Analysis of waveguides containing EMCs (electromagnetic conductors) or PEMCs (perfect electromagnetic conductors)

The concept of a perfect electromagnetic conductor (PEMC) was introduced to generalize and unify two well-known and apparently disjoint concepts in electromagnetics: the perfect electric conductor (PEC) and the perfect magnetic conductor (PMC). Although the PEMC has proven a fertile tool in electromagnetic analyses dealing with new and complex boundaries, its corresponding definition as a medium has, nevertheless, raised several problems. In fact, according to its initial 3D definition, the PEMC cannot be considered a unique and well-defined medium: it leads to extraneous fields without physical meaning. By using a previously published generalization of a PEMC that regards this concept both as a boundary and as a medium – which was dubbed an MIM (Minkowskian isotropic medium) and acts, in practice, as an actual electromagnetic conductor (EMC) – it is herein presented a straightforward analysis of waveguides containing PEMCs that readily and systematically follows from the general framework of waveguides containing EMCs.     

Complementary cloak based on conventional cloak with axial symmetrical cloaked region

Based on the concept of complementary medium, a method which can make the conventional cylindrical cloak with axial symmetrical cloaked region to be not blind by filling the isotropic complementary in inner cloaked region is proposed. Firstly, the perfect electric conductor cylindrical shell was removed. Secondly, the symmetrical cloaked region was separated into two symmetrical regions along the symmetry axis and filled with isotropic complementary medium according to folding transformation. Full wave simulations are performed to confirm the effectiveness of the proposed method. The simulation results show that the converted cloak not only can exchange information with the outside, but also its presence cannot be detected.     

Helicity injection and diagnostics for orbitron millimeter wave source

Conventional orbitrons utilize the radially injected electrons for production of electromagnetic waves. In such a scheme, however, more than half of the electrons would not participate in the orbital motion around the anode due to the lack of acceleration. Only the electrons who did not suffer collisions till the radius 2/3 of the outer conductor (cathode) radius are possible to acquire the azimuthal velocity, via collisions, as large as the critical velocity with which the electrons can undergo circular equilibrium orbits. The axisymmetric injection is also a problem; 50% of electrons would be lost directly to the anode by the head-on collisions. This paper discusses various ways to enhance the efficiency and absolute power of an orbitron millimeterwave source. Experimental results are described on employment of a tapered metal-end, tangential injection of a thin electron beam, axial injection of rotating annular electron beams, and application of external magnetic fields. Further problem of conventional orbitrons is in its construction in which the potential-well is prematurely destroyed due to the shortening discharge current. Its diagnostics and consequence are discussed together with a new scheme leading towards the goal, an efficient injection of helicity (or helical electron-beam) into the potential-well conserved orbitron interation region.     

Scattering from a coated nihility circular cylinder placed in chiral metamaterial

The scattering of electromagnetic plane wave from a coated nihility circular cylinder placed in chiral metamaterial is investigated. The nihility cylinder is coated with chiral or chiral-nihility metamaterial and the medium hosting the coated cylinder is also considered as chiral or chiral-nihility metamaterial. The vector wave equation is used to find out the solution for the fields scattered from the concentric chiral ciruclar cylinders immersed in chiral metamaterial. Inner chiral cylinder is reduced to nihility cylinder taking permittivity and permeability approaching to zero with chirality parameter equal to zero. Coated perfect electric conductor (PEC)/perfect magnetic conductor (PMC) are obtained by taking very large value of permittivity/permeability of the inner cylinder. Numerical results for fields reflected from coated nihility cylinder are compared with those obtained for coated PEC/PMC cylinder. Our results for the special case of dielectric coated nihility/PEC cylinders in free space are shown to be in agreement with already published results thus validating the scheme of analysis.     

A Mixed-Transfer-Matrix Method for Simulating Normal Conductor/Perfect Insulator/Perfect Conductor Random Networks

We develop a mixed-transfer-matrix approach for computing the macroscopic conductivity of a three-constituent normal conductor/perfect insulator/perfect conductor random network. This is applied to two-dimensional and three-dimensional samples at a percolation threshold. Such networks are simulated in order to test whether a diluted percolating network of normal conducting bonds remains in the same universality class of critical behavior when a finite fraction of those bonds have been replaced by perfectly conducting bonds. Also tested by such simulations is whether a percolating mixture of normal and perfectly conducting bonds remains in the same universality class of critical behavior when a finite fraction of the normal bonds are replaced by perfectly insulating bonds. These questions are crucial for some recently published exact results which connect the macroscopic electrical and elastic responses of percolating networks.     

Angular spectrum representation of the electromagnetic multipole fields, and their reflection at a perfect conductor

Angular spectrum representations are derived for electric and magnetic multipole fields of arbitrary order. The result involves generalized spherical harmonics and generalized vector spherical harmonics, and the representations are in the form of integrals over the k_∥-plane. The representations are especially useful for the study of reflection and transmission of multipole radiation by a plane interface. As an example, we have considered the reflection at a perfect conductor. The reflected field of a multipole field could be expressed in the form of an angular spectrum with a very simple relation to the angular spectrum of the source field. The radiation pattern of a multipole near the perfect conductor is obtained with the method of stationary phase. We also introduce a method for determining the mirror image of the source of an arbitrary multipole.     

On the Decay Analysis of Electroproduced Higher-Spin Hadrons

We study exclusive electroproduction of two hadrons where one or both of the hadrons is a higherspin resonance whose decay is analysed. Interesting electroproduction experiments of this type are discussed. A complete formal apparatus is given for the decay analysis of spin-J particles produced in this way with polarized or unpolarized electron beams and targets. The cases J = 1, 3/2, 2 and 5/2 are worked out in detail. A conventional helicity frame analysis in terms of s-channel helicity amplitudes is given. Also we rearrange the formalism for use in the Gottfried-Jackson frame with everything given in terms of t-channel helicity amplitudes. The t-channel formalism makes it possible to completely separate the contributions from longitudinal and transverse virtual photon t-channel helicity states when only the laboratory azimuthal angle between the lepton and hadron planes is variable.     

Enhancement of conductivity due to local disorder in a one-dimensional conductor

We theoretically investigate electron transport in a one-dimensional conductor with a locally disordered potential by using the non-equilibrium Green's function theory. It is found that, by changing the energy of a site in a one-dimensional atomic chain, the electron conductivity can be larger when the modulated site energy is smaller than that of the other sites. This contradicts the conventional picture that an electron is scattered by the disorder of the potential, because such a scattering process usually causes resistivity. We show that the enhancement of conductivity that seems contradictory to the conventional picture of electron motion is explained by the change of energy of quasi bound states in the conductor.     

Impulse formulations of Hall magnetohydrodynamic equations

Impulse formulations of Hall magnetohydrodynamic (MHD) equations are developed. The Lagrange invariance of a generalized ion magnetic helicity is established for Hall MHD. The physical implications of this Lagrange invariant are discussed. The discussion is then extended to compressible Hall MHD and a generalized ion magnetic potential helicity Lagrange invariant is established. The physical implications of the generalized ion magnetic potential helicity Lagrange invariant are shown to be the same, as to be expected, as those of the generalized ion magnetic helicity Lagrange invariant.     

Modification of Spalart-Allmaras model with consideration of turbulence energy backscatter using velocity helicity

The correlation between the velocity helicity and the energy backscatter is proved in a DNS case of 256³-grid homogeneous isotropic decaying turbulence. The helicity is then proposed to be employed to improve turbulence models and SGS models. Then Spalart-Allmaras turbulence model (SA) is modified with the helicity to take account of the energy backscatter, which is significant in the region of corner separation in compressors. By comparing the numerical results with experiments, it can be concluded that the modification for SA model with helicity can appropriately represent the energy backscatter, and greatly improves the predictive accuracy for simulating the corner separation flow in compressors.     

Galloping of iced quad-conductors bundles based on curved beam theory

Galloping refers to wind-induced, low-frequency, large-amplitude oscillations that have been more frequently observed for a bundle conductor than for a single conductor. In the present work two different models are built to investigate the galloping of a bundle conductor: (1) a finite curved beam element method and (2) a hybrid model based on curved beam element theory. The finite curved beam element model is effective in dealing with the spacers between the bundled conductors and the joint between the conductors and spacers that can be simulated as a rigid joint or a hinge. Furthermore, the finite curved beam element model can be used to deal with large deformation. The hybrid model invokes the small deformation hypothesis and has a high computational efficiency. A hybrid model based on conventional cable element theory is also programmed to be compared with the aforementioned models based on curved beam element theory. Numerical examples are presented to assess the accuracy of the different models in predicting the equilibrium conductor position, natural frequencies and galloping amplitude. The results show that the curved beam element models, involving more degrees of freedom and coupling of translational and torsional motion, are more accurate at simulating the static and dynamic characters of an iced quad-conductor bundle. The use of hinges, rather than rigid connections, reduces the structural response amplitudes of a galloping conductor bundle.     

Calculation of the resonance frequencies of an open dielectric axially symmetric resonator of piecewise constant radius

An algorithm is suggested for calculating the resonance frequencies of open dielectric axially symmetric resonators of piecewise constant radius suitable for an arbitrary layered axially symmetric dielectric filling. The resonator is placed into a case with ideally conducting walls of a sufficiently large radius. Cases are analyzed where the resonator structure is partly coated with a perfect conductor.     

Helicity generation in turbulent MHD flows

We study turbulent flow of a conducting liquid in a uniform external magnetic field. It is shown that intense helicity generation is possible in the presence of a mean shear flow. It is noted that even though the mean helicity of the initial flow can be zero, the presence of internal topological structure of the flow, for example the presence of helicity of different signs at different scales, is nevertheless necessary for helicity generation. Zh. éksp. Teor. Fiz. 114, 946–955 (September 1998)     

Optical microstrip patch antennas design and analysis

This paper has presented transparent conductor oxide materials (TCOMs) based microstrip patch antennas with glass substrate and copper ground plane, which have been deeply analyzed in the visible spectrum region in comparison with the practical patch antenna model of indium tin oxide patch with glass substrate and different TCOMs based ground plane. As well as the study have investigated the effect of transparent oxide materials on patch antenna design instead of perfect conductor materials such as copper that has low cost and weight. The tradeoff between optical transparency and electrical conductivity will be evaluated for a range of visible regions. Microstrip transmission line feed method is used to predict the skin effects on a patch antenna and their impact on antenna efficiency, resonance frequency and optical transmission are also described. This study have discussed assessment of these tradeoffs and effect of TCOMs parameters on antenna design.     

Global weak solutions of the Vlasov-Maxwell system with boundary conditions

Boundaries occur naturally in physucal systems which satisfy the Vlasov-Maxwell system. Assume perfect conductor boundary conditions for Maxwell, and either specular reflection or partial absorption for Vlasov. Then weak solutions with finite energy exist for all time.This research is supported in part by NSF Grant DMS 90-23864     

Diffraction radiation from an inhomogeneous dielectric film on the surface of a perfect conductor

Diffraction radiation generated by a charged particle moving uniformly parallel to the surface of a perfect conductor coated with a dielectric film is considered; the thickness of the film is an arbitrary function of coordinates. A particular case is considered when this function is periodic in one coordinate. The dependence of radiation on the profile of an individual irregularity of the periodic film is analyzed in detail for an arbitrary energy of the particle.     

Guided modes in chiroplasma-filled perfect electromagnetic conductor parallel-plate waveguides

Theoretical analysis of electromagnetic wave propagation in a perfect electromagnetic conductor (PEMC) parallel-plate waveguide filled with a chiroplasma material is presented in this article. The derived formulations are general and can analyze perfect electric, perfect magnetic, or PEMC waveguides filled with any general isotropic/anisotropic material including plasma and metamaterials. The characteristic equation for the modes in this waveguide is obtained, and the behavior of the dispersion curves and the energy flux are examined and evaluated numerically. The results demonstrate that the chirality parameter, the plasma frequency, and the cyclotron frequency influence the behavior of the energy flux transported in the guide, in magnitude and orientation. The bifurcated mode cutoff frequencies are sensitive to the variations in the filling material parameters and likewise effected by the variations in the PEMC walls admittance parameter.     

X射线吸收谱研究碳与硅的纳米线/管

由于X射线吸收谱中的总电子产额(TEY)和荧光产额(FLY)具有不同的取样探测深度,分别对样品的表面和体内敏感,因而两者的综合应用为纳米材料的整体分析提供了有力的依据,是透射电子显微镜(TEM)、X射线衍射(XRD)等传统方法分析纳米材料时的补充。同时,通过对TEY和FLY记录的X射线吸收谱的评述,作者认为X射线吸收谱可以准确、可靠地用来进行纳米线和纳米管的生长及其机理、取向、化学键合、缺陷与螺旋性等方面的研究。因此X射线吸收谱具有传统方法无法比拟的优势,是纳米材料研究领域强有力的表征工具。     

Helical Mode Absolute Statistical Equilibrium of Ideal Three-Dimensional Hall Magnetohydrodynamics

Using the Fourier helical decomposition,we obtain the absolute statistical equilibrium spectra of left-and righthanded helical modes in the incompressible ideal Hall magnetohydrodynamics(MHD). It is shown that the left-handed helical modes play a major role on the spectral transfer properties of turbulence when the generalized helicity and magnetic helicity are both positive. In contrast, the right-handed helical modes will play a major role when both are negative. Furthermore, we also find that if the generalized helicity and magnetic helicity have opposite signs, the tendency of equilibrium spectra to condense at the large or small wave numbers will be presented in different helical sectors. This indicates that the generalized helicity dominates the forward cascade and the magnetic helicity dominates the inverse cascade properties of the Hall MHD turbulence.     

Amplification of mean magnetic field and magnetic helicity production in hot lepton plasma of early universe

We argue that the magnetic helicity conservation is violated at the lepton stage in the evolution of early Universe owing to the parity violation in the Standard Model of electroweak interactions. As a result, a cosmological magnetic field which can be a seed for the galactic dynamo obtains from the beginning a substantial magnetic helicity which has to be taken into account in the magnetic helicity balance at the later stage of galactic dynamo. The particle physics mechanism suggested in our works depends neither on helicity of matter turbulence with plasma vortices resulting in the standard α effect in dynamo theory nor on general rotation. The mechanism can result in a self-exitation of an (almost) uniform cosmological magnetic field. The text was submitted by the authors in English.