Vibrational Wave Research Articles

Semiclassical Approach to Computing Vibrationally Resolved Ionization Cross Sections for Molecular Nitrogen.

A semiclassical model based on the Gryzinski theory is used to compute vibrationally resolved electron-impact ionization cross sections for molecular nitrogen. This model extends the approach used by Wünderlich for molecular hydrogen and its isotopomeres. The multireference configuration interaction (MRCI) method in Molpro is used with complete active space self-consistent field reference wave functions to compute potential energy curves (PECs) and electronic wave functions for several states of interest. Nuclear wave functions and vibrational energy levels are computed from the MRCI PECs using the Fourier grid Hamiltonian method. The target orbital electron kinetic energies, Franck-Condon factors, and transition energies are parameters for the semiclassical model and are calculated directly from the computed electronic and nuclear wave functions and vibrational energy levels. The target electron kinetic energies are computed as the expectation value of the one-electron kinetic energy operator for the product of the appropriate nuclear vibrational wave function and the MRCI natural orbital for a particular state-to-state ionization process. From the fully vibrationally resolved ionization cross sections, lumped and total cross sections are calculated by summing the partial cross sections over the closure relationship of the Franck-Condon theory.

Explaining Kinetic Isotope Effects in Proton-Coupled Electron Transfer Reactions.

ConspectusProton-coupled electron transfer (PCET) is essential for a wide range of chemical and biological processes. Understanding the mechanism of PCET reactions is important for controlling and tuning these processes. The kinetic isotope effect (KIE), defined as the ratio of the rate constants for hydrogen and deuterium transfer, is used to probe PCET mechanisms experimentally but is often challenging to interpret. Herein, a theoretical framework is described for interpreting KIEs of concerted PCET reactions. The first step is to classify the reaction in terms of vibronic and electron-proton nonadiabaticities, which reflect the relative time scales of the electrons, protons, and environment. The second step is to select the appropriate rate constant expression based on this classification. The third step is to compute the input quantities with computational methods.Vibronically adiabatic PCET reactions occur on the electronic and vibrational ground state and can be described within the transition state theory framework. The nuclear-electronic orbital (NEO) method, which treats specified protons quantum mechanically on the same level as the electrons, can be used to generate the electron-proton vibronic free energy surface for hydrogen and deuterium and to compute the corresponding free energy barriers. Such reactions typically exhibit moderate KIEs that arise from zero-point energy and shallow tunneling effects.Vibronically nonadiabatic PCET reactions involve excited electron-proton vibronic states and can be described with a golden rule formalism corresponding to nonadiabatic transitions between pairs of reactant and product vibronic states. Such reactions can exhibit KIEs ranging from unity, or even slightly less than unity, to more than 500. These KIEs can be explained in terms of multiple, competing reaction pathways corresponding to electron and proton tunneling between different pairs of vibronic states. The tunneling probability is determined by the vibronic coupling, which can be computed using a general expression but often is proportional to the overlap between the reactant and product proton vibrational wave functions. In this regime, the KIE is influenced by the vibronic couplings, the proton donor-acceptor equilibrium distance and motion, and contributions from excited vibronic states.Three illustrative examples of vibronically nonadiabatic PCET are discussed. The unusually large KIEs in soybean lipoxygenase of ∼80 for the wild-type enzyme and ∼700 for a double mutant are explained in terms of a large equilibrium proton donor-acceptor distance and nonoptimal orientation, leading to a small overlap between vibrational wave functions and therefore a large difference in hydrogen and deuterium tunneling probabilities. The KIEs for benzimidazole-phenol molecules ranging from unity to moderate are explained in terms of the dominance of different pairs of vibronic states with different vibrational wave function overlaps. The potential-dependent KIE observed for proton discharge from triethylammonium acid to a gold surface in acetonitrile is explained in terms of different pairs of vibronic states contributing for hydrogen and deuterium, with the reaction channels exhibiting different dependencies on the applied potential. These examples show that the KIE can vary widely, depending on which pairs of vibronic states dominate and their corresponding vibronic couplings. This work has broad implications for the interpretation of experimentally measured KIEs of PCET reactions.

Laser-induced fluorescence spectroscopy of TIPS-pentacene

Polycyclic aromatic hydrocarbons, particularly acenes, are gaining attention as candidates for organic semiconductors. TIPS-pentacene, a functionalized acene with triisopropylsilyl (TIPS) side groups, demonstrates enhanced physical stability, solubility, and superior charge transport properties due to improved molecular packing. This study presents a high-resolution laser-induced fluorescence study comparing TIPS-pentacene and pentacene isolated in helium nanodroplets and attached to solid rare-gas clusters (neon and argon). Our findings reveal distinct differences in the vibronic structures of these molecules, with TIPS-pentacene displaying pronounced vibrational progressions of low frequency vibrational modes of the molecular side groups. The results offer insights into matrix effects and advance our understanding of TIPS-pentacene’s vibronic structure, recently reported to contribute via coherent vibrational wave packets to ultrafast singlet fission processes.

Dynamic-Constrained Nonlinear Stiffness Method for Low-Frequency Wave Energy Harvesting and Vibration Isolation

Ocean waves are abundant in energy; however, they also cause ships to sway and can disrupt the operation of precision equipment. Harvesting energy from ocean waves and isolating vibrations in marine precision equipment have long posed significant challenges due to the inherently low-frequency nature of ocean waves. This study proposes a dynamic-constrained nonlinear (DCN) stiffness method for low-frequency energy harvesting and vibration isolation. A generalized mathematical model of the DCN stiffness system is established, and its semi-analytical solution is derived using the harmonic balance method and the arc-length extension method. Finally, various application scenarios for energy harvesting and vibration isolation using the nonlinear stiffness method are explored. The results demonstrate that the DCN stiffness method can significantly enhance the performance of low-frequency wave energy, capture and provide excellent low-frequency vibration isolation. Notably, this method exhibits a strong adaptive capability to excitation compared to traditional nonlinear stiffness methods.

A mechanics-based approach using machine learning, analytical, and numerical methods for SH wave propagation in viscoelastic structure

This study investigates shear-horizontal (SH) wave propagation in a pre-stressed, functionally graded viscoelastic layer lying over a similar substrate (without initial stress), offering insights into wave behavior in complex layered systems. Combining analytical methods, the finite element method—specifically the semi-analytical finite element-perfectly matched layer (SAFE-PML) and the semi-analytical infinite element (SAIFE) with ( 1 / d ) type decay behavior, and machine learning techniques, the study examines wave dynamics under varying material gradation and pre-stress. The analytical solution provides a precise dispersion relation, highlighting the impact of key material parameters on wave velocity. Comparisons with two machine learning models—polynomial regression and principal component analysis (PCA)—show that while both models validate the analytical findings, PCA offers superior alignment and uncovers deeper insights into wave propagation patterns. Numerical simulations further reinforce the robustness of the results, offering a comprehensive framework for material selection and optimization in surface acoustic wave devices and vibration control.

Sequential Synchronous Mechanism for Double-Electron Capture: Insights into Unforeseen Large Cross Sections in Low-Energy Sn^{3+}+H_{2} Collisions.

Remarkably large double electron capture cross sections, on the scale of 10^{-15} cm^{2}, are observed in low-energy (<50 eV/u) collisions between Sn^{3+} and H_{2}. Given that the reaction is energetically highly unfavorable, one would expect negligibly small cross sections. Through the propagation of vibrational wave packets on coupled multiple potential energy surfaces, a novel charge transfer mechanism, driven in tandem by ion motion and molecular vibration, is revealed, offering insights into the unusual energy dependence of the measured cross sections.

A Generalized Shape Function for Vibration Suppression Analysis of Acoustic Black Hole Beams Based on Fractional Calculus Theory

In this paper, a generalized acoustic black hole (ABH) beam covered with a viscoelastic layer is proposed to improve the energy dissipation based on the double-parameter Mittag–Leffler (ML) function. Since fractional-order constitutive models can more accurately capture the properties of viscoelastic materials, a fractional dynamic model of an ABH structure covered with viscoelastic film is established based on the fractional Kelvin–Voigt constitutive equation and the mechanical analysis of composite structures. To analyze the energy dissipation of the viscoelastic ML-ABH structures under steady-state conditions, the wave method is introduced, and the theory of vibration wave transmission in such non-uniform structures is extended. The effects of the fractional order, the film thickness and length, and shape function parameters on the dynamic characteristics of the ABH structure are systematically investigated. The study reveals that these parameters have a significant impact on the vibration characteristics of the ABH structure. To obtain the best parameters of the shape function under various parameters, the Particle Swarm Optimization (PSO) algorithm is employed. The results demonstrate that by selecting appropriate ML parameters and viscoelastic materials, the dissipation characteristics of the structure can be significantly improved. This research provides a theoretical foundation for structural vibration reduction in ABH structures.

Study on the propagation law of blast-induced vibration waves in landfill

Study on the propagation law of blast-induced vibration waves in landfill

Influence of meso-phenyl substituents on the free base and Co(II)porphyrins through the looking glass: experimental and theoretical studies

The successful synthesis and characterization of Co(II)porphyrin complexes has been carried out, in which the electronic absorption spectra displayed in different solvents revealed the solvent-dependent absorption bands, offering insights into the electronic behavior of the Co(II)porphyrin complexes, whereas the photoluminescence shows the quenching that attributed to the paramagnetic properties of the Co(II)porphyrins inducing the intersystem crossing, thereby reducing fluorescence. The vibrational wave numbers that are influenced by the bonding between the Co(II) and macrocyclic ligand (porphyrin) serve as a crucial indicator for the interaction between these components. The 1HNMR spectra disclosed insights into β-pyrrolic and meso-aryl protons, showing deshielding associated with meso-phenyl substituents. The thermogravimetric analysis offers a comprehensive understanding of the synthesized Co(II)porphyrin complexes robustness under increasing temperatures. The different phases and structural evolutions Co(II)porphyrin complexes are extrapolated through powder X-ray diffraction (PXRD), providing the valuable information about their crystalline nature and structural transformations. The geometrical optimization of the different Co(II)porphyrins was carried out by employing PM6-D3H4X method implemented in MOPAC package revealed the key parameters such as the HOMOs-LUMOs energy levels gap, suggesting the planarity/non-planarity of the Co(II)porphyrins complexes that provide the crucial information about the molecular geometry and overall structure.

A Wide-Range, Highly Stable Intelligent Flexible Pressure Sensor Based on Micro-Wrinkled SWCNT/rGO-PDMS with Efficient Thermal Shrinkage.

Flexible pressure sensors have drawn growing attention in areas like human physiological signal monitoring and human-computer interaction. Nevertheless, it still remains a significant challenge to guarantee their long-term stability while attaining a wide detection range, a minute pressure testing limit, and high sensitivity. Inspired by the wrinkles on animal skins, this paper introduces a flexible pressure sensor with wrinkled microstructures. This sensor is composed of a composite of reduced graphene oxide (rGO), single-walled carbon nanotubes (SWCNTs), and polydimethylsiloxane (PDMS). After optimizing the proportion of the composite materials, the flexible pressure sensor was manufactured using highly efficient heat-shrinkable films. It has a sensitivity as high as 15.364 kPa-1. Owing to the wrinkled microstructures, the sensor can achieve an ultra-wide pressure detection range, with the maximum reaching 1150 kPa, and is capable of detecting water wave vibrations at the minimum level. Moreover, the wrinkled microstructures were locked by PDMS. The sensor acquired waterproof performance and its mechanical stability was enhanced. Even after 18,000 cycles of repeated loading and unloading, its performance remained unchanged. By combining with an artificial neural network, high-precision recognition of different sounds and postures when grasping different objects was realized, with the accuracies reaching 98.3333% and 99.1111%, respectively. Through the integration of flexible WIFI, real-time wireless transmission of sensing data was made possible. In general, the studied sensor can facilitate the application of flexible pressure sensors in fields such as drowning monitoring, remote traditional Chinese medicine, and intelligent voice.

Dynamic Response and Settlement Cause Analysis of Roadbed–Soft Clay Foundation System Under Traffic Vibration Loads

Roadbeds constructed on soft clay foundations often experience substantial post-construction settlement under long-term traffic loading. To investigate this phenomenon, numerical simulations were conducted to study the vibration response of various roadbed–foundation systems subjected to pavement vibration loads, and the propagation patterns of vibration waves within these systems were analyzed. Vibration reconsolidation tests were performed to examine the reconsolidation behavior of soft clays under vibration loads (cyclic loads without overall compressive or tensile tendencies) following initial consolidation under static loads. The influence of vibration load frequency and amplitude on the reconsolidation effect was briefly analyzed. By combining the analysis of the consolidation mechanism of soft clays under vibration loads, this study investigated the reasons for the large post-construction settlement of roadbed–soft clay foundation systems under traffic vibration loads from both wave propagation and vibration perspectives. Based on the focus on the equilibrium state reached by the soil under vibration loads, the vibration reconsolidation test represents a new research approach. In addition to deepening the understanding of the post-construction settlement phenomenon of foundations under traffic loads, it can also provide guidance for practical engineering applications such as foundation treatment and sludge solidification using vibration loads, generating potential economic benefits.

Theoretical study on vibration transmission characteristics of vertical coupling plates considering flexible connection

Complex structures are usually assembled by basic structure components, such as beams, plates, etc. It is necessary to study the vibration transmission characteristics of coupling structures considering the connection effects, which is the basis for structural vibration suppression and high-precision control of engineering structure. In this work, the structural vibration transmission efficiency between vertical plates considering the connection characteristics is investigated using traveling wave method. Firstly, the mathematical model of flexible connection between vertical coupling plates is established by using spring damping model. Subsequently, the theoretical model of traveling wave transmission between vertical plates is established. Furthermore, the energy transmission coefficient and reflection coefficient are introduced to study the vibration transmission efficiency of the vibration wave in the coupling plates. Then, the effects of connection stiffness and damping characteristics on the vibration energy transmission characteristics between vertical connecting plates are investigated. The simulation results indicate that the propagation of vibration waves in the vertical coupling plates is dominated by bending waves, and the energy transmission efficiency of bending waves can be effectively reduced by adopting different thicknesses of the connecting plates. Additionally, an impedance matching frequency can be observed. At this frequency, the amplitude of the bending wave impedance matches the amplitude of the connection stiffness impedance, which leads to a lowest transmission efficiency of bending wave. Also, the increase in connection damping increases the energy transfer efficiency of bending waves in the coupling plates. This investigation provides a theoretical basis for vibration suppression and high-precision control of complex structures.

Feasibility using a compact fiber optic Sagnac interferometer for non-contact soft tissue surface mechanical wave speed detection.

The Sagnac interferometer offers distinct advantages in vibrational wave detection. In this study, an air-coupled transducer and a compact fiber-optic Sagnac interferometer were developed for non-contact elasticity characterization in biological tissues. Given the challenge of limited light collection by a compact fiber optic Sagnac interferometer in biological tissues, this study aims to explore the potential of using a compact Sagnac interferometer to measure vibrational waves in biological tissues. The speeds of the generated vibrational surface waves in tissue-mimic phantoms were measured. Measurement errors caused by cross-correlation wave tracking were analyzed, and the performance of the integrated system was characterized. The results demonstrated the effectiveness of the integrated system and the cross-correlation algorithm in tracing the speed of vibrational surface waves in tissue-mimicking phantoms. They suggested potential applications for the non-invasive, contactless characterization of the mechanical properties in soft biological tissues.

The reasonableness and feasibility of replacing standing wave vibration with air piston mode vibration in thermoacoustic refrigerator

The reasonableness and feasibility of replacing standing wave vibration with air piston mode vibration in thermoacoustic refrigerator

Active traveling wave vibration control of elastic supported conical shells with smart micro fiber composites based on the differential quadrature method

Active traveling wave vibration control of elastic supported conical shells with smart micro fiber composites based on the differential quadrature method

Experimental study and field application of hydraulic flushing technology in soft coal seam

To enhance the safety of coal mining operations and improve the efficiency of gas extraction, hydraulic flushing technology has been widely used in low permeability coal seams. This study aims to investigate the mechanism of hydraulic flushing by conducting experiments focusing on four aspects: sample strength, punching pressure, punching position and vibration direction. The results show that an increase in hydraulic flushing pressure leads to a deeper impact groove, whereas higher sample strength results in a shallower groove. Additionally, the amplitude of stress wave is positively correlated with the density of the sample, with low-strength samples exhibiting extensive stress wave propagation and minimal attenuation. The stress wave vibration is multi-directional, which can maximize the instability and destruction of the internal structure of the coal body. To validate the practical efficacy of hydraulic flushing, a field test was conducted at the Yuwu Coal Mine in Changzhi City, Shanxi Province. The field trial shows that the effective influence radius of hydraulic flushing can reach 4 m, with a significantly lower gas flow attenuation coefficient compared to ordinary borehole. Notably, the permeability of coal seam in hydraulic flushing area is close to twice that of ordinary drilling area.

Blocking effect of double-row periodic pile barriers on vibration waves

With the rapid development of China’s transportation, the problem of environmental vibration is becoming increasingly prominent, and the traffic lines are inevitably close to the building, and the environmental vibration caused by it has a serious negative impact on the safety of the building, the use of precision instruments and the physical and mental health of residents. In this study, the vibration damping barrier is designed periodically, and its unique band gap characteristics can be used to perform directional vibration damping in specific vibration reduction frequency bands. In this paper, the band gap of the periodic row piles is calculated by the periodic theory, and then the measured attenuation domain characteristics of the periodic row piles in the bandgap frequency band are verified by indoor model tests, and the effects of the length of the concrete row piles, the row spacing, the train speed and the load on the vibration isolation effect are discussed. The results show that with the increase of pile length, the vibration isolation effect gradually increases, in addition, the larger row spacing will reduce the vibration isolation effect, and the increase of train speed and amplitude will also lead to poor vibration isolation effect. This study provides a useful reference for the application of concrete row piles in practical engineering.

Research on the Dynamic Response Patterns of Layered Slopes Considering Non-Homogeneity Under Blast-Induced Vibration Effects

To investigate the dynamic wave propagation characteristics and dynamic response of heterogeneous layered slopes under a blasting vibration, a modeling method considering the slope’s layered dip angle and heterogeneity was proposed. Different dip jointed slope models were established using the Weibull random distribution function introduced to realize the stochastic distribution of rock mechanics parameters, representing heterogeneity. Taking the background project of the Sijiaying Yanshan Open-Pit Iron Mine as an example, through numerical simulation, the effects of different joint dip angles and rock hardness on the slope’s dynamic response were analyzed in detail. The sensitivity of the elastic modulus, cohesion, and friction angle to the slope dynamic response was also investigated. A comparative analysis of the amplification effects between a jointed slope and heterogeneous slope was conducted. Finally, the dynamic stability of the jointed slope and heterogeneous slope under a blasting load was analyzed. The results indicate that the Peak Ground Acceleration (PGA) of jointed slopes with dip angles of 45° and 60° is generally higher than that of slopes with a 0° dip angle and without joints. The smaller the rock mass heterogeneity, the smaller the PGA at the measuring points, and the less sensitive the PGA is to variations in the three quantities. Under the same physical and mechanical parameters of the rock, the amplification factor of jointed slopes is generally greater than that of heterogeneous slopes. Under the blasting load, the overall dynamic time-series safety factors of both slopes decrease first and then increase, with the safety factor reaching its lowest value at the location of the strongest blasting vibration wave. This study can provide guidance for the blasting design and safety protection of layered dip slopes and serve as a reference for the analysis of blasting impact laws in similar mines.

Hydrogen Tunneling and Conformational Motions in Nonadiabatic Proton-Coupled Electron Transfer between Interfacial Tyrosines in Ribonucleotide Reductase.

Ribonucleotide reductase (RNR) is essential for DNA synthesis and repair in all living organisms. The mechanism of E. coli RNR requires long-range radical transport through a proton-coupled electron transfer (PCET) pathway spanning two different protein subunits. Herein, the direct PCET reaction between the interfacial tyrosine residues, Y356 and Y731, is investigated with a vibronically nonadiabatic theory that treats the transferring proton and all electrons quantum mechanically. The input quantities to the PCET rate constant expression are computed with a combination of density functional theory and molecular dynamics simulations. The calculations highlight the importance of hydrogen tunneling in this PCET reaction. Compression of the distance between the proton donor and acceptor oxygen atoms of the interfacial tyrosine residues is essential to facilitate hydrogen tunneling by increasing the overlap between the reactant and product proton vibrational wave functions. This compression occurs by thermal conformational fluctuations of these interfacial tyrosine residues. N733 and R411 are identified as key residues that can hydrogen bond to Y731 and Y356, respectively, and thereby compete with the hydrogen-bonding interaction between Y731 and Y356 required for direct PCET. Understanding the roles of hydrogen tunneling and conformational motions in this interfacial PCET reaction, as well as identifying other residues that may impact the kinetics, is important for targeted protein engineering efforts to modulate RNR activity.

Theoretical calculations of vibration reduction band gaps characteristics of novel phononic-like crystal Euler beam structure

The elastic wave band gap (BG) property of locally resonant phononic crystal (LRPC) enables it to control and attenuate the propagation of elastic waves in its internal structure in the BG frequency range. In particular, it has unique advantages in obtaining low-frequency BG and can be used for the control and attenuation of low-frequency vibration. Therefore, the LRPC is of great significance in the field of low-frequency vibration reduction and has broad application value and prospect. However, the LRPC has the defects of narrow BG width and only one BG, which makes it limited in engineering application. In response to the problems of narrow BG width and only one BG in traditional LRPC Euler beams, this paper establishes a novel phononic-like crystal (PLC) Euler beam model that can open up multi-frequency and low-frequency vibration reduction BGs. The PLC Euler beam model considers the non rigidity of the contact interface between the wrapping layer and the scatterer and matrix, the foundation constraint effect, and the damping characteristics of the wrapping layer material. The vibration reduction BG characteristics of the PLC Euler beam are studied through theoretical calculations and analysis. Firstly, the improved transfer matrix method (ITMM) is derived for calculating the band structure of the PLC Euler beam, and the results are compared and verified with those obtained from the finite element method (FEM). Secondly, the spectral element method (SEM) is derived for calculating the frequency response function (FRF) of the PLC Euler beam, and to evaluate its attenuation effect on vibration elastic waves. The theoretical calculation results show that the PLC Euler beam opens up 6 low-frequency vibration reduction BGs, exhibiting good attenuation effects on vibrational elastic waves within the BG frequency range, with the maximum attenuation value at the BG starting frequency. The novel PLC Euler beam has a broad prospect in controlling and attenuating low-frequency and multi-frequency vibrations, and its design idea has a unique novelty, which provides theoretical support and design idea for broadening the BG width and number of LRPC Euler beam structures, and provides theoretical methods and ideas for designing and studying LRPC with low-frequency and multi-frequency BGs.