H.A. Sharshar

Bio: H.A. Sharshar is an academic researcher from Menoufia University. The author has contributed to research in topics: Microstrip antenna & Input impedance. The author has an hindex of 15, co-authored 38 publications receiving 770 citations.

Efficient sidelobe reduction technique for small-sized concentric circular arrays

Abstract: Concentric circular antenna array (CCAA) has interesting features over other array configurations.A uniform arrangement of elements is assumed where the interelement spacing is kept almost half of the wavelength and the array parameters such as the steering matrix and gain are determined.The array performance such as beam power pattern, sidelobe level and beamwidth are discussed in two cases of central element feeding.The two cases are compared showing the reduction in the sidelobe level to more than 20 dB in the case of central element feeding without extra signal processing especially for small- sized arrays that have smaller number of elements and rings.

A Novel Tapered Beamforming Window for Uniform Concentric Circular Arrays

Abstract: A new tapering window is proposed for the uniform concentric circular arrays (UCCA) in order to reduce the sidelobe level at lower cost of wider beams and more practical feasibility and stability. The window has decaying exponential variation with the number of rings depending on the exponent used. The optimum value of the exponent is found to be between 0.4 and 0.5 for noncentral element UCCA and between 0.2 and 0.3 for central element UCCA. The sidelobe level can be reduced to about 26 dB and this level occurs when the number of rings equals the number of elements of the innermost ring at the optimum values of the exponent.

Breast cancer detection using a hybrid Finite difference frequency domain and particle swarm optimization techniques

Abstract: A hybrid technique based on finite-difference frequency domain (FDFD) and particle swarm optimization (PSO) techniques is proposed to reconstruct the angular crack width and its position in the conductor and ability to detect the crack width, position, and its depth in single and multilayer dielectric objects. FDFD is formulated to calculate the scattered field after illuminating the object by a microwave transmitter. Two-dimensional model for the object is used. Computer simulations have been performed by means of a numerical program; results show the capabilities of the proposed approach. This paper presents a computational approach to the two dimensional inverse scattering problem based on FDFD method and PSO technique to determine the crack position, width and depth. By using the scattered field, the specifications of the crack are reconstructed.

Microstrip antenna with defected ground plane structure as a sensor for landmines detection

Abstract: A proposed sensor for landmines detection consists of two parallel microstrip antennas placed on the same ground plane and with defected ground structure between them has been investigated The microstrip patch array with defected ground structure has the advantage of a low mutual coupling compared with the classic one The Finite-Difference Time-Domain (FDTD) is used to simulate the sensor for landmines detection

Performance Evaluation of Short Range Underwater Optical Wireless Communications for Different Ocean Water Types

Abstract: This paper has presented our interesting in wireless underwater communications for different ocean water types Recent interest in ocean exploration has brought about a desire for developing wireless communication techniques in this challenging environment Due to its high attenuation in water, a radio frequency (RF) carrier is not the optimum choice Acoustic techniques have made tremendous progress in establishing wireless underwater links, but they are ultimately limited in bandwidth In traditional communication systems, constructing a link budget is often relatively straight forward In the case of underwater optical systems the variations in the optical properties of ocean water lead to interesting problems when considering the feasibility and reliability of underwater optical links The main focus of this paper is to construct an underwater link budget which includes the effects of scattering and absorption of realistic ocean water As well as we have developed the underwater optical wireless communication systems to have shorter ranges, that can provide higher bandwidth (up to several hundred Mbit/s) communications by the assistant of exciting high brightness blue LED sources, and laser diodes suggest that high speed optical links can be viable for short range application The received signal power, signal to noise ratio, bit error rate, transmitted signal bandwidth, and transmission bit rates are the major interesting parameters for different ocean water mediums as a criteria of the best signal transmission characteristics of short wireless optical communications over wide range of the affecting parameters

An Overview on Defected Ground Structure

Abstract: This paper focuses on a tutorial overview of defected ground structure (DGS). The basic conceptions and transmission characteristics of DGS are introduced and the equivalent circuit models of varieties of DGS units are also presented. Finally, the main applications of DGS in microwave technology field are summarized and the evolution trend of DGS is given.

Evolutionary optimization as applied to inverse scattering problems

Abstract: This review is aimed at presenting an overview of evolutionary algorithms (EAs) as applied to the solution of inverse scattering problems. The focus of this work is on the use of different population-based optimization algorithms for the reconstruction of unknown objects embedded in an inaccessible region when illuminated by a set of microwaves. Starting from a general description of the structure of EAs, the classical stochastic operators responsible for the evolution process are described. The extension to hybrid implementations when integrated with local search techniques and the exploitation of the 'domain knowledge', either a priori obtained or collected during the optimization process, are also presented. Some theoretical discussions concerned with the convergence issues and a sensitivity analysis on the parameters influencing the stochastic process are reported as well. Successively, a review on how various researchers have applied or customized different evolutionary approaches to inverse scattering problems is carried out ranging from the shape reconstruction of perfectly conducting objects to the detection of the dielectric properties of unknown scatterers up to applications to sub-surface or biomedical imaging. Finally, open problems and envisaged developments are discussed.

Bio-inspired computation: Where we stand and what's next

Abstract: In recent years, the research community has witnessed an explosion of literature dealing with the mimicking of behavioral patterns and social phenomena observed in nature towards efficiently solving complex computational tasks. This trend has been especially dramatic in what relates to optimization problems, mainly due to the unprecedented complexity of problem instances, arising from a diverse spectrum of domains such as transportation, logistics, energy, climate, social networks, health and industry 4.0, among many others. Notwithstanding this upsurge of activity, research in this vibrant topic should be steered towards certain areas that, despite their eventual value and impact on the field of bio-inspired computation, still remain insufficiently explored to date. The main purpose of this paper is to outline the state of the art and to identify open challenges concerning the most relevant areas within bio-inspired optimization. An analysis and discussion are also carried out over the general trajectory followed in recent years by the community working in this field, thereby highlighting the need for reaching a consensus and joining forces towards achieving valuable insights into the understanding of this family of optimization techniques.

Artificial gorilla troops optimizer: A new nature-inspired metaheuristic algorithm for global optimization problems

Abstract: Metaheuristics play a critical role in solving optimization problems, and most of them have been inspired by the collective intelligence of natural organisms in nature. This paper proposes a new metaheuristic algorithm inspired by gorilla troops' social intelligence in nature, called Artificial Gorilla Troops Optimizer (GTO). In this algorithm, gorillas' collective life is mathematically formulated, and new mechanisms are designed to perform exploration and exploitation. To evaluate the GTO, we apply it to 52 standard benchmark functions and seven engineering problems. Friedman's test and Wilcoxon rank-sum statistical tests statistically compared the proposed method with several existing metaheuristics. The results demonstrate that the GTO performs better than comparative algorithms on most benchmark functions, particularly on high-dimensional problems. The results demonstrate that the GTO can provide superior results compared with other metaheuristics.