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1

Rate-dependent hysteresis losses in ensembles of magnetic nanoparticle clusters  

NASA Astrophysics Data System (ADS)

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

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

2012-02-01

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

Magnetization Process: Hysteresis.  

National Technical Information Service (NTIS)

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

R. Balsamel

1990-01-01

4

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

NASA Astrophysics Data System (ADS)

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

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

2008-01-01

5

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

6

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

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

7

An Analysis of the Hysteresis Motor Part III: Parasitic Losses  

Microsoft Academic Search

A major constraint on the performance prediction of a hysteresis machine arises from the parasitic losses associated with the rotor magnetic material. These losses can be high enough to absorb much of the developed torque, particularly for small sizes and large numbers of poles. In this paper the phenomena which cause parasitic losses are examined in detail. Analytical expressions are

M. A. Rahman; Miles Copeland; Gordon Slemon

1969-01-01

8

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

9

Hysteresis motor using magnetically anisotropic Fe-Cr-Co magnet  

Microsoft Academic Search

For the rotor ring of the hysteresis motor, semihard Alnico magnets have been almost applied until now. However, the hysteresis motor using Alnico magnets has several disadvantages. In order to improve the disadvantages of conventional hysteresis motors, the Fe-Cr-Co magnet steel with magnetic anisotropy is applied for hysteresis rotor ring. Magnetic anisotropy is used to cause large reluctance torque and

Tomotsugu Kubota; Genjiro Wakui; Minoru Itagaki

1998-01-01

10

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

11

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

12

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

13

PERFORMANCE OF HYSTERESIS PERMANENT MAGNET MOTORS  

Microsoft Academic Search

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

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

1989-01-01

14

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.

15

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

16

Magnetic equivalent circuit of PM hysteresis synchronous motor  

Microsoft Academic Search

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

R. Qin; M. A. Rahman

2003-01-01

17

Starting and synchronization of permanent magnet hysteresis motors  

Microsoft Academic Search

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

M. A. Rahman; Ruifeng Qin

1994-01-01

18

Starting and synchronization of permanent magnet hysteresis motors  

Microsoft Academic Search

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

M. Azizur Rahman; Ruifeng Qin

1996-01-01

19

Magnetic equivalent circuit of PM hysteresis synchronous motor  

Microsoft Academic Search

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

Ruifeng Qin; M. A. Rahman

2003-01-01

20

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

SciTech Connect

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

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

1999-05-01

21

A permanent magnet hysteresis hybrid synchronous motor for electric vehicles  

Microsoft Academic Search

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

M. Azizur Rahman; Ruifeng Qin

1997-01-01

22

A permanent magnet hysteresis hybrid motor drive for electric vehicles  

Microsoft Academic Search

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

M. A. Rahman; Ruifeng Qin

1996-01-01

23

Transient performance analysis for permanent-magnet hysteresis synchronous motor  

Microsoft Academic Search

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

Kazumi Kurihara; M. Azizur Rahman

2004-01-01

24

Coupling currents and hysteresis losses in MgB2 superconductors  

NASA Astrophysics Data System (ADS)

MgB2 multi-filamentary superconductors are widely considered for use in dc applications. To expand the possible application range to ac apparatuses, the development of a low ac loss wire is needed. This development involves several steps, and a solid understanding of the loss mechanisms is important to optimize that process as well as for evaluating dc wires exposed to current or magnetic field ripple. In this study we discuss the coupling currents and their influence on hysteresis loss as well as on coupling current loss. We give a phenomenological explanation of the origin and behaviour of the coupling currents and describe the loss patterns for hysteresis loss and coupling current loss separately. Finally, we interpret measured ac losses in an MgB2 wire cut into different lengths representing different equivalent twist pitches. Under certain circumstances short sample lengths are shown to give inaccurate measurement results. On the other hand, short sample lengths of non-twisted wires can be used to estimate the twist pitch necessary to electromagnetically decouple the superconducting filaments. For the studied MgB2 wire, with a pure titanium matrix, the losses were mainly hysteretic, although the level of these losses was lowered when reducing the equivalent twist pitch, and thereby the coupling currents. At 35 K the reduction in loss started at an equivalent twist pitch of approximately 36 mm, where the filaments were assumed practically fully coupled. The decoupling then continued all down to the shortest equivalent twist pitch of 9 mm.

Magnusson, N.; Lindau, S.; Taxt, H.; Runde, M.

2014-10-01

25

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

26

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.

27

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

Microsoft Academic Search

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

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

1992-01-01

28

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

29

Finite element analysis of hysteresis motor using the vector magnetization-dependent model  

Microsoft Academic Search

This paper presents a finite element analysis procedure combined with a vector hysteresis model for the accurate analysis of an hysteresis motor. The vector magnetization-dependent model is adopted to calculate the vector magnetization of the hysteresis ring. From the magnitude and direction of the magnetic field intensity, the magnetization of each ring element is calculated by the vector model. By

Hong-Kyu Kim; Hyun-Kyo Jung; Sun-Ki Hong

1998-01-01

30

Diagonal Mesh Equivalent (DME) for the calculation of the hysteresis losses in electrical machines  

NASA Astrophysics Data System (ADS)

The Magnetic Equivalent Circuits (MECs) technique is a powerful tool for machine analysis and power losses computation. Here, use is made of the Diagonal Mesh Equivalent (DME) to solve the equivalent electrical circuit for the branch fluxes to be easily computed and related to the machine compartments of technical interest. These are represented by the air gap, stator and rotor to name a few. Hysteresis loops have been computed, along with the static power losses, for assigned stator thicknesses and compared to ones alternatively obtained by the Modified Scalar Preisach Model. This study is especially aimed at giving improved issues to those who are engaged in the design of magnetic components for electrical machines.

Vergura, S.; Carpentieri, M.; Lattarulo, F.

2014-02-01

31

Transient Performance of Hysteresis Motors with Ferrite Magnets  

Microsoft Academic Search

This paper presents a general picture of basic features of the transient performance of circumferential-flux hysteresis motors when ferrite magnets (Ceramic–8) are oriented within the rotor. Based on the parallelogram approximation of the B-H loops of the magnetic materials, a mathematical model to predict the transient performance of such motors is given. This simple analysis is used in demonstrating various

A. M. Osheiba; M. A. Rahman

1986-01-01

32

Torque computation of hysteresis motor using finite element analysis with asymmetric two dimensional magnetic permeability tensor  

Microsoft Academic Search

This paper deals with the analysis of the generated torque of the hysteresis motor using finite element method, The material property of the hysteresis ring in the hysteresis motor is characterized by the asymmetric two dimensional magnetic permeability tensor. The torque has been computed effectively by using permeability tensor instead of full hysteresis modeling or Maxwell stress tensor. The proposed

Hak-Yong Lee; Song-Yop Hahn; Gwan-Soo Park; Ki-Sik Lee

1998-01-01

33

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

34

Analysis of hysteresis motor using finite element method and magnetization-dependent model  

Microsoft Academic Search

In this paper, finite element analysis (FEA) of a hysteresis motor using a magnetization-dependent model is presented. The hysteresis loop in the hysteresis ring is calculated from the maximum flux density which is obtained by the FEA. The proposed method is applied to a sample motor and the simulation result shows a very good agreement with the experimental one. Various

Hong-Kyu Kim; Sun-Ki Hong; Hyun-Kyo Jung

2000-01-01

35

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

36

Isochronal annealing studies of a plastically deformed ferromagnetic metal using magnetic hysteresis measurements  

Microsoft Academic Search

An experimental study has been made of magnetic hysteresis in plastically deformed and annealed gadolinium (Gd) metal as a function of annealing temperature. Seven plastically deformed samples were annealed at temperatures ranging from 155° to 916°C; major and minor magnetic hysteresis loops of these seven samples plus one as-deformed sample were examined. The results are discussed in terms of the

Frederick Milstein; John A. Baldwin; Timothy W. James

1973-01-01

37

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

Microsoft Academic Search

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

J. Qian; M. Azizur Rahman

1991-01-01

38

Magnetoabsorption and magnetic hysteresis in Ni ferrite nanoparticles  

NASA Astrophysics Data System (ADS)

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

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

2013-01-01

39

Power losses in magnetic bearing system for flywheel energy storage  

SciTech Connect

A magnetically suspended flywheel energy storage system has generated unexpected large power losses during spin down tests. Since the system operates in a high vacuum condition, possible power losses come from the hysteresis and eddy current losses of magnetic bearing return rings. To find out their losses, the magnetic properties of the return rings are tested using DC and AC magnetization tests. The results show that the return rings have low AC permeability and huge eddy current loss, which differ greatly from the manufacturer`s specifications. Because of non-laminated magnetic materials, the skin effect of the eddy currents prevents magnetic flux penetration and contributes to higher power loss. A one-dimensional eddy current model is derived and used to confirm the skin effect on the magnetic bearing return rings. In order to eliminate large eddy current loss at high speeds, the usage of thin laminations of high electrical resistance materials is suggested.

Pang, D.C. [Huafan College of Humanities and Technology, Taipei Hsien (Taiwan, Province of China)

1995-12-31

40

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

41

Effects of temperature ramp rate during heat treatment on hysteresis loss and critical current density of internal tin processed wires  

SciTech Connect

It has been shown that temperature ramp rates utilized in heat treatment schedules for internal tin processed Nb{sub 3}Sn wires substantially influence both hysteresis loss and critical current density J{sub c} of the wires, i.e. a slow ramp rate (e.g. 6{degree}C/h) favors a higher J{sub c} while a fast ramp (e.g. 60{degree}C/h)results in a low hysteresis loss of the wire.

Suenaga, M.; Sabatini, R.L.

1995-04-01

42

Computerized magnetic test and evaluation of hysteretic materials [hysteresis motors  

Microsoft Academic Search

Techniques are described which enable highly nonlinear hysteretic materials to be fully characterized. Major hysteresis loops and minor trajectories are presented for one particular material sample. Test time is reduced to less than 10s, ensuring that heating effects in the ring sample are negligible. The method is appropriate for detailed material investigation for design or development applications. It is recognized,

P. T. Jowett; D. I. MacInnes

1989-01-01

43

Fuzzy control design of a magnetically actuated optical image stabilizer with hysteresis compensation  

NASA Astrophysics Data System (ADS)

A fuzzy controller (FC) is designed for a magnetically actuated optical image stabilizer (OIS) in order to suppress the vibrations caused by hand shakings and hysteresis. To this end, the dynamic model of the OIS with consideration of hysteresis is first established, along with assuming the hand-shaking vibration as sinusoidal excitations. It is clearly shown that with capability of continuing parameter tuning, the FC is superior to the conventional PID for vibration suppression.

Tu, Tse-Yi; Chao, Paul C.-P.; Chiu, Chi-Wei; Wang, Chun-Chieh; Huang, Jeng-Shen

2009-04-01

44

Analysis of field oriented control for permanent magnet hysteresis synchronous motors  

Microsoft Academic Search

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

Jianhua Qian; M. Azizur Rahman

1993-01-01

45

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

46

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

SciTech Connect

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

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

2005-04-09

47

A guided enquiry approach to introduce basic concepts concerning magnetic hysteresis to minimize student misconceptions  

NASA Astrophysics Data System (ADS)

Basic concepts concerning magnetic hysteresis are of vital importance in understanding magnetic materials. However, these concepts are often misinterpreted by many students and even textbooks. We summarize the most common misconceptions and present a new approach to help clarify these misconceptions and enhance students’ understanding of the hysteresis loop. In this approach, students are required to perform an experiment and plot the measured magnetization values and thereby calculated demagnetizing field, internal field, and magnetic induction as functions of the applied field point by point on the same graph. The concepts of the various coercivity, remanence, saturation magnetization, and saturation induction will not be introduced until this stage. By plotting this graph, students are able to interlink all the preceding concepts and intuitively visualize the underlying physical relations between them.

Wei, Yajun; Zhai, Zhaohui; Gunnarsson, Klas; Svedlindh, Peter

2014-11-01

48

A mechanism of magnetic hysteresis in heterogeneous alloys  

Microsoft Academic Search

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

E. C. Stoner; E. P. Wohlfarth

1991-01-01

49

Pentacobalt(II) cluster based pcu network exhibits both magnetic slow-relaxation and hysteresis behaviour.  

PubMed

A pentacobalt(II) cluster based 3D pcu network, [Co(5)(?(3)-OH)(2)(bpdc)(4)(dabco)(H(2)O)(2)] (bpdc = benzophenone-2,4'-dicarboxylate and dabco = 1,4-diazabicyclo[2,2,2] octane), exhibiting both slow magnetic relaxation and hysteresis behavior, has been hydrothermally synthesized. PMID:21069241

Hu, Sheng; Liu, Jun-Liang; Meng, Zhao-Sha; Zheng, Yan-Zhen; Lan, Yanhua; Powell, Annie K; Tong, Ming-Liang

2011-01-01

50

Magnetically hard materials for the motors of synchronous hysteresis electric motors  

Microsoft Academic Search

Synchronous hysteresis electric motors are widely used in automatic systems, high-speed mechanisms, and gyroscope drives in high-precision systems. The stator of such motors is the same as that of a synchronous or asynchronous electric motor, whereas the rotor is a hollow cylinder of magnetically hard alloy, mounted on a nonmagnetic bush. The cylinder may be monolithic or may consist of

E. V. Artamonov; M. A. Libman; N. N. Rudanovskii

2007-01-01

51

Analysis of field oriented control for permanent magnet hysteresis synchronous motors  

Microsoft Academic Search

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

J. Qian; M. A. Rahman

2009-01-01

52

Finite element analysis of hysteresis motor combined with magnetization-dependent model  

Microsoft Academic Search

This paper presents a method which combines the finite element method with the magnetization-dependent Preisach model for analyzing the hysteresis motor. The proposed method is applied to a sample motor. From the obtained results, it is found that the output torque of the rotor can be estimated by considering harmonic effects due to slot and winding distributions

Hong-Kyu Kin; Hyun-Kyo Jung; Sun-Ki Hong

1997-01-01

53

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

Microsoft Academic Search

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

Ruifeng Qin; M. A. Rahman

1997-01-01

54

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

E-print Network

High Gain Observer for Induction Motor in Presence of Magnetic Hysteresis H. Ouadi1 , F. Giri2 , L in induction motors is considered in this paper. In most previous works, motor observers have been designed significant load torque changes. In this paper, a high gain observer is designed for induction motors based

Paris-Sud XI, Université de

55

Magnetic hysteresis in young mid-ocean ridge basalts: Dominant cubic anisotropy?  

Microsoft Academic Search

Magnetic hysteresis data from young mid-ocean ridge basalts include samples with saturation remanence to saturation magnetization (Mrs\\/Ms) ratios greater than 0.5, the theoretical limit for an assemblage of single domain grains with uniaxial anisotropy. Under the usual assumption of dominant uniaxial anisotropy, the narrow single domain grain size implied by the high Mrs\\/Ms values is difficult to reconcile with petrographic

Jeff Gee; Dennis V. Kent

1995-01-01

56

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

57

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

58

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

59

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

Microsoft Academic Search

Rotor power losses in magnetic bearings cannot be accurately calculated at this time because of the complexity of the magnetic field distribution and several other effects. The losses are due to eddy currents, hysteresis, and windage. This paper presents measured results in radial magnetic bearing configurations with eight pole and 16 pole stators and two laminated rotors. Two different air

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

1999-01-01

60

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

61

Magnetic processes in hysteresis motors equipped with melt-textured YBCO  

Microsoft Academic Search

Several hysteresis motors have been constructed with an output power up to 500 W at T=77 K. The rotors of these machines consist of melt-textured YBCO. In this work, the authors present detailed investigations on the magnetic processes in these rotors. Spheres were cut from melt-textured YBCO and investigated by rotating in vector-VSM. From these measurements, torque moments on the

T. Habisreuther; T. Strasser; W. Gawalek; P. Gornert; K. V. Ilushin; L. K. Kovalev

1997-01-01

62

Energy loss in magnetic switching cores  

SciTech Connect

This analytical study had two objectives. The first was to develop a computer code to model, temporally and spatially, the magnetization of amorphous ferrous materials (specifically Metglas) in an inductive circuit element under high surface field conditions while including the interaction of that element with the electrical circuit in a self-consistent manner. The second goal was to partition the energy losses experimentally measured in such a ferrous core according to loss mechanism by making comparisons between the experimental data and the computer simulation. The loss mechanisms considered were eddy current, hysteresis, and other. Experimental data to be compared with the results of the simulation had been previously collected at Los Alamos National Laboratory in the course of a program in which a 1 kHz, three stage magnetic modulator was built. However, inconsistencies in the experimental data became apparent as comparisons were being made between the results of the computer simulation and the LANL data. For this reason, the results in this report have been derived from experimental data supplied by Sandia National Laboratories. A key portion of this work was the development of a computer code to model the magnetization of the ferrous core material. The beginnings of the code had been developed by Howard Rhinehart and Bill Nunnally at Los Alamos, and were written in LASAN, the Los Alamos Systems Analysis language. In the early stages of this project, a great deal of time was spent adapting the LASAN program to run on the VAX computer here at South Carolina. Insufficient documentation proved to be the downfall of these efforts, and later (in retrospect, far to late) we abandoned the idea of running the simulation under LASN, and instead rewrote the simulation in ACSL, a systems simulation code which is supported on our VAX. 18 figs., 1 tab.

Dougal, R.A.

1988-07-01

63

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

64

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

65

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

Microsoft Academic Search

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

Yuichi Suzuki; Masato Sagawa; Masanori Okada; Zenzo Henmi

1979-01-01

66

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

NASA Astrophysics Data System (ADS)

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

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

2013-05-01

67

Hysteresis 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

68

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

NASA Astrophysics Data System (ADS)

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

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

2013-07-01

69

Torque calculation of hysteresis motor using vector hysteresis model  

Microsoft Academic Search

This paper presents how to determine the thickness of the hysteresis ring of hysteresis motor using the finite element method combined with a vector hysteresis model. From the magnitude and direction of the magnetic field intensity, the magnetization of each ring element is calculated by the vector hysteresis model and the torque can be obtained from the vector sum of

Sun-Ki Hong; Kong-Kyu Kim; Hyeong-Seok Kim; Hyun-Kyo Jung

2000-01-01

70

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

71

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

NASA Astrophysics Data System (ADS)

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

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

2009-08-01

72

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

NASA Astrophysics Data System (ADS)

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

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

2010-10-01

73

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

74

A Jiles-Atherton and fixed-point combined technique for time periodic magnetic field problems with hysteresis  

SciTech Connect

The hysteresis phenomenon can significantly affect the behavior of magnetic cores in electrical machines and devices. This paper presents a finite element solution of periodic steady state magnetic field problems in soft materials with scalar hysteresis. The Jiles-Atherton model is employed for the generation of symmetric B-H loops and it is coupled with the Fixed Point Technique for handling magnetic nonlinearities. The proposed procedure is applied to a hysteretic model problem whose analytical solution is available. The results show that the Fixed Point Technique can efficiently deal with non-single valued material characteristics under periodic operating conditions.

Chiampi, M.; Repetto, M. [Politecnico di Torino (Italy). Dipt. di Ingegneria Elettrica Industriale] [Politecnico di Torino (Italy). Dipt. di Ingegneria Elettrica Industriale; Chiarabaglio, D. [Istituto Elettrotecnico Nazionale Galileo Ferraris, Torino (Italy)] [Istituto Elettrotecnico Nazionale Galileo Ferraris, Torino (Italy)

1995-11-01

75

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

NASA Astrophysics Data System (ADS)

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

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

2012-04-01

76

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

77

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

SciTech Connect

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

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

1983-01-01

78

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

SciTech Connect

The series of ferromagnetic intermetallics Gd/sub 1-x/ Er/sub x/Al/sub 2/ are candidate working materials for magnetic refrigeration because of their large moment, small anisotropy, and their wide range of Curie temperatures (14 to 164 K). We have measured the magnitude of the magnetic hysteresis as a function of temperature from 4 K to T/sub C/ for polycrystalline samples of these materials by ac magnetic susceptibility and magnetization hysteresis loops. We found, as expected, virtually no hysteresis in GdAl/sub 2/, and, more surprisingly, less than 3000 A/m hysteresis in ErAl/sub 2/ and 2 x 10/sup 4/ A/m in Gd/sub 0.5/ Er/sub 0.5/Al/sub 2/. Moreover, the hysteresis in Gd/sub 0.5/ Er/sub 0.5/Al/sub 2/ was <100 A/m for T-T/sub C/< 20 K.

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

1984-03-20

79

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

80

Mechanical hysteresis in iron: Magnetomechanical damping (MMD), magnetic flux variations and harmonics at 22.5 KHz  

NASA Astrophysics Data System (ADS)

We studied the magnetomechanical damping, the flux variations, and the corresponding harmonics of two purities of iron at 22.5 KHz as a function of strain amplitude, applied magnetic field, and state of annealing at room temperature. We extended the range of strain amplitude two orders of magnitude lower, and uncovered five distinct regions of magnetomechanical damping contrary to the three regions described by the standard picture. This regions are: (i) a new amplitude dependent, for epsilon < 3x10-7, with increasing damping in applied fields, a region not previously known and inconsistent with the existing picture of magnetomechanical models, (ii) a well known amplitude independent region attributed to microeddy damping, (iii) an amplitude dependent region called the Rayleigh region, with decreasing damping in applied fields, (iv) another amplitude dependent region, the super-Rayleigh region, with decreasing damping in applied fields, and (v) a region of damping peak, where the damping begins to fall. This observations challenge the standard description of magnetomechanical damping, specially the low amplitude dependent region is at low end of Rayleigh range where the hysteretic damping or the Rayleigh damping increases linearly with amplitude, an increase that is scarcely observable at strain amplitudes below 10-6. We also examined the nonlinear hysteretic behavior of magnetomechanical damping using the method of flux signal and the corresponding harmonics. The observed power laws for the harmonics tend, particularly at lower strain amplitude, agree to a limited extent with the hysteresis theory prediction that the amplitudes varies as a second power of the strain amplitude, a prediction directly related to the linear increase of damping in the Rayleigh range. The exceptions at higher amplitudes indicate that another form of damping is appearing, with it own characteristic laws, not fully understood. The prediction by Rayleigh law Fourier analysis that only odd harmonics is produced in harmonic generation in magnetic driven specimen is less well obeyed, as both odd and even harmonics are observed. Magnetomechanical damping hysteresis up to now faced a significant theoretical challenge, because of its complexity. This complexity of the damping mechanisms rapidly increases when one considers the different process taking place between domain walls, defects and dislocations. Responding to this, we proposed mechanical hysteresis model for magnetomechanical hysteresis especially for Rayleigh damping to account for the large damping of demagnetized specimens. The model is based on Landau's arrangement of magnetic domains with no overall magnetic moment. To analyze the model, we use the nature of magnetostriction to transform our experimental damping data into energy loss and volume fraction reoriented by stress as functions of strain amplitude. Our model predicts fairly well the magnetomechanical damping peak above the upper end of the Rayleigh range, which is attributed to change in number of domain walls. The Rayleigh region is attributed to dynamics of closure domains on a finer scale, and the lower end of the range to the wall displacements, while the super-Rayleigh region to is the onset of gross changes in the domain structure.

Vunni, George Blue

81

Application of hysteresis modeling to magnetic techniques for monitoring biaxial stress  

SciTech Connect

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

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

1993-12-31

82

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

83

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

NASA Astrophysics Data System (ADS)

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

Narod, B. B.

2014-06-01

84

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

NASA Astrophysics Data System (ADS)

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

Narod, B. B.

2014-09-01

85

Magnetic hysteresis properties of melt-spun Nd-Fe-B alloys prepared by centrifugal method  

NASA Astrophysics Data System (ADS)

Magnetic hysteresis properties and microstructure peculiarities of melt spun Nd-Fe-B alloys (ribbons) prepared by melt quenching onto the internal surface of an iron spinning wheel at tangential speeds in the range 5-20 m/s are reported. The alloy composition was Nd-36% wt, B-1.2% wt. and Fe-remainder. It was found that the coercivity of ribbons does not practically depend on the wheel speed in applied range (18 kOe at 5 m/s and 22 kOe at 20 m/s), whereas the grain size of the basic phase (2-14-1) steadily decreases when the speed rises, starting from 2-3 ?m for 5 m/s alloy down to the 200-300 nm for 20 m/s alloy. All ribbons have normal convex demagnetization curves, even those prepared at low wheel speeds (without peculiar step near H˜0, which usually exists on such curves for traditionally prepared underquenched melt-spun Nd-Fe-B alloys). Grinding the ribbon in a vibration mill causes the coersivity drop to 7 kOe after 120 min of treatment. However, this operation increases the powder alignment ability and, as a result, the energy product for a fully dense magnet from anisotropic powder prepared from some ribbons rises to 20-23 MGOe.

Andreev, S. V.; Kudrevatykh, N. V.; Pushkarsky, V. I.; Markin, P. E.; Zaikov, N. K.; Tarasov, E. N.

1998-08-01

86

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

NASA Astrophysics Data System (ADS)

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

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

2013-09-01

87

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

88

Optimum energy loss in electro magnetic bearing  

Microsoft Academic Search

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

Santosh Shelke; R. V. Chalam

2011-01-01

89

Hysteresis Loss in Power Cables Made of 2G HTS Wires With NiW Alloy Substrate  

Microsoft Academic Search

G HTS wires produced with the MOD\\/RABiTS process with NiW substrates have weak magnetism and therefore extra losses in a substrate. The goal of this paper is to find out the model that could describe losses just in a substrate only. Two and three dimensional numerical electromagnetic field analysis has been developed for two-layer cables made of 2G HTS conductors

Vasily V. Zubko; Alexander A. Nosov; Nelly V. Polyakova; Sergey S. Fetisov; Vitaly V. Vysotsky

2011-01-01

90

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

NASA Astrophysics Data System (ADS)

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.

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

2014-09-01

91

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

92

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

93

Roughness dependent magnetic hysteresis of a few monolayer thick Fe films on Au(001)  

Microsoft Academic Search

We have studied quantitatively the surface and interface roughness of Fe films in a new monolayer regime on an Au(001) surface using the high-resolution low-energy electron diffraction technique. The hysteresis loops of those films were also measured in situ by the surface magneto-optical kerr effect technique. A correlation between the shape of hysteresis loops and the roughness of films was

Y.-L. He; G.-C. Wang

1994-01-01

94

Roughness dependent magnetic hysteresis of a few monolayer thick Fe films on Au(001)  

Microsoft Academic Search

We have studied quantitatively the surface and interface roughness of Fe films in a few monolayer regime on an Au(001) surface using the high-resolution low-energy electron diffraction technique. The hysteresis loops of those films were also measured insitu by the surface magneto-optical kerr effect technique. A correlation between the shape of hysteresis loops and the roughness of films was observed.

Y.-L. He; G.-C. Wang

1994-01-01

95

Truth about motor core loss  

SciTech Connect

The phenomena of energy losses in electric motors known as core losses is discussed. Both hysteresis losses and eddy losses were included in the presentation. Factors affecting hysteresis losses include the chemical composition of the steel, the physical properties of the steel, the strength of the magnetic field, and the frequency of the applied voltage. The lamination of cores for the reduction of eddy losses is also mentioned.

Nailen, R.L.

1983-03-01

96

Core losses in permanent magnet motors  

Microsoft Academic Search

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

G. R. Slemon; X. Liu

1990-01-01

97

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

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

98

Investigation into loss in ferrofluid magnetization  

NASA Astrophysics Data System (ADS)

Ferrofluids containing ?-Fe2O3/Ni2O3 nanoparticles (not chemically treated) were synthesized using water and mixed water-glycerol as carrier liquid and the ferrofluid viscosity was modified by varying the glycerol content in the carrier liquid. The apparent magnetization of the ferrofluids decreased with increasing glycerol content. The loss in magnetization is described by the ratio of effective magnetic volume fraction to physical volume fraction of nanoparticles in the ferrofluids as a characteristic parameter. We ascribe the loss to the formation of "dead aggregates" having a ring-like structure of closed magnetic flux rather than to any chemical reaction. Such dead aggregates exist in zero magnetic field and do not contribute to the magnetization in the low or high field regime, so that the effective magnetic volume fraction in the ferrofluids decrease. An increase in carrier liquid viscosity is similar to a weakening of the thermal effect, so the number of dead aggregates increases and the magnetization decreases in inverse proportion to the viscosity. This relationship between the apparent magnetization and ferrofluid carrier liquid viscosity can be termed the "viscomagnetic effect".

Li, J.; Gong, X. M.; Lin, Y. Q.; Liu, X. D.; Chen, L. L.; Li, J. M.; Mao, H.; Li, D. C.

2014-07-01

99

Mass loss from warm giants: Magnetic effects  

NASA Technical Reports Server (NTRS)

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

Mullan, D. J.

1980-01-01

100

Photoneutrino energy loss rates under magnetic field  

Microsoft Academic Search

The neutrino energy loss rate is calculated due to the photoneutrino process in a hot plasma, under magnetic field.\\u000a \\u000a The calculations done for low densities and relatively low temperatures may be used for astrophysical estimations in neutron\\u000a stars.

M. El-Khishen; A. El-Gowhari; M. Toubia

1975-01-01

101

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

102

Experimentally determined rotor power losses in homopolar and heteropolar magnetic bearings  

SciTech Connect

The identification of parameters that dictate the magnitude of rotor power losses in radial magnetic bearings is very important for many applications. Low loss performance of magnetic bearings in aerospace equipment such as jet engines and flywheel energy storage systems is especially critical. Two basic magnetic bearing designs are employed in industrial practice today: the homopolar design, where the flux paths are of mixed radial/axial orientation, and the heteropolar design, where the flux paths are primarily radial in nature. The stator geometry and flux path of a specific bearing can have a significant effect on the rotor losses. This paper describes the detailed measurement of rotor losses for experimentally comparable homopolar and heteropolar designs. The two test bearing configurations are identical except for geometric features that determine the direction of the flux path. Both test bearing design have the same air gap length, tip clearance ratio, surface area under the poles, and bias flux levels. An experimental test apparatus was used where run down tests were performed on a test rotor with both bearing designs to measure power losses. Numerous test runs where made for each bearing configuration by running multiple levels of flux density. The components of the overall measured power loss, due to hysteresis, eddy currents, and windage, were determined based on theoretical expressions for power loss. It was found that the homopolar bearing had significantly lower power losses than the heteropolar bearing.

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

1999-10-01

103

Hysteresis loops of individual Co nanostripes measured by magnetic force microscopy  

PubMed Central

High-resolution magnetic imaging is of utmost importance to understand magnetism at the nanoscale. In the present work, we use a magnetic force microscope (MFM) operating under in-plane magnetic field in order to observe with high accuracy the domain configuration changes in Co nanowires as a function of the externally applied magnetic field. The main result is the quantitative evaluation of the coercive field of the individual nanostructures. Such characterization is performed by using an MFM-based technique in which a map of the magnetic signal is obtained as a function of both the lateral displacement and the magnetic field. PMID:21711935

2011-01-01

104

Steady-State Performance of Polyphase Hysteresis-Reluctance Motors  

Microsoft Academic Search

It is well known that the hysteresis-reluctance motor produces a torque that combines hysteresis and reluctance effects. Consequently, the performance characteristics would be increased when compared to that of the plain hysteresis motor. This paper presents a new design of a hysteresis-reluctance rotor in which the magnetic saliency was created by cutting slots in the inside diameter of the hysteresis

M. A. Rahman; A. M. Osheiba

1986-01-01

105

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

106

Test Analysis and Calculation of Polyphase Hysteresis Motors  

Microsoft Academic Search

This paper presents a method of analyzing hysteresis motors for their parameters, gross power, losses and magnetizing ampere turns. A method is shown for calculating performance from either calculated or tested parameters. A synthesis method is given for determining rotor ring thickness.

P. H. Trickey

1972-01-01

107

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

NASA Astrophysics Data System (ADS)

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

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

2010-12-01

108

Mathematical Models of Hysteresis (Dynamic Problems in Hysteresis).  

National Technical Information Service (NTIS)

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

I. Mayergoyz

2006-01-01

109

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

Microsoft Academic Search

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

Melanie Dillon; Christine Franke

2009-01-01

110

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

NASA Astrophysics Data System (ADS)

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

Garshelis, I. J.; Crevecoeur, G.

2014-05-01

111

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

SciTech Connect

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

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

1999-04-01

112

Wireless and passive temperature indicator utilizing the large hysteresis of magnetic shape memory alloys  

NASA Astrophysics Data System (ADS)

An ultra-low cost, wireless magnetoelastic temperature indicator is presented. It comprises a magnetostrictive amorphous ribbon, a Ni-Mn-Sn-Co magnetic shape memory alloy with a highly tunable transformation temperature, and a bias magnet. It allows to remotely detect irreversible changes due to transgressions of upper or lower temperature thresholds. Therefore, the proposed temperature indicator is particularly suitable for monitoring the temperature-controlled supply chain of, e.g., deep frozen and chilled food or pharmaceuticals.

Bergmair, Bernhard; Liu, Jian; Huber, Thomas; Gutfleisch, Oliver; Suess, Dieter

2012-07-01

113

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

114

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

NASA Astrophysics Data System (ADS)

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

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

115

AC loss of HTSC bulks for magnetic levitation  

Microsoft Academic Search

The new simulation method was developed based on the T-method to simulate the AC loss of high temperature superconducting magnetic flywheel when the magnetic rotor rotates with the inhomogeneous component of the magnetic field. The dependencies of AC loss upon some conditions such as the wave number, the amplitude of inhomogeneous component and so on were analyzed.

Kazuyuki Demachi; Ryusuke Numata; Ryota Shimizu; Kenzo Miya; Hiromasa Higasa

2001-01-01

116

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

117

Low-loss energy storage flywheel  

NASA Technical Reports Server (NTRS)

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

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

1977-01-01

118

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

119

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

Microsoft Academic Search

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

Mohammad Modarres; Abolfazl Vahedi; Mohammadreza Ghazanchaei

2010-01-01

120

[Mathematical models of hysteresis  

SciTech Connect

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

Mayergoyz, I.D.

1991-01-01

121

Study on the hunting in high speed hysteresis motors due to the rotor hysteresis material  

Microsoft Academic Search

Hysteresis motors behave very much like to classical synchronous motors, except that the motor magnetic pole definition varies slightly with torque. This paper presents a study on the hunting of a radial-flux type, high speed hysteresis motor caused by the hysteresis material of the rotor. Firstly, a nonlinear dynamic model of the PWM-controlled hysteresis motor drive is developed in d-q

H. R. Soroush; A. R. Rahmati; H. Moghbelli; A. Vahedi; A. H. Niasar

2009-01-01

122

Design of experiment for hysteresis loops measurement  

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

123

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

124

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

125

Steady-State Performance of Polyphase Hysteresis-Reluctance Motors  

Microsoft Academic Search

It is well known that the hysteresis-reluctance motor produces a torque that is a combination of the hysteresis and reluctance effects. Consequently, the performance characteristics of a hysteresis-reluctance motor would be improved when compared to that of the plain hysteresis motor. This paper presents a new design of a hysteresis-reluctance rotor in which the magnetic saliency is created by cutting

M. A. Rahman; A. M. Osheiba

1986-01-01

126

Loss Investigation of Interior Permanent-Magnet Motors Considering Carrier Harmonics and Magnet Eddy Currents  

Microsoft Academic Search

In this paper, we investigate losses of interior permanent-magnet motors driven by pulsewidth-modulated inverters using 3D finite-element analysis, which can estimate the Eddy-current loss in the permanent magnet accurately. The calculated losses are compared with the measured results and the theoretical solution to verify the validity of the analysis. The variation of the magnet Eddy-current loss due to the division

Katsumi Yamazaki; Atsushi Abe

2009-01-01

127

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

NASA Astrophysics Data System (ADS)

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

Dupré, Luc; Sergeant, Peter; Vandenbossche, Lode

2005-05-01

128

MATHEMATICAL MODELS OF HYSTERESIS (DYNAMIC PROBLEMS IN HYSTERESIS)  

SciTech Connect

This research has further advanced the current state of the art in the areas of dynamic aspects of hysteresis and nonlinear large scale magnetization dynamics. The results of this research will find important engineering applications in the areas of magnetic data storage technology and the emerging technology of “spintronics”. Our research efforts have been focused on the following tasks: • Study of fast (pulse) precessional switching of magnetization in magnetic materials. • Analysis of critical fields and critical angles for precessional switching of magnetization. • Development of inverse problem approach to the design of magnetic field pulses for precessional switching of magnetization. • Study of magnetization dynamics induced by spin polarized current injection. • Construction of complete stability diagrams for spin polarized current induced magnetization dynamics. • Development of the averaging technique for the analysis of the slow time scale magnetization dynamics. • Study of thermal effects on magnetization dynamics by using the theory of stochastic processes on graphs.

Professor Isaak Mayergoyz

2006-08-21

129

Field Analysis of Polyphase Hysteresis Motor  

Microsoft Academic Search

A comprehensive theoretical field model has been developed for hysteresis motors. Using the stator current sheet technique, the motor field equations are rigoriously derived for the air gap and hysteresis ring regions. The analysis takes into account the contribution of the reaction field of rotor magnetization to the primary air gap field due to stator current sheets alone. Unlike induction

M. A. Rahman

1980-01-01

130

Analysis of a hysteresis motor with overexcitation  

Microsoft Academic Search

The performance of a hysteresis motor can be improved greatly if it is overexcited for a short period when running at synchronous speed. The change in the magnetic state of the rotor hysteresis material, when the stator voltage is raised and then reduced to the original value, is described in detail. Based on this, a method for the calculation of

T. Kataoka; T. Ishikawa; T. Takahashi

1982-01-01

131

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

132

Anomalous Ferroelectric Hysteresis Loops.  

National Technical Information Service (NTIS)

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

F. J. Murdoch

1971-01-01

133

Magnetic circular dichroism in reflection electron energy loss spectroscopy?  

SciTech Connect

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

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

1996-07-01

134

AC magnetization losses in striated YBCO-123\\/Hastelloy coated conductors  

Microsoft Academic Search

In this work we present experimental results of reductions in AC magnetization losses due to a striation process in YBCO-123\\/Hastelloy coated conductors. The measurements were carried out in a sinusoidally varying external magnetic field, with amplitudes up to 100 mT, in a frequency range of 8.5-85.4 Hz, and at a temperature of 77 K. The field was oriented perpendicularly to

O. Tsukamoto; M. Ciszek

2007-01-01

135

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

NASA Astrophysics Data System (ADS)

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

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

2010-08-01

136

AC magnetic field losses in BSCCO-2223 superconducting tapes  

SciTech Connect

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

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

1997-09-01

137

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

SciTech Connect

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

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

1992-08-24

138

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

SciTech Connect

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

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

1992-08-24

139

Temperature hysteresis of magnetic phase transitions in Tb1 - x Ce x Mn2O5 ( x = 0, 0.20, 0.25)  

NASA Astrophysics Data System (ADS)

The temperature evolution of the magnetic structure of multiferroics Tb1 - x Ce x Mn2O5 ( x = 0, 0.20, 0.25) has been investigated using the neutron scattering methods. It has been found that, despite the qualitative similarity of the magnetic states and the series of phase transitions for pure TbMn2O5 (TMO) and doped crystals Tb1 - x Ce x Mn2O5 (TCMO, x = 0.20 and 0.25), there are significant differences in their properties. In contrast to TMO, where there are three magnetic phases, TCMO can include two magnetic phases that coexist in a wide temperature range and exhibit a rather wide temperature hysteresis. One of these phases with wave vector k 1 = (0.5, 0, k z1), k z1 = 0.25, is commensurate and arises at temperatures below T N ˜ 39 K (for x = 0.2) and T N ˜ 38 K ( x = 0.25). The second phase is incommensurate with wave vector k 2 = (1/2, 0, k z2), k z2 = 0.256(2), and appears upon cooling at T = 21 K ( x = 0.2) and T = 19 K ( x = 0.25). Upon further cooling to 16 K, the component k z2 increases to 0.292(2) and then remains constant. The component k z1 increases to the value of 0.280(2) upon cooling in the range from 15 to 10 K and then remains constant down to 1.5 K. With an increase in the temperature, the components k z1 and k z2 undergo reverse changes to their initial values, but these changes occur at temperatures 7 K higher than those observed with a decrease in the temperature. For TMO, two phases also coexist, but the temperature hysteresis in this case is considerably smaller than for TCMO. This is explained by different densities of domain walls and different sizes of domains in pure and doped crystals.

Zobkalo, I. A.; Gavrilov, S. V.; Sanina, V. A.; Golovenchits, E. I.

2014-01-01

140

Containment can losses in permanent-magnet pump drives  

NASA Astrophysics Data System (ADS)

The integrated ``pump-motor-containment'' concept is a development in the chemical process industry. Both the stator and rotor members are isolated using stainless-steel containment cans. During normal operation, however, losses are generated in the stator can due to the stator excitation and the permanent magnets mounted on the rotor. A layer model has been developed to analyze the pseudothree-dimensional current flow in the stator can and hence predict the can losses. This represents an application of this particular analytical approach. The layer model is validated using a 10 kW experimental pump motor and a subsequent design study has demonstrated that the stator can losses are a significant factor in ensuring the integrity of the containment system. It has also been shown that the thickness and overhang length of the stator containment should be minimized to reduce the losses subject to mechanical constraints.

Smith, A. C.; Peralta-Sanchez, E.

2006-04-01

141

Annealing effects on magnetic properties of silicone-coated iron-based soft magnetic composites  

E-print Network

magnetic materials in motor applications, they need to have higher density and electrical resistance of imperfections, resulting in higher hysteresis losses. Therefore, an annealing treatment is employed to minimize

Volinsky, Alex A.

142

Optimization of a new type of hysteresis motor using genetic algorithm  

Microsoft Academic Search

HYSTERESIS motors are self-starting synchronous motors that take advantage of the hysteresis characteristics of the magnetic materials. Robust structure, flat speed-torque characteristics, smooth operation and constant low starting current are the outstanding specifications of these machines. Nevertheless, low efficiency and low power factor are among the disadvantages of common hysteresis motors. Very recently, Coreless Dual Discs Hysteresis Motor (CDDHM) has

M. H. Sadeghi; A. Darabi

2010-01-01

143

Zero loss magnetic metamaterials using powered active unit cells.  

PubMed

We report the design and experimental measurement of a powered active magnetic metamaterial with tunable permeability. The unit cell is based on the combination of an embedded radiofrequency amplifier and a tunable phase shifter, which together control the response of the medium. The measurements show that a negative permeability metamaterial with zero loss or even gain can be achieved through an array of such metamaterial cells. This kind of active metamaterial can find use in applications that are performance limited due to material losses. PMID:19724613

Yuan, Yu; Popa, Bogdan-Ioan; Cummer, Steven A

2009-08-31

144

Analytical Models for Polyphase Hysteresis Motor  

Microsoft Academic Search

Using parallelogram model to the B-H characteristic of the hysteresis material, general expressions for the terminal quantities of a polyphase hysteresis machine are derived. Steady-state equivalent circuit models are developed for both the synchronous and sub-synchronous modes of operation. A comprehensive analysis of rotor parasitic loss components and stator saturation effects is made and these are represented by suitable parameters

M. Azizur Rahman

1973-01-01

145

Spin flip loss in magnetic storage of ultracold neutrons  

E-print Network

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

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

2013-07-19

146

AC losses in a HTS coil carrying DC current in AC external magnetic field  

Microsoft Academic Search

We electrically measured AC losses in a Bi2223\\/Ag-sheathed pancake coil excited by a DC current in AC external magnetic field. Losses in the coil contain two kinds of loss components that are the magnetization losses and dynamic resistance losses. In the measurement, current leads to supply a current to the coil were specially arranged to suppress electromagnetic coupling between the

J. Ogawa; Y. Zushi; M. Fukushima; O. Tsukamoto; E. Suzuki; M. Hirakawa; K. Kikukawa

2003-01-01

147

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

PubMed

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

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

2013-10-22

148

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

149

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

150

Extended frequency analysis of magnetic losses under rotating induction in soft magnetic composites  

NASA Astrophysics Data System (ADS)

We present novel results on magnetic losses in soft magnetic composites (SMCs) excited with rotating field. Soft composites are very promising in electrical engineering applications, where new topologies of electrical machines with two- and three-dimensional induction loci are increasingly found. An experimental characterization of industrial SMC products has, therefore, been carried out, up to the kilohertz range, under alternating and circular flux loci, making use of a specifically designed and optimized loss measuring setup. The obtained results have been analyzed for all kinds of excitation, according to the loss separation concept, with the emphasis being placed on the relationship between the rotational and the alternating loss components. In particular, it is found that the ratio between the rotational and the alternating losses is, for any given peak induction, independent of frequency.

de la Barrière, O.; Appino, C.; Fiorillo, F.; Ragusa, C.; Lecrivain, M.; Rocchino, L.; Ben Ahmed, H.; Gabsi, M.; Mazaleyrat, F.; LoBue, M.

2012-04-01

151

Calculation of the energy loss in giant magnetic impedance elements using the complex magnetic permeability spectra  

NASA Astrophysics Data System (ADS)

The giant magnetic impedance (GMI) effect in ferromagnetic materials has been investigated for sensing applications. The GMI properties were evaluated via numerical solution of the complex magnetic permeability of the material. MATLAB simulation was carried out to study the frequency dependence of magnetic permeability via obtaining solutions of the Landau-Lifshitz-Gilbert (LLG) and the Maxwell's equations. The results indicate that the complex magnetic permeability peaks at a frequency of 6 GHz, corresponding to the ferromagnetic resonant (FMR) frequency, where the energy loss is maximum. A variation of the Gilbert damping parameter (?) associated with the LLG equation inversely affects this peak value. The area under the curve of complex magnetic permeability, calculated through counting the number of pixels within the image, provides an estimate of the average energy loss density within the material and appears to be consistent with the variation of the peak intensity.

Rustemaj, Driton; Mukherjee, Debashis

2013-01-01

152

Steady-State Performance Analysis of Polyphase Hysteresis-Reluctance Motors  

Microsoft Academic Search

It is well-known that the hysteresis-reluctance motor produces a torque that is a combination of the hysteresis and reluctance effects. Consequently, the performance characteristics of a hysteresis-reluctance motor would be improved when compared to that of the plain hysteresis motor. A new design of a hysteresis-reluctance rotor is presented in which the magnetic saliency is created by cutting slots in

M. Azizur Rahman; Ali M. Osheiba

1985-01-01

153

Magnetic measurement of creep damage: modeling and measurement  

Microsoft Academic Search

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

M. J. Sablik; David C. Jiles

1996-01-01

154

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

E-print Network

magnetic bearing FWB flywheel battery CMG control moment gyroscope ESCMG energy storage control momentImplementation of the Generalized Complementary Flux Constraint for Low-Loss Active Magnetic on a spacecraft reaction wheel that is magnetically suspended by a low-loss active magnetic bearing (AMB

Tsiotras, Panagiotis

155

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

SciTech Connect

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

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

2005-05-15

156

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

157

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

158

Shaft torsional oscillation of induction machine including saturation and hysteresis of magnetizing branch with an inertia load  

SciTech Connect

This paper describes the torsional oscillation phenomenon occurring in a multiple winding induction machine. It includes the effects of nonlinearity and component interactions between driver and inertia load through mass spring coupling system under starting transient disturbance. The model fidelity is evaluated from the foreseen torsional torque of the motor driving system by several excitation sources. Steady state and transient analysis are presented to show the significant influence of the magnetizing branch nonlinearity on the torque oscillation for an induction machine with sinusoidal or pulse width modulation (PWM) inverter excitation to drive inertia load. Simulation results and Fast-Fourier-Transform (FFT) analysis demonstrate that not only can the torsional oscillation amplitude be reduced, but the system dynamic performance is also improved through a multiple terminal inverter feeding with proper displacement angle between stator winding sets. In addition, starting process analysis shows that the torsional oscillation components can be substantially reduced by the selected starting methods with proper switching coordination. The risk of premature component failure due to the excess of the designed limit for dynamic torsional stresses can also be diminished.

Lee, Y.S.; Hsu, K.C. [Fu-Jen Catholic Univ., Hsin-Chuang Taipei (Taiwan, Province of China). Dept. of Electronic Engineering

1995-12-31

159

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

NASA Astrophysics Data System (ADS)

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

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

2014-01-01

160

Beam loss reduction by magnetic shielding using beam pipes and bellows of soft magnetic materials  

NASA Astrophysics Data System (ADS)

One of the main sources of beam loss in high power accelerators is unwanted stray magnetic fields from magnets near the beam line, which can distort the beam orbit. The most effective way to shield such magnetic fields is to perfectly surround the beam region without any gaps with a soft magnetic high permeability material. This leads to the manufacture of vacuum chambers (beam pipes and bellows) with soft magnetic materials. A Ni-Fe alloy (permalloy) was selected for the material of the pipe parts and outer bellows parts, while a ferritic stainless steel was selected for the flanges. An austenitic stainless steel, which is non-magnetic material, was used for the inner bellows for vacuum tightness. To achieve good magnetic shielding and vacuum performances, a heat treatment under high vacuum was applied during the manufacturing process of the vacuum chambers. Using this heat treatment, the ratio of the integrated magnetic flux density along the beam orbit between the inside and outside of the beam pipe and bellows became small enough to suppress beam orbit distortion. The outgassing rate of the materials with this heat treatment was reduced by one order magnitude compared to that without heat treatment. By installing the beam pipes and bellows of soft magnetic materials as part of the Japan Proton Accelerator Research Complex 3 GeV rapid cycling synchrotron beam line, the closed orbit distortion (COD) was reduced by more than 80%. In addition, a 95.5% beam survival ratio was achieved by this COD improvement.

Kamiya, J.; Ogiwara, N.; Hotchi, H.; Hayashi, N.; Kinsho, M.

2014-11-01

161

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

162

Densification and magnetization of rare earth magnets  

NASA Astrophysics Data System (ADS)

Hot isostatic pressing of SmCo5 magnets has been evaluated as a means for increasing the density, remanence, and energy product of rare earth magnets. The results indicate 99% density can be achieved without loss in the magnetic properties. Magnetization studies up to 100 kOe were conducted on SmCo5 magnets and the results indicate that fields in excess of 60 kOe are required to achieve maximum values of remanence in a magnetically demagnetized magnet as is produced by running a hysteresis loop. Thermally demagnetized magnets, however, require less than 15 kOe to realize the full potential for all practical applications.

Narasimhan, K. S. V. L.; Lizzi, T.

1985-04-01

163

Sensitivity analysis to the design parameters of a hysteresis motor  

Microsoft Academic Search

Hysteresis motors are mainly used for some applications that need very smooth torque from starting to synchronous speed such as gyroscope and gas centrifuge. This paper presents a sensitivity analysis of 60 W, 400 V, 6000 rpm super-high speed hysteresis motor characteristics including electromagnetic torque, power factor, efficiency and stator current to the design parameters including mechanical, electrical and magnetic

Abolfazl Halvaei Niasar; Hassan Moghbelli

2012-01-01

164

Determination of the magnetic losses in induction motors based on the generalized Epstein test  

Microsoft Academic Search

The results obtained from the standard method for the characterization of magnetic materials - the Epstein test - lead to significant errors in the estimation of magnetic losses in induction motors. Among the induction motor characteristics not accounted for in the Epstein test method, one can point out: winding distribution, cutting stresses, anisotropy, PWM supply and rotor losses (surface losses

André G. Tôrres; B. J. C. Filho; R. O. C. Lyra; Marco A. Cunha; Sebastião C. Paolinelli

2004-01-01

165

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

E-print Network

magnetic bearing FWB flywheel battery CMG control moment gyroscope ESCMG energy storage control momentExperimental Validation of Control Designs for Low-Loss Active Magnetic Bearings Brian C. Wilson by a low-loss active magnetic bearing (AMB). The electromagnets of the AMB are constrained by a generalized

Tsiotras, Panagiotis

166

Experimentally determined rotor power losses in homopolar and heteropolar magnetic bearings  

Microsoft Academic Search

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

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

1999-01-01

167

Mathematical models of hysteresis  

SciTech Connect

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

NONE

1998-08-01

168

Terfenol-D elastomagnetic properties under varied operating conditions using hysteresis loop analysis  

NASA Astrophysics Data System (ADS)

This paper presents an experimental study of the effects of varied magnetic bias, AC magnetic field amplitude and frequency on the characteristics of hysteresis loops produced in a magnetostrictive transducer. The study uses a magnetostrictive transducer designed at Iowa State University that utilizes an 11.5 cm (4.54 in) long by 1.27 cm (0.5 in) diameter cylindrical Terfenol-D rod. This transducer allows controlled variation of the following operating conditions: mechanical prestress, magnitude and frequency of AC magnetic field, and magnetic bias. By performing extensive experimental tests, material property trends can be developed for use in the optimization of transducer design parameters for different applications. For the results presented, the magnetic bias, the AC magnetic field amplitude, and the frequency of excitation were independently varied while temperature, mass load and prestress were kept constant. The minor hysteresis loops of the strain versus applied magnetic field, flux density versus applied magnetic field, and magnetization versus applied magnetic field are presented and compared. Material property trends identified from the minor loops are presented for the axial strain coefficient, permeability, susceptibility, and energy losses.

Faidley, LeAnn E.; Lund, Brian J.; Flatau, Alison B.; Calkins, Frederick T.

1998-07-01

169

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

170

The Hysteresis Motor with an Anisotropic Rotor  

Microsoft Academic Search

An analysis of the hysterezis motor with anisotropic rotor has been carried out. Using an elliptical approximation for the hysteresis loop, the expression of the magnetic vector potential in the anisotropic region of the rotor has been obtained both in the case of a stator surface carrying a curent sheet with sinusoidal variation, and in the case of a rotor

N. Galan

1987-01-01

171

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

Microsoft Academic Search

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

Katsumi Yamazaki; Yoshiaki Seto

2006-01-01

172

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

NASA Astrophysics Data System (ADS)

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

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

173

Effect of magnetic field applied during secondary annealing on texture and grain size of silicon steel  

E-print Network

plant gen- erators and electric motors. The magnetic behav- iour of this material is mainly controlled when efficiency is required. When the grain size diameter d increases, the hysteresis loss de- creases

Garmestani, Hamid

174

AC losses in a HTS coil carrying DC current in AC external magnetic field  

NASA Astrophysics Data System (ADS)

We electrically measured AC losses in a Bi2223/Ag-sheathed pancake coil excited by a DC current in AC external magnetic field. Losses in the coil contain two kinds of loss components that are the magnetization losses and dynamic resistance losses. In the measurement, current leads to supply a current to the coil were specially arranged to suppress electromagnetic coupling between the coil current and the AC external magnetic field. A double pick-up coils method was used to suppress a large inductive voltage component contained in voltage signal for measuring the magnetization losses. It was observed that the magnetization losses were dependent on the coil current and that a peak of a curve of the loss factor vs. amplitude of the AC external magnetic field shifted to lower amplitude of the AC magnetic field as the coil current increased. This result suggests the full penetration magnetic field of the coil tape decreases as the coil current increases. The dynamic resistance losses were measured by measuring a DC voltage appearing between the coil terminals. It was observed that the DC voltage appearing in the coil subject to the AC external magnetic field was much larger than that in the coil subject to DC magnetic field.

Ogawa, J.; Zushi, Y.; Fukushima, M.; Tsukamoto, O.; Suzuki, E.; Hirakawa, M.; Kikukawa, K.

175

Calculation of rotational power losses in eight pole radial magnetic bearings  

E-print Network

The need for low-loss high speed bearings in rotating machinery invites the use of active control magnetic bearings. The present study investigates the theoretical power losses of these bearings associated with shaft rotation at a constant angular...

Havelka, Daniel Louis

2012-06-07

176

IEEE TRANSACTIONS ON ENERGY CONVERSION, VOL. 20, NO. 1, MARCH 2005 121 Minimization of Iron Losses of Permanent  

E-print Network

importance in PM motor de- sign. This paper considers the minimizing of iron losses of PM syn- chronous in this paper to draw the conclusions. Index Terms--Eddy currents, hysteresis, magnetic losses, per- manent magnet machines, synchronous machines. I. INTRODUCTION ELECTRIC motor-driven equipment utilizes

Mi, Chunting "Chris"

177

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

PubMed

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

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

2012-10-01

178

Optimizing the Jiles-Atherton model of hysteresis by a genetic algorithm  

Microsoft Academic Search

Modeling magnetic components for simulation in electric circuits requires an accurate model of the hysteresis loop of the core material used. It is important that the parameters extracted for the hysteresis model be optimized across the range of operating conditions that may occur in circuit simulation. This paper shows how to extract optimal parameters for the Jiles-Atherton model of hysteresis

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

2001-01-01

179

PC Based Pulsed Field Hysteresis Loop Tracer  

NASA Astrophysics Data System (ADS)

The present paper describes the design and setting up of a PC based hysteresis loop tracer that enables quick characterization of magnetic materials at room temperature. A high magnetic field is generated in a solenoid by passing a pulse current of sinusoidal shape at an interval slow enough to produce minimum heating in the solenoid. A pickup coil system is kept in the solenoid to detect field and magnetization signal of a sample placed in the pickup coil. These transitory analog signals are converted into digital signals by a micro-controller integrated circuit. These digital signals are sent to a computer through a serial port. A software has been developed to interface the system to the PC and processing the data to calculate hysteresis parameters like saturation magnetization Ms, coercivity Hc and remanence Mr followed by plotting of the hysteresis loop. The data and graphs can be printed or stored as files. The sample holder is designed for samples in powder or pellet form. The data acquired for some standard magnetic samples are presented.

Likhite, S. D.; Likhite, Prachi; Radha, S.

2011-07-01

180

3-D Analysis of Loss Distribution in an Interior Permanent Magnet Motor Driven by PWM Inverter  

NASA Astrophysics Data System (ADS)

Electrical loss of an interior permanent magnet motor (IPM motor) driven by the pulse width modulation inverter (PWM inverter) is analyzed using the three-dimensional finite element method (3-D FEM). The distributions of the eddy currents in the permanent magnet, the iron loss characteristics, and the torque characteristics were quantitatively clarified.

Kawase, Yoshihiro; Yamaguchi, Tadashi; Yano, Toshiyuki; Suzuki, Satoshi; Ida, Kazuo; Yamagiwa, Akio

181

Investigation of Proximity Losses in a High Speed Brushless Permanent Magnet Motor  

Microsoft Academic Search

This paper presents a finite element investigation into the proximity losses in brushless AC permanent magnet motors used in hybrid\\/electric vehicle applications. The proximity effect in winding conductors is as a result of eddy-currents caused by magnetic fields generated by nearby conductors. This paper considers the influence of the conductor shape and disposition on the losses for a given stator

Phil H. Mellor; Rafal Wrobel; Neville McNeill

2006-01-01

182

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

NASA Astrophysics Data System (ADS)

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

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

1999-04-01

183

Energy Loss by Drag Force of Superconductor Flywheel Energy Storage System With Permanent Magnet Rotor  

Microsoft Academic Search

Energy loss is one of the most important problems for the practical use of superconductor flywheel energy storage (SFES) system. The energy loss of the SFES is mainly caused by drag force induced by magnetic field parts such as the superconductor magnetic bearing (SMB) and permanent magnet (PM)-type motor\\/generator (PMSM\\/G). In this paper, a vertical-shaft-type SFES with journal-type SMB was

Jeong-Phil Lee; Byung-Jun. Park; Young-Hee Han; Se-Yong Jung; Tae-Hyun Sung

2008-01-01

184

Loss analysis of the thermodynamic cycle of magnetic heat pumps  

Microsoft Academic Search

The needs for developing non-ozone-depleting, no-greenhouse-effect heat pump systems and for exploring the potential of new high-temperature superconducting materials have prompted a renewed interest in the study of magnetic heat pumps. The new materials can provide the high magnetic field that an effective superconducting magnetic heat pump requires, and magnetic heat pumps do not use freon for a working fluid.

F. C. Chen; R. W. Murphy; V. C. Mei; G. L. Chen; J. W. Lue; M. S. Lubell

1991-01-01

185

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

E-print Network

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

186

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

NASA Astrophysics Data System (ADS)

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

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

1999-04-01

187

Rotation losses in the superconducting bearing based on magnetic gradient levitation concept  

NASA Astrophysics Data System (ADS)

Magnetic bearings using bulk superconductors as field shaping materials have been under development for several years. The magnetic bearings need only a steel component on the rotor side for stable operation. In this system, using a bulk superconductor as a field shaping material generates a magnetic gradient that is stable against both vertical and radial displacement. Several tests were performed to better understand the loss mechanisms during rotation. Results from rotation tests using an iron rotor or a ferrite rotor indicate eddy current loss is the dominant cause of rotational losses.

Kubo, Y.; Ohsaki, H.

2001-09-01

188

Influence of a Stainless Steel Core on Coupling Loss, Interstrand Contact Resistance, and Magnetization of an Rutherford Cable  

Microsoft Academic Search

Calorimetric and magnetic AC loss measurements were made on a pair of TQ (ldquotechnology quadrupolerdquo) class cables, one with and the other without a stainless steel core. The coupling losses are compared to the cables' hysteretic losses determined at the same time; the latter being compared to the magnetically measured hysteretic losses of individual strand segments. The outcomes of these

E. W. Collings; M. D. Sumption; M. A. Susner; D. R. Dietderich; E. Barzi; A. V. Zlobin; Y. Ilyin; A. Nijhuis

2008-01-01

189

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

Microsoft Academic Search

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

Enric Pardo; Francesco Grilli

2012-01-01

190

Hysteresis multicycles in nanomagnet arrays J. M. Deutsch, Trieu Mai, and Onuttom Narayan  

E-print Network

. INTRODUCTION Hysteresis in magnets 1,2 is a paradigm for all history dependent behavior in nature 3­5 . In addition, hysteresis is the cornerstone of the magnetic data storage industry, and of great technological- graph was measured. Whether a multicycle is present, and if so, its order, depended on the realization

California at Santa Cruz, University of

191

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

192

Dynamical aspects of the adsorption hysteresis phenomenon.  

PubMed

Equilibrium and nonequilibrium transport properties of adsorbates in mesoporous Vycor porous glass have been experimentally studied using nuclear magnetic resonance techniques. With the known geometrical characteristics of porous glass and with measured self-diffusivities, transient sorption curves have been quantitatively compared to those predicted within a Fick's law model. This model correctly describes data outside a hysteresis region. In contrast, in the hysteresis region, a two-step mechanism of density relaxation is required to explain the behavior. These two mechanisms are identified as diffusion at early stages and activated density redistribution at later stages of adsorption. The latter mechanism, being intrinsically slow in nature, is anticipated to prevent the system from reaching equilibrium. PMID:17466768

Valiullin, Rustem; Naumov, Sergej; Galvosas, Petrik; Kärger, Jörg; Monson, Peter A

2007-05-01

193

Modeling of dynamic hysteresis for grain-oriented laminations using a viscosity-based modified dynamic Jiles-Atherton model  

NASA Astrophysics Data System (ADS)

Grain-oriented (GO) materials exhibit arbitrary frequency-loss behaviors and anomalies in dynamic hysteresis loop shapes. Significant attempts have been made in the literature to approximate dynamic hysteresis loops using the dynamic Jiles-Atherton (JA) model based Bertotti's approach. Such a model is inefficient in accurate loss computation over a wide range of frequencies and in predictions of correct loop shapes. Moreover, the original static JA model also needs to be improved for accurate prediction of highly steep, gooseneck, and narrow-waist static loops of GO materials. An alternative approach based on magnetic viscosity provides flexibilities to handle indefinite frequency dependence of the losses and to control the anomalous loop shapes. This paper proposes a viscosity-based dynamic JA model which gives accurate prediction of dynamic loops of GO materials. A modified static JA model which considers crystalline and textured structures of GO materials is used to predict static hysteresis loops. The dynamic losses are included in the modified model using the field separation approach. The proposed model is validated using experimental measurements. The computed and measured dynamic loops are in close agreement in the frequency range of 1-200 Hz.

Baghel, A. P. S.; Shekhawat, S. K.; Kulkarni, S. V.; Samajdar, I.

2014-09-01

194

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

195

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

Microsoft Academic Search

Magnetic field fluctuations are inevitable in practical applications of superconductors and it is often necessary to estimate the ac losses these fluctuations induce. If the fluctuation wavelength is greater than the size of a superconductor, known estimates for an alternating uniform external magnetic field can be employed. The authors consider the opposite case and analyze, using a model critical-state problem,

Leonid Prigozhin; Vladimir Sokolovsky

2004-01-01

196

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

Microsoft Academic Search

Magnetic field fluctuations are inevitable in practical applications of superconductors and it is often necessary to estimate the AC losses these fluctuations induce. If the fluctuation wavelength is greater than the size of a superconductor, known estimates for an alternating uniform external magnetic field can be employed. Here we consider the opposite case and analyze, using a model critical-state problem,

Leonid Prigozhin; Vladimir Sokolovsky

2003-01-01

197

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

198

A modified Jiles method for hysteresis computation including minor loops  

NASA Astrophysics Data System (ADS)

This work presents a new methodology for determination of hysteresis curves based on the Jiles-Atherton method. The magnetic induction is adopted as an independent variable which is available in the vector potential magnetic field formulation. The presented method can be directly incorporated in a finite element software.

Koltermann, P. I.; Righi, L. A.; Bastos, J. P. A.; Carlson, R.; Sadowski, N.; Batistela, N. J.

2000-01-01

199

Angular momentum loss and stellar spin-down in magnetic massive stars  

Microsoft Academic Search

We examine the angular momentum loss and associated rotational spin-down for magnetic hot stars with a line-driven stellar wind and a rotation-aligned dipole magnetic field. Our analysis here is based on our previous 2-D numerical MHD simulation study that examines the interplay among wind, field, and rotation as a function of two dimensionless parameters, W(=Vrot\\/Vorb) and `wind magnetic confinement', eta*

Asif ud-Doula; Richard H. D. Townsend

2009-01-01

200

Precision of an eddy current sensor with magnetic circuit losses  

Microsoft Academic Search

This paper describes an inductive magnetic sensor for the translation measurement of a metal sheet during the drop-stamping process. This electromagnetic sensor consists of a cast-iron core coil sensor. The classical coil system approach does not include the eddy current effect in the transducer core. The main feature of this paper is to define the eddy current effect on the

P. Reghem; E. Destobbeleer; T. Derrey; L. Protin

1994-01-01

201

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

202

Effect of chemically active medium on frequency dependence of magnetic losses in soft magnetic Fe-based amorphous alloys  

NASA Astrophysics Data System (ADS)

The effects of the electrolytic hydrogenation and oxidation and of the interaction of the surface ribbon with water and vapor on the frequency dependence of magnetic losses per magnetization-reversal cycle are studied based on the example of soft magnetic Fe81B13Si4C2 amorphous alloy, which exhibits a positive saturation magnetostriction. It was shown that, after the hydrogenation and oxidation of soft magnetic amorphous alloys, their frequency dependences of magnetic losses per magnetization-reversal cycle, which are reduced to unit induction, exhibit groups of hydrogen- and oxygen-related peaks in the frequency ranges of 35-55 and 55-80 Hz, which can be explained by the formation of O- A and H- A atomic pairs (where A are atoms of alloy components) and their reorientation in a magnetic field in the course of magnetization reversal at certain frequencies. The formation of analogous groups of peaks for samples of soft magnetic Fe-based amorphous alloys was observed after the interaction of the ribbon surface with water and vapor and after heat treatment in air. This fact confirms the possibility of the hydrogenation and oxidation of the alloys during the aforementioned processes.

Skulkina, N. A.; Ivanov, O. A.; Stepanova, E. A.; Pavlova, I. O.

2013-03-01

203

Hybrid superconducting magnetic bearing and its frictional energy loss and dynamics  

SciTech Connect

A hybrid superconducting magnetic bearing (SMB) has been designed and tested. A flywheel energy storage (FES) prototype has been constructed for testing bearing friction loss and characterizing the dynamics of the rotor. The hybrid SMB design uses magnetic forces from permanent magnets for levitation and high temperature superconductor YBCO in between the magnets for stabilization. A 42 lb. flywheel currently can rotate up to 6,000 RPM with kinetic energy of 8 Wh stored. The result from the recent rotor spin-down experiment indicates an average frictional energy loss <2% per hour in a vacuum of 10 {sup {minus}5} torr, with imperfect system alignment and balance of rotor. The system dynamics has been conducted to improve upon the energy loss and rotor-bearing modeling.

Xia, Z.; Ma, K.B.; Chen, Q.Y.; Cooley, R.R. [Univ. of Houston, TX (United States)] [and others

1995-12-31

204

Study on ac losses of HTS coil carrying ac transport current  

NASA Astrophysics Data System (ADS)

Ac loss has an important influence on the thermal performances of HTS coil. It is necessary to quantify ac loss to ascertain its impact on coil stability and for sizing the coil refrigeration system. In this paper, we analyzed in detail the ac loss components, hysteresis loss, eddy loss and flux flow loss in the pancake HTS coil carrying ac transport current by finite element method. We also investigated the distribution of the ac losses in the coil to study the effects of magnetic field distribution on ac losses.

Dai, Taozhen; Tang, Yuejin; Li, Jingdong; Zhou, Yusheng; Cheng, Shijie; Pan, Yuan

2005-10-01

205

Influence on the rectifiers of rotor losses in high-speed permanent magnet synchronous alternator  

NASA Astrophysics Data System (ADS)

This article deals with the rotor losses in the high-speed permanent magnet (PM) synchronous alternator for distributed power generation system. Specifically, the influence of rectifiers on the rotor losses is investigated. On the basis of analytical field analysis and two-dimensional finite element analysis, this article predicts the flux harmonics and rotor losses in the PM alternator considering the rectifier load. The prototype machine with the rectifier load has been fabricated and tested. Moreover, the difference of rotor losses between the high-speed alternator with and without the rectifier is made quantitatively clear in this work.

Jang, Seok-Myeong; Cho, Han-Wook; Jeong, Yeon-Ho

2006-04-01

206

Losses at magnetic nulls in pulsed-power transmission line systems  

SciTech Connect

Pulsed-power systems operating in the terawatt regime must deal with large electron flows in vacuum transmission lines. In most parts of these transmission lines the electrons are constrained by the self-magnetic field to flow parallel to the conductors. In very low impedance systems, such as those used to drive Z-pinch radiation sources, the currents from multiple transmission lines are added together. This addition necessarily involves magnetic nulls that connect the positive and negative electrodes. The resultant local loss of magnetic insulation results in electron losses at the anode in the vicinity of the nulls. The lost current due to the magnetic null might or might not be appreciable. In some cases the lost current due to the null is not large, but is spatially localized, and may create a gas and plasma release from the anode that can lead to an excessive loss, and possibly to catastrophic damage to the hardware. In this paper we describe an analytic model that uses one geometric parameter (aside from straightforward hardware size measurements) that determines the loss to the anode, and the extent of the loss region when the driving source and load are known. The parameter can be calculated in terms of the magnetic field in the region of the null calculated when no electron flow is present. The model is compared to some experimental data, and to simulations of several different hardware geometries, including some cases with multiple nulls, and unbalanced feeds.

Mendel, C.W. Jr.; Pointon, T.D.; Savage, M.E.; Seidel, D.B.; Magne, I.; Vezinet, R. [Sandia National Laboratories, Albuquerque, New Mexico 87185-1152 (United States); Centre d'Etudes de Gramat, Gramat (France)

2006-04-15

207

Losses at magnetic nulls in pulsed-power transmission line systems.  

SciTech Connect

Pulsed-power systems operating in the terawatt regime must deal with large electron flows in vacuum transmission lines. In most parts of these transmission lines the electrons are constrained by the self-magnetic field to flow parallel to the conductors. In very low impedance systems, such as those used to drive Z-pinch radiation sources, the currents from multiple transmission lines are added together. This addition necessarily involves magnetic nulls that connect the positive and negative electrodes. The resultant local loss of magnetic insulation results in electron losses at the anode in the vicinity of the nulls. The lost current due to the magnetic null might or might not be appreciable. In some cases the lost current due to the null is not large, but is spatially localized, and may create a gas and plasma release from the anode that can lead to an excessive loss, and possibly to catastrophic damage to the hardware. In this paper we describe an analytic model that uses one geometric parameter (aside from straightforward hardware size measurements) that determines the loss to the anode, and the extent of the loss region when the driving source and load are known. The parameter can be calculated in terms of the magnetic field in the region of the null calculated when no electron flow is present. The model is compared to some experimental data, and to simulations of several different hardware geometries, including some cases with multiple nulls, and unbalanced feeds.

Magne, I. (Centre d'Etudes de Gramat, Gramat, France); Savage, Mark Edward; Seidel, David Bruce; Mendel, Clifford Will, Jr.; Pointon, Timothy David; Vezinet, R. (Centre d'Etudes de Gramat, Gramat, France)

2004-08-01

208

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

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

209

Modelling and analysis of a hysteresis motor used in space application  

Microsoft Academic Search

Summary form only given, as follows. We present the computer-aided modelling and analysis of a three-phase hysteresis synchronous motor used in the gyroscope as the gyro-rotor drive motor. A computer program is developed for the performance analysis of the hysteresis motor. The program accounts for all known losses in the hysteresis motor. The simulation program is tuned by incorporating the

K. R. Rajagopal; Christian Coltelli; Vasca Navale

2002-01-01

210

Hysteresis Model for Piezoceramic Materials.  

National Technical Information Service (NTIS)

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 ...

R. C. Smith, Z. Ounaies

1999-01-01

211

Analysis of eddy current losses in cylindrical linear oscillatory actuator with Halbach permanent magnet array mover  

NASA Astrophysics Data System (ADS)

This paper describes calculations and comparisons of eddy current losses in a cylindrical linear oscillatory actuator with a Halbach array permanent magnet mover for different voltage source waveforms. Using the magnetic vector potential and a two-dimensional cylindrical coordinate system, the paper presents an analytical procedure and obtains solutions for the eddy current losses using the Poynting theorem. To verify the proposed method, the eddy current losses obtained from the analytical solutions are compared with the results of a non-linear finite element method. Moreover, this paper shows that the eddy current losses are more significant when the actuator is driven by a square voltage waveform than when it is driven by a sinusoidal voltage waveform.

Ko, Kyoung-Jin; Choi, Ji-Hwan; Jang, Seok-Myeong; Choi, Jang-Young

2012-04-01

212

Vector hysteresis measurements via a single disk tester  

NASA Astrophysics Data System (ADS)

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

Cardelli, E.; Faba, A.

2006-02-01

213

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

PubMed Central

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

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

2014-01-01

214

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

SciTech Connect

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

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

1996-12-31

215

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

216

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

PubMed

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

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

2014-01-01

217

Angular Momentum and Mass Loss From Magnetized Solar-Like Winds  

NASA Astrophysics Data System (ADS)

We investigate angular momentum and mass loss from magnetized solar-like winds in cool stars. We present a physically motivated formulation and investigate two key phenomena: the F star transition from effective to ineffective spin down and the mass dependence of the spin down timescale in lower mass stars. We demonstrate that both phenomena are naturally explained within our framework. Tests of angular momentum loss models from upcoming Kepler data are discussed.

Pinsonneault, Marc H.; Matt, S.; MacGregor, K. B.

2013-01-01

218

Inkjet printing of magnetic materials with aligned anisotropy  

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

219

AC magnetization loss reduction by striation in YBCO-123\\/Hastelloy coated conductors  

Microsoft Academic Search

In the work we present experimental results of AC magnetization losses reduction due to striation process in YBCO-123\\/Hastelloy coated conductors. The measurements were carried out in a sinusoidally varying external magnetic field, with amplitudes up to 100 mT, in a frequency range of 8.5-85.4 Hz, and at temperature of 77 K. The field was oriented perpendicularly to the face of

O. Tsukamoto; M. Ciszek; N. Sekine; H. Suzuki

2005-01-01

220

AC losses in stacks and arrays of YBCO\\/hastelloy and monofilamentary Bi2223\\/Ag tapes  

Microsoft Academic Search

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

K.-H. Müller

1999-01-01

221

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

NASA Astrophysics Data System (ADS)

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

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

2013-09-01

222

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

NASA Astrophysics Data System (ADS)

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

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

2014-03-01

223

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

NASA Astrophysics Data System (ADS)

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

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

2014-04-01

224

Analysis of a Hysteresis Motor on Asynchronous Speed Using Complex Permeability  

Microsoft Academic Search

This paper deals with a method for determining the complex permeability in analysis of hysteresis motors. The method assumes that the magnetic intensity distribution is sinusoidal in the direction of rotation. Analysis of the asynchronous speed of a hysteresis motor is then performed for cylindrical coordinates, using modified Bessel functions. The results of calculations are in good agreement with experimental

T. Horii; N. Yuge; G. Wakui

1994-01-01

225

ASYNCHRONOUS PERFORMANCE OF HYSTERESIS MOTOR CONSIDERING EDDY-CURRENT EFFECTS  

Microsoft Academic Search

A simplified model of the hysteresis motor is introduced, with eddy-current effects taken into consideration. The field analysis is based on Maxweell's equations; the output relations, such as forces, power and heat losses, are derived via Maxwell's stress tensor and Poynting's theorem, and a special variant of the circle diagram is proposed.

S. GAVRIL; A. MOR

1983-01-01

226

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

NASA Astrophysics Data System (ADS)

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

Nándori, I.; Rácz, J.

2012-12-01

227

Magnetic flux penetration and AC loss in a composite superconducting wire with ferromagnetic parts  

Microsoft Academic Search

The current distribution and the AC loss in a composite superconducting tape containing a layer of magnetic material is calculated and compared with experiments, showing a very good agreement. The situations of an alternating uniform applied field or a transport current are studied. The newly developed numerical model is an approximation to the critical state model, adapted for applicability to

F. Gömöry; M. Vojenciak; E. Pardo; J. Souc

2009-01-01

228

Mass Loss Rates, Ionization Fractions, Shock Velocities and Magnetic Fields of Stellar Jets  

E-print Network

Mass Loss Rates, Ionization Fractions, Shock Velocities and Magnetic Fields of Stellar Jets Patrick and shock velocities in jets directly from observations of the strong emission lines in these flows estimates, and the shock velocities are ¸ 30 km s \\Gamma1 . For each jet the ionization fractions were found

Hartigan, Patrick

229

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

230

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.

231

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

PubMed

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

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

2012-10-10

232

A Precise Open-Loop Torque Control for an Interior Permanent Magnet Synchronous Motor  

E-print Network

. Iron losses are mainly caused by hysteresis and eddy currents and therefore depend on the actual motorA Precise Open-Loop Torque Control for an Interior Permanent Magnet Synchronous Motor (IPMSM@lea.upb.de Abstract-Interior permanent magnet synchronous motors (IPMSM) are preferentially chosen as traction drives

Paderborn, Universität

233

Compact dielectric particles as a building block for low-loss magnetic metamaterials.  

PubMed

We characterize experimentally a compact dielectric particle that can be used to design very low-loss artificial electromagnetic materials (metamaterials). Focusing on magnetic media, we show that the particle can behave almost identically to the well-known split-ring resonators (SRRs) widely used in present designs, without suffering from the Ohmic losses that can limit the applicability of SRRs especially at high frequencies. We experimentally compare qualitatively and quantitatively the dielectric particle with a typical split-ring resonator of the same size built on a low-loss dielectric substrate and show that at GHz frequencies the quality factor of the dielectric particle is more than 3 times bigger than that of its metallic counterpart. Low-loss and simple geometry are significant advantages compared to conventional metal SRRs. PMID:18518576

Popa, Bogdan-Ioan; Cummer, Steven A

2008-05-23

234

Domain-wall motion in random potential and hysteresis modeling  

SciTech Connect

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

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

1998-06-01

235

Magnetopause Losses of Radiation Belt Electrons During a Recent Magnetic Storm  

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

236

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

237

An Energy-Based Hysteresis Model for Magnetostrictive Transducers  

NASA Technical Reports Server (NTRS)

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

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

1997-01-01

238

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

239

Hysteresis in quantized vortex shedding  

NASA Astrophysics Data System (ADS)

It is shown using numerical simulations that flow patterns around an obstacle potential moving in a superfluid exhibit hysteresis. In a certain velocity region, there is a bistability between stationary laminar flow and periodic vortex shedding. The bistability exists in two- and three-dimensional systems.

Kadokura, Tsuyoshi; Yoshida, Jun; Saito, Hiroki

2014-07-01

240

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

NASA Astrophysics Data System (ADS)

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

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

241

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

242

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

NASA Astrophysics Data System (ADS)

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

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

2010-03-01

243

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

244

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

245

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

Microsoft Academic Search

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

Jakob Rhyner

1993-01-01

246

Magnetic flux penetration and AC loss in a composite superconducting wire with ferromagnetic parts  

Microsoft Academic Search

The current distribution and the AC loss in a composite superconducting tape\\u000acontaining a layer from magnetic material is calculated and compared with\\u000aexperiments, showing a very good agreement. The situations of an alternating\\u000auniform applied field or a transport current are studied. The newly developed\\u000anumerical model is an approximation to the critical state model, adapted for\\u000athe applicability

F. Gömöry; M. Vojen?iak; E. Pardo; J. Šouc

2008-01-01

247

Analysis of flux distribution and core losses in interior permanent magnet motor  

Microsoft Academic Search

The interior permanent magnet (IPM) motor with its robust rotor construction, hybrid torque production nature and flux-weakening capability is suitable for electric vehicle applications when wide speed and torque range is required. At high-speed operations, core losses become an important issue because they affect efficiency and raise operating temperatures. This paper discusses the results of two-dimensional finite element analysis into

K. J. Tseng; S. B. Wee

1999-01-01

248

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

NASA Astrophysics Data System (ADS)

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

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

2012-04-01

249

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

NASA Astrophysics Data System (ADS)

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

Kuczmann, Miklós

2008-02-01

250

Energy loss magnetic chiral dichroism: A new technique for the study of magnetic properties in the electron microscope (invited)  

NASA Astrophysics Data System (ADS)

The similarity between x-ray absorption near edge structure and electron energy loss near edge structure is well known. However, "exporting" x-ray magnetic circular dichroism (XMCD) to the transmission electron microscope (TEM) was considered impossible with present technology since electron probes possessing chirality (i.e., spin polarization) cannot be set up with sufficient intensity. But recently magnetically induced chiral electronic transitions were detected in the TEM. In analogy to XMCD we introduced the term EMCD (energy loss magnetic chiral dichroism). The mechanism builds upon the formal equivalence between the mixed dynamic form factor for inelastic electron scattering and the absorption cross section for x-rays. Experiments on the 3d ferromagnets show effects very similar to XMCD. Calculations based on the WIEN2K package are in good agreement with experiments. The recent improvement in signal strength and spatial resolution allows now to study atom specific spin and orbital moments on a scale of less than 10nm, an important progress for spintronics and nanomagnetism.

Schattschneider, P.; Rubino, S.; Stoeger-Pollach, M.; Hébert, C.; Rusz, J.; Calmels, L.; Snoeck, E.

2008-04-01

251

Analysis of flux distribution and core losses in interior permanent magnet motor  

SciTech Connect

The interior permanent magnet (IPM) motor with its robust rotor construction, hybrid torque production nature and flux-weakening capability is suitable for electric vehicle applications where wide speed and torque range is required. At high-speed operations, core losses become an important issue because they affect efficiency and raise operating temperatures. This paper discusses the results of two-dimensional finite element analysis into the relationship between flux distribution and core losses in the IPM motor. The analysis is further supported by flux measurements using search coils installed in an experimental motor. Three methods of predicting the core losses in IPM motor are also investigated. These methods are the empirical formula method, finite element computed waveform method and the search coil induced voltage method.

Tseng, K.J.; Wee, S.B.

1999-12-01

252

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

253

Analysis of wasp-waist hysteresis loops  

NASA Astrophysics Data System (ADS)

Wasp-waist and pot-belly hysteresis loops have been observed in many materials. When only the major loop is reported, the results are insufficient to establish which processes are involved. We present two models for wasp-waist materials that produce virtually indistinguishable major loops, but show that first-order reversal curves can be used to separate the effects. In the simplest model, we take a soft magnetic material and a hard material and exchange couple them. When the exchange is positive, the loop is conventional. However, for negative (antiferromagnetic) exchange, the wasp-waist loop is obtained. Negative coupling of two materials with different switching field distributions leads to pot-bellied loops.

Bennett, Lawrence H.; Della Torre, Edward

2005-05-01

254

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

255

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

NASA Astrophysics Data System (ADS)

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

Wilson, Brian Christopher David

256

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

NASA Astrophysics Data System (ADS)

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

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

2007-07-01

257

Reduction of Thermal Loss in HTS Windings by Using Magnetic Flux Deflection  

NASA Astrophysics Data System (ADS)

Efforts on the generation of intensified magnetic flux have been made for the optimized shape of HTS winding applications. This contributes to the high efficiency of the rotating machines using HTS windings. Heat generation from the HTS windings requires to be suppressed as much as possible, when those coils are under operation with either direct or alternative currents. Presently, the reduction of such thermal loss generated by the applied currents on the HTS coils is reported with a magnetic flux deflection system. The HTS coils are fixed together with flattened magnetic materials to realize a kind of redirection of the flux pathway. Eventually, the magnetic flux density perpendicular to the tape surface (equivalent to the a-b plane) of the HTS tape materials is reduced to the proximity of the HTS coil. To verify the new geometry of the surroundings of the HTS coils with magnetic materials, a comparative study of the DC coil voltage was done for different applied currents in prototype field-pole coils of a ship propulsion motor.

Tsuzuki, K.; Miki, M.; Felder, B.; Koshiba, Y.; Izumi, M.; Umemoto, K.; Aizawa, K.; Yanamoto, T.

258

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

PubMed

A complete time-dependent physics theory of symmetric unperturbed driven hybrid birdcage resonator was developed for general application. In particular, the theory can be applied for radiofrequency (RF) coil engineering, computer simulations of coil-sample interaction, etc. Explicit time dependence is evaluated for different forms of driving voltage. The major steps of the solution development are shown and appropriate explanations are given. Green's functions and spectral density formula were developed for any form of periodic driving voltage. The concept of distributed power losses based on transmission line theory is developed for evaluation of local losses of a coil. Three major types of power losses are estimated as equivalent series resistances in the circuit of the birdcage resonator. Values of generated resistances in legs and end-rings are estimated. An application of the theory is shown for many practical cases. Experimental curve of B(1) field polarization dependence is measured for eight-sections birdcage coil. It was shown that the steady-state driven resonance frequencies do not depend on damping factor unlike the free oscillation (transient) frequencies. An equivalent active resistance is generated due to interaction of RF electromagnetic field with a sample. Resistance of the conductor (enhanced by skin effect), Eddy currents and dielectric losses are the major types of losses which contribute to the values of generated resistances. A biomedical sample for magnetic resonance imaging and spectroscopy is the source of the both Eddy current and dielectric losses of a coil. As demonstrated by the theory, Eddy current loss is the major effect of coil shielding. PMID:20869184

Novikov, Alexander

2011-02-01

259

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

260

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

261

Transient analysis of spectrally asymmetric magnetic photonic crystals with ferromagnetic losses  

NASA Astrophysics Data System (ADS)

We analyze transient electromagnetic pulse propagation in spectrally asymmetric magnetic photonic crystals (MPCs) with ferromagnetic losses. MPCs are dispersion-engineered materials consisting of a periodic arrangement of misaligned anisotropic dielectric and ferromagnetic layers that exhibit a stationary inflection point in the (asymmetric) dispersion diagram and unidirectional frozen modes. The analysis is performed via a late-time stable finite-difference time-domain method (FDTD) implemented with perfectly matched layer (PML) absorbing boundary conditions, and extended to handle (simultaneously) dispersive and anisotropic media. The proposed PML-FDTD algorithm is based on a D - H and B - E combined field approach that naturally decouples the FDTD update into two steps, one involving the (anisotropic and dispersive) constitutive material tensors and the other involving Maxwell’s equations in a complex coordinate space (to incorporate the PML). For ferromagnetic layers, a fully dispersive modeling of the permeability tensor is implemented to include magnetic losses in a consistent fashion. The numerical results illustrate some striking properties of MPCs, such as wave slowdown (frozen modes), amplitude increase (pulse compression), and unidirectional characteristics. The numerical model is also used to investigate the sensitivity of the MPC response against excitation (frequency and bandwidth), material (ferromagnetic losses), and geometric (layer misalignment and thickness) parameter variations.

Jung, K.-Y.; Donderici, B.; Teixeira, F. L.

2006-10-01

262

Low loss pole configuration for multi-pole homopolar magnetic bearings  

NASA Technical Reports Server (NTRS)

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

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

2001-01-01

263

Standardization of the pickup coil method for AC loss measurement of three-component superconducting wires  

NASA Astrophysics Data System (ADS)

In order to extend the scope of the proposed standard of the pickup coil method for AC loss measurement in IEC/TC90-WG9, a round robin test (RRT) of AC loss measurement for three-component (Cu/Cu-Ni/Nb-Ti) superconducting wires has been carried out. Three kinds of three-component superconducting wires were supplied and two laboratories participated in the RRT. The frequency dependence of total AC loss was measured in an alternating transverse magnetic field with the amplitude of 0.5 and 1 T at 4.2 K in the frequency range between 0.01 and 20 Hz. The hysteresis loss per cycle was obtained as an extrapolated value of the total AC loss per cycle at f=0 Hz. The coupling loss was also obtained by subtracting the hysteresis loss from the total AC loss. From the RRT between the two laboratories, the coefficients of variation of hysteresis loss and coupling time constant were both within 2%. Consequently, it was found that the procedure of AC loss measurement for the three-component wires was in principle the same as that for the Cu/Nb-Ti composite ones by extending the upper point of the measuring frequency range from 1 Hz up to about 10 Hz.

Kawabata, S.; Tsuzura, H.; Fukuda, Y.; Funaki, K.; Osamura, K.

264

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

SciTech Connect

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

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

2010-04-15

265

Equivalent Circuits for Single-Phase Induction and Hysteresis Motors  

Microsoft Academic Search

General steady-state equivalent circuits are derived for the family of single-phase motors with unequal contrarotating magnetic fields produced by one or two stator windings and\\/or stator saliency, and rotor torque due to hysteresis and\\/or eddy- current action. The derivation of an equivalent quadrature motor, first shown by Kron, is extended to the range of motors under consideration. The idealized treatment

Denis O'Kelly

1971-01-01

266

ASYNCHRONOUS PERFORMANCES OF HYSTERESIS MOTORS UNDER UNBALANCED CONDITIONS  

Microsoft Academic Search

The torque-speed curves of an hysteresis motor under unbalanced conditions are computed by a numerical method. The magnetic characteristic of the rotor ring is represented by the Preisach-Néel's model. This method takes into account the minor loops which appear on the B(H) characteristic in the case under consideration. Computed and experimental curves are compared. This work shows that eddy currents

J. PERARD; M. POLOUJADOFF

1977-01-01

267

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

Microsoft Academic Search

We examine the angular momentum loss and associated rotational spin-down for\\u000amagnetic hot stars with a line-driven stellar wind and a rotation-aligned\\u000adipole magnetic field. Our analysis here is based on our previous 2-D numerical\\u000aMHD simulation study that examines the interplay among wind, field, and\\u000arotation as a function of two dimensionless parameters, W(=Vrot\\/Vorb) and 'wind\\u000amagnetic confinement', $\\\\eta_\\\\ast$

Richard H. D. Townsend

2008-01-01

268

The effect of coolant loss on current leads for superconducting magnets  

NASA Astrophysics Data System (ADS)

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

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

1981-10-01

269

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

270

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

Microsoft Academic Search

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

Katsumi Yamazaki

2003-01-01

271

Hysteresis and compensation behaviors of spin-3/2 cylindrical Ising nanotube system  

NASA Astrophysics Data System (ADS)

The hysteresis and compensation behaviors of the spin-3/2 cylindrical Ising nanotube system are studied within the framework of the effective-field theory with correlations. The effects of the Hamiltonian parameters are investigated on the magnetic and thermodynamic quantities, such as the total magnetization, hysteresis curves, and compensation behaviors of the system. Depending on the Hamiltonian parameters, some characteristic hysteresis behaviors are found, such as the existence of double and triple hysteresis loops. According to Néel classification nomenclature, the system displays Q-, R-, P-, N-, M-, and S- types of compensation behaviors for the appropriate values of the system parameters. We also compare our results with some recently published theoretical and experimental works and find a qualitatively good agreement.

Kocakaplan, Yusuf; Keskin, Mustafa

2014-09-01

272

Performance predictions for large hysteresis motors  

Microsoft Academic Search

This paper examines the possibilities of designing large, integral-horsepower hysteresis motors to have efficiency and power factor comparable with that of induction motors. Scaling techniques are used, together with a previously published analytical method, to scale up an existing laboratory hysteresis motor of 3 kW rating. The resulting design for a 200 kW hysteresis motor is predicted to have an

G. R. Slemon; R. D. Jackson; M. A. Rahman

1977-01-01

273

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

E-print Network

on new machine topologies, such as hybrid excitation [1]14 motors. Since 3D flux paths are encountered in23 the center of a three phase motor stator. In each case, the maximum frequency does not exceed, the non-monotonous behavior of the hysteresis part30 versus the peak induction under circular excitation

Paris-Sud XI, Université de

274

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

275

Hysteresis phenomenon in turbulent convection  

E-print Network

Coherent large-scale circulations of turbulent thermal convection in air have been studied experimentally in a rectangular box heated from below and cooled from above using Particle Image Velocimetry. The hysteresis phenomenon in turbulent convection was found by varying the temperature difference between the bottom and the top walls of the chamber (the Rayleigh number was changed within the range of $10^7 - 10^8$). The hysteresis loop comprises the one-cell and two-cells flow patterns while the aspect ratio is kept constant ($A=2 - 2.23$). We found that the change of the sign of the degree of the anisotropy of turbulence was accompanied by the change of the flow pattern. The developed theory of coherent structures in turbulent convection (Elperin et al. 2002; 2005) is in agreement with the experimental observations. The observed coherent structures are superimposed on a small-scale turbulent convection. The redistribution of the turbulent heat flux plays a crucial role in the formation of coherent large-scal...

Eidelman, A; Kleeorin, N; Markovich, A; Rogachevskii, I

2006-01-01

276

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

277

3-D eddy current analysis in a silicon steel sheet of an interior permanent magnet motor  

Microsoft Academic Search

Interior permanent magnet (IPM) motors are widely used in various fields. It is important for the high-efficiency operation of IPM motors to clarify the iron loss. In this paper, the harmonic eddy current loss and the hysteresis loss of a piece of silicon steel sheet of an IPM motor are calculated using the three-dimensional finite-element method (3-D FEM). It quantitatively

Yoshihiro Kawase; Tadashi Yamaguchi; Shinya Sano; Masao Igata; Kazuo Ida; Akio Yamagiwa

2003-01-01

278

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

PubMed

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

Burdt, Russell; Curry, Randy D

2008-09-01

279

Influence of control strategy on stator and rotor losses in high-speed permanent magnet brushless motors  

NASA Astrophysics Data System (ADS)

The stator iron loss and rotor eddy current loss which results in a high-speed permanent magnet brushless motor when operated in brushless dc and ac modes, on both open-circuit and at rated load, with four different current control strategies, is investigated by finite element analysis. It has highlighted the significant influence of the phase current wave form. It has also shown that, on load, the rotor eddy current loss can be the dominant loss component, particularly in brushless dc mode.

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

2005-05-01

280

Hysteresis in a quantized superfluid `atomtronic' circuit  

NASA Astrophysics Data System (ADS)

Atomtronics is an emerging interdisciplinary field that seeks to develop new functional methods by creating devices and circuits where ultracold atoms, often superfluids, have a role analogous to that of electrons in electronics. Hysteresis is widely used in electronic circuits--it is routinely observed in superconducting circuits and is essential in radio-frequency superconducting quantum interference devices. Furthermore, it is as fundamental to superfluidity (and superconductivity) as quantized persistent currents, critical velocity and Josephson effects. Nevertheless, despite multiple theoretical predictions, hysteresis has not been previously observed in any superfluid, atomic-gas Bose-Einstein condensate. Here we directly detect hysteresis between quantized circulation states in an atomtronic circuit formed from a ring of superfluid Bose-Einstein condensate obstructed by a rotating weak link (a region of low atomic density). This contrasts with previous experiments on superfluid liquid helium where hysteresis was observed directly in systems in which the quantization of flow could not be observed, and indirectly in systems that showed quantized flow. Our techniques allow us to tune the size of the hysteresis loop and to consider the fundamental excitations that accompany hysteresis. The results suggest that the relevant excitations involved in hysteresis are vortices, and indicate that dissipation has an important role in the dynamics. Controlled hysteresis in atomtronic circuits may prove to be a crucial feature for the development of practical devices, just as it has in electronic circuits such as memories, digital noise filters (for example Schmitt triggers) and magnetometers (for example superconducting quantum interference devices).

Eckel, Stephen; Lee, Jeffrey G.; Jendrzejewski, Fred; Murray, Noel; Clark, Charles W.; Lobb, Christopher J.; Phillips, William D.; Edwards, Mark; Campbell, Gretchen K.

2014-02-01

281

Hysteresis in a quantized superfluid 'atomtronic' circuit.  

PubMed

Atomtronics is an emerging interdisciplinary field that seeks to develop new functional methods by creating devices and circuits where ultracold atoms, often superfluids, have a role analogous to that of electrons in electronics. Hysteresis is widely used in electronic circuits-it is routinely observed in superconducting circuits and is essential in radio-frequency superconducting quantum interference devices. Furthermore, it is as fundamental to superfluidity (and superconductivity) as quantized persistent currents, critical velocity and Josephson effects. Nevertheless, despite multiple theoretical predictions, hysteresis has not been previously observed in any superfluid, atomic-gas Bose-Einstein condensate. Here we directly detect hysteresis between quantized circulation states in an atomtronic circuit formed from a ring of superfluid Bose-Einstein condensate obstructed by a rotating weak link (a region of low atomic density). This contrasts with previous experiments on superfluid liquid helium where hysteresis was observed directly in systems in which the quantization of flow could not be observed, and indirectly in systems that showed quantized flow. Our techniques allow us to tune the size of the hysteresis loop and to consider the fundamental excitations that accompany hysteresis. The results suggest that the relevant excitations involved in hysteresis are vortices, and indicate that dissipation has an important role in the dynamics. Controlled hysteresis in atomtronic circuits may prove to be a crucial feature for the development of practical devices, just as it has in electronic circuits such as memories, digital noise filters (for example Schmitt triggers) and magnetometers (for example superconducting quantum interference devices). PMID:24522597

Eckel, Stephen; Lee, Jeffrey G; Jendrzejewski, Fred; Murray, Noel; Clark, Charles W; Lobb, Christopher J; Phillips, William D; Edwards, Mark; Campbell, Gretchen K

2014-02-13

282

Dynamic performance prediction of polyphase hysteresis motors  

Microsoft Academic Search

The dynamic performance characteristics of polyphase hysteresis motors are presented. A mathematical model to predict the starting and synchronization process of such motors under various operating conditions is given. The model offers a tool for studying the dynamic stability of the hysteresis motor for small-scale disturbances such as changes in load torque, supply voltage, and frequency. A parametric variation is

M. A. Rahman; ALI M. OSHEIBA

1990-01-01

283

Equivalent Circuit Modeling of Hysteresis Motors  

Microsoft Academic Search

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

J J Nitao; E T Scharlemann; B A Kirkendall

2009-01-01

284

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

285

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

286

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

NASA Technical Reports Server (NTRS)

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

Barranger, J. P.

1966-01-01

287

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

288

Metal loss characterization in 55-gallon drum steel by the magnetic flux leakage method  

SciTech Connect

A technique, using Magnetic Flux Leakage (MFL), has been developed for imaging corrosion damage in real-time on the inner surface of sealed 55-gallon drums. An experimental study and theoretical background are presented showing the sensitivity of an MFL technique for detecting and imaging both general and localized corrosion on the inner surface of sealed 55-gallon drums, inspected from the outer surface. Measurements resulting from studies on natural corrosion and machined defects in 55-gallon drum steel will be discussed. Image processing techniques applied to scan data show metal loss in 2-D gray scale images. This work suggests an approach to designing a real-time, full-coverage, 55-gallon drum inspection system to characterize drum wall thickness for comparison over time to determine corrosion rate.

Hockey, R.; Riechers, D. [Pacific Northwest Lab., Richland, WA (United States); Duncan, D. [Westinghouse Hanford Co., Richland, WA (United States)

1995-12-31

289

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

290

Loss cone evolution and particle escape in collapsing magnetic trap models in solar flares  

E-print Network

Collapsing magnetic traps (CMTs) have been suggested as one possible mechanism responsible for the acceleration of high-energy particles during solar flares. An important question regarding the CMT acceleration mechanism is which particle orbits escape and which are trapped during the time evolution of a CMT. While some models predict the escape of the majority of particle orbits, other more sophisticated CMT models show that, in particular, the highest-energy particles remain trapped at all times. The exact prediction is not straightforward because both the loss cone angle and the particle orbit pitch angle evolve in time in a CMT. Our aim is to gain a better understanding of the conditions leading to either particle orbit escape or trapping in CMTs.

Oskoui, Solmaz Eradat; Grady, Keith James

2014-01-01

291

Study of a Radial-Exiting Hysteresis Gyro Motor.  

National Technical Information Service (NTIS)

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

H. Yamada

1973-01-01

292

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

293

Joining of parts via magnetic heating of metal aluminum powders  

DOEpatents

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

Baker, Ian

2013-05-21

294

IMPLICATIONS OF MASS AND ENERGY LOSS DUE TO CORONAL MASS EJECTIONS ON MAGNETICALLY ACTIVE STARS  

SciTech Connect

Analysis of a database of solar coronal mass ejections (CMEs) and associated flares over the period 1996-2007 finds well-behaved power-law relationships between the 1-8 A flare X-ray fluence and CME mass and kinetic energy. We extrapolate these relationships to lower and higher flare energies to estimate the mass and energy loss due to CMEs from stellar coronae, assuming that the observed X-ray emission of the latter is dominated by flares with a frequency as a function of energy dn/dE = kE {sup -{alpha}}. For solar-like stars at saturated levels of X-ray activity, the implied losses depend fairly weakly on the assumed value of {alpha} and are very large: M-dot {approx}5 Multiplication-Sign 10{sup -10} M{sub sun} yr{sup -1} and E-dot {approx}0.1 L{sub sun}. In order to avoid such large energy requirements, either the relationships between CME mass and speed and flare energy must flatten for X-ray fluence {approx}> 10{sup 31} erg, or the flare-CME association must drop significantly below 1 for more energetic events. If active coronae are dominated by flares, then the total coronal energy budget is likely to be up to an order of magnitude larger than the canonical 10{sup -3} L {sub bol} X-ray saturation threshold. This raises the question of what is the maximum energy a magnetic dynamo can extract from a star? For an energy budget of 1% of L {sub bol}, the CME mass loss rate is about 5 Multiplication-Sign 10{sup -11} M {sub Sun} yr{sup -1}.

Drake, Jeremy J.; Cohen, Ofer [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)] [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Yashiro, Seiji [Interferometrics Inc., Herndon, VA 20171 (United States)] [Interferometrics Inc., Herndon, VA 20171 (United States); Gopalswamy, Nat, E-mail: jdrake@cfa.harvard.edu [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)] [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)

2013-02-20

295

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

296

Magnetic bearings for inertial energy storage  

SciTech Connect

The selection of a noncontacting bearing technique with no wear out phenomena and which is vacuum compatible which is the decisive factor in selecting magnetic bearings for kinetic energy storage was investigated. Unlimited cycle life without degradation is a primary goal. Storage efficiency is a key parameter which is defined as the ratio of the energy remaining to energy stored after a fixed time interval at no load conditions. Magnetic bearings, although noncontacting, are not perfectly frictionless in that magnetic losses due to eddy currents and hysteresis can occur. Practical magnetic bearings, however, deviate from perfect symmetry and have discontinuities and asymmetric flux paths either by design or when controlled in the presence of disturbances, which cause losses. These losses can be kept smaller in the bearings than in a high power motor/generator, however, are a significant factor in selecting the magnetic bearing type.

Studer, P.A.

1983-12-01

297

Phase-coexistence and thermal hysteresis in samples comprising adventitiously doped MnAs nanocrystals: programming of aggregate properties in magnetostructural nanomaterials.  

PubMed

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

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

2014-07-22

298

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

Microsoft Academic Search

We have investigated the frequency dependent contributions to the magnetic ac loss in a 10 strand Roebel cable with 2 mm wide non-insulated strands and a transposition length of 90 mm. This cable is made from 40 mm wide YBCO coated conductor tape manufactured by AMSC and stabilized by electroplating 25 µm thick copper on either side prior to the

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

2010-01-01

299

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

Microsoft Academic Search

We have investigated the frequency dependent contributions to the magnetic ac loss in a 10 strand Roebel cable with 2 mm wide non-insulated strands and a transposition length of 90 mm. This cable is made from 40 mm wide YBCO coated conductor tape manufactured by AMSC and stabilized by electroplating 25 µm thick copper on either side prior to the

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

2010-01-01

300

Gap Loss Function and Determination of Certain Critical Parameters in Magnetic Data Recording Instruments and Storage Systems  

Microsoft Academic Search

After a brief review of Westmijze's semi-infinite model for the reading of recorded signals in magnetic media by gapped ring heads, a program for the computation of the gap loss function S is described. By introducing the higher order sine and cosine integrals, this function can be evaluated to any degree of accuracy over its useful range. A four decimal

H. S. C. Wang

1966-01-01

301

Evaluation of wear-induced material loss in case-hardened steel using magnetic Barkhausen emission measurement  

Microsoft Academic Search

The feasibility of using magnetic Barkhausen emission (MBE) measurement for the evaluation of wear-induced material loss in case-hardened steel is examined in this paper. MBE measurements were carried out on two case hardened carburized steel disks. The MBE signals from the carburized material were significantly different from the base metal. On both disks it was observed that the MBE level

B. Zhu; M. J. Johnson; D. C. Jiles

2000-01-01

302

Percolation model of relative permeability hysteresis  

NASA Astrophysics Data System (ADS)

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

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

2013-05-01

303

Quantized hysteresis in a superfluid atomtronic circuit  

E-print Network

Atomtronics is an emerging interdisciplinary field that seeks new functionality by creating devices and circuits where ultra-cold atoms play a role analogous to the electrons in electronics. Hysteresis in atomtronic circuits may prove to be a crucial feature for the development of practical devices, just as it has in electronic circuits like memory, digital noise filters (e.g., Schmitt triggers), and magnetometers (e.g., superconducting quantum interference devices [SQUIDs]). Here we demonstrate quantized hysteresis in an atomtronic circuit: a ring of superfluid, dilute-gas, Bose-Einstein condenstate (BEC) obstructed by a rotating weak link. Hysteresis is as fundamental to superfluidity (and superconductivity) as quantized persistent currents, critical velocity, and Josephson effects, but has not been previously observed in any atomic-gas, superfluid BEC despite multiple theoretical predictions. By contrast, hysteresis is routinely observed in superconducting circuits, and it is essential in rf-SQUIDs. Superf...

Eckel, Stephen; Jendrzejewski, Fred; Murray, Noel; Clark, Charles W; Lobb, Christopher J; Phillips, William D; Edwards, Mark; Campbell, Gretchen K

2014-01-01

304

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

305

Hysteresis effects in Bose-Einstein condensates  

E-print Network

Here, we consider damped two-components Bose-Einstein condensates with many-body interactions. We show that, when the external trapping potential has a double-well shape and when the nonlinear coupling factors are modulated in time, hysteresis effects may appear under some circumstances. Such hysteresis phenomena are a result of the joint contribution between the appearance of saddle node bifurcations and damping effect.

Andrea Sacchetti

2010-06-16

306

Dynamic performance prediction of hysteresis motors  

Microsoft Academic Search

The dynamic performance characteristics of polyphase hysteresis motors are presented. A mathematical model, based on the d-q-axis theory, for predicting the starting and synchronization processes of such motors under various operating conditions is presented. The model offers a tool for studying the dynamic stability of the hysteresis motor for small-scale disturbances such as load torque, supply voltage, and frequency. Moreover,

M. A. Rahman; A. M. Osheiba

1989-01-01

307

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

308

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

309

Loss Calculation of Induction Motors Considering Harmonic Electromagnetic Fields in Stator and Rotor  

NASA Astrophysics Data System (ADS)

A method of loss calculation for induction motors is proposed. The combined 3D-2D time stepping finite element analysis is carried out to obtain the copper loss and the time-variation of the magnetic field in the motor. The iron loss is calculated approximately considering the time-variation of the magnetic field direction and the minor hysteresis loops caused by the time-harmonic fields using practical computer resources. The proposed method is applied to 4 types of induction motors, which are the solid rotor induction motors with/without slot and the cage induction motors with/without skew. The measured and the calculated total losses and the iron losses agree well in all cases. The differences of the loss distributions of each motor are also compared and investigated.

Yamazaki, Katsumi

310

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

SciTech Connect

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

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

1997-09-01

311

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

SciTech Connect

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

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

2006-07-15

312

Magnetic resonance morphometry of the loss of gray matter volume in Parkinson's disease patients.  

PubMed

Voxel-based morphometry can be used to quantitatively compare structural differences and func-tional changes of gray matter in subjects. In the present study, we compared gray matter images of 32 patients with Parkinson's disease and 25 healthy controls using voxel-based morphometry based on 3.0 T high-field magnetic resonance T1-weighted imaging and clinical neurological scale scores. Results showed that the scores in Mini-Mental State Examination and Montreal Cognitive Assessment were lower in patients compared with controls. In particular, the scores of visuospa-tial/executive function items in Montreal Cognitive Assessment were significantly reduced, but mean scores of non-motor symptoms significantly increased, in patients with Parkinson's disease. In dition, gray matter volume was significantly diminished in Parkinson's disease patients compared with normal controls, including bilateral temporal lobe, bilateral occipital lobe, bilateral parietal lobe, bilateral frontal lobe, bilateral insular lobe, bilateral parahippocampal gyrus, bilateral amygdale, right uncus, and right posterior lobe of the cerebellum. These findings indicate that voxel-based phometry can accurately and quantitatively assess the loss of gray matter volume in patients with Parkinson' disease, and provide essential neuroimaging evidence for multisystem pathological mechanisms involved in Parkinson's disease. PMID:25206566

Xia, Jianguo; Wang, Juan; Tian, Weizhong; Ding, Hongbin; Wei, Qilin; Huang, Huanxin; Wang, Jun; Zhao, Jinli; Gu, Hongmei; Tang, Lemin

2013-09-25

313

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

314

Core loss prediction combining physical models with numerical field analysis  

NASA Astrophysics Data System (ADS)

An improved procedure for calculating iron losses in electrical machine cores is presented. It is based on physical models and experiments on losses in magnetic laminations, under one- and two-dimensional fields, and exploits a finite element computation of the flux distribution in the core. Physical modelling relies on the basic concept of loss separation, extended to the case of vectorial magnetic flux with generic elliptical loci. Starting from a theoretical formulation of power losses under unidirectional fields and generic induction waveform and its extension to the case of elliptical flux, general expressions are derived for the hysteresis, excess and classical loss components in two dimensions. Quasi-static and 50 Hz total losses under alternating sinusoidal flux and pure rotational flux are the sole experimental data needed for a complete loss prediction. In the present work, two different types of nonoriented FeSi 3.2% laminations are considered, which are assumed to be assembled into a model three-phase motor core. By means of a 2D finite element analysis, the distribution of magnetic field and induction in the core is obtained for different values of the supply current and the loss calculation is carried out. A comparison with standard loss calculation methods points to the detrimental role of two-dimensional fluxes, although this may not be fully appreciated in conventional 50 Hz induction motors.

Bertotti, G.; Canova, A.; Chiampi, M.; Chiarabaglio, D.; Fiorillo, F.; Rietto, A. M.

1994-05-01

315

Towards beyond 1 GHz NMR: Mechanism of the long-term drift of screening current-induced magnetic field in a Bi2223 coil  

Microsoft Academic Search

The screening current-induced magnetic field in the (Bi,Pb)2Sr2Ca2Cu3Ox (Bi-2223) insert coil proposed for a beyond 1GHz nuclear magnetic resonance (NMR) spectrometer may generate a long-term field drift, resulting in a loss of field-frequency lock operation and an inability to make high resolution NMR measurements. The measured screening current-induced magnetic field of a Bi-2223 double-pancake coil exhibits a hysteresis effect at

Y. Koyama; T. Takao; Y. Yanagisawa; H. Nakagome; M. Hamada; T. Kiyoshi; M. Takahashi; H. Maeda

2009-01-01

316

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

NASA Astrophysics Data System (ADS)

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 Ampère'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.

Halleröd, Tomas; Rylander, Thomas

2008-04-01

317

Dependence of self field AC losses in AC multifilamentary composites and cables on external AC magnetic field  

SciTech Connect

The authors measured AC losses of AC multifilamentary wires (NbTi and Nb{sub 3}Sn) and a cable of (6+1) configuration due to transport currents in an AC external magnetic field at 50Hz. They also studied the stabilities of the NbTi and Nb{sub 3}Sn wires and the cable. The Nb{sub 3}Sn AC wire has thinner filamentary zone than the NbTi wire. It was shown by the experiment that the Nb{sub 3}Sn wire had better stability against the magnetic instability and that AC quench currents of the Nb{sub 3}Sn wire reached the critical current in DC back ground field, while the AC quench currents of the NbTi wire were far below the critical current due to the magnetic instability. The AC losses of the Nb{sub 3}Sn wire due to the wire transport current are higher and less dependent on the direction of the external magnetic field than those of the NbTi wire. AC losses of a cable of (6+1) configuration made of the NbTi wire were higher than those estimated from the single wire. Those experimental results are discussed and is explained by estimating thickness of saturated zone in the wire where the filaments carry their critical current.

Fukui, S.; Ito, M.; Tsukamoto, O. [Yokohama National Univ. (Japan)] [and others

1997-06-01

318

High electrical resistance hot-pressed NdFeB magnet for low loss motors  

NASA Astrophysics Data System (ADS)

Fluoride-coated hot-pressed NdFeB magnets with electrical resistivity of 1.4m?cm, which is ten times larger than that of a noncoated sintered NdFeB magnet, were prepared using fluoride coating powders. The high resistive NdFeB magnets consist of coated powders and are sintered with a neodymium fluoride layer, which was grown using a fluoride solution. No degradation of coercivity was observed in the fluoride coated NdFeB powders. The increase in magnet temperature caused by an alternating magnetic field (Eddy currents) was eightfold with the use of a fluoride-treated magnet. Furthermore, the increase in temperature at the magnet's rotor was reduced by 50% when the high resistive hot-pressed magnet was substituted for the conventional commercial magnet.

Komuro, Matahiro; Satsu, Yuichi; Enomoto, Yuji; Koharagi, Haruo

2007-09-01

319

Influence of External Magnetic Field on AC Losses at EF Coil Joints of JT-60SA  

Microsoft Academic Search

We experimentally and numerically evaluated the AC loss occurred in joints of the EF coil in JT60-SA. There are two kinds of the joints (pancake joint and terminal joint) in the EF coil. Firstly, the AC losses of the joints were experimentally obtained. The experimental results showed that the AC losses in the pancake and the terminal joints were smaller

Tomoaki Takao; Kazuya Nakamura; Toshiyuki Takagi; Naoki Tanoue; Haruyuki Murakami; Kiyoshi Yoshida

2012-01-01

320

A Domain Wall Model for Ferroelectric Hysteresis Ralph C. Smith 1 and Craig L. Hom 2  

E-print Network

A Domain Wall Model for Ferroelectric Hysteresis Ralph C. Smith 1 and Craig L. Hom 2 1 Center on the quantification of energy required to bend and translate domain walls and is developed in two steps. In the first the consideration of domain wall motion and the quantification of energy losses due to inherent inclusions

321

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

Microsoft Academic Search

Baking (Pb, La)(Zr, Ti)O3 capacitors in a hydrogen atmosphere causes a significant loss of remanent polarization even at 150 °C. The hysteresis variations depend on the polarization states during baking. The hysteresis loop showed voltage shifts when the capacitor was polarized before baking, whereas it became a cramped shape when the baking was carried out on a virgin capacitor. Although

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

1999-01-01

322

Permanent magnets models and losses in 2D FEM simulation of electrical machines  

Microsoft Academic Search

This paper presents different methods to model permanent magnet materials within the 2D finite element simulation of electrical machines and discuss them. The modeling deals with both the material magnetic properties and the circuit equations related to different parts of the machine. The emphasis is on modeling permanent magnets as part of the rotor electrical circuit. The methods presented are

Anouar Belahcen; Antero Arkkio

2010-01-01

323

Hysteresis in corticospinal excitability during gradual muscle contraction and relaxation in humans  

Microsoft Academic Search

Many studies have demonstrated that the firing behavior of single motor units varies in a nonlinear manner to the exerted torque during gradual muscle contraction and relaxation. However, it is unclear whether corticospinal excitability has such a hysteresis-like feature. In this study, we examined corticospinal excitability using transcranial magnetic stimulation (TMS) during gradual muscle contraction and relaxation for torque regulation

Toshitaka Kimura; Kentaro Yamanaka; Daichi Nozaki; Kimitaka Nakazawa; Tasuku Miyoshi; Masami Akai; Tatsuyuki Ohtsuki

2003-01-01

324

An Analysis of the Hysteresis Motor I - Analysis of the Idealized Machine  

Microsoft Academic Search

This paper presents an analysis of an idealized polyphase hysteresis machine. The distributed magnetic field within the machine is described in terms of dimensions and windings. A single-phase equivalent circuit is developed for the machine and expressions are given for the parameters of this equivalent circuit and for the machine torque. Improvement of power factor by reduction of stator voltage

M. A. Copeland; G. R. Slemon

1963-01-01

325

Dynamics and hysteresis in square lattice artificial spin-ice G. M. Wysin  

E-print Network

-dimensional spin ice materials that exhibit geometrical frustration effects: not all the pair- wise spin-range dipolar forces, which leads to geometrical frustration. Each island is assumed to possess a three, spin-ice, frustration, magnetic hysteresis, susceptibility. I. INTRODUCTION: SQUARE SPIN ICE

Wysin, Gary

326

Hysteresis and after-effects in massive substances. From spin-glasses to the sand hill  

E-print Network

to the spin-glass case. The magnetization relaxations at different temperatures (S(T) curves) and the Fulcher1095 Hysteresis and after-effects in massive substances. From spin-glasses to the sand hill J]. This will be done with the particular hindsight resulting from our spin-glass directed state of mind N6el

Boyer, Edmond

327

734 IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, VOL. 39, NO. 3, MAY/JUNE 2003 Modeling of Iron Losses of Permanent-Magnet  

E-print Network

Losses of Permanent-Magnet Synchronous Motors Chunting Mi, Member, IEEE, Gordon R. Slemon, Life Fellow, IEEE, and Richard Bonert, Member, IEEE Abstract--Permanent-magnet (PM) motors offer potential en- ergy motors. I. INTRODUCTION PERMANENT-MAGNET (PM) motors are challenging the monopoly of induction machines

Mi, Chunting "Chris"

328

Field dependent resonance frequency of hysteresis loops in a few monolayer thick Co\\/Cu(001) films  

Microsoft Academic Search

Dynamic responses of magnetic hysteresis loops in a few monolayer (ML) thick Co\\/Cu(001) films were studied using surface magneto-optic Kerr effect (SMOKE). For a fixed external field strength H0, the hysteresis loop area increases as a function of frequency with a power law and reaches a maximum at a resonance frequency ?0. This ?0 depends on the external periodic field

Q. Jiang; H.-N. Yang; G.-C. Wang

1996-01-01

329

A Study on Shield Property of Transfixion Hole for Power Wire Filled with Dielectric and Magnetic Loss Material  

NASA Astrophysics Data System (ADS)

In this study, we focus on deterioration in the shield property caused by penetrating a power wire through a transfixion hole. The shield structure of circular transfixion hole filled the space between the cable and the penetration part with dielectric and magnetic loss material is proposed, and shield property is evaluated by FDTD method and measuerment. As a result, it is confirmed that shield property decreases in case of penetrating a power wire through a circular transfixion hole compared with that of only circular hole, because this structure becomes circular coaxial line. Moreover, dielectric and magnetic loss material is filled in the space between the cable and the penetration part, it is clarified that shield property is improved about 20dB. Therefore, the effectiveness of this proposed structure to real transfixion hole can be confirmed quantitatively.

Ra, Fumio; Matsumoto, Kouta; Endo, Tetsuo; Hashimoto, Osamu

330

Statistical mechanical origin of hysteresis in ferroelectrics  

NASA Astrophysics Data System (ADS)

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

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

2012-08-01

331

AC losses and heat removal in three-dimensional winding pack of Samsung superconducting test facility under pulsed magnetic field operation  

NASA Astrophysics Data System (ADS)

The Samsung superconducting test facility (SSTF) will be operated under the highly pulsed field to simulate the operating conditions of KSTAR. An analysis has been performed to study the transient heat removal characteristics and temperature margin for the main, blip and compensating coils in the SSTF. This method is based on a quasi-three-dimensional model, which the thermal coupling of turn-to-turn, pancake-to-pancake and channel-to-channel is taken into account, to simulate the conductor temperature rise and the thermal expansion of supercritical helium due to the high AC losses under the pulsed field. The local AC losses, which include coupling loss, eddy current loss and hysteresis loss in the cable-in-conduit conductor, are estimated. The temperature margin, mass flow rate, distribution of AC losses are studied under the given operating scenario. The mass flow reduction and peak temperature rise depending on the inlet pressure and inlet position of CICC are studied. It is shown that the initial mass flow rate remarkably influences on the peak temperature of superconducting strands. The large mass flow rate can reduce the temperature rise when the inlet of helium is located at the high field region. By contrast, because of heat induced flow to improve the cooling condition of the superconducting strands, the small initial mass flow rate results in the low peak temperature in strands when the inlet of helium is located at the low field region.

Wang, Qiuliang; Seong Yoon, Cheon; Baang, Sungkeun; Kim, Myungkyu; Park, Hyunki; Kim, Yongjin; Lee, Sangil; Kim, Keeman

2001-04-01

332

Physiological thermoregulation in a crustacean? Heart rate hysteresis in the freshwater crayfish Cherax destructor.  

PubMed

Differential heart rates during heating and cooling (heart rate hysteresis) are an important thermoregulatory mechanism in ectothermic reptiles. We speculate that heart rate hysteresis has evolved alongside vascularisation, and to determine whether this phenomenon occurs in a lineage with vascularised circulatory systems that is phylogenetically distant from reptiles, we measured the response of heart rate to convective heat transfer in the Australian freshwater crayfish, Cherax destructor. Heart rate during convective heating (from 20 to 30 degrees C) was significantly faster than during cooling for any given body temperature. Heart rate declined rapidly immediately following the removal of the heat source, despite only negligible losses in body temperature. This heart rate 'hysteresis' is similar to the pattern reported in many reptiles and, by varying peripheral blood flow, it is presumed to confer thermoregulatory benefits particularly given the thermal sensitivity of many physiological rate functions in crustaceans. PMID:15313496

Goudkamp, Jacqueline E; Seebacher, Frank; Ahern, Mark; Franklin, Craig E

2004-07-01

333

A Test of HTS Power Cable in a Sweeping Magnetic Field  

E-print Network

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 rate. The B-field orientation toward the HTS strands wide surface was varied from 0 deg. to 10 deg., in steps of 1 deg.. 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; Blowers, J; Shiltsev, V

2012-01-01

334

AVERAGING PRINCIPLE FOR DIFFERENTIAL EQUATIONS WITH HYSTERESIS  

E-print Network

this approximation holds is inverse propor- tional to the rate of change of slow variables. The system is described on the systems with the classical Preisach nonlinearity. Key words: Averaging technique, Hysteresis, Sweeping to Boole Centre for Research in Informatics and Department of Applied Mathematics, University College Cork

Schellekens, Michel P.

335

AN ANALYSIS OF THE HYSTERESIS MOTOR  

Microsoft Academic Search

The analysis of the hysteresis motor Is undertaken on the basis of a “rectified” representation of its structure. Maxwell's equations and Poyntlng's theorem are used In order to obtain the dependency of the developed force on the physical parameters and dimensions of the machine. Three different limiting cases are studied and their characteristics computed

S. GAVRIL; A. MOR

1982-01-01

336

Hunting in hysteresis motors, impact of supply  

Microsoft Academic Search

Hunting in synchronous motor is the continuous speed oscillation with a frequency around 3 to 5 Hz which arises from voltage or load distortions. This oscillation descends with exponential trend-line to steady state relative lower amplitude. This paper presents an investigation of hunting when a synchronous hysteresis motor is supplied with non-ideal input voltage sources. For studying of machine performance

Ahmad Darabi; Mohamadreza Rafiei; Teimoor Ghanbari

2007-01-01

337

Equivalent Circuit Modeling of Hysteresis Motors.  

National Technical Information Service (NTIS)

We performed a literature review and found that many equivalent circuit models of hysteresis motors in use today are incorrect. The model by Miyairi and Kataoka (1965) is the correct one. We extended the model by transforming it to quadrature coordinates,...

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

2009-01-01

338

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

339

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

340

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

341

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

342

Numerical and experimental comparison of electromechanical properties and efficiency of HTS and ferromagnetic hysteresis motors  

NASA Astrophysics Data System (ADS)

Hysteresis motors are very attractive in a wide range of fractional power applications, due to its torque-speed characteristics and simplicity of construction. This motor's performance is expected to improve when HTS rotors are used, and in fact, hysteresis motors have shown to be probably the most viable electrical machines using HTS materials. While these motors, either conventional or HTS, are both hysteresis motors, they base their operation on different physical phenomena: hysteretic behaviour in conventional ferromagnetic materials is due to the material's non-linear magnetic properties, while in HTS materials the hysteresis has an ohmic nature and is related with vortices' dynamics. In this paper, theoretical aspects of both conventional and HTS hysteresis motors are discussed, its operation principles are highlighted, and the characteristics of both motors are presented. The characteristics, obtained both by experimental tests and numerical simulation (made with commercial software), are compared, in order to evaluate not only the motor's electromechanical performances but also the overall systems efficiency, including cryogenics for the HTS device.

Inácio, D.; Inácio, S.; Pina, J.; Gonçalves, A.; Ventim Neves, M.; Leão Rodrigues, A.

2008-02-01

343

A Combined Experimental and Finite Element Analysis Method for the Estimation of Eddy-Current Loss in NdFeB Magnets  

PubMed Central

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

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

2014-01-01

344

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

345

Reduction of hysteresis in PI-controlled systems  

SciTech Connect

Motorized dampers and valves generally possess some hysteresis. Hysteresis may result in poor repeatability of experimental data. It also may result in the deviation of a response of a proportional integral (PI) controlled system from its target response and in hunting. In some applications, it may be desirable to reduce the effects of hysteresis. A method to reduce the effects of hysteresis is presented here. This method is based on software, not hardware, modification.

Krakow, K.I. [Concordia Univ., Montreal, Quebec (Canada). Dept. of Mechanical Engineering

1998-10-01

346

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

347

Extending hysteresis operators to spaces of piecewise continuous functions  

E-print Network

.D. MAWBY Department of Mathematical Sciences, University of Bath, Bath BA2 7AY, United Kingdom Email: hl@maths.bath.ac.uk, am@maths.bath.ac.uk Abstract: We consider continuous-time hysteresis operators, de#12;ned of \\hysteresis" loops. The memory e#11;ects exhibited by hysteresis phenomena are rate independent in contrast

Bath, University of

348

A Free Energy Model for Hysteresis in Ferroelectric Materials  

E-print Network

A Free Energy Model for Hysteresis in Ferroelectric Materials Ralph C. Smith Stefan Seelecke.ncsu.edu Abstract This paper provides a theory for quantifying the hysteresis and constitutive nonlinearities in#ects, and extreme electromechanical sensitivity, also produce varying degrees of hysteresis and constitutive

349

A Free Energy Model for Hysteresis in Ferroelectric Materials  

E-print Network

A Free Energy Model for Hysteresis in Ferroelectric Materials Ralph C. Smith Stefan Seelecke.ncsu.edu Abstract This paper provides a theory for quantifying the hysteresis and constitutive nonlinearities in, and extreme electromechanical sensitivity, also produce varying degrees of hysteresis and constitutive

350

EXPERIMENTAL MEASUREMENTS OF CAPILLARY PRESSURE AND RELATIVE PERMEABILITY HYSTERESIS  

Microsoft Academic Search

Capillary pressure and relative permeability hysteresis have been investigated on core samples with different wetting characteristics. The relative permeability and capillary pressure curves depend on the direction of saturation changes and on the maximum and minimum achieved saturations. A conceptual model to explain the hysteresis trends in both the relative permeability and capillary pressure is presented. The model attributes hysteresis

Shehadeh K. Masalmeh

351

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

352

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

Microsoft Academic Search

Development of a 600kJ superconducting magnetic energy storage (SMES) system is being in progress by Korea Electrotechnology Research Institute (KERI). 3-ply BSCCO-2223 wire was considered as a conductor for the winding of the SMES system and auto-tuning niching genetic algorithm was adopted for an optimization method of the HTS magnets in the 600kJ SMES system. Several constraint conditions were considered

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

2007-01-01

353

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

NASA Astrophysics Data System (ADS)

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

Li, Longbiao; Song, Yingdong

2013-12-01

354

Hybrid magnetic field formulation based on the losses separation method for modified dynamic inverse Jiles-Atherton model  

NASA Astrophysics Data System (ADS)

Dynamic formulation based on the losses separation method in conducting media for the inverse Jiles-Atherton model is proposed. This formulation is based on the concept of the Hybrid Magnetic Field model (HMF). The HMF consists of the modification of the effective field by introducing two counter-fields associated, respectively, with the eddy current and excess losses. Such a formulation is characterized by seven parameters with five parameters issued from the quasi-static Jiles-Atherton model. Thus, two new parameters related to these fields are added to that defined in the quasi-static model. The identification of these new parameters is based on the measurements of the volumetric energy density. To validate this formulation, measurements are carried out on grain non-oriented Fe-Si 3% electrical sheets.

Hamimid, M.; Mimoune, S. M.; Feliachi, M.

2011-07-01

355

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

356

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

357

Comparison of AC losses, magnetic field\\/current distributions and critical currents of superconducting circular pancake coils and infinitely long stacks using coated conductors  

Microsoft Academic Search

A model is presented for calculating the AC losses, magnetic field\\/current density distribution and critical currents of a circular superconducting pancake coil. The assumption is that the magnetic flux lines will lie parallel to the wide faces of tapes in the unpenetrated area of the coil. Instead of using an infinitely long stack to approximate the circular coil, this paper

Weijia Yuan; A. M. Campbell; Z. Hong; M. D. Ainslie; T. A. Coombs

2010-01-01

358

Analytic synthesis of a hysteresis motor  

Microsoft Academic Search

This paper presents the unique synthesis of a motor with a hysteresis torque–speed characteristic. The machine is synthesized from a conventional polyphase squirrel cage induction motor (SCIM) with a high rotor resistance to leakage reactance r2\\/x2 ratio, which is mechanically coupled to a polyphase transfer field (TF) machine but with an inversion of the usual torque–speed characteristic of the latter

Linus U. Anih; Emeka S. Obe; Eugene O. Agbachi

2011-01-01

359

Barley viability during storage: use of magnetic resonance as a potential tool to study viability loss.  

PubMed

Malting-quality barley samples of the varieties Harrington, Manley, and TR118, each from two locations in Saskatchewan, were collected directly from the producers and sent to China for storage. At regular intervals samples were shipped back to Canada for analysis consisting of germination studies, alpha-amylase tests, magnetic resonance imaging (MRI), and magnetic relaxation (NMR) studies. Samples showing a decrease in germinative energy and elevated levels of alpha-amylase also showed a rapid uptake of water in the area between the embryo and the endosperm as observed by MRI. Using NMR relaxation experiments, viable and nonviable barley samples could be distinguished after 2 h of imbibition. PMID:11829626

Gruwel, Marco L H; Yin, Xiang S; Edney, Michael J; Schroeder, Steve W; MacGregor, Alex W; Abrams, Suzanne

2002-02-13

360

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

361

Noninvasive quantification of fluid mechanical energy losses in the total cavopulmonary connection with magnetic resonance phase velocity mapping.  

PubMed

A major determinant of the success of surgical vascular modifications, such as the total cavopulmonary connection (TCPC), is the energetic efficiency that is assessed by calculating the mechanical energy loss of blood flow through the new connection. Currently, however, to determine the energy loss, invasive pressure measurements are necessary. Therefore, this study evaluated the feasibility of the viscous dissipation (VD) method, which has the potential to provide the energy loss without the need for invasive pressure measurements. Two experimental phantoms, a U-shaped tube and a glass TCPC, were scanned in a magnetic resonance (MR) imaging scanner and the images were used to construct computational models of both geometries. MR phase velocity mapping (PVM) acquisitions of all three spatial components of the fluid velocity were made in both phantoms and the VD was calculated. VD results from MR PVM experiments were compared with VD results from computational fluid dynamics (CFD) simulations on the image-based computational models. The results showed an overall agreement between MR PVM and CFD. There was a similar ascending tendency in the VD values as the image spatial resolution increased. The most accurate computations of the energy loss were achieved for a CFD grid density that was too high for MR to achieve under current MR system capabilities (in-plane pixel size of less than 0.4 mm). Nevertheless, the agreement between the MR PVM and the CFD VD results under the same resolution settings suggests that the VD method implemented with a clinical imaging modality such as MR has good potential to quantify the energy loss in vascular geometries such as the TCPC. PMID:17222721

Venkatachari, Anand K; Halliburton, Sandra S; Setser, Randolph M; White, Richard D; Chatzimavroudis, George P

2007-01-01

362

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

363

Finite-element simulations of hysteretic ac losses in a bilayer superconductor/ferromagnet heterostructure subject to an oscillating transverse magnetic field  

NASA Astrophysics Data System (ADS)

Numerical simulations of hysteretic ac losses in a bilayer superconductor/ferromagnet heterostructure subject to an oscillating transverse magnetic field are performed within the quasistatic approach, calling upon the ANSYS finite-element software program and exploiting magnetostatic-electrostatic analogs. It is shown that one-sided magnetic shielding of a thin, type-II superconductor strip can lead to an enhancement or, respectively, a reduction of hysteretic ac losses as compared to those for a nonmagnetic support, depending on the amplitude of the applied magnetic field.

Genenko, Y. A.; Rauh, H.; Krüger, P.

2011-04-01

364

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

365

Numerical modelling in the time domain of dynamic hysteresis of soft materials in cylindrical coordinates  

NASA Astrophysics Data System (ADS)

This paper deals with the numerical analysis of soft magnetic materials with hysteresis in dynamic axial symmetric problems. We present a procedure based on a 1D Finite Difference Time Domain (FDTD) algorithm where there are implemented magnetization dependent Preisach based models. Experimental measurements of the virgin curve and the major loop are used to identify the models. The numerical scheme in the time domain proposed is discussed and a probe of its intrinsic stability is given. Numerical codes based on the above algorithm are used to show some of the possibilities of this numerical tool for the dynamic magnetic analysis.

Cardelli, Ermanno; Torre, Edward Della; Pinzaglia, Enrico

2003-05-01

366

Estimate Interface Shear Stress of Unidirectional C/SiC Ceramic Matrix Composites from Hysteresis Loops  

NASA Astrophysics Data System (ADS)

The tensile-tensile fatigue behavior of unidirectional C/SiC ceramic matrix composites at room and elevated temperature has been investigated. An approach to estimate the interface shear stress of ceramic matrix composites under fatigue loading has been developed. Based on the damage mechanisms of fiber sliding relative to matrix in the interface debonded region upon unloading and subsequent reloading, the unloading interface reverse slip length and reloading interface new slip length are determined by the fracture mechanics approach. The hysteresis loss energy for the strain energy lost per volume during corresponding cycle is formulatd in terms of interface shear stress. By comparing the experimental hysteresis loss energy with the computational values, the interface shear stress of unidirectional C/SiC ceramic composites corresponding to different cycles at room and elevated temperatures has been predicted.

Longbiao, Li; Yingdong, Song; Youchao, Sun

2013-08-01

367

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

368

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

NASA Astrophysics Data System (ADS)

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

May, Mark Joseph

1998-07-01

369

Mechano-electric optoisolator transducer with hysteresis  

NASA Astrophysics Data System (ADS)

This article presents a theoretical and experimental study of designing a mechano-electric optoisolator transducer with hysteresis. Our research is centred upon designing transducers on the basis of optical sensors, as photoelectric conversions eliminate the influence of electromagnetic disturbances. Conversion of the rotation/translation motions into electric signals is performed with the help of a LED-photoresistor Polaroid optocoupler. The driver of the optocoupler's transmitter module is an independent current source. The signal conditioning circuit is a Schmitt trigger circuit. The device is designed to be applied in the field of automation and mechatronics.

Ciuru?, I. M.; Dimian, M.; Graur, A.

2011-01-01

370

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

371

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

372

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

373

Magnetic confinement, Alfven wave reflection, and the origins of X-ray and mass-loss 'dividing lines' for late-type giants and supergiants  

NASA Technical Reports Server (NTRS)

A simple qualitative model for the origin of the coronal and mass-loss dividing lines separating late-type giants and supergiants with and without hot, X-ray-emitting corona, and with and without significant mass loss is discussed. The basic physical effects considered are the necessity of magnetic confinement for hot coronal material on the surface of such stars and the large reflection efficiency for Alfven waves in cool exponential atmospheres. The model assumes that the magnetic field geometry of these stars changes across the observed 'dividing lines' from being mostly closed on the high effective temperature side to being mostly open on the low effective temperature side.

Rosner, R.; An, C.-H.; Musielak, Z. E.; Moore, R. L.; Suess, S. T.

1991-01-01

374

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

SciTech Connect

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

Mayergoyz, I.D.

1991-12-31

375

ac losses in a YBa2Cu3O7-x coil  

NASA Astrophysics Data System (ADS)

The properties of a small pancake coil made with a 10mm wide copper-stabilized YBa2Cu3O7-x (YBCO) coated conductor were investigated. The radial component of the magnetic field was mapped at the coil edge in both the dc and ac regimes and differs significantly from that calculated assuming a uniform current distribution. The observed hysteresis indicates the strong influence of the ferromagnetic properties of the substrate. The ac losses of the coil were measured for ac frequencies between 60 and 1000Hz. The differences in properties of the YBCO coil and a similarly prepared copper coil are discussed.

Polak, M.; Demencik, E.; Jansak, L.; Mozola, P.; Aized, D.; Thieme, C. L. H.; Levin, G. A.; Barnes, P. N.

2006-06-01

376

Efficient parameter estimation techniques for hysteresis models  

NASA Astrophysics Data System (ADS)

Actuators employing ferroelectric or ferromagnetic compounds are solid-state, efficient, and compact making them well-suited for aerospace, aeronautic, industrial and military applications. However, they also exhibit frequency, stress and thermally-dependent hysteresis and constitutive nonlinearities which must be incorporated in models for accurate device characterization and control design. A critical step in the use of these models is the estimation or re-estimation of parameters in a manner that is both efficient and robust. In this presentation, we discuss techniques to estimate densities in the homogenized energy model based on Galerkin expansions using physically motivated basis functions. The yields highly tractable optimization algorithms in which initial parameter estimates can be obtained from measured properties of the data. The efficiency and accuracy of the models and estimation algorithms are validated with experimental data.

Ernstberger, J. M.; Smith, R. C.

2009-03-01

377

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

378

Application of the Preisach model in soil-moisture hysteresis  

E-print Network

Application of the Preisach model in soil-moisture hysteresis Denis Flynn, Hugh McNamara, Philip O- teresis effects in the relation between water retention and soil-moisture ten- sion. Special, one parameter, classes of Preisach operators are proposed to construct models of the soil-moisture hysteresis

Schellekens, Michel P.

379

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

380

A Temperature-Dependent Hysteresis Model for Relaxor Ferroelectric Compounds  

E-print Network

subsequently incorporated the hysteretic low-temperature behavior through the development of domain wall modelsA Temperature-Dependent Hysteresis Model for Relaxor Ferroelectric Compounds Julie K. Raye- ature-dependent hysteresis and constitutive nonlinearities inherent to relaxor ferroelectric materials

381

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 and control design, we consider a theory for ferroelectric hysteresis which is based on domain wall dynamics been recognized that domain and domain wall mechanisms within ferroelectric materi- als result

382

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 and control design, we consider a theory for ferroelectric hysteresis which is based on domain wall dynamics been recognized that domain and domain wall mechanisms within ferroelectric materi­ als result

383

Analysis and Determination of Ring Flux Distribution in Hysteresis Motors  

Microsoft Academic Search

This paper presents the results of an experimental determination of the flux distributions inside different layers of the hysteresis ring. The flux measurements were made by means of search coils embedded in the stationary ring of an inside-out three phase hysteresis motor. It is found that the flux distribution is quite nonuniform and there exist phase shift between the flux

R. D. Jackson; M. A. Rahman; G. R. Slemon

1983-01-01

384

Design of a compact hysteresis motor used in a gyroscope  

Microsoft Academic Search

In this paper, it presents the computer-aided design and test results of a compact hysteresis synchronous motor used as the drive motor of a gyroscope. Hysteresis motor is the best choice for this application because of its compactness and reliability. Also it has self-starting capability and it does not require any position sensor and communication circuits.

Rajagopal KR

2003-01-01

385

Analysis and Determination of Ring Flux Distribution in Hysteresis Motors  

Microsoft Academic Search

This paper presents the results of an experimental determination of the flux distributions inside different layers of the hysteresis ring. The flux measurements were made by means of search coils embedded in the stationary ring of an inside-out three phase hysteresis motor. It is found that the flux distribution is quite non-uniform and there exist phase shift between the flux

R. D. Jackson; M. A. Rahman; G. R. Slemon

1983-01-01

386

Performance simulation of hysteresis motors using accurate rotor media models  

Microsoft Academic Search

Recently, there has been an increased demand for small and medium sized brushless-type synchronous motors. Among these types, hysteresis motors have been especially used in those applications requiring precise speed and constant starting torque capabilities. In the past, several digital techniques for simulating the performance of hysteresis motors have been developed. These technique, however, involved significant approximations to the rotor

Amr A. Adly

1995-01-01

387

Impact of relative permeability hysteresis on geological CO2 storage  

Microsoft Academic Search

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

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

2006-01-01

388

Bistability and Hysteresis in the Organization of Apparent Motion Patterns  

Microsoft Academic Search

In a paradigm for which 2 distinct patterns are perceived for the same stimulus, perceptual hysteresis (persistence of a percept despite parameter change to values favoring the alternative pattern) and temporal stability (persistence despite intrinsic propensities toward spontaneous change) are interdependent. Greater persistence during parameter change reduces temporal stability, slowing the rate of parameter change reduces hysteresis by increasing opportunity

Howard S. Hock; J. A. Scott Kelso; Gregor Schöner

1993-01-01

389

Preisach modeling of piezoceramic and shape memory alloy hysteresis  

Microsoft Academic Search

Smart materials such as piezoceramics and shape memory alloys (SMAs) exhibit significant hysteresis and in order to estimate the effect on open and closed loop control a suitable model is needed. One promising candidate is the Preisach independent domain hysteresis model that is characterized by the congruent minor loop and wiping out properties. Comparable minor loop and decaying oscillation test

Declan Hughes; John T. Wen

1995-01-01

390

Lumped-circuit models for nonlinear inductors exhibiting hysteresis loops  

Microsoft Academic Search

A new mathematical model of dynamic hysteresis loops is presented. The model is completely specified by two strictly monotonically increasing functions: a restoring function f(.) and a dissipation function g(.). Simple procedures are given for constructing these two functions so that the resulting model will simulate a given hysteresis loop exactly. The model is shown to exhibit many important hysteretic

L. Chua; K. Stromsmoe

1970-01-01

391

The Effect of Liquid Structure on Contact Angle Hysteresis.  

National Technical Information Service (NTIS)

Contact angle hysteresis was measured for a variety of liquids on condensed monolayers of 17-(perfluoroheptyl)-heptadecanoic acid adsorbed on polished chromium. The hysteresis was shown to be simply related to the molecular volume of the liquid and to res...

C. O. Timmons, W. A. Zisman

1966-01-01

392

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

393

Contact Angle Hysteresis on Superhydrophobic Stripes  

E-print Network

We study experimentally and discuss quantitatively the contact angle hysteresis on striped superhydrophobic surfaces as a function of a solid fraction, $\\phi_S$. It is shown that the receding regime is determined by a longitudinal sliding motion 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 $\\phi_S$, in contrast to predictions of the Cassie equation. To interpret this we develop a simple theoretical model, which shows that the value of the receding angle depends both on weak defects at smooth solid areas and on the elastic energy of strong defects at the borders of stripes, which scales as $\\phi_S^2 \\ln \\phi_S$. The advancing contact angle was found to be anisotropic, except as in a dilute regime, and its value is determined by the rolling motion of the drop. The cosine of the longitudinal advancing angle depends linearly on $\\phi_S$, 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 $\\phi_S\\simeq 0.5$. 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 proportional to $\\phi_S^2$. Finally, the contact angle hysteresis is found to be quite large and generally anisotropic, but it becomes isotropic when $\\phi_S\\leq 0.2$.

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

2014-02-11

394

Positive hysteresis of Ce-doped GAGG scintillator  

NASA Astrophysics Data System (ADS)

Positive hysteresis and radiation tolerance to high-dose radiation exposure were investigated for Ce 1% and 3% doped Gd3(Al, Ga)5O12 (Ce:GAGG) crystal scintillator on comparison with other garnet scintillators such Ce:YAG, Ce:LuAG, Pr:LuAG, and ceramic Ce:GAGG. When they were irradiated by several Gy 60Co ?-rays, Ce 1% doped GAGG crystal exhibited ?20% light yield enhancement (positive hysteresis). This is the first time to observe positive hysteresis in Ce doped GAGG. On the other hand, other garnet materials did not show the positive hysteresis and their light yields were stable after 800 Gy irradiation except Pr:LuAG. The light yield of Pr:LuAG decreased largely. When irradiated Ce:GAGG which showed positive hysteresis was evaluated in Synchrotron facility (UVSOR), new excitation band was created around 60 nm.

Yanagida, Takayuki; Fujimoto, Yutaka; Koshimizu, Masanori; Watanabe, Kenichi; Sato, Hiroki; Yagi, Hideki; Yanagitani, Takagimi

2014-10-01

395

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

E-print Network

Quantification of Hysteresis and Nonlinear Effects on the Frequency Response of Ferroelectric. However, these materials also exhibit hysteresis and constitutive nonlinearities at all drive levels of hysteresis and nonlinearities on the frequency behavior of devices that employ these compounds. Whereas

396

Control of Hysteresis in Smart Actuators. Part 1. Modeling, Parameter Identification, and Inverse Control.  

National Technical Information Service (NTIS)

Hysteresis in smart actuators presents a challenge in control of these actuators. A fundamental idea to cope with hysteresis is inverse compensation. In this paper we study modeling, identification and inverse control of hysteresis in smart actuators thro...

X. Tan, J. S. Baras

2002-01-01

397

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

NASA Astrophysics Data System (ADS)

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

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

2008-09-01

398

Comparison of hysteresis loop area scaling behavior of Co/Pt multilayers: Discrete and continuous field sweeping  

NASA Astrophysics Data System (ADS)

We have investigated the hysteresis loop shape changes with discrete and continuous magnetic field sweeping for Co/Pt multilayers with a perpendicular magnetic anisotropy. The hysteresis loop shape was observed by measuring a polar magneto-optical Kerr effect. The loop area has been found to increase rapidly with an increase of the field step size as well as the sweeping frequency until the area reaches a maximum. The increase of the loop area has been analyzed based on the Steinmetz law, where a loop area scaling exponent determined from discrete field sweeping is compared to a scaling exponent from continuous field sweeping. The dynamic coercivity behavior with respect to discrete and continuous field sweeping is analyzed together with the loop area scaling behavior, suggesting that details of magnetic configuration disorders do not modify the loop area scaling exponent.

Handoko, Djati; Lee, Sang-Hyuk; Min Lee, Kyung; Jeong, Jong-Ryul; Kim, Dong-Hyun

2014-02-01

399

AC losses in thin coated conductors under non-sinusoidal conditions  

NASA Astrophysics Data System (ADS)

AC losses in superconducting wires and tapes are usually studied for applied sinusoidal currents and/or magnetic fields. However, currents in electric power systems contain a variety of harmonics. We solved analytically and numerically, in the infinitely thin approximation, the transport current and magnetization problems for coated conductors under non-sinusoidal conditions. The analytical expressions for eddy current and hysteresis losses have been obtained in the framework of the critical state model neglecting the response of the normal-metal substrate and stabilization layers. The contribution of higher harmonics to losses per cycle is determined by both their phase shift relative to the main harmonic and their amplitude. It has been shown that the 5% third current harmonic (for the phase shift ?) increases eddy losses in the normal-metal parts by up to 90% at a transport current close to the critical value. Numerically, for the power law current-voltage characteristic of a superconductor, the contribution of higher harmonics to the total losses in a coated conductor was investigated in a wide range of the power index. It has been shown that even at a low power index (n = 4) this contribution can achieve 44% of losses caused by the main harmonic only. For high external magnetic fields an approximate analytical solution has also been derived and compared to the numerical solution.

Spektor, M.; Meerovich, V.; Sokolovsky, V.; Prigozhin, L.

2012-02-01

400

High contact angle hysteresis of superhydrophobic surfaces: Hydrophobic defects  

NASA Astrophysics Data System (ADS)

A typical superhydrophobic surface is essentially nonadhesive and exhibits very low water contact angle (CA) hysteresis, so-called Lotus effect. However, leaves of some plants such as scallion and garlic with an advancing angle exceeding 150° show very serious CA hysteresis. Although surface roughness and epicuticular wax can explain the very high advancing CA, our analysis indicates that the unusual hydrophobic defect, diallyl disulfide, is the key element responsible for contact line pinning on allium leaves. After smearing diallyl disulfide on an extended polytetrafluoroethylene (PTFE) film, which is originally absent of CA hysteresis, the surface remains superhydrophobic but becomes highly adhesive.

Chang, Feng-Ming; Hong, Siang-Jie; Sheng, Yu-Jane; Tsao, Heng-Kwong

2009-08-01

401

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

402

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

403

Significance of conservative asparagine residues in the thermal hysteresis activity of carrot antifreeze protein.  

PubMed Central

The approximately 24-amino-acid leucine-rich tandem repeat motif (PXXXXXLXXLXXLXLSXNXLXGXI) of carrot antifreeze protein comprises most of the processed protein and should contribute at least partly to the ice-binding site. Structural predictions using publicly available online sources indicated that the theoretical three-dimensional model of this plant protein includes a 10-loop beta-helix containing the approximately 24-amino-acid tandem repeat. This theoretical model indicated that conservative asparagine residues create putative ice-binding sites with surface complementarity to the 1010 prism plane of ice. We used site-specific mutagenesis to test the importance of these residues, and observed a distinct loss of thermal hysteresis activity when conservative asparagines were replaced with valine or glutamine, whereas a large increase in thermal hysteresis was observed when phenylalanine or threonine residues were replaced with asparagine, putatively resulting in the formation of an ice-binding site. These results confirmed that the ice-binding site of carrot antifreeze protein consists of conservative asparagine residues in each beta-loop. We also found that its thermal hysteresis activity is directly correlated with the length of its asparagine-rich binding site, and hence with the size of its ice-binding face. PMID:14531728

Zhang, Dang-Quan; Liu, Bing; Feng, Dong-Ru; He, Yan-Ming; Wang, Shu-Qi; Wang, Hong-Bin; Wang, Jin-Fa

2004-01-01

404

Sintered soft magnetic materials. Properties and applications  

NASA Astrophysics Data System (ADS)

A comparison is presented of the characteristics and production requirements of a variety of materials used to produce sintered soft magnetic parts. These include pure iron, phosphorous-iron, silicon-iron, nickel-iron, and cobalt-iron, together with new coated materials based on encapsulated iron powders. In these bonded materials an organic and/or inorganic insulator is used to coat the metallic powder particles giving a magnetic composite. The suitability of the different materials for use in both direct and alternating current applications is reviewed, and examples are provided of their application in both the automotive and other sectors. The results of a comparative study of motors using stators and rotors based on both conventional laminated materials and the insulated iron powders are presented, in which the new materials show advantages of reduced hysteresis losses at high frequencies, and isotropy of magnetic properties. Nevertheless, the applications of these materials in electrical motors requires the modification of existing designs.

Bas, J. A.; Calero, J. A.; Dougan, M. J.

2003-01-01

405

A homogenized energy framework for ferromagnetic hysteresis  

Microsoft Academic Search

This paper focuses on the development of a homogenized energy model which quantifies certain facets of the direct magnetomechanical effect. In the first step of the development, Gibbs energy analysis at the lattice level is combined with Boltzmann principles to quantify the local average magnetization as a function of input fields and stresses. A macroscopic magnetization model, which incorporates the

Ralph C. Smith; Marcelo J. Dapino; Thomas R. Braun; Anthony P. Mortensen

2006-01-01

406

Estimation of high-frequency loss properties through analytical calculation for semiconducting soft magnetic films in a near-field electromagnetic wave  

NASA Astrophysics Data System (ADS)

Gigahertz frequency characteristics were appraised by theoretical calculation based on a modified Landau-Lifshitz-Gilbert equation in order to examine the effect of electromagnetic induction and artificially controlled shape anisotropy in micropatterned magnetic films. Electromagnetic loss behaviors and magnetic fields of semiconducting soft magnetic films on a coplanar transmission line were numerically analyzed using a finite-element based electromagnetic solver. The combined relative permeability due to the electromagnetic induction and demagnetizing effect showed to be highly dependent on electrical resistivity and film thickness. Higher resistivity films at the same thickness of 2 ?m showed higher loss in power and lower reflection because of the reduced electromagnetic induction. Thinner magnetic films at the same resistivity of 100 ?? cm exhibited lower reflection due to the reduced electromagnetic induction and maxima of the reflection shifted to higher frequencies because of demagnetization associated with the structure of magnetic flux path. A severe increment of the radiated electromagnetic noise with decreasing resistivity was caused by the reflection of the radiated noise from the surface of the low resistivity films on the coplanar line in gigahertz frequency bands. A slight increase in the radiation noise with increasing thickness at the same resistivity confirmed to be caused by the increased reflection.

Kim, Sang Woo; Lee, Jung Hwan

2009-04-01

407

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

408

Hysteresis as a Marker for Complex, Overlapping Landscapes in Proteins  

PubMed Central

Topologically complex proteins fold by multiple routes as a result of hard-to-fold regions of the proteins. Oftentimes these regions are introduced into the protein scaffold for function and increase frustration in the otherwise smooth-funneled landscape. Interestingly, while functional regions add complexity to folding landscapes, they may also contribute to a unique behavior referred to as hysteresis. While hysteresis is predicted to be rare, it is observed in various proteins, including proteins containing a unique peptide cyclization to form a fluorescent chromophore as well as proteins containing a knotted topology in their native fold. Here, hysteresis is demonstrated to be a consequence of the decoupling of unfolding events from the isomerization or hula-twist of a chromophore in one protein and the untying of the knot in a second protein system. The question now is- can hysteresis be a marker for the interplay of landscapes where complex folding and functional regions overlap? PMID:23525263

Andrews, Benjamin T.; Capraro, Dominique T.; Sulkowska, Joanna I.; Onuchic, Jose N.; Jennings, Patricia A.

2013-01-01

409

Contact angle hysteresis: a review of fundamentals and applications  

E-print Network

Contact angle hysteresis is an important physical phenomenon. It is omnipresent in nature and also plays a crucial role in various industrial processes. Despite its relevance, there is a lack of consensus on how to incorporate ...

’t Mannetje, D. J. C. M.

410

Dynamic wetting on superhydrophobic surfaces: Droplet impact and wetting hysteresis  

E-print Network

We study the wetting energetics and wetting hysteresis of sessile and impacting water droplets on superhydrophobic surfaces as a function of surface texture and surface energy. For sessile drops, we find three wetting ...

Smyth, Katherine M.

411

A high-speed hysteresis motor spindle for machining applications  

E-print Network

An analysis of suitable drive technologies for use in a new high-speed machining spindle was performed to determine critical research areas. The focus is on a hysteresis motor topology using a solid, inherently-balanced ...

Bayless, Jacob D. (Jacob Daniel)

2014-01-01

412

Hysteresis characterization using charge feedback control for a LIPCA device  

NASA Astrophysics Data System (ADS)

In this paper, we study the no-load behavior of a lightweight piezo-composite curved actuator (LIPCA) subjected to voltage and charge control. First, we examine the effect of hysteresis and creep when the actuator is voltage controlled at a slow scan speed. The experimental results show that creep increases the displacement hysteresis by over 25% when scanning at 1/60 Hz. Afterwards, we discuss the design and implementation of a charge-feedback circuit to control the displacement of the actuator. The hysteresis curves between voltage- and charge-control modes are compared for the scan frequencies of 1 and 5 Hz. The results show that charge control (compared to voltage control) of a LIPCA device exhibits significantly less hysteresis, over 80% less.

Beck, James; Noras, Maciej; Kieres, Jerzy; Speich, John E.; Mossi, Karla M.; Leang, Kam K.

2006-03-01

413

Revisiting the hysteresis effect in surface energy budgets  

NASA Astrophysics Data System (ADS)

The hysteresis effect in diurnal cycles of net radiation Rn and ground heat flux G0 has been observed in many studies, while the governing mechanism remains vague. In this study, we link the phenomenology of hysteresis loops to the wave phase difference between the diurnal evolutions of various terms in the surface energy balance. Rn and G0 are parameterized with the incoming solar radiation and the surface temperature as two control parameters of the surface energy partitioning. The theoretical analysis shows that the vertical water flux W and the scaled ratio As*>/AT* (net shortwave radiation to outgoing longwave radiation) play crucial roles in shaping hysteresis loops of Rn and G0. Comparisons to field measurements indicate that hysteresis loops for different land covers can be well captured by the theoretical model, which is also consistent with Camuffo-Bernadi formula. This study provides insight into the surface partitioning and temporal evolution of the energy budget at the land surface.

Sun, Ting; Wang, Zhi-Hua; Ni, Guang-Heng

2013-05-01

414

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

415

Hysteresis in Thin-Film Rechargeable Lithium Batteries  

SciTech Connect

Discharge - charge cycling of thin-film rechargeable lithium batteries with an amorphous or nanocrystalline LiXMn2.Y04 cathode reveals evidence for a true hysteresis in the lithium insertion reaction. This is compared with an apparent hysteresis attributed to a kinetically hindered phase transition near 3 V for batteries with either a crystalline or a nanocrystalline LiJ@Yo4 cathode.

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

1999-04-25

416

Design of a compact hysteresis motor used in a gyroscope  

Microsoft Academic Search

This paper presents the computer-aided design and test results of a compact three-phase hysteresis synchronous motor used as the drive motor of a gyroscope. Hysteresis motor is the best choice for this application because of its compactness and reliability. Also, it has a self-starting capability and it does not require any position sensor and commutation circuits. The design of a

K. R. Rajagopal

2003-01-01

417

Stabilization of supercooled fluids by thermal hysteresis proteins.  

PubMed Central

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

1995-01-01

418

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

419

Hysteresis as an Implicit Prior in Tactile Spatial Decision Making  

PubMed Central

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

420

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

421

Compensator design for hysteresis of a stacked PZT actuator using a congruency-based hysteresis model  

NASA Astrophysics Data System (ADS)

This paper proposes a rate-independent hysteresis compensator for a stacked PZT (lead zirconate titanate) actuator. From a congruency-based hysteresis (CBH) model which is derived from the inherent properties of this actuator, especially the congruency, a feedforward compensator associated with it is developed. The formulation of the proposed compensator is based on an assumption that the inverse operator also possesses the same properties as the CBH model does. This implies that the compensator also possesses properties such as the wiped-out loop closing between the consecutive control points and congruency. Consequently, the expressions for the compensator can be conducted by exploiting the equations for the CBH model in two cases of monotonic increase and monotonic decrease of input excitation. In order to assess the performance of the compensator, several experiments in both open-loop and closed-loop controls are undertaken. In the open-loop control experiment, the performance of the feedforward compensator using the CBH model is compared with the classical Preisach model-based one in three cases of reference waveforms. In the closed-loop control experiment, the proposed compensator is incorporated into a PID (proportional-integral-derivative) control system and the performance of this integrated system is then evaluated and compared to that of the PID with and without compensator.

Nguyen, Phuong-Bac; Choi, Seung-Bok

2012-01-01

422

Modelling the Hysteresis of Interacting Pseudo-Single-Domain Magnetite Particles  

NASA Astrophysics Data System (ADS)

Recent studies have shown the importance of fine magnetite exsolution structures as remanence carriers in igneous rocks. These structures often form arrays of tightly spaced individual grains straddling the single domain (SD) to pseudo-single-domain (PSD) threshold. Due to the proximity of neighbouring particles, magnetostatic interactions are expected to play an important role for the magnetic properties of these particle assemblages. We have used an unconstrained, fully three dimensional finite element (FE) micromagnetic model to calculate hysteresis curves of 3x3 arrays of magnetite particles with aligned easy axes with grain sizes r=50 ... 200nm and grain spacings d=0 ... 3· r . The calculations show that the domain state of individual particles is not only dependent on their grain size but also on the grain separation. Closer d generally leads to an increased SD-PSD size threshold. Associated with that is a characteristic change in magnetic stability: For d<50nm MRS/MS decreases sharply for all modelled grain sizes. This decrease is related to the appearance of supervortex structures at zero external field. Our modelling approach allowed us to observe the formation of these supervortices in the course of a hysteresis cycle. As expected, SD sized particles retain a uniform particle magnetisation throughout the whole hysteresis cycle. The particle arrays, however, form intermediate supervortex structures even for relatively large d because the individual particles' magnetisation cannot collapse into a vortex state to reduce its magnetic stray field. Only when the spacing increases to 150nm (i. e. d=3· r), does the magnetisation of all particles in the array rotate coherently. In contrast, PSD particle arrays generally reverse their magnetisation by spin curling and the formation of individual vortex states. For almost touching particles, though, an SD like magnetisation structure of individual grains is maintained throughout the hysteresis cycle by forming supervortex states. The individual vortex state, however, is energetically more favourable as soon as d is only slightly increased. The paper will discuss the particle size and spacing dependence of the average interaction field and its influence on magnetic grain size determinations.

Krása, D.; Williams, W.

2007-12-01

423

Experimental investigation of AC loss in a conduction-cooled layer-wound (RE)BCO magnet for continuous Adiabatic Demagnetization Refrigerator (ADR)  

NASA Astrophysics Data System (ADS)

This paper discusses the fabrication of a (RE)BCO solenoid magnet and its experimental results from the aspect of AC loss and thermal characteristics. A (RE)BCO coated conductor with polyimide tape insulation was utilized for a coil and wound by a standard layer-wound method. The (RE)BCO solenoid magnet consists of a stainless steel bore and a pair of OFHC copper supporting plates assembled at both ends. The coil winding has a novel thermal drain structure that can withstand high AC thermal loads generated externally and internally. The OFHC copper strips were installed between the interlayers in the perpendicular direction to the (RE)BCO conductor winding to mitigate both thermal resistance in the axial direction of the (RE)BCO coil and eddy current loss by an external magnetic field. Apiezon® N grease with hexane solution was applied on the entire (RE)BCO coil winding to minimize thermal contact resistance between the conductor and the OFHC copper strips. The (RE)BCO coil carried 150 A at 14.7 K and generated 3.5 T at the center of the coil. A sinusoidal current waveform (operating frequency from 0.1 Hz to 1.0 Hz) was applied with peaks of 25 A, 50 A, and 70 A (the corresponding magnetic field of 0.54 T, 1.08 T, and 1.54 T) and the corresponding AC losses were measured by both calorimetric and electrical methods. The AC losses measured by both methods were in good agreement. The experimental results were compared with theoretical and numerical solutions.

Park, Jiho; Kim, Seokho; Park, Inmyong; Jeong, Sangkwon

2014-09-01

424

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

425

Cold test facility for 1.8 m superconducting model magnets at the SSCL  

SciTech Connect

A new facility has been constructed to measure the characteristic features of superconducting model magnets and cable at cryogenic temperatures--a function which supports the design and development process for building full-scale accelerator magnets. There are multiple systems operating in concert to test the model magnets, namely, cryogenic, magnet power, data acquisition and system control. A typical model magnet test includes the following items: warm measurements of magnet coils, strain gauges and voltage taps; hipot testing of insulation integrity; cooling with liquid nitrogen and then liquid helium; measuring quench current and magnetic field; (5) magnet warm-up. While the magnet is being cooled to 4.22 K, the mechanical stress is monitored through strain gauges. Current is then ramped into the magnet until it reaches some maximum value and the magnet transitions from the superconducting state to the normal state. Normal-zone propagation is monitored using voltage taps on the magnet coils during this process, thus indicating where the transition began. The current ramp is usually repeated until a plateau current is reached, where the magnet has mechanically settled. Many variations on the current ramping sequence are used to study different phenomena associated with magnet performance, e.g. magnetization hysteresis, eddy current losses, cryogenic stability, etc. A warm bore cryostat with a rotating coil is inserted in the magnet to measure field strength and homogeneity. These types of measurements yield multipole and current versus field data.

LaBarge, A.; Althaus, R.; Bird, R.; Baron, J.; Chagnon, J.; Deak, M.; Scott, M.; Vasilyev, V.; Williamson, G.

1993-05-01

426

Self consistent generalized model for the calculation of minor loop excursions in the theory of hysteresis.  

National Technical Information Service (NTIS)

In the previous work it has been shown that the magnetization curves of a wide range of ferromagnetic materials can be calculated from a simple theory which invokes a constant energy loss per unit change in magnetization. The energy loss, which is therefo...

D. C. Jiles

1992-01-01

427

Influence of the exchange bias on the magnetic losses in CoFeB/MgO/CoFeB tunnel junctions  

NASA Astrophysics Data System (ADS)

We report the influence of the exchange bias on the low-frequency magnetic losses of the reference layer in CoFeB/MgO/CoFeB tunnel junctions near maximum resistance susceptibility. The phase lag associated with the magnetic losses in the reference layer, ?, is field-dependent during its magnetic reversal, being largest around the antiparallel state and slowly decreasing with higher applied fields. Such behavior would indicate a direct influence of the exchange bias strength. Its strength is determined by the magnitude of the reference layer switching field, Href. This is defined as the field at which the magnetoresistance-sensitivity product exhibits its maximum. Devices with the strongest exchange bias tend to have the thickest seed layers and exhibit elevated values for Href and ?. However, ones with weakened exchange bias due to prolonged annealing show a reduction in Href and ? with increased annealing time. A comparison between top and bottom pinning configurations is also discussed along with its impact on double-barrier magnetic tunnel junctions.

Stearrett, Ryan; Wang, W. G.; Kou, Xiaoming; Shah, L. R.; Xiao, J. Q.; Nowak, E. R.

2012-02-01

428

398 IEEE TRANSACTIONS ON MAGNETICS, VOL. 42, NO. 3, MARCH 2006 Introducing Dynamic Behavior of Magnetic Materials  

E-print Network

--Eddy currents, finite-element method, magnetic hysteresis, reluctance motors. I. INTRODUCTION DYNAMIC hysteresis of Magnetic Materials Into a Model of a Switched Reluctance Motor Drive F. Sixdenier, L. Morel, and J. P, we present the model of an ultrafast switched reluctance motor, in which the control of the power

Boyer, Edmond

429

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

430

Nonlinear Control of a Planar Magnetic Levitation System Michel Levis and Manfredi Maggiore  

E-print Network

actuators that are capable of fine resolution but possess severe hysteresis nonlinearity [7]. Mechanical motors. Linear motors are indeed particularly suitable for magnetic levita- tion applications due

Maggiore, Manfredi

431

Hysteresis in the production of force by larval Dipteran muscle.  

PubMed

We describe neuromuscular hysteresis - the dependence of muscle force on recent motoneuron activity - in the body wall muscles of larval Sarcophaga bullata and Drosophila melanogaster. In semi-intact preparations, isometric force produced by a train of nerve impulses at a constant rate was significantly less than that produced by the same train of stimuli with a brief (200 ms) high-frequency burst of impulses interspersed. Elevated force did not decay back to predicted values after the burst but instead remained high throughout the duration of the stimulus train. The increased force was not due to a change in excitatory junction potentials (EJPs); EJP voltage and time course before and after the high-frequency burst were not statistically different. Single muscle and semi-intact preparations exhibited hysteresis similarly, suggesting that connective tissues of the origin or insertion are not crucial to the mechanism of hysteresis. Hysteresis was greatest at low motoneuron rates - yielding a approximately 100% increase over predicted values based on constant-rate stimulation alone - and decreased as impulse rate increased. We modulated motoneuron frequency rhythmically across rates and cycle periods similar to those observed during kinematic analysis of larval crawling. Positive force hysteresis was also evident within these more physiological activation parameters. PMID:20581278

Paterson, Bethany A; Anikin, Ilya Marko; Krans, Jacob L

2010-07-15

432

Effect of soft ferromagnetic substrate on ac loss in 2G HTS power transmission cables consisting of coated conductors  

NASA Astrophysics Data System (ADS)

As a model of second-generation high-temperature superconducting (2G HTS) power transmission cable, the effect of soft ferromagnetic (FM) substrate on hysteretic ac loss in a round cable carrying transport current or exposed to radial magnetic field is investigated theoretically. We consider the FM substrates as ideal soft magnets with an infinite permeability, neglecting the magnetic hysteresis. The analytical expressions of field and current distribution around a curved superconductor tape with FM substrate were derived applying the complex-field approach. FM components can strongly influence the ac loss behaviors in a round cable composed of coated conductors. The approximate expressions for ac loss in a round cable at small currents or low fields are obtained. It is shown that at small currents the ac loss QFM in a round cable for FM substrate depended on ac current amplitude ia and central angle ?n as {\\propto }{i}_{{a}}^{2.7}({\\theta }_{n}\\cot {\\theta }_{n})^{1.8 6}, while at low fields ha {Q}_{{FM}}\\propto {h}_{{a}}^{2.7 5}/({\\theta }_{n}\\cot {\\theta }_{n})^{0.3 5}, the order of which differs significantly from QNM for nonmagnetic (NM) substrate. Additionally, the influence of the central angle as well as tape-width of coated conductors on the ac loss characteristic in a round cable is discussed. The ac loss QFM can be reduced by a suitable tape-width of coated conductor at higher fields as compared with QNM.

He, An; Xue, Cun; Yong, Huadong; Zhou, Youhe

2014-02-01

433

The magnetostriction and its ratio to hysteresis for Tb-Dy-Ho-Fe alloys  

NASA Astrophysics Data System (ADS)

The x(Tb0.15Ho0.85Fe2) + (1 - x)(Tb0.3Dy0.7Fe2) alloys were prepared in an arc furnace under high purity argon. The as-cast samples wrapped in Mo foil were sealed in a silica tube filled with high purity argon. The static measurement of magnetostriction (?//, ??) was made by standard strain gauge, and the magnetization M was measured by a vibrating sample magnetometer. It is found that the magnetostriction ?// of x(Tb0.15Ho0.85Fe2) + (1 - x)(Tb0.3Dy0.7Fe2) alloys decreases with increasing x and it does from 880 × 10-6 for x = 0 to 210 × 10-6 for x = 0.9 at the magnetic field of 640 kA/m. The ratio (?///Wh) of magnetostriction to hysteresis exhibits a peak when x = 0.1, and it means that the Tb0.285Dy0.63Ho0.085Fe2 (x = 0.1) alloy possesses both large magnetostriction and small magnetostrictive hysteresis.

Wang, Bowen; Lv, Yan; Li, Guolu; Huang, Wenmei; Sun, Ying; Cui, Baozhi

2014-05-01

434

Single molecule magnets: a new class of magnetic materials  

Microsoft Academic Search

Recently it has been discovered that some molecules comprising a large number of coupled metal ions show slow relaxation of the magnetization at low temperature. This gives rise to magnetic hysteresis effects of molecular origin which in principle allow the storage of information in a single molecule (Single molecule magnets). A short overview of the current status of research in

Dante Gatteschi

2001-01-01

435

Comparison of AC losses, magnetic field/current distributions and critical currents of superconducting circular pancake coils and infinitely long stacks using coated conductors  

NASA Astrophysics Data System (ADS)

A model is presented for calculating the AC losses, magnetic field/current density distribution and critical currents of a circular superconducting pancake coil. The assumption is that the magnetic flux lines will lie parallel to the wide faces of tapes in the unpenetrated area of the coil. Instead of using an infinitely long stack to approximate the circular coil, this paper gives an exact circular coil model using elliptic integrals. A new efficient numerical method is introduced to yield more accurate and fast computation. The computation results are in good agreement with the assumptions. For a small value of the coil radius, there is an asymmetry along the coil radius direction. As the coil radius increases, this asymmetry will gradually decrease, and the AC losses and penetration depth will increase, but the critical current will decrease. We find that if the internal radius is equal to the winding thickness, the infinitely long stack approximation overestimates the loss by 10% and even if the internal radius is reduced to zero, the error is still only 60%. The infinitely long stack approximation is therefore adequate for most practical purposes. In addition, the comparison result shows that the infinitely long stack approximation saves computation time significantly.

Yuan, Weijia; Campbell, A. M.; Hong, Z.; Ainslie, M. D.; Coombs, T. A.

2010-08-01

436

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

E-print Network

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, $\\Gamma$ and absorption coefficient, $\\alpha$. The variation of $\\Gamma$ and $\\alpha$ as a function of frequency and the tube's plasma properties is studied in detail. Previous similar studies have considered only a subphotospheric layer, modelled as a polytrope that has been truncated at the photosphere (Bogdan et al. (1996), Hindman & Jain 2008, Gascoyne et al. (2011)). Such studies have found that the resulting energy loss by the $p$ modes is very sensitiv...

Gascoyne, Andrew; Hindman, Bradley

2014-01-01

437

A Fluid Mechanical Interpretation of Hysteresis in Rhinomanometry  

PubMed Central

A hysteresis effect in the pressure/flow rate relationship of nasal breathing has frequently been observed in clinical tests and in lab investigations. Explanations that have been given in the literature are missing a fluid mechanic storage effect coming into play in reciprocating flows. This effect depends primarily on the way the rhinomanometric measurements are set up and not so much on the nose flow itself. This is to be shown by calculations and experiments. The experiments are carried out with orifices because they can represent nose flow and are often implemented in rhinomanometric equipment as flow gauges. To mimic reality also a 1?:?1 nose model is used. It is shown where the hysteresis comes from and what the key parameters for its prediction are. With these results hysteresis in nasal breathing appears in a new light. PMID:23724249

Gross, T. F.; Peters, F.

2011-01-01

438

The apparent hysteresis in hormone-agonist relationships  

PubMed Central

It has been noted in multiple studies that the calcium–PTH axis, among others, is subject to an apparent hysteresis. We sought to explain a major component of the observed phenomenon by constructing a simple mathematical model of a hormone and secretagogue system with concentration dependent secretion and containing two delays. We constructed profiles of the hormone–agonist axis in this model via four types of protocols, three of which emulating experiments from the literature, and observed a delay- and load-dependent hysteresis that is an expected mathematical artifact of the system described. In particular, the delay associated with correction allows for over-secretion of the hormone influencing the corrective mechanism; thus rate dependence is an artifact of the corrective mechanism, not a sensitivity of the gland to the magnitude of change. From these observations, the detected hysteresis is due to delays inherent in the systems being studied, not in the secretory mechanism. PMID:22154846

Pruett, William A.; Hester, Robert L.; Coleman, Thomas G.

2011-01-01

439

A modified Prandtl-Ishlinskii modeling method for hysteresis  

NASA Astrophysics Data System (ADS)

A modified Prandtl-Ishlinskii modeling method for rate-independent hysteresis in piezoelectric actuators is proposed in this paper. In this method, a generalized backlash operator (GBO) regarded as the elementary operator is introduced into the model so as to be more flexible for modeling of complex hysteresis. Moreover, the Levenberg-Marquardt algorithm is used to estimate the parameters of the model. Thus, all the parameters of the modified PI model can be determined automatically. From this way, it avoids the tedious procedure for the selection of the operator parameters by trial and error. Then, a group of proper Clarke subgradients of the GBO outputs with respect to their parameters at a non-smooth point is obtained based on the bundle method. Finally, the experimental results of applying the proposed method to the modeling of hysteresis in a piezoelectric actuator and an ultrasonic motor (USM) are illustrated, respectively.

Dong, Ruili; Tan, Yonghong

2009-05-01

440

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

441

Completely inverted hysteresis loops: Inhomogeneity effects or experimental artifacts  

SciTech Connect

Completely inverted hysteresis loops (IHL) are obtained by the superconducting quantum interference device with large cooling fields (>10 kOe) in (La,Sr)MnO{sub 3} films with self-assembled LaSrMnO{sub 4}, an antiferromagnetic interface. Although the behaviours of measured loops show many features characteristic to the IHL, its origin, however, is not due to the exchange coupling between (La,Sr)MnO{sub 3}/LaSrMnO{sub 4}, an often accepted view on IHL. Instead, we demonstrate that the negative remanence arises from the hysteresis of superconducting coils, which drops abruptly when lower cooling fields are utilized. Hence the completely inverted hysteresis loops are experimental artifacts rather than previously proposed inhomogeneity effects in complicated materials.

Song, C., E-mail: songcheng@mail.tsinghua.edu.cn; Cui, B.; Pan, F., E-mail: panf@mail.tsinghua.edu.cn [Key Laboratory of Advanced Materials (MOE), School of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China); Yu, H. Y. [Center for Testing and Analyzing of Materials, School of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China)

2013-11-14

442

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

443

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

444

Analysis of coupled electromagnetic-thermal effects in superconducting accelerator magnets  

NASA Astrophysics Data System (ADS)

FAIR will built 5 magnet rings including two superconducting synchotrons. The SIS100 is the core component of the facility and will be equipped with 2 Tesla dipole magnets pulsed with 4 Tesla/s. The cable of the magnet coils is made of a hollow NbTi composite cable of about 7 mm outer diameter, cooled with two phase helium flow at 4.5 K. We calculate the heat load, the eddy and the hysteresis losses, investigate the impact of the ramping on the magnetic field, on the safety margin of the conductor and the required cooling for all different elements of the magnet including: the coil, the yoke, the bus bars and the beam pipe. This analysis is based on properties measured at cryogenic temperatures and fine detailed FEM models.

Fischer, E.; Kurnyshov, R.; Shcherbakov, P.

2008-02-01

445

Hidden hysteresis - population dynamics can obscure gene network dynamics  

PubMed Central

Background Positive feedback is a common motif in gene regulatory networks. It can be used in synthetic networks as an amplifier to increase the level of gene expression, as well as a nonlinear module to create bistable gene networks that display hysteresis in response to a given stimulus. Using a synthetic positive feedback-based tetracycline sensor in E. coli, we show that the population dynamics of a cell culture has a profound effect on the observed hysteretic response of a population of cells with this synthetic gene circuit. Results The amount of observable hysteresis in a cell culture harboring the gene circuit depended on the initial concentration of cells within the culture. The magnitude of the hysteresis observed was inversely related to the dilution procedure used to inoculate the subcultures; the higher the dilution of the cell culture, lower was the observed hysteresis of that culture at steady state. Although the behavior of the gene circuit in individual cells did not change significantly in the different subcultures, the proportion of cells exhibiting high levels of steady-state gene expression did change. Although the interrelated kinetics of gene expression and cell growth are unpredictable at first sight, we were able to resolve the surprising dilution-dependent hysteresis as a result of two interrelated phenomena - the stochastic switching between the ON and OFF phenotypes that led to the cumulative failure of the gene circuit over time, and the nonlinear, logistic growth of the cell in the batch culture. Conclusions These findings reinforce the fact that population dynamics cannot be ignored in analyzing the dynamics of gene networks. Indeed population dynamics may play a significant role in the manifestation of bistability and hysteresis, and is an important consideration when designing synthetic gene circuits intended for long-term application. PMID:23800122

2013-01-01

446

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 (·3H2O)] has been prepared and characterized. Structural studies and Hirshfeld surface analysis for complex ·3H2O at three different temperatures (300, 240 and 130 K) are described. The UV-vis absorption spectrum of a water-free sample () in methanol solution and magnetic susceptibility measurements for solid-state samples ·3H2O and revealed that the removal of lattice water molecules from complex ·3H2O changed the magnetic properties from the low-spin state (·3H2O) to the complete spin-crossover () 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

2014-10-22

447

A survey on hysteresis modeling, identification and control  

NASA Astrophysics Data System (ADS)

The various mathematical models for hysteresis such as Preisach, Krasnosel'skii-Pokrovskii (KP), Prandtl-Ishlinskii (PI), Maxwell-Slip, Bouc-Wen and Duhem are surveyed in terms of their applications in modeling, control and identification of dynamical systems. In the first step, the classical formalisms of the models are presented to the reader, and more broadly, the utilization of the classical models is considered for development of more comprehensive models and appropriate controllers for corresponding systems. In addition, the authors attempt to encourage the reader to follow the existing mathematical models of hysteresis to resolve the open problems.

Hassani, Vahid; Tjahjowidodo, Tegoeh; Do, Thanh Nho

2014-12-01

448

Hysteresis in Granular Media Subjected to Axisymmetrical Rotation  

NASA Astrophysics Data System (ADS)

In this work we have studied the hysteretic behavior for the mean slope of the free surface of noncohesive granular media under axisymmetricalrotation. In order to study the hysteresis loop the relationship between theaverage slope of the free surface (most important measurable quantity) andthe Froude number has been established. Differences between experiments andtheoretical predictions are also shown. Theory predicts that hysteresis mustdisappear as the friction coefficient µ of the granular materialreaches unity. However, this condition could not be reached experimentallyusing tapioca (where µ˜1), due to the important difference betweenthe angle of internal friction and the angle of repose for small containers.

Medina, Abraham; Treviño, Casay

1999-06-01

449

A compensation method for the hysteresis error of DVD VCM  

NASA Astrophysics Data System (ADS)

The present study considers an autofocusing laser probe system used for the measurement of the surface profile and roughness of an object. The system is based upon a modified pickup head of a commercially available DVD player which uses a voice coil motor (VCM) to drive an objective lens during the autofocusing process. It is known that hysteresis of the VCM during the autofocusing process reduces the precision of the measurement results. Consequently, the present investigation adopts a hysteresis model to develop a compensation method which can improve the accuracy of the optical pickup head within the measurement system.

Chu, Chih-Liang; Fan, Kuang-Chao; Chen, Ye-Jing

2004-04-01

450

Wave interaction in acoustic resonators with and without hysteresis.  

PubMed

Nonlinear interaction of counterpropagating waves in solids is considered by using a general approach taking into account only the cumulative (resonant) nonlinear perturbations giving a nonzero contribution over the period and, consecutively, potentially able to significantly modify the linear solution. Different stress-strain relations are addressed, including those with hysteresis which serve as basic models for the recent acoustic experiments with rock and metals. An important case of the interaction of counterpropagating waves with close amplitudes in a high-Q resonator (bar) with hysteresis is specially addressed and compared with the case of a ring resonator. PMID:15658687

Ostrovsky, Lev A

2004-12-01

451

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

452

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

453

Low-Loss Photonic Crystal Defect Waveguides and Taper Designs in InP/InGaAsP for Transverse Magnetic Polarized Light  

NASA Astrophysics Data System (ADS)

We present the simulation, fabrication and characterization of novel low-loss photonic crystal (PhC) defect waveguides for transverse magnetic (TM) polarized light in the InP/InGaAsP material system. Minimal propagation losses for the proposed W4 PhC waveguides as low as ˜300 dB/cm at ? = 1550 nm for lattice constant a = 350 nm, and ˜500 dB/cm at ? = 1532 nm for lattice constant a = 590 nm are obtained from the cut-back analysis. In addition, an associated application of proposed wide PhC waveguides as intermediate short tapers between deeply etched access waveguides and narrower quas