Search Results (51)

Directional flying ad hoc networks (FANETs) equipped with phased array antennas are pivotal for applications demanding high-capacity, low-latency communications. While directional beamforming extends the communication range, it necessitates the intricate joint optimization of the beam direction, power, and time-slot scheduling under hardware constraints. Existing resource allocation schemes predominantly follow two paradigms: (i) conventional physical-layer multiple access (CPMA) approaches, which enforce strict orthogonality within each beam and thus limit spatial efficiency; and (ii) advanced physical-layer techniques like rate-splitting multiple access (RSMA), which have been applied to terrestrial and omnidirectional UAV networks but not systematically integrated with the beam-based scheduling constraints of directional FANETs. Consequently, jointly optimizing the beam direction, intra-beam rate-splitting-based node pairing, transmit power, and time-slot scheduling remains largely unexplored. To bridge this gap, this paper introduces an intra-beam rate-splitting-based resource allocation (IBRSRA) framework for directional FANETs. This paper formulates an optimization problem that jointly designs the beam direction, constrained rate-splitting (CRS)-based node pairing, power control, modulation and coding scheme (MCS) selection, and time-slot scheduling, aiming to minimize the total number of time slots required for data transmission. The resulting mixed-integer nonlinear programming (MINLP) problem is solved via a computationally efficient two-stage algorithm, combining greedy scheduling with successive convex approximation (SCA) for non-convex optimization. Simulation results demonstrate that the proposed IBRSRA algorithm substantially enhances spectral efficiency and reduces latency. Specifically, for a network with 16 nodes, IBRSRA reduces the required number of transmission time slots by more than 42% compared to the best-performing baseline scheme. This confirms the significant practical benefit of integrating CRS into the resource allocation design of directional FANETs. Full article

Multifunctional metasurfaces, capable of flexible electromagnetic wave manipulation, have become a focus of research for their high integration and utility. In particular, those operating simultaneously in transmission and reflection modes have attracted growing interest, as they integrate multiple functions within a single aperture, save physical space, and further expand wave control capabilities across full space. In this work, an inspiring strategy of transmission-reflection-integrated bifunctional metasurface by hybridizing geometric phase and propagation phase is proposed. The transmission and reflection modes can be independently and flexibly controlled in full space: the co-polarized reflection under left-handed circular polarization (LCP) incidence is governed by rotation-induced geometric phase modulation, while the co-polarized transmission under right-handed circular polarization (RCP) incidence is modulated through scaling-induced propagation phase modulation. Moreover, arbitrary amplitude modulation of the co-polarized transmission under RCP incidence can be realized by incorporating lumped resistors. As a proof of concept, a bifunctional meta-device is constructed, which can generate vortex beam carrying arbitrary topological charge for LCP reflected wave and achieve high-quality holographic imaging for RCP transmitted wave. Both the simulated and experimental results validate the feasibility of the proposed strategy, which significantly enhances the integration density of multifunctional metasurfaces while reducing inter-functional crosstalk, expanding its potential applications in electronic engineering. Moreover, it can also serve as a fundamental machine learning platform, facilitating multimodal fusion and cross-modal learning in radar signals and visual imaging. Full article

Traffic-induced vibrations from road and rail systems pose a significant threat to the structural integrity and operational safety of buildings, especially masonry structures located near planned infrastructure such as tunnels. This study investigates the dynamic impact of such vibrations on a representative early 20th-century masonry building situated within the influence zone of a design railway tunnel. A comprehensive analysis combining geological, structural, and vibration propagation data was conducted. A detailed 3D finite element model was developed in Diana FEA v10.7, incorporating building material properties, subsoil conditions, and anticipated train-induced excitations. Various vibration isolation strategies were evaluated, including the use of block supports and vibro-isolation mats. The model was calibrated using pre-construction measurements, and simulations were carried out in the linear-elastic range to prevent resident-related claims. Results showed that dynamic stresses in masonry walls and wooden floor beams remain well below critical thresholds, even in areas with stress concentration. Among the tested configurations, vibration mitigation systems significantly reduced the transmitted forces. This research highlights the effectiveness of integrated numerical modelling and vibration control solutions in protecting structures from traffic-induced vibrations and supports informed engineering decisions in tunnel design and urban development planning. Full article

The active pile underpinning technology when a tunnel passes under a bridge involves complex force conditions, making construction monitoring and control extremely challenging. However, there is a lack of research on the laws governing the stress and deformation responses of bridges during the construction process. This paper takes an active pile underpinning project of a metro line passing under a bridge as a case study. Design and construction plans are taken as the basis, and on-site monitoring data are incorporated. A three-dimensional finite element simulation model is established. This model is used to analyze the distribution and variation laws of stress and settlement during the pile underpinning process. The results show that: considering the traffic conditions of the bridge and the requirements for additional stress, it is reasonable to suggest that the actual settlement of the bridge deck should be 2–3 mm; the determination of the jacking force should generally be greater than the load transmitted from the pier column to the underpinning beam and less than 75% of the maximum bearing capacity, which is more reasonable. Full article

This paper presents a fully electronic, CMOS-compatible ultrasonic sensing system integrated into a 3D beamforming architecture for advanced automotive applications. The proposed system eliminates mechanical scanning by implementing a dual-path beamforming structure comprising programmable transmit (TX) and receive (RX) paths. The TX beamformer introduces per-element time delays derived from steering angles to control the direction of ultrasonic wave propagation, while the RX beamformer aligns echo signals for spatial focusing. Electrostatic actuation governs the CMOS-compatible ultrasonic transmission mechanism, whereas dynamic modulation under acoustic pressure forms the reception mechanism. The system architecture supports full horizontal and vertical angular coverage, leveraging delay-and-sum processing to achieve electronically steerable beams. The system enables low-power, compact, and high-resolution sensing modules by integrating signal generation, beam control, and delay logic within a CMOS framework. Theoretical modeling demonstrates its capability to support fine spatial resolution and fast response, making it suitable for integration into autonomous vehicle platforms and driver-assistance systems. Full article

The positioning accuracy of the end effector is the core index that affects the robot’s performance. However, to achieve lightweight and functional requirements, the construction of end effectors is becoming more complex. Lightweight design through slotting is becoming more common. This leads to the fact that the traditional mathematical model cannot accurately characterize the vibration of the end effector. This study proposed the multi-stepwise beam model. It employed the separation of variables and element transmitting method to obtain the mathematical model of the modal shape functions and the natural frequencies. Meanwhile, the vibration response of the end effector under fixed-end excitation was analyzed, and the conclusions were made through experimental research. The direct inverse controller was presented to achieve vibration suppression. The experimental results indicate that the amplitude suppression rate reaches 50%. The system’s equations of motion were solved numerically to analyze the exact relationships for the response and excitation of the beam considered. Full article

In order to implement multiple electromagnetic (EM) wave front control, a reconfigurable multifunctional metasurface (RMM) has been investigated in this paper. It can meet the requirements for 6G communication systems. Considering the full-space working modes simultaneously, both reflection and transmission modes, the flexible transmission-reflection-integrated RMM with p-i-n diodes and anisotropic structures is proposed. By introducing a 45°-inclined H-shaped AS and grating-like micro-structure, the polarization conversion of linear to circular polarization (LP-to-CP) is achieved with good angular stability, in the transmission mode from top to bottom. Meanwhile, reflection beam patterns can be tuned by switching four p-i-n diodes to achieve a 1-bit reflection phase, which are embedded in the bottom of unit cells. To demonstrate the multiple reconfigurable abilities of RMMs to regulate EM waves, the RMMs working in polarization conversion mode, transmitted mode, reflected mode, and transmission-reflection-integrated mode are designed and simulated. Furthermore, by encoding two proper reflection sequences with $13\times 13$ elements, reflection beam patterns with two beams and four beams can be achieved, respectively. The simulation results are consistent with the theoretical method. The suggested metasurface is helpful for radar and wireless communications because of its compact size, simple construction, angular stability, and multi-functionality. Full article

In the process of wireless energy transmission from a Space Solar Power Station (SSPS) to a satellite, the efficiency of energy transmission is closely related to the accuracy of beam control. The existing methods commonly ignore the impact of array position, structural deviation of the transmitting antenna, and modulation errors, which leads to the deviation error in actual energy transmission beams and the reduction of energy transmission efficiency. This paper innovatively proposes a high-precision bi-directional beam-pointing measurement method, which provides a technical basis for advancing the beam-pointing control accuracy from the perspective of improving the beam-pointing measurement accuracy. The method consists of (1) the interferometer goniometry method to realize high-precision guiding beam pointing measurement; and (2) the power field reconstruction method to realize offset angle measurement of the energy-transmitting beam. Simulation results demonstrate that under dynamic conditions, the guiding beam-pointing measurement accuracy of this method reaches 0.05°, which is better than the traditional 0.1° measurement accuracy based on the guiding beam. The measurement accuracy of the offset distance of the energy center is better than 0.11 m, and the measurement accuracy of the offset angle is better than 0.012°. Full article

In this work, we consider a point-to-point underwater optical wireless communication scenario where an underwater sensor (US) transmits its sensing data to a remotely operated vehicle (ROV). Before the US transmits its data to the ROV, the ROV performs simultaneous lightwave information and power transfer (SLIPT), delivering both control data and lightwave power to the US. Under the considered scenario, our objective is to maximize energy harvesting at the US while supporting predetermined communication performance between the two nodes. To achieve this objective, we develop a hierarchical deep Q-network (DQN)–deep deterministic policy gradient (DDPG)-based online algorithm. This algorithm involves two reinforcement learning agents: the ROV and US. The role of the ROV agent is to determine an optimal beam-divergence angle that maximizes the received optical signal power at the US while ensuring a seamless optical link. Meanwhile, the US agent, which is influenced by the decision of the ROV agent, is responsible for determining the time-switching and power-splitting ratios to maximize energy harvesting without compromising the required communication performance. Unlike existing studies that do not account for adaptive parameter control in underwater SLIPT, the proposed algorithm’s adaptive nature allows for the dynamic fine-tuning of optimization parameters in response to varying underwater environmental conditions and diverse user requirements. Full article

We proposed a novel fiber Mach–Zehnder interferometer (FMZI) that can perform an ultrahigh extinction ratio (ER), ultracompact, and ultra-broadband interference characteristics. The FMZI structure is based on an extremely tiny hollow core fiber (HCF) with a small diameter of 10 μm (named HCF₁₀) connected with a beam splitter of a large core of 50 μm HCF (named HCF₅₀). The refractive index (RI) of the air core is lower than that of the HCF cladding; a leaky-guided fiber waveguide (LGFW) occurs in such a short-section HCF₁₀ waveguide to simultaneously have the core and cladding modes. To achieve better fringe visibility of the interference, the section of HCF₅₀ assists in splitting the optical light into core and cladding beams launched into the HCF₁₀ with appropriate intensities. Experimental and simulation results show that the optical characteristics of the proposed LGFW-FMZI are very similar. Based on the results of the study, the length of the HCF₁₀ primarily influences the free spectral range (FSR) of the interference spectra, and the HCF₅₀ splitter significantly controls the optimal extinction ratio (ER) of the interference fringes. By exactly adjusting the lengths of HCF₁₀ and HCF₅₀, the proposed fiber interferometers can perform the capability of an ultrahigh ER over 50 dB with the arbitrary FSR in the transmitted interference spectra over an ultra-broad wavelength range of 1250 nm to 1650 nm. Full article

Aim: With modern dentistry advancements, children and parents have significantly raised aesthetic expectations in pediatric dentistry. Pediatric zirconia crowns (PZCs) provide a superior aesthetic appearance compared with stainless steel crowns (SSCs), making them a popular treatment option. However, a comparison of the compressive stresses caused by these crowns on the roots of primary teeth and alveolar bones has not been conducted. Materials and Methods: Cone beam computed tomography (CBCT) images of an eight-year-old female patient who experienced premature loss of a primary mandibular left second molar were obtained from a dental hospital database. Rhinoceros 4.0 software was used to process and simulate images. Under simulated chewing forces, stress on the PZC, SSC, and intact primary first molars as control groups, as well as their roots and alveolar bone structures, was assessed with finite element analysis. Statistical Analyses: Depending on whether the descriptive data were normally distributed, the Student t-test and Mann–Whitney U test were used. Quantitative variables differ between the two categories of qualitative variables. One-way ANOVA and Kruskal–Wallis H tests were used depending on standard distribution assumptions. p < 0.05 indicates statistical significance differences. Results: PZCs, SSCs, and cement layers were stressed according to von Mises values, while roots and alveolar bones were stressed according to maximum and minimum stress values. When assessing crowns, SSCs exhibited the highest von Mises stress values, followed by PZCs and control groups (p < 0.001). In the cement layer, SSCs obtained significantly higher values (p = 0.003). In the root area, minimum principal stress values are more critical. The highest values were obtained from the intact tooth, PZC, and SSC, respectively (p < 0.001). Alveolar bones did not differ significantly in minimum principal stress (p = 0.950). Conclusions: Restorative full-coverage crowns exhibited higher von Mises values than intact teeth, as per current research findings. The von Mises values were highest in SSC, while lowest in PZC. As a result of this condition, the cement layer and root areas had higher von Mises stress and compressive stress. Alveolar bones were not affected regardless of restoration type. PZC transmits higher stress due to its properties. Full article

Traditional methods for monitoring the foundation settlement of airport runways predominantly employ equipment such as leveling instruments, total stations, layered settlement instruments, magnetic ring settlement instruments, ground-penetrating radar (GPR), and synthetic aperture radar. These methods suffer from low automation levels, are time-consuming, labor-intensive, and can significantly disrupt airport operations. An alternative electromagnetic detection technique, Controlled Source Audio-Frequency Magnetotellurics (CSAMT), offers deep-depth detection capabilities. However, CSAMT faces significant challenges, particularly in generating high signal-to-noise ratio (SNR) signals in the far-field region (FfR). Traditional CSAMT utilizes grounded horizontal dipoles (GHDs), which radiate symmetric beams. Due to the low directivity of GHDs, only a small fraction of the radiated energy is effectively utilized in FfR observations. Enhancing the SNR in FfR typically requires either reducing the transceiving distance or increasing the transmitting power, both of which introduce substantial complications. This paper proposes an airborne-dangled monopole-antenna symmetric remote-sensing radiation source for airport runway monitoring, which replaces the conventional GHD. The analytical, simulation, and experimental verification results indicate that the energy required by the airborne-dangled symmetric source to generate the same electric field amplitude in the FfR is only one-third of that needed by traditional CSAMT. This results in significant energy savings and reduced emissions, underscoring the advantages of the airborne-dangled monopole-antenna symmetric source in enhancing energy efficiency for CSAMT. The theoretical analysis, simulations, and experimental results consistently verify the validity and efficacy of the proposed airborne-dangled monopole-antenna symmetric remote-sensing radiation source in CSAMT. This innovative approach holds substantial promise for airport runway monitoring, offering a more efficient and less intrusive solution compared to traditional methods. Full article

A one-dimensional active broadband phased array based on microwave photonics that works in the Ku band is proposed to achieve a large instantaneous bandwidth. The phased array uses a feeding network based on microwave photonics to provide the true time delay and a wide operating bandwidth. The array is mainly composed of a broadband horn antenna, an RF transmitting/receiving module, an optical network module, and a temperature control module. The form of a horn was selected for the antenna unit, and it was fed through a waveguide to obtain a wide operating bandwidth. An optical fiber delay line that could realize the true time delay at different frequencies was adopted for the time-delay module of the optical network. To obtain a large time delay and small quantization error, a hybrid time-delay diagram utilizing electrical and optical time delays was used in the design. In addition, a temperature control module was added to the antenna system to enhance the stability of the photonic time-delay module. For verification, a prototype of the presented antenna system was designed, fabricated, and measured. The experimental results showed that the optical phased array antenna was able to scan ±20° from 12 GHz to 17 GHz, and the beam pointing did not appear to be offset over the wide operating bandwidth. Full article

This paper presents a 5G new radio (NR) FR2 beamforming system with an integrated transceiver module. A real-time operating module providing enhanced flexibility and capability has been proposed. The integrated RF beamforming system with an integrated transceiver module can be operated in 8Tx-8Rx mode configuration simultaneously. A series-fed structure 8 × 7 microstrip antenna array for compact size and improved directivity is employed in the RF beamforming module. The RF beamforming module incorporates a custom 28 GHz, eight-channel fully differential beamforming IC (BFIC). An eight-channel BFIC in a phased-array beamforming system offers advantages in terms of increased antenna density and improved beam steering precision. The RF beamforming module is integrated with an RF transceiver module that enables the simultaneous up-conversion and down-conversion of the baseband signal. The RF transmitter module consists of a transmitter, a receiver, a signal generator, a power supply, and a control unit. The RF beamforming system can scan horizontally from −50° to +50° with a step of 10°. To achieve an optimized beam pattern, a calibration was conducted. The transmit and receive conversion gain of around 20 dB is achieved with the transceiver module. To verify the communication performance of the manufactured integrated RF beamforming system, a real-time wireless video transmission/reception test was performed at a frequency of 28 GHz, and the video file was transmitted smoothly in real time without interruption within a range of ±50°. Full article

Free-space optical (FSO) communication is a line-of-sight (LOS) communication technology that uses light, typically lasers, to transmit data through the atmosphere. FSO can provide high data transfer rates, but factors like weather conditions can affect its performance. Like fog, smog also degrades the availability and reliability of FSO links, as the particulate matter (PM) present in smog scatters the light beam, causing perceptible attenuation. In this paper, we have investigated the attenuation of an optical signal under laboratory-controlled smog conditions, using both theoretical and experimental approaches. A 6 m long acrylic chamber is used to contain artificial smog and measure the optical attenuation through it. The experimental result shows that smog attenuation is approximately 1.705 times more than fog attenuation. The findings of this study offer valuable insights into the effects of smog on optical links and can contribute to the development and optimization of these systems in regions with high levels of smog. Full article