A hybrid technique based on Finite-difference frequency domain and particle swarm optimization techniques is proposed to reconstruct the breast cancer cell dimension and determines its position. Finite-difference frequency domain is formulated to calculate the scattered field after illuminating the breast by a microwave transmitter. Two-dimensional and three-dimensional models for the breast are used. The models include randomly distributed fatty breast tissue, glandular tissue, 2-mm thick skin, as well as chest wall tissue. The models are characterized by the dielectric properties of the normal breast tissue and malignant tissue at 800 MHz. Computer simulations have been performed by means of a numerical program; results show the capabilities of the proposed approach.

The interaction between a metamaterial cylindrical structure and an incident plane wave is investigated. The structure is comprised of two cylinders, one embedded into the other, whose effective characteristics vary with the operating frequency following similar laws. Such a model can be used to describe periodic structures, constituting metamaterials, with slightly different features. The well-known eigenfunction expansions are adopted, while the boundary conditions are manipulated with help of the translation theorem for cylindrical coordinates. A first-order perturbation solution is obtained leading to simple and computationally efficient formulas. The fluctuations of near-field and far-field responses with respect to the position of the internal cylinder, the permittivities and the frequency are observed and discussed.

Testing electronic equipment for radiated emissions requires the accurate calibration of EMI sensor. The performance of the sensor depends on its Antenna Factor (AF), which is the ratio of the incident electric field on the antenna surface to the received voltage at the load end across 50Ω resistance. The theoretical prediction of the AF of EMI sensors is a very attractive alternative if one takes into consideration the enormous expenditure and time required for calibrating a sensor experimentally. In this work, FDTD is developed to predict the performance of rectangular waveguide for EMI sensors.

The electronic structure and mobility trends in a n-type delta-doped quantum well in Si, matched between p-type delta-doped barriers of the same material, is presented. The distance between the n-type well and p-type barriers is varied from 50A to 500A; and also the impurity density from 5 × 10¹² cm^-2 to 5 × 10¹³ cm^-2, for both, donors and acceptors. An increase in the mobility by a factor of 1.6 at interwell distance of 50A with donor and acceptor concentrations of 5 × 10¹² cm^-2 and 5 × 10¹³ cm^-2 compared with a single delta-doped well without p-type barriers is found. This improvement in mobility could be attributed to a better confinement of carriers, which favors excited levels with nodes in the donor plane. This trade-off between carrier concentration and mobility could be exploited in high-speed, high-power and high-frequency applications.

We present the electronic spectrum of a n-type deltadoped quantum well in Si coupled to a p-type delta-doped barrier within the envelope function effective mass approximation. We applied the Thomas-Fermi approximation to derive an analytical expression for the confining potential, and thus, we obtain the electronic structure in a simple manner. We analyzed the electron subband structure varying the distance between the doping planes (l) as well as the impurity density in them (n_2D, p_2D). We also study the mobility trends through an empirical formula that is based on the electron levels, the electron wave functions and the Fermi level. We find a monotonic decrease in the mobility as the p-type barrier moves away from the n-type well, and optimum parameters, l = 70A and n_2D = 5 × 10¹² cm^-2 and p_2D = 5×10¹³ cm^-2, for maximum mobility.

In this paper, two different neural models are proposed for calculating the quasi-static parameters of multilayer cylindrical coplanar waveguides and strip lines. These models were basically developed by training the artificial neural networks with the numerical results of quasi-static analysis. Neural models were trained with four different learning algorithms to obtain better performance and faster convergence with simpler structure. When the performances of neural models are compared with each other, the best test results are obtained from the multilayered perceptrons trained by the Levenberg- Marquardt algorithm. The results obtained from the neural models are in very good agreements with the theoretical results available in the literature.

An analytical formula of the current distribution for the VLF horizontal wire antenna located above the ground is presented in this paper. This formula is suitable for the VLF horizontal antenna which is fed at arbitrary position and with arbitrary loaded impedance at the end. In order to validate the analytical formula, a numerical code based on MoM is also developed. The comparison between the results obtained by two methods proves the validity of the analytical formula proposed in this paper.

Long-term variations in strong geomagnetic storms are analyzed and linked to electric fields induced on Earth. In fact, geomagnetic disturbances generate electric fields that drive currents in the Earth which may have significant effects on electrical systems and pipelines. The present study will be carried out using aa, AE and Dst index data to estimate long-term variations in strong geomagnetic disturbances. The results are extended then to the space weather topic through a rough assessment of the expected Earth electric field from measured horizontal components of the surface magnetic field, and also through a qualitative estimation of the consequent currents and voltages induced in a pipeline using the distributed source transmission line (DSTL) theory.

An all-optical microwave generation using a multiwavelength photonic crystal fiber Brillouin laser is presented. A highly nonlinear photonic crystal fiber with the length of 25m is used as Brillouin gain medium. A Fabry-Perot cavity with two fiber Bragg gratings as reflectors are designed in order to enhance the Brillouin conversion efficiency. The fiber Bragg gratings can be used to selectively excite the jth-order Stokes' wave and suppress other order Stokes' waves. The mechanism for microwave/millimeterwave generation is theoretically analyzed. In the experiment, both 9.788 GHz and 19.579 GHz microwave signals are achieved through mixing the pump wave with the first-order and the second-order Stokes' waves.

The electromagnetic scattering from a conducting object coated with metamaterials, which have both negative permittivity and permeability is derived rigorously by using finite difference frequency domain (FDFD). A formulation for the FDFD method is presented. The scattering from circular and multilayers elliptic cylinder coated by metamaterial are investigated. Also, the scattering from dielectric and metamaterial sphere is depicted. Numerical results are compared with the available data in the literature.

A proposed sensor for landmines detection consists of two parallel microstrip antennas placed on the same ground plane and with corrugated ground surface between the arrays has been investigated. The microstrip patch array with corrugated ground surface has the advantage of a low mutual coupling compared with the classic arrays. The Finite-Difference Time-Domain (FDTD) is used to simulate the sensor for landmines detection.

In this paper, three analytic closed form solutions are introduced for arbitrary Nonuniform Transmission Lines (NTLs). The differential equations of NTLs are written in three suitable matrix equation forms, first. Then the matrix equations are solved to obtain the chain parameter matrix of NTLs. The obtained solutions are applicable to arbitrary lossy and dispersive NTLs. The validation of the proposed solutions is verified using some comprehensive examples.

A simple and inexpensive method for the qualitative characterization of wood surfaces is presented. It is based on the iterative autocorrelation of laser speckle patterns produced by diffuse laser illumination of the wood surfaces.The method exploits the high spatial frequency content of speckle images. A similar approach with raw conventional photographs taken with ordinary light would be very difficult. A few iterations of the algorithm are necessary, typically three or four, in order to visualize the most important periodic features of the surface. The processed patterns help in the study of surface parameters, to design new scattering models and to classify the wood species.

Improving the performance of a microstrip antenna array has been considered based on the innovative use of an absorbing radar cover.Since the surface wave between antennas array elements plays a major role in mutual coupling and scattering behavior of array antenna. The main objective of this work is to reduce the effect of surface wave between array elements using radar absorbing cover.The absorbing cover has been designed with spatial configuration to get maximum performance at the resonant frequency of the fabricated microstrip antenna array.The measured results of the tested antenna array show a significant reduction of both mutual coupling between array patches and radar cross section of the tested antenna array with minimum side effects on the antenna parameters.

Setting up ground based antennas for operation in the HF and longer wavelength bands frequently involves clearing large areas of land for the installation of ground mats to provide a high conductivity return path for the displacement currents. In moving from the cleared area to the virgin scrubland beyond, which is assumed to be forested with bushes and small trees, there is the possibility of an abrupt change in surface properties at the boundary resulting from the discontinuity in the vegetation which at longer wavelengths can be modelled as a change in surface impedance. By modelling the trees and bushes as point dipole moments, the aim of this paper is to estimate the significance of any such effect in terms of the gross physical properties of the vegetation. The result is to show that in normal circumstances the effect can be expected to be slight. A solution to this problem has application in helping determine the environmental footprint of the antenna installation, the amount of land that needs to be cleared to satisfactorily accommodate it.

Based on both the modified Rytov method and the altitude-dependent model of the ITU-R slant atmospheric turbulence structure constant, the uniform model of scintillation index considering inner- and outer-scales is derived form weak to strong fluctuation regions with Gaussian beam propagation on the slant path, and can be degenerated to the result of the horizontal path with atmospheric structure constant is a fixed value. The numerical conclusions indicate the smaller wavelength, the inner-scale has a stronger impact on scintillation than outer-scale. But, in strong fluctuation, the outerscale effect is prominence. Finally, the numerical results are compared and verified with the experimental data.

In this paper two multi-clad RI- and RII-type optical fiber structures for small dispersion and dispersion slope as well as large bandwidth are considered and novel design strategy for this purpose is presented. The suggested design method uses the Differential Evolution (DE) approach. We put absolute value of dispersion factor as fitness function in differential evolution method. This algorithm successfully introduces a special fiber including so small dispersion and dispersion slope in the predefined wavelength duration. Also, the proposed method can set zero dispersion wavelengths with high accuracy compared other traditional methods. The designed dispersion-shifted RI single-mode fiber has the bandwidth of 600nm and the max amount of 1.36 (ps/km/nm) in that duration which is an ideal result.

Spatial focusing characteristics of time reversal (TR) electromagnetic waves are studied in this paper. Different antenna arrays are used as a TR mirror and their elements are arranged in one and two dimensions in the horizontal plane. The focused energy density around initial source location is investigated in non-line-ofsight (NLOS) and line-of-sight (LOS) cases, respectively. The results demonstrated that, roughly speaking, under the case of fixed space between two adjacent elements, the more the number of the array elements, the stronger the focused average energy density. However, in the case of fixed TR mirror array aperture, some abnormal phenomena are observed when additional elements are inset into the initial one.

The paper presents the faster, simpler, and accurate algorithm to solve time independent Schrodinger equation based on transfer matrix method. We can thus calculate all bound and quasi bound energy and the corresponding probability density. A central part of this paper deals with the solving of Schrodinger equation for quantum well structure. Our results show that the transfer matrix method is accurate, it is easier to implement. The increase in well width increases the FWHM from 5.4 nanometer to 9.4 nanometer, while the increase in the Aluminum concentration the FWHM decreases from 8.98 to 5.4.

The enigma of the wave-particle duality of photon has remained unimpressively explained for a century since Einstein presents the concept of the photon in 1905. This article establishes a classical geometric structure model of a single photon based on field matter, educes a formula for the size of a photon; assumes that there only are two kinds of photon of right hand and left hand circular polarized, and suggests the frequency ω of photon polarization rotated to be its spin frequency. It ascribes the wavelike of photon to its spin motion and the particle-like to its translation motion. From the point of photon particle instead of wave view to re-analyze Young's double-slit interference and polarizer experiments, gives reasonable mechanism. It defines the phase velocity and the group velocity of a photon. It gives a unified and consistent understanding of quantum particle of light and classical electromagnetic waves field. Evidently, such a precisely defined conceptual model is reasonable, objective and easy to accept for classical physicists.