Oblique Angle Research Articles

Impact of Droplets on Surfaces Designed with Wettability-Gradient Properties: Directional Migration, Oblique Rebound, and Reduced Contact Time.

Efficiently regulating the rebound behavior of droplets post-impact is crucial for various fields, mainly including the development of self-cleaning applications, the design of surface functional materials, and the advancement of industrial techniques. By performing molecular dynamics simulations, we investigated the impact and jumping behavior of droplets on heterogeneous substrates with different wetting regions. We found that, during the impacting evolution process, the retracted droplets would move toward regions with stronger wettability due to the unbalanced force caused by the wettability difference, revealing the directional migration ability. The values of the wettability difference strongly affect the degree of oblique rebound and contact time when droplets can jump off the substrate. We then designed the surfaces with a wettability gradient and found that the oblique rebound angle could be well controlled and the contact time further reduced. Our findings may provide valuable insight into the relationship between the wettability gradient and the behavior of liquid droplets on surfaces, with broad implications for various fields such as surface engineering, materials science, microfluidics, etc.

Improving Urban Mapping Accuracy: Investigating the Role of Data Acquisition Methods and SfM Processing Modes in UAS-Based Survey Through Explainable AI Metrics

In this study, we investigated the accuracy of surface models and orthophoto mosaics generated from images acquired using different data acquisition methods at different processing levels in two urban study areas with different characteristics. Experimental investigations employed single- and double-grid flight directions with nadir and tilted (60°) camera angles, alongside the Perimeter 3D method. Three processing levels (low, medium, and high) were applied using SfM software, resulting in 42 models. Ground truth data from RTK GNSS points and aerial LiDAR surveys were used to assess horizontal and vertical accuracies. For the horizontal accuracy test, neither the oblique camera angle nor the double grid resulted in an improvement in accuracy. In contrast, when examining the vertical accuracy, it was concluded that for several processing levels, the tilted camera angle yielded better results, and in these cases, the double grid also improved accuracy. Feature importance analysis revealed that, among the four variables, the data acquisition method was the most important factor affecting accuracy in two out of three cases.

Thermohydraulic performance analysis and optimization of stripe patterned hybrid-wetting surface condensation by 3D steady simulation

The configuration parameters of stripe patterned hybrid-wetting surfaces (SPHWSs) had a significant effect on the thermohydraulic performance of condensation. By using Taguchi-GRA method modified by entropy weight for optimization, Nusselt number (Nu) and thermal performance factor (TPF) reached the highest increment of 225.9% and 252.8% at vapor mass fraction (ω) equal to 15%, respectively, and the maximum reduction of Fanning friction coefficient (f) was −41.7% at ω = 30%, as compared without SPHWSs. A 3D steady CFD-aided method based on pseudo transient under-relaxation model was developed to predict Nu, f, and TPF of SPHWSs for different configuration parameters, including oblique pattern angle (β), hydrophilic (Wi) and hydrophobic (Wo) pattern width, hydrophilic (θi), and hydrophobic (θo) contact angle. The result indicated that the simulation was in good agreement with the experimental data. θi had a more pronounced effect on the thermohydraulic performance compared to other factors. Notably, the droplet reached a specific dynamic force balance at θi = 60°, effectively restraining near-wall erratic flow and enabling cost-optimal heat transfer.

Oblique impingement of binary droplets at the nanoscale on superhydrophobic surfaces: A molecular dynamics study.

The impacting phenomenon of nanodroplets has received much attention due to their importance in various industrial applications. The oblique impingement of single droplets is well understood; however, the effect of oblique angle on impacting the dynamics of multiple droplets at the nanoscale is very limited. To address this gap, we perform molecular dynamics (MD) simulations to study the impacting dynamics of binary nanodroplets with various oblique angles (αob) and Weber numbers (We). Using MD simulations, we directly capture the detailed morphological evolution of the impacting binary droplets with various given conditions. Compared to the oblique impingement of a single droplet, the evolution of impacting binary droplets involves two novel dynamic characteristics: the asymmetric dynamics with droplet preferential spreading in the y direction and the rotating of the coalescing droplet. The mechanisms underlying are well studied. The asymmetric dynamics is a result of the velocity gradient of the outer edge of the spreading droplet, and the rotating effect is due to the change in angular momentum induced by surface force. The analysis and study of these phenomena have never been mentioned in previous studies of single droplet. Finally, we investigate the effect of αob and We on normalized moving distance (L/Dsin) and contact time (tc). This work paves the way for offering a comprehensive understanding of the oblique impingement of binary nanodroplets.

Spinopelvic interactions in total hip arthroplasty: 295 patients followed for a minimum follow-up of 10 years.

Concurrent spinal pathology is frequent in patients undergoing total hip arthroplasty (THA). In this study we examined whether spinopelvic interactions affect THA outcomes at a minimum follow-up of 10 years. 295 patients with a mean age of 63.3 (range 56‒80) years receiving a THA between 2006 and 2009 were assessed. Of these, 195 had mild lumbar disc degeneration and 100 had advanced lumbar spondylosis. We analysed the changes in the Harris Hip Score (HHS) and the survival rate for postoperative low back pain (LBP) and dislocation. Changes in acetabular component position, sacro-femoral-pubic (SFP) and pelvic obliquity (PO) angles were assessed with radiological images. The mean HHS was lower in female patients (p = 0.009), patients >65 years of age (p < 0.001) and those with advanced lumbar spondylosis (p = 0.002). 52 (71.2%) of the patients reporting preoperative LBP experienced improvement after THA while 47 (21.1%) of those without preoperative LBP postoperatively reported new onset LBP. Female patients (p = 0.025; hazard ratio [HR]: 1.831; 95% CI, 1.081-3.101) and those with preoperative LBP (p = 0.007; HR 2.068; 95% CI, 1.221-3.504) were at a higher risk of developing postoperative LBP at 10 years. 4 out of 9 THA dislocations were late and had shown decreasing SFP angle values over time. Acetabular component inclination and anteversion angles increased over time, whereas the SFP angle was associated with sex and age and the PO angle with age and the severity of any preoperative lumbar degeneration. Concurrent spinal pathology influences THA outcomes at a minimum follow-up of 10 years. Sex, age, and associated lumbar degeneration can affect clinical and radiological changes over time. A decrease in SFP angle values over time was found in patients sustaining late dislocation.

5G-enabled, battery-less smart skins for self-monitoring megastructures and digital twin applications.

With the current development of the 5G infrastructure, there presents a unique opportunity for the deployment of battery-less mmWave reflect-array-based sensors. These fully-passive devices benefit from having a larger detectability than alternative battery-less solutions to create self-monitoring megastructures. The presented 'smart' skin sensor uses a Van-Atta array design enabling ubiquitous local strain monitoring for the structural health monitoring of composite materials featuring wide interrogation angles. Proof-of-concept prototypes of these 'smart' skin millimeter-wave identification tags, that can be mounted on or embedded within common materials used in wind turbine blades, present a highly-detectable radar cross-section of - 33.75 dBsm and - 35.00 dBsm for mounted and embedded sensors respectively. Both sensors display a minimum resolution of 202 -strain even at 40 off-axis enabling interrogation of the fully-passive sensor at oblique angles of incidence. When interrogated from a proof-of-concept reader, the fully-passive, sticker-like mmID enables local strain monitoring of both carbon fiber and glass fiber composite materials. The sensors display a repeatable and recoverable response over 0-3000 -strain and a sensitivity of 7.55 kHz/ -strain and 7.92 kHz/ -strain for mounted and embedded sensors, respectively. Thus, the presented 5G-enabled battery-less sensor presents massive potential for the development of ubiquitous Digital Twinning of composite materials in future smart cities architectures.

Development of a Method for Estimating the Angle of Lumbar Spine X-ray Images Using Deep Learning with Pseudo X-ray Images Generated from Computed Tomography

Background and Objectives: In lumbar spine radiography, the oblique view is frequently utilized to assess the presence of spondylolysis and the morphology of facet joints. It is crucial to instantly determine whether the oblique angle is appropriate for the evaluation and the necessity of retakes after imaging. This study investigates the feasibility of using a convolutional neural network (CNN) to estimate the angle of lumbar oblique images. Since there are no existing lumbar oblique images with known angles, we aimed to generate synthetic lumbar X-ray images at arbitrary angles from computed tomography (CT) images and to estimate the angles of these images using a trained CNN. Methods: Synthetic lumbar spine X-ray images were created from CT images of 174 individuals by rotating the lumbar spine from 0° to 60° in 5° increments. A line connecting the center of the spinal canal and the spinous process was used as the baseline to define the shooting angle of the synthetic X-ray images based on how much they were tilted from the baseline. These images were divided into five subsets and trained using ResNet50, a CNN for image classification, implementing 5-fold cross-validation. The models were trained for angle estimation regression and image classification into 13 classes at 5° increments from 0° to 60°. For model evaluation, mean squared error (MSE), root mean squared error (RMSE), and the correlation coefficient (r) were calculated for regression analysis, and the area under the curve (AUC) was calculated for classification. Results: In the regression analysis for angles from 0° to 60°, the MSE was 14.833 degree2, the RMSE was 3.820 degrees, and r was 0.981. The average AUC for the 13-class classification was 0.953. Conclusion: The CNN developed in this study was able to estimate the angle of an lumbar oblique image with high accuracy, suggesting its usefulness.

Robust broadband dual-polarized rectenna with high conversion efficiency

In this paper, a robust wide-beam dual-polarized broadband rectenna with high conversion efficiency is proposed. First, a metal wall-loaded broadband cross-dipole antenna is designed as the receiving antenna. With the metal wall, the bandwidth of the receiving antenna is greatly improved. The measured results show that the −10 dB impedance bandwidth is 820 MHz from 1.65 to 2.47 GHz, and the 3-dB beamwidth is over 80° within the operating bandwidth. Besides, a novel impedance matching network is introduced to help the rectifier achieve high conversion efficiency in a wide bandwidth. The measured results show that the RF-DC conversion efficiency is maintained above 50 % with a maximum of 78 % within the bandwidth from 1.56 to 2.53 GHz when the load impedance is 840 Ω and the input power is 12.0 dBm. Finally, the receiving antenna and rectifier are integrated and measured. The results illustrate that the proposed design can be robustly against dynamic ambient power density, large oblique incidence angle, and arbitrarily polarized wave. Specifically, the measured conversion efficiency is over 49 % at an ambient power density of 200 μW/cm2 within the incident angle from −40° to 40° under arbitrary polarization. Hence, it could be a feasible solution to wireless energy harvesting (WEH) applications.

A miniaturized dual band pass frequency selective surface insensitive to oblique angles and polarizations of wave

Abstract A Dualband Pass Frequency Selective Structure (DPSFSS) with miniaturized elements is proposed in this article. The miniaturized elements induce high inductance and capacitance values. The meandered line concept is used which extensively increases inductance of the dipole element. Very large capacitance is obtained between two meandered elements which have wide common area perpendicular to electric field for wave propagating in Z-direction. Two pass band poles and two zeros are obtained by perpendicular arrangement of meandered patterns on two sides of the substrate. Orthogonal arrangement of patterns ensure polarization symmetry (polarization insensitive) for Transverse Electric (TE) and Transverse Magnetic (TM) modes of exciting wave. Two pass band pole frequencies are positioned at 1.84 GHz and 4.53 GHz with low Insertion Losses (IL) of 0.67 dB and 1 dB, respectively. The lower and higher frequency bands have factional bandwidths of 41 % and 46 %, respectively. The transmission nulls occupy 2.8 GHz and 6.58 GHz frequencies. The structure is miniaturized to 0.032λ 0 × 0.032λ 0 dimensions with respect to lowest resonance residing at 1.83 GHz. The low IL at both pass bands is realized despite of using a lossy FR-4 material that can be improved to less than 0.5 dB at both the bands using less lossy materials such as F4BME or RO4003C. The proposed DPSFSS design is elaborated using Equivalent Circuit Model (ECM) and Surface Current Distribution (SCD). Measurements are performed on fabricated DPSFSS prototype and it is observed that the measured results coincide well with the simulated response. Angle stability of the DPSFSS is excellent and no unwanted resonances are observed at oblique angles upto 80° for dual polarizations of wave.

Enhanced magnetic anisotropy and its thermal stability in obliquely deposited Co-Film on the nanopatterned substrate

The deliberate manipulation of magnetic anisotropy through controlled adjustments to surface and interface morphology has become important due to its potential applications in spintronics and magnetic memory devices. In the present work, oblique angle deposition (OAD) at 65° to the surface normal on a rippled substrate, keeping nanopatterns on the SiO2 substrate perpendicular to the OAD projection, has been used to induce in-plane uniaxial magnetic anisotropy (UMA) and its thermal stability in cobalt (Co) thin film. Prior to film preparation, the patterned substrate of wavelength 68 ± 4 nm and amplitude 3.4 ± 0.2 nm was prepared separately using a low-energy ion beam erosion (IBE) process. Grazing incidence small-angle X-ray scattering (GISAXS) and magneto-optical Kerr effect (MOKE) techniques have been used for film characterization. While GISAXS provided information about film structure and morphology, MOKE provided information about magnetic properties, thus making it possible to correlate the temperature-dependent evolution of morphology with that of UMA in the film. A clear anisotropy in the growth of Co film is found to result in strong UMA. Unlike previous studies, which typically observe a reduction in UMA strength with thermal annealing, the present work demonstrates a 31 % increase in UMA strength after annealing up to 200 °C, underscoring the importance of oblique angle deposition on nano-rippled substrates for achieving high UMA and ensuring its thermal stability up to moderate temperatures. The appearance of large UMA and its unusual temperature dependence is understood in terms of the shadowing effects and column coalescence, resulting in more robust shape anisotropy. This work provides insights into morphological anisotropy, elucidating the interplay of shadowing effects, shape anisotropy, and dipolar interactions within interacting column and ripple structures. This method gives rise to morphology-induced anisotropy, which can also be applied to other ferromagnetic films to enhance the magnetic anisotropy and ensure thermal stability.

The Relationships between Emission Geometry and Jitter Noise in Millisecond Pulsars

The relationships between several parameters of an emission geometry and jitter noise in 17 millisecond pulsars (MSPs) are investigated. By assuming the jitter noise is due only to a pulse variation in phase, the former can be modeled as changes in the plasma flow rate leading to variation in the measured pulse arrival time relative to the predicted time. In the model for pulsar magnetospheres with multiple emission states, the plasma flow is associated with the emission states, and a change in the emission state corresponds to a change in the plasma flow causing variation in the pulse arrival time. These can be specified in an emission geometry defined by the obliquity and viewing angles, measured from the rotation axis to the magnetic axis and to the line of sight, respectively. We calculate the maximum change in the emission state based on the reported jitter noise for each of the MSPs. Using the results, we show that the MSPs possess relatively large obliquity angles, which is consistent with observation, and the jitter noise exhibits dependency on frequency. We find that the jitter noise in our sample displays an exponential decay as a function that combines the obliquity angle and the rotation period, revealing the correlation among the three parameters. This suggests that the magnitude of the jitter noise is likely specific to an MSP. We discuss how jitter noise may be related to the evolution of an MSP.

Design of polarization convert metasurface element with high angle stability

This paper proposed a high angle stability polarization convert metasurface element. The element has one dielectric substrate with the bending lines on the top layer and metallic ground on the bottom layer. A method of priority optimize polarization conversion ratio(PCR) under oblique incident angle based on impedance analysis is proposed to realize high angle stability. And the proposed element can convert linear polarization to orthogonality polarization at 60° incident angle with 17.8% relative bandwidth with more resonances compared with normal incident. Both the PCR and bandwidth of the proposed element increase from 0° to 45° incident angle which different with traditional polarization convert elements. A metasurface with the high angle stability element is fabricated and the measured results are in good agreement with simulated results.

Research on Dynamic Pig Counting Method Based on Improved YOLOv7 Combined with DeepSORT.

A pig inventory is a crucial component of achieving precise and large-scale farming. In complex pigsty environments, due to pigs' stress reactions and frequent obstructions, it is challenging to count them accurately and automatically. This difficulty contrasts with most current deep learning studies, which rely on overhead views or static images for counting. This research proposes a video-based dynamic counting method, combining YOLOv7 with DeepSORT. By utilizing the YOLOv7 network structure and optimizing the second and third 3 × 3 convolution operations in the head network ELAN-W with PConv, the model reduces the computational demand and improves the inference speed without sacrificing accuracy. To ensure that the network acquires accurate position perception information at oblique angles and extracts rich semantic information, we introduce the coordinate attention (CA) mechanism before the three re-referentialization paths (REPConv) in the head network, enhancing robustness in complex scenarios. Experimental results show that, compared to the original model, the improved model increases the mAP by 3.24, 0.05, and 1.00 percentage points for oblique, overhead, and all pig counting datasets, respectively, while reducing the computational cost by 3.6 GFLOPS. The enhanced YOLOv7 outperforms YOLOv5, YOLOv4, YOLOv3, Faster RCNN, and SSD in target detection with mAP improvements of 2.07, 5.20, 2.16, 7.05, and 19.73 percentage points, respectively. In dynamic counting experiments, the improved YOLOv7 combined with DeepSORT was tested on videos with total pig counts of 144, 201, 285, and 295, yielding errors of -3, -3, -4, and -26, respectively, with an average accuracy of 96.58% and an FPS of 22. This demonstrates the model's capability of performing the real-time counting of pigs in various scenes, providing valuable data and references for automated pig counting research.

Clutch model for focal adhesions predicts reduced self-stabilization under oblique pulling

Cell-matrix adhesions connect the cytoskeleton to the extracellular environment and are essential for maintaining the integrity of tissue and whole organisms. Remarkably, cell adhesions can adapt their size and composition to an applied force such that their size and strength increases proportionally to the load. Mathematical models for the clutch-like force transmission at adhesions are frequently based on the assumption that mechanical load is applied tangentially to the adhesion plane. Recently, we suggested a molecular mechanism that can explain adhesion growth under load for planar cell adhesions. The mechanism is based on conformation changes of adhesion molecules that are dynamically exchanged with a reservoir. Tangential loading drives the occupation of some states out of equilibrium, which for thermodynamic reasons, leads to the association of further molecules with the cluster, which we refer to as self-stabilization. Here, we generalize this model to forces that pull at an oblique angle to the plane supporting the cell, and examine if this idealized model also predicts self-stabilization. We also allow for a variable distance between the parallel planes representing cytoskeletal F-actin and transmembrane integrins. Simulation results demonstrate that the binding mechanism and the geometry of the cluster have a strong influence on the response of adhesion clusters to force. For oblique angles smaller than about 40∘, we observe a growth of the adhesion site under force. However this self-stabilization is reduced as the angle between the force and substrate plane increases, with vanishing self-stabilization for normal pulling. Overall, these results highlight the fundamental difference between the assumption of pulling and shearing forces in commonly used models of cell adhesion.

Numerical investigation on the behaviour of concrete barriers subjected to vehicle impacts using modified K&C material model

Full-scale experimental crash tests are important to determine the occupant risk factors and understand barrier system behaviour in vehicle-barrier impacts. Due to the expensive and time-consuming nature of such crash tests, finite element simulations of full-scale crash tests to analyse and design road safety structures have gained popularity as a more practical method of assessment. In this research, a simplified simulation technique was employed by dividing the barrier system into two sections called the Impact Zone and the Rigid Zone, which was adopted for concrete crash barriers for the first time. A previously performed experimental crash test was used to successfully validate the numerical model. The numerical crash model accurately predicted the critical parameters of the barrier performance. The numerical simulation was further used to extract otherwise difficult or impossible results from the experimental crash test, such as internal energies and exit angles. The importance of the use of optimised Karagozian and Case concrete material parameters was demonstrated through a parametric study carried out with autogenerated parameters. A parametric study performed with impact speed and angle proved that increased speed is more harmful for occupants than a more oblique impact angle. The potential benefits of replacing traditional concrete with improved energy absorbing concrete to reduce occupant risks were also investigated. The comparison of results between the numerical models and experimental crash test confirms the trustworthiness of the developed models to simulate the vehicle-barrier crashes for analysing existing barrier designs and further developing new barrier designs to increase road safety.

Investigation on the Mechanical Characteristics of the Excavation of a Double-Line Highway Tunnel Underpass Existing Railway Tunnel under the Influence of Dynamic and Static Load

Research on the excavation mechanical properties of underpass tunnels has already had certain results, but only a few of them consider the effects of dynamic and static loads on the excavation mechanical properties of underground tunnels at the same time; particularly, there is a lack of research investigating double-line highway tunnels with angled underpasses of existing railway tunnels. In this paper, based on the tunnel project of the new double-line Shiqian Highway Tunnel passing under the Hurong Railway with an oblique angle, based on the method of over-advance geological prediction and investigations into the palm face surrounding the rock, the rock degradation caused by dynamic and static loads is quantified using the perturbation system. Additionally, the mechanical parameters of the rock under the influence of dynamic and static load coupling in the influence area of the cross-tunneling project are determined using the Hoek–Brown criterion, and the mechanical characteristics of the excavation of a tunnel under the double-lane highway tunnel passing under the existing railroad are constructed with the mechanical characteristics of the double-lane highway tunnel, taking into consideration the influence of the dynamic and static load coupling in a three-dimensional model. The results show that, in line with the new tunnel rock movement law for the top of the arch sinking, the bottom plate bulging, the side wall outward movement, the height and width of the arch, and the bottom plate arch show an increase with the tunnel excavation, while the side wall rock displacement effect is smaller; the left and right line tunnel disturbed area of the rule of change is similar; the existing tunnel bottom plate displacement is larger than the top plate and the left and right side wall, under the influence of the excavation time step. Typical profile point displacement is mainly determined by the distance from the excavation surface; von Mises stress extremes are observed in the top plate and side walls of the existing tunnel, which occur in the tunnel structure, and there are unloading and pressure-bearing zones in the bottom plate; the new tunnel has the same rock disturbance angle under the four calculation conditions and, based on the displacement control criterion, the excavation method is preferred and the upper and lower step blasting excavation method is recommended.

Trajectory prediction of rigid projectile for oblique penetration into multi-layer aluminum targets

Multi-layer targets and nonideal initial conditions significantly increase the complexity of penetration trajectory prediction. To address this issue, a general multi-layer target trajectory model was developed based on expanding spherical cavity in layered finite targets, comprising the wake separation and finite free-surface effects. The trajectory prediction model adopted the developed geometric description of the ogive- and conical-nosed projectiles, combined with the proposed transfer functions and plane motion equation. Experiments of the two types projectiles penetration into layered 2A12 aluminum targets were conducted, and the actual projectile trajectories in targets were obtained through the section scan method. The predicted trajectories aligned well with the experimental data within the application range. The layering effect considerably influences the projectile trajectories impacting at higher velocities and oblique angles. More layers reduce the resistance of the targets, increasing the penetration but reducing the angle deflection of the trajectory performance. Compared with the ogive projectile, the conical projectile exhibited a deeper penetration and improved anti-deflection capabilities. This preliminary study on penetration trajectory characteristics of multi-layer targets provides experimental and theoretical support for correcting penetration trajectories.

Preparation of a double-layer bionic bamboo structure absorber based on CB/PLA-TPU composites and its broadband microwave absorption characteristics

The study of the mechanical characteristics and microwave absorption capabilities of multifunctional composite materials in complex environments has attracted considerable interest in recent years. Inspired by the structure of bamboo in nature, a novel double-layer microwave absorber structure, a CB/PLA-TPU composite bionic bamboo joint’s structure, was conceived and manufactured for this investigation. This structure ingeniously integrates the load-bearing attributes of bamboo joints with the microwave absorption qualities of CB composites. At the material level, enhancing the CB particle content enhances the matrix's folds and defects, thereby improving its dielectric polarization loss capacity. An effective absorption bandwidth of 3.84 GHz was achieved, with a minimum reflection loss of −60.24 dB at a 2.58 mm thickness and a 9.2 GHz frequency. The bionic bamboo absorber's unit structure is meticulously engineered, with experimental simulations validating its performance. According to the findings, the structure attains a 10.03 GHz broadband absorption and a yield strength of 11.6 MPa. It maintains broadband absorption capabilities above 9 GHz even at oblique incidence angles for TM polar wave (0–60°) and TE polar wave (0–30°). The biomimetic design based on bamboo offers significant potential for engineering applications in stealth technology under adverse conditions.

Design, optimization, and comparative analysis of wide-band polarization conversion along with dual coding sequences for RCS reduction

In this paper, a wideband polarization conversion metasurface is designed. Additionally, coding and chessboard metasurfaces are specifically tailored for radar cross-section reduction (RCS). Initially, a compact unit cell demonstrating exceptional polarization conversion performance is introduced, achieving a polarization conversion ratio (PCR) exceeding 90%\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\%$$\\end{document} across frequencies ranging from 7.9 to 22.7 GHz. The PCR remains effective even when oblique incidence angles of up to 30∘\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^\\circ$$\\end{document} are utilized across this frequency band. Roger RT5880, with a thickness of 0.254 mm, serves as the substrate. An airgap is introduced between the substrate and the ground plane to enhance the polarization conversion bandwidth. This unit cell serves as the fundamental building block for subsequent metasurface configurations. To assess the scalability and effectiveness, a 36 ×\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ imes$$\\end{document} 36 unit array is assembled, confirming efficient polarization conversion capabilities extending to larger structures. Moreover, a 1-bit coding unit “0” and “1” are formed by the Pancharatnam-Berry phase based on the same-sized meta-atom with 90∘\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^\\circ$$\\end{document} orientations. The robustness and practicality of the design are demonstrated by creating 12 ×\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ imes$$\\end{document} 12 lattices and evaluating their RCS reduction potential under two distinct scenarios: a chessboard pattern and a coding-based scheme. Notably, its results indicate substantial RCS reduction across a broad frequency spectrum (7.9 to 22.7 GHz) for both configurations. This study demonstrates the wide-ranging applicability of metasurface design, making it a valuable contribution to the fields of microwave engineering, polarization control, and radar stealth technology. Owing to its simplicity, bandwidth, and versatility, this approach offers innovative solutions for diverse real-world applications.

Angle-corrected GPR hyperbolic fitting models for improved parameter estimation

Ground-penetrating radar (GPR) is commonly employed as a non-destructive technique for detecting subsurface cylindrical objects such as pipes, cables, rebars, and tree roots. Hyperbolic features generated in GPR radargrams are often used to estimate key parameters like burial depth, object radius, and electromagnetic wave velocity. However, traditional approaches frequently rely on the assumption that GPR traverses are perpendicular to the alignment of target—an assumption or a negligence that is not always valid in real-world scenarios. To address this limitation, a novel method is introduced for simultaneously estimating the orientation and burial depth of pipes, as well as wave velocity, from the hyperbolic patterns observed in GPR data. The method innovates by incorporating an angle correction index into the classical hyperbolic fitting model. This modified model is then formulated as an optimization problem, which is solved using a hybrid approach combining the Multi-Verse Optimizer (MVO) and Gradient Descent (GD) algorithms. A unique index, termed the “C-value,” is introduced to quantitatively analyse the influence of oblique angles on the hyperbolic fitting models. Two distinct fitting models are validated through both simulation and field experiments. The study also scrutinizes the impact of varying pipe radius and burial depth on the accuracy of parameter estimation at different pipe orientation. The methodology presented herein enables the simultaneous estimation of burial depth, wave velocity, and pipe orientation directly from hyperbolic fitting—a significant advancement, as orientation is typically assumed as a known input yet is often challenging to ascertain obtain in practical field situations.