Cu multilayers with reduced hysteresis and low-field response  

SciTech Connect

We present the results of a systematic study on optimization of the giant magnetoresistance (GMR) response in Co/Cu multilayers (MLs) for copper layer thickness near the second oscillatory peak. Co/Cu MLs with alternating thick (t(1)Co) and thin (t(2)Co) layers have been prepared in the from of [Cot(1)CoA/Cu20A/Cot(2)CoA/Cu20A]15. We have found that the magnetoresistive hysteresis of these MLs is reduced with decreasing t(2)Co and has disappeared when t(2)Co<4.5A. We have obtained an optimal GMR response with a field sensitivity of 0. 013%/Oe over a field region of -60 Oe centered at -50 Oe. This architecture may enable the use of Cu/Co MLs in low-field magnetic sensor applications.

Mao, M.; Gibbons, M.; Law, B.; Grabner, F.; Veron, S.; Cerjan, C.

1997-02-01

425

Magnetic fabrics  

NASA Astrophysics Data System (ADS)

Since Graham [1954; 1967] demonstrated in the 1950s and 1960s that magnetic anisotropy was a quick and non-destructive way of measuring rock fabric, magnetic fabric measurements have become increasingly prevalent in the study of earth and environmental processes (see Table 1 for definitions of magnetic terms). The accomplishments of U.S. workers over the past 4 years show that the U.S. community continues to contribute to the growth and development of the field. In addition to the more traditional anisotropy of magnetic susceptibility (AMS) measurements work is branching out to include anisotropy of remanence studies, particularly anisotropy of anhysteretic remanence (AAR) [McCabe et al, 1985] and anisotropy of isothermal remanence (AIR), since these parameters can be tied directly to the remanence-carrying grains in a rock and hence have relevance to the effects of magnetic fabric on natural remanent magnetization (NRM). Along with this shift is the realization, as a result of combining nonmagnetic observations (e.g.. scanning electron microscopy (SEM), finite strain measurements) with rock magnetic measurements (e.g.. hysteresis parameters), that magnetic mineral composition (paramagnetic and ferromagnetic) has an important control on magnetic anisotropy.

Kodama, Kenneth P.

1995-07-01

426

Computation of Core Losses in Electrical Machines Using Improved Models for Laminated Steel  

Microsoft Academic Search

Two new models for specific power losses in cold rolled motor lamination steel are described together with procedures for coefficient identification from standard multi-frequency Epstein or single sheet tests. The eddy current and hysteresis loss coefficients of the improved models are dependent of induction (flux density) and\\/or frequency and the errors are substantially lower than those of conventional models over

D. M. Ionel; M. Popescu; M. McGilp; T. J. E. Miller; S. Dellinser; R. J. Heideman

2006-01-01

427

Magnetism  

NSDL National Science Digital Library

This overview of magnetism provides a brief history prior to 1600 and continues with the work of William Gilbert, Hans Christian Oersted, and Andre-Marie Ampere in describing and exploring the magnetosphere and learning the role that electric current plays in producing magnetism. Magnetic field lines are then discussed, citing the work of Michael Faraday. The work of James Clerk Maxwell and Heinrich Hertz is mentioned in a discussion of the relationship of light waves and radio waves as part of the electromagnetic spectrum.

Stern, David

428

Hair Loss  

MedlinePLUS

... hair production and cause hair loss. People with lupus can also lose hair. The hormone imbalance that happens in polycystic ovary syndrome can cause hair loss in teen girls as well as adult women. Medicines. Sometimes doctors prescribe medicines that have hair loss ...

429

Synthesis and magnetic properties of ?-Ni(OH)2 and NiO nanosheets  

NASA Astrophysics Data System (ADS)

In this report, we have synthesized hexagonal phase ?-Ni(OH)2 nanosheets through a facile hydrothermal route. NiO nanosheets were obtained by thermal decomposition of the obtained ?-Ni(OH)2 nanosheets at 450 °C for 3 h in air. The obtained samples were characterized by transmission electron microscopy (TEM), revealing that the obtained ?-Ni(OH)2 and NiO nanosheets have the length and width of several decade nanometers. Thermogravimetric (TG) measurement showed that ?-Ni(OH)2 nanosheets started to decompose at about 250 °C with the major weight loss that happened between 270 and 323 °C. The magnetic measurement results showed that ?-Ni(OH)2 nanosheets have ferromagnetic behavior at 5 K and paramagnetic behavior at 300 K. NiO nanosheets exhibited an obvious hysteresis loops both at 5 K and 300 K due to the magnetization relaxation process. At the same time, the origin of magnetic properties of the obtained ?-Ni(OH)2 and NiO nanosheets is discussed in detail. ?-Ni(OH)2 nanosheets were obtained through a facile hydrothermal method. NiO was obtained by annealing ?-Ni(OH)2 at 450 °C for 3 h in air. The morphology of NiO was unchanged through the annealing process. ?-Ni(OH)2 has ferromagnetic behavior at 5 K and paramagnetic behavior at 300 K. NiO exhibits an obvious hysteresis in M-H loops at 5 K and 300 K.

Zhao, Jingang; Yang, Mao; Hua, Zhenghe

2014-12-01

430

Method of thermal strain hysteresis reduction in metal matrix composites  

NASA Technical Reports Server (NTRS)

A method is disclosed for treating graphite reinforced metal matrix composites so as to eliminate thermal strain hysteresis and impart dimensional stability through a large thermal cycle. The method is applied to the composite post fabrication and is effective on metal matrix materials using graphite fibers manufactured by both the hot roll bonding and diffusion bonding techniques. The method consists of first heat treating the material in a solution anneal oven followed by a water quench and then subjecting the material to a cryogenic treatment in a cryogenic oven. This heat treatment and cryogenic stress reflief is effective in imparting a dimensional stability and reduced thermal strain hysteresis in the material over a -250.degree. F. to +250.degree. F. thermal cycle.

Dries, Gregory A. (Inventor); Tompkins, Stephen S. (Inventor)

1987-01-01

431

Hysteresis Behaviors of Poly (Naphthalene Quinone) Radical Electrorheological Fluid  

NASA Astrophysics Data System (ADS)

As a potential electrorheological(ER) material, poly(naphthalene quinone) radical (PNQR) ER fluid was prepared, and its rheological behavior and hysteresis phenomenon were investigated. PNQR was synthesized by Friedel-Crafts acylation between naphthalene and phthalic anhydride, using zinc chloride as a catalyst at 256°C. A Physica rheometer equipped with a high voltage generator was used to measure the rheological properties of the ER fluids, which were prepared by dispersing PNQR in silicone oil at several particle concentrations. Shear stresses were observed to decrease as shear rate increased in the region of slow deformation rate. It was further found that ER fluid showed different hysteresis behaviors according to the shear rate ranges; thixotropy was observed in the low shear rate region (0.007-0.51/s) and anti-thixotropy in the high shear rate region (0.5-10001/s). Controlled shear stress mode was also applied to observe similar behaviors.

Choi, Hyoung J.; Cho, Min S.; Jhon, Myung S.

432

The Effects of Crystal Fractionation and Magma Mixing on Remanent and Induced Magnetic Anomalies over a Layered Intrusion  

NASA Astrophysics Data System (ADS)

The Bjerkreim-Sokndal layered intrusion lies in the Rogaland Igneous Complex (~930 Ma) within the Baltic Shield in southern Norway. This 7 km-thick intrusion is divided into six Megacyclic units topped by mangerite and quartz-mangerite units. The course of crystal fractionation punctuated by the influx and mixing of more primitive magmas produces sequences of early plagioclase norites, intermediate hemo-ilmenite norites, and late magnetite-rich norites with subordinate ilmenite. Oriented samples were collected from 46 sites through the stratigraphy of the intrusion and subjected to petrophysical, paleomagnetic and rock magnetic measurements. Magnetic properties show a large range of values, with susceptibilities ranging from 1.47x10-4 to 2.15x10-1 SI, NRM intensities ranging from 0.104 to 58.8 A/m and corresponding Q values of 0.1 to 85. When induced and remanent magnetizations are averaged for each subdivided mega-unit a pattern of remanence-dominance at the base to induced-dominance at the top of each cycle is clear. Hysteresis properties indicate PSD to MD size magnetites with a continuous trend between them, indicative of the magnetite-rich rocks. Hysteresis properties falling outside the magnetite PSD-MD ranges are interpreted as hemo-ilmenite samples, in good agreement with the observed oxide mineralogy. Distinctive differences in the magnetic mineralogy also shows up in demagnetization behavior. Thermal plots show either a loss of magnetization at 580C, or above 600C. AF demagnetization plots show two separate populations - one with high coercivity (hemo-ilmenite) and one with low coercivity (magnetite). Magnetic anomalies over the body correspond directly to the magnetic properties, with positive (induced) anomalies over the magnetite-rich layers and magnetic lows (due to reversed magnetic signal) over layers with hemo-ilmenite present.

Brown, L. L.; McEnroe, S. A.; Robinson, P.

2005-05-01

433

Novel thermal hysteresis proteins from low temperature basidiomycete, Coprinus psychromorbidus.  

PubMed

The low temperature basidiomycete, Coprinus psychromorbidus, produced three kinds of thermal hysteresis proteins (THPs) in the extracellular space. Molecular mass of purified fungal THPs were approximately 23 kDa, respectively, however those fungal THPs had different N-terminal amino acid sequences. Those fungal THPs formed ice crystals resembling "stone Age arrow head". These observations indicate that fungal THPs did not form hexagonal ice crystals to inhibit its growth. PMID:12908023

Hoshino, T; Kiriaki, M; Nakajima, T

2003-01-01

434

A calorimetric study of thermal hysteresis effects in ganglioside micelles  

Microsoft Academic Search

Light, X-ray and neutron scattering measurements clearly showed strong temperature-related variations in micellar mean aggregation\\u000a number, accompanied by dramatic thermal hysteresis effects, for a variety of micelle-forming gangliosides. Gangliosides, sialic-acid-containing\\u000a glycosphingolipids, are amphiphilic molecules of biological origin with a ceramide (a double-tailed hydrophobic part, like\\u000a phospholipids) and an oligosaccharide chain as the headgroup. When temperature is varied in the range

L. Cantù; M. Corti; E. Del Favero; E. Muller; A. Raudino; S. Sonnino

435

An analysis of metal fatigue based on hysteresis energy  

Microsoft Academic Search

Halford's plastic-energy concept for lowcycle fatigue is extended to the medium- and high-cycle ranges. The resulting equations are compared with 74 sets of data in the medium- and high-cycle ranges. The difference in stress between theory and experimental data is less than ±5 percent.The plastic-hysteresis-energy analysis for fatigue is shown to be consistent with the octahedral shear-stress theory. In addition,

C. S. Chang; W. T. Pimbley; H. D. Conway

1968-01-01

436

Hysteresis in acoustical media with relaxational nonlinearity and viscosity  

NASA Astrophysics Data System (ADS)

Loading and unloading waves in nonlinear relaxational and dissipative medium of type compacted ground are studied. Suggested by J. Stokes method and new asymptotic small-distance approach are used for construction of solution. We obtain explicit approximation solutions for different values of relaxation and viscous parameters. It is described influence of type of medium on form of hysteresis curves and on value of residual deformation.

Molotkov, I. A.

2008-06-01

437

Negative resistance and anomalous hysteresis in a collective molecular motor  

PubMed

A spatially extended model for a collective molecular motor is presented. The system is driven far from equilibrium by a quenched additive noise. As a result, it exhibits anomalous transport properties, namely, negative resistance and a clockwise hysteresis cycle. The phase diagram and the region of negative resistance are calculated using a Weiss mean field theory. Intuitive explanations of the anomalous transport properties as well as details of its energetics are given. PMID:11088302

Buceta; Parrondo; Van Den Broeck C; de La Rubia FJ

2000-06-01

438

The field-space perspective on hysteresis in uniaxial ferromagnets  

Microsoft Academic Search

A procedure for the analysis of hysteresis in the H space of a uniaxial ferromagnet with higher-order anisotropy is put forward. The formulation is valid to any order n in the anisotropy expansion. The critical boundaries separating stable from metastable states are cast in a formally decoupled parametric way as Hx=Hx(Mx), Hz=Hz(Mz). The analytic expressions provide the basis for the

Y. T. Millev; J. R. Cullen; H. P. Oepen

1998-01-01

439

The Field-Space Perspective on Hysteresis in Uniaxial Ferromagnets  

Microsoft Academic Search

A procedure for the analysis of hysteresis in the H space of a uniaxial ferromagnet with higher-order anisotropy is put forward. The formulation is valid to any order n in the anisotropy expansion. The critical boundaries separating stable from metastable states are cast in a formally decoupled parametric way as Hx5Hx( Mx), Hz5Hz(Mz). The analytic expressions provide the basis for

Y. T. Miller; J. R. Cullen; H. P. Oepen; J. Kirschner

1998-01-01

440

The field-space perspective on hysteresis in uniaxial ferromagnets  

Microsoft Academic Search

A procedure for the analysis of hysteresis in the H space of a uniaxial ferromagnet with higher-order anisotropy is put forward. The formulation is valid to any order n in the anisotropy expansion. The critical boundaries separating stable from metastable states are cast in a formally decoupled parametric way as Hx=Hx(Mx),Hz=Hz(Mz). The analytic expressions provide the basis for the construction

Y. T. Millev; J. R. Cullen; H. P. Oepen

1998-01-01

441

Characterization of magnetic degradation mechanism in a high-neutron-flux environment  

NASA Astrophysics Data System (ADS)

Radiation-induced demagnetization of permanent magnets can result in the failure of magnet-based devices operating in high-radiation environments. To understand the mechanism underlying demagnetization, Nd-Fe-B magnets were irradiated with fast and fast plus thermal neutrons at fluences of 1012, 1013, 1014, and 1015 n/cm2, respectively. After irradiation, magnetic flux losses were shown to increase with the fluence. Compared with samples irradiated only with fast neutrons, the samples exposed to the fast plus thermal neutrons have higher magnetic flux losses, which is attributed to the thermal neutron capture reaction of boron. Hysteresis loops of the Nd-Fe-B magnets reveal a slightly increase in the coercivity after irradiation. Full remagnetization of the samples after irradiation was possible, which indicates that structural damage is unlikely an important factor in the demagnetization process at these levels of neutron flux and fluence. Finally, we performed a preliminary Molecular Dynamic (MD) simulation on a cube of ions to obtain a better understanding of the thermal spike mechanism.

Samin, Adib; Qiu, Jie; Hattrick-Simpers, Jason; Dai-Hattrick, Liyang; Zheng, Yuan F.; Cao, Lei

2014-09-01

442

Hysteresis and Wavenumber Vacillation in Unstable Baroclinic Flows  

NASA Technical Reports Server (NTRS)

Hysteresis and wavenumber vacillation are studied numerically in a weakly stratified quasigeostrophic model. In general, the amplitude of the most unstable wave increases, as the flow becomes more unstable. When the wave becomes saturated, the next longer wave will grow at the expanse of the most unstable wave and becomes the dominant wave. However, once the longwave state is established, it may remain in that regime even as the instability is decreased beyond the threshold where it first developed, thus constituting a hysteresis loop. In a highly unstable case, the flow may not show a preference for any single wave. Instead, the dominant wave aperiodically varies among several long waves. This phenomenon is known as wavenumber vacillation. Hysteresis is further examined in terms of eddy heat flux. It is shown that total eddy heat flux increases as the flow becomes more unstable, but displays a sharp drop when transition to a longer wave occurs. However, in a longwave state, the heat flux always decreases with decreasing instability even pass the threshold when wave transition first occurs.

Chou, Shih-Hung; Goodman, H. Michael (Technical Monitor)

2001-01-01

443

Spin transition with a very large thermal hysteresis in a molecular crystal: an EPR study of Fe( PM-PEA) 2(NCS) 2  

Microsoft Academic Search

Magnetic susceptibility and X- and Q-band EPR studies are reported for the Fe2+ spin transition compound (Fe(PM-PEA)2(NCS)2) in powder form. An exceptionally large thermal hysteresis loop, about 60 K, has been found by both techniques. The EPR studies have been carried out on compound doped with Mn2+ (0.1‰ of Mn\\/Fe). An original EPR spectra simulation program has been elaborated in

Hervé Daubric; Christophe Cantin; Cyrille Thomas; Janis Kliava; Jean-François Létard; Olivier Kahn

1999-01-01

444

Passive Magnetic Attitude Control System for the Munin Nanosatellite  

NASA Astrophysics Data System (ADS)

The instrumental and applied problems related to the design of a passive magnetic attitude control system for the Munin nanosatellite are considered. The system is constructed from a strong permanent magnet and a set of hysteresis rods. These rods are made of magnetically soft material using a special technology, and they allow us to support the satellite orientation with respect to the local magnetic field vector with a given accuracy and time response. By using asymptotic and numerical methods, we investigate the satellite dynamics for different models of hysteresis. The issues concerning the arrangement of the rods and their interaction with the fields of permanent magnets mounted onboard the satellite are discussed.

Ovchinnikov, M. Yu.; Penkov, V. I.

2002-03-01

445

A significant reduction of hysteresis in MnFe(P,Si) compounds  

NASA Astrophysics Data System (ADS)

The magnetocaloric effects in Mn1.3Fe0.7- x Co x P0.46Si0.54 compounds ( x = 0, 0.025, 0.05 and 0.1) were investigated systematically. X-ray diffraction shows that the compounds crystallize in the Fe2P-type hexagonal structure with space group P-62m symmetry. Magnetic measurements show that the paramagnetic-ferromagnetic transition temperatures range from 247 to 298 K. The maximal magnetic entropy changes in the Mn1.3Fe0.7P0.46Si0.54 compound reaches 8.3 J/kgK for a field change from 0 to 1.5 T. The thermal hysteresis of these compounds is less than 3 K. The maximum adiabatic temperature change is 2.2 K in Mn1.3Fe0.7P0.46Si0.54 and Mn1.3Fe0.65Co0.05P0.46Si0.54 compounds for a field change from 0 to 1.48 T, indicating this material system has potential for room-temperature magnetic refrigeration applications.

Huliyageqi, B.; Geng, Yao-xiang; Li, Ying-jie; Tegus, O.

2013-08-01

446

Electronic and magnetic properties of manganite thin films with different compositions and its correlation with transport properties: An X-ray resonant magnetic scattering study  

NASA Astrophysics Data System (ADS)

Here, we present x-ray resonant magnetic dichroism and x-ray resonant magnetic scattering measurements of the temperature dependence of magnetism in Pr-doped La-Ca-Mn-O films grown on (110) NdGaO3 substrates. We observed thermal hysteresis of the ferromagnetism in one film that also showed large thermal hysteresis of ˜18 K in transport measurements. While in a second film of a different nominal chemistry, which showed very small thermal hysteresis ˜3 K in transport measurements, no thermal hysteresis of the ferromagnetism was observed. These macroscopic properties are correlated with evolution of surface magnetization across metal insulator transition for these films as observed by soft x-ray resonant magnetic scattering measurements.

Singh, Surendra; Freeland, J. W.; Fitzsimmons, M. R.; Jeen, H.; Biswas, A.

2014-12-01

447

Magnetic ?-Fe2O3, Fe3O4, and Fe nanoparticles confined within ordered mesoporous carbons as efficient microwave absorbers.  

PubMed

A series of magnetic ?-Fe2O3, Fe3O4, and Fe nanoparticles have been successfully introduced into the mesochannels of ordered mesoporous carbons by the combination of the impregnation of iron salt precursors and then in situ hydrolysis, pyrolysis and reduction processes. The magnetic nanoparticles are uniformly dispersed and confined within the mesopores of mesoporous carbons. Although the as-prepared magnetic mesoporous carbon composites have high contents of magnetic components, they still possess very high specific surface areas and pore volumes. The magnetic hysteresis loops measurements indicate that the magnetic constituents are poorly-crystalline nanoparticles and their saturation magnetization is evidently smaller than bulky magnetic materials. The confinement of magnetic nanoparticles within the mesopores of mesoporous carbons results in the decrease of the complex permittivity and the increase of the complex permeability of the magnetic nanocomposites. The maximum reflection loss (RL) values of -32 dB at 11.3 GHz and a broad absorption band (over 2 GHz) with RL values <-10 dB are obtained for 10-Fe3O4-CMK-3 and 10-?-Fe2O3-CMK-3 composites in a frequency range of 8.2-12.4 GHz (X-band), showing their great potentials in microwave absorption. This research opens a new method and idea for developing novel magnetic mesoporous carbon composites as high-performance microwave absorbing materials. PMID:25562071

Wang, Jiacheng; Zhou, Hu; Zhuang, Jiandong; Liu, Qian

2015-02-01

448

Structural and magnetic study of La0.7Sr0.3MnO3 nanoparticles and AC magnetic heating characteristics for hyperthermia applications  

NASA Astrophysics Data System (ADS)

We investigated structural and magnetic properties and alternating current magnetic heating characteristics of La0.7Sr0.3MnO3 nanoparticles with respect to the possible application for magnetic hyperthermia treatments. Using Rietveld Profile refinement of powder X-ray diffraction data, the hexagonal structure has been observed. The particle sizes varied from 20 to 50 nm as the annealing temperature increases from 700 to 900 °C. The hysteresis loop is not observed and the good fit of Langevin function with magnetization data reveals the superparamagnetic nature at room temperature for all samples. Characteristic magnetic parameters of the particles including saturation magnetization in the temperature range 10-300 K, an effective anisotropy constant and a magnetocrystalline anisotropy constant have been determined. The Specific Absorption Rate for 15 mg/mL sample concentration was measured in alternating magnetic fields of 50-80 Oe at a fixed frequency of 236 kHz. In addition, the intrinsic loss power (ILP) has been calculated from SAR values. It is believed that La0.7Sr0.3MnO3 nanoparticles with a high ILP will be useful for the in situ hyperthermia treatment of cancer.

Manh, D. H.; Phong, P. T.; Nam, P. H.; Tung, D. K.; Phuc, N. X.; Lee, In-Ja

449

Microstructural and magnetic properties study of Fe-P rolled sheet alloys  

NASA Astrophysics Data System (ADS)

In the work presented here, the soft magnetic properties of Fe1-xPx (x=0.36, 0.7, 1.1 at%) rolled sheet alloys were investigated. In this respect, the as-rolled sheets were subjected to a two steps annealing processes; the first one between 800 and 1000 °C for 1 h referred as first stage annealing and the second one at lower temperatures (500 and 600 °C) for 30 min, referred as second step annealing. BH tracer measurements at 50 Hz showed that for all of the phosphorous containing alloys, in general, the magnitude of coercivity decreased by applying these two annealing steps compared to those of as-rolled samples. For all of the studied samples, the B50 values measured at 50 Hz were in the range of 1.6-1.7 tesla (T). Samples having highest amount of phosphorous (1.1 at%) exhibited lower eddy current loss compared to the rest of the specimens due to the increased electrical resistivity. Besides, microstructural studies revealed that the prepared samples were free from Fe3P phase precipitation and the average grain size increased (~three times) with increasing the phosphorous content giving rise to the decrease of hysteresis losses. Further, amongst the whole prepared samples, the alloy containing 1.1 at% P showed the lowest hysteresis loss (6.99 W/kg), eddy current loss (9.25 W/kg) as well as the highest magnetic induction (1.7 T) at 5000 A/M (B50).

Jafari, S.; Beitollahi, A.; EftekhariYekta, B.; Kanada, Keiu; Ohkubo, T.; Gopalan, R.; Herzer, Giselher; Hono, K.

2014-05-01

450

Non-uniform magnetization reversal in nanocomposite magnets  

NASA Astrophysics Data System (ADS)

Magnetization reversal and exchange coupling are investigated in Pr-Fe-B melt-spun ribbons. In nanocomposite magnets, not only does the coercivity decrease but also magnetization reversal becomes more non-uniform in hard grains. The non-uniform magnetization reversal, resulting in a deterioration of squareness in hysteresis loop and a drop of the maximum Henkel plot value, mainly is caused by random arrangement of easy axes and intergranular soft regions among hard grains even with well exchange coupling between soft-hard grains in these ribbons. It is expected that the uniformity in magnetization reversal could be improved with the perfection of easy axes alignment in anisotropy nanocomposites.

Li, Z. B.; Zhang, M.; Shen, B. G.; Sun, J. R.

2013-03-01

451

Hysteresis Phenomena for the Series Circuit of Two Identical Negative Differential Resistance Devices  

Microsoft Academic Search

The hysteresis phenomena and current-voltage (I-V) characteristics of a series combination of two identical negative differential resistance (NDR) devices are analyzed. In this study, two different cases are discussed. The analysis shows that hysteresis phenomena in the combined I-V characteristics depend upon the electrical parameters of the series-connected NDR devices. The relationships between the hysteresis voltage and electrical parameters are

Kwang-Jow Gan

2001-01-01

452

Hysteresis zone or locus - Aerodynamic of bulbous based bodies at low speeds  

NASA Technical Reports Server (NTRS)

Experimental data are presented which seem to suggest that a well-defined hysteresis locus on bulbous based bodies at low speeds does not exist. Instead, if the experiment is repeated several times, the entire hysteresis region seems to fill with data rather than trace out a specific hysteresis locus. Data obtained on an oscillating model even at low reduced frequencies may be well defined but when applied to arbitrary motion lead to less accurate results than desired.

Covert, E. E.

1979-01-01

453

Quenching of giant hysteresis effects in La1-zYzHx switchable mirrors  

Microsoft Academic Search

The giant intrinsic hysteresis as a function of hydrogen concentration x in the optical and electrical properties of the archetypal switchable mirror YHx is eliminated by alloying Y with the chemically similar La. The La1-zYzHx films with z?0.67 are essentially hysteresis-free. The origin of the large hysteresis of alloys with z?0.86 is the large uniaxial lattice expansion that accompanies their

Gogh van A. T. M; D. G. Nagengast; E. S. Kooij; N. J. Koeman; R. P. Griessen

2000-01-01

454

Modeling and adaptive inverse control of hysteresis and creep in ionic polymer-metal composite actuators  

Microsoft Academic Search

Like most smart materials, such as piezoelectric materials and shape memory alloys, ion-exchange polymer-metal composite (IPMC), which is a kind of electroactive polymer material, exhibits the properties of hysteresis and creep. In this paper we explain the hysteresis and creep properties of IPMC, analyze the hysteresis using a discrete Prandtl-lshlinskii model, obtain a creep model of IPMC through modifying the

Lina Hao; Zhi Li

2010-01-01

455

Evolution of magnetic properties and magnetocaloric effect in TmNi1-xCuxAl (x = 0, 0.1, 0.3, 0.5, 0.7, 0.9, 1) compounds  

NASA Astrophysics Data System (ADS)

The magnetic and magnetocaloric properties of TmNi1-xCuxAl (x = 0, 0.1, 0.3, 0.5, 0.7, 0.9, 1) compounds have been investigated. With the substitution of Ni by Cu, the Tm-magnetic moment rotates its direction from basal plane to the c-axis and finally becomes canted antiferromagnetism structure with larger projected moments along the c-axis near Tord. Furthermore, large reversible magnetocaloric effects have been observed in TmNi1-xCuxAl compounds around Tord, with no thermal hysteresis and magnetic hysteresis loss. The values of -?SMmax and refrigerant capacity are greatly improved when the part of Ni was superseded by Cu. In particular, under the magnetic field change of 2 T, a large -?SMmax of TmNi0.7Cu0.3Al (10.7 J/kg K) is almost twice that of TmNiAl (5.5 J/kg K) and 17.2 J/kg K for TmCuAl around 4 K. The present results indicate that TmNi1-xCuxAl (x ? 0.3) compounds could be considered as good candidate materials for low-temperature and low-field magnetic refrigerant.

Mo, Zhao-Jun; Shen, Jun; Chen, Gui-Feng; Yan, Li-Qin; Zheng, Xinqi; Wu, Jian-Feng; Tang, Cheng-Chun; sun, Ji-Rong; Shen, Bao-Gen

2014-05-01

456

Fabrication of surfaces with extremely high contact angle hysteresis from polyelectrolyte multilayer.  

PubMed

High contact angle hysteresis on polyelectrolyte multilayers (PEMs) ion-paired with hydrophobic perfluorooctanoate anions is reported. Both the bilayer number of PEMs and the ionic strength of deposition solutions have significant influence on contact angle hysteresis: higher ionic strength and greater bilayer number cause increased contact angle hysteresis values. The hysteresis values of ~100° were observed on smooth PEMs and pinning of the receding contact line on hydrophilic defects is implicated as the cause of hysteresis. Surface roughness can be used to further tune the contact angle hysteresis on the PEMs. A surface with extremely high contact angle hysteresis of 156° was fabricated when a PEM was deposited on a rough substrate coated with submicrometer scale silica spheres. It was demonstrated that this extremely high value of contact angle hysteresis resulted from the penetration of water into the rough asperities on the substrate. The same substrate hydrophobized by chemical vapor deposition of 1H,1H,2H,2H-perfluorooctyltriethoxysilane exhibits high advancing contact angle and low hysteresis. PMID:22044032

Wang, Liming; Wei, Jingjing; Su, Zhaohui

2011-12-20

457

Effect of contact angle hysteresis on moving liquid film integrity.  

NASA Technical Reports Server (NTRS)

A study was made of the formation and breakdown of a water film moving over solid surfaces (teflon, lucite, stainless steel, and copper). The flow rate associated with film formation was found to be higher than the flow rate at which film breakdown occurred. The difference in the flow rates for film formation and film breakdown was attributed to contact angle hysteresis. Analysis and experiment, which are in good agreement, indicated that film formation and film breakdown are functions of the advancing and receding angles, respectively.

Simon, F. F.; Hsu, Y. Y.

1972-01-01

458

Effect of contact angle hysteresis on moving liquid film integrity  

NASA Technical Reports Server (NTRS)

A study was made of the formation and breakdown of a water film moving over solid surfaces (teflon, lucite, stainless steel, and copper). The flow rate associated with film formation was found to be higher than the flow rate at which film breakdown occurred. The difference in the flow rates for film formation and film breakdown was attributed to contact angle hysteresis. Analysis and experiment, which are in good agreement, indicated that film formation and film breakdown are functions of the advancing and receding angles, respectively.

Simon, F. F.; Hsu, Y. Y.

1972-01-01

459

A General Model for Estimating the Laminated Steel Losses Under PWM Voltage Supply  

Microsoft Academic Search

The new model is based on a modified Steinmetz equation and employs a hysteresis-loss multiplicative coefficient and a combined coefficient for eddy-current and excess losses, both coefficients being variable with induction and frequency. The material model coefficients are first identified through multifrequency tests with sine-wave excitation. The iron-loss increase due to pulsewidth-modulation supply is estimated using global waveform parameters of

Mircea Popescu; Dan M. Ionel; Aldo Boglietti; Andrea Cavagnino; Calum Cossar; Malcolm Iain McGilp

2010-01-01

460

Frequency dependence of core loss in rapidly quenched Fe6.5 wt. %Si  

Microsoft Academic Search

The frequency, field, and temperature dependencies of core loss in rapidly quenched Fe-6.5 wt. %Si ribbons are reported. The annealed material exhibits (001)?uv0? fiber texture, resulting in isotropic properties in plane; equivalent losses and B-H loops are seen in tape-wound toroids and in annuli punched from ribbon. Hysteresis losses predominate in the present Fe-6.5%Si up to about 1 kHz, as

G. E. Fish; C.-F. Chang; R. Bye

1988-01-01

461

A General Model of the Laminated Steel Losses in Electric Motors with PWM Voltage Supply  

Microsoft Academic Search

A procedure is described for identifying a general mathematical model of core losses in ferromagnetic steel when the voltage supply is non-sinusoidal, i.e. PWM inverter-fed type. This model has a hysteresis loss multiplicative coefficient variable with frequency and induction and a combined coefficient for eddy-current and excess losses that is also variable with frequency and induction. The effect of the

Dan Ionel; Mircea Popescu; C. Cossar; M. I. McGilp; A. Boglietti; A. Cavagnino

2008-01-01

462

Lattice water molecules tuned spin-crossover for an iron(II) complex with thermal hysteresis.  

PubMed

A new iron(II) complex based on the 4,4'-dimethyl-2,2'-bipyridine ligand [Fe(4,4'-dmbpy)3(ClO4)(SCN)·3H2O (1·3H2O)] has been prepared and characterized. Structural studies and Hirshfeld surface analysis for complex 1·3H2O at three different temperatures (300, 240 and 130 K) are described. The UV-vis absorption spectrum of a water-free sample (1) in methanol solution and magnetic susceptibility measurements for solid-state samples 1·3H2O and 1 revealed that the removal of lattice water molecules from complex 1·3H2O changed the magnetic properties from the low-spin state (1·3H2O) to the complete spin-crossover (1) between 350-220 K with a thermal hysteresis of 7 K, and was accompanied by a colour change from brown to red. PMID:25301143

Luo, Yang-Hui; Yang, Li-Jing; Liu, Qing-Ling; Ling, Yang; Wang, Wei; Sun, Bai-Wang

2014-11-28

463

Hysteresis, avalanches, and disorder-induced critical scaling: A renormalization-group approach  

SciTech Connect

Hysteresis loops are often seen in experiments at first-order phase transformations, when the system goes out of equilibrium. They may have a macroscopic jump (roughly as in the supercooling of liquids) or they may be smoothly varying (as seen in most magnets). We have studied the nonequilibrium zero-temperature random-field Is