Experimental Vibrational Study Research Articles

Sertraline and its iodine product: Experimental and theoretical vibrational studies: Potential in vitro anti-thyroid activity of sertraline and iodine product toxicity with respect to male Wistar rats

Mayor depression, obsessive–compulsive panic, social anxiety disorders are common diseases that are usually treated with sertraline hydrochloride which is the active ingredient of the well known drugs as Zoloft and Lustral. In this work, we presented a more complete vibrational characterization of the solid phase FT-IR spectra of Sertraline hydrochloride and its sertraline–iodine product in which the conformational space of the molecules was investigated performing molecular dynamic simulations within an NVT ensemble. Geometrical, electronic and vibrational properties were calculated with the density functional theory. Comparison of the simulated spectra with the experimental spectra provides important information about the ability of the computational method to describe the vibrational modes of both molecules. In addition, for the first time we present the evaluation of anti-thyroid activity of sertraline hydrochloride by using the Lang’s method. Also, with the aim to evaluate the antidepressant effect of its iodine product we demonstrated for this compound the toxic effect towards the male Wistar rats.

Experimental and Numerical Studies of Nonstationary Random Vibrations for a High-Pier Bridge under Vehicular Loads

In the current study, the nonstationary random responses of moving wheels induced by road roughness in a time domain were obtained and treated as the nonstationary inputs to study the nonstationary vibration of a high-pier bridge under vehicles with variable speed. A full-scale vehicle model with 12 degrees of freedom was used; vehicle wheels were considered as patch contact instead of point contact with the bridge road surface. The vehicle-bridge coupling equations were established by combining the equations of motion of both the bridge and vehicle using the displacement relationship and the interaction force relationship at the contact patches. The midspan deflections caused by the stationary and nonstationary inputs were compared with the measured responses under different parameters including vehicle acceleration and vehicle deceleration. The verified results showed that the proposed method can accurately simulate the vibration of the bridge under vehicles moving with variable speeds. Using the stationary random process to model the road surface disturbance to vehicles with variable speeds, the dynamic effects can be either underestimated or overestimated. The proposed method was then used to study the ride comfort for vehicles moving with a variable speed on high-pier bridges.

Complex Vibrational Analysis of an Antiferroelectric Liquid Crystal Based on Solid-State Oriented Quantum Chemical Calculations and Experimental Molecular Spectroscopy

The experimental and theoretical vibrational spectroscopic study of one of a novel antiferroelectric liquid crystals (AFLC), known under the MHPSBO10 acronym, have been undertaken. The interpretation of both FT-IR and FT-Raman spectra was focused mainly on the solid-state data. To analyze the experimental results along with the molecular properties, density functional theory (DFT) computations were performed using several modern theoretical approaches. The presented calculations were performed within the isolated molecule model, probing the performance of modern exchange-correlations functionals, as well as going beyond, i.e., within hybrid (ONIOM) and periodic boundary conditions (PBC) methodologies. A detailed band assignment was supported by the normal-mode analysis with SQM ab initio force field scaling. The results are supplemented by the noncovalent interactions analysis (NCI). The relatively noticeable spectral differences observed upon Crystal to AFLC phase transition have also been reported. For the most prominent vibrational modes, the geometries of the transition dipole moments along with the main components of vibrational polarizability were analyzed in terms of the molecular frame. One of the goals of the paper was to optimize the procedure of solid-state calculations to obtain the results comparable with the all electron calculations, performed routinely for isolated molecules, and to test their performance. The presented study delivers a complex insight into the vibrational spectrum with a noticeable improvement of the theoretical results obtained for significantly attracting mesogens using modern molecular modeling approaches. The presented modeling conditions are very promising for further description of similar large molecular crystals.

Experimental vibrational spectra and computational study of 1,4-diazabicyclo[2.2.2]octane

The FT-IR and FT-Raman spectra of the colorless crystals of the 1,4-diazabicyclo[2.2.2]octane (DABCO) were recorded in the region 4000–400cm−1 and 3600–20cm−1 respectively. The assignment of the bands in the vibrational spectra has been made on the basis of quantum-chemical calculations. Detailed description of less characteristic skeletal modes is given using the visualization of the calculated vibrations.

Experimental study of vortex-induced vibrations of a tethered cylinder

This paper presents an experimental study of the motions, forces and flow patterns of a positively buoyant tethered cylinder (m⁎<1) in uniform flow undergoing vortex-induced vibration (VIV). The flow fields have been measured using digital Particle Image Velocimetry (PIV) technique, in conjunction with a piezoelectric load cell for direct measurement of drag and lift forces acting on the tethered cylinder. The effects of varying mass ratio and Reynolds number over the range 0.61≤m⁎≤0.92 and 4000≤Re≤12 000 are examined. Results of a fixed (or stationary) cylinder at the same Reynolds numbers are provided to serve as the benchmark reference. The peak amplitude of oscillation, θmax/θD, generally increases with Re and deceases with m⁎. Similar to previous studies, the results reveal the existence of a critical mass ratio mcrit⁎≈0.7, below which large-amplitude oscillations would take place when Re is high enough, with the largest peak amplitude of θmax/θD=0.9 observed for the case of m⁎=0.61 and Re=12 000. Thus two distinct states of oscillation are categorized, namely, the small- and large-amplitude oscillation states. The distinction between the two states is also vivid in the mean and root-mean-square (r.m.s.) force coefficients (including C¯D, CD′ and CL′). The frequency of vortex shedding (fV) from the tethered cylinder is always synchronized with the cylinder's oscillation frequency (fosc), regardless of the oscillation state. A time series of instantaneous vorticity fields illustrate that vortex shedding from the tethered cylinder undergoing VIV maintains the 2S mode, but at an inclined angle to the free stream, which is most obvious in the large-amplitude oscillation state. This leads to an asymmetry in the shear layers separated from opposite sides of the cylinder, as shown by the distribution of ensemble-averaged Reynolds stress.

NUMERICAL AND EXPERIMENTAL STUDY ON FREE VIBRATION OF DELAMINATED WOVEN FIBER GLASS/EPOXY COMPOSITE PLATES

This paper presents a combined experimental and numerical study of free vibration of industry-driven woven fiber glass/epoxy (G/E) composite plates with delamination. Using the first-order shear deformation theory, an eight-noded two-dimensional quadratic isoparametric element was developed, which has five degrees of freedom per node. In the experimental study, the influence of various parameters such as the delamination size, boundary conditions, fiber orientations, number of layers, and aspect ratio on the natural frequencies of delaminated composite plates are investigated. Comparison of the numerical results with experimental ones shows good agreement. Fundamental natural frequencies are found to decrease with the increase in the delamination size and fiber orientation and increases with the increase in the number of layers and aspect ratio of delaminated composite plates. The natural frequency of the delaminated composite plate varies significantly for different boundary conditions.

Experimental Study of Resonant Vibrations of Suspended Steel Cables Using a 3D Motion Analysis System

AbstractThis paper presents the results of an experimental study of regular resonant vibrations of steel cables using a camera-based three-dimensional (3D) motion analysis system. The cable had one fixed end, and the other end was subjected to harmonic vertical excitation. Retroreflective markers were fixed to the cable and evenly distributed along it. The 3D motion analysis system was used to obtain 3D time traces of all marker vibrations; these traces were then entered into other programs for further signal processing. Time-varying modal coordinates were extracted from the trajectories of the markers using a modal decomposition technique. The resonant vibrations observed include isolated and simultaneous 1∶1, 2∶2∶1, 1∶1∶2∶2, and 4∶2∶4∶2 internal resonances. Subharmonic and superharmonic resonances, period-doubling bifurcations, hardening nonlinearity effect, and complex traveling vibrations were observed and studied. The resonant vibrations were characterized by examining time-varying vibration profiles...

Molecular Structure and Vibrational Spectra of Mixed MDyX4 (M = Li, Na, K, Rb, Cs; X = F, Cl, Br, I) Vapor Complexes: A Computational and Matrix-Isolation Infrared Spectroscopic Study

The structures, energetic, and vibrational properties of MDyX(4) (M = Li, Na, K, Rb, Cs; X = F, Cl, Br, I) mixed alkali halide/dysprosium halide complexes have been investigated by a joint computational and experimental, matrix-isolation Fourier-transform infrared spectroscopic (MI-IR), study. According to our DFT computations for the complexes with heavier halides and alkali metals the ground-state structure is the tridentate isomer; while at high temperatures the bidentate structural isomer dominates. The survey of various dissociation processes revealed the preference of the dissociation to neutral MX and DyX(3) fragments over ionic and radical dissociation products. Cationic complexes are considerably less stable at 1000 K than the neutral complexes, and they prefer to dissociate to M(+) + DyX(4)(•) fragments. The vapor species of selected mixtures of NaBr and CsBr with DyBr(3) and of CsI with DyI(3) in the temperature range 900-1000 K have been isolated in krypton and xenon matrices and investigated by infrared spectroscopy. Besides the characteristic vibrational frequencies of the monomeric and dimeric alkali halide species and of the dysprosium trihalide molecules, certain signals indicated the formation of MDyX(4) (M = Na, Cs; X = Br, I) mixed complexes. Comparison with the computed vibrational and thermodynamic characteristics of the relevant species lead to the conclusion that these complexes appear in the vapor predominantly as the C(2v)-symmetry bidentate isomer. This is the first time that this structure was identified in an experimental vibrational spectroscopic study. The signals appearing upon performing a thermal anneal cycle were tentatively assigned to the double complex M(2)DyX(5) (M = Na, Cs; X = Br, I). A structure in which one alkali atom is bound to dysprosium by three and the other by two bridges is proposed for these double complexes.

The Experimental Study and CFD Analysis of Vortex-Excited Vibration of the Central-Open Box Section Cable Bridge

As a new type of section, central-open box sections are more and more popular. Some existed bridges of central-open box section can not to be used because of vortex-excited resonance. Based on this situation, the paper taking the Hongkong-Zhuhai-Macao River-sea ship canal Bridge for example, takes measures of taking the central bottom plate opening hole, changing the angle of web, and setting baffle, according the experimental study and CFD analysis, it is obtained that different aerodynamic sections are various in the character of vortex-excited, although taking the central bottom plate opening hole is effective, it only refers to the best opening ratio, changing the angle of web can not improve the vortex-excited effectively, setting baffle on the lateral sides is the most effective measure to forbid the vortex-excited resonance.

Experimental Vibration Study on the Healthy and Delaminated Composite Plates

Vibration based damage, in particular delamination detection, in the composite structures is an active research area. The present study is also on the dynamics of the composite plates with and without delamination based on the experimental study. The test plate made of E-glass fibre and epoxy resins has been used here. A piezo-electric shaker has been used to excite the composite plate and the acceleration responses were measured using the number of accelerometers. The dynamics of the delaminated composite plates were then compared with a healthy composite plate when the vibration experiments have been conducted at the lower modes. The paper will discuss the observations made on the measured vibration responses from both the healthy and the delaminated plates and the possibility of the delamination detection from the experimental vibration data.

Experimental study of thickness-shear vibration of AT-Cut quartz resonators loaded with microparticles

We study experimentally thickness-shear (TSh) vibrations of an AT-cut quartz resonator loaded with a thin layer of microparticles. The effects of the particles on TSh resonant frequencies are examined. The inertia of the particles lowers the frequencies as expected. However, the frequency shift is found to be dependent on the particle size, and it may also be nonlinear in the particle layer thickness.

Theoretical structural and experimental vibrational study of niobyl nitrate

We have prepared niobyl nitrate, Nb(NO 3) 3 and characterized it by infrared and Raman spectroscopies. The Density functional theory (DFT) has been used to study its structure and vibrational properties. We have made a comparative work for this compound to evaluate not only the best level of theory but also the best basis set to be used to reproduce the experimental wavenumbers. These calculations gave us a precise knowledge of the normal modes of vibration taking into account the type of coordination adopted by nitrate groups of this compound as monodentate and bidentate ligands. The calculated harmonic vibrational frequencies for niobyl nitrate are consistent with the experimental vibrational spectra. An assignment of the observed spectral features is proposed. The nature of the Nb O and Nb ← O bonds and the topological properties of electronic charge density in the compound were systematically and quantitatively investigated by means of Natural Bond Order (NBO) and the Bader’s Atoms in Molecules theory (AIM), respectively.

An Experimental and Analytical Vibration Study of a Thin Cylindrical Shell Treated with Constrained Layer Damping

This paper presents a experimental optimization method for a thin cylindrical shell with a partially passive constrained layer damping (PCLD) treatment. Vibration level difference theory is employed to evaluate damping effect of PCLD structures which the thicknesses of damping layer and constrained layer are different.

Research on Grinding Characteristics of Ultrasonic Aided Grinding

Experimental study of radial ultrasonic vibration aided grinding of sintered Nd-Fe-B permanent magnetic material was conducted contrasted with traditional grinding. The effect on normal grinding force of grinding parameters was analyzed respectively in the two grinding processes. Experimental results indicate that the discontinuous grinding mechanism caused by ultrasonic vibration is the main factor that reducing the normal grinding force. The process of radial ultrasonic vibration aided grinding is especially suitable for shape machining of sintered Nd-Fe-B permanent magnet.

An Experimental Study of Train-Induced Structural and Environmental Vibrations of a Rail Transit Elevated Bridge with Ladder Tracks

An Experimental Study of Train-Induced Structural and Environmental Vibrations of a Rail Transit Elevated Bridge with Ladder Tracks

Experimental and numerical investigation of friction-induced vibration of a beam-on-beam in contact with friction

The vibrations generated by friction are responsible for various noises such as squealing, squeaking and chatter. Although these phenomena have been studied for a long time, it is not well-understood. In this study, an experimental and numerical study of friction-induced vibrations of a system composed of two beams in contact is proposed. The experimental system exhibits periodic steady state vibrations of different types. To model and understand this experimental vibratory phenomenon, complex eigenvalue and dynamic transient analyses are performed. In the linear complex eigenvalue analysis, flutter instability occurs via the coalescence of two eigenmodes of the system. This linear study provides an accurate value of the experimental frequency of vibration. To understand what happens physically during friction-induced instability, a dynamic transient analysis that takes account of the non-linear aspect of a frictional contact is performed. In this analysis, friction-induced instability is characterized by self-sustained vibrations and by stick, slip and separation zones occurring at the surface of the contact. The results stemming from this analysis show that good correlation between numerical and experimental vibrations can be obtained (in time and frequency domains). Moreover, time domain simulations permit understanding the physical phenomena involved in two different vibratory behaviours observed experimentally.

Reduction of Vibrations of Pedestrian Bridges Using Tuned Mass Dampers (TMD)

Abstract The reduction of structural vibrations on the example of two pedestrian bridges (in Poznań and Wrocław) with using of tuned mass dampers (TMD) has been presented in the paper. The results of theoretical and experimental studies of pedestrian bridge vibrations has been described and discussed. Basing on the results of calculations and measurements, tuned mass dampers (TMD) has been designed and mounted in the structure of the bridges. The measurements after the assembly of TMD show a high efficiency of vibration damping.

An experimental study of train-induced structural and environmental vibrations of a rail transit elevated bridge with ladder tracks

The ladder track is a new type of elastically supported vibration-reduction track system that has been applied to several urban railways in China. A field experiment was carried out at the trial section of an elevated bridge on Beijing Metro Line 5 where the ladder track is installed. The vibration responses of rails, sleepers, bridge deck, and the surrounding ground surface were measured when the train traversed on the ladder track and on the common non-ballasted slab track. The data were analysed in the time domain and the frequency domain. The experimental results show that as compared to the common non-ballasted track, the ladder track has special vibration reduction characteristics.

An experimental and theoretical vibrational spectroscopic study on niflumic acid, a non-steroidal anti-inflammatory drug

The theoretically possible stable conformers of niflumic acid (NFA) molecule in electronic ground state were investigated by means of potential energy surface scan and thermochemistry calculations carried out at room temperature using DFT-B3LYP method and different Pople-style basis sets. The data obtained from these calculations confirmed that the two planar conformers in which the carboxyl and fluoromethyl functional groups are located either in “trans” or in “cis” position to each other are the most favorable ones in energy among all the stable conformers of the free molecule. This conclusion was also confirmed by the energy values obtained from the higher-accuracy thermochemistry calculations carried out using G3MP2B3 composite method. For both conformers and also for their most favorable dimer forms in energy, the equilibrium geometry, force field and vibrational spectral data were calculated first at B3LYP/6-31G(d) and then at B3LYP/6-311++G(d,p) levels of theory. On the basis of these theoretical data, the effects of the conformation and dimerization on the corresponding experimental data of NFA molecule were discussed in detail. The overestimations of the calculated harmonic wavenumbers were corrected by the aid of two different empirical scaling procedures referred to as “scaled quantum mechanical force field (SQM FF) methodology” and “dual scale factors”. In the light of the improved theoretical data obtained in these two approaches applied independently from each other, a successful assignment of the fundamental bands observed in the room-temperature IR and Raman spectra of the molecule was given.

Study on Comparison of Atmospheric and Vacuum Environment of Thermally-Induced Vibration Using Vacuum Chamber

The present paper studies the thermally-induced vibration phenomenon of the flexible space boom structure. In order to simulate the thermally-induced vibration phenomenon of the flexible thin boom structure of the spacecraft with the attached tip mass in space, the thermally-induced vibration including thermal flutter is experimentally investigated at various thermal environments using a heating lamp in vacuum chamber. In this experimental study, fluctuating characteristics, natural frequency and thermal strains of the thermally-induced vibration are parametrically investigated at various thermal environment conditions. Finally the thermally-induced vibration of the flexible boom structure of the orbiting earth satellite in solar radiation environment from the earth eclipse region including umbra and penumbra is simulated using the power control of the heating lamp in the vacuum chamber.