Search Results (533)

Obstructive sleep apnea (OSA) is characterized by recurrent partial or complete upper airway collapse during sleep. Accurate assessment of airway anatomy is crucial for risk stratification, diagnosis, and treatment planning. While polysomnography (PSG) is considered the gold standard for OSA diagnosis, it provides limited anatomical insights. Cone-beam computed tomography (CBCT) has emerged as a valuable tool with lower radiation dose for three-dimensional (3D) assessment of the upper airway space and craniofacial structures. CBCT enables precise measurement of critical airway parameters including total airway volume and length, minimum cross-sectional area, linear dimensions of anteroposterior and lateral diameters, as well as soft tissue structures such as tongue, tonsils, and adenoids. This review aims to explore and comprehensively review the role of CBCT, primarily in upper airway assessment for OSA, with an emphasis on airway measurement parameters, anatomical reference landmarks, and the variabilities, in addition to its clinical applications in treatment planning and simulation and post-treatment efficacy evaluation. This review also highlights the technical considerations such image acquisition protocols, machine specifications and software algorithm, and patient positioning, which may affect measurement reliability and diagnostic accuracy. CBCT serves as a powerful adjunct in OSA diagnosis and management, enabling comprehensive assessment of the airway space and hard and soft tissue structures. It complements PSG by guiding personalized interventions such as maxillomandibular advancement or CPAP optimization. Standardized imaging protocols and consideration of patient positioning can further improve its clinical utility. Full article

Accurate modeling of stem taper is essential for forest management decisions, including the definition of cutting cycles, the feasibility of annual harvesting, assortment classification, size and volume estimation, and ensuring sustainable production continuity. This study modeled the stem taper of Araucaria angustifolia (Bertol.) Kuntze stands in southern Brazil using Kozak’s variable-exponent model fitted with nonlinear mixed-effects techniques. Both fixed- and mixed-effects models showed high predictive performance, regardless of calibration. An unstructured (UN) covariance structure was required to reduce autocorrelation. The mixed-effects model improved predictive accuracy by up to 22%, achieved R² values above 0.99 with RMSE < 0.74 cm, and significantly reduced residual autocorrelation in diameter estimates. The most effective calibration of random effects was achieved using diameter measurements taken at heights between 0.3 and 6.3 m above ground (approximately between 1.3% and 28.3% of the total height, considering the tallest tree as a reference). This research improves the accuracy of volume estimation and the definition of timber assortments for A. angustifolia, thereby supporting forest management decision-making in southern Brazil. Full article

Under the condition of gas–liquid two-phase flow, traditional sucker rod pumps are prone to gas locking due to the high compressibility of gas, and their volumetric efficiency is usually less than 30%, which seriously restricts the exploitation benefits of oil wells. To solve this difficult problem, this study proposes a variable-diameter tube pump structure that adopts an optimized cone angle of the pump cylinder. The results of computational fluid dynamics simulations using dynamic mesh modeling indicate that the stepped change in the pump barrel diameter can enhance the gas–liquid separation effect caused by vortices, while the flow-guiding grooves on the valve seat can reduce the response delay. Comparative calculations and analyses show that compared with the traditional design, its head increases to 13.89 m, and the hydraulic power rises to 1431.01 W, respectively, representing an increase of 17%. This is attributed to the reduction in the gas retention time during piston reciprocation and the stability of the flow field. This structural innovation effectively alleviates the gas lock problem and provides a feasible approach for improving energy efficiency in oil wells prone to vaporization, which is of great significance in oilfield development operations. Full article

The use of miniscrews as Temporary Skeletal Anchorage Devices (TSAD) in orthodontics has allowed clinicians to perform challenging tooth movements by dissipating undesired forces into the bone structure; thus, avoiding unwanted movement of the adjacent teeth. It is essential for miniscrews to be highly resistant to fracture during clinical use. While many studies have analysed torsional loads, none have measured the changes in flexural and bending strength of miniscrews before and after an ageing process. This study aims to analyse the resistance to orthogonal forces of miniscrews with different diameters, focusing on both new and aged materials, the latter subjected to thermocycling and autoclaving laboratory processes to simulate a 3- and a 6-month exposure to the oral environment. A total of 105 pristine miniscrews have been tested; specimens were divided into seven groups based on the different endosseous body diameters. Each group was further subdivided into three subgroups, according to the simulated ageing of the miniscrews (intact, 3 months of ageing and 6 months of ageing, respectively). An Instron Universal Testing Machine has been used to measure deflection at 0.1 mm and 0.2 mm, as well as maximum load at fracture. The results evidenced that miniscrews respond differently to cutting forces; in particular, the resistance to orthogonal loads increases as the diameter of the miniscrews increases. Linear regression analysis revealed a significant influence between all the dependent variables—maximum load, 0.1 mm deflection load, and 0.2 mm deflection load—and the independent variables, such as diameter and thermocycling (p < 0.05). Both new and aged miniscrews are suitable for orthodontic and orthopaedic loads; moreover, ageing up to 6 months does not seem to significantly decrease the resistance to shear forces for the same diameter. Linear regression analysis of the miniscrews subjected to experimental ageing showed a slight but significant decrease in resistance to orthogonal loading. Full article

Shear connections between concrete structural elements play a vital role in defining performance and overall stability. However, limitations in traditional methods for predicting the shear capacity (Vu) of stud connectors in concrete have been highlighted. Developing strategies that precisely describe the performance of stud-headed connectors requires insight into their failure mechanisms and the corresponding shear transmission. Therefore, leveraging advancements in machine learning, this study aims to predict the Vu of the headed stud connector in concrete structures using various input parameters. A database (1121) of the shear strength collected from the literature was trained using six machine learning (ML) algorithms: extreme learning machine (ELM), decision tree (DT), artificial neural network (ANN), multi-linear regression (MLR), support vector machine (SVM), and hybrid ANN–particle swarm optimization (ANN-PSO). Feature selection methods and system identification were applied to explore the optimal or most relevant input parameters. The feature selection techniques indicated that the geometric properties of the stud connector (diameter and cross-sectional area), the concrete modulus of elasticity (Ec), and the height of the weld collar (h_w) are the most relevant input variables. The ANN-PSO model outperformed the other classical models in estimating the shear capacity at two modeling stages. The hybrid ANN-PSO achieved R² = 0.976, MAE = 7.61 kN, RMSE = 10.8 kN, and MAPE = 8.04%, demonstrating the best predictive accuracy among the classical models. On the other hand, DT is the second-best model, with an R² of 0.958, MAE of 10.27 kN, RMSE of 14.43 kN, and MAPE of 8.53 kN for forecasting the shear capacity of stud connectors in concrete. Full article

Traditional wheeled ground robots offer high energy efficiency and excellent mobility on flat terrain but are constrained by their fixed structures, making it difficult to overcome obstacles or adapt to complex environments. To address these limitations, this paper presents a morphing wheeled land–air robot (MW-LAR) that integrates ground locomotion and quadrotor flight. By incorporating foldable arms and variable-diameter wheels, the MW-LAR can not only switch between ground and flight modes, but also achieve transitions between wheeled and legged locomotion in the ground mode. The foldable arms support seamless aerial-to-ground transitions and in-flight morphing, while the variable-diameter wheels facilitate efficient obstacle traversal on the ground. Benefiting from the design of foldable arms, two complementary landing approaches, namely direct quadrotor landing and ground-mode landing, are implemented to explore different aerial-to-ground transition modes and to improve landing safety and switching efficiency. Experimental results demonstrate that the MW-LAR achieves stable and energy-efficient performance across multiple locomotion modes and complex environments, highlighting its potential for integrated land–air mobility applications. Full article

Nest architecture and surrounding habitat features can strongly influence the reproductive success of cavity-nesting birds; however, quantitative data from natural environments remain limited. We examined how nest structure and surrounding habitat features correlate with reproduction in the small bee-eater (Merops orientalis). A total of 38 natural nests were monitored during the breeding season. The Conway–Maxwell–Poisson model showed that cavity depth was a significant positive predictor of clutch size (β = 0.46 ± 0.22 SE, p = 0.036), whereas entrance diameter and nest height were not significantly related. Principal component analysis (PCA) of standardized cavity dimensions (cavity depth, entrance diameter, and nest height) showed that nest height (captured by PC2) was strongly associated with higher breeding success (OR = 0.002, p = 0.021), whereas overall cavity size (PC1) had a weaker, marginally positive correlation (OR = 3.87, p = 0.09). Habitat distance variables showed only weak, non-significant trends after accounting for multicollinearity. Nest structural traits explained more variation in reproductive performance than landscape variables (pseudo-R² = 0.80 for clutch size; 0.59 for breeding success). Field monitoring of 38 nests showed a mean clutch size of 3.9 eggs, an overall hatching success of 77.5%, and a fledging success of 51.2%, yielding a 37.1% breeding success. Our results highlight the importance of conserving sandy streambanks and mitigating human disturbance in proximity to active nests to conserve breeding success in small bee-eaters. As these findings were based on one site and a single breeding season, broader generalizations will require replication across additional years and locations. Full article

ANSYS software was used to analyze the moment-rotation relationship of semi-rigid steel structure joints with bolted connection. A parametric study was conducted to examine the influence of eight key variables—including bolt number, bolt grade, angle steel grade, bolt diameter, angle steel thickness, angle steel width, preload magnitude, and friction coefficient—on the bending behavior of semi-rigid joints with bolted connection. Parametric analysis reveals that the initial rotational stiffness is most significantly influenced by the bolt diameter, the width and thickness of the angle steel, the bolt preload, the coefficient of friction, and the bolt number. The stiffness exhibited an average increase of 50.6% for every 4 mm increment in bolt diameter from 12 mm to 24 mm. Expanding the angle steel width from 50 mm to 75 mm resulted in a substantial 88.5% average increase in stiffness, while a further width increase from 75 mm to 110 mm led to a smaller average increase of 17.4% per 17.5 mm. Similarly, the stiffness rose by an average of 33.8% for every 2 mm increase in the thickness of the angle steel within the 4 mm to 10 mm range. A 25% increase in bolt preload correlated with a modest average stiffness gain of 2.7%. The rate of stiffness improvement diminished with increasing friction coefficient. In contrast, the initial rotational stiffness exhibited a relationship that is approximately linear with respect to the quantity of bolts. Regarding the ultimate bending moment, the key influencing factors were identified as bolt diameter, preload, coefficient of friction, and number of bolts. The ultimate moment demonstrated a non-monotonic relationship with bolt diameter, characterized by an initial increase, followed by a decrease, and then a sharp subsequent rise. Linear enhancements in the ultimate moment were observed with increases in both bolt preload and coefficient of friction. Furthermore, the ultimate bending moment showed a gradual increase with the number of bolts. Based on the results, a bending moment-rotation curve model of joints with bolted connection is established, and the expression of each parameter in the model is calculated. This model can be applied to simulation of the bending performance of semi-rigid joints with bolted connection. Full article

Knowledge of the reduction in tree stem diameter with increasing height is considered significant for reliable tree taper prediction. Tree taper modeling offers a comprehensive framework that connects tree form to growth processes, enabling precise estimates of volume and biomass. In this context, machine learning modeling approaches offer strong potential for predicting difficult-to-measure field biometric variables, such as tree stem diameters. Two promising machine learning approaches, temporal convolutional networks (TCNs) and extreme gradient boosting (XGBoost), were evaluated for their ability to accurately predict trees’ stem profiles, suggesting a powerful and safe strategy for predicting tree stem sectional volume with minimal ground-truth measurements. The comparative analysis of TCN- and XGBoost-constructed models showed their strong ability to capture the taper trend of the trees. XGBoost proved particularly well adapted to the stem profile of black pine (Pinus nigra) trees in the Karya forest of Mount Olympus, Greece, by summarizing its spatial structure, substantially improving the accuracy of total stem volume up to RMSE% equal to 3.71% and 7.94% of all ranges of the observed stem volume for the fitting and test data sets. The same trend was followed for the 1 m sectional mean stem-volume predictions. The tested machine learning methodologies provide a stable basis for robust tree stem volume predictions, utilizing easily obtained field measurements. Full article

This study evaluated the properties of two commercial filaments intended for medical and sterile applications: PLACTIVE (Copper 3D, Santiago, Chile) and CPE ANTIBAC (Fiberlogy, Brzezie, Poland). The aim of the research was to compare the dimensional accuracy, repeatability of the fused deposition modeling (FDM) 3D printing process, and the antibacterial properties of the samples using standardized procedures. Four types of samples were manufactured: geometrically differentiated specimens for metrological measurements (S1); cylinders with a diameter of 15 mm and a height of 40 mm for assessing process repeatability (S2); rectangular specimens measuring 40 × 40 × 2 mm for surface topography analysis (S3); and rectangular samples measuring 20 × 20 × 2 mm for biocidal property evaluation (S4). The results demonstrated that PLACTIVE samples exhibited higher dimensional conformity with nominal values and lower variability of diameters than CPE ANTIBAC samples, which may be associated with greater process stability. For both materials, the PSm parameter was correlated with layer height only in the 90° printing orientation. Surface topography analysis showed that increasing the layer height from 0.08 mm to 0.20 mm led to a significant rise in Rsm, Ra, and Sa values, indicating deterioration in the reproduction of micro-irregularities and increased spatial differentiation of the surface. For PLACTIVE samples, a tendency toward more convex structures with positive Rsk values and moderate kurtosis (Rku) was observed, suggesting uniform plasticization and stable interlayer bonding, particularly at the 0° orientation. In contrast, CPE ANTIBAC samples (especially those printed at 90°) were characterized by higher Ra and Sa values and negative skewness (Rsk), indicating valley-dominated, sharper surface morphology resulting from different rheological behavior and faster solidification of the material. PLACTIVE samples did not exhibit antibacterial properties against Escherichia coli (E. coli), while for Staphylococcus aureus (S. aureus), the activity was independent of printing direction and layer height. The CPE ANTIBAC material showed antibacterial effects against both tested strains in approximately 50% of the samples. The findings provide insights into the relationships between material type, printing orientation, and process parameters in shaping the dimensional and biocidal properties of FDM filaments. Full article

To investigate the flexural behavior of steel–concrete composite bridge decks with stud–perfobond leist (PBL) shear connectors, two specimens were designed with the stud spacing as the main variable, and static bending tests were conducted. Additionally, refined finite element models were constructed for evaluating the influence of shear connector types, concrete strength, stud diameter, stud height, and PBL hole diameter on the performance and flexural capacity of the structure. The results show that, under bending loads, the failure of the composite bridge deck is mainly concrete crushing and steel plate yielding. When the spacing of the stud decreases, both the flexural behavior of the composite bridge decks and the shear resistance at the steel–concrete interface are enhanced. The steel–concrete composite bridge decks with stud–PBL shear connectors showed higher overall flexural stiffness and flexural capacity than the steel–concrete composite bridge decks with single-type shear connectors. Concrete strength had a pronounced influence on the flexural capacity of the deck system, while the effects of stud diameter and height were minor. As the PBL hole diameter increased, the flexural capacity of the specimens exhibited a decreasing tendency. Full article

To address the limitations of traditional energy dissipation technologies, such as difficulty in arranging energy dissipators due to narrow river valleys and complex geological conditions and the low energy dissipation efficiency of existing air jet collision methods, this study proposes a novel structural form of a horizontal opposing jet energy dissipator. Water is diverted to the open area downstream of the reservoir hub via diversion pipelines, and energy dissipation is achieved through horizontal opposing collision of jets in the air. Focusing on this new energy dissipator, numerical simulations combined with physical experiments were conducted to investigate its energy dissipation characteristics, with the dimensionless parameters l/d (collision distance/pipeline diameter) and Reynolds number (Re) as the main variables. The results indicate that two opposing jets formed a crown-shaped water jet after horizontal collision in the air. The rising height in the Z-direction and expanding width in the Y-direction of the crown-shaped water jet exhibit a negative correlation with l/d and a positive correlation with Re. Energy dissipation was achieved through jet collision, mixing, friction, diffusion, aeration, and fragmentation in the air. This energy dissipation method improved the energy dissipation rate by extending the collision time and mixing length of jets in the air. The primary factors influencing the energy dissipation rate were l/d and Re. Under the study conditions, the energy dissipation rate of jet collision in the air ranged from 16.25% to 39.54%. The energy dissipation efficiency exhibits a negative correlation with l/d and a positive correlation with Re. This study provides a new approach for energy dissipation in hydraulic engineering. Full article

The SBPDN (Steel Bar Prestressed Deformed Normal relaxation) bar, which has ultra-high yield strength yet much lower bond resistance than conventional deformed bars, has been recently proposed to be used as the longitudinal rebar instead of a normal-strength deformed bar to simply realize strong earthquake-resilient concrete components. To facilitate and promote the application of concrete components reinforced with SBPDN rebars to the structures located in earthquake-prone regions, it is indispensable to develop reliable and effective anchoring means and clarify the bond strength of SBPDN bars embedded in concrete and/or grout mortar. This paper presents experimental information on the pull-out tests of fifteen SBPDN bars embedded in grout mortar, along with a discussion on the effective anchorage details and the bond strength of SBPDN bars. The tested SBPDN bars have a nominal diameter of 22.2 mm, the maximum diameter currently available on the market. All SBPDN bars were embedded in high-strength grout mortar with a targeted compressive strength of 60 MPa. The primary experimental variables included the end anchorage details, the diameter of sheath ducts, and the embedded length of the bars. Test results demonstrated that either screwing two nuts and a washer at the end of SBPDN bars or providing a rolling-threaded end region was effective in preventing them from premature slip from grout mortar. If the embedment length was 20 times the bar diameter or longer, the proposed two anchorages could ensure the SBPDN bar to fully develop its specific yielding strength as high as 1275 MPa. In addition, it has also been experimentally revealed that the bond strength of SBPDN bars embedded in grout mortar was much lower than that of conventional deformed bars and varied between 2.84 MPa and 3.98 MPa. Full article

Background/Objectives: Adenomyosis (A) is a benign but invasive uterine condition frequently associated with structural changes in the uterine wall that may contribute to infertility. Methods: This is a retrospective study involving 140 patients: 100 diagnosed with primary infertility (PI) or secondary infertility (SI) and 40 in the control group. All patients were assessed using transvaginal two-dimensional, three-dimensional, and hysterosalpingo-contrast sonography (HyCoSy), performed in the early proliferative phase. Evaluated parameters included uterine dimensions, endometrial thickness, and characteristics of the junctional zone (JZ). Criteria such as JZmax > 5 mm or JZmax − JZmin > 5 mm, alongside other findings, supported the diagnosis of adenomyosis. Results: Patients with PI showed larger uterine longitudinal diameters, while SI patients had thicker JZ measurements. PI patients were significantly younger. Histopathological examination confirmed the presence of endometrial glands and periglandular stroma disrupting myometrial architecture, forming chronic lesions potentially linked to infertility. Conclusions: HyCoSy revealed variable depths of myometrial invasion by A, with some cases extending near the serosa. The chronic lesions found in histopathological examination were potentially linked to infertility. Full article

Subtropical deciduous broad-leaved forests in eastern China form a key ecotone between temperate and subtropical biomes, yet their vegetation–environment relationships remain insufficiently understood. This study examined community structure, species diversity, and their associations with topographic and soil variables in a 25 ha forest dynamics plot in the Lushan Mountains. All woody plants with a diameter at breast height (DBH) ≥ 1 cm were surveyed, and detailed topographic attributes and soil physicochemical properties were measured. Community structure showed strong linkages with species diversity: tree-layer structural characteristics were generally negatively correlated with diversity, whereas in the shrub layer, density was negatively but height and DBH were positively correlated with diversity. Species diversity in the two layers was positively associated, while tree-layer structure was negatively related to shrub-layer diversity. Among topographic factors, altitude and the topographic solar radiation aspect index (TRASP) exerted the strongest influences on soil properties, with altitude negatively correlated with soil pH and available nutrients but positively correlated with C:N, C:P, and total carbon, and TRASP showing negative correlations with most nutrients except total phosphorus. Redundancy analysis revealed that topographic heterogeneity and soil conditions jointly shaped community structure and species diversity, with soil C:N ratio, altitude, pH, total phosphorus, and total carbon emerging as key drivers. These findings demonstrate that areas with high plant diversity do not always correspond to high soil nutrient content and underscore the importance of integrating both topographic and edaphic factors into biodiversity conservation and forest management in subtropical deciduous broad-leaved forests. Full article