Vibrational Frequencies Research Articles

Study on behavior rules of the licorice-soil-licorice oscillating harvester coupled system using numerical method

Licorice oscillating harvester is a new type of energy-saving and resistance-reducing licorice harvester, and the interaction of licorice-soil-harvester is the critical factor affecting the working performance. Based on the licorice distribution in the harvested field and soil characteristics, a licorice-soil-licorice oscillating harvester coupled model was developed using the discrete element method. An efficient simulation method of a complex mechanism combined with a kinematic solution was proposed to study the behavior rules of the coupled system. The results indicate that licorice on the working surface was transported and separated by the topsoil’s holding effect and the front soil’s pushing effect; more than 70 % of the soil fell to the surface through the dispersion area, and the soil separation velocity in the dispersion area was lower than 0.3 m/s. When the harvester’s amplitude and forward speed increased, the licorice’s horizontal displacement was reduced, and the translational kinetic energy increased to obtain a strong transport ability. When the harvester’s amplitude and vibration frequency increased, the licorice’s separation velocity, the licorice force, and the rotational kinetic energy increased, and the relative motion between the licorice and shovel-rod working surface was violent, reducing the licorice’s buried mass. The forward speed has the greatest influence on the driving force of harvester. With an amplitude of 10 mm, a vibration frequency of 9 Hz, and a forward speed of 0.2 m/s, the shovel-rod working surface has a strong transporting ability for licorice, a strong relative motion, and a simulated licorice harvesting rate of 98.04 %. The field test results showed that the harvester worked smoothly, and the licorice harvesting rate was 97.26 %. The simulation model can predict the behavior rules of the coupled system. This study provides technical support for researching new principles and methods for deep-rooted crop harvesting.

Performance compensation model of turbine flowmeter under vibration conditions

Vibration conditions will affect the performance of the turbine flowmeters, resulting in inaccurate or unstable measurement results. A DN10 turbine flowmeter is taken as an example to study the influence rule of vibration conditions on the turbine flowmeter performance. An experimental facility is built to simulate the vibration conditions with amplitude ranging from 35 mm to 90 mm and frequency ranging from 0 Hz to 4 Hz. A simulation method for simulating a turbine flowmeter under vibration conditions based on a dynamic coordinate system and 6DOF (Six Degrees of Freedom) is proposed. Based on the experiments and CFD (Computational Fluid Dynamics) simulation, the results show that the average meter factor of the turbine flowmeter under vibration conditions is larger than that under non-vibration conditions. The average meter factor increases with vibration amplitude and vibration frequency. The maximum relative error of the measured flow rate is 9.73 %. To reduce the measurement error, a performance compensation model of the turbine flowmeter applied to vibration conditions is proposed. The meter factor increment is taken as the dependent variable, and the frequency, amplitude, and flow rate are taken as independent variables. The results show that compared to the original model, the relative error of the turbine flowmeter with the compensation model shows an average reduction of 76.61 %.

Dynamic distributed Brillouin sensing based on pump frequency-agile quadrupling modulation

We propose a dynamic distributed Brillouin sensing based on a frequency-agile quadrupling method. A common low-bandwidth direct digital frequency synthesizer (DDS) is employed to generate a few hundred MHz of frequency-agile pump pulses for Brillouin gain spectrum (BGS) scanning, and polarization multiplexing technology is utilized to further decrease the bandwidth requirement for the frequency-agile microwave signal to one-quarter. This method has low requirements for electronic devices and significantly reduces costs in systems. Static and dynamic measurement capabilities of 2 km fiber were demonstrated experimentally, the vibration frequencies of 183 Hz were measured with a sampling rate of 400 Sa/s.

Molecular structure, thermodynamic and spectral characteristics of chloroboron(III) subphthalocyanine and its dodecafluorinated derivative

A comprehensive study of the structural, spectral and energetic properties of chloroboron(III) complexes of subphthalocyanine (H[Formula: see text]SubPc, for the first time) and dodecafluorosubphthalocyanine (F[Formula: see text]SubPc, reinvestigation) was performed by mass-spectroscopy (MS), gas-phase electron diffraction (GED), IR spectroscopy and quantum-chemical (QC) calculations. A synchronous GED/MS method showed that at T = 630 K and T = 540 K, thermally stable H[Formula: see text]SubPc and F[Formula: see text]SubPc molecular forms are present in the gas phase. The geometric structure of free molecules has been determined, in which the N3-B-Cl fragment has the structure of a distorted tetrahedron, and the phthalocyanine skeleton has a dome shape. QC calculations of the geometry agree well with the GED results. The similarities and differences of the molecular structure in the gas and solid phases were discussed. It is shown, that despite the similarity of most geometric parameters, the H[Formula: see text]SubPc and F[Formula: see text]SubPc have significant differences in electronic characteristics, which determines the differences in their physicochemical properties. The interpretation of the experimental IR spectra was carried out. The distribution of potential energy of normal vibrations over the internal vibrational coordinates has been analyzed. The sublimation enthalpies of H[Formula: see text]SubPc ([Formula: see text]H[Formula: see text](589 K) = 135(5) kJ ⋅ mol[Formula: see text] and F[Formula: see text]SubPc ([Formula: see text]H[Formula: see text](516 K) = 189(3) kJ ⋅ mol[Formula: see text] were determined by the mass spectrometric Knudsen effusion method. The obtained data is important for designing processes employed in fabricating optoelectronic devices based on subphthalocyanines by PVD. Experimental geometric parameters for free molecules and vibrational frequencies can be used to calculate the thermodynamic functions of gaseous H[Formula: see text]SubPc and F[Formula: see text]SubPc.

Influence of Seal Structure on the Motion Characteristics and Stability of a Steam Turbine Rotor

Sealing aerodynamic characteristics are affected by the seal structure, and thus the stability of the rotor system is affected too. A 1.5-stage, three-dimensional, full-cycle model of the high-pressure cylinder of a 1000 MW steam turbine was established. The high eccentricity whirl of the rotor was realized using mesh deformation technology and the multi-frequency whirl model. The nonlinear steam-flow-exciting force of different sealing structures was obtained using CFD/FLUENT, and the motion equations with a nonlinear steam-exciting force were solved using the Runge–Kutta method. The motion characteristics and stability of the rotor system with different sealing structures were obtained. The results show that there are “inverted bifurcation” and “double bifurcation” phenomena in the bifurcation diagrams of different tooth numbers, boss numbers, and tooth lengths, and a 1/2 power frequency of different sealing structures goes through the process of weakening, disappearing, reproducing, and evolving into a 1/3 power frequency and a 2/3 power frequency. With the increasing load, the steam-flow-exciting force becomes stronger, and the multi-frequency vibration and dense frequency phenomena are significant. Under some load conditions, the change curves of three kinds of teeth in 1/3 and 2/3 power frequency vibrations are highly similar, and the tooth number has little influence on the system stability. Under the high load condition, with the boss number increasing, the chaos phenomenon is weakened. Increasing the tooth length is beneficial to the stability of the rotor.

Experimental and theoretical vibrational analysis, structural conformations, DFT estimations, antibacterial, antifungal, DPPH,H2O2, Nitric oxide scavenging activity drug, in silico molecular docking, and ADMET studies of N-(2-carboxylphenyl) phthalimide (CPPD)

The title compound N-(2-carboxylphenyl) phthalimide (CPPD)was purchased with a stated purity of 99 % from M/S. Sigma-Aldrich Co. and utilized as such with no additional purification,CPPD is a thalidomide based derivative, which have led to the uses of most important drugs from 1950 and their mechanisms of action is essential for a better understanding of molecular targets with broad spectrum of biological activity. The obtained FTIR spectral data of the compound were compared to harmonic vibrational frequencies calculated using the ab initio DFT (B3LYP) technique with 6–311++G (d,p)basis sets. Furthermore, 13C and 1H NMR, first-order hyperpolarizability (βo) associated parameters (π, αo)of the compound, theSubsequent to recording the molecule’sUV–Visible spectra, DFT was used to analyze its electronic characteristics, including its HOMO and LUMO energies, molecular electrostatic potential (MESP), and Mulliken population studies were using ab initio DFT6-311++G (d,p)basis sets. Pharmacological Screening investigation of the title molecule showed a strong broad-spectrum of antifungal and antibacterial activity against various Gram (+) and Gram (−) bacteria using Ciprofloxacin as a positive control. The headline molecule is subjected toIn-silico molecular docking research with the purpose of improved recognize its biological activities, in addition with the minimal binding energy and hydrogen bond interaction that can view by Discovery Studio 4.0 visualizers. and drug likeness using Swiss ADME predictor (http://www.swissadme.ch/index.php) along with AdmetSAR-2.0 online software analysis tools features were investigated. The compound CPPD’s ability to degrade DPPH increased as a dose-dependent manner, with its maximal DPPH scavenging characteristic spanning from (18.2 ± 1.5 % to 73.2 ± 1.7 %) and maximum H2O2 scavenging trait ranging from (35.5 ± 5.3to 88.8 ± 3.1 %). The NO free radical scavenging property is linearly dependent on CPPD concentration. The interaction between the CPPD ligands and the 1HD2 protein is demonstrated by these data, as the protein displays a reduced binding energy value of −7.3 (Kcal/mol) and an inhibitory constant (ki) value of 4.39 μM. In swiss ADME prediction, CPPD is an evident from the physicochemical data that has an efficient receptor site binding mechanism. The lipophilicity of a drug is determined by its partition coefficient (Log P=log Po/w) between water and N-(2-carboxylphenyl) phthalimide. The paper further explains that the title compound can act as promising antibacterial and antioxidant agent throughin-vitro and molecular docking studies.

Supramolecular structure, DFT calculation and vibrational characterization of melamin-1-ium oxalurate monohydrate

Crystallization from an aqueous solution of melamine with parabanic acid was taken in a molar ratio of 1:1 leads to the formation of melamin-1-ium oxalurate monohydrate (MOX) crystals. The compound crystallizes in the centrosymmetric space group P21/n of the monoclinic system with four molecules per unit cell. The molecular geometry and vibrational frequencies of MOX in the ground state have been calculated by using the density functional hybrid function B3LYP 6–31+G(d) basis set. The results of optimized molecular structure are presented and compared with the experimental X-ray diffraction data. Furthermore, Fourier Transform Infrared (FT-IR) and Raman Spectra were used to conduct vibrational characterization to study the compound's structural groups. The calculated Highest Occupied Molecular Orbital (HOMO) and Lowest Unoccupied Molecular Orbital (LUMO) energies show that charge transfer occurs in the molecule and other related electronic properties have also been calculated. Besides, Molecular Electrostatic Potential (MEP) was performed to identify the possible electrophilic and nucleophilic sites. First order hyperpolarizability results establish the nonlinear response of the grown MOX crystal with respect to the electric field. Further, the crystal packing behaviour of MOX was studied quantitatively with the aid of Hirshfeld surface analysis.

Unlocking the enigma: Spectroscopic insights, molecular modelling, molecular docking, simulation and MMPBSA analysis of L-ornithine

L-ornithine (APA) has been thoroughly investigated in quantum chemistry using vibrational spectroscopy and density functional theory (DFT). The B3LYP/6-311++G(d,p) basis set was utilized to calculate optimal structure, vibration frequencies, and relevant variables. The computational results were validated by comparing the generated estimates of IR and Raman spectra with stated spectra. The MEP was applied to determine the molecule’s reactive areas and gain an understanding of its chemical responsiveness. Also, the UV–Vis spectrum was generated by combining the methods of the Polarizable Continuum Model (PCM) with Time-Dependent DFT, and comparisons were done with experimental data that was published in the literature. The FMO energy, with an energy gap of 6.095 eV, determines the structural chemical equilibrium. Electronegativity, which measures an atom’s attraction to electrons in a covalent bond, was found to be 3.589, and the electrophilicity index was determined to be 2.320 eV. Local reactivity descriptors were utilized to comprehend interactions within physiologically relevant molecular systems and facilitate the development of novel pharmaceutical drugs. Protein-ligand connections and stability were investigated using molecular docking and molecular dynamics (MD) modeling, which provided useful insights into possible therapeutic uses. To further aid in the comprehension of APA’s pharmacological profile and potential as a pharmaceutical agent, assessments of drug-likeness and ADME were accomplished to appraise the biological characteristics of the substance.

Anisotropic elasticity measurements of the retina using optical coherence elastography

Anisotropic elasticity measurements of the retina are essential for retinal disease diagnosis and function assessment. Optical coherence elastography (OCE) is a high-resolution imaging technique for mapping the elasticity distribution of tissues. However, previous OCE measurements quantified the tissue elasticity in a single direction, resulting in a biased estimation of the elastic properties. In this study, we propose an OCE method with acoustic radiation force (ARF) excitation to map the retinal anisotropic elasticity in the depth and lateral directions. The axial elasticity was analyzed using the natural frequency of free vibration, and the lateral elasticity was quantified using the elastic wave velocity. After evaluating the feasibility of the OCE method on the phantoms, the anisotropic elasticity of ex vivo porcine retinas was mapped. The results show that the OCE method with ARF excitation can assess the elasticity in orthogonal directions and provide a comprehensive understanding of the elasticity of the anisotropic tissues.

Features of cavitation wear of chrome electrolytic coatings

Cavitation wear is a pervasive phenomenon on water transport. The parts of ship propulsion system as well as the water-cooled surface of cylinder liners of high-speed ship diesels are subjected to cavitation attack. Bright chromium deposits are used to protect the water-cooled surface of liners. Nevertheless, the effect of cracks appearing in the electrolytic chrome coating upon depositing on the cavitation resistance of coating is still an open relevant problem. The goal of the study is to analyze the kinetics and mechanism of the destruction of the bright chrome electrolytic deposit under cavitation attack. The cavitation resistance of chrome electrolytic coatings after grinding and after polishing was studied. The chrome electrolytic coatings were obtained on the plates (90 × 30 × 7 mm in size) made of cast iron SCh21. The chrome was deposited on one side (90 × 30 mm) of the plate placed vertically by flow anodic jet chrome plating in standard electrolyte (kg/m3): chrome anhydride — 250; sulfuric acid — 2.5; trivalent chrome — no more than 5; trivalent iron ions — no more than 10. The electrolyte was prepared using distilled water of a single distillation. The parameters of depositing: electrolyte temperature is 50°C; the current density amounts to 60 A/dm2. Four samples cut from the same plate were used. The coatings on the first two samples were ground using the abrasive paper number 320. The coatings on the second pair of samples were first ground successively on the abrasive paper of different grit: 320, 500, 800, 1000, and 1200, and then polished on the cloth with GOI paste. The cavitation wear tests were carried out on a magnetostrictive vibratory rig in fresh water, the frequency and amplitude of the rig horn vibration was equal to 22 kHz and 28 μm, respectively. The spacing between the chrome-plated sample surface and the horn butt was 0.5 mm. The wear of the samples was evaluated by periodical weighing during testing. The wear of the ground samples turned to be significantly higher, than that of polished samples. The photographs of the surface after different duration of the cavitation attack show that the initial cracks formed on the coating during chrome plating are the centers of cavitation destruction. To reduce the negative impact of initial cracks on the cavitation resistance of the bright chrome electrolytic coatings deposited on the water-cooled surface of the cylinder liners of diesels it is shown expedient to include polishing in the technological process of depositing chrome coatings.

Anti-Vibration Method for the Near-Bit Measurement While Drilling of Pneumatic Down-the-Hole Hammer Drilling

Pneumatic down-the-hole (DTH) hammer drilling technology has been used extensively in the fields of heat reservoir exploitation and geological exploration owing to its advantages of high efficiency and low pollution. However, the vibration near the bit is up to 40 g while DTH hammer drilling, which significantly affects the performance and longevity of the near-bit measurement while drilling (MWD). To enhance the environmental adaptability of the near-bit MWD in pneumatic DTH operations, a design method for a vibration-damping system based on the parameter optimization of a non-dominated sorting genetic algorithm II (NSGA-II) is proposed in this study. First, the whole structure of the near-bit MWD is designed, including the MWD sub-shell, sensors, measurement circuits, batteries, and connecting structures (the circuit unit). Secondly, this study analyzes the vibration characteristics of the pneumatic DTH hammer near the bit. According to the damping structure, the vibration response model for the circuit unit and the damping model are established. Thirdly, NSGA-II is employed to optimize the parameters of the damping model in terms of the low-frequency, high-intensity vibration characteristics near the bit in pneumatic DTH operations, thereby devising a damping scheme tailored to the unique conditions of DTH hammer drilling. Finally, vibration experiments were conducted to verify the effectiveness of the vibration-damping device. The experimental results indicate that within the vibration frequency range of 5–20 Hz and vibration level of 10–40 g, the peak attenuation rate of the circuit unit is more than 86.446%, and the improvement rate of the vibration stability of the system is more than 75.214%; the anti-vibration performance of the near-bit MWD system in DTH hammer drilling is improved remarkably. This study provides strong technical support for the stability of MWD equipment under such special working conditions. It has broad engineering application prospects.

Effect of circular and elliptical cutouts on the free vibration analysis of sandwich FGM plate under the elastic foundations

The present article investigates the effect of circular and elliptical cutouts on vibrational characteristics of porous sandwich functionally graded material (SFGM) plates with FGM core resting on Pasternak elastic foundation. The structural kinematics of the plate are formulated based on nonpolynomial-based higher-order shear deformation theory (HSDT). Geometric discontinuities have been incorporated in terms of circular and elliptical cutouts in the SFGM plates. The sandwich structure is considered to be comprised of two homogeneous face sheets and a porous FGM core with various cutout shapes and sizes. The variation of material properties from the homogeneous face sheet to the FGM core has been carefully modeled using modified power law distribution. Further, a C0 continuous finite element formulation with a four-noded, isoparametric quadrilateral element with seven degrees of freedom (DOFs) per node has been employed to accomplish the results. The accuracy of the present results has been demonstrated through convergence and validation studies. A comprehensive study has been carried out to investigate the influence of volume fraction index, even and uneven porosity distribution, circular and elliptical cutouts, as well as H-elliptical and V-elliptical type cutout shapes on the frequency parameter of SFGM plates with the elastic foundation. The numerical results demonstrate the aforementioned parameters significantly impact the vibrational frequency of the SFGM plates.

Uncertainty-informed identification of tie-rod mechanical properties in monumental buildings

Tie-rods are classic structural elements that have been used for centuries to enhance stability in historic masonry buildings and offer valuable insights into structural performance over time through dynamic vibration measurements. This paper tackles the inverse problem, aiming to quantify uncertainties in mechanical properties, tensile axial force and boundary conditions of tie-rods based on experimental vibration frequencies. The approach assumes known probabilistic models for random parameters, such as mass per unit length, bending stiffness, tensile force and boundary conditions, with certain parameters requiring estimation. Finite dimensional models, i.e., deterministic functions in time and/or space, and a finite number of random variables are employed to discretize both physical and probability spaces. The paper concludes with a Monte Carlo simulation, that provides a comprehensive characterization of uncertainties and the best estimates for unknown features, including mass per unit length, stiffness, boundary conditions and tensile force necessary for achieving target free vibration modal parameters, i.e. natural frequencies.

Automatic Differentiation for Explicitly Correlated MP2.

Automatic differentiation (AD) offers a route to achieve arbitrary-order derivatives of challenging wave function methods without the use of analytic gradients or response theory. Currently, AD has been predominantly used in methods where first- and/or second-order derivatives are available, but it has not been applied to methods lacking available derivatives. The most robust approximation of explicitly correlated MP2, MP2-F12/3C(FIX)+CABS, is one such method. By comparing the results of MP2-F12 computed with AD versus finite-differences, it is shown that (a) optimized geometries match to about 10-3 Å for bond lengths and a 10-6 degree for angles, and (b) dipole moments match to about 10-6 D. Hessians were observed to have poorer agreement with numerical results (10-5), which is attributed to deficiencies in AD implementations currently. However, it is notable that vibrational frequencies match within 10-2 cm-1. The use of AD also allowed the prediction of MP2-F12/3C(FIX)+CABS IR intensities for the first time.

Control of deposits on pipeline systems by the method of free oscillations

RELEVANCE. There are a large number of heat exchangers in operation enterprises that operate under various temperature conditions. Steam, hot water, heated products of oil refining and other industries, which may contain oxides of iron, aluminum, calcium sulfate silicates, etc., are used as a heating agent. The efficiency of the heat exchange equipment depends on the condition of the heating surfaces. Contamination of these surfaces with various deposits dramatically reduces the heat transfer coefficient, which leads to a significant increase in heat consumption. The nature of the deposits depends on the properties of the heating agent and the heated medium.THE PURPOSE. The purpose is to assess the possibility of controlling deposits on the surfaces of heat exchange equipment by the free oscillation method. The presence of deposits changes the mass of structures and, consequently, the natural frequencies of vibrations, the analysis of which can determine not only the presence and thickness of deposits, as well as their appearance.METHODS. The paper shows the results of experimental studies conducted using a hardware and software package and calculations of natural vibrations of the surfaces of heat exchange equipment in the ANSYS software package to identify their dependence on the thickness and density of deposits. A plate, a pipe, and a pressurized pipe were modeled as heat transfer surfaces.RESULTS. The results obtained experimentally and computationally coincided, and it was concluded that the free oscillation method makes it possible to determine not only the presence of deposits on heat exchange surfaces, but their thickness and appearance.CONCLUSION. The free oscillation method can detect deposits in a timely manner and monitor their condition, which in turn will, reduce overall operating costs, increase energy efficiency and extend service life.

Modal analysis of Lamb waves of steel pipeline with calcium deposits

The relevance of the work lies in the study of the effect of calcium deposits of various thicknesses on the inner walls of the pipeline on the parameters of its own vibrations.OBJECTIVE: To construct a mathematical model of a steel pipeline without deposits and with calcium deposits of various thicknesses on its inner walls. To perform a modal analysis of the natural vibrations of the steel pipeline. Theoretically confirm the dependence of the change in the oscillation frequency of the pipeline when exposed to sediments.METHODS. The paper highlights a method for analyzing the natural frequencies of the pipeline using the acoustic method of non-destructive testing, since it can be implemented with one-way access and does not violate the integrity of the object of control. In solving this problem, the method of mathematical analysis in the software package of finite element analysis was used. results. The article describes the relevance of the topic, discusses the main methods of non-destructive testing, and defines Lamb waves. A mathematical model of a steel pipeline section with out internal deposits and with calcium deposits of 5 different thicknesses has been constructed.CONCLUSION. Calculations have shown that the natural vibration frequencies of the pipeline without deposits and with calcium deposits change in the direction of increasing values, the frequency increase occurs in waves. The highest frequency values are obtained when modeling calcium deposits with a thickness of 10 mm on the walls of the pipeline.

Effect of vibration frequency on mechanical properties and microstructure of metal inert gas welded dissimilar AA5083 and AA6061 aluminum alloy joints

This study explores how the frequency of vibrations affects the physical, mechanical, and residual stress properties in dissimilar metals welding between AA5083 and AA6061. The vibration-assisted welding process involves the application of vibration frequencies; 0 Hz, 10 Hz, 30 Hz, and 50 Hz. Weld joints were then examined for their microstructure, tensile strength and impact strength. They were also examined using X-ray diffraction to quantify surface residual stress. The findings suggest that welding with a 50 Hz vibration frequency produced weld metal characterized by a fine and consistent equiaxed microstructure. This welded joint exhibited exceptional mechanical property, boasting an ultimate tensile strength (UTS) of 197.87 MPa, an elongation of 15.28 %, and an impact strength of 8.10 J (J). Moreover, this welded joint displayed the lowest surface residual stress within the weld metal, measuring at 110.9 MPa. The application of high-frequency vibrations during aluminum welding promotes a more homogeneous mixing of molten metals between AA5083 and AA6061 in the weld metal. These vibrations also result in increased internal pressure within the molten weld metal, causing dissolved gas bubbles like H2, O2, and N2 to break and release.

Failure law of hydraulic pipe joints sealing performance under vibration loads

Aviation hydraulic pipe joints are inevitably affected by vibration loads during service. Fatigue relaxation occurs in the pipe joint structure by vibration, and fretting fatigue wear occurs in its sealing interface, leading to a decline in sealing performance. In order to investigate the sealing performance of hydraulic pipe joints affected by vibration load, this paper first analyzes the modal distribution of the sealing system pipeline under different hydraulic pressures and hydraulic fluid flow rates through vibration frequency sweeping experiments. Secondly, the vibration load is applied to the pipe joints for different numbers of cycles, which reveals the microscopic wear behavior of the sealing interfaces under different tightening torques. Finally, by carrying out the leakage measurement experiment under vibration load, the evolution law of the sealing performance of pipe joints under different hydraulic fluid pressures and tightening torques was obtained.

Integrating low-cost GNSS and MEMS accelerometer for precise dynamic displacement monitoring

We assess the performance of the self-developed receiver coupling dual-frequency low-cost GNSS chipset and IMU MEMS sensor. The system also comprises software dedicated to vibration monitoring based on relative kinematic positioning in a post-processing mode. The observation assessment reveals high accuracy of low-cost GNSS and MEMS accelerometer data. The Septentrio Mosaic X5 chipset exhibits competitive to high-grade receivers’ phase observation noise, outperformance in code noise level and observation auto-correlation at a level that may be neglected even in high-rate applications. The evaluation of the MEMS accelerometer data proves that the sensor accuracy is adequate for vibration monitoring. With the shake table experiment, we examine the performance of vibration recovery. An advantage of the coupled solution over a GNSS-only one is documented with a 15 % reduction of the amplitude error. The backward smoothing of coupled solutions drives the next 20 % error drop. Finally, the high performance of the coupled solution based on low-cost GNSS & accelerometer is confirmed by a mean amplitude error of 0.4 mm. The frequency analyses indicate that both coupled and single-sensor solutions precisely detect the vibration frequencies; however, they also confirm the outperformance of the former over the latter. The power spectra of the recovered displacement time series accentuate the benefits of GNSS + accelerometer fusion and backward filtering for reducing displacement noise.

Solvent Effect on Dative and Ionic Bond Strengths: A Unified Theory from Potential Analysis and Valence-Bond Computations.

Solvent molecules interact with a solute through various intermolecular forces. Here we employed a potential energy surface (PES) analysis to interpret the solvent-induced variations in the strengths of dative (Me3NBH3) and ionic (LiCl) bonds, which possess both ionic and covalent (neutral) characteristics. The change of a bond is driven by the gradient (force) of the solvent-solute interaction energy with respect to the focused bond length. Positive force shortens the bond length and increases the bond force constant, leading to a blue-shift of the bond stretching vibrational frequency upon solvation. Conversely, negative force elongates the bond, resulting in a reduced bond force constant and red-shift of the stretching vibrational frequency. The different responses of Me3NBH3 and LiCl to solvation are studied with valence bond (VB) theory, as Me3NBH3 and LiCl are dominated by the neutral covalent VB structure and the ionic VB structure, respectively. The dipole moment of an ionic VB structure increases along the increasing bond distance, while the dipole moment of a neutral covalent VB structure increases with the decreasing bond distance. The roles of the dominating VB structures are further examined by the geometry optimizations and frequency calculations with the block-localized wavefunction (BLW) method.