Evaluation Of Shielding Effectiveness Research Articles

Analysis of structural, optical, mechanical properties and evaluation of radiation shielding effectiveness of strontium borate glasses doped with ZnO nanoparticles

This research meticulously explores the synthesis, structural, thermal and optical characterization of zinc oxide nanoparticles (NPs) infused strontium borate glasses (termed SZ glasses) and their applicability as radiation shielding. The glasses have been produced using the melt quenching process in the composition series of (60-x)B2O3: xZnO: 10SrO: 10Na2O: 10CaO: 10BaO, where x varied from 0 to 20 % mol. In order to dope ZnO into glasses, its structural and morphological characteristics were investigated after it was synthesized by solution combustion method. It was found that the inclusion of ZnO significantly impacted the glasses' density, molar volume, hardness, yield stress, and thermal stability. The optical properties of the produced glasses, such as transmittance, reflection, transparency, opacity and band gap energies, were examined and the effect of ZnO on the optical properties of the glasses was investigated. Crucially, the SZ glasses exhibited notable efficiency in shielding against gamma photons and fast neutrons. This is evidenced by the favourable change in the mass attenuation coefficients with increasing ZnO concentration. Parameters like the half-value layer, effective atomic number, and energy absorption buildup factors were calculated to gauge the radiation attenuation proficiency of the SZ glasses, demonstrating their potential utility in radiation protection. In conclusion, the developed SZ glasses display advantageous structural, thermal, and optical qualities, along with robust shielding capabilities against gamma photons and fast neutrons. This study contributes significant knowledge to the field of novel glass materials, paving the way for their application in various industrial and medical contexts requiring radiation shielding.

Universal Statistical Tradeoffs for Shielding Effectiveness Evaluation of Electrically Large Enclosures in Reverberation Chambers

Shielding effectiveness (SE) evaluation of electrically large enclosures within reverberation chambers (RCs) is standardized procedure for electromagnetic compatibility (EMC) applications. In this work the potential relationship between SE and electromagnetic resonances have been investigated with respect to the ambiguity in definition of SE for the international standards, e.g., IEC 61000-4-21 or IEEE Std 299.1. From a statistical point of view, we derive the expansions of SE defined by the ratio of the maxima and the averages respectively. To evaluate SE more prudently as well as to obtain a much smaller uncertainty, we can make the tradeoffs for SE, which should be defined as the ratio of the averages for the overmoded frequency, and the ratio of the maxima for the undermoded using a common criterion aimed to discriminate the electromagnetic field behavior between the undermoded and the overmoded, and also verify the corresponding results by numerical simulations and measurement performed in RC.

Evaluation of Near-Field Electromagnetic Shielding Effectiveness at Low Frequencies

Magnetic induction tomography (MIT) is a novel technology for flow measurement offering significant promise in the measurement of multiphase flows containing low-conductivity fluids such as saline water. Such measurements rely on optimal effective shielding to avoid external field interference and extraneous capacitive coupling that can lead to false readings and overestimations of the eddy current-induced fields. The performance of various attenuation materials in the low megahertz frequency spectrum is presented and compared with outcomes from a numerical computational method. The results demonstrate that the shielding mechanism that prevails at low frequencies is that of reflection. Consequently, hard shields such as metals show superior wave attenuation performance for MIT systems operating below 13 MHz. For higher frequencies, the absorption effect on the incident wave path within soft electromagnetic shields presents enhanced shielding properties. This paper also explores the limitations of traditional testing geometry for shielding effectiveness and proposes an alternative approach to near-field, free-space measurement for MIT sensors. The proposed semi-enclosed approach shows enhanced shielding effectiveness measurements compared with the traditional transversal barrier method. The proposed method was used to assess the electromagnetic shielding effectiveness of ferromagnetic and various metallic materials.

Analytical Formulation for Shielding Effectiveness of a Lossy Enclosure Containing Apertures

The paper deals with an analytical formulation for shielding effectiveness evaluation of a lossy rectangular enclosure containing apertures. On the basis of circuit model theory, an extremely fast technique to include conductor losses into the model is derived. The enclosure is taken into account as a short-circuited waveguide. Lossy conductive walls of the cavity are modeled using a surface impedance boundary condition and electromagnetic field attenuation in waveguide propagation is considered. Our model takes readily accounts higher order resonant modes. Several enclosures with different conductivities and apertures are studied. Results predicted with the model shows very good agreement with those obtained using a full wave method. Our model is more accurate compared to existing ones.

Evaluation of the Electromagnetic Shielding Effectiveness of Carbon-Based Screen Printed Polyester Fabrics

Electromagnetic shielding has a very emerging role in the textile applications. Screen-printing is a well-known, easy and cost effective process for textile printing. In this study, carbon black and graphite particles were used to impart electromagnetic shielding property to polyester fabric by screen printing technique. To this aim, printing pastes containing carbon materials were prepared with different binder concentrations. The electrical resistance, surface morphology, color coordinates and washing fastness properties of screen printed polyester fabrics were investigated. The washing durability of electromagnetic shielding effectiveness of carbon based printed fabrics as a function of binder concentration have also been studied. Electromagnetic shielding effectiveness was evaluated in the frequency ranges between 15-3000 MHz. The results showed that the electromagnetic shielding properties of fabric were affected by increased binder concentration. The most durable electromagnetic shielding effectiveness after washing process was obtained at highest binder concentration. The surface morphologies and color difference values of printed fabrics after washing process also provided a positive contribution.

Evaluation of electromagnetic shielding effectiveness of fabrics produced from yarns containing metal wire with a mobile based measurement system

Evaluation of electromagnetic shielding effectiveness of fabrics produced from yarns containing metal wire with a mobile based measurement system

Generation of uniform diffraction pattern and high EMI shielding performance by metallic mesh composed of ring and rotated sub-ring arrays.

We present an optical transmission model and a fast shielding effectiveness (SE) evaluation method for the inductive mesh comprising metallic rings with rotated sub-ring arrays, which can be extended for designing and optimizing other ring-based mesh structures. The theoretical analysis and experimental verification show that the established model and method are valid. A Ku-band SE >17 dB (98% energy attenuation) is observed for a triangular ring mesh with rotated sub-rings, and a normalized visible transmittance >95% is obtained with an ultra-uniform diffraction pattern, thus indicating the possibilities of our approach for high-optical-transmittance, strong-SE, reduced-image-degradation shielding applications.

Evaluation of electromagnetic shielding effectiveness of multi-axial fabrics and their reinforced PES composites

The usage of electrical and electronic equipments has been increasing in daily life, which has a potential hazardous impact on humans and other living organisms. In this paper, multi-axial fabrics containing steel yarns and carbon filaments, and their polyester (PES) resin-reinforced composites have been prepared for electromagnetic shielding applications. The electromagnetic shielding effectiveness (EMSE) of these structures was determined by using coaxial transmission line measurement technique. There were eight different multi-axial fabrics constructed. It was observed that the amount and the orientation of carbon and stainless steel yarns influenced the EMSE performances of multi-axial fabrics and their reinforced PES composites. The structures containing both carbon filaments and stainless steel yarns exhibited better EMSE than the ones including only one type of conductive yarns or filaments. Also, the EMSE performance of multi-axial fabrics was found better than their reinforced composites. The best EMSE results were obtained for the fabric, including two layers of yarns (steel and carbon) on top of each other in the centre with the angle of 45 and −45°.

Verification and improvement of equivalent refractive index models for evaluating the shielding effectiveness of high-transmittance double-layer metallic meshes.

The validity of real and complex equivalent refractive index models (ERIMs) is verified for a shielding effectiveness evaluation of high-transmittance double-layer metallic meshes. Theoretical and experimental studies show that the real ERIM is invalid for thin substrates and inaccurate for thick substrates for double-layer meshes, although it has long been used successfully for single-layer meshes. However, the complex ERIM shows more reasonable results not only for double-layer but also for single-layer meshes, and the evaluation accuracy is further improved by modifying the equivalent reactance coefficient using least-squares fitting. Therefore, the modified complex ERIM is applicable in most conditions.

방호 시설 크기에 따른 전계강도 및 차폐 효과 비교

In modern times, threat of high power electromagnetic wave is increasing. When the electrical grid and communication network are attacked by these high power electromagnetic wave, the whole infrastructure is paralyzed. To protect the infrastructure from these high power electromagnetic wave threat, the shielding facility that can block high power electromagnetic wave is constructed. Also shielding effectiveness evaluation about the constructed facility is important. But, because of space efficiency and saving of construction cost to construct the actual shielding facility, the shielding room wall is generally adjacent to exterior concrete structures. As space between shielding facility wall and concrete structures is very small, arranging the transmitting antenna exterior shielding facility is realistically difficult. Therefore, in this research, The shielding effectiveness measurement plan in the state of exterior narrow space of HEMP shielding facility is presented. And to apply this plan, The influence of shielding effectiveness according to the size of the shielding facility is analyzed.

Improved modal method of moments technique to compensate the effect of wall dimension in shielding effectiveness evaluation

In the conventional modal method of moments (MoM) method, when shielding effectiveness (SE) of a rectangular enclosure is the goal, it is assumed that the incident wave is reflected from an infinite wall. This assumption makes the results inaccurate specifically at low frequencies where the wall size is not large compared to the illumination wavelength. In this study, the mentioned reflected wave is corrected by considering the reflection from a box without any aperture. To obtain the reflected wave from the box, an induced electric current on the metallic surface is assumed. Using Rao Wilton Glisson basis functions along with free space Green's function, the unknown electric currents and consequently the reflected wave are calculated. The results are compared with full wave numerical methods. A very good agreement is observed between the results and it is shown that for lower frequencies the proposed method has more accuracy rather than the modal MoM itself specifically for an enclosure with a very large aperture.

On Measuring Shielding Effectiveness of Sparsely Moded Enclosures in a Reverberation Chamber

Recently, there has been great interest in evaluating the shielding effectiveness of physically small enclosures (all linear dimensions between 0.1 and 2 m) using a reverberation chamber. In cases where the enclosure is also electrically small (linear dimensions on the order of a free-space wavelength or less), the enclosure supports only discrete resonant modes whose lineshapes have little or no overlap in frequency. This sparsely moded or “undermoded” cavity poses a number of complex challenges to defining and measuring shielding effectiveness. This study contributes to the development of a measurement process for evaluating shielding effectiveness in electrically small enclosures. Specifically, we demonstrate the performance advantages of a traveling-wave antenna (long-wire probe) as a means of fully sampling the field throughout the volume of the enclosure without the need for multiple, wall-mounted probes. Furthermore, the good impedance match of the long-wire antenna permits a large dynamic range in the shielding effectiveness measurements. A simple and fast test method is presented that is accurate and repeatable, and embodies the desired “dovetailing” of shielding effectiveness values obtained as frequency increases and the enclosure transitions from undermoded to overmoded operation. Finally, a rudimentary statistical analysis is provided to assess typical uncertainties inherent in the shielding effectiveness evaluation.

Fabrication and shielding effectiveness evaluation of curved mesh optical windows using ray-optic tracing and equivalent film methods

A model with curved mesh optical windows is built using ray-optic tracing method for shielding effectiveness evaluation. Due to its unique zero order diffraction transmission characteristics, the metallic mesh used to build the model is treated in the model as a layer of optical film, and the transmission field of curved mesh optical windows is calculated using ray-optic tracing method. A cylindrical mesh optical window sample is fabricated and its shielding effectiveness is measured using a shielding effectiveness measurement system. Simulation results obtained with the model agree well with the experimental results, which proves the validity of the model.

An Efficient and Reliable Shielding Effectiveness Evaluation of a Rectangular Enclosure With Numerous Apertures

An efficient analytical and accurate model to predict the shielding effectiveness of a rectangular enclosure with numerous small apertures is presented. In this paper, an appropriate equivalent admittance for the perforated side is suggested amid the free space and the enclosure, utilizing the traditional waveguide circuit model where the enclosure is represented by a short-circuited rectangular waveguide. The simulation results of this model are in better agreement with measurements than that of the original waveguide equivalent circuit model. This method is applicable to an array of square and circular holes of staggered and square configurations.

Shielding Effectiveness Evaluation of Metallized and Polypyrrole-coated Fabrics

Materials for electromagnetic shielding are increasingly needed to protect electronic devices from interference problems and to avoid dangerous effects on human health due to electromagnetic radiation. Several shielding applications require solutions that textiles can suitably fulfill. Here the electromagnetic interference shielding of metallized, PPy-coated woven and non-woven polyester fabrics is provided in the frequency range 100—1000 MHz, measuring the insertion losses produced by these conductive fabrics in a dual TEM cell. From the insertion loss data, the shielding effectiveness, and the reflection and absorption coefficients are estimated.

Reduction of SAR in a human‐head model wrapped in clothing materials

AbstractAn analysis of clothing material for reducing RF energy absorption in a human‐head model has been studied using the finite‐difference time‐domain (FDTD) method. The local maximum specific absorption ratio (SAR) induced in the human head model is used for the evaluation of the clothing material's shielding effectiveness for EM exposure. It is found that clothing material with a dielectric constant close to that of human skin will induce higher RF energy absorption in the human‐head model. On the other hand, clothing material with a higher relative dielectric constant and permeability can greatly reduce RF energy absorption. If the clothing material is mixed with conducting materials or magnetic materials, a remarkable reduction of RF energy absorption in the human‐head model will be obtained. These preliminary results provide valuable knowledge to help in the manufacture of anti‐electromagnetic wave clothing. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 37: 305–308, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10902

Magnetic shielding effects of the superposition of a ferromagnetic cylinder over an HTS cylinder: magnetic shielding dependence on the air gap between the BPSCCO and soft-iron cylinders

Ideal magnetic shielded vessels can be realized by making use of a high-critical temperature superconductor (HTS). Use of such shielding does not, however, generally satisfy the maximum shielded magnetic flux density B s required of an HTS vessel for practical applications. The present authors have improved the value of B s by the superposition of a ferromagnetic cylinder over an HTS cylinder, termed the superimposed cylinder. The evaluation of the magnetic shielding effects was limited to the superimposed cylinder, in order to simplify the theoretical analysis. Nevertheless, little is known of the resulting characteristics and evaluation procedures when changing the size of the air gap δ between the HTS and ferromagnetic cylinders for applications of an external magnetic field B ex less than the value of B s. The values of B s were systematically measured by for different values of δ, and in addition, were theoretically analyzed. It was found that the experimental values of B s agreed well with theoretical values. Furthermore, measurements were taken of the magnetic noise power spectrum for various values of δ, with the use of the HTS dc-SQUID system and spectrum analyzer. From these results, the characteristics of the magnetic behavior for different values of δ within the superimposed cylinder were clarified. In addition, an important criterion is discussed for the design of an effective magnetic shielding vessel.