Resonant Vibration Research Articles

INVESTIGATION OF SOLVATION IN LITHIUM PERCHLORATE -PROPYLENE CARBONATE-DIMETHYL CARBONATE SYSTEM BY RAMAN SPECTROSCOPY

The difference of solvent properties can significantly affect the solvation phenomena in individual and, especially, in mixed solutions. In particular, it can be assumed that in mixed solvents, i.e. in systems with intermediate dielectric permittivity (mixtures of linear and cyclic carbonic acid esters), cations will bind molecules of linear esters more strongly and bind molecules of cyclic esters more weakly than it takes place in individual solvents. In the present work the Raman spectra of lithium perchlorate solvents in propylene carbonate (PC), dimethyl carbonate (DMC) and their mixture in a wide range of salt concentrations are studied. It is shown that the solvation effects of the cation are clearly traced in the region of symmetric ring vibrations (~690-730 cm-1) of propylene carbonate and in the region of deformation vibrations of CCA (~520 cm-1) of dimethyl carbonate. These effects are also evident in the mixed solvent. The so-called method of differential spectroscopy was used to judge the structural changes of mixed-solvent systems. It consisted in constructing spectra of lithium salt solutions in mixed solvents, additive sum of spectra of lithium salt solutions in PC and DMC, as well as their difference (differential spectra). The analysis of differential spectra allows us to conclude that in systems with mixed solvent there is a weakening of interaction of propylene carbonate molecules with ions, and there is a preferential solvation of cations and anions by dimethyl carbonate molecules. Also, unlike propylene carbonate, dimethyl carbonate solvates perchlorate ions, which follows from the line contour changes in the region of CH3-group vibrations (2970 cm-1) solvation of anions is also observed in the mixed solvent. For citation: Rabadanov K.Sh., Gafurov M.M., Akhmedov M.A., Rabadanova D.I., Magomedova A.G. Investigation of solvation in lithium perchlorate -propylene carbonate-dimethyl carbonate system by raman spectroscopy. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2024. V. 67. N 5. P. 36-42. DOI: 10.6060/ivkkt.20246705.6967.

Enhancing the Biosorption Potential of Pichia kluyveri FM012 for 4-Bromophenols

AbstractThe use of toxic and persistent pesticides in agriculture results in serious and lasting environmental impacts. Although traditional methods, such as physical and chemical reclamation, yield the best results, treating these contaminants requires a high cost and expertise. Therefore, this study focuses on bioremediation recovery, which is more efficient, economical, and safer for removal. In this case, the newly isolated potential of Pichia kluyveri FM012 in degrading 4-bromophenol was investigated. The impact of optimized parameters such as agitation, pH, nitrogen, and carbon source were also studied. After extensive testing, the best optimal degradation occurred at pH 5 with a stirrer speed of 150 rpm. Glucose and yeast performed the best compared to other carbon and nitrogen sources. The Langmuir model predicted the maximum biosorption capacity (qm = 38.46 mg/g biomass), but the Freundlich model provided a better value of R2 = 0.999. The pseudo-second-order kinetic model was fitting for the study of biosorption kinetics. The FTIR spectrum revealed the presence of asymmetric and symmetric vibrations of the aromatic ring and was assigned to C = C or C = O. Fungi showed biosorption ability across broad functional groups. These results provide interesting information about the ability of Pichia kluyveri FM012 and its potential applications for remediating resistant pesticides.

Vibration-Induced Flow and Streaming in Oscillatory Flow of Thermoacoustics

Induced acoustic streaming flow in thermoacoustic systems occurs due to acoustic vibrations, causing changes to the mean flow in the systems. This phenomenon creates a tendency to generate net fluid flow that can cause energy change within certain areas inside the system. However, the effects of the entire system’s vibrations on the flow streaming are not yet fully understood, yet it is important for a more effective operation. This study experimentally investigated the flow streaming resulting from vibration in a standing-wave thermoacoustic test rig with a flow frequency of 23.6 Hz. The existence of flow streaming due to vibration which was not counted in the theoretical formula is shown and indicated by experimental values. The result shows that there is a correlation between the amplitude of the drive ratio (DR) and the velocity of the oscillation of the flow. Upon examining both the theoretical and the practical evidence, it becomes clear that there exists a marginal flow velocity in directions other than the main flow due to the vibration of resonator’s wall as measured at the intake and outflow areas of the stack. This marginal flow velocity amplifies as the drive ratio of flow increases and it may potentially explain the observed difference between measured flow amplitude and the theoretical value.

Investigation of Gear Meshing Vibration and Meshing Impact Resonance Intensity Assessment

Abstract Gear drive is one of the most widely used transmission forms. Its vibration analysis plays an important role in design and operation. Considering the gear meshing resonance phenomenon (MRP), the paper analyzes the influences of rotating speed and load on meshing resonance intensity (MRI). Based on the gear meshing impact mechanism, meshing force variation during the engagement process were obtained. It was considered as meshing impacts exerted on the gear system. By comparing the maximum meshing force under different circumstances, it was found that rotating speeds and loads were positively related to meshing forces. The vibration signals with different load torques and rotating speeds obtained from the gear pair were analyzed. The experiment results showed that the intensity of meshing impact increased with the increases of both rotating speed and load. It was also observed that due to the MRP, the gear meshing frequency was modulated to the resonance frequency band as meshing impacts. Consequently, the resonance frequency band contained most of the energy of the meshing impact. An indicator called resonance energy ratio (RER) was defined to represent the proportion of resonance energy due to meshing impact. The simulation and experiment result show that the proposed RER indicator can well assess the intensity of the vibration. By comparing the RER values of 20 sets of gear vibration data, the influences of rotating speed and load on MRI were discussed. The result shows that the proposed method is helpful to the vibration assessment and condition monitoring in different operational states.

Predictive dynamic modeling and analysis of blisks through digital representations constructed upon precise geometry measurements

Blade geometric variations generally have a significant impact on the structural dynamics of integrally bladed disks widely used in the advanced aero-engines. This paper presents a holistic research in regard to the predictive dynamic modeling, analysis and experimental verification for a blisk by taking advantage of the advanced 3D optical geometry measurement technology. Geometrically mistuned models (GMMs) are semi-automatically constructed upon the precisely measured blisk geometry by an efficient FE mesh updating strategy. They provide explicit, high-fidelity digital representations of the geometric variations within the integrally manufactured blisk. A ‘Sector Mode Assembling Reduction Technique’ is developed and specifically tailored for efficient dynamic analysis of the large-sized GMMs at a relatively low computational cost and memory requirement. Intensive test campaigns, including forced response tests in the stationary/spinning rig under well-controlled laboratory conditions, are carried out for a full assessment of the GMMs’ dynamic prediction capability. Experimental verification results show that the GMM is able to capture the modal dynamics and resonant vibration of the stationary/rotating blisk with satisfactory accuracy. The physical-reality-based GMM converted directly from the precise geometry measurement data can be considered as a viable and valuable tool for predictive vibration evaluation of blisks. However, its model accuracy exhibits a mode-related dependence on the mesh density. The tradeoff between model accuracy and prohibitive computational cost proved to be the bottleneck of this promising blisk modeling approach.

Effects of high-low frequency electromagnetic radiation on vibrational resonance in Hodgkin–Huxley neuronal system

In this paper, based on the Hodgkin–Huxley (H–H) neuron model, the effects of high-low frequency (HLF) electromagnetic radiation on vibrational resonance (VR) in a single neuron is investigated. It is found that VR can be observed in a single H–H neuron model with or without considering HLF electromagnetic radiation. However, HLF electromagnetic radiation can cause changes in the structure of the resonance peaks and make the maximum region and intensity of the response amplitude smaller, which weakens the VR in the neuronal system. This is because the HLF electromagnetic radiation makes the neuronal electrical activities less regular, resulting in weaker synchronization between input low-frequency signal and output firing. In addition, the effects of the system parameters such as the HF electromagnetic radiation amplitude on the Fourier coefficients are investigated, and it is found that these parameters can also cause changes in the number of resonance peaks, resulting in vibrational mono-resonance and vibrational bi-resonances. When the frequency of the HLF electromagnetic radiation is between 0.014 and 0.041, local anti-resonance can be also observed. This has practical significance in reducing some of the unexpected vibration in aerospace engineering and mechanical fields. The HLF electromagnetic radiation plays an important role in weakening the VR of neuronal systems. Therefore, this study could provide new insights to further control the abnormal electrical activities and information transmission of neurons, which can lead to better design and development of therapeutic programs for neurological disorders and neuroplasticity therapies, and advance neuroscience.

Lagrangian of extended multiconfigurational self-consistent field second-order quasidegenerate perturbation theory combined with reference interaction site model self-consistent field constraint spatial electron density.

Lagrangians of the state-averaged multiconfigurational self-consistent field (SA-MCSCF) and multistate extended second-order quasidegenerate perturbation theory (MS-XMCQDPT2) coupled with the reference interaction site model self-consistent field constraint spatial electron density are defined. In addition, variational equations were derived to calculate the excitation energies of the target molecules dissolved in various solvents. The theory was applied to a phenol molecule in various solutions, and the gradients and Hessian matrices were calculated to evaluate the absorption spectral lines, including the broadening bandwidth. Numerical calculations revealed fine structures in any solvent surroundings. The main intramolecular vibrational modes related to such fine structures were stretching vibrations of the aromatic ring and the oxygen atom of the phenol molecule. The present theory plays an important role in predicting the structure of potential energy surfaces, such as Hessian matrices for various solvent types, during the photoexcitation process.

Frequency characteristics of an ultrasonic varifocal liquid crystal lens.

Compound lens systems with mechanical actuators are used to focus objects at near to far distances. The focal length of ultrasound varifocal liquid crystal (LC) lenses can be controlled by modulating the refractive index spatial distribution of the medium through the acoustic radiation force, resulting in thin and fast-response varifocal lenses. The frequency characteristics of such a lens are evaluated in this paper, and several axisymmetric resonant vibration modes over 20kHz are observed. The effective lens aperture decreased with the wavelength of the resonant flexural vibration generated on the lens, meaning that this parameter can be controlled with the driving frequency.

Vibration resonance and cancellation of medium–low speed maglev train-simply supported beam under moving loads

Vibration resonance and cancellation of medium–low speed maglev train-simply supported beam under moving loads

Vibrational resonance mechanism in the high-order-degradation bistable system and its application in fault diagnosis

Bearings play an important role in the rotating machinery. Timely fault detection and maintenance can prevent catastrophic incidents caused by bearing faults. As one of the advanced techniques to extract the weak characteristics of bearing fault, the methods based on the vibrational resonance (VR) mechanism can effectively amplify the weak characteristics. However, first, the effect of the barrier width and the barrier height on the VR mechanism has not been investigated. Second, the application of the VR mechanism requires accurate prior knowledge, which limits its application. In this paper, the high-order-degradation bistable potential is decoupled so that the effect of the barrier width or the barrier height on the VR mechanism can be easily analyzed. Then, the initial frequency detection technique based on the 1.5-dimension envelope spectrum and the logical operation of sets is proposed, which helps to adaptively provide accurate prior knowledge for the application of the VR mechanism in the high-order-degradation bistable system (HBSVR). Finally, experimental results show that the proposed method is more advantageous in detecting single and compound faults compared with other state-of-the-art methods.

Multimodal vibration damping of a three-dimensional circular ring coupled to analogous piezoelectric networks

Analogous piezoelectric networks have been shown to be effective for multimodal vibration attenuation in structures, including beams, plates, and rings. Previous studies for rings have only accounted for in-plane transverse vibration attenuation and disregarded the out-of-plane vibration modes. Furthermore, these previous numerical models and experiments have only been studied on thin rings, which ignore the effects of shear deformation and rotary inertia. As a result, these networks are not suitable for attenuating vibrations in thick rings. This study enhances on the previous electrical networks, considering both shear deformation and rotary inertia for both in-plane and out-of-plane vibrations. A new passive network topology is developed for the out-of-plane dynamics of thick rings, and the existing passive analogous network of in-plane vibration of thin rings is enhanced by considering the effects of shear deformation and rotary inertia. Combined, these new networks are capable of multimodal vibration damping of a thick ring in three-dimensions, encompassing primarily six types of vibration modes: the inextensional bending modes, the extensional modes, the thickness-shear modes, the coupled twist-bending modes, the torsional modes, and the transverse thickness-shear modes. By using piezoelectric elements to couple two separate analogous passive electrical networks derived from both the in-plane and out-of-plane governing equations of a ring and optimizing the internal resistance in each unit cell, it becomes possible to replicate the dynamics and effectively attenuate different types of vibration modes. This study serves as a theoretical foundation for implementations of passive vibration attenuation in ring structures.

Effects of Temperature and Layer Thickness on the Static and Dynamic Behaviors of Biocomposite Materials with Interleaved Viscoelastic Layers

This study investigated the influence of temperature variations on the mechanical and dynamic behaviors of biobased composites incorporating a passive control layer. These composites, which include an external layer made up of Flax/polylactic acid (PLA) and an internal layer of rubber, were manufactured using 3D printing technique. To better understand their mechanical characteristics, bending tests were carried out on samples of Flax/PLA with and without a rubber coating at temperatures ranging from [Formula: see text]C to [Formula: see text]C. To evaluate the bending response of the materials under several temperatures settings, three-point bending tests were also conducted on the materials with different viscoelastic layer thicknesses. Additionally, resonance vibration studies were carried out at various temperatures to explore dynamic characteristics like frequencies and damping factors. The analysis of the data revealed the consequences of incorporating a functional rubber layer under diverse circumstances. The results demonstrated that increasing temperatures negatively impacts the mechanical and dynamic characteristics degradation of the composite with the viscoelastic layer. The main objective of this work is that under various thermal settings, passive control layers in biocomposites can display modified mechanical and dynamic behaviors. This understanding of how these biobased composites perform in different environments offers significant context for their possible applications.

Structural design and dynamic characteristics analysis of braided composite two-stage gear transmission system

In order to realize the lightweight design of the transmission system, the braided composite material is applied to the two-stage gear transmission system. According to the structural characteristics of the two-stage gear reducer box, the whole box is designed to be assembled with the braided base and the box wall. Woven composite materials are applied to the web parts of mixed metal composite gears to realize the design goal of lightweight gears. Then, under the assumption of ignoring the influence of friction, bearings and other factors on the system, the dynamic model of the two-stage gear transmission system considering the box is established. By normalizing and dimensionless processing of the equations, the dimensionless differential equations of motion are obtained. The fourth-order Runge–Kutta method is used to analyze the relationship between the connection parameters and the dynamic characteristics of the system under the two working conditions of rigid and flexible connection between the composite base and the box wall.Through the analytical analysis of vibration displacement of two-stage gear reducer and box, the theoretical basis is found for the numerical analysis results. Finally, the dynamic characteristics of the transmission system are studied by vibration resonance analysis through high and low frequency interference. It is found that in a certain frequency range, with the decrease of the mass and moment of inertia of the transmission parts corresponding to the mixed metal composite gear, the amplitude-frequency characteristic Q of the lightweight gear and gearbox transmission system is slightly lower than that of the common gear and gearbox system, and the stability of the system is increased, and the dynamic characteristics of the system are improved.

Dynamic characteristics of scraper conveyor chain drive system under the impact condition of lump coal.

Scraper conveyor is the most important transportation equipment in the comprehensive mining equipment, and the chain drive system is its core subsystem, its dynamic characteristics will significantly affect the efficiency of coal transportation in the comprehensive mining face. In this paper, the dynamic characteristics of chain drive system when impacted by falling coal are investigated by means of test. The impact test bench of scraper conveyor was set up to analyze the effects of chain speed, impact height and impact load mass on the dynamic characteristics of the chain drive system of scraper conveyor under the working conditions of unloaded and loaded. The results show that the longitudinal vibration of the scraper conveyor is most obvious when it is impacted by the falling coal, and the chain speed, impact height and impact load mass of the scraper conveyor all play an excitation role on the vibration of the chain drive system, and the vibration of the chain ring is the most intense in the chain drive system, and the loaded coal pile conveyed on the scraper conveyor plays an inhibiting role on the vibration of the chain drive system. This study can help to identify the location where the scraper conveyor fails first in the impact condition, so as to provide a basis for its structural design and improvement, which is of great significance for the stable operation and structural optimization of the scraper conveyor.

Resonant Acoustic Vibration-Assisted Cathode Stripping for Efficient Recycling of Spent Li-Ion Batteries

Abstract The emerging field of direct recycling for spent Li-ion batteries offers significant advantages, such as reduced energy expenses and minimized secondary pollution, when compared to traditional pyrometallurgical and hydrometallurgical methods. This is due to its direct utilization of the spent cathodes as raw materials. However, efficient harvesting of spent cathode particles remains a challenge. To address this issue, this technical brief is the first to incorporate resonant acoustic vibration technology (RAV) as an efficient method for stripping cathode powders from spent Li-ion batteries. Our findings indicate that RAV-based techniques can achieve a stripping efficiency of up to 92%. A comparative analysis with conventional stripping methods, such as magnetic stirring, sonication, and curling–uncurling, reveals that RAV coupled with heat treatment provides unparalleled scalability and efficiency, eliminating the need for post-processing. Furthermore, the resulting cathode powders retain their original polycrystalline particle structures, with no impurities, such as carbon black or small aluminum fragments detected. These findings highlight the promise of RAV technology for large-scale recovery of electrode powders and its potential role in direct recycling of spent Li-ion batteries.

Parametric Vibration and Combined Resonance of a Bending-Torsional Coupled Turbine Blade With a Preset Angle

Abstract The parametric vibration and combined resonance of a turbine blade with a preset angle subjected to the combined effect of parametric and forced excitation were investigated. The blade was modeled as a rotating beam considering the effects of centrifugal, gyroscopic, and bending-torsion coupling. The instability region of the corresponding linear system with parametric excitation was analyzed using Floquet theory, and the effect of blade parameters on this region was discussed. Notably, the parametric vibration of the torsional degree-of-freedom (DOF) caused by parametric excitation of the bending degree-of-freedom has been found. The results show that the size and position of the parameter resonance region are affected by the blade aspect ratio and preset angle, respectively. Furthermore, the multiscale method was employed to solve the blade equation under the combined action of parametric and forced excitation to study the combined resonance caused by forced excitation and gyroscopic items. The effect of blade parameters and excitation characteristics on regions of combined resonance were investigated. The phenomenon of heteroclinic bifurcation was observed due to changes in the excitation frequency, and the harmonic components that accompanied the bifurcation changed. Specifically, a multiperiod response dominated by the excitation frequency and subharmonic components shifted to a single-period response dominated by subharmonic components. This study provides a theoretical explanation for the nonsynchronous resonance of blades and the subharmonic signals in blade vibration and guides blade parameter design, especially for wind turbines.

Overview of piezoelectric energy harvester based on wind-induced vibration effect

In the field of new environmental energy harvesting technology, wind energy and piezoelectric energy harvesting have become research hotspots. By utilizing wind energy into vibration energy, i.e., wind-induced vibration effect is a research hotspot in the field of environmental energy harvesting. This article comprehensively analyzes the research status and development trend of piezoelectric energy harvesters based on wind-induced vibration effects at home and abroad. It was found that the conversion process of wind energy to vibration energy is mainly based on flutter, galloping, and acoustic resonance. The conversion of vibration energy into electrical energy is mainly piezoelectric power generation, supplemented by magnetic induction power generation and friction power generation. For high power density and small volume application scenarios, resonant cavity type wind vibration energy collection is the main development trend.

Bio-Inspired Space Robotic Control Compared to Alternatives.

Controlling robots in space with necessarily low material and structural stiffness is quite challenging at least in part due to the resulting very low structural resonant frequencies or natural vibration. The frequencies are sometimes so low that the very act of controlling the robot with medium or high bandwidth controllers leads to excitation of resonant vibrations in the robot appendages. Biomimetics or biomimicry emulates models, systems, and elements of nature for solving such complex problems. Recent seminal publications have re-introduced the viability of optimal command shaping, and one recent instantiation mimics baseball pitching to propose control of highly flexible space robots. The readership will find a perhaps dizzying array of thirteen decently performing alternatives in the literature but could be left bereft selecting a method(s) deemed to be best suited for a particular application. Bio-inspired control of space robotics is presented in a quite substantial (perhaps not comprehensive) comparison, and the conclusions of this study indicate the three top performing methods based on minimizing control effort (i.e., fuel) usage, tracking error mean, and tracking error deviation, where 96%, 119%, and 80% performance improvement, respectively, are achieved.

Ru‐supported Cu nanowire catalyst enabling to suppress C–C coupling for high‐selectivity ethylamine electrosynthesis

AbstractElectrochemical acetonitrile hydrogenation compared with thermocatalytic hydrogenation provides a potential route to produce ethylamine in mild conditions. It is challenging to suppress the C–C coupling for improving ethylamine selectivity. Here, Ru‐supported Cu nanowire catalysts (Ru‐Cu NWs) are designed to achieve nearly 100% specific selectivity of ethylamine without coupling byproducts. In situ vibrational spectroscopy and electron spin resonance results reveal that the Ru‐Cu NWs provide a high active adsorption hydrogen (H*) coverage at the electrified interface so that the imine intermediates are more readily hydrogenated to generate ethylamine, thus suppressing the C–C coupling. Density functional theory calculations disclose that the formation of H* occurs more readily over Ru‐Cu NWs than Cu NWs. Moreover, the presence of Ru changes the potential‐determining step and facilitates the entire hydrogenation process. The strategy and understanding established here can be extended to other electrocatalytic hydrogenation reactions.

Chaotic dynamics of two-dimensional flows around a cylinder

We study flow around a cylinder from a dynamics perspective, using drag and lift as indicators. We observe that the mean drag coefficient bifurcates from the steady case when the Karman vortex street emerges. We use standard dynamics metrics to analyze the drag/lift phase diagram. We also find a jump in the dimension of the drag/lift attractor just above Reynolds number of 200, indicating a breakdown of periodicity. We compare the simulated drag values with experimental data obtained over the last hundred years. Although there is substantial agreement, we note a Reynolds number range where there is a substantial, unexplained discrepancy with data from over a hundred years ago. Our simulations suggest that a vibrational resonance in the cylinder would be unlikely for Reynolds numbers greater than 1000, where the drag/lift behavior is fully chaotic.