Diffraction Properties of Absorbing Cylinders Suspended in Outside Absorbing Media

The forms of the diffracted E and H fields, for absorbing cylinders with radii small compared to the wavelength and suspended in outside absorbing media, have been determined from Maxwell's equations and boundary conditions, when these cylinders are illuminated by plane periodic electromagnetic waves in a direction perpendicular to their axes, and the electric vector is parallel or perpendicular to the axes. From these E and H fields the time averages of the radiant flux and the electric field energy densities consist of exponentially increasing or decreasing background terms, characteristic of the incident and diffracted waves, and interaction terms, which generate exponentially decreasing maxima and minima or interference fringes, whose radial spacings increase with the angle from the direction of incidence. The radiant fluxes have properties characteristic of creeping waves. Particular attention has been devoted to determining the boundary conditions for each of the vector fields and retaining the proper coefficients, so that direct comparisons can be made between the two polarizations. In all cases the magnitudes and forms of these vector fields are functions of the material constants of both media, the wavelength, the modes being excited, the cylinder radius and the polarization used.     

Application of finite-part integrals to three-dimensional fracture problems for piezoelectric media Part I: Hypersingular integral equation and theoretical analysis

This paper deals with some basic linear elastic fracture problems for an arbitrary-shaped planar crack in a three-dimensional infinite transversely isotropic piezoelectric media. The finite-part integral concept is used to derive hypersingular integral equations for the crack from the point force and charge solutions with distinct eigenvalues s _i(i=1,2,3) of an infinite transversely isotropic piezoelectric media. Investigations on the singularities and the singular stress fields and electric displacement fields in the vicinity of the crack are made by the dominant-part analysis of the two-dimensional integrals. Thereafter the stress and electric displacement intensity factor K-fields and the energy release rate G are exactly obtained by using the definitions of stress and electric displacement intensity factors and the principle of virtual work, respectively. The hypersingular integral equations under axially symmetric mechanical and electric loadings are solved analytically for the case of a penny-shaped crack.     

The charges,currents and near‐field characteristics of the transparent source for the FDTD method

Abstract

The electromagnetic characteristics of a transparent source for the finite‐difference time‐domain (FDTD) method are investigated. The approximate formulations for the corresponding electric and magnetic fields at the source are first reported, while the associated charges and current are also demonstrated. The approximate E field and H field are very closely related to the FDTD simulated results. It is shown that the magnetic field is proportional to the temporal derivative of the electric field at the source node, while the electric field is proportional to the temporal integration of the driving function. Static charges may be built up to produce static E fields after the driving function has passed, which are responsible for the dc offset problem in the pulsed FDTD algorithm. The dc offset is verified for the case of Gaussian pulse excitation and is avoided via the use of a bipolar pulse.     

Wave propagation of a gravitated piezo-thermoelastic half-space via a refined multi-phase-lags theory

Abstract

This work presents a refined multi-phase-lags theory for thermoelastic response of half-space medium with the inclusion of gravity. The wave propagation of a gravitated piezo-thermoelastic half-space has been presented. Additional equation for the piezoelectric material is added to get four partial differential equations. All coupled equations have been resolved exactly due to the normal mode model. A harmonic wave solution is adopted to derive the main variables of the medium. The displacements, temperature, and electric potential have been obtained. Consequently, the electric displacements and thermomechanical stresses have been also obtained. A comparison is made to show the dependency of all field on the inclusion of gravity. Most fields are very sensitive to the variation of the gravity factor. Results are tabulated to serve as benchmarks for future comparisons and other results have been displayed to show the physical meaning of the phenomena.     

Flexural vibration of a lithium niobate piezoelectric plate with a ferroelectric inversion layer

Abstract

Two-dimensional equations for flexural motions of a lithium niobate piezoelectric plate are derived from three-dimensional equations. The plate has a ferroelectric inversion layer where the piezoelectric constants reverse signs. The equations show an unconventional behavior that a uniform electric field along the plate thickness can produce bending. This offers many possibilities for new designs of devices. Waves in unbounded plates are examined for the accuracy of the equations. A piezoelectric energy harvester based on such a plate is analyzed as an example of the application of the equations derived in vibrations of finite plates.     

Three‐dimensional FDTD modeling of neurons to solve EEG and MEG forward problem

Neuronal activities including calcium sodium current, ligands current, and synaptic transmembrane current create electromagnetic fields. Here, an analytic method is suggested to obtain the electromagnetic fields and potential signals resulting from the function of nerve cells inside the brain. Modeling simulates the behavior of cells three‐dimensionally. The proposed method employs the electric scalar potential and magnetic vector potential to solve the time‐domain three‐dimensional equations using the partial differential method. All ion flows are considered as electrical current densities. In this method, the brain and desired cells are meshed to solve the problem using the numerical method. As an example, the electric fields, magnetic fields, and signals generated by cingulum nerve fibers are illustrated and compared in C_z, F_z, and T3 electrode positions. A direct analysis method based on the same mechanism and biophysics of the nervous system is proposed. Employing this direct method leads not only to a better understanding of neuronal activity but also to a more accurate vision regarding the accuracy/inaccuracy of experimental and inverse methods. The analysis of these data provides insights into the brain function processes.     

Fracture analysis of a magnetoelectroelastic solid with a penny-shaped crack by considering the effects of the opening crack interior

A magnetoelectroelastic analysis for a penny-shaped crack embedded in an infinite piezoelectromagnetic material is made. Taking into account the fact that electric and magnetic fields can permeate through the opening crack, the electric and magnetic boundary conditions at the crack surfaces are assumed to be semi-permeable, or depend nonlinearly on the crack opening displacement. For the case of a circular crack normal to the poling direction, the associated mixed boundary value problem is reduced to solving dual integral equations by applying the Hankel transform technique. An entire magnetoelectroelastic field is obtained in simple and explicit form. Numerical results for a cracked BaTiO₃-CoFe₂O₄ material reveal the dependence of the electric displacement and magnetic induction at the crack surfaces with applied mechanical loading. The influences of applied electric and magnetic loadings on normalized fracture parameters are illustrated graphically for a vacuum circular crack. The impermeable and permeable cracks can be treated as two limiting cases of the present.     

Vector diffraction problem of focusing a category 1 aberrated wavefront through a multilayered lossless medium

Abstract

In optical storage and other imaging applications, a laser beam is focused through a transparent lossless medium of different refractive index. Applications include optical and magneto-optical recording. It is highly likely that, in the near future, conventional magnetic recording will transition to optically/thermally assisted magnetic recording technology. In all these applications, it is necessary to ascertain the quality of the image formed by the focusing apparatus on an imaging surface when in the neighbourhood of the focus, the focused beam of light passes through a stratified lossless medium. This paper examines the vector diffraction problem of focusing radiation through a multilayered medium. The solution is accomplished by first deriving a general solution of the focusing problem in any homogenous medium. This solution is then used to obtain the solution in the multilayered medium by applying continuity of the electric and magnetic fields at the interfaces. The technique used here allows one to calculate the field quantities in the entire image space. Furthermore, the focusing lens may have Seidel aberrations of the fourth order. The salient feature of this method is that the vector diffraction problem is solved only once - for the zeroth layer, immediately next to the exit pupil. In the remaining layers, the results are obtained by solving linear algebraic equations. The solution of the algebraic equations is obtained in closed form.     

Enhancement of antibacterial properties of Ag nanorods by electric field

Abstract

The effect of an electric field on the antibacterial activity of columnar aligned silver nanorods was investigated. Silver nanorods with a polygonal cross section, a width of 20–60 nm and a length of 260–550 nm, were grown on a titanium interlayer by applying an electric field perpendicular to the surface of a Ag/Ti/Si(100) thin film during its heat treatment at 700 °C in an Ar+H₂ environment. The optical absorption spectrum of the silver nanorods exhibited two peaks at wavelengths of 350 and 395 nm corresponding to the main surface plasmon resonance bands of the one-dimensional silver nanostructures. It was found that the silver nanorods with an fcc structure were bounded mainly by {100} facets. The antibacterial activity of the silver nanorods against Escherichia coli bacteria was evaluated at various electric fields applied in the direction of the nanorods without any electrical connection between the nanorods and the capacitor plates producing the electric field. Increasing the electric field from 0 to 50 V cm^?1 resulted in an exponential increase in the relative rate of reduction of the bacteria from 3.9×10^?2 to 10.5×10^?2 min^?1. This indicates that the antibacterial activity of silver nanorods can be enhanced by applying an electric field, for application in medical and food-preserving fields.     

Restriction of the efficiency of photoinduced second-harmonic generation during optical poling of germanium-silicate glass

Abstract

The large growth of the absorption of radiation with doubled frequency in a region of high values for the induced electric fields has been detected during the investigation of an optical poling process in germaniumsilicate glass. The absorption suppresses the writing of the second-order susceptibility grating and leads to restriction of the maximum efficiency of the photoinduced second-harmonic generation in the glass.     

Modeling and Analysis of a Long Thin Conducting Stripline

A long thin conducting stripline embedded in a dielectric and centered between two large conducting plates, i.e., the stripline environment, is considered. The stripline is modeled as infinitely long, infinitely thin, and perfectly conducting by first considering a stripline of finite length, thickness, and conductivity in a dielectric layer. Starting from Maxwell's equations and assuming that the current on the stripline is a propagating wave in length direction, asymptotic expressions for the fields inside and in the neighbourhood of the stripline are deduced. These expressions are used to model the stripline in the stripline environment, which leads to a boundary-value problem for the electric potential. This problem is solved by two different approaches, leading to integral equations for the current and for an auxiliary function describing the electric potential. A relation between the current and the auxiliary function is deduced, which is used to obtain asymptotic expressions for current and impedance. Results are compared with a numerical solution of the integral equation for the current and with results in literature.     

Output Properties of Non-degenerate Parametric Amplifiers with Non-homogeneous Linear Losses

Abstract

The noise properties of non-degenerate parametric amplifiers with absorption losses which are different for the two beams are analysed by means of a semiclassical approach which enables the direct derivation of the Langevin equations for the optical fields from the quantum Heisenberg equations. Several statistical quantities are calculated and the implications of the present results for sub shot-noise absorption measurements are discussed finally.     

An Examination of the Nature of Propagating Optical Modes in a Thin Liquid-crystal Layer

Abstract

The optical modes excited in a thin homogeneous liquid-crystal layer are found to exist at momenta closely related to the pure eigenmodes of a simple uniaxial slab. However, when the electric field vectors within the liquid-crystal layer are examined, they demonstrate that the modes are not the simple pure orthogonalized eigenmodes. Furthermore, when an idealized three-media system is modelled to eliminate the influence of external fields, the same results apply. These results are attributable to the presence of boundaries.     

Optical properties of the polarized Dirac vacuum

An investigation is made of the propagation of laser radiation through the Dirac vacuum polarized by a strong electric field. Calculations are made of the refractive index of the vacuum and the angle of rotation of the plane of polarization of the radiation. The possibility of measuring strong electric fields is assessed. Pis’ma Zh. Tekh. Fiz. 24, 45–47 (July 26, 1998)     

Can a Travelling Electromagnetic Wave be Present in a Layered Medium?

Abstract

The problem of the presence of a travelling electromagnetic wave in an inhomogeneous medium is addressed. An argument is presented in favour of the option that the Poynting vector determines whether the wave is travelling or not. A strict harmonic solution to the Maxwell equations in a plane stratified medium is shown not to be a travelling wave. This solution can be decomposed into two travelling fields which separately do not satisfy the Maxwell equations and which are identified as the transmitted and return fields. The direction of the Poynting vector for the transmitted field satisfies the generalized Snell's law. The reflectance of a layer of such a medium is calculated and shown to be zero for some incidence angles. Phases of the two travelling fields are considered and shown to be different from those of geometric optics.     

Separation of Fullerene and Endofullerene Molecules in Inhomogeneous Electric Field

Abstract

The present study makes use of the neutral molecule motion model in the inhomogeneous static electric fields. We show the possibility of separating molecules with high polarizability and/or a permanent electric dipole moment in these fields. On the simple example of the electric field of the system of charged parallel metallic wires we have estimated the angle dispersion of the endofullerene molecules Gd@C₈₂, La@C₈₂, Sc@C₈₂, and Y@C₈₂ from the known values of the permanent dipole moments.     

Optical solitons in a new type of coupled nonlinear Schrödinger equations

Abstract

We consider a new type of integrable coupled nonlinear Schrödinger (CNLS) equations proposed by Park and Shin [1999, Phys. Rev. E, 59, 2372]. Using the Ablowitz-Kaup-Newell-Segur method, we construct the Lax pair for simultaneous propagation of four fields in the new type of CNLS equations. The explicit form of soliton solutions are derived using the Hirota bilinear method.     

Electrophoretic motion of two solid particles embedded in an unbounded and viscous electrolyte

 This work determines the electrophoretic motion of two colloidal particles embedded in a viscous and unbounded electrolyte. Contrary to other works in the field, the advocated method does not calculate the perturbation electric potential and the electrolyte Stokes flow in the whole fluid domain and its range of applications is not restricted to the case of uniformly charged particles embedded in a uniform electric field E _∞. The idea consists in establishing and solving thirteen Fredholm boundary integral equations (one of the second kind plus twelve of the first kind). The numerical implementation is briefly reported. Numerical benchmarks and new results are both presented and discussed with a special attention to the interactions between the particles. Received 26 February 2001     

Parametric down and up conversion in the Wigner representation of quantum optics

Abstract

We study spontaneous parametric processes starting from the quantized field equations in the Heisenberg picture using the common approximation of treating the laser pump as classical. After a (standard) linearization procedure we pass to the Wigner representation and the process becomes formally equivalent to the parametric interaction of two incoming zero-point modes with a pumping laser wave coupled by an optically nonlinear medium. Then the treatment of parametric down conversion and parametric up conversion are described by the Maxwell equations and look like a parametric amplification of the vacuum field. The fourth-order correlation function between the signal and idler fields is obtained in a form that makes for easy comparison with experimental results.