Axial Ratio Research Articles

High-Quality Factor Ultrathin Polarization-Insensitive Wide Angular Stable Elliptical-Shaped Microwave Absorber with Reconfigurability Features

This paper introduces an ultrathin, polarization-insensitive, wide angular stable microwave absorber characterized by a high-Quality (Q) factor. The absorber consists of elliptical metallic rings with a thickness of 0.035 mm on the top of Roger’s RT 5880 substrate with a thickness of 0.51 mm and a metallic ground plane with a thickness of 0.035 mm at the bottom. The proposed structure is fourfold symmetric which makes it polarization insensitive. The structure offers angular stability till 60° for the angle of incidence for both Transverse Electric (TE) and Transverse Magnetic (TM) modes under oblique incidence. The structure provides a high-quality factor of 155 at an operating frequency of 7.75 GHz. Also, the structure provides reconfigurability with a change in the axis ratio of the elliptical structure from 7.30 to 9.48 GHz when the axis ratio changes from 0.26 to 0.36 without any change in the unit cell size. The unit cell dimension is 1.07 λg x 1.07 λg x 0.022 λg. With its high Q-factor, thin size, structural simplicity, insensitivity to polarization, and incident angle stability suggested prototype is apt for microwave sensors and antennas to reduce Radar cross-section and X-band satellite communication.

Flexible Circularly Polarized CPW Antenna for X-Band: Design, Simulation, and Experimental Validation

Abstract This paper presents the design and analysis of a circularly polarized coplanar waveguide (CPW) antenna specifically tailored for X-band applications. The antenna, with compact dimensions of 27 mm x 28 mm, is fabricated on a flexible 0.1 mm thick polyimide substrate. It operates effectively within the frequency range of 10.5 GHz to 12 GHz. To enhance performance metrics such as gain and radiation characteristics, two complementary split-ring resonators (CSRRs) are integrated into the radiating patch. Comprehensive simulations were conducted, followed by the fabrication and experimental testing of the antenna. The results indicate a high degree of agreement between the simulated and measured performance parameters. The antenna achieves a gain of up to 6 dBi, with an axial ratio maintained below 3 dB across the operating frequency band, signifying excellent circular polarization characteristics. These findings underscore the potential of the proposed CPW antenna design as a highly efficient solution for X-band applications, offering notable improvements in gain and axial ratio performance. This work contributes to the development of advanced antenna technologies suitable for modern communication systems operating in the X-band spectrum.

Sub-6GHz and circularly polarized mm-wave DNG-CMM tri-patch MIMO radiator for 5G applications

ABSTRACT In present days, wideband circularly polarised antennas are best candidates for 5G to meet the challenges of effective utility of spectrum, large data rates, strong channel capacity, communication with low latency and enormous connectivity of device. Mobile users have to choose the devices that ran at sub-6 GHz or mm-wave, though, as the maximum users aim to employ distinct frequency bands for their 5G services, it is crucial to use both. For the 5G necessities, a 35.8 × 6.8 × 0.254 mm3 under-6 GHz and circular polarised mm-wave double negative complementary metamaterial (DNG-CMM) three patched MIMO antenna was structured and also explored the various 5G bands in below 6 GHz and mm-waves in several nations. The frequency ranges that the recommended MIMO radiator is covering 14.66–41.49 GHz and 5.24–6.01 GHz. Below 3 dB axial ratio (circular polarisation) was noted at 24.64–36.52 GHz and 38.25 GHz. The gain 3.07–4.2 dBi and 3.85–22.89 dBi were attained at lower and higher operating bands, respectively. This MIMO radiator underwent testing and fabrication. There was considerable accuracy in the similarity between the simulated and measured findings. The findings showed that the EM wave emitting structure that was provided may cover the 5G NR n-46 band under 6 GHz as well as the 5G NR n-257, n-258, n-260 and n-261 bands in the mm-wave frequencies with notable radiation features. Therefore, it is a good fit for 5G (mm-wave and sub-6 GHz) applications.

Nonlinear Analysis and Optimization of Recycled Aggregate Concrete Cross-Sections Based on Restoring Force Models

This research presents a simplified approach using a uniaxial restoring force model to analyze the seismic response of recycled aggregate concrete (RAC) frames. Nonlinear simulations were conducted to explore how factors like axial compression ratio, reinforcement ratio, and cross-sectional geometry affect the ductility and seismic performance of RAC sections. The findings reveal that a reduction in the axial compression ratio from 0.60 to 0.57 results in a 15% increase in ductility, while a higher reinforcement ratio leads to a 20% enhancement. In addition, rectangular sections were found to be more sensitive to variations in material strength than square sections, offering key insights for structural optimization. The method proposed here also enhances computational efficiency by minimizing resource consumption and improving the convergence of nonlinear iterative procedures. These findings provide a theoretical foundation for optimizing the design and seismic evaluation of RAC structures, promoting their broader application in engineering practice.

Dual circularly polarized dual-band antenna combining transmitarray and reflectarray for K/Ka-band uplink and downlink satellite communication

This paper presents a dual-band antenna system utilizing transmitarray (TA) and reflectarray (RA) having dual-circularly polarized (CP) characteristics for K/Ka-band satellite communication. The antenna consists of the TA and RA surfaces operating at 19.5 GHz and 29.7 GHz respectively. The RA is designed on a single substrate layer with element size of 0.30 λ × 0.30 λ (λ corresponding to 30 GHz), whereas the TA is designed on two substrate layers with element size of 0.33 λ × 0.33 λ (λ corresponding to 20 GHz). The equivalent circuit model (ECM) of the TA and RA elements is extracted to validate the working of the proposed elements. A small window of the size of a patch antenna is cut in both the RA and TA surfaces to accommodate the coaxially-fed illuminating sources. The antenna shows the peak gain of 17 dBiC at 19.5 and 29.7 GHz. The 3 dB axial ratio bandwidths range from 19.3–19.6 GHz (1.55 % ) and 29.5–29.9 GHz (1.35 % ) in the two frequency bands. The antenna radiates two orthogonally polarized CP waves at two frequency bands which makes the antenna suitable for satellite communication applications.

Probing the formation of megaparsec-scale giant radio galaxies

Context. Constituting a relatively small fraction of the extended-jetted population, giant radio galaxies (GRGs) form in a wide range of jet and environment configurations. This observed diversity complicates the identification of the growth factors that facilitate their attainment of megaparsec scales. Aims. This study aims to numerically investigate the hypothesized formation mechanisms of GRGs extending ≳1 Mpc in order to assess their general applicability. Methods. We employed tri-axial ambient medium settings to generate varying levels of jet frustration and simulated jets with a low and a high power from different locations in the environment. This approach formulated five representations evolving under a relativistic magnetohydrodynamic framework. Results. The emergence of distinct giant phases in all five simulated scenarios suggests that GRGs may be more common than previously believed. This prediction can be verified with contemporary and forthcoming radio telescopes. We find that different combinations of jet morphology, power, and evolutionary age of the formed structure hold the potential to elucidate different formation scenarios. In all of these cases, the lobes are overpressured, prompting further investigation into pressure profiles when jet activity ceases, potentially distinguishing between relic and active GRGs. We observed a potential phase transition in GRGs marked by differences in lobe expansion speed and pressure variations compared to their smaller evolutionary phases. This suggests the need for further investigation across a broader parameter space to determine if lobe evolution in GRGs fundamentally differs from smaller radio galaxies. The axial ratio analysis reveals self-similar expansion in rapidly propagating jets, while there is a notable deviation when the jet forms wider lobes. Overall, this study emphasizes that multiple growth factors simultaneously at work can better elucidate the current-day population of GRGs, including scenarios such as the growth of GRGs in dense environments, GRGs extending several megaparsecs, development of GRGs in low-powered jets, and the formation of morphologies such as GRG-XRGs.

Seismic Performance of X-shaped Stud Steel Reinforced Concrete Columns Under Composite Torsion

To investigate the seismic performance of X-shaped steel-reinforced concrete (SSRC) columns subjected to combined torsion, eleven specimens were designed with varying parameters including torsion-to-bending ratio, axial load ratio, steel ratio, longitudinal reinforcement ratio, stirrup reinforcement ratio, and stud spacing. Quasi-static loading tests were conducted to observe the failure process and failure modes. The results indicate that the SSRC column ultimate failure mode is predominantly determined by the stirrup reinforcement ratio, leading to either flexural-torsional failure or torsional failure. The torque-torsion angle hysteresis loops exhibit a pinched, inverted "S" shape, while the moment-displacement hysteresis loops display a more pronounced, spindle-like shape. The axial load ratio and torsion-to-bending ratio exert the most significant influence on the seismic performance of the specimens. As the steel ratio, longitudinal reinforcement ratio, and stirrup reinforcement ratio increase, the ductility, energy dissipation capacity, and other seismic performance indicators of the components improve to varying degrees. Among these parameters, the steel ratio has the most pronounced impact on energy dissipation capacity. When the steel ratio increases from 2.39% to 2.90%, the energy dissipation capacity of the component improves by 36.8%. Reducing the stud spacing appropriately enhances the seismic performance of the component, but excessively sparse or dense stud spacing can have detrimental effects. Based on the experimental results and existing research, a formula for calculating the torsional capacity of X-shaped SSRC columns subjected to combined torsion was developed using the superposition principle. The calculated results align well with the experimental results, with an average error within 5%.

Wideband Circularly Polarized Multimode Horn Array Antenna Using Single Layer E‐Plane Waveguide Sequential Feeding Network

ABSTRACTThis paper presents the design and fabrication of a 4×4 array antenna based on multi‐mode horn elements and sequential feeding network. The multi‐mode horn antenna is a structure that can suppress grating lobes and side lobe levels by excitation and combining different modes of electromagnetic wave radiation. The sequential feeding network is a technique that can generate circularly polarized radiation from linearly polarized elements by arranging them in a square array with 90° rotations and feeding them with 90° phase difference. The proposed array antenna achieves wideband impedance matching and axial ratio performance, as well as high gain and low complexity. The array antenna operates from 9.9 to 12.6 GHz, with a maximum gain of 24.5 dBi at 11 GHz. The array antenna is fabricated using CNC milling and measured in an anechoic chamber. The measured results agree well with the simulated ones, validating the effectiveness of the proposed design.

Axial ratio improvement for wide-angle scanning circularly-polarized phased array of circular patch antennas

Axial ratio improvement for wide-angle scanning circularly-polarized phased array of circular patch antennas

Precise Measurements of the LMC Bar’s Geometry with Gaia DR3 and a Novel Solution to Crowding-induced Incompleteness in Star Counting

Abstract We present new measurements of the 2D geometry of the LMC’s stellar bar with precise astrometric observations of red clump stars in Gaia DR3. We develop a novel solution to tackle crowding-induced incompleteness in Gaia data sets with the Gaia BP-RP color excess. Utilizing the color excess information, we derive a 2D completeness map of the LMC’s disk. We find that incompleteness biases the bar measurements and induces large uncertainties. With the completeness-corrected 2D red clump map, we precisely measure the LMC bar’s properties using Fourier decomposition. The bar radius (semimajor axis) is R bar = 2.13 − 0.04 + 0.03 kpc, and its position angle is 121.°26 ± 0.°21. The bar’s strength as quantified by the Fourier bi-symmetric amplitude is S bar = 0.27, indicating that the LMC has a significant bar perturbation. We find the bar has an axis ratio of 0.54 ± 0.03, and is offset with respect to the center of the outer disk isophote at R ≈ 5 kpc by 0.76 ± 0.01 kpc. These LMC bar properties agree with a hydrodynamic model where the SMC has undergone a recent direct collision with the LMC. We compare the LMC’s bar properties with other barred galaxies in the local Universe, and discover that the LMC is similar to other barred galaxies in terms of bar-galaxy scaling relations. We discuss how our completeness correction framework can be applied to other systems in the Local Group.

Design of polarization reconfigurable Koch fractal antenna for S-and C-band applications

Abstract In this research, a novel polarization reconfigurable fractal antenna with high gain is proposed for wideband applications. This antenna consists of a Koch curve based hexagonal ring patch, two Positive-Intrinsic-Negative (PIN) diodes, and partial ground. The patch is positioned on a Rogers RT/Duroid 5880 substrate (ϵr = 2.2) with overall dimensions 33 × 30 × 1.6 mm3. It has three frequency bands with three different cases i.e., case I, 3–7.91 (90%); case II, 3–7.73 (88.16%); and case III, 3.54–6.7 GHz (61.7%). As a result, the proposed antenna’s impedance bandwidth (IBW) offers constant wideband coverage ranging from 3–7.91 GHz (90%). The axial ratio bandwidth (ARBW) is below 3 dB over 3.6–6.9 (62.86%) and 3.33–7.14 GHz (72.78%) for LHCP (Case I) and RHCP modes (Case II), respectively. The value for LP mode (Case III) is 3.54–6.7 GHz (61.7%). A peak realized gains of 4.75, 5.07, and 3.8 dBi are achieved at 6.2, 6.3, and 6 GHz for Case I, Case II, and Case III, respectively. Both linear and circular polarization prototype was developed and the performance was verified through measurements. The design confirms good polarization-reconfigurable characteristics within the band of 3.91 – 7.91 GHz.

High-Performance CP Magneto-Electric Dipole Antenna Fed by Printed Ridge Gap Waveguide at Millimeter-Wave.

This paper presents a high-performance circularly polarized (CP) magneto-electric (ME) dipole antenna optimized for wideband millimeter-wave (mm-wave) frequencies, specifically targeting advancements in 5G and 6G technologies. The CP antenna is excited through a transverse slot in a printed ridge gap waveguide (PRGW), which operates in a quasi-transverse electromagnetic (Q-TEM) mode. Fabricated on Rogers RT 3003 substrate, selected for its low-loss and cost-effective properties at high frequencies, the design significantly enhances both impedance and axial ratio (AR) bandwidths. The antenna achieves an impressive impedance bandwidth of 31% (25.24-34.50 GHz) and an AR bandwidth of 24.9% (26.40-33.91 GHz), with a peak gain of up to 8.4 dBic, demonstrating a high cross-polarization level. The experimental results validate the high-performance characteristics of the antenna, making it a robust candidate for next-generation wireless communication systems requiring CP capabilities.

Numerical simulation study of enhanced heat transfer and flow resistance characteristics of twisted tape and twisted elliptical tube composite

ABSTRACT In this paper, the numerical simulation method is used to explore the effect of wall twisting and twisted tape composite to enhance heat transfer in tubes. Comparative analysis of the flow characteristics of fluids in tubes with different Reynolds numbers between 10,000 and 20,000, and with different length/short axis ratios and twist ratios. The results showed that when the length/short axis ratio of twisted elliptical tubes is increased from 1.30 to 2.15, the Nusselt number of twisted elliptical tubes with inserted twisted tapes increases by 10.5–28.6% and the friction coefficient increases by 101.5–128.8% compared with that of smooth elliptical tubes. When the twist ratio is reduced from 2/3 to 1/6, the Nusselt number of the twisted elliptical tube with inserted twisted tape increases by 9.8–37.7%, and the friction coefficient increases by 101.9–164.7%. Increasing the length/short axis ratio and decreasing twist ratio can help to improve the heat transfer performance of the twisted elliptical tube, but all of them are at the expense of increasing the resistance to flow of the fluid inside the tube.

Design and Optimization of Dielectric Resonator–Based Two‐Port Filtering Radiator With Machine Learning for Sub‐6 GHz 5G Wireless Applications

ABSTRACTThis paper proposes the structured and investigation of multi‐port ceramic‐based aerial with filtering, high gain, and circular polarization features. The alumina ceramic is excited using a cross‐shaped microstrip line. Defected ground structure (DGS) is utilized to provide good impedance matching within the operating band. Metasurface suspension over the two‐port aerial improves the gain level by an amount of 10.2 dBi. The application of polarization diversity idea helps to improve separation between aerial ports by 25 dB. The prediction of |S11| and axial ratio using random forest and XGBoost‐built machine learning (ML) technique reduces the computational complexity. Fabricated prototype confirms that the designed antenna operates in between 2.55 and 3.45 GHz, and 3‐dB axial ratio is found in between 2.75 and 3.15 GHz. Directive far‐field attributes and suitable amount of diversity parameters confirm its applicability for sub‐6 GHz‐based 5G communication system.

Compact triple-band ring-shaped printed antenna with circular polarization

This research proposed a planar printed antenna with circularly polarized (CP) ability. The antenna can supply an impedance bandwidth (│S11│<−10 dB) of 60% (2.3–4.3 GHz), 32.4% (4.8–6.8 GHz), 5.5% (7–7.4 GHz), and 24.4% (8.6–11 GHz) in the operative frequency band. The designed antenna has a 3 dB polarization axial ratio (AR) bandwidth (BW) of 88% (1.4–3.6 GHz), 11.3% (5–5.6 GHz), and 1.15% (8.6–8.7 GHz). The patch antenna dimensions are 20mm × 20 mm. To enhance AR bandwidth, an inverted L-formed strip line is added to the radiator to generate two electric fields with 900 phase differences. The measurement maximum gain of this patch antenna is about 7 dBi from 2.5 to 4.4 GHz. This structure has a wide AR beam width from – 30° to +110° at 2.4 GHz, – 70° to +70° at 5.2 GHz, and – 60° to +20° at 8.65 GHz. The CP antenna exhibits a miniaturized size and low-cost structure with suitable CP radiation characteristics.

Influence of Particle Orientation Angle and Axial Diameter Ratio on the Magnetic Properties of Soft Magnetic Composites by Finite Element Method

Influence of Particle Orientation Angle and Axial Diameter Ratio on the Magnetic Properties of Soft Magnetic Composites by Finite Element Method

Enhancing the assessment of in situ beam–column strength through probing and machine learning

Beam–columns are designed to withstand the concurrent action of both axial and bending stresses. Therefore, when assessing the structural health of an in situ beam–column, both of these load effects must be considered. Probing, having been shown recently to be an effective methodology for predicting the in situ health of prestressed stayed columns under axial compression, is applied currently for predicting the in situ health of beam–columns. Although probing stiffness was sufficient for predicting the health of prestressed stayed columns, additional data are required to predict both the moment and axial utilisation ratios. It is shown that the initial lateral deflection is a suitable measure considered alongside the probing stiffness measured at various probing locations within a revised machine learning (ML) framework. The inclusion of both terms in the ML framework produced an almost exact prediction of both the aforementioned utilisation ratios for various design combinations, thereby demonstrating that the probing framework proposed herein is an appropriate methodology for evaluating the structural strength reserves of beam–columns.

The selective consumption of European ivy (Hedera helix) berries by the Common Blackbird (Turdus merula)

Seed dispersal of plants affects the spatial structure and population dynamics, contributing to ecosystem functioning. Birds are among the most important seed dispersers. Preferences of birds in fruit and berry consumption are potentially significant selective pressures on the evolution of fruit traits that affect plant fitness. European ivy (Hedera helix) is a widespread deciduous species in Europe and the Common Blackbird (Turdus merula) is important seed disperser. This study investigates blackbird feeding preferences for specific sizes of ivy seeds. Field data was collected in a small settlement east of Simferopol city in Crimea and included a collection of reference seeds gathered from plants and seeds found in bird excretions. The length of the major axis, minor axis, and aspect ratio were measured, and statistical analysis was performed. The length of the major and minor axes of seeds consumed by blackbirds was higher compared with the reference collection, the aspect ratio was the opposite. Evidence of size differences could suggest weak effect of selective consumption of blackbirds on seed shape. This research extends our knowledge of the ecological relationship between frugivorous birds and plants and the role of birds in directional selection in a particular locality.

Quasi-Static Finite Element Analysis and Damage Quantitative Evaluation of Special-Shaped Concrete-Filled Steel Tubular Column Composite Frame Structure

ABSTRACT Based on the elaborate 3D solid finite element (FE) model established by ABAQUS software, a pseudo-static analysis was conducted on a special-shaped concrete-filled steel tubular column composite frame structure. The FE model considers the confinement effect of both the steel tubes and the tensile bars exerting on the core concrete. The results of the numerical analysis concerning failure modes, load-displacement hysteretic curves, load-displacement skeleton curves and stiffness degradation-displacement curves demonstrate a strong correlation with the existing quasi-static test data. Furthermore, an in-depth analysis was conducted on the impact of the axial compression ratio of column on the plastic energy dissipation distribution mechanism. With an axial compression ratio of the column ranging from 0.1 to 0.55, the composite frame structure primarily relies on the energy dissipation of beams, while the columns serve as supplementary support, thereby exemplifying the principle of “strong column-weak beam.” As the axial compression ratio rises to the range of 0.6–0.8, the composite frame structure transitions a “strong beam-weak column” structural system. Combined with the longitudinal compressive strain of the steel tube at the bottom of the column, a quantitative evaluation method for seismic damage is proposed, grounded in indexes of “stiffness damage” and “energy damage.” Then, the threshold values of energy damage and stiffness damage are determined across four distinct levels: “elastic stage in small earthquake,” “elasto-plastic stage in medium earthquake,” “plastic stage in heavy earthquake” and “failure stage.” The proposed method effectively evaluate the damage severity of special-shaped CFT column composite frame structure subjected to seismic events.

Clinical Outcomes Through Two Years for Infants With Bronchopulmonary Dysplasia and Tracheomalacia.

Tracheomalacia (TM) is common in infants with bronchopulmonary dysplasia (BPD) and associated with respiratory morbidity. Assessment of TM was historically via bronchoscopy, but recent studies demonstrate that ultrashort echo-time (UTE) magnetic resonance imaging (MRI) can accurately assess TM in neonates. Do neonates with MRI-identified TM and BPD have increased respiratory morbidity through age 2 years? We performed an observational cohort study of 54 subjects with BPD and assessed TM using UTE MRI at term-equivalent age. TM was defined as an airway minor/major axis ratio (rd,min) of < 0.7. Outcomes through 2 years of life were evaluated via electronic medical record review. There were 23 subjects (43%) with TM. Modified Ochiai MRI scores were similar between the subjects with and without TM (7.3 ± 4.1 vs. 7.4 ± 4.1). Subjects with TM were more likely to require respiratory support at age 2 years (62% vs. 30%, p = 0.04) and be prescribed systemic corticosteroids (71% vs. 27%, p = 0.004). Most patients with TM were prescribed bronchodilators (90% vs. 60%, p = 0.04). A 10% increase in tracheal collapse correlated with a 28-day increased hospital length of stay (p = 0.047), increased likelihood of pneumonia (p = 0.05), and treatment with antibiotics (p = 0.04) and systemic steroids (p = 0.008). TM in the neonatal period was associated with increased respiratory morbidity through age 2 years, demonstrated by increased respiratory support and more frequent usage of systemic corticosteroids and bronchodilators, independent of the severity of BPD. These results highlight the significance of central airway disease in neonates with BPD.