Showing papers on "Magneto published in 2012"

Reflection of Plane Waves in a Rotating Transversly Isotropic Magneto-Thermoelastic Solid Half-Space

Abstract: Reflection of Plane Waves in a Rotating Transversly Isotropic Magneto-Thermoelastic Solid Half-Space The governing equations of a rotating transversely isotropic magneto-thermoelastic medium are solved to obtain the velocity equation, which indicates the existence of three quasi plane waves. Reflection of these plane waves from a stress-free thermally insulated surface is studied to obtain the reflection coefficients of various reflected waves. The effects of anisotropy, rotation, thermal and magnetic fields are shown graphically on these coefficients.

Influence of Gd-doping in La0.7Ca0.3MnO3 on its structural and Magneto-Electrical Properties

Abstract: Abstract Bulk samples of gadolinium doped manganites with compositional formula La 0.7 − x Gd x Ca 0.3 MnO 3 ( x =0.0 and 0.1) were prepared by conventional solid state reaction method. After characterizing the samples by X-ray diffraction, scanning electron microscope and energy dispersive X-ray spectrometer, a systematic investigation of electrical and magneto-transport properties has been investigated. The replacement of La ion by Gd results in a decrease of the metal–insulator transition temperature T MI and the magnetoresistance as well as the resistivity are found to increase. The electrical resistivity in the entire temperature range fit well with the phenomenological percolation model, which is based upon an approach that the system consists of the phase separated ferromagnetic metallic and paramagnetic insulating regions.

Experimental and Numerical Investigations of the Interaction between a Plasma Arc And a Laser

Abstract: Plasma arc welding (PAW) is a modern welding technique for challenging joining tasks in a wide range of materials and plate thicknesses, A further improvement of the welding characteristics involving achievable welding speed, process stability and penetration depth is expected by an additional low energy laser beam with a maximum output power of 600 W, The paper presents an experimental and numerical analysis of the interaction between a plasma arc and a superimposed laser beam, The experiments are carried out with a non-concentric set-up of the plasma arc column and the laser beam, As results of bead-on-plate welding trials the cross-sectional weld areas were presented in order to demonstrate benefits of the combined process in comparison to separately conducted arc and laser welding, Furthermore, high speed video images (1 kHz frame rate) with synchronized current and voltage recording (1 MHz frame rate) were used, The experimental results demonstrate a different behaviour for welding steel and aluminium, In case of welding aluminium, an arc guidance was observed whereas destabilization effects occur for welding ferrous alloys, A numerical magneto hydro dynamical (MHD) arc model with a concentric set-up of arc column and laser beam set-up was aimed to improve our understanding of relevant interaction phenomena between the plasma arc and the laser beam.

From first-order magneto-elastic to magneto-structural transition in (Mn,Fe)1.95P0.50Si0.50 compounds

Abstract: We report on structural, magnetic and magnetocaloric properties of MnxFe1.95-xP0.50Si0.50 (x > 1.10) compounds. With increasing the Mn:Fe ratio, a first-order magneto-elastic transition gradually changes into a first-order magneto-structural transition via a second-order magnetic transition. The study also shows that thermal hysteresis can be tuned by varying the Mn:Fe ratio. Small thermal hysteresis (less than 1 K) can be obtained while maintaining a giant magnetocaloric effect. This achievement paves the way for real refrigeration applications using magnetic refrigerants.

Unbalanced Magnetic Forces in Rotational Unsymmetrical Transverse Flux Machine

Abstract: The torque and unbalanced magnetic forces in permanent magnet machines are resultants of the tangential, axial and normal magnetic forces, respectively. Those are in general influenced by pole-teeth-winding configuration. A study of the torque and unbalanced magnetic forces of a small flux concentrating permanent magnet transverse flux machine (FCPM-TFM) in segmented compact structure is presented in this paper. By using FLUX3D software from Cedrat, Maxwell stress tensor has been solved. Finite element (FE-) magneto static study followed by transient analysis has been conducted to investigate the influence of unsymmetrical winding pattern, in respect to the rotor, on the performance of the FCPM-TFM. Calculating the magnetic field components in the air gap has required an introduction of a 2D grid in the middle of the air gap, whereby good estimations of the forces are obtained. In this machine, the axial magnetic forces reveal relatively higher amplitudes compared to the normal forces. Practical results of a prototype motor are demonstrated through the analysis.

Magneto-Electric Coupling in a Multiferroic Tunnel Junction Functioning as a Magnetic-Field-Effect Transistor

Abstract: A nanoscaled multilayered composite structure made of a ferroelectric tunnel capacitor attached to a magnetic sensor layer is studied using a Landau-Ginzburg thermodynamic model. The relation between the polarization and the mechanical load induced by the magnetic signal via electrostriction is established. Our results suggest that the spin-flip-induced resistance change of such a structure may reach hundreds of percents to orders of magnitude, which is sufficiently strong to allow its use as a magnetic-field-effect transistor.

Motion detection of a micromechanical cantilever through magneto-piezovoltage in two-dimensional electron systems

Abstract: We study the strain-induced voltage generation, i.e., piezovoltage, in a two-dimensional electron system under a magnetic field at low temperature. We find its strong magnetic-field dependence, where the voltage increases up to several microvolts at the boundaries between localized and extended electronic states. The order of magnitude of the generated electrical power is comparable to that of the energy dissipation in mechanical vibration, indicating high-efficiency mechanical-to-electrical energy transduction.

Fabrication of Microcavity with Magneto- and Electro-Optical Film

Abstract: We fabricated a microcavity –a magneto-optical (MO) film and an electro-optical (EO) film are sandwiched between two Bragg mirrors (BMs)– for development of magneto-optical spatial light modulators driven by electric field (e-MOSLMs). We used (Bi0.5Dy0.7Y1.8)3(Fe3.3Al1.7)5O12 as a MO film and (Pb91La9)1(Zr65Ti35)1O3 (PLZT) as an EO film. The samples showed enhanced Faraday rotation loops and electrical polarization loops, simultaneously. The X-ray diffraction patterns, MO and EO characteristics were measured. Experimental results showed that EO and MO films were successfully formed between BMs.

Low power field generation for magneto-optic fiber-based interferometric switches

Abstract: A new fiber-based, magneto-optic switch is proposed with a novel approach for low power and efficient operation. The switch, with reasonable switching speed compared to competitive designs, operates at considerably reduced power levels, which makes it a practical deployable solution. The basic switch setup consists of a Faraday rotator in a Sagnac fiber-optic interferometer in which optical switching is controlled by an electronic driving circuit. The electronic system generates a magnetic field through the Faraday rotator by driving current through a specially designed two-coil system. The new coil system allows for sufficient field generation at low quiescent power levels while maintaining very short optical rise and fall times. The design and considerations as well as the effect of mutual inductance between the two coils and its influence on switching times are investigated. The optical system consists of a Sagnac interferometer with a Faraday rotator within the Sagnac loop. Appropriate phase shift for...

Transient dynamic behavior of two phase magneto-electro-elastic sensors bonded to elastic rectangular plates

Abstract: Transient dynamic behavior of Magneto-electro-elastic (MEE) sensors bonded to a mild steel plate using 3D magnetic vector potential approach is presented. The electric field induced by time varying magnetic field is non-conservative and can be described by electric scalar potential and magnetic vector potentials. The aim of the study is to find how different volume fractions of the MEE composite behave in sensor applications at various locations on the plate subjected to different boundary conditions. The 3D plate and the sensor are modeled using eight nodded brick element with sufficient numbers of elements across the thickness direction to capture the bending behavior of the plate correctly. The four boundary conditions chosen are one symmetric boundary condition (CCCC), one free edge (CCFC), two adjacent free edges (CFFC) and two opposite free edges (FCFC). It is seen that the electric response is maximum when volume fraction vf=0.2 for all sensor locations with different boundary conditions. The boundary conditions significantly influence the magnetic response; volume fraction vf=0.4 gives noticeably higher values of magnetic potential in almost all the cases except for CFFC boundary condition with sensor near the edge and FCFC boundary condition with sensor at an off set distance from the edge.

Unified Continuum Modeling of Fully Coupled Thermo-Electro-Magneto-Mechanical Behavior, with Applications to Multifunctional Materials and Structures

Abstract: Multifunctional structures based on active or smart materials are being implemented in a wide range of aerospace, infrastructural, automotive, and biomedical applications. However, smart materials are underutilized in these applications, as majority of the modeling and characterization techniques of smart materials limit the understanding of material behavior to low-signal, small-deformation ranges of operation, or regimes where only a subset of the thermal, electrical, magnetic, and mechanical interactions are dominant. By modeling smart materials in their fully coupled, nonlinear, three-dimensional, multiphysics process domain rather than in a specific regime of behavior, design of the next-generation of load-carrying smart structures with superior performance capabilities can be enabled. The objective of this work is to develop mathematical and computational models for modern multifunctional materials and devices. This dissertation focuses on development of a first-principle based theoretical framework for modeling and characterization of fully coupled thermo-electro-magnetomechanical behavior in a multiphysics process domain, that can be utilized to (i) develop constitutive models and free energy functions for a broad range of smart materials using the fundamentals of equilibrium and non-equilibrium thermodynamics, (ii) develop asymptotic models for design and analysis of load-bearing antenna, which

Solar magneto-convection

Abstract: An overview is given about recent developments and results of comprehensive simulations of magneto-convective processes in the near-surface layers and photosphere of the Sun. Simulations now cover a wide range of phenomena, from whole active regions, over individual sunspots and pores, magnetic flux concentrations and vortices in intergranular lanes, down to the intricate mixed-polarity structure of the magnetic field generated by small-scale dynamo action. The simulations in concert with high-resolution observations have provided breakthroughs in our understanding of the structure and dynamics of the magnetic fields in the solar photosphere.

Ignition energy detection device for magneto

Abstract: The utility model discloses an ignition energy detection device for a magneto, which belongs to the field of magnetos. The ignition energy detection device comprises a discharge probe, a first probe, a second probe, a resistor, an oscilloscope and an ignition energy calculation module, wherein the discharge probe discharges electricity to enable a secondary coil loop of an ignition system of the magneto to generate discharge current and voltage, the first probe collects discharge voltage and transmits the discharge voltage to the oscilloscope, the second probe collects the voltage value of the resistor and transmits the voltage value to the oscilloscope, if the resistance value of the resistor is X Ohm, the voltage value of the resistor is equivalent to the discharge current magnified by X times, so the oscilloscope obtains a discharge current-voltage curve, and the ignition energy calculation module works out the ignition energy of the magneto according to the discharge current-voltage curve. Due to adoption of the ignition energy detection device, the manufacturing cost, the fault rate and the maintenance cost of the detection device are reduced.

Magnetic Force Control Technique for Recycling and Environmental Preservation

Abstract: The applicability of the two types of magnetic separation system, high gradient magnetic separation (HGMS) and Magneto Archimedes method were studied considering the magnetic susceptibility of targeted substances. It was noted that the combination of the two methods can control the almost all the substances, paramagnetic and diamagnetic in addition to ferromagnetic substances. The principle of the methods was given and the conceput of the magnet force control technology is discussed. The practical applications of the technique were introduced together with the new application of HGMS.

Free vibration studies of Functionally Graded magneto-electro- elastic plates/shells by using solid-shell elements

Abstract: In this article, free vibration studies on functionally graded magneto-electro-elastic plates and cylindrical shells have been carried out by means of finite element method. The functionally graded material is assumed to be exponential in the thickness direction. The present finite element is formulated on the basis of assumed natural strain, enhanced assumed strain method and using displacement components, electric potential and magnetic potentials as nodal degrees of freedom. This element can be used as solid element and can also be applied to model thin curved shell structures. Numerical studies include the influence of the different exponential factor, magnetic and piezoelectric effect on the natural frequencies. Obtained numerical results are in good agreement with the semi-analytical finite element solutions available in the literature.

Magneto-Thermo-Mechanical Response and Magneto-Caloric Effect in Magnetic Shape Memory Alloys

Abstract: Magneto-Thermo-Mechanical Response and Magneto-Caloric Effect in Magnetic Shape Memory Alloys. (May 2012) Cengiz Yegin, B.S., Bogazici University, Turkey Chair of Advisory Committee: Dr. Ibrahim Karaman Ni-Co-Mn-In system is a new type of magnetic shape memory alloys (MSMAs) where the first order structural and magnetic phase transitions overlap. These materials can generate large reversible shape changes due to magnetic-field-induced martensitic transformation, and exhibit magneto-caloric effect and magnetoresistance. Ni-Co-Mn-Sn alloys are inexpensive alternatives of the Ni-Co-Mn-In alloys. In both materials, austenite has higher magnetization levels than martensite. Fe-Mn-Ga is another MSMA system, however, whose magnetization trend is opposite to those of the Ni-Co-Mn-X (In-Sn) systems upon phase transformation. The MSMAs have attracted great interest in recent years, and their magnetic and thermo-mechanical properties need to be further investigated. In the present study, the effects of indium concentration, cooling, and annealing on martensitic transformation and magnetic response of single crystalline Ni-Co-Mn-In alloys were investigated. Increasing indium content reduced the martensitic transformation start (Ms) temperature, while increasing temperature hysteresis and saturation magnetization. Increasing annealing temperature led to an increase in the Ms

Magnet temperature estimation device, and magnet temperature estimation method of rotary electric machine

Abstract: PROBLEM TO BE SOLVED: To provide a magnet temperature estimation device and a magnet temperature estimation method, capable of accurately estimating the magnet temperature of a magnet included in a rotor of a rotary electric machine.SOLUTION: A magnet temperature estimation device 10 has a magnet temperature calculation part 132 for estimating the magnet temperature of a magnet included in a rotor of a rotary electric machine 12. The magneto temperature calculation part 132 estimates the magnet temperature using at least a parameter related to a transmission 22 (a planetary gear mechanism) coupled with the rotary electric machine 12.