Electromagnetic Tensor Research Articles

Effect of Gas Dynamic Conditions in Plasma Reactor on Efficiency of Boron and Silicon Synthesis in Inductively Coupled Argon–Hydrogen Plasma

A thermal/gas dynamic model of the plasma-assisted method for producing boron and silicon carbides is proposed. The turbulent flow of a mixture of ideal viscous compressible gases is considered taking into account inductive heating and the influence of the electromagnetic field strength on the plasma motion. The composition of the conversion products is determined in accordance with the results of thermodynamic calculations, while taking into account the influence of the main synthesis products on the temperature field and gas dynamic flow in the reactor. The distribution of powder particles of the desired synthesis products in the stream is described by the diffusion mechanism. The possibilities of synthesis of boron and silicon carbides from their fluorides in a radiofrequency induction plasma torch with vortex flow stabilization have been explored.

Collective excitation of plasmon-coupled Au-nanochain boosts photocatalytic hydrogen evolution of semiconductor

Localized surface plasmon resonance (LSPR) offers a valuable opportunity to improve the efficiency of photocatalysts. However, plasmonic enhancement of photoconversion is still limited, as most of metal-semiconductor building blocks depend on LSPR contribution of isolated metal nanoparticles. In this contribution, the concept of collective excitation of embedded metal nanoparticles is demonstrated as an effective strategy to enhance the utilization of plasmonic energy. The contribution of Au-nanochain to the enhancement of photoconversion is 3.5 times increase in comparison with that of conventional isolated Au nanoparticles. Experimental characterization and theoretical simulation show that strongly coupled plasmonic nanostructure of Au-nanochain give rise to highly intensive electromagnetic field. The enhanced strength of electromagnetic field essentially boosts the formation rate of electron-hole pair in semiconductor, and ultimately improves photocatalytic hydrogen evolution activity of semiconductor photocatalysts. The concept of embedded coupled-metal nanostructure represents a promising strategy for the rational design of high-performance photocatalysts.

CALCULATION OF ELECTROMAGNETIC FIELDS IN INHOMOGENEOUS MEDIA FOR SELECTION OF PROTECTIVE COATINGS

The aim of the work is to develop a method for high-frequency EMFs calculation in terms of the modified vector potential and to use it for choice of the parameters of the layered absorbing coatings that provide effective absorption of radio wave radiation. Methodology. A method for calculation of electromagnetic fields in inhomogeneous media is described. It is performed in terms of the modified magnetic potential at presented a plane electromagnetic wave as an incident and reflected one. To reduce the computational domain size, additional uniaxially perfectly matched layers ensuring fast and non-reflective attenuation of electromagnetic field (EMF) strengths are used at its boundaries. It is supposed that electrical parameters of such layers have not only resistive, but also magnetic losses. Results. Modification of the known methods for dividing the wave into the incident and reflected, as well as introducing uniaxially perfectly matched layers at the domain boundaries and formulation of the problem in terms of the modified vector potential, provide a possibility to solve the problem of the electromagnetic wave incidence onto heterogeneous media at reduced memory and counting time compared to the formulation tasks through the EMF strengths. Practical value. The described method was used to select parameters of radio-absorbing coatings, application of which on conductive bodies reduces the reflections from them of the incident electromagnetic waves. This provides a possibility to choose the electrical parameters of layered coatings with active losses, as well as magnetic losses, which provide a decrease of the reflected waves amplitude by an order of magnitude or more. Originality. For the first time, the problem of calculating the incidence of an electromagnetic wave on an inhomogeneous medium with active electrical and magnetic losses was formulated in terms of the modified vector potential. The parameters of a multilayer lossy coating, which ensures decrease of the reflected EMF wave strengths by an order of magnitude or more are determined.

Excited-state effects in nucleon structure on the lattice using hybrid interpolators

It would be very useful to find a way of reducing excited-state effects in lattice QCD calculations of nucleon structure that has a low computational cost. We explore the use of hybrid interpolators, which contain a nontrivial gluonic excitation, in a variational basis together with the standard interpolator with tuned smearing width. Using the clover discretization of the field strength tensor, a calculation using a fixed linear combination of standard and hybrid interpolators can be done using the same number of quark propagators as a standard calculation, making this a cost-effective option. We find that such an interpolator, optimized by solving a generalized eigenvalue problem, reduces excited-state contributions in two-point correlators. However, the effect in three-point correlators, which are needed for computing nucleon matrix elements, is mixed: for some matrix elements such as the tensor charge, excited-state effects are suppressed, whereas for others such as the axial charge, they are enhanced. The results illustrate that the variational method is not guaranteed to reduce the net contribution from excited states except in its asymptotic regime, and suggest that it may be important to use a large basis of interpolators capable of isolating all of the relevant low-lying states.

3D Bioconvective multiple slip flow of chemically reactive Casson nanofluid with gyrotactic micro‐organisms

AbstractIn the present study, we investigate the velocity, thermal, solutal, and motile micro‐organism (MM) slip effects on the flow of chemically reactive Casson nanofluid flowing over an exponentially stretched electromagnetic sheet in the presence of a chemical reaction. In addition, a mechanism of improving the motion of nanoparticles (Brownian motion and thermophoresis) is incorporated. The nondimensionalized ordinary differential equations are tackled by using symbolic computation software, MATLAB 2012b, with bvp4c function. Some significant and relevant characteristics of associated profiles are displayed graphically and discussed beautifully with the aid of tables through comprehensive numerical computations. The results of the study show that elevated Casson fluid parameter, gyrotactic micro‐organism, and electromagnetic strength belittle both axial as well as transverse velocities and the related momentum boundary layer thickness. Another important outcome is that low Prandtl fluids and enhancement in the strength of electromagnetic field fasten the diffusion of micro‐organisms, thereby augmenting the density of MM in the related boundary layer.

Tunable spoof surface plasmon polariton transmission line based on ferroelectric thick film

Spoof surface plasmon polaritons (SSPPs) provide a high field confinement in the sub-wavelength scale and low transmission loss in the propagation, which are widely used in microwave functional devices. In this paper, we first propose a tunable SSPP transmission line (TL) based on ferroelectric thick film. The ferroelectric thick film associated with the SSPP planar waveguide can provide an electrically tunable transmission phase. Two electric-field-coupled inductive–capacitive (ELC) resonators are added in the configuration to inspire the coupling between ELC resonant modes and SSPPs, enabling the tunable TL to work in the frequency-selective transmission passband. It is demonstrated that the SSPP mode can be designed in higher or lower confinement to modulate the electromagnetic field strength inside the ferroelectric thick film. This property promotes a balanced design between low transmission loss and large phase change for tunable TL. As a result, this study provides an alternative route to design tunable SSPP devices based on ferroelectric thick film, which may open up new applications in tunable microwave devices.

Boundedness and decay for the Teukolsky equation of spin ±1 on Reissner–Nordström spacetime: the spherical mode

We prove boundedness and polynomial decay statements for solutions to the spin 1 Teukolsky-type equation projected to the spherical harmonic on Reissner–Nordström spacetime. The equation is verified by a gauge-invariant quantity which we identify and which involves the electromagnetic and curvature tensor. This gives a first description in physical space of gauge-invariant quantities transporting the electromagnetic radiation in perturbations of a charged black hole.The proof is based on the use of derived quantities, introduced in previous works on linear stability of Schwarzschild (Dafermos et al 2019 Acta Math. 222 1–214). The derived quantity verifies a Fackerell–Ipser-type equation, with right hand side vanishing at the spherical harmonics. The boundedness and decay for the projection to the spherical harmonics are implied by the boundedness and decay for the Teukolsky system of spin 2 obtained in Giorgi (2018 (arXiv:1811.03526)).The spin 1 Teukolsky-type equation is verified by the curvature and electromagnetic components of a gravitational and electromagnetic perturbation of the Reissner–Nordström spacetime. Consequently, together with the estimates obtained in Giorgi (2018 (arXiv:1811.03526)), these bounds allow to prove the full linear stability of Reissner–Nordström metric for small charge to coupled gravitational and electromagnetic perturbations.

Consistency of an alternative CPT-odd and Lorentz-violating extension of QED

We investigate an alternative CPT-odd Lorentz-breaking QED which includes the Carroll–Field–Jackiw (CFJ) term of the Standard Model Extension (SME), writing the gauge sector in the action in a Palatini-like form, in which the vectorial field and the field-strength tensor are treated as independent entities. Interestingly, this naturally induces a Lorentz-violating mass term in the classical action. We study physical consistency aspects of the model both at classical and quantum levels.

A Study on the Heating Method and Implementation of a Shrink-Fit Tool Holder

A novel induction heating coil is proposed and designed as a shrink-fit tool holder. An electromagnetic field analysis of the coil with different winding methods is conducted using the ANSYS finite element analysis software and an appropriate coil structure is determined, based on the simulated electromagnetic field distribution cloud maps. The magnetic field in the X–Y plane is increased by one order of magnitude around the surface with the addition of the designed magnetic slot, as well as improving the magnetic leakage. The electromagnetic field strength in the middle of the coil is greatly increased, up to 2.312 × 104 A/m, by the addition of a designed magnetic ring covering the top of the coil. The distribution of the three-dimensional temperature field is obtained by the ANSYS workbench transient thermal analysis software, based on the selected coil. Hot-loading equipment used for shrink-fit tool holders are implemented with diameter-selection, power, and heating time-setting functions. Experiments on different types of tool holders are carried out to obtain optimal heating parameters and to verify the reliability of the implemented heating equipment. Through experimental testing, the inserting and pulling out temperature is found to be about 270 °C for the BT40-SF06 and about 285 °C for the BT40-SF10. According to the experimental results, the simulated temperature field is in good agreement with the measured result. The optimal heating parameters of the heating equipment are determined, which proves the correctness of the heating method of the shrink-fit tool holder.

Cross-correlation between 21-cm radiation and CMB B modes from the cosmic birefringence in the presence of a light scalar field

We study the cross-correlation between the 21-cm and cosmic microwave background (CMB) $B$ mode fluctuations which are induced by the cosmic birefringence when the nonconstant scalar field couples to the electromagnetic field strength. Such multiwavelength signals can potentially probe the reionization history of the Universe and also explore the nature of fundamental physics such as the parity violation and the scalar field dynamics in the early Universe. We illustrate the feasibility to detect such 21-cm-$B$ mode cross-correlations through commonly discussed scalar field models, the quintessence-like scalar field which is responsible for the current dark energy and the axionlike scalar field which is responsible for the current dark matter density.

Thermodynamics of logarithmic charged black holes in the Einstein-dilaton gravity theory

Starting from the suitable action of four-dimensional Einstein-dilaton gravity with the logarithmic nonlinear electrodynamics, the explicit form of the coupled scalar, electromagnetic and gravitational field equations have been obtained. Through the exact solution of the field equations, the nonvanishing component of the electromagnetic tensor have been obtained and it has been shown that dilaton potential can be written as the suitable combination of two terms similar to the Liouville potentials. Three classes of novel electrically charged hairy black holes have been introduced with the regular and well-defined metric functions for all values of the parameters in the theory. The solutions reduce to their corresponding values in the Einstein-Maxwell-dilaton theory when the nonlinearity parameter of the electrodynamics goes to infinity. The thermodynamic quantities, such as temperature, entropy, mass, electric charge and electric potential, have been calculated and it has been demonstrated that the first law of black hole thermodynamics is valid for all of the new solutions. Thermodynamic stability or phase transition of the black holes have been investigated based on the canonical ensemble method. By calculating the black hole heat capacity type-1 and type-2 phase transition points have been determined. Also, it has been found that in order for the new nonlinearly charged dilaton black holes to remain locally stable some simple conditions must be fulfilled.

Achieving colossal Kerr nonlinearity via multiphoton atomic coherence in a five-level Λ − Ξ system

We propose to utilize a five-level Λ − Ξ system to achieve large self-Kerr nonlinearity under multiphoton resonance conditions. Using a density matrix formulation along with an iterative perturbation technique, analytic expressions of linear and nonlinear susceptibilities are derived for stationary as well as for moving atoms. Variation of first- and third-order susceptibilities with respect to frequency and intensity of switching field is then discussed. The dressed-state picture is employed to explain the amplitude and position of each peak in linear and nonlinear absorption profiles. It is found that under slow light conditions, large controllable Kerr nonlinearity with reduced linear and nonlinear absorption is achieved by properly adjusting the strength and detunings of strong electromagnetic (e.m.) fields. Our numerical results also reveal that the Kerr nonlinear index of our considered system is greater than that of existing three-level Λ and four-level N systems. Finally, it is substantiated that self-Kerr nonlinearity is proliferated by taking the Doppler effect into account.

Green functions and propagation in the Bopp–Podolsky electrodynamics

In this paper, we investigate the so-called Bopp–Podolsky electrodynamics. The Bopp–Podolsky electrodynamics is a prototypical gradient field theory with weak nonlocality in space and time. The Bopp–Podolsky electrodynamics is a Lorentz and gauge invariant generalization of the Maxwell electrodynamics. We derive the retarded Green functions, first derivatives of the retarded Green functions, retarded potentials, retarded electromagnetic field strengths, generalized Liénard–Wiechert potentials and the corresponding electromagnetic field strengths in the framework of the Bopp–Podolsky electrodynamics for three, two and one spatial dimensions. We investigate the behaviour of these electromagnetic fields in the neighbourhood of the light cone. In the Bopp–Podolsky electrodynamics, the retarded Green functions and their first derivatives show fast decreasing oscillations inside the forward light cone.

Electromagnetic analysis of composite structures subjected to transient magnetic fields

When carbon composites are exposed to a transient electromagnetic field, a rapid temperature increase can be observed due to joule heating from magnetic induction. The electromagnetic induction heating and heat transfer in the composite are anisotropic and concentrated upon the carbon fiber orientation and distribution. In addition, the strength and frequency of transient electromagnetic fields have great influence on the final quality of the composite. A computational model has been developed by solving coupled Maxwell’s and heat transfer equations. The analysis accounts for the three-dimensional transient electromagnetic field and electrical conductivity of the composite material. This paper will illustrate the derived formulation and numerical solution based on finite element methods. The developed code is validated with a 2D closed-form solution. Numerical simulations of a cylinder and a flat laminated plate are conducted to illustrate the computational capability. The induction heating for composite manufacture is also discussed for current Army’s applications.

What Are Observables in Hamiltonian Einstein–Maxwell Theory?

Is change missing in Hamiltonian Einstein-Maxwell theory? Given the most common definition of observables (having weakly vanishing Poisson bracket with each first-class constraint), observables are constants of the motion and nonlocal. Unfortunately this definition also implies that the observables for massive electromagnetism with gauge freedom (Stueckelberg) are inequivalent to those of massive electromagnetism without gauge freedom (Proca). The alternative Pons-Salisbury-Sundermeyer definition of observables, aiming for Hamiltonian-Lagrangian equivalence, uses the gauge generator G, a tuned sum of first-class constraints, rather than each first-class constraint separately, and implies equivalent observables for equivalent massive electromagnetisms. For General Relativity, G generates 4-dimensional Lie derivatives for solutions. The Lie derivative compares different space-time points with the same coordinate value in different coordinate systems, like 1 a.m. summer time vs. 1 a.m. standard time, so a vanishing Lie derivative implies constancy rather than covariance. Requiring equivalent observables for equivalent formulations of massive gravity confirms that G must generate the 4-dimensional Lie derivative (not 0) for observables. These separate results indicate that observables are invariant under internal gauge symmetries but covariant under external gauge symmetries, but can this bifurcated definition work for mixed theories such as Einstein-Maxwell theory? Pons, Salisbury and Shepley have studied G for Einstein-Yang-Mills. For Einstein-Maxwell, both the electromagnetic field strength F and the metric g are invariant under electromagnetic gauge transformations and covariant (changing by a Lie derivative) under 4-dimensional coordinate transformations. Using the bifurcated definition, these quantities count as observables, as one would expect on non-Hamiltonian grounds.

Reply to “Comment on ‘Analysis of recent interpretations of the Abraham-Minkowski problem’ ”

The Comment of M. Partanen and J. Tulkki [Phys. Rev. A {\bf 100}, 017801 (2019)] claims that my criticism expressed in Phys. Rev. A {\bf 98}, 043847 (2018) of the earlier paper of Partanen {\it et al.} [Phys. Rev. A {\bf 95}, 063850 (2017)] was incorrect. There are essentially three points involved here: (1) the first one regards the physical interpretation of the radiation pressure experiment of A. Kundu {\it et al.} [Sci. Rep. {\bf 7}, 42538 (2017)]. My mathematical analysis of this situation, although simple, was able to illustrate the main property of the experiment, namely that it showed the action from the radiation forces on the dielectric boundaries, and from the Lorentz force in the interior, but it had not any relationship to the Abraham-Minkowski momentum problem as was originally stated by the investigators. (2) The second point was my emphasis on the fact that in an electromagnetic pulse in a medium there cannot be an accompanying mechanical energy density of the same order of magnitude as the electromagnetic energy density itself. The electromagnetic wave carries with it a mechanical {\it momentum}, but not a mechanical {\it energy}. Here I illustrate this point by a simple numerical analysis. (3) When going to a relativistic formulation of the electromagnetic theory in matter, care must be taken to secure that fundamental conditions from field theory are satisfied. In particular, one cannot in general take the electromagnetic total energy and momentum of a radiation pulse to constitute a four-vector; such a property holds only if the electromagnetic energy-momentum tensor is divergence-free. For the Minkowski tensor this condition is satisfied, whereas for the Abraham tensor it is not.

On the Risk to Declare EMC Compliant a Faulty EUT During Radiated Susceptibility Tests in Reverberation Chambers

This paper presents a general method, experimentally validated, highlighting the influence of the number of stirring configurations used during radiated susceptibility tests performed in reverberation chambers in terms of reliability and confidence of the obtained results. This Monte-Carlo based approach (with routines available on demand) computes the risk to declare compliant from an electromagnetic compatibility (EMC) point of view a faulty equipment under test. This risk is calculated according to the number of stirring configurations chosen for the test and to the uncertainty of the electromagnetic field strength applied on the equipment. The proposed method is shown to be applicable for any equipment independently of its size and directivity (or more precisely its receiving polarization pattern). Overtesting is shown in this context to be a promising solution able to increase the confidence of the users about the EMC compliance of tested equipment. The paper also illustrates the possibility to extract the minimum susceptibility level of a valid EUT as a function of the testing conditions.

PROFESIONALNI DETEKTOR BEŽIČNIH SIGNALA (PSD-100) – PREVENCIJA VISOKOTEHNOLOŠKIH PREVARA

In this paper the implementation of the device for wireless communication detection is presented. The system measures RF electromagnetic field strength for frequencies from 1 MHz up to 10 GHz and has wide range of adjustable sensitivity. Implemented device provides detection of cellular phone activities in all three main operating bands, and detection of other types of wireless communication such as radio communications, Bluetooth, Wi-Fi and so on. The device presents an improvement of a previous version of the detector UD-100. Measurement results are displayed on graphical display providing easy user readings and device operating. Device is operated by four touch sensitive keypads, the system is battery powered, portable and can fit in any pocket.

Research on Electromagnetic Radiation Model of Corona Discharge with UHV AC Transmission Lines

The corona discharge pulse current has double exponential distribution characteristics. On this basis, the electromagnetic radiation model of corona discharge is established by using the theory of electric dipole. The corona discharge characteristics are analysed and compared with the measured results of 1000kV UHV ac transmission line. The results show that the electromagnetic field strength increases first and then decreases with time, and at the same time, the electromagnetic field strength decreases exponentially with distance. The simulated and predicted corona discharge radiation characteristics have the same variation law as the measured data, which verifies the correctness of the model.

Portable neutron generator with microwave ion source for wide applications

The paper presents the issues related to the development of a portable neutron generator with a microwave source of heavy hydrogen ions for a wide range of applications. The paper analyzes the effect of electromagnetic microwave field strength and the magnetic induction value of a constant external magnetic field on the ionization rate of molecular deuterium and determines their optimal ratios. It also describes the configuration of the magnetic system of permanent magnets made of NdFeB material, which provide a homogeneous magnetic field with an induction of 850 Gs necessary for the effective operation of the device using the electron cyclotron resonance (ECR). The dynamics of the primary deuteron flux, as well as secondary particles in the ion-optical system are analyzed. Elements of a conceptual design of a portable neutron generator are described.