Search Results (120)

Corrosion-induced cracking of reinforced-concrete (RC) covers is well known, yet key knowledge gaps persist. Most studies isolate uniform corrosion or a single non-uniform corrosion pattern and ignore the effects of boundary restraint and structural configurations, leading to inaccurate predictions of cracking thresholds and crack propagation patterns. This study systematically investigates the influence mechanisms of constraint conditions and structural configurations on corrosion-induced cracking behavior using the phase-field model. The results indicate that the non-uniformity of steel corrosion is a critical factor governing cover cracking. As the corrosion non-uniformity coefficient increases, the critical corrosion level exhibits a monotonic decreasing trend—from 0.95% to 0.15% under strong constraints and from 0.52% to 0.15% under weak constraints. Concurrently, the crack morphology evolves from a single radial crack to a wedge-shaped crack oriented toward the peak corrosion side. The influence of constraint conditions is dualistic, while strong constraints enhance the failure threshold, their mitigating effect diminishes markedly under highly non-uniform corrosion. The critical corrosion threshold for eccentrically arranged corner reinforcement is significantly lower than that for centrally arranged reinforcement; the corrosion angle only induces slight crack deflection and minor threshold fluctuations; and the curved top section, due to its weaker equivalent constraint, exhibits inferior crack resistance compared to the linear top section. Three-dimensional analysis reveals a pronounced longitudinal discreteness effect, which not only substantially elevates the critical corrosion threshold but also leads to diverse spatial failure modes. This work links rust-expansion eigen-displacement to crack propagation within a unified phase-field framework, providing materials-level criteria for evaluating corrosion tolerance and guiding the design of cover materials and reinforcement layouts to enhance durability. Full article

This study considers a robust design methodology to reduce cogging torque in the EPS (Electric Power Steering) of an automotive system. Cogging torque reduction is the key design factor to improve steering feeling and drive stability in an EPS system. For this reason, an SPMSM (Surface Permanent Magnet Synchronous Motor) has been widely applied to drive a motor in an EPS system. Furthermore, two design methods, which are a magnet shape and step-skew design for rotor assembly, have been mainly used to reduce cogging torque in an SPMSM. In this paper, an SPMSM is selected as the drive motor and a robust design methodology is proposed to reduce cogging torque in an EPS system. Firstly, a cycloid curve is used for the magnet shape to reduce cogging torque. An evaluation index δq is also used to compare this with a conventional magnet shape design. Secondly, based on the results of the magnet shape design with the cycloid curve, a step-skew design for rotor assembly is also applied to reduce cogging torque. In order to validate the effectiveness of the robust design for the cycloid curve and conventional magnet shape with rotor step-skew, the results from FEM (Finite Element Method) analysis and prototype tests are compared. The cycloid curve magnet shape model with rotor step-skew was verified to reduce the cogging torque and enhance the robustness for cogging torque variation through the analysis and protype test results. The verified results for the proposed model will be extended to meet the required cogging torque variation for the various applications driven by SPMSM with the robust design model. Full article

This study describes and validates a novel method for assessing anterior crystalline lens curvature along vertical and horizontal meridians using radial measurements derived from Scheimpflug imaging. The aim was to evaluate whether pupil diameter (PD), anterior lens curvature, and anterior chamber depth (ACD) change during accommodation and whether these changes are age-dependent. A cross-sectional study was conducted on 104 right eyes from healthy participants aged 21–62 years. Sixteen radial images per eye were acquired using the Galilei Dual Scheimpflug Placido Disk Topographer under four accommodative demands (0, 1, 3, and 5 dioptres (D)). Custom software analysed lens curvature by calculating eccentricity in both meridians. Participants were analysed as a total group and by age subgroups. Accommodative amplitude and monocular accommodative facility were inversely correlated with age. Both PD and ACD significantly decreased with higher accommodative demands and age. Relative eccentricity decreased under accommodation, indicating increased lens curvature, especially in younger participants. Significant curvature changes were detected in the horizontal meridian only, although no statistically significant differences between meridians were found overall. The vertical meridian showed slightly higher eccentricity values, suggesting that it remained less curved. By enabling detailed, meridionally stratified in vivo assessment of anterior lens curvature, this novel method provides a valuable non-invasive approach for characterizing age-related biomechanical changes during accommodation. The resulting insights enhance our understanding of presbyopia progression, particularly regarding the spatial remodelling of the anterior lens surface. Full article

To analyze the hydrodynamic performance of the Voith–Schneider Propeller (VSP) under high eccentricity (e = 0.9), open-water performance numerical calculations were conducted for the VSP at different eccentricities. The results were compared with experimental data, revealing significant discrepancies at high eccentricity. Analysis identified that during the experiment, the VSP blades did not strictly move according to the prescribed “normal intersection principle” when passing near the eccentric point, which was the primary cause of the errors between the calculation and experiment. Further research demonstrated that when the blades pass near the eccentric point, both the individual blade and the overall propeller exhibit strong unsteady pulsation phenomena. The characteristics of these unsteady forces become more pronounced with increasing eccentricity. For the VSP under high eccentricity (e = 0.9), different Blade Steering Curves near the eccentric point were designed using a parametric method. The hydrodynamic performance of the VSP under these different curves was compared. The study demonstrates that rationally optimizing the motion of blades is a key approach to improving their hydrodynamic performance. At J = 2.4, the adoption of Opt-5 enables a 4.67% increase in thrust, a 25.19% reduction in thrust pulsation, a 12.74% reduction in torque, an 81.94% reduction in torque pulsation, and a 19.95% improvement in efficiency for the VSP. Full article

The aim of this study is to establish an accurate calculation method for the deflection caused by the effect of pre-stress in a steel truss web–concrete composite girder bridge based on the energy variational principle, considering the influence of shear deformation and the shear lag effect of the steel truss web member on the accuracy of the deflection calculation. The pre-stress effect is determined by the equivalent load method, and the deflection analytical solution for a composite girder bridge under straight-line, broken-line, and curve pre-stressing tendon arrangements is established. The reliability of the formula is verified using ANSYS 2022 finite element numerical simulation. At the same time, the influence of shear deformation, the shear lag effect, and their combined (dual) effect on the deflection calculation accuracy is analyzed under different linear pre-stressed reinforcement arrangements and comprehensive arrangements of pre-stressed reinforcement. The analysis of the example shows that the analytical solution for the deflection of the steel truss web–concrete composite beam, when considering only the shear deformation and the dual effect, is more consistent with the finite element numerical solution. The shear deformation of the steel truss web member under the eccentric straight-line arrangement alone does not cause additional deflection, and the additional deflection caused by the shear lag effect can be ignored. The influence of shear deformation on deflection is higher than that of the shear lag effect. The contribution ratio of the additional deflection caused by the dual effect is greater than 14%, and the influence of the dual effect on deflection is more obvious under a broken-line arrangement. Under the comprehensive arrangement of pre-stressing tendons, the contribution rate of shear deformation to the total deflection is about 3.5 times that of shear lag. Compared with the deflection value of the primary beam, the mid-span deflection is increased by 3.0%, 11.0%, and 13.9% when only considering the shear lag effect, only considering shear deformation, and considering the dual effect, respectively. Therefore, shear deformation and the shear lag effect should be considered when calculating the camber of a steel truss web–concrete composite girder bridge to improve the calculation accuracy. Full article

The purpose of this study was to determine the power produced by knee muscles in normal adults when performing self-selected walking. The power of a single knee muscle is not directly measurable without invasive methods. An EMG-to-force processing (EFP) model was developed, which scaled muscle–tendon unit (MTU) power output to gait EMG. Positive power by each muscle occurred when force was developed during concentric contractions, and negative power occurred with lengthening contractions. The sum of EFP power produced by knee muscles was compared with the kinematics plus kinetics (KIN) knee power at percent gait cycle intervals. Closeness-of-fit of the EFP and KIN power curves (during active muscle forces) was used to validate the model. Key findings were that most knee muscles have a characteristic eccentric-then-concentric contraction pattern, and greatest power was produced by the Semimembranosis, with peak magnitude nearly matched by two vastus muscles (VL, VMO). The EMG-to-force processing approach provides reasonable estimates of active individual knee muscle power in self-selected speed walking in neurologically intact adults. Further, a prolonged period of the gait cycle showed substantial knee flexion or extension in the absence of power produced by muscles acting at the knee. Full article

Background/Objectives: Diagnosing interstitial pregnancy (IP) using ultrasonography can be challenging, as it is often mistaken for eccentrically located intrauterine pregnancy (IUP). In this retrospective cohort study, we aimed to develop a predictive scoring model using multiple clinical factors to enhance the diagnosis of IP and facilitate timely interventions in suspected cases. Methods: We enrolled 63 pregnant women with a diagnosis of suspected IP who visited a single tertiary center between January 2006 and December 2023. Data on the clinical risk factors, symptoms, laboratory test results, and ultrasound findings were analyzed. A statistical predictive score was developed using logistic regression analysis with feature selection based on the least absolute shrinkage and selection operator to optimize the predictive accuracy and clinical applicability. Results: From a total of 12 factors, a scoring model was constructed from the three most prominent factors—ultrasound findings showing no surrounding endometrium, myometrial thinning of less than 5 mm, and vaginal bleeding—all of which demonstrated high feature importance. This predictive score identified IP with a negative predictive value of 0.950 in the low-risk group and a positive predictive value of 1.000 in the high-risk group, whereas the overall area under the curve was 0.998 (95% confidence interval, 0.992–1.000). Conclusions: The statistically derived predictive model––ultrasound showing no surrounding endometrium and myometrial thinning < 5 mm combined with vaginal bleeding––demonstrated high accuracy and practical applicability for IP diagnosis, providing a robust tool to enhance clinical decision-making and optimize routine management strategies for IP. Full article

Compared with planar layering, the morphology of spatial GMA deposition beads formed by curved layering is influenced by gravity, resulting in asymmetric and complex cross-sections. To quantitatively describe the bead orientation and cross-sectional shape, this study introduces the path inclination angle and path direction angle, along with five characteristic parameters—height, width, eccentricity, upper plumpness, and lower plumpness—using piecewise polynomial fitting for profile modeling. A full-factorial experiment was conducted to establish the relationship between deposition speed, bead spatial orientation, and cross-sectional features. The obtained fitting equation had a mean relative error of less than 2.5%, and an overlapping strategy was proposed to achieve flat, curved GMA layers. The proposed bead characterization method, parameter planning model, and overlap strategy were validated through deposition experiments on cylindrical surfaces without a positioner, providing a foundation for high-precision curved GMA additive manufacturing. Full article

This study investigates the failure modes and damage extent of reinforced concrete (RC) columns under the combined action of eccentric blast loading and axial compressive loading through experimental tests and numerical simulations. Field blast tests were performed using half-scaled-down models for close-in airburst tests. The effects of charge mass, explosive position, and axial load on the failure modes and damage levels of RC columns under close-range blast loading were investigated. Eight experimental datasets of blast overpressure were obtained, and curve fitting was performed on these data to establish an empirical formula, thereby enhancing the predictive accuracy of blast effect assessment in practical engineering scenarios. The test results indicated that when the explosive position is closer to the column base, the structural failure mode becomes closer to shear failure. To further interpret the experimental data, a detailed finite element model of RC columns was developed. Numerical simulations of RC columns were conducted using the RHT model. The rationality of the model was validated through comparison with experimental data and the SDOF method, with dynamic response analyses performed on cross-sectional dimensions, the longitudinal reinforcement ratio, the scaled distance, the explosion location, and axial compression. An empirical formula was ultimately established to predict the maximum support rotation of RC columns. Studies have shown that when the explosive position is closer to the column base, the structural failure mode approaches shear failure, and axial compression significantly increases the propensity for shear failure. Full article

Fine-grained sedimentary rocks are ideal carriers for astronomical cycle analysis as they can record and preserve significant astronomical cycle signals. Spectral analysis using the Multi-taper Method (MTM) and Evolutionary Harmonic Analysis (EHA) using the Fast Fourier Transform (FFT) were conducted on natural gamma data from key wells in the Es₃l sub-member in the Bonan Sag, Bohai Bay Basin, China. Gaussian bandpass filtering was applied using a short eccentricity cycle of 100 ka, and a “floating” astronomical time scale for the Es₃l sub-member (Lower 3rd sub-member of Shahejie Formation in Eocene) was established using magnetic stratigraphic ages as boundaries. Stratigraphic divisions were made for single wells in the Es₃l of the Bonan Sag, and a stratigraphic framework was established based on correlations between key wells. The research results indicate the following: Firstly, the Es₃l of the Bonan Sag records significant astronomical cycle signals, with an optimal sedimentation rate of 8.39 cm/ka identified. Secondly, the cyclical thicknesses corresponding to long eccentricity, short eccentricity, obliquity, and precession cycles are 38.9 m, 9.7 m, 4.6–3.4 m, and 1.96–1.66 m, respectively. Thirdly, the Es₃l sub-member stably records 6 long eccentricity cycles and 26 short eccentricity cycles, and the short eccentricity curve is used as a basis for stratigraphic division for high-precision stratigraphic correlations. Fourthly, the quality of sandstone-interbedded mudrock is jointly controlled by the short eccentricity and precession. Eccentricity maximum values result in thicker sandstone interlayers, while minimum precession values promote the thickness of sandstone interlayers. Through astronomical cycle analysis, the depositional evolution mechanism of sandstone-interbedded mudrock is revealed. Combined with the results of high-precision stratigraphic division, this can provide a basis for fine evaluation and “sweet spot” prediction of lacustrine shale oil reservoirs. Full article

The overturning resistance of curved single-column pier bridges has garnered increasing attention with the rise in infrastructure demands. However, aspects such as the secondary effects of overturning and the dynamic interactions between vehicles and bridges have not been fully explored. Hence, a refined finite element model incorporating Vehicle–Bridge Interaction (VBI) dynamics has been applied to a highway ramp bridge in this study, aiming to elucidate how VBI-induced vibrations contribute to bridge overturning and to develop effective reinforcement strategies for enhanced stability under eccentric loads. The analysis suggests that the rotation of the main girder, influenced by eccentric overload, is a significant factor in the overturning process. The initial overturning stability coefficient was found to be 0.948, pointing to potential areas for improvement. By implementing targeted reinforcement measures, specifically the addition of cover beams, the stability coefficient was improved to 2.626. The study provides insights into VBI-induced overturning in curved single-column pier bridges, offering a reinforcement strategy aimed at enhancing stability under eccentric loads. Full article

A series of fault depressions developed in the Kailu area on the southwestern margin of the Songliao Basin, where thick lacustrine fine-grained sedimentary rocks were widely deposited during the initial faulting stage in the Early Cretaceous. These formations serve as the primary source rocks within the depressions. To investigate the depositional cyclicity framework, paleoenvironmental conditions, and source rock development patterns of fine-grained sedimentary strata, this study focuses on the Naiman Sag, selecting Well Nai-10 for wavelet transform and spectral analysis based on natural gamma ray logs. Combining core, well logging, and geochemical element analyses, Milankovitch cycles within the Yixian Formation were identified. The relationship between theoretical orbital periods and sedimentary cycles in a single well was established, enabling the high-precision identification and classification of fine-grained sedimentary cycles. Furthermore, the study explores the sedimentary response to orbital forcing and the development patterns of source rocks. The results indicate that fine-grained sedimentary strata exhibit distinct Milankovitch cyclicity, with a strong correlation between astronomical periods and sedimentary cycles. Using the 100 kyr short eccentricity cycle as the tuning curve, an astronomical timescale and high-frequency cyclic division for the target interval were established. Under the control of long eccentricity cycles, sedimentation exhibits strong response characteristics: near the peak of short eccentricity cycles, the climate was warm and humid, redox conditions were strong, and precipitation was high, facilitating organic matter accumulation. Based on this response relationship, two ideal enrichment models of mudstone and shale under different paleoclimatic conditions are proposed, providing valuable insights for identifying high-quality source rocks and unconventional hydrocarbons in hydrocarbon exploration. Full article

By integrating a very short shear link–shear slotted bolted connection (VSSL-SSBC) and two self-centering SMA braces (SCBs), a novel self-centering shear link (SC-SL) was developed for installation between a steel brace and steel beam in an eccentrically braced frame (EBF). The SC-SL can enhance the seismic performance and seismic resilience capacity of the EBF by achieving a high bearing capacity and low residual deformation. The mechanical properties of the VSSL-SSBC and SC-SL were designed and analyzed using both experimental and numerical methods. Subsequently, the seismic performances of EBFs equipped with VSSL-SSBC and SC-SL were analyzed under different earthquakes. Validated numerical methods were employed to investigate the deformation modes, stress nephograms, and hysteresis curves of the EBFs. The deformation mode and hysteresis curve of the VSSL-SSBC exhibit an initial frictional slip of the SSBC, followed by the load-bearing response of the VSSL. The skeleton curve of the VSSL-SSBC consists of elastic, slip, elastoplastic, and plastic stages, and the deformation and damage are significantly reduced at the same displacement. In the SC-SL, the SCB undergoes substantial deformation when the SMA is in tension, effectively minimizing residual deformation. Under frequent earthquakes, the stress and displacement of all components in both the EBF-VSSL-SSBC and EBF-SC-SL are essentially equivalent, and the VSSL-SSBC remains elastic, without significant yielding deformation. Under rare earthquakes, incorporating SCB in EBF-SC-SL significantly enhances the ultimate load capacity by 19.66% and reduces the residual deformation by 27.90%. This improvement greatly contributes to the seismic resilience of the EBF. Full article

The elastic ring squeeze film damper (ERSFD), due to its compact structure and excellent mechanical properties, has been increasingly applied in various types of combination bearings for aero-engines. During operation, the force state of the elastic ring varies with different precession angles of the journal, leading to changes in the stiffness of the elastic ring. This study, based on a bidirectional fluid–structure interaction (FSI) theory, analyzes the deformation and stiffness of the elastic ring under different contact conditions. The time-varying stiffness curve of the elastic ring is obtained, and the influence of various parameters on its time-varying stiffness characteristics is further investigated. An equivalent stiffness method for the elastic ring is proposed, which improves accuracy by more than 3% at low speeds compared to traditional methods. Using this equivalent method, the effects of parameters such as the number of ring protrusions, protrusion width, protrusion angle, elastic ring thickness, and oil film eccentricity on the pressure distribution of the inner and outer oil films are analyzed. The results indicate that an increase in the number of elastic rings, protrusion width, axial length, and ring thickness leads to a rise in stiffness, with the number of protrusions having the strongest effect and the axial length having the weakest effect. Additionally, as the number of protrusions, protrusion width, and protrusion angle increase, both the damping and stiffness of the inner and outer oil films decrease by approximately 10%, with a more significant impact on the outer oil film than on the inner oil film. When the axial length and oil film eccentricity increase, both the damping and stiffness of the inner and outer oil films also increase, with the inner oil film being highly sensitive to eccentricity. However, excessive eccentricity enhances the nonlinearity of the oil film. The findings of this study provide a theoretical foundation for the design, application, and maintenance of combination bearings incorporating elastic ring squeeze film dampers. Full article

Concrete-filled steel tube (CFST) columns reinforced with latticed steel angles (LSA), referred to as CFST-LSA columns, have been widely adopted in practical engineering. Understanding their mechanical behavior under eccentric loading is crucial for ensuring structural safety and performance in engineering applications. Previous experimental studies have demonstrated that the incorporation of steel angles substantially improves both the axial capacity and ductility of CFST-LSA columns. Existing methods for determining the eccentric bearing capacity of CFST-LSA columns primarily rely on the normalized N/N_u-M/M_u interaction curve. However, this approach involves a complex calculation procedure for evaluating the eccentric bearing capacity. To address this limitation, this study proposes a theoretical model based on the limit equilibrium method to predict the eccentric bearing capacity of CFST-LSA columns. The proposed model explicitly integrates fundamental geometric and material parameters, thereby enabling a more efficient and programmable calculation of the eccentric bearing capacity. Comparisons between the proposed model and experimental results show good agreement, with a tested-to-predicted eccentric resistance ratio of 1.085 and a coefficient of variation (COV) of 0.022. The proposed model can serve as a practical calculation method for eccentric loading of CFST-LSA columns, facilitating their application in high-rise buildings and long-span bridges. Full article