Showing papers on "Magneto published in 2009"

FEM for directly coupled magneto-mechanical phenomena in electrical machinesKatarzyna

Abstract: A directly coupled magneto-mechanical model is proposed for simulating the effect of the magnetostriction and electromagnetic stress in iron. The model is based on the general balance laws of electromagnetism, mechanics, and continuum thermodynamics. It is implemented in 2-D by using a conforming finite element method for the magnetic vector potential and the displacement field. The method is applied to two different types of induction machines.

Heat capacity study of magneto-electronic phase separation in La1-xSrxCoO3 single crystals.

Abstract: We present a detailed investigation of the specific heat $(0.35lTl270\\text{ }\\text{K})$ and ordinary Hall effect (300 K) in ${\\text{La}}_{1\\ensuremath{-}x}{\\text{Sr}}_{x}{\\text{CoO}}_{3}$ single crystals at 11 doping values in the range $0.00lxl0.30$. The data reveal a considerable amount of information on the nature of the percolation transition, the crystal and electronic structures, and, most significantly, the magnetoelectronic phase inhomogeneity that has attracted such attention in this material. The observations include a discontinuity in Debye temperature accompanying the insulator-metal transition, direct evidence for the percolative nature of this transition, and a large electron mass enhancement in the metallic state, likely due to strong electron correlation effects. The various contributions to the heat capacity are shown to provide a detailed picture of the phase-separated state and its evolution with doping and are discussed in light of prior neutron-scattering and heat capacity data. This doping dependence provides strong evidence that the phase separation is restricted to a well-defined doping range, $0.04lxl0.22$, in agreement with a recently proposed model.

Magneto-sensitive wire, magneto-impedance element and magneto-impedance sensor

Abstract: The magneto-sensitive wire of the invention has a vortex-spin structure and hence includes no magnetic domain walls, so that the magneto-sensitive wire of the invention has an excellent hysteresis characteristic exhibiting nearly zero hysteresis. Therefore, the linearity related to the output voltage characteristic for the applied magnetic field in the determination range of an MI sensor is significantly improved as compared to MI sensors using the conventional magneto-sensitive wires. Using the magneto-sensitive wire of the invention makes it possible to provide a magneto-impedance (MI) element exhibiting a higher precision than the conventional ones and further provide a sensor using such an MI element.

Harmonic Response of Three-phase Magneto-electro-elastic Beam Under Mechanical, Electrical and Magnetic Environment

Abstract: Magneto-electro-elastic (MEE) materials show a significant coupling between the mechanical, electrical, and magnetic fields. A three-phase MEE composite consisting of piezoelectric and piezomagneti...

Magneto-optics: Hot atoms rotate light rapidly

Abstract: The ability to harness the Faraday effect on a short timescale in an ensemble of hot atoms may prove useful as a read-out tool for quantum information based on microscale vapour cells.

Finite Volume Methods for Wave Propagation in Stratified Magneto-atmospheres

Abstract: We present a model for simulating wave propagation in stratified magnetoatmospheres. The model is based on equations of ideal MHD together with gravitational source terms. In addition, we present suitable boundary data and steady states to model wave propagation. A finite volume framework is developed to simulate the waves. The framework is based on HLL and Roe type approximate Riemann solvers for numerical fluxes, a positivity preserving fractional steps method for discretizing the source and modified characteristic and Neumann type numerical boundary conditions. Second-order spatial and temporal accuracy is obtained by using an ENO piecewise linear reconstruction and a stability preserving Runge-Kutta method respectively. The boundary closures are suitably modified to ensure mass balance. The numerical framework is tested on a variety of test problems both for hydrodynamic as well as magnetohydrodynamic configurations. It is observed that only suitable choices of HLL solvers for the numerical fluxes and balanced Neumann type boundary closures yield stable results for numerical wave propagation in the presence of complex magnetic fields. AMS subject classifications: 65M06, 35L45, 8508

Three-Dimensional Fundamental Solution for Transversely Isotropic Electro-Magneto-Thermo-Elastic Materials

Abstract: Fundamental solutions play an important role in the analyses of coupled fields in electro-magneto-thermo-elastic material. However, most works available on this topic address the case of uniform temperature. Based on the compact general solution of transversely isotropic electro-magneto-thermo-elastic material, which is expressed in harmonic functions, and employing the trial-and-error method, the three-dimensional fundamental solution for a steady point heat source in an infinite transversely isotropic electro-magneto-thermo-elastic material is presented by five newly induced harmonic functions. Numerical results are given graphically by contours.

Fracture Analysis for Two-dimensional Plane Problems of Nonhomogeneous Magneto-electro-thermo-elastic Plates Subjected to Thermal Shock by Using the Meshless Local Petrov-Galerkin Method

Abstract: The two-dimensional (2D) fracture problem of nonhomogeneous magneto-electro-thermo-elastic materials under dynamically thermal loading is investigated by the meshless local Petrov-Galerkin (MLPG) method. The material parameters are assumed to vary in either the height or width direction of the plates. The Laplace-transform technique is utilized to solve the time-dependent problems. In this MLPG analysis, the moving least squares (MLS) method is adopted to approximate the physical quantities, and the Heaviside step function is taken as a test function. The validity and efficiency of the MLPG method are firstly examined. The crack problem of a nonhomogeneous magneto-electro-thermo-elastic plate is then considered. The field intensity factors (FIFs) including the stress intensity factor (SIF), electric displacement intensity factor (EDIF), magnetic induction intensity factor (MIIF) and mechanical mode-I strain energy release rate (MSERR) of the magneto-electro-thermo-elastic materials are computed. The effects of the nonhomogeneous parameters especially the thermal nonhomogeneous parameters on the fracture behavior of crack tips are emphatically evaluated and discussed according the energy release rate criterion. The results seem useful for the design of nonhomogeneous material worked in high or low temperature environments.

State space approach to one-dimensional magneto-thermoelasticity under the Green- Naghdi theories

Abstract: A model of the equations of generalized magneto-thermoelasticity for perfectly conducting isotropic media is given The formulation is applied to the generalized thermoelasticity theories: Green–Na

Magneto-Thermo-Gravimetric technique to investigate the structural and magnetic properties of Fe-B-Nb-Y Bulk Metallic Glass

Abstract: Magneto-thermo-gravimetric (MTG) technique is highly informative about the changes in the magnetic state, as well as structural changes in a system, which cannot be often noticed in calorimetric me ...

Green's functions for semi-infinite transversely isotropic electro-magneto-thermo-elastic material

Abstract: We use the compact harmonic general solutions of transversely isotropic electro-magneto-thermo-elastic material to construct the three-dimensional Green's function for a steady point heat source acted in the interior of a semi-infinite transversely isotropic electro-magneto-thermo-elastic material by five newly introduced harmonic functions. All components of coupled field are expressed in terms of elementary functions and are convenient to use. Numerical results are given graphically by contours.

Open loop magneto-resistive magnetic field sensor

Abstract: An apparatus and a general method to measure a magnetic field using magneto-resistive sensors in an open-loop configuration are disclosed. A key feature is the regular in-situ normalization of the sensors to compensate for the effects of sensor aging.

Application of the homotopy perturbation method to a magneto-elastico-viscous fluid along a semi-infinite plate

Abstract: The equations governing the flow of an electrically conducting,, incompressible viscous fluid over an infinite flat plate in the presence of a magnetic field are investigated using the homotopy perturbation method (HPM) with Fade approximants (PA) and 4 order Rung!e*-Kutta method (4RKM). Approximate analytical and numerical solutions for the velocity field and heat transfer are obtained and compared with each other, showing excellent agreement. The effects of the magnetic parameter and Prandtl number on velocity field, shear stress, temperature and heat transfer are discussed as well.

Resonant magneto-conductance through a vibrating nanotube

Abstract: We address the electronic resonant transport in presence of a transverse magnetic field through the single level of a suspended carbon nanotube acting as a quantum oscillator. We predict a negative magneto-conductance with a magnetic-field induced narrowing of the resonance line and a reduction of the conductance peak when the nanotube is asymmetrically contacted to the leads. At finite bias voltage we study the threshold for phonon-assisted transport.

Magneto-Transport and Optical Control of Magnetization in Organic Systems: From Polymers to Molecule-based Magnets

Abstract: Organic systems can be synthesized to have various impressive properties such as room temperature magnetism, electrical conductivity as high as conventional metals and magnetic field dependent transport. In this dissertation, we report comprehensive experimental studies in two different classes of organic systems, V-Cr Prussian blue molecule-based magnets and polyaniline nanofiber networks. The first system, V-Cr Prussian blue magnets, belongs to a family of cyano-bridged bi-metallic compounds which display a broad range of interesting photoinduced magnetic properties. A notable example for optically controllable molecule-based magnets is Co-Fe Prussian blue magnet (Tc ∼ 12 K), which exhibits light-induced changes in between magnetic states together with glassy behavior. In this dissertation, the first reports of reversible photoinduced magnetic phenomena in V-Cr Prussian blue analogs and the analysis of its AC and DC magnetization behavior are presented. Optical excitation of V-Cr Prussian blue, one of the few room temperature molecule-based magnets, with UV light (λ = 350 nm) suppresses magnetization, whereas subsequent excitation with green light (λ = 514 nm) increases magnetization. The partial recovery effect of green light is observed only when the sample is previously UV-irradiated. Moreover the photoinduced state has a long lifetime at low temperatures (τ > 10 s at T = 10 K) indicating that V-Cr Prussian blue reaches a hidden metastable state upon illumination with UV light. The effects of optical excitation are maintained up ii to 200 K and completely erased when the sample is warmed above 250 K. Results of detailed magnetic studies and the likely microscopic mechanisms for the photo illumination effects on magnetic properties are discussed. The second organic system, polyaniline nanofiber networks, was synthesized via dilute polymerization and studied at low and high electric and magnetic fields for temperatures 2 K 250 K for their magneto-transport behavior. We observed large magnetoresistance (up to 55 % at H = 8 T and T = 3 K) in polymer networks composed of nanofibers with an average diameter of about 80 nm. A crossover from positive MR to negative MR is observed at ∼ 87 K. The positive and negative MR are attributed to two competing mechanisms; shrinkage of the localized electron wavefunction and suppression of quantum interference of electron wavefunctions propagating along different current paths in the hopping process by the applied magnetic field. In addition to temperature dependence of magnetoresistance, dependencies on morphology of the nanofibers and applied electric field are observed. Detailed DC electrical transport results of various polyaniline nanofiber samples and possible mechanisms responsible for the magneto-transport behavior are discussed.

Permanent magnet generator rotor

Abstract: The utility model discloses a dynamo magneto rotor, which comprises a rotation shaft, an iron core (2) and permanent magnet steels (3), wherein the iron core (2) is punched and laminated into a cylindrical shape through a ring-shaped silicon-steel plate, the upper surface and the lower surface are pressed through pressure plates (1,4), the middle portion of the pressure plates (1,4) is welded and fixed with a matching position of the rotation shaft, a plurality of permanent magnet steels (3) whose polarities are alternated and interphase are evenly fixed on the outer circumference of the iron core (2), the shapes of the permanent magnet steels (3) are trapezoids and are combined with a rectangle, after the polarities are positioned, then, epoxy resin is used to seal along the circumference of the permanent magnet steels (3), and the rotor takes a cylinder shape wholly. The dynamo magneto rotor has small magnetic steel consumption and good magnetic performance, which not only alleviates weight, but also is even with a gap (air gap) of an inner cavity of a stator, the manufacture and installation are simple and reliable, and the specific power is high. Bigger power can be output under same set weight, the weight is lightest under same power, and the dynamo magneto rotor is in particular suitable for being assembled on a wind-driven generator on a tower rod.

Modeling and simulation of the operation of a rotary magnetic refrigerator

Abstract: Magnetic refrigeration is a new environmentally benign technology and a promising alternative to conventional vapor-cycle refrigeration. The household refrigerator without a freezing compartment shows very good prospects for a successful application. This article starts with the general principle of magnetic refrigeration. An example of a magnet assembly is proposed and the corresponding magnetic flux lines are evaluated with a three-dimensional finite-element method (FEM). The maximum specific cooling capacity of magneto caloric materials is described. The specific cooling power of a magneto caloric material is found to be large even for medium magnetic field changes, especially if the frequency is not too small. For a domestic magnetic refrigerator, a comparison with a standard compressor refrigerator is presented. The modeling of a rotary magnetic refrigerator is described and its dynamic behavior is investigated. The physical model is based on a mapping of the magneto-thermodynamic problem from a cylinder onto two rectangles. In this model, in a basic centre cell, two coupled linear partial differential equations are solved, which have been programmed in the Modelica language. Steady-state solutions are envisaged to determine the coefficient of performance, COP, for these conditions. In future work the developed model shall be applied for an optimization of the magnetic refrigerator and to determine the related best parameters.

Fully-Coupled Characterization of Thermo-Electro-Magneto-Mechanical Materials

Abstract: Smart materials exhibit powerful nonlinear 3D coupling and anisotropy. However, the design and associated models, experimental characterization, and control design of smart systems are in general 1D. This reduced framework severely limits applications to 1D. The research presented here enables the tailoring of composition and processing to produce multifunctional materials with targeted performance properties that are fully nonlinear and 3D. A complete combinatorial analysis of seventy-two possible energy functions and state variables that describe 3D, nonlinear, coupled behavior of thermo-electro-magneto-mechanical materials is created. Each set of state variables and corresponding energy function correlates with a given set of experiments, the independent variables being controlled and the dependent variables being the measured responses. The constitutive equations with respect to each of these energy functions are derived in a systematic way by combining the mesoscale Maxwell equations, the balance laws of mechanics, and the balance law of entropy. The application of this framework to a new class of magnetostrictive Iron-Gallium alloys (Galfenol) is investigated with the intent to implement these alloys in a new class of fuel injectors to achieve unprecedented dynamic response and performance. The possibility of determining the full 3D constitutive behavior of Galfenol from simple, 1D macroscopic experiments in combination with analytical models based on knowledge of the crystal structure is explored. In this respect, a FEM formulation is presented. ii

Ignition system of double-fuel motorcycle engine

Abstract: The utility model requests to protect a dual-fuel ignition system for a motorcycle engine, which comprises an engine magneto, an igniter, a high-voltage coil and a spark plug, and is characterized in that gasoline ignition magnetic steel is arranged in the position of a gasoline ignition advance angle on a rotor of the engine magneto, and a gasoline ignition sensor is correspondingly arranged on an identical circular plane of a stator; natural gas ignition magnetic steel is arranged in the position of a natural gas ignition advance angle on the rotor, and natural gas ignition magnetic steel is arranged on the identical circular plane of the stator corresponding to the rotor; signal lines of the gasoline ignition sensor and a natural gas ignition sensor are connected with the igniter through a single-pole double-throw switch. By adopting the dual-fuel ignition system, magnetic steel and two sensors are arranged on the magneto, so as to ensure that different ignition advance angles are obtained when different fuels are used, and achieve the purposes of fully burning the fuel, reducing pollution emission, saving energy resources, and improving power.

Brushless magneto for ignition, electricity production and starting of motorcycle

Abstract: The utility model discloses a brushless magneto with functions of ignition action, power generation and startup for motorcycle, the rotor of the magneto is a flywheel fixedly connected with the end portion of a crankshaft, a fan is fixedly connected on the flywheel, a stator of the magneto is fixed on a crankshaft case by a support, splines are homogeneous distribution at the circumference of a iron-core of the stator, the stator is provided with magnetic field phase sensor, three magnetic induction elements of the sensor are respectively inserted into three adjacent splines in the splines at the circumference of the iron-core, the center of each magnetic induction element is positioned at the symmetric centre plane surface which is tangential with the iron-core circumference in the splines, the three magnetic induction elements are connected with a circuit board, the circuit board is fixed at one axial direction end surface by the support, the axial direction end wall of the flywheel is provided with a plurality of ventilating openings for dissipating heat for the magnetic field phase sensor The utility model leads the magnetic field phase sensor to be positioned in the appropriate temperature environment, the performance of the magnetic field phase sensor is not easily invalid, the accuracy of detection can be improved, and meet the startup requirement of the middle and small displacement engines on the basis of the functions of ignition action and power generation