Search Results (701)

Biomimetic pectoral fin propulsion offers a low-noise, highly maneuverable alternative to conventional propellers for next-generation underwater robotic systems. This study develops a manta ray-inspired dual-servo pectoral fin module with a CPG-based controller and employs it as a single-fin test article in a recirculating water tunnel to quantify its hydrodynamic performance. Controlled experiments demonstrate that the fin generates stable thrust over a range of flapping amplitudes, with mean thrust increasing markedly as the amplitude rises, while also revealing an optimal frequency band in which thrust and thrust work are maximized and beyond which efficiency saturates. To interpret these trends, a quasi-steady CFD analysis using the k–ω SST turbulence model is conducted for a series of static angles of attack representative of the instantaneous effective angles experienced during flapping. The simulations show a transition from attached flow with favorable lift-to-drag ratios at moderate angles of attack to massive separation, deep stall, and high drag at extreme angles, corresponding to high-amplitude fin motion. By linking the experimentally observed thrust saturation to the onset of deep stall in the numerical flow fields, this work establishes a unified experimental–numerical framework that clarifies the hydrodynamic limits of pectoral fin propulsion and provides guidance for the design and operation of low-noise, highly maneuverable biomimetic underwater robots. Full article

Water-lubricated bearings are critical components in marine propulsion systems, necessitating materials with exceptional tribological properties to ensure reliability. Filament-winding technology is an effective molding method for enhancing the comprehensive properties of polymers, and the selection of fiber materials has a significant impact on the performance of polymers. In this study, three types of polyurethane (PU) matrix filament-winding composites were fabricated via filament-winding technology. Under water-lubricated conditions, a friction test (disk-to-disk) with a duration of 2 h was performed, followed by systematic observations of the resultant wear behavior. The results indicate that aramid fibers exhibited the superior reinforcing effect on the PU matrix, effectively suppressing wear while enhancing mechanical properties. Specifically, under the conditions of 0.5 MPa-250 r/min (0.314 m/s), the minimum friction coefficient of the aramid fiber-wound composite material was 0.093, which was 57.73% lower than that of pure polyurethane. Under the conditions of 0.7 MPa-50 r/min (0.0628 m/s), the wear mass of the sample was limited to only 1.5 mg, which was 12% lower than that of polyurethane. This research can provide a practical reference for the application of filament-wound composite materials in water-lubricated bearings. Full article

Wheel load is a critical information source reflecting the status of vehicle load distribution and motion. Yet, existing in-wheel motor products are primarily designed as propulsion units and inherently lack the load-sensing capabilities required by intelligent vehicles. To address this research gap, this paper presents a novel intelligent electric drive wheel (i-EDW) with an integrated transmission system and a load-sensing unit (LSU). The i-EDW adopts an Axial Flux Permanent Magnet Synchronous Motor (AFPMSM), while the integrated LSU ensures high-precision measurement of six-dimensional wheel forces and moments. According to this multi-axis force information, a real-time estimation and stability control method based on the tire–road friction circle concept is proposed. Instead of the complex decoupling and multi-objective optimization with the multi-actuator systems, this paper focuses on minimizing the tire load rate of i-EDWs, which significantly advances the state of the art in terms of calculation efficiency and respond speed. To validate this theoretical framework, a full-vehicle model equipped with four i-EDWs is developed. In the MATLAB R2022A/Simulink co-simulation environment, a virtual prototype is tested under typical driving scenarios, including the straight-line acceleration and double-moving-lane (DML) steering. The simulation results prove a reliable safety margin from the friction circle boundaries, laying a solid foundation for precise motion control and improved system robustness in future intelligent vehicles. Full article

Background: Deceptive caffeine ingestion has shown inconsistent effects as an ergogenic aid for short-term exercises. Objective: Therefore, the aim of this study was to evaluate the potential placebo effect of deceptive caffeine ingestion on short-term performance during countermovement and repeated-jump tests, as well as bench press throw and bench press-to-failure assessments, and to document any associated side effects. Methods: A repeated, randomized, and counterbalanced design was implemented to compare the effects of ingesting a placebo claimed to be caffeine with a control condition in which no substance was consumed. Twenty-five physically active young adults (17 men and 8 women) completed a countermovement jump (CMJ) test, a 15 s repeated-jump test, bench press throws at 25%, 50%, and 75% of 1RM, and a bench press-to-failure test at 75% of 1RM and also completed a questionnaire regarding potential side effects. Results: Performance was similar between the placebo and control in the CMJ (38.1 ± 6.8 vs. 37.5 ± 6.8 cm; p = 0.225; d = 0.25) and in the 15 s repeated-jump test (p > 0.05; trivial–small effects). In the bench press throw, propulsive mean velocity did not differ at 25% 1RM (p = 0.296; d = 0.23) or 50% 1RM (p = 0.626; d = 0.10). However, deceptive caffeine ingestion increased propulsive mean velocity at 75% 1RM (0.500 ± 0.131 vs. 0.480 ± 0.131 m/s; p = 0.024; d = 0.48) and increased repetitions to failure at the same load (11.9 ± 3.7 vs. 11.0 ± 3.1; p = 0.047; d = 0.42). Mean velocity during the first 3 repetitions tended to be higher with the placebo (p = 0.064; d = 0.39), while final repetitions were similar (p = 0.469; d = 0.15). The most common side effects were increased activeness (34.8%) and nervousness (17.4%). Conclusions: In summary, deceptive caffeine ingestion had minimal impact on jump and ballistic bench press performance in physically active individuals. However, repetitions to failure were improved by ≈1 repetition (+8.2%). These findings suggest that the placebo effect of caffeine is unlikely to serve as a reliable strategy for enhancing short-term exercise performance. Full article

A new type of transportation vehicle, the maglev car, is gaining attention in the automotive and maglev industries due to its potential to meet personalized urban mobility and future travel needs. To optimize the chassis layout of maglev cars, this paper proposes a compact powertrain integrating electrodynamic suspension with in-wheel motor technology, in which a permanent magnet electrodynamic in-wheel motor (PMEIM) enables integrated propulsion and levitation. First, the PMEIM external magnetic field distribution is characterized by analytical and finite element (FEM) approaches, revealing the magnetic field distortion of the contactless powertrain. Subsequently, the steady-state electromagnetic force is modeled and the operating states of the PMEIM powertrain are calculated and determined. Next, the PMEIM electromagnetic design is conducted, and its electromagnetic structure rationality is verified through magnetic circuit and parametric analysis. Finally, an equivalent prototype is constructed, and the non-contact electromagnetic forces of the PMEIM are measured in bench testing. Results indicate that the PMEIM powertrain performs propulsion and levitation functions, demonstrating 14.2 N propulsion force and 45.8 N levitation force under the rated condition, with a levitation–weight ratio of 2.52, which hold promise as a compact and flexible drivetrain solution for maglev cars. Full article

Inspired by the movements of sea turtle forelimbs, this study presents a bio-inspired underwater flapping wing with three degrees of freedom. This flapping wing mechanism can more accurately simulate the rotational motion of a sea turtle’s forelimbs to generate greater propulsive force. The highlight is the gear transmission mechanism arranged along the wingspan, enabling a preset increasing twist angle along the wingspan. Computational fluid dynamics simulations are conducted to evaluate the hydrodynamic performance of the proposed flapping wing system. The effects of different spanwise twist angles along the wingspan on thrust generation are quantitatively analyzed, as well as the influence of key kinematic parameters, including the longitudinal flapping angle, spanwise increasing twist angle, and elevation angle. The results indicate that, compared with a uniform twist angle, the spanwise increasing twist significantly increases the peak thrust during specific phases of the flapping cycle. It is further revealed by flow field analyses that the formation of vortices near the trailing edge enhances the propulsive force in the streamwise direction. To further validate the proposed concept, a prototype of the mechanism is fabricated and experimentally tested under low-frequency actuation, confirming the feasibility of the mechanical design. Overall, these results demonstrate the potential of the proposed approach for bio-inspired underwater propulsion and provide useful guidance for future flapping wing mechanisms and kinematic design. Full article

Monitoring mechanical vibration is crucial for ensuring the structural integrity and optimal performance of unmanned aerial vehicles (UAVs). This study introduces a portable and low-cost system that enables integrated acquisition and analysis of UAV vibration data in a single step, using a Raspberry Pi 4B, data acquisition (DAQ) through a MCC128 DAQ HAT card, and six accelerometers positioned at strategic structural points. Ground-based engine tests at 2700 RPM allowed vibration data to be recorded under conditions similar to those of real operation. Data was processed with a Kalman filter, a Hann window function application, and frequency analysis via Fast Fourier Transform (FFT). The first and second wing bending natural frequencies were identified at 12.3 Hz and 17.5 Hz, respectively, as well as a significant component around 23 Hz, which is a subharmonic of the propulsion system excitation frequency near 45 Hz. The results indicate that the highest vibration amplitudes are concentrated at the wingtips and near the engine. The proposed system offers an accessible and flexible alternative to commercial equipment, integrating acquisition, processing, and real-time visualization. Moreover, its implementation facilitates the early detection of structural anomalies and improves the reliability and safety of UAVs. Full article

This paper presents an integrated study on the design, simulation, manufacturing, and experimental testing of a three-blade tritoroidal propeller compared to a conventional two-blade configuration for small UAVs. The aerodynamic analysis was performed in ANSYS Fluent 2022 R1 using the k–ω SST turbulence model at 6000 rpm, while structural integrity was assessed through FEM simulations in ANSYS Mechanical 2022 R1. Both propellers were fabricated via SLA additive manufacturing using Rigid 4000 resin and evaluated on an RCbenchmark 1585 test stand. The CFD results revealed smoother flow attachment and reduced tip vortex intensity for the tritoroidal geometry, while FEM analyses confirmed lower deformation and a more uniform stress distribution. Experimental tests showed that the tritoroidal propeller produces thrust comparable to the conventional one (within 1%) but at a 58% higher torque, resulting in slightly lower efficiency. However, vibration amplitude decreased by up to 70%, and the SPL was reduced by 0.1–6.2 dB at low and moderate speeds. These results validate the tritoroidal concept as a structurally robust and acoustically efficient alternative, with strong potential for optimization in low-noise UAV propulsion systems. Full article

Running shoe midsoles are designed to attenuate impact forces while maintaining or improving performance. However, the literature is equivocal, likely due to measurement systems, whereas in vitro testing is conclusively favourable. This study investigated three densities of ATPU foam, comparing in vitro mechanical properties with in vivo plantar force spectral characteristics derived from individualised pressure distributions during treadmill running at varied speeds. In vitro results of slab foam and shoes showed strong positive relationships between impact variables normalised to total impact energy and foam density (r² > 0.90), and strong negative relationships for time-domain variables normalised to deformation (mm) as density increased (r² > 0.89). During running, lower midsole density increased ground contact time across speeds (p = 0.041), while spatially resolved high-frequency PSD and peak impact force both decreased (p = 0.043; p = 0.030). However, there were no differences between total vertical force and midsole density (p = 0.232). Relationships between in vitro Peak G and high-frequency PSD were strong across all speeds (r² = 0.63–0.91). Conversely, reducing midsole density increased active peak force across speeds (p = 0.003), which was strongly related to in vitro energy return (r² > 0.89). Therefore, plantar force spectra and spatially resolved analyses demonstrate how foam density properties translate from in vitro to in vivo treadmill running, with lower-density foam improving impact attenuation but elevating propulsive forces. Future work needs to verify this in an outdoor setting. Full article

Nowadays, the automotive industry is primarily driven by the CO₂ policy that targets net zero carbon emissions by 2035 from passenger cars and commercial vehicles. The main path to achieve this goal is the implementation of electric powertrains with the energy stored in batteries, as the case for battery electric vehicles (BEV). However, this technology still faces some difficulties in terms of energy density, overall weight, charging time, and vehicle autonomy. From the other point of view, fuel cell electric vehicles (FCEV) offer the same advantages as BEV in terms of CO₂ reduction, providing better autonomy and lower refueling time. The energy demand by the electric powertrain strongly depends on the vehicle driving conditions as it directly affects energy consumption. In that context, the article aims to study the electrical energy demand of an ultra-energy efficient vehicle intended for a Shell eco-marathon competition in order to minimize hydrogen consumption. The study was carried out over a single lap on the racing track in Nogaro, France while applying the race rules from the competition in 2023. It includes a numerical evaluation of the vehicle resistance forces in different driving strategies and experimental validation on the propulsion test bench. Full article

Wind-assisted ship propulsion (WASP) has gained considerable interest as a means of reducing fuel consumption and Greenhouse Gas (GHG) emissions, with further benefits when combined with weather-optimized routing. This study employs and extends a National Technical University of Athens (NTUA) weather-routing optimization tool to more realistically assess WASP performance through integrated modeling. The original tool minimized fuel consumption using forecasted weather data and a physics-based performance model. A previous extension to account for the WASP effect introduced a 1-Degree Of Freedom (DOF) model that accounted only for longitudinal hydrodynamic and aerodynamic forces, estimating the reduced main-engine power required to maintain speed in given conditions. The current study incorporates a 3-DOF model that includes side forces and yaw moments, capturing resulting drift and rudder deflection effects. A Kamsarmax bulk carrier equipped with suction sails served as the case study. Initial simulations across various operating and weather conditions compared the two models. The 1-DOF model predicted fuel-saving potential up to 26% for the tested apparent wind speed and the range of possible headings, whereas the 3-DOF model indicated that transverse effects reduce WASP benefits by 2–7%. Differences in Main Engine (ME) power estimates between the two models reached up to 7% Maximum Continuous Rating (MCR) depending on the speed of wind. The study then applied both models within a weather-routing optimization framework to assess whether the optimal routes produced by each model differ and to quantify performance losses. It was found that the revised optimal route derived from the 3-DOF model improved total Fuel Oil Consumption (FOC) savings by 1.25% compared with the route optimized using the 1-DOF model when both were evaluated with the 3-DOF model. Full article

Accurately predicting the full-scale performance of submarines is challenging due to their complex propulsor systems and limited sea-trial information. This study investigated a full-scale extrapolation method from model tests for a submarine pumpjet propulsor, as a reliable method has not been established. Three extrapolation methods from ITTC reports were reviewed and applied to the pumpjet propulsor of the SUBOFF submarine, then compared with full-scale CFD results. Among the reviewed methods (Methods 1 to 3), Method 3, which separates the duct and stator as appendages of the hull and includes the entire pumpjet in the POW test but uses only the rotor’s force, was the most reasonable, but showed significant differences from the calculated results, especially in the $P_D$. This study proposed a modified Method 3, improving it by adopting the continuity theory to predict the oncoming velocity of a rotor and by applying a correction factor for the drag of the duct and stator. The modified PJP extrapolation method 3 showed excellent agreement with the full-scale CFD analysis results across all propulsion coefficients, with a minimal error of 0.45% for $P_D$. Despite the structural differences in PJPs, such as stators and longer ducts, velocity changes are dominated by the duct’s internal area. Therefore, the proposed extrapolation method is equally applicable to general ducted propellers. Full article

Background: The traditional formula Liqi Yangyin (LQYY) has shown clinical and preclinical efficacy for depression with constipation, yet its molecular mechanisms remain incompletely defined. This study aimed to elucidate its mechanisms using an integrative approach. Methods: Constituents of LQYY were profiled by UPLC-MS/MS and integrated with network pharmacology and molecular docking to identify brain-accessible components and putative targets. A chronic unpredictable mild stress (CUMS) model was used for experimental validation. Outcomes included behavioral tests (sucrose preference test, open field test, and forced swimming test), gastrointestinal indices, including fecal water content, time of first black stool, and intestinal propulsion rate, histopathology of the prefrontal cortex (PFC) and colon, TUNEL staining, NeuN immunofluorescence, Western blotting, and qRT-PCR. Results: LQYY attenuated CUMS-induced weight loss and depressive-like behaviors and improved intestinal transit metrics. It reduced neuronal apoptosis in the PFC and ameliorated colonic injury. Mechanistically, docking and enrichment analyses highlighted hub targets (STAT3, AKT1, ESR1, IL-6, TNF, TP53) and the JAK/STAT pathway. In vivo, LQYY decreased IL-6, TNF-α, ESR1, TP53, and STAT3, and increased AKT1 in the PFC and colon; it also reduced the TUNEL-positive rate and restored NeuN labeling, upregulated Bcl-2, and downregulated p-JAK2/JAK2 and p-STAT3/STAT3 ratios, and the expression of Bax and cleaved-caspase-3 in the PFC, consistent with the suppression of pro-inflammatory and apoptotic signaling. Conclusions: LQYY exerts antidepressant and pro-motility effects in CUMS mice by modulating JAK2/STAT3-centered networks and inhibiting neuronal apoptosis, thus supporting a multi-component, multi-target strategy for treating depression with constipation, and providing a defined molecular hypothesis for future investigation. Full article

Amphibious light sport aircraft (LSA) combine the versatility of land and water operations but suffer aerodynamic penalties from their inherent design requirements, limiting cruise performance. This study investigates two drag reduction features for a proposed high-performance amphibious LSA developed by Altavia Aerospace. The concept targets a cruise speed of 140 KTAS, using retractable wingtip pontoons and a novel retractable hull step fairing. A 1/5-scale flying model was built and flight tested to assess the aerodynamic benefits of these features and evaluate sub-scale flight testing as a tool for drag measurement. Estimated propulsive power and GPS-based speed data corrected for wind were used to compute an estimated 17% reduction in drag coefficient by retracting the pontoons. The hull step fairing showed no measurable gains, likely due to inconsistent battery voltage, despite literature indicating potential 5% drag savings. Drag measurement precision of 7–9% was achieved using the power-based method, with potential precision better than 3% achievable if the designed thrust data system were fully validated and an autopilot integrated. A performance estimation for Altavia Aerospace’s concept predicts a cruise speed of 134 KTAS at 10,000 ft. Achieving the target of 140 KTAS may require further aerodynamic refinement, with investigation of a tandem seating configuration to reduce frontal area recommended. The study provides an initial drag assessment of retractable wingtip pontoons and demonstrates the potential of sub-scale flight testing for comparative drag analysis—two novel contributions to the field. Full article

Ammonia serves as a critical medium for hydrogen storage and energy transportation, making the development of efficient ammonia cracking technologies essential for advancing hydrogen energy applications. Plasma-assisted ammonia cracking has emerged as a promising approach for clean energy conversion, leveraging non-thermal plasma to effectively decompose ammonia into hydrogen and nitrogen. Compared to conventional thermal catalytic cracking, this method offers several advantages, including rapid startup and response, operational flexibility, and the ability to operate under low-temperature and atmospheric pressure conditions. This study presents a novel high-pressure plasma reactor designed to overcome the high-energy barriers associated with conventional methods. Through systematic optimization of discharge parameters, reactor configuration, and catalyst integration, significant improvements in both ammonia conversion efficiency and energy utilization have been achieved. Experimental results demonstrate that increased discharge power and reduced ammonia flow rate enhance cracking performance. In the absence of a catalyst, conversion efficiency initially increases with pressure but subsequently decreases at higher pressures. However, the incorporation of a catalyst markedly improves overall performance across all tested conditions. These advancements support the practical implementation of ammonia-based systems for distributed hydrogen supply and clean propulsion technologies. Full article