Search Results (279)

Taking a large single-phase generator transformer product as the research object, this paper applied the finite element simulation method to analyze the vibration characteristics of its core. Firstly, through the analysis of vibration theory, the vibration laws and characteristics of the core are clarified, and a three-dimensional equivalent model of the transformer is constructed. The B-H curve of the silicon steel sheet is measured through experiments and used for the assignment of the core material when calculating the electromagnetic field later. Then, based on the simulation calculation of multi-physical field coupling, the no-load current on the primary side, the distribution and variation characteristics of the magnetic field inside the core are solved and analyzed. On this basis, the sequential coupling method was adopted to solve the displacement distribution of the core vibration and the displacement changes at different position points and conduct a comparative analysis. Subsequently, the accuracy of the simulation calculation method was verified through the test of a small prototype. Finally, based on the comparison of the dry and wet modal simulation results, the impact of transformer oil on the vibration characteristics of the core was evaluated and analyzed. It can be seen from the analysis that the core vibration is generally more intense at the upper part and corners; the impact of the internal oil flow on the vibration of the body of large transformers is relatively complex and thus cannot be ignored. Full article

This study systematically investigates the post-construction settlement behavior of high-fill red clay embankments, focusing on the influences of three key factors (water content, degree of compaction, and lift thickness) and the effectiveness of geogrid-based reinforcement measures. A three-dimensional finite-element model based on the Mohr–Coulomb constitutive theory was established using MIDAS GTS NX 2022 R1 to simulate staged construction processes and long-term settlement under self-weight loading. The results indicate that settlement is predominantly concentrated in the upper fill zone adjacent to the slope surface, with displacement contours sagging inward toward the fill interior, while the underlying foundation undergoes negligible deformation. An elevated water content and reduced degree of compaction significantly enhance the compressibility of red clay, leading to increased settlement magnitudes and prolonged stabilization periods. Excessively thick lifts result in inadequate deep compaction, thereby inducing larger final settlements. Two reinforcement schemes (geogrid combined with anti-slide piles and geogrid combined with a gravity retaining wall) were verified to effectively mitigate post-construction settlement, with the former achieving a more pronounced improvement in the embankment stability coefficient. Based on the comprehensive analysis, optimal construction control parameters for high-fill red clay embankments are proposed: precise regulation of water content, maximization of compaction degree, and adoption of a lift thickness of approximately 30 cm. The findings of this study provide quantitative technical support and design references for the settlement control of similar high-fill red clay embankment projects in southern China’s mountainous and hilly regions. Full article

Background/Objectives: Stability, retention, and support are removable partial denture (RPD) biomechanical principles. The literature shows contradictory opinions on indirect retention in RPDs, but no solid scientific evidence exists. This in vitro research aims to analyze indirect retainers’ (IRs) influence on forces transmitted to abutment teeth of a Kennedy Class I mandibular RPD. Methods: Bilateral distal-extension mandibular RPDs—differing only in the presence or absence of an IR on tooth 44 (IR model vs. nonIR model, respectively)—were installed on an acrylic master model. Tensile forces were applied perpendicularly to the occlusal plane on the longest free-end saddle’s distal aspect. Electronic speckle pattern interferometry (ESPI) measurements were obtained with and without an IR. The three-dimensional out-of-plane displacements of both models were acquired. Results: Abutment teeth 46 and 47 contralateral to the longest distal extension suffered more deformation under displacement forces when an IR was used. In turn, the IR’s influence on the deformation values of the abutment tooth 34 adjacent to the larger edentulous area depended on the intensity of the tensile force exerted: low-intensity forces resulted in reduced deformation, while higher-intensity forces resulted in higher deformation. Conclusions: This study’s findings indicate that indirect retention promotes better tensile force distribution in the existent teeth. However, they also question the IR’s role in protecting abutment teeth against excessive torque forces. This study’s preliminary results highlight the need for research on indirect retention principles using new methodologies, namely, in silico and ex vivo studies, and their experimental and clinical validation. Full article

This study investigated the kinematic characteristics of center of mass (CoM) movement in elite standing para table tennis players during a controlled 20-ball displacement speed test, focusing on displacement, velocity, acceleration, and jerk as indicators of movement coordination and control. Twenty-one national-level athletes (classes 6–11) performed alternating forehand and backhand strokes while three-dimensional motion analysis captured CoM trajectories. The primary aim was to characterize directional CoM kinematics, and the secondary aim was to examine associations with functional ability, stroke accuracy, and expert-rated technical performance. Results indicated that the range of CoM displacement was largest in the medio-lateral direction, reflecting the sport-specific demands of side-to-side repositioning, while mean displacement did not differ significantly between the medio-lateral and antero-posterior axes. Similarly, velocity, acceleration, and jerk ranges were greatest laterally, highlighting the dynamic requirements of lateral movement. Correlation analyses revealed no statistically significant associations between CoM metrics and functional ability, stroke accuracy, or expert-rated performance after Bonferroni correction, though exploratory trends suggested that higher-functioning athletes may exhibit greater lateral displacement. Jerk, as a measure of movement smoothness, did not systematically differentiate performance or functional class. These findings underscore the predominance of lateral CoM control in para table tennis and provide a biomechanical basis for training interventions aimed at improving lateral stability, coordination, and functional efficiency. Full article

Zygomaticomaxillary complex (ZMC) fractures are among the most common midfacial injuries, with significant implications for both function and facial esthetics. Optimal management requires restoring the normal anatomical alignment and symmetry of the zygomatic region to prevent long-term deformity and functional deficits. However, the decision-making surrounding surgical intervention, particularly in isolated ZMC fractures with moderate displacement, remains nuanced. This review discusses contemporary surgical approaches for isolated ZMC fractures and examines how objective morphometric analysis can guide critical decisions such as the timing of surgery, choice of surgical approach, and extent of fixation. Conventional assessment tools like computed tomography (CT), cephalometric measurements, and intraoperative imaging provide foundational data on fracture anatomy. Emerging technologies, including three-dimensional (3D) photogrammetry, stereophotogrammetry, artificial intelligence (AI)-based symmetry analysis, and surgical navigation systems, offer advanced means to quantify facial symmetry and bone alignment. By integrating these objective metrics into clinical practice, surgeons can enhance preoperative planning and postoperative outcome evaluation, with a particular focus on achieving facial symmetry for optimal esthetic and functional results. We also outline clinical decision-making frameworks that incorporate quantitative measurements, and we discuss current limitations, future directions, and the potential for standardizing protocols in the management of ZMC fractures. Full article

In Global Navigation Satellite System (GNSS)-denied environments, reconstructing three dimensional trajectories using only an Inertial Measurement Unit faces challenges such as heading drift, stride error accumulation, and gait recognition uncertainty. This paper proposes a path estimation method with a nine-axis inertial sensor that continuously and accurately estimates an agent’s path without external support. The method detects stationary states and halts updates to suppress error propagation. During motion, gait modes including flat walking, stair ascent, and stair descent are classified using vertical acceleration with dynamic thresholds. Vertical displacement is estimated by combining gait pattern and posture angle during stair traversal, while planar displacement is updated through adaptive stride length adjustment based on gait cycle and movement magnitude. Heading is derived from the attitude matrix aligned with magnetic north, enabling projection of displacements onto a unified frame. Experiments show planar errors below three percent for one-hundred-meter paths and vertical errors under two percent in stair environments up to ten stories, with stable heading maintained. Overall, the method achieves reliable gait recognition and continuous three-dimensional trajectory reconstruction with low computational cost, using only a single inertial sensor and no additional devices. Full article

Background: Acromegaly, typically caused by growth hormone (GH)-secreting pituitary adenomas, leads to chronic GH and insulin-like growth factor-1 overproduction, resulting in significant cardiovascular complications, including left ventricular (LV) hypertrophy, myocardial fibrosis, diastolic/systolic LV dysfunction, and frequent valvular disease. Although aortic root dilation has been documented, the morphology and function of the aortic valve annulus (AVA) and its relationship with LV performance remain unexplored. Methods: The present study comprised a total of 31 patients with acromegaly, from which eight subjects were excluded due to inferior image quality. The remaining group of acromegalics consisted of 23 cases (mean age: 54.3 ± 14.5 years, 6 males). Their results were compared to 31 age- and gender-matched healthy subjects (mean age: 50.0 ± 7.4 years, 9 males). Cardiac assessment involved routine two-dimensional Doppler echocardiography and three-dimensional speckle-tracking echocardiography (3DSTE) to quantify basal regional and global longitudinal strains. Detailed planimetric measurements of AVA dimensions and its spatial displacement, called AVA plane systolic excursion (AAPSE), were also obtained. Results: Among 12 patients with inactive acromegaly, 7 patients (58%) showed larger end-systolic AVA area (AVA-A), while 5 patients (42%) had larger end-diastolic AVA-A. Among the 11 patients with active acromegaly, 3 patients (27%) had larger end-systolic AVA-A and 5 patients (45%) had larger end-diastolic AVA-A, while in 3 patients (27%) end-systolic and end-diastolic AVA-A proved to be equal. All end-systolic and end-diastolic AVA dimensions were tendentiously greater in acromegaly, with more pronounced values seen in the presence of an active disease. AAPSE was reduced both in all acromegaly patients and in those with active disease compared to controls. From LV strains, basal and global LV longitudinal strain (LS) and basal LV circumferential strain (CS) were similar when comparing acromegaly patients and those with active and inactive disorder to controls. However, basal and global LV-LS tended to be reduced, while basal LV-CS tended to be increased. Significantly increased global LV-CS were present in active acromegaly patients compared to inactive acromegaly patients and controls Conclusions: Significant aortic valve annular dilation is present in acromegaly, which is associated with its reduced spatial systolic displacement. Full article

In the semi-desert aeolian sand areas of Northern China, surface deformation monitoring with SAR is challenged by loss of coherence due to mobile dunes, seasonal vegetation changes, and large-gradient, nonlinear subsidence from underground mining. This study utilizes PALSAR-2 (L-band, 3 m resolution) and Sentinel-1 (C-band, 30 m resolution) data, applying InSAR and Offset tracking methods combined with differential, Stacking, and SBAS techniques to analyze deformation monitoring effectiveness and propose an efficient dynamic monitoring strategy for the Shendong Coalfield. The main conclusions can be summarized as follows: (1) PALSAR-2 data, which has advantages in wavelength and resolution (L-band, multi-look spatial resolution of 3 m), exhibits better interference effects and deformation details compared to Sentinel-1 data (C-band, multi-look spatial resolution of 30 m). The highly sensitive differential-InSAR (D-InSAR) can promptly detect new deformations, while Stacking-InSAR can accurately delineate the range of rock strata movement. SBAS-InSAR can reflect the dynamic growth process of the deformation range as a whole, and SBAS-Offset is suitable for observing the absolute values and morphology of the surface moving basin. The combined application of Stacking-InSAR and Stacking-Offset methods can accurately acquire the three-dimensional deformation field of mining-induced strata movement. (2) The spatiotemporal process of surface deformation caused by coal mining-induced strata movement revealed by InSAR exhibits good correspondence with both the underground mining progress and the development of ground fissures identified in UAV images. (3) The maximum displacement along the line of sight (LOS) measured in the mining area is approximately 2 to 3 m, which is close to the 2.14 m observed on site and aligns with previous studies. The calculated advance influence angle of the No. 22308 working face in the study area is about 38.3°. The influence angle on the solid coal side is 49°, while that on the goaf side approaches 90°. These findings further deepen the understanding of rock movement and surface displacement parameters in this region. The dynamic monitoring strategy proposed in this study is cost-effective and operational, enhancing the observational effectiveness of InSAR technology for surface deformation due to coal mining in this area, and it enriches the understanding of surface strata movement patterns and parameters in this region. Full article

The external floating roof of a large storage tank directly covers the liquid surface as the liquid level rises and falls, enhancing the tank’s safety and environmental performance. It is fabricated from thin SA516 Gr.70 steel plates, with a carbon equivalent of 0.37% calculated according to AWS standards, using single-sided butt welding. Such plates are susceptible to welding-induced deformations, resulting in irregular warping of the bottom plate. Current research on floating roofs for storage tanks mostly relies on idealized models that assume no deformation, thereby neglecting the actual deformation characteristics of the floating roof structure. To address this, the present study develops an automated modeling approach that reconstructs a three-dimensional floating roof model based on measured deformation data, accurately capturing the initial irregular geometry of the bottom plate. This method employs parametric numerical reconstruction and automatic finite element model generation techniques, enabling efficient creation of the irregular initial deformation caused by welding of the floating roof bottom plate and its automatic integration into the finite element analysis process. It overcomes the inefficiencies, inconsistent accuracy, and challenges associated with traditional manual modeling when conducting large-scale strength analyses under in-service conditions. Based on this research, a strength analysis of the deformed floating roof structure was conducted under in-service conditions, including normal floating, extreme rainfall, and outrigger contact scenarios. An idealized geometric model was also established for comparative analysis. The results indicate that under the normal floating condition, the initial irregular deformation increases the local stress peak of the floating roof bottom plate by 19%, while the maximum positive and negative displacements increase by 22% and 83%, respectively. Under extreme uniform rainfall conditions, it raises the stress peak of the bottom plate by 24%, with maximum positive and negative displacements increasing by 21% and 28%, respectively. Under the extreme non-uniform rainfall condition, it significantly elevates the stress peak of the bottom plate by 227%, and the maximum positive and negative displacements increase by 45% and 47%, respectively. Under the outrigger bottoming condition, it increases the local stress peak of the bottom plate by 25%, with maximum positive and negative displacements remaining similar. The initial irregular deformation not only significantly amplifies the stress and displacement responses of the floating roof bottom plate but also intensifies the deformation response of the top plate through structural stiffness weakening and deformation coupling, thereby reducing the safety margin of the floating roof structure. This study fills the knowledge gap regarding the effect of welding-induced irregular deformation on floating roof performance and provides a validated workflow for automated modeling and mechanical assessment of large-scale welded steel structures. Full article

Taking a completely stacked section of Beijing Metro Line 22 as the research background, a three-dimensional finite element model was established to study and analyze the displacement and stress variation laws of the existing lower tunnel under different working conditions. The results show that the combined reinforcement measures of radial grouting and trolley support can effectively reduce the adverse effects of the upper tunnel on the lower tunnel during the construction of the overlapping tunnel. It cut the vault vertical displacement from 5.31 mm to 2.67 mm and reduced the stress range from 2.30 MPa to 0.71 MPa, reducing vertical displacement by 50% and maximum principal stress changes by 40% compared to the unreinforced condition. Furthermore, a parametric study indicated an optimal grouting scheme with a 2 m thickness, 120° angle, and 200 MPa modulus, which achieved similar reinforcement effectiveness with a 50% reduction in grout volume. Full article

Photogrammetry offers a non-contact and efficient alternative for monitoring structural deformation and is particularly suited to large or complex surfaces such as masonry walls. This study proposes a spatio-temporal photogrammetric refinement framework that enhances the accuracy of three-dimensional (3D) deformation and strain analysis by integrating advanced filtering techniques into markerless image-based measurement workflows. A hybrid methodology was developed using natural image features extracted using the Speeded-Up Robust Features algorithm and refined through a three-stage filtering process: median absolute deviation filtering, Gaussian smoothing, and representative point selection. These techniques significantly mitigated the influence of noise and outliers on deformation and strain analysis. Comparative experiments using both manually placed targets and automatically extracted feature points on a full-scale masonry wall under destructive loading demonstrated that the proposed spatio-temporal filtering effectively improves the consistency of displacement and strain fields, achieving results comparable to traditional marker-based methods. Validation against laser rangefinder measurements confirmed sub-millimeter accuracy in displacement estimates. Additionally, strain analysis based on filtered data captured crack evolution patterns and spatial deformation behavior. Therefore, integrating photogrammetric 3D point tracking with spatio-temporal refinement provides a practical, accurate, and scalable approach to monitor structural deformation in civil engineering applications. Full article

In advanced manufacturing, nanotechnology, and aerospace fields, the demand for precision is increasing. Driven by this demand, multi-degree-of-freedom grating encoders have become particularly crucial in high-precision displacement and angle measurement. Over the years, these encoders have evolved from one-dimensional systems to complex multi-degree-of-freedom measurement solutions that can achieve real-time synchronization. There can also be high-resolution feedback. Its structure is relatively compact, the signal output is also very stable, and the integration degree is high. This gives it a significant advantage in complex measurement tasks. Recently, there have been new developments. The functions of grating encoders in terms of principle, system architecture, error modeling, and signal processing strategies have all been expanded. For instance, accuracy can be improved by integrating multiple reading-heads, while innovative strategies such as error decoupling and robustness enhancement have further advanced system performance. This article will focus on the development of two-dimensional, three-dimensional and multi-degree-of-freedom grating encoders, exploring how the measurement degrees of freedom have evolved, and emphasizing key developments in spatial decoupling, error compensation and system integration. At the same time, it will also discuss some challenges, such as error coupling, system stability and intelligent algorithms for integrating real-time error correction. The future of grating encoders holds great potential. Their applications in precision control, semiconductor calibration, calibration systems, and next-generation intelligent manufacturing technologies can bring promising progress to both industrial and scientific fields. Full article

Urban deep excavations conducted near operational tunnels necessitate stringent deformation control. This study investigates the Baiyun Station excavation by employing a three-dimensional finite-element model based on the Hardening Soil Small-strain (HSS) constitutive law, calibrated using Phase I field monitoring data on wall deflection, ground settlement, and tunnel displacement. Material parameters for the HSS model derived from the prior Phase I numerical simulation were held fixed and used to simulate the Phase II excavation, with peak errors of less than 5.8% for wall deflection and less than 2.9% for ground settlement. The model was subsequently applied to evaluate the impacts of Phase II excavation. The key contribution of this study is a monitoring-driven HSS modeling framework that integrates staged excavation simulation with field-based calibration, enabling quantitative assessment of tunnel responses—including settlement troughs, bow-shaped wall deflection patterns, and the distance-decay characteristics of lining displacement—to support structural safety evaluations and protective design measures. The results demonstrate that the predicted deformations and lining stresses in adjacent power and metro tunnels remain within permissible limits, offering practical guidance for excavation control in densely populated urban areas. Full article

Background/Objectives: While skeletal facial asymmetry is commonly assessed using posteroanterior (PA) cephalometric radiographs, the association between skeletal measurements and volumetric soft tissue asymmetry remains unclear. This study aimed to identify which skeletal parameters are most strongly correlated with soft tissue asymmetry measured using three-dimensional (3D) imaging. Methods: Thirty-three Japanese patients (8 males and 25 females; mean age: 26.85 ± 12.13 years) undergoing orthodontic–orthognathic treatment were included. Three-dimensional facial surface data were acquired using the VECTRA^® H1 imaging system. Soft tissue asymmetry was quantified by calculating the volumetric difference between the original and mirrored 3D facial images, divided into three regions: whole face, midface, and lower face. PA cephalometric radiographs were traced, and 28 skeletal variables were measured. Pearson correlation coefficients were calculated between skeletal variables and asymmetry volumes and squared to obtain R² values. Results: The strongest correlation with whole facial soft tissue asymmetry was found for menton deviation from the midline (R² = 0.630). Similar trends were observed for the lower face. In contrast, only one skeletal variable showed a moderate correlation with midfacial asymmetry (maximum R² = 0.186), and skeletal parameters related to maxillary occlusal cant did not show significant associations. Conclusions: Volumetric soft tissue asymmetry is strongly associated with mandibular skeletal deviation, particularly menton displacement, whereas midfacial skeletal morphology may have a limited impact. Further studies including more patients with pronounced midfacial soft tissue asymmetry are warranted. Full article

For the possible damage to overhead pipelines caused by gas explosions in utility tunnels, an overall three-dimensional finite-element model of utility tunnel–soil–pipeline is established, the overpressure loads are applied to the inner wall of the gas chamber in the utility tunnel, the dynamic response laws of the utility tunnel and the pipeline are calculated and analyzed, and anti-explosion protection measures are proposed. The results show that the degree of damage to the pipe wall is determined by both the explosion-impacted area and the soil constraint. Under the same explosion-impacted area, the peak horizontal displacement of the monitoring point without soil constraint is 1.64 times that with soil constraint, and 1.29 times for the peak vertical displacement. The damage to the lower part of the pipeline is significantly greater than that to the upper part of the pipeline, and the damage to the pipeline decreases with an increase in the horizontal angle between the utility tunnel and the pipeline. The diameter deformation rates were 49% at α = 0° and 84% at α = 45°, with α = 90° showing the least damage. Therefore, it is suggested that the overhead pipeline is perpendicular to the utility tunnel. As the vertical distance between the utility tunnel and the pipeline increases, the diameter deformation rate and displacement of the pipeline both decrease, and when this distance is greater than 3 m, the influence on the pipeline significantly decreases. Therefore, it is recommended that the distance between the pipeline and the utility tunnel should be at least 3 m. In addition, the damage caused by gas explosions to the overhead pipeline can be reduced by reinforcing the gas chamber, using energy-absorbing materials around the utility tunnel, and setting up hollow piles between the utility tunnel and pipelines. Full article