Search Results (211)

To mitigate potential interference in a coexisting system, an ultra-wideband (UWB) antenna with triple-band-notched characteristics is proposed. Based on transmission line theory, three notched bands are achieved by utilizing the open- or short-circuited properties of microstrip line resonators and slot resonators. Each antenna element consists of a patch etched with three half-wavelength slots and a one-wavelength strip. Measurement results demonstrate that the antenna exhibits excellent rejection performance at the three designated frequency bands. Furthermore, the effects of array configuration and element deflection angle on mutual coupling are investigated using a 2 × 1 face-to-face multiple-in, multiple-out (MIMO) array. Finally, a two-element MIMO array with high isolation was fabricated and measured. Experimental results show that an isolation level better than 24.6 dB is maintained across the operating band. Full article

This paper studies the exact and approximate relations between fluctuations in thermodynamic variables (pressure, density and temperature) that are imposed by the dilute-gas ($\mathcal{Z}=1$) equation-of-state (0.80EoS), which is a satisfactory approximation of air thermodynamics for a wide range of pressures and temperatures. It focuses on triple- and higher-order correlations, extending previous studies that concentrated on second-order moments, with emphasis on the mathematical relations, which are generally valid independently of the particular flow configuration. Exact equations are developed both involving only single-variable moments and relating the correlations between variables. These contain nonlinear terms generated by the density-temperature fluctuation product in the fluctuating 0.80EoS. The importance of the nonlinear terms in the 6 exact equations between the 10 third-order moments is assessed using 0.80DNS (direct numerical simulation) data for compressible turbulent plane channel (0.80TPC) flows and analyzed using general statistical inequalities involving third-order and fourth-order moments. The corresponding linearized system between third-order moments is studied to determine approximate relations and 4-tuples of linearly independent moments. These mathematical tools are then used to analyze 0.80TPC flow 0.80DNS data on the triple correlations between the thermodynamic variables. Full article

With accelerating urbanization, subway stations, as high-energy-consumption sectors, face significant challenges in maintaining power supply stability and ensuring power quality. This paper proposed a novel voltage compensation solution utilizing superconducting magnetic energy storage (SMES) to suppress voltage fluctuations in the traction system of a large subway station with multiple lines, which was caused by frequent acceleration and regenerative braking of multiple subway trains. Using the MATLAB/Simulink platform, a model of the traction power system with SMES for a large subway station with multiple lines was constructed. Appropriate control methods and hierarchical control strategies were used to suppress voltage fluctuations in both single-line and multi-line configurations at subway stations. The technical advantages of SMES in rapid response and efficient charging/discharging were explored. Overall, results show SMES with the novel control strategies can effectively suppress voltage fluctuations on both single- and triple-line configurations, validating the feasibility in mitigating voltage fluctuations and enhancing regenerative braking energy utilization. Full article

Rigid wingsails are increasingly adopted for wind-assisted ship propulsion, with Symmetrically Cambered (SC) profiles identified as highly efficient for thrust generation. This study investigates installation layouts for multiple SC wingsails, focusing on aerodynamic interference that limits their performance. A fast 2D potential-flow panel method is employed and benchmarked against wind tunnel and 3D IDDES data. Two representative layouts are analyzed: triple-in-line (TL) and quad-in-parallel (QP). Layout optimization is performed using a genetic algorithm with distances between sails as design variables, constrained by the total installation span, at apparent wind angles (AWAs) of $60°$, $90°$, and $120°$. Results show that thrust generation decreases progressively from upstream to downstream sails due to interference effects, with penalties of about 4–6% in the TL and up to 28% in the QP layout. The optimization improves performance only for the TL layout at $60°$, while the QP layout shows negligible gains. Analysis of pressure distributions confirms that downstream sails suffer from reduced suction on the leading edge caused by upstream wakes. Overall, the TL layout demonstrates significantly higher aerodynamic reliability than the QP layout. These findings provide new insights into multi-sail configurations and highlight the importance of layout optimization in maximizing thrust efficiency. Full article

This study investigated differences in energy-expenditure (EE) modeling between badminton players of varying competitive levels during aerobic training. It evaluated the impact of sensor quantity and sample size on prediction model accuracy and generalizability, providing evidence for personalized training-load monitoring. Fifty badminton players (25 elite, 25 enthusiasts) performed treadmill running, cycling, rope skipping, and stair walking. Data were collected using accelerometers (waist, wrists, ankles), a heart rate monitor, and indirect calorimetry (criterion EE). Multiple machine learning models (Linear Regression, Bayesian Ridge Regression, Random Forest, Gradient Boosting) were employed to develop EE prediction models. Performance was assessed using R², mean absolute percentage error (MAPE), and root mean square error (RMSE), with further evaluation via the Triple-E framework (Effectiveness, Efficiency, Extension). Elite athletes demonstrated stable, coordinated movement patterns, achieving the best values for R² and the smallest errors using minimal core sensors (typically dominant side). Enthusiasts required multi-site sensors to compensate for greater execution variability. Increasing sensors beyond three yielded no performance gains; optimal configurations involved 2–3 core accelerometers combined with heart rate data. Expanding sample size significantly enhanced model stability and generalizability (e.g., running task R² increased from 0.49 (N = 20) to 0.95 (N = 40)). Triple-E evaluation indicated that strategic sensor minimization coupled with sufficient sample size maximized predictive performance while reducing computational cost and deployment burden. Competitive level significantly influences EE modeling requirements. Elite athletes are suited to a “low-sensor, small-sample” scenario, whereas enthusiasts necessitate a “multi-sensor, large-sample” strategy. Full article

Anthropogenic barriers fragment Portuguese rivers, threatening endemic freshwater fish communities. This study compiled national inventories and peer-reviewed research (2002–2024) to quantify fishway implementation, evolution and typology, while evaluating fish performance from published research. One hundred fishways built between 1950 and 2024 were recorded, half of which were constructed after the implementation of the Water Framework Directive in Portugal (29 Dec 2005), tripling the annual construction rate. Fishways were found to be associated mainly with weirs (46%) and small hydropower plants (44%), with typology being dominated by the pool-type design (67%), nature-like facilities (18%), fish locks and combined systems (6% each), fish lifts (2%) and a single eel pass. Forty scientific contributions addressed fishway effectiveness; three-quarters dealt with pool-type facilities, while 12.5% and 10% focused on nature-like fishways and lifts, respectively. Experimental and field studies highlighted species-specific hydraulic preferences, the benefits of vertical slot and multislot configurations, and the potential of retrofitting fishways with macro-rugosities (i.e., fixed structural elements placed on the bottom) to improve non-salmonid fish passage. However, low attraction efficiency, limited multi-season monitoring and risks of aiding invasive species remain a concern. Research needs are proposed, including the refinement of species-specific hydrodynamic criteria, and the development of standardized efficiency metrics and of selective passage solutions, to advance fishway performance under Mediterranean hydrological constraints. Full article

This study presents a comparative analysis of efficiency and harmonic generation in Triple Active Bridge (TAB) converters under two operating configurations: Case I, with one input source and two loads, and Case II, with two input sources and one load. Two modulation strategies, Single-Phase Shift (SPS) and Dual-Phase Shift (DPS), are evaluated through frequency-domain modeling and simulations performed in MATLAB/Simulink. The analysis is complemented by experimental validation on a laboratory prototype. The results show that DPS reduces harmonic amplitudes, decreases conduction losses, and improves output waveform quality, leading to higher efficiency compared to SPS. Harmonic current spectra and total harmonic distortion (THD) are analyzed to quantify the impact of each modulation method. The findings highlight that DPS is more suitable for applications requiring stable power transfer and improved efficiency, such as renewable energy systems, electric vehicles, and multi-source DC microgrids. Full article

The efficient degradation of antibiotics in pharmaceutical wastewater remains a critical challenge against environmental contaminants. Conventional photocatalysts face potential limitations such as narrow visible-light absorption, rapid carrier recombination, and reliance on precious metal cocatalysts. This review investigates the coordination structure of MXene as a cocatalyst to synergistically enhance photocatalytic antibiotic degradation efficiency and the coordination structure modification mechanisms. MXene’s tunable bandgap (0.92–1.75 eV), exceptional conductivity (100–20,000 S/cm), and abundant surface terminations (-O, -OH, -F) enable the construction of Schottky or Z-scheme heterojunctions with semiconductors (Cu₂O, TiO₂, g-C₃N₄), achieving 50–70% efficiency improvement compared to pristine semiconductors. The “electron sponge” effect of MXene suppresses electron-hole recombination by 3–5 times, while its surface functional groups dynamically optimize pollutant adsorption. Notably, MXene’s localized surface plasmon resonance extends light harvesting from visible (400–800 nm) to near-infrared regions (800–2000 nm), tripling photon utilization efficiency. Theoretical simulations demonstrate that d-orbital electronic configurations and terminal groups cooperatively regulate catalytic active sites at atomic scales. The MXene composites demonstrate remarkable environmental stability, maintaining over 90% degradation efficiency of antibiotic under high salinity (2 M NaCl) and broad pH range (4–10). Future research should prioritize green synthesis protocols and mechanistic investigations of interfacial dynamics in multicomponent wastewater systems to facilitate engineering applications. This work provides fundamental insights into designing MXene-based photocatalysts for sustainable water purification. Full article

High-power nitride-based edge-emitting lasers with low-divergence Gaussian beams are useful for applications including laser surgery, material processing, and 3D printing. Fundamental lateral mode operation is typically achieved using narrow or shallow ridges. However, narrow ridges limit the active region, while shallow ridges can allow higher-order mode lasing. To address these challenges, this study applies a supersymmetry approach using optical coupling between neighbouring ridges to confine the fundamental mode while suppressing higher-order modes. Two nitride-based edge-emitting laser configurations—double-ridge and triple-ridge waveguides—are analysed, with a focus on ridge-width tolerances and the effects of gain and absorption. Both configurations achieve strong mode discrimination. However, the triple-ridge waveguide structure exhibits a mode separation ratio more than twice that of the double-ridge waveguide, making it promising for high-power single-mode operation. The results of this study provide a basis for further study of supersymmetry effects in nitride lasers. Full article

This paper presents a triple-ring optical filter designed through direct binary search inverse design, comprising three cascaded rings in an add–drop configuration. We established a physical model using temporal coupled-mode theory to derive theoretical spectra and analyze key transmission parameters. Subsequently, we encoded the target transmission performance into a figure of merit to optimize the coupling coefficients between ring resonators and waveguides. We verify the theoretical parameters using three-dimensional finite-difference time-domain simulations. The optimized filter achieves a free spectral range of 86 nm, an insertion loss of 0.4 dB, an extinction ratio of 20 dB, and a narrow spectral linewidth of 0.2 nm within a compact footprint of $29 \mathsf{\mu }\mathrm{m}\times 46.5 \mathsf{\mu }\mathrm{m}$. This device demonstrates significant application potential, particularly in laser external cavities, dense wavelength division multiplexing systems, and sensing applications. Furthermore, this work provides a systematic design framework for the precision design of photonic devices. Full article

This study presents an innovative strategy for the electrochemical degradation of methylene blue (MB) using 3D-printed helical anode electrodes fabricated from commercially available conductive Polylactic acid/carbon black (PLA/CB) filaments. The choice of PLA/CB is particularly significant, since the amorphous PLA matrix combined with a percolating carbon black network provides a biodegradable, low-cost, and chemically versatile polymer composite that can be transformed from a simple prototyping filament into a functional electrochemical platform. Through a combination of chemical/electrochemical activation and electrodeposition of copper nanoparticles (Cu NPs), the polymer electrodes were successfully converted into highly efficient catalytic platforms. Beyond material functionalization, the influence of electrode geometry was systematically investigated, comparing single-, double-, and triple-spiral helical configurations. The double-spiral geometry proved the most effective, offering the best balance between active surface area and electrolyte flow dynamics. Under mild conditions (2 V, pH 6, 0.1 M NaCl), the system achieved up to 97% MB removal, while also demonstrating remarkable stability and reusability over at least ten consecutive cycles. These results highlight the synergistic role of polymer chemistry, arrangement, and metal decoration, demonstrating how 3D printing can be a useful platform for the easy production of electrodes with different geometries, even starting from simple conductive filaments reused in sustainable and scalable functional materials for advanced wastewater treatment. Full article

Savonius drag-based rotors, a type of vertical-axis wind turbine (VAWT), are well-suited for urban environments—particularly residential rooftops—owing to their compact design and ability to capture wind from all directions. However, their relatively low efficiency and narrow operational range pose significant challenges, such as limited energy output under variable wind conditions and reduced performance across a broad range of tip speed ratios. To address these issues, this study explores flow augmentation using strategically placed deflectors, referred to as Wind Accelerators and Guiding Rotor Houses (WAG-RHs). Four different configurations, including double, triple, oblique, and straight designs, were evaluated against both omni-directional guide vanes (ODGVs) and a conventional rotor. The findings show that the ODGV configuration successfully extends the operational range from a tip speed ratio of 0.5 to 0.6—termed the extended performance point (EPP)—and increases the power coefficient ($C_p$) by up to 300% compared to the conventional design. Among all setups, the straight WAG-RH configuration proved most effective, not only achieving the EPP but also delivering a 385% and 264.3% increase in local and AVE $C_p$ values, respectively compared to the conventional rotor. It also outperformed the ODGV-equipped rotor by 25%, thanks to its radial and dual-plane arrangement. Full article

This study investigates the effects of magnetic field orientation and axial extent on convective heat transfer in a laminar flow of water-based ferrofluid through a heated horizontal tube. Experiments were conducted at Reynolds numbers of 109, 150, and 164 using two field configurations: lateral fields, with magnets positioned on opposite sides of the tube with varying polarities, and axial fields, with one to three magnets arranged sequentially underneath the tube to vary the magnetic interaction length. In lateral configurations, the impact on the local Nusselt number was negligible or slightly negative depending on magnet orientation. In contrast, axial configurations demonstrated a clear relationship between the magnetic field interaction length and heat transfer enhancement. The local Nusselt number increased progressively with the number of magnets, reaching a maximum of 28.0% for the triple-magnet configuration at Re = 109. The average improvements in the magnetically influenced region were 6.8%, 10.3%, and 14.7% for the single, double, and triple magnet configurations, respectively. These values resulted from the combined effect of magnetic field geometry and Reynolds number, emphasizing the importance of both interaction length and flow conditions in shaping convective heat transfer in ferronanofluid systems. Full article

This paper presents a thermal study of a lithium-ion traction battery with different cooling configurations during simulated city driving and high-power charging. Four liquid cooling configurations—single or triple plates with straight or U-shaped tubes—were evaluated using finite element models in the Q-Bat Toolbox for MATLAB. Simulations were conducted using the Worldwide Harmonized Light Vehicles Test Cycle (WLTC) and a high-current charging profile based on the CHAdeMO standard (up to 400 A). The results indicate that while cooling is not strictly necessary under typical driving conditions, it significantly improves thermal stability and reduces peak temperatures. The best configuration reduced peak cell temperatures by 1.96% during driving and by 16% during fast charging. The cooling system also minimized temperature gradients within the battery, reducing the risk of degradation. Box-plot analysis confirmed that an efficient cooling system stabilizes the temperature distribution and smooths out extreme values. The results highlight the importance of thermal management for extending battery life and ensuring safe operation, particularly during fast charging conditions. Full article

To address the triple bottlenecks of data scarcity, oversized models, and slow inference that hinder Cantonese automatic speech recognition (ASR) in low-resource and edge-deployment settings, this study proposes a cost-effective Cantonese ASR system based on LoRA fine-tuning and INT8 quantization. First, Whisper-tiny is parameter-efficiently fine-tuned on the Common Voice zh-HK training set using LoRA with rank = 8. Only 1.6% of the original weights are updated, reducing the character error rate (CER) from 49.5% to 11.1%, a performance close to full fine-tuning (10.3%), while cutting the training memory footprint and computational cost by approximately one order of magnitude. Next, the fine-tuned model is compressed into a 60 MB INT8 checkpoint via dynamic quantization in ONNX Runtime. On a MacBook Pro M1 Max CPU, the quantized model achieves an RTF = 0.20 (offline inference 5 × real-time) and 43% lower latency than the FP16 baseline; on an NVIDIA A10 GPU, it reaches RTF = 0.06, meeting the requirements of high-concurrency cloud services. Ablation studies confirm that the LoRA-INT8 configuration offers the best trade-off among accuracy, speed, and model size. Limitations include the absence of spontaneous-speech noise data, extreme-hardware validation, and adaptive LoRA structure optimization. Future work will incorporate large-scale self-supervised pre-training, tone-aware loss functions, AdaLoRA architecture search, and INT4/NPU quantization, and will establish an mJ/char energy–accuracy curve. The ultimate goal is to achieve CER ≤ 8%, RTF < 0.1, and mJ/char < 1 for low-power real-time Cantonese ASR in practical IoT scenarios. Full article