Search Results (1,355)

Background: This paper concerns the study of forces acting on the upper ankle joint of a human in static and quasi-dynamic positions. This paper aimed to determine the pressure forces on the axis of the upper ankle joint in the position of the body tilting forward and backward, as well as in a neutral position. Methods: A model with designated centres of gravity (including and excluding the weight of the platform imitating the foot) and the point of gravity imitating the proximal insertion of the triceps surae and tibialis anterior muscles was developed for this study. The forces and the weight of the tilted object were measured using dynamometers. A method for determining the arms of gravitational forces and the angle of inclination of an object is presented. The function describing the distribution of gravitational loading along its tilting part was described. Next, all measurements and calculations were referred to the human body. Results: Measurements of muscle force, body gravity, the arms of these forces, and the angles of the object’s inclination on the axis of rotation are presented. A methodology for determining the pressure force on the human upper ankle joint axis is presented. The distribution of the value of the pressure force and its components from the maximal forward, through the vertical body position, up to the maximal backward position of the body tilt, is provided. Conclusions: The ankle joint pressure force is the vector sum of the force of gravity and the force of the muscle counteracting the body tilt. This force is the smallest in the vertical body position and increases with the body tilt. It reaches 5.23 times the weight of the tilting part of the body when the body is tilted to its maximum forward position, and 3.57 times the weight when the body tilts backward. Regardless of the direction of the body tilt, the joint pressure vector always runs through the axis of the upper ankle joint. Full article

Traditional manufacturing methods struggle to incorporate complex internal configurations within structures, thus restricting the potential for enhancing the strength of offshore structures through internal design. However, the advent of 3D printing technology presents innovative solutions to this challenge. Previous research has investigated the use of 3D printing to integrate lattice-like structures within conventional frameworks to achieve lightweight designs. Building upon this foundation, this paper models an embedded structure and other marine structures subjected to similar loads using simplified models and conducts a thorough investigation into their mechanical properties. Specifically, it examines the effects of the 3D-printed infill structure, infill rate, and tilt angle of printed specimens on the mechanical properties of 3D-printed components. The goal is to identify the optimal parameter combinations that ensure structural strength while also achieving a lightweight design and a secondary lightweight design for the embedded structure. This paper concludes, from tensile, torsional, and compressive experiments, that honeycomb infill structures, with specimens printed at an inclination angle of 0°, exhibit superior performance across all properties. Additionally, the bonding between the layers of the printed parts is identified as a key factor influencing the tensile and torsional properties. While increasing the infill rate can significantly improve the overall mechanical properties of specimens, it also results in a corresponding reduction in the lightweighting index. Full article

Background/Objectives: Knee osteoarthritis (KOA) is multifactorial, and longitudinal evidence isolating early predictors remains limited. We investigated predictors of incident KOA in community-dwelling older adult Japanese women. Methods: We analyzed 191 knees from 105 women aged ≥50 years (baseline Kellgren–Lawrence (KL) grade 0–1) and followed them for 8 years. Incident KOA was defined as KL ≥ 2 at the 8-year follow-up. Baseline measures included body mass index (BMI), physical function (one-leg stance, functional reach), Geriatric Locomotive Function Scale (GLFS-25), EuroQol 5-Dimension (EQ-5D) questionnaire, standing lateral whole-spine radiographs (sagittal spinopelvic parameters), and standing full-length anteroposterior (AP) lower-limb radiographs (coronal alignment parameters). Incident KOA was defined as KL ≥ 2 at follow-up. Group comparisons, multivariable logistic regression, and receiver operating characteristic analyses were conducted. Results: Incident KOA occurred in 58/191 knees (mean participant age 69.3 ± 6.1 years). Compared with non-incident knees, incident knees had higher BMI (23.8 vs. 21.1 kg/m²), higher GLFS-25, greater pelvic tilt and pelvic incidence minus lumbar lordosis (PI–LL) mismatch (11.5° vs. 5.3°), and lower EQ-5D, medial proximal tibial angle, and joint line obliquity. BMI was the strongest single predictor (area under the curve [AUC] 0.753). PI–LL mismatch showed limited standalone discrimination (AUC 0.596) but improved discrimination when combined with BMI (AUC 0.803). Conclusions: BMI was the primary predictor of incident KOA in this cohort. PI–LL mismatch, while not strongly discriminative alone, acted as a complementary marker consistent with sagittal-alignment-related mechanical stress. Results suggest that early screening and prevention should prioritize weight management, using spinopelvic parameters to refine risk stratification. Full article

This work is motivated by the need to enhance efficiency and radiation resistance and reduce weight in high-performance photovoltaic devices, with applications spanning both terrestrial and space environments. Metamorphic buffers are key enablers for reducing defect formation in lattice-mismatched structures, which are among the most widespread technologies for high-efficiency photovoltaic energy conversion. Although many systems have been created, absolute certainty about the effective relaxation mechanism remains unattained. In this work, MOVPE-grown step-graded buffers with variable In content were obtained on Ge substrates and investigated to identify the critical thresholds that govern strain relaxation and defect formation. The results show that the buffers are fully strained when the In top-layer content is <6.0%, while a degree of relaxation in the entire structure appears when the In top-layer content is >6.0%. In addition, the relaxation phenomenon is paralleled by the formation of a tilt angle between the layers and the substrate. We also found evidence that the appearance of relaxation is not limited to the upper layer but is presented by the structure as a whole. The effects of Te doping inside the InGaAs layers were also investigated: Te does not influence the structure of the crystal, but it introduces a Burstein–Moss blue shift in the photoluminescence energy of about 20 meV. Eventually, to reduce defect formation with the goal of achieving high-efficiency photovoltaic devices, a thick layer with a lower In content was grown onto the overshoot material (In_0.12Ga_0.88As). The results obtained confirm the high quality of the buffers and unveil the critical points, which are responsible for the most important changes in the buffer architecture and should be considered in future material engineering. The results provide valuable insights for the design of high-performance, sustainable photovoltaic devices and contribute to the advancement of III–V semiconductor integration on Ge substrates. Full article

Transmission towers located above mined-out areas may experience collapse or instability due to mining-induced ground subsidence and deformation, which poses significant risks to the safe operation of power transmission lines. To clearly evaluate the deformation resistance and failure threshold of transmission towers under mining-induced ground deformation, this article examines a typical 220 kV self-supporting transmission tower located in a mining area of Northern Shaanxi Province through a detailed three-dimensional finite element model constructed and simulated using ANSYS 2022. The mechanical response and failure process of the tower structure were systematically simulated under five typical deformation conditions: tilt, horizontal compression, horizontal tension, tilt–compression, and tilt–tension. The results indicate that under individual deformation conditions, the critical deformation values of the tower are 35 mm/m for tilt, 10 mm/m for horizontal compression, and 8 mm/m for horizontal tension, demonstrating that the structure is most sensitive to horizontal tensile deformation. Under combined deformation conditions, the critical deformation values for the combined tilt–compression and tilt–tension conditions exhibited a marked reduction, reaching 8 mm/m and 6 mm/m. Compared to individual deformation conditions, transmission towers demonstrate a significantly higher susceptibility to structural failure under combined deformation conditions. The displacement at the tower head and the tower tilt angle exhibit a linear positive correlation with the values of ground surface deformation. Under individual deformation conditions, the tilt of the tower was approximately 0.903 times the tilt deformation value and 0.089 times the values of horizontal compression and tension deformation, indicating that tilt deformation exerts a more pronounced influence on the inclination of the tower. Under combined deformation conditions, the tilt of the tower reached approximately 0.981 times that of the tilt–compression deformation value and 0.829 times that of the tilt–tension deformation value. Compared to the tower tilt induced individually by horizontal compression or tension deformation, the tilt under combined deformation conditions demonstrated a significantly greater value. Under mining-induced ground deformation, a redistribution of support reactions occurs, exhibiting either nonlinear or linear increasing trends depending on the type of deformation. The findings of this article provide a theoretical basis and data support for disaster prevention and control, safety evaluation, and structural design of transmission lines in mining areas. Full article

Azimuth sensing plays a vital role in numerous industrial applications where tilt angle serves as a key parameter. To address the demand for accurate and reliable measurements, we propose an all-fiber two-dimensional inclinometer based on the Vernier effect in a multi-core fiber Fabry–Perot interferometer. The sensor is capable of simultaneously measuring both inclination and azimuth angles with high accuracy. A cascaded Fabry–Perot interferometer was inscribed in a seven-core fiber using a femtosecond laser plane-by-plane direct writing technique. By monitoring the wavelength shifts in two peripheral cores, we demonstrated the feasibility and performance of the proposed sensor. The experimental results showed that the inclinometer exhibited high sensitivity, with maximum values of −0.5272 nm/° for azimuth measurement (maximum measurement error: 7.33°) and −0.5557 nm/° for inclination measurement (maximum measurement error: 5.97°). The measurement ranges extended from 0° to 360° for azimuth and from –90° to 90° for inclination. Owing to its wide measurement range, compact structure, and high sensitivity, the proposed all-fiber two-dimensional inclinometer holds significant potential for practical applications. Full article

Glancing angle deposition (GLAD) is a unique physical vapor deposition technique to enable wafer-scale production of close-packed nanopillar arrays (NaPAs) made of a wide range of inorganic and organic materials and engineerable structures, offering great potential for advanced optoelectronic applications. By flexibly controlling substrate rotation during GLAD, this technique enables intricate sculpture of nanopillars in vertical/tilted column, helix, zigzag, and square spiral shapes or a combination of these shapes along the vertical growth axis. In particular, NaPAs exhibit unique engineerability in their material/structure-determined optical, electronic, chemical, mechanical, and morphological properties, making them versatile for significant applications in photovoltaics, photodetection, photocatalysis, and advanced displaying. In this review, we provide a comprehensive overview of recent advancements in optoelectronic applications of GLAD-fabricated NaPAs by exploring the relationship between structural features and device functionality. Additionally, we discuss the technical challenges associated with GLAD, such as scalability, material compatibility, and fabrication precision, and address prospects to produce next-generation optoelectronic devices. Full article

The prolonged retention of senescent branches and needles (canopy litter) in Cunninghamia lanceolata canopies is an evolutionary adaptation, yet its impacts on stand microenvironment and understory succession remain poorly quantified. To address this gap, we conducted a 5-year field experiment across six planting densities (1800, 2400, 3000, 3600, 4200, and 4800 trees·ha⁻¹), aiming to evaluate the effects of canopy litter removal on canopy structure, forest light environment, and understory biodiversity. Results demonstrated that leaf area index (LAI) and mean tilt angle of the leaf (MTA) significantly increased with density (p < 0.05), leading to marked reductions in photosynthetic photon flux density (PPFD) and light transmittance (T). Canopy litter removal significantly reduced LAI across all densities after 4–5 years (p < 0.05) and consistently enhanced PPFD and transmittance (p < 0.01). MTA and light quality parameters (red:blue and red:far-red ratios) both exhibited variable responses to litter removal, driven by density and time interactions, with effects diminishing over time. Understory vegetation diversity exhibited pronounced temporal dynamics and density-dependent responses to canopy litter removal, with increases in species richness (S), Simpson diversity (D), and Shannon–Wiener diversity (H), while Pielou Evenness (J) responded more variably. The most notable increase in species richness occurred in the 4th year, when 21 new species were recorded, largely due to the expansion of light-demanding bamboos (e.g., Indocalamus tessellatus and Pleioblastus amarus), heliophilic grasses (e.g., Lophatherum gracile) and pioneer ferns (e.g., Pteris dispar and Microlepia hancei). Correlation analyses confirmed PPFD as a key positive driver of all diversity indices (p < 0.01), whereas LAI was significantly negatively correlated with PPFD, light transmittance, and understory diversity (p < 0.01). These findings demonstrate that strategic management of canopy litter incorporating stand density regulation can improve understory light availability, thereby facilitating heliophilic species recruitment and biodiversity enhancement in subtropical coniferous plantations. Full article

This study systematically investigates the variation in the ceiling flame tilt angle in an immersed tube tunnel under the combined effect of longitudinal ventilation and sidewall smoke extraction. The experimental program considers different longitudinal velocities, various sidewall smoke exhaust rates and multiple relative distances between the fire source and the sidewall exhaust outlet, aiming to comprehensively reveal the flame tilt angle under multi-factor coupling conditions. Experiments were carried out in a reduced-scale tunnel model (6.64 m long, 0.96 m wide and 0.5 m high). A porous gas burner supplied a steady heat release, with its distance from the sidewall exhaust outlet systematically varied. Results indicate that the flame tilt angle decreases as the distance between the fire source and the sidewall exhaust outlet increases. A theoretical model was developed to predict the flame tilt angle by incorporating both the sidewall smoke exhaust rate and the relative fire source–exhaust distance. The model accounts for mass loss due to smoke extraction, estimated from the local longitudinal velocity distribution. Predictions from the proposed model agree well with the experimental data. Full article

Background: Carbon-fiber-reinforced polyetheretherketone (CFR-PEEK) vertebral-body replacements (VBRs) aim to mitigate subsidence, minimize imaging artifacts, and facilitate radiation planning while preserving fusion potential. We assessed the safety and efficacy of a novel modular, titanium-coated CFR-PEEK VBR (Kong^®) for anterior column reconstruction (ACR) in the thoracolumbar spine. Primary question: Does the implant safely and effectively achieve and maintain kyphosis correction after ACR for trauma and neoplasms? Methods: A single-center retrospective case series was performed on 28 patients who underwent thoracolumbar ACR with the Kong^® VBR for fractures or tumors (2020–2021). The primary outcome was the bi-segmental kyphotic angle (BKA). Secondary outcomes were screw loosening, cage height loss, fusion rate, subsidence, and tilting. Clinical status was recorded with Odom criteria, Karnofsky Performance Status (KPS), and AOSpine PROST. Results: Twenty-eight patients (mean age, 61 yr; 33% female; mean follow-up, 17.7 mts) were studied. Mean postoperative BKA correction was 16.5° (p = 0.006) and remained 14.5° at final follow-up (p = 0.008); loss of correction was 2.0° (p = 0.568). Subsidence, cage height, and sagittal tilt were unchanged. Fusion (Bridwell grade I/II) was observed in 95% on CT. One deep surgical-site infection occurred. At final follow-up, 91% of patients were graded “excellent” or “good” by Odom. KPS improved by 20 points (p = 0.031), and mean AOSpine PROST was 56.9. Conclusions: Single-center early results indicate that the modular titanium-coated CFR-PEEK VBR is a safe, effective adjunct for thoracolumbar ACR in trauma and neoplasm, providing durable kyphosis correction, mechanical stability and high fusion rates and grants for improved follow-up imaging quality. Full article

The Volume Bragg Grating (VBG) imaging technique provides a novel approach to gaze-type hyperspectral imaging. However, collimation constraints of the incident beam during narrow-band filtering and high-spatial-resolution imaging introduce system complexity, hindering miniaturization and modularization of the optical system. To address these limitations, this paper proposes a convex transmissive VBG structure with tunable design parameters to enhance the field of view (FOV), relax collimation requirements, improve imaging quality, narrow filter spectral bandwidth, and simplify the optical system design. For the precise analysis and optimization of convex VBG performance, we established a physical model for filtered imaging using a convex transmissive VBG with polychromatic extended sources. An evaluation metric termed the “Maximal Splitting Angle (MSA)” was introduced to quantify the dispersion extent of image spots. This approach was employed to investigate the intrinsic correlations between structural parameters (such as the radius of curvature, vector tilt angle, grating period, and thickness) and key system performance indicators (spatial resolution and spectral resolution). The necessity of optimizing these parameters was rigorously demonstrated. Theoretical analysis confirms that convex transmissive VBG achieves superior spatial and spectral resolution over planar VBG under reduced collimation constraints. The experimental results show a 58.5% enhancement in spatial resolution and a 63.6% improvement in spectral bandwidth for the convex transmissive VBG system. Crucially, while planar transmissive VBG suffers from stray fringe interference during wavelength tuning, its convex counterpart remains unaffected. This study proposes a novel device structure, offering new perspectives for optimizing VBG-filtered spectral imaging systems. Full article

In recent years, the amount of electricity produced by photovoltaic systems in Poland has increased significantly. This paper presents an evaluation of commercial software (PVGIS 5.3, ENERAD, and PVGIS 24) used for simulating energy produced by four photovoltaic installations. The results of the simulation were compared with the real energy production. The installations differ in terms of panel orientation (S, SE, SE-NW), tilt angle (12°, 25°, 37°) and location (roof- or ground-mounted). The average annual electricity production per 1 kW of module power for each installation was as follows: PV1—1104 kWh·kW⁻¹, PV2—1169 kWh·kW⁻¹, PV3—927 kWh·kW⁻¹, and PV4—831 kWh·kW⁻¹. The highest values were recorded for ground-mounted installations facing south. Simulations carried out using computer programs show differences between simulated and real electricity production values of 35–41% for the ENERAD software, 3–13% for the PVGIS 5.3 software, and 3–32% for the PVGIS 24 software. The most accurate forecasts were obtained for the PV2 system in the PVGIS 24 software (MPE 3%, RMSE 12%), and the most unfavorable for the same installation in the ENERAD software (MPE 41%, RMSE 48%). Full article

The optimal utilization of UAV-integrated photovoltaic (PV) systems demands accurate modeling that accounts for dynamic flight conditions. This paper introduces a novel computational intelligence-based framework that models the behavior of a moving PV system mounted on a UAV. A unique mathematical approach is developed to translate UAV flight dynamics, specifically roll, pitch, and yaw, into the tilt and azimuth angles of the PV module. To adaptively estimate the diode ideality factor under varying conditions, the Grey Wolf Optimization (GWO) algorithm is employed, outperforming traditional methods like Particle Swarm Optimization (PSO). Using a one-year environmental dataset, multiple machine learning (ML) models are trained to predict maximum power point (MPP) parameters for a commercial PV panel. The best-performing model, Rational Quadratic Gaussian Process Regression (RQGPR), demonstrates high accuracy and low computational cost. Furthermore, the proposed ML-based model is experimentally integrated into an incremental conductance (IC) MPPT technique, forming a hybrid MPPT controller. Hardware and experimental validations confirm the model’s effectiveness in real-time MPP prediction and tracking, highlighting its potential for enhancing UAV endurance and energy efficiency. Full article

As interest in PV installation has spiked in recent years, the need for optimizing several factors of PV performance has become crucial. These are tilt angle and solar cell temperature (taking into account ambient temperature) and their effect on solar insolation for solar photovoltaic (PV) systems. The objective of this study is to achieve the optimal tilt angle and cell temperature accordingly by developing a MATLAB program to reach the target of maximizing the received solar insolation. To achieve this, additional solar angles such as the azimuth, hour, latitude angle, declination angle, hour angle, and azimuth angle need to be calculated. By computing the solar insolation for specific regions of interest, specifically the Gulf Cooperation Council (GCC) countries, the desired results can be obtained. Additionally, the study aims to assess the influence of PV cell temperature on the I–V curves of commercially available PV modules, which will provide insights into the impact of temperature on the performance characteristics of PV cells. By employing a developed model, the study examined the combined collective influences of solar received radiation, tilt angle, and ambient temperature on the output power of PV systems in five different cities. The annual optimal tilt angles were found to be as follows: Mecca (21.4° N)—21.48°, Fujairah (25.13° N)—25.21°, Kuwait (29.3° N)—29.38°, Baghdad (33.3° N)—33.38°, and Mostaganem (35.9° N)—2535.98°. Notably, the estimated yearly optimal tilt angles closely corresponded to the latitudes of the respective cities. Additionally, the study explored the impact of ambient temperature on PV module performance. It was observed that an increase in ambient temperature resulted in a corresponding rise in the temperature of the PV cells, indicating the significant influence of environmental temperature on PV module efficiency. Overall, the findings demonstrate that adjusting the tilt angle of PV modules on a monthly basis led to higher solar power output compared to yearly adjustments. These results underscore the importance of considering both solar radiation and ambient temperature when optimizing PV power generation. Full article

Shaft deflection degrades roller alignment and intensifies stress concentration/edge effects at roller-ends and raceway edges, ultimately compromising service performance of tapered roller bearings (TRBs). Therefore, a dynamic model was developed for a TRB subjected to a deflected shaft in which Johnson’s load–deformation relationship was applied to reflect non-uniform cross-sectional structures of the tapered rollers and raceways, viscous damping was integrated into the roller/cage interaction, and friction actions at the raceways and flange areas were treated separately. Then, moment load and angular misalignment of the tapered roller were analyzed under various shaft deflection and operating conditions. Results indicate that tilt angle remains orders of magnitude smaller than skew angle. Shaft deflection amplifies both skew and tilt, and the influence level is proportional to the bearing size. Centrifugal effect primarily affects skew motion, whereas gyroscopic effect mainly influences tilt motion. Axial forces exert greater influence on roller skew than tilt. The flange typically constrains roller skew, whereas both raceways may induce bidirectional tilt/skew motion. Full article