Reflection Of Electromagnetic Radiation Research Articles

Complex permittivity and electromagnetic interference shielding properties of Ti3SiC2/polyaniline composites

Ti3SiC2/insulating polyaniline (Ti3SiC2/PANI) composites were prepared by solution blending and subsequently by hot-pressing process. The dielectric permittivity and electromagnetic interference (EMI) shielding effectiveness (SE) of the composites were determined in the frequency range of 8.2–12.4 GHz (X-band). Both real and imaginary permittivities increase with the increasing Ti3SiC2 content, and which are attributed to the enhanced displacement current and conduction current. The EMI SE of the composites can be greatly improved by addition of Ti3SiC2 filler, which may be ascribed to the increase of electrical conductivity of the composites. It is also found that the reflection of electromagnetic radiation is a dominant mechanism for EMI shielding of the composite. An average EMI SE of 23 dB can be achieved in the X-band range for the composite with 25 wt% Ti3SiC2 content, which shows the potential of the Ti3SiC2/PANI composites as EMI shielding materials for commercial applications.

Effects of gas temperature and electron temperature on species concentration of air plasmas

The applications of atmospheric pressure air plasma, such as absorption and reflection of electromagnetic radiation, require an electron density of 1012cm−3 or higher. To achieve the required electron density, the electron temperature needs to reach certain level for a given gas temperature. In this manuscript, to obtain an electron density of 1012cm−3 in one atmospheric pressure air, the required electron temperatures are studied for the given gas temperatures from 500to2000K. It is found that the required electron temperatures decrease dramatically from 15310to11750K when the gas temperature increases from 500to1000K, but further increase the gas temperature to 2000K; the electron temperature of 11315K is still needed to achieve an electron density of 1012cm−3.

Variation of the type of resonance reflection of electromagnetic radiation from metal nanolayer-dielectric layer structures

Two types of resonance reflection of electromagnetic radiation from metal nanolayer-dielectric layer structures have been theoretically predicted and observed in experiment. These structures can obey the conditions of a half-wave resonance at a small metal layer thickness, and a quarter-wave resonance at a greater metal layer thickness.

Microwave Tomographic Imaging of the Heart in Intact Swine

Microwave tomography is a new imaging modality based on differentiation of tissue dielectric properties. The main objective of our research project is to develop a microwave tomographic approach for non-invasive assessment of functional viability of myocardial tissue, including detection of infarcted tissue. Imaging of the heart in intact, euthanized animals is the first step towards this objective. When microwave tomography is used to image the thorax of intact animals, it faces two major problems: — the structural complexity of the rib area with high reflection of electromagnetic (EM) radiation from its boundaries, and the potential for high reflection of EM radiation from the lung, filled with air. In addition, when a targeted object (a heart in our case) is located inside of a larger high scattered object (a torso), the level of EM field scattered by the internal object has to be technically detectable from the stronger EM field scattered by torso. The goal of this research study is to evaluate the degree of complexity of these problems, to understand some technical requirements for clinically applicable MWT system and to demonstrate the feasibility of microwave tomography for imaging of the heart in intact mammals using a swine model. Experiments were conducted on pigs (Yorkshire Domestic Cross/Farm Pigs) using a modified three-dimensional (3D) microwave tomographic (MWT) system operating at frequency 0.9 GHz. The presence of the heart in torso changes the amplitude of EM field by about 10–20% and changes the phase of EM field by about 7–10 degrees (mean absolute differences). Microwave tomographic images of swine torso and intact euthanized animals were obtained and discussed. Images reveal intra-torso and organ anatomy, including the heart and left ventricular chamber.

High-Frequency Nonlinear Response of Thin Superconducting Films with a Mixed d and s Symmetry of the Order Parameter

Third-harmonic generation during reflection of electromagnetic radiation from a thin superconducting film with a mixed d-and s-order parameter is studied theoretically. The dependence of the third harmonic intensity on the temperature and amplitude of an incident wave is calculated in the framework of the Ginzburg-Landau theory for superconductors with a two-component order parameter, and its behavior in the vicinity of transitions between phases with different symmetries is analyzed. It is shown, in particular, that the third harmonic intensity in the vicinity of the temperature corresponding to the d ⇆ d + s phase transition substantially increases and is a nonanalytic function of the amplitude of the incident wave, while no singularity in the nonlinear response is observed for the d ⇆ d + is transition. The linear reflection coefficient is found to be virtually insensitive to these phase transitions.

Nongyrotropic magneto-optical effects in metal-insulator magnetic multilayer thin films

Nongyrotropic magneto-optical effects are investigated in metal-insulator magnetic multilayer thin films. These effects manifest themselves in changes in the coefficients of transmission and reflection of electromagnetic radiation from the surface of a multilayer film due to the crossover of the magnetic structure from an antiferromagnetic configuration to a ferromagnetic configuration. The nongyrotropic magneto-optical effect observed in reflected light is analyzed theoretically. It is assumed that the multilayer structure is exposed to radiation of a monochromatic plane wave polarized along the direction of magnetization of the film. The magneto-optical effect is described in terms of the permittivity tensor of the multilayer medium, which depends only on the light frequency. The Boltzmann kinetic equation is treated with allowance made for spin-dependent electron scattering both inside conducting layers and at rough interfaces. Using an Fe/C multilayer as an example, it is demonstrated that the nongyrotropic magneto-optical effect is equal in order of magnitude to the equatorial Kerr effect or other strong magneto-optical effects.

Measurement of dielectric properties of high-absorption materials at microwave frequencies

A method is proposed for measuring the dielectric constant e′ and dielectric loss e″ of high-absorption dielectric materials by measuring the reflection of electromagnetic radiation with the aid of an adjustable quarter-wave matching plate of nonabsorbing material close to the dielectric surface.

Asymptotic theory of the reflection of electromagnetic radiation by moderately and highly conductive bodies

In this paper a method of deriving generalized impedance boundary conditions continuing tangential derivatives of high order is proposed. The case of reflection of an arbitrary electromagnetic wave by a curvilinear surface on which a generalized impedance condition holds is considered. The phenomenon of diffusion polarization dependent on the material and geometric properties of the reflecting surface is investigated. Bibliography: 5 titles.

Reflection of electromagnetic radiation from structured metallic magnets.

Reflection of electromagnetic radiation from structured metallic magnets.

Total backward reflection of electromagnetic radiation due to resonant excitation of surface waves.

We consider a p-polarized electromagnetic wave incident on a semi-infinite plasma covered by a dielectric layer. The plasma density is supposed to vary periodically along the plasma surface. The coefficients for specular as well as backward reflection are calculated. We show that, for certain parameter values, the specular reflection vanishes completely because all the energy is reflected in the backward direction due to the excitation of leaking surface waves.

Exciting new synthesis of a novel theoretically interesting zeolite ZOO-451F, partial characterization, and its novel and unusual catalytic effect in a new reaction: Part CXLVIII

Hydrothermal synthesis of a new, theoretically interesting zeolite ZOO-451F [1] is reported under new conditions (warm hot plate in the back of a hood for sixth months while the graduate student took a short vacation) using a new template (plastic) and seed (grapefruit). Ion exchange, carried out by a novel procedure that we will report (in Part MCXIII), gave a catalyst which, under carefully selected conditions (selected from Thomas' Proven Catalysts and Catalytic Processes), converted ethanol (a pretentious young red wine) to ethylene; the conversion and yield were industrially significant (but were too embarassingly small to be reported in public). Characterization of the catalyst by terran gravitational attraction, approximate visual electromagnetic radiation reflection spectrum, and relative ambrosia content are reported. The enourmous theoretical importance of this zeolite will be reported, and its use as a support for cold fusion will be speculated on.

Reflection-absorption of ultrathin films on the surface of semiconductors and dielectrics by the method of IR spectroscopy

For the parameter of the change in the reflection coefficient owing to the presence of a film on the surface and thus the sensitivity of the method we employed the ratio of the difference of the reflection coefficients of a pure substrate and a substrate with a film to the reflection coefficient for the pure substrate AR/R = (R~ ~ usually called in the literature the absorption factor, for which calculations have been performed for a wide range of optical constants and angles of incidence andpolarization direction of IR radiation. The values of the optical constants were given for strongly absorbing materials for the example of the absorption band near ii00 cm-* of an SiO2 film [2] and for weakly absorbing materials for a film of organic material with n~ = 1.3 and k~ = 0.14 The absorbing film was assumed to be homogeneous, isotropic, and with plane-parallel interfaces at the substrate and external medium. The case of reflection of electromagnetic radiation from the film--substrate system under the given assumptions was studied in detail in [6]. The exact expression for the reflection coefficient as a function of the optical constants of the bounding media, the ratio of the film thickness to the wavelength of the radiation, and the angle of incidence can be represented in the following form, convenient for programming:

The phase of reflection from a conducting grating

The phase of zeroth order reflection of electromagnetic radiation from an echelette grating is investigated for the two characteristics polarisations at normal incidence. An exact formalism for the problem is developed, and the phases evaluated in the case of radiation wavelength much longer than the groove depth. The difference in phase between the two polarisations amounts to a difference in the equivalent position of reflection of about 20% of the groove depth. Experimental measurements at 337 μm wavelength confirm the phase difference.

Comments on the Photon Echoes

Abstract The coherent light pulses obtained in the experiments of light echoes type [1] (as induction and echoes signals) and generated by the electric dipole system bring the information about the dynamical properties of the dipole system and are used for the registration of that information. As to the dynamics of the emitted photons them-selves at the present time the effects of pulse form changing [2] and self-induced transperancy [3] caused by the photon system interaction with the matter were taken into consideration only. In this work we discuss the memory effects of the system of photons itself spreading into the vacuum. The discussed effect is the method of the space-time coherence re-establishment of the laser radiation on the basis of application the effect which we called the photon echoes. The point of the method is in the plural reflection of electromagnetic radiation from the mirrors which gives the steady-state conditions of the electromagnetic wave spreading and is caused by diffraction. In itself the steady-state conditions of the electromagnetic wave spreading denote that the mutual intensity function J(n)(x1, x2) is not dependent of the X1 and x2 coordinates if the n is sufficiently large (it is the factorisation condition of the mutual intensity function), and as it was shown in the work [4] the

Average irregularity representation of a rough surface for ray reflection

A new ray model is presented for the reflection of electromagnetic radiation from the rough air-material interface of a randomly rough surface. Unlike previous derivations that modeled the rough interface as consisting of microareas randomly oriented but flat (facets), this derivation models it as consisting of microareas not only randomly oriented but also randomly curved. Physically, the models are the same, but this new derivation leads to some new results. (1) For any given rough surface, there exists a single, optically smooth, curved surface of revolution of very restricted shape that will reflect radiation in the same distribution as that reflected by the rough interface. (2) Modeling that surface as an ellipsoid of revolution gives a surface-structure function that appears more accurate and useful than existing ones. (3) Unlike the facet derivations, this derivation lends itself to a normalization that gives the absolute, instead of just a comparative, reflectance-distribution function.

The reflection and emission of electromagnetic radiation by planetary surfaces and clouds

Planetary surface investigation by electromagnetic radiation reflection and emission observation techniques