Showing papers on "Magneto published in 2001"

A minute magneto hydro dynamic (MHD) mixer

Abstract: A theoretical and experimental investigation of a magneto hydrodynamic (MHD) stirrer is presented. Such a stirrer can be used to enhance mixing in micrototal analysis systems. The stirrer utilizes arrays of electrodes deposited on a conduit’s walls. The conduit is filled with an electrolyte solution. By applying alternating potential differences across pairs of electrodes, currents are induced in various directions in the solution. In the presence of a magnetic field, the coupling between the magnetic and electric fields induces body (Lorentz) forces in the fluid. Since, the electrodes can be patterned in various ways, fairly complex flow fields can be generated. In particular, in this paper, we describe the induction of cellular motion. This motion can be used to deform and stretch material interfaces and to enhance mixing. The MHD stirrer does not utilize any moving parts. The experimental observations are in good agreement with theoretical predictions.

Global accretion disk simulations of magneto-rotational instability

Abstract: We perform global three-dimensional simulations of accretion disks integrating the compressible, non- viscous, but diusive MHD equations. The disk is supposed to be isothermal. We make use of the ZEUS-3D code integrating the MHD equations and added magnetic diusivity. We measure the eciency of the angular- momentum transport. Various model simulations delivered transport parameters of SS =0 :01 to 0.05 which are consistent with several local numerical investigations. Two of the models reach a highly turbulent state at which SS is of the order of 0.1. After a certain stage of saturating of the turbulence, Reynolds stress is found to be negative (inward transport) in many of the models, whereas Maxwell stresses dominate and deliver a positive (outward) total transport. Several of the models yield strongly fluctuating Reynolds stresses, while Maxwell stresses are smooth and always transport outwards. Dynamo action is found in the accretion disk simulations. A positive dynamo- is indicated in the northern hemisphere of the most prominent run, coming along with negative kinetic and current helicities (all having the opposite sign on the southern side). The dipolar structure of the magnetic eld is maintained throughout the simulations, although indication for a decay of antisymmetry is found. The simulations covered relatively thick disks, and results of thin-disk dynamo models showing quadrupolar elds may not be compatible with the results presented here.

Global accretion disk simulations of magneto-rotational instability

Abstract: We perform global three-dimensional simulations of accretion disks integrating the compressible, non-viscous, but diffusive MHD equations. The disk is supposed to be isothermal. We make use of the ZEUS-3D code integrating the MHD equations and added magnetic diffusivity. We measure the efficiency of the angular-momentum transport. Various model simulations delivered transport parameters of alpha_SS=0.01 to 0.05 which are consistent with several local numerical investigations. Two of the models reach a highly turbulent state at which alpha_SS is of the order of 0.1. After a certain stage of saturating of the turbulence, Reynolds stress is found to be negative (inward transport) in many of the models, whereas Maxwell stresses dominate and deliver a positive (outward) total transport. Several of the models yield strongly fluctuating Reynolds stresses, while Maxwell stresses are smooth and always transport outwards. Dynamo action is found in the accretion disk simulations. A positive dynamo-alpha is indicated in the northern hemisphere of the most prominent run, coming along with negative kinetic and current helicities (all having the opposite sign on the southern side). The dipolar structure of the magnetic field is maintained throughout the simulations, although indication for a decay of antisymmetry is found. The simulations covered relatively thick disks, and results of thin-disk dynamo models showing quadrupolar fields may not be compatible with the results presented here.

The application of linear Halbach array to eddy current rail brake system

Abstract: This paper proposes two kinds of eddy current brakes with permanent magnet, One consists of hexahedron shape of a segmented permanent magnet and iron core (et seq. iron core-PM array). The other is composed of only a segmented permanent magnet (et seq. Halbach array). We use a finite element method to compute the magneto static field. Also, we use the Galerkin-FEM with linear interpolation function may oscillate between the adjacent nodes to calculate the braking and attraction force. The advantages of the Halbach array compared with the iron core-PM array are discussed.

Fast switching of magnetic fields in a magneto-optic trap

Abstract: Magneto-optic traps which employ current windings to generate pulsed magnetic fields require rapid switch-off times for many applications. Practical difficulties in attaining rapid switch-off of the magnetic field, including the generation of induced currents, are addressed. Several methods for minimizing the switch-off time are presented which do not require complex feedback mechanisms involving direct measurement of the magnetic field.

Optical magnetic head and magneto-optical disk device

Abstract: PROBLEM TO BE SOLVED: To provide an optical magnetic head and a magneto-optical disk device that are high in the utilization efficiency of a laser beam, suitable for high recording density, small in size and high in reliability. SOLUTION: This optical magnetic head 1 is integrated with a magneto- resistive sensor 3 and a thin film magnetic recording head 4 on a back end surface 2a of a flying slider 2 and is constituted so as to locate an optical waveguide 5 in a magnetic gap 43 of the thin film magnetic recording head 4. The distance between the position of near field light 7a output from an outgoing radiation edge 5c of optical waveguides 5 and magnetic field 44 formed by an air gaps 43 becomes shortest. Heating by near field light 7a, since recording is carried out simultaneously or just after it, allows the effect of thermal diffusion to be ignored and the utilization efficiency of a laser beam to be enhanced. Since a heating area is not spread by the thermal diffusion, a recorded area can be narrowed and high recording density can be achieved.

Bimodal biasing of magneto resistive heads

Abstract: A system and method for selecting between two biasing modes for biasing magneto resistive heads in a disk drive. A mode selector selects either a voltage biasing circuit or a current biasing circuit to supply the bias voltage or bias current, respectively, to a magneto resistive head. The selection can be based on changes in parameters in the disk drive or magneto resistive heads during disk drive operation.

Method for separation of plastic mixtures based on magneto-archimedes levitation

Abstract: Under a magnetic field gradient, solid particles floating and/or sinking in a supporting liquid (most suitably a paramagnetic one) are levitated or anti-levitated at different locations depending on their densities and diamagnetic susceptibilities.

Mechanisms of Magneto- and Electro-Rheology: Recent Progress and Unresolved Issues

Abstract: Abstract An electrorheological fluid (ERF) (magnetorheological fluid - MRF) is a particulate suspension which shows a dramatic increase in flow resistance upon application of an external electric (magnetic) field. In both systems, the fundamental physical process is believed to be that the field induces polarization of each particle with respect to the carrier material, and the resulting interparticle forces cause elongated aggregates of particles to form in the field direction. While recent years have witnessed the appearance of several applications using these tunable flow properties, optimal use of this technology is still hindered by our incomplete understanding of the underlying mechanisms. This paper surveys our current understanding of several of the key issues governing the rheological behavior of MRF and ERF, with particular focus on recent progress made in important areas such as the behavior under high fields, sedimentation, temperature dependence, effect of wall surface conditions, and advances made in developing practical modelling strategies.

Magneto-resistive device having soft reference layer

Abstract: A magneto-resistive device includes first and second ferromagnetic layers having different coercivities, and a spacer layer between the first and second layers. Each ferromagnetic layer has a magnetization that can be oriented in either of two directions.

Combined low-temperature scanning probe microscopy and magneto-transport experiments for the local investigation of mesoscopic systems

Abstract: Hi

Magneto-resistive device including soft synthetic ferrimagnet reference layer

Abstract: A memory device includes a data layer having a magnetization that can be oriented in first and second directions; and a synthetic ferrimagnet reference layer. The data and reference layers have different coercivities.

Magneto-Inductive Communications

Abstract: Utilizing quasi-static AC magnetic fields as the channel, MISL has developed a group of unique communication, signaling and navigation systems. We refer to this technology as magneto-inductive (MI). The physical properties of magnetic fields enable these system to operate through any natural medium or medium boundary. Working with the US Navy's Coastal Systems Station, MISL has conducted several test and evaluations of MI system components operating in very shallow water, surf zone and beach zone environments.

Numerical Simulation of Solar Magneto-Convection

Abstract: Numerical simulations of the interaction of magnetic field and solar surface convection are reviewed. Emphasis is laid upon the relevant physical processes and on work with implications for the interpretation of observational results. We outline the development of the two main lines of research in the past 35 years, namely studies of idealized magneto-convection and ‘realistic’ solar simulations, and discuss representative results.

Magneto resistive sensor

Abstract: A magneto resistive sensor having a GMR magnetic laminated film is disclosed. The GMR magnetic laminated film comprises a plurality of magnetic thin layers having a NiCoFeB composition alternately laminated with a nonmagnetic thin layer, such as copper layer. Since the magnetic thin layer contains B in its composition, the GMR magnetic laminated film can stand in magneto resistance ratio (ΔR/R %) under a high temperature of up to 250 degrees centigrade. By the reason, electric wiring can be connected by a lead-free solder to assemble a magnetic resistive sensor for a magnetic rotary encoder. The thermal resistance variation and the magneto resistance ratio are further improved when a NiFeCr underlayer is used under the GMR magnetic laminated film.

Method and device for magnetizing and inspecting a rotor for magneto generators

Abstract: A single apparatus for magnetizing permanent magnet segments mounted on a cylindrical shell for use in a flywheel magneto or the like. Not only are the segments magnetized but also their magnetic strength is measured when the magnetized element is moved out of the magnetizing section. Prior to that, however, the circumferential location of the timing mark on the flywheel is also verified, within the single apparatus.

Sensor module with stamped sheet metal part ( magneto resistive throttle valve sensor )

Abstract: A magneto resistive position sensor module (12) has flexible planar connections (14a,14b) to the processing electronics (13).

Barkhausen Noise Application in the Detection of Stress and Fatigue Damage

Abstract: Aimed at the measuring means and methods of mechanical parameters, such as stress, fatigue life, and hardness of ferromagnetic materials, this paper applies one of the properties of ferromagnetic materials, that is, magnetic Barkhausen noise effect, and adopts magneto -elasticity noise theory in the research into the mechanism for the generation of magneto -elasticity noise Thus, a magneto -elasticity noise sensor and a relative detector for the stress of ferromagnetic materials and fatigue damage are developed, which is of high speed, high accuracy, and is easy to carry

Magneto-resistive element, magneto-resistive head, magneto-resistance detecting system and magnetic storage system

Abstract: PROBLEM TO BE SOLVED: To obtain a head corresponding to a narrow track reproducing by reducing an effective reproducing track width of a reproducing part in a recording/reproducing head. SOLUTION: A magneto-resistive element comprising a magneto-resistive layer 3 having a width almost corresponding to a recording track width of a magnetic recording medium, a vertical bias layer 4 disposed adjacent to both sides of the magneto-resistive layer 3 and a pair of electrodes 6 which is provided on the vertical bias layer 4 and electrically connected with the magneto- resistive layer 3 comprises an insulating layer 5 provided between the vertical bias layer 4 and the electrodes 6. And a part of the electrodes 6 is in contact with the magneto-resistive layer 3 and the interval between the electrodes 6 is formed so as to be narrower than the width of the magneto-resistive layer 3.

Temperature Dependence of Magneto Current in Spin Valve Transistor: A phenomenological Study

Abstract: The temperature dependence of magneto current in the spin spin valve transistor system is theoretically explored based on phenomenological model. We find that the collector current strongly depends on the relative orientation of magnetic moment of ferromagnetic metals due to spin mixing effect. For example, the collector current is decreasing in the parallel case with increasing temperature, and it is increasing in anti-parallel configuration. We then obtain decreasing magneto current with increasing temperature. The result accords with the experimental data in qualitative manner. This phenomenological model calculations suggest that spin mixing effect may play an important role in the spin valve transistor system at finite temperature.

Magneto-hydrodynamically (MHD) directed flow in microfluidic networks

Abstract: Magneto-hydrodynamic flow is applied to generate rotation of liquid around a wire electrode. An interesting approach is to apply the effect in a microfabricated device. A buffer solution is pumped by EOF in a magnetic field through the channel network. The Lorentz-force causes the flow to deviate into one of the side channels. Thus, an external magnetic flow-switch for use in EOF driven flow systems has been realized.

Enclosed permanent-magnetic power frequency alternator

Abstract: The utility model discloses a closed-type magneto alternator structure. Both ends of a casing of the utility model are provided with end caps. Main shafts are fixed on the end caps. A stator is fixed in the casing. A stator winding is fixed in a stator core. A rare earth magnetic steel and a magnetic yoke are fixed on the main shafts. The utility model is characterized in that from two to five sections of homopolarity magnetic steels are arrayed with gaps to form the rare earth magnetic steel. The magnetic steels are provided with blades. An outer main shaft of a back end cap is provided with a metallic blade. The temperature rise of the alternator is low. The utility model can work continuously and reliably.