Electromagnetic Waves In Order Research Articles

Spatial light modulator design and generation of structured electromagnetic waves using digital light processors

Spatial light modulators (SLMs) are versatile devices used for optical studies. These instruments have a wide area of application in photonics. Additionally, SLMs have potential utility in different applications, such as biomedical applications, laser based surgery for precise cutting and as optical tweezers to separate cells in a petri container. However, the high cost of SLM devices prevents their widespread use in many areas, including industrial areas and scientific research laboratories. This paper demonstrates how to design a digital light processor (DLP) based low-cost SLM and describes how to obtain structured electromagnetic waves with the designed SLM. Therefore, this research was undertaken to design and produce a low-cost SLM device for optical applications. For this purpose, two prerequisites had to be fulfilled, the first was to use suitable components of a projection device with DLP-based digital micro-mirror device (DMD), and the second was to eliminate unnecessary SLM components from the system. Finally, holographic images reflected on the SLM screen were created by using Mathematica software program to change the amplitude and phase of the electromagnetic waves in order to obtain the structured electromagnetic waves.

Pengaruh Temperatur Karbonisasi terhadap Mikrostruktur dan Pembentukan Kristal pada Biokarbon Eceng Gondok sebagai Bahan Dasar Absorber Gelombang Elektromagnetik Radar

Radar Absorbing Materials (RAM) or radar absorbing materials of radar electromagnetic waves are materials used to reduce or eliminate radiation of radar electromagnetic waves in order to avoid reflection of waves. At this time the development of RAM research leads to materials derived from nature. Some materials derived from nature that has been used as RAM such as rice husk, bamboo, coconut shell, coconut husk, wood fiber, and wood flour. In this study, eichornia crassipe is made into biocarbon or activated carbon for use as a base material for RAM. Carbonization is one way to transform water hyacinth into biocarbon or activated carbon. The method used in this research is Experimental Research. The independent variables of this research are carbonization temperature starting from temperature 500 o C, 600 o C, 700 o C, 800 o C, 900 o C and 1000 o C. The results showed that the higher the carbonization temperature, the more open pores will be with 2 μm diameter at 1000 o C, and the higher the carbonization temperature than the percentage of carbon crystal formed higher with the value of 14% at temperatures 900 o C and 1000 o C. The biocarbon structure of eichornia crassipe is crystalline and amorphous making it suitable for use as RAM material.

Highly stable dielectric frequency response of chemically synthesized Mn-substituted ZnFe2O4

The tenacity of the present study was to develop a material using an economical chemical route, having balance between magnetic and dielectric order parameters for maximum transmittance of electromagnetic waves in order to use them in shielding materials. In this context, Mn-Zn ferrites were prepared using a wet chemical based sol-gel auto-combustion technique. X-ray diffraction confirmed the pure phase formation of samples, while some impurity peaks were also present for the higher value of Mn substitution. Field emission scanning electron microscopy revealed a decrease in grain size with increasing Mn substitution. While energy dispersive X-ray spectroscopy confirmed the elemental composition of pure and Mn substituted samples, the dielectric constant, dielectric loss and tangent loss were decreased with increasing frequency and increasing Mn substitution. The complex electric modulus was found to be a function of frequency and values of complex electric modulus were increased with increasing frequency and Mn substitution. The complex impedance of RC series circuit and RC parallel circuit was also decreased with increasing both the parameters while AC conductivity was increased in the series. Dielectric frequency response was also studied for the prepared samples and the best match was found with expected results. The Nyquist and Cole-Cole plots revealed the semi-conductive behavior at higher frequency and Mn substitution also yielded the same results. The relative stability of the samples to be used as dielectric materials was also studied using Bode and Nichols plots, and a comparatively high gain margin was observed, well suitable for potential applications in electromagnetic shielding.

Automatic Detection and Classification of Buried Objects Using Ground‐Penetrating Radar for Counter‐Improvised Explosive Devices

AbstractIn this paper, a technique that can automatically detect and classify objects buried under the ground is proposed. The technique employs a ground‐penetrating radar that transmits electromagnetic waves in order to strike the objects and then receives the backscattering electromagnetic wave to perform signal processing. This signal processing is divided into four main steps as follows. First, preprocessing is used to reduce the clutter due to the effect of the media layer interface. Second, the late time of the scattering signal is estimated using a simple cross correlation. Third, a few successive poles are extracted from the scattering response at the estimated late time by using the short‐time matrix pencil method. Finally, the extracted poles are fed for object classification with different constitutions and/or shapes using a support vector machine. Simulations according to the practical situation in three southern provinces of Thailand to counter the improvised explosive devices were set up. The performance of the proposed technique was evaluated. The simulation results showed that the proposed technique can efficiently detect and classify buried objects for counter‐improvised explosive device operations in the military.

Near field focusing for nondestructive microwave testing at 24 GHz – Theory and experimental verification

This paper describes the development of different novel antenna concepts for improving the spatial resolution of microwave based non-destructive testing (NDT) at 24 GHz. In a great number of applications the antenna of the sensor can be brought very close to the device under test. In these cases, the near field characteristics of the antennas are crucial for a high resolution. However, common sensor heads offer either a high image resolution or a high penetration depth. In order to combine both of the characteristics different antenna concepts have been developed. The objectives were to obtain a high return loss combined with a sufficient high dynamic range and a near field focusing of electromagnetic waves in order to yield a high resolution. Altogether, three antennas have been set up. Each antenna has been calculated analytically, followed by a FEM simulation, near field measurements and an experimental verification.

Lossy chaotic electromagnetic reverberation chambers: Universal statistical behavior of the vectorial field.

The effective Hamiltonian formalism is extended to vectorial electromagnetic waves in order to describe statistical properties of the field in reverberation chambers. The latter are commonly used in electromagnetic compatibility tests. As a first step, the distribution of wave intensities in chaotic systems with varying opening in the weak coupling limit for scalar quantum waves is derived by means of random matrix theory. In this limit the only parameters are the modal overlap and the number of open channels. Using the extended effective Hamiltonian, we describe the intensity statistics of the vectorial electromagnetic eigenmodes of lossy reverberation chambers. Finally, the typical quantity of interest in such chambers, namely, the distribution of the electromagnetic response, is discussed. By determining the distribution of the phase rigidity, describing the coupling to the environment, using random matrix numerical data, we find good agreement between the theoretical prediction and numerical calculations of the response.

Composite Materials Based on Silicone Rubber Used to Mitigation Electromagnetic Pollution

Rapid developments in telecommunications and digital processing of information are facing the problem of electromagnetic wave pollution and interference. The aim of this article is the characterization at microwave frequencies of composite materials based on silicone rubber. These materials contain 80% siloxane rubber and only 20% powdery feeling like nanocarbon and pyrite cinder. To achieve these objectives were reviewed and selected raw materials and characteristics were determined in a structural material, the electromagnetic attenuation as well as electrically, by making measurements of electrical conductivity of thin layers of polymer matrix composites produced by the doctor blade technique. Starting from sample siloxane rubber, i.e. without additives or filler reinforcement in compression analysis we find that reinforcing agents leads to increased values of the modulus of elasticity in especially for pyrite ashes. For materials analyzed in this paper, measurements were made in the frequency range between (1-18) GHz and have found high attenuation over 45 dB in the case of composite materials with pyrite ash filler. So we can say that this materials can used for shielding against electromagnetic waves in order to protect the human factor. The novelty of the paper consists in the compositions of the specimens and their mechanical and electromagnetic characteristics.

Experimental Study of the Invariants of the Time-Reversal Operator for a Dielectric Cylinder Using Separate Transmit and Receive Arrays

The decomposition of the time reversal operator (DORT method) is applied to electromagnetic waves in order to characterize a dielectric cylinder. It consists in determining the Time Reversal Invariants of the Time Reversal Operator. Here, this matrix is built from the inter-element responses between distinct transmit and receive arrays. In this paper experimental results obtained between 2 and 4 GHz are compared to a theoretical model, developed in an other paper (Minonzio , ¿Theory of the time-reversal operator for a dielectric cylinder using separate transmit and receive arrays,¿ <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">IEEE Trans. Antennas Propag.</i> , vol. 57, pp. 2331-2340, 2009). The DORT method is then applied to an inverse problem to determine the diameter and the permittivity of the cylinder. It is shown experimentally that different experimental parameters can be estimated from the singular values of the time reversal operator.

Classical treatment of the Franson two-photon correlation experiment

A two-photon correlation experiment that was proposed by Franson [ Phys. Rev. Lett.62, 2205 ( 1989)] and was recently carried out is analyzed in terms of electromagnetic waves in order to see whether the observed fourth-order interference effects can be explained classically. The conclusion is that, although a classical field can give rise to such interference effects, no classical field can actually account for the observations reported.