Search Results (51)

Unmanned Aerial Vehicles (UAVs) are seeing increased use in agricultural settings due to their potential to be integrated with systems for applying pesticides. They can target specific areas while offering the potential to reduce chemical waste and improve application efficiency. However, this means that spray deposition efficiency is strongly influenced by rotor-induced downwash, which affects droplet transport, drift, and uniformity. This study presents a combined computational and experimental investigation of downwash–spray interactions in a hexacopter platform. CFD is used to predict the performance of various sprayer configurations that differ in the number, spacing, and positioning of nozzles. Rotor-induced airflow is modeled using an actuator disk approach in ANSYS Fluent 2025, and spray behavior is predicted using the Discrete Phase Model. Pure water was used as the working fluid for both the CFD simulations and experimental validation to ensure consistency between numerical and physical testing conditions. Numerical results indicate that a two-nozzle under-rotor setup maximizes performance characteristics such as deposition area, density, and uniformity for the designed agricultural UAV, providing a theoretically effective deposition area of 9.375 m², an effective application rate of 0.03387 mL/m², and a coefficient of variation of 45.3%. Compared to the best-performing boom configuration, this represents an approximately 13.5% improvement in spray uniformity. These results are validated through experimental testing using a modular UAV sprayer system and deposition measurements obtained from water-sensitive paper in controlled indoor conditions, achieving a droplet size of 502 µm, swath width of 1.8 m, 0.8% area coverage, and a coefficient of variation of 36.5%. While differences were observed between predicted and measured droplet size distributions, the CFD and experimental results demonstrated similar trends in spray coverage and deposition uniformity. Future work will refine simulations to better match experimental conditions and investigate canopy interaction, crosswind effects, and field-scale performance. Full article

This paper presents an optimization-based framework for active vibration control of rotor bearing systems using external surface-bonded piezoelectric patches. The rotor bearing system is modelled using the Finite Element Method (FEM), enabling the coupling between the shaft and the flexible piezoelectric actuators. A Linear Quadratic Regulator (LQR) is adopted to achieve optimal feedback control considering the balance between vibration reduction and control effort. The central contribution of this work is a comprehensive actuator placement optimization of the axial and angular position of the piezoelectric patches along the shaft. Firstly, axial positions are selected by maximizing a multimodal weighted Modal Strain Energy (MSE) criterion over a selected number of bending modes. In the second stage, which constitutes the main novelty of this work, the angular position of each pair of bonded piezoelectric patches is optimized. Each piezoelectric pair generates control moments at each extremity of the patch. The influence of the angular separation between independent piezoelectric pairs bonded at different axial locations is investigated through an iterative optimization framework. The optimized actuator placements are subsequently employed within an LQR-based active vibration control framework. The parameters of the controller are selected using a Genetic Algorithm (GA). Numerical simulations are performed on a bi-disk flexible rotor bearing system. The results of the numerical simulations demonstrate that the combined axial-circumferential optimization significantly enhances the controllability of the rotor system and improves the multimodal vibration suppression capability, achieving an improvement of approximately 93%. The proposed methodology offers a physically meaningful and computationally efficient framework, guaranteeing symmetric and effective vibration control. Full article

We perform three-dimensional general relativistic magnetohydrodynamic (GRMHD) simulations of a near-maximally spinning black hole (spin parameter $a=0.998$) with varying initial magnetic field geometries, systematically exploring the parameter space connecting magnetically arrested disk (MAD), intermediate (INT), and standard and normal evolution (SANE) accretion states. The magnetic flux threading the black hole horizon emerges as the fundamental state variable controlling jet efficiency, flow magnetization, and radiative output across all three states. We introduce complementary diagnostics—broadband spectral energy distributions spanning radio through hard X-ray frequencies and time-resolved X-ray light curves—that together connect simulation dynamics directly to multiwavelength observables. The radiative output follows a clear MAD > INT > SANE hierarchy in time-averaged luminosity, mean X-ray emission, as well as variability. Furthermore, MAD exhibits the highest fractional variability through quasi-periodic magnetic flux eruption events, and INT and SANE show moderate variability driven by episodic reconnection and stochastic MRI turbulence, respectively. Scaling to GRS 1915+105, Cyg X-1, and HLX-1, we demonstrate that all twelve temporal classes of GRS 1915+105 map naturally onto our three magnetic states, Cyg X-1’s persistent hard state is reproduced by a sustained INT configuration, and HLX-1’s extreme luminosities arise through efficient Blandford–Znajek extraction in MAD states scaled to higher black hole mass. Full article

Let $G\subset \mathbb{C}$ be a bounded simply connected domain with rectifiable Jordan boundary. Denote by $\varphi$ the conformal map of the exterior of G onto the exterior of the unit disk. For $R>1$, let ${\mathsf{\Gamma }}_R$ be the level curve defined by $\left|\varphi \left(z\right)\right|=R$, and let $G_R$ denote its interior, so that $G\subset G_R$. Suppose that f is analytic in $G_R$. In this paper, we investigate the maximal convergence properties of the Fourier series of f with respect to the Bergman orthogonal polynomials of G. By employing the strong asymptotics of Bergman polynomials outside the domain G of orthogonality, determined by the boundary properties of G, we obtain estimates for the maximal convergence rate of the partial sums of the Fourier series of f in the uniform norm on $\overline{G}$. These estimates are expressed in terms of the best polynomial approximation of f in the domain $G_R$ where f is analytic. Full article

The derivations presented in this paper suggest an intimate relationship between geometry and the electroweak sector at the Planck scale. A Lorentz-invariant maximally symmetric stochastically perturbed spacetime transformed to spherical coordinates reveals an emergent Schwarzschild metric, entirely a statistical structure of stochastic spacetime. Similarly, the transition from a maximally symmetric universe with a complex $SU\left(2\right)$ scalar doublet $\varphi$, comprising four independent real scalar fields with a zero vacuum expectation value (VEV), to spherical coordinates at the Planck scale reveals the spontaneously broken electroweak (EW) sector. Working in the unitarity gauge, the resulting EW potential can be simultaneously mapped in space at the Planck scale and across the EW sector. In space, the resulting EW potential includes a deep well within the Schwarzschild sphere and a shallow well just outside corresponding to an accretion disk. The same potential mapped in the EW space provides an entire family of possible sombrero hat potentials with fourth-order coupling specific to a point in space. At the minimum points of the potential in space, inside the Schwarzschild sphere and at the accretion disk, the $\lambda$ corresponding to the Standard Model (SM) fourth-order coupling is instead derived as $\frac{\lambda }{5}$. The factor of $\frac{1}{5}$ is a simple consequence of the conservation of the EW VEV and the fact that the SM formulation of the EW potential does not account for situations where the perturbations in $\varphi$ dominate. A more general formulation of the EW potential restores the SM quartic coupling and preserves $\lambda$ in space. An emergent Higgs field inside the Schwarzschild black hole is found to directly relate to the stochastic spacetime fields normalized by the Schwarzschild radius. The corresponding Higgs vacuum has both a ground and excited state and the possibility of both positive and negative vacuum entropy. Finally, the scalar-field VEV degeneracy in EW space of the metastable Higgs vacuum appears instead differentiated in space with possible probability, tunneling, and entropy implications. Full article

Motivated by the fact that the Fibonacci sequence is the simplest nontrivial second-order recurrence with a rational generating function, we develop a Fibonacci-weighted Hardy theory for bicomplex holomorphic functions. Starting from the coefficient norm ${\sum }_{n\ge 0}{\left|a_n\right|}^2/F_{n+1}$, we obtain a bicomplex Hilbert module whose reproducing kernel is governed by ${(1-t-t^2)}^{-1}$ and whose maximal disk of holomorphy is determined sharply by the nearest kernel singularity, giving the radius ${\rho }_F={\phi }^{-1/2}$ (the square-root inverse of the golden ratio $\phi$). The arithmetic recurrence makes several objects fully explicit: we derive closed formulas for the kernels through the idempotent decomposition of $\mathbb{BC}$, compute exact norms of the shift powers and a golden-ratio spectral radius, and package the local theory into a sheaf of Fibonacci-holomorphic germs that are compatible with the bicomplex idempotent splitting. We also treat $(p,q)$-Fibonacci weights, obtaining a one-parameter family of rational kernels ${(1-pt-q{t}^2)}^{-1}$ and corresponding operator bounds. In addition to providing a concrete bicomplex model within weighted Hardy theory, the resulting explicit kernels furnish benchmark examples for kernel-based interpolation and for the operator theory of unilateral weighted shifts. Full article

How ordered and mutually independent are semiflexible ring polymers (RPs) confined to a spherical cavity of variable radius? By varying the cavity radius, we systematically investigate the effect of the confinement size on the conformations of RPs using the coarse-grained molecular dynamics simulations. The results reveal that as the bending energy increases, the RPs exhibit a transition from a purely flexible coil to an elongated oblate-shaped object and, eventually, to a disk-like conformation. Simultaneously, the stacked aggregates composed of adjacent, mutually nearly parallel, semiflexible RPs emerge for stiffer chains. We find that the structural modulation of the stacked aggregates is regulated by the confinement size. For the conditions of strong confinement ($R<2R_g$, where $R_g$ is the radius of gyration of an RP), the semiflexible RPs undergo peculiar deformations and twisting that lead to disruption of the stacked aggregates. At $R\approx 2R_g$, the average number of the RPs per stack reaches a maximum. Concurrently, the order of spatial alignment of all semiflexible RPs is maximized with the global orientational-order parameter reaching the value $S\approx 0.79$. As the cavity radius further increases, at $R>3R_g$, the semiflexible RPs gain greater mobility resulting in diverse orientations of the aggregates being formed, with the order parameter dropping to $S\approx 0.05$. These findings provide important quantitative insights for future applications of the RPs, i.e., in micro- and nanodevice assembly. Full article

Background/Objectives: Recurrence of glioblastoma (GBM) mostly occurs in close vicinity to the resection cavity. Therefore, our group has previously designed an implant to locally apply repetitive photodynamic therapy to mitigate tumor recurrence. The penetration depths of different wavelengths in brain tissue were exhaustively studied before. However, the PDT-induced biological effects of 5-ALA-based PDT against GBM cells at different depths have not been evaluated yet. Methods: Therefore, a synthetic brain substitute material of 1–10 mm thickness and with optical properties comparable to the white or gray matter of pig brain was developed. Tumor cell viability was assessed in spheroids from six GBM cell lines using disks of varying thickness prepared from pig brain substitute material to mimic in vivo radiation attenuation. Results: Using an artificial brain tissue optical model based on material science, we have established a relationship between the PDT-induced effect of our PDT implant and the distance of migrating GBM cells from the resection cavity wall. Conclusions: This model may be helpful to aid optimization of the irradiation doses and fractionation required to attain the maximal therapeutic effect by long-term PDT applications. Full article

This study proposes a novel expandable spinal cage to maximize the effectiveness of spinal fusion surgery in the treatment of lumbar disk disorders and aims to verify its mechanical stability through finite element method (FEM) analysis and mechanical testing. To address the limitations of existing cages, which do not provide sufficient height and angle expansion and have constraints in independently adjusting height and angle with continuous fine-tuning, this study introduces a new linkage mechanism. This design enables precise spinal alignment restoration tailored to the individual anatomical characteristics of patients, even in minimally invasive surgical environments, distinguishing itself from traditional rack-and-pinion or wedge-based designs. The results of FEM analysis and static load testing demonstrated a high correlation between the predicted yield locations in FEM analysis and actual test results. Furthermore, the compression and compression–shear load tests confirmed that the proposed cage achieved an ultimate load exceeding the lowest fifth percentile of FDA-approved products, meeting clinical requirements. The proposed expandable spinal cage offers significant improvements over existing products and has the potential to evolve into a safer and more effective spinal fusion device through further dynamic fatigue testing and clinical studies to assess long-term durability and practical applicability. Full article

Background/Objectives: One common musculoskeletal disorder seriously compromising quality of life and burdening healthcare systems is lumbar disk herniation (LDH). LDH affects quality of life, healthcare costs, and occupational productivity, and it is expected to affect 40% of the population, mostly between 30 and 50 years of age. Methods: Over three years, this research assessed treatment results and the effect of comorbidities in a sample of 3074 individuals. Results: Surgical treatments—especially microdiscectomy—have a high success rate; over 90% of patients said their pain and functioning six months after surgery had improved significantly. Comparatively, conservative treatment approaches—physical therapy and epidural steroid injections—showed about 60% success in 70% of patients, indicating a clear need for early surgical assessment since 25% of originally conservatively managed patients needed surgery within one year. Significantly affecting treatment success are demographic variables; patients with preoperative Oswestry Disability Index (ODI) scores above 50 saw a 40-point improvement post-surgery compared to a 20-point gain for those following conservative therapy. High comorbidity rates—including obesity (mean of 148.33) and cardiovascular illnesses (mean of 530.33)—that are associated with extended recovery durations and complications were also seen in this research. Conclusions: Our results support a customized treatment plan, stressing the need of integrating thorough rehabilitation plans with prompt surgical interventions to maximize patient outcomes. This study emphasizes the need for a patient-centered treatment paradigm in controlling LDH, thereby trying to improve recovery and lower the healthcare load. Full article

Maps of road layouts play an essential role in autonomous driving, and it is often advantageous to represent them in a compact form, using a sparse set of surveyed points of the lane boundaries. While lane centerlines are valuable references in the prediction and planning of trajectories, most centerline extraction methods only achieve satisfactory accuracy with high computational cost and limited performance in sparsely described scenarios. This paper explores the problem of centerline extraction based on a sparse set of border points, evaluating the performance of different approaches on both a self-created and a public dataset, and proposing a novel method to extract the lane centerline by searching and linking the internal maximal circles along the lane. Compared with other centerline extraction methods producing similar numbers of center points, the proposed approach is significantly more accurate: in our experiments, based on a self-created dataset of road layouts, it achieves a max deviation below 0.15 m and an overall RMSE less than 0.01 m, against the respective values of 1.7 m and 0.35 m for a popular approach based on Voronoi tessellation, and 1 m and 0.25 m for an alternative approach based on distance transform. Full article

This study presents an experimental and computational analysis of the specific draft (SD) and specific torque (ST) requirements of an energy-efficient tillage implement, the active–passive disk harrow (APDH). Soil bin trials were conducted to develop multiple regression models predicting SD and ST based on operational parameters such as gang angle (α), speed ratio (u/v), soil cone index, and working depth. Model’s accuracy was assessed through statistical indices such as R², RMSE, MIE, and MAE. The high R² and low RMSE confirmed the reliability of the developed models in capturing the relationships between input and output variables. A genetic algorithm-based multi-objective optimization was implemented in MATLAB R2016a to determine optimal operational settings that minimize total power consumption while maximizing soil pulverization. The optimized values of α and u/v were determined to be in the ranges of 35.91° to 36.98° and 3.27 to 3.87, respectively. Model validation with laboratory and field data demonstrated acceptable prediction accuracy despite minor deviations attributed to soil variability and measurement errors. The developed models provide a predictive framework for optimizing tillage performance, aiding in tractor-implement selection, and enhancing energy efficiency in agricultural operations. Full article

The windage loss in impeller back gap and labyrinth seal cavities significantly impacts the aerodynamic performances of supercritical carbon dioxide (sCO₂) compressors. To accurately calculate windage loss, essential factors affecting the skin friction coefficients C_f,d (disk-type gap) and C_f,s (shaft-type gap), including Reynolds number Re, pressure ratio π, and radius ratio η, are investigated in this paper. The flow characteristics of the gap are analyzed and prediction models are proposed. The results indicate that both C_f,d and C_f,s decrease with increasing Re and grow with π and η, attributable to expanded high-vorticity regions caused by enhanced flow instability and larger vortices. The leakage flow rate m is unchanged for Re < 10⁶ since the fluid can flow into the impeller back gap, and slightly decreases for Re ≥ 10⁶ due to the centrifugal force and the inhibition effect of the vortices filling inlet regions. Moreover, the m grows with π and η due to a larger pressure difference and through-flow area. Maximal relative deviations of 6.23% and 6.83% can satisfy the requirements for calculating accurate windage loss in the impeller back gap and labyrinth seal cavities, which help the primary design of sCO₂ compressors. Full article

For a given starlike function $F_{\alpha }={\displaystyle \frac{z}{1-\alpha z^2}}, \alpha \in [-1,1]$, the class ${\mathcal{C}}_0\left(F_{\alpha }\right)$ is defined as follows: an analytic normalized function f belongs to ${\mathcal{C}}_0\left(F_{\alpha }\right)$ if it satisfies $\mathrm{Re}{\displaystyle \frac{z{f}^{\prime }\left(z\right)}{F_{\alpha }\left(z\right)}}>0$ in the open unit disk $∆$. The condition defining this class can be rewritten in the following equivalent form $\mathrm{Re}\left\{(1-\alpha z^2)f^{\prime }\left(z\right)\right\}>0, z\in ∆$. The family ${\mathcal{C}}_0\left(F_{\alpha }\right)$ is a subclass of the class of close-to-convex functions. The main aim of this paper is to maximize the modulus of a functional which is a linear combination with coefficients symmetric with respect to zero and is defined on the subfamily of ${\mathcal{C}}_0\left(F_{\alpha }\right)$ of functions with a fixed second coefficient in its Taylor series expansion. Full article

This study develops the heliostat curve tracing parametric model (HCTPM) to predict solar energy distribution in concentrated solar power (CSP) systems with sun-tracking capabilities. HCTPM uses curve tracing techniques to visualize flux distribution on mirrors and receivers, producing results that align closely with established models like HFLCAL, which use Gaussian and Tonatiuh ray-tracing methods. Simulations revealed that deviations in energy distribution increase as Sun shape error decreases, with greater impact on flux density and sensitivity. Variations in Sun disk radius caused notable deviations, especially in elliptical projections. The model’s flexibility in adjusting mirror shapes and sizes allows for the evaluation of spill losses, optimizing mirror designs for different positions. Spill loss analysis showed that larger mirrors reduce spill loss on mirrors but increase it on receivers, particularly when mirrors deviate from the north. Although total spill loss decreases with larger mirrors, this effect weakens as receiver spill loss grows. These findings emphasize the importance of optimizing mirror and receiver design to maximize energy efficiency and minimize resource waste, contributing to more sustainable solar energy systems. The HCTPM model plays a crucial role in improving the sustainability of CSP systems by optimizing configurations based on Sun disk characteristics, reducing energy losses, and promoting efficient resource use. Full article