Search Results (453)

Multiphase swirling flows in confined spaces induce highly destructive, nonlinear fluid–structure interaction (FSI) vibrations. Understanding the underlying physical mechanisms is critical for ensuring the safety of industrial operations. This study proposes a mesoscopic multiscale framework coupling the Multi-Relaxation Time Lattice Boltzmann Method with Large Eddy Simulation (MRT-LBM-LES) and the Flügge thin-walled cylindrical shell equations to analyze two-way FSI responses. Variational Mode Decomposition (VMD) and the Hilbert–Huang Transform (HHT) are employed to decouple non-stationary broadband excitation signals. The macroscopic topological evolution of the swirling air core—from initial depression to critical breakthrough—is accurately captured. Dynamic mapping reveals a strict time-domain phase-locking mechanism between macroscopic flow instability and microscopic high-frequency structural excitation caused by cavitation bubble collapse. Furthermore, a dimensionless cross-scale energy cascade index is defined to quantify energy transfer. Results indicate that while higher discharge flow rates delay the critical breakthrough, they trigger a delayed, high-amplitude step mutation in the energy cascade, amplifying the global cumulative excitation energy by nearly 75%. Notably, the dominant high-frequency excitation consistently converges within a narrow band of 760 Hz to 790 Hz, independent of flow rate variations. These findings provide a theoretical foundation for unsteady excitation source localization and targeted vibration reduction in complex industrial pipeline networks. Full article

As a key energy-conversion component of tower gravity energy storage systems (T-SGESs), the hoisting structure is susceptible to large-amplitude coupled vibrations when the dominant frequency of a continuous external excitation approaches one of its natural frequencies, potentially compromising operational stability and safety. To characterize this behavior, a two-degree-of-freedom nonlinear dynamic model is developed based on Hamilton’s principle. Eigenvalue and modal analyses are performed to determine the natural frequencies and modal characteristics of the coupled system, while the second-mode primary resonance is further analyzed using the method of multiple scales and validated through numerical frequency-sweep simulations. Near the second-mode primary resonance, the system exhibits a pronounced hardening-type nonlinear response characterized by multistability, saddle-node bifurcations, jump transitions, and hysteresis. Parametric analysis indicates that greater attention should be paid to short-rope and low-payload operating conditions, under which the system tends to exhibit stronger nonlinear responses and larger payload swing amplitudes near the second-mode primary resonance. Meanwhile, the nonlinear resonance response of the hoisting structure can be effectively mitigated through enhanced equivalent stiffness and damping, which substantially narrow the multistable frequency interval. At a damping ratio of 0.04, the system transitions from a multivalued response to a single stable branch, with a marked reduction in payload swing amplitude. These findings identify the second-mode primary resonance as a critical nonlinear operating regime and provide a quantitative basis for resonance avoidance and parameter regulation in T-SGES hoisting systems. Full article

This study presents a comprehensive thermodynamic evaluation of several CO₂ conversion pathways, both non-catalytic and catalyst-assisted, using density functional theory (DFT) calculations in Gaussian 16 (B3LYP/6-311++G(d,p)). In the non-catalyzed section, three key routes are examined: hydrogenation (CO₂ + H₂ → CO + H₂O), dry methane reforming, and the reverse water–gas shift (RWGS). For the hydrogenation reaction, the Gibbs free energy change (ΔG) decreases from +0.018 to +0.005 Hartree as the temperature increases from 298.15 K to 1173.15 K, indicating a slight improvement in feasibility but still a high activation barrier of 0.326 Hartree, underscoring the need for catalysis. Dry methane reforming is both exothermic and spontaneous, with ΔG ≈ = −0.049 Hartree at 298.15 K and −0.030 Hartree at 593.15 K; however, operating under harsh conditions may accelerate degradation of reactor materials. In the catalyst-assisted section, copper surfaces and Cu₃M clusters (M = Sc, V, Ni, Cu, Co and Fe) are evaluated alongside two bimetallic catalysts, Fe₂ and Ni₂, under electrochemical CO₂ reduction (eCO₂RR) conditions. Scandium- and vanadium-doped clusters exhibit significant CO₂ adsorption, as evidenced by shifted vibrational frequencies between 800 and 1800 cm⁻¹ that signal C=O bond weakening. Under the evaluated thermobarometric conditions, Ni₂-containing systems displayed lower Gibbs energy values within their own optimized intermediate set and higher entropy values than the corresponding Fe₂-containing set, suggesting greater configurational flexibility and favorable stabilization trends. However, because Fe₂ and Ni₂ systems are chemically different, absolute total energies were not used as a standalone criterion for intrinsic catalytic superiority. Overall, while some non-catalytic routes become thermodynamically more favorable only at high temperature, the explicit inclusion of catalytic models, particularly doped Cu₃M clusters and Ni-containing systems, indicates enhanced CO₂ activation through stronger catalyst–adsorbate interactions, vibrational weakening of C=O bonds, and favorable electronic descriptors. These results suggest that catalytic systems may enable CO₂ conversion under milder conditions, although full kinetic confirmation requires comparative transition state calculations for each elementary catalytic step. Full article

This study presents a full polymer piezoelectric flextensional energy harvester (FPPFEH) comprising a single-layer poly(vinylidene fluoride) (PVDF) film bonded to a 3D-printed polylactic acid (PLA) flextensional frame. For an arm inclination angle of $\theta =10°$, the free-body model gives a theoretical geometric force-amplification factor of $M_{\mathrm{F}}=\cot \theta \approx 5.67$; this value represents an ideal upper bound and was not independently validated by local force or strain measurements. During assembly, the film was tensioned only to remove visible slack and maintain a flat configuration. No intentional pretension was applied, and any residual tension was not measured. Off-resonance force-controlled tests showed that the generated voltage was approximately proportional to the dynamic input force and nearly independent of frequency after accounting for attenuation caused by the finite measurement-input impedance. The ideal quasi-static model overpredicted the absolute voltage by a nearly constant factor across the tested force range. This offset is consistent with a lumped reduction associated with frame compliance and the in-plane anisotropy of the PVDF film, neither of which was independently measured. At $30\mathrm{Hz}$ and $12.32{\mathrm{N}}_{\mathrm{rms}}$, the rectified output charged a $6600\mathsf{\mu }\mathrm{F}$ supercapacitor to $2.10\mathrm{V}$ in $14\min$, corresponding to $14.55\mathrm{mJ}$ of stored energy. Under base-acceleration excitation from $0.05$ g to 1 g, the voltage peak occurred between $112.88$ and $116.49\mathrm{Hz}$, close to the electrical anti-resonance near $114\mathrm{Hz}$, and reached $12.11{\mathrm{V}}_{\mathrm{peak}}$ at 1 g. Near resonance, the highest measured power among the tested resistive loads occurred between 150 and $200\mathrm{k}\Omega$; however, the exact optimal resistance could not be resolved from the four tested loads. These results demonstrate off-resonance force-driven energy storage and resonance-mode vibration energy harvesting within the tested conditions. Full article

This study aimed to synthesize copper(I) iodide nanoparticles (CuI NPs) through a green route using taxo (banana passion fruit) extract as a natural capping and stabilizing agent, and to evaluate their antimicrobial performance against microorganisms isolated from concrete, together with a preliminary cytotoxicity screening. The obtained nanoparticles were characterized by ultraviolet–visible spectroscopy (UV–Vis), Fourier-transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM–EDS), dynamic light scattering (DLS), and X-ray diffraction (XRD). UV–Vis spectra recorded in the 200–704 nm range showed a strong absorption band at 224 nm, consistent with electronic transitions associated with nanostructured CuI. FTIR analysis revealed extract-derived biomolecules adsorbed on the nanoparticle surface, with bands assigned to aliphatic C–H, aromatic moieties, and C–O/C–O–C vibrations, supporting the formation of an organic capping layer. DLS analysis showed a mean hydrodynamic diameter of approximately 32 nm in aqueous suspension, whereas TEM revealed particle sizes ranging from 13 to 42 nm. XRD confirmed a predominantly cubic CuI phase, while SEM–EDS identified Cu and I as the main elements, with minor signals attributed to residual organic coating and/or trace species from the synthesis medium. The CuI NPs exhibited antimicrobial activity against microorganisms isolated from medium-strength concrete, producing inhibitory effects at all tested concentrations (0.014, 0.0087, and 0.0035 mol/L). Preliminary cytotoxicity screening using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay in human foreskin fibroblast (HFF), human breast adenocarcinoma (MCF7), and human glioblastoma (U251) cell lines showed dose- and time-dependent reductions in metabolic viability. The 1.0 mol/L formulations, particularly the precipitated fraction, produced stronger cytotoxic effects, whereas the 0.1 mol/L formulations, especially the residual fraction, preserved comparatively higher metabolic viability. Overall, these findings suggest that taxo-mediated CuI NPs are promising antimicrobial candidates for concrete biodeterioration control, while further colloidal and biological studies are required to better define their behavior under cell-culture conditions and optimize their safe application. Full article

The Cretaceous shallow oil sands in the Dagang area, located on the western slope of the Songliao Basin, are characterized by a burial depth of ≤182 m, an average reservoir temperature of 11.8 °C, an extremely high crude oil viscosity of 1,750,000 mPa·s at 15 °C, and water-bearing layers in both the roof and floor. Conventional thermal recovery methods such as SAGD and CSS are geologically unsuitable for this deposit and suffer from high energy consumption and carbon emissions. As microbial oil recovery is a technically advanced enhanced oil recovery technology that leverages microbial growth, reproduction and metabolism in the reservoir to alter the properties of oil, rock, gas and water through interaction with these components, and petroleum biotechnology research confirms that microorganisms can degrade high-molecular-weight petroleum hydrocarbons to reduce crude oil viscosity and improve its fluidity, this study explores the technical feasibility of microbial cold recovery for in situ extraction of such low-temperature, high-viscosity oil sands. The study adopts a five-well pilot pattern (one injector and four producers) with an integrated approach combining reservoir unblocking, microbial viscosity reduction, and vibration-assisted production. Systematic screening identified Pseudomonas, Chryseobacterium, and Citrobacter as the most efficient indigenous microbial strains. Pseudomonas exhibited a crude oil degradation rate of 32.17%, reducing asphaltene content from 7.47% to 3.56%, and achieved large-scale proliferation (2.5 × 10⁸ cfu/mL) at 15 °C. It also achieved a 40.8% reduction in crude oil viscosity and a desulfurization rate, alongside 56.6% denitrification. With the optimal activator No. 3, the viscosity reduction rate reached 45.18%, and the viable cell count exceeded 9.45 × 10⁸ cfu/mL. The synergistic action of Pseudomonas and an A-type nano-microemulsion surfactant reduced the oil–water interfacial tension from 49.56 to 1.25 mN/m (a 97.48% reduction) and lowered the crude oil viscosity at 25 °C from 302,000 to 11,023 mPa·s (a 96.35% reduction). Core flooding tests demonstrated an incremental oil recovery of 7.38% compared with the water-flooded control, with interfacial tension dropping from 48.21 to 1.18 mN/m. In the field trial, composite perforation (32 shots/m, 1610 mm penetration) and two cycles of oil-based fermentation fluid huff-n-puff reduced injection pressure from 2.0 to 2.5 MPa to 1.0–1.8 MPa. A total of 1489 m³ of microbial agent was injected into five wells, followed by a 125-day shut-in period. Nano-microemulsion single-well huff-n-puff (579 m³ over 87 days) further decreased injection pressure to 0 MPa. A downhole harmonic vibration source (≤20 Hz) was also applied during the trial. During the production phase, Pseudomonas was found to dominate the produced fluid, with its peak relative abundance exceeding 70%. Cumulative fluid production reached 4114 m³, yielding 21 m³ of oil sand oil. Wells with vibration assistance showed significantly higher oil content and better emulsification performance than wells without vibration assistance. Full article

The acoustic black hole (ABH) effect, achieved through a power-law thickness profile, has emerged as a powerful technique for passive vibration and noise control in thin-walled structures by slowing and trapping bending waves. However, prevailing research and designs predominantly focus on concave ABH indentations, which inherently require material removal and can consequently compromise structural strength and load-bearing capacity. To overcome this limitation, this paper introduces a novel symmetrical ring-shaped convex acoustic black hole (CX-ABH) plate. This innovative configuration transitions from the conventional concave geometry to a convex profile, aiming to preserve or even enhance vibration reduction performance while simultaneously improving structural integrity. A finite element model of the proposed ring-shaped CX-ABH plate is established and its calculation accuracy has been numerically validated through mesh independence testing. Vibration response analyses demonstrate its superior performance against a baseline rectangular plate at approximately 1270 Hz, achieving a maximum vibration reduction of 28.26 dB; the kinetic energy density is decreased by up to 2.82 J/m³ and effective energy concentration is achieved within the CX-ABH region. A parametric study was conducted to investigate the influence of key geometric parameters: the ABH radius R, the power exponent m, and the central frustum radius d. To achieve an optimal design, a Kriging surrogate model is constructed based on simulation data and subsequently coupled with a multi-objective genetic algorithm (MOGA) for systematic optimization. The derived optimal parameter set (d = 13.5 mm, m = 2.4, R = 58.9 mm) yields a 16.53% reduction in the mean peak kinetic energy density, validating the effectiveness of the optimization framework. The results conclusively demonstrate that the ring-shaped CX-ABH plate offers a promising and novel structural paradigm, successfully balancing high-efficiency broadband vibration attenuation with a robust structural design. Full article

The optimal design of a three-element dynamic vibration absorber (TEDVA) involves a fundamental trade-off between minimizing the peak amplitude magnification ($H_{\infty }$ norm) and the broadband energy absorption ($H_2$ proxy), a conflict that is further complicated by the lack of closed-form solutions, even for undamped primary systems. In this paper, we present an algorithm that extends the golden jackal optimizer with dynamic multi-map chaotic initialization, a Pareto-guided two-leader search structure driven by crowding distance, and a Pareto-gated self-adaptive differential evolution mutation to jointly ensure convergence and diversity. The algorithm is validated on the benchmark TEDVA case with mass ratio $\mu = 0.1$ and primary damping ${\zeta }_1 = 0.3$, and benchmarked against standard multi-objective algorithms (NSGA-II and MOPSO) as well as the single-objective AM-PSO baseline. Simulation results indicate that MODCGJO achieves a 7.3% reduction in peak amplitude compared to the state-of-the-art single-objective adaptive multi-swarm particle swarm optimization (AM-PSO), while maintaining a competitive $H_2$ performance and converging to the same Pareto-optimal region as NSGA-II and MOPSO. Comprehensive Pareto metrics—hypervolume, generational distance, spread, and spacing—are adopted, validating the front’s superior quality and uniform distribution. Sensitivity analyses on both physical design parameters (spring and damping ratios) and algorithmic control parameters (population size, iteration count, and archive size) confirm the robustness of the obtained solution and the stability of MODCGJO’s performance across varying configurations. The results show that MODCGJO is an effective and reliable tool for the multi-objective design of vibration absorbers, providing a superior trade-off between conflicting performance criteria, with the Pareto front offering engineers flexible design choices for different application requirements. Full article

In response to common issues with traditional automotive switches, such as poor contact of terminals, low durability, and weak vibration resistance, this paper proposes and designs a novel high-performance automotive toggle switch. Through structural design and parameter optimization, a new solution is provided to enhance the structural strength and service life of automotive electronic components. After completing three-dimensional modeling based on SolidWorks 2025, a full set of simulation analyses was carried out using ANSYS Workbench 2024 R2. After structural optimization, the maximum stress of the core valve stem decreased from 17.19 MPa to 14.877 MPa, a reduction of 13.5%; meanwhile, the fatigue life increased to 2.51 times that before optimization, indicating that for polycarbonate materials, a slight reduction in stress can significantly slow the rate of component damage accumulation. The switch’s first-order natural frequency is 1171.7 Hz, and a random vibration analysis of the switch was conducted according to the industry standard ISO 16750-3:2023. Under excitations covering the entire 2000 Hz frequency range, the switch structure did not show deformation or fatigue risks caused by resonance, indirectly confirming that vibration energy density is often more concentrated at low frequencies. This study not only completes the innovative design and performance verification of the novel toggle switch but also demonstrates that the comprehensive research methods employed provide a systematic analytical approach for developing high-performance, highly reliable automotive electronic components under stringent industry standards. Full article

The structural safety of a marine remotely operated vehicle (ROV) launch and recovery system (LARS) under extreme sea conditions determines the reliability of underwater exploration. To address the susceptibility of traditional rigid frames to local yielding and dynamic instability under transient high-frequency impacts from a mother ship, this study conducts structural dynamics simulation and vibration reduction optimization for a heavy-duty ROV LARS. A spatial finite element model was established, introducing boundary conditions that decouple the static gravity field from the transient inertial mass. Mechanical responses under eight typical operating conditions were systematically evaluated. Results indicate that the rigid frame experiences significant limitations under a 1 g horizontal transient impact, with peak stress reaching 195.38 MPa and deformation exceeding 20 mm. Consequently, a non-invasive vibration reduction strategy using viscoelastic damping boundaries is proposed, alongside an equivalent buffer dynamics model. Verifications demonstrate that this flexible damping constraint prolongs collision momentum transfer time and dissipates impact kinetic energy. Post-optimization, maximum transverse and longitudinal von Mises stresses decrease by over 37%, and transient deformation is reduced by over 64%. This study addresses the weight penalty of traditional strengthening designs, providing a mechanical reference for the lightweight design and impact protection of heavy-duty marine equipment. Full article

The superposition of normal and tangential oscillations in frictional contacts can fundamentally alter the macroscopic friction law and generate directed motion and force. In this work, we investigate the transition between friction reduction, dynamic ratcheting, and vibrational actuation within a unified numerical framework based on a compliant Coulomb friction contact. The system is subjected to simultaneous harmonic oscillations in the normal and tangential directions with an arbitrary phase shift. First, the limiting cases of purely normal and purely tangential oscillations are revisited, demonstrating that both produce equivalent friction–reduction behavior when expressed in terms of appropriate dimensionless parameters. For sufficiently large tangential oscillation amplitudes, a transition to a bidirectional stick-slip regime is identified, characterized by alternating forward and backward motion within a single oscillation cycle. The general case of dual-mode excitation is then analyzed over a broad parameter range. Numerical simulations show that the macroscopic friction coefficient is governed by four dimensionless parameters: the normalized sliding velocity, the normal oscillation ratio, the tangential oscillation parameter, and the phase shift between the oscillation modes. The combined oscillations break the symmetry of the friction law with respect to the direction of motion, resulting in different critical velocities and friction coefficients for positive and negative sliding directions. Depending on the parameter combination, the system exhibits three distinct operational regimes: active friction control, dynamic ratcheting, and vibrational actuation. In the latter regime, the effective friction coefficient becomes negative, indicating a conversion of oscillatory energy into directed mechanical work. The results provide a unified physical interpretation of oscillation-induced transport and force generation in frictional contacts and establish general design principles for vibration-assisted friction-control systems, dynamic ratchets, and oscillatory actuators. Full article

This study investigates predictive modeling of failure states in manufacturing systems using artificial intelligence in the context of sustainable maintenance and Industry 4.0. The proposed methodological framework is based on historical operational and maintenance data from a single manufacturing device, encompassing multiple process and operational signals such as vibrations, temperature, electric current, and operational logs. The aim is to predict failure within a short-term horizon to support maintenance planning. The article compares Random Forest and XGBoost algorithms at different prediction horizons (8 h and 16 h) to identify the trade-off between classification accuracy and lead time for maintenance planning. Model outputs are analyzed using explainable artificial intelligence and transformed into a risk index compatible with the FMEA methodology. The practical contribution of the proposed approach is illustrated through a scenario-based what-if assessment of potential sustainability impacts, particularly in terms of estimated reductions in unplanned downtime, material waste, and energy consumption. The results point to the potential of integrating AI-supported maintenance as a tool for increasing the reliability and sustainability of manufacturing systems. The novelty of the proposed framework lies in the integration of predictive maintenance, explainable artificial intelligence, replay-based maintenance assessment, dynamic FMEA risk assessment, and sustainability impact quantification into a unified decision-support framework. Full article

This study aimed to verify the morphology, biochemical composition, and thermal characterization of hydrated human amniotic membrane (HAM) processed in an ozonated water hydrodynamic system. This is an in vitro experimental study in which HAM samples were divided into two groups: in natura (IN) and ozonated (O₃). Analyses were performed using histology, Fourier-transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA/DTG), and differential scanning calorimetry (DSC/dDSC). Ozonation for 40 min preserved the biochemical integrity of HAM, maintaining the characteristic vibrational bands of Amides I, II, and III. Histological analysis showed morphological changes in epithelial cells, with partial removal in some regions, while the basement membrane and the scaffold remained preserved. Thermal analysis revealed that the in natura sample presented a bimodal dehydration profile, with a first event occurring between 60 and 65 °C associated with the evaporation of free or weakly bound water, and a second event peaking around 80 °C related to the removal of structural water. In contrast, the ozonated HAM exhibited a unimodal profile, with the mass loss peak shifted to approximately 70 °C. These findings were corroborated by DSC analysis, which showed a reduction in denaturation temperature from approximately 85 °C in the in natura sample to around 75 °C in the ozonated sample. The dDSC analysis confirmed the transition from a bimodal to a unimodal behavior after treatment, indicating a reduced energy barrier for protein denaturation and lower thermal stability of the collagen matrix. These results suggest that ozonation promotes alterations in the epithelial layer, which may favor the loss of both free and bound water. It is concluded that processing with ozonated water induces structural modifications, especially in the epithelial layer, and reduces the thermal stability of hydrated HAM without significantly altering the biochemical signature of collagen. This approach shows potential as an alternative method for membrane processing; however, functional evaluations are required to confirm its clinical applicability. Full article

Borosilicate glass is widely used in microfluidic chips, optical components, and precision devices, but it is susceptible to cracking and subsurface damage during machining because of its high hardness and brittleness. Longitudinal–torsional ultrasonic vibration-assisted milling (LTUVAM) can improve material removal stability, whereas the Rehbinder effect can reduce surface energy and weaken local material resistance. In this study, the additional effect of a Rehbinder-active medium under LTUVAM conditions was investigated to reduce crack-related surface damage and improve surface integrity. First, a two-dimensional cutting model of borosilicate glass was established using Particle Flow Code in two dimensions (PFC2D) to simulate crack initiation and propagation under conventional milling (CM) and LTUVAM conditions. The simulation results show that ultrasonic vibration promoted finer and more distributed microcracks and reduced the development of large-scale fractures, thereby modifying the brittle material removal behavior. Subsequently, milling experiments were conducted under LTUVAM conditions with a Rehbinder-active medium supplied to the cutting zone. Compared with LTUVAM without the solution, the proposed process significantly reduced surface roughness, with maximum reductions of 40.7% in S_a and 32.3% in S_q at a cutting depth of 50 μm. Finally, the simulated force variation and crack evolution were qualitatively compared with the experimental roughness trends and reported results, showing consistent mechanism-level trends. This work provides a theoretical and experimental basis for improving the machining quality of hard and brittle materials through the coupling of ultrasonic vibration and surface-active effects. Full article

In this study, we reveal the emergence of a tri-regime gradient in stiffness across substrate-supported poly(3-alkylthiophene) (P3AT) thin films, comprising an adsorbed region, a bulk-like region, and a free surface region. The stiffness distribution is found to be largely independent of the degree of polymerization but is significantly modulated by side chain length and temperature. Specifically, longer side chains (bead count = 4) expand the adsorbed and free surface regions, while elevating temperature above the glass transition leads to an order-of-magnitude reduction in stiffness. Phonon mode analysis demonstrates a clear inverse correlation between vibrational frequency and both the degree of polymerization and temperature, with side chain length exerting minimal influence. A high phonon mode similarity index between the main and side chains indicates coupled vibrational dynamics. Interfacial energy decomposition confirms that van der Waals interactions, particularly through distinct π–π stacking, dominate the substrate adhesion. These findings provide fundamental insights into the nanoscale thermomechanical properties of P3AT thin films on silica substrates, offering valuable guidance for the interface engineering of P3AT-on-silica systems in organic electronics. Full article