Vibrational Dependence Research Articles

Flow-induced vibrations of an equilateral triangular prism at subcritical Reynolds number

It has been well known that the shear layers behind a prism at subcritical Reynolds number (Re) remain persistently stable. However, potential response of an elastically mounted non-circular prism at subcritical Re is still open. In this study, we numerically investigate the flow-induced vibrations of an equilateral triangular prism at subcritical laminar flow using the immersed boundary method. The prism is allowed to vibrate only in the transverse direction. It is found that the prism vibration could be excited and sustained at subcritical Re due to the instability triggered by the prism's movability. Within angles of attack α = 0°–60°, the triangular prism experiences three responses: i.e., vortex-induced vibration (VIV) at α = 0°–30°, large-amplitude vibration at α = 37.5°–46.5°, and galloping at α = 47.5°–60°. The characteristics of vibration amplitude, frequency, and dependence of fluid forces on reduced velocity and α are investigated. Eight different wake modes exist behind the prism, i.e., one stable mode, two shear layer modes, and five vortex shedding modes. In the VIV regime, the 2S mode (2 single vortices per vibration cycle) is the only vortex shedding mode, while the vortex shedding mode with more than two vortices is unique in the other two regimes. In the end, we discuss (i) the influences of Re and mass ratio and (ii) prediction of the galloping instability using quasi-steady analysis. It is found that three different response regimes are noticed, although their characteristics are strongly affected by the two factors. Quasi-steady approach could provide a reasonable prediction of the emergence of galloping instability for non-circular prism.

Calculation of collisional line-broadening and shifting of acetylene using Complex Robert–Bonamy–Ma approach

A comprehensive semi-classical study of the collisional line broadening and shift coefficients of C2H2 by several key perturbers (H2, He, N2, C2H2, CO, and CO2) for astronomical applications using the Complex Robert–Bonamy–Ma (CRBM) framework is presented. Following the CRBM computational protocol, the intermolecular interaction potentials are constructed from atom-atom and electrostatic interactions, and then fitted to reproduce experimental room-temperature line-broadening parameters taken from the literature. In total, 657 experimental values are used in the fitting. The empirical potentials are then used to predict line broadening coefficients over a wide temperature range. Reference collisional line widths γ0 and temperature exponents n for the commonly used single-power law are produced, as well as a set of parameters for the double-power law, which better reproduces the temperature dependence of theoretical predictions. The vibrational dependence of the line widths is studied using a new ab initio isotropic polarizability surface of C2H2 and is found to be negligible. The computed line broadening parameters are found to agree well with the experimental data, while the modelling of line shits of HCCH is not satisfactory when compared to the experiment. The new line broadening data of C2H2 with the J (or m) dependence have been used to populate the ExoMol database www.exomol.com as part of the ExoMol pressure-broadening diet and can be used to model opacities of atmosphere of (extrasolar) planets. The CRBM methodology tested here on C2H2 can be used for other similar (closed-shell) systems in ExoMol that are important for exoplanetary atmospheric studies.

Isotopic species, vibrational states and nuclear quadrupole splitting in CH[formula omitted]Cl[formula omitted] from rotational spectroscopy at 8–18 GHz

The present work fills several significant gaps in the study of the rotational spectrum of the methylene chloride molecule. Two Fourier transform microwave spectrometers were used, providing complementary coverage of the 8–18 GHz region, at room temperature and in supersonic expansion. Hyperfine resolved measurements were made and fitted for ground states of the CH235Cl2, CH235Cl37Cl, CH237Cl2, and 13CH235Cl2 isotopic species, as well as for nine different excited vibrational states. Transitions in the v4=2, v4=3, v3=1, v9=1 states in CH235Cl2, and transitions in excited states of the ν4 mode in 35Cl37Cl and 37Cl2 isotopic species have been assigned for the first time. Vibrational and isotopic dependence of nuclear quadrupole coupling constants was identified. The v3=1 and v9=1 states in CH235Cl2 were found to be significantly coupled by c-axis Coriolis interaction, while transitions in v4=2 and v4=3 states exhibited hyperfine mediated perturbations enhancing the determination of the χab parameter and allowing assessment of its vibrational dependence.

Defect‐Driven Light Perception and Memristor Storage with Phase Transition in Vanadium Dioxide

AbstractTunable optical information storage is crucial in artificial retinal systems for mimicking neurobiological visual characteristics. The perception and storage of light signals rely heavily on the regulation of the conductivity states of memristor materials (e.g., transition metal oxides). Controlling light memristor behavior via defects and polymorphic phases remains underexplored and differs from traditional plasticity training via repeated testing. In this study, defect‐driven ultraviolet light perception and memristor storage with phase transitions in vanadium dioxide (VO2) thin films are presented. The effects of oxygen defects and the corresponding polymorphic phases on ultraviolet light memristors are investigated. The dependence of phonon vibrations and insulator–metal transition behavior on defect levels are revealed. Self‐doping and polymorphs enable VO2 to exhibit distinct ultraviolet memristor performance. It is anticipated that defect‐driven light memristors significantly contribute to the realization of artificial synaptic devices and the implementation of advanced electronic neuron systems.

Extended measurements and calculations of CH3C14N-N2 rotational lineshape parameters

Spectroscopic parameters of methyl cyanide are of interest for astrophysical applications because of presence of this molecule in planetary atmospheres, comets, and interstellar medium. For radiative-transfer modeling a key role is played by the pressure-induced linewidths which are strongly influenced by the collision partner and the temperature. To complete the extremely scarce experimental data available, rotational lines of room-temperature CH3C14N in collision with molecular nitrogen have been recorded in a very large (180–1400 GHz) frequency range for J = 9 → 10, 12 → 13, 15 → 16, 21 → 22, 27 → 28, 33 → 34, 42 → 43, 48 → 49, 63 → 64, 69 → 70, 75 → 76 and K = 0–15. The high sensitivity of the frequency-modulated spectrometer has enabled observation of clear deviations of the recorded lineshapes from the usual Voigt profile. Their additional analyses performed with advanced non-Voigt models have demonstrated that the observed lineshapes are mainly governed by the speed dependence of relaxation rates and that the optical diffusion related to velocity changing collisions (Dicke effect) has a nearly negligible role. Compared to infrared-region results available in the literature, our Voigt-profile values lie systematically lower by about 0.5 MHz/Torr, which argues in favor of observable vibrational dependence for the CH3CN-N2 system. Line-broadening parameters have been also evaluated by a semi-empirical method based on the Anderson-Tsao-Curnutte theory. The model parameters determined from fits on some selected experimental values confirm the tendences previously stated for the case of vibrotational transitions and allow better theoretical predictions for extended ranges of rotational quantum numbers. Being temperature-independent, these parameters can be directly used in calculations for other temperatures concerned by radiative transfer models.

Low-Frequency Spectra of Hydrated Ionic Liquids with Kosmotropic and Chaotropic Anions.

In this study, we investigated the water concentration dependence of the intermolecular vibrations of two hydrated ionic liquids (ILs), cholinium dihydrogen phosphate ([ch][dhp]) and cholinium bromide ([ch]Br), using femtosecond Raman-induced Kerr effect spectroscopy (fs-RIKES). The anions of the former and latter hydrated ILs are kosmotropic and chaotropic, respectively. We found that the spectral peak of ∼50 cm-1 shifted to the low-frequency side in hydrated [ch][dhp], indicating the weakening of its intermolecular interactions. In contrast, no change in the peak frequency of the low-frequency band at ∼50 cm-1 was observed with increasing water concentration in hydrated [ch]Br. The vibrational density of states (VDOS) spectra generated from molecular dynamics (MD) simulations were in qualitative agreement with the experimental results. Decomposition analysis of the VDOS spectra for each component revealed that the red shift of the low-frequency band in the hydrated [ch][dhp] upon water addition was essentially due to the contributions of anions and water rather than that of the cholinium cation. We also found from the low-frequency spectra of the two hydrated ILs that they differed in the concentration dependence of the 180 cm-1 band, which is assigned as a hindered translational motion of water molecules combined to form O···O stretching motions. From the relationship between the peak frequency of the low-frequency band and the bulk parameter, which is the square root of the surface tension divided by the density, we found that the peak frequency in the hydrated IL with kosmotropic [dhp]- depends on the bulk parameter, similar to the case for an aqueous solution of the typical deep eutectic solvent reline. However, the peak frequency of the hydrated IL with chaotropic Br- is constant with the bulk parameter.

Fingerprint Raman spectroscopy for two-dimensional MoS2x Se2(1−x) alloys

Two-dimensional transition metal dichalcogenides (TMDs) and alloys based on them, is a promising platform for creating opto- and nanoelectronic devices. For layered alloys, there is a strong need to theoretically determine the frequencies of vibrational modes and dependences of their energies on the stoichiometric composition. By comparing experimentally measured Raman modes with theoretical predictions, it becomes possible to determine the stoichiometric composition of the manufactured alloys. In this work, we investigated the vibrational properties of monolayer MoS2x Se2(1−x) alloys utilizing density functional theory method and confirmed them experimentally by Raman spectroscopy. The dependence of A1ʹ and E1 2g ‘dactylographic’ modes on the stoichiometric composition of alloys has been calculated. When in pure MoSe2 structure Se atoms are substituted by S atoms, the in-plane E1 2g (S–Mo), E1 2g (Se–Mo) and out-plane A1ʹ (S–Mo) modes shifted linearly in x to higher frequencies, while the out-plane A1ʹ (Se–Mo) mode did the same in nonlinear way. We also identified the E1 2g (Se–Mo–S) mode, which specific for the MoS2x Se2(1-x) alloys and does not appear in pure two-component TMDs.

Rapid generation of massive thermodynamic datasets using frequency comb spectroscopy.

We demonstrate massively parallel spectroscopic measurements of 12C2H2 using an optical frequency comb. This allows for the rapid and simultaneous estimation of self-broadening and self-shifting of more than 50 optical transitions between 1512 and 1538nm. The use of a temperature-controlled sealed gas cell allows us to measure both pressure- and temperature-mediated broadening and shifting. We present the results for the pressure-mediated self-broadening and self-shifting coefficients for 59 optical lines that make up the v1 + v3 combination band and a selection of hot bands. Our ability to measure the broadening of numerous transitions allows for the confirmation of prior work that shows that there is no measurable vibrational dependence across all acetylene bands, despite the strong dependence of the broadening coefficient on the rotational number. We also present an extensive measurement of the temperature dependence of the self-broadening for each of these 59 lines. This work shows the revolutionary power afforded by the frequency combs for rapid generation of large datasets related to thermodynamic variations of the key spectroscopic parameters of important gases.

Airborne ultrasound for the contactless mapping of surface thoracic vibrations during human vocalizations: A pilot study

Physical examination of the thorax is key to the clinical diagnosis of respiratory diseases. Among other examination techniques, palpation evaluates the transmission of high-frequency vibrations produced by vocalizations (tactile fremitus), which helps the physicians to identify abnormalities within the respiratory system. We propose the use of an airborne ultrasound surface motion camera (AUSMC) to quantitatively map the vibrations induced by subject vocalization. This approach could make the examination of vocal fremitus quantifiable, reproducible, and archivable. Massive data collection of vocal fremitus could allow using artificial intelligence algorithms to isolate vibration patterns that could help disease identification. Until now, in contrast, the interpretation of vocal fremitus has been subject to the physician’s experience and remains subjective. In the present work, we demonstrate the capabilities of the AUSMC to measure vocal fremitus thoracic vibration maps on 77 healthy volunteers. We have observed a spatial dependence of vibration maps on vocalization frequency. We observed that the left lung generates fewer surface vibrations than the right one, which was expected according to their respective dimensions. We also discuss the implications of our findings.

CRDS line-shape study of the (7–0) band of CO

We present the results of the spectral line-shape study of the first measurement of the extremely weak (7–0) band of the 12C16O molecule. Measurements were done with a highly sensitive cavity ring-down spectrometer. Collisional narrowing, analyzed in terms of speed-dependent effects, was observed for the first time for transitions with line intensities below 2⋅10−29 cm/molecule at 296 K. We provide a full set of line-shape parameters of the speed-dependent and regular Voigt profile analysis for 14 transitions from P and R branches. Experimental verification of a strong vibrational dependence of the pressure shifting described by the Hartmann model (Hartmann, 2009) is extended up to the sixth overtone highly sensitive to the model parameter.

Charge-lattice coupling effects in organic isomeric charge transfer crystals

One of the most important features of organic cocrystals is the interaction between electrons and lattices, which brings interesting physical phenomena. In this work, we prepared two isomeric crystals in which the isomeric donors are used to fabricate charge transfer crystals. Isomeric crystals present different electron–lattice coupling strengths to further affect the charge localization, which leads to different dielectric constants and fluorescence lifetimes. Furthermore, external magnetic field and electric field exhibit different tunability on the photoluminescence and dielectric constants of the isomeric cocrystals due to the significant differences in the coupling between the charge and lattice vibration. Overall, through fabricating isomeric organic crystals, neighbor molecular vibration dependence of electron–lattice coupling is studied, which provides a platform to further understand the lattice vibration dependent spin and optics.

Temperature dependence of optical fiber current sensor with external conversion

The paper presents the research of a optical fiber current sensor with external conversion (OFCS-EC) as a function of temperature. The sensor was developed in the Department of Optoelectronics. The sensor was tested in the temperature range from 23 °C – 80 °C. For each of the temperatures, the sensitivity was determined on the basis of a sinusoidal waveform. Thus, the linearity of the transfer characteristics was checked. The main purpose of the experiment was to check the limits of sensitivity changes in changing thermal conditions and whether the sensor meets the standards used in the power industry. Full Text: PDF References M.J. Weber, "CRC Handbook of Laser Science and Technology. Supplement 2: Optical Materials", CRC Press, Boca Raton, FL, USA (1995). CrossRef S. Ju, Y. Lee, Y.T. Ryu, S.G. Kang, J. Kim, P.R. Watekar, B.H. Kim, Y. Lee, Y.H. An, C.J. Kim, W.T. Han, "Temperature Dependence of Faraday Rotation of Glass Optical Fibers Doped with Quantum Dots of CdSe and CdMnTe", Phys. Status Solidi A, 216: 1800549 (2019). CrossRef E. Lage, L. Beran, A.U. Quindeau, L. Ohnoutek, M. Kucera, R. Antos, S. R. Sani, G.F. Dionne, M. Veis, C.A. Ross; Temperature-dependent Faraday rotation and magnetization reorientation in cerium-substituted yttrium iron garnet thin films. APL Mater. 5, 036104 (2017). CrossRef S. Ju, J. Kim, K. Linganna, P.R. Watekar, S.G. Kang, B.H. Kim, S. Boo, Y. Lee, Y.H. An, C.J. Kim, et al. "Temperature and Vibration Dependence of the Faraday Effect of Gd2O3 NPs-Doped Alumino-Silicate Glass Optical Fiber". Sensors, 18, 988 (2018). CrossRef A. Jeffrey, D. and R.M. Bunch, "Temperature dependence of the Faraday rotation of Hoya FR-5 glass," Appl. Opt. 23, 633 (1984). CrossRef K. Barczak, J. Juraszek, "Optoelectronic system for detecting short-circuits in low voltage networks", Photon. Lett. Pol, 14, 37 (2022). CrossRef K. Barczak, K. Mazniewski, "Optical fiber current sensor with external conversion for measurements of low AC electric currents", Proc. SPIE, 10455 (2017). CrossRef

Global modelling of the observed line positions for the spectra of ultraviolet bands: Dunham coefficients for the A2Σ+ excited state of the 16OH molecule

A global treatment of the available experimental data on transition frequencies both in the A2Σ+state and in the A2Σ+−X2Π, and B2Σ+−A2Σ+ electronic systems of 16OH molecule was carried out. In this analysis, a global model with vibrational dependences of the parameters of the effective Hamiltonian for the diatomic molecule in different electronic state was used. As a result of the fit, a set of the ‘Dunham-type’ coefficients for A2Σ+ electronic state was obtained. They reproduce the experimental dataset within estimated experimental uncertainties. The determined ‘Dunham-type’ coefficients were employed to generate the potential energy curve in the A2Σ+ electronic state using the RKR method.

Resonance-state selective photodissociation dynamics of OCS + hv → CS(X1Σ+) + O(3Pj=2,1,0) via the 21Σ+ state.

Understanding vacuum ultraviolet photodissociation dynamics of Carbonyl sulfide (OCS) is of considerable importance in the study of atmospheric chemistry. Yet, photodissociation dynamics of the CS(X1Σ+) + O(3Pj=2,1,0) channels following excitation to the 21Σ+(ν1',1,0) state has not been clearly understood so far. Here, we investigate the O(3Pj=2,1,0) elimination dissociation processes in the resonance-state selective photodissociation of OCS between 147.24 and 156.48nm by using the time-sliced velocity-mapped ion imaging technique. The total kinetic energy release spectra are found to exhibit highly structured profiles, indicative of the formation of a broad range of vibrational states of CS(1Σ+). The fitted CS(1Σ+) vibrational state distributions differ for the three 3Pj spin-orbit states, but a general trend of the inverted characteristics is observed. Additionally, the wavelength-dependent behaviors are also observed in the vibrational populations for CS(1Σ+, v). The CS(X1Σ+, v = 0) has a significantly strong population at several shorter wavelengths, and the most populated CS(X1Σ+, v) is gradually transferred to a higher vibrational state with the decrease in the photolysis wavelength. The measured overall β-values for the three 3Pj spin-orbit channels slightly increase and then abruptly decrease as the photolysis wavelength increases, while the vibrational dependences of β-values show an irregularly decreasing trend with increasing CS(1Σ+) vibrational excitation at all studied photolysis wavelengths. The comparison of the experimental observations for this titled channel and the S(3Pj) channel reveals that two different intersystem crossing mechanisms may be involved in the formation of the CS(X1Σ+) + O(3Pj=2,1,0) photoproducts via the 21Σ+ state.

Тауарлы бетонды тасымалдау кезінде автомобиль дірілін азайту

This article discusses the research of one of the urgent problems of transportation of binding materials by cars on domestic highways. The study examined the oscillations of cars by disturbing forces, as well as the main sources of disturbances of the oscillations of cars, i.e. road surface bumps; eccentricity, uneven movement and imbalance of the wheels; rotating parts of the engine; transmissions. The idea of the dependence of vehicle vibrations on a road with an uneven surface is traced, while usually experiencing random vibrations. The microprofile of the road is compared as a random function of the length of the road, the distance traveled is taken as the value of X, this tells us that its ordinates at any value of X are a random value. The article clearly explains the statistical characteristics of the random function in relation to the microprofile of the road. It represents the average values, which are different if averaged over the aggregate implementation or for one implementation, i.e. on time.

Line shape parameters of air-broadened 12CO2 transitions in the 2.0 µm region, with their temperature dependence

The 20013–00001 and 20012–00001 bands of 12C16O2 in the 2 µm region are used by many instruments on-board satellites and in ground-based networks to monitor the CO2 column-averaged dry air mole fraction in the Earth's atmosphere. An accurate knowledge of the corresponding spectroscopic parameters and their temperature dependence is thus needed to map sources and sinks of carbon dioxide. In this work, we retrieve the line-shape parameters and their temperature dependence exponents/coefficients for the P(16) and P(28) transitions of the 20012–00001 band, and the R(24) and R(30) transitions of the 20013–00001 band. These parameters are obtained from a multi-spectrum fit procedure using a speed-dependent Nelkin-Ghatak profile including the line-mixing effect in its first-order approximation. High signal-to-noise spectra (quality factor between typically 3000 and 6000) are recorded at different conditions of pressure (from 50 to 750 Torr) and temperature (from 245 to 330 K) for mixtures of CO2 in air using a comb-assisted cavity ring down spectrometer with a temperature stabilized high finesse cavity. Air-broadening coefficients are measured with an estimated uncertainty better than 0.1% and absolute frequencies of the transitions are obtained with uncertainty better than 100 kHz. The determined line-shape parameters are consistent with previous values derived in the 1.6 µm region confirming the absence of significant vibrational dependence (except for the air-pressure shift coefficient). The retrieved parameters agree well with literature values by Fourier transform spectroscopy and classical molecular dynamic simulations. The parameters of the speed-dependent Voigt profiles provided by the HITRAN2020 database are mostly validated. The comparison to the CO2 line parameters adopted for the OCO missions is discussed.

Magnetic and vibrational amplitude dependences of MRE grid composite sandwich plates

In this work, both magnetic and vibration amplitude dependent properties of magnetorheological elastomer (MRE) grid composite sandwich plates (MREGCSPs) are investigated. Initially, to prove such a nonlinearly dependent phenomenon, a series of characterization tests are performed on the MREGCSP specimens with different magnetic field intensities and base vibrational amplitudes. Then, using the Jones-Nelson nonlinear material theory, the strain energy density function method, the complex modulus approach, and the Biot-Savart law, the nonlinear material assumption of MRE is defined. A theoretical model consisting of an MRE grid core and two fiber-reinforced polymer (FRP) skins is also proposed to obtain the solutions for the nonlinear frequency, damping, and vibration response parameters, which is based on the modified first-order shear deformation theory, the energy principle, the eigenvalue increment method, the Newmark- beta approach, etc. Finally, a detailed comparison of magnetic and vibrational amplitude dependent natural frequencies, loss factors, and vibration responses is performed to confirm the effectiveness and superiority of the current model over a linear model. This provides a solid basis to reveal the nonlinear dynamic mechanism of the studied smart structure subjected to complex excitation loads. Also, some practical suggestions are summarized for improving its active vibration control capability.

Experimental investigation for non-linear vibrations of free supported and cantilever FFF rectangular plates

The aim of this paper is to investigate experimentally the effect of large vibration of a cantilever and a fully free rectangular plate made by a Fused Filament Fabrication process. Furthermore, this investigation attempts to compare our measurements and those obtained in the literature experimentally. For this purpose, a test rig was designed and manufactured for all experimental trials. The plate was excited randomly and harmonically at large displacement respectively, to obtain the linear and non-linear frequencies parameter. The non-linear dynamic behaviour of our structure at forced vibration is figured by exciting the plate at large displacement. The dependence of frequency and amplitude vibration are examined for the first, second, and third mode shapes. The non-linear dynamic behaviour of cantilever plates is compared with literature to illustrate the convergence of our results by using our specific mechanical properties, printing parameters, and process. Furthermore, the non-dimensional comparison is shown by 33.38%, 5.83%, and 20.58% for the first, second, and third mode shapes, respectively. Experimental tests will be performed on a 3D-printed metal plate to improve the present work. This work is intended to determine the dynamic proprieties of our parts in order to manufacture a safe and comfort machine. Actually, the dynamic behaviour of our 3D printing plates is compared with the obtained in the case of the isotropic plate for the aim to predict the convergence of both structures.

Response of mechanical and optoelectronic properties for InPxAsySb1–x–y/InAs system to composition

The compositional dependence of optical, mechanical, thermal properties, and lattice vibrations of InPxAsySb1–x–y quaternary semiconductor alloys lattice-matched to InAs substrate has been studied. In this study, the physical properties of the binary elements InAs, InSb, and InP that make up the quaternary alloy were employed. Under the virtual crystal approximation (VCA), the empirical pseudo-potential model (EPM) was used to carry out the research. Our findings are in good agreement with the available experimental and theoretical values. In the literature, the composition effect on the optical, mechanical and thermal properties of the InPxAsySb1–x–y/InAs system has not been thoroughly investigated. As a result, we focused on these properties as a function of composition.

Chatter Monitoring of Machining Center Using Head Stock Structural Vibration Analyzed with a 1D Convolutional Neural Network.

Real-time chatter detection is crucial for the milling process to maintain the workpiece surface quality and minimize the generation of defective parts. In this study, we propose a new methodology based on the measurement of machine head stock structural vibration. A short-pass lifter was applied to the cepstrum to effectively remove components resulting from spindle rotations and to extract structural vibration modal components of the machine. The vibration modal components include information about the wave propagation from the cutter impact to the head stock. The force excitation from the interactions between the cutter and workpiece induces structural vibrations of the head stock. The vibration magnitude for the rigid body modes was smaller in the chatter state compared to that in the stable state. The opposite variation was observed for the bending modes. The liftered spectrum was used to obtain this dependence of vibration on the cutting states. The one-dimensional convolutional neural network extracted the required features from the liftered spectrum for pattern recognition. The classified features allowed demarcation between the stable and chatter states. The chatter detection efficiency was demonstrated by application to the machining process using different cutting parameters. The classification performance of the proposed method was verified with comparison between different classifiers.