Higher College of Telecommunications and Posts

www.hctp.acad.bg
Sofia, Bulgaria
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Al-Hartomy O.A.,King Abdulaziz University | Al-Hartomy O.A.,University of Tabuk | Al-Ghamdi A.A.,King Abdulaziz University | Al-Salamy F.,King Abdulaziz University | And 5 more authors.
Fullerenes Nanotubes and Carbon Nanostructures | Year: 2014

In this study, the influence of fullerenes in concentrations from 0.5 to 1.5 phr on the dielectric (dielectric permittivity, dielectric loss angle tangent) and microwave (reflection coefficient, attenuation coefficient, shielding effectiveness) properties of nanocomposites on the basis of natural rubber has been investigated in the 1-12 GHz frequency range. Some additional investigations on the morphology and microstructure of the studied composites have been carried out by scanning electron microscopy and transmission electron microscopy. To confirm to the high purity of the fullerene used Raman spectra and X-ray diffraction analysis were carried out. © 2014 Taylor and Francis Group, LLC.


Al-Hartomy O.A.,King Abdulaziz University | Al-Hartomy O.A.,University of Tabuk | Al-Ghamdi A.,King Abdulaziz University | Dishovsky N.,University of Chemical Technology and Metallurgy of Sofia | And 3 more authors.
Journal of Elastomers and Plastics | Year: 2013

In this study, the influence of hybrid combination of fillers (carbon black in concentrations from 0 to 100 phr and conducting nickel (Ni) or cobalt particles in concentration 10 phr on the dielectric (dielectric permittivity and dielectric loss angle tangent)) and microwave (reflection coefficient, attenuation coefficient, and shielding effectiveness) properties of chloroprene rubber composites has been investigated in the wide frequency range (1-12 GHz). The results achieved showed that the hybrid combination of Ni powder and active furnace carbon black gives an opportunity of considerable increase in the dielectric permittivity and also a possibility for its adjustment varying carbon black content. The comparison in the behavior of prepared composites can be explained by the differences in some characteristics of two metals and influence of these differences on the real and imaginary parts of the complex dielectric permittivity and magnetic permeability. © The Author(s) 2012.


Al-Hartomy O.A.,King Abdulaziz University | Al-Hartomy O.A.,University of Tabuk | Al-Ghamdi A.,King Abdulaziz University | Dishovsky N.,University of Chemical Technology and Metallurgy of Sofia | And 4 more authors.
Fullerenes Nanotubes and Carbon Nanostructures | Year: 2014

In this study, the influence of carbon nanotubes (CNT) in concentrations from 2 to 10 phr on the dielectric (dielectric permittivity, dielectric loss angle tangent) and microwave (reflection coefficient, attenuation coefficient, shielding effectiveness) properties of nanocomposites on the basis of natural rubber has been investigated in the wide frequency range (2-12 GHz). Some additional investigations on the morphology and microstructure of the CNT used and studied composites have been carried out by transmission electron microscopy (TEM) and selected area electron diffraction (SAED). The results achieved allow recommending carbon nanotubes as filler for natural rubber based composites to afford specific dielectric and microwave properties. © 2014 Copyright Taylor & Francis Group, LLC.


Al-Hartomy O.A.,University of Tabuk | Al-Hartomy O.A.,King Abdulaziz University | Al-Solamy F.,University of Tabuk | Al-Ghamdi A.,King Abdulaziz University | And 3 more authors.
International Journal of Polymer Science | Year: 2011

In this paper, the dielectric and microwave properties of carbon black/siloxane rubber-based nanocomposites have been investigated in the frequency range from 1 GHz till 12GHz according to the content of carbon black and the frequency. It has been established that the increasing frequency and filler content lead to an increase in the relative permittivity and tangent of dielectric loss angle. At higher filler content, the effects become more pronounced, especially those upon dielectric loss. It has been also established that there are two well-distinguished areas in all dependences of microwave properties on frequency and filler content increasing. The first is between 1 and 8 GHz wherein the reflection and attenuation of microwaves do not change considerably with frequency and filler content alternation while shielding effectiveness worsens. The second area is between 8 and 12 GHz wherein the reflection and attenuation of microwaves increase drastically with the increasing frequency and filler content. Shielding effectiveness improves, too. It has been established that in all cases the degree of correlation between dielectric and microwave properties evaluated on the basis of the coefficients of correlation calculation is perfect. Copyright © 2011 Omar A. Al-Hartomy et al.


Al-Hartomy O.A.,King Abdulaziz University | Al-Hartomy O.A.,University of Tabuk | Al-Ghamdi A.A.,King Abdulaziz University | Al-Salamy F.,King Abdulaziz University | And 6 more authors.
Polymer - Plastics Technology and Engineering | Year: 2013

Virgin and carbon black-filled composites have been prepared using two completely different matrixes - natural rubber (a non-polar, crystallizing elastomer) and nitrile butadiene rubber (a polar, non-crystallizing elastomer). The investigations reported reveal how the chemical nature of the rubber matrixes affects the dielectric (dielectric permittivity and dielectric loss angle tangent) and microwave (reflection coefficient, electromagnetic attenuation and electromagnetic shielding) properties of the obtained materials. The effects observed have been explained by the fact that interface polarization, relaxation processes, wetting and distribution of the absorption active filler are strongly dependent on the matrix character. The chemical nature of the matrix used predetermines composites properties through the effects related to the mechanisms of dielectric losses and electromagnetic interaction. The results obtained allow an appropriate choice of elastomeric matrixes for the production of composites designed for microwave absorbers. © 2013 Copyright Taylor and Francis Group, LLC.


Al-Hartomy A.O.,University of Tabuk | Al-Ghamdi A.A.,King Abdulaziz University | Al-Solamy R.F.,King Abdulaziz University | Al-Solamy R.F.,University of Tabuk | And 5 more authors.
KGK Kautschuk Gummi Kunststoffe | Year: 2012

In this paper, the dielectric and microwave properties of chloroprene rubber (CR) ased composites comprising different amounts of furnace carbon black in the range 0-100 phr have been investigated in the frequency range from 1 to 12 GHz. In the frequency range from 1 to 8 GHz the values of the dielectric permittivity and dielectric loss angle tangent are relatively low and do not change significantly with the increase of frequency. In the range from 8 to 12 GHz, the increase in frequency leads to increasing values of relative dielectric permittivity and dielectric loss angle tangent. Increasing the amount of carbon black leads to improved microwave properties of the investigated composites. The composites based on CR containing 60-100 phr furnace carbon black have very good microwave properties and can be used for the needs of anti-radar camouflage and for electromagnetic shielding.


Al-Hartomy O.A.,King Abdulaziz University | Al-Hartomy O.A.,University of Tabuk | Al-Ghamdi A.,King Abdulaziz University | Al-Salamy F.,King Abdulaziz University | And 5 more authors.
Advanced Composite Materials | Year: 2013

In this study, the effect of carbon nanotubes (CNT) and graphene nanoplatelets (GNP) at various weight ratios between them on the dielectric (dielectric permittivity, dielectric loss angle tangent) and microwave (reflection coefficient, attenuation coefficient, shielding effectiveness) properties of nanocomposites on the basis of natural rubber has been investigated in the wide frequency range (1-12 GHz). Some additional investigations on the morphology and microstructure of the graphene particles and CNT used have been carried out by transmission electron microscopy and selected area electron diffraction. The results achieved reveal how by using the selected combinations between CNT and GNP the microwave and dielectric properties of natural rubber nanocomposites can be tailored depending on the need for real practical application. © 2013 Japan Society for Composite Materials, Korean Society for Composite Materials and Taylor & Francis.


Al-Hartomy O.A.,King Abdulaziz University | Al-Hartomy O.A.,University of Tabuk | Al-Ghamdi A.A.,King Abdulaziz University | Al-Salamy F.,King Abdulaziz University | And 4 more authors.
Plastics, Rubber and Composites | Year: 2012

Natural rubber (NR) based nanocomposites containing a constant amount (50 phr) of standard furnace carbon black and carbon nanotube (CNT) at a concentration from 1 to 5 phr have been prepared. Their dielectric (dielectric permittivity and dielectric loss) and microwave properties (coefficients of absorption and reflection of the electromagnetic waves and electromagnetic interference shielding effectiveness) have been investigated in the 1-12 GHz frequency range. The results achieved allow recommending CNTs as second filler for NR based composites to afford specific absorbing properties. © Institute of Materials, Minerals and Mining 2012.


Al-Hartomy O.A.,King Abdulaziz University | Al-Hartomy O.A.,University of Tabuk | Al-Ghamdi A.A.,King Abdulaziz University | Al-Solamy F.R.,University of Tabuk | And 5 more authors.
Proceedings of the Institution of Mechanical Engineers, Part L: Journal of Materials: Design and Applications | Year: 2013

This article presents the results on the effect of specific characteristics of four completely different carbon black types upon the dielectric and microwave properties of natural rubber based composites. It has been found that the proneness of carbon black particles to interact, aggregate and agglomerate affects the dielectric properties of the composites much more than their microwave ones. The proneness of carbon black particles to form chains, aggregates and agglomerates affects unfavorably the microwave properties of the composite thus filled. Fullerene carbon black having the lowest specific surface area and proneness to aggregate and agglomerate yields good microwave properties of the composites.The study demonstrates that the dielectric and microwave properties of rubber composites can be tailored via an appropriate selection of filler which specific chemical nature and structure are capable of yielding the parameters required for the particular applications. © IMechE 2012.


Ivanova E.P.,University of Ruse | Iliev T.,University of Ruse | Mihaylov Gr.,University of Ruse | Stoyanov I.,University of Ruse | And 3 more authors.
2015 38th International Convention on Information and Communication Technology, Electronics and Microelectronics, MIPRO 2015 - Proceedings | Year: 2015

Advances in the new mobile networks are steadily increasing the demand on network resources, and new standards must ensure that the networks are managed effectively in order to ensure that users of the network remain satisfied with their Quality of Service (QoS) and Quality of Experience (QoE). The simulations opportunities represent a chance to reduce the digital divide and to ensure the new 5G networks with minimum cost of time and financials. The simulation of teletraffic models allows the modeling of resource management issues, admission of system users with different parameters. © 2015 MIPRO.

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