Vibrational Components Research Articles

Strong Exciton-Vibrational Coupling in Molecular Assemblies. Dynamics Using the Polaron Transformation in HEOM Space.

In Frenkel exciton dynamics of aggregated molecules, the polaron transformation (PT) technique leads to decoupling of diagonal elements in the subspace of excited electronic states from vibrations. In this article we describe for the first time how PT becomes applicable in the framework of the "Hierarchical Equations of Motion" (HEOM) approach for treatment of open quantum systems. We extend the concept of formulating operators in HEOM space by deriving hierarchical equations of PT which lead to a shift in the excited state potential energy surface to compensate its displacement. While the assumption of thermal equilibration of the vibrational oscillators, introduced by PT, results in a stationary state in a monomer, in a dimer under the same assumption nonequilibrium dynamics appears because of the interplay of the transfer process and vibrational equilibration. Both vertical transitions generating a vibrationally hot state and initially equilibrated vibrational oscillators evolve toward the same stationary asymptotic state associated with polaron formation. The effect of PT on the dynamics of this process depends on initial excitation and basis representation of the electronic system. The developed approach facilitates a generic formulation of quantum master equations involving perturbative treatment of polaron dynamics.

Thermodynamics of lattice vibrations in non-cubic crystals: the zinc structure revisited.

A phenomenological model of anisotropic lattice vibrations is proposed, using a temperature-dependent spectral cutoff and varying Debye temperatures for the vibrational normal components. The internal lattice energy, entropy and Debye-Waller B factors of non-cubic elemental crystals are derived. The formalism developed is non-perturbative, based on temperature-dependent linear dispersion relations for the normal modes. The Debye temperatures of the vibrational normal components differ in anisotropic crystals; their temperature dependence and the varying spectral cutoff can be inferred from the experimental lattice heat capacity and B factors by least-squares regression. The zero-point internal energy of the phonons is related to the low-temperature limits of the mean-squared vibrational amplitudes of the lattice measured by X-ray and γ-ray diffraction. A specific example is discussed, the thermodynamic variables of the hexagonal close-packed zinc structure, including the temperature evolution of the B factors of zinc. In this case, the lattice vibrations are partitioned into axial and basal normal components, which admit largely differing B factors and Debye temperatures. The second-order B factors defining the non-Gaussian contribution to the Debye-Waller damping factors of zinc are obtained as well. Anharmonicity of the oscillator potential and deviations from the uniform phonon frequency distribution of the Debye theory are modeled effectively by the temperature dependence of the spectral cutoff and Debye temperatures.

Damage Identification of Semi-Rigid Connection in Structures Based on Nonlinear Vibration Characteristics

A damage-detection methodology based on nonlinear vibration characteristics was presented in this paper to identify damage of semi-rigid connections due to looseness of high strength bolts. In various damage cases caused by different loose severity of bolts in different positions, a specimen with semi-rigid connections was test and acceleration signals of free vibration were recorded by sensors placed at its both ends. The recorded signals were then dealt with by wavelet de-noising and blind source separation to get the first vibrational components. By Hilbert transform of these components, the amplitude-frequency curve of each case was obtained. The results showed that vibration of the specimen with semi-rigid connections presented typical nonlinear characteristics. With the increase of connection damage, the nonlinear degree increased accordingly. When one end had larger connection damage than the other one, it exhibited greater nonlinear extent. The results prove that it is valuable to apply the suggested nonlinear vibration characteristics based procedure to identification of semi-rigid connection damage.

'DIS_turbation': An Artistic Approach to Foster Nature-Connectedness

This paper presents practice-based research on ecoacoustics, ocean soundscapes and anthropogenic noise. It explores creative strategies to the introduction, experience and performance of ocean soundscapes in artistic creation. As ocean soundscapes are increasingly a topic of concern globally, they become a crucial tool to foster an emotional affinity between people and natural environments. This research questions how to convey the experience of oceanic soundscapes and their human disruption. The paper details an artistic artefact - DIS_turbation - and its integrative approach, by exploring the vibrational and particle-motion component of ocean sound. The methods include place attachment, creative development, nature-connectedness and ecology of AEffect. The novelty lies in addressing biological processes as a creative resource to intervene in underwater noise dialogue, reveal hidden qualities of vibroacoustic ecology, develop artistic artefacts to translate particle-motion in a more grasping way, and foster inclusion with nature.

Energy relaxation path of excited free OH vibration at an air/water interface revealed by nonequilibrium ab initio molecular dynamics simulation.

Nonequilibrium ab initio molecular dynamics (NE-AIMD) simulations are conducted at an air/water interface to elucidate the vibrational energy relaxation path of excited non-hydrogen-bonded (free) OH. A recent time-resolved vibrational sum frequency generation (TR-VSFG) spectroscopy experiment revealed that the relaxation time scales of free OH at the surface of pure water and isotopically diluted water are very similar to each other. In the present study, the dynamics of free OH excited at the surface of pure water and deuterated water are examined with an NE-AIMD simulation, which reproduces the experimentally observed features. The relaxation paths are examined by introducing constraints for the bonds and angles of water molecules relevant to specific vibrational modes in NE-AIMD simulations. In the case of free OH relaxation at the pure water surface, stretching vibrational coupling with the conjugate bond makes a significant contribution to the relaxation path. In the case of the isotopically diluted water surface, the bend (HOD)-stretching (OD) combination band couples with the free OH vibration, generating a relaxation rate similar to that in the pure water case. It is also found that the reorientation of the free OH bond contributes substantially to the relaxation of the free OH vibrational frequency component measured by TR-VSFG spectroscopy.

Analysis of Solid-State Reaction Mechanisms with Two-Dimensional Fourier Transform Infrared Correlation Spectroscopy.

The utility of two-dimensional generalized correlation spectroscopy (2D-COS) for tracking complex solid-state reactions is demonstrated using infrared spectra acquired during a photochemically induced decomposition reaction. Eleven different thin films, consisting of six monometallic and five bimetallic 2-ethylhexanoate complexes, were tracked as a function of photolysis time. Overlapping peaks in the infrared fingerprint region are readily discriminated using 2D-COS, enabling individual vibrational components to be used to distinguish whether carboxylate ligands are free/ionic or bound in a chelating, bridging, or monodentate fashion. This classification enables the decomposition mechanism to be tracked for all 11 samples, revealing that ligands bound in monodentate and bridging fashions are first converted to chelates before being lost as volatile products for all samples. The magnitude of the measured first-order rate constants for loss of chelated ligands is found to correlate linearly to the asymmetric stretching frequency of monodentate ligands but exhibits a V shape when plotted against the electronegativity of the metal center. We propose that loss of chelated ligands proceeds via C-O scission for highly electronegative transition metals but M-O scission for transition metals with low electronegativity. These results establish 2D-COS as a powerful tool to deconvolute and correlate individual components, enabling mechanistic analysis of complex chemical reactions.

Plasmon-enhanced coherent anti-stokes Raman scattering vs plasmon-enhanced stimulated Raman scattering: Comparison of line shape and enhancement factor.

Plasmon-enhanced coherent Raman scattering microscopy has reached single-molecule detection sensitivity. Due to the different driven fields, there are significant differences between a coherent Raman scattering process and its plasmon-enhanced derivative. The commonly accepted line shapes for coherent anti-Stokes Raman scattering and stimulated Raman scattering do not hold for the plasmon-enhanced condition. Here, we present a theoretical model that describes the spectral line shapes in plasmon-enhanced coherent anti-Stokes Raman scattering (PECARS). Experimentally, we measured PECARS and plasmon-enhanced stimulated Raman scattering (PESRS) spectra of 4-mercaptopyridine adsorbed on the self-assembled Au nanoparticle (NP) substrate and aggregated Au NP colloids. The PECARS spectra show a nondispersive line shape, while the PESRS spectra exhibit a dispersive line shape. PECARS shows a higher signal to noise ratio and a larger enhancement factor than PESRS from the same specimen. It is verified that the nonresonant background in PECARS originates from the photoluminescence of nanostructures. The decoupling of background and the vibrational resonance component results in the nondispersive line shape in PECARS. More local electric field enhancements are involved in the PECARS process than in PESRS, which results in a higher enhancement factor in PECARS. The current work provides new insight into the mechanism of plasmon-enhanced coherent Raman scattering and helps to optimize the experimental design for ultrasensitive chemical imaging.

Multi-body simulation and validation of fault vibrations from rolling-element bearings

Dynamic simulations are often used to evaluate the vibrational response of rolling-element bearings experiencing defects. Previously, the optimal accelerometer position has been found to be as close as possible to the bearing. However, further details about the influence of rotational symmetry have not been closely investigated. This paper presents a dynamic simulation model of a radially loaded complete spherical roller bearing with a defect in the inner ring and placed in a housing with 72 equally spaced accelerometer positions around the circumference. Surface accelerations have been extracted and transformed into the frequency domain. Thereafter, the vibrational components indicating the defect have been evaluated around the circumference. The results show an optimal position as close as possible to the primary loaded zone and validation test rig experiments show a reasonable qualitative agreement.

A study on whipping related double bottom response as well as its statistical characteristics based on full-scale measurements

Recently, the great enlargement of container ships has brought broad concern on the effect of whipping response. Meanwhile, the accompanying wider width of double bottom may cause more flexible responses of the double bottom structures. The numerical simulation studies have shown that the longitudinal stresses of the hold central bottom of a container ship due to the double bottom bending superimpose on the longitudinal stresses due to hull girder bending in both wave response component and vibrational response component. In this research, the authors firstly extract the full scale measurements data whose sea states are closest to that of numerical simulation among existing time series, with the purpose of analyzing correlation between double bottom bending and hull girder bending in wave response and vibrational response. As a result, studies from full scale measurements well verified the phenomenon that double bottom of larger container ship responds to forced vibration due to whipping excitation as observed in theoretical studies. Then, the statistical characteristics of correlation factor between hull girder bending stress and double bottom bending stress were investigated, based on relatively large number of data with regard to wave height and relative wave direction, as well as the classification between low- and high-frequency-dominant response cases. All these studies may contribute to future optimized operation, maintenance and design of ship.

МОДЕЛЮВАННЯ РОЗДРІБНЕННЯ ГАЗОВОЇ БУЛЬБАШКИ НА ОСНОВІ АНАЛОГІЇ З ХИТНОЮ ПРУЖИНОЮ

Extinguishing fires in gas-liquid mixtures in vertical tanks containing flammable liquids should be accompanied by constant crushing of gas bubbles in these mixtures. The mechanical method makes it possible to crush the bubbles due to acoustic pressure waves generated by impacts on the metal membrane. A more progressive method of crushing involves the action of an acoustic wave directly on the bubbles. This allows you to intervene in the process of grinding the bubbles by changing the pressure frequency, which affects the quality of the gas-liquid mixture. In the works of Petrov A. and his students proposed a resonant model of grinding a gas bubble in a liquid in an unsteady pressure field. Resonant fragmentation of a bubble in a liquid occurs due to the transfer of energy between the radial and deformation modes of vibrations. An interesting effect is observed - with a relatively small amplitude of the alternating pressure of the acoustic wave in the liquid, a sufficiently large amplitude of deformation vibrations develops - due to which the bubble is crushed. A feature of research is the use for this mechanical analogue - a swinging spring (swinging spring). That is, a variety of a pendulum consisting of a point load attached to a weightless spring. The second end of the spring is fixed motionless. The pendulum oscillations of the spring in the vertical plane are studied, provided that its axis are straightforward. The feasibility of choosing such an analogue is explained by the need to study the dynamic system "grinding of the bubble" when nonlinearly coupled vibrational components exchange energy with each other. Indeed, in the case of a bubble, an energy exchange occurs between the radial and deformation modes of vibrations. In this paper, this phenomenon is investigated using the mathematical apparatus of a swinging spring, which illustrates the energy exchange between pendulum and spring oscillations. Keywords: swing spring, Lagrange mechanics, generalized coordinates, load path.

Dynamic response and mechanical deformation properties of the soil cutting slope under train cyclic loads

A series of large-scale geotechnical model tests and numerical simulations were carried out to study the dynamic behavior and the mechanical deformation mechanism of the railway slope subjected to train cyclic load. We investigated the frequency domain and deformation mechanism of the railway slope. It was found that the high-frequency vibrational component is greater close to the track, and the dominant frequency is concentrated in the region 35~45 Hz. Moreover, the impact of the platform width, slope ratio, and slope steps on the dynamic mechanical properties are further studied. The design parameters of slope types have a strong influence on the dynamic behavior of the railway slope under cyclic load. Under unfavorable parametric conditions, it is possible to form a cumulative tension strain band extending to the interior of the slope, which will result in a large-scale landslide. In contrast, with the optimization of the slope design parameters, when the platform width exceeds 4 m or the slope rate is in the range of 1:1.25~1:1.5, no tension strain zone appears inside the slope, and a compression strain zone easily occurs at the foot of the slope, which will form compression deformation in the shallow portion of the slope surface. It can be noticed that the attenuation rate is the maximum close to the track and reduces gradually in the far field. Besides the vibration intensity in platform area decreases, the acceleration amplitudes are attenuated by more than 70%. Optimization of the slope design parameters can effectively reduce the risk of severe large-scale sliding and improve the stability of the railway slope. Furthermore, the fluctuation effect is more noticeable as the number of slope steps increase.

Rectification of acoustic phonons in harmonic chains with nonreciprocal spring defects

The scattering of acoustic phonons by nonreciprocal spring defects inserted in an harmonic chain is investigated. The degree of nonreciprocity of the forces mediated by the defect springs is parameterized by a single quantity Δ that effectively takes into account the interaction of the coupled masses with hidden degrees of freedom of an underlying nonequilibrium system. We demonstrate a pronounced rectification effect with transmission having a preferential direction. Nonreciprocity also allows energy exchange between the system and the medium. Further, we show a cooperative action between defects mediated by resonant cavity modes. The influence of damping forces is also explored and shown to promote the rectification of the reflected vibrational wave component.

Развитие инструментария управления предприятиями радиоэлектронной промышленности в условиях их диверсификации

The article presents the results of the research, the relevance of which is determined by the urgent need to improve the management tools of enterprises of the radio–electronic industry at the present time. The subject of the study is this tool used in the conditions of incomplete initial data and uncertainty of the external environment of enterprises due to changes in their production and economic activities during the period of production diversification. Some models describing the analyzed process taking into account its specifics are considered, which allow obtaining probabilistic–time estimates of the development of enterprises in the studied conditions. For this purpose, we used methods that take into account the vibrational component in the analyzed time series, as well as expert methods. The application of the proposed algorithms in practice helps to optimize diversification measures, accelerate the innovative development of radio–electronic industry enterprises and increase its efficiency.

Evaluation of Polaron Transport in Solids from First‐principles

AbstractPolarons are formed in polar or ionic solids, either molecular or crystalline, due to local distortions of the lattice induced by charge carriers. Polaron hopping is the primary mechanism of charge transport in these materials, such as functional ceramic compounds, with applications in photovoltaics, thermoelectrics, two‐dimensional electron gas transistors, magnetic sensors, spin valve devices, and memories. Understanding the fundamental physics of polaron hopping is, therefore, of prime technological importance. This article provides a brief physical background of polarons and their hopping mechanism, focusing on first‐principles calculations of polaron properties. Herein, we review recent selected studies applying the density functional theory (DFT), and describe the merits and challenges in applying DFT for such calculations, highlighting the need to address both electronic and vibrational aspects. The vibrational component of the polaron is evaluated based on structural and total energy calculations, whereas the electronic component is derived from both total energy and electron density calculations. To address the most compelling challenge of calculating polaron properties using DFT, which is the issue of electron localization, we propose to employ calculations of selected vibrational properties, such as the sound velocity, shear modulus, and Grüneisen parameter, to represent the polaron hopping energy; all of which originate from the stiffness of inter‐atomic bonds. Such methodology is expected to be more straightforward than the existing ones, however demands standardization.

The Perihelion Shift of Mercury’s Orbit

Influence of planets of the solar system on the precession of the orbit of Mercury is studied in the framework of classical mechanics. It is shown that the average perihelion shift of the orbit of Mercury, calculated in the framework of the planar limited problem, is 556.5 arc seconds per century and coincides with the observed one with a relative accuracy of 2.5%. The incomplete coincidence between the calculated average displacement and the observational data is explained by the presence in the observed displacement of vibrational components with a total amplitude of up to 80 arc seconds and periods from several years to tens of years.

Transmission of the frequency components of the vibrational signal of the glassy-winged sharpshooter, Homalodisca vitripennis, within and between grapevines

The agricultural pest, Homalodisca vitripennis, relies on vibrational communication through plants for species identification, location, and courtship. Their vibrational signal exhibits a dominant frequency between 80 and 120 Hz, with higher frequency, lower intensity harmonics occurring approximately every 100 Hz. However, previous research revealed that not all harmonics are recorded in every signal. Therefore, how the female H. vitripennis vibrational signal changes as it travels through the plant was investigated. Results confirmed that transmission was a bending wave, with decreased signal intensity for increasing distance from the source; moreover, at distances of 50 cm, higher frequencies traveled faster than lower frequencies, suggesting that dispersion of H. vitripennis signal components may enable signaling partners to encode distance. Finally, H. vitripennis generates no detectable airborne signal (pressure wave), yet their low vibrational frequency components are detectable in neighboring plants as a result of leaf-to-air-to-leaf propagation. For instance, with isolated key female signal frequencies, 100 Hz was detected at a 10 cm gap between leaves, whereas 600 Hz was detectable only with a 0.1 cm gap. Together, these results highlight the complexity of vibration propagation in plants and suggest the possibility of the animals using the harmonic content to determine distance to the signaling H. vitripennis source.

High pressure thermoelasticity and sound velocities of Fe-Ni-Si alloys

The Earth's iron-dominant core is known to contain nickel from cosmochemical analysis and some amount of light elements from geophysical constraints on density and seismic wave velocities. Although there have been several studies to constrain thermoelastic properties of iron-alloys, there has been no systematic study on the effects of nickel and light elements on properties of iron using the same experimental methods and data analysis approach. We conducted nuclear resonant inelastic X-ray scattering and X-ray diffraction experiments on body-centered cubic and hexagonal close-packed (hcp) Fe0.91Ni0.09 and Fe0.8Ni0.1Si0.1 up to 104 GPa and 86 GPa, respectively, and compare to similar measurements conducted on hcp-Fe up to 171 GPa. Specifically, we determine the Debye sound velocity from the low-energy transfer region of the (partial) phonon density of states (DOS) using the equation of state determined for each material and a new approach which utilizes information criteria and probability distributions. Nickel decreases the shear velocity of iron, while 10 at% Si has little to no effect on the shear velocity of Fe0.91Ni0.09. We observe that the shape of the phonon DOS of these alloys remains similar with increasing pressure. In the measured compression range, we therefore apply a generalized scaling law to describe the volume dependence of the phonon DOS and find that the vibrational Grüneisen parameters of hcp-Fe0.91Ni0.09 are nearly indistinguishable from those hcp-Fe and those for Fe0.8Ni0.1Si0.1 trend lower. From the vibrational free energy, we constrain the harmonic vibrational component of thermal pressure, which shows a significant positive deviation from theoretical calculations of hcp-Fe at pressures and temperatures of Earth's core. Collectively, our results demonstrate that the effects of nickel should be considered when modeling iron-rich planetary cores.

Dynamics of Dicyanamide in Ionic Liquids is Dominated by Local Interactions.

The dynamics of probe molecules is commonly used to investigate the structural dynamics of room-temperature ionic liquids; however, the extent to which this dynamics reflects the dynamics of the ionic liquids or is probe specific has remained debated. Here, we explore to what extent the vibrational and rotational dynamics of the dicyanamide anion, a common ionic liquid anion, correlates with the structural relaxation of ionic liquids. We use polarization-resolved, ultrafast infrared spectroscopy to probe the temperature- and probe-concentration-dependent dynamics of samples with small amounts of 1-ethyl-3-methylimidazolium ([emim]+) dicyanamide ([DCA]−) dissolved in four [emim]+-based ionic liquids with tetrafluoroborate ([BF4]−), bis(trifluoromethylsulfonyl)imide ([NTf2]−), ethylsufate ([EtSO4]−), and triflate ([OTf]−) as anions. The transient spectra after broad-band excitation at 2000–2300 cm–1, resonant with the symmetric and antisymmetric C≡N stretching vibrations, initially contain oscillatory signatures due to the vibrational coherence between both modes. Vibrational population relaxation occurs on two distinct time scales, ∼6–7 and ∼15–20 ps. The vibrational dynamics is rather insensitive to the details of the ionic liquid anion and temperature, except for the slow vibrational relaxation component. The decay of the excitation anisotropy, a measure of the rotational dynamics of [DCA]−, markedly depends on temperature, and the obtained decay time exhibits an activation energy of ∼15–21 kJ/mol. Remarkably, neither the rotation time nor the activation energy can be simply explained by the variation of the macroscopic viscosity. Hence, our results suggest that the dynamics of dicyanamide is only in part representative of the ionic liquid structural dynamics. Rather, the dynamics of the probe anion seems to be determined by the specific interaction of [DCA]− with the ionic liquid’s ions for the class of [emim]+-based ionic liquids studied here.

Studies on a Robotic Device that Minimizes End-Point Vibrations for Parkinson Tremor

Parkinson tremor is a neuromotor condition that produces involuntary oscillation movements in some parts of the body, especially at the upper limbs. This disease affects more than 10 million people in the world and around 150 thousand people in Turkey, according to the report by the World Health Organization. This work focuses on simulating a robotic device in the shape of a glass for drinking liquids, which is an ordinary action for a normal person but can be very difficult for a Parkinson patient. This robotic device can minimize end-point vibrations when it is manipulated by people suffering from tremor. The work makes use of real-time data gathered from a patient, presents studies to characterize the main frequency of the tremor, and employs this information for designing an active control method. The proposed control method is based on the inverse dynamics of the vibrating system to damp the tremor’s first vibrational frequency component. The work consists of three stages: data acquisition, characterization and simulation of the control action. The first stage involves acceleration sensors based movement analysis to identify the frequencies and the behavior of the tremor; followed by a signal processing approach is developed using the fast Fourier transform. The studies indicate that the tremor could be represented by a harmonic signal in which the first frequency mode is the most representative. This assumption allows for simplifying our control strategy: inverse dynamics in an open-loop control along with proportional-derivative closed-loop controller are performed. The experimental data acquisition, signal analysis and control simulations were realized via Matlab/Simulink. The results illustrate the system performance validating our assumptions and the success of the control method we propose, which could lead to the design of a device to minimize vibrations at the end-point of the glass.

Diskretna Furijeova transformacija i cepstrum analiza pojave vibracija kod kamiona sa poluprikolicom

The aim of this paper is to present a novel technique to analyse the vibration signals during transportation in order to give new information to engineers to better understand these physical events. One of the primary sources of damages during transportation is the permanent vibration transmitted from the platform of semi-trailer to the cargo. The nature of this vibration depends on the road conditions and the features of the vehicle. In this study, a 2-axle-truck with a 3-axle-semi-trailer equipped with air spring suspension was observed to analyse the vibration circumstances. The affecting factors during the transportation were the type of the road (motorway, primary road, secondary road, tertiary road), and different vehicle speed levels. The vibration events were measured and registered on the platform of the trailer, then these values were evaluated in MATLAB environment. The presence of the harmonic vibrational components, the stationarity of the mode shapes, the characteristic frequency narrow-bands of the RMS and PSD values were primarily studied. The applied methods that were used are: discrete Fourier transformation, autocorrelation-, cross-correlation functions and cepstrum analysis.