scholarly journals Electromagnetic response from composite carbon-containing structures with technological inhomogeneities at EHF

2021 ◽  
Vol 2140 (1) ◽  
pp. 012010
Author(s):  
E A Trofimov ◽  
G E Kuleshov ◽  
V D Moskalenko ◽  
A V Badin ◽  
K V Dorozhkin
Keyword(s):  
3D Printing ◽  
Transmission Coefficient ◽  
Composite Structures ◽  
Electromagnetic Response ◽  
Frequency Range ◽  
Absorption Coefficients ◽  
Polymer Volume ◽  
Composite Carbon ◽  
Frequency Dependences

Abstract The results of studies of the electromagnetic response from composite structures made of a carbon-containing polymer with the inclusion of spherical pores in the bulk of the material and with pyramidal corrugation on the surface of the material are presented. The results of modeling the frequency dependences of the transmission, reflection and absorption coefficients in the EHF range are shown. Samples of composite carbon-containing structures with technological inhomogeneities have been fabricated by 3D printing. Measurements of the electromagnetic response from experimental samples were carried out in the frequency range from 100 to 1000 GHz. At frequencies up to 250 GHz, the inclusion of air pores in the polymer volume reduces the transmission coefficient, practically does not affect the reflection, and increases the absorption. Pyramid corrugated material absorbs more than 99% of radiation in the frequency range from 200 to 635 GHz.

scholarly journals Electromagnetic response from multilayer composite coatings based on carbonyl iron, ferroelectrics and MWCNTs at microwave

2019 ◽  
Vol 30 ◽  
pp. 07011
Author(s):  
Grigoriy E. Kuleshov ◽  
Alexey V. Sbrodov ◽  
Tatyana N. Shematilo
Keyword(s):  
Experimental Study ◽  
Composite Materials ◽  
Carbonyl Iron ◽  
Composite Coatings ◽  
Dielectric Constants ◽  
Electromagnetic Response ◽  
Multilayer Composite ◽  
Frequency Range ◽  
Electromagnetic Characteristics ◽  
Frequency Dependences

The electromagnetic characteristics of composite materials based on carbonyl iron, ferroelectrics, and MWCNTs were studied in this article. The complex magnetic and dielectric constants of the experimental samples were measured in the frequency range from 1 GHz to 18 GHz. The results of calculation and the experimental study of the frequency dependences of the reflection coefficient on a multilayer composite coating located on a reflective surface are presented.

scholarly journals Diffuse Sound Absorptive Properties of Parallel-Arranged Perforated Plates with Extended Tubes and Porous Materials

Materials ◽  
2020 ◽  
Vol 13 (5) ◽  
pp. 1091 ◽  
Author(s):  
Dengke Li ◽  
Daoqing Chang ◽  
Bilong Liu
Keyword(s):  
Boundary Condition ◽  
Porous Material ◽  
Porous Materials ◽  
Sound Absorption ◽  
Azimuthal Angle ◽  
Octave Band ◽  
Frequency Range ◽  
Absorption Coefficients ◽  
Perforated Plates ◽  
Absorption Performance

The diffuse sound absorption was investigated theoretically and experimentally for a periodically arranged sound absorber composed of perforated plates with extended tubes (PPETs) and porous materials. The calculation formulae related to the boundary condition are derived for the periodic absorbers, and then the equations are solved numerically. The influences of the incidence and azimuthal angle, and the period of absorber arrangement are investigated on the sound absorption. The sound-absorption coefficients are tested in a standard reverberation room for a periodic absorber composed of units of three parallel-arranged PPETs and porous material. The measured 1/3-octave band sound-absorption coefficients agree well with the theoretical prediction. Both theoretical and measured results suggest that the periodic PPET absorbers have good sound-absorption performance in the low- to mid-frequency range in diffuse field.

A DoD Perspective on Left Handed Negative Index Materials and Potential Applications

2006 ◽  
Vol 919 ◽  
Author(s):  
Valerie Browning ◽  
Minas H Tanielian ◽  
Richard W. Ziolkowski ◽  
Nader Engheta ◽  
David R. Smith
Keyword(s):  
Composite Structures ◽  
Beam Steering ◽  
Electromagnetic Response ◽  
Electromagnetic Spectrum ◽  
Negative Index ◽  
Negative Index Materials ◽  
Left Handed ◽  
Potential Applications ◽  
Novel Approaches ◽  
Electromagnetic Transport

AbstractIn the quest for ever smaller, lighter weight, and conformal components and devices for radar and communication applications, researchers in the RF community have increasingly turned to artificially engineered, composite structures (or “metamaterials”) in order to exploit the extraordinary electromagnetic response these materials offer. One particularly promising class of metamaterials that has recently received a great deal of attention are “left-handed” or negative index materials. Because these metamaterials exhibit the unique ability to bend and focus light in ways no other conventional materials can, they hold great potential for enabling a number of innovative lens and antenna structures for a broad range of commercial and DoD relevant applications. Exploring the possible implementation of negative index materials for such applications will require significant enhancements in the properties of existing Negative Index Materials (NIM) (bandwidth, loss, operational frequency, etc.), as well as improved understanding of the physics of their electromagnetic transport properties. For this reason the Defense Advanced Research Project Agency (DARPA) has initiated a program that seeks to further develop and demonstrate NIM for future DoD missions including, but not limited to, the following: 1) lightweight, compact lenses with improved optics; 2) sub wavelength/high resolution imaging across the electromagnetic spectrum; 3) novel approaches to beam steering for radar, RF, and/or optical communications; and 4) novel approaches for integrating optics with semiconductor electronics. A brief overview of the salient properties of NIM will be presented as well as a general discussion of a few of their potential applications.

scholarly journals Modelling natural electromagnetic interference in man-made conductors for space weather applications

2016 ◽  
Vol 34 (4) ◽  
pp. 427-436 ◽  
Author(s):  
Larisa Trichtchenko
Keyword(s):  
Exact Solution ◽  
Space Weather ◽  
Electromagnetic Interference ◽  
Geomagnetic Storms ◽  
Electromagnetic Properties ◽  
Electromagnetic Response ◽  
Frequency Range ◽  
Geomagnetically Induced Currents ◽  
Geomagnetic Variations ◽  
Wide Range

Abstract. Power transmission lines above the ground, cables and pipelines in the ground and under the sea, and in general all man-made long grounded conductors are exposed to the variations of the natural electromagnetic field. The resulting currents in the networks (commonly named geomagnetically induced currents, GIC), are produced by the conductive and/or inductive coupling and can compromise or even disrupt system operations and, in extreme cases, cause power blackouts, railway signalling mis-operation, or interfere with pipeline corrosion protection systems. To properly model the GIC in order to mitigate their impacts it is necessary to know the frequency dependence of the response of these systems to the geomagnetic variations which naturally span a wide frequency range. For that, the general equations of the electromagnetic induction in a multi-layered infinitely long cylinder (representing cable, power line wire, rail or pipeline) embedded in uniform media have been solved utilising methods widely used in geophysics. The derived electromagnetic fields and currents include the effects of the electromagnetic properties of each layer and of the different types of the surrounding media. This exact solution then has been used to examine the electromagnetic response of particular samples of long conducting structures to the external electromagnetic wave for a wide range of frequencies. Because the exact solution has a rather complicated structure, simple approximate analytical formulas have been proposed, analysed and compared with the results from the exact model. These approximate formulas show good coincidence in the frequency range spanning from geomagnetic storms (less than mHz) to pulsations (mHz to Hz) to atmospherics (kHz) and above, and can be recommended for use in space weather applications.

Path-designed 3D printing for topological optimized continuous carbon fibre reinforced composite structures

2020 ◽  
Vol 182 ◽  
pp. 107612 ◽  
Author(s):  
Nanya Li ◽  
Guido Link ◽  
Ting Wang ◽  
Vasileios Ramopoulos ◽  
Dominik Neumaier ◽  
...  
Keyword(s):  
3D Printing ◽  
Carbon Fibre ◽  
Composite Structures ◽  
Reinforced Composite

scholarly journals Asymptotic analysis of an anti-plane dynamic problem for a three-layered strongly inhomogeneous laminate

2018 ◽  
Vol 25 (1) ◽  
pp. 3-16 ◽  
Author(s):  
Ludmila Prikazchikova ◽  
Yağmur Ece Aydın ◽  
Barış Erbaş ◽  
Julius Kaplunov
Keyword(s):  
Asymptotic Analysis ◽  
Plane Problem ◽  
Dynamic Problem ◽  
Composite Structures ◽  
Vibration Mode ◽  
Low Frequency ◽  
Layered Plate ◽  
Dynamic Shear ◽  
Frequency Range ◽  
Asymptotic Equation

Anti-plane dynamic shear of a strongly inhomogeneous dynamic laminate with traction-free faces is analysed. Two types of contrast are considered, including those for composite structures with thick or thin stiff outer layers. In both cases, the value of the cut-off frequency corresponding to the lowest antisymmetric vibration mode tends to zero. For this mode, the shortened dispersion relations and the associated formulae for displacement and stresses are obtained. The latter motivate the choice of appropriate settings, supporting the limiting forms of the original anti-plane problem. The asymptotic equation derived for a three-layered plate with thick faces is valid over the whole low-frequency range, whereas the range of validity of its counterpart for another type of contrast is restricted to a narrow vicinity of the cut-off frequency.

scholarly journals Improving and Optimizing Sound Absorption Performance of Polyurethane Foam by Prepositive Microperforated Polymethyl Methacrylate Panel

2020 ◽  
Vol 10 (6) ◽  
pp. 2103
Author(s):  
Xiaocui Yang ◽  
Xinmin Shen ◽  
Haiqin Duan ◽  
Fei Yang ◽  
Xiaonan Zhang ◽  
...  
Keyword(s):  
Polyurethane Foam ◽  
Composite Structures ◽  
Sound Absorption ◽  
Search Algorithm ◽  
Cuckoo Search ◽  
Cuckoo Search Algorithm ◽  
Absorption Model ◽  
Absorption Coefficients ◽  
Element Simulation ◽  
Absorption Performance

Sound absorption performance of polyurethane foam could be improved by adding a prepositive microperforated polymethyl methacrylate panel to form a composite sound-absorbing structure. A theoretical sound absorption model of polyurethane foam and that of the composite structure were constructed by the transfer matrix method based on the Johnson–Champoux–Allard model and Maa’s theory. Acoustic parameter identification of the polyurethane foam and structural parameter optimization of the composite structures were obtained by the cuckoo search algorithm. The identified porosity and static flow resistivity were 0.958 and 13078 Pa·s/m2 respectively, and their accuracies were proved by the experimental validation. Sound absorption characteristics of the composite structures were verified by finite element simulation in virtual acoustic laboratory and validated through standing wave tube measurement in AWA6128A detector. Consistencies among the theoretical data, simulation data, and experimental data of sound absorption coefficients of the composite structures proved the effectiveness of the theoretical sound absorption model, cuckoo search algorithm, and finite element simulation method. Comparisons of actual average sound absorption coefficients of the optimal composite structure with those of the original polyurethane foam proved the practicability of this identification and optimization method, which was propitious to promote its practical application in noise reduction.

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