Arabian Journal for Science and Engineering最新文献

The growing need for remote healthcare monitoring and personalized treatment has driven the evolution of Wireless Body Area Networks (WBAN). This paper presents a new multiband antenna design for WBAN, featuring a dual wideband antenna that operates from 2.22 to 3.52 GHz and 4.98–11.13 GHz. The design also includes an integrated 4 × 4 artificial magnetic conductor (AMC) surface and a 4 × 3 frequency selective surface (FSS) superstrate layer that works together to reduce back radiation and improve radiation performance. The AMC unit cell produces a quintuple zero-degree reflection phase response at 2.5 GHz, 4.8 GHz, 6.5 GHz, 9.1 GHz, and 11 GHz, and the FSS superstrate generates a multiband response of the transmission coefficient at 3.24 GHz, 6.68 GHz, and 9.25 GHz, behaving as a Double Negative material at their corresponding resonant frequency. The integrated antenna design measures 0.425λ₀ ×  0.425λ₀ × 0.17λ₀ (λ₀ at 2.45 GHz) and covers the most common wireless frequency bands, with an impedance bandwidth of 23.74% (2.19–2.78 GHz), 1.739% (3.99–4.06 GHz), and 72.46% (5.13–10.96 GHz). Furthermore, the integrated antenna showcases a peak gain of 11.98dBi at 7.5 GHz, a notable Front-to-Back Ratio of 25.15 dB at 8.2 GHz, and a minimal specific absorption rate (SAR) of 0.0142 W/kg at 9 GHz. These accomplishments resulted in a considerable 99.45% reduction in the overall average SAR values and achieved an 83% radiation efficiency. The effectiveness of the proposed multiband antenna design was evaluated by fabricating and testing an experimental prototype using a Vector Network Analyzer and Anechoic Chamber. Overall, the integrated AMC and FSS structures enable multiband resonance and improved radiation performance, making the presented antenna design a promising solution for future WBAN applications.

The modern power systems incorporate high penetration of renewable is a large, composite, interconnected network with dynamic behavior. The small disturbances occurring in the system may induce low-frequency oscillations (LFOs) in the system. If the (LFOs) are not suppressed within a stipulated time, it may cause system islanding or even blackouts. Hence, it is essential to investigate the behavior of the system under various levels of disturbances and control action must be taken to damp these oscillations. The established approach to damping the LFOs is by installing power system stabilizers (PSS). PSS uses the local signals from generators to control the oscillations. The dominant source of inter-area oscillations in power systems is due to overloaded weak interconnected lines, converter-interfaced generation, and the action of the high gain exciter present in the system. Consequently, wide area control is needed to control the inter-area oscillations existent in the system. This paper developed a coordinated design of conventional PSS, static compensator, renewable converters, and wide area controller for damping the local and inter-area oscillations in renewable incorporated power systems. The performance of the developed controller is evaluated through the time domain analysis and eigenvalue analysis. A comparison of the introduced controller has been done with other standard conventional methods. The choice of input signals for the wide area controller from the wide-area measurement system is done based on the controllability index. Additionally, the location of the controller must be identified to dampen the inter-area oscillations in the system. In this paper, the controllability index is calculated to find out the highly affected wide area signals for considering it as the feedback signal to a developed controller. The location of the controller is recognized by computing the participation factor. The developed controller has experimented on renewable incorporated large study power systems when time delay and noise are present in wide area signals.

This paper proposes a system-based approach to classify metamaterials based on the behavior of the complex poles and residues of the electromagnetic fields in the materials. Metamaterials are classified into 12 types, depending on their nature as double-positive permittivity and permeability (DPS), double-negative permittivity and permeability (DNG), epsilon-negative (ENG), or mu-negative (MNG) metamaterials. The presented method expands the metamaterials’ reflection and transmission impulse responses as a superposition of damped sinusoids using the singular expansion method (SEM). The matrix pencil method is then employed to efficiently extract the SEM poles and residues of the transmitted and reflected impulse responses for each investigated metamaterial. The damping factor of the transmitted wave response and the real part of the residues of the reflected wave response differentiate between DPS and DNG metamaterials. Both the real and imaginary parts of the residues of the transmitted wave response and the damping factors of the reflected wave response are utilized to differentiate between ENG and MNG metamaterials. The results demonstrate this classification procedure, which is further described in a flow chart.

For the first time, flexoelectric and actual surface effects are applied to analyze the free oscillation of viscoelastic nanosheets resting on visco-Pasternak medium in hygro-temperature environment. The material characteristics of nanosheets are viscoelastic based on the Kelvin–Voigt model, and the visco-Pasternak medium has two layers, in which the sliding layer and the other layer are described as a spring system interspersed with a damping system. The general equation of motion of the nanosheets is established by applying Kirchhoff plate theory along with Hamilton's principle and the nonlocal strain gradient hypothesis. To solve the free vibration equations of nanosheets with various boundary conditions, the Navier and Galerkin approaches are employed. The presence of the viscoelastic component causes the nanosheets' inherent frequency to oscillate in the general situation with both imaginary and real components. Finally, the impact of coefficients on vibration of viscoelastic nanosheets is discussed in the numerical examples. This is the work that calculates the flexoelectric, surface effects, and viscoelastic-based nanosheet structures under varied loads, which serves as a precondition for their manufacture and use in reality. The present work is general because it combines the theories of nonlocal strain gradient, flexoelectricity, and actual surface effects for viscoelastic nanoplate. Currently, no research has been performed on this issue, and this study makes clear on understanding the underlying physics of electromechanical coupling at the nanoscale.

A circular ring structure monopolar printed antenna for Doppler and automotive radar systems (24 GHz) is designed with a size of 1.4λ₀ × 1.4λ₀ × 0.095λ₀ mm³ observing |S₁₁|> −20 dB, B.W. of 1.8 GHz and a peak gain of 5.1 dBi. This antenna upgraded initially into 2 × 1 and finally 4 × 1 array, having resonant frequencies at 24 GHz and 28 GHz, respectively. A peak gain of 7.12 and 7.16 dBi through 2 × 1 and 9 and 8.65 dBi through 4 × 1 array is observed at respective operating frequencies. Finally, the 4 × 1 array antenna with the tapered feed of size 4.4λ₀ × 2.2λ₀ × 0.095λ₀ mm³ having |S₁₁|≤ 40 dB at ISM-III (24 GHz) and |S₁₁|≤ −30 dB at 5G (28 GHz) with B.W. of 0.77 GHz and 5.1 GHz, respectively, is proposed, qualifying the obtained measured results. Isolation between each antenna element for the 4 × 1 array is ≤ −20 dB with a maximum value of −65 dB. The ECC observed between antenna elements is less than 0.045 and DG is 10. An equivalent circuit is also evaluated for the proposed antenna. The quantification results present that the developed array antenna has excellent performance over the dual band.

The use of nano-fillers as reinforcement in natural fibers-based hybrid composites has gained prominence in multiple sectors in recent years because of their virtuous mechanical and physical characteristics. The impeccable properties of nano-fillers like their high aspect ratio and larger surface area have made them to be used in areas for instance, sectors like aviation, automotive, and biotechnology fields. This study focuses on examining how various weight percentages of nano-calcium carbonate (NCaCO₃) fillers (2%, 5%, 7%) impact the elastic properties of innovative hybrid composites blended with banana and kenaf fibers, combined with epoxy. The elastic characteristics of the suggested composite, including longitudinal elastic modulus (LEM), transverse elastic modulus (TEM), longitudinal Poisson’s ratio (LPR), and longitudinal shear modulus (LSM), are analyzed through micromechanical models such as the Mori–Tanaka (M–TA) model, generalized self-consistent (GS-C) model, and modified Halpin–Tsai (M-HT) model. The composite consisting of a solitary banana fiber sheet, a solitary NCaCO₃ mix epoxy sheet, and another solitary kenaf fiber sheet is modeled in ANSYS APDL simulation software. The composite’s layers are organized in a specific order: starting with banana fiber at 90° orientations, followed by a layer of NCaCO₃ and epoxy at 0° orientations, and concluding with kenaf fiber at 90° orientations. The ANSYS software is employed to analyze the total sum deformation and strength of the suggested composite. The outcomes obtained from this research are contrasted and confirmed through comparison with existing literature. The inclusion of 7 wt% of NCaCO₃ in the suggested hybrid composite is found to have the highest elasticity and ductility in comparison with 2 wt% and 5 wt% of NCaCO₃. The composite containing 7 wt% NCaCO₃ demonstrates the greatest load-bearing capability. Additionally, while calculating the elastic characteristics of the proposed composite, both the modified Halpin–Tsai (M-HT) model and the generalized self-consistent model (GS-C) outperform the Mori–Tanaka model (M–TA). Furthermore, the hybrid impact is computed for the suggested composite to analyze the tensile strain rates at which failure occurs for banana and kenaf fibers within the composite hybrid structure. The computed hybrid value of 0.5 indicates that the failure rate of a non-hybridized composite is 50% more than the hybridized composite. This signifies that the hybrid composites have high load-bearing strength, high elasticity, and stiffness.

This paper proposes a method for harmonic time–frequency analysis and detection based on an improved multi-synchrosqueezing transform (MSST). The aim is to address the significant endpoint problem of the synchrosqueezing transform (SST) in power harmonic analysis. This approach initially employs the Burg method to estimate the parameters of the auto-regressive (AR) model for the harmonic signal. Subsequently, it conducts multiple iterative computations on the SST results of the extended harmonic signal, further compressing the time–frequency spectrum energy to obtain a more precise time–frequency spectrum of the harmonic signal. Additionally, it utilizes the robust reconstruction capability of MSST to decompose the harmonic signal and obtain a series of intrinsic mode functions (IMF) with different frequencies. Finally, the Hilbert Transform is applied to identify the harmonic parameters of each IMF component and accomplish harmonic detection. The simulation experiments and measured data results demonstrate that the proposed method outperforms the Hilbert-Huang Transform (HHT) and SST methods in achieving more accurate time–frequency analysis and detection of harmonic signals. It also reveals the time–frequency characteristics and variation patterns of power grid harmonics, making it of great significance for harmonic control.

Flow field organization significantly influences the performance criterion of a scramjet combustor. Recently, DLR scramjet combustor with strut injector has been mostly used to alter the flow field. Researchers have used innovative strut injectors to enhance the performance of the DLR scramjet combustor. However, the effect of utilizing a strut with both parallel and normal injections of air and fuel in the DLR scramjet combustor has not been investigated till date. Hence, in this study, the DLR combustor is numerically investigated using a modified strut injector with both parallel and normal injections of air and fuel. The 2D numerical solver is validated with the experimental results having a maximum deviation of 7.3%. The analysis shows that the combustors with modified strut injectors produce better turbulence mixing compared to the DLR combustor, resulting in higher combustion performance. The modified strut combustors, i.e., CMSI-1, CMSI-2, and CMSI-3 produced a combustion efficiency of 76%, 79%, and 81%. In contrast, the maximum combustion efficiency produced by the DLR combustor is 50%. This improvement in the combustion performance of the combustors with modified strut injectors resulted in higher thrust force than the DLR combustor. The thrust force produced by CMSI-1, CMSI-2 and CMSI-3 are 3160 Pa.m², 3200 Pa.m² and 3216 Pa.m², respectively. Finally, it has been found that the CMSI-3 has produced the maximum combustion efficiency and better thrust force among all the scramjet combustor models considered in the study.

In sophisticated engineering machining, ceramic materials are in great demand in today’s precision industries because they have a wide range of potential applications, including automobiles, aircraft, and biomedical engineering. Silicon nitride ceramics (Si₃N₄) are difficult to manufacture using conventional machining processes. Modern technology allows Ultrasonic Micro-machining (USMM) to create almost any kind of material. Abrasive particles made of silicon carbide are used in this research work to look into the Si₃N₄ USMM process parameters. The physical structure and chemical composition have been examined in a scanning electron microscope with an integrated energy-dispersive X-ray analyzer. Particle swam optimization and Response Surface Methodology (RSM) desirability were the two types of optimizations used to find the best USMM process parameters. It has been shown that both techniques can be used together to get the best Material Removal Rate (MRR). The best settings were Slurry Concentration: 50 (g/l), Power Rating: 329 (W), and Tool Feed Rate: 1.06 (mm/min). Similarly, to minimize Overcut (OC) and Taper Angle (TA), the ideal method is to use a slurry concentration of 50 (g/l), a power rating of 400 (W), and a tool feed rate of 1.2 (mm/min). Finally, using the RSM, the USMM process was optimized in a way that maximized the MRR while minimizing OC and TA. It was found that the slurry concentration of 42.7 g/l, the power rating of 357.6 W, and the tool feed rate of 1.2 mm/min were the ideal settings for the USMM process.

A reliable and efficient RSM with BBD was established to speedily analyze empagliflozin in wastewater and pharmaceutical formulation samples using HPLC. The Taguchi method was initially applied to determine the critical parameters among all selected variables and was then optimized with BBD. This development has numerous advantages, such as minimum organic solvent usage, short analysis times, and small sample volume with lesser waste generation. The chromatographic separation was accomplished with BDS Hypersil C18 (150 mm × 4.6 mm, 5 µm) as stationary phase using buffer: methanol (92.4:7.6, v/v) with a flow rate of 0.89 mL/min and detected at 240 nm. The calibration plot was linear between 2.5 and 20.0 μg/mL with LOD and LOQ values of 0.83 μg/mL and 2.52 μg/mL, respectively. The developed HPLC method was a superior technique linked with green chemistry based on the penalty points or analytical eco-scale score, which enhanced the method's reliability. The isolates were analyzed using FTIR spectroscopy, and the observed spectrum is comparable to the simulated spectrum obtained at the B3LYP/6-311G(d,p) level of theory. In addition, molecular structure, UV–visible spectral, electronic properties and molecular electrostatic potential of EMP were examined, and the findings will be useful for further research on EMP.