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Article
Publication date: 27 September 2011

Oleg Rybin, Konstantin Yemelyanov, Amjad Pitafi and Tahira Nawaz

The purpose of this paper is to study the microwave behaviour of effective magnetic permeability for two‐component ferrite like metamaterial medium in the direction of a…

Abstract

Purpose

The purpose of this paper is to study the microwave behaviour of effective magnetic permeability for two‐component ferrite like metamaterial medium in the direction of a biasing magnetic field. The metamaterial medium is presented as an infinite host dielectric material (air) with periodically embedded ferric cylindrical and spherical inclusions saturated with an external dc magnetic field. The study is based on the effective medium theory developed for polycrystalline metaferrites. The simulations show that the presented metamaterial can exhibit the ultra‐low refractive index (ULI) phenomenon and the phenomenon of negative magnetic permeability for the case of microwave propagation in the direction of bias.

Design/methodology/approach

The obtained results are based on the wave long approximation of permeability tensor of the presented metamaterial media obtained earlier by the first author. Using the standard approach, the authors apply the above expressions for the microwave propagation in direction of biasing dc magnetic field considering different polarization of the incident microwave.

Findings

The considered artificial material media can become either material with a ULI or with negative values in the GHz frequencies.

Originality/value

The paper is concerned with part of the theory of a new generation of artificial ferrites.

Details

Multidiscipline Modeling in Materials and Structures, vol. 7 no. 3
Type: Research Article
ISSN: 1573-6105

Keywords

Article
Publication date: 9 August 2011

Oleg Rybin, Konstantin Yemelyanov and Tahira Nawaz

The purpose of this paper is to obtain the long‐wave approximations for the effective electromagnetic response of two‐dimensional sandwich composite structure, as infinite…

Abstract

Purpose

The purpose of this paper is to obtain the long‐wave approximations for the effective electromagnetic response of two‐dimensional sandwich composite structure, as infinite chain of infinitely long metal cylinders symmetrically immersed in an infinite metamaterial slab are obtained. The slab is an infinite magneto‐dielectric matrix with periodically imbedded infinitely long metal cylinders whose diameter is smaller than those of the chain cylinders. The case of ferrite‐like metallic saturated inclusions is considered in the study.

Design/methodology/approach

The result is presented as a generalized expression of the electromagnetic response of the infinite periodic chain of infinitely long metallic cylinders immersed into the flat magneto‐dielectric host medium. Those expressions were obtained utilizing S‐ and T‐matrices approaches.

Findings

A good coincidence between the results of analytical modeling and numerical simulations was found.

Research limitations/implications

Low values of the metal volume fraction; microwave frequency range.

Practical implications

An improving of directivity of patch antennas; a minimization of patch antennas.

Originality/value

The analytical characterization of new artificial substrate‐like structure to be utilized for designing patch antennas of a new generation.

Details

Multidiscipline Modeling in Materials and Structures, vol. 7 no. 2
Type: Research Article
ISSN: 1573-6105

Keywords

Open Access
Article
Publication date: 6 April 2021

Ahmed Elbassoussy

The purpose of this study is to identify various Russian manifestations on expanding its role in sub-Saharan Africa, as well as shed light on the major obstacles it may face.

4855

Abstract

Purpose

The purpose of this study is to identify various Russian manifestations on expanding its role in sub-Saharan Africa, as well as shed light on the major obstacles it may face.

Design/methodology/approach

The research paper uses the “national role theory” to analyze the factors that helped in the growing Russian role in sub-Saharan African countries. It assumes that every state seeks to play a particular role, and that role is reflected in its foreign policy, which is known as “role performance,” and this role originates from several sources. On the other hand, this role faces various obstacles, mostly from the external environment, especially the international system’s structure, global values and international obligations, known as “role prescriptions.”

Findings

Despite Russia’s ability to use all its capacities in expanding its role in the African continent, the degree of its influence varied from one field to another. While it was very influential in the military, security, political, diplomatic and technical fields, it is relatively less in the economic and counter-terrorism areas.

Research limitations/implications

This study paves the way for further researches related to international competition over sub-Saharan Africa, whether economically, militarily or politically, in addition to other studies related to potential cooperation opportunities, especially in security and combating terrorism.

Originality/value

This research’s significance stems from using the existing theoretical structure represented in national role theory in analyzing the Russian orientation toward sub-Saharan Africa, giving more attention to the latest developments in Russian strategy, as well as clarifying the major obstacles that may hinder its activities.

Details

Journal of Humanities and Applied Social Sciences, vol. 4 no. 3
Type: Research Article
ISSN:

Keywords

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