scholarly journals Ablation in Externally Applied Electric and Magnetic Fields

Nanomaterials ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 182
Author(s):  
Jovan Maksimovic ◽  
Soon-Hock Ng ◽  
Tomas Katkus ◽  
Nguyen Hoai An Le ◽  
James W.M. Chon ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Laser Ablation ◽  
Lorentz Force ◽  
Negative Electrode ◽  
Magnetic Flux Density ◽  
Ripple Formation ◽  
Electric And Magnetic Fields ◽  
Potential Applications ◽  
Application Potential ◽  
X Ray Absorption

To harness light-matter interactions at the nano-/micro-scale, better tools for control must be developed. Here, it is shown that by applying an external electric and/or magnetic field, ablation of Si and glass under ultra-short (sub-1 ps) laser pulse irradiation can be controlled via the Lorentz force F = e E + e [ v × B ] , where v is velocity of charge e, E is the applied electrical bias and B is the magnetic flux density. The external electric E-field was applied during laser ablation using suspended micro-electrodes above a glass substrate with an air gap for the incident laser beam. The counter-facing Al-electrodes on Si surface were used to study debris formation patterns on Si. Debris was deposited preferentially towards the negative electrode in the case of glass and Si ablation. Also, an external magnetic field was applied during laser ablation of Si in different geometries and is shown to affect ripple formation. Chemical analysis of ablated areas with and without a magnetic field showed strong chemical differences, revealed by synchrotron near-edge X-ray absorption fine structure (NEXAFS) measurements. Harnessing the vectorial nature of the Lorentz force widens application potential of surface modifications and debris formation in external E-/B-fields, with potential applications in mass and charge spectroscopes.

PDMS Membrane Microactuator for Focal Tunable Microlens

2006 ◽  
Author(s):  
Seok Woo Lee ◽  
Seung S. Lee
Keyword(s):  
Magnetic Field ◽  
Magnetic Flux ◽  
Flux Density ◽  
Lorentz Force ◽  
Spin Coating ◽  
Large Displacement ◽  
Pdms Membrane ◽  
Magnetic Flux Density ◽  
Optical Performance ◽  
Electrical Components

In this paper, PDMS membrane for a large displacement is fabricated by new fabrication process which can be integrated with electrical components on substrates fabricated by conventional microfabrication processes and the performance of the membrane using electromagnetism was evaluated. Rectangular PDMS membranes are designed as 2mm and 3mm in width, respectively and are actuated by Lorentz force induced by current paths spread on the membrane. The PDMS membrane is fabricated by reducing a viscosity of uncured PDMS with dilution and spin coating on the substrate on which electric components generating Lorentz force. Finally, PDMS membrane including electric components is opened by a bulk micromachining. The device is tested in magnetic field induced by Nd-Fe-B magnet whose magnetic flux density is 90G. When applied currents are 20, 25, and 30mA, the maximum deflections of membranes are 1.21, 3.07, and 20.2μm for 1.5mm width membrane and 3.34, 31.0, and 50.9μm for width 3mm membrane, respectively. The large displacement PDMS membrane actuator has potentially various applications such as fluidics, optics, acoustics, and electronics. Currently, we are planning to measure the optical performance of the actuator as a focal tunable liquid lens.

Galvanomagnetic and thermomagnetic phenomena

2004 ◽  
Author(s):  
Robert E. Newnham
Keyword(s):  
Magnetic Field ◽  
Heat Flow ◽  
Magnetic Fields ◽  
Hall Effect ◽  
Electric Current ◽  
Lorentz Force ◽  
Electrical Resistance ◽  
Magnetic Flux Density ◽  
Wide Range ◽  
The Magnetic Field

The Lorentz force that a magnetic field exerts on a moving charge carrier is perpendicular to the direction of motion and to the magnetic field. Since both electric and thermal currents are carried by mobile electrons and ions, a wide range of galvanomagnetic and thermomagnetic effects result. The effects that occur in an isotropic polycrystalline metal are illustrated in Fig. 20.1. As to be expected, many more cross-coupled effects occur in less symmetric solids. The galvanomagnetic experiments involve electric field, electric current, and magnetic field as variables. The Hall Effect, transverse magnetoresistance, and longitudinal magnetoresistance all describe the effects of magnetic fields on electrical resistance. Analogous experiments on thermal conductivity are referred to as thermomagnetic effects. In this case the variables are heat flow, temperature gradient, and magnetic field. The Righi–Leduc Effect is the thermal Hall Effect in which magnetic fields deflect heat flow rather than electric current. The transverse thermal magnetoresistance (the Maggi–Righi–Leduc Effect) and the longitudinal thermal magnetoresistance are analogous to the two galvanomagnetic magnetoresistance effects. Additional interaction phenomena related to the thermoelectric and piezoresistance effects will be discussed in the next two chapters. In tensor form Ohm’s Law is . . .Ei = ρijJj , . . . where Ei is electrical field, Jj electric current density, and ρij the electrical resistivity in Ωm. In describing the effect of magnetic field on electrical resistance, we expand the resistivity in a power series in magnetic flux density B. B is used rather than the magnetic field H because the Lorentz force acting on the charge carriers depends on B not H.

Analysis On the Inception of the Magnetohydrodynamic Flow Instability in the Annular Linear Induction Pump Channel

2021 ◽  
Author(s):  
Ruijie Zhao ◽  
Xiaohui Dou ◽  
Qiang Pan ◽  
ZHANG Desheng ◽  
Bart van Esch
Keyword(s):  
Magnetic Field ◽  
Pressure Gradient ◽  
Lorentz Force ◽  
Flow Rate ◽  
Flow Instability ◽  
Fluid Velocity ◽  
Magnetic Reynolds Number ◽  
Wave Number ◽  
Magnetic Flux Density ◽  
Linear Induction

Abstract Flow instability is the intricate phenomenon in the Annular Linear Induction Pump when the pump runs at off-design working condition. A 3D numerical model is built to simulate the flow in the pump channel. The pump heads at different flow rates are accurately predicted by comparing with experiment. The simulation results show the fluid velocity is circumferentially non-uniform in the pump channel even at the nominal flow rate. The flow in the middle sector continuously decelerates to nearly zero with the reducing flow rate. Reversed flow occurs in the azimuthal plane, followed by vortex flow. The reason for the heterogeneous velocity field is attributed to the mismatch between non-uniform Lorentz force and relatively even pressure gradient. It is seen that the flow in the region of small Lorentz force has to sacrifice its velocity to match with the pressure gradient. An analytic expression of the axial Lorentz force is then developed and it is clearly demonstrated the Lorentz force could be influenced by the profiles of velocity and radial magnetic flux density. The coupling between velocity and magnetic field is studied by analyzing the magnitudes of different terms in the dimensionless magnetic induction equation. It is found the dissipation term is determined not only by the magnetic Reynolds number but the square of wave number of the disturbance in each direction. The smaller disturbing wave number weakens the dissipating effect, resulting in the larger non-uniform magnetic field and axial Lorentz force.

Numerical Simulation of Electromagnetic Phenomena and Solidification under a Pulsed Magnetic Field

2019 ◽  
Vol 944 ◽  
pp. 52-58
Author(s):  
Qi Peng Chen ◽  
Hidetaka Oguma ◽  
Hou Fa Shen
Keyword(s):  
Magnetic Field ◽  
Temperature Field ◽  
Lorentz Force ◽  
Periodic Oscillation ◽  
Side Surface ◽  
Pulsed Magnetic Field ◽  
Magnetic Flux Density ◽  
Meridian Plane ◽  
Cu Alloy ◽  
Transient Electromagnetic

The transient electromagnetic phenomena and solidification of Al-Cu alloy under a typical pulsed magnetic field (PMF) are numerically studied by a two-dimensional (2D) axisymmetric model. The results show that the magnetic flux density, eddy current density, Lorentz force and Joule heat all inherit the instantaneous and intermittent feature of the PMF, and their amplitudes and phases decrease with the increasing distance to the side surface of the ingot. The Lorentz force appears alternatively as pressure force and pull force mainly in the radial direction. Forced convection is induced in the liquid metal, and the flow field is composed of a clockwise vortex and a counter-clockwise vortex in the meridian plane of the ingot. The melt velocity is accompanied with a dramatic periodic oscillation. The temperature field in the ingot with the PMF tends uniform due to the mixing effect of the melt flow. However, the convection is damped soon after the solidification starts due to the increasing penetration resistance, and the temperature field gradually approximates that in the case without the PMF.

Modelling of the Computer Classroom Electromagnetic Field

1970 ◽  
Vol 109 (3) ◽  
pp. 75-80 ◽  
Author(s):  
P. Baltrenas ◽  
R. Buckus ◽  
S. Vasarevicius
Keyword(s):  
Magnetic Field ◽  
Electromagnetic Field ◽  
Magnetic Flux ◽  
Electric Field ◽  
Electromagnetic Fields ◽  
Magnetic Flux Density ◽  
Computer Classroom ◽  
Electric And Magnetic Fields ◽  
Long Time ◽  
Video And Audio

Operation of office, video and audio equipment generates electromagnetic fields. Many employees who use computers for a long time complain of headaches and other health troubles. This has become a serious problem as electromagnetic fields are invisible and intangible and an employee, therefore, is unaware of how to protect oneself from them. This work involves modelling of the strengths of computer-generated electric and magnetic fields in the frequency ranges 5 Hz - 2 kHz and 2 kHz - 400 kHz in a computer classroom. After measuring the initial parameters of an electric and a magnetic field, electromagnetic fields propagating in the classroom were modelled with the help of the software VIZIMAG. Propagation and directions of electromagnetic field isolines are also presented. The modelling software VIZIMAG allows us to identify the strength of electric field or the frequency of magnetic field as well as the area of a room where they are present. Separate models are designed for both electric strength and magnetic flux density. Ill. 9, bibl. 11, tabl. 1 (in English; abstracts in English and Lithuanian).http://dx.doi.org/10.5755/j01.eee.109.3.175

Transmission line sanitary protective zones. Electromagnetic safety problems

2020 ◽  
pp. 736-736
Author(s):  
N. B. Rubtsova ◽  
A. Y. Tokarskiy
Keyword(s):  
Magnetic Field ◽  
Risk Factor ◽  
Transmission Lines ◽  
General Public ◽  
Field Component ◽  
Regulatory Requirements ◽  
Protection Zones ◽  
Electric And Magnetic Fields ◽  
Health Risk Factor ◽  
The Magnetic Field

The main problems of overhead and cable transmission lines with voltage >=110 kV electric and magnetic fields general public protection are presented. It is shown that it is necessary to develop regulatory requirements for these lines’ sanitary protection zones organization, taking into account the magnetic field component, because its possible health risk factor, up to carcinogenic.

scholarly journals Design of a New 1D Halbach Magnet Array with Good Sinusoidal Magnetic Field by Analyzing the Curved Surface

Sensors ◽  
2021 ◽  
Vol 21 (7) ◽  
pp. 2522
Author(s):  
Guangdou Liu ◽  
Shiqin Hou ◽  
Xingping Xu ◽  
Wensheng Xiao
Keyword(s):  
Magnetic Field ◽  
Magnetic Flux ◽  
Permanent Magnet ◽  
Flux Density ◽  
Permanent Magnets ◽  
Air Gap ◽  
Curved Surface ◽  
Magnetic Flux Density ◽  
Sinusoidal Magnetic Field ◽  
The Magnetic Field

In the linear and planar motors, the 1D Halbach magnet array is extensively used. The sinusoidal property of the magnetic field deteriorates by analyzing the magnetic field at a small air gap. Therefore, a new 1D Halbach magnet array is proposed, in which the permanent magnet with a curved surface is applied. Based on the superposition of principle and Fourier series, the magnetic flux density distribution is derived. The optimized curved surface is obtained and fitted by a polynomial. The sinusoidal magnetic field is verified by comparing it with the magnetic flux density of the finite element model. Through the analysis of different dimensions of the permanent magnet array, the optimization result has good applicability. The force ripple can be significantly reduced by the new magnet array. The effect on the mass and air gap is investigated compared with a conventional magnet array with rectangular permanent magnets. In conclusion, the new magnet array design has the scalability to be extended to various sizes of motor and is especially suitable for small air gap applications.

scholarly journals Generation of Reverse Meniscus Flow by Applying An Electromagnetic Brake

2021 ◽  
Author(s):  
Alexander Vakhrushev ◽  
Abdellah Kharicha ◽  
Ebrahim Karimi-Sibaki ◽  
Menghuai Wu ◽  
Andreas Ludwig ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Lorentz Force ◽  
Applied Magnetic Field ◽  
Numerical Study ◽  
Flow Direction ◽  
Experimental Studies ◽  
Submerged Entry Nozzle ◽  
Mean Flow ◽  
Slab Caster ◽  
The Mean

AbstractA numerical study is presented that deals with the flow in the mold of a continuous slab caster under the influence of a DC magnetic field (electromagnetic brakes (EMBrs)). The arrangement and geometry investigated here is based on a series of previous experimental studies carried out at the mini-LIMMCAST facility at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR). The magnetic field models a ruler-type EMBr and is installed in the region of the ports of the submerged entry nozzle (SEN). The current article considers magnet field strengths up to 441 mT, corresponding to a Hartmann number of about 600, and takes the electrical conductivity of the solidified shell into account. The numerical model of the turbulent flow under the applied magnetic field is implemented using the open-source CFD package OpenFOAM®. Our numerical results reveal that a growing magnitude of the applied magnetic field may cause a reversal of the flow direction at the meniscus surface, which is related the formation of a “multiroll” flow pattern in the mold. This phenomenon can be explained as a classical magnetohydrodynamics (MHD) effect: (1) the closure of the induced electric current results not primarily in a braking Lorentz force inside the jet but in an acceleration in regions of previously weak velocities, which initiates the formation of an opposite vortex (OV) close to the mean jet; (2) this vortex develops in size at the expense of the main vortex until it reaches the meniscus surface, where it becomes clearly visible. We also show that an acceleration of the meniscus flow must be expected when the applied magnetic field is smaller than a critical value. This acceleration is due to the transfer of kinetic energy from smaller turbulent structures into the mean flow. A further increase in the EMBr intensity leads to the expected damping of the mean flow and, consequently, to a reduction in the size of the upper roll. These investigations show that the Lorentz force cannot be reduced to a simple damping effect; depending on the field strength, its action is found to be topologically complex.

scholarly journals Calculation of Transient Magnetic Field and Induced Voltage in Photovoltaic Bracket System during a Lightning Stroke

2021 ◽  
Vol 11 (10) ◽  
pp. 4567
Author(s):  
Xiaoqing Zhang ◽  
Yaowu Wang
Keyword(s):  
Magnetic Field ◽  
Time Derivative ◽  
Equivalent Circuit Model ◽  
Magnetic Flux Density ◽  
Induced Voltage ◽  
Lightning Stroke ◽  
Transient Magnetic Field ◽  
Lightning Current ◽  
Time Space ◽  
The Magnetic Field

An effective method is proposed in this paper for calculating the transient magnetic field and induced voltage in the photovoltaic bracket system under lightning stroke. Considering the need for the lightning current responses on various branches of the photovoltaic bracket system, a brief outline is given to the equivalent circuit model of the photovoltaic bracket system. The analytic formulas of the transient magnetic field are derived from the vector potential for the tilted, vertical and horizontal branches in the photovoltaic bracket system. With a time–space discretization scheme put forward for theses formulas, the magnetic field distribution in an assigned spatial domain is determined on the basis of the lightning current responses. The magnetic linkage passing through a conductor loop is evaluated by the surface integral of the magnetic flux density and the induced voltage is obtained from the time derivative of the magnetic linkage. In order to check the validity of the proposed method, an experiment is made on a reduced-scale photovoltaic bracket system. Then, the proposed method is applied to an actual photovoltaic bracket system. The calculations are performed for the magnetic field distributions and induced voltages under positive and negative lightning strokes.

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