Quasi-static Field Research Articles

Solitary and periodic waves in two-fluid magnetohydrodynamics

A system of equations of two-fluid magnetohydrodynamics is studied. An ordinary differential equation describing traveling waves in an ideal cold quasi-neutral plasma is obtained in the case of quasi-stationary electromagnetic field. The Painlevé analysis of this equation is carried out and the general solution of the equation is constructed in terms of the Weierstrass elliptic function. Solitary and periodic wave solutions for the components of magnetic field are found and analyzed.

Technical solution for reducing values of electromagnetic induction in the apartment above the transformer substation TS 10 kV/0,4 kV Z-325

Due to urban demands a considerable number of transformer substations (TS) 10 kV/0,4 kV is placed within residential and commertial buildings in central city zones of Belgrade. Non-ionizing radiation from TS 10 kV/0,4 kV, in residential or commercial areas that are placed right next to or above TS 10 kV/0,4 kV depending on the power of the transformer in TS 10 kV/0,4 kV and applied disposition solutions, may exceed the accepted levels in particular cases. The aim of this paper is to present a technical solution for reducing of electromagnetic induction in quasi stationary (low variable) fields in the apartment above TS 10 kV/0,4 kV Z-325 in Belgrade.

Study of strong enhancement of synchrotron radiation via surface plasma waves excitation by particle-in-cell simulations

Synchrotron radiation is strongly enhanced by the resonant excitation of surface plasma waves (SPWs). Two-dimensional particle-in-cell simulations show that energy conversion efficiency from laser to radiation in the case of SPWs excitation is about 18.7%, which is improved by more than 2 orders of magnitude compared with that of no SPWs excitation. Besides the high energy conversion efficiency, the frequency spectrum and the angular distribution of the radiation are also improved in the case of SPWs excitation because of the quasi-static magnet field induced by surface plasma waves excitation.

PECULIARITIES OF CALCULATION OF MAGNETIC SYSTEMS WITH SHORT-CIRCUITED SECONDARY WINDINGS IN IN-PLANE FORMULATION

Introduction. A feature of quasi-static calculation of plane electromagnetic fields is unlimited volume occupied by the current. This condition imposes certain requirements on the choice of boundary conditions for solving such problems (the vanishing of the algebraic sum of the currents flowing through the cross section of all wires), failure of which leads to incorrect results. Purpose. The mathematical formulation of the boundary conditions corresponding to real physical processes in solving problems of plane quasi-static field by Kelvin transformation and development of a technique for calculating the induced currents in closed circuits in the calculation of AC electromagnet in the quasi-static mode. Methods. Investigation of nonlinear model of the current transformer in in-plane electromagnetic field calculation and the AC electromagnet is carried by the finite element method using a specific software package. Results. A possible error in the boundary conditions and summarizes the estimated model corresponds to the physics of the process using the Kelvin transform, proposed method of calculating currents in closed loop AC electromagnet in the calculation of plane problems of the field. Conclusions. The specificity of the problem of calculating the electromagnetic field in in-plane formulation requires a special approach to the assignment of boundary conditions and calculation of the currents induced in a closed loop.

Measurement of the Spin-Dipolar Part of the Tensor Polarizability of ^{87}Rb.

We report on the measurement of the contribution of the magnetic-dipole hyperfine interaction to the tensor polarizaility of the electronic ground state in ^{87}Rb. This contribution was isolated by measuring the differential shift of the clock transition frequency in ^{87}Rb atoms that were optically trapped in the focus of an intense CO_{2} laser beam. By comparing to previous tensor polarizability measurements in ^{87}Rb, the contribution of the interaction with the nuclear electric-quadrupole moment was isolated as well. Our measurement will enable better estimation of blackbody shifts in Rb atomic clocks. The methods reported here are applicable for future spectroscopic studies of atoms and molecules under strong quasistatic fields.

DFT studies of surface-enhanced Raman spectroscopy of 1,4-benzenedithiol-Au2 complex under the effect of static electric fields

In this work, we demonstrate that the applied electric-field strength and orientation can multiply modulate the Raman intensity and vibrational wavenumber of small molecule–metal complex, 1,4-benzenedithiol–Au2 (1,4BDT–Au2), by density functional theory and time-dependent density functional theory simulations. The polarizabilities are changed by the applied electric fields, leading to enhanced specific vibrational intensity and shifted vibrational wavenumber of the surface-enhanced Raman scattering effect. The applied electric fields perturb the bonds and angles of the 1,4BDT–Au2 complex. Owing to this reason, the peaks of Raman spectra related to these structures exhibit distinguishable responses in quasi-static field (low-frequency oscillating electric field). We use the visualized method of charge difference density to show that the electric fields tune the traditional excited state to pure charge-transfer excited state. The charge-transfer resonance transition produces enhanced Raman intensities for non-totally symmetric modes and totally symmetric modes. These simulation results of the function of static electric field provide new guidance for the surface-enhanced Raman scattering measurements. Copyright © 2015 John Wiley & Sons, Ltd.

Fast nonlinear finite element analysis using Newton-Raphson method implemented by Krylov subspace method with relaxed convergence criterion

Purpose – The purpose of this paper is the realization of Fast nonlinear finite element analysis (FEA). Design/methodology/approach – Nonlinear magnetic field analysis is achieved by using Newton-Raphson method implemented by relaxed convergence criterion of Krylov subspace method. Findings – This paper mathematically analyzes the reason why nonlinear convergence can be achieved if the convergence criterion for linearized equation is relaxed. Research limitations/implications – The proposed method is essential to reduce the elapsed time in nonlinear magnetic field analysis of quasi-stationary field. Practical implications – The proposed method is able to be extended to not only static field but also time domain FEA strongly coupled with circuit equation. Social implications – Because the speedup of performance evaluation of electrical machines would be achieved using proposed method, the work efficiency in manufacturing would be accelerated. Originality/value – It can be seen that the nonlinear convergenc...

Optimizing power converter PCB design for lower EMI

Purpose – The purpose of this paper is to develop a novel technique for the pre-design of a printed circuit board (PCB) of a DC-DC power converters where the placement of electric components can cancel the electromagnetic emissions through subtractive coupling and in this sense to minimize the stray magnetic and electric fields at a specific location. For this work the location of interest is a current transducer used for control purposes positioned in the center of a DC-DC Cuk converter board as a constrain. Design/methodology/approach – The methodology of design is based on the development of an interface software platform through MatLab script coding which interconnects the solution of a numerical analysis software and an optimization technique. The numerical analysis software is based on finite element calculations where quasi-static field analysis are performed to calculate the radiated electric and magnetic fields. The optimization technique is conducted by genetic algorithms (GAs). Findings – The r...

ITER design features serving for suppression of eddy- and halo related electromagnetic loads

As any tokamak, ITER will operate with rather high magnetic fields. Quasi-static toroidal field inside of the vacuum vessel reaches ∼9T and slow transient poloidal field ∼2.5T. In a case of plasma vertical drift and disruption, characteristic times of magnetic fields variation are short: 1–2ms at thermal quench phase and 10–300ms at current quench phase, thus magnetic field derivative reaches 50–150T/s. These fast transients induce intensive currents and ElectroMagnetic (EM) loads in conductive structures. EM loads at in-vessel components typically exceed gravity and seismic loads by two orders of magnitude. Induced currents are split in two groups: eddy currents closed completely in conductive structures, and halo currents closed partly through plasma periphery and partly through structures. This article describes various design features serving for suppression of eddy- and halo related EM loads in ITER. Parallel slits and various kinds of reshaping help suppress eddy related EM loads in massive parts such as shield blocks and first wall panels. A principle of force- and torque-free current paths is used in electrical straps passing pre-defined waveforms of halo and eddy currents. Multiple electro-insulating breaks were proven necessary to suppress eddy related EM loads at blanket manifolds. In all listed cases workable design solutions have been found in a frame of pre-defined tight interfaces.

Proper Generalized Decomposition Method Applied to Solve 3-D Magnetoquasi-Static Field Problems Coupling With External Electric Circuits

In the domain of numerical computation, proper generalized decomposition (PGD), which consist in approximating the solution by a truncated sum of separable functions, is applied more and more in mechanics, and has shown its efficiency in terms of computation time and memory requirements. We propose to evaluate the PGD method to solve three-dimensional (3-D) quasi-static field problems coupling with an external electric circuit. The numerical model, obtained from the PGD formulation, is used to study the 3-D examples. The results are compared with those obtained when solving the full original problem. It is shown in this paper that the computation time rate versus the number of time steps is very small compared with the one in a classical time-stepping method, and can be very efficient to solve problems when small time steps are required.

Quasi-Stationary Temperature Field of Two-Layer Half-Space With Moving Boundary

Quasi-Stationary Temperature Field of Two-Layer Half-Space With Moving Boundary

Relativistic tunneling picture of electron-positron pair creation

The common tunneling picture of electron-positron pair creation in a strong electric field is generalized to pair creation in combined crossed electric and magnetic fields. This enhanced picture, being symmetric for electrons and positrons, is formulated in a gauge-invariant and Lorentz-invariant manner for quasistatic fields. It may be used to infer qualitative features of the pair creation process. In particular, it allows for an intuitive interpretation of how the presence of a magnetic field modifies and, in particular cases, even enhances pair creation. The creation of electrons and positrons from the vacuum may be assisted by an energetic photon, which can also be incorporated into this picture of pair creation.

Enhanced relativistic laser–plasma coupling utilizing laser-induced micromodified target

The interaction of slighly relativistic femtosecond laser radiation with microstructured Si targets was studied. The microstructuring was performed by nanosecond pulse laser ablation with additional chemical etching of the target material. An analysis was made of the optical damage under the action of femtosecond radiation near the ablation threshold. It was experimentally demonstrated that the hot electron temperature increases appreciably in the laser-driven plasma (from ~370 to almost 500 keV) as well as radiation yield in the MeV range at the interaction of a high power femtosecond laser pulse with a microstructured surface in comparison with a flat surface. Numerical simulations using 3D3V PIC code Mandor revealed that the charged particle energy growth is caused by the stochastic motion of electrons in the complex field formed by the laser field and the quasistatic field at the sharp tips of micromodifications.

Influence of quenching conditions on the kinetics of formation of a domain structure of ferroelectrics

The kinetics of the formation and growth of 180° domains in a weak quasi-stationary external electric field has been investigated theoretically in the framework of the Ginzburg-Landau model within the statistical approach for proper ferroelectrics used as an example. The influence of the temperature quenching and the strength of an external electric field applied after quenching on the subsequent evolution of the system toward the thermodynamic equilibrium has been analyzed. It has been shown that, despite the polarizing role of the external electric field, in the case of a weak field the formation of a multi-domain structure is more preferable than the direct transition to a single-domain state of ordering. It has been established that the formation of nonequilibrium (“virtual”) multi-domain states is possible under the given initial conditions for specific quenching temperatures of the sample and at particular strengths of the electric field applied to the ferroelectric after quenching. It has been found that, for all depths of quenching, there is a time delay (incubation period) in the formation of a multi-domain structure of the ferroelectric. This situation occurs when, immediately after the quenching of the sample, the dispersion of the polarization is sufficiently large and the initial size of quenched polarization inhomogeneities is relatively small.

Finite Element Simulation of Impedance Measurement Effects of NFC Antennas

In this paper, the problem of connecting the unbalanced measurement setup on the balanced antenna of the near-field communication (NFC) system is addressed. The parameters of the antenna's equivalent circuit were determined using quasi-static and full-wave vector field finite element simulations. Measurements and simulations are carried out on three different prototypes of 13.56 MHz NFC rectangular four turns antenna printed on FR4 substrate material. The obtained results concerning the RLC equivalent circuit parameters show that a direct connection of the unbalanced measurement devices to the balanced antenna structure impairs the accuracy of the obtained measurement data because of the mode mismatch at the antenna terminals.

Fast Computation of the Fields Diffracted by a Multi-Layered Conductor With Non-Parallel Rough Interfaces. Application to Eddy-Current Non-Destructive Testing Simulation

This paper deals with the computation of quasi-static fields induced in a conductor by a 3-D eddy-current probe. The shape of the slab is locally distorted and constituted by several homogeneous layers with non-parallel interfaces. The approach is based on writing Maxwell equations in a curvilinear system, leading to a simple analytical expression of boundary conditions. Near every interface, the fields are expanded as sums of eigenfunctions depending on the analytical expression of the 1-D profile describing each interface. Finally, a global S-matrix is computed using a stable recursive algorithm which includes the local change of basis needed for a modal description of the fields in layers presenting non-parallel interfaces. Numerical results are presented and compared with other numerical data.

Shielding Effectiveness Analysis of a Spherical Shield Made of Medium Conductivity Material against Low-Frequency Electric Field

With quasi-static field approximation, an analytic formula is derived for shielding effectiveness analysis of a spherical shield made of medium conductivity material (10 S/m-1000 S/m) against low-frequency electric field. The effects of frequency, material conductivity, and shield dimensions on shielding effectiveness are investigated. It is shown that the shielding effectiveness decreases at first and then increases with the frequency increasing from DC to MHz if the thickness of the shield is large. However, the shielding effectiveness decreases versus the increase of frequency continuously if the thickness is small. The shielding effectiveness can be enhanced by increasing either the material conductivity or the shield thickness. This research is helpful for the evaluation of composite conductive material for electromagnetic shielding applications.

Relativity of Time and Instantaneous Interaction of Charged Particles

The interaction between charged particles through quasi-static fields must occur instantaneously; otherwise a violation of the energy principle would occur. As a consequence, the instantaneous transmission of both energy and information over macroscopic distances is feasible by using the quasi-static fields which are predicted by Maxwell’s equations. This finding is incompatible with the «relative simultaneity» following from the time transformation postulated by the special theory of rela-tivity.

Engine-driven electrization of aircraft as a radio interference source

Field measurements of the quasi-static electrical fields emerging due to the in-flight electrization of low-speed low-altitude aircraft (helicopters) were performed for the first time. It was found that the electrization of helicopters with gas turbine power plants is of a engine-driven nature: the accumulation of static positive charge at the fuselage is induced by a unipolar negatively charged exhaust stream. A static positive fuselage potential that reaches +30 or even +35 kV for certain helicopter models was determined. If dielectric and composite materials are used in the construction of helicopters and specific parts of the aircraft are isolated electrically from the fuselage, differential electrization occurs. In view of the high absolute value of the fuselage potential, this electrization results in the generation of high-voltage discharges that serve as a source of intense radio interference within a frequency band of from several megahertz to several hundred megahertz.

Strong-field perspective on high-harmonic radiation from bulk solids.

Mechanisms of high-harmonic generation from crystals are described by treating the electric field of a laser as a quasistatic strong field. Under the quasistatic electric field, electrons in periodic potentials form dressed states, known as Wannier-Stark states. The energy differences between the dressed states determine the frequencies of the radiation. The radiation yield is determined by the magnitudes of the interband and intraband current matrix elements between the dressed states. The generation of attosecond pulses from solids is predicted. Ramifications for strong-field physics are discussed.