Displacement Correlation Research Articles

Experimental study on the aeroelastic response of a square supertall building considering twisted wind effect

For high-slenderness supertall buildings, the aeroelastic effect has been carefully addressed, as the ignorance of aeroelastic response may significantly affect the serviceability of the building. Several state-of-the-art researches have analyzed the influence of twisted wind field (TWF) on aerodynamic wind loads on tall buildings. In this study, the influence of TWF on the aeroelastic response of buildings is studied experimentally. The displacement time histories, trajectories and correlation coefficients of wind-induced responses, statistical characteristics, probability density functions and power spectra of across-wind displacement under various levels of reduced wind speeds are examined. The experimental results show that TWF greatly affects the aeroelastic behaviors of buildings. When reduced wind speed is lower than the critical vortex-resonance wind speed, TWF strengthens the coupling effect between the along-wind and across-wind responses, while for reduced wind speed beyond the critical vortex-resonance wind speed, TWF weakens the coupling effect, and weakens more for the case of larger structural damping level. Also, it is found in this study that TWF strengthens stochastic buffeting and suppresses the vortex-resonance vibration. Furthermore, TWF may modify the lock-in region of vortex-resonance. Overall, it is crucial to reproduce TWF when reduced wind speed is lower than the critical vortex-resonance wind speed, as the TWF-induced across-wind responses can be increased by 89 % in this wind speed region, while for larger wind speeds (i.e., Ur > 10), the across-wind responses are generally weakened in the presence of twisted wind and the wind-resistance design can be accomplished based on the experimental results obtained under CWF. This study contributes to a better understanding for the aeroelastic characteristics of buildings under twisted wind.

Axial and Sagittal Rotation of Cementless Tibial Baseplates Occurs in Bone Under Joint Loading

BackgroundThere has been a recent increase in the use of cementless fixation for primary total knee arthroplasty. While the early results of contemporary cementless implants are promising, understanding the behavior of cementless tibial baseplates under loading remains an ongoing interest. The objective of this study was to identify the pattern of displacement that occurred under loading for a single cementless tibial baseplate design at one year post operation for stable and continuously migrating implants. MethodsThere were 28 subjects from a previous trial of a pegged highly porous cementless tibial baseplate evaluated. Subjects underwent supine radiostereometric exams from two weeks through one year after surgery. At one year, subjects also underwent a standing radiostereometric exam. Fictive points on the tibial baseplate model were used to relate translations to anatomical locations. Migration over time was calculated to determine if subjects displayed stable or continuous migration. The magnitude of inducible displacement between the supine and standing exams was calculated. ResultsInducible displacement patterns were similar between stable and continuously migrating tibial baseplates. Displacements were greatest in the anterior-posterior axis followed by the lateral-medial axis. Correlation of displacements between adjacent fictive points in these axes indicated an axial rotation of the baseplate occurred under loading (r2 = 0.689-0.977, P < .001). Less displacement occurred in the superior-inferior axis and correlations indicated an anterior-posterior tilt of the baseplate occurred under loading (r2 = 0.178-0.226, P = .009-.023). DiscussionFrom supine to standing position the predominant pattern of displacement for this cementless tibial baseplate was axial rotation, with some subjects also displaying an anterior-posterior tilt.

Structural stress prediction based on deformations using artificial neural networks trained with artificial noise

AbstractArtificial Neural Networks (ANN) have found application for multiple problems in structural mechanics and civil engineering. In the new approach developed here, ANNs are used for the determination of the maximum stress resultants in a structure on the basis of monitored displacements. Initially, a simple supported beam subjected up to two vertical forces is considered. The beam is solved analytically for different combinations of load positions and magnitudes defined by Monte‐Carlo sampling. The resulting beam deflections and maximum stress resultants are employed for the training of feedforward neural networks in order to generate metamodels able to predict the maximum bending moment knowing only a few beam input deflections. Subsequently, the concept is applied to a real beam experiment, where a reinforced concrete beam has been tested. It is shown, that the perfect correlation of the beam displacements used as inputs for the ANN training leads to extrapolations when the metamodel is applied to the measured displacements of the real experiment, which are not perfectly correlated. This is source of wrong predictions when the network is applied to these data. The introduction of artificial noise in the synthetic input data in a controlled way before training helps to overcome extrapolation and to increase repeatability and robustness of the metamodels. Various noise levels are applied to the synthetic data to monitor how the ANN performances change over increasing noise and the results along with the limitations of the approach are illustrated.

Study of the Axial Compressive Behaviour of Cross-Shaped CFST and ST Columns with Inner Changes

In this study, novel cross-shaped concrete-filled steel tube (CFST) and steel tube (ST) columns were developed. CFST columns have a high load-carrying capacity and excellent performance under seismic conditions, and the construction process is fast. In order to investigate the axial load bearings and failure mechanisms, six specimens of CFST and ST columns were tested under the axial load. Three different forms of CFST were employed in this study; one was an ordinary cross-shaped CFST (OC-CFST), while the other two were executed with significant inner changes; namely, stiffeners cross-shaped CFST (SC-CFST), and multi-cell cross-shaped CFST (MC-CFST) filled with concrete. The other group has the same OC-ST, SC-ST, and MC-ST, but these test subjects were without filled concrete. Through discussion of the failure mechanism, load displacement and load strain correlations are determined. The effects of parameters on ultimate resistance, failure pattern, and ductility index were studied. The axial load-carrying performance of the cross-shaped CFST columns was 75–80% better than that of ST columns; and each ST column displayed cooperative behavior. The finite element model (FEM) was simulated, and the outcomes of the experiments were used to validate it. The load–displacement relationships were established using parametric analysis. Existing design standards were used to calculate CFST column loading capacity. Finally, mathematical formulas were improvised to determine the ultimate load of the cross-shaped CFST column.

Mechanical stress affects dynamics and rheology of the human genome.

Material properties of the genome are critical for proper cellular function - they directly affect timescales and length scales of DNA transactions such as transcription, replication and DNA repair, which in turn impact all cellular processes via the central dogma. Hence, elucidating the genome's rheology in vivo may help reveal physical principles underlying the genome's organization and function. Here, we present a novel noninvasive approach to study the genome's rheology and its response to mechanical stress inform of nuclear injection. Specifically, we use Displacement Correlation Spectroscopy [1] to map nucleus-wide genomic motions pre/post injection, during which we deposit rheological probes inside the nucleus [2]. While the former informs on the bulk rheology of the genome pre/post injection, the latter informs on the rheology of the probe's surroundings. Our results reveal that mechanical stress of injection leads to local as well as nucleus-wide changes in the genome's compaction, dynamics and rheology. We find that the genome pre-injection exhibits subdiffusive motions, which are coherent over several micrometers. In contrast, genomic motions post-injection become faster and uncorrelated, moreover, the genome becomes less compact and more viscous across the entire nucleus. In addition, we use the injected particles as rheological probes and find the genome to condense locally around them, mounting a local elastic response. Taken together, our results show that mechanical stress alters both dynamics and material properties of the genome. These changes are consistent with those observed upon DNA damage, suggesting that the genome experiences similar effects during the injection process [2].

On enrichment strategies and methods to extract stress intensity factors using extended finite element method for bimaterials

The eXtended Finite Element Method (X-FEM) is a versatile tool to model cracks and interfaces where sharp gradients and even discontinuity of deformation across the interface may occur. The enrichment functions are introduced to depict possible discontinuity and singularity known from analytical solutions. For bimaterials, the gradients of the displacements are discontinuous across the interface, which can be modeled by ramp functions. In this work, we check the role of the enrichment strategies with and without ramp functions for the accuracy of enriching schemes, and also compare three different methods, i.e. the Interaction Integral Method (IIM), Contour Integration Method (CIM), and Displacement Correlation Method (DCM), to extract the Stress Intensity Factors (SIFs). Both planar and non-planar examples are employed to examine the enriching strategies and the three SIF extraction methods. We find that the enriched ramp functions can improve the accuracy in terms of strain energy, but do not significantly affect the SIFs. The IIM is the best choice to extract SIFs and the DCM can provide enough accuracy with a careful choice of extraction parameters. This work can help a reader when choose the enriching strategies and the extraction methods of the SIFs for interface cracks between dissimilar materials.

Inclinometer and Improved SBAS Methods with a Random Forest for Monitoring Landslides and Anchor Degradation in Otoyo Town, Japan

Kochi Prefecture is located in an active zone of Japan that is frequently subjected to landslides due to heavy precipitation in typhoon seasons. Slow-moving landslides have been reported by both the local prefectural authorities and the National Government of Japan. We observed landslide movements in Otoyo Town by using ground- and satellite-based tools. Despite the high cost of establishing a borehole inclinometer survey to obtain accurate ground-based measurements, no previous InSAR study has been conducted in Otoyo Town, and the capacity for regional discrimination between active and inactive slow-moving landslides when using these tools remains unclear. We found that the horizontal velocity component was dominant at a rate of 21.4 mm/year across the whole of Otoyo Town. Satellite-based monitoring of ground-anchor efficiency may be possible in combination with ground-based inclinometer surveys. Three types of land cover are present in the study area—urban, field, and forests—and we selected a random forest (RF) model to extract low-coherence pixels by using optical and radar satellite sensors to identify important features and precisely remove pixels causing decorrelation. Long-term monitoring results from ground-based surveys, including inclinometer (boreholes) and anchor tension distribution data, were compared with the results of synthetic radar by using coherence-based small baseline subset (CB-SBAS) measurements. Generally, landslide occurrence was investigated across the whole of Otoyo Town, and we specifically evaluated the reliability of InSAR measurements in the Kawai landslide as a study site scale. The activity of the Kawai landslide channel was evaluated with borehole inclinometer displacement measurements (15.46 mm) and an anchor pressure survey (736 kN) from 2016 to 2019, as well as the steady state of the area (1.7 mm for the borehole inclinometer and 175 kN for the anchor pressure measurements), although a high cumulative precipitation of 3520 mm was reached during 2020 due to the ground anchor efficiency, which showed a consistent tendency with respect to the InSAR displacement measurements (14 mm during 2018 and 2019 and 0.7 mm during 2020). This comparison showed a consistent time-series displacement correlation, which was strengthened after introducing the RF mask into the analysis procedure, as the RF model correction reduced the standard deviation from the line-of-sight (LoS) average velocity estimation by 1.9 mm/year. Our research will help mitigate landslide impacts in Otoyo Town and its surroundings.

Spatiotemporal prediction of landslide displacement using deep learning approaches based on monitored time-series displacement data: a case in the Huanglianshu landslide

ABSTRACT The use of deep learning approaches to predict landslide displacement based on monitored time-series data is an effective method for the early-warning of landslides. Currently, most prediction models focus on the temporal correlation of displacements from a single monitoring point, ignoring the spatial influence of other monitoring points. To fully consider the spatiotemporal features of the displacement data, this paper develops three deep learning models based on graph convolution networks to spatiotemporally predict the landslide displacements of the Huanglianshu landslide. Specifically, we first establish a fully connected graph to represent the spatial relationships of all the deployed monitoring points. Second, we develop a temporal graph convolutional network-long short term memory (TGCN-LSTM) model and an Attention-TGCN model based on the temporal graph convolutional network-gate recurrent unit (TGCN-GRU) deep learning model and employ the three models to spatiotemporally predict displacements of the Huanglianshu landslide. The proposed spatiotemporal prediction models accurately predict the displacements at seven monitoring points, with a maximum R 2 of 0.85 at the individual monitoring points. The comparative results show that the proposed Attention-TGCN model achieves the highest spatiotemporal prediction accuracy, and the accuracy of the Attention-TGCN model can further improve after considering the movement of the monitoring points.

Pinning effect on the correlations of nonaffine displacement in metallic glasses

We mimic the structural heterogeneity of inclusions in nanoscale by pinning a portion of atoms in CuZr metallic glasses (MGs) on molecular dynamics simulations with shear deformation. Results show yielding of the MGs transits from a system-spanning shear band (SB) to a localized plastic flow with pinning, due to the constrained length scale for the organization of the plastic events imposed by pinning. Spatial correlation of the nonaffine displacement exhibits a quadrupolar symmetry that shrinks with pinning, giving two characteristic lengths in the maximum and minimum directions that are both constrained by the static length for the pinned atoms. The two characteristic lengths signify the anisotropic nature of the plastic regions, which diminishes with pinning. These results shed light on the microscopic mechanism of tailoring the mechanical properties by tuning the static structure in MGs.

Partitions among elastic waves for dynamic surface loads in a layered medium

SUMMARY The relationship between the Green's function and the average correlations of the elastic displacements within a diffuse field has been firmly established. The energies of horizontal and vertical motion in such a field are proportional to the imaginary part of the corresponding diagonal components of the Green's tensor for coincident source and receiver. Given this remarkable connection, we examine the partitions of elastic waves due to dynamic horizontal and vertical surface loads in a layered elastic media. The elastic radiation characteristics for horizontally layered media are much more complicated than for the homogeneous half-space. While the corresponding power partitions of the different types of waves in a half-space do not vary with respect to frequency, even in an elastic medium consisting of layers over a half-space, the modal structure shows strong variations in the frequency, mainly around the main peak and the minimum of the horizontal-to-vertical spectral ratio (HVSR). Using a test model with a moderately high impedance contrast, we find that most of the energy density of the horizontal displacements is concentrated in the fundamental mode of the Love waves, reaching ∼80 per cent of the power in the horizontal components. The vertical displacement of the P-SV body waves reaches a maximum of ∼85 per cent, while the fundamental mode of Rayleigh waves reaches a maximum of ∼99 per cent of the available power in the vertical motion. With this analysis, it is possible to analyse the multimodal effects in the dispersion diagrams and explicitly relate the partition of the energy density with the dispersion curves and the HVSR under the diffuse field assumption.

Coupled multiphysics 3-D generalized finite element method simulations of hydraulic fracture propagation experiments

Intentional creation and propagation of fractures driven by fluid under high pressure have several applications in oil and gas exploration, geological mining, disposal of toxic waste, flow of molten magma within crevices/fissures, etc. Due to the need to design hydraulic fractures, especially in the oil and gas industry, and the limitation of their full scale/field testing, the use of laboratory experiments and/or numerical simulations remain viable alternatives. While several computational methods for this class of problems exist in the literature, their reliability and robustness hinge on their ability to replicate experimental results with acceptable confidence. This paper presents the application of a coupled multiphysics 3-D generalized finite element method (GFEM) for the simulation of hydraulic fracture experiments based on a regularized Irwin criterion and adaptive mesh refinement. Built with an automatic time step search, the algorithm computes the time step size that ensures the satisfaction of the propagation criterion. Modes I, II, and III stress intensity factors are computed using the displacement correlation method, while the fracture propagation direction is determined using the Schöllmann’s criterion, which is a generalization of the maximum tangential stress criterion for 3-D stress state. The GFEM is validated against a hydraulic fracture experiment on PMMA specimen, on one hand, and against four different cases of experimental fractures within concrete (a granite-like) material which serves as the pioneer application of the algorithm to verify hydraulic fracture simulation in non-PMMA materials. The influence of the initial shear stresses along the fracture plane (assuming unnotched condition) on the resulting propagation paths in the latter benchmarked problem is also assessed and found to have good agreement with experimental observations.

Experimental Investigation on Behavior of Single-Helix Anchor in Sand Subjected to Uplift Cyclic Loading

Helical anchors have been widely used in geotechnical engineering due to their large uplift resistance. However, the current knowledge of the cyclic performance of helical anchors is still insufficient. Consequently, a series of small-scale model tests are carried out in sand to investigate the influences of embedment ratio, sand compactness and the cyclic parameters on the monotonic, cyclic and post-cyclic performance of single-helix anchors. The tests results indicate that the single-helix anchors with optimal embedment ratio still exhibit a relatively high uplift capacity after suffering cyclic load. The cyclic frequency has the greatest influence on the accumulated displacement, and the influence of amplitude is relatively greater than that of the mean cyclic load. The anchors in dense sand exhibit better performance to resist pullout than those in medium–dense sand under the same cyclic parameter ratios. Moreover, the correlation of post-cyclic uplift capacity and displacement after cyclic loading as well as the possible influence of the upward displacement on the sand flow above the helix are discussed.

Displacement Correlations in Disordered Athermal Networks

We derive exact results for correlations in the displacement fields \(\{ \delta \mathbf {r} \} \equiv \{ \delta r_{\mu = x,y} \}\) in near-crystalline athermal systems in two dimensions. We analyze the displacement correlations produced by different types of microscopic disorder, and show that disorder at the microscopic scale gives rise to long-range correlations with a dependence on the system size L given by \(\langle \delta r_{\mu } \delta r_{\nu } \rangle \sim c_{\mu \nu }(r/L,\theta )\). In addition, we show that polydispersity in the constituent particle sizes and random bond disorder give rise to a logarithmic system size scaling, with \(c_{\mu \nu }(\rho ,\theta ) \sim \text {const}_{\mu \nu } - \text {a}_{\mu \nu }(\theta )\log \rho + \text {b}_{\mu \nu }(\theta ) \rho ^{2} \) for \(\rho ~(=r/L) \rightarrow 0\). This scaling is different for the case of displacement correlations produced by random external forces at each vertex of the network, given by \(c^{f}_{\mu \nu }(\rho ,\theta ) \sim \text {const}^{f}_{\mu \nu } -( \text {a}^{f}_{\mu \nu }(\theta ) + \text {b}^{f}_{\mu \nu }(\theta ) \log \rho ) \rho ^2 \). Additionally, we find that correlations produced by polydispersity and the correlations produced by disorder in bond stiffness differ in their symmetry properties. Finally, we also predict the displacement correlations for a model of polydispersed soft disks subject to external pinning forces, that involve two different types of microscopic disorder. We verify our theoretical predictions using numerical simulations of polydispersed soft disks with random spring contacts in two dimensions.

Three-dimensional displacement field of the 2010 Mw 8.8 Maule earthquake from GPS and InSAR data with the improved ESISTEM-VCE method

The 2010 Mw 8.8 Maule earthquake occurred offshore central Chile and ruptured ∼500 km along the megathrust fault resulting from the oceanic Nazca plate subducting beneath the continental South American plate. The Maule earthquake produced remnant crustal displacements captured by a vast set of geodetic observations. However, given the nature of the observational techniques, it is challenging to extract its accurate three-dimensional coseismic deformation field with high spatial resolution. In this study, we modified the extended simultaneous and integrated strain tensor estimation from geodetic and satellite deformation measurements (ESISTEM) method with variance component estimation algorithm (ESISTEM-VCE) to retrieve the three-dimensional surface displacement field of this event by integrating the interferometric synthetic aperture radar (InSAR) and global positioning system (GPS) measurements. The ESISTEM-VCE method accounts for the spatial correlation of surface displacement among the adjacent points and determine the accurate weight ratios for different data sets, but also uses the uncertainties of GPS data and considers the different spatial scales from the different datasets. In the simulation experiments, the RMSEs of the ESISTEM-VCE method are smaller than those of the ESISTEM and ESISTEM-VCE (same d0) methods, and the improvements of 97.1%, 3.9%, and 84% are achieved in the east-west, north-south, and vertical components, respectively. Then, we apply the proposed methodology to the 2010 Mw 8.8 Maule earthquake, to obtain a three-dimensional displacement field that could provide fine deformation information. In the east-west component, the significant deformation is in the north of the epicenter, closed to the Constitución, with a maximum westward displacement of 495.5 cm. The displacement in the north-south component is relatively small compared to that in the east-west component. The maximum uplift reaches 211.8 cm, located at the southwest of the Concepción. Finally, the derived vertical displacements are also compared with field investigations, indicating that the ESISTEM-VCE method can obtain more accurate weight of different datasets and perform better than the ESISTEM method. The results highlight that the earthquake ruptured along the NE-SW direction, with a dominant thrust and a relatively small component of right-lateral strike-slip, coinciding with the characteristics of subduction and right-lateral shear. The experiments with the simulated and real data suggest that the improved ESISTEM-VCE method in this study is feasible and effective.

Anisotropic correlations of plasticity on the yielding of metallic glasses.

We report computer simulations on the shear deformation of CuZr metallic glasses at zero and room temperatures. Shear bands emerge in athermal alloys at strain γ_{c}, with a finite-size effect found. The correlation of nonaffine displacement exhibits an exponential decay even after yielding in thermal alloys, but transits to a power law at γ>γ_{c} in athermal ones. The algebraic exponent is around -1 for the decay inside shear bands, consistent with the theoretical prediction in random elastic media. We quantify the anisotropic correlation with harmonic projection, finding the spectrum is weak in the exponential-decay regime, while it displays a strong polar and quadrupolar symmetry in the power-law regime. The nonvanishing quadrupolar symmetry at long distance signifies the nonlocality of plastic correlation in the athermal alloys. In contrast, the plastic correlation was found to be isotropic and localized at the yielding in the thermal alloys without shear bands.

ГЕОДИНАМІКА

The work analyzes the current horizontal and vertical displacement territory of Western Ukraine according to GNSS data, including the creation of special maps of modern displacements and the allocation of deformation zones of the upper crust. The object of study is the horizontal and vertical deformations of the upper crust. The aim is to identify and analyze deformation zones in Western Ukraine. The initial data are horizontal and vertical velocities of 48 continuous GNSS stations from 2018 to 2021 of Geoterrace network, known tectonic maps of the territory and descriptive materials. The methods include comparison and analysis of modern Earth crust deformations of the region with its known tectonic structure. As a result, for the first time it was possible to create the maps of horizontal velocities of continuous GNSS stations and deformations as well as vertical velocities of GNSS stations of the upper crust of Western Ukraine as a whole region. It is established that the deformations of the territory of Western Ukraine are complex and only partially correlate with the known tectonic structure in the region. Most continuous GNSS stations subside in vertical components, possible due to denudation processes. The Galicia–Volyn depression, however, practically does not subside. On the slopes of the Ukrainian Shield there is a noticeable correlation of vertical displacements and the depth of the surface of crystalline rocks. Zones of compression are identified in Zakarpattia, which corresponds to the Zakarpathian (Transcarpathian) deep fault, and in the north-west of the region. It is necessary to mark the zone around the city of Khmelnytskyi, where abnormal vertical and horizontal displacements are observed. Geodynamic interpretation of anomalous deformation zones is given. Determined velocities of continuous GNSS stations with the increasing observation time interval will make it possible to establish the features of the spatial distribution of Western Ukraine crustal movement as well as create an appropriate regional geodynamic model in the future.

Propagation mechanisms and parametric influence in multiple interacting hydraulic fractures: A 3‐D G/XFEM hydro‐mechanical modeling

AbstractUsing a robust three‐dimensional generalized/eXtended finite element method (G/XFEM) algorithm, this paper presents a comprehensive study on multiple hydraulic fracture propagation and their interactions under different treatment conditions. Aimed at capturing the complex multiphysics behavior, the resulting nonplanar fracture footprints under mixed‐mode conditions are simulated using a formulation, which couples the solid/rock domain equations and the fluid flow within the fractures/crevices. Due to the small length scale of the fracture process zone relative to the surrounding formation size, as typically encountered in tight shale reservoirs, linear elastic fracture mechanics based on a regularized Irwin criterion is adopted to describe the fractured solid/rock response while a power law is used for the fluid flow by assuming a Newtonian fluid behavior. Equipped with the capability for mesh adaptivity and automatic time step search algorithms, the G/XFEM utilized to discretize the resulting system of coupled nonlinear equations allows the adoption of independent meshes for the background solid domain and the fracture surfaces without any matching/compatibility requirement between the two. Fracture propagation directions are decided based on the modes I, II, and III stress intensity factors that are extracted using the displacement correlation method. The presented model is first applied to a pair of misaligned fractures and then to an array of en échelon fractures for qualitative verification against a literature prediction by the boundary element method (BEM) and an observed field behavior, respectively. Next, simulation of several sets and configurations of multiple hydraulic fractures, resulting in a total of 23 parametric studies, are carried out to investigate the influences of fracture spacing, injection fluid viscosity, number of fracture clusters, and the type of remote stress conditions.

Sorption of Per- and Polyfluoroalkyl Substances (PFAS) using Polyethylene (PE) microplastics as adsorbent: Grand Canonical Monte Carlo and Molecular Dynamics (GCMC-MD) studies

ABSTRACT Per- and Polyfluoroalkyl Substances (PFAS) and microplastics (MPs) removal is one of the main technical measures in these emerging pollutant control and MPs can sorb PFAS acting as carriers. In order to explore the sorption process of polyethylene (PE MPs) for different PFAS, Grand Canonical Monte Carlo and molecular dynamics simulation was used. Seven commonly found PFAS compounds including PFNA (Perfluorononanoic acid), PFHxS (Perfluorohexanesulphonic acid), PFHxA (Perfluorohexanoic acid), PFDA (Perfluorodecanoic acid), PFOS (Perfluorooctanesulfonic acid), PFBS (Perfluorobutanesulfonic acid) and Perfluorooctanoic acid (PFOA) were selected. The sorption on PE MPs was based on fixed loading and the sorption (PE MPs+PFAS) average total energy for all simulation steps followed PFHxA (−29.17 kcal/mol) < PFBS (−52.71 kcal/mol) < PFOA (−57.12 kcal/mol) < PFNA (−70.58 kcal/mol) < PFDA (−78.27 kcal/mol) < PFHxS (−80.06 kcal/mol) < PFOS (−102.30 kcal/mol). However, the binding/interaction energies followed PFHxS > PFOS > PFNA > PFDA > PFOA > PFBS > PFHxA. The MD simulation was carried out under NVT ensemble at 298 K, the thermodynamic states and relaxation pretreatment procedures were then examined quantitatively by radial distribution function, X-ray scattering, relative concentration profile, mean square displacement and space time correlation function. The results show that effective sorption of PFAS molecule by PE MPs involves hydrogen or chemical bonding as well non-bond energy such as Van der Waals (VdW), electrostatic and intramolecular energies. The cell volume did not change during single and multicomponent sorption while the sorption density increased about threefold the single component (0.36 g/cm3), suggesting that as the pollutant number increased the sorption capacity increased. This study showed that PE MPs can used for single and multicomponent sorption of PFASs effectively and also provided theoretical support for our knowledge of the sorption mechanism at the molecular level, which will help in better understanding of PFAS removal by MPs.

Using lightweight convolutional neural network to track vibration displacement in rotating body video

The non-contact visual displacement measurement methods can detect problems such as rigid body deformation and structural wear of structural bodies due to long-term service life. However, the traditional visual vibration measurement methods are limited by the inherent sampling constraint of ordinary image sensors, which cannot achieve efficient vibration target identification and correlation tracking for rotating body targets in low-resolution videos under the premise of high sampling rate. Therefore, this paper uses high-speed industrial camera as the acquisition medium, introduces deep convolutional neural networks into the field of visual vibration measurement, on this basis, weighs the target detection accuracy and displacement tracking speed, uses the designed lightweight convolutional neural networks model to vibration displacement tracking in rotating body videos. We ensure that the computational efficiency and parameter quantity of the convolutional networks are solved with low loss accuracy. First of all, we take the lightweight convolutional neural network as the backbone network, replace the standard convolutional neural network with depthwise separable convolution and pointwise convolution. Considering the speed and accuracy advantages of deep learning algorithms for video object tracking, we estimate the heat map, object center offsets and bounding box sizes use an anchor-free detection algorithm on the network framework. In order to prevent the loss of vibrating target identity in rotating body videos, we use re-identification(re-ID) method to strengthen the correlation of target displacement between adjacent frames. In experiments with traditional visual vibration measurement and recent deep learning measurement methods for performance testing, the network model we designed can demonstrate absolute advantages that traditional convolutional neural networks do not have. On the one hand, our comparison of time–frequency characteristics at different speeds shows that the vibration displacement curve regressed by the lightweight convolutional neural network has a high degree of fit with the displacement signal obtained by the eddy current sensor;on the other hand, when the target object is blurred, the generalization ability of our algorithm is proved, which also reflects the engineering application value of visual vibration measurement in the field of vibration displacement tracking of rotating bodies.

Getting the nod: Pediatric head motion in a transdiagnostic sample during movie- and resting-state fMRI.

Head motion continues to be a major problem in fMRI research, particularly in developmental studies where an inverse relationship exists between head motion and age. Despite multifaceted and costly efforts to mitigate motion and motion-related signal artifact, few studies have characterized in-scanner head motion itself. This study leverages a large transdiagnostic public dataset (N = 1388, age 5-21y, The Healthy Brain Network Biobank) to characterize pediatric head motion in space, frequency, and time. We focus on practical aspects of head motion that could impact future study design, including comparing motion across groups (low, medium, and high movers), across conditions (movie-watching and rest), and between males and females. Analyses showed that in all conditions, high movers exhibited a different pattern of motion than low and medium movers that was dominated by x-rotation, and z- and y-translation. High motion spikes (>0.3mm) from all participants also showed this pitch-z-y pattern. Problematic head motion is thus composed of a single type of biomechanical motion, which we infer to be a nodding movement, providing a focused target for motion reduction strategies. A second type of motion was evident via spectral analysis of raw displacement data. This was observed in low and medium movers and was consistent with respiration rates. We consider this to be a baseline of motion best targeted in data preprocessing. Further, we found that males moved more than, but not differently from, females. Significant cross-condition differences in head motion were found. Movies had lower mean motion, and especially in high movers, movie-watching reduced within-run linear increases in head motion (i.e., temporal drift). Finally, we used intersubject correlations of framewise displacement (FD-ISCs) to assess for stimulus-correlated motion trends. Subject motion was more correlated in movie than rest, and 8 out of top 10 FD-ISC windows had FD below the mean. Possible reasons and future implications of these findings are discussed.