Vibrational Frequencies Research Articles

Compaction behavior of coarse-grained soil under various vibration frequencies: a DEM study

PurposeThis paper investigates the vibration compaction mechanism and evaluates the impact of vibration frequencies on the stability of coarse-grained soil, aiming to optimize the subgrade filling process.Design/methodology/approachThis study examines the vibratory compaction behavior of coarse-grained soils through indoor vibration tests and discrete element simulations. Focusing on angular gravel (breccias) of varying sizes, the simulations were calibrated using parameters such as Young’s modulus, restitution and friction coefficients. The analysis highlights how particle shape influences compaction, revealing mesoscopic mechanisms that drive macroscopic compaction outcomes.FindingsThis study investigates the influence of vibration frequency on the compaction behavior of coarse-grained soils using discrete element simulation. By analyzing particle contact and motion, the mesoscopic mechanisms driving compaction are explored. The study establishes a positive linear correlation between contact force anisotropy (Cv) and deformation, demonstrating that higher anisotropy leads to greater structural disruption. Additionally, the increase in sliding contact percentage (SCP) at higher frequencies indicates instability in the skeletal structure, driven by uneven contact force distribution. These findings reveal how frequency-induced stress concentration affects the stability and deformation of the soil skeleton.Originality/valueThis research explores the effect of various vibration frequencies on the compaction behavior of coarse-grained soils, examining microscopic interactions to reveal their impact on soil stability and deformation.

Impact of chlorine substitution on valence orbitals and ionization dynamics in 3-chloropyridine: Insights from high-resolution vacuum ultraviolet mass-analyzed threshold ionization study.

In this study, the effects of chlorine substitution on the valence orbitals and electronic states of 3-chloropyridine (3-CP) were investigated utilizing high-resolution vacuum ultraviolet mass-analyzed threshold ionization (VUV-MATI) spectroscopy and computational methods. High-quality vibrational spectra were obtained from the VUV-MATI spectra of 3-CP isotopomers (35Cl and 37Cl), revealing high-quality vibrational spectra for the lowest cationic states. The adiabatic ionization energies (AIEs) of these isotopomers were accurately determined, providing detailed information about the electronic structure and ionization dynamics. Intense spectra peaks were linked with the D1 excited state of the 3-CP cation, with vibronic transitions in this state closely matching those predicted by Franck-Condon simulations. This provided insights into the cationic structure and the roles of the highest occupied molecular orbital (HOMO) and the HOMO-1. The HOMO was primarily a π orbital of the pyridine ring, while the HOMO-1 consisted of nonbonding orbitals. The AIEs suggested that meta-chlorine substitution stabilizes nonbonding orbitals less effectively than ortho substitution, indicating closely spaced electronic states in the 3-CP cation. Minor discrepancies in vibrational frequencies and intensities, particularly above 800cm-1, suggested the presence of vibronic coupling, warranting further investigation. Overall, this study provided a comprehensive understanding of the vibronic and ionization properties of 3-CP, emphasizing the influence of the position of the chlorine substitution on molecular orbitals and the value of advanced theoretical and experimental approaches for analyzing the vibrational spectra of complex molecules.

Shaking Table Test Studies on Adaptive-Passive Variable Frequency Gas-Spring DVA for Structural Seismic Response Mitigation

The control performance of a passive dynamic vibration absorber (DVA) is known to be sensitive to its frequency deviation. This study upgrades the conventional device and proposes an adaptive-passive variable frequency gas-spring DVA (APVF-GSDVA) for controlling the structural seismic response, while an adaptive control algorithm is developed that requires only a single input signal. The DVA’s vibration frequency is precisely modulated by adjusting the gas pressure in the gas-spring, aligning it with the inherent frequency of the multi-degree-of-freedom (MDOF) structure. The working principle and control algorithm of the APVF system is introduced and derived in detail, the corresponding gas-spring DVA and implementation are designed, and the configuration of the entire control system is realized. An adaptive variable frequency test scheme is designed and the frequency retuning function of the prototype APVF-GSDVA device installed on an MDOF structure is experimentally validated. The seismic response control effectiveness of the retuned DVA is demonstrated by comparing the detuned DVA, highlighting the necessity of implementing adaptive frequency adjustment of the gas-spring DVA. Experimental findings demonstrate that APVF-GSDVA accurately identifies the inherent frequency of the MDOF structure in ambient excitation, it then adjusts the pressure of the gas-spring according to the frequency-pressure relationship, optimally retuning the DVA. A retuned GSDVA can effectively suppress the structural seismic responses, compared to a detuned DVA, its control effectiveness on peak and RMS responses can be improved by a maximum of nearly 13.5% and 53.3% at a frequency deviation of 10%. Furthermore, results from two “detuning-retuning” test paths with distinct seismic excitations indicate that the retuned DVA exhibits superior control effectiveness, underscoring the significance of the adaptive frequency adjustment function in passive DVAs.

Application of the Finite Element Method for Analyzing the Vibration Characteristics of a Spindle System and Fault Diagnosis

The performance of a spindle will gradually decline, the vibration intensity will increase, and the temperature rise will become abnormal with the accumulation of service time. Consequently, the accuracy of the machining product will not meet its production requirements. Studies on the variation characteristics of the spindle unit have clarified the reasons for its abnormal vibration and temperature rise, in principle, to help enterprises conduct preventive maintenance before any serious failure occurs and improve production efficiency. Based on the Timoshenko beam model and rotor dynamics theory, this study uses the finite element method (FEM) to analyze the vibration characteristics of the spindle rotor system. Moreover, it thoroughly analyzes the influence of the spindle bearing heat on the stiffness of the spindle system and identifies the resonance conditions of the spindle rotor within the power frequency range. This research has identified that when the vibration frequency of the spindle operates at a speed of 12,000 r/min, if its vibration frequency is lower than 200 Hz, it will be affected by abnormal vibrations during startup, which will weaken the health status of the spindle and reduce its service life. Similarly, when the working speed of the spindle is 30,000 r/min, if its vibration frequency is lower than 50 Hz, abnormal vibration will occur during startup and operation, thereby reducing its service life.

Analysis of Vibration Characteristics for Rotating Braided Fiber-Reinforced Composite Annular Plates with Perforations

In the current study, a comprehensive numerical model for analyzing the vibrational characteristics of braided fiber-reinforced composite (BFRC) rotating annular plate with perforations under diverse boundary constraints was introduced. This model employs the differential quadrature finite element method (DQFEM), which was developed based on the first-order shear deformation theory (FSDT) and coordinate transformation approach. The BFRC material, specifically a two-dimensional biaxial orthogonal fabric, was utilized to fabricate the annular plate with two distinct types of holes: circular and sector-shaped. The model’s convergence, accuracy, numerical stability, and reliability were confirmed through comparative assessments utilizing data from the literature, from ABAQUS software, and from experimental findings. The analysis focuses on studying the influences of structural properties, material parameters, and boundary restraints on the frequencies of vibration for BFRC rotating annular plates with holes. This theoretical model helps provide scientific basis and technical guidance for the stability and lightweight design of rotating annular plates, such as rotor structures in aircraft engines.

Computational and experimental studies of vibration-protective properties of a pneumatic wheel of the MTZ-82 BELARUS tractor with external spring-hydraulic mini-suspension

BACKGROUND: Currently used in various sectors of the national economy, numerous wheeled suspensionless vehicles on pneumatic tires have a low level of vibration protection of the frame and limited cross-country ability. Therefore, the development and study of the design characteristics of a pneumatic wheel with increased elastic-damping properties and cross-country ability is a relevant technical problem. AIM: Development of the design and study the vibration-protective properties of a pneumatic wheel with an external spring-hydraulic mini-suspension to improve the ride smoothness and cross-country ability of large-sized suspensionless vehicles. METHODS: A description of the design of a wheel with mini-suspension and a support roller is presented. The wheel modeling was carried out in the PascalABC software, which takes into account the nonlinearity of the total force of the pneumatic tire and the spring-hydraulic mini-suspension, which is installed parallel to the tire at an angle to the vertical axis of the wheel. The test method consisted of comparison of free and forced vibrations of the rear pneumatic wheel of the MTZ-82 BELARUS tractor with a 400-965/15.5-38 tire, which operated without and with mini-suspension at a vertical load of 0.6 tons and various excessive pressure in the tire. RESULTS: The results of computational and experimental studies show that if the tire is radially compressed by 75 mm, the excess pressure inside the pneumatic wheel almost does not change, and if the pressure in the tire decreases from 1.6 to 0.4 bar, the resonant vibration frequency of the standard wheel axle decreases by 25%, while the dynamic coefficient remains unacceptably high (more than 5), leading to the tire breakaway from the supporting surface. Installing a mini-suspension parallel to the wheel in the form of a spring-hydraulic shock-absorbing strut leads to an increase in the resonant frequency by 1 Hz, however, the resonant peaks are reduced by almost 3 times to a dynamic coefficient of 2.5...2, which significantly increases the ride smoothness of suspensionless vehicles and reduces the likelihood of wheel breakaway from the supporting surface. CONCLUSION: It was found with the studies that the proposed wheel with a mini-suspension as a spring-hydraulic strut and a support roller has a relatively simple design, ensures high vibration-protective properties with small amplitudes of kinematic disturbance and can be used to improve the ride smoothness and cross-country ability of wheeled suspensionless vehicles.

Electronic Structure of Diatomic Nickel Sulfide.

The nature of the Ni-S bond is investigated due to its role in the absorption of atmospheric Lewis acid gases such as SO2 and SO3 onto Ni surfaces. The vibrational frequency and electronic structure of NiS were predicted using CCSD(T), CASSCF, and internally contracted multireference configuration interaction (icMRCI) + Q. 43 density functional theory (DFT) functionals were benchmarked. CASSCF predicted the ground state of NiS to be the 5Δ state arising from the 3d8(3F)4s2 (3F) and 3d9(2D)4s (3D) electronic configurations of Ni. When dynamical correlation effects are included at the icMRCI + Q level, the ground state of Ni-S is predicted to be 3Σ- consistent with the experiment. The vibrational frequency of Ni-S is calculated to be 519.1 cm-1 at the icMRCI + Q level, in reasonable agreement with the experimental value of 512.68 cm-1. CCSD(T) predicts the frequency of Ni-S to be 543.2 cm-1 when extrapolated to the complete basis set (CBS) limit. The Feller-Peterson-Dixon value based on the CCSD(T)/CBS extrapolation for the bond dissociation energy of NiS is 350.6 kJ/mol, within <4 kJ/mol of experiment. Of the 43 DFT functionals, BP86 and O3LYP predicted the vibrational frequency in closest agreement with the experiment. The applicability of DFT to such acid gas systems was further demonstrated by calculating the energy for displacement of NiO by SO to yield NiS and O2. This displacement energy was calculated to be within experimental error for ∼50% of the DFT functionals, but large differences were also predicted for some functionals.

Impact of electrolyte on the structure and orientation of water at air/water-polyethylene glycol polymer interface.

Polyethylene glycol (PEG) is a water soluble, non-ionic polymer with applications in drug delivery, protein precipitation, anti-biofouling, water-splitting, Li-ion batteries, and fuel cells. The interaction of PEG with water and electrolytes plays pivotal roles in such applications. Using interface-selective spectroscopy, heterodyne-detected vibrational sum frequency generation, and Raman difference spectroscopy with simultaneous curve fitting analysis, we show that water adopts different structures and orientations at the air/water-PEG interface, which depends on the molar mass of the PEG. At the air/water-PEG4000 (MW 4000u) interface, water is H-up oriented (i.e., water Hs are pointed away from the aqueous bulk) around 3200cm-1 and H-down oriented (i.e., water Hs are pointed toward the aqueous bulk) around 3470cm-1. Variation of the bulk concentration of PEG4000 does not change the dual orientation of interfacial water. The presence of an electrolyte (1.0M NaCl) selectively reduces the H-up oriented water without affecting the H-down oriented water at the air/water-PEG4000 interface. The selective reorganization of the interfacial water is assigned to the disruption of the asymmetric hydration around ether-oxygen of the surface-adsorbed PEG4000 by the Na+ ion of the electrolyte. Interestingly, in the case of low molar mass PEG (air/water-PEG200), the interfacial water neither shows the dual orientation nor is affected by 1.0M NaCl.

Improved Thermal Dissipation in a MoS2 Field-Effect Transistor by Hybrid High-k Dielectric Layers.

Transition metal dichalcogenides like MoS2 have been considered as crucial channel materials beyond silicon to continuously advance transistor scaling down owing to their two-dimensional structure and exceptional electrical properties. However, the undesirable interface morphology and vibrational phonon frequency mismatch between MoS2 and the dielectric layer induce low thermal boundary conductance, resulting in overheating issues and impeding electrical performance improvement in the MoS2 field-effect transistors. Here, we employed hybrid high-k dielectric layers of Al2O3/HfO2 to simultaneously reduce the interfacial thermal resistance and improve device electrical performance. The enhanced contact, greater vibrational phonon overlapping region, and stronger interfacial bonding force between the top Al2O3 layer and MoS2 promote the heat removal efficiency across the interface to the substrate. Under the same input power density, the temperature profile of the MoS2 transistor on the Al2O3/HfO2 has been largely reduced compared to that of the device on HfO2, with a maximum reduction of 49.5 °C. In addition, the field-effect mobility and current of MoS2 devices on the Al2O3/HfO2 high-k dielectric layers have been significantly improved, attributed to the depressed electron scattering and trap states at the interface. The design of the hybrid high-k dielectric layers provides an efficient solution to simultaneously improve the thermal and electrical performance of the two-dimensional devices.

Vibration Analysis of the Bow Bridge With and Without the Soil Foundation

Abstract. Earthquakes can impart the phenomenon of resonance, where the frequencies of seismic waves align with a bridge's natural frequency, causing amplification of vibrations that can lead to structural failures. Aiming to accurately predict potential vulnerabilities posed to the bridge when subjected to earthquakes, this research presents a vibration analysis of the Bow Bridge. Two models, which simulate the Bow Bridge with and without soil foundation, are conducted to investigate the bridges natural frequencies and mode shapes under soilless and soiled conditions. The research result shows that the average vibration frequency in a soiled environment is much lower than that in a non-soil environment, intuitively proving the mitigation of soil environment to bridges vibration frequencies. Based on the agreeable data output, this research demonstrates the feasibility of modeling in the prediction of practical construction.

Effect of the electronic properties of the side charges of neutral solvent molecules on the charges of the N and H atoms of the carbazole molecule: IR experiment and DFT calculations

The IR spectral parameters of the absorption band of the valence vibration of the NH bond of the carbazole molecule in several neutral solvents (n-hexane C6H14, carbon tetrachloride CCl4, chloroform CHCl3, benzene C6H6) have been measured. It has been experimentally established that the position of the maximum of the NH vibrational band of the carbazole molecule in solvents undergoes a low-frequency shift relative to the gas phase. This shift increases in the series C6H14, CCl4, CHCl3, C6H6. The change in the magnitude of the linear shift is well described by the Kirkwood-Bauer-Magat KBM ratio in C6H14, CCl4, CHCl3. The presence of a linear shift may indicate that only universal interactions take place. The deviation of this ratio of shift magnitude for carbazole in benzene is interpreted as a manifestation of intermolecular complexation. Quantum-chemical calculations of the position of the absorption band position of the valence vibration of the NH bond of the carbazole molecule in these solvents, carried out by the electron density functional method B3LYP/6-31G using the Gaussian 09W program package, also showed a low-frequency shift relative to the gas phase.It was found that for the carbazole molecule in the condensed phase relative to the gas phase the following effects of changing the magnitude of charges on atoms N13 and H14 take place: 1 – increase in the positive sign of the charge on both atoms; 2 – the change in charge magnitude is larger on the nitrogen atom than on the hydrogen atom for both solvents (whose molecules have a dipole moment ∼0: C6H14, CCl4); 3 – the chlorine containing environment has a greater effect on the charge change in the carbazole molecule than the proton containing environment (whose molecules have a dipole moment ∼0: C6H14, CCl4).The correlation between the change of charges on atoms N13 and H14 with the value of electronegativity ξ of the side solvent atoms was established.Thus, it is shown that the charges on the 13N and 14H atoms of the carbazole molecule undergo changes in the presence of universal interactions, and the magnitude of the charge change depends on the electronic properties of the side atoms of the nearest solvent molecules. A hypothesis is proposed to explain the different frequency shift of the NH vibrational frequency of the molecule for chlorine-containing and hydrogen-containing side atoms of neutral solvent molecules, which takes into account different values of ξ for nitrogen and hydrogen atoms.

Identification of incipient cavitation in control valve

Control valves as important elements in hydraulic systems are used to transport liquid and gaseous media, for example, water, water vapor, and hydrogen. They are mainly used in the power engineering, chemical industry, and so forth. Due to their large dimensions, the verification of hydraulic parameters is problematic. In the case of liquid flow, cavitation can occur, which is mainly characterized by noise, vibrations, or changes of hydraulic parameters. During the incipient cavitation in the valve, there are no noticeable changes in the hydraulic characteristics. The article, therefore, deals with the methodology of determining the cavitation by measuring and evaluating the characteristics of the valve, spectral analysis of noise, and vibrations during water flow. Mathematical modeling is also a suitable tool for determining the extent of cavitation in valve design. Newly created modified cavitation model, where the flowing medium is defined as a mixture of incompressible water and compressible gases (vapor and air), better corresponds to physical principles than the two-phase approach (water and vapor) with experimentally modified density and viscosity. Measured noise and vibration frequency characteristics and mathematically modeled pressure frequency characteristics identify cavitation in the (1 to 10) kHz range. The article proves that when identifying cavitation, the method of measuring hydraulic characteristics fails, but the method of measuring noise and vibrations is suitable in practice, i.e., in real industrial equipment, and the modified cavitation model is suitable for identifying cavitation regions in structural designs of the hydraulic elements.

Modeling of drilling tool vibration in the process of drilling blast wells

Purpose. To determine the characteristic features and model bit vibration during its interaction with rock in the process of drilling technical (blast) wells in open pit mines. Methodology. The following methods were used in the work: analysis of scientific and practical solutions; statistical methods for processing the results of experimental studies; methods of analytical synthesis; computer modeling methods for synthesis and analysis of mathematical models. Findings. The process of interaction between a drill bit and a rock was analyzed. The conditions and causes of vibration of drilling equipment are determined. The spectral analysis of the vibration signal, the formation and analysis of the map of the order of rotation of the rotating parts of the drilling rig during the drilling of technical (blast) wells were performed to identify the bit in the frequency domain of the measured concomitant integrated vibration signal as a source of high-amplitude vibration. The modulated signal measured in the time domain at the specified frequency carries information about the physical and mechanical characteristics of the drilled rock and the state of the bit. The analysis of the experimental studies and modeling of the process of interaction of the bit with the rock allows us to conclude that the obtained statistical indicators of the accompanying vibration signal really adequately characterize the process of well drilling. Originality. A method for determining the characteristics of the interaction of a drill bit with rock in the process of drilling technical (blast) wells based on measuring the parameters of the accompanying vibration signal is proposed. The method differs from the known ones in the fact that in the process of changing the operating mode of the drive of the rotating parts of the drilling rig, an order map is formed over the entire range of its revolutions, the frequency of high-amplitude vibration of the bit is determined, which corresponds to a certain peak order of revolutions, and at this frequency the statistical parameters of changes are measured. Practical value. This approach to the process of drilling wells in open pit mines makes it possible to quickly determine the physical and mechanical characteristics of the drilled rock and adjust the process parameters accordingly to increase its productivity and energy saving.

Structural Insight into Ionogels: A Case Study of 1-Methyl-3-octyl-imidazolium Tetrafluoroborate Confined in Aerosil.

Ionogels were obtained by impregnating Aerosil A380 with 1-methyl-3-octyl-imidazolium tetrafluoroborate (OMIM BF4) ionic liquid (IL). The IL content of the ionogels varied from 16.3 to 79.9 mol %. There was evidence of the confinement of the IL in silica in the shift and broadening of the BF4- 19F NMR signal and in the noticeable (∼50 °C) decrease in the temperature of IL decomposition. For both the ionogels and the pure IL, the frequencies of IR vibrations were different, providing further evidence of the confinement effect. An analysis of textural characteristics revealed that, upon its addition to Aerosil, the IL sequentially adsorbed in the micropores, mesopores and interparticle space. SAXS measurements showed that, in the confined IL, the size of nonpolar correlations substantially increased, from 21.5 Å in the bare IL to 25.6 Å in the ionogel containing 28.1 mol % IL. Unexpectedly, for the ionogel with the lowest IL content (16.3 mol %), no nonpolar correlations were observed, indicating the strong distortion of the structure of the confined ionic liquid. To the best of the authors' knowledge, this is the first report on regular changes in nonpolar correlations in ionic liquids upon confinement in a porous solid. These structural correlations can easily be tuned by simply changing the IL content in the ionogel material.

Negative impact of vibration on process pipelines of a compressor station with electrically driven gas pumping units

Relevance. In gas industry, the amount of equipment that has outlived its intended service life is increasing every year. In accordance with the law “On Industrial Safety of Hazardous Production Facilities,” compressor stations are dangerous objects, the reliable operation of which largely determines the condition of main gas pipelines. Technological pipelines of a compressor station are important objects of this system. They are subject to strict requirements due to the action of static and dynamic loads on them. Reliability of compressor stations is based on the results of a study of the condition of the object and the main factors affecting increased wear of equipment. The solution to wear problem is timely monitoring of equipment, in particular level measurement and determining the causes of pipeline vibrations using vibration diagnostics methods, and frequency and modal analysis methods. Aim. To study the causes of increased dynamic loads on the technological piping that arise during the operation of electric and gas pumping units at a compressor station using vibration monitoring methods. Methods. Vibration monitoring methods to analyze the causes of increased vibration values in the process piping of a compressor station with an electric gas pumping unit. Results and conclusions. The authors have measured vibration in a wide frequency band and assessed the technological condition of the main equipment of the compressor station with EGPA-6.3/8200-56/1.44-R based on the regulatory documentation STO Gazprom 2-2.3-324-2009. The main frequencies of the root-mean-square value of the vibration velocity, at which the highest vibration values were observed, were identified, and a modal analysis was performed using ANSYS software. Based on the results of natural studies and modal analysis, it was concluded about the occurrence of resonant high-frequency oscillations, multiple of the rotor rotation frequency.

Development and Experimental Study of an Experimental Setup for an Online Vibrating Tube Liquid Densitometer

Density is a crucial parameter for quantitatively describing the physical properties of liquids. It serves as an important indicator for scientific research, production process control, pipeline transportation, and other aspects. In oil pipeline transportation and raw material processing, the real-time online measurement of liquid density is of great significance. This paper analyzes the working principle of an online vibrating tube densitometer and derives the fitting equation for temperature, pressure, and density; it also conducts experiments with an online vibrating tube liquid densitometer and establishes a traceability chain for the experimental device. The experimental setup includes a desktop densitometer system, a multi-temperature field constant-temperature stirring system, a walk-in constant-temperature box, an automatic blowing system, and a frequency acquisition and calculation system. The uncertainty of the device’s evaluation is U = 0.08 kg/m3, k = 2. We built a set of pressure-density static test systems, statically testing the online vibrating tube’s liquid-density meter vibration frequency at different pressures; the whole set of systems can be used to assess the specific density, temperature, and pressure range of online vibrating tube liquid density meters in the experimental research to derive the standard temperature. Through the experimental research, we can accurately derive the fitting coefficients under the standard temperature, specific temperature, and pressure of online vibrating tube liquid densitometers, and calculate the fitting error of online vibrating tube liquid densitometers under different temperatures and pressures within the experimental range through fitting equations and coefficients, so as to realize the practical application of online vibrating tube liquid densitometers in engineering by utilizing straight-tube-type and curved-type online vibrating tube densitometers. A preliminary study was conducted on the effects of different densities, temperatures, and pressures on the vibrating tube system’s vibration cycle. The fit coefficient and error were calculated, and the experimental results were compared to the theoretical analysis to confirm the device’s conformity. The study verified the device’s scientific and reasonable design, and demonstrated that it is feasible to use the device for follow-up research. Using this device in subsequent experiments can verify the effects of viscosity, inlet, installation, and other factors on the online vibrating tube liquid densitometer’s metrological performance. Further experimental research on the pressure–frequency–density test system and the establishment of a wide range of temperatures and pressures within the pressure standard density test system are needed to achieve a wide range of temperatures and pressures under the standard density test.

Machining mechanism of CoCrFeNiAlX high entropy alloys via ultrasonic elliptical vibration cutting

Abstract This study investigates the micro-cutting mechanism of CoCrFeNiAl X high entropy alloys, focusing on the impact of amplitude, vibration frequency, cutting depth, and the Al element content. The mechanical response of the material is analyzed using simulation methods for both conventional cutting and ultrasonic elliptical vibration assisted cutting (UEVAC). The results show that under different vibration parameters and cutting depth, the cutting temperature produced by UEVAC is significantly higher than that of conventional cutting temperature. When the Y-axis amplitude is reduced from 90 μm to 30 μm, the cutting temperature is reduced by 50%. In addition, the cutting temperature is positively correlated with the Al content, and when the molar ratio is 20%, the cutting temperature is about 2.1 times that of 13%. While keeping the cutting parameters unchanged, the cutting force generated by UEVAC is significantly reduced compared to conventional cutting. It is worth noting that when the X-axis amplitude is 40 μm, the Y-axis amplitude is 90 μm, and the vibration frequency is 25 KHz, the cutting force of UEVAC is the smallest, which is only about 13% of the conventional cutting force. With the increase of the mole ratio of aluminum in the high entropy alloy, when the mole ratio of aluminum increases from 0% to 13%, the cutting force begins to decrease by about 33%. However, when the molar ratio increases from 13% to 20%, the cutting force increases by about 214%. On the surface of the workpiece (within the range of 0–3 μm from the machining surface), the residual stress generated by UEVAC is mainly manifested as compressive stress or tensile stress, which is significantly less than the residual stress generated by conventional cutting. The relation of residual compressive stress of workpiece under different aluminum content is Al1 &gt; Al0.6 &gt; Al0.

In-plane orientational motions of the functional groups of molecules at the air/water interface by time-resolved vibrational sum frequency generation.

The movements of molecules at interfaces and surfaces are restricted by their asymmetric environments, leading to anisotropic orientational motions. In this work, in-plane orientational motions of the -C=O and -CF3 groups of coumarin 153 (C153) at the air/water interface were measured using time-resolved (TR) vibrational sum frequency generation (SFG). The in-plane orientational time constants of the -C=O and -CF3 groups of C153 are found to be 41.5 ± 8.2 and 36.0 ± 4.5ps. These values are over five-times faster than that of 198 ± 15ps for the permanent dipole of the whole C153molecule at the interface, which may indicate that the two groups experience different interfacial friction in the plane. These differences could also be the result of the permanent dipole of C153 being almost five times those of the -C=O and -CF3 groups. The difference in orientational motions reveals the microscopic heterogeneous environment that molecules experience at the interface. While the interfacial dynamics of the two functional groups are similar, our TR-SFG experiments allowed the quantification of the in-plane dynamics of individual functional groups for the first time. Our experimental findings about the interfacial molecular motion have implications for molecular rotations, energy transfer, and charge transfer at material interfaces, photocatalysis interfaces, and biological cell/membrane aqueous interfaces.

Evaluation of hand-arm vibration (HAV)exposure among groundskeepers in the southeastern United States.

The objectives of this study were to evaluate daily hand-arm vibration (HAV)exposure among groundskeepers, characterize power tools used, and estimate lifetime cumulative HAV exposure dose. Seventeen groundskeepers and ten office workers employed at two US southeasterrn institutions were recruited as a target exposure group and a reference group, respectively. A 6-dexposure assessment of HAV was scheduled, and vibration dosimeters were used to obtain daily vibration exposure value, A(8). Information on power tools used and corresponding operation duration was recorded to assign the real-time vibration data collected from the dosimeters for tool characterization in terms of vibration total value (ahv) and frequency. Lifetime cumulative exposure dose, ahv-lifetime, was determined using ahv for all tools used and lifetime exposure duration obtained through a questionnaire. The individual groundskeepers' average A(8) ranged from0.8 to 2.6 and from1.0 to 2.6 m/s2 for the right hand and left hands, respectively. Among 11 power tools used by the groundskeepers, grass trimmers contributed the most to the vibration exposure. The average ahv of the individual tools ranged from 8.0 (chainsaws) to 1.9 m/s2 (seating mowers and handheld blowers) for the right hand and from 6.4 (push mowers) to 1.4 m/s2 (backpack blowers) for the left hand. The highest acceleration peak of grass trimmers, edgers, backpack blowers, pole saws, riding blowers, and hedgers was observed between 100 and 200 Hz while riding mowers, seating mowers, push mowers, and chainsaws showed the highest acceleration peak at lower frequencies (≤63.5 Hz). The groundskeepers' average ahv-lifetime was 76,520.6 and 61,955.5 h m/s2 for the right and left hands, respectively. The average ahv-lifetime of office workers was 2,306.2 and 2,205.8 h m/s2 for the right and left hands, respectively, which was attributed to personal hobby activities. Three groundskeepers' average A(8) reached 2.5 m/s2, the Action Limit recommended by the American Conference of Governmental Industrial Hygienists (ACGIH). The highest contribution to the vibration exposure was observed during grass trimmer operations with a major acceleration peak at 100 Hz. The groundskeepers' ahv-lifetime was 33 and 28 times higher for the right and left hands, respectively, than the office workers.

DFT calculations of structural, chemical, electronic and thermodynamic properties of Rifampicin and Oxalic Acid

The thermodynamic properties of the compounds contribute to the theoretical analysis of the results of favorable energies that are subject to interaction. In this work, through the DFT study, the comparison of the functionals ωB97XD and B3LYP. Geometry optimization calculations and vibrational frequencies were performed for the individual ions and for the interactions. In all cases, all calculated vibrational frequencies are positive, confirming the optimized geometry obtained as a minimum on the potential energy surface. The calculations were carried out in solvent, considering the solvation effect in methanol using the IEFPCM (Integral Equation Formalism of the Polarizable Continuum Model) method. The present work aims to carry out a theoretical study, for in-depth investigations of structural, electronic and thermodynamic properties. In usability in the calculation of the thermodynamic properties, Rifampicin (RIF) and Oxalic Acid (OXA) and the interaction between RIF-OXA in the protonated form protonated RIF with charge +1 and deprotonated OXA with charge -1. In this context, the most favorable thermodynamic parameters in the interaction calculated RIF+-OXA- the values of ∆EZPVE+BSSE, ∆G298 and ∆H in kcal/mol more favorable are -19.62, -14.81 and -25,77.