Search Results (17,518)

Hairpin windings are increasingly adopted in permanent magnet (PM) traction machines owing to their high slot fill factor, compact end-winding structure, and suitability for automated manufacturing. However, limited heat dissipation and high copper losses under peak loading and high-frequency operation result in severe thermal constraints, which restrict the power rating of the machine. This paper presents a multi-physics comparison of different winding cooling topologies for a PM machine with hairpin winding, including hollow conductor cooling, end-winding cooling, and cooling channel insertion at slot-bottom, slot-middle, and slot-opening regions. A coupled electromagnetic–thermal model based on the finite element method (FEM), which accounts the heat transfer between different components, is used to analyze temperature distribution, losses, efficiency, loading capacity, and hydraulic requirements. The results show that the position of the cooling channel has great influence on the thermal behavior and electromagnetic performance of the machine under different working conditions. The study emphasizes the strong coupling between cooling design, conductor geometry, AC loss behavior, and efficiency and provides practical design guidelines for selecting appropriate cooling techniques in high-power-density traction machines. Consequently, an improved cooling system results in a reduced amount of PM for the same output power range. Full article

Vertical take-off and landing (VTOL) configurations incur a structural weight penalty that reduces payload fraction and endurance compared to conventional fixed-wing and multirotor aircraft of comparable gross weight. To extend the endurance of VTOL UAVs, this work presents the design, analysis and control of a novel unmanned tilt trirotor aircraft with tandem wings, named Gong-H, featuring VTOL capability and high aerodynamic efficiency. A prototype of this aircraft was built with the rotor system mounted between tandem wings with a high wing coverage rate, which can achieve a more compact structure than other VTOL aircraft. The control forces and torques are provided not only by the rotor system in VTOL flight mode and the two tandem wings in cruise mode, but also by both the rotor system and wings in transition mode. Additionally, Computational Fluid Dynamics (CFD) simulations are conducted to optimize the wing configuration to improve the efficiency of cruise mode. Moreover, an airspeed-scheduled hybrid control framework based on incremental nonlinear dynamic inversion (INDI) and PID is adopted for different flight modes to improve the robustness of control and the stability of flight mode switching. Hover experiments confirm improved power efficiency compared to tilt quadrotor configuration, which extends endurance time and increases range. Additionally, complete flight cycle field experiments were conducted to demonstrate the aerodynamic feasibility of the prototype, including VTOL flight, cruise flight, and transition flight modes. Control surface redundancy tests and comparative INDI-PID validation under asymmetric disturbances further verify the practical robustness of the control framework. This work provides a design concept of VTOL aircraft and a practical solution for VTOL applications. Full article

This paper presents the sizing and performance evaluation of a natural draft air-cooled condenser, with a nominal heat rejection rate of 75 MW_th, for implementation at a concentrated solar power plant in the Northern Cape province of South Africa. Initial sizing and optimization of the tower geometry is done with the aid of a one-dimensional thermofluid model at design point conditions. A high-density Latin hypercube sampling-based parametric sweep was conducted that covers the geometric design envelope, which is defined via the tower and heat exchanger heights, and the tower base and outlet diameters. Following this, the performance of the best-performing tower geometry is verified via detailed three-dimensional computational fluid dynamics (CFD), and the geometry adjusted slightly to achieve the desired heat rejection rate. This process includes refinement and validation of the CFD model compared to previous work, with the heat rejection rate matching the previous results within 0.1%, as well as performing grid convergence studies to ensure mesh independence. The refinements include a more direct coupling with the solver continuity equation, improving the accuracy of the heat exchanger integration via porous media, and a decrease in computational overhead to reduce the time required for parametric studies. The best-performing geometry implemented in the CFD model features a tower height of 80 m, base diameter of 58 m, outlet diameter of 40.15 m, heat exchanger height of 11.25 m and heat exchanger width of 3.551 m, with the model predicting a conservative heat rejection rate of 76 MW_th at the design point. Finally, a methodology is presented to evaluate the performance of the system over the full range of ambient conditions encountered during an annual operating cycle. The methodology will be applied in further work to develop a reduced-order surrogate model for application in annual performance studies. Full article

Ensuring adequate indoor air quality (IAQ) in industrial environments is essential for protecting worker health, particularly in facilities characterized by chemical emissions and complex layouts, such as automotive painting lines. This study presents the implementation and field evaluation of a low-cost multisensory electronic system prototype designed for continuous, long-term monitoring of six key environmental parameters: temperature, relative humidity, atmospheric pressure, carbon dioxide equivalent (CO₂ eq), total volatile organic compounds (VOC), and an overall Indoor Air Quality (IAQ) index. The system consists of autonomous sensing stations with integrated multi-parameter MEMS sensors and a centralized data aggregation hub. The system was engineered to ensure metrological stability across power cycles, adaptive energy management, and robust long-range wireless communication, thereby addressing common limitations of conventional industrial monitoring solutions. The prototype was deployed in an operational automotive manufacturing plant, where seven sensing stations were installed along the painting line for a two-week continuous monitoring campaign, identifying process-dependent peaks in CO₂ and VOC concentrations and corresponding reductions in IAQ values. The system was able to identify CO₂ peaks as high as 2997.7 ppm (Sensor 3) in localized industrial zones, significantly exceeding standard indoor thresholds. At the same time the system demonstrated the ability to detect VOC fluctuations with a resolution capable of capturing peaks up to 144.1 ppb (Sensor 3) during high-activity shifts. All sensors provided continuous and reliable data over an extended monitoring period. The measured trends and value ranges were consistent with expected industrial conditions, indicating satisfactory system performance under real operating conditions. Overall, the results demonstrate that the developed multisensory prototype is a promising, portable, and economically sustainable solution for distributed continuous IAQ assessment in complex industrial environments, with strong potential for scalable large-scale implementation in occupational health protection and environmental sustainability frameworks. Full article

Apricot powder functionality after drying, grinding and sieving remains insufficiently understood. This study prepared powders from diluted Diaoganxing apricot pulp using hot-air drying (HAD), infrared drying (IRD), vacuum-pulsed drying (VPD) and vacuum freeze drying (VFD), followed by identical grinding and 60-mesh sieving. Moisture status, density, calculated porosity, particle characteristics, reconstitution, flowability, color, selected phytochemical indicators, ferric reducing antioxidant power (FRAP) and supplementary electronic-nose fingerprints were evaluated. The drying route markedly affected powder properties: moisture content and water activity ranged from 7.23 ± 0.38% to 9.85 ± 0.02% and 0.218 ± 0.002 to 0.370 ± 0.007, respectively. VFD gave the highest calculated porosity (59.09 ± 0.84%), shortest wettability time (46.05 ± 1.71 s), highest water-holding capacity (3.63 ± 0.07 g/g), smallest color difference (ΔE = 1.12 ± 0.47), and highest TPC, TCC, AAC and FRAP values. VPD showed the best handling indices, with the lowest angle of repose (28.44 ± 0.34°), Hausner ratio (1.07 ± 0.01) and Carr index (6.33 ± 0.66%). Correlation/PCA indicated treatment-level co-variation, not causality. Under the tested processing conditions, VFD may be preferable for rapid reconstitution and the measured quality indicators, whereas VPD may be more suitable for powder handling. Full article

This paper proposes an original method for selecting cylindrical Li-Ion cells in the popular 18650 format, sourced from the disassembly of laptop batteries, for reuse and to give them a second life. The Introduction analyzes the key properties of Li-Ion cells in comparison with other solutions, with a particular focus on the latest battery technologies based on Na-Ion cells, which are built using less expensive sodium. The work involved disassembling damaged batteries, followed by an initial selection of cells based on voltage and internal resistance measurements. A key part of the work was developing a simulation based on a random arrangement of cells in a 4s6p pack and identifying the optimal configuration based on three established criteria. Finally, a prototype battery was constructed, and its discharge curves were analyzed at three constant power levels ranging from 50 W to 150 W. In conclusion, it was found that the developed method is of significant importance from an environmental protection perspective and can be applied to the construction of other battery packs using various Li-Ion cells; the optimal load level for the tested prototype in the case study was a constant load of 50 W. Full article

A hypothesis was proposed that continuous dual-circuit mixing can be achieved by equipping a feed mixer-distributor with two leveling–mixing finger shafts, which, after lifting the feed mass to a certain height, collect it in the central part of the hopper and divide it into two flows directed toward the end walls of the hopper. In this case, continuous dual-circuit mixing is performed during each rotation of the leveling–mixing shaft. A structural and technological scheme, engineering documentation, and an experimental prototype of the feed mixer-distributor were developed. The machine consists of a 3.0 m³ hopper, two horizontal augers, two leveling–mixing finger shafts, a loading conveyor, and a drive mechanism. Theoretical investigations were carried out, and analytical expressions were obtained to determine the circumferential velocity of the fingers of the leveling–mixing device. This velocity must ensure the movement of the feed mixture without scattering and guarantee the release of the feed mass from the finger surface when the finger rotation angle exceeds 20°. Calculations based on the obtained analytical expressions showed that the critical circumferential velocity of the fingers is 0.866 m/s, while the calculated minimum rotational speed of the finger shaft is 20.7 min⁻¹. Therefore, a rotational speed of approximately 20 min⁻¹ was adopted for the experimental investigations. Experimental studies conducted at different rotational speeds of the leveling–mixing device showed that the optimal rotational speed of the finger shaft is 20 min⁻¹. At this rotational speed, the mixture uniformity exceeded 90%. An analytical expression was also derived to determine the velocity of feed mixture movement along the finger surface. Calculations showed that the optimal velocity ranged from 0.5 to 0.94 m/s. This value corresponds to the rational velocity of feed mixture transportation toward the end walls of the hopper. Laboratory experiments were carried out using the feed mixer-distributor at a leveling–mixing finger shaft rotational speed of n = 20 min⁻¹. The optimal mixing time required to achieve the target mixture uniformity was 5.5 min under the tested operating conditions. Comparative experiments also showed that operation of the feed mixer-distributor without the leveling–mixing device resulted in a 34% higher power consumption than operation with the leveling–mixing device. Full article

This study aimed to analyse how wind-farm location and line-loading characteristics affect voltage variations in medium-voltage distribution networks. Simulations were performed in DIgSILENT PowerFactory using three 20 km radial MV lines with different conductor cross-sections. The wind farm was connected successively at selected line nodes, and its power was adjusted in each case to produce a 3% voltage rise at the point of connection. Three operating scenarios were considered: an unloaded line, a line with a resistive-inductive load and a line with a resistive-capacitive load. For the unloaded line, the voltage rise downstream of the wind farm remained constant at 3%, whereas the source’s effect on nodes closer to the HV/MV substation diminished rapidly, with values ranging from 0.021% to 0.097%. Under load, the voltage-change profiles became non-linear, and the maximum deviations exceeded those observed for the unloaded line. For a resistive-inductive load, the voltage change reached approximately 3.1–3.3%, and the largest deviations occurred not at the point of connection but farther downstream. These findings demonstrate that wind-farm hosting capacity cannot be assessed solely from the voltage at the point of connection. In many cases, the 3% criterion is satisfied at the point of connection while the same threshold is exceeded elsewhere in the network. The full line voltage profile and load characteristics should therefore be considered when planning the integration of renewable energy sources into MV networks. Full article

Urban heat intensification is an increasing concern in rapidly urbanizing arid cities, where extreme climatic conditions intersect with expansive urban growth. This study examines the spatiotemporal dynamics of urban thermal patterns in the Doha metropolitan region, Qatar, by integrating multi-season remote sensing with urban morphological analysis. Seasonal composites of land surface temperature (LST), Urban Heat Island (UHI) intensity, and Normalized Difference Vegetation Index (NDVI) were derived from Landsat 8–9 Collection 2 Level-2 imagery across eight seasons from Spring 2024 to Winter 2026. Urban form was characterized using Local Climate Zones (LCZs) and quantified through class-level landscape metrics, i.e., Largest Patch Index (LPI), Number of Patches (NP), and CLUMPY. The results showed a pronounced seasonal variability, with LST ranging from approximately 12.5 °C in winter to 61.3 °C in summer, and intra-urban UHI exceeding 10 °C during peak conditions. The bare soil/sand, with relative coverage of 52.84% and LPI of 25.45%, and the large low-rise, with relative coverage of 38.60% and LPI of 14.70%, typologies dominate the landscape, forming highly aggregated spatial structures, while vegetation cover remained minimal. Weak negative relationships between NDVI and thermal indicators revealed that vegetation alone had limited explanatory power. In contrast, LCZ-based analysis revealed a better thermal differentiation across urban typologies, with compact forms associated with higher thermal intensities. These findings highlight the dominant role of urban morphology and spatial configuration in shaping thermal patterns and support the need for morphology-sensitive planning strategies in arid urban environments. Full article

Individual differences in outdoor thermal comfort (OTC) are critical to the healthy use of urban public spaces, yet whether thermal preference can shape OTC independently of demographic characteristics remains largely unexamined. Using residential outdoor spaces in Fuzhou, a representative hot-humid city in China, as a case, this study combines field measurements and questionnaire data from 296 respondents (72.6% aged 60 or above) with explainable machine learning and K-Modes clustering to examine how thermal preference drives individual differences in OTC. Three stable preference profiles were identified—heat-sensitive (56.4%), wind-seeking (20.3%), and heat-tolerant (23.3%)—which exhibit markedly different thermal responses. The neutral globe temperature ranges from 29.90 °C for the heat-sensitive profile to 35.85 °C for the heat-tolerant profile, a difference of 5.95 °C, whereas the comfort bandwidth is widest for the heat-sensitive profile (9.03 °C) and narrowest for the heat-tolerant profile (4.13 °C), the former being 2.2 times the latter. The profiles are independent of sex and BMI and only weakly correlated with age, yet their explanatory power for the variance in thermal comfort vote (TCV) (η² = 0.254) is 4.9 to 23.1 times that of the demographic variables. The thermal environment contributes far more to TCV than the visual environment (74.4% versus 25.6%), with globe temperature (Tg) as the strongest single factor. Overall, differentiated design that adopts the most heat-sensitive profile as the constraint boundary covers the comfort needs of a broad population more effectively than demographic stratification. The novelty of this study lies in introducing psychologically grounded thermal-preference profiles as an operational stratification dimension for architectural design, offering age-friendly hot-humid residential environments a preference-oriented pathway toward refined, human-centered outdoor space design. Full article

Graph Neural Networks (GNNs) have become essential for analyzing graph-structured data, yet their deployment on resource-constrained edge devices is severely limited by high computational complexity and irregular memory access patterns. Here, we introduce DynamiGraph, a specialized FPGA-based overlay accelerator engineered for ultra-low-latency GNN inference in edge computing scenarios. Unlike general-purpose accelerators that incur high resource overhead to support a broad range of operators, DynamiGraph adopts a streamlined architecture focusing exclusively on essential General Matrix Multiplication (GEMM) and Sparse–Dense Matrix Multiplication (SpDMM) kernels. We implement a hardware-native runtime optimization mechanism that dynamically exploits graph sparsity via an edge-centric execution flow, eliminating redundant computations without requiring complex static preprocessing. Experimental results on an AXU2CGA edge platform demonstrate that DynamiGraph achieves sub-millisecond inference latencies on small-scale benchmarks (e.g., Cora) and a peak throughput of 1467 inferences per second. Furthermore, our runtime sparsity exploitation yields over 2000× reductions in floating-point operations compared to dense equivalents. These findings indicate that trading off model generality for architectural specialization and runtime awareness offers an efficient architectural alternative for enabling real-time graph intelligence in power- and bandwidth-limited edge environments. Full article

Oscillating water column wave energy converters require self-rectifying turbines capable of maintaining stable performance under bidirectional airflow. This study numerically investigates the aerodynamic performance and internal flow characteristics of an axial-flow impulse turbine using OpenFOAM under both uniform and reciprocating airflow conditions. Rotor motion was modeled using the Multiple Reference Frame approach, and the numerical model was validated against experimental data for one-way flow at an inlet velocity of 8.71 m s⁻¹ and rotational speeds ranging from 300 to 1300 rpm. The CFD results successfully reproduced the experimental efficiency trend, yielding a peak efficiency of η = 0.4269 at 700 rpm and ϕ ≈ 0.95, which closely aligns with the experimental peak efficiency of η = 0.4425. Validation metrics demonstrated a high degree of accuracy, with an RMSE of 0.0219, a mean absolute error of 0.0197, a maximum absolute error of 0.0399, a squared Pearson correlation coefficient of 0.826, and a peak-efficiency difference of 3.5%. Flow-field analysis revealed that low rotational speeds resulted in high outlet velocities and incomplete energy extraction, whereas excessive rotational speeds caused flow misalignment, downstream vortex formation, and additional aerodynamic losses. Under reciprocating flow conditions, characterized by a sinusoidal velocity amplitude of 8.71 m s⁻¹ and periods of 0.5–2.0 s at 700 rpm, both input and torque coefficients exhibited hysteresis, with the strongest loops observed at the shortest periods. Examinations of streamline, pressure, and velocity distributions indicated that residual flow during flow reversal alters the effective inlet direction in the subsequent half-cycle, resulting in flow memory and a phase-dependent turbine response. As the present computational domain excludes the OWC chamber, these findings characterize turbine-level aerodynamic performance rather than the complete system power coefficient. Full article

Mitochondria regulate cellular energetics, redox balance, apoptosis, and inflammatory signaling in oral, airway, and systemic tissues. Hypoxia is a powerful modulator of mitochondrial function, with effects ranging from adaptive hormesis to overt injury. Cyclic altitude training, most often delivered as intermittent hypoxic exposure or intermittent hypoxia training (IHT), has been proposed as a strategy to improve mitochondrial efficiency and exercise performance. By contrast, obstructive sleep apnea (OSA) exposes patients to uncontrolled chronic intermittent hypoxia (CIH), a pattern increasingly linked to endothelial dysfunction, ceramide-mediated mitochondrial dysfunction, insulin resistance, systemic inflammation, oral dysbiosis, and periodontitis. This narrative review covers intermittent hypoxia, mitochondrial biogenesis, hypoxia-inducible factor signaling, OSA, periodontitis, oral microbiome shifts, nitric oxide biology, and smoke-related mitochondrial injury. Appropriately dosed IHT can increase mitochondrial biogenesis, improve mitochondrial morphology, and augment oxidative capacity through pathways involving PGC-1alpha, hypoxia-inducible signaling, mitochondrial dynamics, and reactive oxygen species-dependent hormesis. In contrast, CIH in OSA promotes oxidative stress, sympathetic activation, endothelial injury, and inflammatory signaling and is associated with worse periodontal status and altered salivary microbiome profiles. Controlled IHT and OSA-related CIH, therefore, represent opposite ends of a hypoxia continuum, and mitochondrial health connects sleep-disordered breathing, periodontal inflammation, environmental exposures, and systemic cardiometabolic risk within a single conceptual frame. Sphingolipid signaling—particularly hypoxia- and toxicant-driven ceramide accumulation—connects CIH, inhaled environmental exposures, mitochondrial fragmentation, and the development of insulin resistance. Full article

Low Power Wide Area Networks (LPWANs) are essential for enabling Internet-of-Things (IoT) technologies in utility environments. Utilities can leverage these networks to monitor critical remote assets, especially where mobile technologies are unsuitable due to poor power efficiency or insufficient coverage. This paper investigates the use of Long Range (LoRa) Wide Area Network (LoRaWAN) technology as an LPWAN solution for remote grid monitoring within the eThekwini Municipal Area. In addition to evaluating range performance (distance) and the packet reception ratio (PRR) across configurable parameters, such as spreading factor and transmit power, this paper introduces a data-packet security extension for LoRaWAN using NTRU post-quantum cryptography (PQC). The proposed security enhancement provides quantum-resistant encryption for application-layer payloads without violating LoRaWAN duty-cycle constraints or significantly increasing energy consumption. Field tests were performed at 11 geographically dispersed substations using a handheld LoRa device. Test signals were transmitted at four power levels (2 dBm, 8 dBm, 14 dBm, and 20 dBm) and spreading factors (SF7–SF12). Results show that the public LoRaWAN network can achieve communication distances of approximately 30 km in an urban environment, with PRR strongly dependent on SFs and transmit power. The integration of lightweight NTRU-protected payloads was found to be feasible for typical smart grid use cases involving small data packets (1–13 bytes). Full article

Electric ducted fans (EDFs) have emerged as promising propulsion systems due to their compact design, high thrust density, and enhanced operational safety. Accurate prediction of aerodynamic thrust is essential for EDF design and performance evaluation; however, existing numerical studies have not yet provided a systematic comparison of the thrust-prediction capability of different k-ω-based turbulence models in micro-EDF applications. In this study, a dedicated thrust-measurement platform was developed for a 120 mm EDF, and experimental thrust data were obtained under three representative hover operating conditions. Based on these measurements, six turbulence models, including SST, SKω, BSL, GEKO, EARSM, and SST-γ(alg.), were evaluated using three-dimensional CFD simulations. The numerical model was assessed through thrust validation, centerline velocity comparison, power-consistency analysis, grid independence verification, and qualitative flow-field interpretation. A two-factor full-factorial analysis was further conducted to quantify the effects of rotational speed and turbulence model on prediction accuracy and computational cost. The results show that the turbulence model has a stronger influence on the normalized thrust-prediction error than the rotational speed factor over the investigated operating range. The SST-γ(alg.) model achieves the highest thrust-prediction accuracy, with an average relative deviation of 0.47%, but requires the highest computational cost. In comparison, the SST model provides a favorable balance between accuracy and efficiency, with an average relative deviation of 1.79% and an average computation time of 184.33 min, approximately 33% lower than that of the SST-γ(alg.) model. The centerline velocity and power-consistency results further support the comparative model assessment. Overall, this study provides an experimentally validated comparative reference for turbulence model selection in simulations of similar 120 mm EDF under hover conditions. Considering both prediction accuracy and computational efficiency, the SST model can serve as a practical turbulence model choice for engineering parameter optimization of similar micro-EDF configurations.$k-\omega$ Full article