A novel beamforming emulating photonic nanojets for wireless relay networks

© 2021 Tech Science Press. All rights reserved.In this article, a low-cost electromagnetic structure emulating photonic nanojets is utilized to improve the efficiency of wireless relay networks. The spectral element method, due to its high accuracy, is used to verify the efficiency of the proposed structure by solving the associate field distribution. The application of optimal single-relay selection method shows that full diversity gain with low complexity can be achieved. In this paper, the proposed technique using smart relays combines the aforementioned two methods to attain the benefits of both methods by achieving the highest coding and diversity gain and enhances the overall network performance in terms of bit error rate (BER). Moreover, we analytically prove the advantage of using the proposed technique. In our simulations, it can be shown that the proposed technique outperforms the best known state-of-the-art single relay selection technique. Furthermore, the BER expressions obtained from the theoretical analysis are perfectly matched to those obtained from the conducted simulations

Estimating the heat capacity of non-Newtonian ionanofluid systems using ANN, ANFIS, and SGB tree algorithms

This work investigated the capability of multilayer perceptron artificial neural network (MLP–ANN), stochastic gradient boosting (SGB) tree, radial basis function artificial neural network (RBF–ANN), and adaptive neuro-fuzzy inference system (ANFIS) models to determine the heat capacity (Cp) of ionanofluids in terms of the nanoparticle concentration (x) and the critical temperature (Tc), operational temperature (T), acentric factor (ω), and molecular weight (Mw) of pure ionic liquids (ILs). To this end, a comprehensive database of literature reviews was searched. The results of the SGB model were more satisfactory than the other models. Furthermore, an analysis was done to determine the outlying bad data points. It showed that most of the experimental data points were located in a reliable zone for the development of the model. The mean squared error and R 2 were 0.00249 and 0.987, 0.0132 and 0.9434, 0.0320 and 0.8754, and 0.0201 and 0.9204 for the SGB, MLP–ANN, ANFIS, and RBF–ANN, respectively. According to this study, the ability of SGB for estimating the Cp of ionanofluids was shown to be greater than other models. By eliminating the need for conducting costly and time-consuming experiments, the SGB strategy showed its superiority compared with experimental measurements. Furthermore, the SGB displayed great generalizability because of the stochastic element. Therefore, it can be highly applicable to unseen conditions. Furthermore, it can help chemical engineers and chemists by providing a model with low parameters that yields satisfactory results for estimating the Cp of ionanofluids. Additionally, the sensitivity analysis showed that Cp is directly related to T, Mw, and Tc, and has an inverse relation with ω and x. Mw and Tc had the highest impact and ω had the lowest impact on Cp.https://www.mdpi.com/journal/applscipm2021Mechanical and Aeronautical Engineerin

Çift taraflı çıkık kutuplu yapılar için normalize edilmiş moment ve permeans veri tabanı.

In this study, a model is developed to represent doubly-salient magnetic circuits and to fit finite element analysis for the aim of obtaining a set of normalized normal force, tangential force, and permeance variation data. To obtain the desired data FE field solution method is used. The reliability of finite element results have been verified by three steps; first, comparing the numerical results with analytically calculated permeance, second, by solving two switch reluctance motors and comparing the results with the measurements of static torque and flux linkage. The third step is by using the normalized data obtained by solving the model with the aid of an available software that is capable to predict the behavior of switched reluctance motors. Once the reliability of the data is assured, the desired data set is produced and presented in tables.M.S. - Master of Scienc

Optik rezonatörler: Fotonik nanojet ve fısıldayan galeri modu

Bir dielektrik mikro-küre veya mikro-silindir gelen düzlem dalga tarafından aydınlatıldığında gölge tarafında güçlü bir şekilde odaklanmış bir ışın oluşur ve bu olgu nanojet olarak adlandırılır. Bu tezde, farklı yapılar ve farklı uyartımlar için oluşan fotonik jetlerin davranışlarını incelemek için spektral eleman yöntemi kullanılmıştır. İki boyutlu, frekans domeni elektromanyetik saçılma problemlerinin sayısal modellemesi için spektral eleman metodunun genel formülasyonu sunulmuştur. Spektral eleman yönteminin, sonlu elemanlar ve sonlu fark yöntemlerinden kesinlik açısından üstünlüğünü göstermek için bir ve iki boyutlu örnekler seçilmiştir. Ardından, fotonik jetlerin SEM ile başarılı şekilde modellenmesine ek olarak birkaç rezonans modu tarafından oluşan düzlem dalga uyartımlı dielektrik silindirler de SEM tarafından modellenmiştir. Güçlü alan kısıtlamasını doğrulamak için üç farklı senaryo dikkate alınmıştır; birincisi Bessel ışın aydınlatması altında, ikincisi silindiri oluşturan materyalin heterojenliğinin ortaya çıkması, üçüncüsü ise nokta kaynaktan uyartılan silindirler. Dahası, normal giren düzlem dalga aydınlatması altında yarı-silindir ve oluklu silindirlerden ortaya çıkan nanojet ve rezonans incelenmiştir. Son olarak, bir birim yoğunluklu düzlem dalga tarafından aydınlatıldığında hava arka planına gömülü homojen ve izotropik manyeto-dielektrik mikro silindirler de araştırılmıştır.When a dielectric micro-sphere or micro-cylinder is illuminated by an incident plane wave, a strongly focused beam at the shadow side is formed and such phenomenon is known as photonic nanojet. In this thesis, the spectral element method (SEM) is adopted to investigate the behaviour of photonic jets resulting from different structures and excitations. The general formulation of SEM is presented for the sake of numerical modelling of two-dimensional, frequency-domain electromagnetic scattering problems. For the purpose of accuracy demonstration, one- and two-dimensional examples were chosen to show that SEM dominates the finite difference method and finite element method in terms of accuracy. Then, in addition to the successful modelling of photonic jets by SEM, several resonance modes that result in planewave-excited dielectric cylinders are also captured by SEM. Three different scenarios are also considered in the current study in order to verify the strong field confinement; one is under Bessel beam illumination, the second is the introduction of non-homogeneity in the material forming the cylinder, and the third is that the cylinders are excited by a point source. Moreover, nanojets and resonance resulting from hemicylindrical and corrugated cylinders under normally incident plane-wave illumination are studied. Finally, homogenous and isotropic magneto-dielectric micro-cylinders embedded in air background when illuminated by a unit-intensity plane wave are also investigated

Spektral element methoduyla iki boyutlu elektromanyetik radyasyon ve saçılma modellenmesi.

In this thesis, the spectral element method is utilized in numerical modeling of two-dimensional, frequency-domain electromagnetic scattering and radiation problems. We perform domain truncation by the well-known perfectly matched layer (PML) and provide the corresponding formulation. The attenuation factor associated with the PML formulation is optimized so that the best accuracy is achieved for a wide range of Gauss- Legendre -Lobatto grids per wavelength. The optimality of the provided attenuation factor is verified by several numerical demonstrations and by comparing the numerical solutions with those obtained under the absence of PML in problems whose analytical solutions are available. Further, these values of attenuation are applied to solve electromagnetic scattering by dielectric micro cylinders (photonic nanojets). Some interesting cases that contribute to whispering gallery modes are reported where finite-difference time-domain method is found to fail in numerical modeling of such cases. In addition, the resulting linear system of equations is also approached iteratively and a comparison among successive over relaxation, Jacobi and incomplete LU preconditioners is presented.Ph.D. - Doctoral Progra

Reply to Minin, I.V.; Minin, O.V. Comment on “Mahariq et al. Investigation and Analysis of Acoustojets by Spectral Element Method. Mathematics 2022, 10, 3145”

This reply provides one-to-one responses to comments regarding the article entitled: “Investigation and Analysis of Acoustojets by Spectral Element Method” that has been published in Mathematics by MDPI. As a corresponding author, I am happy to receive constructive criticism about the aforementioned article, in particular, suggestions and/or comments that, when addressed, may further help the reader in understanding the published material

Persistence of photonic nanojet formation under the deformation of circular boundary

A photonic nanojet is a highly focused optical beam with a subwavelength waist on the shadow side of the dielectric microsphere or microcylinder. In this paper, photonic nanojets resulting from corrugated cylinders (with irregular boundaries) under normally incident plane-wave illumination are studied. Different levels of corrugations induced at the boundaries of the dielectric microcylinders produce strong light focusing as well as a photonic nanojet with unique performance compared to perfectly smooth cylinders. The spectral element method is utilized in this study for the sake of high accuracy. Interestingly, we found that under some geometrical/material parameters one may not need a highly perfect cylinder in order to obtain a photonic nanojet. In addition, resonance behavior is reported and examined under larger variations in the parameters defining corrugated cylinders when compared with circular dielectric cylinders. (C) 2016 Optical Society of AmericaH. K. acknowledges partial support of the Turkish Academy of Sciences

On-and off-optical-resonance dynamics of dielectric microcylinders under plane wave illumination

We explore the on-resonance and off-resonance optical response of dielectric cylinders excited by normal incident plane waves. Both the analytical method, based on Mie theory, and the numerical method, implemented with the spectral element method, are undertaken in the study. We demonstrate that the whispering gallery mode characteristic of resonance behavior is strongly dependent on the refractive index and radius changes. Detuning of either parameter deteriorates the resonance action and creates yet another exciting phenomenon known as photonic nanojets. The subwavelength light focusing property can be associated with nanojets, and engineering the parameters yields strong field confinement and slowly diffracting beam propagation. The current work investigates the optical properties of the dielectric microcylinders at close proximity to the resonance condition. Both strong field focusing associated with photonic nanojets and enhanced field localization linked with the resonance condition are desired for photon manipulation scenarios in nanophotonics. © 2015 Optical Society of America