Design and Magnetic Field Uniformity of Giant Magnetostrictive Ultrasonic Transducer for Progressive Sheet Forming

Design of a giant magnetostrictive ultrasonic transducer for progressive sheet forming was presented.A dynamic analysis of the theoretically designed ultrasonic vibration system was carried out using the finite element method(FEM).In addition,simulations were performed to verify the theoretical design.Then,a magnetically conductive material was added between the giant magnetostrictive rod and the permanent magnet.Besides,magnetic field simulations of the transducer were performed.The influence of the material thickness of the magnetically conductive material on uniformity of the induced magnetic field was studied.Furthermore,the impedance analysis and amplitude measurement were performed to compare the performance of transducers with and without the magnetically conductive material.The experimental results show that the magnetic field uniformity is the highest when the magnetically conductive material has a thickness of about 1.6 mm.The output amplitude of the giant magnetostrictive transducer is improved by adding the magnetically conductive material.Moreover,the mechanical quality factor and impedance are reduced,while the transducer operates more stably.

Research on electromagnetic relay's dynamic characteristics disturbed by uniform static magnetic field

Electromagnetic relay is a widely used apparatus which usually works in a magnetic disturbance environment. To evaluate its electromagnetic compatibility (EMC) in a static magnetic field, dynamic characteristics of a clapper relay in a uniform static magnetic field situation based on the finite element method (FEM) is studied. Influences of the magnetic field on dynamic parameters (delay time, pick-up time, end pressure, and final velocity) as well as a situation in which the relay cannot function normally are analyzed. Simulation reveals that the external magnetic field which weakens the relay’s air-gap field has a greater influence on the relay’s dynamic parameters than the one strengthening the field. The validity of the simulation is verified by measured results of coil current and armature displacement.

Donor-bound electron states in a two-dimensional quantum ring under uniform magnetic field

The electron states in a two-dimensional GaAs/AlGaAs quantum ring are theoretically studied in effective mass approximation. On-centre donor impurity and uniform magnetic field perpendicular to the ring plane are taken into account. The energy spectrum with different angular momentum changes dramatically with the geometry of the ring. The donor impurity reduces the energies with an almost fixed value; however, the magnetic field alters energies in a more complex way. For example, energy levels under magnetic field will cross each other when increasing the inner radius and outer radius of the ring, leading to the fact that the arrangement of energy levels is distinct in certain geometry of the ring. Moreover, energy levels with negative angular momentum exhibit the non-monotonous dependence on the increasing magnetic field.

Entropy optimization in cubic autocatalysis chemical reactive flow of Williamson fluid subjected to viscous dissipation and uniform magnetic field

This research elaborates magnetohydrodynamics (MHD) impact on non-Newtonian (Williamson) fluid flow by stretchable rotating disks.Both disks are rotating with different angular velocities and different stretching rates.Viscous dissipation aspect is considered for energy expression formulation.Entropy generation analysis is described via implementation of thermodynamic second law.Chemical processes (heterogeneous and homogeneous) subjected to entropy generation are introduced first time in literature.Boundary-layer approach is employed for modeling.Apposite variables are introduced for non-dimensionalization of governing systems.Homotopy procedure yields convergence of solutions subjected to computations of highly nonlinear expressions.The significant characteristics of sundry factors against thermal,velocity and solutal fields are described graphically.Besides,tabular results are addressed for engineering quantities (skin-friction coefficient,Nusselt number).The outcomes certify an increment in temperature distribution for Weissenberg (We) and Eckert (Ec) numbers.

Design and implementation of square Helmholtz coil for uniform magnetic field generation

In order to calibrate electrical instruments and generate a constant magnetic field, a novel design method for square Helmholtz coil is proposed. According to the superposition principle in electromagnetics, the theory of the square Helmholtz coil is established, and the design method is verified by Matlab calculation. Compared with conventional circular Helmholtz coil, the novel square one is with a larger uniform region. Simulation work is conducted in Maxwell, and the distribution of the magnetic field is obtained. The results demonstrate the validation of the applied calculation method of the proposed Helmholtz model. The space utilization rate η is used to make a comparison between the square and circular coils for the uniform region. The square Helmholtz coil is fabricated, the length of a single square coil is 1.5 m, and the amplitude of the magnetic field is controlled by the current. The GSM-19 T proton magnetometer is used to measure the amplitude of the magnetic field generated by the square Helmholtz coil. Experimental results indicate that a wide-range variable uniform magnetic field from 0 to 120 μT is generated in the center of Helmholtz coils.

Quantum Mechanical Fourier-Hankel Representation Transform for an ElectronMoving in a Uniform Magnetic Field

We find quantum mechanical Fourier-Hankel representation transform for an electron moving in a uniform magnetic field. The physical meaning of Fourier decomposition states of electron's coordinate eigenstate and the momentum eigenstate are revealed.

Atomic coherent states as energy eigenstates of a Hamiltonian describing a two-dimensional anisotropic harmonic potential in a uniform magnetic field

In this paper we find that a set of energy eigenstates of a two-dimensional anisotropic harmonic potential in a uniform magnetic field is classified as the atomic coherent states ｜τ） in terms of the spin values of j in the Schwinger bosonic realization. The correctness of the above conclusions can be verified by virtue of the entangled state 〈η｜ representation of the state ｜τ）.

Electron-Cyclotron Laser Using Free-Electron Two-Quantum Stark Radiation in a Strong Uniform Axial Magnetic Field and an Alternating Axial Electric Field in a Voltage-Supplied Pill-Box Cavity

We consider the radiation from the beam electrons traveling in a strong uniform axial magnetic field and an axial alternating electric field of wavelength Aw generated by a voltage-supplied pill-box cavity. The beam electrons emit genuine laser radiation that propagates only in the axial direction through free-electron two- quantum Stark radiation. We find that laser radiation takes place only at the expense of the axial kinetic energy when Aw 〈〈 c/（ωc/γ）, where ωc/γ is the relativistic electron--cyclotron frequency. We formulate the laser power based on quantum-wiggler electrodynamics, and envision a laser of length lore with estimated power 0.1 GW/（kA） in the 10-4 cm wavelength range.

Electrostatic Modes of Dusty Plasmas in a Uniform Magnetic Field

Electrostatic dusty plasma waves in a uniform magnetic field are studied. Unless the magnetic field is extremely strong, the dust particles can hardly be magnetized, while however, electrons and ions are easily done so. Electrostatic modes in such dusty plasmas can then be investigated by making use of the 'moderately magnetized' assumption of magnetized electrons and ions, and unmagnetized dust particles. In a high frequency range, due to the existence of dust component, both frequencies of Lang- muir waves (parallel to the magnetic field) and upper hybrid waves (perpendicular to the field) are reduced. In the frequency range of ion waves, besides the effect on dust-ion-acoustic waves propagating parallel to the magnetic field, the frequency of ion cyclotron waves perpendicular to the magnetic field is also enhanced. In a very low dust frequency range, we find an 'ion-cyclotron- dust-acoustic' mode propagating across the field line with a frequency even slower than dust acoustic waves.

Electron Transport Behavior in a Mirror Magnetic Field and a Uniform Electric Field

A Monte Carlo simulation technique has been used to model the electron transport' behavior, especially the electron density and energy distributions under the influence of a mirror magnetic field and a uniform electric field in a positive column of helium direct current(DC) gas discharge Graphs showing the electron density and energy distributions, and the percentage of electrons that reach the wall and the end of the positive column are presented. The results indicate that the mirror magnetic field can control the electron transport behavior in the positive column which are in good agreement with experimental results.

Design of Braunbeck Coil for Nuclear Magnetic Resonance Gyro Magnetic Field Excitation

For generating a uniform and steady magnetic field, Helmholtz coil is extensively used in nuclear magnetic resonance gyro(NMRG). Unfortunately, the volume of Helmholtz coil makes it inconvenient to miniaturize NMRG. This study introduces Braunbeck coil that can be used in magnetic field excitation system. Braunbeck coil can produce homogeneous magnetic field within a limit space, and occupy a small volume. In addition, this study presents mathematical expressions that can be used to calculate the area of uniform magnetic field. Experimental test verifies the effectiveness of the proposed design, and the results accord closely with the actual simulation.

Study of heat transfer and flow of nanofluid in permeable channel in the presence of magnetic field

In this paper,laminar fluid flow and heat transfer in channel with permeable walls in the presence of a transverse magnetic field is investigated.Least square method(LSM)for computing approximate solutions of nonlinear differential equations governing the problem.We have tried to show reliability and performance of the present method compared with the numerical method(Runge-Kutta fourth-rate)to solve this problem.The influence of the four dimensionless numbers:the Hartmann number,Reynolds number,Prandtl number and Eckert number on non-dimensional velocity and temperature profiles are considered.The results show analytical present method is very close to numerically method.In general,increasing the Reynolds and Hartman number is reduces the nanofluid flow velocity in the channel and the maximum amount of temperature increase and increasing the Prandtl and Eckert number will increase the maximum amount of theta.

Microscopic calculation of the magnetic field of neutron stars

Based on the Dirac equation describing an electron moving in a uniform and cylindrically symmetric magnetic field which may be the result of the self-consistent mean field of the electrons themselves in a neutron star, we have obtained the eigen solutions and the orbital magnetic moments of electrons in which each eigen orbital can be calculated. From the eigen energy spectrum we find that the lowest energy level is the highly degenerate orbitals with the quantum numbers pz = 0, n = 0, and m ≥0. At the ground state, the electrons fill the lowest eigen states to form many Landau magnetic cells and each cell is a circular disk with the radius λfree and the thickness λe, where λfree is the electron mean free path determined by Coulomb cross section and electron density and λe is the electron Compton wavelength. The magnetic moment of each cell and the number of cells in the neutron star are calculated, from which the total magnetic moment and magnetic field of the neutron star can be calculated. The results are compared with the observational data and the agreement is reasonable.

Analysis of the Effect of Field Distribution of Chamber in Dipole

With the calculation and measuring experiment methods,the effect of vacuum chamber materials' magnetic permeability on field distribution in a dipole magnet is discussed.The results show that when the relative magnetic permeability of chamber materialμ_r≠1,it will affect the field uniformity.Once the high field uniformity is required, the material property and size of vacuum chamber in a dipole magnet have to be taken into account carefully.

Reconfigurable Transmitter Coil Structure for Highly Efficient and Misalignment-insensitive Wireless Power Transfer Systems in Megahertz Range

The structural optimization of coils is a key issue in wireless power transfer(WPT)applications owing to size limitations.In this study,a novel planar-spiral transmitter coil(TX-coil)with an outer-tight and inner-sparse configuration is proposed to achieve a high quality factor(Q-factor)and uniform magnetic field,which ensures high efficiency and improves the misalignment tolerance for several-megahertz WPT systems.Furthermore,a closed-form expression for the Q-factor is provided and analyzed for coil optimization.By using this method,a TX-coil with an outer diameter of 100 mm and a wire diameter of 1.5 mm is designed and tested at 1 MHz.Finite element method simulations and experimental results demonstrate that the Q-factor is increased by about 8%in comparison with evenly spaced planar spiral coils,which is achieved while ensuring a relatively uniform magnetic field.