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Direction-of-arrival (DOA) estimation for wideband sources has attracted a growing interest in the recent decade because wideband sources are incorporated in many real-world applications such as communication systems, radar, sonar and acoustics. One way to estimate the DOAs of wideband signals is to decompose it into narrowband signals using discrete Fourier transform (DFT) and then apply well-established narrowband algorithms to each signal. Afterwards, results are averaged to yield the final DOAs. These techniques require scanning the full band of wideband sources, ultimately degrading the resolution and increasing complexity. This paper aims to propose a new DOA estimation methodology to solve these problems.

The new DOA estimation methodology is based on incoherent signal subspace method (ISSM). The proposed approach presents a criterion to select a single sub-band of the selected narrowband signals instead of scanning the whole signal spectrum. Then, the DOAs of wideband signals are estimated using the selected sub-band. Therefore, it is named as single sub-band (SSB)-ISSM.

The computational complexity of the proposed method is much lower than that of traditional DFT-based methods. The effectiveness and advantages of the proposed methodology are theoretically investigated, and computational complexity is also addressed.

To verify the theoretical analysis, computer simulations are implemented, and comparisons with other algorithms are made. The simulation results show that the proposed method achieves better performance and accurately estimates the DOAs of wideband sources.

Antenna miniaturization, multiband operation and wider operational bandwidth are vital to achieve optimal design for modern wireless communication devices. Using fractal geometries is recognized as one of the most promising solutions to attain these characteristics. The purpose of this paper is to present a unique structure of patch antenna using hybrid fractal technique to enhance the performance characteristics for various wireless applications and to achieve better miniaturization.

In this paper, the authors propose a novel hybrid fractal antenna by combining Koch and Minkowski (K-M) fractal geometries. A microstrip patch antenna (MPA) operating at 1.8 GHz is incorporated with a novel K-M hybrid fractal geometry. The proposed fractal antenna is designed and simulated in CST Microwave studio and compared with existing Koch fractal geometry. The prototype for the third iteration of the K-M fractal antenna is then fabricated on FR-4 substrate and tested through vector network analyzer for operating band/voltage standing wave ratio.

The third iteration of the proposed K-M fractal geometry results in achieving a 20% size reduction as compared to an ordinary MPA for the same resonant frequency with impedance bandwidth of 16.25 MHz and a directional gain of 6.48 dB, respectively. The operating frequency of MPA also lowers down to 1.44 GHz.

Further testing for the radiation patterns in an anechoic chamber shows good agreement to those of simulated results.

The purpose of this study is to investigate the monodisperse cavitation of bubbly mixture flow for water and hydrogen mixture flows through a nozzle having a stenosis on the wall.

Two flow regions, namely, quasi-statically stable and quasi-statically unstable increase in the bubble radius, are considered. Different oscillating periods of bubbles in downstream corresponding to various values of Reynolds number are taken into account. The Range–Kutta method is used to tackle nonlinear coupled system of governing equations.

It is observed that for the larger values of Reynolds number, the void fraction at the upstream section, even at small values, yields instabilities at the downstream. Consequently, owing to sudden increase in the velocity, the bubbles strike the wall with high speed that eventually remove the existing stenosis. This process can be considered as an effective cardiac surgery for arteries with semi-blockage.

Original research work and to the best of author’s knowledge, this model is reported for the first time.

A rapid increase in traditional industries is creating social and environmental problems through extensive usage of natural resources and polluting the environment. A circular economy provides curative and renewing lines of action about these problems. Therefore, this study aims to examine the factors that lead toward sustainable performance in a circular economy context and empirically test the relationships between green technology adoption (GTA), circular economy principles (CEP), sustainable supply chain practices (SSCM) and sustainable performance (SP).

Using the well-developed governmental databases, data from 435 small and medium enterprises (SMEs) in the textile sector of Pakistan were collected and tested through AMOS using a structural equation model.

The results disclosed that GTA, CEP and SSCM have significant and positive direct relationships and facilitate improving SMEs’ SP. Circular economy entrepreneurship (CEE) and customer pressure (CP) were found to have a significant and positive influence on the relationships of GTA and CEP with SSCM.

The role of GTA in circular economy and the moderating effect of CEE and CP is an addition to the literature. SMEs’ GTA allows them to reuse, reduce and recycle natural resources rather than obtain new ones from the ecosystem.

The COVID-19 pandemic has popularized wearing face masks for personal protection. However, the protection afforded by a mask is decreased if an individual accidently touches the outer surface of the mask and then touches other parts of their face. To overcome this problem, antimicrobial masks have become commercially available. However, many are disposable and/or made from synthetic antimicrobial agents which have a negative impact on the environment. The purpose of this study was to create material for stitching antimicrobial masks that are reusable and natural.

The authors developed natural antimicrobial finishes from Azadirachata indica, Butea monosperma and Litchi chinensis leaves. The authors used biodegradable polyurethane binder and pad-dry-cure method to apply them on 100% cotton fabric. The authors used Fourier-transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscope (SEM) to confirm the application and ASTM E2149 to assess the efficacy and wash-resistance of the finish.

Fabric treated with leaves of A. indica, B. monosperma and L. chinensis showed 80%, 100 and 100% antimicrobial activity, respectively. All fabrics were washed 25 times in home laundry cycles and maintained 100% of their antimicrobial effect.

These findings highlight that B. monosperma and L. chinensis finishes on cotton fabric can be a used as a material for stitching antimicrobial, natural and reusable masks that provide more protection than traditional masks but do not pose the environmental concerns of disposable masks or synthetic finishes. This study can be furthered by performing more laundry cycles to determine if the finishes remain 100% effective beyond 25 cycles.

The present work is devoted to investigating the sensitivity analysis of the electroosmotic peristaltic motion of non-Newtonian Casson fluid with the effect of the chemical reaction and magnetohydrodynamics through the porous medium. The main focus is on flow efficiency quantities such as pressure rise per wavelength, frictional forces on the upper wall and frictional forces on the lower wall. This initiative is to bridge the existing gap in the available literature.

The governing equations of the problem are mathematically formulated and subsequently simplified for sensitivity analysis under the assumptions of a long wavelength and a small Reynolds number. The simplified equations take the form of coupled nonlinear differential equations, which are solved using the built-in Matlab routine bvp4c. The response surface methodology and artificial neural networks are used to develop the empirical model for pressure rise per wavelength, frictional forces on the upper wall and frictional forces on the lower wall.

The empirical model demonstrates an excellent fit with a coefficient of determination reaching 100% for responses, frictional forces on the upper wall and frictional forces on the lower wall and 99.99% for response, for pressure rise per wavelength. It is revealed through the sensitivity analysis that pressure rise per wavelength, frictional forces on the upper wall and frictional forces on the lower wall are most sensitive to the permeability parameter at all levels.

The objective of this study is to use artificial neural networks simulation and analyze the sensitivity of electroosmotic peristaltic motion of non-Newtonian fluid with the effect of chemical reaction.

Numerous researchers have probed the peristaltic flows because of their immense usage in industrial engineering, biomedical engineering and biological sciences. However, the investigation of peristaltic flow in two-phase fluid of a rotating frame in the presence of a magnetic field has not been yet discussed. Therefore, to fulfill this gap in the existing literature, this paper will explicate the peristaltic flow of two-phase fluid across a rotating channel with the effect of wall properties in the presence of a magnetic field. The purpose of this study is to investigate the two-phase velocity distribution and rotation parameter when magneto-hydrodynamics is applied.

The constituent equations are solved under the condition of low Reynolds number and long wavelength. The exact method is used to attain the subsequent equations and a comprehensive graphical study for fluid phase, particulate phase velocity and flow rates are furnished. The impacts of pertinent parameters, magnetic field and rotation are discussed in detail.

It is witnessed that the velocity profile of particulate phase gets higher values for the same parameters as compared to the fluid phase velocity. Moreover, the axial velocity increases with different values of particle volume fraction, but in case of magnetic field and rotation parameter, it shows the opposite behavior.

The outcomes of study have viable industrial implementations in systems comprising solid-liquid based flows of fluids involving peristaltic movement.

The investigation of peristaltic flow in two-phase fluid of a rotating frame in the presence of a magnetic field has not been yet discussed. Therefore, to fulfill this gap, the present study will explicate the peristaltic flow of two-phase fluid across a rotating channel with the effect of wall properties in the presence of magnetic field.

This paper aims to investigate non-Darcy magnetohydrodynamic nanofluid flow in a uniformly porous medium. It is assumed that viscosity of nanofluid (Fe₃O₄-water) is a function of external magnetic field. Roles of Darcy number, inclination angle, volume fraction of nanofluid, Hartmann and Rayleigh numbers are demonstrated graphically.

The problem is modeled, and simulation has been done by means of control volume base finite element method.

Results proved that Nusselt number enhances with augment of buoyancy forces and Darcy number while it decreases with the increase of Lorentz forces. Isotherms become denser near the inner cylinder with increase of inclination angle and the Darcy number.

As per the authors’ knowledge, this problem is new and not been published before.

The purpose of this study is to examine the impact of activation energy with binary chemical reaction for unsteady flow on permeable stretching surface.

The simultaneous effects of multiple slip and magneto-hydrodynamic effects at the boundary are taken into account. The thermal buoyancy parameter and thermal radiation are included in both energy and momentum equations, while expression of activation energy is considered in concentration equation. Three-stage Lobatto IIIa finite difference collocation technique with bvp4c MATLAB package is used to obtained numerical results.

The influence of key elements (Schmidt number, buoyancy force ratio factor, factor of radiation, magnetic element, unsteadiness factor, suction/injection parameter, Prandtl number, activation energy, chemical reaction rate parameter, heat source and sink parameters, velocity, thermal and concentration slips, porosity parameter and temperature difference parameter) on velocity, temperature and concentration profiles are illustrated pictorially. A detailed discussion is presented to see how the graphical aspects justify the physical prospect.

In the best of author’s knowledge, this work is yet not available in existing literature.

Entropy generation in nanofluids with peristaltic scheme occupies a primary consideration in the sense of its application in clinical, as well as the industrial field in terms of improved thermal conductivity of the original fluid. Three-dimensional cylindrical configurations are the most realistic and commonly used geometries which incorporate most of the experimental equipment. In the current study, three-dimensional cylindrical enclosures have been assumed to receive the results of entropy generation occurring due to viscous dissipation, heat transfer of nanofluid and mass concentration of nanoparticles through peristaltic pumping. Applications of the study can be found in peristaltic micro-pumps and novel drug delivery mechanism in pharmacological engineering.

The equations of interest have been structured under physical constraints of lubrication theory and dimensionless strategy. Finalized relations involve highly complicated partial differential equations whose solutions are tabulated through some perturbation procedure and expression of pressure rise is manipulated by a numerical technique through built-in command NIntegrate on Mathematical tool “Mathematica.”

It is evaluated that entropy production goes linear with the greater magnitudes of Brownian motion but inverse characteristics have been sorted against thermophoresis factor.

To the best of authors’ knowledge, this study does not exist in literature yet and it contains a new innovative idea.