Search Results (1,431)

Accurate target localization via matching real-time UAV images with reference satellite imagery is essential for autonomous environmental perception. Nonetheless, operational constraints and weather conditions often necessitate oblique photography. This large-tilt mode causes significant perspective and radiometric distortions, resulting in a substantial domain gap between UAV and vertical satellite imagery. The scarcity of datasets featuring extreme viewpoint shifts and fine-grained ground-truth labels hinders the validation of image matching algorithms in multi-tilt-angle environments. To address this issue, we introduce the multiple-tilt-angle dataset (MTA-Dataset), containing 1892 UAV images with tilt angles spanning $\left[0°,\right.\left.90°\right)$ and flight altitudes up to 300 m, supported by high-precision five-point manual annotations. Based on this benchmark, we evaluate state-of-the-art matching algorithms and propose a spatial-resolution-based cropping strategy. Experimental results demonstrate that, as the UAV tilt angle increases within the range of $\left[0°,\right.\left.90°\right)$, although the expanding field of view provides richer contextual information, the localization errors of all methods increase significantly and matching precision drops sharply due to severe geometric distortions in far-field regions and interference from redundant background information, with performance deteriorating most drastically in the $\left[50°,\right.\left.90°\right)$ range. With the integration of our strategy, the average matching localization errors of SuperPoint + SuperGlue baseline for UAV images within the tilt-angle ranges of $\left[50°,\right.\left.60°\right)$, $\left[60°,\right.\left.70°\right)$, $\left[70°,\right.\left.80°\right)$, and $\left[80°,\right.\left.90°\right)$ are reduced by 33.49 m, 37.86 m, 98.3 m, and 109.95 m, respectively. Our study provides a more comprehensive evaluation framework for robust UAV–satellite image matching algorithms in multi-tilt-angle scenarios. Full article

In the optical fiber Fabry–Perot (FP) multi-dimensional acceleration sensing system, multi-dimensional acceleration measurement is realized based on a single optical path, resulting in the existence of multi-channel interference signals in the spectrum, and the traditional cavity length demodulation algorithm cannot achieve efficient separation of aliasing signals and high-precision demodulation of FP cavity length. To solve this problem, an adaptive filtering–multiple peaks–cooperative least squares algorithm (AF-MP-LS) is proposed for cavity length demodulation of optical fiber FP multi-dimensional accelerometer. The adaptive Gaussian filter is used to dynamically adjust the parameters according to the frequency difference in the aliasing optical signal, and the interference spectra of each channel are efficiently separated. The multiple peaks–least squares method is used to demodulate the separated signals, improve the demodulation resolution, and solve the problem of limited dynamic range of spectral signals. Furthermore, based on the multiplexing structure, a complementary correction method utilizing ‘triple-interferometric’ information—derived from the FP cavities and the auxiliary Michelson interference component—is proposed to improve the demodulation accuracy and stability of the system. The performance of the proposed method was verified through simulations, multi-angle vibration experiments and comparative algorithm analysis. The experimental results show that this algorithm can accurately demodulate multi-dimensional signals under different tilt angles of vibration excitation. Particularly, after compensating for the triple interference information, the mean square error (MSE) of the demodulated acceleration decreased by 0.0044 g, and the accuracy increased by 70.9% compared to before correction. Full article

UAV-based rice direct seeding offers high operational efficiency and reduced labor demand, yet seed distribution uniformity remains a major limitation for centrifugal spreading devices. This study aims to design and optimize a novel centrifugal drone rice direct seeding device to improve seed lateral distribution uniformity. In this study, a centrifugal drone rice direct seeding device was developed with a concave perforated disc and double-arc seed-pushing blades to regulate seed motion and improve lateral distribution uniformity. Discrete element method (DEM) simulations were conducted to examine the effects of disc tilt angle, blade type, and blade number. Single-factor and response-surface simulation results identified an optimal parameter combination of a 29.0° disc tilt angle, double-arc blades with a 110° arc angle, and six blades. Based on these results, the disc structure was further refined, and the simulated lateral coefficient of variation (CV) of seed distribution reached 18.22%. Bench tests yielded a minimum CV of 16.34%, an average CV of 19.36%, and a total discharge coefficient of variation of 0.276%, which agrees with the simulation outcomes and supports the validity of the DEM model. Overall, the proposed device demonstrates improved seeding uniformity and meets agronomic requirements for rice cultivation, offering farmers a high-efficiency planting solution and providing UAV manufacturers with a validated double-arc disc design for equipment optimization. Full article

Background: Awkward postures are among the most prevalent ergonomic risk factors in occupational environments, including industrial settings. Conventional ergonomic risk assessments rarely address the relationship between sustained awkward postures and alterations in sagittal spinal curvatures. The primary objective of this study was to analyze the association between sagittal spinal posture parameters and exposure to awkward postures in male workers from the mattress manufacturing industry. The potential confounding effects of age, job seniority, body mass index (BMI), and physical activity level were also examined. Methods: An analytical cross-sectional study was conducted. Data collected included age, job seniority, anthropometric variables, and physical activity level. Sagittal spinal posture parameters—head alignment, thoracic kyphotic curvature, lumbar lordotic curvature, and pelvic tilt—were assessed using photogrammetry. Exposure to awkward postures was recorded according to occupational health surveillance criteria. Results: A total of 116 male workers were randomly selected. BMI showed a significant negative association with head alignment (p = 0.001), with a medium effect size (η² = 0.090). Lower BMI values (β = −0.517) were observed in association with a more posterior head position. In addition, participants not exposed to awkward postures presented, on average, a 6.479° lower thoracic kyphotic curvature angle compared with exposed workers (p = 0.050), indicating a greater kyphotic curvature among those exposed. Conclusions: In this sample, lower BMI was associated with a more posterior head position and improved alignment with the upper trunk. Furthermore, exposure to awkward postures was related to a modest increase in thoracic kyphotic curvature, suggesting postural adaptations to occupational demands. Full article

Hybrid photovoltaic (PV) systems augmented by wind-induced energy contributions can improve energy reliability under variable atmospheric conditions. However, their performance remains highly sensitive to site-specific weather patterns, panel orientation, and system parameter selection. This study presents a computational optimization framework based on Differential Evolution (DE) to enhance the combined energy output of a hybrid PV–wind system using high-resolution reanalysis data. Hourly solar irradiance from NASA POWER and near-surface wind components from ERA5 were processed through a unified data ingestion and preprocessing pipeline supporting GRIB and NetCDF formats to evaluate seasonal and annual energy production. The optimization jointly adjusted PV tilt angle, effective PV area scaling, and a wind energy scaling parameter to maximize total energy yield. Case studies for San Antonio (TX), Denver (CO), and Albuquerque (NM) demonstrate seasonal energy gains of 36–57% and annual improvements of 36.9–56.2% relative to baseline fixed-parameter configurations. The results indicate that evolutionary optimization combined with reanalysis-driven energy modeling provides a robust and scalable approach for improving hybrid renewable energy performance across diverse climatic regions. Full article

The aerodynamic behavior of small-scale UAV propellers operating under non-axial inflow conditions poses a significant prediction challenge due to the presence of strong azimuthal asymmetries, inherently unsteady flow phenomena, and Reynolds number effects that dominate forward flight conditions. Although numerical models based on the Moving Reference Frame (MRF) formulation combined with steady RANS solvers are widely used in engineering practice because of their low computational cost, the precise limits of their applicability in crossflow configurations remain poorly defined. This work conducts a comprehensive numerical investigation that systematically compares steady RANS–MRF predictions against time-accurate URANS simulations across a wide range of advanced ratios and rotor tilt angles. Rigorous validation of the computational framework against experimental data in axial and near-axial regimes demonstrates excellent agreement, with deviations below 5% in propulsive efficiency. The results clearly identify the operational envelope within which MRF-based steady models remain valid under non-axial inflow. In particular, the steady approach exhibits robust performance for low-to-moderate advance ratios, where global errors in thrust and power remain below 10% for $\mu =0.40$. However, the fidelity of the method deteriorates sharply under extreme edgewise-flight conditions ($\mu =0.70)$, in which the crossflow component dominates the aerodynamic field, the “frozen-rotor” assumption progressively loses mathematical consistency, and the solver may converge toward steady solutions that no longer represent a physically meaningful flow state. The URANS analysis further reveals two critical phenomena that cannot be captured by steady-state models. First, at high advance ratios, the retreating blade encounters an extensive region of reverse flow, which induces negative sectional thrust and strongly anharmonic load waveforms. This behavior has direct implications for structural design: the peak-to-peak amplitude of thrust oscillation in edgewise flight can exceed the mean thrust level, implying extreme cyclic loading and a high risk of high-cycle fatigue. Second, the simulations quantify the emergence of off-axis parasitic moments (pitching and rolling), which are negligible in vertical flight but reach magnitudes comparable to the total aerodynamic torque in forward-flight conditions. Taken together, these findings highlight the need for a hybrid-fidelity strategy in UAV propulsion analysis: employing steady RANS–MRF within the validated domain for energetic assessments, while relying on time-accurate URANS for mandatory evaluation of structural loading, vibration, and control logic in critical high-speed regimes. Full article

Background/Objectives: The benefit of patellar resurfacing (PR) in total knee arthroplasty (TKA) remains controversial. No previous study has examined the impact of PR in valgus osteoarthritis (OA) with compromised patellofemoral joint (PFJ) status. Methods: We retrospectively reviewed 2250 primary TKAs performed between 2011 and 2025. Among 152 valgus OA cases, 87 had compromised PFJ status, defined as Outerbridge grade 3–4 chondral damage or patellar tilt >10° on Merchant-view radiographs. Two surgeons with identical protocols operated during overlapping periods; one typically performed PR (n = 47) and the other did not (n = 40). Primary outcomes included the American Knee Society (AKS) score and Kujala Anterior Knee Pain Scale. Secondary outcomes included radiologic measures (HKA angle, patellar tilt, and lateral patella shift) and patellar-related complications (crepitus, fracture, subluxation, and maltracking). Results: At a mean follow-up of 7.1 years in the non-PR group and 6.5 years in the PR group, no significant differences were observed between groups in KSS function scores (non-PR 92.4 ± 3.5 vs. PR 93.0 ± 4.6, p = 0.54) or Kujala scores (non-PR 76.9 ± 3.5 vs. PR 77.7 ± 4.2, p = 0.33). Both patellar tilt and lateral patella shift showed slight postoperative reductions, but no significant difference was observed between groups (patellar tilt: non-PR 5.4° ± 0.8° vs. PR 5.7° ± 0.6°, p = 0.11; lateral patella shift: non-PR 2.4 ± 0.6 mm vs. PR 2.3 ± 0.7 mm, p = 0.75). Patellar-related complications were infrequent and showed no significant differences. Conclusions: Overall, PR did not demonstrate superior outcomes compared with non-PR in valgus OA patients with compromised PFJ status at mid-term follow-up. Full article

In response to the problems of poor operating stability and easy tipping of small agricultural machinery under the complex terrain of hilly and mountainous areas, this study designed a tracked mobile platform suitable for hilly and mountainous areas and equipped with an omnidirectional leveling function. The omnidirectional leveling system adopted an innovative coordinated leveling scheme with four servo-electric cylinders of “dual lateral and dual longitudinal” structure. Integrated with dual-axis tilt sensors and a PLC control system, the system enabled decoupled leveling in both the lateral and longitudinal directions. Dynamic simulations of the platform’s leveling process under typical working conditions were performed using ADAMS. The simulation results verified the feasibility of the omnidirectional leveling system. Field tests on slopes in hilly and mountainous areas demonstrated that the omnidirectional leveling system achieves rapid leveling on steep slopes within 5–6 s. After leveling, the average fuselage inclination angle was stabilized within 2°, with a standard deviation of less than 3.4°. This study provided a reliable technical solution and design reference for agricultural machinery manufacturers, while offering users a safer and more efficient platform for operations in complex mountainous areas, significantly reducing the risk of overturning. Full article

The swimming tilt angle of fish is one of the key factors influencing the estimation of target strength (TS). Therefore, understanding how TS varies with changes in swimming tilt angle is essential. This study employed the Kirchhoff-ray-mode (KRM) model to estimate TS and examine variations in the swimming tilt angle of sardines under flowing water conditions. Swimming tilt angles were measured at flow velocities of 30 and 50 cm/s. The KRM model was utilized to estimate TS for 17 sardine samples (total length: 13.0–24.6 cm) across four frequency bands (38, 70, 120, and 200 kHz). At a flow velocity of 30 cm/s, sardines swimming against the flow exhibited a mean swimming tilt angle of 4.0° ± 14.0°, with normalized mean TS_cm values of −64.7 dB at 38 kHz, −65.7 dB at 70 kHz, −66.4 dB at 120 kHz, and −66.9 dB at 200 kHz. At a flow velocity of 50 cm/s, sardines swimming against the flow showed a mean swimming tilt angle of −2.2° ± 10.1°, with normalized mean TS_cm values of −62.9 dB at 38 kHz, −63.7 dB at 70 kHz, −64.3 dB at 120 kHz, and −64.8 dB at 200 kHz. Considering the results of this study and the swimming behavior of sardines against the flow, the target strength of sardines swimming with the flow may be of less concern. Therefore, when conducting acoustic surveys, it is more efficient to account for flow velocity conditions rather than swimming direction. Full article

Background: Prolonged tablet use for digital handwriting is increasingly common in educational settings, yet optimal ergonomic positioning remains unclear. This exploratory, cross-sectional study examined how tablet tilt angle affects hand and wrist muscle activation patterns during digital handwriting. Methods: This cross-sectional study recruited fifteen healthy university students (age 22.3 ± 2.2 years) who completed standardized writing tasks at three tablet tilt angles (0°, 20°, 60°). Surface electromyography recorded activation from four muscles responsible for the dynamic tripod grip: abductor pollicis brevis (APB), flexor pollicis longus (FPL), flexor digitorum superficialis (FDS), and extensor carpi ulnaris (ECU). Results: Significant differences in muscle activation were observed across angles (p < 0.05) for three muscles. APB activation was higher at 0° (18.68 ± 11.88% MVIC) and 20° (18.72 ± 12.13% MVIC) than at 60° (14.67 ± 10.38% MVIC), while FDS use decreased from 0° (10.98 ± 4.80% MVIC) to 60° (6.43 ± 3.14% MVIC). Conversely, ECU use increased from 0° (11.76 ± 6.96% MVIC) to 60° (16.15 ± 8.02% MVIC). FPL showed no significant differences. Conclusions: Tablet tilt angle substantially affects neuromuscular activation patterns during digital handwriting. In healthy young adults, these findings may help inform preventive ergonomic strategies for prolonged tablet handwriting; however, direct clinical extrapolation requires validation in clinical and more diverse populations. Full article

Vertical takeoff and landing (VTOL) aircraft must balance the conflicting demands of hover and cruise performance. To address the lack of integrated design methodologies in the existing literature, a unified design-optimization framework is presented, coupling high-fidelity CFD simulations with a genetic algorithm to refine a gas-driven thrust fan (GDTF) VTOL nacelle. Key geometric parameters—fan pressure ratio pressure ratio, fan tilt, nozzle angle, tail inclination, and tip shape—were varied in a comprehensive parametric study to maximize lift-to-drag ratio and maintain constant mass flow. The optimization reveals that a nearly horizontal fan axis maximizes cruise efficiency (${\displaystyle \frac{L}{D}}\approx 2.98$), a nozzle angle of about $22°$ offers the best lift-vs-drag compromise during transition, and refining the tip geometry yields a $10$–$20\%$ performance boost. To validate the numerical predictions, a 1:1.05 scale VTOL nacelle model (fan diameter $D = 0.42 \mathrm{m}$) was fabricated and tested in a low-speed wind tunnel at $52 {\displaystyle \frac{\mathrm{m}}{\mathrm{s}}}$ ($Re \approx 5 \times {10}^6$, turbulence intensity ≈ 2%). Total-pressure probes at the intake exit plane and static taps along the inner cowl wall provided detailed pressure distributions, from which exit Mach number, velocity and the equivalent flow coefficient φ (≈0.68 under test conditions) were derived. Oil-flow visualization on the external cowl surface confirmed smooth, attached streamlines with no large separation bubbles. This dual validation combining surface-flow visualization and pressure-recovery mapping demonstrates the accuracy and reliability of the proposed simulation methodology. By successfully bridging detailed CFD with genetic-algorithm-driven design and validating against comprehensive wind-tunnel measurements, this integrated approach paves the way for next-generation VTOL configurations with longer range and lower fuel consumption. Full article

A significant proportion of photovoltaic power plant designs utilize fixed tilt angle systems. However, these designs exhibit inherent limitations that can be mitigated through the application of the methodology proposed in this study. The methodology used includes the following steps: (i) maximization of the total area of the photovoltaic field; (ii) calculation of the operating periods of the proposed mounting system and proposed improvement strategies; (iii) calculation of the effective area of the photovoltaic field; and (iv) maximization of effective annual energy incident on the photovoltaic field. The analysis has focused on the Sigena I$PV$ power plant (Spain). The proposed design is compared with the actual design of the Sigena I$PV$ power plant from different perspectives. The principal conclusions derived from this study are as follows: (i) The proposed configuration increases the photovoltaic field surface area by $10.63\%$ and yields a $12.07\%$ higher annual energy production relative to the existing layout. (ii) The current mounting system at the Sigena I$PV$ power plant experiences wind loads that are $78.23\%$ greater than those associated with the proposed design. (iii) Owing to the increased number of mounting structures required, the proposed layout results in a $14.03\%$ rise in mounting-system costs. (iv) The proposed design achieves a marginal improvement in the levelized cost of electricity (LCOE), with a reduction of $0.42\%$ compared to the reference case. (v) Under the constraint of a constant number of mounting systems, the proposed design would reduce land requirements by $12\%$. Overall, these results indicate that the proposed configuration delivers superior techno-economic performance. Full article

To address the challenges of the lack of specialized machinery adapted to traditional agronomic requirements, high labor intensity, and low efficiency in the planting of Ligusticum chuanxiong stalk segments (commonly known as Chuanxiong seed stalk or Lingzhong), a planting mechanism for the cutting of Chuanxiong seed stalk was developed in accordance with traditional agronomic requirements. A kinematic model of the gripping point was established, from which a plant spacing formula was derived. Based on the zero-speed planting principle, a cuttage planting scheme for Chuanxiong seed stalks was proposed, in which the gripper trajectory as well as the forward-tilt x_t and correction x_c were defined, and the decisive role of installation height on planting depth and the influence of driven-sprocket motion parameters on planting uprightness were elucidated. A 3D model and a DEM-MBD coupled simulation model were constructed to analyze planter–soil–seed interaction. A three-factor, three-level Box–Behnken experiment was conducted, and a response surface model was built and optimized using ‘Design-Expert’ software. The optimal parameters were a driven sprocket angular velocity of 0.654 rad/s, a rotation radius of 100.787 mm, and a release angle of 90.647°, yielding an average planting uprightness of 85.264°, with the corresponding x_t and x_c of 5.18 mm and 2.69 mm, respectively; the factor influence ranked as angular velocity > rotation radius > release angle. Seed–soil interaction analysis verified the mechanism’s feasibility and the accuracy of the theoretical models. Field tests showed average qualification rates of 87.13% for plant spacing, 96.01% for planting depth, and 90.41% for uprightness, with corresponding coefficients of variation of 4.37%, 2.95%, and 3.73%, indicating stable and reliable field performance. Full article

This paper reports magnetic microscopy using high-sensitivity room-temperature tunnel magnetoresistance (TMR) devices for thin geological sections. The sensitivity region of the TMR sensor has dimensions of 178 µm (L) × 0.1 µm (W) × 100 µm (H), consisting of two TMR devices. Magnetic images were obtained for a vertically magnetized Hawaii basalt thin section in two sensor configurations, with the sensor length aligned parallel to the X- (lift-off = 174 μm) and Y-axes (lift-off = 200 μm), without introducing anisotropic distortion in the magnetic images. Although the magnetic images obtained with a scanning SQUID microscope (SSM) were similar, slight discrepancies were observed in the high-spatial-resolution region. A magnetic point source (50 μm × 50 μm) with a perpendicular magnetization film was prepared for evaluation. The SSM measurements showed a clear magnetic dipole at an angle of approximately 1° from the vertical direction. The FWHMs for both the SSM and TMR sensors increased linearly with lift-off. However, the peak magnetic fields, magnetic moments, and dipole tilts of the TMR sensor were significantly larger than those of the SSM sensor. This discrepancy may be due to the vertical extent of the active region of the TMR sensor, as well as due to sensor noise and drift. Full article

Analysis of the rock mining process using an experimental cutterhead employing milling and chipping processes is the subject of this article. Based on a bibliographic review of the energy consumption of rock mining and wear and tear of various mining tools, a stand test programme for the rock mining process using the experimental cutterhead was developed. Based on the following measured parameters—hydraulic motor supply pressure and displacement, hydraulic motor shaft speed, cutterhead web depth, cutterhead tilt angle relative to the mining direction, feed pressure in the advance cylinder, duration of each mining stages, cutterhead travel distance, angle of the cutterhead chipping part, and known physical and strength parameters of the mined rock—the following parameters were determined: cutterhead advance speed, cutterhead advancing force, cutterhead driving motor power, advancing cylinder power, and the parameters of energy consumption in the mining process, including specific energy of mining, specific energy of feed, and specific energy of cutting. The effects of cutterhead advance speed and tilt angle on the specific mining energy and the grain size distribution of the mined rock were determined. Analysis of test results enabled the development of the procedure for selecting the most favourable parameters of rock mining technology when using an experimental cutterhead. Full article