Search Results (3,578)

The central purpose of this study is to develop and validate an advanced numerical model capable of simulating the vibrational behavior of the operator’s seat in a tractor-type agricultural vehicle designed for operation in protected horticultural environments, such as vegetable greenhouses. The three-dimensional (3D) model of the seat was created using SolidWorks 2023, while its dynamic response was investigated through Finite Element Analysis (FEA) in Altair SimSolid, enabling a detailed evaluation of the natural vibration modes within the 0–80 Hz frequency range. Within this interval, eight significant natural frequencies were identified and correlated with the real structural behavior of the seat assembly. For experimental validation, direct time-domain measurements were performed at a constant speed of 5 km/h on an uneven, grass-covered dirt track within the research infrastructure of INMA Bucharest, using the TE-0 self-propelled electric tractor prototype. At the operator’s seat level, vibration data were collected considering the average anthropometric characteristics of a homogeneous group of subjects representative of typical tractor operators. The sample of participating operators, consisting exclusively of males aged between 27 and 50 years, was selected to ensure representative anthropometric characteristics and ergonomic consistency for typical agricultural tractor operators. Triaxial accelerometer sensors (NexGen Ergonomics, Pointe-Claire, Canada, and Biometrics Ltd., Gwent, UK) were strategically positioned on the seat cushion and backrest to record accelerations along the X, Y, and Z spatial axes. The recorded acceleration data were processed and converted into the frequency domain using Fast Fourier Transform (FFT), allowing the assessment of vibration transmissibility and resonance amplification between the floor and seat. The combined numerical–experimental approach provided high-fidelity validation of the seat’s dynamic model, confirming the structural modes most responsible for vibration transmission in the 4–8 Hz range—a critical sensitivity band for human comfort and health as established in previous studies on whole-body vibration exposure. Beyond validating the model, this integrated methodology offers a predictive framework for assessing different seat suspension configurations under controlled conditions, reducing experimental costs and enabling optimization of ergonomic design before physical prototyping. The correlation between FEA-based modal results and field measurements allows a deeper understanding of vibration propagation mechanisms within the operator–seat system, supporting efforts to mitigate whole-body vibration exposure and improve long-term operator safety in horticultural mechanization. Full article

Background: Metabolic dysfunction-associated steatotic liver disease (MASLD) is common in T2DM, likely due to insulin resistance and obesity. Although screening is recommended in high-risk patients, its prevalence in outpatient cardiovascular clinical settings remains unclear. Methods: We analyzed data from 475 patients attending a cardiovascular outpatient clinic: 142 with T2DM, 78 with T1DM, and 255 non-diabetic individuals at elevated cardiovascular risk. Liver steatosis and fibrosis were assessed using vibration-controlled transient elastography (Fibroscan^®): steatosis by controlled attenuation parameter (CAP ≥ 275 dB/m), and fibrosis risk by liver stiffness measurement (LSM ≥ 8.1 kPa). Carotid intima-media thickness (cIMT) was also measured. Results: The cohort (47% women, mean age 53 years, BMI 29.8 kg/m²) showed MASLD in 39.2% and fibrosis risk in 18.3%. MASLD was most prevalent in T2DM (57.0%), followed by non-diabetics (35.3%) and T1DM (19.2%) (p < 0.001). Fibrosis risk was also highest in T2DM (22.5%) vs. T1DM (7.7%) and non-diabetics (19.2%) (p = 0.02). CAP values were higher in those with fibrosis risk. T2DM patients with MASLD had higher LSM (7.0 ± 3.0 kPa) compared to those without MASLD (5.1 ± 2.2 kPa; p < 0.001). cIMT was highest in T2DM (0.73 ± 0.12 mm; p = 0.04), but not associated with MASLD or fibrosis. BMI and triglycerides were the strongest predictors of both MASLD and fibrosis. Conclusions: MASLD and risk of significant fibrosis were highest among T2DM patients. Within T2DM, those with MASLD had higher LSM, indicating increased risk of fibrosis. The presence of MASLD and risk of significant fibrosis was not associated with cIMT in this cardiometabolic cohort. BMI and plasma TG were consistent predictors across groups urging for more strict control by body weight reduction and lifestyle interventions. Full article

Incorporating cyclodextrins (CDs) into ionically crosslinked polysaccharide matrices offers a promising strategy for developing well-defined, safe-by-design and biocompatible carrier systems with tunable rheological properties. In this study, β-cyclodextrin (β-CD) was functionalized with citric acid (CDC) and maleic anhydride (CDM) using solvent-free synthesis to improve compatibility with alginate hydrogels. The modified CDs were characterized by FTIR, ¹H NMR, DLS, zeta potential, and MS, confirming successful esterification (4.0 and 3.4 –OH substitution for CDC and CDM, respectively) and stable aqueous dispersion. Rheological measurements showed that native CD accelerated gelation (within approximately 30 s), while CDC and CDM delayed crosslinking (by 2 to 13 min) and reduced gel strength, narrowing the linear viscoelastic range to 0.015–0.089% strain due to competition between polycarboxylated CDs and alginate chains for Ca²⁺ ions. Vibrational prilling produced alginate microbeads with diameters of 800–1000 µm and a simultaneous increase in size and CD concentration. Hydrogels demonstrated high CD retention (>80% after 28 h) and slightly greater release of CDC and CDM than native CD. Overall, solvent-free modification of CDs with citric and maleic acids provides a sustainable approach to tailoring the gelation kinetics, viscoelasticity, and release behavior of alginate-based hydrogels, offering a versatile, food- and health-compliant platform for controlled delivery of bioactive compounds. Full article

In CO₂ flooding technology, the injection tubing string is prone to intense fluid–structure interaction (FSI) vibrations and water hammer effects during transient start-up and shutdown processes, which seriously threaten injection safety. This study is based on a four-equation FSI model and employs the method of characteristics (MOC) and numerical simulations to analyze the dynamic responses of fluid velocity, pressure, axial vibration velocity, and additional stress in the tubing string during start-up and shutdown processes. The results indicate that the most severe vibrations occur within 12 s after pump start-up, with a significant increase in the amplitude of axial additional stress. Increasing the injection rate leads to a notable rise in the peak water hammer pressure. Extending the shutdown time effectively reduces impact loads. This research provides an important theoretical basis for the safe design and operational control of the CO₂ injection wells. It is recommended to adopt operational strategies such as low rate, slow start-up, and reasonably extended shutdown times to mitigate vibration hazards. Full article

This paper theoretically and numerically investigates temperature-dependent band structures in elastic metamaterial lattices using a plane wave expansion method incorporating thermal effects. We first analyze a one-dimensional (1D) elastic metamaterials beam, demonstrating that band frequencies decrease with rising temperature and increase with cooling. Then, the method is extended to square and rectangular 2D lattices, where temperature variations show remarkable influence on individual bands; while all bands shift to higher frequencies monotonically with cooling, their rates of change diminish asymptotically as they approach characteristic limiting values. Band structure predictions are validated against frequency response simulations of finite-structure. We further characterize temperature dependence of bands and bandgap widths, and quantify thermal sensitivity for the first four bands. These findings establish passive, robust thermal tuning strategies for ultralow frequency vibration suppression, offering new design routes for space-deployed lattice structures. Full article

Transdermal hydrogel films were fabricated from gellan gum, chitosan, and agar–agar, employing glutaraldehyde as a covalent crosslinker. The obtained formulation exhibited structural stability, pH-sensitive swelling, and high biocompatibility without the participation of metal ions. FTIR spectra showed the emergence of a characteristic imine (C=N) vibration near 1630 cm⁻¹, confirming covalent network formation through Schiff-base reactions. SEM imaging revealed a homogeneous porous architecture (45–120 μm) that enhances moisture absorption and molecular diffusion. The swelling ratio reached 410 ± 12% at pH 9.18 and 275 ± 9% at pH 4.01, evidencing pronounced pH responsiveness. Mechanical strength measured 0.82 ± 0.03 MPa with elongation of 42 ± 2%, ensuring flexibility for skin application. The temperature-controlled release of methylene blue achieved 78 ± 4% at 40 °C after 24 h, consistent with diffusion-limited transport. This gellan–chitosan–agar hydrogel network crosslinked with glutaraldehyde represents a stable, pH-responsive, and biocompatible platform suitable for wound care and transdermal drug delivery. Full article

Diesel engines remain the foundation for obtaining mechanical energy in sectors where autonomy and reliability are required; however, predictive diagnostics under real-world conditions remain challenging. The purpose of this scoping review is the investigation and systematization of published scientific data on the application of vibration methods for monitoring the technical condition of diesel engines in industrial or controlled laboratory conditions. Based on numerous results of publication analysis, sensor configurations, diagnosed components, signal analysis methods, and their application for assessing engine technical condition are considered. As methods for determining vibration parameters, time-domain and frequency-domain analysis, adaptive decompositions, and machine and deep learning algorithms predominate; high accuracy is more often achieved under controlled conditions, while confirmations of robustness on industrial installations are still insufficient. Key limitations for the application of vibration monitoring methods include the multicomponent and non-stationary nature of signals, a high level of noise, requirements for sensor placement, communication channel limitations, and the need for on-site processing; meanwhile, the assessment of torsional vibrations remains technically challenging. It is concluded that field validations of vibroacoustic data, the use of multimodal sensor platforms, noise-immune algorithms, and model adaptation to the specific environment are necessary, taking into account fuel quality, transient conditions, and climatic factors. Full article

Vibrations induced by marine environmental loads can compromise the operational performance of offshore platforms and, in severe cases, result in structural instability or overturning. This study proposes a biomimetic nonlinear X-shaped vibration isolation system (NXVIS) to suppress earthquake-induced vibration response in offshore platforms. Compared with traditional passive vibration isolators, the key innovations of the NXVIS include: (1) the proposed NXVIS can be tailored to different load requirements and resonant frequencies to accommodate diverse offshore platforms and environmental loads; (2) By adjusting isolator parameters (e.g., link length and spring stiffness, etc.), the anti-vibration system can achieve different types of nonlinear stiffness and a large-stroke quasi-zero stiffness (QZS) range, enabling ultra-low frequency (ULF) vibration control without compromising load capacity. To evaluate the effectiveness of the designed NXVIS for vibration suppression of jacket offshore platforms under seismic loads, numerical analysis was performed on a real offshore platform subjected to seismic loads. The results show that the proposed nonlinear vibration isolation solution significantly reduces the dynamic response of deck displacement and acceleration under seismic loads, demonstrating effective low-frequency vibration control. This proposed NXVIS provides a novel and effective method for manipulating beneficial nonlinearities to achieve improved anti-vibration performance. Full article

The current study focuses on axial ultrasonic vibration-assisted micro-milling as an advanced technique to improve the machining performance of Ti6Al4V, a material whose difficult-to-cut properties present a significant barrier to manufacturing the high-quality micro-components essential for aerospace and biomedical applications. A full factorial design was employed to evaluate the influence of feed-per-tooth (f_z), axial depth-of-cut (a_p), and ultrasonic vibration on cutting forces, surface roughness, burr formation, and tool wear. Experimental results demonstrate that ultrasonic assistance significantly reduces cutting forces by 20.09% and tool wear by promoting periodic tool–workpiece separation and improving chip evacuation. However, it increases surface roughness due to the formation of uniform micro-dimples, which may enhance tribological properties. Burr dimensions were primarily governed by feed-per-tooth, with higher feeds minimizing burr size. The study provides actionable insights into optimizing machining parameters for cutting Ti6Al4V, highlighting the trade-offs between force reduction, surface texture, and burr control. These findings contribute to advancing ultrasonic-assisted micro-milling for industrial applications, namely aerospace and biomedical applications requiring high precision and extended tool life. Full article

With the comprehensive digitalization and electrification of aircraft, electromechanical actuation systems (EAS) have been increasingly applied. However, EAS are affected by various nonlinear factors, such as friction and mechanical backlash, which can compromise system stability and control accuracy, thereby reducing the operational lifespan of the EAS. This study focuses on these two nonlinear factors and proposes a hybrid control approach to mitigate their effects. In the speed loop of the EAS, a Super-Twisting sliding mode controller combined with a generalized proportional–integral observer (GPIO) is designed, while in the position loop, a hybrid controller integrating a radial basis function (RBF) neural network with sliding mode control is implemented. Leveraging the advantages of numerical analysis in SIMULINK and dynamic simulation in ADAMS, a co-simulation framework is established to evaluate the hybrid control algorithm under nonlinear effects. Furthermore, a control test bench for the control surface transmission system is constructed to analyze the dynamic and static performance of the system under different control strategies and input commands. The experimental results show that, compared with the PID control, the hybrid control method reduces the steady-state error and vibration amplitude of the step response displacement by 51% and 75%, respectively, and decreases the amplitude of speed fluctuations by 75%. For the sinusoidal response, the displacement lag is reduced by 76%, and the amplitude of speed fluctuations is reduced by 50%. Full article

To meet pose-control and vibration-suppression requirements in confined spaces, a compact, noncontact six-degree-of-freedom (6-DoF) displacement-sensing method is proposed. The method is based on laser reflection and a position-sensitive detector (PSD) and features an adjustable incidence angle. An adjustable-incidence-angle PSD–corner-cube retro-reflector (CCR) configuration is devised, which reduces the PSD’s spatial footprint to 10.4% of that of a conventional layout. Building on this configuration, an analytical model is derived that maps the target’s 6-DoF displacement to the PSD spot motion as a function of the fixed relative pose between the PSD and the CCR mounted on the target. The model is linearized under the small-angle assumption. Experiments show an accuracy of 5.89 μm for translation within ±1.5 mm and 0.0027° for rotation within ±0.5°. The method couples a compact architecture with high precision and provides both a theoretical basis and an engineering-ready pathway for high-bandwidth pose sensing in confined spaces. Full article

Geosynthetics are increasingly used in forest road construction for their potential to improve structural performance and reduce material consumption. However, little is known about their influence on dynamic modulus measurements derived from Light Weight Deflectometer (LWD) testing. This study investigates how different geotextiles affect stiffness measurements immediately after construction and two years later. Five reconstructed forest roads in the Czech Republic were divided into control and geotextile-reinforced subsections (PP150 with geogrid, PP200, and PP800). Modulus differences between the surface and subgrade (S–SG) and differences after two years (S2–SG) were analysed using permutation ANOVA, Cohen’s d, and linear mixed-effects models. The results showed significant short-term reductions in measured modulus for PP150 and PP800, which diminished over time. Only PP800 maintained a strong effect at the two-year mark. Interaction effects with base material types revealed potentially adverse synergies, particularly between PP800 and vibrated gravel. These findings suggest that as LWD is commonly used during road construction for quality control, these early misleading readings may lead to unnecessary over-compaction or increased layer thicknesses, resulting in elevated construction costs and a higher carbon footprint, which counteract the sustainability goals often associated with geosynthetic use. The study highlights the need for long-term monitoring and method refinement in evaluating geosynthetic-reinforced unpaved roads. Full article

Background/Objectives: Activities of daily living (ADL) are critical for independence after stroke, yet many survivors remain functionally limited. Vibration therapy (VT), including whole-body and focal modalities, has been proposed as an adjunct to enhance recovery, but effects on ADL remain unclear. This study aimed to evaluate the overall effectiveness of VT on ADL and to identify moderating factors. Methods: A systematic review and meta-analysis were conducted following PRISMA 2020 guidelines. Thirteen controlled trials (12 RCTs, 1 nRCT) involving VT in stroke were included. Standardized mean differences (Hedges’ g) were synthesized using random-effects models. Meta-regression and subgroup analyses examined moderators such as session number, vibration parameters, stroke stage, and ADL subdomains. Risk of bias was assessed with RoB 2 and ROBINS-I. Results: VT produced a small but significant effect on ADL (Hedges’ g = 0.19; 95% CI: 0.06–0.33; p = 0.008), though significance was lost after adjustment for publication bias. Heterogeneity was moderate (I² = 34%). Session number was the only significant moderator (p = 0.045), explaining ~24% of variance, with the greatest benefit in the 13–24 session range (g = 0.34; 95% CI: 0.05–0.63). Subgroup analysis showed improvement in physical function/mobility (g = 0.32; p = 0.048), but not in self-care or quality-of-life outcomes. Other parameters were not significant moderators. Conclusions: VT confers modest benefits for ADL after stroke, particularly in mobility-related domains. Session number appears clinically important, with 13–24 sessions suggesting an optimal dose window. Full article

Lubricants significantly influence the performance and durability of internal combustion engines (ICEs), yet fresh oils seldom represent in-service conditions. To replicate realistic end-of-life scenarios, lubricants were artificially degraded in sufficient quantities for experimental investigation. This study introduces a methodology to evaluate the impact of altered lubricants on turbocharger dynamics under controlled laboratory conditions. A comparative analysis was performed on turbochargers operating with fresh and aged oils of varying compositions to establish correlations between lubricant properties and vibrational response. Particular attention was given to sub-synchronous phenomena and their implications for rotordynamic stability. Variations in damping and stiffness were assessed under constant pressure and temperature to support mathematical modeling of lubricant degradation and viscosity evolution. Experiments were conducted on a cold turbocharger test bench equipped with acceleration, speed, and displacement sensors, while a mobile oil control unit ensured precise regulation of inlet oil pressure and temperature. Full article

Servo motors, which are critical for high-precision industrial applications, require predictive maintenance to minimize downtime, aligning with Industry 5.0’s human-centric manufacturing. This study presents a system for Delta servo motors using acoustic data. An ESP32 LyraT module streams audio via HTTP to a server, which forwards it to Apache Kafka. Convolutional neural networks (CNNs) detect anomalies; Statistical Process Control (SPC) identifies early faults; and ARIMA, LSTM, and Prophet forecast maintenance. A device architecture with IP-based device ID and a GUI supports monitoring. Experiments with an ESP32 LyraT (Espressif Systems, Shanghai, China) monitoring Delta ASDA-A3 motors (Delta Electronics, Taipei, Taiwan) over 72 h achieved 91% anomaly detection accuracy for anomalous sounds, 84% early fault detection, and LSTM forecasting of MSE trends with MAE 0.0078 for 24 h predictions. The system supported 32 kB/s with <1% packet loss. The system offers accurate monitoring, advancing Industry 5.0. Future work will include vibration data and web dashboards. Full article