Vibrational Interaction Research Articles

Study on Acoustic–Vibration Characteristics and Noise Reduction Methods for Elbows

Fluid pipelines with large flow changes often result in noise due to multi-physical interactions (fluid–structure and acoustic–vibration interactions) between the pulsating fluid and the pipe wall, especially at the elbows. Therefore, the acoustic–vibration characteristics and noise reduction methods of elbows are studied in this paper. Firstly, a two-way fluid–structure interaction (FSI) model is established to analyze the vibration characteristics of the elbow under water excitation. Maximum stress occurs at the elbow inlet, with maximum deformation in the elbow. Experimental validation confirms the model’s accuracy. Secondly, the effects of water and structural parameters on elbow vibration are studied, revealing that increased water pressure, pulsating frequency, and flow rate intensify pipe vibration. Finally, an acoustic–vibration coupled model is built; the simulations suggest that increasing wall thickness and elbow radius and reducing elbow angle effectively reduce the noise level of the elbow. Using elastic supports and damping materials can reduce elbow noise by at least 26.3%. This study provides guidance for the noise reduction and structural optimization of elbows by coupled multi-physics.

Interstellar spectroscopic detection of HC(S)NC and DC(S)NC.

The detection of HC(S)CN in TMC-1 suggests that HC(S)NC may also exist. To aid in its possible detection, HC(S)NC and its deuterated isotopologue DC(S)NC were investigated via high-level abinitio methods, specifically CCSD(T) and CCSD(T)-F12. By utilizing multidimensional potential energy surfaces derived from explicitly correlated coupled-cluster calculations, we analyzed their geometrical parameters, vibrational frequencies, rotational constants, and a comprehensive set of spectroscopic constants generated via the vibrational second-order perturbation theory, vibrational self-consistent field, and vibrational configuration interaction theory(VCI) approaches. HC(S)NC is thermodynamically stable relative to the HCS + NC dissociation limit, with a predicted bond dissociation energy of 4.1eV. The calculated vibrational frequencies are characterized by two bright modes that correspond to CN stretching. Finally, HC(S)NC shows a significant dipole moment, predicted to be 1.9D, making its detection via rotational spectroscopy plausible.

Magnetic Properties, Spin-Vibration Couplings, and Temperature Effects in Phenalenyl and Triangulene.

We introduce a computational methodology for evaluating and analyzing spin-vibration couplings in molecular systems, enabling insights into the interplay between electronic spins and molecular vibrations. By mapping ab initio electronic structure calculations onto molecular spin Hamiltonians, our approach captures those vibrational interactions potentially driving spin relaxation process. Spin-vibration couplings, derived from Holstein and Peierls terms, highlight the pivotal role of vibrational mode symmetry in spin decoherence and efficient energy dissipation. Additionally, second-order couplings provide a framework to explore the temperature dependence of spin properties via the thermal population of higher vibrational levels. Applied to phenalenyl and [3]triangulene, the results indicate that direct spin transitions dominate over Orbach relaxation in both systems. Hyperfine interactions primarily dictate spin-vibration couplings and thermal effects in phenalenyl, whereas zero-field splitting contributions are dominant in [3]triangulene. These findings advance the understanding of spin relaxation mechanisms in organic molecular systems.

Water-mediated cytosine self-assembly in infrared perspective.

Self-assembly plays a crucial role in the formation and allosteric processes of many biomolecules, water molecules can affect these processes. Cytosine (Cyt) has excellent self-assembly ability, forming a flat and ordered structure through hydrogen bonds (HBs) in the presence of water molecules. However, the vibration dynamics and interaction mechanism of water induced Cyt self-assembly are still unclear. In this work, infrared spectroscopy techniques, combined with density functional theory (DFT) theoretical calculations, were employed to investigate the vibrational characteristics and interactions of water molecule mediated self-assembly of Cyt and its reverse process. The results indicate that the induction of Cyt self-assembly by water molecules has differential effects on the various vibrational modes of the Cyt molecule. Multi-view infrared spectroscopy provides a powerful tool for the characterization of biomolecules in situ. This study will contribute to a deeper understanding and application of nucleic acid biological nanostructures.

Controlling MMIT, Fano resonance, and slow/fast light in a magnomechanical system with an optical parametric amplifier

We study the slow-fast light effect and multi-transparency induced by magnomechanical systems. The system incorporates two magnons, which are collective magnetic excitations, placed alongside a degenerate optical parametric amplifier (OPA) within a cavity. The interaction between phonons, magnons, and light inside the cavity leads to two phenomena: magnomechanically induced transparency (MMIT) and magnon-induced transparency (MIT). We show how an OPA alters the absorption and dispersion characteristics of the light spectrum. The observation of the Fano resonance through magnon-mechanical coupling with the degenerate OPA is discussed. Through tuning vibration interactions and the OPA, we achieve the improvement of slow light. We hope that our findings can pave the way for advancements in quantum information processing.

Influence of Strong Molecular Vibrations on Decoherence of Molecular Polaritons.

We derive the transition rates, dephasing rates, and Lamb shifts for a system consisting of many molecules collectively coupled to a resonant cavity mode. Using a variational polaron master equation, we show that strong vibrational interactions inherent to molecules give rise to multi-phonon processes and suppress the light-matter coupling. In the strong light-matter coupling limit, multiphonon contributions to the transition and dephasing rates strongly dominate over single-phonon contributions for typical molecular parameters. This leads to novel dependencies of the rates and spectral line widths on the number of molecules in the cavity. We also find that vibrational Lamb shifts can substantially modify the polariton energies in the strong light-matter coupling limit.

Influence of spanwise wall vibration on non-modal perturbations subject to freestream vortical disturbances in hypersonic boundary layers

In this paper, we study the effect of lateral wall vibrations on the excitation and evolution of non-modal perturbations in hypersonic boundary layers subject to low-frequency freestream vortical disturbances (FSVDs). A novel, high-efficiency numerical approach, combining the harmonic weakly nonlinear Navier–Stokes and nonlinear parabolised stability equation approaches, is developed, which is sufficient to accommodate both the rapid distortion of the perturbation in the leading-edge vicinity and the nonlinear development of finite-amplitude high-order harmonics in the downstream region. The boundary-layer response to low-frequency FSVDs shows a longitudinal streaky structure, for which the temperature perturbation shows much greater magnitude than the streamwise velocity perturbation. The lateral vibration induces a Stokes layer solution for the spanwise velocity perturbation, which interacts with the FSVD-induced perturbations and leads to a suppression of the non-modal perturbation and an enhancement of the downstream modal perturbation. The new perturbations excited by the FSVD–vibration interaction strengthen as the vibration intensifies, and they could become comparable with the FSVD-induced perturbations in downstream locations at a high vibration intensity, indicating a remarkable modification of the streaky structure and its instability property. Secondary instability (SI) analyses based on the streaky base flow indicate that the vibration could enhance or suppress the SI modes, depending on their initial phases over the vibration period. Overall, the average effect is that the low-frequency and high-frequency SI modes are stabilised and destabilised by the vibration, respectively. Since the high-frequency SI modes undergo higher amplifications, the subsequent bypass transition is likely to be promoted by relatively strong vibrations.

Solving the Puzzle of the Carbonic Acid Vibrational Spectrum - an Anharmonic Story.

Against the general belief that carbonic acid is too unstable for synthesis, it was possible to synthesize the solid[1,2] as well as gas-phase carbonic acid.[3] It was suggested that solid carbonic acid might exist in Earth's upper troposphere and in the harsh environments of other solar bodies,[4] where it undergoes a cycle of synthesis, decomposition, and dimerization.[5] To provide spectroscopic data for probing the existence of extraterrestrial carbonic acid,[2,6] matrix-isolation infrared (MI-IR) spectroscopy has shown to be essential.[3,4,6-8] However, early assignments within the harmonic approximation using scaling factors impeded a full interpretation of the rather complex MI-IR spectrum of H2CO3. Recently, carbonic acid was detected in the Galactic center molecular cloud,[9] triggering new interest in the anharmonic spectrum.[10] In this regard, we substantially reassign our argon MI-IR spectra based on accurate anharmonic calculations. We calculate a four-mode potential energy surface (PES) at the explicitly correlated coupled-cluster theory using up to triple-zeta basis sets, i. e., CCSD(T)-F12/cc-pVTZ-F12. On this PES, we perform vibrational self-consistent field and configuration interaction (VSCF/VCI) calculations to obtain accurate vibrational transition frequencies and resonance analysis of the fundamentals, first overtones, and combination bands. In total, 12 new bands can be assigned, extending the spectral data for carbonic acid and thus simplifying detection in more complex environments. Furthermore, we clarify disputed assignments between the cc- and ct-conformer.

Analysis of dynamic levitation process of the particle chain in a nonlinear standing wave field.

This research delves into the dynamic behavior of acoustic levitation of the particle chain in a nonlinear standing wave field. Experimental acoustic levitation control tests reveal bifurcation and jump phenomena during dynamic adjustments to resonant cavity height. Employing the 10-particle chain experiments and the COMSOL simulation models, the Sine-Gordon 2D vibration model is established to study the dynamic deformation process of the particle chain. The study uncovers the nonlinear interaction of particle lateral vibrations, horizontal acoustic radiation force, and conical wave fields that generate the jumping standing wave field. Notably, the fourth particle acts as a prominent jumping critical point in the secondary standing wave field, facilitating the derivation of the particle chain's nonlinear levitation dynamics. This discovery provides us with a new method to regulate the particle chain system.

How Vibrational Notations Can Spoil Infrared Spectroscopy: A Case Study on Isolated Methanol.

Unraveling methanol's infrared spectrum has challenged spectroscopists for a century, with numerous loose ends still to be explored. We engage in this exploration based on experiments of isolating single methanol molecules in solid argon and neon matrices. We report infrared spectra of methanol in its natural isotopic composition and with partial and full deuteration. These experiments are accompanied by calculating wavenumbers involving anharmonicity and mode-coupling based on the vibrational configuration interaction approach. This allows for an unambiguous assignment of all fundamentals and resonances in the mid-infrared spectrum. An increasing degree of deuteration lifts resonances and aids in assigning bands uniquely. It also becomes evident that different notations typically used in chemistry or physics to describe molecular vibration from spectroscopy fail to describe the spectra appropriately. We highlight the shortcomings and suggest a more elaborate analysis using Sankey diagrams to unambiguously identify spectral features. Consequently, we demystify debated resonances occurring from various stretches and deformations of the methyl group.

Effect of Blade Material of Steam Turbine Rotor on Aeroelastic Characteristics

Elements of powerful steam turbines are subjected to significant unsteady loads, in particular the rotor blades of the last stages. These loads, in some cases, can cause self-excited oscillations, which are extremely dangerous and have a negative impact on the efficiency and service life of the blade cascade. Therefore, when designing new or modernizing existing steam turbine stages, it is recommended to study the aeroelastic characteristics of the blades. The conditions for the occurrence of self-excited oscillations are influenced by both the geometric characteristics and the alloy from which the blade is made. To determine the effect of the blade material on the aeroelastic behaviour, a numerical analysis of the aeroelastic characteristics of the last stage blades made of steel and titanium alloy was performed. For the analysis, the method of simultaneous modeling of unsteady gas flow through the blade cascades and elastic vibrations of the blades (coupled problem) was used, which allows obtaining the amplitude-frequency spectrum of the interaction of unsteady loads and blade vibrations. The paper presents the results of numerical analysis for harmonic oscillations with a given amplitude and a given inter-blade phase angle, as well as for the regime of coupled vibration of blades under the action of unsteady aerodynamic forces. The dependences of the aerodamping coefficient on the inter-blade phase angle and the distribution of the coefficient along the blade are presented. The results of modeling the coupled vibration of the blades for the first six natural forms are presented in the form of a time-evolving displacement of the blade peripheral section, as well as forces and moments acting on the peripheral section. The corresponding amplitude-frequency spectra of displacements and loads in the peripheral section are also presented. The analysis of the results showed an insignificant difference in the characteristics of the proposed blade materials. For the first natural form of blade oscillations, the possibility of self-excited oscillations was found, and for the second form, there are conditions for the appearance of stable self-oscillations.

Comparison of curvilinear coordinates within vibrational structure calculations based on automatically generated potential energy surfaces.

For floppy molecules showing internal rotations and/or large amplitude motions, curvilinear internal coordinates are known to be superior to rectilinear normal coordinates within vibrational structure calculations. Due to the myriad definitions of internal coordinates, automated and efficient potential energy surface generators necessitate a high degree of flexibility, supporting the properties arising from these coordinates. Within this work, an approach to deal with these challenges is presented, including key elements, such as the selection of appropriate fit functions, the exploitation of symmetry, the positioning of grid points, or elongation limits for different coordinates. These elements are tested for five definitions of curvilinear coordinates, with three of them being generated in an automated manner. Calculations for semi-rigid molecules, namely H2O, H2CO, CH2F2, and H2CNH, demonstrate the general functionality of the implemented algorithms. Additional calculations for the HOPO molecule highlight the benefits of these curvilinear coordinates for systems with large amplitude motions. This new implementation allowed us to compare the performance of these different coordinate systems with respect to the convergence of the underlying expansion of the potential energy surface and subsequent vibrational configuration interaction calculations.

A compact microfluidic platform for rapid multiplex detection of respiratory viruses via centrifugal polar-absorbance spectroscopy

Nucleic acid detection technology has become a crucial tool in cutting-edge research within the life sciences and clinical diagnosis domains. Its significance is particularly highlighted during the respiratory virus pandemic, where nucleic acid testing plays a pivotal role in accurately detecting the virus. Isothermal amplification technologies have been developed and offer advantages such as rapidity, mild reaction conditions and excellent stability. Among these methods, recombinase polymerase amplification (RPA) has gained significant attention due to its simple primer design and resistance to multiple reaction inhibitors. However, the detection of RPA amplicons hinders the widespread adoption of this technology, leading to a research focus on cost-effective and convenient detection methods for RPA nucleic acid testing. In this study, we propose a novel computational absorption spectrum approach that utilizes the polar GelRed dye to efficiently detect RPA amplicons. By exploiting the asymmetry of GelRed molecules upon binding with DNA, polar electric dipoles are formed, leading to precipitate formation through centrifugal vibration and electrostatic interaction. The quantification of amplicon content is achieved by measuring the residual GelRed concentration in the supernatant. Our proposed portable and integrated microfluidic device successfully detected five respiratory virus genes simultaneously. The optimized linear detection was achieved and the sensitivity for all the targets reached 100 copies/μL. The total experiment could be finished in 27 min. The clinical experiments demonstrated the practicality and accuracy. This cost-effective and convenient detection scheme presents a promising biosensor for rapid virus detection, contributing to the advancement of RPA technology.

Accelerated Electron-Hole Separation at the Organic-Inorganic Anthracene/Janus MoSSe Interface.

Organic light-absorbing materials with two-dimensional semiconductor layers as contact electrodes are promising for efficient and flexible low-cost solar cells. Considering anthracene as an absorber and a MoSSe Janus monolayer, we use non-adiabatic molecular dynamics to show that electron transfer from anthracene to MoSSe is faster on the Se side than the S side. The transfer from anthracene to MoS2 and MoSe2 monolayers takes intermediate times. As a rule, we find that a shorter adsorption distance produces a stronger donor-acceptor coupling. The smaller distance on the Se side is rationalized by the attractive force between the intrinsic dipole moment of the Janus structure and that of the molecule induced due to adsorption. Quantum coherence also affects the transfer time. The study provides detailed insights into adsorption of molecules on Janus structures and the resulting electronic and electron vibrational interactions. The results suggest that the dipole interaction plays an important role in the thermodynamic stability, alignment of electronic levels, and electron vibrational dynamics.

Kylin-V: An open-source package calculating the dynamic and spectroscopic properties of large systems.

Quantum dynamics simulation and computational spectroscopy serve as indispensable tools for the theoretical understanding of various fundamental physical and chemical processes, ranging from charge transfer to photochemical reactions. When simulating realistic systems, the primary challenge stems from the overwhelming number of degrees of freedom and the pronounced many-body correlations. Here, we present Kylin-V, an innovative quantum dynamics package designed for accurate and efficient simulations of dynamics and spectroscopic properties of vibronic Hamiltonians for molecular systems and their aggregates. Kylin-V supports various quantum dynamics and computational spectroscopy methods, such as time-dependent density matrix renormalization group and our recently proposed single-site and hierarchical mapping approaches, as well as vibrational heat-bath configuration interaction. In this paper, we introduce the methodologies implemented in Kylin-V and illustrate their performances through a diverse collection of numerical examples.

Zero-Point-Energy Driven Isotopic Exchange of the [H3O]- anion Probed by Mid-Infrared Action Spectroscopy.

We present the first observation of vibrational transitions in the [H3O]- anion, an intermediate in the anion-molecule reaction of water, H2O, and hydride, H-, using a laser-induced isotopic H/D exchange reaction action spectroscopy scheme applied to anions. The observed bands are assigned as the fundamental and first overtone of the H2O-H- vibrational stretching mode, based on anharmonic calculations within the vibrational perturbation theory and vibrational configuration interaction. Although the D2O·D- species has the lowest energy, our experiments confirm the D2O·H- isotope to be a sink of the H/D exchange reaction. Ab initio calculations corroborate that the formation of D2O·H- is favored, as the zero-point-energy difference is larger between D2 and H2 than between D2O·H- and D2O·D-.

Analysis of vibrational modes and weak interactions in terahertz spectra of γ-aminobutyric acid and its isomer L-2-aminobutyric acid

Aminobutyric acid, a non-proteinogenic amino acid, is present in the human body and influences physiological functions, exhibiting promising pharmaceutical prospects. γ-Aminobutyric Acid (GABA) and its isomer, L-2-Aminobutyric Acid (L-AABA), exhibit unique characteristic absorption peaks in the 0.6 to 2.5 THz range. To elucidate the mechanisms behind these absorption peaks, this study employed Density Functional Theory (DFT) for theoretical simulations of the crystal cell models of L-AABA and GABA, achieving terahertz spectra consistent with experimental results. Additionally, the study utilized Vibrational Mode Automatic Relevance Determination (VMARD) and Interaction Region Indicator (IRI) methodologies to interpret the vibrational modes corresponding to different absorption peaks and to detail the locations and types of intermolecular interactions within the crystals. Research indicates that the combination of terahertz time-domain spectroscopy (THz-TDS) and theoretical calculations can serve as an effective method for identifying isomers of Aminobutyric Acid and detecting intermolecular weak interactions such as hydrogen bonds within these crystals.

Analysis of Vibration Characteristics of Tractor–Rotary Cultivator Combination Based on Time Domain and Frequency Domain

A good planting bed is a prerequisite for improving planting quality, while complex ground excitation often leads to machine bouncing and operation vibration, which then affects the operation effect. In order to improve the quality of rotary tillage operations, it is necessary to study the effects of various vibration excitations on the unit during tractor rotary tillage operations and analyze the vibration interaction relationship among the tractor, the three-point suspension mechanism, and the rotary tiller. For this purpose, multiple three-way acceleration sensors were installed at different positions on the rotary tiller unit of a Lexing LS1004 tractor(Lexing Agricultural Equipment Co. Ltd., Qingdao, China) to collect vibration data at different operating speeds and conduct vibration characteristic analysis between different components. The test results showed that when the unit moved forward at 2.1 km/h, 3.6 km/h, and 4.5 km/h, respectively, the vibration acceleration of the tractor, the three-point suspension mechanism, and the rotary tiller increased with the increase in speed, and there was indeed interaction between them. The vertical acceleration change during the test in the three-point suspension mechanism was the most significant (5.914 m/s2) and was related to the increase in the speed of the vehicle and the vibration transfer of the rotary tiller. Meanwhile, the vertical vibration acceleration of the tractor’s symmetrical structure was not similar, suggesting the existence of structural assembly problems. From the perspective of frequency domain analysis, the resonant frequency at the cab of the tractor was reduced in a vertical vibration environment, with relatively low frequencies (0~80 Hz) and small magnitudes, which might be beneficial to the driver’s health. The rotary tillage group resonated around 350 Hz, and this characteristic can be used to appropriately increase the vibration of the rotary tiller to reduce resistance. The tractor cab resonated around 280 Hz, which must be avoided during field operations to ensure driver health and reduce machine wear. The research results can provide a reference for reducing vibration and resistance during tractor rotary tillage operations, as well as optimizing and improving the structure of rotary tillers and tractors.

Enhancement in Heat Transfer Performance of Water Vapor Condensation on Graphene-Coated Copper Surfaces: A Molecular Dynamics Study.

The condensation of water vapor plays a crucial role in various applications, including combating water scarcity. In this study, by employing molecular dynamics simulations, we delved into the impact of graphene coatings on water vapor condensation on copper surfaces. Unique to this work was the exploration of various levels of graphene coverage and distribution, a facet largely unexplored in prior investigations. The findings demonstrated a notable increase in the rate of water vapor condensation and heat transfer performance as the graphene coverage was reduced. Using graphene coverages of 84%, 68%, and 52%, the numbers of condensed water molecules were 664, 735, and 880 molecules/ns, respectively. One of the most important findings was that when using the same graphene coverage of 68%, the rate of water vapor condensation and heat transfer performance increased as the graphene coating became more distributed. The overall performance of the water condensation correlated well with the energy and vibrational interaction between the graphene and the copper. This phenomenon suggests how a hybrid surface can enhance the nucleation and growth of a droplet, which might be beneficial for tailoring graphene-coated copper surfaces for applications demanding efficient water vapor condensation.

VSCF/VCI theory based on the Podolsky Hamiltonian.

While the vibrational spectra of semi-rigid molecules can be computed on approaches relying on the Watson Hamiltonian, floppy molecules or molecular clusters are better described by Hamiltonians, which are capable of dealing with any curvilinear coordinates. It is the kinetic energy operator (KEO) of these Hamiltonians, which render the correlated calculations relying on them rather costly. Novel implementation of vibrational self-consistent field theory and vibrational configuration interaction theory on the basis of the Podolsky Hamiltonian are reported, in which the inverse of the metric tensor, i.e., the G matrix, is represented by an n-mode expansion expressed in terms of polynomials. An analysis of the importance of the individual terms of the KEO with respect to the truncation orders of the n-mode expansion is provided. Benchmark calculations have been performed for the cis-HOPO and methanimine, H2CNH, molecules and are compared to experimental data and to calculations based on the Watson Hamiltonian and the internal coordinate path Hamiltonian.