Vibrational Study Research Articles

Charge Transfer Induced Phase Transition in Li2MnO3at High Pressure.

Efficient and better energy storage materials are of utmost technological importance to reduce energy dependence on the fossil fuels. Li2MnO3is one such material having potential to meet most of the requirements for energy storage. This material has been synthesized using solid state synthesis route. High pressure structural and vibrational studies on this material have been carried out upto~ 22 and 26 GPa respectively. These investigations show occurrence of a hitherto unknown second order phase transition to a new low symmetry phase whose symmetry is constrained to be monoclinic with space group P21/n at pressure of ~ 2.3 GPa in Li2MnO3. The bulk modulus and its derivative determined by fitting the P-V data with third order Birch-Murnaghan (B-M) equation of state (EOS) are 113.3 ± 13.1 GPa and 4.1 ± 1.2 respectively. Mode Grüneisen parameter calculated for all the Raman modes show positive values which indicates the absence of any soft mode in this material. A microscopic mechanism based on bond-charge transfer is invoked and applied to understand the spectroscopic changes occurring in this material which also manifests second order structural phase transition. Enhancement in covalent character of Li-O bonds in the Li-O polyhedra is inferred based on the spectroscopic observation and above mechanism.&#xD.

Role of Intermolecular Interactions in Deep Eutectic Solvents for CO2 Capture: Vibrational Spectroscopy and Quantum Chemical Studies.

Recent research and reviews on CO2 capture methods, along with advancements in industry, have highlighted high costs and energy-intensive nature as the primary limitations of conventional direct air capture and storage (DACS) methods. In response to these challenges, deep eutectic solvents (DESs) have emerged as promising absorbents due to their scalability, selectivity, and lower environmental impact compared to other absorbents. However, the molecular origins of their enhanced thermal stability and selectivity for DAC applications have not been explored before. Therefore, the current study focuses on a comprehensive investigation into the molecular interactions within an alkaline DES composed of potassium hydroxide (KOH) and ethylene glycol (EG). Combining Fourier transform infrared (FT-IR) and quantum chemical calculations, the study reports structural changes and intermolecular interactions induced in EG upon addition of KOH and its implications on CO2 capture. Experimental and computational spectroscopic studies confirm the presence of noncovalent interactions (hydrogen bonds) within both EG and the KOH-EG system and point to the aggregation of ions at higher KOH concentrations. Additionally, molecular electrostatic potential (MESP) surface analysis, natural bond orbital (NBO) analysis, quantum theory of atoms-in-molecules (QTAIM) analysis, and reduced density gradient-noncovalent interaction (RDG-NCI) plot analysis elucidate changes in polarizability, charge distribution, hydrogen bond types, noncovalent interactions, and interaction strengths, respectively. Evaluation of explicit and hybrid models assesses their effectiveness in representing intermolecular interactions. This research enhances our understanding of molecular interactions in the KOH-EG system, which are essential for both the absorption and desorption of CO2. The study also aids in predicting and selecting DES components, optimizing their ratios with salts, and fine-tuning the properties of similar solvents and salts for enhanced CO2 capture efficiency.

A Novel Application of Computational Contact Tools on Nonlinear Finite Element Analysis to Predict Ground-Borne Vibrations Generated by Trains in Ballasted Tracks

Predictive numerical models in the study of ground-borne vibrations generated by railway systems have traditionally relied on the subsystem partition approach (segmented). In such a method, loads are individually applied, and the cumulative effect of the rolling stock is obtained through superposition. While this method serves to mitigate computational costs, it may not fully capture the complex interactions involved in ground-borne vibrations—especially in the frequency domain. Recent advancements in computation and software have enabled the development of more sophisticated vibrational contamination prediction models that encompass the entire dynamics of the system, from the rolling stock to the terrain, allowing continuous simulations with a defined time step. Furthermore, the incorporation of computational contact mechanics tools between various elements not only ensures accuracy in the time domain but also extends the analysis into the frequency domain. In this novel approach, the segmented models are shifted to continuous simulations where the nonlinear problem of a rigid–flexible multibody system is fully considered. The model can predict the impact of a high-speed rail (HSR) vehicle passing, capturing the key intricacies of ground-borne vibrations and their impact on the surrounding environment due to a deeper comprehension of the occurrences in the frequency domain.

Solution and Surface Solvation of Nitrate Anions with Iron(III) and Aluminum(III) in Aqueous Environments: A Raman and Vibrational Sum Frequency Generation Study.

Hydrated trivalent metal nitrate salts, Fe(NO3)3·9H2O and Al(NO3)3·9H2O, in both solid and aqueous phases are investigated. Raman and surface-selective vibrational sum frequency generation (SFG) spectroscopy, are used to shed light on ion-ion interactions and hydration in several spectral regions spanning low frequency (440-550 cm-1) to higher frequency modes of nitrate and water (720, 1050, 1250-1450, and 2800-3750 cm-1). These frequencies span the metal-water mode, nitrate in-plane deformation, nitrate symmetric and asymmetric modes, and the OH stretch of condensed phase water molecules. Comparison to NaNO3, and in some cases KNO3, is also shown, providing insight. Splitting and frequency shifts are observed and discussed for both the solid state and solution phase. The Lewis acidity of Fe3+ and Al3+ ions plays a significant role in the observed spectra, in particular for the nitrate asymmetric band splitting and frequency shift. The spectral response from water solvation for iron and aluminum nitrates is nonlinear as compared to linear for sodium nitrate, suggesting significantly different solvation environments that are limited by water hydration capacity at higher concentrations. Moreover, a non-hydrogen bonded OH, dangling OH, from hydrating water molecules is observed spectroscopically for Al and Fe nitrate solutions. Furthermore, aluminum nitrate perturbs the surface water structure more than iron nitrate despite aluminum being a weaker Lewis acid. The surface water structure is thus found to be unique for the Al(NO3)3 solutions as compared to both Fe(NO3)3 and NaNO3, such that surface solvation is more pronounced. This observation exemplifies the nature of the Fe(III) and Al(III) ions and their substantial influence on the surface water structure.

A Novel Approach of the Viscoelasticity of Axially Functional Graded Bar and Application of Harmonic Vibration Analysis of an Isotropic Beam as Support

The use of smart materials and passive controllers in modern technologies has stimulated the study of vibration in elastic systems with viscoelastic damping. It is also possible to create components with precise material distribution coefficients and distinct properties, such as Functionally Graded Materials. This work investigates the resonant frequency characteristics of a beam supported at its ends by Axially Functionally Graded (AFG) viscoelastic bars using the finite element method. The set of equations governing motion is obtained by assuming Euler–Bernoulli beam theory for the beam and bar theory for the bars using Lagrange’s equations. The material properties of the functionally graded bar is assumed to vary through the length according to the power law distribution. The longitudinal loss factor values are used to define the internal damping coefficient, which is also dependent on the Young’s modulus value varying along the bar. The effects of the length-varying material properties and internal damping of the FG support bars on the force transmission TR and frequency parameters λ are examined in detail. No study has been found in the literature on the vibration of viscoelastic FG bar-supported beams subjected to a harmonic force at the centre point. It is shown that using bars formed with combinations of different materials considering material damping will be useful to keep the vibration level and force transmission at a certain value and control the frequency parameters.

Synthesis, vibrational, thermal, topological, electronic, electrochemical stability and DFT studies of new DABCO based ionic liquids

The design of new ILs with different anions could provide interesting physico-chemical properties and for these reasons, the knowledge about the synthesis, the thermal, vibrational, topological, electronic, electrochemical properties and interaction between the selected cation-anion in these ILs are important subjects. Therefore, the understanding about these properties of these compounds is an important subject of study. In this work, we studied three ionic liquids based on the 1-decyl-1,4-diazabicyclo[2.2.2]octane, DABCO-cation, where the corresponding anions were [Br]-, [PF6]-, and [N(SO₂CF₃)₂]-. The syntheses of these bicyclic DABCO ionic liquids are based on an alkylation reaction of 1,4-diazabicyclo[2.2.2] octane and 1-bromodecanefollowed by anion exchange. The obtained ILs are characterized by 1H, 13C, 19F and 31P-NMR spectroscopy. Vibrational spectroscopy studies are conducted by infrared (FTIR/ATR) and Raman spectroscopy in the wavenumber range 600–4000 cm-1 and 45–3500 cm-1, respectively. Furthermore, the thermal stabilities were investigated using the thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) methods. Results indicate that the thermal stability follow the order [C10DABCO][Br]<[C10DABCO][PF6]<[C10DABCO][N(SO₂CF₃)₂]. Additionally, the structural parameters, electrostatic potential (ESP) maps, interaction energies, non-covalent interaction (NCI), atoms in molecule (AIM) analysis, natural bond orbital (NBO), frontier molecular orbital (FMO) analysis and Electrochemical window (ECW) are studied and analyzed by means of DFT calculations at the M06–2X-GD3/AUG–cc–pVDZ level of theory.

Thermal-biomechanical manikin applied in turbulent airflow and vibration systems in transient conditions

This paper applied a thermal-biomechanical manikin in turbulent airflow and vibration systems in transient conditions. This numerical model evaluated the thermal and biomechanical components to which the human body is subjected. The first one considers the first-order equations systems based on the thermal numerical model, while the second one considers the second-order equations systems based on the vibration numerical model. This second-order equations system is converted into a first-order equation system. The resolution of the thermal and biomechanical numerical models is made through the Runge-Kutta-Fehlberg method with error control. The thermal numerical model is used in the study of the steady-state and transient conditions when the skin is subjected to mean and turbulent airflow. The biomechanical numerical model is used in the study of the human body vibrations applied to the feet, that a standing person is subjected, using periodical and random vibration signals of the floor. The thermal analysis shows that with an air fluctuation velocity, the skin temperature reduces slightly. The amplitude of the vibration in the lower body section is higher than in the upper body section. The introduction of the randomised vibration, in the periodical vibration, the human body vibration increases the fluctuation level.

Numerical study of the vortex-induced vibrations of a cantilevered pipe with a concentrated mass end using a wake oscillator model

In this paper, a numerical study based on a wake oscillator model has been carried out to determine the vortex-induced vibration (VIV) response characteristics of a flexible cantilevered pipe with a concentrated mass at the free end. First, a coupled model consisting of a cantilevered pipe and a wake oscillator is established, followed by discretization of the model and an iterative solution using the second-order central difference method. The displacement response and frequency response characteristics for different flow velocities and concentrated end masses have been compared. The numerical results reveal that the maximum value of the structural vibration displacement occurs at the bottom; i.e., free boundary end, for the cantilevered pipe with a concentrated mass at the free end. The dominant vibration mode typically shows a stepwise increase for an increase of the maximum flow velocity. As the vibration mode is transmitted from a lower order to a higher one, the vibration displacement of the structural end decreases fast. As the concentrated end mass increases, the dominant vibration mode shows a stepwise decrease, and as the vibration mode is transmitted from a higher order to a lower one, the vibration displacement of the structural end experiences a sharp increase.

A new organic–inorganic chloride (H3N–(CH2)6–NH3)[SnCl6]: Crystal structure, thermal analysis, vibrational study, and electrical properties

In this work, a new Organic-Inorganic chloride (H3N–(CH2)6-NH3)[SnCl6] (1) has been synthesized and characterized by single crystal X-ray diffraction (XRD), IR, Raman and impedance spectroscopies. The crystallographic study displays that the title compound crystallizes in the triclinic system with the P−1 space group. The vibrational study (IR, Raman) at room temperature confirmed the existence of the organic and inorganic functional groups. Differential scanning calorimetry (DSC) analysis reveals the existence of three reversible phase transitions at T1 = 345/325 K, T2 = 483/443 K, and T3 = 496/465 K (Heating/Cooling). Furthermore, the conductivity analysis and the dielectric properties confirm the presence of these phase transitions. AC-conductivity measurement of (1) has been investigated using complex impedance spectroscopy in frequency and temperature range 10 Hz–5 MHz and 313–523 K, respectively. The study of Nyquist plots showed the contribution of grains and grain boundaries in the electrical study, confirming the existence of a non-Debye type relaxation. The AC conductivity shows that the material has the potential of impedance sensors.

Structural, vibrational, and electrical study of the topological insulator PbBi2Te4 at high pressure

We report a joint experimental and theoretical study of the structural, vibrational, and electric properties of the topological insulator PbBi2Te4 under compression through X-ray diffraction, Raman scattering, and electrical measurements at high pressure, which are complemented with theoretical calculations that include the analysis of the topological electron density. The internal polyhedral compressibility of the rhombohedral phase, the behavior of its Raman-active modes, the electrical behavior, and the nature of its different bonds under compression are discussed and compared with their parent binary compounds and with related ternary materials. Interestingly, PbBi2Te4 retains its topological insulating properties as far as the rhombohedral tetradymite-like phase is retained under compression, unlike other tetradymite-like compounds. In addition, PbBi2Te4 undergoes an unconventional reversible pressure-induced decomposition into the high-pressure phases of its parent binary compounds (PbTe and Bi2Te3) above 8 GPa. Finally, we discuss that the intralayer bonds in the tetradymite-like structure of PbBi2Te4 are electron-deficient multicenter bonds; i.e. bonds of the same kind as those present in its parent binary compounds, in related chalcogenides, such as SnSb2Te4, and in general in chalcogenide-based phase change materials. These unconventional bonds are intermediate between covalent and metallic bonds and provide exceptional properties to the materials.

Developing a virtual physical system for vortex-induced vibration studies of a bluff body

A virtual physical system (VPS) for VIV studies of a bluff body is developed to replace the actual physical systems. It can arbitrarily and accurately control and edit the physical parameters, including mass, damping ratio and spring stiffness, specifically for the mass-spring-damper system. The recursive Duhamel integral method (DIM) with unconditional stability was used for the VPS control system, addressing real-time noise filtering problem and simplifying the system as a single input and single output (SISO) one. Delay compensation and inertial force elimination methods were investigated and proposed to overcome the crucial unwanted damping effects. An experimental facility for VIV model tests by VPS was manufactured, and the bluff body model with a measurement system was specially designed to accurately sense the hydrodynamic force during VPS operation. Systematic verification experiments for parameter editing and control of an actual physical target system were conducted, showing that the VPS can reproduce the equivalent spring-damper-mass system in high fidelity with an accuracy error of less than 5%. VIV model tests for a bluff body at Reynolds numbers (Re= UD/υ, where U is the flow velocity, D represents the diameter of cylinder model, and υ is the kinematic viscosity coefficient) of 5.7E4 and 2.3E5 were performed using the VPS experimental facility, presenting well-repeated VIV responses at low Re and unexpected VIV response with a large amplitude of 2.4 D at high Re, which can cause severe fatigue damage for relevant structures. The present VPS will provide promising and powerful experimental tools for VIV studies of a bluff body to reveal the related sensitive parameter effects.

Air-stable Palladium N-Heterocyclic Carbene based CCC-NHC Pincer Complexes: Synthesis, Characterization, Photophysical and Raman Vibrational Studies, and DFT Studies, Plus Observation of an Abnormal Carbene Pincer

A series of CCC-NHC pincer Pd(II)X complexes, where X = Cl, Br, or I, were synthesized by a metalation/transmetalation reaction sequence and characterized by NMR and Raman spectroscopy, photophysical studies, X-ray crystallography, and DFT computational studies. This is the first detailed report of the CCC-NHC pincer Pd complexes analogous the previously reported Pt analogs. Photophysical measurements show that by varying the X ligand, the emission wavelength can be tuned. The chloride complex is a water and air stable blue emitter with a quantum yield of 46% and all three complexes have photostabilities >90%. A combined DFT and TD-DFT study has been carried out to investigate ground state and excited state geometries as well as absorption and emission processes of CCC-NHC Pd complexes. Theoretical results were compared with the corresponding experimental results and showed good agreement. Raman spectroscopy (computational and experimental) was used to examine Pd-X vibrations which have been rarely reported in the literature. Several by-products of the metalation/transmetalation procedure were identified. A rare mixed normal/abnormal carbene pincer Pd(II)Cl complex was isolated and crystallographically characterized.

Non-smooth self-excited vibration of a novel dynamical model for a disc brake

This paper proposes a new dynamic model for the study of friction-induced self-excited vibration of a disc brake system, where the pad’s motions in both radial and circumferential/tangential directions are included, which is in stark contrast to the previous studies that normally consider the pad’s motion in the tangential/circumferential direction only. The non-smooth dynamics of the system including three different states of motion, i.e., stick, slip and separation, is investigated. Both the linear stability analysis and the transient dynamic analysis are performed. The numerical results in the linear stability analysis indicate that the inclusion of pad’s radial motion in the present brake model significantly expands the ranges of operating parameters for dynamic instability than the brake model with only circumferential/tangential motion for the pad. For the transient dynamic analysis, two different methods, i.e., the time integration method and the shooting method, are employed for the calculation of steady-state response. The accuracy and efficiency of the shooting method are subsequently examined. The numerical results show rich bifurcation behaviours of the steady-state response in the present brake model with the variations of brake pressure and disc speed , and (the stiffness of the inclined spring in the radial direction) is a key parameter for controlling the occurrence of chaotic vibration in the system. Conflict of Interest Statement The authors declare no conflicts of interest.

Layer stacking effect on structural, vibrational, and electronic properties of Janus-Ga2SeTe crystals

The van der Waals stacking of Janus Ga2SeTe quadruple-atomic layers leads to the formation of polytype bulk crystals, where the stacking order plays a critical yet elusive role in their fundamental properties. Here, we perform first-principles density functional theory calculations to investigate the stacking-dependent structural, electronic, and vibrational properties of four Ga2SeTe polytypes. Our results indicate that the γ polytype has two sub-phases of γ [ABC] and γ [ACB]. Lattice vibration studies manifest that symmetry operations depend on the stacking orders, in which the irreducible representations of optically active modes at Γ for the β, ε, γ, and δ phases are Γ = 3A1 + 4B1 + 4E2 + 3E1, Γ = 7E+7A1, Γ = 11A1 + 11E, and Γ = 8E2 + 7E1 + 8B1 + 7A1, respectively. Moreover, taking spin–orbit coupling into account, the estimated indirect bandgaps are 0.967, 0.926, 0.879, 0.925, and 0.950 eV for β, ε, γ [ABC], γ [ACB], and δ polytypes, respectively, in which the bandgap differences between indirect and direct transitions are within 10 meV. The Bader charge analysis indicates that the stacking order modulates the charge distribution among the compositional layers. These findings provide valuable insights for the development of optoelectronic devices based on Janus structures.

Charge storage mechanism and pseudocapacitance performance of NiO and Ce-doped NiO synthesized via modified combustion technique

Supercapacitors, as promising energy storage devices, have gained significant attention due to their ability to deliver high power and efficient charge storage mechanisms. In this work, we report the synthesis and electrochemical characterization of pristine NiO and Ni1-xCexO (x = 0.01, 0.02, 0.03) nanoparticles using a single-step auto ignition combustion method. Preliminary investigations indicate that Ni1-xCexO (x = 0.02) nanoparticles (2 % Ce doping) exhibit superior specific capacitance compared to other compositions. Therefore, we focused on structural, morphological, and vibrational studies on pristine and 2 % Ce-doped NiO. XPS and BET techniques were explored to assess the electronic state and porosity of the samples. Subsequent electrochemical performance evaluations included Cyclic Voltammetry (CV) at various scan rates, Galvanostatic Charge-Discharge (GCD), and Electrochemical Impedance Spectroscopic (EIS) techniques. From CV at a scan rate of 5 mVs−1, specific capacitance values of 419 Fg-1 and 604 Fg-1 were obtained for pristine and 2 % Ce-doped NiO, respectively. GCD studies revealed a specific capacitance of 381 Fg-1 for 2 % Ce-doped NiO at a current density of 1 Ag-1 and demonstrated capacitance retention of 95.1 % over 3000 GCD cycles for a current density of 4 Ag-1. The symmetric two-electrode supercapacitor cell demonstrates exceptional electrochemical performance, exhibiting a high specific capacitance of 122 Fg-1, an impressive energy density of 8.17 WhKg−1, a power density of 700 WKg-1 at 1 Ag-1, and a remarkable 88 % capacitance retention after 5000 GCD cycles. DFT calculations suggest that Ce doping significantly alters pristine NiO's electronic and structural features due to lattice strain. Our work highlights the enhanced electrochemical performance of 2 % Ce-doped NiO and its potential as a good-quality supercapacitor material.

Novel copper-drugs bearing dipodal bis-mercaptobenzimidazoles: Synthesis, crystal structures, in vitro biological activities, DNA binding, DFT calculations and molecular docking

Three novel copper(II) complexes, 1–3, bearing dipodal bis-mercaptobenzimidazole derivatives based on ortho-, meta- or para-xylene (L1, L2, and L3) were successfully prepared and characterized by using various spectral techniques, including elemental analysis, FT-IR, 1H NMR, and UV–Vis spectroscopy, LC-MS spectrometry and TGA. The analysis revealed that the ligand/metal molar ratio in all copper(II) complexes is 1:1 and the ligand coordinates as a neutral N-donor onto metal center. Additionally, the crystal structures of L1, L2, L3, and copper(II) complex 2 were determined using single crystal X-ray diffraction (SC-XRD) analysis. Copper(II) complexes 1–3 displayed significant stability at pH range of 4–10. The antibacterial effect of ligands and complexes was tested against both gram-negative (Escherichia coli, E. coli ATCC 25922 PTCC 1399) and gram-positive (Staphylococcus aureus, S. aureus ATCC 6538 PTCC 1112) bacterial strains. It should be noted that the complexes showed enhanced antibacterial activity (up to 99 %) when compared to their free ligands. The in vitro studies of all synthesized compounds consisted of testing them against the human colorectal carcinoma cancer cell line (HCT-116) using the MTT assay. The findings revealed that the copper(II) complexes exhibited lower CC50 values (CC50 ranging from 0.045 mM to 0.135 mM) compared to their corresponding ligands (CC50 ranging from 0.150 mM to 0.240 mM) and carboplatin (CC50 = 0.165 mM), indicating higher anticancer activity of the complexes. Additionally, DAPI staining and fluorescence spectroscopy (at three different temperatures) were performed to further examine the impact of complexes 1–3 on inducing apoptosis and to explore their interaction with DNA, respectively. The results revealed a dynamic quenching mechanism, with hydrophobic forces playing a dominant role in the binding process. The viscosity measurements indicated that all complexes could interact in a groove binding manner with DNA. Density functional theory (DFT) calculations were employed to support the structural and vibrational studies and to predict the chemical reactivity. Docking simulations were conducted to evaluate their behavior of the synthesized compounds towards DNA (PDB: 1BNA). These results suggested that various elements, including NH groups, imidazole rings, thioetheric sulfur atom and sulfate moieties of ligands and complexes, are involved in groove binding with DNA.

Experimental study of vortex-induced vibration of stay cables installed with two types of perforated shroud light devices

To address both illumination issues and the common vortex-induced vibration (VIV) of bridge cables, a perforated shroud light device is proposed. The effect of the different porosities (20%, 35%, 42%, and 55%) on VIV of the rigid segmented shroud cable models is studied first by wind tunnel tests. It reveals that shrouds with porosities of 20% and 35% could reduce the VIV amplitude of the smooth cables by 26% and 46%, respectively. However, shrouds with porosities of 42% and 55% tend to increase the complexity and risk associated with VIV. Vibration measurements on flexible should cable with 20% porosity were conducted for both vertical and inclined models with an inclination of 35° and yaw angles of 0°, 30° and 60°. Shrouds with a porosity of 20% exhibit similar effects on vertical flexible cables as on horizontal rigid cables, in both cases mitigating VIV. The impact on the inclined flexible cables depends on the yaw angle. At the yaw angle of 0°, the shroud effectively mitigates VIV in flexible cables. However, at yaw angles of 30° and 60°, the same porosity level shroud exacerbates the risk of VIV in the inclined flexible cable. This may be due to the enhanced wind velocity along the cable axial direction and decreased penetrating flow rate through the shroud as the wind yaw angle increases. Overall, it was found that a shroud with a porosity of 20%–35% performed the best and was recommended for applications on cables with no inclination and inclined cable at yaw angle β = 0°.

Characteristics and control of impact vibration and noise in rail belt conveyor

The rail belt conveyor is an innovative energy-saving belt conveyor. Revolutionizing the traditional roller support, it utilizes interval-spaced carriages to support the conveyor belt. The study of impact vibrations in rail belt conveyors remains underexplored in current research. This paper investigates the impact vibration and noise characteristics of the wheel–rail-steel structure coupling system, as well as their control and optimization strategies. First, vibration and noise measurements were conducted along the track. Results indicate that impact vibrations and noise originating from expansion joints and inserted joints fall within the frequency range of 1.5 kHz–5 kHz. Particularly noteworthy is the pronounced impact noise near inserted joints, with dominant frequencies ranging from 1.5 kHz to 2.5 kHz. Further investigation has revealed that the impacts on inserted joints encompass interactions between the wheel and rail, as well as between different sections of the rail itself. Next, the characteristics of filler materials such as polyurethane rubber, silicone, polyurethane resin, and epoxy resin were analyzed and compared. The experimental results show that filling rubber in expansion joints can reduce lateral impact vibrations by 61% and vertical impact vibrations by 66%. Additionally, the sound pressure level was reduced by approximately 1.7 dBA. Finally, welding the guiding rail to its preceding rail and grinding the welded surface effectively eliminated the composite impact vibrations and sharp noise at the inserted joint, resulting in a decrease of approximately 3 dBA in the sound pressure level. This paper provides guidance on the structural improvement and acoustic optimization of rail belt conveyors.

Influence of support on Rh-Co bimetallic catalysts for ethylene hydroformylation

Bimetallic Rh- and Co-based catalysts are promising materials for the heterogenous ethylene hydroformylation reaction. Here, the influence of a mesoporous silica (SBA-15) support on Rh and Co bimetallic interactions was investigated through a comparison with silica gel and gamma-alumina supports. The bimetallic catalyst supported on mesoporous silica (RhCo3/SBA-15) showed the best C3 oxygenate yield among the three bimetallic catalysts. In-situ vibrational studies suggested moderate binding of the gem-dicarbonyl and Rh(CO)(C2H4) intermediates due to this bimetallic interaction that led to improved hydroformylation performance. Kinetic studies revealed a lower hydroformylation barrier for the bimetallic compared to a Rh monometallic catalyst, and in-situ X-ray absorption spectroscopy investigations showed clear Rh-Co alloy formation on RhCo3/SBA-15. The bimetallic enhancement effect from the interaction with the mesoporous silica support shown here can be further optimized to design olefin hydroformylation catalysts.

Molecular spectroscopy, solvent effect, and DFT studies of azithromycin solvate

Azithromycin ethanol solvate monohydrate [C38H72N2O120.5(C2H6O)H2O], abbreviated by AZM-MH-EtOH, was synthesized by slow evaporation method and investigated by powder X-ray diffraction, Raman and infrared (IR) spectroscopy combined with density functional theory (DFT) studies. Electronic and vibrational properties were properly investigated based on a theoretical study of solvation effects, using implicit solvation and solute electron density models. The electronic and vibrational studies were evaluated under aqueous, ethanolic, and vacuum conditions. The electronic structure calculations indicated that the AZM-MH-EtOH is chemically more stable in solvents compared to vacuum condition. Ultraviolet–visible (UV–vis) measurements confirmed the stability of the material in ethanolic medium, due to higher absorbance values compared to the aqueous medium. Vibrational changes were observed in the Raman and IR bands, which have connection with hydrogen bonds. The experimental vibration modes showed better accordance with the predicted modes’ values under solvation effects, but a slight divergence is noticed when we compared to vibration modes obtained in vacuum. Furthermore, the results have revealed a greater affinity profile of AZM-MH-EtOH for water and ethanol solvents compared to theoretical data under vacuum condition.