Elementary Displacement Research Articles

Digital image correlation analyses of masonry infilled frame: Uncertainty-based mesh refinement and damage quantification

Masonry walls are subjected to cyclic lateral loads to study damage caused by earthquakes. Imaging techniques are useful to quantify crack networks in such tests, where preferential locations for their initiation are not present. However, detecting small cracks in large structures is challenging. It is shown that finite element (FE)-based digital image correlation (DIC) can detect and quantify cracks by combining optical and mechanical information of a cyclic shear experiment performed on a full-size masonry wall. Pixel-wise gray-level residuals and elementary crack opening displacement fields are the key quantities of the proposed framework. Detection criteria based on standard uncertainties guided the application of new DIC strategies (i.e., mechanical regularization, mesh adaption, and damage). Two damage regimes were quantified. Zigzagged cracks were first formed, for which their opening displacements were on average less than 0.5 mm with very limited damage. They were followed by sliding shear cracks, whose mean opening displacements varied between 1 and 3 mm, and damage developed in a more gradual and extended way. Such rich full-field data set may be used for validating damage models up to full-scale simulations.

Virtual volume correlation of lattice structures: From volumetric data to geometrical and dimensional defects identification

Additively manufactured lattice structures are widely studied in the literature for their advantageous properties. Manufacturing steps introduce defects that are often classified amongst geometry and dimension, surface quality, and porosity defects. Because these defects drastically affect lattice structures’ behaviour, the manufactured parts might lack their required properties. Assessments of these properties are mainly performed by finite-element analysis. This approach primarily relies on meshed X-ray computed tomography (XCT) measurements or meshed computer-aided design (CAD) models and less on parametric models where defects can be easily implemented. Although the former is the most representative of the real part geometry, measured geometrical features are implicit in this analysis and cannot be identified in a direct parametric approach. This paper proposes a virtual volume correlation (V2C) methodology to extract geometrical and dimensional defects of laser powder bed fusion lattice structures. The V2C methodology only relies on volumetric measurement and does not require additional XCT post-reconstruction steps. Such a methodology combines strut and node displacement fields that are decomposed as a sum of chosen parametric elementary displacement fields. V2C is first validated on generated volumes where known defects are introduced, and its ability to relocate these introduced defects is evaluated. Relocation errors are found to be lower than half a voxel. Then, V2C is applied to manufactured lattice structures that differ in position and orientation. Results show the dependence of strut typology, whether vertical or inclined strut, on the resulting geometrical and dimensional defects. V2C also shows the orientation and the position effect of the lattice structure’s geometrical and dimensional defect within the building chamber where lattice nodes’ displacement amplitudes are about 30 μm. The conclusion outlines the parametric identification of geometrical and dimensional defects that can be easily implemented for further finite element models.

АНТИАЛІАЙЗИНГ ЗОБРАЖЕННЯ ТРАЄКТОРІЇ ГІПЕРБОЛИ

At the present stage of development of computer graphics, special attention is paid to improving the realism of synthesized images. One of the factors that significantly affects the realism of the image is the aliasing effect, which is caused by insufficient resolution of display devices and manifests itself in the form of pronounced "teeth" on the edges of graphics. Peculiarities of step increments formation for different areas of hyperbole trajectory formation are considered. Recurrent expressions are obtained to calculate the estimating function, the sign of which determines the type of elementary displacement. An algorithm for determining the coordinates of the points of the hyperbola trajectory is proposed. The proposed algorithm does not contain "long" operations, which ensures its high speed and ease of hardware implementation. Peculiarities of hyperbole trajectory formation with cracking of intensities of background and foreground points are considered. The developed method can be used in systems of highly realistic computer graphics, computer-aided design systems.

Analysis of acoustic-gravity waves in the mesosphere using VLF radio signal measurements

A simple method has been proposed to determine acoustic-gravity wave (AGW) characteristics at lower ionosphere (mesosphere) heights by measuring VLF radio signal amplitudes. For relatively short radio paths (less than ∼ 1500 km long) we obtained the simple relations for estimation of AGW neutral density fluctuation and for vertical displacement of an elementary volume of atmospheric gas. The proposed method has been verified by using VLF radio wave amplitude measurements on several radio paths. AGW properties based on these measurements are approximately calculated at heights of radio signal reflection. The relative fluctuation of 3%–6% of neutral particle concentration and elementary volume displacement of 0.6–1.2 km have been obtained. These results are in good agreement with AGW theory in the Earth atmosphere.

Analysis of Acoustic-Gravity Waves in the Mesosphere Using VLF Radio Signal Measurements

A simple method has been proposed to determine acoustic-gravity wave (AGW) characteristics at lower ionosphere (mesosphere) heights by measuring VLF radio signal amplitudes. For relatively short radio paths (less than ~ 2000 km long) it has been obtained the simple relations for estimation of AGW neutral density fluctuation and for vertical displacement of an elementary volume of atmospheric gas. The proposed method has been verified by using VLF radio wave amplitude measurements on several radio paths. AGW properties based on these measurements are approximately calculated at heights of radio signal reflection. The relative fluctuation of 3—6 % of neutral particle concentration and elementary volume displacement of 0.6--1.2 km have been obtained. These results are in good agreement with AGW theory in the Earth atmosphere.

Reconstruction of substrate’s diffusion landscape by the wavelet analysis of single particle diffusion tracks

We propose an approach to analysing single trajectories of a particle, which moves randomly on a landscape distinct parts of which result in sufficiently various diffusion coefficients. The method based on the mapping the cumulative sum of step-wise elementary displacement squared into a complex oscillating function with the subsequent continuous wavelet analysis of the later allows the localization of relatively homogeneous sub-regions and determining values of the diffusion coefficient within each such sub-region. This approach is applied to demonstrable test examples as well as to the reconstruction of the biological membrane’s properties from the real data of single molecule walk tracing.

Prediction on landslide displacement using a new combination model: a case study of Qinglong landslide in China

Prediction on landslide displacement plays an important role in landslide early warning. Many models have been proposed for this purpose. However, the accuracy of the prediction results by these models often varies under different conditions. Rational evaluation and comprehensive consideration of these results still remain a scientific challenge. A new comprehensive combination model is proposed to predict the landslides displacement. The elementary displacement prediction is made by the support vector machine model, the exponential smoothing model, and the gray model (GM)(1,1). The results of the models are comprehensively evaluated by combining the results and introducing the accuracy matrix. The optimal weight in the evaluation work is obtained. A rational prediction result can be attained based on the so-called combination model. The proposed method has been tested by the application of Qinglong landslides in Guizhou Province, China. The comparison between the prediction results and in situ measurement shows that the prediction precision of the proposed model is satisfactory. The root-mean-square error (RMSE) of the combination model can be reduced to 1.4316 (monitoring site JCK2), 1.2623 (monitoring site JCK4), 2.3758 (monitoring site JCK6), 2.2704 (monitoring site JCK8), 1.4247 (monitoring site JCK11), and 0.9449 (monitoring site JCK12), which is much lower than the RMSE of the individual models.

Temperature dependence of the violation of Purcell's theorem experienced by a folding molecular motor.

We investigate the violation of Purcell's scallop theorem experienced by a mono-molecular motor, successively folding and unfolding inside a soft matter environment due to an external stimulus. We find a breakdown of the Purcell theorem due to fluctuations, that permits the molecular motor's efficient motion. The diffusion of the motor, its efficiency and its elementary displacement strongly depend on the characteristic time of the folding, but only slightly on the temperature. The increase of the motor's efficiency when the folding characteristic time τ decreases agrees with the fluctuation theorem expectation as the entropy generated inside the medium increases. The constant efficiency with respect to temperature is more difficult to understand as it suggests a generated entropy independent of temperature. In contrast with these results, the diffusion of the medium induced by the motor's folding strongly depends on the temperature, but doesn't depend on the characteristic time of the folding. That result suggests that the medium's diffusion is not due to the motor's displacement. We find that cooperative motions known as dynamic heterogeneity depend significantly on both temperature and folding time, leading in some conditions to a decoupling between dynamic heterogeneity and the medium's diffusion. Eventually, we find that the cooperative motions induced by the folding are larger when the motor cannot move.

Shear-enhanced diffraction from thin permanent gratings in dye-doped nematic liquid crystal cells

Permanent gratings are recorded in planar-aligned dye-doped nematic liquid crystal cells under visible light illumination. By increasing the irradiation intensity and exposure time, several diffraction orders of the recorded gratings are obtained in the Raman-Nath diffraction regime. By applying a dynamic transverse shear on one of the confining plates of the cell, an enhancement of the diffraction efficiency is achieved, which follows the period of the grating. By microscope inspection under static displacement of the upper plate, surface gratings formed by the dye adsorption are revealed in both the front and rear windows of the cell, indicating that the diffraction amplification originates from a coherent superposition of the diffracted orders when the gratings are displaced half a period. The effect provides self-matched amplification of diffraction with a simple cell, a single photo-inscription stage, and elementary displacement steps.

A relaxation model of ideal folding in a homogenous viscous medium

The problem of 3D biopolymer structure formation is investigated by the methods of a theory of stochastic dynamics. The variational principle for. elementary displacement and velocity of conformational movements and its implications for the folding process of the polymer chain in a viscous medium are formulated. The result is a most smooth decrease in potential energy during conformational relaxation of the system (a timid mountain-skier principle), which is in consistence with the Onsager principle for kinetics in weakly nonequilibrium systems. The model is in accordance with the results of molecular simulations of the similar systems. The relationship between the structure of the multidimensional potential energy surface and folding kinetics is discussed. The model of a parabolic energy funnel formed by non-bonded interactions is developed. The folding kinetics in the parabolic model of energy funnel is almost close to exponential law.

Condensation rate of light vapour molecules in the transition regime

In order to overcome uncertainties of semi-empirical models based on the flux matching theory and to resolve discrepancies between more accurate interpolation formulas, obtained from various solutions of the Boltzmann equation, a new approach, similar to that recently proposed by the authors to consideration of the heavy vapour molecules condensation, is applied to light vapours. In this limit the transport of light vapour molecules to the central particle can be strictly considered as specific random walks, characterized by the exponential distribution of the elementary displacement distances for each walker migrating with a fixed speed and changing direction randomly, whereas the condensation rate is related to the mean volume swept per unit time by the migrating effective particle of radius equal to the radius of the central particle. Results of numerical calculations of the condensation rate at different values of the Knudsen number are approximated by the interpolation expression with a relatively high accuracy in comparison with the traditional expressions.

Conformational Changes in Voltage-Sensing Domains: Concerted Simulation and Scattering Studies

Electrical signals in excitable tissues such as nerves and muscles are generated by the synchronized opening and closing of ion channels in cell membranes, which generate transient transmembrane gradients in the concentrations of sodium and potassium ions. These channels open and close in response to local changes in transmembrane potential as the signal propagates, and it is well established that their voltage sensitivity is conferred by charged structural elements, referred to as voltage-sensing domains. The details of how conformational changes in the voltage-sensing domains lead to opening/closing of the ion-conducting pores of the channels are still being worked out. Crystal structures of the open states of voltage-gated potassium channels are available, but the structure of the closed/resting state has not been determined to high resolution experimentally. In this talk I will report our efforts to generate a model of the resting state of the archaeal KvAP potassium channel based on atomistic molecular dynamics (MD) simulations in explicit membrane environments, with restraints derived from experimental functional data. I will also present results from simulation studies of an isolated voltage-sensing domain in a hydrated membrane, which include validation by neutron diffraction measurements, and direct observations of elementary gating charge displacement events during a 30-microsecond MD simulation under applied transmembrane potential. Finally, I will discuss prospects for and present preliminary results on using x-ray and neutron interferometry measurements, carried out by our collaborators, to validate and refine simulation-based models of the resting state and the voltage-sensing mechanism.

Small Molecule Modulation of Voltage-Gated Ion Channels

Small Molecule Modulation of Voltage-Gated Ion Channels

Real-time 3D imaging of Haines jumps in porous media flow

Newly developed high-speed, synchrotron-based X-ray computed microtomography enabled us to directly image pore-scale displacement events in porous rock in real time. Common approaches to modeling macroscopic fluid behavior are phenomenological, have many shortcomings, and lack consistent links to elementary pore-scale displacement processes, such as Haines jumps and snap-off. Unlike the common singular pore jump paradigm based on observations of restricted artificial capillaries, we found that Haines jumps typically cascade through 10-20 geometrically defined pores per event, accounting for 64% of the energy dissipation. Real-time imaging provided a more detailed fundamental understanding of the elementary processes in porous media, such as hysteresis, snap-off, and nonwetting phase entrapment, and it opens the way for a rigorous process for upscaling based on thermodynamic models.

Charge transfer in composites “dielectric + metal nanoparticles”: Effect of electric and magnetic fields

AbstractTheory of tunneling conductivity in metal‐containing nanocomposites has been developed. Three regimes of charge transport, corresponding to weak, strong, and super‐strong applied electric fields were found to be characterized by different dependences of the nanocomposite's conductivity on the applied electric field and temperature. In the absence of external electric field, the metal nanoparticles become charged due to tunneling jumps between them. In case of weak electric field, the statistical distribution of positive and negative charges on nanoparticles is in quasi‐equilibrium, and these charges make the dominant contribution to the charge transport. In the opposite case of strong and super‐strong electric fields, the charge transfer consists of jumps of the electrons between neutral adjacent nanoparticles. In the strong field case, once the charges are created, they jump along or against electric field thus creating cumulative elementary charge displacement. The distribution of interparticle distances is derived based on distribution of their radii. This allows us to calculate the total tunneling current through the composite film as the function of the temperature and concentration of the nanoparticles. The magnetoresistance of ferromagnetic nanocomposites was found to be the same in cases of weak and super‐strong electric fields, but differs from that in the strong field. © 2012 Wiley Periodicals, Inc.

ASYMPTOTIC BEHAVIOR OF STRUCTURES MADE OF CURVED RODS

In this paper, we study the asymptotic behavior of a structure made of curved rods of thickness 2δ when δ tends to 0. This study is carried on within the frame of linear elasticity by using the unfolding method. It is based on several decompositions of the structure displacements and on the passing to the limit in fixed domains. We show that any displacement of a structure is the sum of an elementary rods-structure displacement (e.r.s.d.) concerning the rods' cross sections and a residual one related to the deformation of the cross section. The e.r.s.d. coincides with rigid body displacements in the junctions. Any e.r.s.d. is given by two functions belonging to [Formula: see text] where [Formula: see text] is the skeleton structure (i.e. the set of rods with middle lines). One of this function [Formula: see text] is the skeleton displacement, the other [Formula: see text] gives the cross section rotation. We show that [Formula: see text] is the sum of an extensional displacement and an inextensional one. We establish a priori estimates and then, we characterize the unfolded limits of the rods-structure displacements. Eventually, we pass to the limit in the linearized elasticity system and using all results in [6], where on one hand, we obtain a variational problem that is satisfied by the limit extensional displacement, and on the other hand, a variational problem coupling the limit of inextensional displacement and the limit of the rod torsion angles.

Decompositions of displacements of thin structures

In this study we present first the main theorem of the unfolding method in linearized elasticity. Then we prove that every displacement of a thin structure (curved rod or shell) is the sum of an elementary displacement and a warping. Thanks to the previous theorem we obtain sharp estimates of the displacements of this decomposition.

Future Haptic Science Encyclopedia: Realistic Stable Haptic Interaction with Highly Deformable Objects Using HIRO-II

Maintaining a stable haptic interaction with virtual environments, especially with physically-based deformable objects, has long been an active area of research. We address this issue by presenting a comprehensive haptic system architecture and virtual reality simulation, where a physically-based modeling using the Finite Element Method (FEM) combined with an “elementary displacement” approach has been implemented. This approach ensures the stability of haptic interaction with deformable objects and considers interaction with multipoints contacts. The Future Haptic Science Encyclopedia (FHSE) we developed to verify our proposal and demonstrate the new haptic interface HIRO II. We also present an objective and subjective evaluation of FHSE simulation.

ASYMPTOTIC BEHAVIOR OF STRUCTURES MADE OF PLATES

The aim of this paper is to study the asymptotic behavior of a structure made of plates of thickness 2δ when δ → 0. This study is carried out within the frame of linear elasticity by using the unfolding method. It is based on several decompositions of displacements of the structure and on the passing to the limit in fixed domains.We begin by studying the displacements of a plate. We show that any displacement is the sum of an elementary displacement concerning the normal lines on the middle surface of the plate and a warping. An elementary displacement is linear with respect to the variable x3. It is written [Formula: see text] where [Formula: see text] is a displacement of the mid-surface of the plate. We show a priori estimates and convergence results when δ → 0. We characterize the limits of the unfolded displacements of a plate as well as the limits of the unfolded strained tensor.Then, we extend these results to structures made of plates. We show that any displacement of a structure is the sum of an elementary displacement of each plate and of a residual displacement. The elementary displacements of the structure (e.p.s.d.) coincide with elementary rod displacements in the junctions. Any e.p.s.d. is given by two functions belonging to H1( S ; ℝ3) where S is the skeleton of the structure (the set formed by the mid-surfaces of the plates constituting the surface). One of these functions, [Formula: see text], is the skeleton displacement. We show that [Formula: see text] is the sum of an extensional displacement and of an inextensional one. The first one characterizes the membrane displacements and the second one is a rigid displacement in the direction of the plates and it characterizes the flexion of the plates.Eventually, we pass to the limit as δ → 0 in the linearized elasticity system. On the one hand, we obtain a variational problem that is satisfied by the limit extensional displacement, and on the other hand, a variational problem satisfied by the limit of inextensional displacements.

Anharmonic vibrations and grüneisen parameter of the quasi-lattice of glassy arsenic chalcogenides in the free-volume approach

It is shown that the free-volume approach offers the possibility of taking into account the anharmonicity of vibrations and nonlinearity of interatomic interactions in glassy arsenic chalcogenides. The Gruneisen parameters calculated by different formulas are compared, and the bond-breaking strain is correlated with the maximum possible bond elongation. The elementary atomic displacement in the structure of the glasses is evaluated. The ratio of the fraction of fluctuation-induced free volume to the lattice Gruneisen parameter in glassy arsenic chalcogenides is shown to differ from that in silicate glasses. The parameters of the free-volume model are correlated with those of the models relying on the present-day views of the structure of chalcogenide glasses.