Dynamical Displacement Research Articles

Comparison of coarse-grained models for cis-1,4-polyisoprene-graphite system

ABSTRACT Structural and dynamical properties of cis-1,4-polyisoprene-graphite system were compared by four coarse-grained models. Coarse-graining of graphene layers replaced four carbon atoms by a single bead while four mapping schemes were used for the polymer. Pressure-correction was applied to the nonbonded part of the coarse-grained potential among coarse-grained polyisoprene beads. Among structural properties density profiles, bond orientation and conformation tensor as function of distance from the graphite surface were studied. Bulk values were achieved at around 2 nm from the graphite surface. Higher degree of coarse-graining showed comparatively larger fluctuations in data. Among dynamical properties mean square displacement and autocorrelation of end-to-end unit vectors for varied distances from the graphite surface were studied. Dynamics study indicated that pressure-correction method used to optimise pressure of the system resulted in slower dynamics for the higher degree of coarse-graining.

Theoretical investigations on a variable-coefficient generalized forced–perturbed Korteweg–de Vries–Burgers model for a dilated artery, blood vessel or circulatory system with experimental support

Recent theoretical physics efforts have been focused on the probes for nonlinear pulse waves in, for example, variable-radius arteries. With respect to the nonlinear waves in an artery full of blood with certain aneurysm, pulses in a blood vessel, or features in a circulatory system, this paper symbolically computes out an auto-Bäcklund transformation via a noncharacteristic movable singular manifold, certain families of the solitonic solutions, as well as a family of the similarity reductions for a variable-coefficient generalized forced–perturbed Korteweg–de Vries–Burgers equation. Aiming, e.g., at the dynamical radial displacement superimposed on the original static deformation from an arterial wall, our results rely on the axial stretch of the injured artery, blood as an incompressible Newtonian fluid, radius variation along the axial direction or aneurysmal geometry, viscosity of the fluid, thickness of the artery, mass density of the membrane material, mass density of the fluid, strain energy density of the artery, shear modulus, stretch ratio, etc. We also highlight that the shock-wave structures from our solutions agree well with those dusty-plasma-experimentally reported.

Dual Optomechanical Cavities for All-Optical Actuation and Sensing of Mechanical Motion

Cavity optomechanics in the photonic devices enables a light-matter interaction in the chip-scale systems via the optical force driven mechanical motion. In this paper, a pump-probe scheme consisting of dual optomechanical cavities is proposed for the first time, where one optical cavity driven by a high input power act as a pump channel and the other one is used as a probe channel to detect the dynamical motion of mechanical resonator. Moreover, modulation of the optical force in the pump channel is achieved to observe the amplification of mechanical motions. As the light input of the pump channel increases, the dynamical displacement of the mechanical resonator is theoretically actuated to 4.8 nm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$/\!\sqrt {\text{Hz}} $</tex-math></inline-formula> at the pump power of 0.75 mW. This all-optical amplification of mechanical motion based on the pump-probe scheme potentially paves the way for the development of optomechanical actuation and switch for the photonic integrated circuits.

A novel method to predict surface topography in robotic milling of directional plexiglas considering cutter dynamical displacement

Recently, industrial robots have been applied to the machining of non-metallic materials because of the advantages of low cutting force requirements, low cost, and high flexibility, etc. Due to the limited static/dynamic stiffness of robot joints and links, the accuracy of robotic machining, especially the surface topography, is more susceptible to the cutting forces and dynamic vibrations, compared with CNC machining. To provide clear insights into the formation process of surface topography in robotic machining of oriented Plexiglas and choose reasonably the machining parameters, a method to predict the surface topography in the robotic machining of oriented plexiglas is presented, considering fully the tool dynamic vibrations. In this method, the dynamic intersection behavior in the cutting zones of the robotic machining process is first modeled, which is then used to determine the dynamic displacements. The gained vibration displacements are integrated into the sweep surfaces of the cutter cutting edges by changing the theoretical equations of cutting edges, in order to more accurately calculate the machining scallop points in the presence of tool vibrations. After that, between the discrete sweep surfaces and the workpiece, a mapping-based intersecting method is proposed to compute the intersections with the lowest scallop heights, and these intersections are used to construct the 3D graph, which can represent the topography of the resulting machined surface. Finally, the computer simulation and machining experiments are conducted, and it is shown that the predicted and physically measured surface topography have a good agreement.

Influence of Blending Nanoparticles with Lubricating Oils on the Performance of Rotor Bearings Systems

The dynamic performance of rotor and bearings of rotating systems due to using a blend of nanoparticles and lubricants oils has been studied. The modified oil viscosity of the blend of nanoparticles with the lubricants is used to compute the bearings forces, pressure, stiffness and damping parameters, theoretically using the Reynolds equation. The study results show that the lubricating oil blend pressure is significantly increased when the percentage of aggregate and volume nanoparticles fractions are increased up to 130° angular position and then it is decreased. Generally, the bearings dynamic parameters (stiffness and damping) are reasonably improved. The dynamical response displacement is increased when the aggregate and volume fractions are increasing. The blending of nanoparticles with lubricating oils has no influence on the critical angular speed of rotor shaft.

A novel theory of generalized thermoelasticity based on thermomass motion and two-temperature heat conduction

The present paper constructs a new theory of two-temperature generalized thermoelasticity based on thermomass motion consideration. The governing equations of the theory are formulated for heterogeneous, anisotropic, and homogenous materials. Moreover, the uniqueness theorem of the equations of the new theory is proved. The theory based on the motion of thermomass predicts the propagation of thermoelastic waves in the micro-scale heat conduction with finite speed. The two-temperature parameter has significant effects on the conductive temperature increment, dynamical temperature increment, strain, displacement, and stress distributions. The two-temperature generalized thermoelasticity with thermomass motion theory introduces a successful thermoelastic model.

Large-Stroke Capacitive MEMS Accelerometer Without Pull-In

In this study, the feasibility of obtaining electrical read-out data from a capacitive MEMS accelerometer that employs repulsive electrode configuration is demonstrated. This configuration allows for large-stroke vibrations of microstructures without suffering from pull-in failure that exists in conventional accelerometers based on the parallel-plate configuration. With initial fabrication gap of 2.75μm, the accelerometer can reach a 4.2μm dynamical displacement amplitude. The accelerometer is tested up to 95(V) without exhibiting pull-in failure. For comparison, the pull-in voltage of an accelerometer with same dimensions but with conventional parallel-plate electrode configuration is 0.8(V). The MEMS device is fabricated using the POLYMUMPs fabrication standard. An electrical circuit is built to measure the capacitance change due to motion of the accelerometer proof-mass. The accelerometer has a mechanical sensitivity of 35nm/g and electrical sensitivity of 5.3mV/g. The ability to use large bias voltages without the typical adverse effects on the stability of the moving electrode will enable the design of capacitive MEMS accelerometers with enhanced resolution and tunable frequency range.

Numerical and Dynamic Errors Analysis of Planar Multibody Mechanical Systems With Adjustable Clearance Joints Based on Lagrange Equations and Experiment.

For theoretical study and engineering application, it is necessary to provide an accurate and simple dynamical model to simulate the multibody mechanical systems with clearance joints and it is also the subject of this article. Based on Lagrange equations of the first kind, a different numerical methodology, the length and rotation angle of the clearance joints are looked as independent coordinates for the first time, is presented in detail. The slider-crank mechanism, with a single or double adjustable revolute clearance joints, is used as a numerical model. A test rig and a simulink model, fully in accordance with the numerical model, are used to measure the velocity, displacement, and acceleration. The numerical results tally with experimental and simulink results reveal that the new methodology, presented in this paper, provides a correct approach to build the dynamical equations of mechanism with clearance joints. Lyapunov exponent is used to analyze the motion status, chaotic or periodic, of the slider. Based on data points, mean absolute deviation (MAD) is applied to judge the dynamical errors, displacement, velocity, and acceleration, of the slider due to clearance joints. With the help of Lyapunov exponent and MAD, the results indicated that various clearance sizes and drive speeds can change the dynamical behaviors of the slider, which is complex but can be predicted in some way.

Earthquakes Effect on the Behavior of Multi-Story RC Building Using Non-Linear Dynamic Analysis

One of the buildings that were designed depending on the old Syrian Code is selected and modeled using SAP2000 by taking its non-linear properties to be checked under dynamical loading. Three earthquake records are taken and applied to the model as Time History loading cases. The dynamical displacement of the top roof of the building and the hysterical diagrams of the relation between base shear and roof displacement is compared and discussed. Asymmetry of shear walls and cores is responsible of the differences in responses of building elements, and insufficient nonlinear modeling of shear walls prevents from finding the real capacity of the system, although comparing pushover curves with hysteric loops from the applied ground motion excitations shows that the building is capable, depending on its old design, to withstand various types of extreme ground motions and earthquakes.

High-speed AFM reveals subsecond dynamics of cardiac thin filaments upon Ca2+ activation and heavy meromyosin binding

High-speed atomic force microscopy (HS-AFM) can be used to study dynamic processes with real-time imaging of molecules within 1- to 5-nm spatial resolution. In the current study, we evaluated the 3-state model of activation of cardiac thin filaments (cTFs) isolated as a complex and deposited on a mica-supported lipid bilayer. We studied this complex for dynamic conformational changes 1) at low and high [Ca2+] (pCa 9.0 and 4.5), and 2) upon myosin binding to the cTF in the nucleotide-free state or in the presence of ATP. HS-AFM was used to directly visualize the tropomyosin-troponin complex and Ca2+-induced tropomyosin movements accompanied by structural transitions of actin monomers within cTFs. Our data show that cTFs at relaxing or activating conditions are not ultimately in a blocked or activated state, respectively, but rather the combination of states with a prevalence that is dependent on the [Ca2+] and the presence of weakly or strongly bound myosin. The weakly and strongly bound myosin induce similar changes in the structure of cTFs as confirmed by the local dynamical displacement of individual tropomyosin strands in the center of a regulatory unit of cTF at the relaxed and activation conditions. The displacement of tropomyosin at the relaxed conditions had never been visualized directly and explains the ability of myosin binding to TF at the relaxed conditions. Based on the ratios of nonactivated and activated segments within cTFs, we proposed a mechanism of tropomyosin switching from different states that includes both weakly and strongly bound myosin.

Hot-Atom-Mediated Dynamical Displacement of CO Adsorbed on Cu(111) by Incident H Atoms: An Ab Initio Molecular Dynamics Study

Nonthermal reactions between gaseous particles and adsorbates on a solid surface commonly exist at the gas–surface interface. Besides the well-known “Eley–Rideal” abstraction reaction, the adsorbate can also be exchanged by the gaseous species via dynamic displacement. We present here the first ab initio molecular dynamics study on the dynamical displacement of CO adsorbed on Cu(111) by incident H atoms. Our results agree reasonably well with the measured displacement cross section, product energy, and angular distributions. More importantly, we explicitly demonstrate that this displacement takes place via a hot atom mechanism. The energetic H atom, accelerated by its chemisorption energy near the surface, could cause CO desorption in various ways accompanied by a surprisingly large-energy dissipation to the surface phonons. As the CO–Cu binding is weakened, the metastable HCO intermediate is possibly formed. This scenario provides a common picture for similar processes with a strong repulsion between the...

Extended finite element method for analysis of the acoustic emission response by a crack under moving heat source

PurposeThis paper aims to study acoustic emission (AE) propagation characteristics by a crack under a moving heat source, which mainly provides theoretical basis and method for the actual crack detection during welding process.Design/methodology/approachThe paper studied the AE characteristics in welding using thermoelastic theory, which investigates the dynamical displacement field caused by a crack and the welding heating effect. In the calculation model, the crack initiation and extension are represented by moment tensor as the AE source, and the welding heat source is the Gauss heat flux distribution. The extended finite element method (XFEM) is implemented to calculate and solve the AE response of a thermoelastic plate with a crack during the welding heating effect. The wavelet transform is applied to the time–frequency analysis of the AE signals.FindingsThe paper provides insights about the changing rule of the acoustic radiation patterns influenced by the heating effect of the moving heat source and the AE signal characteristics in thermoelastic plate by different crack lengths and depths. It reveals that the time–frequency characteristics of the AE signals from the simulation are in good agreement with the theoretical ones. The energy ratio of the antisymmetric mode A0 to symmetric mode S0 is a valuable quantitative inductor to estimate the crack depth with a certain regularity.Research limitations/implicationsThis paper mainly discusses the application of XFEM to calculate and analyze thermoelastic problems, and has presented few cases based on a specified configuration. Further work will focus on the calculation and analysis under different plate configurations and conditions, which is to obtain more interesting and general conclusions for guiding practice.Originality/valueThe paper is a successful application of XFEM to solve the problem of AE response of a crack in the dynamic welding inhomogeneous heating effect. The paper provides an effective way to obtain the AE signal characteristics in monitoring the welding crack.

The Rotation Effect on Shear Horizontal Surface Wave in a Piezoelectric Semi-Space Covered by a Semiconductor Film

In this study, a mathematical model of the rotation effect on Shear Horizontally wave (SH-wave) propagation in a piezoelectric semi-space covered by a semiconductor film is investigated. The semiconducting layer is rotating with a constant angular velocity and the interface between the piezoelectric substrate and the semiconductor layer is imperfectly bonded. Furthermore, the surfaces of the bilayer system assumed free of traction and electrically shorted or open. The governing equations of the dynamical displacement and electrical potential function under the effect of rotation are driven by solving the coupled electromechanical field equations of the piezoelectric half-space and the semiconductor film. In addition, the exact frequency equations of SH waves are derived. Next, the numerical examples are considered to clarify the effects of rotation and electromagnetic boundary conditions for the different values of the film thickness and wave number on the dispersion behaviors. Finally, the effect of rotation on the frequency equation is investigated in detail for piezoelectric material PZT-5H and the semiconductor silicon. The obtained results provide a predictable and theoretical basis for applications of piezoelectric and semiconductor structures to surface acoustic wave equipments.

Dynamical failure index of single layer Keiwitt latticed shell structures

Based on the double control criterion of displacement and energy, a new index, dynamical damage index, for describing the dynamical damage extent in the single layer latticed shell structure is set up. The calculate method and change law of all kinds of consuming energy under the seismic action in the latticed shell structures are studied. Then the expression of dynamical damage index erected by combining the plastic consuming energy and maximum displacement is present. Moreover, the compare among the three index, dynamical damage index, displacement and plastic bar quantity, is completed by large numbers of parameter analysis in the single latticed shell structures. The results show that the discrepancy of analytical conclusion is distinct among the three index, dynamical damage index, displacement and plastic bar quantity to the latticed shell with local weakening stiffness, and the results of dynamical damage index are more reasonable. The dynamical failure index is in effect for the quantificational analysis of dynamical failure for single layer latticed shells.

Conception and development of an optical methodology applied to long-distance measurement of suspension bridges dynamic displacement

This paper describes the conception and development of an optical system applied to suspension bridge structural monitoring, aiming real-time and long-distance measurement of dynamical three-dimensional displacement, namely, in the central section of the main span. The main innovative issues related to this optical approach are described and a comparison with other optical and non-optical measurement systems is performed. Moreover, a computational simulator tool developed for the optical system design and validation of the implemented image processing and calculation algorithms is also presented.

Chemical shrinkage and thermomechanical characterization of an epoxy resin during cure by a novel in situ measurement method

In this study, a novel technique is presented to enable the characterization of the dimensional changes and evolution of mechanical properties of a resin during cure. This is achieved using an innovative in situ device called thermal flux cell combined with a Dynamical Mechanical thermal Analyser (DMA). With this system, it is now possible to eliminate the sources of error induced while combining two or more instruments. This device consists into a mold containing the resin where the upper and lower surfaces acting as heat flux sensors. Changes in temperature and thermal flux are directly monitored as well as the dynamical displacement and the stiffness during the curing process. In this work, an epoxy DGEBA resin was used to demonstrate the innovative approach. The tested resin was characterized using different vibration frequencies and amplitudes of the DMA. The results were then processed in order to provide accurate data on gel time and cure kinetics behavior. The volume and mechanical changes were also derived from experimental data and linked to the degree of cure. Chemo and thermo-mechanical models were created to predict the changes in chemical shrinkage and stiffness during cure.

High-Pressure Raman Spectroscopy of Transition Metal Cyanides

The Prussian blue lattice is known to show characteristic thermal response; the coefficient (β≡d a /d T ; a is lattice constant) of the thermal expansion changes its sign from positive to negative with increasing a . In order to comprehend the curious thermal response, we systematically investigated the pressure response of the lattice for A x M 2+ [Fe 3+ (CN) 6 ] y z H 2 O ( A = Rb and Cs, M = Ni, Zn, and Cd) by means of high-pressure Raman spectroscopy. We found that pressure coefficients (\(\alpha\equiv\mathrm{d}\hbar\omega/\mathrm{d}P\)) of the Raman shift (\(\hbar\omega\)) for the CN stretching modes are small in the M = Cd compounds. The small-α is interpreted in terms of the dynamical rotational displacement of the Fe(CN) 6 octahedra in the large- a region.

Anisotropic polarizationπ-molecular skeleton coupled dynamics in proton-displacive organic ferroelectrics

We have investigated the polarization $\ensuremath{\pi}$-molecular skeleton coupled dynamics for the proton-displacive organic ferroelectrics, cocrystal of phenazine with the 2,5-dihalo-3,6-dihydroxy-p-benzoquinones by measurements of the terahertz/infrared spectroscopy. In the course of the ferroelectric-to-paraelectric transition, the ferroelectric soft phonon mode originating from the intermolecular dynamical displacement is observed in the imaginary part of dielectric spectra ${ϵ}_{2}$, when the electric field of the light $(E)$ is parallel to the spontaneous polarization $(P)$. The soft phonon mode is isolated from the intramolecular vibrational mode and hence the intramolecular skeleton dynamics is almost decoupled from the polarization fluctuation. In the spectra for $E$ parallel to the hydrogen-bonded supramolecular chain, by contrast, the vibrational mode mainly originating from the oxygen atom motion within the $\ensuremath{\pi}$-molecular plane is anomalously blurred and amalgamated into the polarization relaxation mode concomitantly with the dynamical proton disorder. This indicates that the dynamical disorder of the intramolecular skeleton structure, specifically that of oxygen atom, is strongly enhanced by the proton fluctuation and is significantly coupled to the polarization fluctuation along the hydrogen-bonded supramolecular chain. The results are discussed in terms of the proton-mediated anisotropic polarization $\ensuremath{\pi}$-molecular skeleton interaction, which characterizes these emerging proton-displacive ferroelectrics.

Exchange and Spin Jahn–Teller Distortions for Triangular Cluster of Spin-1/2

We study the effects of magnetoelastic coupling on the degenerate ground state of the spin-1/2 antiferromagnetic Heisenberg model for a regular triangular spin cluster. Static displacement of spins spontaneously lifts the degeneracy of the ground state through the distance dependence of exchange coupling, i.e., a spin Jahn–Teller mechanism takes place. On the other hand, dynamical displacement does not lift the degeneracy, although the cluster distorts spontaneously. The energy decrease obtained by dynamical theory is twice that obtained by static theory because of quantum fluctuation.

Displacement of chemisorbed12COfrom Pd{110} by adsorbing hot precursor13COmolecules

The dynamic displacement from CO precovered Pd{110} surface by incident CO is investigated as a function of surface temperature and translational energy by employing a molecular beam surface scattering technique with supersonic molecular beams of isotopically labeled 1 3 CO. A strong and kinetically prompt displacement of preadsorbed 1 2 CO by incoming 1 3 CO molecules is observed. The displacement kinetics are found to be only weakly dependent on the translational energy. The activation energy of desorption for CO in an adlayer of 0.65 ML is found to decrease from 1.3 eV to 52 meV due to the presence of gas phase CO. Direct collision induced desorption, thermodynamic displacement, and dynamical displacement processes such as collisions with hot precursors, local hot-spot formation, and electronic nonadiabaticity are discussed.