Displacement Analysis Research Articles

Co-seismic surface displacement of the June 21, 2022 MW6 Khōst, Afghanistan earthquake from InSAR observations

A robust estimation of the earthquake location, seismic moment, and fault geometry is essential for objective seismic hazard assessment. Seismic events in a remote location, specifically in the absence of seismic and GNSS networks, can be investigated effectively using the InSAR-based technique. This study adopts the Differential Interferometric SAR (DInSAR) technique to quantify the co-seismic surface displacement caused by the June 21, 2022, Khōst MW6 earthquake that occurred along the western plate boundary between the Indian and Eurasian plate. The interferograms show that the maximum surface deformation occurred on the northwest and southwest of the fault line. From coherence, the Line of Sight (LOS) displacement, and the co-seismic surface displacement analysis, it has been observed that surface deformation was most pronounced in the southwest region of the fault line, and the surface has moved to the opposite direction along the fault line, which indicates a sinistral slightly oblique strike-slip movement. This InSAR-based observation appears consistent with the seismic waveforms derived from co-seismic surface displacements. Further, it has been argued that the slip deficit accumulated during the period of the last about 48 years along the frontal region of the northward extension of the Suleiman range and associated fault zone is qualitatively estimated at about 1.5 m, which is consistent with the seismic waveforms derived finite slip model.

Stress analysis of laminated and sandwich beams subjected to concentrated load by using quasi-two-dimensional theory

This study presents a quasi-two-dimensional higher-order shear deformation theory for stress and displacement analysis of isotropic, laminated, and sandwich beams subjected to concentrated load. The assumed displacement field includes the effect of transverse shear and normal deformations. The condition of zero transverse shear stresses on the upper and lower surface of beams is satisfied, hence the present formulation does not require the shear correction factor generally associated with first-order models. By applying the principle of virtual work, the governing equations and boundary conditions for laminated and sandwich beams are derived. Transverse shear and normal stresses are determined from the stress-equilibrium equations of elasticity theory. The transverse stresses obtained using this approach satisfy the continuity condition at layer interfaces and the stress boundary conditions at the external surfaces. The outcomes of the present theory are compared with those of third-order, and first-order shear deformation models, and the classical beam model. The results highlight the significant deviation in displacements and stresses of laminated and sandwich beams when normal strain is included in the model, as compared to the prediction made by lower-order models.

Study on small modulus modified gear damage fault and electromechanical coupling vibration characteristics under multiple working conditions

The fault of transmission system seriously affects the life of robot joints, so it is urgent to study the crack of the displacement wheel set. Firstly, the tooth profile equation of the modified gear is established, and the time-varying mesh stiffness (TVMS) is obtained. Secondly, the multi-degree-of-freedom electromechanical coupling dynamic equation is established. Finally, the vibration displacement under steady state, start-up and shock conditions is analyzed. The results show that: (a)The positive displacement can increase TVMS, while negative displacement is the opposite. (b) The appearance of cracks accelerates the damage to two adjacent teeth. (c) The decrease of TVMS increases with the increase of crack depth. (d) The crack causes the gear pair to generate vibration shock, and the vibration displacement increases significantly in the case of broken teeth. (e) Statistical analysis of the vibration displacement reveals that the root means square value can detect early cracks, and the kurtosis index can predict life. (f) Cracks have a large effect on the transient process at start-up and shock, but the effect of cracks is weakened during no-load steady-state operation.

Seismic reliability analysis of slope in spatially variable soils using multiple response surfaces

PurposeThis paper aims to develop an efficient algorithm combining straightforward response surface functions with Monte Carlo simulation to conduct seismic reliability analysis in a systematical way.Design/methodology/approachThe representative slip surfaces are identified and based on to calibrate multiple response surface functions with acceptable accuracy. The calibrated response surfaces are used to determine the yield acceleration in Newmark sliding displacement analysis. Then, the displacement-based limit state function is adopted to conduct seismic reliability analysis.FindingsThe calibrated response surface functions have fairly good accuracy in predicting the yield acceleration in Newmark sliding displacement analysis. The seismic reliability is influenced by such factors as PGA, spatial variability and threshold value. The proposed methodology serves as an effective tool for geotechnical practitioners.Originality/valueThe multiple sources of a seismic slope response can be effectively determined using the multiple response surface functions, which are easily implemented within geotechnical engineering.

Fracture behaviour characterisation of FRP-reinforced concrete based on digital image correlation and acoustic emission technology

In order to identify the dynamic fracture characteristics of fibre-reinforced polymer (FRP)-reinforced concrete, three-point bending fracture tests of FRP-reinforced concrete with five different strain loading rates (10−1/s, 10−2/s, 10−3/s, 10−4/s and 10−5/s) are carried out. The fracture behaviour of FRP-reinforced concrete is analysed using digital image correlation (DIC) and acoustic emission (AE) techniques. Crack propagation in FRP-reinforced concrete beams during the fracture process is observed and a quantitative relationship is established between the AE parameters and the load level before the ultimate load is reached. Test results on the variation of the AE parameters can characterise the internal damage behaviour of the FRP-reinforced concrete beams and monitor the distribution characteristics of any cracks. The crack propagation trajectory of the FRP-reinforced concrete beams can be observed using the DIC technique and quantitative analysis of the crack opening displacement (COD) can be achieved.

An algorithm to couple smoothed particle hydrodynamics and finite element method for fluid–structure interaction problems

An algorithm for coupling the smoothed particle hydrodynamics (SPH) method and the finite element method (FEM) is proposed for fluid–structure interaction (FSI) problems. The SPH module solves the fluid motion, and the FEM module describes the deformation of structures. In the algorithm, a structure is considered as a solid boundary in the SPH module and dealt with using the dynamic boundary condition. Only three layers of SPH boundary particles are set to represent the structure surface, and the interaction forces between the SPH boundary and fluid particles, including the water pressure and the viscous shear stress, are quantified in a same way as the inter-fluid particle forces. Further, the computed forces on the SPH boundary particles exerted by the fluid are redistributed to the structure FEM nodes based on a well-defined projection scheme. In the FEM module, the deformation and motion of the structure under the exerted fluid forces are solved, and accordingly, the position and velocity of the SPH boundary particles are updated by interpolation from the new properties at the FEM nodes. The proposed SPH-FEM coupled model is validated in three FSI benchmarks. For the deformation of an elastic plate under hydrostatic water pressure, the relative difference between the computed and the analytical maximum vertical displacement at the plate midpoint is about 1.5%. For the deformation of an elastic gate subjected to a time-varying dam-break flow, the relative root mean squared errors in the computed vertical and horizontal displacement of the gate are, respectively, 5.5% and 2.2%. It is demonstrated that the proposed model performs well in simulating the deformation of structures under both hydrostatic water pressure and dynamic impacts of dam-break flows.

Permanent Displacement Analysis of Multistage Loess Slopes with Multiple Slip Surfaces Based on Energy Methods

Permanent Displacement Analysis of Multistage Loess Slopes with Multiple Slip Surfaces Based on Energy Methods

Effect of specimen size on creep crack growth rate in superalloys IN625 and IN783

To further clarify the relation between the intensity of specimen size effect on creep crack growth (CCG) rate and operative creep fracture mechanisms, CCG testing and mechanism observation were carried out for two superalloys IN625 and IN783. Results show that the CCG data of different specimen types for IN625 basically coincide at 650 °C. In contrast, strong specimen size effect was observed in IN783 at 560 °C, that is, the CCG rate increases with the increase in specimen thickness, producing the largest CCG ratio of approximately seven. The load-line displacement and fracture mechanism analyses indicate that the IN625 specimens failed in a ductile and intergranular manner, while the IN783 specimens in a brittle and intergranular manner. The present study suggests that the influence of creep fracture mechanisms should be considered in the characterization of the specimen size effect on CCG rate.

A corotational isogeometric assumed natural strain shell element in updated lagrangian formulation for general geometric nonlinear analysis of thin-walled structures

A new general geometric nonlinear curved quadrilateral shell element, which can handle large displacements and large rotations, is presented in this paper. It is formulated based on the incremental virtual work equation in updated Lagrangian formulation for general large displacement analysis. The kinematics of shell element is described using non-uniform B-spline patch, which results in the element displacement field with higher order continuity and the element performance more resistive to shear locking and membrane locking. In order to perfectly avoid such membrane locking and shear locking behaviors, the assumed in-plane membrane strain field and the assumed transverse shear strain field for the incremental covariant Green-Lagrange strain are constructed as linear combinations of non-uniform B-spline basis functions with degrees lower than those adopted by the original displacement field interpolation. In addition, based on Euler parameters, the corotational procedure available for high order isogeometric shell element is developed to extract the strain-producing deformational displacements and rotations and to update the element stresses and realistic internal force vectors. The accuracy and robustness of proposed shell element are demonstrated through the solutions of various benchmark problems.

Design of a dynamic measurement system for Bl factor spatial distribution of resonant blood viscoelastic sensor

Bl factor is a key system parameter of the resonant blood viscoelastic sensor. In this paper, a dynamic measurement system for the spatial distribution of Bl factor based on velocity amplitude and motional impedance was designed. The system extracted the velocity amplitude and motional impedance of the coil under the dynamic condition of driving the sensor to generate simple harmonic oscillations using laser displacement and impedance analysis combined with in-phase/quadrature demodulation algorithm, and controlled the equilibrium position of the coil by adjusting the direct current component of the excitation current to realize the position scanning. In the position interval of [-240, 240] μm, the maximum coefficient of variation of the measurement results was 0.077 3%, and the maximum relative error to the simulation results was 2.937 9%, with a linear fitting correlation coefficient R 2 = 0.996 8. The system can be used to accurately measure the spatial distribution of Bl factor of the resonant blood viscoelastic sensor, which provides a technical support for the verification of the design of the sensor magnetic circuit.

Wind Field Digital Twins Sandbox System for Transmission Towers.

Given the digitalization trends within the field of engineering, we propose a practical approach to engineering digitization. This method is established based on a physical sandbox model, camera equipment and simulation technology. We propose an image processing modeling method to establish high-precision continuous mathematical models of transmission towers. The calculation of the wind field is realized by using wind speed calculations, a load-wind-direction-time algorithm and the Continuum-Discontinuum Element Method (CDEM). The sensitivity analysis of displacement- and acceleration-controlled transmission tower loads under two different wind direction conditions is conducted. The results show that the digital model exhibits a proportional relationship with the physical dimensions of the transmission tower model. The error between the numerical simulation results and the experimental results falls within a reasonable range. Nodes at higher positions of the transmission tower experience significantly higher forces compared to those at lower positions, and the structural forms with larger windward projected areas yield similar simulation results. The proposed digital twin system can help monitor the performance of structural bodies and assess the disaster degree in extreme conditions. It can guide specific maintenance and repair tasks.

Analysis of thermally-induced displacements of the HartRAO Lunar Laser Ranger optical tube: impact on pointing

The Hartebeesthoek Radio Astronomy Observatory (HartRAO) of South Africa is developing a Lunar Laser Ranging (LLR) system to achieve sub-centimetre range precision to the Moon. Key to this high precision expectation, which includes improving the overall operational performance of its telescope, is the thermal analysis of the telescope structure. In this study, thermal sensors were mounted on the thermally- important areas of the tube structure to measure the tube displacements emanating from the varying ambient air temperatures. A laser distance-measurement system was used for this purpose. Results showed that while the optical tube undergoes structural changes with changes in temperature, the tube position closer to the place where the spider assembly is mounted is unevenly displaced in three directions. In particular, for the time period considered in this study, it was found that the relative displacements on average at prisms 1, 2 and 3 in the vertical direction were 2.5540 ± 0.0007 m, 1.3750 ± 0.0008 m and 1.9780 ± 0.0007 m, respectively. The corresponding standard deviation (SD) values of ±0.0007 m, ±0.0008 m and ±0.0007 m denotes the average deviations that occurred in the vertical direction at the centre of prisms 1, 2 and 3, respectively. The generally higher SD of relative displacements in the vertical direction rather than in the easting and northing directions, suggest that the tube experienced greater variations in the vertical direction. Furthermore, the lower arc of the tube front, was found to have increased variability, and therefore it was hypothesised to introduce more elevation pointing offsets than azimuth for the LLR. This information constitutes an important input for guiding the efforts to determine the extent of the correction needed to be fed into the LLR telescope pointing model to counteract expected thermally induced pointing offsets.

A comparative study on penetration mechanisms of drug-loaded carbon and boron nitride nanotubes through biological membranes by steered molecular dynamics simulations

Understanding the mechanism by which nanotubes penetrate cell membranes is challenging from multiple perspectives. As a drug delivery system, boron nitride nanotubes (BNNTs) have a similar structure to carbon nanotubes but with B–N bonds instead of C–C bonds. Through a remarkable series of direct and indirect observations within specific cells, these nanotubes are popularly attributed as superior penetrant into cell membrane. Suitable functional groups and polymers are often needed to enhance the biocompatibility and solubility of BNNTs and CNTs in biological media. In addition, to figure out the effect of functional groups, the nanostructures without functional groups were first examined together with their anticancer drugs (fluorouracil and letrozole). All partial charges of the drug and nanotube have been investigated through population analysis. After that, with a total of 40 simulations (MD and SMD simulations), various analytical techniques were employed to examine the interaction between drugs and nanotubes with POPE, which is a class of phospholipids existing in biological membrane, in aqueous media. Noteworthy among these techniques is the mean-squared displacement analysis to compare the diffusion rate of nanocarriers and the radial distribution function analysis, which was utilized to compare water concentrations surrounding nanotubes. Additionally, the stability of the drug within the nanotube was assessed through mass center distance analysis. The diffusion coefficients of the nanotube-membrane complex were compared against various chemical agents by employing mean squared displacement analysis. The findings of the study revealed that the tethering of tetra ethylene glycol results in the augmentation of the water molecules surrounding the nanotubes while simultaneously enhancing the durability of the drug being conveyed. Nonetheless, the addition of tetra ethylene glycol resulted in a reduction in the nanocarrier’s diffusion coefficient. Communicated by Ramaswamy H. Sarma

Conformal Geometric Algebra–Based Geometric Modeling Method for Forward Displacement Analysis of 6-4 Stewart Platforms

Abstract This paper presents a novel geometric modeling method for direct displacement analysis of 6-4 Stewart platforms based on conformal geometric algebra (CGA). First, a geometric constraint relationship of four lines and a plane intersecting at a point is published. Second, a new coordinate-invariant geometric constraint equation of 6-4 Stewart platforms is deduced by CGA operation. Third, five polynomial equations are established by CGA theory. Fourth, based on the above six equations, a 5 × 5 Sylvester’s matrix is formulated by using Sylvester’s Dialytic elimination method and Gröbner bases method under the graded reverse lexicographical order. Finally, the coordinates of four points on the moving platform are revealed. Besides, a numerical example is used to prove the validity of the proposed method. The novelty of this study is that a whole geometric modeling method by geometric constraint relationship of four lines and a plane intersecting at a point is put forward under the CGA framework, which has good intuition and offers a novel idea for solving the other complex mechanisms. At the same time, Sylvester’s matrix constructed by this method is the smallest one in the known literature for forward displacement analysis of 6-4 Stewart platforms.

“Analysis of Stress and Displacement of Simply Supported Symmetric Cross-Ply [0/90/90/0] Square Laminated Composite Plate Under Sinusoidal Loading Using Finite Element Method”

“Analysis of Stress and Displacement of Simply Supported Symmetric Cross-Ply [0/90/90/0] Square Laminated Composite Plate Under Sinusoidal Loading Using Finite Element Method”

The mathematical model and analysis of the nanoparticle-stabilized foam displacement

This work proposes a mathematical model to study the foam displacement in porous media stabilized by nanoparticles. We consider a simplification of the Stochastic Bubble Population balance model in local equilibrium, with nanoparticle dependence inspired by the experimental data from the literature. It consists of a non-strictly hyperbolic system of conservation laws, which is solved for the generic initial and injection conditions. We investigate the existence of a global solution as a sequence of waves following the Conservation Laws Theory. When the solution is composed of two or more waves, we present necessary and sufficient conditions to guarantee the compatibility of these wave sequences. The analytical solution for the nanoparticle-stabilized foam displacement in porous media allowed us to quantify the effect of nanoparticles on foam displacement, focusing on the breakthrough time and cumulative water production. In agreement with the literature, when only gas is injected, the breakthrough time and the water production increase with the nanoparticle concentration. Although, we also observe that the effect of nanoparticles is less pronounced for high nanoparticle concentration. Counterintuitively, during gas-water co-injection for a certain parameter range, adding nanoparticles changes the mathematical solution qualitatively, yielding a negligible effect on water production. We discuss the most favorable conditions to observe the action of nanoparticles in laboratory experiments.

Percutaneous tracheostomy in the surgical management of oral malignancy: an emerging standard of care

Percutaneous tracheostomy insertion is commonly performed in the critical care setting. However, its applicability and safety in head and neck (H&N) surgery remains uncertain. This study aimed to compare complications and postoperative recovery for percutaneous tracheostomy versus surgical tracheostomy in H&N surgery. A total of 66 patients undergoing percutaneous tracheostomy as part of H&N microvascular surgery were identified retrospectively. A control cohort of 70 consecutive surgical tracheostomy cases performed by another surgical team in the same department was similarly determined. Generally, the complication rates in the percutaneous and surgical tracheostomy groups were similar, with overall rates being 42% and 31%, respectively. The percutaneous group experienced a higher rate of airway obstruction (15%), primarily due to tube displacement. Time to decannulation and duration of inpatient stay were similar in both groups. Notably, an analysis of tracheostomy tube displacement identified high body mass index (BMI) and bilateral neck dissection as potential risk factors, and all cases occurred on postoperative day one. To mitigate this risk we recommend implementation of a percutaneous tracheostomy management protocol, precise tube selection using preoperative imaging, and careful passage of the stoma intraoperatively. In conclusion, this study found that the percutaneous technique exhibited a similar complication profile. It remains unclear whether the rates of longer-term complications, such as delayed stoma healing and tracheal stenosis, differ between techniques. A future prospective study with appropriate elimination of selection and reporting bias would help address this and similar pertinent issues, including patients' perspectives.

Reproducibility of 3D thoracic aortic displacement from 3D cine balanced SSFP at 3 T without contrast enhancement.

Aortic motion has direct impact on the mechanical stresses acting on the aorta. In aortic disease, increased stiffness of the aorta may lead to decreased aortic motion over time, which could be a predictor for aortic dissection or rupture. This study investigates the reproducibility of obtaining 3D displacement and diameter maps quantified using accelerated 3D cine MRI at 3 T. A noncontrast-enhanced, free-breathing 3D cine sequence based on balanced SSFP and pseudo-spiral undersampling with high spatial isotropic resolution was developed (spatial/temporal resolution [1.6 mm]3 /67 ms). The thoracic aorta of 14 healthy volunteers was prospectively scanned three times at 3 T: twice on the same day and a third time 2 weeks later. Aortic displacement was calculated using iterative closest point nonrigid registration of manual segmentations of the 3D aorta at end-systole and mid-diastole. Interexamination and interobserver regional analysis of mean displacement for five regions of interest was performed using Bland-Altman analysis. Additionally, a complementary voxel-by-voxel analysis was done, allowing a more local inspection of the method. No significant differences were found in mean and maximum displacement for any of the regions of interest for the interexamination and interobserver analysis. The maximum displacement measured in the lower half of the ascending aorta was 11.0 ± 3.4 mm (range: 3.0-17.5 mm) for the first scan. The smallest detectable change in mean displacement in the lower half of the ascending aorta was 3 mm. Detailed 3D cine balanced SSFP at 3 T allows for reproducible quantification of systolic-diastolic mean aortic displacement within acceptable limits.

Comparison of MSD analysis from single particle tracking with MSD from images. Getting the best of both worlds

Fluorescence microscopy can provide valuable information about cell interior dynamics. Particularly, mean squared displacement (MSD) analysis is widely used to characterize proteins and sub-cellular structures’ mobility providing the laws of molecular diffusion. The MSD curve is traditionally extracted from individual trajectories recorded by single-particle tracking-based techniques. More recently, image correlation methods like iMSD have been shown capable of providing averaged dynamic information directly from images, without the need for isolation and localization of individual particles. iMSD is a powerful technique that has been successfully applied to many different biological problems, over a wide spatial and temporal scales. The aim of this work is to review and compare these two well-established methodologies and their performance in different situations, to give an insight on how to make the most out of their unique characteristics. We show the analysis of the same datasets by the two methods. Regardless of the experimental differences in the input data for MSD or iMSD analysis, our results show that the two approaches can address equivalent questions for free diffusing systems. We focused on studying a range of diffusion coefficients between D = 0.001 μm2 s−1 and D = 0.1 μm2 s−1, where we verified that the equivalence is maintained even for the case of isolated particles. This opens new opportunities for studying intracellular dynamics using equipment commonly available in any biophysical laboratory.

Advanced monitoring and numerical modelling of the stability, safety and reliability indicators of the earthen dam of Songloulou (Cameroon).

For the determination of global stability after long term advanced monitoring, artificial intelligence have been used for the data analysis of water level and displacements of Songloulou earth dam at Cameroon. Measurements of safety and reliability indicators follow changes set by piezometric and pendulums measurements. The results obtained from the artificial intelligence on the base of many years recording data have confirmed the relevance and robustness of this model. The ANFIS model combining the concept of neural network and fuzzy logic was used to simulate the behaviour of piezometers and pendulums in the dam. This model has provided satisfactory results, given in the large amount of data to be processed. The water level evolution is modelled using the ANFIS function integrated in the MATLAB software and the result is compared to that obtained by the HST method. Afterwards, the state of stress on the structure and stability of the slope at shear have been assessed based on the hydro mechanical behaviour using the GEOSTUDIO Finite Element computation software. The input parameters are: the head of water recorded in the piezometers and geotechnical parameters of the dam. The modelling results in terms of displacement are accurately consistent with the displacement measurements. The horizontal displacement of pendulums obtained by GEOSTUDIO is 80 mm and those measured directly of the pendulums have 70 mm of average value. The safety factor for slope stability according to 530 m water level is 1.5.