Vibrational Study Research Articles

Vibrational spectroscopic studies, DFT, and molecular docking investigations of 4-fluoro- 3-methyl benzophenone

Potential energy distribution was used to describe the optimum molecular geometry, FT-IR, FT-Raman, and UV-Vis spectra, vibrational frequency bands, and assignment of suitable vibrational modes of 4-fluoro-3-methyl benzophenone. Utilizing DFT/B3LYP with a 6–31 +G level, spectroscopic investigations are conducted. The findings of the computation were utilized to model 4-fluoro-3-methyl benzophenone, which has a very good correlation with the spectra that were observed. The TDFT was used so that oscillator strengths could be determined. In order to determine how much charge was transferred by the molecule, HOMO and LUMO analyses were performed. Through the use of the NBO analysis, it was feasible to determine the existence of internal charge transfer, hyperconjugation, and stabilizing energy. DFT techniques were applied to investigate Mulliken's charges and hyperpolarizability characteristics. In the molecular docking investigation, the 4-Fluoro-3-methylbenzophenone molecule was docked with Prostaglandin H2 Synthase-1 and Prostaglandin H2 Synthase-2. Due to their hormone-like properties, the phospholipid molecules known as prostaglandins (PGs) play a crucial part in the body's pain and inflammatory responses. These compounds are composed of fatty acids, which are prevalent in cell membranes. Membrane-associated enzyme cyclooxygenase (COX) is responsible for this process. There are two isoforms of this enzyme: COX-1 and COX-2.

Polarized Raman Study of Internal Vibrations of the Organic Cation in 3-Cyanopyridinium Lead Tribromide Post-perovskite

In this work, we apply polarized Raman spectroscopy for study of internal vibrations of the 3-cyanopyridinium cation in the halide post-perovskite (3cp)PbBr3 (3cp = 3-CN-C5H5NH+). For a single cation, the vibrational frequencies and intensities of the Raman signal were calculated using the density functional theory. Selection rules were established for vibrations of cations in the crystal. These rules together with modeling results were used to identify the internal vibrations of the cation in the Raman spectrum of the crystal. Narrow and isolated internal vibrations of cations could be used as spectators of the crystalline environment.

Vibrational and computational study on the characterization of Ag-Threonine complex

The current manuscript is emphasized on the vibrational spectroscopic study of l-Threonine-TCA (LTh-TCA) complex and metal-based complexes such as (l-Threonine-TCA)Ag [(LTh-TCA)Ag] and (l-Threonine-TCA)Ag2 [(LTh-TCA)Ag2] investigated under the Raman, FTIR and UV–vis techniques. The most favourable binding sites of the mentioned complexes were predicted under the density functional theory (DFT) evaluated using the B3LYP method and LANL2DZ basis set. The quantum chemical parameters of the complexes calculated under the DFT method affirm the chemical reactivity, bioactive property and distribution of electrons within the atoms of the molecules. The electronic transition of the atoms are analysed using the UV–vis simulation method performed under the IEFPCM solvation model by employing methanol as solvent. The AIM analysis is carried out to understand the interaction types manifested by the mentioned complexes. The bioactivity score and drug-likeness properties of the complexes are also analysed. The theoretical and experimental vibrational wave numbers of L-Th-TCA complex and its metal-based complexes are compared with each other and are found in good agreement with each other. The potential binding regions of the mentioned compounds with 1QCY collagen receptor is evaluated using the molecular docking analysis.

Study of Vortex-Induced Vibration of a Pipe-in-Pipe System by Using a Wake Oscillator Model

A pipe-in-pipe (PIP) system is an important engineering structure in the petroleum industry. Under the excitation of ocean fluids, the PIP system produces vortex-induced vibration (VIV), which can affect the oil recovery efficiency of large offshore drilling platforms and cause various engineering accidents. In this work, a fluid–structure coupled vibration model of the PIP system excited by a vortex-induced force is established based on an Euler–Bernoulli double-beam model and a wake oscillator model. The harmonic balance method is used to solve the coupled vibration model. Influences of the connection layer stiffness, tension, mass ratio, phase angle, and frequency ratio on displacements of the PIP system are studied. It is shown from numerical results that displacements of inner and outer pipes increase with the slenderness ratio. Displacements of inner and outer pipes decrease with the connection layer stiffness, but the frequency ratio and traveling wave velocity increase with it. In addition, the frequency ratio of the PIP system exhibits a multivalued characteristic, which is the characteristic of a nonlinear system. A small stiffness of the connection layer can induce unstable vibrations. Displacements of inner and outer pipes decrease with the tension, but the frequency ratio increases with it. The collision time of the inner and outer pipes gradually increases with the tension. The pipe displacements decrease with the mass ratio.

Comparative Study of Vibration on 10-Pole 12-Slot and 14-Pole 12-Slot PMSM Considering Tooth Modulation Effect

In this study, the electromagnetic force and vibration characteristics of 10-pole 12-slot and 14-pole 12-slot permanent magnet synchronous motors (PMSMs) are examined considering the tooth modulation effect. In contrast to the conventional electromagnetic force analysis process which considers only the radial force of the lowest spatial harmonic order, the radial and tangential forces include low and high spatial harmonic orders which can be modulated with a lower spatial harmonic order, are analyzed. Then, a structural finite element (FE) model is developed, and vibration analysis is performed by applying a modulated force and moment. In the analysis, the amplitude and phase of the modulated radial force, tangential force, and moment are considered. The vibration analysis result shows that the 10-pole 12-slot PMSM is disadvantageous with respect to vibration when compared to the 14-pole 12-slot PMSM owing to the large modulated force. Also, it is confirmed that the effect of modulated tangential force and moment cannot be neglected, and the phase difference between modulated radial, tangential force and moment is also an important factor in vibration. Finally, the two motors are fabricated, and the validity of the FE analysis results is verified using the test results.

Experimental Study of Coupled Torsional and Lateral Vibration of Vertical Rotor-to-Stator Contact in an Inviscid Fluid

Diagnosis of faults in a rotor system operating in a fluid is a complex task in the field of rotating machinery. In an ideal scenario, a forced shutdown due to rotor-stator contact failure would necessitate the replacement of the rotor or stator. However, factors such as time constraints, economic considerations, and the aging of infrastructure make it imprudent to abruptly shut down machinery that can still be safe to operate. The purpose of this paper is to present an experimental study that validates the theoretical results of the dynamic behavior and friction detection using the wavelet synchrosqueezing transformation (WSST) method for recurrent rotor-stator contacts in a fluid environment, as presented in a previous study. The investigation focused on the analysis of whirl orbits, shaft deflection, and fluctuation frequency during passage through critical speeds. The WSST method was used to decompose the dynamic responses of the rotor in the supercritical speed zone into several supercomponents. The variation of the high-frequency component was studied based on the fluctuation of the instantaneous frequency (IF) technique. Additionally, the fast Fourier transform (FFT) method, in conjunction with the WSST technique, was used to calculate the variation in the amplitude of high-order frequencies in the vibration signal spectrum. The experimental study revealed that the split in resonance caused by rubbing effects is reduced when the rotor and stator interact with an inviscid fluid. However, despite the effects of elasticity and fluid boundaries generating self-excitation at low frequencies and uneven motion due to stator clearance, the experimental results were consistent with the theoretical analysis, demonstrating the effectiveness of the contact detection method based on WSST.

Numerical study of the vortex-induced vibration of a riser taking into account the variation of the tension

ABSTRACT Previous studies of the marine riser VIV have primarily considered the constant values of the tension, but limited work has been done to consider the variations of the tension with riser vibrations. In addition, previous studies have mainly focused on the effect of the inflow velocity profile on a riser VIV, while a study of a riser VIV at a wide range of velocities is still lacking. This study presents a model that can take into account the variation of the tension with riser vibrations. The VIV characteristics of the riser were investigated based on the fluid-structure coupling methods. It is shown that the model that takes into account the variation of the tension is able to accurately capture the bimodal character of the amplitude-ratio curve and the vortex shedding pattern, and to calculate the vibration frequencies accurately.

Laser Scanning and Ambient Vibration Study of Juma Mosque in Khiva (Uzbekistan) with Subsequent Finite Element Modeling of Its Minaret

This paper presents the results of a multiyear program conducted in Khiva, by a research team from the University of California, Berkeley (USA) and Urgench State University, Urgench (Uzbekistan). It was focused on the Juma (Djuma) Mosque in Itchan Kala (Khiva, Uzbekistan). The main objective was to generate a digital twin of the mosque, with an accuracy of a few millimeters, by utilizing a laser scanner. The idea of a digital twin was expanded further, to ensure that the physical properties and structural response of the digital twin were closely correlated to that of the actual object. To achieve this objective, the following was conducted. First, a laser scanning of the historic monument was conducted. The laser scans were collected by a terrestrial laser scanner. Subsequently, a study of the monument’s structural response was conducted in ambient vibration tests that focused on measuring the resonant frequencies of the mosque’s minaret. Based on all of the information collected during both field studies, a sophisticated finite element model of the minaret was developed. The calibration of the model was based on the results of the ambient vibration study. The performance of the model was shown to be close to that of the actual monument. The digital twin and associated numerical model will be used in structural health monitoring, numerical predictions of the structural performance, and in the development of restoration strategies.

Vibrational studies of 2,3,5,6-tetrachloro-1,4-benzoquinone and its reactivity: An ab-initio computational method

The IR spectrum of 2,3,5,6-Tetrachloro-1,4-benzoquinone (p-chloranil) has been recorded in the solid phase in the range 4000 – 400 cm-1. ab initio calculations have been performed using Gaussian 03 program to compute optimized geometry, harmonic vibrational frequencies along with intensities in IR and Raman spectra and atomic charges at RHF/6–31+G*, B3LYP/6-31+G*, B3LYP/6-31++G** and B3LYP/6-311++G** levels for p-chloranil and parent molecule p-benzoquinone. The optimized molecular structures are found to be planar and possess D2h point group symmetry for both the molecules. The C=C bond lengths are larger whereas the C=O bond lengths are shorter in p-chloranil as compared to p-benzoquinone which is also reflected in the corresponding vibrational frequencies. The atomic arrangements in p-benzoquinone and p-chloranil possess two concentric hexagonal arrays and both the arrays of p-benzoquinone contain mixed charges. In the case of the p-chloranil molecule, the outer array is negatively charged and the inner array is positively charged which leads to increased susceptibility at the sites to which chlorine atoms are attached in p-chloranil towards the nucleophile. Consequently, p-chloranil is a good candidate for synthesis of many derivatives of 1,4-benzoquinone. The optimized geometrical structures along with the atomic charges on the atomic sites of p-benzoquinone and p-chloranil reveal the reactivity of p-chloranil molecules towards nucleophilic substitution reactions as compared to p-benzoquinone.

Vibrational Study on the Structure, Bioactivity, and Silver Adsorption of Silk Fibroin Fibers Grafted with Methacrylonitrile

Natural fibers have received increasing attention as starting materials for innovative applications in many research fields, from biomedicine to engineering. Bombyx mori silk fibroin has become a material of choice in the development of many biomedical devices. Grafting represents a good strategy to improve the material properties according to the desired function. In the present study, Bombyx mori silk fibroin fibers were grafted with methacrylonitrile (MAN) with different weight gains. The potential interest in biomedical applications of MAN functionalization relies on the presence of the nitrile group, which is an acceptor of H bonds and can bind metals. IR and Raman spectroscopy were used to characterize the grafted samples and the possible structural changes induced by grafting. Afterward, the same techniques were used to study the bioactivity (i.e., the calcium phosphate nucleation ability) of MAN-grafted silk fibroins after ageing in simulated body fluid (SBF) for possible application in bone tissue engineering, and their interaction with Ag+ ions, for the development of biomaterials with enhanced anti-microbial properties. MAN was found to efficiently polymerize on silk fibroin through polar amino acids (i.e., serine and tryptophan), inducing an enrichment in silk fibroin-ordered domains. IR spectroscopy allowed us to detect the nucleation of a thin calcium phosphate layer and the uptake of Ag+ ions through the nitrile group, which may foster the application of these grafted materials in biomedical applications.

Physics of molecular deformation mechanism in 6H-SiC

Even though there have been several studies in literature of 6H SiC, a proper physics based understanding of the molecular deformation mechanisms of the material under different loading conditions is still lacking. Experimentally, the brittle nature of the material leads to difficulties associated with in-situ determination of molecular deformation mechanisms of the material under an applied load; whereas, the complex material structure along with the bonding environment prevents proper computational identification of different types of inelasticity mechanisms within the material. Molecular dynamics study (on successful verification of the interatomic potential with experimental results) of pristine single crystals of 6H SiC have been used to probe the physics of molecular deformation mechanisms of the material along with its inherent orientational anisotropy. The study elucidates the experimentally observed mechanisms of defect nucleation and evolution through a detailed analysis of radial distribution functions, x-ray diffraction as well as phonon vibrational studies of the single crystal. Studies have been presented at room temperature, initial high temperature and different types of confinement effects of the material (including hydrostatic and different biaxial loading cases). The confinement resulted in an increase in stress and stiffness whereas increase in initial temperature resulted in a decrease compared to uniaxial stress loading conditions at room temperature.

Laboratory Vibration Studies of Metro Tracks Equipped with Tuned Rail Dampers

Laboratory Vibration Studies of Metro Tracks Equipped with Tuned Rail Dampers

Combustion synthesis, characterization, and photodegradation performance of La2-xBixCuO4

Quaternary metal oxide system of the type, La2-xBixCuO4, where x = 0, 0.01, 0.03, 0.06, 0.08 have been synthesized by the combustion method. The crystalline phases and purity of nanostructures were confirmed by X-ray diffraction, which showed that they crystallized in the orthorhombic system of Bamb space group. Furthermore, they tend to adopt the quadratic system upon the incorporation of Bi atom into the lattices of the compound. A vibrational study shows the disappearance of absorption band around 680 cm−1 due to crystallographic system transformation. Morphological characterization by scanning electron microscopy (SEM) indicated that the micrographs are composed of nanometric crystallite particles with porous microstructure. The photocatalytic property of these materials was evaluated by monitoring the degradation of Malachite green under sunlight and the disappearance of the band characteristic of malachite green around 620 nm occurred after 240 min. The efficiency of La2-xBixCuO4 is 64, 68, 75, 89, and 83% for the nanostructures for x = 0, 0.01, 0.03, 0.06, 0.08, respectively.

Catenated pyrrolidinium-magnesium-organochlorostannate ionic liquid electrolytes for multivalent metal batteries

The quest for the development of high performing secondary batteries is prompting the research activities in this field towards the exploitation of new cell concepts. In this concern, next-generation secondary batteries based on multivalent metals such as magnesium and tin are an important promise. In this report, a new family of multivalent metal-based ionic liquid (IL) electrolytes is developed. The proposed ILs are obtained by reacting 1-butyl-1-methylpyrrolidinium chloride (Pyr14Cl), dimethyl-tin dichloride and the highly electroactive δ-MgCl2 material. Thermal and vibrational spectroscopy studies reveal that the proposed electrolytes consist of domains of complex catenated 3D magnesium-organochlorostannate coordination networks neutralized by aggregates of Pyr14+ stacks. The anionic domains are composed by a network of catenated [Me2xSnxCl2x+y]y− repeat units bonded by MgClx bridges. Cyclic voltammetry studies reveal that the metal deposition and stripping processes occur with a low overpotential in the order of few tens of mV. Finally, broadband electrical spectroscopy studies show that these new IL electrolytes: (i) are characterized by a room temperature ionic conductivity in the order of 10−3 S cm−1; and (ii) exhibit host matrix relaxations which are very effective in facilitating the long-range charge migration processes responsible for the overall conductivity of materials.

Hygro-thermal vibration study of nanobeams on size-dependent visco-Pasternak foundation via stress-driven nonlocal theory in conjunction with two-variable shear deformation assumption

This article presents a hygro-thermal-damping vibration analysis of two-variable shear deformation beams supported by a visco-Pasternak foundation. In contrast to the majority of the literature on this subject, the hygro-thermal load, and external foundation are simultaneously presented as nonlocal, by employing the well-posed stress-driven local/nonlocal mixture formulation with a set of constitutive constraints. The Generalized Differential Quadrature Method (GDQM) is adopted to solve the complex eigenvalue problem at hand. In the numerical simulation section, we first conduct comparison studies to validate the accuracy of the present formulation and results. Then, a series of benchmark results for the vibration frequency of different bounded higher-order shear deformation beams supported by the elastic foundation are presented. Subsequently, the effects of simultaneously applying stress-driven nonlocal assumptions on the foundation and hygro-thermal load in the undamped and damping vibration of the shear deformation beams are examined.

Free vibration analysis of curved asymmetric sandwich structures

This study deals with free vibration analysis of asymmetric sandwich structures that have different curvature angles. Polyvinyl chloride (PVC) foam, carbon fiber, and glass fiber were used as the core and surface sheets of the sandwich structures, respectively. The finite element method is used for the study. Commercially available software ANSYS apdl is employed to investigate the vibration study of curved asymmetric sandwich structures. Firstly, the accuracy of the finite element method is determined by making a comparison with the literature. Following that, the first six natural frequencies of sandwich structures were obtained for various sandwich configurations to examine the effects of asymmetry and curvature angle on the sandwich structures' characteristics. To achieve that two different configurations of sandwich structures are modeled. Each configuration has 5 different sandwich structures whose curvature angles are 0,15,30,45 and 60 degrees. All of the sandwich structures were modeled and solved using ANSYS apdl. Results show the impact of asymmetry and curvature angles on sandwich structure free vibration behavior. Also, it was obtained that free vibration analysis of curved sandwich structure can be performed by the proposed method accurately, which is hard to obtain by the analytical method and expensive by the experimental method. Using this method one can investigate different scenarios in a short time. Also, one can use this method before production to see if it is good for application.

Flap-wise vibrations of non-uniform rotating cantilever beams: An investigation with operational experiments

Representing an important kind of engineering component, rotating beams with axially functionally graded cross sections have been studied by researchers through analytical and numerical methods extensively, but experimental studies for verification are yet comparatively limited. To make up for this, this paper presents an experimental study of the flap-wise vibration of three rotating beams with different cross section patterns under different speeds. Quality data is obtained with Digital Image Correlation measurement with Phase Mapping Method on rotation targets, and is used to extract the natural frequencies and mode shapes with Frequency Domain Decomposition. The variance of natural frequencies and mode shapes are discussed with experimental data and are compared to those from an extensively studied analytical model, which show that natural frequencies and mode shapes obtained from the introduced experiment are of high accuracy. In addition, a method to apply stable excitations that can be quantitatively analyzed on rotation structures is proposed in this paper in the applied experimental setup.

Uncertainties Propagation and Global Sensitivity Analysis of the Aeolian Vibration of OPGW Cables

AbstractThis paper is devoted to evaluating the quantification of uncertainty involved in the study of Aeolian vibrations of optical ground wire (OPGW) cable systems installed on overhead power transmission lines. The energy balance method (EBM) is widely used to estimate the severity of steady-state Aeolian vibrations. Although the EBM requires some experimental characterization of system parameters (as indicated by international standards), it is necessary to mention that such a procedure is connected with uncertainties which makes it difficult for the proper homologation of the cable systems. In this article, the parametric probabilistic approach is employed to quantify the level of uncertainty associated with the EBM in the study of Aeolian vibrations of OPGW. The relevant parameters of the EBM (damper properties, cable self-damping, and the power imparted by the wind) are assumed as random variables whose distribution is deduced by means of the maximum entropy principle. Then a Monte Carlo simulation is performed, and the input and output uncertainties are contrasted. Finally, a global sensitivity analysis is conducted to identify the Sobol' indices. Results indicate that parameters related to self-damping and damper are the most influential on uncertainty and output variability. In this sense, the present framework constitutes a powerful tool in the robust design of damper systems for OPGW cables.

Vibrational coupling mechanism and experimental study of rotor system with double-disk magnetic coupler

At present, the vibrational coupling mechanism of the rotor system with a double-disk magnetic coupler has not been sufficiently studied. Based on the mechanical impedance theory, the patterns of structural mass and stiffness distribution were quantitatively described, to establish the model for the vibrational coupling mechanism. Methods were proposed to determine the vibrational coupling point and to simulate the transient response to the interacting excitations, so as to analyze the potential vibrational coupling point and the dynamic response characteristics. Then, the Campbell diagram of the shared support-dual rotor system was combined with the mechanical impedance characteristics of the shared support. As a result, it was found that although the base vibration of the shared support was significantly amplified, the single-axis trajectory showed that both the output and input rotors were synchronized with the forward vortex motion, with almost no coupling between them. A double-disk magnetic coupler test bench with a rated power of 55 kW was designed to verify the experiments. The results showed that the vibration displacement occurred in a periodic variation pattern. Moreover, the maximum errors between the theoretical, simulated, and experimental values of the vibration displacement at different input speeds were less than 5%. The experiments verified the validity of the model for the vibrational coupling mechanism and the simulation of the transient response to the interacting excitation. The results of the study could be used as a basis for calculating the vibration of the rotor system with a double-disk magnetic coupler.

Quantum chemical analysis and spectroscopic characterization of Escitalopram

Escitalopram is a selective serotonin reuptake inhibitor (SSRI) and is clinically used as anti-depressant. In the present work, the vibrational study of the molecule Escitalopram is carried out by different spectroscopic (FTIR, Raman and SERS) methods. The optimized molecular structure and its geometrical properties (bond length and bond angle) are obtained by DFT method at B3LYP/6-311G + + (d, p) level of theory. The NBO analysis is performed for determining the intramolecular charge transfer within the molecule. The first order hyperpolarizability, HOMO-LUMO energy gap, molecular electrostatic potential (MEP) and Mulliken charge distribution are also investigated by DFT method. The atom in molecule (AIM) analysis is carried out by using Multifwn software. The Autodock 4.0 tool is used for performing the molecular docking between the title compound and TLR4 receptor.