Changes In Vibrational Frequencies Research Articles

Probing conformational dynamics of DNA binding by CO-sensing transcription factor, CooA

The transcription factor CooA is a CRP/FNR (cAMP receptor protein/ fumarate and nitrate reductase) superfamily protein that uses heme to sense carbon monoxide (CO). Allosteric activation of CooA in response to CO binding is currently described as a series of discrete structural changes, without much consideration for the potential role of protein dynamics in the process of DNA binding. This work uses site-directed spin-label electron paramagnetic resonance spectroscopy (SDSL-EPR) to probe slow timescale (μs-ms) conformational dynamics of CooA with the redox-stable MAL-6 nitroxide spin label, and IR spectroscopy to probe the environment at the CO-bound heme. A series of cysteine substitution variants were created to selectively label CooA in key functional regions, the heme-binding domain, the 4/5-loop, the hinge region, and the DNA binding domain. The EPR spectra of labeled CooA variants are compared across three functional states: Fe(III) “locked off”, Fe(II)-CO “on”, and Fe(II)-CO bound to DNA. We observe changes in the multicomponent EPR spectra at each location; most notably in the hinge region and DNA binding domain, broadening the description of the CooA allosteric mechanism to include the role of protein dynamics in DNA binding. DNA-dependent changes in IR vibrational frequency and band broadening further suggest that there is conformational heterogeneity in the active WT protein and that DNA binding alters the environment of the heme-bound CO.

Analysis of bending vibrations of a three-layered pre-twisted sandwich beam with an exact dynamic stiffness matrix

This paper presents the novel development of the dynamic stiffness matrix for a three-layered symmetric pre-twisted sandwich beam (PTSB), aiming to investigate its free vibration characteristics. The outer layers of the beam are modeled using the Euler–Bernoulli theory, while the core is assumed to deform solely in shear. The boundary conditions and governing partial differential equations of motion are derived based on Hamilton's principle. By applying harmonic variations of displacements, the governing equations of motion are expressed as a tenth-order equation, which is solved to obtain the desired dynamic stiffness matrix. To compute the natural frequencies of in-plane and out-of-plane free vibration for both uniform and PTSBs, the Wittrick–Williams algorithm is employed. The computed frequencies are compared with the results obtained by other authors as well as those obtained from ABAQUS simulations. Various vibration modes of uniform and twisted sandwich beams are plotted and thoroughly discussed. Interestingly, contrary to straight symmetric sandwich beams, the results indicate that flexural displacements in pre-twisted symmetric sandwich beams exhibit coupling in two planes. Additionally, although there are minor changes in vibration frequencies, the mode shapes undergo significant transformations as the pre-twist angle is altered.

A piezoelectric energy harvester with parallel connection using beams of different lengths to improve output performance

The purpose of this paper is to design an energy harvester to improve output performance. The theoretical analysis of the piezoelectric energy harvester has been performed. Reducing the length of one cantilever beam, thereby changing the relative impact position, causing the amplitude of the two cantilever beams to be different, and making the waveform of two beams different. Some experiments have been tested to verify the feasibility of the device and compare the differences with Plan A. Based on the experiment, it can be concluded that the output voltage is higher at both high and low speeds. When the rotation speed is 255 r min−1, Plan B arrives at the optimum speed, and the maximum output voltage is 166.2 V, which significantly increases from 97.2 V of Plan A. The maximum output power is 0.966 W under the load resistance of 10 kΩ. The maximum voltage is 157.7 V under the load resistance of 120 kΩ. Nevertheless, the maximum voltage and maximum power of Plan A are 92.62 V and 0.52 W. Besides, the prototype has fewer materials and nearly 1.5 times the energy conversion rate compares to Plan A. It can light up 42 LEDs easily and can adapt to environmental vibration frequency changes, so it has an intensely adaptable and outstanding performance in practical applications.

Crystal structure of strontium aluminates phosphors containing bismuth oxides

The composite phosphors SrAl2O4/Sr3Al2O6:Bi2O3/Bi2O4 synthesized by a solid-phase approach have been studied by means of X-ray diffraction, Raman spectroscopy, and optical spectroscopy methods. A redistribution of Bi3+ ions between two phases was observed by changes in crystal parameters, bond length, and vibrational frequencies on Raman spectra. A relationship between the structure of the host matrix and the optical characteristics of phosphors has been established.

Numerical simulation and experimental study of fluid–structure interactions in elastic structures based on the SPH method

The study of fluid–structure interactions in elastic structures is highly important in hydraulic structural engineering. This paper adopts the smooth particle hydrodynamics (SPH) coupling method to simulate dam failure water impact elastic plate flow and solid coupling problems. In addition, a numerical simulation is performed on the study of the free surface flow impact of the elastic plate structure on the main dynamic characteristics, including the impact force distribution and the change process. Additionally, the elastic structure of the vibration amplitude and frequency change rule, as well as the drastic changes in free surface flow, are also carried out. In this paper, the synchronous finite element algorithm is used to analyze the problem to obtain FEM results Additionally, two-dimensional benchmark physical tests are designed for dam-break water flow impacting an elastic plate are conducted, focusing on a comparative analysis of the numerical results of the SPH method with the results of physical tests and verifying the validity, accuracy, and superiority of the SPH coupling method for solving the problem of fluid‒solid coupling in elastic structures. On this basis, to explore the relevant physical quantities that cannot be measured or described during the test process, the flow–solid coupling characteristics of the elastic plate impacted by water flow are further understood by analyzing the nature of the flow field, the change in the flow–solid force of the elastic plate and the change rule of the frequency spectrum. The results show the following: (i) The jumps in velocity between the streams and the strong curvature of the free liquid surface lead to the creation of vortices at the cavities. (ii) The flow solid force under the impact of water flow increases and then decreases, and the smaller the deformation of the elastic structure is, the greater the force is. (iii) The vibration frequency of the fixed end of the elastic structure gradually decreases along the free end frequency, and the larger the deformation of the free end of the elastic plate is, the weaker its vibration response is. In addition, the natural frequency of the elastic plate under water flow impact is slightly lower than that under free vibration of the elastic plate. The related research results provide reference and guidance for the fluid–structure interaction problem.

Evaluation of Pipe Thickness by Magnetic Hammer Test with a Tunnel Magnetoresistive Sensor.

A new nondestructive inspection method, the magnetic hammer test (MHT), which uses a compact and highly sensitive tunnel magnetoresistance (TMR) sensor, is proposed. This method complements the magnetic flux leakage method and eliminates the issues of the hammer test. It can therefore detect weak magnetic fields generated by the natural vibration of a pipe with a high signal-to-noise ratio. In this study, several steel pipes with different wall thicknesses were measured using a TMR sensor to demonstrate the superiority of MHT. The results of the measurement show that wall thickness can be evaluated with the accuracy of several tens of microns from the change in the natural vibration frequency of the specimen pipe. The pipes were also inspected underwater using a waterproofed TMR sensor, which demonstrated an accuracy of less than 100 μm. The validity of these results was by simulating the shielding of magnetic fields and vibration of the pipes with the finite element method (FEM) analysis. The proposed noncontact, fast, and accurate method for thickness testing of long-distance pipes will contribute to unmanned, manpower-saving nondestructive testing (NDT) in the future.

Hybrid Approach for Multiscale and Multimodal Time-Resolved Diagnosis of Ultrafast Processes in Materials via Tailored Synchronization of Laser and X-ray Sources at MHz Repetition Rates

The synchronization of laser and X-ray sources is essential for time-resolved measurements in the study of ultrafast processes, including photo-induced piezo-effects, shock wave generation, and phase transitions. On the one hand, optical diagnostics (by synchronization of two laser sources) provides information about changes in vibration frequencies, shock wave dynamics, and linear and nonlinear refractive index behavior. On the other hand, optical pump–X-ray probe diagnostics provide an opportunity to directly reveal lattice dynamics. To integrate two approaches into a unified whole, one needs to create a robust method for the synchronization of two systems with different repetition rates up to the MHz range. In this paper, we propose a universal approach utilizing a field-programmable gate array (FPGA) to achieve precise synchronization between different MHz sources such as various lasers and synchrotron X-ray sources. This synchronization method offers numerous advantages, such as high flexibility, fast response, and low jitter. Experimental results demonstrate the successful synchronization of two different MHz systems with a temporal resolution of 250 ps. This enables ultrafast measurements with a sub-nanosecond resolution, facilitating the uncovering of complex dynamics in ultrafast processes.

Complexes of phosphine oxides with substituted phenols: hydrogen bond characterization based on shifts of PO stretching bands.

In this work IR spectral characteristics of PO groups are used to evaluate the strength of OHO hydrogen bonds. Three phosphine oxides: triphenylphosphine oxide, tributylphosphine oxide and hexamethylphosphoramide are investigated as proton acceptors. The results of the experimental IR study and DFT calculation of 30 complexes formed by phosphine oxides with various substituted phenols or CF3CH2OH in CCl4 solution at room temperature are reported. We show that the PO vibrational frequency changes non-linearly upon hydrogen bond formation and strengthening and that the shift of the PO band could be used for the estimation of hydrogen bond strength in complexes with phosphine oxides. The accuracy of these estimations and the influence of solvation effects on the main characteristics of complexes are discussed.

Collinear optical links based on a GaN-integrated chip for fiber-optic acoustic detection.

This Letter reports a collinear optical interconnect architecture for acoustic sensing via a monolithic integrated GaN optoelectronic chip. The chip is designed with a ring-shaped photodiode (PD) surrounding a light-emitting diode (LED) of a spectral range from 420-530 nm. The axisymmetric structure helps the coaxial propagation of light transmission and reception. By placing this multiple-quantum wells (MQW)-based device and a piece of aluminum-coated polyethylene terephthalate (Al/PET) film on fiber ends, an ultra-compact acoustic sensing system is built. The sound vibrations can be simply detected by direct measurement of the diaphragm deformation-induced power change. An average signal noise ratio (SNR) of 40 dB and a maximum sensitivity of 82 mV/Pa are obtained when the acoustic vibration frequency changes from 400 Hz to 3.2 kHz. This work provides a feasible solution to miniaturize the sensing system footprint and reduce the cost.

Vibration-assisted material damage mechanism: From indentation cracks to scratch cracks

Vibration-assisted grinding is one of the most promising technologies for manufacturing optical components due to its efficiency and quality advantages. However, the damage and crack propagation mechanisms of materials in vibration-assisted grinding are not well understood. In order to elucidate the mechanism of abrasive scratching during vibration-assisted grinding, a kinematic model of vibration scratching was developed. The influence of process parameters on the evolution of vibration scratches to indentation or straight scratches is revealed by displacement metrics and velocity metrics. Indentation, scratch and vibration scratch experiments were performed on quartz glass, and the results showed that the vibration scratch cracks are a combination of indentation cracks and scratch cracks. Vibration scratch cracks change from indentation cracks to scratch cracks as the indenter moves from the entrance to the exit of the workpiece or as the vibration frequency changes from high to low. A vertical vibration scratch stress field model is established for the first time, which reveals that the maximum principal stress and tensile stress distribution is the fundamental cause for inducing the transformation of the vibration scratch cracking system. This model provides a theoretical basis for understanding of the mechanism of material damage and crack propagation during vibration-assisted grinding.

Vibration analysis of radial tire using the 3D rotating hyperelastic composite REF based on ANCF

In order to analyze the influence of tread structure and rotating angular speed on the vibration characteristics of radial tire, a 3D rotating hyperelastic composite REF (3D-RHCREF) model is proposed. Different form uniform cylindrical tread in other REF models, the tread is simplified as a hyperelastic composite revolving shell, whose discretization and parameterization are achieved by using three-order segmented Bézier curve and complete-gradient ANCF space curved trapezoid element. In the proposed 3D-RHCREF, the generalized inertial force with the centrifugal force and Coriolis force are obtained by introducing a rotation matrix into the framework of ANCF. Based on Kirchhoff-Love theory and hyperelastic constitutive relation, the generalized hyperelastic force of composite tread is derived and the compensation of initial generalized hyperelastic force is proposed. According to the D'Alembert principle, the nonlinear dynamic differential equations are established, then the modal equations are derived on the basis of the equilibrium position. By comparing with the FEM model of radial tire, the validity of the proposed model and calculation method is verified. The 3D-RHCREF is used to analyze the influences of internal pressure, tread pressure sharing ratio, belt structure and rotating angle speed on the vibration characteristics of radial tire. The vibration frequency will increase with the increase of internal pressure and the decrease of tread pressure sharing ratio; different belt structures of tread will cause changes in vibration frequency; the radial vibration frequency will be split into two traveling wave frequencies in two directions with the increase of rotating angular speed, and the circumferential/lateral vibration frequencies will almost only increase slightly with the increase of rotating angular speed.

Modeling the effects of external oscillations on mucus clearance in obstructed airways.

Various therapeutic methods are employed to facilitate the clearance of secretions accumulated in the respiratory tracts of individuals with lower respiratory tract disorders. High-frequency chest wall oscillation (HFCWO) device, designed to apply variable amplitude and frequency vibrations to the individuals' chests, stands out among these therapies. In this study, the effectiveness of this treatment method was investigated numerically using computational fluid dynamics (CFD) on the generated mucus-obstructed bronchial geometry. The conducted analyses compared the effects of vibrations acting in the axial, radial, and tangential directions on the clearance of mucus, which exhibits non-Newtonian flow behavior with shear-thinning properties. Simultaneously, the effects of changes in vibration amplitude and frequency, pressure differentials, fluid properties, and ciliary movements on the flow were separately examined and interpreted. The findings demonstrate that ciliary movements are insufficient in mucus-accumulated airways, applied vibrations enhance mucus clearance, and potential improvements in flow are quite sensitive to boundary conditions.

Effect of mechanical vibration on thermal performance of PCM-fin structure Li-ion battery thermal management system under high-rate discharge and high-temperature environment

The PCM-fin structure battery thermal management system (PCM-fin structure BTMS) has garnered significant attention due to its exceptional thermal performance. However, existing research has overlooked the presence of mechanical vibration that is inevitable in the operational environment of electric vehicle BTMS. This study aims to address this knowledge gap by comprehensively analyzing the effect of mechanical vibration on the thermal performance of the BTMS under high-temperature and high-rate discharge condition. Four novel findings are introduced for the first time: Firstly, mechanical vibration can significantly enhance the thermal performance of the BTMS, and the enhancement effect is more pronounced compared to the PCM-based BTMS without fins. Secondly, mechanical vibration also affects the ideal fin quantity for the BTMS. Under no vibration condition, the ideal quantity of fins is 10, while under mechanical vibration condition of 30 mm amplitude and 20 Hz frequency, the ideal fin quantity is 8. Thirdly, the thermal performance of the BTMS can be improved by increasing the vibration amplitude. Nevertheless, once a certain high value is reached, further increasing the vibration amplitude has a negligible effect on the enhancement of thermal performance. Lastly, even under low vibration frequency of 10 Hz, the BTMS can still perform well. However, as the vibration frequency increases, the thermal performance of the BTMS becomes progressively less sensitive to changes in vibration frequency. This work can provide guidance for the design and practical application of PCM-fin structure BTMS.

Innovative nonlinear vibration control of beam structures using shear thickening fluid dampers

This paper investigates the use of shear thickening fluid (STF) dampers for reducing vibrations in beam-based structures. Designing and analyzing these systems is challenging because STF’s viscosity changes as the fluid’s vibration frequency changes. To understand the impact of key design parameters, the behavior of STF dampers in various configurations of supports is analyzed. The governing equations are derived, considering the STF dampers as nonlinear damping forces, and solved/validated using Galerkin/Hencky’s discretization methods. An energy reduction factor is introduced to compare the performance of different configurations in the frequency domain to obtain the optimal design. The results show that although the performance of STF dampers is highly dependent on the excitation frequency (with high efficiency in reducing vibrations near the resonance frequencies), the STF dampers fail to dissipate vibrations in some frequency regions. Surprising ranges of dynamic behavior, from Quasi-periodic to chaotic, are detected and analyzed. The findings also reveal that by analyzing only the shape of force–velocity curves of the STF damper, one can accurately predict the system’s performance, without the need for a full system analysis.

Random analysis of train-bridge coupled system under non-uniform ground motion

The increasing prevalence of simply supported bridges in high-speed railway (HSR) lines has raised concerns about the safety of trains crossing these bridges during an earthquake. As these bridges are typically continuous and long, it is essential to consider the effects of traveling seismic waves on the random vibration of the train-bridge coupled (TBC) system. To address this issue, the new point estimate method (NPEM) is used to analyze the dynamic response and parametric sensitivity of a three-dimensional TBC system subjected to non-uniform ground motion with multiple random parameters. The motion equations of the TBC system are derived using bridge seismic theory under multi-support excitations. The analysis incorporates random variables such as the damping ratio, density, Young’s modulus, and seismic magnitude to capture the influence of traveling seismic waves on the random vibration of the TBC system. Simulation results show that the traveling seismic wave effect can cause changes in the first vibration frequencies of the train and bridge, potentially leading to the first few frequencies reordering. Additionally, considering the traveling wave effect will make the TBC system’s response less apparent than without considering the traveling wave effect. The uncertainty of bridge and seismic parameters can seriously affect the train’s running safety. The sensitivity of the bridge density and seismic magnitude is particularly prominent for bridge responses when the traveling seismic waves effect is strong. This methodology can be used for random and sensitivity analysis of a train running over a long bridge under non-uniform earthquake conditions. Overall, the NPEM can provide valuable insights into the dynamic behavior and safety of TBC systems, enabling more effective design and maintenance of HSR bridges.

Design and Analysis of Electromagnetic Linear Actuation-Energy-Reclaiming Device Applied to a New-Type Energy-Reclaiming Suspension

In order to meet the increasing demand for high-performance and high-efficiency vehicles, this paper proposes a novel electromagnetic linear energy-reclaiming suspension technology based on the McPherson independent suspension, and analyzes its core component—ELA-ERD (Electromagnetic Linear Actuation Energy-Reclaiming Device). ELA-ERD, taking a shock absorber piston rod as the inner yoke, has a compact structure and reasonable layout by integrating the structural features of the suspension. In this paper, the design process of ELA-ERD is elaborated in detail. Aiming at the problem of over-saturation of the inner yoke magnetic density, this paper proposes a method to optimize the magnetic circuit by increasing the size of the inner yoke within the effective working area of the moving coil, thus effectively improving the electromagnetic characteristics of ELA-ERD. Moreover, the effect and potential of energy reclaiming on ELA-ERD were studied by using finite element software. The study on the energy-reclaiming law of ELA-ERD was carried out from the perspective of the changes in vibration frequency and amplitude. In addition, the internal relationship between the energy-reclaiming voltage and the vibration velocity was revealed in this work, and the energy-reclaiming voltage coefficient Ke was defined. Through calculation of a large amount of model data, the Ke value applicable to the designed ELA-ERD in this paper was approximately set to 4.5. This study lays an important theoretical foundation for the follow-up studies.

Structural, magnetic and electrical transport properties of the sol-gel derived La1-xCaxMnO3 (0≤x≤0.3) nanoparticles

Sol-gel (SG) prepared calcium doped La1-xCaxMnO3 (0 ≤ x ≤ 0.3) nanoparticles (>35 nm) show a phase transformation from rhombohedral-R3c to orthorhombic-Pnma. The dopant concentration influences the bond length and lattice parameters and their variations as observed from the rietveld refinement. The phase stability and chemical compositions are confirmed using the Thermogravimetric and differential thermal analysis (TG-DTA) and Fourier transform infrared (FTIR) spectroscopy measurements. The latter confirms the presence of dangling bonds from the changes in the characteristic vibrational frequencies and intensities. Field emission scanning electron microscope-energy dispersive X-ray analysis (FESEM-EDAX) confirms the nano-dimension of the particles and good chemical homogeneity of the samples. The Curie temperature Tc, estimated from the field cooled magnetization curve, shifts towards room temperature (Tc = 160–270 K) with the increase of dopant concentration. The samples exhibit a clear metal to insulator transition, the temperature of which shifts to higher values (169–267 K) with increase in dopant content. With the application of an external magnetic field, local ordering of magnetic moments occurs and the evolution of a ferromagnetic metallic phase suppresses the existing paramagnetic insulating phase, decreasing the value of resistivity. Three different temperature ranges demarked in the resistivity curves are studied using different theoretical models. The observed low temperature resistivity upturn is explained on the basis of the Kondo-like model while the ferromagnetic metallic region is studied using different scattering processes like electron – electron, electron – magnon etc. The variable range and small polaron hopping (VRH and SPH) models are used in the high-temperature region data and with the aid of Holstein's relation the non-adiabatic SPH model it is found to be most suitable to understand the conductivity behavior. The temperature dependent evolution of the Griffith's like phase can explain and correlate the electric transport and magnetic properties exhibited by the samples. This highlights the evolution of Mn3+-O2--Mn4+ FM oriented networks, which form conduction channels with the lowering of temperatures. These channels mediate the enhanced conduction and helps set in long-range FM ordering in the samples/

Twin Vibrational Power Generators and Extremum Seeking Control

Vibration power generation using environmental vibrations to generate electricity has attracted attention as a sustainable independent power source such as wireless sensors placed under vibration. However, for efficient power generation, the resonant frequency of the vibration power generator must be automatically adjusted to the environmental vibrations. To achieve it, the author's group proposes installing a variable capacitance in the device and adjusting its capacitance by extremum seeking control. Therefore, this study proposes a generator configuration “twin generators” and a new extremum seeking control. Compared to the method employing conventional extremum seeking control, the proposed method increases power generation efficiency under damped vibration excitation, even when the vibration's amplitude and frequency change randomly. © 2023 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.

Suppression of kernel vibrations by layer-by-layer ligand engineering boosts photoluminescence efficiency of gold nanoclusters

The restriction of structural vibration has assumed great importance in attaining bright emission of luminescent metal nanoclusters (NCs), where tremendous efforts are devoted to manipulating the surface landscape yet remain challenges for modulation of the structural vibration of the metal kernel. Here, we report efficient suppression of kernel vibration achieving enhancement in emission intensity, by rigidifying the surface of metal NCs and propagating as-developed strains into the metal core. Specifically, a layer-by-layer triple-ligands surface engineering is deployed to allow the solution-phase Au NCs with strong metal core-dictated fluorescence, up to the high absolute quantum yields of 90.3 ± 3.5%. The as-rigidified surface imposed by synergistic supramolecular interactions greatly influences the low-frequency acoustic vibration of the metal kernel, resulting in a subtle change in vibration frequency but a reduction in amplitude of oscillation. This scenario therewith impedes the non-radiative relaxation of electron dynamics, rendering the Au NCs with strong emission. The presented study exemplifies the linkage between surface chemistry and core-state emission of metal NCs, and proposes a strategy for brighter emitting metal NCs by regulating their interior metal core-involved motion.

Experimental and modeling study of surface topography generation considering tool-workpiece vibration in high-precision turning

High-precision turning (HPT) is a main processing method for manufacturing rotary high-precision components, especially for metallic parts. However, the generated vibration between tool tip and workpiece during turning may seriously deteriorate the surface integrity. Therefore, exploring the effect of vibration on turning surface morphology and quality of copper parts using 3D surface topography regeneration model is crucial for predicting HPT performance. This developed model can update the machined surface topology in real time. In this study, the effects of tool arc radius, feed rate, radial vibration, axial vibration and tangential vibration on the surface topography and surface roughness were explored. The results show that the effect of radial vibration on surface topography is greater than that of axial vibration and tangential vibration. The radial vibration frequency is also critical. When vibration frequency changes, the surface topography profile presents three different types: the standard sinusoidal curve, the sinusoidal curve whose low-frequency signal envelopes high-frequency signal, and the oscillation curve whose low-frequency signal superimposes high-frequency signal. In addition, HPT experiment was carried out to validate the developed model. The surface roughness obtained in the experiment was Ra=53 nm, while the roughness obtained by the simulation was Ra = 46 nm, achieving a prediction accuracy of 86.7 %.Received 4 September 2022; revised 3 October 2022; accepted 17 October 2022.