Search Results (227)

Background: The maxillary canine is the second-most frequently impacted tooth, affecting 1–3% of the population. It plays a crucial role in occlusion, facial esthetics, and arch development, making orthodontic traction the preferred approach over extraction or clinical monitoring without intervention. This systematic review aimed to identify the factors associated with the duration of orthodontic traction for impacted maxillary canines and to evaluate their influence. Methods: A systematic search was conducted in MEDLINE, Cochrane Library, Embase, Web of Science, and grey literature following PRISMA guidelines. Traction duration was defined as follows: (A) time from traction initiation to alignment; (B) time to cusp emergence; and (C) time to appliance removal. Risk of bias was assessed using RoB 2 and ROBINS-I v2. Results: Out of 1156 initial studies, 43 were included in qualitative analysis and 24 in quantitative analysis. The pooled mean treatment duration was 43.13 months (95% CI: 32.50–53.77; I² = 99.6%) for definition A, 44.81 months (95% CI: 23.28–66.34; I² = 99.8%) for definition B, and 87.48 months (95% CI: 69.80–106.07) for definition C. Alpha angle, vertical height, and sector were the most frequently reported factors, potentially influencing traction duration. Meta-regression showed a significant association between mean patient age and treatment duration for definition B (β = −8.168, 95% CI: −15.299 to −1.037; p = 0.025), whereas no significant associations were observed for definition A. Heterogeneity across studies was high, and most non-randomized studies showed moderate to serious risk of bias, while randomized trials presented some concerns. Conclusions: Patient- and treatment-related factors, including higher alpha angle, greater vertical height, and more midline positioning, appear to influence traction duration. Despite variability across studies, these findings provide valuable insights for clinical practice. Full article

Objectives: To investigate the association between calcaneal bump height and hindfoot radiographic parameters on weight-bearing lateral radiographs in adult males with Progressive Collapsing Foot Deformity (PCFD), and to determine whether posterior calcaneal morphology differs between feet with and without PCFD-related flatfoot alignment. Materials: We retrospectively reviewed 583 men (1166 feet), aged 17–46 years, who underwent standing weight-bearing lateral foot radiographs between 1 January 2024 and 31 August 2025. Radiographic measurements included calcaneal pitch, Meary’s angle, navicular height, tibiocalcaneal angle, Böhler’s angle, Fowler–Philip angle, calcaneal bump height, and additional calcaneal morphological indices. A flatfoot alignment consistent with PCFD was defined as a calcaneal pitch < 18°. Receiver operating characteristic (ROC) analysis and multivariable logistic regression were performed to assess diagnostic performance and identify parameters independently associated with flatfoot alignment. Results: Flatfoot alignment was identified in 232 feet (19.9%) from 153 patients (26.2%). Compared with normally aligned feet, the flatfoot group demonstrated significantly lower navicular height, calcaneal bump height, and Böhler’s angle, along with higher tibiocalcaneal and Meary’s angles (all p < 0.001). ROC analysis showed navicular height to be the most accurate diagnostic parameter (AUC = 0.75), followed by the tibiocalcaneal angle (AUC = 0.69). Multivariable logistic regression revealed that navicular height ≤ 52.7 mm, tibiocalcaneal angle > 64.6°, Böhler’s angle ≤ 32.9°, Meary’s angle > 4.9°, calcaneal bump height ≤ 3.9 mm, and Fowler–Philip angle > 61.1° were independently associated with flatfoot alignment (Nagelkerke R² = 0.293, p < 0.001). Conclusions: Calcaneal bump height is reduced in PCFD and reflects posterior calcaneal remodelling associated with hindfoot malalignment and medial arch collapse. Although not a primary diagnostic parameter, calcaneal bump height provides complementary morphological information that may inform surgical planning and osteotomy strategy aimed at restoring physiologic hindfoot biomechanics and Achilles tendon loading in patients with PCFD. Full article

Longwall top coal caving is one of the most effective methods for extracting steeply inclined and ultra-thick coal seams. To investigate the influence of caving ratio (the proportion between mining height and top coal thickness) on top coal recovery behavior and ground pressure characteristics, this study employs both the Particle Flow Code (PFC) discrete element method and a coupled FLAC^3D–PFC^3D numerical simulation approach. The effects of different caving ratios (1:3, 1:3.2, and 1:3.4) on the top coal recovery ratio, stress distribution, and gangue accumulation characteristics were analyzed. The results show that the caving ratio has a significant impact on top coal recovery. At a caving ratio of 1:3.2, adopting a two-cut-one-cave interval resulted in a top coal recovery ratio as high as 94.8%. A stress-relief zone with an arch-like distribution formed above the goaf, while a stress concentration zone developed ahead of the coal wall, where the coal–rock mass underwent compression and failure. The roof displacement exhibited an arch-shaped distribution, while the floor displacement was asymmetrical, with greater heaving observed at the lower end. As the working face advanced, the horizontal development of the plastic zone expanded rapidly, while the vertical extent changed only slightly. Throughout the caving process, the top coal demonstrated favorable caving behavior with good flowability and accumulation characteristics. These findings provide theoretical support for achieving high mining recovery in thick coal seam operations and offer practical guidance for optimizing caving process parameters in practice. Full article

Background: Flatfoot is an alteration of the normal structure of the foot, characterized by a partial or total reduction of the medial longitudinal plantar arch, valgus deformity of the heel, and abduction of the forefoot. While treatments often include strengthening of the intrinsic foot muscles, evidence of its efficacy in adults with flatfoot remains limited. Objectives: The main objective of this review was to evaluate the effects of strengthening the plantar intrinsic muscles in adults with flatfoot. Methods: Searches were conducted in PubMed, Embase, Cochrane, PEDro, and Web of Science databases up to October 2023. The review protocol was developed and followed according to the PRISMA Extension for Scoping Reviews (PRISMA-ScR) guidelines. Studies included were those published on intrinsic muscle strengthening in adult populations. A qualitative synthesis of all included articles was performed, along with a quantitative sub-analysis of randomized controlled trials and a critical methodological assessment. Results: Eleven studies involving a total of 374 participants were selected. Most studies identified the “short foot exercise” as the optimal exercise for isolating and training the plantar intrinsic foot muscles. The most commonly analyzed variables were the Foot Posture Index and the Navicular Drop Test. Conclusions: Strengthening the plantar intrinsic muscles enhances the height of the medial longitudinal arch, improves hindfoot posture and balance, and increases hallux abductor muscle activity. This strengthening, whether achieved through short foot exercises alone or in combination with other techniques, is effective in treating adult flatfoot. Current literature suggests that a duration of 4–6 weeks may be sufficient to achieve beneficial outcomes. Full article

Karst soil caves are prone to induce insufficient bearing capacity and excessive settlement of engineering foundations, which in turn trigger sudden ground surface collapse. In this study, multi-stage cyclic loads were designed to simulate traffic loads, and model tests were conducted to measure and analyze the variation laws of foundation settlement, peak vertical earth pressure within the foundation, and reinforcement strain at different positions under cyclic dynamic loading. The results show that the following: ① under cyclic dynamic loading, the collapse of soil caves significantly reduces the bearing capacity of reinforced foundations with an influence range of up to 3B; ② affected by karst soil caves, reinforced foundations only experience a short elastic compaction stage under cyclic loading, followed by rapid deformation until failure; ③ a critical value exists in the earth pressure distribution at a distance of 1B–2B from the soil cave to the foundation center, which governs the abrupt pressure drop behavior in the collapse zone; ④ under the same level of cyclic loading, the height and number of soil arches are independent of the number of loading cycles, and the soil arching effect exerts the most significant influence on the bearing capacity of reinforced foundations at the initial stage of loading application. Full article

Inflatable structures have attracted increasing attention in recent years due to their light weight, translucency, rapid assembly or disassembly, mobility, and self-cleaning performance. Meanwhile, their flexible characteristics and low-damping behavior render the structures prone to significant deformation and vibration under wind and snow loads and may even lead to structural failure. Therefore, numerous researchers have conducted in-depth investigations into the mechanical response of such structures under wind and snow loads. However, existing studies on inflatable structures subjected to wind and snow loads have mainly focused on an air-supported form, and the mechanical behavior of inflatable ribbed arch structures has not yet been sufficiently investigated. To investigate the mechanical behavior and deformation patterns of inflatable ribbed arch structures subjected to wind and snow loads, static tests were conducted on three specimens with varying spans, heights, and cable arrangements. Following inflation to an internal pressure of 250 kPa and preloading with the tarpaulin weight, the wind load and snow load were converted to the equivalent concentrated loads and applied in five incremental stages. Displacement monitoring points (DMPs) were tracked using a total station. Under the wind load, a consistent wind-induced deformation pattern was observed across specimens characterized by inward displacement in Region I, upward displacement in Region II, and negligible change in Region III. The maximum horizontal displacements of Specimens A, B, and C were 76 mm, 140 mm, and 249 mm, respectively. Under snow load, the upper sections of all three specimens experienced significant downward displacement, while both sides demonstrated a slight tendency for outward expansion and upward lift. The maximum vertical displacements of Specimens A, B, and C were −27 mm, −233 mm, and −255 mm, respectively. The findings of this study provide deeper insights into the mechanical behavior of inflatable arch structures under wind and snow loads and can serve as a valuable reference for their design and optimization. Full article

Lateral pressure on a retaining wall could be a critical parameter that affects the stability and efficiency of the wall design. Traditional methods to estimate active lateral earth pressure is often inadequate in cases where geometric constraints, or arching effects play significant roles. An analytical method has been used in this study to estimate soil and geotextile stresses in reinforced retaining walls by considering the arching effect. It presents a clear analytical solution for calculating lateral earth pressure in narrow Mechanically Stabilized Earth (MSE) walls. The model includes bilinear failure surfaces and nonlinear stress paths, which better reflect real soil behavior in comparison to the traditional methods with linear failure surfaces. The proposed method demonstrated excellent agreement with both field data and centrifuge test results. According to the proposed analytical approach, the distribution of horizontal soil pressure is not linear. The lateral soil pressure is zero at the top and bottom, while the maximum pressure is between 0.4 and 0.9 of the wall height. The formulation further indicates that the higher the friction at the interfaces, the greater the arching effect, so reducing the lateral earth pressure on the retaining wall. Moreover, narrowing the backfill space leads to a significant reduction in lateral earth pressure. Full article

Cascade dams describe an arrangement of several dam structures built along a flow path. Failure of one upstream dam in the cascade system can trigger catastrophic consequences to the downstream dams, as evidenced recently in the Edenville Dam and Sanford Dam. Previous research has mainly focused on rainfall-induced dam failures, although recent failures have demonstrated a combination of floods and earthquakes. Moreover, limited studies have analyzed the sensitivity of dam breach parameters, such as dam breach height and width in dams arranged in a cascade system for seismic events. Most hydraulic simulations that model seismic-induced dam failures assume the complete collapse of dams to analyze the downstream consequences. Hence, this study presents a novel analysis in simulating earthquake-induced failures in a cascade dam system, considering the sensitivity of dam breach parameters. In addition, dam breach parameters have been derived from the structural analysis of dams employing Finite Element Models (FEMs) to a critical Peak Ground Acceleration (PGA) of 0.3 g. Two-dimensional hydrodynamic simulations, along with the full dynamic wave equations, are undertaken in the study to model the earthquake-induced cascade dam failures. The results further elaborate on the significance of modeling cascade dam failures in terms of the consecutive arrival of floods and total flow compared to individual dam failures. Sensitivity analysis of dam breach parameters shows that the breach height is more significant than the breach width and breach slope. However, its significance decreases as the dam breach flood flow path increases in distance. The study further confirms the novel utilization of structural analysis to derive dam breach parameters for seismic-induced dam failures of concrete arch dams and rockfill dams, which will guide the optimization of disaster mitigation strategies and the operational resilience of the dams. Full article

Underground coal gasification (UCG) is an emerging energy technology that involves the in situ conversion of coal into syngas through controlled combustion within a subsurface excavation. The geomechanical processes associated with UCG can lead to significant overburden caving and surface subsidence, posing risks to surface infrastructure and groundwater systems. To accurately predict the size of overburden caving zones and associated surface subsidence, a prediction model was developed based on simulation results using discrete element method (DEM) numerical models. The main purpose of developing such a model is to establish a systematic and computationally efficient method for the rapid prediction of the height of overburden caving and its associated surface subsidence induced by underground excavation. The model is broadly applicable to different types of underground excavations, and UCG is used in this study as a representative application scenario to demonstrate the relevance and performance of the model. Sensitivity analysis indicates that excavation span, tensile strength, and burial depth are the primary controls on the height of the caving zone within the ranges of parameters investigated. Rock density is retained as a secondary background parameter to represent gravitational loading and its contribution to the in situ stress level. The derived model was validated using published numerical, experimental, and field measurement data, showing good agreement within practical ranges. To further demonstrate the application of the model developed, the predicted caving geometries were incorporated into finite element method (FEM) models to simulate surface subsidence under different geological conditions. The results highlight that the arch structure formed by overburden caving can help redistribute stresses and thereby reduce surface deformation. The proposed model provides a practical, parameter-driven tool to assist in underground excavation design, environmental risk evaluation, and ground stability management. Full article

The mechanical behavior of assembled culverts under high rocky backfill presents significant challenges due to the complex interaction between the rigid structure and coarse-grained fill. This study investigates the full-process mechanical performance of an assembled culvert through comprehensive in situ monitoring and three-dimensional finite element numerical analysis. Key parameters, including earth pressure distribution, structural deformation, and joint strain, were continuously monitored throughout the backfilling process. A high-fidelity numerical model considering the soil-structure interaction was established and strictly validated against field data. The results indicate that the earth pressure growth rate gradually decreases with fill height, confirming the development of a soil arching effect within the rocky backfill. The numerical predictions show strong consistency with experimental measurements, verifying the model’s accuracy. Crucially, the culvert exhibited minimal deformation, with cumulative settlement less than 25 mm, fully meeting safety requirements. Furthermore, a distinct alternating tension-compression strain pattern was observed at the joints during early backfilling, highlighting the critical necessity of symmetrical layered compaction. These findings validate the safety of the proposed construction methodology and provide a theoretical basis for optimizing the design and quality control of high-fill infrastructure in mountainous terrain. Full article

The present work explores the effects of dental splints from a mechanical standpoint, aiming to provide a practical tool for the surgical decision-making process regarding splint cross-section dimensions. Our investigation centers on the anatomical structure of a pentamorphic dental arch encompassing central and lateral incisors and one canine on each side. Using parametric in silico models built up by means of an ad-hoc procedure, geometry, material properties, and boundary conditions are defined on a parametric anatomical model that can be tailored using RX-derived geometrical information. Two general cases have been considered, one with the splint and the other splintless, and a sensitivity analysis has been performed by varying the splint section height and thickness. The results show the diminishing mobility at the apex and basis of the diseased incisors, demonstrating the effectiveness of the periodontal treatment. Moreover, the stress due to physiological loads moves away from diseased teeth toward the healthy ones due to the splint effects, focusing on the splint–glue–canine contact zone and highlighting the crucial role played by the canine in fixing the entire dental structure. To establish a preliminary mechanical assessment of the dental structure’s safety and to confine its actual value within a mechanically reasonable range, a synthetic “traffic-light” indicator of stress-based failure risk is proposed. It is felt that the tool proposed in this study can help surgeons assess the pre-operative patient-specific mechanical effects of the splint treatment, driving the design and choice of periodontal splints. By linking splint geometry to mechanical safety via a stress-based indicator, the method supports the optimized design and selection of splints, improving treatment reliability while preserving comfort and clinical effectiveness. Full article

To address the collaborative requirements of high precision, high efficiency, low cost, and non-contact measurement for wheel arch detection in the calibration of Advanced Driver Assistance Systems (ADAS) during vehicle production, this study proposes a monocular machine vision-based detection methodology. The hardware system incorporates an industrial camera, priced at approximately 1000 CNY, and a custom light source. The YOLOv5s model is employed for rapid localization of the wheel hub, while the MSER algorithm, in conjunction with Canny edge detection, is utilized for robust feature extraction of the wheel arch. A geometric computation model, referenced to the wheel hub, is subsequently established to quantify the wheel arch height. Experimental results indicate that, for seven vehicle models, the method achieves an average absolute error (MAE) of ≤0.25 mm, with a maximum error of ≤0.545 mm and a single measurement time of ≤3.2 s, making it suitable for a 60 JPH production line. Additionally, under lighting conditions ranging from 500 to 1500 lux and dust concentrations of ≤10 mg/m³, the MAE fluctuation remains within ≤0.08 mm, ensuring consistent measurement accuracy. This methodology offers a cost-effective, reliable, and fully automated solution for wheel arch detection in ADAS calibration, demonstrating strong adaptability to production lines and considerable potential for industrial applications. Full article

Current small arch shed machine designs rely on manual pole placements, resulting in low construction efficiency and mechanized levels. These machines were not designed with key components tailored to the agronomic requirements of Xinjiang’s small arch shed cotton cultivation model. An automated rod-feeding mechanism for a small arch shed was designed using SolidWorks 2023 to bridge this gap. Its major components include rod separation and conveying units, enabling the separation and orderly transportation of tunnel rods. A kinematic simulation of the conveyor rod during the transport process using ADAMS 2024.1 software was performed to examine the effects of motor speed, synchronous belt stop block height, and horizontal distance on the conveyor rod. Using MATLAB 2023a to fit the center-of-mass distance curve yields the optimal values for the parameters (motor speed = 17.57 rpm, stop block height = 16.79 mm, and horizontal distance = 103.95 mm). Bench test results confirmed the simulation performance of the device with a motor speed of 17 rpm, a synchronous belt stop block height of 15 mm, and a horizontal distance of 100 mm. The automated rod-feeding device exhibited an 80.8% feeding rate. The prototype operates stably, and this design can serve as a reference for developing automated equipment for small arch sheds. Full article

This paper addresses the issue of stress redistribution in surrounding soil during the construction of shallow-buried, large-section loess tunnels. Using the Luochuan Tunnel as a case study, we employ the FLAC 3D numerical simulation method to investigate the effects of advanced pipe roof support on the stability of the surrounding soil. The results demonstrate that advanced pipe umbrella reduces the stress release amplitude at the vault by 50% compared to the unsupported condition, due to a “pre-support-load bearing mechanism”, while promoting orderly stress recovery. The “longitudinal beam effect” and “transverse arch effect” of soils effectively suppress the plastic zone area of the surrounding soil from 413.3 m² (unsupported) to 95.0 m², achieving a reduction exceeding 77%. Furthermore, the pipe umbrella support facilitates the formation of a more efficient “active soil arch”, which exhibits distinct symmetrical characteristics. The arch’s stress distribution and spatial structure both follow symmetrical patterns, significantly enhancing the self-stabilizing capacity of the surrounding soil. As a result, the height of the stress release zone at the tunnel excavation face and the surrounding soil stability areas is reduced by 45.9% and 63.3%, respectively, compared to the unsupported condition. This study also establishes a Pasternak elastic foundation beam model that accounts for the spatiotemporal effects of support, elucidating the mechanism of pipe umbrella support and providing a theoretical foundation for the design and construction risk control of shallow large-section loess tunnels. Full article

While the Seokguram Grotto is celebrated in art history for its sculptural mastery, its architectural identity as a constructed stone dome—distinct from excavated caves—remains under-researched. Existing studies have largely relied on geometric analyses based on irrational numbers, which lack a historical basis. This study aims to reconstruct the logical design process of Seokguram by distinguishing between architectural planning and the realities of construction. Methodologically, we employ the concept of design constraints to analyze the grotto’s dimensional system and scene perception. We identify external constraints, such as the recorded dimensions of the Bodhgaya Buddha and cosmological symbolism (rectangular antechamber and circular posterior), and internal constraints, specifically the need for complete visual coordination between the Buddha’s head and the detached nimbus stone. Our analysis reveals that the designers negotiated these constraints through an iterative process. Key findings demonstrate that the pedestal’s height and position were adjusted, and the arched headstone was strategically designed as a threshold to ensure the perfect alignment of the Buddha and the nimbus from the viewer’s perspective. Furthermore, contrary to previous hypotheses proposing the use of irrational numbers (e.g., √2), this study proves that the grotto follows a proportional system based on integer modules (with 12 cheok as the main module) and binary division, which facilitated practical construction. In conclusion, Seokguram is not merely a product of aesthetic intuition but a masterpiece of rational design. In contrast to the vertical transcendence of Western Cathedrals, Seokguram Grotto embodies tectonics of empathy, prioritizing human-scale intimacy and visual harmony. Full article