Showing papers on "Magneto published in 2007"

Buckling and Vibration Analysis of Layered and Multiphase Magneto‐Electro‐Elastic Beam Under Thermal Environment

Abstract: The paper deals with the investigation of linear buckling and free vibration behavior of layered and multiphase magneto‐electro‐elastic (MEE) beam under thermal environment. The constitutive equations of magneto‐electro‐elastic materials are used to derive finite element equations involving the coupling between mechanical, electrical and magnetic fields. The finite element model has been verified with the commercial finite element package ANSYS. The influence of magneto electric coupling on critical buckling temperature is investigated between layered and multiphase magneto‐electro‐elastic beam. Furthermore, the influence of temperature rise on natural frequencies of magneto‐electro‐elastic beam with layered and different volume fraction is presented.

Modular magneto-mechanical device

Abstract: An electromechanical device has a rotor, a stator, and a module that at least partially houses the rotor. During normal operation of the electromechanical device, the stator is positioned external to and separate from the module.

Magnetic and magneto-mechanical properties of Ni-Mn-Ga magnetic shape memory alloys

Abstract: OF DOCTORAL DISSERTATION HELSINKI UNIVERSITY OF TECHNOLOGY P. O. BOX 1000, FI-02015 TKK http://www.tkk.fi Author Ladislav Straka Name of the dissertation Manuscript submitted 6.2.2007 Manuscript revised 22.5.2007 Date of the defence 15.6.2007 Article dissertation (summary + original articles) Monograph Department Laboratory Field of research Opponent(s) Supervisor Instructor Abstract

Magnetoresistive sensor as temperature sensor

Abstract: A detection system (100, 150) for qualitative or quantitative detection of a magnetic field property of a modulated magnetic field is described. The modulated magnetic field may e.g. stem from an adjacent electrical current (Iadj) or magnetic particles. The detection system (100, 150) comprises at least one magneto resistive sensor element (102), a current controller (104) for providing a sensing current (Isense) flowing through the magnetic sensor element (102) and a controlling means (108). The controlling means (108) is adapted for deriving at a first frequency f1 a temperature-related parameter of the at least one magneto resistive sensor. The controlling means (108) furthermore is adapted for deriving a qualitative or quantitative characteristic of the adjacent electrical current (Iadj) or magnetic particles, taking into account the derived temperature-related parameter. This second frequency (f1) is different from the first frequency (f1}). The invention also relates to a corresponding method.

Enhanced magneto-optic imaging system for nondestructive evaluation

Abstract: An enhanced magneto-optic (MO) imaging system is presented in this paper to detect hidden and buried subsurface flaws in metallic specimens. The characters of the MO imaging system are mainly given by the parameters of the MO thin films, the magnetic excitation device and image-processing algorithms. In this paper, the choice of the MO thin films, the design of the magnetic excitation device and the development of the image processing approaches are introduced in detail. Experimental tests have been done and the method presented is evaluated by the experimental results.

Simulation of Hypersonic Flow Within a Strong Magnetic Field

Abstract: The equations of magneto fluid dynamics (MFD) are solved for flow within a simplified “energy bypass” scramjet engine. This engine extracts electrical power from the flow through electric and magnetic field interaction just ahead of the combustor section and then returns it to accelerate the flow downstream of it. This problem has been chose to develop an algorithm to solve the MFD equations with strong electric and magnetic field interaction with weakly ionized flows. Although an attempt is made to make the flow as realistically as possible, the main emphasis is on algorithm development. The effects of the Hall current and ion slip are included. Equilibrium gas conditions are assumed. Electron and ion number densities are calculated and used to determine the local electrical conductivity of the gas.

Nonreciprocal device based on magneto-optical resonator cavity

Abstract: The invention discloses non reciprocal device based on magneto optic resonance cavity. The magneto optical material containing optical micro resonance structure processes power couple with the input and output ports of the optical coupled structure by its one side to form isolator; or it processes between them by optical coupled structure two sides to form ring circuit machine. The invention uses magneto-optic wave guide non reciprocal property, combines with magneto-optic resonance cavity anomalous property, optimize structure parameter to process multi-path frequency light waves at the same time. Thus it has the advantages of popular structure, simple technology, flexible design, strong functionality, wide application prospect in light wave multiplexing network, light bilateral network, light information processing etc.

System and methods for actuation on magnetoresistive sensors

Abstract: The present invention relates to systems and methods for magnetic actuation of particles from and toward the surface of a sensor with a magneto -resistive element The orientation of magnetic fields and arrangement of magnetic field generating means with respect to the sensor maintains or restores the sensitivity of the magneto -resistive element after actuation

Device based on a magneto-resistive mixed sensor without low frequency noise and associated method

Abstract: A device comprises a mixed sensor design with at least one superconducting loop (1) containing at least one constriction (3) and a magneto-resistive element (2) located next to the constriction (3). The device contains at least one heating element (5) that allows switching at sufficiently high frequency of at least one part of the superconducting loop (1) above its critical temperature, such that the super-current flowing through the at least one constriction (3) containing the at least one magneto-resistive element (2) is temporarily suppressed.

A magnetic heat pump with porous magneto caloric material

Abstract: At present magnetic refrigeration shows a realistic potential to penetrate into some niche markets in the field of cold and hot "production". It is well known that a refrigerator for cooling and a heat pump for heating are machines based on the same principle. A small review on magnetic heat pump studies is outlined and a simple engineering calculation scheme to determine the coefficient of performance for a magnetic heat pump with a rotary porous structure heat exchanger is presented. Magnetic heat flux line distributions are calculated by a 2-d finite element method numerical simulation program with the objective to obtain high field's mu H-0 with not too heavy permanent magnets assemblies. The porous structures are geometrically optimised to obtain maximal magnetic field inductions. It is shown that for a water/ethylene-glycol magnetic heat pump the coefficient of performance is higher than that of a conventional heat pump. (c) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Magneto-caloric cooling device and method of operation

Abstract: A method of operating a cooling device is provided. The method includes sequentially regulating a temperature of a plurality of thermally coupled magneto-caloric elements for maximizing a magneto-caloric effect for each of the magneto-caloric elements when subjected to a magnetic regenerative refrigeration cycle.

A disk type low magnetic reluctance permanent magnet AC generator

Abstract: The utility model relates to a low reluctance magneto alternator, which is composed of two stators and a rotor; wherein the two stators are arranged in an upper and a lower shell respectively; the rotor is arranged in a rotor shaft. The utility model is characterized in that: a stator module is composed of an iron core and coils and is fixed on the shells in sequence; each stator coil is connected together in parallel or in series. As the coils and the iron core is modularized, magnetic field loss can be reduced when the alternator is in operation and electricity generating efficiency is improved by improving processing accuracy and quality of the coil winding. The utility model is easy to form large scale production, thereby simplifying the producing techniques and reducing manufacturing cost.

Electrostatic discharge protection circuit for preamps connected to magneto-resistive read elements

Abstract: A magnetic storage system comprises a read element and an electrostatic discharge (ESD) protection circuit that communicates with the read element and that includes a normally-on transistor that shorts the read element when the magnetic storage system is unpowered.

Giant Magneto Resistive (GMR) effect based Current Sensing Technique for DC/DC Converters

Abstract: Current sensing is one of the important function in a DC-DC Converter. It may be used for implementing current mode control or for achieving current sharing in a paralleled converters. Many current sensing schemes have been reported in literature, but they are either lossy or they require precise knowledge of the component value. In this paper a new giant magneto resistive (GMR) effect based sensor is used for low voltage, high current VRM type applications. Since the current sensing is based on magnetic field, thus the sensing accuracy depends upon the placement of sensor on the conductor. Various implementation issues while using such a sensor are studied and finally the performance of the sensor is studied on a 1 V / 15 A buck converter switching at 1 MHz.

Performance Analysis and Characterisation of a new Magneto-Electrical Measurement System for Electrical Conductivity Imaging

Abstract: An often used proxy in hydrogeology is the electrical condutctivity distributioni to study flow and transport of groundwater in soil. In order to map the electrical conductivity distribution of soil columns (length 0.5 m and 0.1 m radius), traditionally ERT (Electrical Resistivity Tomography) is used. In this thesis the ERT measurements will be complimented by magnetometric resistivity (MMR) mearurements. Due to a low frequency current injection (25 Hz) a current distribution is generated in the soil column of which the electrical potential is measured at several electrodes. This current has an associated magnetic field, also depending on the internal electrical conductivity distribution, this resulting magnetic field is measured in the MMR method. The magneto-electrical resistivity imaging technique (MERIT) combines the measurement of both electric and magnetic parameters. In this thesis the development of a small laboratory scale system will be described. The electrical potentials are measured by small stainless steel screws inserted into the plexiglass mantle of the soil column, the magnetic fields are measured with especially designed sensor modules. The three component magnetic field modules are composed of AMR sensors, and are located on a vertical moving scanning torus. The magnetic field measurement system is designed to operate under ’typical’ laboratory noise conditions. The development of this new measurement system also includes optimization of the sensor positions and current injection geometries. The technique of singular value decomposition is applied to the Jacobian (or sensitivity matrix) of a combined ERT and MMR dataset in order to obtain information on the behaviour of the system in the so-called model space as well as its data space. This information can be used to obtain a quantitative measure of the optimum measurement configuration and the optimum resolution of the MERIT system, depending on the target of the survey. Finally a 2D quasi-Newton inversion algorithm with Broyden type Jacobian updating is used in order to image the electrical conductivity distribution of the soil column.

Rotary electromagnetic generator

Abstract: PROBLEM TO BE SOLVED: To provide a rotary electromagnetic generator that is reduced in weight by reducing the amount of permanent magnets used to thereby provide high efficiency. SOLUTION: The rotary electromagnetic generator 1 is constituted of: a rotating shaft 2; rotating magnet holders 4 so constructed that they are coupled with the rotating shaft 2 and rotatable; multiple permanent magnets 11, 12, 13, 14 disposed on the rotating magnet holders 4 with their identical magnetic poles opposed to each other; and magneto coils 21, 22, 23, 24 disposed around the rotating magnet holders 4 and the permanent magnets 11, 12, 13, 14. The multiple rotating magnet holders 4 are coupled with the rotating shaft 2 so that they are stacked together. COPYRIGHT: (C)2009,JPO&INPIT

Electro-magneto-phoresis of slender bodies

Abstract: Slender-body asymptotic theory is applied to determine the electro-magneto-phoretic motion of a freely suspended elongated particle which is arbitrarily oriented relative to uniformly applied electric and magnetic fields.

Magneto-optic iron-garnet thin films for integrated optical applications

Abstract: Optical isolators allow polarized light to transmit in only one direction. These devices are used to prevent unwanted feedback into photonics components such as amplifiers and lasers. The realization of optical isolators in an integrated waveguide configuration, however, while still a challenging proposition, will potentially result in reduced costs and dimensions, as well as in increased integrability and improved fabrication yield for integrated optics. Yttrium iron garnet (Y3Fe5O12, or YIG) and its substitutes are among the materials of choice for integrated optical isolators due to their high Verdet constant, i.e., the nonreciprocal Faraday rotation of the polarization experienced by light in the presence of a magnetic field. Pulsed laser deposition (PLD) is potentially the technique of choice for fabricating ferrite thin films, primarily because of its proven simplicity and efficiency. However, PLD-fabricated garnet films on non-garnet substrates are usually amorphous and require post-deposition annealing. Here we demonstrate that the effect of oxygen inclusion is actually a major component in these processes. Interestingly, very few studies have been conducted to understand why and how oxygen affects the microstructure of magneto-optic thin films, which is closely linked to their physical characteristics. We investigate the effect of oxygen in both the deposition and the subsequent thermal annealing steps. To study the role of oxygen during the fabrication process, we performed a series of six depositions at a fixed temperature of 800◦C, while setting the oxygen pressure at a value of either 0 or 50mTorr. (More precisely, what we call 0mTorr is actually the background pressure in the deposition chamber, which was Figure 1. X-ray diffraction spectra for sample 5 of an yttrium-irongarnet (YIG) thin film after post-deposition heat treatment. (I) After first anneal in Ar; (II) after second anneal in air. The YIG peaks are denoted with corresponding (h k l) values. On the y axis: counts per second.

A Survey in Mathematics for Industry An efficient method for the numerical simulation of magneto-mechanical sensors and actuators

Abstract: The dynamic behaviour of magneto-mechanical sensors and actuators can be completely described by Maxwell's and Navier-Lamé's partial differential equations (PDEs) with appropriate coupling terms reflecting the interactions of these fields and with the corresponding initial, boundary and interface conditions. Neglecting the displacement currents, which can be done for the classes of problems considered in this paper, and introducing the vector potential for the magnetic field, we arrive at a system of degenerate parabolic PDEs for the vector potential coupled with the hyperbolic PDEs for the displacements.Usually the computational domain, the finite element discretization, the time integration, and the solver are different for the magnetic and mechanical parts. For instance, the vector potential is approximated by edge elements whereas the finite element discretization of the displacements is based on nodal elements on different meshes. The most time consuming modules in the solution procedure are the solvers for both, the magnetical and the mechanical finite element equations arising at each step of the time integration procedure. We use geometrical multigrid solvers which are different for both parts. These multigrid solvers enable us to solve quite efficiently not only academic test problems, but also transient 3D technical magneto-mechanical systems of high complexity such as solenoid valves and electro-magnetic-acoustic transducers. The results of the computer simulation are in very good agreement with the experimental data.

Generalized Maxwell equations in exterior domains 3, Electro-magneto statics

Abstract: We develop a solution theory for a generalized electro-magneto static Maxwell system in an exterior domain Ω ⊂ RN with anisotropic coefficients converging at infinity with a rate r−τ , τ > 0 , towards the identity. Our main goal is to treat right hand side data from some polynomially weighted Sobolev spaces and obtain solutions which are up to a finite sum of special generalized spherical harmonics in another appropriately weighted Sobolev space. As a byproduct we prove a generalized spherical harmonics expansion suited for Maxwell equations. In particular, our solution theory will allow us to give meaning to higher powers of a special static solution operator. Finally we show, how this weighted static solution theory can be extended to handle inhomogeneous boundary data as well. This paper is the second one in a series of three papers, which will completely reveal the low frequency behavior of solutions to the time-harmonic Maxwell equations.

Method and apparatus for boosting power in a bicycle electrical device

Abstract: A bicycle electric power device includes a dynamo, an electrical device, a power source and a switch. The electrical device is electrically connected to the dynamo. The power source is electrically connected to the dynamo in parallel with the electrical device and configured to chargeably connect to the dynamo. The switch is connected in series with the power source and configured to controllably connect the power source to the dynamo with the dynamo producing no power of its own such that with the switch closed the dynamo is charged by the power source and with the switch opened the dynamo provides boosted voltage to the bicycle electrical device.