Search Results (7,456)

Courses in electromagnetism and related technical subjects are often dominated by lecture-heavy instruction and complex mathematical concepts, which can make it difficult for students to stay engaged. This is particularly problematic in today’s hyper-digitalized society, where constant screen exposure and shortened attention spans challenge traditional learning methods. While computer-based tools and hands-on laboratories offer some pedagogical improvements, they often fall short in terms of interactivity, dynamism, adaptiveness, and student engagement. In an effort to enrich the learning experience and boost student motivation, we have created a gamified learning activity for the undergraduate course “Radiocommunications”—commonly referred to as Antennas and Propagation in other institutions— implemented in the form of a question-based board game. The activity, carried out over three academic years, is fully aligned with the course syllabus and encourages active learning, healthy competition, and collaborative problem-solving. Custom-made materials—including a game board, 270 question cards, wildcards, and incentive-based rewards—were developed specifically for this purpose. The qualitative results from a student survey, together with statistical evidence from hypothesis testing, suggest that the activity enhances conceptual understanding, helps students connect ideas across related subjects, and contributes to a more motivating and enjoyable learning experience. Full article

Studies related to the mechanization of coffee transplanting combined with precision agriculture techniques demonstrate a need to verify the quality of the operation to optimize future production processes in the field and reduce costs. The objective of this study was to analyze the operational costs arising from a semi-mechanized coffee transplanting process using an autopilot. The study was conducted on a rural property in the municipality of Santo Antônio do Amparo—MG—where 7458 coffee seedlings were transplanted using a planting platform pulled by a tractor equipped with an autopilot and a GNSS antenna, over a period of 4 days. The date and time data of the operation, recorded every second by the autopilot, were collected and recorded in spreadsheets to assist in calculating operational costs. Two semi-mechanized transplanting scenarios were compared: one using autopilot and the other using conventional semi-mechanized transplanting. The results indicated that the hourly cost of operation with autopilot was US$2130.42 h⁻¹, while the conventional system presented US$326.03 h⁻¹. The effective operational cost was US$3975.61 ha⁻¹ for the system with autopilot and US$442.31 ha⁻¹ for the conventional system in 2020. After monetary updating to 2025, the operational costs increased to US$1845.19 ha⁻¹ and US$116.28 ha⁻¹, respectively. The investment analysis indicated an Internal Rate of Return of 89.7%, highlighting the potential return on investment in the study. Therefore, it was emphasized that even with a high investment cost, the application of autopilot is viable for improving tractor steering during operation and ensuring uniformity in the positioning of coffee seedlings. Full article

This work proposes a polarization-insensitive scalable wide-angle metasurface array for highly efficient ambient energy harvesting in the 5.8 GHz Wi-Fi band. Inspired by dipole antenna principles, we design an asymmetric planar orthogonal dipole-based metasurface featuring monolithic integration of Schottky diodes (HSMS-2860) at unit cell feed gaps. This novel direct-impedance-matching strategy eliminates conventional matching networks, reducing energy conversion losses while enabling 99% radiation-to-AC efficiency across all polarization angles at 5.8 GHz. The coplanar architecture interconnects metasurface unit cells via inductors, simultaneously establishing low-loss DC channels and suppressing RF leakage. Fabricated as a 5 × 5 array, the prototype achieves 77.9% peak RF-to-DC efficiency with polarization insensitivity at an incident power of 25 dBm. Furthermore, with incident powers of 15 dBm and 20 dBm, the proposed metasurface array attained RF-to-DC conversion efficiencies exceeding 40% and 60%, respectively. This result indicates that the array is capable of achieving high energy harvesting efficiency across a broad power range. This scalable, drill-free, and polarization-insensitive design demonstrates strong potential for harvesting ambient RF energy in real-world multipath environments. Full article

This paper proposes a generalized high-order linear active disturbance rejection control (GHO-LADRC) method to suppress non-stationary disturbances in VICTS antenna direct-drive motors during high-dynamic scanning. First, a fourth-order generalized extended state observer is constructed, in which the derivative of the total disturbance is explicitly modeled as an extended state. This configuration enables real-time observation of the disturbance rate of change and suppresses the phase lag inherent in traditional ADRC during rapid disturbance variations through disturbance feedforward compensation. Secondly, drawing on singular perturbation theory and the motor’s dual-time-scale characteristics, this work precisely decouples and explicitly extracts the nonlinear friction and electromagnetic damping terms during the modeling stage. By integrating the extracted electromagnetic damping terms and the disturbance variation rate, an improved model-assisted control law is formulated, enabling active compensation for intense dynamic interference. Theoretical analysis and experimental results demonstrate that the proposed method significantly enhances disturbance rejection capability and satellite communication accuracy. As the first application of GHO-LADRC in the field of direct-drive VICTS antenna control, this work validates its effectiveness in improving system robustness within complex dynamic environments. Full article

This study aims to evaluate the potential of Global Navigation Satellite System Interferometric Reflectometry (GNSS-IR) based on signal-to-noise ratio (SNR) analysis for monitoring crop structure and moisture. Data were collected using a GNSS antenna placed within an experimental meadow located in NW Italy. GNSS-IR exploits the interference between direct and ground-reflected signals to derive physical parameters such as the vegetation phase center height and soil moisture. In this work, by analyzing and modeling the oscillations in SNR time series, the sensitivity to crop growth dynamics was assessed. Vegetation height and dielectric parameters were compared against corresponding ground-surveyed values collected using a ruler and buried soil moisture sensors. Results suggest that GNSS-IR can detect canopy height with a high degree of consistency (Pearson’s r = 0.89, MAPE = 18%). Results also show that changes in the amplitude and phase of the interference pattern are sensitive to biomass density and dielectric properties of the reflecting surface (r = −0.81 and r = 0.86 respectively). GNSS-IR observables were analyzed across four representative measurement campaigns capturing distinct seasonal stages of meadow development. Despite the limited temporal sampling (n = 4), the selected observations correspond to contrasting vegetation and soil moisture conditions, allowing the identification of systematic variations in crop biophysical properties. These findings open promising perspectives for the development of innovative monitoring strategies in precision agriculture, leveraging existing GNSS infrastructure to obtain key biophysical parameters with minimal additional equipment and operational complexity. Full article

The design of stretchable energy harvesting systems entails complex multiphysics coupling between electromagnetic and mechanical domains, typically requiring engineers to proficiently use disparate simulation tools and optimization algorithms. This steep learning curve, combined with the absence of integrated workflows, poses a substantial obstacle to efficient design. To overcome these challenges, we present StretchCopilot, a multi-agent collaborative framework driven by Large Language Models (LLMs) for the generative design of stretchable radio frequency (RF) energy harvesters operating in the 2.45 GHz band. In contrast to conventional approaches dependent on manual iteration or isolated algorithmic methods, our framework utilizes a graph-based state machine architecture (LangGraph) to coordinate specialized agents. It interprets high-level user instructions, such as “design a robust energy harvester capable of withstanding 15% strain”, and autonomously manages domain-specific solvers, including inverse design networks and rectifier circuit synthesis tools, through a unified interface. Experimental evaluations indicate that the framework effectively streamlines the design workflow, allowing users to produce desired rectenna (rectifying antenna) systems via natural language interactions. Case studies confirm that, once the underlying surrogate models are fully trained, the proposed approach compresses the marginal design time from several hours to within minutes, while ensuring consistent energy harvesting performance under mechanical deformation. Full article

Rhoptroceros cyatheae (Hymenoptera: Selandriidae) is a dominant herbivorous pest of Alsophila spinulosa in southwestern China, including Guizhou and Sichuan provinces. Infestation by this pest impairs spore reproduction of A. spinulosa and reduces the photosynthetic capacity of host plants. However, the chemosensory genes of R. cyatheae have not been reported, and the molecular basis of antennal detection of host volatile organic compounds (VOCs) is poorly understood. This study aims to screen and identify bioactive VOCs potentially involved in host searching behavior of R. cyatheae, analyze antennal VOC detection patterns, and explore the in vitro binding characteristics of an odorant-binding protein (OBP) involved in olfactory recognition, thereby providing a preliminary theoretical basis for the green management of R. cyatheae. Dynamic headspace sampling, gas chromatography-mass spectrometry (GC-MS), and gas chromatography-electroantennography (GC-EAD) were used to measure antennal electrophysiological responses of R. cyatheae to volatiles from its host A. spinulosa. Y-tube olfactometer assays were conducted to evaluate behavioral responses. For RcyaOBP7, fluorescence competitive binding assays, structural modeling, and molecular docking were integrated to investigate its in vitro binding characteristics with nine selected bioactive VOCs. Nine A. spinulosa volatiles were identified that elicited antennal electrophysiological responses in R. cyatheae, and the sawfly showed behavioral orientation to these VOCs, confirming that its antennae can detect host VOCs. In vitro binding assays showed that RcyaOBP7 exhibited strong binding affinity to p-ethylacetophenone, suggesting its potential involvement in antennal olfactory recognition of this volatile. Specific VOCs released by A. spinulosa are among the signaling molecules detected by the antennae of R. cyatheae. In vitro findings indicate that RcyaOBP7 binds specifically to p-ethylacetophenone, suggesting a possible role in antennal olfactory recognition and behaviors such as host location. However, in vivo functional validation and field trials under ecologically relevant conditions are needed to confirm these roles. This study characterizes the in vitro binding properties of RcyaOBP7 and provides a basis for further research on green management strategies for R. cyatheae based on antennal olfactory signals. Full article

Many authors consider modified SIQR (susceptible, infected, isolated (quarantined), and recovered individuals) models for childhood diseases. In this paper, we examine a modified differential system with N free parameters that may be of interest to epidemiology experts. We pay special attention to the Melnikov function, which corresponds to the proposed new model. We create the Melnikov equation ($M\left(t\right)=0$) and analyze all of its roots using a specially designed software program. This gives the researcher the chance to accurately comprehend and articulate the classical Melnikov criterion for the potential appearance of chaos in the dynamical system. Additionally, we present a few specific modules for examining the new model’s dynamics. Additionally covered is a potential use of the Melnikov function that corresponds to the differential model under consideration, with particular potential in the modeling and synthesis of antenna diagrams. Last but not least, we consider the proposed generalization from a stochastic point of view. Full article

Reliable and fast radiation pattern prediction is critical for large-scale tightly coupled linear antenna arrays. Strong mutual coupling and finite-array edge effects limit the accuracy of conventional array factor methods, while full-wave simulations become computationally prohibitive for large arrays. To address this issue, a fast and efficient radiation pattern prediction method (FERPP) is proposed. For central elements, the far-field response is obtained from a calibrated reference array and extended through position-dependent phase compensation. For edge elements, responses are extracted from independent local full-wave simulations. All element responses are assembled into a global far-field response matrix, enabling direct radiation pattern synthesis using the extended method of maximum power transmission efficiency. Simulation results obtained with a 1024-element linear microstrip patch antenna array operating at 3.5 GHz, with small inter-element spacing, demonstrate close agreement with full-wave simulations. For a broadside single-beam case, the predicted peak gain is 29.10 dBi, compared with 29.02 dBi from full-wave simulation. For a scanned beam at 30°, the predicted peak gain is 28.22 dBi, while the full-wave result is 28.99 dBi. For an equal-weight three-beam configuration at −30°, 0°, and 30°, the proposed method yields a peak gain of 23.87 dBi, compared with 24.21 dBi from full-wave simulation. In terms of computational efficiency, the proposed method requires only about 1.8% of the computational time required for a full-wave simulation. These results demonstrate that the proposed FERPP method provides a practical and efficient solution for radiation pattern prediction and beamforming analysis of large-scale tightly coupled linear antenna arrays. Full article

The purpose of this research is to determine which factors contribute to extending the read range of transponders equipped with different coupling-circuit topologies operating within selected RFID frequency bands. The analysis covered transponders that varied in both the configuration of their coupling circuits and their geometric dimensions. To accomplish this, transponder models were created using the EMCoS Studio electromagnetic simulation environment. Each model was subjected to simulations that yielded the mutual inductance and the voltage induced at the chip terminals. This study examines how the impedance of the embroidered antenna, the impedance of the chip’s coupling circuit, and the magnetic flux density affect the resulting chip voltage. In several of the investigated configurations, the peak chip voltage appeared outside the frequency range normally associated with RFID systems. The frequency at which this maximum occurred was dependent on the mutual inductance value. Understanding how individual parameters influence mutual inductance makes it possible to shift the voltage peak into a target operating band. Numerical simulation results, combined with the transponder’s mathematical model, enabled the calculation of the mutual inductance and the terminal voltage—quantities that directly determine the achievable read range. This study focuses on factors such as the resonant frequencies of the antenna and coupling circuit, their impedances, and the characteristics of the magnetic field. The findings show that tuning these parameters can affect not only the location of the voltage maximum, but also its amplitude. This effect introduces additional complexity in designing and selecting suitable transponder configurations. Full article

This work introduces a wideband four-element multiple-input multiple-output (MIMO) antenna system with four rectangular patches arranged in a sequentially rotated configuration. Wideband frequency operation is realized by exploiting the TM₁₀, TM₀₁ and TM_11δ modes through the utilization of a slot and metallized vias in the patch design. Another group of metallized vias are used to control coupling between the antenna elements, achieving an isolation level of over 17 dB. A prototype is fabricated and measured, demonstrating −6 dB impedance bandwidth ranging from 4.23 GHz to 5.96 GHz, enabling coverage of the N79 (4.4–5 GHz), V2X (5.905–5.925 GHz) and Wi-Fi 5/6 (5.150–5.850 GHz) frequency bands. The MIMO antenna features an efficiency of over 45% and a low envelope correlation coefficient (ECC) lower than 0.25. Owing to its broad bandwidth, compact geometry, and good isolation, the proposed MIMO antenna provides an efficient and practical solution for 5G MIMO applications integrated within mobile terminal back covers. Full article

Nymphaea candida Presl is a rare and endangered waterlily species, and cultivating robust seedlings suitable for artificial propagation has become a critical issue for the conservation of this species. In this study, Aspergillus sp., an endophytic fungus isolated from the roots of N. candida, showed the capability of solubilizing phosphate and potassium and producing siderophores. The application of Aspergillus sp. significantly increased leaf length, leaf width, leaf number, and root length of N. candida seedlings by 97.83%, 131.37%, 94.12%, and 171.25%, respectively. Meanwhile, Aspergillus sp. application significantly enhanced soil organic matter content, alkali-hydrolyzable nitrogen content, sucrase activity, and peroxidase activity by 6.57%, 31.62%, 23.26%, and 7.53%, respectively. Moreover, Aspergillus sp. enriched beneficial microorganisms including Cyanobium, Aquicella, and Cryptomycota to form a more stable rhizosphere soil microenvironment. Additionally, Aspergillus sp. upregulated genes involved in photosynthesis and photosynthesis–antenna protein pathways in N. candida leaves, with the expression levels of psbA, petG, and psbH significantly increasing by 2.17, 4.48, and 0.28-fold, respectively. Therefore, the endophytic fungus Aspergillus sp. might be a reliable tool for the propagation of N. candida seedlings, which would be helpful for the conservation of this rare and endangered aquatic plant species. Full article

In this paper, a multi-feed transmitarray with high-gain, wide-angle beam-scanning, and low-cost features is presented. A novel hybrid phase distribution (HPD) method is proposed to improve the beam-scanning range by combining the single-focal and bifocal principles according to the actual feed illumination area. By using the proposed method, the phase distribution of the transmitarray for different scanning angles can be obtained more accurately, thereby reducing the phase error between the actual and ideal phase distributions. To construct the transmitarray, a three-layer polarization conversion unit cell, consisting of two orthogonal polarizers in the outermost layers and a polarization rotating patch in the middle layer, is designed to provide high-efficiency transmission and full 360° phase coverage. Based on the HPD method, a single-polarized transmitarray antenna with a focal diameter ratio of 0.28 is designed and simulated. The simulated results show that the enhancement of the beam-scanning range is successfully realized. This design can perform a discrete ±60° beam-scanning range with a peak gain of 24 dBi. The gain losses of 0.7 dB at ±30° and 4.7 dB at ±60° are achieved. The cross-polarization levels are about 44 dB and 35 dB at 0° and −60° scanning angles, indicating low cross-polarization of the proposed solution. A five-beam prototype is fabricated and measured for experimental verification purposes. The measured results demonstrate good consistency with the simulations in the main lobe, with slight deviations due to practical fabrication and measurement constraints. The proposed design has advantages such as low-cost, wide beam-scanning angle, high-gain, low-profile and easy fabrication. Full article

Continuous introduction of advanced optimization algorithms promotes the development of electromagnetic (EM) technology in radar and communication systems. Wideband antenna design within a given space and wideband array pattern synthesis, especially in the scenario of strong mutual coupling, are two typical challenging electromagnetic problems. In this paper, a nature-inspired algorithm, i.e., the water cycle algorithm (WCA), is introduced to resolve the above two EM problems. Two typical wideband antennas, i.e., the dual-band E-shaped microstrip antenna and the typical magnetoelectric (ME) dipole antenna, are designed on the basis of the established WCA-based antenna design scheme. Compared with the well-known algorithms that have been introduced in antenna design, including the differential evolution (DE) algorithm and the gray wolf optimizer (GWO), better results can be achieved with WCA. In the sequel, a WCA-based low peak sidelobe level (PSLL) pattern synthesis is implemented based on a uniformly spaced 27-element folded fractal ME dipole array antenna with mutual coupling as high as −10 dB, the results of which further validate the superiority of WCA in array pattern synthesis and demonstrate the value of this application innovation. Full article

Background/Objectives: Accurate intraoperative tumour localisation remains challenging in minimally invasive colorectal surgery, where conventional tattooing methods suffer from marker migration, tissue diffusion, and potential allergic reactions. Radio frequency identification (RFID) technology offers a promising alternative through implantable passive transponders detectable via electromagnetic coupling, eliminating ionising radiation exposure. Methods: This preclinical feasibility study evaluated three RFID frequency bands for surgical tumour marking: 134 kHz (low frequency, LF), 13.56 MHz (high frequency, HF), and 868 MHz (ultra-high frequency, UHF). Finite element electromagnetic simulations characterised antenna field distributions, while experimental validation employed glass-encapsulated transponders in air and tissue-simulating saline (0.9% NaCl, σ ≈ 1.5 S/m). Detection ranges were measured across 28 angular configurations with expanded measurement uncertainty (k = 2) ranging from ±0.9 to ±3.2 mm. Results: Maximum detection distances in air were 25.0 ± 0.9 mm (LF), 23.0 ± 1.1 mm (HF), and 68.0 ± 2.3 mm (UHF). In saline, ranges decreased to 22.5 ± 1.0 mm, 20.7 ± 1.2 mm, and 18.0 ± 1.4 mm, respectively, demonstrating tissue attenuation of 10% at LF/HF vs. 74% at UHF. Angular characterisation revealed 64–70% range reduction at orthogonal orientation for LF/HF systems. Computational–experimental correlation yielded r² = 0.975 across 154 paired observations. Conclusions: The 13.56 MHz HF band emerges as the optimal candidate for clinical translation, offering adequate tissue penetration (20.7 mm), superior antenna miniaturisation potential (5 mm diameter), established biocompatibility pathways, and mature near-field communication ecosystem support. Future development should address angular sensitivity through multi-axis antenna configurations and validation in anatomically realistic tissue phantoms. This study establishes the electromagnetic evidence base for clinical system development; translation to clinical practice requires sequential preclinical and clinical evaluation. Full article