Search Results (127)

Gantry cranes play a pivotal role in industrial production. Gantry cranes exhibit clear double-swing characteristics in actual working conditions, complicating anti-swing control. Most existing anti-swing control methods are based on a simplified single-pendulum model. The present paper puts forward a double-pendulum model for gantry cranes and proposes an adaptive hierarchical sliding mode control based on a neural network according to the actual working conditions. The use of a neural network and adaptive layered sliding mode control can effectively inhibit chattering, thus improving control performance and stability and achieving the goal of anti-shaking control, thus effectively inhibiting residual oscillation. This method has been demonstrated to be effective in achieving the objective of anti-shudder control, thereby effectively suppressing residual oscillation. Compared with hierarchical sliding mode control, the proposed method reduces the maximum residual oscillation angle of the hook and payload by approximately 80%. In comparison with the conventional sliding mode control, the maximum residual oscillation angle is reduced by approximately 84%. Furthermore, the control force amplitude is reduced to 5.23 N, representing decreases of 30.2% and 37.4%, respectively. These comparative results demonstrate the superior oscillation suppression. The system also shows a reliable performance against potential disturbances. Full article

It is well known that aqueous solutions can emit electromagnetic waves in the radio frequency range. However, the physical nature of this process is not yet fully understood. In this work, the possible role of gas nanobubbles formed in the bulk liquid is considered. We develop a theoretical model based on the concept of gas bubbles stabilized by ions, or “bubstons”. The role of bicarbonate and hydronium ions in the formation and stabilization of bubstons is explained through the use of quantum chemical simulations. A new model of oscillating bubstons, which takes into account the double electric layer formed around their gas core, is proposed. Theoretical estimates of the frequencies and intensities of oscillations of such compound species are obtained. It was determined that oscillations of negatively charged bubstons can occur in the GHz frequency range, and should be accompanied by the emission of electromagnetic waves. To validate the theoretical assumptions, we used dynamic light scattering (DLS) and showed that, after subjecting aqueous solutions to vigorous shaking with a force of 4 or 8 N (kg·m/s²) and a frequency of 4–5 Hz, the volume number density of bubstons increased by about two orders of magnitude. Radiometric measurements in the frequency range of 50 MHz to 3.5 GHz revealed an increase in the intensity of radiation emitted by water samples upon the vibrational treatment. It is argued that, according to our new theoretical model, this radiation can be caused by oscillating bubstons. Full article

Balancing mechanisms require the minimization of both the Shaking Moment ($ShM$) and Shaking Force ($\mathbf{ShF}$), a complex multi-criteria challenge often tackled using single-objective algorithms. However, these methods face difficulties in navigating competing objectives. In contrast, multi-objective algorithms provide a more efficient and adaptable framework, while Fully Cartesian Coordinates ($FCC$) simplify the balancing equations compared to conventional Cartesian formulations. This study focuses on optimizing the dynamic balance of a six-bar Watt linkage using $FCC$. A wide set of optimization methods is analyzed and compared, and among them, the S-Metric Selection Evolutionary Multi-objective Optimization Algorithm (SMS-EMOA) demonstrates superior performance. This algorithm achieves the most significant hypervolume value in only 10.44 min of execution. The results indicate that multi-objective algorithms outperform single-objective approaches, offering faster and more diverse optimization solutions. Additionally, this study introduces an analytical method that enables the straightforward identification of removable counterweights, achieving an equally effective balance while minimizing the number of counterweights required. Full article

Background/Objectives: Traditional diagnostic criteria for SBS include subdural, subarachnoid, and retinal hemorrhages. While intentional shaking is a known cause, the potential for similar forces acting on the head resulting from accidental trauma has not been fully explored. This study investigated the biomechanical forces on a model infant’s head during improper handling to determine if such forces could contribute to SBS without malicious intent. Methods: A realistic silicone infant model was equipped with an inertial measurement unit (IMU) to quantify head accelerations during two conditions: (1) placement of the infant model on a table with the head unsupported, and (2) manual shaking at maximum effort by 2 participants holding the model by the torso. Peak head accelerations were recorded for both conditions, and the results were analyzed for comparative assessment of the forces involved. Results: The average peak head acceleration when placing the infant model on a table with the head unsupported was +31,000 ± 7000 mg, with a range of +19,000.00 to +43,000 mg across trials. The average peak head accelerations during maximum effort shaking were significantly lower than placing the infant on the table, averaging 11,000 ± 10,000 vs. 31,000 ± 7000 mg, p < 0.0001). There were no significant differences in head accelerations between participants when placing the infant model on the table with the head unsupported (p = 0.89) nor with shaking the baby with maximum effort (p = 0.96). Conclusions: The study highlights that even accidental non-recommended handling of infants can result in high G-forces to the head, potentially leading to injuries similar to those observed in SBS. These findings highlight the necessity of supporting an infant’s head during handling and warrants caution against prematurely attributing physical abuse in SBS cases without considering unintentional causes. Full article

The control accuracy and stability requirements for rotating payloads in remote sensing satellites are becoming increasingly higher. Typically, rotating payloads such as cameras are connected to the satellite body through mechanical bearings. However, clearances in conventional mechanical bearings are inevitable due to assembly tolerances, manufacturing errors, and wear. When clearances exist in the mechanical bearings of cameras, the clearance between the mechanical bearing and the journal can cause impact-induced vibrations. This paper proposes the implementation of magnetic bearings instead of mechanical bearings to connect the payload with the spacecraft body. First, the magnetic bearing is modeled as a rotational joint with clearance in the dynamic system with magnetic constraints. Subsequently, radial and axial magnetic force models are established. Furthermore, a comparative analysis is conducted to investigate the effects of connection approaches, namely traditional mechanical bearing connections and magnetic bearing connections for rotating payloads. Simultaneously, the dynamic responses of rotating payloads under different connections are discussed. The simulation results demonstrate that the camera attitude motion accuracy is improved and the vibration amplitude under disturbance is reduced when using magnetic bearings. Consequently, the magnetic bearing can effectively isolate vibrations and mitigate disturbances, thereby significantly reducing the attitude shake of rotating payloads. Full article

Composite reinforcement concrete square piles exhibit excellent bending resistance and deformation capacity, along with construction advantages such as ease of transportation. In recent years, they have been widely adopted in building pile foundation applications. However, their seismic behavior, particularly under multi-directional excitation, remains inadequately explored. This study employs large-scale shaking table tests to evaluate the seismic response of a single composite reinforcement square pile embedded in a soft clay foundation under different horizontal excitations (0° and 45°) and two distinct ground motions (Wenchuan Songpan and Chi-Chi) to assess directional anisotropy and resonance effects, with explicit consideration of soil–structure interaction (SSI). The key findings include the following: the dynamic earth pressure along the pile exhibits a distribution pattern of “large at the top, small at the middle and bottom”. And SSI reduced pile–soil compression by 20–30% under 45° excitation compared to 0°. The dynamic strain in outer longitudinal reinforcement in pile corners increased by 30–60% under 45° excitation compared to 0°. Under seismic excitation considering SSI, the bending moment along the pile exhibited an “upper-middle maximum” pattern, peaking at depths of 3–5 times the pile diameter. Axial forces peaked at the pile head and decreased with depth. While bending moment responses were consistent between 0° and 45° excitations, axial forces under 45° loading were marginally greater than those under 0°. The Chi-Chi motion induced a bending moment about four times greater than the Songpan motion, highlighting the resonance risks when the ground motion frequencies align with the pile–soil system’s fundamental frequency. Full article

The establishment of a linear seismic response analysis model that considers ground rotation effects and eccentric torsion informed the investigation of the linear response characteristics of coupled lateral–torsional vibration, considering eccentricity and ground rotation, after which the lateral–torsional coupling linear response pattern of special-shaped column structures is examined. The results show that the torsion angle of a floor is equal to the sum of the interlayer torsion angle caused by eccentric torsion and the pure torsion angle caused by ground rotation, respectively. The natural vibration frequency of the structure considering ground rotation effects is a function of relative eccentricity; the period ratio of translation to torsion caused by ground rotation; and the period ratio of translation to torsion when considering only eccentric torsion. When the translation to torsion period ratio, considering eccentric torsion, is greater than 1.0, the torsional amplitude increases remarkably, but the first-order participation mode is considerably higher under the same conditions. The natural vibration characteristics, translational response, torsional response, and seismic force distribution are obtained for special-shaped columns by conducting the shaking table test on steel-reinforced concrete (SRC) frame structures. After comparative analysis, the maximum ratio of the maximum torsional displacement of the bottom layer of the structure to the horizontal displacement in the X direction is 0.0007. The maximum ratio of the base shear force to the theoretical base shear force of the structure without considering coupling is 0.93. The maximum ratio of the measured shear force of the special-shaped column to the theoretical shear force without considering coupling is 0.65. This indicates that ground rotation has a significant amplification effect on structural response. The research results provide a reference for the seismic design of special-shaped column structures. Full article

Finding appropriate shaking parameters is crucial in designing effective mechanical harvesters. The maximum fruit removal can be achieved when the machine operator properly adjusts the amplitude and frequency for shaking each tree. This review covers the progress in research and development over the past decades on using mechanical harvesters for nut trees, such as almonds, pistachios, walnuts, and hickories, with a specific focus on the natural frequency of individual trees. Furthermore, the reported values of shaking frequency and amplitude from previous studies were discussed and compared, along with frequency calculation approaches based on various shaking mechanisms. Additionally, other parameters, such as clamping force, height, and shaking amplitude, were investigated to determine optimal values for minimizing tree damage. This review emphasizes that the tree’s diameter, height, and canopy morphology should be the primary factors considered when estimating the optimal shaking frequency for nut trees. It also highlights that, to date, the shaking amplitude, frequency, and duration set by field managers or machine operators tend to remain consistent for all trees, which can limit harvesting efficiency. The findings suggest that selecting these parameters uniformly across all trees may not result in efficient fruit removal for individual trees. However, with the assistance of modern computing technology and its adaptation for in-field applications, it is feasible to determine the optimal shaking frequency for each tree mathematically. This approach can maximize fruit removal rates while minimizing tree damage. Finally, the review suggests that improving existing harvesting machines by incorporating better vibratory patterns could offer benefits such as enhanced productivity, reduced labor costs, and decreased permanent tree damage. Full article

Variable-coefficient viscous dampers (VVDs) have a variable annular gap, allowing them to dynamically adjust the damping coefficient at different displacement stages and provide higher damping forces during large displacement phases. This study evaluates the seismic performance of a steel frame equipped with VVDs. A shaking table test was conducted on a two-story, single-span steel frame with the VVDs to assess its seismic response, and the results were compared with those of the same frame equipped with conventional viscous dampers (VD). The experimental results demonstrated that the VVDs significantly reduced the structural dynamic response at various levels of earthquake intensity, consistently outperforming the VDs in terms of the seismic reduction effectiveness. Subsequently, a constitutive model for the VVD element was developed using the open-source finite element software OpenSees3.3.0. The accuracy of the developed element was validated by comparing the finite-element analysis results with mechanical performance tests of the VVD. Based on the developed VVD element, a numerical model of test structure was established in OpenSees for time–history analyses. The results showed good agreement between the numerical simulations and shaking table test data. Finally, a parametric study was conducted on the effects of the ratio $r$ of the second-order damping coefficient to the first-order damping coefficient and the velocity index α of the VVD on the seismic response of the numerical model of the tested structure. The results indicated that the seismic reduction rate of the tested structure increased with $r$, with a maximum improvement of 24%, while it decreased with increasing α, with a maximum reduction of 27%. Full article

Liquefaction and earthquake damage to coral sand sites can cause engineering structure failure. Both testing and analyzing the seismic response characteristics of pile groups on coral sand sites are highly important for the seismic design of engineering structures. To address the lack of research on the seismic dynamic response of group pile foundations in coral sand sites, this study analyzes the characteristics of the seismic dynamic response of vertical and batter pile foundations for bridges in coral sand liquefaction foundations via the shaking table model test and investigates the variation patterns of acceleration, excess pore water pressure (EPWP), and the bending moment and displacement of foundations, soil, and superstructures under different vibration intensities. Results show that the excitation wave type significantly affects liquefaction: at 0.1 g of peak acceleration, only high-frequency sine wave tests liquefied, with small EPWP ratios, while at 0.2 g, all tests liquefied. Vertical pile foundations had lower soil acceleration than batter piles due to differences in bearing mechanisms. Before liquefaction, batter piles had smaller EPWP ratios but experienced greater bending moments under the same horizontal force. Overall, batter piles showed higher dynamic stability and anti-tilt capabilities but endured larger bending moments compared to vertical piles in coral sand foundations. In conclusion, batter pile foundations demonstrate superior seismic performance in coral sand sites, offering enhanced stability and resistance to liquefaction-induced failures. Full article

Structural damages occurred during any earthquake arise not only from structural design flaw but also from the variability of sub-base soil behavior and the foundation system. For this reason, structure–soil–pile interaction has an important place in evaluating the behavior of a structure under dynamic effects. Bored pile application, which is one of the deep foundation systems, is a widely used method in the world to transfer the loads coming from the structure to the ground safely in problematic grounds. For this reason, in pile foundation system designs, how bored pile foundation systems will affect the structural design under earthquake loads is considered an important issue. In particular, how diagonally braced steel structures with piled raft foundation systems will behave under earthquake effects has been evaluated as a subject that needs to be examined. For this reason, this situation was evaluated as the main purpose of this study. The effect of the bored pile systems designed in different orientations on the behavior of diagonally braced steel structures during an earthquake under kinematic and inertial effects was investigated in detail within the scope of this study. Numerical analyses, based on data from shake table experiments on a scaled superstructure, examine various pile design scenarios. Experimental base shear force measurements informed the development of numerical scenarios, which varied pile lengths and inter-pile distances while maintaining constant pile diameters. This study analyzed the kinematic and inertial effects on the piles, offering insights into their structural behavior under seismic conditions. The increase in pile length and the increase in the distance between the piles caused a significant increase in the bending moment and shear force, which have an important place in pile design. Full article

The majority of electromagnetic force calculation models employed in maglev vehicle system dynamics focus exclusively on vertical and lateral movement while neglecting the nonlinear magnetization properties of ferromagnetic materials. This oversight leads to discrepancies between the dynamics simulations and actual conditions. To enhance the accuracy of dynamics simulations and evaluate the performance of maglev vehicle systems under various operational conditions, it is imperative to identify an electromagnetic force calculation model that combines accuracy and applicability. To address this objective, this paper examines a U-shaped electromagnet in medium–low-speed maglev vehicles as a case study. It constructs a spatial electromagnetic force calculation surrogate model using a Shallow Neural Network. The surrogate model is capable of accurately calculating electromagnetic forces considering relative position deviations in the lateral, vertical, rolling, pitching, and shaking directions. Moreover, it can be integrated into vehicle system dynamics simulations. The accuracy of the electromagnetic force calculation surrogate model is confirmed by extensive comparisons with finite element simulation results across various conditions, achieving an impressive concordance rate of up to 95%. An illustrative application of the electromagnetic force calculation surrogate model in maglev vehicle system dynamics simulation is provided to showcase its practical utility. Full article

The objective of this study was to carry out a study on continuous and intermittent drying (intermittency ratio α = 2/3) of osmotically pretreated melon pieces, cut in the form of a parallelepiped. An osmotic dehydration pretreatment was performed using an incubator with mechanical shaking. Drying processes were carried out using an oven with forced air circulation at temperatures of 50 and 70 °C. The data were modeled by means of empirical equations, in order to compare the drying kinetics and analyze the impact of the intermittent process on energy savings and preservation of bioactive compounds in the final product. The experiments were also described using a diffusion model in Cartesian coordinates, with a third-kind boundary condition, in order to analyze the moisture distribution inside each piece of fruit over time. Among the empirical equations analyzed, Page’s was the one that best described the continuous and intermittent drying of osmotically pretreated melon pieces. In order to obtain dried melon, intermittent drying significantly reduced the effective processing time and, consequently, energy consumption, preserving the bioactive compounds more intensely (particularly at a temperature of 50 °C), compared to continuous drying. The diffusion model adequately described all the drying experiments, and it was found that the effective mass diffusivity increased significantly with the application of intermittency. Full article

Micropiles are a new type of retaining structure widely used in slope engineering due to their small footprint, low vibration and noise emissions, and simple construction process. This study aims to investigate the dynamic response and failure mechanisms of micropiles used in retaining accumulation landslides under seismic loading through shaking table tests and numerical simulation. The failure process, observed phenomena, and bending moments of micropiles in the test were discussed, and the shear force distribution of micropiles was thoroughly analyzed based on numerical simulation. The findings reveal that the natural frequency of the entire landslide system exhibits a gradual decrease and tends to stabilize under sustained earthquake excitation. The bending moment of micropiles follows an “S” shape, with a larger magnitude at the top and a smaller one at the bottom. Additionally, the shear force distribution exhibits a “W-shaped” pattern. Damage to micropiles mainly includes the flexural shear combination failure at the load-bearing section (which occurs within 1.4–3.6 times the pile diameter above the sliding surface) and the shear failure near the sliding surface. This study provides significant insights into the strengthening mechanisms of micropiles under seismic action and offers valuable guidance for the design of slope support. Full article

Old Cairo is a unique site in the world because of its historical, cultural, and religious values. Old Cairo, a UNESCO World Heritage site, represents a rich tapestry of history and culture. Its significance lies in its role as a center of Coptic and Islamic civilizations and its preservation of numerous historical monuments. Today, the conservation of cultural heritage demands a proactive approach that integrates a robust multidisciplinary strategy. This approach must consider the unique characteristics of the heritage itself and the extensive research and efforts devoted to various scientific fields and avenues. As a case study, the focus is on the Religions Complex, the target of the “Particular Relevance” bilateral Italy–Egypt “CoReng” project. The historic Religions Complex in Old Cairo, a UNESCO World Heritage site, faces significant seismic hazards, threatening its irreplaceable Coptic and Islamic heritage. This research contribution focuses on reviewing and assessing aspects of geological and seismic hazards. This assessment serves as a crucial foundation for future vulnerability analyses and the development of effective retrofitting strategies for the Complex’s historic structures. The current work identifies critical vulnerabilities related to sub-surface geology and geotechnical conditions, various deterioration driving forces, rising groundwater levels, and earthquake ground shaking of the complex site to mitigate these risks and ensure the long-term preservation of this invaluable cultural heritage. In addition, attention is given to missing/weak characterization aspects and the proposal of possible future solutions and research developments. Full article