Nonlinear anomalies of conducting media with conical microconstrictions

An investigation is made of the divergence of the higher moments of the field in conducting structures with conical singular regions. Calculations are made of the critical values of the parameters which determine the nonlinear anomalies of a medium. Pis’ma Zh. Tekh. Fiz. 25, 42–47 (February 26, 1999)     

Scattering of electromagnetic waves by a perfect electromagnetic conducting sphero

An exact solution to the problem of scattering of electromagnetic waves from a perfect electromagnetic conducting spheroid is presented, using the method of separation of variables. The formulation of the problem is realised by expanding the incident as well as the scattered electromagnetic fields in terms of appropriate spheroidal vector wave functions and imposing the appropriate boundary conditions at the surface of the spheroid. This generates a set of simultaneous equations, the solution of which yields the unknown coefficients associated with the expansion of the scattered electromagnetic field. Results are presented in the form of normalised bistatic and backscattering cross-sections for spheroids of different axial ratios, sizes and admittances, for both transverse electric and transverse magnetic polarisations of the incident wave.     

On the quantization of the electromagnetic field in conducting media

In this work we investigate the quantization of electromagnetic waves propagating through homogeneous conducting linear media with no charge density. We use Coulomb's gauge to reduce the problem to that of a time-dependent harmonic oscillator, which is described by the Caldirola–Kanai Hamiltonian. Furthermore, we obtain the corresponding exact wave functions with the help of quadratic invariants and of the dynamic invariant method. These wave functions are written in terms of a particular solution of the Milne–Pinney equation. We also construct coherent and squeezed states for the quantized electromagnetic waves and evaluate the quantum fluctuations in coordinates and momentum as well as the uncertainty product for each mode of the electromagnetic field.     

Configurational forces and gauge conditions in electromagnetic bodies

Material inhomogeneities, defective materials or fractured solids address the notion of configurational force. In electromagnetic deformable bodies this force also depends upon the electromagnetic potentials, which unfortunately are not uniquely defined. In electrostatics the problem of uniqueness is scarcely relevant, as only the scalar potential plays a role. Thus, dielectrics are adequately described in this context, even in the presence of a crack-line. In electrodynamics also the vector potential plays a prominent role and the lack of uniqueness of the electromagnetic potentials cannot be disregarded. The problem of solving this indeterminacy for the quantities of interest appeals to additional conditions, the gauge conditions. Gauge transformations, which leave invariant the Maxwell equations and the balance of momentum in material form, are here examined. In configurational mechanics of electromagnetic solids, a possible gauge dependent quantity is the material momentum, which seems to be related to some extent to supercurrents in deformable superconductors.     

Low frequency electromagnetic scattering by a perfectly conducting moving sphere

The paper investigates the propagation of a plane electromagnetic waves in the exterior of a moving obstacle. Under the assumption that the obstacle moves with uniform velocity and more slowly than the incident field, we apply the Lorentz transformation. In the object’s frame, where the scatterer is stationary, we introduce the low-frequency approximation technique. For the near electromagnetic field we obtain the Rayleigh low-frequency coefficients while in the far field we derive the leading non-vanishing terms for the scattering amplitude and scattering cross-section. Finally, using the inverse transformation we express the same quantities in the observer’s frame.     

The covariant electromagnetic Casimir effect for real conducting spherical shells

Using the covariant electromagnetic Casimir effect (recently introduced for real conducting cylindrical shells) 1 Razmi, H and Fadaei, N. 2009. Nucl. Phys. B, 814: 582–593.  [Google Scholar] (Razmi, Fadaei. Nucl. Phys. B 2009, 814, 582), the Casimir force experienced by a spherical shell, under Dirichlet boundary condition, is calculated. The renormalization procedure is based on the plasma cut-off frequency for real conductors. The real case of a gold (silver) sphere is considered and the corresponding electromagnetic Casimir force is computed. In the covariant approach, there is no decomposition of fields to TE and TM modes; thus, we do not need to consider the Neumann boundary condition in parallel to the Dirichlet problem and then add their corresponding results.     

Determining the temperature of a conducting material by an electromagnetic method

Translated from Izmeritel'naya Tekhnika, No. 5, pp. 25–26, May, 1991.     

Penetration of electromagnetic waves through composite screens containing ideally conducting helices

A complex procedure of numerical analytical modeling of the interaction of elecromagnetic fields with the plane layer of a composite material containing conducting helices has been presented. The procedure involves determination of the effective electromagnetic parameters of composite materials containing stochastically distributed thin-wire elements with the use of Pocklington’s equation. As a result the medium with helical inclusions has been replaced by the equivalent homogeneous chiral medium characterized by the effective parameters. The coefficients of reflection and transmission of waves by a screen have numerically been investigated.     

Scattering of electromagnetic waves by a coated not perfectly conducting sphere

We consider the low-frequency scattering problem of a plane electromagnetic wave by a sphere, which is covered by a penetrable concentric spherical shell. The medium, occupying the shell, is lossless while on the surface of the core an impedance boundary condition is satisfied. The impedance boundary condition was introduced by Leontovich (Investigations of Radiowave Propagation. Part II, Academy of Science, Moscow, 1948) and it accounts for situations where the obstacle is not perfectly conducting but the exterior field will not penetrate deeply into the scatterer. For the near electromagnetic field we obtain the low-frequency coefficients of the zeroth and the first orders while in the far field we derive the leading non-vanishing terms for the scattering amplitude and the scattering cross-section. Spherical coated obstacles are very important in applications. Small particles in biological suspensions, cells, some human organs, atmospheric particles and granules within composite materials are only a few examples of applied interest in science and technology.     

AC susceptibilities of conducting cylinders and their applications in electromagnetic measurements

We present accurate calculations and tabulations of the volume and midplane-averaged complex ac susceptibilities of nonmagnetic conducting cylinders with aspect ratio ranging from 0.1 to 10 as functions of a dimensionless frequency. We discuss their features in terms of eddy-current demagnetizing effect. We explain their applications in high-sensitivity, low-temperature, and high-field ac susceptometers and contactless conductivity measurements.     

Finite element solution for electromagnetic scattering from two-dimensional bodies

The problem of scattering from bodies in free space is formulated using a differential equation approach. The finite element mesh extends outward into the far field region of the scattering body, where the outer boundary condition is evaluated using the asymptotic expression for the scattered field. Numerical results for two scattering bodies are presented and discussed. Non-physical, standing waves appear in the results due to the inadequacy of the outer boundary condition in fulfilling the radiation condition for the scattered field. The differential equation approach does not appear to be competitive with integral equation approaches for thin bodies, but seems promising for handling scattering from thick inhomogeneous bodies into which the field penetrates.     

Three-dimensional electromagnetic diffraction of a Gaussian beam by a perfectly conducting half-plane

Formulas are derived for the diffraction of a three-dimensional electromagnetic Gaussian beam by a perfectly conducting half-plane. The beam can be incident from any direction, and the main component of the electric field can point in any direction on the plane of the beam waist. The center of the beam waist is on the edge of the half-plane. The incident beam is constructed as a superposition of plane waves, and the total diffracted field is obtained from a superposition of the diffracted fields that are due to each plane wave. Physical constraints that limit the size and direction of the beam relative to the half-plane are described and incorporated into the theory. The scattered field in the far zone is obtained by asymptotic evaluation of the general formulas. Graphical results for the near-field as well as far-field patterns are presented and discussed.     

Measurement of rapidly changing temperatures of conducting solid bodies by means of thermocouples

Conclusions A thermocouple with welded electrodes possesses a considerable thermal inertia. Thermocouples without junctions are virtually inertialess and are capable of measuring rapidly changing temperatures on the surfaces of solid conducting bodies.The contact resistance between the thermal electrodes and the body with which they make contact has the maximum effect on the precision of measurements in the case when current-measuring instruments are used. This error can be reduced by increasing the contact pressure up to 2–2.5 kg-wt/mm² (196.13·10⁵–245.17·10⁵ N/m²), cleaning the contact surfaces and preheating the contact.     

Solution of the thermal problem of the vaporization of conical bodies in strong radiation fluxes

The paper gives approximate calculations for the rate of change of the axial dimensions and the temperature at the vertex of conical bodies vaporizing under the action of a powerful laser radiation.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 39, No. 3, pp. 532–537, September, 1980.