Wall Displacement Research Articles

Design and locomotion analysis of modular soft robot

AbstractIn the paper, a novel modular soft robot that can crawl and turn is presented. The modular soft robot is composed of multiple drive modules connected in series, including one head module, one tail module and three body modules. Each module is actuated by the air chamber. Due to the nonlinear performance of the air chamber, the strain energy function of the air chamber is established. The relationship between the displacement of the air chamber expansion wall and the inflation pressure is obtained, and the manufacturing parameters of the air chamber are determined. By dividing the body of the robot into a series of continuous flexible models, the driving force and the friction force of the robot in locomotion are analyzed. An inflation and deflation control method is presented to complete the locomotion. According to the experiment, the crawling speed of the robot can reach 15.53 mm/s (0.03 body length per second). The turning speed of the robot can reach 1.273 °/s. The robot can crawl and turn on the rough blanket surface effectively. The robot can explore and move in a complex and changeable environment.

Evolution of double-eye wall hurricanes and emergence of complex tripolar end states in moist-convective rotating shallow water model

A detailed investigation of linear instabilities of double-eyewall hurricane-like vortices with double maxima (“walls”) of azimuthal velocity and vorticity around the central minimum (“eye”) and of their nonlinear saturation is carried out in the framework of the moist-convective rotating shallow water model. It is shown that developing barotropic instability leads to inward displacement and gradual disappearance of the inner wall and to the formation of a nontrivial tripolar quasi-stationary structure, provided the second, outer, wall of the initial vortex is high enough. The effects of moist convection lead to the enhancement of the outer wall. In comparison, under the influence of the same instability, vortices with an inner wall stronger than the outer one evolve toward monopolar single-eyewall structures.

Finite Element Method for Designing Large Section Underground Works by Sequential Excavation Method. Study Case: Lugoj-Deva Road Tunnel

Abstract Any underground work requires the knowledge and application of appropriate techniques and technologies in all stages of implementation of such a project. An important problem in the design of underground works is the knowledge of the characteristics and behaviour of the massif in which the work will be carried out. It depends on the choice of the excavation solution appropriate to the existing real conditions, which will influence the duration of the work and the costs associated with it. The objective of this paper was to analyse and compare the total deformations of the contour of the underground work, assuming that the work is performed by sequential excavation method (S.E.M.): excavation in the horizontal direction and in the vertical direction. The finite element numerical simulation method was used for the convergence analysis, which showed that the total displacements of the tunnel gallery wall are smaller for the horizontal sequential excavation (SEM) variant, both for the hypothesis of coefficient of pressure in state of rest having the value K0 = 0.6, as well as for the hypothesis in which K0 = 2.27.

Mechano-biological phenotype in post-infarction cardiac remodeling

Ischemic heart disease is one of the leading cause of death in developed countries. In 30% of patients with heart infarction, inadequate cardiac fibrosis leads to terminal failure. We believe that local mechanical forces (inherent to the pump function of the heart) after cardiac infarction play a key role in the outcome of cardiac remodeling, in particular by modifying the response of microvascular endothelial cells (MECs), main players accompanying myocardial healing processes. Dynamic data, accessible by ultrasound, are however not widely used in the clinic, and could help to understand why patients remain refractory to treatments for heart failure. We aimed at studying the mechano-biological coupling that exists between mechanical stress applied to ischemic lesions, and the local biological response of cardiac cells. Using a mouse model of myocardial infarction (coronary artery ligation), we analyzed heart deformation using dynamic ultrasound imaging 1 month post-infarction (speckle tracking, VevoLabs). Mice were then sacrificed, and the hearts were harvested and processed for immunohistochemical analysis. Multiparametric mechanical maps (strain, displacement and velocity) were obtained using a morphometry program developed in the laboratory, and compared to a spatial transcriptomic analysis in the corresponding section planes (Visium, 10X genomics), in 4 infarcted heart of various size and localization. The transcriptomic data were validated in situ by immunofluorescence, in contiguous mouse heart sections ( Fig. 1 ). Generated big data highlight a panel of transcripts which expression highly correlates with radial strain and displacement of the heart wall. Among these factors, neuregulin-1 (involved in cardiac remodeling), and TRPC6 or PECAM-1 (sensors of mechanical forces) were found highly expressed in the mouse heart sections (immunofluorescence). Neuregulin-1 and TRPC6 strongly co-localized with MECs and coronary artery SMCs bordering the infarcted area, while PECAM-1 activation (phosphorylation) in MECs was found highly correlated with radial strain. These results support a mechano-biological coupling in infarcted hearts, modulating the expression of factors involved in its repair. Understanding the biology associated with mechanical stress could improve the management of patients after a heart attack, on the sole basis of dynamic imaging.

Time-resolved absolute radius estimation of vibrating contrast microbubbles using an acoustical camera.

Ultrasound (US) contrast agents consist of microbubbles ranging from 1 to 10 μm in size. The acoustical response of individual microbubbles can be studied with high-frame-rate optics or an "acoustical camera" (AC). The AC measures the relative microbubble oscillation while the optical camera measures the absolute oscillation. In this article, the capabilities of the AC are extended to measure the absolute oscillations. In the AC setup, microbubbles are insonified with a high- (25 MHz) and low-frequency US wave (1-2.5 MHz). Other than the amplitude modulation (AM) from the relative size change of the microbubble (employed in Renaud, Bosch, van der Steen, and de Jong (2012a). "An 'acoustical camera' for in vitro characterization of contrast agent microbubble vibrations," Appl. Phys. Lett. 100(10), 101911, the high-frequency response from individual vibrating microbubbles contains a phase modulation (PM) from the microbubble wall displacement, which is the extension described here. The ratio of PM and AM is used to determine the absolute radius, R0. To test this sizing, the size distributions of two monodisperse microbubble populations ( R = 2.1 and 3.5 μm) acquired with the AC were matched to the distribution acquired with a Coulter counter. As a result of measuring the absolute size of the microbubbles, this "extended AC" can capture the full radial dynamics of single freely floating microbubbles with a throughput of hundreds of microbubbles per hour.

Safety analysis of a deep foundation ditch using deep learning methods

Rapid safety evaluation of foundation ditch during construction process has gained significant attention in recent years. In this study, safety monitoring of a foundation ditch was proposed using different sensing technologies including distributed fiber optic sensors (FOS) and micro-electro-mechanical (MEMS) sensors. Four different artificial neural network methods, including back propagation neural network, genetic algorithm optimized back propagation (GA-BP) neural network, nonlinear autoregressive network with exogenous inputs neural network, and Elman neural network, were used to predict the monitored axial force of concrete support, settlement of foundation ditch, and horizontal displacement of diagraph wall during construction process. The monitoring result shows both MEMS based sensors and FOS are effective for monitoring settlement, horizontal displacement and axial force change of the foundation ditch. Four ANN methods demonstrate a good predication of settlement, horizontal displacement, and axial force with a limited error range (less than 5%). Comparative study indicates that the GA-BP method is the best ANN method for prediction analysis of these parameters. Safety condition of those parameter increments can be divided into four different levels using 68-95-99.7 rule in statistics. Finally, a typical example based on monitored and predicted data was presented to validate the feasibility of using Euclidean distance to obtain safety levels of a foundation ditch.

Time-frequency analysis of venous pulsatile flow and sigmoid sinus vascular wall displacement causing pulsatile tinnitus using time series and magnitude squared coherence methods

Displacement of the sigmoid sinus vascular wall and intrasinus blood flow motion is known to cause pulsatile tinnitus (PT) in patients with sigmoid plate dehiscence. To investigate the source of sound that causes PT, this study sought to determine the correlation between in vivo displacement of the vascular wall and intrasinus flow hemodynamics. A confocal laser displacement sensor and color-coded Doppler ultrasound system were implemented on a participant diagnosed with venous PT. The displacement and Doppler velocity data were analyzed using time series and magnitude squared coherence methods. The median and peak displacement values of the vascular wall were 6.7 [Formula: see text]m and 11.7 [Formula: see text]m, respectively. The major frequency range of vascular displacement was below 4 Hz. The portmanteau test was rejected for different values of m. The cross-correlation of the two processes was not zero, indicating the existence of cross-correlation. The peak magnitude squared coherence of the two gauged signals was 0.3 at 7.143 Hz. The displacement of the sigmoid sinus vascular wall was temporally correlated with the intrasinus flow, although the major frequency range of the induced vascular displacement fell below the human hearing threshold. Therefore, the hydroacoustic and vibroacoustic sounds induced by the fluid–structure interaction between the vascular and osseous structures overweighed the displacement of the vascular wall at the focal dehiscence area in PT production.

Performance of helical soil-nailed walls under bridge abutment

In the current study, the performance of helical soil-nailed walls (HSNWs) was evaluated under bridge abutment using reduced-scale model tests. For this purpose, sixteen wall models were constructed with different lengths, patterns and inclinations of the helical nails and then were loaded to failure using the strip footing. Findings indicated that 15° can be introduced as the optimal inclination for installing helical nails in walls under bridge abutments to achieve the maximum bearing capacity and minimum lateral wall displacements. It was found that although using longer nails and installing them in a square pattern and optimal angle reduced the penetration depth of the slip surface, but caused more portion of the bridge footing pressure to be converted to connection load and, consequently, bending in the wall facing. Moreover, the role of the lower rows of nails in the stability of HSNWs was found to be more prominent than the upper rows. Also, it was concluded that the method proposed by FHWA [1] to calculate the connection load could be used as an upper bound in helical soil-nailed walls under bridge abutment.

Passive earth pressure under various modes of wall movement: a numerical approach

Numerical computations using an explicit-finite difference code were carried out to evaluate the passive earth pressure magnitude and distribution against a retaining wall subjected to different wall movement modes: translation (T), rotation about the bottom (RB) and rotation about the top (RT). In agreement with classical solutions, the results showed that, in T mode, passive earth pressure distribution was substantially hydrostatic with depth for all the wall displacement stages. However, when either RT or RB was considered, a clear non-linear distribution that was strongly affected by the wall displacement magnitude was noted. For the RT mode, due to the arching effect, the increase in earth pressure behind the lower half of the wall was more pronounced, with the wall displacement hardly affecting the centroid of the passive load distribution located below the commonly used one-third of the wall height. In RB mode, as wall rotation progressed, the passive earth pressure mobilised in upper part of the wall increased and its distribution gradually changed from a non-linear to linear distribution. Compared with previous experimental results available in the literature, it was found that mobilised passive earth pressure in RB and RT modes needs more displacement than in the T mode.

3D Physical Experimental Study of Shield–Strata Interaction Under Dynamic and Static Disturbance

With the increasing depth and intensity of coal mining, there is an increasing risk to the working face due to high static load and periodic breakage of the roof. The relation between the support and the surrounding rock under static–dynamic coupling loading disturbance is an important factor affecting the stability of the working face. In this study, a 3D physical modeling platform is developed to study the interaction between the shield and strata under dynamic and static disturbance. In the experiment, the static load is set to 0, 0.5, 1, and 2 MPa, respectively. The different dynamic load is realized by changing the fall height of the iron plate. The change in hydraulic support resistance is recorded by the pressure monitoring system. The displacement of the coal wall is monitored by using an infrared rangefinder. The results show that the change in static load and dynamic load will affect the support resistance and coal wall displacement. With the increase in dynamic load, coal wall displacement, and bracket resistance increase, the increase is not linear. The larger the dynamic load, the greater the increase. Static load change has little effect on bracket resistance, and the impact on coal wall displacement is large. With the increase in static load, coal wall displacement is reduced and then increased. In static load, for the stability of coal wall, there is a threshold; below the threshold, the static load can improve the stability of coal wall, exceed the threshold, but accelerate the destruction of coal wall. At the same time, the stability coefficient of the quarry bracket and surrounding rock is defined. The sensitivity analysis of the main parameters is carried out. The method of controlling the stability of the quarry bracket and surrounding rock is proposed.

Lightweight soundproofing membrane acoustic metamaterial for broadband sound insulation

According to the mass law, a dense and thick soundproofing material is generally used to block low-frequency sounds. However, lightweight thin soundproofing materials in the form of metamaterials can also be implemented with high sound transmission loss. In this study, we present a soundproofing comprising a thin membrane coupled with an ultralight membrane-type acoustic metamaterial (MAM). Owing to the vibration in the membrane, the structure-borne acoustic radiation of the soundproofing can be easily tuned, making broadband sound insulation possible. The anti-resonance generated by the membrane and thin plate surface minimizes the response of the radiating surface to the acoustic load. Thus, the dynamic effective density and acoustic impedance become extremely high, whereas the normal displacement of the radiating surface is almost zero. We numerically and experimentally demonstrated an open-field test for a plate-type and an enclosure-type of soundproofing MAM. In addition, the vibration displacement of the MAM enclosure exterior wall is measured using laser Doppler vibrometer. The results show that the soundproofing MAM exhibits excellent sound-blocking characteristics at multiple anti-resonance frequencies compared to homogeneous materials of the same weight. We expect that its simple construction can be used in noise-insulation applications in acoustic enclosures, automobile insulation, walls, and engine rooms.

Slope displacement and soil pressure of soilbag-retaining wall influenced by arrangement

Soilbags have a good effect on slope reinforcement. In this paper, five kinds of physical model tests were carried out on slopes strengthened by reinforced soilbag-retaining wall, namely analysis of the failure mode and failure pressure of the slope, the variation trend of horizontal displacement of the slope, the maximum horizontal displacement and the horizontal transmission and vertical distribution of earth pressure. Thus, the influence of the arrangement mode of the soilbags on the slope reinforcement effect were studied. The results show that the alternate arrangement between layers (arrangement mode 1) had the deepest slip surface, the maximum bearing capacity and the minimum horizontal displacement, thus its reinforcement effect was the best. In addition, the reinforcement effect of the slope was related to the amount of tail embedded into the slope body, the interaction of soilbags in the layer and the embedment between the upper and the lower layers of soilbags. It was found that when the embedding degree of the tails into the slope was higher, the horizontal deformation constraint of the slope was stronger, resulting in a deeper sliding surface and a higher ultimate bearing capacity of the slope. This shows that the slope reinforcement effect was better with soilbags.

Influence of Varying Tensile Stress on Domain Motion.

Magnetic domain motion has been widely studied in the fields of spintronics, nanowires, and thin films. However, there is a lack of such studies on industrial steels, especially for domain motion under the action of varying stress. Understanding domain motion under stress is helpful for the improvement of evaluation accuracy and the establishment of theoretical models of passive, nondestructive testing technology. This paper presents the influence of varying tensile stresses on the magnetic domain motion of silicon steel sheets. Magnetic domain rotation and domain wall displacement were characterized using magnetic domain images, and their motion mechanisms under elastic and plastic stresses are presented. The results show that the domain rotation under stress involves reversible and irreversible changes. The effect of material rearrangement on domain rotation and domain wall displacement after plastic deformation is discussed. Based on the motion mechanism, a threshold stress value (TSV) required for the complete disappearance of the supplementary domains in the elastic range is proposed, enabling the classification of the elastic stress ranges in which the reversible and irreversible domain rotations occur. In addition, the effect of microstructure on TSV is also discussed, and the results show that the regions far away from the grain boundary need larger stresses to complete an irreversible domain rotation. Additionally, the domain width and orientation also affect the TSV. These findings regarding the domain motion mechanism and TSV can help to explain the sequence of domain rotation under stress and modify the stress assessment under dynamic loads in electromagnetic nondestructive evaluation, especially in the magnetic memory method.

Electromagnetic field controlled domain wall displacement for induced strain tailoring in BaTiO3-epoxy nanocomposite

Failure in an epoxy polymer composite material is prone to initiate by the coalescence of microcracks in its polymer matrix. As such, matrix toughening via addition of a second phase as rigid or/and rubber nano/micro-particles is one of the most popular approaches to improve the fracture toughness across multiple scales in a polymer composite, which dissipates fracture energy via deformation mechanisms and microcracks arrest. Few studies have focused on tailorable and variable toughening, so-called ‘active toughening’, mainly suggesting thermally induced strains which offer slow and irreversible toughening due to polymer’s poor thermal conductivity. The research presented in the current article has developed an instantaneous, reversible extrinsic strain field via remote electromagnetic radiation. Quantification of the extrinsic strain evolving in the composite with the microwave energy has been conducted using in-situ real-time fibre optic sensing. A theoretical constitutive equation correlating the exposure energy to micro-strains has been developed, with its solution validating the experimental data and describing their underlying physics. The research has utilised functionalised dielectric ferroelectric nanomaterials, barium titanate (BaTiO3), as a second phase dispersed in an epoxy matrix, able to introduce microscopic electro-strains to their surrounding rigid epoxy subjected to an external electric field (microwaves, herein), as result of their domain walls dipole displacements. Epoxy Araldite LY1564, a diglycidyl ether of bisphenol A associated with the curing agent Aradur 3487 were embedded with the BaTiO3 nanoparticles. The silane coupling agent for the nanoparticles’ surface functionalisation was 3-glycidoxypropyl trimethoxysilane (3-GPS). Hydrogen peroxide (H2O2, 30%) and acetic acid (C2H4O2, 99.9%) used as functionalisation aids, and the ethanol (C2H6O, 99.9%) used for BaTiO3 dispersion. Firstly, the crystal microstructure of the functionalised nanoparticles and the thermal and dielectric properties of the achieved epoxy composite materials have been characterised. It has been observed that the addition of the dielectric nanoparticles has a slight impact on the curing extent of the epoxy. Secondly, the surface-bonded fibre Bragg grating (FBG) sensors have been employed to investigate the real-time variation of strain and temperature in the epoxy composites exposed to microwaves at 2.45 GHz and at different exposure energy. The strains developed due to the in-situ exposure at composite, adhesive and their holding fixture material were evaluated using the FBG. The domain wall induced extrinsic strains were distinguished from the thermally induced strains, and found that the increasing exposure energy has an instantaneously increasing effect on the development of such strains. Post-exposure Raman spectra showed no residual field in the composite indicating no remnant strain field examined under microwave powers < 1000 W, thus suggesting a reversible strain introduction mechanism, i.e. the composite retaining its nominal properties post exposure. The dielectric composite development and quantifications presented in this article proposes a novel active toughening technology for high-performance composite applications in numerous sectors.

Quantification of the heterogeneous effect of static and dynamic perivascular structures on patient-specific local aortic wall mechanics using inverse finite element modeling and DENSE MRI

Recent studies have highlighted the relevance of perivascular interactions on aortic wall mechanics. Most of the approaches assume static perivascular structures; however, the beating heart dynamically displaces the neighboring aorta. We develop a model to account for the effect of periaortic interactions due to static and dynamic structures by prescribing a moving elastic foundation boundary condition (EFBC) embedded into an inverse finite element algorithm using in vivo displacements from 2D displacement encoding with stimulated echoes (DENSE) MRI as target data. We applied this method at three different locations of interest, the distal aortic arch (DAA), descending thoracic aorta (DTA), and infrarenal abdominal aorta (IAA) for a total of 27 cases in healthy humans. The model reproduces the target diastole-to-systole deformation and bulk displacement of the aortic wall with median displacement errors below 0.5mm. The EFBC showed good agreement with the location of anatomical features and was consistent among individuals of similar characteristics. Results show that an energy source acting on the adventitia is required to reproduce the displacements measured at the vicinity of the heart, but not at the abdomen. The average adventitial load as a percentage of the luminal pulse-pressure was found to increase with age and to decrease along the descending aorta, from 61% at the DAA to 37% at the DTA, and 30% at the IAA. This approach offers a patient-specific method to estimate in vivo adventitial loads and aortic wall stiffness, which can bring a better understanding of normal and pathological in vivo aortic function.

Extremely large deformation of tunnel induced by rock mass fracture using GPGPU parallel FDEM

AbstractIt is essential to better understand the large deformation behavior of deep tunnels in weak rock mass to improve the long‐term stability of tunnel surrounding rock mass and design effective supports for squeezing tunnels. This paper introduces two representative large deformation engineering examples to study squeezing behavior. First, new algorithms of contact search, determination of actual contact, and calculation law of contact pairs are proposed for general‐purpose computing on graphics processing units (GPGPUs), by improving the original serial algorithms and developing a compute unified device architecture (CUDA) parallel program, to satisfy the large‐scale rock fracture process simulation. Then, tunnels excavation and rock reinforcement effect including the combination of U‐shaped steel and steel fabric, spray concrete (SMC), and grouting were modeled. The verification, done by comparing the field observation data and the FDEM simulation results of progressive fracture and the tunnel wall convergence displacement, shows that stress remarkable rebalancing after excavation because of high in situ stress, low rock mass strength, and rock mass long‐term strength reduction properties, thus, the rock mass fracture progressively and the rock blocks move continuously, leading to the rock mass volume increase significantly. The result demonstrates one of the root causes of squeezing. To effectively reduce the tunnel wall displacement and maintain tunnel stability, support with higher stiffness or multifactorial combined support methods and grouting with a better bonding effect should be used together. The findings provide insights into the progress of tunnel squeezing and the basis for support design in the squeezing tunnel.

A plastic-damage approach to the excavation response of a circular opening in weak rock

During opening construction, the accumulated wall displacement and the developing excavation damaged zone are the results of stress redistribution and inelastic behavior induced by both the microcracking damage and the irreversible plastic deformation. The current approach to predict ground response to excavation disturbance is usually based on the Convergence-Confinement Method, which fails to consider the rock damage and the plastic-damage coupled mechanism, resulting in inaccurate estimation of rock deformation, particularly in the case of the weak rock with high deformability. This study establishes a plastic-damage theoretical approach for a circular opening by a kinematic decomposition of strains into an elastic, plastic and damage parts within the framework of finite strain using a hypoelastic–plastic theory, in order to investigate the inelastic behavior-induced excavation response. In this regard, the damage model provides the effective stress to the plasticity model defining the yield criterion, in combination with the strength-stiffness degradation and damage evolution. The numerical implementation is given and two examples are considered for validation. Extensive works are then carried out to clarify some issues, including the capacity of the model to characterize the inelastic behavior, the role of rock damage and confining stress dependence on ground response, and the preliminary critical support pressure for the residual failure zone.

Pediatric Advanced Life Support in a Neonatal Context.

Pediatric Advanced Life Support in a Neonatal Context.

EXAMINED AND ANALYSIS OF EMPIRICAL SEISMIC DAMAGE OF WORKSHOP BUILDING

To deeply explore the typical damage characteristics and vulnerability characteristics of workshop building (WB) in actual earthquakes, the empirical field reconnaissance and observation of the WB damaged to varying degrees in the Mw 8.0 earthquake in Wenchuan County, Sichuan Province, China on May 12, 2008 were conducted. The investigation results indicated that the typical seismic damage forms of industrial buildings in multiple intensity regions were: local and overall collapse, column cracking and crane beam displacement, collapse and cracking of wall, and damage of supporting and connecting members, the field investigation pictures of typical seismic damage were provided, respectively. According to different typical failure characteristics, the seismic damage mechanism and seismic capacity were analyzed, and the measures and suggestions to improve the seismic capacity of industrial buildings with different material categories were conducted. The conclusions can provide necessary reference for the revision of the seismic code of industrial plants and the seismic intensity scale of China.

Effects of spatial variability and correlation in stochastic discontinuum analysis of unreinforced masonry walls

This study investigates the influence of the uncertainty in material properties on the in-plane lateral behavior and capacity of stone masonry walls via a stochastic discontinuum analysis framework. The framework is demonstrated via the 3D numerical assessment of an unreinforced masonry (URM) wall using a stochastic analysis in the form of Monte Carlo simulations. The random parameters considered in this study are the prism compressive strength of masonry, the tensile strength of the masonry units and joints, and the friction angle for joints and units. Novel research is conducted using a fast and accurate DEM model to determine whether the spatial variability of the material properties should be taken into account. In addition, the effects of joint-to-joint correlation of modeling parameters are examined to identify if such a correlation exists. A total of 1200 stochastic discontinuum analyses for 12 different cases are carried out. The results call attention to considering the spatial variability of the modeling parameters in the stochastic analysis, as they significantly reduce the variation in the wall's strength and displacement capacity. Results also demonstrate the influence of the correlation between bed-joint parameters on the strength and failure mode of the walls. Ultimately, propagation of the uncertainty in the joint friction angle into the strength and displacement capacity of the walls is quantified.