Asymmetric Vibration Research Articles

Photoionization of Oriented HD(1Σ+) Yields Vibrating HD+(2Σ+) with Charge Breathing and Small Charge Transfer.

The eigenfunctions of the Hamiltonian associated with the oriented vibrating HD+(2Σ+) ion are calculated beyond the Born-Oppenheimer approximation in the nuclear frame. This makes it possible to study the fully correlated electron-nuclear dynamics of the HD+(2Σ+) after ionization of the HD(1Σ+) molecule. The dynamics is then characterized by the time-dependent probability densities and flux densities of the individual particles, i.e., deuteron, proton, and electron. The flux densities confirm that, although the electric dipole moment changes over time, there is no charge migration, as might be expected from the separation of energy levels of the vibronic states. Instead, the variations of the electric dipole moment over time are caused by small charge transfer and asymmetric charge vibration. Fourier transforms of the time-dependent probability and flux densities uncover the net asymmetric effective potential acting on the electron.

Microstructure, Raman spectroscopy, THz time domain spectrum and microwave dielectric properties of Li2Ti1-x(Zn1/3Ta2/3)xO3 ceramics

Li2Ti1-x(Zn1/3Ta2/3)xO3 (0.00 ≤ x ≤ 0.30) (LTZTx) ceramics were successfully prepared by the traditional solid phase method. The order-disorder phase transition for LTZTx ceramics was detected by the X-ray diffractometer (XRD). The scanning electron microscope (SEM) was used to measure the microstructure for LTZTx ceramics. The evolution in crystal structure for LTZTx ceramics was studied by Raman spectroscopy. The reduction of dielectric loss for LTZTx ceramics was caused by the weakening of asymmetric vibration in Li–O bond. The excellent dielectric properties (εr = 18.69, Q×f = 97,763 GHz, τf = +11.08 ppm/°C) were obtained in the LTZT0.15 ceramic fired at 1250 °C. Besides, by the addition of 5 wt % LiF, the sintering temperature of LTZT0.15 ceramic was reduced. The optimal dielectric properties (εr = 19.4773, Q×f = 102,531 GHz, τf = - 8.08 ppm/°C) of LTZT0.15 + 5 wt % LiF were obtained at 1100 °C. The THz time domain spectrum (THz-TDS) was implemented to investigate the polarization mechanism and dielectric properties during 0.5–1.5 THz. The LTZT0.15 and LTZT0.15 + 5 wt % LiF ceramics still own the high Q×f values at the band of THz, which is expected to be used in the future of 6G communication.

Estimate of chaotic threshold of tristable vibration energy harvesters

Tristable vibration energy harvesters own excellent energy harvesting performance, which has been verified theoretically and experimentally. Obviously, the response mechanism of an asymmetric tristable vibration energy harvester is more complex than a symmetric bi-stable vibration energy harvester. The ambient vibrations have a great impact on the harvester. Due to the complexities and the lack of analytical solutions, the streamlined design methodologies are inhibited. To facilitate future innovation and research on asymmetric tristable vibration energy harvester, this paper uses Melnikov function and modified Lindstedt-Poincaré method are adopted to study the asymmetric tristable vibration energy harvester which has higher order nonlinear terms in the dynamic equation. Analytical results are consistent with numerical simulation results. The paper uses chaotic dynamical theory to provide a simplified analytical framework for which the deeper insight into the performance of the tristable vibration energy harvester can be obtained.

A modulated positioning scheme for asymmetric vibration sensor using high-frequency carrier

The asymmetric dual Mach-Zehnder interferometer can be used in the vibration sensing system for the long-distance monitoring. It can effectively suppress the backscattering noises of the system. However, it will also seriously deteriorate the positioning accuracy because of the asymmetry of the interferometer. In this paper, a modulated asymmetric dual Mach Zehnder interferometer (ADMZI) system using a high-frequency carrier scheme has been theoretically proposed and experimentally demonstrated. Field trials have been carried out to verify the effectiveness. Our experimental results show that the standard deviation of the proposed scheme is less than 60 m for a sensing length of 51 km, with an average processing time of 106 ms. Compared to traditional methods, the proposed approach can also be applied to weak signals with low frequencies and small amplitudes. This indicates that the proposed scheme can significantly improve the applicability of the asymmetry based distributed sensing systems.

Carbon nanotube reinforced epoxy based adhesive: Correlations between chemical functional and failure modes

This paper addresses correlational studies among failure mode analysis, fracture morphology, and the chemical changes for a single-lap bonded joint (SLJ) based on an industrial adhesive. The SLJ bonded joint was selected due to its stress combination inside the adhesive, i.e., peel and shear. The increase in the Fourier-transform Infrared (FTIR) intensity of chemical functional, i.e., rocking of CH2 group, C–O–C stretching of oxirane group, C–C stretching vibration, C=C aromatic ring stretching, are related to the ductile-like fracture morphology due to more molecular mobility. At meanwhile, the increase in intensity of asymmetrical vibration CH2 and O–H stretching vibrations are related to brittle-like morphology fracture. The cohesive failure is related to the ductile-like failure morphology, while the adhesive failure is linked to brittle-like morphology fracture. At room temperature, then best option is the 0.25 wt % carbon nanotubes (CNT), as cohesive failure modes are prevalent. The addition of carbon nanotubes to the industrial adhesive reduces the high temperature environmental degradation. However, the addition of carbon nanotubes had small influence into glass transition temperature variations. Considering the amount of CNT dispersed into the epoxy system, and the 100 °C long time exposures, it seems that the 1.0 wt % CNT content is the best option. The reasons for such differences are due to changes at chemical functional caused by the prolonged exposure to temperature higher than the glass transition temperature. Such changes were identified by the FTIR spectroscopy analysis.

Neural dynamics of illusory tactile pulling sensations

SummaryDirectional tactile pulling sensations are integral to everyday life, but their neural mechanisms remain unknown. Prior accounts hold that primary somatosensory (SI) activity is sufficient to generate pulling sensations, with alternative proposals suggesting that amodal frontal or parietal regions may be critical. We combined high-density EEG with asymmetric vibration, which creates an illusory pulling sensation, thereby unconfounding pulling sensations from unrelated sensorimotor processes. Oddballs that created opposite direction pulls to common stimuli were compared to the same oddballs after neutral common stimuli (symmetric vibration) and to neutral oddballs. We found evidence against the sensory-frontal N140 and in favor of the midline P200 tracking the emergence of pulling sensations, specifically contralateral parietal lobe activity 264-320ms, centered on the intraparietal sulcus. This suggests that SI is not sufficient to generate pulling sensations, which instead depend on the parietal association cortex, and may reflect the extraction of orientation information and related spatial processing.

Thermoelastic Damping in Vibrations of Small-Scaled Rings with Rectangular Cross-Section by Considering Size Effect on Both Structural and Thermal Domains

In this paper, thermoelastic dissipation or thermoelastic damping (TED) in micro/nanorings with rectangular cross-section is examined by accounting for small-scale effect on both structural and thermal areas. The modified couple stress theory (MCST) and nonlocal dual-phase-lag (NDPL) heat conduction model are exploited for incorporating size effect within constitutive relations and heat conduction equation. By employing simple harmonic form for asymmetric vibrations of the miniaturized ring and solving the heat conduction equation, for one-dimensional (1D) and two-dimensional (2D) cases of heat transfer, the solution of temperature distribution in the ring is extracted in the form of infinite series. By employing the definition of TED on the basis of entropy generation approach, an analytical relation in the series form containing structural and thermal scale parameters is established to estimate TED value. To appraise the precision and validity of the developed solution, a comparison study is performed by utilizing the outcomes of researches published in the literature. An exhaustive parametric study is then conducted to ascertain the role of structural and thermal scale parameters in the magnitude of TED. The influence of some key parameters such as vibration mode, geometrical properties, directions of heat conduction (1D and 2D model) and material on TED is also addressed.

Development of a dual-stator piezoelectric motor operated in resonance and quasi-static states

A dual-stator piezoelectric motor that can work in resonant and quasi-static states is proposed in this study to achieve high speed and high resolution cross-scale output. Two piezoelectric stators with a frequency of 1:2 and a vibration amplitude ratio of 2:1 are used for driving the sliding table with multipoint friction coupling to produce asymmetric sawtooth wave vibration. Then, they are used with the inertia force of the sliding table to achieve stepping motion. A dual-stator piezoelectric motor prototype is designed, and modal analysis is conducted using ANSYS software to obtain the resonant frequencies of the longitudinal vibration modes of the two stators. The dynamic model is established, and the numerical analysis is performed to obtain the trajectory and output characteristics of the sliding table. Finally, the prototype of the piezoelectric motor is constructed. Experimental results show that the minimum speed of the piezoelectric motor is 0.013 mm/s, the resolution is 0.5 μm, the maximum speed is 11.14 mm/s, and the maximum load is 40 g.

Modelling and Design of Asymmetric Vibrations to Induce Bidirectional Force Sensation for Portable Rehabilitation Devices.

Assistive rehabilitation devices have been developed to help post-stroke patients to recover and live independently for a number of years. As a way to communicate with the physical world, force sensation is extremely helpful to rebuild neuroplasticity [1] during the rehabilitation process. This paper presents a model and design of asymmetric vibrations to provide bidirectional force sensation, which can be beneficial to design a portable rehabilitation haptic device. Users will feel a directional cue generated by asymmetric vibrations by holding the device. This directional cue can navigate users around in a rehabilitation training along with visual guidance and provide physical force sensations. The system consists of a current-drive single solenoid rigidly attached to a base. The system's model is verified through experiment at three different frequencies. Our analysis shows that by varying the signal's duty ratio, the direction of peak accelerations change from positive to negative. In addition, two other waveforms (saw-tooth and step-ramp) at several frequencies and different spring's stiffness are also discussed to determine the ideal characteristics of the input signal for rehabilitation applications.

Directed transport of a particle on a horizontal surface under asymmetric vibrations

Asymmetric unbiased fluctuations coupled with the effect of nonlinear dry (Coulombic) friction are observed to generate a directed transport even in the absence of any net external force or gradient. This phenomenon, called the ratchet effect, occurs when the driving force does not overcome the static friction threshold symmetrically. An elementary model is used to generate directed and unidirectional motion of a particle placed on top of a horizontal rigid surface which is given a zero mean spatially asymmetric motion through a multi-frequency in-plane excitation. We obtain steady-state periodic solutions of the nondimensional transport equations analytically to assess the distinct single/multiple sticking and sliding phases of particle motion and various parametric conditions for phase transitions. These analytical results are then validated by solutions obtained semi-analytically using Galerkin projection and numerically using the fourth-order Runge–Kutta method (RK4) and Newton–Raphson method with a fixed arc-length based continuation scheme. Also, a multibody dynamics model of this particle-on-plate system is built in MSC Adams to help us visualize the actual particle behavior under real dimensional system parameters and compare it with the foregoing analyses. A highly counter-intuitive phenomenon is encountered as the particle drift velocity increases non-monotonically with the increase in friction whereas a very high or a very low amount of friction impedes motion. Maximum transport velocity is found to be independent of the amplitude ratio of the vibratory input for low values of kinetic friction and is observed to manifest at a critical static friction threshold beyond which the particle motion becomes unidirectional. The effect of viscous drag of the ambient fluid on transport is assessed to be quite insignificant. Optimal vibratory input parameters to achieve the best transport current under varying friction conditions are determined. At low kinetic friction, a fixed set of system parameters is observed to generate distinct solution branches that coexisted just beyond the static friction threshold corresponding to a motion transition from “slip” to “stick–slip”.

Effect of thermal environment on the asymmetric vibration of temperature-dependent two-dimensional functionally graded annular plate by Chebyshev polynomials

In the present paper, an accurate numerical technique is employed to analyze the effect of two-dimensional temperature variation on the free asymmetric vibrations of functionally graded (FG) annular plates using the first-order shear deformation theory. The temperature-dependent mechanical properties of the plate material are graded along the thickness and radial directions. The governing differential equations for asymmetric motion are derived from Hamilton’s principle and the exact solution for the two-dimensional heat conduction equation is obtained using the separation of variables method considering thermal boundary conditions. The Chebyshev collocation technique is adopted to compute the numerical values of fundamental frequency for different boundary conditions. The impact of volume fraction index, heterogeneity parameter, density parameter, nodal lines, radii ratio, and thermal boundary conditions on the frequencies of the plate is investigated. An excellent agreement between the results obtained by the present approach and other methods available in the literature validated the authors’ model and technique. Three-dimensional normalized mode shapes with different nodal lines are illustrated for the specified plates.

ФИЗИЧЕСКАЯ МОДЕЛЬ ДВУХСТУПЕНЧАТОЙ ВИБРАЦИОННОЙ УСТАНОВКИ ДЛЯ ГЕНЕРИРОВАНИЯ АСИММЕТРИЧНЫХ КОЛЕБАНИЙ

Vibrating devices occupy a large cluster in the construction and road construction industry. The improvement of all vibration machines begins, first of all, with a vibration device, as the main working body of the machine. Basically, vibrators acted as a vibrating device for all road construction equipment. Initially, vibrators with circular vibrations were used, which are not so effective and not always sufficient for performing special work on driving piles into the ground and also extracting them from the soil. Vibratory systems with asymmetric vibrations are increasingly being used in the construction industry. For example, when driving piles, pile drivers are used. Their principle of operation is similar in its action to the operation of a vibration plant with asymmetric vibrations. However, a vibration plant with asymmetric oscillations, when the direction of the driving force is turned in the opposite direction, not down, but up, also makes it possible to extract worn-out piles and sheet piles from the soil. Based on the above, we propose a description, a method for calculating the optimal values of the asymmetry coefficient, driving force and set out the principle of operation of a physical model of a vibration plant with two stages of generating asymmetric vibrations, consisting of standard vibration equipment: the first stage: a table of the brand EV-341 and the second stage : vibrator of directional vibrations brand IV-99B, manufactured by OOO Yaroslavl Plant Krasny Mayak.

Tracing the Anharmonicity and Superionic Phase Transition of Hydrous FeO2H

The weak x-ray scattering of hydrogen (H) has brought major challenges to the characterization of superionic transitions in high-pressure ice, hydrides, and hydroxides. Combining first-principles molecular dynamics and simulated nuclear magnetic resonance (NMR) spectroscopy, we investigated the behavior of the hydroxyl bonding and structural transitions in the hydrous FeO2H between 300 and 2750 K and up to 130 GPa. Evidence show that an intermediate plastic state with regional H diffusion and anharmonic O-H vibration exists in between the ordinary solid and the superionic phase. The intermediate state features asymmetric hydrogen bonds and anharmonic vibrations, which are readily distinguished from the high-temperature superionic phase. Our work shows NMR is a more sensitive probe to detect H diffusion in superionic solids even in the extreme conditions of Earth’s deep interiors.

Identifying Key Descriptors for the Single-Atom Catalyzed CO Oxidation

Identifying Key Descriptors for the Single-Atom Catalyzed CO Oxidation

Classical Intermolecular Hydrogen Bonding Motifs of Heterocyclic rac-2-Amino-3-carbonitrile Derivatives: Linking Hirshfeld Surface Analysis, CT-DNA Binding Affinity, and Molecular Docking

Four 2-amino-4-(aryl)-7,7-dimethyl-5-oxo-5,6,7,8-tetrahydro-4H-chromene-3-carbonitrile (Series I) and three 2-amino-1-phenyl-7,7-dimethyl-5-oxo-4-(aryl)-1,4,5,6,7,8-hexahydroquinoline-3-carbonitrile (Series II) derivatives were formed via multicomponent microwave reactions as racemic mixtures. The solid-state IR spectra revealed bands in the region between 3190 and 3414 cm–1 attributed to the amino functional group’s asymmetric, symmetric, and bending overtone vibration modes. Furthermore, the IR spectra of some of the compounds in each series were similar and this served as an indication of similar structural features in the solid state. This was confirmed via single-crystal X-ray diffraction. A detailed survey of the related 2-amino-3-carbonitrile derivatives in the Cambridge Structural Database revealed 12 classical intermolecular hydrogen-bonding motifs involving the amino functional group. The vast variation in the hydrogen bonding motifs was found to be caused by the type of group bonded to the 4H-pyran (in Series I) or dihydropyridine (in Series II) moiety. In this work, an unprecedented hydrogen bonding motif comprising a non-classical hydrogen bond acceptor was found in one instance. For both Series I and II, the N–H···N and N–H···O hydrogen bonds were investigated using noncovalent interaction (NCI) plots and molecular pairwise energy calculations. The contributions of reciprocal N···H and O···H contacts (attributed to N–H···N and N–H···O, respectively) toward the Hirshfeld surface range between 9.9 and 15.3% in Series I and between 10.8 and 15.0% in Series II. In addition, the compounds showed moderate to good binding affinity to calf thymus DNA (CT-DNA) with intrinsic binding constants (Kb) between 8.00 × 104 and 5.00 × 105 M–1 for Series I compounds and between 6.60 × 104 and 1.45 × 105 M–1 for Series II. A relationship was established between the reciprocal N···H to O···H contributions ratio from the Hirshfeld surface analysis and Kb. Molecular docking studies of each compound’s respective enantiomers into DNA were done using canonical–DNA dodecamer (B-DNA) as a model for CT-DNA. The compounds were found to interact with DNA via a minor groove-binding mode. The S-enantiomer for most of the compounds bound favorably compared to their respective R-enantiomers. The ratio of calculated ΔG for the DNA binding of the R-enantiomer to that of the S-enantiomer (ΔGR/ΔGS) follows the same positive trend as the experimental Kb value for each compound in Series I while a negative trend was observed for Series II. Finally, a relationship between the Hirshfeld surface analysis and calculated ΔG values was also established in this work.

Solution structures and ultrafast vibrational energy dissipation dynamics in cyclotetramethylene tetranitramine.

Steady-state and time-resolved infrared (IR) studies of cyclotetramethylene tetranitramine (HMX) were carried out, using the asymmetric nitro-stretch as probe, to investigate its solution structures and vibrational energy transfer processes in pure dimethyl sulfoxide (DMSO) and in a DMSO/water mixture. A linear IR spectrum in the nitro-stretching mode region shows two major bands and one minor band in DMSO but changes to the two major bands mainly picture when adding water as an antisolvent of HMX, suggesting a transition from well-solvated and less perfect β-conformation to a less-solvated and close-to-perfect β-conformation. The latter bears a similar asymmetric nitro-stretch vibration profile to the β-polymorph in the crystal form. Density functional theory computations of the nitro-stretching vibrations suggest that HMX in DMSO may be in a NO2 group rotated β-conformation. Two-dimensional IR cross-peak intensity reveals intramolecular energy transfer between the axial and equatorial nitro-groups in the β-HMX on the ps time scale, which is slightly faster in the mixed solvent case. The importance of water as an antisolvent in influencing the equilibrium solvation structure, as well as the vibrational and orientational relaxation dynamics of HMX, is discussed.

On the dynamic behavior of an asymmetric self-regulated planetary-type vibration exciter

The problems of studying the dynamic behavior and improving the operational efficiency of various vibratory equipment are currently of significant interest. Special attention is paid to the possibilities of developing the enhanced designs of the planetary-type vibration exciters for the conveying, screening, and sieving machines. The novelty of the present research consists in providing the changeable inertial parameters of the improved planetary-type vibration exciter in order to adjust its operational conditions in accordance with the technological requirements. The mathematical model of the single-mass vibratory screening conveyor equipped with the proposed exciter is developed using the Lagrange-d’Alembert principle. The simulation of the system kinematic and dynamic characteristics under different operational conditions is carried out in the Mathematica software using the integrated Runge-Kutta methods.

Temperature quenching of Cr3+ in ASc(Si1-xGex)2O6 (A=Li/Na) solid solutions

Blue absorbing near infrared (NIR) emitting phosphors are a promising class of materials for phosphor converted NIR LEDs, which can be used in compact NIR spectrometers. Preferably, these phosphors have a broad emission spectrum and show negligible luminescence quenching at LED operating temperatures (100 °C). Here, we investigated ASc(Si1-xGex)2O6 (A = Li/Na, x = 0,0.2,0.4,0.6,0.8,1) solid solutions doped with Cr3+ to tune and optimize the emission maximum and bandwidth to cover the full 700–1100 nm range. With increasing Ge content an emission redshift was observed, along with emission band broadening at intermediate Ge/Si ratio, which is explained by disorder around Cr3+ in the second coordination sphere (mixed Si/Ge). Temperature dependent emission spectra and luminescence decay curves were measured between 90 K and 670 K to determine the quenching temperature TQ. With increasing Ge content TQ drops from 550 K to below 400 K. Interestingly, Cr3+ emission in the highly symmetric site in LiScSi2O6 shows a strongly temperature dependent lifetime before thermal quenching sets in. DFT calculations on LiScSi2O6 indicate that asymmetric vibrations at the Sc site are involved and calculated phonon energies were confirmed by measuring FTIR. Our study indicates that a solid solution is a promising way to increase the emission bandwidth. However, with increasing Ge content TQ decreases. An optimum Ge-content in LiSc(Si1-xGex)2O6:Cr3+ is x = 0.2–0.4 as it redshifts the NIR band maximum close to 900 nm and offers a FWHM bandwidth around 180 nm, while keeping the thermal quenching temperature high enough for application in NIR-LEDs.

Relationship between the Vibration Acceleration and Stability of a Continuous Girder Bridge during Horizontal Rotation

To ensure the safety of bridges during horizontal rotation, we propose a method through which it is possible to evaluate the stability of structures in real time by measuring the vibration acceleration of the rotating structure. First, the vibration characteristics collected during the horizontal rotation of a typical high-speed railway bridge were compared with the results of a finite element analysis. Second, the analytic formula to calculate the ratio of vibration acceleration and the pier-bottom-section bending moment for the rotating structure was deduced by considering the beam and pier as an infinite-degree-of-freedom rod. Then, the results of the analytical formula were compared with those of the finite element calculation. Overall, the results showed that the bending moment of the pier bottom (which was related to the stability of the rotating bridge) was affected only by the two asymmetrical vibration modes. The analytic formula built by considering the beam and pier as an infinite degree-of-freedom rod with equal cross-section effectively described the relationship between the vibration acceleration and pier-bottom-bending moment. Finally, the vibration of the rotating bridge was simplified to the superposition of the first two asymmetric vibration modes in the facade. Based on our findings, we were able to provide a formula and some check tables to calculate the permissible value of vibration acceleration for typical high-speed railway bridges.

FTIR Spectroscopy Reveals Molecular Changes in BPC 157 Treated Blood Vessels

From the rats treated with stable gastric pentadecapeptide BPC 157 (10ng/kg ip) or saline (5ml/kg ip) at 5 min before sacrifice, the spectra of thoracic aorta tissue samples were compared. From each rat, 20 samples were cut and FTIR spectra were recorded.Vibrational spectra of the samples were recorded with a Perkin‐Elmer Spectrum GX spectrometer equipped with liquid N2 refrigerated Mercury Cadmium Telluride (MCT) detector. Data were acquired in 450 ‐ 4000 cm‐1 spectral range, in transmission mode with a resolution of 4 cm‐1.First, all recorded spectra were baseline corrected and normalized. Then we utilized the principal component analysis (PCA) to examine the possibility of separating BPC treated and control samples on a PCA score‐score graph. Using 100 spectra of BPC treated and 100 spectra of control samples, a PCA model was made. As seen in Figure 1, there is a clear distinction, mostly due to the PC1 score, between spectra of BPC treated (red) from the control group (green).To identify the parts of FTIR spectra that contributed the most to the separation between BPC treated and the control group of spectra differential spectrum was calculated and compared with PC1 loadings.Differential spectrum and PC loadings show that main bands responsible for separation of the BPC treated and control sample spectra are in the range from 930‐1200 cm‐1, then vibrational bands at 1660 cm‐1,1730 cm‐1, 1120 cm‐1 and in the range from 2840 – 3090 cm‐1. In the first range, there are three vibrational bands at 968 cm‐1, 1087 cm‐1 and 1240 cm‐1 that belong to P‐O symmetric and asymmetric vibrations in nucleic acids respectably, and vibrational band 1170 cm‐1 that belongs to C‐O and C‐O‐C stretching vibrations of carbohydrate. The vibrational band at 1660cm‐1 belongs to amid I stretching vibrations of proteins, and the last range of spectral lines belongs to C‐H symmetric and asymmetric C‐H, C‐H2 and C‐H3 vibrations in lipids. The line at 1730 cm‐1 that is very pronounced in control group spectra is C‐O symmetric vibration in fatty acids. Most prominent difference between BPC treated and control group was observed region of C‐H vibrations of lipids and vibrational line at 1730 cm‐1 of fatty acids.Thus, different FTIR spectra evidenced that BPC treatment causes changes of the tissue at molecular level.