Search Results (2,458)

This paper investigates the channel performance through a high-gain, circularly polarized microstrip patch antenna that is developed for contemporary wireless communication systems. The proposed antenna creates two orthogonal modes for circular propagation with slightly varying resonance frequencies by using a cross line and truncations to circulate surface currents. Compactness, reduced surface wave losses, and enhanced impedance bandwidth are made possible by the coaxial probe feed, periodic electromagnetic gap (EBG) slots, and fractal patch geometry. For in-phase reflection and beam focusing, a specially designed single-layer metasurface (MTS) reflector with an 11 × 11 circular aperture array is placed 20 mm behind the antenna. A log-normal shadowing model was used to test the antenna in real-world scenarios, and the results showed a strong correlation between the model predictions and actual data. At up to 250 m, the polarization-agile, high-gain antenna demonstrated reliable performance across a variety of channel conditions, enabling accurate characterization of the Channel Quality Indicator (CQI), Signal-to-Noise Ratio (SNR), and Reference Signal Received Power (RSRP). By combining cutting-edge antenna architecture with an empirical channel performance study, this research presents a compact, affordable, and fabrication-friendly solution for increased wireless coverage and efficiency. Full article

This study investigates the structural behavior of composite double-web steel beams filled with different types of concrete made from a combination of recycled concrete aggregates and normal aggregates. The research includes both experimental and numerical analyses. Seven specimens were tested under symmetrical two-point loading, all having identical geometric properties: a span length of 1100 mm, flange plates 120 mm wide and 6 mm thick, and web plates 3 mm thick and 188 mm deep. The specimens were divided into two groups, with a control beam without concrete infill. Group one included beams filled with normal concrete in different locations (middle region, two sides, and fully filled), while group two mirrored the same fill locations but used recycled concrete instead. The experimental results showed that using normal concrete improved the ultimate load by 10.19% to 55.30%, with the fully filled beam achieving a maximum increase in ductility of about 568% and a stiffness improvement ranging from 2.6% to 39% compared to the control beam. Beams filled with recycled concrete showed increases in ultimate load from 9.52% to 42.03%, ductility improvements of up to 380%, and stiffness enhancements between 4.5% and 8.03%. Numerical modeling using ABAQUS (2021) showed excellent agreement with the experimental results, with differences in ultimate load and maximum deflection averaging 5.5% and 7.9%, respectively. Full article

Powder Bed Fusion-Laser Beam/Metals (PBF-LB/M) enables the layer-by-layer fabrication of complex parts; however, non-uniform thermal transients during the process induce high stresses. Geometric constraints dominate stress–relaxation behavior, which is the primary mechanism leading to part distortion. Therefore, the printing structure serves as a major factor influencing the distortion of PBF-LB/M-fabricated components, of which the forming angle and support structure parameters are the two key factors affecting the printing structure. This study investigates the effects of forming angles and support parameters on the distortion behavior of oral stents manufactured via PBF-LB/M. The results indicate that the magnitude of distortion varies significantly with the forming angle, with the minimum distortion of 0.667 mm occurring at 75°, while the maximum distortion reaches 1.706 mm at 30°. Combined stiffness theory and thermal stress analysis reveal that the thermal stress peaks at a forming angle of 30°, which is governed mainly by the printed cross-sectional area per layer and the cumulative build height. Meanwhile, structural stiffness gradually decreases as the forming angle increases. The study also confirms that support parameters significantly affect distortion, confirming that larger support mesh size and spacing directly contribute to increased maximum distortion. Based on stiffness theory and thermal stress analysis, it is concluded that support structures reduce distortion primarily through two mechanisms: enhancing the overall structural stiffness and facilitating force transmission. Full article

After the original support system in the auxiliary transportation roadway of the northern wing of the Zhaoxian Mine failed, the extent of damage and deformation varied significantly across different sections of the drift. A single support method could not meet the engineering requirements. Therefore, this paper conducted research on the classification of roadway damage and zoning repair. The overall damage characteristics of the roadway are described by three indicators: roadway deformation, development of rock mass fractures, and water seepage conditions. These are further refined into nine secondary indicators. In summary, a rock mass damage combination weighting evaluation model based on the FAHP–entropy weight TOPSIS method is proposed. According to this model, the degree of damage to the roadway is divided into five grades. After analyzing the damage conditions and support requirements at each grade, corresponding zoning repair plans are formulated by adjusting the parameters of bolts, cables, channel steel beams, and grouting materials. At the same time, the reliability of partition repair is verified using FLAC3D 6.0 numerical simulation software. Field monitoring results demonstrated that this approach not only met the support requirements for the roadway but also improved the utilization rate of support materials. This provides valuable guidance for the design of support systems for roadways with similar heterogeneous damage. Full article

In this study, the nonlinear forced vibration response of fiber-reinforced laminated composite beams coated with functionally graded materials (FGMs) is investigated under the combined action of aero-thermoelastic loads and a concentrated harmonic excitation. The mathematical formulation is established using the Euler–Bernoulli beam theory, where von Kármán geometric nonlinearities are taken into account, along with the modified third-order piston theory to represent aerodynamic effects. By neglecting axial inertia, the resulting set of nonlinear governing equations is simplified into a single equation. This equation is discretized through the Galerkin procedure, yielding a nonlinear ordinary differential equation. An analytical solution is, then, obtained by applying the method of multiple time scales (MTS). Furthermore, a comprehensive parametric analysis is carried out to evaluate how factors such as the power-law index, stacking sequence, temperature field, load amplitude and position, free-stream velocity, and Mach number influence both the lateral dynamic deflection and the frequency response characteristics (FRCs) of the beams, offering useful guidelines for structural design optimization. Full article

The calculation of internal forces is a critical aspect in the design of statically indeterminate structures. Local trapezoidal loads, as a common loading configuration in practical engineering (e.g., earth pressure, uneven surcharge), make it essential to investigate how to compute the internal forces of statically indeterminate structures under such loads by using the displacement method. The key to displacement-based analysis lies in deriving the fixed-end moment formulas for local trapezoidal loads. Traditional methods, such as the force method, virtual beam method, or integral method, often involve complex computations. Therefore, this study aims to derive a general formula for fixed-end moments in statically indeterminate beams subjected to local trapezoidal loads by using the integral method, providing a more efficient and clear theoretical tool for engineering practice while addressing the limitations of existing educational and applied methodologies. The integral method is employed to derive fixed-end moment expressions for three types of statically indeterminate beams: (1) a beam fixed at both ends, (2) an an-end-fixed another-end-simple-support beam, and (3) a beam fixed at one end and sliding at the other. This approach eliminates the redundant equations of the traditional force method or the indirect transformations of the virtual beam method, directly linking boundary conditions through integral operations on load distributions, thereby significantly simplifying the solving process. Three representative numerical examples validate the correctness and universality of the derived formulas. The results demonstrate that the solutions obtained via the integral method align with software-calculated results, yet the proposed method yields analytical expressions for structural internal forces. Comparative analysis shows that the integral method surpasses traditional approaches (e.g., force method, virtual beam method) in terms of conceptual clarity and computational efficiency, making it particularly suitable for instructional demonstrations and rapid engineering calculations. The proposed integral method provides a systematic analytical framework for the internal force analysis of statically indeterminate structures under local trapezoidal loads, combining mathematical rigor with engineering practicality. The derived formulas can be directly applied to real-world designs, substantially reducing computational complexity. Moreover, this method offers a more intuitive theoretical case for structural mechanics education, enhancing students’ understanding of the mathematical–mechanical relationship between loads and internal forces. The research outcomes hold both theoretical significance and practical engineering value, establishing a solving paradigm for the displacement-based analysis of statically indeterminate structures under complex local trapezoidal loading conditions. Full article

This paper presents an innovative end-to-end framework for conformal antenna array design and beam steering in Low Earth Orbit (LEO) satellite-based IoT communication systems. We propose a multi-stage learning architecture that integrates machine learning (ML) for antenna parameter prediction with reinforcement learning (RL) for adaptive beam steering. The ML module predicts optimal geometric and material parameters for conformal antenna arrays based on mission-specific performance requirements such as frequency, gain, coverage angle, and satellite constraints with an accuracy of 99%. These predictions are then passed to a Deep Q-Network (DQN)-based offline RL model, which learns beamforming strategies to maximize gain toward dynamic ground terminals, without requiring real-time interaction. To enable this, a synthetic dataset grounded in statistical principles and a static dataset is generated using CST Studio Suite and COMSOL Multiphysics simulations, capturing the electromagnetic behavior of various conformal geometries. The results from both the machine learning and reinforcement learning models show that the predicted antenna designs and beam steering angles closely align with simulation benchmarks. Our approach demonstrates the potential of combining data-driven ensemble models with offline reinforcement learning for scalable, efficient, and autonomous antenna synthesis in resource-constrained space environments. Full article

Wavefront aberrations caused by thermal flows or arising from the quality of optical components can significantly impair wireless communication links. Such aberrations may result in an increased error rate in the received signal, leading to data loss in laser communication applications. In this study, we explored a newly developed combined stochastic gradient descent optimization algorithm aimed at compensating for optical distortions. The algorithm we developed exhibits linear time and space complexity and demonstrates low sensitivity to variations in input parameters. Furthermore, its implementation is relatively straightforward and does not necessitate an in-depth understanding of the underlying system, in contrast to the Stochastic Parallel Gradient Descent (SPGD) method. In addition, a developed switch-mode approach allows us to use a stochastic component of the algorithm as a rapid, rough-tuning mechanism, while the gradient descent component is used as a slower, more precise fine-tuning method. This dual-mode operation proves particularly advantageous in scenarios where there are no rapid dynamic wavefront distortions. The results demonstrated that the proposed algorithm significantly enhanced the total collected power of the beam passing through the 10 μm diaphragm that simulated a 10 μm fiber core, increasing it from 0.33 mW to 2.3 mW. Furthermore, the residual root mean square (RMS) aberration was reduced from 0.63 μm to 0.12 μm, which suggests a potential improvement in coupling efficiency from 0.1 to 0.6. Full article

Background: Orthodontically driven osteogenesis (ODO) is a surgical tunnel modification of periodontally accelerated osteogenic orthodontics (PAOO), combining selective corticotomy with bone grafting in sequential and/or segmental fashion. This is a minimally invasive approach that enhances periodontal health and allows orthodontic tooth movement beyond the original alveolar envelope. Considering the lack of long-term three-dimensional data on orthodontically driven osteogenesis (ODO), this study aims to quantitatively assess the long-term stability of alveolar bone and buccal cortical thickness following ODO, using CBCT imaging. The null hypothesis is that ODO does not result in significant changes in alveolar bone volume or cortical thickness over a seven-year follow-up period. Methods: Twenty patients (13 females, 7 males; mean age 27.4 ± 5.3 years) who had undergone orthodontically driven osteogenesis (ODO) using a minimally invasive tunnel approach and segmental corticotomy protocol followed by clear aligner therapy were retrospectively evaluated. The mean follow-up period after treatment was 7 years (range: 5–15 years). Cone beam computed tomography (CBCT) scans were obtained at one year postoperatively (T1) and again at the long-term follow-up visit (T2). Buccal bone thickness measurements were taken at standardized levels (3 mm, 5 mm, and 7 mm apical to the cementoenamel junction) and compared between T1 and T2 to evaluate bone stability over time. In addition, histologic evaluation of the previously grafted area was performed in two patients: one sample was collected during an alveolar ridge augmentation procedure six months after ODO, and the other during orthognathic surgery eight months after ODO. The samples were analyzed to assess new bone formation and integration of graft material. Results: Radiographic analysis showed long term stability of the new bone support. Histologic examination showed newly formed lamellar and reticular bone. Bone marrow showed no inflammatory infiltration, and bone particles were still detectable but incorporated in the newly created bone. Conclusions: Based on these findings, ODO appears to be a promising technique that could induce stable bone osteogenesis. A larger cohort study can enhance the evidence of these promising results to popularize this technique. Full article

Unripe Pisang Awak banana is rich in resistant starch and dietary fiber, which are recognized for supporting digestive health and bowel regularity, yet its limited solubility restricts its application in instant beverages. This study aimed to improve the functional quality of Pisang Awak banana powder (PABP) through drum drying, electron beam irradiation, and inulin supplementation. PABP was produced by tray or drum drying and irradiated at 0, 2, 4, 6, and 8 kGy. Drum-dried powder treated with 8 kGy was identified as optimal and further fortified with inulin at 0–10% (w/w). Compared with tray drying, drum drying with irradiation markedly accelerated rehydration and enhanced solubility. Incorporation of 10% inulin produced the best overall performance, yielding faster reconstitution, greater solubility at 80–90 °C, and lower viscosity values across all pasting parameters. Collectively, the combination of drum drying, irradiation, and inulin addition yielded a banana powder with improved reconstitution and reduced gelation upon cooling. This optimized formulation demonstrates potential as a model for starch-based instant powders, while also contributing to the sustainable utilization of local banana resources. Full article

Background: We evaluated the long-term treatment outcomes of patients with clinically localized and locally advanced prostate cancer (PC) who underwent high-dose-rate brachytherapy (HDR-BT) combined with external beam radiotherapy (EBRT). The primary objective was to identify the optimal timing for discontinuing prostate-specific antigen (PSA) monitoring after HDR-BT. Methods: This analysis included 338 patients with PC who received HDR-BT combined with EBRT between 2006 and 2022 and had a minimum follow-up of 5 years. The patients were stratified based on their PSA levels, and factors associated with recurrence were identified. Results: The median observation period was 8.9 years (range, 5.0–19.0 years). The 10-year recurrence-free survival rate was 92.0%, with 26 recurrences. PSA levels at 5 and 7 years were significantly correlated with oncological outcomes after HDR-BT. Multivariate analysis revealed that a PSA level of >0.2 ng/mL at 5 years was an independent poor prognostic factor for recurrence (hazard ratio, 117.57; 95% confidence interval, 6.22–2223.37; p = 0.001). No patient with a PSA level of ≤0.2 ng/mL at 7 years developed recurrences. Conclusions: Based on our long-term data, we propose that PSA monitoring may be safely discontinued in patients with a PSA level of ≤0.2 ng/mL 7 years after HDR-BT because the risk of recurrence beyond this point is exceedingly low. Full article

In laser wireless power transmission systems, the powersphere serves as a spherical enclosed receiver that performs photoelectric conversion, achieving uniform light distribution within the cavity through infinite internal light reflection. However, in practical applications, the high level of light absorption displayed by photovoltaic cells leads to significant disparities in light intensity between directly irradiated regions and reflected regions on the inner surface of the powersphere, resulting in poor light uniformity. One approach aimed at addressing this issue uses a spectroscope to split the incident beam into multiple paths, allowing the direct illumination of all inner surfaces of the powersphere and reducing the light intensity difference between direct and reflected regions. However, experimental results indicate that light transmission through lenses introduces power losses, leading to improved uniformity but reduced output power. To address this limitation, this study proposes a method that utilizes multiple incident laser beams combined with a centrally positioned spherical reflector within the powersphere. A wireless power transmission system model was developed using optical simulation software, and the uniformity of the intracavity light field in the system was analyzed through simulation. To validate the design and simulation accuracy, an experimental system incorporating semiconductor lasers, spherical mirrors, and a powersphere was constructed. The data from the experiments aligned with the simulation results, jointly confirming that integrating a spherical reflector and distributed incident lasers enhances the uniformity of the internal light field within the powersphere and improves the system’s efficiency. Full article

Following World War II, the rapid expansion of construction led to intensive use of natural resources, leading to resource depletion and accelerating climate change. Prioritising sustainability in structural design has therefore become essential. This study investigates three reinforced concrete (RC) slab systems typical of office buildings: flat slab, beam and slab, and two-way joist slab, using Eurocode 2 design principles. A 3 × 3 bay model with spans from 4 m to 14 m and three concrete grades (C25/30, C32/40, C40/50) was analysed through nonlinear finite element modelling. The methodology uniquely combines structural optimisation with embodied carbon and cost assessments across multiple slab typologies and span configurations, an approach rarely addressed in prior research. Results show that two-way joist slabs achieve the most favourable balance, reducing embodied carbon by 25–35% and construction cost by up to 15% compared to flat and beam and slab systems. This advantage is particularly evident at spans of 10 m or more, where the ribbed geometry significantly reduces concrete volume. Flat slabs are cost-efficient for short spans of up to 8 m but incur up to 40% higher carbon at longer spans due to increased thickness and punching shear reinforcement requirements. Beam and slab systems consistently recorded the highest cost and carbon values, offering limited environmental benefits despite their structural stiffness. The findings provide practical guidance for span-sensitive slab selection in early design, enabling the delivery of reinforced concrete buildings that are both cost-effective and environmentally responsible. Full article

Indirect detection phase control algorithms, such as the dithering algorithm and the stochastic parallel gradient descent algorithm (SPGD), have simple system structures and are applicable to filled-aperture coherent combinations with high efficiency. The performances of these algorithms are limited when applied to a coherent combination of pulsed fiber lasers with a low repetition rate (≤5 kHz). Firstly, due to the overlap of the phase noise frequency and repetition rate, conventional algorithms cannot effectively distinguish the phase noise from the pulse fluctuation, and directly applying filtering will result in the phase information being filtered out. Secondly, if the pulse fluctuation is ignored and only the continuous part of the phase information is utilized, it relies on the presetting of conditions to separate the pulse from the continuous part and loses the phase information of the pulse part. In this article, we propose a waveform self-referencing algorithm (WSRA) based on a two-channel near-infrared laser coherent combination system to overcome the above challenges. Firstly, by modelling a self-referencing waveform, a nonlinear scaling operation is performed on the combined signal to generate a pseudo-continuous signal, which removes the intrinsic pulse fluctuation while preserving the phase noise information. Secondly, the phase control signal is calculated based on the pseudo-continuous signals after parallel perturbation. Finally, the phase noise is corrected by optimization. The results show that our method effectively suppresses the waveform fluctuation at a 5 kHz repetition rate, the light intensity reaches an ideal value (0.9939 $I_{\max }$), and the root-mean-square (RMS) phase error is only 0.0130 $\lambda$. This method does not require the presetting of pulse detection thresholds or conditions, and solves the challenge of coherent combination at a low repetition rate, with adaptability to different pulse waveforms. Full article

Uveal melanoma (UM) is the most common primary intraocular malignancy in adults, associated with a high tendency for metastasis to the liver. Proton beam therapy (PBT) is the preferred external radiotherapy treatment for primary UM of certain sizes and locations in the eye, due to its efficacy and good local tumour control, as well as its precision to spare surrounding ocular structures. PBT is an effective alternative to surgical enucleation and other non-precision-targeted radiotherapies. Despite this, the radiobiology of UM in response to PBT is still not fully understood. This enhanced knowledge would help to further optimise UM treatment and improve patient outcomes through reducing radiation dosage to ocular structures, treating larger tumours that would otherwise require enucleation, or even offering a treatment strategy for the otherwise fatal liver metastases. In this review, we explore current knowledge of the treatment of UM with PBT, evaluating the biological responses to the therapy. Molecular factors, such as tumour size, oxygen tension levels, DNA damage proficiency, and autophagy, are known to influence the cellular response to radiotherapy, and these will be discussed. Furthermore, we examine innovative strategies to enhance radiotherapy outcomes, such as combination therapies with DNA damage repair and autophagy modulators, as well as advancements in PBT planning and delivery. By integrating current research and emerging technologies, we aim to provide opportunities to improve the therapeutic effectiveness of PBT in UM management. Full article